The shock and spall response of three industrially important hexagonal close-packed metals: magnesium, titanium and zirconium.

PubMed

Hazell, P J; Appleby-Thomas, G J; Wielewski, E; Escobedo, J P

2014-08-28

Magnesium, titanium and zirconium and their alloys are extensively used in industrial and military applications where they would be subjected to extreme environments of high stress and strain-rate loading. Their hexagonal close-packed (HCP) crystal lattice structures present interesting challenges for optimizing their mechanical response under such loading conditions. In this paper, we review how these materials respond to shock loading via plate-impact experiments. We also discuss the relationship between a heterogeneous and anisotropic microstructure, typical of HCP materials, and the directional dependency of the elastic limit and, in some cases, the strength prior to failure. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Communication: From close-packed to topologically close-packed: Formation of Laves phases in moderately polydisperse hard-sphere mixtures

NASA Astrophysics Data System (ADS)

Lindquist, Beth A.; Jadrich, Ryan B.; Truskett, Thomas M.

2018-05-01

Particle size polydispersity can help to inhibit crystallization of the hard-sphere fluid into close-packed structures at high packing fractions and thus is often employed to create model glass-forming systems. Nonetheless, it is known that hard-sphere mixtures with modest polydispersity still have ordered ground states. Here, we demonstrate by computer simulation that hard-sphere mixtures with increased polydispersity fractionate on the basis of particle size and a bimodal subpopulation favors the formation of topologically close-packed C14 and C15 Laves phases in coexistence with a disordered phase. The generality of this result is supported by simulations of hard-sphere mixtures with particle-size distributions of four different forms.

A Method of Assembling Compact Coherent Fiber-Optic Bundles

NASA Technical Reports Server (NTRS)

Martin, Stefan; Liu, Duncan; Levine, Bruce Martin; Shao, Michael; Wallace, James

2007-01-01

A method of assembling coherent fiber-optic bundles in which all the fibers are packed together as closely as possible is undergoing development. The method is based, straightforwardly, on the established concept of hexagonal close packing; hence, the development efforts are focused on fixtures and techniques for practical implementation of hexagonal close packing of parallel optical fibers.

Random close packing of disks and spheres in confined geometries

NASA Astrophysics Data System (ADS)

Desmond, Kenneth W.; Weeks, Eric R.

2009-11-01

Studies of random close packing of spheres have advanced our knowledge about the structure of systems such as liquids, glasses, emulsions, granular media, and amorphous solids. In confined geometries, the structural properties of random-packed systems will change. To understand these changes, we study random close packing in finite-sized confined systems, in both two and three dimensions. Each packing consists of a 50-50 binary mixture with particle size ratio of 1.4. The presence of confining walls significantly lowers the overall maximum area fraction (or volume fraction in three dimensions). A simple model is presented, which quantifies the reduction in packing due to wall-induced structure. This wall-induced structure decays rapidly away from the wall, with characteristic length scales comparable to the small particle diameter.

Packing loops into annular cavities.

PubMed

Sobral, T A; Gomes, M A F

2017-02-01

The continuous packing of a flexible rod in two-dimensional cavities yields a countable set of interacting domains that resembles nonequilibrium cellular systems and belongs to a new class of lightweight material. However, the link between the length of the rod and the number of domains requires investigation, especially in the case of non-simply connected cavities, where the number of avoided regions emulates an effective topological temperature. In the present article we report the results of an experiment of injection of a single flexible rod into annular cavities in order to find the total length needed to insert a given number of loops (domains of one vertex). Using an exponential model to describe the experimental data we quite minutely analyze the initial conditions, the intermediary behavior, and the tight packing limit. This method allows the observation of a new fluctuation phenomenon associated with instabilities in the dynamic evolution of the packing process. Furthermore, the fractal dimension of the global pattern enters the discussion under a novel point of view. A comparison with the classical problems of the random close packing of disks and jammed disk packings is made.

Packing loops into annular cavities

NASA Astrophysics Data System (ADS)

Sobral, T. A.; Gomes, M. A. F.

2017-02-01

The continuous packing of a flexible rod in two-dimensional cavities yields a countable set of interacting domains that resembles nonequilibrium cellular systems and belongs to a new class of lightweight material. However, the link between the length of the rod and the number of domains requires investigation, especially in the case of non-simply connected cavities, where the number of avoided regions emulates an effective topological temperature. In the present article we report the results of an experiment of injection of a single flexible rod into annular cavities in order to find the total length needed to insert a given number of loops (domains of one vertex). Using an exponential model to describe the experimental data we quite minutely analyze the initial conditions, the intermediary behavior, and the tight packing limit. This method allows the observation of a new fluctuation phenomenon associated with instabilities in the dynamic evolution of the packing process. Furthermore, the fractal dimension of the global pattern enters the discussion under a novel point of view. A comparison with the classical problems of the random close packing of disks and jammed disk packings is made.

Capillary Pressure of a Liquid Between Uniform Spheres Arranged in a Square-Packed Layer

NASA Technical Reports Server (NTRS)

Alexader, J. Iwan D.; Slobozhanin, Lev A.; Collicott, Steven H.

2004-01-01

The capillary pressure in the pores defined by equidimensional close-packed spheres is analyzed numerically. In the absence of gravity the menisci shapes are constructed using Surface Evolver code. This permits calculation the free surface mean curvature and hence the capillary pressure. The dependences of capillary pressure on the liquid volume constructed here for a set of contact angles allow one to determine the evolution of basic capillary characteristics under quasi-static infiltration and drainage. The maximum pressure difference between liquid and gas required for a meniscus passing through a pore is calculated and compared with that for hexagonal packing and with approximate solution given by Mason and Morrow [l]. The lower and upper critical liquid volumes that determine the stability limits for the equilibrium capillary liquid in contact with square packed array of spheres are tabulated for a set of contact angles.

The shelf life of chilled sheep livers packed in closed tubs.

PubMed

Gill, C O; Penny, N

1984-01-01

Livers incubated at 30°C in closed tubs developed floras dominated by Enterobacteriaceae. At chiller temperatures, floras were ultimately dominated by psychrotrophic lactobacilli. Tub-packed livers can have an extended shelf life similar to that reported for vacuum-packed liver. Copyright © 1984. Published by Elsevier Ltd.

Crystallization of sheared hard spheres at 64.5% volume fraction

NASA Astrophysics Data System (ADS)

Swinney, H. L.; Rietz, F.; Schroeter, M.; Radin, C.

2017-11-01

A classic experiment by G.D. Scott Nature 188, 908, 1960) showed that pouring balls into a rigid container filled the volume to an upper limit of 64% of the container volume, which is well below the 74% volume fraction filled by spheres in a hexagonal close packed (HCP) or face center cubic (FCC) lattice. Subsequent experiments have confirmed a ``random closed packed'' (RCP) fraction of about 64%. However, the physics of the RCP limit has remained a mystery. Our experiment on a cubical box filled with 49400 weakly sheared glass spheres reveals a first order phase transition from a disordered to an ordered state at a volume fraction of 64.5%. The ordered state consists of crystallites of mixed FCC and HCP symmetry that coexist with the amorphous bulk. The transition is initiated by homogeneous nucleation: in the shearing process small crystallites with about ten or fewer spheres dissolve, while larger crystallites grow. A movie illustrates the crystallization process. German Academic Exchange Service (DAAD), German Research Foundation (DFG), NSF DMS, and R.A. Welch Foundation.

How hollow melanosomes affect iridescent colour production in birds

PubMed Central

Eliason, Chad M.; Bitton, Pierre-Paul; Shawkey, Matthew D.

2013-01-01

Developmental constraints and trade-offs can limit diversity, but organisms have repeatedly evolved morphological innovations that overcome these limits by expanding the range and functionality of traits. Iridescent colours in birds are commonly produced by melanin-containing organelles (melanosomes) organized into nanostructured arrays within feather barbules. Variation in array type (e.g. multilayers and photonic crystals, PCs) is known to have remarkable effects on plumage colour, but the optical consequences of variation in melanosome shape remain poorly understood. Here, we used a combination of spectrophotometric, experimental and theoretical methods to test how melanosome hollowness—a morphological innovation largely restricted to birds—affects feather colour. Optical analyses of hexagonal close-packed arrays of hollow melanosomes in two species, wild turkeys (Meleagris gallopavo) and violet-backed starlings (Cinnyricinclus leucogaster), indicated that they function as two-dimensional PCs. Incorporation of a larger dataset and optical modelling showed that, compared with solid melanosomes, hollow melanosomes allow birds to produce distinct colours with the same energetically favourable, close-packed configurations. These data suggest that a morphological novelty has, at least in part, allowed birds to achieve their vast morphological and colour diversity. PMID:23902909

Soil strength and macropore volume limit root elongation rates in many UK agricultural soils.

PubMed

Valentine, Tracy A; Hallett, Paul D; Binnie, Kirsty; Young, Mark W; Squire, Geoffrey R; Hawes, Cathy; Bengough, A Glyn

2012-07-01

Simple indicators of crop and cultivar performance across a range of soil types and management are needed for designing and testing sustainable cropping practices. This paper determined the extent to which soil chemical and physical properties, particularly soil strength and pore-size distribution influences root elongation in a wide range of agricultural top soils, using a seedling-based indicator. Intact soil cores were sampled from the topsoil of 59 agricultural fields in Scotland, representing a wide geographic spread, range of textures and management practices. Water release characteristics, dry bulk density and needle penetrometer resistance were measured on three cores from each field. Soil samples from the same locations were sieved, analysed for chemical characteristics, and packed to dry bulk density of 1.0 g cm(-3) to minimize physical constraints. Root elongation rates were determined for barley seedlings planted in both intact field and packed soil cores at a water content close to field capacity (-20 kPa matric potential). Root elongation in field soil was typically less than half of that in packed soils. Penetrometer resistance was typically between 1 and 3 MPa for field soils, indicating the soils were relatively hard, despite their moderately wet condition (compared with <0.2 MPa for packed soil). Root elongation was strongly linked to differences in physical rather than chemical properties. In field soil root elongation was related most closely to the volume of soil pores between 60 µm and 300 µm equivalent diameter, as estimated from water-release characteristics, accounting for 65.7 % of the variation in the elongation rates. Root elongation rate in the majority of field soils was slower than half of the unimpeded (packed) rate. Such major reductions in root elongation rates will decrease rooting volumes and limit crop growth in soils where nutrients and water are scarce.

Frictionless bead packs have macroscopic friction, but no dilatancy.

PubMed

Peyneau, Pierre-Emmanuel; Roux, Jean-Noël

2008-07-01

The statement of the title is shown by numerical simulation of homogeneously sheared assemblies of frictionless, nearly rigid beads in the quasistatic limit. Results coincide for steady flows at constant shear rate gamma[over ] in the limit of small gamma[over ] and static approaches, in which packings are equilibrated under growing deviator stresses. The internal friction angle phi , equal to 5.76 degrees +/-0.22 degrees in simple shear, is independent of average pressure P in the rigid limit and stems from the ability of stable frictionless contact networks to form stress-induced anisotropic fabrics. No enduring strain localization is observed. Dissipation at the macroscopic level results from repeated network rearrangements, similar to the effective friction of a frictionless slider on a bumpy surface. Solid fraction Phi remains equal to the random close packing value approximately 0.64 in slowly or statically sheared systems. Fluctuations of stresses and volume are observed to regress in the large system limit. Defining the inertial number as I=gamma radical m/(aP), with m the grain mass and a its diameter, both internal friction coefficient mu*=tan phi and volume 1/Phi increase as powers of I in the quasistatic limit of vanishing I , in which all mechanical properties are determined by contact network geometry. The microstructure of the sheared material is characterized with a suitable parametrization of the fabric tensor and measurements of coordination numbers.

Jamming II: Edwards’ statistical mechanics of random packings of hard spheres

NASA Astrophysics Data System (ADS)

Wang, Ping; Song, Chaoming; Jin, Yuliang; Makse, Hernán A.

2011-02-01

The problem of finding the most efficient way to pack spheres has an illustrious history, dating back to the crystalline arrays conjectured by Kepler and the random geometries explored by Bernal in the 1960s. This problem finds applications spanning from the mathematician’s pencil, the processing of granular materials, the jamming and glass transitions, all the way to fruit packing in every grocery. There are presently numerous experiments showing that the loosest way to pack spheres gives a density of ∼55% (named random loose packing, RLP) while filling all the loose voids results in a maximum density of ∼63%-64% (named random close packing, RCP). While those values seem robustly true, to this date there is no well-accepted physical explanation or theoretical prediction for them. Here we develop a common framework for understanding the random packings of monodisperse hard spheres whose limits can be interpreted as the experimentally observed RLP and RCP. The reason for these limits arises from a statistical picture of jammed states in which the RCP can be interpreted as the ground state of the ensemble of jammed matter with zero compactivity, while the RLP arises in the infinite compactivity limit. We combine an extended statistical mechanics approach ‘a la Edwards’ (where the role traditionally played by the energy and temperature in thermal systems is substituted by the volume and compactivity) with a constraint on mechanical stability imposed by the isostatic condition. We show how such approaches can bring results that can be compared to experiments and allow for an exploitation of the statistical mechanics framework. The key result is the use of a relation between the local Voronoi volumes of the constituent grains (denoted the volume function) and the number of neighbors in contact that permits us to simply combine the two approaches to develop a theory of volume fluctuations in jammed matter. Ultimately, our results lead to a phase diagram that provides a unifying view of the disordered hard sphere packing problem and further sheds light on a diverse spectrum of data, including the RLP state. Theoretical results are well reproduced by numerical simulations that confirm the essential role played by friction in determining both the RLP and RCP limits. The RLP values depend on friction, explaining why varied experimental results can be obtained.

Multilayer DNA origami packed on hexagonal and hybrid lattices.

PubMed

Ke, Yonggang; Voigt, Niels V; Gothelf, Kurt V; Shih, William M

2012-01-25

"Scaffolded DNA origami" has been proven to be a powerful and efficient approach to construct two-dimensional or three-dimensional objects with great complexity. Multilayer DNA origami has been demonstrated with helices packing along either honeycomb-lattice geometry or square-lattice geometry. Here we report successful folding of multilayer DNA origami with helices arranged on a close-packed hexagonal lattice. This arrangement yields a higher density of helical packing and therefore higher resolution of spatial addressing than has been shown previously. We also demonstrate hybrid multilayer DNA origami with honeycomb-lattice, square-lattice, and hexagonal-lattice packing of helices all in one design. The availability of hexagonal close-packing of helices extends our ability to build complex structures using DNA nanotechnology. © 2011 American Chemical Society

Assembling substrate-less plasmonic metacrystals at the oil/water interface for multiplex ultratrace analyte detection.

PubMed

Lee, Yih Hong; Lee, Hiang Kwee; Ho, Jonathan Yong Chew; Yang, Yijie; Ling, Xing Yi

2016-08-15

Current substrate-less SERS platforms are limited to uncontrolled aggregation of plasmonic nanoparticles or quasi-crystalline arrays of spherical nanoparticles, with no study on how the lattice structures formed by nanoparticle self-assembly affect their detection capabilities. Here, we organize Ag octahedral building blocks into two large-area plasmonic metacrystals at the oil/water interface, and investigate their in situ SERS sensing capabilities. Amphiphilic octahedra assemble into a hexagonal close-packed metacrystal, while hydrophobic octahedra assemble into an open square metacrystal. The lower packing density square metacrystal gives rise to much stronger SERS enhancement than the denser packing hexagonal metacrystal, arising from the larger areas of plasmonic hotspots within the square metacrystal at the excitation wavelength. We further demonstrate the ability of the square metacrystal to achieve quantitative ultratrace detection of analytes from both the aqueous and organic phases. Detection limits are at the nano-molar levels, with analytical enhancement factors reaching 10(8). In addition, multiplex detection across both phases can be achieved in situ without any loss of signal quantitation.

Use of the Primitive Unit Cell in Understanding Subtle Features of the Cubic Closest-Packed Structure

ERIC Educational Resources Information Center

Hawkins, John A.; Rittenhouse, Jeffrey L.; Soper, Linda M.; Rittenhouse, Robert C.

2008-01-01

One of the most important crystal structures adopted by metals is characterized by the "abcabc"...stacking of close-packed layers. This structure is commonly referred to in textbooks as the cubic close-packed (ccp) or face-centered cubic (fcc) structure, since the entire lattice can be generated by replication of a face-centered cubic unit cell…

Close-Packed Silicon Microelectrodes for Scalable Spatially Oversampled Neural Recording

PubMed Central

Scholvin, Jörg; Kinney, Justin P.; Bernstein, Jacob G.; Moore-Kochlacs, Caroline; Kopell, Nancy; Fonstad, Clifton G.; Boyden, Edward S.

2015-01-01

Objective Neural recording electrodes are important tools for understanding neural codes and brain dynamics. Neural electrodes that are close-packed, such as in tetrodes, enable spatial oversampling of neural activity, which facilitates data analysis. Here we present the design and implementation of close-packed silicon microelectrodes, to enable spatially oversampled recording of neural activity in a scalable fashion. Methods Our probes are fabricated in a hybrid lithography process, resulting in a dense array of recording sites connected to submicron dimension wiring. Results We demonstrate an implementation of a probe comprising 1000 electrode pads, each 9 × 9 μm, at a pitch of 11 μm. We introduce design automation and packaging methods that allow us to readily create a large variety of different designs. Significance Finally, we perform neural recordings with such probes in the live mammalian brain that illustrate the spatial oversampling potential of closely packed electrode sites. PMID:26699649

Cooperative Effects in Closely Packed Quantum Emitters with Collective Dephasing

NASA Astrophysics Data System (ADS)

Prasanna Venkatesh, B.; Juan, M. L.; Romero-Isart, O.

2018-01-01

In a closely packed ensemble of quantum emitters, cooperative effects are typically suppressed due to the dephasing induced by the dipole-dipole interactions. Here, we show that by adding sufficiently strong collective dephasing, cooperative effects can be restored. Specifically, we show that the dipole force on a closely packed ensemble of strongly driven two-level quantum emitters, which collectively dephase, is enhanced in comparison to the dipole force on an independent noninteracting ensemble. Our results are relevant to solid-state systems with embedded quantum emitters such as color centers in diamond and superconducting qubits in microwave cavities and waveguides.

Phonons and superconductivity in fcc and dhcp lanthanum

NASA Astrophysics Data System (ADS)

Baǧcı, S.; Tütüncü, H. M.; Duman, S.; Srivastava, G. P.

2010-04-01

We have investigated the structural and electronic properties of lanthanum in the face-centered-cubic (fcc) and double hexagonal-close-packed (dhcp) phases using a generalized gradient approximation of the density functional theory and the ab initio pseudopotential method. It is found that double hexagonal-close-packed is the more stable phase for lanthanum. Differences in the density of states at the Fermi level between these two phases are pointed out and discussed in detail. Using the calculated lattice constant and electronic band structure for both phases, a linear response approach based on the density functional theory has been applied to study phonon modes, polarization characteristics of phonon modes, and electron-phonon interaction. Our phonon results show a softening behavior of the transverse acoustic branch along the Γ-L direction and the Γ-M direction for face-centered-cubic and double hexagonal-close-packed phases, respectively. Thus, the transverse-phonon linewidth shows a maximum at the zone boundary M(L) for the double hexagonal-close-packed phase (face-centered-cubic phase), where the transverse-phonon branch exhibits a dip. The electron-phonon coupling parameter λ is found to be 0.97 (1.06) for the double hexagonal-close-packed phase (face-centered-cubic phase), and the superconducting critical temperature is estimated to be 4.87 (dhcp) and 5.88 K (fcc), in good agreement with experimental values of around 5.0 (dhcp) and 6.0 K (fcc). A few superconducting parameters for the double hexagonal-close-packed phase have been calculated and compared with available theoretical and experimental results. Furthermore, the calculated superconducting parameters for both phases are compared between each other in detail.

Asphaltene-laden interfaces form soft glassy layers in contraction experiments: a mechanism for coalescence blocking.

PubMed

Pauchard, Vincent; Rane, Jayant P; Banerjee, Sanjoy

2014-11-04

In previous studies, the adsorption kinetics of asphaltenes at the water-oil interface were interpreted utilizing a Langmuir equation of state (EOS) based on droplet expansion experiments.1-3 Long-term adsorption kinetics followed random sequential adsorption (RSA) theory predictions, asymptotically reaching ∼85% limiting surface coverage, which is similar to limiting random 2D close packing of disks. To extend this work beyond this slow adsorption process, we performed rapid contractions and contraction-expansions of asphaltene-laden interfaces using the pendant drop experiment to emulate a Langmuir trough. This simulates the rapid increase in interfacial asphaltene concentration that occurs during coalescence events. For the contraction of droplets aged in asphaltene solutions, deviation from the EOS consistently occurs at a surface pressure value ∼21 mN/m corresponding to a surface coverage ∼80%. At this point droplets lose the shape required for validity of the Laplace-Young equation, indicating solidlike surface behavior. On further contraction wrinkles appear, which disappear when the droplet is held at constant volume. Surface pressure also decreases down to an equilibrium value near that measured for slow adsorption experiments. This behavior appears to be due to a transition to a glassy interface on contraction past the packing limit, followed by relaxation toward equilibrium by desorption at constant volume. This hypothesis is supported by cycling experiments around the close-packed limit where the transition to and from a solidlike state appears to be both fast and reversible, with little hysteresis. Also, the soft glass rheology model of Sollich is shown to capture previously reported shear behavior during adsorption. The results suggest that the mechanism by which asphaltenes stabilize water-in-oil emulsions is by blocking coalescence due to rapid formation of a glassy interface, in turn caused by interfacial asphaltenes rapidly increasing in concentration beyond the glass transition point.

Static high pressure studies on Nd and Sc

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

Akella, J.; Xu, J.; Smith, G.S.

1985-06-24

We have investigated the crystal structural transformations in neodymium and scandium up to 4.0 GPa pressure and at room temperature, in a diamond-anvil high pressure apparatus. Nd has a double hexagonal-close packed (dhcp) structure at ambient pressure and temperature. Then it transforms to a face-centered cubic (fcc) structure at 3.8 GPa, which further transforms to a triple hexagonal-close packed structure (thcp) at about 18.0 GPa. In scandium we observed only one transformation from the hexagonal-close packed (hcp) structure at room temperature to a tetragonal structure. This transformation occurs between 19.0 and 23.2 GPa pressure.

7 CFR 51.311 - Marking requirements.

Code of Federal Regulations, 2012 CFR

2012-01-01

... STANDARDS) United States Standards for Grades of Apples Marking Requirements § 51.311 Marking requirements... minimum diameter of apples packed in a closed container shall be indicated on the container. For apple... varieties, the minimum diameter and minimum weight of apples packed in a closed container shall be indicated...

7 CFR 51.311 - Marking requirements.

Code of Federal Regulations, 2010 CFR

2010-01-01

... STANDARDS) United States Standards for Grades of Apples Marking Requirements § 51.311 Marking requirements... minimum diameter of apples packed in a closed container shall be indicated on the container. For apple... varieties, the minimum diameter and minimum weight of apples packed in a closed container shall be indicated...

7 CFR 51.311 - Marking requirements.

Code of Federal Regulations, 2011 CFR

2011-01-01

... STANDARDS) United States Standards for Grades of Apples Marking Requirements § 51.311 Marking requirements... minimum diameter of apples packed in a closed container shall be indicated on the container. For apple... varieties, the minimum diameter and minimum weight of apples packed in a closed container shall be indicated...

Crystallographic parameters of compounds and solid solutions in binary systems Cu-Pt and Ga-Pt

NASA Astrophysics Data System (ADS)

Potekaev, Alexandr; Probova, Svetlana; Klopotov, Anatolii; Vlasov, Viktor; Markov, Tatiana; Klopotov, Vladimir

2015-10-01

The study establishes that the packing index in compounds of the system Cu-Pt is close to the value 0.74 against a slight deviation from the Zen law of atomic volumes. The compounds in the system Ga-Pt have the highest values of the packing index in the range of the equiatomic composition, which greatly exceed ψ for close-packed structures based on FCC and HCP lattices for compounds made of the same kind of atoms. A correlation between singular points on the phase diagram of the system Ga-Pt and high values of the packing index in compounds is established.

Wetting behavior on hexagonally close-packed polystyrene bead arrays with different topographies.

PubMed

Park, Yi-Seul; Yoon, Seo Young; Lee, Jin Seok

2016-01-21

Herein, we investigated the wetting behavior of hexagonally close-packed polystyrene bead arrays with different bead diameters and surface flatness. The contact angle was found to be influenced by the surface roughness as well as the contact area of the polystyrene bead array with a water droplet.

GaN microrod sidewall epitaxial lateral overgrowth on a close-packed microrod template

NASA Astrophysics Data System (ADS)

Duan, Xiaoling; Zhang, Jincheng; Xiao, Ming; Zhang, Jinfeng; Hao, Yue

2018-05-01

We demonstrate a GaN growth method using microrod sidewall epitaxial lateral overgrowth (MSELO) on a close-packed microrod template by a nonlithographic technique. The density and distribution of threading dislocations were determined by the density and distribution of microrods and the nucleation model. MSELO exhibited two different nucleation models determined by the direction and degree of substrate misorientation and the sidewall curvature: one-sidewall and three-sidewall nucleation, predicting the dislocation density values. As a result, the threading dislocation density was markedly decreased from 2 × 109 to 5 × 107 cm‑2 with a small coalescence thickness of ∼2 µm for the close-packed 3000 nm microrod sample.

Insight into the defects of cage-type silica mesoporous crystals with Fd3m symmetry: TEM observations and a new proposal of "polyhedron packing" for the crystals.

PubMed

Han, Lu; Sakamoto, Yasuhiro; Che, Shunai; Terasaki, Osamu

2009-01-01

Silica mesoporous crystals were synthesized by using a gemini cationic surfactant (C(18-3-1)) as the directing agent, carboxyethylsilanetriol sodium salt as the co-structure directing agent (CSDA), and varying amounts of HCl. By using transmission electron microscopy (TEM) we observed 1) a structural change from the close-packed structures of spherical micelles--face-centered cubic (Fm3m) and hexagonal close-packed (P6(3)/mmc)--to Fd3m structures with an increase of HCl and 2) a few structural defects in the crystals with Fd3m symmetry. The structure of a crystal with Fd3m symmetry is described as one of the tetrahedrally close-packed (tcp) structures consisting of 5(12) and 5(12)6(4) polyhedra. The observed TEM images of the structural defects were explained well through use of simulated TEM images by introducing new 13-15 polyhedra comprising 5(12)6(2), 5(12)6(3), 4(1)5(10)6(2), 4(2)5(8)6(5), and 4(1)5(10)6(4), which have been observed in bubbles by Matzke. The mesostructural changes and defect formation are discussed in terms of the hardness of micelles composed of surfactant/CSDA/silica species that have formed through a change of the interaction between the surfactant and CSDA, which causes the micelles to change from a regime of close-packing to one of minimum-area packing.

Stuffed Derivatives of Close-Packed Structures

ERIC Educational Resources Information Center

Douglas, Bodie E.

2007-01-01

Decades ago Buerger described and later Palmer reviewed stuffed silica crystal structures widely used by mineralogists. Many publications and books have discussed common crystal structures in terms of close-packing of one set of atoms or ions (P sites) with other atoms or ions in tetrahedral (T) or octahedral (O) sites. Douglas and Ho described…

Periodic and Aperiodic Close Packing: A Spontaneous Hard-Sphere Model.

ERIC Educational Resources Information Center

van de Waal, B. W.

1985-01-01

Shows how to make close-packed models from balloons and table tennis balls to illustrate structural features of clusters and organometallic cluster-compounds (which are of great interest in the study of chemical reactions). These models provide a very inexpensive and tactile illustration of the organization of matter for concrete operational…

Charge Stabilized Crystalline Colloidal Arrays As Templates For Fabrication of Non-Close-Packed Inverted Photonic Crystals

PubMed Central

Bohn, Justin J.; Ben-Moshe, Matti; Tikhonov, Alexander; Qu, Dan; Lamont, Daniel N.

2010-01-01

We developed a straightforward method to form non close-packed highly ordered fcc direct and inverse opal silica photonic crystals. We utilize an electrostatically self assembled crystalline colloidal array (CCA) template formed by monodisperse, highly charged polystyrene particles. We then polymerize a hydrogel around the CCA (PCCA) and condense the silica to form a highly ordered silica impregnated (siPCCA) photonic crystal. Heating at 450 °C removes the organic polymer leaving a silica inverse opal structure. By altering the colloidal particle concentration we independently control the particle spacing and the wall thickness of the inverse opal photonic crystals. This allows us to control the optical dielectric constant modulation in order to optimize the diffraction; the dielectric constant modulation is controlled independently of the photonic crystal periodicity. These fcc photonic crystals are better ordered than typical close-packed photonic crystals because their self assembly utilizes soft electrostatic repulsive potentials. We show that colloidal particle size and charge polydispersity has modest impact on ordering, in contrast to that for close-packed crystals. PMID:20163800

The relative energy of fcc and hcp foams

NASA Astrophysics Data System (ADS)

Whyte, D.; Weaire, D.; Drenckhan, W.; Hutzler, S.

2015-06-01

The energies of face-centred cubic (fcc) and hexagonal close-packed (hcp) monodisperse foams, associated with their total surface area, are equal in the wet and dry limits, in the usual model. We prove that for all intermediate values of liquid fraction, hcp has lower energy. Energy considerations are thus not sufficient to explain the observed preference for crystallization into fcc over hcp in experiments using monodisperse bubbles.

Packing Regularities in Biological Structures Relate to Their Dynamics

PubMed Central

Jernigan, Robert L.; Kloczkowski, Andrzej

2007-01-01

The high packing density inside proteins leads to certain geometric regularities and also is one of the most important contributors to the high extent of cooperativity manifested by proteins in their cohesive domain motions. The orientations between neighboring non-bonded residues in proteins substantially follow the similar geometric regularities, regardless of whether the residues are on the surface or buried - a direct result of hydrophobicity forces. These orientations are relatively fixed and correspond closely to small deformations from those of the face-centered cubic lattice, which is the way in which identical spheres pack at the highest density. Packing density also is related to the extent of conservation of residues, and we show this relationship for residue packing densities by averaging over a large sample or residue packings. There are three regimes: 1) over a broad range of packing densities the relationship between sequence entropy and inverse packing density is nearly linear, 2) over a limited range of low packing densities the sequence entropy is nearly constant, and 3) at extremely low packing densities the sequence entropy is highly variable. These packing results provide important justification for the simple elastic network models that have been shown for a large number of proteins to represent protein dynamics so successfully, even when the models are extremely coarse-grained. Elastic network models for polymeric chains are simple and could be combined with these protein elastic networks to represent partially denatured parts of proteins. Finally, we show results of applications of the elastic network model to study the functional motions of the ribosome, based on its known structure. These results indicate expected correlations among its components for the step-wise processing steps in protein synthesis, and suggest ways to use these elastic network models to develop more detailed mechanisms - an important possibility, since most experiments yield only static structures. PMID:16957327

Hard sphere packings within cylinders.

PubMed

Fu, Lin; Steinhardt, William; Zhao, Hao; Socolar, Joshua E S; Charbonneau, Patrick

2016-03-07

Arrangements of identical hard spheres confined to a cylinder with hard walls have been used to model experimental systems, such as fullerenes in nanotubes and colloidal wire assembly. Finding the densest configurations, called close packings, of hard spheres of diameter σ in a cylinder of diameter D is a purely geometric problem that grows increasingly complex as D/σ increases, and little is thus known about the regime for D > 2.873σ. In this work, we extend the identification of close packings up to D = 4.00σ by adapting Torquato-Jiao's adaptive-shrinking-cell formulation and sequential-linear-programming (SLP) technique. We identify 17 new structures, almost all of them chiral. Beyond D ≈ 2.85σ, most of the structures consist of an outer shell and an inner core that compete for being close packed. In some cases, the shell adopts its own maximum density configuration, and the stacking of core spheres within it is quasiperiodic. In other cases, an interplay between the two components is observed, which may result in simple periodic structures. In yet other cases, the very distinction between the core and shell vanishes, resulting in more exotic packing geometries, including some that are three-dimensional extensions of structures obtained from packing hard disks in a circle.

Hydrogen powered sports car series (internal combustion engine and fuel cells)

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

Gotthold, J.P.

The electric hybrid vehicle can solve the problems which today make the pure electric car limited in its acceptance. The primary limitations are excess weight and short range due to a heavy battery pack of limited energy density. Our basic vehicular design makes use of three power technologies in a balanced way. The chassis is the standard Volkswagen Beetle type which carried many millions of the {open_quotes}beetles{close_quotes} across all the Earth`s continents. The body is a fiberfab replica of a 1970s design sports car which provides three compartments from it`s original mid engine design and a classic aerodynamic shape.

Bidisperse silica nanoparticles close-packed monolayer on silicon substrate by three step spin method

NASA Astrophysics Data System (ADS)

Khanna, Sakshum; Marathey, Priyanka; Utsav, Chaliawala, Harsh; Mukhopadhyay, Indrajit

2018-05-01

We present the studies on the structural properties of monolayer Bidisperse silica (SiO2) nanoparticles (BDS) on Silicon (Si-100) substrate using spin coating technique. The Bidisperse silica nanoparticle was synthesised by the modified sol-gel process. Nanoparticles on the substrate are generally assembled in non-close/close-packed monolayer (CPM) form. The CPM form is obtained by depositing the colloidal suspension onto the silicon substrate using complex techniques. Here we report an effective method for forming a monolayer of bidisperse silica nanoparticle by three step spin coating technique. The samples were prepared by mixing the monodisperse solutions of different particles size 40 and 100 nm diameters. The bidisperse silica nanoparticles were self-assembled on the silicon substrate forming a close-packed monolayer film. The scanning electron microscope images of bidisperse films provided in-depth film structure of the film. The maximum surface coverage obtained was around 70-80%.

Two-Dimensional Ordering of Solute Nanoclusters at a Close-Packed Stacking Fault: Modeling and Experimental Analysis

PubMed Central

Kimizuka, Hajime; Kurokawa, Shu; Yamaguchi, Akihiro; Sakai, Akira; Ogata, Shigenobu

2014-01-01

Predicting the equilibrium ordered structures at internal interfaces, especially in the case of nanometer-scale chemical heterogeneities, is an ongoing challenge in materials science. In this study, we established an ab-initio coarse-grained modeling technique for describing the phase-like behavior of a close-packed stacking-fault-type interface containing solute nanoclusters, which undergo a two-dimensional disorder-order transition, depending on the temperature and composition. Notably, this approach can predict the two-dimensional medium-range ordering in the nanocluster arrays realized in Mg-based alloys, in a manner consistent with scanning tunneling microscopy-based measurements. We predicted that the repulsively interacting solute-cluster system undergoes a continuous evolution into a highly ordered densely packed morphology while maintaining a high degree of six-fold orientational order, which is attributable mainly to an entropic effect. The uncovered interaction-dependent ordering properties may be useful for the design of nanostructured materials utilizing the self-organization of two-dimensional nanocluster arrays in the close-packed interfaces. PMID:25471232

Microbial Penetration of Muslin- and Paper-Wrapped Sterile Packs Stored on Open Shelves and in Closed Cabinets

PubMed Central

Standard, Paul G.; Mackel, Don C.; Mallison, G. F.

1971-01-01

Microbial penetration of sterile packs was studied using single-wrap (two layers) muslin, double-wrap (four layers) muslin, and two-way crepe paper (single layer) to wrap 20 gauze sponges (2 by 2 inch). These packs were stored in the central sterile supply departments of two hospitals and processed for sterility at predetermined intervals. Microorganisms penetrated single-wrap muslin as early as 3 days and double-wrap muslin and single-wrap two-way crepe paper in 21 to 28 days stored in open shelves. The time required for microbial penetration was at least twice as long when closed cabinets were used. Single-wrap muslin packs stored in sealed, impervious plastic bags remained sterile for at least 9 months. All sterile materials in pervious wrappers should be handled as little as possible and then only with extreme care and caution. Closed cabinets offer more protection than open shelves, and single wrappers are not recommended. Images PMID:5119207

Viscosity of a concentrated suspension of rigid monosized particles

NASA Astrophysics Data System (ADS)

Brouwers, H. J. H.

2010-05-01

This paper addresses the relative viscosity of concentrated suspensions loaded with unimodal hard particles. So far, exact equations have only been put forward in the dilute limit, e.g., by Einstein [A. Einstein, Ann. Phys. 19, 289 (1906) (in German); Ann. Phys. 34, 591 (1911) (in German)] for spheres. For larger concentrations, a number of phenomenological models for the relative viscosity was presented, which depend on particle concentration only. Here, an original and exact closed form expression is derived based on geometrical considerations that predicts the viscosity of a concentrated suspension of monosized particles. This master curve for the suspension viscosity is governed by the relative viscosity-concentration gradient in the dilute limit (for spheres the Einstein limit) and by random close packing of the unimodal particles in the concentrated limit. The analytical expression of the relative viscosity is thoroughly compared with experiments and simulations reported in the literature, concerning both dilute and concentrated suspensions of spheres, and good agreement is found.

Order - disorder transitions in granular sphere packings

NASA Astrophysics Data System (ADS)

Panaitescu, Andreea M.

Granular materials are ubiquitous in many industrial and natural processes, yet their complex behaviors characterized by unusual static and dynamic properties are still poorly understood. In this dissertation we investigate both the geometrical structure and the dynamical properties (the response to shear deformations, disorder-order transition and crystallization) of packings of mono-sized spheres as a function of the packing volume fraction. Different average packing fractions were obtained by submitting a dense granular material to periodic shear deformations and by epitaxy. Using advanced imaging techniques including the refractive index matched imaging (RIM) and X-ray computed tomography (CT) enables us to determine the three dimensional particles position inside the packing. From positions we obtain the Voronoi tessellation corresponding to the particles in the bulk and calculate the radial distribution and the bond-order metric. These two parameters are widely used to quantify the structure of the spherical particle systems. A granular packing undergoing periodic shear deformations is observed to slowly evolve towards crystallization and the packing fraction is correspondingly observed to increase smoothly from loose packing fraction, 0.59, well above the random close packing fraction, 0.637. Tracking the particles over several shear cycles allows us to obtain the probability distributions of particle displacements and the mean-square displacements and to compute the components of the diffusion tensor. We find that in a shear flow, the initial self-diffusion of the particles is anisotropic with diffusion greater in the flow direction compared with the velocity gradient direction which in turn is greater than in the vorticity direction. We further find that the granular matter under cyclic shear shows reversible as well as irreversible or plastic response for small enough strain amplitude. The appearance and the propagation of the crystalline order were studied using the orientational order metric. By following the evolution of the nucleating crystallites, we identified critical nuclei, determined their size and symmetry, and measured the average surface free energy. The structure of the nuclei was found to be random hexagonal close-packed, their average shape was non-spherical and they were oriented preferentially along the shear axis. When the packing volume fraction approaches a value close to the random close packing, crystallites with face centered cubic (fcc) order are observed with increasing probability, and ordered domains grow rapidly. A polycrystalline phase with domains of fcc and hcp order is obtained after hundreds of thousands of shear cycles. Depositing spheres on a substrate under the influence of gravity gives rise to a wide range of volume fractions and packing structures by simply controlling the nature of the substrate, the deposition rate and the energy of the particles. We analyzed the structures formed and investigate the development of the disordered phases as a function of the deposition rate. Furthermore, by comparing these structures with packings obtained by cyclic shear we showed that the structure of a granular packing depends strongly on the protocol used.

Systematic comparison of a new generation of columns packed with sub-2 μm superficially porous particles.

PubMed

Bobály, Balázs; Guillarme, Davy; Fekete, Szabolcs

2014-02-01

The aim of this study was to evaluate the possibilities/limitations of recent RP-LC columns packed with 1.6 μm superficially porous particles (Waters Cortecs) and to compare its potential to other existing sub-2 μm core-shell packings. The kinetic performance of Kinetex 1.3 μm, Kinetex 1.7 μm and Cortecs 1.6 μm stationary phases was assessed. It was found that the Kinetex 1.3 μm phase outperforms its counterparts for ultra-fast separations. Conversely, the Cortecs 1.6 μm packing seemed to be the best stationary phase for assays with longer analysis time in isocratic and gradient modes, considering small molecules and peptides as test probes. This exceptional behaviour was attributed to its favourable permeability and somewhat higher mechanical stability (ΔPmax of 1200 bar). The loading capacity of these three columns was also investigated with basic and neutral drugs analysed under acidic conditions. It appears that the loading capacities of Cortecs 1.6 μm and Kinetex 1.7 μm were very close, while it was reduced by 2-7-fold on the Kinetex 1.3 μm packing. However, this observation is dependent on the nature of the compound and certainly also on mobile phase conditions. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Vortex circulation and polarity patterns in closely packed cap arrays

DOE PAGES

Streubel, Robert; Kronast, Florian; Reiche, Christopher F.; ...

2016-01-25

For this work, we studied curvature-driven modifications to the magnetostatic coupling of vortex circulation and polarity in soft-magnetic closely packed cap arrays. A phase diagram for the magnetic remanent/transition states at room temperature as a function of diameter and thickness was assembled. For specimens with vortex remanent state (40 nm-thick Permalloy on 330 nm spherical nanoparticles), both vortex circulation and polarity were visualized. Intercap coupling upon vortex nucleation leads to the formation of vortex circulation patterns in closely packed arrays. The remanent circulation pattern can be tailored choosing the direction of the applied magnetic field with respect to the symmetrymore » axis of the hexagonal array. An even and random distribution of vortex polarity indicates the absence of any circulation-polarity coupling.« less

Adolescents' response to pictorial warnings on the reverse panel of cigarette packs: a repeat cross-sectional study.

PubMed

Moodie, Crawford; Mackintosh, Anne M; Hastings, Gerard

2015-03-01

The UK (UK) became the third country in the European Union to require pictorial warnings on the back of cigarette packs, in October 2008. A repeat cross-sectional survey was conducted with 11-16-year-olds in the UK between August and September 2008 (N=1401) and August and September 2011 (N=1373). At both waves the same text warnings appeared on the front and back of packs, with the only difference being the inclusion of images on the back of packs to support the text warnings in 2011. Warning related measures assessed were salience (noticing, looking closely at warnings), depth of processing (thinking about warnings, discussing them with others), comprehension and credibility (warning comprehensibility, believability and truthfulness), unaided recall, persuasiveness (warnings as a deterrent to smoking), avoidance techniques (eg, hiding packs) and a behavioural indicator (forgoing cigarettes due to warnings). For never smokers, warning persuasiveness and thinking about what warnings are telling them when the pack is in sight significantly increased from 2008 to 2011, but warning comprehensibility significantly decreased. For experimental smokers, there was a significant increase from 2008 to 2011 for warning persuasiveness, believing warnings and considering them truthful. For regular smokers, there were no significant changes from 2008 to 2011, except for an increase in hiding packs to avoid warnings and a decrease in warning salience. Including pictorial images on the back of cigarette packaging improved warning persuasiveness for never and experimental smokers, but had a negligible impact on regular smokers. The findings have implications for warning design. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Simulation of abuse tolerance of lithium-ion battery packs

NASA Astrophysics Data System (ADS)

Spotnitz, Robert M.; Weaver, James; Yeduvaka, Gowri; Doughty, D. H.; Roth, E. P.

A simple approach for using accelerating rate calorimetry data to simulate the thermal abuse resistance of battery packs is described. The thermal abuse tolerance of battery packs is estimated based on the exothermic behavior of a single cell and an energy balance than accounts for radiative, conductive, and convective heat transfer modes of the pack. For the specific example of a notebook computer pack containing eight 18650-size cells, the effects of cell position, heat of reaction, and heat-transfer coefficient are explored. Thermal runaway of the pack is more likely to be induced by thermal runaway of a single cell when that cell is in good contact with other cells and is close to the pack wall.

Linear and nonlinear response in sheared soft spheres

NASA Astrophysics Data System (ADS)

Tighe, Brian

2013-11-01

Packings of soft spheres provide an idealized model of foams, emulsions, and grains, while also serving as the canonical example of a system undergoing a jamming transition. Packings' mechanical response has now been studied exhaustively in the context of ``strict linear response,'' i.e. by linearizing about a stable static packing and solving the resulting equations of motion. Both because the system is close to a critical point and because the soft sphere pair potential is non-analytic at the point of contact, it is reasonable to ask under what circumstances strict linear response provides a good approximation to the actual response. We simulate sheared soft sphere packings close to jamming and identify two distinct strain scales: (i) the scale on which strict linear response fails, coinciding with a topological change in the packing's contact network; and (ii) the scale on which linear superposition of the averaged stress-strain curve breaks down. This latter scale provides a ``weak linear response'' criterion and is likely to be more experimentally relevant.

Evaluation of the filler packing structures in dental resin composites: From theory to practice.

PubMed

Wang, Ruili; Habib, Eric; Zhu, X X

2018-07-01

The aim of this study is to evaluate the packing properties of uniform silica particles and their mixture with secondary particles yielding maximally loaded dental composites. We intend to verify the difference between the idealized models (the close-packed structures and the random-packed structures) and the actual experimental results, in order to provide guidance for the preparation of dental composites. The influence of secondary particle size and the resin composition on the physical-mechanical properties and the rheological properties of the experimental dental composites was also investigated. Silica particles (S-920, S-360, and S-195) with average diameters of 920, 360, and 195nm were synthesized via the Stöber process. Their morphology and size distribution were determined by field-emission scanning electron microscopy and laser particle sizer. A series of silica fillers, S-920, S-920+195, S-920+360, and S-920+360+195, were then formulated with two Bis-GMA/TEGDMA resins (weight ratios of 70:30 and 50:50). For these experimental dental composites, their maximum filler loadings were assessed and compared to the theory. The mechanical properties, degree of conversion, depth of cure, and polymerization shrinkage of these composites were then evaluated. Their rheological behaviors were measured with a rheometer. Unimodal S-920 had the maximally filler loading of 70.80wt% with the 5B5T resin, close to the theoretical estimation of the random loose packing (71.92wt%). The maximum loading of the S-920+360+195 filled composite was 72.92wt% for the same resin, compared to the theoretical estimation of 89.29wt% obtained for the close-packed structures. These findings indicate that random loose packing matches more closely to the real packing state for the filler formulations used. When maximally loaded, the composite with S-920+360+195 produced the best mechanical properties and the lowest polymerization shrinkage. The degree of conversion and depth of cure were higher with secondary particles added, and the viscosity of all unpolymerized pastes exhibited shear thinning behavior. Theoretical estimations of filler packing structures provide a useful guidance in the design of multimodal filler formulations and the preparation of dental composites with higher filler loading, improved physical-mechanical properties. Copyright © 2018 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Stabilizing the hexagonal close packed structure of hard spheres with polymers: Phase diagram, structure, and dynamics

NASA Astrophysics Data System (ADS)

Edison, John R.; Dasgupta, Tonnishtha; Dijkstra, Marjolein

2016-08-01

We study the phase behaviour of a binary mixture of colloidal hard spheres and freely jointed chains of beads using Monte Carlo simulations. Recently Panagiotopoulos and co-workers predicted [Nat. Commun. 5, 4472 (2014)] that the hexagonal close packed (HCP) structure of hard spheres can be stabilized in such a mixture due to the interplay between polymer and the void structure in the crystal phase. Their predictions were based on estimates of the free-energy penalty for adding a single hard polymer chain in the HCP and the competing face centered cubic (FCC) phase. Here we calculate the phase diagram using free-energy calculations of the full binary mixture and find a broad fluid-solid coexistence region and a metastable gas-liquid coexistence region. For the colloid-monomer size ratio considered in this work, we find that the HCP phase is only stable in a small window at relatively high polymer reservoir packing fractions, where the coexisting HCP phase is nearly close packed. Additionally we investigate the structure and dynamic behaviour of these mixtures.

Application of close-packed structures in dental resin composites.

PubMed

Wang, Ruili; Habib, Eric; Zhu, X X

2017-03-01

The inorganic filler particles in dental resin composites serve to improve their mechanical properties and reduce polymerization shrinkage during their use. Efforts have been made in academia and industry to increase the filler particle content, but, few studies examine the theoretical basis for the maximum particle loading. This work evaluates the packing of spherical particles in a close-packed state for highly loaded composites. Calculations show that for low dispersity particles, the maximum amount of particles is 74.05vol%, regardless of the particle size. This can be further improved by using a mix of large and small particles or by the use of non-spherical particles. For representative spherical particles with a diameter of 1000nm, two types of secondary particles with respective sizes of 414nm (d I ) and 225nm (d II ) are selected. The results show that after embedding secondary particles I & II into primary spherical particles, the packing factor is increased to 81.19% for the close-packed structures, which shows an improvement of 9.64%, compared to the 74.05% obtained only with primary spherical particles. This packing factor is also higher than either structure with the embedded secondary particles I or II. Examples of these mixtures with different spherical particle sizes are shown as a theoretical estimation, serving as a guideline for the design and formulation of new dental resin composites with better properties and improved performance. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Consumer perceptions of cigarette pack design in France: a comparison of regular, limited edition and plain packaging.

PubMed

Gallopel-Morvan, Karine; Moodie, Crawford; Hammond, David; Eker, Figen; Beguinot, Emmanuelle; Martinet, Yves

2012-09-01

In the face of comprehensive bans on the marketing of tobacco products, packaging has become an increasingly important promotional tool for the tobacco industry. A ban on the use of branding on tobacco packaging, known as 'plain' packaging, has emerged as a promising regulatory strategy. The current study sought to examine perceptions of cigarette packaging among adults in France. Adult smokers and non-smokers (N=836) were surveyed using computer-assisted personal interviewing to assess perceptions of pack design by comparing 'regular' branded packs and 'limited edition' packs (with novel designs or innovations) with 'plain' versions of these packs with all branding, including colour, removed. Plain packs (PP) were less likely than regular packs, and particularly limited edition packs, to be considered attractive, attention grabbing and likely to motivate youth purchase. PPs were also rated as the most effective in convincing non-smokers not to start and smokers to reduce consumption and quit. Logistic regression showed that smokers motivated to quit, in comparison to smokers not motivated to quit, were significantly more likely to consider the PPs as the packs most likely to motivate cessation. Novel cigarette packaging, in the form of limited edition packs, had the highest ratings of consumer appeal, ahead of regular branded packs and also PPs. Interestingly, PPs were perceived to be the packs most likely to promote cessation among those adults with quitting intentions. Plain packaging, therefore, may be a means of helping existing adult smokers motivated to quit to do so.

Notes on the ExactPack Implementation of the DSD Rate Stick Solver

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

Kaul, Ann

It has been shown above that the discretization scheme implemented in the ExactPack solver for the DSD Rate Stick equation is consistent with the Rate Stick PDE. In addition, a stability analysis has provided a CFL condition for a stable time step. Together, consistency and stability imply convergence of the scheme, which is expected to be close to first-order in time and second-order in space. It is understood that the nonlinearity of the underlying PDE will affect this rate somewhat. In the solver I implemented in ExactPack, I used the one-sided boundary condition described above at the outer boundary. Inmore » addition, I used 80% of the time step calculated in the stability analysis above. By making these two changes, I was able to implement a solver that calculates the solution without any arbitrary limits placed on the values of the curvature at the boundary. Thus, the calculation is driven directly by the conditions at the boundary as formulated in the DSD theory. The chosen scheme is completely coherent and defensible from a mathematical standpoint.« less

A first-passage scheme for determination of overall rate constants for non-diffusion-limited suspensions

NASA Astrophysics Data System (ADS)

Lu, Shih-Yuan; Yen, Yi-Ming

2002-02-01

A first-passage scheme is devised to determine the overall rate constant of suspensions under the non-diffusion-limited condition. The original first-passage scheme developed for diffusion-limited processes is modified to account for the finite incorporation rate at the inclusion surface by using a concept of the nonzero survival probability of the diffusing entity at entity-inclusion encounters. This nonzero survival probability is obtained from solving a relevant boundary value problem. The new first-passage scheme is validated by an excellent agreement between overall rate constant results from the present development and from an accurate boundary collocation calculation for the three common spherical arrays [J. Chem. Phys. 109, 4985 (1998)], namely simple cubic, body-centered cubic, and face-centered cubic arrays, for a wide range of P and f. Here, P is a dimensionless quantity characterizing the relative rate of diffusion versus surface incorporation, and f is the volume fraction of the inclusion. The scheme is further applied to random spherical suspensions and to investigate the effect of inclusion coagulation on overall rate constants. It is found that randomness in inclusion arrangement tends to lower the overall rate constant for f up to the near close-packing value of the regular arrays because of the inclusion screening effect. This screening effect turns stronger for regular arrays when f is near and above the close-packing value of the regular arrays, and consequently the overall rate constant of the random array exceeds that of the regular array. Inclusion coagulation too induces the inclusion screening effect, and leads to lower overall rate constants.

Dispersal of sticky particles

NASA Astrophysics Data System (ADS)

Reddy, Ramana; Kumar, Sanjeev

2007-12-01

In this paper, we show through simulations that when sticky particles are broken continually, particles are dispersed into fine dust only if they are present in a narrow range of volume fractions. The upper limit of this range is 0.20 in the 2D and 0.10 in the 3D space. An increase in the dimensionality of space reduces the upper limit nearly by a factor of two. This scaling holds for dispersal of particles in hyperdimensional space of dimensions up to ten, the maximum dimension studied in this work. The maximum values of volume fractions obtained are significantly lower than those required for close packing and random packing of discs in 2D and spheres in 3D space. These values are also smaller than those required for critical phenomena of cluster percolation. The results obtained are attributed to merger cascades of sticky particles, triggered by breakup events. A simple theory that incorporates this cascade is developed to quantitatively explain the observed scaling of the upper limit with the dimensionality of space. The theory also captures the dynamics of the dispersal process in the corresponding range of particle volume fractions. The theory suggests that cascades of order one and two predominantly decide the upper limit for complete dispersal of particles.

Simulation study of a high power density rectenna array for biomedical implantable devices

NASA Astrophysics Data System (ADS)

Day, John; Yoon, Hargsoon; Kim, Jaehwan; Choi, Sang H.; Song, Kyo D.

2016-04-01

The integration of wireless power transmission devices using microwaves into the biomedical field is close to a practical reality. Implanted biomedical devices need a long lasting power source or continuous power supply. Recent development of high efficiency rectenna technology enables continuous power supply to these implanted devices. Due to the size limit of most of medical devices, it is imperative to minimize the rectenna as well. The research reported in this paper reviews the effects of close packing the rectenna elements which show the potential of directly empowering the implanted devices, especially within a confined area. The rectenna array is tested in the X band frequency range.

Marginal rigidity and history dependence in packings of attractive athermal emulsions

NASA Astrophysics Data System (ADS)

Bargteil, Dylan; Pontani, Lea-Laetitia; Brujic, Jasna

2014-03-01

The geometry and stress through particulate packings depends on the method of preparation and the interaction potential between the particles. Previously, we discovered that creaming frictionless, athermal emulsions with a short-range depletion attraction leads to an initial increase in the packing density above random close packing, followed by a monotonic decrease in density (Jorjadze et al, PNAS, 2011). This decrease is because the attractive force stabilizes loose voids, thus reducing the average coordination number, , of the packing. In order to understand the mechanism of packing creation, we investigate whether the final density is influenced by the polydispersity or the initial volume fraction of droplets, as it is in frictional packings. Finally, we compress the attractive packings by centrifugation to probe the scaling laws of pressure versus density and and compare them with those found in repulsive packings (Jorjadze et al, PRL, 2013).

Measure and dimension functions: measurability and densities

NASA Astrophysics Data System (ADS)

Mattila, Pertti; Mauldin, R. Daniel

1997-01-01

During the past several years, new types of geometric measure and dimension have been introduced; the packing measure and dimension, see [Su], [Tr] and [TT1]. These notions are playing an increasingly prevalent role in various aspects of dynamics and measure theory. Packing measure is a sort of dual of Hausdorff measure in that it is defined in terms of packings rather than coverings. However, in contrast to Hausdorff measure, the usual definition of packing measure requires two limiting procedures, first the construction of a premeasure and then a second standard limiting process to obtain the measure. This makes packing measure somewhat delicate to deal with. The question arises as to whether there is some simpler method for defining packing measure and dimension. In this paper, we find a basic limitation on this possibility. We do this by determining the descriptive set-theoretic complexity of the packing functions. Whereas the Hausdorff dimension function on the space of compact sets is Borel measurable, the packing dimension function is not. On the other hand, we show that the packing dimension functions are measurable with respect to the [sigma]-algebra generated by the analytic sets. Thus, the usual sorts of measurability properties used in connection with Hausdorff measure, for example measures of sections and projections, remain true for packing measure.

Comparative study of crystallization process in metallic melts using ab initio molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Debela, Tekalign T.; Wang, X. D.; Cao, Q. P.; Zhang, D. X.; Jiang, J. Z.

2017-05-01

The crystallization process of liquid metals is studied using ab initio molecular dynamics simulations. The evolution of short-range order during quenching in Pb and Zn liquids is compared with body-centered cubic (bcc) Nb and V, and hexagonal closed-packed (hcp) Mg. We found that the fraction and type of the short-range order depends on the system under consideration, in which the icosahedral symmetry seems to dominate in the body-centered cubic metals. Although the local atomic structures in stable liquids are similar, liquid hcp-like Zn, bcc-like Nb and V can be deeply supercooled far below its melting point before crystallization while the supercooled temperature range in liquid Pb is limited. Further investigations into the nucleation process reveal the process of polymorph selection. In the body-centered cubic systems, the polymorph selection occurs in the supercooled state before the nucleation is initiated, while in the closed-packed systems it starts at the time of onset of crystallization. Atoms with bcc-like lattices in all studied supercooled liquids are always detected before the polymorph selection. It is also found that the bond orientational ordering is strongly correlated with the crystallization process in supercooled Zn and Pb liquids.

The first effects of fluid inertia on flows in ordered and random arrays of spheres

NASA Astrophysics Data System (ADS)

Hill, Reghan J.; Koch, Donald L.; Ladd, Anthony J. C.

2001-12-01

Theory and lattice-Boltzmann simulations are used to examine the effects of fluid inertia, at small Reynolds numbers, on flows in simple cubic, face-centred cubic and random arrays of spheres. The drag force on the spheres, and hence the permeability of the arrays, is determined at small but finite Reynolds numbers, at solid volume fractions up to the close-packed limits of the arrays. For small solid volume fraction, the simulations are compared to theory, showing that the first inertial contribution to the drag force, when scaled with the Stokes drag force on a single sphere in an unbounded fluid, is proportional to the square of the Reynolds number. The simulations show that this scaling persists at solid volume fractions up to the close-packed limits of the arrays, and that the first inertial contribution to the drag force relative to the Stokes-flow drag force decreases with increasing solid volume fraction. The temporal evolution of the spatially averaged velocity and the drag force is examined when the fluid is accelerated from rest by a constant average pressure gradient toward a steady Stokes flow. Theory for the short- and long-time behaviour is in good agreement with simulations, showing that the unsteady force is dominated by quasi-steady drag and added-mass forces. The short- and long-time added-mass coefficients are obtained from potential-flow and quasi-steady viscous-flow approximations, respectively.

Effect of packing method on the randomness of disc packings

NASA Astrophysics Data System (ADS)

Zhang, Z. P.; Yu, A. B.; Oakeshott, R. B. S.

1996-06-01

The randomness of disc packings, generated by random sequential adsorption (RSA), random packing under gravity (RPG) and Mason packing (MP) which gives a packing density close to that of the RSA packing, has been analysed, based on the Delaunay tessellation, and is evaluated at two levels, i.e. the randomness at individual subunit level which relates to the construction of a triangle from a given edge length distribution and the randomness at network level which relates to the connection between triangles from a given triangle frequency distribution. The Delaunay tessellation itself is also analysed and its almost perfect randomness at the two levels is demonstrated, which verifies the proposed approach and provides a random reference system for the present analysis. It is found that (i) the construction of a triangle subunit is not random for the RSA, MP and RPG packings, with the degree of randomness decreasing from the RSA to MP and then to RPG packing; (ii) the connection of triangular subunits in the network is almost perfectly random for the RSA packing, acceptable for the MP packing and not good for the RPG packing. Packing method is an important factor governing the randomness of disc packings.

On the kinetics of the pack - Aluminization process

NASA Technical Reports Server (NTRS)

Sivakumar, R.; Seigle, L. L.

1976-01-01

An investigation has been made of the aluminization of unalloyed Ni in fluoride-activated packs of varying Al activity. In packs of low Al activity, in which the ratio of Al to Ni was less than 50 at. pct, the specimen surface quickly came to equilibrium with the pack and remained close to equilibrium for the duration of normal coating runs. In these packs the kinetics of aluminization was controlled by diffusion in the solid. In packs of higher Al activity the surface of the specimen did not come to equilibrium with the pack and the kinetics of the process was governed by a combination of solid and gas diffusion rates. Under most conditions however, the surface composition was time-invariant and a steady-state appeared to exist at the pack-coating interface. By combining Levine and Caves' model for gaseous diffusion in pure-Al packs with calculations of solid diffusion rates some success has been achieved in explaining the results.

Robust excitons inhabit soft supramolecular nanotubes

PubMed Central

Eisele, Dörthe M.; Arias, Dylan H.; Fu, Xiaofeng; Bloemsma, Erik A.; Steiner, Colby P.; Jensen, Russell A.; Rebentrost, Patrick; Eisele, Holger; Tokmakoff, Andrei; Lloyd, Seth; Nelson, Keith A.; Nicastro, Daniela; Knoester, Jasper; Bawendi, Moungi G.

2014-01-01

Nature's highly efficient light-harvesting antennae, such as those found in green sulfur bacteria, consist of supramolecular building blocks that self-assemble into a hierarchy of close-packed structures. In an effort to mimic the fundamental processes that govern nature’s efficient systems, it is important to elucidate the role of each level of hierarchy: from molecule, to supramolecular building block, to close-packed building blocks. Here, we study the impact of hierarchical structure. We present a model system that mirrors nature’s complexity: cylinders self-assembled from cyanine-dye molecules. Our work reveals that even though close-packing may alter the cylinders’ soft mesoscopic structure, robust delocalized excitons are retained: Internal order and strong excitation-transfer interactions—prerequisites for efficient energy transport—are both maintained. Our results suggest that the cylindrical geometry strongly favors robust excitons; it presents a rational design that is potentially key to nature’s high efficiency, allowing construction of efficient light-harvesting devices even from soft, supramolecular materials. PMID:25092336

The phase diagram of high-pressure superionic ice

DOE PAGES

Sun, Jiming; Clark, Bryan K.; Torquato, Salvatore; ...

2015-08-28

Superionic ice is a special group of ice phases at high temperature and pressure, which may exist in ice-rich planets and exoplanets. In superionic ice liquid hydrogen coexists with a crystalline oxygen sublattice. At high pressures, the properties of superionic ice are largely unknown. Here we report evidence that from 280 GPa to 1.3 TPa, there are several competing phases within the close-packed oxygen sublattice. At even higher pressure, the close-packed structure of the oxygen sublattice becomes unstable to a new unusual superionic phase in which the oxygen sublattice takes the P2 1/c symmetry. We also discover that higher pressuremore » phases have lower transition temperatures. The diffusive hydrogen in the P2 1/c superionic phase shows strong anisotropic behaviour and forms a quasi-two-dimensional liquid. The ionic conductivity changes abruptly in the solid to close-packed superionic phase transition, but continuously in the solid to P2 1/c superionic phase transition.« less

Simulations of wave propagation and disorder in 3D non-close-packed colloidal photonic crystals with low refractive index contrast.

PubMed

Glushko, O; Meisels, R; Kuchar, F

2010-03-29

The plane-wave expansion method (PWEM), the multiple-scattering method (MSM) and the 3D finite-difference time-domain method (FDTD) are applied for simulations of propagation of electromagnetic waves through 3D colloidal photonic crystals. The system investigated is not a "usual" artificial opal with close-packed fcc lattice but a dilute bcc structure which occurs due to long-range repulsive interaction between electrically charged colloidal particles during the growth process. The basic optical properties of non-close-packed colloidal PhCs are explored by examining the band structure and reflection spectra for a bcc lattice of silica spheres in an aqueous medium. Finite size effects and correspondence between the Bragg model, band structure and reflection spectra are discussed. The effects of size, positional and missing-spheres disorder are investigated. In addition, by analyzing the results of experimental work we show that the fabricated structures have reduced plane-to-plane distance probably due to the effect of gravity during growth.

Fabrication of Microstripline Wiring for Large Format Transition Edge Sensor Arrays

NASA Technical Reports Server (NTRS)

Chervenak, James A.; Adams, J. M.; Bailey, C. N.; Bandler, S.; Brekosky, R. P.; Eckart, M. E.; Erwin, A. E.; Finkbeiner, F. M.; Kelley, R. L.; Kilbourne, C. A.;

Packed Bed Bioreactor for the Isolation and Expansion of Placental-Derived Mesenchymal Stromal Cells

PubMed Central

Osiecki, Michael J.; Michl, Thomas D.; Kul Babur, Betul; Kabiri, Mahboubeh; Atkinson, Kerry; Lott, William B.; Griesser, Hans J.; Doran, Michael R.

2015-01-01

Large numbers of Mesenchymal stem/stromal cells (MSCs) are required for clinical relevant doses to treat a number of diseases. To economically manufacture these MSCs, an automated bioreactor system will be required. Herein we describe the development of a scalable closed-system, packed bed bioreactor suitable for large-scale MSCs expansion. The packed bed was formed from fused polystyrene pellets that were air plasma treated to endow them with a surface chemistry similar to traditional tissue culture plastic. The packed bed was encased within a gas permeable shell to decouple the medium nutrient supply and gas exchange. This enabled a significant reduction in medium flow rates, thus reducing shear and even facilitating single pass medium exchange. The system was optimised in a small-scale bioreactor format (160 cm2) with murine-derived green fluorescent protein-expressing MSCs, and then scaled-up to a 2800 cm2 format. We demonstrated that placental derived MSCs could be isolated directly within the bioreactor and subsequently expanded. Our results demonstrate that the closed system large-scale packed bed bioreactor is an effective and scalable tool for large-scale isolation and expansion of MSCs. PMID:26660475

Packed Bed Bioreactor for the Isolation and Expansion of Placental-Derived Mesenchymal Stromal Cells.

PubMed

Osiecki, Michael J; Michl, Thomas D; Kul Babur, Betul; Kabiri, Mahboubeh; Atkinson, Kerry; Lott, William B; Griesser, Hans J; Doran, Michael R

2015-01-01

Large numbers of Mesenchymal stem/stromal cells (MSCs) are required for clinical relevant doses to treat a number of diseases. To economically manufacture these MSCs, an automated bioreactor system will be required. Herein we describe the development of a scalable closed-system, packed bed bioreactor suitable for large-scale MSCs expansion. The packed bed was formed from fused polystyrene pellets that were air plasma treated to endow them with a surface chemistry similar to traditional tissue culture plastic. The packed bed was encased within a gas permeable shell to decouple the medium nutrient supply and gas exchange. This enabled a significant reduction in medium flow rates, thus reducing shear and even facilitating single pass medium exchange. The system was optimised in a small-scale bioreactor format (160 cm2) with murine-derived green fluorescent protein-expressing MSCs, and then scaled-up to a 2800 cm2 format. We demonstrated that placental derived MSCs could be isolated directly within the bioreactor and subsequently expanded. Our results demonstrate that the closed system large-scale packed bed bioreactor is an effective and scalable tool for large-scale isolation and expansion of MSCs.

Potential environmental effects of pack stock on meadow ecosystems of the Sierra Nevada, USA

USGS Publications Warehouse

Ostoja, Steven M.; Brooks, Matthew L.; Moore, Peggy E.; Berlow, Eric L.; Robert Blank,; Roche, Jim; Chase, Jennifer T.; Sylvia Haultain,

2014-01-01

Pack and saddle stock, including, but not limited to domesticated horses, mules, and burros, are used to support commercial, private and administrative activities in the Sierra Nevada. The use of pack stock has become a contentious and litigious issue for land management agencies in the region inter alia due to concerns over effects on the environment. The potential environmental effects of pack stock on Sierra Nevada meadow ecosystems are reviewed and it is concluded that the use of pack stock has the potential to influence the following: (1) water nutrient dynamics, sedimentation, temperature, and microbial pathogen content; (2) soil chemistry, nutrient cycling, soil compaction and hydrology; (3) plant individuals, populations and community dynamics, non-native invasive species, and encroachment of woody species; and (4) wildlife individuals, populations and communities. It is considered from currently available information that management objectives of pack stock should include the following: minimise bare ground, maximise plant cover, maintain species composition of native plants, minimise trampling, especially on wet soils and stream banks, and minimise direct urination and defecation by pack stock into water. However, incomplete documentation of patterns of pack stock use and limited past research limits current understanding of the effects of pack stock, especially their effects on water, soils and wildlife. To improve management of pack stock in this region, research is needed on linking measurable monitoring variables (e.g. plant cover) with environmental relevancy (e.g. soil erosion processes, wildlife habitat use), and identifying specific environmental thresholds of degradation along gradients of pack stock use in Sierra Nevada meadows.

Experimental and Numerical Investigation of Two Dimensional CO2 Adsorption/Desorption in Packed Sorption Beds under Non-Ideal Flows

NASA Technical Reports Server (NTRS)

Mohamadinejad, H.; Knox, J. C.; Smith, J. E.; Croomes, Scott (Technical Monitor)

2001-01-01

The experimental results of CO2 adsorption and desorption in a packed column indicated that the concentration wave front at the center of the packed column differs from those which are close to the wall of column filled with adsorbent material even though the ratio of column diameter to the particle size is greater than 20. The comparison of the experimental results with one dimensional model of packed column shows that in order to simulate the average breakthrough in a packed column a two dimensional (radial and axial) model of packed column is needed. In this paper the mathematical model of a non-slip flow through a packed column with 2 inches in diameter and 18 inches in length filled with 5A zeolite pellets is presented. The comparison of experimental results of CO2 absorption and desorption for the mixed and central breakthrough of the packed column with numerical results is also presented.

Fatal canine distemper infection in a pack of African wild dogs in the Serengeti ecosystem, Tanzania.

PubMed

Goller, Katja V; Fyumagwa, Robert D; Nikolin, Veljko; East, Marion L; Kilewo, Morris; Speck, Stephanie; Müller, Thomas; Matzke, Martina; Wibbelt, Gudrun

2010-12-15

In 2007, disease related mortality occurred in one African wild dog (Lycaon pictus) pack close to the north-eastern boundary of the Serengeti National Park, Tanzania. Histopathological examination of tissues from six animals revealed that the main pathologic changes comprised interstitial pneumonia and suppurative to necrotizing bronchopneumonia. Respiratory epithelial cells contained numerous eosinophilic intracytoplasmic inclusion bodies and multiple syncytial cells were found throughout the parenchymal tissue, both reacting clearly positive with antibodies against canine distemper virus (CDV) antigen. Phylogenetic analysis based on a 388 nucleotide (nt) fragment of the CDV phosphoprotein (P) gene revealed that the pack was infected with a CDV variant most closely related to Tanzanian variants, including those obtained in 1994 during a CDV epidemic in the Serengeti National Park and from captive African wild dogs in the Mkomazi Game Reserve in 2000. Phylogenetic analysis of a 335-nt fragment of the fusion (F) gene confirmed that the pack in 2007 was infected with a variant most closely related to one variant from 1994 during the epidemic in the Serengeti National Park from which a comparable fragment is available. Screening of tissue samples for concurrent infections revealed evidence of canine parvovirus, Streptococcus equi subsp. ruminatorum and Hepatozoon sp. No evidence of infection with Babesia sp. or rabies virus was found. Possible implications of concurrent infections are discussed. This is the first molecular characterisation of CDV in free-ranging African wild dogs and only the third confirmed case of fatal CDV infection in a free-ranging pack. Copyright © 2010 Elsevier B.V. All rights reserved.

Adhesive loose packings of small dry particles.

PubMed

Liu, Wenwei; Li, Shuiqing; Baule, Adrian; Makse, Hernán A

2015-08-28

We explore adhesive loose packings of small dry spherical particles of micrometer size using 3D discrete-element simulations with adhesive contact mechanics and statistical ensemble theory. A dimensionless adhesion parameter (Ad) successfully combines the effects of particle velocities, sizes and the work of adhesion, identifying a universal regime of adhesive packings for Ad > 1. The structural properties of the packings in this regime are well described by an ensemble approach based on a coarse-grained volume function that includes the correlation between bulk and contact spheres. Our theoretical and numerical results predict: (i) an equation of state for adhesive loose packings that appear as a continuation from the frictionless random close packing (RCP) point in the jamming phase diagram and (ii) the existence of an asymptotic adhesive loose packing point at a coordination number Z = 2 and a packing fraction ϕ = 1/2(3). Our results highlight that adhesion leads to a universal packing regime at packing fractions much smaller than the random loose packing (RLP), which can be described within a statistical mechanical framework. We present a general phase diagram of jammed matter comprising frictionless, frictional, adhesive as well as non-spherical particles, providing a classification of packings in terms of their continuation from the spherical frictionless RCP.

Packing Fraction of a Two-dimensional Eden Model with Random-Sized Particles

NASA Astrophysics Data System (ADS)

Kobayashi, Naoki; Yamazaki, Hiroshi

2018-01-01

We have performed a numerical simulation of a two-dimensional Eden model with random-size particles. In the present model, the particle radii are generated from a Gaussian distribution with mean μ and standard deviation σ. First, we have examined the bulk packing fraction for the Eden cluster and investigated the effects of the standard deviation and the total number of particles NT. We show that the bulk packing fraction depends on the number of particles and the standard deviation. In particular, for the dependence on the standard deviation, we have determined the asymptotic value of the bulk packing fraction in the limit of the dimensionless standard deviation. This value is larger than the packing fraction obtained in a previous study of the Eden model with uniform-size particles. Secondly, we have investigated the packing fraction of the entire Eden cluster including the effect of the interface fluctuation. We find that the entire packing fraction depends on the number of particles while it is independent of the standard deviation, in contrast to the bulk packing fraction. In a similar way to the bulk packing fraction, we have obtained the asymptotic value of the entire packing fraction in the limit NT → ∞. The obtained value of the entire packing fraction is smaller than that of the bulk value. This fact suggests that the interface fluctuation of the Eden cluster influences the packing fraction.

Controllable Fabrication of Non-Close-Packed Colloidal Nanoparticle Arrays by Ion Beam Etching

NASA Astrophysics Data System (ADS)

Yang, Jie; Zhang, Mingling; Lan, Xu; Weng, Xiaokang; Shu, Qijiang; Wang, Rongfei; Qiu, Feng; Wang, Chong; Yang, Yu

2018-06-01

Polystyrene (PS) nanoparticle films with non-close-packed arrays were prepared by using ion beam etching technology. The effects of etching time, beam current, and voltage on the size reduction of PS particles were well investigated. A slow etching rate, about 9.2 nm/min, is obtained for the nanospheres with the diameter of 100 nm. The rate does not maintain constant with increasing the etching time. This may result from the thermal energy accumulated gradually in a long-time bombardment of ion beam. The etching rate increases nonlinearly with the increase of beam current, while it increases firstly then reach its saturation with the increase of beam voltage. The diameter of PS nanoparticles can be controlled in the range from 34 to 88 nm. Based on the non-close-packed arrays of PS nanoparticles, the ordered silicon (Si) nanopillars with their average diameter of 54 nm are fabricated by employing metal-assisted chemical etching technique. Our results pave an effective way to fabricate the ordered nanostructures with the size less than 100 nm.

Internet survey of home storage of paracetamol by individuals in the UK.

PubMed

Shah, A D; Wood, D M; Dargan, P I

2013-03-01

Paracetamol (acetaminophen) is a common cause of liver failure due to overdose. Legislation introduced in the UK in 1998 to limit pack sizes of paracetamol has had limited impact on the overall number and severity of paracetamol overdoses. This may be because people have large amounts of paracetamol stored at home, but no previous studies have explored this question. Individuals who regularly take part in market research surveys were invited to take part in an Internet survey. They were asked to supply demographic details, the frequency with which they use paracetamol and ibuprofen, and details of the amount and location of these drugs that they possessed. The mean age of respondents was 43.3 years (standard deviation 14.5 years), and 49.9% were female. People with both ibuprofen and paracetamol tended to have more packs and tablets of paracetamol (P < 0.001) and over a third had 32 or more paracetamol tablets. The most common pack size was 16 tablet packs (44.8% of all packs), which accounted for 39.4% of tablets. The most common site of paracetamol storage in the home was the kitchen (63.8% of people, 95% confidence interval 60.7, 66.7). This study suggests that pack size legislation in the UK has had limited effect on the amount of paracetamol that individuals have access to in the home. This may explain, at least in part, the limited impact of the pack size legislation on paracetamol overdoses in the UK.

Pack Density Limitations of Hybrid Parachutes

NASA Technical Reports Server (NTRS)

Zwicker, Matthew L.; Sinclair, Robert J.

2013-01-01

The development and testing of the Orion crew capsule parachute system has provided a unique opportunity to study dense parachute packing techniques and limits, in order to establish a new baseline for future programs. The density of parachute packs has a significant influence on vibration loads, retention system stresses, and parachute mortar performance. Material compositions and pack densities of existing designs for space capsule recovery were compared, using the pack density of the Apollo main parachutes as the current baseline. The composition of parachutes has changed since Apollo, incorporating new materials such as Kevlar , Vectran , Teflon and Spectra . These materials have different specific densities than Nylon, so the densities of hybrid parachute packs cannot be directly compared to Nylon parachutes for determination of feasibility or volume allocation. Six parachute packs were evaluated in terms of weighted average solid density in order to achieve a non-dimensional comparison of packing density. Means of mitigating damage due to packing pressure and mortar firing were examined in light of the Capsule Parachute Assembly System (CPAS) and Apollo experience. Parachute design improvements including incorporation of modern materials and manufacturing processes serves to make CPAS the new knowledge base on which future spacecraft parachute systems will be built.

Imaging phospholipid conformational disorder and packing in giant multilamellar liposome by confocal Raman microspectroscopy

NASA Astrophysics Data System (ADS)

Noothalapati, Hemanth; Iwasaki, Keita; Yoshimoto, Chikako; Yoshikiyo, Keisuke; Nishikawa, Tomoe; Ando, Masahiro; Hamaguchi, Hiro-o.; Yamamoto, Tatsuyuki

2017-12-01

Liposomes are closed phospholipid bilayer systems that have profound applications in fundamental cell biology, pharmaceutics and medicine. Depending on the composition (pure or mixture of phospholipids, presence of cholesterol) and preparation protocol, intra- and inter-chain molecular interactions vary leading to changes in the quality (order and packing) of liposomes. So far it is not possible to image conformational disorders and packing densities within a liposome in a straightforward manner. In this study, we utilized confocal Raman microspectroscopy to visualize structural disorders and packing efficiency within a giant multilamellar liposome model by focusing mainly on three regions in the vibrational spectrum (Csbnd C stretching, Csbnd H deformation and Csbnd H stretching). We estimated properties such as trans/gauche isomers and lateral packing probability. Interestingly, our Raman imaging studies revealed gel phase rich domains and heterogeneous lateral packing within the giant multilamellar liposome.

Multi-pack Disposal Concepts for Spent Fuel (Rev. 0)

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

Hadgu, Teklu; Hardin, Ernest; Matteo, Edward N.

2015-12-01

At the initiation of the Used Fuel Disposition (UFD) R&D campaign, international geologic disposal programs and past work in the U.S. were surveyed to identify viable disposal concepts for crystalline, clay/shale, and salt host media (Hardin et al., 2012). Concepts for disposal of commercial spent nuclear fuel (SNF) and high-level waste (HLW) from reprocessing are relatively advanced in countries such as Finland, France, and Sweden. The UFD work quickly showed that these international concepts are all “enclosed,” whereby waste packages are emplaced in direct or close contact with natural or engineered materials . Alternative “open” modes (emplacement tunnels are keptmore » open after emplacement for extended ventilation) have been limited to the Yucca Mountain License Application Design (CRWMS M&O, 1999). Thermal analysis showed that, if “enclosed” concepts are constrained by peak package/buffer temperature, waste package capacity is limited to 4 PWR assemblies (or 9-BWR) in all media except salt. This information motivated separate studies: 1) extend the peak temperature tolerance of backfill materials, which is ongoing; and 2) develop small canisters (up to 4-PWR size) that can be grouped in larger multi-pack units for convenience of storage, transportation, and possibly disposal (should the disposal concept permit larger packages). A recent result from the second line of investigation is the Task Order 18 report: Generic Design for Small Standardized Transportation, Aging and Disposal Canister Systems (EnergySolution, 2015). This report identifies disposal concepts for the small canisters (4-PWR size) drawing heavily on previous work, and for the multi-pack (16-PWR or 36-BWR).« less

Multi-Pack Disposal Concepts for Spent Fuel (Revision 1)

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

Hardin, Ernest; Matteo, Edward N.; Hadgu, Teklu

2016-01-01

At the initiation of the Used Fuel Disposition (UFD) R&D campaign, international geologic disposal programs and past work in the U.S. were surveyed to identify viable disposal concepts for crystalline, clay/shale, and salt host media. Concepts for disposal of commercial spent nuclear fuel (SNF) and high-level waste (HLW) from reprocessing are relatively advanced in countries such as Finland, France, and Sweden. The UFD work quickly showed that these international concepts are all “enclosed,” whereby waste packages are emplaced in direct or close contact with natural or engineered materials . Alternative “open” modes (emplacement tunnels are kept open after emplacement formore » extended ventilation) have been limited to the Yucca Mountain License Application Design. Thermal analysis showed that if “enclosed” concepts are constrained by peak package/buffer temperature, that waste package capacity is limited to 4 PWR assemblies (or 9 BWR) in all media except salt. This information motivated separate studies: 1) extend the peak temperature tolerance of backfill materials, which is ongoing; and 2) develop small canisters (up to 4-PWR size) that can be grouped in larger multi-pack units for convenience of storage, transportation, and possibly disposal (should the disposal concept permit larger packages). A recent result from the second line of investigation is the Task Order 18 report: Generic Design for Small Standardized Transportation, Aging and Disposal Canister Systems. This report identifies disposal concepts for the small canisters (4-PWR size) drawing heavily on previous work, and for the multi-pack (16-PWR or 36-BWR).« less

Sampling for silver nanoparticles in aqueous media using a rotating disk electrode: evidence for selective sampling of silver nanoparticles in the presence of ionic silver.

PubMed

Steinberg, Spencer; Hodge, Vernon; Schumacher, Brian; Sovocool, Wayne

2017-03-01

Amendment of a carbon paste electrode consisting of graphite and Nujol®, with a variety of organic and inorganic materials, allows direct adsorption of silver nanoparticles (AgNPs) from aqueous solution in either open or close circuit modes. The adsorbed AgNPs are detected by stripping voltammetry. Detection limits of less than 1 ppb Ag are achievable with a rotating disk system. More than one silver peak was apparent in many of the stripping voltammograms. The appearance of multiple peaks could be due to different species of silver formed upon stripping or variation in the state of aggregation or size of nanoparticles. With most of these packing materials, dissolved Ag + was also extracted from aqueous solution, but, with a packing material made with Fe(II,III) oxide nanoparticles, only AgNPs were extracted. Therefore, it is the best candidate for determination of metallic AgNPs in aqueous environmental samples without interference from Ag + .

Supersonic N-Crowdions in a Two-Dimensional Morse Crystal

NASA Astrophysics Data System (ADS)

Dmitriev, S. V.; Korznikova, E. A.; Chetverikov, A. P.

2018-03-01

An interstitial atom placed in a close-packed atomic row of a crystal is called crowdion. Such defects are highly mobile; they can move along the row, transferring mass and energy. We generalize the concept of a classical supersonic crowdion to an N-crowdion in which not one but N atoms move simultaneously with a high velocity. Using molecular dynamics simulations for a close-packed two-dimensional Morse crystal, we show that N-crowdions transfer mass much more efficiently, because they are capable of covering large distances while having a lower total energy than that of a classical 1-crowdion.

Are artificial opals non-close-packed fcc structures?

NASA Astrophysics Data System (ADS)

García-Santamaría, F.; Braun, P. V.

2007-06-01

The authors report a simple experimental method to accurately measure the volume fraction of artificial opals. The results are modeled using several methods, and they find that some of the most common yield very inaccurate results. Both finite size and substrate effects play an important role in calculations of the volume fraction. The experimental results show that the interstitial pore volume is 4%-15% larger than expected for close-packed structures. Consequently, calculations performed in previous work relating the amount of material synthesized in the opal interstices with the optical properties may need revision, especially in the case of high refractive index materials.

Effects of plain package branding and graphic health warnings on adolescent smokers in the USA, Spain and France.

PubMed

Andrews, J Craig; Netemeyer, Richard G; Burton, Scot; Kees, Jeremy

2016-12-01

The purpose of this study is to provide an experimental test of the effects of plain pack branding and graphic health warnings (GHWs) in three different countries for an important and vulnerable population, that is, adolescents who are experimenting with smoking. The effects of plain pack branding (logo present, logo absent), and graphic visual warning level (absent, low, medium, high) are studied experimentally for their impact on adolescent cigarette craving, evoked fear, pack feelings and thoughts of quitting in the USA, Spain and France. A total of 1066 adolescents who were experimenting with smoking served as participants in the study. A quota sample produced 375 respondents in the USA, 337 in Spain and 354 in France. Overall findings indicate that the GHWs were effective in impacting adolescent cigarette craving, evoked fear, pack feelings and thoughts of quitting. The plain pack effects were not as strong, yet reduced craving, increased fear, and decreased pack feelings for all three samples combined, and for US adolescent smokers individually, irrespective of the GHWs. For French adolescent smokers, plain pack effects for craving were limited to low/moderate GHW levels. For Spanish adolescent smokers, plain pack feeling effects were limited to the absence of the GHWs. The results show that plain packs can independently strengthen the more instantaneous, direct effects (short of quitting thoughts) found with the GHWs. Yet, the plain pack results were attenuated for Spanish and French adolescent smokers, who are currently exposed to GHWs. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

Limited indications of tax stamp discordance and counterfeiting on cigarette packs purchased in tobacco retailers, 97 counties, USA, 2012.

PubMed

Lee, Joseph G L; Golden, Shelley D; Ribisl, Kurt M

2017-12-01

Increasing the per-unit cost of tobacco products is one of the strongest interventions for tobacco control. In jurisdictions with higher taxes in the U.S., however, cigarette pack litter studies show a substantial proportion of littered packs lack the appropriate tax stamp. More limited but still present counterfeiting also exists. We sought to examine the role of tobacco retailers as a source for untaxed and counterfeit products. Data collectors purchased Newport Green (menthol) or Marlboro Red cigarette packs in a national probability-based sample of tobacco retailers (in 97 counties) from June-October 2012. They made no effort to buy counterfeit or untaxed cigarettes. In this cross-sectional study, we assessed the presence, tax authority, and type (low-tech thermal vs. encrypted) of cigarette pack tax stamps; concordance of tax stamps with where the pack was purchased; and, for Marlboro cigarettes, publicly available visible indicators of counterfeiting. We purchased 2147 packs of which 2033 had tax stamps. Packs missing stamps were in states that do not require them. We found very limited discordance between store location and tax stamp(s) (< 1%). However, a substantial minority of cigarette packs had damaged tax stamps (13%). This occurred entirely with low-tech tax stamps and was not identified with encrypted tax stamps. We found no clear evidence of counterfeit products. Almost all tax stamps matched the location of purchase. Litter studies may be picking up legal tax avoidance instead of illegal tax evasion or, alternatively, purchase of illicit products requires special request by the purchaser.

Closed Small Cell Clouds

Atmospheric Science Data Center

2013-04-19

... (right)   The structure of tightly packed "closed cells" in a layer of marine stratocumulus over the southeastern Pacific Ocean ... they are bright and abundant, and reflect a large amount of solar energy toward space. They are difficult to represent in climate models ...

Construction of single-crystalline supramolecular networks of perchlorinated hexa-peri-hexabenzocoronene on Au(111)

NASA Astrophysics Data System (ADS)

Zhang, Yi; Zhang, Yanfang; Li, Geng; Lu, Jianchen; Lin, Xiao; Tan, Yuanzhi; Feng, Xinliang; Du, Shixuan; Müllen, Klaus; Gao, Hong-Jun

2015-03-01

The self-assembly of the perchlorinated hexa-peri-hexabenzocoronene (PCHBC) molecules on Au(111) has been studied by a low temperature scanning tunneling microscopy (STM) combining with density functional theory based first principle calculations. Highly ordered supramolecular networks with single domains limited by the terraces are formed on Au(111) substrate. High resolution images of the PCHBC molecules, confirmed by first principle simulations, are obtained. It reveals the close-packed arrangement of the PCHBC molecules on Au(111). The calculated charge distribution of PCHBC molecules shows the existence of attractive halogen-halogen interaction between neighboring molecules. Compared with the disordered adsorption of hexa-peri-hexabenzocoronene on Au(111), we conclude that the formation of attractive ClCl interactions between neighbors is the key factor to form the highly ordered, close-packed networks. Due to the steric hindrance resulted from the peripheral chlorine atoms, the PCHBC molecule is contorted and forms the doubly concave conformation, which is different from the hexa-peri-hexabenzocoronene with a planar structure. By using this supramolecular network as a template, we deposited C60 molecules on it at room temperature with low coverage. The STM images taken at low temperature show that the C60 molecules are mono-dispersed on the networks and adsorb on top of the PCHBC molecules, forming a typical concave-convex host-guest system.

49 CFR 173.121 - Class 3-Assignment of packing group.

Code of Federal Regulations, 2011 CFR

2011-10-01

... packing group must be determined by applying the following criteria: Flash point (closed-cup) Initial... (73.4 °F) using the ISO standard cup with a 4 mm (0.16 inch) jet as set forth in ISO 2431 (IBR, see... using the ISO standard cup with a 6 mm (0.24 inch) jet. (ii) Solvent Separation Test. This test is...

Packed rod neutron shield for fast nuclear reactors

DOEpatents

Eck, John E.; Kasberg, Alvin H.

1978-01-01

A fast neutron nuclear reactor including a core and a plurality of vertically oriented neutron shield assemblies surrounding the core. Each assembly includes closely packed cylindrical rods within a polygonal metallic duct. The shield assemblies are less susceptible to thermal stresses and are less massive than solid shield assemblies, and are cooled by liquid coolant flow through interstices among the rods and duct.

Clot contraction: compression of erythrocytes into tightly packed polyhedra and redistribution of platelets and fibrin

PubMed Central

Cines, Douglas B.; Lebedeva, Tatiana; Nagaswami, Chandrasekaran; Hayes, Vincent; Massefski, Walter; Litvinov, Rustem I.; Rauova, Lubica; Lowery, Thomas J.

2014-01-01

Contraction of blood clots is necessary for hemostasis and wound healing and to restore flow past obstructive thrombi, but little is known about the structure of contracted clots or the role of erythrocytes in contraction. We found that contracted blood clots develop a remarkable structure, with a meshwork of fibrin and platelet aggregates on the exterior of the clot and a close-packed, tessellated array of compressed polyhedral erythrocytes within. The same results were obtained after initiation of clotting with various activators and also with clots from reconstituted human blood and mouse blood. Such close-packed arrays of polyhedral erythrocytes, or polyhedrocytes, were also observed in human arterial thrombi taken from patients. The mechanical nature of this shape change was confirmed by polyhedrocyte formation from the forces of centrifugation of blood without clotting. Platelets (with their cytoskeletal motility proteins) and fibrin(ogen) (as the substrate bridging platelets for contraction) are required to generate the forces necessary to segregate platelets/fibrin from erythrocytes and to compress erythrocytes into a tightly packed array. These results demonstrate how contracted clots form an impermeable barrier important for hemostasis and wound healing and help explain how fibrinolysis is greatly retarded as clots contract. PMID:24335500

Pressure-Driven Suspension Flow near Jamming

NASA Astrophysics Data System (ADS)

Oh, Sangwon; Song, Yi-qiao; Garagash, Dmitry I.; Lecampion, Brice; Desroches, Jean

2015-02-01

We report here magnetic resonance imaging measurements performed on suspensions with a bulk solid volume fraction (ϕ0) up to 0.55 flowing in a pipe. We visualize and quantify spatial distributions of ϕ and velocity across the pipe at different axial positions. For dense suspensions (ϕ0>0.5 ), we found a different behavior compared to the known cases of lower ϕ0. Our experimental results demonstrate compaction within the jammed region (characterized by a zero macroscopic shear rate) from the jamming limit ϕm≈0.58 at its outer boundary to the random close packing limit ϕrcp≈0.64 at the center. Additionally, we show that ϕ and velocity profiles can be fairly well captured by a frictional rheology accounting for both further compaction of jammed regions as well as normal stress differences.

Superconductivity of lanthanum revisited: enhanced critical temperature in the clean limit.

PubMed

Löptien, P; Zhou, L; Khajetoorians, A A; Wiebe, J; Wiesendanger, R

2014-10-22

The thickness dependence of the superconducting energy gap ΔLa of double hexagonally close packed (dhcp) lanthanum islands grown on W(110) is studied by scanning tunneling spectroscopy, from the bulk to the thin-film limit. Superconductivity is suppressed by the boundary conditions for the superconducting wavefunction on the surface and W/La interface, leading to a linear decrease of the critical temperature Tc as a function of the inverse film thickness. For the thick, bulk-like films, ΔLa and Tc are 40% larger compared to the literature values of dhcp La as measured by other techniques. This finding is reconciled by examining the effects of surface contamination as probed by modifications of the surface state, suggesting that the large Tc originates in the superior purity of the samples investigated here.

Superconductivity of lanthanum revisited: enhanced critical temperature in the clean limit

NASA Astrophysics Data System (ADS)

Löptien, P.; Zhou, L.; Khajetoorians, A. A.; Wiebe, J.; Wiesendanger, R.

2014-10-01

The thickness dependence of the superconducting energy gap ΔLa of double hexagonally close packed (dhcp) lanthanum islands grown on W(110) is studied by scanning tunneling spectroscopy, from the bulk to the thin-film limit. Superconductivity is suppressed by the boundary conditions for the superconducting wavefunction on the surface and W/La interface, leading to a linear decrease of the critical temperature Tc as a function of the inverse film thickness. For the thick, bulk-like films, ΔLa and Tc are 40% larger compared to the literature values of dhcp La as measured by other techniques. This finding is reconciled by examining the effects of surface contamination as probed by modifications of the surface state, suggesting that the large Tc originates in the superior purity of the samples investigated here.

Face Centered Cubic and Hexagonal Close Packed Skyrmion Crystals in Centrosymmetric Magnets

NASA Astrophysics Data System (ADS)

Lin, Shi-Zeng; Batista, Cristian D.

2018-02-01

Skyrmions are disklike objects that typically form triangular crystals in two-dimensional systems. This situation is analogous to the so-called pancake vortices of quasi-two-dimensional superconductors. The way in which Skyrmion disks or "pancake Skyrmions" pile up in layered centrosymmetric materials is dictated by the interlayer exchange. Unbiased Monte Carlo simulations and simple stabilization arguments reveal face centered cubic and hexagonal close packed Skyrmion crystals for different choices of the interlayer exchange, in addition to the conventional triangular crystal of Skyrmion lines. Moreover, an inhomogeneous current induces a sliding motion of pancake Skyrmions, indicating that they behave as effective mesoscale particles.

High pressure synthesis of a hexagonal close-packed phase of the high-entropy alloy CrMnFeCoNi

DOE PAGES

Tracy, Cameron L.; Park, Sulgiye; Rittman, Dylan R.; ...

2017-05-25

High pressure x-ray diffraction measurements reveal that the face-centered cubic (fcc) high-entropy alloy CrMnFeCoNi transforms martensitically to a hexagonal close-packed (hcp) phase at ~14 GPa. We attribute this to suppression of the local magnetic moments, destabilizing the fcc phase. Similar to fcc-to-hcp transformations in Al and the noble gases, this transformation is sluggish, occurring over a range of >40 GPa. But, the behavior of CrMnFeCoNi is unique in that the hcp phase is retained following decompression to ambient pressure, yielding metastable fcc-hcp mixtures.

Femtosecond transient absorption dynamics of close-packed gold nanocrystal monolayer arrays*1

NASA Astrophysics Data System (ADS)

Eah, Sang-Kee; Jaeger, Heinrich M.; Scherer, Norbert F.; Lin, Xiao-Min; Wiederrecht, Gary P.

2004-03-01

Femtosecond transient absorption spectroscopy is used to investigate hot electron dynamics of close-packed 6 nm gold nanocrystal monolayers. Morphology changes of the monolayer caused by the laser pump pulse are monitored by transmission electron microscopy. At low pump power, the monolayer maintains its structural integrity. Hot electrons induced by the pump pulse decay through electron-phonon (e-ph) coupling inside the nanocrystals with a decay constant that is similar to the value for bulk films. At high pump power, irreversible particle aggregation and sintering occur in the nanocrystal monolayer, which cause damping and peak shifting of the transient bleach signal.

Templated electrokinetic directed chemical assembly for the fabrication of close-packed plasmonic metamolecules

NASA Astrophysics Data System (ADS)

Thrift, W. J.; Darvishzadeh-Varcheie, M.; Capolino, F.; Ragan, R.

2017-08-01

Colloidal self-assembly combined with templated surfaces holds the promise of fabricating large area devices in a low cost facile manner. This directed assembly approach improves the complexity of assemblies that can be achieved with self-assembly while maintaining advantages of molecular scale control. In this work, electrokinetic driving forces, i.e., electrohydrodynamic flow, are paired with chemical crosslinking between colloidal particles to form close-packed plasmonic metamolecules. This method addresses challenges of obtaining uniformity in nanostructure geometry and nanometer scale gap spacings in structures. Electrohydrodynamic flows yield robust driving forces between the template and nanoparticles as well as between nanoparticles on the surface promoting the assembly of close-packed metamolecules. Here, electron beam lithography defined Au pillars are used as seed structures that generate electrohydrodynamic flows. Chemical crosslinking between Au surfaces enables molecular control over gap spacings between nanoparticles and Au pillars. An as-fabricated structure is analyzed via full wave electromagnetic simulations and shown to produce large magnetic field enhancements on the order of 3.5 at optical frequencies. This novel method for directed self-assembly demonstrates the synergy between colloidal driving forces and chemical crosslinking for the fabrication of plasmonic metamolecules with unique electromagnetic properties.

Incommensurate growth of Co thin film on close-packed Ag(111) surface

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

Barman, Sukanta, E-mail: sukanta.ac@gmail.com; Menon, Krishna Kumar S. R., E-mail: krishna.menon@saha.ac.in

2016-05-06

Growth of ultrathin Co layers on close-packed Ag(111)were investigated by means of Low Energy Electron Diffraction (LEED), X-ray Photoelectron Spectroscopy (XPS) and Angle-resolved Photoemission Spectroscopy(ARPES) techniques. The close-packed hexagonal face of Co(0001), exhibits a lattice misfit about 13% with Ag(111) surface which manipulates the growth to be incommensurate up to a certain thickness. The strain field causes aperiodic height undulation in the sub-angstrom regime of the film which was confirmed by p(1 × 1) LEED pattern along with a 6-fold moiré reconstruction pattern in the lower film thickness (up to ∼2ML). The evolution of the LEED pattern was studied withmore » increasing film coverage. Lattice strain was measured with respect to the relative positions of these double spots as a functionof film thickness. Almost a constant strain (∼13%) in the full range of film thickness explains the moiré pattern formation in order to stabilize the incommensurate growth. For higher film coverages, an epitaxial well-ordered commensurate growth was observed. Core level and valance band electronic structures of these films were studied by XPS and ARPES techniques.« less

Quasi-Dual-Packed-Kerneled Au49 (2,4-DMBT)27 Nanoclusters and the Influence of Kernel Packing on the Electrochemical Gap.

PubMed

Liao, Lingwen; Zhuang, Shengli; Wang, Pu; Xu, Yanan; Yan, Nan; Dong, Hongwei; Wang, Chengming; Zhao, Yan; Xia, Nan; Li, Jin; Deng, Haiteng; Pei, Yong; Tian, Shi-Kai; Wu, Zhikun

2017-10-02

Although face-centered cubic (fcc), body-centered cubic (bcc), hexagonal close-packed (hcp), and other structured gold nanoclusters have been reported, it was unclear whether gold nanoclusters with mix-packed (fcc and non-fcc) kernels exist, and the correlation between kernel packing and the properties of gold nanoclusters is unknown. A Au 49 (2,4-DMBT) 27 nanocluster with a shell electron count of 22 has now been been synthesized and structurally resolved by single-crystal X-ray crystallography, which revealed that Au 49 (2,4-DMBT) 27 contains a unique Au 34 kernel consisting of one quasi-fcc-structured Au 21 and one non-fcc-structured Au 13 unit (where 2,4-DMBTH=2,4-dimethylbenzenethiol). Further experiments revealed that the kernel packing greatly influences the electrochemical gap (EG) and the fcc structure has a larger EG than the investigated non-fcc structure. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Critical scaling near the yielding transition in granular media

NASA Astrophysics Data System (ADS)

Clark, Abram H.; Thompson, Jacob D.; Shattuck, Mark D.; Ouellette, Nicholas T.; O'Hern, Corey S.

2018-06-01

We show that the yielding transition in granular media displays second-order critical-point scaling behavior. We carry out discrete element simulations in the low-inertial-number limit for frictionless, purely repulsive spherical grains undergoing simple shear at fixed nondimensional shear stress Σ in two and three spatial dimensions. To find a mechanically stable (MS) packing that can support the applied Σ , isotropically prepared states with size L must undergo a total strain γms(Σ ,L ) . The number density of MS packings (∝γms-1 ) vanishes for Σ >Σc≈0.11 according to a critical scaling form with a length scale ξ ∝|Σ - Σc|-ν , where ν ≈1.7 -1.8 . Above the yield stress (Σ >Σc ), no MS packings that can support Σ exist in the large-system limit L /ξ ≫1 . MS packings generated via shear possess anisotropic force and contact networks, suggesting that Σc is associated with an upper limit in the degree to which these networks can be deformed away from those for isotropic packings.

Self-diffusion coefficients and shear viscosity of inverse power fluids: from hard- to soft-spheres.

PubMed

Heyes, D M; Brańka, A C

2008-07-21

Molecular dynamics computer simulation has been used to compute the self-diffusion coefficient, D, and shear viscosity, eta(s), of soft-sphere fluids, in which the particles interact through the soft-sphere or inverse power pair potential, phi(r) = epsilon(sigma/r)(n), where n measures the steepness or stiffness of the potential, and epsilon and sigma are a characteristic energy and distance, respectively. The simulations were carried out on monodisperse systems for a range of n values from the hard-sphere (n --> infinity) limit down to n = 4, and up to densities in excess of the fluid-solid co-existence value. A new analytical procedure is proposed which reproduces the transport coefficients at high densities, and can be used to extrapolate the data to densities higher than accurately accessible by simulation or experiment, and tending to the glass transition. This formula, DX(c-1) proportional, variant A/X + B, where c is an adjustable parameter, and X is either the packing fraction or the pressure, is a development of one proposed by Dymond. In the expression, -A/B is the value of X at the ideal glass transition (i.e., where D and eta(s)(-1) --> 0). Estimated values are presented for the packing fraction and the pressure at the glass transition for n values between the hard and soft particle limits. The above expression is also shown to reproduce the high density viscosity data of supercritical argon, krypton and nitrogen. Fits to the soft-sphere simulation transport coefficients close to solid-fluid co-existence are also made using the analytic form, ln(D) = alpha(X)X, and n-dependence of the alpha(X) is presented (X is either the packing fraction or the pressure).

Chiral Structures of Thermoresponsive Soft Spheres in Hollow Cylinders

NASA Astrophysics Data System (ADS)

Lohr, Matthew A.; Alsayed, Ahmed; Zhang, Zexin; Yodh, Arjun G.

2009-03-01

We experimentally observe the formation of closely packed crystalline structures in hollow cylinders. The structures have varying degrees of chiral order. The systems are created from aqueous suspensions of thermoresponsive N-isopropylacrylamide (NIPA) microgel particles packed in micron-diameter glass capillaries. We categorize these structures according to classifications used by Erickson for tubular packings of hard spheres [1]. By varying the temperature-tunable diameter of these particles, the system's volume fraction is changed, permitting observations of the resilience of these structures and their melting transitions. Melting of these thermal crystalline structures is observed. [1] R. O. Erickson, Science 181 (1973) 705-716.

X-Ray Absorption Spectroscopy of Electrochemically Generated Species

DTIC Science & Technology

1993-02-01

that is a modification of our previously reported design (17) with reticulated vitreous carbon (RVC) as the working electrode. A peristaltic pump...and a flowing analyte stream. A packed carbon -bed bulk electrolysis cell generates the desired metal oxidation state. Completa oxidation and...packed carbon -bed bulk electrolysis cell generates the desired metal oxidation state. The system consists of a closed loop of electrolyte solution

Packing microstructure and local density variations of experimental and computational pebble beds

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

Auwerda, G. J.; Kloosterman, J. L.; Lathouwers, D.

2012-07-01

In pebble bed type nuclear reactors the fuel is contained in graphite pebbles, which form a randomly stacked bed with a non-uniform packing density. These variations can influence local coolant flow and power density and are a possible cause of hotspots. To analyse local density variations computational methods are needed that can generate randomly stacked pebble beds with a realistic packing structure on a pebble-to-pebble level. We first compare various properties of the local packing structure of a computed bed with those of an image made using computer aided X-ray tomography, looking at properties in the bulk of the bedmore » and near the wall separately. Especially for the bulk of the bed, properties of the computed bed show good comparison with the scanned bed and with literature, giving confidence our method generates beds with realistic packing microstructure. Results also show the packing structure is different near the wall than in the bulk of the bed, with pebbles near the wall forming ordered layers similar to hexagonal close packing. Next, variations in the local packing density are investigated by comparing probability density functions of the packing fraction of small clusters of pebbles throughout the bed. Especially near the wall large variations in local packing fractions exists, with a higher probability for both clusters of pebbles with low (<0.6) and high (>0.65) packing fraction, which could significantly affect flow rates and, together with higher power densities, could result in hotspots. (authors)« less

A unified picture of the crystal structures of metals

NASA Astrophysics Data System (ADS)

Söderlind, Per; Eriksson, Olle; Johansson, Börje; Wills, J. M.; Boring, A. M.

1995-04-01

THE crystal structures of the light actinides have intrigued physicists and chemists for several decades1. Simple metals and transition metals have close-packed, high-symmetry structures, such as body-centred cubic, face-centred cubic and hexagonal close packing. In contrast, the structures of the light actinides are very loosely packed and of low symmetry-tetragonal, orthorhombic and monoclinic. To understand these differences, we have performed total-energy calculations, as a function of volume, for both high-and low-symmetry structures of a simple metal (aluminium), a non-magnetic transition metal (niobium), a ferromagnetic transition metal (iron) and a light actinide (uranium). We find that the crystal structure of all of these metals is determined by the balance between electrostatic (Madelung) interactions, which favour high symmetry, and a Peierls distortion of the crystal lattice, which favours low symmetry. We show that simple metals and transition metals can adopt low-symmetry structures on expansion of the lattice; and we predict that, conversely, the light actinides will undergo transitions to structures of higher symmetry on compression.

How changes in top water bother big turning packs of up-going wet air

NASA Astrophysics Data System (ADS)

Wood, K.

2017-12-01

Big turning packs of up-going wet air form near areas of warm water at the top of big bodies of water. After these turning packs form, they usually get stronger if the top water stays warm. If the top water becomes less warm, the turning packs usually get less strong. Other things can change how strong a turning pack gets, like how wet the air around it is and if that air moves faster higher up than lower down. When these turning packs hit land, their rain and winds can hurt people and the stuff they own, especially if the turning pack is really strong. But it's hard to know how much stronger or less strong it will become before it hits land. Warm top water gives a turning pack of up-going wet air a lot of power, but cool top water doesn't, so we need to know how warm the top water is. Because I can't go into every turning pack myself, flying computers in outer space tell me what the top water is doing. I look at the top water near turning packs that get strong and see how it's different from the top water near those that get less strong. Top water that changes from warm to cool in a small area bothers a turning pack of up-going wet air, which then gets less strong. If we see these top water changes ahead of time, that might help us know what a turning pack will do before it gets close to land.

Measurement of Body-Centered-Cubic Aluminum at 475 GPa [Observation of Body-Centered-Cubic Aluminum at 475 GPa

DOE PAGES

Polsin, D. N.; Fratanduono, D. E.; Rygg, J. R.; ...

2017-10-27

Nanosecond in situ x-ray diffraction and simultaneous velocimetry measurements were used to determine the crystal structure and pressure, respectively, of ramp compressed aluminum at stress states between 111 and 475 GPa. The solid-solid Al phase transformations, fcc-hcp and hcp-bcc, are observed at 216 ± 9 GPa and 321 ± 12 GPa, respectively, with the bcc phase persisting to 475 GPa. Here, this is the first in situ observation of the high-pressure bcc phase of Al. High-pressure texture of the hcp and bcc phases suggests close-packed or nearly close-packed lattice planes remain parallel through both transformations.

Measurement of Body-Centered-Cubic Aluminum at 475 GPa [Observation of Body-Centered-Cubic Aluminum at 475 GPa

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

Polsin, D. N.; Fratanduono, D. E.; Rygg, J. R.

Nanosecond in situ x-ray diffraction and simultaneous velocimetry measurements were used to determine the crystal structure and pressure, respectively, of ramp compressed aluminum at stress states between 111 and 475 GPa. The solid-solid Al phase transformations, fcc-hcp and hcp-bcc, are observed at 216 ± 9 GPa and 321 ± 12 GPa, respectively, with the bcc phase persisting to 475 GPa. Here, this is the first in situ observation of the high-pressure bcc phase of Al. High-pressure texture of the hcp and bcc phases suggests close-packed or nearly close-packed lattice planes remain parallel through both transformations.

Metastable phases of silver and gold in hexagonal structure

NASA Astrophysics Data System (ADS)

Jona, F.; Marcus, P. M.

2004-07-01

Metastable phases of silver and gold in hexagonal close-packed structures are investigated by means of first-principles total-energy calculations. Two different methods are employed to find the equilibrium states: determination of the minima along the hexagonal epitaxial Bain path, and direct determination of minima of the total energy by a new minimum-path procedure. Both metals have two equilibrium states at different values of the hexagonal axial ratio c/a. For both metals, the elastic constants show that the high-c/a states are stable, hence, since the ground states are face-centred cubic, these states represent hexagonal close-packed metastable phases. The elastic constants of the low-c/a states show that they are unstable.

Modeling for Ultrasonic Health Monitoring of Foams with Embedded Sensors

NASA Technical Reports Server (NTRS)

Wang, L.; Rokhlin, S. I.; Rokhlin, Stanislav, I.

2005-01-01

In this report analytical and numerical methods are proposed to estimate the effective elastic properties of regular and random open-cell foams. The methods are based on the principle of minimum energy and on structural beam models. The analytical solutions are obtained using symbolic processing software. The microstructure of the random foam is simulated using Voronoi tessellation together with a rate-dependent random close-packing algorithm. The statistics of the geometrical properties of random foams corresponding to different packing fractions have been studied. The effects of the packing fraction on elastic properties of the foams have been investigated by decomposing the compliance into bending and axial compliance components. It is shown that the bending compliance increases and the axial compliance decreases when the packing fraction increases. Keywords: Foam; Elastic properties; Finite element; Randomness

Close packing in curved space by simulated annealing

NASA Astrophysics Data System (ADS)

Wille, L. T.

1987-12-01

The problem of packing spheres of a maximum radius on the surface of a four-dimensional hypersphere is considered. It is shown how near-optimal solutions can be obtained by packing soft spheres, modelled as classical particles interacting under an inverse power potential, followed by a subsequent hardening of the interaction. In order to avoid trapping in high-lying local minima, the simulated annealing method is used to optimise the soft-sphere packing. Several improvements over other work (based on local optimisation of random initial configurations of hard spheres) have been found. The freezing behaviour of this system is discussed as a function of particle number, softness of the potential and cooling rate. Apart from their geometric interest, these results are useful in the study of topological frustration, metallic glasses and quasicrystals.

Fabrication and characterization of non-Brownian particle-based crystals.

PubMed

Lash, Melissa H; Fedorchak, Morgan V; Little, Steven R; McCarthy, Joseph J

2015-01-27

Particle-based crystals have been explored in the literature for applications in molecular electronics, photonics, sensors, and drug delivery. However, much of the research on these crystals has been focused on particles of nano- and submicrometer dimensions (so-called colloidal crystals) with limited attention directed toward building blocks with dimensions ranging from tens to hundreds of micrometers. This can be attributed, in part, to the fact that the underlying thermal effects in these larger systems typically cannot naturally overcome kinetic barriers at the meso- and macroscales so that many of the methods used for nanoscale particle assembly cannot be directly applied to larger components, as they become kinetically arrested in nonequilibrium states. In this work, ultrasonic agitation is being explored as a means of allowing large, non-Brownian microparticles (18-750 μm) to overcome the kinetic barriers to packing in the creation of close-packed, highly ordered, crystalline structures. In addition, we study how the energy input affects bulk particle behavior and describe several new ways to characterize particle-based crystals made from microparticles.

Molecular structures of the inclusion complexes beta-cyclodextrin-1,2-bis(4-aminophenyl)ethane and beta-cyclodextrin-4,4'-diaminobiphenyl; packing of dimeric beta-cyclodextrin inclusion complexes.

PubMed

Giastas, Petros; Yannakopoulou, Konstantina; Mavridis, Irene M

2003-04-01

The present investigation is part of an ongoing study on the influence of the long end-functonalized guest molecules DBA and BNZ in the crystal packing of beta-cyclodextrin (betaCD) dimeric complexes. The title compounds are 2:2 host:guest complexes showing limited host-guest hydrogen bonding at the primary faces of the betaCD dimers. Within the betaCD cavity the guests exhibit mutual pi...pi interactions and between betaCD dimers perpendicular NH...pi interactions. The DBA guest molecule exhibits one extended and two bent conformations in the complex. The BNZ guest molecule is not planar inside betaCD, in contrast to the structure of BNZ itself, which indicates that the cavity isolates the molecules and forbids the pi...pi stacking of the aromatic rings. NMR spectroscopy studies show that in aqueous solution both DBA and BNZ form strong complexes that have 1:1 stoichiometry and structures similar to the solid state ones. The relative packing of the dimers is the same in both complexes. The axes of two adjacent dimers form an angle close to 20 degrees and have a lateral displacement approximately 2.45 A, both of which characterize the screw-channel mode of packing. Although the betaCD/BNZ complex indeed crystallizes in a space group characterizing the latter mode, the betaCD/DBA complex crystallizes in a space group with novel dimensions not resembling any of the packing modes reported so far. The new lattice is attributed to the three conformations exhibited by the guest in the crystals. However, this lattice can be transformed into another, which is isostructural to that of the betaCD/BNZ inclusion complex, if the conformation of the guest is not taken into account.

Granular mechanics of normally consolidated fine soils

NASA Astrophysics Data System (ADS)

Yanqui, Calixtro

2017-06-01

In this paper, duality is demonstrated to be one of the inherent properties of granular packings, by mapping the stress-strain curve into the diagram that relates the pore ratio and the localization of the contact point. In this way, it is demonstrated that critical state is not related to the maximum void ratio, but to a unique value related to two different angles of packing, one limiting the domain of the dense state, and other limiting the domain of the loose state. As a consequence, packings can be dilative or contractive, as mutually exclusive states, except by the critical state point, where equations for both granular packings are equally valid. Further analysis shows that stresses, in a dilative packing, are transmitted by chains of contact forces, and, in a contractive packing, by shear forces. So that, stresses, for the first case, depend on the initial void ratio, and, for the second case, are independent. As it is known, normally consolidated and lightly overconsolidated fine soils are in loose state, and, hence, their strength is constant, because it does not depend on their initial void ratio; except at the critical state, for which, the consolidated-drained angle of friction is related to the plasticity index or the liquid limit. In this fashion, experimental results reported by several authors around the world are confronted with the theory, showing a good agreement.

Modeling thermal infrared (2-14 micrometer) reflectance spectra of frost and snow

NASA Technical Reports Server (NTRS)

Wald, Andrew E.

1994-01-01

Existing theories of radiative transfer in close-packed media assume that each particle scatters independently of its neighbors. For opaque particles, such as are common in the thermal infrared, this assumption is not valid, and these radiative transfer theories will not be accurate. A new method is proposed, called 'diffraction subtraction', which modifies the scattering cross section of close-packed large, opaque spheres to account for the effect of close packing on the diffraction cross section of a scattering particle. This method predicts the thermal infrared reflectance of coarse (greater than 50 micrometers radius), disaggregated granular snow. However, such coarse snow is typically old and metamorphosed, with adjacent grains welded together. The reflectance of such a welded block can be described as partly Fresnel in nature and cannot be predicted using Mie inputs to radiative transfer theory. Owing to the high absorption coefficient of ice in the thermal infrared, a rough surface reflectance model can be used to calculate reflectance from such a block. For very small (less than 50 micrometers), disaggregated particles, it is incorrect in principle to treat diffraction independently of reflection and refraction, and the theory fails. However, for particles larger than 50 micrometers, independent scattering is a valid assumption, and standard radiative transfer theory works.

Using Shock Waves to Improve the Acoustic Properties of Closed-Cell Foams

NASA Astrophysics Data System (ADS)

Brouillette, M.; Hébert, C.; Atalla, N.; Doutres, O.

Foam microstructure can be seen as a collection of interlinked struts forming a packing of cells interconnected to others through pores. Materials with a totality of pores closed by thin membranes are called closed-cell foams. The filtration and acoustic efficiency of closed-cell foams is poor compared to open-cell foams since it is very difficult for the fluid or the acoustic waves to penetrate inside the material.

Random close packing of polydisperse jammed emulsions

NASA Astrophysics Data System (ADS)

Brujic, Jasna

2010-03-01

Packing problems are everywhere, ranging from oil extraction through porous rocks to grain storage in silos and the compaction of pharmaceutical powders into tablets. At a given density, particulate systems pack into a mechanically stable and amorphous jammed state. Theoretical frameworks have proposed a connection between this jammed state and the glass transition, a thermodynamics of jamming, as well as geometric modeling of random packings. Nevertheless, a simple underlying mechanism for the random assembly of athermal particles, analogous to crystalline ordering, remains unknown. Here we use 3D measurements of polydisperse packings of emulsion droplets to build a simple statistical model in which the complexity of the global packing is distilled into a local stochastic process. From the perspective of a single particle the packing problem is reduced to the random formation of nearest neighbors, followed by a choice of contacts among them. The two key parameters in the model, the available space around a particle and the ratio of contacts to neighbors, are directly obtained from experiments. Remarkably, we demonstrate that this ``granocentric'' view captures the properties of the polydisperse emulsion packing, ranging from the microscopic distributions of nearest neighbors and contacts to local density fluctuations and all the way to the global packing density. Further applications to monodisperse and bidisperse systems quantitatively agree with previously measured trends in global density. This model therefore reveals a general principle of organization for random packing and lays the foundations for a theory of jammed matter.

A study of the genetic relationships within and among wolf packs using DNA fingerprinting and mitochondrial DNA

USGS Publications Warehouse

Lehman, Niles; Clarkson, Peter; Mech, L. David; Meier, Thomas J.; Wayne, Robert K.

1992-01-01

DNA fingerprinting and mitochondrial DNA analyses have not been used in combination to study relatedness in natural populations. We present an approach that involves defining the mean fingerprint similarities among individuals thought to be unrelated because they have different mtDNA genotypes. Two classes of related individuals are identified by their distance in standard errors above this mean value. The number of standard errors is determined by analysis of the association between fingerprint similarity and relatedness in a population with a known genealogy. We apply this approach to gray wolf packs from Minnesota, Alaska, and the Northwest Territories. Our results show that: (1) wolf packs consist primarily of individuals that are closely related genetically, but some packs contain unrelated, non-reproducing individuals; (2) dispersal among packs within the same area is common; and (3) short-range dispersal appears more common for female than male wolves. The first two of these genetically-based observations are consistent with behavioral data on pack structure and dispersal in wolves, while the apparent sex bias in dispersal was not expected.

49 CFR 172.102 - Special provisions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... design type that has passed a leakproofness test at the Packing Group II level. Small inner packagings... packaging or transport unit is closed. Each packaging must correspond to a design type that has passed a... transport unit is closed. Each packaging must correspond to a design type that has passed a leakproofness...

49 CFR 172.102 - Special provisions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... design type that has passed a leakproofness test at the Packing Group II level. Small inner packagings... packaging or transport unit is closed. Each packaging must correspond to a design type that has passed a... transport unit is closed. Each packaging must correspond to a design type that has passed a leakproofness...

49 CFR 173.151 - Exceptions for Class 4.

Code of Federal Regulations, 2010 CFR

2010-10-01

... of Division 4.1. Limited quantities of flammable solids (Division 4.1) in Packing Group II or III are... are authorized: (1) For flammable solids in Packing Group II, inner packagings not over 1.0 kg (2.2... strong outer packaging. (2) For flammable solids in Packing Group III, inner packagings not over 5.0 kg...

Innovative enclosure dome/observing aperture system design for the MROI Array Telescopes

NASA Astrophysics Data System (ADS)

Busatta, A.; Marchiori, G.; Mian, S.; Payne, I.; Pozzobon, M.

2010-07-01

The close-pack array of the MROI necessitated an original design for the Unit Telescope Enclosure (UTE) at Magdalena Ridge Observatory. The Magdalena Ridge Observatory Interferometer (MROI) is a project which comprises an array of up to ten (10) 1.4m diameter mirror telescopes arranged in a "Y" configuration. Each of these telescopes will be housed inside a Unit Telescope Enclosure (UTE) which are relocatable onto any of 28 stations. The most compact configuration includes all ten telescopes, several of which are at a relative distance of less than 8m center to center from each other. Since the minimum angle of the field of regard is 30° with respect to the horizon, it is difficult to prevent optical blockage caused by adjacent UTEs in this compact array. This paper presents the design constraints inherent in meeting the requirement for the close-pack array. An innovative design enclosure was created which incorporates an unique dome/observing aperture system. The description of this system focuses on how the field of regard requirement led to an unique and highly innovative concept that had to be able to operate in the harsh environmental conditions encountered at an altitude of 10,460ft (3,188m). Finally, we describe the wide use of composites materials and structures (e.g. glass/carbon fibres, sandwich panels etc.) on the aperture system which represents the only way to guarantee adequate thermal and environmental protection, compactness, structural stability and limited power consumption due to reduced mass.

Effect of different packaging methods and storage temperature on microbiological and physicochemical quality characteristics of meatball.

PubMed

Yilmaz, I; Demirci, M

2010-06-01

The objective of this research was to determine physicochemical changes and microbiological quality of the different packaged meatball samples. Meatball samples in polystyrene tray were closed with polyethylene film (PS packs), vacuumed and modified atmosphere packaged, (MAP) (65% N(2), 35% CO(2)), and held under refrigerated display (4 °C) for 8, 16 and 16 days for PS packs, vacuum and MAP, respectively. Microbial load, free fatty acids and thiobarbituric acid values of the samples tended to increase with storage time. Bacteria counts of the raw meatball samples increased 2 log cycles at the end of storage compared with initial values. Meatball samples can be stored without any microbiological problem for 7 days at 4 °C. Results from this study suggested that shelf-life assigned to modified-MAP and vacuum-packed meatballs may be appropriate. Meatball samples underwent physical deformation when they were packed before vacuum process. With these negative factors considered, MAP is superior to other two packs methods.

Method of densifying an article formed of reaction bonded silicon nitride

NASA Technical Reports Server (NTRS)

Mangels, John A. (Inventor)

1982-01-01

A method of densifying an article formed of reaction bonded silicon nitride is disclosed. The reaction bonded silicon nitride article is packed in a packing mixture consisting of silicon nitride powder and a densification aid. The reaction bonded silicon nitride article and packing powder are sujected to a positive, low pressure nitrogen gas treatment while being heated to a treatment temperature and for a treatment time to cause any open porosity originally found in the reaction bonded silicon nitride article to be substantially closed. Thereafter, the reaction bonded silicon nitride article and packing powder are subjected to a positive high pressure nitrogen gas treatment while being heated to a treatment temperature and for a treatment time to cause a sintering of the reaction bonded silicon nitride article whereby the strength of the reaction bonded silicon nitride article is increased.

Close-packed monolayer self-assembly of silica nanospheres assisted by infrared irradiation

NASA Astrophysics Data System (ADS)

Minh, Nguyen Van; Hue, Nguyen Thi; Lien, Nghiem Thi Ha; Hoang, Chu Manh

2018-01-01

In this paper, we report on a fast and cost-effective drop coating technique for the self-assembly of silica nano-spheres from a mono-dispersed colloidal suspension into close-packed monolayer (CMP) on hydrophilic single-crystal silicon substrate. The technique includes the self-assembly of silica nano-spheres on slanted silicon substrate and infrared irradiation during evaporation process of the coated droplet. The influence of the substrate slant angle and infrared irradiation on the formation of silica nano-sphere monolayer is investigated. This achievement is promising for various applications, such as a mask layer for nano-sphere lithography that is employed for producing fundamental elements in photonics, plasmonics, and solar cell. [Figure not available: see fulltext.

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

Streubel, Robert; Kronast, Florian; Reiche, Christopher F.

For this work, we studied curvature-driven modifications to the magnetostatic coupling of vortex circulation and polarity in soft-magnetic closely packed cap arrays. A phase diagram for the magnetic remanent/transition states at room temperature as a function of diameter and thickness was assembled. For specimens with vortex remanent state (40 nm-thick Permalloy on 330 nm spherical nanoparticles), both vortex circulation and polarity were visualized. Intercap coupling upon vortex nucleation leads to the formation of vortex circulation patterns in closely packed arrays. The remanent circulation pattern can be tailored choosing the direction of the applied magnetic field with respect to the symmetrymore » axis of the hexagonal array. An even and random distribution of vortex polarity indicates the absence of any circulation-polarity coupling.« less

Effect of Isothermal Temperature on Growth Behavior of Nanostructured Bainite in Laser Cladded Coatings

PubMed Central

Guo, Yanbing; Yao, Chengwu; Feng, Kai; Li, Zhuguo; Chu, Paul K.; Wu, Yixiong

2017-01-01

The growth and propagation behavior of austenite-to-bainite isothermal transformation in laser-cladded, Si-rich, and Fe-based coatings is investigated. The crystallographic features, orientation relationship at different isothermal temperatures, and the morphology of the nanostructured bainite are determined. The Nishiyama-Wassermann type orientation relationship is observed at a high temperature and at a low temperature, and mixed Nishiyama-Wassermann and Kurdjumov-Sach mechanisms are seen. The growth direction is investigated by the partial dislocation theory and an extrapolated model based on the repeated formation of lenticular-shaped subunits and pile-up along the close-packed directions of the close-packed planes. The variants of the bainite growth directions would be more selective at the high transformation temperature. PMID:28773161

Simple fabrication of closed-packed IR microlens arrays on silicon by femtosecond laser wet etching

NASA Astrophysics Data System (ADS)

Meng, Xiangwei; Chen, Feng; Yang, Qing; Bian, Hao; Du, Guangqing; Hou, Xun

2015-10-01

We demonstrate a simple route to fabricate closed-packed infrared (IR) silicon microlens arrays (MLAs) based on femtosecond laser irradiation assisted by wet etching method. The fabricated MLAs show high fill factor, smooth surface and good uniformity. They can be used as optical devices for IR applications. The exposure and etching parameters are optimized to obtain reproducible microlens with hexagonal and rectangular arrangements. The surface roughness of the concave MLAs is only 56 nm. This presented method is a maskless process and can flexibly change the size, shape and the fill factor of the MLAs by controlling the experimental parameters. The concave MLAs on silicon can work in IR region and can be used for IR sensors and imaging applications.

Entropy favours open colloidal lattices

NASA Astrophysics Data System (ADS)

Mao, Xiaoming; Chen, Qian; Granick, Steve

2013-03-01

Burgeoning experimental and simulation activity seeks to understand the existence of self-assembled colloidal structures that are not close-packed. Here we describe an analytical theory based on lattice dynamics and supported by experiments that reveals the fundamental role entropy can play in stabilizing open lattices. The entropy we consider is associated with the rotational and vibrational modes unique to colloids interacting through extended attractive patches. The theory makes predictions of the implied temperature, pressure and patch-size dependence of the phase diagram of open and close-packed structures. More generally, it provides guidance for the conditions at which targeted patchy colloidal assemblies in two and three dimensions are stable, thus overcoming the difficulty in exploring by experiment or simulation the full range of conceivable parameters.

Nuclear thermionic converter. [tungsten-thorium oxide rods

NASA Technical Reports Server (NTRS)

Phillips, W. M.; Mondt, J. F. (Inventor)

1977-01-01

Efficient nuclear reactor thermionic converter units are described which can be constructed at low cost and assembled in a reactor which requires a minimum of fuel. Each converter unit utilizes an emitter rod with a fluted exterior, several fuel passages located in the bulges that are formed in the rod between the flutes, and a collector receiving passage formed through the center of the rod. An array of rods is closely packed in an interfitting arrangement, with the bulges of the rods received in the recesses formed between the bulges of other rods, thereby closely packing the nuclear fuel. The rods are constructed of a mixture of tungsten and thorium oxide to provide high power output, high efficiency, high strength, and good machinability.

Non-parametric correlative uncertainty quantification and sensitivity analysis: Application to a Langmuir bimolecular adsorption model

NASA Astrophysics Data System (ADS)

Feng, Jinchao; Lansford, Joshua; Mironenko, Alexander; Pourkargar, Davood Babaei; Vlachos, Dionisios G.; Katsoulakis, Markos A.

2018-03-01

We propose non-parametric methods for both local and global sensitivity analysis of chemical reaction models with correlated parameter dependencies. The developed mathematical and statistical tools are applied to a benchmark Langmuir competitive adsorption model on a close packed platinum surface, whose parameters, estimated from quantum-scale computations, are correlated and are limited in size (small data). The proposed mathematical methodology employs gradient-based methods to compute sensitivity indices. We observe that ranking influential parameters depends critically on whether or not correlations between parameters are taken into account. The impact of uncertainty in the correlation and the necessity of the proposed non-parametric perspective are demonstrated.

PCR detection of psychrophilic Clostridium spp. causing 'blown pack' spoilage of vacuum-packed chilled meats.

PubMed

Broda, D M; Boerema, J A; Bell, R G

2003-01-01

To develop a practical molecular procedure that directly, without isolation, and specifically detects the presence of clostridia which cause 'blown pack' spoilage of vacuum-packed meat. Primer sets and PCR amplification procedures were developed that detect the presence of 16S rDNA gene and/or 16S-23S rDNA internal transcribed spacer fragments of 'blown pack' causing clostridia in meat. The specificity of the developed procedures was evaluated with DNA obtained from close phylogenetic neighbours of 'blown pack' causing clostridia, food clostridia and common meat spoilage microorganisms. The sensitivity of detection was assessed in non-enriched and low-temperature-enriched beef mince inoculated with serially diluted pure cultures of Clostridium estertheticum DSMZ 8809T and Cl. gasigenes DB1AT. The efficacy of detection procedures was evaluated for naturally contaminated vacuum-packed meat samples. Three primer sets, 16SE, 16SDB and EISR, produced amplicons of the expected size with DNA templates from target clostridia, but failed to yield PCR products with DNAs from any other microorganisms tested. With 16SE and 16SDB primers, minimum levels of detection were 104 CFU g(-1) for non-enriched, and 102 CFU g(-1) for enriched meat samples. Based on the established specificity of these primers, as well as DNA sequencing of amplicons, Cl. gasigenes was confirmed as the causative agent of 'blown pack' spoilage in two packs, and Cl. estertheticum as the causative agent in the third. The developed method can be used for rapid detection of 'blown pack' causing clostridia in commercial blown packs, or following low temperature enrichment, for detection of these microorganisms in meat containing as few as 100 clostridial cells per gram. The paper reports practical procedures that can be used for rapid confirmation of the causative agents of clostridial 'blown pack' spoilage in commercial spoiled packs, or for detection of psychrophilic clostridia in epidemiological trace back of 'blown pack' spoilage incidents in meat processing plants.

Effects of ageing on the hydraulics of water wells and the influence of non-Darcy flow

NASA Astrophysics Data System (ADS)

Houben, Georg J.; Wachenhausen, Julia; Guevara Morel, Carlos R.

2018-04-01

Well ageing is mostly caused by mechanical and biogeochemical clogging processes, which affect the gravel pack, screen slots and casing. Clogging deposits increase head losses due to a constriction of the hydraulically effective area. For this study, clogging is mimicked by systematically reducing the gravel pack porosity, the screen open area and the nominal inner casing diameter. Groundwater flow velocity strongly increases close to the well, inducing inertial and turbulent flow components. Therefore, gravel pack head losses were calculated using the Forchheimer-Engelund equation, in conjunction with the Kozeny-Carman equation, which relates gravel pack porosity and hydraulic conductivity. Screen losses were assessed using the Orifice equation and turbulent casing losses with the Darcy-Weisbach equation. For the settings chosen here, a dramatic increase of head losses occurs when the clogging has reduced the effective porosity in the gravel pack by 65%, the open area of the screen by ≥98%, and the casing diameter by 50%. Since the latter two conditions are rarely reached in actual wells, the clogging of the gravel pack is the decisive parameter that controls well ageing. Regular monitoring of the well yield is therefore needed, since processes in the gravel pack are difficult to track directly. Unlike the deposits on the casing and in the screen slots, obstructions in the gravel pack are much more difficult to remove.

Effects of ageing on the hydraulics of water wells and the influence of non-Darcy flow

NASA Astrophysics Data System (ADS)

Houben, Georg J.; Wachenhausen, Julia; Guevara Morel, Carlos R.

2018-06-01

Well ageing is mostly caused by mechanical and biogeochemical clogging processes, which affect the gravel pack, screen slots and casing. Clogging deposits increase head losses due to a constriction of the hydraulically effective area. For this study, clogging is mimicked by systematically reducing the gravel pack porosity, the screen open area and the nominal inner casing diameter. Groundwater flow velocity strongly increases close to the well, inducing inertial and turbulent flow components. Therefore, gravel pack head losses were calculated using the Forchheimer-Engelund equation, in conjunction with the Kozeny-Carman equation, which relates gravel pack porosity and hydraulic conductivity. Screen losses were assessed using the Orifice equation and turbulent casing losses with the Darcy-Weisbach equation. For the settings chosen here, a dramatic increase of head losses occurs when the clogging has reduced the effective porosity in the gravel pack by 65%, the open area of the screen by ≥98%, and the casing diameter by 50%. Since the latter two conditions are rarely reached in actual wells, the clogging of the gravel pack is the decisive parameter that controls well ageing. Regular monitoring of the well yield is therefore needed, since processes in the gravel pack are difficult to track directly. Unlike the deposits on the casing and in the screen slots, obstructions in the gravel pack are much more difficult to remove.

Predicting Instability Timescales in Closely-Packed Planetary Systems

NASA Astrophysics Data System (ADS)

Tamayo, Daniel; Hadden, Samuel; Hussain, Naireen; Silburt, Ari; Gilbertson, Christian; Rein, Hanno; Menou, Kristen

2018-04-01

Many of the multi-planet systems discovered around other stars are maximally packed. This implies that simulations with masses or orbital parameters too far from the actual values will destabilize on short timescales; thus, long-term dynamics allows one to constrain the orbital architectures of many closely packed multi-planet systems. A central challenge in such efforts is the large computational cost of N-body simulations, which preclude a full survey of the high-dimensional parameter space of orbital architectures allowed by observations. I will present our recent successes in training machine learning models capable of reliably predicting orbital stability a million times faster than N-body simulations. By engineering dynamically relevant features that we feed to a gradient-boosted decision tree algorithm (XGBoost), we are able to achieve a precision and recall of 90% on a holdout test set of N-body simulations. This opens a wide discovery space for characterizing new exoplanet discoveries and for elucidating how orbital architectures evolve through time as the next generation of spaceborne exoplanet surveys prepare for launch this year.

Size and structure dependent ultrafast dynamics of plasmonic gold nanosphere heterostructures on poly (ethylene glycol) brushes

NASA Astrophysics Data System (ADS)

Karatay, Ahmet; Küçüköz, Betül; Pekdemir, Sami; Onses, Mustafa Serdar; Elmali, Ayhan

2017-11-01

We have investigated the plasmonic properties of heterostructures that consist of gold nanosphere (NSs) with average diameters of 60 nm, 40 nm and 20 nm on poly (ethylene glycol) (PEG) brushes by using ultrafast pump-probe spectroscopy experiments. Gold NSs start to behave like gold nanorods with increasing number of immobilization cycles due to the close proximity. Gold NSs immobilized by 3 and 5 deposition cycles show longitudinal modes of plasmon bands at long wavelengths which are characteristic behaviors for gold nanorods. Increasing the number of immobilization cycle also increase relaxation times of samples due to the close proximity. Linear absorption spectra and scanning electron microscopy images show that there are close packing assemblies for heterostructures containing 20 nm gold NSs as the small particle. Ultrafast electron transfer (<100 fs) occurs between transverse and longitudinal modes by exciting the samples at both 520 nm and 650 nm. Further, experimental results indicate that, heterostructures with the small particles have faster relaxation times than other heterostructures due to closed packing of 20 nm gold NSs.

Understanding the General Packing Rearrangements Required for Successful Template Based Modeling of Protein Structure from a CASP Experiment

PubMed Central

Day, Ryan; Joo, Hyun; Chavan, Archana; Lennox, Kristin P.; Chen, Ann; Dahl, David B.; Vannucci, Marina; Tsai, Jerry W.

2012-01-01

As an alternative to the common template based protein structure prediction methods based on main-chain position, a novel side-chain centric approach has been developed. Together with a Bayesian loop modeling procedure and a combination scoring function, the Stone Soup algorithm was applied to the CASP9 set of template based modeling targets. Although the method did not generate as large of perturbations to the template structures as necessary, the analysis of the results gives unique insights into the differences in packing between the target structures and their templates. Considerable variation in packing is found between target and template structures even when the structures are close, and this variation is found due to 2 and 3 body packing interactions. Outside the inherent restrictions in packing representation of the PDB, the first steps in correctly defining those regions of variable packing have been mapped primarily to local interactions, as the packing at the secondary and tertiary structure are largely conserved. Of the scoring functions used, a loop scoring function based on water structure exhibited some promise for discrimination. These results present a clear structural path for further development of a side-chain centered approach to template based modeling. PMID:23266765

Understanding the general packing rearrangements required for successful template based modeling of protein structure from a CASP experiment.

PubMed

Day, Ryan; Joo, Hyun; Chavan, Archana C; Lennox, Kristin P; Chen, Y Ann; Dahl, David B; Vannucci, Marina; Tsai, Jerry W

2013-02-01

As an alternative to the common template based protein structure prediction methods based on main-chain position, a novel side-chain centric approach has been developed. Together with a Bayesian loop modeling procedure and a combination scoring function, the Stone Soup algorithm was applied to the CASP9 set of template based modeling targets. Although the method did not generate as large of perturbations to the template structures as necessary, the analysis of the results gives unique insights into the differences in packing between the target structures and their templates. Considerable variation in packing is found between target and template structures even when the structures are close, and this variation is found due to 2 and 3 body packing interactions. Outside the inherent restrictions in packing representation of the PDB, the first steps in correctly defining those regions of variable packing have been mapped primarily to local interactions, as the packing at the secondary and tertiary structure are largely conserved. Of the scoring functions used, a loop scoring function based on water structure exhibited some promise for discrimination. These results present a clear structural path for further development of a side-chain centered approach to template based modeling. Copyright © 2012 Elsevier Ltd. All rights reserved.

Partitioning and packing mathematical simulation models for calculation on parallel computers

NASA Technical Reports Server (NTRS)

Arpasi, D. J.; Milner, E. J.

1986-01-01

The development of multiprocessor simulations from a serial set of ordinary differential equations describing a physical system is described. Degrees of parallelism (i.e., coupling between the equations) and their impact on parallel processing are discussed. The problem of identifying computational parallelism within sets of closely coupled equations that require the exchange of current values of variables is described. A technique is presented for identifying this parallelism and for partitioning the equations for parallel solution on a multiprocessor. An algorithm which packs the equations into a minimum number of processors is also described. The results of the packing algorithm when applied to a turbojet engine model are presented in terms of processor utilization.

Electron microscope study of the vitelline body of some spider oocytes.

PubMed

SOTELO, J R; TRUJILLO-CENOZ, O

1957-03-25

THE STRUCTURE OF THE VITELLINE NUCLEI OF LYCOSIDAE AND THOMISIDAE WAS DESCRIBED AS FOLLOWS: Vitelline nuclei are constituted of two parts: (a) a peripheral layer (vitelline body cortex), and (b) a central core. The vitelline body cortex is demonstrated to be formed by many cisternae of the endoplasmic reticulum among which mitochondria and Golgi elements are intermingled. The central core is made up mainly of a special type of body described under the name of "capsulated body." Capsulated bodies comprise a capsular layer, limited by a membrane, and two central masses called "geminated masses," each one limited by a double membrane. Irregular masses of closely packed vesicles are found in some cases among the capsulated bodies and free vesicles are present in large numbers. The optical properties of the vitelline body cortex compared with the electron microscope findings lead us to the concept that this layer is a "composite body" according to Weiner's theory.

Specific inhibition of Photobacterium phosphoreum extends the shelf life of modified-atmosphere-packed cod fillets.

PubMed

Dalgaard, P; Garcia Munoz, L; Mejlholm, O

1998-09-01

Inhibition of the specific spoilage organism, Photobacterium phosphoreum, was studied in model substrates and in modified-atmosphere-packed cod fillets. The objective was to determine how inhibition of this organism influenced spoilage. The spoilage reactions limiting shelf life were studied rather than the development of a new product. In naturally contaminated modified-atmosphere-packed cod fillets, 500 ppm Na2CaEDTA reduced the growth rate of P. phosphoreum by 40% and shelf life was increased proportionally by 40%, from 15 to 17 days to 21 to 23 days at 0 degree C. In aerobically stored cod fillets other microorganisms were responsible for spoilage and Na2CaEDTA had no effect on shelf life. The extension of the shelf life of modified-atmosphere-packed cod therefore was a result of the reduced growth of P. phosphoreum and no other microbial or nonmicrobial spoilage reactions limited shelf life. These results confirmed P. phosphoreum as the specific spoilage organism in modified-atmosphere-packed cod and showed the organism to have an extensive spoilage domain. Consequently, any preservation procedure able to reduce growth of P. phosphoreum is likely to extend shelf life of packed cod. However, the effect of different inhibitory compounds in model systems as well as results from packed cod indicated the need to include product studies in the screening of antimicrobials and in the development of preservation procedures.

Biomimetic synthesis of sericin and silica hybrid colloidosomes for stimuli-responsive anti-cancer drug delivery systems.

PubMed

Yang, Ying; Cai, Yurong; Sun, Ning; Li, Ruijing; Li, Wenhua; Kundu, Subhas C; Kong, Xiangdong; Yao, Juming

2017-03-01

Colloidosomes are becoming popular due to their significant flexibility with respect to microcapsule functionality. This study reports a facile approach for synthesizing silica colloidosomes by using sericin microcapsule as the matrix in an environment-friendly method. The silica colloid arrangement on the sericin microcapsules are orchestrated by altering the reaction parameters. Doxorubicin (DOX), used as a hydrophilic anti-cancer drug model, is encapsulated into the colloidosomes in a mild aqueous solution and becomes stimuli-responsive to different external environments, including pH values, protease, and ionic strength are also observed. Colloidosomes with sub-monolayers, close-packed monolayers, and close-packed multi-layered SiO 2 colloid shells can be fabricated under the optimized reaction conditions. A flexible DOX release from colloidosomes can be obtained via modulating the SiO 2 colloid layer arrangement and thickness. The close-packed and multi-layered SiO 2 colloid shells can best protect the colloidosomes and delay the rapid cargo release. MG-63 cells are killed when doxorubicin is released from the microcapsules due to degradation in the microenvironment of cancer cells. The drug release period is prolonged as SiO 2 shell thickness and integrity increase. This work suggests that the hybrid colloidosomes can be effective in a bioactive molecule delivery system. Copyright © 2016 Elsevier B.V. All rights reserved.

Ultrathin free-standing close-packed gold nanoparticle films: conductivity and Raman scattering enhancement.

PubMed

Yu, Qing; Huang, Hongwen; Peng, Xinsheng; Ye, Zhizhen

2011-09-01

A simple filtration technique was developed to prepare large scale free-standing close-packed gold nanoparticle ultrathin films using metal hydroxide nanostrands as both barrier layer and sacrificial layer. As thin as 70 nm, centimeter scale robust free-standing gold nanoparticle thin film was obtained. The thickness of the films could be easily tuned by the filtration volumes. The electronic conductivities of these films varied with the size of the gold nanoparticles, post-treatment temperature, and thickness, respectively. The conductivity of the film prepared from 20 nm gold nanoparticles is higher than that of the film prepared from 40 nm gold nanoparticle by filtering the same filtration volume of their solution, respectively. Their conductivities are comparable to that of the 220 nm thick ITO film. Furthermore, these films demonstrated an average surface Raman scattering enhancement up to 6.59 × 10(5) for Rhodamine 6 G molecules on the film prepared from 40 nm gold nanoparticles. Due to a lot of nano interspaces generated from the close-packed structures, two abnormal enhancements and relative stronger intensities of the asymmetrical vibrations at 1534 and 1594 cm(-1) of R6G were observed, respectively. These robust free-standing gold nanoparticle films could be easily transferred onto various solid substrates and hold the potential application for electrodes and surface enhanced Raman detectors. This method is applicable for preparation of other nanoparticle free-standing thin films.

Low-symmetry sphere packings of simple surfactant micelles induced by ionic sphericity

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

Kim, Sung A.; Jeong, Kyeong-Jun; Yethiraj, Arun

We report the discovery of an ionic small molecule surfactant that undergoes water-drive self- assembly into quasispherical micelles, which pack into the first lyotropic liquid crystalline Frank–Kasper σ phase. Small-angle X-ray scattering studies indicate that this unexpected, low-symmetry phase is characterized by a tetragonal unit cell, in which 30 sub-2 nm micelles of five discrete types are arranged into a tetrahedral close packing with exceptional translational order. Varying the relative amounts of surfactant and water in these lyotropic phases enables formation of a Frank–Kasper A15 sphere packing and a more common body-centered cubic structure. MD simulations reveal that the symmetrymore » breaking that drives the selection of the σ and A15 phases arises from a delicate interplay between the drive to maintain local spherical particle symmetry and the maximization of electrostatic cohesion between the soft micellar particles.« less

Low-symmetry sphere packings of simple surfactant micelles induced by ionic sphericity

DOE PAGES

Kim, Sung A.; Jeong, Kyeong-Jun; Yethiraj, Arun; ...

2017-04-03

We report the discovery of an ionic small molecule surfactant that undergoes water-drive self- assembly into quasispherical micelles, which pack into the first lyotropic liquid crystalline Frank–Kasper σ phase. Small-angle X-ray scattering studies indicate that this unexpected, low-symmetry phase is characterized by a tetragonal unit cell, in which 30 sub-2 nm micelles of five discrete types are arranged into a tetrahedral close packing with exceptional translational order. Varying the relative amounts of surfactant and water in these lyotropic phases enables formation of a Frank–Kasper A15 sphere packing and a more common body-centered cubic structure. MD simulations reveal that the symmetrymore » breaking that drives the selection of the σ and A15 phases arises from a delicate interplay between the drive to maintain local spherical particle symmetry and the maximization of electrostatic cohesion between the soft micellar particles.« less

21 CFR 110.40 - Equipment and utensils.

Code of Federal Regulations, 2011 CFR

2011-04-01

... HUMAN CONSUMPTION CURRENT GOOD MANUFACTURING PRACTICE IN MANUFACTURING, PACKING, OR HOLDING HUMAN FOOD... manufacturing systems, including gravimetric, pneumatic, closed, and automated systems, shall be of a design and...

21 CFR 110.40 - Equipment and utensils.

Code of Federal Regulations, 2013 CFR

2013-04-01

... HUMAN CONSUMPTION CURRENT GOOD MANUFACTURING PRACTICE IN MANUFACTURING, PACKING, OR HOLDING HUMAN FOOD... manufacturing systems, including gravimetric, pneumatic, closed, and automated systems, shall be of a design and...

21 CFR 110.40 - Equipment and utensils.

Code of Federal Regulations, 2012 CFR

2012-04-01

... HUMAN CONSUMPTION CURRENT GOOD MANUFACTURING PRACTICE IN MANUFACTURING, PACKING, OR HOLDING HUMAN FOOD... manufacturing systems, including gravimetric, pneumatic, closed, and automated systems, shall be of a design and...

21 CFR 110.40 - Equipment and utensils.

Code of Federal Regulations, 2014 CFR

2014-04-01

... HUMAN CONSUMPTION CURRENT GOOD MANUFACTURING PRACTICE IN MANUFACTURING, PACKING, OR HOLDING HUMAN FOOD... manufacturing systems, including gravimetric, pneumatic, closed, and automated systems, shall be of a design and...

21 CFR 110.40 - Equipment and utensils.

Code of Federal Regulations, 2010 CFR

2010-04-01

... HUMAN CONSUMPTION CURRENT GOOD MANUFACTURING PRACTICE IN MANUFACTURING, PACKING, OR HOLDING HUMAN FOOD... manufacturing systems, including gravimetric, pneumatic, closed, and automated systems, shall be of a design and...

The Pack Method for Compressive Tests of Thin Specimens of Materials Used in Thin-Wall Structures

NASA Technical Reports Server (NTRS)

Aitchison, C S; Tuckerman, L B

1939-01-01

The strength of modern lightweight thin-wall structures is generally limited by the strength of the compression members. An adequate design of these members requires a knowledge of the compressive stress-strain graph of the thin-wall material. The "pack" method was developed at the National Bureau of Standards with the support of the National Advisory Committee for Aeronautics to make possible a determination of compressive stress-strain graphs for such material. In the pack test an odd number of specimens are assembled into a relatively stable pack, like a "pack of cards." Additional lateral stability is obtained from lateral supports between the external sheet faces of the pack and outside reactions. The tests seems adequate for many problems in structural research.

Standard atomic volumes in double-stranded DNA and packing in protein–DNA interfaces

PubMed Central

Nadassy, Katalin; Tomás-Oliveira, Isabel; Alberts, Ian; Janin, Joël; Wodak, Shoshana J.

2001-01-01

Standard volumes for atoms in double-stranded B-DNA are derived using high resolution crystal structures from the Nucleic Acid Database (NDB) and compared with corresponding values derived from crystal structures of small organic compounds in the Cambridge Structural Database (CSD). Two different methods are used to compute these volumes: the classical Voronoi method, which does not depend on the size of atoms, and the related Radical Planes method which does. Results show that atomic groups buried in the interior of double-stranded DNA are, on average, more tightly packed than in related small molecules in the CSD. The packing efficiency of DNA atoms at the interfaces of 25 high resolution protein–DNA complexes is determined by computing the ratios between the volumes of interfacial DNA atoms and the corresponding standard volumes. These ratios are found to be close to unity, indicating that the DNA atoms at protein–DNA interfaces are as closely packed as in crystals of B-DNA. Analogous volume ratios, computed for buried protein atoms, are also near unity, confirming our earlier conclusions that the packing efficiency of these atoms is similar to that in the protein interior. In addition, we examine the number, volume and solvent occupation of cavities located at the protein–DNA interfaces and compared them with those in the protein interior. Cavities are found to be ubiquitous in the interfaces as well as inside the protein moieties. The frequency of solvent occupation of cavities is however higher in the interfaces, indicating that those are more hydrated than protein interiors. Lastly, we compare our results with those obtained using two different measures of shape complementarity of the analysed interfaces, and find that the correlation between our volume ratios and these measures, as well as between the measures themselves, is weak. Our results indicate that a tightly packed environment made up of DNA, protein and solvent atoms plays a significant role in protein–DNA recognition. PMID:11504874

Grain neighbour effects on twin transmission in hexagonal close-packed materials

NASA Astrophysics Data System (ADS)

Arul Kumar, M.; Beyerlein, I. J.; McCabe, R. J.; Tomé, C. N.

2016-12-01

Materials with a hexagonal close-packed (hcp) crystal structure such as Mg, Ti and Zr are being used in the transportation, aerospace and nuclear industry, respectively. Material strength and formability are critical qualities for shaping these materials into parts and a pervasive deformation mechanism that significantly affects their formability is deformation twinning. The interaction between grain boundaries and twins has an important influence on the deformation behaviour and fracture of hcp metals. Here, statistical analysis of large data sets reveals that whether twins transmit across grain boundaries depends not only on crystallography but also strongly on the anisotropy in crystallographic slip. We show that increases in crystal plastic anisotropy enhance the probability of twin transmission by comparing the relative ease of twin transmission in hcp materials such as Mg, Zr and Ti.

Coverage Dependent Assembly of Anthraquinone on Au(111)

NASA Astrophysics Data System (ADS)

Conrad, Brad; Deloach, Andrew; Einstein, Theodore; Dougherty, Daniel

A study of adsorbate-adsorbate and surface state mediated interactions of anthraquinone (AnQ) on Au(111) is presented. We utilize scanning tunneling microscopy (STM) to characterize the coverage dependence of AnQ structure formation. Ordered structures are observed up to a single monolayer (ML) and are found to be strongly dependent on molecular surface density. While the complete ML forms a well-ordered close-packed layer, for a narrow range of sub-ML coverages irregular close-packed islands are observed to coexist with a disordered pore network linking neighboring islands. This network displays a characteristic pore size and at lower coverages, the soliton walls of the herringbone reconstruction are shown to promote formation of distinct pore nanostructures. We will discuss these nanostructure formations in the context of surface mediated and more direct adsorbate interactions.

Grain neighbour effects on twin transmission in hexagonal close-packed materials.

PubMed

Arul Kumar, M; Beyerlein, I J; McCabe, R J; Tomé, C N

2016-12-19

Materials with a hexagonal close-packed (hcp) crystal structure such as Mg, Ti and Zr are being used in the transportation, aerospace and nuclear industry, respectively. Material strength and formability are critical qualities for shaping these materials into parts and a pervasive deformation mechanism that significantly affects their formability is deformation twinning. The interaction between grain boundaries and twins has an important influence on the deformation behaviour and fracture of hcp metals. Here, statistical analysis of large data sets reveals that whether twins transmit across grain boundaries depends not only on crystallography but also strongly on the anisotropy in crystallographic slip. We show that increases in crystal plastic anisotropy enhance the probability of twin transmission by comparing the relative ease of twin transmission in hcp materials such as Mg, Zr and Ti.

Dynamic Properties of DNA-Programmable Nanoparticle Crystallization.

PubMed

Yu, Qiuyan; Zhang, Xuena; Hu, Yi; Zhang, Zhihao; Wang, Rong

2016-08-23

The dynamics of DNA hybridization is very important in DNA-programmable nanoparticle crystallization. Here, coarse-grained molecular dynamics is utilized to explore the structural and dynamic properties of DNA hybridizations for a self-complementary DNA-directed nanoparticle self-assembly system. The hexagonal close-packed (HCP) and close-packed face-centered cubic (FCC) ordered structures are identified for the systems of different grafted DNA chains per nanoparticle, which are in good agreement with the experimental results. Most importantly, the dynamic crystallization processes of DNA hybridizations are elucidated by virtue of the mean square displacement, the percentage of hybridizations, and the lifetime of DNA bonds. The lifetime can be modeled by the DNA dehybridization, which has an exponential form. The lifetime of DNA bonds closely depends on the temperature. A suitable temperature for the DNA-nanoparticle crystallization is obtained in the work. Moreover, a too large volume fraction hinders the self-assembly process due to steric effects. This work provides some essential information for future design of nanomaterials.

How does increasingly plainer cigarette packaging influence adult smokers’ perceptions about brand image? An experimental study

PubMed Central

Wakefield, M A; Germain, D; Durkin, S J

2008-01-01

Background: Cigarette packaging is a key marketing strategy for promoting brand image. Plain packaging has been proposed to limit brand image, but tobacco companies would resist removal of branding design elements. Method: A 3 (brand types) × 4 (degree of plain packaging) between-subject experimental design was used, using an internet online method, to expose 813 adult Australian smokers to one randomly selected cigarette pack, after which respondents completed ratings of the pack. Results: Compared with current cigarette packs with full branding, cigarette packs that displayed progressively fewer branding design elements were perceived increasingly unfavourably in terms of smokers’ appraisals of the packs, the smokers who might smoke such packs, and the inferred experience of smoking a cigarette from these packs. For example, cardboard brown packs with the number of enclosed cigarettes displayed on the front of the pack and featuring only the brand name in small standard font at the bottom of the pack face were rated as significantly less attractive and popular than original branded packs. Smokers of these plain packs were rated as significantly less trendy/stylish, less sociable/outgoing and less mature than smokers of the original pack. Compared with original packs, smokers inferred that cigarettes from these plain packs would be less rich in tobacco, less satisfying and of lower quality tobacco. Conclusion: Plain packaging policies that remove most brand design elements are likely to be most successful in removing cigarette brand image associations. PMID:18827035

How does increasingly plainer cigarette packaging influence adult smokers' perceptions about brand image? An experimental study.

PubMed

Wakefield, M A; Germain, D; Durkin, S J

2008-12-01

Cigarette packaging is a key marketing strategy for promoting brand image. Plain packaging has been proposed to limit brand image, but tobacco companies would resist removal of branding design elements. A 3 (brand types) x 4 (degree of plain packaging) between-subject experimental design was used, using an internet online method, to expose 813 adult Australian smokers to one randomly selected cigarette pack, after which respondents completed ratings of the pack. Compared with current cigarette packs with full branding, cigarette packs that displayed progressively fewer branding design elements were perceived increasingly unfavourably in terms of smokers' appraisals of the packs, the smokers who might smoke such packs, and the inferred experience of smoking a cigarette from these packs. For example, cardboard brown packs with the number of enclosed cigarettes displayed on the front of the pack and featuring only the brand name in small standard font at the bottom of the pack face were rated as significantly less attractive and popular than original branded packs. Smokers of these plain packs were rated as significantly less trendy/stylish, less sociable/outgoing and less mature than smokers of the original pack. Compared with original packs, smokers inferred that cigarettes from these plain packs would be less rich in tobacco, less satisfying and of lower quality tobacco. Plain packaging policies that remove most brand design elements are likely to be most successful in removing cigarette brand image associations.

Effects of first exposure to plain cigarette packaging on smoking behaviour and attitudes: a randomised controlled study.

PubMed

Maynard, Olivia M; Leonards, Ute; Attwood, Angela S; Bauld, Linda; Hogarth, Lee; Munafò, Marcus R

2015-03-13

Plain packaging requires tobacco products to be sold in packs with a standard shape, method of opening and colour, leaving the brand name in a standard font and location. We ran a randomised controlled trial to investigate the impact of plain packaging on smoking behaviour and attitudes. In a parallel group randomised trial design, 128 daily smokers smoked cigarettes from their usual UK brand, or a plain Australian brand that was closely matched to their usual UK brand for 24 hours. Primary outcomes were number of cigarettes smoked and volume of smoke inhaled per cigarette. Secondary outcomes were self-reported ratings of motivation to quit, cigarette taste, experience of using the pack, experience of smoking, attributes of the pack, perceptions of the health warning, changes in smoking behaviour, and views on plain packaging. There was no evidence that pack type had an effect on either of the primary measures (ps > 0.279). However, smokers using plain cigarette packs rated the experience of using the pack more negatively (-0.52, 95% CI -0.82 to -0.22, p = 0.001), rated the pack attributes more negatively (-1.59, 95% CI -1.80 to -1.39, p < 0.001), and rated the health warning as more impactful (+0.51, 95% CI 0.24 to 0.78, p < 0.001). Plain cigarette packs reduce ratings of the experience of using the cigarette pack, and ratings of the pack attributes, and increase the self-perceived impact of the health warning, but do not change smoking behaviour, at least in the short term. Current Controlled Trials ISRCTN52982308. Registered 27 June 2013.

Software For Nearly Optimal Packing Of Cargo

NASA Technical Reports Server (NTRS)

Fennel, Theron R.; Daughtrey, Rodney S.; Schwaab, Doug G.

1994-01-01

PACKMAN computer program used to find nearly optimal arrangements of cargo items in storage containers, subject to such multiple packing objectives as utilization of volumes of containers, utilization of containers up to limits on weights, and other considerations. Automatic packing algorithm employed attempts to find best positioning of cargo items in container, such that volume and weight capacity of container both utilized to maximum extent possible. Written in Common LISP.

Notes on the ExactPack Implementation of the DSD Explosive Arc Solver

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

Kaul, Ann; Doebling, Scott William

It has been shown above that the discretization scheme implemented in the ExactPack solver for the DSD Explosive Arc equation is consistent with the Explosive Arc PDE. In addition, a stability analysis has provided a CFL condition for a stable time step. Together, consistency and stability imply convergence of the scheme, which is expected to be close to first-order in time and second-order in space. It is understood that the nonlinearity of the underlying PDE will affect this rate somewhat.

Close packing of rods on spherical surfaces

NASA Astrophysics Data System (ADS)

Smallenburg, Frank; Löwen, Hartmut

2016-04-01

We study the optimal packing of short, hard spherocylinders confined to lie tangential to a spherical surface, using simulated annealing and molecular dynamics simulations. For clusters of up to twelve particles, we map out the changes in the geometry of the closest-packed configuration as a function of the aspect ratio L/D, where L is the cylinder length and D the diameter of the rods. We find a rich variety of cluster structures. For larger clusters, we find that the best-packed configurations up to around 100 particles are highly dependent on the exact number of particles and aspect ratio. For even larger clusters, we find largely disordered clusters for very short rods (L/D = 0.25), while slightly longer rods (L/D = 0.5 or 1) prefer a global baseball-like geometry of smectic-like domains, similar to the behavior of large-scale nematic shells. Intriguingly, we observe that when compared to their optimal flat-plane packing, short rods adapt to the spherical geometry more efficiently than both spheres and longer rods. Our results provide predictions for experimentally realizable systems of colloidal rods trapped at the interface of emulsion droplets.

Tropomodulin1 is required for membrane skeleton organization and hexagonal geometry of fiber cells in the mouse lens

PubMed Central

Nowak, Roberta B.; Fischer, Robert S.; Zoltoski, Rebecca K.; Kuszak, Jerome R.

2009-01-01

Hexagonal packing geometry is a hallmark of close-packed epithelial cells in metazoans. Here, we used fiber cells of the vertebrate eye lens as a model system to determine how the membrane skeleton controls hexagonal packing of post-mitotic cells. The membrane skeleton consists of spectrin tetramers linked to actin filaments (F-actin), which are capped by tropomodulin1 (Tmod1) and stabilized by tropomyosin (TM). In mouse lenses lacking Tmod1, initial fiber cell morphogenesis is normal, but fiber cell hexagonal shapes and packing geometry are not maintained as fiber cells mature. Absence of Tmod1 leads to decreased γTM levels, loss of F-actin from membranes, and disrupted distribution of β2-spectrin along fiber cell membranes. Regular interlocking membrane protrusions on fiber cells are replaced by irregularly spaced and misshapen protrusions. We conclude that Tmod1 and γTM regulation of F-actin stability on fiber cell membranes is critical for the long-range connectivity of the spectrin–actin network, which functions to maintain regular fiber cell hexagonal morphology and packing geometry. PMID:19752024

Imaging of drug smuggling by body packing.

PubMed

Sica, Giacomo; Guida, Franco; Bocchini, Giorgio; Iaselli, Francesco; Iadevito, Isabella; Scaglione, Mariano

2015-02-01

Body packing, pushing, and stuffing are hazardous practices with complex medicolegal and social implications. A radiologist plays both a social and a medicolegal role in their assessment, and it should not be limited only to the identification of the packages but must also provide accurate information about their number and their exact location so as to prevent any package remains in the body packer. Radiologists must also be able to recognize the complications associated with these risky practices. Imaging assessment of body packing is performed essentially through plain abdominal X-ray and computed tomography scans. Ultrasound and magnetic resonance imaging, although with some advantages, actually have a limited use. Copyright © 2014 Elsevier Inc. All rights reserved.

Valve stem and packing assembly

DOEpatents

Wordin, J.J.

1991-09-03

A valve stem and packing assembly is provided in which a rotatable valve stem includes a first tractrix surface for sliding contact with a stem packing and also includes a second tractrix surface for sliding contact with a bonnet. Force is applied by means of a spring, gland flange, and gland on the stem packing so the stem packing seals to the valve stem and bonnet. This configuration serves to create and maintain a reliable seal between the stem packing and the valve stem. The bonnet includes a second complementary tractrix surface for contacting the second sliding tractrix surface, the combination serving as a journal bearing for the entire valve stem and packing assembly. The journal bearing so configured is known as a Schiele's pivot. The Schiele's pivot also serves to maintain proper alignment of the valve stem with respect to the bonnet. Vertical wear between the surfaces of the Schiele's pivot is uniform at all points of contact between the second sliding tractrix surface and the second complementary tractrix surface of a bonnet. The valve stem is connected to a valve plug by means of a slip joint. The valve is opened and closed by rotating the valve stem. The slip joint compensates for wear on the Schiele's pivot and on the valve plug. A ledge is provided on the valve bonnet for the retaining nut to bear against. The ledge prevents over tightening of the retaining nut and the resulting excessive friction between stem and stem packing. 2 figures.

Valve stem and packing assembly

DOEpatents

Wordin, John J.

1991-01-01

A valve stem and packing assembly is provided in which a rotatable valve stem includes a first tractrix surface for sliding contact with a stem packing and also includes a second tractrix surface for sliding contact with a bonnet. Force is applied by means of a spring, gland flange, and gland on the stem packing so the stem packing seals to the valve stem and bonnet. This configuration serves to create and maintain a reliable seal between the stem packing and the valve stem. The bonnet includes a second complementary tractrix surface for contacting the second sliding tractrix surface, the combination serving as a journal bearing for the entire valve stem and packing assembly. The journal bearing so configured is known as a Schiele's pivot. The Schiele's pivot also serves to maintain proper alignment of the valve stem with respect to the bonnet. Vertical wear between the surfaces of the Schiele's pivot is uniform at all points of contact between the second sliding tractrix surface and the second complementary tractrix surface of a bonnet. The valve stem is connected to a valve plug by means of a slip joint. The valve is opened and closed by rotating the valve stem. The slip joint compensates for wear on the Schiele's pivot and on the valve plug. A ledge is provided on the valve bonnet for the retaining nut to bear against. The ledge prevents overtightening of the retaining nut and the resulting excessive friction between stem and stem packing.

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

NASA Astrophysics Data System (ADS)

Skripnyak, Vladimir

2012-03-01

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

Design of an ammonia closed-loop storage system in a CSP power plant with a power tower cavity receiver

NASA Astrophysics Data System (ADS)

Abdiwe, Ramadan; Haider, Markus

2017-06-01

In this study the thermochemical system using ammonia as energy storage carrier is investigated and a transient mathematical model using MATLAB software was developed to predict the behavior of the ammonia closed-loop storage system including but not limited to the ammonia solar reactor and the ammonia synthesis reactor. The MATLAB model contains transient mass and energy balances as well as chemical equilibrium model for each relevant system component. For the importance of the dissociation and formation processes in the system, a Computational Fluid Dynamics (CFD) simulation on the ammonia solar and synthesis reactors has been performed. The CFD commercial package FLUENT is used for the simulation study and all the important mechanisms for packed bed reactors are taken into account, such as momentum, heat and mass transfer, and chemical reactions. The FLUENT simulation reveals the profiles inside both reactors and compared them with the profiles from the MATLAB code.

Understanding the Impact of Model Surfactants on Cloud Condensation Nuclei Activity of Sea Spray Aerosols

NASA Astrophysics Data System (ADS)

Forestieri, S.; Cappa, C. D.; Ruehl, C. R.; Bertram, T. H.; Staudt, S.; Kuborn, T.

2017-12-01

Aerosol impacts on cloud properties, also known as indirect effects, remain a major source of uncertainty in modeling global radiative forcing. Reducing this uncertainty necessitates better understanding of how aerosol chemical composition impacts the cloud-forming ability of aerosols. The presence of surfactants in aerosols can decrease the surface tension of activating droplets relative to water and lead to more efficient activation. The importance of this effect has been debated, but recent surface tension measurements of microscopic droplets indicate that surface tension is substantially depressed relative to water for lab-generated particles consisting of salt and a single organic species and for complex mixtures of organic matter. However, little work has been done on understanding how chemical complexity (i.e. interaction between different surfactant species) impacts surface tension for particles containing mixtures of surfactants. In this work, we quantified the surface tension of lab-generated aerosols containing surfactants that are commonly found in nascent sea spray aerosol (SSA) at humidities close to activation using a continuous flow stream-wise thermal gradient chamber (CFSTGC). Surface tension was quantified for particles containing single surfactant species and mixtures of these surfactants to investigate the role of chemical complexity on surface tension and molecular packing at the air-water interface. For all surfactants tested in this study, substantial surface tension depression (20-40 mN/m) relative to water was observed for particles containing large fractions of organic matter at humidities just below activation. However, the presence of these surfactants only weakly depressed surface tension at activation. Kinetic limitations were observed for particles coated with just palmitic acid, since palmitic acid molecules inhibit water uptake through their ability to pack tightly at the surface. However, these kinetic limitations disappeared when palmitic acid was mixed with oleic acid, indicating a disruption in packing. The impact of oxidation on droplet surface tension will also be discussed.

Simulation of lithium ion battery replacement in a battery pack for application in electric vehicles

NASA Astrophysics Data System (ADS)

Mathew, M.; Kong, Q. H.; McGrory, J.; Fowler, M.

2017-05-01

The design and optimization of the battery pack in an electric vehicle (EV) is essential for continued integration of EVs into the global market. Reconfigurable battery packs are of significant interest lately as they allow for damaged cells to be removed from the circuit, limiting their impact on the entire pack. This paper provides a simulation framework that models a battery pack and examines the effect of replacing damaged cells with new ones. The cells within the battery pack vary stochastically and the performance of the entire pack is evaluated under different conditions. The results show that by changing out cells in the battery pack, the state of health of the pack can be consistently maintained above a certain threshold value selected by the user. In situations where the cells are checked for replacement at discrete intervals, referred to as maintenance event intervals, it is found that the length of the interval is dependent on the mean time to failure of the individual cells. The simulation framework as well as the results from this paper can be utilized to better optimize lithium ion battery pack design in EVs and make long term deployment of EVs more economically feasible.

Diffusion NMR methods applied to xenon gas for materials study

NASA Technical Reports Server (NTRS)

Mair, R. W.; Rosen, M. S.; Wang, R.; Cory, D. G.; Walsworth, R. L.

2002-01-01

We report initial NMR studies of (i) xenon gas diffusion in model heterogeneous porous media and (ii) continuous flow laser-polarized xenon gas. Both areas utilize the pulsed gradient spin-echo (PGSE) techniques in the gas phase, with the aim of obtaining more sophisticated information than just translational self-diffusion coefficients--a brief overview of this area is provided in the Introduction. The heterogeneous or multiple-length scale model porous media consisted of random packs of mixed glass beads of two different sizes. We focus on observing the approach of the time-dependent gas diffusion coefficient, D(t) (an indicator of mean squared displacement), to the long-time asymptote, with the aim of understanding the long-length scale structural information that may be derived from a heterogeneous porous system. We find that D(t) of imbibed xenon gas at short diffusion times is similar for the mixed bead pack and a pack of the smaller sized beads alone, hence reflecting the pore surface area to volume ratio of the smaller bead sample. The approach of D(t) to the long-time limit follows that of a pack of the larger sized beads alone, although the limiting D(t) for the mixed bead pack is lower, reflecting the lower porosity of the sample compared to that of a pack of mono-sized glass beads. The Pade approximation is used to interpolate D(t) data between the short- and long-time limits. Initial studies of continuous flow laser-polarized xenon gas demonstrate velocity-sensitive imaging of much higher flows than can generally be obtained with liquids (20-200 mm s-1). Gas velocity imaging is, however, found to be limited to a resolution of about 1 mm s-1 owing to the high diffusivity of gases compared with liquids. We also present the first gas-phase NMR scattering, or diffusive-diffraction, data, namely flow-enhanced structural features in the echo attenuation data from laser-polarized xenon flowing through a 2 mm glass bead pack. c2002 John Wiley & Sons, Ltd.

An Engineering Evaluation of Spherical Resorcinol Formaldehyde Resin

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

Birdwell Jr, Joseph F; Lee, Denise L; Taylor, Paul Allen

2010-09-01

A small column ion exchange (SCIX) system has been proposed for removal of cesium from caustic, supernatant, and dissolved salt solutions stored or generated from high-level tank wastes at the US Department of Energy (DOE) Hanford Site and Savannah River Sites. In both instances, deployment of SCIX systems, either in-tank or near-tank, is a means of expediting waste pretreatment and dispositioning with minimal or no new infrastructure requirements. Conceptually, the treatment approach can utilize a range of ion exchange media. Previously, both crystalline silicotitanate (CST), an inorganic, nonelutable sorbent, and resorcinol-formaldehyde (RF), an organic, elutable resin, have been considered formore » cesium removal from tank waste. More recently, Pacific Northwest National Laboratory (PNNL) evaluated use of SuperLig{reg_sign} 644, an elutable ion exchange medium, for the subject application. Results of testing indicate hydraulic limitations of the SuperLig{reg_sign} resin, specifically a high pressure drop through packed ion exchange columns. This limitation is likely the result of swelling and shrinkage of the irregularly shaped (granular) resin during repeated conversions between sodium and hydrogen forms as the resin is first loaded then eluted. It is anticipated that a similar flow limitation would exist in columns packed with conventional, granular RF resin. However, use of spherical RF resin is a likely means of mitigating processing limitations due to excessive pressure drop. Although size changes occur as the spherical resin is cycled through loading and elution operations, the geometry of the resin is expected to effectively mitigate the close packing that leads to high pressure drops across ion exchange columns. Multiple evaluations have been performed to determine the feasibility of using spherical RF resin and to obtain data necessary for design of an SCIX process. The work performed consisted of examination of radiation effects on resin performance, quantification of cesium adsorption performance as a function of operating temperature and pH, and evaluation of sodium uptake (titration) as function of pH and counteranion concentration. The results of these efforts are presented in this report. Hydraulic performance of the resin and the use of eluant alternatives to nitric acid have also been evaluated and have been reported elsewhere (Taylor 2009, Taylor and Johnson 2009).« less

Tuning jammed frictionless disk packings from isostatic to hyperstatic.

PubMed

Schreck, Carl F; O'Hern, Corey S; Silbert, Leonardo E

2011-07-01

We perform extensive computational studies of two-dimensional static bidisperse disk packings using two distinct packing-generation protocols. The first involves thermally quenching equilibrated liquid configurations to zero temperature over a range of thermal quench rates r and initial packing fractions followed by compression and decompression in small steps to reach packing fractions φ(J) at jamming onset. For the second, we seed the system with initial configurations that promote micro- and macrophase-separated packings followed by compression and decompression to φ(J). Using these protocols, we generate more than 10(4) static packings over a wide range of packing fraction, contact number, and compositional and positional order. We find that disordered, isostatic packings exist over a finite range of packing fractions in the large-system limit. In agreement with previous calculations, the most dilute mechanically stable packings with φ min ≈ 0.84 are obtained for r > r*, where r* is the rate above which φ(J) is insensitive to rate. We further compare the structural and mechanical properties of isostatic versus hyperstatic packings. The structural characterizations include the contact number, several order parameters, and mixing ratios of the large and small particles. We find that the isostatic packings are positionally and compositionally disordered (with only small changes in a number of order parameters), whereas bond-orientational and compositional order increase strongly with contact number for hyperstatic packings. In addition, we calculate the static shear modulus and normal mode frequencies (in the harmonic approximation) of the static packings to understand the extent to which the mechanical properties of disordered, isostatic packings differ from partially ordered packings. We find that the mechanical properties of the packings change continuously as the contact number increases from isostatic to hyperstatic.

Transmission spectra changes produced by decreasing compactness of opal-like structures

NASA Astrophysics Data System (ADS)

Andueza, A.; Echeverría, R.; Morales, P.; Sevilla, J.

2009-01-01

Artificial opal-like structures based on spheres and colloidal particles have been fabricated in a controlled way, presenting optical band-gap properties in the optical frequency range. Nonclose packed artificial opals have also been fabricated and studied recently. In order to gain a better understanding of these phenomena, we have studied macroscopic models of nonclose packed fcc lattices using glass spheres (ɛ =7) of 8 mm diameter, and measuring in the microwave region (from 10 to 30 GHz). The results have shown a Bragg resonance tunable with filling factor of the opal, and a strong rejected band similar, also present in close packed samples, much less affected by compactness. The relation of this high order band with spheres single layer behavior is also discussed.

Ellipsoids beat Spheres: Experiments with Candies, Colloids and Crystals

NASA Astrophysics Data System (ADS)

Chaikin, Paul

2006-04-01

How many gumballs fit in the glass sphere of a gumball machine? Scientists have been puzzling over problems like this since the Ancient Greeks. Yet it was only recently proven that the standard way of stacking oranges at a grocery store--with one orange on top of each set of three below--is the densist packing for spheres, with a packing fraction φ˜ 0.74. Random (amorphous) packings of spheres have a lower density, with φ ˜0.64. The density of crystalline and random packings of atoms is intimately related to the melting transition in matter. We have studied the crystal-liquid transition in spherical colloidal systems on earth and in microgravity. The simplest objects to study after spheres are squashed spheres -- ellipsoids. Surprisingly we find that ellipsoids can randomly pack more densely than spheres, up to φ˜0.68 - 0.71 for a shape close to that of M&M's^ Candies, and even approach φ˜0.75 for general ellipsoids. The higher density relates directly to the higher number of neighbors needed to prevent the more asymetric ellipsoid from rotating. We have also found the ellipsoids can be packed in a crystalline array to a density, φ˜.7707 which exceeds the highest previous packing. Our findings provide insights into granular materials, rigidity, crystals and glasses, and they may lead to higher quality ceramic materials.

Simulation of the inhibition of microbial sulfate reduction in a two-compartment upflow bioreactor subjected to molybdate injection.

PubMed

de Jesus, E B; de Andrade Lima, L R P

2016-08-01

Souring of oil fields during secondary oil recovery by water injection occurs mainly due to the action of sulfate-reducing bacteria (SRB) adhered to the rock surface in the vicinity of injection wells. Upflow packed-bed bioreactors have been used in petroleum microbiology because of its similarity to the oil field near the injection wells or production. However, these reactors do not realistically describe the regions near the injection wells, which are characterized by the presence of a saturated zone and a void region close to the well. In this study, the hydrodynamics of the two-compartment packing-free/packed-bed pilot bioreactor that mimics an oil reservoir was studied. The packed-free compartment was modeled using a continuous stirred tank model with mass exchange between active and stagnant zones, whereas the packed-bed compartment was modeled using a piston-dispersion-exchange model. The proposed model adequately represents the hydrodynamic of the packed-free/packed-bed bioreactor while the simulations provide important information about the characteristics of the residence time distribution (RTD) curves for different sets of model parameters. Simulations were performed to represent the control of the sulfate-reducing bacteria activity in the bioreactor with the use of molybdate in different scenarios. The simulations show that increased amounts of molybdate cause an effective inhibition of the souring sulfate-reducing bacteria activity.

Effects of lead structure in Bering Sea pack ice on the flight costs of wintering spectacled eiders

NASA Astrophysics Data System (ADS)

Bump, Joseph K.; Lovvorn, James R.

2004-10-01

In polar regions, sea ice is critical habitat for many marine birds and mammals. The quality of pack ice habitat depends on the duration and spacing of leads (openings in the ice), which determine access to water and air for diving endotherms, and how often and how far they must move as leads open and close. Recent warming trends have caused major changes in the extent and nature of sea ice at large scales used in climate models. However, no studies have analyzed lead structure in terms of habitat for ice-dependent endotherms, or effects of climate on ice habitat at scales relevant to their daily movements. Based on observations from an icebreaker and synthetic aperture radar (SAR) images, we developed methods to describe the dynamics and thermodynamics of lead structure relative to use by spectacled eiders ( Somateria fischeri) wintering in pack ice of the Bering Sea. By correlating lead structure with weather variables, we then used these methods to estimate changes in lead dynamics from 1945 to 2002, and effects of such changes on flight costs of the eiders. For 1991-1992, when images were available about every 3 days throughout winter, SAR images were divided among five weather regimes defined by wind speed, wind direction, and air temperature. Based on 12.5-m pixels, lead shape, compass orientation, and fetch across leads did not differ among the weather regimes. However, the five regimes differed in total area of open water, leads per unit area, and distance between leads. Lead duration was modeled based on air temperature, wind, and fetch. Estimates of mean daily flight time for eiders, based on lead duration and distance between neighboring leads, differed among regimes by 0 to 15 min. Resulting flight costs varied from 0 to 158 kJ day -1, or from 0% to 11% of estimated field metabolic rate. Over 57 winters (1945-2002), variation among years in mean daily flight time was most influenced by the north-south wind component, which determined pack divergence (lead opening) during northerly winds or pack convergence (lead closing) during southerly winds. Mean daily flight time and flight cost during winter did not differ among proposed periods of decadal-scale climate shifts in the North Pacific Ocean. Although leads in mobile pack ice constantly open and close with variations in wind, under most conditions in the Bering Sea there appeared to be a shifting-mosaic steady-state of lead availability. Long-term trends in the extent and timing of Bering Sea pack ice may have affected spectacled eiders more by altering foodweb processes than by changing flight costs relative to lead structure.

Eating less from bigger packs: Preventing the pack size effect with diet primes.

PubMed

Versluis, Iris; Papies, Esther K

2016-05-01

An increase in the package size of food has been shown to lead to an increase in energy intake from this food, the so-called pack size effect. Previous research has shown that providing diet-concerned individuals with a reminder, or prime, of their dieting goal can help them control their consumption. Here, we investigated if providing such a prime is also effective for reducing the magnitude of the pack size effect. We conducted two experiments in which the cover of a dieting magazine (Experiment 1) and diet-related commercials (Experiment 2) served as diet goal primes. Both experiments had a 2 (pack size: small vs. large) × 2 (prime: diet vs. control) × 2 (dietary restraint: high vs. low) between participants design. We measured expected consumption of four snack foods in Experiment 1 (N = 477), and actual consumption of M&M's in Experiment 2 (N = 224). Results showed that the diet prime reduced the pack size effect for both restrained and unrestrained eaters in Experiment 1 and for restrained eaters only in Experiment 2. Although effect sizes were small, these findings suggest that a diet prime motivates restrained eaters to limit their consumption, and as a result the pack size has less influence on the amount consumed. We discuss limitations of this research as well as potential avenues for further research and theoretical and practical implications. Copyright © 2016 Elsevier Ltd. All rights reserved.

Inverse Opal Scaffolds with Gradations in Mineral Content for Spatial Control of Osteogenesis.

PubMed

Zhu, Chunlei; Qiu, Jichuan; Pongkitwitoon, Suphannee; Thomopoulos, Stavros; Xia, Younan

2018-05-30

The design and fabrication of inverse opal scaffolds with gradations in mineral content to achieve spatial control of osteogenesis are described. The gradient in mineral content is established via the diffusion-limited transport of hydroxyapatite nanoparticles in a closely packed lattice of gelatin microbeads. The mineral-graded scaffold has an array of uniform pores and interconnected windows to facilitate efficient transport of nutrients and metabolic wastes, ensuring high cell viability. The graded distribution of mineral content can provide biochemical and mechanical cues for spatially regulating the osteogenic differentiation of adipose-derived stromal cells. This new class of scaffolds holds promise for engineering the interfaces between mineralized and unmineralized tissues. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of small floating disks on the propagation of gravity waves

NASA Astrophysics Data System (ADS)

De Santi, F.; Olla, P.

2017-04-01

A dispersion relation for gravity waves in water covered by disk-like impurities embedded in a viscous matrix is derived. The macroscopic equations are obtained by ensemble-averaging the fluid equations at the disk scale in the asymptotic limit of long waves and low disk surface fraction. Various regimes are identified depending on the disk radii and the thickness and viscosity of the top layer. Semi-quantitative analysis in the close-packing regime suggests dramatic modification of the dynamics, with orders of magnitude increase in wave damping and wave dispersion. A simplified model working in this regime is proposed. Possible applications to wave propagation in an ice-covered ocean are discussed and comparison with field data is provided.

Percolation transition in Yang-Mills matter at a finite number of colors.

PubMed

Lottini, Stefano; Torrieri, Giorgio

2011-10-07

We examine baryonic matter at a quark chemical potential of the order of the confinement scale μ(q)∼Λ(QCD). In this regime, quarks are supposed to be confined but baryons are close to the "tightly packed limit" where they nearly overlap in configuration space. We show that this system will exhibit a percolation phase transition when varied in the number of colors N(c): at high N(c), large distance correlations at the quark level are possible even if the quarks are essentially confined. At low N(c), this does not happen. We discuss the relevance of this for dense nuclear matter, and argue that our results suggest a new "phase transition," varying N(c) at constant μ(q).

Lattice softening in body-centered-cubic lithium-magnesium alloys

NASA Astrophysics Data System (ADS)

Winter, I. S.; Tsuru, T.; Chrzan, D. C.

2017-08-01

A first-principles investigation of the influence of lattice softening on lithium-magnesium alloys near the body-centered-cubic (bcc)/hexagonal close-packed (hcp) transition composition is presented. Results show that lithium-magnesium alloys display a softening of the shear modulus C11-C12 , and an acoustic phonon branch between the Γ and N high symmetry points, as the composition approaches the stability limit for the bcc phase. This softening is accompanied by an increase in the size of the dislocation core region. Ideal tensile strength calculations predict that ordered phases of lithium-magnesium alloys are intrinsically brittle. Methods to make the alloys more ductile are discussed, and the propensity for these alloys to display gum-metal-like behavior is assessed.

Lithium-Ion Battery Failure: Effects of State of Charge and Packing Configuration

DTIC Science & Technology

2016-08-22

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6180--16-9689 Lithium - Ion Battery Failure: Effects of State of Charge and Packing...PAGES 17. LIMITATION OF ABSTRACT Lithium - Ion Battery Failure: Effects of State of Charge and Packing Configuration Neil S. Spinner,* Katherine M. Hinnant...Steven G. Tuttle (202) 404-3419 Lithium - ion battery safety remains a significant concern, as battery failure leads to ejection of hazardous materials

Thioarsenides: A case for long-range Lewis acid-base-directed van der Waals interactions

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

Gibbs, Gerald V.; Wallace, Adam F.; Downs, R. T.

2011-04-01

Electron density distributions, bond paths, Laplacian and local energy density properties have been calculated for a number of As4Sn (n = 3,4,5) thioarsenide molecular crystals. On the basis of the distributions, the intramolecular As-S and As-As interactions classify as shared bonded interactions and the intermolecular As-S, As-As and S-S interactions classify as closed-shell van der Waals bonded interactions. The bulk of the intermolecular As-S bond paths link regions of locally concentrated electron density (Lewis base regions) with aligned regions of locally depleted electron density (Lewis acid regions) on adjacent molecules. The paths are comparable with intermolecular paths reported for severalmore » other molecular crystals that link aligned Lewis base and acid regions in a key-lock fashion, interactions that classified as long range Lewis acid-base directed van der Waals interactions. As the bulk of the intermolecular As-S bond paths (~70%) link Lewis acid-base regions on adjacent molecules, it appears that molecules adopt an arrangement that maximizes the number of As-S Lewis acid-base intermolecular bonded interactions. The maximization of the number of Lewis acid-base interactions appears to be connected with the close-packed array adopted by molecules: distorted cubic close-packed arrays are adopted for alacránite, pararealgar, uzonite, realgar and β-AsS and the distorted hexagonal close-packed arrays adopted by α- and β-dimorphite. A growth mechanism is proposed for thioarsenide molecular crystals from aqueous species that maximizes the number of long range Lewis acid-base vdW As-S bonded interactions with the resulting directed bond paths structuralizing the molecules as a molecular crystal.« less

2D-crystallization of Rhodococcus 20S proteasome at the liquid-liquid interface

NASA Astrophysics Data System (ADS)

Aoyama, Kazuhiro

1996-10-01

The 2D-crystallization method using the liquid-liquid interface between a aqueous phase (protein solution) and a thin organic liquid (dehydroabietylamine) layer has been applied to the Rhodococcus 20S proteasome. The 20S proteasome is known to be the core complex of the 26S proteasome, which is the central protease of the ubiquitin-dependent pathway. Two types of ordered arrays were obtained, both large enough for high resolution analysis by electron crystallography. The first one had a four-fold symmetry, whereas the second one was found out to be a hexagonally close-packed array. By image analysis based on a real space correlation averaging (CAV) technique, the close-packed array was found to be hexagonally packed, but the molecules had presumably rotational freedom. The four-fold array was found to be a true crystal with p4 symmetry. Lattice constants were a = b = 20.0 nm and α = 90°. The unit cell of this crystal contained two molecules. The diffraction pattern computed from the original picture showed spots up to (4, 5) that corresponds to 3.1 nm resolution. After applying an unbending procedure, the diffraction pattern showed spots extending to 1.8 nm resolution.

The crystal chemistry of inorganic metal borohydrides and their relation to metal oxides.

PubMed

Černý, Radovan; Schouwink, Pascal

2015-12-01

The crystal structures of inorganic homoleptic metal borohydrides are analysed with respect to their structural prototypes found amongst metal oxides in the inorganic databases such as Pearson's Crystal Data [Villars & Cenzual (2015). Pearson's Crystal Data. Crystal Structure Database for Inorganic Compounds, Release 2014/2015, ASM International, Materials Park, Ohio, USA]. The coordination polyhedra around the cations and the borohydride anion are determined, and constitute the basis of the structural systematics underlying metal borohydride chemistry in various frameworks and variants of ionic packing, including complex anions and the packing of neutral molecules in the crystal. Underlying nets are determined by topology analysis using the program TOPOS [Blatov (2006). IUCr CompComm. Newsl. 7, 4-38]. It is found that the Pauling rules for ionic crystals apply to all non-molecular borohydride crystal structures, and that the latter can often be derived by simple deformation of the close-packed anionic lattices c.c.p. and h.c.p., by partially removing anions and filling tetrahedral or octahedral sites. The deviation from an ideal close packing is facilitated in metal borohydrides with respect to the oxide due to geometrical and electronic considerations of the BH4(-) anion (tetrahedral shape, polarizability). This review on crystal chemistry of borohydrides and their similarity to oxides is a contribution which should serve materials engineers as a roadmap to design new materials, synthetic chemists in their search for promising compounds to be prepared, and materials scientists in understanding the properties of novel materials.

Close-packed structure dynamics with finite-range interaction: computational mechanics with individual layer interaction.

PubMed

Rodriguez-Horta, Edwin; Estevez-Rams, Ernesto; Lora-Serrano, Raimundo; Neder, Reinhard

2017-09-01

This is the second contribution in a series of papers dealing with dynamical models in equilibrium theories of polytypism. A Hamiltonian introduced by Ahmad & Khan [Phys. Status Solidi B (2000), 218, 425-430] avoids the unphysical assignment of interaction terms to fictitious entities given by spins in the Hägg coding of the stacking arrangement. In this paper an analysis of polytype generation and disorder in close-packed structures is made for such a Hamiltonian. Results are compared with a previous analysis using the Ising model. Computational mechanics is the framework under which the analysis is performed. The competing effects of disorder and structure, as given by entropy density and excess entropy, respectively, are discussed. It is argued that the Ahmad & Khan model is simpler and predicts a larger set of polytypes than previous treatments.

Frequency dependent ac transport of films of close-packed carbon nanotube arrays

NASA Astrophysics Data System (ADS)

Endo, A.; Katsumoto, S.; Matsuda, K.; Norimatsu, W.; Kusunoki, M.

2018-03-01

We have measured low-temperature ac impedance of films of closely-packed, highly-aligned carbon nanotubes prepared by thermal decomposition of silicon carbide wafers. The measurement was performed on films with the thickness (the length of the nanotubes) ranging from 6.5 to 65 nm. We found that the impedance rapidly decreases with the frequency. This can be interpreted as resulting from the electric transport via capacitive coupling between adjacent nanotubes. We also found numbers of sharp spikes superposed on frequency vs. impedance curves, which presumably represent resonant frequencies seen in the calculated conductivity of random capacitance networks. Capacitive coupling between the nanotubes was reduced by the magnetic field perpendicular to the films at 8.2 mK, resulting in the transition from negative to positive magnetoresistance with an increase of the frequency.

Influence of hydrogen on the stability of iron phases under pressure

NASA Astrophysics Data System (ADS)

Skorodumova, N. V.; Ahuja, R.; Johansson, B.

2004-04-01

The influence of hydrogen presence on the stability of iron phases (bcc, hcp, dhcp, fcc, simple cubic) in a wide pressure interval at 0 K has been studied by the first-principles projector augmented-wave (PAW) method. Hydrogen is shown to occupy different interstitial lattice positions depending on the type of structure and pressure. An introduction of hydrogen impurities (˜6 at. %) leads to a stabilization of the close-packed iron structures, shifting the calculated pressure of the bcc-hcp transition from ˜9 GPa for pure iron to 7 GPa for Fe (6 at. % H). This tendency is further enhanced in the iron hydride structures. The iron hydrides in the close-packed structures (hcp, dhcp, fcc) are essentially degenerate in energy and found to be most stable in the whole pressure range.

Dislocation dynamics in hexagonal close-packed crystals

DOE PAGES

Aubry, S.; Rhee, M.; Hommes, G.; ...

2016-04-14

Extensions of the dislocation dynamics methodology necessary to enable accurate simulations of crystal plasticity in hexagonal close-packed (HCP) metals are presented. They concern the introduction of dislocation motion in HCP crystals through linear and non-linear mobility laws, as well as the treatment of composite dislocation physics. Formation, stability and dissociation of and other dislocations with large Burgers vectors defined as composite dislocations are examined and a new topological operation is proposed to enable their dissociation. Furthermore, the results of our simulations suggest that composite dislocations are omnipresent and may play important roles both in specific dislocation mechanisms and in bulkmore » crystal plasticity in HCP materials. While fully microscopic, our bulk DD simulations provide wealth of data that can be used to develop and parameterize constitutive models of crystal plasticity at the mesoscale.« less

3D-Printed Broadband Dielectric Tube Terahertz Waveguide with Anti-Reflection Structure

NASA Astrophysics Data System (ADS)

Vogt, Dominik Walter; Leonhardt, Rainer

2016-11-01

We demonstrate broadband, low loss, and close-to-zero dispersion guidance of terahertz (THz) radiation in a dielectric tube with an anti-reflection structure (AR-tube waveguide) in the frequency range from 0.2 to 1.0 THz. The anti-reflection structure (ARS) consists of close-packed cones in a hexagonal lattice arranged on the outer surface of the tube cladding. The feature size of the ARS is in the order of the wavelength between 0.2 and 1.0 THz. The waveguides are fabricated with the versatile and cost efficient 3D-printing method. Terahertz time-domain spectroscopy (THz-TDS) measurements as well as 3D finite-difference time-domain simulations (FDTD) are performed to extensively characterize the AR-tube waveguides. Spectrograms, attenuation spectra, effective phase refractive indices, and the group-velocity dispersion parameters β 2 of the AR-tube waveguides are presented. Both the experimental and numerical results confirm the extended bandwidth and smaller group-velocity dispersion of the AR-tube waveguide compared to a low loss plain dielectric tube THz waveguide. The AR-tube waveguide prototypes show an attenuation spectrum close to the theoretical limit given by the infinite cladding tube waveguide.

Approximate transient and long time limit solutions for the band broadening induced by the thin sidewall-layer in liquid chromatography columns.

PubMed

Broeckhoven, Ken; Desmet, Gert

2007-11-16

Using a combination of both analytical and numerical techniques, approximate analytical expressions have been established for the transient and long time limit band broadening, originating from the presence of a thin disturbed sidewall layer in liquid chromatography columns, including packed, monolithic as well as microfabricated columns. The established expressions can be used to compare the importance of a thin disturbed sidewall layer with that of other radial heterogeneity effects (such as transcolumn packing density variations due to the relief of packing stresses). The expressions are independent of the actual velocity profile inside the layer as long as the disturbed sidewall layer occupies less than 2.5% of the column width.

The silent salesman: an observational study of personal tobacco pack display at outdoor café strips in Australia.

PubMed

Wakefield, Melanie A; Zacher, Meghan; Bayly, Megan; Brennan, Emily; Dono, Joanne; Miller, Caroline; Durkin, Sarah J; Scollo, Michelle M

2014-07-01

We sought to determine the relative frequency and nature of personal display of cigarette packs by smokers in two Australian cities where 30% front-of-pack and 90% back-of-pack health warnings have been used since 2006 and comprehensive tobacco marketing restrictions apply. An observational study counted patrons, active smokers and tobacco packs at cafés, restaurants and bars with outdoor seating. Pack orientation and use of cigarette cases were also noted. Overall, 18954 patrons, 1576 active smokers and 2153 packs were observed, meaning that one out of every 12.0 patrons was actively smoking, and one of every 8.8 patrons displayed a pack. Packs were more frequently observed in lower socio-economic neighbourhoods, reflecting the higher prevalence of smoking in those regions. Packs were displayed less often in venues where children were present, suggesting a greater tendency not to smoke around children. Most packs (81.4%) were oriented face-up, permitting prominent brand display. Only 1.5% of observed packs were cigarette cases, and 4.2% of packs were concealed by another item, such as a phone or wallet. Tobacco packs are frequently seen on table-tops in café strips, providing many opportunities for other patrons and passers-by to be incidentally exposed to cigarette brand names and imagery. Use of cigarette cases is rare, suggesting that smokers eventually habituate to pictorial warnings on branded packs and/or find repeated decanting of each newly purchased branded pack into a case to be inconvenient. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Crystallization of micrometer-sized particles with molecular contours.

PubMed

Song, Pengcheng; Olmsted, Brian K; Chaikin, Paul; Ward, Michael D

2013-11-12

The crystallization of micrometer-sized particles with shapes mimicking those of tetrabenzoheptacene (TBH) and 1,2:5,6-dibenzanthracene (DBT), both flat polyacenes, in an electric field results in the formation of ordered 2D packings that mimic the plane group symmetries in their respective molecular crystal equivalents. Whereas the particles packed in low-density disordered arrangements under a gravitational gradient, dielectrophoresis (under an ac electric field) produced ordered high-density packings with readily identifiable plane group symmetry. The ordered colloidal assemblies were stable for hours, with the packing density decreasing slowly but with recognizable symmetry for up to 12 h for the TBH-shaped particles and up to 4 h for the DBT-shaped particles. This unexpected stability is attributed to jamming behavior associated with interlocking of the dogbone-shaped (TBH) and Z-block (DBT) particles, contrasting with the more rapid reduction of packing density and loss of hexagonal symmetry for disk-shaped particles upon removal of the electric field. The TBH-shaped and DBT-shaped particles assemble into the p2 plane group, which corresponds to the densest particle packing among the possible close-packed plane groups for these particle symmetries. The p2 symmetry observed for the TBH-shaped and DBT-shaped colloid crystal emulates the p2 symmetry of the (010) layers in their respective molecular crystals, which crystallize in monoclinic lattices. Notably, DBT-shaped particles also form ordered domains with pgg symmetry, replicating the plane group symmetry of the (100) layer in the orthorhombic polymorph of DBT. These observations illustrate that the 2D ordering of colloid particles can mimic the packing of molecules with similar shapes, demonstrating that packing can transcend length scales from the molecular to the colloidal.

Critical role of alkyl chain branching of organic semiconductors in enabling solution-processed N-channel organic thin-film transistors with mobility of up to 3.50 cm² V(-1) s(-1).

PubMed

Zhang, Fengjiao; Hu, Yunbin; Schuettfort, Torben; Di, Chong-an; Gao, Xike; McNeill, Christopher R; Thomsen, Lars; Mannsfeld, Stefan C B; Yuan, Wei; Sirringhaus, Henning; Zhu, Daoben

2013-02-13

Substituted side chains are fundamental units in solution processable organic semiconductors in order to achieve a balance of close intermolecular stacking, high crystallinity, and good compatibility with different wet techniques. Based on four air-stable solution-processed naphthalene diimides fused with 2-(1,3-dithiol-2-ylidene)malononitrile groups (NDI-DTYM2) that bear branched alkyl chains with varied side-chain length and different branching position, we have carried out systematic studies on the relationship between film microstructure and charge transport in their organic thin-film transistors (OTFTs). In particular synchrotron measurements (grazing incidence X-ray diffraction and near-edge X-ray absorption fine structure) are combined with device optimization studies to probe the interplay between molecular structure, molecular packing, and OTFT mobility. It is found that the side-chain length has a moderate influence on thin-film microstructure but leads to only limited changes in OTFT performance. In contrast, the position of branching point results in subtle, yet critical changes in molecular packing and leads to dramatic differences in electron mobility ranging from ~0.001 to >3.0 cm(2) V(-1) s(-1). Incorporating a NDI-DTYM2 core with three-branched N-alkyl substituents of C(11,6) results in a dense in-plane molecular packing with an unit cell area of 127 Å(2), larger domain sizes of up to 1000 × 3000 nm(2), and an electron mobility of up to 3.50 cm(2) V(-1) s(-1), which is an unprecedented value for ambient stable n-channel solution-processed OTFTs reported to date. These results demonstrate that variation of the alkyl chain branching point is a powerful strategy for tuning of molecular packing to enable high charge transport mobilities.

Enzymatic synthesis of farnesyl laurate in organic solvent: initial water activity, kinetics mechanism, optimization of continuous operation using packed bed reactor and mass transfer studies.

PubMed

Rahman, N K; Kamaruddin, A H; Uzir, M H

2011-08-01

The influence of water activity and water content was investigated with farnesyl laurate synthesis catalyzed by Lipozyme RM IM. Lipozyme RM IM activity depended strongly on initial water activity value. The best results were achieved for a reaction medium with an initial water activity of 0.11 since it gives the best conversion value of 96.80%. The rate constants obtained in the kinetics study using Ping-Pong-Bi-Bi and Ordered-Bi-Bi mechanisms with dead-end complex inhibition of lauric acid were compared. The corresponding parameters were found to obey the Ordered-Bi-Bi mechanism with dead-end complex inhibition of lauric acid. Kinetic parameters were calculated based on this model as follows: V (max) = 5.80 mmol l(-1) min(-1) g enzyme(-1), K (m,A) = 0.70 mmol l(-1) g enzyme(-1), K (m,B) = 115.48 mmol l(-1) g enzyme(-1), K (i) = 11.25 mmol l(-1) g enzyme(-1). The optimum conditions for the esterification of farnesol with lauric acid in a continuous packed bed reactor were found as the following: 18.18 cm packed bed height and 0.9 ml/min substrate flow rate. The optimum molar conversion of lauric acid to farnesyl laurate was 98.07 ± 0.82%. The effect of mass transfer in the packed bed reactor has also been studied using two models for cases of reaction limited and mass transfer limited. A very good agreement between the mass transfer limited model and the experimental data obtained indicating that the esterification in a packed bed reactor was mass transfer limited.

Variation of Cone Photoreceptor Packing Density with Retinal Eccentricity and Age

PubMed Central

Song, Hongxin; Chui, Toco Yuen Ping; Zhong, Zhangyi; Elsner, Ann E.

2011-01-01

Purpose. To study the variation of cone photoreceptor packing density across the retina in healthy subjects of different ages. Methods. High-resolution adaptive optics scanning laser ophthalmoscope (AOSLO) systems were used to systematically image the retinas of two groups of subjects of different ages. Ten younger subjects (age range, 22–35 years) and 10 older subjects (age range, 50–65 years) were tested. Strips of cone photoreceptors, approximately 12° × 1.8° long were imaged for each of the four primary retinal meridians: superior, inferior, nasal, and temporal. Cone photoreceptors within the strips were counted, and cone photoreceptor packing density was calculated. Statistical analysis (three-way ANOVA) was used to calculate the interaction for cone photoreceptor packing density between age, meridian, and eccentricity. Results. As expected, cone photoreceptor packing density was higher close to the fovea and decreased with increasing retinal eccentricity from 0.18 to 3.5 mm (∼0.6–12°). Older subjects had approximately 75% of the cone density at 0.18 mm (∼0.6°), and this difference decreased rapidly with eccentricity, with the two groups having similar cone photoreceptor packing densities beyond 0.5 mm retinal eccentricity on average. Conclusions. Cone packing density in the living human retina decreases as a function of age within the foveal center with the largest difference being found at our most central measurement site. At all ages, the retina showed meridional difference in cone densities, with cone photoreceptor packing density decreasing faster with increasing eccentricity in the vertical dimensions than in the horizontal dimensions. PMID:21724911

Variation of cone photoreceptor packing density with retinal eccentricity and age.

PubMed

Song, Hongxin; Chui, Toco Yuen Ping; Zhong, Zhangyi; Elsner, Ann E; Burns, Stephen A

2011-09-01

To study the variation of cone photoreceptor packing density across the retina in healthy subjects of different ages. High-resolution adaptive optics scanning laser ophthalmoscope (AOSLO) systems were used to systematically image the retinas of two groups of subjects of different ages. Ten younger subjects (age range, 22-35 years) and 10 older subjects (age range, 50-65 years) were tested. Strips of cone photoreceptors, approximately 12° × 1.8° long were imaged for each of the four primary retinal meridians: superior, inferior, nasal, and temporal. Cone photoreceptors within the strips were counted, and cone photoreceptor packing density was calculated. Statistical analysis (three-way ANOVA) was used to calculate the interaction for cone photoreceptor packing density between age, meridian, and eccentricity. As expected, cone photoreceptor packing density was higher close to the fovea and decreased with increasing retinal eccentricity from 0.18 to 3.5 mm (∼0.6-12°). Older subjects had approximately 75% of the cone density at 0.18 mm (∼0.6°), and this difference decreased rapidly with eccentricity, with the two groups having similar cone photoreceptor packing densities beyond 0.5 mm retinal eccentricity on average. Cone packing density in the living human retina decreases as a function of age within the foveal center with the largest difference being found at our most central measurement site. At all ages, the retina showed meridional difference in cone densities, with cone photoreceptor packing density decreasing faster with increasing eccentricity in the vertical dimensions than in the horizontal dimensions.

Packing interface energetics in different crystal forms of the λ Cro dimer.

PubMed

Ahlstrom, Logan S; Miyashita, Osamu

2014-07-01

Variation among crystal structures of the λ Cro dimer highlights conformational flexibility. The structures range from a wild type closed to a mutant fully open conformation, but it is unclear if each represents a stable solution state or if one may be the result of crystal packing. Here we use molecular dynamics (MD) simulation to investigate the energetics of crystal packing interfaces and the influence of site-directed mutagenesis on them in order to examine the effect of crystal packing on wild type and mutant Cro dimer conformation. Replica exchange MD of mutant Cro in solution shows that the observed conformational differences between the wild type and mutant protein are not the direct consequence of mutation. Instead, simulation of Cro in different crystal environments reveals that mutation affects the stability of crystal forms. Molecular Mechanics Poisson-Boltzmann Surface Area binding energy calculations reveal the detailed energetics of packing interfaces. Packing interfaces can have diverse properties in strength, energetic components, and some are stronger than the biological dimer interface. Further analysis shows that mutation can strengthen packing interfaces by as much as ∼5 kcal/mol in either crystal environment. Thus, in the case of Cro, mutation provides an additional energetic contribution during crystal formation that may stabilize a fully open higher energy state. Moreover, the effect of mutation in the lattice can extend to packing interfaces not involving mutation sites. Our results provide insight into possible models for the effect of crystallization on Cro conformational dynamics and emphasize careful consideration of protein crystal structures. © 2013 Wiley Periodicals, Inc.

Packing Interface Energetics in Different Crystal Forms of the λ Cro Dimer

PubMed Central

Ahlstrom, Logan S.; Miyashita, Osamu

2014-01-01

Variation among crystal structures of the λ Cro dimer highlights conformational flexibility. The structures range from a wild type closed to a mutant fully open conformation, but it is unclear if each represents a stable solution state or if one may be the result of crystal packing. Here we use molecular dynamics (MD) simulation to investigate the energetics of crystal packing interfaces and the influence of site-directed mutagenesis on them, in order to examine the effect of crystal packing on wild type and mutant Cro dimer conformation. Replica exchange MD of mutant Cro in solution shows that the observed conformational differences between the wild type and mutant protein are not the direct consequence of mutation. Instead, simulation of Cro in different crystal environments reveals that mutation affects the stability of crystal forms. Molecular Mechanics Poisson-Boltzmann Surface Area binding energy calculations reveal the detailed energetics of packing interfaces. Packing interfaces can have diverse properties in strength, energetic components, and some are stronger than the biological dimer interface. Further analysis shows that mutation can strengthen packing interfaces by as much as ~5 kcal/mol in either crystal environment. Thus, in the case of Cro, mutation provides an additional energetic contribution during crystal formation that may stabilize a fully open higher energy state. Moreover, the effect of mutation in the lattice can extend to packing interfaces not involving mutation sites. Our results provide insight into possible models for the effect of crystallization on Cro conformational dynamics and emphasize careful consideration of protein crystal structures. PMID:24218107

Relative importance of column and adsorption parameters on the productivity in preparative liquid chromatography II: Investigation of separation systems with competitive Langmuir adsorption isotherms.

PubMed

Forssén, Patrik; Samuelsson, Jörgen; Fornstedt, Torgny

2014-06-20

In this study we investigated how the maximum productivity for commonly used, realistic separation system with a competitive Langmuir adsorption isotherm is affected by changes in column length, packing particle size, mobile phase viscosity, maximum allowed column pressure, column efficiency, sample concentration/solubility, selectivity, monolayer saturation capacity and retention factor of the first eluting compound. The study was performed by generating 1000 random separation systems whose optimal injection volume was determined, i.e., the injection volume that gives the largest achievable productivity. The relative changes in largest achievable productivity when one of the parameters above changes was then studied for each system and the productivity changes for all systems were presented as distributions. We found that it is almost always beneficial to use shorter columns with high pressure drops over the column and that the selectivity should be greater than 2. However, the sample concentration and column efficiency have very limited effect on the maximum productivity. The effect of packing particle size depends on the flow rate limiting factor. If the pumps maximum flow rate is the limiting factor use smaller packing, but if the pressure of the system is the limiting factor use larger packing up to about 40μm. Copyright © 2014 Elsevier B.V. All rights reserved.

Icosahedral and decagonal quasicrystals of intermetallic compounds are multiple twins of cubic or orthorhombic crystals composed of very large atomic complexes with icosahedral point-group symmetry in cubic close packing or body-centered packing: Structure of decagonal Al6Pd

PubMed Central

Pauling, Linus

1989-01-01

A doubly icosahedral complex involves roughly spherical clusters of atoms with icosahedral point-group symmetry, which are themselves, in parallel orientation, icosahedrally packed. These complexes may form cubic crystallites; three structures of this sort have been identified. Analysis of electron diffraction photographs of the decagonal quasicrystal Al6Pd has led to its description as involving pentagonal twinning of an orthorhombic crystal with a = 51.6 Å, b = 37.6 Å, and c = 33.24 Å, with about 4202 atoms in the unit, comprising two 1980-atom doubly icosahedral complexes, each involving icosahedral packing of 45 44-atom icosahedral complexes (at 0 0 0 and 1/2 1/2 1/2) and 242 interstitial atoms. The complexes and clusters are oriented with one of their fivefold axes in the c-axis direction. Images PMID:16594092

Icosahedral and decagonal quasicrystals of intermetallic compounds are multiple twins of cubic or orthorhombic crystals composed of very large atomic complexes with icosahedral point-group symmetry in cubic close packing or body-centered packing: Structure of decagonal Al(6)Pd.

PubMed

Pauling, L

1989-12-01

A doubly icosahedral complex involves roughly spherical clusters of atoms with icosahedral point-group symmetry, which are themselves, in parallel orientation, icosahedrally packed. These complexes may form cubic crystallites; three structures of this sort have been identified. Analysis of electron diffraction photographs of the decagonal quasicrystal Al(6)Pd has led to its description as involving pentagonal twinning of an orthorhombic crystal with a = 51.6 A, b = 37.6 A, and c = 33.24 A, with about 4202 atoms in the unit, comprising two 1980-atom doubly icosahedral complexes, each involving icosahedral packing of 45 44-atom icosahedral complexes (at 0 0 0 and 1/2 1/2 1/2) and 242 interstitial atoms. The complexes and clusters are oriented with one of their fivefold axes in the c-axis direction.

Subject competency of teachers and level of dependence on resource packs to teach levers, gears and pulleys

NASA Astrophysics Data System (ADS)

Jarvis, Tina; Cavendish, Sue

1994-12-01

This pilot study set out to ascertain whether the level of dependence on resource material is related to teaching experience, existing understanding in mechanics, and perceived self confidence in science and technology. Details of teaching experience and qualifications were obtained from 11 experienced teachers and 10 initial teacher trainees, and understanding of mechanics was assessed by a written test. Each teacher worked through one commercially produced inservice pack about levers, pulleys or gears, and then prepared a 30 minute session for 4 ten year old children. Videos of the sessions were analysed with respect to the extent to which the pack was the sole focus; the amount of integration with other teaching aids and approaches; and the extent individual children's needs were satisfied. Although science qualifications influenced teacher confidence, they were not accurate predictors of relevant knowledge and teaching competence. As the majority of teachers followed pack instructions closely, the children's needs were not always well matched.

Space filling minimal surfaces and sphere packings

NASA Astrophysics Data System (ADS)

Elser, Veit

1994-05-01

A space filling minimal surface is defined to be any embedded minimal surface without boundary with the property that the area and genus enclosed by any large spherical region scales in proportion to the volume of the region. The triply periodic minimal surfaces are one realization, but not necessarily the only one. By using the genus per unit volume of the surface, a meaningful comparison of surface areas can be made even in cases where there is no unit cell. Of the known periodic minimal surfaces this measure of the surface area is smallest for Schoen's FRD surface. This surface is one of several that is closely related to packings of spheres. Its low area is largely due to the fact that the corresponding sphere packing (fcc) has the maximal kissing number.

Simple heuristic for the viscosity of polydisperse hard spheres

NASA Astrophysics Data System (ADS)

Farr, Robert S.

2014-12-01

We build on the work of Mooney [Colloids Sci. 6, 162 (1951)] to obtain an heuristic analytic approximation to the viscosity of a suspension any size distribution of hard spheres in a Newtonian solvent. The result agrees reasonably well with rheological data on monodispserse and bidisperse hard spheres, and also provides an approximation to the random close packing fraction of polydisperse spheres. The implied packing fraction is less accurate than that obtained by Farr and Groot [J. Chem. Phys. 131(24), 244104 (2009)], but has the advantage of being quick and simple to evaluate.

Microstructure of cotton fibrous assemblies based on computed tomography

NASA Astrophysics Data System (ADS)

Jing, Hui; Yu, Weidong

2017-12-01

This paper describes for the first time the analysis of inner microstructure of cotton fibrous assemblies using computed tomography. Microstructure parameters such as packing density, fractal dimension as well as porosity including open porosity, closed porosity and total porosity are calculated based on 2D data from computed tomography. Values of packing density and fractal dimension are stable in random oriented fibrous assemblies, and there exists a satisfactory approximate linear relationship between them. Moreover, poles analysis indicates that porosity represents the tightness of fibrous assemblies and open poles are main existence.

7 CFR 52.53 - Approved identification.

Code of Federal Regulations, 2010 CFR

2010-01-01

...; (2) Have been produced or packed in an approved plant. (3) Are truthfully and accurately labeled. (4.... The official marks approved for use by plants operating under USDA continuous inspection service...: Provided, That the official marks illustrated by figures 8 and 9 are limited to products packed by plants...

Electrophobic interaction induced impurity clustering in metals

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

Zhou, Hong-Bo; Wang, Jin-Long; Jiang, W.

2016-10-01

We introduce the concept of electrophobic interaction, analogous to hydrophobic interaction, for describing the behavior of impurity atoms in a metal, a 'solvent of electrons'. We demonstrate that there exists a form of electrophobic interaction between impurities with closed electron shell structure, which governs their dissolution behavior in a metal. Using He, Be and Ar as examples, we predict by first-principles calculations that the electrophobic interaction drives He, Be or Ar to form a close-packed cluster with a clustering energy that follows a universal power-law scaling with the number of atoms (N) dissolved in a free electron gas, as wellmore » as W or Al lattice, as Ec is proportional to (N2/3-N). This new concept unifies the explanation for a series of experimental observations of close-packed inert-gas bubble formation in metals, and significantly advances our fundamental understanding and capacity to predict the solute behavior of impurities in metals, a useful contribution to be considered in future material design of metals for nuclear, metallurgical, and energy applications.« less

Order and Jamming on Curved Surfaces

NASA Astrophysics Data System (ADS)

Burke, Christopher J.

Geometric frustration occurs when a physical system's preferred ordering (e.g. spherical particles packing in a hexagonal lattice) is incompatible with the system's geometry. An example of this occurs in arrested relaxation in Pickering emulsions. Pickering emulsions are emulsions (e.g. mixtures of oil and water) with colloidal particles mixed in. The particles tend to lie at an oil-water interface, and can coat the surface of droplets within the emulsion (e.g. an oil droplet surrounded by water.) If a droplet is deformed from its spherical ground state, more particles adsorb at the surface, and the droplet is allowed to relax, then the particles on the surface can become close packed and prevent further relaxation, arresting the droplet in a non-spherical shape. The resulting structures tend to be relatively well ordered with regions of highly hexagonal packings; however, the curvature of the surface prevents perfect ordering and defects in the packing are required. These defects may influence the stability of these structures, making it important to understand how to predict and control them for applications in the food, cosmetic, oil, and medical industries. In this work, we use simulations to study the ordering and stability of sphere packings on arrested emulsions droplets. We first isolate the role of surface geometry by creating packings on a static ellipsoidal surface. Next we perform simulations which include dynamic effects that are present in the experimental Pickering emulsion system. Packings are created by evolving an ellipsoidal surface towards a spherical shape at fixed volume; the effects of relaxation rate, interparticle attraction, and gravity are determined. Finally, we study jamming on curved surfaces. Packings of hard particles are used to study marginally stable packings and the role curvature plays in constraining them. We also study packings of soft particles, compressed beyond marginal stability, and find that geometric frustration plays an important role in determining their mechanical properties.

Power and thermal characterization of a lithium-ion battery pack for hybrid-electric vehicles

NASA Astrophysics Data System (ADS)

Smith, Kandler; Wang, Chao-Yang

A 1D electrochemical, lumped thermal model is used to explore pulse power limitations and thermal behavior of a 6 Ah, 72 cell, 276 V nominal Li-ion hybrid-electric vehicle (HEV) battery pack. Depleted/saturated active material Li surface concentrations in the negative/positive electrodes consistently cause end of high-rate (∼25 C) pulse discharge at the 2.7 V cell -1 minimum limit, indicating solid-state diffusion is the limiting mechanism. The 3.9 V cell -1 maximum limit, meant to protect the negative electrode from lithium deposition side reaction during charge, is overly conservative for high-rate (∼15 C) pulse charges initiated from states-of-charge (SOCs) less than 100%. Two-second maximum pulse charge rate from the 50% SOC initial condition can be increased by as much as 50% without risk of lithium deposition. Controlled to minimum/maximum voltage limits, the pack meets partnership for next generation vehicles (PNGV) power assist mode pulse power goals (at operating temperatures >16 °C), but falls short of the available energy goal. In a vehicle simulation, the pack generates heat at a 320 W rate on a US06 driving cycle at 25 °C, with more heat generated at lower temperatures. Less aggressive FUDS and HWFET cycles generate 6-12 times less heat. Contact resistance ohmic heating dominates all other mechanisms, followed by electrolyte phase ohmic heating. Reaction and electronic phase ohmic heats are negligible. A convective heat transfer coefficient of h = 10.1 W m -2 K -1 maintains cell temperature at or below the 52 °C PNGV operating limit under aggressive US06 driving.

Grain neighbour effects on twin transmission in hexagonal close-packed materials

DOE PAGES

Arul Kumar, Mariyappan; Beyerlein, Irene Jane; McCabe, Rodney James; ...

2016-12-19

Materials with a hexagonal close-packed (hcp) crystal structure such as Mg, Ti and Zr are being used in the transportation, aerospace and nuclear industry, respectively. Material strength and formability are critical qualities for shaping these materials into parts and a pervasive deformation mechanism that significantly affects their formability is deformation twinning. The interaction between grain boundaries and twins has an important influence on the deformation behaviour and fracture of hcp metals. Here, statistical analysis of large data sets reveals that whether twins transmit across grain boundaries depends not only on crystallography but also strongly on the anisotropy in crystallographic slip.more » As a result, we show that increases in crystal plastic anisotropy enhance the probability of twin transmission by comparing the relative ease of twin transmission in hcp materials such as Mg, Zr and Ti.« less

A new constitutive analysis of hexagonal close-packed metal in equal channel angular pressing by crystal plasticity finite element method

NASA Astrophysics Data System (ADS)

Li, Hejie; Öchsner, Andreas; Yarlagadda, Prasad K. D. V.; Xiao, Yin; Furushima, Tsuyoshi; Wei, Dongbin; Jiang, Zhengyi; Manabe, Ken-ichi

2018-01-01

Most of hexagonal close-packed (HCP) metals are lightweight metals. With the increasing application of light metal products, the production of light metal is increasingly attracting the attentions of researchers worldwide. To obtain a better understanding of the deformation mechanism of HCP metals (especially for Mg and its alloys), a new constitutive analysis was carried out based on previous research. In this study, combining the theories of strain gradient and continuum mechanics, the equal channel angular pressing process is analyzed and a HCP crystal plasticity constitutive model is developed especially for Mg and its alloys. The influence of elevated temperature on the deformation mechanism of the Mg alloy (slip and twin) is novelly introduced into a crystal plasticity constitutive model. The solution for the new developed constitutive model is established on the basis of the Lagrangian iterations and Newton Raphson simplification.

Heat Sinking, Cross Talk, and Temperature Stability for Large, Close-Packed Arrays of Microcalorimeters

NASA Technical Reports Server (NTRS)

Imoto, Naoko; Bandler, SImon; Brekosky, Regis; Chervenak, James; Figueroa-Felicano, Enectali; Finkbeiner, Frederick; Kelley, Richard; Kilbourne, Caroline; Porter, Frederick; Sadleir, Jack;

Navier-Stokes hydrodynamics of thermal collapse in a freely cooling granular gas.

PubMed

Kolvin, Itamar; Livne, Eli; Meerson, Baruch

2010-08-01

We show that, in dimension higher than one, heat diffusion and viscosity cannot arrest thermal collapse in a freely evolving dilute granular gas, even in the absence of gravity. Thermal collapse involves a finite-time blowup of the gas density. It was predicted earlier in ideal, Euler hydrodynamics of dilute granular gases in the absence of gravity, and in nonideal, Navier-Stokes granular hydrodynamics in the presence of gravity. We determine, analytically and numerically, the dynamic scaling laws that characterize the gas flow close to collapse. We also investigate bifurcations of a freely evolving dilute granular gas in circular and wedge-shaped containers. Our results imply that, in general, thermal collapse can only be arrested when the gas density becomes comparable with the close-packing density of grains. This provides a natural explanation to the formation of densely packed clusters of particles in a variety of initially dilute granular flows.

Shearing single crystal magnesium in the close-packed basal plane at different temperatures

NASA Astrophysics Data System (ADS)

Han, Ming; Li, Lili; Zhao, Guangming

2018-05-01

Shear behaviors of single crystal magnesium (Mg) in close-packed (0001) basal plane along the [ 1 bar 2 1 bar 0 ], [ 1 2 bar 10 ], [ 10 1 bar 0 ] and [ 1 bar 010 ] directions were studied using molecular dynamics simulations via EAM potential. The results show that both shear stress-strain curves along the four directions and the motion path of free atoms during shearing behave periodic characteristics. It reveals that the periodic shear displacement is inherently related to the crystallographic orientation in single crystal Mg. Moreover, different temperatures in a range from 10 to 750 K were considered, demonstrating that shear modulus decreases with increasing temperatures. The results agree well with the MTS model. It is manifested that the modulus is independent with the shear direction and the size of the atomic model. This work also demonstrates that the classical description of shear modulus is still effective at the nanoscale.

Topologically Close-packed Phase Formation in High Entropy Alloys: A Review of Calphad and Experimental Results

NASA Astrophysics Data System (ADS)

Guruvidyathri, K.; Hari Kumar, K. C.; Yeh, J. W.; Murty, B. S.

2017-11-01

One of the major challenges in high entropy alloy (HEA) research is to obtain single-phase solid solutions by proper selection of components and processing techniques. Often one encounters situations where topologically close-packed (TCP) phases are present in the HEA microstructures. TCP phases are a class of intermetallic phases that are in general considered undesirable. The ability to predict these phases in HEAs using the Calphad (CALculation of PHAse Diagrams) method has been shown to accelerate the identification of promising compositions. In this review, an analysis of the reported Calphad studies and corresponding microstructural information on HEAs is done to evaluate the success of the Calphad method for TCP phases. A total of 52 alloys with 123 post-heat treatment microstructures reported so far have been compared. Challenges and issues in experiments and calculations are brought out with a possible way forward.

Electronic structure and electron-phonon interaction in hexagonal yttrium by density functional calculations

NASA Astrophysics Data System (ADS)

Singh, Prabhakar P.

2007-03-01

To understand the pressure-induced changes in the electronic structure and the electron-phonon interaction in yttrium, we have studied hexagonal-close-packed (hcp) yttrium, stable at ambient pressure, and double hexagonal-close-packed (dhcp) yttrium, stable up to around 44GPa , using density-functional-based methods. Our results show that as one goes from hcp yttrium to dhcp yttrium, there are (i) a substantial charge transfer from s→d with extensive modifications of the d band and a sizable reduction in the density of states at the Fermi energy, (ii) a substantial stiffening of phonon modes with the electron-phonon coupling covering the entire frequency range, and (iii) an increase in the electron-phonon coupling constant λ from 0.55 to 1.24, leading to a change in the superconducting transition temperature Tc from 0.3to15.3K for μ*=0.2 .

Valve leakage inspection, testing, and maintenance process

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

Aikin, J.A.; Reinwald, J.W.

1989-01-01

Atomic Energy of Canada Limited-Research Company (AECL-RC), Chalk River, has more than 50 person-years dedicated toward the leak-free valve. In the early 1970s, the Chalk River Nuclear Laboratories (CRNL) developed valve stem live-loading and recently completed the packing tests for the Electric Power Research Institute (EPRI)-funded Valve Packing Improvement Study. Current safety concerns with asbestos-based valve packings and the difficulty in removing newer graphite packings prompted CRNL to investigate methods to improve valve repacking procedures. The present practice of valve packing replacement is very labor-intensive, requiring use of hand tools such as corkscrew devices and special packing picks. Use ofmore » water jets to cut or fragment the packing for withdrawal from the stuffing box does improve the process, but removal of the lantern or junk rings is still difficult. To address these problems, AECL-RC has developed a unique valve maintenance process designed to reduce person-rem exposures, the risk of scoring the stem or stuffing box, and maintenance costs and to improve the engineering quality of valve repair.« less

High magnesium mobility in ternary spinel chalcogenides

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

Canepa, Pieremanuele; Bo, Shou-Hang; Sai Gautam, Gopalakrishnan

Magnesium batteries appear a viable alternative to overcome the safety and energy density limitations faced by current lithium-ion technology. Furthermore, the development of a competitive magnesium battery is plagued by the existing notion of poor magnesium mobility in solids. We demonstrate by using ab initio calculations, nuclear magnetic resonance, and impedance spectroscopy measurements that substantial magnesium ion mobility can indeed be achieved in close-packed frameworks (~ 0.01-0.1 mS cm -1 at 298 K), specifically in the magnesium scandium selenide spinel. Our theoretical predictions also indicate that high magnesium ion mobility is possible in other chalcogenide spinels, opening the door formore » the realization of other magnesium solid ionic conductors and the eventual development of an all-solid-state magnesium battery.« less

Micro-Masonry: Construction of 3D Structures by Mesoscale Self-Assembly

PubMed Central

Fernandez, Javier G.; Khademhosseini, Ali

2010-01-01

A general method for construction of three dimensional structures by directed assembly of microscale polymeric sub-units is presented. Shape-controlled microgels are directed to assemble into different shapes by limiting their movement onto a molded substrate. The capillary forces, resulting from the presence of a liquid polymer, assemble the microgels in close contact with the rest of the units and with the free surface, the latter imposing the final geometry of the resulting construct. The result is a freestanding structure composed of one or multiple layers of sub-units assembled in a tightly packed conformation. The applicability of the technique for the construction of scaffolds with cell-laden sub-units is demonstrated. In addition, scaffolds formed by the sequential aggregation of sub-units are produced. PMID:20440697

High magnesium mobility in ternary spinel chalcogenides

DOE PAGES

Canepa, Pieremanuele; Bo, Shou-Hang; Sai Gautam, Gopalakrishnan; ...

2017-11-24

Magnesium batteries appear a viable alternative to overcome the safety and energy density limitations faced by current lithium-ion technology. Furthermore, the development of a competitive magnesium battery is plagued by the existing notion of poor magnesium mobility in solids. We demonstrate by using ab initio calculations, nuclear magnetic resonance, and impedance spectroscopy measurements that substantial magnesium ion mobility can indeed be achieved in close-packed frameworks (~ 0.01-0.1 mS cm -1 at 298 K), specifically in the magnesium scandium selenide spinel. Our theoretical predictions also indicate that high magnesium ion mobility is possible in other chalcogenide spinels, opening the door formore » the realization of other magnesium solid ionic conductors and the eventual development of an all-solid-state magnesium battery.« less

Staging in polyacetylene-iodine conductors

NASA Astrophysics Data System (ADS)

Baughman, R. H.; Murthy, N. S.; Miller, G. G.; Shacklette, L. W.

1983-07-01

Evidence is presented for the existence of highly conducting polyacetylene complexes with structures related to high-stage graphite, as well as structures related to first-stage graphite. X-ray diffraction measurements on polyacetylene-iodine complexes indicate equatorial lines at 7.7-8.0 and 13.8-14.3 Å. The shorter spacing arises in part from a structure in which iodine-rich planes alternate with planes of polyacetylene chains. The longer spacing, which disappears upon atmospheric exposure, is consistent with a structure analogous to third-stage graphite in which dopant-rich planes are separated by three close-packed planes of polyacetylene chains. The third-stage complex can be viewed as a perturbation of the structure of undoped polyacetylene, with the region between dopant layers consisting essentially of a one unit cell thickness of the parent polymer structure. Packing calculations for this model, in which a linear column of anions (I3- and/or I5-) displaces either every chain or every other chain in the dopant-rich layer, provide an interlayer spacing which is equal to that observed. Evidence consistent with third-stage structures (with both fractional occupation and complete occupation of the dopant plane) is also found by reexamination of published sorption data, which provides slope changes at close to the calculated limiting compositions for these structures [(CHI0.056)x and (CHI0.13)x]. However, a first-stage structure with alternating dopant arrays and polymer chains in the dopant plane [for which (CHI0.13)x is calculated] provides a better explanation for the second slope change, as well as for the composition obtained under dynamic vacuum, (CHI0.14)x. These results for iodine complexes are compared with those derived for the group VA halide complexes of polyacetylene.

A theoretical study on pure bending of hexagonal close-packed metal sheet

NASA Astrophysics Data System (ADS)

Mehrabi, Hamed; Yang, Chunhui

2018-05-01

Hexagonal close-packed (HCP) metals have quite different mechanical behaviours in comparison to conventional cubic metals such as steels and aluminum alloys [1, 2]. They exhibit a significant tension-compression asymmetry in initial yielding and subsequent plastic hardening. The reason for this unique behaviour can be attributed to their limited symmetric crystal structure, which leads to twining deformation [3-5]. This unique behaviour strongly influences sheet metal forming of such metals, especially for roll forming, in which the bending is dominant. Hence, it is crucial to represent constitutive relations of HCP metals for accurate estimation of bending moment-curvature behaviours. In this paper, an analytical model for asymmetric elastoplastic pure bending with an application of Cazacu-Barlat asymmetric yield function [6] is presented. This yield function considers the asymmetrical tension-compression behaviour of HCP metals by using second and third invariants of the stress deviator tensor and a specified constant, which can be expressed in terms of uniaxial yield stresses in tension and compression. As a case study, the analytical model is applied to predict the moment-curvature behaviours of AZ31B magnesium alloy sheets under uniaxial loading condition. Furthermore, the analytical model is implemented as a user-defined material through the UMAT interface in Abaqus [7, 8] for conducting pure bending simulations. The results show that the analytical model can reasonably capture the asymmetric tension-compression behaviour of the magnesium alloy. The predicted moment-curvature behaviour has good agreement with the experimental results. Furthermore, numerical results show a better accuracy by the application of the Cazacu-Barlat yield function than those using the von-Mises yield function, which are more conservative than analytical results.

A novel filter bank for biotelemetry.

PubMed

Karagözoglu, B

2001-03-01

In a multichannel biotelemetry system, signals taken from a patient are distributed along the available frequency range (bandwidth) of the system through frequency-division-multiplexing, and combined into a single composite signal. Biological signals that are limited to low frequencies (below 10 Hz) modulate the frequencies of respective sub-carriers. Other biological signals are carried in amplitude-modulated forms. It is recognized that recovering original signals from a composite signal at the receiver side is a technical challenge when a telemetry system with narrow bandwidth capacity is used, since such a system leaves little frequency spacing between information channels. A filter bank is therefore utilized for recovering biological signals that are transmitted. The filter bank contains filter units comprising switched-capacitor filter integrated circuits. The filters have two distinct and opposing outputs (band-stop (notch) and band-pass). Since most biological signals are at low frequencies, and modulated signals occupy a narrow band around the carrier, notch filters can be used to efficiently stop signals in the narrow frequency range. Once the interim channels are removed, other channels become well separated from each other, and band-pass filters can select them. In the proposed system, efficient filtering of closely packed channels is achieved, with low interference, from neighboring channels. The filter bank is applied to a system that carries four biological signals and a battery status indicator signal. Experimental results reinforce theoretical predictions that the filter bank successfully de-multiplexes closely packed information channels with low crosstalk between them. It is concluded that the proposed filter bank allows utilization of cost-effective multichannel biotelemetry systems that are designed around commercial audio devices, and that it can be readily adapted to a broad range of physiological recording requirements.

AC electroosmosis in microchannels packed with a porous medium

NASA Astrophysics Data System (ADS)

Kang, Yuejun; Yang, Chun; Huang, Xiaoyang

2004-08-01

This paper presents a theoretical study on ac-driven electroosmotic flow in both open-end and closed-end microchannels packed with uniform charged spherical microparticles. The time-periodic oscillating electroosmotic flow in an open-end capillary in response to the application of an alternating (ac) electric field is obtained using the Green function approach. The analysis is based on the Carman-Kozeny theory. The backpressure associated with the counter-flow in a closed-end capillary is obtained by analytically solving the modified Brinkman momentum equation. It is demonstrated that in a microchannel with its two ends connected to reservoirs and subject to ambient pressure, the oscillating Darcy velocity profile depends on both the pore size and the excitation frequency; such effects are coupled through an important aspect ratio of the tubule radius to the Stokes penetration depth. For a fixed pore size, the magnitude of the ac electroosmotic flow decreases with increasing frequency. With increasing pore size, however, the magnitude of the maximum velocity shows two different trends with respect to the excitation frequency: it gets higher in the low frequency domain, and gets lower in the high frequency domain. In a microchannel with closed ends, for a fixed excitation frequency, use of smaller packing particles can generate higher backpressure. For a fixed pore size, the backpressure magnitude shows two different trends changing with the excitation frequency. When the excitation frequency is lower than the system characteristic frequency, the backpressure decreases with increasing excitation frequency. When the excitation frequency is higher than the system characteristic frequency, the backpressure increases with increasing excitation frequency.

Self assembly of magnetic nanoparticles at silicon surfaces.

PubMed

Theis-Bröhl, Katharina; Gutfreund, Philipp; Vorobiev, Alexei; Wolff, Max; Toperverg, Boris P; Dura, Joseph A; Borchers, Julie A

2015-06-21

Neutron reflectometry was used to study the assembly of magnetite nanoparticles in a water-based ferrofluid close to a silicon surface. Under three conditions, static, under shear and with a magnetic field, the depth profile is extracted. The particles have an average diameter of 11 nm and a volume density of 5% in a D2O-H2O mixture. They are surrounded by a 4 nm thick bilayer of carboxylic acid for steric repulsion. The reflectivity data were fitted to a model using a least square routine based on the Parratt formalism. From the scattering length density depth profiles the following behavior is concluded: the fits indicate that excess carboxylic acid covers the silicon surface and almost eliminates the water in the densely packed wetting layer that forms close to the silicon surface. Under constant shear the wetting layer persists but a depletion layer forms between the wetting layer and the moving ferrofluid. Once the flow is stopped, the wetting layer becomes more pronounced with dense packing and is accompanied by a looser packed second layer. In the case of an applied magnetic field the prolate particles experience a torque and align with their long axes along the silicon surface which leads to a higher particle density.

Flexible fiber in interaction with a dense granular flow close to the jamming transition

NASA Astrophysics Data System (ADS)

Algarra, Nicolas; Leang, Marguerite; Lazarus, Arnaud; Vandembroucq, Damien; Kolb, Evelyne

2017-06-01

We propose a new fluid/structure interaction in the unusual case of a dense granular medium flowing against an elastic fiber acting as a flexible intruder. We study experimentally the reconfiguration and the forces exerted on the flexible fiber produced by the flow at a constant and low velocity of a two-dimensional disordered packing of grains close but below the jamming transition.

Biofiltration of methanol vapor

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

Shareefdeen, Z.; Baltzis, B.C.; Oh, Youngsook

1993-03-05

Biofiltration of solvent and fuel vapors may offer a cost-effective way to comply with increasingly strict air emission standards. An important step in the development of this technology is to derive and validate mathematical models of the biofiltration process for predictive and scaleup calculations. For the study of methanol vapor biofiltration, an 8-membered bacterial consortium was obtained from methanol-exposed soil. The bacteria were immobilized on solid support and packed into a 5-cm diameter, 60-cm-high column provided with appropriate flowmeters and sampling ports. The solid support was prepared by mixing two volumes of peat with three volumes of perlite particles. Twomore » series of experiments were performed. In the first, the inlet methanol concentration was kept constant while the superficial air velocity was varied from run to run. In the second series, the air flow rate (velocity) was kept constant while the inlet methanol concentration was varied. The unit proved effective in removing methanol at rates up to 112.8 g h[sup [minus]1] m[sup [minus]3] packing. A mathematical model has been derived and validated. The model described and predicted experimental results closely. Both experimental data and model predictions suggest that the methanol biofiltration process was limited by oxygen diffusion and methanol degradation kinetics.« less

Experimental validation of a 0-D numerical model for phase change thermal management systems in lithium-ion batteries

NASA Astrophysics Data System (ADS)

Schweitzer, Ben; Wilke, Stephen; Khateeb, Siddique; Al-Hallaj, Said

2015-08-01

A lumped (0-D) numerical model has been developed for simulating the thermal response of a lithium-ion battery pack with a phase-change composite (PCC™) thermal management system. A small 10s4p battery pack utilizing PCC material was constructed and subjected to discharge at various C-rates in order to validate the lumped model. The 18650 size Li-ion cells used in the pack were electrically characterized to determine their heat generation, and various PCC materials were thermally characterized to determine their apparent specific heat as a function of temperature. Additionally, a 2-D FEA thermal model was constructed to help understand the magnitude of spatial temperature variation in the pack, and to understand the limitations of the lumped model. Overall, good agreement is seen between experimentally measured pack temperatures and the 0-D model, and the 2-D FEA model predicts minimal spatial temperature variation for PCC-based packs at C-rates of 1C and below.

A New Supercapacitor and Li-ion Battery Hybrid System for Electric Vehicle in ADVISOR

NASA Astrophysics Data System (ADS)

Peng, Xiao; Shuhai, Quan; Changjun, Xie

2017-02-01

The supercapacitor (SC) and Li-ion battery(BT) hybrid energy storage system(HESS) electric vehicle(EV) is gaining universal attention. The topology is of importance for the SC/BT HESS. A new SC/BT topology HESS with a rule-based energy management strategy for EV was proposed. The BT pack is connected directly to the DC link via a controlled switch. The SC pack is connected to the DC link via a controlled switch. A uni-directional DC/DC converter is connected between the SC pack and the BT pack. The braking regeneration energy is all harvested by the SC pack. The output power of BT pack is limited. The different SC/BT configurations with varied BT maximum Ah capacity factor and SC maximum capacity factor are simulated in ADVISOR. Simulation results show that BT maximum Ah capacity factor has little impact on vehicle acceleration performance and maximum speed. SC maximum capacity factor has significant impact on vehicle acceleration performance and maximum speed. The fuel economy isn’t affected.

Precise algorithm to generate random sequential adsorption of hard polygons at saturation

NASA Astrophysics Data System (ADS)

Zhang, G.

2018-04-01

Random sequential adsorption (RSA) is a time-dependent packing process, in which particles of certain shapes are randomly and sequentially placed into an empty space without overlap. In the infinite-time limit, the density approaches a "saturation" limit. Although this limit has attracted particular research interest, the majority of past studies could only probe this limit by extrapolation. We have previously found an algorithm to reach this limit using finite computational time for spherical particles and could thus determine the saturation density of spheres with high accuracy. In this paper, we generalize this algorithm to generate saturated RSA packings of two-dimensional polygons. We also calculate the saturation density for regular polygons of three to ten sides and obtain results that are consistent with previous, extrapolation-based studies.

Precise algorithm to generate random sequential adsorption of hard polygons at saturation.

PubMed

Zhang, G

2018-04-01

Random sequential adsorption (RSA) is a time-dependent packing process, in which particles of certain shapes are randomly and sequentially placed into an empty space without overlap. In the infinite-time limit, the density approaches a "saturation" limit. Although this limit has attracted particular research interest, the majority of past studies could only probe this limit by extrapolation. We have previously found an algorithm to reach this limit using finite computational time for spherical particles and could thus determine the saturation density of spheres with high accuracy. In this paper, we generalize this algorithm to generate saturated RSA packings of two-dimensional polygons. We also calculate the saturation density for regular polygons of three to ten sides and obtain results that are consistent with previous, extrapolation-based studies.

"The L Pack": Addressing the Sexual Health Needs of Young Lesbians

ERIC Educational Resources Information Center

McAlister, Siobhan; Neill, Gail

2009-01-01

Concerns about the sexual health of women who identify as other than heterosexual have been highlighted in numerous research reports, yet access to information, advice and services remains limited within Northern Ireland. In response to this, a group of young women have produced a sexual health resource ("The L Pack") specifically for…

Migration of selected hydrocarbon contaminants into dry semolina and egg pasta packed in direct contact with virgin paperboard and polypropylene film.

PubMed

Barp, Laura; Suman, Michele; Lambertini, Francesca; Moret, Sabrina

2015-01-01

Migration of mineral oil saturated hydrocarbons (MOSH), polyolefin oligomeric saturated hydrocarbons (POSH), and polyalphaolefins (PAO from hot melts) into dry semolina and egg pasta packed in direct contact with virgin paperboard or polypropylene (PP) flexible film was studied. Migration was monitored during shelf life (up to 24 months), through storage in a real supermarket (packs kept on shelves), conditions preventing exchange with the surrounding environment (packs wrapped in aluminium foil), and storage in a warehouse (packs inside of the transport box of corrugated board). Semolina pasta packed in virgin paperboard (without hot melts) had a MOSH content lower than 1.0 mg kg(-1). An increasing contamination with PAO belonging to the adhesives used to close the boxes was detected in egg pasta, wrapped in aluminium (1.5 and 5 mg kg(-1) after 3 and 24 months, respectively). An environmental contribution to total hydrocarbon contamination was observed in egg pasta kept on shelves that, after 3 and 24 months, showed levels of PAO/MOSH < C25 around 3 and 10 mg kg(-1), respectively. The migration of POSH from PP film into egg pasta wrapped in aluminium was around 0.6 mg kg(-1) after 3 months of contact and reached 1.7 mg kg(-1) after 24 months of contact. After 9 months of contact, semolina pasta packed in PP film and stored in the transport box showed that some MOSH migrated into the pasta from the board of the transport box (through the plastic film).

Cycle life test of secondary spacecraft cells

NASA Technical Reports Server (NTRS)

Harkness, J. D.

1980-01-01

The results of the life cycling program on rechargeable calls are reported. Information on required data, the use of which the data will be put, application details, including orbital description, charge control methods, load rquirements, etc., are given. Cycle tests were performed on 660 sealed, nickel cadmium cells. The cells consisted of seven sample classifications ranging form 3.0 to 20 amp. hours. Nickel cadmium, silver cadmium, and silver zinc sealed cells, excluding synchronous orbit and accelerated test packs were added. The capacities of the nickel cadmium cells, the silver cadmium and the silver zinc cells differed in range of amp hrs. The cells were cylced under different load, charge control, and temperature conditions. All cell packs are recharged by use of a pack voltage limit. All charging is constant current until the voltage limit is reached.

Poisson's ratio and the densification of glass under high pressure.

PubMed

Rouxel, T; Ji, H; Hammouda, T; Moréac, A

2008-06-06

Because of a relatively low atomic packing density, (Cg) glasses experience significant densification under high hydrostatic pressure. Poisson's ratio (nu) is correlated to Cg and typically varies from 0.15 for glasses with low Cg such as amorphous silica to 0.38 for close-packed atomic networks such as in bulk metallic glasses. Pressure experiments were conducted up to 25 GPa at 293 K on silica, soda-lime-silica, chalcogenide, and bulk metallic glasses. We show from these high-pressure data that there is a direct correlation between nu and the maximum post-decompression density change.

New techniques for fusion bonding and replication for large glass reflectors

NASA Technical Reports Server (NTRS)

Angel, J. R. P.

1983-01-01

Lightweight, space-deployable glass honeycomb telescope primary mirror structures are produced by a novel method which involves the heating to softening temperature of many borosilicate or silica glass tube sections that are packed to form a honeycomb matrix and filled with a high expansion coefficient refractory sand. The close packed tubes yield a hexagonal-cell honeycomb. Attention is given to the results of an experiment in which a highly refractory master was used to shape a honeycomb of less refractory glass, employing a 1-micron thick, vacuum-deposited gold coating as a parting layer between the two.

The Morphology of Titanium Dioxide Aerogels

NASA Astrophysics Data System (ADS)

Zhu, Zhu

The morphology of titanium dioxide TiO _2 aerogels has been characterized by four major techniques. This work will discuss these complementary techniques such as nitrogen adsorption, X-ray powder diffraction (XRD), electron microscopies (EM- TEM, SEM), and small angle neutron scattering (SANS). The results of these characterizations have shown that the morphology of titanium dioxide TiO_2 aerogels can be characterized in terms of two length scales: 5 nm diameter, crystalline nanoparticles of anatase closely packed into mesoaggregates about 50 nm in size. The mesoaggregates are, in turn, packed into a loosely linked structure with an overall porosity of 80%.

LEGO Materials.

PubMed

Talapin, Dmitri V

2008-06-01

Two papers in this issue report important developments in the field of inorganic nanomaterials. Chen and O'Brien discuss self-assembly of semiconductor nanocrystals into binary nanoparticle superlattices (BNSLs). They show that simple geometrical principles based on maximizing the packing density can determine BNSL symmetry in the absence of cohesive electrostatic interactions. This finding highlights the role of entropy as the driving force for ordering nanoparticles. The other paper, by Weller and co-workers, addresses an important problem related to device integration of nanoparticle assemblies. They employ the Langmuir-Blodgett technique to prepare long-range ordered monolayers of close-packed nanocrystals and transfer them to different substrates.

Atomic force microscope studies of fullerene films - Highly stable C60 fcc (311) free surfaces

NASA Technical Reports Server (NTRS)

Snyder, Eric J.; Tong, William M.; Williams, R. S.; Anz, Samir J.; Anderson, Mark S.

1991-01-01

Atomic force microscopy and X-ray diffractometry were used to study 1500 A-thick films of pure C60 grown by sublimation in ultrahigh vacuum onto a CaF2 (111) substrte. Topographs of the films did not reveal the expected close-packed structures, but they showed instead large regions that correspond to a face-centered cubic (311) surface and distortions of this surface. The open (311) structure may have a relatively low free energy because the low packing density contributes to a high entropy of the exposed surface.

The retail display life of steaks prepared from chill stored vacuum and carbon dioxide-packed sub-primal beef cuts.

PubMed

Bell, R G; Penney, N; Moorhead, S M

1996-01-01

Chilled striploins and cube rolls from ten Australian steers (grain-fed for 150 days) were trimmed of external fat and cut transversely into portions approximately 10 cm thick, each weighing between 750 and 1000 g. These 'retailer-ready' cuts were each wrapped in drip saver pads and slid inside a plastic sleeve before being individually placed into a clear plastic high oxygen barrier film, metallized film or conventional vacuum bag. Cuts in clear plastic and metallized film packs were packaged in an oxygen-free saturated carbon dioxide atmosphere (CO(2)-CAP), those in vacuum bags were conventionally vacuum-packed. All packs were returned to the chiller for further cooling. After 24 hr, half the clear plastic and metallized CO(2)-CAP packs were carbon dioxide master-packed in groups of eight. Retailer-ready cuts in both clear plastic and metallized film single unit and master-packed CO(2)-CAP packs were air freighted to New Zealand and sea freighted to Japan for assessment. The control vacuum packs were all consigned to New Zealand. Assessments in both countries after 39-89 days storage at between 0 °C and -1.0 °C indicated that fat colour stability limited the retail display life of steaks cut from meat in these retailer-ready packs to approximately 48 hr. In this regard, meat from single unit CO(2)-CAP, master pack CO(2)-CAP and vacuum packs performed similarly. Lean meat colour and sensory attributes remained acceptable for up to 48 hr after displayed product was rejected because of grey-green fat discoloration. The microbiological status of retailer-ready cuts removed from CO(2)-CAP packs after 89 days chilled storage was superior to that of cuts from vacuum packs. Clear plastic and metallized film CO(2)-CAP packs performed comparably.

Bulk Kosterlitz-Thouless Type Molecular Superconductor β″-(BEDT-TTF)2[(H2O)(NH4)2Cr(C2O4)3]·18-crown-6.

PubMed

Martin, Lee; Lopez, Jordan R; Akutsu, Hiroki; Nakazawa, Yasuhiro; Imajo, Shusaku

2017-11-20

A new molecular superconductor, β″-(BEDT-TTF) 2 [(H 2 O)(NH 4 ) 2 Cr(C 2 O 4 ) 3 ]·18-crown-6, has been synthesized from the organic donor molecule BEDT-TTF with the anion Cr(C 2 O 4 ) 3 3- . The crystal structure consists of conducting organic layers of BEDT-TTF molecules which adopt the β″ packing motif (layer A), layers of NH 4 + and Λ-Cr(C 2 O 4 ) 3 3- (layer B), layers of (H 2 O)(NH 4 )18-crown-6 (layer C), and layers of NH 4 + and Δ-Cr(C 2 O 4 ) 3 3- (layer D) which produce a superstructure with a repeating pattern of ABCDABCDA. As a result of this packing arrangement, this is the 2D superconductor with the widest gap between conducting layers where only a single donor packing motif is present (β″). Superconducting critical temperatures at ambient pressure observed by electrical transport and magnetic measurements are 4.0-4.9 and 2.5 K, respectively. The strong 2D nature of this system, the broad transition to T zero at 1.8K, and the transition of α of V ∝ I α from 1 to 3 on I-V curves strongly suggest that the superconducting transition is very close to a Kosterlitz-Thouless transition. The magnetic field dependence of the superconducting critical temperature parallel to the conducting plane gives an upper critical field μ 0 H c2∥ > 8 T, which is over the calculated Pauli-Clogston limit for this material.

Latent heat of traffic moving from rest

NASA Astrophysics Data System (ADS)

Farzad Ahmadi, S.; Berrier, Austin S.; Doty, William M.; Greer, Pat G.; Habibi, Mohammad; Morgan, Hunter A.; Waterman, Josam H. C.; Abaid, Nicole; Boreyko, Jonathan B.

2017-11-01

Contrary to traditional thinking and driver intuition, here we show that there is no benefit to ground vehicles increasing their packing density at stoppages. By systematically controlling the packing density of vehicles queued at a traffic light on a Smart Road, drone footage revealed that the benefit of an initial increase in displacement for close-packed vehicles is completely offset by the lag time inherent to changing back into a ‘liquid phase’ when flow resumes. This lag is analogous to the thermodynamic concept of the latent heat of fusion, as the ‘temperature’ (kinetic energy) of the vehicles cannot increase until the traffic ‘melts’ into the liquid phase. These findings suggest that in situations where gridlock is not an issue, drivers should not decrease their spacing during stoppages in order to lessen the likelihood of collisions with no loss in flow efficiency. In contrast, motion capture experiments of a line of people walking from rest showed higher flow efficiency with increased packing densities, indicating that the importance of latent heat becomes trivial for slower moving systems.

Whitey SCHe Ball Valves Provide Test Port Isolation

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

MISKA, C.R.

2000-09-15

These valves are 1/4 inch ball valves fabricated of 316 stainless steel. Packing is TFE (standard). They are used as normally closed isolation valves for test ports in the SCHe System between the gage root valve and the pressure indicator.

Structures having enhanced biaxial texture and method of fabricating same

DOEpatents

Goyal, Amit; Budai, John D.; Kroeger, Donald M.; Norton, David P.; Specht, Eliot D.; Christen, David K.

1998-01-01

A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon.

Structures having enhanced biaxial texture and method of fabricating same

DOEpatents

Goyal, Amit; Budai, John D.; Kroeger, Donald M.; Norton, David P.; Specht, Eliot D.; Christen, David K.

1999-01-01

A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon.

Constraint counting for frictional jamming

NASA Astrophysics Data System (ADS)

Quint, D. A.; Henkes, S.; Schwarz, J. M.

2012-02-01

While the frictionless jamming transition has been intensely studied in recent years, more realistic frictional packings are less well understood. In frictionless sphere packings, the transition is predicted by a simple mean-field constraint counting argument, the isostaticity argument. For frictional packings, a modified constraint counting argument, which includes slipping contacts at the Coulomb threshold, has had limited success in accounting for the transition. We propose that the frictional jamming transition is not mean field and is triggered by the nucleation of unstable regions, which are themselves dynamical objects due to the Coulomb criterion. We create frictional packings using MD simulations and test for the presence and shape of rigid clusters with the pebble game to identify the partition of the packing into stable and unstable regions. To understand the dynamics of these unstable regions we follow perturbations at contacts crucial to the stability of the ``frictional house of cards.''

Indexing Volumetric Shapes with Matching and Packing

PubMed Central

Koes, David Ryan; Camacho, Carlos J.

2014-01-01

We describe a novel algorithm for bulk-loading an index with high-dimensional data and apply it to the problem of volumetric shape matching. Our matching and packing algorithm is a general approach for packing data according to a similarity metric. First an approximate k-nearest neighbor graph is constructed using vantage-point initialization, an improvement to previous work that decreases construction time while improving the quality of approximation. Then graph matching is iteratively performed to pack related items closely together. The end result is a dense index with good performance. We define a new query specification for shape matching that uses minimum and maximum shape constraints to explicitly specify the spatial requirements of the desired shape. This specification provides a natural language for performing volumetric shape matching and is readily supported by the geometry-based similarity search (GSS) tree, an indexing structure that maintains explicit representations of volumetric shape. We describe our implementation of a GSS tree for volumetric shape matching and provide a comprehensive evaluation of parameter sensitivity, performance, and scalability. Compared to previous bulk-loading algorithms, we find that matching and packing can construct a GSS-tree index in the same amount of time that is denser, flatter, and better performing, with an observed average performance improvement of 2X. PMID:26085707

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

Kuz'mina, L. G., E-mail: kuzmina@igic.ras.ru; Kucherepa, N. S.; Rodnikova, M. N.

The molecular and crystal structures of two p-(alkoxybenzylidene)-p'-toluidines C{sub 5}H{sub 11}O-C{sub 6}H{sub 4}-CH=N-C{sub 6}H{sub 4}-CH{sub 3} (1) and C{sub 8}H{sub 17}O-C{sub 6}H{sub 4}-CH=N-C{sub 6}H{sub 4}-CH{sub 3} (2), which form the nematic phase upon melting, is determined by X-ray diffraction. The geometry of the benzylideneaniline fragments in molecules 1 and 2 is actually identical. The crystal packings of 1 and 2 are characterized by the alternation of layers formed by loosely packed aliphatic fragments of molecules and layers of closely packed aromatic fragments. The packing in the aromatic regions of 1 follows the parquet pattern. The crystal packing of 2 hasmore » a stacking structure, which is formed by {pi}-stacking dimers superimposed on one another. The formation of the mesogenic phase upon melting of crystals 1 is due to the disturbance of the structurality of loose aliphatic layers with retention of the structure of the aromatic regions, which are stabilized by the cooperative effect of weak directed C-H ... {pi}-system interactions. The mesogenic phase of crystals 2 is formed upon melting as a consequence of the retention of the structure of {pi}-stacking dimers.« less

Packing of nonoverlapping cubic particles: Computational algorithms and microstructural characteristics

NASA Astrophysics Data System (ADS)

Malmir, Hessam; Sahimi, Muhammad; Tabar, M. Reza Rahimi

2016-12-01

Packing of cubic particles arises in a variety of problems, ranging from biological materials to colloids and the fabrication of new types of porous materials with controlled morphology. The properties of such packings may also be relevant to problems involving suspensions of cubic zeolites, precipitation of salt crystals during CO2 sequestration in rock, and intrusion of fresh water in aquifers by saline water. Not much is known, however, about the structure and statistical descriptors of such packings. We present a detailed simulation and microstructural characterization of packings of nonoverlapping monodisperse cubic particles, following up on our preliminary results [H. Malmir et al., Sci. Rep. 6, 35024 (2016), 10.1038/srep35024]. A modification of the random sequential addition (RSA) algorithm has been developed to generate such packings, and a variety of microstructural descriptors, including the radial distribution function, the face-normal correlation function, two-point probability and cluster functions, the lineal-path function, the pore-size distribution function, and surface-surface and surface-void correlation functions, have been computed, along with the specific surface and mean chord length of the packings. The results indicate the existence of both spatial and orientational long-range order as the the packing density increases. The maximum packing fraction achievable with the RSA method is about 0.57, which represents the limit for a structure similar to liquid crystals.

Packing of muscles in the rabbit shank influences three-dimensional architecture of M. soleus.

PubMed

Wick, Carolin; Böl, Markus; Müller, Florian; Blickhan, Reinhard; Siebert, Tobias

2018-07-01

Isolated and packed muscles (e.g. in the calf) exhibit different three-dimensional muscle shapes. In packed muscles, cross-sections are more angular compared to the more elliptical ones in isolated muscles. As far as we know, it has not been examined yet, whether the shape of the muscle in its packed condition influences its internal arrangement of muscle fascicles and accordingly the contraction behavior in comparison to the isolated condition. To evaluate the impact of muscle packing, we examined the three-dimensional muscle architecture of isolated and packed rabbit M. soleus for different ankle angles (65°, 75°, 85°, 90°, and 95°) using manual digitization (MicroScribe ® MLX). In general, significantly increased values of pennation angle and fascicle curvature were found in packed compared to isolated M. soleus (except for fascicle curvature at 90° ankle angle). On average, fascicle length of isolated muscles exceeded fascicle lengths of packed muscles by 2.6%. Reduction of pennation angle in the packed condition had only marginal influence on force generation (about 1% of maximum isometric force) in longitudinal direction (along the line of action) although an increase of transversal force component (perpendicular to the line of action) of about 26% is expected. Results of this study provide initial evidence that muscle packing limits maximum muscle performance observed in isolated M. soleus. Besides an enhanced understanding of the impact of muscle packing on architectural parameters, the outcomes of this study are essential for realistic three-dimensional muscle modeling and model validation. Copyright © 2018 Elsevier Ltd. All rights reserved.

Perceptions of plain packaging among young adult roll-your-own smokers in France: a naturalistic approach.

PubMed

Gallopel-Morvan, Karine; Moodie, Crawford; Eker, Figen; Beguinot, Emmanuelle; Martinet, Yves

2015-03-01

We explored, for the first time, young adult roll-your-own smokers' response to using plain packaging in real-world settings. Naturalistic research was employed, where 133 French young adult smokers (18-25 years of age) used plain roll-your-own packs for 10 days; the plain packs they were provided with contained their usual brand of rolling tobacco and displayed the name of their usual brand. Participants were recruited in five cities in France (Paris, Marseille, Metz, Nantes, Toulouse) and completed two questionnaires to measure their response to their own branded packs and the plain packs. Both questionnaires assessed pack perceptions, brand attachment, product perceptions (eg, taste, quality, natural), feelings about smoking (satisfying, pleasurable), feelings when using the pack in front of others (embarrassment, image), warning response (credibility, awareness of risks) and smoking-related behaviour (eg, consumption, quitting). Compared to their own fully branded packs, plain packs were associated with less positive pack and product perceptions, lower brand attachment and less positive feelings about smoking and feelings when using the pack in front of others. Participants were also more likely to report feeling like reducing consumption and quitting when using the plain packs, and more likely to feel like missing out on rolling a cigarette. No significant differences between the two pack types (plain and branded) were found in terms of credibility of warnings and perceptions of level of tar. The study suggests that the impacts of plain packaging for roll-your-own cigarette smokers are the same as for smokers of factory-made cigarettes. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

46 CFR 133.105 - Survival craft.

Code of Federal Regulations, 2013 CFR

2013-10-01

... approval series 160.151 and be equipped with a SOLAS A pack; (ii) On an OSV on an oceans route limited to within 50 nautical miles of the shore, must be approved under approval series 160.151 and be equipped... under approval series 160.051 or 160.151, with any approved equipment pack. (2) Each rigid liferaft must...

Bidispersed Sphere Packing on Spherical Surfaces

NASA Astrophysics Data System (ADS)

Atherton, Timothy; Mascioli, Andrew; Burke, Christopher

Packing problems on spherical surfaces have a long history, originating in the classic Thompson problem of finding the ground state configuration of charges on a sphere. Such packings contain a minimal number of defects needed to accommodate the curvature; this is predictable using the Gauss-Bonnet theorem from knowledge of the topology of the surface and the local symmetry of the ordering. Famously, the packing of spherical particles on a sphere contains a 'scar' transition, where additional defects over those required by topology appear above a certain critical number of particles and self-organize into chains or scars. In this work, we study the packing of bidispersed packings on a sphere, and hence determine the interaction of bidispersity and curvature. The resultant configurations are nearly crystalline for low values of bidispersity and retain scar-like structures; these rapidly become disordered for intermediate values and approach a so-called Appollonian limit at the point where smaller particles can be entirely accommodated within the voids left by the larger particles. We connect our results with studies of bidispersed packings in the bulk and on flat surfaces from the literature on glassy systems and jamming. Supported by a Cottrell Award from the Research Corporation for Science Advancement.

Precise algorithm to generate random sequential adsorption of hard polygons at saturation

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

Zhang, G.

Random sequential adsorption (RSA) is a time-dependent packing process, in which particles of certain shapes are randomly and sequentially placed into an empty space without overlap. In the infinite-time limit, the density approaches a "saturation'' limit. Although this limit has attracted particular research interest, the majority of past studies could only probe this limit by extrapolation. We have previously found an algorithm to reach this limit using finite computational time for spherical particles, and could thus determine the saturation density of spheres with high accuracy. Here in this paper, we generalize this algorithm to generate saturated RSA packings of two-dimensionalmore » polygons. We also calculate the saturation density for regular polygons of three to ten sides, and obtain results that are consistent with previous, extrapolation-based studies.« less

Precise algorithm to generate random sequential adsorption of hard polygons at saturation

DOE PAGES

Zhang, G.

2018-04-30

Random sequential adsorption (RSA) is a time-dependent packing process, in which particles of certain shapes are randomly and sequentially placed into an empty space without overlap. In the infinite-time limit, the density approaches a "saturation'' limit. Although this limit has attracted particular research interest, the majority of past studies could only probe this limit by extrapolation. We have previously found an algorithm to reach this limit using finite computational time for spherical particles, and could thus determine the saturation density of spheres with high accuracy. Here in this paper, we generalize this algorithm to generate saturated RSA packings of two-dimensionalmore » polygons. We also calculate the saturation density for regular polygons of three to ten sides, and obtain results that are consistent with previous, extrapolation-based studies.« less

Three-Dimensional Modeling of the Brain's ECS by Minimum Configurational Energy Packing of Fluid Vesicles

PubMed Central

Nandigam, Ravi K.; Kroll, Daniel M.

2007-01-01

The extracellular space of the brain is the heterogeneous porous medium formed by the spaces between the brain cells. Diffusion in this interstitial space is the mechanism by which glucose and oxygen are delivered to the brain cells from the vascular system. It is also a medium for the transport of certain informational substances between the cells (called volume transmission), and for drug delivery. This work involves three-dimensional modeling of the extracellular space as void space in close-packed arrays of fluid membrane vesicles. These packings are generated by minimizing the configurational energy using a Monte Carlo procedure. Both regular and random packs of vesicles are considered. A random walk algorithm is then used to compute the geometric tortuosities, and the results are compared with published experimental data. For the random packings, it is found that although the absolute values for the tortuosities differ, the dependence of the tortuosity on pore volume fraction is very similar to that observed in experiment. The tortuosities we measure are larger than those computed in previous studies of packings of convex polytopes, and modeling improvements, which require higher resolution studies and an improved modeling of brain cell shapes and mechanical properties, could help resolve remaining discrepancies between model simulations and experiment. It is also shown that the specular reflection scheme is the appropriate technique for implementing zero-flux boundary conditions in random walk simulations commonly encountered in diffusion problems. PMID:17307830

Three-dimensional modeling of the brain's ECS by minimum configurational energy packing of fluid vesicles.

PubMed

Nandigam, Ravi K; Kroll, Daniel M

2007-05-15

The extracellular space of the brain is the heterogeneous porous medium formed by the spaces between the brain cells. Diffusion in this interstitial space is the mechanism by which glucose and oxygen are delivered to the brain cells from the vascular system. It is also a medium for the transport of certain informational substances between the cells (called volume transmission), and for drug delivery. This work involves three-dimensional modeling of the extracellular space as void space in close-packed arrays of fluid membrane vesicles. These packings are generated by minimizing the configurational energy using a Monte Carlo procedure. Both regular and random packs of vesicles are considered. A random walk algorithm is then used to compute the geometric tortuosities, and the results are compared with published experimental data. For the random packings, it is found that although the absolute values for the tortuosities differ, the dependence of the tortuosity on pore volume fraction is very similar to that observed in experiment. The tortuosities we measure are larger than those computed in previous studies of packings of convex polytopes, and modeling improvements, which require higher resolution studies and an improved modeling of brain cell shapes and mechanical properties, could help resolve remaining discrepancies between model simulations and experiment. It is also shown that the specular reflection scheme is the appropriate technique for implementing zero-flux boundary conditions in random walk simulations commonly encountered in diffusion problems.

Ultrathin free-standing close-packed gold nanoparticle films: Conductivity and Raman scattering enhancement

NASA Astrophysics Data System (ADS)

Yu, Qing; Huang, Hongwen; Peng, Xinsheng; Ye, Zhizhen

2011-09-01

A simple filtration technique was developed to prepare large scale free-standing close-packed gold nanoparticle ultrathin films using metal hydroxide nanostrands as both barrier layer and sacrificial layer. As thin as 70 nm, centimeter scale robust free-standing gold nanoparticle thin film was obtained. The thickness of the films could be easily tuned by the filtration volumes. The electronic conductivities of these films varied with the size of the gold nanoparticles, post-treatment temperature, and thickness, respectively. The conductivity of the film prepared from 20 nm gold nanoparticles is higher than that of the film prepared from 40 nm gold nanoparticle by filtering the same filtration volume of their solution, respectively. Their conductivities are comparable to that of the 220 nm thick ITO film. Furthermore, these films demonstrated an average surface Raman scattering enhancement up to 6.59 × 105 for Rhodamine 6 G molecules on the film prepared from 40 nm gold nanoparticles. Due to a lot of nano interspaces generated from the close-packed structures, two abnormal enhancements and relative stronger intensities of the asymmetrical vibrations at 1534 and 1594 cm-1 of R6G were observed, respectively. These robust free-standing gold nanoparticle films could be easily transferred onto various solid substrates and hold the potential application for electrodes and surface enhanced Raman detectors. This method is applicable for preparation of other nanoparticle free-standing thin films.A simple filtration technique was developed to prepare large scale free-standing close-packed gold nanoparticle ultrathin films using metal hydroxide nanostrands as both barrier layer and sacrificial layer. As thin as 70 nm, centimeter scale robust free-standing gold nanoparticle thin film was obtained. The thickness of the films could be easily tuned by the filtration volumes. The electronic conductivities of these films varied with the size of the gold nanoparticles, post-treatment temperature, and thickness, respectively. The conductivity of the film prepared from 20 nm gold nanoparticles is higher than that of the film prepared from 40 nm gold nanoparticle by filtering the same filtration volume of their solution, respectively. Their conductivities are comparable to that of the 220 nm thick ITO film. Furthermore, these films demonstrated an average surface Raman scattering enhancement up to 6.59 × 105 for Rhodamine 6 G molecules on the film prepared from 40 nm gold nanoparticles. Due to a lot of nano interspaces generated from the close-packed structures, two abnormal enhancements and relative stronger intensities of the asymmetrical vibrations at 1534 and 1594 cm-1 of R6G were observed, respectively. These robust free-standing gold nanoparticle films could be easily transferred onto various solid substrates and hold the potential application for electrodes and surface enhanced Raman detectors. This method is applicable for preparation of other nanoparticle free-standing thin films. Electronic supplementary information (ESI) available: Figure S1, the SEM images and photograph of the films prepared from 10 ml, 20 nm gold nanoparticles. Scheme S1, the vibrations of 1534 and 1594 cm-1 of R6G. See DOI: 10.1039/c1nr10578g

Mobility of icy sand packs, with application to Martian permafrost

USGS Publications Warehouse

Durham, W.B.; Pathare, A.V.; Stern, L.A.; Lenferink, H.J.

2009-01-01

[1] The physical state of water on Mars has fundamental ramifications for both climatology and astrobiology. The widespread presence of "softened" Martian landforms (such as impact craters) can be attributed to viscous creep of subsurface ground ice. We present laboratory experiments designed to determine the minimum amount of ice necessary to mobilize topography within Martian permafrost. Our results show that the jammed-to-mobile transition of icy sand packs neither occurs at fixed ice content nor is dependent on temperature or stress, but instead correlates strongly with the maximum dry packing density of the sand component. Viscosity also changes rapidly near the mobility transition. The results suggest a potentially lower minimum volatile inventory for the impact-pulverized megaregolith of Mars. Furthermore, the long-term preservation of partially relaxed craters implies that the ice content of Martian permafrost has remained close to that at the mobility transition throughout Martian history. Copyright 2009 by the American Geophysical Union.

On plastic flow in notched hexagonal close packed single crystals

NASA Astrophysics Data System (ADS)

Selvarajou, Balaji; Kondori, Babak; Benzerga, A. Amine; Joshi, Shailendra P.

2016-09-01

The micromechanics of anisotropic plastic flow by combined slip and twinning is investigated computationally in single crystal notched specimens. Constitutive relations for hexagonal close packed materials are used which take into account elastic anisotropy, thirty potential deformation systems, various hardening mechanisms and rate-sensitivity. The specimens are loaded perpendicular to the c-axis but the presence of a notch generates three-dimensional triaxial stress states. The study is motivated by recent experiments on a polycrystalline magnesium alloy. To enable comparisons with these where appropriate, three sets of activation thresholds for the various deformation systems are used. For the conditions that most closely mimic the alloy material, attention is focused on the relative roles of pyramidal 〈 c + a 〉 and prismatic 〈 a 〉 slip, as well as on the emergence of {1012bar}[101bar1] extension twinning at sufficiently high triaxiality. In all cases, the spatial variations of stress triaxiality and plastic strain, inclusive of various system activities, are quantified along with their evolution upon straining. The implications of these findings in fundamental understanding of ductile failure of HCP alloys in general and Mg alloys in particular are discussed.

7 CFR 51.311 - Marking requirements.

Code of Federal Regulations, 2014 CFR

2014-01-01

... (INSPECTION, CERTIFICATION, AND STANDARDS) United States Standards for Grades of Apples Marking Requirements...), grade, and the numerical count or minimum diameter of apples packed in a closed container shall be indicated on the container. For apple lots utilizing the combined diameter/weight designations for Red...

7 CFR 51.311 - Marking requirements.

Code of Federal Regulations, 2013 CFR

2013-01-01

... (INSPECTION, CERTIFICATION, AND STANDARDS) United States Standards for Grades of Apples Marking Requirements...), grade, and the numerical count or minimum diameter of apples packed in a closed container shall be indicated on the container. For apple lots utilizing the combined diameter/weight designations for Red...

Structures having enhanced biaxial texture and method of fabricating same

DOEpatents

Goyal, A.; Budai, J.D.; Kroeger, D.M.; Norton, D.P.; Specht, E.D.; Christen, D.K.

1999-04-27

A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon. 11 figs.

Gradient index retroreflector

DOEpatents

Layne, Clyde B.

1988-01-01

A retroreflector is formed of a graded index lens with a reflective coating at one end. The lens has a length of an odd multiple of a quarter period thereof. Hexagonally shaped graded index lenses may be closely packed in an array to form a retroreflecting surface.

Structures having enhanced biaxial texture and method of fabricating same

DOEpatents

Goyal, A.; Budai, J.D.; Kroeger, D.M.; Norton, D.P.; Specht, E.D.; Christen, D.K.

1998-04-21

A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon. 11 figs.

Structures having enhanced biaxial texture and method of fabricating same

DOEpatents

Goyal, A.; Budai, J.D.; Kroeger, D.M.; Norton, D.P.; Specht, E.D.; Christen, D.K.

1998-04-14

A biaxially textured article includes a rolled and annealed, biaxially textured substrate of a metal having a face-centered cubic, body-centered cubic, or hexagonal close-packed crystalline structure; and an epitaxial superconductor or other device epitaxially deposited thereon. 11 figs.

49 CFR 173.227 - Materials poisonous by inhalation, Division 6.1, Packing Group I, Hazard Zone B.

Code of Federal Regulations, 2013 CFR

2013-10-01

... are— (i) Closed and tightened to a torque prescribed by the closure manufacturer, using a properly calibrated device that is capable of measuring torque; (ii) Physically held in place by any means capable of...

49 CFR 173.226 - Materials poisonous by inhalation, Division 6.1, Packing Group I, Hazard Zone A.

Code of Federal Regulations, 2011 CFR

2011-10-01

...; (3) Have screw-type closures that are— (i) Closed and tightened to a torque prescribed by the closure manufacturer, using a properly calibrated device that is capable of measuring torque; (ii) Physically held in...

49 CFR 173.227 - Materials poisonous by inhalation, Division 6.1, Packing Group I, Hazard Zone B.

Code of Federal Regulations, 2010 CFR

2010-10-01

... are— (i) Closed and tightened to a torque prescribed by the closure manufacturer, using a properly calibrated device that is capable of measuring torque; (ii) Physically held in place by any means capable of...

49 CFR 173.226 - Materials poisonous by inhalation, Division 6.1, Packing Group I, Hazard Zone A.

Code of Federal Regulations, 2012 CFR

2012-10-01

...; (3) Have screw-type closures that are— (i) Closed and tightened to a torque prescribed by the closure manufacturer, using a properly calibrated device that is capable of measuring torque; (ii) Physically held in...

49 CFR 173.226 - Materials poisonous by inhalation, Division 6.1, Packing Group I, Hazard Zone A.

Code of Federal Regulations, 2013 CFR

2013-10-01

...; (3) Have screw-type closures that are— (i) Closed and tightened to a torque prescribed by the closure manufacturer, using a properly calibrated device that is capable of measuring torque; (ii) Physically held in...

49 CFR 173.226 - Materials poisonous by inhalation, Division 6.1, Packing Group I, Hazard Zone A.

Code of Federal Regulations, 2010 CFR

2010-10-01

...; (3) Have screw-type closures that are— (i) Closed and tightened to a torque prescribed by the closure manufacturer, using a properly calibrated device that is capable of measuring torque; (ii) Physically held in...

49 CFR 173.227 - Materials poisonous by inhalation, Division 6.1, Packing Group I, Hazard Zone B.

Code of Federal Regulations, 2014 CFR

2014-10-01

... are— (i) Closed and tightened to a torque prescribed by the closure manufacturer, using a properly calibrated device that is capable of measuring torque; (ii) Physically held in place by any means capable of...

49 CFR 173.227 - Materials poisonous by inhalation, Division 6.1, Packing Group I, Hazard Zone B.

Code of Federal Regulations, 2011 CFR

2011-10-01

... are— (i) Closed and tightened to a torque prescribed by the closure manufacturer, using a properly calibrated device that is capable of measuring torque; (ii) Physically held in place by any means capable of...

49 CFR 173.226 - Materials poisonous by inhalation, Division 6.1, Packing Group I, Hazard Zone A.

Code of Federal Regulations, 2014 CFR

2014-10-01

...; (3) Have screw-type closures that are— (i) Closed and tightened to a torque prescribed by the closure manufacturer, using a properly calibrated device that is capable of measuring torque; (ii) Physically held in...

49 CFR 173.227 - Materials poisonous by inhalation, Division 6.1, Packing Group I, Hazard Zone B.

Code of Federal Regulations, 2012 CFR

2012-10-01

... are— (i) Closed and tightened to a torque prescribed by the closure manufacturer, using a properly calibrated device that is capable of measuring torque; (ii) Physically held in place by any means capable of...

Intruder Dynamic Response in Particulate Media

NASA Astrophysics Data System (ADS)

Warnakulasooriya, Niranjan

Many everyday materials, broadly classified as "particulate media", are at the heart of many industries and natural phenomena. Examples range from the storage and transport of bulk foods and aggregates such as grains and coal; the processing of pharmaceutical pills and the grinding coffee beans; to the mitigation and cost control of life-threatening events like landslides, earthquakes, and silo failures. The common theme connecting all these phenomena is the mechanical stability of the granular material that arises from interactions at the microscopic level of the grain scale, and how this influences collective properties at the bulk, macroscopic scale. In this dissertation, we present an extensive study of the mechanical properties of a physics-based model of granular particle systems in two dimensions using computer simulations. Specifically, we study the dynamics of an intruder particle that is driven through a dense, disordered packing of particles. This practical technique has the benefit of being amenable to experimental application which we expect will motivate future studies in the area. We find the 'microrheology' of the intruder can be traced back to the properties of underlying, original, unperturbed packing, thereby providing a method to characterize the mechanical properties of the material that may otherwise be unavailable. To perform this study, we initially created mechanically stable granular packings of bidisperse discs, for several orders of magnitude of particle friction coefficient mu, over a range in packing densities, or packing fractions φ, in the vicinity of the critical packing fraction φc, the density below which the packing is no longer stable. This range in φ translates to a range in packing pressures P, spanning several orders of magnitude down to the P → 0 limit. For each packing, we apply a driving force to the intruder probe particle and find the critical force Fc, the minimum force required to induce motion of the probe as it is dragged through the system. We find that Fc(mu) for the different friction packings, scales with the packing pressure P as a power-law according to:Fc(mu) - Fo cmu) Pbeta(mu). The power-law exponent, beta(mu) becomes friction dependent, but approaches the value, beta(mu → 0) = 1.0 +/- 0.1 in the zero-friction limit. Focmu) is the value of F c in the limit P → 0, that similarly depends on the friction coefficient as, Focmu) → 0, when mu → infinity. We use this property of Fo cmu) to characterize the mechanical properties of different frictional packings. Another focus of this study is the 'microrheology' of the intruder through force-velocity dependencies in mu = 0 systems at different P. For this case, the intruder is driven through the packing at a steady-state velocity , for driving forces above the critical force FD > Fc. We introduce a scaling function that collapses the force-velocity curves onto a single master curve. This power law scaling of the collapsed curve as P → 0 is reminiscent of a continuous phase transition, reinforcing the notion that the mechanical state of the system exhibits critical-like features. Furthermore, we also find an alternative scaling collapse of the form: - (FD - Fc) alpha, where represents a constant velocity term in the limit of small excess forcing, and the critical force Fc now appears as fitting parameter that matches our explicit calculations. Thence, we are able to extract Fc from a driven probe without a-priori having any knowledge about the state of the system. To further investigate the transition of the system through the different intruder force perturbations, we implemented a coarse graining (CG) technique that transforms our discrete particle interaction force information into continuous stress fields. Through this methodology, we are able to calculate the kinetic and contact stresses as the intruder is driven through the system. We are able to qualify and quantify the directional and distance dependencies of the stress response of the packing due to the driven probe via radial and azimuthal stress calculations. In particular, we find how the stress response not only captures the wake region behind the driven intruder, but also how the stress decays in the forward direction of the intruder, which follows universal behavior.

Electromagnetic energy transport in nanoparticle chains via dark plasmon modes.

PubMed

Solis, David; Willingham, Britain; Nauert, Scott L; Slaughter, Liane S; Olson, Jana; Swanglap, Pattanawit; Paul, Aniruddha; Chang, Wei-Shun; Link, Stephan

2012-03-14

Using light to exchange information offers large bandwidths and high speeds, but the miniaturization of optical components is limited by diffraction. Converting light into electron waves in metals allows one to overcome this problem. However, metals are lossy at optical frequencies and large-area fabrication of nanometer-sized structures by conventional top-down methods can be cost-prohibitive. We show electromagnetic energy transport with gold nanoparticles that were assembled into close-packed linear chains. The small interparticle distances enabled strong electromagnetic coupling causing the formation of low-loss subradiant plasmons, which facilitated energy propagation over many micrometers. Electrodynamic calculations confirmed the dark nature of the propagating mode and showed that disorder in the nanoparticle arrangement enhances energy transport, demonstrating the viability of using bottom-up nanoparticle assemblies for ultracompact opto-electronic devices. © 2012 American Chemical Society

Evaluate interference in digital channels

NASA Technical Reports Server (NTRS)

Davarian, F.; Sumida, J.

1985-01-01

Any future mobile satellite service (MSS) which is to provide simultaneous mobile communications for a large number of users will have to make very efficient use of the spectrum. As the spectrum available for an MSS is limited, the system's channels should be packed as closely together as possible, with minimum-width guard bands. In addition the employment of frequency reuse schemes is an important factor. Difficulties regarding these solutions are related to the introduction of interference in the link. A balance must be achieved between the competing aims of spectrum conservation and low interference. While the interference phenomenon in narrowband FM voice channels is reasonably well understood, very little effort, however, has been devoted to the problem in digital radios. Attention is given to work, which illuminates the effects of cochannel and adjacent channel interference on digital FM (FSK) radios.

Reconfiguration of a flexible fiber immersed in a 2D dense granular flow close to the jamming transition

NASA Astrophysics Data System (ADS)

Kolb, Evelyne; Algarra, Nicolas; Vandembroucq, Damien; Lazarus, Arnaud

2015-11-01

We propose a new fluid/structure interaction in the unusual case of a dense granular medium flowing against an elastic fibre acting as a flexible intruder. We experimentally studied the deflection of a mylar flexible beam clamped at one side, the other free side facing a 2D granular flow in a horizontal cell moving at a constant velocity. We investigated the reconfiguration of the fibre as a function of the fibre's rigidity and of the granular packing fraction close but below the jamming in 2D. Imposing the fibre geometry like its length or thickness sets the critical buckling force the fibre is able to resist if it was not supported by lateral grains, while increasing the granular packing fraction might laterally consolidate the fibre and prevent it from buckling. But on the other side, the approach to jamming transition by increasing the granular packing fraction will be characterized by a dramatically increasing size of the cluster of connected grains forming a solid block acting against the fibre, which might promote the fibre's deflection. Thus, we investigated the granular flow fields, the fibre's deflexion as well as the forces experienced by the fibre and compared them with theoretical predictions from elastica for different loadings along the fibre. PMMH, CNRS UMR 7636, UPMC, ESPCI-ParisTech, 10 rue Vauquelin, 75231 Paris Cedex 05, France.

Adolescent girls and young adult women's perceptions of superslims cigarette packaging: a qualitative study.

PubMed

Ford, Allison; Moodie, Crawford; Purves, Richard; MacKintosh, Anne Marie

2016-01-08

To explore perceptions of superslims packaging, including compact 'lipstick' packs, in line with 3 potential impacts identified within the impact assessment of the European Union (EU) Tobacco Products Directive: appeal, harm perceptions and the seriousness of warning of health risks. Qualitative focus group study. Informal community venues in Scotland, UK. 75 female non-smokers and occasional smokers (age range 12-24). Compact 'lipstick'-type superslims packs were perceived most positively and rated as most appealing. They were also viewed as less harmful than more standard sized cigarette packs because of their smaller size and likeness to cosmetics. Additionally, 'lipstick' packs were rated as less serious in terms of warning about the health risks associated with smoking, either because the small font size of the warnings was difficult to read or because the small pack size prevented the text on the warnings from being displayed properly. Bright pack colours and floral designs were also thought to detract from the health warning. As superslims packs were found to increase appeal, mislead with respect to level of harm, and undermine the on-pack health warnings, this provides support for the decision to ban 'lipstick'-style cigarette packs in the EU and has implications for policy elsewhere. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Aneurysm permeability following coil embolization: packing density and coil distribution.

PubMed

Chueh, Ju-Yu; Vedantham, Srinivasan; Wakhloo, Ajay K; Carniato, Sarena L; Puri, Ajit S; Bzura, Conrad; Coffin, Spencer; Bogdanov, Alexei A; Gounis, Matthew J

2015-09-01

Rates of durable aneurysm occlusion following coil embolization vary widely, and a better understanding of coil mass mechanics is desired. The goal of this study is to evaluate the impact of packing density and coil uniformity on aneurysm permeability. Aneurysm models were coiled using either Guglielmi detachable coils or Target coils. The permeability was assessed by taking the ratio of microspheres passing through the coil mass to those in the working fluid. Aneurysms containing coil masses were sectioned for image analysis to determine surface area fraction and coil uniformity. All aneurysms were coiled to a packing density of at least 27%. Packing density, surface area fraction of the dome and neck, and uniformity of the dome were significantly correlated (p<0.05). Hence, multivariate principal components-based partial least squares regression models were used to predict permeability. Similar loading vectors were obtained for packing and uniformity measures. Coil mass permeability was modeled better with the inclusion of packing and uniformity measures of the dome (r(2)=0.73) than with packing density alone (r(2)=0.45). The analysis indicates the importance of including a uniformity measure for coil distribution in the dome along with packing measures. A densely packed aneurysm with a high degree of coil mass uniformity will reduce permeability. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Influence of geometry on pressure and velocity distribution in packed-bed methanol steam reforming reactor

NASA Astrophysics Data System (ADS)

Ivanović, Ivana; Sedmak, Aleksandar; Milošević, Miloš; Cvetković, Ivana; Pohar, Andrej; Likozar, Blaž

2017-07-01

The main tasks of this research is to propose several changes in the packed bed micro methanol steam reformer geometry in order to ensure its performance. The reformer is an integral part of the existing indirect internal reforming high temperature PEMFC and most of its geometry is already defined. The space for remodeling is very limited.

Magnetic vortices in nanocaps induced by curvature

NASA Astrophysics Data System (ADS)

Abdelgawad, Ahmed M.; Nambiar, Nikhil; Bapna, Mukund; Chen, Hao; Majetich, Sara A.

2018-05-01

Magnetic nanoparticles with room temperature remanent magnetic vortices stabilized by their curvature are very intriguing due to their potential use in biomedicine. In the present study, we investigate room temperature magnetic chirality in 100 nm diameter permalloy spherical caps with 10 nm and 30 nm thicknesses. Micromagnetic OOMMF simulations predict the equilibrium spin structure for these caps to form a vortex state. We fabricate the permalloy caps by sputtering permalloy on both close-packed and sparse arrays of polystyrene nanoparticles. Magnetic force microscopy scans show a clear signature of a vortex state in close-packed caps of both 10 nm and 30 nm thicknesses. Alternating gradient magnetometry measurements of the caps are consistent with a remnant vortex state in 30 nm thick caps and a transition to an onion state followed by a vortex state in 10 nm thick caps. Out-of-plane measurements supported by micromagnetic simulations shows that an out-of-plane field can stabilize a vortex state down to a diameter of 15 nm.

Binding of an adatom to a simple metal surface

NASA Technical Reports Server (NTRS)

Huntington, H. B.; Turk, L. A.; White, W. W., III

1975-01-01

The density functional formalism of Hohenberg and Kohn is used to investigate the energies, charge densities and forces which hold an adatom on the surface of a simple metal. The valence wavefunction of the adatom is fitted to the Herman-Skillman solutions at large distance and is simplified somewhat in the core region. The field of the ion is represented by the Ashcroft pseudopotential. For the metal the jellium model is used. Detailed calculations are carried out for a sodium adatom on a sodium surface. Simply juxtaposing adatom and surface gives a binding energy of about 1/3 eV. This value is approximately twice the surface energy per atom in the close-packed plane. Charge redistributions as determined variationally increase the binding energy by about 10%. The equilibrium distance for the adatom turns out to be 1.66 A from the surface, as compared with 1.52 A, the observed value for one-half the distance between the close-packed planes.

Electron core ionization in compressed alkali metal cesium

NASA Astrophysics Data System (ADS)

Degtyareva, V. F.

2018-01-01

Elements of groups I and II in the periodic table have valence electrons of s-type and are usually considered as simple metals. Crystal structures of these elements at ambient pressure are close-packed and high-symmetry of bcc and fcc-types, defined by electrostatic (Madelung) energy. Diverse structures were found under high pressure with decrease of the coordination number, packing fraction and symmetry. Formation of complex structures can be understood within the model of Fermi sphere-Brillouin zone interactions and supported by Hume-Rothery arguments. With the volume decrease there is a gain of band structure energy accompanied by a formation of many-faced Brillouin zone polyhedra. Under compression to less than a half of the initial volume the interatomic distances become close to or smaller than the ionic radius which should lead to the electron core ionization. At strong compression it is necessary to assume that for alkali metals the valence electron band overlaps with the upper core electrons, which increases the valence electron count under compression.

Segregation of large granules from close-packed cluster of small granules due to buoyancy.

PubMed

Yang, Xian-qing; Zhou, Kun; Qiu, Kang; Zhao, Yue-min

2006-03-01

Segregation of large granules in a vibrofluidized granular bed with inhomogeneous granular number density distribution is studied by an event-driven algorithm. Simulation results show that the mean vertical position of large granules decreases with the increase of the density ration of the large granules to the small ones. This conclusion is consistent with the explanation that the net pressure due to the small surrounding particle impacts balances the large granular weight, and indict that the upward movement of the large granules is driven by the buoyancy. The values of temperature, density, and pressure of the systems are also computed by changing the conditions such as heating temperature on the bottom and restitution coefficient of particles. These results indicate that the segregation of large granules also happen in the systems with density inversion or even close-packed cluster of particles floating on a low-density fluid, due to the buoyancy. An equation of state is proposed to explain the buoyancy.

Magnetic ordering temperatures in rare earth metal dysprosium under ultrahigh pressures

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

Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.

Magnetic ordering temperatures in heavy rare earth metal Dysprosium (Dy) have been studied using an ultrasensitive electrical transport measurement technique in a designer diamond anvil cell to extreme conditions of pressure to 69 GPa and temperature to 10 K. Previous studies using magnetic susceptibility measurements at high pressures were only able to track magnetic ordering temperature till 7 GPa in the hexagonal close packed ( hcp) phase of Dy. Our studies indicate that the magnetic ordering temperature shows an abrupt drop of 80 K at the hcp-Sm phase transition followed by a gradual decrease that continues till 17 GPa. Thismore » is followed by a rapid increase in the magnetic ordering temperatures in the double hexagonal close packed phase and finally leveling off in the distorted face centered cubic phase of Dy. Lastly, our studies reaffirm that 4f-shell remain localized in Dy and there is no loss of magnetic moment or 4f-shell delocalization for pressures up to 69 GPa.« less

Intragranular twinning, detwinning, and twinning-like lattice reorientation in magnesium alloys

DOE PAGES

Wu, Wei; Gao, Yanfei; Oak Ridge National Lab.; ...

2016-09-11

We present that deformation twinning plays a critical role on improving metals or alloys ductility, especially for hexagonal close-packed materials with low symmetry crystal structure. A rolled Mg alloy was selected as a model system to investigate the extension twinning behaviors and characteristics of parent-twin interactions by nondestructive in situ 3D synchrotron X-ray microbeam diffraction. Besides twinning- detwinning process, the twinning-like lattice reorientation process was captured within an individual grain inside a bulk material during the strain reversal. The distributions of parent, twin, and reorientated grains and sub-micron level strain variation across the twin boundary are revealed. A theoretical calculationmore » of the lattice strain confirms that the internal strain distribution in parent and twinned grains correlates with the experimental setup, grain orientation of parent, twin, and surrounding grains, as well as the strain path changes. In conclusion, the study suggests a novel deformation mechanism within the hexagonal close-packed structure that cannot be determined from surface-based characterization methods.« less

Magnetic ordering temperatures in rare earth metal dysprosium under ultrahigh pressures

DOE PAGES

Samudrala, Gopi K.; Tsoi, Georgiy M.; Weir, Samuel T.; ...

2014-04-03

Magnetic ordering temperatures in heavy rare earth metal Dysprosium (Dy) have been studied using an ultrasensitive electrical transport measurement technique in a designer diamond anvil cell to extreme conditions of pressure to 69 GPa and temperature to 10 K. Previous studies using magnetic susceptibility measurements at high pressures were only able to track magnetic ordering temperature till 7 GPa in the hexagonal close packed ( hcp) phase of Dy. Our studies indicate that the magnetic ordering temperature shows an abrupt drop of 80 K at the hcp-Sm phase transition followed by a gradual decrease that continues till 17 GPa. Thismore » is followed by a rapid increase in the magnetic ordering temperatures in the double hexagonal close packed phase and finally leveling off in the distorted face centered cubic phase of Dy. Lastly, our studies reaffirm that 4f-shell remain localized in Dy and there is no loss of magnetic moment or 4f-shell delocalization for pressures up to 69 GPa.« less

Near-zero thermal expansion in magnetically ordered state in dysprosium at high pressures and low temperatures

NASA Astrophysics Data System (ADS)

Hope, Kevin M.; Samudrala, Gopi K.; Vohra, Yogesh K.

2017-01-01

The atomic volume of rare earth metal dysprosium (Dy) has been measured up to high pressures of 35 GPa and low temperatures between 200 and 7 K in a diamond anvil cell using angle dispersive X-ray diffraction at a synchrotron source. The hexagonal close-packed (hcp), alpha-Samarium (α-Sm), and double hexagonal close-packed (dhcp) phases are observed to be stable in Dy under high-pressure and low-temperature conditions achieved in our experiments. Dy is known to undergo magnetic ordering below 176 K at ambient pressure with magnetic ordering Néel temperature (TN) that changes rapidly with increasing pressure. Our experimental measurement shows that Dy has near-zero thermal expansion in the magnetically ordered state and normal thermal expansion in the paramagnetic state for all the three known high pressure phases (hcp, α-Sm, and dhcp) to 35 GPa. This near-zero thermal expansion behavior in Dy is observed below the magnetic ordering temperature TN at all pressures up to 35 GPa.

A 90GHz Bolometer Camera Detector System for the Green Bank Telescope

NASA Technical Reports Server (NTRS)

Benford, Dominic J.; Allen, Christine A.; Buchanan, Ernest D.; Chen, Tina C.; Chervenak, James A.; Devlin, Mark J.; Dicker, Simon R.; Forgione, Joshua B.

2004-01-01

We describe a close-packed, two-dimensional imaging detector system for operation at 90GHz (3.3mm) for the 100 m Green Bank Telescope (GBT) This system will provide high sensitivity (<1mjy in 1s rapid imaging (15'x15' to 250 microJy in 1 hr) at the world's largest steerable aperture. The heart of this camera is an 8x8 close packed, Nyquist-sampled array of superconducting transition edge sensor bolometers. We have designed and are producing a functional superconducting bolometer array system using a monolithic planar architecture and high-speed multiplexed readout electronics. With an NEP of approx. 2.10(exp 17) W/square root Hz, the TES bolometers will provide fast linear sensitive response for high performance imaging. The detectors are read out by and 8x8 time domain SQUID multiplexer. A digital/analog electronics system has been designed to enable read out by SQUID multiplexers. First light for this instrument on the GBT is expected within a year.

A 90GHz Bolometer Camera Detector System for the Green

NASA Technical Reports Server (NTRS)

Benford, Dominic J.; Allen, Christine A.; Buchanan, Ernest; Chen, Tina C.; Chervenak, James A.; Devlin, Mark J.; Dicker, Simon R.; Forgione, Joshua B.

2004-01-01

We describe a close-packed, two-dimensional imaging detector system for operation at 90GHz (3.3 mm) for the 100m Green Bank Telescope (GBT). This system will provide high sensitivity (less than 1mJy in 1s) rapid imaging (15'x15' to 150 micron Jy in 1 hr) at the world's largest steerable aperture. The heart of this camera is an 8x8 close-packed, Nyquist-sampled array of superconducting transition edge sensor (TES) bolometers. We have designed and are producing a functional superconducting bolometer array system using a monolithic planar architecture and high-speed multiplexed readout electronics. With an NEP of approximately 2 x 10(exp -17) W/square root of Hz, the TES bolometers will provide fast, linear, sensitive response for high performance imaging. The detectors are read out by an 8x8 time domain SQUID multiplexer. A digital/analog electronics system has been designed to enable read out by SQUID multiplexers. First light for this instrument on the GBT is expected within a year.

Fabrication of non-hexagonal close packed colloidal array on a substrate by transfer

NASA Astrophysics Data System (ADS)

Banik, Meneka; Mukherjee, Rabibrata

Self-organized colloidal arrays find application in fabrication of solar cells with advanced light management strategies. We report a simple spincoating based approach for fabricating two dimensional colloidal crystals with hexagonal and non-hexagonal close packed assembly on flat and nanopatterned substrates. The non-HCP arrays were fabricated by spin coating the particles onto soft lithographically fabricated substrates. The substrate patterns impose directionality to the particles by confining them within the grooves. We have developed a technique by which the HCP and non-HCP arrays can be transferred to any surface. For this purpose the colloidal arrays were fabricated on a UV degradable PMMA layer, resulting in transfer of the particles on UV exposure. This allows the colloidal structures to be transported across substrates irrespective of their surface energy, wettability or morphology. Since the particles are transferred without exposing it to any kind of chemical or thermal environment, it can be utilized for placing particles on top of thin film solar cells for improving their absorption efficiency.

Poisson's Ratio and the Densification of Glass under High Pressure

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

Rouxel, T.; Ji, H.; Hammouda, T.

2008-06-06

Because of a relatively low atomic packing density, (C{sub g}) glasses experience significant densification under high hydrostatic pressure. Poisson's ratio ({nu}) is correlated to C{sub g} and typically varies from 0.15 for glasses with low C{sub g} such as amorphous silica to 0.38 for close-packed atomic networks such as in bulk metallic glasses. Pressure experiments were conducted up to 25 GPa at 293 K on silica, soda-lime-silica, chalcogenide, and bulk metallic glasses. We show from these high-pressure data that there is a direct correlation between {nu} and the maximum post-decompression density change.

Evidence of rayleigh-hertz surface waves and shear stiffness anomaly in granular media.

PubMed

Bonneau, L; Andreotti, B; Clément, E

2008-09-12

Using the nonlinear dependence of sound propagation speed with pressure, we evidence the anomalous elastic softness of a granular packing in the vicinity of the jamming transition. Under gravity and close to a free surface, the acoustic propagation is only possible through surface modes guided by the stiffness gradient. These Rayleigh-Hertz modes are evidenced in a controlled laboratory experiment. The shape and the dispersion relation of both transverse and sagittal modes are compared to the prediction of nonlinear elasticity including finite size effects. These results allow one to access the elastic properties of the packing under vanishing confining pressure.

Origin of Noncubic Scaling Law in Disordered Granular Packing.

PubMed

Xia, Chengjie; Li, Jindong; Kou, Binquan; Cao, Yixin; Li, Zhifeng; Xiao, Xianghui; Fu, Yanan; Xiao, Tiqiao; Hong, Liang; Zhang, Jie; Kob, Walter; Wang, Yujie

2017-06-09

Recent diffraction experiments on metallic glasses have unveiled an unexpected noncubic scaling law between density and average interatomic distance, which led to the speculation of the presence of fractal glass order. Using x-ray tomography we identify here a similar noncubic scaling law in disordered granular packing of spherical particles. We find that the scaling law is directly related to the contact neighbors within the first nearest neighbor shell, and, therefore, is closely connected to the phenomenon of jamming. The seemingly universal scaling exponent around 2.5 arises due to the isostatic condition with a contact number around 6, and we argue that the exponent should not be universal.

Molecular characterization of organic electronic films.

PubMed

DeLongchamp, Dean M; Kline, R Joseph; Fischer, Daniel A; Richter, Lee J; Toney, Michael F

2011-01-18

Organic electronics have emerged as a viable competitor to amorphous silicon for the active layer in low-cost electronics. The critical performance of organic electronic materials is closely related to their morphology and molecular packing. Unlike their inorganic counterparts, polymers combine complex repeat unit structure and crystalline disorder. This combination prevents any single technique from being able to uniquely solve the packing arrangement of the molecules. Here, a general methodology for combining multiple, complementary techniques that provide accurate unit cell dimensions and molecular orientation is described. The combination of measurements results in a nearly complete picture of the organic film morphology. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Packing and self-assembly of truncated triangular bipyramids

NASA Astrophysics Data System (ADS)

Haji-Akbari, Amir; Chen, Elizabeth R.; Engel, Michael; Glotzer, Sharon C.

2013-07-01

Motivated by breakthroughs in the synthesis of faceted nano- and colloidal particles, as well as theoretical and computational studies of their packings, we investigate a family of truncated triangular bipyramids. We report dense periodic packings with small unit cells that were obtained via numerical and analytical optimization. The maximal packing fraction ϕmax changes continuously with the truncation parameter t. Eight distinct packings are identified based on discontinuities in the first and second derivatives of ϕmax(t). These packings differ in the number of particles in the fundamental domain (unit cell) and the type of contacts between the particles. In particular, we report two packings with four particles in the unit cell for which both ϕmax(t) and ϕmax'(t) are continuous and the discontinuity occurs in the second derivative only. In the self-assembly simulations that we perform for larger boxes with 2048 particles, only one out of eight packings is found to assemble. In addition, the degenerate quasicrystal reported previously for triangular bipyramids without truncation [Haji-Akbari , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.107.215702 107, 215702 (2011)] assembles for truncations as high as 0.45. The self-assembly propensities for the structures formed in the thermodynamic limit are explained using the isoperimetric quotient of the particles and the coordination number in the disordered fluid and in the assembled structure.

Predator-dependent functional response in wolves: from food limitation to surplus killing.

PubMed

Zimmermann, Barbara; Sand, Håkan; Wabakken, Petter; Liberg, Olof; Andreassen, Harry Peter

2015-01-01

The functional response of a predator describes the change in per capita kill rate to changes in prey density. This response can be influenced by predator densities, giving a predator-dependent functional response. In social carnivores which defend a territory, kill rates also depend on the individual energetic requirements of group members and their contribution to the kill rate. This study aims to provide empirical data for the functional response of wolves Canis lupus to the highly managed moose Alces alces population in Scandinavia. We explored prey and predator dependence, and how the functional response relates to the energetic requirements of wolf packs. Winter kill rates of GPS-collared wolves and densities of cervids were estimated for a total of 22 study periods in 15 wolf territories. The adult wolves were identified as the individuals responsible for providing kills to the wolf pack, while pups could be described as inept hunters. The predator-dependent, asymptotic functional response models (i.e. Hassell-Varley type II and Crowley-Martin) performed best among a set of 23 competing linear, asymptotic and sigmoid models. Small wolf packs acquired >3 times as much moose biomass as required to sustain their field metabolic rate (FMR), even at relatively low moose abundances. Large packs (6-9 wolves) acquired less biomass than required in territories with low moose abundance. We suggest the surplus killing by small packs is a result of an optimal foraging strategy to consume only the most nutritious parts of easy accessible prey while avoiding the risk of being detected by humans. Food limitation may have a stabilizing effect on pack size in wolves, as supported by the observed negative relationship between body weight of pups and pack size. © 2014 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.

Exposure to airborne asbestos during removal and installation of gaskets and packings: a review of published and unpublished studies.

PubMed

Madl, Amy K; Clark, Katherine; Paustenbach, Dennis J

2007-01-01

In recent years, questions have been raised about the health risks to persons who have been occupationally exposed to asbestos-containing gaskets and packing materials used in pipes, valves, and machinery (pumps, autos, etc.). Up until the late 1970s, these materials were widely used throughout industrial and maritime operations, refineries, chemical plants, naval ships, and energy plants. Seven simulation studies and four work-site industrial hygiene studies of industrial and maritime settings involving the collection of more than 300 air samples were evaluated to determine the likely airborne fiber concentrations to which a worker may have been exposed while working with encapsulated asbestos-containing gaskets and packing materials. Each study was evaluated for the representativeness of work practices, analytical methods, sample size, and potential for asbestos contamination (e.g., insulation on valves or pipes used in the study). Specific activities evaluated included the removal and installation of gaskets and packings, flange cleaning, and gasket formation. In all but one of the studies relating to the replacement of gaskets and packing using hand-held tools, the short-term average exposures were less than the current 30-min OSHA excursion limit of 1 fiber per cubic centimeter (f/cc) and all of the long-term average exposures were less than the current 8-h permissible exposure limit time-weighted average (PEL-TWA) of 0.1 f/cc. The weight of evidence indicates that the use of hand tools and hand-operated power tools to remove or install gaskets or packing as performed by pipefitters or other tradesmen in nearly all plausible situations would not have produced airborne concentrations in excess of contemporaneous regulatory levels.

Powder X-ray diffraction, infrared and 13C NMR spectroscopic studies of the homologous series of some solid-state zinc(II) and sodium(I) n-alkanoates

NASA Astrophysics Data System (ADS)

Nelson, Peter N.; Taylor, Richard A.

2015-03-01

A comparative study of the room temperature molecular packing and lattice structures for the homologous series of zinc(II) and sodium(I) n-alkanoates adduced from Fourier transform infrared and solid-state 13C NMR spectroscopic data in conjunction with X-ray powder diffraction measurements is carried out. For zinc carboxylates, metal-carboxyl bonding is via asymmetric bridging bidentate coordination whilst for the sodium adducts, coordination is via asymmetric chelating bidentate bonding. All compounds are packed in a monoclinic crystal system. Furthermore, the fully extended all-trans hydrocarbon chains are arranged as lamellar bilayers. For zinc compounds, there is bilayer overlap, for long chain adducts (nc > 8) but not for sodium compounds where methyl groups from opposing layers in the lamellar are only closely packed. Additionally, the hydrocarbon chains are extended along the a-axis of the unit cell for zinc compounds whilst for sodium carboxylates they are extended along the c-axis. These packing differences are responsible for different levels of Van der Waals effects in the lattices of these two series of compounds, hence, observed odd-even alternation is different. The significant difference in lattice packing observed for these two series of compounds is proposed to be due to the difference in metal-carboxyl coordination mode, arising from the different electronic structure of the central metal ions.

Structural and mechanical features of the order-disorder transition in experimental hard-sphere packings

NASA Astrophysics Data System (ADS)

Hanifpour, M.; Francois, N.; Robins, V.; Kingston, A.; Vaez Allaei, S. M.; Saadatfar, M.

2015-06-01

Here we present an experimental and numerical investigation on the grain-scale geometrical and mechanical properties of partially crystallized structures made of macroscopic frictional grains. Crystallization is inevitable in arrangements of monosized hard spheres with packing densities exceeding Bernal's limiting density ϕBernal≈0.64 . We study packings of monosized hard spheres whose density spans over a wide range (0.59 <ϕ <0.72 ) . These experiments harness x-ray computed tomography, three-dimensional image analysis, and numerical simulations to access precisely the geometry and the 3D structure of internal forces within the sphere packings. We show that clear geometrical transitions coincide with modifications of the mechanical backbone of the packing both at the grain and global scale. Notably, two transitions are identified at ϕBernal≈0.64 and ϕc≈0.68 . These results provide insights on how geometrical and mechanical features at the grain scale conspire to yield partially crystallized structures that are mechanically stable.

49 CFR 171.8 - Definitions and abbreviations.

Code of Federal Regulations, 2013 CFR

2013-10-01

... definitions relating to radioactive materials. Rail car means a car designed to carry freight or non-passenger... Materials Safety Administration. Aerosol means any non-refillable receptacle containing a gas compressed... Division 6.1 Packing Group III material) liquid, paste, or powder and fitted with a self-closing release...

49 CFR 171.8 - Definitions and abbreviations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... definitions relating to radioactive materials. Rail car means a car designed to carry freight or non-passenger... Materials Safety Administration. Aerosol means any non-refillable receptacle containing a gas compressed... Division 6.1 Packing Group III material) liquid, paste, or powder and fitted with a self-closing release...

49 CFR 171.8 - Definitions and abbreviations.

Code of Federal Regulations, 2014 CFR

2014-10-01

... definitions relating to radioactive materials. Rail car means a car designed to carry freight or non-passenger... Materials Safety Administration. Aerosol means any non-refillable receptacle containing a gas compressed... Division 6.1 Packing Group III material) liquid, paste, or powder and fitted with a self-closing release...

49 CFR 171.8 - Definitions and abbreviations.

Code of Federal Regulations, 2011 CFR

2011-10-01

... definitions relating to radioactive materials. Rail car means a car designed to carry freight or non-passenger... Materials Safety Administration. Aerosol means any non-refillable receptacle containing a gas compressed... Division 6.1 Packing Group III material) liquid, paste, or powder and fitted with a self-closing release...

Visualization of Flows in Packed Beds of Twisted Tapes

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Braun, M. J.; Peloso, D.; Athavale, M. M.; Mullen, R. L.

2002-01-01

A videotape presentation of the flow field in a packed bed of 48 twisted tapes which can be simulated by very thin virtual cylinders has been assembled. The indices of refraction of the oil and the Lucite twisted tapes were closely matched, and the flow was seeded with magnesium oxide particles. Planar laser light projected the flow field in two dimensions both along and transverse to the flow axis. The flow field was three dimensional and complex to describe, yet the most prominent finding was flow threads. It appeared that axial flow spiraled along either within the confines of a virtual cylindrical boundary or within the exterior region, between the tangency points, of the virtual cylinders. Random packing and bed voids created vortices and disrupted the laminar flow but minimized the entrance effects. The flow-pressure drops in the packed bed fell below the Ergun model for porous-media flows. Single-twisted-tape results of Smithberg and Landis (1964) were used to guide the analysis. In appendix A the results of several investigators are scaled to the Ergun model. Further investigations including different geometric configurations, computational fluid dynamic (CFD) gridding, and analysis are required.

Biofiltration of isopentane in peat and compost packed beds

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

Wang, Z.; Govind, R.

1997-05-01

Commercially available biofiltration systems have used natural bioactive materials in packed beds due to low media cost and easy availability. Detailed understanding and modeling of biofiltration systems are lacking in existing literature. Experimental studies on the isopentane treatment in air using peat- and compost-packed beds were conducted with inlet isopentane concentrations of 360 to 960 ppmv, and empty-bed gas-phase residence times of 2 to 10 min. High removal efficiencies (>90%) were achieved at low contaminant concentrations (<500 ppmv) and large empty-bed gas-phase residence times (>8 min). For both peat and compost biofilters, there was an optimal water content that gavemore » the highest removal efficiency. For higher water content, mass transfer of isopentane through the liquid phase controlled the biofiltration removal efficiency. At low water content, irreversible changes in the bioactivity of peat and compost occurred, resulting in an irrecoverable loss of removal efficiency. Increases in biofilter bed temperature from 25 to 40 C improved the removal efficiency. A mathematical model incorporating the effect of water content and temperature was developed to describe the packed-bed biofilter performance. Model predictions agreed closely with experimental data.« less

Novel thermal management system design methodology for power lithium-ion battery

NASA Astrophysics Data System (ADS)

Nieto, Nerea; Díaz, Luis; Gastelurrutia, Jon; Blanco, Francisco; Ramos, Juan Carlos; Rivas, Alejandro

2014-12-01

Battery packs conformed by large format lithium-ion cells are increasingly being adopted in hybrid and pure electric vehicles in order to use the energy more efficiently and for a better environmental performance. Safety and cycle life are two of the main concerns regarding this technology, which are closely related to the cell's operating behavior and temperature asymmetries in the system. Therefore, the temperature of the cells in battery packs needs to be controlled by thermal management systems (TMSs). In the present paper an improved design methodology for developing TMSs is proposed. This methodology involves the development of different mathematical models for heat generation, transmission, and dissipation and their coupling and integration in the battery pack product design methodology in order to improve the overall safety and performance. The methodology is validated by comparing simulation results with laboratory measurements on a single module of the battery pack designed at IK4-IKERLAN for a traction application. The maximum difference between model predictions and experimental temperature data is 2 °C. The models developed have shown potential for use in battery thermal management studies for EV/HEV applications since they allow for scalability with accuracy and reasonable simulation time.

Removal of hexavalent chromium by biosorption process in rotating packed bed.

PubMed

Panda, M; Bhowal, A; Datta, S

2011-10-01

Removal of hexavalent chromium ions from an aqueous solution by crude tamarind (Tamarindus indica) fruit shell was examined in a rotating packed bed contactor by continuously recirculating a given volume of solution through the bed. Reduction of Cr(VI) to Cr(III) within the biosorbent appeared to be the removal mechanism. Depletion rate of Cr(VI) from, and release of reduced Cr(III) ions into the aqueous phase, was influenced by mass transfer resistance besides pH and packing depth. A mathematical model considering the reduction reaction to be irreversible and incorporating intraparticle and external phase mass transfer resistances represented the experimental data adequately. The study indicated that the limitations of fixed bed contactor operating under terrestrial gravity in intensifying mass transfer rates for this system can be overcome with rotating packed bed due to liquid flow under centrifugal acceleration.

On-surface synthesis: a promising strategy toward the encapsulation of air unstable ultra-thin 2D materials.

PubMed

Li, Qiang; Zhao, Yinghe; Guo, Jiyuan; Zhou, Qionghua; Chen, Qian; Wang, Jinlan

2018-02-22

2D black phosphorus (BP) and transition metal chalcogenides (TMCs) have beneficial electronic, optical, and physical properties at the few-layer limit. However, irreversible degradation of exfoliated or chemical vapor deposition-grown ultrathin BP and TMCs like GaSe via oxidation under ambient conditions limits their applications. Herein, the on-surface growth of an oxidation-resistant 2D thin film of a metal coordination polymer is demonstrated by multiscale simulations. We show that the preparation of such heterostructures can be conducted in solution, in which pristine BP and GaSe present better stability than in an air environment. Our calculations reveal that the interaction between the polymer layer and 2D materials is dominated by van der Waals forces; thus, the electronic properties of pristine BP and GaSe are well preserved. Meanwhile, the isolation from oxygen and water can be achieved by monolayer polymers, due to the nature of their close-packed layers. Our facile strategy for enhancing the environmental stability of ultrathin materials is expected to accelerate efforts to implement 2D materials in electronic and optoelectronic applications.

Different phases of a system of hard rods on three dimensional cubic lattice

NASA Astrophysics Data System (ADS)

Vigneshwar, N.; Dhar, Deepak; Rajesh, R.

2017-11-01

We study the different phases of a system of monodispersed hard rods of length k on a cubic lattice, using an efficient cluster algorithm able to simulate densities close to the fully-packed limit. For k≤slant 4 , the system is disordered at all densities. For k=5, 6 , we find a single density-driven transition, from a disordered phase to high density layered-disordered phase, in which the density of rods of one orientation is strongly suppressed, breaking the system into weakly coupled layers. Within a layer, the system is disordered. For k ≥slant 7 , three density-driven transitions are observed numerically: isotropic to nematic to layered-nematic to layered-disordered. In the layered-nematic phase, the system breaks up into layers, with nematic order in each layer, but very weak correlation between the ordering directions of different layers. We argue that the layered-nematic phase is a finite-size effect, and in the thermodynamic limit, the nematic phase will have higher entropy per site. We expect the systems of rods in four and higher dimensions will have a qualitatively similar phase diagram.

Personalizing annual lung cancer screening for patients with chronic obstructive pulmonary disease: A decision analysis.

PubMed

Lowry, Kathryn P; Gazelle, G Scott; Gilmore, Michael E; Johanson, Colden; Munshi, Vidit; Choi, Sung Eun; Tramontano, Angela C; Kong, Chung Yin; McMahon, Pamela M

2015-05-15

Lung cancer screening with annual chest computed tomography (CT) is recommended for current and former smokers with a ≥30-pack-year smoking history. Patients with chronic obstructive pulmonary disease (COPD) are at increased risk of developing lung cancer and may benefit from screening at lower pack-year thresholds. We used a previously validated simulation model to compare the health benefits of lung cancer screening in current and former smokers ages 55-80 with ≥30 pack-years with hypothetical programs using lower pack-year thresholds for individuals with COPD (≥20, ≥10, and ≥1 pack-years). Calibration targets for COPD prevalence and associated lung cancer risk were derived using the Framingham Offspring Study limited data set. We performed sensitivity analyses to evaluate the stability of results across different rates of adherence to screening, increased competing mortality risk from COPD, and increased surgical ineligibility in individuals with COPD. The primary outcome was projected life expectancy. Programs using lower pack-year thresholds for individuals with COPD yielded the highest life expectancy gains for a given number of screens. Highest life expectancy was achieved when lowering the pack-year threshold to ≥1 pack-year for individuals with COPD, which dominated all other screening strategies. These results were stable across different adherence rates to screening and increases in competing mortality risk for COPD and surgical ineligibility. Current and former smokers with COPD may disproportionately benefit from lung cancer screening. A lower pack-year threshold for screening eligibility may benefit this high-risk patient population. © 2015 American Cancer Society.

Testing warning messages on smokers' cigarette packages: a standardised protocol.

PubMed

Brewer, Noel T; Hall, Marissa G; Lee, Joseph G L; Peebles, Kathryn; Noar, Seth M; Ribisl, Kurt M

2016-03-01

Lab experiments on cigarette warnings typically use a brief one-time exposure that is not paired with the cigarette packs smokers use every day, leaving open the question of how repeated warning exposure over several weeks may affect smokers. This proof of principle study sought to develop a new protocol for testing cigarette warnings that better reflects real-world exposure by presenting them on cigarette smokers' own packs. We tested a cigarette pack labelling protocol with 76 US smokers ages 18 and older. We applied graphic warnings to the front and back of smokers' cigarette packs. Most smokers reported that at least 75% of the packs of cigarettes they smoked during the study had our warnings. Nearly all said they would participate in the study again. Using cigarette packs with the study warnings increased quit intentions (p<0.05). Our findings suggest a feasible pack labelling protocol with six steps: (1) schedule appointments at brief intervals; (2) determine typical cigarette consumption; (3) ask smokers to bring a supply of cigarette packs to study appointments; (4) apply labels to smokers' cigarette packs; (5) provide participation incentives at the end of appointments; and (6) refer smokers to cessation services at end of the study. When used in randomised controlled trials in settings with real-world message exposure over time, this protocol may help identify the true impact of warnings and thus better inform tobacco product labelling policy. NCT02247908. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

Physics and the New Games -- or Pretend You're an Atom.

ERIC Educational Resources Information Center

Edge, Ronald D.

1982-01-01

Describes several games in which physics principles are demonstrated using students. These include Pirates Treasure Game (vectors), Three-Meter Dash (kinematics), Knee-Bend Game (energy and power), Wave Game, Reaction Kinematics, Statics-People Pyramids, and games demonstrating nuclear reactions, collisions, electrons in a wire, close packing, and…

Morphological Control of Co3O4 and Its Photocatalytic Properties

EPA Science Inventory

Cobaltosic oxide (Co3O4), a p-type semiconductor, belongs to the normal spinel crystal structure based on a cubic close packing array of oxide ions. The size, surface, geometry, and crystal phase of catalysts are important parameters for controlling their chemical, optical, and ...

Thomas Gennett | NREL

Science.gov Websites

catalysts through ion implantation and sputtering Non-aqueous flow batteries based on organic energy-storage organic radical polymer in the solid state," Journal of Physical Chemistry C (2015) 119(37), 21369 . Braunecker, T.W. Kemper, R.E. Larsen, T. Gennett, "Close packing of nitroxide radicals in stable organic

Hinge specification for a square-faceted tetrahedral truss

NASA Technical Reports Server (NTRS)

Adams, L. R.

1984-01-01

A square-faceted tetrahedral truss is geometrically analyzed. Expressions are developed for single degree of freedom hinges which allow packaging of the structure into a configuration in which all members are parallel and closely packed in a square pattern. Deployment is sequential, thus providing control over the structure during deployment.

Interacting Compasses

ERIC Educational Resources Information Center

Riveros, Hector G.; Betancourt, Julian

2009-01-01

The use of multiple compasses to map and visualize magnetic fields is well-known. The magnetic field exerts a torque on the compasses aligning them along the lines of force. Some science museums show the field of a magnet using a table with many compasses in a closely packed arrangement. However, the very interesting interactions that occur…

Jacketed lamp bulb envelope

DOEpatents

MacLennan, Donald A.; Turner, Brian P.; Gitsevich, Aleksandr; Bass, Gary K.; Dolan, James T.; Kipling, Kent; Kirkpatrick, Douglas A.; Leng, Yongzhang; Levin, Izrail; Roy, Robert J.; Shanks, Bruce; Smith, Malcolm; Trimble, William C.; Tsai, Peter

2001-01-01

A jacketed lamp bulb envelope includes a ceramic cup having an open end and a partially closed end, the partially closed end defining an aperture, a lamp bulb positioned inside the ceramic cup abutting the aperture, and a reflective ceramic material at least partially covering a portion of the bulb not abutting the aperture. The reflective ceramic material may substantially fill an interior volume of the ceramic cup not occupied by the bulb. The ceramic cup may include a structural feature for aiding in alignment of the jacketed lamp bulb envelope in a lamp. The ceramic cup may include an external flange about a periphery thereof. One example of a jacketed lamp bulb envelope includes a ceramic cup having an open end and a closed end, a ceramic washer covering the open end of the ceramic cup, the washer defining an aperture therethrough, a lamp bulb positioned inside the ceramic cup abutting the aperture, and a reflective ceramic material filling an interior volume of the ceramic cup not occupied by the bulb. A method of packing a jacketed lamp bulb envelope of the type comprising a ceramic cup with a lamp bulb disposed therein includes the steps of filling the ceramic cup with a flowable slurry of reflective material, and applying centrifugal force to the cup to pack the reflective material therein.

Effective cluster model of dielectric enhancement in metal-insulator composites

NASA Astrophysics Data System (ADS)

Doyle, W. T.; Jacobs, I. S.

1990-11-01

The electrical permittivity of a suspension of conducting spheres at high volume loading exhibits a large enhancement above the value predicted by the Clausius-Mossotti approximation. The permittivity enhancement is a dielectric anomaly accompanying a metallization transition that occurs when conducting particles are close packed. In disordered suspensions, close encounters can cause a permittivity enhancement at any volume loading. We attribute the permittivity enhancements typically observed in monodisperse disordered suspensions of conducting spheres to local metallized regions of high density produced by density fluctuations. We model a disordered suspension as a mixture, or mesosuspension, of isolated spheres and random close-packed spherical clusters of arbitrary size. Multipole interactions within the clusters are treated exactly. External interactions between clusters and isolated spheres are treated in the dipole approximation. Model permittivities are compared with Guillien's experimental permittivity measurements [Ann. Phys. (Paris) Ser. 11, 16, 205 (1941)] on liquid suspensions of Hg droplets in oil and with Turner's conductivity measurements [Chem. Eng. Sci. 31, 487 (1976)] on fluidized bed suspensions of ion-exchange resin beads in aqueous solution. New permittivity measurements at 10 GHz on solid suspensions of monodisperse metal spheres in polyurethane are presented and compared with the model permittivities. The effective spherical cluster model is in excellent agreement with the experiments over the entire accessible range of volume loading.

Self Assembly of Hard, Space-Filling Polytopes

NASA Astrophysics Data System (ADS)

Schultz, Benjamin; Damasceno, Pablo; Engel, Michael; Glotzer, Sharon

2012-02-01

The thermodynamic behavior of systems of hard particles in the limit of infinite pressure is known to yield the densest possible packing [1,2]. Hard polytopes that tile or fill space in two or three spatial dimensions are guaranteed to obtain packing fractions of unity in the infinite pressure limit. Away from this limit, however, other structures may be possible [3]. We present the results of a simulation study of the thermodynamic self-assembly of hard, space-filling particles from disordered initial conditions. We show that for many polytopes, the infinite pressure structure readily assembles at intermediate pressures and packing fractions significantly less than one; in others, assembly of the infinite pressure structure is foiled by mesophases, jamming and phase separation. Common features of these latter systems are identified and strategies for enhancing assembly of the infinite pressure structure at intermediate pressures through building block modification are discussed.[4pt] [1] P. F. Damasceno, M. Engel, S.C. Glotzer arXiv:1109.1323v1 [cond-mat.soft][0pt] [2] A. Haji-Akbari, M. Engel, S.C. Glotzer arXiv:1106.4765v2 [cond-mat.soft][0pt] [3] U. Agarwal, F.A. Escobedo, Nature Materials 10, 230--235 (2011)

Cyclone: A close air support aircraft for tomorrow

NASA Technical Reports Server (NTRS)

Cox, George; Croulet, Donald; Dunn, James; Graham, Michael; Ip, Phillip; Low, Scott; Vance, Gregg; Volckaert, Eric

1991-01-01

To meet the threat of the battlefield of the future, the U.S. ground forces will require reliable air support. To provide this support, future aircrews demand a versatile close air support aircraft capable of delivering ordinance during the day, night, or in adverse weather with pin-point accuracy. The Cyclone aircraft meets these requirements, packing the 'punch' necessary to clear the way for effective ground operations. Possessing anti-armor, missile, and precision bombing capability, the Cyclone will counter the threat into the 21st Century. Here, it is shown that the Cyclone is a realistic, economical answer to the demand for a capable close air support aircraft.

Immobilized polysaccharide derivatives: chiral packing materials for efficient HPLC resolution.

PubMed

Ikai, Tomoyuki; Yamamoto, Chiyo; Kamigaito, Masami; Okamoto, Yoshio

2007-01-01

Polysaccharide-based chiral packing materials (CPMs) for high-performance liquid chromatography have frequently been used not only to determine the enantiomeric excess of chiral compounds but also to preparatively resolve a wide range of racemates. However, these CPMs can be used with only a limited number of solvents as mobile phases because some organic solvents, such as tetrahydrofuran, chloroform, and so on, dissolve or swell the polysaccharide derivatives coated on a support, e.g., silica gel, and destroy their packed columns. The limitation of mobile phase selection is sometimes a serious problem for the efficient analytical and preparative resolution of enantiomers. This defect can be resolved by the immobilization of the polysaccharide derivatives onto silica gel. Efficient immobilizations have been attained through the radical copolymerization of the polysaccharide derivatives bearing small amounts of polymerizable residues and also through the polycondensation of the polysaccharide derivatives containing a few percent of 3-(triethoxysilyl)propyl residue. (c) 2007 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

Random sphere packing model of heterogeneous propellants

NASA Astrophysics Data System (ADS)

Kochevets, Sergei Victorovich

It is well recognized that combustion of heterogeneous propellants is strongly dependent on the propellant morphology. Recent developments in computing systems make it possible to start three-dimensional modeling of heterogeneous propellant combustion. A key component of such large scale computations is a realistic model of industrial propellants which retains the true morphology---a goal never achieved before. The research presented develops the Random Sphere Packing Model of heterogeneous propellants and generates numerical samples of actual industrial propellants. This is done by developing a sphere packing algorithm which randomly packs a large number of spheres with a polydisperse size distribution within a rectangular domain. First, the packing code is developed, optimized for performance, and parallelized using the OpenMP shared memory architecture. Second, the morphology and packing fraction of two simple cases of unimodal and bimodal packs are investigated computationally and analytically. It is shown that both the Loose Random Packing and Dense Random Packing limits are not well defined and the growth rate of the spheres is identified as the key parameter controlling the efficiency of the packing. For a properly chosen growth rate, computational results are found to be in excellent agreement with experimental data. Third, two strategies are developed to define numerical samples of polydisperse heterogeneous propellants: the Deterministic Strategy and the Random Selection Strategy. Using these strategies, numerical samples of industrial propellants are generated. The packing fraction is investigated and it is shown that the experimental values of the packing fraction can be achieved computationally. It is strongly believed that this Random Sphere Packing Model of propellants is a major step forward in the realistic computational modeling of heterogeneous propellant of combustion. In addition, a method of analysis of the morphology of heterogeneous propellants is developed which uses the concept of multi-point correlation functions. A set of intrinsic length scales of local density fluctuations in random heterogeneous propellants is identified by performing a Monte-Carlo study of the correlation functions. This method of analysis shows great promise for understanding the origins of the combustion instability of heterogeneous propellants, and is believed to become a valuable tool for the development of safe and reliable rocket engines.

Origin of Noncubic Scaling Law in Disordered Granular Packing

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

Xia, Chengjie; Li, Jindong; Kou, Binquan

Recent diffraction experiments on metallic glasses have unveiled an unexpected non-cubic scaling law between density and average interatomic distance, which lead to the speculations on the presence of fractal glass order. Using X-ray tomography we identify here a similar non-cubic scaling law in disordered granular packing of spherical particles. We find that the scaling law is directly related to the contact neighbors within first nearest neighbor shell, and therefore is closely connected to the phenomenon of jamming. The seemingly universal scaling exponent around 2.5 arises due to the isostatic condition with contact number around 6, and we argue that themore » exponent should not be universal.« less

The Response of a 2D Emulsion to Local Perturbations

NASA Astrophysics Data System (ADS)

Hong, Xia; Orellana, Carlos; Weeks, Eric

2015-03-01

We experimentally perturb a quasi-two-dimensional emulsion packing by inflating an oil droplet into the system in a controlled way. Our samples are oil-in-water emulsion confined between two close-spaced parallel plates, so that the droplets are deformed into pancake shapes. In this system, there is only viscous friction and no static friction between droplets. By imaging the droplets with a video microscopy, we observe rearrangement events induced by the local perturbation. Simultaneously, we measure droplet-droplet contact forces by analyzing the outlines of each droplet in our movies. These allow us to study how the packings with varying degrees of spatial order have different responses to the local perturbation.

Are Front of Pack Claims Indicators of Nutrition Quality? Evidence from 2 Product Categories.

PubMed

Schaefer, Debra; Hooker, Neal H; Stanton, John L

2016-01-01

American grocery shoppers face an array of front of pack (FOP) nutrition and health claims when making food selections. Such systems have been categorized as summary or nutrient specific. Either type should help consumers make judgments about the nutrition quality of a product. This research tests if the type or quantity of FOP claims are indeed good indicators of objective nutrition quality. Claim and nutrition information from more than 2200 breakfast cereals and prepared meals launched between 2006 and 2010 were analyzed using binary and multinomial logistic regression models. Results suggest that no type or number of front of pack claims could distinguish "healthy" foods. However, some types and frequencies of FOP claims were significant predictors of higher or lower levels of certain key nutrients. Given the complex and crowded label environment in which these FOP claims reside, one may be concerned that such cues are not closely related to objective measures of nutrition quality. © 2015 Institute of Food Technologists®

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

Kuz'mina, L. G., E-mail: kuzmina@igic.ras.ru; Kucherepa, N. S.; Rodnikova, M. N.

The molecular and crystal structures of two p-alkoxybenzylidene)-p'-toluidines C{sub 2}H{sub 5}O-C{sub 6}H{sub 4}-CH=N-C{sub 6}H{sub 4}-CH{sub 3} (1) and C{sub 4}H{sub 9}O-C{sub 6}H{sub 4}-CH=N-C{sub 6}H{sub 4}-CH{sub 3} (2) are determined by X-ray diffraction. Crystals 1 and 2 contain four and two crystallographically independent molecules, respectively. In 1, the geometry of the independent molecules is almost identical. In 2, the independent molecules differ in the conformation of the alkyl chain, which is disordered in one of them. An analysis of the crystal packing of 2 reveals the alternation of spacious layers formed by loosely packed aliphatic fragments of molecules and layers ofmore » closely packed aromatic fragments, which ensures the formation of the mesogenic phase in the course of melting of crystals 2. In crystal 1, loose aliphatic layers are absent.« less

Approaching an experimental electron density model of the biologically active trans -epoxysuccinyl amide group-Substituent effects vs. crystal packing

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

Shi, Ming W.; Stewart, Scott G.; Sobolev, Alexandre N.

The trans-epoxysuccinyl amide group as a biologically active moiety in cysteine protease inhibitors such as loxistatin acid E64c has been used as a benchmark system for theoretical studies of environmental effects on the electron density of small active ingredients in relation to their biological activity. Here, the synthesis and the electronic properties of the smallest possible active site model compound are reported to close the gap between the unknown experimental electron density of trans-epoxysuccinyl amides and the well-known function of related drugs. Intramolecular substituent effects are separated from intermolecular crystal packing effects on the electron density, which allows us tomore » predict the conditions under which an experimental electron density investigation on trans-epoxysuccinyl amides will be possible. In this context, the special importance of the carboxylic acid function in the model compound for both crystal packing and biological activity is revealed through the novel tool of model energy analysis.« less

Self-assembly of (perfluoroalkyl)alkanes on a substrate surface from solutions in supercritical carbon dioxide.

PubMed

Gallyamov, Marat O; Mourran, Ahmed; Tartsch, Bernd; Vinokur, Rostislav A; Nikitin, Lev N; Khokhlov, Alexei R; Schaumburg, Kjeld; Möller, Martin

2006-06-14

Toroidal self-assembled structures of perfluorododecylnonadecane and perfluorotetradecyloctadecane have been deposited on mica and highly oriented pyrolytic graphite surfaces by exposure of the substrates to solutions of the (pefluoroalkyl)alkanes in supercritical carbon dioxide. Scanning force microscopy (SFM) images have displayed a high degree of regularity of these self-assembled nanoobjects regarding size, shape, and packing in a monolayer. Analysis of SFM images allowed us to estimate that each toroidal domain has an outer diameter of about 50 nm and consists of several thousands of molecules. We propose a simple model explaining the clustering of the molecules to objects with a finite size. The model based on the close-packing principles predicts formation of toroids, whose size is determined by the molecular geometry. Here, we consider the amphiphilic nature of the (perfluoroalkyl)alkane molecules in combination with incommensurable packing parameters of the alkyl- and the perfluoralkyl-segments to be a key factor for such a self-assembly.

Polycatenar Ligand Control of the Synthesis and Self-Assembly of Colloidal Nanocrystals.

PubMed

Diroll, Benjamin T; Jishkariani, Davit; Cargnello, Matteo; Murray, Christopher B; Donnio, Bertrand

2016-08-24

Hydrophobic colloidal nanocrystals are typically synthesized and manipulated with commercially available ligands, and surface functionalization is therefore typically limited to a small number of molecules. Here, we report the use of polycatenar ligands derived from polyalkylbenzoates for the direct synthesis of metallic, chalcogenide, pnictide, and oxide nanocrystals. Polycatenar molecules, branched structures bearing diverging chains in which the terminal substitution pattern, functionality, and binding group can be independently modified, offer a modular platform for the development of ligands with targeted properties. Not only are these ligands used for the direct synthesis of monodisperse nanocrystals, but nanocrystals coated with polycatenar ligands self-assemble into softer bcc superlattices that deviate from conventional harder close-packed structures (fcc or hcp) formed by the same nanocrystals coated with commercial ligands. Self-assembly experiments demonstrate that the molecular structure of polycatenar ligands encodes interparticle spacings and attractions, engineering self-assembly, which is tunable from hard sphere to soft sphere behavior.

Self-organization of S adatoms on Au(111): √3R30° rows at low coverage

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

Walen, Holly, E-mail: hwalen@iastate.edu; Liu, Da-Jiang; Oh, Junepyo

Using scanning tunneling microscopy, we observe an adlayer structure that is dominated by short rows of S atoms, on unreconstructed regions of a Au(111) surface. This structure forms upon adsorption of low S coverage (less than 0.1 monolayer) on a fully reconstructed clean surface at 300 K, then cooling to 5 K for observation. The rows adopt one of three orientations that are rotated by 30° from the close-packed directions of the Au(111) substrate, and adjacent S atoms in the rows are separated by √3 times the surface lattice constant, a. Monte Carlo simulations are performed on lattice-gas models, derivedmore » using a limited cluster expansion based on density functional theory energetics. Models which include long-range pairwise interactions (extending to 5a), plus selected trio interactions, successfully reproduce the linear rows of S atoms at reasonable temperatures.« less

Self-organization of S adatoms on Au(111): √3R30° rows at low coverage

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

Walen, Holly; Liu, Da -Jiang; Oh, Junepyo

Using scanning tunneling microscopy, we observe an adlayer structure that is dominated by short rows of S atoms, on unreconstructed regions of a Au(111) surface. This structure forms upon adsorption of low S coverage (less than 0.1 monolayer) on a fully reconstructed cleansurface at 300 K, then cooling to 5 K for observation. The rows adopt one of three orientations that are rotated by 30° from the close-packed directions of the Au(111) substrate, and adjacent S atoms in the rows are separated by √3 times the surface lattice constant, a. Monte Carlo simulations are performed on lattice-gas models, we derivedmore » using a limited cluster expansion based on density functional theory energetics. Furthermore, models which include long-range pairwise interactions (extending to 5a), plus selected trio interactions, successfully reproduce the linear rows of S atoms at reasonable temperatures.« less

Self-organization of S adatoms on Au(111): √3R30° rows at low coverage

DOE PAGES

Walen, Holly; Liu, Da -Jiang; Oh, Junepyo; ...

2015-07-06

Using scanning tunneling microscopy, we observe an adlayer structure that is dominated by short rows of S atoms, on unreconstructed regions of a Au(111) surface. This structure forms upon adsorption of low S coverage (less than 0.1 monolayer) on a fully reconstructed cleansurface at 300 K, then cooling to 5 K for observation. The rows adopt one of three orientations that are rotated by 30° from the close-packed directions of the Au(111) substrate, and adjacent S atoms in the rows are separated by √3 times the surface lattice constant, a. Monte Carlo simulations are performed on lattice-gas models, we derivedmore » using a limited cluster expansion based on density functional theory energetics. Furthermore, models which include long-range pairwise interactions (extending to 5a), plus selected trio interactions, successfully reproduce the linear rows of S atoms at reasonable temperatures.« less

Growth of Bacterial Colonies

NASA Astrophysics Data System (ADS)

Warren, Mya; Hwa, Terence

2013-03-01

On hard agar gel, there is insufficient surface hydration for bacteria to swim or swarm. Instead, growth occurs in colonies of close-packed cells, which expand purely due to repulsive interactions: individual bacteria push each other out of the way through the force of their growth. In this way, bacterial colonies represent a new type of ``active'' granular matter. In this study, we investigate the physical, biochemical, and genetic elements that determine the static and dynamic aspects of this mode of bacterial growth for E. coli. We characterize the process of colony expansion empirically, and use discrete and continuum models to examine the extent to which our observations can be explained by the growth characteristics of non-communicating cells, coupled together by physical forces, nutrients, and waste products. Our results challenge the commonly accepted modes of bacterial colony growth and provide insight into sources of growth limitation in crowded bacterial communities.

Self-organization of S adatoms on Au(111): √3R30° rows at low coverage.

PubMed

Walen, Holly; Liu, Da-Jiang; Oh, Junepyo; Lim, Hyunseob; Evans, J W; Kim, Yousoo; Thiel, P A

2015-07-07

Using scanning tunneling microscopy, we observe an adlayer structure that is dominated by short rows of S atoms, on unreconstructed regions of a Au(111) surface. This structure forms upon adsorption of low S coverage (less than 0.1 monolayer) on a fully reconstructed clean surface at 300 K, then cooling to 5 K for observation. The rows adopt one of three orientations that are rotated by 30° from the close-packed directions of the Au(111) substrate, and adjacent S atoms in the rows are separated by √3 times the surface lattice constant, a. Monte Carlo simulations are performed on lattice-gas models, derived using a limited cluster expansion based on density functional theory energetics. Models which include long-range pairwise interactions (extending to 5a), plus selected trio interactions, successfully reproduce the linear rows of S atoms at reasonable temperatures.

Bragg projection ptychography on niobium phase domains

NASA Astrophysics Data System (ADS)

Burdet, Nicolas; Shi, Xiaowen; Clark, Jesse N.; Huang, Xiaojing; Harder, Ross; Robinson, Ian

2017-07-01

Bragg projection ptychography (BPP) is a coherent x-ray diffraction imaging technique which combines the strengths of scanning microscopy with the phase contrast of x-ray ptychography. Here we apply it for high resolution imaging of the phase-shifted crystalline domains associated with epitaxial growth. The advantages of BPP are that the spatial extent of the sample is arbitrary, it is nondestructive, and it gives potentially diffraction limited spatial resolution. Here we demonstrate the application of BPP for revealing the domain structure caused by epitaxial misfit in a nanostructured metallic thin film. Experimental coherent diffraction data were collected from a niobium thin film, epitaxially grown on a sapphire substrate as the beam was scanned across the sample. The data were analyzed by BPP using a carefully selected combination of refinement procedures. The resulting image shows a close packed array of epitaxial domains, shifted with respect to each other due to misfit between the film and its substrate.

Development of improved high temperature seals and lubricants for downhole motors in geothermal applications

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

De La Fosse, P.H.; Black, A.D.; DiBona, B.G.

1983-01-01

A major limitation of downhole mud motors for geothermal drilling, as well as straight-hole oil and gas drilling, is the bearing section. Reduced bearing life results from the inability to seal a lubricant in the bearing pack. A reliable rotary seal will extend the bearing life and will allow high pressure drops across the bit for improved bottomhole cleaning and increased drilling rate. This paper summarizes the results of a six-year program funded by the U.S. Department of Energy/Division of Geothermal Energy to develop a sealed bearing pack for use with downhole motors in geothermal applications. Descriptions of the Sealmore » Test Machine, Lubricant Test Machine and Bearing Pack Test Facility are presented. Summaries of all seal tests, lubricant tests and bearing pack tests are provided; and a comprehensive program bibliography is presented.« less

The effect of microscopic attractive interactions on piezoelectric coefficients of nanoscale DNA films and its resultant mirocantilever-based biosensor signals

NASA Astrophysics Data System (ADS)

Wu, Jun-Zheng; Zhou, Mei-Hong; Zhang, Neng-Hui

2017-10-01

The adsorption of charged biomolecules on a substrate will trigger a self-induced electric potential field that could deflect microcantilever biosensors in the nanometer regime. The paper is devoted to a multiscale characterization of the piezoelectric coefficient of double-stranded DNA (dsDNA) films with microscopic attractive interactions in multivalence salt solutions, which has a close relationship with biosensor signals. First, two different analytical models of cantilever deflections based on macroscopic piezoelectric theories or mesoscopic liquid crystal theories were combined in the sense of equivalent deformation in order to bridge the relation between the macroscopic piezoelectric coefficient of an adsorbate film and the sensitivity of its microstructure to surrounding conditions. Second, two interaction potentials of the free energy for repulsion-dominated DNA films in NaCl solution or attraction-repulsion-coexisted DNA films in multivalent salt solutions were used to compare the piezoelectric effect and the resultant cantilever deformation at various packing conditions, such as different packing density, various nucleotide numbers and two packing technologies, i.e. nano-grafting or self-assembling technology. The variational tendency of microcantilever deflections predicted by the present multiscale analytical model agrees well with the related DNA-mirocantilever experiments. Negative piezoelectric coefficient of dsDNA film exists in multivalent salt solutions, and its distinctive size effect with different packing densities and nucleotide numbers provides us with an opportunity to obtain a more sensitive microcantilever sensor by careful control of packing conditions.

Hydraulic fracture conductivity: effects of rod-shaped proppant from lattice-Boltzmann simulations and lab tests

NASA Astrophysics Data System (ADS)

Osiptsov, Andrei A.

2017-06-01

The goal of this study is to evaluate the conductivity of random close packings of non-spherical, rod-shaped proppant particles under the closure stress using numerical simulation and lab tests, with application to the conductivity of hydraulic fractures created in subterranean formation to stimulate production from oil and gas reservoirs. Numerical simulations of a steady viscous flow through proppant packs are carried out using the lattice Boltzmann method for the Darcy flow regime. The particle packings were generated numerically using the sequential deposition method. The simulations are conducted for packings of spheres, ellipsoids, cylinders, and mixtures of spheres with cylinders at various volumetric concentrations. It is demonstrated that cylinders provide the highest permeability among the proppants studied. The dependence of the nondimensional permeability (scaled by the equivalent particle radius squared) on porosity obtained numerically is well approximated by the power-law function: K /Rv2 = 0.204ϕ4.58 in a wide range of porosity: 0.3 ≤ ϕ ≤ 0.7. Lattice-Boltzmann simulations are cross-verified against finite-volume simulations using Navier-Stokes equations for inertial flow regime. Correlations for the normalized beta-factor as a function of porosity and normalized permeability are presented as well. These formulae are in a good agreement with the experimental measurements (including packings of rod-shaped particles) and existing laboratory data, available in the porosity range 0.3 ≤ ϕ ≤ 0.5. Comparison with correlations by other authors is also given.

Effects of grain size distribution on the packing fraction and shear strength of frictionless disk packings.

PubMed

Estrada, Nicolas

2016-12-01

Using discrete element methods, the effects of the grain size distribution on the density and the shear strength of frictionless disk packings are analyzed. Specifically, two recent findings on the relationship between the system's grain size distribution and its rheology are revisited, and their validity is tested across a broader range of distributions than what has been used in previous studies. First, the effects of the distribution on the solid fraction are explored. It is found that the distribution that produces the densest packing is not the uniform distribution by volume fractions as suggested in a recent publication. In fact, the maximal packing fraction is obtained when the grading curve follows a power law with an exponent close to 0.5 as suggested by Fuller and Thompson in 1907 and 1919 [Trans Am. Soc. Civ. Eng. 59, 1 (1907) and A Treatise on Concrete, Plain and Reinforced (1919), respectively] while studying mixtures of cement and stone aggregates. Second, the effects of the distribution on the shear strength are analyzed. It is confirmed that these systems exhibit a small shear strength, even if composed of frictionless particles as has been shown recently in several works. It is also found that this shear strength is independent of the grain size distribution. This counterintuitive result has previously been shown for the uniform distribution by volume fractions. In this paper, it is shown that this observation keeps true for different shapes of the grain size distribution.

Estimating cigarette tax avoidance and evasion: evidence from a national sample of littered packs.

PubMed

Barker, Dianne C; Wang, Shu; Merriman, David; Crosby, Andrew; Resnick, Elissa A; Chaloupka, Frank J

2016-10-01

A number of recent studies document the proportion of all cigarette packs that are 'contraband' using discarded packs to measure tax avoidance and evasion, which we call tax non-compliance. To date, academic studies using discarded packs focused on relatively small geographical areas such as a city or a neighbourhood. We visited 160 communities across 38 US states in 2012 and collected data from littered cigarette packs as part of the State and Community Tobacco Control (SCTC) Research Initiative and the Bridging the Gap Community Obesity Measures Project (BTG-COMP). Data collectors were trained in a previously tested littered pack data collection protocol. Field teams collected 2116 packs with cellophane across 132 communities. We estimate a national tax non-compliance rate of 18.5% with considerable variation across regions. Suburban areas had lower non-compliance than urban areas as well as areas with high and low median household income areas compared with middle income areas. We present the first academic national study of tax non-compliance using littered cigarette packs. We demonstrate the feasibility of meaningful large-scale data collection using this methodology and document considerable variation in tax non-compliance across areas, suggesting that both policy differences and geography may be important in control of illicit tobacco use. Given the geography of open borders among countries with varying tax rates, this simple methodology may be appropriate to estimate tax non-compliance in countries that use tax stamps or other pack markings, such as health warnings. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

The impact of cigarette pack design, descriptors, and warning labels on risk perception in the U.S.

PubMed

Bansal-Travers, Maansi; Hammond, David; Smith, Philip; Cummings, K Michael

2011-06-01

In the U.S., limited evidence exists on the impact of colors and brand imagery used in cigarette pack design. This study examined the impact of pack design, product descriptors, and health warnings on risk perception and brand appeal. A cross-sectional mall-intercept study was conducted with 197 adult smokers and 200 nonsmokers in Buffalo NY from June to July 2009 (data analysis from July 2009 to December 2010). Participants were shown 12 sets of packs randomly; each set varied by a particular design feature (color, descriptor) or warning label style (text versus graphic, size, attribution, message framing). Packs were rated on criteria including risk perceptions, quit motivation, and purchase interest. Participants selected larger, pictorial, and loss-framed warning labels as more likely to attract attention, encourage thoughts about health risks, motivate quitting, and be most effective. Participants were more likely to select packs with lighter color shading and descriptors such as light, silver, and smooth as delivering less tar, smoother taste, and lower health risk, compared to darker-shaded or full-flavor packs. Additionally, participants were more likely to select the branded compared to plain white pack when asked which delivered the most tar, smoothest taste, was more attractive, appealed to youth aged <18 years, and contained cigarettes of better quality. The findings support larger, graphic health warnings that convey loss-framed messages as most effective in communicating health risks to U.S. adults. The results also indicate that color and product descriptors are associated with false beliefs about risks. Plain packaging may reduce many of the erroneous misperceptions of risk communicated through pack design features. Copyright © 2011 American Journal of Preventive Medicine. Published by Elsevier Inc. All rights reserved.

The Impact of Cigarette Pack Design, Descriptors, and Warning Labels on Risk Perception in the U.S

PubMed Central

Bansal-Travers, Maansi; Hammond, David; Smith, Philip; Cummings, K. Michael

2011-01-01

Background In the U.S., limited evidence exists on the impact of colors and brand imagery used in cigarette pack design. Purpose This study examined the impact of pack design, product descriptors, and health warnings on risk perception and brand appeal. Methods A cross-sectional mall-intercept study was conducted with 197 adult smokers and 200 nonsmokers in Buffalo, NY from June to July 2009 (data analysis from July 2009 to December 2010). Participants were shown 12 sets of packs randomly; each set varied by a particular design feature (color, descriptor) or warning label style (text vs graphic, size, attribution, message framing). Packs were rated on criteria including risk perceptions, quit motivation, and purchase interest. Results Participants selected larger, pictorial, and loss-framed warning labels as more likely to attract attention, encourage thoughts about health risks, motivate quitting, and most effective. Participants were more likely to select packs with lighter color shading and descriptors such as light, silver, and smooth as delivering less tar, smoother taste, and lower health risk, compared to darker-shaded or full flavor packs. Additionally, participants were more likely to select the branded compared to plain white pack when asked which delivered the most tar, smoothest taste, was more attractive, appealed to youth aged <18 years, and contained cigarettes of better quality. Conclusions The findings support larger, graphic health warnings that convey loss-framed messages as most effective in communicating health risks to U.S. adults. The results also indicate that color and product descriptors are associated with false beliefs about risks. Plain packaging may reduce many of the erroneous misperceptions of risk communicated through pack design features. PMID:21565661

Face-specific Replacement of Calcite by Amorphous Silica Nanoparticles

NASA Astrophysics Data System (ADS)

Liesegang, M.; Milke, R.; Neusser, G.; Mizaikoff, B.

2016-12-01

Amorphous silica, composed of nanoscale spheres, is an important biomineral, alteration product of silicate rocks on the Earth's surface, and precursor material for stable silicate minerals. Despite constant progress in silica sphere synthesis, fundamental knowledge of natural silica particle interaction and ordering processes leading to colloidal crystals is absent so far. To understand the formation pathways of silica spheres in a geologic environment, we investigated silicified Cretaceous mollusk shell pseudomorphs from Coober Pedy (South Australia) using focused ion beam (FIB)-SEM tomography, petrographic microscopy, µ-XRD, and EMPA. The shells consist of replaced calcite crystals (<2 mm) composed of ordered arrays of uniform, close-packed silica spheres 300 ± 10 nm in size. Concentric layered spheres composed of 40 nm-sized subparticles provide evidence that, at least in the final stage, particle aggregation was the major sphere growth mechanism. Silica sphere arrays in periodically changing orientations perfectly replicate polysynthetic twinning planes of calcite. FIB-SEM tomography shows that cubic closed-packed sphere arrangements preserve the twin lamellae, while the twin plane consists of a submicrometer layer of randomly ordered spheres and vacancies. To transfer crystallographic information from parent to product, the advancement of synchronized dissolution and precipitation fronts along lattice planes is essential. We assume that the volume-preserving replacement process proceeds via a face-specific dissolution-precipitation mechanism with intermediate subparticle aggregation and subsequent layer-by-layer deposition of spheres along a planar surface. Porosity created during the replacement reaction allows permanent fluid access to the propagating reaction interface. Fluid pH and ionic strength remain constant throughout the replacement process, permitting continuous silica nanoparticle formation and diffusion-limited colloid aggregation. Our study provides a natural example of the transformation of an atomic crystal to an amorphous, mesoscale ordered material; thus, links the research fields of natural colloidal crystal formation, carbonate-silica replacement, and crystallization by oriented particle aggregation (CPA).

The effects of ethanol on the size-exclusion characteristics of type I dentin collagen to adhesive resin monomers.

PubMed

Chiba, A; Zhou, J; Nakajima, M; Tan, J; Tagami, J; Scheffel, D L S; Hebling, J; Agee, K A; Breschi, L; Grégoire, G; Jang, S S; Tay, F R; Pashley, D H

2016-03-01

During dentin bonding with etch-and-rinse adhesive systems, phosphoric acid etching of mineralized dentin solubilizes the mineral crystallites and replaces them with bound and unbound water. During the infiltration phase of dentin bonding, solvated adhesive resin comonomers are supposed to replace all of the unbound collagen water and polymerize into copolymers. A recently published review suggested that dental monomers are too large to enter and displace water from tightly-packed collagen molecules. Conversely, recent work from the authors' laboratory demonstrated that HEMA and TEGDMA freely equilibrate with water-saturated dentin matrices. However, because adhesive blends are solvated in organic solvents, those solvents may remove enough free water to allow collagen molecules to come close enough to exclude adhesive monomer permeation. The present study analyzed the size-exclusion characteristics of dentin collagen, using a gel permeation-like column chromatography technique, filled with dentin powder instead of Sephadex beads as the stationary phase. The elution volumes of different sized test molecules, including adhesive resin monomers, studied in both water-saturated dentin, and again in ethanol-dehydrated dentin powder, showed that adhesive resin monomers can freely diffuse into both hydrated and dehydrated collagen molecules. Under these in vitro conditions, all free and some of the loosely-bound water seems to have been removed by ethanol. These results validate the concept that adhesive resin monomers can permeate tightly-bound water in ethanol-saturated collagen molecules during infiltration by etch-and-rinse adhesives. It has been reported that collagen molecules in dentin matrices are packed too close together to allow permeation of adhesive monomers between them. Resin infiltration, in this view, would be limited to extrafibrillar spaces. Our work suggests that monomers equilibrate with collagen water in both water and ethanol-saturated dentin matrices. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Disk Density Tuning of a Maximal Random Packing

PubMed Central

Ebeida, Mohamed S.; Rushdi, Ahmad A.; Awad, Muhammad A.; Mahmoud, Ahmed H.; Yan, Dong-Ming; English, Shawn A.; Owens, John D.; Bajaj, Chandrajit L.; Mitchell, Scott A.

2016-01-01

We introduce an algorithmic framework for tuning the spatial density of disks in a maximal random packing, without changing the sizing function or radii of disks. Starting from any maximal random packing such as a Maximal Poisson-disk Sampling (MPS), we iteratively relocate, inject (add), or eject (remove) disks, using a set of three successively more-aggressive local operations. We may achieve a user-defined density, either more dense or more sparse, almost up to the theoretical structured limits. The tuned samples are conflict-free, retain coverage maximality, and, except in the extremes, retain the blue noise randomness properties of the input. We change the density of the packing one disk at a time, maintaining the minimum disk separation distance and the maximum domain coverage distance required of any maximal packing. These properties are local, and we can handle spatially-varying sizing functions. Using fewer points to satisfy a sizing function improves the efficiency of some applications. We apply the framework to improve the quality of meshes, removing non-obtuse angles; and to more accurately model fiber reinforced polymers for elastic and failure simulations. PMID:27563162

Disk Density Tuning of a Maximal Random Packing.

PubMed

Ebeida, Mohamed S; Rushdi, Ahmad A; Awad, Muhammad A; Mahmoud, Ahmed H; Yan, Dong-Ming; English, Shawn A; Owens, John D; Bajaj, Chandrajit L; Mitchell, Scott A

2016-08-01

We introduce an algorithmic framework for tuning the spatial density of disks in a maximal random packing, without changing the sizing function or radii of disks. Starting from any maximal random packing such as a Maximal Poisson-disk Sampling (MPS), we iteratively relocate, inject (add), or eject (remove) disks, using a set of three successively more-aggressive local operations. We may achieve a user-defined density, either more dense or more sparse, almost up to the theoretical structured limits. The tuned samples are conflict-free, retain coverage maximality, and, except in the extremes, retain the blue noise randomness properties of the input. We change the density of the packing one disk at a time, maintaining the minimum disk separation distance and the maximum domain coverage distance required of any maximal packing. These properties are local, and we can handle spatially-varying sizing functions. Using fewer points to satisfy a sizing function improves the efficiency of some applications. We apply the framework to improve the quality of meshes, removing non-obtuse angles; and to more accurately model fiber reinforced polymers for elastic and failure simulations.

Over-the-counter sales of out-of-state and counterfeit tax stamp cigarettes in New York City.

PubMed

Silver, Diana; Giorgio, Margaret M; Bae, Jin Yung; Jimenez, Geronimo; Macinko, James

2016-09-01

New York City (NYC) has strict minimum cigarette price and tax stamp laws, but evidence regarding the extent of evasion of such laws in over-the-counter sales is scarce. 830 packs were purchased at licensed tobacco retailers at 92 randomly selected neighbourhoods in NYC in spring and fall 2014, following the establishment of NYC's minimum price law. The χ(2) analyses of illegal tax stamps on pack, by retailer type and data collection period, are presented. Over 15% of packs purchased had out-of-state (4.5%) or counterfeit tax stamps (10.6%). Purchases resulted in at least one illegal pack obtained in 70% of neighbourhoods, largely from independent stores. In 21.5% of sampled neighbourhoods, it was possible to purchase an illegal pack each collection period. Enhanced enforcement of retail sales of cigarettes is needed to ensure the full benefit of existing tobacco control laws in NYC. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

The connectivity of the brain: multi-level quantitative analysis.

PubMed

Murre, J M; Sturdy, D P

1995-11-01

We develop a mathematical formalism or calculating connectivity volumes generated by specific topologies with various physical packing strategies. We consider four topologies (full, random, nearest-neighbor, and modular connectivity) and three physical models: (i) interior packing, where neurons and connection fibers are intermixed, (ii) sheeted packing where neurons are located on a sheet with fibers running underneath, and (iii) exterior packing where the neurons are located at the surfaces of a cube or sphere with fibers taking up the internal volume. By extensive cross-referencing of available human neuroanatomical data we produce a consistent set of parameters for the whole brain, the cerebral cortex, and the cerebellar cortex. By comparing these inferred values with those predicted by the expressions, we draw the following general conclusions for the human brain, cortex, and cerebellum: (i) Interior packing is less efficient than exterior packing (in a sphere). (ii) Fully and randomly connected topologies are extremely inefficient. More specifically we find evidence that different topologies and physical packing strategies might be used at different scales. (iii) For the human brain at a macro-structural level, modular topologies on an exterior sphere approach the data most closely. (iv) On a mesostructural level, laminarization and columnarization are evidence of the superior efficiency of organizing the wiring as sheets. (v) Within sheets, microstructures emerge in which interior models are shown to be the most efficient. With regard to interspecies similarities and differences we conjecture (vi) that the remarkable constancy of number of neurons per underlying square millimeter of cortex may be the result of evolution minimizing interneuron distance in grey matter, and (vii) that the topologies that best fit the human brain data should not be assumed to apply to other mammals, such as the mouse for which we show that a random topology may be feasible for the cortex.

49 CFR 173.334 - Organic phosphates mixed with compressed gas.

Code of Federal Regulations, 2014 CFR

2014-10-01

...) Cylinders may be packed in strong wooden boxes with valves or other closing devices protected from damage, with not more than twelve cylinders in one outside wooden box. An outer fiberboard box may be used when... must be overpacked in a box, crate, or other strong outer packaging conforming to the requirements of...

49 CFR 173.334 - Organic phosphates mixed with compressed gas.

Code of Federal Regulations, 2012 CFR

2012-10-01

...) Cylinders may be packed in strong wooden boxes with valves or other closing devices protected from damage, with not more than twelve cylinders in one outside wooden box. An outer fiberboard box may be used when... must be overpacked in a box, crate, or other strong outer packaging conforming to the requirements of...

49 CFR 173.334 - Organic phosphates mixed with compressed gas.

Code of Federal Regulations, 2013 CFR

2013-10-01

...) Cylinders may be packed in strong wooden boxes with valves or other closing devices protected from damage, with not more than twelve cylinders in one outside wooden box. An outer fiberboard box may be used when... must be overpacked in a box, crate, or other strong outer packaging conforming to the requirements of...

49 CFR 173.334 - Organic phosphates mixed with compressed gas.

Code of Federal Regulations, 2011 CFR

2011-10-01

...) Cylinders may be packed in strong wooden boxes with valves or other closing devices protected from damage, with not more than twelve cylinders in one outside wooden box. An outer fiberboard box may be used when... must be overpacked in a box, crate, or other strong outer packaging conforming to the requirements of...

Breaking away from the Pack: Positioning the Marketing Discipline through a Triangular Analysis.

ERIC Educational Resources Information Center

Bonnici, Joseph L.; Reddy, Allan C.

1993-01-01

College and university marketing departments should use the technique of positioning to increase enrollments. The triangular approach to positioning uses close scrutiny of the student profile, the benefits marketing courses offer, and the competition the department faces within and outside the business school. The technique can also be used by…

CO2 as a smart gelator for Pluronic aqueous solutions.

PubMed

Liu, Chengcheng; Mei, Qingqing; Zhang, Jianling; Kang, Xinchen; Peng, Li; Han, Buxing; Xue, Zhimin; Sang, Xinxin; Yang, Xiaogan; Wu, Zhonghua; Li, Zhihong; Mo, Guang

2014-11-25

It was found that CO2 could induce the gelation of Pluronic aqueous solutions, during which the microstructure of the solution transforms from randomly dispersed spherical micelles to cubic close packed micelles. The gelation switched by compressed CO2 has many advantages and can be applied in the synthesis of porous materials.

How To Use Crystallographic Information in Teaching First-Year Chemistry.

ERIC Educational Resources Information Center

Bevan, D. J. M.; And Others

1988-01-01

Emphasizes the role that crystallography plays and has played in building up the body of chemical fact. Shows how the teaching of much of this material is illuminated by reference to crystal structures and crystallochemical relationships in all areas of chemistry. Discusses close packing, silicate structures, and salt hydrates. (CW)

High pressure synthesis of a hexagonal close-packed phase of the high-entropy alloy CrMnFeCoNi

NASA Astrophysics Data System (ADS)

Tracy, Cameron L.; Park, Sulgiye; Rittman, Dylan R.; Zinkle, Steven J.; Bei, Hongbin; Lang, Maik; Ewing, Rodney C.; Mao, Wendy L.

2017-05-01

High-entropy alloys, near-equiatomic solid solutions of five or more elements, represent a new strategy for the design of materials with properties superior to those of conventional alloys. However, their phase space remains constrained, with transition metal high-entropy alloys exhibiting only face- or body-centered cubic structures. Here, we report the high-pressure synthesis of a hexagonal close-packed phase of the prototypical high-entropy alloy CrMnFeCoNi. This martensitic transformation begins at 14 GPa and is attributed to suppression of the local magnetic moments, destabilizing the initial fcc structure. Similar to fcc-to-hcp transformations in Al and the noble gases, the transformation is sluggish, occurring over a range of >40 GPa. However, the behaviour of CrMnFeCoNi is unique in that the hcp phase is retained following decompression to ambient pressure, yielding metastable fcc-hcp mixtures. This demonstrates a means of tuning the structures and properties of high-entropy alloys in a manner not achievable by conventional processing techniques.

Intragranular twinning, detwinning, and twinning-like lattice reorientation in magnesium alloys

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

Wu, Wei; Gao, Yanfei; Li, Nan

2016-12-01

Deformation twinning plays a critical role on improving metals or alloys ductility, especially for hexagonal close-packed materials with low symmetry crystal structure. A rolled Mg alloy was selected as a model system to investigate the extension twinning behaviors and characteristics of parent-twin interactions by nondestructive in situ 3D synchrotron X-ray microbeam diffraction. Besides twinning-detwinning process, the "twinning-like" lattice reorientation process was captured within an individual grain inside a bulk material during the strain reversal. The distributions of parent, twin, and reorientated grains and sub-micron level strain variation across the twin boundary are revealed. A theoretical calculation of the lattice strainmore » confirms that the internal strain distribution in parent and twinned grains correlates with the experimental setup, grain orientation of parent, twin, and surrounding grains, as well as the strain path changes. The study suggests a novel deformation mechanism within the hexagonal close-packed structure that cannot be determined from surface-based characterization methods. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.« less

Near-zero thermal expansion in magnetically ordered state in dysprosium at high pressures and low temperatures

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

Hope, Kevin M.; Samudrala, Gopi K.; Vohra, Yogesh K.

The atomic volume of rare earth metal Dysprosium (Dy) has been measured up to high pressures of 35 GPa and low temperatures between 200 K and 7 K in a diamond anvil cell using angle dispersive x-ray diffraction at a synchrotron source. The hexagonal close-packed (hcp), alpha-Samarium (α-Sm), and double hexagonal close packed (dhcp) phases are observed to be stable in Dy under high-pressure and low-temperature conditions achieved in our experiments. Dy is known to undergo magnetic ordering below 176 K at ambient pressure with magnetic ordering Néel temperature (T N) that changes rapidly with increasing pressure. Our experimental measurementmore » shows that Dy has near-zero thermal expansion in the magnetically ordered state and normal thermal expansion in the paramagnetic state for all the three known high pressure phases (hcp, α-Sm, and dhcp) to 35 GPa. This near-zero thermal expansion behavior in Dy is observed below the magnetic ordering temperature T N at all pressures up to 35 GPa.« less

Coverage dependent molecular assembly of anthraquinone on Au(111)

NASA Astrophysics Data System (ADS)

DeLoach, Andrew S.; Conrad, Brad R.; Einstein, T. L.; Dougherty, Daniel B.

2017-11-01

A scanning tunneling microscopy study of anthraquinone (AQ) on the Au(111) surface shows that the molecules self-assemble into several structures depending on the local surface coverage. At high coverages, a close-packed saturated monolayer is observed, while at low coverages, mobile surface molecules coexist with stable chiral hexamer clusters. At intermediate coverages, a disordered 2D porous network interlinking close-packed islands is observed in contrast to the giant honeycomb networks observed for the same molecule on Cu(111). This difference verifies the predicted extreme sensitivity [J. Wyrick et al., Nano Lett. 11, 2944 (2011)] of the pore network to small changes in the surface electronic structure. Quantitative analysis of the 2D pore network reveals that the areas of the vacancy islands are distributed log-normally. Log-normal distributions are typically associated with the product of random variables (multiplicative noise), and we propose that the distribution of pore sizes for AQ on Au(111) originates from random linear rate constants for molecules to either desorb from the surface or detach from the region of a nucleated pore.

Coverage dependent molecular assembly of anthraquinone on Au(111).

PubMed

DeLoach, Andrew S; Conrad, Brad R; Einstein, T L; Dougherty, Daniel B

2017-11-14

A scanning tunneling microscopy study of anthraquinone (AQ) on the Au(111) surface shows that the molecules self-assemble into several structures depending on the local surface coverage. At high coverages, a close-packed saturated monolayer is observed, while at low coverages, mobile surface molecules coexist with stable chiral hexamer clusters. At intermediate coverages, a disordered 2D porous network interlinking close-packed islands is observed in contrast to the giant honeycomb networks observed for the same molecule on Cu(111). This difference verifies the predicted extreme sensitivity [J. Wyrick et al., Nano Lett. 11, 2944 (2011)] of the pore network to small changes in the surface electronic structure. Quantitative analysis of the 2D pore network reveals that the areas of the vacancy islands are distributed log-normally. Log-normal distributions are typically associated with the product of random variables (multiplicative noise), and we propose that the distribution of pore sizes for AQ on Au(111) originates from random linear rate constants for molecules to either desorb from the surface or detach from the region of a nucleated pore.

Three-dimensional nonsteady heat-transfer analysis of an indirect heating furnace

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

Ito, H.; Umeda, Y.; Nakamura, Y.

1991-01-01

This paper reports on an accurate design method for industrial furnaces from the viewpoint of heat transfer. The authors carried out a three-dimensional nonsteady heat-transfer analysis for a practical-size heat- treatment furnace equipped with radiant heaters. The authors applied three software package programs, STREAM, MORSE, and TRUMP, for the analysis of the combined heat-transfer problems of radiation, conduction, and convection. The authors also carried out experiments of the heating of a charge consisting of packed bolts. The authors found that the air swirled inside the furnace. As for the temperature in each part in the furnace, analytical results were generallymore » in close agreement with the experimental ones. This suggests that our analytical method is useful for a fundamental heat- transfer-based design of a practical-size industrial furnace with an actual charge such as packed bolts. As for the temperature distribution inside the bolt charge (work), the analytical results were also in close agreement with the experimental ones. Consequently, it was found that the heat transfer in the bolt charge could be described with an effective thermal conductivity.« less

Fabrication of close-packed TES microcalorimeter arrays using superconducting molybdenum/gold transition-edge sensors

NASA Astrophysics Data System (ADS)

Finkbeiner, F. M.; Brekosky, R. P.; Chervenak, J. A.; Figueroa-Feliciano, E.; Li, M. J.; Lindeman, M. A.; Stahle, C. K.; Stahle, C. M.; Tralshawala, N.

2002-02-01

We present an overview of our efforts in fabricating Transition-Edge Sensor (TES) microcalorimeter arrays for use in astronomical x-ray spectroscopy. Two distinct types of array schemes are currently pursued: 5×5 single pixel TES array where each pixel is a TES microcalorimeter, and Position-Sensing TES (PoST) array. In the latter, a row of 7 or 15 thermally-linked absorber pixels is read out by two TES at its ends. Both schemes employ superconducting Mo/Au bilayers as the TES. The TES are placed on silicon nitride membranes for thermal isolation from the structural frame. The silicon nitride membranes are prepared by a Deep Reactive Ion Etch (DRIE) process into a silicon wafer. In order to achieve the concept of closely packed arrays without decreasing its structural and functional integrity, we have already developed the technology to fabricate arrays of cantilevered pixel-sized absorbers and slit membranes in silicon nitride films. Furthermore, we have started to investigate ultra-low resistance through-wafer micro-vias to bring the electrical contact out to the back of a wafer. .

Grain size constraints on twin expansion in hexagonal close packed crystals

DOE PAGES

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

2016-10-20

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

A nanoporous gold membrane for sensing applications

PubMed Central

Oo, Swe Zin; Silva, Gloria; Carpignano, Francesca; Noual, Adnane; Pechstedt, Katrin; Mateos, Luis; Grant-Jacob, James A.; Brocklesby, Bill; Horak, Peter; Charlton, Martin; Boden, Stuart A.; Melvin, Tracy

2016-01-01

Design and fabrication of three-dimensionally structured, gold membranes containing hexagonally close-packed microcavities with nanopores in the base, are described. Our aim is to create a nanoporous structure with localized enhancement of the fluorescence or Raman scattering at, and in the nanopore when excited with light of approximately 600 nm, with a view to provide sensitive detection of biomolecules. A range of geometries of the nanopore integrated into hexagonally close-packed assemblies of gold micro-cavities was first evaluated theoretically. The optimal size and shape of the nanopore in a single microcavity were then considered to provide the highest localized plasmon enhancement (of fluorescence or Raman scattering) at the very center of the nanopore for a bioanalyte traversing through. The optimized design was established to be a 1200 nm diameter cavity of 600 nm depth with a 50 nm square nanopore with rounded corners in the base. A gold 3D-structured membrane containing these sized microcavities with the integrated nanopore was successfully fabricated and ‘proof of concept’ Raman scattering experiments are described. PMID:26973809

A Phosphanthrene Oxide Host with Close Sphere Packing for Ultralow-Voltage-Driven Efficient Blue Thermally Activated Delayed Fluorescence Diodes.

PubMed

Yang, He; Liang, Qianqian; Han, Chunmiao; Zhang, Jing; Xu, Hui

2017-10-01

A phosphanthrene oxide host, 5,10-diphenyl-phosphanthrene 5,10-dioxide (DPDPO 2 A), with intra- and intermolecular hydrogen bonds achieves spheroidal cis-configuration and close sphere packing. DPDPO 2 A realizes effective exciton suppression and excellent and balanced carrier transporting ability, both at the same time, demonstrating favorable photoluminescence quantum yield of 84% from its blue thermally activated delayed fluorescence (TADF) dye, namely bis[4-(9,9-dimethyl-9,10-dihydroacridine) phenyl]sulfone, doped films and high electron and hole mobility at the level of 10 -4 and 10 -5 cm 2 V -1 s -1 , respectively. DPDPO 2 A endows its blue TADF devices with record-low driving voltages, e.g., turn-on voltage of 2.5 V, and the state-of-the-art efficiencies with maxima of 22.5% for external quantum efficiency and 52.9 lm W -1 for power efficiency, which is the best comprehensive performance to date of ultralow-voltage-driven blue TADF diodes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nb-H system at high pressures and temperatures

NASA Astrophysics Data System (ADS)

Liu, Guangtao; Besedin, Stanislav; Irodova, Alla; Liu, Hanyu; Gao, Guoying; Eremets, Mikhail; Wang, Xin; Ma, Yanming

2017-03-01

We studied the Nb-H system over extended pressure and temperature ranges to establish the highest level of hydrogen abundance we could achieve from the resulting alloy. We probed the Nb-H system with laser heating and x-ray diffraction complemented by numerical density functional theory-based simulations. New quenched double hexagonal close-packed (hcp) Nb H2.5 appears under 46 GPa, and above 56 GPa cubic Nb H3 is formed as theoretically predicted. Nb atoms are arranged in close-packed lattices which are martensitically transformed in the sequence: face-centered cubic (fcc) → hcp → double hcp (dhcp) → distorted body-centered cubic (bcc) as pressure increases. The appearance of fcc Nb H2.5 -3 and dhcp Nb H2.5 cannot be understood in terms of enthalpic stability, but can be rationalized when finite temperatures are taken into account. The structural and compressional behavior of Nb Hx >2 is similar to that of NbH. Nevertheless, a direct H-H interaction emerges with hydrogen concentration increases, which manifests itself via a reduction in the lattice expansion induced by hydrogen dissolution.

First-Principles Study on the Structural and Magnetic Properties of Iron Hydride

NASA Astrophysics Data System (ADS)

Tsumuraya, Takao; Matsuura, Yasuyuki; Shishidou, Tatsuya; Oguchi, Tamio

2012-06-01

The magnetic and structural properties of iron hydride FeH with the double hexagonal close-packed (dhcp) and hexagonal close-packed (hcp) structures are investigated by first-principles density-functional theory calculations with a spin-polarized form of generalized gradient approximation. All the calculations are performed using all-electron full-potential linearized augmented plane wave method. Both dhcp and hcp FeH are ferromagnetic at ambient pressure. The ferromagnetic ordering of the dhcp structure collapses at a pressure of 48 GPa, while that of the hcp structure vanishes gradually from 48 GPa. The modification in the density of states (DOS) due to the applied pressure causes the collapse of the magnetization. The difference in magnetic moment reduction between dhcp and hcp FeH is attributed to their DOS around the Fermi level. The calculated magnetocrystalline anisotropy energies between in-plane and out-of-plane spin orientations are found to be 124 μeV/Fe for the dhcp structure, and 100 μeV/Fe for the hcp structure. The easy axis is in-plane direction for both structures.

Near-zero thermal expansion in magnetically ordered state in dysprosium at high pressures and low temperatures

DOE PAGES

Hope, Kevin M.; Samudrala, Gopi K.; Vohra, Yogesh K.

2017-01-01

The atomic volume of rare earth metal Dysprosium (Dy) has been measured up to high pressures of 35 GPa and low temperatures between 200 K and 7 K in a diamond anvil cell using angle dispersive x-ray diffraction at a synchrotron source. The hexagonal close-packed (hcp), alpha-Samarium (α-Sm), and double hexagonal close packed (dhcp) phases are observed to be stable in Dy under high-pressure and low-temperature conditions achieved in our experiments. Dy is known to undergo magnetic ordering below 176 K at ambient pressure with magnetic ordering Néel temperature (T N) that changes rapidly with increasing pressure. Our experimental measurementmore » shows that Dy has near-zero thermal expansion in the magnetically ordered state and normal thermal expansion in the paramagnetic state for all the three known high pressure phases (hcp, α-Sm, and dhcp) to 35 GPa. This near-zero thermal expansion behavior in Dy is observed below the magnetic ordering temperature T N at all pressures up to 35 GPa.« less

A LDA + U study of the photoemission spectra of the double hexagonal close packed phases of Am and Cm

NASA Astrophysics Data System (ADS)

Islam, M. Fhokrul; Ray, Asok K.

2010-05-01

We have investigated the photoemission spectra and other electronic structure properties such as equilibrium volume and bulk modulus of double hexagonal close packed (dhcp) americium and the density of states (DOS) and magnetic properties of dhcp curium using the LDA+U method. Our calculations show that spin polarized americium is energetically favorable but spin degenerate configuration produces experimental quantities significantly better than those calculated using the spin polarized configuration. The density of states calculated using LDA+U with both non-magnetic and spin polarized configurations is compared and the non-magnetic DOS is shown to be in good agreement with experimental photoemission spectra when U=4.5 eV. In spin polarized case, the onsite interaction parameter, U, is observed to increase the splitting between occupied and unoccupied bands by enhancing the Stoner parameter. The DOS of both non-magnetic americium and anti-ferromagnetic curium are shown to be in good agreement with that calculated using dynamical mean field theory for these two heavy actinides. For curium exchange interaction appears to play a dominant role in magnetic stability.

Toward rational nanoparticle synthesis: predicting surface intermixing in bimetallic alloy nanocatalysts

DOE PAGES

Roling, Luke T.; Mavrikakis, Manos

2017-09-19

In this paper, we present a database of first-principles calculated activation energy barriers for two competitive processes involving bimetallic adatom-surface permutations of ten transition metals: (i) adatom “hopping” diffusion and (ii) adatom substitution into the surface. We consider the surface structure sensitivity of these events as well as coverage effects. We find that surface hopping mechanisms are facile and always preferred to substitution events on close-packed fcc(111) and hcp(0001) surfaces. However, surface atom substitution is more facile on the more open fcc(100) surfaces and is competitive with adatom surface hopping, which is more difficult than on the close-packed surfaces. Finally,more » by comparing the absolute and relative magnitudes of the energetics of hopping and substitution, our calculations can offer qualitative predictions of intermixing and other phenomena relevant to nanocrystal growth, such as the tendency to form intermixed alloys or core–shell structures during layer-by-layer nanoparticle synthesis involving a given bimetallic pair, and thereby inform the rational design and synthesis of novel bimetallic nanomaterials.« less

Natural Deposition Strategy for Interfacial, Self-Assembled, Large-Scale, Densely Packed, Monolayer Film with Ligand-Exchanged Gold Nanorods for In Situ Surface-Enhanced Raman Scattering Drug Detection.

PubMed

Mao, Mei; Zhou, Binbin; Tang, Xianghu; Chen, Cheng; Ge, Meihong; Li, Pan; Huang, Xingjiu; Yang, Liangbao; Liu, Jinhuai

2018-03-15

Liquid interfacial self-assembly of metal nanoparticles holds great promise for its various applications, such as in tunable optical devices, plasmonics, sensors, and catalysis. However, the construction of large-area, ordered, anisotropic, nanoparticle monolayers and the acquisition of self-assembled interface films are still significant challenges. Herein, a rapid, validated method to fabricate large-scale, close-packed nanomaterials at the cyclohexane/water interface, in which hydrophilic cetyltrimethylammonium bromide coated nanoparticles and gold nanorods (AuNRs) self-assemble into densely packed 2D arrays by regulating the surface ligand and suitable inducer, is reported. Decorating AuNRs with polyvinylpyrrolidone not only extensively decreases the charge of AuNRs, but also diminishes repulsive forces. More importantly, a general, facile, novel technique to transfer an interfacial monolayer through a designed in situ reaction cell linked to a microfluidic chip is revealed. The self-assembled nanofilm can then automatically settle on the substrate and be directly detected in the reaction cell in situ by means of a portable Raman spectrometer. Moreover, a close-packed monolayer of self-assembled AuNRs provides massive, efficient hotspots to create great surface-enhanced Raman scattering (SERS) enhancement, which provides high sensitivity and reproducibility as the SERS-active substrate. Furthermore, this strategy was exploited to detect drug molecules in human urine for cyclohexane-extracted targets acting as the oil phase to form an oil/water interface. A portable Raman spectrometer was employed to detect methamphetamine down to 100 ppb levels in human urine, exhibiting excellent practicability. As a universal platform, handy tool, and fast pretreatment method with a good capability for drug detection in biological systems, this technique shows great promise for rapid, credible, and on-spot drug detection. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Estimating the 'consumer surplus' for branded versus standardised tobacco packaging.

PubMed

Gendall, Philip; Eckert, Christine; Hoek, Janet; Farley, Tessa; Louviere, Jordan; Wilson, Nick; Edwards, Richard

2016-11-01

Tobacco companies question whether standardised (or 'plain') packaging will change smokers' behaviour. We addressed this question by estimating how standardised packaging compared to a proven tobacco control intervention, price increases through excise taxes, thus providing a quantitative measure of standardised packaging's likely effect. We conducted an online study of 311 New Zealand smokers aged 18 years and above that comprised a willingness-to-pay task comparing a branded and a standardised pack at four different price levels, and a choice experiment. The latter used an alternative-specific design, where the alternatives were a branded pack or a standardised pack, with warning theme and price varied for each pack. Respondents had higher purchase likelihoods for the branded pack (with a 30% warning) than the standardised pack (with a 75% warning) at each price level tested, and, on average, were willing to pay approximately 5% more for a branded pack. The choice experiment produced a very similar estimate of 'consumer surplus' for a branded pack. However, the size of the 'consumer surplus' varied between warning themes and by respondents' demographic characteristics. These two experiments suggest standardised packaging and larger warning labels could have a similar overall effect on adult New Zealand smokers as a 5% tobacco price increase. The findings provide further evidence for the efficacy of standardised packaging, which focuses primarily on reducing youth initiation, and suggest this measure will also bring notable benefits to adult smokers. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

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

Kuz'mina, L. G., E-mail: kuzmina@igic.ras.ru; Gunina, M. A.; Churakov, A. V.

Two aromatic esters with the formulas C{sub 6}H{sub 13}-O-C{sub 6}H{sub 4}-C(O)O-C{sub 6}H{sub 4}-O-C{sub 7}H{sub 15} (1) and C{sub 7}H{sub 15}-O-C{sub 6}H{sub 4}-C(O)O-C{sub 6}H{sub 4}-O-C{sub 4}H{sub 9} (2) belonging to nematic liquid-crystal compounds were studied by X-ray diffraction. Compound 1 crystallizes in two modifications: monoclinic (1-m) and triclinic (1-tr). The crystal packing of 1 and 2 is built from alternating loosely packed aliphatic regions and closely packed aromatic regions. In crystal structures 1-m and 2, the aromatic regions are linked into chains by hydrogen bonds with the participation of the carbonyl oxygen atom of the ester group and the C-H fragmentmore » of the benzene ring, but these hydrogen bonds in 1-m are much weaker than in 2. In 1-m there are {pi}-stacking interactions between the molecules, resulting in the formation of centrosymmetric dimers with an interplanar distance of 3.45 A. In 1-tr, the aromatic fragments form a herringbone packing motif favorable for a two-dimensional network of directional C-H...{pi}-system interactions.« less

Quality of comminuted sausages formulated from mechanically deboned poultry meat.

PubMed

Mielnik, Maria B; Aaby, Kjersti; Rolfsen, Knut; Ellekjær, Marit R; Nilsson, Astrid

2002-05-01

Comminuted sausages formulated with mechanically deboned poultry meat-MDPM (turkey or chicken, frame or neck) treated in different ways before production (vacuum packed MDPM or air packed skeletons deboned at production) and stored frozen for 6 or 18 weeks have been studied using a full-factorial design and chemical, physical and sensory analysis. MDPM was obtained from a Beehive separator. Comminuted sausages with MDPM from turkey frames, stored at -25 °C as skeletons, packed in air for 18 weeks developed marked rancid odour and flavour which could also be detected by thiobarbituric acid reactive substances (TBARS) and the concentration of volatile compounds. Vacuum packed mechanically deboned meat irrespective of species and carcass part could be stored for up to 18 weeks and used in formulation of sausages without any serious changes in their sensory profiles. Instrumental colour differences between sausages were mainly due to species. Turkey sausages were darker, redder and less yellow than chicken sausages. Moisture and fat contents were influenced by carcass part and to a lesser extent depended on species and storage time. Principal least squares regression (PLS2) showed close relationships between instrumental parameters and sensory attributes. TBARS, hexanal and volatile compounds were highly correlated with rancid flavour while redness (a(∗)) was strongly related to sensory colour hue and colour strength.

Enantioseparation of omeprazole--effect of different packing particle size on productivity.

PubMed

Enmark, Martin; Samuelsson, Jörgen; Forssén, Patrik; Fornstedt, Torgny

2012-06-01

Enantiomeric separation of omeprazole has been extensively studied regarding both product analysis and preparation using several different chiral stationary phases. In this study, the preparative chiral separation of omeprazole is optimized for productivity using three different columns packed with amylose tris (3,5-dimethyl phenyl carbamate) coated macroporous silica (5, 10 and 25 μm) with a maximum allowed pressure drop ranging from 50 to 400 bar. This pressure range both covers low pressure process systems (50-100 bar) and investigates the potential for allowing higher pressure limits in preparative applications in a future. The process optimization clearly show that the larger 25 μm packing material show higher productivity at low pressure drops whereas with increasing pressure drops the smaller packing materials have substantially higher productivity. Interestingly, at all pressure drops, the smaller packing material result in lower solvent consumption (L solvent/kg product); the higher the accepted pressure drop, the larger the gain in reduced solvent consumption. The experimental adsorption isotherms were not identical for the different packing material sizes; therefore all calculations were recalculated and reevaluated assuming identical adsorption isotherms (with the 10 μm isotherm as reference) which confirmed the trends regarding productivity and solvent consumption. Copyright © 2012 Elsevier B.V. All rights reserved.

Packing extra mass in compact stellar structures: an interplay between Kalb-Ramond field and extra dimensions

NASA Astrophysics Data System (ADS)

Chakraborty, Sumanta; SenGupta, Soumitra

2018-05-01

We have derived the Buchdahl's limit for a relativistic star in presence of the Kalb-Ramond field in four as well as in higher dimensions. It turns out that the Buchdahl's limit gets severely affected by the inclusion of the Kalb-Ramond field. In particular, the Kalb-Ramond field in four spacetime dimensions enables one to pack extra mass in any compact stellar structure of a given radius. On the other hand, a completely opposite picture emerges if the Kalb-Ramond field exists in higher dimensions, where the mass content of a compact star is smaller compared to that in general relativity. Implications are discussed.

On-Orbit and Ground Performance of the PGBA Plant Growth Facility

NASA Technical Reports Server (NTRS)

Hoehn, A.; Chamberlain, D. J.; Forsyth, S. W.; Hanna, D. S.; Scovazzo, P.; Stodieck, L. S.; Heyenga, G.; Kliss, Mark

1997-01-01

PGBA, a plant growth facility developed for commercial space biotechnology research, successfully grew a total of 30 plants (6 species) for 10 days on board the Space Shuttle Endeavour (STS-77) and is scheduled for reflight on board MSL-1 (STS-83) for a 16 day flight. The PGBA life support systems provide atmospheric, thermal, and humidity control as well as lighting and nutrient supply in a 23.6 liter chamber. Atmosphere treatment includes ethylene and other hydrocarbon removal, CO2 replenishment, and O2 control. The normally closed system uses controlled CO2 replenishment from the crew cabin as required by the plants. Temperature is controlled (1 C) at user-specified setpoints between 20-32 C, using water-filled coolant loops, solid state Peltier thermoelectric devices, and liquid heat exchangers. The thermoelectric cooling systems were optimized for low power consumption and high cooling efficiencies. Relative humidity is maintained between 60-100% using a cooled porous metal plate to remove water vapor from the air stream without cooling the bulk air below the dew point. The lighting system utilizes three compact fluorescent bi-axial lights with variable lighting control and light intensity (PAR) between 220 and 330 micromol/sq m/s at a distance of 20 cm in spaceflight configuration (on orbit power limited to 230 Watt for entire payload). A ground, up to 550 micromol/sq m/s light intensity can be achieved with 330 Watt payload power consumption. Plant water and nutrient support is sustained via the 'Nutrient Pack' system including the passive or active 'Water Replenishable Nutrient Pack.' The root matrix material (soil or Agar) and nutrient formulation of each pack is prepared according to plant species and experimental requirements. These systems were designed by NASA Ames personnel. Data acquisition and control systems provide 32 channels of environmental data as well as digitized or analog video signals for downlink.

Reversible switch between the nanoporous and the nonporous state of amphiphilic block copolymer films regulated by selective swelling.

PubMed

Yan, Nina; Wang, Yong

2015-09-21

Switchable nanoporous films, which can repeatedly alternate their porosities, are of great interest in a diversity of fields. Currently these intelligent materials are mostly based on polyelectrolytes and their porosities can change only in relatively narrow ranges, typically under wet conditions, severely limiting their applications. Here we develop a new system, which is capable of reversibly switching between a highly porous state and a nonporous state dozens of times regulated simply by exposure to selective solvents. In this system nanopores are created or reversibly eliminated in films of a block copolymer, polystyrene-block-poly(2-vinyl pyridine) (PS-b-P2VP), by exposing the films to P2VP-selective or PS-selective solvents, respectively. The mechanism of the switch is based on the selective swelling of the constituent blocks in corresponding solvents, which is a nondestructive and easily controllable process enabling the repeatable and ample switch between the open and the closed state. Systematic microscopic and ellipsometric characterization methods are performed to elucidate the pore-closing course induced by nonsolvents and the cycling between the pore-open and the pore-closed state up to 20 times. The affinity of the solvent for PS blocks is found to play a dominating role in determining the pore-closing process and the porosities of the pore-open films increase with the cycling numbers as a result of loose packing conditions of the polymer chains. We finally demonstrate the potential applications of these films as intelligent antireflection coatings and drug carriers.

Packed Planetary Systems

NASA Astrophysics Data System (ADS)

Barnes, R.; Greenberg, R.

2005-08-01

Planetary systems display a wide range of appearances, with apparently arbitrary values of semi-major axis, eccentricity, etc. We reduce the complexity of orbital configurations to a single value, δ , which is a measure of how close, over secular timescales ( ˜10,000 orbits), two consecutive planets come to each other. We measure this distance relative to the sum of the radii of their Hill spheres, sometimes referred to as mutual Hill radii (MHR). We determine the closest approach distance by numerically integrating the entire system on coplanar orbits, using minimum masses. For non-resonant systems, close approach occurs during apsidal alignment, either parallel or anti-parallel. For resonant pairs the distance at conjunction determines the closest approach distance. Previous analytic work found that planets on circular orbits were assuredly unstable if they came within 3.5 MHR (i.e. Gladman 1993; Chambers, Wetherill & Boss 1996). We find that most known pairs of jovian planets (including those in our solar system) come within 3.5 -- 7 MHR of each other. We also find that several systems are unstable (their closest approach distance is less than 3.5 MHR). These systems, if they are real, probably exist in an observationally permitted location somewhat different from the current best fit. In these cases, the planets' closest approach distance will most likely also be slightly larger than 3.5 MHR. Most pairs beyond 7 MHR probably experienced post-formation migration (i.e. tidal circularization, inward scattering of small bodies) which moved them further apart. This result is even more remarkable since we have used the minimum masses; most likely the systems are inclined to the line of sight, making the Hill spheres larger, and shrinking δ . This dense packing may reflect a tendency for planets to form as close together as they can without being dynamically unstable. This result further implies there may be a large number of smaller, currently undetectable companions packed in orbits around stars with known planets.

Characterization of supramolecular (H2O)18 water morphology and water-methanol (H2O)15(CH3OH)3 clusters in a novel phosphorus functionalized trimeric amino acid host.

PubMed

Raghuraman, Kannan; Katti, Kavita K; Barbour, Leonard J; Pillarsetty, Nagavarakishore; Barnes, Charles L; Katti, Kattesh V

2003-06-11

Phosphorus functionalized trimeric alanine compounds (l)- and (d)-P(CH(2)NHCH(CH(3))COOH)(3) 2 are prepared in 90% yields by the Mannich reaction of Tris(hydroxymethyl)phosphine 1 with (l)- or (d)- Alanine in aqueous media. The hydration properties of (l)-2 and (d)-2 in water and water-methanol mixtures are described. The crystal structure analysis of (l)-2.4H(2)O, reveals that the alanine molecules pack to form two-dimensional bilayers running parallel to (001). The layered structural motif depicts two closely packed monolayers of 2 each oriented with its phosphorus atoms projected at the center of the bilayer and adjacent monolayers are held together by hydrogen bonds between amine and carboxylate groups. The water bilayers are juxtaposed with the H-bonded alanine trimers leading to 18-membered (H(2)O)(18) water rings. Exposure of aqueous solution of (l)-2 and (d)-2 to methanol vapors resulted in closely packed (l)-2 and (d)-2 solvated with mixed water-methanol (H(2)O)(15)(CH(3)OH)(3) clusters. The O-O distances in the mixed methanol-water clusters of (l)-2.3H(2)O.CH(3)OH and (d)-2.3H(2)O.CH(3)OH (O-O(average) = 2.857 A) are nearly identical to the O-O distance observed in the supramolecular (H(2)O)(18) water structure (O-O(average) = 2.859 A) implying the retention of the hydrogen bonded structure in water despite the accommodation of hydrophobic methanol groups within the supramolecular (H(2)O)(15)(CH(3)OH)(3) framework. The O-O distances in (l)-2.3H(2)O.CH(3)OH and (d)-2.3H(2)O.CH(3)OH and in (H(2)O)(18) are very close to the O-O distance reported for liquid water (2.85 A).

Bed morphological features associated with an optimal slurry concentration for reproducible preparation of efficient capillary ultrahigh pressure liquid chromatography columns.

PubMed

Reising, Arved E; Godinho, Justin M; Jorgenson, James W; Tallarek, Ulrich

2017-06-30

Column wall effects and the formation of larger voids in the bed during column packing are factors limiting the achievement of highly efficient columns. Systematic variation of packing conditions, combined with three-dimensional bed reconstruction and detailed morphological analysis of column beds, provide valuable insights into the packing process. Here, we study a set of sixteen 75μm i.d. fused-silica capillary columns packed with 1.9μm, C18-modified, bridged-ethyl hybrid silica particles slurried in acetone to concentrations ranging from 5 to 200mg/mL. Bed reconstructions for three of these columns (representing low, optimal, and high slurry concentrations), based on confocal laser scanning microscopy, reveal morphological features associated with the implemented slurry concentration, that lead to differences in column efficiency. At a low slurry concentration, the bed microstructure includes systematic radial heterogeneities such as particle size-segregation and local deviations from bulk packing density near the wall. These effects are suppressed (or at least reduced) with higher slurry concentrations. Concomitantly, larger voids (relative to the mean particle diameter) begin to form in the packing and increase in size and number with the slurry concentration. The most efficient columns are packed at slurry concentrations that balance these counteracting effects. Videos are taken at low and high slurry concentration to elucidate the bed formation process. At low slurry concentrations, particles arrive and settle individually, allowing for rearrangements. At high slurry concentrations, they arrive and pack as large patches (reflecting particle aggregation in the slurry). These processes are discussed with respect to column packing, chromatographic performance, and bed microstructure to help reinforce general trends previously described. Conclusions based on this comprehensive analysis guide us towards further improvement of the packing process. Copyright © 2017 Elsevier B.V. All rights reserved.

Structures of M2(SO2)6B12F12 (M = Ag or K) and Ag2(H2O)4B12F12: Comparison of the Coordination of SO2 versus H2O and of B12F122- versus Other Weakly Coordinating Anions to Metal Ions in the Solid State.

PubMed

Malischewski, Moritz; Peryshkov, Dmitry V; Bukovsky, Eric V; Seppelt, Konrad; Strauss, Steven H

2016-12-05

The structures of three solvated monovalent cation salts of the superweak anion B 12 F 12 2- (Y 2- ), K 2 (SO 2 ) 6 Y, Ag 2 (SO 2 ) 6 Y, and Ag 2 (H 2 O) 4 Y, are reported and discussed with respect to previously reported structures of Ag + and K + with other weakly coordinating anions. The structures of K 2 (SO 2 ) 6 Y and Ag 2 (SO 2 ) 6 Y are isomorphous and are based on expanded cubic close-packed arrays of Y 2- anions with M(OSO) 6 + complexes centered in the trigonal holes of one expanded close-packed layer of B 12 centroids (⊙). The K + and Ag + ions have virtually identical bicapped trigonal prism MO 6 F 2 coordination spheres, with M-O distances of 2.735(1)-3.032(2) Å for the potassium salt and 2.526(5)-2.790(5) Å for the silver salt. Each M(OSO) 6 + complex is connected to three other cationic complexes through their six μ-SO 2 -κ 1 O,κ 2 O' ligands. The structure of Ag 2 (H 2 O) 4 Y is unique [different from that of K 2 (H 2 O) 4 Y]. Planes of close-packed arrays of anions are offset from neighboring planes along only one of the linear ⊙···⊙···⊙ directions of the close-packed arrays, with [Ag(μ-H 2 O) 2 Ag(μ-H 2 O) 2 )] ∞ infinite chains between the planes of anions. There are two nearly identical AgO 4 F 2 coordination spheres, with Ag-O distances of 2.371(5)-2.524(5) Å and Ag-F distances of 2.734(4)-2.751(4) Å. This is only the second structurally characterized compound with four H 2 O molecules coordinated to a Ag + ion in the solid state. Comparisons with crystalline H 2 O and SO 2 solvates of other Ag + and K + salts of weakly coordinating anions show that (i) N[(SO 2 ) 2 (1,2-C 6 H 4 )] - , BF 4 - , SbF 6 - , and Al(OC(CF 3 ) 3 ) 4 - coordinate much more strongly to Ag + than does Y 2- , (ii) SnF 6 2- coordinates somewhat more strongly to K + than does Y 2- , and (iii) B 12 Cl 12 2- coordinates to K + about the same as, if not slightly weaker than, Y 2- .

Air-stable n-channel organic thin-film transistors with high field-effect mobility based on N ,N'-bis(heptafluorobutyl)-3,4:9,10-perylene diimide

NASA Astrophysics Data System (ADS)

Oh, Joon Hak; Liu, Shuhong; Bao, Zhenan; Schmidt, Rüdiger; Würthner, Frank

2007-11-01

The thin-film transistor characteristics of n-channel organic semiconductor, N ,N'-bis(2,2,3,3,4,4,4-heptafluorobutyl)-perylene tetracarboxylic diimide, are described. The slip-stacked face-to-face molecular packing allows a very dense parallel arrangement of the molecules, leading to field-effect mobility as high as 0.72cm2V-1s-1. The mobility only slightly decreased after exposure to air and remained stable for more than 50days. Our results reveal that molecular packing effects such as close stacking of perylene diimide units and segregation effects imparted by the fluorinated side chains are crucial for the air stability.

Ground state of dipolar hard spheres confined in channels

NASA Astrophysics Data System (ADS)

Deißenbeck, Florian; Löwen, Hartmut; Oǧuz, Erdal C.

2018-05-01

We investigate the ground state of a classical two-dimensional system of hard-sphere dipoles confined between two hard walls. Using lattice sum minimization techniques we reveal that at fixed wall separations, a first-order transition from a vacuum to a straight one-dimensional chain of dipoles occurs upon increasing the density. Further increase in the density yields the stability of an undulated chain as well as nontrivial buckling structures. We explore the close-packed configurations of dipoles in detail, and we find that, in general, the densest packings of dipoles possess complex magnetizations along the principal axis of the slit. Our predictions serve as a guideline for experiments with granular dipolar and magnetic colloidal suspensions confined in slitlike channel geometry.

Corrosion Behaviour of Sn-based Lead-Free Solders in Acidic Solution

NASA Astrophysics Data System (ADS)

Nordarina, J.; Mohd, H. Z.; Ahmad, A. M.; Muhammad, F. M. N.

2018-03-01

The corrosion properties of Sn-9(5Al-Zn), Sn-Cu and SAC305 were studied via potentiodynamic polarization method in an acidic solution of 1 M hydrochloric acid (HCl). Sn-9(5Al-Zn) produced different polarization profile compared with Sn-Cu and SAC305. The morphological analysis showed that small, deep grooves shaped of corrosion product formed on top of Sn-9(5Al-Zn) solder while two distinctive structures of closely packed and loosely packed corrosion product formed on top of Sn-Cu and SAC305 solder alloys. Phase analysis revealed the formations of various corrosion products such as SnO and SnO2 mainly dominant on surface of solder alloys after potentiodynamic polarization in 1 M hydrochloric acid (HCl).

Biomass growth restriction in a packed bed reactor

DOEpatents

Griffith, William L.; Compere, Alicia L.

1978-01-01

When carrying out continuous biologically catalyzed reactions with anaerobic microorganisms attached to a support in an upflow packed bed column, growth of the microorganisms is restricted to prevent the microorganisms from plugging the column by limiting the availability of an essential nutrient and/or by the presence of predatory protozoa which consume the anaerobic microorganisms. A membrane disruptive detergent may be provided in the column to lyse dead microorganisms to make them available as nutrients for live microorganisms.

Directional Auger Electron Spectroscopy — Physical Foundations and Applications

NASA Astrophysics Data System (ADS)

Mróz, S.

Experimental data about the dependence of the Auger signal from crystalline samples on the primary beam direction are presented and discussed. It is shown that, for Auger electrons and elastically and inelastically backscattered electrons, maxima of the signal in its dependence on the polar and azimuth angles of the primary beam (in polar and azimuth profiles, respectively) appear when the primary beam is parallel either to one of the close-packed rows of atoms or to one of the densely packed atomic planes in the sample. This indicates that the diffraction of the primary electron beam is responsible for the dependence mentioned above. Mechanisms proposed for simple explanation of this dependence (channeling and forward focusing of primary electrons) are presented and results of their application are discussed. It is shown that both those mechanisms play an important role in the creation of the Auger signal contrast. The possibilities and limitations of the application of polar and azimuth Auger emission profiles in the determination of the surface layer crystalline structure (directional Auger electron spectroscopy — DAES) are presented and discussed. It is shown that the thickness of the investigated surface layer can be decreased up to a few monolayers. Results obtained with DAES are similar to those provided by X-ray photoelectron diffraction (XPD) and Auger electron diffraction (AED), but the DAES experimental equipment is simple and inexpensive and measurements are fast. Finally, experimental systems for DAES are described and examples of DAES applications are presented.

Fabrication of a Stable New Polymorph Gold Nanowire with Sixfold Rotational Symmetry.

PubMed

Lee, Seonhee; Bae, Changdeuck; Lee, Jubok; Lee, Subin; Oh, Sang Ho; Kim, Jeongyong; Park, Gyeong-Su; Jung, Hyun Suk; Shin, Hyunjung

2018-04-01

Gold is known as the most noblest metal with only face-centered cubic (fcc) structure in ambient conditions. Here, stable hexagonal non-close-packed (ncp) gold nanowires (NWs), having a diameter of about 50 nm and aspect ratios of well over 400, are reported. Au NWs are grown in the confined system of nanotubular TiO 2 arrays via photoelectrochemical reduction of HAuCl 4 precursors. Some of the resulting Au NWs are proved to have sixfold rotational symmetry, observed by transmission electron microscopy tilting experiments. This new polymorph is identified as a hexagonal ncp-structure with lattice parameters of a = 2.884 Å and c = 7.150 Å, showing quite a large interplanar spacing (c/a ≈ 2.48). That is, Au atoms are close-packed along the ab plane, but each plane is not closely stacked along the c axis like in graphite. The structure is usually expected to be unstable, but the present ncp-2H gold is stable under ambient conditions and intense electron beam irradiation, and shows thermal stability up to 400 °C. Moreover, the resulting physical properties as a result of the corresponding change in electronic structures are investigated by comparing the optical properties of fcc and ncp-2H Au NWs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Continuous aryl alcohol oxidase production under growth-limited conditions using a trickle bed reactor.

PubMed

Pardo-Planas, Oscar; Atiyeh, Hasan K; Prade, Rolf A; Müller, Michael; Wilkins, Mark R

2018-05-01

An A. nidulans strain with a pyridoxine marker was used for continuous production of aryl alcohol oxidase (AAO) in a trickle bed reactor (TBR). Modified medium with reduced zinc, no copper, and 5 g/L ascorbic acid that reduced melanin production and increased AAO productivity under growth limited conditions was used. Two air flow rates, 0.11 L/min (0.1 vvm) and 1.1 L/min (1.0 vvm) were tested. More melanin formation and reduced protein productivity were observed with air flow rate of 1.1 L/min. Three random packings were used as support for the fungus inside the TBR column, two of which were hydrophobic and one which was hydrophilic, and three different dilution rates were tested. The use of GEA BCN 030 hydrophobic packing resulted in greater AAO yield and productivity than the other packings. Increasing dilution rates favored melanin formation and citric, lactic and succinic acid accumulation, which decreased AAO yield and productivity. Copyright © 2018 Elsevier Ltd. All rights reserved.

A designed metal-organic framework based on a metal-organic polyhedron.

PubMed

Zou, Yang; Park, Mira; Hong, Seunghee; Lah, Myoung Soo

2008-05-28

A C(3) symmetric ligand with three 1,3-benzenedicarboxylate units has been used to construct a metal-organic framework with a (3,24)-connected network topology, where the nanometre-sized metal-organic cuboctahedra (MOCs) have been incorporated solely into a cubic close packing (CCP) arrangement, which led to superoctahedral and supertetrahedral cavities.

REFLECTOR FOR NEUTRONIC REACTORS

DOEpatents

Fraas, A.P.

1963-08-01

A reflector for nuclear reactors that comprises an assembly of closely packed graphite rods disposed with their major axes substantially perpendicular to the interface between the reactor core and the reflector is described. Each graphite rod is round in transverse cross section at (at least) its interface end and is provided, at that end, with a coaxial, inwardly tapering hole. (AEC)

49 CFR 173.35 - Hazardous materials in IBCs.

Code of Federal Regulations, 2011 CFR

2011-10-01

... plastic or composite IBC may only be filled with a liquid having a vapor pressure less than or equal to... -57 portable tanks. (j) No IBC may be filled with a Packing Group I liquid. Rigid plastic, composite... point of 60 °C (140 °F) (closed cup) or lower, or powders with the potential for dust explosion...

Island in Crisis: Response to Puerto Rico

ERIC Educational Resources Information Center

Zenere, Frank J.

2018-01-01

On September 6, 2017, Hurricane Irma, a Category 5 storm packing winds of 185 miles per hour skirted the northern coast of Puerto Rico, leaving 1 million residents without electrical power. Schools were closed for 5 days, but a major calamity was narrowly avoided. Overall, residents were grateful for their good fortune, but the same could not be…

Novel micro-extraction by packed sorbent procedure for the liquid chromatographic analysis of antiepileptic drugs in human plasma and urine.

PubMed

Rani, Susheela; Malik, Ashok K; Singh, Baldev

2012-02-01

A method for the simultaneous determination of the antiepileptic drugs, phenobarbital (PHB), phenytoin (PTN), carbamazepine (CBZ), primidone (PRM) and oxcarbazepine (OXC) in human plasma and urine samples by using micro-extraction in a packed syringe as the sample preparation method connected with LC/UV (MEPS/LC/UV) is described. Micro-extraction in a packed syringe (MEPS) is a new miniaturized, solid-phase extraction technique that can be connected online to gas or liquid chromatography without any modifications. In MEPS approximately 1 mg of the solid packing material is inserted into a syringe (100-250 μL) as a plug. Sample preparation takes place on the packed bed. The bed can be coated to provide selective and suitable sampling conditions. The new method is very promising, easy to use, fully automated, inexpensive and quick. The standard curves were obtained within the concentration range 1-500 ng/mL in both plasma and urine samples. The results showed high correlation coefficients (R(2) >0.988) for all of the analytes within the calibration range. The extraction recovery was found to be between 88.56 and 99.38%. The limit of quantification was found to be between 0.132 and 1.956 ng/mL. The precision (RSD) values of quality control samples (QC) had a maximum deviation of 4.9%. A comparison of the detection limits with similar methods indicates high sensitivity of the present method. The method is applied for the analysis of these drugs in real urine and plasma samples of epileptic patients. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Movie of the structural changes during a catalytic cycle of nucleoside monophosphate kinases.

PubMed

Vonrhein, C; Schlauderer, G J; Schulz, G E

1995-05-15

There are 17 crystal structures of nucleoside monophosphate kinases known. As expected for kinases, they show large conformational changes upon binding of substrates. These are concentrated in two chain segments, or domains, of 30 and 38 residues that are involved in binding of the substrates N1TP and N2MP (nucleoside tri- and monophosphates with bases N1 and N2), respectively. After aligning the 17 structures on the main parts of their polypeptide chains, two domains in various conformational states were revealed. These states were caused by bound substrate (or analogues) and by crystal-packing forces, and ranged between a 'closed' conformation and a less well defined 'open' conformation. The structures were visually sorted yielding an approximately evenly spaced series of domain states that outlines the closing motions when the substrates bind. The packing forces in the crystals are weak, leaving the natural domain trajectories essentially intact. Packing is necessary, however, to produce stable intermediates. The ordered experimental structures were then recorded as still pictures of a movie and animated to represent the motions of the molecule during a catalytic cycle. The motions were smoothed out by adding interpolated structures to the observed ones. The resulting movies are available through the World Wide Web (http:@bio5.chemie.uni-freiburg.de/ak movie.html). Given the proliferating number of homologous proteins known to exist in different conformational states, it is becoming possible to outline the motions of chain segments and combine them into a movie, which can then represent protein action much more effectively than static pictures alone are able to do.

Airborne asbestos exposures associated with gasket and packing replacement: a simulation study and meta-analysis.

PubMed

Madl, Amy K; Hollins, Dana M; Devlin, Kathryn D; Donovan, Ellen P; Dopart, Pamela J; Scott, Paul K; Perez, Angela L

2014-08-01

Exposures to airborne asbestos during the removal and installation of internal gaskets and packing associated with a valve overhaul were characterized and compared to published data according to different variables (e.g., product, equipment, task, tool, setting, duration). Personal breathing zone and area samples were collected during twelve events simulating gasket and packing replacement, clean-up and clothing handling. These samples were analyzed using PCM and TEM methods and PCM-equivalent (PCME) airborne asbestos concentrations were calculated. A meta-analysis was performed to compare these data with airborne asbestos concentrations measured in other studies involving gaskets and packing. Short-term mechanic and assistant airborne asbestos concentrations during valve work averaged 0.013f/cc and 0.008f/cc (PCME), respectively. Area samples averaged 0.008f/cc, 0.005f/cc, and 0.003f/cc (PCME) for center, bystander, and remote background, respectively. Assuming a tradesman conservatively performs 1-3 gasket and/or packing replacements daily, an average 8-h TWA was estimated to be 0.002-0.010f/cc (PCME). Combining these results in a meta-analysis of the published exposure data showed that the majority of airborne asbestos exposures during work with gaskets and packing fall within a consistent and low range. Significant differences in airborne concentrations were observed between power versus manual tools and removal versus installation tasks. Airborne asbestos concentrations resulting from gasket and packing work during a valve overhaul are consistent with historical exposure data on replacement of asbestos-containing gasket and packing materials involving multiple variables and, in nearly all plausible scenarios, result in average airborne asbestos concentrations below contemporaneous occupational exposure limits for asbestos. Copyright © 2014 Elsevier Inc. All rights reserved.

How tobacco companies in the UK prepared for and responded to standardised packaging of cigarettes and rolling tobacco.

PubMed

Moodie, Crawford; Angus, Kathryn; Mitchell, Danielle; Critchlow, Nathan

2018-01-10

As a result of the Standardised Packaging of Tobacco Products Regulations and Tobacco Products Directive, all packs of cigarettes (factory-made and hand-rolled) in the UK must be drab brown, display pictorial warnings on the principal display areas and contain no less than 20 cigarettes or 30 g of tobacco. The legislation was phased in between May 2016 and May 2017. Our objective was to monitor pack, brand and product changes preimplementation and postimplementation. Our surveillance of the cigarette market involved a review of the trade press, a monthly monitor of online supermarkets and regular visits to stores, from May 2015 to June 2017. Before standardised packaging there were changes to the pack graphics (eg, redesigned packs and limited editions) and pack structure (eg, resealable inner foil) and the issue of a number of reusable tins. After standardised packaging, changes included newer cigarette pack sizes for some brand variants (eg, 23 and 24 packs). Changes to the branding prestandardised packaging included brand extensions, and poststandardised packaging included brand and/or variant name change, often with the inclusion of colour descriptors and brand migrations. Product changes prestandardised packaging included the introduction of novel filters (eg, filters with two flavour-changing capsules, tube filters, firmer filters and filters with granular additives). There was non-compliance with the legislation, with slim packs, which are not permitted, on sale after standardised packaging was implemented. Our findings highlight the need to monitor developments in markets introducing standardised packaging and have policy implications for countries considering this measure. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Valuation of plug-in vehicle life-cycle air emissions and oil displacement benefits

PubMed Central

Michalek, Jeremy J.; Chester, Mikhail; Jaramillo, Paulina; Samaras, Constantine; Shiau, Ching-Shin Norman; Lave, Lester B.

2011-01-01

We assess the economic value of life-cycle air emissions and oil consumption from conventional vehicles, hybrid-electric vehicles (HEVs), plug-in hybrid-electric vehicles (PHEVs), and battery electric vehicles in the US. We find that plug-in vehicles may reduce or increase externality costs relative to grid-independent HEVs, depending largely on greenhouse gas and SO2 emissions produced during vehicle charging and battery manufacturing. However, even if future marginal damages from emissions of battery and electricity production drop dramatically, the damage reduction potential of plug-in vehicles remains small compared to ownership cost. As such, to offer a socially efficient approach to emissions and oil consumption reduction, lifetime cost of plug-in vehicles must be competitive with HEVs. Current subsidies intended to encourage sales of plug-in vehicles with large capacity battery packs exceed our externality estimates considerably, and taxes that optimally correct for externality damages would not close the gap in ownership cost. In contrast, HEVs and PHEVs with small battery packs reduce externality damages at low (or no) additional cost over their lifetime. Although large battery packs allow vehicles to travel longer distances using electricity instead of gasoline, large packs are more expensive, heavier, and more emissions intensive to produce, with lower utilization factors, greater charging infrastructure requirements, and life-cycle implications that are more sensitive to uncertain, time-sensitive, and location-specific factors. To reduce air emission and oil dependency impacts from passenger vehicles, strategies to promote adoption of HEVs and PHEVs with small battery packs offer more social benefits per dollar spent. PMID:21949359

Valuation of plug-in vehicle life-cycle air emissions and oil displacement benefits.

PubMed

Michalek, Jeremy J; Chester, Mikhail; Jaramillo, Paulina; Samaras, Constantine; Shiau, Ching-Shin Norman; Lave, Lester B

2011-10-04

We assess the economic value of life-cycle air emissions and oil consumption from conventional vehicles, hybrid-electric vehicles (HEVs), plug-in hybrid-electric vehicles (PHEVs), and battery electric vehicles in the US. We find that plug-in vehicles may reduce or increase externality costs relative to grid-independent HEVs, depending largely on greenhouse gas and SO(2) emissions produced during vehicle charging and battery manufacturing. However, even if future marginal damages from emissions of battery and electricity production drop dramatically, the damage reduction potential of plug-in vehicles remains small compared to ownership cost. As such, to offer a socially efficient approach to emissions and oil consumption reduction, lifetime cost of plug-in vehicles must be competitive with HEVs. Current subsidies intended to encourage sales of plug-in vehicles with large capacity battery packs exceed our externality estimates considerably, and taxes that optimally correct for externality damages would not close the gap in ownership cost. In contrast, HEVs and PHEVs with small battery packs reduce externality damages at low (or no) additional cost over their lifetime. Although large battery packs allow vehicles to travel longer distances using electricity instead of gasoline, large packs are more expensive, heavier, and more emissions intensive to produce, with lower utilization factors, greater charging infrastructure requirements, and life-cycle implications that are more sensitive to uncertain, time-sensitive, and location-specific factors. To reduce air emission and oil dependency impacts from passenger vehicles, strategies to promote adoption of HEVs and PHEVs with small battery packs offer more social benefits per dollar spent.

Virtual and Experimental Visualization of Flows in Packed Beds of Spheres Simulating Porous Media Flows

NASA Technical Reports Server (NTRS)

Hendricks, R. C.; Athavale, M. M.; Lattime, S. B.; Braun, M. J.

1998-01-01

A videotape presentation of flow in a packed bed of spheres is provided. The flow experiment consisted of three principal elements: (1) an oil tunnel 76.2 mm by 76.2 mm in cross section, (2) a packed bed of spheres in regular and irregular arrays, and (3) a flow characterization methodology, either (a) full flow field tracking (FFFT) or (b) computational fluid dynamic (CFD) simulation. The refraction indices of the oil and the test array of spheres were closely matched, and the flow was seeded with aluminum oxide particles. Planar laser light provided a two-dimensional projection of the flow field, and a traverse simulated a three-dimensional image of the entire flow field. Light focusing and reflection rendered the spheres black, permitting visualization of the planar circular interfaces in both the axial and transverse directions. Flows were observed near the wall-sphere interface and within the set of spheres. The CFD model required that a representative section of a packed bed be formed and gridded, enclosing and cutting six spheres so that symmetry conditions could be imposed at all cross-boundaries. Simulations had to be made with the flow direction at right angles to that used in the experiments, however, to take advantage of flow symmetry. Careful attention to detail was required for proper gridding. The flow field was three-dimensional and complex to describe, yet the most prominent finding was flow threads, as computed in the representative 'cube' of spheres with face symmetry and conclusively demonstrated experimentally herein. Random packing and bed voids tended to disrupt the laminar flow, creating vortices.

Cortical cell and neuron density estimates in one chimpanzee hemisphere.

PubMed

Collins, Christine E; Turner, Emily C; Sawyer, Eva Kille; Reed, Jamie L; Young, Nicole A; Flaherty, David K; Kaas, Jon H

2016-01-19

The density of cells and neurons in the neocortex of many mammals varies across cortical areas and regions. This variability is, perhaps, most pronounced in primates. Nonuniformity in the composition of cortex suggests regions of the cortex have different specializations. Specifically, regions with densely packed neurons contain smaller neurons that are activated by relatively few inputs, thereby preserving information, whereas regions that are less densely packed have larger neurons that have more integrative functions. Here we present the numbers of cells and neurons for 742 discrete locations across the neocortex in a chimpanzee. Using isotropic fractionation and flow fractionation methods for cell and neuron counts, we estimate that neocortex of one hemisphere contains 9.5 billion cells and 3.7 billion neurons. Primary visual cortex occupies 35 cm(2) of surface, 10% of the total, and contains 737 million densely packed neurons, 20% of the total neurons contained within the hemisphere. Other areas of high neuron packing include secondary visual areas, somatosensory cortex, and prefrontal granular cortex. Areas of low levels of neuron packing density include motor and premotor cortex. These values reflect those obtained from more limited samples of cortex in humans and other primates.

Self-Assembled Layering of Magnetic Nanoparticles in a Ferrofluid on Silicon Surfaces.

PubMed

Theis-Bröhl, Katharina; Vreeland, Erika C; Gomez, Andrew; Huber, Dale L; Saini, Apurve; Wolff, Max; Maranville, Brian B; Brok, Erik; Krycka, Kathryn L; Dura, Joseph A; Borchers, Julie A

2018-02-07

This article describes the three-dimensional self-assembly of monodisperse colloidal magnetite nanoparticles (NPs) from a dilute water-based ferrofluid onto a silicon surface and the dependence of the resultant magnetic structure on the applied field. The NPs assemble into close-packed layers on the surface followed by more loosely packed ones. The magnetic field-dependent magnetization of the individual NP layers depends on both the rotational freedom of the layer and the magnetization of the adjacent layers. For layers in which the NPs are more free to rotate, the easy axis of the NP can readily orient along the field direction. In more dense packing, free rotation of the NPs is hampered, and the NP ensembles likely build up quasi-domain states to minimize energy, which leads to lower magnetization in those layers. Detailed analysis of polarized neutron reflectometry data together with model calculations of the arrangement of the NPs within the layers and input from small-angle scattering measurements provide full characterization of the core/shell NP dimensions, degree of chaining, arrangement of the NPs within the different layers, and magnetization depth profile.

Dish-based CPV-T for rooftop generation

NASA Astrophysics Data System (ADS)

Davila-Peralta, Christian; Hyatt, Justin; Alfred, Dan; Struble, Morgan; Sodari, Frank; Angel, Roger

2017-09-01

Hybrid CPV-T with combined electrical and thermal output is well suited to solar generation from fixed limited areas, such as on the roof of an industrial or commercial facility with need for heat. This application will become especially attractive once overall electrical conversion efficiency of 40% is reached, as is projected for REhnu CPV systems using multijunction cells of 50% efficiency, anticipated in a few years. We outline here a configuration of dish- based CPV trackers optimized for close packing on a flat roof in a triangular grid, with a mirror area-to-ground area ratio of 50%. When the geometry of shadowing averaged over a year is taken into account, 80% of all the sunlight that would strike the rooftop is directed into the receivers. Such an array on a given area of flat roof will generate more electrical energy than would be possible with conventional PV panels, even if covering the entire rooftop, because of silicon's relative inefficiency. For example, in Tucson, the annual average global flux of 5.7 kWh/m2/day on a horizontal surface covered with 22% silicon modules will yield 1.25 kWh/m2/day. We show that a CPV system collecting 80% of all the direct sunlight of 7.0 kWh/m2 and converting it with 40% efficiency will yield 2.24 kWh/m2/day of rooftop area, nearly twice as much4. Thermal power will double again the total energy yield. A dual axis CPV-T tracker designed specifically very close spacing has been built to carry a single dish mirror of the standard type used in REhnu's M-8 generator, described by Stalcup et al in these proceedings1,2. Sunlight is collected and focused by a single square paraboloidal mirror, 1.65 × 1.65 m with focal length of 1.5 m. For closest possible packing without mechanical interference, and for broad distribution of load on a rooftop, the mirror and receiver are mounted to a C-ring structure, configured such that the elevation and azimuth axes intersect at a virtual pivot, at the center of the sphere that just clears the receiver and the corners of the mirror. Initial tests of closed loop tracking show an accuracy of 0.03° rms under calm conditions, and 0.04° rms in 6 m/sec wind.

Quantitative Scrutinization of Aflatoxins in Different Spices from Pakistan

PubMed Central

Kashif, Aiza; Kanwal, Kinza; Khan, Abdul Muqeet; Abbas, Mateen

2016-01-01

The current research work aimed to access the contamination level of aflatoxins B1, B2, G1, and G2 in the household spices that are widely consumed in huge amounts. 200 different spice samples, 100 packed and 100 unpacked, were analyzed for the aflatoxins profile by HPLC with an incidence of 61.5% contamination out of which 53.66% samples exceed the EU limit. The results disclosed that the unpacked samples are more contaminated as compared to the packed samples except for white cumin seeds. Among packed and unpacked samples of spices, the maximum value of aflatoxins was detected in fennel, that is, 27.93 μg/kg and 67.04 μg/kg, respectively. The lowest concentration of aflatoxin was detected in cinnamon in packed form (0.79 μg/kg) and in the unpacked samples of white cumin seeds which is 1.75 μg/kg. Caraway seeds and coriander in its unpacked form showed positive results whereas black pepper (packed and unpacked) was found free from aflatoxins. This is the first report on the occurrence of aflatoxins in packed and unpacked samples of spices from Pakistan. To ensure safe consumption of spices, there should be constant monitoring of aflatoxin and more studies need to be executed with the intention of preventing mycotoxin accretion in this commodity. PMID:27781067

Energy conservation strategy in Hydraulic Power Packs using Variable Frequency Drive IOP Conference Series: Materials Science and Engineering

NASA Astrophysics Data System (ADS)

Ramesh, S.; Ashok, S. Denis; Nagaraj, Shanmukha; Reddy, M. Lohith Kumar; Naulakha, Niranjan Kumar; Adithyakumar, C. R.

2018-02-01

At present, energy consumption is to such an extent that if the same trend goes on then in the future at some point of time, the energy sources will all be exploited. Energy conservation in a hydraulic power pack refers to the reduction in the energy consumed by the power pack. Many experiments have been conducted to reduce the energy consumption and one of those methods is by introducing a variable frequency drive. The main objective of the present work is to reduce the energy consumed by the hydraulic power pack using variable frequency drive. Variable Frequency drive is used to vary the speed of the motor by receiving electrical signals from the pressure switch which acts as the feedback system. Using this concept, the speed of the motor can be varied between the specified limits. In the present work, a basic hydraulic power pack and a variable frequency drive based hydraulic power pack were designed and compared both of them with the results obtained. The comparison was based on the power consumed, rise in temperature, noise levels, and flow of oil through pressure relief valve, total oil flow during loading cycle. By comparing both the circuits, it is found that for the proposed system, consumption of power reduces by 78.4% and is as powerful as the present system.

Prolonged storage of packed red blood cells for blood transfusion.

PubMed

Martí-Carvajal, Arturo J; Simancas-Racines, Daniel; Peña-González, Barbra S

2015-07-14

A blood transfusion is an acute intervention, used to address life- and health-threatening conditions on a short-term basis. Packed red blood cells are most often used for blood transfusion. Sometimes blood is transfused after prolonged storage but there is continuing debate as to whether transfusion of 'older' blood is as beneficial as transfusion of 'fresher' blood. To assess the clinical benefits and harms of prolonged storage of packed red blood cells, in comparison with fresh, on recipients of blood transfusion. We ran the search on 1st May 2014. We searched the Cochrane Injuries Group Specialized Register, Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE (OvidSP), Embase (OvidSP), CINAHL (EBSCO Host) and two other databases. We also searched clinical trials registers and screened reference lists of the retrieved publications and reviews. We updated this search in June 2015 but these results have not yet been incorporated. Randomised clinical trials including participants assessed as requiring red blood cell transfusion were eligible for inclusion. Prolonged storage was defined as red blood cells stored for ≥ 21 days in a blood bank. We did not apply limits regarding the duration of follow-up, or country where the study took place. We excluded trials where patients received a combination of short- and long-stored blood products, and also trials without a clear definition of prolonged storage. We independently performed study selection, risk of bias assessment and data extraction by at least two review authors. The major outcomes were death from any cause, transfusion-related acute lung injury, and adverse events. We estimated relative risk for dichotomous outcomes. We measured statistical heterogeneity using I(2). We used a random-effects model to synthesise the findings. We identified three randomised clinical trials, involving a total of 120 participants, comparing packed red blood cells with ≥ 21 days storage ('prolonged' or 'older') versus packed red blood cells with < 21 days storage ('fresh'). We pooled data to assess the effect of prolonged storage on death from any cause. The confidence in the results from these trials was very low, due to the bias in their design and their limited sample sizes.The estimated effect of packed red blood cells with ≥ 21 days storage versus packed red blood cells with < 21 days storage for the outcome death from any cause was imprecise (5/45 [11.11%] versus 2/46 [4.34%]; RR 2.36; 95% CI 0.65 to 8.52; I(2): 0%, P = 0.26, very low quality of evidence). Trial sequential analysis, with only two trials, shows that we do not yet have convincing evidence that older packed red blood cells induce a 20% relative risk reduction of death from any cause compared with fresher packed red blood cells. No trial included other outcomes of interest specified in this review, namely transfusion-related acute lung injury, postoperative infections, and adverse events. The safety profile is unknown. Recognising the limitations of the review, relating to the size and nature of the included trials, this Cochrane Review provides no evidence to support or reject the use of packed red blood cells for blood transfusion which have been stored for ≥ 21 days ('prolonged' or 'older') compared with those stored for < 21 days ('fresh'). These results are based on three small single centre trials with high risks of bias. There is insufficient evidence to determine the effects of fresh or older packed red blood cells for blood transfusion. Therefore, we urge readers to interpret the trial results with caution. The results from four large ongoing trials will help to inform future updates of this review.

Studies of Water V. Five Phonons in Protonic Semiconductor Lattice Model of Pure Liquid Water

NASA Astrophysics Data System (ADS)

Jie, Binbin; Sah, Chihtang

2017-07-01

We report physics based confirmation (~1% RMS deviation), by existing experimental data, of proton-prohol (proton-hole) ion product (pH) and mobilities in pure liquid water (0-100{}{{o}}C, 1-atm pressure) anticipated from our melted-ice Hexagonal-Close-Packed (H{}2O){}4 Lattice Model. Five phonons are identified. (1) A propagating protonic phonon (520.9 meV from lone-pair-blue-shifted stretching mode of isolated water molecule) absorbed to generate a proton-prohol pair or detrap a tightly-bound proton. (2) Two (173.4 and 196.6 meV) bending-breathing protonic-proholic or protonic phonons absorbed during de-trapping-limited proton or proton-prohol mobilities. (3) Two propagating oxygenic-wateric Debye-Dispersive phonons (30.3 and 27.5 meV) absorbed during scattering-limited proton or proton-prohol mobilities. Summer School in Theoretical Physics funded by the National Natural Science Foundation of China, on Soft Materials Physics, hosted by the Physics Department of Xiamen University, China, during August 1 to 14, 2016. This was also just presented at the 2017 March Meeting (March 14 to 16) of the American Physical Society in New Orleans, USA.

Characteristics and Limitations of Submerged GPS L1 Observations

NASA Astrophysics Data System (ADS)

Steiner, Ladina; Geiger, Alain

2017-04-01

Extensive amount of water stored in snow covers has a high impact on flood development during snow melting periods. Early assessment of these parameters in mountain environments enhance early-warning and thus prevention of major impacts. Sub-snow GNSS techniques are lately suggested to determine liquid water content, snow water equivalent or considered for avalanche rescue. This technique is affordable, flexible, and provides accurate and continuous observations independent on weather conditions. However, the characteristics of GNSS observations for applications within a snow-pack still need to be further investigated. The magnitude of the main interaction processes involved for the GPS wavelength propagating through different layers of snow, ice or water is theoretically examined. Liquid water exerts the largest influence on GPS signal propagation through a snow-pack. Therefore, we focus on determining the characteristics of GNSS observables under water. An experiment was set-up to investigate the characteristics and limitations of submerged GPS observations using a pool, a level control by communicating pipes, a geodetic and a low-cost GPS antenna, and a water level sensor. The GPS antennas were placed into the water. The water level was increased daily by a step of two millimeters up to thirty millimeters above the antenna. Based on this experiment, the signal penetration depth, satellite availability, the attenuation of signal strength and the quality of solutions are analyzed. Our experimental results show an agreement with the theoretically derived attenuation parameter and signal penetration depth. The assumption of water as the limiting parameter for GPS observations within a snow-pack can be confirmed. Higher wetness in a snow-pack leads to less transmission, higher refraction, higher attenuation and thus a decreased penetration depth as well as a reduced quality of the solutions. In consequence, GPS applications within a snow-pack are heavily impacted by wetness which is even more pronounced during melting period. In this poster, we present a short introduction to the principle, explain the developed algorithms and show results of experiments dedicated to the signal propagation in water.

Study of the effect of soil disturbance on vapor transport through integrated modeling of the atmospheric boundary layer and shallow subsurface

NASA Astrophysics Data System (ADS)

Trautz, A.; Smits, K. M.; Cihan, A.; Wallen, B.

2014-12-01

Soil-water evaporation is one of the governing processes responsible for controlling water and energy exchanges between the land and atmosphere. Despite its wide relevance and application in many natural and manmade environments (e.g. soil tillage practices, wheel-track compaction, fire burn environments, textural layering and buried ordinances), there are very few studies of evaporation from disturbed soil profiles. The purpose of this study was to explore the effect of soil disturbance and capillary coupling on water distribution and fluxes. We modified a theory previously developed by the authors that allows for coupling single-phase (gas), two-component (air and water vapor) transfer in the atmosphere and two-phase (gas, liquid), two-component (air and water vapor) flow in porous media at the REV scale under non-isothermal, non-equilibrium conditions to better account for the hydraulic and thermal interactions within the media. Modeling results were validated and compared using precision data generated in a two-dimensional soil tank consisting of a loosely packed soil surrounded by a tightly packed soil. The soil tank was outfitted with an array of sensors for the measurement of wind velocity, soil and air temperature, relative humidity, soil moisture, and weight. Results demonstrated that, by using this coupling approach, it is possible to predict the different stages of the drying process in heterogeneous soils with good accuracy. Evaporation from a heterogeneous soil consisting of a loose and tight packing condition is larger than the homogeneous equivalent systems. Liquid water is supplied from the loosely packed soil region to the tightly packed soil regions, sustaining a longer Stage I evaporation in the tightly packed regions with overall greater evaporation rate than uniform homogeneous packing. In contrast, lower evaporation rates from the loosely packed regions are observed due to a limited liquid water supply resulting from capillary flow to the tightly packed regions and a shorter stage 1 evaporation period.

The influence of relationships on neophobia and exploration in wolves and dogs.

PubMed

Moretti, Lucia; Hentrup, Marleen; Kotrschal, Kurt; Range, Friederike

2015-09-01

Exploration is important for animals to be able to gather information about features of their environment that may directly or indirectly influence survival and reproduction. Closely related to exploration is neophobia, which may reduce exposure to danger, but also constrain explorative behaviour. Here we investigated the effects of social relationships on neophobia and exploration in wolves, Canis lupus , and dogs, Canis familiaris . Eleven pack-living wolves reared by human foster parents and 13 identically raised and kept dogs were tested in a novel object test under three different conditions: (1) alone, (2) paired with a pack mate and (3) together with the entire pack. Dogs were less neophobic than wolves and interacted faster with the novel objects. However, the dogs showed overall less interest in the novel objects than wolves, which investigated the objects for longer than the dogs. Both wolves and dogs manipulated objects for longer when paired or in the pack than when alone. While kinship facilitated the investigation of novel objects in the pair condition in both wolves and dogs, rank distance had opposite effects. Our results suggest that the presence of conspecifics supported the exploration of novel objects in both wolves and dogs, particularly within kin and that this may be interpreted as risk sharing. The reduced latency to approach objects and less time spent exploring objects in dogs compared to wolves may be interpreted as an effect of domestication.

Characterization of the mechanical behavior of sea ice as a frictional material

NASA Astrophysics Data System (ADS)

Lade, Poul V.

2002-12-01

The mechanical properties of sea ice are determined by the formation process, and the consequent material behavior at the element scale exhibits viscoelastic behavior at the early loading stages, followed by brittle fracture or ductile, irrecoverable deformation that may be captured by hardening/softening plasticity models with nonassociated flow. Failure of sea ice under different loading conditions follows a pattern that demonstrates its highly cross-anisotropic nature as well as its behavior as a frictional material. The interactions between the floes in the pack ice resemble those observed in granular materials. These materials are frictional in nature, they exhibit both contractive and dilative volume changes, the plastic flow is nonassociated, and their stiffnesses and strengths increase with confining pressure, but they do not have any strength when unconfined. The overall behavior of the pack ice may be close to isotropic. Constitutive modeling of this behavior may be achieved by models used in geotechnical engineering. Formation of leads and subsequent freezing of the water results in cementation between the ice floes, and the pack ice becomes stronger. The behavior of the pack ice may now be compared with that observed in cemented soils or concrete. For these materials, increasing amounts of cementation result in increasing rates of dilation when sheared, and this accounts for the largest contribution to the increase in shear strength.

Free energy of singular sticky-sphere clusters.

PubMed

Kallus, Yoav; Holmes-Cerfon, Miranda

2017-02-01

Networks of particles connected by springs model many condensed-matter systems, from colloids interacting with a short-range potential and complex fluids near jamming, to self-assembled lattices and various metamaterials. Under small thermal fluctuations the vibrational entropy of a ground state is given by the harmonic approximation if it has no zero-frequency vibrational modes, yet such singular modes are at the epicenter of many interesting behaviors in the systems above. We consider a system of N spherical particles, and directly account for the singularities that arise in the sticky limit where the pairwise interaction is strong and short ranged. Although the contribution to the partition function from singular clusters diverges in the limit, its asymptotic value can be calculated and depends on only two parameters, characterizing the depth and range of the potential. The result holds for systems that are second-order rigid, a geometric characterization that describes all known ground-state (rigid) sticky clusters. To illustrate the applications of our theory we address the question of emergence: how does crystalline order arise in large systems when it is strongly disfavored in small ones? We calculate the partition functions of all known rigid clusters up to N≤21 and show the cluster landscape is dominated by hyperstatic clusters (those with more than 3N-6 contacts); singular and isostatic clusters are far less frequent, despite their extra vibrational and configurational entropies. Since the most hyperstatic clusters are close to fragments of a close-packed lattice, this underlies the emergence of order in sticky-sphere systems, even those as small as N=10.

Free energy of singular sticky-sphere clusters

NASA Astrophysics Data System (ADS)

Kallus, Yoav; Holmes-Cerfon, Miranda

2017-02-01

Networks of particles connected by springs model many condensed-matter systems, from colloids interacting with a short-range potential and complex fluids near jamming, to self-assembled lattices and various metamaterials. Under small thermal fluctuations the vibrational entropy of a ground state is given by the harmonic approximation if it has no zero-frequency vibrational modes, yet such singular modes are at the epicenter of many interesting behaviors in the systems above. We consider a system of N spherical particles, and directly account for the singularities that arise in the sticky limit where the pairwise interaction is strong and short ranged. Although the contribution to the partition function from singular clusters diverges in the limit, its asymptotic value can be calculated and depends on only two parameters, characterizing the depth and range of the potential. The result holds for systems that are second-order rigid, a geometric characterization that describes all known ground-state (rigid) sticky clusters. To illustrate the applications of our theory we address the question of emergence: how does crystalline order arise in large systems when it is strongly disfavored in small ones? We calculate the partition functions of all known rigid clusters up to N ≤21 and show the cluster landscape is dominated by hyperstatic clusters (those with more than 3 N -6 contacts); singular and isostatic clusters are far less frequent, despite their extra vibrational and configurational entropies. Since the most hyperstatic clusters are close to fragments of a close-packed lattice, this underlies the emergence of order in sticky-sphere systems, even those as small as N =10 .

Rigidity of a Vibrated Amorphous Bi-Dimensional Packing of Grains

NASA Astrophysics Data System (ADS)

Coulais, C.; Dauchot, O.

The Jamming transition can be seen as a general phenomenon occurring whenever a dense assembly of ``things'' gets stuck and resists to an externally applied shear stress. The mechanical response of a vibrated amorphous bi-dimensional packing of grains close to the Jamming transition is investigated. Stress is applied to the media through a constant torque rheometer while surface fraction is tuned around the jamming transition. The rheometer turns, no matter how low is the applied torque. However, its motion is strongly intermittent and displays scale invariance, the fluctuations being maximal at the Jamming transition, where dynamical correlation length had been found to be divergent. We compare our results to previous ones obtained while dragging an intruder at constant force in the same experimental set-up.

Ultrahigh Ionic Conduction in Water-Stable Close-Packed Metal-Carbonate Frameworks.

PubMed

Manna, Biplab; Desai, Aamod V; Illathvalappil, Rajith; Gupta, Kriti; Sen, Arunabha; Kurungot, Sreekumar; Ghosh, Sujit K

2017-08-21

Utilization of the robust metal-carbonate backbone in a series of water-stable, anionic frameworks has been harnessed for the function of highly efficient solid-state ion-conduction. The compact organization of hydrophilic guest ions facilitates water-assisted ion-conduction in all the compounds. The dense packing of the compounds imparts high ion-conducting ability and minimizes the possibility of fuel crossover, making this approach promising for design and development of compounds as potential components of energy devices. This work presents the first report of evaluating ion-conduction in a purely metal-carbonate framework, which exhibits high ion-conductivity on the order of 10 -2 S cm -1 along with very low activation energy, which is comparable to highly conducting well-known crystalline coordination polymers or commercialized organic polymers like Nafion.

Implementing High-Performance Geometric Multigrid Solver with Naturally Grained Messages

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

Shan, Hongzhang; Williams, Samuel; Zheng, Yili

2015-10-26

Structured-grid linear solvers often require manually packing and unpacking of communication data to achieve high performance.Orchestrating this process efficiently is challenging, labor-intensive, and potentially error-prone.In this paper, we explore an alternative approach that communicates the data with naturally grained messagesizes without manual packing and unpacking. This approach is the distributed analogue of shared-memory programming, taking advantage of the global addressspace in PGAS languages to provide substantial programming ease. However, its performance may suffer from the large number of small messages. We investigate theruntime support required in the UPC ++ library for this naturally grained version to close the performance gapmore » between the two approaches and attain comparable performance at scale using the High-Performance Geometric Multgrid (HPGMG-FV) benchmark as a driver.« less

Tunable porous nanoallotropes prepared by post-assembly etching of binary nanoparticle superlattices

NASA Astrophysics Data System (ADS)

Udayabhaskararao, Thumu; Altantzis, Thomas; Houben, Lothar; Coronado-Puchau, Marc; Langer, Judith; Popovitz-Biro, Ronit; Liz-Marzán, Luis M.; Vuković, Lela; Král, Petr; Bals, Sara; Klajn, Rafal

2017-10-01

Self-assembly of inorganic nanoparticles has been used to prepare hundreds of different colloidal crystals, but almost invariably with the restriction that the particles must be densely packed. Here, we show that non-close-packed nanoparticle arrays can be fabricated through the selective removal of one of two components comprising binary nanoparticle superlattices. First, a variety of binary nanoparticle superlattices were prepared at the liquid-air interface, including several arrangements that were previously unknown. Molecular dynamics simulations revealed the particular role of the liquid in templating the formation of superlattices not achievable through self-assembly in bulk solution. Second, upon stabilization, all of these binary superlattices could be transformed into distinct “nanoallotropes”—nanoporous materials having the same chemical composition but differing in their nanoscale architectures.

How Rosalind Franklin Discovered the Helical Structure of DNA: Experiments in Diffraction

ERIC Educational Resources Information Center

Braun, Gregory; Tierney, Dennis; Schmitzer, Heidrun

2011-01-01

Rosalind Franklin, a chemical physicist (1920-1958), used x-ray diffraction to determine the structure of DNA. What exactly could she read out from her x-ray pattern, shown in Fig. 1? In lecture notes dated November 1951, R. Franklin wrote the following: "The results suggest a helical structure (which must be very closely packed) containing 2, 3…

A Handheld LED Coloured-Light Mixer for Students to Learn Collaboratively the Primary Colours of Light

ERIC Educational Resources Information Center

Nopparatjamjomras, Suchai; Chitaree, Ratchapak; Panijpan, Bhinyo

2009-01-01

To overcome students' inaccurate prior knowledge on primary additive colours, a coloured-light mixer has been constructed to enable students to observe directly the colours produced and reach the conclusion by themselves that the three primary colours of light are red, green, and blue (NOT red, yellow, and blue). Three closely packed tiny…

Method and apparatus for imaging through 3-dimensional tracking of protons

NASA Technical Reports Server (NTRS)

Ryan, James M. (Inventor); Macri, John R. (Inventor); McConnell, Mark L. (Inventor)

2001-01-01

A method and apparatus for creating density images of an object through the 3-dimensional tracking of protons that have passed through the object are provided. More specifically, the 3-dimensional tracking of the protons is accomplished by gathering and analyzing images of the ionization tracks of the protons in a closely packed stack of scintillating fibers.

Using the Plan View to Teach Basic Crystallography in General Chemistry

ERIC Educational Resources Information Center

Cushman, Cody V.; Linford, Matthew R.

2015-01-01

The plan view is used in crystallography and materials science to show the positions of atoms in crystal structures. However, it is not widely used in teaching general chemistry. In this contribution, we introduce the plan view, and show these views for the simple cubic, body-centered cubic, face-centered cubic, hexagonal close packed, CsCl, NaCl,…

Investigation of “benign” ionic content in epoxy that induces microelectronic device failure

Treesearch

Gregory T. Schueneman; Jeffery Kingsbury; Edmund Klinkerch

2011-01-01

Microelectronics and the devices dependent upon them have the extremely challenging requirements of becoming more capable and less expensive every year. This drives the industry to pack more functions into an ever smaller footprint until the next technological revolution. Adding to this situation is the removal of lead from the bill of materials followed closely by...

Use of Chemical Fractionation and Proton Nuclear Magnetic Resonance to Probe the Physical Structure of the Primary Plant Cell Wall 1

PubMed Central

Taylor, Iain E. P.; Wallace, Julia C.; MacKay, Alex L.; Volke, Frank

1990-01-01

Proton magnetic resonance has been used to monitor the microscopic physical properties of etiolated hypocotyl cell walls from Phaseolus vulgaris L. at all stages in a series of chemical fractionations with ammonium oxalate and potassium hydroxide. Solid echo measurements indicate that 75% of the polymers in the intact cell wall, including the cellulose and most of the hemicelluloses, are arranged such that there is almost complete restraint of molecular motion. The chemical fractionations generally altered the physical structures of the remaining cell wall components. Digestion with 0.25% ammonium oxalate/oxalic acid solubilized the pectin and increased the mobility of the hemicellulose I component. Extraction with 4% potassium hydroxide removed the hemicellulose I component and loosened the hemicellulose II. Further extraction with 24% potassium hydroxide removed the hemicellulose II and loosened some of the cellulose. The cellulose crystallinity, as monitored by Jeener echo measurements decreased from 83% to 63% during these fractionations. We conclude that, while hemicellulose I is firmly attached to hemicellulose II, it is not in a closely packed structure. Hemicellulose II is strongly bound to cellulose and has a much more closely packed structure. PMID:16667683

Precision-Trimming 2D Inverse-Opal Lattice on Elastomer to Ordered Nanostructures with Variable Size and Morphology.

PubMed

Zhan, Haoran; Chen, Yanqiu; Liu, Yu; Lau, Woonming; Bao, Chao; Li, Minggan; Lu, Yunlong; Mei, Jun; Hui, David

2017-05-23

A low-cost and scalable method is developed for producing large-area elastomer surfaces having ordered nanostructures with a variety of lattice features controllable to nanometer precision. The method adopts the known technique of molding a PDMS precursor film with a close-packed monolayer of monodisperse submicron polystyrene beads on water to form an inverse-opal dimple lattice with the dimple size controlled by the bead selection and the dimple depth by the molding condition. The subsequent novel precision engineering of the inverse-opal lattice comprises trimming the PDMS precursor by a combination of polymer curing temperature/time and polymer dissolution parameters. The resultant ordered surface nanostructures, fabricated with an increasing degree of trimming, include (a) submicron hemispherical dimples with nanothin interdimple rims and walls; (b) nanocones with variable degrees of tip-sharpness by trimming off the top part of the nanothin interdimple walls; and (c) soup-plate-like submicron shallow dimples with interdimple rims and walls by anisotropically trimming off the nanocones and forming close-packed shallow dimples. As exemplars of industrial relevance of these lattice features, tunable Young's modulus and wettability are demonstrated.

Binary dislocation junction formation and strength in hexagonal close-packed crystals

DOE PAGES

Wu, Chi -Chin; Aubry, Sylvie; Arsenlis, Athanasios; ...

2015-12-17

This work examines binary dislocation interactions, junction formation and junction strengths in hexagonal close-packed ( hcp ) crystals. Through a line-tension model and dislocation dynamics (DD) simulations, the interaction and dissociation of different sets of binary junctions are investigated involving one dislocation on the (011¯0) prismatic plane and a second dislocation on one of the following planes: (0001) basal, (11¯00) prismatic, (11¯01) primary pyramidal, or (2¯112) secondary pyramidal. Varying pairs of Burgers vectors are chosen from among the common types the basal type < a > 1/3 < 112¯0 >, prismatic type < c > <0001>, and pyramidal type 1/3 < 112¯3¯ >. For binary interaction due to dislocation intersection, both the analytical results and DD-simulations indicate a relationship between symmetry of interaction maps and the relative magnitude of the Burgers vectors that constitute the junction. Using analytical formulae, a simple regressive model is also developed to represent the junction yield surface. The equation is treated as a degenerated super elliptical equation to quantify the aspect ratio and tilting angle. Lastly, the results provide analytical insights on binary dislocation interactions that may occur in general hcp metals.« less

The Effect of Alloying on Topologically Close Packed Phase Instability in Advanced Nickel-Based Superalloy Rene N6

NASA Technical Reports Server (NTRS)

Ritzert, Frank; Arenas, David; Keller, Dennis; Vasudevan, Vijay

1998-01-01

An investigation was conducted to describe topologically close packed (TCP) phase instability as a function of composition in the advanced Ni-base superalloy Rene N6. TCP phases are detrimental to overall high-temperature performance of Ni-base superalloys because of their brittle nature and because they deplete the Ni-rich matrix of potent solid solution strengthening elements. Thirty-four variations of polycrystalline Rene N6 determined from a design-of-experiments approach were cast and homogenized at 1315"C for 80 hours followed by exposure at 10930C for 400 hours to promote TCP formation. The alloys had the following composition ranges in atomic percent: Co 10.61 to 16.73%, Mo 0.32 to 1.34%, W 1.85 to 2.52%, Re 1.80 to 2.1 1 %, Ta 2.36 to 3.02%, Al 11.90 to 14.75%, and Cr 3.57 to 6.23%. Physical and chemical characteristics of all n-ticrostructures obtained were described using various analytical techniques. From these observations, a mathematical description of TCP occurrence (omega and P phase) was generated for polycrystalline Rene N6.

Two-Dimensional Algal Collection and Assembly by Combining AC-Dielectrophoresis with Fluorescence Detection for Contaminant-Induced Oxidative Stress Sensing.

PubMed

Siebman, Coralie; Velev, Orlin D; Slaveykova, Vera I

2015-06-15

An alternative current (AC) dielectrophoretic lab-on-chip setup was evaluated as a rapid tool of capture and assembly of microalga Chlamydomonas reinhardtii in two-dimensional (2D) close-packed arrays. An electric field of 100 V·cm⁻¹, 100 Hz applied for 30 min was found optimal to collect and assemble the algae into single-layer structures of closely packed cells without inducing cellular oxidative stress. Combined with oxidative stress specific staining and fluorescence microscopy detection, the capability of using the 2D whole-cell assembly on-chip to follow the reactive oxygen species (ROS) production and oxidative stress during short-term exposure to several environmental contaminants, including mercury, methylmercury, copper, copper oxide nanoparticles (CuO-NPs), and diuron was explored. The results showed significant increase of the cellular ROS when C. reinhardtii was exposed to high concentrations of methylmercury, CuO-NPs, and 10⁻⁵ M Cu. Overall, this study demonstrates the potential of combining AC-dielectrophoretically assembled two-dimensional algal structures with cell metabolic analysis using fluorescence staining, as a rapid analytical tool for probing the effect of contaminants in highly impacted environment.

Generalized-stacking-fault energy and twin-boundary energy of hexagonal close-packed Au: A first-principles calculation.

PubMed

Wang, Cheng; Wang, Huiyuan; Huang, Tianlong; Xue, Xuena; Qiu, Feng; Jiang, Qichuan

2015-05-22

Although solid Au is usually most stable as a face-centered cubic (fcc) structure, pure hexagonal close-packed (hcp) Au has been successfully fabricated recently. However, the phase stability and mechanical property of this new material are unclear, which may restrict its further applications. Here we present the evidence that hcp → fcc phase transformation can proceed easily in Au by first-principles calculations. The extremely low generalized-stacking-fault (GSF) energy in the basal slip system implies a great tendency to form basal stacking faults, which opens the door to phase transformation from hcp to fcc. Moreover, the Au lattice extends slightly within the superficial layers due to the self-assembly of alkanethiolate species on hcp Au (0001) surface, which may also contribute to the hcp → fcc phase transformation. Compared with hcp Mg, the GSF energies for non-basal slip systems and the twin-boundary (TB) energies for and twins are larger in hcp Au, which indicates the more difficulty in generating non-basal stacking faults and twins. The findings provide new insights for understanding the nature of the hcp → fcc phase transformation and guide the experiments of fabricating and developing materials with new structures.

Monolith electroplating process

DOEpatents

Agarrwal, Rajev R.

2001-01-01

An electroplating process for preparing a monolith metal layer over a polycrystalline base metal and the plated monolith product. A monolith layer has a variable thickness of one crystal. The process is typically carried in molten salts electrolytes, such as the halide salts under an inert atmosphere at an elevated temperature, and over deposition time periods and film thickness sufficient to sinter and recrystallize completely the nucleating metal particles into one single crystal or crystals having very large grains. In the process, a close-packed film of submicron particle (20) is formed on a suitable substrate at an elevated temperature. The temperature has the significance of annealing particles as they are formed, and substrates on which the particles can populate are desirable. As the packed bed thickens, the submicron particles develop necks (21) and as they merge into each other shrinkage (22) occurs. Then as micropores also close (23) by surface tension, metal density is reached and the film consists of unstable metal grain (24) that at high enough temperature recrystallize (25) and recrystallized grains grow into an annealed single crystal over the electroplating time span. While cadmium was used in the experimental work, other soft metals may be used.

A crystal plasticity model for slip in hexagonal close packed metals based on discrete dislocation simulations

NASA Astrophysics Data System (ADS)

Messner, Mark C.; Rhee, Moono; Arsenlis, Athanasios; Barton, Nathan R.

2017-06-01

This work develops a method for calibrating a crystal plasticity model to the results of discrete dislocation (DD) simulations. The crystal model explicitly represents junction formation and annihilation mechanisms and applies these mechanisms to describe hardening in hexagonal close packed metals. The model treats these dislocation mechanisms separately from elastic interactions among populations of dislocations, which the model represents through a conventional strength-interaction matrix. This split between elastic interactions and junction formation mechanisms more accurately reproduces the DD data and results in a multi-scale model that better represents the lower scale physics. The fitting procedure employs concepts of machine learning—feature selection by regularized regression and cross-validation—to develop a robust, physically accurate crystal model. The work also presents a method for ensuring the final, calibrated crystal model respects the physical symmetries of the crystal system. Calibrating the crystal model requires fitting two linear operators: one describing elastic dislocation interactions and another describing junction formation and annihilation dislocation reactions. The structure of these operators in the final, calibrated model reflect the crystal symmetry and slip system geometry of the DD simulations.

Self-assembly of three-dimensional open structures using patchy colloidal particles.

PubMed

Rocklin, D Zeb; Mao, Xiaoming

2014-10-14

Open structures can display a number of unusual properties, including a negative Poisson's ratio, negative thermal expansion, and holographic elasticity, and have many interesting applications in engineering. However, it is a grand challenge to self-assemble open structures at the colloidal scale, where short-range interactions and low coordination number can leave them mechanically unstable. In this paper we discuss the self-assembly of three-dimensional open structures using triblock Janus particles, which have two large attractive patches that can form multiple bonds, separated by a band with purely hard-sphere repulsion. Such surface patterning leads to open structures that are stabilized by orientational entropy (in an order-by-disorder effect) and selected over close-packed structures by vibrational entropy. For different patch sizes the particles can form into either tetrahedral or octahedral structural motifs which then compose open lattices, including the pyrochlore, the hexagonal tetrastack and the perovskite lattices. Using an analytic theory, we examine the phase diagrams of these possible open and close-packed structures for triblock Janus particles and characterize the mechanical properties of these structures. Our theory leads to rational designs of particles for the self-assembly of three-dimensional colloidal structures that are possible using current experimental techniques.

Increased functional properties and thermal stability of flexible cellulose nanocrystal/ZnO films.

PubMed

Lizundia, E; Urruchi, A; Vilas, J L; León, L M

2016-01-20

In this work we attempt to improve the functional properties and thermal stability of cellulose nanocrystal (CNC) films by means of eco-friendly materials and processes. Mechanically flexible films of closely packed CNCs with concentrations up to 5 wt.% of zinc oxide (ZnO) nanoparticles have been prepared by a simple, standard and environmentally friendly method using solely water. Results reveal that ultraviolet light is blocked by 98.5% at 1 wt.% ZnO while good transparency is maintained. A sharp hydrophobicity increase is observed with the addition of ZnO which would enhance the durability of films by decreasing the water diffusion through the material. The thermal degradation activation energy (E) presents an increase of 141%, denoting a high thermal stability of films, which would result beneficial for their potential application in the field of flexible electronics. Mechanical results demonstrate a high structural integrity of CNC/ZnO as a result of the occurring strong cellulosic inter- and intramolecular interactions within the closely packed CNC network. In overall, this work highlights the potential for environmentally friendly processing of sustainable nanostructured functional materials based on cellulose. Copyright © 2015 Elsevier Ltd. All rights reserved.

The stability of self-organized 1-nonanethiol-capped gold nanoparticle monolayer

NASA Astrophysics Data System (ADS)

Jiang, Peng; Xie, Si-shen; Yao, Jian-nian; Pang, Shi-jin; Gao, Hong-jun

2001-08-01

1-Nonanethiol-protected gold nanoparticles with the size of about 2 nm have been prepared by a wet chemical method through choosing a suitable ratio of Au:S (2.5:1). Size selective precipitation of nanoparticles has been used to narrow their size distribution, which facilitates the formation of an ordered nanoparticle close-packed structure. A Fourier transform infrared investigation provides the evidence of the encapsulation of Au nanoparticles by 1-nonanethiol while an ultraviolet-visible spectrum shows a broad absorption around 520 nm, corresponding to surface plasmon band of Au nanoparticles. X-ray photoelectron spectroscopy of the samples demonstrates the metallic state of the gold (Au0) and the existence of sulfur (S). The data from x-ray powder diffraction measurements confirm that the gold nanoparticles have the same face-centred cubic crystalline structure as the bulk gold phase. Finally, transmission electron microscopy (TEM) characterization indicates that the size of the monodisperse colloidal gold nanoparticles is about 2 nm and they can self-organize to form a two-dimensional hexagonal close-packed structure after evaporating a concentrated drop of nanoparticles-toluene solution on a carbon-coated TEM copper grid.

Cryo-electron microscopy of vitrified SV40 minichromosomes: the liquid drop model.

PubMed

Dubochet, J; Adrian, M; Schultz, P; Oudet, P

1986-03-01

The structure of SV40 minichromosomes has been studied by cryo-electron microscopy of vitrified thin layers of solution. In high-salt buffer (130 mM NaCl), freshly prepared minichromosomes are condensed into globules 30 nm or more in diameter. On the micrograph, they appear to be formed by the close packing of 10 nm granules which give rise to a 10 nm reflection in the optical diffractogram. The globules can adopt many different conformations. At high concentration, they fuse into a homogeneous 'sea' of closely packed 10 nm granules. In low-salt buffer (less than 10 mM NaCl), the globules open, first into 10 nm filaments, and then into nucleosome-strings. The 'liquid drop' model is proposed to explain the condensed structure of the minichromosome in high-salt buffer: nucleosomes stack specifically on top of one another, thus forming the 10 nm filaments. 10 nm filaments in turn, tend to aggregate laterally. Optimizing both these interactions results in the condensation of 10 nm filaments or portions thereof into a structure similar to that of a liquid. Some implications of this model for the structure of cellular chromatin are discussed.

Reconstructive structural phase transitions in dense Mg

NASA Astrophysics Data System (ADS)

Yao, Yansun; Klug, Dennis D.

2012-07-01

The question raised recently about whether the high-pressure phase transitions of Mg follow a hexagonal close-packed (hcp) → body centered cubic (bcc) or hcp → double hexagonal close-packed (dhcp) → bcc sequence at room temperature is examined by the use of first principles density functional methods. Enthalpy calculations show that the bcc structure replaces the hcp structure to become the most stable structure near 48 GPa, whereas the dhcp structure is never the most stable structure in the pressure range of interest. The characterized phase-transition mechanisms indicate that the hcp → dhcp transition is also associated with a higher enthalpy barrier. At room temperature, the structural sequence hcp → bcc is therefore more energetically favorable for Mg. The same conclusion is also reached from the simulations of the phase transitions using metadynamics methods. At room temperature, the metadynamics simulations predict the onset of a hcp → bcc transition at 40 GPa and the transition becomes more prominent upon further compression. At high temperatures, the metadynamics simulations reveal a structural fluctuation among the hcp, dhcp, and bcc structures at 15 GPa. With increasing pressure, the structural evolution at high temperatures becomes more unambiguous and eventually settles to a bcc structure once sufficient pressure is applied.

Reconstructive structural phase transitions in dense Mg.

PubMed

Yao, Yansun; Klug, Dennis D

2012-07-04

The question raised recently about whether the high-pressure phase transitions of Mg follow a hexagonal close-packed (hcp) → body centered cubic (bcc) or hcp → double hexagonal close-packed (dhcp) → bcc sequence at room temperature is examined by the use of first principles density functional methods. Enthalpy calculations show that the bcc structure replaces the hcp structure to become the most stable structure near 48 GPa, whereas the dhcp structure is never the most stable structure in the pressure range of interest. The characterized phase-transition mechanisms indicate that the hcp → dhcp transition is also associated with a higher enthalpy barrier. At room temperature, the structural sequence hcp → bcc is therefore more energetically favorable for Mg. The same conclusion is also reached from the simulations of the phase transitions using metadynamics methods. At room temperature, the metadynamics simulations predict the onset of a hcp → bcc transition at 40 GPa and the transition becomes more prominent upon further compression. At high temperatures, the metadynamics simulations reveal a structural fluctuation among the hcp, dhcp, and bcc structures at 15 GPa. With increasing pressure, the structural evolution at high temperatures becomes more unambiguous and eventually settles to a bcc structure once sufficient pressure is applied.

AxonPacking: An Open-Source Software to Simulate Arrangements of Axons in White Matter

PubMed Central

Mingasson, Tom; Duval, Tanguy; Stikov, Nikola; Cohen-Adad, Julien

2017-01-01

HIGHLIGHTS AxonPacking: Open-source software for simulating white matter microstructure.Validation on a theoretical disk packing problem.Reproducible and stable for various densities and diameter distributions.Can be used to study interplay between myelin/fiber density and restricted fraction. Quantitative Magnetic Resonance Imaging (MRI) can provide parameters that describe white matter microstructure, such as the fiber volume fraction (FVF), the myelin volume fraction (MVF) or the axon volume fraction (AVF) via the fraction of restricted water (fr). While already being used for clinical application, the complex interplay between these parameters requires thorough validation via simulations. These simulations required a realistic, controlled and adaptable model of the white matter axons with the surrounding myelin sheath. While there already exist useful algorithms to perform this task, none of them combine optimisation of axon packing, presence of myelin sheath and availability as free and open source software. Here, we introduce a novel disk packing algorithm that addresses these issues. The performance of the algorithm is tested in term of reproducibility over 50 runs, resulting density, and stability over iterations. This tool was then used to derive multiple values of FVF and to study the impact of this parameter on fr and MVF in light of the known microstructure based on histology sample. The standard deviation of the axon density over runs was lower than 10−3 and the expected hexagonal packing for monodisperse disks was obtained with a density close to the optimal density (obtained: 0.892, theoretical: 0.907). Using an FVF ranging within [0.58, 0.82] and a mean inter-axon gap ranging within [0.1, 1.1] μm, MVF ranged within [0.32, 0.44] and fr ranged within [0.39, 0.71], which is consistent with the histology. The proposed algorithm is implemented in the open-source software AxonPacking (https://github.com/neuropoly/axonpacking) and can be useful for validating diffusion models as well as for enabling researchers to study the interplay between microstructure parameters when evaluating qMRI methods. PMID:28197091

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

Spurzem, R.; Giersz, M.; Heggie, D. C.

At least 10%-15% of nearby Sunlike stars have known Jupiter-mass planets. In contrast, very few planets are found in mature open and globular clusters such as the Hyades and 47 Tuc. We explore here the possibility that this dichotomy is due to the postformation disruption of planetary systems associated with the stellar encounters in long-lived clusters. One supporting piece of evidence for this scenario is the discovery of freely floating low-mass objects in star forming regions. We use two independent numerical approaches, a hybrid Monte Carlo and a direct N-body method, to simulate the impact of the encounters. We showmore » that the results of numerical simulations are in reasonable agreement with analytical determinations in the adiabatic and impulsive limits. They indicate that distant stellar encounters generally do not significantly modify the compact and nearly circular orbits. However, moderately close stellar encounters, which are likely to occur in dense clusters, can excite planets' orbital eccentricity and induce dynamical instability in systems that are closely packed with multiple planets. The disruption of planetary systems occurs primarily through occasional nearly parabolic, nonadiabatic encounters, though eccentricity of the planets evolves through repeated hyperbolic adiabatic encounters that accumulate small-amplitude changes. The detached planets are generally retained by the potential of their host clusters as free floaters in young stellar clusters such as {sigma} Orionis. We compute effective cross sections for the dissolution of planetary systems and show that, for all initial eccentricities, dissolution occurs on timescales that are longer than the dispersion of small stellar associations, but shorter than the age of typical open and globular clusters. Although it is much more difficult to disrupt short-period planets, close encounters can excite modest eccentricity among them, such that subsequent tidal dissipation leads to orbital decay, tidal inflation, and even disruption of the close-in planets.« less

41 CFR 109-50.106 - Procedure.

Code of Federal Regulations, 2011 CFR

2011-01-01

... Research provides this information to prospective grantees through an automated system. (c) The following... institution. Such costs may consist of packing, crating, shipping and insurance, and are limited to actual...

41 CFR 109-50.106 - Procedure.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Research provides this information to prospective grantees through an automated system. (c) The following... institution. Such costs may consist of packing, crating, shipping and insurance, and are limited to actual...

41 CFR 109-50.106 - Procedure.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Research provides this information to prospective grantees through an automated system. (c) The following... institution. Such costs may consist of packing, crating, shipping and insurance, and are limited to actual...

41 CFR 109-50.106 - Procedure.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Research provides this information to prospective grantees through an automated system. (c) The following... institution. Such costs may consist of packing, crating, shipping and insurance, and are limited to actual...

41 CFR 109-50.106 - Procedure.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Research provides this information to prospective grantees through an automated system. (c) The following... institution. Such costs may consist of packing, crating, shipping and insurance, and are limited to actual...

7 CFR 945.15 - Pack.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE IRISH POTATOES GROWN IN CERTAIN DESIGNATED... means a quantity of potatoes in any type of container and which falls within specific weight limits or...

7 CFR 945.15 - Pack.

Code of Federal Regulations, 2014 CFR

2014-01-01

... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE IRISH POTATOES GROWN IN CERTAIN DESIGNATED... means a quantity of potatoes in any type of container and which falls within specific weight limits or...

Thermodynamics of dilute 3He-4He solid solutions with hcp structure

NASA Astrophysics Data System (ADS)

Chishko, K. A.

2018-02-01

To interpret the anomalies in heat capacity CV(T) and temperature-dependent pressure P(T) of solid hexagonal close-packed (hcp) 4He we exploit the model of hcp crystalline polytype with specific lattice degrees of freedom and describe the thermodynamics of impurity-free 4He solid as superposition of phononic and polytypic contributions. The hcp-based polytype is a stack of 2D basal atomic monolayers on triangular lattice packed with arbitrary long (up to infinity) spatial period along the hexagonal c axis perpendicular to the basal planes. It is a crystal with perfect ordering along the layers, but without microscopic translational symmetry in perpendicular direction (which remains, nevertheless, the rotational crystallographic axis of third order, so that the polytype can be considered as semidisordered system). Each atom of the hcp polytype has twelve crystallographic neighbors in both first and second coordination spheres at any arbitrary packing order. It is shown that the crystal of such structure behaves as anisotropic elastic medium with specific dispersion law of phonon excitations along c axis. The free energy and the heat capacity consist of two terms: one of them is a normal contribution [with CV(T) ˜ T3] from phonon excitations in an anisotropic lattice of hexagonal symmetry, and another term (an "excessive" heat) is a contribution resulted by packing entropy from quasi-one-dimensional system of 2D basal planes on triangular lattice stacked randomly along c axis without braking the closest pack between neighboring atomic layers. The excessive part of the free energy has been treated within 1D quasi-Ising (lattice gas) model using the transfer matrix approach. This model makes us possible to interpret successfully the thermodynamic anomaly (heat capacity peak in hcp 4He) observed experimentally.

Do gray wolves (Canis lupus) support pack mates during aggressive inter-pack interactions?

PubMed

Cassidy, Kira A; McIntyre, Richard T

2016-09-01

For group-living mammals, social coordination increases success in everything from hunting and foraging (Crofoot and Wrangham in Mind the Gap, Springer, Berlin, 2010; Bailey et al. in Behav Ecol Sociobiol 67:1-17, 2013) to agonism (Mosser and Packer in Anim Behav 78:359-370, 2009; Wilson et al. in Anim Behav 83:277-291, 2012; Cassidy et al. in Behav Ecol 26:1352-1360, 2015). Cooperation is found in many species and, due to its low costs, likely is a determining factor in the evolution of living in social groups (Smith in Anim Behav 92:291-304, 2014). Beyond cooperation, many mammals perform costly behaviors for the benefit of group mates (e.g., parental care, food sharing, grooming). Altruism is considered the most extreme case of cooperation where the altruist increases the fitness of the recipient while decreasing its own fitness (Bell in Selection: the mechanism of evolution. Oxford University Press, Oxford 2008). Gray wolf life history requires intra-pack familiarity, communication, and cooperation in order to succeed in hunting (MacNulty et al. in Behav Ecol doi: 10.1093/beheco/arr159 2011) and protecting group resources (Stahler et al. in J Anim Ecol 82: 222-234, 2013; Cassidy et al. in Behav Ecol 26:1352-1360, 2015). Here, we report 121 territorial aggressive inter-pack interactions in Yellowstone National Park between 1 April 1995 and 1 April 2011 (>5300 days of observation) and examine each interaction where one wolf interferes when its pack mate is being attacked by a rival group. This behavior was recorded six times (17.6 % of interactions involving an attack) and often occurred between dyads of closely related individuals. We discuss this behavior as it relates to the evolution of cooperation, sociality, and altruism.

Pre-packed vacuum bone cement mixing systems. A further step in reducing methylmethacrylate exposure in surgery.

PubMed

Schlegel, Ulf J; Sturm, Michael; Eysel, Peer; Breusch, Steffen J

2010-11-01

Polymethylmethacrylate bone cements are widely used in orthopaedic and trauma surgery as well as in dentistry. The toxic side effects of inhaled methylmethacrylate (MMA) fumes generated during mixing have been well studied. Vacuum cement mixing systems have been shown to reduce the risk of airborne MMA significantly compared to handmixing. In an effort to further reduce MMA exposure, the latest generation of mixing devices are pre-packed with the ingredients and thus allow preparation in nearly closed circuits. Until now, there has been no study proofing the efficacy of those systems in protecting theatre staff from MMA vapours. A pre-packed vacuum mixing system (Optipac®) was compared with two standard systems (Palamix® and Easymix®) regarding MMA emission. The latter systems require loading with the bone cement compounds prior to mixing. Following a standardized procedure, 10 mixes were performed with each system and the emission of MMA vapours in the breathing zone was recorded using photoionization detection over a period of 3 min. The mean MMA exposure was reduced when using the pre-packed system compared to the devices that require filling with the components. The highest emission peaks were recorded during the mixing and preparation steps in all systems. Modern pre-packed vacuum mixing systems further help to reduce the occupational hazards created by bone cement preparation. However, MMA fumes can still be detected using this technique. Although this is an important step in reducing MMA exposure in the operating theatre, further technical effort has to be taken to eliminate the continuous leakage of monomer from the devices while mixing and to minimize necessary manipulation for final delivery.

An efficient method and device for transfer of semisolid materials into solid-state NMR spectroscopy rotors.

PubMed

Hisao, Grant S; Harland, Michael A; Brown, Robert A; Berthold, Deborah A; Wilson, Thomas E; Rienstra, Chad M

2016-04-01

The study of mass-limited biological samples by magic angle spinning (MAS) solid-state NMR spectroscopy critically relies upon the high-yield transfer of material from a biological preparation into the MAS rotor. This issue is particularly important for maintaining biological activity and hydration of semi-solid samples such as membrane proteins in lipid bilayers, pharmaceutical formulations, microcrystalline proteins and protein fibrils. Here we present protocols and designs for rotor-packing devices specifically suited for packing hydrated samples into Pencil-style 1.6 mm, 3.2 mm standard, and 3.2 mm limited speed MAS rotors. The devices are modular and therefore readily adaptable to other rotor and/or ultracentrifugation tube geometries. Copyright © 2016 Elsevier Inc. All rights reserved.

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

Zhdankin, Vladimir; Boldyrev, Stanislav; Perez, Jean Carlos

We investigate the intermittency of energy dissipation in magnetohydrodynamic (MHD) turbulence by identifying dissipative structures and measuring their characteristic scales. We find that the probability distribution of energy dissipation rates exhibits a power-law tail with an index very close to the critical value of –2.0, which indicates that structures of all intensities contribute equally to energy dissipation. We find that energy dissipation is uniformly spread among coherent structures with lengths and widths in the inertial range. At the same time, these structures have thicknesses deep within the dissipative regime. As the Reynolds number is increased, structures become thinner and moremore » numerous, while the energy dissipation continues to occur mainly in large-scale coherent structures. This implies that in the limit of high Reynolds number, energy dissipation occurs in thin, tightly packed current sheets which nevertheless span a continuum of scales up to the system size, exhibiting features of both coherent structures and nanoflares previously conjectured as a coronal heating mechanism.« less

An efficicient data structure for three-dimensional vertex based finite volume method

NASA Astrophysics Data System (ADS)

Akkurt, Semih; Sahin, Mehmet

2017-11-01

A vertex based three-dimensional finite volume algorithm has been developed using an edge based data structure.The mesh data structure of the given algorithm is similar to ones that exist in the literature. However, the data structures are redesigned and simplied in order to fit requirements of the vertex based finite volume method. In order to increase the cache efficiency, the data access patterns for the vertex based finite volume method are investigated and these datas are packed/allocated in a way that they are close to each other in the memory. The present data structure is not limited with tetrahedrons, arbitrary polyhedrons are also supported in the mesh without putting any additional effort. Furthermore, the present data structure also supports adaptive refinement and coarsening. For the implicit and parallel implementation of the FVM algorithm, PETSc and MPI libraries are employed. The performance and accuracy of the present algorithm are tested for the classical benchmark problems by comparing the CPU time for the open source algorithms.

Impact of electrode geometry on an atmospheric pressure surface barrier discharge

NASA Astrophysics Data System (ADS)

Hasan, M. I.; Morabit, Y.; Dickenson, A.; Walsh, J. L.

2017-06-01

Several of the key characteristics of an atmospheric pressure surface barrier discharge (SBD) are heavily dependent on the geometrical configuration of the plasma generating electrodes. This paper reveals that increasing the surface area of an SBD device by reducing the gaps within the electrodes can have major and unforeseen consequence on the discharge properties. It is experimentally demonstrated that a critical limit exists when reducing the diameter of a circular electrode gap below 5 mm, beyond which the required breakdown voltage increases exponentially and the power deposited in the discharge is impeded. Using a numerical model, it is shown that a reduced electrode gap diameter yields a decrease in the voltage difference between the electrode and dielectric surface, thus lowering the maximum electric field. This study indicates a link between the electrode geometry and the nature of the reactive chemistry produced in the plasma, findings which have wide-reaching implications for many applications where multiple closely packed surface barrier discharges are employed to achieve uniform and large area plasma processing.

Spectroscopic Terahertz Imaging at Room Temperature Employing Microbolometer Terahertz Sensors and Its Application to the Study of Carcinoma Tissues

PubMed Central

Kašalynas, Irmantas; Venckevičius, Rimvydas; Minkevičius, Linas; Sešek, Aleksander; Wahaia, Faustino; Tamošiūnas, Vincas; Voisiat, Bogdan; Seliuta, Dalius; Valušis, Gintaras; Švigelj, Andrej; Trontelj, Janez

2016-01-01

A terahertz (THz) imaging system based on narrow band microbolometer sensors (NBMS) and a novel diffractive lens was developed for spectroscopic microscopy applications. The frequency response characteristics of the THz antenna-coupled NBMS were determined employing Fourier transform spectroscopy. The NBMS was found to be a very sensitive frequency selective sensor which was used to develop a compact all-electronic system for multispectral THz measurements. This system was successfully applied for principal components analysis of optically opaque packed samples. A thin diffractive lens with a numerical aperture of 0.62 was proposed for the reduction of system dimensions. The THz imaging system enhanced with novel optics was used to image for the first time non-neoplastic and neoplastic human colon tissues with close to wavelength-limited spatial resolution at 584 GHz frequency. The results demonstrated the new potential of compact RT THz imaging systems in the fields of spectroscopic analysis of materials and medical diagnostics. PMID:27023551

A Lamellar Complex of Lecithin and Poly-l-Tyrosine

PubMed Central

Giannoni, G.; Padden, F. J.; Roe, R. J.

1971-01-01

Complexes of poly-L-tyrosine (PT) with dipalmitoyllecithin, synthetic, (DPL) and with egg lecithin (EL) have been obtained by precipitation from methanol-water solutions. Chemical analysis indicates that both lecithins bind PT up to a limiting ratio of about 4 tyrosine residues/lecithin molecule. DPL-PT complexes have a lamellar structure closely resembling lecithin itself. In fact, DPL and DPL-PT lamellae have very nearly the same thickness as precipitated from methanol-water, although their swelling behavior on resuspension in pure water is different. The complexes crystallize in the form of hexagonal platelets, some monolayers and some with terraced spiral growths, with a thickness of 50-55 A. In X-ray and electron diffraction they yield sharp reflections at 4.14 A which are characteristic of hexagonal packing of phospholipid paraffinic chains. The order-disorder transition temperature of this crystalline lattice, determined by differential scanning calorimetry, is somewhat higher in the complex than in pure DPL. Physical models consistent with these observations are discussed. ImagesFIGURE 1 aFIGURE 1 b PMID:5134208

Fabrication of three-dimensionally interconnected nanoparticle superlattices and their lithium-ion storage properties

PubMed Central

Jiao, Yucong; Han, Dandan; Ding, Yi; Zhang, Xianfeng; Guo, Guannan; Hu, Jianhua; Yang, Dong; Dong, Angang

2015-01-01

Three-dimensional superlattices consisting of nanoparticles represent a new class of condensed materials with collective properties arising from coupling interactions between close-packed nanoparticles. Despite recent advances in self-assembly of nanoparticle superlattices, the constituent materials have been limited to those that are attainable as monodisperse nanoparticles. In addition, self-assembled nanoparticle superlattices are generally weakly coupled due to the surface-coating ligands. Here we report the fabrication of three-dimensionally interconnected nanoparticle superlattices with face-centered cubic symmetry without the presynthesis of the constituent nanoparticles. We show that mesoporous carbon frameworks derived from self-assembled supercrystals can be used as a robust matrix for the growth of nanoparticle superlattices with diverse compositions. The resulting interconnected nanoparticle superlattices embedded in a carbon matrix are particularly suitable for energy storage applications. We demonstrate this by incorporating tin oxide nanoparticle superlattices as anode materials for lithium-ion batteries, and the resulting electrochemical performance is attributable to their unique architectures. PMID:25739732

Rational design of alpha-helical tandem repeat proteins with closed architectures

PubMed Central

Doyle, Lindsey; Hallinan, Jazmine; Bolduc, Jill; Parmeggiani, Fabio; Baker, David; Stoddard, Barry L.; Bradley, Philip

2015-01-01

Tandem repeat proteins, which are formed by repetition of modular units of protein sequence and structure, play important biological roles as macromolecular binding and scaffolding domains, enzymes, and building blocks for the assembly of fibrous materials1,2. The modular nature of repeat proteins enables the rapid construction and diversification of extended binding surfaces by duplication and recombination of simple building blocks3,4. The overall architecture of tandem repeat protein structures – which is dictated by the internal geometry and local packing of the repeat building blocks – is highly diverse, ranging from extended, super-helical folds that bind peptide, DNA, and RNA partners5–9, to closed and compact conformations with internal cavities suitable for small molecule binding and catalysis10. Here we report the development and validation of computational methods for de novo design of tandem repeat protein architectures driven purely by geometric criteria defining the inter-repeat geometry, without reference to the sequences and structures of existing repeat protein families. We have applied these methods to design a series of closed alpha-solenoid11 repeat structures (alpha-toroids) in which the inter-repeat packing geometry is constrained so as to juxtapose the N- and C-termini; several of these designed structures have been validated by X-ray crystallography. Unlike previous approaches to tandem repeat protein engineering12–20, our design procedure does not rely on template sequence or structural information taken from natural repeat proteins and hence can produce structures unlike those seen in nature. As an example, we have successfully designed and validated closed alpha-solenoid repeats with a left-handed helical architecture that – to our knowledge – is not yet present in the protein structure database21. PMID:26675735

Phthalates and food-contact materials: enforcing the 2008 European Union plastics legislation.

PubMed

Petersen, J H; Jensen, L K

2010-11-01

The migration of phthalates into foodstuffs from food-contact materials (FCM) is a well-known source of food contamination. In 2005, the European Food Safety Authority finalized its risk assessment for several of the classical phthalate plasticizers. In their risk management procedure the European Commission transformed the tolerable daily intakes established by the Authority into legislative limits for phthalates in both plastic and food simulants, while taking exposure from other sources into consideration. These limits have been into force since 1 July 2008. A detailed interpretation of the regulation of these substances was agreed upon in the European network of FCM reference laboratories. This paper reports results from a Danish control campaign of samples collected by official food inspectors and analysed by a newly validated analytical method run under accreditation. Samples were from FCM producers, FCM importers and importers of packed foodstuffs from third-party countries. Products containing phthalates above the current limits were found in several categories of FCM: conveyor belts (six of six), lids from packed foodstuffs in glasses (eight of 28), tubes for liquid foodstuffs (four of five) and gloves (five of 14). More than 20% of the samples analysed contained dibutylphthalate (DBP) or di-(2-ethylhexyl)phthalate (DEHP) above the compositional limits of 0.05% and 0.1%, respectively. Analysis of residual phthalates in metal lid gaskets instead of analysis of phthalates in the food when controlling foodstuffs packed outside the European Union proved to be an efficient and simple control method. All findings of phthalates were associated with the use of plasticized polyvinylchloride (PVC).

I Situ Structural Study of Underpotential Deposition and Electrocatalysis on GOLD(111) Electrodes

NASA Astrophysics Data System (ADS)

Chen, Chun-Hsien

This thesis work has studied systems of Bi, Pb, Ag, and Hg underpotential deposition (UPD) on Au(111) electrodes. The application of the atomic force microscope (AFM), the scanning tunneling microscope (STM), and the surface x-ray scattering (SXS) to these UPD studies has provided in situ measurements from which we investigate factors that determine UPD surface structures and correlate these structures with surface reactivity. For all the UPD systems in this thesis work, atomic level features of the electrode surface have been revealed. In the case of Pb UPD, Pb starts to deposit by forming islands which exhibit a hexagonal close packed structure of Pb adatoms, while, in the other systems, the UPD adatoms form open lattices. In the Bi and Pb studies, we correlate the activities of the modified surface toward electroreduction of H_2O_2 with the adlattice structures. A heterobimetallic bridge model for H_2O_2 on the surface could explain the enhanced reactivity. The full monolayers of Bi and Hg, rhombohedral metals, form rectangular lattice structures on the hexagonal Au(111) surfaces. The partial charge retention on the Bi and Hg adatom opens the adlayer structure when the coverage is less than a full monolayer. The structure of the first submonolayers of Ag UPD is electrolyte-dependent. The electrode surface exhibits 3 x 3 and 4 x 4 overlayer structures in solutions containing sulfate and nitrate, respectively. In perchloric acid another open structure is observed and a close-packed monolayer is formed in acetic acid. The different monolayer structures give rise to packing densities which correlate with electrolyte size. This implies that the anions participate in reducing metal ions.

Portal vein thrombosis is a potentially preventable complication in clinical islet transplantation

PubMed Central

Kawahara, Toshiyasu; Kin, Tatsuya; Kashkoush, Samy; Gala-Lopez, Boris; Bigam, David L.; Kneteman, Norman M.; Koh, Angela; Senior, Peter A.; Shapiro, A.M. James

2011-01-01

Percutaneous transhepatic portal access avoids surgery, but is rarely associated with bleeding or portal venous thrombosis. We herein report our large, single-center experience of percutaneous islet implantation, and evaluate risk factors of portal vein thrombosis and graft function. Prospective data was collected on 268 intraportal islet transplants (122 subjects). A portal venous Doppler ultrasound was obtained on Days 1 and 7 days posttransplant. Therapeutic heparinization, complete ablation of the portal catheter tract with Avitene paste, and limiting packed cell volume to < 5 ml completely prevented any portal thrombosis in the most recent 101 islet transplant procedures over the past 5 years. In the previous cumulative experience, partial thrombosis did not affect islet function. Standard liver volume correlated negatively (r=−0.257, P<0.001), and packed cell volume correlated positively with portal pressure rise (r=0.463, P<0.001). Overall, partial portal thrombosis occurred after 10 procedures (overall incidence 3.7%, most recent 101 patient incidence 0%). There were no cases of complete thrombosis, and no patient developed sequelae of portal hypertension. In conclusion, portal thrombosis is a preventable complication in clinical islet transplantation, provided therapeutic anticoagulation is maintained, and packed cell volume is limited to <5 ml. PMID:21883914

Evaluation of natural antimicrobials on typical meat spoilage bacteria in vitro and in vacuum-packed pork meat.

PubMed

Schirmer, Bjørn Christian; Langsrud, Solveig

2010-03-01

The aim of this study was to investigate the inhibitory effect of natural antimicrobials on the growth of typical spoilage bacteria from marinated pork. Minimum inhibitory concentrations (MIC) of thymol, cinnamaldehyde, allyl isothiocyanate, citric acid, ascorbic acid, a rosemary extract, and a grapefruit seed extract against Lactobacillus algidus, Leuconostoc mesenteroides, Leuconostoc carnosum, Carnobacterium maltaromaticum, Carnobacterium divergens, Brochothrix thermosphacta, and Serratia proteamaculans were determined in a microplate assay. Combinations of antimicrobials were tested and several combinations showed synergistic effects in inhibiting bacterial growth. Single and combined antimicrobials were added to vacuum-packed pork meat to evaluate preserving effects. Antimicrobial concentrations of up to 10 times the MIC values showed no effect on total bacterial growth in vacuum packed pork meaning that although most antimicrobials inhibited the growth of spoilage bacteria in vitro, results from the microplate assay could not be transferred to the meat system. Most natural antimicrobials possess strong odor and flavor that limit their use as a food preservative. In conclusion, this study showed that the use of natural antimicrobials in meat products is limited and that bacterial quality and shelf life was not enhanced under the chosen conditions.

Dimension dependence of clustering dynamics in models of ballistic aggregation and freely cooling granular gas

NASA Astrophysics Data System (ADS)

Paul, Subhajit; Das, Subir K.

2018-03-01

Via event-driven molecular dynamics simulations we study kinetics of clustering in assemblies of inelastic particles in various space dimensions. We consider two models, viz., the ballistic aggregation model (BAM) and the freely cooling granular gas model (GGM), for each of which we quantify the time dependence of kinetic energy and average mass of clusters (that form due to inelastic collisions). These quantities, for both the models, exhibit power-law behavior, at least in the long time limit. For the BAM, corresponding exponents exhibit strong dimension dependence and follow a hyperscaling relation. In addition, in the high packing fraction limit the behavior of these quantities become consistent with a scaling theory that predicts an inverse relation between energy and mass. On the other hand, in the case of the GGM we do not find any evidence for such a picture. In this case, even though the energy decay, irrespective of packing fraction, matches quantitatively with that for the high packing fraction picture of the BAM, it is inversely proportional to the growth of mass only in one dimension, and the growth appears to be rather insensitive to the choice of the dimension, unlike the BAM.

High-Altitude Illness

MedlinePlus

... after you travel. Make sure you pack enough water while you are active. Avoid or limit the amount of alcohol you consume. High-altitude illness treatment It is important to treat high-altitude illness ...

Microbiological Evaluation of Production Procedures for Frozen Foil Pack Meals at the Central Preparation Facility of the Francis E. Warren Air Force Base

DTIC Science & Technology

1976-01-01

ACT (Continue an revere* side If necessary and Identify by block numbor) Food items produced at F.E. Warren AFB met the microbiological constraints...of SA(Regulation 146-1. A Hazard Analysis (HA) to aid in production guidance was of limited valuedue to a lack of predictability of production...II I UNCLASSIFIED/ it - RUITY CLASSIFICATO FTI PAGE(Wh.n Dal& Emted) I’ FSUMMARY The APC’s of the six raw beef and chicken samples used for foil pack

Application of Nanofiber-packed SPE for Determination of Urinary 1-Hydroxypyrene Level Using HPLC.

PubMed

Ifegwu, Okechukwu Clinton; Anyakora, Chimezie; Chigome, Samuel; Torto, Nelson

2014-01-01

It is always desirable to achieve maximum sample clean-up, extraction, and pre-concentration with the minimum possible organic solvent. The miniaturization of sample preparation devices was successfully demonstrated by packing 10 mg of 11 electrospun polymer nanofibers into pipette tip micro column and mini disc cartridges for efficient pre-concentration of 1-hydroxypyrene in urine samples. 1-hydroxypyrene is an extensively studied biomarker of the largest class of chemical carcinogens. Excretory 1-hydroxypyrene was monitored with HPLC/fluorescence detector. Important parameters influencing the percentage recovery such as fiber diameter, fiber packing amount, eluent, fiber packing format, eluent volume, surface area, porosity, and breakthrough parameters were thoroughly studied and optimized. Under optimized condition, there was a near perfect linearity of response in the range of 1-1000 μg/L with a coefficient of determination (r (2)) between 0.9992 and 0.9999 and precision (% RSD) ≤7.64% (n = 6) for all the analysis (10, 25, and 50 μg/L). The Limit of detection (LOD) was between 0.022 and 0.15 μg/L. When compared to the batch studies, both disc packed nanofiber sorbents and pipette tip packed sorbents exhibited evident dominance based on their efficiencies. The experimental results showed comparable absolute recoveries for the mini disc packed fibers (84% for Nylon 6) and micro columns (80% for Nylon 6), although the disc displayed slightly higher recoveries possibly due to the exposure of the analyte to a larger reacting surface. The results also showed highly comparative extraction efficiencies between the nanofibers and conventional C-18 SPE sorbent. Nevertheless, miniaturized SPE devices simplified sample preparation, reducing back pressure, time of the analysis with acceptable reliability, selectivity, detection levels, and environmental friendliness, hence promoting green chemistry.

Inertial shear flow of assemblies of frictionless polygons: Rheology and microstructure.

PubMed

Azéma, Émilien; Radjaï, Farhang; Roux, Jean-Noël

2018-01-05

Motivated by the understanding of shape effects in granular materials, we numerically investigate the macroscopic and microstructural properties of anisotropic dense assemblies of frictionless polydisperse rigid pentagons in shear flow, and compare them with similar systems of disks. Once subjected to large cumulative shear strains their rheology and microstructure are investigated in uniform steady states, depending on inertial number I, which ranges from the quasistatic limit ([Formula: see text]) to 0.2. In the quasistatic limit both systems are devoid of Reynolds dilatancy, i.e., flow at their random close packing density. Both macroscopic friction angle [Formula: see text], an increasing function of I , and solid fraction [Formula: see text], a decreasing function of I, are larger with pentagons than with disks at small I, but the differences decline for larger I and, remarkably, nearly vanish for [Formula: see text]. Under growing I , the depletion of contact networks is considerably slower with pentagons, in which increasingly anisotropic, but still well-connected force-transmitting structures are maintained throughout the studied range. Whereas contact anisotropy and force anisotropy contribute nearly equally to the shear strength in disk assemblies, the latter effect dominates with pentagons at small I, while the former takes over for I of the order of 10 -2 . The size of clusters of grains in side-to-side contact, typically comprising more than 10 pentagons in the quasistatic limit, very gradually decreases for growing I.

Electric-field induced phase transitions of dielectric colloids: Impact of multiparticle effects

NASA Astrophysics Data System (ADS)

Wood, Jeffery A.; Docoslis, Aristides

2012-05-01

The thermodynamic framework for predicting the electric-field induced fluid like-solid like phase transition of dielectric colloids developed by Khusid and Acrivos [Phys. Rev. E. 54, 5428 (1996)] is extended to examine the impact of multiscattering/multiparticle effects on the resulting phase diagrams. This was accomplished using effective permittivity models suitable both over the entire composition region for hard spheres (0≤c

Domestication Does Not Explain the Presence of Inequity Aversion in Dogs.

PubMed

Essler, Jennifer L; Marshall-Pescini, Sarah; Range, Friederike

2017-06-19

Sensitivity to inequity is thought to be an important mechanism for recognizing undesirable cooperative partners and thus crucial for the evolution of human cooperation [1]. This link may not be unique to humans, as cooperative non-human primates also react to unequal outcomes [2], whereas non-cooperative species do not [3]. Although this hypothesis has not been tested in non-primate species, studies revealed that pet dogs show a limited form of inequity aversion, responding to reward, but not quality inequity [4-6]. It has been proposed that this primitive form of inequity aversion was selected for during domestication and thus absent in their ancestors, wolves. Alternatively, wolves, which hunt, raise pups, and defend their territory cooperatively, are similarly inequity averse as non-human primates, or at least to the same degree as pet dogs. Testing similarly raised and kept pack-living dogs and wolves, we found both to be inequity averse when their partner was being rewarded but they were not for performing the same action. Additionally, both wolves and dogs reacted to receiving a lower-quality reward than their partner. These results suggest that the inequity response found in pack-living dogs and wolves is comparable to that observed in non-human primates; results from studies on pet dogs may be confounded by the dogs' relationship with humans. Consequently, our results suggest that inequity aversion was present already in the common-probably cooperative-ancestor of wolves and dogs and thus support the hypothesis of a close link of cooperation and inequity aversion. Copyright © 2017 Elsevier Ltd. All rights reserved.

Solid-phase microextraction followed by gas chromatography-mass spectrometry for the determination of ink photo-initiators in packed milk.

PubMed

Negreira, N; Rodríguez, I; Rubí, E; Cela, R

2010-06-30

A novel, single step method for the determination of seven ink photo-initiators in carton packed milk samples is described. Solid-phase microextraction (SPME) and gas chromatography (GC), combined with mass spectrometry (MS), were used as sample preparation and determination techniques, respectively. Parameters affecting the performance of the microextraction process were thoroughly evaluated using uni- and multivariate optimization strategies, based on the use of experimental factorial designs. The coating of the SPME fibre, together with the sampling mode and the temperature were the factors playing a major influence on the efficiency of the extraction. Under final conditions, 1.5 mL of milk and 8.5 mL of ultrapure water were poured in a glass vessel, which was closed and immersed in a water boiling bath. A poly(dimethylsiloxane)-divinylbenzene (PDMS-DVB) coated fibre was exposed directly to the diluted sample for 40 min. After that, the fibre was desorbed in the injector of the GC-MS system for 3 min. The optimized method provided limits of quantification (LOQs) between 0.2 and 1 microg L(-1) and a good linearity in the range between 1 and 250 microg L(-1). The inter-day precision remained below 15% for all compounds in spiked whole milk. The efficiency of the extraction changed for whole, semi-skimmed and skimmed milk; however, no differences were noticed among the relative recoveries achieved for milk samples, from different brands, with the same fat content. Copyright 2010 Elsevier B.V. All rights reserved.

An Investigation into the Effects of Process Conditions on the Tribological Performance of Pack Carburized Titanium with Limited Oxygen Diffusion

NASA Astrophysics Data System (ADS)

Bailey, R.; Sun, Y.

2018-04-01

In the present study, a new pack carburization technique for titanium has been investigated. The aim of this treatment is to produce a titanium carbide/oxycarbide layer atop of an extended oxygen diffusion zone [α-Ti(O)]. The effects of treatment temperature and pack composition have been investigated in order to determine the optimal conditions required to grant the best tribological response. The resulting structural features were investigated with particular interest in the carbon and oxygen concentrations across the samples cross section. The optimization showed that a temperature of 925 °C with a pack composition of 1 part carbon to 1 part energizer produced surface capable of withstanding a contact pressure of ≈ 1.5 GPa for 1 h. The process resulted in TiC surface structure which offers enhanced hardness (2100 HV) and generates a low friction coefficient (μ ≈ 0.2) when in dry sliding contact with an alumina (Al2O3) ball. The process also produced an extended oxygen diffusion zone that helps to improve the load bearing capacity of the substrate.

Hyperkalemia after irradiation of packed red blood cells: Possible effects with intravascular fetal transfusion

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

Thorp, J.A.; Plapp, F.V.; Cohen, G.R.

1990-08-01

Plasma potassium, calcium, and albumin concentrations in irradiated blood, and in fetal blood before and after transfusion, were measured. Dangerously high plasma potassium levels were observed in some units of irradiated packed red blood cells (range, 13.9 to 66.5 mEq/L; mean, 44.7 mEq/L) and could be one possible explanation for the high incidence of fetal arrhythmia associated with fetal intravascular transfusion. There are many factors operative in the preparation of irradiated packed red blood cells that may predispose to high potassium levels: the age of the red blood cells, the number of procedures used to concentrate the blood, the durationmore » of time elapsed from concentration, the duration of time elapsed from irradiation, and the hematocrit. Use of fresh blood, avoidance of multiple packing procedures, limiting the hematocrit in the donor unit to less than or equal to 80%, and minimizing the time between concentration, irradiation and transfusion may minimize the potassium levels, and therefore making an additional washing procedure unnecessary.« less

Diffusion in Jammed Particle Packs.

PubMed

Bolintineanu, Dan S; Grest, Gary S; Lechman, Jeremy B; Silbert, Leonardo E

2015-08-21

Using random walk simulations we explore diffusive transport through monodisperse sphere packings over a range of packing fractions ϕ in the vicinity of the jamming transition at ϕ(c). Various diffusion properties are computed over several orders of magnitude in both time and packing pressure. Two well-separated regimes of normal "Fickian" diffusion, where the mean squared displacement is linear in time, are observed. The first corresponds to diffusion inside individual spheres, while the latter is the long-time bulk diffusion. The intermediate anomalous diffusion regime and the long-time value of the diffusion coefficient are both shown to be controlled by particle contacts, which in turn depend on proximity to ϕ(c). The time required to recover normal diffusion t* scales as (ϕ-ϕ(c))(-0.5) and the long-time diffusivity D(∞)∼(ϕ-ϕ(c))0.5, or D(∞)∼1/t*. It is shown that the distribution of mean first passage times associated with the escape of random walkers between neighboring particles controls both t* and D(∞) in the limit ϕ→ϕ(c).

Assembly of barcode-like nucleic acid nanostructures.

PubMed

Wang, Pengfei; Tian, Cheng; Li, Xiang; Mao, Chengde

2014-10-15

Barcode-like (BC) nanopatterns from programmed self-assembly of nucleic acids (DNA and RNA) are reported. BC nanostructures are generated by the introduction of open spaces at selected sites to an otherwise closely packed, plain, rectangle nucleic acid nanostructure. This strategy is applied to nanostructures assembled from both origami approach and single stranded tile approach. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Magnetic resonance imaging of the saccular otolithic mass.

PubMed Central

Sbarbati, A; Leclercq, F; Antonakis, K; Osculati, F

1992-01-01

The frog's inner ear was studied in vivo by high spatial resolution magnetic resonance imaging at 7 Tesla. The vestibule, the internal acoustic meatus, and the auditory tube have been identified. The large otolithic mass contained in the vestibule showed a virtual absence of magnetic resonance signal probably due to its composition of closely packed otoconia. Images Fig. 1 Fig. 2 Fig. 3 Fig. 5 PMID:1295875

Fiscal Year 1996 Annual Report and Five-Year (1996-2000) Strategic Investment Plan

DTIC Science & Technology

1996-03-01

dissolved and solid-associated organic carbon compounds associated with sorption and biodegradative processes. The participation of faculty and graduate...created by adsorbed monolayers of closely packed perfluorinated compounds . Since adsorbed monolayers are not practical as hull coatings, we propose to...the perfluorinated compounds into a polymeric backbone to create comb type polymers with perfluoroalkyl sidechains. These types of polymeric

Annual Report (1994) and Five-Year (1994-1998) Strategic Investment Plan.

DTIC Science & Technology

1994-09-01

include identification of dissolved and solid-associated organic carbon compounds associated with sorption and biodegradative processes. The participation...exploiting the low surface energy of surface oriented perfluorinated alkyl compounds . This project is a continuation of the FY93 funded "innovative Very Low...adsorbed monolayers of closely packed perfluorinated compounds . Since adsorbed monolayers are not practical as hull coatings, we propose to simulate

Primary intraosseous fibrosarcoma in a cat.

PubMed

Fox, S M; Cooke, M M; Beban, H J

1995-10-01

A case of primary intraosseous fibrosarcoma of the left femur in a cat was diagnosed at necropsy following 9 months of managing a fracture of the same bone. Case features were those of probable pathological fracture, fracture repair and ultimate lysis of all but a fragment of the distal femoral epiphysis. Histology revealed closely packed whorls of fibroblasts typical of fibrosarcoma. This neoplasm is rare in the cat.

Young people's perceptions of tobacco packaging: a comparison of EU Tobacco Products Directive & Ireland's Standardisation of Tobacco Act.

PubMed

Babineau, Kate; Clancy, Luke

2015-06-05

To measure young people's perceptions of tobacco packaging according to two current pieces of legislation: The EU Tobacco Products Directive (TPD) and Ireland's Public Health (Standardisation of Tobacco Products) Act. Within-subject experimental cross-sectional survey of a representative sample of secondary school students. School-based pen and paper survey. 27 secondary schools across Ireland, randomly stratified for size, geographic location, gender, religious affiliation and school-level socioeconomic status. Data were collected between March and May 2014. 1378 fifth year secondary school students aged 16-17 in Ireland. Young people's perceptions of attractiveness, health risk and smoker characteristics of packs according to EU and Irish branding and packaging guidelines. Packs with more branding elements were thought to be healthier than standardised packs for Silk Cut (χ(2)=158.58, p<0.001), Marlboro (χ(2)=113.65, p<0.001), and Benson and Hedges (χ(2)=137.95, p<0.001) brands. Generalized estimating equation binary regressions found that gender was a significant predictor of pack attractiveness for Silk Cut, with females being more likely to find the EU packs attractive (β=-0.45, p=0.007). Gender was a significant predictor for females with regards to the perceived popularity of the Silk Cut brand (β=-0.37, p=0.03). The removal of brand identifiers, including colour, font and embossing, reduces the perceived appeal of cigarette packs for young people across all three tested brands. Packs standardised according to Irish legislation are perceived as less attractive, less healthy and smoked by less popular people than packs which conform to the EU TPD 2014 guidelines. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

A Matter of Millimeters: Defining the Processes for Critical Clearances on Curiosity

NASA Technical Reports Server (NTRS)

Florow, Brandon

2013-01-01

The Mars Science Laboratory (MSL) mission presents an immense packaging problem in that it takes a rover the size of a car with a sky crane landing system and packs it tightly into a spacecraft. This creates many areas of close and critical clearances. Critical Clearances are defined as hardware-to-hardware or hardware-to-envelope clearances which fall below a pre-established location dependent threshold and pose a risk of hardware to hardware contact during events such as launch, entry, landing, and operations. Close Clearances, on the other hand, are defined as any clearance value that is chosen to be tracked but is larger than the critical clearance threshold for its region. Close clearances may be tracked for various reasons including uncertainty in design, large expected dynamic motion, etc.