Preparation and characterization of nanocrystalline CuO powders with the different surfactants and complexing agent mediated precipitation method

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

Rajendran, V.; Gajendiran, J., E-mail: gaja.nanotech@gmail.com

2014-08-15

Highlights: • CuO nanostructures by surfactants mediated method. • Structural and optical properties of CuO nanostructures changes under the effect of surface modifier. • Citric acid assisted is the best, in terms of size, morphology and optical properties than that of CTAB, SDS and PEG-400. - Abstract: Nanostructures of copper oxide (CuO) was synthesized into crystallite sized ranging from 20 to 50 nm in the presence of different surfactants, and complex agent such as cityl tri methyl ammonium bromide (CTAB), sodium do decyl sulfate (SDS), poly ethylene glycol (PEG-400) and citric acid via a precipitation route. Variations in several parametersmore » and their effects on the structural and optical properties of CuO nanostructures (crystallite size, morphology and band gap) were investigated by XRD, FTIR, SEM and UV analysis. The UV–visible absorption spectra of the different surfactants and complexing agent assisted CuO nanostructures indicates that the estimated optical band gap energy value (1.94–1.98 eV) is higher than that of the bulk CuO value (1.4 eV), which is attributed to the quantum confinement effect. The formation mechanism of different surfactants and complexing agent assisted CuO nanostructures is also proposed.« less

Crystallization features of normal alkanes in confined geometry.

PubMed

Su, Yunlan; Liu, Guoming; Xie, Baoquan; Fu, Dongsheng; Wang, Dujin

2014-01-21

How polymers crystallize can greatly affect their thermal and mechanical properties, which influence the practical applications of these materials. Polymeric materials, such as block copolymers, graft polymers, and polymer blends, have complex molecular structures. Due to the multiple hierarchical structures and different size domains in polymer systems, confined hard environments for polymer crystallization exist widely in these materials. The confined geometry is closely related to both the phase metastability and lifetime of polymer. This affects the phase miscibility, microphase separation, and crystallization behaviors and determines both the performance of polymer materials and how easily these materials can be processed. Furthermore, the size effect of metastable states needs to be clarified in polymers. However, scientists find it difficult to propose a quantitative formula to describe the transition dynamics of metastable states in these complex systems. Normal alkanes [CnH2n+2, n-alkanes], especially linear saturated hydrocarbons, can provide a well-defined model system for studying the complex crystallization behaviors of polymer materials, surfactants, and lipids. Therefore, a deeper investigation of normal alkane phase behavior in confinement will help scientists to understand the crystalline phase transition and ultimate properties of many polymeric materials, especially polyolefins. In this Account, we provide an in-depth look at the research concerning the confined crystallization behavior of n-alkanes and binary mixtures in microcapsules by our laboratory and others. Since 2006, our group has developed a technique for synthesizing nearly monodispersed n-alkane containing microcapsules with controllable size and surface porous morphology. We applied an in situ polymerization method, using melamine-formaldehyde resin as shell material and nonionic surfactants as emulsifiers. The solid shell of microcapsules can provide a stable three-dimensional (3-D) confining environment. We have studied multiple parameters of these microencapsulated n-alkanes, including surface freezing, metastability of the rotator phase, and the phase separation behaviors of n-alkane mixtures using differential scanning calorimetry (DSC), temperature-dependent X-ray diffraction (XRD), and variable-temperature solid-state nuclear magnetic resonance (NMR). Our investigations revealed new direct evidence for the existence of surface freezing in microencapsulated n-alkanes. By examining the differences among chain packing and nucleation kinetics between bulk alkane solid solutions and their microencapsulated counterparts, we also discovered a mechanism responsible for the formation of a new metastable bulk phase. In addition, we found that confinement suppresses lamellar ordering and longitudinal diffusion, which play an important role in stabilizing the binary n-alkane solid solution in microcapsules. Our work also provided new insights into the phase separation of other mixed system, such as waxes, lipids, and polymer blends in confined geometry. These works provide a profound understanding of the relationship between molecular structure and material properties in the context of crystallization and therefore advance our ability to improve applications incorporating polymeric and molecular materials.

Synthetic Biology in Aqueous Compartments at the Micro- and Nanoscale

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

Boreyko, Jonathan; Caveney, Patrick M.; Norred, Sarah L.

ABSTRACT Aqueous two-phase systems and related emulsion-based structures defined within micro- and nanoscale environments enable a bottom-up synthetic biological approach to mimicking the dynamic compartmentation of biomaterial that naturally occurs within cells. Model systems we have developed to aid in understanding these phenomena include on-demand generation and triggering of reversible phase transitions in ATPS confined in microscale droplets, morpho-logical changes in networks of femtoliter-volume aqueous droplet interface bilayers (DIBs) formulated in microfluidic channels, and temperature-driven phase transitions in interfacial lipid bilayer systems supported on micro and nanostructured substrates. For each of these cases, the dynamics were intimately linked to changesmore » in the chemical potential of water, which becomes increasingly susceptible to confinement and crowding. At these length scales, where interfacial and surface areas predominate over compartment volumes, both evaporation and osmotic forces become enhanced relative to ideal dilute solutions. Finally, consequences of confinement and crowding in cell-sized microcompartments for increasingly complex scenarios will be discussed, from single-molecule mobility measurements with fluorescence correlation spectroscopy to spatio-temporal modulation of resource sharing in cell-free gene expression bursting.« less

Synthetic Biology in Aqueous Compartments at the Micro- and Nanoscale

DOE PAGES

Boreyko, Jonathan; Caveney, Patrick M.; Norred, Sarah L.; ...

2017-07-10

ABSTRACT Aqueous two-phase systems and related emulsion-based structures defined within micro- and nanoscale environments enable a bottom-up synthetic biological approach to mimicking the dynamic compartmentation of biomaterial that naturally occurs within cells. Model systems we have developed to aid in understanding these phenomena include on-demand generation and triggering of reversible phase transitions in ATPS confined in microscale droplets, morpho-logical changes in networks of femtoliter-volume aqueous droplet interface bilayers (DIBs) formulated in microfluidic channels, and temperature-driven phase transitions in interfacial lipid bilayer systems supported on micro and nanostructured substrates. For each of these cases, the dynamics were intimately linked to changesmore » in the chemical potential of water, which becomes increasingly susceptible to confinement and crowding. At these length scales, where interfacial and surface areas predominate over compartment volumes, both evaporation and osmotic forces become enhanced relative to ideal dilute solutions. Finally, consequences of confinement and crowding in cell-sized microcompartments for increasingly complex scenarios will be discussed, from single-molecule mobility measurements with fluorescence correlation spectroscopy to spatio-temporal modulation of resource sharing in cell-free gene expression bursting.« less

Spatial confinement effects on spectroscopic and morphological studies of nanosecond laser-ablated Zirconium

NASA Astrophysics Data System (ADS)

Hayat, Asma; Bashir, Shazia; Rafique, Muhammad Shahid; Ahmad, Riaz; Akram, Mahreen; Mahmood, Khaliq; Zaheer, Ali

2017-12-01

Spatial confinement effects on plasma parameters and surface morphology of laser ablated Zr (Zirconium) are studied by introducing a metallic blocker. Nd:YAG laser at various fluencies ranging from 8 J cm-2 to 32 J cm-2 was employed as an irradiation source. All measurements were performed in the presence of Ar under different pressures. Confinement effects offered by metallic blocker are investigated by placing the blocker at different distances of 6 mm, 8 mm and 10 mm from the target surface. It is revealed from LIBS analysis that both plasma parameters i.e. excitation temperature and electron number density increase with increasing laser fluence due to enhancement in energy deposition. It is also observed that spatial confinement offered by metallic blocker is responsible for the enhancement of both electron temperature and electron number density of Zr plasma. This is true for all laser fluences and pressures of Ar. Maximum values of electron temperature and electron number density without blocker are 12,600 K and 14 × 1017 cm-3 respectively whereas, these values are enhanced to 15,000 K and 21 × 1017 cm-3 in the presence of blocker. The physical mechanisms responsible for the enhancement of Zr plasma parameters are plasma compression, confinement and pronounced collisional excitations due to reflection of shock waves. Scanning Electron Microscope (SEM) analysis was performed to explore the surface morphology of laser ablated Zr. It reveals the formation of cones, cavities and ripples. These features become more distinct and well defined in the presence of blocker due to plasma confinement. The optimum combination of blocker distance, fluence and Ar pressure can identify the suitable conditions for defining the role of plasma parameters for surface structuring.

Multiple patterns of diblock copolymer confined in irregular geometries with soft surface

NASA Astrophysics Data System (ADS)

Li, Ying; Sun, Min-Na; Zhang, Jin-Jun; Pan, Jun-Xing; Guo, Yu-Qi; Wang, Bao-Feng; Wu, Hai-Shun

2015-12-01

The different confinement shapes can induce the formation of various interesting and novel morphologies, which might inspire potential applications of materials. In this paper, we study the directed self-assembly of diblock copolymer confined in irregular geometries with a soft surface by using self-consistent field theory. Two types of confinement geometries are considered, namely, one is the concave pore with one groove and the other is the concave pore with two grooves. We obtain more novel and different structures which could not be produced in other two-dimensional (2D) confinements. Comparing these new structures with those obtained in regular square confinement, we find that the range of ordered lamellae is enlarged and the range of disordered structure is narrowed down under the concave pore confinement. We also compare the different structures obtained under the two types of confinement geometries, the results show that the effect of confinement would increase, which might induce the diblock copolymer to form novel structures. We construct the phase diagram as a function of the fraction of B block and the ratio of h/L of the groove. The simulation reveals that the wetting effect of brushes and the shape of confinement geometries play important roles in determining the morphologies of the system. Our results improve the applications in the directed self-assembly of diblock copolymer for fabricating the irregular structures. Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20121404110004), the Research Foundation for Excellent Talents of Shanxi Provincial Department of Human Resources and Social Security, China, and the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi Province, China.

Kinetic Transition of Crystal Morphology from Nanoparticles to Dendrites during Electron Beam Induced Deposition of Gold

NASA Astrophysics Data System (ADS)

Park, Jeung Hun; Schneider, Nicholas; Bau, Haim; Kodambaka, Suneel; Ross, Frances

2015-03-01

We studied the kinetic transition from compact nanoparticle to dendritic morphology during electron beam-induced Au deposition using in situ liquid cell-based transmission electron microcopy. Radiolysis of water by electrons generates radicals and molecular species. Hydrated electrons and hydrogen and hydroxide radicals can act as reducing agents and initiate the reduction of the water-soluble precursor, HAuCl4, resulting in the precipitation of Au as nanostructures. We tracked nucleation, growth, and morphological transition of Au from movies recorded in situ, as a function of irradiated dose and liquid thickness. We identified several distinct regimes that depend on the irradiation time: (1) nucleation; (2) linear volumetric growth; (3) formation of dendritic structures; (4) coalescence and dissolution. A diffusion and reaction model for the radiolytic species and metal ions in the confined geometry of the irradiated volume is used to understand the nucleation sites and morphological transitions. We finally describe how nanoparticles can be made to grow in a stepwise manner by switching the supply of Au ions on and off electrochemically, and discuss possibilities for creating more complex nanostructures. This research was partially funded by the National Science Foundation (DMR-1310639, CMMI-1129722, and CBET-1066573).

Space confinement and rotation stress induced self-organization of double-helix nanostructure: a nanotube twist with a moving catalyst head.

PubMed

Zhao, Meng-Qiang; Zhang, Qiang; Tian, Gui-Li; Huang, Jia-Qi; Wei, Fei

2012-05-22

Inorganic materials with double-helix structure have attracted intensive attention due to not only their elegant morphology but also their amazing morphology-related potential applications. The investigation on the formation mechanism of the inorganic double-helix nanostructure is the first step for the fundamental studies of their materials or physical properties. Herein, we demonstrated the space confinement and rotation stress induced self-organization mechanism of the carbon nanotube (CNT)-array double helices under scanning electron microscopy by directly observing their formation process from individual layered double hydroxide flakes, which is a kind of hydrotalcite-like material composed of positively charged layers and charge-balancing interlayer anions. Space confinement is considered to be the most important extrinsic factor for the formation of CNT-array double helices. Synchronous growth of the CNT arrays oppositely from LDH flakes with space confinement on both sides at the same time is essential for the growth of CNT-array double helices. Coiling of the as-grown CNT arrays into double helices will proceed by self-organization, tending to the most stable morphology in order to release their internal rotation stress. Based on the demonstrated mechanism, effective routes were carried out to improve the selectivity for CNT-array double helices. The work provides a promising method for the fabrication of double-helix nanostructures with their two helices connected at the end by self-assembly.

Confinement effects on thin polymer films

NASA Astrophysics Data System (ADS)

Dalnoki-Veress, Karoly J. T.

We present the results of four projects investigating the effects of confinement on polymeric systems. The first study dealt with polymer blends that are quenched using a spincoating technique rather than a temperature quench. The mass fraction of two blends was varied to determine the effect of the substrate-blend interface on the thin film phase separation morphology. Quantitative measurements of the morphology on three different substrates revealed significant differences in the phase separation morphology as a result of the different wetting properties of the polymer blend on the substrates. The second project dealt with the effect of mechanical confinement on the phase separation of polymer blend thin films. We measured the phase separation morphology of polystyrene/poly (methyl methacrylate) (PS/PMMA) blend films of thickness h on a silicon oxide (SiOx) substrate with a SiOx capping layer. A novel phase separation morphology was observed for small capping layer thicknesses L as well as a transition from lateral to lamellar morphology as L is increased. A simple model is presented which explains the observed lateral morphology, and the morphology transition, in terms of a balance between the free energy increase associated with forming the interfaces between PS-rich and PMMA-rich domains, and the free energy increase associated with the elastic bending of the SiOx capping layer. Direct control of the amplitude and period of the deformation is achieved by varying h and L. Reasonable agreement is obtained between the predicted amplitude of the rippling of the film surface and that measured directly using atomic force microscopy. For temperatures greater than the glass transition temperature Tg, thin freely-standing polymer films are unstable to the formation of holes. In the third project, we have studied the formation and growth of two types of holes: those which form spontaneously when the films are heated above Tg, and those purposely nucleated using a heated scanning tunneling microscope tip. For both types of holes, we observe exponential growth of the hole radius, corresponding to the viscous regime of hole formation, and a decrease in the film viscosity with decreasing film thickness h for h < 250 nm. In the last project the thermal stability of freely-standing films was enhanced by symmetrically confining the films between thin layers of silicon oxide to form SiOx/PS/SiOx trilayer films. Aggressive annealing of the films produced a novel morphology consisting of long, parallel domains with a well-defined periodicity. A simple model is presented which describes the scaling behavior of the morphology. We discuss the direct control of the morphology through manipulation of the individual film thicknesses and the long-range Van der Waals or dispersion interactions.

A finite element approach to self-consistent field theory calculations of multiblock polymers

NASA Astrophysics Data System (ADS)

Ackerman, David M.; Delaney, Kris; Fredrickson, Glenn H.; Ganapathysubramanian, Baskar

2017-02-01

Self-consistent field theory (SCFT) has proven to be a powerful tool for modeling equilibrium microstructures of soft materials, particularly for multiblock polymers. A very successful approach to numerically solving the SCFT set of equations is based on using a spectral approach. While widely successful, this approach has limitations especially in the context of current technologically relevant applications. These limitations include non-trivial approaches for modeling complex geometries, difficulties in extending to non-periodic domains, as well as non-trivial extensions for spatial adaptivity. As a viable alternative to spectral schemes, we develop a finite element formulation of the SCFT paradigm for calculating equilibrium polymer morphologies. We discuss the formulation and address implementation challenges that ensure accuracy and efficiency. We explore higher order chain contour steppers that are efficiently implemented with Richardson Extrapolation. This approach is highly scalable and suitable for systems with arbitrary shapes. We show spatial and temporal convergence and illustrate scaling on up to 2048 cores. Finally, we illustrate confinement effects for selected complex geometries. This has implications for materials design for nanoscale applications where dimensions are such that equilibrium morphologies dramatically differ from the bulk phases.

A finite element approach to self-consistent field theory calculations of multiblock polymers

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

Ackerman, David M.; Delaney, Kris; Fredrickson, Glenn H.

Self-consistent field theory (SCFT) has proven to be a powerful tool for modeling equilibrium microstructures of soft materials, particularly for multiblock polymers. A very successful approach to numerically solving the SCFT set of equations is based on using a spectral approach. While widely successful, this approach has limitations especially in the context of current technologically relevant applications. These limitations include non-trivial approaches for modeling complex geometries, difficulties in extending to non-periodic domains, as well as non-trivial extensions for spatial adaptivity. As a viable alternative to spectral schemes, we develop a finite element formulation of the SCFT paradigm for calculating equilibriummore » polymer morphologies. We discuss the formulation and address implementation challenges that ensure accuracy and efficiency. We explore higher order chain contour steppers that are efficiently implemented with Richardson Extrapolation. This approach is highly scalable and suitable for systems with arbitrary shapes. We show spatial and temporal convergence and illustrate scaling on up to 2048 cores. Finally, we illustrate confinement effects for selected complex geometries. This has implications for materials design for nanoscale applications where dimensions are such that equilibrium morphologies dramatically differ from the bulk phases.« less

Immunohistochemical distribution of Ki67 in epidermis of thick glabrous skin of human digits.

PubMed

Petrovic, Aleksandar; Petrovic, Vladimir; Milojkovic, Bobana; Nikolic, Ivan; Jovanovic, Dragan; Antovic, Aleksandra; Milic, Miroslav

2018-01-01

The glabrous skin on the flexor sides of hands and feet, compared to other integument regions, has thicker epidermis and more complex pattern of epidermal ridges, wherefore in microscopy is denominated as thick skin. The epidermis of this skin type has individually unique and permanent superficial patterns, called dermatoglyphics, which are maintained by regenerative potential of deep epidermal rete ridges, that interdigitate with adjacent dermis. Using light microscopy, we analyzed cadaveric big toes thick skin samples, described histology of deep epidermal ridges (intermediate, limiting, and transverse), and quantitatively evidenced their pattern of proliferation by immunohistochemical assessment of Ki67. Immunohistochemical distribution of Ki67 was confined to basal and suprabasal layers, with pattern of distribution specific for intermediate, limiting and transverse ridges that gradually transform within epidermal height. Deep epidermal ridges, interdigitating with dermal papillae, participate in construction of intricate epidermal base, whose possible role in epidermal regeneration was also discussed. Having a prominent morphology, this type of epidermis offers the best morphological insight in complexities of skin organization, and its understanding could challenge and improve currently accepted models of epidermal organization.

Controllable Fabrication of Au Nanocups by Confined-Space Thermal Dewetting for OCT Imaging.

PubMed

Gao, Aiqin; Xu, Wenjing; Ponce de León, Yenisey; Bai, Yaocai; Gong, Mingfu; Xie, Kongliang; Park, Boris Hyle; Yin, Yadong

2017-07-01

Here, this study reports a novel confined-space thermal dewetting strategy for the fabrication of Au nanocups with tunable diameter, height, and size of cup opening. The nanocup morphology is defined by the cup-shaped void space created by a yolk-shell silica template that spontaneously takes an eccentric configuration during annealing. Thermal dewetting of Au, which is sandwiched between the yolk and shell, leads to the desired nanocup morphology. With strong scattering in near infrared, the Au nanocups exhibit superior efficiency as contrast agents for spectral-domain optical coherence tomography imaging. This confined-space thermal dewetting strategy is scalable and general, and can be potentially extended to the synthesis of novel anisotropic nanostructures of various compositions that are difficult to produce by conventional wet chemical or physical methods, thus opening up opportunities for many new applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The role of confined collagen geometry in decreasing nucleation energy barriers to intrafibrillar mineralization.

PubMed

Kim, Doyoon; Lee, Byeongdu; Thomopoulos, Stavros; Jun, Young-Shin

2018-03-06

Mineralization of collagen is critical for the mechanical functions of bones and teeth. Calcium phosphate nucleation in collagenous structures follows distinctly different patterns in highly confined gap regions (nanoscale confinement) than in less confined extrafibrillar spaces (microscale confinement). Although the mechanism(s) driving these differences are still largely unknown, differences in the free energy for nucleation may explain these two mineralization behaviors. Here, we report on experimentally obtained nucleation energy barriers to intra- and extrafibrillar mineralization, using in situ X-ray scattering observations and classical nucleation theory. Polyaspartic acid, an extrafibrillar nucleation inhibitor, increases interfacial energies between nuclei and mineralization fluids. In contrast, the confined gap spaces inside collagen fibrils lower the energy barrier by reducing the reactive surface area of nuclei, decreasing the surface energy penalty. The confined gap geometry, therefore, guides the two-dimensional morphology and structure of bioapatite and changes the nucleation pathway by reducing the total energy barrier.

Antecedent topography and morphological controls on sediment accumulation and slope stability of the U.S. Atlantic margin

NASA Astrophysics Data System (ADS)

Hill, J. C.; Brothers, D. S.; Ten Brink, U. S.; Andrews, B. D.

2017-12-01

The U.S. Atlantic margin encompasses a wide variety of slope failure processes, ranging from small canyon-confined failures on the upper slope to large, open slope landslides originating in deeper water. Here we used a suite of high-resolution multibeam bathymetry and detailed multichannel seismic data coverage to investigate the relationship between modern seafloor morphology, pre-existing stratigraphy and sediment accumulation patterns. We suggest that a combination of sediment supply and antecedent margin physiography, whereby variations in margin evolution during the Miocene have influenced the modern seafloor morphology, controls both the location of slope sediment accumulation and the style of slope failure. Oversteepened margins with angular shelf breaks and steep upper slopes, referred to as oblique margins, are characterized by downslope mass transport and densely-spaced canyon formation. These margins are most likely the locus of canyon-confined failures and smaller lower slope fan-apron failures (e.g., much of the Mid-Atlantic). Sigmoidal margins with prograded slopes, a rounded shelf edge, and a low gradient slope morphology can support significant sediment accumulation across a broad area, with limited canyon development. These margins are often associated with high sediment supply and are prone to large, upper slope slab-style failures (e.g., the Hudson Apron, southwestern New England, the Currituck and Cape Fear Slide complexes). Areas with morphologies in between these two end members are characterized by limited shelf-edge accommodation space and large-scale lower slope accumulation and onlap, representing transitional stages of equilibrium slope adjustment. Large failures along these intermediate-type margins tend to develop lower on the slope where thick wedges of onlapping sediment are found (e.g., around Washington Canyon, Cape Lookout and southeastern New England). As antecedent topography and sediment loading appear to play an important role in determining the spatial distribution of submarine slope failures, other key processes that contribute to the development of overpressure (e.g., sediment compaction and fluid migration) should be examined with this in mind to improve our understanding of the geologic factors that precondition slopes for failure.

Bulk and monolayer ordering of block copolymer blends

NASA Astrophysics Data System (ADS)

Onikoyi, Adetunji J.

The control of the nanoscale structure or morphology of a block copolymer is a desired goal for nanolithography applications. In this work, we are particularly interested in providing guides for controlling domain size, domain shape and defect densities in block copolymers and their blends for thin film applications. To reach this goal, a sphere forming PS-b-P2VP (having a PS majority block) and its blends with PS homopolymer or cylinder forming PS-b-P2VP are studied in both the bulk and thin films. Structure characterization is performed using a variety of experimental techniques including small angle X-ray scattering, scanning force microscopy and transmission electron microscopy. In the bulk, the spherical domains of the pure, sphere forming PS-b-P2VP arrange on a BCC lattice. On adding PS homopolymer (hPS), the lattice parameter of the BCC spheres increases, while the order-to-disorder temperature (ODT) of the BCC lattice simultaneously decreases. At a given hPS composition, the use of larger sized hPS leads to larger increases in the lattice parameter and larger decreases in the ODT. In bulk blends of cylinder forming PS-b-P2VP with sphere forming PS-b-P2VP, the ordered morphology changes (e.g., cylindrical morphology → coexisting spherical and cylindrical morphologies → spherical morphology) as the sphere forming PS-b-P2VP volume fraction phis increases, while the ODT of the cylindrical morphology decreases. The phase boundaries of these morphologies in monolayers shift to lower phis compared to those of the bulk, apparently caused by a selective adsorption of the cylindrical PS-b-P2VP to form a brush on the substrate. This selective adsorption leads to a preference for spherical domains in diamond-shaped lateral confinements when cylindrical domains are stabilized outside the confinements on the same substrate. Finally, we explore the use of graphoepitaxy to order monolayers of sphere forming PS-b-P2VP and its blends with hPS. The probability of forming isolated dislocations, or of adding (or removing) a full row of spherical domains, in diamond-shaped lateral confinements is shown to be higher when the well size is incommensurate with the lattice parameter. Square-shaped lateral confinement leads to a preference for square sphere packing if the PS-b-P2VP is blended with appropriate amounts of hPS.

Substrate effect on nanoporous structure of silica wires by channel-confined self-assembly of block-copolymer and sol-gel precursors

DOE PAGES

Hu, Michael Z.; Lai, Peng

2015-09-22

Nanoporous silica wires of various wire diameters were developed by space-confined molecular self-assembly of triblock copolymer ethylene/propylene/ethylene (P123) and silica alkoxide precursor (tetraethylorthosilicate, TEOS). Two distinctive hard-templating substrates, anodized aluminum oxide (AAO) and track-etched polycarbonate (EPC), with channel diameters in the range between 10 nm and 200 nm were employed for space-confinement of soft molecular self-assembly driven by the block-copolymer microphase separation. It was observed in the scanning and transmission electron microscope (STEM) studies that the substrate geometry and material characteristics had pronounced effects on the structure and morphology of the silica nanowires. A substrate wall effect was proposed tomore » explain the ordering and orientation of the intra-wire mesostructure. Circular and spiral nanostructures were found only in wires formed in AAO substrate, not in EPC. Pore-size differences and distinctive wall morphologies of the nanowires relating to the substrates were discussed. It was shown that the material and channel wall characteristics of different substrates play key roles in the ordering and morphology of the intra-wire nanostructures.« less

An emerging pore-making strategy: confined swelling-induced pore generation in block copolymer materials.

PubMed

Wang, Yong; Li, Fengbin

2011-05-17

Block copolymers (BCPs) composed of two or more thermodynamically incompatible homopolymers self-assemble into periodic microdomains. Exposing self-assembled BCPs with solvents selective to one block causes a swelling of the domains composed of this block. Strong swelling in the confinement imposed by the matrix of the other glassy block leads to well-defined porous structures via morphology reconstruction. This confined swelling-induced pore-making process has emerged recently as a new strategy to produce porous materials due to synergic advantages that include extreme simplicity, high pore regularity, involvement of no chemical reactions, no weight loss, reversibility of the pore forming process, etc. The mechanism, kinetics, morphology, and governing parameters of the confined swelling-induced pore-making process in BCP thin films are discussed, and the main applications of nanoporous thin films in the fields of template synthesis, surface patterning, and guidance for the areal arrangements of nanomaterials and biomolecules are summarized. Recent, promising results of extending this mechanism to produce BCP nanofibers or nanotubes and bulk materials with well-defined porosity, which makes this strategy also attractive to researchers outside the nanocommunity, are also presented. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The role of confined collagen geometry in decreasing nucleation energy barriers to intrafibrillar mineralization

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

Kim, Doyoon; Lee, Byeongdu; Thomopoulos, Stavros

Mineralization of collagen is critical for the mechanical functions of bones and teeth. Calcium phosphate nucleation in collagenous structures follows distinctly different patterns in highly confined gap regions (nanoscale confinement) than in less confined extrafibrillar spaces (microscale confinement). Although the mechanism(s) driving these differences are still largely unknown, differences in the free energy for nucleation may explain these two mineralization behaviors. Here, we report on experimentally obtained nucleation energy barriers to intra- and extrafibrillar mineralization, using in situ X-ray scattering observations and classical nucleation theory. Polyaspartic acid, an extrafibrillar nucleation inhibitor, increases interfacial energies between nuclei and mineralization fluids. Inmore » contrast, the confined gap spaces inside collagen fibrils lower the energy barrier by reducing the reactive surface area of nuclei, decreasing the surface energy penalty. The confined gap geometry, therefore, guides the two-dimensional morphology and structure of bioapatite and changes the nucleation pathway by reducing the total energy barrier.« less

The role of confined collagen geometry in decreasing nucleation energy barriers to intrafibrillar mineralization

DOE PAGES

Kim, Doyoon; Lee, Byeongdu; Thomopoulos, Stavros; ...

2018-03-06

Mineralization of collagen is critical for the mechanical functions of bones and teeth. Calcium phosphate nucleation in collagenous structures follows distinctly different patterns in highly confined gap regions (nanoscale confinement) than in less confined extrafibrillar spaces (microscale confinement). Although the mechanism(s) driving these differences are still largely unknown, differences in the free energy for nucleation may explain these two mineralization behaviors. Here, we report on experimentally obtained nucleation energy barriers to intra- and extrafibrillar mineralization, using in situ X-ray scattering observations and classical nucleation theory. Polyaspartic acid, an extrafibrillar nucleation inhibitor, increases interfacial energies between nuclei and mineralization fluids. Inmore » contrast, the confined gap spaces inside collagen fibrils lower the energy barrier by reducing the reactive surface area of nuclei, decreasing the surface energy penalty. The confined gap geometry, therefore, guides the two-dimensional morphology and structure of bioapatite and changes the nucleation pathway by reducing the total energy barrier.« less

Control of morphology and formation of highly geometrically confined magnetic skyrmions

PubMed Central

Jin, Chiming; Li, Zi-An; Kovács, András; Caron, Jan; Zheng, Fengshan; Rybakov, Filipp N.; Kiselev, Nikolai S.; Du, Haifeng; Blügel, Stefan; Tian, Mingliang; Zhang, Yuheng; Farle, Michael; Dunin-Borkowski, Rafal E

2017-01-01

The ability to controllably manipulate magnetic skyrmions, small magnetic whirls with particle-like properties, in nanostructured elements is a prerequisite for incorporating them into spintronic devices. Here, we use state-of-the-art electron holographic imaging to directly visualize the morphology and nucleation of magnetic skyrmions in a wedge-shaped FeGe nanostripe that has a width in the range of 45–150 nm. We find that geometrically-confined skyrmions are able to adopt a wide range of sizes and ellipticities in a nanostripe that are absent in both thin films and bulk materials and can be created from a helical magnetic state with a distorted edge twist in a simple and efficient manner. We perform a theoretical analysis based on a three-dimensional general model of isotropic chiral magnets to confirm our experimental results. The flexibility and ease of formation of geometrically confined magnetic skyrmions may help to optimize the design of skyrmion-based memory devices. PMID:28580935

Self-Assembly of Supramolecular Composites under Cylindrical Confinement

NASA Astrophysics Data System (ADS)

Bai, Peter; Thorkelsson, Kari; Ercius, Peter; Xu, Ting

2014-03-01

Block copolymer (BCP) or BCP-based supramolecules are useful platforms to direct nanoparticle (NP) assemblies. However, the variety of NP assemblies is rather limited in comparison to those shown by DNA-guided approach. By subjecting supramolecular nanocomposites to 2-D cylindrical confinement afforded by anodic aluminum oxide membranes, a range of new NP assemblies such as stacked rings, and single and double helices can be readily obtained, as confirmed by TEM and TEM tomography. At low NP loadings (3 v%), the nanostructure conforms to the supramolecule morphology. However, at higher NP loadings (6-9 v%), the nanostructure deviates significantly from the morphology of supramolecular nanocomposites in bulk or in thin film, suggesting that frustrated NP packing, in addition to simple supramolecule templating, may play a significant role in the self-assembly process. The present studies demonstrate that 2-D confinement can be an effective means to tailor self-assembled NP structures and may open further opportunities to manipulate the macroscopic properties of NP assemblies.

Inorganic Nanoparticle Induced Morphological Transition for Confined Self-Assembly of Block Copolymers within Emulsion Droplets.

PubMed

Zhang, Yan; He, Yun; Yan, Nan; Zhu, Yutian; Hu, Yuexin

2017-09-07

Recently, it has been reported that the incorporation of functional inorganic nanoparticles (NPs) into the three-dimensional (3D) confined self-assembly of block copolymers (BCPs) creates the unique nanostructured hybrid composites, which can not only introduce new functions to BCPs but also induce some interesting morphological transitions of BCPs. In the current study, we systematically investigate the cooperative self-assembly of a series of size-controlled and surface chemistry-tunable gold nanoparticles (AuNPs) and polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymer within the emulsion droplets. The influences of the size, content, and surface chemistry of the AuNPs on the coassembled nanostructures as well as the spatial distribution of AuNPs in the hybrid particles are examined. It is found that the size and content of the AuNPs are related to the entropic interaction, while the surface chemistry of AuNPs is related to the enthalpic interaction, which can be utilized to tailor the self-assembled morphologies of block copolymer confined in the emulsion droplets. As the content of PS-coated AuNPs increases, the morphology of the resulting AuNPs/PS-b-P2VP hybrid particles changes from the pupa-like particles to the bud-like particles and then to the onion-like particles. However, a unique morphological transition from the pupa-like particles to the mushroom-like particles is observed as the content of P4VP-coated AuNPs increases. More interestingly, it is observed that the large AuNPs are expelled to the surface of the BCP particles to reduce the loss in the conformational entropy of the block segment, which can arrange into the strings of necklaces on the surfaces of the hybrid particles.

Semi-crystalline morphologies of linear and cyclic poly(ɛ-caprolactones) in the diffusion-limited film thickness regime

NASA Astrophysics Data System (ADS)

Kelly, Giovanni; Bergeson, Amelia; Haque, Farihah; Grayson, Scott; Albert, Julie

Thin and ultrathin films of semi-crystalline polymers have been studied for decades due to their far-reaching applications including opto-electronic materials and biological studies of drug delivery and cell adhesion. This body of work has focused on every aspect of crystallization, from the fundamental thermodynamics and kinetics of crystal growth to methods for affecting crystalline morphologies via blending with other polymers. Due to significant synthetic challenges, one area where progress has lagged behind is the study of non-linear architectures, especially ring polymers. However, pioneering work by polymer chemists around the world has closed that gap, and we are beginning to observe important differences between ring and linear polymers in bulk materials. As a complement to those advances, this work aims to compare the morphologies of linear and cyclic poly(ɛ-caprolactones) (PCL) observed in heavily-confined ultrathin films where crystal growth is diffusion-limited. Understanding how confinement effects alter morphology will provide invaluable insight into differences in crystal growth as a function of molecular architecture.

Combination of cylindrical confinement and spark discharge for signal improvement using laser induced breakdown spectroscopy.

PubMed

Hou, Zongyu; Wang, Zhe; Liu, Jianmin; Ni, Weidou; Li, Zheng

2014-06-02

Spark discharge has been proved to be an effective way to enhance the LIBS signal while moderate cylindrical confinement is able to increase the signal repeatability with limited signal enhancement effects. In the present work, these two methods were combined together not only to improve the pulse-to-pulse signal repeatability but also to simultaneously and significantly enhance the signal as well as SNR. Plasma images showed that the confinement stabilized the morphology of the plasma, especially for the discharge assisted process, which explained the improvement of the signal repeatability.

Fabrication of a form- and size-variable microcellular-polymer-stabilized metal nanocomposite using supercritical foaming and impregnation for catalytic hydrogenation

PubMed Central

2012-01-01

This article presents the fabrication of size-controllable and shape-flexible microcellular high-density polyethylene-stabilized palladium nanoparticles (Pd/m-HDPE) using supercritical foaming, followed by supercritical impregnation. These nanomaterials are investigated for use as heterogeneous hydrogenation catalysts of biphenyls in supercritical carbon dioxide with no significant surface and inner mass transfer resistance. The morphology of the Pd/m-HDPE is examined using scanning electron microscopy images of the pores inside Pd/m-HDPE catalysts and transmission electron microscopy images of the Pd particles confined in an HDPE structure. This nanocomposite simplifies industrial design and operation. These Pd/m-HDPE catalysts can be recycled easily and reused without complex recovery and cleaning procedures. PMID:22651135

Structure and morphology of magnetron sputter deposited ultrathin ZnO films on confined polymeric template

NASA Astrophysics Data System (ADS)

Singh, Ajaib; Schipmann, Susanne; Mathur, Aakash; Pal, Dipayan; Sengupta, Amartya; Klemradt, Uwe; Chattopadhyay, Sudeshna

2017-08-01

The structure and morphology of ultra-thin zinc oxide (ZnO) films with different film thicknesses on confined polymer template were studied through X-ray reflectivity (XRR) and grazing incidence small angle X-ray scattering (GISAXS). Using magnetron sputter deposition technique ZnO thin films with different film thicknesses (<10 nm) were grown on confined polystyrene with ∼2Rg film thickness, where Rg ∼ 20 nm (Rg is the unperturbed radius of gyration of polystyrene, defined by Rg = 0.272 √M0, and M0 is the molecular weight of polystyrene). The detailed internal structure, along the surface/interfaces and the growth direction of the system were explored in this study, which provides insight into the growth procedure of ZnO on confined polymer and reveals that a thin layer of ZnO, with very low surface and interface roughness, can be grown by DC magnetron sputtering technique, with approximately full coverage (with bulk like electron density) even in nm order of thickness, in 2-7 nm range on confined polymer template, without disturbing the structure of the underneath template. The resulting ZnO-polystyrene hybrid systems show strong ZnO near band edge (NBE) and deep-level (DLE) emissions in their room temperature photoluminescence spectra, where the contribution of DLE gets relatively stronger with decreasing ZnO film thickness, indicating a significant enhancement of surface defects because of the greater surface to volume ratio in thinner films.

Study of Polymer Crystallization by Physical Vapor Deposition

NASA Astrophysics Data System (ADS)

Jeong, Hyuncheol

When a polymer is confined under the submicron length scale, confinement size and interfaces can significantly impact the crystallization kinetics and resulting morphology. The ability to tune the morphology of confined polymer systems is of critical importance for the development of high-performance polymer microelectronics. The wisdom from the research on confined crystallization suggests that it would be beneficial to have a processing route in which the crystallization of polymers is driven by interface and temperature effects at a nanometer-scale confinement. In practice, for atomic and small-molecular systems, physical vapor deposition (PVD) has been recognized as the most successful processing route for the precise control of the film structure at surface utilizing confinement effects. While standard PVD technologies are not generally applicable to the deposition of the chemically fragile macromolecules, the development of matrix-assisted pulsed laser evaporation (MAPLE) now enables the non-destructive PVD of high-molecular weight polymers. In this thesis work, we investigated the use of MAPLE for the precise control of the crystallization of polymer films at a molecular level. We also sought to decipher the rules governing the crystallization of confined polymers, by using MAPLE as a tool to form confined polymer systems onto substrates with a controlled temperature. We first explored the early stages of film growth and crystallization of poly(ethylene oxide) (PEO) at the substrate surface formed by MAPLE. The unique mechanism of film formation in MAPLE, the deposition of submicron-sized polymer droplets, allowed for the manifestation of confinement and substrate effects in the crystallization of MAPLE-deposited PEO. Furthermore, we also focused on the property of the amorphous PEO film formed by MAPLE, showing the dependence of polymer crystallization kinetics on the thermal history of the amorphous phase. Lastly, we probed how MAPLE processing affected the semi-crystalline structure in MAPLE-deposited polyethylene (PE) films. Depositing PE at various temperatures remarkably allowed for the tunability of the melting temperature and crystallinity of the PE films, thus manipulating the semi-crystalline structure. By comparing the structure of PE formed by different processing routes, i.e., MAPLE and melt-crystallization, we discussed how processing routes affect the development of semi-crystalline phase in polymer films.

Geomorphic effects, flood power, and channel competence of a catastrophic flood in confined and unconfined reaches of the upper Lockyer valley, southeast Queensland, Australia

NASA Astrophysics Data System (ADS)

Thompson, Chris; Croke, Jacky

2013-09-01

Flooding is a persistent natural hazard, and even modest changes in future climate are believed to lead to large increases in flood magnitude. Previous studies of extreme floods have reported a range of geomorphic responses from negligible change to catastrophic channel change. This paper provides an assessment of the geomorphic effects of a rare, high magnitude event that occurred in the Lockyer valley, southeast Queensland in January 2011. The average return interval of the resulting flood was ~ 2000 years in the upper catchment and decreased to ~ 30 years downstream. A multitemporal LiDAR-derived DEM of Difference (DoD) is used to quantify morphological change in two study reaches with contrasting valley settings (confined and unconfined). Differences in geomorphic response between reaches are examined in the context of changes in flood power, channel competence and degree of valley confinement using a combination of one-dimensional (1-D) and two-dimensional (2-D) hydraulic modelling. Flood power peaked at 9800 W m- 2 along the confined reach and was 2-3 times lower along the unconfined reach. Results from the DoD confirm that the confined reach was net erosional, exporting ~ 287,000 m3 of sediment whilst the unconfined reach was net depositional gaining ~ 209,000 m3 of sediment, 70% of the amount exported from the upstream, confined reach. The major sources of eroded sediment in the confined reach were within channel benches and macrochannel banks resulting in a significant increase of channel width. In the unconfined reach, the benches and floodplains were the major loci for deposition, whilst the inner channel exhibited minor width increases. The presence of high stream power values, and resultant high erosion rates, within the confined reach is a function of the higher energy gradient of the steeper channel that is associated with knickpoint development. Dramatic differences in geomorphic responses were observed between the two adjacent reaches of contrasting valley configuration. The confined reach experienced large-scale erosion and reorganisation of the channel morphology that resulted in significantly different areal representations of the five geomorphic features classified in this study.

Physical confinement signals regulate the organization of stem cells in three dimensions

PubMed Central

Sean, David; Ignacio, Maxime; Godin, Michel; Slater, Gary W.; Pelling, Andrew E.

2016-01-01

During embryogenesis, the spherical inner cell mass (ICM) proliferates in the confined environment of a blastocyst. Embryonic stem cells (ESCs) are derived from the ICM, and mimicking embryogenesis in vitro, mouse ESCs (mESCs) are often cultured in hanging droplets. This promotes the formation of a spheroid as the cells sediment and aggregate owing to increased physical confinement and cell–cell interactions. In contrast, mESCs form two-dimensional monolayers on flat substrates and it remains unclear if the difference in organization is owing to a lack of physical confinement or increased cell–substrate versus cell–cell interactions. Employing microfabricated substrates, we demonstrate that a single geometric degree of physical confinement on a surface can also initiate spherogenesis. Experiment and computation reveal that a balance between cell–cell and cell–substrate interactions finely controls the morphology and organization of mESC aggregates. Physical confinement is thus an important regulatory cue in the three-dimensional organization and morphogenesis of developing cells. PMID:27798278

Three-dimensional block copolymer nanostructures by the solvent-annealing-induced wetting in anodic aluminum oxide templates.

PubMed

Chu, Chiang-Jui; Chung, Pei-Yun; Chi, Mu-Huan; Kao, Yi-Huei; Chen, Jiun-Tai

2014-09-01

Block copolymers have been extensively studied over the last few decades because they can self-assemble into well-ordered nanoscale structures. The morphologies of block copolymers in confined geometries, however, are still not fully understood. In this work, the fabrication and morphologies of three-dimensional polystyrene-block-polydimethylsiloxane (PS-b-PDMS) nanostructures confined in the nanopores of anodic aluminum oxide (AAO) templates are studied. It is discovered that the block copolymers can wet the nanopores using a novel solvent-annealing-induced nanowetting in templates (SAINT) method. The unique advantage of this method is that the problem of thermal degradation can be avoided. In addition, the morphologies of PS-b-PDMS nanostructures can be controlled by changing the wetting conditions. Different solvents are used as the annealing solvent, including toluene, hexane, and a co-solvent of toluene and hexane. When the block copolymer wets the nanopores in toluene vapors, a perpendicular morphology is observed. When the block copolymer wets the nanopores in co-solvent vapors (toluene/hexane = 3:2), unusual circular and helical morphologies are obtained. These three-dimensional nanostructures can serve as naontemplates for refilling with other functional materials, such as Au, Ag, ZnO, and TiO2 . © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Multiyear Downstream Response to Dam Removal on the White Salmon River, WA

NASA Astrophysics Data System (ADS)

Wilcox, A. C.; O'Connor, J. E.; Major, J. J.

2017-12-01

The 2011 removal of the 38 m tall Condit Dam on the White Salmon River, Washington was one of the largest dam removals to date, in terms of both dam height and sediment release. We examined the multiyear geomorphic response to this event, through 2015, including in a bedrock-confined canyon and in a less-confined, backwater-influenced pool reach near the river's mouth, to the large, rapid influx of fine reservoir sediment produced by the breach and to subsequent sediment transfer in the free-flowing White Salmon River. In the canyon reach, aggraded sediments were rapidly eroded from riffles, returning them toward pre-breach bed elevations within weeks, but pool aggradation persisted for longer. The downstream, less-confined reach transformed from a deep pool to a narrower pool-riffle channel with alternate bars; multiyear observations showed persistence of bars and of this new and distinct morphology. This downstream reach marks a rare case in post-dam removal channel response; in most dam removals, channels have rapidly reverted toward pre-removal morphology, as in the canyon reach here. Comparison of the multiyear geomorphic evolution of the White Salmon River to other recent large dam removals in the U.S. allows evaluation of the relative influences of antecedent channel morphology, post-breach hydrology, and dam removal style, as well as providing a basis for predicting responses to future dam removals.

Molecular Insights into the Complex Relationship between Capacitance and Pore Morphology in Nanoporous Carbon-based Supercapacitors.

PubMed

Pak, Alexander J; Hwang, Gyeong S

2016-12-21

Electrochemical double layer capacitors, or supercapacitors, are high-power energy storage devices that consist of large surface area electrodes (filled with electrolyte) to accommodate ion packing in accordance with classical electric double layer (EDL) theory. Nanoporous carbons (NPCs) have recently emerged as a class of electrode materials with the potential to dramatically improve the capacitance of these devices by leveraging ion confinement. However, the molecular mechanisms underlying such enhancements are a clear departure from EDL theory and remain an open question. In this paper, we present the concept of ion reorganization kinetics during charge/discharge cycles, especially within highly confining subnanometer pores, which necessarily dictates the capacitance. Our molecular dynamics voltammetric simulations of ionic liquid immersed in NPC electrodes (of varying pore size distributions) demonstrate that the most efficient ion migration, and thereby largest capacitance, is facilitated by nonuniformity of shape (e.g., from cylindrical to slitlike) along nanopore channels. On the basis of this understanding, we propose that a new structural descriptor, coined as the pore shape factor, can provide a new avenue for materials optimization. These findings also present a framework to understand and evaluate ion migration kinetics within charged nanoporous materials.

Organic bioelectronics probing conformational changes in surface confined proteins

NASA Astrophysics Data System (ADS)

Macchia, Eleonora; Alberga, Domenico; Manoli, Kyriaki; Mangiatordi, Giuseppe F.; Magliulo, Maria; Palazzo, Gerardo; Giordano, Francesco; Lattanzi, Gianluca; Torsi, Luisa

2016-06-01

The study of proteins confined on a surface has attracted a great deal of attention due to its relevance in the development of bio-systems for laboratory and clinical settings. In this respect, organic bio-electronic platforms can be used as tools to achieve a deeper understanding of the processes involving protein interfaces. In this work, biotin-binding proteins have been integrated in two different organic thin-film transistor (TFT) configurations to separately address the changes occurring in the protein-ligand complex morphology and dipole moment. This has been achieved by decoupling the output current change upon binding, taken as the transducing signal, into its component figures of merit. In particular, the threshold voltage is related to the protein dipole moment, while the field-effect mobility is associated with conformational changes occurring in the proteins of the layer when ligand binding occurs. Molecular Dynamics simulations on the whole avidin tetramer in presence and absence of ligands were carried out, to evaluate how the tight interactions with the ligand affect the protein dipole moment and the conformation of the loops surrounding the binding pocket. These simulations allow assembling a rather complete picture of the studied interaction processes and support the interpretation of the experimental results.

Organic bioelectronics probing conformational changes in surface confined proteins

PubMed Central

Macchia, Eleonora; Alberga, Domenico; Manoli, Kyriaki; Mangiatordi, Giuseppe F.; Magliulo, Maria; Palazzo, Gerardo; Giordano, Francesco; Lattanzi, Gianluca; Torsi, Luisa

2016-01-01

The study of proteins confined on a surface has attracted a great deal of attention due to its relevance in the development of bio-systems for laboratory and clinical settings. In this respect, organic bio-electronic platforms can be used as tools to achieve a deeper understanding of the processes involving protein interfaces. In this work, biotin-binding proteins have been integrated in two different organic thin-film transistor (TFT) configurations to separately address the changes occurring in the protein-ligand complex morphology and dipole moment. This has been achieved by decoupling the output current change upon binding, taken as the transducing signal, into its component figures of merit. In particular, the threshold voltage is related to the protein dipole moment, while the field-effect mobility is associated with conformational changes occurring in the proteins of the layer when ligand binding occurs. Molecular Dynamics simulations on the whole avidin tetramer in presence and absence of ligands were carried out, to evaluate how the tight interactions with the ligand affect the protein dipole moment and the conformation of the loops surrounding the binding pocket. These simulations allow assembling a rather complete picture of the studied interaction processes and support the interpretation of the experimental results. PMID:27312768

Differences in aquatic habitat quality as an impact of one- and two-dimensional hydrodynamic model simulated flow variables

NASA Astrophysics Data System (ADS)

Benjankar, R. M.; Sohrabi, M.; Tonina, D.; McKean, J. A.

2013-12-01

Aquatic habitat models utilize flow variables which may be predicted with one-dimensional (1D) or two-dimensional (2D) hydrodynamic models to simulate aquatic habitat quality. Studies focusing on the effects of hydrodynamic model dimensionality on predicted aquatic habitat quality are limited. Here we present the analysis of the impact of flow variables predicted with 1D and 2D hydrodynamic models on simulated spatial distribution of habitat quality and Weighted Usable Area (WUA) for fall-spawning Chinook salmon. Our study focuses on three river systems located in central Idaho (USA), which are a straight and pool-riffle reach (South Fork Boise River), small pool-riffle sinuous streams in a large meadow (Bear Valley Creek) and a steep-confined plane-bed stream with occasional deep forced pools (Deadwood River). We consider low and high flows in simple and complex morphologic reaches. Results show that 1D and 2D modeling approaches have effects on both the spatial distribution of the habitat and WUA for both discharge scenarios, but we did not find noticeable differences between complex and simple reaches. In general, the differences in WUA were small, but depended on stream type. Nevertheless, spatially distributed habitat quality difference is considerable in all streams. The steep-confined plane bed stream had larger differences between aquatic habitat quality defined with 1D and 2D flow models compared to results for streams with well defined macro-topographies, such as pool-riffle bed forms. KEY WORDS: one- and two-dimensional hydrodynamic models, habitat modeling, weighted usable area (WUA), hydraulic habitat suitability, high and low discharges, simple and complex reaches

Europium (III) Organic Complexes in Porous Boron Nitride Microfibers: Efficient Hybrid Luminescent Material

NASA Astrophysics Data System (ADS)

Lin, Jing; Feng, Congcong; He, Xin; Wang, Weijia; Fang, Yi; Liu, Zhenya; Li, Jie; Tang, Chengchun; Huang, Yang

2016-09-01

We report the design and synthesis of a novel kind of organic-inorganic hybrid material via the incorporation of europium (III) β-diketonate complexes (Eu(TTA)3, TTA = 2-thenoyltrifluoroacetone) into one-dimensional (1D) porous boron nitride (BN) microfibers. The developed Eu(TTA)3@BN hybrid composites with typical 1D fibrous morphology exhibit bright visible red-light emission on UV illumination. The confinement of Eu(TTA)3 within pores of BN microfibers not only decreases the aggregation-caused quenching in solid Eu(TTA)3, but also improves their thermal stabilities. Moreover, The strong interactions between Eu(TTA)3 and porous BN matrix result in an interesting energy transfer process from BN host to TTA ligand and TTA ligand to Eu3+ ions, leading to the remarkable increase of red emission. The synthetic approach should be a very promising strategy which can be easily expanded to other hybrid luminescent materials based on porous BN.

Europium (III) Organic Complexes in Porous Boron Nitride Microfibers: Efficient Hybrid Luminescent Material

PubMed Central

Lin, Jing; Feng, Congcong; He, Xin; Wang, Weijia; Fang, Yi; Liu, Zhenya; Li, Jie; Tang, Chengchun; Huang, Yang

2016-01-01

We report the design and synthesis of a novel kind of organic-inorganic hybrid material via the incorporation of europium (III) β-diketonate complexes (Eu(TTA)3, TTA = 2-thenoyltrifluoroacetone) into one-dimensional (1D) porous boron nitride (BN) microfibers. The developed Eu(TTA)3@BN hybrid composites with typical 1D fibrous morphology exhibit bright visible red-light emission on UV illumination. The confinement of Eu(TTA)3 within pores of BN microfibers not only decreases the aggregation-caused quenching in solid Eu(TTA)3, but also improves their thermal stabilities. Moreover, The strong interactions between Eu(TTA)3 and porous BN matrix result in an interesting energy transfer process from BN host to TTA ligand and TTA ligand to Eu3+ ions, leading to the remarkable increase of red emission. The synthetic approach should be a very promising strategy which can be easily expanded to other hybrid luminescent materials based on porous BN. PMID:27687246

Genetic diversity within the morphological species Giardia intestinalis and its relationship to host origin.

PubMed

Monis, Paul T; Andrews, Ross H; Mayrhofer, Graham; Ey, Peter L

2003-05-01

A genetic analysis of Giardia intestinalis, a parasitic protozoan species that is ubiquitous in mammals worldwide, was undertaken using organisms derived from a variety of mammalian hosts in different geographical locations. The test panel of 53 Giardia isolates comprised 48 samples of G. intestinalis, including representatives of all known genetic subgroups, plus an isolate of G. ardeae and four isolates of G. muris. The isolates were compared by allozymic analysis of electrophoretic data obtained for 21 cytosolic enzymes, representing 23 gene loci. Neighbour Joining analysis of the allelic profiles supported the monophyly of G. intestinalis but showed that the species encompasses a rich population substructure. Seven major clusters were evident within G. intestinalis, corresponding to lineages designated previously as genetic assemblages A-G. Some genotypes, e.g. those defining assemblage A, are found in divergent host species and may be zoonotic. However other genotypes, e.g. those defining assemblages C-G, appear to be confined to particular hosts or host groups. The findings reinforce other evidence that G. intestinalis, which was defined on the basis of morphological criteria only, is a species complex.

Digital holographic microscopy as a technique to monitor macrophages infected by leishmania

NASA Astrophysics Data System (ADS)

Mendoza-Rodríguez, E.; Organista-Castelblanco, C.; Camacho, M.; Monroy-Ramírez, F.

2017-06-01

The Digital Holographic Microscopy in Transmission technique (DHM) is considered a useful tool in the noninvasive quantifying of transparent biological objects like living cells. In this work, we propose this technique to study and to monitor control macrophages infected by Leishmania (mouse lineJ774.A1). When the promastigotes enter in contact with healthy macrophages, they got phagocytosed and latterly confined in the formed parasitophorous vacuole. These processes change the morphology and density of the host macrophage. Both parameters can be measured in a label-free analysis of cells with the aid of the DHM technique. Our technique begins with the optical record of the holograms using a modified Mach-Zehnder interferometer and the reconstruction of the complex optical field transmitted by macrophages. In the latter point, we employ the angular spectrum algorithm. With the complex optical field reconstruction, we compute the field amplitude and the phase difference maps, which leads to describe one morphological characterization for the samples. Using phase difference maps is possible to measure internal variations for the integral refractive index, estimating the infection level of macrophages. Through the changes in the integral refractive index, it is also possible to describe and quantify in two different states the evolution of the infection. With these results some parameters of cells have been quantified, making the DHM technique a viable tool for diagnosis of biological samples under the presence of some pathogen.

Signal quality improvement using cylindrical confinement for laser induced breakdown spectroscopy.

PubMed

Hou, Zongyu; Wang, Zhe; Liu, Jianmin; Ni, Weidou; Li, Zheng

2013-07-01

In our previous work, we found that there was great potential to improve the pulse-to-pulse signal repeatability using a moderate cylindrical cavity confinement. However, the improvement was achieved only with certain experimental parameters; while under other conditions, there was no improvement or even worse repeatability. In the present work, the experimental configuration was redesigned and unexpected uncertainty from the variation of the laser and cavity alignment and the laser ablated aerosols were avoided. With these two improvements, we demonstrated that the cavity can always increase the signal repeatability. In addition, image taken by ICCD verified that the confinement improved the stability of the plasma morphology as expected.

Controlled synthesis of quantum confined CsPbBr3 perovskite nanocrystals under ambient conditions

NASA Astrophysics Data System (ADS)

He, Huimei; Tang, Bing; Ma, Ying

2018-02-01

Room temperature recrystallization is a simple and convenient method for synthesis of all-inorganic perovskite nanomaterials with excellent luminescent properties. However, the fast crystallization usually brings the colloidal stability and uncontrollable synthesis issues in the formation of all-inorganic perovskite. In the present study, we present a new strategy to prepare the quantum confined CsPbBr3 nanocrystals with controlled morphology under ambient condition. With the assist of fatty acid-capped precursor, the crystallization and the following growth rate can be retarded. Thanks to the retarded reaction, the morphology can be varied from nanowires to nanoplates and the thickness can be controlled from 5-7 monolayers by simply adjusting the amount of octylammonium cations and oleic acid. The nanoplates exhibit a higher photoluminescence quantum yield than the nanowires possibly due to fewer defects in the nanoplates.

Ground state atoms confined in a real Rydberg and complex Rydberg-Scarf II potential

NASA Astrophysics Data System (ADS)

Mansoori Kermani, Maryam

2017-12-01

In this work, a system of two ground state atoms confined in a one-dimensional real Rydberg potential was modeled. The atom-atom interaction was considered as a nonlocal separable potential (NLSP) of rank one. This potential was assumed because it leads to an analytical solution of the Lippmann-Schwinger equation. The NLSPs are useful in the few body problems that the many-body potential at each point is replaced by a projective two-body nonlocal potential operator. Analytical expressions for the confined particle resolvent were calculated as a key function in this study. The contributions of the bound and virtual states in the complex energy plane were obtained via the derived transition matrix. Since the low energy quantum scattering problems scattering length is an important quantity, the behavior of this parameter was described versus the reduced energy considering various values of potential parameters. In a one-dimensional model, the total cross section in units of the area is not a meaningful property; however, the reflectance coefficient has a similar role. Therefore the reflectance probability and its behavior were investigated. Then a new confined potential via combining the complex absorbing Scarf II potential with the real Rydberg potential, called the Rydberg-Scarf II potential, was introduced to construct a non-Hermitian Hamiltonian. In order to investigate the effect of the complex potential, the scattering length and reflectance coefficient were calculated. It was concluded that in addition to the competition between the repulsive and attractive parts of both potentials, the imaginary part of the complex potential has an important effect on the properties of the system. The complex potential also reduces the reflectance probability via increasing the absorption probability. For all numerical computations, the parameters of a system including argon gas confined in graphite were considered.

Crystal morphology variation in inkjet-printed organic materials

NASA Astrophysics Data System (ADS)

Ihnen, Andrew C.; Petrock, Anne M.; Chou, Tsengming; Samuels, Phillip J.; Fuchs, Brian E.; Lee, Woo Y.

2011-11-01

The recent commercialization of piezoelectric-based drop-on-demand inkjet printers provides an additive processing platform for producing and micropatterning organic crystal structures. We report an inkjet printing approach where macro- and nano-scale energetic composites composed of cyclotrimethylenetrinitramine (RDX) crystals dispersed in a cellulose acetate butyrate (CAB) matrix are produced by direct phase transformation from organic solvent-based all-liquid inks. The characterization of printed composites illustrates distinct morphological changes dependent on ink deposition parameters. When 10 pL ink droplets rapidly formed a liquid pool, a coffee ring structure containing dendritic RDX crystals was produced. By increasing the substrate temperature, and consequently the evaporation rate of the pooled ink, the coffee ring structure was mitigated and shorter dendrites from up to ∼1 to 0.2 mm with closer arm spacing from ∼15 to 1 μm were produced. When the nucleation and growth of RDX and CAB were confined within the evaporating droplets, a granular structure containing nanoscale RDX crystals was produced. The results suggest that evaporation rate and microfluidic droplet confinement can effectively be used to tailor the morphology of inkjet-printed energetic composites.

Improvement in dehydrogenation of MXH4 where M = Na, Li and X = Al, B confined in CNTs: a DFT investigation

NASA Astrophysics Data System (ADS)

Meenakshi; Agnihotri, Deepak; Jeet, Kiran; Sharma, Hitesh

2016-11-01

Nanoconfinement improves dehydrogenation kinetics of complex metal hydrides. The present paper reports effect of confinement of MXH4, where M = Na, Li and X = Al, B inside carbon nanotubes (CNTs) (n, 0) n = 9-11 chirality and diameter of 7.47 Å, 7.87 Å, 8.73 Å, respectively, using Density Functional calculations. The MXH4 interacts strongly with the surface atoms of CNT (11, 0) and is found to be the smallest stable system for confinement of MXH4 clusters. The Hydrogen release energy (E Hre) of NaAlH4 decreases sharply by 68.3 % , w.r.t. pure NaAlH4 cluster when confined inside CNT(11, 0). Similarly, in CNT (11, 0) E Hre decreases by 38.1 % for LiAlH4, 12.7 % for NaBH4 and 19.1 % for LiBH4. Thus, resulting confinement had a profound effect in improving the energetics of complex metal hydride nanoparticles without catalyst.

Effect of aging and ice structuring proteins on the morphology of frozen hydrated gluten networks.

PubMed

Kontogiorgos, Vassilis; Goff, H Douglas; Kasapis, Stefan

2007-04-01

The present investigation constitutes an attempt to rationalize the effect of aging and ice structuring proteins (ISPs) on the network morphology of frozen hydrated gluten. In doing so, it employs differential scanning calorimetry, time-domain NMR, dynamic oscillation on shear, creep testing, and electron microscopy. Experimentation and first principles modeling allows identification and description of the processes of ice formation and recrystallization in molecular terms. It is demonstrated that in the absence of a readily discernible glass transition temperature in gluten-ice composites, the approach of considering the melting point and aging at constant or fluctuating temperature conditions in the vicinity of this point can provide a valid index of functional quality. A theoretical framework supporting the concept of capillary confined frozen water in the gluten matrix was advanced, and it was found that ISPs were effective in controlling recrystallization both within these confines and within ice in the bulk.

First Observation of Cross-Beam Energy Transfer Mitigation for Direct-Drive Inertial Confinement Fusion Implosions Using Wavelength Detuning at the National Ignition Facility.

PubMed

Marozas, J A; Hohenberger, M; Rosenberg, M J; Turnbull, D; Collins, T J B; Radha, P B; McKenty, P W; Zuegel, J D; Marshall, F J; Regan, S P; Sangster, T C; Seka, W; Campbell, E M; Goncharov, V N; Bowers, M W; Di Nicola, J-M G; Erbert, G; MacGowan, B J; Pelz, L J; Yang, S T

2018-02-23

Cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces ablation pressure and implosion velocity in direct-drive inertial confinement fusion. Mitigating CBET is demonstrated for the first time in inertial-confinement implosions at the National Ignition Facility by detuning the laser-source wavelengths (±2.3  Å UV) of the interacting beams. We show that, in polar direct-drive, wavelength detuning increases the equatorial region velocity experimentally by 16% and alters the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation-hydrodynamic simulations that indicate a 10% increase in the average ablation pressure.

First Observation of Cross-Beam Energy Transfer Mitigation for Direct-Drive Inertial Confinement Fusion Implosions Using Wavelength Detuning at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Marozas, J. A.; Hohenberger, M.; Rosenberg, M. J.; Turnbull, D.; Collins, T. J. B.; Radha, P. B.; McKenty, P. W.; Zuegel, J. D.; Marshall, F. J.; Regan, S. P.; Sangster, T. C.; Seka, W.; Campbell, E. M.; Goncharov, V. N.; Bowers, M. W.; Di Nicola, J.-M. G.; Erbert, G.; MacGowan, B. J.; Pelz, L. J.; Yang, S. T.

2018-02-01

Cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces ablation pressure and implosion velocity in direct-drive inertial confinement fusion. Mitigating CBET is demonstrated for the first time in inertial-confinement implosions at the National Ignition Facility by detuning the laser-source wavelengths (±2.3 Å UV) of the interacting beams. We show that, in polar direct-drive, wavelength detuning increases the equatorial region velocity experimentally by 16% and alters the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation-hydrodynamic simulations that indicate a 10% increase in the average ablation pressure.

Turbulence measurements in a complex plowfield using a crossed hot-wire. M.S. Thesis

NASA Technical Reports Server (NTRS)

Mckillop, B. E.

1983-01-01

Turbulence was quantified in complex axisymmetric, nonreacting, nonswirling flowfields using a crossed hot-wire anemometer. Mean velocity, turbulence intensities, turbulent viscosity, and Reynolds tree were measured in round free jet and confined jet flowfields. The confined jet, a model of an axisymmetric can combustor, had an expansion ratio D/d=2, an expansion angle of 90 deg, and an axial location increments of 0.5 diameters. The confined jet was studied with and without a contraction nozzle. Free jet measurements validated the experimental technique and data reduction. Results show good agreement with those of previous research. Measurements in the confined jet indicate that the cross hot-wire used cannot handle axial flow reversal and the experimental technique is inadequate for measuring time-mean radial velocity. Other quantities show a high level of comparability.

Life cycle of Hammondia hammondi (Apicomplexa: Sarcocystidae) in cats

USDA-ARS?s Scientific Manuscript database

Hammondia hammondi and Toxoplasma gondii are feline coccidian that are morphologically, antigenically, and phylogenitically related. Both parasites multiply asexually and sexually in feline intestinal enterocytes but H. hammondi remains confined to enterocytes whereas T. gondii also parasitizes extr...

Mesoscale simulations of confined Nafion thin films.

PubMed

Vanya, P; Sharman, J; Elliott, J A

2017-12-07

The morphology and transport properties of thin films of the ionomer Nafion, with thicknesses on the order of the bulk cluster size, have been investigated as a model system to explain the anomalous behaviour of catalyst/electrode-polymer interfaces in membrane electrode assemblies. We have employed dissipative particle dynamics (DPD) to investigate the interaction of water and fluorocarbon chains, with carbon and quartz as confining materials, for a wide range of operational water contents and film thicknesses. We found confinement-induced clustering of water perpendicular to the thin film. Hydrophobic carbon forms a water depletion zone near the film interface, whereas hydrophilic quartz results in a zone with excess water. There are, on average, oscillating water-rich and fluorocarbon-rich regions, in agreement with experimental results from neutron reflectometry. Water diffusivity shows increasing directional anisotropy of up to 30% with decreasing film thickness, depending on the hydrophilicity of the confining material. A percolation analysis revealed significant differences in water clustering and connectivity with the confining material. These findings indicate the fundamentally different nature of ionomer thin films, compared to membranes, and suggest explanations for increased ionic resistances observed in the catalyst layer.

The development of a laterally confined laboratory fan delta under sediment supply reduction

NASA Astrophysics Data System (ADS)

Zhang, Xiaofeng; Wang, Siqiang; Wu, Xi; Xu, Shun; Li, Zhangyong

2016-03-01

In previous fan delta experiments, the effect of lateral confinement was generally ignored as these fans were usually unconfined with semiconical geometries. However, in gorge areas, fan development is usually laterally confined by valley walls. This study investigates autogenic processes of fan deltas in a laterally confined experimental tank. The experiment is divided into three phases. The sediment supply is held constant within each phase, so the autogenic processes of the fan are separated from the allogenic forcings. Results indicate that laterally confined fan deltas have higher progradation and aggradation potential, more regular channel braiding, and more even transverse sedimentation than unconfined fans. Besides, responses of fan deltas to sediment supply reduction are investigated in this research. At the initiation of the second and third phases, sediment feed rates are instantaneously reduced so that the allogenic forcings are predominant. Observations show that under sediment supply reduction, channelization on fan deltas are more pronounced and durations of the fluvial cycles are longer. The adjustment of fan morphology becomes slower as the self-regulation capacity of the fan decreases with reduced sediment supply.

Mesoscale simulations of confined Nafion thin films

NASA Astrophysics Data System (ADS)

Vanya, P.; Sharman, J.; Elliott, J. A.

2017-12-01

The morphology and transport properties of thin films of the ionomer Nafion, with thicknesses on the order of the bulk cluster size, have been investigated as a model system to explain the anomalous behaviour of catalyst/electrode-polymer interfaces in membrane electrode assemblies. We have employed dissipative particle dynamics (DPD) to investigate the interaction of water and fluorocarbon chains, with carbon and quartz as confining materials, for a wide range of operational water contents and film thicknesses. We found confinement-induced clustering of water perpendicular to the thin film. Hydrophobic carbon forms a water depletion zone near the film interface, whereas hydrophilic quartz results in a zone with excess water. There are, on average, oscillating water-rich and fluorocarbon-rich regions, in agreement with experimental results from neutron reflectometry. Water diffusivity shows increasing directional anisotropy of up to 30% with decreasing film thickness, depending on the hydrophilicity of the confining material. A percolation analysis revealed significant differences in water clustering and connectivity with the confining material. These findings indicate the fundamentally different nature of ionomer thin films, compared to membranes, and suggest explanations for increased ionic resistances observed in the catalyst layer.

Collective Behavior of Quorum-Sensing Run-and-Tumble Particles under Confinement.

PubMed

Rein, Markus; Heinß, Nike; Schmid, Friederike; Speck, Thomas

2016-02-05

We study a generic model for quorum-sensing bacteria in circular confinement. Every bacterium produces signaling molecules, the local concentration of which triggers a response when a certain threshold is reached. If this response lowers the motility, then an aggregation of bacteria occurs which differs fundamentally from standard motility-induced phase separation due to the long-ranged nature of the concentration of signal molecules. We analyze this phenomenon analytically and by numerical simulations employing two different protocols leading to stationary cluster and ring morphologies, respectively.

Reappraisal of Hydatigera taeniaeformis (Batsch, 1786) (Cestoda: Taeniidae) sensu lato with description of Hydatigera kamiyai n. sp.

PubMed

Lavikainen, Antti; Iwaki, Takashi; Haukisalmi, Voitto; Konyaev, Sergey V; Casiraghi, Maurizio; Dokuchaev, Nikolai E; Galimberti, Andrea; Halajian, Ali; Henttonen, Heikki; Ichikawa-Seki, Madoka; Itagaki, Tadashi; Krivopalov, Anton V; Meri, Seppo; Morand, Serge; Näreaho, Anu; Olsson, Gert E; Ribas, Alexis; Terefe, Yitagele; Nakao, Minoru

2016-05-01

The common cat tapeworm Hydatigera taeniaeformis is a complex of three morphologically cryptic entities, which can be differentiated genetically. To clarify the biogeography and the host spectrum of the cryptic lineages, 150 specimens of H. taeniaeformis in various definitive and intermediate hosts from Eurasia, Africa and Australia were identified with DNA barcoding using partial mitochondrial cytochrome c oxidase subunit 1 gene sequences and compared with previously published data. Additional phylogenetic analyses of selected isolates were performed using nuclear DNA and mitochondrial genome sequences. Based on molecular data and morphological analysis, Hydatigera kamiyai n. sp. Iwaki is proposed for a cryptic lineage, which is predominantly northern Eurasian and uses mainly arvicoline rodents (voles) and mice of the genus Apodemus as intermediate hosts. Hydatigera taeniaeformis sensu stricto (s.s.) is restricted to murine rodents (rats and mice) as intermediate hosts. It probably originates from Asia but has spread worldwide. Despite remarkable genetic divergence between H. taeniaeformis s.s. and H. kamiyai, interspecific morphological differences are evident only in dimensions of rostellar hooks. The third cryptic lineage is closely related to H. kamiyai, but its taxonomic status remains unresolved due to limited morphological, molecular, biogeographical and ecological data. This Hydatigera sp. is confined to the Mediterranean and its intermediate hosts are unknown. Further studies are needed to classify Hydatigera sp. either as a distinct species or a variant of H. kamiyai. According to previously published limited data, all three entities occur in the Americas, probably due to human-mediated introductions. Copyright © 2016 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

Evaluating channel morphologic changes and bed-material transport using airborne lidar, upper Colorado River, Rocky Mountain National Park, Colorado

NASA Astrophysics Data System (ADS)

Mangano, Joseph F.

A debris flow associated with the 2003 breach of Grand Ditch in Rocky Mountain National Park, Colorado provided an opportunity to determine controls on channel geomorphic responses following a large sedimentation event. Due to the remote site location and high spatial and temporal variability of processes controlling channel response, repeat airborne lidar surveys in 2004 and 2012 were used to capture conditions along the upper Colorado River and tributary Lulu Creek i) one year following the initial debris flow, and ii) following two bankfull flows (2009 and 2010) and a record-breaking long duration, high intensity snowmelt runoff season (2011). Locations and volumes of aggradation and degradation were determined using lidar differencing. Channel and valley metrics measured from the lidar surveys included water surface slope, valley slope, changes in bankfull width, sinuosity, braiding index, channel migration, valley confinement, height above the water surface along the floodplain, and longitudinal profiles. Reaches of aggradation and degradation along the upper Colorado River are influenced by valley confinement and local controls. Aggradational reaches occurred predominantly in locations where the valley was unconfined and valley slope remained constant through the length of the reach. Channel avulsions, migration, and changes in sinuosity were common in all unconfined reaches, whether aggradational or degradational. Bankfull width in both aggradational and degradational reaches showed greater changes closer to the sediment source, with the magnitude of change decreasing downstream. Local variations in channel morphology, site specific channel conditions, and the distance from the sediment source influence the balance of transport supply and capacity and, therefore, locations of aggradation, degradation, and associated morphologic changes. Additionally, a complex response initially seen in repeat cross-sections is broadly supported by lidar differencing, although the differencing captures only the net change over eight years and not annual changes. Lidar differencing shows great promise because it reveals vertical and horizontal trends in morphologic changes at a high resolution over a large area. Repeat lidar surveys were also used to create a sediment budget along the upper Colorado River by means of the morphologic inverse method. In addition to the geomorphic changes detected by lidar, several levels of attrition of the weak clasts within debris flow sediment were applied to the sediment budget to reduce gaps in expected inputs and outputs. Bed-material estimates using the morphologic inverse method were greater than field-measured transport estimates, but the two were within an order of magnitude. Field measurements and observations are critical for robust interpretation of the lidar-based analyses because applying lidar differencing without field control may not identify local controls on valley and channel geometry and sediment characteristics. The final sediment budget helps define variability in bed-material transport and constrain transport rates through the site, which will be beneficial for restoration planning. The morphologic inverse method approach using repeat lidar surveys appears promising, especially if lidar resolution is similar between sequential surveys.

A Study of Energy Conversion Devices Using Photoactive Organometallic Electrocatalysts.

DTIC Science & Technology

1986-05-23

arylisocyanide complexes confined to polymeric thin films in solar energy conversion systems . The chemical systems of interest were chromium...The goals of the project then became threefold: 1) examine the thermo- dynamics an- ’ kinetics of charge transfer in the systems in which we had shown...complexes confined to polymeric thin films in solar energy conversion systems . The chemical systems of interest were chromium, molybdenum and

Molecular systematics of the parasitic protozoan Giardia intestinalis.

PubMed

Monis, P T; Andrews, R H; Mayrhofer, G; Ey, P L

1999-09-01

The long-standing controversy regarding whether Giardia intestinalis is a single species prevalent in both human and animal hosts or a species complex consisting of morphologically similar organisms that differ in host range and other biotypic characteristics is an issue with important medical, veterinary, and environmental management implications. In the past decade, highly distinct genotypes (some apparently confined to particular host groups) have been identified by genetic analysis of samples isolated from different host species. The aim of this study was to undertake a phylogenetic analysis of G. intestinalis that were representative of all known major genetic groups and compare them with other Giardia species, viz. G. ardeae, G. muris, and G. microti. Segments from four "housekeeping" genes (specifying glutamate dehydrogenase, triose phosphate isomerase, elongation factor 1 alpha, and 18S ribosomal RNA) were examined by analysis of 0.48-0.69-kb nucleotide sequences determined from DNA amplified in polymerase chain reactions from each locus. In addition, isolates were compared by allozymic analysis of electrophoretic data obtained for 21 enzymes representing 23 gene loci. The results obtained from these independent techniques and different loci were essentially congruous. Analyses using G. ardeae and/or G. muris as outgroups supported the monophyly of G. intestinalis and also showed that this species includes genotypes that represent at least seven deeply rooted lineages, herein designated assemblages A-G. Inclusion of G. microti in the analysis of 18S rRNA sequence data demonstrated the monophyly of Giardia with the same median body morphology but did not support the monophyly of G. intestinalis, instead placing G. microti within G. intestinalis. The findings support the hypothesis that G. intestinalis is a species complex and suggest that G. microti is a member of this complex.

Morphology dependent near-field response in atomistic plasmonic nanocavities.

PubMed

Chen, Xing; Jensen, Lasse

2018-06-21

In this work we examine how the atomistic morphologies of plasmonic dimers control the near-field response by using an atomistic electrodynamics model. At large separations, the field enhancement in the junction follows a simple inverse power law as a function of the gap separation, which agrees with classical antenna theory. However, when the separations are smaller than 0.8 nm, the so-called quantum size regime, the field enhancement is screened and thus deviates from the simple power law. Our results show that the threshold distance for the deviation depends on the specific morphology of the junction. The near field in the junction can be localized to an area of less than 1 nm2 in the presence of an atomically sharp tip, but the separation distances leading to a large confinement of near field depend strongly on the specific atomistic configuration. More importantly, the highly confined fields lead to large field gradients particularly in a tip-to-surface junction, which indicates that such a plasmonic structure favors observing strong field gradient effects in near-field spectroscopy. We find that for atomically sharp tips the field gradient becomes significant and depends strongly on the local morphology of a tip. We expect our findings to be crucial for understanding the origin of high-resolution near-field spectroscopy and for manipulating optical cavities through atomic structures in the strongly coupled plasmonic systems.

Building solids inside nano-space: from confined amorphous through confined solvate to confined 'metastable' polymorph.

PubMed

Nartowski, K P; Tedder, J; Braun, D E; Fábián, L; Khimyak, Y Z

2015-10-14

The nanocrystallisation of complex molecules inside mesoporous hosts and control over the resulting structure is a significant challenge. To date the largest organic molecule crystallised inside the nano-pores is a known pharmaceutical intermediate - ROY (259.3 g mol(-1)). In this work we demonstrate smart manipulation of the phase of a larger confined pharmaceutical - indomethacin (IMC, 357.8 g mol(-1)), a substance with known conformational flexibility and complex polymorphic behaviour. We show the detailed structural analysis and the control of solid state transformations of encapsulated molecules inside the pores of mesoscopic cellular foam (MCF, pore size ca. 29 nm) and controlled pore glass (CPG, pore size ca. 55 nm). Starting from confined amorphous IMC we drive crystallisation into a confined methanol solvate, which upon vacuum drying leads to the stabilised rare form V of IMC inside the MCF host. In contrast to the pure form, encapsulated form V does not transform into a more stable polymorph upon heating. The size of the constraining pores and the drug concentration within the pores determine whether the amorphous state of the drug is stabilised or it recrystallises into confined nanocrystals. The work presents, in a critical manner, an application of complementary techniques (DSC, PXRD, solid-state NMR, N2 adsorption) to confirm unambiguously the phase transitions under confinement and offers a comprehensive strategy towards the formation and control of nano-crystalline encapsulated organic solids.

Surface-Activated Coupling Reactions Confined on a Surface.

PubMed

Dong, Lei; Liu, Pei Nian; Lin, Nian

2015-10-20

Chemical reactions may take place in a pure phase of gas or liquid or at the interface of two phases (gas-solid or liquid-solid). Recently, the emerging field of "surface-confined coupling reactions" has attracted intensive attention. In this process, reactants, intermediates, and products of a coupling reaction are adsorbed on a solid-vacuum or a solid-liquid interface. The solid surface restricts all reaction steps on the interface, in other words, the reaction takes place within a lower-dimensional, for example, two-dimensional, space. Surface atoms that are fixed in the surface and adatoms that move on the surface often activate the surface-confined coupling reactions. The synergy of surface morphology and activity allow some reactions that are inefficient or prohibited in the gas or liquid phase to proceed efficiently when the reactions are confined on a surface. Over the past decade, dozens of well-known "textbook" coupling reactions have been shown to proceed as surface-confined coupling reactions. In most cases, the surface-confined coupling reactions were discovered by trial and error, and the reaction pathways are largely unknown. It is thus highly desirable to unravel the mechanisms, mechanisms of surface activation in particular, of the surface-confined coupling reactions. Because the reactions take place on surfaces, advanced surface science techniques can be applied to study the surface-confined coupling reactions. Among them, scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) are the two most extensively used experimental tools. The former resolves submolecular structures of individual reactants, intermediates, and products in real space, while the latter monitors the chemical states during the reactions in real time. Combination of the two methods provides unprecedented spatial and temporal information on the reaction pathways. The experimental findings are complemented by theoretical modeling. In particular, density-functional theory (DFT) transition-state calculations have been used to shed light on reaction mechanisms and to unravel the trends of different surface materials. In this Account, we discuss recent progress made in two widely studied surface-confined coupling reactions, aryl-aryl (Ullmann-type) coupling and alkyne-alkyne (Glaser-type) coupling, and focus on surface activation effects. Combined experimental and theoretical studies on the same reactions taking place on different metal surfaces have clearly demonstrated that different surfaces not only reduce the reaction barrier differently and render different reaction pathways but also control the morphology of the reaction products and, to some degree, select the reaction products. We end the Account with a list of questions to be addressed in the future. Satisfactorily answering these questions may lead to using the surface-confined coupling reactions to synthesize predefined products with high yield.

Spontaneous ordering and vortex states of active fluids in circular confinement

NASA Astrophysics Data System (ADS)

Theillard, Maxime; Ezhilan, Barath; Saintillan, David

2015-11-01

Recent experimental, theoretical and simulation studies have shown that confinement can profoundly affect self-organization in active suspensions leading to striking features such as directed fluid pumping in planar confinement, formation of steady and spontaneous vortices in radial confinement. Motivated by this, we study the dynamics in a suspension of biologically active particles confined in spherical geometries using a mean-field kinetic theory for which we developed a novel numerical solver. In the case of circular confinement, we conduct a systematic exploration of the entire parameter space and distinguish 3 broad states: no-flow, stable vortex and chaotic and several interesting sub-states. Our efficient numerical framework is also employed to study 3D effects and dynamics in more complex geometries.

Physical confinement alters tumor cell adhesion and migration phenotypes

PubMed Central

Balzer, Eric M.; Tong, Ziqiu; Paul, Colin D.; Hung, Wei-Chien; Stroka, Kimberly M.; Boggs, Amanda E.; Martin, Stuart S.; Konstantopoulos, Konstantinos

2012-01-01

Cell migration on planar surfaces is driven by cycles of actin protrusion, integrin-mediated adhesion, and myosin-mediated contraction; however, this mechanism may not accurately describe movement in 3-dimensional (3D) space. By subjecting cells to restrictive 3D environments, we demonstrate that physical confinement constitutes a biophysical stimulus that alters cell morphology and suppresses mesenchymal motility in human breast carcinoma (MDA-MB-231). Dorsoventral polarity, stress fibers, and focal adhesions are markedly attenuated by confinement. Inhibitors of myosin, Rho/ROCK, or β1-integrins do not impair migration through 3-μm-wide channels (confinement), even though these treatments repress motility in 50-μm-wide channels (unconfined migration) by ≥50%. Strikingly, confined migration persists even when F-actin is disrupted, but depends largely on microtubule (MT) dynamics. Interfering with MT polymerization/depolymerization causes confined cells to undergo frequent directional changes, thereby reducing the average net displacement by ≥80% relative to vehicle controls. Live-cell EB1-GFP imaging reveals that confinement redirects MT polymerization toward the leading edge, where MTs continuously impact during advancement of the cell front. These results demonstrate that physical confinement can induce cytoskeletal alterations that reduce the dependence of migrating cells on adhesion-contraction force coupling. This mechanism may explain why integrins can exhibit reduced or altered function during migration in 3D environments.—Balzer, E. M., Tong, Z., Paul, C. D., Hung, W.-C., Stroka, K. M., Boggs, A. E., Martin, S. S., Konstantopoulos, K. Physical confinement alters tumor cell adhesion and migration phenotypes. PMID:22707566

Scattering of particles in the presence of harmonic confinement perturbed by a complex absorbing potential

NASA Astrophysics Data System (ADS)

Maghari, A.; Kermani, M. M.

2018-04-01

A system of two interacting atoms confined in 1D harmonic trap and perturbed by an absorbing boundary potential is studied using the Lippmann-Schwinger formalism. The atom-atom interaction potential was considered as a nonlocal separable model. The perturbed absorbing boundary potential was also assumed in the form of Scarf II complex absorbing potential. The model is used for the study of 1D optical lattices that support the trapping of a pair atom within a unit cell. Moreover, it allows to describe the scattering particles in a tight smooth trapping surface and to analyze the bound and resonance states. The analytical expressions for wavefunctions and transition matrix as well as the absorption probabilities are calculated. A demonstration of how the complex absorbing potential affecting the bound states and resonances of particles confined in a harmonic trap is described.

FINE STRUCTURES AND OVERLYING LOOPS OF CONFINED SOLAR FLARES

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

Yang, Shuhong; Zhang, Jun; Xiang, Yongyuan, E-mail: shuhongyang@nao.cas.cn

2014-10-01

Using the Hα observations from the New Vacuum Solar Telescope at the Fuxian Solar Observatory, we focus on the fine structures of three confined flares and the issue why all the three flares are confined instead of eruptive. All the three confined flares take place successively at the same location and have similar morphologies, so can be termed homologous confined flares. In the simultaneous images obtained by the Solar Dynamics Observatory, many large-scale coronal loops above the confined flares are clearly observed in multi-wavelengths. At the pre-flare stage, two dipoles emerge near the negative sunspot, and the dipolar patches aremore » connected by small loops appearing as arch-shaped Hα fibrils. There exists a reconnection between the small loops, and thus the Hα fibrils change their configuration. The reconnection also occurs between a set of emerging Hα fibrils and a set of pre-existing large loops, which are rooted in the negative sunspot, a nearby positive patch, and some remote positive faculae, forming a typical three-legged structure. During the flare processes, the overlying loops, some of which are tracked by activated dark materials, do not break out. These direct observations may illustrate the physical mechanism of confined flares, i.e., magnetic reconnection between the emerging loops and the pre-existing loops triggers flares and the overlying loops prevent the flares from being eruptive.« less

Morphological Consequences of Frustration in ABC Triblock Polymers

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

Radlauer, Madalyn R.; Sinturel, Christophe; Asai, Yusuke

2016-12-19

Three poly(styrene)-block-poly(isoprene)-block-poly(lactide) (PS-b-PI-b-PLA, SIL) triblock terpolymers were synthesized and characterized in the bulk and as thin films. The pronounced incompatibility of the covalently connected PI and PLA led to significant frustration and the tendency to minimize their intermaterial dividing surface area. This resulted in the formation of a core–shell cylinder morphology with exaggerated nonconstant mean curvature from triblock polymers with equal block volume fractions rather than the more typical lamellar morphology. The effect of frustration was magnified in thin films by both confinement and interfacial interactions such that the PI domains became discontinuous. Self-consistent field theory (SCFT) calculations emphasize thatmore » the marked difference in the PS/PI and PI/PLA interaction parameters promotes the formation of nonlamellar morphologies. However, SCFT predicts that lamellar morphology is more stable than the observed cylindrical morphology, demonstrating a limitation that arises from the underlying assumptions.« less

Chemical reactions confined within carbon nanotubes.

PubMed

Miners, Scott A; Rance, Graham A; Khlobystov, Andrei N

2016-08-22

In this critical review, we survey the wide range of chemical reactions that have been confined within carbon nanotubes, particularly emphasising how the pairwise interactions between the catalysts, reactants, transition states and products of a particular molecular transformation with the host nanotube can be used to control the yields and distributions of products of chemical reactions. We demonstrate that nanoscale confinement within carbon nanotubes enables the control of catalyst activity, morphology and stability, influences the local concentration of reactants and products thus affecting equilibria, rates and selectivity, pre-arranges the reactants for desired reactions and alters the relative stability of isomeric products. We critically evaluate the relative advantages and disadvantages of the confinement of chemical reactions inside carbon nanotubes from a chemical perspective and describe how further developments in the controlled synthesis of carbon nanotubes and the incorporation of multifunctionality are essential for the development of this ever-expanding field, ultimately leading to the effective control of the pathways of chemical reactions through the rational design of multi-functional carbon nanoreactors.

Dynamics of Water in Gemini Surfactant-Based Lyotropic Liquid Crystals

DOE PAGES

McDaniel, Jesse G.; Mantha, Sriteja; Yethiraj, Arun

2016-09-26

The dynamics of water confined to nanometer-sized domains is important in a variety of applications ranging from proton exchange membranes to crowding effects in biophysics. In this work we study the dynamics of water in gemini surfactant-based lyotropic liquid crystals (LLCs) using molecular dynamics simulations. These systems have well characterized morphologies, e.g., hexagonal, gyroid, and lamellar, and the surfaces of the confining regions can be controlled by modifying the headgroup of the surfactants. This allows one to study the effect of topology, functionalization, and interfacial curvature on the dynamics of confined water. Through analysis of the translational diffusion and rotationalmore » relaxation we conclude that the hydration level and resulting confinement lengthscale is the predominate determiner of the rates of water dynamics, and other effects, namely surface functionality and curvature, are largely secondary. In conclusion, this novel analysis of the water dynamics in these LLC systems provides an important comparison for previous studies of water dynamics in lipid bilayers and reverse micelles.« less

Morphology-dependent low-frequency Raman scattering in ultrathin spherical, cubic, and cuboid SnO2 nanocrystals

NASA Astrophysics Data System (ADS)

Liu, L. Z.; Wu, X. L.; Li, T. H.; Xiong, S. J.; Chen, H. T.; Chu, Paul K.

2011-12-01

Nanoscale spherical, cubic, and cuboid SnO2 nanocrystals (NCs) are used to investigate morphology-dependent low-frequency Raman scattering. A double-peak structure in which the linewidths and energy separation between two subpeaks decrease with increasing sizes of cuboid NCs is observed and attributed to the surface acoustic phonon modes confined in three dimensional directions and determined by the surface/interface compositions. The decrease in energy separation is due to weaker coupling between the acoustic modes in different vibration directions. Our experimental and theoretical studies clearly disclose the morphology-dependent surface vibrational behavior in self-assembled NCs.

Picosecond to nanosecond reorganization of water in AOT/lecithin mixed reverse micelles of different morphology

NASA Astrophysics Data System (ADS)

Narayanan, S. Shankara; Sinha, Sudarson Sekhar; Sarkar, Rupa; Pal, Samir Kumar

2008-02-01

We report the effect of different geometrical restrictions on the dynamical properties of water using dynamic light scattering (DLS), Fourier transform infrared (FTIR) and picosecond-resolved fluorescence studies. By preparing AOT/lecithin mixed reverse micelles (RMs) of different morphologies (spherical and ellipsoidal), we have investigated the effect of the degree of confinement on the mobility of water in the mixed RMs of similar degree of hydration. The FTIR studies along with solvation dynamics of two fluorescent probes, ANS and coumarin 500 in the RMs reveal structural and dynamical information about the micellar water, which varies with the morphology of the mixed RMs.

Geomorphic clues to the Martian volatile inventory: Landslides

NASA Technical Reports Server (NTRS)

Pieri, D.; Kirkpatrick, A.

1984-01-01

Eight landslide locales were selected in Valles Marineris for preliminary geomorphological mapping. Four main suites of morphological features were identified. In four order outward from the head scarp they are: (1) large ridges in head area, transverse to movement direction, probably slump blocks or pieces of wall that fell or toppled, possibly backward rotated; (2) smaller ridges, convex toward distal edge of slides, many with lobate pattern, some possibly step like scarps rather than ridges; (3) thin, sheet like debris cover, forms discrete fan shaped lobe with edge scarps unconfined; and (4) low transverse, continuous ridges (possibly folds) found at distal edge of slides, where debris appears to have encountered obstructions (e.g., opposing canyon walls), but not all confined slides exhibit this feature. Any one landslide can possess all or some of these features. Slides in the western Valles Marineris are more complex and show more variety than those in the eastern part.

Fracture surfaces of granular pastes.

PubMed

Mohamed Abdelhaye, Y O; Chaouche, M; Van Damme, H

2013-11-01

Granular pastes are dense dispersions of non-colloidal grains in a simple or a complex fluid. Typical examples are the coating, gluing or sealing mortars used in building applications. We study the cohesive rupture of thick mortar layers in a simple pulling test where the paste is initially confined between two flat surfaces. After hardening, the morphology of the fracture surfaces was investigated, using either the box counting method to analyze fracture profiles perpendicular to the mean fracture plane, or the slit-island method to analyze the islands obtained by cutting the fracture surfaces at different heights, parallel to the mean fracture plane. The fracture surfaces were shown to exhibit scaling properties over several decades. However, contrary to what has been observed in the brittle or ductile fracture of solid materials, the islands were shown to be mass fractals. This was related to the extensive plastic flow involved in the fracture process.

Defect-mediated spatial complexity and chaos in a phase-conjugate resonator

NASA Technical Reports Server (NTRS)

Indebetouw, Guy; Liu, Siuying R.

1992-01-01

We have studied the spatiotemporal dynamics of a phase-conjugate resonator. The cavity Fresnel number is used to vary the degree of transverse confinement of the system. The generation and subsequent motion of the phase defects in the wave front are seen to mediate the system's dynamics. The number of defects and the complexity of their motion increases as the confinement is relaxed, leading the system through a sequence of bifurcations and eventually to chaos.

Surfactant-thermal method to synthesize a new Zn(II)-trimesic MOF with confined Ru(bpy){sub 3}{sup 2+} complex

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

Xu, Hui; Gao, Junkuo, E-mail: jkgao@zstu.edu.cn; Wang, Jiangpeng

2015-03-15

A surfactant-thermal method was used to prepare a new zinc-1,3,5-benzentricarboxylate-based metal-organic framework (ZJU-100) with confined Ru(bpy){sub 3}{sup 2+} (RuBpy) complex by using surfactant PEG 400 as reaction medium. The RuBpy molecules were encapsulated between the 2-D sheets in ZJU-100. ZJU-100 showed bathochromic shift in the steady-state emission spectrum and increased emission lifetimes relative to RuBpy molecules. The extended lifetime is attributed to the reduced nonradiative decay rate due to the stabilization of RuBpy within the rigid MOF framework. These results represent the first example of MOF with confined complex synthesized by surfactant, indicating that the surfactant-thermal method could offer excitingmore » opportunities for preparing new MOFs host/guest materials with novel structures and interesting luminescent properties. - Graphical abstract: A surfactant-thermal method was used to prepare a new zinc-1,3,5-benzentricarboxylate-based metal-organic framework (ZJU-100) with confined Ru(bpy){sub 3}{sup 2+} (RuBpy) complex by using surfactant PEG 400 as reaction medium. - Highlights: • Surfactant-thermal synthesis of crystalline metal-organic framework host/guest materials. • RuBpy molecules were encapsulated between the 2-D sheets of MOFs. • Extended lifetime is observed due to the stabilization of RuBpy within the rigid MOF framework.« less

Effects of lateral confinement in natural and leveed reaches of a gravel-bed river: Snake River, Wyoming, USA

USGS Publications Warehouse

Leonard, Christina M.; Legleiter, Carl; Overstreet, Brandon T.

2017-01-01

This study examined the effects of natural and anthropogenic changes in confining margin width by applying remote sensing techniques – fusing LiDAR topography with image-derived bathymetry – over a large spatial extent: 58 km of the Snake River, Wyoming, USA. Fused digital elevation models from 2007 and 2012 were differenced to quantify changes in the volume of stored sediment, develop morphological sediment budgets, and infer spatial gradients in bed material transport. Our study spanned two similar reaches that were subject to different controls on confining margin width: natural terraces versus artificial levees. Channel planform in reaches with similar slope and confining margin width differed depending on whether the margins were natural or anthropogenic. The effects of tributaries also differed between the two reaches. Generally, the natural reach featured greater confining margin widths and was depositional, whereas artificial lateral constriction in the leveed reach produced a sediment budget that was closer to balanced. Although our remote sensing methods provided topographic data over a large area, net volumetric changes were not statistically significant due to the uncertainty associated with bed elevation estimates. We therefore focused on along-channel spatial differences in bed material transport rather than absolute volumes of sediment. To complement indirect estimates of sediment transport derived by morphological sediment budgeting, we collected field data on bed mobility through a tracer study. Surface and subsurface grain size measurements were combined with bed mobility observations to calculate armoring and dimensionless sediment transport ratios, which indicated that sediment supply exceeded transport capacity in the natural reach and vice versa in the leveed reach. We hypothesize that constriction by levees induced an initial phase of incision and bed armoring. Because levees prevented bank erosion, the channel excavated sediment by migrating rapidly across the restricted braidplain and eroding bars and islands. 

Fabrication of an ionic-liquid-based polymer monolithic column and its application in the fractionation of proteins from complex biosamples.

PubMed

Zhang, Doudou; Zhang, Qian; Bai, Ligai; Han, Dandan; Liu, Haiyan; Yan, Hongyuan

2018-05-01

An ionic-liquid-based polymer monolithic column was synthesized by free radical polymerization within the confines of a stainless-steel column (50 mm × 4.6 mm id). In the processes, ionic liquid and stearyl methacrylate were used as dual monomers, ethylene glycol dimethacrylate as the cross-linking agent, and polyethylene glycol 200 and isopropanol as co-porogens. Effects of the prepolymerization solution components on the properties of the resulting monoliths were studied in detail. Scanning electron microscopy, nitrogen adsorption-desorption measurements, and mercury intrusion porosimetry were used to investigate the morphology and pore size distribution of the prepared monoliths, which showed that the homemade ionic-liquid-based monolith column possessed a relatively uniform macropore structure with a total macropore specific surface area of 44.72 m 2 /g. Compared to a non-ionic-liquid-based monolith prepared under the same conditions, the ionic-liquid-based monolith exhibited excellent selectivity and high performance for separating proteins from complex biosamples, such as egg white, snailase, bovine serum albumin digest solution, human plasma, etc., indicating promising applications in the fractionation and analysis of proteins from the complex biosamples in proteomics research. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Engineered Models of Confined Cell Migration

PubMed Central

Paul, Colin D.; Hung, Wei-Chien; Wirtz, Denis; Konstantopoulos, Konstantinos

2017-01-01

Cells in the body are physically confined by neighboring cells, tissues, and the extracellular matrix. Although physical confinement modulates intracellular signaling and the underlying mechanisms of cell migration, it is difficult to study in vivo. Furthermore, traditional two-dimensional cell migration assays do not recapitulate the complex topographies found in the body. Therefore, a number of experimental in vitro models that confine and impose forces on cells in well-defined microenvironments have been engineered. We describe the design and use of microfluidic microchannel devices, grooved substrates, micropatterned lines, vertical confinement devices, patterned hydrogels, and micropipette aspiration assays for studying cell responses to confinement. Use of these devices has enabled the delineation of changes in cytoskeletal reorganization, cell–substrate adhesions, intracellular signaling, nuclear shape, and gene expression that result from physical confinement. These assays and the physiologically relevant signaling pathways that have been elucidated are beginning to have a translational and clinical impact. PMID:27420571

A computational investigation of the phase behavior and capillary sublimation of water confined between nanoscale hydrophobic plates

NASA Astrophysics Data System (ADS)

Ferguson, Andrew L.; Giovambattista, Nicolás; Rossky, Peter J.; Panagiotopoulos, Athanassios Z.; Debenedetti, Pablo G.

2012-10-01

Thin films of water under nanoscopic confinement are prevalent in natural and manufactured materials. To investigate the equilibrium and dynamic behavior of water in such environments, we perform molecular dynamics simulations of water confined between atomistically detailed hydrophobic plates at T = 298 K for pressures (-0.1) ⩽ P ⩽ 1.0 GPa and plate separations of 0.40 ⩽ d ⩽ 0.80 nm. From these simulations, we construct an expanded P-d phase diagram for confined water, and identify and characterize a previously unreported confined monolayer ice morphology. We also study the decompression-induced sublimation of bilayer ice in a d = 0.6 nm slit, employing principal component analysis to synthesize low-dimensional embeddings of the drying trajectories and develop insight into the sublimation mechanism. Drying is observed to proceed by the nucleation of a bridging vapor cavity at one corner of the crystalline slab, followed by expansion of the cavity along two edges of the plates, and the subsequent recession of the remaining promontory of bilayer crystal into the bulk fluid. Our findings have implications for the understanding of diverse phenomena in materials science, nanofluidics, and protein folding and aggregation.

The Contribution of Morphological Awareness to the Spelling of Morphemes and Morphologically Complex Words in French

ERIC Educational Resources Information Center

Fejzo, Anila

2016-01-01

The goal of this study was to explore the relationship between morphological awareness and the spelling of morphemes and morphologically complex words among 75 third- and fourth-grade Francophone students of low socio-economic status. To reach this objective, we administered a dictation comprised of morphologically complex words with prefixes,…

Selective Metallization of Well Aligned PS-b-P2VP Block Copolymers in Thin Films and in Confined Geometries

NASA Astrophysics Data System (ADS)

Sievert, James D.; Watkins, James J.; Russell, Thomas P.

2006-03-01

Well aligned, microphase-separated structures of styrene-2-vinylpyridine block copolymers are being used as templates for macromolecule-metal nanocomposites. These composites are either prepared as thin films or confined in nanoporous aluminum oxide membranes. Under optimal conditions, templates are prepared as thin films or confined nanorods and metallized without disturbing the ordered structure. We have developed a procedure that deposits metal within the polymer using supercritical carbon dioxide-soluble metal precursors. The use of supercritical carbon dioxide allows for selective metallization of the polymer at or below the glass transition, without disrupting the morphology. In addition, similar procedures have been investigated using metal salts and acids. Using these techniques, metals and metal-sulfides including silver, gold, platinum and zinc sulfide have been selectively deposited.

Confinement of β1- and β2-adrenergic receptors in the plasma membrane of cardiomyocyte-like H9c2 cells is mediated by selective interactions with PDZ domain and A-kinase anchoring proteins but not caveolae

PubMed Central

Valentine, Cathleen D.; Haggie, Peter M.

2011-01-01

The sympathetic nervous system regulates cardiac output by activating adrenergic receptors (ARs) in cardiac myocytes. The predominant cardiac ARs, β1- and β2AR, are structurally similar but mediate distinct signaling responses. Scaffold protein–mediated compartmentalization of ARs into discrete, multiprotein complexes has been proposed to dictate differential signaling responses. To test the hypothesis that βARs integrate into complexes in live cells, we measured receptor diffusion and interactions by single-particle tracking. Unstimulated β1- and β2AR were highly confined in the membrane of H9c2 cardiomyocyte-like cells, indicating that receptors are tethered and presumably integrated into protein complexes. Selective disruption of interactions with postsynaptic density protein 95/disks large/zonula occludens-1 (PDZ)–domain proteins and A-kinase anchoring proteins (AKAPs) increased receptor diffusion, indicating that these scaffold proteins participate in receptor confinement. In contrast, modulation of interactions between the putative scaffold caveolae and β2AR did not alter receptor dynamics, suggesting that these membrane domains are not involved in β2AR confinement. For both β1- and β2AR, the receptor carboxy-terminus was uniquely responsible for scaffold interactions. Our data formally demonstrate that distinct and stable protein complexes containing β1- or β2AR are formed in the plasma membrane of cardiomyocyte-like cells and that selective PDZ and AKAP interactions are responsible for the integration of receptors into complexes. PMID:21680711

Confinement of β(1)- and β(2)-adrenergic receptors in the plasma membrane of cardiomyocyte-like H9c2 cells is mediated by selective interactions with PDZ domain and A-kinase anchoring proteins but not caveolae.

PubMed

Valentine, Cathleen D; Haggie, Peter M

2011-08-15

The sympathetic nervous system regulates cardiac output by activating adrenergic receptors (ARs) in cardiac myocytes. The predominant cardiac ARs, β(1)- and β(2)AR, are structurally similar but mediate distinct signaling responses. Scaffold protein-mediated compartmentalization of ARs into discrete, multiprotein complexes has been proposed to dictate differential signaling responses. To test the hypothesis that βARs integrate into complexes in live cells, we measured receptor diffusion and interactions by single-particle tracking. Unstimulated β(1)- and β(2)AR were highly confined in the membrane of H9c2 cardiomyocyte-like cells, indicating that receptors are tethered and presumably integrated into protein complexes. Selective disruption of interactions with postsynaptic density protein 95/disks large/zonula occludens-1 (PDZ)-domain proteins and A-kinase anchoring proteins (AKAPs) increased receptor diffusion, indicating that these scaffold proteins participate in receptor confinement. In contrast, modulation of interactions between the putative scaffold caveolae and β(2)AR did not alter receptor dynamics, suggesting that these membrane domains are not involved in β(2)AR confinement. For both β(1)- and β(2)AR, the receptor carboxy-terminus was uniquely responsible for scaffold interactions. Our data formally demonstrate that distinct and stable protein complexes containing β(1)- or β(2)AR are formed in the plasma membrane of cardiomyocyte-like cells and that selective PDZ and AKAP interactions are responsible for the integration of receptors into complexes.

Vesicle dynamics in a confined Poiseuille flow: from steady state to chaos.

PubMed

Aouane, Othmane; Thiébaud, Marine; Benyoussef, Abdelilah; Wagner, Christian; Misbah, Chaouqi

2014-09-01

Red blood cells (RBCs) are the major component of blood, and the flow of blood is dictated by that of RBCs. We employ vesicles, which consist of closed bilayer membranes enclosing a fluid, as a model system to study the behavior of RBCs under a confined Poiseuille flow. We extensively explore two main parameters: (i) the degree of confinement of vesicles within the channel and (ii) the flow strength. Rich and complex dynamics for vesicles are revealed, ranging from steady-state shapes (in the form of parachute and slipper shapes) to chaotic dynamics of shape. Chaos occurs through a cascade of multiple periodic oscillations of the vesicle shape. We summarize our results in a phase diagram in the parameter plane (degree of confinement and flow strength). This finding highlights the level of complexity of a flowing vesicle in the small Reynolds number where the flow is laminar in the absence of vesicles and can be rendered turbulent due to elasticity of vesicles.

A new spruce hybrid - Picea schrenkiana x P. glauca

Treesearch

D.P. Fowler

1966-01-01

Picea schrenkiana Fisch and Meyer is a relatively unknown central Asiatic species confined to the Ala Tau and Thian Shan mountains of Turkestan. Morphologically the species is most closely related to P. spinulosa (Griff.) Henry and, to a lesser degree, to P. obovata Ledeb. (Wright 1955).

Genetic structuring, dispersal and taxonomy of the high-alpine populations of the Geranium arabicum/kilimandscharicum complex in tropical eastern Africa

PubMed Central

Gizaw, Abel; Tusiime, Felly M.; Masao, Catherine A.; Abdi, Ahmed A.; Hou, Yan; Nemomissa, Sileshi; Brochmann, Christian

2017-01-01

The scattered eastern African high mountains harbor a renowned and highly endemic flora, but the taxonomy and phylogeographic history of many plant groups are still insufficiently known. The high-alpine populations of the Geranium arabicum/kilimandscharicum complex present intricate morphological variation and have recently been suggested to comprise two new endemic taxa. Here we aim to contribute to a clarification of the taxonomy of these populations by analyzing genetic (AFLP) variation in range-wide high-alpine samples, and we address whether hybridization has contributed to taxonomic problems. We identified only two genetic groups. One corresponded to G. kilimandscharicum, which has been reported as exclusively high-alpine and confined to the eastern Rift mountains in East Africa. The other corresponded to G. arabicum, reported from lower altitudes on the same mountains as well as from a wide altitudinal span in Ethiopia and on the western Rift mountains in East Africa. The four populations analyzed of a recently described species from the Bale Mts in Ethiopia were admixed, indicating that they result from recent long-distance dispersal of G. kilimandscharicum from East Africa followed by hybridization with local G. arabicum in naturally disturbed habitats. Some admixture between the two genetic groups was also inferred on other mountains, supporting earlier suggestions of introgression based on morphology. We did not find support for recognition of the recently suggested new subspecies of G. arabicum in Ethiopia. Interestingly, the high-alpine G. kilimandscharicum lacked clear geographic structuring, suggesting a recent history of colonization of the different mountains or extensive intermountain gene flow. PMID:28552970

Self-assembled morphologies of an amphiphilic Y-shaped weak polyelectrolyte in a thin film.

PubMed

Mu, Dan; Li, Jian-Quan; Feng, Sheng-Yu

2017-11-29

Different from the self-assembly of neutral polymers, polyelectrolytes self-assemble into smaller aggregates with a more loosely assembled structure, which results from the repulsive forces acting between similar electrical compositions with the introduction of ions. The Y-shaped weak polyelectrolytes self-assemble into a core-shell type cylindrical structure with a hexagonal arrangement in a thin film, whose thickness is smaller than the gyration radius of the polymer chain. The corresponding formation mechanism consists of enrichment of the same components, adjustment of the shape of the aggregate, and the subsequent separation into individual aggregates. With the increase in the thickness of the thin film until it exceeds the gyration radius of the polymer chain, combined with the greater freedom of movement along the direction of thin film thickness, the self-assembled structure changes into a micellar structure. Under confinement, the repulsive force to the polymeric components is weakened by the repulsive forces among polyelectrolyte components with like charges, and this helps in generating aggregates with more uniform size and density distribution. In particular, when the repulsive force between the walls and the core forming components is greater than that between the walls and the shell forming components, such asymmetric confinement produces a crossed-cylindrical structure with nearly perpendicular arrangement of two cylinder arrays. Similarly, a novel three-crossed cylinder morphology is self-assembled upon removal of confinement.

Elastic membranes in confinement.

PubMed

Bostwick, J B; Miksis, M J; Davis, S H

2016-07-01

An elastic membrane stretched between two walls takes a shape defined by its length and the volume of fluid it encloses. Many biological structures, such as cells, mitochondria and coiled DNA, have fine internal structure in which a membrane (or elastic member) is geometrically 'confined' by another object. Here, the two-dimensional shape of an elastic membrane in a 'confining' box is studied by introducing a repulsive confinement pressure that prevents the membrane from intersecting the wall. The stage is set by contrasting confined and unconfined solutions. Continuation methods are then used to compute response diagrams, from which we identify the particular membrane mechanics that generate mitochondria-like shapes. Large confinement pressures yield complex response diagrams with secondary bifurcations and multiple turning points where modal identities may change. Regions in parameter space where such behaviour occurs are then mapped. © 2016 The Author(s).

An open access microfluidic device for the study of the physical limits of cancer cell deformation during migration in confined environments.

PubMed

Malboubi, Majid; Jayo, Asier; Parsons, Maddy; Charras, Guillaume

2015-08-16

During metastasis, cancerous cells leave the primary tumour, pass into the circulatory system, and invade into new tissues. To migrate through the wide variety of environments they encounter, the cells must be able to remodel their cell shape efficiently to squeeze through small gaps in the extracellular matrix or extravasate into the blood stream or lymphatic system. Several studies have shown that the nucleus is the main limiting factor to migration through small gaps (Wolf et al., 2013; Harada et al., 2014; Mak et al., 2013). To understand the physical limits of cancer cell translocation in confined environments, we have fabricated a microfluidic device to study their ability to adapt their nuclear and cellular shape when passing through small gaps. The device is open access for ease of use and enables examination of the effect of different levels of spatial confinement on cell behaviour and morphology simultaneously. The results show that increasing cell confinement decreases the ability of cells to translocate into small gaps and that cells cannot penetrate into the microchannels below a threshold cross-section.

Hydrodynamic interaction of two deformable drops in confined shear flow.

PubMed

Chen, Yongping; Wang, Chengyao

2014-09-01

We investigate hydrodynamic interaction between two neutrally buoyant circular drops in a confined shear flow based on a computational fluid dynamics simulation using the volume-of-fluid method. The rheological behaviors of interactive drops and the flow regimes are explored with a focus on elucidation of underlying physical mechanisms. We find that two types of drop behaviors during interaction occur, including passing-over motion and reversing motion, which are governed by the competition between the drag of passing flow and the entrainment of reversing flow in matrix fluid. With the increasing confinement, the drop behavior transits from the passing-over motion to reversing motion, because the entrainment of the reversing-flow matrix fluid turns to play the dominant role. The drag of the ambient passing flow is increased by enlarging the initial lateral separation due to the departure of the drop from the reversing flow in matrix fluid, resulting in the emergence of passing-over motion. In particular, a corresponding phase diagram is plotted to quantitatively illustrate the dependence of drop morphologies during interaction on confinement and initial lateral separation.

Characteristic Features of Water Dynamics in Restricted Geometries Investigated with Quasi-Elastic Neutron Scattering

DOE PAGES

Osti, Naresh C.; Mamontov, Eugene; Ramirez-cuesta, A.; ...

2015-12-10

Understanding the molecular behavior of water in spatially restricted environments is important to better understanding its role in many biological, chemical and geological processes. Here we examine the translational diffusion of water confined to a variety of substrates, from flat surfaces to nanoporous media, in the context of a recently proposed universal scaling law (Chiavazzo 2014) [1]. Using over a dozen previous neutron scattering results, we test the validity of this law, evaluating separately the influence of the hydration amount, and the effects of the size and morphology of the confining medium. Additionally, we investigate the effects of changing instrumentmore » resolutions and fitting models on the applicability of this law. Finally, we perform quasi-elastic neutron scattering measurements on water confined inside nanoporous silica to further evaluate this predictive law, in the temperature range 250≤T≤290 K.« less

The antagonistic modulation of Arp2/3 activity by N-WASP, WAVE2 and PICK1 defines dynamic changes in astrocyte morphology.

PubMed

Murk, Kai; Blanco Suarez, Elena M; Cockbill, Louisa M R; Banks, Paul; Hanley, Jonathan G

2013-09-01

Astrocytes exhibit a complex, branched morphology, allowing them to functionally interact with numerous blood vessels, neighboring glial processes and neuronal elements, including synapses. They also respond to central nervous system (CNS) injury by a process known as astrogliosis, which involves morphological changes, including cell body hypertrophy and thickening of major processes. Following severe injury, astrocytes exhibit drastically reduced morphological complexity and collectively form a glial scar. The mechanistic details behind these morphological changes are unknown. Here, we investigate the regulation of the actin-nucleating Arp2/3 complex in controlling dynamic changes in astrocyte morphology. In contrast to other cell types, Arp2/3 inhibition drives the rapid expansion of astrocyte cell bodies and major processes. This intervention results in a reduced morphological complexity of astrocytes in both dissociated culture and in brain slices. We show that this expansion requires functional myosin II downstream of ROCK and RhoA. Knockdown of the Arp2/3 subunit Arp3 or the Arp2/3 activator N-WASP by siRNA also results in cell body expansion and reduced morphological complexity, whereas depleting WAVE2 specifically reduces the branching complexity of astrocyte processes. By contrast, knockdown of the Arp2/3 inhibitor PICK1 increases astrocyte branching complexity. Furthermore, astrocyte expansion induced by ischemic conditions is delayed by PICK1 knockdown or N-WASP overexpression. Our findings identify a new morphological outcome for Arp2/3 activation in restricting rather than promoting outwards movement of the plasma membrane in astrocytes. The Arp2/3 regulators PICK1, and N-WASP and WAVE2 function antagonistically to control the complexity of astrocyte branched morphology, and this mechanism underlies the morphological changes seen in astrocytes during their response to pathological insult.

Nonlinear spectral singularities for confined nonlinearities.

PubMed

Mostafazadeh, Ali

2013-06-28

We introduce a notion of spectral singularity that applies for a general class of nonlinear Schrödinger operators involving a confined nonlinearity. The presence of the nonlinearity does not break the parity-reflection symmetry of spectral singularities but makes them amplitude dependent. Nonlinear spectral singularities are, therefore, associated with a resonance effect that produces amplified waves with a specific amplitude-wavelength profile. We explore the consequences of this phenomenon for a complex δ-function potential that is subject to a general confined nonlinearity.

Proceedings of the Ground-Water Detection Workshop Held at Vicksburg, Mississippi on 12-14 January 1982.

DTIC Science & Technology

1984-12-01

shales and hard aquiferic car- bonates. Therefore, small confined and perched aquifers can occur in a number of localities. The basement complex...the region that extends from Saudia Arabia all the way into Algeria, Morocco, and Tunisia is from older to younger strata. The major aquifer in the... aquifers all the way down the stratigraphic section--a phreatic one at the top, then semi- confined and confined aquifers until we get to upper

Oxide nanoelectronics on demand.

PubMed

Cen, Cheng; Thiel, Stefan; Mannhart, Jochen; Levy, Jeremy

2009-02-20

Electronic confinement at nanoscale dimensions remains a central means of science and technology. We demonstrate nanoscale lateral confinement of a quasi-two-dimensional electron gas at a lanthanum aluminate-strontium titanate interface. Control of this confinement using an atomic force microscope lithography technique enabled us to create tunnel junctions and field-effect transistors with characteristic dimensions as small as 2 nanometers. These electronic devices can be modified or erased without the need for complex lithographic procedures. Our on-demand nanoelectronics fabrication platform has the potential for widespread technological application.

Total curvature and total torsion of knotted random polygons in confinement

NASA Astrophysics Data System (ADS)

Diao, Yuanan; Ernst, Claus; Rawdon, Eric J.; Ziegler, Uta

2018-04-01

Knots in nature are typically confined spatially. The confinement affects the possible configurations, which in turn affects the spectrum of possible knot types as well as the geometry of the configurations within each knot type. The goal of this paper is to determine how confinement, length, and knotting affect the total curvature and total torsion of random polygons. Previously published papers have investigated these effects in the unconstrained case. In particular, we analyze how the total curvature and total torsion are affected by (1) varying the length of polygons within a fixed confinement radius and (2) varying the confinement radius of polygons with a fixed length. We also compare the total curvature and total torsion of groups of knots with similar complexity (measured as crossing number). While some of our results fall in line with what has been observed in the studies of the unconfined random polygons, a few surprising results emerge from our study, showing some properties that are unique due to the effect of knotting in confinement.

Local structural ordering in surface-confined liquid crystals

NASA Astrophysics Data System (ADS)

Śliwa, I.; Jeżewski, W.; Zakharov, A. V.

2017-06-01

The effect of the interplay between attractive nonlocal surface interactions and attractive pair long-range intermolecular couplings on molecular structures of liquid crystals confined in thin cells with flat solid surfaces has been studied. Extending the McMillan mean field theory to include finite systems, it has been shown that confining surfaces can induce complex orientational and translational ordering of molecules. Typically, local smectic A, nematic, and isotropic phases have been shown to coexist in certain temperature ranges, provided that confining cells are sufficiently thick, albeit finite. Due to the nonlocality of surface interactions, the spatial arrangement of these local phases can display, in general, an unexpected complexity along the surface normal direction. In particular, molecules located in the vicinity of surfaces can still be organized in smectic layers, even though nematic and/or isotropic order can simultaneously appear in the interior of cells. The resulting surface freezing of smectic layers has been confirmed to occur even for rather weak surface interactions. The surface interactions cannot, however, prevent smectic layers from melting relatively close to system boundaries, even when molecules are still arranged in layers within the central region of the system. The internal interfaces, separating individual liquid-crystal phases, are demonstrated here to form fronts of local finite-size transitions that move across cells under temperature changes. Although the complex molecular ordering in surface confined liquid-crystal systems can essentially be controlled by temperature variations, specific thermal properties of these systems, especially the nature of the local transitions, are argued to be strongly conditioned to the degree of molecular packing.

Are Complex Magnetic Field Structures Responsible for the Confined X-class Flares in Super Active Region 12192?

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

Zhang, Jun; Li, Ting; Chen, Huadong, E-mail: zjun@nao.cas.cn, E-mail: hdchen@nao.cas.cn

From 2014 October 19 to 27, six X-class flares occurred in super active region (AR) 12192. They were all confined flares and were not followed by coronal mass ejections. To examine the structures of the four flares close to the solar disk center from October 22 to 26, we firstly employ composite triple-time images in each flare process to display the stratified structure of these flare loops. The loop structures of each flare in both the lower (171 Å) and higher (131 Å) temperature channels are complex, e.g., the flare loops rooting at flare ribbons are sheared or twisted (enwound)more » together, and the complex structures were not destroyed during the flares. For the first flare, although the flare loop system appears as a spindle shape, we can estimate its structures from observations, with lengths ranging from 130 to 300 Mm, heights from 65 to 150 Mm, widths at the middle part of the spindle from 40 to 100 Mm, and shear angles from 16° to 90°. Moreover, the flare ribbons display irregular movements, such as the left ribbon fragments of the flare on October 22 sweeping a small region repeatedly, and both ribbons of the flare on October 26 moved along the same direction instead of separating from each other. These irregular movements also imply that the corresponding flare loops are complex, e.g., several sets of flare loops are twisted together. Although previous studies have suggested that the background magnetic fields prevent confined flares from erupting,based on these observations, we suggest that complex flare loop structures may be responsible for these confined flares.« less

Confinement and surface effects on the physical properties of rhombohedral-shape hematite (α-Fe{sub 2}O{sub 3}) nanocrystals

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

Luna, Carlos, E-mail: carlos.lunacd@uanl.edu.mx; Cuan-Guerra, Aída D.; Barriga-Castro, Enrique D.

2016-08-15

Highlights: • Uniform rhombohedral hematite nanocrystals (RHNCs) have been obtained. • A detailed formation mechanism of these HNCS has been proposed. • Phonon confinement effects were revealed in the RHNCS vibrational bands. • Quantum confinement effects on the optical and electronic properties were found. - Abstract: Morphological, microstructural and vibrational properties of hematite (α-Fe{sub 2}O{sub 3}) nanocrystals with a rhombohedral shape and rounded edges, obtained by forced hydrolysis of iron(III) solutions under a fast nucleation, have been investigated in detail as a function of aging time. These studies allowed us to propose a detailed formation mechanism and revealed that thesemore » nanocrystals are composed of four {104} side facets, two {110} faces at the edges of the long diagonal of the nanocrystals and two {−441} facets as the top and bottom faces. Also, the presence of nanoscopic pores and fissures was evidenced. The vibrational bands of such nanocrystals were shifted to lower frequencies in comparison with bulk hematite ones as the nanocrystal size was reduced due to phonon confinement effects. Also, the indirect and direct transition band gaps displayed interesting dependences on the aging time arising from quantum confinement and surface effects.« less

Magnetic force micropiston: an integrated force/microfluidic device for the application of compressive forces in a confined environment.

PubMed

Fisher, J K; Kleckner, N

2014-02-01

Cellular biology takes place inside confining spaces. For example, bacteria grow in crevices, red blood cells squeeze through capillaries, and chromosomes replicate inside the nucleus. Frequently, the extent of this confinement varies. Bacteria grow longer and divide, red blood cells move through smaller and smaller passages as they travel to capillary beds, and replication doubles the amount of DNA inside the nucleus. This increase in confinement, either due to a decrease in the available space or an increase in the amount of material contained in a constant volume, has the potential to squeeze and stress objects in ways that may lead to changes in morphology, dynamics, and ultimately biological function. Here, we describe a device developed to probe the interplay between confinement and the mechanical properties of cells and cellular structures, and forces that arise due to changes in a structure's state. In this system, the manipulation of a magnetic bead exerts a compressive force upon a target contained in the confining space of a microfluidic channel. This magnetic force microfluidic piston is constructed in such a way that we can measure (a) target compliance and changes in compliance as induced by changes in buffer, extract, or biochemical composition, (b) target expansion force generated by changes in the same parameters, and (c) the effects of compression stress on a target's structure and function. Beyond these issues, our system has general applicability to a variety of questions requiring the combination of mechanical forces, confinement, and optical imaging.

Magnetic force micropiston: An integrated force/microfluidic device for the application of compressive forces in a confined environment

NASA Astrophysics Data System (ADS)

Fisher, J. K.; Kleckner, N.

2014-02-01

Cellular biology takes place inside confining spaces. For example, bacteria grow in crevices, red blood cells squeeze through capillaries, and chromosomes replicate inside the nucleus. Frequently, the extent of this confinement varies. Bacteria grow longer and divide, red blood cells move through smaller and smaller passages as they travel to capillary beds, and replication doubles the amount of DNA inside the nucleus. This increase in confinement, either due to a decrease in the available space or an increase in the amount of material contained in a constant volume, has the potential to squeeze and stress objects in ways that may lead to changes in morphology, dynamics, and ultimately biological function. Here, we describe a device developed to probe the interplay between confinement and the mechanical properties of cells and cellular structures, and forces that arise due to changes in a structure's state. In this system, the manipulation of a magnetic bead exerts a compressive force upon a target contained in the confining space of a microfluidic channel. This magnetic force microfluidic piston is constructed in such a way that we can measure (a) target compliance and changes in compliance as induced by changes in buffer, extract, or biochemical composition, (b) target expansion force generated by changes in the same parameters, and (c) the effects of compression stress on a target's structure and function. Beyond these issues, our system has general applicability to a variety of questions requiring the combination of mechanical forces, confinement, and optical imaging.

Environmental Influence on the Evolution of Morphological Complexity in Machines

PubMed Central

Auerbach, Joshua E.; Bongard, Josh C.

2014-01-01

Whether, when, how, and why increased complexity evolves in biological populations is a longstanding open question. In this work we combine a recently developed method for evolving virtual organisms with an information-theoretic metric of morphological complexity in order to investigate how the complexity of morphologies, which are evolved for locomotion, varies across different environments. We first demonstrate that selection for locomotion results in the evolution of organisms with morphologies that increase in complexity over evolutionary time beyond what would be expected due to random chance. This provides evidence that the increase in complexity observed is a result of a driven rather than a passive trend. In subsequent experiments we demonstrate that morphologies having greater complexity evolve in complex environments, when compared to a simple environment when a cost of complexity is imposed. This suggests that in some niches, evolution may act to complexify the body plans of organisms while in other niches selection favors simpler body plans. PMID:24391483

Functional morphology of the honey stomach wall of European honey bees (Apis mellifera L.)

USDA-ARS?s Scientific Manuscript database

The honey bee crop, or honey stomach, is designed with cords of muscles that are numerous enough in both latitudinal and longitudinal directions to fully enclose and confine the underlying, cuticle-lines epithelium. Although appressed against the inner wall of this enclosure by the crop's contents,...

Self-Template-Directed Metal-Organic Frameworks Network and the Derived Honeycomb-Like Carbon Flakes via Confinement Pyrolysis.

PubMed

Wang, Jie; Tang, Jing; Ding, Bing; Chang, Zhi; Hao, Xiaodong; Takei, Toshiaki; Kobayashi, Naoya; Bando, Yoshio; Zhang, Xiaogang; Yamauchi, Yusuke

2018-04-01

Metal-organic frameworks (MOFs) have become a research hotspot since they have been explored as convenient precursors for preparing various multifunctional nanomaterials. However, the preparation of MOF networks with controllable flake morphology in large scale is not realized yet. Herein, a self-template strategy is developed to prepare MOF networks. In this work, layered double-metal hydroxide (LDH) and other layered metal hydroxides are used not only as a scaffold but also as a self-sacrificed metal source. After capturing the abundant metal cations identically from the LDH by the organic linkers, MOF networks are in situ formed. It is interesting that the MOF network-derived carbon materials retain the flake morphology and exhibit a unique honeycomb-like macroporous structure due to the confined shrinkage of the polyhedral facets. The overall properties of the carbon networks are adjustable according to the tailored metal compositions in LDH and the derived MOFs, which are desirable for target-oriented applications as exemplified by the electrochemical application in supercapacitors. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Confined Floodplain Dynamics on Semi-Arid Systems

NASA Astrophysics Data System (ADS)

Entwistle, N. S.

2017-12-01

Many watercourses across southern Africa are characterised by a bedrock influenced `macro-channel' created as a result of geologically recent fluvial incision into ancient planation surfaces. The rivers of the Kruger National Park in Mpumalanga Province, South Africa are no exception, displaying a varied set of channel types within a bedrock template. Contemporary flows are largely contained within the confines of this `macro-channel' and a diverse valley bottom morphology and ecology has developed in response to this flow regime coupled with intermittent fine sediment delivery from the catchment. Aerial imagery and field monitoring of the impact of two cyclone driven extreme flows and subsequent recovery phases suggests that flood impact is spatially variable with bedrock exposure greatest along watercourses already severely impacted by previous events. Subsequent system development has been characterised by the redistribution and vegetative colonisation of unconsolidated sandy sediment over bedrock. On less impacted systems vegetative induced recovery has, in contrast, been rapid with many of the species present displaying significant resilience to extreme flows forming residual pockets which are subsequently developing alongside embryonic morphologic recovery. Using these observations a model of valley bottom recovery is presented.

Effect of fast mold surface temperature evolution on iPP part morphology gradients

NASA Astrophysics Data System (ADS)

Liparoti, Sara; Sorrentino, Andrea; Guzman, Gustavo; Cakmak, Mukerrem; Titomanlio, Giuseppe

2016-03-01

The control of mold surface temperature is an important factor that affects the sample surface morphology as well as the structural gradients (orientation crystal size, and type) as well as cooling stresses. The frozen layer thickness formed during the filling stage also has a very significant effect on the flow resistance and thus on the resulting pressure drop and flow length in thin wall parts. The possibility to have a hot mold during filling and a quick cooling soon afterward is a significant process enhancement particularly for specialized applications such as micro injection molding and for the reproduction of micro structured surfaces. Up to now, several methods (electromagnetic, infrared, hot vapor fleshing etc,) were tried to achieve fast temperature evolution of the mold. Unfortunately, all these methods require a complex balance between thermal and mechanical problems, equipment cost, energy consumption, safety, molding cycle time and part quality achievable. In this work, a thin electrical resistance was designed and used to generate a fast and confined temperature variation on mold surface (by joule effect). Since the whole temperature evolution can take place in a few seconds, one can couple the advantages of a high surface temperature during filling with the advantages of a low mold temperature, fast cooling and low heating dissipation. Some experiments were performed with a commercial iPP resin. The effects of the surface temperature and of the heating time (under constant electric power) on surface finishing and on the final morphology (thickness and structure of the different layers) are explored and discussed.

Effect of fast mold surface temperature evolution on iPP part morphology gradients

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

Liparoti, Sara; Sorrentino, Andrea; Guzman, Gustavo

The control of mold surface temperature is an important factor that affects the sample surface morphology as well as the structural gradients (orientation crystal size, and type) as well as cooling stresses. The frozen layer thickness formed during the filling stage also has a very significant effect on the flow resistance and thus on the resulting pressure drop and flow length in thin wall parts. The possibility to have a hot mold during filling and a quick cooling soon afterward is a significant process enhancement particularly for specialized applications such as micro injection molding and for the reproduction of micromore » structured surfaces. Up to now, several methods (electromagnetic, infrared, hot vapor fleshing etc,) were tried to achieve fast temperature evolution of the mold. Unfortunately, all these methods require a complex balance between thermal and mechanical problems, equipment cost, energy consumption, safety, molding cycle time and part quality achievable. In this work, a thin electrical resistance was designed and used to generate a fast and confined temperature variation on mold surface (by joule effect). Since the whole temperature evolution can take place in a few seconds, one can couple the advantages of a high surface temperature during filling with the advantages of a low mold temperature, fast cooling and low heating dissipation. Some experiments were performed with a commercial iPP resin. The effects of the surface temperature and of the heating time (under constant electric power) on surface finishing and on the final morphology (thickness and structure of the different layers) are explored and discussed.« less

Individual Neurons Confined to Distinct Antennal-Lobe Tracts in the Heliothine Moth: Morphological Characteristics and Global Projection Patterns

PubMed Central

Ian, Elena; Zhao, Xin C.; Lande, Andreas; Berg, Bente G.

2016-01-01

To explore fundamental principles characterizing chemosensory information processing, we have identified antennal-lobe projection neurons in the heliothine moth, including several neuron types not previously described. Generally, odor information is conveyed from the primary olfactory center of the moth brain, the antennal lobe, to higher brain centers via projection neuron axons passing along several parallel pathways, of which the medial, mediolateral, and lateral antennal-lobe tract are considered the classical ones. Recent data have revealed the projections of the individual tracts more in detail demonstrating three main target regions in the protocerebrum; the calyces are innervated mainly by the medial tract, the superior intermediate protocerebrum by the lateral tract exclusively, and the lateral horn by all tracts. In the present study, we have identified, via iontophoretic intracellular staining combined with confocal microscopy, individual projection neurons confined to the tracts mentioned above, plus two additional ones. Further, using the visualization software AMIRA, we reconstructed the stained neurons and registered the models into a standard brain atlas, which allowed us to compare the termination areas of individual projection neurons both across and within distinct tracts. The data demonstrate a morphological diversity of the projection neurons within distinct tracts. Comparison of the output areas of the neurons confined to the three main tracts in the lateral horn showed overlapping terminal regions for the medial and mediolateral tracts; the lateral tract neurons, on the contrary, targeted mostly other output areas in the protocerebrum. PMID:27822181

Synthesis and photocatalytic studies of ZnS nanoparticles from heteroleptic complex of Zn(II) 1-cyano-1-carboethoxy-2,-2-ethylenedithiolato diisopropylthiourea and its adducts with N-donor ligands

NASA Astrophysics Data System (ADS)

Osuntokun, Jejenija; Ajibade, Peter A.; Onwudiwe, Damian C.

2016-12-01

Zinc complexes of the type [Zn(diptu)2(ced)] (1), [Zn(diptu)2(ced)py] (2), [Zn(diptu)2(ced)bpy] (3), and [Zn(diptu)2(ced)phen] (4), (where (diptu)2(ced) = 1-cyano-1-carboethoxyethylene-2,2-dithiolato-κS,S‧-bis(N,N-diisopropyllthiourea), py = pyridine, bpy = 2, 2‧ bipyridine and phen = 1, 10 phenanthroline have been synthesized and characterized by elemental analyses, Fourier transform infra-red (FTIR) and Nuclear magnetic resonance (NMR) spectroscopies. The parent complex (1) was formulated as four coordinate species, which gave rise to 5 coordinate complex in (2) and six coordinate compounds in (3) and (4), with the dithiolate acting as bidentate chelating ligand. The complexes were used as single-source precursors for the synthesis of HDA-capped ZnS nanoparticles. The nanoparticles gave different morphologies with sizes in the range of 1.92-4.72 nm as observed from the TEM analysis and supported by XRD. The UV-vis spectroscopy showed that all the ZnS nanoparticles are blue shifted, with respect to the bulk, which confirmed quantum confinement. The photoluminescence spectra showed narrow and broad emission peaks around 290 and 360 nm which are ascribed to spontaneous emission peaks from band to band transition and surface states respectively. Photocatalytic activities of all the nanoparticles were investigated with methylene blue (MB) acting as the organic dye, and the UV-vis spectral revealed a gradual decrease in absorption peak that confirmed the degradation of the MB.

PERMANGANATE FIXATION OF THE GOLGI COMPLEX AND OTHER CYTOPLASMIC STRUCTURES OF MAMMALIAN TESTES

PubMed Central

Mollenhauer, Hilton H.; Zebrun, William

1960-01-01

Observations on the fine structure of KMnO4-fixed testes of small mammals (guinea pig, rat, and mouse) reveal certain morphological differences between the spermatogenic and Sertoli cells which have not been demonstrated in the same tissue fixed with OsO4. Aggregates of minute circular profiles, much smaller than the spherical Golgi vesicles, are described in close association with the Golgi complex of developing spermatids. Groups of dense flattened vesicles, individually surrounded by a membrane of different dimensions than that which bounds most of the other cell organelles, appear dispersed within the cytoplasm of some spermatogenic cells. Flattened vesicles of greater density than those belonging to the Golgi complex are reported confined to the inner Golgi zone of developing guinea pig spermatids between the Golgi cisternae and the head cap. The profiles of endoplasmic reticulum within spermatocytes appear shorter, wider, and more tortuous than those of Sertoli cells. Minute cytoplasmic particles approximately 300 A in diameter and of high electron opacity appear randomly disposed in some Sertoli cells. Groups of irregular-shaped ovoid bodies within the developing spermatids are described as resembling portions of cytoplasm from closely adjacent spermatids. Interpretation is presented regarding the fine structure of KMnO4-fixed testes in view of what has already been reported for mammalian testes fixed in OsO4. PMID:13771855

The influence of semantic and morphological complexity of verbs on sentence recall: Implications for the nature of conceptual representation and category-specific deficits.

PubMed

Mobayyen, Forouzan; de Almeida, Roberto G

2005-03-01

One hundred and forty normal undergraduate students participated in a Proactive Interference (PI) experiment with sentences containing verbs from four different semantic and morphological classes (lexical causatives, morphological causatives, and morphologically complex and simplex perception verbs). Past research has shown significant PI build-up effects for semantically and morphologically complex verbs in isolation (de Almeida & Mobayyen, 2004). The results of the present study show that, when embedded into sentence contexts, semantically and morphologically complex verbs do not produce significant PI build-up effects. Different verb classes, however, yield different recall patterns: sentences with semantically complex verbs (e.g., causatives) were recalled significantly better than sentences with semantically simplex verbs (e.g., perception verbs). The implications for the nature of both verb-conceptual representations and category-specific semantic deficits are discussed.

The antagonistic modulation of Arp2/3 activity by N-WASP, WAVE2 and PICK1 defines dynamic changes in astrocyte morphology

PubMed Central

Murk, Kai; Blanco Suarez, Elena M.; Cockbill, Louisa M. R.; Banks, Paul; Hanley, Jonathan G.

2013-01-01

Summary Astrocytes exhibit a complex, branched morphology, allowing them to functionally interact with numerous blood vessels, neighboring glial processes and neuronal elements, including synapses. They also respond to central nervous system (CNS) injury by a process known as astrogliosis, which involves morphological changes, including cell body hypertrophy and thickening of major processes. Following severe injury, astrocytes exhibit drastically reduced morphological complexity and collectively form a glial scar. The mechanistic details behind these morphological changes are unknown. Here, we investigate the regulation of the actin-nucleating Arp2/3 complex in controlling dynamic changes in astrocyte morphology. In contrast to other cell types, Arp2/3 inhibition drives the rapid expansion of astrocyte cell bodies and major processes. This intervention results in a reduced morphological complexity of astrocytes in both dissociated culture and in brain slices. We show that this expansion requires functional myosin II downstream of ROCK and RhoA. Knockdown of the Arp2/3 subunit Arp3 or the Arp2/3 activator N-WASP by siRNA also results in cell body expansion and reduced morphological complexity, whereas depleting WAVE2 specifically reduces the branching complexity of astrocyte processes. By contrast, knockdown of the Arp2/3 inhibitor PICK1 increases astrocyte branching complexity. Furthermore, astrocyte expansion induced by ischemic conditions is delayed by PICK1 knockdown or N-WASP overexpression. Our findings identify a new morphological outcome for Arp2/3 activation in restricting rather than promoting outwards movement of the plasma membrane in astrocytes. The Arp2/3 regulators PICK1, and N-WASP and WAVE2 function antagonistically to control the complexity of astrocyte branched morphology, and this mechanism underlies the morphological changes seen in astrocytes during their response to pathological insult. PMID:23843614

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

Saxena, Shailendra K., E-mail: phd1211512@iiti.ac.in; Sahu, Gayatri; Sagdeo, Pankaj R.

Quantum confinement effect has been studied in cheese like silicon nano-structures (Ch-SiNS) fabricated by metal induced chemical etching using different etching times. Scanning electron microscopy is used for the morphological study of these Ch-SiNS. A visible photoluminescence (PL) emission is observed from the samples under UV excitation at room temperature due to quantum confinement effect. The average size of Silicon Nanostructures (SiNS) present in the samples has been estimated by bond polarizability model using Raman Spectroscopy from the red-shift observed from SiNSs as compared to its bulk counterpart. The sizes of SiNS present in the samples decreases as etching timemore » increase from 45 to 75 mintunes.« less

Strain-induced fundamental optical transition in (In,Ga)As/GaP quantum dots

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

Robert, C., E-mail: cedric.robert@insa-rennes.fr, E-mail: cedric.robert@tyndall.ie; Pedesseau, L.; Cornet, C.

The nature of the ground optical transition in an (In,Ga)As/GaP quantum dot is thoroughly investigated through a million atoms supercell tight-binding simulation. Precise quantum dot morphology is deduced from previously reported scanning-tunneling-microscopy images. The strain field is calculated with the valence force field method and has a strong influence on the confinement potentials, principally, for the conduction band states. Indeed, the wavefunction of the ground electron state is spatially confined in the GaP matrix, close to the dot apex, in a large tensile strain region, having mainly Xz character. Photoluminescence experiments under hydrostatic pressure strongly support the theoretical conclusions.

Landslides in Valles Marineris, Mars.

USGS Publications Warehouse

Lucchitta, B.K.

1979-01-01

Large landslides in the Martian equatorial troughs have been investigated with respect to morphology, geologic structure of the troughs, time of emplacement, similarity to terrestrial landslides, and origin and mechanism of transport. The morphologic variations of the landslides can be attributed mainly to their degree of confinement on trough floors. The huge size of many landslides is due to their occurrence on fault scarps that may have attained several kilometers in height in the absence of vigorous fluvial erosion on Mars. The mechanical efficiency of the Martian landslides is high but in accord with predictions from large landslides on earth. -from Author

Various complexity measures in confined hydrogen atom

NASA Astrophysics Data System (ADS)

Majumdar, Sangita; Mukherjee, Neetik; Roy, Amlan K.

2017-11-01

Several well-known statistical measures similar to LMC and Fisher-Shannon complexity have been computed for confined hydrogen atom in both position (r) and momentum (p) spaces. Further, a more generalized form of these quantities with Rényi entropy (R) is explored here. The role of scaling parameter in the exponential part is also pursued. R is evaluated taking order of entropic moments α, β as (2/3, 3) in r and p spaces. Detailed systematic results of these measures with respect to variation of confinement radius rc is presented for low-lying states such as, 1 s - 3 d, 4 f and 5 g . For nodal states, such as 2 s, 3 s and 3 p , as rc progresses there appears a maximum followed by a minimum in r space, having certain values of the scaling parameter. However, the corresponding p-space results lack such distinct patterns. This study reveals many other interesting features.

Mitochondrial and Nucleolar Localization of Cysteine Desulfurase Nfs and the Scaffold Protein Isu in Trypanosoma brucei

PubMed Central

Kovářová, Julie; Horáková, Eva; Changmai, Piya; Vancová, Marie

2014-01-01

Trypanosoma brucei has a complex life cycle during which its single mitochondrion is subjected to major metabolic and morphological changes. While the procyclic stage (PS) of the insect vector contains a large and reticulated mitochondrion, its counterpart in the bloodstream stage (BS) parasitizing mammals is highly reduced and seems to be devoid of most functions. We show here that key Fe-S cluster assembly proteins are still present and active in this organelle and that produced clusters are incorporated into overexpressed enzymes. Importantly, the cysteine desulfurase Nfs, equipped with the nuclear localization signal, was detected in the nucleolus of both T. brucei life stages. The scaffold protein Isu, an interacting partner of Nfs, was also found to have a dual localization in the mitochondrion and the nucleolus, while frataxin and both ferredoxins are confined to the mitochondrion. Moreover, upon depletion of Isu, cytosolic tRNA thiolation dropped in the PS but not BS parasites. PMID:24243795

Mitochondrial and nucleolar localization of cysteine desulfurase Nfs and the scaffold protein Isu in Trypanosoma brucei.

PubMed

Kovárová, Julie; Horáková, Eva; Changmai, Piya; Vancová, Marie; Lukeš, Julius

2014-03-01

Trypanosoma brucei has a complex life cycle during which its single mitochondrion is subjected to major metabolic and morphological changes. While the procyclic stage (PS) of the insect vector contains a large and reticulated mitochondrion, its counterpart in the bloodstream stage (BS) parasitizing mammals is highly reduced and seems to be devoid of most functions. We show here that key Fe-S cluster assembly proteins are still present and active in this organelle and that produced clusters are incorporated into overexpressed enzymes. Importantly, the cysteine desulfurase Nfs, equipped with the nuclear localization signal, was detected in the nucleolus of both T. brucei life stages. The scaffold protein Isu, an interacting partner of Nfs, was also found to have a dual localization in the mitochondrion and the nucleolus, while frataxin and both ferredoxins are confined to the mitochondrion. Moreover, upon depletion of Isu, cytosolic tRNA thiolation dropped in the PS but not BS parasites.

A lateral signalling pathway coordinates shape volatility during cell migration

PubMed Central

Zhang, Liang; Luga, Valbona; Armitage, Sarah K.; Musiol, Martin; Won, Amy; Yip, Christopher M.; Plotnikov, Sergey V.; Wrana, Jeffrey L.

2016-01-01

Cell migration is fundamental for both physiological and pathological processes. Migrating cells usually display high dynamics in morphology, which is orchestrated by an integrative array of signalling pathways. Here we identify a novel pathway, we term lateral signalling, comprised of the planar cell polarity (PCP) protein Pk1 and the RhoGAPs, Arhgap21/23. We show that the Pk1–Arhgap21/23 complex inhibits RhoA, is localized on the non-protrusive lateral membrane cortex and its disruption leads to the disorganization of the actomyosin network and altered focal adhesion dynamics. Pk1-mediated lateral signalling confines protrusive activity and is regulated by Smurf2, an E3 ubiquitin ligase in the PCP pathway. Furthermore, we demonstrate that dynamic interplay between lateral and protrusive signalling generates cyclical fluctuations in cell shape that we quantify here as shape volatility, which strongly correlates with migration speed. These studies uncover a previously unrecognized lateral signalling pathway that coordinates shape volatility during productive cell migration. PMID:27226243

Vibrational nonlinear optical properties of spatially confined weakly bound complexes.

PubMed

Zaleśny, Robert; Chołuj, Marta; Kozłowska, Justyna; Bartkowiak, Wojciech; Luis, Josep M

2017-09-13

This study focuses on the theoretical description of the influence of spatial confinement on the electronic and vibrational contributions to (hyper)polarizabilities of two dimeric hydrogen bonded systems, namely HCNHCN and HCNHNC. A two-dimensional analytical potential is employed to render the confining environment (e.g. carbon nanotube). Based on the results of the state-of-the-art calculations, performed at the CCSD(T)/aug-cc-pVTZ level of theory, we established that: (i) the influence of spatial confinement increases with increasing order of the electrical properties, (ii) the effect of spatial confinement is much larger in the case of the electronic than vibrational contribution (this holds for each order of the electrical properties) and (iii) the decrease in the static nuclear relaxation first hyperpolarizability upon the increase of confinement strength is mainly due to changes in the harmonic term, however, in the case of nuclear relaxation second hyperpolarizability the anharmonic terms contribute more to the drop of this property.

Water Dynamics in Gyroid Phases of Self-Assembled Gemini Surfactants

DOE PAGES

Roy, Santanu; Skoff, David; Perroni, Dominic V.; ...

2016-02-14

Water-mediated ion transport through functional nanoporous materials depends on the dynamics of water confined within a given nanostructured morphology. In this study, we investigate hydrogen-bonding dynamics of interfacial water within a ‘normal’ (Type I) lyotropic gyroid phase formed by a gemini dicarboxylate surfactant self-assembly using a combina- tion of 2DIR spectroscopy and molecular dynamics simulations. Experiments and simulations demonstrate that water dynamics in the normal gyroid phase is one order of magnitude slower than that in bulk water, due to specific interactions between water, the ionic surfactant headgroups, and counterions. However, the dynamics of water in the normal gyroid phasemore » are faster than those of water confined in a reverse spherical micelle of a sulfonate surfactant, given that the water pool in the reverse micelle and the water pore in the gyroid phase have roughly the same diameters. This difference in confined water dynamics likely arises from the significantly reduced curvature- induced frustration at the convex interfaces of the normal gyroid, as compared to the concave interfaces of a reverse spherical micelle. These detailed insights into confined water dynamics may guide the future design of artificial membranes that rapidly transport protons and other ions.« less

Fabrication of hierarchical porous N-doping carbon membrane by using ;confined nanospace deposition; method for supercapacitor

NASA Astrophysics Data System (ADS)

Wang, Guoxu; Liu, Meng; Du, Juan; Liu, Lei; Yu, Yifeng; Sha, Jitong; Chen, Aibing

2018-03-01

The membrane carbon materials with hierarchical porous architecture are attractive because they can provide more channels for ion transport and shorten the ions transport path. Herein, we develop a facile way based on "confined nanospace deposition" to fabricate N-dopi-ng three dimensional hierarchical porous membrane carbon material (N-THPMC) via coating the nickel nitrate, silicate oligomers and triblock copolymer P123 on the branches of commercial polyamide membrane (PAM). During high temperature treatment, the mesoporous silica layer and Ni species serve as a "confined nanospace" and catalyst respectively, which are indispensable elements for formation of carbon framework, and the gas-phase carbon precursors which derive from the decomposition of PAM are deposited into the "confined nanospace" forming carbon framework. The N-THPMC with hierarchical macro/meso/microporous structure, N-doping (2.9%) and large specific surface area (994m2 g-1) well inherits the membrane morphology and hierarchical porous structure of PAM. The N-THPMC as electrode without binder exhibits a specific capacitance of 252 F g-1 at the current density of 1 A g-1 in 6 M KOH electrolyte and excellent cycling stability of 92.7% even after 5000 cycles.

Interaction between a steady detonation wave in nitromethane and geometrical complex confinement defects.

NASA Astrophysics Data System (ADS)

Crouzet, Blandine; Carion, Noel; Manczur, Philippe

2007-06-01

It is well known that detonation propagation is altered if the explosive is encased in an inert confining material. But in practice, explosives are rarely used without confinement and particular attention must be paid to the problem of explosive/confinement interactions. In this work, we have carried out two copper cylinder expansion tests on nitromethane. They differ from the classical cylinder test in that the liner includes evenly-spaced protruding circular defects. The aim is to study how a detonation front propagating in the liquid explosive interacts with the confining material defects. The subsequent motion of the metal, accelerated by the expanding detonation products, is measured using a range of diagnostic techniques: electrical probes, rapid framing camera, glass block associated with streak camera and velocity laser interferometers. The different experimental records have been examined in the light of a simple 2D theoretical shock polar analysis and 2D numerical simulations.

Morphological Decomposition Based on the Analysis of Orthography

ERIC Educational Resources Information Center

Rastle, Kathleen; Davis, Matthew H.

2008-01-01

Recent theories of morphological processing have been dominated by the notion that morphologically complex words are decomposed into their constituents on the basis of their semantic properties. In this article we argue that the weight of evidence now suggests that the recognition of morphologically complex words begins with a rapid morphemic…

Structural dependence of MEH-PPV chromism in solution.

PubMed

de Magalhães, Carlos E T; Savedra, Ranylson M L; Dias, Karina S; Ramos, Rodrigo; Siqueira, Melissa F

2017-03-01

The chromism observed in the MEH-PPV polymer in tetrahydrofuran (THF) solution is discussed as a function of the structural morphology of the backbone chains. To evaluate this phenomenon, we carried out simulations employing a hybrid methodology using molecular dynamics and quantum mechanical approaches. Our results support the hypothesis that the morphological order-disorder transition is related to the change from red to blue phase observed experimentally. The morphological disorder is associated with total or partial twisted arrangements in the polymer backbone, which induces an electronic conjugation length more confined to shorter segments. In addition, the main band of the MEH-PPV UV-Vis spectrum at the lower wavelength is related to the blue phase, in contrast to the red phase found for the more planar backbone chains.

Real-Time Reciprocal Space Mapping of Nano-Islands Induced by Quantum Confinement

NASA Astrophysics Data System (ADS)

Hong, Hawoong; Gray, Aaron; Chiang, T.-C.

2011-01-01

The effects of quantum confinement have been observed pronouncedly in the island morphology of Pb thin films. The evolution of these nano-islands on Si (111)-(7 × 7) and sapphire (001) surfaces has been studied with a new X-ray diffraction method. A charge-coupled device (CCD) camera was used to collect two- and three-dimensional (2-D and 3-D, respectively) maps of the surface X-ray diffraction in real time. Large ranges of the reflectivity curves, with rocking curves at every point on the reflectivity curves, could be measured continuously in a relatively short amount of time. The abundance of information from 2-D k-space maps reveals clear changes in the growth modes of these thin Pb films. With the 3-D extension of this method, it was possible to observe the ordering of the islands. The islands maintain a nearly uniform interisland distance but lack any angular correlation. The interisland ordering is correlated well with the development of "magic" island heights caused by quantum confinement.

ZnO nanostructures with different morphology for enhanced photocatalytic activity

NASA Astrophysics Data System (ADS)

Peter, I. John; Praveen, E.; Vignesh, G.; Nithiananthi, P.

2017-12-01

ZnO nanomaterials of different morphologies have been synthesized and the effect of morphology on Photocatalytic activity on natural dye has been investigated. Crystalline size and lattice strain of the synthesized particles are determined by XRD analysis and Williamson-Hall (W-H) method respectively. All other important physical parameters such as strain, stress and energy density values are also calculated using W-H analysis using different models such as uniform deformation model, uniform deformation stress model and uniform deformation energy density model. A shift in the peak of FTIR spectrum of ZnO is observed due to morphology effects. The SEM analysis reveals that the synthesized ZnO nanoparticles appear as flake, rod and dot. ZnO quantum dot exhibits higher photocatalytic activity comparing to the other morphologies. Larger surface area, high adsorption rate, large charge separation and the slow recombination of electrons/holes in ZnO dots establish dots as favorable morphology for good photocatalysis. Among the three, ZnO quantum dot shows three-times enhancement in the kinetic rate constants of photocatalysis. The results confirm that availability of specific (active) surface area, photocatalytic potential and quantum confinement of photo-induced carriers differ with morphology.

Innovative NMR strategies for complex macromolecules

USDA-ARS?s Scientific Manuscript database

In recent years there has been an increasing research emphasis on complex macromolecular systems. These include polymers with precise control of structures, multicomponent systems with higher degrees of organization, polymers involved in micelles, interfaces, and confined environments, nanochemistr...

Field Investigations of the July 2015 Pyroclastic Density Current Deposits of Volcán de Colima, Mexico

NASA Astrophysics Data System (ADS)

Atlas, Z. D.; Macorps, E.; Charbonnier, S. J.; Varley, N. R.

2016-12-01

Small-volume pyroclastic density currents (PDCs) occur relatively frequently and pose severe threats to surrounding populations and infrastructures at active explosive volcanoes. They are characterized by short duration and complex multiphase flow dynamics due to time and space variability in their properties, which include amongst others, particle concentration, granulometry, componentry, bulk rheology and velocity. Field investigations of the deposits emplaced by small-volume concentrated PDCs aim to improve our understanding of the transport and depositional processes of these flows: time and space variations in flow dynamics within a PDC moving downslope will reflect on the distribution, grainsize and component characteristics of its deposits. Our study focuses on the recent events of July 10th and 11th, 2015 at Volcán de Colima (Mexico) where the collapse of the recent lava dome complex and a portion of the southern crater rim led to the emplacement of successive pulses of small-volume concentrated PDCs on the southern flank, along the Montegrande and San Antonio ravines. A 3-dimensional field analysis of the PDCs' deposit architecture, total grain size distribution and component properties together with a geomorphic analysis of the affected ravines provide new insights on the lateral and vertical variations of flow dynamics for some of these small-volume concentrated PDCs. Preliminary results reveal three stratigraphic units with massive block, lapilli, ash facies within the valley confined and concentrated overbank deposits with increasing content in fines with distance from the summit, suggesting an increase in fragmentation processes within the PDCs. The middle unit is characterized by a finer grainsize, a higher accidental lithic content and a lower free crystal content. Moreover, direct correlations are found between rapid changes in channel morphology and generation of overbank (unconfined) flows that escaped valley confines, which could provide the basis for defining hazard zonations of key areas at risk from future eruptions at Colima.

Confinement induced ordering in dewetting of ultra-thin polymer bilayers on nanopatterned substrates.

PubMed

Bhandaru, Nandini; Das, Anuja; Mukherjee, Rabibrata

2016-01-14

We report the dewetting of a thin bilayer of polystyrene (PS) and poly(methylmethacrylate) (PMMA) on a topographically patterned nonwettable substrate comprising an array of pillars, arranged in a square lattice. With a gradual increase in the concentration of the PMMA solution (Cn-PMMA), the morphology of the bottom layer changes to: (1) an aligned array of spin dewetted droplets arranged along substrate grooves at very low Cn-PMMA; (2) an interconnected network of threads surrounding each pillar at intermediate Cn-PMMA; and (3) a continuous bottom layer at higher Cn-PMMA. On the other hand the morphology of the PS top layer depends largely on the nature of the pre-existing bottom layer, in addition to Cn-PS. An ordered array of PMMA core-PS shell droplets forms right after spin coating when both Cn-PMMA and Cn-PS are very low. Bilayers with all other initial configurations evolve during thermal annealing, resulting in a variety of ordered structures. Unique morphologies realized include laterally coexisting structures of the two polymers confined within the substrate grooves due to initial rupture of the bottom layer on the substrate followed by a squeezing flow of the top layer; an array of core-shell and single polymer droplets arranged in an alternating order etc., to highlight a few. Such structures cannot be fabricated by any stand-alone lithography technique. On the other hand, in some cases the partially dewetted bottom layer imparts stability to an intact top PS layer against dewetting. Apart from ordering, under certain specific conditions significant miniaturization and downsizing of dewetted feature periodicity and dimension as compared to dewetting of a single layer on a flat substrate is observed. With the help of a morphology phase diagram we show that ordering is achieved over a wide combination of Cn-PMMA and Cn-PS, though the morphology and dewetting pathway differs significantly with variation in the thickness of the individual layers.

Non-covalent synthesis of supermicelles with complex architectures using spatially confined hydrogen-bonding interactions

PubMed Central

Li, Xiaoyu; Gao, Yang; Boott, Charlotte E.; Winnik, Mitchell A.; Manners, Ian

2015-01-01

Nature uses orthogonal interactions over different length scales to construct structures with hierarchical levels of order and provides an important source of inspiration for the creation of synthetic functional materials. Here, we report the programmed assembly of monodisperse cylindrical block comicelle building blocks with crystalline cores to create supermicelles using spatially confined hydrogen-bonding interactions. We also demonstrate that it is possible to further program the self-assembly of these synthetic building blocks into structures of increased complexity by combining hydrogen-bonding interactions with segment solvophobicity. The overall approach offers an efficient, non-covalent synthesis method for the solution-phase fabrication of a range of complex and potentially functional supermicelle architectures in which the crystallization, hydrogen-bonding and solvophobic interactions are combined in an orthogonal manner. PMID:26337527

Molecular Species Delimitation in the Racomitrium canescens Complex (Grimmiaceae) and Implications for DNA Barcoding of Species Complexes in Mosses

PubMed Central

Stech, Michael; Veldman, Sarina; Larraín, Juan; Muñoz, Jesús; Quandt, Dietmar; Hassel, Kristian; Kruijer, Hans

2013-01-01

In bryophytes a morphological species concept is still most commonly employed, but delimitation of closely related species based on morphological characters is often difficult. Here we test morphological species circumscriptions in a species complex of the moss genus Racomitrium, the R. canescens complex, based on variable DNA sequence markers from the plastid (rps4-trnT-trnL region) and nuclear (nrITS) genomes. The extensive morphological variability within the complex has led to different opinions about the number of species and intraspecific taxa to be distinguished. Molecular phylogenetic reconstructions allowed to clearly distinguish all eight currently recognised species of the complex plus a ninth species that was inferred to belong to the complex in earlier molecular analyses. The taxonomic significance of intraspecific sequence variation is discussed. The present molecular data do not support the division of the R. canescens complex into two groups of species (subsections or sections). Most morphological characters, albeit being in part difficult to apply, are reliable for species identification in the R. canescens complex. However, misidentification of collections that were morphologically intermediate between species questioned the suitability of leaf shape as diagnostic character. Four partitions of the molecular markers (rps4-trnT, trnT-trnL, ITS1, ITS2) that could potentially be used for molecular species identification (DNA barcoding) performed almost equally well concerning amplification and sequencing success. Of these, ITS1 provided the highest species discrimination capacity and should be considered as a DNA barcoding marker for mosses, especially in complexes of closely related species. Molecular species identification should be complemented by redefining morphological characters, to develop a set of easy-to-use molecular and non-molecular identification tools for improving biodiversity assessments and ecological research including mosses. PMID:23341927

Computational Nonlinear Morphology with Emphasis on Semitic Languages. Studies in Natural Language Processing.

ERIC Educational Resources Information Center

Kiraz, George Anton

This book presents a tractable computational model that can cope with complex morphological operations, especially in Semitic languages, and less complex morphological systems present in Western languages. It outlines a new generalized regular rewrite rule system that uses multiple finite-state automata to cater to root-and-pattern morphology,…

The effects of morphological irregularity on the mechanical behavior of interdigitated biological sutures under tension.

PubMed

Liu, Lei; Jiang, Yunyao; Boyce, Mary; Ortiz, Christine; Baur, Jeffery; Song, Juha; Li, Yaning

2017-06-14

Irregular interdigitated morphology is prevalent in biological sutures in nature. Suture complexity index has long been recognized as the most important morphological parameter to govern the mechanical properties of biological sutures. However, the suture complexity index alone does not reflect all aspects of suture morphology. The goal of this investigation was to determine that besides suture complexity index, whether the degree of morphological irregularity of biological sutures has influences on the mechanical properties, and if there is any, how to quantify these influences. To explore these issues, theoretical and finite element (FE) suture models with the same suture complexity index but different levels of morphological irregularity were developed. The quasi-static stiffness, strength for damage initiation and post-failure process of irregular sutures were studied. It was shown that for the same suture complexity index, when the level of morphological irregularity increases, the overall strain to failure will increase while tensile stiffness is retained; also, the total energy to fracture increases with a sacrifice in strength to damage initiation. These results reveal that morphological irregularity is another important independent parameter to govern and balance the mechanical properties of biological sutures. Therefore, from the mechanics point of view, the prevalence of irregular suture morphology in nature is a merit, not a defect. Copyright © 2017 Elsevier Ltd. All rights reserved.

Crystallization of Polymers in Confined Environments: Structural Development of Semi-crystalline Polymer-Layered Silicate Nanocomposites

NASA Astrophysics Data System (ADS)

Vaia, Richard A.; Lincoln, Derek M.; Wang, Zhi-Gang; Hsiao, Benjamin S.; Krishnamoorti, Ramanan

2000-03-01

Over the last decade, the utility of ultrafine dispersions of inorganic nanoparticles to enhance polymer performance and function as precursors to form self-passivating / self-healing inorganic coatings on the polymer surface has been established. Before developing the fundamental structure-property relationships though, a detailed understanding of processing / morphology relationships is necessary. As with other multiphase systems exhibiting nano (1-100 nm) and meso (100-500 nm) order (such as biopolymers, block-copolymers, colloidal suspensions, liquid crystals), physical properties ranging from toughness to optical clarity are determined by morphology on various length scales which in turn arise from processing history. This is anticipated to be especially important for blends containing two or more constituents with fundamental structural features on the nanoscale, such as crystal lamellae and aluminosilicate sheets. Small-angle x-ray scattering experiments with synchrotron radiation reveal the presence of ultra-long range (20-60 nm) mesoscopic ordering of the layered silicate in molten polyamide 6-layered silicate nanocomposites. This superstructure of these semi-rigid inorganic sheets provides a confined environment to examine the crystallization of polyamide 6 with traditional bulk characterization techniques. In addition to a change lamellae organization and lamellae size, the presence of the aluminosilicate layers and extent of interfacial interactions (end-tethered v. physiadsorbed chains) substantially alters the nucleation rate, growth kinetics and Brill transition of the crystal phase as revealed by isothermal crystallization experiments monitored in-situ with synchrotron radiation. These exfoliated nanocomposites provide new opportunities to investigate confined polymer crystallization as well as provide insight into the origin of various property enhancements in these systems.

Confinement regulates complex biochemical networks: initiation of blood clotting by "diffusion acting".

PubMed

Shen, Feng; Pompano, Rebecca R; Kastrup, Christian J; Ismagilov, Rustem F

2009-10-21

This study shows that environmental confinement strongly affects the activation of nonlinear reaction networks, such as blood coagulation (clotting), by small quantities of activators. Blood coagulation is sensitive to the local concentration of soluble activators, initiating only when the activators surpass a threshold concentration, and therefore is regulated by mass transport phenomena such as flow and diffusion. Here, diffusion was limited by decreasing the size of microfluidic chambers, and it was found that microparticles carrying either the classical stimulus, tissue factor, or a bacterial stimulus, Bacillus cereus, initiated coagulation of human platelet-poor plasma only when confined. A simple analytical argument and numerical model were used to describe the mechanism for this phenomenon: confinement causes diffusible activators to accumulate locally and surpass the threshold concentration. To interpret the results, a dimensionless confinement number, Cn, was used to describe whether a stimulus was confined, and a Damköhler number, Da(2), was used to describe whether a subthreshold stimulus could initiate coagulation. In the context of initiation of coagulation by bacteria, this mechanism can be thought of as "diffusion acting", which is distinct from "diffusion sensing". The ability of confinement and diffusion acting to change the outcome of coagulation suggests that confinement should also regulate other biological "on" and "off" processes that are controlled by thresholds.

Single molecule tracking fluorescence microscopy in mitochondria reveals highly dynamic but confined movement of Tom40

NASA Astrophysics Data System (ADS)

Kuzmenko, Anton; Tankov, Stoyan; English, Brian P.; Tarassov, Ivan; Tenson, Tanel; Kamenski, Piotr; Elf, Johan; Hauryliuk, Vasili

2011-12-01

Tom40 is an integral protein of the mitochondrial outer membrane, which as the central component of the Translocase of the Outer Membrane (TOM) complex forms a channel for protein import. We characterize the diffusion properties of individual Tom40 molecules fused to the photoconvertable fluorescent protein Dendra2 with millisecond temporal resolution. By imaging individual Tom40 molecules in intact isolated yeast mitochondria using photoactivated localization microscopy with sub-diffraction limited spatial precision, we demonstrate that Tom40 movement in the outer mitochondrial membrane is highly dynamic but confined in nature, suggesting anchoring of the TOM complex as a whole.

A modified preparation procedure for carbon nanotube-confined Nd/Na heterobimetallic catalyst for anti-selective catalytic asymmetric nitroaldol reactions.

PubMed

Sureshkumar, Devarajulu; Hashimoto, Kazuki; Kumagai, Naoya; Shibasaki, Masakatsu

2013-11-15

A recyclable asymmetric metal-based catalyst is a rare entity among the vast collection of asymmetric catalysts developed so far. Recently we found that the combination of a self-assembling metal-based asymmetric catalyst and multiwalled carbon nanotubes (MWNTs) produced a highly active and recyclable catalyst in which the catalytically active metal complex was dispersed in the MWNT network. Herein we describe an improved preparation procedure and full details of a Nd/Na heterobimetallic complex confined in MWNTs. Facilitated self-assembly of the catalyst with MWNTs avoided the sacrificial use of excess chiral ligand for the formation of the heterobimetallic complex, improving the loading ratio of the catalyst components. Eighty-five percent of the catalyst components were incorporated onto MWNTs to produce the confined catalyst, which was a highly efficient and recyclable catalyst for the anti-selective asymmetric nitroaldol reaction. The requisite precautions for the catalyst preparation to elicit reproducible catalytic performance are summarized. Superior catalytic profiles over the prototype catalyst without MWNTs were revealed in the synthesis of optically active 1,2-nitroalkanols, which are key intermediates for the synthesis of therapeutics.

Morphology and stratal geometry of the Antarctic continental shelf: Insights from models

USGS Publications Warehouse

Cooper, Alan K.; Barker, Peter F.; Brancolini, Giuliano

1997-01-01

Reconstruction of past ice-sheet fluctuations from the stratigraphy of glaciated continental shelves requires understanding of the relationships among the stratal geometry, glacial and marine sedimentary processes, and ice dynamics. We investigate the formation of the morphology and the broad stratal geometry of topsets on the Antarctic continental shelf with numerical models. Our models assume that the stratal geometry and morphology are principally the results of time-integrated effects of glacial erosion and sedimentation related to the location of the seaward edge of the grounded ice. The location of the grounding line varies with time almost randomly across the shelf. With these simple assumptions, the models can successfully mimic salient features of the morphology and the stratal geometry. The models suggest that the current shelf has gradually evolved to its present geometry by many glacial advances and retreats of the grounding line to different locations across the shelf. The locations of the grounding line do not appear to be linearly correlated with either fluctuations in the 5 l s O record (which presumably represents changes in the global ice volume) or with the global sea-level curve, suggesting that either a more complex relationship exists or local effects dominate. The models suggest that erosion of preglacial sediments is confined to the inner shelf, and erosion decreases and deposition increases toward the shelf edge. Some of the deposited glacial sediments must be derived from continental erosion. The sediments probably undergo extensive transport and reworking obliterating much of the evidence for their original depositional environment. The flexural rigidity and the tectonic subsidence of the underlying lithosphere modify the bathymetry of the shelf, but probably have little effect on the stratal geometry. Our models provide several guidelines for the interpretation of unconformities, the nature of preserved topset deposits, and the significance of progradation versus aggradation of shelf sediments.

Wavelength-detuning cross-beam energy transfer mitigation scheme for direct drive: Modeling and evidence from National Ignition Facility implosions

NASA Astrophysics Data System (ADS)

Marozas, J. A.; Hohenberger, M.; Rosenberg, M. J.; Turnbull, D.; Collins, T. J. B.; Radha, P. B.; McKenty, P. W.; Zuegel, J. D.; Marshall, F. J.; Regan, S. P.; Sangster, T. C.; Seka, W.; Campbell, E. M.; Goncharov, V. N.; Bowers, M. W.; Di Nicola, J.-M. G.; Erbert, G.; MacGowan, B. J.; Pelz, L. J.; Moody, J.; Yang, S. T.

2018-05-01

Cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces laser-energy absorption for direct-drive inertial confinement fusion. Consequently, ablation pressure and implosion velocity suffer from the decreased absorption, reducing target performance in both symmetric and polar direct drive. Additionally, CBET alters the time-resolved scattered-light spectra and redistributes absorbed and scattered-light-changing shell morphology and low-mode drive symmetry. Mitigating CBET is demonstrated in inertial confinement implosions at the National Ignition Facility by detuning the laser-source wavelengths (±2.3 Å UV) of the interacting beams. In polar direct drive, wavelength detuning was shown to increase the equatorial region velocity experimentally by 16% and to alter the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation-hydrodynamic simulations that indicate a 10% increase in the average ablation pressure. These results indicate that wavelength detuning successfully mitigates CBET. Simulations predict that optimized phase plates and wavelength-detuning CBET mitigation utilizing the three-legged beam layout of the OMEGA Laser System significantly increase absorption and achieve >100-Gbar hot-spot pressures in symmetric direct drive.

Nucleation of uniform mono- and bilayer epitaxial graphene on SiC(0001)

NASA Astrophysics Data System (ADS)

Wu, Xiaosong; Zhang, Rui; Dong, Yunliang; Guo, Shuai; Kong, Wenjie; Liao, Zhimin; Yu, Dapeng

2012-02-01

Early stage of epitaxial graphene growth on SiC(0001) has been investigated. Using the confinement controlled sublimation (CCS) method, we has achieved well controlled growth and been able to see the formation of mono- and bilayer graphene islands. The growth features reveal the intriguing growth mechanism. In particular, a new ``stepdown'' growth mode has been identified. Graphene can propagate tens of micrometers across many SiC steps, while, most importantly, step bunching is avoided and the initial regular stepped SiC surface morphology is preserved. The stepdown growth demonstrates a route towards uniform epitaxial graphene in wafer size without sacrificing the initial substrate surface morphology.

Polymeric Thin Films for Organic Electronics: Properties and Adaptive Structures

PubMed Central

Cataldo, Sebastiano; Pignataro, Bruno

2013-01-01

This review deals with the correlation between morphology, structure and performance of organic electronic devices including thin film transistors and solar cells. In particular, we report on solution processed devices going into the role of the 3D supramolecular organization in determining their electronic properties. A selection of case studies from recent literature are reviewed, relying on solution methods for organic thin-film deposition which allow fine control of the supramolecular aggregation of polymers confined at surfaces in nanoscopic layers. A special focus is given to issues exploiting morphological structures stemming from the intrinsic polymeric dynamic adaptation under non-equilibrium conditions. PMID:28809362

Catalytic Micromotors Moving Near Polyelectrolyte-Modified Substrates: The Roles of Surface Charges, Morphology, and Released Ions.

PubMed

Wei, Mengshi; Zhou, Chao; Tang, Jinyao; Wang, Wei

2018-01-24

Synthetic microswimmers, or micromotors, are finding potential uses in a wide range of applications, most of which involve boundaries. However, subtle yet important effects beyond physical confinement on the motor dynamics remain less understood. In this letter, glass substrates were functionalized with positively and negatively charged polyelectrolytes, and the dynamics of micromotors moving close to the modified surfaces was examined. Using acoustic levitation and numerical simulation, we reveal how the speed of a chemically propelled micromotor slows down significantly near a polyelectrolyte-modified surface by the combined effects of surface charges, surface morphology, and ions released from the films.

Differential recall of derived and inflected word forms in working memory: examining the role of morphological information in simple and complex working memory tasks

PubMed Central

Service, Elisabet; Maury, Sini

2015-01-01

Working memory (WM) has been described as an interface between cognition and action, or a system for access to a limited amount of information needed in complex cognition. Access to morphological information is needed for comprehending and producing sentences. The present study probed WM for morphologically complex word forms in Finnish, a morphologically rich language. We studied monomorphemic (boy), inflected (boy+’s), and derived (boy+hood) words in three tasks. Simple span, immediate serial recall of words, in Experiment 1, is assumed to mainly rely on information in the focus of attention. Sentence span, a dual task combining sentence reading with recall of the last word (Experiment 2) or of a word not included in the sentence (Experiment 3) is assumed to involve establishment of a search set in long-term memory for fast activation into the focus of attention. Recall was best for monomorphemic and worst for inflected word forms with performance on derived words in between. However, there was an interaction between word type and experiment, suggesting that complex span is more sensitive to morphological complexity in derivations than simple span. This was explored in a within-subjects Experiment 4 combining all three tasks. An interaction between morphological complexity and task was replicated. Both inflected and derived forms increased load in WM. In simple span, recall of inflectional forms resulted in form errors. Complex span tasks were more sensitive to morphological load in derived words, possibly resulting from interference from morphological neighbors in the mental lexicon. The results are best understood as involving competition among inflectional forms when binding words from input into an output structure, and competition from morphological neighbors in secondary memory during cumulative retrieval-encoding cycles. Models of verbal recall need to be able to represent morphological as well as phonological and semantic information. PMID:25642181

Confinement of anomalous liquids in nanoporous matrices.

PubMed

Strekalova, Elena G; Luo, Jiayuan; Stanley, H Eugene; Franzese, Giancarlo; Buldyrev, Sergey V

2012-09-07

Using molecular dynamics simulations, we investigate the effects of different nanoconfinements on complex liquids-e.g., colloids or protein solutions-with density anomalies and a liquid-liquid phase transition (LLPT). In all the confinements, we find a strong depletion effect with a large increase in liquid density near the confining surface. If the nanoconfinement is modeled by an ordered matrix of nanoparticles, we find that the anomalies are preserved. On the contrary, if the confinement is modeled by a disordered matrix of nanoparticles, we find a drastically different phase diagram: the LLPT shifts to lower pressures and temperatures, and the anomalies become weaker, as the disorder increases. We find that the density heterogeneities induced by the disordered matrix are responsible for the weakening of the LLPT and the disappearance of the anomalies.

The Influence of Semantic and Morphological Complexity of Verbs on Sentence Recall: Implications for the Nature of Conceptual Representation and Category-Specific Deficits

ERIC Educational Resources Information Center

Mobayyen, F.; de Almeida, R.G.

2005-01-01

One hundred and forty normal undergraduate students participated in a Proactive Interference (PI) experiment with sentences containing verbs from four different semantic and morphological classes (lexical causatives, morphological causatives, and morphologically complex and simplex perception verbs). Past research has shown significant PI build-up…

Receptor dimer stabilization by hierarchical plasma membrane microcompartments regulates cytokine signaling

PubMed Central

You, Changjiang; Marquez-Lago, Tatiana T.; Richter, Christian Paolo; Wilmes, Stephan; Moraga, Ignacio; Garcia, K. Christopher; Leier, André; Piehler, Jacob

2016-01-01

The interaction dynamics of signaling complexes is emerging as a key determinant that regulates the specificity of cellular responses. We present a combined experimental and computational study that quantifies the consequences of plasma membrane microcompartmentalization for the dynamics of type I interferon receptor complexes. By using long-term dual-color quantum dot (QD) tracking, we found that the lifetime of individual ligand-induced receptor heterodimers depends on the integrity of the membrane skeleton (MSK), which also proved important for efficient downstream signaling. By pair correlation tracking and localization microscopy as well as by fast QD tracking, we identified a secondary confinement within ~300-nm-sized zones. A quantitative spatial stochastic diffusion-reaction model, entirely parameterized on the basis of experimental data, predicts that transient receptor confinement by the MSK meshwork allows for rapid reassociation of dissociated receptor dimers. Moreover, the experimentally observed apparent stabilization of receptor dimers in the plasma membrane was reproduced by simulations of a refined, hierarchical compartment model. Our simulations further revealed that the two-dimensional association rate constant is a key parameter for controlling the extent of MSK-mediated stabilization of protein complexes, thus ensuring the specificity of this effect. Together, experimental evidence and simulations support the hypothesis that passive receptor confinement by MSK-based microcompartmentalization promotes maintenance of signaling complexes in the plasma membrane. PMID:27957535

DNA condensing effects and sequence selectivity of DNA binding of antitumor noncovalent polynuclear platinum complexes.

PubMed

Malina, Jaroslav; Farrell, Nicholas P; Brabec, Viktor

2014-02-03

The noncovalent analogues of antitumor polynuclear platinum complexes represent a structurally discrete class of platinum drugs. Their chemical and biological properties differ significantly from those of most platinum chemotherapeutics, which bind to DNA in a covalent manner by formation of Pt-DNA adducts. In spite of the fact that these noncovalent polynuclear platinum complexes contain no leaving groups, they have been shown to bind to DNA with high affinity. We report here on the DNA condensation properties of a series of noncovalent analogues of antitumor polynuclear platinum complexes described by biophysical and biochemical methods. The results demonstrate that these polynuclear platinum compounds are capable of inducing DNA condensation at more than 1 order of magnitude lower concentrations than conventional spermine. Atomic force microscopy studies of DNA condensation confined to a mica substrate have revealed that the DNA morphologies become more compact with increasing concentration of the platinum complexes. Moreover, we also found that the noncovalent polynuclear platinum complex [{Pt(NH3)3}2-μ-{trans-Pt(NH3)2(NH2(CH2)6NH2)2}](6+) (TriplatinNC-A) binds to DNA in a sequence-dependent manner, namely, to A/T-rich sequences and A-tract regions, and that noncovalent polynuclear platinum complexes protect DNA from enzymatic cleavage by DNase I. The results suggest that mechanisms of antitumor and cytotoxic activities of these complexes may be associated with their unique ability to condense DNA along with their sequence-specific DNA binding. Owing to their high cellular accumulation, it is also reasonable to suggest that their mechanism of action is based on the competition with naturally occurring DNA condensing agents, such as polyamines spermine, spermidine, and putrescine, for intracellular binding sites, resulting in the disturbance of the correct binding of regulatory proteins initiating the onset of apoptosis.

Complex dynamics induced by strong confinement - From tracer diffusion in strongly heterogeneous media to glassy relaxation of dense fluids in narrow slits

NASA Astrophysics Data System (ADS)

Mandal, Suvendu; Spanner-Denzer, Markus; Leitmann, Sebastian; Franosch, Thomas

2017-08-01

We provide an overview of recent advances of the complex dynamics of particles in strong confinements. The first paradigm is the Lorentz model where tracers explore a quenched disordered host structure. Such systems naturally occur as limiting cases of binary glass-forming systems if the dynamics of one component is much faster than the other. For a certain critical density of the host structure the tracers undergo a localization transition which constitutes a critical phenomenon. A series of predictions in the vicinity of the transition have been elaborated and tested versus computer simulations. Analytical progress is achieved for small obstacle densities. The second paradigm is a dense strongly interacting liquid confined to a narrow slab. Then the glass transition depends nonmonotonically on the separation of the plates due to an interplay of local packing and layering. Very small slab widths allow to address certain features of the statics and dynamics analytically.

Sociolinguistic Typology and Sign Languages.

PubMed

Schembri, Adam; Fenlon, Jordan; Cormier, Kearsy; Johnston, Trevor

2018-01-01

This paper examines the possible relationship between proposed social determinants of morphological 'complexity' and how this contributes to linguistic diversity, specifically via the typological nature of the sign languages of deaf communities. We sketch how the notion of morphological complexity, as defined by Trudgill (2011), applies to sign languages. Using these criteria, sign languages appear to be languages with low to moderate levels of morphological complexity. This may partly reflect the influence of key social characteristics of communities on the typological nature of languages. Although many deaf communities are relatively small and may involve dense social networks (both social characteristics that Trudgill claimed may lend themselves to morphological 'complexification'), the picture is complicated by the highly variable nature of the sign language acquisition for most deaf people, and the ongoing contact between native signers, hearing non-native signers, and those deaf individuals who only acquire sign languages in later childhood and early adulthood. These are all factors that may work against the emergence of morphological complexification. The relationship between linguistic typology and these key social factors may lead to a better understanding of the nature of sign language grammar. This perspective stands in contrast to other work where sign languages are sometimes presented as having complex morphology despite being young languages (e.g., Aronoff et al., 2005); in some descriptions, the social determinants of morphological complexity have not received much attention, nor has the notion of complexity itself been specifically explored.

Synthesis of ZnS films on Si(100) wafers by using chemical bath deposition assisted by the complexing agent ethylenediamine

NASA Astrophysics Data System (ADS)

Zhu, He-Jie; Wang, Xue-Mei; Gao, Xiao-Yong

2015-07-01

Low-cost synthesis of high-quality ZnS films on silicon wafers is of much importance to the ZnSbased heterojunction blue light-emitting device integrated with silicon. Thus, a series of ZnS films were chemically synthesized at low cost on Si(100) wafers at 353 K under a mixed acidic solution with a pH of 4 with zinc acetate and thioacetamide as precursors and with ethylenediamine and hydrochloric acid as the complexing agent and the pH value modifier, respectively. The effects of the ethylenediamine concentration on the crystallization, surface morphology, and optical properties of the ZnS films were investigated by using X-ray diffractometry, scanning electron microscopy, spectrophotometry, and fluorescence spectroscopy. A mechanism for the formation of ZnS film under an acidic condition was also proposed. All of the ZnS films were polycrystalline in nature, with a dominant cubic phase and a small amounts of hexagonal phases. The crystallization and the surface pattern of the films were clearly improved with increasing ethylenediamine concentration due to its enhanced complexing role. The absorption edge of the films almost underwent a blue shift with increasing ethylenediamine concentration, which was largely attributed to the quantum confinement effects caused by the small particle size of the polycrystalline ZnS films. Defect species and the corresponding strengths of the ZnS films were strongly affected by the ethylenediamine concentration.

Cryptic or pseudocryptic: can morphological methods inform copepod taxonomy? An analysis of publications and a case study of the Eurytemora affinis species complex

PubMed Central

Lajus, Dmitry; Sukhikh, Natalia; Alekseev, Victor

2015-01-01

Interest in cryptic species has increased significantly with current progress in genetic methods. The large number of cryptic species suggests that the resolution of traditional morphological techniques may be insufficient for taxonomical research. However, some species now considered to be cryptic may, in fact, be designated pseudocryptic after close morphological examination. Thus the “cryptic or pseudocryptic” dilemma speaks to the resolution of morphological analysis and its utility for identifying species. We address this dilemma first by systematically reviewing data published from 1980 to 2013 on cryptic species of Copepoda and then by performing an in-depth morphological study of the former Eurytemora affinis complex of cryptic species. Analyzing the published data showed that, in 5 of 24 revisions eligible for systematic review, cryptic species assignment was based solely on the genetic variation of forms without detailed morphological analysis to confirm the assignment. Therefore, some newly described cryptic species might be designated pseudocryptic under more detailed morphological analysis as happened with Eurytemora affinis complex. Recent genetic analyses of the complex found high levels of heterogeneity without morphological differences; it is argued to be cryptic. However, next detailed morphological analyses allowed to describe a number of valid species. Our study, using deep statistical analyses usually not applied for new species describing, of this species complex confirmed considerable differences between former cryptic species. In particular, fluctuating asymmetry (FA), the random variation of left and right structures, was significantly different between forms and provided independent information about their status. Our work showed that multivariate statistical approaches, such as principal component analysis, can be powerful techniques for the morphological discrimination of cryptic taxons. Despite increasing cryptic species designations, morphological techniques have great potential in determining copepod taxonomy. PMID:26120427

Confinement Effects on Carbon Dioxide Methanation: A Novel Mechanism for Abiotic Methane Formation

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

Le, Thu; Striolo, Alberto; Turner, C. Heath

An important scientific debate focuses on the possibility of abiotic synthesis of hydrocarbons during oceanic crust-seawater interactions. While on-site measurements near hydrothermal vents support this possibility, laboratory studies have provided data that are in some cases contradictory. At conditions relevant for sub-surface environments it has been shown that classic thermodynamics favour the production of CO 2 from CH 4, while abiotic methane synthesis would require the opposite. However, confinement effects are known to alter reaction equilibria. This report shows that indeed thermodynamic equilibrium can be shifted towards methane production, suggesting that thermal hydrocarbon synthesis near hydrothermal vents and deeper inmore » the magma-hydrothermal system is possible. We report reactive ensemble Monte Carlo simulations for the CO 2 methanation reaction. We compare the predicted equilibrium composition in the bulk gaseous phase to that expected in the presence of confinement. In the bulk phase we obtain excellent agreement with classic thermodynamic expectations. When the reactants can exchange between bulk and a confined phase our results show strong dependency of the reaction equilibrium conversions, X CO2, on nanopore size, nanopore chemistry, and nanopore morphology. Some physical conditions that could shift significantly the equilibrium composition of the reactive system with respect to bulk observations are discussed.« less

Confinement Effects on Carbon Dioxide Methanation: A Novel Mechanism for Abiotic Methane Formation

DOE PAGES

Le, Thu; Striolo, Alberto; Turner, C. Heath; ...

2017-08-21

An important scientific debate focuses on the possibility of abiotic synthesis of hydrocarbons during oceanic crust-seawater interactions. While on-site measurements near hydrothermal vents support this possibility, laboratory studies have provided data that are in some cases contradictory. At conditions relevant for sub-surface environments it has been shown that classic thermodynamics favour the production of CO 2 from CH 4, while abiotic methane synthesis would require the opposite. However, confinement effects are known to alter reaction equilibria. This report shows that indeed thermodynamic equilibrium can be shifted towards methane production, suggesting that thermal hydrocarbon synthesis near hydrothermal vents and deeper inmore » the magma-hydrothermal system is possible. We report reactive ensemble Monte Carlo simulations for the CO 2 methanation reaction. We compare the predicted equilibrium composition in the bulk gaseous phase to that expected in the presence of confinement. In the bulk phase we obtain excellent agreement with classic thermodynamic expectations. When the reactants can exchange between bulk and a confined phase our results show strong dependency of the reaction equilibrium conversions, X CO2, on nanopore size, nanopore chemistry, and nanopore morphology. Some physical conditions that could shift significantly the equilibrium composition of the reactive system with respect to bulk observations are discussed.« less

Comparing morphologies of drainage basins on Mars and Earth using integral-geometry and neural maps

NASA Technical Reports Server (NTRS)

Stepinski, T. F.; Coradetti, S.

2004-01-01

We compare morphologies of drainage basins on Mars and Earth in order to confine the formation process of Martian valley networks. Basins on both planets are computationally extracted from digital topography. Integral-geometry methods are used to represent each basin by a circularity function that encapsulates its internal structure. The shape of such a function is an indicator of the style of fluvial erosion. We use the self-organizing map technique to construct a similarity graph for all basins. The graph reveals systematic differences between morphologies of basins on the two planets. This dichotomy indicates that terrestrial and Martian surfaces were eroded differently. We argue that morphologies of Martian basins are incompatible with runoff from sustained, homogeneous rainfall. Fluvial environments compatible with observed morphologies are discussed. We also construct a similarity graph based on the comparison of basins hypsometric curves to demonstrate that hypsometry is incapable of discriminating between terrestrial and Martian basins. INDEX TERMS: 1824 Hydrology: Geomorphology (1625); 1886 Hydrology: Weathering (1625); 5415 Planetology: Solid Surface Planets: Erosion and weathering; 6225 Planetology: Solar System Objects Mars. Citation: Stepinski, T. F., and S. Coradetti (2004), Comparing morphologies of drainage basins on Mars and Earth using integral-ge

Hydrodynamics of confined colloidal fluids in two dimensions

NASA Astrophysics Data System (ADS)

Sané, Jimaan; Padding, Johan T.; Louis, Ard A.

2009-05-01

We apply a hybrid molecular dynamics and mesoscopic simulation technique to study the dynamics of two-dimensional colloidal disks in confined geometries. We calculate the velocity autocorrelation functions and observe the predicted t-1 long-time hydrodynamic tail that characterizes unconfined fluids, as well as more complex oscillating behavior and negative tails for strongly confined geometries. Because the t-1 tail of the velocity autocorrelation function is cut off for longer times in finite systems, the related diffusion coefficient does not diverge but instead depends logarithmically on the overall size of the system. The Langevin equation gives a poor approximation to the velocity autocorrelation function at both short and long times.

A Programmable DNA Origami Platform for Organizing Intrinsically Disordered Nucleoporins within Nanopore Confinement.

PubMed

Fisher, Patrick D Ellis; Shen, Qi; Akpinar, Bernice; Davis, Luke K; Chung, Kenny Kwok Hin; Baddeley, David; Šarić, Anđela; Melia, Thomas J; Hoogenboom, Bart W; Lin, Chenxiang; Lusk, C Patrick

2018-02-27

Nuclear pore complexes (NPCs) form gateways that control molecular exchange between the nucleus and the cytoplasm. They impose a diffusion barrier to macromolecules and enable the selective transport of nuclear transport receptors with bound cargo. The underlying mechanisms that establish these permeability properties remain to be fully elucidated but require unstructured nuclear pore proteins rich in Phe-Gly (FG)-repeat domains of different types, such as FxFG and GLFG. While physical modeling and in vitro approaches have provided a framework for explaining how the FG network contributes to the barrier and transport properties of the NPC, it remains unknown whether the number and/or the spatial positioning of different FG-domains along a cylindrical, ∼40 nm diameter transport channel contributes to their collective properties and function. To begin to answer these questions, we have used DNA origami to build a cylinder that mimics the dimensions of the central transport channel and can house a specified number of FG-domains at specific positions with easily tunable design parameters, such as grafting density and topology. We find the overall morphology of the FG-domain assemblies to be dependent on their chemical composition, determined by the type and density of FG-repeat, and on their architectural confinement provided by the DNA cylinder, largely consistent with here presented molecular dynamics simulations based on a coarse-grained polymer model. In addition, high-speed atomic force microscopy reveals local and reversible FG-domain condensation that transiently occludes the lumen of the DNA central channel mimics, suggestive of how the NPC might establish its permeability properties.

Confinement Regulates Complex Biochemical Networks: Initiation of Blood Clotting by “Diffusion Acting”

PubMed Central

Shen, Feng; Pompano, Rebecca R.; Kastrup, Christian J.; Ismagilov, Rustem F.

2009-01-01

Abstract This study shows that environmental confinement strongly affects the activation of nonlinear reaction networks, such as blood coagulation (clotting), by small quantities of activators. Blood coagulation is sensitive to the local concentration of soluble activators, initiating only when the activators surpass a threshold concentration, and therefore is regulated by mass transport phenomena such as flow and diffusion. Here, diffusion was limited by decreasing the size of microfluidic chambers, and it was found that microparticles carrying either the classical stimulus, tissue factor, or a bacterial stimulus, Bacillus cereus, initiated coagulation of human platelet-poor plasma only when confined. A simple analytical argument and numerical model were used to describe the mechanism for this phenomenon: confinement causes diffusible activators to accumulate locally and surpass the threshold concentration. To interpret the results, a dimensionless confinement number, Cn, was used to describe whether a stimulus was confined, and a Damköhler number, Da2, was used to describe whether a subthreshold stimulus could initiate coagulation. In the context of initiation of coagulation by bacteria, this mechanism can be thought of as “diffusion acting”, which is distinct from “diffusion sensing”. The ability of confinement and diffusion acting to change the outcome of coagulation suggests that confinement should also regulate other biological “on” and “off” processes that are controlled by thresholds. PMID:19843446

Airflow-aligned helical nanofilament (B4) phase in topographic confinement

PubMed Central

Gim, Min-Jun; Kim, Hanim; Chen, Dong; Shen, Yongqiang; Yi, Youngwoo; Korblova, Eva; Walba, David M.; Clark, Noel A.; Yoon, Dong Ki

2016-01-01

We investigated a controlled helical nanofilament (HNF: B4) phase under topographic confinement with airflow that can induce a shear force and temperature gradient on the sample. The resulting orientation and ordering of the B4 phase in this combinational effort was directly investigated using microscopy. The structural freedom of the complex B7 phase, which is a higher temperature phase than the B4 phase, can result in relatively complex microscopic arrangements of HNFs compared with the B4 phase generated from the simple layer structure of the B2 phase. This interesting chiral/polar nanofilament behaviour offers new opportunities for further exploration of the exotic physical properties of the B4 phase. PMID:27384747

Nonperturbative quark-gluon thermodynamics at finite density

NASA Astrophysics Data System (ADS)

Andreichikov, M. A.; Lukashov, M. S.; Simonov, Yu. A.

2018-03-01

Thermodynamics of the quark-gluon plasma at finite density is studied in the framework of the Field Correlator Method, where thermodynamical effects of Polyakov loops and color magnetic confinement are taken into account. Having found good agreement with numerical lattice data for zero density, we calculate pressure P(T,μ), for 0 < μ < 400 MeV and 150 < T < 1000 MeV. For the first time, the explicit integral form is found in this region, demonstrating analytic structure in the complex μ plane. The resulting multiple complex branch points are found at the Roberge-Weiss values of Imμ, with Reμ defined by the values of Polyakov lines and color magnetic confinement.

Measuring orthographic transparency and morphological-syllabic complexity in alphabetic orthographies: a narrative review.

PubMed

Borleffs, Elisabeth; Maassen, Ben A M; Lyytinen, Heikki; Zwarts, Frans

2017-01-01

This narrative review discusses quantitative indices measuring differences between alphabetic languages that are related to the process of word recognition. The specific orthography that a child is acquiring has been identified as a central element influencing reading acquisition and dyslexia. However, the development of reliable metrics to measure differences between language scripts hasn't received much attention so far. This paper therefore reviews metrics proposed in the literature for quantifying orthographic transparency, syllabic complexity, and morphological complexity of alphabetic languages. The review included searches of Web of Science, PubMed, PsychInfo, Google Scholar, and various online sources. Search terms pertained to orthographic transparency, morphological complexity, and syllabic complexity in relation to reading acquisition, and dyslexia. Although the predictive value of these metrics is promising, more research is needed to validate the value of the metrics discussed and to understand the 'developmental footprint' of orthographic transparency, morphological complexity, and syllabic complexity in the lexical organization and processing strategies.

The Ba 4d-4f giant dipole resonance in complex Ba/Si compounds

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

Sahle, Ch. J.; Sternemann, C.; Sternemann, H.

2014-08-06

The shape of the Ba 4d–4f giant dipole resonance is studied for Ba atoms embedded inside complex Si networks covering structures consisting of Si nanocages and nanotubes, i.e. the clathrate Ba 8Si 46, the complex compound BaSi 6, and the semiconducting BaSi 2. Here, non-resonant x-ray Raman scattering is used to investigate confinement effects on the shape of the giant resonance in the vicinity of the Ba NIV, V-edge. The distinct momentum transfer dependence of the spectra is analyzed and discussed. The measurements are compared to calculations of the giant resonance within time-dependent local density approximation in the dipole limit.more » No modulation of the giant resonance's shape for Ba atoms confined in different local environments was observed, in contrast to the calculations. The absence of such shape modulation for complex Ba/Si compounds is discussed providing important implications for further studies of giant resonance phenomena utilizing both theory and experiment.« less

The Ba 4d-4f giant dipole resonance in complex Ba/Si compounds

NASA Astrophysics Data System (ADS)

Sahle, Ch J.; Sternemann, C.; Sternemann, H.; Tse, J. S.; Gordon, R. A.; Desgreniers, S.; Maekawa, S.; Yamanaka, S.; Lehmkühler, F.; Wieland, D. C. F.; Mende, K.; Huotari, S.; Tolan, M.

2014-02-01

The shape of the Ba 4d-4f giant dipole resonance is studied for Ba atoms embedded inside complex Si networks covering structures consisting of Si nanocages and nanotubes, i.e. the clathrate Ba8Si46, the complex compound BaSi6, and the semiconducting BaSi2. Here, non-resonant x-ray Raman scattering is used to investigate confinement effects on the shape of the giant resonance in the vicinity of the Ba NIV, V-edge. The distinct momentum transfer dependence of the spectra is analyzed and discussed. The measurements are compared to calculations of the giant resonance within time-dependent local density approximation in the dipole limit. No modulation of the giant resonance’s shape for Ba atoms confined in different local environments was observed, in contrast to the calculations. The absence of such shape modulation for complex Ba/Si compounds is discussed providing important implications for further studies of giant resonance phenomena utilizing both theory and experiment.

First Observation of Cross-Beam Energy Transfer Mitigation for Direct-Drive Inertial Confinement Fusion Implosions Using Wavelength Detuning at the National Ignition Facility

DOE PAGES

Marozas, J. A.; Hohenberger, M.; Rosenberg, M. J.; ...

2018-02-22

Cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces ablation pressure and implosion velocity in direct-drive inertial confinement fusion. Direct-drive implosions at the National Ignition Facility were conducted to reduce CBET by detuning the laser-source wavelengths (±2.3 Å UV) of the interacting beams over the equatorial region of the target. For the first time, wavelength detuning was shown to increase the equatorial region velocity experimentally by 16% and to alter the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation–hydrodynamic simulations that indicate a 10% increase in themore » average ablation pressure.« less

First Observation of Cross-Beam Energy Transfer Mitigation for Direct-Drive Inertial Confinement Fusion Implosions Using Wavelength Detuning at the National Ignition Facility

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

Marozas, J. A.; Hohenberger, M.; Rosenberg, M. J.

Cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces ablation pressure and implosion velocity in direct-drive inertial confinement fusion. Direct-drive implosions at the National Ignition Facility were conducted to reduce CBET by detuning the laser-source wavelengths (±2.3 Å UV) of the interacting beams over the equatorial region of the target. For the first time, wavelength detuning was shown to increase the equatorial region velocity experimentally by 16% and to alter the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation–hydrodynamic simulations that indicate a 10% increase in themore » average ablation pressure.« less

Morphological Decomposition and Semantic Integration in Word Processing

ERIC Educational Resources Information Center

Meunier, Fanny; Longtin, Catherine-Marie

2007-01-01

In the present study, we looked at cross-modal priming effects produced by auditory presentation of morphologically complex pseudowords in order to investigate semantic integration during the processing of French morphologically complex items. In Experiment 1, we used as primes pseudowords consisting of a non-interpretable combination of roots and…

A Comprehensive Numerical Model for Simulating Fluid Transport in Nanopores

PubMed Central

Zhang, Yuan; Yu, Wei; Sepehrnoori, Kamy; Di, Yuan

2017-01-01

Since a large amount of nanopores exist in tight oil reservoirs, fluid transport in nanopores is complex due to large capillary pressure. Recent studies only focus on the effect of nanopore confinement on single-well performance with simple planar fractures in tight oil reservoirs. Its impacts on multi-well performance with complex fracture geometries have not been reported. In this study, a numerical model was developed to investigate the effect of confined phase behavior on cumulative oil and gas production of four horizontal wells with different fracture geometries. Its pore sizes were divided into five regions based on nanopore size distribution. Then, fluid properties were evaluated under different levels of capillary pressure using Peng-Robinson equation of state. Afterwards, an efficient approach of Embedded Discrete Fracture Model (EDFM) was applied to explicitly model hydraulic and natural fractures in the reservoirs. Finally, three fracture geometries, i.e. non-planar hydraulic fractures, non-planar hydraulic fractures with one set natural fractures, and non-planar hydraulic fractures with two sets natural fractures, are evaluated. The multi-well performance with confined phase behavior is analyzed with permeabilities of 0.01 md and 0.1 md. This work improves the analysis of capillarity effect on multi-well performance with complex fracture geometries in tight oil reservoirs. PMID:28091599

A Comprehensive Numerical Model for Simulating Fluid Transport in Nanopores

NASA Astrophysics Data System (ADS)

Zhang, Yuan; Yu, Wei; Sepehrnoori, Kamy; di, Yuan

2017-01-01

Since a large amount of nanopores exist in tight oil reservoirs, fluid transport in nanopores is complex due to large capillary pressure. Recent studies only focus on the effect of nanopore confinement on single-well performance with simple planar fractures in tight oil reservoirs. Its impacts on multi-well performance with complex fracture geometries have not been reported. In this study, a numerical model was developed to investigate the effect of confined phase behavior on cumulative oil and gas production of four horizontal wells with different fracture geometries. Its pore sizes were divided into five regions based on nanopore size distribution. Then, fluid properties were evaluated under different levels of capillary pressure using Peng-Robinson equation of state. Afterwards, an efficient approach of Embedded Discrete Fracture Model (EDFM) was applied to explicitly model hydraulic and natural fractures in the reservoirs. Finally, three fracture geometries, i.e. non-planar hydraulic fractures, non-planar hydraulic fractures with one set natural fractures, and non-planar hydraulic fractures with two sets natural fractures, are evaluated. The multi-well performance with confined phase behavior is analyzed with permeabilities of 0.01 md and 0.1 md. This work improves the analysis of capillarity effect on multi-well performance with complex fracture geometries in tight oil reservoirs.

Tapping-mode AFM study of tip-induced polymer deformation under geometrical confinement.

PubMed

Zhang, Hong; Honda, Yukio; Takeoka, Shinji

2013-02-05

The morphological stability of polymer films is critically important to their application as functional materials. The deformation of polymer surfaces on the nanoscale may be significantly influenced by geometrical confinement. Herein, we constructed a mechanically heterogeneous polymer surface by phase separation in a thin polymer film and investigated the deformation behavior of its nanostructure (∼30 nm thickness and ∼100 nm average diameter) with tapping-mode atomic force microscopy. By changing different scan parameters, we could induce deformation localized to the nanostructure in a controllable manner. A quantity called the deformation index is defined and shown to be correlated to energy dissipation by tip-sample interaction. We clarified that the plastic deformation of a polymer on the nanoscale is energy-dependent and is related to the glass-to-rubber transition. The mobility of polymer chains beneath the tapping tip is enhanced, and in the corresponding region a rubberlike deformation with the lateral motion of the tip is performed. The method we developed can provide insight into the geometrical confinement effects on polymer behavior.

Molecular dynamic heterogeneity of confined lipid films by 1H magnetization-exchange nuclear magnetic resonance

NASA Astrophysics Data System (ADS)

Buda, A.; Demco, D. E.; Jagadeesh, B.; Blümich, B.

2005-01-01

The molecular dynamic heterogeneity of monolayer to submonolayer thin lecithin films confined to submicron cylindrical pores were investigated by 1H magnetization exchange nuclear magnetic resonance. In this experiment a z-magnetization gradient was generated by a double-quantum dipolar filter. The magnetization-exchange decay and buildup curves were interpreted with the help of a theoretical model based on the approximation of a one-dimensional spin-diffusion process in a three-domain morphology. The dynamic heterogeneity of the fatty acid chains and the effects of the surface area per molecule, the diameter of the pores, and the temperature were characterized with the help of local spin-diffusion coefficients. The effect of various parameters on the molecular dynamics of the mobile region of the fatty acid chains was quantified by introducing an ad hoc Gaussian distribution function of the 1H residual dipolar couplings. For the lipid films investigated in this study, the surface induced order and the geometrical confinement affect the chain dynamics of the entire molecule. Therefore, each part of the chain independently reflects the effect of surface coverage, pore size, and temperature.

Supramolecular Nanocomposites Under Confinement: Chiral Optically Active Nanoparticle Assemblies and Beyond

NASA Astrophysics Data System (ADS)

Bai, Peter; Yang, Sui; Bao, Wei; Salmeron, Miquel; Zhang, Xiang; Xu, Ting

2015-03-01

Block copolymer-based supramolecules provide a versatile platform to direct the self-assembly of nanoparticles (NPs) into precisely controlled nanostructures in bulk and thin film geometries. A supramolecule, PS-b-P4VP(PDP), composed of the small molecule 3-pentadecylphenol (PDP) hydrogen bonded to a diblock copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP), was subjected to 2-D volume confinement in cylindrical anodic aluminum oxide (AAO) membrane pores. TEM and 3-D TEM tomography reveal that the morphologies accessible by the supramolecule and supramolecule/NP composites, such as NP clusters, arrays, stacked rings, and single and double helical ribbons, are significantly different from those in the bulk or thin film. Furthermore, single molecule dark field scattering measurements demonstrate strong chiral optical response of single helical Au NP ribbon nanostructures in the near infrared wavelength regime. These studies demonstrate 2-D confinement to be an effective means to tailor self-assembled NP structure within supramolecule nanocomposites and pave the way for this assembly approach to be applied towards next generation chiral metamaterials and optoelectronic devices.

Advancing flexible volatile compound sensors using liquid crystals encapsulated in polymer fibers

NASA Astrophysics Data System (ADS)

Reyes, Catherine G.; Lagerwall, Jan P. F.

2018-02-01

Until recently, organic vapor sensors using liquid crystals (LCs) have employed rigid glass substrates for confining the LC, and bulky equipment for vapor detection. Previously, we demonstrated that coaxially electrospinning nematic LC within the core of polymer fibers provides an alternative and improved form factor for confinement. This enables ppm level sensitivity to harmful industrial organics, such as toluene, while giving the flexibility of textile-like sheets (imparted by polymer encapsulation). Moreover, toluene vapor responses of the LC-core fiber mats were visible macroscopically with the naked eye depending on the morphology of the fibers produced, and whether they were oriented in specific geometries (aligned, or random). We identified two types of responses: one corresponds to the LC transition from nematic to isotropic, and the other we suggest is due to an anchoring change at the LC-polymer interface that influences the alignment. While we need to study the presence that defects can have in more detail, we noted that fiber mat thickness is crucial in attempting to understand how and why we are able to visualize two responses in aligned LC-fiber mats. Ultimately, we noted that the response of the polymer sheath itself (softening) to organic vapor exposure affects the liquid crystal confinement in the core. From the microscopic point of view, this will influence the threshold concentration that fibers in a mat will overall respond to. In this paper we will discuss three findings the morphologies enabling LC-core fiber mat response to vapor seen both micro- and macroscopically, how thickness of the fiber mat can play a role in the visualization of the responses, and the effect that the polymer structure has in the mat's sensitivity threshold.

Revealing Nanostructures through Plasmon Polarimetry.

PubMed

Kleemann, Marie-Elena; Mertens, Jan; Zheng, Xuezhi; Cormier, Sean; Turek, Vladimir; Benz, Felix; Chikkaraddy, Rohit; Deacon, William; Lombardi, Anna; Moshchalkov, Victor V; Vandenbosch, Guy A E; Baumberg, Jeremy J

2017-01-24

Polarized optical dark-field spectroscopy is shown to be a versatile noninvasive probe of plasmonic structures that trap light to the nanoscale. Clear spectral polarization splittings are found to be directly related to the asymmetric morphology of nanocavities formed between faceted gold nanoparticles and an underlying gold substrate. Both experiment and simulation show the influence of geometry on the coupled system, with spectral shifts Δλ = 3 nm from single atoms. Analytical models allow us to identify the split resonances as transverse cavity modes, tightly confined to the nanogap. The direct correlation of resonance splitting with atomistic morphology allows mapping of subnanometre structures, which is crucial for progress in extreme nano-optics involving chemistry, nanophotonics, and quantum devices.

Method of fabricating a catalytic structure

DOEpatents

Rollins, Harry W [Idaho Falls, ID; Petkovic, Lucia M [Idaho Falls, ID; Ginosar, Daniel M [Idaho Falls, ID

2009-09-22

A precursor to a catalytic structure comprising zinc oxide and copper oxide. The zinc oxide has a sheet-like morphology or a spherical morphology and the copper oxide comprises particles of copper oxide. The copper oxide is reduced to copper, producing the catalytic structure. The catalytic structure is fabricated by a hydrothermal process. A reaction mixture comprising a zinc salt, a copper salt, a hydroxyl ion source, and a structure-directing agent is formed. The reaction mixture is heated under confined volume conditions to produce the precursor. The copper oxide in the precursor is reduced to copper. A method of hydrogenating a carbon oxide using the catalytic structure is also disclosed, as is a system that includes the catalytic structure.

Cellulose Nanocrystal Templated Graphene Nanoscrolls for High Performance Supercapacitors and Hydrogen Storage: An Experimental and Molecular Simulation Study.

PubMed

Dhar, Prodyut; Gaur, Surendra Singh; Kumar, Amit; Katiyar, Vimal

2018-03-01

Graphene nanoscrolls (GNS), due to their remarkably interesting properties, have attracted significant interest with applications in various engineering sectors. However, uncontrolled morphologies, poor yield and low quality GNS produced through traditional routes are major challenges associated. We demonstrate sustainable approach of utilizing bio-derived cellulose nanocrystals (CNCs) as template for fabrication of GNS with tunable morphological dimensions ranging from micron-to-nanoscale(controlled length < 1 μm or >1 μm), alongwith encapsulation of catalytically active metallic-species in scroll interlayers. The surface-modified magnetic CNCs acts as structural-directing agents which provides enough momentum to initiate self-scrolling phenomenon of graphene through van der Waals forces and π-π interactions, mechanism of which is demonstrated through experimental and molecular simulation studies. The proposed approach of GNS fabrication provides flexibility to tune physico-chemical properties of GNS by simply varying interlayer spacing, scrolling density and fraction of encapsulated metallic nanoparticles. The hybrid GNS with confined palladium or platinum nanoparticles (at lower loading ~1 wt.%) shows enhanced hydrogen storage capacity (~0.2 wt.% at~20 bar and ~273 K) and excellent supercapacitance behavior (~223-357 F/g) for prolonged cycles (retention ~93.5-96.4% at ~10000 cycles). The current strategy of utilizing bio-based templates can be further extended to incorporate complex architectures or nanomaterials in GNS core or inter-layers, which will potentially broaden its applications in fabrication of high-performance devices.

Nanocontainers made of Various Materials with Tunable Shape and Size

NASA Astrophysics Data System (ADS)

Zhao, Xianglong; Meng, Guowen; Han, Fangming; Li, Xiangdong; Chen, Bensong; Xu, Qiaoling; Zhu, Xiaoguang; Chu, Zhaoqin; Kong, Mingguang; Huang, Qing

2013-07-01

Nanocontainers have great potentials in targeted drug delivery and nanospace-confined reactions. However, the previous synthetic approaches exhibited limited control over the morphology, size and materials of the nanocontainers, which are crucial in practical applications. Here, we present a synthetic approach to multi-segment linear-shaped nanopores with pre-designed morphologies inside anodic aluminium oxide (AAO), by tailoring the anodizing duration after a rational increase of the applied anodizing voltage and the number of voltage increase during Al foil anodization. Then, we achieve nanocontainers with designed morphologies, such as nanofunnels, nanobottles, nano-separating-funnels and nanodroppers, with tunable sizes and diverse materials of carbon, silicon, germanium, hafnium oxide, silica and nickel/carbon magnetic composite, by depositing a thin layer of materials on the inner walls of the pre-designed AAO nanopores. The strategy has far-reaching implications in the designing and large-scale fabrication of nanocontainers, opening up new opportunities in nanotechnology applications.

Solvent-assisted morphology confinement of a nickel sulfide nanostructure and its application for non-enzymatic glucose sensor.

PubMed

Kim, Soochan; Lee, Sang Ha; Cho, Misuk; Lee, Youngkwan

2016-11-15

Morphology-controlled synthesis of nickel sulfide (Ni3S2) was performed directly on Ni foam using thioacetamide as a sulfur ion source. Various morphologies of nickel sulfide were fabricated using a hydrothermal process by adjusting the solvent composition of ethanol and water. In the water-dominant condition, a dendrite structure was obtained; otherwise, a flaky structure was achieved. A hierarchical cauliflower-like structure was obtained at a solvent mixture composition of 1:1 and was used as non-enzymatic glucose sensor. The hierarchical Ni3S2 electrode showed a high level of electro-catalytic activity toward the oxidation of glucose (16,460μAmM(-1)cm(-2)) over a wide range of detection (0.0005-3mM) and a low detection limit (0.82μM) with excellent selectivity in the presence of several electroactive species. Copyright © 2016 Elsevier B.V. All rights reserved.

Nanocontainers made of Various Materials with Tunable Shape and Size

PubMed Central

Zhao, Xianglong; Meng, Guowen; Han, Fangming; Li, Xiangdong; Chen, Bensong; Xu, Qiaoling; Zhu, Xiaoguang; Chu, Zhaoqin; Kong, Mingguang; Huang, Qing

2013-01-01

Nanocontainers have great potentials in targeted drug delivery and nanospace-confined reactions. However, the previous synthetic approaches exhibited limited control over the morphology, size and materials of the nanocontainers, which are crucial in practical applications. Here, we present a synthetic approach to multi-segment linear-shaped nanopores with pre-designed morphologies inside anodic aluminium oxide (AAO), by tailoring the anodizing duration after a rational increase of the applied anodizing voltage and the number of voltage increase during Al foil anodization. Then, we achieve nanocontainers with designed morphologies, such as nanofunnels, nanobottles, nano-separating-funnels and nanodroppers, with tunable sizes and diverse materials of carbon, silicon, germanium, hafnium oxide, silica and nickel/carbon magnetic composite, by depositing a thin layer of materials on the inner walls of the pre-designed AAO nanopores. The strategy has far-reaching implications in the designing and large-scale fabrication of nanocontainers, opening up new opportunities in nanotechnology applications. PMID:23867836

Compact seaweed growth of peritectic phase on confined, flat properitectic dendrites

NASA Astrophysics Data System (ADS)

Ludwig, A.; Mogeritsch, J.

2016-12-01

Peritectic alloys form a variety of different solidification morphologies at low growth rates. An alloy with a concentration that corresponds to the hyper-peritectic limit should show a cellular/dendritic solidification of the peritectic phase for growth velocities above the corresponding constitutional undercooling limit. However, due to nucleation retardation of the peritectic phase we observed growth of properitectic dendrites before cellular growth of the peritectic could established. The transition happened via an overgrowth of dendrites with a thin layer of peritectic phase. The observations were made using a transparent, metal-like solidifying peritectic system that was solidified directionally in thin samples. In the gap between the flat dendrites and the tubing walls, the peritectic phase grew with a compact seaweed morphology, whereas in the interdendritic spacing it formed small-curved bumps. At same distance behind the tip region, more and more polycrystalline-like objects appeared at the elongated traces of the compact seaweed morphology.

Structure and catalytic activities of ferrous centers confined on the interface between carbon nanotubes and humic acid

NASA Astrophysics Data System (ADS)

Wang, Bing; Zhou, Xiaoyan; Wang, Dongqi; Yin, Jun-Jie; Chen, Hanqing; Gao, Xingfa; Zhang, Jing; Ibrahim, Kurash; Chai, Zhifang; Feng, Weiyue; Zhao, Yuliang

2015-01-01

Preparation of heterogeneous catalysts with active ferrous centers is of great significance for industrial and environmental catalytic processes. Nanostructured carbon materials (NCM), which possess free-flowing π electrons, can coordinate with transition metals, provide a confinement environment for catalysis, and act as potential supports or ligands to construct analogous complexes. However, designing such catalysts using NCM is still seldom studied to date. Herein, we synthesized a sandwich structured ternary complex via the coordination of Fe-loaded humic acid (HA) with C&z.dbd;C bonds in the aromatic rings of carbon nanotubes (CNTs), in which the O/N-Fe-C interface configuration provides the confinement environment for the ferrous sites. The experimental and theoretical results revealed octahedrally/tetrahedrally coordinated geometry at Fe centers, and the strong hybridization between CNT C π* and Fe 3d orbitals induces discretization of the atomic charges on aromatic rings of CNTs, which facilitates O2 adsorption and electron transfer from carbon to O2, which enhances O2 activation. The O2 activation by the novel HA/Fe-CNT complex can be applied in the oxidative degradation of phenol red (PR) and bisphenol A (BPA) in aqueous media.Preparation of heterogeneous catalysts with active ferrous centers is of great significance for industrial and environmental catalytic processes. Nanostructured carbon materials (NCM), which possess free-flowing π electrons, can coordinate with transition metals, provide a confinement environment for catalysis, and act as potential supports or ligands to construct analogous complexes. However, designing such catalysts using NCM is still seldom studied to date. Herein, we synthesized a sandwich structured ternary complex via the coordination of Fe-loaded humic acid (HA) with C&z.dbd;C bonds in the aromatic rings of carbon nanotubes (CNTs), in which the O/N-Fe-C interface configuration provides the confinement environment for the ferrous sites. The experimental and theoretical results revealed octahedrally/tetrahedrally coordinated geometry at Fe centers, and the strong hybridization between CNT C π* and Fe 3d orbitals induces discretization of the atomic charges on aromatic rings of CNTs, which facilitates O2 adsorption and electron transfer from carbon to O2, which enhances O2 activation. The O2 activation by the novel HA/Fe-CNT complex can be applied in the oxidative degradation of phenol red (PR) and bisphenol A (BPA) in aqueous media. Electronic supplementary information (ESI) available: Optimization of the mass ratios of HA to CNTs and the reaction pH conditions for Fe loading; scanning electron microscope (SEM), UV-Vis-near-infrared, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) for CNT-HA; EPR experiment and UPLC-ESI-MS analysis; and DFT calculation. See DOI: 10.1039/c4nr06665k

Dewetting-mediated pattern formation in nanoparticle assemblies

NASA Astrophysics Data System (ADS)

Stannard, Andrew

2011-03-01

The deposition of nanoparticles from solution onto solid substrates is a diverse subfield of current nanoscience research. Complex physical and chemical processes underpin the self-assembly and self-organization of colloidal nanoparticles at two-phase (solid-liquid, liquid-air) interfaces and three-phase (solid-liquid-air) contact lines. This review discusses key recent advances made in the understanding of nonequilibrium dewetting processes of nanoparticle-containing solutions, detailing how such an apparently simple experimental system can give rise to such a strikingly varied palette of two-dimensional self-organized nanoparticle array morphologies. Patterns discussed include worm-like domains, cellular networks, microscale rings, and fractal-like fingering structures. There remain many unresolved issues regarding the role of the solvent dewetting dynamics in assembly processes of this type, with a significant focus on how dewetting can be coerced to produce nanoparticle arrays with desirable characteristics such as long-range order. In addition to these topics, methods developed to control nanofluid dewetting through routes such as confining the geometries of drying solutions, depositing onto pre-patterned heterogeneous substrates, and post-dewetting pattern evolution via local or global manipulation are covered.

Dewetting-mediated pattern formation in nanoparticle assemblies.

PubMed

Stannard, Andrew

2011-03-02

The deposition of nanoparticles from solution onto solid substrates is a diverse subfield of current nanoscience research. Complex physical and chemical processes underpin the self-assembly and self-organization of colloidal nanoparticles at two-phase (solid-liquid, liquid-air) interfaces and three-phase (solid-liquid-air) contact lines. This review discusses key recent advances made in the understanding of nonequilibrium dewetting processes of nanoparticle-containing solutions, detailing how such an apparently simple experimental system can give rise to such a strikingly varied palette of two-dimensional self-organized nanoparticle array morphologies. Patterns discussed include worm-like domains, cellular networks, microscale rings, and fractal-like fingering structures. There remain many unresolved issues regarding the role of the solvent dewetting dynamics in assembly processes of this type, with a significant focus on how dewetting can be coerced to produce nanoparticle arrays with desirable characteristics such as long-range order. In addition to these topics, methods developed to control nanofluid dewetting through routes such as confining the geometries of drying solutions, depositing onto pre-patterned heterogeneous substrates, and post-dewetting pattern evolution via local or global manipulation are covered.

Blood Perfusion in Microfluidic Models of Pulmonary Capillary Networks: Role of Geometry and Hematocrit

NASA Astrophysics Data System (ADS)

Stauber, Hagit; Waisman, Dan; Sznitman, Josue; Technion-IIT Team; Department of Neonatology Carmel Medical Center; Faculty of Medicine-Technion IIT Collaboration

2015-11-01

Microfluidic platforms are increasingly used to study blood microflows at true physiological scale due to their ability to overcome manufacturing obstacle of complex anatomical morphologies, such as the organ-specific architectures of the microcirculation. In the present work, we utilize microfluidic platforms to devise in vitro models of the underlying pulmonary capillary networks (PCN), where capillary lengths and diameters are similar to the size of RBCs (~ 5-10 μm). To better understand flow characteristics and dispersion of red blood cells (RBCs) in PCNs, we have designed microfluidic models of alveolar capillary beds inspired by the seminal ``sheet flow'' model of Fung and Sobin (1969). Our microfluidic PCNs feature confined arrays of staggered pillars with diameters of ~ 5,7 and 10 μm, mimicking the dense structure of pulmonary capillary meshes. The devices are perfused with suspensions of RBCs at varying hematocrit levels under different flow rates. Whole-field velocity patterns using micro-PIV and single-cell tracking using PTV are obtained with fluorescently-labelled RBCs and discussed. Our experiments deliver a real-scale quantitative description of RBC perfusion characteristics across the pulmonary capillary microcirculation.

Butyrophenone on O-TiO2(110): one-dimensional motion in a weakly confined potential well.

PubMed

Jensen, Stephen C; Shank, Alex; Madix, Robert J; Friend, Cynthia M

2012-04-24

We demonstrate the one-dimensional confinement of weakly bound butyrophenone molecules between strongly bound complexes formed via reaction with oxygen on TiO(2)(110). Butyrophenone weakly bound to Ti rows through the carbonyl oxygen diffuses freely in one dimension along the rows even at 55 K, persisting for many minutes before hopping out of the 1-D well. Quantitative analysis yields an estimate of the migration barrier of 0.11 eV and a frequency factor of 6.5 × 10(9) Hz. These studies demonstrate that weakly bound organic molecules can be confined on a surface by creating molecular barriers, potentially altering their assembly.

Complex and oriented ZnO nanostructures.

PubMed

Tian, Zhengrong R; Voigt, James A; Liu, Jun; McKenzie, Bonnie; McDermott, Matthew J; Rodriguez, Mark A; Konishi, Hiromi; Xu, Huifang

2003-12-01

Extended and oriented nanostructures are desirable for many applications, but direct fabrication of complex nanostructures with controlled crystalline morphology, orientation and surface architectures remains a significant challenge. Here we report a low-temperature, environmentally benign, solution-based approach for the preparation of complex and oriented ZnO nanostructures, and the systematic modification of their crystal morphology. Using controlled seeded growth and citrate anions that selectively adsorb on ZnO basal planes as the structure-directing agent, we prepared large arrays of oriented ZnO nanorods with controlled aspect ratios, complex film morphologies made of oriented nanocolumns and nanoplates (remarkably similar to biomineral structures in red abalone shells) and complex bilayers showing in situ column-to-rod morphological transitions. The advantages of some of these ZnO structures for photocatalytic decompositions of volatile organic compounds were demonstrated. The novel ZnO nanostructures are expected to have great potential for sensing, catalysis, optical emission, piezoelectric transduction, and actuations.

Ullmann-like reactions for the synthesis of complex two-dimensional materials

NASA Astrophysics Data System (ADS)

Quardokus, Rebecca C.; Tewary, V. K.; DelRio, Frank W.

2016-11-01

Engineering two-dimensional materials through surface-confined synthetic techniques is a promising avenue for designing new materials with tailored properties. Developing and understanding reaction mechanisms for surface-confined synthesis of two-dimensional materials requires atomic-level characterization and chemical analysis. Beggan et al (2015 Nanotechnology 26 365602) used scanning tunneling microscopy and x-ray photoelectron spectroscopy to elucidate the formation mechanism of surface-confined Ullmann-like coupling of thiophene substituted porphyrins on Ag(111). Upon surface deposition, bromine is dissociated and the porphyrins couple with surface adatoms to create linear strands and hexagonally packed molecules. Annealing the sample results in covalently-bonded networks of thienylporphyrin derivatives. A deeper understanding of surface-confined Ullmann-like coupling has the potential to lead to precision-engineered nano-structures through synthetic techniques. Contribution of the National Institute of Standards and Technology, not subject to copyright in the United States of America.

On the buckling of elastic rings by external confinement.

PubMed

Hazel, Andrew L; Mullin, Tom

2017-05-13

We report the results of an experimental and numerical investigation into the buckling of thin elastic rings confined within containers of circular or regular polygonal cross section. The rings float on the surface of water held in the container and controlled removal of the fluid increases the confinement of the ring. The increased compressive forces can cause the ring to buckle into a variety of shapes. For the circular container, finite perturbations are required to induce buckling, whereas in polygonal containers the buckling occurs through a linear instability that is closely related to the canonical Euler column buckling. A model based on Kirchhoff-Love beam theory is developed and solved numerically, showing good agreement with the experiments and revealing that in polygons increasing the number of sides means that buckling occurs at reduced levels of confinement.This article is part of the themed issue 'Patterning through instabilities in complex media: theory and applications.' © 2017 The Author(s).

Communication: Slow relaxation, spatial mobility gradients, and vitrification in confined films.

PubMed

Mirigian, Stephen; Schweizer, Kenneth S

2014-10-28

Two decades of experimental research indicate that spatial confinement of glass-forming molecular and polymeric liquids results in major changes of their slow dynamics beginning at large confinement distances. A fundamental understanding remains elusive given the generic complexity of activated relaxation in supercooled liquids and the major complications of geometric confinement, interfacial effects, and spatial inhomogeneity. We construct a predictive, quantitative, force-level theory of relaxation in free-standing films for the central question of the nature of the spatial mobility gradient. The key new idea is that vapor interfaces speed up barrier hopping in two distinct, but coupled, ways by reducing near surface local caging constraints and spatially long range collective elastic distortion. Effective vitrification temperatures, dynamic length scales, and mobile layer thicknesses naturally follow. Our results provide a unified basis for central observations of dynamic and pseudo-thermodynamic measurements.

On the buckling of elastic rings by external confinement

PubMed Central

Hazel, Andrew L.

2017-01-01

We report the results of an experimental and numerical investigation into the buckling of thin elastic rings confined within containers of circular or regular polygonal cross section. The rings float on the surface of water held in the container and controlled removal of the fluid increases the confinement of the ring. The increased compressive forces can cause the ring to buckle into a variety of shapes. For the circular container, finite perturbations are required to induce buckling, whereas in polygonal containers the buckling occurs through a linear instability that is closely related to the canonical Euler column buckling. A model based on Kirchhoff–Love beam theory is developed and solved numerically, showing good agreement with the experiments and revealing that in polygons increasing the number of sides means that buckling occurs at reduced levels of confinement. This article is part of the themed issue ‘Patterning through instabilities in complex media: theory and applications.’ PMID:28373386

Modification of the coil-stretch transition by confinement

NASA Astrophysics Data System (ADS)

Doyle, Patick; Tang, Jing; Jones, Jeremy

2010-03-01

Large double stranded DNA are both a powerful system to study polymer dynamics at the single molecule level and also important molecules for genomic applications. While homogenous electric fields are routinely used to separate DNA in gels, DNA deformation in more complex fields has been less widely studied. We will demonstrate how micro/nanofluidic devices allow for the generation of electric fields with well-defined kinematics for trapping, stretching and then watching DNA relax back to equilibrium. The dimensions of the devices highly confine DNA and subsequently change both their conformation and dynamics. We will show how these confinements effects change the coil-stretch transition of a DNA being electrophoretically stretched in a purely elongational electrical field. We experimentally show that a two-stage coil stretch transition occurs and develop a simple dumbbell model which captures most of the relevant physics. We trace the origin of this phenomena to the modification of the effective spring law due to confinement.

Communication: slow relaxation, spatial mobility gradients, and vitrification in confined films

DOE PAGES

Mirigian, Stephen; Schweizer, Kenneth S.

2014-10-31

Two decades of experimental research indicate that spatial confinement of glass-forming molecular and polymeric liquids results in major changes of their slow dynamics beginning at large confinement distances. A fundamental understanding remains elusive given the generic complexity of activated relaxation in supercooled liquids and the major complications of geometric confinement, interfacial effects, and spatial inhomogeneity. For this research, we construct a predictive, quantitative, force-level theory of relaxation in free-standing films for the central question of the nature of the spatial mobility gradient. The key new idea is that vapor interfaces speed up barrier hopping in two distinct, but coupled, waysmore » by reducing near surface local caging constraints and spatially long range collective elastic distortion. Effective vitrification temperatures, dynamic length scales, and mobile layer thicknesses naturally follow. In conclusion, our results provide a unified basis for central observations of dynamic and pseudo-thermodynamic measurements.« less

Absorption and emission spectroscopy of individual semiconductor nanostructures

NASA Astrophysics Data System (ADS)

McDonald, Matthew P.

The advent of controllable synthetic methods for the production of semiconductor nanostructures has led to their use in a host of applications, including light-emitting diodes, field effect transistors, sensors, and even television displays. This is, in part, due to the size, shape, and morphologically dependent optical and electrical properties that make this class of materials extremely customizable; wire-, rod- and sphere-shaped nanocrystals are readily synthesized through common wet chemical methods. Most notably, confining the physical dimension of the nanostructure to a size below its Bohr radius (aB) results in quantum confinement effects that increase its optical energy gap. Not only the size, but the shape of a particle can be exploited to tailor its optical and electrical properties. For example, confined CdSe quantum dots (QDs) and nanowires (NWs) of equivalent diameter possess significantly different optical gaps. This phenomenon has been ascribed to electrostatic contributions arising from dielectric screening effects that are more pronounced in an elongated (wire-like) morphology. Semiconducting nanostructures have thus received significant attention over the past two decades. However, surprisingly little work has been done to elucidate their basic photophysics on a single particle basis. What has been done has generally been accomplished through emission-based measurements, and thus does not fully capture the full breadth of these intriguing systems. What is therefore needed then are absorption-based studies that probe the size and shape dependent evolution of nanostructure photophysics. This thesis summarizes the single particle absorption spectroscopy that we have carried out to fill this knowledge gap. Specifically, the diameter-dependent progression of one-dimensional (1D) excitonic states in CdSe NWs has been revealed. This is followed by a study that focuses on the polarization selection rules of 1D excitons within single CdSe NWs. Finally, shape effects are explored by probing the absorption spectra of CdSe nanowires and nanorods of varying length. All experimental studies are complemented by theoretical predictions from an effective mass model that takes electrostatic interactions into account. Thus, this thesis seeks to show the delicate interplay between quantum confinement and dielectric screening effects in single CdSe nanostructures.

Spatiotemporal Patterns of Noise-Driven Confined Actin Waves in Living Cells.

PubMed

Bernitt, Erik; Döbereiner, Hans-Günther

2017-01-27

Cells utilize waves of polymerizing actin to reshape their morphologies, which is central to physiological and pathological processes alike. Here, we force dorsal actin waves to propagate on one-dimensional domains with periodic boundary conditions, which results in striking spatiotemporal patterns with a clear signature of noise-driven dynamics. We show that these patterns can be very closely reproduced with a noise-driven active medium at coherence resonance.

Wavelength-detuning cross-beam energy transfer mitigation scheme for direct drive: Modeling and evidence from National Ignition Facility implosions

DOE PAGES

Marozas, J. A.; Hohenberger, M.; Rosenberg, M. J.; ...

2018-05-25

Here, cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces laser-energy absorption for direct-drive inertial confinement fusion. Consequently, ablation pressure and implosion velocity suffer from the decreased absorption, reducing target performance in both symmetric and polar direct drive. Additionally, CBET alters the time-resolved scattered-light spectra and redistributes absorbed and scattered-light–changing shell morphology and low-mode drive symmetry. Mitigating CBET is demonstrated in inertial confinement implosions at the National Ignition Facility by detuning the laser-source wavelengths (±2.3 Å UV) of the interacting beams. In polar direct drive, wavelength detuning was shown to increase themore » equatorial region velocity experimentally by 16% and to alter the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation–hydrodynamic simulations that indicate a 10% increase in the average ablation pressure. These results indicate that wavelength detuning successfully mitigates CBET. Simulations predict that optimized phase plates and wavelength-detuning CBET mitigation utilizing the three-legged beam layout of the OMEGA Laser System significantly increase absorption and achieve >100-Gbar hot-spot pressures in symmetric direct drive.« less

Wavelength-detuning cross-beam energy transfer mitigation scheme for direct drive: Modeling and evidence from National Ignition Facility implosions

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

Marozas, J. A.; Hohenberger, M.; Rosenberg, M. J.

Here, cross-beam energy transfer (CBET) results from two-beam energy exchange via seeded stimulated Brillouin scattering, which detrimentally reduces laser-energy absorption for direct-drive inertial confinement fusion. Consequently, ablation pressure and implosion velocity suffer from the decreased absorption, reducing target performance in both symmetric and polar direct drive. Additionally, CBET alters the time-resolved scattered-light spectra and redistributes absorbed and scattered-light–changing shell morphology and low-mode drive symmetry. Mitigating CBET is demonstrated in inertial confinement implosions at the National Ignition Facility by detuning the laser-source wavelengths (±2.3 Å UV) of the interacting beams. In polar direct drive, wavelength detuning was shown to increase themore » equatorial region velocity experimentally by 16% and to alter the in-flight shell morphology. These experimental observations are consistent with design predictions of radiation–hydrodynamic simulations that indicate a 10% increase in the average ablation pressure. These results indicate that wavelength detuning successfully mitigates CBET. Simulations predict that optimized phase plates and wavelength-detuning CBET mitigation utilizing the three-legged beam layout of the OMEGA Laser System significantly increase absorption and achieve >100-Gbar hot-spot pressures in symmetric direct drive.« less

Observation of confinement effects through liner and nonlinear absorption spectroscopy in cuprous oxide

NASA Astrophysics Data System (ADS)

Sekhar, H.; Rakesh Kumar, Y.; Narayana Rao, D.

2015-02-01

Cuprous oxide nano clusters, micro cubes and micro particles were successfully synthesized by reducing copper (II) salt with ascorbic acid in the presence of sodium hydroxide via a co-precipitation method. The X-ray diffraction studies revealed the formation of pure single phase cubic. Raman spectrum shows the inevitable presence of CuO on the surface of the Cu2O powders which may have an impact on the stability of the phase. Transmission electron microscopy (TEM) data revealed that the morphology evolves from nanoclusters to micro cubes and micro particles by increasing the concentration of NaOH. Linear optical measurements show that the absorption peak maximum shifts towards red with changing morphology from nano clusters to micro cubes and micro particles. The nonlinear optical properties were studied using open aperture Z-scan technique with 532 nm, 6 ns laser pulses. Samples exhibited saturable as well as reverse saturable absorption. The results show that the transition from SA to RSA is ascribed to excited-state absorption (ESA) induced by two-photon absorption (TPA) process. Due to confinement effects (enhanced band gap) we observed enhanced nonlinear absorption coefficient (βeff) in the case of nano-clusters compared to their micro-cubes and micro-particles.

The neural correlates of morphological complexity processing: Detecting structure in pseudowords.

PubMed

Schuster, Swetlana; Scharinger, Mathias; Brooks, Colin; Lahiri, Aditi; Hartwigsen, Gesa

2018-06-01

Morphological complexity is a highly debated issue in visual word recognition. Previous neuroimaging studies have shown that speakers are sensitive to degrees of morphological complexity. Two-step derived complex words (bridging through bridge N  > bridge V  > bridging) led to more enhanced activation in the left inferior frontal gyrus than their 1-step derived counterparts (running through run V  > running). However, it remains unclear whether sensitivity to degrees of morphological complexity extends to pseudowords. If this were the case, it would indicate that abstract knowledge of morphological structure is independent of lexicality. We addressed this question by investigating the processing of two sets of pseudowords in German. Both sets contained morphologically viable two-step derived pseudowords differing in the number of derivational steps required to access an existing lexical representation and therefore the degree of structural analysis expected during processing. Using a 2 × 2 factorial design, we found lexicality effects to be distinct from processing signatures relating to structural analysis in pseudowords. Semantically-driven processes such as lexical search showed a more frontal distribution while combinatorial processes related to structural analysis engaged more parietal parts of the network. Specifically, more complex pseudowords showed increased activation in parietal regions (right superior parietal lobe and left precuneus) relative to pseudowords that required less structural analysis to arrive at an existing lexical representation. As the two sets were matched on cohort size and surface form, these results highlight the role of internal levels of morphological structure even in forms that do not possess a lexical representation. © 2018 Wiley Periodicals, Inc.

The role of traditional confinement practices in determining postpartum depression in women in Chinese cultures: a systematic review of the English language evidence.

PubMed

Wong, Josephine; Fisher, Jane

2009-08-01

The Chinese postpartum custom of "confinement" or "doing-the-month" involves formalised social support and recognition of the status of motherhood and has been presumed in anthropological literature to protect mothers of newborns from postpartum depression. The aim of this review was to examine systematically the evidence about the relationship between confinement practices and postpartum depression in Chinese cultures. A systematic search of the English-language literature. Sixteen studies met inclusion criteria. It was found that the role of confinement in postpartum depression is complex: eight studies concluded that it had a protective role; four that it increased risk of postpartum mood disturbance and four studies had inconclusive findings. Aspects of the confinement practice that could contribute to or fail to protect against postpartum depression include the generally diminished social support in contemporary society, conflict with a mother-in-law and the tension experienced by modern women as they work to balance traditional with contemporary values. Methodological differences limit meaningful comparisons between the reviewed studies and generalizations from them. There is little consistent evidence that confinement practices reduce postpartum depression in Chinese cultures. Specific components of confinement practices might reduce psychological distress in Chinese mothers of newborns, but these cannot be discerned from the existing evidence. Confinement cannot be presumed to be available to, welcomed by or effective for all Chinese women or to be a substitute for health service provision.

Optimal remediation of unconfined aquifers: Numerical applications and derivative calculations

NASA Astrophysics Data System (ADS)

Mansfield, Christopher M.; Shoemaker, Christine A.

1999-05-01

This paper extends earlier work on derivative-based optimization for cost-effective remediation to unconfined aquifers, which have more complex, nonlinear flow dynamics than confined aquifers. Most previous derivative-based optimization of contaminant removal has been limited to consideration of confined aquifers; however, contamination is more common in unconfined aquifers. Exact derivative equations are presented, and two computationally efficient approximations, the quasi-confined (QC) and head independent from previous (HIP) unconfined-aquifer finite element equation derivative approximations, are presented and demonstrated to be highly accurate. The derivative approximations can be used with any nonlinear optimization method requiring derivatives for computation of either time-invariant or time-varying pumping rates. The QC and HIP approximations are combined with the nonlinear optimal control algorithm SALQR into the unconfined-aquifer algorithm, which is shown to compute solutions for unconfined aquifers in CPU times that were not significantly longer than those required by the confined-aquifer optimization model. Two of the three example unconfined-aquifer cases considered obtained pumping policies with substantially lower objective function values with the unconfined model than were obtained with the confined-aquifer optimization, even though the mean differences in hydraulic heads predicted by the unconfined- and confined-aquifer models were small (less than 0.1%). We suggest a possible geophysical index based on differences in drawdown predictions between unconfined- and confined-aquifer models to estimate which aquifers require unconfined-aquifer optimization and which can be adequately approximated by the simpler confined-aquifer analysis.

Automated entry technologies for confined space work activities: A survey.

PubMed

Botti, Lucia; Ferrari, Emilio; Mora, Cristina

2017-04-01

Work in confined spaces poses a significant risk to workers and rescuers involved in the emergency response when an accident occurs. Despite several standards and regulations define the safety requirements for such activities, injuries, and fatalities still occur. Furthermore, the on-site inspections after accidents often reveal that both employers and employees fail to implement safe entry procedures. Removing the risk is possible by avoiding the worker entry, but many activities require the presence of the operator inside the confined space to perform manual tasks. The following study investigates the available technologies for hazardous confined space work activities, e.g., cleaning, inspecting, and maintenance tasks. The aim is to provide a systematic review of the automated solutions for high-risk activities in confined spaces, considering the non-man entry as the most effective confined space safety strategy. Second, this survey aims to provide suggestions for future research addressing the design of new technologies. The survey consists of about 60 papers concerning innovative technologies for confined space work activities. The document review shows that several solutions have been developed and automation can replace the workers for a limited number of hazardous tasks. Several activities still require the manual intervention due to the complex characteristics of confined spaces, e.g., to remove the remains of the automatic cleaning process from the bottom of a tank. The results show that available technologies require more flexibility to adapt to such occupational environments and further research is needed.

The Impact of Entropy on the Spatial Organization of Synaptonemal Complexes within the Cell Nucleus

PubMed Central

Fritsche, Miriam; Reinholdt, Laura G.; Lessard, Mark; Handel, Mary Ann; Bewersdorf, Jörg; Heermann, Dieter W.

2012-01-01

We employ 4Pi-microscopy to study SC organization in mouse spermatocyte nuclei allowing for the three-dimensional reconstruction of the SC's backbone arrangement. Additionally, we model the SCs in the cell nucleus by confined, self-avoiding polymers, whose chain ends are attached to the envelope of the confining cavity and diffuse along it. This work helps to elucidate the role of entropy in shaping pachytene SC organization. The framework provided by the complex interplay between SC polymer rigidity, tethering and confinement is able to qualitatively explain features of SC organization, such as mean squared end-to-end distances, mean squared center-of-mass distances, or SC density distributions. However, it fails in correctly assessing SC entanglement within the nucleus. In fact, our analysis of the 4Pi-microscopy images reveals a higher ordering of SCs within the nuclear volume than what is expected by our numerical model. This suggests that while effects of entropy impact SC organization, the dedicated action of proteins or actin cables is required to fine-tune the spatial ordering of SCs within the cell nucleus. PMID:22574147

Microfluidics with fluid walls.

PubMed

Walsh, Edmond J; Feuerborn, Alexander; Wheeler, James H R; Tan, Ann Na; Durham, William M; Foster, Kevin R; Cook, Peter R

2017-10-10

Microfluidics has great potential, but the complexity of fabricating and operating devices has limited its use. Here we describe a method - Freestyle Fluidics - that overcomes many key limitations. In this method, liquids are confined by fluid (not solid) walls. Aqueous circuits with any 2D shape are printed in seconds on plastic or glass Petri dishes; then, interfacial forces pin liquids to substrates, and overlaying an immiscible liquid prevents evaporation. Confining fluid walls are pliant and resilient; they self-heal when liquids are pipetted through them. We drive flow through a wide range of circuits passively by manipulating surface tension and hydrostatic pressure, and actively using external pumps. Finally, we validate the technology with two challenging applications - triggering an inflammatory response in human cells and chemotaxis in bacterial biofilms. This approach provides a powerful and versatile alternative to traditional microfluidics.The complexity of fabricating and operating microfluidic devices limits their use. Walsh et al. describe a method in which circuits are printed as quickly and simply as writing with a pen, and liquids in them are confined by fluid instead of solid walls.

Linear and ring polymers in confined geometries

NASA Astrophysics Data System (ADS)

Usatenko, Zoryana; Kuterba, Piotr; Chamati, Hassan; Romeis, Dirk

2017-03-01

A short overview of the theoretical and experimental works on the polymer-colloid mixtures is given. The behaviour of a dilute solution of linear and ring polymers in confined geometries like slit of two parallel walls or in the solution of mesoscopic colloidal particles of big size with different adsorbing or repelling properties in respect to polymers is discussed. Besides, we consider the massive field theory approach in fixed space dimensions d = 3 for the investigation of the interaction between long flexible polymers and mesoscopic colloidal particles of big size and for the calculation of the correspondent depletion interaction potentials and the depletion forces between confining walls. The presented results indicate the interesting and nontrivial behavior of linear and ring polymers in confined geometries and give possibility better to understand the complexity of physical effects arising from confinement and chain topology which plays a significant role in the shaping of individual chromosomes and in the process of their segregation, especially in the case of elongated bacterial cells. The possibility of using linear and ring polymers for production of new types of nano- and micro-electromechanical devices is analyzed.

Effect of capsid confinement on the chromatin organization of the SV40 minichromosome

PubMed Central

Saper, Gadiel; Kler, Stanislav; Asor, Roi; Oppenheim, Ariella; Raviv, Uri; Harries, Daniel

2013-01-01

Using small-angle X-ray scattering, we determined the three-dimensional packing architecture of the minichromosome confined within the SV40 virus. In solution, the minichromosome, composed of closed circular dsDNA complexed in nucleosomes, was shown to be structurally similar to cellular chromatin. In contrast, we find a unique organization of the nanometrically encapsidated chromatin, whereby minichromosomal density is somewhat higher at the center of the capsid and decreases towards the walls. This organization is in excellent agreement with a coarse-grained computer model, accounting for tethered nucleosomal interactions under viral capsid confinement. With analogy to confined liquid crystals, but contrary to the solenoid structure of cellular chromatin, our simulations indicate that the nucleosomes within the capsid lack orientational order. Nucleosomes in the layer adjacent to the capsid wall, however, align with the boundary, thereby inducing a ‘molten droplet’ state of the chromatin. These findings indicate that nucleosomal interactions suffice to predict the genome organization in polyomavirus capsids and underscore the adaptable nature of the eukaryotic chromatin architecture to nanoscale confinement. PMID:23258701

Effect of capsid confinement on the chromatin organization of the SV40 minichromosome.

PubMed

Saper, Gadiel; Kler, Stanislav; Asor, Roi; Oppenheim, Ariella; Raviv, Uri; Harries, Daniel

2013-02-01

Using small-angle X-ray scattering, we determined the three-dimensional packing architecture of the minichromosome confined within the SV40 virus. In solution, the minichromosome, composed of closed circular dsDNA complexed in nucleosomes, was shown to be structurally similar to cellular chromatin. In contrast, we find a unique organization of the nanometrically encapsidated chromatin, whereby minichromosomal density is somewhat higher at the center of the capsid and decreases towards the walls. This organization is in excellent agreement with a coarse-grained computer model, accounting for tethered nucleosomal interactions under viral capsid confinement. With analogy to confined liquid crystals, but contrary to the solenoid structure of cellular chromatin, our simulations indicate that the nucleosomes within the capsid lack orientational order. Nucleosomes in the layer adjacent to the capsid wall, however, align with the boundary, thereby inducing a 'molten droplet' state of the chromatin. These findings indicate that nucleosomal interactions suffice to predict the genome organization in polyomavirus capsids and underscore the adaptable nature of the eukaryotic chromatin architecture to nanoscale confinement.

Perivascular epithelioid cell tumor (PEComa) of gynecologic origin: a clinicopathological study of three cases.

PubMed

Ye, H Y; Chen, J G; Luo, D L; Jiang, Z M; Chen, Z H

2012-01-01

Perivascular epithelioid cell tumors (PEComas), occasionally associated with the tuberous sclerosis complex, are characterized by varying amounts of spindle and epithelioid cells with clear to eosinophilic cytoplasm that display immunoreactivity for melanocytic markers, most frequently HMB-45. Perivascular epithelioid cell tumor of gynecologic origin is very rare, and there have been only a few reported cases. This study describes the clinical, histological, and immunohistochemical features and prognoses of three cases of gynecologic origin. Two of the three tumors were confined to the uterus and one to the vagina. None of the patients had tuberous sclerosis complex. Immunohistochemistry indicated that all three cases expressed at least one melanocytic marker, and HMB45 was a positive marker for all of them. These markers can be found in both epithelial cells and spindle cells. Except for MiTF, which was located in the nucleus, all the other antibodies were located in the cytoplasm. The three cases have been followed up for 26, 22, and three months, respectively, with disease-free survival in all cases. We conclude that PEComas of gynecologic origin have morphological and immunohistochemical features of the PEComa family, which are rare and should be included in the differential diagnosis with other tumors. Until more cases of this rare tumor are evaluated with longer follow-up, firm criteria for malignancy remain uncertain.

Morphology of a highly asymmetric double crystallizable poly(ɛ-caprolactone-b-ethylene oxide) block copolymer

NASA Astrophysics Data System (ADS)

Li, Liangbin; Meng, Fenghua; Zhong, Zhiyuan; Byelov, Dmytro; de Jeu, Wim H.; Feijen, Jan

2007-01-01

The morphology of a highly asymmetric double crystallizable poly(ɛ-caprolactone-b-ethylene oxide) (PCL-b-PEO) block copolymer has been studied with in situ simultaneously small and wide-angle x-ray scattering as well as atomic force microscopy. The molecular masses Mn of the PCL and PEO blocks are 24 000 and 5800, respectively. X-ray scattering and rheological measurements indicate that no microphase separation occurs in the melt. Decreasing the temperature simultaneously triggers off a crystallization of PCL and microphase separation between the PCL and PEO blocks. Coupling and competition between microphase separation and crystallization results in a morphology of PEO spheres surrounded by PCL partially crystallized in lamella. Further decreasing temperature induces the crystallization of PEO spheres, which have a preferred orientation due to the confinements from hard PCL crystalline lamella and from soft amorphous PCL segments in different sides. The final morphology of this highly asymmetric block copolymer is similar to the granular morphology reported for syndiotactic polypropylene and other (co-) polymers. This implies a similar underlying mechanism of coupling and competition of various phase transitions, which is worth further exploration.

Cryptic Speciation Patterns in Iranian Rock Lizards Uncovered by Integrative Taxonomy

PubMed Central

Ahmadzadeh, Faraham; Flecks, Morris; Carretero, Miguel A.; Mozaffari, Omid; Böhme, Wolfgang; Harris, D. James; Freitas, Susana; Rödder, Dennis

2013-01-01

While traditionally species recognition has been based solely on morphological differences either typological or quantitative, several newly developed methods can be used for a more objective and integrative approach on species delimitation. This may be especially relevant when dealing with cryptic species or species complexes, where high overall resemblance between species is coupled with comparatively high morphological variation within populations. Rock lizards, genus Darevskia, are such an example, as many of its members offer few diagnostic morphological features. Herein, we use a combination of genetic, morphological and ecological criteria to delimit cryptic species within two species complexes, D. chlorogaster and D. defilippii, both distributed in northern Iran. Our analyses are based on molecular information from two nuclear and two mitochondrial genes, morphological data (15 morphometric, 16 meristic and four categorical characters) and eleven newly calculated spatial environmental predictors. The phylogeny inferred for Darevskia confirmed monophyly of each species complex, with each of them comprising several highly divergent clades, especially when compared to other congeners. We identified seven candidate species within each complex, of which three and four species were supported by Bayesian species delimitation within D. chlorogaster and D. defilippii, respectively. Trained with genetically determined clades, Ecological Niche Modeling provided additional support for these cryptic species. Especially those within the D. defilippii-complex exhibit well-differentiated niches. Due to overall morphological resemblance, in a first approach PCA with mixed variables only showed the separation between the two complexes. However, MANCOVA and subsequent Discriminant Analysis performed separately for both complexes allowed for distinction of the species when sample size was large enough, namely within the D. chlorogaster-complex. In conclusion, the results support four new species, which are described herein. PMID:24324611

Reticulate Structures Reveal the Significance of Cell Motility in the Morphogenesis of Complex Microbial Structures in Pavilion Lake, British Columbia

NASA Astrophysics Data System (ADS)

Shepard, R.

2008-12-01

Microbial communities are architects of incredibly complex and diverse morphological structures. Each morphology is a snapshot that reflects the complex interactions within the microbial community and between the community and its environment. Characterizing morphology as an emergent property of microbial communities is thus relevant to understanding the evolution of multicellularity and complexity in developmental systems, to the identification of biosignatures, and to furthering our understanding of modern and ancient microbial ecology. Recently discovered cyanobacterial mats in Pavilion Lake, British Columbia construct unusual complex architecture on the scale of decimeters that incorporates significant void space. Fundamental mesoscale morphological elements include terraces, arches, bridges, depressions, domes, and pillars. The mats themselves also exhibit several microscale morphologies, with reticulate structures being the dominant example. The reticulate structures exhibit a diverse spectrum of morphologies with endmembers characterized by either angular or curvilinear ridges. In laboratory studies, aggregation into reticulate structures occurs as a result of the random gliding and colliding among motile cyanobacterial filaments. Likewise, when Pavilion reticulate mats were sampled and brought to the surface, cyanobacteria invariably migrated out of the mat onto surrounding surfaces. Filaments were observed to move rapidly in clumps, preferentially following paths of previous filaments. The migrating filaments organized into new angular and ropey reticulate biofilms within hours of sampling, demonstrating that cell motility is responsible for the reticulate patterns. Because the morphogenesis of reticulate structures can be linked to motility behaviors of filamentous cyanobacteria, the Willow Point mats provide a unique natural laboratory in which to elucidate the connections between a specific microbial behavior and the construction of complex microbial community morphology. To this end, we identified and characterized fundamental building blocks of the mesoscale morphologies, including bridges, anchors, and curved edges. These morphological building blocks were compared with the suite of motility behaviors and patterns observed in reticulate morphogenesis. Results of this comparison suggest that cyanobacterial motility plays a significant and often dominant role in the morphogenesis of the entire suite of morphologies observed in the microbial mats of Pavilion Lake.

Morphological characterization of rat entorhinal neurons in vivo: soma-dendritic structure and axonal domains.

PubMed

Lingenhöhl, K; Finch, D M

1991-01-01

We used in vivo intracellular labeling with horseradish peroxidase in order to study the soma-dendritic morphology and axonal projections of rat entorhinal neurons. The cells responded to hippocampal stimulation with inhibitory postsynaptic potentials, and thus likely received direct or indirect hippocampal input. All cells (n = 24) showed extensive dendritic domains that extended in some cases for more than 1 mm. The dendrites of layer II neurons were largely restricted to layers I and II or layers I-III, while the dendrites of deeper cells could extend through all cortical layers. Computed 3D rotations showed that the basilar dendrites of deep pyramids extended roughly parallel to the cortical layering, and that they were mostly confined to the layer containing the soma and layers immediately adjacent. Total dendritic lengths averaged 9.8 mm +/- 3.8 (SD), and ranged from 5 mm to more than 18 mm. Axonal processes could be visualized in 21 cells. Most of these showed axonal branching within the entorhinal cortex, sometimes extensive. Efferent axonal domains were reconstructed in detail in 3 layer II stellate cells. All 3 projected axons across the subicular complex to the dentate gyrus. One of these cells showed an extensive net-like axonal domain that also projected to several other structures, including the hippocampus proper, subicular complex, and the amygdalo-piriform transition area. The axons of layer III and IV cells projected to the angular bundle, where they continued in a rostral direction. In contrast to the layer II, III and IV cells, no efferent axonal branches leaving the entorhinal cortex could be visualized in 5 layer V neurons. The data indicate that entorhinal neurons can integrate input from a considerable volume of entorhinal cortex by virtue of their extensive dendritic domains, and provide a further basis for specifying the layers in which cells receive synaptic input. The extensive axonal branching pattern seen in most of the cells would support divergent propagation of their activity.

SOFIA Observations of S106: Dynamics of the Warm Gas

NASA Technical Reports Server (NTRS)

Simon, R.; Schneider, N.; Stutzki, J.; Gusten, R.; Graf, U. U.; Hartogh, P.; Guan, X.; Staguhn, J. G.; Benford, D. J.

2012-01-01

Context The H II region/PDR/molecular cloud complex S106 is excited by a single O-star. The full extent of the warm and dense gas close to the star has not been mapped in spectrally resolved high-J CO or [C II] lines, so the kinematics of the warm. partially ionized gas, are unknown. Whether the prominent dark lane bisecting the hourglass-shaped nebula is due solely to the shadow cast by a small disk around the exciting star or also to extinction in high column foreground gas was an open question until now. Aims. To disentangle the morphology and kinematics of warm neutral and ionized gas close to the star, study their relation to the bulk of the molecular gas. and to investigate the nature of the dark lane. Methods. We use the heterodyne receiver GREAT on board SOFIA to observe velocity resolved spectral lines of [C II] and CO 11 yields 10 in comparison with so far unpublished submm continuum data at 350 micron (8HARC-Il) and complementary molecular line data. Results. The high angular and spectral resolution observations show a very complex morphology and kinematics of the inner S106 region, with many different components at different excitation conditions contributing to the observed emission. The [C II] lines are found to be bright and very broad. tracing high velocity gas close to the interface of molecular cloud and H II region. CO 11 yields 10 emission is more confined.. both spatially and in velocity, to the immediate surroundings of S 106 IR showing the presence of warm, high density (clumpy) gas. Our high angular resolution submm continuum observations rule out the scenario where the dark lane separating the two lobes is due solely to the shadow cast by a small disk close to the star. The lane is clearly seen also as warm, high column density gas at the boundary of the molecular cloud and H II region.

Moesin and myosin phosphatase confine neutrophil orientation in a chemotactic gradient

PubMed Central

Liu, Xiaowen; Yang, Tao; Suzuki, Koya; Tsukita, Sachiko; Ishii, Masaru; Zhou, Shuping; Wang, Gang; Cao, Luyang; Qian, Feng; Taylor, Shalina; Oh, Myung-Jin; Levitan, Irena; Ye, Richard D.; Carnegie, Graeme K.; Malik, Asrar B.

2015-01-01

Neutrophils respond to invading bacteria by adopting a polarized morphology, migrating in the correct direction, and engulfing the bacteria. How neutrophils establish and precisely orient this polarity toward pathogens remains unclear. Here we report that in resting neutrophils, the ERM (ezrin, radixin, and moesin) protein moesin in its active form (phosphorylated and membrane bound) prevented cell polarization by inhibiting the small GTPases Rac, Rho, and Cdc42. Attractant-induced activation of myosin phosphatase deactivated moesin at the prospective leading edge to break symmetry and establish polarity. Subsequent translocation of moesin to the trailing edge confined the formation of a prominent pseudopod directed toward pathogens and prevented secondary pseudopod formation in other directions. Therefore, both moesin-mediated inhibition and its localized deactivation by myosin phosphatase are essential for neutrophil polarization and effective neutrophil tracking of pathogens. PMID:25601651

Urban habitat complexity affects species richness but not environmental filtering of morphologically-diverse ants

PubMed Central

Nash, Michael A.; Christie, Fiona J.; Hahs, Amy K.; Livesley, Stephen J.

2015-01-01

Habitat complexity is a major determinant of structure and diversity of ant assemblages. Following the size-grain hypothesis, smaller ant species are likely to be advantaged in more complex habitats compared to larger species. Habitat complexity can act as an environmental filter based on species size and morphological traits, therefore affecting the overall structure and diversity of ant assemblages. In natural and semi-natural ecosystems, habitat complexity is principally regulated by ecological successions or disturbance such as fire and grazing. Urban ecosystems provide an opportunity to test relationships between habitat, ant assemblage structure and ant traits using novel combinations of habitat complexity generated and sustained by human management. We sampled ant assemblages in low-complexity and high-complexity parks, and high-complexity woodland remnants, hypothesizing that (i) ant abundance and species richness would be higher in high-complexity urban habitats, (ii) ant assemblages would differ between low- and high-complexity habitats and (iii) ants living in high-complexity habitats would be smaller than those living in low-complexity habitats. Contrary to our hypothesis, ant species richness was higher in low-complexity habitats compared to high-complexity habitats. Overall, ant assemblages were significantly different among the habitat complexity types investigated, although ant size and morphology remained the same. Habitat complexity appears to affect the structure of ant assemblages in urban ecosystems as previously observed in natural and semi-natural ecosystems. However, the habitat complexity filter does not seem to be linked to ant morphological traits related to body size. PMID:26528416

Sociolinguistic Typology and Sign Languages

PubMed Central

Schembri, Adam; Fenlon, Jordan; Cormier, Kearsy; Johnston, Trevor

2018-01-01

This paper examines the possible relationship between proposed social determinants of morphological ‘complexity’ and how this contributes to linguistic diversity, specifically via the typological nature of the sign languages of deaf communities. We sketch how the notion of morphological complexity, as defined by Trudgill (2011), applies to sign languages. Using these criteria, sign languages appear to be languages with low to moderate levels of morphological complexity. This may partly reflect the influence of key social characteristics of communities on the typological nature of languages. Although many deaf communities are relatively small and may involve dense social networks (both social characteristics that Trudgill claimed may lend themselves to morphological ‘complexification’), the picture is complicated by the highly variable nature of the sign language acquisition for most deaf people, and the ongoing contact between native signers, hearing non-native signers, and those deaf individuals who only acquire sign languages in later childhood and early adulthood. These are all factors that may work against the emergence of morphological complexification. The relationship between linguistic typology and these key social factors may lead to a better understanding of the nature of sign language grammar. This perspective stands in contrast to other work where sign languages are sometimes presented as having complex morphology despite being young languages (e.g., Aronoff et al., 2005); in some descriptions, the social determinants of morphological complexity have not received much attention, nor has the notion of complexity itself been specifically explored. PMID:29515506

Color from hierarchy: Diverse optical properties of micron-sized spherical colloidal assemblies.

PubMed

Vogel, Nicolas; Utech, Stefanie; England, Grant T; Shirman, Tanya; Phillips, Katherine R; Koay, Natalie; Burgess, Ian B; Kolle, Mathias; Weitz, David A; Aizenberg, Joanna

2015-09-01

Materials in nature are characterized by structural order over multiple length scales have evolved for maximum performance and multifunctionality, and are often produced by self-assembly processes. A striking example of this design principle is structural coloration, where interference, diffraction, and absorption effects result in vivid colors. Mimicking this emergence of complex effects from simple building blocks is a key challenge for man-made materials. Here, we show that a simple confined self-assembly process leads to a complex hierarchical geometry that displays a variety of optical effects. Colloidal crystallization in an emulsion droplet creates micron-sized superstructures, termed photonic balls. The curvature imposed by the emulsion droplet leads to frustrated crystallization. We observe spherical colloidal crystals with ordered, crystalline layers and a disordered core. This geometry produces multiple optical effects. The ordered layers give rise to structural color from Bragg diffraction with limited angular dependence and unusual transmission due to the curved nature of the individual crystals. The disordered core contributes nonresonant scattering that induces a macroscopically whitish appearance, which we mitigate by incorporating absorbing gold nanoparticles that suppress scattering and macroscopically purify the color. With increasing size of the constituent colloidal particles, grating diffraction effects dominate, which result from order along the crystal's curved surface and induce a vivid polychromatic appearance. The control of multiple optical effects induced by the hierarchical morphology in photonic balls paves the way to use them as building blocks for complex optical assemblies--potentially as more efficient mimics of structural color as it occurs in nature.

Color from hierarchy: Diverse optical properties of micron-sized spherical colloidal assemblies

PubMed Central

Vogel, Nicolas; Utech, Stefanie; England, Grant T.; Shirman, Tanya; Phillips, Katherine R.; Koay, Natalie; Burgess, Ian B.; Kolle, Mathias; Weitz, David A.; Aizenberg, Joanna

2015-01-01

Materials in nature are characterized by structural order over multiple length scales have evolved for maximum performance and multifunctionality, and are often produced by self-assembly processes. A striking example of this design principle is structural coloration, where interference, diffraction, and absorption effects result in vivid colors. Mimicking this emergence of complex effects from simple building blocks is a key challenge for man-made materials. Here, we show that a simple confined self-assembly process leads to a complex hierarchical geometry that displays a variety of optical effects. Colloidal crystallization in an emulsion droplet creates micron-sized superstructures, termed photonic balls. The curvature imposed by the emulsion droplet leads to frustrated crystallization. We observe spherical colloidal crystals with ordered, crystalline layers and a disordered core. This geometry produces multiple optical effects. The ordered layers give rise to structural color from Bragg diffraction with limited angular dependence and unusual transmission due to the curved nature of the individual crystals. The disordered core contributes nonresonant scattering that induces a macroscopically whitish appearance, which we mitigate by incorporating absorbing gold nanoparticles that suppress scattering and macroscopically purify the color. With increasing size of the constituent colloidal particles, grating diffraction effects dominate, which result from order along the crystal’s curved surface and induce a vivid polychromatic appearance. The control of multiple optical effects induced by the hierarchical morphology in photonic balls paves the way to use them as building blocks for complex optical assemblies—potentially as more efficient mimics of structural color as it occurs in nature. PMID:26290583

Personality and morphological traits affect pigeon survival from raptor attacks.

PubMed

Santos, Carlos D; Cramer, Julia F; Pârâu, Liviu G; Miranda, Ana C; Wikelski, Martin; Dechmann, Dina K N

2015-10-22

Personality traits have recently been shown to impact fitness in different animal species, potentially making them similarly relevant drivers as morphological and life history traits along the evolutionary pathways of organisms. Predation is a major force of natural selection through its deterministic effects on individual survival, but how predation pressure has helped to shape personality trait selection, especially in free-ranging animals, remains poorly understood. We used high-precision GPS tracking to follow whole flocks of homing pigeons (Columba livia) with known personalities and morphology during homing flights where they were severely predated by raptors. This allowed us to determine how the personality and morphology traits of pigeons may affect their risk of being predated by raptors. Our survival model showed that individual pigeons, which were more tolerant to human approach, slower to escape from a confined environment, more resistant to human handling, with larger tarsi, and with lighter plumage, were more likely to be predated by raptors. We provide rare empirical evidence that the personality of prey influences their risk of being predated under free-ranging circumstances.

Personality and morphological traits affect pigeon survival from raptor attacks

PubMed Central

Santos, Carlos D.; Cramer, Julia F.; Pârâu, Liviu G.; Miranda, Ana C.; Wikelski, Martin; Dechmann, Dina K. N.

2015-01-01

Personality traits have recently been shown to impact fitness in different animal species, potentially making them similarly relevant drivers as morphological and life history traits along the evolutionary pathways of organisms. Predation is a major force of natural selection through its deterministic effects on individual survival, but how predation pressure has helped to shape personality trait selection, especially in free-ranging animals, remains poorly understood. We used high-precision GPS tracking to follow whole flocks of homing pigeons (Columba livia) with known personalities and morphology during homing flights where they were severely predated by raptors. This allowed us to determine how the personality and morphology traits of pigeons may affect their risk of being predated by raptors. Our survival model showed that individual pigeons, which were more tolerant to human approach, slower to escape from a confined environment, more resistant to human handling, with larger tarsi, and with lighter plumage, were more likely to be predated by raptors. We provide rare empirical evidence that the personality of prey influences their risk of being predated under free-ranging circumstances. PMID:26489437

The effect of particle size on the morphology and thermodynamics of diblock copolymer/tethered-particle membranes.

PubMed

Zhang, Bo; Edwards, Brian J

2015-06-07

A combination of self-consistent field theory and density functional theory was used to examine the effect of particle size on the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Particle size was varied between one and four tenths of the radius of gyration of the diblock polymer chain for neutral particles as well as those either favoring or disfavoring segments of the copolymer blocks. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the physics associated with the molecular-level self-assembly processes. Typical morphologies were observed, such as lamellar, spheroidal, cylindrical, gyroidal, and perforated lamellar, with the primary concentration region of the tethered particles being influenced heavily by particle size and tethering location, strength of the particle-segment energetic interactions, chain length, and copolymer radius of gyration. The effect of the simulation box size on the observed morphology and system thermodynamics was also investigated, indicating possible effects of confinement upon the system self-assembly processes.

Morphological Complexity as a Floral Signal: From Perception by Insect Pollinators to Co-Evolutionary Implications.

PubMed

Krishna, Shivani; Keasar, Tamar

2018-06-06

Morphologically complex flowers are characterized by bilateral symmetry, tube-like shapes, deep corolla tubes, fused petals, and/or poricidal anthers, all of which constrain the access of insect visitors to floral nectar and pollen rewards. Only a subset of potential pollinators, mainly large bees, learn to successfully forage on such flowers. Thus, complexity may comprise a morphological filter that restricts the range of visitors and thereby increases food intake for successful foragers. Such pollinator specialization, in turn, promotes flower constancy and reduces cross-species pollen transfer, providing fitness benefits to plants with complex flowers. Since visual signals associated with floral morphological complexity are generally honest (i.e., indicate food rewards), pollinators need to perceive and process them. Physiological studies show that bees detect distant flowers through long-wavelength sensitive photoreceptors. Bees effectively perceive complex shapes and learn the positions of contours based on their spatial frequencies. Complex flowers require long handling times by naive visitors, and become highly profitable only for experienced foragers. To explore possible pathways towards the evolution of floral complexity, we discuss cognitive mechanisms that potentially allow insects to persist on complex flowers despite low initial foraging gains, suggest experiments to test these mechanisms, and speculate on their adaptive value.

Sexual selection and the evolution of genital shape and complexity in water striders.

PubMed

Rowe, Locke; Arnqvist, Göran

2012-01-01

Animal genitalia show two striking but incompletely understood evolutionary trends: a great evolutionary divergence in the shape of genitalic structures, and characteristic structural complexity. Both features are thought to result from sexual selection, but explicit comparative tests are hampered by the fact that it is difficult to quantify both morphological complexity and divergence in shape. We undertake a comparative study of multiple nongenitalic and male genital traits in a clade of 15 water strider species to quantify complexity and shape divergence. We show that genital structures are more complex and their shape more divergent among species than nongenital traits. Further, intromittent genital traits are more complex and have evolved more divergently than nonintromittent genital traits. More importantly, shape and complexity of nonintromittent genital traits show correlated evolution with indices of premating sexual selection and intromittent genital traits with postmating sexual selection, suggesting that the evolution of different components of genital morphology are shaped independently by distinct forms of sexual selection. Our quantitative results provide direct comparative support for the hypothesis that sexual selection is associated with morphological complexity in genitalic traits and highlight the importance of quantifying morphological shape and complexity, rather than size in studies of genital evolution. © 2011 The Author(s). Evolution © 2011 The Society for the Study of Evolution.

Computational modeling and statistical analyses on individual contact rate and exposure to disease in complex and confined transportation hubs

NASA Astrophysics Data System (ADS)

Wang, W. L.; Tsui, K. L.; Lo, S. M.; Liu, S. B.

2018-01-01

Crowded transportation hubs such as metro stations are thought as ideal places for the development and spread of epidemics. However, for the special features of complex spatial layout, confined environment with a large number of highly mobile individuals, it is difficult to quantify human contacts in such environments, wherein disease spreading dynamics were less explored in the previous studies. Due to the heterogeneity and dynamic nature of human interactions, increasing studies proved the importance of contact distance and length of contact in transmission probabilities. In this study, we show how detailed information on contact and exposure patterns can be obtained by statistical analyses on microscopic crowd simulation data. To be specific, a pedestrian simulation model-CityFlow was employed to reproduce individuals' movements in a metro station based on site survey data, values and distributions of individual contact rate and exposure in different simulation cases were obtained and analyzed. It is interesting that Weibull distribution fitted the histogram values of individual-based exposure in each case very well. Moreover, we found both individual contact rate and exposure had linear relationship with the average crowd densities of the environments. The results obtained in this paper can provide reference to epidemic study in complex and confined transportation hubs and refine the existing disease spreading models.

3D cancer cell migration in a confined matrix

NASA Astrophysics Data System (ADS)

Alobaidi, Amani; Sun, Bo

Cancer cell migration is widely studied in 2D motion, which does not mimic the invasion processes in vivo. More recently, 3D cell migration studies have been performed. The ability of cancer cells to migrate within the extracellular matrix depends on the physical and biochemical features of the extracellular matrix. We present a model of cell motility in confined matrix geometry. The aim of the study is to study cancer migration in collagen matrix, as a soft tissue, to investigate their motility within the confined and surrounding collagen environment. Different collagen concentrations have been used to show the ability of these cancer cells to move through such a complex structure by measuring Cancer cell migration velocity as well as the displacement. Graduate student physics department.

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.

Bilingual Children's Acquisition of English Verb Morphology: Effects of Language Exposure, Structure Complexity, and Task Type

ERIC Educational Resources Information Center

Paradis, Johanne

2010-01-01

This study investigated whether bilingual-monolingual differences would be apparent in school-age children's use and knowledge of English verb morphology and whether differences would be influenced by amount of exposure to English, complexity of the morphological structure, or the type of task given. French-English bilinguals (mean age = 6;10)…

Morphological and molecular characterization of Cladosporium cladosporioides species complex causing pecan tree leaf spot.

PubMed

Walker, C; Muniz, M F B; Rolim, J M; Martins, R R O; Rosenthal, V C; Maciel, C G; Mezzomo, R; Reiniger, L R S

2016-09-16

The objective of this study was to characterize species of the Cladosporium cladosporioides complex isolated from pecan trees (Carya illinoinensis) with symptoms of leaf spot, based on morphological and molecular approaches. Morphological attributes were assessed using monosporic cultures on potato dextrose agar medium, which were examined for mycelial growth, sporulation, color, and conidia and ramoconidia size. Molecular characterization comprised isolation of DNA and subsequent amplification of the translation elongation factor 1α (TEF-1α) region. Three species of the C. cladosporioides complex were identified: C. cladosporioides, Cladosporium pseudocladosporioides, and Cladosporium subuliforme. Sporulation was the most important characteristic differentiating species of this genus. However, morphological features must be considered together with molecular analysis, as certain characters are indistinguishable between species. TEF-1αcan be effectively used to identify and group isolates belonging to the C. cladosporioides complex. The present study provides an important example of a methodology to ascertain similarity between isolates of this complex causing leaf spot in pecan trees, which should facilitate future pathogenicity studies.

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

Youm, Sang Gil; Hwang, Euiyong; Chavez, Carlos A.

The ability to control nanoscale morphology and molecular organization in organic semiconducting polymer thin films is an important prerequisite for enhancing the efficiency of organic thin-film devices including organic light-emitting and photovoltaic devices. The current “top-down” paradigm for making such devices is based on utilizing solution-based processing (e.g., spin-casting) of soluble semiconducting polymers. This approach typically provides only modest control over nanoscale molecular organization and polymer chain alignment. A promising alternative to using solutions of presynthesized semiconducting polymers pursues instead a “bottom-up” approach to prepare surface-grafted semiconducting polymer thin films by surface-initiated polymerization of small-molecule monomers. Herein, we describe themore » development of an efficient method to prepare polythiophene thin films utilizing surface-initiated Kumada catalyst transfer polymerization. In this study, we provided evidence that the surface-initiated polymerization occurs by the highly robust controlled (quasi-“living”) chain-growth mechanism. Further optimization of this method enabled reliable preparation of polythiophene thin films with thickness up to 100 nm. Extensive structural studies of the resulting thin films using X-ray and neutron scattering methods as well as ultraviolet photoemission spectroscopy revealed detailed information on molecular organization and the bulk morphology of the films, and enabled further optimization of the polymerization protocol. One of the remarkable findings was that surface-initiated polymerization delivers polymer thin films showing complex molecular organization, where polythiophene chains assemble into lateral crystalline domains of about 3.2 nm size, with individual polymer chains folded to form in-plane aligned and densely packed oligomeric segments (7-8 thiophene units per each segment) within each domain. Achieving such a complex mesoscale organization is virtually impossible with traditional methods relying on solution processing of presynthesized polymers. Another significant advantage of surface-confined polymer thin films is their remarkable stability toward organic solvents and other processing conditions. In addition to controlled bulk morphology, uniform molecular organization, and stability, a unique feature of the surface-initiated polymerization is that it can be used for the preparation of large-area uniformly nanopatterned polymer thin films. Lastly, this was demonstrated using a combination of particle lithography and surface-initiated polymerization. In general, surface-initiated polymerization is not limited to polythiophene but can be also expanded toward other classes of semiconducting polymers and copolymers.« less

Polythiophene thin films by surface-initiated polymerization: Mechanistic and structural studies

DOE PAGES

Youm, Sang Gil; Hwang, Euiyong; Chavez, Carlos A.; ...

2016-06-15

The ability to control nanoscale morphology and molecular organization in organic semiconducting polymer thin films is an important prerequisite for enhancing the efficiency of organic thin-film devices including organic light-emitting and photovoltaic devices. The current “top-down” paradigm for making such devices is based on utilizing solution-based processing (e.g., spin-casting) of soluble semiconducting polymers. This approach typically provides only modest control over nanoscale molecular organization and polymer chain alignment. A promising alternative to using solutions of presynthesized semiconducting polymers pursues instead a “bottom-up” approach to prepare surface-grafted semiconducting polymer thin films by surface-initiated polymerization of small-molecule monomers. Herein, we describe themore » development of an efficient method to prepare polythiophene thin films utilizing surface-initiated Kumada catalyst transfer polymerization. In this study, we provided evidence that the surface-initiated polymerization occurs by the highly robust controlled (quasi-“living”) chain-growth mechanism. Further optimization of this method enabled reliable preparation of polythiophene thin films with thickness up to 100 nm. Extensive structural studies of the resulting thin films using X-ray and neutron scattering methods as well as ultraviolet photoemission spectroscopy revealed detailed information on molecular organization and the bulk morphology of the films, and enabled further optimization of the polymerization protocol. One of the remarkable findings was that surface-initiated polymerization delivers polymer thin films showing complex molecular organization, where polythiophene chains assemble into lateral crystalline domains of about 3.2 nm size, with individual polymer chains folded to form in-plane aligned and densely packed oligomeric segments (7-8 thiophene units per each segment) within each domain. Achieving such a complex mesoscale organization is virtually impossible with traditional methods relying on solution processing of presynthesized polymers. Another significant advantage of surface-confined polymer thin films is their remarkable stability toward organic solvents and other processing conditions. In addition to controlled bulk morphology, uniform molecular organization, and stability, a unique feature of the surface-initiated polymerization is that it can be used for the preparation of large-area uniformly nanopatterned polymer thin films. Lastly, this was demonstrated using a combination of particle lithography and surface-initiated polymerization. In general, surface-initiated polymerization is not limited to polythiophene but can be also expanded toward other classes of semiconducting polymers and copolymers.« less

Study of confinement and sliding friction of fluids using sum frequency generation spectroscopy

NASA Astrophysics Data System (ADS)

Nanjundiah, Kumar

2007-12-01

Friction and wear are important technologically. Tires on wet roads, windshield wipers and human joints are examples where nanometer-thick liquids are confined between flexible-rigid contact interfaces. Fundamental understanding of the structure of these liquids can assist in the design of products such as artificial joints and lubricants for Micro-electromechanical systems [MEMS]. Prior force measurements have suggested an increase in apparent viscosity of confined liquid and sometimes solid-like responses. But, these have not given the state of molecules under confinement. In the present study, we have used a surface sensitive, non-linear optical technique (infrared-visible sum frequency generation spectroscopy [SFG]) to investigate molecular structure at hidden interfaces. SFG can identify chemical groups, concentration and orientation of molecules at an interface. A friction cell was developed to study sliding of a smooth elastomeric lens against a sapphire surface. Experiments were done with dry sliding as well as lubricated sliding in the presence of linear alkane liquids. SFG spectra at the alkane/sapphire interface revealed ordering of the confined alkane molecules. These were more ordered than alkane liquid, but less ordered than alkane crystal. Cooling of the confined alkane below its melting temperature [TM] led to molecular orientation that was different from that of bulk crystal next to a sapphire surface. Molecules were oriented with their symmetry axis parallel to the surface normal. In addition, the melting temperature [Tconf] under confinement for a series of linear alkanes (n =15--27) showed a surprising trend. Intermediate molecular weights showed melting point depression. The T conf values suggested that melting started at the alkane/sapphire interface. In another investigation, confinement of water between an elastomeric PDMS lens and sapphire was studied. SFG spectra at the sapphire/water/PDMS interface revealed a heterogeneous morphology. The presence of peaks related to PDMS, as well as water, suggested water puddles in the contact area and the sapphire surface had a layer of bound water. This heterogeneity picture provides insight into high friction and stick-slip behavior found in boundary lubrication. For the first time, a broadband SFG system has been coupled with a friction cell to study dynamics and molecular changes at an interface during sliding; sliding of confined alkane between sapphire and PDMS was investigated. A series of SFG spectra were taken while the confined alkane contact spot moved in and out of the laser beam. Even though the experiments were done 15°C above melting temperature, the spectra showed ordering of alkane molecules, similar to that of the confined crystal at the leading and trailing edge. The results suggest that a large portion of the resistance to sliding may come from ordering of molecules at the lens front.

Translational diffusion of cumene and 3-methylpentane on free surfaces and pore walls studied by time-of-flight secondary ion mass spectrometry

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

Souda, Ryutaro

2010-12-07

Mobility of molecules in confined geometry has been studied extensively, but the origins of finite size effects on reduction of the glass transition temperature, T{sub g}, are controversial especially for supported thin films. We investigate uptake of probe molecules in vapor-deposited thin films of cumene, 3-methylpentane, and heavy water using secondary ion mass spectrometry and discuss roles of individual molecular motion during structural relaxation and glass-liquid transition. The surface mobility is found to be enhanced for low-density glasses in the sub-T{sub g} region because of the diffusion of molecules on pore walls, resulting in densification of a film via poremore » collapse. Even for high-density glasses without pores, self-diffusion commences prior to the film morphology change at T{sub g}, which is thought to be related to decoupling between translational diffusivity and viscosity. The diffusivity of deeply supercooled liquid tends to be enhanced when it is confined in pores of amorphous solid water. The diffusivity of molecules is further enhanced at temperatures higher than 1.2-1.3 T{sub g} irrespective of the confinement.« less

Dual emissions from MnS clusters confined in the sodalite nanocage of a chalcogenide-based semiconductor zeolite.

PubMed

Hu, Dandan; Zhang, Yingying; Lin, Jian; Hou, Yike; Li, Dongsheng; Wu, Tao

2017-03-21

A new host-guest hybrid system with MnS clusters confined in a chalcogenide-based semiconductor zeolite was for the first time constructed and its photoluminescence (PL) properties were also investigated. The existence of MnS clusters in the nanopores of the semiconductor zeolite was revealed by UV-Vis absorption spectroscopy, steady-state fluorescence analysis, Raman as well as Fourier transform infrared (FTIR) spectroscopy. The aggregation state of the entrapped MnS clusters at different measurement temperatures was probed by electron paramagnetic resonance (EPR) spectroscopy. Of significant importance is the fact that the entrapped MnS clusters displayed dual emissions at 518 nm (2.39 eV) and 746 nm (1.66 eV), respectively, and the long-wavelength emission has never been observed in other MnS-confined host-guest systems. These two emission peaks displayed tunable PL intensity affected by the loading level and measurement temperature. This can be explained by the different morphologies of MnS clusters with different aggregation states at the corresponding loading level or measurement temperature. The current study opens a new avenue to construct inorganic chalcogenide cluster involved host-guest systems with a semiconductor zeolite as the host matrix.

Crystallization, Crystal Orientation and Morphology of Poly(ethylene oxide) under 1D Defect-Free Nanoscale Confinement

NASA Astrophysics Data System (ADS)

Hsiao, Ming-Siao; Zheng, Joseph X.; van Horn, Ryan M.; Quirk, Roderic P.; Thomas, Edwin L.; Lotz, Bernard; Cheng, Stephen Z. D.

2009-03-01

One-dimensional (1-D) defect-free nanoscale confinement is created by growing single crystals of PS-b-PEO block copolymers in dilute solution. Those defect-free, 1-D confined lamellae having different PEO layer thicknesses in PS-b-PEO lamellar single crystals (or crystal mats) were used to study the polymer recrystallization and crystal orientation evolution as a function of recrystallization temperature (Trx) because the Tg^PS is larger than Tm^PEO in the PS-b-PEO single crystal. The results are summarized as follows. First, by the combination of electron diffraction and known PEO crystallography, the crystallization of PEO only takes place at Trx<-5^oC. Meanwhile a unique tilted PEO orientation is formed at Trx >-5^oC after self-seeding. The origin of the formation of tilted chains in the PEO crystal will be addressed. Second, from the analysis of 2D WAXD patterns of crystal mats, it is shown that the change in PEO c-axis orientation from homogeneous at low Trx to homeotropic at higher Trx transitions sharply, within 1^oC. The mechanism inducing this dramatic change in crystal orientation will be investigated in detail.

Insights into drying of non-circular sessile nanofluid droplet towards multi-scale surface patterning using a wall-less confinement architecture.

PubMed

Kabi, Prasenjit; Chaudhuri, Swetaprovo; Basu, Saptarshi

2016-10-04

Surface patterning with functional colloids is an important research area due to its widespread applicability in domains ranging from nano-electronics, pharmaceutics, semi-conductors, photovoltaics among others. To this endeavour, we propose a low-cost patterning technique that aspires to eliminate the more expensive methodologies presently in practise. Using a simple document stamp on which patterns of any geometry can be embossed, we are able to print two-dimensional mm-scale "wall-less confinement" using ink based hydrophobic fence on any plasma treated superhydrophilic surface. The confinement is subsequently filled with nanocolloidal liquid(s). Using the confinement geometry, we are able to control the 3D shape of the droplet to exhibit multiple interfacial curvatures. The droplet in the "wall-less confinements" evaporates naturally exhibiting unique geometry (curvature) induced flow structures which induce the nanoparticles to self-assemble into functional patterns. We have also shown that by modifying the geometry of the pattern, evaporation, flow and particle deposition dynamics get altered leading to precipitate topologies from macro to microscales. We, present two such geometrical designs which demonstrate the capability of modifying both the macroscopic as well as the microscopic features of the final precipitate. We have also provided a description of the physical mechanisms of the drying process by resolving the unique flow pattern using a combination of imaging and μPIV (micro particle image velocimetry). These provide insights into the coupled dynamics of evaporation and flow responsible for the evolution of particle deposition pattern. Precipitate characterization using SEM and dark-field microscopy highlight the transformation in the deposit morphology.

Fe-tannic acid complex dye as photo sensitizer for different morphological ZnO based DSSCs

NASA Astrophysics Data System (ADS)

Çakar, Soner; Özacar, Mahmut

2016-06-01

In this paper we have synthesized different morphological ZnO nanostructures via microwave hydrothermal methods at low temperature within a short time. We described different morphologies of ZnO at different Zn(NO3)2/KOH mole ratio. The ZnO nanostructures were characterized via X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and UV-vis spectrophotometry. All ZnO structures have hexagonal wurtzite type structures. The FESEM images showed various morphologies of ZnO such as plate, rod and nanoparticles. Dye sensitized solar cells have been assembled by these different morphological structures photo electrode and tannic acid or Fe-tannic acid complex dye as sensitizer. We have achieved at maximum efficiencies of photovoltaic cells prepared with ZnO plate in all dye systems. The conversion efficiencies of dye sensitized solar cells are 0.37% and 1.00% with tannic acid and Fe-tannic acid complex dye, respectively.

Shear zones of the Verkhoyansk fold-and-thrust belt, Northeast Russia

NASA Astrophysics Data System (ADS)

Fridovsky, Valery; Polufuntikova, Lena

2017-04-01

The Verkhoyansk fold-and-thrust belt is situated on the submerged eastern margin of the North Asian craton, and is largely composed of the Ediacaran - Middle Paleozoic carbonate and the Upper Paleozoic-Mesozoic terrigenous rocks. The Upper Carboniferous - Jurassic sediments constitute the Verkhoyansk terrigenous complex containing economically viable orogenic gold deposits. The structure of the belt is mainly controlled by thrusts and associated diagonal strike slips. Linear concentric folds are common all over the area of the belt. Shear zones with associated similar folds are confined to long narrow areas. Shear zones were formed during the early stages of the Oxfordian-Kimmeridgian collisional and accretionary events prior to the emplacement of large orogenic granitoid plutons. The main ore-controlling structures are shear zones associated with slaty cleavage, shear folds, mullion- and boudinage-structures, and transposition features. The shear zones are listric-type, and represent branches of a detachment structure, which is assumed to be present at the base of the Verkhoyansk fold-and-thrust belt. A vertical zonation of shear zones is correlated with the distance to the detachment. Changes in the dip angle of the shear zones (as indicated mainly by cleavage), structural paragenesis, the degree of microdeformation of the host rocks, and the type of ore-controlling structures can be clearly observed in the direction away from the detachment. Structural zoning is evidenced, among other things, by changing morphologic types of microstructures and by strain-indicators of the degree of rock metamorphism. Four morphologic types of microstructures are identified. The first platy-shear type is characterized by aggregate cleavage and the coefficient of deformation (Cd) of single grains from 1.0 to 2.0. Irregular angular fragments of variously oriented grains can be observed in thin sections. The second shear-cataclastic morphologic type (Cd from 2.0 to 3.0) exhibits combined aggregate and intergranular cleavage. The third cataclastic-segregation morphologic type (Cd from 3.0 to 4.5) is distinguished by a wide distribution of lentelliptical grains of rock-forming minerals in a finely-crystalline matrix and by intergranular cleavage. The rocks of the fourth segregation-striate morphologic type (Cd >5.0) contain lenticular segregations of quartz and feldspar in an intensely linearized mylonite groundmass.

Kelley Hot Spring Geothermal Project: Kelly Hot Spring Agricultural Center conceptual design

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

Longyear, A.B.

1980-06-01

The proposed core activity in the Kelly Hot Spring Agricultural Center is a nominal 1200 sow swine raising complex. The swine raising is to be a totally confined operation for producing premium pork in controlled environment facilities that utilize geothermal energy. The complex will include a feedmill for producing the various feed formulae required for the animals from breeding through gestation, farrowing, nursery, growing and finishing. The market animals are shipped live by truck to slaughter in Modesto, California. A complete waste management facility will include manure collection from all raising areas, transport via a water flush sysem to methanemore » (biogas) generators, manure separation, settling ponds and disposition of the surplus agricultural quality water. The design is based upon the best commercial practices in confined swine raising in the US today. The most unique feature of the facility is the utilization of geothermal hot water for space heating and process energy throughout the complex.« less

Confined polyelectrolytes: The complexity of a simple system.

PubMed

Nunes, Sandra C C; Skepö, Marie; Pais, Alberto A C C

2015-08-05

The interaction between polyelectrolytes and counterions in confined situations and the mutual relationship between chain conformation and ion condensation is an important issue in several areas. In the biological field, it assumes particular relevance in the understanding of the packaging of nucleic acids, which is crucial in the design of gene delivery systems. In this work, a simple coarse-grained model is used to assess the cooperativity between conformational change and ion condensation in spherically confined backbones, with capsides permeable to the counterions. It is seen that the variation on the degree of condensation depends on counterion valence. For monovalent counterions, the degree of condensation passes through a minimum before increasing as the confining space diminishes. In contrast, for trivalent ions, the overall tendency is to decrease the degree of condensation as the confinement space also decreases. Most of the particles reside close to the spherical wall, even for systems in which the density is higher closer to the cavity center. This effect is more pronounced, when monovalent counterions are present. Additionally, there are clear variations in the charge along the concentric layers that cannot be totally ascribed to polyelectrolyte behavior, as shown by decoupling the chain into monomers. If both chain and counterions are confined, the formation of a counterion rich region immediately before the wall is observed. Spool and doughnut-like structures are formed for stiff chains, within a nontrivial evolution with increasing confinement. © 2015 Wiley Periodicals, Inc.

Photonic confinement in laterally structured metal-organic microcavities

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

Mischok, Andreas, E-mail: andreas.mischok@iapp.de; Brückner, Robert; Sudzius, Markas

2014-08-04

We investigate the formation of optical modes in organic microcavities with an incorporated perforated silver layer. The metal leads to a formation of Tamm-plasmon-polaritons and thus separates the sample into metal-free or metal-containing areas, supporting different resonances. This mode splitting is exploited to confine photons in elliptic holes and triangular cuts, forming distinctive standing wave patterns showing the strong lateral confinement. A comparison with a Maxwell-Bloch based rate equation model clearly shows the nonlinear transition into the lasing regime. The concentration of the electric field density and inhibition of lateral loss channels in turn decreases the lasing threshold by upmore » to one order of magnitude, to 0.1 nJ. By spectroscopic investigation of such a triangular wedge, we observe the transition from the unperturbed cavity state to a strongly confined complex transversal mode. Such a structured silver layer can be utilized in future for charge carrier injection in an electrically driven organic solid state laser.« less

Demixing of polymers under nanoimprinting process

NASA Astrophysics Data System (ADS)

Wang, Zhen

Polymer blend has been an important area in polymer science for decades. The knowledge of polymer blend in bulk is well established and technologies based on it have created products ubiquitous in our daily life. More intriguing problem arises when the phase separation of a polymer blend occurs under physical confinement. In this thesis, we investigated the effect of interfacial interactions between constituent polymers and confinement environment on phase evolution. Specifically, morphologies of thin films of binary polymer blends were examined on chemically homogenous substrates (preferential surface, neutral surface), on chemical pattern, between two parallel rigid substrates, and under thermal embossing/step-and-flash nanoimprint lithography conditions. We found that preferential wetting of selective component dominates the phase evolution, which can be suppressed by the use of neutral surfaces or external pressure. By manipulating these factors, a wide range of unique non-equilibrium micro or nanostructures can thus be achieved.

Experimental investigation of the hydraulic and heat-transfer properties of artificially fractured granite.

PubMed

Luo, Jin; Zhu, Yongqiang; Guo, Qinghai; Tan, Long; Zhuang, Yaqin; Liu, Mingliang; Zhang, Canhai; Xiang, Wei; Rohn, Joachim

2017-01-05

In this paper, the hydraulic and heat-transfer properties of two sets of artificially fractured granite samples are investigated. First, the morphological information is determined using 3D modelling technology. The area ratio is used to describe the roughness of the fracture surface. Second, the hydraulic properties of fractured granite are tested by exposing samples to different confining pressures and temperatures. The results show that the hydraulic properties of the fractures are affected mainly by the area ratio, with a larger area ratio producing a larger fracture aperture and higher hydraulic conductivity. Both the hydraulic apertureand the hydraulic conductivity decrease with an increase in the confining pressure. Furthermore, the fracture aperture decreases with increasing rock temperature, but the hydraulic conductivity increases owing to a reduction of the viscosity of the fluid flowing through. Finally, the heat-transfer efficiency of the samples under coupled hydro-thermal-mechanical conditions is analysed and discussed.

Experimental investigation of the hydraulic and heat-transfer properties of artificially fractured granite

PubMed Central

Luo, Jin; Zhu, Yongqiang; Guo, Qinghai; Tan, Long; Zhuang, Yaqin; Liu, Mingliang; Zhang, Canhai; Xiang, Wei; Rohn, Joachim

2017-01-01

In this paper, the hydraulic and heat-transfer properties of two sets of artificially fractured granite samples are investigated. First, the morphological information is determined using 3D modelling technology. The area ratio is used to describe the roughness of the fracture surface. Second, the hydraulic properties of fractured granite are tested by exposing samples to different confining pressures and temperatures. The results show that the hydraulic properties of the fractures are affected mainly by the area ratio, with a larger area ratio producing a larger fracture aperture and higher hydraulic conductivity. Both the hydraulic apertureand the hydraulic conductivity decrease with an increase in the confining pressure. Furthermore, the fracture aperture decreases with increasing rock temperature, but the hydraulic conductivity increases owing to a reduction of the viscosity of the fluid flowing through. Finally, the heat-transfer efficiency of the samples under coupled hydro-thermal-mechanical conditions is analysed and discussed. PMID:28054594

Angular trapping of anisometric nano-objects in a fluid.

PubMed

Celebrano, Michele; Rosman, Christina; Sönnichsen, Carsten; Krishnan, Madhavi

2012-11-14

We demonstrate the ability to trap, levitate, and orient single anisometric nanoscale objects with high angular precision in a fluid. An electrostatic fluidic trap confines a spherical object at a spatial location defined by the minimum of the electrostatic system free energy. For an anisometric object and a potential well lacking angular symmetry, the system free energy can further strongly depend on the object's orientation in the trap. Engineering the morphology of the trap thus enables precise spatial and angular confinement of a single levitating nano-object, and the process can be massively parallelized. Since the physics of the trap depends strongly on the surface charge of the object, the method is insensitive to the object's dielectric function. Furthermore, levitation of the assembled objects renders them amenable to individual manipulation using externally applied optical, electrical, or hydrodynamic fields, raising prospects for reconfigurable chip-based nano-object assemblies.

Thin Polymer Films with Continuous Vertically Aligned 1 nm Pores Fabricated by Soft Confinement

DOE PAGES

Feng, Xunda; Nejati, Siamak; Cowan, Matthew G.; ...

2015-12-03

Membrane separations are critically important in areas ranging from health care and analytical chemistry to bioprocessing and water purification. An ideal nanoporous membrane would consist of a thin film with physically continuous and vertically aligned nanopores and would display a narrow distribution of pore sizes. However, the current state of the art departs considerably from this ideal and is beset by intrinsic trade-offs between permeability and selectivity. We demonstrate an effective and scalable method to fabricate polymer films with ideal membrane morphologies consisting of submicron thickness films with physically continuous and vertically aligned 1 nm pores. The approach is basedmore » on soft confinement to control the orientation of a cross-linkable mesophase in which the pores are produced by self-assembly. The scalability, exceptional ease of fabrication, and potential to create a new class of nanofiltration membranes stand out as compelling aspects.« less

Effect of acoustic coupling on power-law flame acceleration in spherical confinement

NASA Astrophysics Data System (ADS)

Akkerman, V'yacheslav; Law, Chung K.

2013-01-01

A model describing acoustically-generated parametric instability in a spherical chamber is developed for quasi-one-dimensional, low-Mach number flames. We demonstrate how sound waves generated by a centrally-ignited, outwardly-propagating accelerating flamefront can be incorporated into an existing theory of self-similar flame acceleration in free space [V. Akkerman, C. K. Law, and V. Bychkov, "Self-similar accelerative propagation of expanding wrinkled flames and explosion triggering," Phys. Rev. E 83, 026305 (2011)], 10.1103/PhysRevE.83.026305. Being reflected from the chamber wall, flame-generated acoustics interact with the flamefront and the attendant hydrodynamic flamefront cellular instability. This in turn affects the subsequent flame morphology and propagation speed. It is shown that the acoustics modify the power-law flame acceleration, concomitantly facilitating or inhibiting the transition to detonation in confinement, which allows reconciliation of a discrepancy in experimental measurements of different groups.

Pattern Transitions in Bacterial Oscillating System under Nanofluidic Confinement

NASA Astrophysics Data System (ADS)

Shen, Jie-Pan; Chou, Chia-Fu

2011-03-01

Successful binary fission in E. coli relies on remarkable oscillatory behavior of the MinCDE protein system to determine the exact division site. The most favorable models to explain this fascinating spatiotemporal regulation on dynamic MinDE pattern formation in cells are based on reaction-diffusion scenario. Although not fully understood, geometric factors caused by bacterial morphology play a crucial role in MinDE dynamics. In the present study, bacteria were cultured, confined and reshaped in various micro/nanofluidic devices, to mimic either curvature changes of cell peripherals. Fluorescence imaging was utilized to detail the mode transitions in multiple MinDE patterns. The understanding of the physics in multiple pattern formations is further complemented via in silico modeling. The study synergizes the join merits of in vivo, in vitro and in silico approaches, to grasp the insight of stochastic dynamics inherited from the noisy mesoscopic biophysics. We acknowledge support from the Foresight Project, Academia Sinica.

How thermal stress alters the confinement of polymers vitrificated in nanopores

NASA Astrophysics Data System (ADS)

Teng, Chao; Li, Linling; Wang, Yong; Wang, Rong; Chen, Wei; Wang, Xiaoliang; Xue, Gi

2017-05-01

Understanding and controlling the glass transition temperature (Tg) and dynamics of polymers in confined geometries are of significance in both academia and industry. Here, we investigate how the thermal stress induced by a mismatch in the coefficient of thermal expansion affects the Tg behavior of polystyrene (PS) nanorods located inside cylindrical alumina nanopores. The size effects and molecular weight dependence of the Tg are also studied. A multi-step relaxation process was employed to study the relationship between thermal stress and cooling rate. At fast cooling rates, the imparted thermal stress would overcome the yield stress of PS and peel chains off the pore walls, while at slow cooling rates, chains are kept in contact with the pore walls due to timely dissipation of the produced thermal stress during vitrification. In smaller nanopores, more PS chains closely contact with pore walls, then stronger internal thermal stress would be generated between core and shell of PS nanorod, which results in a larger deviation between two Tgs. The core part of PS shows lower Tg than bulk value, which can induce faster dynamics in the center region. A complex and important role stress plays is supposed in complex confinement condition, e.g., in nanopores, during vitrification.

Oligomers of the ATPase EHD2 confine caveolae to the plasma membrane through association with actin.

PubMed

Stoeber, Miriam; Stoeck, Ina Karen; Hänni, Christine; Bleck, Christopher Karl Ernst; Balistreri, Giuseppe; Helenius, Ari

2012-05-16

Caveolae are specialized domains present in the plasma membrane (PM) of most mammalian cell types. They function in signalling, membrane regulation, and endocytosis. We found that the Eps-15 homology domain-containing protein 2 (EHD2, an ATPase) associated with the static population of PM caveolae. Recruitment to the PM involved ATP binding, interaction with anionic lipids, and oligomerization into large complexes (60-75S) via interaction of the EH domains with intrinsic NPF/KPF motifs. Hydrolysis of ATP was essential for binding of EHD2 complexes to caveolae. EHD2 was found to undergo dynamic exchange at caveolae, a process that depended on a functional ATPase cycle. Depletion of EHD2 by siRNA or expression of a dominant-negative mutant dramatically increased the fraction of mobile caveolar vesicles coming from the PM. Overexpression of EHD2, in turn, caused confinement of cholera toxin B in caveolae. The confining role of EHD2 relied on its capacity to link caveolae to actin filaments. Thus, EHD2 likely plays a key role in adjusting the balance between PM functions of stationary caveolae and the role of caveolae as vesicular carriers.

Oligomers of the ATPase EHD2 confine caveolae to the plasma membrane through association with actin

PubMed Central

Stoeber, Miriam; Stoeck, Ina Karen; Hänni, Christine; Bleck, Christopher Karl Ernst; Balistreri, Giuseppe; Helenius, Ari

2012-01-01

Caveolae are specialized domains present in the plasma membrane (PM) of most mammalian cell types. They function in signalling, membrane regulation, and endocytosis. We found that the Eps-15 homology domain-containing protein 2 (EHD2, an ATPase) associated with the static population of PM caveolae. Recruitment to the PM involved ATP binding, interaction with anionic lipids, and oligomerization into large complexes (60–75S) via interaction of the EH domains with intrinsic NPF/KPF motifs. Hydrolysis of ATP was essential for binding of EHD2 complexes to caveolae. EHD2 was found to undergo dynamic exchange at caveolae, a process that depended on a functional ATPase cycle. Depletion of EHD2 by siRNA or expression of a dominant-negative mutant dramatically increased the fraction of mobile caveolar vesicles coming from the PM. Overexpression of EHD2, in turn, caused confinement of cholera toxin B in caveolae. The confining role of EHD2 relied on its capacity to link caveolae to actin filaments. Thus, EHD2 likely plays a key role in adjusting the balance between PM functions of stationary caveolae and the role of caveolae as vesicular carriers. PMID:22505029

Forced Imbibition in Porous Media: A Fourfold Scenario

NASA Astrophysics Data System (ADS)

Odier, Céleste; Levaché, Bertrand; Santanach-Carreras, Enric; Bartolo, Denis

2017-11-01

We establish a comprehensive description of the patterns formed when a wetting liquid displaces a viscous fluid confined in a porous medium. Building on model microfluidic experiments, we evidence four imbibition scenarios all yielding different large-scale morphologies. Combining high-resolution imaging and confocal microscopy, we show that they originate from two liquid-entrainment transitions and a Rayleigh-Plateau instability at the pore scale. Finally, we demonstrate and explain the long-time coarsening of the resulting patterns.

Molecular environment and X-ray study of the metal-rich thermal composite supernova remnant Kes 79

NASA Astrophysics Data System (ADS)

Zhou, Ping; Chen, Yang; Safi-Harb, Samar; Sun, Ming

2015-08-01

Kes 79 is a thermal composite SNR hosting a central compact object (anti-magnetar) and with a transient magnetar in the south. The SNR has an intriguing double radio shell structure and the nature of the centrally-filled X-ray morphology is still unclear. We have performed 13CO 1-0, 12CO 1-0, 12CO 2-1, and 12CO 3-2 study towards this remnant to investigate the molecular environment. SNR Kes 79 is found to be associated with the molecular cloud in LSR velocity 100-120 km/s. The inner radio shell appears to be well confined by a molecular shell at VLSR˜113 km/s. We also revisited the 380 ks XMM-Newton data of Kes 79, which reveals many bright filamentary structures well coincident with 24 um infrared filaments and an X-ray faint halo confined by the outer radio shell. We performed a spatially resolved spectroscopic analysis for the X-ray filaments and the halo emission. We also study the overabundant metal species Mg, Si, S and Ar, and show their asymmetric distribution across the remnant. The broadband observations suggest that the centrally filled X-ray morphology is a projection effect. Finally, we will discuss the progenitor star of Kes 79 based on the molecular line and X-ray properties.

Molecular Insights into Division of Single Human Cancer Cells in On-Chip Transparent Microtubes

PubMed Central

2016-01-01

In vivo, mammalian cells proliferate within 3D environments consisting of numerous microcavities and channels, which contain a variety of chemical and physical cues. External environments often differ between normal and pathological states, such as the unique spatial constraints that metastasizing cancer cells experience as they circulate the vasculature through arterioles and narrow capillaries, where they can divide and acquire elongated cylindrical shapes. While metastatic tumors cause most cancer deaths, factors impacting early cancer cell proliferation inside the vasculature and those that can promote the formation of secondary tumors remain largely unknown. Prior studies investigating confined mitosis have mainly used 2D cell culture systems. Here, we mimic aspects of metastasizing tumor cells dividing inside blood capillaries by investigating single-cell divisions of living human cancer cells, trapped inside 3D rolled-up, transparent nanomembranes. We assess the molecular effects of tubular confinement on key mitotic features, using optical high- and super-resolution microscopy. Our experiments show that tubular confinement affects the morphology and dynamics of the mitotic spindle, chromosome arrangements, and the organization of the cell cortex. Moreover, we reveal that membrane blebbing and/or associated processes act as a potential genome-safety mechanism, limiting the extent of genomic instability caused by mitosis in confined circumstances, especially in tubular 3D microenvironments. Collectively, our study demonstrates the potential of rolled-up nanomembranes for gaining molecular insights into key cellular events occurring in tubular 3D microenvironments in vivo. PMID:27267364

Morphological and Compositional (S)TEM Analysis of Multiple Exciton Generation Solar Cells

NASA Astrophysics Data System (ADS)

Wisnivesky-Rocca-Rivarola, F.; Davis, N. J. L. K.; Bohm, M.; Ducati, C.

2015-10-01

Quantum confinement of charge carriers in semiconductor nanocrystals produces optical and electronic properties that have the potential to enhance the power conversion efficiency of solar cells. One of these properties is the efficient formation of more than one electron-hole pair from a single absorbed photon, in a process called multiple exciton generation (MEG). In this work we studied the morphology of nanocrystal multilayers of PbSe treated with CdCl2 using complementary imaging and spectroscopy techniques to characterise the chemical composition and morphology of full MEG devices made with PbSe nanorods (NRs). IN the scanning TEM (STEM), plan view images and chemical maps were obtained of the nanocrystal layers, which allowed for the analysis of crystal structure and orientation, as well as size distribution and aspect ratio. These results were complemented by cross-sectional images of full devices, which allowed accessing the structure of each layer that composes the device, including the nanorod packing in the active nanocrystal layer.

Hidden diversity within the lizard genus Liolaemus: Genetic vs morphological divergence in the L. rothi complex (Squamata:Liolaeminae).

PubMed

Olave, Melisa; Avila, Luciano J; Sites, Jack W; Morando, Mariana

2017-02-01

Currently, Liolaemus is the second most species-rich reptile genus in the world (257 species), and predictions of its real diversity suggest that it may be the most diverse genus. Originally, Liolaemus species were described as widely distributed and morphologically variable taxa, but extensive sampling in previously unexplored geographic areas, coupled with molecular and more extensive morphological studies, have discovered an unexpectedly high number of previously undetected species. Here, we study the level of molecular vs. morphological divergence within the L. rothi complex, combining a total of 14 loci (2 mitochondrial and 12 nuclear loci) for 97 individuals, as well as morphological data (nine morphometric and 15 color pattern variables), that represent all six described species of the L. rothi complex, plus two candidate species. We use the multi-coalescent species delimitation program iBPP and resolve strong differences in molecular divergence; and each species is inferred as an independent lineage supported by high posterior probabilities. However, morphological differences are not that clear, and our modeling of morphological characters suggests differential selection pressures implying some level of morphological stasis. We discuss the role of natural selection on phenotypic traits, which may be an important factor in "hiding" the real diversity of the genus. Copyright © 2016. Published by Elsevier Inc.

Variations in interior morphology of 15-20 km lunar craters - Implications for a major subsurface discontinuity

NASA Technical Reports Server (NTRS)

De Hon, R. A.

1980-01-01

Craters vary in morphology as a function of crater diameter, age, and mode of origin. This study concentrates on the morphology of young lunar impact craters within a limited size range. Elimination of morphologic variations generally attributed to crater size or age leaves a small population which should nearly reflect the varying properties of the lunar substrate. The sample consists of 17 craters 15-20 km in diameter with both simple and complex morphologies. While depth/diameter ratios do not obviously differ between mare and highland subsets, apparent depth, rim height, and profile data do differ distinctly. Highland craters tend to be deep, simple, and bowl-shaped. Mare craters tend to be shallow and flat-floored. Rim heights of complex mare craters are typically greater than those of simple craters. Differences of highland and mare crater morphologies are attributed to variations in the thickness of the lunar megaregolith. Highland craters in this size range do not penetrate the megaregolith. The depth and morphology of complex craters are controlled by the discontinuity at the transition from highly brecciated megaregolith to more coherent crystalline material of the upper crust.

Packing of flexible 2D materials in vesicles

NASA Astrophysics Data System (ADS)

Zou, Guijin; Yi, Xin; Zhu, Wenpeng; Gao, Huajian

2018-06-01

To understand the mechanics of cellular packing of two-dimensional (2D) materials, we perform systematic molecular dynamics simulations and theoretical analysis to investigate the packing of a flexible circular sheet in a spherical vesicle and the 2D packing problem of a strip in a cylindrical vesicle. Depending on the system dimensions and the bending rigidity ratio between the confined sheet and the vesicle membrane, a variety of packing morphologies are observed, including a conical shape, a shape of three-fold symmetry, a cylindrically curved shape, an axisymmetrically buckled shape, as well as the initial circular shape. A set of buckling analyses lead to phase diagrams of the packing morphologies of the encapsulated sheets. These results may have important implications on the mechanism of intracellular packing and toxicity of 2D materials.

Sputtering of rough surfaces: a 3D simulation study

NASA Astrophysics Data System (ADS)

von Toussaint, U.; Mutzke, A.; Manhard, A.

2017-12-01

The lifetime of plasma-facing components is critical for future magnetic confinement fusion power plants. A key process limiting the lifetime of the first-wall is sputtering by energetic ions. To provide a consistent modeling of the sputtering process of realistic geometries, the SDTrimSP-code has been extended to enable the processing of analytic as well as measured arbitrary 3D surface morphologies. The code has been applied to study the effect of varying the impact angle of ions on rough surfaces on the sputter yield as well as the influence of the aspect ratio of surface structures on the 2D distribution of the local sputtering yields. Depending on the surface morphologies reductions of the effective sputter yields to less than 25% have been observed in the simulation results.

Control of exciton confinement in quantum dot-organic complexes through energetic alignment of interfacial orbitals.

PubMed

Frederick, Matthew T; Amin, Victor A; Swenson, Nathaniel K; Ho, Andrew Y; Weiss, Emily A

2013-01-09

This paper describes a method to control the quantum confinement, and therefore the energy, of excitonic holes in CdSe QDs through adsorption of the hole-delocalizing ligand phenyldithiocarbamate, PTC, and para substitutions of the phenyl ring of this ligand with electron-donating or -withdrawing groups. These substitutions control hole delocalization in the QDs through the energetic alignment of the highest occupied orbitals of PTC with the highest density-of-states region of the CdSe valence band, to which PTC couples selectively.

Bold endeavors: behavioral lessons from polar and space exploration

NASA Technical Reports Server (NTRS)

Stuster, J. W.

2000-01-01

Anecdotal comparisons frequently are made between expeditions of the past and space missions of the future. Spacecraft are far more complex than sailing ships, but from a psychological perspective, the differences are few between confinement in a small wooden ship locked in the polar ice cap and confinement in a small high-technology ship hurtling through interplanetary space. This paper discusses some of the behavioral lessons that can be learned from previous expeditions and applied to facilitate human adjustment and performance during future space expeditions of long duration.

Spacer length controlled lamello-columnar to oblique-columnar mesophase transition in liquid crystalline DNA - discotic cationic lipid complexes

NASA Astrophysics Data System (ADS)

Zhu, Lei; Cui, Li; Miao, Jianjun

2006-03-01

A series of asymmetric triphenylene imidazolium salts with different spacer lengths (C5, C8, and C11) were synthesized and their ionic complexes with double-strand DNA were prepared in aqueous solution. The molecular composition of the complexes was determined by FTIR analysis. The liquid crystalline morphology was characterized by polarized light microscopy, X-ray diffraction (XRD), and transmission electron microscope. 2D XRD results indicated an oblique columnar phase for the complex with a short spacer length of C5, while lamello-columnar phases for those with longer spacer lengths (C8 and C11). Thin film circular dichroism results showed the disappearing of any helical conformation in the DNA in all the complexes. Instead, the complexation between single-strand RNA and discotic cationic lipids did not show columnar morphology; therefore, the columnar liquid crystalline morphology in the DNA-discotic cationic lipid complexes was attributed to the DNA double-strand chain rigidity.

Generative complexity of Gray-Scott model

NASA Astrophysics Data System (ADS)

Adamatzky, Andrew

2018-03-01

In the Gray-Scott reaction-diffusion system one reactant is constantly fed in the system, another reactant is reproduced by consuming the supplied reactant and also converted to an inert product. The rate of feeding one reactant in the system and the rate of removing another reactant from the system determine configurations of concentration profiles: stripes, spots, waves. We calculate the generative complexity-a morphological complexity of concentration profiles grown from a point-wise perturbation of the medium-of the Gray-Scott system for a range of the feeding and removal rates. The morphological complexity is evaluated using Shannon entropy, Simpson diversity, approximation of Lempel-Ziv complexity, and expressivity (Shannon entropy divided by space-filling). We analyse behaviour of the systems with highest values of the generative morphological complexity and show that the Gray-Scott systems expressing highest levels of the complexity are composed of the wave-fragments (similar to wave-fragments in sub-excitable media) and travelling localisations (similar to quasi-dissipative solitons and gliders in Conway's Game of Life).

Topology of polymer chains under nanoscale confinement.

PubMed

Satarifard, Vahid; Heidari, Maziar; Mashaghi, Samaneh; Tans, Sander J; Ejtehadi, Mohammad Reza; Mashaghi, Alireza

2017-08-24

Spatial confinement limits the conformational space accessible to biomolecules but the implications for bimolecular topology are not yet known. Folded linear biopolymers can be seen as molecular circuits formed by intramolecular contacts. The pairwise arrangement of intra-chain contacts can be categorized as parallel, series or cross, and has been identified as a topological property. Using molecular dynamics simulations, we determine the contact order distributions and topological circuits of short semi-flexible linear and ring polymer chains with a persistence length of l p under a spherical confinement of radius R c . At low values of l p /R c , the entropy of the linear chain leads to the formation of independent contacts along the chain and accordingly, increases the fraction of series topology with respect to other topologies. However, at high l p /R c , the fraction of cross and parallel topologies are enhanced in the chain topological circuits with cross becoming predominant. At an intermediate confining regime, we identify a critical value of l p /R c , at which all topological states have equal probability. Confinement thus equalizes the probability of more complex cross and parallel topologies to the level of the more simple, non-cooperative series topology. Moreover, our topology analysis reveals distinct behaviours for ring- and linear polymers under weak confinement; however, we find no difference between ring- and linear polymers under strong confinement. Under weak confinement, ring polymers adopt parallel and series topologies with equal likelihood, while linear polymers show a higher tendency for series arrangement. The radial distribution analysis of the topology reveals a non-uniform effect of confinement on the topology of polymer chains, thereby imposing more pronounced effects on the core region than on the confinement surface. Additionally, our results reveal that over a wide range of confining radii, loops arranged in parallel and cross topologies have nearly the same contact orders. Such degeneracy implies that the kinetics and transition rates between the topological states cannot be solely explained by contact order. We expect these findings to be of general importance in understanding chaperone assisted protein folding, chromosome architecture, and the evolution of molecular folds.

Evidence for Early Morphological Decomposition: Combining Masked Priming with Magnetoencephalography

ERIC Educational Resources Information Center

Lehtonen, Minna; Monahan, Philip J.; Poeppel, David

2011-01-01

Are words stored as morphologically structured representations? If so, when during word recognition are morphological pieces accessed? Recent masked priming studies support models that assume early decomposition of (potentially) morphologically complex words. The electrophysiological evidence, however, is inconsistent. We combined masked…

A transition in the viscous fingering instability in miscible fluids

NASA Astrophysics Data System (ADS)

Videbaek, Thomas; Nagel, Sidney R.

2017-11-01

The viscous fingering instability in a quasi-two dimensional Hele-Shaw cell is an example of complex structure formation from benign initial conditions. When the invading fluid has the lesser viscosity, the interface between the two fluids is unstable to finger formation. Here, we study the instability between pairs of miscible fluids in a circular cell with fluid injected at its center. As the injection rate is decreased, diffusion will smooth out the discontinuity in the gap-averaged viscosity at the interface between the fluids. At high injection rates (i.e., high Péclet number, Pe), fingering is associated with three-dimensional structure within the gap between the confining plates. On lowering Pe, we find a sharp transition in the finger morphology at a critical value, Pec (ηi /ηo) 1 / 2 , with ηi (ηo) being the viscosity of the inner (outer) fluid; at this point, the width of the fingers jumps, the length of the fingers shrinks towards zero and the three-dimensional structure goes from half filling to fully filling the gap. Thus, by controlling the viscosity contrast at the interface, one can alter and even completely suppress the instability.

New algorithms for field-theoretic block copolymer simulations: Progress on using adaptive-mesh refinement and sparse matrix solvers in SCFT calculations

NASA Astrophysics Data System (ADS)

Sides, Scott; Jamroz, Ben; Crockett, Robert; Pletzer, Alexander

2012-02-01

Self-consistent field theory (SCFT) for dense polymer melts has been highly successful in describing complex morphologies in block copolymers. Field-theoretic simulations such as these are able to access large length and time scales that are difficult or impossible for particle-based simulations such as molecular dynamics. The modified diffusion equations that arise as a consequence of the coarse-graining procedure in the SCF theory can be efficiently solved with a pseudo-spectral (PS) method that uses fast-Fourier transforms on uniform Cartesian grids. However, PS methods can be difficult to apply in many block copolymer SCFT simulations (eg. confinement, interface adsorption) in which small spatial regions might require finer resolution than most of the simulation grid. Progress on using new solver algorithms to address these problems will be presented. The Tech-X Chompst project aims at marrying the best of adaptive mesh refinement with linear matrix solver algorithms. The Tech-X code PolySwift++ is an SCFT simulation platform that leverages ongoing development in coupling Chombo, a package for solving PDEs via block-structured AMR calculations and embedded boundaries, with PETSc, a toolkit that includes a large assortment of sparse linear solvers.

Rapid construction of mechanically- confined multi- cellular structures using dendrimeric intercellular linker.

PubMed

Mo, Xuejun; Li, Qiushi; Yi Lui, Lena Wai; Zheng, Baixue; Kang, Chiang Huen; Nugraha, Bramasta; Yue, Zhilian; Jia, Rui Rui; Fu, Hong Xia; Choudhury, Deepak; Arooz, Talha; Yan, Jie; Lim, Chwee Teck; Shen, Shali; Hong Tan, Choon; Yu, Hanry

2010-10-01

Tissue constructs that mimic the in vivo cell-cell and cell-matrix interactions are especially useful for applications involving the cell- dense and matrix- poor internal organs. Rapid and precise arrangement of cells into functional tissue constructs remains a challenge in tissue engineering. We demonstrate rapid assembly of C3A cells into multi- cell structures using a dendrimeric intercellular linker. The linker is composed of oleyl- polyethylene glycol (PEG) derivatives conjugated to a 16 arms- polypropylenimine hexadecaamine (DAB) dendrimer. The positively charged multivalent dendrimer concentrates the linker onto the negatively charged cell surface to facilitate efficient insertion of the hydrophobic oleyl groups into the cellular membrane. Bringing linker- treated cells into close proximity to each other via mechanical means such as centrifugation and micromanipulation enables their rapid assembly into multi- cellular structures within minutes. The cells exhibit high levels of viability, proliferation, three- dimensional (3D) cell morphology and other functions in the constructs. We constructed defined multi- cellular structures such as rings, sheets or branching rods that can serve as potential tissue building blocks to be further assembled into complex 3D tissue constructs for biomedical applications. 2010 Elsevier Ltd. All rights reserved.

The effect of particle size on the morphology and thermodynamics of diblock copolymer/tethered-particle membranes

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

Zhang, Bo; Edwards, Brian J., E-mail: bje@utk.edu

A combination of self-consistent field theory and density functional theory was used to examine the effect of particle size on the stable, 3-dimensional equilibrium morphologies formed by diblock copolymers with a tethered nanoparticle attached either between the two blocks or at the end of one of the blocks. Particle size was varied between one and four tenths of the radius of gyration of the diblock polymer chain for neutral particles as well as those either favoring or disfavoring segments of the copolymer blocks. Phase diagrams were constructed and analyzed in terms of thermodynamic diagrams to understand the physics associated withmore » the molecular-level self-assembly processes. Typical morphologies were observed, such as lamellar, spheroidal, cylindrical, gyroidal, and perforated lamellar, with the primary concentration region of the tethered particles being influenced heavily by particle size and tethering location, strength of the particle-segment energetic interactions, chain length, and copolymer radius of gyration. The effect of the simulation box size on the observed morphology and system thermodynamics was also investigated, indicating possible effects of confinement upon the system self-assembly processes.« less

Confined in-fiber solidification and structural control of silicon and silicon−germanium microparticles

PubMed Central

Gumennik, Alexander; Levy, Etgar C.; Grena, Benjamin; Hou, Chong; Rein, Michael; Abouraddy, Ayman F.; Joannopoulos, John D.; Fink, Yoel

2017-01-01

Crystallization of microdroplets of molten alloys could, in principle, present a number of possible morphological outcomes, depending on the symmetry of the propagating solidification front and its velocity, such as axial or spherically symmetric species segregation. However, because of thermal or constitutional supercooling, resulting droplets often only display dendritic morphologies. Here we report on the crystallization of alloyed droplets of controlled micrometer dimensions comprising silicon and germanium, leading to a number of surprising outcomes. We first produce an array of silicon−germanium particles embedded in silica, through capillary breakup of an alloy-core silica-cladding fiber. Heating and subsequent controlled cooling of individual particles with a two-wavelength laser setup allows us to realize two different morphologies, the first being a silicon−germanium compositionally segregated Janus particle oriented with respect to the illumination axis and the second being a sphere made of dendrites of germanium in silicon. Gigapascal-level compressive stresses are measured within pure silicon solidified in silica as a direct consequence of volume-constrained solidification of a material undergoing anomalous expansion. The ability to generate microspheres with controlled morphology and unusual stresses could pave the way toward advanced integrated in-fiber electronic or optoelectronic devices. PMID:28642348

Confined in-fiber solidification and structural control of silicon and silicon-germanium microparticles.

PubMed

Gumennik, Alexander; Levy, Etgar C; Grena, Benjamin; Hou, Chong; Rein, Michael; Abouraddy, Ayman F; Joannopoulos, John D; Fink, Yoel

2017-07-11

Crystallization of microdroplets of molten alloys could, in principle, present a number of possible morphological outcomes, depending on the symmetry of the propagating solidification front and its velocity, such as axial or spherically symmetric species segregation. However, because of thermal or constitutional supercooling, resulting droplets often only display dendritic morphologies. Here we report on the crystallization of alloyed droplets of controlled micrometer dimensions comprising silicon and germanium, leading to a number of surprising outcomes. We first produce an array of silicon-germanium particles embedded in silica, through capillary breakup of an alloy-core silica-cladding fiber. Heating and subsequent controlled cooling of individual particles with a two-wavelength laser setup allows us to realize two different morphologies, the first being a silicon-germanium compositionally segregated Janus particle oriented with respect to the illumination axis and the second being a sphere made of dendrites of germanium in silicon. Gigapascal-level compressive stresses are measured within pure silicon solidified in silica as a direct consequence of volume-constrained solidification of a material undergoing anomalous expansion. The ability to generate microspheres with controlled morphology and unusual stresses could pave the way toward advanced integrated in-fiber electronic or optoelectronic devices.

Diversity and Distribution of Cryptic Species of the Bemisia tabaci (Hemiptera: Aleyrodidae) complex in Pakistan.

PubMed

Masood, Mariyam; Amin, Imran; Hassan, Ishtiaq; Mansoor, Shahid; Brown, Judith K; Briddon, Rob W

2017-12-05

Bemisia tabaci (Gennadius; Hempitera: Aleyrodidae) is considered to be a cryptic (sibling) species complex, the members of which exhibit morphological invariability while being genetically and behaviorally distinct. Members of the complex are agricultural pests that cause direct damage by feeding on plants, and indirectly by transmitting viruses that cause diseases leading to reduced crop yield and quality. In Pakistan, cotton leaf curl disease, caused by multiple begomovirus species, is the most economically important viral disease of cotton. In the study outlined here, the diversity and geographic distribution of B. tabaci cryptic species was investigated by analyzing a taxonomically informative fragment of the mitochondrial cytochrome c oxidase 1 gene (mtCOI-3'). The mtCOI-3' sequence was determined for 285 adult whiteflies and found to represent six cryptic species, the most numerous being Asia II-1 and Middle East Asia Minor 1 (MEAM-1), the later also referred to as the B-biotype, which was previously thought to be confined to Sindh province but herein, was also found to be present in the Punjab province. The endemic Asia I was restricted to Sindh province, while an individual in the Asia II-8 was identified in Pakistan for the first time. Also for the first time, samples were collected from northwestern Pakistan and Asia II-1 was identified. Results indicate that in Pakistan the overall diversity of B. tabaci cryptic species is high and, based on comparisons with findings from previous studies, the distribution is dynamic. © The Author(s) 2017. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Computational approach to integrate 3D X-ray microtomography and NMR data

NASA Astrophysics Data System (ADS)

Lucas-Oliveira, Everton; Araujo-Ferreira, Arthur G.; Trevizan, Willian A.; Fortulan, Carlos A.; Bonagamba, Tito J.

2018-07-01

Nowadays, most of the efforts in NMR applied to porous media are dedicated to studying the molecular fluid dynamics within and among the pores. These analyses have a higher complexity due to morphology and chemical composition of rocks, besides dynamic effects as restricted diffusion, diffusional coupling, and exchange processes. Since the translational nuclear spin diffusion in a confined geometry (e.g. pores and fractures) requires specific boundary conditions, the theoretical solutions are restricted to some special problems and, in many cases, computational methods are required. The Random Walk Method is a classic way to simulate self-diffusion along a Digital Porous Medium. Bergman model considers the magnetic relaxation process of the fluid molecules by including a probability rate of magnetization survival under surface interactions. Here we propose a statistical approach to correlate surface magnetic relaxivity with the computational method applied to the NMR relaxation in order to elucidate the relationship between simulated relaxation time and pore size of the Digital Porous Medium. The proposed computational method simulates one- and two-dimensional NMR techniques reproducing, for example, longitudinal and transverse relaxation times (T1 and T2, respectively), diffusion coefficients (D), as well as their correlations. For a good approximation between the numerical and experimental results, it is necessary to preserve the complexity of translational diffusion through the microstructures in the digital rocks. Therefore, we use Digital Porous Media obtained by 3D X-ray microtomography. To validate the method, relaxation times of ideal spherical pores were obtained and compared with the previous determinations by the Brownstein-Tarr model, as well as the computational approach proposed by Bergman. Furthermore, simulated and experimental results of synthetic porous media are compared. These results make evident the potential of computational physics in the analysis of the NMR data for complex porous materials.

A new Eastern Central Atlantic skate Raja parva sp. nov. (Rajoidei: Rajidae) belonging to the Raja miraletus species complex.

PubMed

Last, Peter R; Séret, Bernard

2016-08-05

An investigation of combined CO1 and NADH2 data for rajid skates referable to Raja miraletus provided evidence that populations ranging from southern Africa to the North-East Atlantic and Mediterranean Sea, once considered to represent a cline, belong to a species complex consisting of at least four valid species. Raja miraletus appears to be confined to the Mediterranean Sea, and the North-East Atlantic from the Bay of Biscay south to Morocco and Madeira. The southernmost species, referable to the resurrected Raja ocellifera, occurs off southern Africa, off Namibia and from False Bay to Durban (South Africa). Two species occur off tropical West Africa, including Raja parva sp. nov. (Senegal, Liberia and Angola but is probably more widespread within the region), and another unidentified species needing further investigation. Raja cf. miraletus, confirmed from Mauritania and Senegal, appears to be a larger skate with a broader disc, more broadly pointed snout, larger spiracles, and a slightly longer and broader tail. Raja parva sp. nov. differs from nominal members of the complex in having an unusually long procaudal tail (exceeding 22% TL), as well as a combination of other external characters. Past investigators observed morphological and anatomical differences between these forms but these were thought to be due to intraspecific variability. They postulated that an upwelling at Cape Blanco (21°N) may have isolated the Mediterranean form (R. miraletus) from Mauritania-Senegal form (now known to be two species). Similarly, the Benguela Current and upwelling off Cape Frio (18°S) were thought to be responsible for separating the Angolan form (R. parva) and South African form (R. ocellifera).

Granulomatous mastitis: a report of seven cases

PubMed Central

Fletcher, A; Magrath, IM; Riddell, RH; Talbot, IC

1982-01-01

The clinical history and histological features of seven cases of granulomatous mastitis are presented. The lesion occurs in young parous women as a tender extra-areolar breast lump. Histologically, non-caseating discrete granulomas are present, confined to breast lobules with, in three cases, coalescence of the granulomas and microabscess formation. Pathogenesis of the changes is discussed. It is thought that granulomatous mastitis is an entity morphologically distinct from duct ectasia/plasma cell mastitis and the commoner forms of granulomatous breast diseases. Images PMID:6889612

Electrooxidation of pyrrole-terminated self-assembled lipoic acid derivatives

NASA Astrophysics Data System (ADS)

Cabrita, Joana F.; Viana, Ana S.; Eberle, Christoph; Montforts, Franz-Peter; Mourato, Ana; Abrantes, Luisa M.

2009-08-01

New pyrrole derivatives, pyrrolyl lipoic acid (Py-LA 3) and dipyrrolyl lipoic acid (Py 2-LA 2) have been used for surface attachment and immobilisation on gold surfaces, by self-assembly. The electrooxidation of the surface-confined pyrroles was analysed by cyclic voltammetry and the modified electrodes morphological and thickness changes addressed by scanning probe microscopy and ellipsometry. The data support the formation of oligomers as a result of the pendant-pyrrolyl units ease oxidation but provide no evidence of an effective subsequent polymerisation.

Template confined synthesis of amorphous carbon nanotubes and its confocal Raman microscopy

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

Maity, Supratim; Roychowdhury, Tuhin; Chattopadhyay, Kalyan Kumar, E-mail: kalyan-chattopadhyay@yahoo.com

2014-04-24

Amorphous carbon nanotubes (aCNTs) were synthesized by AAO (anodic aluminum oxide) template at a temperature 500 °C in nitrogen atmosphere using the citric acid as a carbon source without the help of any catalyst particles. Morphological analysis of the as prepared samples was carried out by field emission scanning electron microscopy (FESEM). Confocal Raman imaging has been studied and an attempt has been made to find out the graphitic (sp{sup 2}) and disordered phase of the CNTs.

Spectroscopic Feedback for High Density Data Storage and Micromachining

DOEpatents

Carr, Christopher W.; Demos, Stavros; Feit, Michael D.; Rubenchik, Alexander M.

2008-09-16

Optical breakdown by predetermined laser pulses in transparent dielectrics produces an ionized region of dense plasma confined within the bulk of the material. Such an ionized region is responsible for broadband radiation that accompanies a desired breakdown process. Spectroscopic monitoring of the accompanying light in real-time is utilized to ascertain the morphology of the radiated interaction volume. Such a method and apparatus as presented herein, provides commercial realization of rapid prototyping of optoelectronic devices, optical three-dimensional data storage devices, and waveguide writing.

Coarse Grained Modeling of Block Copolymer Lithography: The Effects of Pattern Design on the Thermodynamics and Kinetics of the Directed Self Assembly of Block Copolymers

NASA Astrophysics Data System (ADS)

Garner, Grant Parker

The directed self assembly of block copolymers is an exciting complimentary technique for the fabrication of nanoscale structures for lithographic applications. Typically a directed self assembly process is driven through substrates with chemical (chemoepitaxy) or topographical (graphoepitaxy) guiding features. These patterning strategies have led to the ability to assemble structures with a high degree of perfection over large areas. However, a guiding pattern has not been created which assembles the desired features with a defect density that is commensurate with industrial standards of 1 defect/100cm 2. This work focuses on using molecular simulations on the Theoretically Informed Coarse Grained model to provide design rules for substrate patterns which drive the assembly of desired, device-oriented morphologies. Prior to the work presented in Chapter 2, the TICG model has been used in conjunction with a chemical pattern that is approximated as a hard-impenetrable surface. As many experimental systems use polymer brushes to help guide the polymer melt deposited on the substrate, this work analyzes the consequences of such an assumption by comparing a model where the polymer brush is explicitly implemented to the hard-wall substrate used in the past. Then, a methodology which utilizes a evolutionary optimization method is used to map the parameters of the more detailed model to the hard-surface model. This provides a qualitative understanding of how to interpret the model parameters used in previous works in the context of real experimental pattern designs. Chapter 3 discuss the concept of competitive assemblies in regards to defining a thermodynamic processing window in design space for assembling lines-and-spaces. The most competitive assembly to the desired orientation of the lamella is defined as a rotation of assembled lamella to the underlying pattern. Thermodynamic integration is used to calculate the free-energy difference between these assemblies over chemical patterns with varied design parameters. Local maximums in the free-energy difference are observed over pattern designs that are in qualitatively agreement with the pattern designs which produce the most perfect assemblies in experiments. The analysis is extended to study how choice of chemistry impacts this thermodynamic selection for the desired morphology. Finally, Chapter 4 provides insight into the kinetics of patterned directed self-assembly by investigating cylinder forming block copolymers within cylindrical confinements. Through the use of the string method, the minimum free-energy path between a defective state and the desired assembled morphology is calculated and clear transition states are highlighted. The effects of key parameters of the confinement design on the calculated minimum free energy path are calculated to identify design rules which should lead to a better understanding of optimal connement design for eliminating defects. In addition, a specific modification to existing cylindrical confinements is discussed as a possibility for tackling the problem of placement accuracy for a cylinder that is assembled within the confinement.

Motifs for molecular recognition exploiting hydrophobic enclosure in protein-ligand binding.

PubMed

Young, Tom; Abel, Robert; Kim, Byungchan; Berne, Bruce J; Friesner, Richard A

2007-01-16

The thermodynamic properties and phase behavior of water in confined regions can vary significantly from that observed in the bulk. This is particularly true for systems in which the confinement is on the molecular-length scale. In this study, we use molecular dynamics simulations and a powerful solvent analysis technique based on inhomogenous solvation theory to investigate the properties of water molecules that solvate the confined regions of protein active sites. Our simulations and analysis indicate that the solvation of protein active sites that are characterized by hydrophobic enclosure and correlated hydrogen bonds induce atypical entropic and enthalpic penalties of hydration. These penalties apparently stabilize the protein-ligand complex with respect to the independently solvated ligand and protein, which leads to enhanced binding affinities. Our analysis elucidates several challenging cases, including the super affinity of the streptavidin-biotin system.

Unusual large-pitch banding in poly(L-lactic acid): Effects of composition and geometry confinement

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

Woo, Eamor M.; Lugito, Graecia; Hsieh, Ya-Ting

2014-02-24

Lamellar patterns and orientations in blends of two crystalline polymers: poly(ethylene oxide) (PEO) and low-molecular-weight poly(L-lactic acid) (PLLA) were investigated using polarizing light optical microscopy (POM), and atomic and scanning electron microscopy (AFM, SEM). Specific etching off of PEO was used to reveal the complex earlier-grown PLLA lamellae patterns with various PEO content in blends. Banding of extremely long pitch (50 μm) in crystallized PLLA spherulites was induced by two kinetic factors: geometry confinement by top cover and introduction of diluent such as PEO. The mechanisms and correlation among the lamellar assembly, ring bands, and cracks are exemplified. Lamellar patternsmore » and ring-band types in blends were found to vary with respect to not only blend compositions, but also confinement of top-cover.« less

The kinetic stabilizer: a route to simpler tandem mirror systems

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

Post, R F

2001-02-02

As we enter the new millennium there is a growing urgency to address the issue of finding long-range solutions to the world's energy needs. Fusion offers such a solution, provided economically viable means can be found to extract useful energy from fusion reactions. While the magnetic confinement approach to fusion has a long and productive history, to date the mainline approaches to magnetic confinement, namely closed systems such as the tokamak, appear to many as being too large and complex to be acceptable economically, despite the impressive progress that has made toward the achievement of fusion-relevant confinement parameters. Thus theremore » is a growing feeling that it is imperative to search for new and simpler approaches to magnetic fusion, ones that might lead to smaller and more economically attractive fusion power plants.« less

Complex networks in confined comminution

NASA Astrophysics Data System (ADS)

Walker, David M.; Tordesillas, Antoinette; Einav, Itai; Small, Michael

2011-08-01

The physical process of confined comminution is investigated within the framework of complex networks. We first characterize the topology of the unweighted contact networks as generated by the confined comminution process. We find this process gives rise to an ultimate contact network which exhibits a scale-free degree distribution and small world properties. In particular, if viewed in the context of networks through which information travels along shortest paths, we find that the global average of the node vulnerability decreases as the comminution process continues, with individual node vulnerability correlating with grain size. A possible application to the design of synthetic networks (e.g., sensor networks) is highlighted. Next we turn our attention to the physics of the granular comminution process and examine force transmission with respect to the weighted contact networks, where each link is weighted by the inverse magnitude of the normal force acting at the associated contact. We find that the strong forces (i.e., force chains) are transmitted along pathways in the network which are mainly following shortest-path routing protocols, as typically found, for example, in communication systems. Motivated by our earlier studies of the building blocks for self-organization in dense granular systems, we also explore the properties of the minimal contact cycles. The distribution of the contact strain energy intensity of 4-cycle motifs in the ultimate state of the confined comminution process is shown to be consistent with a scale-free distribution with infinite variance, thereby suggesting that 4-cycle arrangements of grains are capable of storing vast amounts of energy in their contacts without breaking.

Space-confined fabrication of silver nanodendrites and their enhanced SERS activity

NASA Astrophysics Data System (ADS)

Wang, Shuqi; Xu, Li-Ping; Wen, Yongqiang; Du, Hongwu; Wang, Shutao; Zhang, Xueji

2013-05-01

Here we report a controllable method based on electrodeposition to fabricate Ag nanodendrites (NDs) on a microwell patterned electrode. The microwell patterns on the ITO electrode are fabricated via the microcontact printing technique. By varying the microwell size and electrodeposition time, the morphology of metal deposits on the microwell patterned ITO electrode can be tuned from boulders to dendrites. At the edge of the microwells, the current density was strengthened, which incurs rapid nucleation. The nucleus develops into dendrites because of Mullins-Sekerka instability. However, only boulders were observed at the center of microwells. By reducing the size of the microwells, only NDs were fabricated due to the edge effect. On the basis of understanding the underlying mechanism for dendritic growth in a confined space, our method is used for fabricating other noble metal (Au, Pt) nanodendrites. The controllable synthesis of Au and Pt NDs indicates the universality of this method. Compared with Ag film obtained from electron beam evaporation, the as-prepared Ag NDs exhibit highly enhanced surface-enhanced Raman scattering (SERS) sensitivity when they are used to detect rhodamine 6G (R6G). This approach provides a very controllable, reliable and general way for space-confined fabricating the noble metal nanodendrite arrays which show great promise in catalysis, sensing, biomedicine, electronic and magnetic devices.Here we report a controllable method based on electrodeposition to fabricate Ag nanodendrites (NDs) on a microwell patterned electrode. The microwell patterns on the ITO electrode are fabricated via the microcontact printing technique. By varying the microwell size and electrodeposition time, the morphology of metal deposits on the microwell patterned ITO electrode can be tuned from boulders to dendrites. At the edge of the microwells, the current density was strengthened, which incurs rapid nucleation. The nucleus develops into dendrites because of Mullins-Sekerka instability. However, only boulders were observed at the center of microwells. By reducing the size of the microwells, only NDs were fabricated due to the edge effect. On the basis of understanding the underlying mechanism for dendritic growth in a confined space, our method is used for fabricating other noble metal (Au, Pt) nanodendrites. The controllable synthesis of Au and Pt NDs indicates the universality of this method. Compared with Ag film obtained from electron beam evaporation, the as-prepared Ag NDs exhibit highly enhanced surface-enhanced Raman scattering (SERS) sensitivity when they are used to detect rhodamine 6G (R6G). This approach provides a very controllable, reliable and general way for space-confined fabricating the noble metal nanodendrite arrays which show great promise in catalysis, sensing, biomedicine, electronic and magnetic devices. Electronic supplementary information (ESI) available: SEM images. See DOI: 10.1039/c3nr00313b

Large Bore Powder Gun Qualification (U)

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

Rabern, Donald A.; Valdiviez, Robert

A Large Bore Powder Gun (LBPG) is being designed to enable experimentalists to characterize material behavior outside the capabilities of the NNSS JASPER and LANL TA-55 PF-4 guns. The combination of these three guns will create a capability to conduct impact experiments over a wide range of pressures and shock profiles. The Large Bore Powder Gun will be fielded at the Nevada National Security Site (NNSS) U1a Complex. The Complex is nearly 1000 ft below ground with dedicated drifts for testing, instrumentation, and post-shot entombment. To ensure the reliability, safety, and performance of the LBPG, a qualification plan has beenmore » established and documented here. Requirements for the LBPG have been established and documented in WE-14-TR-0065 U A, Large Bore Powder Gun Customer Requirements. The document includes the requirements for the physics experiments, the gun and confinement systems, and operations at NNSS. A detailed description of the requirements is established in that document and is referred to and quoted throughout this document. Two Gun and Confinement Systems will be fielded. The Prototype Gun will be used primarily to characterize the gun and confinement performance and be the primary platform for qualification actions. This gun will also be used to investigate and qualify target and diagnostic modifications through the life of the program (U1a.104 Drift). An identical gun, the Physics Gun, will be fielded for confirmatory and Pu experiments (U1a.102D Drift). Both guns will be qualified for operation. The Gun and Confinement System design will be qualified through analysis, inspection, and testing using the Prototype Gun for the majority of process. The Physics Gun will be qualified through inspection and a limited number of qualification tests to ensure performance and behavior equivalent to the Prototype gun. Figure 1.1 shows the partial configuration of U1a and the locations of the Prototype and Physics Gun/Confinement Systems.« less

Complex Fluids at Interfaces and Interfaces of Complex Fluids

NASA Astrophysics Data System (ADS)

Nouri, Mariam

The present thesis deals with two independent projects and is consequently divided into two parts. The first part details a computational study of the fluid structure of ring-shaped molecules and their positional and orientational molecular organizations in different degrees of confinement, while the second part concerns an experimental study of phase behavior and interfacial phenomena in confined colloid-polymer systems. In the first part, ring-shaped molecules are studied using Monte Carlo simulation techniques in one, two and three dimensions. The model used to describe ring-shaped molecules is composed of hard-spheres linked together to form planar rigid rings. For rings of various sizes and for a wide range of densities, positional and orientational orderings are reported in forms of pair distribution functions of the ring centers and correlation functions of the ring normal orientations. Special emphasis is given to understand structural formation at interfaces, i.e., the structure and orderings of these molecules when they are confined to two dimensions. In a plane but the rings themselves are free to rotate around all axes, nematic ordering is observed at sufficiently high densities. In the second part, phase equilibria of confined aqueous colloid-polymer systems are studied experimentally using fluorescence microscopy. Aqueous mixtures of fluorescent polystyrene spheres and polyacrylamide are confined between a glass slide and a coverslip. The phase diagram is determined as a function of the colloidal and polymer concentrations. Liquid-liquid phase coexistence between a colloid-rich phase and a polymer-rich phase occurs at intermediate polymer concentrations, while liquid-solid phase coexistence between a polymer-rich liquid and a colloid-rich solid is observed at high polymer concentrations. Interfacial thickness and tension of the interface between these coexisting phases are measured using image analysis techniques. It is also observed that the colloid-rich solid and liquid domains coarsen mainly by Ostwald ripening.

Neutrophils establish rapid and robust WAVE complex polarity in an actin-dependent fashion.

PubMed

Millius, Arthur; Dandekar, Sheel N; Houk, Andrew R; Weiner, Orion D

2009-02-10

Asymmetric intracellular signals enable cells to migrate in response to external cues. The multiprotein WAVE (also known as SCAR or WASF) complex activates the actin-nucleating Arp2/3 complex [1-4] and localizes to propagating "waves," which direct actin assembly during neutrophil migration [5, 6]. Here, we observe similar WAVE complex dynamics in other mammalian cells and analyze WAVE complex dynamics during establishment of neutrophil polarity. Earlier models proposed that spatially biased generation [7] or selection of protrusions [8] enables chemotaxis. These models require existing morphological polarity to control protrusions. We show that spatially biased generation and selection of WAVE complex recruitment also occur in morphologically unpolarized neutrophils during development of their first protrusions. Additionally, several mechanisms limit WAVE complex recruitment during polarization and movement: Intrinsic cues restrict WAVE complex distribution during establishment of polarity, and asymmetric intracellular signals constrain it in morphologically polarized cells. External gradients can overcome both intrinsic biases and control WAVE complex localization. After latrunculin-mediated inhibition of actin polymerization, addition and removal of agonist gradients globally recruits and releases the WAVE complex from the membrane. Under these conditions, the WAVE complex no longer polarizes, despite the presence of strong external gradients. Thus, actin polymer and the WAVE complex reciprocally interact during polarization.

Learning to Construct Verbs in Navajo and Quechua

ERIC Educational Resources Information Center

Courtney, Ellen H.; Saville-Troike, Muriel

2002-01-01

Navajo and Quechua, both languages with a highly complex morphology, provide intriguing insights into the acquisition of inflectional systems. The development of the verb in the two languages is especially interesting, since the morphology encodes diverse grammatical notions, with the complex verb often constituting the entire sentence. While the…

Scaling of Linking and Writhing Numbers for Spherically Confined and Topologically Equilibrated Flexible Polymers

PubMed Central

Marko, John F.

2011-01-01

Scaling laws for Gauss linking number Ca and writhing number Wr for spherically confined flexible polymers with thermally fluctuating topology are analyzed. For ideal (phantom) polymers each of N segments of length unity confined to a spherical pore of radius R there are two scaling regimes: for sufficiently weak confinement (R ⪢ N1/3) each chain has |Wr| ≈ N1/2, and each pair of chains has average |Ca| ≈ N/R3/2; alternately for sufficiently tight confinement (N1/3 ⪢ R), |Wr| ≈ |CA| ≈ N/R3/2. Adding segment-segment avoidance modifies this result: for n chains with excluded volume interactions |Ca| ≈ (N/n)1/2f(ϕ) where f is a scaling function that depends approximately linearly on the segment concentration ϕ = nN/R3. Scaling results for writhe are used to estimate the maximum writhe of a polymer; this is demonstrated to be realizable through a writhing instability that occurs for a polymer which is able to change knotting topology and which is subject to an applied torque. Finally, scaling results for linking are used to estimate bounds on the entanglement complexity of long chromosomal DNA molecules inside cells, and to show how “lengthwise” chromosome condensation can suppress DNA entanglement. PMID:21686050

Active and passive transport of cargo in a corrugated channel: A lattice model study

NASA Astrophysics Data System (ADS)

Dey, Supravat; Ching, Kevin; Das, Moumita

2018-04-01

Inside cells, cargos such as vesicles and organelles are transported by molecular motors to their correct locations via active motion on cytoskeletal tracks and passive, Brownian diffusion. During the transportation of cargos, motor-cargo complexes (MCCs) navigate the confining and crowded environment of the cytoskeletal network and other macromolecules. Motivated by this, we study a minimal two-state model of motor-driven cargo transport in confinement and predict transport properties that can be tested in experiments. We assume that the motion of the MCC is directly affected by the entropic barrier due to confinement if it is in the passive, unbound state but not in the active, bound state where it moves with a constant bound velocity. We construct a lattice model based on a Fokker Planck description of the two-state system, study it using a kinetic Monte Carlo method and compare our numerical results with analytical expressions for a mean field limit. We find that the effect of confinement strongly depends on the bound velocity and the binding kinetics of the MCC. Confinement effectively reduces the effective diffusivity and average velocity, except when it results in an enhanced average binding rate and thereby leads to a larger average velocity than when unconfined.

Electrostatic-Dipole (ED) Fusion Confinement Studies

NASA Astrophysics Data System (ADS)

Miley, George H.; Shrestha, Prajakti J.; Yang, Yang; Thomas, Robert

2004-11-01

The Electrostatic-Dipole (ED) concept significantly differs from a "pure" dipole confinement device [1] in that the charged particles are preferentially confined to the high-pressure region interior of the dipole coil by the assistance of a surrounding spherical electrostatic grid. In present ED experiments, a current carrying coil is embedded inside the grid of an IEC such as to produce a magnetic dipole field. Charged particles are injected axisymmetrically from an ion gun (or duo-plasmatron) into the center of the ED confinement grid/dipole ring where they oscillate along the magnetic field lines and pass the peak field region at the center of the dipole region. As particles begin accelerating away from the center region towards the outer electrostatic grid region, they encounter a strong electrostatic potential (order of 10's of kilovolts) retarding force. The particles then decelerate, reverse direction and re-enter the dipole field region where again magnetic confinement dominates. This process continues, emulating a complex harmonic oscillator motion. The resulting pressure profile averaged over the field curvature offers good plasma stability in the ED configuration. The basic concept and results from preliminary experiments will be described. [1] M.E. Mauel, et al. "Dipole Equilibrium and Stability," 18th IAEA Conference of Plasma Phys. and Control. Nuclear Fusion, Varenna, Italy 2000, IAEA-F1-CN-70/TH

Soft matter in hard confinement: phase transition thermodynamics, structure, texture, diffusion and flow in nanoporous media.

PubMed

Huber, Patrick

2015-03-18

Spatial confinement in nanoporous media affects the structure, thermodynamics and mobility of molecular soft matter often markedly. This article reviews thermodynamic equilibrium phenomena, such as physisorption, capillary condensation, crystallisation, self-diffusion, and structural phase transitions as well as selected aspects of the emerging field of spatially confined, non-equilibrium physics, i.e. the rheology of liquids, capillarity-driven flow phenomena, and imbibition front broadening in nanoporous materials. The observations in the nanoscale systems are related to the corresponding bulk phenomenologies. The complexity of the confined molecular species is varied from simple building blocks, like noble gas atoms, normal alkanes and alcohols to liquid crystals, polymers, ionic liquids, proteins and water. Mostly, experiments with mesoporous solids of alumina, gold, carbon, silica, and silicon with pore diameters ranging from a few up to 50 nm are presented. The observed peculiarities of nanopore-confined condensed matter are also discussed with regard to applications. A particular emphasis is put on texture formation upon crystallisation in nanoporous media, a topic both of high fundamental interest and of increasing nanotechnological importance, e.g. for the synthesis of organic/inorganic hybrid materials by melt infiltration, the usage of nanoporous solids in crystal nucleation or in template-assisted electrochemical deposition of nano structures.

Soft matter in hard confinement: phase transition thermodynamics, structure, texture, diffusion and flow in nanoporous media

NASA Astrophysics Data System (ADS)

Huber, Patrick

2015-03-01

Spatial confinement in nanoporous media affects the structure, thermodynamics and mobility of molecular soft matter often markedly. This article reviews thermodynamic equilibrium phenomena, such as physisorption, capillary condensation, crystallisation, self-diffusion, and structural phase transitions as well as selected aspects of the emerging field of spatially confined, non-equilibrium physics, i.e. the rheology of liquids, capillarity-driven flow phenomena, and imbibition front broadening in nanoporous materials. The observations in the nanoscale systems are related to the corresponding bulk phenomenologies. The complexity of the confined molecular species is varied from simple building blocks, like noble gas atoms, normal alkanes and alcohols to liquid crystals, polymers, ionic liquids, proteins and water. Mostly, experiments with mesoporous solids of alumina, gold, carbon, silica, and silicon with pore diameters ranging from a few up to 50 nm are presented. The observed peculiarities of nanopore-confined condensed matter are also discussed with regard to applications. A particular emphasis is put on texture formation upon crystallisation in nanoporous media, a topic both of high fundamental interest and of increasing nanotechnological importance, e.g. for the synthesis of organic/inorganic hybrid materials by melt infiltration, the usage of nanoporous solids in crystal nucleation or in template-assisted electrochemical deposition of nano structures.

Space-confined fabrication of silver nanodendrites and their enhanced SERS activity.

PubMed

Wang, Shuqi; Xu, Li-Ping; Wen, Yongqiang; Du, Hongwu; Wang, Shutao; Zhang, Xueji

2013-05-21

Here we report a controllable method based on electrodeposition to fabricate Ag nanodendrites (NDs) on a microwell patterned electrode. The microwell patterns on the ITO electrode are fabricated via the microcontact printing technique. By varying the microwell size and electrodeposition time, the morphology of metal deposits on the microwell patterned ITO electrode can be tuned from boulders to dendrites. At the edge of the microwells, the current density was strengthened, which incurs rapid nucleation. The nucleus develops into dendrites because of Mullins-Sekerka instability. However, only boulders were observed at the center of microwells. By reducing the size of the microwells, only NDs were fabricated due to the edge effect. On the basis of understanding the underlying mechanism for dendritic growth in a confined space, our method is used for fabricating other noble metal (Au, Pt) nanodendrites. The controllable synthesis of Au and Pt NDs indicates the universality of this method. Compared with Ag film obtained from electron beam evaporation, the as-prepared Ag NDs exhibit highly enhanced surface-enhanced Raman scattering (SERS) sensitivity when they are used to detect rhodamine 6G (R6G). This approach provides a very controllable, reliable and general way for space-confined fabricating the noble metal nanodendrite arrays which show great promise in catalysis, sensing, biomedicine, electronic and magnetic devices.

Physicochemical characterization, and relaxometry studies of micro-graphite oxide, graphene nanoplatelets, and nanoribbons.

PubMed

Paratala, Bhavna S; Jacobson, Barry D; Kanakia, Shruti; Francis, Leonard Deepak; Sitharaman, Balaji

2012-01-01

The chemistry of high-performance magnetic resonance imaging contrast agents remains an active area of research. In this work, we demonstrate that the potassium permanganate-based oxidative chemical procedures used to synthesize graphite oxide or graphene nanoparticles leads to the confinement (intercalation) of trace amounts of Mn(2+) ions between the graphene sheets, and that these manganese intercalated graphitic and graphene structures show disparate structural, chemical and magnetic properties, and high relaxivity (up to 2 order) and distinctly different nuclear magnetic resonance dispersion profiles compared to paramagnetic chelate compounds. The results taken together with other published reports on confinement of paramagnetic metal ions within single-walled carbon nanotubes (a rolled up graphene sheet) show that confinement (encapsulation or intercalation) of paramagnetic metal ions within graphene sheets, and not the size, shape or architecture of the graphitic carbon particles is the key determinant for increasing relaxivity, and thus, identifies nano confinement of paramagnetic ions as novel general strategy to develop paramagnetic metal-ion graphitic-carbon complexes as high relaxivity MRI contrast agents.

Physicochemical Characterization, and Relaxometry Studies of Micro-Graphite Oxide, Graphene Nanoplatelets, and Nanoribbons

PubMed Central

Paratala, Bhavna S.; Jacobson, Barry D.; Kanakia, Shruti; Francis, Leonard Deepak; Sitharaman, Balaji

2012-01-01

The chemistry of high-performance magnetic resonance imaging contrast agents remains an active area of research. In this work, we demonstrate that the potassium permanganate-based oxidative chemical procedures used to synthesize graphite oxide or graphene nanoparticles leads to the confinement (intercalation) of trace amounts of Mn2+ ions between the graphene sheets, and that these manganese intercalated graphitic and graphene structures show disparate structural, chemical and magnetic properties, and high relaxivity (up to 2 order) and distinctly different nuclear magnetic resonance dispersion profiles compared to paramagnetic chelate compounds. The results taken together with other published reports on confinement of paramagnetic metal ions within single-walled carbon nanotubes (a rolled up graphene sheet) show that confinement (encapsulation or intercalation) of paramagnetic metal ions within graphene sheets, and not the size, shape or architecture of the graphitic carbon particles is the key determinant for increasing relaxivity, and thus, identifies nano confinement of paramagnetic ions as novel general strategy to develop paramagnetic metal-ion graphitic-carbon complexes as high relaxivity MRI contrast agents. PMID:22685555

Markov-state model for CO2 binding with carbonic anhydrase under confinement

NASA Astrophysics Data System (ADS)

Chen, Gong; Xu, Weina; Lu, Diannan; Wu, Jianzhong; Liu, Zheng

2018-01-01

Enzyme immobilization with a nanostructure material can enhance its stability and facilitate reusability. However, the apparent activity is often compromised due to additional diffusion barriers and complex interactions with the substrates and solvent molecules. The present study elucidates the effects of the surface hydrophobicity of nano-confinement on CO2 diffusion to the active site of human carbonic anhydrase II (CA), an enzyme that is able to catalyze CO2 hydration at extremely high turnover rates. Using the Markov-state model in combination with coarse-grained molecular dynamics simulations, we demonstrate that a hydrophobic cage increases CO2 local density but hinders its diffusion towards the active site of CA under confinement. By contrast, a hydrophilic cage hinders CO2 adsorption but promotes its binding with CA. An optimal surface hydrophobicity can be identified to maximize both the CO2 occupation probability and the diffusion rate. The simulation results offer insight into understanding enzyme performance under nano-confinement and help us to advance broader applications of CA for CO2 absorption and recovery.

Dynamic and structural properties of room-temperature ionic liquids near silica and carbon surfaces.

PubMed

Li, Song; Han, Kee Sung; Feng, Guang; Hagaman, Edward W; Vlcek, Lukas; Cummings, Peter T

2013-08-06

The dynamic and structural properties of a room-temperature ionic liquid (RTIL) 1-butyl-3-methyl-imidazolium(trifluoromethanesulfonimide) ([C4mim][Tf2N]) confined in silica and carbon mesopores were investigated by molecular dynamics (MD) simulations and nuclear magnetic resonance (NMR) experiments. The complex interfacial microstructures of confined [C4mim][Tf2N] are attributed to the distinctive surface features of the silica mesopore. The temperature-dependent diffusion coefficients of [C4mim][Tf2N] confined in the silica or carbon mesopore exhibit divergent behavior. The loading fraction (f = 1.0, 0.5, and 0.25) has a large effect on the magnitude of the diffusion coefficient in the silica pore and displays weaker temperature dependence as the loading fraction decreases. The diffusion coefficients of mesoporous carbon-confined [C4mim][Tf2N] are relatively insensitive to the loading faction and exhibit a temperature dependence that is similar to the bulk dependence at all loading levels. Such phenomena can be attributed to the unique surface heterogeneity, dissimilar interfacial microstructures, and interaction potential profile of RTILs near silica and carbon walls.

Surviving blind decomposition: A distributional analysis of the time-course of complex word recognition.

PubMed

Schmidtke, Daniel; Matsuki, Kazunaga; Kuperman, Victor

2017-11-01

The current study addresses a discrepancy in the psycholinguistic literature about the chronology of information processing during the visual recognition of morphologically complex words. Form-then-meaning accounts of complex word recognition claim that morphemes are processed as units of form prior to any influence of their meanings, whereas form-and-meaning models posit that recognition of complex word forms involves the simultaneous access of morphological and semantic information. The study reported here addresses this theoretical discrepancy by applying a nonparametric distributional technique of survival analysis (Reingold & Sheridan, 2014) to 2 behavioral measures of complex word processing. Across 7 experiments reported here, this technique is employed to estimate the point in time at which orthographic, morphological, and semantic variables exert their earliest discernible influence on lexical decision RTs and eye movement fixation durations. Contrary to form-then-meaning predictions, Experiments 1-4 reveal that surface frequency is the earliest lexical variable to exert a demonstrable influence on lexical decision RTs for English and Dutch derived words (e.g., badness ; bad + ness ), English pseudoderived words (e.g., wander ; wand + er ) and morphologically simple control words (e.g., ballad ; ball + ad ). Furthermore, for derived word processing across lexical decision and eye-tracking paradigms (Experiments 1-2; 5-7), semantic effects emerge early in the time-course of word recognition, and their effects either precede or emerge simultaneously with morphological effects. These results are not consistent with the premises of the form-then-meaning view of complex word recognition, but are convergent with a form-and-meaning account of complex word recognition. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Computer modeling and simulation in inertial confinement fusion

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

McCrory, R.L.; Verdon, C.P.

1989-03-01

The complex hydrodynamic and transport processes associated with the implosion of an inertial confinement fusion (ICF) pellet place considerable demands on numerical simulation programs. Processes associated with implosion can usually be described using relatively simple models, but their complex interplay requires that programs model most of the relevant physical phenomena accurately. Most hydrodynamic codes used in ICF incorporate a one-fluid, two-temperature model. Electrons and ions are assumed to flow as one fluid (no charge separation). Due to the relatively weak coupling between the ions and electrons, each species is treated separately in terms of its temperature. In this paper wemore » describe some of the major components associated with an ICF hydrodynamics simulation code. To serve as an example we draw heavily on a two-dimensional Lagrangian hydrodynamic code (ORCHID) written at the University of Rochester's Laboratory for Laser Energetics. 46 refs., 19 figs., 1 tab.« less

Arsenic distribution and valence state variation studied by fast hierarchical length-scale morphological, compositional, and speciation imaging at the Nanoscopium, Synchrotron Soleil

NASA Astrophysics Data System (ADS)

Somogyi, Andrea; Medjoubi, Kadda; Sancho-Tomas, Maria; Visscher, P. T.; Baranton, Gil; Philippot, Pascal

2017-09-01

The understanding of real complex geological, environmental and geo-biological processes depends increasingly on in-depth non-invasive study of chemical composition and morphology. In this paper we used scanning hard X-ray nanoprobe techniques in order to study the elemental composition, morphology and As speciation in complex highly heterogeneous geological samples. Multivariate statistical analytical techniques, such as principal component analysis and clustering were used for data interpretation. These measurements revealed the quantitative and valance state inhomogeneity of As and its relation to the total compositional and morphological variation of the sample at sub-μm scales.

PREFACE: Complex dynamics of fluids in disordered and crowded environments Complex dynamics of fluids in disordered and crowded environments

NASA Astrophysics Data System (ADS)

Coslovich, Daniele; Kahl, Gerhard; Krakoviack, Vincent

2011-06-01

Over the past two decades, the dynamics of fluids under nanoscale confinement has attracted much attention. Motivation for this rapidly increasing interest is based on both practical and fundamental reasons. On the practical and rather applied side, problems in a wide range of scientific topics, such as polymer and colloidal sciences, rheology, geology, or biophysics, benefit from a profound understanding of the dynamical behaviour of confined fluids. Further, effects similar to those observed in confinement are expected in fluids whose constituents have strong size or mass asymmetry, and in biological systems where crowding and obstruction phenomena in the cytosol are responsible for clear separations of time scales for macromolecular transport in the cell. In fundamental research, on the other hand, the interest focuses on the complex interplay between confinement and structural relaxation, which is responsible for the emergence of new phenomena in the dynamics of the system: in confinement, geometric constraints associated with the pore shape are imposed to the adsorbed fluids and an additional characteristic length scale, i.e. the pore size, comes into play. For many years, the topic has been mostly experimentally driven. Indeed, a broad spectrum of systems has been investigated by sophisticated experimental techniques, while theoretical and simulation studies were rather scarce due to conceptual and computational issues. In the past few years, however, theory and simulations could largely catch up with experiments. On one side, new theories have been put forward that duly take into account the porosity, the connectivity, and the randomness of the confinement. On the other side, the ever increasing available computational power now allows investigations that were far out of reach a few years ago. Nowadays, instead of isolated state points, systematic investigations on the dynamics of confined fluids, covering a wide range of system parameters, can be realized. In fact, theory and simulations were recently able to predict new and surprising dynamical features, such as the occurrence of sub-diffusive laws, which result from the trapping due to the geometric and topological constraints and/or quenched disorder, the presence of both continuous and discontinuous glass transitions, and diffusion-localization transitions. Together, theory and simulations are thus able to contribute to a deeper insight into the complex dynamical behaviour of fluids in disordered confinement. Still, many yet unsolved problems remain. The fact that theoretical and simulation approaches have caught up with experimental investigations, has motivated us to organize a workshop on the dynamics of fluids confined in disordered environments, so as to bring together the different communities working in this field: theory and simulations, with their recent developments based on the mode-coupling theory of the glass transition, and experiments, with particular emphasis on colloidal systems and novel techniques. In an effort to give credit to recent developments in related problems of biophysical relevance, an entire session of the programme was dedicated to anomalous diffusion in crowded environments. The workshop was thus aimed at providing a deeper understanding of the complex dynamics of fluids in confinement as well as up-to-date perspectives on the interdisciplinary applications of this field of research. We are proud to say that all 32 contacted speakers accepted our invitation. Additional participants were attracted by our scientific programme, contributing poster presentations to the workshop. In total, close to 50 participants were registered, arriving from 11 different countries (including the US, Japan, and Mexico). Thus we conclude that the workshop indeed addressed a highly topical scientific field. From the scientific point of view a broad range of problems was covered, ranging from biophysics over soft matter to fermion systems. From the vivid discussions it became evident that the close scientific contact between theory, simulation and experiment brought along a fruitful and mutually inspiring atmosphere. On the theoretical side, these discussions have allowed clarification of several connections between the dynamics of models of fluids in porous media (quenched-annealed, pinned particles models), those of well-known limiting cases (Lorentz gas), of realistic models of liquids with strong dynamic asymmetry (asymmetric size and mass mixtures, sodium silicates, polymers blends) and even of bulk glass-formers. On the experimental side, it appeared that soft matter systems may provide an excellent test-bed to verify the theoretical predictions. From the concluding discussion it was also clear that addressing related issues relevant to biology still remains an open challenge for the future. In view of all this, it was concluded that within a short time period a workshop with analogous scope should be organized to address the progress made on both fundamental and interdisciplinary aspects. The realization of this workshop was made possible by generous financial support from CECAM, Centre Blaise Pascal-ENS de Lyon, and the ESF network 'Molecular Simulations in Biosystems and Material Science' (SimBioMa). Complex dynamics of fluids in disordered and crowded environments contents Phonon dispersions of cluster crystals Tim Neuhaus and Christos N Likos Challenges in determining anomalous diffusion in crowded fluids Marcel Hellmann, Joseph Klafter, Dieter W Heermann and Matthias Weiss Diffusion of active tracers in fluctuating fields David S Dean and Vincent Démery Self-diffusion of non-interacting hard spheres in particle gels Jean-Christophe Gimel and Taco Nicolai Probing glassy states in binary mixtures of soft interpenetrable colloids E Stiakakis, B M Erwin, D Vlassopoulos, M Cloitre, A Munam, M Gauthier, H Iatrou and N Hadjichristidis Fluids with quenched disorder: scaling of the free energy barrier near critical points T Fischer and R L C Vink Lennard-Jones binary mixture in disordered matrices: exploring the mode coupling scenario at increasing confinement P Gallo and M Rovere Static and dynamic contributions to anomalous chain dynamics in polymer blends Marco Bernabei, Angel J Moreno and J Colmenero Anomalous transport of a tracer on percolating clusters Markus Spanner, Felix Höfling, Gerd E Schröder-Turk, Klaus Mecke and Thomas Franosch Long-wavelength anomalies in the asymptotic behavior of mode-coupling theory S K Schnyder, F Höfling, T Franosch and Th Voigtmann Dynamic arrest of colloids in porous environments: disentangling crowding and confinement Jan Kurzidim, Daniele Coslovich and Gerhard Kahl Slow dynamics, dynamic heterogeneities, and fragility of supercooled liquids confined in random media Kang Kim, Kunimasa Miyazaki and Shinji Saito

Evolution of complex fruiting-body morphologies in homobasidiomycetes.

PubMed Central

Hibbett, David S; Binder, Manfred

2002-01-01

The fruiting bodies of homobasidiomycetes include some of the most complex forms that have evolved in the fungi, such as gilled mushrooms, bracket fungi and puffballs ('pileate-erect') forms. Homobasidiomycetes also include relatively simple crust-like 'resupinate' forms, however, which account for ca. 13-15% of the described species in the group. Resupinate homobasidiomycetes have been interpreted either as a paraphyletic grade of plesiomorphic forms or a polyphyletic assemblage of reduced forms. The former view suggests that morphological evolution in homobasidiomycetes has been marked by independent elaboration in many clades, whereas the latter view suggests that parallel simplification has been a common mode of evolution. To infer patterns of morphological evolution in homobasidiomycetes, we constructed phylogenetic trees from a dataset of 481 species and performed ancestral state reconstruction (ASR) using parsimony and maximum likelihood (ML) methods. ASR with both parsimony and ML implies that the ancestor of the homobasidiomycetes was resupinate, and that there have been multiple gains and losses of complex forms in the homobasidiomycetes. We also used ML to address whether there is an asymmetry in the rate of transformations between simple and complex forms. Models of morphological evolution inferred with ML indicate that the rate of transformations from simple to complex forms is about three to six times greater than the rate of transformations in the reverse direction. A null model of morphological evolution, in which there is no asymmetry in transformation rates, was rejected. These results suggest that there is a 'driven' trend towards the evolution of complex forms in homobasidiomycetes. PMID:12396494

Morphological Evolution of Block Copolymer Particles: Effect of Solvent Evaporation Rate on Particle Shape and Morphology.

PubMed

Shin, Jae Man; Kim, YongJoo; Yun, Hongseok; Yi, Gi-Ra; Kim, Bumjoon J

2017-02-28

Shape and morphology of polymeric particles are of great importance in controlling their optical properties or self-assembly into unusual superstructures. Confinement of block copolymers (BCPs) in evaporative emulsions affords particles with diverse structures, including prolate ellipsoids, onion-like spheres, oblate ellipsoids, and others. Herein, we report that the evaporation rate of solvent from emulsions encapsulating symmetric polystyrene-b-polybutadiene (PS-b-PB) determines the shape and internal nanostructure of micron-sized BCP particles. A distinct morphological transition from the ellipsoids with striped lamellae to the onion-like spheres was observed with decreasing evaporation rate. Experiments and dissipative particle dynamics (DPD) simulations showed that the evaporation rate affected the organization of BCPs at the particle surface, which determined the final shape and internal nanostructure of the particles. Differences in the solvent diffusion rates in PS and PB at rapid evaporation rates induced alignment of both domains perpendicular to the particle surface, resulting in ellipsoids with axial lamellar stripes. Slower evaporation rates provided sufficient time for BCP organization into onion-like structures with PB as the outermost layer, owing to the preferential interaction of PB with the surroundings. BCP molecular weight was found to influence the critical evaporation rate corresponding to the morphological transition from ellipsoid to onion-like particles, as well as the ellipsoid aspect ratio. DPD simulations produced morphologies similar to those obtained from experiments and thus elucidated the mechanism and driving forces responsible for the evaporation-induced assembly of BCPs into particles with well-defined shapes and morphologies.

Thickness-dependent blue shift in the excitonic peak of conformally grown ZnO:Al on ion-beam fabricated self-organized Si ripples

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

Basu, T.; Kumar, M.; Som, T., E-mail: tsom@iopb.res.in

2015-09-14

Al-doped ZnO (AZO) thin films of thicknesses 5,10, 15, 20, and 30 nm were deposited on 500 eV argon ion-beam fabricated nanoscale self-organized rippled-Si substrates at room temperature and are compared with similar films deposited on pristine-Si substrates (without ripples). It is observed that morphology of self-organized AZO films is driven by the underlying substrate morphology. For instance, for pristine-Si substrates, a granular morphology evolves for all AZO films. On the other hand, for rippled-Si substrates, morphologies having chain-like arrangement (anisotropic in nature) are observed up to a thickness of 20 nm, while a granular morphology evolves (isotropic in nature) for 30 nm-thick film.more » Photoluminescence studies reveal that excitonic peaks corresponding to 5–15 nm-thick AZO films, grown on rippled-Si templates, show a blue shift of 8 nm and 3 nm, respectively, whereas the peak shift is negligible for 20-nm thick film (with respect to their pristine counter parts). The observed blue shifts are substantiated by diffuse reflectance study and attributed to quantum confinement effect, associated with the size of the AZO grains and their spatial arrangements driven by the anisotropic morphology of underlying rippled-Si templates. The present findings will be useful for making tunable AZO-based light-emitting devices.« less

Effects of nanoparticle shape on the morphology and properties of porous CdSe assemblies (aerogels).

PubMed

Yu, Hongtao; Brock, Stephanie L

2008-08-01

We demonstrate the effect of differently shaped CdSe nanoscale building blocks (dots, rods, branched nanoparticles, and hyperbranched nanoparticles) on the morphologies, surface characteristics, and optical properties of resultant porous CdSe nanostructured aerogels. Monolithic CdSe aerogels were produced by controlled oxidative removal of surface thiolate ligands from differently shaped CdSe nanoparticles to yield a wet gel, followed by CO(2) supercritical drying. The X-ray diffraction data show that the resultant CdSe aerogels maintain the crystalline phase of the building blocks without significant grain growth. However, the transmission electron microscopy images indicate that the morphology of CdSe aerogels changes from a colloid-type morphology to a polymer-type morphology when the building block changes from dot to rod or the branched nanoparticle. The morphology of the CdSe aerogel assembled from hyperbranched nanoparticles appears to be intermediate between the colloid-type and the polymer-type. Nitrogen physisorption measurements suggest that the surface areas and porosity are a direct function of the shape of the primary building blocks, with aerogels formed from rods or branched particles exhibiting the greatest surface areas (>200 m(2)/g) and those prepared from hyperbranched nanoparticles exhibiting the least (<100 m(2)/g). Band gap measurements and photoluminescence studies show that the as-prepared CdSe aerogels retain to a large extent the intrinsic quantum confinement of the differently shaped building blocks, despite being connected into a 3D network.

Patterns and processes: Subaerial lava flow morphologies: A review

NASA Astrophysics Data System (ADS)

Gregg, Tracy K. P.

2017-08-01

Most lava flows have been emplaced away from the watchful eyes of volcanologists, so there is a desire to use solidified lava-flow morphologies to reveal important information about the eruption that formed them. Our current understanding of the relationship between solidified basaltic lava morphology and the responsible eruption and emplacement processes is based on decades of fieldwork, laboratory analyses and simulations, and computer models. These studies have vastly improved our understanding of the complex interactions between the solids, liquids, and gases that comprise cooling lava flows. However, the complex interactions (at millimeter and sub-millimeter scales) between the temperature-dependent abundances of the distinct phases that comprise a lava flow and the final morphology remain challenging to model and to predict. Similarly, the complex behavior of an active pahoehoe flow, although almost ubiquitous on Earth, remains difficult to quantitatively model and precisely predict.

Compaction of quasi-one-dimensional elastoplastic materials.

PubMed

Shaebani, M Reza; Najafi, Javad; Farnudi, Ali; Bonn, Daniel; Habibi, Mehdi

2017-06-06

Insight into crumpling or compaction of one-dimensional objects is important for understanding biopolymer packaging and designing innovative technological devices. By compacting various types of wires in rigid confinements and characterizing the morphology of the resulting crumpled structures, here, we report how friction, plasticity and torsion enhance disorder, leading to a transition from coiled to folded morphologies. In the latter case, where folding dominates the crumpling process, we find that reducing the relative wire thickness counter-intuitively causes the maximum packing density to decrease. The segment size distribution gradually becomes more asymmetric during compaction, reflecting an increase of spatial correlations. We introduce a self-avoiding random walk model and verify that the cumulative injected wire length follows a universal dependence on segment size, allowing for the prediction of the efficiency of compaction as a function of material properties, container size and injection force.

Paramecium swimming in a capillary tube

NASA Astrophysics Data System (ADS)

Jana, Saikat; Jung, Sunghwan

2010-03-01

Micro-organisms exhibit different strategies for swimming in complex environments. Many micro-swimmers such as paramecium congregate and tend to live near wall. We investigate how paramecium moves in a confined space as compared to its motion in an unbounded fluid. A new theoretical model based on Taylor's sheet is developed, to study such boundary effects. In experiments, paramecia are put inside capillary tubes and their swimming behavior is observed. The data obtained from experiments is used to test the validity of our theoretical model and understand how the cilia influence the locomotion of paramecia in confined geometries.

Local regulation of interchange turbulence in a dipole-confined plasma torus using current-collection feedback

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

Roberts, T. M., E-mail: tmr2122@columbia.edu; Mauel, M. E., E-mail: mauel@columbia.edu; Worstell, M. W.

2015-05-15

Turbulence in plasma confined by a magnetic dipole is dominated by interchange fluctuations with complex dynamics and short spatial coherence. We report the first use of local current-collection feedback to modify, amplify, and suppress these fluctuations. The spatial extent of turbulence regulation is limited to a correlation length near the collector. Changing the gain and phase of collection results in power either extracted from or injected into the turbulence. The measured plasma response shows some agreement with calculations of the linear response of global interchange-like MHD and entropy modes to current-collection feedback.

A numerical and experimental study of confined swirling jets

NASA Technical Reports Server (NTRS)

Nikjooy, M.; Mongia, H. C.; Samuelsen, G. S.; Mcdonell, V. G.

1989-01-01

A numerical and experimental study of a confined strong swirling flow is presented. Detailed velocity measurements are made using a two-component laser Doppler velocimeter (LDV) technique. Computations are performed using a differential second-moment (DSM) closure. The effect of inlet dissipation rate on calculated mean and turbulence fields is investigated. Various model constants are employed in the pressure-strain model to demonstrate their influences on the predicted results. Finally, comparison of the DSM calculations with the algebraic second-monent (ASM) closure results shows that the DSM is better suited for complex swirling flow analysis.

Comparison of deformation mechanics for two different carbonates: oolitic limestone and laminites

NASA Astrophysics Data System (ADS)

Zihms, Stephanie; Lewis, Helen; Couples, Gary; Hall, Stephen; Somerville, Jim

2016-04-01

Carbonate rocks form under a range of conditions which leads to a diverse rock group. Even though carbonates are overall mineralogically simple, the solid-space distribution ranges from simple compositions such as oolitic limestones to highly complex networks of pores and solids as seen in coquinas. Their fundamental mechanical behaviour has been identified to be like clastic rocks (Vajdova 2004, Brantut, Heap et al. 2014). However it is very likely that this observation is not true for more complex carbonates. Triaxial tests were performed on cylindrical samples of two different carbonates; a) oolitic limestone (Bicqueley quarry, France) and b) laminite (Ariripe basin, Brazil). The samples were deformed under confining pressures of 8, 12 and 20MPa, and 20, 30 and 40MPa, respectively. All tests were stopped as soon as peak load was observed to preserve as many deformation characteristics as possible. Photographs of the samples were taken before and after deformation to allow surface analysis of deformation features. Additionally, samples were analysed post-deformation with X-ray tomography (XRT) (using the Zeiss XRadia XRM 520 at the 4D Imaging Lab at Lund University). The 3D tomography images represent the post-deformation samples' density distribution, allowing detailed, non-destructive, 3D analysis of the deformation features that developed in the triaxial testing, including the complex geometries and interactions of fractures, deformation bands and sedimentary layering. They also provide an insight into the complexity of deformation features produced due to the carbonate response. Initial results show that the oolitic limestone forms single shear bands almost the length of the sample, exhibiting similar characteristics to sandstones deformed under similar conditions. These features are observed for all three applied loads. The laminate sample deformed at the lowest confining pressure exhibits compactive features. However, the laminite samples deformed at the two higher confining pressures both show highly complex fracture networks comprising open fractures and fracture propagation. This suggests that the laminate changes from compactive to dilational responses over the selected confining conditions. The XRT analysis indicates that a more complex fracture distribution could be linked to rock component properties e.g. grain size and composition. For the laminite these are variable with the layers. This is in agreement with field observations of laminite microfabrics (Calvo, Rodriguez-Pascua et al. 1998). Additionally, the typical grain size of the laminate (μm) is much smaller than the oolitic limestone (mm), which suggests that fracture network complexity can also be linked to bulk system complexity i.e. pore & grain network. These deformation experiments show that, as previously observed, oolitic limestones seem to behave similarly to sandstones. However this observation is not true for laminites and it is very likely that more complex carbonates will develop even more complicated deformation behaviour. It is therefore necessary to systematically test different carbonate rocks to understand the impact of geometry and composition, as well as the interplay with the pore network. Brantut, N., et al. (2014). Journal of Geophysical Research: Solid Earth 119(7): 5444-5463. Calvo, J. P., et al. (1998). Sedimentology 45: 279-292. Vajdova, V. (2004). Journal of Geophysical Research 109(B5).

First instalment in resolution of the Banksia spinulosa complex (Proteaceae): B. neoanglica, a new species supported by phenetic analysis, ecology and geography

PubMed Central

Stimpson, Margaret L.; Weston, Peter H.; Telford, Ian R.H.; Bruhl, Jeremy J.

2012-01-01

Abstract Taxa in the Banksia spinulosa Sm. complex (Proteaceae) have populations with sympatric, parapatric and allopatric distributions and unclear or disputed boundaries. Our hypothesis is that under biological, phenetic and diagnosable species concepts that each of the currently named taxa within the Banksia spinulosa complex is a separate species. Based on specimens collected as part of this study, and data recorded from specimens in six Australian herbaria, complemented by phenetic analysis (semi–strong multidimensional scaling and UPGMA clustering) and a detailed morphological study, we investigated both morphological variation and geographic distribution in the Banksia spinulosa complex. All specimens used for this study are held at the N.C.W. Beadle Herbarium or the National Herbarium of New South Wales. In total 23 morphological characters (11 quantitative, five binary, and seven multistate characters) were analysed phenetically for 89 specimens. Ordination and cluster analysis resulted in individuals grouping strongly allowing recognition of distinct groups consistent with their recognition as separate species. Additional morphological analysis was completed on all specimens using leaf, floral, fruit and stem morphology, providing clear cut diagnosable groups and strong support for the recognition of Banksia spinulosa var. cunninghamii and Banksia spinulosa var. neoanglica as species. PMID:23170073

Pore-scale investigation on stress-dependent characteristics of granular packs and the impact of pore deformation on fluid distribution

DOE PAGES

Yoon, Hongkyu; Klise, Katherine A.; Torrealba, Victor A.; ...

2015-05-25

Understanding the effect of changing stress conditions on multiphase flow in porous media is of fundamental importance for many subsurface activities including enhanced oil recovery, water drawdown from aquifers, soil confinement, and geologic carbon storage. Geomechanical properties of complex porous systems are dynamically linked to flow conditions, but their feedback relationship is often oversimplified due to the difficulty of representing pore-scale stress deformation and multiphase flow characteristics in high fidelity. In this work, we performed pore-scale experiments of single- and multiphase flow through bead packs at different confining pressure conditions to elucidate compaction-dependent characteristics of granular packs and their impactmore » on fluid flow. A series of drainage and imbibition cycles were conducted on a water-wet, soda-lime glass bead pack under varying confining stress conditions. Simultaneously, X-ray micro-CT was used to visualize and quantify the degree of deformation and fluid distribution corresponding with each stress condition and injection cycle. Micro-CT images were segmented using a gradient-based method to identify fluids (e.g., oil and water), and solid phase redistribution throughout the different experimental stages. Changes in porosity, tortuosity, and specific surface area were quantified as a function of applied confining pressure. Results demonstrate varying degrees of sensitivity of these properties to confining pressure, which suggests that caution must be taken when considering scalability of these properties for practical modeling purposes. Changes in capillary number with confining pressure are attributed to the increase in pore velocity as a result of pore contraction. Furthermore, this increase in pore velocity was found to have a marginal impact on average phase trapping at different confining pressures.« less

Potential Benefits of Manmade Opals Demonstrated for First Time (Fact Sheet)

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

Not Available

NREL experiments show that disordered inverse opals significantly scatter and trap near-infrared light, with possible impact on optoelectronic materials. Inverse opals, familiar in the form of brilliantly colored opal gemstones, are a class of materials that has astounding optical properties. Scientists have been exploring the ability of inverse opals to manipulate light in the hopes of harnessing this capacity for advanced technologies such as displays, detectors, lasers, and photovoltaics. A research group at the National Renewable Energy Laboratory (NREL) discovered that man-made inverse opal films containing significant morphological disorder exhibit substantial light scattering, consequently trapping wavelengths in the near-infrared (NIR),more » which is important to a number of technologies. This discovery is the first experimental evidence to validate a 2005 theoretical model predicting the confinement of light in such structures, and it holds great promise for improving the performance of technologies that rely on careful light control. This breakthrough also makes possible optoelectronic technologies that use a range of low-cost molecular and semiconductor species that otherwise absorb light too weakly to be useful. The disordered inverse opal architecture validates the theoretical model that predicts the diffusion and confinement of light in such structures. Electrochemically deposited CdSe inverse opal films containing significant morphological disorder exhibit substantial light scattering and consequent NIR light trapping. This discovery holds promise for NIR light management in optoelectronic technologies, particularly those involving weakly absorbing molecular and semiconductor photomaterials.« less

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

Evmenenko, Guennadi; Fister, Timothy T.; Buchholz, D. Bruce

Oxide conversion reactions in lithium ion batteries are challenged by substantial irreversibility associated with significant volume change during the phase separation of an oxide into lithia and metal species (e.g., NiO + 2Li(+) + 2e(-) -> Ni + Li2O). We demonstrate that the confinement of nanometer-scale NiO layers within a Ni/NiO multilayer electrode can direct lithium transport and reactivity, leading to coherent expansion of the multilayer. The morphological changes accompanying lithiation were tracked in real-time by in-operando X-ray reflectivity (XRR) and ex situ cross-sectional transmission electron microscopy on well-defined periodic Ni/NiO multilayers grown by pulsed-laser deposition. Comparison of pristine andmore » lithiated structures reveals that the nm-thick nickel layers help initiate the conversion process at the interface and then provide an architecture that confines the lithiation to the individual oxide layers. XRR data reveal that the lithiation process starts at the top and progressed through the electrode stack, layer by layer resulting in a purely vertical expansion. Longer term cycling showed significant reversible capacity (similar to 800 mA h g(-1) after similar to 100 cycles), which we attribute to a combination of the intrinsic bulk lithiation capacity of the NiO and additional interfacial lithiation capacity. These observations provide new insight into the role of metal/metal oxide interfaces in controlling lithium ion conversion reactions by defining the relationships between morphological changes and film architecture during reaction.« less

Unidirectional Fast Growth and Forced Jumping of Stretched Droplets on Nanostructured Microporous Surfaces.

PubMed

Aili, Abulimiti; Li, Hongxia; Alhosani, Mohamed H; Zhang, TieJun

2016-08-24

Superhydrophobic nanostructured surfaces have demonstrated outstanding capability in energy and water applications by promoting dropwise condensation, where fast droplet growth and efficient condensate removal are two key parameters. However, these parameters remain contradictory. Although efficient droplet removal is easily obtained through coalescence jumping on uniform superhydrophobic surfaces, simultaneously achieving fast droplet growth is still challenging. Also, on such surfaces droplets can grow to larger sizes without restriction if there is no coalescence. In this work, we show that superhydrophobic nanostructured microporous surfaces can manipulate the droplet growth and jumping. Microporous surface morphology effectively enhances the growth of droplets in pores owing to large solid-liquid contact area. At low supersaturations, the upward growth rate (1-1.5 μm/s) of these droplets in pores is observed to be around 15-25 times that of the droplets outside the pores. Meanwhile, their top curvature radius increases relatively slowly (∼0.25 μm/s) due to pore confinement, which results in a highly stretched droplet surface. We also observed forced jumping of stretched droplets in pores either through coalescence with spherical droplets outside pores or through self-pulling without coalescence. Both experimental observation and theoretical modeling reveal that excess surface free energy stored in the stretched droplet surface and micropore confinement are responsible for this pore-scale-forced jumping. These findings reveal the insightful physics of stretched droplet dynamics and offer guidelines for the design and fabrication of novel super-repellent surfaces with microporous morphology.

Directed self-assembly of diblock copolymers in cylindrical confinement: effect of underfilling and air-polymer interactions on configurations

NASA Astrophysics Data System (ADS)

Carpenter, Corinne L.; Delaney, Kris T.; Laachi, Nabil; Fredrickson, Glenn H.

2015-03-01

Directed self-assembly (DSA) of block copolymers has attracted attention for its use as a simple, cost- effective patterning tool for creating vertical interconnect access (VIA) channels in nanoelectronic devices.1, 2 This technique supplements existing lithographic technologies to allow for the creation of high-resolution cylindrical holes whose diameter and placement can be precisely controlled. In this study, we use self-consistent field theory (SCFT) simulations to investigate the equilibrium configurations of under-filled DSA systems with air-polymer interactions. We report on a series of SCFT simulations of our three species (PMMA-b-PS diblock and air) model in cylindrical confinement to explore the role of template diameter, under-fill fraction (i.e. volume fraction of air), air-polymer surface interaction and polymer-side wall/substrate interactions on equilibrium morphologies in an under-filled template with a free top surface. We identify parameters and system configurations where a meniscus appears and explore cases with PMMA-attractive, PS-attractive, and all-neutral walls to understand the effects of wall properties on meniscus geometry and DSA morphology. An important outcome is an understanding of the parameters that control the contact angle of the meniscus with the wall, as it is one of the simplest quantitative measures of the meniscus shape. Ultimately, we seek to identify DSA formulations, templates, and surface treatments with predictable central cylinder diameter and a shallow contact angle, as these factors would facilitate broad process windows and ease of manufacturing.

Knowledge of Morphologically Complex Words: A Developmental Study of Older Children and Young Adolescents

ERIC Educational Resources Information Center

Nippold, Marilyn A.; Sun, Lei

2008-01-01

Purpose: This study examined knowledge of derived nominals (e.g., measurement, prediction) and derived adjectives (e.g., algebraic, molecular) in older children and young adolescents. Little was known about students' comprehension of these morphologically complex words that occur in textbooks that are used in public schools to teach challenging…

Species delimitation in the Stenocereus griseus (Cactaceae) species complex reveals a new species, S. huastecorum

PubMed Central

Alvarado-Sizzo, Hernán; Parra, Fabiola; Arreola-Nava, Hilda Julieta; Terrazas, Teresa; Sánchez, Cristian

2018-01-01

The Stenocereus griseus species complex (SGSC) has long been considered taxonomically challenging because the number of taxa belonging to the complex and their geographical boundaries remain poorly understood. Bayesian clustering and genetic distance-based methods were used based on nine microsatellite loci in 377 individuals of three main putative species of the complex. The resulting genetic clusters were assessed for ecological niche divergence and areolar morphology, particularly spination patterns. We based our species boundaries on concordance between genetic, ecological, and morphological data, and were able to resolve four species, three of them corresponding to S. pruinosus from central Mexico, S. laevigatus from southern Mexico, and S. griseus from northern South America. A fourth species, previously considered to be S. griseus and commonly misidentified as S. pruinosus in northern Mexico showed significant genetic, ecological, and morphological differentiation suggesting that it should be considered a new species, S. huastecorum, which we describe here. We show that population genetic analyses, ecological niche modeling, and morphological studies are complementary approaches for delimiting species in taxonomically challenging plant groups such as the SGSC. PMID:29342184

Species delimitation in the Stenocereus griseus (Cactaceae) species complex reveals a new species, S. huastecorum.

PubMed

Alvarado-Sizzo, Hernán; Casas, Alejandro; Parra, Fabiola; Arreola-Nava, Hilda Julieta; Terrazas, Teresa; Sánchez, Cristian

2018-01-01

The Stenocereus griseus species complex (SGSC) has long been considered taxonomically challenging because the number of taxa belonging to the complex and their geographical boundaries remain poorly understood. Bayesian clustering and genetic distance-based methods were used based on nine microsatellite loci in 377 individuals of three main putative species of the complex. The resulting genetic clusters were assessed for ecological niche divergence and areolar morphology, particularly spination patterns. We based our species boundaries on concordance between genetic, ecological, and morphological data, and were able to resolve four species, three of them corresponding to S. pruinosus from central Mexico, S. laevigatus from southern Mexico, and S. griseus from northern South America. A fourth species, previously considered to be S. griseus and commonly misidentified as S. pruinosus in northern Mexico showed significant genetic, ecological, and morphological differentiation suggesting that it should be considered a new species, S. huastecorum, which we describe here. We show that population genetic analyses, ecological niche modeling, and morphological studies are complementary approaches for delimiting species in taxonomically challenging plant groups such as the SGSC.

Corallite skeletal morphological variation in Hawaiian Porites lobata

NASA Astrophysics Data System (ADS)

Tisthammer, Kaho H.; Richmond, Robert H.

2018-06-01

Due to their high morphological plasticity and complex evolutionary history, the species boundaries of many reef-building corals are poorly understood. The skeletal structures of corals have traditionally been used for species identification, but these structures can be highly variable, and currently we lack knowledge regarding the extent of morphological variation within species. Porites species are notorious for their taxonomic difficulties, both morphologically and genetically, and currently there are several unresolved species complexes in the Pacific. Despite its ubiquitous presence and broad use in coral research, Porites lobata belongs to one such unresolved species complex. To understand the degree of intraspecific variation in skeletal morphology, 120 corallites from the Hawaiian P. lobata were examined. A subset of samples from two genetically differentiated populations from contrasting high- and low-stress environments in Maunalua Bay, Hawaii, were then quantitatively analyzed using multivariate morphometrics. Our observations revealed high intraspecific variation in corallite morphology, as well as significant morphological differences between the two populations of P. lobata. Additionally, significant correlation was found between the morphological and genetic distances calculated from approximately 18,000 loci generated from restriction site-associated DNA sequencing. The unique morphological characters observed from the genetically differentiated population under environmental stress suggest that these characters may have adaptive values, but how such traits relate to fitness and how much plasticity they can exhibit remain to be determined by future studies. Relatively simple morphometric analyses used in our study can be useful in clarifying the existing ambiguity in skeletal architecture, thus contributing to resolving species issues in corals.

Optical properties of voltage sensitive hemicyanine dyes of variable hydrophobicity confined within surfactant micelles

NASA Astrophysics Data System (ADS)

Naeem, Kashif; Naseem, Bushra; Shah, S. S.; Shah, Syed W. H.

2017-11-01

The optical properties of amphiphilic hemicyanine dyes with variable hydrophobicity, confined within anionic micelles of sodium dodecylbenzenesulfonate (NaDDBS) have been studied by UV-visible absorption spectroscopy. The confinement constant, K conf has been determined for each entrapped dye. The ion-pair formation between dye and surfactant causes a decline in electronic transition energy (ΔE T) when dye alkyl chains are smaller due to stabilization of both the ground and excited state. ΔE T values gradually increase with increase in dye hydrophobicity that hampers the electrostatic interaction with dialkylammonium moiety and consequently excited state stabilization is compromised. The average number of dye molecules trapped in a single micelle was also determined. The negative values of Gibbs free energy indicate that the dye entrapment within micelles is energetically favored. These findings have significance for developing functional materials with peculiar luminescent properties, especially for more effective probing of complex biological systems.

From the nonlinear Fokker-Planck equation to the Vlasov description and back: Confined interacting particles with drag

NASA Astrophysics Data System (ADS)

Plastino, A. R.; Curado, E. M. F.; Nobre, F. D.; Tsallis, C.

2018-02-01

Nonlinear Fokker-Planck equations endowed with power-law diffusion terms have proven to be valuable tools for the study of diverse complex systems in physics, biology, and other fields. The nonlinearity appearing in these evolution equations can be interpreted as providing an effective description of a system of particles interacting via short-range forces while performing overdamped motion under the effect of an external confining potential. This point of view has been recently applied to the study of thermodynamical features of interacting vortices in type II superconductors. In the present work we explore an embedding of the nonlinear Fokker-Planck equation within a Vlasov equation, thus incorporating inertial effects to the concomitant particle dynamics. Exact time-dependent solutions of the q -Gaussian form (with compact support) are obtained for the Vlasov equation in the case of quadratic confining potentials.

Enzymatic reactions in confined environments

NASA Astrophysics Data System (ADS)

Küchler, Andreas; Yoshimoto, Makoto; Luginbühl, Sandra; Mavelli, Fabio; Walde, Peter

2016-05-01

Within each biological cell, surface- and volume-confined enzymes control a highly complex network of chemical reactions. These reactions are efficient, timely, and spatially defined. Efforts to transfer such appealing features to in vitro systems have led to several successful examples of chemical reactions catalysed by isolated and immobilized enzymes. In most cases, these enzymes are either bound or adsorbed to an insoluble support, physically trapped in a macromolecular network, or encapsulated within compartments. Advanced applications of enzymatic cascade reactions with immobilized enzymes include enzymatic fuel cells and enzymatic nanoreactors, both for in vitro and possible in vivo applications. In this Review, we discuss some of the general principles of enzymatic reactions confined on surfaces, at interfaces, and inside small volumes. We also highlight the similarities and differences between the in vivo and in vitro cases and attempt to critically evaluate some of the necessary future steps to improve our fundamental understanding of these systems.

Confinement of activating receptors at the plasma membrane controls natural killer cell tolerance.

PubMed

Guia, Sophie; Jaeger, Baptiste N; Piatek, Stefan; Mailfert, Sébastien; Trombik, Tomasz; Fenis, Aurore; Chevrier, Nicolas; Walzer, Thierry; Kerdiles, Yann M; Marguet, Didier; Vivier, Eric; Ugolini, Sophie

2011-04-05

Natural killer (NK) cell tolerance to self is partly ensured by major histocompatibility complex (MHC) class I-specific inhibitory receptors on NK cells, which dampen their reactivity when engaged. However, NK cells that do not detect self MHC class I are not autoreactive. We used dynamic fluorescence correlation spectroscopy to show that MHC class I-independent NK cell tolerance in mice was associated with the presence of hyporesponsive NK cells in which both activating and inhibitory receptors were confined in an actin meshwork at the plasma membrane. In contrast, the recognition of self MHC class I by inhibitory receptors "educated" NK cells to become fully reactive, and activating NK cell receptors became dynamically compartmentalized in membrane nanodomains. We propose that the confinement of activating receptors at the plasma membrane is pivotal to ensuring the self-tolerance of NK cells.

Nonlinear adhesion dynamics of confined lipid membranes

NASA Astrophysics Data System (ADS)

To, Tung; Le Goff, Thomas; Pierre-Louis, Olivier

Lipid membranes, which are ubiquitous objects in biological environments are often confined. For example, they can be sandwiched between a substrate and the cytoskeleton between cell adhesion, or between other membranes in stacks, or in the Golgi apparatus. We present a study of the nonlinear dynamics of membranes in a model system, where the membrane is confined between two flat walls. The dynamics derived from the lubrication approximation is highly nonlinear and nonlocal. The solution of this model in one dimension exhibits frozen states due to oscillatory interactions between membranes caused by the bending rigidity. We develope a kink model for these phenomena based on the historical work of Kawasaki and Otha. In two dimensions, the dynamics is more complex, and depends strongly on the amount of excess area in the system. We discuss the relevance of our findings for experiments on model membranes, and for biological systems. Supported by the grand ANR Biolub.

Probing Nitrosyl Ligation of Surface-Confined Metalloporphyrins by Inelastic Electron Tunneling Spectroscopy

PubMed Central

2013-01-01

Complexes obtained by the ligation of nitric oxide (NO) to metalloporphyrins represent important model systems with biological relevance. Herein we report a molecular-level investigation of surface-confined cobalt tetraphenyl porphyrin (Co-TPP) species and their interaction with NO under ultrahigh vacuum conditions. It is demonstrated that individual NO adducts can be desorbed using the atomically sharp tip of a scanning tunneling microscope, whereby a writing process is implemented for fully saturated regular metalloporphyrin arrays. The low-energy vibrational characteristics of individual Co-TPP-nitrosyl complexes probed by inelastic electron tunneling spectroscopy (IETS) reveal a prominent signature at an energy of ≃31 meV. Using density functional theory-based IETS simulations—the first to be performed on such an extensive interfacial nanosystem—we succeed to reproduce the low-frequency spectrum for the NO-ligated complex and explain the absence of IETS activity for bare Co-TPP. Moreover, we can conclusively assign the IETS peak of NO-Co-TPP to a unique vibration mode involving the NO complexation site, namely, the in-plane Co–N–O rocking mode. In addition, we verify that the propensity rules previously designed on small aromatic systems and molecular fragments hold true for a metal–organic entity. This work notably permits one to envisage IETS spectroscopy as a sensitive tool to chemically characterize hybrid interfaces formed by complex metal–organic units and gaseous adducts. PMID:23718257

1-D Metal Nanobead Arrays within Encapsulated Nanowires via a Red-Ox-Induced Dewetting: Mechanism Study by Atom-Probe Tomography.

PubMed

Sun, Zhiyuan; Tzaguy, Avra; Hazut, Ori; Lauhon, Lincoln J; Yerushalmi, Roie; Seidman, David N

2017-12-13

Metal nanoparticle arrays are excellent candidates for a variety of applications due to the versatility of their morphology and structure at the nanoscale. Bottom-up self-assembly of metal nanoparticles provides an important complementary alternative to the traditional top-down lithography method and makes it possible to assemble structures with higher-order complexity, for example, nanospheres, nanocubes, and core-shell nanostructures. Here we present a mechanism study of the self-assembly process of 1-D noble metal nanoparticles arrays, composed of Au, Ag, and AuAg alloy nanoparticles. These are prepared within an encapsulated germanium nanowire, obtained by the oxidation of a metal-germanium nanowire hybrid structure. The resulting structure is a 1-D array of equidistant metal nanoparticles with the same diameter, the so-called nanobead (NB) array structure. Atom-probe tomography and transmission electron microscopy were utilized to investigate the details of the morphological and chemical evolution during the oxidation of the encapsulated metal-germanium nanowire hybrid-structures. The self-assembly of nanoparticles relies on the formation of a metal-germanium liquid alloy and the migration of the liquid alloy into the nanowire, followed by dewetting of the liquid during shape-confined oxidation where the liquid column breaks-up into nanoparticles due to the Plateau-Rayleigh instability. Our results demonstrate that the encapsulating oxide layer serves as a structural scaffold, retaining the overall shape during the eutectic liquid formation and demonstrates the relationship between the oxide mechanical properties and the final structural characteristics of the 1-D arrays. The mechanistic details revealed here provide a versatile tool-box for the bottom-up fabrication of 1-D arrays nanopatterning that can be modified for multiple applications according to the RedOx properties of the material system components.

Processing of zero-derived words in English: an fMRI investigation.

PubMed

Pliatsikas, Christos; Wheeldon, Linda; Lahiri, Aditi; Hansen, Peter C

2014-01-01

Derivational morphological processes allow us to create new words (e.g. punish (V) to noun (N) punishment) from base forms. The number of steps from the basic units to derived words often varies (e.g., nationalitybridge-V) i.e., zero-derivation (Aronoff, 1980). We compared the processing of one-step (soaking

Calibration of an Unsteady Groundwater Flow Model for a Complex, Strongly Heterogeneous Aquifer

NASA Astrophysics Data System (ADS)

Curtis, Z. K.; Liao, H.; Li, S. G.; Phanikumar, M. S.; Lusch, D.

2016-12-01

Modeling of groundwater systems characterized by complex three-dimensional structure and heterogeneity remains a significant challenge. Most of today's groundwater models are developed based on relatively simple conceptual representations in favor of model calibratibility. As more complexities are modeled, e.g., by adding more layers and/or zones, or introducing transient processes, more parameters have to be estimated and issues related to ill-posed groundwater problems and non-unique calibration arise. Here, we explore the use of an alternative conceptual representation for groundwater modeling that is fully three-dimensional and can capture complex 3D heterogeneity (both systematic and "random") without over-parameterizing the aquifer system. In particular, we apply Transition Probability (TP) geostatistics on high resolution borehole data from a water well database to characterize the complex 3D geology. Different aquifer material classes, e.g., `AQ' (aquifer material), `MAQ' (marginal aquifer material'), `PCM' (partially confining material), and `CM' (confining material), are simulated, with the hydraulic properties of each material type as tuning parameters during calibration. The TP-based approach is applied to simulate unsteady groundwater flow in a large, complex, and strongly heterogeneous glacial aquifer system in Michigan across multiple spatial and temporal scales. The resulting model is calibrated to observed static water level data over a time span of 50 years. The results show that the TP-based conceptualization enables much more accurate and robust calibration/simulation than that based on conventional deterministic layer/zone based conceptual representations.

The role of polyploidy in shaping morphological diversity in natural populations of Phlox amabilis.

PubMed

Chansler, Matthew T; Ferguson, Carolyn J; Fehlberg, Shannon D; Prather, L Alan

2016-09-01

Studies of natural populations of polyploids increasingly highlight complex patterns of variation in ploidy and geographic distribution of cytotypes. As our understanding of the complexity of polyploidy grows, our understanding of the morphological correlates of polyploidy should expand as well. Here we examine in what ways, and to what degree, polyploidy affects the overall phenotype of a species across its distribution when there are three ploidies and geographic complexity in cytotype distribution. We measured 31 morphological traits from stems, leaves, and flowers from up to 25 individuals from 11 sites across the distribution of Phlox amabilis. Chromosome counts and flow cytometry confirmed and expanded upon earlier research documenting diploid, tetraploid, and hexaploid populations, and also identified a site with two ploidies. Univariate and multivariate statistics were used to characterize the morphological effects of polyploidy. We detected significant associations between morphology and ploidy in 11 traits spread across vegetative and reproductive structures. Generally, diploid individuals differed from polyploid individuals to a greater extent, and in different ways, than tetraploid and hexaploid plants differed from each other. Multivariate morphometrics demonstrated that the two primary axes of overall variation are driven by morphological traits associated with polyploidy, and individuals of different ploidies can be discriminated with 95% success. Polyploidy plays a major role in shaping overall morphological diversity in natural populations of P. amabilis. © 2016 Botanical Society of America.

Synthesis and Characterization of 2-D Materials

NASA Astrophysics Data System (ADS)

Pazos, S.; Sahoo, P.; Afaneh, T.; Rodriguez Gutierrez, H.

Atomically thin transition-metal dichacogenides (TMD), graphene, and boron nitride (BN) are two-dimensional materials where the charge carriers (electrons and holes) are confined to move in a plane. They exhibit distinctive optoelectronic properties compared to their bulk layered counterparts. When combined into heterostructures, these materials open more possibilities in terms of new properties and device functionality. In this work, WSe2 and graphene were grown using Chemical Vapor Deposition (CVD) and Physical Vapor Deposition (PVD) techniques. The quality and morphology of each material was checked using Raman, Photoluminescence Spectroscopy, and Scanning Electron Microscopy. Graphene had been successfully grown homogenously, characterized, and transferred from copper to silicon dioxide substrates; these films will be used in future studies to build 2-D devices. Different morphologies of WSe2 2-D islands were successfully grown on SiO2 substrates. Depending on the synthesis conditions, the material on each sample had single layer, double layer, and multi-layer areas. A variety of 2-D morphologies were also observed in the 2-D islands. This project is supported by the NSF REU Grant #1560090 and NSF Grant #DMR-1557434.

A General Approach to Access Morphologies of Polyoxometalates in Solution by Using SAXS: An Ab Initio Modeling Protocol.

PubMed

Li, Mu; Wang, Weiyu; Yin, Panchao

2018-05-02

Herein, we reported a general protocol for an ab initio modeling approach to deduce structure information of polyoxometalates (POMs) in solutions from scattering data collected by the small-angle X-ray scattering (SAXS) technique. To validate the protocol, the morphologies of a serious of known POMs in either aqueous or organic solvents were analyzed. The obtained particle morphologies were compared and confirmed with previous reported crystal structures. To extend the feasibility of the protocol to an unknown system of aqueous solutions of Na 2 MoO 4 with the pH ranging from -1 to 8.35, the formation of {Mo 36 } clusters was probed, identified, and confirmed by SAXS. The approach was further optimized with a multi-processing capability to achieve fast analysis of experimental data, thereby, facilitating in situ studies of formations of POMs in solutions. The advantage of this approach is to generate intuitive 3D models of POMs in solutions without confining information such as symmetries and possible sizes. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Delimiting Species Boundaries within a Paraphyletic Species Complex: Insights from Morphological, Genetic, and Molecular Data on Paramecium sonneborni (Paramecium aurelia species complex, Ciliophora, Protozoa).

PubMed

Przyboś, Ewa; Tarcz, Sebastian; Rautian, Maria; Sawka, Natalia

2015-09-01

The demarcation of boundaries between protist species is often problematic because of the absence of a uniform species definition, the abundance of cryptic diversity, and the occurrence of convergent morphology. The ciliates belonging to the Paramecium aurelia complex, consisting of 15 species, are a good model for such systematic and evolutionary studies. One member of the complex is P. sonneborni, previously known only from one stand in Texas (USA), but recently found in two new sampling sites in Cyprus (creeks running to Salt Lake and Oroklini Lake near Larnaca). The studied Paramecium sonneborni strains (from the USA and Cyprus) reveal low viability in the F1 and F2 generations of interstrain hybrids and may be an example of ongoing allopatric speciation. Despite its molecular distinctiveness, we postulate that P. sonneborni should remain in the P. aurelia complex, making it a paraphyletic taxon. Morphological studies have revealed that some features of the nuclear apparatus of P. sonneborni correspond to the P. aurelia spp. complex, while others are similar to P. jenningsi and P. schewiakoffi. The observed discordance indicates rapid splitting of the P. aurelia-P. jenningsi-P. schewiakoffi group, in which genetic, morphological, and molecular boundaries between species are not congruent. Copyright © 2015 Elsevier GmbH. All rights reserved.

Geologic controls on submarine slope failure along the central U.S. Atlantic margin: Insights from the Currituck Slide Complex

USGS Publications Warehouse

Hill, Jenna C.; Brothers, Daniel S.; Craig, Bradley K.; ten Brink, Uri S.; Chaytor, Jason D.; Flores, Claudia

2017-01-01

Multiple styles of failure, ranging from densely spaced, mass transport driven canyons to the large, slab-type slope failure of the Currituck Slide, characterize adjacent sections of the central U.S. Atlantic margin that appear to be defined by variations in geologic framework. Here we use regionally extensive, deep penetration multichannel seismic (MCS) profiles to reconstruct the influence of the antecedent margin physiography on sediment accumulation along the central U.S. Atlantic continental shelf-edge, slope, and uppermost rise from the Miocene to Present. These data are combined with high-resolution sparker MCS reflection profiles and multibeam bathymetry data across the Currituck Slide Complex. Pre-Neogene allostratigraphic horizons beneath the slope are generally characterized by low gradients and convex downslope profiles. This is followed by the development of thick, prograded deltaic clinoforms during the middle Miocene. Along-strike variations in morphology of a regional unconformity at the top of this middle Miocene unit appear to have set the stage for differing styles of mass transport along the margin. Areas north and south of the Currituck Slide are characterized by oblique margin morphology, defined by an angular shelf-edge and a relatively steep (> 8°), concave slope profile. Upper slope sediment bypass, closely spaced submarine canyons, and small, localized landslides confined to canyon heads and sidewalls characterize these sectors of the margin. In contrast, the Currituck region is defined by a sigmoidal geometry, with a rounded shelf-edge rollover and gentler slope gradient (< 6°). Thick (> 800 m), regionally continuous stratified slope deposits suggest the low gradient Currituck region was a primary depocenter for fluvial inputs during multiple sea level lowstands. These results imply that the rounded, gentle slope physiography developed during the middle Miocene allowed for a relatively high rate of subsequent sediment accumulation, thus providing a mechanism for compaction–induced overpressure that preconditioned the Currituck region for failure. Detailed examination of the regional geological framework illustrates the importance of both sediment supply and antecedent slope physiography in the development of large, potentially unstable depocenters along passive margins.

Two new species of Indigofera L. (Leguminosae) from the Sneeuberg Centre of Floristic Endemism, Great Escarpment (Eastern and Western Cape, South Africa).

PubMed

Clark, V Ralph; Schrire, Brian D; Barker, Nigel P

2015-01-01

Two new species of Indigofera L. (Leguminosae) are described from the Sneeuberg Centre of Floristic Endemism on the southern Great Escarpment, Eastern and Western Cape Provinces, South Africa. Both species are localised high-altitude endemics. Indigoferamagnifica Schrire & V.R. Clark is confined to the summit plateau of the Toorberg-Koudeveldberg-Meelberg west of Graaff-Reinet, and complements other western Sneeuberg endemics such as Ericapasserinoides (Bolus) E.G.H. Oliv. and Faurearecondita Rourke & V.R. Clark. Indigoferaasantasanensis Schrire & V.R. Clark is confined to a small area east of Graaff-Reinet, and complements several other eastern Sneeuberg endemics such as Euryopsexsudans B. Nord & V.R. Clark and Euryopsproteoides B. Nord. & V.R. Clark. Based on morphology, both new species belong to the Cape Clade of Indigofera, supporting a biogeographical link between the Cape Floristic Region and the Sneeuberg, as well as with the rest of the eastern Great Escarpment.

Using Polymer Confinement for Stem Cell Differentiation: 3D Printed vs Molded Scaffolds

NASA Astrophysics Data System (ADS)

Rafailovich, Miriam

Additive manufacturing technologies are increasingly being used to replace standard extrusion or molding methods in engineering polymeric biomedical implants, which can be further seeded with cells for tissue regeneration. The principal advantage of this new technology is the ability to print directly from a scan and hence produce parts which are an ideal fit for an individual, eliminating much of the sizing and fitting associated with standard manufacturing methods. The question though arises whether devices which may be macroscopically similar, serve identical functions and are produced from the same material, interact in the same manner with cells and living tissue. Here we show that fundamental differences can exist between 3-D printed and extruded scaffolds which can impact stem cell differentiation and lineage selection. We will show how polymer confinement inherent in these methods affect the printed features on multiple length scales. We will also and how the differentiation of stem cells is affected by substrate heterogeneity in both morphological and mechanical features. NSF-Inspire award # 1344267.

Linearly polarized emission from an embedded quantum dot using nanowire morphology control.

PubMed

Foster, Andrew P; Bradley, John P; Gardner, Kirsty; Krysa, Andrey B; Royall, Ben; Skolnick, Maurice S; Wilson, Luke R

2015-03-11

GaAs nanowires with elongated cross sections are formed using a catalyst-free growth technique. This is achieved by patterning elongated nanoscale openings within a silicon dioxide growth mask on a (111)B GaAs substrate. It is observed that MOVPE-grown vertical nanowires with cross section elongated in the [21̅1̅] and [1̅12] directions remain faithful to the geometry of the openings. An InGaAs quantum dot with weak radial confinement is realized within each nanowire by briefly introducing indium into the reactor during nanowire growth. Photoluminescence emission from an embedded nanowire quantum dot is strongly linearly polarized (typically >90%) with the polarization direction coincident with the axis of elongation. Linearly polarized PL emission is a result of embedding the quantum dot in an anisotropic nanowire structure that supports a single strongly confined, linearly polarized optical mode. This research provides a route to the bottom-up growth of linearly polarized single photon sources of interest for quantum information applications.

Dynamic "Scanning-Mode" Meniscus Confined Electrodepositing and Micropatterning of Individually Addressable Ultraconductive Copper Line Arrays.

PubMed

Lei, Yu; Zhang, Xianyun; Xu, Dingding; Yu, Minfeng; Yi, Zhiran; Li, Zhixiang; Sun, Aihua; Xu, Gaojie; Cui, Ping; Guo, Jianjun

2018-05-03

Micro- and nanopatterning of cost-effective addressable metallic nanostructures has been a long endeavor in terms of both scientific understanding and industrial needs. Herein, a simple and efficient dynamic meniscus-confined electrodeposition (MCED) technique for precisely positioned copper line micropatterns with superior electrical conductivity (greater than 1.57 × 10 4 S/cm) on glass, silicon, and gold substrates is reported. An unexpected higher printing speed in the evaporative regime is realized for precisely positioned copper lines patterns with uniform width and height under horizontal scanning-mode. The final line height and width depend on the typical behavior of traditional flow coating process, while the surface morphologies and roughness are mainly governed by evaporation-driven electrocrystallization dynamics near the receding moving contact line. Integrated 3D structures and a rapid prototyping of 3D hot-wire anemometer are further demonstrated, which is very important for the freedom integration applications in advanced conceptual devices, such as miniaturized electronics and biomedical sensors and actuators.

Self-doped polyaniline multifunctional optical probes in confined nanostructure for pH sensing

NASA Astrophysics Data System (ADS)

Hong, Yoochan; Hwang, Seungyeon; Yang, Jaemoon

2017-07-01

We have successfully fabricated nanocomposite, which is composed of polyaniline (PAni) and pyrene butyric acid (Pyba) via solvent shift method, and the outer layer was enclosed by Tween 80 as a surfactant. First of all, the various ratios between PAni and Pyba were applied for synthesis of polyaniline nanocomposite, and an identical condition for exhibition of proper absorbance and fluorescence properties was found out. The morphology of polyaniline nanocomposite was confirmed via scanning electron microscopic imaging and hydrodynamic size was also confirmed by dynamic light scattering method. We demonstrated that confined self-doped polyaniline nanocomposite as a pH sensing agent are preserved in the doped state even at a neutral pH value. Especially, PAni exhibited strong convertible property at absorbance spectra, on the other hand, Pyba showed changing property at fluorescence spectra at various pH values. In conclude, this polyaniline nanocomposite can accomplish as a fine nanoagent expressing absorbance and fluorescence properties according to surrounding pH values.

Gigantic self-confined pahoehoe inflated lava flows in Argentina

NASA Astrophysics Data System (ADS)

Pasquare', G.; Bistacchi, A.

2007-05-01

The largest lava flows on Earth are pahoehoe basalts emplaced by inflation, a process which can change lava lobes initially a few decimetres thick into large lava sheets several metres thick. Inflation involves the initial formation of a thin, solidified, viscoelastic crust, under which liquid lava is continually added. This thermally efficient endogenous growth process explains the spread of huge volumes of lava over large, almost flat areas, as in the sheet flows which characterise the distal portions of Hawaiian volcanoes or some continental flood basalt provinces. Long, narrow, inflated pahoehoe flows have occasionally been described, either emplaced along pre-existing river channels or confined within topographic barriers. In this contribution we present previously unknown inflated pahoehoe lava flows following very long, narrow pathways over an almost flat surface, with no topographic confinement. Lava, which erupted in Late Quaternary times from the eastern tip of a 60 km long volcanic fissure in Argentina, formed several discrete flows extending as far as 180 km from the source. This fissure was characterized by a long-lasting and complex activity. Alkali-basaltic lava flows were emitted at the two extremities of the fissure system. In the intermediate section of the fissure, the Payun Matru, a great trachitic composite volcano, developed, giving rise to a large caldera which produced large pyroclastic flows. Alkali-basalts predate and postdate the trachitic activity, in fact at the end of the trachitic activity, new basaltic lava flows (mainly aa) were emitted from both ends of the fissure. We studied in details the youngest of the gigantic flows (Pampas Onduladas lava flow), which progressively develops through differing thermally-efficient flow mechanisms. The flow created a large shield volcanic structure at the eastern tip of the E-W fissure and spread to the E forming a very large and thick inflated pahoehoe sheet flow. Leaving the flanks of the volcano, the flow spreads all over a large tectonic depression, forming a large inflated pahoehoe sheet flow. The flow continues downstream, always showing typical inflation features, forming a very long and narrow tongue, developed over the nearly flat Pampa plain (gradient 0.5%) with an average width of 3 km and a length of 120 km. A peculiar feature of this portion of the flow, apart from its exceptional length, is the very low width-to-length ratio. This is even more surprising if we consider that no pre-existing topographic feature (e.g. river channel, etc.) is responsible for this behaviour, which appears to be only the result of some kind of self-confinement mechanism. The structural, morphological and eruptive complexities of this volcanic structure are exceptional by themselves since there are no similar features both in the Andes calcalkaline volcanism or in the Patagonian basaltic plateaus and they pose problems even in the nomenclatural definition of the Payun Matru as an individual volcanic construct. Moreover, understanding the mechanisms responsible for the exceptional behaviour of this lava flow may provide new constraints on the physics of inflated pahoehoe flow emplacement. Results in this direction may also offer useful proxies for interpreting volcanic processes on terrestrial planets such as Mars and Venus, on which individual lava flows of similar shape and dimensions have been observed.

Tuning the non-covalent confinement of Gd(III) complexes in silica nanoparticles for high T1-weighted MR imaging capability.

PubMed

Fedorenko, Svetlana V; Grechkina, Svetlana L; Mustafina, Asiya R; Kholin, Kirill V; Stepanov, Alexey S; Nizameev, Irek R; Ismaev, Ildus E; Kadirov, Marsil K; Zairov, Rustem R; Fattakhova, Alfia N; Amirov, Rustem R; Soloveva, Svetlana E

2017-01-01

The present work introduces deliberate synthesis of Gd(III)-doped silica nanoparticles with high relaxivity at magnetic field strengths below 1.5T. Modified microemulsion water-in-oil procedure was used in order to achieve superficial localization of Gd(III) complexes within 40-55nm sized silica spheres. The relaxivities of the prepared nanoparticles were measured at 0.47, 1.41 and 1.5T with the use of both NMR analyzer and whole body NMR scanner. Longitudinal relaxivities of the obtained silica nanoparticles reveal significant dependence on the confinement mode, changing from 4.1 to 49.6mM -1 s -1 at 0.47T when the localization of Gd(III) complexes changes from core to superficial zones of the silica spheres. The results highlight predominant contribution of the complexes located close to silica/water interface to the relaxivity of the nanoparticles. Low effect of blood proteins on the relaxivity in the aqueous colloids of the nanoparticles was exemplified by serum bovine albumin. T 1 - weighted MRI data indicate that the nanoparticles provide strong positive contrast at 1.5T, which along with low cytotoxicity effect make a good basis for their application as contrast agents. Copyright © 2016 Elsevier B.V. All rights reserved.

Christmas tree worms of Indo-Pacific coral reefs: untangling the Spirobranchus corniculatus (Grube, 1862) complex

NASA Astrophysics Data System (ADS)

Willette, Demian A.; Iñiguez, Abril R.; Kupriyanova, Elena K.; Starger, Craig J.; Varman, Tristan; Toha, Abdul Hamid; Maralit, Benedict A.; Barber, Paul H.

2015-09-01

Christmas tree worm is the common name of a group of colorful serpulid polychaetes from the genus Spirobranchus that are symbionts of hermatypic corals. As is increasingly common with reef-associated organisms, Spirobranchus is arranged as a complex of species with overlapping geographic ranges. Current species delimitations based largely on opercular morphology are problematic because of high intraspecific variation. Here, a multi-gene phylogeny of the Spirobranchus corniculatus complex, which tentatively includes S. corniculatus, S. cruciger, and S. gaymardi, sampled from the Coral Triangle, Australia, and Fiji, was reconstructed to test whether the complex includes three genetically distinct lineages identifiable by their opercula. Maximum-likelihood analyses of nuclear and mitochondrial markers revealed a single, monophyletic clade for the S. corniculatus complex. Furthermore, the genetic and morphological variation observed is not geographically based, indicating that the former S. corniculatus complex of three morphospecies is a single, morphologically variable species across the Central Indo-Pacific. Resolving the taxonomy of S. corniculatus presents novel opportunities to utilize this tentative bio-indicator species for monitoring reef health.

L2 Grammatical Gender in a Complex Morphological System: The Case of German

ERIC Educational Resources Information Center

Spinner, Patti; Juffs, Alan

2008-01-01

In order to determine the nature of naturalistic learners' difficulty with grammatical gender in a complex morphological system, the longitudinal production data of an early naturalistic L1-Italian and L1-Turkish learner who are acquiring German are examined in light of current theories of gender within Chomsky's (1995) Minimalist Program. After…

Probability and surprisal in auditory comprehension of morphologically complex words.

PubMed

Balling, Laura Winther; Baayen, R Harald

2012-10-01

Two auditory lexical decision experiments document for morphologically complex words two points at which the probability of a target word given the evidence shifts dramatically. The first point is reached when morphologically unrelated competitors are no longer compatible with the evidence. Adapting terminology from Marslen-Wilson (1984), we refer to this as the word's initial uniqueness point (UP1). The second point is the complex uniqueness point (CUP) introduced by Balling and Baayen (2008), at which morphologically related competitors become incompatible with the input. Later initial as well as complex uniqueness points predict longer response latencies. We argue that the effects of these uniqueness points arise due to the large surprisal (Levy, 2008) carried by the phonemes at these uniqueness points, and provide independent evidence that how cumulative surprisal builds up in the course of the word co-determines response latencies. The presence of effects of surprisal, both at the initial uniqueness point of complex words, and cumulatively throughout the word, challenges the Shortlist B model of Norris and McQueen (2008), and suggests that a Bayesian approach to auditory comprehension requires complementation from information theory in order to do justice to the cognitive cost of updating probability distributions over lexical candidates. Copyright © 2012 Elsevier B.V. All rights reserved.

Morphological and molecular characterization of Fusarium spp pathogenic to pecan tree in Brazil.

PubMed

Lazarotto, M; Milanesi, P M; Muniz, M F B; Reiniger, L R S; Beltrame, R; Harakava, R; Blume, E

2014-11-11

The occurrence of Fusarium spp associated with pecan tree (Carya illinoinensis) diseases in Brazil has been observed in recent laboratory analyses in Rio Grande do Sul State. Thus, in this study, we i) obtained Fusarium isolates from plants with disease symptoms; ii) tested the pathogenicity of these Fusarium isolates to pecan; iii) characterized and grouped Fusarium isolates that were pathogenic to the pecan tree based on morphological characteristics; iv) identified Fusarium spp to the species complex level through TEF-1α sequencing; and v) compared the identification methods used in the study. Fifteen isolates collected from the inflorescences, roots, and seeds of symptomatic plants (leaf necrosis or root rot) were used for pathogenicity tests. Morphological characterization was conducted using only pathogenic isolates, for a total of 11 isolates, based on the mycelial growth rate, sporulation, colony pigmentation, and conidial length and width variables. Pathogenic isolates were grouped based on morphological characteristics, and molecular characterization was performed by sequencing TEF-1α genes. Pathogenic isolates belonging to the Fusarium chlamydosporum species complex, Fusarium graminearum species complex, Fusarium proliferatum, and Fusarium oxysporum were identified based on the TEF-1α region. Morphological characteristics were used to effectively differentiate isolates and group the isolates according to genetic similarity, particularly conidial width, which emerged as a key morphological descriptor in this study.

Elevated rates of morphological and functional diversification in reef-dwelling haemulid fishes.

PubMed

Price, Samantha A; Tavera, Jose J; Near, Thomas J; Wainwright, Peter C

2013-02-01

The relationship between habitat complexity and species richness is well established but comparatively little is known about the evolution of morphological diversity in complex habitats. Reefs are structurally complex, highly productive shallow-water marine ecosystems found in tropical (coral reefs) and temperate zones (rocky reefs) that harbor exceptional levels of biodiversity. We investigated whether reef habitats promote the evolution of morphological diversity in the feeding and locomotion systems of grunts (Haemulidae), a group of predominantly nocturnal fishes that live on both temperate and tropical reefs. Using phylogenetic comparative methods and statistical analyses that take into account uncertainty in phylogeny and the evolutionary history of reef living, we demonstrate that rates of morphological evolution are faster in reef-dwelling haemulids. The magnitude of this effect depends on the type of trait; on average, traits involved in the functional systems for prey capture and processing evolve twice as fast on reefs as locomotor traits. This result, along with the observation that haemulids do not exploit unique feeding niches on reefs, suggests that fine-scale trophic niche partitioning and character displacement may be driving higher rates of morphological evolution. Whatever the cause, there is growing evidence that reef habitats stimulate morphological and functional diversification in teleost fishes. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

Electron-phonon interactions in semiconductor nanostructures

NASA Astrophysics Data System (ADS)

Yu, Segi

In this dissertation, electron-phonon interactions are studied theoretically in semiconductor nanoscale heterostructures. Interactions of electrons with interface optical phonons dominate over other electron-phonon interactions in narrow width heterostructures. Hence, a transfer matrix method is used to establish a formalism for determining the dispersion relations and electrostatic potentials of the interface phonons for multiple-interface heterostructure within the macroscopic dielectric continuum model. This method facilitates systematic calculations for complex structures where the conventional method is difficult to implement. Several specific cases are treated to illustrate advantages of the formalism. Electrophonon resonance (EPR) is studied in cylindrical quantum wires using the confined/interface optical phonons representation and bulk phonon representation. It has been found that interface phonon contribution to EPR is small compared with confined phonon. Different selection rules for bulk phonons and confined phonons result in different EPR behaviors as the radius of cylindrical wire changes. Experiment is suggested to test which phonon representation is appropriate for EPR. The effects of phonon confinement on elect ron-acoustic-phonon scattering is studied in cylindrical and rectangular quantum wires. In the macroscopic elastic continuum model, the confined-phonon dispersion relations are obtained for several crystallographic directions with free-surface and clamped-surface boundary conditions in cylindrical wires. The scattering rates due to the deformation potential are obtained for these confined phonons and are compared with those of bulk-like phonons. The results show that the inclusion of acoustic phonon confinement may be crucial for calculating accurate low-energy electron scattering rates. Furthermore, it has been found that there is a scaling rule governing the directional dependence of the scattering rates. The Hamiltonian describing the deformation-potential of confined acoustic phonons is derived by quantizing the appropriate, experimentally verified approximate compressional acoustic-phonon modes in a free-standing rectangular quantum wire. The scattering rate is obtained for GaAs quantum wires with a range of cross-sectional dimensions. The results demonstrate that a proper treatment of confined acoustic phonons may be essential to correctly model electron scattering rates at low energies in nanoscale structures.

Is There a "Fete" in "Fetish"? Effects of Orthographic Opacity on Morpho-Orthographic Segmentation in Visual Word Recognition

ERIC Educational Resources Information Center

McCormick, Samantha F.; Rastle, Kathleen; Davis, Matthew H.

2008-01-01

Recent research using masked priming has suggested that there is a form of morphological decomposition that is based solely on the appearance of morphological complexity and that operates independently of semantic information [Longtin, C.M., Segui, J., & Halle, P. A. (2003). Morphological priming without morphological relationship. "Language and…

The Effect of Morphological Awareness on Reading Comprehension: A Study with Adolescent Spanish-English Emergent Bilinguals

ERIC Educational Resources Information Center

Curinga, Rebecca

2014-01-01

The present research examines the role of morphological awareness in reading comprehension of high school emergent bilinguals. As an increasing number of research studies contribute to our understanding of morphological awareness, i.e. the ability to reflect on and manipulate morphologically complex derived words, we are better able to appreciate…

Age, environment, object recognition and morphological diversity of GFAP-immunolabeled astrocytes.

PubMed

Diniz, Daniel Guerreiro; de Oliveira, Marcus Augusto; de Lima, Camila Mendes; Fôro, César Augusto Raiol; Sosthenes, Marcia Consentino Kronka; Bento-Torres, João; da Costa Vasconcelos, Pedro Fernando; Anthony, Daniel Clive; Diniz, Cristovam Wanderley Picanço

2016-10-10

Few studies have explored the glial response to a standard environment and how the response may be associated with age-related cognitive decline in learning and memory. Here we investigated aging and environmental influences on hippocampal-dependent tasks and on the morphology of an unbiased selected population of astrocytes from the molecular layer of dentate gyrus, which is the main target of perforant pathway. Six and twenty-month-old female, albino Swiss mice were housed, from weaning, in a standard or enriched environment, including running wheels for exercise and tested for object recognition and contextual memories. Young adult and aged subjects, independent of environment, were able to distinguish familiar from novel objects. All experimental groups, except aged mice from standard environment, distinguish stationary from displaced objects. Young adult but not aged mice, independent of environment, were able to distinguish older from recent objects. Only young mice from an enriched environment were able to distinguish novel from familiar contexts. Unbiased selected astrocytes from the molecular layer of the dentate gyrus were reconstructed in three-dimensions and classified using hierarchical cluster analysis of bimodal or multimodal morphological features. We found two morphological phenotypes of astrocytes and we designated type I the astrocytes that exhibited significantly higher values of morphological complexity as compared with type II. Complexity = [Sum of the terminal orders + Number of terminals] × [Total branch length/Number of primary branches]. On average, type I morphological complexity seems to be much more sensitive to age and environmental influences than that of type II. Indeed, aging and environmental impoverishment interact and reduce the morphological complexity of type I astrocytes at a point that they could not be distinguished anymore from type II. We suggest these two types of astrocytes may have different physiological roles and that the detrimental effects of aging on memory in mice from a standard environment may be associated with a reduction of astrocytes morphological diversity.

Taxonomy and species boundaries in the coral genus Favia Milne Edwards and Haime, 1857 (Cnidaria: Scleractinia) from Thailand revealed by morphological and genetic data

NASA Astrophysics Data System (ADS)

Kongjandtre, N.; Ridgway, T.; Cook, L. G.; Huelsken, T.; Budd, A. F.; Hoegh-Guldberg, O.

2012-06-01

While Faviidae is a widely and uniformly distributed coral family throughout the Indo-Pacific, the extensive phenotypic plasticity of colony surface and corallite features often confounds the use of macromorphological characters in species identification, and contributes to conflict between traditional classification and molecular analyses of the group. Recent advances in morphological and molecular techniques now provide a suite of methods to re-address coral taxonomy in complex groups, such as that represented by the Faviidae. This study combines morphologic measurements including "3D coordinates landmarks" data with phylogenetic assessments of nuclear (ITS) and mitochondrial (COI-trnM) DNA to assess species boundaries in nine species of Faviidae with para-septothecal walls from Thailand. Strong concordance was found between morphological features and a priori groupings based on both morphospecies and genetically defined groups (ITS and COI-trnM). Favia truncatus was the most well-defined species based on morphological analyses, and it was also shown to be monophyletic using phylogenetic analyses. Besides F. truncatus, the only other species that was found to be monophyletic in analyses of both genes was F. cf. helianthoides, but its skeletal morphology overlapped with the F. favus species complex (comprised of F. favus, F. speciosa, F. matthaii and F. rotumana). Although not genetically monophyletic, the F. favus species complex and F. pallida were fairly well delineated morphologically. Morphospecies within the F. favus species complex are therefore possibly a result of genetic drift and/or stable polymorphisms driven by divergent selection. These results represent a first step toward a taxonomic revision of the Indo-Pacific Favia, which will integrate morphological methods with the study of type material, genetic information, reproductive data, and tests of phenotypic plasticity—given that multiple lines of evidence are needed to resolve ambiguous species and assign species names.

Cockroaches traverse crevices, crawl rapidly in confined spaces, and inspire a soft, legged robot

PubMed Central

Jayaram, Kaushik; Full, Robert J.

2016-01-01

Jointed exoskeletons permit rapid appendage-driven locomotion but retain the soft-bodied, shape-changing ability to explore confined environments. We challenged cockroaches with horizontal crevices smaller than a quarter of their standing body height. Cockroaches rapidly traversed crevices in 300–800 ms by compressing their body 40–60%. High-speed videography revealed crevice negotiation to be a complex, discontinuous maneuver. After traversing horizontal crevices to enter a vertically confined space, cockroaches crawled at velocities approaching 60 cm⋅s−1, despite body compression and postural changes. Running velocity, stride length, and stride period only decreased at the smallest crevice height (4 mm), whereas slipping and the probability of zigzag paths increased. To explain confined-space running performance limits, we altered ceiling and ground friction. Increased ceiling friction decreased velocity by decreasing stride length and increasing slipping. Increased ground friction resulted in velocity and stride length attaining a maximum at intermediate friction levels. These data support a model of an unexplored mode of locomotion—“body-friction legged crawling” with body drag, friction-dominated leg thrust, but no media flow as in air, water, or sand. To define the limits of body compression in confined spaces, we conducted dynamic compressive cycle tests on living animals. Exoskeletal strength allowed cockroaches to withstand forces 300 times body weight when traversing the smallest crevices and up to nearly 900 times body weight without injury. Cockroach exoskeletons provided biological inspiration for the manufacture of an origami-style, soft, legged robot that can locomote rapidly in both open and confined spaces. PMID:26858443

Cockroaches traverse crevices, crawl rapidly in confined spaces, and inspire a soft, legged robot.

PubMed

Jayaram, Kaushik; Full, Robert J

2016-02-23

Jointed exoskeletons permit rapid appendage-driven locomotion but retain the soft-bodied, shape-changing ability to explore confined environments. We challenged cockroaches with horizontal crevices smaller than a quarter of their standing body height. Cockroaches rapidly traversed crevices in 300-800 ms by compressing their body 40-60%. High-speed videography revealed crevice negotiation to be a complex, discontinuous maneuver. After traversing horizontal crevices to enter a vertically confined space, cockroaches crawled at velocities approaching 60 cm⋅s(-1), despite body compression and postural changes. Running velocity, stride length, and stride period only decreased at the smallest crevice height (4 mm), whereas slipping and the probability of zigzag paths increased. To explain confined-space running performance limits, we altered ceiling and ground friction. Increased ceiling friction decreased velocity by decreasing stride length and increasing slipping. Increased ground friction resulted in velocity and stride length attaining a maximum at intermediate friction levels. These data support a model of an unexplored mode of locomotion--"body-friction legged crawling" with body drag, friction-dominated leg thrust, but no media flow as in air, water, or sand. To define the limits of body compression in confined spaces, we conducted dynamic compressive cycle tests on living animals. Exoskeletal strength allowed cockroaches to withstand forces 300 times body weight when traversing the smallest crevices and up to nearly 900 times body weight without injury. Cockroach exoskeletons provided biological inspiration for the manufacture of an origami-style, soft, legged robot that can locomote rapidly in both open and confined spaces.

Loss of the integral nuclear envelope protein SUN1 induces alteration of nucleoli

PubMed Central

Matsumoto, Ayaka; Sakamoto, Chiyomi; Matsumori, Haruka; Katahira, Jun; Yasuda, Yoko; Yoshidome, Katsuhide; Tsujimoto, Masahiko; Goldberg, Ilya G; Matsuura, Nariaki; Nakao, Mitsuyoshi; Saitoh, Noriko; Hieda, Miki

2016-01-01

ABSTRACT A supervised machine learning algorithm, which is qualified for image classification and analyzing similarities, is based on multiple discriminative morphological features that are automatically assembled during the learning processes. The algorithm is suitable for population-based analysis of images of biological materials that are generally complex and heterogeneous. Here we used the algorithm wndchrm to quantify the effects on nucleolar morphology of the loss of the components of nuclear envelope in a human mammary epithelial cell line. The linker of nucleoskeleton and cytoskeleton (LINC) complex, an assembly of nuclear envelope proteins comprising mainly members of the SUN and nesprin families, connects the nuclear lamina and cytoskeletal filaments. The components of the LINC complex are markedly deficient in breast cancer tissues. We found that a reduction in the levels of SUN1, SUN2, and lamin A/C led to significant changes in morphologies that were computationally classified using wndchrm with approximately 100% accuracy. In particular, depletion of SUN1 caused nucleolar hypertrophy and reduced rRNA synthesis. Further, wndchrm revealed a consistent negative correlation between SUN1 expression and the size of nucleoli in human breast cancer tissues. Our unbiased morphological quantitation strategies using wndchrm revealed an unexpected link between the components of the LINC complex and the morphologies of nucleoli that serves as an indicator of the malignant phenotype of breast cancer cells. PMID:26962703

Loss of the integral nuclear envelope protein SUN1 induces alteration of nucleoli.

PubMed

Matsumoto, Ayaka; Sakamoto, Chiyomi; Matsumori, Haruka; Katahira, Jun; Yasuda, Yoko; Yoshidome, Katsuhide; Tsujimoto, Masahiko; Goldberg, Ilya G; Matsuura, Nariaki; Nakao, Mitsuyoshi; Saitoh, Noriko; Hieda, Miki

2016-01-01

A supervised machine learning algorithm, which is qualified for image classification and analyzing similarities, is based on multiple discriminative morphological features that are automatically assembled during the learning processes. The algorithm is suitable for population-based analysis of images of biological materials that are generally complex and heterogeneous. Here we used the algorithm wndchrm to quantify the effects on nucleolar morphology of the loss of the components of nuclear envelope in a human mammary epithelial cell line. The linker of nucleoskeleton and cytoskeleton (LINC) complex, an assembly of nuclear envelope proteins comprising mainly members of the SUN and nesprin families, connects the nuclear lamina and cytoskeletal filaments. The components of the LINC complex are markedly deficient in breast cancer tissues. We found that a reduction in the levels of SUN1, SUN2, and lamin A/C led to significant changes in morphologies that were computationally classified using wndchrm with approximately 100% accuracy. In particular, depletion of SUN1 caused nucleolar hypertrophy and reduced rRNA synthesis. Further, wndchrm revealed a consistent negative correlation between SUN1 expression and the size of nucleoli in human breast cancer tissues. Our unbiased morphological quantitation strategies using wndchrm revealed an unexpected link between the components of the LINC complex and the morphologies of nucleoli that serves as an indicator of the malignant phenotype of breast cancer cells.

Morphological and molecular identification of cryptic species in the Sergentomyia bailyi (Sinton, 1931) complex in Sri Lanka.

PubMed

Tharmatha, T; Gajapathy, K; Ramasamy, R; Surendran, S N

2017-02-01

The correct identification of sand fly vectors of leishmaniasis is important for controlling the disease. Genetic, particularly DNA sequence data, has lately become an important adjunct to the use of morphological criteria for this purpose. A recent DNA sequencing study revealed the presence of two cryptic species in the Sergentomyia bailyi species complex in India. The present study was undertaken to ascertain the presence of cryptic species in the Se. bailyi complex in Sri Lanka using morphological characteristics and DNA sequences from cytochrome c oxidase subunits. Sand flies were collected from leishmaniasis endemic and non-endemic dry zone districts of Sri Lanka. A total of 175 Se. bailyi specimens were initially screened for morphological variations and the identified samples formed two groups, tentatively termed as Se. bailyi species A and B, based on the relative length of the sensilla chaeticum and antennal flagellomere. DNA sequences from the mitochondrial cytochrome c oxidase subunit I (COI) and subunit II (COII) genes of morphologically identified Se. bailyi species A and B were subsequently analyzed. The two species showed differences in the COI and COII gene sequences and were placed in two separate clades by phylogenetic analysis. An allele specific polymerase chain reaction assay based on sequence variation in the COI gene accurately differentiated species A and B. The study therefore describes the first morphological and genetic evidence for the presence of two cryptic species within the Se. bailyi complex in Sri Lanka and a DNA-based laboratory technique for differentiating them.

Water Resources and Supply Adaptation: A paradigm Shifting for Future Climate?

EPA Science Inventory

Climate change adds another layer of complexity in planning, engineering and management of water resources and urban water infrastructures. Yet our current practice is confined to the traditional approach that evaluates developmental scenarios and their sustainability mostly by a...

Experimental Identification of Electric Field Excitation Mechanisms in a Structural Transition of Tokamak Plasmas

PubMed Central

Kobayashi, T.; Itoh, K.; Ido, T.; Kamiya, K.; Itoh, S.-I.; Miura, Y.; Nagashima, Y.; Fujisawa, A.; Inagaki, S.; Ida, K.; Hoshino, K.

2016-01-01

Self-regulation between structure and turbulence, which is a fundamental process in the complex system, has been widely regarded as one of the central issues in modern physics. A typical example of that in magnetically confined plasmas is the Low confinement mode to High confinement mode (L-H) transition, which is intensely studied for more than thirty years since it provides a confinement improvement necessary for the realization of the fusion reactor. An essential issue in the L-H transition physics is the mechanism of the abrupt “radial” electric field generation in toroidal plasmas. To date, several models for the L-H transition have been proposed but the systematic experimental validation is still challenging. Here we report the systematic and quantitative model validations of the radial electric field excitation mechanism for the first time, using a data set of the turbulence and the radial electric field having a high spatiotemporal resolution. Examining time derivative of Poisson’s equation, the sum of the loss-cone loss current and the neoclassical bulk viscosity current is found to behave as the experimentally observed radial current that excites the radial electric field within a few factors of magnitude. PMID:27489128

Biofilm formation in geometries with different surface curvature and oxygen availability

NASA Astrophysics Data System (ADS)

Chang, Ya-Wen; Fragkopoulos, Alexandros A.; Marquez, Samantha M.; Kim, Harold D.; Angelini, Thomas E.; Fernández-Nieves, Alberto

2015-03-01

Bacteria in the natural environment exist as interface-associated colonies known as biofilms . Complex mechanisms are often involved in biofilm formation and development. Despite the understanding of the molecular mechanisms involved in biofilm formation, it remains unclear how physical effects in standing cultures influence biofilm development. The topology of the solid interface has been suggested as one of the physical cues influencing bacteria-surface interactions and biofilm development. Using the model organism Bacillus subtilis, we study the transformation of swimming bacteria in liquid culture into robust biofilms in a range of confinement geometries (planar, spherical and toroidal) and interfaces (air/water, silicone/water, and silicone elastomer/water). We find that B. subtilis form submerged biofilms at both solid and liquid interfaces in addition to air-water pellicles. When confined, bacteria grow on curved surfaces of both positive and negative Gaussian curvature. However, the confinement geometry does affect the resulting biofilm roughness and relative coverage. We also find that the biofilm location is governed by oxygen availability as well as by gravitational effects; these compete with each other in some situations. Overall, our results demonstrate that confinement geometry is an effective way to control oxygen availability and subsequently biofilm growth.

Linear and ultrafast nonlinear plasmonics of single nano-objects

NASA Astrophysics Data System (ADS)

Crut, Aurélien; Maioli, Paolo; Vallée, Fabrice; Del Fatti, Natalia

2017-03-01

Single-particle optical investigations have greatly improved our understanding of the fundamental properties of nano-objects, avoiding the spurious inhomogeneous effects that affect ensemble experiments. Correlation with high-resolution imaging techniques providing morphological information (e.g. electron microscopy) allows a quantitative interpretation of the optical measurements by means of analytical models and numerical simulations. In this topical review, we first briefly recall the principles underlying some of the most commonly used single-particle optical techniques: near-field, dark-field, spatial modulation and photothermal microscopies/spectroscopies. We then focus on the quantitative investigation of the surface plasmon resonance (SPR) of metallic nano-objects using linear and ultrafast optical techniques. While measured SPR positions and spectral areas are found in good agreement with predictions based on Maxwell’s equations, SPR widths are strongly influenced by quantum confinement (or, from a classical standpoint, surface-induced electron scattering) and, for small nano-objects, cannot be reproduced using the dielectric functions of bulk materials. Linear measurements on single nano-objects (silver nanospheres and gold nanorods) allow a quantification of the size and geometry dependences of these effects in confined metals. Addressing the ultrafast response of an individual nano-object is also a powerful tool to elucidate the physical mechanisms at the origin of their optical nonlinearities, and their electronic, vibrational and thermal relaxation processes. Experimental investigations of the dynamical response of gold nanorods are shown to be quantitatively modeled in terms of modifications of the metal dielectric function enhanced by plasmonic effects. Ultrafast spectroscopy can also be exploited to unveil hidden physical properties of more complex nanosystems. In this context, two-color femtosecond pump-probe experiments performed on individual bimetallic heterodimers are discussed in the last part of the review, demonstrating the existence of Fano interferences in the optical absorption of a gold nanoparticle under the influence of a nearby silver one.

Development and Execution of a Large-scale DDT Tube Test for IHE Material Qualification

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

Parker, Gary Robert; Broilo, Robert M.; Lopez-Pulliam, Ian Daniel

Insensitive High Explosive (IHE) Materials are defined in Chapter IX of the DOE Explosive Safety Standard (DOE-STD-1212-2012) as being materials that are massdetonable explosives that are so insensitive that the probability of accidental initiation or transition from burning to detonation is negligible1. There are currently a number of tests included in the standard that are required to qualify a material as IHE, however, none of the tests directly evaluate for the transition from burning to detonation (aka deflagration-to-detonation transition, DDT). Currently, there is a DOE complex-wide effort to revisit the IHE definition in DOE-STD-1212-2012 and change the qualification requirements. Themore » proposal lays out a new approach, requiring fewer, but more appropriate tests, for IHE Material qualification. One of these new tests is the Deflagration-to-Detonation Test. According to the redefinition proposal, the purpose of the new deflagration-todetonation test is “to demonstrate that an IHE material will not undergo deflagration-to-detonation under stockpile relevant conditions of scale, confinement, and material condition. Inherent in this test design is the assumption that ignition does occur, with onset of deflagration. The test design will incorporate large margins and replicates to account for the stochastic nature of DDT events.” In short, the philosophy behind this approach is that if a material fails to undergo DDT in a significant over-test, then it is extremely unlikely to do so in realistic conditions. This effort will be valuable for the B61 LEP to satisfy their need qualify the new production lots of PBX 9502. The work described in this report is intended as a preliminary investigation to support the proposed design of an overly conservative, easily fielded DDT test for updated IHE Material Qualification standard. Specifically, we evaluated the aspects of confinement, geometry, material morphology and temperature. We also developed and tested a thermally robust igniter system.« less

High Confinement Mode and Edge Localized Mode Characteristics in a Near-Unity Aspect Ratio Tokamak.

PubMed

Thome, K E; Bongard, M W; Barr, J L; Bodner, G M; Burke, M G; Fonck, R J; Kriete, D M; Perry, J M; Schlossberg, D J

2016-04-29

Tokamak experiments at near-unity aspect ratio A≲1.2 offer new insights into the self-organized H-mode plasma confinement regime. In contrast to conventional A∼3 plasmas, the L-H power threshold P_{LH} is ∼15× higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. These ultralow-A operations enable heretofore inaccessible J_{edge}(R,t) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament.

High confinement mode and edge localized mode characteristics in a near-unity aspect ratio tokamak

DOE PAGES

Thome, Kathreen E.; Bongard, Michael W.; Barr, Jayson L.; ...

2016-04-27

Tokamak experiments at near-unity aspect ratio A ≲ 1.2 offer new insights into the self-organized H-mode plasma confinement regime. In contrast to conventional A ~ 3 plasmas, the L–H power threshold P LH is ~15× higher than scaling predictions, and it is insensitive to magnetic topology, consistent with modeling. Edge localized mode (ELM) instabilities shift to lower toroidal mode numbers as A decreases. Furthermore, these ultralow-A operations enable heretofore inaccessible J edge(R,t) measurements through an ELM that show a complex multimodal collapse and the ejection of a current-carrying filament.

Exploring Inflated Pahohoe Lava Flow Morphologies and the Effects of Cooling Using a New Simulation Approach

NASA Technical Reports Server (NTRS)

Glaze, L. S.; Baloga, S. M.

2014-01-01

Pahoehoe lavas are recognized as an important landform on Earth, Mars and Io. Observations of such flows on Earth (e.g., Figure 1) indicate that the emplacement process is dominated by random effects. Existing models for lobate a`a lava flows that assume viscous fluid flow on an inclined plane are not appropriate for dealing with the numerous random factors present in pahoehoe emplacement. Thus, interpretation of emplacement conditions for pahoehoe lava flows on Mars requires fundamentally different models. A new model that implements a simulation approach has recently been developed that allows exploration of a variety of key influences on pahoehoe lobe emplacement (e.g., source shape, confinement, slope). One important factor that has an impact on the final topographic shape and morphology of a pahoehoe lobe is the volumetric flow rate of lava, where cooling of lava on the lobe surface influences the likelihood of subsequent breakouts.

Tunable synthesis and in situ growth of silicon-carbon mesostructures using impermeable plasma.

PubMed

Yaghoubi, Alireza; Mélinon, Patrice

2013-01-01

In recent years, plasma-assisted synthesis has been extensively used in large scale production of functional nano- and micro-scale materials for numerous applications in optoelectronics, photonics, plasmonics, magnetism and drug delivery, however systematic formation of these minuscule structures has remained a challenge. Here we demonstrate a new method to closely manipulate mesostructures in terms of size, composition and morphology by controlling permeability at the boundaries of an impermeable plasma surrounded by a blanket of neutrals. In situ and rapid growth of thin films in the core region due to ion screening is among other benefits of our method. Similarly we can take advantage of exceptional properties of plasma to control the morphology of the as deposited nanostructures. Probing the plasma at boundaries by means of observing the nanostructures, further provides interesting insights into the behaviour of gas-insulated plasmas with possible implications on efficacy of viscous heating and non-magnetic confinement.

Tunable synthesis and in situ growth of silicon-carbon mesostructures using impermeable plasma

PubMed Central

Yaghoubi, Alireza; Mélinon, Patrice

2013-01-01

In recent years, plasma-assisted synthesis has been extensively used in large scale production of functional nano- and micro-scale materials for numerous applications in optoelectronics, photonics, plasmonics, magnetism and drug delivery, however systematic formation of these minuscule structures has remained a challenge. Here we demonstrate a new method to closely manipulate mesostructures in terms of size, composition and morphology by controlling permeability at the boundaries of an impermeable plasma surrounded by a blanket of neutrals. In situ and rapid growth of thin films in the core region due to ion screening is among other benefits of our method. Similarly we can take advantage of exceptional properties of plasma to control the morphology of the as deposited nanostructures. Probing the plasma at boundaries by means of observing the nanostructures, further provides interesting insights into the behaviour of gas-insulated plasmas with possible implications on efficacy of viscous heating and non-magnetic confinement. PMID:23330064

Compaction of quasi-one-dimensional elastoplastic materials

PubMed Central

Shaebani, M. Reza; Najafi, Javad; Farnudi, Ali; Bonn, Daniel; Habibi, Mehdi

2017-01-01

Insight into crumpling or compaction of one-dimensional objects is important for understanding biopolymer packaging and designing innovative technological devices. By compacting various types of wires in rigid confinements and characterizing the morphology of the resulting crumpled structures, here, we report how friction, plasticity and torsion enhance disorder, leading to a transition from coiled to folded morphologies. In the latter case, where folding dominates the crumpling process, we find that reducing the relative wire thickness counter-intuitively causes the maximum packing density to decrease. The segment size distribution gradually becomes more asymmetric during compaction, reflecting an increase of spatial correlations. We introduce a self-avoiding random walk model and verify that the cumulative injected wire length follows a universal dependence on segment size, allowing for the prediction of the efficiency of compaction as a function of material properties, container size and injection force. PMID:28585550

Leaf anatomy of a late Palaeozoic cycad

PubMed Central

Lv, Yong; Guo, Yun; Wei, Hai-Bo

2017-01-01

Today, cycads are a small group of gymnospermous plants with a limited distribution in the (sub)tropics, but they were major constituents of Mesozoic floras. Fossil leaves sporadically found in latest Carboniferous and Permian floras have putatively been ascribed to cycads. However, their true affinity remains unclear due to the lack of anatomical evidence. Virtually all modern cycads have pinnate leaves, but this type of leaf morphology is by no means unique for cycads. Pinnate leaves of Plagiozamites oblongifolius Halle 1927 with well-preserved cuticles showing the epidermal anatomy are here described from the upper Permian Xuanwei Formation of Yunnan Province, Southwest China. The cuticles show a clear differentiation into costal and intercostal zones; stomata are confined to the intercostal zones on both the upper and lower leaf surfaces. The external morphology and the epidermal anatomy of these fossil leaves are closely comparable with those of extant cycads, particularly members of the family Zamiaceae. PMID:29093177

A COMPUTATIONAL MODEL OF MOTOR NEURON DEGENERATION

PubMed Central

Le Masson, Gwendal; Przedborski, Serge; Abbott, L.F.

2014-01-01

SUMMARY To explore the link between bioenergetics and motor neuron degeneration, we used a computational model in which detailed morphology and ion conductance are paired with intracellular ATP production and consumption. We found that reduced ATP availability increases the metabolic cost of a single action potential and disrupts K+/Na+ homeostasis, resulting in a chronic depolarization. The magnitude of the ATP shortage at which this ionic instability occurs depends on the morphology and intrinsic conductance characteristic of the neuron. If ATP shortage is confined to the distal part of the axon, the ensuing local ionic instability eventually spreads to the whole neuron and involves fasciculation-like spiking events. A shortage of ATP also causes a rise in intracellular calcium. Our modeling work supports the notion that mitochondrial dysfunction can account for salient features of the paralytic disorder amyotrophic lateral sclerosis, including motor neuron hyperexcitability, fasciculation, and differential vulnerability of motor neuron subpopulations. PMID:25088365

A computational model of motor neuron degeneration.

PubMed

Le Masson, Gwendal; Przedborski, Serge; Abbott, L F

2014-08-20

To explore the link between bioenergetics and motor neuron degeneration, we used a computational model in which detailed morphology and ion conductance are paired with intracellular ATP production and consumption. We found that reduced ATP availability increases the metabolic cost of a single action potential and disrupts K+/Na+ homeostasis, resulting in a chronic depolarization. The magnitude of the ATP shortage at which this ionic instability occurs depends on the morphology and intrinsic conductance characteristic of the neuron. If ATP shortage is confined to the distal part of the axon, the ensuing local ionic instability eventually spreads to the whole neuron and involves fasciculation-like spiking events. A shortage of ATP also causes a rise in intracellular calcium. Our modeling work supports the notion that mitochondrial dysfunction can account for salient features of the paralytic disorder amyotrophic lateral sclerosis, including motor neuron hyperexcitability, fasciculation, and differential vulnerability of motor neuron subpopulations. Copyright © 2014 Elsevier Inc. All rights reserved.

On the Morphological Adaptations of the Thorax of Sphagniana sphagnorum (Ensifera, Tettigoniidae) that Enable Complex Stridulation via the Forewings

NASA Astrophysics Data System (ADS)

Gutierrez, Sara-Jane

Males of the flightless tettigoniid Sphagniana sphagnorum generate a complex two-spectrum signal via stridulation, using acoustically adapted forewings (tegmina). Complex-wave rapidly decaying pulses in trains, made upon the distal half of the file, have a broad-band (17-25 kHz) spectrum; short, spaced, ultrasonic and strongly sinusoidal 35 kHz pulses are emitted as trains over the file's proximal half. I studied how S. sphagnorum tegminal morphology enables the production of these two different spectra with the same forewings. The storage of elastic energy in the scraper is hypothesized to play a key role in driving the scraper over the file at a necessary tooth-contact rate. Scraper morphology indicates structural adaptations enabling storage of elastic energy. Wax loading tested the role of scraper-pit flexibility in scraper movement. Sound levels in resonant spectra were more substantially affected than those associated with broadband generation. Morphology and alignment of pteralia during tegmino-tegminal stridulation is also investigated.

Coronal Loops: Observations and Modeling of Confined Plasma.

PubMed

Reale, Fabio

Coronal loops are the building blocks of the X-ray bright solar corona. They owe their brightness to the dense confined plasma, and this review focuses on loops mostly as structures confining plasma. After a brief historical overview, the review is divided into two separate but not independent parts: the first illustrates the observational framework, the second reviews the theoretical knowledge. Quiescent loops and their confined plasma are considered and, therefore, topics such as loop oscillations and flaring loops (except for non-solar ones, which provide information on stellar loops) are not specifically addressed here. The observational section discusses the classification, populations, and the morphology of coronal loops, its relationship with the magnetic field, and the loop stranded structure. The section continues with the thermal properties and diagnostics of the loop plasma, according to the classification into hot, warm, and cool loops. Then, temporal analyses of loops and the observations of plasma dynamics, hot and cool flows, and waves are illustrated. In the modeling section, some basics of loop physics are provided, supplying fundamental scaling laws and timescales, a useful tool for consultation. The concept of loop modeling is introduced and models are divided into those treating loops as monolithic and static, and those resolving loops into thin and dynamic strands. More specific discussions address modeling the loop fine structure and the plasma flowing along the loops. Special attention is devoted to the question of loop heating, with separate discussion of wave (AC) and impulsive (DC) heating. Large-scale models including atmosphere boxes and the magnetic field are also discussed. Finally, a brief discussion about stellar coronal loops is followed by highlights and open questions.

Morphological Characteristics of Placental Complex in Pregnant Women without Complications in Pregnancy and in the Presence of Severe Preeclampsia

ERIC Educational Resources Information Center

Umbetov, Turakbai Zh.; Berdalinova, Akzhenis K.; Tusupkalieyv, Akylbek B.; Koishybayev, Arip K.; Zharilkasynov, Karaman Ye.

2016-01-01

According to the WHO data, preeclampsia develops during late pregnancy in 2-8% of women. Preeclampsia is a major cause of maternal and perinatal morbidity and mortality, therefore, the study of the morphological features of placental complex, taking into account gestational complications in postpartum women with severe preeclampsia is an important…

Ionic liquid structure, dynamics, and electrosorption in carbon electrodes with bimodal pores and heterogeneous surfaces

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

Dyatkin, Boris; Osti, Naresh C.; Zhang, Yu

In this paper, we investigate the aggregation, diffusion, and resulting electrochemical behavior of ionic liquids inside carbon electrodes with complex pore architectures and surface chemistries. Carbide-derived carbons (CDCs) with bimodal porosities and defunctionalized or oxidized electrode surfaces served as model electrode materials. Our goal was to obtain a fundamental understanding of room-temperature ionic liquid ion orientation, mobility, and electrosorption behavior. Neat 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide confined in CDCs was studied using an integrated experimental and modeling approach, consisting of quasielastic neutron scattering, small-angle neutron scattering, X-ray pair distribution function analysis, and electrochemical measurements, which were combined with molecular dynamics simulations. Our analysismore » shows that surface oxygen groups increase the diffusion of confined electrolytes. Consequently, the ions become more than twice as mobile in oxygen-rich pores. Although greater self-diffusion of ions translates into higher electrochemical mobilities in oxidized pores, bulk-like behavior of ions dominates in the larger mesopores and increases the overall capacitance in defunctionalized pores. Experimental results highlight strong confinement and surface effects of carbon electrodes on electrolyte behavior, and molecular dynamics simulations yield insight into diffusion and capacitance differences in specific pore regions. Finally, we demonstrate the significance of surface defects on electrosorption dynamics of complex electrolytes in hierarchical pore architectures of supercapacitor electrodes.« less

In-vehicle group activity modeling and simulation in sensor-based virtual environment

NASA Astrophysics Data System (ADS)

Shirkhodaie, Amir; Telagamsetti, Durga; Poshtyar, Azin; Chan, Alex; Hu, Shuowen

2016-05-01

Human group activity recognition is a very complex and challenging task, especially for Partially Observable Group Activities (POGA) that occur in confined spaces with limited visual observability and often under severe occultation. In this paper, we present IRIS Virtual Environment Simulation Model (VESM) for the modeling and simulation of dynamic POGA. More specifically, we address sensor-based modeling and simulation of a specific category of POGA, called In-Vehicle Group Activities (IVGA). In VESM, human-alike animated characters, called humanoids, are employed to simulate complex in-vehicle group activities within the confined space of a modeled vehicle. Each articulated humanoid is kinematically modeled with comparable physical attributes and appearances that are linkable to its human counterpart. Each humanoid exhibits harmonious full-body motion - simulating human-like gestures and postures, facial impressions, and hands motions for coordinated dexterity. VESM facilitates the creation of interactive scenarios consisting of multiple humanoids with different personalities and intentions, which are capable of performing complicated human activities within the confined space inside a typical vehicle. In this paper, we demonstrate the efficiency and effectiveness of VESM in terms of its capabilities to seamlessly generate time-synchronized, multi-source, and correlated imagery datasets of IVGA, which are useful for the training and testing of multi-source full-motion video processing and annotation. Furthermore, we demonstrate full-motion video processing of such simulated scenarios under different operational contextual constraints.

Ionic liquid structure, dynamics, and electrosorption in carbon electrodes with bimodal pores and heterogeneous surfaces

DOE PAGES

Dyatkin, Boris; Osti, Naresh C.; Zhang, Yu; ...

2017-12-05

In this paper, we investigate the aggregation, diffusion, and resulting electrochemical behavior of ionic liquids inside carbon electrodes with complex pore architectures and surface chemistries. Carbide-derived carbons (CDCs) with bimodal porosities and defunctionalized or oxidized electrode surfaces served as model electrode materials. Our goal was to obtain a fundamental understanding of room-temperature ionic liquid ion orientation, mobility, and electrosorption behavior. Neat 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide confined in CDCs was studied using an integrated experimental and modeling approach, consisting of quasielastic neutron scattering, small-angle neutron scattering, X-ray pair distribution function analysis, and electrochemical measurements, which were combined with molecular dynamics simulations. Our analysismore » shows that surface oxygen groups increase the diffusion of confined electrolytes. Consequently, the ions become more than twice as mobile in oxygen-rich pores. Although greater self-diffusion of ions translates into higher electrochemical mobilities in oxidized pores, bulk-like behavior of ions dominates in the larger mesopores and increases the overall capacitance in defunctionalized pores. Experimental results highlight strong confinement and surface effects of carbon electrodes on electrolyte behavior, and molecular dynamics simulations yield insight into diffusion and capacitance differences in specific pore regions. Finally, we demonstrate the significance of surface defects on electrosorption dynamics of complex electrolytes in hierarchical pore architectures of supercapacitor electrodes.« less

3D Numerical simulation of bed morphological responses to complex in-streamstructures

NASA Astrophysics Data System (ADS)

Xu, Y.; Liu, X.

2017-12-01

In-stream structures are widely used in stream restoration for both hydraulic and ecologicalpurposes. The geometries of the structures are usually designed to be extremely complex andirregular, so as to provide nature-like physical habitat. The aim of this study is to develop anumerical model to accurately predict the bed-load transport and the morphological changescaused by the complex in-stream structures. This model is developed in the platform ofOpenFOAM. In the hydrodynamics part, it utilizes different turbulence models to capture thedetailed turbulence information near the in-stream structures. The technique of immersedboundary method (IBM) is efficiently implemented in the model to describe the movable bendand the rigid solid body of in-stream structures. With IBM, the difficulty of mesh generation onthe complex geometry is greatly alleviated, and the bed surface deformation is able to becoupled in to flow system. This morphodynamics model is firstly validated by simple structures,such as the morphology of the scour in log-vane structure. Then it is applied in a more complexstructure, engineered log jams (ELJ), which consists of multiple logs piled together. Thenumerical results including turbulence flow information and bed morphological responses areevaluated against the experimental measurement within the exact same flow condition.

Ideal gas behavior of a strongly coupled complex (dusty) plasma.

PubMed

Oxtoby, Neil P; Griffith, Elias J; Durniak, Céline; Ralph, Jason F; Samsonov, Dmitry

2013-07-05

In a laboratory, a two-dimensional complex (dusty) plasma consists of a low-density ionized gas containing a confined suspension of Yukawa-coupled plastic microspheres. For an initial crystal-like form, we report ideal gas behavior in this strongly coupled system during shock-wave experiments. This evidence supports the use of the ideal gas law as the equation of state for soft crystals such as those formed by dusty plasmas.

Volcanism and Fluvio-Glacial Processes on the Interior Layered Deposits of Valles Marineris, Mars?

NASA Astrophysics Data System (ADS)

Chapman, M. G.

2005-12-01

The Interior Layered Deposits (ILDs) in Valles Marineris have been suggested to be possible sub-ice volcanoes. Recent images also show evidence of possible fluvio-glacial processes on the ILDs and hence volcano/ice/water interaction. For example, Mars Express Mission anaglyph from Orbit 334 of central Ophir and Candor Chasmata, THEMIS image V10551002, and MOC images E1700142 and E190020 show 2 ILD mounds in central Candor Chasma that have been sheared off at approximately equal elevations by some material that has been subsequently removed. Level shearing of ILD rock materials and subsequent removal of the abrasive material, suggest ice erosion and glacial processes because glacial ice is mobile enough to grind the rock and can melt away. Another adjacent ILD mound in Central Candor shows an abrupt flank termination and damming of material, rather than flank scour. The dammed material appears to be layers piled up in a ridge at the ILD base. This relation is observed on the HRSC anaglyph and MOC images E0101343 and E201146. Another ILD in Melas Chasma, seen on MOC image M0804981, shows lobes of flank material that terminate along a lineation; possibly suggesting lobe confinement against subsequently removed material. This morphology can also be observed on the flank of the Gangis Chasma ILD in MOC image M0705587. A possible terrestrial volcanic analog for this ILD flank morphology is the Helgafell hyaloclasitic ridge (tindar) in Iceland (Chapman et al., 2004), the eastern flank of which has a linear termination interpreted as largely unmodified and caused by hyalotuff material banked against a former ice wall that has since melted away (Schopka et al., 2003). Glacial shearing of some ILDs and confined banking of other ILDs suggest that these mounds formed at different times, as the sheared ILD likely predated ice and the confined ILD may have formed concurrently with ice. Alternatively, the banking may have been due to lack of shear forces (static ice) and confined post-depositional avalanche deposits. However, exposed in the banked cliff faces are near horizontal bedding planes that can be traced upslope into angled flank layers; a relation that may suggest ice concurrent with volcanic ILD formation (Chapman and Smellie, in press). In addition to glacial processes, many Mars ILDs show fluvial gullies cut into mostly low lying flank deposits. Gullies are eroded into all sides of the ILDs including their north-facing slopes, so solar heating likely did not generate the gullies. Although formal work on the subject is lacking, ongoing terrestrial observation by the author (on an edifice north of Helgafell and in Gjalp eruption films) indicate fluvial erosion of subglacial volcanoes on Earth may be concurrent with their formation, occurring after edifices rise above their surrounding ice-confined meltwater lake. Remnant ice on the top of the edifices can melt to generate streams that erode the growing volcanic flanks.

Dendritic Cytoskeletal Architecture Is Modulated by Combinatorial Transcriptional Regulation in Drosophila melanogaster.

PubMed

Das, Ravi; Bhattacharjee, Shatabdi; Patel, Atit A; Harris, Jenna M; Bhattacharya, Surajit; Letcher, Jamin M; Clark, Sarah G; Nanda, Sumit; Iyer, Eswar Prasad R; Ascoli, Giorgio A; Cox, Daniel N

2017-12-01

Transcription factors (TFs) have emerged as essential cell autonomous mediators of subtype specific dendritogenesis; however, the downstream effectors of these TFs remain largely unknown, as are the cellular events that TFs control to direct morphological change. As dendritic morphology is largely dictated by the organization of the actin and microtubule (MT) cytoskeletons, elucidating TF-mediated cytoskeletal regulatory programs is key to understanding molecular control of diverse dendritic morphologies. Previous studies in Drosophila melanogaster have demonstrated that the conserved TFs Cut and Knot exert combinatorial control over aspects of dendritic cytoskeleton development, promoting actin and MT-based arbor morphology, respectively. To investigate transcriptional targets of Cut and/or Knot regulation, we conducted systematic neurogenomic studies, coupled with in vivo genetic screens utilizing multi-fluor cytoskeletal and membrane marker reporters. These analyses identified a host of putative Cut and/or Knot effector molecules, and a subset of these putative TF targets converge on modulating dendritic cytoskeletal architecture, which are grouped into three major phenotypic categories, based upon neuromorphometric analyses: complexity enhancer, complexity shifter, and complexity suppressor. Complexity enhancer genes normally function to promote higher order dendritic growth and branching with variable effects on MT stabilization and F-actin organization, whereas complexity shifter and complexity suppressor genes normally function in regulating proximal-distal branching distribution or in restricting higher order branching complexity, respectively, with spatially restricted impacts on the dendritic cytoskeleton. Collectively, we implicate novel genes and cellular programs by which TFs distinctly and combinatorially govern dendritogenesis via cytoskeletal modulation. Copyright © 2017 by the Genetics Society of America.

Spelling and Morphology in Dyslexia: A Developmental Study Across the School Years.

PubMed

Schiff, Rachel; Levie, Ronit

2017-11-01

The current study examined the effect of morphological knowledge on spelling development in Hebrew-speaking schoolchildren, adolescents and adults with dyslexia, compared with typically developing (TD) peers. Participants were 238 Hebrew-speaking readers of five grade levels of whom 139 were TD and 99 had developmental dyslexia (DD). Participants were tested on a function letter spelling task, a phonological awareness task and a morphological awareness task. The overall picture that emerged from the results is that performance on all measures increased with grade level, with TD participants always scoring higher than peers with DD. Moreover, the higher the morphological complexity in spelling and irregularity in noun inflection, the higher the differences between the DD and TD participants. Finally, performance on the morphological awareness task contributed to spelling morphologically more complex spelling items in the TD, but not in the DD group. From clinical and educational perspectives, these results strongly suggest that rigorous morphological instruction is necessary in teaching children and adolescents with dyslexia to identify and use morphological cues in spoken and written Hebrew. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

[Utility of the direct culture examination (Ziehl-Neelsen) using the Bactec system for the presumptive identification of Mycobacterium tuberculosis complex, Mycobacterium avium complex, Mycobacterium xenopi, and Mycobacterium kansasii].

PubMed

Moreno, C; Garrigó, M; Sánchez, F; Coll, P

1994-05-01

The usefulness of the microscopic examination of Bactec 12B and 13A growth medium as a method for the possible identification of M. tuberculosis complex, M. avium complex, M. xenopi, and M. kansasii was performed out to guide the selection of different genetic identification probes and, in the case of M. xenopi, the selection of the temperature of subcultures incubation. Upon detection of an index of growth greater than 100 in Bactec tubes, staining was performed by the Ziehl-Neelsen technique. On the basis of the morphology observed, the possible identification was performed by genetic probes. Subcultures were used for definitive identification. Three hundred forty-four positive samples were studied by radiometric technique. A total of 190 strains were identified as M. tuberculosis, 88 strains as M. avium-intracellulare (MAI), 33 strains as M. xenopi, 14 strains as M. kansasii and 19 strains were identified as: M. gordonae (10), unpigmented rapid growth microbacteria (7), and M. simiae (2). Sensitivity, specificity, positive predictive value, and negative predictive value were 97.9%, 95.4%, 96.4%, and 97.3%, respectively for M. tuberculosis complex, 84.0%, 99.2%, 97.3% 94.7% for M. avium complex; 63.6%, 98.3%, 80.7%, 96.2% for M. xenopi; 35.7%, 98.1%, 45.5% 97.2% for M. kansasii. The morphology of M. tuberculosis complex examined in the radiometric system in useful to differentiate this species from other microbacteria (MOTT), allowing the selection of specific probe used. Within the MOTT, M. avium complex also has morphological characteristics which are useful for its differentiation, the morphology usually described for the remaining species was frequently not observed.

Strain-induced alignment and phase behavior of blue phase liquid crystals confined to thin films.

PubMed

Bukusoglu, Emre; Martinez-Gonzalez, Jose A; Wang, Xiaoguang; Zhou, Ye; de Pablo, Juan J; Abbott, Nicholas L

2017-12-06

We report on the influence of surface confinement on the phase behavior and strain-induced alignment of thin films of blue phase liquid crystals (BPs). Confining surfaces comprised of bare glass, dimethyloctadecyl [3-(trimethoxysilyl)propyl] ammonium chloride (DMOAP)-functionalized glass, or polyvinyl alcohol (PVA)-coated glass were used with or without mechanically rubbing to influence the azimuthal anchoring of the BPs. These experiments reveal that confinement can change the phase behavior of the BP films. For example, in experiments performed with rubbed-PVA surfaces, we measured the elastic strain of the BPs to change the isotropic-BPII phase boundary, suppressing formation of BPII for film thicknesses incommensurate with the BPII lattice. In addition, we observed strain-induced alignment of the BPs to exhibit a complex dependence on both the surface chemistry and azimuthal alignment of the BPs. For example, when using bare glass surfaces causing azimuthally degenerate and planar anchoring, BPI oriented with (110) planes of the unit cell parallel to the contacting surfaces for thicknesses below 3 μm but transitioned to an orientation with (200) planes aligned parallel to the contacting surfaces for thicknesses above 4 μm. In contrast, BPI aligned with (110) planes parallel to confining surfaces for all other thicknesses and surface treatments, including bare glass with uniform azimuthal alignment. Complementary simulations based on minimization of the total free energy (Landau-de Gennes formalism) confirmed a thickness-dependent reorientation due to strain of BPI unit cells within a window of surface anchoring energies and in the absence of uniform azimuthal alignment. In contrast to BPI, BPII did not exhibit thickness-dependent orientations but did exhibit orientations that were dependent on the surface chemistry, a result that was also captured in simulations by varying the anchoring energies. Overall, the results in this paper reveal that the orientations assumed by BPs in thin films reflect a complex interplay of surface interactions and elastic energies associated with strain of the BP lattice. The results also provide new principles and methods to control the structure and properties of BP thin films, which may find use in BP-templated material synthesis, and BP-based optical and electronic devices.

Cytogeography and chromosome evolution of subgenus Tridentatae of Artemisia (Asteraceae)

Treesearch

E. Durant McArthur; Stewart C. Sanderson

1999-01-01

The subgenus Tridentatae of Artemisia (Asteraceae: Anthemideae) is composed of 11 species of various taxonomic and geographic complexities. It is centered on Artemisia tridentata with its three widespread common subspecies and two more geographically confined ones. Meiotic chromosome counts on pollen mother cells...

Synthesis and characterization of PVK/AgNPs nanocomposites prepared by laser ablation.

PubMed

Abd El-Kader, F H; Hakeem, N A; Elashmawi, I S; Menazea, A A

2015-03-05

Nanocomposites of Poly (n-vinylcarbazole) PVK/Ag nanoparticles were prepared by laser ablation of a silver plate in aqueous solution of chlorobenzene. The influences of laser parameters such as; time of irradiation, source power and wavelength (photon energy) on structural, morphological and optical properties have been investigated using X-ray diffraction (XRD), Transmission electron microscopy (TEM), Ultraviolet-visible (UV-Vis) and Photoluminescence (PL). A correlation between the investigated properties has been discussed. XRD, TEM and PL indicated that the complexation between AgNPs and PVK in the composite system is possible. Only the reflection peak at 2θ=38° of AgNPs appeared in the composite nanoparticles while the other reflection peaks were destroyed. The nanoparticles shape and size distribution were evaluated from TEM images. TEM analysis revealed a lower average particle size at long laser irradiation time 40min and short laser wavelength 532nm together with high laser power 570mW. From UV-Visible spectra the values of absorption coefficient, absorption edge and energy tail were calculated. The reduction of band tail value with increasing the laser ablation parameters confirms the decrease of the disorder in such composite system. The PL and UV-Vis. spectra confirm that nanocomposite samples showed quantum confinement effect. Copyright © 2014 Elsevier B.V. All rights reserved.

Epithelial cytoskeletal framework and nuclear matrix-intermediate filament scaffold: three-dimensional organization and protein composition.

PubMed

Fey, E G; Wan, K M; Penman, S

1984-06-01

Madin-Darby canine kidney (MDCK) cells grow as differentiated, epithelial colonies that display tissue-like organization. We examined the structural elements underlying the colony morphology in situ using three consecutive extractions that produce well-defined fractions for both microscopy and biochemical analysis. First, soluble proteins and phospholipid were removed with Triton X-100 in a physiological buffer. The resulting skeletal framework retained nuclei, dense cytoplasmic filament networks, intercellular junctional complexes, and apical microvillar structures. Scanning electron microscopy showed that the apical cell morphology is largely unaltered by detergent extraction. Residual desmosomes, as can be seen in thin sections, were also well-preserved. The skeletal framework was visualized in three dimensions as an unembedded whole mount that revealed the filament networks that were masked in Epon-embedded thin sections of the same preparation. The topography of cytoskeletal filaments was relatively constant throughout the epithelial sheet, particularly across intercellular borders. This ordering of epithelial skeletal filaments across contiguous cell boundaries was in sharp contrast to the more independent organization of networks in autonomous cells such as fibroblasts. Further extraction removed the proteins of the salt-labile cytoskeleton and the chromatin as separate fractions, and left the nuclear matrix-intermediate filament (NM-IF) scaffold. The NM-IF contained only 5% of total cellular protein, but whole mount transmission electron microscopy and immunofluorescence showed that this scaffold was organized as in the intact epithelium. Immunoblots demonstrate that vimentin, cytokeratins, desmosomal proteins, and a 52,000-mol-wt nuclear matrix protein were found almost exclusively in the NM-IF scaffold. Vimentin was largely perinuclear while the cytokeratins were localized at the cell borders. The 52,000-mol-wt nuclear matrix protein was confined to the chromatin-depleted matrix and the desmosomal proteins were observed in punctate polygonal arrays at intercellular junctions. The filaments of the NM-IF were seen to be interconnected, via the desmosomes, over the entire epithelial colony. The differentiated epithelial morphology was reflected in both the cytoskeletal framework and the NM-IF scaffold.

Epithelial cytoskeletal framework and nuclear matrix-intermediate filament scaffold: three-dimensional organization and protein composition

PubMed Central

1984-01-01

Madin-Darby canine kidney (MDCK) cells grow as differentiated, epithelial colonies that display tissue-like organization. We examined the structural elements underlying the colony morphology in situ using three consecutive extractions that produce well-defined fractions for both microscopy and biochemical analysis. First, soluble proteins and phospholipid were removed with Triton X-100 in a physiological buffer. The resulting skeletal framework retained nuclei, dense cytoplasmic filament networks, intercellular junctional complexes, and apical microvillar structures. Scanning electron microscopy showed that the apical cell morphology is largely unaltered by detergent extraction. Residual desmosomes, as can be seen in thin sections, were also well- preserved. The skeletal framework was visualized in three dimensions as an unembedded whole mount that revealed the filament networks that were masked in Epon-embedded thin sections of the same preparation. The topography of cytoskeletal filaments was relatively constant throughout the epithelial sheet, particularly across intercellular borders. This ordering of epithelial skeletal filaments across contiguous cell boundaries was in sharp contrast to the more independent organization of networks in autonomous cells such as fibroblasts. Further extraction removed the proteins of the salt-labile cytoskeleton and the chromatin as separate fractions, and left the nuclear matrix-intermediate filament (NM-IF) scaffold. The NM-IF contained only 5% of total cellular protein, but whole mount transmission electron microscopy and immunofluorescence showed that this scaffold was organized as in the intact epithelium. Immunoblots demonstrate that vimentin, cytokeratins, desmosomal proteins, and a 52,000-mol-wt nuclear matrix protein were found almost exclusively in the NM-IF scaffold. Vimentin was largely perinuclear while the cytokeratins were localized at the cell borders. The 52,000-mol-wt nuclear matrix protein was confined to the chromatin- depleted matrix and the desmosomal proteins were observed in punctate polygonal arrays at intercellular junctions. The filaments of the NM-IF were seen to be interconnected, via the desmosomes, over the entire epithelial colony. The differentiated epithelial morphology was reflected in both the cytoskeletal framework and the NM-IF scaffold. PMID:6202700

Development of levees on deep-sea channels: Insights from high-resolution AUV exploration of the Lucia Chica system, offshore central California

NASA Astrophysics Data System (ADS)

Maier, K. L.; Fildani, A.; Romans, B.; Paull, C. K.; McHargue, T.; Graham, S. A.; Caress, D. W.

2010-12-01

The Lucia Chica, a tributary channel system of the Lucia Canyon, offshore central California, was imaged using the Monterey Bay Aquarium Research Institute’s (MBARI) Autonomous Underwater Vehicle (AUV) in order to investigate seafloor and subsurface morphologies associated with low-relief submarine channels. In larger, previously investigated seafloor channel-levee systems, initial deposits are either eroded, compacted, or below the resolution of available imaging. In this dataset from the Lucia Chica, the unprecedented high-resolution multibeam bathymetry (1 m lateral resolution) and chirp sub-bottom profiles (11 cm vertical resolution) reveal a highly irregular seafloor with scours, depressions, and discontinuous low-relief conduits over an area of ~70 km2. Sediment packages associated with channels, levees, and deposits related to less confined flows are correlated between chirp profiles and with the multibeam bathymetric image to determine the stratigraphic evolution of the Lucia Chica and the sequence of channel-levee development. In the Lucia Chica, channels appear to have initiated as trains of scours that eventually coalesced into continuous channel thalwegs carved by erosional turbidity currents. Channel incision and stepped lateral migration led to the development of terraces, complex levee stratigraphy, and distinct morphologies associated with inner and outer bends of sinuous channels. The inner bend levee stratigraphy indicates that the channel position migrated in discrete shifts, as opposed to continuous channel migration associated with lateral accretion. Discrete levee packages, formed from flow-stripped turbidity currents, later infilled abandoned portions of the channel and overbank areas. While processes of initial channel and levee development are well established in fluvial settings, detailed examples are lacking for deep-sea systems. These results highlight the differences in initiation between submarine channel systems, their fluvial counterparts, and larger submarine channel-levee systems imaged only with lower-resolution technologies. High-resolution imaging and detailed mapping made possible by cutting-edge oceanographic technology provide an unprecedented examination of deep-water channel-levee morphology and improve understanding of deep-water channel migration and levee development.

From lizard body form to serpentiform morphology: The atlas-axis complex in African cordyliformes and their relatives.

PubMed

Čerňanský, Andrej

2016-04-01

The comparative vertebral morphology of the atlas-axis complex in cordyliforms, xantusiid and several skinks is studied here. These lizards are particularly interesting because of their different ecological adaptations and anti-predation strategies, where conformation ranges from the lizard-like body to a snake-like body. This transition to serpentiform morphology shows several evolutionary patterns in the atlas-axis complex: 1) the zygapophyseal articulations are lost in the early stage of the transition. In contrast to mammals, the atlas is more or less locked to the axis in lepidosaurs, but the absence of zygapophyseal articulation releases this locking for rotation. However despite its serpentiform morphology, Chamaesaura is different, in possessing this articulation; 2) the first intercentrum of Chamaesaura and Tetradactylus africanus (serpentiform grass-swimmers) is fully curved anteriorly, underlying the occipital condyle. While this limits ventral skull rotation beyond a certain angle, it locks the skull, which is a crucial adaptation for a sit-and-wait position in grassland habitats that needs to keep the head stabilized; and 3) in Acontias, most of the atlas articular surface with the occipital condyle is formed by the lateral aspect of the articulation area relative to the area located in the dorsal region of the slightly reduced intercentrum. A similar state occurs in amphisbaenians, most likely reflecting a fossorial lifestyle of the limbless lizards. Although Chamaesaura and Tetradactylus live sympatrically in grasslands, Chamaesaura differs in several ways in atlas-axis complex: for example, aforementioned presence of the atlas-axis zygapophyseal articulation, and long posterodorsal processes. Its occipital condyle protrudes further posteriorly, placing the atlas-axis complex further from the endocranium than in Tetradactylus. Hence, adaptation in the same niche, even among sister clades, can lead to different atlas-axis morphology due to different lifestyle strategies, for example, different foraging mode, while similar atlas-axis morphology can evolve in two lineages occupying different niches, as in Ablepharus and Scelotes. © 2016 Wiley Periodicals, Inc.

Reverse micelle synthesis of nanoscale metal containing catalysts

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

Darab, J.G.; Fulton, J.L.; Linehan, J.C.

1993-03-01

The need for morphological control during the synthesis of catalyst precursor powders is generally accepted to be important. In the liquefaction of coal, for example, iron-bearing catalyst precursor particles containing individual crystallites with diameters in the 1-100 nanometer range are believed to achieve good dispersion through out the coal-solvent slurry during liquefaction 2 runs and to undergo chemical transformations to catalytically active iron sulfide phases. The production of the nanoscale powders described here employs the confining spherical microdomains comprising the aqueous phase of a modified reverse micelle (MRM) microemulsion system as nanoscale reaction vessels in which polymerization, electrochemical reduction andmore » precipitation of solvated salts can occur. The goal is to take advantage of the confining nature of micelles to kinetically hinder transformation processes which readily occur in bulk aqueous solution in order to control the morphology and phase of the resulting powder. We have prepared a variety of metal, alloy, and metal- and mixed metal-oxide nanoscale powders from appropriate MRM systems. Examples of nanoscale powders produced include Co, Mo-Co, Ni{sub 3}Fe, Ni, and various oxides and oxyhydroxides of iron. Here, we discuss the preparation and characterization of nickel metal (with a nickel oxide surface layer) and iron oxyhydroxide MRM nanoscale powders. We have used extended x-ray absorption fine structure (EXAFS) spectroscopy to study the chemical polymerization process in situ, x-ray diffraction (XRD), scanning and transmission electron microcroscopies (SEM and TEM), elemental analysis and structural modelling to characterize the nanoscale powders produced. The catalytic activity of these powders is currently being studied.« less

Morphological and molecular characterization of a microsporidian parasite, Takaokaspora nipponicus n. gen., n. sp. from the invasive rock pool mosquito, Ochlerotatus japonicus japonicus.

PubMed

Andreadis, Theodore G; Takaoka, Hiroyuki; Otsuka, Yasushi; Vossbrinck, Charles R

2013-10-01

A new genus and species of Microsporidia, Takaokaspora nipponicus n. gen., n. sp. is described from Ochlerotatus japonicus japonicus (Theobald) and Ochlerotatus hatorii (Yamada) based on light microscope and ultrastructural morphology, developmental features, transmission cycles and comparative sequence analyses of the small subunit ribosomal DNA (SSU rDNA). The microsporidium is both vertically and horizontally transmitted, exhibits dimorphic development alternating between diplokaryotic and monokaryotic stages and produces two morphologically distinct spores, one in larvae and another in adult females. Horizontal transmission of infection to larval mosquitoes occurs via direct oral ingestion of uninucleate spores that are produced in vertically-infected larval hosts. Development in horizontally-infected hosts is diplokaryotic following karyokinesis of uninucleate schizonts and binary fission to produce small (4.3μm × 2.0μm) membrane free, ovoid, binucleate spores that are confined to adult female reproductive tissues (ovariole sheath and oviducts). Vertical transmission of the microsporidium from adult females to larval progeny takes place via surface contamination of the egg (transovum). Microsporidian development in vertically-infected larvae is haplophasic with unpaired nuclei throughout, producing rosette-shaped sporogonial plasmodia contained within a thin non-persistent sporophorous vesicle and culminating in the formation of membrane free, uninucleate, conical spores (7.0μm×2.8μm). Development is confined to host fat body tissue which appears as swollen white masses in the thorax and selected segments of the abdomen causing larvae to appear abnormally distorted and results in death during the third and fourth instar stages. The SSU rDNA sequences obtained from the two morphologically identical microsporidia isolated from Oc. j. japonicus and Oc. hatorii were nearly identical and unique when compared with GenBank entries of all other mosquito-parasitic species. Phylogenetic trees constructed by Maximum Parsimony, Maximum Likelihood and bootstrap analyses using the Neighbor Joining search parameter yielded similar typologies. In each case, the novel microsporidium was the sister group to the clade containing Parathelohania species from Anopheles mosquitoes and the monotypic Novothelohania ovalae from Ochlerotatus caspius showing approximately 10-13% sequence divergence to those two genera providing strong support for establishment as a separate genus. Copyright © 2013 Elsevier Inc. All rights reserved.

Linguistic Models, Acquisition Theories, and Learner Corpora: Morphological Productivity in SLA Research Exemplified by Complex Verbs in German

ERIC Educational Resources Information Center

Lüdeling, Anke; Hirschmann, Hagen; Shadrova, Anna

2017-01-01

The present study analyzes morphological productivity for complex verbs in second language acquisition by analyzing a corpus of German as a Foreign Language (GFL). It shows that advanced learners of GFL use prefix and particle verbs relatively frequently and productively but less so than native speakers do and discusses these findings in the light…

New Evidence for Morphological Errors in Deep Dyslexia

ERIC Educational Resources Information Center

Rastle, Kathleen; Tyler, Lorraine K.; Marslen-Wilson, William

2006-01-01

Morphological errors in reading aloud (e.g., "sexist" [right arrow] "sexy") are a central feature of the symptom-complex known as deep dyslexia, and have historically been viewed as evidence that representations at some level of the reading system are morphologically structured. However, it has been proposed (Funnell, 1987) that morphological…

The False-Friend Effect in Three Profoundly Deaf Learners of French: Disentangling Morphology, Phonology and Orthography

ERIC Educational Resources Information Center

Janke, Vikki; Kolokonte, Marina

2015-01-01

Three profoundly deaf individuals undertook a low-frequency backward lexical translation task (French/English), where morphological structure was manipulated and orthographic distance between test items was measured. Conditions included monomorphemic items (simplex), polymorphemic items (complex), items whose French morphological structure…

Reading Error Patterns Prevailing in Arab Emirati First Graders

ERIC Educational Resources Information Center

Natour, Yaser S.; Darawsheh, Wesam; Sartawi, AbdelAziz M.; Marie, Basem A.; Efthymiou, Effie

2016-01-01

There is a contemporary emphasis on researching the effects of phonological awareness on reading skills though morphological awareness correlates more highly with reading. The purpose of the study was to investigate the patterns of reading errors from a morphological perspective (level of morphological complexity) and lexical category. One hundred…

Retro-action model for the erosion of rocky coasts

NASA Astrophysics Data System (ADS)

Sapoval, B.; Baldassarri, A.

2009-12-01

Rocky coasts are estimated to represent 75% of the world’s shorelines [1]. We discuss various situations where the formation of rocky coast morphology could be attributed to the retro-action of the coast morphology on the erosive power of the see. In the case of rocky coasts, erosion can spontaneously create irregular seashores. But, in turn, the geometrical irregularity participates to the damping of sea-waves, decreasing the average wave amplitude and erosive power. There may then exist a mutual self-stabilization of the waves amplitude together with the irregular morphology of the coast. A simple model of such stabilization is discussed. It leads, through a complex dynamics of the earth-sea interface, to the spontaneous appearance of an irregular sea-shore. The final coast morphology is found to depend on the morphology/damping coupling of the coast and on the possible existence of built-in correlations within the coast lithologic properties. This is illustrated in the figure. In the limit case where the morphology/damping coupling is weak and when the earth lithology distribution exhibit only short range correlations, the process spontaneously build fractal morphologies with a dimension close to 4/3 [2]. It is shown that this dimension refers to the dimension of the so-called accessible perimeter in gradient percolation. However, even rugged but non-fractal sea-coasts morphology may emerge for strong damping or during the erosion process. When the distributions of the lithologies exhibit long range correlations, a variety of complex morphologies are obtained which mimics observed coastline complexity, well beyond simple fractality. On a somewhat different perspective, the design of breakwaters is suggested to be improved by using global irregular geometry with features sizes of the order of the wave-length of the sea oscillations. [1] R. A. Davis, Jr, D. M. Fitzgerald, Beaches and Coasts,(Blackwell, Oxford 2004). [2] B. Sapoval, A. Baldassarri, A. Gabrielli, Self-stabilized Fractality of Sea-coasts through Erosion, Phys. Rev. Lett. 93, 098501 (2004). Time evolution of the coastline morphology starting with a flat sea-shore. Left and right columns correspond respectively to weak and strong coupling. Top to bottom: suc- cessive morphologies with the final morphologies at the bottom.

Selective Co-Encapsulation Inside an M6 L4 Cage.

PubMed

Leenders, Stefan H A M; Becker, René; Kumpulainen, Tatu; de Bruin, Bas; Sawada, Tomohisa; Kato, Taito; Fujita, Makoto; Reek, Joost N H

2016-10-17

There is broad interest in molecular encapsulation as such systems can be utilized to stabilize guests, facilitate reactions inside a cavity, or give rise to energy-transfer processes in a confined space. Detailed understanding of encapsulation events is required to facilitate functional molecular encapsulation. In this contribution, it is demonstrated that Ir and Rh-Cp-type metal complexes can be encapsulated inside a self-assembled M 6 L 4 metallocage only in the presence of an aromatic compound as a second guest. The individual guests are not encapsulated, suggesting that only the pair of guests can fill the void of the cage. Hence, selective co-encapsulation is observed. This principle is demonstrated by co-encapsulation of a variety of combinations of metal complexes and aromatic guests, leading to several ternary complexes. These experiments demonstrate that the efficiency of formation of the ternary complexes depends on the individual components. Moreover, selective exchange of the components is possible, leading to formation of the most favorable complex. Besides the obvious size effect, a charge-transfer interaction may also contribute to this effect. Charge-transfer bands are clearly observed by UV/Vis spectrophotometry. A change in the oxidation potential of the encapsulated electron donor also leads to a shift in the charge-transfer energy bands. As expected, metal complexes with a higher oxidation potential give rise to a higher charge-transfer energy and a larger hypsochromic shift in the UV/Vis spectrum. These subtle energy differences may potentially be used to control the binding and reactivity of the complexes bound in a confined space. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Influence of confinement on polymer-electrolyte relaxational dynamics.

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

Zanotti, J.-M.; Smith, L. J.; Price, D. L.

2004-01-01

Conception and industrial production of viable high specific energy/power batteries is a central issue for the development of non-polluting vehicles. In terms of stored energy and safety, solid-state devices using polymer electrolytes are highly desirable. One of the most studied systems is PEO (polyethylene oxide) complexed by Li salts. Polymer segmental motions and ionic conductivity are closely related. Bulk PEO is actually a biphasic system where an amorphous and a crystalline state (Tm 335 K) coexist. To improve ionic conduction in those systems requires a significant increase of the amorphous phase fraction where lithium conduction is known to mainly takemore » place. Confinement strongly affects properties of condensed matter and in particular the collective phenomena inducing crystallization. Confinement of the polymer matrix is therefore a possible alternative route to the unpractical use of high temperature. Results of a quasi-elastic incoherent neutron scattering study of the influence of confinement on polyethylene oxide (PEO) and (PEO)8Li+[(CF3SO2)2N]- (or (POE)8LiTFSI) dynamics are presented. The nano-confining media is Vycor, a silica based hydrophilic porous glass (characteristic size of the 3D pore network 50 {angstrom}). As expected, the presence of Li salt slows down the bulk polymer dynamics. The confinement also affects dramatically the apparent mean-square displacement of the polymer. Local relaxational PEO dynamics is described KWW model. We also present an alternate model and show how the detailed polymer dynamics (correlation times and local geometry of the motions) can be described without the use of such stretched exponentials so as to access a rheology-related meaningful physical quantity: the monomeric friction coefficient.« less

Interplay between morphology and frequency in lexical access: The case of the base frequency effect

PubMed Central

Vannest, Jennifer; Newport, Elissa L.; Newman, Aaron J.; Bavelier, Daphne

2011-01-01

A major issue in lexical processing concerns storage and access of lexical items. Here we make use of the base frequency effect to examine this. Specifically, reaction time to morphologically complex words (words made up of base and suffix, e.g., agree+able) typically reflects frequency of the base element (i.e., total frequency of all words in which agree appears) rather than surface word frequency (i.e., frequency of agreeable itself). We term these complex words decomposable. However, a class of words termed whole-word do not show such sensitivity to base frequency (e.g., serenity). Using an event-related MRI design, we exploited the fact that processing low-frequency words increases BOLD activity relative to high frequency ones, and examined effects of base frequency on brain activity for decomposable and whole-word items. Morphologically complex words, half high and half low base frequency, were compared to matched high and low frequency simple monomorphemic words using a lexical decision task. Morphologically complex words increased activation in left inferior frontal and left superior temporal cortices versus simple words. The only area to mirror the behavioral distinction between decomposable and whole-word types was the thalamus. Surprisingly, most frequency-sensitive areas failed to show base frequency effects. This variety of responses to frequency and word type across brain areas supports an integrative view of multiple variables during lexical access, rather than a dichotomy between memory-based access and on-line computation. Lexical access appears best captured as interplay of several neural processes with different sensitivities to various linguistic factors including frequency and morphological complexity. PMID:21167136

New constraints on the spatial distribution and morphology of the Halimeda bioherms of the Great Barrier Reef, Australia

NASA Astrophysics Data System (ADS)

McNeil, Mardi A.; Webster, Jody M.; Beaman, Robin J.; Graham, Trevor L.

2016-12-01

Halimeda bioherms occur as extensive geological structures on the northern Great Barrier Reef (GBR), Australia. We present the most complete, high-resolution spatial mapping of the northern GBR Halimeda bioherms, based on new airborne lidar and multibeam echosounder bathymetry data. Our analysis reveals that bioherm morphology does not conform to the previous model of parallel ridges and troughs, but is far more complex than previously thought. We define and describe three morphological sub-types: reticulate, annulate, and undulate, which are distributed in a cross-shelf pattern of reduced complexity from east to west. The northern GBR bioherms cover an area of 6095 km2, three times larger than the original estimate, exceeding the area and volume of calcium carbonate in the adjacent modern shelf-edge barrier reefs. We have mapped a 1740 km2 bioherm complex north of Raine Island in the Cape York region not previously recorded, extending the northern limit by more than 1° of latitude. Bioherm formation and distribution are controlled by a complex interaction of outer-shelf geometry, regional and local currents, coupled with the morphology and depth of continental slope submarine canyons determining the delivery of cool, nutrient-rich water upwelling through inter-reef passages. Distribution and mapping of Halimeda bioherms in relation to Great Barrier Reef Marine Park Authority bioregion classifications and management zones are inconsistent and currently poorly defined due to a lack of high-resolution data not available until now. These new estimates of bioherm spatial distribution and morphology have implications for understanding the role these geological features play as structurally complex and productive inter-reef habitats, and as calcium carbonate sinks which record a complete history of the Holocene post-glacial marine transgression in the northern GBR.

The scaling of complex craters

NASA Technical Reports Server (NTRS)

Croft, S. K.

1985-01-01

The empirical relation between the transient crater diameter (Dg) and final crater diameter (Dr) of complex craters and basins is estimated using cumulative terrace widths, central uplift diameters, continuous ejecta radii, and transient crater reconstructions determined from lunar and terrestrial impact structures. The ratio Dg/Dr is a power law function of Dr, decreasing uniformly from unity at the diameter of the simple-complex crater morphology transition to about 0.5 for large multiring basins like Imbrium on the moon. The empirical constants in the Dg/Dr relation are interpreted physically to mean that the position of the final rim relative to the transient crater, and hence the extent of collapse, is controlled or greatly influenced by the properties of the zone of dissociated material produced by the impact shock. The continuity of the Dg/Dr relation over the entire spectrum of morphologic types from complex craters to multiring basins implies that the rims of all these structures form in the same tectonic environment despite morphologic differences.

Kinetic turbulence simulations at extreme scale on leadership-class systems

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

Wang, Bei; Ethier, Stephane; Tang, William

2013-01-01

Reliable predictive simulation capability addressing confinement properties in magnetically confined fusion plasmas is critically-important for ITER, a 20 billion dollar international burning plasma device under construction in France. The complex study of kinetic turbulence, which can severely limit the energy confinement and impact the economic viability of fusion systems, requires simulations at extreme scale for such an unprecedented device size. Our newly optimized, global, ab initio particle-in-cell code solving the nonlinear equations underlying gyrokinetic theory achieves excellent performance with respect to "time to solution" at the full capacity of the IBM Blue Gene/Q on 786,432 cores of Mira at ALCFmore » and recently of the 1,572,864 cores of Sequoia at LLNL. Recent multithreading and domain decomposition optimizations in the new GTC-P code represent critically important software advances for modern, low memory per core systems by enabling routine simulations at unprecedented size (130 million grid points ITER-scale) and resolution (65 billion particles).« less

Tuning and Switching a Plasmonic Quantum Dot "Sandwich" in a Nematic Line Defect.

PubMed

Mundoor, Haridas; Sheetah, Ghadah H; Park, Sungoh; Ackerman, Paul J; Smalyukh, Ivan I; van de Lagemaat, Jao

2018-03-27

We study the quantum-mechanical effects arising in a single semiconductor core/shell quantum dot (QD) controllably sandwiched between two plasmonic nanorods. Control over the position and the "sandwich" confinement structure is achieved by the use of a linear-trap liquid crystal (LC) line defect and laser tweezers that "push" the sandwich together. This arrangement allows for the study of exciton-plasmon interactions in a single structure, unaltered by ensemble effects or the complexity of dielectric interfaces. We demonstrate the effect of plasmonic confinement on the photon antibunching behavior of the QD and its luminescence lifetime. The QD behaves as a single emitter when nanorods are far away from the QD but shows possible multiexciton emission and a significantly decreased lifetime when tightly confined in a plasmonic "sandwich". These findings demonstrate that LC defects, combined with laser tweezers, enable a versatile platform to study plasmonic coupling phenomena in a nanoscale laboratory, where all elements can be arranged almost at will.

Tuning and Switching a Plasmonic Quantum Dot “Sandwich” in a Nematic Line Defect

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

Mundoor, Haridas; Sheetah, Ghadah H.; Park, Sungoh

We study the quantum-mechanical effects arising in a single semiconductor core/shell quantum dot (QD) controllably sandwiched between two plasmonic nanorods. Control over the position and the 'sandwich' confinement structure is achieved by the use of a linear-trap liquid crystal (LC) line defect and laser tweezers that 'push' the sandwich together. This arrangement allows for the study of exciton-plasmon interactions in a single structure, unaltered by ensemble effects or the complexity of dielectric interfaces. We demonstrate the effect of plasmonic confinement on the photon antibunching behavior of the QD and its luminescence lifetime. The QD behaves as a single emitter whenmore » nanorods are far away from the QD but shows possible multiexciton emission and a significantly decreased lifetime when tightly confined in a plasmonic 'sandwich'. These findings demonstrate that LC defects, combined with laser tweezers, enable a versatile platform to study plasmonic coupling phenomena in a nanoscale laboratory, where all elements can be arranged almost at will.« less

Tuning and Switching a Plasmonic Quantum Dot “Sandwich” in a Nematic Line Defect

DOE PAGES

Mundoor, Haridas; Sheetah, Ghadah H.; Park, Sungoh; ...

2018-02-28

We study the quantum-mechanical effects arising in a single semiconductor core/shell quantum dot (QD) controllably sandwiched between two plasmonic nanorods. Control over the position and the 'sandwich' confinement structure is achieved by the use of a linear-trap liquid crystal (LC) line defect and laser tweezers that 'push' the sandwich together. This arrangement allows for the study of exciton-plasmon interactions in a single structure, unaltered by ensemble effects or the complexity of dielectric interfaces. We demonstrate the effect of plasmonic confinement on the photon antibunching behavior of the QD and its luminescence lifetime. The QD behaves as a single emitter whenmore » nanorods are far away from the QD but shows possible multiexciton emission and a significantly decreased lifetime when tightly confined in a plasmonic 'sandwich'. These findings demonstrate that LC defects, combined with laser tweezers, enable a versatile platform to study plasmonic coupling phenomena in a nanoscale laboratory, where all elements can be arranged almost at will.« less

Probing the biology of cell boundary conditions through confinement of Xenopus cell-free cytoplasmic extracts.

PubMed

Bermudez, Jessica G; Chen, Hui; Einstein, Lily C; Good, Matthew C

2017-01-01

Cell-free cytoplasmic extracts prepared from Xenopus eggs and embryos have for decades provided a biochemical system with which to interrogate complex cell biological processes in vitro. Recently, the application of microfabrication and microfluidic strategies in biology has narrowed the gap between in vitro and in vivo studies by enabling formation of cell-size compartments containing functional cytoplasm. These approaches provide numerous advantages over traditional biochemical experiments performed in a test tube. Most notably, the cell-free cytoplasm is confined using a two- or three-dimensional boundary, which mimics the natural configuration of a cell. This strategy enables characterization of the spatial organization of a cell, and the role that boundaries play in regulating intracellular assembly and function. In this review, we describe the marriage of Xenopus cell-free cytoplasm and confinement technologies to generate synthetic cell-like systems, the recent biological insights they have enabled, and the promise they hold for future scientific discovery. © 2017 Wiley Periodicals, Inc.

Investigating ground effects on mixing and afterburning during a TNT explosion

NASA Astrophysics Data System (ADS)

Fedina, E.; Fureby, C.

2013-05-01

In this paper, the unconfined and semi-confined condensed phase explosions of TNT will be studied using large eddy simulations based on the unsteady, compressible, reacting, multi-species Navier-Stokes equations to gain further understanding of the physical processes involved in a condensed phase explosion and the effect of confinement on the physical processes involved. The analysis of the mixing and afterburning of TNT explosions in free air (unconfined) and near the ground (semi-confined) indicates that the combustion region of detonation products and air is determined by the vorticity patterns, which are induced by the Richtmeyer-Meshkov instabilities that arise during the explosion. When the explosive is detonated in the vicinity of a surface, the surface affects the shock propagation by creating complex shock systems, thereby changing the orientation of the vorticity, giving the afterburning a mushroom shape, and increasing performance of an explosive charge by prolonging the existence of the mixing layer and thereby the afterburning.

Advanced particle-in-cell simulation techniques for modeling the Lockheed Martin Compact Fusion Reactor

NASA Astrophysics Data System (ADS)

Welch, Dale; Font, Gabriel; Mitchell, Robert; Rose, David

2017-10-01

We report on particle-in-cell developments of the study of the Compact Fusion Reactor. Millisecond, two and three-dimensional simulations (cubic meter volume) of confinement and neutral beam heating of the magnetic confinement device requires accurate representation of the complex orbits, near perfect energy conservation, and significant computational power. In order to determine initial plasma fill and neutral beam heating, these simulations include ionization, elastic and charge exchange hydrogen reactions. To this end, we are pursuing fast electromagnetic kinetic modeling algorithms including a two implicit techniques and a hybrid quasi-neutral algorithm with kinetic ions. The kinetic modeling includes use of the Poisson-corrected direct implicit, magnetic implicit, as well as second-order cloud-in-cell techniques. The hybrid algorithm, ignoring electron inertial effects, is two orders of magnitude faster than kinetic but not as accurate with respect to confinement. The advantages and disadvantages of these techniques will be presented. Funded by Lockheed Martin.

Non-resonant Nanoscale Extreme Light Confinement

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

Subramania, Ganapathi Subramanian; Huber, Dale L.

2014-09-01

A wide spectrum of photonics activities Sandia is engaged in such as solid state lighting, photovoltaics, infrared imaging and sensing, quantum sources, rely on nanoscale or ultrasubwavelength light-matter interactions (LMI). The fundamental understanding in confining electromagnetic power and enhancing electric fields into ever smaller volumes is key to creating next generation devices for these programs. The prevailing view is that a resonant interaction (e.g. in microcavities or surface-plasmon polaritions) is necessary to achieve the necessary light confinement for absorption or emission enhancement. Here we propose new paradigm that is non-resonant and therefore broadband and can achieve light confinement and fieldmore » enhancement in extremely small areas [~(λ/500)^2 ]. The proposal is based on a theoretical work[1] performed at Sandia. The paradigm structure consists of a periodic arrangement of connected small and large rectangular slits etched into a metal film named double-groove (DG) structure. The degree of electric field enhancement and power confinement can be controlled by the geometry of the structure. The key operational principle is attributed to quasistatic response of the metal electrons to the incoming electromagnetic field that enables non-resonant broadband behavior. For this exploratory LDRD we have fabricated some test double groove structures to enable verification of quasistatic electronic response in the mid IR through IR optical spectroscopy. We have addressed some processing challenges in DG structure fabrication to enable future design of complex sensor and detector geometries that can utilize its non-resonant field enhancement capabilities.].« less

Molecular phylogeny of the Afroedura nivaria (Reptilia: Gekkonidae) species complex in South Africa provides insight on cryptic speciation.

PubMed

Makhubo, Buyisile G; Tolley, Krystal A; Bates, Michael F

2015-01-01

The Afroedura nivaria species complex (A. nivaria, A. karroica, A. amatolica, A. tembulica and A. halli) is a morphologically conservative group of medium-sized flat geckos endemic to South Africa and Lesotho. Species are allopatric, as are some populations within species that are separated by large expanses of unsuitable habitat. Because of this isolation of populations we hypothesised that several cryptic species may be present. To investigate this hypothesis we constructed a molecular phylogeny using multiple markers, and included representatives of other Afroedura species. Bayesian inference and maximum likelihood analyses (439bp 16S, 593bp ND4, 948bp RAG1) strongly supported the genetic distinctiveness of the five described species. However, the A. nivaria species complex as currently described is not monophyletic, as A. karroica was positioned outside a clade containing all other Afroedura species, and A. pondolia (which was presumed to belong to a different species complex) was recovered within the A. nivaria complex. Several distinct clades within A. halli and A. nivaria were also recovered, and the narrowly-distributed A. amatolica consisted of two highly divergent clades. We also conducted a multivariate analysis using 19 morphological characters to investigate whether the clades recovered by the phylogeny were distinct in terms of head, body and limb shape. The analysis showed some variation between clades in terms of locomotor apparatus (forelimbs and feet), head and body dimensions, but overall the morphological differences were minor. This morphological conservatism in the A. nivaria complex may be a result of adaptation to similar microhabitats. Exclusive of A. karroica, the results suggest that there are at least nine species in this complex, of which four are cryptic and undescribed. Copyright © 2014 Elsevier Inc. All rights reserved.

Morphology of Dbx1 respiratory neurons in the preBötzinger complex and reticular formation of neonatal mice.

PubMed

Akins, Victoria T; Weragalaarachchi, Krishanthi; Picardo, Maria Cristina D; Revill, Ann L; Del Negro, Christopher A

2017-08-01

The relationship between neuron morphology and function is a perennial issue in neuroscience. Information about synaptic integration, network connectivity, and the specific roles of neuronal subpopulations can be obtained through morphological analysis of key neurons within a microcircuit. Here we present morphologies of two classes of brainstem respiratory neurons. First, interneurons derived from Dbx1-expressing precursors (Dbx1 neurons) in the preBötzinger complex (preBötC) of the ventral medulla that generate the rhythm for inspiratory breathing movements. Second, Dbx1 neurons of the intermediate reticular formation that influence the motor pattern of pharyngeal and lingual movements during the inspiratory phase of the breathing cycle. We describe the image acquisition and subsequent digitization of morphologies of respiratory Dbx1 neurons from the preBötC and the intermediate reticular formation that were first recorded in vitro. These data can be analyzed comparatively to examine how morphology influences the roles of Dbx1 preBötC and Dbx1 reticular interneurons in respiration and can also be utilized to create morphologically accurate compartmental models for simulation and modeling of respiratory circuits.

Influence of Forest-Canopy Morphology and Relief on Spectral Characteristics of Taiga Forests

NASA Astrophysics Data System (ADS)

Zhirin, V. M.; Knyazeva, S. V.; Eydlina, S. P.

2017-12-01

The article deals with the results of a statistical analysis reflecting tendencies (trends) of the relationship between spectral characteristics of taiga forests, indicators of the morphological structure of forest canopy and illumination of the territory. The study was carried out on the example of the model forest territory of the Priangarskiy taiga region of Eastern Siberia (Krasnoyarsk krai) using historical data (forest inventory 1992, Landsat 5 TM 16.06.1989) and the digital elevation model. This article describes a method for determining the quantitative indicator of morphological structure of forest canopy based on taxation data, and the authors propose to subdivide the morphological structure into high complexity, medium complexity, and relatively simple. As a result of the research, dependences of average values of spectral brightness in near and short-wave infrared channels of a Landsat 5 TM image for dark-coniferous, light-coniferous and deciduous forests from the degree of complexity of the forest-canopy structure are received. A high level of variance and maximum brightness average values are marked in green moss (hilocominosa) dark-coniferous and various-grass (larioherbosa) dark-coniferous forests and light-coniferous forests with a complex structure of canopy. The parvifoliate forests are characterized by high values of brightness in stands with a relatively simple structure of the canopy and by a small variance in brightness of any degree of the structure of the canopy complexity. The increase in brightness for the lit slopes in comparison with shaded ones in all stands with a difficult morphological canopy structure is revealed. However, the brightness values of the lit and shaded slopes do not differ for stands with a medium complexity of the structure. It is noted that, in addition to the indicator of the forest-canopy structure, the possible impact on increasing the variance of spectral brightness for the taxation plot has a variability of the slope ratio of "microslopes" inside the forest plot if it exceeds 60%.

Do Children See the "Danger" in "Dangerous"? Grade 4, 6, and 8 Children's Reading of Morphologically Complex Words

ERIC Educational Resources Information Center

Deacon, S. Helene; Whalen, Rachel; Kirby, John R.

2011-01-01

We examined whether Grade 4, 6, and 8 children access the base form when reading morphologically complex words. We asked children to read words varying systematically in the frequency of the surface and base forms and in the transparency of the base form. At all grade levels, children were faster at reading derived words with high rather than low…

A linear-encoding model explains the variability of the target morphology in regeneration

PubMed Central

Lobo, Daniel; Solano, Mauricio; Bubenik, George A.; Levin, Michael

2014-01-01

A fundamental assumption of today's molecular genetics paradigm is that complex morphology emerges from the combined activity of low-level processes involving proteins and nucleic acids. An inherent characteristic of such nonlinear encodings is the difficulty of creating the genetic and epigenetic information that will produce a given self-assembling complex morphology. This ‘inverse problem’ is vital not only for understanding the evolution, development and regeneration of bodyplans, but also for synthetic biology efforts that seek to engineer biological shapes. Importantly, the regenerative mechanisms in deer antlers, planarian worms and fiddler crabs can solve an inverse problem: their target morphology can be altered specifically and stably by injuries in particular locations. Here, we discuss the class of models that use pre-specified morphological goal states and propose the existence of a linear encoding of the target morphology, making the inverse problem easy for these organisms to solve. Indeed, many model organisms such as Drosophila, hydra and Xenopus also develop according to nonlinear encodings producing linear encodings of their final morphologies. We propose the development of testable models of regeneration regulation that combine emergence with a top-down specification of shape by linear encodings of target morphology, driving transformative applications in biomedicine and synthetic bioengineering. PMID:24402915

Interaction Between a Steady Detonation Wave in Nitromethane and Geometrical Complex Confinement Defects

NASA Astrophysics Data System (ADS)

Crouzet, B.; Soulard, L.; Carion, N.; Manczur, P.

2007-12-01

Two copper cylinder expansion tests were carried out on nitromethane. They differ from the classical cylinder test in that the liner includes evenly-spaced protruding circular defects. The aim is to study how a detonation front propagating in the liquid explosive interacts with the confining material defects. The subsequent motion of the metal, accelerated by the expanding detonation products, is measured using a range of diagnostic techniques: electrical probes, a rapid framing camera, a glass block associated with a streak camera and velocity laser interferometers. The different experimental records have been examined in the light of previous classical cylinder test measurements, simple 2D theoretical shock polar analysis results and 2D numerical simulations.

Interplay between quantum confinement and surface effects in thickness selective stability of thin Ag and Eu films

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

Liu, Xiaojie; Wang, Cai -Zhuang

Using first-principles calculations, we show that both face-centered cubic (fcc) Ag (1 1 0) ultrathin films and body-centered cubic (bcc) Eu(1 1 0) ultrathin films exhibit thickness selective stability. Furthermore, the origin of such thickness selection is different. While the thickness selective stability in fcc Ag(1 1 0) films is mainly due to the well-known quantum well states ascribed to the quantum confinement effects in free-electron-like metal films, the thickness selection in bcc Eu(1 1 0) films is more complex and also strongly correlated with the occupation of the surface and surface resonance states.

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

Granger, J.A.

This project, Energy Recovery Through Termites, was based on the proposed development of an energy recovery system to produce low cost animal protein for use in animal feeds. The result of my study shows that to date we are unable to establish viable colonies of termites. This is based on several key factors as follows: (a) inability to capture reproductives to establish new colonies in a confined area needed to offer recovery or harvest of protein; (b) confinement of colonies (even without queen or reproductives) has proven to be far too complex to establish in low cost and modest facilities;more » (c) the proposal is not cost effective. The resources of skill and materials could not be repaid from the protein recovered.« less

Micro/nanofabricated environments for synthetic biology.

PubMed

Collier, C Patrick; Simpson, Michael L

2011-08-01

A better understanding of how confinement, crowding and reduced dimensionality modulate reactivity and reaction dynamics will aid in the rational and systematic discovery of functionality in complex biological systems. Artificial microfabricated and nanofabricated structures have helped elucidate the effects of nanoscale spatial confinement and segregation on biological behavior, particularly when integrated with microfluidics, through precise control in both space and time of diffusible signals and binding interactions. Examples of nanostructured interfaces for synthetic biology include the development of cell-like compartments for encapsulating biochemical reactions, nanostructured environments for fundamental studies of diffusion, molecular transport and biochemical reaction kinetics, and regulation of biomolecular interactions as functions of microfabricated and nanofabricated topological constraints. Copyright © 2011 Elsevier Ltd. All rights reserved.

Plasmon confinement in fractal quantum systems

NASA Astrophysics Data System (ADS)

Westerhout, Tom; van Veen, Edo; Katsnelson, Mikhail I.; Yuan, Shengjun

2018-05-01

Recent progress in the fabrication of materials has made it possible to create arbitrary nonperiodic two-dimensional structures in the quantum plasmon regime. This paves the way for exploring the quantum plasmonic properties of electron gases in complex geometries. In this work we study systems with a fractal dimension. We calculate the full dielectric functions of two prototypical fractals with different ramification numbers, namely the Sierpinski carpet and gasket. We show that the Sierpinski carpet has a dispersion comparable to a square lattice, but the Sierpinski gasket features highly localized plasmon modes with a flat dispersion. This strong plasmon confinement in finitely ramified fractals can provide a novel setting for manipulating light at the quantum level.

Interplay between quantum confinement and surface effects in thickness selective stability of thin Ag and Eu films

DOE PAGES

Liu, Xiaojie; Wang, Cai -Zhuang

2017-04-03

Using first-principles calculations, we show that both face-centered cubic (fcc) Ag (1 1 0) ultrathin films and body-centered cubic (bcc) Eu(1 1 0) ultrathin films exhibit thickness selective stability. Furthermore, the origin of such thickness selection is different. While the thickness selective stability in fcc Ag(1 1 0) films is mainly due to the well-known quantum well states ascribed to the quantum confinement effects in free-electron-like metal films, the thickness selection in bcc Eu(1 1 0) films is more complex and also strongly correlated with the occupation of the surface and surface resonance states.

Morphological Effects in Auditory Word Recognition: Evidence from Danish

ERIC Educational Resources Information Center

Balling, Laura Winther; Baayen, R. Harald

2008-01-01

In this study, we investigate the processing of morphologically complex words in Danish using auditory lexical decision. We document a second critical point in auditory comprehension in addition to the Uniqueness Point (UP), namely the point at which competing morphological continuation forms of the base cease to be compatible with the input,…

The Impact of Semantic Transparency of Morphologically Complex Words on Picture Naming

ERIC Educational Resources Information Center

Dohmes, Petra; Zwitserlood, Pienie; Bolte, Jens

2004-01-01

We examined the contribution of semantic similarity to morphological priming effects, using the immediate (Exp. 1 and 3) and the delayed variant (Exp. 2) of picture-word interference. Distractor words were either compounds morphologically related to the picture name, but differing with respect to their semantic transparency (hummingbird, jailbird…

Rapid crystallization and morphological adjustment of zeolite ZSM-5 in nonionic emulsions

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

Zhang Ying, E-mail: yingzh1977@163.co; Jin Chao; Research Institute of Petroleum Processing, Beijing 100083

2011-01-15

Zeolite ZSM-5 was synthesized for the first time in a nonionic emulsion composed of polyoxyethylated alkylphenol, butanol, cyclohexane and tetraethylammonium hydroxide (TEAOH)-containing zeolite synthesis mixture. The crystallization kinetics in the emulsion was investigated and the ZSM-5 product was characterized in detail by XRD, SEM, FT-IR, TG, N{sub 2} adsorption and CHN analysis techniques. Compared with the conventionally hydrothermal synthesis with the same structure directing agent TEAOH, the emulsion system allows rapid crystallization of ZSM-5. The ZSM-5 product exhibits unusual agglomerated structure and possesses larger specific surface area. The FT-IR, TG results plus CHN analysis show the encapsulation of a tracemore » of emulsion components in the emulsion ZSM-5. Control experiments show the emulsion system exerts the crystallization induction and morphological adjustment effects mainly during the aging period. The effects are tentatively attributed to the confined space domains, surfactant-water interaction as well as surfactant-growing crystals interaction existing in the emulsion. -- Graphical abstract: The nonionic emulsion synthesis allows rapid crystallization and morphological adjustment of zeolite ZSM-5 compared with the conventional hydrothermal synthesis. Display Omitted« less

Xrt And Shinx Joint Flare Study: Ar 11024

NASA Astrophysics Data System (ADS)

Engell, Alexander; Sylwester, J.; Siarkowski, M.

2010-05-01

From 12:00 UT on July 3 through July 7, 2009 SphinX (Solar Photometer IN X-rays) observes 130 flares with active region (AR) 11024 being the only AR on disk. XRT (X-Ray Telescope) is able to observe 64 of these flare events. The combination of both instruments results in a flare study revealing (1) a relationship between flux emergence and flare rate, (2) that the presence of active region loops typically results in different flare morphologies (single and multiple loop flares) then when there is a lack of an active region loop environment where more cusp and point-like flares are observed, (3) cusp and point-like flares often originate from the same location, and (4) a distribution of flare temperatures corresponding to the different flare morphologies. The differences between the observed flare morphologies may occur as the result of the heated plasma through the flaring process being confined by the proximity of loop structures as for the single and multiple loop flares, while for cusp and point-like flares they occur in an early-phase environment that lack loop presence. The continuing flux emergence of AR 11024 likely provides different magnetic interactions and may be the source responsible for all of the flares.

Macronuclear Cytology of Synchronized Tetrahymena pyriformis

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

Cameron, I. L.; Padilla, G. M.; Miller, Jr., O. L.

1966-05-01

Elliott, Kennedy and Bak ('62) and Elliott ('63) followed fine structural changes in macronuclei of Tetrahymena pyriformis which were synchronized by the heat shock method of Scherbaum and Zeuthen ('54). Using Elliott's morphological descriptions as a basis, we designed our investigations with two main objectives: First, to again study the. morphological changes which occur in the macronucleus of Tetrahymena synchronized by the heat shock method. The second objective was to compare these observations with Tetrahymena synchronized by an alternate method recently reported by Padilla and Cameron ('64). Therefore, we were able to compare the results from two different synchronization methodsmore » and to contrast these findings with the macronuclear cytology of Tetrahymena taken from a logarithmically growing culture. Comparison of cells treated in these three different ways enables us to evaluate the two different synchronization methods and to gain more information on the structural changes taking place in the macronucleus of Tetrahymena as a function of the cell cycle. Our observations were confined primarily to nucleolar morphology. The results indicate that cells synchronized by the Padilla and Cameron method more closely resemble logarithmically growing Tetrahymena in the macronuclear structure than do cells obtained by the Scherbaum and·Zeuthen synchronization method. .« less

Endocrine cells in ectocervical epithelium. An immunohistochemical and ultrastructural analysis.

PubMed

Fetissof, F; Arbeille, B; Boivin, F; Sam-Giao, M; Henrion, C; Lansac, J

1987-01-01

A systematic study of endocrine cells in the ectocervix was carried out using histochemical, immunohistochemical and ultrastructural techniques. Serotonin and calcitonin immunoreactive cells were demonstrated in this site. Serotonin and calcitonin immunoreactivities were coexpressed in the same endocrine cell. These distinctive cells were encountered in two main morphological varieties of ectocervical epithelium. Normal-appearing stratified squamous epithelium contained only very rare serotonin and calcitonin cells. In contrast, endocrine cells were fairly abundant in a specific epithelium termed "transitional-like". This type of epithelium was not only confined to the transformation zone but could also extend onto the portio as far as the vaginal cut margin. In some cases, transitional-like epithelium bore morphological resemblance to urothelium. In other cases, it could be regarded as basal cell hyperplasia or immature squamous metaplasia. Of interest, serotonin and calcitonin cells have been well-documented as normal inhabitants of some other non-squamous epithelia, such as urothelium or pseudostratified columnar epithelium. Therefore, it is suggested that certain ectocervical epithelia show some similarities to urothelium, in respect of their morphological appearance and endocrine profile. Further investigations using more objective and specific markers of urothelial cells are needed to assess the exact degree of homology connecting all these types of epithelium.

Status of beech bark disease in Pennsylvania

Treesearch

Barry Towers

1983-01-01

Results of periodical surveys for beech bark disease in Pennsylvania from 1958 to 1982 reveal that the disease is slowly spreading in a south- and westward direction. Although the disease complex is still confined to the northern and eastern portions of the state, beech mortality is occurring in the areas infested longest.

Design and Implementation of the Game-Design and Learning Program

ERIC Educational Resources Information Center

Akcaoglu, Mete

2016-01-01

Design involves solving complex, ill-structured problems. Design tasks are consequently, appropriate contexts for children to exercise higher-order thinking and problem-solving skills. Although creating engaging and authentic design contexts for young children is difficult within the confines of traditional schooling, recently, game-design has…

Polymer Light-Emitting Diode (PLED) Process Development

DTIC Science & Technology

2003-12-01

conclusions and recommendations for Phase II of the Flexible Display Program. 15. SUBJECT TERMS LIGHT EMITTING DIODES LIQUID CRYSTAL DISPLAY SYSTEMS...space for Phase I and II confined by backplane complexity and substrate form...12 Figure 6. Semi automated I-V curve measurement setup consisting of Keithley power supply, computer and

Optimization of surface morphology and scattering properties of TCO/AIT textured glass front electrode for thin film solar cells

NASA Astrophysics Data System (ADS)

Addonizio, M. L.; Fusco, L.; Antonaia, A.; Cominale, F.; Usatii, I.

2015-12-01

Aluminium induced texture (AIT) method has been used for obtaining highly textured glass substrate suitable for silicon based thin film solar cell technology. Wet etch step parameters of AIT process have been varied and effect of different etchants and different etching times on morphological and optical properties has been analyzed. The resulting morphology features (shape, size distribution, inclination angle) have been optimized in order to obtain the best scattering properties. ZnO:Ga (GZO) films have been deposited by sputtering technique on AIT-processed glass. Two different ZnO surface morphologies have been obtained, strongly depending on the underlying glass substrate morphology induced by different etching times. Very rough and porous texture (σrms ∼ 150 nm) was obtained on glass etched 2 min showing cauliflower-like structure, whereas a softer texture (σrms ∼ 78 nm) was obtained on glass etched 7 min giving wider and smoother U-shaped craters. The effect of different glass textures on optical confinement has been tested in amorphous silicon based p-i-n devices. Devices fabricated on GZO/high textured glass showed a quantum efficiency enhancement due to both an effective light trapping phenomenon and an effective anti-reflective optical behaviour. Short etching time produce smaller cavities (<1 μm) with deep U-shape characterized by high roughness, high inclination angle and low autocorrelation length. This surface morphology promoted a large light scattering phenomenon, as evidenced by haze value and by angular resolved scattering (ARS) behaviour, into a large range of diffraction angles, giving high probability of effective light trapping inside a PV device.

Searching target sites on DNA by proteins: Role of DNA dynamics under confinement

PubMed Central

Mondal, Anupam; Bhattacherjee, Arnab

2015-01-01

DNA-binding proteins (DBPs) rapidly search and specifically bind to their target sites on genomic DNA in order to trigger many cellular regulatory processes. It has been suggested that the facilitation of search dynamics is achieved by combining 3D diffusion with one-dimensional sliding and hopping dynamics of interacting proteins. Although, recent studies have advanced the knowledge of molecular determinants that affect one-dimensional search efficiency, the role of DNA molecule is poorly understood. In this study, by using coarse-grained simulations, we propose that dynamics of DNA molecule and its degree of confinement due to cellular crowding concertedly regulate its groove geometry and modulate the inter-communication with DBPs. Under weak confinement, DNA dynamics promotes many short, rotation-decoupled sliding events interspersed by hopping dynamics. While this results in faster 1D diffusion, associated probability of missing targets by jumping over them increases. In contrast, strong confinement favours rotation-coupled sliding to locate targets but lacks structural flexibility to achieve desired specificity. By testing under physiological crowding, our study provides a plausible mechanism on how DNA molecule may help in maintaining an optimal balance between fast hopping and rotation-coupled sliding dynamics, to locate target sites rapidly and form specific complexes precisely. PMID:26400158

Patterned assembly of colloidal particles by confined dewetting lithography.

PubMed

Celio, Hugo; Barton, Emily; Stevenson, Keith J

2006-12-19

We report the assembly of colloidal particles into confined arrangements and patterns on various cleaned and chemically modified solid substrates using a method which we term "confined dewetting lithography" or CDL for short. The experimental setup for CDL is a simple deposition cell where an aqueous suspension of colloidal particles (e.g., polystyrene spheres) is placed between a floating deposition template (i.e., metal microgrid) and the solid substrate. The voids of the deposition template serve as an array of micrometer-sized reservoirs where several hydrodynamic processes are confined. These processes include water evaporation, meniscus formation, convective flow, rupturing, dewetting, and capillary-bridge formation. We discuss the optimal conditions where the CDL has a high efficiency to deposit intricate patterns of colloidal particles using polystyrene spheres (PS; 4.5, 2.0, 1.7, 0.11, 0.064 microm diameter) and square and hexagonal deposition templates as model systems. We find that the optimization conditions of the CDL method, when using submicrometer, sulfate-functionalized PS particles, are primarily dependent on minimizing attractive particle-substrate interactions. The CDL methodology described herein presents a relatively simple and rapid method to assemble virtually any geometric pattern, including more complex patterns assembled using PS particles with different diameters, from aqueous suspensions by choosing suitable conditions and materials.

Analysis of Molecular Diffusion by First-Passage Time Variance Identifies the Size of Confinement Zones

PubMed Central

Rajani, Vishaal; Carrero, Gustavo; Golan, David E.; de Vries, Gerda; Cairo, Christopher W.

2011-01-01

The diffusion of receptors within the two-dimensional environment of the plasma membrane is a complex process. Although certain components diffuse according to a random walk model (Brownian diffusion), an overwhelming body of work has found that membrane diffusion is nonideal (anomalous diffusion). One of the most powerful methods for studying membrane diffusion is single particle tracking (SPT), which records the trajectory of a label attached to a membrane component of interest. One of the outstanding problems in SPT is the analysis of data to identify the presence of heterogeneity. We have adapted a first-passage time (FPT) algorithm, originally developed for the interpretation of animal movement, for the analysis of SPT data. We discuss the general application of the FPT analysis to molecular diffusion, and use simulations to test the method against data containing known regions of confinement. We conclude that FPT can be used to identify the presence and size of confinement within trajectories of the receptor LFA-1, and these results are consistent with previous reports on the size of LFA-1 clusters. The analysis of trajectory data for cell surface receptors by FPT provides a robust method to determine the presence and size of confined regions of diffusion. PMID:21402028

Residence times and mixing of water in river banks: implications for recharge and groundwater - surface water exchange

NASA Astrophysics Data System (ADS)

Unland, N. P.; Cartwright, I.; Cendón, D. I.; Chisari, R.

2014-02-01

The residence time of groundwater within 50 m of the Tambo River, South East Australia, has been estimated through the combined use of 3H and 14C. Groundwater residence times increase towards the Tambo River which implies a gaining river system and not increasing bank storage with proximity to the Tambo River. Major ion concentrations and δ2H and δ18O values of bank water also indicate that bank infiltration does not significantly impact groundwater chemistry under baseflow and post-flood conditions, suggesting that the gaining nature of the river may be driving the return of bank storage water back into the Tambo River within days of peak flood conditions. The covariance between 3H and 14C indicates the leakage and mixing between old (~17 200 yr) groundwater from a semi-confined aquifer and younger groundwater (<100 yr) near the river where confining layers are less prevalent. The presence of this semi-confined aquifer has also been used to help explain the absence of bank storage, as rapid pressure propagation into the semi-confined aquifer during flooding will minimise bank infiltration. This study illustrates the complex nature of river groundwater interactions and the potential downfall in assuming simple or idealised conditions when conducting hydrogeological studies.

Effect of the geometry of confining media on the stability and folding rate of α -helix proteins

NASA Astrophysics Data System (ADS)

Wang, Congyue; Piroozan, Nariman; Javidpour, Leili; Sahimi, Muhammad

2018-05-01

Protein folding in confined media has attracted wide attention over the past 15 years due to its importance to both in vivo and in vitro applications. It is generally believed that protein stability increases by decreasing the size of the confining medium, if the medium's walls are repulsive, and that the maximum folding temperature in confinement is in a pore whose size D0 is only slightly larger than the smallest dimension of a protein's folded state. Until recently, the stability of proteins in pores with a size very close to that of the folded state has not received the attention it deserves. In a previous paper [L. Javidpour and M. Sahimi, J. Chem. Phys. 135, 125101 (2011)], we showed that, contrary to the current theoretical predictions, the maximum folding temperature occurs in larger pores for smaller α-helices. Moreover, in very tight pores, the free energy surface becomes rough, giving rise to a new barrier for protein folding close to the unfolded state. In contrast to unbounded domains, in small nanopores proteins with an α-helical native state that contain the β structures are entropically stabilized implying that folding rates decrease notably and that the free energy surface becomes rougher. In view of the potential significance of such results to interpretation of many sets of experimental data that could not be explained by the current theories, particularly the reported anomalously low rates of folding and the importance of entropic effects on proteins' misfolded states in highly confined environments, we address the following question in the present paper: To what extent the geometry of a confined medium affects the stability and folding rates of proteins? Using millisecond-long molecular dynamics simulations, we study the problem in three types of confining media, namely, cylindrical and slit pores and spherical cavities. Most importantly, we find that the prediction of the previous theories that the dependence of the maximum folding temperature Tf on the size D of a confined medium occurs in larger media for larger proteins is correct only in spherical geometry, whereas the opposite is true in the two other geometries that we study. Also studied is the effect of the strength of the interaction between the confined media's walls and the proteins. If the walls are only weakly or moderately attractive, a complex behavior emerges that depends on the size of the confining medium.

Fluid flows created by swimming bacteria drive self-organization in confined suspensions

PubMed Central

Lushi, Enkeleida; Wioland, Hugo; Goldstein, Raymond E.

2014-01-01

Concentrated suspensions of swimming microorganisms and other forms of active matter are known to display complex, self-organized spatiotemporal patterns on scales that are large compared with those of the individual motile units. Despite intensive experimental and theoretical study, it has remained unclear the extent to which the hydrodynamic flows generated by swimming cells, rather than purely steric interactions between them, drive the self-organization. Here we use the recent discovery of a spiral-vortex state in confined suspensions of Bacillus subtilis to study this issue in detail. Those experiments showed that if the radius of confinement in a thin cylindrical chamber is below a critical value, the suspension will spontaneously form a steady single-vortex state encircled by a counter-rotating cell boundary layer, with spiral cell orientation within the vortex. Left unclear, however, was the flagellar orientation, and hence the cell swimming direction, within the spiral vortex. Here, using a fast simulation method that captures oriented cell–cell and cell–fluid interactions in a minimal model of discrete particle systems, we predict the striking, counterintuitive result that in the presence of collectively generated fluid motion, the cells within the spiral vortex actually swim upstream against those flows. This prediction is then confirmed by the experiments reported here, which include measurements of flagella bundle orientation and cell tracking in the self-organized state. These results highlight the complex interplay between cell orientation and hydrodynamic flows in concentrated suspensions of microorganisms. PMID:24958878

Evidence of erosional self-channelization of pyroclastic density currents revealed by ground-penetrating radar imaging at Mount St. Helens, Washington (USA)

NASA Astrophysics Data System (ADS)

Gase, Andrew C.; Brand, Brittany D.; Bradford, John H.

2017-03-01

The causes and effects of erosion are among the least understood aspects of pyroclastic density current (PDC) dynamics. Evidence is especially limited for erosional self-channelization, a process whereby PDCs erode a channel that confines the body of the eroding flow or subsequent flows. We use ground-penetrating radar imaging to trace a large PDC scour and fill from outcrop to its point of inception and discover a second, larger PDC scour and fill. The scours are among the largest PDC erosional features on record, at >200 m wide and at least 500 m long; estimated eroded volumes are on the order of 106 m3. The scours are morphologically similar to incipient channels carved by turbidity currents. Erosion may be promoted by a moderate slope (5-15°), substrate pore pressure retention, and pulses of increased flow energy. These findings are the first direct evidence of erosional self-channelization by PDCs, a phenomenon that may increase flow velocity and runout distance through confinement and substrate erosion.

Solution to the problem of the poor cyclic fatigue resistance of bulk metallic glasses

PubMed Central

Launey, Maximilien E.; Hofmann, Douglas C.; Johnson, William L.; Ritchie, Robert O.

2009-01-01

The recent development of metallic glass-matrix composites represents a particular milestone in engineering materials for structural applications owing to their remarkable combination of strength and toughness. However, metallic glasses are highly susceptible to cyclic fatigue damage, and previous attempts to solve this problem have been largely disappointing. Here, we propose and demonstrate a microstructural design strategy to overcome this limitation by matching the microstructural length scales (of the second phase) to mechanical crack-length scales. Specifically, semisolid processing is used to optimize the volume fraction, morphology, and size of second-phase dendrites to confine any initial deformation (shear banding) to the glassy regions separating dendrite arms having length scales of ≈2 μm, i.e., to less than the critical crack size for failure. Confinement of the damage to such interdendritic regions results in enhancement of fatigue lifetimes and increases the fatigue limit by an order of magnitude, making these “designed” composites as resistant to fatigue damage as high-strength steels and aluminum alloys. These design strategies can be universally applied to any other metallic glass systems. PMID:19289820

Groundwater Discharge along a Channelized Coastal Plain Stream

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

LaSage, Danita M; Sexton, Joshua L; Mukherjee, Abhijit

In the Coastal Plain of the southeastern USA, streams have commonly been artificially channelized for flood control and agricultural drainage. However, groundwater discharge along such streams has received relatively little attention. Using a combination of stream- and spring-flow measurements, spring temperature measurements, temperature profiling along the stream-bed, and geologic mapping, we delineated zones of diffuse and focused discharge along Little Bayou Creek, a channelized, first-order perennial stream in western Kentucky. Seasonal variability in groundwater discharge mimics hydraulic-head fluctuations in a nearby monitoring well and spring-discharge fluctuations elsewhere in the region, and is likely to reflect seasonal variability in recharge. Diffusemore » discharge occurs where the stream is incised into the semi-confined regional gravel aquifer, which is comprised of the Mounds Gravel. Focused discharge occurs upstream where the channel appears to have intersected preferential pathways within the confining unit. Seasonal fluctuations in discharge from individual springs are repressed where piping results in bank collapse. Thereby, focused discharge can contribute to the morphological evolution of the stream channel.« less

A conservative, thermodynamically consistent numerical approach for low Mach number combustion. Part I: Single-level integration

NASA Astrophysics Data System (ADS)

Nonaka, Andrew; Day, Marcus S.; Bell, John B.

2018-01-01

We present a numerical approach for low Mach number combustion that conserves both mass and energy while remaining on the equation of state to a desired tolerance. We present both unconfined and confined cases, where in the latter the ambient pressure changes over time. Our overall scheme is a projection method for the velocity coupled to a multi-implicit spectral deferred corrections (SDC) approach to integrate the mass and energy equations. The iterative nature of SDC methods allows us to incorporate a series of pressure discrepancy corrections naturally that lead to additional mass and energy influx/outflux in each finite volume cell in order to satisfy the equation of state. The method is second order, and satisfies the equation of state to a desired tolerance with increasing iterations. Motivated by experimental results, we test our algorithm on hydrogen flames with detailed kinetics. We examine the morphology of thermodiffusively unstable cylindrical premixed flames in high-pressure environments for confined and unconfined cases. We also demonstrate that our algorithm maintains the equation of state for premixed methane flames and non-premixed dimethyl ether jet flames.

The effects of iris-ciliary complex on the organ cultured rabbit ocular lens.

PubMed

Niyogi, T K; Emanuel, K; Parafina, J; Bagchi, M

1991-01-01

Freshly isolated rabbit lenses were cultured with and without attached iris-ciliary (IC)-complex for 24 hours in TC-199 medium. Subsequent morphological analysis revealed that the IC-complex cannot be maintained in serum-free medium. In addition an observed effect of the IC-complex on the co-cultured lenses could not be due only because of the cellular degeneration of the IC-complex. To test this possibility lenses with attached IC-complexes were incubated in 20% serum-containing TC-199 medium. The IC-complex cultured in 20% serum containing medium retained its normal morphology. However co-cultured lens cells displayed vacuoles and other signs of degeneration. The protein synthetic and Na+/K+ pump activities of these lenses were also significantly depressed. These data indicated that the observed effects of IC-complex on the lens were not due to its cellular degradation. Preliminary experiments showed that the IC-complex contains water soluble factor(s) which could effectively inhibit lens protein synthesis and Na+/K+ pump.

Lifetimes of the Vibrational States of DNA Molecules in Functionalized Complexes of Semiconductor Quantum Dots

NASA Astrophysics Data System (ADS)

Bayramov, F. B.; Poloskin, E. D.; Chernev, A. L.; Toporov, V. V.; Dubina, M. V.; Sprung, C.; Lipsanen, H. K.; Bairamov, B. Kh.

2018-01-01

Results of studying nanocrystalline nc-Si/SiO2 quantum dots (QDs) functionalized by short oligonucleotides show that complexes of isolated crystalline semiconductor QDs are unique objects for detecting the manifestation of new quantum confinement phenomena. It is established that narrow lines observed in high-resolution spectra of inelastic light scattering can be used for determining the characteristic time scale of vibrational excitations of separate nucleotide molecules and for studying structural-dynamic properties of fast oscillatory processes in biomacromolecules.

Seven new species within western Atlantic Starksia atlantica, S. lepicoelia, and S. sluiteri (Teleostei, Labrisomidae), with comments on congruence of DNA barcodes and species

PubMed Central

Baldwin, Carole C.; Castillo, Cristina I.; Weigt, Lee A.; Benjamin C., Victor

2011-01-01

Abstract Specimens of Starksia were collected throughout the western Atlantic, and a 650-bp portion of the mitochondrial gene cytochrome oxidase-c subunit I (COl) was sequenced as part of a re-analysis of species diversity of western Central Atlantic shorefishes. A neighbor-joining tree constructed from the sequence data suggests the existence of several cryptic species. Voucher specimens from each genetically distinct lineage and color photographs of vouchers taken prior to dissection and preservation were examined for diagnostic morphological characters. The results suggest that Starksia atlantica, Starksia lepicoelia, and Starksia sluiteri are species complexes, and each comprises three or more species. Seven new species are described. DNA data usually support morphological features, but some incongruence between genetic and morphological data exists. Genetic lineages are only recognized as species if supported by morphology. Genetic lineages within western Atlantic Starksia generally correspond to geography, such that members of each species complex have a very restricted geographical distribution. Increasing geographical coverage of sampling locations will almost certainly increase the number of Starksia species and species complexes recognized in the western Atlantic. Combining molecular and morphological investigations is bringing clarity to the taxonomy of many genera of morphologically similar fishes and increasing the number of currently recognized species. Future phylogenetic studies should help resolve species relationships and shed light on patterns of speciation in western Atlantic Starksia. PMID:21594143

Syntactic and semantic restrictions on morphological recomposition: MEG evidence from Greek.

PubMed

Neophytou, K; Manouilidou, C; Stockall, L; Marantz, A

2018-05-16

Complex morphological processing has been extensively studied in the past decades. However, most of this work has either focused on only certain steps involved in this process, or it has been conducted on a few languages, like English. The purpose of the present study is to investigate the spatiotemporal cortical processing profile of the distinct steps previously reported in the literature, from decomposition to re-composition of morphologically complex items, in a relatively understudied language, Greek. Using magnetoencephalography, we confirm the role of the fusiform gyrus in early, form-based morphological decomposition, we relate the syntactic licensing of stem-suffix combinations to the ventral visual processing stream, somewhat independent from lexical access for the stem, and we further elucidate the role of orbitofrontal regions in semantic composition. Thus, the current study offers the most comprehensive test to date of visual morphological processing and additional, crosslinguistic validation of the steps involved in it. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Complex Morphological Variability in Complex Evaporitic Systems: Thermal Spring Snails from the Chihuahuan Desert, Mexico

NASA Astrophysics Data System (ADS)

Tang, Carol M.; Roopnarine, Peter D.

2003-11-01

Thermal springs in evaporitic environments provide a unique biological laboratory in which to study natural selection and evolutionary diversification. These isolated systems may be an analogue for conditions in early Earth or Mars history. One modern example of such a system can be found in the Chihuahuan Desert of north-central Mexico. The Cuatro Cienegas basin hosts a series of thermal springs that form a complex of aquatic ecosystems under a range of environmental conditions. Using landmark-based morphometric techniques, we have quantified an unusually high level of morphological variability in the endemic gastropod Mexipyrgus from Cuatro Cienegas. The differentiation is seen both within and between hydrological systems. Our results suggest that this type of environmental system is capable of producing and maintaining a high level of morphological diversity on small spatial scales, and thus should be a target for future astrobiological research.

Variation of telencephalon morphology of the threespine stickleback (Gasterosteus aculeatus) in relation to inferred ecology.

PubMed

Park, Peter J; Bell, M A

2010-06-01

We tested the hypothesis that increased telencephalon size has evolved in threespine stickleback fish (Gasterosteus aculeatus) from structurally complex habitats using field-caught samples from one sea-run (ancestral) and 18 ecologically diverse freshwater (descendant) populations. Freshwater habitats ranged from shallow, structurally complex lakes with benthic-foraging stickleback (benthics), to deeper, structurally simple lakes in which stickleback depend more heavily on plankton for prey (generalists). Contrary to our expectations, benthics had smaller telencephala than generalists, but the shape of the telencephalon of the sea-run and benthic populations were more convex laterally. Convex telencephalon shape may indicate enlargement of the dorsolateral region, which is homologous with the tetrapod hippocampus. Telencephalon morphology is also sexually dimorphic, with larger, less convex telencephala in males. Freshwater stickleback from structurally complex habitats have retained the ancestral telencephalon morphology, but populations that feed more in open habitats on plankton have evolved larger, laterally concave telencephala.

The complex evolutionary history of big-eared horseshoe bats (Rhinolophus macrotis complex): insights from genetic, morphological and acoustic data

PubMed Central

Sun, Keping; Kimball, Rebecca T.; Liu, Tong; Wei, Xuewen; Jin, Longru; Jiang, Tinglei; Lin, Aiqing; Feng, Jiang

2016-01-01

Palaeoclimatic oscillations and different landscapes frequently result in complex population-level structure or the evolution of cryptic species. Elucidating the potential mechanisms is vital to understanding speciation events. However, such complex evolutionary patterns have rarely been reported in bats. In China, the Rhinolophus macrotis complex contains a large form and a small form, suggesting the existence of a cryptic bat species. Our field surveys found these two sibling species have a continuous and widespread distribution with partial sympatry. However, their evolutionary history has received little attention. Here, we used extensive sampling, morphological and acoustic data, as well as different genetic markers to investigate their evolutionary history. Genetic analyses revealed discordance between the mitochondrial and nuclear data. Mitochondrial data identified three reciprocally monophyletic lineages: one representing all small forms from Southwest China, and the other two containing all large forms from Central and Southeast China, respectively. The large form showed paraphyly with respect to the small form. However, clustering analyses of microsatellite and Chd1 gene sequences support two divergent clusters separating the large form and the small form. Moreover, morphological and acoustic analyses were consistent with nuclear data. This unusual pattern in the R. macrotis complex might be accounted for by palaeoclimatic oscillations, shared ancestral polymorphism and/or interspecific hybridization. PMID:27748429

Insights of Mixing on the Assembly of DNA Nanoparticles

NASA Astrophysics Data System (ADS)

Williams, Manda S.

Size is a crucial parameter in the delivery of nanoparticle therapeutics, affecting mechanisms such as tissue delivery, clearance, and cellular uptake. The morphology of nanoparticles is dependent both upon chemistry and the physical process of assembly. Polyplexes, a major class of non-viral gene delivery vectors, are conventionally prepared by vortex mixing, resulting in non-uniform nanoparticles and poor reproducibility. Better understanding and control of the physical process of assembly, and mixing in particular, will produce polyplexes of a more uniform and reliable size, optimizing their efficiency for laboratory and clinical use. "Mixing" is the reduction of length scale of a system to accelerate diffusion until a uniform concentration is achieved. Vortex mixing is poorly characterized and sensitive to protocols. Microfluidic systems are notable for predictable fluid behavior, and are ideal for analyzing and controlling the physical interaction of reagents on the microscale, realm where mixing occurs. Several microdevices for the preparation of DNA polyplexes are explored here. Firstly, the staggered herringbone mixer, a chaotic advection micromixer, is used to observe the effects of mixing time on nanoparticle size. Next, a novel device to surround the reagent flows with a sheath of buffer, preventing interaction with the walls and confining the complexation to a zone of lower, less variable shear and residence time, is used to demonstrate the role of shear in nanoparticle assembly. Lastly, uneven diffusion between ion pairs produces a small separation of charge at fluid interfaces; this short-lived electric field has a significant impact on the transport of DNA over the time scales of mixing and complexation. The effects of common buffers on the transport of DNA are examined for possible applications to mixing and complexation. These three investigations demonstrate the importance of the physical process in polyplex assembly, and indicate several important considerations in the development of new protocols and devices.

Computational approach to integrate 3D X-ray microtomography and NMR data.

PubMed

Lucas-Oliveira, Everton; Araujo-Ferreira, Arthur G; Trevizan, Willian A; Fortulan, Carlos A; Bonagamba, Tito J

2018-05-04

Nowadays, most of the efforts in NMR applied to porous media are dedicated to studying the molecular fluid dynamics within and among the pores. These analyses have a higher complexity due to morphology and chemical composition of rocks, besides dynamic effects as restricted diffusion, diffusional coupling, and exchange processes. Since the translational nuclear spin diffusion in a confined geometry (e.g. pores and fractures) requires specific boundary conditions, the theoretical solutions are restricted to some special problems and, in many cases, computational methods are required. The Random Walk Method is a classic way to simulate self-diffusion along a Digital Porous Medium. Bergman model considers the magnetic relaxation process of the fluid molecules by including a probability rate of magnetization survival under surface interactions. Here we propose a statistical approach to correlate surface magnetic relaxivity with the computational method applied to the NMR relaxation in order to elucidate the relationship between simulated relaxation time and pore size of the Digital Porous Medium. The proposed computational method simulates one- and two-dimensional NMR techniques reproducing, for example, longitudinal and transverse relaxation times (T 1 and T 2 , respectively), diffusion coefficients (D), as well as their correlations. For a good approximation between the numerical and experimental results, it is necessary to preserve the complexity of translational diffusion through the microstructures in the digital rocks. Therefore, we use Digital Porous Media obtained by 3D X-ray microtomography. To validate the method, relaxation times of ideal spherical pores were obtained and compared with the previous determinations by the Brownstein-Tarr model, as well as the computational approach proposed by Bergman. Furthermore, simulated and experimental results of synthetic porous media are compared. These results make evident the potential of computational physics in the analysis of the NMR data for complex porous materials. Copyright © 2018 Elsevier Inc. All rights reserved.

Characterizing 3-D flow velocity in evolving pore networks driven by CaCO3 precipitation and dissolution

NASA Astrophysics Data System (ADS)

Chojnicki, K. N.; Yoon, H.; Martinez, M. J.

2015-12-01

Understanding reactive flow in geomaterials is important for optimizing geologic carbon storage practices, such as using pore space efficiently. Flow paths can be complex in large degrees of geologic heterogeneities across scales. In addition, local heterogeneity can evolve as reactive transport processes alter the pore-scale morphology. For example, dissolved carbon dioxide may react with minerals in fractured rocks, confined aquifers, or faults, resulting in heterogeneous cementation (and/or dissolution) and evolving flow conditions. Both path and flow complexities are important and poorly characterized, making it difficult to determine their evolution with traditional 2-D transport models. Here we characterize the development of 3-D pore-scale flow with an evolving pore configuration due to calcium carbonate (CaCO3) precipitation and dissolution. A simple pattern of a microfluidic pore network is used initially and pore structures will become more complex due to precipitation and dissolution processes. At several stages of precipitation and dissolution, we directly visualize 3-D velocity vectors using micro particle image velocimetry and a laser scanning confocal microscope. Measured 3-D velocity vectors are then compared to 3-D simulated flow fields which will be used to simulate reactive transport. Our findings will highlight the importance of the 3-D flow dynamics and its impact on estimating reactive surface area over time. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. This material is based upon work supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001114.

Pleistocene hydrology of North America: The role of ice sheets in reorganizing groundwater flow systems

NASA Astrophysics Data System (ADS)

Person, Mark; McIntosh, Jennifer; Bense, Victor; Remenda, V. H.

2007-09-01

While the geomorphic consequences of Pleistocene megafloods have been known for some time, it has been only in the past 2 decades that hydrogeologists and glaciologists alike have begun to appreciate the important impact that ice sheet-aquifer interactions have had in controlling subsurface flow patterns, recharge rates, and the distribution of fresh water in confined aquifer systems across North America. In this paper, we document the numerous lines of geochemical, isotopic, and geomechanical evidence of ice sheet hydrogeology across North America. We also review the mechanical, thermal, and hydrologic processes that control subsurface fluid migration beneath ice sheets. Finite element models of subsurface fluid flow, permafrost formation, and ice sheet loading are presented to investigate the coupled nature of transport processes during glaciation/deglaciation. These indicate that recharge rates as high as 10 times modern values occurred as the Laurentide Ice Sheet overran the margins of sedimentary basins. The effects of ice sheet loading and permafrost formation result in complex transient flow patterns within aquifers and confining units alike. Using geochemical and environmental isotopic data, we estimate that the volume of glacial meltwater emplaced at the margins of sedimentary basins overrun by the Laurentide Ice Sheet totals about 3.7 × 104 km3, which is about 0.2% of the volume of the Laurentide Ice Sheet. Subglacial infiltration estimates based on continental-scale hydrologic models are even higher (5-10% of meltwater generated). These studies in sum call into question the widely held notion that groundwater flow patterns within confined aquifer systems are controlled primarily by the water table configuration during the Pleistocene. Rather, groundwater flow patterns were likely much more complex and transient in nature than has previously been thought. Because Pleistocene recharge rates are believed to be highly variable, these studies have profound implications for water resource managers charged with determining sustainable pumping rates from confined aquifers that host ice sheet meltwater.

Orca Behavior and Subsequent Aggression Associated with Oceanarium Confinement

PubMed Central

Anderson, Robert; Waayers, Robyn; Knight, Andrew

2016-01-01

Simple Summary Orca behaviors interacting with humans within apparent friendship bonds are reviewed, and some impediments to the human evaluation of delphinid intelligence are discussed. The subsequent involvement of these orcas and their offspring in aggressive incidents with humans is also documented and examined. This is particularly relevant given that the highest recorded rates of aggressive incidents have occurred among orcas who had previously established unstructured human friendship bonds prior to their inclusion within oceanaria performances. It is concluded that the confinement of orcas within aquaria, and their use in entertainment programs, is morally indefensible, given their high intelligence, complex behaviors, and the apparent adverse effects on orcas of such confinement and use. Abstract Based on neuroanatomical indices such as brain size and encephalization quotient, orcas are among the most intelligent animals on Earth. They display a range of complex behaviors indicative of social intelligence, but these are difficult to study in the open ocean where protective laws may apply, or in captivity, where access is constrained for commercial and safety reasons. From 1979 to 1980, however, we were able to interact with juvenile orcas in an unstructured way at San Diego’s SeaWorld facility. We observed in the animals what appeared to be pranks, tests of trust, limited use of tactical deception, emotional self-control, and empathetic behaviors. Our observations were consistent with those of a former Seaworld trainer, and provide important insights into orca cognition, communication, and social intelligence. However, after being trained as performers within Seaworld’s commercial entertainment program, a number of orcas began to exhibit aggressive behaviors. The orcas who previously established apparent friendships with humans were most affected, although significant aggression also occurred in some of their descendants, and among the orcas they lived with. Such oceanaria confinement and commercial use can no longer be considered ethically defensible, given the current understanding of orcas’ advanced cognitive, social, and communicative capacities, and of their behavioral needs. PMID:27548232

Hydrogeologic characteristics and water quality of a confined sand unit in the surficial aquifer system, Hunter Army Airfield, Chatham County, Georgia

USGS Publications Warehouse

Gonthier, Gerard

2012-01-01

An 80-foot-deep well (36Q397, U.S. Geological Survey site identification 320146081073701) was constructed at Hunter Army Airfield to assess the potential of using the surficial aquifer system as a water source to irrigate a ballfield complex. A 300-foot-deep test hole was drilled beneath the ballfield complex to characterize the lithology and water-bearing characteristics of sediments above the Upper Floridan aquifer. The test hole was then completed as well 36Q397 open to a 19-foot-thick shallow, confined sand unit contained within the surficial aquifer system. A single-well, 24-hour aquifer test was performed by pumping well 36Q397 at a rate of 50 gallons per minute during July 13-14, 2011, to characterize the hydrologic properties of the shallow, confined sand unit. Two pumping events prior to the aquifer test affected water levels. Drawdown during all three pumping events and residual drawdown during recovery periods were simulated using the Theis formula on multiple changes in discharge rate. Simulated drawdown and residual drawdown match well with measured drawdown and residual drawdown using values of horizontal hydraulic conductivity and specific storage, which are typical for a confined sand aquifer. Based on the hydrologic parameters used to match simulated drawdown and residual drawdown to measured drawdown and residual drawdown, the transmissivity of the sand was determined to be about 400 feet squared per day. The horizontal hydraulic conductivity of the sand was determined to be about 20 feet per day. Analysis of a water-quality sample indicated that the water is suitable for irrigation. Sample analysis indicated a calcium-carbonate type water having a total dissolved solids concentration of 39 milligrams per liter. Specific conductance and concentrations of all analyzed constituents were below those that would be a concern for irrigation, and were below primary and secondary water-quality criteria levels.

Lithium Ion Recognition with Nanofluidic Diodes through Host-Guest Complexation in Confined Geometries.

PubMed

Ali, Mubarak; Ahmed, Ishtiaq; Ramirez, Patricio; Nasir, Saima; Mafe, Salvador; Niemeyer, Christof M; Ensinger, Wolfgang

2018-05-15

The lithium ion recognition is receiving significant attention because of its application in pharmaceuticals, lubricants and, especially, in energy technology. We present a nanofluidic device for specific lithium ion recognition via host-guest complexation in a confined environment. A lithium-selective receptor molecule, the aminoethyl-benzo-12-crown-4 (BC12C4-NH 2 ), is designed and functionalized on single conical nanopores in polyethylene terephthalate (PET) membranes. The native carboxylic acid groups on the pore walls are covalently linked with the crown ether moieties and the process is monitored from the changes in the current-voltage ( I- V) curves. The B12-crown-4 moieties are known to specifically bind with lithium ions and when the modified pore is exposed to different alkali metal chloride solutions separately, significant changes in the ion current and rectification are only observed for lithium chloride. This fact suggests the generation of positively charged B12C4-Li + complexes on the pore surface. Furthermore, the nanofluidic diode is able to recognize the lithium ion even in the presence of high concentrations of potassium ions in the external electrolyte solution. Thus, this nanodevice suggests a strategy to miniaturize nanofluidic porous systems for efficient recognition, extraction, and separation of lithium from raw materials.

Effect of pore geometry on the compressibility of a confined simple fluid

NASA Astrophysics Data System (ADS)

Dobrzanski, Christopher D.; Maximov, Max A.; Gor, Gennady Y.

2018-02-01

Fluids confined in nanopores exhibit properties different from the properties of the same fluids in bulk; among these properties is the isothermal compressibility or elastic modulus. The modulus of a fluid in nanopores can be extracted from ultrasonic experiments or calculated from molecular simulations. Using Monte Carlo simulations in the grand canonical ensemble, we calculated the modulus for liquid argon at its normal boiling point (87.3 K) adsorbed in model silica pores of two different morphologies and various sizes. For spherical pores, for all the pore sizes (diameters) exceeding 2 nm, we obtained a logarithmic dependence of fluid modulus on the vapor pressure. Calculation of the modulus at saturation showed that the modulus of the fluid in spherical pores is a linear function of the reciprocal pore size. The calculation of the modulus of the fluid in cylindrical pores appeared too scattered to make quantitative conclusions. We performed additional simulations at higher temperature (119.6 K), at which Monte Carlo insertions and removals become more efficient. The results of the simulations at higher temperature confirmed both regularities for cylindrical pores and showed quantitative difference between the fluid moduli in pores of different geometries. Both of the observed regularities for the modulus stem from the Tait-Murnaghan equation applied to the confined fluid. Our results, along with the development of the effective medium theories for nanoporous media, set the groundwork for analysis of the experimentally measured elastic properties of fluid-saturated nanoporous materials.

Changing Places: A Cross-Language Perspective on Frequency and Family Size in Dutch and Hebrew

ERIC Educational Resources Information Center

Moscoso del Prado Martin, Fermin; Deutsch, Avital; Frost, Ram; Schreuder, Robert; De Jong, Nivja H.; Baayen, R. Harald

2005-01-01

This study uses the morphological family size effect as a tool for exploring the degree of isomorphism in the networks of morphologically related words in the Hebrew and Dutch mental lexicon. Hebrew and Dutch are genetically unrelated, and they structure their morphologically complex words in very different ways. Two visual lexical decision…

Effect of morphological changes in feather follicles of chicken carcasses after defeathering and chilling on the degree of skin contamination by Campylobacter species

PubMed Central

LATT, Khin Maung; URATA, Ayaka; SHINKI, Taisuke; SASAKI, Satomi; TANIGUCHI, Takako; MISAWA, Naoaki

2017-01-01

Campylobacter jejuni and C. coli are the leading causes of enteric infections in many developed countries. Healthy chickens are considered to act as reservoirs of campylobacters, as the organisms colonize the intestinal tract. Once infected birds enter a processing plant, contamination of chicken carcasses with campylobacters occurs over the entire skin during defeathering and evisceration due to leakage of crop and/or intestinal contents. Although the role of feather follicles in the contamination of chicken carcasses by campylobacters during processing is still debatable, it has been considered that the microorganisms would be entrapped and retained in the follicles due to the morphological changes resulting from defeathering and chilling. In the present study, we observed the morphology of feather follicles in chicken carcasses after defeathering and chilling. A total of 3,133 feather follicles were examined for morphological changes before and after chilling. Shortly after defeathering, most (91.5%) of the follicles were closed, whereas after chilling they were either closed (85.5%) or open (6%), although a small proportion of enlarged follicles became smaller or closed (2.6%). Moreover, 5.9% of the follicles that were slightly open became further enlarged after chilling. Furthermore, the proportion of enlarged feather follicles that became closed after chilling showed no discernible relationship with the degree of campylobacter contamination in different areas of the carcass skin, suggesting that campylobacters may not be confined to feather follicles as a result of the morphological changes attributable to defeathering and chilling. PMID:29151444

Effect of morphological changes in feather follicles of chicken carcasses after defeathering and chilling on the degree of skin contamination by Campylobacter species.

PubMed

Latt, Khin Maung; Urata, Ayaka; Shinki, Taisuke; Sasaki, Satomi; Taniguchi, Takako; Misawa, Naoaki

2018-01-01

Campylobacter jejuni and C. coli are the leading causes of enteric infections in many developed countries. Healthy chickens are considered to act as reservoirs of campylobacters, as the organisms colonize the intestinal tract. Once infected birds enter a processing plant, contamination of chicken carcasses with campylobacters occurs over the entire skin during defeathering and evisceration due to leakage of crop and/or intestinal contents. Although the role of feather follicles in the contamination of chicken carcasses by campylobacters during processing is still debatable, it has been considered that the microorganisms would be entrapped and retained in the follicles due to the morphological changes resulting from defeathering and chilling. In the present study, we observed the morphology of feather follicles in chicken carcasses after defeathering and chilling. A total of 3,133 feather follicles were examined for morphological changes before and after chilling. Shortly after defeathering, most (91.5%) of the follicles were closed, whereas after chilling they were either closed (85.5%) or open (6%), although a small proportion of enlarged follicles became smaller or closed (2.6%). Moreover, 5.9% of the follicles that were slightly open became further enlarged after chilling. Furthermore, the proportion of enlarged feather follicles that became closed after chilling showed no discernible relationship with the degree of campylobacter contamination in different areas of the carcass skin, suggesting that campylobacters may not be confined to feather follicles as a result of the morphological changes attributable to defeathering and chilling.

Biogeography, phylogeny, and morphological evolution of central Texas cave and spring salamanders

PubMed Central

2013-01-01

Background Subterranean faunal radiations can result in complex patterns of morphological divergence involving both convergent or parallel phenotypic evolution and cryptic species diversity. Salamanders of the genus Eurycea in central Texas provide a particularly challenging example with respect to phylogeny reconstruction, biogeography and taxonomy. These predominantly aquatic species inhabit karst limestone aquifers and spring outflows, and exhibit a wide range of morphological and genetic variation. We extensively sampled spring and cave populations of six Eurycea species within this group (eastern Blepsimolge clade), to reconstruct their phylogenetic and biogeographic history using mtDNA and examine patterns and origins of cave- and surface-associated morphological variation. Results Genetic divergence is generally low, and many populations share ancestral haplotypes and/or show evidence of introgression. This pattern likely indicates a recent radiation coupled with a complex history of intermittent connections within the aquatic karst system. Cave populations that exhibit the most extreme troglobitic morphologies show no or very low divergence from surface populations and are geographically interspersed among them, suggesting multiple instances of rapid, parallel phenotypic evolution. Morphological variation is diffuse among cave populations; this is in contrast to surface populations, which form a tight cluster in morphospace. Unexpectedly, our analyses reveal two distinct and previously unrecognized morphological groups encompassing multiple species that are not correlated with spring or cave habitat, phylogeny or geography, and may be due to developmental plasticity. Conclusions The evolutionary history of this group of spring- and cave-dwelling salamanders reflects patterns of intermittent isolation and gene flow influenced by complex hydrogeologic dynamics that are characteristic of karst regions. Shallow genetic divergences among several species, evidence of genetic exchange, and nested relationships across morphologically disparate cave and spring forms suggests that cave invasion was recent and many troglobitic morphologies arose independently. These patterns are consistent with an adaptive-shift hypothesis of divergence, which has been proposed to explain diversification in other karst fauna. While cave and surface forms often do not appear to be genetically isolated, morphological diversity within and among populations may be maintained by developmental plasticity, selection, or a combination thereof. PMID:24044519

Comparative morphology of the axial complex and interdependence of internal organ systems in sea urchins (Echinodermata: Echinoidea).

PubMed

Ziegler, Alexander; Faber, Cornelius; Bartolomaeus, Thomas

2009-06-09

The axial complex of echinoderms (Echinodermata) is composed of various primary and secondary body cavities that interact with each other. In sea urchins (Echinoidea), structural differences of the axial complex in "regular" and irregular species have been observed, but the reasons underlying these differences are not fully understood. In addition, a better knowledge of axial complex diversity could not only be useful for phylogenetic inferences, but improve also an understanding of the function of this enigmatic structure. We therefore analyzed numerous species of almost all sea urchin orders by magnetic resonance imaging, dissection, histology, and transmission electron microscopy and compared the results with findings from published studies spanning almost two centuries. These combined analyses demonstrate that the axial complex is present in all sea urchin orders and has remained structurally conserved for a long time, at least in the "regular" species. Within the Irregularia, a considerable morphological variation of the axial complex can be observed with gradual changes in topography, size, and internal architecture. These modifications are related to the growing size of the gastric caecum as well as to the rearrangement of the morphology of the digestive tract as a whole. The structurally most divergent axial complex can be observed in the highly derived Atelostomata in which the reorganization of the digestive tract is most pronounced. Our findings demonstrate a structural interdependence of various internal organs, including digestive tract, mesenteries, and the axial complex.

Characterizing and locating air pollution sources in a complex industrial district using optical remote sensing technology and multivariate statistical modeling.

PubMed

Chang, Pao-Erh Paul; Yang, Jen-Chih Rena; Den, Walter; Wu, Chang-Fu

2014-09-01

Emissions of volatile organic compounds (VOCs) are most frequent environmental nuisance complaints in urban areas, especially where industrial districts are nearby. Unfortunately, identifying the responsible emission sources of VOCs is essentially a difficult task. In this study, we proposed a dynamic approach to gradually confine the location of potential VOC emission sources in an industrial complex, by combining multi-path open-path Fourier transform infrared spectrometry (OP-FTIR) measurement and the statistical method of principal component analysis (PCA). Close-cell FTIR was further used to verify the VOC emission source by measuring emitted VOCs from selected exhaust stacks at factories in the confined areas. Multiple open-path monitoring lines were deployed during a 3-month monitoring campaign in a complex industrial district. The emission patterns were identified and locations of emissions were confined by the wind data collected simultaneously. N,N-Dimethyl formamide (DMF), 2-butanone, toluene, and ethyl acetate with mean concentrations of 80.0 ± 1.8, 34.5 ± 0.8, 103.7 ± 2.8, and 26.6 ± 0.7 ppbv, respectively, were identified as the major VOC mixture at all times of the day around the receptor site. As the toxic air pollutant, the concentrations of DMF in air samples were found exceeding the ambient standard despite the path-average effect of OP-FTIR upon concentration levels. The PCA data identified three major emission sources, including PU coating, chemical packaging, and lithographic printing industries. Applying instrumental measurement and statistical modeling, this study has established a systematic approach for locating emission sources. Statistical modeling (PCA) plays an important role in reducing dimensionality of a large measured dataset and identifying underlying emission sources. Instrumental measurement, however, helps verify the outcomes of the statistical modeling. The field study has demonstrated the feasibility of using multi-path OP-FTIR measurement. The wind data incorporating with the statistical modeling (PCA) may successfully identify the major emission source in a complex industrial district.

The comparative osteology of the petrotympanic complex (ear region) of extant baleen whales (Cetacea: Mysticeti).

PubMed

Ekdale, Eric G; Berta, Annalisa; Deméré, Thomas A

2011-01-01

Anatomical comparisons of the ear region of baleen whales (Mysticeti) are provided through detailed osteological descriptions and high-resolution photographs of the petrotympanic complex (tympanic bulla and petrosal bone) of all extant species of mysticete cetaceans. Salient morphological features are illustrated and identified, including overall shape of the bulla, size of the conical process of the bulla, morphology of the promontorium, and the size and shape of the anterior process of the petrosal. We place our comparative osteological observations into a phylogenetic context in order to initiate an exploration into petrotympanic evolution within Mysticeti. The morphology of the petrotympanic complex is diagnostic for individual species of baleen whale (e.g., sigmoid and conical processes positioned at midline of bulla in Balaenoptera musculus; confluence of fenestra cochleae and perilymphatic foramen in Eschrichtius robustus), and several mysticete clades are united by derived characteristics. Balaenids and neobalaenids share derived features of the bulla, such as a rhomboid shape and a reduced anterior lobe (swelling) in ventral aspect, and eschrichtiids share derived morphologies of the petrosal with balaenopterids, including loss of a medial promontory groove and dorsomedial elongation of the promontorium. Monophyly of Balaenoidea (Balaenidae and Neobalaenidae) and Balaenopteroidea (Balaenopteridae and Eschrichtiidae) was recovered in phylogenetic analyses utilizing data exclusively from the petrotympanic complex. This study fills a major gap in our knowledge of the complex structures of the mysticete petrotympanic complex, which is an important anatomical region for the interpretation of the evolutionary history of mammals. In addition, we introduce a novel body of phylogenetically informative characters from the ear region of mysticetes. Our detailed anatomical descriptions, illustrations, and comparisons provide valuable data for current and future studies on the phylogenetic relationships, evolution, and auditory physiology of mysticetes and other cetaceans throughout Earth's history.

Pinus Monophylla (Single Needled Pinyon Pine) show morphological changes in needle cell size and stomata over the past 100 years of rising CO2 in Western Arid Ecosystems.

NASA Astrophysics Data System (ADS)

Van De Water, P. K.

2016-12-01

The size, frequency, and morphology of leaf surface stomata is used to reconstruct past levels of atmospheric carbon dioxide over geologic time. This technique relies on measuring cell and cell-clusters to correlate with changes of known carbon dioxide levels in the atmosphere. Unfortunately, not all plants are suitable because the occurrence and placement of stomatal cell-complexes differ significantly between plant families. Monocot and dicot angiosperms exhibit different types of stomata and stomatal complexes that lack order and thus are unsuitable. But, in gymnosperms, the number and distribution of stomata and pavement cells is formalized and can be used to reconstruct past atmospheric carbon dioxide levels. However, characteristic of each plant species must still be considered. For example, conifers are useful but are divided into two-needle to five-needle pines, or have irregular surface morphology (Pseudotsuga sp. and Tsuga sp. needles). This study uses Pinus monophylla an undivided needle morphology, that being a cylinder has no interior surface cells. Pinus monophylla (single needle pinyon) needles were collected along Geiger Grade (Nevada State Highway 341, Reno) in 2005 and 2013 from 1500m to 2195m. Herbarium samples were also collected from 13 historic collections made between 1911 and 1994. The study determined changes with elevation and/or over time using in these populations. Using Pinus monophylla, insured needles represented a single surface with stomata, stomatal complex cells, and co-occurring pavement cell types. Results show decreased stomatal densities (stomata/area), stomatal index (stomata/stomata + epidermal cells) and stable stomata per row (stomata/row) . Epidermal cell density (Epidermal Cells /Area), and Pavement cell density (Pavement cell/area) track stomatal density similarly. Data comparison, using elevation in the 2005 and 2013 collections showed no-significant trends. Individual stomatal complexes show no differences in the size and shape over time or with elevation. Stomata morphology and the stomatal pores appear conservative. However some complex cells show a morphology suggesting they are not fully formed and functional. These characteristics appear often in the modern material suggesting some stomata never fully develop.

Detecting bacteria and Determining Their Susceptibility to Antibiotics by Stochastic Confinement in Nanoliter Droplets using Plug-Based Microfluidics

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

Boedicker, J.; Li, L; Kline, T

2008-01-01

This article describes plug-based microfluidic technology that enables rapid detection and drug susceptibility screening of bacteria in samples, including complex biological matrices, without pre-incubation. Unlike conventional bacterial culture and detection methods, which rely on incubation of a sample to increase the concentration of bacteria to detectable levels, this method confines individual bacteria into droplets nanoliters in volume. When single cells are confined into plugs of small volume such that the loading is less than one bacterium per plug, the detection time is proportional to plug volume. Confinement increases cell density and allows released molecules to accumulate around the cell, eliminatingmore » the pre-incubation step and reducing the time required to detect the bacteria. We refer to this approach as stochastic confinement. Using the microfluidic hybrid method, this technology was used to determine the antibiogram - or chart of antibiotic sensitivity - of methicillin-resistant Staphylococcus aureus (MRSA) to many antibiotics in a single experiment and to measure the minimal inhibitory concentration (MIC) of the drug cefoxitin (CFX) against this strain. In addition, this technology was used to distinguish between sensitive and resistant strains of S. aureus in samples of human blood plasma. High-throughput microfluidic techniques combined with single-cell measurements also enable multiple tests to be performed simultaneously on a single sample containing bacteria. This technology may provide a method of rapid and effective patient-specific treatment of bacterial infections and could be extended to a variety of applications that require multiple functional tests of bacterial samples on reduced timescales.« less

Laboratory Investigation of Coal Deformation Behavior and Its Influence on Permeability Evolution During Methane Displacement by CO2

NASA Astrophysics Data System (ADS)

Fan, Jingjing; Feng, Ruimin; Wang, Jin; Wang, Yanbin

2017-07-01

Geological sequestration of CO2 in coal seams is of significant interest to both academia and industry. A thorough laboratory investigation of mechanical and flow behaviors is crucial for understanding the complex response of coalbeds to CO2 injection-enhanced coalbed methane recovery (CO2-ECBM) operation. In this work, systematic experiments were carried out on cylindrical coal core specimens under different uniform confining stresses. The coal deformation caused by variations in effective stress as well as the sorption-induced matrix swelling/shrinkage was monitored. The competitive gas sorption characteristics and permeability evolution during the process of methane displacement by CO2 were also investigated. The measured volumetric strain results indicate that sorption-induced strain is the dominant factor in the coal deformation. The relationship between the volumetric strain and the adsorbed gas volume has been revealed to be a linear function. Experimental results obtained under different stress conditions suggest that higher confining stress suppresses the increase in both volumetric strain and the adsorbed gas volume. Furthermore, both methane displacement and CO2 injection are reduced when applying higher confining stresses. In addition, the permeability enhancement is heavily suppressed at higher confining stress. At a certain confining stress, a characteristic "U-shaped" trend of permeability is presented as a function of decreasing pore pressure. This study contributes to the understanding of coal deformation and its impact on permeability evolution under uniformly stressed condition, which has practical significance for CO2 sequestration and CO2-ECBM operation in the Qinshui basin.

Molecular and Morphological Inference of Three Cryptic Species within the Merodon aureus Species Group (Diptera: Syrphidae).

PubMed

Šašić, Ljiljana; Ačanski, Jelena; Vujić, Ante; Ståhls, Gunilla; Radenković, Snežana; Milić, Dubravka; Obreht Vidaković, Dragana; Đan, Mihajla

2016-01-01

The Merodon aureus species group (Diptera: Syrphidae: Eristalinae) comprises a number of different sub-groups and species complexes. In this study we focus on resolving the taxonomic status of the entity previously identified as M. cinereus B, here identified as M. atratus species complex. We used an integrative approach based on morphological descriptions, combined with supporting characters that were obtained from molecular analyses of the mitochondrial cytochrome c oxidase I gene as well as from geometric morphometry of wing and surstylus shapes and environmental niche comparisons. All applied data and methods distinguished and supported three morphologically cryptic species: M. atratus stat. nov., M. virgatus sp. nov. and M. balkanicus sp. nov., which constitute the M. atratus species complex. We present an identification key for the sub-groups and species complexes of the M. aureus species group occurring in Europe, describe the taxa and discuss the utility of the applied methods for species delimitation. The estimated divergence times for the species splits of these taxa coincide with the Pleistocene Günz-Mindel interglaciation and the Great interglaciation (between the Ris and Mindel glacial periods).

Reverse micelle synthesis of nanoscale metal containing catalysts. [Nickel metal (with a nickel oxide surface layer) and iron oxyhydroxide nanoscale powders

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

Darab, J.G.; Fulton, J.L.; Linehan, J.C.

1993-03-01

The need for morphological control during the synthesis of catalyst precursor powders is generally accepted to be important. In the liquefaction of coal, for example, iron-bearing catalyst precursor particles containing individual crystallites with diameters in the 1-100 nanometer range are believed to achieve good dispersion through out the coal-solvent slurry during liquefaction 2 runs and to undergo chemical transformations to catalytically active iron sulfide phases. The production of the nanoscale powders described here employs the confining spherical microdomains comprising the aqueous phase of a modified reverse micelle (MRM) microemulsion system as nanoscale reaction vessels in which polymerization, electrochemical reduction andmore » precipitation of solvated salts can occur. The goal is to take advantage of the confining nature of micelles to kinetically hinder transformation processes which readily occur in bulk aqueous solution in order to control the morphology and phase of the resulting powder. We have prepared a variety of metal, alloy, and metal- and mixed metal-oxide nanoscale powders from appropriate MRM systems. Examples of nanoscale powders produced include Co, Mo-Co, Ni[sub 3]Fe, Ni, and various oxides and oxyhydroxides of iron. Here, we discuss the preparation and characterization of nickel metal (with a nickel oxide surface layer) and iron oxyhydroxide MRM nanoscale powders. We have used extended x-ray absorption fine structure (EXAFS) spectroscopy to study the chemical polymerization process in situ, x-ray diffraction (XRD), scanning and transmission electron microcroscopies (SEM and TEM), elemental analysis and structural modelling to characterize the nanoscale powders produced. The catalytic activity of these powders is currently being studied.« less

Directed ordering of phase separated domains and dewetting of thin polymer blend films on a topographically patterned substrate.

PubMed

Bhandaru, Nandini; Karim, Alamgir; Mukherjee, Rabibrata

2017-07-21

Substrate pattern guided self-organization of ultrathin and confined polymeric films on a topographically patterned substrate is a useful approach for obtaining ordered meso and nano structures over large areas, particularly if the ordering is achieved during film preparation itself, eliminating any post-processing such as thermal or solvent vapor annealing. By casting a dilute solution of two immiscible polymers, polystyrene (PS) and polymethylmethacrylate (PMMA), from a common solvent (toluene) on a topographically patterned substrate with a grating geometry, we show the formation of self-organized meso patterns with various degrees of ordering. The morphology depends on both the concentration of the dispensed solution (C n ) and the blend composition (R B ). Depending on the extent of dewetting during spin coating, the final morphologies can be classified into three distinct categories. At a very low C n the solution dewets fully, resulting in isolated polymer droplets aligned along substrate grooves (Type 1). Type 2 structures comprising isolated threads with aligned phase separated domains along each substrate groove are observed at intermediate C n . A continuous film (Type 3) is obtained above a critical concentration (C n *) that depends on R B . While the extent of ordering of the domains gradually diminishes with an increase in film thickness for Type 3 patterns, the size of the domains remains much smaller than that on a flat substrate, resulting in significant downsizing of the features due to the lateral confinement imposed on the phase separation process by the topographic patterns. Finally, we show that some of these structures exhibit excellent broadband anti-reflection (AR) properties.

A Comparative Study of the Eruptive and Non-eruptive Flares Produced by the Largest Active Region of Solar Cycle 24

NASA Astrophysics Data System (ADS)

Sarkar, Ranadeep; Srivastava, Nandita

2018-02-01

We investigate the morphological and magnetic characteristics of solar active region (AR) NOAA 12192. AR 12192 was the largest region of Solar Cycle 24; it underwent noticeable growth and produced 6 X-class flares, 22 M-class flares, and 53 C-class flares in the course of its disc passage. However, the most peculiar fact of this AR is that it was associated with only one CME in spite of producing several X-class flares. In this work, we carry out a comparative study between the eruptive and non-eruptive flares produced by AR 12192. We find that the magnitude of abrupt and permanent changes in the horizontal magnetic field and Lorentz force are significantly smaller in the case of the confined flares compared to the eruptive one. We present the areal evolution of AR 12192 during its disc passage. We find the flare-related morphological changes to be weaker during the confined flares, whereas the eruptive flare exhibits a rapid and permanent disappearance of penumbral area away from the magnetic neutral line after the flare. Furthermore, from the extrapolated non-linear force-free magnetic field, we examine the overlying coronal magnetic environment over the eruptive and non-eruptive zones of the AR. We find that the critical decay index for the onset of torus instability was achieved at a lower height over the eruptive flaring region, than for the non-eruptive core area. These results suggest that the decay rate of the gradient of overlying magnetic-field strength may play a decisive role to determine the CME productivity of the AR. In addition, the magnitude of changes in the flare-related magnetic characteristics are found to be well correlated with the nature of solar eruptions.

Genetic and morphological heterogeneity among populations of Eurytemora affinis (Crustacea: Copepoda: Temoridae) in European waters.

PubMed

Sukhikh, Natalia; Souissi, Anissa; Souissi, Sami; Winkler, Gesche; Castric, Vincent; Holl, Anne-Catherine; Alekseev, Victor

2016-01-01

Our understanding of the systematics of the Eurytemora affinis complex developed at a fast pace over the last decades. Formerly considered as a complex of cryptic species, it is now believed to include three valid species: E. affinis, Eurytemora carolleeae, and Eurytemora caspica. American and European representatives have been studied in detail with respect to fine-scale geographic distribution, levels of genetic subdivision, evolutionary and demographic histories. Morphological components have been less explored. In this study, an analysis of the phylogeny and morphology of E. affinis was done, with a special focus on European populations. A total of 447 individuals of E. affinis from Europe were analyzed with genetic tools and 170 individuals according to morphological criteria. Common and new morphological and genetic features were analyzed. For this, we used ML and Bayesian methods to analyze the bar coding mt-DNA gene cytochrome c oxidase I subunit. Both genetic and morphological analyses showed high heterogeneities among the E. affinis populations from Europe. As a result, three local populations of E. affinis in Western Europe, including the European part of Russia, were established. Their genetic and morphological heterogeneity corresponded to the subspecies level. Copyright © 2016 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Tectonic and Sedimentation Interactions in the East Caribbean Subduction Zone: AN Overview from the Orinoco Delta to the Barbados Accretionary Prism

NASA Astrophysics Data System (ADS)

Deville, E.

2011-12-01

Recent marine geophysical acquisitions and piston-coring allow to better understand the close interactions between the sand-rich Orinoco turbidite system and the compressional structures of the Barbados prism. Because of the morphologic and tectonic control in the east-Caribbean active margin, the Orinoco turbiditic pattern system does not exhibit a classic fan geometry. The sea-floor geometry between the slope of the front of the Barbados prism and the slope of the South-American margin induces the convergence of the turbidite channels toward the abyssal plain, at the front of the accretionary prism. Also, whereas in most passive margins the turbidite systems are organized upstream to downstream as canyon, then channel-levee, then lobes, here, due to the tectonic control, the sedimentary system is organized as channel-levee, then canyons, then channelized lobes. At the edge of the Orinoco platform, the system has multiple sources with several distributaries and downward the channel courses are complex with frequent convergences or divergences that are emphasized by the effects of the undulating seafloor tectonic morphologies associated with active thrust tectonics and mud volcanism. On top of the accretionary prism, turbidite sediments are filling transported piggy-back basins whose timing of sedimentation vs. deformation is complex. Erosion processes are almost absent on the highly subsiding Orinoco platform and in the upper part of the turbidite system. Erosion processes develop mostly between 2000 and 4000 m of water depth, above the compressional structures of the Barbados prism (canyons up to 3 km wide and 300 m deep). In the abyssal plain, turbiditic channels develop on very long distance (> 1000 km) joining the mid-Atlantic channel (sourced mostly by the Amazon), filling several elongated basins corresponding to transform faults (notably the Barracuda Basin), and finally sourcing the Puerto-Rico trench, the deepest morphologic depression of this region. Piston-core surveys have demonstrated that turbidite sediments above the accretionary prism and in the abyssal plain are mostly coarse sandy deposits covered by recent pelagic planktonic-rich sediments, which indicate that sand deposition has slow down during the post-glacial sea level rise. Numerical stratigraphic modeling suggests that during the last glacial event, the main depocenters were located above the tectonic prism and in the abyssal plain, at the front of the prism and that, during the Holocene eustatic rise, a large accommodation space formed on the shelf confining sedimentation mostly on the Orinoco deltaic platform and producing a starvation downstream in the turbidite system. This is in good agreement with the piston coring results which show low deep turbidite sedimentation rates during recent times.

A Study of Abortion and Problems in Decision-Making

ERIC Educational Resources Information Center

Cotroneo, Margaret; Krasner, Barbara R.

1977-01-01

This paper is directed to people who, sufficiently disturbed by complex realities of problem pregnancies, are prepared to think beyond the confines of ideology. It is a challenge to people who tend to reduce the problem of unwanted pregnancies either to "abortion on demand" or to "right to life" ideologies. (Author)

Paradoxes of Learning: On Becoming an Individual in Society.

ERIC Educational Resources Information Center

Jarvis, Peter

This book explores how learning is the lifetime quest to understand personal identity, purpose, and meaning while conforming and adapting to the perceived and real confines of a paradoxical society. It examines the complex social experience of learning, revealing how culture, gender, race, and other societal factors shape and mold an individual's…

Arabidopsis tetraspanins are confined to discrete expression domains and cell types in reproductive tissues and form homo-and heterodimers when expressed in yeast

USDA-ARS?s Scientific Manuscript database

Tetraspanins are evolutionary conserved transmembrane proteins present in all multicellular organisms. In animals, they are known to act as central organizers of membrane complexes and thought to facilitate diverse biological processes, such as cell proliferation, movement, adhesion, and fusion. The...

Physical modelling of the nuclear pore complex

PubMed Central

Fassati, Ariberto; Ford, Ian J.; Hoogenboom, Bart W.

2013-01-01

Physically interesting behaviour can arise when soft matter is confined to nanoscale dimensions. A highly relevant biological example of such a phenomenon is the Nuclear Pore Complex (NPC) found perforating the nuclear envelope of eukaryotic cells. In the central conduit of the NPC, of ∼30–60 nm diameter, a disordered network of proteins regulates all macromolecular transport between the nucleus and the cytoplasm. In spite of a wealth of experimental data, the selectivity barrier of the NPC has yet to be explained fully. Experimental and theoretical approaches are complicated by the disordered and heterogeneous nature of the NPC conduit. Modelling approaches have focused on the behaviour of the partially unfolded protein domains in the confined geometry of the NPC conduit, and have demonstrated that within the range of parameters thought relevant for the NPC, widely varying behaviour can be observed. In this review, we summarise recent efforts to physically model the NPC barrier and function. We illustrate how attempts to understand NPC barrier function have employed many different modelling techniques, each of which have contributed to our understanding of the NPC.

Surface-confined Ullmann coupling of thiophene substituted porphyrins

NASA Astrophysics Data System (ADS)

Beggan, J. P.; Boyle, N. M.; Pryce, M. T.; Cafolla, A. A.

2015-09-01

The covalent coupling of (5,10,15,20-tetrabromothien-2-ylporphyrinato)zinc(II) (TBrThP) molecules on the Ag(111) surface has been investigated under ultra-high-vacuum conditions, using scanning tunnelling microscopy and x-ray photoelectron spectroscopy. The findings provide atomic-level insight into surface-confined Ullmann coupling of thiophene substituted porphyrins, analyzing the progression of organometallic intermediate to final coupled state. Adsorption of the TBrThP molecules on the Ag(111) surface at room temperature is found to result in the reductive dehalogenation of the bromothienyl substituents and the subsequent formation of single strand and crosslinked coordination networks. The coordinated substrate atoms bridge the proximal thienyl groups of the organometallic intermediate, while the cleaved bromine atoms are bound on the adjacent Ag(111) surface. The intermediate complex displays a thermal lability at ˜423 K that results in the dissociation of the proximal thienyl groups with the concomitant loss of the surface bound bromine. At the thermally induced dissociation of the intermediate complex the resultant thienylporphyrin derivatives covalently couple, leading to the formation of a polymeric network of thiophene linked and meso-meso fused porphyrins.

Looking at hydrogen motions in confinement. The uniqueness of Quasi-Elastic Neutron Scattering

NASA Astrophysics Data System (ADS)

Fischer, J.; Tsapatsaris, N.; de Paula, E.; Bordallo, H. N.

2014-09-01

Why in a barren and hot desert, clays can contain a significant fraction of water? Why does concrete crack? How can we demonstrate that complexation of a drug does not alter its conformation in a way that affects its functionality? In this paper we present results on various studies using Quasi-Elastic Neutron Scattering aimed at clarifying these questions. To allow for a better understanding of neutron scattering, a brief introduction to the basics of its theory is presented. Following the theoretical part, experimental results dealing with the effects of confinement on the water dynamics caused by the interfaces in clays and the nano- and micro-pores of concrete are reviewed in detail. At the end, recent Quasi-Elastic Neutron Scattering investigations on the complexation of the local anesthetics Bupivacaine (BVC.HCl, C18H28N20.HCl.H2O) and Ropivacaine (RVC.HCl, C17H26N20.HCl.H2O) into the cyclic β-cyclodextrin oligosaccharide are presented. To conclude, the perspectives that the European Spallation Source brings to this subject are discussed.

Tailoring graphene layer-to-layer growth

NASA Astrophysics Data System (ADS)

Li, Yongtao; Wu, Bin; Guo, Wei; Wang, Lifeng; Li, Jingbo; Liu, Yunqi

2017-06-01

A layered material grown between a substrate and the upper layer involves complex interactions and a confined reaction space, representing an unusual growth mode. Here, we show multi-layer graphene domains grown on liquid or solid Cu by the chemical vapor deposition method via this ‘double-substrate’ mode. We demonstrate the interlayer-induced coupling effect on the twist angle in bi- and multi-layer graphene. We discover dramatic growth disunity for different graphene layers, which is explained by the ideas of a chemical ‘gate’ and a material transport process within a confined space. These key results lead to a consistent framework for understanding the dynamic evolution of multi-layered graphene flakes and tailoring the layer-to-layer growth for practical applications.

Mean and oscillating plasma flows and turbulence interactions across the L-H confinement transition.

PubMed

Conway, G D; Angioni, C; Ryter, F; Sauter, P; Vicente, J

2011-02-11

A complex interaction between turbulence driven E × B zonal flow oscillations, i.e., geodesic acoustic modes (GAMs), the turbulence, and mean equilibrium flows is observed during the low to high (L-H) plasma confinement mode transition in the ASDEX Upgrade tokamak. Below the L-H threshold at low densities a limit-cycle oscillation forms with competition between the turbulence level and the GAM flow shearing. At higher densities the cycle is diminished, while in the H mode the cycle duration becomes too short to sustain the GAM, which is replaced by large amplitude broadband flow perturbations. Initially GAM amplitude increases as the H-mode transition is approached, but is then suppressed in the H mode by enhanced mean flow shear.

Experimental Observation of Temperature Variation of Surface Magnetization on a Nanostructured Co/Pt Thin Film

NASA Astrophysics Data System (ADS)

Nwokoye, Chidubem; Della Torre, Edward; Bennett, Lawrence; Siddique, Abid; Narducci, Frank A.

2015-04-01

Magneto-optic Kerr effect, MOKE, is used to observe the complex rotation of the polarization plane of linearly polarized incident light reflected from the surface of a magnetic material. The rotation is directly related to the surface magnetization of the material. We report work that extends the experiments in that studied Bose-Einstein Condensation (BEC) of magnons in confined nanostructures. We report the MOKE experimental results of an investigation of surface magnetic remanence and coercivity on a Co/Pt ferromagnetic thin film at low-temperatures. Our findings are explained and are attributed to the BEC of confined magnons in the Co/Pt thin film. We recognize financial support from the Naval Air Systems Command Section 219 grant.

Regulation the morphology of cationized gold nanoparticles for effective gene delivery.

PubMed

Zhang, Peng; Li, Bangbang; Du, Jianwei; Wang, Youxiang

2017-09-01

Recent research indicated that the morphology of nanoparticles could result in distinct biological behaviors, thus played an important role in designing efficient gene delivery systems. Among them, gold nanoparticles (AuNPs) with various shapes were widely studied due to the good biocompatibility and easy modification ability. Our recent research indicated that polyethyleneimine-g-bovine serum albumin (BSA-PEI) as non-viral gene vector showed good colloid stability and high transfection efficiency. In this work, BSA-PEI was utilized to modify gold nanospheres (AuNSs) and gold nanorods (AuNRs) to investigate the influence of the morphology on gene delivery. Both AuNS@BSA-PEI and AuNR@BSA-PEI nanoparticles condensed DNA effectively at N/P ratio above 5 and maintained spherical or rod-like morphology respectively. Due to the higher surface charge density at the tips, the rod-like gene complexes were prone to use the tips to contact with cell membrane, which facilitated to be uptaked by HepG2 cells. The endocytosis inhibition experiments showed some differences in the endocytic pathway. Gene transfection experiment showed that the rod-like complexes had almost 100-fold higher of transfection level than that of spherical complexes at the N/P ratio of 20. This work provided a potential strategy for further design of gene vectors with improved transfection results by adjusting the morphology of gene vectors. Copyright © 2017. Published by Elsevier B.V.

Growth of strained Si/relaxed SiGe heterostructures on Si(110) substrates using solid-source molecular beam epitaxy

NASA Astrophysics Data System (ADS)

Arimoto, Keisuke; Nakazawa, Hiroki; Mitsui, Shohei; Utsuyama, Naoto; Yamanaka, Junji; Hara, Kosuke O.; Usami, Noritaka; Nakagawa, Kiyokazu

2017-11-01

A strained Si/relaxed SiGe heterostructure grown on Si(110) substrate is attractive as a platform for high-hole-mobility Si-based electronic devices. To improve the electrical property, a smoother surface is desirable. In this study, we investigated surface morphology and microstructural aspects of strained Si/relaxed SiGe/Si(110) heterostructures grown by solid-source (SS) molecular beam epitaxy (MBE). It was revealed that SSMBE provides a way to grow strained Si/relaxed SiGe heterostructures with smooth surfaces. In addition, it was found that the strain in the SiGe layer of the SSMBE-grown sample is highly anisotropic whereas that of the GSMBE-grown sample is almost biaxially relaxed. Along with the surface morphology, the symmetry in degree of strain relaxation has implications for the electrical property. Results of a calculation shows that anisotropic strain is preferable for device application since it confines holes solely in the strained Si layer where hole mobility is enhanced.