Raft membrane domains: from a liquid-ordered membrane phase to a site of pathogen attack.

PubMed

van der Goot, F G; Harder, T

2001-04-01

While the existence of cholesterol/sphingolipid (raft) membrane domains in the plasma membrane is now supported by strong experimental evidence, the structure of these domains, their size, their dynamics, and their molecular composition remain to be understood. Raft domains are thought to represent a specific physical state of lipid bilayers, the liquid-ordered phase. Recent observations suggest that in the mammalian plasma membrane small raft domains in ordered lipid phases are in a dynamic equilibrium with a less ordered membrane environment. Rafts may be enlarged and/or stabilized by protein-mediated cross-linking of raft-associated components. These changes of plasma membrane structure are perceived by the cells as signals, most likely an important element of immunoreceptor signalling. Pathogens abuse raft domains on the host cell plasma membrane as concentration devices, as signalling platforms and/or entry sites into the cell. Elucidation of these interactions requires a detailed understanding raft structure and dynamics. Copyright 2001 Academic Press.

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

Armstrong, Clare L; Marquardt, Drew; Dies, Hannah

Rafts, or functional domains, are transient nano- or mesoscopic structures in the exoplasmic leaflet of the plasma membrane, and are thought to be essential for many cellular processes. Using neutron diffraction and computer modelling, we present evidence for the existence of highly ordered lipid domains in the cholesterol-rich (32.5 mol%) liquid-ordered (lo) phase of dipalmitoylphosphatidylcholine membranes. The liquid ordered phase in one-component lipid membranes has previously been thought to be a homogeneous phase. The presence of highly ordered lipid domains embedded in a disordered lipid matrix implies non-uniform distribution of cholesterol between the two phases. The experimental results are inmore » excellent agreement with recent computer simulations of DPPC/cholesterol complexes [Meinhardt, Vink and Schmid (2013). Proc Natl Acad Sci USA 110(12): 4476 4481], which reported the existence of nanometer size lo domains in a liquid disordered lipid environment.« less

Size and mobility of lipid domains tuned by geometrical constraints.

PubMed

Schütte, Ole M; Mey, Ingo; Enderlein, Jörg; Savić, Filip; Geil, Burkhard; Janshoff, Andreas; Steinem, Claudia

2017-07-25

In the plasma membrane of eukaryotic cells, proteins and lipids are organized in clusters, the latter ones often called lipid domains or "lipid rafts." Recent findings highlight the dynamic nature of such domains and the key role of membrane geometry and spatial boundaries. In this study, we used porous substrates with different pore radii to address precisely the extent of the geometric constraint, permitting us to modulate and investigate the size and mobility of lipid domains in phase-separated continuous pore-spanning membranes (PSMs). Fluorescence video microscopy revealed two types of liquid-ordered ( l o ) domains in the freestanding parts of the PSMs: ( i ) immobile domains that were attached to the pore rims and ( ii ) mobile, round-shaped l o domains within the center of the PSMs. Analysis of the diffusion of the mobile l o domains by video microscopy and particle tracking showed that the domains' mobility is slowed down by orders of magnitude compared with the unrestricted case. We attribute the reduced mobility to the geometric confinement of the PSM, because the drag force is increased substantially due to hydrodynamic effects generated by the presence of these boundaries. Our system can serve as an experimental test bed for diffusion of 2D objects in confined geometry. The impact of hydrodynamics on the mobility of enclosed lipid domains can have great implications for the formation and lateral transport of signaling platforms.

Size, Shape, and Lateral Correlation of Highly Uniform, Mesoscopic, Self-Assembled Domains of Fluorocarbon-Hydrocarbon Diblocks at the Air/Water Interface: A GISAXS Study.

PubMed

Veschgini, Mariam; Abuillan, Wasim; Inoue, Shigeto; Yamamoto, Akihisa; Mielke, Salomé; Liu, Xianhe; Konovalov, Oleg; Krafft, Marie Pierre; Tanaka, Motomu

2017-10-06

The shape and size of self-assembled mesoscopic surface domains of fluorocarbon-hydrocarbon (FnHm) diblocks and the lateral correlation between these domains were quantitatively determined from grazing incidence small-angle X-ray scattering (GISAXS). The full calculation of structure and form factors unravels the influence of fluorocarbon and hydrocarbon block lengths on the diameter and height of the domains, and provides the inter-domain correlation length. The diameter of the domains, as determined from the form factor analysis, exhibits a monotonic increase in response to the systematic lengthening of each block, which can be attributed to the increase in van der Waals attraction between molecules. The pair correlation function in real space calculated from the structure factor implies that the inter-domain correlation can reach a distance that is over 25 times larger than the domain's size. The full calculation of the GISAXS signals introduced here opens a potential towards the hierarchical design of mesoscale domains of self-assembled small organic molecules, covering several orders of magnitude in space. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hybrid and Nonhybrid Lipids Exert Common Effects on Membrane Raft Size and Morphology

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

Heberle, Frederick A; Doktorova, Milka; Goh, Shih Lin

2013-01-01

Nanometer-scale domains in cholesterolrich model membranes emulate lipid rafts in cell plasma membranes (PMs). The physicochemical mechanisms that maintain a finite, small domain size are, however, not well understood. A special role has been postulated for chainasymmetric or hybrid lipids having a saturated sn-1 chain and an unsaturated sn-2 chain. Hybrid lipids generate nanodomains in some model membranes and are also abundant in the PM. It was proposed that they align in a preferred orientation at the boundary of ordered and disordered phases, lowering the interfacial energy and thus reducing domain size. We used small-angle neutron scattering and fluorescence techniquesmore » to detect nanoscopic and modulated liquid phase domains in a mixture composed entirely of nonhybrid lipids and cholesterol. Our results are indistinguishable from those obtained previously for mixtures containing hybrid lipids, conclusively showing that hybrid lipids are not required for the formation of nanoscopic liquid domains and strongly implying a common mechanism for the overall control of raft size and morphology. We discuss implications of these findings for theoretical descriptions of nanodomains.« less

Size and mobility of lipid domains tuned by geometrical constraints

PubMed Central

Schütte, Ole M.; Mey, Ingo; Savić, Filip; Geil, Burkhard; Janshoff, Andreas

2017-01-01

In the plasma membrane of eukaryotic cells, proteins and lipids are organized in clusters, the latter ones often called lipid domains or “lipid rafts.” Recent findings highlight the dynamic nature of such domains and the key role of membrane geometry and spatial boundaries. In this study, we used porous substrates with different pore radii to address precisely the extent of the geometric constraint, permitting us to modulate and investigate the size and mobility of lipid domains in phase-separated continuous pore-spanning membranes (PSMs). Fluorescence video microscopy revealed two types of liquid-ordered (lo) domains in the freestanding parts of the PSMs: (i) immobile domains that were attached to the pore rims and (ii) mobile, round-shaped lo domains within the center of the PSMs. Analysis of the diffusion of the mobile lo domains by video microscopy and particle tracking showed that the domains’ mobility is slowed down by orders of magnitude compared with the unrestricted case. We attribute the reduced mobility to the geometric confinement of the PSM, because the drag force is increased substantially due to hydrodynamic effects generated by the presence of these boundaries. Our system can serve as an experimental test bed for diffusion of 2D objects in confined geometry. The impact of hydrodynamics on the mobility of enclosed lipid domains can have great implications for the formation and lateral transport of signaling platforms. PMID:28696315

Hysteresis in single and polycrystalline iron thin films: Major and minor loops, first order reversal curves, and Preisach modeling

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

Cao, Yue; Xu, Ke; Jiang, Weilin

Hysteretic behavior was studied in a series of Fe thin films, grown by molecular beam epitaxy, having different grain sizes and grown on different substrates. Major and minor loops and first order reversal curves (FORCs) were collected to investigate magnetization mechanisms and domain behavior under different magnetic histories. The minor loop coefficient and major loop coercivity increase with decreasing grain size due to higher defect concentration resisting domain wall movement. First order reversal curves allowed estimation of the contribution of irreversible and reversible susceptibilities and switching field distribution. The differences in shape of the major loops and first order reversalmore » curves are described using a classical Preisach model with distributions of hysterons of different switching fields, providing a powerful visualization tool to help understand the magnetization switching behavior of Fe films as manifested in various experimental magnetization measurements.« less

Hysteresis in single and polycrystalline iron thin films: Major and minor loops, first order reversal curves, and Preisach modeling

DOE PAGES

Cao, Yue; Xu, Ke; Jiang, Weilin; ...

2015-07-03

Hysteretic behavior was studied in a series of Fe thin films, grown by molecular beam epitaxy, having different grain sizes and grown on different substrates. Major and minor loops and first order reversal curves (FORCs) were collected to investigate magnetization mechanisms and domain behavior under different magnetic histories. The minor loop coefficient and major loop coercivity increase with decreasing grain size due to higher defect concentration resisting domain wall movement. First order reversal curves allowed estimation of the contribution of irreversible and reversible susceptibilities and switching field distribution. The differences in shape of the major loops and first order reversalmore » curves are described using a classical Preisach model with distributions of hysterons of different switching fields, providing a powerful visualization tool to help understand the magnetization switching behavior of Fe films as manifested in various experimental magnetization measurements.« less

FeTi oxide mineralogy and the origin of normal and reverse remanent magnetization in dacitic pumice blocks from Mt. Shasta, California

USGS Publications Warehouse

Lawson, C.A.; Nord, G.L.; Champion, D.E.

1987-01-01

Detailed mineralogical analyses and rock magnetic experiments have made it possible to directly identify the FeTi oxide phases responsible for the normal and reverse magnetic components of two dacitic pumice blocks from Mt. Shasta, California. Both samples contain a normal component carried by 100 ??m size multi-domain (MD) titanomagnetite (Usp11-24). One sample also contains a second normal component carried by < 10 ??m size pseudo-single domain (PSD) or single domain (SD) Ti-free magnetite (Usp1) found in the dacitic glass. The MD titanomagnetite and PSD or SD magnetite dominate the strong field magnetic signal, but only the PSD or SD magnetite has any influence on the remanence signal. Unlike the strong field signal, the remanence signal of both samples is dominated by a reverse NRM component. This reverse component is carried by 100 ??m size ferrian ilmenite (Ilm53-65). The compositions of the ilmenites in both samples are within the range of compositions (Ilm50-75) known to have the ability to acquire self-reversing thermoremanent magnetizations (TRM). The results of the Lowric-Fuller test indicate that the remanence signal is dominated by PSD or SD carriers. Because one sample contains only large MD titanomagnetite and no SD Ti-free magnetite (in addition to ferrian ilmenite), the ferrian ilmenite must be a PSD or SD carrier. Oxide and pyroxene geothermometry indicate the FeTi oxides in the pumice crystallized at temperatures between 880 and 945??C. This temperature range is within the disordered region of the ilmenite-hematite phase diagram for Ilm53-65. Previous work on synthetic Ilm70 and Ilm80 has shown that cooling through the order-disorder transition into the ordered region develops a transformation-induced microstructure consisting of cation-ordered domains with disordered domain boundaries. An Ilm58-59 grain from one of the Mt. Shasta samples was examined in the transmission electron microscope and was found to contain 100-200 A?? diameter cation-ordered domains. These domains arose during cooling through the transition temperature, which is estimated at 800??C for Ilm58-59. The presence of the disordered domain boundaries provides an explanation for the magnetic behavior of the ferrian ilmenite. (1) The disordered boundaries are the higher Curie point phase necessary for the operation of the self-reversal mechanism. (2) The disordered domain boundaries either inhibit the formation of magnetic domain walls or restrict magnetic domain wall movement accounting for the PSD or SD behavior of the ferrian ilmenite. ?? 1987.

Exact extreme-value statistics at mixed-order transitions.

PubMed

Bar, Amir; Majumdar, Satya N; Schehr, Grégory; Mukamel, David

2016-05-01

We study extreme-value statistics for spatially extended models exhibiting mixed-order phase transitions (MOT). These are phase transitions that exhibit features common to both first-order (discontinuity of the order parameter) and second-order (diverging correlation length) transitions. We consider here the truncated inverse distance squared Ising model, which is a prototypical model exhibiting MOT, and study analytically the extreme-value statistics of the domain lengths The lengths of the domains are identically distributed random variables except for the global constraint that their sum equals the total system size L. In addition, the number of such domains is also a fluctuating variable, and not fixed. In the paramagnetic phase, we show that the distribution of the largest domain length l_{max} converges, in the large L limit, to a Gumbel distribution. However, at the critical point (for a certain range of parameters) and in the ferromagnetic phase, we show that the fluctuations of l_{max} are governed by novel distributions, which we compute exactly. Our main analytical results are verified by numerical simulations.

Colloidal crystal grain boundary formation and motion

PubMed Central

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

2014-01-01

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

Tuning domain size and crystallinity in isoindigo/PCBM organic solar cells via solution shearing

DOE PAGES

Gu, Kevin L.; Zhou, Yan; Gu, Xiaodan; ...

2016-11-01

Despite having achieved the long sought-after performance of 10% power conversion efficiency, high performance organic photovoltaics (OPVs) are still mostly constrained to lab scale devices fabricated by spin coating. Efforts to produce printed OPVs lag considerably behind, and the sensitivity to different fabrication methods highlights the need to develop a comprehensive understanding of the processing-morphology relationship in printing methods. Here we present a systematic experimental investigation of a model low bandgap polymer/fullerene system, poly-isoindigo thienothiophene/PC 61BM, using a lab-scale analogue to roll-to-roll coating as the fabrication tool in order to understand the impact of processing parameters on morphological evolution. Wemore » report that domain size and polymer crystallinity can be tuned by a factor of two by controlling the temperature and coating speed. Lower fabrication temperature simultaneously decreased the phase separation domain size and increased the relative degree of crystallinity in those domains, leading to improved photocurrent. We conclude that domain size in isoindigo/PCBM is dictated by spontaneous phase separation rather than crystal nucleation and growth. Moreover we present a model to describe the temperature dependence of domain size formation in our system, which demonstrates that morphology is not necessarily strictly dependent on the evaporation rate, but rather on the interplay between evaporation and diffusion during the printing process.« less

Boundary and Interface Conditions for High Order Finite Difference Methods Applied to the Euler and Navier-Strokes Equations

NASA Technical Reports Server (NTRS)

Nordstrom, Jan; Carpenter, Mark H.

1998-01-01

Boundary and interface conditions for high order finite difference methods applied to the constant coefficient Euler and Navier-Stokes equations are derived. The boundary conditions lead to strict and strong stability. The interface conditions are stable and conservative even if the finite difference operators and mesh sizes vary from domain to domain. Numerical experiments show that the new conditions also lead to good results for the corresponding nonlinear problems.

Broadening and shifting of Bragg reflections of nanoscale-microtwinned LT-Ni3Sn2

NASA Astrophysics Data System (ADS)

Leineweber, Andreas; Krumeich, Frank

2013-12-01

The effect of nanoscale microtwinning of long-range ordered domains in LT-Ni3Sn2 on its diffraction behaviour was studied by X-ray powder diffraction and electron microscopy. LT-Ni3Sn2 exhibits a Ni2In/NiAs-type structure with a superstructure breaking the symmetry relative to the hexagonal high-temperature (HT) to the orthorhombic low-temperature (LT) phase, implying three different twin-domain orientations. The microstructure was generated by annealing HT-Ni3Sn2 considerably below the order-disorder transition temperature, establishing the LT phase avoiding too much domain coarsening. High-resolution electron microscopy reveals domain sizes of 100-200 Å compatible with the Scherrer broadening of the superstructure reflections recorded by X-ray diffraction. Whereas the orthorhombic symmetry of the LT phase leads in powder-diffraction patterns from coarse-domain size material to splitting of the fundamental reflections, this splitting does not occur for the LT-Ni3Sn2 with nanoscale domains. Instead, a (pseudo)hexagonal indexing is possible giving hexagonal lattice parameters, which are, however, incompatible with the positions of the superstructure reflections. This can be attributed to interference between X-rays scattered by the differently oriented, truly orthorhombic domains leading to merging of the fundamental reflections. These show pronounced anisotropic microstrain-like broadening, where the integral breadths ? on the reciprocal d-spacing scale of a series of higher order reflection increase in a non-linear fashion with upward curvature with the reciprocal d-spacings ? of these reflections. Such a type of unusual microstrain broadening appears to be typical for microstructures which are inhomogeneous on the nanoscale, and in which the structural inhomogeneities lead to small phase shifts of the scattered radiation from different locations (e.g. domains).

Energy-efficient writing scheme for magnetic domain-wall motion memory

NASA Astrophysics Data System (ADS)

Kim, Kab-Jin; Yoshimura, Yoko; Ham, Woo Seung; Ernst, Rick; Hirata, Yuushou; Li, Tian; Kim, Sanghoon; Moriyama, Takahiro; Nakatani, Yoshinobu; Ono, Teruo

2017-04-01

We present an energy-efficient magnetic domain-writing scheme for domain wall (DW) motion-based memory devices. A cross-shaped nanowire is employed to inject a domain into the nanowire through current-induced DW propagation. The energy required for injecting the magnetic domain is more than one order of magnitude lower than that for the conventional field-based writing scheme. The proposed scheme is beneficial for device miniaturization because the threshold current for DW propagation scales with the device size, which cannot be achieved in the conventional field-based technique.

Cation ordering/disordering kinetics in Ba3CoNb2O9: An in situ study using synchrotron x-ray powder diffraction

NASA Astrophysics Data System (ADS)

Mallinson, P. M.; Claridge, J. B.; Rosseinsky, M. J.; Ibberson, R. M.; Wright, J. P.; Fitch, A. N.; Price, T.; Iddles, D. M.

2007-11-01

In situ synchrotron x-ray powder diffraction has been used to study the kinetics of cation ordering and disordering in the microwave dielectric electroceramic Ba3CoNb2O9 with a time resolution of 15s. The method enables the order/disorder temperature (To /d) in this material of 1430°C to be directly observed. The changes in the rate and degree of cation ordering and in the growth of ordered domains between samples ordered from standard precursor material and then subsequently reordered following an annealing period above To /d show that small changes in precursor order state and phase assemblage strongly influence the final domain size.

Asymptotic behavior and interpretation of virtual states: The effects of confinement and of basis sets

NASA Astrophysics Data System (ADS)

Boffi, Nicholas M.; Jain, Manish; Natan, Amir

2016-02-01

A real-space high order finite difference method is used to analyze the effect of spherical domain size on the Hartree-Fock (and density functional theory) virtual eigenstates. We show the domain size dependence of both positive and negative virtual eigenvalues of the Hartree-Fock equations for small molecules. We demonstrate that positive states behave like a particle in spherical well and show how they approach zero. For the negative eigenstates, we show that large domains are needed to get the correct eigenvalues. We compare our results to those of Gaussian basis sets and draw some conclusions for real-space, basis-sets, and plane-waves calculations.

Simple stochastic birth and death models of genome evolution: was there enough time for us to evolve?

PubMed

Karev, Georgy P; Wolf, Yuri I; Koonin, Eugene V

2003-10-12

The distributions of many genome-associated quantities, including the membership of paralogous gene families can be approximated with power laws. We are interested in developing mathematical models of genome evolution that adequately account for the shape of these distributions and describe the evolutionary dynamics of their formation. We show that simple stochastic models of genome evolution lead to power-law asymptotics of protein domain family size distribution. These models, called Birth, Death and Innovation Models (BDIM), represent a special class of balanced birth-and-death processes, in which domain duplication and deletion rates are asymptotically equal up to the second order. The simplest, linear BDIM shows an excellent fit to the observed distributions of domain family size in diverse prokaryotic and eukaryotic genomes. However, the stochastic version of the linear BDIM explored here predicts that the actual size of large paralogous families is reached on an unrealistically long timescale. We show that introduction of non-linearity, which might be interpreted as interaction of a particular order between individual family members, allows the model to achieve genome evolution rates that are much better compatible with the current estimates of the rates of individual duplication/loss events.

Temperature evolution of polar states in GdMn2O5 and Gd0.8Ce0.2Mn2O5

NASA Astrophysics Data System (ADS)

Sanina, V. A.; Golovenchits, E. I.; Khannanov, B. Kh.; Scheglov, M. P.; Zalesskii, V. G.

2014-11-01

The polar order along the c axis is revealed in GdMn2O5 and Gd0.8Ce0.2Mn2O5 at T ≤ T C1 ≈ 160 K for the first time. This polar order is induced by the charge disproportion in the 2D superstructures emerged due to phase separation. The dynamic state with restricted polar domains of different sizes is found at T > T C1 which is typical of the diffuse ferroelectric phase transition. At the lowest temperatures ( T < 40 K) two polar orders of different origins with perpendicular orientations (along the b and c axes) coexist. The 1D superlattices studied by us earlier in the set of RMn2O5 multiferroics are the charged domain walls which separate of these polar order domains.

Emergence of domains and nonlinear transport in the zero-resistance state.

PubMed

Dmitriev, I A; Khodas, M; Mirlin, A D; Polyakov, D G

2013-11-15

We study transport in the domain state, the so-called zero-resistance state, that emerges in a two-dimensional electron system in which the combined action of microwave radiation and magnetic field produces a negative absolute conductivity. We show that the voltage-biased system has a rich phase diagram in the system size and voltage plane, with second- and first-order transitions between the domain and homogeneous states for small and large voltages, respectively. We find the residual negative dissipative resistance in the stable domain state.

Nano-domain states of strontium ferrites SrFe{sub 1−y}M{sub y}O{sub 2.5+x} (M=V, Mo; y≤0.1; x≤0.2)

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

Ancharova, Uliana V., E-mail: ancharova@gmail.com; Cherepanova, Svetlana V., E-mail: svch@catalysis.ru; Novosibirsk State University, Pirogova st., 2, Novosibirsk 630090

Series of the oxygen-deficient strontium ferrites SrFe{sub 1−y}M{sub y}O{sub 2.5+x} (M=V, Mo, y<0.1; x<0.2) substituted with high-charged cations have been investigated by HRTEM and synchrotron radiation XRD. For artificial lowering of x, all the compounds were treated and quenched in vacuum from 950 °C, which led to the formation of the vacancy-ordered brownmillerite phase at local order. Depending on y, the substituted strontium ferrites have three differently disordered nano-domain states. At y≤0.03 there are twinned lamellar 1D nano-domain structures. At 0.04≤y≤0.05 and 0.06≤y≤0.08 the intergrown 3D nano-domain structures with two different types of disorder are formed. The higher the y,more » the lower the domain size. Disordering phenomena of the 3D nano-domain states were examined with local structure simulations followed by the Debye calculation of XRD patterns. - Graphical abstract: Evolution of nano-domain structure with an increase in the substitution degree y in strontium ferrites SrFe{sub 1−y}M{sub y}O{sub 2.5+x} (M=V, Mo; y≤0.1; x≤0.2): an increase in y decreases the average size of domains and increases the degree of disorder, thus producing the lamellar (1D) or 3D nano-domains. - Highlights: • Two major nanodomain states were found for SrFe{sub 1−y}M{sub y}O{sub 2.5+x} (M=V, Mo, y<0.1; x<0.2). • Both contain vacancy-ordered orthorhombic domains intergrown with cubic matrix. • First (y≤0.03) shows orthorhombic and second (0.04≤y≤0.08) – cubic XRD patterns. • First contains 1D twinned lamellar domains with low-angle boundaries and deformations. • Second contains intergrown isotropic in 3D domains perpendicular oriented in matrix.« less

Limits on superconductivity-related magnetization in Sr 2RuO 4 and PrOs 4Sb 12 from scanning SQUID microscopy

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

Moler, Kathryn

2010-08-26

We present scanning SQUID microscopy data on the superconductors Sr{sub 2}RuO{sub 4} (T{sub c} = 1.5 K) and PrOs{sub 4}Sb{sub 12} (T{sub c} = 1.8 K). In both of these materials, superconductivity-related time-reversal symmetry-breaking fields have been observed by muon spin rotation; our aim was to visualize the structure of these fields. However in neither Sr{sub 2}RuO{sub 4} nor PrOs{sub 4}Sb{sub 12} do we observe spontaneous superconductivity-related magnetization. In Sr{sub 2}RuO{sub 4}, many experimental results have been interpreted on the basis of a p{sub x} {+-} ip{sub y} superconducting order parameter. This order parameter is expected to give spontaneous magneticmore » induction at sample edges and order parameter domain walls. Supposing large domains, our data restrict domain wall and edge fields to no more than {approx}0.1% and {approx}0.2% of the expected magnitude, respectively. Alternatively, if the magnetization is of the expected order, the typical domain size is limited to {approx}30 nm for random domains, or {approx} 500 nm for periodic domains.« less

Melting of Domain Wall in Charge Ordered Dirac Electron of Organic Conductor α-(BEDT-TTF)2I3

NASA Astrophysics Data System (ADS)

Ohki, Daigo; Matsuno, Genki; Omori, Yukiko; Kobayashi, Akito

2018-05-01

The origin of charge order melting is identified by using the real space dependent mean-field theory in the extended Hubbard model describing an organic Dirac electron system α-(BEDT-TTF)2I3. In this model, the width of a domain wall which arises between different types of the charge ordered phase exhibits a divergent increase with decreasing the strength of electron-electron correlations. By analyzing the finite-size effect carefully, it is shown that the divergence coincides with a topological transition where a pair of Dirac cones merges in keeping with a finite gap. It is also clarified that the gap opening point and the topological transition point are different, which leads to the existence of an exotic massive Dirac electron phase with melted-type domain wall and gapless edge states. The present result also indicated that multiple metastable states are emerged in massive Dirac Electron phase. In the trivial charge ordered phase, the gapless domain-wall bound state takes place instead of the gapless edge states, accompanying with a form change of the domain wall from melted-type into hyperbolic-tangent-type.

Effect of the computational domain size and shape on the self-diffusion coefficient in a Lennard-Jones liquid.

PubMed

Kikugawa, Gota; Ando, Shotaro; Suzuki, Jo; Naruke, Yoichi; Nakano, Takeo; Ohara, Taku

2015-01-14

In the present study, molecular dynamics (MD) simulations on the monatomic Lennard-Jones liquid in a periodic boundary system were performed in order to elucidate the effect of the computational domain size and shape on the self-diffusion coefficient measured by the system. So far, the system size dependence in cubic computational domains has been intensively investigated and these studies showed that the diffusion coefficient depends linearly on the inverse of the system size, which is theoretically predicted based on the hydrodynamic interaction. We examined the system size effect not only in the cubic cell systems but also in rectangular cell systems which were created by changing one side length of the cubic cell with the system density kept constant. As a result, the diffusion coefficient in the direction perpendicular to the long side of the rectangular cell significantly increases more or less linearly with the side length. On the other hand, the diffusion coefficient in the direction along the long side is almost constant or slightly decreases. Consequently, anisotropy of the diffusion coefficient emerges in a rectangular cell with periodic boundary conditions even in a bulk liquid simulation. This unexpected result is of critical importance because rectangular fluid systems confined in nanospace, which are present in realistic nanoscale technologies, have been widely studied in recent MD simulations. In order to elucidate the underlying mechanism for this serious system shape effect on the diffusion property, the correlation structures of particle velocities were examined.

Fresnel Lorentz Microscopy Imaging of Domains in Fe3O4 Nanoparticle Arrays

NASA Astrophysics Data System (ADS)

Majetich, S. A.; Evarts, E. R.; Hogg, C.; Yamamoto, K.; Hirayama, T.

2009-03-01

Fresnel Lorentz microscopy was used to study the magnetic domain structures of self-assembled nanoparticle arrays as a function of temperature, from 24 to 605 C. 11 nm diameter Fe3O4 nanoparticles with an edge-to-edge spacing of 2.5 nm form magnetic domains through magnetostatic interactions alone. At room temperature stripe domains were evident in monolayer arrays. The average domain size in monolayer regions is larger than that in bilayers. Mean field theories predict a reduced stabilization energy for bilayers, relative to that for monolayers. The domain wall positions were fairly stable up to 500 C, though the contrast in the walls diminished, indicating reduced magnetic order. Above 500 C there were large temperature-dependent changes. The walls surrounding the smaller domains disappeared at lower temperatures than those of the larger domains. Some magnetic contrast was visible up to 575 C, close to the Curie temperature of Fe3O4 (585 C). Transmission electron microscopy after cooling showed that the particle shape and position in the ordered arrays had been preserved during the high temperature imaging experiments.

Simulations of turbulent asymptotic suction boundary layers

NASA Astrophysics Data System (ADS)

Bobke, Alexandra; Örlü, Ramis; Schlatter, Philipp

2016-02-01

A series of large-eddy simulations of a turbulent asymptotic suction boundary layer (TASBL) was performed in a periodic domain, on which uniform suction was applied over a flat plate. Three Reynolds numbers (defined as ratio of free-stream and suction velocity) of Re = 333, 400 and 500 and a variety of domain sizes were considered in temporal simulations in order to investigate the turbulence statistics, the importance of the computational domain size, the arising flow structures as well as temporal development length required to achieve the asymptotic state. The effect of these two important parameters was assessed in terms of their influence on integral quantities, mean velocity, Reynolds stresses, higher order statistics, amplitude modulation and spectral maps. While the near-wall region up to the buffer region appears to scale irrespective of Re and domain size, the parameters of the logarithmic law (i.e. von Kármán and additive coefficient) decrease with increasing Re, while the wake strength decreases with increasing spanwise domain size and vanishes entirely once the spanwise domain size exceeds approximately two boundary-layer thicknesses irrespective of Re. The wake strength also reduces with increasing simulation time. The asymptotic state of the TASBL is characterised by surprisingly large friction Reynolds numbers and inherits features of wall turbulence at numerically high Re. Compared to a turbulent boundary layer (TBL) or a channel flow without suction, the components of the Reynolds-stress tensor are overall reduced, but exhibit a logarithmic increase with decreasing suction rates, i.e. increasing Re. At the same time, the anisotropy is increased compared to canonical wall-bounded flows without suction. The reduced amplitudes in turbulence quantities are discussed in light of the amplitude modulation due to the weakened larger outer structures. The inner peak in the spectral maps is shifted to higher wavelength and the strength of the outer peak is much less than for TBLs. An additional spatial simulation was performed, in order to relate the simulation results to wind tunnel experiments, which - in accordance with the results from the temporal simulation - indicate that a truly TASBL is practically impossible to realise in a wind tunnel. Our unique data set agrees qualitatively with existing literature results for both numerical and experimental studies, and at the same time sheds light on the fact why the asymptotic state could not be established in a wind tunnel experiment, viz. because experimental studies resemble our simulation results from too small simulation boxes or insufficient development times.

Differential Effect of Plant Lipids on Membrane Organization

PubMed Central

Grosjean, Kevin; Mongrand, Sébastien; Beney, Laurent; Simon-Plas, Françoise; Gerbeau-Pissot, Patricia

2015-01-01

The high diversity of the plant lipid mixture raises the question of their respective involvement in the definition of membrane organization. This is particularly the case for plant plasma membrane, which is enriched in specific lipids, such as free and conjugated forms of phytosterols and typical phytosphingolipids, such as glycosylinositolphosphoceramides. This question was here addressed extensively by characterizing the order level of membrane from vesicles prepared using various plant lipid mixtures and labeled with an environment-sensitive probe. Fluorescence spectroscopy experiments showed that among major phytosterols, campesterol exhibits a stronger ability than β-sitosterol and stigmasterol to order model membranes. Multispectral confocal microscopy, allowing spatial analysis of membrane organization, demonstrated accordingly the strong ability of campesterol to promote ordered domain formation and to organize their spatial distribution at the membrane surface. Conjugated sterol forms, alone and in synergy with free sterols, exhibit a striking ability to order membrane. Plant sphingolipids, particularly glycosylinositolphosphoceramides, enhanced the sterol-induced ordering effect, emphasizing the formation and increasing the size of sterol-dependent ordered domains. Altogether, our results support a differential involvement of free and conjugated phytosterols in the formation of ordered domains and suggest that the diversity of plant lipids, allowing various local combinations of lipid species, could be a major contributor to membrane organization in particular through the formation of sphingolipid-sterol interacting domains. PMID:25575593

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.

Effects of random initial conditions on the dynamical scaling behaviors of a fixed-energy Manna sandpile model in one dimension

NASA Astrophysics Data System (ADS)

Kwon, Sungchul; Kim, Jin Min

2015-01-01

For a fixed-energy (FE) Manna sandpile model in one dimension, we investigate the effects of random initial conditions on the dynamical scaling behavior of an order parameter. In the FE Manna model, the density ρ of total particles is conserved, and an absorbing phase transition occurs at ρc as ρ varies. In this work, we show that, for a given ρ , random initial distributions of particles lead to the domain structure in which domains with particle densities higher and lower than ρc alternate with each other. In the domain structure, the dominant length scale is the average domain length, which increases via the coalescence of adjacent domains. At ρc, the domain structure slows down the decay of an order parameter and also causes anomalous finite-size effects, i.e., power-law decay followed by an exponential one before the quasisteady state. As a result, the interplay of particle conservation and random initial conditions causes the domain structure, which is the origin of the anomalous dynamical scaling behaviors for random initial conditions.

Controlled self-assembly of conjugated rod-coil block copolymers for applications in organic optoelectronics

NASA Astrophysics Data System (ADS)

Tao, Yuefei

Organic electronics are of great interest in manufacturing light weight, mechanical flexible, and inexpensive large area devices. While significant improvements have been made over the last several years and it is now clear that morphology on the lengthscale of exciton diffusion (10nm) is of crucial importance, a clear relationship between structure and device properties has not emerged. This lack of understanding largely emerges from an inability to control morphology on this lengthscale. This thesis will center around an approach, based on block copolymer self-assembly, to generate equilibrium nanostructures on the 10 nm lengthscale of exciton diffusion and study their effects on device performance. Self-assembly of semiconducting block copolymers is complicated by the non-classical chain shape of conjugated polymers. Unlike classical polymers, the chains do not assume a Gaussian coil shape which is stretched near block copolymer interfaces, instead the chains are elongated and liquid crystalline. Previous work has demonstrated how these new molecular interactions and shapes control the phase diagram of so-called rod-coil block copolymers. Here, we will focus on controlling domain size, orientation, and chemical structure. While domain size can be controlled directly through molecular weight, this requires significant additional synthesis of domain size is to be varied. Here, the domain size is controlled by blending homopolymers into a self-assembling rod-coil block copolymer. When coil-like blocks are incorporated, the domains swell, as expected. When rod-like blocks are incorporated, they interdigitate with the rods of the block copolymers. This results in an increase in interfacial area which forces the coils to rearrange and an overall decrease in domain size with increasing rod content. Control over lamellar orientation is crucial in order to design and control charge transport pathways and exciton recombination or separation interfaces. While numerous techniques have been demonstrated for classical block copolymers, the pi conjugation in the rod blocks allow for additional control mechanisms. Liquid crystals are traditionally aligned in magnetic fields. Here, it is demonstrated that if the rod-like blocks are aligned unidirectionally, the block copolymer interfaces follow to create macroscopic alignment of the nanostructures. Organic Light Emitting Diodes (OLEDs) are generally composed of electron transporting and hole transporting moieties to balance charge recombination. Here, a new multifunctional bipolar rod-coil block copolymer containing the hole transporting and electron transporting materials is synthesized. Self-assembly of this new block copolymer results in 15nm lamellae oriented in grains both parallel and perpendicula to the anode. The self-assembled block copolymer shows superior device performance to controls consisting of a luminescent, analogous homopolymer, and a blend of the two component homopolymers. The effects of the morphologies and chemical structure on photovoltaics is explored with a rod-coil block copolymer, (poly(3-hexylthiophene-b-acrylic perylene)). By varying the kinetics of self-assembly through processing, the block copolymer can be disordered, ordered with only short range registry between the nanodomains, or with long-range order. The short range ordered samples showed the best device performance suggesting that the connectivity that is a biproduct of poor order is beneficial for device performance.

Computationally efficient algorithm for high sampling-frequency operation of active noise control

NASA Astrophysics Data System (ADS)

Rout, Nirmal Kumar; Das, Debi Prasad; Panda, Ganapati

2015-05-01

In high sampling-frequency operation of active noise control (ANC) system the length of the secondary path estimate and the ANC filter are very long. This increases the computational complexity of the conventional filtered-x least mean square (FXLMS) algorithm. To reduce the computational complexity of long order ANC system using FXLMS algorithm, frequency domain block ANC algorithms have been proposed in past. These full block frequency domain ANC algorithms are associated with some disadvantages such as large block delay, quantization error due to computation of large size transforms and implementation difficulties in existing low-end DSP hardware. To overcome these shortcomings, the partitioned block ANC algorithm is newly proposed where the long length filters in ANC are divided into a number of equal partitions and suitably assembled to perform the FXLMS algorithm in the frequency domain. The complexity of this proposed frequency domain partitioned block FXLMS (FPBFXLMS) algorithm is quite reduced compared to the conventional FXLMS algorithm. It is further reduced by merging one fast Fourier transform (FFT)-inverse fast Fourier transform (IFFT) combination to derive the reduced structure FPBFXLMS (RFPBFXLMS) algorithm. Computational complexity analysis for different orders of filter and partition size are presented. Systematic computer simulations are carried out for both the proposed partitioned block ANC algorithms to show its accuracy compared to the time domain FXLMS algorithm.

Design of Xen Hybrid Multiple Police Model

NASA Astrophysics Data System (ADS)

Sun, Lei; Lin, Renhao; Zhu, Xianwei

2017-10-01

Virtualization Technology has attracted more and more attention. As a popular open-source virtualization tools, XEN is used more and more frequently. Xsm, XEN security model, has also been widespread concern. The safety status classification has not been established in the XSM, and it uses the virtual machine as a managed object to make Dom0 a unique administrative domain that does not meet the minimum privilege. According to these questions, we design a Hybrid multiple police model named SV_HMPMD that organically integrates multiple single security policy models include DTE,RBAC,BLP. It can fullfill the requirement of confidentiality and integrity for security model and use different particle size to different domain. In order to improve BLP’s practicability, the model introduce multi-level security labels. In order to divide the privilege in detail, we combine DTE with RBAC. In order to oversize privilege, we limit the privilege of domain0.

Differential effect of plant lipids on membrane organization: specificities of phytosphingolipids and phytosterols.

PubMed

Grosjean, Kevin; Mongrand, Sébastien; Beney, Laurent; Simon-Plas, Françoise; Gerbeau-Pissot, Patricia

2015-02-27

The high diversity of the plant lipid mixture raises the question of their respective involvement in the definition of membrane organization. This is particularly the case for plant plasma membrane, which is enriched in specific lipids, such as free and conjugated forms of phytosterols and typical phytosphingolipids, such as glycosylinositolphosphoceramides. This question was here addressed extensively by characterizing the order level of membrane from vesicles prepared using various plant lipid mixtures and labeled with an environment-sensitive probe. Fluorescence spectroscopy experiments showed that among major phytosterols, campesterol exhibits a stronger ability than β-sitosterol and stigmasterol to order model membranes. Multispectral confocal microscopy, allowing spatial analysis of membrane organization, demonstrated accordingly the strong ability of campesterol to promote ordered domain formation and to organize their spatial distribution at the membrane surface. Conjugated sterol forms, alone and in synergy with free sterols, exhibit a striking ability to order membrane. Plant sphingolipids, particularly glycosylinositolphosphoceramides, enhanced the sterol-induced ordering effect, emphasizing the formation and increasing the size of sterol-dependent ordered domains. Altogether, our results support a differential involvement of free and conjugated phytosterols in the formation of ordered domains and suggest that the diversity of plant lipids, allowing various local combinations of lipid species, could be a major contributor to membrane organization in particular through the formation of sphingolipid-sterol interacting domains. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Analytical electron microscope study of the omega phase transformation in a zirconium-niobium alloy

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

Zaluzec, N. J.

1979-01-01

The study of the as-quenched omega phase morphology shows that the domain size of Zr-15% Nb is on the order of 30 A. No alignment of omega domains along <222>..beta.. directions was observed and samples having undergone thermal cycling in thin foil form, did not develop a long-period structure of alternating ..beta.. and ..omega.. phases below the omega transformation temperature. (FS)

High-Order Implicit-Explicit Multi-Block Time-stepping Method for Hyperbolic PDEs

NASA Technical Reports Server (NTRS)

Nielsen, Tanner B.; Carpenter, Mark H.; Fisher, Travis C.; Frankel, Steven H.

2014-01-01

This work seeks to explore and improve the current time-stepping schemes used in computational fluid dynamics (CFD) in order to reduce overall computational time. A high-order scheme has been developed using a combination of implicit and explicit (IMEX) time-stepping Runge-Kutta (RK) schemes which increases numerical stability with respect to the time step size, resulting in decreased computational time. The IMEX scheme alone does not yield the desired increase in numerical stability, but when used in conjunction with an overlapping partitioned (multi-block) domain significant increase in stability is observed. To show this, the Overlapping-Partition IMEX (OP IMEX) scheme is applied to both one-dimensional (1D) and two-dimensional (2D) problems, the nonlinear viscous Burger's equation and 2D advection equation, respectively. The method uses two different summation by parts (SBP) derivative approximations, second-order and fourth-order accurate. The Dirichlet boundary conditions are imposed using the Simultaneous Approximation Term (SAT) penalty method. The 6-stage additive Runge-Kutta IMEX time integration schemes are fourth-order accurate in time. An increase in numerical stability 65 times greater than the fully explicit scheme is demonstrated to be achievable with the OP IMEX method applied to 1D Burger's equation. Results from the 2D, purely convective, advection equation show stability increases on the order of 10 times the explicit scheme using the OP IMEX method. Also, the domain partitioning method in this work shows potential for breaking the computational domain into manageable sizes such that implicit solutions for full three-dimensional CFD simulations can be computed using direct solving methods rather than the standard iterative methods currently used.

Pre-ordering of interfacial water in the pathway of heterogeneous ice nucleation does not lead to a two-step crystallization mechanism.

PubMed

Lupi, Laura; Peters, Baron; Molinero, Valeria

2016-12-07

According to Classical Nucleation Theory (CNT), the transition from liquid to crystal occurs in a single activated step with a transition state controlled by the size of the crystal embryo. This picture has been challenged in the last two decades by several reports of two-step crystallization processes in which the liquid first produces pre-ordered or dense domains, within which the crystal nucleates in a second step. Pre-ordering preceding crystal nucleation has been recently reported in simulations of ice crystallization, raising the question of whether the mechanism of ice nucleation involves two steps. In this paper, we investigate the heterogeneous nucleation of ice on carbon surfaces. We use molecular simulations with efficient coarse-grained models combined with rare event sampling methods and free energy calculations to elucidate the role of pre-ordering of liquid water at the carbon surface in the reaction coordinate for heterogeneous nucleation. We find that ice nucleation proceeds through a classical mechanism, with a single barrier between liquid and crystal. The reaction coordinate that determines the crossing of the nucleation barrier is the size of the crystal nucleus, as predicted by CNT. Wetting of the critical ice nuclei within pre-ordered domains decreases the nucleation barrier, increasing the nucleation rates. The preferential pathway for crystallization involves the early creation of pre-ordered domains that are the birthplace of the ice crystallites but do not represent a minimum in the free energy pathway from liquid to ice. We conclude that a preferential pathway through an intermediate-order precursor does not necessarily result in a two-step mechanism.

Rapid Ordering in "Wet Brush" Block Copolymer/Homopolymer Ternary Blends.

PubMed

Doerk, Gregory S; Yager, Kevin G

2017-12-26

The ubiquitous presence of thermodynamically unfavored but kinetically trapped topological defects in nanopatterns formed via self-assembly of block copolymer thin films may prevent their use for many envisioned applications. Here, we demonstrate that lamellae patterns formed by symmetric polystyrene-block-poly(methyl methacrylate) diblock copolymers self-assemble and order extremely rapidly when the diblock copolymers are blended with low molecular weight homopolymers of the constituent blocks. Being in the "wet brush" regime, the homopolymers uniformly distribute within their respective self-assembled microdomains, preventing increases in domain widths. An order-of-magnitude increase in topological grain size in blends over the neat (unblended) diblock copolymer is achieved within minutes of thermal annealing as a result of the significantly higher power law exponent for ordering kinetics in the blends. Moreover, the blends are demonstrated to be capable of rapid and robust domain alignment within micrometer-scale trenches, in contrast to the corresponding neat diblock copolymer. These results can be attributed to the lowering of energy barriers associated with domain boundaries by bringing the system closer to an order-disorder transition through low molecular weight homopolymer blending.

M-Adapting Low Order Mimetic Finite Differences for Dielectric Interface Problems

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

McGregor, Duncan A.; Gyrya, Vitaliy; Manzini, Gianmarco

2016-03-07

We consider a problem of reducing numerical dispersion for electromagnetic wave in the domain with two materials separated by a at interface in 2D with a factor of two di erence in wave speed. The computational mesh in the homogeneous parts of the domain away from the interface consists of square elements. Here the method construction is based on m-adaptation construction in homogeneous domain that leads to fourth-order numerical dispersion (vs. second order in non-optimized method). The size of the elements in two domains also di ers by a factor of two, so as to preserve the same value ofmore » Courant number in each. Near the interface where two meshes merge the mesh with larger elements consists of degenerate pentagons. We demonstrate that prior to m-adaptation the accuracy of the method falls from second to rst due to breaking of symmetry in the mesh. Next we develop m-adaptation framework for the interface region and devise an optimization criteria. We prove that for the interface problem m-adaptation cannot produce increase in method accuracy. This is in contrast to homogeneous medium where m-adaptation can increase accuracy by two orders.« less

Birth and death of protein domains: A simple model of evolution explains power law behavior

PubMed Central

Karev, Georgy P; Wolf, Yuri I; Rzhetsky, Andrey Y; Berezovskaya, Faina S; Koonin, Eugene V

2002-01-01

Background Power distributions appear in numerous biological, physical and other contexts, which appear to be fundamentally different. In biology, power laws have been claimed to describe the distributions of the connections of enzymes and metabolites in metabolic networks, the number of interactions partners of a given protein, the number of members in paralogous families, and other quantities. In network analysis, power laws imply evolution of the network with preferential attachment, i.e. a greater likelihood of nodes being added to pre-existing hubs. Exploration of different types of evolutionary models in an attempt to determine which of them lead to power law distributions has the potential of revealing non-trivial aspects of genome evolution. Results A simple model of evolution of the domain composition of proteomes was developed, with the following elementary processes: i) domain birth (duplication with divergence), ii) death (inactivation and/or deletion), and iii) innovation (emergence from non-coding or non-globular sequences or acquisition via horizontal gene transfer). This formalism can be described as a birth, death and innovation model (BDIM). The formulas for equilibrium frequencies of domain families of different size and the total number of families at equilibrium are derived for a general BDIM. All asymptotics of equilibrium frequencies of domain families possible for the given type of models are found and their appearance depending on model parameters is investigated. It is proved that the power law asymptotics appears if, and only if, the model is balanced, i.e. domain duplication and deletion rates are asymptotically equal up to the second order. It is further proved that any power asymptotic with the degree not equal to -1 can appear only if the hypothesis of independence of the duplication/deletion rates on the size of a domain family is rejected. Specific cases of BDIMs, namely simple, linear, polynomial and rational models, are considered in details and the distributions of the equilibrium frequencies of domain families of different size are determined for each case. We apply the BDIM formalism to the analysis of the domain family size distributions in prokaryotic and eukaryotic proteomes and show an excellent fit between these empirical data and a particular form of the model, the second-order balanced linear BDIM. Calculation of the parameters of these models suggests surprisingly high innovation rates, comparable to the total domain birth (duplication) and elimination rates, particularly for prokaryotic genomes. Conclusions We show that a straightforward model of genome evolution, which does not explicitly include selection, is sufficient to explain the observed distributions of domain family sizes, in which power laws appear as asymptotic. However, for the model to be compatible with the data, there has to be a precise balance between domain birth, death and innovation rates, and this is likely to be maintained by selection. The developed approach is oriented at a mathematical description of evolution of domain composition of proteomes, but a simple reformulation could be applied to models of other evolving networks with preferential attachment. PMID:12379152

Birth and death of protein domains: a simple model of evolution explains power law behavior.

PubMed

Karev, Georgy P; Wolf, Yuri I; Rzhetsky, Andrey Y; Berezovskaya, Faina S; Koonin, Eugene V

2002-10-14

Power distributions appear in numerous biological, physical and other contexts, which appear to be fundamentally different. In biology, power laws have been claimed to describe the distributions of the connections of enzymes and metabolites in metabolic networks, the number of interactions partners of a given protein, the number of members in paralogous families, and other quantities. In network analysis, power laws imply evolution of the network with preferential attachment, i.e. a greater likelihood of nodes being added to pre-existing hubs. Exploration of different types of evolutionary models in an attempt to determine which of them lead to power law distributions has the potential of revealing non-trivial aspects of genome evolution. A simple model of evolution of the domain composition of proteomes was developed, with the following elementary processes: i) domain birth (duplication with divergence), ii) death (inactivation and/or deletion), and iii) innovation (emergence from non-coding or non-globular sequences or acquisition via horizontal gene transfer). This formalism can be described as a birth, death and innovation model (BDIM). The formulas for equilibrium frequencies of domain families of different size and the total number of families at equilibrium are derived for a general BDIM. All asymptotics of equilibrium frequencies of domain families possible for the given type of models are found and their appearance depending on model parameters is investigated. It is proved that the power law asymptotics appears if, and only if, the model is balanced, i.e. domain duplication and deletion rates are asymptotically equal up to the second order. It is further proved that any power asymptotic with the degree not equal to -1 can appear only if the hypothesis of independence of the duplication/deletion rates on the size of a domain family is rejected. Specific cases of BDIMs, namely simple, linear, polynomial and rational models, are considered in details and the distributions of the equilibrium frequencies of domain families of different size are determined for each case. We apply the BDIM formalism to the analysis of the domain family size distributions in prokaryotic and eukaryotic proteomes and show an excellent fit between these empirical data and a particular form of the model, the second-order balanced linear BDIM. Calculation of the parameters of these models suggests surprisingly high innovation rates, comparable to the total domain birth (duplication) and elimination rates, particularly for prokaryotic genomes. We show that a straightforward model of genome evolution, which does not explicitly include selection, is sufficient to explain the observed distributions of domain family sizes, in which power laws appear as asymptotic. However, for the model to be compatible with the data, there has to be a precise balance between domain birth, death and innovation rates, and this is likely to be maintained by selection. The developed approach is oriented at a mathematical description of evolution of domain composition of proteomes, but a simple reformulation could be applied to models of other evolving networks with preferential attachment.

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

Armstrong, Clare L; Haeussler, Wolfgang; Seydel, Tilo

Lipid dynamics in the cholesterol-rich (40 mol%) liquid-ordered (lo) phase of dimyristoylphosphatidylcholine membranes were studied using neutron spin-echo and neutron backscattering. Recent theoretical and experimental evidence supports the notion of the liquid-ordered phase in phospholipid membranes as a locally structured liquid, with small ordered domains of a highly dynamic nature in equilibrium with a disordered matrix [S. Meinhardt, R. L. C. Vink and F. Schmid, Proc. Natl. Acad. Sci. U. S. A., 2013, 110(12), 4476 4481, C. L. Armstrong et al., PLoS One, 2013, 8(6), e66162]. This local structure was found to have a pronounced impact on the membranes' dynamicalmore » properties. We found that the long-wavelength dynamics in the liquid-ordered phase, associated with the elastic properties of the membranes, were faster by two orders of magnitude as compared to the liquid disordered phase. At the same time, collective nanoscale diffusion was significantly slower. The presence of a soft-mode (a slowing down) in the longwavelength dispersion relationship suggests an upper size limit for the ordered lipid domain of ~220 A. Moreover, from the relaxation rate of the collective lipid diffusion of lipid lipid distances, the lifetime of these domains was estimated to be about 100 nanoseconds.« less

Fast marching methods for the continuous traveling salesman problem

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

Andrews, J.; Sethian, J.A.

We consider a problem in which we are given a domain, a cost function which depends on position at each point in the domain, and a subset of points ('cities') in the domain. The goal is to determine the cheapest closed path that visits each city in the domain once. This can be thought of as a version of the Traveling Salesman Problem, in which an underlying known metric determines the cost of moving through each point of the domain, but in which the actual shortest path between cities is unknown at the outset. We describe algorithms for both amore » heuristic and an optimal solution to this problem. The order of the heuristic algorithm is at worst case M * N logN, where M is the number of cities, and N the size of the computational mesh used to approximate the solutions to the shortest paths problems. The average runtime of the heuristic algorithm is linear in the number of cities and O(N log N) in the size N of the mesh.« less

Experimental evidence for stochastic switching of supercooled phases in NdNiO3 nanostructures

NASA Astrophysics Data System (ADS)

Kumar, Devendra; Rajeev, K. P.; Alonso, J. A.

2018-03-01

A first-order phase transition is a dynamic phenomenon. In a multi-domain system, the presence of multiple domains of coexisting phases averages out the dynamical effects, making it nearly impossible to predict the exact nature of phase transition dynamics. Here, we report the metal-insulator transition in samples of sub-micrometer size NdNiO3 where the effect of averaging is minimized by restricting the number of domains under study. We observe the presence of supercooled metallic phases with supercooling of 40 K or more. The transformation from the supercooled metallic to the insulating state is a stochastic process that happens at different temperatures and times in different experimental runs. The experimental results are understood without incorporating material specific properties, suggesting that the behavior is of universal nature. The size of the sample needed to observe individual switching of supercooled domains, the degree of supercooling, and the time-temperature window of switching are expected to depend on the parameters such as quenched disorder, strain, and magnetic field.

Reverse switching of surface roughness in a self-organized polydomain liquid crystal coating.

PubMed

Liu, Danqing; Liu, Ling; Onck, Patrick R; Broer, Dirk J

2015-03-31

In this work we propose randomly ordered polydomain nematic liquid crystal polymer networks to reversibly generate notable jagged relief patterns at a polymer coating surface by light illumination. The domain size is controlled by the addition of traces of partly insoluble fluorinated acrylate. The photoresponse of the coating is induced by a small amount of copolymerized azobenzene monomers. Upon exposure to UV light, azobenzene undergoes trans to cis isomerization, resulting in a change in molecular order and packing within each domain. The extent of this effect and its directionality depends on the domain orientation. Localized to domain level, this morphological change forms large 3D spikes at the surface with a modulation amplitude of more than 20% of the initial thickness. The process is reversible; the surface topographical patterns erase within 10 s by stopping the light exposure. A finite element model is applied to simulate the surface topography changes of the polydomain coating. The simulations describe the formation of the topographic features in terms of light absorption and isomerization process as a function of the director orientation. The random director distribution leads to surface structures which were found to be in close agreement with the ones measured by interference microscopy. The effect of domain size on surface roughness and depth modulation was explored and related to the internal mechanical constraints. The use of nematic liquid crystal polydomains confined in a polymer network largely simplifies the fabrication of smart coatings with a prominent triggered topographic response.

Preliminary investigations into macroscopic attenuated total reflection-fourier transform infrared imaging of intact spherical domains: spatial resolution and image distortion.

PubMed

Everall, Neil J; Priestnall, Ian M; Clarke, Fiona; Jayes, Linda; Poulter, Graham; Coombs, David; George, Michael W

2009-03-01

This paper describes preliminary investigations into the spatial resolution of macro attenuated total reflection (ATR) Fourier transform infrared (FT-IR) imaging and the distortions that arise when imaging intact, convex domains, using spheres as an extreme example. The competing effects of shallow evanescent wave penetration and blurring due to finite spatial resolution meant that spheres within the range 20-140 microm all appeared to be approximately the same size ( approximately 30-35 microm) when imaged with a numerical aperture (NA) of approximately 0.2. A very simple model was developed that predicted this extreme insensitivity to particle size. On the basis of these studies, it is anticipated that ATR imaging at this NA will be insensitive to the size of intact highly convex objects. A higher numerical aperture device should give a better estimate of the size of small spheres, owing to superior spatial resolution, but large spheres should still appear undersized due to the shallow sampling depth. An estimate of the point spread function (PSF) was required in order to develop and apply the model. The PSF was measured by imaging a sharp interface; assuming an Airy profile, the PSF width (distance from central maximum to first minimum) was estimated to be approximately 20 and 30 microm for IR bands at 1600 and 1000 cm(-1), respectively. This work has two significant limitations. First, underestimation of domain size only arises when imaging intact convex objects; if surfaces are prepared that randomly and representatively section through domains, the images can be analyzed to calculate parameters such as domain size, area, and volume. Second, the model ignores reflection and refraction and assumes weak absorption; hence, the predicted intensity profiles are not expected to be accurate; they merely give a rough estimate of the apparent sphere size. Much further work is required to place the field of quantitative ATR-FT-IR imaging on a sound basis.

Molecular dynamics study of the isotropic-nematic quench.

PubMed

Bradac, Z; Kralj, S; Zumer, S

2002-02-01

Effects of cylindrical and spherical confinement on the kinetics of the isotropic-nematic quench is studied numerically. The nematic liquid crystal structure was modeled by a modified induced-dipole--induced-dipole interaction. Molecules were allowed to wander around points of a hexagonal lattice. Brownian molecular dynamics was used in order to access macroscopic time scales. In the bulk we distinguish between the early, domain, and late stage regime. The early regime is characterized by the exponential growth of the nematic uniaxial order parameter. In the domain regime domains are clearly visible and the average nematic domain size xi(d) obeys the dynamical scaling law xi(d)-t(gamma). The late stage evolution is dominated by dynamics of individual defects. In a confined system the qualitative change of the scaling behavior appears when xi(d) becomes comparable to a typical linear dimension R of the confinement. In the confining regime (xi(d)>or=R) the scaling coefficient gamma depends on the details of the confinement and also the final equilibrium nematic structure. The domain growth is well described with the Kibble-Zurek mechanism.

Characteristics of ferroelectric-ferroelastic domains in Néel-type skyrmion host GaV4S8

NASA Astrophysics Data System (ADS)

Butykai, Ádám; Bordács, Sándor; Kézsmárki, István; Tsurkan, Vladimir; Loidl, Alois; Döring, Jonathan; Neuber, Erik; Milde, Peter; Kehr, Susanne C.; Eng, Lukas M.

2017-03-01

GaV4S8 is a multiferroic semiconductor hosting Néel-type magnetic skyrmions dressed with electric polarization. At Ts = 42 K, the compound undergoes a structural phase transition of weakly first-order, from a non-centrosymmetric cubic phase at high temperatures to a polar rhombohedral structure at low temperatures. Below Ts, ferroelectric domains are formed with the electric polarization pointing along any of the four <111> axes. Although in this material the size and the shape of the ferroelectric-ferroelastic domains may act as important limiting factors in the formation of the Néel-type skyrmion lattice emerging below TC = 13 K, the characteristics of polar domains in GaV4S8 have not been studied yet. Here, we report on the inspection of the local-scale ferroelectric domain distribution in rhombohedral GaV4S8 using low-temperature piezoresponse force microscopy. We observed mechanically and electrically compatible lamellar domain patterns, where the lamellae are aligned parallel to the (100)-type planes with a typical spacing between 100 nm-1.2 μm. Since the magnetic pattern, imaged by atomic force microscopy using a magnetically coated tip, abruptly changes at the domain boundaries, we expect that the control of ferroelectric domain size in polar skyrmion hosts can be exploited for the spatial confinement and manipulation of Néel-type skyrmions.

Experimental investigation of the ordering pathway in a Ni-33 at.%Cr alloy

DOE PAGES

Gwalani, B.; Alam, T.; Miller, C.; ...

2016-06-17

The present study involves a detailed experimental investigation of the concurrent compositional clustering and long-range ordering tendencies in a Ni-33 at.%Cr alloy, carried out by coupling synchrotron-based X-ray diffraction (XRD), transmission electron microscopy (TEM), and atom probe tomography (APT). Synchrotron-based XRD results clearly exhibited progressively increasing lattice contraction in the matrix with increasing isothermal aging time, at 475 degrees C, eventually leading to the development of long-range ordering (LRO) of the Pt2Mo-type. Detailed TEM and APT investigations revealed that this LRO in the matrix is manifested in the form of nanometer-scale ordered domains, and the spatial distribution, size, morphology andmore » compositional evolution of these domains have been carefully investigated. Here, the APT results also revealed the early stages of compositional clustering prior to the onset of long-range ordering in this alloy and such compositional clustering can potentially be correlated to the lattice contraction and previously proposed short-range ordering tendencies.« less

Size-sensitive sorting of microparticles through control of flow geometry

NASA Astrophysics Data System (ADS)

Wang, Cheng; Jalikop, Shreyas V.; Hilgenfeldt, Sascha

2011-07-01

We demonstrate a general concept of flow manipulation in microfluidic environments, based on controlling the shape and position of flow domains in order to force switching and sorting of microparticles without moving parts or changes in design geometry. Using microbubble acoustic streaming, we show that regulation of the relative strength of streaming and a superimposed Poiseuille flow allows for size-selective trapping and releasing of particles, with particle size sensitivity much greater than what is imposed by the length scales of microfabrication. A simple criterion allows for quantitative tuning of microfluidic devices for switching and sorting of particles of desired size.

Phase ordering in disordered and inhomogeneous systems

NASA Astrophysics Data System (ADS)

Corberi, Federico; Zannetti, Marco; Lippiello, Eugenio; Burioni, Raffaella; Vezzani, Alessandro

2015-06-01

We study numerically the coarsening dynamics of the Ising model on a regular lattice with random bonds and on deterministic fractal substrates. We propose a unifying interpretation of the phase-ordering processes based on two classes of dynamical behaviors characterized by different growth laws of the ordered domain size, namely logarithmic or power law, respectively. It is conjectured that the interplay between these dynamical classes is regulated by the same topological feature that governs the presence or the absence of a finite-temperature phase transition.

Appropriate Domain Size for Groundwater Flow Modeling with a Discrete Fracture Network Model.

PubMed

Ji, Sung-Hoon; Koh, Yong-Kwon

2017-01-01

When a discrete fracture network (DFN) is constructed from statistical conceptualization, uncertainty in simulating the hydraulic characteristics of a fracture network can arise due to the domain size. In this study, the appropriate domain size, where less significant uncertainty in the stochastic DFN model is expected, was suggested for the Korea Atomic Energy Research Institute Underground Research Tunnel (KURT) site. The stochastic DFN model for the site was established, and the appropriate domain size was determined with the density of the percolating cluster and the percolation probability using the stochastically generated DFNs for various domain sizes. The applicability of the appropriate domain size to our study site was evaluated by comparing the statistical properties of stochastically generated fractures of varying domain sizes and estimating the uncertainty in the equivalent permeability of the generated DFNs. Our results show that the uncertainty of the stochastic DFN model is acceptable when the modeling domain is larger than the determined appropriate domain size, and the appropriate domain size concept is applicable to our study site. © 2016, National Ground Water Association.

Thermal effects in nano-sized adsorbate islands growth processes at vapor deposition

NASA Astrophysics Data System (ADS)

Kharchenko, Vasyl O.; Kharchenko, Dmitrii O.; Dvornichenko, Alina V.

2016-02-01

We study a model of pattern formation in adsorptive systems with a local change in the surface temperature due to adsorption/desorption processes. It is found that thermal effects shrink the domain of main system parameters, when pattern formation is possible. It is shown that an increase in a surface reheat efficiency delays ordering processes. We have found that a distribution of adsorbate islands over sizes depends on relaxation and reheat processes. We have shown that the mean linear size of stationary adsorbate islands is of nano-meter range.

The Molecular Structure of Human Red Blood Cell Membranes from Highly Oriented, Solid Supported Multi-Lamellar Membranes

PubMed Central

Himbert, Sebastian; Alsop, Richard J.; Rose, Markus; Hertz, Laura; Dhaliwal, Alexander; Moran-Mirabal, Jose M.; Verschoor, Chris P.; Bowdish, Dawn M. E.; Kaestner, Lars; Wagner, Christian; Rheinstädter, Maikel C.

2017-01-01

We prepared highly oriented, multi-lamellar stacks of human red blood cell (RBC) membranes applied on silicon wafers. RBC ghosts were prepared by hemolysis and applied onto functionalized silicon chips and annealed into multi-lamellar RBC membranes. High resolution X-ray diffraction was used to determine the molecular structure of the stacked membranes. We present direct experimental evidence that these RBC membranes consist of nanometer sized domains of integral coiled-coil peptides, as well as liquid ordered (lo) and liquid disordered (ld) lipids. Lamellar spacings, membrane and hydration water layer thicknesses, areas per lipid tail and domain sizes were determined. The common drug aspirin was added to the RBC membranes and found to interact with RBC membranes and preferably partition in the head group region of the lo domain leading to a fluidification of the membranes, i.e., a thinning of the bilayers and an increase in lipid tail spacing. Our results further support current models of RBC membranes as patchy structures and provide unprecedented structural details of the molecular organization in the different domains. PMID:28045119

Ultrahigh Molecular Weight Linear Block Copolymers: Rapid Access by Reversible-Deactivation Radical Polymerization and Self- Assembly into Large Domain Nanostructures

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

Mapas, Jose Kenneth D.; Thomay, Tim; Cartwright, Alexander N.

2016-05-05

Block copolymer (BCP) derived periodic nanostructures with domain sizes larger than 150 nm present a versatile platform for the fabrication of photonic materials. So far, the access to such materials has been limited to highly synthetically involved protocols. Herein, we report a simple, “user-friendly” method for the preparation of ultrahigh molecular weight linear poly(solketal methacrylate-b-styrene) block copolymers by a combination of Cu-wire-mediated ATRP and RAFT polymerizations. The synthesized copolymers with molecular weights up to 1.6 million g/mol and moderate dispersities readily assemble into highly ordered cylindrical or lamella microstructures with domain sizes as large as 292 nm, as determined bymore » ultra-small-angle x-ray scattering and scanning electron microscopy analyses. Solvent cast films of the synthesized block copolymers exhibit stop bands in the visible spectrum correlated to their domain spacings. The described method opens new avenues for facilitated fabrication and the advancement of fundamental understanding of BCP-derived photonic nanomaterials for a variety of applications.« less

The Molecular Structure of Human Red Blood Cell Membranes from Highly Oriented, Solid Supported Multi-Lamellar Membranes

NASA Astrophysics Data System (ADS)

Himbert, Sebastian; Alsop, Richard J.; Rose, Markus; Hertz, Laura; Dhaliwal, Alexander; Moran-Mirabal, Jose M.; Verschoor, Chris P.; Bowdish, Dawn M. E.; Kaestner, Lars; Wagner, Christian; Rheinstädter, Maikel C.

2017-01-01

We prepared highly oriented, multi-lamellar stacks of human red blood cell (RBC) membranes applied on silicon wafers. RBC ghosts were prepared by hemolysis and applied onto functionalized silicon chips and annealed into multi-lamellar RBC membranes. High resolution X-ray diffraction was used to determine the molecular structure of the stacked membranes. We present direct experimental evidence that these RBC membranes consist of nanometer sized domains of integral coiled-coil peptides, as well as liquid ordered (lo) and liquid disordered (ld) lipids. Lamellar spacings, membrane and hydration water layer thicknesses, areas per lipid tail and domain sizes were determined. The common drug aspirin was added to the RBC membranes and found to interact with RBC membranes and preferably partition in the head group region of the lo domain leading to a fluidification of the membranes, i.e., a thinning of the bilayers and an increase in lipid tail spacing. Our results further support current models of RBC membranes as patchy structures and provide unprecedented structural details of the molecular organization in the different domains.

Confined Pattern-Directed Assembly of Polymer-Grafted Nanoparticles in a Phase Separating Blend with a Homopolymer Matrix.

PubMed

Zhang, Ren; Lee, Bongjoon; Bockstaller, Michael R; Douglas, Jack F; Stafford, Christopher M; Kumar, Sanat K; Raghavan, Dharmaraj; Karim, Alamgir

The controlled organization of nanoparticle (NP) constituents into superstructures of well-defined shape, composition and connectivity represents a continuing challenge in the development of novel hybrid materials for many technological applications. We show that the phase separation of polymer-tethered nanoparticles immersed in a chemically different polymer matrix provides an effective and scalable method for fabricating defined submicron-sized amorphous NP domains in melt polymer thin films. We investigate this phenomenon with a view towards understanding and controlling the phase separation process through directed nanoparticle assembly. In particular, we consider isothermally annealed thin films of polystyrene-grafted gold nanoparticles (AuPS) dispersed in a poly(methyl methacrylate) (PMMA) matrix. Classic binary polymer blend phase separation related morphology transitions, from discrete AuPS domains to bicontinuous to inverse domain structure with increasing nanoparticle composition is observed, yet the kinetics of the AuPS/PMMA polymer blends system exhibit unique features compared to the parent PS/PMMA homopolymer blend. We further illustrate how to pattern-align the phase-separated AuPS nanoparticle domain shape, size and location through the imposition of a simple and novel external symmetry-breaking perturbation via soft-lithography. Specifically, submicron-sized topographically patterned elastomer confinement is introduced to direct the nanoparticles into kinetically controlled long-range ordered domains, having a dense yet well-dispersed distribution of non-crystallizing nanoparticles. The simplicity, versatility and roll-to-roll adaptability of this novel method for controlled nanoparticle assembly should make it useful in creating desirable patterned nanoparticle domains for a variety of functional materials and applications.

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

Majetich, Sara

In the proposed research program we will investigate the time- and frequency-dependent behavior of ordered nanoparticle assemblies, or nanoparticle crystals. Magnetostatic interactions are long-range and anisotropic, and this leads to complex behavior in nanoparticle assemblies, particularly in the time- and frequency-dependent properties. We hypothesize that the high frequency performance of composite materials has been limited because of the range of relaxation times; if a composite is a dipolar ferromagnet at a particular frequency, it should have the advantages of a single phase material, but without significant eddy current power losses. Arrays of surfactant-coated monodomain magnetic nanoparticles can exhibit long-range magneticmore » order that is stable over time. The magnetic domain size and location of domain walls is governed not by structural grain boundaries but by the shape of the array, due to the local interaction field. Pores or gaps within an assembly pin domain walls and limit the domain size. Measurements of the magnetic order parameter as a function of temperature showed that domains can exist at high temoerature, and that there is a collective phase transition, just as in an exchange-coupled ferromagnet. Dipolar ferromagnets are not merely of fundamental interest; they provide an interesting alternative to exchange-based ferromagnets. Dipolar ferromagnets made with high moment metallic particles in an insulating matrix could have high permeability without large eddy current losses. Such nanocomposites could someday replace the ferrites now used in phase shifters, isolators, circulators, and filters in microwave communications and radar applications. We will investigate the time- and frequency-dependent behavior of nanoparticle crystals with different magnetic core sizes and different interparticle barrier resistances, and will measure the magnetic and electrical properties in the DC, low frequency (0.1 Hz - 1 kHz), moderate frequency (10 Hz - 500 MHz), and high frequency (up to 20 GHz) regimes. Our results will demonstrate whether a DC dipolar ferromagnet shows collective frequency-dependent reponse similar to that of an exchange-based ferromagnet, and will provide data for comparison of optimal nanocomposite properties with those of ferrites used in high frequency applications. Both the magnetic and electronic response of the composites will be examined in order to determine the frequency range where hopping conductivity leads to significant eddy current power losses. In the high frequency regime we will look for evidence of spin wave quantization and the resulting decrease in non-linear spin wave processes that could affect the performance of high frequency magnetic devices.« less

Rapid Ordering in “Wet Brush” Block Copolymer/Homopolymer Ternary Blends

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

Doerk, Gregory S.; Yager, Kevin G.

The ubiquitous presence of thermodynamically unfavored but kinetically trapped topological defects in nanopatterns formed via self-assembly of block copolymer thin films may prevent their use for many envisioned applications. Here, we demonstrate that lamellae patterns formed by symmetric polystyrene-block-poly(methyl methacrylate) diblock copolymers self-assemble and order extremely rapidly when the diblock copolymers are blended with low molecular weight homopolymers of the constituent blocks. Being in the “wet brush” regime, the homopolymers uniformly distribute within their respective self-assembled microdomains, preventing increases in domain widths. An order-of-magnitude increase in topological grain size in blends over the neat (unblended) diblock copolymer is achieved withinmore » minutes of thermal annealing as a result of the significantly higher power law exponent for ordering kinetics in the blends. Moreover, the blends are demonstrated to be capable of rapid and robust domain alignment within micrometer-scale trenches, in contrast to the corresponding neat diblock copolymer. Furthermore, these results can be attributed to the lowering of energy barriers associated with domain boundaries by bringing the system closer to an order–disorder transition through low molecular weight homopolymer blending.« less

Rapid Ordering in “Wet Brush” Block Copolymer/Homopolymer Ternary Blends

DOE PAGES

Doerk, Gregory S.; Yager, Kevin G.

2017-12-01

The ubiquitous presence of thermodynamically unfavored but kinetically trapped topological defects in nanopatterns formed via self-assembly of block copolymer thin films may prevent their use for many envisioned applications. Here, we demonstrate that lamellae patterns formed by symmetric polystyrene-block-poly(methyl methacrylate) diblock copolymers self-assemble and order extremely rapidly when the diblock copolymers are blended with low molecular weight homopolymers of the constituent blocks. Being in the “wet brush” regime, the homopolymers uniformly distribute within their respective self-assembled microdomains, preventing increases in domain widths. An order-of-magnitude increase in topological grain size in blends over the neat (unblended) diblock copolymer is achieved withinmore » minutes of thermal annealing as a result of the significantly higher power law exponent for ordering kinetics in the blends. Moreover, the blends are demonstrated to be capable of rapid and robust domain alignment within micrometer-scale trenches, in contrast to the corresponding neat diblock copolymer. Furthermore, these results can be attributed to the lowering of energy barriers associated with domain boundaries by bringing the system closer to an order–disorder transition through low molecular weight homopolymer blending.« less

General and simple approach for control cage and cylindrical mesopores, and thermal/hydrothermal stable frameworks.

PubMed

El-Safty, Sherif A; Mizukami, Fujio; Hanaoka, Takaaki

2005-05-19

Highly ordered cage and cylindrical mesoporeous silica monoliths (HOM) with 2- and 3-dimensional (2D and 3D, respectively) structures, mesopore/micropore volumes, and thick-walled frameworks were successfully fabricated by instant direct templating of lyotropic phases of copolymer (EO(m)-PO(n)-EO(m)) surfactants. Large cage-like pores with uniform constriction sizes up to 10 nm and open cylindrical channel-like mesopores can be easily achieved by this simple and efficient synthesis design. Our results show that the cage-like pores could be fabricated at relatively lower copolymer concentrations used in the lyotropic phase domains at copolymer/TMOS ratios of 35 wt %. These ordered cage pore architectures underwent transition to open-cylindrical pores by increasing the copolymer concentration. High EO/PO block copolymers, in general, were crucially affected on the increase of the interior cavity sizes and on the stability of the cage mesopore characters. However, for F108 (EO(141)PO(44)EO(141)) systems, the fabrication of ordered and stable cage pore monoliths was achieved with significantly higher copolymer concentrations up to 90 wt %. Interestingly, the effective copolymer molecular nature was also observed in the ability to design various ordered mesophase geometries in large domain sizes. Our findings here show evidence that the synthetic strategy provides realistic control over a wide range of mesostructured phase geometries and their extended long-range ordering in the final replicas of the silica monolith frameworks. In addition, the HOM silica monoliths exhibited considerable structural stability against higher thermal temperature (up to 1000 degrees C) and longer hydrothermal treatment times under boiling water and steam. The remarkable structural findings of 3D frameworks, transparent monoliths, and micropores combined with large cage- and cylindrical-like mesopores are expected to find promising uses in materials chemistry.

Lattice-Boltzmann simulation of coalescence-driven island coarsening

USGS Publications Warehouse

Basagaoglu, H.; Green, C.T.; Meakin, P.; McCoy, B.J.

2004-01-01

The first-order phase separation in a thin fluid film was simulated using a two-dimensional lattice-Boltzman model (LBM) with fluid-fluid interactions. The effects of the domain size on the intermediate asymptotic island size distribution were also discussed. It was observed that the overall process is dominated by coalescence which is independent of island mass. The results show that the combined effects of growth, coalescence, and Ostwald ripening control the phase transition process in the LBM simulations.

Number comparison and number ordering as predictors of arithmetic performance in adults: Exploring the link between the two skills, and investigating the question of domain-specificity.

PubMed

Morsanyi, Kinga; O'Mahony, Eileen; McCormack, Teresa

2017-12-01

Recent evidence has highlighted the important role that number-ordering skills play in arithmetic abilities, both in children and adults. In the current study, we demonstrated that number comparison and ordering skills were both significantly related to arithmetic performance in adults, and the effect size was greater in the case of ordering skills. Additionally, we found that the effect of number comparison skills on arithmetic performance was mediated by number-ordering skills. Moreover, performance on comparison and ordering tasks involving the months of the year was also strongly correlated with arithmetic skills, and participants displayed similar (canonical or reverse) distance effects on the comparison and ordering tasks involving months as when the tasks included numbers. This suggests that the processes responsible for the link between comparison and ordering skills and arithmetic performance are not specific to the domain of numbers. Finally, a factor analysis indicated that performance on comparison and ordering tasks loaded on a factor that included performance on a number line task and self-reported spatial thinking styles. These results substantially extend previous research on the role of order processing abilities in mental arithmetic.

Detection of submicron-sized raft-like domains in membranes by small-angle neutron scattering

NASA Astrophysics Data System (ADS)

Pencer, J.; Mills, T.; Anghel, V.; Krueger, S.; Epand, R. M.; Katsaras, J.

2005-12-01

Using coarse grained models of heterogeneous vesicles we demonstrate the potential for small-angle neutron scattering (SANS) to detect and distinguish between two different categories of lateral segregation: 1) unilamellar vesicles (ULV) containing a single domain and 2) the formation of several small domains or “clusters” (~10 nm in radius) on a ULV. Exploiting the unique sensitivity of neutron scattering to differences between hydrogen and deuterium, we show that the liquid ordered (lo) DPPC-rich phase can be selectively labeled using chain deuterated dipalymitoyl phosphatidylcholine (dDPPC), which greatly facilitates the use of SANS to detect membrane domains. SANS experiments are then performed in order to detect and characterize, on nanometer length scales, lateral heterogeneities, or so-called “rafts”, in ~30 nm radius low polydispersity ULV made up of ternary mixtures of phospholipids and cholesterol. For 1:1:1 DOPC:DPPC:cholesterol (DDC) ULV we find evidence for the formation of lateral heterogeneities on cooling below 30 °C. These heterogeneities do not appear when DOPC is replaced by SOPC. Fits to the experimental data using coarse grained models show that, at room temperature, DDC ULV each exhibit approximately 30 domains with average radii of ~10 nm.

A high-order spatial filter for a cubed-sphere spectral element model

NASA Astrophysics Data System (ADS)

Kang, Hyun-Gyu; Cheong, Hyeong-Bin

2017-04-01

A high-order spatial filter is developed for the spectral-element-method dynamical core on the cubed-sphere grid which employs the Gauss-Lobatto Lagrange interpolating polynomials (GLLIP) as orthogonal basis functions. The filter equation is the high-order Helmholtz equation which corresponds to the implicit time-differencing of a diffusion equation employing the high-order Laplacian. The Laplacian operator is discretized within a cell which is a building block of the cubed sphere grid and consists of the Gauss-Lobatto grid. When discretizing a high-order Laplacian, due to the requirement of C0 continuity along the cell boundaries the grid-points in neighboring cells should be used for the target cell: The number of neighboring cells is nearly quadratically proportional to the filter order. Discrete Helmholtz equation yields a huge-sized and highly sparse matrix equation whose size is N*N with N the number of total grid points on the globe. The number of nonzero entries is also almost in quadratic proportion to the filter order. Filtering is accomplished by solving the huge-matrix equation. While requiring a significant computing time, the solution of global matrix provides the filtered field free of discontinuity along the cell boundaries. To achieve the computational efficiency and the accuracy at the same time, the solution of the matrix equation was obtained by only accounting for the finite number of adjacent cells. This is called as a local-domain filter. It was shown that to remove the numerical noise near the grid-scale, inclusion of 5*5 cells for the local-domain filter was found sufficient, giving the same accuracy as that obtained by global domain solution while reducing the computing time to a considerably lower level. The high-order filter was evaluated using the standard test cases including the baroclinic instability of the zonal flow. Results indicated that the filter performs better on the removal of grid-scale numerical noises than the explicit high-order viscosity. It was also presented that the filter can be easily implemented on the distributed-memory parallel computers with a desirable scalability.

Inducing Order from Disordered Copolymers: On Demand Generation of Triblock Morphologies Including Networks

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

Tureau, Maëva S.; Kuan, Wei-Fan; Rong, Lixia

Disordered block copolymers are generally impractical in nanopatterning applications due to their inability to self-assemble into well-defined nanostructures. However, inducing order in low molecular weight disordered systems permits the design of periodic structures with smaller characteristic sizes. Here, we have induced nanoscale phase separation from disordered triblock copolymer melts to form well-ordered lamellae, hexagonally packed cylinders, and a triply periodic gyroid network structure, using a copolymer/homopolymer blending approach, which incorporates constituent homopolymers into selective block domains. This versatile blending approach allows one to precisely target multiple nanostructures from a single disordered material and can be applied to a wide varietymore » of triblock copolymer systems for nanotemplating and nanoscale separation applications requiring nanoscale feature sizes and/or high areal feature densities.« less

Molecular dynamics exploration of poration and leaking caused by Kalata B1 in HIV-infected cell membrane compared to host and HIV membranes.

PubMed

Nawae, Wanapinun; Hannongbua, Supa; Ruengjitchatchawalya, Marasri

2017-06-15

The membrane disruption activities of kalata B1 (kB1) were investigated using molecular dynamics simulations with membrane models. The models were constructed to mimic the lipid microdomain formation in membranes of HIV particle, HIV-infected cell, and host cell. The differences in the lipid ratios of these membranes caused the formation of liquid ordered (lo) domains of different sizes, which affected the binding and activity of kB1. Stronger kB1 disruptive activity was observed for the membrane with small sized lo domain. Our results show that kB1 causes membrane leaking without bilayer penetration. The membrane poration mechanism involved in the disorganization of the lo domain and in cholesterol inter-leaflet translocation is described. This study enhances our understanding of the membrane activity of kB1, which may be useful for designing novel and potentially therapeutic peptides based on the kB1 framework.

The scaling features of the 3D organization of chromosomes are highlighted by a transformation à la Kadanoff of Hi-C data

NASA Astrophysics Data System (ADS)

Chiariello, Andrea M.; Bianco, Simona; Annunziatella, Carlo; Esposito, Andrea; Nicodemi, Mario

2017-11-01

Technologies such as Hi-C and GAM have revealed that chromosomes are not randomly folded into the nucleus of cells, but are composed by a sequence of contact domains (TADs), each typically 0.5 Mb long. However, the larger scale organization of the genome remains still not well understood. To investigate the scaling behaviour of chromosome folding, here we apply an approach à la Kadanoff, inspired by the Renormalization Group theory, to Hi-C interaction data, across different cell types and chromosomes. We find that the genome is characterized by complex scaling features, where the average size of contact domains exhibits a power-law behaviour with the rescaling level. That is compatible with the existence of contact domains extending across length scales up to chromosomal sizes. The scaling exponent is statistically indistinguishable among the different murine cell types analysed. These results point toward a scenario of a universal higher-order spatial architecture of the genome, which could reflect fundamental, organizational principles.

Bulk heterojunction morphology of polymer:fullerene blends revealed by ultrafast spectroscopy

PubMed Central

Serbenta, Almis; Kozlov, Oleg V.; Portale, Giuseppe; van Loosdrecht, Paul H. M.; Pshenichnikov, Maxim S.

2016-01-01

Morphology of organic photovoltaic bulk heterojunctions (BHJs) – a nanoscale texture of the donor and acceptor phases – is one of the key factors influencing efficiency of organic solar cells. Detailed knowledge of the morphology is hampered by the fact that it is notoriously difficult to investigate by microscopic methods. Here we all-optically track the exciton harvesting dynamics in the fullerene acceptor phase from which subdivision of the fullerene domain sizes into the mixed phase (2–15 nm) and large (>50 nm) domains is readily obtained via the Monte-Carlo simulations. These results were independently confirmed by a combination of X-ray scattering, electron and atomic-force microscopies, and time-resolved photoluminescence spectroscopy. In the large domains, the excitons are lost due to the high energy disorder while in the ordered materials the excitons are harvested with high efficiency even from the domains as large as 100 nm due to the absence of low-energy traps. Therefore, optimizing of blend nanomorphology together with increasing the material order are deemed as winning strategies in the exciton harvesting optimization. PMID:27824085

FSCS Reveals the Complexity of Lipid Domain Dynamics in the Plasma Membrane of Live Cells.

PubMed

Nicovich, Philip R; Kwiatek, Joanna M; Ma, Yuanqing; Benda, Aleš; Gaus, Katharina

2018-06-19

The coexistence of lipid domains with different degrees of lipid packing in the plasma membrane of mammalian cells has been postulated, but direct evidence has so far been challenging to obtain because of the small size and short lifetime of these domains in live cells. Here, we use fluorescence spectral correlation spectroscopy in conjunction with a probe sensitive to the membrane environment to quantify spectral fluctuations associated with dynamics of membrane domains in live cells. With this method, we show that membrane domains are present in live COS-7 cells and have a lifetime lower bound of 5.90 and 14.69 ms for the ordered and disordered phases, respectively. Comparisons to simulations indicate that the underlying mechanism of these fluctuations is complex but qualitatively described by a combination of dye diffusion between membrane domains as well as the motion of domains within the membrane. Copyright © 2018 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Liquid phase blending of metal-organic frameworks.

PubMed

Longley, Louis; Collins, Sean M; Zhou, Chao; Smales, Glen J; Norman, Sarah E; Brownbill, Nick J; Ashling, Christopher W; Chater, Philip A; Tovey, Robert; Schönlieb, Carola-Bibiane; Headen, Thomas F; Terrill, Nicholas J; Yue, Yuanzheng; Smith, Andrew J; Blanc, Frédéric; Keen, David A; Midgley, Paul A; Bennett, Thomas D

2018-06-15

The liquid and glass states of metal-organic frameworks (MOFs) have recently become of interest due to the potential for liquid-phase separations and ion transport, alongside the fundamental nature of the latter as a new, fourth category of melt-quenched glass. Here we show that the MOF liquid state can be blended with another MOF component, resulting in a domain structured MOF glass with a single, tailorable glass transition. Intra-domain connectivity and short range order is confirmed by nuclear magnetic resonance spectroscopy and pair distribution function measurements. The interfacial binding between MOF domains in the glass state is evidenced by electron tomography, and the relationship between domain size and T g investigated. Nanoindentation experiments are also performed to place this new class of MOF materials into context with organic blends and inorganic alloys.

Reverse-mode thermoresponsive light attenuators produced by optical anisotropic composites of nematic liquid crystals and reactive mesogens

NASA Astrophysics Data System (ADS)

Kakiuchida, Hiroshi; Ogiwara, Akifumi

2018-04-01

Polymer network liquid crystals (PNLCs) whose optical transmittance state switches between transparence at low temperatures and haze at high temperatures were fabricated from mixtures of nematic liquid crystals (LCs) and reactive mesogens (RMs). This PNLC structure is simple but effective, namely, consists of micro-scale domains of orientation-ordered LCs and anisotropically polymerized RMs. The domains form through photopolymerization induced phase separation with inhomogeneous irradiation projected by laser speckling techniques. This irradiation method enables you to control the size and shape of phase-separation domains, and these PNLCs can be applied to novel thermoresponsive optical devices; optical isolators, thermometric sheets, and smart windows.

Reduced size first-order subsonic and supersonic aeroelastic modeling

NASA Technical Reports Server (NTRS)

Karpel, Mordechay

1990-01-01

Various aeroelastic, aeroservoelastic, dynamic-response, and sensitivity analyses are based on a time-domain first-order (state-space) formulation of the equations of motion. The formulation of this paper is based on the minimum-state (MS) aerodynamic approximation method, which yields a low number of aerodynamic augmenting states. Modifications of the MS and the physical weighting procedures make the modeling method even more attractive. The flexibility of constraint selection is increased without increasing the approximation problem size; the accuracy of dynamic residualization of high-frequency modes is improved; and the resulting model is less sensitive to parametric changes in subsequent analyses. Applications to subsonic and supersonic cases demonstrate the generality, flexibility, accuracy, and efficiency of the method.

Complex biomembrane mimetics on the sub-nanometer scale

DOE PAGES

Heberle, Frederick A.; Pabst, Georg

2017-07-17

Biomimetic lipid vesicles are indispensable tools for gaining insight into the biophysics of cell physiology on the molecular level. The level of complexity of these model systems has steadily increased, and now spans from domain forming lipid mixtures to asymmetric lipid bilayers. We review recent progress in the development and application of elastic neutron and X-ray scattering techniques for studying these systems in situ and under physiologically relevant conditions on the nanometer to sub-nanometer length scales. Particularly we focus on: (i) structural details of coexisting liquid-ordered and liquid-disordered domains, including their thickness and lipid packing mismatch as a function ofmore » a size transition from nanoscopic to macroscopic domains; (ii) membrane-mediated protein partitioning into lipid domains; (iii) the role of the aqueous medium in tuning interactions between membranes and domains; and (iv) leaflet specific structure in asymmetric bilayers and passive lipid flip-flop.« less

Complex biomembrane mimetics on the sub-nanometer scale

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

Heberle, Frederick A.; Pabst, Georg

Biomimetic lipid vesicles are indispensable tools for gaining insight into the biophysics of cell physiology on the molecular level. The level of complexity of these model systems has steadily increased, and now spans from domain forming lipid mixtures to asymmetric lipid bilayers. We review recent progress in the development and application of elastic neutron and X-ray scattering techniques for studying these systems in situ and under physiologically relevant conditions on the nanometer to sub-nanometer length scales. Particularly we focus on: (i) structural details of coexisting liquid-ordered and liquid-disordered domains, including their thickness and lipid packing mismatch as a function ofmore » a size transition from nanoscopic to macroscopic domains; (ii) membrane-mediated protein partitioning into lipid domains; (iii) the role of the aqueous medium in tuning interactions between membranes and domains; and (iv) leaflet specific structure in asymmetric bilayers and passive lipid flip-flop.« less

FRACTAL DIMENSION OF SPIN-GLASSES INTERFACES IN DIMENSION d = 2 AND d = 3 VIA STRONG DISORDER RENORMALIZATION AT ZERO TEMPERATURE

NASA Astrophysics Data System (ADS)

Monthus, Cécile

2015-09-01

For Gaussian Spin-Glasses in low dimensions, we introduce a simple Strong Disorder renormalization at zero temperature in order to construct ground states for Periodic and Anti-Periodic boundary conditions. The numerical study in dimensions d = 2 (up to sizes 20482) and d = 3 (up to sizes 1283) yields that Domain Walls are fractal of dimensions ds(d = 2) ≃ 1.27 and ds(d = 3) ≃ 2.55, respectively.

A passive chevron replicator

NASA Technical Reports Server (NTRS)

Oeffinger, T. R.; Tocci, L. R.

1977-01-01

Instrument design provides replicate function between device storage area and guardrail detector in order that nondestructive read-out of memory can be achieved. Use of guardrail detectors in magnetic domain (bubble) circuits is proposed method of increasing detector signal output by increasing detector size without dedicating an excessive amount of device chip area to detector portion.

Perfectly matched layers in a divergence preserving ADI scheme for electromagnetics

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

Kraus, C.; ETH Zurich, Chair of Computational Science, 8092 Zuerich; Adelmann, A., E-mail: andreas.adelmann@psi.ch

For numerical simulations of highly relativistic and transversely accelerated charged particles including radiation fast algorithms are needed. While the radiation in particle accelerators has wavelengths in the order of 100 {mu}m the computational domain has dimensions roughly five orders of magnitude larger resulting in very large mesh sizes. The particles are confined to a small area of this domain only. To resolve the smallest scales close to the particles subgrids are envisioned. For reasons of stability the alternating direction implicit (ADI) scheme by Smithe et al. [D.N. Smithe, J.R. Cary, J.A. Carlsson, Divergence preservation in the ADI algorithms for electromagnetics,more » J. Comput. Phys. 228 (2009) 7289-7299] for Maxwell equations has been adopted. At the boundary of the domain absorbing boundary conditions have to be employed to prevent reflection of the radiation. In this paper we show how the divergence preserving ADI scheme has to be formulated in perfectly matched layers (PML) and compare the performance in several scenarios.« less

Bicontinuous structured liquids with sub-micrometre domains using nanoparticle surfactants

DOE PAGES

Huang, Caili; Forth, Joe; Wang, Weiyu; ...

2017-09-25

Bicontinuous jammed emulsions (or bijels) are tortuous, interconnected structures of two immiscible liquids, kinetically trapped by colloidal particles that are irreversibly bound to the oil–water interface. A wealth of applications has been proposed for bijels in catalysis, energy storage and molecular encapsulation, but large domain sizes (on the order of 5 µm or larger) and difficulty in fabrication pose major barriers to their use. In this paper, we show that bijels with sub-micrometre domains can be formed via homogenization, rather than spinodal decomposition. We achieve this by using nanoparticle surfactants: polymers and nanoparticles of complementary functionality (for example, ion-pairing) thatmore » bind to one another at the oil–water interface. This allows the stabilization of the bijel far from the demixing point of the liquids, with interfacial tensions on the order of 20 mN m -1. Finally, furthermore, our strategy is extremely versatile, as solvent, nanoparticle and ligand can all be varied.« less

Bicontinuous structured liquids with sub-micrometre domains using nanoparticle surfactants

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

Huang, Caili; Forth, Joe; Wang, Weiyu

Bicontinuous jammed emulsions (or bijels) are tortuous, interconnected structures of two immiscible liquids, kinetically trapped by colloidal particles that are irreversibly bound to the oil–water interface. A wealth of applications has been proposed for bijels in catalysis, energy storage and molecular encapsulation, but large domain sizes (on the order of 5 µm or larger) and difficulty in fabrication pose major barriers to their use. In this paper, we show that bijels with sub-micrometre domains can be formed via homogenization, rather than spinodal decomposition. We achieve this by using nanoparticle surfactants: polymers and nanoparticles of complementary functionality (for example, ion-pairing) thatmore » bind to one another at the oil–water interface. This allows the stabilization of the bijel far from the demixing point of the liquids, with interfacial tensions on the order of 20 mN m -1. Finally, furthermore, our strategy is extremely versatile, as solvent, nanoparticle and ligand can all be varied.« less

An efficient linear-scaling CCSD(T) method based on local natural orbitals.

PubMed

Rolik, Zoltán; Szegedy, Lóránt; Ladjánszki, István; Ladóczki, Bence; Kállay, Mihály

2013-09-07

An improved version of our general-order local coupled-cluster (CC) approach [Z. Rolik and M. Kállay, J. Chem. Phys. 135, 104111 (2011)] and its efficient implementation at the CC singles and doubles with perturbative triples [CCSD(T)] level is presented. The method combines the cluster-in-molecule approach of Li and co-workers [J. Chem. Phys. 131, 114109 (2009)] with frozen natural orbital (NO) techniques. To break down the unfavorable fifth-power scaling of our original approach a two-level domain construction algorithm has been developed. First, an extended domain of localized molecular orbitals (LMOs) is assembled based on the spatial distance of the orbitals. The necessary integrals are evaluated and transformed in these domains invoking the density fitting approximation. In the second step, for each occupied LMO of the extended domain a local subspace of occupied and virtual orbitals is constructed including approximate second-order Mo̸ller-Plesset NOs. The CC equations are solved and the perturbative corrections are calculated in the local subspace for each occupied LMO using a highly-efficient CCSD(T) code, which was optimized for the typical sizes of the local subspaces. The total correlation energy is evaluated as the sum of the individual contributions. The computation time of our approach scales linearly with the system size, while its memory and disk space requirements are independent thereof. Test calculations demonstrate that currently our method is one of the most efficient local CCSD(T) approaches and can be routinely applied to molecules of up to 100 atoms with reasonable basis sets.

Giant thermo-optical relaxation oscillations in millimeter-size whispering gallery mode disk resonators.

PubMed

Diallo, Souleymane; Lin, Guoping; Chembo, Yanne K

2015-08-15

In this Letter, we show that giant thermo-optical oscillations can be triggered in millimeter (mm)-size whispering gallery mode (WGM) disk resonators when they are pumped by a resonant continuous-wave laser. Our resonator is an ultrahigh-Q barium fluoride cavity that features a positive thermo-optic coefficient and a negative thermo-elastic coefficient. We demonstrate for the first time, to our knowledge, that the complex interplay between these two thermic coefficients and the intrinsic Kerr nonlinearity yields very sharp slow-fast relaxation oscillations with a slow timescale that can be exceptionally large, typically of the order of 1 s. We use a time-domain model to gain understanding into this instability, and we find that both the experimental and theoretical results are in excellent agreement. The understanding of these thermal effects is an essential requirement for every WGM-related application and our study demonstrates that even in the case of mm-size resonators, such effects can still be accurately analyzed using nonlinear time-domain models.

Effects of substrate misorientation and growth rate on ordering in GaInP

NASA Astrophysics Data System (ADS)

Su, L. C.; Ho, I. H.; Stringfellow, G. B.

1994-05-01

Epitaxial layers of GaxIn1-xP with x≊0.52 have been grown by organometallic vapor-phase epitaxy on GaAs substrates misoriented from the (001) plane in the [1¯10] direction by angles ϑm, of 0°, 3°, 6°, and 9°. For each substrate orientation growth rates rg of 1, 2, and 4 μm/h have been used. The ordering was characterized using transmission electron diffraction (TED), dark-field imaging, and photoluminescence. The (110) cross-sectional images show domains of the Cu-Pt structure separated by antiphase boundaries (APBs). The domain size and shape and the degree of order are found to be strongly affected by both the substrate misorientation and the growth rate. For example, lateral domain dimensions range from 50 Å for layers grown with rg=4 μm/h and ϑm=0° to 2500 Å for rg=1 μm/h and ϑm=9°. The APBs generally propagate from the substrate/epilayer interface to the top surface at an angle to the (001) plane that increases dramatically as the angle of misorientation increases. The angle is nearly independent of growth rate. From the superspot intensities in the TED patterns, the degree of order appears to be a maximum for ϑm≊5°. Judging from the reduction in photoluminescence peak energy caused by ordering, the maximum degree of order appears to occur at ϑm≊4°.

Analytic energy derivatives for the calculation of the first-order molecular properties using the domain-based local pair-natural orbital coupled-cluster theory

NASA Astrophysics Data System (ADS)

Datta, Dipayan; Kossmann, Simone; Neese, Frank

2016-09-01

The domain-based local pair-natural orbital coupled-cluster (DLPNO-CC) theory has recently emerged as an efficient and powerful quantum-chemical method for the calculation of energies of molecules comprised of several hundred atoms. It has been demonstrated that the DLPNO-CC approach attains the accuracy of a standard canonical coupled-cluster calculation to about 99.9% of the basis set correlation energy while realizing linear scaling of the computational cost with respect to system size. This is achieved by combining (a) localized occupied orbitals, (b) large virtual orbital correlation domains spanned by the projected atomic orbitals (PAOs), and (c) compaction of the virtual space through a truncated pair natural orbital (PNO) basis. In this paper, we report on the implementation of an analytic scheme for the calculation of the first derivatives of the DLPNO-CC energy for basis set independent perturbations within the singles and doubles approximation (DLPNO-CCSD) for closed-shell molecules. Perturbation-independent one-particle density matrices have been implemented in order to account for the response of the CC wave function to the external perturbation. Orbital-relaxation effects due to external perturbation are not taken into account in the current implementation. We investigate in detail the dependence of the computed first-order electrical properties (e.g., dipole moment) on the three major truncation parameters used in a DLPNO-CC calculation, namely, the natural orbital occupation number cutoff used for the construction of the PNOs, the weak electron-pair cutoff, and the domain size cutoff. No additional truncation parameter has been introduced for property calculation. We present benchmark calculations on dipole moments for a set of 10 molecules consisting of 20-40 atoms. We demonstrate that 98%-99% accuracy relative to the canonical CCSD results can be consistently achieved in these calculations. However, this comes with the price of tightening the threshold for the natural orbital occupation number cutoff by an order of magnitude compared to the DLPNO-CCSD energy calculations.

Size and space controlled hexagonal arrays of superparamagnetic iron oxide nanodots: magnetic studies and application

PubMed Central

Ghoshal, Tandra; Maity, Tuhin; Senthamaraikannan, Ramsankar; Shaw, Matthew T.; Carolan, Patrick; Holmes, Justin D.; Roy, Saibal; Morris, Michael A.

2013-01-01

Highly dense hexagonally arranged iron oxide nanodots array were fabricated using PS-b-PEO self-assembled patterns. The copolymer molecular weight, composition and choice of annealing solvent/s allows dimensional and structural control of the nanopatterns at large scale. A mechanism is proposed to create scaffolds through degradation and/or modification of cylindrical domains. A methodology based on selective metal ion inclusion and subsequent processing was used to create iron oxide nanodots array. The nanodots have uniform size and shape and their placement mimics the original self-assembled nanopatterns. For the first time these precisely defined and size selective systems of ordered nanodots allow careful investigation of magnetic properties in dimensions from 50 nm to 10 nm, which delineate the nanodots are superparamagnetic, well-isolated and size monodispersed. This diameter/spacing controlled iron oxide nanodots systems were demonstrated as a resistant mask over silicon to fabricate densely packed, identical ordered, high aspect ratio silicon nanopillars and nanowire features. PMID:24072037

Sizes of lipid domains: What do we know from artificial lipid membranes? What are the possible shared features with membrane rafts in cells?

PubMed

Rosetti, Carla M; Mangiarotti, Agustín; Wilke, Natalia

2017-05-01

In model lipid membranes with phase coexistence, domain sizes distribute in a very wide range, from the nanometer (reported in vesicles and supported films) to the micrometer (observed in many model membranes). Domain growth by coalescence and Ostwald ripening is slow (minutes to hours), the domain size being correlated with the size of the capture region. Domain sizes thus strongly depend on the number of domains which, in the case of a nucleation process, depends on the oversaturation of the system, on line tension and on the perturbation rate in relation to the membrane dynamics. Here, an overview is given of the factors that affect nucleation or spinodal decomposition and domain growth, and their influence on the distribution of domain sizes in different model membranes is discussed. The parameters analyzed respond to very general physical rules, and we therefore propose a similar behavior for the rafts in the plasma membrane of cells, but with obstructed mobility and with a continuously changing environment. Copyright © 2017 Elsevier B.V. All rights reserved.

Origin of effects of additive solvent on film-morphology in solution-processed nonfullerene solar cells.

PubMed

Chen, Yuxia; Zhang, Xin; Zhan, Chuanlang; Yao, Jiannian

2015-04-01

In this paper, we report an efficient nonfullerene solar cell based on small molecules of p-DTS(FBTTh2)2 and bis-PDI-T. Characterization data indicate that the nature of the acceptor aggregate is a key factor that affects the photocurrent. There is a good relationship between the short-circuit current density (J(SC)) and the phase size of the acceptor-rich domains. The phase size of the acceptor-rich domains is tuned by both the additive types and additive content. As the kind of additive goes from 1-chloronaphthalene (CN) to 1,8-octanedithiol (ODT) and 1,8-diiodooctane (DIO), by this order the solubility of the acceptor in the additive is down, the phase size significantly decreases from over 400 nm down to 30 nm. Also, the acceptor's domain size decreases from 80 to 30 nm as the DIO content ([DIO]) is down from 1% to 0.15%. Following this trend, less DIO remains in the wet film as residue after the host chloroform evaporates, and thus less acceptor can be dissolved in the residue DIO. This decreasing of DIO content acts on the film-morphology similarly as the additive changes down to the one having a lower solubility. Accordingly, our results indicate that it is the dissolved amount of the organic component in the residue additive solvent of the wet film that plays a role in turning the phase size. The efficiency from this small molecule system is significantly raised from 0.02% up to 3.7% by selecting the additive type and fine-tuning the additive content.

Membrane Order Is a Key Regulator of Divalent Cation-Induced Clustering of PI(3,5)P2 and PI(4,5)P2.

PubMed

Sarmento, Maria J; Coutinho, Ana; Fedorov, Aleksander; Prieto, Manuel; Fernandes, Fábio

2017-10-31

Although the evidence for the presence of functionally important nanosized phosphorylated phosphoinositide (PIP)-rich domains within cellular membranes has accumulated, very limited information is available regarding the structural determinants for compartmentalization of these phospholipids. Here, we used a combination of fluorescence spectroscopy and microscopy techniques to characterize differences in divalent cation-induced clustering of PI(4,5)P 2 and PI(3,5)P 2 . Through these methodologies we were able to detect differences in divalent cation-induced clustering efficiency and cluster size. Ca 2+ -induced PI(4,5)P 2 clusters are shown to be significantly larger than the ones observed for PI(3,5)P 2 . Clustering of PI(4,5)P 2 is also detected at physiological concentrations of Mg 2+ , suggesting that in cellular membranes, these molecules are constitutively driven to clustering by the high intracellular concentration of divalent cations. Importantly, it is shown that lipid membrane order is a key factor in the regulation of clustering for both PIP isoforms, with a major impact on cluster sizes. Clustered PI(4,5)P 2 and PI(3,5)P 2 are observed to present considerably higher affinity for more ordered lipid phases than the monomeric species or than PI(4)P, possibly reflecting a more general tendency of clustered lipids for insertion into ordered domains. These results support a model for the description of the lateral organization of PIPs in cellular membranes, where both divalent cation interaction and membrane order are key modulators defining the lateral organization of these lipids.

Figures of Merit for Magnetic Recording Media

NASA Astrophysics Data System (ADS)

Skomski, Ralph; Sellmyer, D. J.

2007-03-01

Since the first nucleation-field calculations for hard-soft nanostructures with multilayered [1] and arbitrary [2] geometries, exchange-spring magnets have attracted much attention in various areas of magnetism, including magnetic recording. Ultrahigh storage densities correspond to the strong-coupling limit, realized on small length scales and described by volume-averaged anisotropies. Second-order perturbation theory yields finite-size corrections that describe a partial decoupling of the phases. Since soft phases reduce the nucleation field, nanostructuring can be used to reduce the coercivity Hc while maintaining the energy barrier EB. However, the ratio EB/Hc is an ill-defined figure of merit, because the comparison with the Stoner-Wohlfarth model requires the introduction of a particle volume, as contrasted to an area. By using elongated particles with a continuous anisotropy gradient, it is possible to reduce the coercivity by a factor scaling as the bit size divided by the domain-wall width of the hard phase. However, with decreasing bit size this effect becomes less pronounced. In the strong-coupling limit, thermal stability yields a maximum storage density of order γ/kBT, where γ is the domain-wall energy of the hard phase. - This research is supported by NSF MRSEC, INSIC, and NCMN. [1] S. Nieber and H. Kronm"uller, phys. stat. sol. (b) 153, 367 (1989). [2] R. Skomski and J. M. D. Coey, Phys. Rev. B 48, 15812 (1993).

Thermodynamic theory of intrinsic finite size effects in PbTiO3 nanocrystals. II. Dielectric and piezoelectric properties

NASA Astrophysics Data System (ADS)

Akdogan, E. K.; Safari, A.

2007-03-01

We compute the intrinsic dielectric and piezoelectric properties of single domain, mechanically free, and surface charge compensated PbTiO3 nanocrystals (n-Pt) with no depolarization fields, undergoing a finite size induced first order tetragonal→cubic ferrodistortive phase transition. By using a Landau-Devonshire type free energy functional, in which Landau coefficients are a function of nanoparticle size, we demonstrate substantial deviations from bulk properties in the range <150 nm. We find a decrease in dielectric susceptibility at the transition temperature with decreasing particle size, which we verify to be in conformity with predictions of lattice dynamics considerations. We also find an anomalous increase in piezocharge coefficients near ˜15 nm , the critical size for n-Pt.

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 2D Daubechies finite wavelet domain method for transient wave response analysis in shear deformable laminated composite plates

NASA Astrophysics Data System (ADS)

Nastos, C. V.; Theodosiou, T. C.; Rekatsinas, C. S.; Saravanos, D. A.

2018-03-01

An efficient numerical method is developed for the simulation of dynamic response and the prediction of the wave propagation in composite plate structures. The method is termed finite wavelet domain method and takes advantage of the outstanding properties of compactly supported 2D Daubechies wavelet scaling functions for the spatial interpolation of displacements in a finite domain of a plate structure. The development of the 2D wavelet element, based on the first order shear deformation laminated plate theory is described and equivalent stiffness, mass matrices and force vectors are calculated and synthesized in the wavelet domain. The transient response is predicted using the explicit central difference time integration scheme. Numerical results for the simulation of wave propagation in isotropic, quasi-isotropic and cross-ply laminated plates are presented and demonstrate the high spatial convergence and problem size reduction obtained by the present method.

Effect of increasing disorder on domains of the 2d Coulomb glass.

PubMed

Bhandari, Preeti; Malik, Vikas

2017-12-06

We have studied a two dimensional lattice model of Coulomb glass for a wide range of disorders at [Formula: see text]. The system was first annealed using Monte Carlo simulation. Further minimization of the total energy of the system was done using an algorithm developed by Baranovskii et al, followed by cluster flipping to obtain the pseudo-ground states. We have shown that the energy required to create a domain of linear size L in d dimensions is proportional to [Formula: see text]. Using Imry-Ma arguments given for random field Ising model, one gets critical dimension [Formula: see text] for Coulomb glass. The investigation of domains in the transition region shows a discontinuity in staggered magnetization which is an indication of a first-order type transition from charge-ordered phase to disordered phase. The structure and nature of random field fluctuations of the second largest domain in Coulomb glass are inconsistent with the assumptions of Imry and Ma, as was also reported for random field Ising model. The study of domains showed that in the transition region there were mostly two large domains, and that as disorder was increased the two large domains remained, but a large number of small domains also opened up. We have also studied the properties of the second largest domain as a function of disorder. We furthermore analysed the effect of disorder on the density of states, and showed a transition from hard gap at low disorders to a soft gap at higher disorders. At [Formula: see text], we have analysed the soft gap in detail, and found that the density of states deviates slightly ([Formula: see text]) from the linear behaviour in two dimensions. Analysis of local minima show that the pseudo-ground states have similar structure.

Molecular emulsions: from charge order to domain order.

PubMed

Perera, Aurélien

2017-10-25

Aqueous mixtures of small molecules, such as lower n-alkanols for example, are known to be micro-segregated, with domains in the nano-meter range. One consequence of this micro-segregation would be the existence of long range domain-domain oscillatory correlations in the various atom-atom pair correlation functions, and subsequent pre-peaks in the corresponding atom-atom structure factors, in the q-vector range corresponding to nano-sized domains. However, no such pre-peak have ever been observed in the large corpus of radiation scattering data published so far on aqueous mixtures of small n-alkanols. By using large scale simulations of aqueous-1propanol mixtures, it is shown herein that the origin for the absence of scattering pre-peak resides in the exact cancellation of the contributions of the various atom-atom correlation pre-peaks to the total scattered intensity. The mechanism for this cancellation is due to the differences in the long range oscillatory behaviour of the correlations (beyond 1 nm), which are exactly out-of-phase between same species and cross species. This is similar to the charge order observed in ionic melts, but differs from room temperature ionic liquids, where the segregation is between charged and neutral groups, instead of species segregation. The consequences of such cancellation in the experimental scattering data are examined, in relation to the possibility of detecting micro-segregation through such methods. In the particular case of aqueous-1propanol mixtures, it is shown the X-ray scattering leads an exact cancellation, while this cancellation in neutron scattering is seen to depend on the deuteration ratio between solvent and solute.

X-ray Diffraction Investigation of Annealing Behavior of Peened Surface Deformation Layer on Precipitation Hardening Stainless Steel

NASA Astrophysics Data System (ADS)

Huang, Junjie; Wang, Zhou; Gan, Jin; Yang, Ying; Huang, Feng; Wu, Gang; Meng, Qingshuai

2018-05-01

In order to investigate the recrystallization behavior of peened surface deformation layer of precipitation hardening stainless steel, a classic x-ray diffraction line profile analysis, Voigt method, was carried out on peened 17-4PH with different isothermal annealing temperatures. The activation energy of domain boundary migration ( Q a) and the activation energy of microstrain relaxation ( Q b) were calculated by regression analysis in different annealing temperature conditions. The results show that the value of Q a decreases with annealing temperature increasing, which is due to the influence of precipitation (ɛ-Cu) size on the movements of grain and subgrain boundaries. The maximum growth rate of ɛ-Cu particles occurs during 400 to 500 °C interval. Compared with growth behavior of domain size, microstrain relaxation behavior is less sensitive to precipitation particle size. The effects of annealing temperature and time on dislocation density are both significant when annealing temperature is lower than 500 °C. However, the effect of annealing temperature on dislocation density becomes insignificant when annealing temperature is higher than 500 °C. 300 °C annealing temperature only leads to the microstrain relaxation but nearly cannot lead to the domain size growth even if prolonging annealing time. Microstructure enhancement effect still exists in plastic deformation layer when 300 °C annealing temperature lasts for 60 min but nearly disappears when 600 °C annealing temperature lasts for 20 min.

X-ray Diffraction Investigation of Annealing Behavior of Peened Surface Deformation Layer on Precipitation Hardening Stainless Steel

NASA Astrophysics Data System (ADS)

Huang, Junjie; Wang, Zhou; Gan, Jin; Yang, Ying; Huang, Feng; Wu, Gang; Meng, Qingshuai

2018-04-01

In order to investigate the recrystallization behavior of peened surface deformation layer of precipitation hardening stainless steel, a classic x-ray diffraction line profile analysis, Voigt method, was carried out on peened 17-4PH with different isothermal annealing temperatures. The activation energy of domain boundary migration (Q a) and the activation energy of microstrain relaxation (Q b) were calculated by regression analysis in different annealing temperature conditions. The results show that the value of Q a decreases with annealing temperature increasing, which is due to the influence of precipitation (ɛ-Cu) size on the movements of grain and subgrain boundaries. The maximum growth rate of ɛ-Cu particles occurs during 400 to 500 °C interval. Compared with growth behavior of domain size, microstrain relaxation behavior is less sensitive to precipitation particle size. The effects of annealing temperature and time on dislocation density are both significant when annealing temperature is lower than 500 °C. However, the effect of annealing temperature on dislocation density becomes insignificant when annealing temperature is higher than 500 °C. 300 °C annealing temperature only leads to the microstrain relaxation but nearly cannot lead to the domain size growth even if prolonging annealing time. Microstructure enhancement effect still exists in plastic deformation layer when 300 °C annealing temperature lasts for 60 min but nearly disappears when 600 °C annealing temperature lasts for 20 min.

Synchrotron x-ray modification of nanoparticle superlattice formation

NASA Astrophysics Data System (ADS)

Lu, Chenguang; Akey, Austin J.; Herman, Irving P.

2012-09-01

The synchrotron x-ray radiation used to perform small angle x-ray scattering (SAXS) during the formation of three-dimensional nanoparticle superlattices by drop casting nanoparticle solutions affects the structure and the local crystalline order of the resulting films. The domain size decreases due to the real-time SAXS analysis during drying and more macroscopic changes are visible to the eye.

Switchable electric polarization and ferroelectric domains in a metal-organic-framework

DOE PAGES

Jain, Prashant; Stroppa, Alessandro; Nabok, Dmitrii; ...

2016-09-30

Multiferroics and magnetoelectrics with coexisting and coupled multiple ferroic orders are materials promising new technological advances. While most studies have focused on single-phase or heterostructures of inorganic materials, a new class of materials called metal–organic frameworks (MOFs) has been recently proposed as candidate materials demonstrating interesting new routes for multiferroism and magnetoelectric coupling. Herein, we report on the origin of multiferroicity of (CH 3) 2NH 2Mn(HCOO) 3 via direct observation of ferroelectric domains using second-harmonic generation techniques. For the first time, we observe how these domains are organized (sized in micrometer range), and how they are mutually affected by appliedmore » electric and magnetic fields. Lastly, calculations provide an estimate of the electric polarization and give insights into its microscopic origin.« less

Microphase separation in random multiblock copolymers

NASA Astrophysics Data System (ADS)

Govorun, E. N.; Chertovich, A. V.

2017-01-01

Microphase separation in random multiblock copolymers is studied with the mean-field theory assuming that long blocks of a copolymer are strongly segregated, whereas short blocks are able to penetrate into "alien" domains and exchange between the domains and interfacial layer. A bidisperse copolymer with blocks of only two sizes (long and short) is considered as a model of multiblock copolymers with high polydispersity in the block size. Short blocks of the copolymer play an important role in the microphase separation. First, their penetration into the "alien" domains leads to the formation of joint long blocks in their own domains. Second, short blocks localized at the interface considerably change the interfacial tension. The possibility of penetration of short blocks into the "alien" domains is controlled by the product χ Nsh (χ is the Flory-Huggins interaction parameter and Nsh is the short block length). At not very large χ Nsh , the domain size is larger than that for a regular copolymer consisting of the same long blocks as in the considered random copolymer. At a fixed mean block size, the domain size grows with an increase in the block size dispersity, the rate of the growth being dependent of the more detailed parameters of the block size distribution.

Morphological Diversity and Polymorphism of Self-Assembling Collagen Peptides Controlled by Length of Hydrophobic Domains

PubMed Central

2015-01-01

Synthetic collagen mimetic peptides are used to probe the role of hydrophobic forces in mediating protein self-assembly. Higher order association is an integral property of natural collagens, which assemble into fibers and meshes that comprise the extracellular matrix of connective tissues. The unique triple-helix fold fully exposes two-thirds of positions in the protein to solvent, providing ample opportunities for engineering interaction sites. Inclusion of just a few hydrophobic groups in a minimal peptide promotes a rich variety of self-assembly behaviors, resulting in hundred-nanometer to micron size nanodiscs and nanofibers. Morphology depends primarily on the length of hydrophobic domains. Peptide discs contain lipophilic domains capable of sequestering small hydrophobic dyes. Combining multiple peptide types result in composite structures of discs and fibers ranging from stars to plates-on-a-string. These systems provide valuable tools to shed insight into the fundamental principles underlying hydrophobicity-driven higher order protein association that will facilitate the design of self-assembling systems in biomaterials and nanomedical applications. PMID:25390880

The elimination of zero-order diffraction of 10.6 μm infrared digital holography

NASA Astrophysics Data System (ADS)

Liu, Ning; Yang, Chao

2017-05-01

A new method of eliminating the zero-order diffraction in infrared digital holography has been raised in this paper. Usually in the reconstruction of digital holography, the spatial frequency of the infrared thermal imager, such as microbolometer, cannot be compared to the common visible CCD or CMOS devices. The infrared imager suffers the problems of large pixel size and low spatial resolution, which cause the zero-order diffraction a severe influence of the reconstruction process of digital holograms. The zero-order diffraction has very large energy and occupies the central region in the spectrum domain. In this paper, we design a new filtering strategy to overcome this problem. This filtering strategy contains two kinds of filtering process which are the Gaussian low-frequency filter and the high-pass phase averaging filter. With the correct set of the calculating parameters, these filtering strategies can work effectively on the holograms and fully eliminate the zero-order diffraction, as well as the two crossover bars shown in the spectrum domain. Detailed explanation and discussion about the new method have been proposed in this paper, and the experiment results are also demonstrated to prove the performance of this method.

A solid-state NMR method to determine domain sizes in multi-component polymer formulations

NASA Astrophysics Data System (ADS)

Schlagnitweit, Judith; Tang, Mingxue; Baias, Maria; Richardson, Sara; Schantz, Staffan; Emsley, Lyndon

2015-12-01

Polymer domain sizes are related to many of the physical properties of polymers. Here we present a solid-state NMR experiment that is capable of measuring domain sizes in multi-component mixtures. The method combines selective excitation of carbon magnetization to isolate a specific component with proton spin diffusion to report on domain size. We demonstrate the method in the context of controlled release formulations, which represents one of today's challenges in pharmaceutical science. We show that we can measure domain sizes of interest in the different components of industrial pharmaceutical formulations at natural isotopic abundance containing various (modified) cellulose derivatives, such as microcrystalline cellulose matrixes that are film-coated with a mixture of ethyl cellulose (EC) and hydroxypropyl cellulose (HPC).

Structure of n-alkyltrichlorosilane mono layers on Si(100)/SiO 2

DOE PAGES

H. -G. Steinruck; Ocko, B.; Will, J.; ...

2015-10-05

The structure of n-alkyltrichlorosilane self-assembled monolayers (SAMs) of alkyl chain lengths n = 12, 14, 18, and 22 formed on the amorphous native oxide of silicon (100) has been investigated via angstrom-resolution surface X-ray scattering techniques, with particular focus on the proliferation of lateral order along the molecules’ long axis. Grazing incidence diffraction shows that the monolayer is composed of hexagonally packed crystalline-like domains for n = 14, 18, and 22 with a lateral size of about 60 Å. However, Bragg rod analysis shows that ~12 of the CH 2 units are not included in the crystalline-like domains. We assignmore » this, and the limited lateral crystallites’ size, to strain induced by the size mismatch between the optimal chain–chain and headgroup–headgroup spacings. Lastly, analysis of X-ray reflectivity profiles for n = 12, 14, and 22 shows that the density profile used to successfully model n = 18 provides an excellent fit where the analysis-derived parameters provide complementary structural information to the grazing incidence results.« less

Calculation of the extinction cross section and lifetime of a gold nanoparticle using FDTD simulations

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

Radhakrishnan, Archana, E-mail: anju.archana@gmail.com; Murugesan, Dr V., E-mail: murugesh@serc.iisc.in

The electromagnetic theory of light explains the behavior of light in most of the domains quite accurately. The problem arises when the exact solution of the Maxwell's equation is not present, in case of objects with arbitrary geometry. To find the extinction cross-section and lifetime of the gold nanoparticle, the software FDTD solutions 8.6 by Lumerical is employed. The extinction cross-sections and lifetimes of Gold nanospheres of different sizes and arrangements are studied using pulse lengths of the order of femtoseconds. The decay constant and other properties are compared. Further, the lifetimes are calculated using frequency and time domain calculations.

FDTD-ANT User Manual

NASA Technical Reports Server (NTRS)

Zimmerman, Martin L.

1995-01-01

This manual explains the theory and operation of the finite-difference time domain code FDTD-ANT developed by Analex Corporation at the NASA Lewis Research Center in Cleveland, Ohio. This code can be used for solving electromagnetic problems that are electrically small or medium (on the order of 1 to 50 cubic wavelengths). Calculated parameters include transmission line impedance, relative effective permittivity, antenna input impedance, and far-field patterns in both the time and frequency domains. The maximum problem size may be adjusted according to the computer used. This code has been run on the DEC VAX and 486 PC's and on workstations such as the Sun Sparc and the IBM RS/6000.

Dynamics and Predictability of The Eta Regional Model: The Role of Domain Size

NASA Astrophysics Data System (ADS)

Vannitsem, S.; Chomé, F.; Nicolis, C.

This paper investigates the dynamical properties of the Eta model, a state-of-the- art nested limited-area model, following the approach previously developed by the present authors. It is first shown that the intrinsic dynamics of the model depends crucially on the size of the domain, with a non-chaotic behavior for small domains, supporting earlier findings on the absence of sensitivity to the initial conditions in these models. The quality of the predictions of several Eta model versions differing by their domain size is next evaluated and compared with the Avn analyses on a targeted region, centered on France. Contrary to what is usually taken for granted, a non-trivial relation between predictability and domain size is found, the best model versions be- ing the ones integrated on the smallest and the largest domain sizes. An explanation in connection with the intrinsic dynamics of the model is advanced.

Triton promotes domain formation in lipid raft mixtures.

PubMed

Heerklotz, H

2002-11-01

Biological membranes are supposed to contain functional domains (lipid rafts) made up in particular of sphingomyelin and cholesterol, glycolipids, and certain proteins. It is often assumed that the application of the detergent Triton at 4 degrees C allows the isolation of these rafts as a detergent-resistant membrane fraction. The current study aims to clarify whether and how Triton changes the domain properties. To this end, temperature-dependent transitions in vesicles of an equimolar mixture of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, egg sphingomyelin, and cholesterol were monitored at different Triton concentrations by differential scanning calorimetry and pressure perturbation calorimetry. Transitions initiated by the addition of Triton to the lipid mixture were studied by isothermal titration calorimetry, and the structure was investigated by (31)P-NMR. The results are discussed in terms of liquid-disordered (ld) and -ordered (lo) bilayer and micellar (mic) phases, and the typical sequence encountered with increasing Triton content or decreasing temperature is ld, ld + lo, ld + lo + mic, and lo + mic. That means that addition of Triton may create ordered domains in a homogeneous fluid membrane, which are, in turn, Triton resistant upon subsequent membrane solubilization. Hence, detergent-resistant membranes should not be assumed to resemble biological rafts in size, structure, composition, or even existence. Functional rafts may not be steady phenomena; they might form, grow, cluster or break up, shrink, and vanish according to functional requirements, regulated by rather subtle changes in the activity of membrane disordering or ordering compounds.

Triton promotes domain formation in lipid raft mixtures.

PubMed Central

Heerklotz, H

2002-01-01

Biological membranes are supposed to contain functional domains (lipid rafts) made up in particular of sphingomyelin and cholesterol, glycolipids, and certain proteins. It is often assumed that the application of the detergent Triton at 4 degrees C allows the isolation of these rafts as a detergent-resistant membrane fraction. The current study aims to clarify whether and how Triton changes the domain properties. To this end, temperature-dependent transitions in vesicles of an equimolar mixture of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, egg sphingomyelin, and cholesterol were monitored at different Triton concentrations by differential scanning calorimetry and pressure perturbation calorimetry. Transitions initiated by the addition of Triton to the lipid mixture were studied by isothermal titration calorimetry, and the structure was investigated by (31)P-NMR. The results are discussed in terms of liquid-disordered (ld) and -ordered (lo) bilayer and micellar (mic) phases, and the typical sequence encountered with increasing Triton content or decreasing temperature is ld, ld + lo, ld + lo + mic, and lo + mic. That means that addition of Triton may create ordered domains in a homogeneous fluid membrane, which are, in turn, Triton resistant upon subsequent membrane solubilization. Hence, detergent-resistant membranes should not be assumed to resemble biological rafts in size, structure, composition, or even existence. Functional rafts may not be steady phenomena; they might form, grow, cluster or break up, shrink, and vanish according to functional requirements, regulated by rather subtle changes in the activity of membrane disordering or ordering compounds. PMID:12414701

Shock-wave propagation and reflection in semicrystalline polyethylene: A molecular-level investigation

NASA Astrophysics Data System (ADS)

Elder, Robert M.; O'Connor, Thomas C.; Chantawansri, Tanya L.; Sliozberg, Yelena R.; Sirk, Timothy W.; Yeh, In-Chul; Robbins, Mark O.; Andzelm, Jan W.

2017-09-01

Semicrystalline polyethylene (PE) is attractive for a variety of mechanically demanding applications, where shock compression can occur. Although often highly crystalline, PE invariably contains nanoscale amorphous domains that influence shock propagation. Our objective in this work is to study the effects of such domains. To this end, we adopt a novel approach wherein we parametrize a simple continuum-level theory based on the shock impedance from molecular dynamics (MD) simulations. Using this theory, we predict how crystalline/amorphous interfaces attenuate shocks via energy reflection due to the impedance mismatch between the phases. The theory predicts that these interfaces attenuate weak shocks more effectively than strong shocks. We compare the theory to explicit nonequilibrium MD simulations of compressive shocks in semicrystalline PE containing nanometer-scale amorphous regions of varying size, where we analyze the pressure response and reflection of energy. The theory and simulations show good agreement for strong shocks (≥1.0 km /s ), but for weak shocks (<1.0 km /s ) the simulations show enhanced energy reflection relative to the continuum predictions. Furthermore, the simulations show an effect not captured by the continuum theory: the size of amorphous regions is important. The theory assumes a sharp (discontinuous) interface between two bulk phases and a sharp change in thermodynamic and hydrodynamic quantities at the shock front. However, the simulations show that when amorphous domains are narrow—with widths comparable to the shock front—reflection is reduced compared to the predictions. We identify several nanoscale mechanisms that reduce the impedance mismatch, and thus reduce reflection, at thin amorphous domains. First, the two-wave elastic-plastic structure of shocks in crystalline PE allows the faster-moving elastic precursor wave to compress small amorphous domains before the plastic wave arrives. Second, confinement between stiff, ordered crystalline domains increases the stiffness and chain ordering in small amorphous regions. Moreover, in terms of stiffness the interfaces are similar in width to the shock front, which may contribute to the underprediction of the theory for weak shocks, where the shock front is widest. We conclude by discussing the significance of these results, namely, how they can be applied to tune shock attenuation for particular applications.

Determination of the extra buffering distance in the one-way nesting procedure for the regional ocean

NASA Astrophysics Data System (ADS)

Hwang, Jin Hwan; Pham, Van Sy

2017-04-01

The Big-Brother Experiment (BBE) evaluates the effect of domain size on the ocean regional circulation model (ORCMs) in the downscaling and nesting from the ocean global circulation (OGCMs). The BBE first establishes a mimic ocean global circulation models (M-OGCMs) data and employs a ORCM to simulate for a highly resolved large domain. This M-OGCM's results were then filtered to remove short scales then used for boundary and initial conditions of the nested ORCMs, which have the same resolution to the M-OGCMs. The various sizes of domain were embedded in the M-OGCMs and the cases were simulated to see the effect of domain size with the extra buffering distance to the results of the ORCMs. The diagnostic variables including temperature, salinity and vorticity of the nested domain are then compared with those of the M-OGCMs before filtering. Differences between them can address the errors associating with the sizes of the domain, which are not attributed unambiguously to models errors or observational errors. The results showed that domain size significantly impacts on the results of ORCMs. As the domain size of the ORCM becomes lager, the distance of the extra space between the area of interest and the updated LBCs increases. So, the results of ORCMs perform more highly correlated with the M-OGCM. But, there are a certain optimal sizes of the OGCMs, which could be larger than nested ORCMs' domain size from 2 to 10 times, depending on the computational costs. Key words: domain size, error, ocean regional circulation model, Big-Brother Experiment. Acknowledgement: This research was supported by grants from the Korean Ministry of Oceans and Fisheries entitled "Development of integrated estuarine management system" and a National Research Foundation of Korea (NRF) Grant (No. 2015R1A5A 7037372) funded by MSIP of Korea. The authors thank the Integrated Research Institute of Construction and Environmental Engineering of Seoul National University for administrative support.

Electro-optic Mach-Zehnder Interferometer based Optical Digital Magnitude Comparator and 1's Complement Calculator

NASA Astrophysics Data System (ADS)

Kumar, Ajay; Raghuwanshi, Sanjeev Kumar

2016-06-01

The optical switching activity is one of the most essential phenomena in the optical domain. The electro-optic effect-based switching phenomena are applicable to generate some effective combinational and sequential logic circuits. The processing of digital computational technique in the optical domain includes some considerable advantages of optical communication technology, e.g. immunity to electro-magnetic interferences, compact size, signal security, parallel computing and larger bandwidth. The paper describes some efficient technique to implement single bit magnitude comparator and 1's complement calculator using the concepts of electro-optic effect. The proposed techniques are simulated on the MATLAB software. However, the suitability of the techniques is verified using the highly reliable Opti-BPM software. It is interesting to analyze the circuits in order to specify some optimized device parameter in order to optimize some performance affecting parameters, e.g. crosstalk, extinction ratio, signal losses through the curved and straight waveguide sections.

Manipulating electronic phase separation in strongly correlated oxides with an ordered array of antidots

DOE PAGES

Zhang, Kai; Du, Kai; Liu, Hao; ...

2015-07-20

The interesting transport and magnetic properties in manganites depend sensitively on the nucleation and growth of electronic phase-separated domains. In this paper, by fabricating antidot arrays in La 0.325Pr 0.3Ca 0.375MnO 3 (LPCMO) epitaxial thin films, we create ordered arrays of micrometer-sized ferromagnetic metallic (FMM) rings in the LPCMO films that lead to dramatically increased metal–insulator transition temperatures and reduced resistances. The FMM rings emerge from the edges of the antidots where the lattice symmetry is broken. Based on our Monte Carlo simulation, these FMM rings assist the nucleation and growth of FMM phase domains increasing the metal–insulator transition withmore » decreasing temperature or increasing magnetic field. Finally, this study points to a way in which electronic phase separation in manganites can be artificially controlled without changing chemical composition or applying external field.« less

Metamorphic reactions, grain size reduction and deformation of mafic lower crustal rocks

NASA Astrophysics Data System (ADS)

Degli Alessandrini, Giulia; Menegon, Luca; Beltrando, Marco; Dijkstra, Arjan; Anderson, Mark

2016-04-01

This study investigates grain-scale deformation mechanisms associated with strain localization in the mafic continental lower crust, with particular focus on the role of syn-kinematic metamorphic reactions and their product - symplectites - in promoting grain size reduction and phase mixing. The investigated shear zone is hosted in the Finero mafic-ultramafic complex in the Italian Southern Alps. Shearing occurred at T ≥ 650° C and P ≥ 0.4-0.6 GPa. The shear zone reworks both mafic and ultramafic lithologies and displays anastomosing patterns of (ultra)mylonitic high strain zones wrapping less foliated, weakly deformed low strain domains. Field and microstructural observations indicate that different compositional layers of the shear zone responded differently to deformation, resulting in strain partitioning. Four distinct microstructural domains have been identified: (1) an ultramylonitic domain characterized by an amph + pl matrix (grain size < 30μm) with large amphibole porphyroclasts (grain size between 200μm and 5000μm) and rare garnets; (2) a domain rich in garnet porphyroclasts embedded in a matrix of monomineralic plagioclase displaying a core and mantle structure (average grain size 45μm) (3) a metagabbroic domain with porphyroclasts of clinopyroxene, orthopyroxene and garnets (200μm average grain size) wrapped by monomineralic ribbons of recrystallized plagioclase and (4) a garnet-free ultramylonitic domain composed of an intermixed amph + cpx + opx + pl matrix (6μm average grain size). In these domains, each porphyroclastic mineral responds differently to deformation: amphibole readily breaks down to symplectitic intergrowths of amph + pl or opx + pl. Garnet undergoes fracturing (in domain 2) or reacts to give symplectites of pl + opx (in domain 3). Plagioclase dynamically recrystallizes in mono-phase aggregates, whereas clinopyroxene undergoes fracturing and orthopyroxene undergoes plastic deformation. The behaviour of the different phases and their relative abundance in the layers are believed to influence the deformation of the layers themselves. In symplectite-rich layers (domains 1, 4) deformation is localised, grain-size is below 30μm and phases are well mixed. On the other hand, in pyroxene or plagioclase-rich layers, deformation is less localised, the phases are less mixed and the grain size is larger (domain 2, 3). These preliminary results suggest that syn-kinematic metamorphic reactions forming symplectites played an essential role in grain size reduction, phase mixing and strain localization. We speculate that the compositional domains with symplectites localized deformation more efficiently, by activation of grain size sensitive creep, most likely because those domains were originally more hydrated than the others. On the contrary, domains without symplectites accommodated deformation less efficiently, either through fracturing (clinopyroxene, garnet) or dislocation creep + recrystallization (orthopyroxene, plagioclase).

Evaluation of a wave-vector-frequency-domain method for nonlinear wave propagation

PubMed Central

Jing, Yun; Tao, Molei; Clement, Greg T.

2011-01-01

A wave-vector-frequency-domain method is presented to describe one-directional forward or backward acoustic wave propagation in a nonlinear homogeneous medium. Starting from a frequency-domain representation of the second-order nonlinear acoustic wave equation, an implicit solution for the nonlinear term is proposed by employing the Green’s function. Its approximation, which is more suitable for numerical implementation, is used. An error study is carried out to test the efficiency of the model by comparing the results with the Fubini solution. It is shown that the error grows as the propagation distance and step-size increase. However, for the specific case tested, even at a step size as large as one wavelength, sufficient accuracy for plane-wave propagation is observed. A two-dimensional steered transducer problem is explored to verify the nonlinear acoustic field directional independence of the model. A three-dimensional single-element transducer problem is solved to verify the forward model by comparing it with an existing nonlinear wave propagation code. Finally, backward-projection behavior is examined. The sound field over a plane in an absorptive medium is backward projected to the source and compared with the initial field, where good agreement is observed. PMID:21302985

Domain wall energy landscapes in amorphous magnetic films with asymmetric arrays of holes

NASA Astrophysics Data System (ADS)

Alija, A.; Pérez-Junquera, A.; Rodríguez-Rodríguez, G.; Vélez, M.; Marconi, V. I.; Kolton, A. B.; Anguita, J. V.; Alameda, J. M.; Parrondo, J. M. R.; Martín, J. I.

2009-02-01

Arrays of asymmetric holes have been defined in amorphous Co-Si films by e-beam lithography in order to study domain wall motion across the array subject to the asymmetric pinning potential created by the holes. Experimental results on Kerr effect magnetooptical measurements and hysteresis loops are compared with micromagnetic simulations in films with arrays of triangular holes. These show that the potential asymmetry favours forward wall propagation for flat walls but, if the wall contains a kink, net backward wall propagation is preferred at low fields, in agreement with minor loop experiments. The difference between the fields needed for forward and backward flat wall propagation increases as the size of the triangular holes is reduced, becoming maximum for 1 µm triangles, which is the characteristic length scale set by domain wall width.

Readiness for the Patient-Centered Medical Home: structural capabilities of Massachusetts primary care practices.

PubMed

Friedberg, Mark W; Safran, Dana G; Coltin, Kathryn L; Dresser, Marguerite; Schneider, Eric C

2009-02-01

The Patient-Centered Medical Home (PCMH), a popular model for primary care reorganization, includes several structural capabilities intended to enhance quality of care. The extent to which different types of primary care practices have adopted these capabilities has not been previously studied. To measure the prevalence of recommended structural capabilities among primary care practices and to determine whether prevalence varies among practices of different size (number of physicians) and administrative affiliation with networks of practices. Cross-sectional analysis. One physician chosen at random from each of 412 primary care practices in Massachusetts was surveyed about practice capabilities during 2007. Practice size and network affiliation were obtained from an existing database. Presence of 13 structural capabilities representing 4 domains relevant to quality: patient assistance and reminders, culture of quality, enhanced access, and electronic health records (EHRs). Three hundred eight (75%) physicians responded, representing practices with a median size of 4 physicians (range 2-74). Among these practices, 64% were affiliated with 1 of 9 networks. The prevalence of surveyed capabilities ranged from 24% to 88%. Larger practice size was associated with higher prevalence for 9 of the 13 capabilities spanning all 4 domains (P < 0.05). Network affiliation was associated with higher prevalence of 5 capabilities (P < 0.05) in 3 domains. Associations were not substantively altered by statistical adjustment for other practice characteristics. Larger and network-affiliated primary care practices are more likely than smaller, non-affiliated practices to have adopted several recommended capabilities. In order to achieve PCMH designation, smaller non-affiliated practices may require the greatest investments.

Self-Consistent Field Theory for the Design of Thermoplastic Elastomers from Miktoarm Block Copolymer - Homopolymer Blends

NASA Astrophysics Data System (ADS)

Hamilton, Andrew Lawrence

We have used self-consistent field theory to study the morphological characteristics of blends of miktoarm block copolymers and homopolymers. More specifically, we have studied the effects of segregation strength, miktoarm block copolymer composition, and homopolymer size and volume fraction on the phase diagrams of these systems. A15 domains with discrete A-monomer spherical domains were found to be stable with A-monomer loading fractions of at least as high as 52%. Hexagonally-packed cylindrical domains were found to be stable at A-monomer loadings of at least as high as 72%. These findings represent a significant improvement from the loading fractions of 43% and 60% reported by Lynd et al. for spherical and cylindrical domains in neat miktoarm block copolymers, respectively. It is also quite possible that even greater loading fractions are achievable in systems too large for our simulations. These results predict exciting new materials for next-generation thermoplastic elastomers, since the ideal TPE has a large loading of A monomers in discrete, crystalline or glassy domains, surrounded by a continuous matrix of elastomeric B domains. Additionally, we have performed SCFT simulations modelled after experimental blends of polystyrene and polyisoprene-based miktoarm block copolymers and homopolymers. Certain experimental samples showed fascinating new "bricks and mortar" phases and swollen asymmetric lamellar phases. In both cases, the A domains are highly swollen with homopolymer, forcing the miktoarm block copolymer to segregate near the interface and adopt the role of a surfactant. The resulting structures maintain separate A and B domains, but lack long-range order. While it is not possible to study these mesophases using SCFT, since they lack long-range order and therefore well-defined symmetry, our SCFT results show the onset of macrophase separation at similar homopolymer loadings, for both the bricks and mortar phases and the highly swollen lamellae. This supports the theory that both phases are fluctuation-induced mesophases, similar to microemulsions in character, that lie in between the typical ordered structures and full macrophase separation.

The physical size of transcription factors is key to transcriptional regulation in chromatin domains

NASA Astrophysics Data System (ADS)

Maeshima, Kazuhiro; Kaizu, Kazunari; Tamura, Sachiko; Nozaki, Tadasu; Kokubo, Tetsuro; Takahashi, Koichi

2015-02-01

Genetic information, which is stored in the long strand of genomic DNA as chromatin, must be scanned and read out by various transcription factors. First, gene-specific transcription factors, which are relatively small (˜50 kDa), scan the genome and bind regulatory elements. Such factors then recruit general transcription factors, Mediators, RNA polymerases, nucleosome remodellers, and histone modifiers, most of which are large protein complexes of 1-3 MDa in size. Here, we propose a new model for the functional significance of the size of transcription factors (or complexes) for gene regulation of chromatin domains. Recent findings suggest that chromatin consists of irregularly folded nucleosome fibres (10 nm fibres) and forms numerous condensed domains (e.g., topologically associating domains). Although the flexibility and dynamics of chromatin allow repositioning of genes within the condensed domains, the size exclusion effect of the domain may limit accessibility of DNA sequences by transcription factors. We used Monte Carlo computer simulations to determine the physical size limit of transcription factors that can enter condensed chromatin domains. Small gene-specific transcription factors can penetrate into the chromatin domains and search their target sequences, whereas large transcription complexes cannot enter the domain. Due to this property, once a large complex binds its target site via gene-specific factors it can act as a ‘buoy’ to keep the target region on the surface of the condensed domain and maintain transcriptional competency. This size-dependent specialization of target-scanning and surface-tethering functions could provide novel insight into the mechanisms of various DNA transactions, such as DNA replication and repair/recombination.

Heating efficiency dependency on size and morphology of magnetite nanoparticles

NASA Astrophysics Data System (ADS)

Parekh, Kinnari; Parmar, Harshida; Sharma, Vinay; Ramanujan, R. V.

2018-04-01

Different size magnetite nanoparticles ranging from superparamagnetic (9 nm) to single domain (27 nm) and multi domain (53 nm) were synthesized using chemical route. Morphology of these particles as seen from TEM images indicates shape change from spherical to cubic with the growth of particles. The saturation magnetization (σs) and Specific Loss Power (SLP) showed maximum for single domain size, 72 emu/g and 102 W/g, respectively then those of multi domain size particles. These samples show higher SLP at relatively low concentration, low frequency and low amplitude compared to samples prepared by other routes.

Effect of dipolar moments in domain sizes of lipid bilayers and monolayers

NASA Astrophysics Data System (ADS)

Travesset, A.

2006-08-01

Lipid domains are found in systems such as multicomponent bilayer membranes and single component monolayers at the air-water interface. It was shown by Keller et al. [J. Phys. Chem. 91, 6417 (1987)] that in monolayers, the size of the domains results from balancing the line tension, which favors the formation of a large single circular domain, against the electrostatic cost of assembling the dipolar moments of the lipids. In this paper, we present an exact analytical expression for the electric potential, ion distribution, and electrostatic free energy for different problems consisting of three different slabs with different dielectric constants and Debye lengths, with a circular homogeneous dipolar density in the middle slab. From these solutions, we extend the calculation of domain sizes for monolayers to include the effects of finite ionic strength, dielectric discontinuities (or image charges), and the polarizability of the dipoles and further generalize the calculations to account for domains in lipid bilayers. In monolayers, the size of the domains is dependent on the different dielectric constants but independent of ionic strength. In asymmetric bilayers, where the inner and outer leaflets have different dipolar densities, domains show a strong size dependence with ionic strength, with molecular-sized domains that grow to macroscopic phase separation with increasing ionic strength. We discuss the implications of the results for experiments and briefly consider their relation to other two dimensional systems such as Wigner crystals or heteroepitaxial growth.

Quantum image median filtering in the spatial domain

NASA Astrophysics Data System (ADS)

Li, Panchi; Liu, Xiande; Xiao, Hong

2018-03-01

Spatial filtering is one principal tool used in image processing for a broad spectrum of applications. Median filtering has become a prominent representation of spatial filtering because its performance in noise reduction is excellent. Although filtering of quantum images in the frequency domain has been described in the literature, and there is a one-to-one correspondence between linear spatial filters and filters in the frequency domain, median filtering is a nonlinear process that cannot be achieved in the frequency domain. We therefore investigated the spatial filtering of quantum image, focusing on the design method of the quantum median filter and applications in image de-noising. To this end, first, we presented the quantum circuits for three basic modules (i.e., Cycle Shift, Comparator, and Swap), and then, we design two composite modules (i.e., Sort and Median Calculation). We next constructed a complete quantum circuit that implements the median filtering task and present the results of several simulation experiments on some grayscale images with different noise patterns. Although experimental results show that the proposed scheme has almost the same noise suppression capacity as its classical counterpart, the complexity analysis shows that the proposed scheme can reduce the computational complexity of the classical median filter from the exponential function of image size n to the second-order polynomial function of image size n, so that the classical method can be speeded up.

A stochastic two-scale model for pressure-driven flow between rough surfaces

PubMed Central

Larsson, Roland; Lundström, Staffan; Wall, Peter; Almqvist, Andreas

2016-01-01

Seal surface topography typically consists of global-scale geometric features as well as local-scale roughness details and homogenization-based approaches are, therefore, readily applied. These provide for resolving the global scale (large domain) with a relatively coarse mesh, while resolving the local scale (small domain) in high detail. As the total flow decreases, however, the flow pattern becomes tortuous and this requires a larger local-scale domain to obtain a converged solution. Therefore, a classical homogenization-based approach might not be feasible for simulation of very small flows. In order to study small flows, a model allowing feasibly-sized local domains, for really small flow rates, is developed. Realization was made possible by coupling the two scales with a stochastic element. Results from numerical experiments, show that the present model is in better agreement with the direct deterministic one than the conventional homogenization type of model, both quantitatively in terms of flow rate and qualitatively in reflecting the flow pattern. PMID:27436975

Solid-liquid critical behavior of water in nanopores.

PubMed

Mochizuki, Kenji; Koga, Kenichiro

2015-07-07

Nanoconfined liquid water can transform into low-dimensional ices whose crystalline structures are dissimilar to any bulk ices and whose melting point may significantly rise with reducing the pore size, as revealed by computer simulation and confirmed by experiment. One of the intriguing, and as yet unresolved, questions concerns the observation that the liquid water may transform into a low-dimensional ice either via a first-order phase change or without any discontinuity in thermodynamic and dynamic properties, which suggests the existence of solid-liquid critical points in this class of nanoconfined systems. Here we explore the phase behavior of a model of water in carbon nanotubes in the temperature-pressure-diameter space by molecular dynamics simulation and provide unambiguous evidence to support solid-liquid critical phenomena of nanoconfined water. Solid-liquid first-order phase boundaries are determined by tracing spontaneous phase separation at various temperatures. All of the boundaries eventually cease to exist at the critical points and there appear loci of response function maxima, or the Widom lines, extending to the supercritical region. The finite-size scaling analysis of the density distribution supports the presence of both first-order and continuous phase changes between solid and liquid. At around the Widom line, there are microscopic domains of two phases, and continuous solid-liquid phase changes occur in such a way that the domains of one phase grow and those of the other evanesce as the thermodynamic state departs from the Widom line.

Cascading failures in interdependent networks with finite functional components

NASA Astrophysics Data System (ADS)

Di Muro, M. A.; Buldyrev, S. V.; Stanley, H. E.; Braunstein, L. A.

2016-10-01

We present a cascading failure model of two interdependent networks in which functional nodes belong to components of size greater than or equal to s . We find theoretically and via simulation that in complex networks with random dependency links the transition is first order for s ≥3 and continuous for s =2 . We also study interdependent lattices with a distance constraint r in the dependency links and find that increasing r moves the system from a regime without a phase transition to one with a second-order transition. As r continues to increase, the system collapses in a first-order transition. Each regime is associated with a different structure of domain formation of functional nodes.

Nano-polarization-converter based on magnetic plasmon resonance excitation in an L-shaped slot antenna.

PubMed

Yang, Jing; Zhang, Jiasen

2013-04-08

We propose a nano-polarization-converter made of a resonant L-shaped slot antenna in a gold film and study its optical properties using the finite-difference time-domain method. Phase retardation between the fast and slow axes of the nano-polarization-converter originates from the simultaneous excitation of both single-surface first-order magnetic plasmon resonance mode and second-order magnetic plasmon resonance mode at the working wavelength. By adjusting the size of the slot antenna, which is still much smaller than the wavelength, the working wavelength can be tuned within a large wavelength range.

Efficient Computation of Closed-loop Frequency Response for Large Order Flexible Systems

NASA Technical Reports Server (NTRS)

Maghami, Peiman G.; Giesy, Daniel P.

1997-01-01

An efficient and robust computational scheme is given for the calculation of the frequency response function of a large order, flexible system implemented with a linear, time invariant control system. Advantage is taken of the highly structured sparsity of the system matrix of the plant based on a model of the structure using normal mode coordinates. The computational time per frequency point of the new computational scheme is a linear function of system size, a significant improvement over traditional, full-matrix techniques whose computational times per frequency point range from quadratic to cubic functions of system size. This permits the practical frequency domain analysis of systems of much larger order than by traditional, full-matrix techniques. Formulations are given for both open and closed loop loop systems. Numerical examples are presented showing the advantages of the present formulation over traditional approaches, both in speed and in accuracy. Using a model with 703 structural modes, a speed-up of almost two orders of magnitude was observed while accuracy improved by up to 5 decimal places.

Lipid domains in zwitterionic-anionic lipid mixtures induced by combined effect of monovalent and divalent ions

NASA Astrophysics Data System (ADS)

Xu, Hongcheng; Ganesan, Sai; Matysiak, Silvina

Lipid domain formation is an important process for many cellular processes. In experiment, the effects of Ba2+, Sr2+, Ca2+ and Mg2+ in inducing lateral phase separation in the binary phosphatidylcholine-phosphatidylserine (PC-PS) bilayer are quite different, of which the molecular mechanism remains to be understood. We have explored the effect of monovalent (MI) and divalent (MII) cationic radii on lipid domain formation in mixed zwitterionic-anionic lipid bilayers. We propose a mechanism for the formation of divalent-cation-induced lipid domains based on MD simulations with our Water-Explicit Polarizable MEMbrane (WEPMEM) coarse-grained model, which uses PC as the model for zwitterionic and PS for anionic lipids. Lipid aggregation only occurs with limited range of monovalent and divalent ion sizes in agreement with experimental observations. More ordering and closer packing of the lipids are noted within the domains, which correlate with bilayer thickness, curvature and lipid asymmetry. The results of the simulations reveal that the lipid domain consists of MII-mediated anionic lipid dimer/trimer complexes bridged by monovalent ions MI and provide a stereochemical insight in understanding the experimentally observed calcium-induced phase separation.

Thermomagnetic Stability in Pseudo Single Domain Grains

NASA Astrophysics Data System (ADS)

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

2016-04-01

The reliability of paleomagnetic remanences are well understood for fine grains of magnetite that are single-domain (SD, uniformly magnetized). In particular Néel's theory [1] outlined the thermal energies required to block and unblock magnetic remanences. This lead to determination of thermal stability for magnetization in fine grains as outlined in Pullaiah et. al. [2] and a comprehensive understanding of SD paleomagnetic recordings. It has been known for some time that single domain magnetite is possible only in the grain size range 30 - 80nm, which may only account for a small fraction of the grain size distribution in any rock sample. Indeed rocks are often dominated by grains in the pseudo single domain (PSD) size range, at approximately 80 - 1000nm. Toward the top end of this range multi-domain features begin to dominate. In order to determine thermomagnetic stability in PSD grains we need to identify the energy barriers between all possible pairs of local energy minima (LEM) domain states as a function of both temperature and grain size. We have attempted to do this using the nudged elastic band (NEB) method [3] which searches for minimum energy paths between any given pair of LEM states. Using this technique we have determined, for the first time, complete thermomagnetic stability curves for PSD magnetite. The work presented is at a preliminary stage. However it can be shown that PSD grains of magnetite with simple geometries (e.g. cubes or cuboctahedra) have very few low energy transition paths and the stability is likely to be similar to that observed for SD grains (as expected form experimental observations). The results will provide a basis for a much more rigorous understanding of the fidelity of paleomagnetic signals in assemblages of PSD grains and their ability to retain ancient recordings of the geomagnetic field. References: [1] Néel, Louis. "Théorie du traînage magnétique des ferromagnétiques en grains fins avec applications aux terres cuites." Ann. géophys 5.2 (1949): 99-136. [2] Pullaiah, G., et al. "Magnetization changes caused by burial and uplift." Earth and Planetary Science Letters 28.2 (1975): 133-143. [3] D. Sheppard, R. Terrell, and G. Henkelman, "Optimization methods for finding minimum energy paths", J. Chem. Phys. 128, 134106 (2008).

Size-dependent geometrically nonlinear free vibration analysis of fractional viscoelastic nanobeams based on the nonlocal elasticity theory

NASA Astrophysics Data System (ADS)

Ansari, R.; Faraji Oskouie, M.; Gholami, R.

2016-01-01

In recent decades, mathematical modeling and engineering applications of fractional-order calculus have been extensively utilized to provide efficient simulation tools in the field of solid mechanics. In this paper, a nonlinear fractional nonlocal Euler-Bernoulli beam model is established using the concept of fractional derivative and nonlocal elasticity theory to investigate the size-dependent geometrically nonlinear free vibration of fractional viscoelastic nanobeams. The non-classical fractional integro-differential Euler-Bernoulli beam model contains the nonlocal parameter, viscoelasticity coefficient and order of the fractional derivative to interpret the size effect, viscoelastic material and fractional behavior in the nanoscale fractional viscoelastic structures, respectively. In the solution procedure, the Galerkin method is employed to reduce the fractional integro-partial differential governing equation to a fractional ordinary differential equation in the time domain. Afterwards, the predictor-corrector method is used to solve the nonlinear fractional time-dependent equation. Finally, the influences of nonlocal parameter, order of fractional derivative and viscoelasticity coefficient on the nonlinear time response of fractional viscoelastic nanobeams are discussed in detail. Moreover, comparisons are made between the time responses of linear and nonlinear models.

Regulation of adhesion behavior of murine macrophage using supported lipid membranes displaying tunable mannose domains

NASA Astrophysics Data System (ADS)

Kaindl, T.; Oelke, J.; Pasc, A.; Kaufmann, S.; Konovalov, O. V.; Funari, S. S.; Engel, U.; Wixforth, A.; Tanaka, M.

2010-07-01

Highly uniform, strongly correlated domains of synthetically designed lipids can be incorporated into supported lipid membranes. The systematic characterization of membranes displaying a variety of domains revealed that the equilibrium size of domains significantly depends on the length of fluorocarbon chains, which can be quantitatively interpreted within the framework of an equivalent dipole model. A mono-dispersive, narrow size distribution of the domains enables us to treat the inter-domain correlations as two-dimensional colloidal crystallization and calculate the potentials of mean force. The obtained results demonstrated that both size and inter-domain correlation can precisely be controlled by the molecular structures. By coupling α-D-mannose to lipid head groups, we studied the adhesion behavior of the murine macrophage (J774A.1) on supported membranes. Specific adhesion and spreading of macrophages showed a clear dependence on the density of functional lipids. The obtained results suggest that such synthetic lipid domains can be used as a defined platform to study how cells sense the size and distribution of functional molecules during adhesion and spreading.

An impulsive receptance technique for the time domain computation of the vibration of a whole aero-engine model with nonlinear bearings

NASA Astrophysics Data System (ADS)

Hai, Pham Minh; Bonello, Philip

2008-12-01

The direct study of the vibration of real engine structures with nonlinear bearings, particularly aero-engines, has been severely limited by the fact that current nonlinear computational techniques are not well-suited for complex large-order systems. This paper introduces a novel implicit "impulsive receptance method" (IRM) for the time domain analysis of such structures. The IRM's computational efficiency is largely immune to the number of modes used and dependent only on the number of nonlinear elements. This means that, apart from retaining numerical accuracy, a much more physically accurate solution is achievable within a short timeframe. Simulation tests on a realistically sized representative twin-spool aero-engine showed that the new method was around 40 times faster than a conventional implicit integration scheme. Preliminary results for a given rotor unbalance distribution revealed the varying degree of journal lift, orbit size and shape at the example engine's squeeze-film damper bearings, and the effect of end-sealing at these bearings.

Random-field-induced disordering mechanism in a disordered ferromagnet: Between the Imry-Ma and the standard disordering mechanism

NASA Astrophysics Data System (ADS)

Andresen, Juan Carlos; Katzgraber, Helmut G.; Schechter, Moshe

2017-12-01

Random fields disorder Ising ferromagnets by aligning single spins in the direction of the random field in three space dimensions, or by flipping large ferromagnetic domains at dimensions two and below. While the former requires random fields of typical magnitude similar to the interaction strength, the latter Imry-Ma mechanism only requires infinitesimal random fields. Recently, it has been shown that for dilute anisotropic dipolar systems a third mechanism exists, where the ferromagnetic phase is disordered by finite-size glassy domains at a random field of finite magnitude that is considerably smaller than the typical interaction strength. Using large-scale Monte Carlo simulations and zero-temperature numerical approaches, we show that this mechanism applies to disordered ferromagnets with competing short-range ferromagnetic and antiferromagnetic interactions, suggesting its generality in ferromagnetic systems with competing interactions and an underlying spin-glass phase. A finite-size-scaling analysis of the magnetization distribution suggests that the transition might be first order.

Force measurement-based discontinuity detection during friction stir welding

DOE PAGES

Shrivastava, Amber; Zinn, Michael; Duffie, Neil A.; ...

2017-02-23

Here, the objective of this work is to develop a method for detecting the creation of discontinuities ( i.e., voids, volume defects) during friction stir welding. Friction stir welding is inherently cost effective, however, the need for significant weld inspection can make the process cost prohibitive. A new approach to weld inspection is required in which an in situ characterization of weld quality can be obtained, reducing the need for postprocess inspection. To this end, friction stir welds with subsurface voids and without voids were created. The subsurface voids were generated by reducing the friction stir tool rotation frequency andmore » increasing the tool traverse speed in order to create “colder” welds. Process forces were measured during welding, and the void sizes were measured postprocess by computerized tomography ( i.e., 3D X-ray imaging). Two parameters, based on frequency domain content and time-domain average of the force signals, were found to be correlated with void size. Criteria for subsurface void detection and size prediction were developed and shown to be in good agreement with experimental observations. Furthermore, with the proper choice of data acquisition system and frequency analyzer the occurrence of subsurface voids can be detected in real time.« less

Force measurement-based discontinuity detection during friction stir welding

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

Shrivastava, Amber; Zinn, Michael; Duffie, Neil A.

Here, the objective of this work is to develop a method for detecting the creation of discontinuities ( i.e., voids, volume defects) during friction stir welding. Friction stir welding is inherently cost effective, however, the need for significant weld inspection can make the process cost prohibitive. A new approach to weld inspection is required in which an in situ characterization of weld quality can be obtained, reducing the need for postprocess inspection. To this end, friction stir welds with subsurface voids and without voids were created. The subsurface voids were generated by reducing the friction stir tool rotation frequency andmore » increasing the tool traverse speed in order to create “colder” welds. Process forces were measured during welding, and the void sizes were measured postprocess by computerized tomography ( i.e., 3D X-ray imaging). Two parameters, based on frequency domain content and time-domain average of the force signals, were found to be correlated with void size. Criteria for subsurface void detection and size prediction were developed and shown to be in good agreement with experimental observations. Furthermore, with the proper choice of data acquisition system and frequency analyzer the occurrence of subsurface voids can be detected in real time.« less

Geometry and mechanics of growing bacterial colonies

NASA Astrophysics Data System (ADS)

You, Zhihong; Pearce, Daniel; Sengupta, Anupam; Giomi, Luca

Bacterial colonies are abundant on living and non-living surfaces, and are known to mediate a broad range of processes in ecology, medicine and industry. Although extensively researched - from single cells up to the population levels - a comprehensive biophysical picture, highlighting the cell-to-colony dynamics, is still lacking. Here, using numerical and analytical models, we study the mechanics of self-organization leading to the colony morphology of cells growing on a substrate with free boundary. We consider hard rods to mimic the growth of rod-shaped non-motile cells, and show that the colony, as a whole, does not form an ordered nematic phase, nor does it result in a purely disordered (isotropic) phase. Instead, different sizes of domains, in which cells are highly aligned at specific orientations, are found. The distribution of the domain sizes follows an exponential relation - indicating the existence of a characteristic length scale that determines the domain size relative to that of the colony. A continuum theory, based on the hydrodynamics of liquid crystals, is built to account for these phenomena, and is applied to describe the buckling transition from a planar to three-dimensional (3D) colony. The theory supports preliminary experiments conducted with different strains of rod shaped bacterial cells, and reveals that the buckling transition can be regulated by varying the cell stiffness and aspect ratio. This work proposes that, in addition to biochemical pathways, the spatio-temporal organization in microbial colonies is significantly tuned by the biomechanical and geometric properties of the microbes in consideration.

a Unified Matrix Polynomial Approach to Modal Identification

NASA Astrophysics Data System (ADS)

Allemang, R. J.; Brown, D. L.

1998-04-01

One important current focus of modal identification is a reformulation of modal parameter estimation algorithms into a single, consistent mathematical formulation with a corresponding set of definitions and unifying concepts. Particularly, a matrix polynomial approach is used to unify the presentation with respect to current algorithms such as the least-squares complex exponential (LSCE), the polyreference time domain (PTD), Ibrahim time domain (ITD), eigensystem realization algorithm (ERA), rational fraction polynomial (RFP), polyreference frequency domain (PFD) and the complex mode indication function (CMIF) methods. Using this unified matrix polynomial approach (UMPA) allows a discussion of the similarities and differences of the commonly used methods. the use of least squares (LS), total least squares (TLS), double least squares (DLS) and singular value decomposition (SVD) methods is discussed in order to take advantage of redundant measurement data. Eigenvalue and SVD transformation methods are utilized to reduce the effective size of the resulting eigenvalue-eigenvector problem as well.

Electroformation of Janus and patchy capsules

NASA Astrophysics Data System (ADS)

Rozynek, Zbigniew; Mikkelsen, Alexander; Dommersnes, Paul; Fossum, Jon Otto

2014-05-01

Janus and patchy particles have designed heterogeneous surfaces that consist of two or several patches with different materials properties. These particles are emerging as building blocks for a new class of soft matter and functional materials. Here we introduce a route for forming heterogeneous capsules by producing highly ordered jammed colloidal shells of various shapes with domains of controlled size and composition. These structures combine the functionalities offered by Janus or patchy particles, and those given by permeable shells such as colloidosomes. The simple assembly route involves the synergetic action of electro-hydrodynamic flow and electro-coalescence. We demonstrate that the method is robust and straightforwardly extendable to production of multi-patchy capsules. This forms a starting point for producing patchy colloidosomes with domains of anisotropic chemical surface properties, permeability or mixed liquid-solid phase domains, which could be exploited to produce functional emulsions, light and hollow supra-colloidosome structures, or scaffolds.

Looking at the world with your ears: how do we get the size of an object from its sound?

PubMed

Grassi, Massimo; Pastore, Massimiliano; Lemaitre, Guillaume

2013-05-01

Identifying the properties of on-going events by the sound they produce is crucial for our interaction with the environment when visual information is not available. Here, we investigated the ability of listeners to estimate the size of an object (a ball) dropped on a plate with ecological listening conditions (balls were dropped in real time) and response methods (listeners estimate ball-size by drawing a disk). Previous studies had shown that listeners can veridically estimate the size of objects by the sound they produce, but it is yet unclear which acoustical index listeners use to produce their estimates. In particular, it is unclear whether listeners listen to amplitude (related to loudness) or frequency (related to the sound's brightness) domain cue to produce their estimates. In the current study, in order to understand which cue is used by the listener to recover the size of the object, we manipulated the sound source event in such a way that frequency and amplitude cues provided contrasting size-information (balls were dropped from various heights). Results showed that listeners' estimations were accurate regardless of the experimental manipulations performed in the experiments. In addition, results suggest that listeners were likely integrating frequency and amplitude acoustical cues in order to produce their estimate and although these cues were often providing contrasting size-information. Copyright © 2013 Elsevier B.V. All rights reserved.

Defect ordering in YBa 2Cu 3O 6.5 and YBa 2Cu 3O 6.6: Synthesis and characterization by neutron and electron diffraction

NASA Astrophysics Data System (ADS)

Lin, Y. P.; Greedan, J. E.; O'Reilly, A. H.; Reimers, J. N.; Stager, C. V.; Post, M. L.

1990-02-01

Polycrystalline samples of YBa 2Cu 3O 6.5 and YBa 2Cu 3O 6.6 were prepared by oxygen titration of YBa 2 Cu 3O 6.0 at 450°C followed by slow cooling to room temperature. Both samples showed evidence for the a' = 2a supercell in individual grains by electron diffraction as reported previously. In addition the superlattice was observed in neutron powder diffraction indicating that the bulk material is also well ordered. In this study the YBa 2Cu 3O 6.6 phase showed longer correlation lengths for ordering along both a* and b* than YBa 2Cu 3O 6.5. For the former compound the powder-averaged, sample-averaged a* correlation distance is 26A˚from neutron diffraction. Analysis of electron diffraction profiles on selected single crystals give correlation lengths along a*, b*, and c* of 100, 200, and 50A˚, respectively. Dark field imaging discloses the presence of striped, ordered domains elongated along b* with a distribution of sizes. Both neutron diffraction and dark field imaging indicate that the volume fraction of the ordered domains is about 50%. A correlation is noted between the Meissner Effect and the extent of defect ordering in the bulk samples of the two phases.

What does it mean to be pseudo single domain? Demystifying the PSD state

NASA Astrophysics Data System (ADS)

Lascu, I.; Harrison, R. J.; Einsle, J. F.; Ball, M.

2016-12-01

Until recently, non-interacting stable single domain grains were thought to be the sole reliable paleomagnetic recorders. However most natural samples contain so-called "non-ideal" paleomagnetic recorders, which are either interacting single domain particles, or magnetic grains larger than single domain grains, but smaller than proper multi domain grains, which are poor paleomagnetic recorders. The grain size range for these recorders, which for magnetite comprises grains from 100 nm to a few μm in size, is known as the pseudo single domain (PSD) state. Natural samples containing abundant PSD grains have been shown time and again to reliably record thermomagnetic remanent magnetizations that are stable over billions of years. Here we attempt to shed new light on the PSD state by investigating obsidian varieties found at Glass Butte, Oregon, which present the opportunity to study simple cases of magnetic grains encapsulated in volcanic glass. We do this by combining rock magnetism, scanning electron microscopy (SEM) nanotomography, and finite-element micromagnetic modeling. Using rock magnetism we have identified PSD signatures in these samples via their fingerprint in first-order reversal curve (FORC) diagrams. Tomographic reconstructions obtained by stacking SEM images acquired via sequential milling through sample volumes of a few tens of cubic μm reveal the presence of abundant grains that span the PSD grain size interval. These grains have a variety of shapes, from simple ellipsoidal particles, to more complex morphologies attained through the coalescence of neighboring grains during crystallization, to intricate "rolling snowball" morphologies in larger grains that contain appendices formed as a result of particle growth in a dynamic environment as the flowing lava cooled. Micromagnetic modeling of the simplest morphologies reveals that these grains are in single vortex states, with the remanence controlled by irregularities in grain morphology. Coalesced grains present extreme cases of shape anisotropy, which will control the remanence. The remanence of the largest grains is controlled by the collection of PSD states from areas of the grain with pronounced shape anisotropy. Finally, micromagnetic modeling of realistic grain shapes allows the understanding of PSD signatures in FORC diagrams.

Porous media flux sensitivity to pore-scale geostatistics: A bottom-up approach

NASA Astrophysics Data System (ADS)

Di Palma, P. R.; Guyennon, N.; Heße, F.; Romano, E.

2017-04-01

Macroscopic properties of flow through porous media can be directly computed by solving the Navier-Stokes equations at the scales related to the actual flow processes, while considering the porous structures in an explicit way. The aim of this paper is to investigate the effects of the pore-scale spatial distribution on seepage velocity through numerical simulations of 3D fluid flow performed by the lattice Boltzmann method. To this end, we generate multiple random Gaussian fields whose spatial correlation follows an assigned semi-variogram function. The Exponential and Gaussian semi-variograms are chosen as extreme-cases of correlation for short distances and statistical properties of the resulting porous media (indicator field) are described using the Matèrn covariance model, with characteristic lengths of spatial autocorrelation (pore size) varying from 2% to 13% of the linear domain. To consider the sensitivity of the modeling results to the geostatistical representativeness of the domain as well as to the adopted resolution, porous media have been generated repetitively with re-initialized random seeds and three different resolutions have been tested for each resulting realization. The main difference among results is observed between the two adopted semi-variograms, indicating that the roughness (short distances autocorrelation) is the property mainly affecting the flux. However, computed seepage velocities show additionally a wide variability (about three orders of magnitude) for each semi-variogram model in relation to the assigned correlation length, corresponding to pore sizes. The spatial resolution affects more the results for short correlation lengths (i.e., small pore sizes), resulting in an increasing underestimation of the seepage velocity with the decreasing correlation length. On the other hand, results show an increasing uncertainty as the correlation length approaches the domain size.

Reversible Dissolution of Microdomains in Detergent-Resistant Membranes at Physiological Temperature

PubMed Central

Cremona, Andrea; Orsini, Francesco; Corsetto, Paola A.; Hoogenboom, Bart W.; Rizzo, Angela M.

2015-01-01

The formation of lipid microdomains (“rafts”) is presumed to play an important role in various cellular functions, but their nature remains controversial. Here we report on microdomain formation in isolated, detergent-resistant membranes from MDA-MB-231 human breast cancer cells, studied by atomic force microscopy (AFM). Whereas microdomains were readily observed at room temperature, they shrunk in size and mostly disappeared at higher temperatures. This shrinking in microdomain size was accompanied by a gradual reduction of the height difference between the microdomains and the surrounding membrane, consistent with the behaviour expected for lipids that are laterally segregated in liquid ordered and liquid disordered domains. Immunolabeling experiments demonstrated that the microdomains contained flotillin-1, a protein associated with lipid rafts. The microdomains reversibly dissolved and reappeared, respectively, on heating to and cooling below temperatures around 37°C, which is indicative of radical changes in local membrane order close to physiological temperature. PMID:26147107

Centromeric Heterochromatin: The Primordial Segregation Machine

PubMed Central

Bloom, Kerry S.

2014-01-01

Centromeres are specialized domains of heterochromatin that provide the foundation for the kinetochore. Centromeric heterochromatin is characterized by specific histone modifications, a centromere-specific histone H3 variant (CENP-A), and the enrichment of cohesin, condensin, and topo-isomerase II. Centromere DNA varies orders of magnitude in size from 125 bp (budding yeast) to several megabases (human). In metaphase, sister kinetochores on the surface of replicated chromosomes face away from each other, where they establish microtubule attachment and bi-orientation. Despite the disparity in centromere size, the distance between separated sister kinetochores is remarkably conserved (approximately 1 μm) throughout phylogeny. The centromere functions as a molecular spring that resists microtubule-based extensional forces in mitosis. This review explores the physical properties of DNA in order to understand how the molecular spring is built and how it contributes to the fidelity of chromosome segregation. PMID:25251850

Variable-order fractional MSD function to describe the evolution of protein lateral diffusion ability in cell membranes

NASA Astrophysics Data System (ADS)

Yin, Deshun; Qu, Pengfei

2018-02-01

Protein lateral diffusion is considered anomalous in the plasma membrane. And this diffusion is related to membrane microstructure. In order to better describe the property of protein lateral diffusion and find out the inner relationship between protein lateral diffusion and membrane microstructure, this article applies variable-order fractional mean square displacement (f-MSD) function for characterizing the anomalous diffusion. It is found that the variable order can reflect the evolution of diffusion ability. The results of numerical simulation demonstrate variable-order f-MSD function can predict the tendency of anomalous diffusion during the process of confined diffusion. It is also noted that protein lateral diffusion ability during the processes of confined and hop diffusion can be split into three parts. In addition, the comparative analyses reveal that the variable order is related to the confinement-domain size and microstructure of compartment boundary too.

Antiferromagnetic and Orbital Ordering on a Diamond Lattice Near Quantum Criticality

NASA Astrophysics Data System (ADS)

Plumb, K. W.; Morey, J. R.; Rodriguez-Rivera, J. A.; Wu, Hui; Podlesnyak, A. A.; McQueen, T. M.; Broholm, C. L.

2016-10-01

We present neutron scattering measurements on powder samples of the spinel FeSc2S4 that reveal a previously unobserved magnetic ordering transition occurring at 11.8(2) K. Magnetic ordering occurs subsequent to a subtle cubic-to-tetragonal structural transition that distorts Fe coordinating sulfur tetrahedra and lifts the orbital degeneracy. The orbital ordering is not truly long ranged, but occurs over finite-sized domains that limit magnetic correlation lengths. The application of 1 GPa hydrostatic pressure appears to destabilize this Néel state, reducing the transition temperature to 8.6(8) K and redistributing magnetic spectral weight to higher energies. The relative magnitudes of ordered ⟨m ⟩2=3.1 (2 ) μB2 and fluctuating moments ⟨δ m ⟩=13 (1 ) μB2 show that the magnetically ordered state of FeSc2 S4 is drastically renormalized and close to criticality.

Antiferromagnetic and Orbital Ordering on a Diamond Lattice Near Quantum Criticality

DOE PAGES

Plumb, K. W.; Morey, J. R.; Rodriguez-Rivera, J. A.; ...

2016-12-01

Here, we present neutron scattering measurements on powder samples of the spinel FeSc 2 S 4 that reveal a previously unobserved magnetic ordering transition occurring at 11.8(2) K. Magnetic ordering occurs subsequent to a subtle cubic-to-tetragonal structural transition that distorts Fe coordinating sulfur tetrahedra and lifts the orbital degeneracy. Furthermore, the orbital ordering is not truly long ranged, but occurs over finite-sized domains that limit magnetic correlation lengths. During the application of 1 GPa hydrostatic pressure appears to destabilize this Néel state, reducing the transition temperature to 8.6(8) K and redistributing magnetic spectral weight to higher energies. The relative magnitudes of ordered 2= 3.1(2) μmore » $$2\\atop{B}$$ and fluctuating moments < δm >= 13(1) μ$$2\\atop{B}$$ show that the magnetically ordered state of FeSc 2 S 4 is drastically renormalized and close to criticality.« less

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

NASA Astrophysics Data System (ADS)

Bose, Narayan; Dutta, Dripta; Mukherjee, Soumyajit

2018-07-01

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

Myonuclear domain size and myosin isoform expression in muscle fibres from mammals representing a 100,000-fold difference in body size.

PubMed

Liu, Jing-Xia; Höglund, Anna-Stina; Karlsson, Patrick; Lindblad, Joakim; Qaisar, Rizwan; Aare, Sudhakar; Bengtsson, Ewert; Larsson, Lars

2009-01-01

This comparative study of myonuclear domain (MND) size in mammalian species representing a 100,000-fold difference in body mass, ranging from 25 g to 2500 kg, was undertaken to improve our understanding of myonuclear organization in skeletal muscle fibres. Myonuclear domain size was calculated from three-dimensional reconstructions in a total of 235 single muscle fibre segments at a fixed sarcomere length. Irrespective of species, the largest MND size was observed in muscle fibres expressing fast myosin heavy chain (MyHC) isoforms, but in the two smallest mammalian species studied (mouse and rat), MND size was not larger in the fast-twitch fibres expressing the IIA MyHC isofom than in the slow-twitch type I fibres. In the larger mammals, the type I fibres always had the smallest average MND size, but contrary to mouse and rat muscles, type IIA fibres had lower mitochondrial enzyme activities than type I fibres. Myonuclear domain size was highly dependent on body mass in the two muscle fibre types expressed in all species, i.e. types I and IIA. Myonuclear domain size increased in muscle fibres expressing both the beta/slow (type I; r = 0.84, P < 0.001) and the fast IIA MyHC isoform (r = 0.90; P < 0.001). Thus, MND size scales with body size and is highly dependent on muscle fibre type, independent of species. However, myosin isoform expression is not the sole protein determining MND size, and other protein systems, such as mitochondrial proteins, may be equally or more important determinants of MND size.

Ageing influences myonuclear domain size differently in fast and slow skeletal muscle of rats.

PubMed

Brooks, Naomi E; Schuenke, M D; Hikida, R S

2009-09-01

In multinucleated skeletal muscle, a myonuclear domain is the region of cytoplasm governed by one nucleus, and myofibres are mosaics of overlapping myonuclear domains. Association of ageing and myonuclear domain is important in the understanding of sarcopenia and with prevention or combating age-related muscle declines. This study examined the effects of age, fibre type and muscle on nucleo-cytoplasmic (N/C) relationships as reflecting myonuclear domain size. The N/C was compared in fibre types of soleus and plantaris muscles from young (n = 6) and ageing (n = 8) male Fisher 344 rats. There were no significant differences in fibre type composition or cross-sectional area of the soleus across ages. The old soleus had significantly more myonuclei, resulting in a significantly smaller myonuclear domain size. The plantaris muscle showed a higher percentage of slow fibres in old compared with young fibres. There were no differences in the number of myonuclei or in myonuclear domain size between young and older animals. We found muscle-specific differences in the effects of ageing on myonuclear domain, possibly as a result of reduced efficiency of the myonuclei in the slow muscles.

Exploring the impact of multiple grain sizes in numerical landscape evolution model

NASA Astrophysics Data System (ADS)

Guerit, Laure; Braun, Jean; Yuan, Xiaoping; Rouby, Delphine

2017-04-01

Numerical evolution models have been widely developed in order to understand the evolution of landscape over different time-scales, but also the response of the topography to changes in external conditions, such as tectonics or climate, or to changes in the bedrock characteristics, such as its density or its erodability. Few models have coupled the evolution of the relief in erosion to the evolution of the related area in deposition, and in addition, such models generally do not consider the role of the size of the sediments reached the depositional domain. Here, we present a preliminary work based on an enhanced version of Fastscape, a very-efficient model solving the stream power equation, which now integrates a sedimentary basin at the front of a relief, together with the integration of multiple grain sizes in the system. Several simulations were performed in order to explore the impact of several grain sizes in terms of stratigraphy in the marine basin. A simple setting is considered, with uniform uplift rate, precipitation rate, and rock properties onshore. The pros and cons of this approach are discussed with respect to similar simulations performed considering only flux.

Steric Pressure among Membrane-Bound Polymers Opposes Lipid Phase Separation.

PubMed

Imam, Zachary I; Kenyon, Laura E; Carrillo, Adelita; Espinoza, Isai; Nagib, Fatema; Stachowiak, Jeanne C

2016-04-19

Lipid rafts are thought to be key organizers of membrane-protein complexes in cells. Many proteins that interact with rafts have bulky polymeric components such as intrinsically disordered protein domains and polysaccharide chains. Therefore, understanding the interaction between membrane domains and membrane-bound polymers provides insights into the roles rafts play in cells. Multiple studies have demonstrated that high concentrations of membrane-bound polymeric domains create significant lateral steric pressure at membrane surfaces. Furthermore, our recent work has shown that lateral steric pressure at membrane surfaces opposes the assembly of membrane domains. Building on these findings, here we report that membrane-bound polymers are potent suppressors of membrane phase separation, which can destabilize lipid domains with substantially greater efficiency than globular domains such as membrane-bound proteins. Specifically, we created giant vesicles with a ternary lipid composition, which separated into coexisting liquid ordered and disordered phases. Lipids with saturated tails and poly(ethylene glycol) (PEG) chains conjugated to their head groups were included at increasing molar concentrations. When these lipids were sparse on the membrane surface they partitioned to the liquid ordered phase. However, as they became more concentrated, the fraction of GUVs that were phase-separated decreased dramatically, ultimately yielding a population of homogeneous membrane vesicles. Experiments and physical modeling using compositions of increasing PEG molecular weight and lipid miscibility phase transition temperature demonstrate that longer polymers are the most efficient suppressors of membrane phase separation when the energetic barrier to lipid mixing is low. In contrast, as the miscibility transition temperature increases, longer polymers are more readily driven out of domains by the increased steric pressure. Therefore, the concentration of shorter polymers required to suppress phase separation decreases relative to longer polymers. Collectively, our results demonstrate that crowded, membrane-bound polymers are highly efficient suppressors of phase separation and suggest that the ability of lipid domains to resist steric pressure depends on both their lipid composition and the size and concentration of the membrane-bound polymers they incorporate.

Model Order Reduction Algorithm for Estimating the Absorption Spectrum

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

Van Beeumen, Roel; Williams-Young, David B.; Kasper, Joseph M.

The ab initio description of the spectral interior of the absorption spectrum poses both a theoretical and computational challenge for modern electronic structure theory. Due to the often spectrally dense character of this domain in the quantum propagator’s eigenspectrum for medium-to-large sized systems, traditional approaches based on the partial diagonalization of the propagator often encounter oscillatory and stagnating convergence. Electronic structure methods which solve the molecular response problem through the solution of spectrally shifted linear systems, such as the complex polarization propagator, offer an alternative approach which is agnostic to the underlying spectral density or domain location. This generality comesmore » at a seemingly high computational cost associated with solving a large linear system for each spectral shift in some discretization of the spectral domain of interest. In this work, we present a novel, adaptive solution to this high computational overhead based on model order reduction techniques via interpolation. Model order reduction reduces the computational complexity of mathematical models and is ubiquitous in the simulation of dynamical systems and control theory. The efficiency and effectiveness of the proposed algorithm in the ab initio prediction of X-ray absorption spectra is demonstrated using a test set of challenging water clusters which are spectrally dense in the neighborhood of the oxygen K-edge. On the basis of a single, user defined tolerance we automatically determine the order of the reduced models and approximate the absorption spectrum up to the given tolerance. We also illustrate that, for the systems studied, the automatically determined model order increases logarithmically with the problem dimension, compared to a linear increase of the number of eigenvalues within the energy window. Furthermore, we observed that the computational cost of the proposed algorithm only scales quadratically with respect to the problem dimension.« less

Highly thermally conductive and mechanically strong graphene fibers.

PubMed

Xin, Guoqing; Yao, Tiankai; Sun, Hongtao; Scott, Spencer Michael; Shao, Dali; Wang, Gongkai; Lian, Jie

2015-09-04

Graphene, a single layer of carbon atoms bonded in a hexagonal lattice, is the thinnest, strongest, and stiffest known material and an excellent conductor of heat and electricity. However, these superior properties have yet to be realized for graphene-derived macroscopic structures such as graphene fibers. We report the fabrication of graphene fibers with high thermal and electrical conductivity and enhanced mechanical strength. The inner fiber structure consists of large-sized graphene sheets forming a highly ordered arrangement intercalated with small-sized graphene sheets filling the space and microvoids. The graphene fibers exhibit a submicrometer crystallite domain size through high-temperature treatment, achieving an enhanced thermal conductivity up to 1290 watts per meter per kelvin. The tensile strength of the graphene fiber reaches 1080 megapascals. Copyright © 2015, American Association for the Advancement of Science.

Physical and Structural Studies on the Cryo-cooling of Insulin Crystals

NASA Technical Reports Server (NTRS)

Lovelace, J.; Bellamy, H.; Snell, E. H.; Borgstahl, G.

2003-01-01

Reflection profiles were analyzed from microgravity-(mg) and earth-grown insulin crystals to measure mosaicity (h) and to reveal mosaic domain structure and composition. The effects of cryocooling on single and multi-domain crystals were compared. The effects of cryocooling on insulin structure were also re-examined. Microgravity crystals were larger, more homogeneous, and more perfect than earth crystals. Several mg crystals contained primarily a single mosaic domain with havg of 0.005deg. The earth crystals varied in quality and all contained multiple domains with havg of 0.031deg. Cryocooling caused a 43-fold increase in h for mg crystals (havg=0.217deg) and an %fold increase for earth crystals (havg=0.246deg). These results indicate that very well-ordered crystals are not completely protected from the stresses associated with cryocooling, especially when structural perturbations occur. However, there were differences in the reflection profiles. For multi-mosaic domain crystals, each domain individually broadened and separated from the other domains upon cryo-cooling. Cryo-cooling did not cause an increase in the number of domains. A crystal composed of a single domain retained this domain structure and the reflection profiles simply broadened. Therefore, an improved signal-to-noise ratio for each reflection was measured from cryo-cooled single domain crystals relative to cryo-cooled multi-domain crystals. This improved signal, along with the increase in crystal size, facilitated the measurement of the weaker high- resolution reflections. The observed broadening of reflection profiles indicates increased variation in unit cell dimensions which may be linked to cryo-cooling-associated structural changes and disorder.

Partial glass isosymmetry transition in multiferroic hexagonal ErMn O 3

DOE PAGES

Barbour, A.; Alatas, A.; Liu, Y.; ...

2016-02-08

Ferroelectric transitions of a hexagonal multiferroic, ErMnO 3, are studied by x-ray scattering techniques. An isosymmetry transition, similar to that previously observed for YMnO 3, approximately 300 K below the well-known ferroic transition temperature is investigated. The partial glassy behavior of the isosymmetry transition is identified by appearance of quasi-elastic scattering lines in high-energy-resolution scans. The glassy behavior is further supported by the increased interlayer decorrelation of (√3×√3)R30º ordering below the isosymmetry transition. The transition behavior is considered for possible hidden sluggish modes and two-step phase transitions theoretically predicted for the stacked triangular antiferromagnets. The in-plane azimuthal (orientational) ordering behaviorsmore » were also compared to the theoretical predictions. Coherent x-ray speckle measurements show unambiguously that the domain sizes decrease anomalously near both the isosymmetry and ferroic transitions. However, domain boundary fluctuations increase monotonically with an Arrhenius form with an activation energy of 0.54(5) eV through both transitions.« less

Low energy constants of S U ( 2 ) partially quenched chiral perturbation theory from N f = 2 + 1 domain wall QCD

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

Boyle, P. A.; Christ, N. H.; Garron, N.

2016-03-09

Here, we have performed fits of the pseudoscalar masses and decay constants, from a variety of the RBC-UKQCD Collaboration’s domain wall fermion ensembles, to SU(2) partially quenched chiral perturbation theory at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO). We report values for 9 NLO and 8 linearly independent combinations of NNLO partially quenched low-energy constants, which we compare to other lattice and phenomenological determinations. We discuss the size of successive terms in the chiral expansion and use our large set of low-energy constants to make predictions for mass splittings due to QCD isospin-breaking effects and the S-wave ππ scattering lengths.more » Lastly, we conclude that, for the range of pseudoscalar masses explored in this work, 115 MeV≲mPS≲430 MeV, the NNLO SU(2) expansion is quite robust and can fit lattice data with percent-scale accuracy.« less

Directing self-assembly of gold nanoparticles in diblock copolymer scaffold

NASA Astrophysics Data System (ADS)

Li, Qifang; He, Jinbo; Glogowski, Elizabeth; Emrick, Todd; Russell, Thomas

2007-03-01

A versatile hierarchical approach for directing self -assembly of gold nanostructures with size 2-3nm in diblock copolymer scaffolds is found. Diblock copolymer polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) is used to form a regular scaffold of highly anisotropic, stripe-like domains, and controlled differential wetting by dichloromethane and thermal annealing guides gold nanoparticles with half hydrophilic ligand to aggregate selectively along the scaffold, producing highly organized metal nanostructures. In as-cast block-copolymer and gold nanoparticles thin films, micelle structure and gold nanoparticles random distribution on scaffold are typically observed. However, samples annealed in dichloromethane exhibit well-defined short-range ordered nanostructure with gold nanoparticles located at the interface of PS and P2VP nanoscale domain. After annealing at 170 C, the gold nanoparticles at interface migrated into the middle of P2VP phase and exhibited long-range ordered hierarchical structures. Synergistic interactions between the gold nanoparticles and the PS-b-P2VP caused an orientation of the microdomains normal to the film surface.

Eye Size, Fovea, and Foraging Ecology in Accipitriform Raptors.

PubMed

Potier, Simon; Mitkus, Mindaugas; Bonadonna, Francesco; Duriez, Olivier; Isard, Pierre-François; Dulaurent, Thomas; Mentek, Marielle; Kelber, Almut

2017-01-01

Birds with larger eyes are predicted to have higher spatial resolution because of their larger retinal image. Raptors are well known for their acute vision, mediated by their deep central fovea. Because foraging strategies may demand specific visual adaptations, eye size and fovea may differ between species with different foraging ecology. We tested whether predators (actively hunting mobile prey) and carrion eaters (eating dead prey) from the order Accipitriformes differ in eye size, foveal depth, and retinal thickness using spectral domain optical coherence tomography and comparative phylogenetic methods. We found that (1) all studied predators (except one) had a central and a temporal fovea, but all carrion eaters had only the central fovea; (2) eye size scaled with body mass both in predators and carrion eaters; (3) predators had larger eyes relative to body mass and a thicker retina at the edge of the fovea than carrion eaters, but there was no difference in the depth of the central fovea between the groups. Finally, we found that (4) larger eyes generally had a deeper central fovea. These results suggest that the visual system of raptors within the order Accipitriformes may be highly adapted to the foraging strategy, except for the foveal depth, which seems mostly dependent upon the eye size. © 2017 S. Karger AG, Basel.

Accessing Colony Boundary Strengthening of Fully Lamellar TiAl Alloys via Micromechanical Modeling

PubMed Central

Bargmann, Swantje

2017-01-01

In this article, we present a strategy to decouple the relative influences of colony, domain and lamella boundary strengthening in fully lamellar titanium aluminide alloys, using a physics-based crystal plasticity modeling strategy. While lamella and domain boundary strengthening can be isolated in experiments using polysynthetically twinned crystals or mircomechanical testing, colony boundary strengthening can only be investigated in specimens in which all three strengthening mechanisms act simultaneously. Thus, isolating the colony boundary strengthening Hall–Petch coefficient KC experimentally requires a sufficient number of specimens with different colony sizes λC but constant lamella thickness λL and domain size λD, difficult to produce even with sophisticated alloying techniques. The here presented crystal plasticity model enables identification of the colony boundary strengthening coefficient KC as a function of lamella thickness λL. The constitutive description is based on the model of a polysynthetically twinned crystal which is adopted to a representative volume element of a fully lamellar microstructure. In order to capture the micro yield and subsequent micro hardening in weakly oriented colonies prior to macroscopic yield, the hardening relations of the adopted model are revised and calibrated against experiments with polysynthetically twinned crystals for plastic strains up to 15%. PMID:28771218

Accessing Colony Boundary Strengthening of Fully Lamellar TiAl Alloys via Micromechanical Modeling.

PubMed

Schnabel, Jan Eike; Bargmann, Swantje

2017-08-03

In this article, we present a strategy to decouple the relative influences of colony, domain and lamella boundary strengthening in fully lamellar titanium aluminide alloys, using a physics-based crystal plasticity modeling strategy. While lamella and domain boundary strengthening can be isolated in experiments using polysynthetically twinned crystals or mircomechanical testing, colony boundary strengthening can only be investigated in specimens in which all three strengthening mechanisms act simultaneously. Thus, isolating the colony boundary strengthening Hall-Petch coefficient K C experimentally requires a sufficient number of specimens with different colony sizes λ C but constant lamella thickness λ L and domain size λ D , difficult to produce even with sophisticated alloying techniques. The here presented crystal plasticity model enables identification of the colony boundary strengthening coefficient K C as a function of lamella thickness λ L . The constitutive description is based on the model of a polysynthetically twinned crystal which is adopted to a representative volume element of a fully lamellar microstructure. In order to capture the micro yield and subsequent micro hardening in weakly oriented colonies prior to macroscopic yield, the hardening relations of the adopted model are revised and calibrated against experiments with polysynthetically twinned crystals for plastic strains up to 15%.

Full waveform time domain solutions for source and induced magnetotelluric and controlled-source electromagnetic fields using quasi-equivalent time domain decomposition and GPU parallelization

NASA Astrophysics Data System (ADS)

Imamura, N.; Schultz, A.

2015-12-01

Recently, a full waveform time domain solution has been developed for the magnetotelluric (MT) and controlled-source electromagnetic (CSEM) methods. The ultimate goal of this approach is to obtain a computationally tractable direct waveform joint inversion for source fields and earth conductivity structure in three and four dimensions. This is desirable on several grounds, including the improved spatial resolving power expected from use of a multitude of source illuminations of non-zero wavenumber, the ability to operate in areas of high levels of source signal spatial complexity and non-stationarity, etc. This goal would not be obtainable if one were to adopt the finite difference time-domain (FDTD) approach for the forward problem. This is particularly true for the case of MT surveys, since an enormous number of degrees of freedom are required to represent the observed MT waveforms across the large frequency bandwidth. It means that for FDTD simulation, the smallest time steps should be finer than that required to represent the highest frequency, while the number of time steps should also cover the lowest frequency. This leads to a linear system that is computationally burdensome to solve. We have implemented our code that addresses this situation through the use of a fictitious wave domain method and GPUs to speed up the computation time. We also substantially reduce the size of the linear systems by applying concepts from successive cascade decimation, through quasi-equivalent time domain decomposition. By combining these refinements, we have made good progress toward implementing the core of a full waveform joint source field/earth conductivity inverse modeling method. From results, we found the use of previous generation of CPU/GPU speeds computations by an order of magnitude over a parallel CPU only approach. In part, this arises from the use of the quasi-equivalent time domain decomposition, which shrinks the size of the linear system dramatically.

Tracking of large-scale structures in turbulent channel with direct numerical simulation of low Prandtl number passive scalar

NASA Astrophysics Data System (ADS)

Tiselj, Iztok

2014-12-01

Channel flow DNS (Direct Numerical Simulation) at friction Reynolds number 180 and with passive scalars of Prandtl numbers 1 and 0.01 was performed in various computational domains. The "normal" size domain was ˜2300 wall units long and ˜750 wall units wide; size taken from the similar DNS of Moser et al. The "large" computational domain, which is supposed to be sufficient to describe the largest structures of the turbulent flows was 3 times longer and 3 times wider than the "normal" domain. The "very large" domain was 6 times longer and 6 times wider than the "normal" domain. All simulations were performed with the same spatial and temporal resolution. Comparison of the standard and large computational domains shows the velocity field statistics (mean velocity, root-mean-square (RMS) fluctuations, and turbulent Reynolds stresses) that are within 1%-2%. Similar agreement is observed for Pr = 1 temperature fields and can be observed also for the mean temperature profiles at Pr = 0.01. These differences can be attributed to the statistical uncertainties of the DNS. However, second-order moments, i.e., RMS temperature fluctuations of standard and large computational domains at Pr = 0.01 show significant differences of up to 20%. Stronger temperature fluctuations in the "large" and "very large" domains confirm the existence of the large-scale structures. Their influence is more or less invisible in the main velocity field statistics or in the statistics of the temperature fields at Prandtl numbers around 1. However, these structures play visible role in the temperature fluctuations at low Prandtl number, where high temperature diffusivity effectively smears the small-scale structures in the thermal field and enhances the relative contribution of large-scales. These large thermal structures represent some kind of an echo of the large scale velocity structures: the highest temperature-velocity correlations are not observed between the instantaneous temperatures and instantaneous streamwise velocities, but between the instantaneous temperatures and velocities averaged over certain time interval.

Dendritic Growth of Hard-Sphere Crystals. Experiment 34

NASA Technical Reports Server (NTRS)

Russel, W. B.; Chaikin, P. M.; Zhu, Ji-Xiang; Meyer, W. V.; Rogers, R.

1998-01-01

Recent observations of the disorder-order transition for colloidal hard spheres under microgravity revealed dendritic crystallites roughly 1-2 mm in size for samples in the coexistence region of the phase diagram. Order-of-magnitude estimates rationalize the absence of large or dendritic crystals under normal gravity and their stability to annealing in microgravity. A linear stability analysis of the Ackerson and Schaetzel model for crystallization of hard spheres establishes the domain of instability for diffusion-limited growth at small supersaturations. The relationship between hard-sphere and molecular crystal growth is established and exploited to relate the predicted linear instability to the well-developed dendrites observed.

Multicomponent order parameter superconductivity of Sr2RuO4 revealed by topological junctions

NASA Astrophysics Data System (ADS)

Anwar, M. S.; Ishiguro, R.; Nakamura, T.; Yakabe, M.; Yonezawa, S.; Takayanagi, H.; Maeno, Y.

2017-06-01

Single crystals of the Sr2RuO4 -Ru eutectic system are known to exhibit enhanced superconductivity at 3 K in addition to the bulk superconductivity of Sr2RuO4 at 1.5 K. The 1.5 K phase is believed to be a spin-triplet, chiral p -wave state with a multicomponent order parameter, giving rise to chiral domain structure. In contrast, the 3 K phase is attributable to enhanced superconductivity of Sr2RuO4 in the strained interface region between Ru inclusion of a few to tens of micrometers in size and the surrounding Sr2RuO4 . We investigate the dynamic behavior of a topological junction, where a superconductor is surrounded by another superconductor. Specifically, we fabricated Nb/Ru/Sr2RuO4 topological superconducting junctions, in which the difference in phase winding between the s -wave superconductivity in Ru microislands induced from Nb and the superconductivity of Sr2RuO4 mainly governs the junction behavior. Comparative results of the asymmetry, hysteresis, and noise in junctions with different sizes, shapes, and configurations of Ru inclusions are explained by the chiral domain-wall motion in these topological junctions. Furthermore, a striking difference between the 1.5 and 3 K phases is clearly revealed: the large noise in the 1.5 K phase sharply disappears in the 3 K phase. These results confirm the multicomponent order-parameter superconductivity of the bulk Sr2RuO4 , consistent with the chiral p -wave state, and the proposed nonchiral single-component superconductivity of the 3 K phase.

Effect of the centrifugal force on domain chaos in Rayleigh-Bénard convection.

PubMed

Becker, Nathan; Scheel, J D; Cross, M C; Ahlers, Guenter

2006-06-01

Experiments and simulations from a variety of sample sizes indicated that the centrifugal force significantly affects the domain-chaos state observed in rotating Rayleigh-Bénard convection-patterns. In a large-aspect-ratio sample, we observed a hybrid state consisting of domain chaos close to the sample center, surrounded by an annulus of nearly stationary nearly radial rolls populated by occasional defects reminiscent of undulation chaos. Although the Coriolis force is responsible for domain chaos, by comparing experiment and simulation we show that the centrifugal force is responsible for the radial rolls. Furthermore, simulations of the Boussinesq equations for smaller aspect ratios neglecting the centrifugal force yielded a domain precession-frequency f approximately epsilon(mu) with mu approximately equal to 1 as predicted by the amplitude-equation model for domain chaos, but contradicted by previous experiment. Additionally the simulations gave a domain size that was larger than in the experiment. When the centrifugal force was included in the simulation, mu and the domain size were consistent with experiment.

Nanoporous anodic aluminum oxide with a long-range order and tunable cell sizes by phosphoric acid anodization on pre-patterned substrates

PubMed Central

Surawathanawises, Krissada; Cheng, Xuanhong

2014-01-01

Nanoporous anodic aluminum oxide (AAO) has been explored for various applications due to its regular cell arrangement and relatively easy fabrication processes. However, conventional two-step anodization based on self-organization only allows the fabrication of a few discrete cell sizes and formation of small domains of hexagonally packed pores. Recent efforts to pre-pattern aluminum followed with anodization significantly improve the regularity and available pore geometries in AAO, while systematic study of the anodization condition, especially the impact of acid composition on pore formation guided by nanoindentation is still lacking. In this work, we pre-patterned aluminium thin films using ordered monolayers of silica beads and formed porous AAO in a single-step anodization in phosphoric acid. Controllable cell sizes ranging from 280 nm to 760 nm were obtained, matching the diameters of the silica nanobead molds used. This range of cell size is significantly greater than what has been reported for AAO formed in phosphoric acid in the literature. In addition, the relationships between the acid concentration, cell size, pore size, anodization voltage and film growth rate were studied quantitatively. The results are consistent with the theory of oxide formation through an electrochemical reaction. Not only does this study provide useful operational conditions of nanoindentation induced anodization in phosphoric acid, it also generates significant information for fundamental understanding of AAO formation. PMID:24535886

Low-temperature magnetic properties of greigite (Fe3S4)

NASA Astrophysics Data System (ADS)

Chang, Liao; Roberts, Andrew P.; Rowan, Christopher J.; Tang, Yan; Pruner, Petr; Chen, Qianwang; Horng, Chorng-Shern

2009-01-01

We provide comprehensive low-temperature magnetic results for greigite (Fe3S4) across the spectrum from superparamagnetic (SP) to multidomain (MD) behavior. It is well known that greigite has no low-temperature magnetic transitions, but we also document that it has strong domain-state dependence of magnetic properties at low temperatures. Blocking of SP grains and increasing thermal stability with decreasing temperature is apparent in many magnetic measurements. Thermally stable single-domain greigite undergoes little change in magnetic properties below room temperature. For pseudo-single-domain (PSD)/MD greigite, hysteresis properties and first-order reversal curve diagrams exhibit minor changes at low temperatures, while remanence continuously demagnetizes because of progressive domain wall unpinning. The low-temperature demagnetization is grain size dependent for PSD/MD greigite, with coarser grains undergoing larger remanence loss. AC susceptibility measurements indicate consistent blocking temperatures (TB) for all synthetic and natural greigite samples, which are probably associated with surficial oxidation. Low-temperature magnetic analysis provides much more information about magnetic mineralogy and domain state than room temperature measurements and enables discrimination of individual components within mixed magnetic mineral assemblages. Low-temperature rock magnetometry is therefore a useful tool for studying magnetic mineralogy and granulometry of greigite-bearing sediments.

Visualization of molecular packing and tilting domains and interface effects in tetracene thin films on H/Si(001)

DOE PAGES

Tersigni, Andrew; Sadowski, Jerzy T.; Qin, Xiao-Rong

2017-03-27

Visualizing molecular crystalline domains and influence of substrate defects are important in understanding the charge transport in organic thin film devices. Vacuum evaporated tetracene films of four monolayers on hydrogen-terminated Si(001)-2x1 substrate, as a prototypical system, have been studied with ex situ atomic force microscopy (AFM), transverse shear microscopy (TSM), friction force microscopy (FFM), and low-energy electron microscopy (LEEM). Two differently oriented in-plane lattice domains are found due to the symmetry of the substrate lattice, with no visible azimuthal twist between adjacent molecular layers in surface islands, indicating significant bulk-like crystallization in the film. Meanwhile, two types of subdomains aremore » observed inside of each in-plane lattice domain. The subdomains are anisotropic in shape, and their sizes and distribution are highly influenced by the substrate atomic steps. TSM and FFM measurements indicate that these subdomains result from molecule-tilt orderings within the bulk-like lattice domains. Lastly, TSM evidently shows a sensitivity to probe vertical molecule-tilt anisotropy for the molecular crystals, in addition to its known ability to map the lateral lattice orientations.« less

Electron microscope studies of nano-domain structures in Ru-based magneto-superconductors: RuSr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-delta) (Ru-1222) and RuSr(2)GdCu(2)O(8) (Ru-1212).

PubMed

Yokosawa, Tadahiro; Awana, V P S Veer Pal Singh; Kimoto, Koji; Takayama-Muromachi, Eiji; Karppinen, Maarit; Yamauchi, Hisao; Matsui, Yoshio

2004-01-01

Microstructures of the RuSr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-delta) (Ru-1222) and RuSr(2)GdCu(2)O(8) (Ru-1212) magneto-superconductors have been investigated by using selected-area electron diffraction, convergent-beam electron diffraction, dark-field electron microscopy and high-resolution electron microscopy at room temperature. Both Ru-1212 and Ru-1222 consist of nm-size domains stacked along the [Formula: see text] direction, where the domains are formed by two types of superstructures due to ordering of rotated RuO(6) octahedra about the c-axis. In Ru-1212, both primitive-and body-centered tetragonal superstructures (the possible space groups: P4/mbm and I4/mcm) are derived to form the corresponding nm-domains. It is of great interest that Ru-1212 consists of domains of two crystallographically different superstructures, while the similar domains observed in Ru-1222 have crystallographically identical superstructure with an orthorhombic symmetry (possible space group: Aeam), related by 90 degrees rotation around the c-axis (Yokosawa et al., 2003, submitted for publication).

Changes in myonuclear domain size do not precede muscle hypertrophy during prolonged resistance-type exercise training.

PubMed

Snijders, T; Smeets, J S J; van Kranenburg, J; Kies, A K; van Loon, L J C; Verdijk, L B

2016-02-01

Muscle fibre hypertrophy is accompanied by an increase in myonuclear number, an increase in myonuclear domain size or both. It has been suggested that increases in myonuclear domain size precede myonuclear accretion and subsequent muscle fibre hypertrophy during prolonged exercise training. In this study, we assessed the changes in muscle fibre size, myonuclear and satellite cell content throughout 12 weeks of resistance-type exercise training in young men. Twenty-two young men (23 ± 1 year) were assigned to a progressive, 12-weeks resistance-type exercise training programme (3 sessions per week). Muscle biopsies from the vastus lateralis muscle were taken before and after 2, 4, 8 and 12 weeks of exercise training. Muscle fibre size, myonuclear content, myonuclear domain size and satellite cell content were assessed by immunohistochemistry. Type I and type II muscle fibre size increased gradually throughout the 12 weeks of training (type I: 18 ± 5%, type II: 41 ± 6%, P < 0.01). Myonuclear content increased significantly over time in both the type I (P < 0.01) and type II (P < 0.001) muscle fibres. No changes in type I and type II myonuclear domain size were observed at any time point throughout the intervention. Satellite cell content increased significantly over time in both type I and type II muscle fibres (P < 0.001). Increases in myonuclear domain size do not appear to drive myonuclear accretion and muscle fibre hypertrophy during prolonged resistance-type exercise training in vivo in humans. © 2015 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

Domain size polydispersity effects on the structural and dynamical properties in lipid monolayers with phase coexistence

NASA Astrophysics Data System (ADS)

Rufeil-Fiori, Elena; Banchio, Adolfo J.

Lipid monolayers with phase coexistence are a frequently used model for lipid membranes. In these systems, domains of the liquid-condensed phase always present size polydispersity. However, very few theoretical works consider size distribution effects on the monolayer properties. Because of the difference in surface densities, domains have excess dipolar density with respect to the surrounding liquid expanded phase, originating a dipolar inter-domain interaction. This interaction depends on the domain area, and hence the presence of a domain size distribution is associated with interaction polydispersity. Inter-domain interactions are fundamental to understanding the structure and dynamics of the monolayer. For this reason, it is expected that polydispersity significantly alters monolayer properties. By means of Brownian dynamics simulations, we study the radial distribution function (RDF), the average mean square displacement and the average time-dependent self-diffusion coefficient, D(t), of lipid monolayers with normal distributed size domains. It was found that polydispersity strongly affects the value of the interaction strength obtained, which is greatly underestimated if polydispersity is not considered. However, within a certain range of parameters, the RDF obtained from a polydisperse model can be well approximated by that of a monodisperse model, suitably fitting the interaction strength, even for 40% polydispersities. For small interaction strengths or small polydispersities, the polydisperse systems obtained from fitting the experimental RDF have an average mean square displacement and D(t) in good agreement with that of the monodisperse system.

Large-Signal Lyapunov-Based Stability Analysis of DC/AC Inverters and Inverter-Based Microgrids

NASA Astrophysics Data System (ADS)

Kabalan, Mahmoud

Microgrid stability studies have been largely based on small-signal linearization techniques. However, the validity and magnitude of the linearization domain is limited to small perturbations. Thus, there is a need to examine microgrids with large-signal nonlinear techniques to fully understand and examine their stability. Large-signal stability analysis can be accomplished by Lyapunov-based mathematical methods. These Lyapunov methods estimate the domain of asymptotic stability of the studied system. A survey of Lyapunov-based large-signal stability studies showed that few large-signal studies have been completed on either individual systems (dc/ac inverters, dc/dc rectifiers, etc.) or microgrids. The research presented in this thesis addresses the large-signal stability of droop-controlled dc/ac inverters and inverter-based microgrids. Dc/ac power electronic inverters allow microgrids to be technically feasible. Thus, as a prelude to examining the stability of microgrids, the research presented in Chapter 3 analyzes the stability of inverters. First, the 13 th order large-signal nonlinear model of a droop-controlled dc/ac inverter connected to an infinite bus is presented. The singular perturbation method is used to decompose the nonlinear model into 11th, 9th, 7th, 5th, 3rd and 1st order models. Each model ignores certain control or structural components of the full order model. The aim of the study is to understand the accuracy and validity of the reduced order models in replicating the performance of the full order nonlinear model. The performance of each model is studied in three different areas: time domain simulations, Lyapunov's indirect method and domain of attraction estimation. The work aims to present the best model to use in each of the three domains of study. Results show that certain reduced order models are capable of accurately reproducing the performance of the full order model while others can be used to gain insights into those three areas of study. This will enable future studies to save computational effort and produce the most accurate results according to the needs of the study being performed. Moreover, the effect of grid (line) impedance on the accuracy of droop control is explored using the 5th order model. Simulation results show that traditional droop control is valid up to R/X line impedance value of 2. Furthermore, the 3rd order nonlinear model improves the currently available inverter-infinite bus models by accounting for grid impedance, active power-frequency droop and reactive power-voltage droop. Results show the 3rd order model's ability to account for voltage and reactive power changes during a transient event. Finally, the large-signal Lyapunov-based stability analysis is completed for a 3 bus microgrid system (made up of 2 inverters and 1 linear load). The thesis provides a systematic state space large-signal nonlinear mathematical modeling method of inverter-based microgrids. The inverters include the dc-side dynamics associated with dc sources. The mathematical model is then used to estimate the domain of asymptotic stability of the 3 bus microgrid. The three bus microgrid system was used as a case study to highlight the design and optimization capability of a large-signal-based approach. The study explores the effect of system component sizing, load transient and generation variations on the asymptotic stability of the microgrid. Essentially, this advancement gives microgrid designers and engineers the ability to manipulate the domain of asymptotic stability depending on performance requirements. Especially important, this research was able to couple the domain of asymptotic stability of the ac microgrid with that of the dc side voltage source. Time domain simulations were used to demonstrate the mathematical nonlinear analysis results.

Neuropsychological profile in adult schizophrenia measured with the CMINDS.

PubMed

van Erp, Theo G M; Preda, Adrian; Turner, Jessica A; Callahan, Shawn; Calhoun, Vince D; Bustillo, Juan R; Lim, Kelvin O; Mueller, Bryon; Brown, Gregory G; Vaidya, Jatin G; McEwen, Sarah; Belger, Aysenil; Voyvodic, James; Mathalon, Daniel H; Nguyen, Dana; Ford, Judith M; Potkin, Steven G

2015-12-30

Schizophrenia neurocognitive domain profiles are predominantly based on paper-and-pencil batteries. This study presents the first schizophrenia domain profile based on the Computerized Multiphasic Interactive Neurocognitive System (CMINDS(®)). Neurocognitive domain z-scores were computed from computerized neuropsychological tests, similar to those in the Measurement and Treatment Research to Improve Cognition in Schizophrenia Consensus Cognitive Battery (MCCB), administered to 175 patients with schizophrenia and 169 demographically similar healthy volunteers. The schizophrenia domain profile order by effect size was Speed of Processing (d=-1.14), Attention/Vigilance (d=-1.04), Working Memory (d=-1.03), Verbal Learning (d=-1.02), Visual Learning (d=-0.91), and Reasoning/Problem Solving (d=-0.67). There were no significant group by sex interactions, but overall women, compared to men, showed advantages on Attention/Vigilance, Verbal Learning, and Visual Learning compared to Reasoning/Problem Solving on which men showed an advantage over women. The CMINDS can readily be employed in the assessment of cognitive deficits in neuropsychiatric disorders; particularly in large-scale studies that may benefit most from electronic data capture. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Long-range single domain array of a 5 nm pattern of supramolecules via solvent annealing in a double-sandwich cell.

PubMed

Kwon, Kiok; Park, Kangho; Jung, Hee-Tae

2018-05-10

In nanotechnology and microelectronics research, the generation of an ultradense, single-grain nanostructure with a long-range lateral order is challenging. In this paper, we report upon a new solvent-annealing method using a double-sandwich confinement to promote the formation of a large-area, single-domain array (>0.3 × 0.3 mm2) of supramolecular cylinders with a small feature size (4.7 nm). The in situ GISAXS experiment result shows the ordering process during solvent evaporation. The diffusion of the solvent molecules led to the disassembly of the supramolecules confined between the top and bottom surfaces and their subsequent mobilization, thereby producing a highly ordered hexagonal array of supramolecular materials under the double-sandwich confinement upon solvent evaporation. In addition, two key factors were found to be crucial in this process for generating highly-ordered supramolecular building blocks: (i) the presence of a top coat during solvent evaporation to provide a geometric confinement template, and (ii) the control of the solvent evaporation rate during the solvent evaporation step to provide the dendrimer sufficient time to self-assemble into the highly ordered state over a large area. Our developed approach, which can be extended to be used for a large family of supramolecules, is of critical importance in providing a new bottom-up lithographic method based on supramolecular self-assembly.

Imaging the coexistence of superconductivity and antiferromagnetism in Fe1+yTe1-xSex (x=0.1) using spin-polarized scanning tunneling microscopy

NASA Astrophysics Data System (ADS)

Zhou, Haibiao; Aluru, Ramakrishna; Tsurkan, Vladimir; Loidl, Alois; Deisenhofer, Joachim; Wahl, Peter

Magnetism has been widely thought to play an important role in unconventional superconductivity. In iron chalcogenide Fe1+yTe, the bicollinear antiferromagnetim (AFM) can be suppressed by Se doping, and consequently superconductivity appears. Though a competition between the two orders is expected, their relation has never been shown in details. Here, using spin-polarized scanning tunneling microscopy, we explore their relation at the atomic scale in an Fe1+yTe1-xSex (x=0.1) single crystal with TC = 10 K, in a regime of the phase diagram where a spin-glass phase has been detected. We clearly observe the short-range AFM order with domains of a lateral size of 10 nm embedded in a non-magnetic matrix. In addition we observe a superconducting gap with prominent coherent peaks in differential conductance spectroscopy with a gap size 2 Δ 4 mV. Surprisingly, no correlation between the superconducting properties (gap size and zero bias conductance) and the local AFM order is observed, while the coherence peaks are weakened by the existence of excess iron atoms. Our observations put constraints on theories that are aimed at explaining the relation between magnetism and unconventional superconductivity.

Ordered alternating binary polymer nanodroplet array by sequential spin dewetting.

PubMed

Bhandaru, Nandini; Das, Anuja; Salunke, Namrata; Mukherjee, Rabibrata

2014-12-10

We report a facile technique for fabricating an ordered array of nearly equal-sized mesoscale polymer droplets of two constituent polymers (polystyrene, PS and poly(methyl methacrylate), PMMA) arranged in an alternating manner on a topographically patterned substrate. The self-organized array of binary polymers is realized by sequential spin dewetting. First, a dilute solution of PMMA is spin-dewetted on a patterned substrate, resulting in an array of isolated PMMA droplets arranged along the substrate grooves due to self-organization during spin coating itself. The sample is then silanized with octadecyltrichlorosilane (OTS), and subsequently, a dilute solution of PS is spin-coated on to it, which also undergoes spin dewetting. The spin-dewetted PS drops having a size nearly equal to the pre-existing PMMA droplets position themselves between two adjacent PMMA drops under appropriate conditions, forming an alternating binary polymer droplet array. The alternating array formation takes place for a narrow range of solution concentration for both the polymers and depends on the geometry of the substrate. The size of the droplets depends on the extent of confinement, and droplets as small as 100 nm can be obtained by this method, on a suitable template. The findings open up the possibility of creating novel surfaces having ordered multimaterial domains with a potential multifunctional capability.

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

El-Gendy, AA; Bertino, M; Clifford, D

Attainment of magnetic order in nanoparticles at room temperature is an issue of critical importance for many different technologies. For ordinary ferromagnetic materials, a reduction in size leads to decreased magnetic anisotropy and results in superparamagnetic relaxations. If, instead, anisotropy could be enhanced at reduced particle sizes, then it would be possible to attain stable magnetic order at room temperature. Herein, we provide experimental evidence substantiating the synthesis of a cobalt iron carbide phase (CoFe2C) of nanoparticles. Structural characterization of the CoFe2C carbide phase was performed by transmission electron microscopy, electron diffraction and energy electron spectroscopy. X-ray diffraction was alsomore » performed as a complimentary analysis. Magnetic characterization of the carbide phase revealed a blocking temperature, TB, of 790K for particles with a domain size as small as 5 +/- 1 nm. The particles have magnetocrystalline anisotropy of 4.662 +/- 10 6 J/m(3), which is ten times larger than that of Co nanoparticles. Such colossal anisotropy leads to thermally stable long range magnetic order. Moreover, the thermal stability constant is much larger than that of the commonly used FePt nanoparticles. With thermal stability and colossal anisotropy, the CoFe2C nanoparticles have huge potential for enhanced magnetic data storage devices. (C) 2015 AIP Publishing LLC.« less

Enhanced THz extinction in arrays of resonant semiconductor particles.

PubMed

Schaafsma, Martijn C; Georgiou, Giorgos; Rivas, Jaime Gómez

2015-09-21

We demonstrate experimentally the enhanced THz extinction by periodic arrays of resonant semiconductor particles. This phenomenon is explained in terms of the radiative coupling of localized resonances with diffractive orders in the plane of the array (Rayleigh anomalies). The experimental results are described by numerical calculations using a coupled dipole model and by Finite-Difference in Time-Domain simulations. An optimum particle size for enhancing the extinction efficiency of the array is found. This optimum is determined by the frequency detuning between the localized resonances in the individual particles and the Rayleigh anomaly. The extinction calculations and measurements are also compared to near-field simulations illustrating the optimum particle size for the enhancement of the near-field.

Phase behavior of block copolymers in compressed carbon dioxide and as single domain-layer, nanolithographic etch resists for sub-10 nm pattern transfer

NASA Astrophysics Data System (ADS)

Chandler, Curran Matthew

Diblock copolymers have many interesting properties, which first and foremost include their ability to self-assemble into various ordered, regularly spaced domains with nanometer-scale feature sizes. The work in this dissertation can be logically divided into two parts -- the first and the majority of this work describes the phase behavior of certain block copolymer systems, and the second discusses real applications possible with block copolymer templates. Many compressible fluids have solvent-like properties dependent on fluid pressure and can be used as processing aids similar to liquid solvents. Here, compressed CO2 was shown to swell several thin homopolymer films, including polystyrene and polyisoprene, as measured by high pressure ellipsometry at elevated temperatures and pressures. The ellipsometric technique was modified to produce accurate data at these conditions through a custom pressure vessel design. The order-disorder transition (ODT) temperatures of several poly(styrene-bisoprene) diblock copolymers were also investigated by static birefringence when dilated with compressed CO2. Sorption of CO2 in each copolymer resulted in significant depressions of the ODT temperature as a function of fluid pressure, and the data above was used to estimate the quantitative amount of solvent in each of the diblock copolymers. These depressions were not shown to follow dilution approximation, and showed interesting, exaggerated scaling of the ODT at near-bulk polymer concentrations. The phase behavior of block copolymer surfactants was studied when blended with polymer or small molecule additives capable of selective hydrogen bonds. This work used small angle X-ray scattering (SAXS) to identify several low molecular weight systems with strong phase separation and ordered domains as small as 2--3 nanometers upon blending. One blend of a commercially-available surfactant with a small molecule additive was further developed and showed promise as a thin-film pattern transfer template. In this scenario, block copolymer thin films on domain thick with self-assembled feature sizes of only 6--7 nm were used as plasma etch resists. Here the block copolymer's pattern was successfully transferred into the underlying SiO2 substrate using CF4--based reactive ion etching. The result was a parallel, cylindrical nanostructure etched into SiO2.

Coarse-coded higher-order neural networks for PSRI object recognition. [position, scale, and rotation invariant

NASA Technical Reports Server (NTRS)

Spirkovska, Lilly; Reid, Max B.

1993-01-01

A higher-order neural network (HONN) can be designed to be invariant to changes in scale, translation, and inplane rotation. Invariances are built directly into the architecture of a HONN and do not need to be learned. Consequently, fewer training passes and a smaller training set are required to learn to distinguish between objects. The size of the input field is limited, however, because of the memory required for the large number of interconnections in a fully connected HONN. By coarse coding the input image, the input field size can be increased to allow the larger input scenes required for practical object recognition problems. We describe a coarse coding technique and present simulation results illustrating its usefulness and its limitations. Our simulations show that a third-order neural network can be trained to distinguish between two objects in a 4096 x 4096 pixel input field independent of transformations in translation, in-plane rotation, and scale in less than ten passes through the training set. Furthermore, we empirically determine the limits of the coarse coding technique in the object recognition domain.

Algorithms for Efficient Computation of Transfer Functions for Large Order Flexible Systems

NASA Technical Reports Server (NTRS)

Maghami, Peiman G.; Giesy, Daniel P.

1998-01-01

An efficient and robust computational scheme is given for the calculation of the frequency response function of a large order, flexible system implemented with a linear, time invariant control system. Advantage is taken of the highly structured sparsity of the system matrix of the plant based on a model of the structure using normal mode coordinates. The computational time per frequency point of the new computational scheme is a linear function of system size, a significant improvement over traditional, still-matrix techniques whose computational times per frequency point range from quadratic to cubic functions of system size. This permits the practical frequency domain analysis of systems of much larger order than by traditional, full-matrix techniques. Formulations are given for both open- and closed-loop systems. Numerical examples are presented showing the advantages of the present formulation over traditional approaches, both in speed and in accuracy. Using a model with 703 structural modes, the present method was up to two orders of magnitude faster than a traditional method. The present method generally showed good to excellent accuracy throughout the range of test frequencies, while traditional methods gave adequate accuracy for lower frequencies, but generally deteriorated in performance at higher frequencies with worst case errors being many orders of magnitude times the correct values.

Low statistical power in biomedical science: a review of three human research domains.

PubMed

Dumas-Mallet, Estelle; Button, Katherine S; Boraud, Thomas; Gonon, Francois; Munafò, Marcus R

2017-02-01

Studies with low statistical power increase the likelihood that a statistically significant finding represents a false positive result. We conducted a review of meta-analyses of studies investigating the association of biological, environmental or cognitive parameters with neurological, psychiatric and somatic diseases, excluding treatment studies, in order to estimate the average statistical power across these domains. Taking the effect size indicated by a meta-analysis as the best estimate of the likely true effect size, and assuming a threshold for declaring statistical significance of 5%, we found that approximately 50% of studies have statistical power in the 0-10% or 11-20% range, well below the minimum of 80% that is often considered conventional. Studies with low statistical power appear to be common in the biomedical sciences, at least in the specific subject areas captured by our search strategy. However, we also observe evidence that this depends in part on research methodology, with candidate gene studies showing very low average power and studies using cognitive/behavioural measures showing high average power. This warrants further investigation.

Low statistical power in biomedical science: a review of three human research domains

PubMed Central

Dumas-Mallet, Estelle; Button, Katherine S.; Boraud, Thomas; Gonon, Francois

2017-01-01

Studies with low statistical power increase the likelihood that a statistically significant finding represents a false positive result. We conducted a review of meta-analyses of studies investigating the association of biological, environmental or cognitive parameters with neurological, psychiatric and somatic diseases, excluding treatment studies, in order to estimate the average statistical power across these domains. Taking the effect size indicated by a meta-analysis as the best estimate of the likely true effect size, and assuming a threshold for declaring statistical significance of 5%, we found that approximately 50% of studies have statistical power in the 0–10% or 11–20% range, well below the minimum of 80% that is often considered conventional. Studies with low statistical power appear to be common in the biomedical sciences, at least in the specific subject areas captured by our search strategy. However, we also observe evidence that this depends in part on research methodology, with candidate gene studies showing very low average power and studies using cognitive/behavioural measures showing high average power. This warrants further investigation. PMID:28386409

Mode-coupling theoretical study on the roles of heterogeneous structure in rheology of ionic liquids.

PubMed

Yamaguchi, Tsuyoshi

2016-03-28

Theoretical calculations of the rheological properties of coarse-grained model ionic liquids were performed using mode-coupling theory. The nonpolar part of the cation was systematically increased in order to clarify the effects of the heterogeneous structure on shear viscosity. The shear viscosity showed a minimum as the function of the size of the nonpolar part, as had been reported in literatures. The minimum was ascribed to the interplay between the increase in the shear relaxation time and the decrease in the high-frequency shear modulus with increasing the size of the nonpolar part of the cation. The ionic liquids with symmetric charge distribution of cations were less viscous than those with asymmetric cations, which is also in harmony with experiments. The theoretical analysis demonstrated that there are two mechanisms for the higher viscosity of the asymmetric model. The first one is the direct coupling between the domain dynamics and the shear stress. The second one is that the microscopic dynamics within the polar domain is retarded due to the nonlinear coupling with the heterogeneous structure.

Protein domain organisation: adding order.

PubMed

Kummerfeld, Sarah K; Teichmann, Sarah A

2009-01-29

Domains are the building blocks of proteins. During evolution, they have been duplicated, fused and recombined, to produce proteins with novel structures and functions. Structural and genome-scale studies have shown that pairs or groups of domains observed together in a protein are almost always found in only one N to C terminal order and are the result of a single recombination event that has been propagated by duplication of the multi-domain unit. Previous studies of domain organisation have used graph theory to represent the co-occurrence of domains within proteins. We build on this approach by adding directionality to the graphs and connecting nodes based on their relative order in the protein. Most of the time, the linear order of domains is conserved. However, using the directed graph representation we have identified non-linear features of domain organization that are over-represented in genomes. Recognising these patterns and unravelling how they have arisen may allow us to understand the functional relationships between domains and understand how the protein repertoire has evolved. We identify groups of domains that are not linearly conserved, but instead have been shuffled during evolution so that they occur in multiple different orders. We consider 192 genomes across all three kingdoms of life and use domain and protein annotation to understand their functional significance. To identify these features and assess their statistical significance, we represent the linear order of domains in proteins as a directed graph and apply graph theoretical methods. We describe two higher-order patterns of domain organisation: clusters and bi-directionally associated domain pairs and explore their functional importance and phylogenetic conservation. Taking into account the order of domains, we have derived a novel picture of global protein organization. We found that all genomes have a higher than expected degree of clustering and more domain pairs in forward and reverse orientation in different proteins relative to random graphs with identical degree distributions. While these features were statistically over-represented, they are still fairly rare. Looking in detail at the proteins involved, we found strong functional relationships within each cluster. In addition, the domains tended to be involved in protein-protein interaction and are able to function as independent structural units. A particularly striking example was the human Jak-STAT signalling pathway which makes use of a set of domains in a range of orders and orientations to provide nuanced signaling functionality. This illustrated the importance of functional and structural constraints (or lack thereof) on domain organisation.

Scattering from phase-separated vesicles. I. An analytical form factor for multiple static domains

DOE PAGES

Heberle, Frederick A.; Anghel, Vinicius N. P.; Katsaras, John

2015-08-18

This is the first in a series of studies considering elastic scattering from laterally heterogeneous lipid vesicles containing multiple domains. Unique among biophysical tools, small-angle neutron scattering can in principle give detailed information about the size, shape and spatial arrangement of domains. A general theory for scattering from laterally heterogeneous vesicles is presented, and the analytical form factor for static domains with arbitrary spatial configuration is derived, including a simplification for uniformly sized round domains. The validity of the model, including series truncation effects, is assessed by comparison with simulated data obtained from a Monte Carlo method. Several aspects ofmore » the analytical solution for scattering intensity are discussed in the context of small-angle neutron scattering data, including the effect of varying domain size and number, as well as solvent contrast. Finally, the analysis indicates that effects of domain formation are most pronounced when the vesicle's average scattering length density matches that of the surrounding solvent.« less

A comparison of serial order short-term memory effects across verbal and musical domains.

PubMed

Gorin, Simon; Mengal, Pierre; Majerus, Steve

2018-04-01

Recent studies suggest that the mechanisms involved in the short-term retention of serial order information may be shared across short-term memory (STM) domains such as verbal and visuospatial STM. Given the intrinsic sequential organization of musical material, the study of STM for musical information may be particularly informative about serial order retention processes and their domain-generality. The present experiment examined serial order STM for verbal and musical sequences in participants with no advanced musical expertise and experienced musicians. Serial order STM for verbal information was assessed via a serial order reconstruction task for digit sequences. In the musical domain, serial order STM was assessed using a novel melodic sequence reconstruction task maximizing the retention of tone order information. We observed that performance for the verbal and musical tasks was characterized by sequence length as well as primacy and recency effects. Serial order errors in both tasks were characterized by similar transposition gradients and ratios of fill-in:infill errors. These effects were observed for both participant groups, although the transposition gradients and ratios of fill-in:infill errors showed additional specificities for musician participants in the musical task. The data support domain-general serial order STM effects but also suggest the existence of additional domain-specific effects. Implications for models of serial order STM in verbal and musical domains are discussed.

Signatures of Pleiotropy, Economy and Convergent Evolution in a Domain-Resolved Map of Human–Virus Protein–Protein Interaction Networks

PubMed Central

Garamszegi, Sara; Franzosa, Eric A.; Xia, Yu

2013-01-01

A central challenge in host-pathogen systems biology is the elucidation of general, systems-level principles that distinguish host-pathogen interactions from within-host interactions. Current analyses of host-pathogen and within-host protein-protein interaction networks are largely limited by their resolution, treating proteins as nodes and interactions as edges. Here, we construct a domain-resolved map of human-virus and within-human protein-protein interaction networks by annotating protein interactions with high-coverage, high-accuracy, domain-centric interaction mechanisms: (1) domain-domain interactions, in which a domain in one protein binds to a domain in a second protein, and (2) domain-motif interactions, in which a domain in one protein binds to a short, linear peptide motif in a second protein. Analysis of these domain-resolved networks reveals, for the first time, significant mechanistic differences between virus-human and within-human interactions at the resolution of single domains. While human proteins tend to compete with each other for domain binding sites by means of sequence similarity, viral proteins tend to compete with human proteins for domain binding sites in the absence of sequence similarity. Independent of their previously established preference for targeting human protein hubs, viral proteins also preferentially target human proteins containing linear motif-binding domains. Compared to human proteins, viral proteins participate in more domain-motif interactions, target more unique linear motif-binding domains per residue, and contain more unique linear motifs per residue. Together, these results suggest that viruses surmount genome size constraints by convergently evolving multiple short linear motifs in order to effectively mimic, hijack, and manipulate complex host processes for their survival. Our domain-resolved analyses reveal unique signatures of pleiotropy, economy, and convergent evolution in viral-host interactions that are otherwise hidden in the traditional binary network, highlighting the power and necessity of high-resolution approaches in host-pathogen systems biology. PMID:24339775

Signatures of pleiotropy, economy and convergent evolution in a domain-resolved map of human-virus protein-protein interaction networks.

PubMed

Garamszegi, Sara; Franzosa, Eric A; Xia, Yu

2013-01-01

A central challenge in host-pathogen systems biology is the elucidation of general, systems-level principles that distinguish host-pathogen interactions from within-host interactions. Current analyses of host-pathogen and within-host protein-protein interaction networks are largely limited by their resolution, treating proteins as nodes and interactions as edges. Here, we construct a domain-resolved map of human-virus and within-human protein-protein interaction networks by annotating protein interactions with high-coverage, high-accuracy, domain-centric interaction mechanisms: (1) domain-domain interactions, in which a domain in one protein binds to a domain in a second protein, and (2) domain-motif interactions, in which a domain in one protein binds to a short, linear peptide motif in a second protein. Analysis of these domain-resolved networks reveals, for the first time, significant mechanistic differences between virus-human and within-human interactions at the resolution of single domains. While human proteins tend to compete with each other for domain binding sites by means of sequence similarity, viral proteins tend to compete with human proteins for domain binding sites in the absence of sequence similarity. Independent of their previously established preference for targeting human protein hubs, viral proteins also preferentially target human proteins containing linear motif-binding domains. Compared to human proteins, viral proteins participate in more domain-motif interactions, target more unique linear motif-binding domains per residue, and contain more unique linear motifs per residue. Together, these results suggest that viruses surmount genome size constraints by convergently evolving multiple short linear motifs in order to effectively mimic, hijack, and manipulate complex host processes for their survival. Our domain-resolved analyses reveal unique signatures of pleiotropy, economy, and convergent evolution in viral-host interactions that are otherwise hidden in the traditional binary network, highlighting the power and necessity of high-resolution approaches in host-pathogen systems biology.

Smectic Layer Origami via Preprogrammed Photoalignment.

PubMed

Ma, Ling-Ling; Tang, Ming-Jie; Hu, Wei; Cui, Ze-Qun; Ge, Shi-Jun; Chen, Peng; Chen, Lu-Jian; Qian, Hao; Chi, Li-Feng; Lu, Yan-Qing

2017-04-01

Hierarchical architecture is of vital importance in soft materials. Focal conic domains (FCDs) of smectic liquid crystals, characterized by an ordered lamellar structure, attract intensive attention. Simultaneously tailoring the geometry and clustering characteristics of FCDs remains a challenge. Here, the 3D smectic layer origami via a 2D preprogrammed photoalignment film is accomplished. Full control of hierarchical superstructures is demonstrated, including the domain size, shape, and orientation, and the lattice symmetry of fragmented toric FCDs. The unique symmetry breaking of resultant superstructures combined with the optical anisotropy of the liquid crystals induces an intriguing polarization-dependent diffraction. This work broadens the scientific understanding of self-assembled soft materials and may inspire new opportunities for advanced functional materials and devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of the condensed-phase environment on the vibrational frequency shift of a hydrogen molecule inside clathrate hydrates

NASA Astrophysics Data System (ADS)

Powers, Anna; Scribano, Yohann; Lauvergnat, David; Mebe, Elsy; Benoit, David M.; Bačić, Zlatko

2018-04-01

We report a theoretical study of the frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the vibrational frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v =0 and v =1 vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2-H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the vibrational state of H2, v =0 or v =1 , is derived from the high-quality ab initio full-dimensional (9D) PES of the H2-H2O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H2 vibrational frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H2 change very little with the domain size, unlike the H2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the vibrational frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H2O molecules in the first three complete hydration shells around H2.

The influence of chain rigidity and the degree of sulfonation on the morphology of block copolymers as nano reactor

NASA Astrophysics Data System (ADS)

Hong, K.; Zhang, X.

2005-03-01

Polyelectrolyte block copolymer was used to form an ordered domain of ionic block as a ``nanoreactor'' due to its ability to bind oppositely charged metal ion, Zn^2+, Fe^2+ etc. The purpose of our research is to investigate the controllability of the size and morphology of domains (inorganic nano particles) by changing backbone stiffness, the charge density and the volume fraction of ionic block. Poly(styrene sulfonate) (PSS), which backbone is flexible, and poly(cyclohexadiene sulfonate) (PCHDS), which backbone is ``semiflexible'', were used as ionic blocks. We synthesized PtBS-PSS and PS-PCHDS with various degree of sulfonation and the volume fraction. Zinc oxide (ZnO) nano particles successfully formed in the ionic domain of microphase separated block copolymers. We used SANS to characterize the morphology of block copolymers and TEM for block copolymer containing ZnO nano particles. Our experimental results show that the chemistry of ``sulfonation'' of block copolymers can be successfully used to synthesize nano composite materials.

The Work Softening by Deformation-Induced Disordering and Cold Rolling of 6.5 wt pct Si Steel Thin Sheets

NASA Astrophysics Data System (ADS)

Wang, Xianglong; Li, Haoze; Zhang, Weina; Liu, Zhenyu; Wang, Guodong; Luo, Zhonghan; Zhang, Fengquan

2016-09-01

As-cast strip of 6.5 wt pct Si steel was fabricated by twin-roll strip casting. After hot rolling at 1323 K (1050 °C), thin sheets with the thickness of 0.35 mm were produced by warm rolling at 373 K (100 °C) with rolling reductions of 15, 25, 35, 45, 55, and 65 pct. Influence of warm rolling reduction on ductility was investigated by room temperature bending test. The measurement of macro-hardness showed that "work softening" could begin when the warm rolling reduction exceeded 35 pct. The room temperature ductility of the thin sheets gradually increased with the increase of warm rolling reductions, and the plastic deformation during bending began to form when the warm rolling reduction was greater than 45 pct, the 65 pct rolled thin sheet exhibited the maximum plastic deformation of about 0.6 pct during bending at room temperature, with a few small dimples having been observed on the fracture surfaces. B2-ordered domains were formed in the 15, 25, 35, 45, and 55 pct rolled specimens, and their average size decreased with the increase of warm rolling reductions. By contrast, no B2-ordered domain could be found in the 65 pct rolled specimen. It had been observed that large-ordered domains could be split into several small parts by the slip of partial super-dislocations during warm rolling, which led to significant decrease of the order degree to cause the phenomenon of deformation-induced disordering. On the basis of these results, cold rolling schedule was developed to successfully fabricate 0.25-mm-thick sheets with good surface qualities and magnetic properties from warm rolled sheets.

The effect of anti-phase domain size on the ductility of a rapidly solidified Ni3Al-Cr alloy

NASA Technical Reports Server (NTRS)

Carro, G.; Bertero, G. A.; Wittig, J. E.; Flanagan, W. F.

1989-01-01

Tensile tests on splat-quenched Ni3Al-Cr alloys showed a sharp decrease in ductility with long-time annealing. The growth of the initially very-fine-size anti-phase domains showed a tenuous correlation with ductility up to a critical size, where ductility was lost. The grain size was relatively unaffected by these annealing treatments, but the grain-boundary curvature decreased, implying less toughness. An important observation was that, for the longest annealing time, a chromium-rich precipitate formed, which the data indicate could be a boride. Miniaturized tensile tests were performed on samples which were all obtained from the same splat-quenched foil, and the various domain sizes were controlled by subsequent annealing treatments.

Neuronal differentiation of human mesenchymal stem cells in response to the domain size of graphene substrates.

PubMed

Lee, Yoo-Jung; Seo, Tae Hoon; Lee, Seula; Jang, Wonhee; Kim, Myung Jong; Sung, Jung-Suk

2018-01-01

Graphene is a noncytotoxic monolayer platform with unique physical, chemical, and biological properties. It has been demonstrated that graphene substrate may provide a promising biocompatible scaffold for stem cell therapy. Because chemical vapor deposited graphene has a two dimensional polycrystalline structure, it is important to control the individual domain size to obtain desirable properties for nano-material. However, the biological effects mediated by differences in domain size of graphene have not yet been reported. On the basis of the control of graphene domain achieved by one-step growth (1step-G, small domain) and two-step growth (2step-G, large domain) process, we found that the neuronal differentiation of bone marrow-derived human mesenchymal stem cells (hMSCs) highly depended on the graphene domain size. The defects at the domain boundaries in 1step-G graphene was higher (×8.5) and had a relatively low (13% lower) contact angle of water droplet than 2step-G graphene, leading to enhanced cell-substrate adhesion and upregulated neuronal differentiation of hMSCs. We confirmed that the strong interactions between cells and defects at the domain boundaries in 1step-G graphene can be obtained due to their relatively high surface energy, which is stronger than interactions between cells and graphene surfaces. Our results may provide valuable information on the development of graphene-based scaffold by understanding which properties of graphene domain influence cell adhesion efficacy and stem cell differentiation. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 43-51, 2018. © 2017 Wiley Periodicals, Inc.

Multiferroic Applications of Nanoarchitectured, Solution-Processed Materials

NASA Astrophysics Data System (ADS)

Buditama, Abraham Nataniel

This dissertation compiles work on sol-gel syntheses of multiferroic materials and applications thereof. Multiferroics, or materials that simultaneously exhibit multiple order parameters such as ferromagnetism, ferroelectricity, or ferroelasticity, may be fabricated by solution processing techniques. Specifically, these techniques may be used to control both the atomic and the nanoscale structures of piezoelectric lead zirconate titanate (PbZrxTi 1-xO3 or PZT) and magnetostrictive cobalt ferrite (CoFe 2O4 or CFO). The first part of this work focuses on strain-coupling PZT and CFO into a magnetoelectric composite. A mesoporous CFO framework was synthesized using block copolymer templating, which was subsequently conformally filled by PZT by atomic layer deposition (ALD). The final porosity of the film is controlled by the ALD PZT layer, and we show that this porosity influences the magnetoelectric coupling of the composite. An ex situ external electric field is applied to the composite, and samples with the greatest porosity, and thus greatest mechanical flexibility, were able to accommodate strain transfer to the CFO, resulting in a greater reduction of the sample saturation magnetization. The second part of this work focuses on using solution processing to control domain-level contributions to the material's ferroic properties. An iterative spin coating process can be used to create PZT films of arbitrary thickness. Electric domains are generally pinned in nanoscale PZT thin films, but models of PZT films on the mesoscale must consider domain reorientation. As for CFO, solution processing may be used to control the CFO grain size, which in turn limits the size of its magnetic domains, and subsequently its static magnetic properties.

Structure and texture analysis of PVC foils by neutron diffraction.

PubMed

Kalvoda, L; Dlouhá, M; Vratislav, S

2010-01-01

Crystalline order of molded and then bi-axially stretched foils prepared from atactic PVC resin is investigated by means of wide-angle neutron diffraction (WAND). The observed high-resolution WAND patterns of all samples are dominated by a sharp maximum corresponding to the inter-planar distance 0.52 nm. Two weaker maxima are also resolved at 0.62 and 0.78 nm. Intensities of the peaks vary with deformation ratios of the samples and their diffraction position. Average size of the coherently scattering domains is estimated as approximately 4-8 nm. Based on the experimental data, a novel model of crystalline order of atactic PVC is proposed. Copyright 2009 Elsevier Ltd. All rights reserved.

Line active hybrid lipids determine domain size in phase separation of saturated and unsaturated lipids.

PubMed

Brewster, Robert; Safran, Samuel A

2010-03-17

A simple model of the line activity of a hybrid lipid (e.g., POPC) with one fully saturated chain and one partially unsaturated chain demonstrates that these lipids preferentially pack at curved interfaces between phase-separated saturated and unsaturated domains. We predict that the domain sizes typically range from tens to hundreds of nm, depending on molecular interactions and parameters such as molecular volume and area per headgroup in the bulk fluid phase. The role of cholesterol is taken into account by an effective change in the headgroup areas and the domain sizes are predicted to increase with cholesterol concentration. Copyright 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Finite difference time domain analysis of chirped dielectric gratings

NASA Technical Reports Server (NTRS)

Hochmuth, Diane H.; Johnson, Eric G.

1993-01-01

The finite difference time domain (FDTD) method for solving Maxwell's time-dependent curl equations is accurate, computationally efficient, and straight-forward to implement. Since both time and space derivatives are employed, the propagation of an electromagnetic wave can be treated as an initial-value problem. Second-order central-difference approximations are applied to the space and time derivatives of the electric and magnetic fields providing a discretization of the fields in a volume of space, for a period of time. The solution to this system of equations is stepped through time, thus, simulating the propagation of the incident wave. If the simulation is continued until a steady-state is reached, an appropriate far-field transformation can be applied to the time-domain scattered fields to obtain reflected and transmitted powers. From this information diffraction efficiencies can also be determined. In analyzing the chirped structure, a mesh is applied only to the area immediately around the grating. The size of the mesh is then proportional to the electric size of the grating. Doing this, however, imposes an artificial boundary around the area of interest. An absorbing boundary condition must be applied along the artificial boundary so that the outgoing waves are absorbed as if the boundary were absent. Many such boundary conditions have been developed that give near-perfect absorption. In this analysis, the Mur absorbing boundary conditions are employed. Several grating structures were analyzed using the FDTD method.

Microstructural characterisation of proton irradiated niobium using X-ray diffraction technique

NASA Astrophysics Data System (ADS)

Dutta, Argha; Gayathri, N.; Neogy, S.; Mukherjee, P.

2018-04-01

The microstructural parameters in pure Nb, irradiated with 5 MeV proton beam have been evaluated as a function of dose using X-ray diffraction line profile analysis. In order to assess the microstructural changes in the homogeneous region and in the peak damage region of the damage energy deposition profile, X-ray diffraction patterns have been collected using two different geometries (Bragg-Brentano and parallel beam geometries). Different X-ray line profile analysis like Williamson-Hall (W-H) analysis, modified W-H analysis, double-Voigt analysis, modified Rietveld technique and convolutional multiple whole profile fitting have been employed to extract the microstructural parameters like coherent domain size, microstrain within the domain, dislocation density and arrangement of dislocations. The coherent domain size decreases drastically along with increase in microstrain and dislocation density in the first dose for both the geometries. With increasing dose, a decreasing trend in microstrain associated with decrease in dislocation density is observed for both the geometries. This is attributed to the formation of defect clusters due to irradiation which with increasing dose collapse to dislocation loops to minimise the strain in the matrix. This is corroborated with the observation of black dots and loops in the TEM images. No significant difference is observed in the trend of microstructural parameters between the homogeneous and peak damage region of the damage profile.

Harmonic Domains and Synchronization in Typically and Atypically Developing Hebrew-Speaking Children

ERIC Educational Resources Information Center

Bat-El, Outi

2009-01-01

This paper presents a comparative study of typical and atypical consonant harmony (onset-onset place harmony), with emphasis on (i) the size of the harmonic domain, (ii) the position of the harmonic domain within the prosodic word, and (iii) the maximal size of the prosodic word that exhibits consonant harmony. The data, drawn from typically and…

Coiled-coil length: Size does matter.

PubMed

Surkont, Jaroslaw; Diekmann, Yoan; Ryder, Pearl V; Pereira-Leal, Jose B

2015-12-01

Protein evolution is governed by processes that alter primary sequence but also the length of proteins. Protein length may change in different ways, but insertions, deletions and duplications are the most common. An optimal protein size is a trade-off between sequence extension, which may change protein stability or lead to acquisition of a new function, and shrinkage that decreases metabolic cost of protein synthesis. Despite the general tendency for length conservation across orthologous proteins, the propensity to accept insertions and deletions is heterogeneous along the sequence. For example, protein regions rich in repetitive peptide motifs are well known to extensively vary their length across species. Here, we analyze length conservation of coiled-coils, domains formed by an ubiquitous, repetitive peptide motif present in all domains of life, that frequently plays a structural role in the cell. We observed that, despite the repetitive nature, the length of coiled-coil domains is generally highly conserved throughout the tree of life, even when the remaining parts of the protein change, including globular domains. Length conservation is independent of primary amino acid sequence variation, and represents a conservation of domain physical size. This suggests that the conservation of domain size is due to functional constraints. © 2015 Wiley Periodicals, Inc.

Sizes of X-ray radiation coherent domains in thin SmS films and their visualization

NASA Astrophysics Data System (ADS)

Sharenkova, N. V.; Kaminskii, V. V.; Petrov, S. N.

2011-09-01

The size of X-ray radiation coherent domains (250 ± 20 Å) is determined in a thin polycrystalline SmS film using X-ray diffraction patterns (θ-2θ scanning, DRON-2 diffractometer, Cu K α radiation) and the Selyakov-Scherrer formula with allowance for the effect of microstrains. An image of this film is taken with a transmission electron microscope, and regions with a characteristic size of 240 Å are clearly visible in it. It is concluded that X-ray radiation coherent domains are visualized.

Small domain-size multiblock copolymer electrolytes

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

Pistorino, Jonathan; Eitouni, Hany Basam

2016-09-20

New block polymer electrolytes have been developed which have higher conductivities than previously reported for other block copolymer electrolytes. The new materials are constructed of multiple blocks (>5) of relatively low domain size. The small domain size provides greater protection against formation of dendrites during cycling against lithium in an electrochemical cell, while the large total molecular weight insures poor long range alignment, which leads to higher conductivity. In addition to higher conductivity, these materials can be more easily synthesized because of reduced requirements on the purity level of the reagents.

Self-organization of the magnetization in ferromagnetic nanowires

NASA Astrophysics Data System (ADS)

Ivanov, A. A.; Orlov, V. A.

2017-10-01

In this work we demonstrate the occurrence of the characteristic spatial scale in the distribution of magnetization unrelated to the domain wall or crystallite size with using computer simulation of magnetization in a polycrystalline ferromagnetic nanowire. This is the stochastic domain size. We show that this length is included in the spectral density of the pinning force of domain wall on inhomogeneities of the crystallographic anisotropy. The constant and distribution of easy axes directions of the effective anisotropy of stochastic domain, are analytically calculated.

Lithographed Superconducting Resonator Development for Next-Generation Frequency Multiplexing Readout of Transition-Edge Sensors

NASA Astrophysics Data System (ADS)

Faramarzi, F.; De Haan, T.; Kusaka, A.; Lee, A.; Neuhauser, B.; Plambeck, R.; Raum, C.; Suzuki, A.; Westbrook, B.

2018-03-01

Ground-based cosmic microwave background (CMB) experiments are undergoing a period of exponential growth. Current experiments are observing with 1000-10,000 detectors, and the next-generation experiment (CMB stage 4) is proposing to deploy approximately 500,000 detectors. This order of magnitude increase in detector count will require a new approach for readout electronics. We have developed superconducting resonators for next-generation frequency-domain multiplexing (fMUX) readout architecture. Our goal is to reduce the physical size of resonators, such that resonators and detectors can eventually be integrated on a single wafer. To reduce the size of these resonators, we have designed spiral inductors and interdigitated capacitors that resonate around 10-100 MHz, an order of magnitude higher frequency compared to current fMUX readout systems. The higher frequency leads to a wider bandwidth and would enable higher multiplexing factor than the current ˜ 50 detectors per readout channel. We will report on the simulation, fabrication method, characterization technique, and measurement of quality factor of these resonators.

A third-order silicon racetrack add-drop filter with a moderate feature size

NASA Astrophysics Data System (ADS)

Wang, Ying; Zhou, Xin; Chen, Qian; Shao, Yue; Chen, Xiangning; Huang, Qingzhong; Jiang, Wei

2018-01-01

In this work, we design and fabricate a highly compact third-order racetrack add-drop filter consisting of silicon waveguides with modified widths on a silicon-on-insulator (SOI) wafer. Compared to the previous approach that requires an exceedingly narrow coupling gap less than 100nm, we propose a new approach that enlarges the minimum feature size of the whole device to be 300 nm to reduce the process requirement. The three-dimensional finite-difference time-domain (3D-FDTD) method is used for simulation. Experiment results show good agreement with simulation results in property. In the experiment, the filter shows a nearly box-like channel dropping response, which has a large flat 3-dB bandwidth ({3 nm), relatively large FSR ({13.3 nm) and out-of-band rejection larger than 14 dB at the drop port with a footprint of 0.0006 mm2 . The device is small and simple enough to have a wide range of applications in large scale on-chip photonic integration circuits.

Investigation of half-quantized fluxoid states in strontium ruthenate mesoscopic superconducting rings

NASA Astrophysics Data System (ADS)

Jang, Joonho

Spin-triplet superconductors can support exotic objects, such as chiral edge currents and half-quantum vortices (HQVs) characterized by the nontrivial winding of the spin structure. In this dissertation, we present cantilever magnetometry measurements performed on mesoscopic samples of Sr2RuO 4, a spin-triplet superconductor. Satisfying the total anti-symmetric property of the Cooper pair wave function, Sr2RuO4 is theoretically suggested to have angular momentum L = 1 and form domain structure with px +/- ipy order parameter that corresponds to Lz = +/-1. For micron-size samples, only a few number of domains would exist and signatures of domain walls and edge currents are expected to be measurable with current sensitivity. From the measurements of fluctuations of magnetic signal and the signatures of vortex entries, we found no evidence to support broken time-reversal symmetry (TRS) in these crystals. We argue that various scenarios exist to explain the negative result while still assuming the TRS breaking chiral order parameter. Also, micron-size annular-shaped Sr2RuO4 crystals were used to observe transitions between fluxoid states. Our observation of half-integer transitions is consistent with the existence of HQVs in a spin-triplet superconductor. Stability of the half states with an in-plane magnetic field is explained by the spin polarization in consequence of a differential phase winding of up and down spin components. These spin and charge dynamics can also be revealed in the current response to phase winding across a weak-link junction. The junctions were fabricated within ring geometry. The phase is varied by the external magnetic field and the current is calculated by measuring the magnetic moments of the ring. The current response shows second harmonics when the in-plane magnetic field is applied, and the data are successfully fitted when Gibbs free energy is expressed with additional spin degree of freedom. Our observations are consistent with spin-triplet pairing of the Sr 2RuO4, while requiring more investigations to confirm px +/- ipy order parameter in the crystal.

Domain size polydispersity effects on the structural and dynamical properties in lipid monolayers with phase coexistence.

PubMed

Rufeil-Fiori, Elena; Banchio, Adolfo J

2018-03-07

In lipid monolayers with phase coexistence, domains of the liquid-condensed phase always present size polydispersity. However, very few theoretical works consider size distribution effects on the monolayer properties. Because of the difference in surface densities, domains have excess dipolar density with respect to the surrounding liquid expanded phase, originating a dipolar inter-domain interaction. This interaction depends on the domain area, and hence the presence of a domain size distribution is associated with interaction polydispersity. Inter-domain interactions are fundamental to understanding the structure and dynamics of the monolayer. For this reason, it is expected that polydispersity significantly alters monolayer properties. By means of Brownian dynamics simulations, we study the radial distribution function (RDF), the average mean square displacement and the average time-dependent self-diffusion coefficient, D(t), of lipid monolayers with normally distributed size domains. For this purpose, we vary the relevant system parameters, polydispersity and interaction strength, within a range of experimental interest. We also analyze the consequences of using a monodisperse model to determine the interaction strength from an experimental RDF. We find that polydispersity strongly affects the value of the interaction strength, which is greatly underestimated if polydispersity is not considered. However, within a certain range of parameters, the RDF obtained from a polydisperse model can be well approximated by that of a monodisperse model, by suitably fitting the interaction strength, even for 40% polydispersities. For small interaction strengths or small polydispersities, the polydisperse systems obtained from fitting the experimental RDF have an average mean square displacement and D(t) in good agreement with that of the monodisperse system.

Thermal Unfolding Simulations of Bacterial Flagellin: Insight into its Refolding Before Assembly

PubMed Central

Chng, Choon-Peng; Kitao, Akio

2008-01-01

Flagellin is the subunit of the bacterial filament, the micrometer-long propeller of a bacterial flagellum. The protein is believed to undergo unfolding for transport through the channel of the filament and to refold in a chamber at the end of the channel before being assembled into the growing filament. We report a thermal unfolding simulation study of S. typhimurium flagellin in aqueous solution as an attempt to gain atomic-level insight into the refolding process. Each molecule comprises two filament-core domains {D0, D1} and two hypervariable-region domains {D2, D3}. D2 can be separated into subdomains D2a and D2b. We observed a similar unfolding order of the domains as reported in experimental thermal denaturation. D2a and D3 exhibited high thermal stability and contained persistent three-stranded β-sheets in the denatured state which could serve as folding cores to guide refolding. A recent mutagenesis study on flagellin stability seems to suggest the importance of the folding cores. Using crude size estimates, our data suggests that the chamber might be large enough for either denatured hypervariable-region domains or filament-core domains, but not whole flagellin; this implicates a two-staged refolding process. PMID:18263660

Magnetic stripes and skyrmions with helicity reversals.

PubMed

Yu, Xiuzhen; Mostovoy, Maxim; Tokunaga, Yusuke; Zhang, Weizhu; Kimoto, Koji; Matsui, Yoshio; Kaneko, Yoshio; Nagaosa, Naoto; Tokura, Yoshinori

2012-06-05

It was recently realized that topological spin textures do not merely have mathematical beauty but can also give rise to unique functionalities of magnetic materials. An example is the skyrmion--a nano-sized bundle of noncoplanar spins--that by virtue of its nontrivial topology acts as a flux of magnetic field on spin-polarized electrons. Lorentz transmission electron microscopy recently emerged as a powerful tool for direct visualization of skyrmions in noncentrosymmetric helimagnets. Topologically, skyrmions are equivalent to magnetic bubbles (cylindrical domains) in ferromagnetic thin films, which were extensively explored in the 1970s for data storage applications. In this study we use Lorentz microscopy to image magnetic domain patterns in the prototypical magnetic oxide-M-type hexaferrite with a hint of scandium. Surprisingly, we find that the magnetic bubbles and stripes in the hexaferrite have a much more complex structure than the skyrmions and spirals in helimagnets, which we associate with the new degree of freedom--helicity (or vector spin chirality) describing the direction of spin rotation across the domain walls. We observe numerous random reversals of helicity in the stripe domain state. Random helicity of cylindrical domain walls coexists with the positional order of magnetic bubbles in a triangular lattice. Most unexpectedly, we observe regular helicity reversals inside skyrmions with an unusual multiple-ring structure.

Fast algorithms for chiral fermions in 2 dimensions

NASA Astrophysics Data System (ADS)

Hyka (Xhako), Dafina; Osmanaj (Zeqirllari), Rudina

2018-03-01

In lattice QCD simulations the formulation of the theory in lattice should be chiral in order that symmetry breaking happens dynamically from interactions. In order to guarantee this symmetry on the lattice one uses overlap and domain wall fermions. On the other hand high computational cost of lattice QCD simulations with overlap or domain wall fermions remains a major obstacle of research in the field of elementary particles. We have developed the preconditioned GMRESR algorithm as fast inverting algorithm for chiral fermions in U(1) lattice gauge theory. In this algorithm we used the geometric multigrid idea along the extra dimension.The main result of this work is that the preconditioned GMRESR is capable to accelerate the convergence 2 to 12 times faster than the other optimal algorithms (SHUMR) for different coupling constant and lattice 32x32. Also, in this paper we tested it for larger lattice size 64x64. From the results of simulations we can see that our algorithm is faster than SHUMR. This is a very promising result that this algorithm can be adapted also in 4 dimension.

Photonic crystal ring resonator based optical filters for photonic integrated circuits

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

Robinson, S., E-mail: mail2robinson@gmail.com

In this paper, a two Dimensional (2D) Photonic Crystal Ring Resonator (PCRR) based optical Filters namely Add Drop Filter, Bandpass Filter, and Bandstop Filter are designed for Photonic Integrated Circuits (PICs). The normalized output response of the filters is obtained using 2D Finite Difference Time Domain (FDTD) method and the band diagram of periodic and non-periodic structure is attained by Plane Wave Expansion (PWE) method. The size of the device is minimized from a scale of few tens of millimeters to the order of micrometers. The overall size of the filters is around 11.4 μm × 11.4 μm which ismore » highly suitable of photonic integrated circuits.« less

First-principles analysis of phase stability in layered-layered composite cathodes for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Iddir, Hakim; Benedek, Roy; Voltage Fade Team

2014-03-01

The atomic order in layered-layered composites with composition xLi2MnO3 .(1-x)LiCoO2 is investigated with first-principles calculations at the GGA +U level. This material, and others in its class, are often regarded as solid solutions, however, only a minute solubility of Li2MnO3 in a LiCoO2 host is predicted. Calculations of Co-vacancy formation and migration energies in LiCoO2 are presented, to elucidate the rate of vacancy-mediated ordering in the transition-metal-layer, and thus determine whether low vacancy mobility could result in slow equilibration. The Co-vacancy formation energy can be predicted only to within a range, because of uncertainty in the chemical potentials. Predicted migration energies, however, are approximately 1 eV, small enough to be consistent with rapid ordering in the transition metal layer, and therefore separated Li2MnO3 and LiCoO2 phases. The relatively small (of the order of a few nm) Li2MnO3 domain sizes observed with TEM in some xLi2MnO3 .(1-x)LiMO2 composites may result from other factors, such as coherency strain, which perhaps block further domain coarsening in these materials. Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

Size-Dependent Couple-Stress Fluid Mechanics and Application to the Lid-Driven Square Cavity Flow

NASA Astrophysics Data System (ADS)

Hajesfandiari, Arezoo; Dargush, Gary; Hadjesfandiari, Ali

2012-11-01

We consider a size-dependent fluid that possesses a characteristic material length l, which becomes increasingly important as the characteristic geometric dimension of the problem decreases. The term involving l in the modified Navier-Stokes equations ρDv/Dt = - ∇ p + μ∇2 v - μl2∇2∇2 v generates a new mechanism for energy dissipation in the flow, which has stabilizing effects at high Reynolds numbers. Interestingly, the idea of adding a fourth order term has been introduced long ago in the form of an artificial dissipation term to stabilize numerical results in CFD methods. However, this additional dissipation has no physical basis for inclusion in the differential equations of motion and is never considered at the boundary nodes of the domain. On the other hand, our couple stress-related dissipation is physically motivated, resulting from the consistent application of energy principles, kinematics and boundary conditions. We should note, in particular, that the boundary conditions in the size-dependent theory must be modified from the classical case to include specification of either rotations or moment-tractions. In order to validate the approach, we focus on the lid-driven cavity problem.

System design of an optical interferometer based on compressive sensing

NASA Astrophysics Data System (ADS)

Liu, Gang; Wen, De-Sheng; Song, Zong-Xi

2018-07-01

In this paper, we develop a new optical interferometric telescope architecture based on compressive sensing (CS) theory. Traditional optical telescopes with large apertures must be large in size, heavy and have high-power consumption, which limits the development of space-based telescopes. A turning point has occurred in the advent of imaging technology that utilizes Fourier-domain interferometry. This technology can reduce the system size, weight and power consumption by an order of magnitude compared to traditional optical telescopes at the same resolution. CS theory demonstrates that incomplete and noisy Fourier measurements may suffice for the exact reconstruction of sparse or compressible signals. Our proposed architecture combines advantages from the two frameworks, and the performance is evaluated through simulations. The results indicate the ability to efficiently sample spatial frequencies, while being lightweight and compact in size. Another attractive property of our architecture is the strong denoising ability for Gaussian noise.

Particle systems for adaptive, isotropic meshing of CAD models

PubMed Central

Levine, Joshua A.; Whitaker, Ross T.

2012-01-01

We present a particle-based approach for generating adaptive triangular surface and tetrahedral volume meshes from computer-aided design models. Input shapes are treated as a collection of smooth, parametric surface patches that can meet non-smoothly on boundaries. Our approach uses a hierarchical sampling scheme that places particles on features in order of increasing dimensionality. These particles reach a good distribution by minimizing an energy computed in 3D world space, with movements occurring in the parametric space of each surface patch. Rather than using a pre-computed measure of feature size, our system automatically adapts to both curvature as well as a notion of topological separation. It also enforces a measure of smoothness on these constraints to construct a sizing field that acts as a proxy to piecewise-smooth feature size. We evaluate our technique with comparisons against other popular triangular meshing techniques for this domain. PMID:23162181

Direct Solve of Electrically Large Integral Equations for Problem Sizes to 1M Unknowns

NASA Technical Reports Server (NTRS)

Shaeffer, John

2008-01-01

Matrix methods for solving integral equations via direct solve LU factorization are presently limited to weeks to months of very expensive supercomputer time for problems sizes of several hundred thousand unknowns. This report presents matrix LU factor solutions for electromagnetic scattering problems for problem sizes to one million unknowns with thousands of right hand sides that run in mere days on PC level hardware. This EM solution is accomplished by utilizing the numerical low rank nature of spatially blocked unknowns using the Adaptive Cross Approximation for compressing the rank deficient blocks of the system Z matrix, the L and U factors, the right hand side forcing function and the final current solution. This compressed matrix solution is applied to a frequency domain EM solution of Maxwell's equations using standard Method of Moments approach. Compressed matrix storage and operations count leads to orders of magnitude reduction in memory and run time.

Distinct polymer physics principles govern chromatin dynamics in mouse and Drosophila topological domains.

PubMed

Ea, Vuthy; Sexton, Tom; Gostan, Thierry; Herviou, Laurie; Baudement, Marie-Odile; Zhang, Yunzhe; Berlivet, Soizik; Le Lay-Taha, Marie-Noëlle; Cathala, Guy; Lesne, Annick; Victor, Jean-Marc; Fan, Yuhong; Cavalli, Giacomo; Forné, Thierry

2015-08-15

In higher eukaryotes, the genome is partitioned into large "Topologically Associating Domains" (TADs) in which the chromatin displays favoured long-range contacts. While a crumpled/fractal globule organization has received experimental supports at higher-order levels, the organization principles that govern chromatin dynamics within these TADs remain unclear. Using simple polymer models, we previously showed that, in mouse liver cells, gene-rich domains tend to adopt a statistical helix shape when no significant locus-specific interaction takes place. Here, we use data from diverse 3C-derived methods to explore chromatin dynamics within mouse and Drosophila TADs. In mouse Embryonic Stem Cells (mESC), that possess large TADs (median size of 840 kb), we show that the statistical helix model, but not globule models, is relevant not only in gene-rich TADs, but also in gene-poor and gene-desert TADs. Interestingly, this statistical helix organization is considerably relaxed in mESC compared to liver cells, indicating that the impact of the constraints responsible for this organization is weaker in pluripotent cells. Finally, depletion of histone H1 in mESC alters local chromatin flexibility but not the statistical helix organization. In Drosophila, which possesses TADs of smaller sizes (median size of 70 kb), we show that, while chromatin compaction and flexibility are finely tuned according to the epigenetic landscape, chromatin dynamics within TADs is generally compatible with an unconstrained polymer configuration. Models issued from polymer physics can accurately describe the organization principles governing chromatin dynamics in both mouse and Drosophila TADs. However, constraints applied on this dynamics within mammalian TADs have a peculiar impact resulting in a statistical helix organization.

Mapping of non-numerical domains on space: a systematic review and meta-analysis.

PubMed

Macnamara, Anne; Keage, Hannah A D; Loetscher, Tobias

2018-02-01

The spatial numerical association of response code (SNARC) effect is characterized by low numbers mapped to the left side of space and high numbers mapped to the right side of space. In addition to numbers, SNARC-like effects have been found in non-numerical magnitude domains such as time, size, letters, luminance, and more, whereby the smaller/earlier and larger/later magnitudes are typically mapped to the left and right of space, respectively. The purpose of this systematic and meta-analytic review was to identify and summarise all empirical papers that have investigated horizontal (left-right) SNARC-like mappings using non-numerical stimuli. A systematic search was conducted using EMBASE, Medline, and PsycINFO, where 2216 publications were identified, with 57 papers meeting the inclusion criteria (representing 112 experiments). Ninety-five of these experiments were included in a meta-analysis, resulting in an overall effect size of d = .488 for a SNARC-like effect. Additional analyses revealed a significant effect size advantage for explicit instruction tasks compared with implicit instructions, yet yielded no difference for the role of expertise on SNARC-like effects. There was clear evidence for a publication bias in the field, but the impact of this bias is likely to be modest, and it is unlikely that the SNARC-like effect is a pure artefact of this bias. The similarities in the response properties for the spatial mappings of numerical and non-numerical domains support the concept of a general higher order magnitude system. Yet, further research will need to be conducted to identify all the factors modulating the strength of the spatial associations.

Primordial black hole and wormhole formation by domain walls

NASA Astrophysics Data System (ADS)

Deng, Heling; Garriga, Jaume; Vilenkin, Alexander

2017-04-01

In theories with a broken discrete symmetry, Hubble sized spherical domain walls may spontaneously nucleate during inflation. These objects are subsequently stretched by the inflationary expansion, resulting in a broad distribution of sizes. The fate of the walls after inflation depends on their radius. Walls smaller than a critical radius fall within the cosmological horizon early on and collapse due to their own tension, forming ordinary black holes. But if a wall is large enough, its repulsive gravitational field becomes dominant much before the wall can fall within the cosmological horizon. In this ``supercritical'' case, a wormhole throat develops, connecting the ambient exterior FRW universe with an interior baby universe, where the exponential growth of the wall radius takes place. The wormhole pinches off in a time-scale comparable to its light-crossing time, and black holes are formed at its two mouths. As discussed in previous work, the resulting black hole population has a wide distribution of masses and can have significant astrophysical effects. The mechanism of black hole formation has been previously studied for a dust-dominated universe. Here we investigate the case of a radiation-dominated universe, which is more relevant cosmologically, by using numerical simulations in order to find the initial mass of a black hole as a function of the wall size at the end of inflation. For large supercritical domain walls, this mass nearly saturates the upper bound according to which the black hole cannot be larger than the cosmological horizon. We also find that the subsequent accretion of radiation satisfies a scaling relation, resulting in a mass increase by about a factor of 2.

Primordial black hole and wormhole formation by domain walls

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

Deng, Heling; Garriga, Jaume; Vilenkin, Alexander, E-mail: heling.deng@tufts.edu, E-mail: garriga@cosmos.phy.tufts.edu, E-mail: vilenkin@cosmos.phy.tufts.edu

In theories with a broken discrete symmetry, Hubble sized spherical domain walls may spontaneously nucleate during inflation. These objects are subsequently stretched by the inflationary expansion, resulting in a broad distribution of sizes. The fate of the walls after inflation depends on their radius. Walls smaller than a critical radius fall within the cosmological horizon early on and collapse due to their own tension, forming ordinary black holes. But if a wall is large enough, its repulsive gravitational field becomes dominant much before the wall can fall within the cosmological horizon. In this ''supercritical'' case, a wormhole throat develops, connectingmore » the ambient exterior FRW universe with an interior baby universe, where the exponential growth of the wall radius takes place. The wormhole pinches off in a time-scale comparable to its light-crossing time, and black holes are formed at its two mouths. As discussed in previous work, the resulting black hole population has a wide distribution of masses and can have significant astrophysical effects. The mechanism of black hole formation has been previously studied for a dust-dominated universe. Here we investigate the case of a radiation-dominated universe, which is more relevant cosmologically, by using numerical simulations in order to find the initial mass of a black hole as a function of the wall size at the end of inflation. For large supercritical domain walls, this mass nearly saturates the upper bound according to which the black hole cannot be larger than the cosmological horizon. We also find that the subsequent accretion of radiation satisfies a scaling relation, resulting in a mass increase by about a factor of 2.« less

A new scaling approach for the mesoscale simulation of magnetic domain structures using Monte Carlo simulations

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

Radhakrishnan, B.; Eisenbach, M.; Burress, Timothy A.

2017-01-24

A new scaling approach has been proposed for the spin exchange and the dipole–dipole interaction energy as a function of the system size. The computed scaling laws are used in atomistic Monte Carlo simulations of magnetic moment evolution to predict the transition from single domain to a vortex structure as the system size increases. The width of a 180° – domain wall extracted from the simulated structures is in close agreement with experimentally values for an F–Si alloy. In conclusion, the transition size from a single domain to a vortex structure is also in close agreement with theoretically predicted andmore » experimentally measured values for Fe.« less

Readiness for the Patient-Centered Medical Home: Structural Capabilities of Massachusetts Primary Care Practices

PubMed Central

Friedberg, Mark W.; Safran, Dana G.; Coltin, Kathryn L.; Dresser, Marguerite

2008-01-01

Background The Patient-Centered Medical Home (PCMH), a popular model for primary care reorganization, includes several structural capabilities intended to enhance quality of care. The extent to which different types of primary care practices have adopted these capabilities has not been previously studied. Objective To measure the prevalence of recommended structural capabilities among primary care practices and to determine whether prevalence varies among practices of different size (number of physicians) and administrative affiliation with networks of practices. Design Cross-sectional analysis. Participants One physician chosen at random from each of 412 primary care practices in Massachusetts was surveyed about practice capabilities during 2007. Practice size and network affiliation were obtained from an existing database. Measurements Presence of 13 structural capabilities representing 4 domains relevant to quality: patient assistance and reminders, culture of quality, enhanced access, and electronic health records (EHRs). Main Results Three hundred eight (75%) physicians responded, representing practices with a median size of 4 physicians (range 2–74). Among these practices, 64% were affiliated with 1 of 9 networks. The prevalence of surveyed capabilities ranged from 24% to 88%. Larger practice size was associated with higher prevalence for 9 of the 13 capabilities spanning all 4 domains (P < 0.05). Network affiliation was associated with higher prevalence of 5 capabilities (P < 0.05) in 3 domains. Associations were not substantively altered by statistical adjustment for other practice characteristics. Conclusions Larger and network-affiliated primary care practices are more likely than smaller, non-affiliated practices to have adopted several recommended capabilities. In order to achieve PCMH designation, smaller non-affiliated practices may require the greatest investments. Electronic supplementary material The online version of this article (doi:10.1007/s11606-008-0856-x) contains supplementary material, which is available to authorized users. PMID:19050977

Controlled phase evolution and the occurrence of single domain CoFe2O4 nanoparticles synthesized by PVA assisted sol-gel method

NASA Astrophysics Data System (ADS)

Srinivasa Rao, K.; Ranga Nayakulu, S. V.; Chaitanya Varma, M.; Choudary, G. S. V. R. K.; Rao, K. H.

2018-04-01

The present investigation describes the development of cobalt ferrite nanoparticles having size less than 10 nm, by a sol-gel method using polyvinyl alcohol as chelating agent. X-ray results show all the samples, annealed above 700 °C have spinel structure. The information about phase evolution with reaction temperatures was obtained by subjecting the as-prepared powder for DSC/TGA study. High saturation magnetization of 84.63 emu/g has been observed for a particle size of 8.1 nm, a rare event reported till date. The dM/dH versus H curves suggest that the transition from single domain state to multi-domain state occurs with increasing annealing temperature and the critical size for the single domain nature of CoFe2O4 is around 6.5 nm. The estimated critical diameter for single domain particle (6.7 nm) is in good agreement with that (6.5 nm) obtained from Transmission Electron Micrographs. The highest coercivity (1645 Oe) has been found for a particle of size 6.5 nm.

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

El-Gendy, Ahmed A., E-mail: aelgendy@vcu.edu, E-mail: ecarpenter2@vcu.edu, E-mail: snkhanna@vcu.edu; Nanotechnology and Nanometrology Lab., National institute for standards; Bertino, Massimo

Attainment of magnetic order in nanoparticles at room temperature is an issue of critical importance for many different technologies. For ordinary ferromagnetic materials, a reduction in size leads to decreased magnetic anisotropy and results in superparamagnetic relaxations. If, instead, anisotropy could be enhanced at reduced particle sizes, then it would be possible to attain stable magnetic order at room temperature. Herein, we provide experimental evidence substantiating the synthesis of a cobalt iron carbide phase (CoFe{sub 2}C) of nanoparticles. Structural characterization of the CoFe{sub 2}C carbide phase was performed by transmission electron microscopy, electron diffraction and energy electron spectroscopy. X-ray diffractionmore » was also performed as a complimentary analysis. Magnetic characterization of the carbide phase revealed a blocking temperature, T{sub B}, of 790 K for particles with a domain size as small as 5 ± 1 nm. The particles have magnetocrystalline anisotropy of 4.6 ± 2 × 10{sup 6 }J/m{sup 3}, which is ten times larger than that of Co nanoparticles. Such colossal anisotropy leads to thermally stable long range magnetic order. Moreover, the thermal stability constant is much larger than that of the commonly used FePt nanoparticles. With thermal stability and colossal anisotropy, the CoFe{sub 2}C nanoparticles have huge potential for enhanced magnetic data storage devices.« less

Self-Assembling Block Copolymer Resist Mixtures towards Lithographic Resists for Sub-10 nm Features

NASA Astrophysics Data System (ADS)

Chandler, Curran; Daga, Vikram; Watkins, James

2009-03-01

Significant improvements in 193 nm photolithography have enabled the extension of device feature sizes beyond the 45 nm and 32 nm nodes, yet uncertainty lies beyond 22 nm features as no single replacement has emerged. Here we show that low molecular weight, nonionic block copolymer surfactant blends are capable of self-assembling into highly ordered domains with feature sizes on the order of 5 nm. These surfactants, most of which lack the required χN for microphase separation on their own, exhibit strong segregation and long-range order upon addition of a component capable of multi-point hydrogen bonding that is specific for one of the blocks in the copolymer. This has been demonstrated by our SAXS data for several Pluronic (PEO-b-PPO-b-PEO) and Brij (PEO-b-[CH2]nCH3) surfactants of various molecular weights and PEO volume fractions. Furthermore, we employ these highly-ordered systems as thin film, nanolithographic etch masks for the transfer of sub-10 nm patterns into silicon-based substrates. Small molecule, hydrogen bonding additives containing aromatic or silsesquioxane structure are also used to tune etch contrast between the blocks which is important for reducing line edge roughness (LER) of such small features.

Method for increasing thermostability in cellulase ennzymes

DOEpatents

Adney, William S.; Thomas, Steven R.; Baker, John O.; Himmel, Michael E.; Chou, Yat-Chen

1998-01-01

The gene encoding Acidothermus cellulolyticus E1 endoglucanase is cloned and expressed in Pichia pastoris. A new modified E1 endoglucanase enzyme comprising the catalytic domain of the full size E1 enzyme demonstrates enhanced thermostability and is produced by two methods. The first method of producing the new modified E1 is proteolytic cleavage to remove the cellulose binding domain and linker peptide of the full size E1. The second method of producing the new modified E1 is genetic truncation of the gene encoding the full size E1 so that the catalytic domain is expressed in the expression product.

Coherent combining pulse bursts in time domain

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

Galvanauskas, Almantas

A beam combining and pulse stacking technique is provided that enhances laser pulse energy by coherent stacking pulse bursts (i.e. non-periodic pulsed signals) in time domain. This energy enhancement is achieved by using various configurations of Fabry-Perot, Gires-Tournois and other types of resonant cavities, so that a multiple-pulse burst incident at either a single input or multiple inputs of the system produces an output with a solitary pulse, which contains the summed energy of the incident multiple pulses from all beams. This disclosure provides a substantial improvement over conventional coherent-combining methods in that it achieves very high pulse energies usingmore » a relatively small number of combined laser systems, thus providing with orders of magnitude reduction in system size, complexity, and cost compared to current combining approaches.« less

Ubiquitous Robotic Technology for Smart Manufacturing System.

PubMed

Wang, Wenshan; Zhu, Xiaoxiao; Wang, Liyu; Qiu, Qiang; Cao, Qixin

2016-01-01

As the manufacturing tasks become more individualized and more flexible, the machines in smart factory are required to do variable tasks collaboratively without reprogramming. This paper for the first time discusses the similarity between smart manufacturing systems and the ubiquitous robotic systems and makes an effort on deploying ubiquitous robotic technology to the smart factory. Specifically, a component based framework is proposed in order to enable the communication and cooperation of the heterogeneous robotic devices. Further, compared to the service robotic domain, the smart manufacturing systems are often in larger size. So a hierarchical planning method was implemented to improve the planning efficiency. A test bed of smart factory is developed. It demonstrates that the proposed framework is suitable for industrial domain, and the hierarchical planning method is able to solve large problems intractable with flat methods.

Ubiquitous Robotic Technology for Smart Manufacturing System

PubMed Central

Zhu, Xiaoxiao; Wang, Liyu; Qiu, Qiang; Cao, Qixin

2016-01-01

As the manufacturing tasks become more individualized and more flexible, the machines in smart factory are required to do variable tasks collaboratively without reprogramming. This paper for the first time discusses the similarity between smart manufacturing systems and the ubiquitous robotic systems and makes an effort on deploying ubiquitous robotic technology to the smart factory. Specifically, a component based framework is proposed in order to enable the communication and cooperation of the heterogeneous robotic devices. Further, compared to the service robotic domain, the smart manufacturing systems are often in larger size. So a hierarchical planning method was implemented to improve the planning efficiency. A test bed of smart factory is developed. It demonstrates that the proposed framework is suitable for industrial domain, and the hierarchical planning method is able to solve large problems intractable with flat methods. PMID:27446206

Hubris and Humility Effect and the Domain-Masculine Intelligence Type in Two Countries: Colombia and the UK.

PubMed

Storek, Josephine; Furnham, Adrian

2016-11-23

Spanish-speaking Colombian (n = 50) and English-speaking British (N = 52) adults completed a self-assessed intelligence measure that yielded a score on domain-masculine intelligence (DMIQ), a composite of mathematical/logical and spatial intelligences. They also completed a Sex Role inventory in order to establish their masculinity and femininity. Males in both countries gave significantly higher self-estimates (Colombia: Males 110.36, Females 100.75, d = .94; England: Males 114.37, Females 105.75, d = .86; both p < .01) than females but sex role was note related to DMIQ. However there was a positive relationship between masculinity and DMIQ (r = .45, r = .39, p < .01), but only for males. Cultural issues in self-assessed intelligence and limitations, particularly sample size of this exploratory study are considered.

Domain and network aggregation of CdTe quantum rods within Langmuir Blodgett monolayers

NASA Astrophysics Data System (ADS)

Zimnitsky, Dmitry; Xu, Jun; Lin, Zhiqun; Tsukruk, Vladimir V.

2008-05-01

Control over the organization of quantum rods was demonstrated by changing the surface area at the air-liquid interface by means of the Langmuir-Blodgett (LB) technique. The LB isotherm of CdTe quantum rods capped with a mixture of alkylphosphines shows a transition point in the liquid-solid state, which is caused by the inter-rod reorganization. As we observed, at low surface pressure the quantum rods are assembled into round-shaped aggregates composed of a monolayer of nanorods packed in limited-size clusters with random orientation. The increase of the surface pressure leads to the rearrangement of these aggregates into elongated bundles composed of uniformly oriented nanorod clusters. Further compression results in denser packing of nanorods aggregates and in the transformation of monolayered domains into a continuous network of locally ordered quantum rods.

Domain-Generality of Timing-Based Serial Order Processes in Short-Term Memory: New Insights from Musical and Verbal Domains

PubMed Central

Kowialiewski, Benjamin; Majerus, Steve

2016-01-01

Several models in the verbal domain of short-term memory (STM) consider a dissociation between item and order processing. This view is supported by data demonstrating that different types of time-based interference have a greater effect on memory for the order of to-be-remembered items than on memory for the items themselves. The present study investigated the domain-generality of the item versus serial order dissociation by comparing the differential effects of time-based interfering tasks, such as rhythmic interference and articulatory suppression, on item and order processing in verbal and musical STM domains. In Experiment 1, participants had to maintain sequences of verbal or musical information in STM, followed by a probe sequence, this under different conditions of interference (no-interference, rhythmic interference, articulatory suppression). They were required to decide whether all items of the probe list matched those of the memory list (item condition) or whether the order of the items in the probe sequence matched the order in the memory list (order condition). In Experiment 2, participants performed a serial order probe recognition task for verbal and musical sequences ensuring sequential maintenance processes, under no-interference or rhythmic interference conditions. For Experiment 1, serial order recognition was not significantly more impacted by interfering tasks than was item recognition, this for both verbal and musical domains. For Experiment 2, we observed selective interference of the rhythmic interference condition on both musical and verbal order STM tasks. Overall, the results suggest a similar and selective sensitivity to time-based interference for serial order STM in verbal and musical domains, but only when the STM tasks ensure sequential maintenance processes. PMID:27992565

Domain-Generality of Timing-Based Serial Order Processes in Short-Term Memory: New Insights from Musical and Verbal Domains.

PubMed

Gorin, Simon; Kowialiewski, Benjamin; Majerus, Steve

2016-01-01

Several models in the verbal domain of short-term memory (STM) consider a dissociation between item and order processing. This view is supported by data demonstrating that different types of time-based interference have a greater effect on memory for the order of to-be-remembered items than on memory for the items themselves. The present study investigated the domain-generality of the item versus serial order dissociation by comparing the differential effects of time-based interfering tasks, such as rhythmic interference and articulatory suppression, on item and order processing in verbal and musical STM domains. In Experiment 1, participants had to maintain sequences of verbal or musical information in STM, followed by a probe sequence, this under different conditions of interference (no-interference, rhythmic interference, articulatory suppression). They were required to decide whether all items of the probe list matched those of the memory list (item condition) or whether the order of the items in the probe sequence matched the order in the memory list (order condition). In Experiment 2, participants performed a serial order probe recognition task for verbal and musical sequences ensuring sequential maintenance processes, under no-interference or rhythmic interference conditions. For Experiment 1, serial order recognition was not significantly more impacted by interfering tasks than was item recognition, this for both verbal and musical domains. For Experiment 2, we observed selective interference of the rhythmic interference condition on both musical and verbal order STM tasks. Overall, the results suggest a similar and selective sensitivity to time-based interference for serial order STM in verbal and musical domains, but only when the STM tasks ensure sequential maintenance processes.

Ordered Materials via Additive Driven Assembly and Reaction using Surfactant-Based Templates

NASA Astrophysics Data System (ADS)

Beaulieu, Michael R.; Daga, Vikram K.; Lesser, Alan J.; Watkins, James J.

2011-03-01

We recently reported (1) the ordering behavior of Pluronic surfactant melts through the addition of aromatic additives with hydrogen bond donating groups, which exhibit selective interactions with the polyethylene oxide (PEO) block. The ordered blends had domain sizes ranging from 12 to 16 nm at additive loadings up to 80%.The goal of this work is to utilize condensation chemistries based on the functionality of similar additives, to yield ordered composite materials that could be used for applications involving membranes or dielectric materials. The structure of the blends and composites are determined by small angle x-ray scattering, which indicates that the ordered structure is preserved following reaction of the additives. Differential scanning calorimetry indicates that an increase in additive loading causes a decrease in the melting temperature and enthalpy of melting of the PEO, which demonstrates that the interaction between the PEO segments and the additive is strong. (1) Daga, V.K., Watkins, J. J. Macromolecules, ASAP.

Enhancement of Device Performances in GaN-Based Light-Emitting Diodes Using Nano-Sized Surface Pit.

PubMed

Yeon, Seunghwan; Son, Taejoon; Shin, Dong Su; Jung, Kyung-Young; Park, Jinsub

2015-07-01

We report the improvement in optical and electrical properties of GaN-based green light-emitting diodes (LEDs) with nano-sized etch pits formed by the surface chemical etching. In order to control the density and sizes of etch pits formed on top surface of green LEDs, H3PO4 solution is used as a etchant with different etching time. When the etching time was increased from 0 min to 20 min, both the etch pit size and density were gradually increased. The improvement of extraction efficiency of LEDs using surface etching method can be attributed to the enlarged escape angle of generated photon by roughened p-GaN surface. The finite-difference time-domain (FDTD) simulation results well agreed with experimentally observed results. Moreover, the LED with etched p-GaN surface for 5 min shows the lowest leakage current value and the further increase of etching time resulting in increase of densities of the large-sized etch pit makes the degradation of electrical properties of LEDs.

Magnetic properties in an ash flow tuff with continuous grain size variation: a natural reference for magnetic particle granulometry

USGS Publications Warehouse

Till, J.L.; Jackson, M.J.; Rosenbaum, J.G.; Solheid, P.

2011-01-01

The Tiva Canyon Tuff contains dispersed nanoscale Fe-Ti-oxide grains with a narrow magnetic grain size distribution, making it an ideal material in which to identify and study grain-size-sensitive magnetic behavior in rocks. A detailed magnetic characterization was performed on samples from the basal 5 m of the tuff. The magnetic materials in this basal section consist primarily of (low-impurity) magnetite in the form of elongated submicron grains exsolved from volcanic glass. Magnetic properties studied include bulk magnetic susceptibility, frequency-dependent and temperature-dependent magnetic susceptibility, anhysteretic remanence acquisition, and hysteresis properties. The combined data constitute a distinct magnetic signature at each stratigraphic level in the section corresponding to different grain size distributions. The inferred magnetic domain state changes progressively upward from superparamagnetic grains near the base to particles with pseudo-single-domain or metastable single-domain characteristics near the top of the sampled section. Direct observations of magnetic grain size confirm that distinct transitions in room temperature magnetic susceptibility and remanence probably denote the limits of stable single-domain behavior in the section. These results provide a unique example of grain-size-dependent magnetic properties in noninteracting particle assemblages over three decades of grain size, including close approximations of ideal Stoner-Wohlfarth assemblages, and may be considered a useful reference for future rock magnetic studies involving grain-size-sensitive properties.

Spontaneous Symmetry Breaking of Domain Walls in Phase-Competing Regions

NASA Astrophysics Data System (ADS)

Ishizuka, Hiroaki; Yamada, Yasusada; Nagaosa, Naoto

2018-05-01

In this study, we investigate the nature of domain walls in an ordered phase in the phase-competing region of two Ising-type order parameters. We consider a two-component ϕ4 theory and show that the domain wall of the ground-state (primary) order parameter shows a second-order phase transition associated with the secondary order parameter of the competing phase; the effective theory of the phase transition is given by the Landau theory of an Ising-type phase transition. We find that the phase boundary of this phase transition is different from the spinodal line of the competing order. The phase transition is detected experimentally by the divergence of the susceptibility corresponding to the secondary order when the temperature is quenched to introduce the domain walls.

Development of a Tsunami Scenario Database for Marmara Sea

NASA Astrophysics Data System (ADS)

Ozer Sozdinler, Ceren; Necmioglu, Ocal; Meral Ozel, Nurcan

2016-04-01

Due to the very short travel times in Marmara Sea, a Tsunami Early Warning System (TEWS) has to be strongly coupled with the earthquake early warning system and should be supported with a pre-computed tsunami scenario database to be queried in near real-time based on the initial earthquake parameters. To address this problem, 30 different composite earthquake scenarios with maximum credible Mw values based on 32 fault segments have been identified to produce a detailed scenario database for all possible earthquakes in the Marmara Sea with a tsunamigenic potential. The bathy/topo data of Marmara Sea was prepared using GEBCO and ASTER data, bathymetric measurements along Bosphorus, Istanbul and Dardanelle, Canakkale and the coastline digitized from satellite images. The coarser domain in 90m-grid size was divided into 11 sub-regions having 30m-grid size in order to increase the data resolution and precision of the calculation results. The analyses were performed in nested domains with numerical model NAMIDANCE using non-linear shallow water equations. In order to cover all the residential areas, industrial facilities and touristic locations, more than 1000 numerical gauge points were selected along the coasts of Marmara Sea, which are located at water depth of 5 to 10m in finer domain. The distributions of tsunami hydrodynamic parameters were investigated together with the change of water surface elevations, current velocities, momentum fluxes and other important parameters at the gauge points. This work is funded by the project MARsite - New Directions in Seismic Hazard assessment through Focused Earth Observation in the Marmara Supersite (FP7-ENV.2012 6.4-2, Grant 308417 - see NH2.3/GMPV7.4/SM7.7) and supported by SATREPS-MarDim Project (Earthquake and Tsunami Disaster Mitigation in the Marmara Region and Disaster Education in Turkey) and JICA (Japan International Cooperation Agency). The authors would like to acknowledge Ms. Basak Firat for her assistance in preparation of the database.

From multidimensional neuropsychological outcomes to a cognitive complication rate: The International Subarachnoid Aneurysm Trial

PubMed Central

Scott, Richard B; Eccles, Fiona; Lloyd, Andrew; Carpenter, Katherine

2008-01-01

Background The neuropsychological arm of the International Subarachnoid Aneurysm Trial (N-ISAT) evaluated the cognitive outcome of 573 patients at 12 months following subarachnoid haemorrhage (SAH). The assessment included 29 psychometric measures, yielding a substantial and complex body of data. We have explored alternative and optimal methodologies for analysing and summarising these data to enable the estimation of a cognitive complication rate (CCR). Any differences in cognitive outcome between the two arms of the trial are not however reported here. Methods All individual test scores were transformed into z-scores and a 5th percentile cut-off for impairment was established. A principal components analysis (PCA) was applied to these data to mathematically transform correlated test scores into a smaller number of uncorrelated principal components, or cognitive 'domains'. These domains formed the basis for grouping and weighting individual patients' impaired scores on individual measures. In order to increase the sample size, a series of methods for handling missing data were applied. Results We estimated a 34.1% CCR in all those patients seen face-to-face, rising to 37.4% CCR with the inclusion of patients who were unable to attend assessment for reason related to the index SAH. This group demonstrated significantly more self and carer/relative rated disability on a Health Related Quality of Life questionnaire, than patients classified as having no functionally significant cognitive deficits. Conclusion Evaluating neuropsychological outcome in a large RCT involves unique methodological and organizational challenges. We have demonstrated how these problems may be addressed by re-classifying interval data from 29 measures into a dichotomous CCR. We have presented a 'sliding scale' of undifferentiated individual cognitive impairments, and then on the basis of PCA-derived cognitive 'domains', included consideration of the distribution of impairments in these terms. In order to maximize sample size we have suggested ways for patients who did not complete the entire protocol to be included in the overall CCR. ISAT trial registration ISRCTN49866681 PMID:18341689

Free-space wavelength-multiplexed optical scanner.

PubMed

Yaqoob, Z; Rizvi, A A; Riza, N A

2001-12-10

A wavelength-multiplexed optical scanning scheme is proposed for deflecting a free-space optical beam by selection of the wavelength of the light incident on a wavelength-dispersive optical element. With fast tunable lasers or optical filters, this scanner features microsecond domain scan setting speeds and large- diameter apertures of several centimeters or more for subdegree angular scans. Analysis performed indicates an optimum scan range for a given diffraction order and grating period. Limitations include beam-spreading effects based on the varying scanner aperture sizes and the instantaneous information bandwidth of the data-carrying laser beam.

Characterization of quantum well structures using a photocathode electron microscope

NASA Technical Reports Server (NTRS)

Spencer, Michael G.; Scott, Craig J.

1989-01-01

Present day integrated circuits pose a challenge to conventional electronic and mechanical test methods. Feature sizes in the submicron and nanometric regime require radical approaches in order to facilitate electrical contact to circuits and devices being tested. In addition, microwave operating frequencies require careful attention to distributed effects when considering the electrical signal paths within and external to the device under test. An alternative testing approach which combines the best of electrical and optical time domain testing is presented, namely photocathode electron microscope quantitative voltage contrast (PEMQVC).

On the complexity of turbulence near a wall

NASA Technical Reports Server (NTRS)

Moin, Parviz

1992-01-01

Some measures of the intrinsic complexity of the near wall turbulence are reviewed. The number of modes required in an 'optimal' eigenfunction expansion is compared with the dimension obtained from the calculation of Liapunov exponents. These measures are of the same order, but they are very large. It is argued that the basic building block element of the near wall turbulence can be isolated in a small region of space (minimal flow unit). When the size of the domain is taken into account, the dimension becomes more manageable.

Nonequilibrium Phase Transition in a Model for Social Influence

NASA Astrophysics Data System (ADS)

Castellano, Claudio; Marsili, Matteo; Vespignani, Alessandro

2000-10-01

We present extensive numerical simulations of the Axelrod's model for social influence, aimed at understanding the formation of cultural domains. This is a nonequilibrium model with short range interactions and a remarkably rich dynamical behavior. We study the phase diagram of the model and uncover a nonequilibrium phase transition separating an ordered (culturally polarized) phase from a disordered (culturally fragmented) one. The nature of the phase transition can be continuous or discontinuous depending on the model parameters. At the transition, the size of cultural regions is power-law distributed.

Topological Structures in Multiferroics - Domain Walls, Skyrmions and Vortices

DOE PAGES

Seidel, Jan; Vasudevan, Rama K.; Valanoor, Nagarajan

2015-12-15

Topological structures in multiferroic materials have recently received considerable attention because of their potential use as nanoscale functional elements. Their reduced size in conjunction with exotic arrangement of the ferroic order parameter and potential order parameter coupling allows for emergent and unexplored phenomena in condensed matter and functional materials systems. This will lead to exciting new fundamental discoveries as well as application concepts that exploit their response to external stimuli such as mechanical strain, electric and magnetic fields. In this review we capture the current development of this rapidly moving field with specific emphasis on key achievements that have castmore » light on how such topological structures in multiferroic materials systems can be exploited for use in complex oxide nanoelectronics and spintronics.« less

Molecular origin of photovoltaic performance in donor- block-acceptor all-conjugated block copolymers

DOE PAGES

Smith, Kendall A.; Lin, Yen -Hao; Mok, Jorge W.; ...

2015-11-03

All-conjugated block copolymers may be an effective route to self-assembled photovoltaic devices, but we lack basic information on the relationship between molecular characteristics and photovoltaic performance. Here, we synthesize a library of poly(3-hexylthiophene) (P3HT) block poly((9,9-dialkylfluorene)-2,7-diyl-alt-[4,7-bis(alkylthiophen-5-yl)-2,1,3-benzothiadiazole]-2',2''-diyl) (PFTBT) donor- block-acceptor all-conjugated block copolymers and carry out a comprehensive study of processing conditions, crystallinity, domain sizes, and side-chain structure on photovoltaic device performance. We find that all block copolymers studied exhibit an out-of-plane crystal orientation after deposition, and on thermal annealing at high temperatures the crystal orientation flips to an in-plane orientation. By varying processing conditions on polymer photovoltaic devices, we showmore » that the crystal orientation has only a modest effect (15-20%) on photovoltaic performance. The addition of side-chains to the PFTBT block is found to decrease photovoltaic power conversion efficiencies by at least an order of magnitude. Through grazing-incidence X-ray measurements we find that the addition of side-chains to the PFTBT acceptor block results in weak segregation and small (< 10 nm) block copolymer self-assembled donor and acceptor domains. This work is the most comprehensive to date on all-conjugated block copolymer systems and suggests that photovoltaic performance of block copolymers depends strongly on the miscibility of donor and acceptor blocks, which impacts donor and acceptor domain sizes and purity. Lastly, strategies for improving the device performance of block copolymer photovoltaics should seek to increase segregation between donor and acceptor polymer domains.« less

Molecular origin of photovoltaic performance in donor- block-acceptor all-conjugated block copolymers

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

Smith, Kendall A.; Lin, Yen -Hao; Mok, Jorge W.

All-conjugated block copolymers may be an effective route to self-assembled photovoltaic devices, but we lack basic information on the relationship between molecular characteristics and photovoltaic performance. Here, we synthesize a library of poly(3-hexylthiophene) (P3HT) block poly((9,9-dialkylfluorene)-2,7-diyl-alt-[4,7-bis(alkylthiophen-5-yl)-2,1,3-benzothiadiazole]-2',2''-diyl) (PFTBT) donor- block-acceptor all-conjugated block copolymers and carry out a comprehensive study of processing conditions, crystallinity, domain sizes, and side-chain structure on photovoltaic device performance. We find that all block copolymers studied exhibit an out-of-plane crystal orientation after deposition, and on thermal annealing at high temperatures the crystal orientation flips to an in-plane orientation. By varying processing conditions on polymer photovoltaic devices, we showmore » that the crystal orientation has only a modest effect (15-20%) on photovoltaic performance. The addition of side-chains to the PFTBT block is found to decrease photovoltaic power conversion efficiencies by at least an order of magnitude. Through grazing-incidence X-ray measurements we find that the addition of side-chains to the PFTBT acceptor block results in weak segregation and small (< 10 nm) block copolymer self-assembled donor and acceptor domains. This work is the most comprehensive to date on all-conjugated block copolymer systems and suggests that photovoltaic performance of block copolymers depends strongly on the miscibility of donor and acceptor blocks, which impacts donor and acceptor domain sizes and purity. Lastly, strategies for improving the device performance of block copolymer photovoltaics should seek to increase segregation between donor and acceptor polymer domains.« less

Bifurcation and stability analysis of rotating chemical spirals in circular domains: Boundary-induced meandering and stabilization

NASA Astrophysics Data System (ADS)

Bär, Markus; Bangia, Anil K.; Kevrekidis, Ioannis G.

2003-05-01

Recent experimental and model studies have revealed that the domain size may strongly influence the dynamics of rotating spirals in two-dimensional pattern forming chemical reactions. Hartmann et al. [Phys. Rev. Lett. 76, 1384 (1996)], report a frequency increase of spirals in circular domains with diameters substantially smaller than the spiral wavelength in a large domain for the catalytic NO+CO reaction on a microstructured platinum surface. Accompanying simulations with a simple reaction-diffusion system reproduced the behavior. Here, we supplement these studies by a numerical bifurcation and stability analysis of rotating spirals in a simple activator-inhibitor model. The problem is solved in a corotating frame of reference. No-flux conditions are imposed at the boundary of the circular domain. At large domain sizes, eigenvalues and eigenvectors very close to those corresponding to infinite medium translational invariance are observed. Upon decrease of domain size, we observe a simultaneous change in the rotation frequency and a deviation of these eigenvalues from being neutrally stable (zero real part). The latter phenomenon indicates that the translation symmetry of the spiral solution is appreciably broken due to the interaction with the (now nearby) wall. Various dynamical regimes are found: first, the spiral simply tries to avoid the boundary and its tip moves towards the center of the circular domain corresponding to a negative real part of the “translational” eigenvalues. This effect is noticeable at a domain radius of R

Ordered Self-Assembly Mechanism of a Spherical Oncoprotein Oligomer Triggered by Zinc Removal and Stabilized by an Intrinsically Disordered Domain

PubMed Central

Smal, Clara; Alonso, Leonardo G.; Wetzler, Diana E.; Heer, Angeles; de Prat Gay, Gonzalo

2012-01-01

Background Self-assembly is a common theme in proteins of unrelated sequences or functions. The human papillomavirus E7 oncoprotein is an extended dimer with an intrinsically disordered domain, that can form large spherical oligomers. These are the major species in the cytosol of HPV transformed and cancerous cells. E7 binds to a large number of targets, some of which lead to cell transformation. Thus, the assembly process not only is of biological relevance, but represents a model system to investigate a widely distributed mechanism. Methodology/Principal Findings Using various techniques, we monitored changes in secondary, tertiary and quaternary structure in a time course manner. By applying a robust kinetic model developed by Zlotnik, we determined the slow formation of a monomeric “Z-nucleus” after zinc removal, followed by an elongation phase consisting of sequential second-order events whereby one monomer is added at a time. This elongation process takes place at a strikingly slow overall average rate of one monomer added every 28 seconds at 20 µM protein concentration, strongly suggesting either a rearrangement of the growing complex after binding of each monomer or the existence of a “conformation editing” mechanism through which the monomer binds and releases until the appropriate conformation is adopted. The oligomerization determinant lies within its small 5 kDa C-terminal globular domain and, remarkably, the E7 N-terminal intrinsically disordered domain stabilizes the oligomer, preventing an insoluble amyloid route. Conclusion We described a controlled ordered mechanism with features in common with soluble amyloid precursors, chaperones, and other spherical oligomers, thus sharing determining factors for symmetry, size and shape. In addition, such a controlled and discrete polymerization reaction provides a valuable tool for nanotechnological applications. Finally, its increased immunogenicity related to its supramolecular structure is the basis for the development of a promising therapeutic vaccine candidate for treating HPV cancerous lesions. PMID:22590549

Domain engineering of the metastable domains in the 4f-uniaxial-ferromagnet CeRu2Ga2B

NASA Astrophysics Data System (ADS)

Wulferding, D.; Kim, H.; Yang, I.; Jeong, J.; Barros, K.; Kato, Y.; Martin, I.; Ayala-Valenzuela, O. E.; Lee, M.; Choi, H. C.; Ronning, F.; Civale, L.; Baumbach, R. E.; Bauer, E. D.; Thompson, J. D.; Movshovich, R.; Kim, Jeehoon

2017-04-01

In search of novel, improved materials for magnetic data storage and spintronic devices, compounds that allow a tailoring of magnetic domain shapes and sizes are essential. Good candidates are materials with intrinsic anisotropies or competing interactions, as they are prone to host various domain phases that can be easily and precisely selected by external tuning parameters such as temperature and magnetic field. Here, we utilize vector magnetic fields to visualize directly the magnetic anisotropy in the uniaxial ferromagnet CeRu2Ga2B. We demonstrate a feasible control both globally and locally of domain shapes and sizes by the external field as well as a smooth transition from single stripe to bubble domains, which opens the door to future applications based on magnetic domain tailoring.

Domain engineering of the metastable domains in the 4f-uniaxial-ferromagnet CeRu 2Ga 2B

DOE PAGES

Wulferding, Dirk; Kim, Hoon; Yang, Ilkyu; ...

2017-04-10

In search of novel, improved materials for magnetic data storage and spintronic devices, compounds that allow a tailoring of magnetic domain shapes and sizes are essential. Good candidates are materials with intrinsic anisotropies or competing interactions, as they are prone to host various domain phases that can be easily and precisely selected by external tuning parameters such as temperature and magnetic field. Here, we utilize vector magnetic fields to visualize directly the magnetic anisotropy in the uniaxial ferromagnet CeRu 2Ga 2B. We demonstrate a feasible control both globally and locally of domain shapes and sizes by the external field asmore » well as a smooth transition from single stripe to bubble domains, which opens the door to future applications based on magnetic domain tailoring.« less

A Third-Order Item Response Theory Model for Modeling the Effects of Domains and Subdomains in Large-Scale Educational Assessment Surveys

ERIC Educational Resources Information Center

Rijmen, Frank; Jeon, Minjeong; von Davier, Matthias; Rabe-Hesketh, Sophia

2014-01-01

Second-order item response theory models have been used for assessments consisting of several domains, such as content areas. We extend the second-order model to a third-order model for assessments that include subdomains nested in domains. Using a graphical model framework, it is shown how the model does not suffer from the curse of…

A systematic review of electronic audit and feedback: intervention effectiveness and use of behaviour change theory.

PubMed

Tuti, Timothy; Nzinga, Jacinta; Njoroge, Martin; Brown, Benjamin; Peek, Niels; English, Mike; Paton, Chris; van der Veer, Sabine N

2017-05-12

Audit and feedback is a common intervention for supporting clinical behaviour change. Increasingly, health data are available in electronic format. Yet, little is known regarding if and how electronic audit and feedback (e-A&F) improves quality of care in practice. The study aimed to assess the effectiveness of e-A&F interventions in a primary care and hospital context and to identify theoretical mechanisms of behaviour change underlying these interventions. In August 2016, we searched five electronic databases, including MEDLINE and EMBASE via Ovid, and the Cochrane Central Register of Controlled Trials for published randomised controlled trials. We included studies that evaluated e-A&F interventions, defined as a summary of clinical performance delivered through an interactive computer interface to healthcare providers. Data on feedback characteristics, underlying theoretical domains, effect size and risk of bias were extracted by two independent review authors, who determined the domains within the Theoretical Domains Framework (TDF). We performed a meta-analysis of e-A&F effectiveness, and a narrative analysis of the nature and patterns of TDF domains and potential links with the intervention effect. We included seven studies comprising of 81,700 patients being cared for by 329 healthcare professionals/primary care facilities. Given the extremely high heterogeneity of the e-A&F interventions and five studies having a medium or high risk of bias, the average effect was deemed unreliable. Only two studies explicitly used theory to guide intervention design. The most frequent theoretical domains targeted by the e-A&F interventions included 'knowledge', 'social influences', 'goals' and 'behaviour regulation', with each intervention targeting a combination of at least three. None of the interventions addressed the domains 'social/professional role and identity' or 'emotion'. Analyses identified the number of different domains coded in control arm to have the biggest role in heterogeneity in e-A&F effect size. Given the high heterogeneity of identified studies, the effects of e-A&F were found to be highly variable. Additionally, e-A&F interventions tend to implicitly target only a fraction of known theoretical domains, even after omitting domains presumed not to be linked to e-A&F. Also, little evaluation of comparative effectiveness across trial arms was conducted. Future research should seek to further unpack the theoretical domains essential for effective e-A&F in order to better support strategic individual and team goals.

Social cognitive functioning in prodromal psychosis: A meta-analysis.

PubMed

Lee, Tae Young; Hong, Sang Bin; Shin, Na Young; Kwon, Jun Soo

2015-05-01

There is substantial evidence regarding a social cognitive deficit in schizophrenia, and it has been suggested to be a trait-marker of this disorder. However, a domain-by-domain analysis of social cognitive deficits in individuals at clinical high risk (CHR) for psychosis has not been performed. Electronic databases were searched for studies regarding social cognitive performance in individuals at CHR. The included social cognitive domains, which were classified based on the Social Cognition Psychometric Evaluation (SCOPE) initiative of the National Institute of Mental Health (NIMH), were as follows: theory of mind (ToM), social perception (SP), attributional bias (AB), and emotion processing (EP). Twenty studies that included 1229 individuals at CHR and 825 healthy controls met the inclusion criteria. The overall effect size for social cognition was medium (g=-0.477). The largest effect size was identified for AB (g=-0.708). A medium effect size was identified for EP (g=-0.446) and ToM (g=-0.425), and small effects were identified for SP (g=-0.383). This is the first quantitative domain-by-domain social cognitive meta-analysis regarding CHR individuals. The present study indicated that individuals at CHR exhibited significant impairments in all domains of social cognition compared with healthy controls, with the largest effect size identified for AB. The identification of social cognitive domains that reflect an increased risk for impending psychosis and of predictors of the conversion to psychosis via a longitudinal follow-up study is required. Copyright © 2015 Elsevier B.V. All rights reserved.

Magnetization mechanisms in ordered arrays of polycrystalline Fe100-xCox nanowires

NASA Astrophysics Data System (ADS)

Viqueira, M. S.; Bajales, N.; Urreta, S. E.; Bercoff, P. G.

2015-05-01

Magnetization reversal processes and coercivity mechanisms in polycrystalline Fe100-xCox nanowire arrays, resulting from an AC electrodeposition process, are investigated. The array coercivity is described on the basis of polarization reversal mechanisms operating in individual wires, under the effect of inter-wire dipolar interactions described by a mean field approximation. For individual wires, a reversal mechanism involving the nucleation and further expansion of domain-wall like spin configuration is considered. The wires have a mean grain size larger than both the nanowire diameter and the exchange length, so localized and non-cooperative nucleation modes are considered. As the Co content increases, the alloy saturation polarization gradually decreases, but the coercive field and the relative remanence of the arrays increase, indicating that they are not controlled by the shape anisotropy in all the composition range. The coercive field dependence on the angle between the applied field and the wire long axis is not well described by reversal mechanisms involving nucleation and further displacement of neither vortex nor transverse ideal domain walls. On the contrary, the angular dependence of the coercive field observed at room temperature is well predicted by a model considering nucleation of inverse domains by localized curling, in regions smaller than the grain size, exhibiting quite small aspect ratios as compared to those of the entire nanowire. In arrays with higher Co contents, a transition from an initial (small angle) localized curling nucleation mechanism to another one, involving localized coherent rotation is observed at about π/4.

Protein sorting by lipid phase-like domains supports emergent signaling function in B lymphocyte plasma membranes.

PubMed

Stone, Matthew B; Shelby, Sarah A; Núñez, Marcos F; Wisser, Kathleen; Veatch, Sarah L

2017-02-01

Diverse cellular signaling events, including B cell receptor (BCR) activation, are hypothesized to be facilitated by domains enriched in specific plasma membrane lipids and proteins that resemble liquid-ordered phase-separated domains in model membranes. This concept remains controversial and lacks direct experimental support in intact cells. Here, we visualize ordered and disordered domains in mouse B lymphoma cell membranes using super-resolution fluorescence localization microscopy, demonstrate that clustered BCR resides within ordered phase-like domains capable of sorting key regulators of BCR activation, and present a minimal, predictive model where clustering receptors leads to their collective activation by stabilizing an extended ordered domain. These results provide evidence for the role of membrane domains in BCR signaling and a plausible mechanism of BCR activation via receptor clustering that could be generalized to other signaling pathways. Overall, these studies demonstrate that lipid mediated forces can bias biochemical networks in ways that broadly impact signal transduction.

Activity of a social dynamics model

NASA Astrophysics Data System (ADS)

Reia, Sandro M.; Neves, Ubiraci P. C.

2015-10-01

Axelrod's model was proposed to study interactions between agents and the formation of cultural domains. It presents a transition from a monocultural to a multicultural steady state which has been studied in the literature by evaluation of the relative size of the largest cluster. In this article, we propose new measurements based on the concept of activity per agent to study the Axelrod's model on the square lattice. We show that the variance of system activity can be used to indicate the critical points of the transition. Furthermore the frequency distribution of the system activity is able to show a coexistence of phases typical of a first order phase transition. Finally, we verify a power law dependence between cluster activity and cluster size for multicultural steady state configurations at the critical point.

Going from microscopic to macroscopic on nonuniform growing domains.

PubMed

Yates, Christian A; Baker, Ruth E; Erban, Radek; Maini, Philip K

2012-08-01

Throughout development, chemical cues are employed to guide the functional specification of underlying tissues while the spatiotemporal distributions of such chemicals can be influenced by the growth of the tissue itself. These chemicals, termed morphogens, are often modeled using partial differential equations (PDEs). The connection between discrete stochastic and deterministic continuum models of particle migration on growing domains was elucidated by Baker, Yates, and Erban [Bull. Math. Biol. 72, 719 (2010)] in which the migration of individual particles was modeled as an on-lattice position-jump process. We build on this work by incorporating a more physically reasonable description of domain growth. Instead of allowing underlying lattice elements to instantaneously double in size and divide, we allow incremental element growth and splitting upon reaching a predefined threshold size. Such a description of domain growth necessitates a nonuniform partition of the domain. We first demonstrate that an individual-based stochastic model for particle diffusion on such a nonuniform domain partition is equivalent to a PDE model of the same phenomenon on a nongrowing domain, providing the transition rates (which we derive) are chosen correctly and we partition the domain in the correct manner. We extend this analysis to the case where the domain is allowed to change in size, altering the transition rates as necessary. Through application of the master equation formalism we derive a PDE for particle density on this growing domain and corroborate our findings with numerical simulations.

Transition metal-chelating surfactant micelle templates for facile synthesis of mesoporous silica nanoparticles

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

Lee, Hye Sun; Department of Materials Science and Engineering, Yonsei University, Seoul 120-749; Kim, Won Hee

2012-01-15

Highly ordered mesoporous silica nanoparticles with tunable morphology and pore-size are prepared by the use of a transition metal-chelating surfactant micelle complex using Co{sup 2+}, Ni{sup 2+}, Cu{sup 2+}, and Zn{sup 2+} ions. These metal ions formed a metal-P123 micelle complex in an aqueous solution, while the metal ions are chelated to the hydrophilic domain such as the poly(ethylene oxide) group of a P123 surfactant. The different complexation abilities of the utilized transition metal ions play an important role in determining the formation of nano-sized ordered MSNs due to the different stabilization constant of the metal-P123 complex. Consequently, from amore » particle length of 1700 nm in the original mesoporous silica materials, the particle length of ordered MSNs through the metal-chelating P123 micelle templates can be reduced to a range of 180-800 nm. Furthermore, the variation of pore size shows a slight change from 8.8 to 6.6 nm. In particular, the Cu{sup 2+}-chelated MSNs show only decreased particle size to 180 nm. The stability constants for the metal-P123 complex are calculated on the basis of molar conductance measurements in order to elucidate the formation mechanism of MSNs by the metal-chelating P123 complex templates. In addition, solid-state {sup 29}Si, {sup 13}C-NMR and ICP-OES measurements are used for quantitative characterization reveal that the utilized metal ions affect only the formation of a metal-P123 complex in a micelle as a template. - Graphical abstract: Metal-chelating surfactant micelle templates support a simple and facile preparations of size-tunable ordered MSNs. Black-Small-Square Highlights: Black-Right-Pointing-Pointer Facile preparation of mesoporous silica nanoparticles (MSNs) was achieved by metal-chelating surfactant micelle complex using Co{sup 2+}, Ni{sup 2+}, Cu{sup 2+}, and Zn{sup 2+} ions. Black-Right-Pointing-Pointer Different complexation of metal ions plays an important role in determining the formation of nano-sized ordered MSNs. Black-Right-Pointing-Pointer Systematic characterization of the synthesized materials was achieved by solid-state {sup 29}Si and {sup 13}C-NMR techniques, BET, FT-IR, and XPS. Black-Right-Pointing-Pointer Stability constants for the metal-P123 complex are calculated on the basis of molar conductance measurements in order to elucidate the formation mechanism.« less

Method for increasing thermostability in cellulase ennzymes

DOEpatents

Adney, W.S.; Thomas, S.R.; Baker, J.O.; Himmel, M.E.; Chou, Y.C.

1998-01-27

The gene encoding Acidothermus cellulolyticus E1 endoglucanase is cloned and expressed in Pichia pastoris. A new modified E1 endoglucanase enzyme comprising the catalytic domain of the full size E1 enzyme demonstrates enhanced thermostability and is produced by two methods. The first method of producing the new modified E1 is proteolytic cleavage to remove the cellulose binding domain and linker peptide of the full size E1. The second method of producing the new modified E1 is genetic truncation of the gene encoding the full size E1 so that the catalytic domain is expressed in the expression product. 8 figs.

Modeling and simulating vortex pinning and transport currents for high temperature superconductors

NASA Astrophysics Data System (ADS)

Sockwell, K. Chad

Superconductivity is a phenomenon characterized by two hallmark properties, zero electrical resistance and the Meissner effect. These properties give great promise to a new generation of resistance free electronics and powerful superconducting magnets. However this possibility is limited by the extremely low critical temperature the superconductors must operate under, typically close to 0K. The recent discovery of high temperature superconductors has brought the critical temperature closer to room temperature than ever before, making the realization of room temperature superconductivity a possibility. Simulations of superconducting technology and materials will be necessary to usher in the new wave of superconducting electronics. Unfortunately these new materials come with new properties such as effects from multiple electron bands, as is the case for magnesium diboride. Moreover, we must consider that all high temperature superconductors are of a Type II variety, which possess magnetic tubes of flux, known as vortices. These vortices interact with transport currents, creating an electrical resistance through a process known as flux flow. Thankfully this process can be prevented by placing impurities in the superconductor, pinning the vortices, making vortex pinning a necessary aspect of our model. At this time there are no other models or simulations that are aimed at modeling vortex pinning, using impurities, in two-band materials. In this work we modify an existing Ginzburg-Landau model for two-band superconductors and add the ability to model normal inclusions (impurities) with a new approach which is unique to the two-band model. Simulations in an attempt to model the material magnesium diboride are also presented. In particular simulations of vortex pinning and transport currents are shown using the modified model. The qualitative properties of magnesium diboride are used to validate the model and its simulations. One main goal from the computational end of the simulations is to enlarge the domain size to produce more realistic simulations that avoid boundary pinning effects. In this work we also implement the numerical software library Trilinos in order to parallelize the simulation to enlarge the domain size. Decoupling methods are also investigated with a goal of enlarging the domain size as well. The One-Band Ginzburg-Landau model serves as a prototypical problem in this endeavor and the methods shown that enlarge the domain size can be easily implemented in the two-band model.

Mobile metallic domain walls in an all-in-all-out magnetic insulator

DOE PAGES

Ma, Eric Yue; Cui, Yong -Tao; Ueda, Kentaro; ...

2015-10-30

Magnetic domain walls are boundaries between regions with different configurations of the same magnetic order. In a magnetic insulator, where the magnetic order is tied to its bulk insulating property, it has been postulated that electrical properties are drastically different along the domain walls, where the order is inevitably disturbed. Here we report the discovery of highly conductive magnetic domain walls in a magnetic insulator, Nd 2Ir 2O 7, that has an unusual all-in-all-out magnetic order, via transport and spatially resolved microwave impedance microscopy. The domain walls have a virtually temperature-independent sheet resistance of ~1 kilohm per square, show smoothmore » morphology with no preferred orientation, are free from pinning by disorders, and have strong thermal and magnetic field responses that agree with expectations for all-in-all-out magnetic order.« less

Mobile metallic domain walls in an all-in-all-out magnetic insulator.

PubMed

Ma, Eric Yue; Cui, Yong-Tao; Ueda, Kentaro; Tang, Shujie; Chen, Kai; Tamura, Nobumichi; Wu, Phillip M; Fujioka, Jun; Tokura, Yoshinori; Shen, Zhi-Xun

2015-10-30

Magnetic domain walls are boundaries between regions with different configurations of the same magnetic order. In a magnetic insulator, where the magnetic order is tied to its bulk insulating property, it has been postulated that electrical properties are drastically different along the domain walls, where the order is inevitably disturbed. Here we report the discovery of highly conductive magnetic domain walls in a magnetic insulator, Nd2Ir2O7, that has an unusual all-in-all-out magnetic order, via transport and spatially resolved microwave impedance microscopy. The domain walls have a virtually temperature-independent sheet resistance of ~1 kilohm per square, show smooth morphology with no preferred orientation, are free from pinning by disorders, and have strong thermal and magnetic field responses that agree with expectations for all-in-all-out magnetic order. Copyright © 2015, American Association for the Advancement of Science.

A novel partitioning method for block-structured adaptive meshes

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

Fu, Lin, E-mail: lin.fu@tum.de; Litvinov, Sergej, E-mail: sergej.litvinov@aer.mw.tum.de; Hu, Xiangyu Y., E-mail: xiangyu.hu@tum.de

We propose a novel partitioning method for block-structured adaptive meshes utilizing the meshless Lagrangian particle concept. With the observation that an optimum partitioning has high analogy to the relaxation of a multi-phase fluid to steady state, physically motivated model equations are developed to characterize the background mesh topology and are solved by multi-phase smoothed-particle hydrodynamics. In contrast to well established partitioning approaches, all optimization objectives are implicitly incorporated and achieved during the particle relaxation to stationary state. Distinct partitioning sub-domains are represented by colored particles and separated by a sharp interface with a surface tension model. In order to obtainmore » the particle relaxation, special viscous and skin friction models, coupled with a tailored time integration algorithm are proposed. Numerical experiments show that the present method has several important properties: generation of approximately equal-sized partitions without dependence on the mesh-element type, optimized interface communication between distinct partitioning sub-domains, continuous domain decomposition which is physically localized and implicitly incremental. Therefore it is particularly suitable for load-balancing of high-performance CFD simulations.« less

A novel partitioning method for block-structured adaptive meshes

NASA Astrophysics Data System (ADS)

Fu, Lin; Litvinov, Sergej; Hu, Xiangyu Y.; Adams, Nikolaus A.

2017-07-01

We propose a novel partitioning method for block-structured adaptive meshes utilizing the meshless Lagrangian particle concept. With the observation that an optimum partitioning has high analogy to the relaxation of a multi-phase fluid to steady state, physically motivated model equations are developed to characterize the background mesh topology and are solved by multi-phase smoothed-particle hydrodynamics. In contrast to well established partitioning approaches, all optimization objectives are implicitly incorporated and achieved during the particle relaxation to stationary state. Distinct partitioning sub-domains are represented by colored particles and separated by a sharp interface with a surface tension model. In order to obtain the particle relaxation, special viscous and skin friction models, coupled with a tailored time integration algorithm are proposed. Numerical experiments show that the present method has several important properties: generation of approximately equal-sized partitions without dependence on the mesh-element type, optimized interface communication between distinct partitioning sub-domains, continuous domain decomposition which is physically localized and implicitly incremental. Therefore it is particularly suitable for load-balancing of high-performance CFD simulations.

Time-domain diffuse optics: towards next generation devices

NASA Astrophysics Data System (ADS)

Contini, Davide; Dalla Mora, Alberto; Arridge, Simon; Martelli, Fabrizio; Tosi, Alberto; Boso, Gianluca; Farina, Andrea; Durduran, Turgut; Martinenghi, Edoardo; Torricelli, Alessandro; Pifferi, Antonio

2015-07-01

Diffuse optics is a powerful tool for clinical applications ranging from oncology to neurology, but also for molecular imaging, and quality assessment of food, wood and pharmaceuticals. We show that ideally time-domain diffuse optics can give higher contrast and a higher penetration depth with respect to standard technology. In order to completely exploit the advantages of a time-domain system a distribution of sources and detectors with fast gating capabilities covering all the sample surface is needed. Here, we present the building block to build up such system. This basic component is made of a miniaturised source-detector pair embedded into the probe based on pulsed Vertical-Cavity Surface-Emitting Lasers (VCSEL) as sources and Single-Photon Avalanche Diodes (SPAD) or Silicon Photomultipliers (SiPM) as detectors. The possibility to miniaturized and dramatically increase the number of source detectors pairs open the way to an advancement of diffuse optics in terms of improvement of performances and exploration of new applications. Furthermore, availability of compact devices with reduction in size and cost can boost the application of this technique.

Secondary resonances and the boundary of effective stability of Trojan motions

NASA Astrophysics Data System (ADS)

Páez, Rocío Isabel; Efthymiopoulos, Christos

2018-02-01

One of the most interesting features in the libration domain of co-orbital motions is the existence of secondary resonances. For some combinations of physical parameters, these resonances occupy a large fraction of the domain of stability and rule the dynamics within the stable tadpole region. In this work, we present an application of a recently introduced `basic Hamiltonian model' H_b for Trojan dynamics (Páez and Efthymiopoulos in Celest Mech Dyn Astron 121(2):139, 2015; Páez et al. in Celest Mech Dyn Astron 126:519, 2016): we show that the inner border of the secondary resonance of lowermost order, as defined by H_b, provides a good estimation of the region in phase space for which the orbits remain regular regardless of the orbital parameters of the system. The computation of this boundary is straightforward by combining a resonant normal form calculation in conjunction with an `asymmetric expansion' of the Hamiltonian around the libration points, which speeds up convergence. Applications to the determination of the effective stability domain for exoplanetary Trojans (planet-sized objects or asteroids) which may accompany giant exoplanets are discussed.

Computational Design of High-χ Block Oligomers for Accessing 1 nm Domains.

PubMed

Chen, Qile P; Barreda, Leonel; Oquendo, Luis E; Hillmyer, Marc A; Lodge, Timothy P; Siepmann, J Ilja

2018-05-22

Molecular dynamics simulations are used to design a series of high-χ block oligomers (HCBOs) that can self-assemble into a variety of mesophases with domain sizes as small as 1 nm. The exploration of these oligomers with various chain lengths, volume fractions, and chain architectures at multiple temperatures reveals the presence of ordered lamellae, perforated lamellae, and hexagonally packed cylinders. The achieved periods are as small as 3.0 and 2.1 nm for lamellae and cylinders, respectively, which correspond to polar domains of approximately 1 nm. Interestingly, the detailed phase behavior of these oligomers is distinct from that of either solvent-free surfactants or block polymers. The simulations reveal that the behavior of these HCBOs is a product of an interplay between both "surfactant factors" (headgroup interactions, chain flexibility, and interfacial curvature) and "block polymer factors" (χ, chain length N, and volume fraction f). This insight promotes the understanding of molecular features pivotal for mesophase formation at the sub-5 nm length scale, which facilitates the design of HCBOs tailored toward particular desired morphologies.

Dynamics of domain coverage of the protein sequence universe.

PubMed

Rekapalli, Bhanu; Wuichet, Kristin; Peterson, Gregory D; Zhulin, Igor B

2012-11-16

The currently known protein sequence space consists of millions of sequences in public databases and is rapidly expanding. Assigning sequences to families leads to a better understanding of protein function and the nature of the protein universe. However, a large portion of the current protein space remains unassigned and is referred to as its "dark matter". Here we suggest that true size of "dark matter" is much larger than stated by current definitions. We propose an approach to reducing the size of "dark matter" by identifying and subtracting regions in protein sequences that are not likely to contain any domain. Recent improvements in computational domain modeling result in a decrease, albeit slowly, in the relative size of "dark matter"; however, its absolute size increases substantially with the growth of sequence data.

Unfolding grain size effects in barium titanate ferroelectric ceramics

PubMed Central

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

2015-01-01

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

Observations and simulations of the interactions between clouds, radiation, and precipitation

NASA Astrophysics Data System (ADS)

Naegele, Alexandra Claire

The first part of this study focuses on the radiative constraint on the hydrologic cycle as seen in observations. In the global energy budget, the atmospheric radiative cooling (ARC) is approximately balanced by latent heating, but on regional scales, the ARC and precipitation are inversely related. We use precipitation data from the Global Precipitation Climatology Project and radiative flux data from the Clouds and the Earth's Radiant Energy System (CERES) project to investigate the radiative constraint on the hydrologic cycle and how it changes in both space and time. We find that the effect of clouds is to decrease the ARC in the tropics, and to increase the ARC in middle and higher latitudes. We find that, spatially, precipitation and the ARC are negatively correlated in the tropics, and positively correlated in middle and higher latitudes. In terms of the global mean, the precipitation rate and the ARC are temporally out-of-phase during the Northern Hemisphere winter. In the second part of this study, we use a cloud-resolving model to gain a deeper understanding of the relationship between precipitation and the ARC. In particular, we explore how the relationship between precipitation and the ARC is affected by convective aggregation, in which the convective activity is confined to a small portion of the domain that is surrounded by a much larger region of dry, subsiding air. We investigate the responses of the ARC and precipitation rate to changes in the sea surface temperature (SST), domain size, and microphysics parameterization. Both fields increase with increasing SST and the use of 2-moment microphysics. The precipitation and ARC show evidence of convective aggregation, and in the domain average, both fields increase as a result. While running these sensitivity tests, we observed a pulsation in the convective precipitation rate, once aggregation had occurred. The period of the pulsation is on the order of ten simulated hours for a domain size of 768 km. The sensitivity tests mentioned above were used to investigate the mechanism of the pulsation. We also performed an additional test with no evaporation of falling rain, which leads to no cold pools in the boundary layer. Our results show that the period of the pulsation is noticeably sensitive to microphysics and domain size. The pulsation disappears completely when cold pools are prevented from forming, which suggests a "discharge-recharge" mechanism.

Morphology, directed self-assembly and pattern transfer from a high molecular weight polystyrene-block-poly(dimethylsiloxane) block copolymer film

NASA Astrophysics Data System (ADS)

Cheng, Li-Chen; Bai, Wubin; Fernandez Martin, Eduardo; Tu, Kun-Hua; Ntetsikas, Konstantinos; Liontos, George; Avgeropoulos, Apostolos; Ross, C. A.

2017-04-01

The self-assembly of block copolymers with large feature sizes is inherently challenging as the large kinetic barrier arising from chain entanglement of high molecular weight (MW) polymers limits the extent over which long-range ordered microdomains can be achieved. Here, we illustrate the evolution of thin film morphology from a diblock copolymer of polystyrene-block-poly(dimethylsiloxane) exhibiting total number average MW of 123 kg mol-1, and demonstrate the formation of layers of well-ordered cylindrical microdomains under appropriate conditions of binary solvent mix ratio, commensurate film thickness, and solvent vapor annealing time. Directed self-assembly of the block copolymer within lithographically patterned trenches occurs with alignment of cylinders parallel to the sidewalls. Fabrication of ordered cobalt nanowire arrays by pattern transfer was also implemented, and their magnetic properties and domain wall behavior were characterized.

Structural considerations for functional anti-EGFR × anti-CD3 bispecific diabodies in light of domain order and binding affinity.

PubMed

Asano, Ryutaro; Nagai, Keisuke; Makabe, Koki; Takahashi, Kento; Kumagai, Takashi; Kawaguchi, Hiroko; Ogata, Hiromi; Arai, Kyoko; Umetsu, Mitsuo; Kumagai, Izumi

2018-03-02

We previously reported a functional humanized bispecific diabody (bsDb) that targeted EGFR and CD3 (hEx3-Db) and enhancement of its cytotoxicity by rearranging the domain order in the V domain. Here, we further dissected the effect of domain order in bsDbs on their cross-linking ability and binding kinetics to elucidate general rules regarding the design of functional bsDbs. Using Ex3-Db as a model system, we first classified the four possible domain orders as anti-parallel (where both chimeric single-chain components are variable heavy domain (VH)-variable light domain (VL) or VL-VH order) and parallel types (both chimeric single-chain components are mixed with VH-VL and VL-VH order). Although anti-parallel Ex3-Dbs could cross-link the soluble target antigens, their cross-linking ability between soluble targets had no correlation with their growth inhibitory effects. In contrast, the binding affinity of one of the two constructs with a parallel-arrangement V domain was particularly low, and structural modeling supported this phenomenon. Similar results were observed with E2x3-Dbs, in which the V region of the anti-EGFR antibody clone in hEx3 was replaced with that of another anti-EGFR clone. Only anti-parallel types showed affinity-dependent cancer inhibitory effects in each molecule, and E2x3-LH (both components in VL-VH order) showed the most intense anti-tumor activity in vitro and in vivo . Our results showed that, in addition to rearranging the domain order of bsDbs, increasing their binding affinity may be an ideal strategy for enhancing the cytotoxicity of anti-parallel constructs and that E2x3-LH is particularly attractive as a candidate next-generation anti-cancer drug.

Template-directed atomically precise self-organization of perfectly ordered parallel cerium silicide nanowire arrays on Si(110)-16 × 2 surfaces.

PubMed

Hong, Ie-Hong; Liao, Yung-Cheng; Tsai, Yung-Feng

2013-11-05

The perfectly ordered parallel arrays of periodic Ce silicide nanowires can self-organize with atomic precision on single-domain Si(110)-16 × 2 surfaces. The growth evolution of self-ordered parallel Ce silicide nanowire arrays is investigated over a broad range of Ce coverages on single-domain Si(110)-16 × 2 surfaces by scanning tunneling microscopy (STM). Three different types of well-ordered parallel arrays, consisting of uniformly spaced and atomically identical Ce silicide nanowires, are self-organized through the heteroepitaxial growth of Ce silicides on a long-range grating-like 16 × 2 reconstruction at the deposition of various Ce coverages. Each atomically precise Ce silicide nanowire consists of a bundle of chains and rows with different atomic structures. The atomic-resolution dual-polarity STM images reveal that the interchain coupling leads to the formation of the registry-aligned chain bundles within individual Ce silicide nanowire. The nanowire width and the interchain coupling can be adjusted systematically by varying the Ce coverage on a Si(110) surface. This natural template-directed self-organization of perfectly regular parallel nanowire arrays allows for the precise control of the feature size and positions within ±0.2 nm over a large area. Thus, it is a promising route to produce parallel nanowire arrays in a straightforward, low-cost, high-throughput process.

Template-directed atomically precise self-organization of perfectly ordered parallel cerium silicide nanowire arrays on Si(110)-16 × 2 surfaces

PubMed Central

2013-01-01

The perfectly ordered parallel arrays of periodic Ce silicide nanowires can self-organize with atomic precision on single-domain Si(110)-16 × 2 surfaces. The growth evolution of self-ordered parallel Ce silicide nanowire arrays is investigated over a broad range of Ce coverages on single-domain Si(110)-16 × 2 surfaces by scanning tunneling microscopy (STM). Three different types of well-ordered parallel arrays, consisting of uniformly spaced and atomically identical Ce silicide nanowires, are self-organized through the heteroepitaxial growth of Ce silicides on a long-range grating-like 16 × 2 reconstruction at the deposition of various Ce coverages. Each atomically precise Ce silicide nanowire consists of a bundle of chains and rows with different atomic structures. The atomic-resolution dual-polarity STM images reveal that the interchain coupling leads to the formation of the registry-aligned chain bundles within individual Ce silicide nanowire. The nanowire width and the interchain coupling can be adjusted systematically by varying the Ce coverage on a Si(110) surface. This natural template-directed self-organization of perfectly regular parallel nanowire arrays allows for the precise control of the feature size and positions within ±0.2 nm over a large area. Thus, it is a promising route to produce parallel nanowire arrays in a straightforward, low-cost, high-throughput process. PMID:24188092

Visual Acuity does not Moderate Effect Sizes of Higher-Level Cognitive Tasks

PubMed Central

Houston, James R.; Bennett, Ilana J.; Allen, Philip A.; Madden, David J.

2016-01-01

Background Declining visual capacities in older adults have been posited as a driving force behind adult age differences in higher-order cognitive functions (e.g., the “common cause” hypothesis of Lindenberger & Baltes, 1994). McGowan, Patterson and Jordan (2013) also found that a surprisingly large number of published cognitive aging studies failed to include adequate measures of visual acuity. However, a recent meta-analysis of three studies (LaFleur & Salthouse, 2014) failed to find evidence that visual acuity moderated or mediated age differences in higher-level cognitive processes. In order to provide a more extensive test of whether visual acuity moderates age differences in higher-level cognitive processes, we conducted a more extensive meta-analysis of topic. Methods Using results from 456 studies, we calculated effect sizes for the main effect of age across four cognitive domains (attention, executive function, memory, and perception/language) separately for five levels of visual acuity criteria (no criteria, undisclosed criteria, self-reported acuity, 20/80-20/31, and 20/30 or better). Results As expected, age had a significant effect on each cognitive domain. However, these age effects did not further differ as a function of visual acuity criteria. Conclusion The current meta-analytic, cross-sectional results suggest that visual acuity is not significantly related to age group differences in higher-level cognitive performance—thereby replicating LaFleur and Salthouse (2014). Further efforts are needed to determine whether other measures of visual functioning (e.g. contrast sensitivity, luminance) affect age differences in cognitive functioning. PMID:27070044

Multiscale modelling of dual-porosity porous media; a computational pore-scale study for flow and solute transport

NASA Astrophysics Data System (ADS)

de Vries, Enno T.; Raoof, Amir; van Genuchten, Martinus Th.

2017-07-01

Many environmental and agricultural applications involve the transport of water and dissolved constituents through aggregated soil profiles, or porous media that are structured, fractured or macroporous in other ways. During the past several decades, various process-based macroscopic models have been used to simulate contaminant transport in such media. Many of these models consider advective-dispersive transport through relatively large inter-aggregate pore domains, while exchange with the smaller intra-aggregate pores is assumed to be controlled by diffusion. Exchange of solute between the two domains is often represented using a first-order mass transfer coefficient, which is commonly obtained by fitting to observed data. This study aims to understand and quantify the solute exchange term by applying a dual-porosity pore-scale network model to relatively large domains, and analysing the pore-scale results in terms of the classical dual-porosity (mobile-immobile) transport formulation. We examined the effects of key parameters (notably aggregate porosity and aggregate permeability) on the main dual-porosity model parameters, i.e., the mobile water fraction (ϕm) and the mass transfer coefficient (α). Results were obtained for a wide range of aggregate porosities (between 0.082 and 0.700). The effect of aggregate permeability was explored by varying pore throat sizes within the aggregates. Solute breakthrough curves (BTCs) obtained with the pore-scale network model at several locations along the domain were analysed using analytical solutions of the dual-porosity model to obtain estimates of ϕm and α. An increase in aggregate porosity was found to decrease ϕm and increase α, leading to considerable tailing in the BTCs. Changes in the aggregate pore throat size affected the relative flow velocity between the intra- and inter-aggregate domains. Higher flow velocities within the aggregates caused a change in the transport regime from diffusion dominated to more advection dominated. This change increased the exchange rate of solutes between the mobile and immobile domains, with a related increase in the value of the mass transfer coefficient and less tailing in the BTCs.

The Spatial Scale of Convective Aggregation in Cloud Resolving Simulations of Radiative Convective Equilibrium

NASA Astrophysics Data System (ADS)

Patrizio, Casey

A three-dimensional cloud-resolving model (CRM) was used to investigate the preferred separation distance between humid, rainy regions formed by convective aggregation in radiative-convective equilibrium without rotation. We performed the simulations with doubly-periodic square domains of widths 768 km, 1536 km and 3072 km over a time period of about 200 days. The simulations in the larger domains were initialized using multiple copies of the results in the small domain at day 90, plus a small perturbation. With all three domain sizes, the simulations evolved to a single statistically steady convective cluster surrounded by a broader region of dry, subsiding air by about day 150. In the largest domain case, however, we found that an additional convective cluster formed when we the simulation was run for an extended period of time. Specifically, a smaller convective cluster formed at around day 185 at a maximum radial distance from the larger cluster and then re-merged with the larger cluster after about 10 days. We explored how the aggregated state was different in each domain case, before the smaller cluster formed in the large domain. In particular, we investigated changes in the radial structure of the aggregated state by calculating profiles for the water, dynamics and radiation as a function of distance from the center of the convective region. Changes in the vertical structure were also investigated by compositing on the convective region and dry, subsiding region at each height. We found that, with increasing domain size, the convective region boundary layer became more buoyant, the convective cores reached deeper into the troposphere, the mesoscale convective updraft became weaker, and the mesoscale convective region spread out. Additionally, as the domain size was increased, conditions in the remote environment became favorable for convection. We describe a physical mechanism for the weakening of the mesoscale convective updraft and associated broadening of the convective region with increasing domain size, which involves mid-level stable layer enhancement as a result of the deeper convection. Finally, a simple analytical model of the aggregated state was used to explore the dependency of the convective fractional area on the domain size. The simple model solutions that had net radiative cooling and surface evaporation in the convective region were consistent with the simulation results. In particular, the solutions captured the broadening of the convective region, the weakening of the convective region updraft, as well as the positive and declining gross moist stability (GMS) that occurred with increasing domain size in the simulations. Furthermore, the simple model transitioned from positive to negative GMS at a domain length of about 7000 km because the convective region boundary layer became progressively more humid with increasing domain size. This suggests that the spatial scale of the aggregated RCE state in the simulations would be limited to a length scale of about 7000 km, as convectively-active areas are commonly observed to have positive GMS. This work additionally suggests that the processes that influence the water vapor content in the convective region boundary layer, such as convectively-driven turbulent water vapor fluxes, are important for determining the spatial scale of the aggregated RCE state.

Topologically associating domains are stable units of replication-timing regulation.

PubMed

Pope, Benjamin D; Ryba, Tyrone; Dileep, Vishnu; Yue, Feng; Wu, Weisheng; Denas, Olgert; Vera, Daniel L; Wang, Yanli; Hansen, R Scott; Canfield, Theresa K; Thurman, Robert E; Cheng, Yong; Gülsoy, Günhan; Dennis, Jonathan H; Snyder, Michael P; Stamatoyannopoulos, John A; Taylor, James; Hardison, Ross C; Kahveci, Tamer; Ren, Bing; Gilbert, David M

2014-11-20

Eukaryotic chromosomes replicate in a temporal order known as the replication-timing program. In mammals, replication timing is cell-type-specific with at least half the genome switching replication timing during development, primarily in units of 400-800 kilobases ('replication domains'), whose positions are preserved in different cell types, conserved between species, and appear to confine long-range effects of chromosome rearrangements. Early and late replication correlate, respectively, with open and closed three-dimensional chromatin compartments identified by high-resolution chromosome conformation capture (Hi-C), and, to a lesser extent, late replication correlates with lamina-associated domains (LADs). Recent Hi-C mapping has unveiled substructure within chromatin compartments called topologically associating domains (TADs) that are largely conserved in their positions between cell types and are similar in size to replication domains. However, TADs can be further sub-stratified into smaller domains, challenging the significance of structures at any particular scale. Moreover, attempts to reconcile TADs and LADs to replication-timing data have not revealed a common, underlying domain structure. Here we localize boundaries of replication domains to the early-replicating border of replication-timing transitions and map their positions in 18 human and 13 mouse cell types. We demonstrate that, collectively, replication domain boundaries share a near one-to-one correlation with TAD boundaries, whereas within a cell type, adjacent TADs that replicate at similar times obscure replication domain boundaries, largely accounting for the previously reported lack of alignment. Moreover, cell-type-specific replication timing of TADs partitions the genome into two large-scale sub-nuclear compartments revealing that replication-timing transitions are indistinguishable from late-replicating regions in chromatin composition and lamina association and accounting for the reduced correlation of replication timing to LADs and heterochromatin. Our results reconcile cell-type-specific sub-nuclear compartmentalization and replication timing with developmentally stable structural domains and offer a unified model for large-scale chromosome structure and function.

Fokker-Planck equation for particle growth by monomer attachment.

PubMed

Matsoukas, Themis; Lin, Yulan

2006-09-01

The population balance equation (PBE) for growth by attachment of a monomeric unit is described in the discrete domain by an infinite set of differential equations. Transforming the discrete problem into the continuous domain produces a series expansion which is usually truncated past the first term. We study the effect of this truncation and we show that by including the second-order term one obtains a Fokker-Planck approximation of the continuous PBE whose first and second moments are exact. We use this truncation to study the asymptotic behavior of the variance of the size distribution with growth rate that is a power-law function of the particle mass with exponent a . We obtain analytic expressions for the variance and show that its asymptotic behavior is different in the regimes a<1/2 and a>1/2. These conclusions are corroborated by Monte Carlo simulations.

A Comparison of Techniques for Scheduling Fleets of Earth-Observing Satellites

NASA Technical Reports Server (NTRS)

Globus, Al; Crawford, James; Lohn, Jason; Pryor, Anna

2003-01-01

Earth observing satellite (EOS) scheduling is a complex real-world domain representative of a broad class of over-subscription scheduling problems. Over-subscription problems are those where requests for a facility exceed its capacity. These problems arise in a wide variety of NASA and terrestrial domains and are .XI important class of scheduling problems because such facilities often represent large capital investments. We have run experiments comparing multiple variants of the genetic algorithm, hill climbing, simulated annealing, squeaky wheel optimization and iterated sampling on two variants of a realistically-sized model of the EOS scheduling problem. These are implemented as permutation-based methods; methods that search in the space of priority orderings of observation requests and evaluate each permutation by using it to drive a greedy scheduler. Simulated annealing performs best and random mutation operators outperform our squeaky (more intelligent) operator. Furthermore, taking smaller steps towards the end of the search improves performance.

Approaching the theoretical limit in periodic local MP2 calculations with atomic-orbital basis sets: the case of LiH.

PubMed

Usvyat, Denis; Civalleri, Bartolomeo; Maschio, Lorenzo; Dovesi, Roberto; Pisani, Cesare; Schütz, Martin

2011-06-07

The atomic orbital basis set limit is approached in periodic correlated calculations for solid LiH. The valence correlation energy is evaluated at the level of the local periodic second order Møller-Plesset perturbation theory (MP2), using basis sets of progressively increasing size, and also employing "bond"-centered basis functions in addition to the standard atom-centered ones. Extended basis sets, which contain linear dependencies, are processed only at the MP2 stage via a dual basis set scheme. The local approximation (domain) error has been consistently eliminated by expanding the orbital excitation domains. As a final result, it is demonstrated that the complete basis set limit can be reached for both HF and local MP2 periodic calculations, and a general scheme is outlined for the definition of high-quality atomic-orbital basis sets for solids. © 2011 American Institute of Physics

Computational Aeroacoustics: An Overview

NASA Technical Reports Server (NTRS)

Tam, Christopher K. W.

2003-01-01

An overview of recent advances in computational aeroacoustics (CAA) is presented. CAA algorithms must not be dispersive and dissipative. It should propagate waves supported by the Euler equations with the correct group velocities. Computation domains are inevitably finite in size. To avoid the reflection of acoustic and other outgoing waves at the boundaries of the computation domain, it is required that special boundary conditions be imposed at the boundary region. These boundary conditions either absorb all the outgoing waves without reflection or allow the waves to exit smoothly. High-order schemes, invariably, supports spurious short waves. These spurious waves tend to pollute the numerical solution. They must be selectively damped or filtered out. All these issues and relevant computation methods are briefly reviewed. Jet screech tones are known to have caused structural fatigue in military combat aircrafts. Numerical simulation of the jet screech phenomenon is presented as an example of a successful application of CAA.

Novel structure formation at the bottom surface of porous anodic alumina fabricated by single step anodization process.

PubMed

Ali, Ghafar; Ahmad, Maqsood; Akhter, Javed Iqbal; Maqbool, Muhammad; Cho, Sung Oh

2010-08-01

A simple approach for the growth of long-range highly ordered nanoporous anodic alumina film in H(2)SO(4) electrolyte through a single step anodization without any additional pre-anodizing procedure is reported. Free-standing porous anodic alumina film of 180 microm thickness with through hole morphology was obtained. A simple and single step process was used for the detachment of alumina from aluminum substrate. The effect of anodizing conditions, such as anodizing voltage and time on the pore diameter and pore ordering is discussed. The metal/oxide and oxide/electrolyte interfaces were examined by high resolution scanning transmission electron microscope. The arrangement of pores on metal/oxide interface was well ordered with smaller diameters than that of the oxide/electrolyte interface. The inter-pore distance was larger in metal/oxide interface as compared to the oxide/electrolyte interface. The size of the ordered domain was found to depend strongly upon anodizing voltage and time. (c) 2010 Elsevier Ltd. All rights reserved.

A Critical Appraisal of the `Day' Diagram

NASA Astrophysics Data System (ADS)

Roberts, A. P.; Tauxe, L.; Heslop, D.

2017-12-01

The `Day' diagram [Day et al., 1977; doi:10.1016/0031-9201(77)90108-X] is used widely to infer the mean domain state of magnetic mineral assemblages. The Day plot coordinates are the ratios of the saturation remanent magnetization to saturation magnetization (Mrs/Ms) and the coercivity of remanence to coercivity (Bcr/Bc), as determined from a major hysteresis loop and a backfield demagnetization curve. Based on theoretical and empirical arguments, Day plots are typically demarcated into stable single domain (SD), `pseudosingle domain' (`PSD'), and multidomain (MD) zones. It is a simple task to determine Mrs/Ms and Bcr/Bc for a sample and to assign a mean domain state based on the boundaries defined by Day et al. [1977]. Many other parameters contribute to variability in a Day diagram, including surface oxidation, mineral stoichiometry, stress state, magnetostatic interactions, and mixtures of magnetic particles with different sizes and shapes. Bulk magnetic measurements usually lack detailed independent evidence to constrain each free parameter, which makes the Day diagram fundamentally ambiguous. This raises questions about its usefulness for diagnosing magnetic particle size variations. The Day diagram is also used to make inferences about binary mixing of magnetic particles, where, for example, mixtures of SD and MD particles give rise to a bulk `PSD' response even though the concentration of `PSD' grains could be zero. In our assessment of thousands of hysteresis measurements of geological samples, binary mixing occurs in a tiny number of cases. Ternary, quaternary, and higher order mixing are usually observed. Also, uniaxial SD and MD end-members are nearly always inappropriate for considering mixing because uniaxial SD particles are virtually non-existent in igneous rocks. Thus, use of mixing lines in Day diagrams routinely provides unsatisfactory representations of particle size variations. We critically appraise the Day diagram and argue that its many ambiguities limit its use so severely that it should be abandoned. A suitable alternative is not obvious, but new approaches need to be developed to understand the magnetic properties of individual magnetic components in samples with mixed magnetic mineral assemblages.

Geometry of phase-separated domains in phospholipid bilayers by diffraction-contrast electron microscopy.

PubMed Central

Hui, S W

1981-01-01

The sizes and shapes of solidus (gel) phase domains in the hydrated molecular bilayers of dilauroylphosphatidylcholine/dipalmitoylphasphatidylcholine (DLPC/DPPC) (1:1) and phosphatidylserine (PS)/DPPC (1:2) are visualized directly by low dose diffraction-contrast electron microscopy. The temperature and humidity of the bilayers are controlled by an environmental chamber set in an electron microscope. The contrast between crystalline domains is enhanced by electron optical filtering of the diffraction patterns of the bilayers. The domains are seen as a patchwork in the plane of the bilayer, with an average width of 0.2-0.5 micrometer. The percentage of solidus area measured from diffraction-contrast micrographs at various temperatures agrees in general with those depicted by known phase diagrams. The shape and size of the domains resemble those seen by freeze-fracture in multilamellar vesicles. Temperature-related changes in domain size and in phase boundary per unit area are more pronounced in the less miscible DLPC/DPPC mixture. No significant change in these geometric parameters with temperature is found in the PS/DPPC mixture. Mapping domains by their molecular diffraction signals not only verifies the existance of areas of different molecular packing during phase separation but also provides a quantitative measurement of structural boundaries and defects in lipid bilayers. Images FIGURE 1 FIGURE 3 FIGURE 6 PMID:6894707

Solution of the three-dimensional Helmholtz equation with nonlocal boundary conditions

NASA Technical Reports Server (NTRS)

Hodge, Steve L.; Zorumski, William E.; Watson, Willie R.

1995-01-01

The Helmholtz equation is solved within a three-dimensional rectangular duct with a nonlocal radiation boundary condition at the duct exit plane. This condition accurately models the acoustic admittance at an arbitrarily-located computational boundary plane. A linear system of equations is constructed with second-order central differences for the Helmholtz operator and second-order backward differences for both local admittance conditions and the gradient term in the nonlocal radiation boundary condition. The resulting matrix equation is large, sparse, and non-Hermitian. The size and structure of the matrix makes direct solution techniques impractical; as a result, a nonstationary iterative technique is used for its solution. The theory behind the nonstationary technique is reviewed, and numerical results are presented for radiation from both a point source and a planar acoustic source. The solutions with the nonlocal boundary conditions are invariant to the location of the computational boundary, and the same nonlocal conditions are valid for all solutions. The nonlocal conditions thus provide a means of minimizing the size of three-dimensional computational domains.

Extended domains of organized nanorings of silver grains as surface-enhanced Raman scattering sensors for molecular detection

NASA Astrophysics Data System (ADS)

Bechelany, M.; Brodard, P.; Philippe, L.; Michler, J.

2009-11-01

The possibility to synthesize large areas of silver grains organized in nanorings using a simple technique based on nanosphere lithography and electroless plating as a metal deposition method is described for the first time. In addition, we present a systematic SERS study of the obtained long-range ordered silver nanodots and nanorings. The possibility to precisely control the size, the interdistance and the morphology of these nanostructures allows us to systematically investigate the influence of these parameters on SERS. We show that the best possible SERS substrates should not only present optimal sizes, interdistances and shapes, but also a grain-like structure composed of sub-100 nm grains in order to maximize the number of hot-spots. In addition, we show that grains arranged in nanorings present higher enhancement factors (EF = 5.5 × 105) as compared to similar arrays made of nanodots. A wide range of applications, including real-time monitoring of catalytic surface reactions, environmental and security monitoring as well as clinical and pharmaceutical screening, can be envisaged for these SERS substrates.

Extended domains of organized nanorings of silver grains as surface-enhanced Raman scattering sensors for molecular detection.

PubMed

Bechelany, M; Brodard, P; Philippe, L; Michler, J

2009-11-11

The possibility to synthesize large areas of silver grains organized in nanorings using a simple technique based on nanosphere lithography and electroless plating as a metal deposition method is described for the first time. In addition, we present a systematic SERS study of the obtained long-range ordered silver nanodots and nanorings. The possibility to precisely control the size, the interdistance and the morphology of these nanostructures allows us to systematically investigate the influence of these parameters on SERS. We show that the best possible SERS substrates should not only present optimal sizes, interdistances and shapes, but also a grain-like structure composed of sub-100 nm grains in order to maximize the number of hot-spots. In addition, we show that grains arranged in nanorings present higher enhancement factors (E(F) = 5.5 x 10(5)) as compared to similar arrays made of nanodots. A wide range of applications, including real-time monitoring of catalytic surface reactions, environmental and security monitoring as well as clinical and pharmaceutical screening, can be envisaged for these SERS substrates.

Effects of interfacial debonding and fiber breakage on static and dynamic buckling of fibers embedded in matrices

NASA Astrophysics Data System (ADS)

Serttunc, Metin

1992-09-01

Analyses were performed for static and dynamic buckling of a continuous fiber embedded in a matrix in order to determine the effects of interfacial debonding and fiber breakage on the critical buckling load and the domain of instability. A beam on elastic foundation model was used. The study showed that a local interfacial debonding between a fiber and a surrounding matrix resulted in an increase of the wavelength of the buckling mode. An increase of the wave length yielded a decrease of the static buckling load and lowered the dynamic instability domain. In general, the effect of a partial or complete interfacial debonding was more significant on the domain of dynamic instability than on the effects of static buckling load. For dynamic buckling of a fiber, a local debonding of size 10 to 20 percent of the fiber length had the most important influence on the domains of dynamic instability regardless of the location of debonding and the boundary conditions of the fiber. For static buckling, the location of a local debonding was critical to a free-simply supported fiber but not to a fiber with both ends simply supported. Fiber breakage also lowered the critical buckling load significantly.

Dynamics of domain coverage of the protein sequence universe

PubMed Central

2012-01-01

Background The currently known protein sequence space consists of millions of sequences in public databases and is rapidly expanding. Assigning sequences to families leads to a better understanding of protein function and the nature of the protein universe. However, a large portion of the current protein space remains unassigned and is referred to as its “dark matter”. Results Here we suggest that true size of “dark matter” is much larger than stated by current definitions. We propose an approach to reducing the size of “dark matter” by identifying and subtracting regions in protein sequences that are not likely to contain any domain. Conclusions Recent improvements in computational domain modeling result in a decrease, albeit slowly, in the relative size of “dark matter”; however, its absolute size increases substantially with the growth of sequence data. PMID:23157439

MIMO equalization with adaptive step size for few-mode fiber transmission systems.

PubMed

van Uden, Roy G H; Okonkwo, Chigo M; Sleiffer, Vincent A J M; de Waardt, Hugo; Koonen, Antonius M J

2014-01-13

Optical multiple-input multiple-output (MIMO) transmission systems generally employ minimum mean squared error time or frequency domain equalizers. Using an experimental 3-mode dual polarization coherent transmission setup, we show that the convergence time of the MMSE time domain equalizer (TDE) and frequency domain equalizer (FDE) can be reduced by approximately 50% and 30%, respectively. The criterion used to estimate the system convergence time is the time it takes for the MIMO equalizer to reach an average output error which is within a margin of 5% of the average output error after 50,000 symbols. The convergence reduction difference between the TDE and FDE is attributed to the limited maximum step size for stable convergence of the frequency domain equalizer. The adaptive step size requires a small overhead in the form of a lookup table. It is highlighted that the convergence time reduction is achieved without sacrificing optical signal-to-noise ratio performance.

Magnetic Force Microscopy Investigation of Magnetic Domains in Nd2Fe14B

NASA Astrophysics Data System (ADS)

Talari, Mahesh Kumar; Markandeyulu, G.; Rao, K. Prasad

2010-07-01

Remenance and coercivity in Nd2Fe14B materials are strongly dependent on the microstructural aspects like phases morphology and grain size. The coercivity (Hc) of a magnetic material varies inversely with the grain size (D) and there is a critical size below which Hc∝D6. Domain wall pinning by grain boundaries and foreign phases is the important mechanism in explaining the improvement in coercivity and remenance. Nd2Fe14B intermetallic compound with stochiometric composition was prepared from pure elements (Nd -99.5%, Fe—99.95%, B -99.99%) by arc melting in argon atmosphere. Magnetic Force Microscope (MFM) gives high-resolution magnetic domain structural information of ferromagnetic samples. DI-3100 Scanning Probe Microscope with MESP probes was used For MFM characterization of the samples. Magnetic domains observed in cast ingots were very long (up to 40 μm were observed) and approximately 1-5 μm wide due to high anisotropy of the compounds. Magnetic domains have displayed different image contrast and morphologies at different locations of the samples. The domain morphologies and image contrast obtained in this analysis were explained in this paper.

Photonic nanojet super-resolution in immersed ordered assembly of dielectric microspheres

NASA Astrophysics Data System (ADS)

Geints, Y. E.; Zemlyanov, A. A.

2017-10-01

Specific spatially-localized optical field structure, which is often referred to as a photonic nanojet (PNJ), is formed in the near-field scattering area of non-absorbing dielectric micron-sized particle exposed to an optical radiation. By virtue of the finite-difference time-domain technique we numerically simulate the two-dimensional array of PNJs created by an ordered single-layer microassembly of glass microspheres immersed in a transparent polymer matrix. The behavior of the main PNJ parameters (length, diameter, and intensity) is analyzed subject to the immersion depth of the microparticles and cooperative interference effects of the neighboring microspheres. We show that depending on microassembly configuration, the PNJ quality can be significantly improved; in particular, the PNJ spatial resolution better than λ/5 can be achieved.

Overset meshing coupled with hybridizable discontinuous Galerkin finite elements

DOE PAGES

Kauffman, Justin A.; Sheldon, Jason P.; Miller, Scott T.

2017-03-01

We introduce the use of hybridizable discontinuous Galerkin (HDG) finite element methods on overlapping (overset) meshes. Overset mesh methods are advantageous for solving problems on complex geometrical domains. We also combine geometric flexibility of overset methods with the advantages of HDG methods: arbitrarily high-order accuracy, reduced size of the global discrete problem, and the ability to solve elliptic, parabolic, and/or hyperbolic problems with a unified form of discretization. This approach to developing the ‘overset HDG’ method is to couple the global solution from one mesh to the local solution on the overset mesh. We present numerical examples for steady convection–diffusionmore » and static elasticity problems. The examples demonstrate optimal order convergence in all primal fields for an arbitrary amount of overlap of the underlying meshes.« less

Formation of metastable phases by spinodal decomposition

PubMed Central

Alert, Ricard; Tierno, Pietro; Casademunt, Jaume

2016-01-01

Metastable phases may be spontaneously formed from other metastable phases through nucleation. Here we demonstrate the spontaneous formation of a metastable phase from an unstable equilibrium by spinodal decomposition, which leads to a transient coexistence of stable and metastable phases. This phenomenon is generic within the recently introduced scenario of the landscape-inversion phase transitions, which we experimentally realize as a structural transition in a colloidal crystal. This transition exhibits a rich repertoire of new phase-ordering phenomena, including the coexistence of two equilibrium phases connected by two physically different interfaces. In addition, this scenario enables the control of sizes and lifetimes of metastable domains. Our findings open a new setting that broadens the fundamental understanding of phase-ordering kinetics, and yield new prospects of applications in materials science. PMID:27713406

The 4D Nucleome: Genome Compartmentalization in an Evolutionary Context.

PubMed

Cremer, T; Cremer, M; Cremer, C

2018-04-01

4D nucleome research aims to understand the impact of nuclear organization in space and time on nuclear functions, such as gene expression patterns, chromatin replication, and the maintenance of genome integrity. In this review we describe evidence that the origin of 4D genome compartmentalization can be traced back to the prokaryotic world. In cell nuclei of animals and plants chromosomes occupy distinct territories, built up from ~1 Mb chromatin domains, which in turn are composed of smaller chromatin subdomains and also form larger chromatin domain clusters. Microscopic evidence for this higher order chromatin landscape was strengthened by chromosome conformation capture studies, in particular Hi-C. This approach demonstrated ~1 Mb sized, topologically associating domains in mammalian cell nuclei separated by boundaries. Mutations, which destroy boundaries, can result in developmental disorders and cancer. Nucleosomes appeared first as tetramers in the Archaea kingdom and later evolved to octamers built up each from two H2A, two H2B, two H3, and two H4 proteins. Notably, nucleosomes were lost during the evolution of the Dinoflagellata phylum. Dinoflagellate chromosomes remain condensed during the entire cell cycle, but their chromosome architecture differs radically from the architecture of other eukaryotes. In summary, the conservation of fundamental features of higher order chromatin arrangements throughout the evolution of metazoan animals suggests the existence of conserved, but still unknown mechanism(s) controlling this architecture. Notwithstanding this conservation, a comparison of metazoans and protists also demonstrates species-specific structural and functional features of nuclear organization.

iPixel: a visual content-based and semantic search engine for retrieving digitized mammograms by using collective intelligence.

PubMed

Alor-Hernández, Giner; Pérez-Gallardo, Yuliana; Posada-Gómez, Rubén; Cortes-Robles, Guillermo; Rodríguez-González, Alejandro; Aguilar-Laserre, Alberto A

2012-09-01

Nowadays, traditional search engines such as Google, Yahoo and Bing facilitate the retrieval of information in the format of images, but the results are not always useful for the users. This is mainly due to two problems: (1) the semantic keywords are not taken into consideration and (2) it is not always possible to establish a query using the image features. This issue has been covered in different domains in order to develop content-based image retrieval (CBIR) systems. The expert community has focussed their attention on the healthcare domain, where a lot of visual information for medical analysis is available. This paper provides a solution called iPixel Visual Search Engine, which involves semantics and content issues in order to search for digitized mammograms. iPixel offers the possibility of retrieving mammogram features using collective intelligence and implementing a CBIR algorithm. Our proposal compares not only features with similar semantic meaning, but also visual features. In this sense, the comparisons are made in different ways: by the number of regions per image, by maximum and minimum size of regions per image and by average intensity level of each region. iPixel Visual Search Engine supports the medical community in differential diagnoses related to the diseases of the breast. The iPixel Visual Search Engine has been validated by experts in the healthcare domain, such as radiologists, in addition to experts in digital image analysis.

Multisubunit DNA-Dependent RNA Polymerases from Vaccinia Virus and Other Nucleocytoplasmic Large-DNA Viruses: Impressions from the Age of Structure.

PubMed

Mirzakhanyan, Yeva; Gershon, Paul D

2017-09-01

The past 17 years have been marked by a revolution in our understanding of cellular multisubunit DNA-dependent RNA polymerases (MSDDRPs) at the structural level. A parallel development over the past 15 years has been the emerging story of the giant viruses, which encode MSDDRPs. Here we link the two in an attempt to understand the specialization of multisubunit RNA polymerases in the domain of life encompassing the large nucleocytoplasmic DNA viruses (NCLDV), a superclade that includes the giant viruses and the biochemically well-characterized poxvirus vaccinia virus. The first half of this review surveys the recently determined structural biology of cellular RNA polymerases for a microbiology readership. The second half discusses a reannotation of MSDDRP subunits from NCLDV families and the apparent specialization of these enzymes by virus family and by subunit with regard to subunit or domain loss, subunit dissociability, endogenous control of polymerase arrest, and the elimination/customization of regulatory interactions that would confer higher-order cellular control. Some themes are apparent in linking subunit function to structure in the viral world: as with cellular RNA polymerases I and III and unlike cellular RNA polymerase II, the viral enzymes seem to opt for speed and processivity and seem to have eliminated domains associated with higher-order regulation. The adoption/loss of viral RNA polymerase proofreading functions may have played a part in matching intrinsic mutability to genome size. Copyright © 2017 American Society for Microbiology.

Rationally designed mutations convert complexes of human recombinant T cell receptor ligands into monomers that retain biological activity

PubMed Central

Huan, Jianya Y; Meza-Romero, Roberto; Mooney, Jeffery L; Chou, Yuan K; Edwards, David M; Rich, Cathleen; Link, Jason M; Vandenbark, Arthur A; Bourdette, Dennis N; Bächinger, Hans-Peter; Burrows, Gregory G

2012-01-01

Single-chain human recombinant T cell receptor ligands derived from the peptide binding/TCR recognition domain of human HLA-DR2b (DRA*0101/DRB1*1501) produced in Escherichia coli with and without amino-terminal extensions containing antigenic peptides have been described previously. While molecules with the native sequence retained biological activity, they formed higher order aggregates in solution. In this study, we used site-directed mutagenesis to modify the β-sheet platform of the DR2-derived RTLs, obtaining two variants that were monomeric in solution by replacing hydrophobic residues with polar (serine) or charged (aspartic acid) residues. Size exclusion chromatography and dynamic light scattering demonstrated that the modified RTLs were monomeric in solution, and structural characterization using circular dichroism demonstrated the highly ordered secondary structure of the RTLs. Peptide binding to the `empty' RTLs was quantified using biotinylated peptides, and functional studies showed that the modified RTLs containing covalently tethered peptides were able to inhibit antigen-specific T cell proliferation in vitro, as well as suppress experimental autoimmune encephalomyelitis in vivo. These studies demonstrated that RTLs encoding the Ag-binding/TCR recognition domain of MHC class II molecules are innately very robust structures, capable of retaining potent biological activity separate from the Ig-fold domains of the progenitor class II structure, with prevention of aggregation accomplished by modification of an exposed surface that was buried in the progenitor structure. PMID:22973070

Field-theoretic simulations of block copolymer nanocomposites in a constant interfacial tension ensemble.

PubMed

Koski, Jason P; Riggleman, Robert A

2017-04-28

Block copolymers, due to their ability to self-assemble into periodic structures with long range order, are appealing candidates to control the ordering of functionalized nanoparticles where it is well-accepted that the spatial distribution of nanoparticles in a polymer matrix dictates the resulting material properties. The large parameter space associated with block copolymer nanocomposites makes theory and simulation tools appealing to guide experiments and effectively isolate parameters of interest. We demonstrate a method for performing field-theoretic simulations in a constant volume-constant interfacial tension ensemble (nVγT) that enables the determination of the equilibrium properties of block copolymer nanocomposites, including when the composites are placed under tensile or compressive loads. Our approach is compatible with the complex Langevin simulation framework, which allows us to go beyond the mean-field approximation. We validate our approach by comparing our nVγT approach with free energy calculations to determine the ideal domain spacing and modulus of a symmetric block copolymer melt. We analyze the effect of numerical and thermodynamic parameters on the efficiency of the nVγT ensemble and subsequently use our method to investigate the ideal domain spacing, modulus, and nanoparticle distribution of a lamellar forming block copolymer nanocomposite. We find that the nanoparticle distribution is directly linked to the resultant domain spacing and is dependent on polymer chain density, nanoparticle size, and nanoparticle chemistry. Furthermore, placing the system under tension or compression can qualitatively alter the nanoparticle distribution within the block copolymer.

Fe–Ni solid solutions in nano-size dimensions: Effect of hydrogen annealing

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

Kumar, Asheesh, E-mail: asheeshk@barc.gov.in; Meena, S.S.; Banerjee, S.

Highlights: • Fe–Ni solid solution with nano-size dimensions were prepared and characterized. • Both as prepared and hydrogenated solid solutions have FCC structure of Ni. • Paramagnetic and ferromagnetic domains coexist in these samples. - Abstract: Nanoparticles of Ni{sub 0.50}Fe{sub 0.50} and Ni{sub 0.75}Fe{sub 0.25} alloys were prepared by chemical reduction in ethylene glycol medium. XRD and {sup 57}Fe Mössbauer studies have confirmed the formation of Fe–Ni solid solution in nano-size dimensions with FCC structure. These samples consist of both ferromagnetic and paramagnetic domains which have been attributed to the coexistence of large and small particles as confirmed by atomicmore » force microscopic (AFM) and {sup 57}Fe Mössbauer spectroscopic studies. Improved extent of Fe–Fe exchange interaction existing in Ni{sub 0.50}Fe{sub 0.50} alloy compared to Ni{sub 0.75}Fe{sub 0.25} alloy explains the observed increase in the relative extent of ferromagnetic domains compared to paramagnetic domains in the former sample. Increase in the relative extent of ferromagnetic domains for hydrogenated alloys is due to increase in particle size brought about by the high temperature activation prior to hydrogenation.« less

Sensitivity studies of high-resolution RegCM3 simulations of precipitation over the European Alps: the effect of lateral boundary conditions and domain size

NASA Astrophysics Data System (ADS)

Nadeem, Imran; Formayer, Herbert

2016-11-01

A suite of high-resolution (10 km) simulations were performed with the International Centre for Theoretical Physics (ICTP) Regional Climate Model (RegCM3) to study the effect of various lateral boundary conditions (LBCs), domain size, and intermediate domains on simulated precipitation over the Great Alpine Region. The boundary conditions used were ECMWF ERA-Interim Reanalysis with grid spacing 0.75∘, the ECMWF ERA-40 Reanalysis with grid spacing 1.125 and 2.5∘, and finally the 2.5∘ NCEP/DOE AMIP-II Reanalysis. The model was run in one-way nesting mode with direct nesting of the high-resolution RCM (horizontal grid spacing Δx = 10 km) with driving reanalysis, with one intermediate resolution nest (Δx = 30 km) between high-resolution RCM and reanalysis forcings, and also with two intermediate resolution nests (Δx = 90 km and Δx = 30 km) for simulations forced with LBC of resolution 2.5∘. Additionally, the impact of domain size was investigated. The results of multiple simulations were evaluated using different analysis techniques, e.g., Taylor diagram and a newly defined useful statistical parameter, called Skill-Score, for evaluation of daily precipitation simulated by the model. It has been found that domain size has the major impact on the results, while different resolution and versions of LBCs, e.g., 1.125∘ ERA40 and 0.7∘ ERA-Interim, do not produce significantly different results. It is also noticed that direct nesting with reasonable domain size, seems to be the most adequate method for reproducing precipitation over complex terrain, while introducing intermediate resolution nests seems to deteriorate the results.

Nonrotating Convective Self-Aggregation in a Limited Area AGCM

NASA Astrophysics Data System (ADS)

Arnold, Nathan P.; Putman, William M.

2018-04-01

We present nonrotating simulations with the Goddard Earth Observing System (GEOS) atmospheric general circulation model (AGCM) in a square limited area domain over uniform sea surface temperature. As in previous studies, convection spontaneously aggregates into humid clusters, driven by a combination of radiative and moisture-convective feedbacks. The aggregation is qualitatively independent of resolution, with horizontal grid spacing from 3 to 110 km, with both explicit and parameterized deep convection. A budget for the spatial variance of column moist static energy suggests that longwave radiative and surface flux feedbacks help establish aggregation, while the shortwave feedback contributes to its maintenance. Mechanism-denial experiments confirm that aggregation does not occur without interactive longwave radiation. Ice cloud radiative effects help support the humid convecting regions but are not essential for aggregation, while liquid clouds have a negligible effect. Removing the dependence of parameterized convection on tropospheric humidity reduces the intensity of aggregation but does not prevent the formation of dry regions. In domain sizes less than (5,000 km)2, the aggregation forms a single cluster, while larger domains develop multiple clusters. Larger domains initialized with a single large cluster are unable to maintain them, suggesting an upper size limit. Surface wind speed increases with domain size, implying that maintenance of the boundary layer winds may limit cluster size. As cluster size increases, large boundary layer temperature anomalies develop to maintain the surface pressure gradient, leading to an increase in the depth of parameterized convective heating and an increase in gross moist stability.

Theoretical Studies of the Kinetics of First-Order Phase Transitions.

NASA Astrophysics Data System (ADS)

Zheng, Qiang

This thesis involves theoretical studies of the kinetics of orderings in three classes of systems. The first class involves problems of phase separation in which the order parameter is conserved, such as occurs in the binary alloy Al-Zn. A theory is developed for the late stages of phase separation in the droplet regime for two -dimensional systems, namely, Ostwald ripening in two dimensions. The theory considers droplet correlations, which was neglected before, by a proper treatment of the screening effect of the correlations. This correlation effect is found that it does not alert the scaling features of phase separation, but significantly changes the shape of droplet-size distribution function. Further experiments and computer simulations are needed before this long-time subject may be closed. A second class of problem involves a study of the finite-size effects on domain growth described by the Allen-Cahn dynamics. Based on a theoretical approach of Ohta, Jasnow, and Kawasaki the explicit scaling functions for the scattering intensity for hypercubes and films are obtained. These results are for the cases in which the order-parameter is not conserved, such as in an order-disorder transition in alloys. These studies will be relevant to the experimental and computer simulation research projects currently being carried out in the United States and Europe. The last class of problems involves orderings in strong correlated systems, namely, the growth of Breath Figures. A special feature of this class of problems is that the coalescence effect. A theoretical model is proposed which can handle the two growth mechanisms, the individual droplet growth and coalescence simultaneously. Under certain approximations, the droplet-size distribution function is obtained analytically, and is in qualitative agreement with computer simulations. Our model also suggests that there may be an interesting relationship between the growth of Breath Figures and a geometric structure (ultrametricity) of general complex systems.

Electrical and structural investigations, and ferroelectric domains in nanoscale structures

NASA Astrophysics Data System (ADS)

Alexe, Marin

2005-03-01

Generally speaking material properties are expected to change as the characteristic dimension of a system approaches at the nanometer scale. In the case of ferroelectric materials fundamental problems such as the super-paraelectric limit, influence of the free surface and/or of the interface and bulk defects on ferroelectric switching, etc. arise when scaling the systems into the sub-100 nm range. In order to study these size effects, fabrication methods of high quality nanoscale ferroelectric crystals as well as AFM-based investigations methods have been developed in the last few years. The present talk will briefly review self-patterning and self- assembly fabrication methods, including chemical routes, morphological instability of ultrathin films, and self-assembly lift-off, employed up to the date to fabricate ferroelectric nanoscale structures with lateral size in the range of few tens of nanometers. Moreover, in depth structural and electrical investigations of interfaces performed to differentiate between intrinsic and extrinsic size effects will be also presented.

Computational analysis of particle reinforced viscoelastic polymer nanocomposites - statistical study of representative volume element

NASA Astrophysics Data System (ADS)

Hu, Anqi; Li, Xiaolin; Ajdari, Amin; Jiang, Bing; Burkhart, Craig; Chen, Wei; Brinson, L. Catherine

2018-05-01

The concept of representative volume element (RVE) is widely used to determine the effective material properties of random heterogeneous materials. In the present work, the RVE is investigated for the viscoelastic response of particle-reinforced polymer nanocomposites in the frequency domain. The smallest RVE size and the minimum number of realizations at a given volume size for both structural and mechanical properties are determined for a given precision using the concept of margin of error. It is concluded that using the mean of many realizations of a small RVE instead of a single large RVE can retain the desired precision of a result with much lower computational cost (up to three orders of magnitude reduced computation time) for the property of interest. Both the smallest RVE size and the minimum number of realizations for a microstructure with higher volume fraction (VF) are larger compared to those of one with lower VF at the same desired precision. Similarly, a clustered structure is shown to require a larger minimum RVE size as well as a larger number of realizations at a given volume size compared to the well-dispersed microstructures.

Changepoint detection in base-resolution methylome data reveals a robust signature of methylated domain landscape.

PubMed

Yokoyama, Takao; Miura, Fumihito; Araki, Hiromitsu; Okamura, Kohji; Ito, Takashi

2015-08-12

Base-resolution methylome data generated by whole-genome bisulfite sequencing (WGBS) is often used to segment the genome into domains with distinct methylation levels. However, most segmentation methods include many parameters to be carefully tuned and/or fail to exploit the unsurpassed resolution of the data. Furthermore, there is no simple method that displays the composition of the domains to grasp global trends in each methylome. We propose to use changepoint detection for domain demarcation based on base-resolution methylome data. While the proposed method segments the methylome in a largely comparable manner to conventional approaches, it has only a single parameter to be tuned. Furthermore, it fully exploits the base-resolution of the data to enable simultaneous detection of methylation changes in even contrasting size ranges, such as focal hypermethylation and global hypomethylation in cancer methylomes. We also propose a simple plot termed methylated domain landscape (MDL) that globally displays the size, the methylation level and the number of the domains thus defined, thereby enabling one to intuitively grasp trends in each methylome. Since the pattern of MDL often reflects cell lineages and is largely unaffected by data size, it can serve as a novel signature of methylome. Changepoint detection in base-resolution methylome data followed by MDL plotting provides a novel method for methylome characterization and will facilitate global comparison among various WGBS data differing in size and even species origin.

Signaling-Dependent Control of Apical Membrane Size and Self-Renewal in Rosette-Stage Human Neuroepithelial Stem Cells.

PubMed

Medelnik, Jan-Philip; Roensch, Kathleen; Okawa, Satoshi; Del Sol, Antonio; Chara, Osvaldo; Mchedlishvili, Levan; Tanaka, Elly M

2018-06-05

In the developing nervous system, neural stem cells are polarized and maintain an apical domain facing a central lumen. The presence of apical membrane is thought to have a profound influence on maintaining the stem cell state. With the onset of neurogenesis, cells lose their polarization, and the concomitant loss of the apical domain coincides with a loss of the stem cell identity. Little is known about the molecular signals controlling apical membrane size. Here, we use two neuroepithelial cell systems, one derived from regenerating axolotl spinal cord and the other from human embryonic stem cells, to identify a molecular signaling pathway initiated by lysophosphatidic acid that controls apical membrane size and consequently controls and maintains epithelial organization and lumen size in neuroepithelial rosettes. This apical domain size increase occurs independently of effects on proliferation and involves a serum response factor-dependent transcriptional induction of junctional and apical membrane components. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Speckle size in optical Fourier domain imaging

NASA Astrophysics Data System (ADS)

Lamouche, G.; Vergnole, S.; Bisaillon, C.-E.; Dufour, M.; Maciejko, R.; Monchalin, J.-P.

2007-06-01

As in conventional time-domain optical coherence tomography (OCT), speckle is inherent to any Optical Fourier Domain Imaging (OFDI) of biological tissue. OFDI is also known as swept-source OCT (SS-OCT). The axial speckle size is mainly determined by the OCT resolution length and the transverse speckle size by the focusing optics illuminating the sample. There is also a contribution from the sample related to the number of scatterers contained within the probed volume. In the OFDI data processing, there is some liberty in selecting the range of wavelengths used and this allows variation in the OCT resolution length. Consequently the probed volume can be varied. By performing measurements on an optical phantom with a controlled density of discrete scatterers and by changing the probed volume with different range of wavelengths in the OFDI data processing, there is an obvious change in the axial speckle size, but we show that there is also a less obvious variation in the transverse speckle size. This work contributes to a better understanding of speckle in OCT.

The grain size(s) of Black Hills Quartzite deformed in the dislocation creep regime

NASA Astrophysics Data System (ADS)

Heilbronner, Renée; Kilian, Rüdiger

2017-10-01

General shear experiments on Black Hills Quartzite (BHQ) deformed in the dislocation creep regimes 1 to 3 have been previously analyzed using the CIP method (Heilbronner and Tullis, 2002, 2006). They are reexamined using the higher spatial and orientational resolution of EBSD. Criteria for coherent segmentations based on c-axis orientation and on full crystallographic orientations are determined. Texture domains of preferred c-axis orientation (Y and B domains) are extracted and analyzed separately. Subdomains are recognized, and their shape and size are related to the kinematic framework and the original grains in the BHQ. Grain size analysis is carried out for all samples, high- and low-strain samples, and separately for a number of texture domains. When comparing the results to the recrystallized quartz piezometer of Stipp and Tullis (2003), it is found that grain sizes are consistently larger for a given flow stress. It is therefore suggested that the recrystallized grain size also depends on texture, grain-scale deformation intensity, and the kinematic framework (of axial vs. general shear experiments).

Preparation and characterization of SiO2-coated submicron-sized L10 Fe-Pt particles

NASA Astrophysics Data System (ADS)

Hayashi, Yoshiaki; Ogawa, Tomoyuki; Ishiyama, Kazushi

2018-05-01

The development of magnets with higher performance is attracting increasing interest. The optimization of their microstructure is essential to enhance their properties, and a microstructure comprising magnetically isolated hard magnetic grains of a single-domain size has been proposed as an ideal structure for enhancing the coercivity of magnets. To obtain magnets with an ideal structure, we consider the fabrication of magnets by an approach based on core/shell nanoparticles with a hard magnetic core and a non-magnetic shell. In this study, to obtain particles for our proposed approach, we attempted to fabricate L10 Fe-Pt/SiO2-core/shell particles with submicron-sized cores less than the critical single-domain size. The fabrication of such core/shell particles was confirmed from morphology observations and XRD analysis of the particles. Although the formation of more desirable core/shell particles with submicron-sized single-crystal cores in the single-domain size range was not achieved, the fabricated core/shell particles showed a high coercivity of 25 kOe.

Vortex Domain Structure in Ferroelectric Nanoplatelets and Control of its Transformation by Mechanical Load

PubMed Central

Chen, W. J.; Zheng, Yue; Wang, Biao

2012-01-01

Vortex domain patterns in low-dimensional ferroelectrics and multiferroics have been extensively studied with the aim of developing nanoscale functional devices. However, control of the vortex domain structure has not been investigated systematically. Taking into account effects of inhomogeneous electromechanical fields, ambient temperature, surface and size, we demonstrate significant influence of mechanical load on the vortex domain structure in ferroelectric nanoplatelets. Our analysis shows that the size and number of dipole vortices can be controlled by mechanical load, and yields rich temperature-stress (T-S) phase diagrams. Simulations also reveal that transformations between “vortex states” induced by the mechanical load are possible, which is totally different from the conventional way controlled on the vortex domain by the electric field. These results are relevant to application of vortex domain structures in ferroelectric nanodevices, and suggest a novel route to applications including memories, mechanical sensors and transducers. PMID:23150769

Advances in the Application of High-order Techniques in Simulation of Multi-disciplinary Phenomena

NASA Astrophysics Data System (ADS)

Gaitonde, D. V.; Visbal, M. R.

2003-03-01

This paper describes the development of a comprehensive high-fidelity algorithmic framework to simulate the three-dimensional fields associated with multi-disciplinary physics. A wide range of phenomena is considered, from aero-acoustics and turbulence to electromagnetics, non-linear fluid-structure interactions, and magnetogasdynamics. The scheme depends primarily on "spectral-like," up to sixth-order accurate compact-differencing and up to tenth-order filtering techniques. The tightly coupled procedure suppresses numerical instabilities commonly encountered with high-order methods on non-uniform meshes, near computational boundaries or in the simulation of nonlinear dynamics. Particular emphasis is placed on developing the proper metric evaluation procedures for three-dimensional moving and curvilinear meshes so that the advantages of higher-order schemes are retained in practical calculations. A domain-decomposition strategy based on finite-sized overlap regions and interface boundary treatments enables the development of highly scalable solvers. The utility of the method to simulate problems governed by widely disparate governing equations is demonstrated with several examples encompassing vortex dynamics, wave scattering, electro-fluid plasma interactions, and panel flutter.

Precise Aperture-Dependent Motion Compensation with Frequency Domain Fast Back-Projection Algorithm.

PubMed

Zhang, Man; Wang, Guanyong; Zhang, Lei

2017-10-26

Precise azimuth-variant motion compensation (MOCO) is an essential and difficult task for high-resolution synthetic aperture radar (SAR) imagery. In conventional post-filtering approaches, residual azimuth-variant motion errors are generally compensated through a set of spatial post-filters, where the coarse-focused image is segmented into overlapped blocks concerning the azimuth-dependent residual errors. However, image domain post-filtering approaches, such as precise topography- and aperture-dependent motion compensation algorithm (PTA), have difficulty of robustness in declining, when strong motion errors are involved in the coarse-focused image. In this case, in order to capture the complete motion blurring function within each image block, both the block size and the overlapped part need necessary extension leading to degeneration of efficiency and robustness inevitably. Herein, a frequency domain fast back-projection algorithm (FDFBPA) is introduced to deal with strong azimuth-variant motion errors. FDFBPA disposes of the azimuth-variant motion errors based on a precise azimuth spectrum expression in the azimuth wavenumber domain. First, a wavenumber domain sub-aperture processing strategy is introduced to accelerate computation. After that, the azimuth wavenumber spectrum is partitioned into a set of wavenumber blocks, and each block is formed into a sub-aperture coarse resolution image via the back-projection integral. Then, the sub-aperture images are straightforwardly fused together in azimuth wavenumber domain to obtain a full resolution image. Moreover, chirp-Z transform (CZT) is also introduced to implement the sub-aperture back-projection integral, increasing the efficiency of the algorithm. By disusing the image domain post-filtering strategy, robustness of the proposed algorithm is improved. Both simulation and real-measured data experiments demonstrate the effectiveness and superiority of the proposal.

Domain-area distribution anomaly in segregating multicomponent superfluids

NASA Astrophysics Data System (ADS)

Takeuchi, Hiromitsu

2018-01-01

The domain-area distribution in the phase transition dynamics of Z2 symmetry breaking is studied theoretically and numerically for segregating binary Bose-Einstein condensates in quasi-two-dimensional systems. Due to the dynamic-scaling law of the phase ordering kinetics, the domain-area distribution is described by a universal function of the domain area, rescaled by the mean distance between domain walls. The scaling theory for general coarsening dynamics in two dimensions hypothesizes that the distribution during the coarsening dynamics has a hierarchy with the two scaling regimes, the microscopic and macroscopic regimes with distinct power-law exponents. The power law in the macroscopic regime, where the domain size is larger than the mean distance, is universally represented with the Fisher's exponent of the percolation theory in two dimensions. On the other hand, the power-law exponent in the microscopic regime is sensitive to the microscopic dynamics of the system. This conjecture is confirmed by large-scale numerical simulations of the coupled Gross-Pitaevskii equation for binary condensates. In the numerical experiments of the superfluid system, the exponent in the microscopic regime anomalously reaches to its theoretical upper limit of the general scaling theory. The anomaly comes from the quantum-fluid effect in the presence of circular vortex sheets, described by the hydrodynamic approximation neglecting the fluid compressibility. It is also found that the distribution of superfluid circulation along vortex sheets obeys a dynamic-scaling law with different power-law exponents in the two regimes. An analogy to quantum turbulence on the hierarchy of vorticity distribution and the applicability to chiral superfluid 3He in a slab are also discussed.

Monomeric CH3: A Small, Stable Antibody Domain with Therapeutic Promise | Poster

Cancer.gov

By Ashley DeVine, Staff Writer Antibody domains are emerging as promising biopharmaceuticals because of their relatively small size compared to full-sized antibodies, which are too large to effectively penetrate tumors and bind to sterically restricted therapeutic targets. In an article published in The Journal of Biological Chemistry, Tianlei Ying, Ph.D., Dimiter Dimitrov,

Fear on the move: predator hunting mode predicts variation in prey mortality and plasticity in prey spatial response.

PubMed

Miller, Jennifer R B; Ament, Judith M; Schmitz, Oswald J

2014-01-01

Ecologists have long searched for a framework of a priori species traits to help predict predator-prey interactions in food webs. Empirical evidence has shown that predator hunting mode and predator and prey habitat domain are useful traits for explaining predator-prey interactions. Yet, individual experiments have yet to replicate predator hunting mode, calling into question whether predator impacts can be attributed to hunting mode or merely species identity. We tested the effects of spider predators with sit-and-wait, sit-and-pursue and active hunting modes on grasshopper habitat domain, activity and mortality in a grassland system. We replicated hunting mode by testing two spider predator species of each hunting mode on the same grasshopper prey species. We observed grasshoppers with and without each spider species in behavioural cages and measured their mortality rates, movements and habitat domains. We likewise measured the movements and habitat domains of spiders to characterize hunting modes. We found that predator hunting mode explained grasshopper mortality and spider and grasshopper movement activity and habitat domain size. Sit-and-wait spider predators covered small distances over a narrow domain space and killed fewer grasshoppers than sit-and-pursue and active predators, which ranged farther distances across broader domains and killed more grasshoppers, respectively. Prey adjusted their activity levels and horizontal habitat domains in response to predator presence and hunting mode: sedentary sit-and-wait predators with narrow domains caused grasshoppers to reduce activity in the same-sized domain space; more mobile sit-and-pursue predators with broader domains caused prey to reduce their activity within a contracted horizontal (but not vertical) domain space; and highly mobile active spiders led grasshoppers to increase their activity across the same domain area. All predators impacted prey activity, and sit-and-pursue predators generated strong effects on domain size. This study demonstrates the validity of utilizing hunting mode and habitat domain for predicting predator-prey interactions. Results also highlight the importance of accounting for flexibility in prey movement ranges as an anti-predator response rather than treating the domain as a static attribute. © 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society.

Comparative studies on the properties of glycyrrhetinic acid-loaded PLGA microparticles prepared by emulsion and template methods.

PubMed

Wang, Hong; Zhang, Guangxing; Sui, Hong; Liu, Yanhua; Park, Kinam; Wang, Wenping

2015-12-30

The O/W emulsion method has been widely used for the production of poly (lactide-co-glycolide) (PLGA) microparticles. Recently, a template method has been used to make homogeneous microparticles with predefined size and shape, and shown to be useful in encapsulating different types of active compounds. However, differences between the template method and emulsion method have not been examined. In the current study, PLGA microparticles were prepared by the two methods using glycyrrhetinic acid (GA) as a model drug. The properties of obtained microparticles were characterized and compared on drug distribution, in vitro release, and degradation. An encapsulation efficiency of over 70% and a mean particle size of about 40μm were found for both methods. DSC thermograms and XRPD diffractograms indicated that GA was highly dispersed or in the amorphous state in the matrix of microparticles. The emulsion method produced microparticles of a broad size distribution with a core-shell type structure and many drug-rich domains inside each microparticle. Its drug release and matrix degradation was slow before Day 50 and then accelerated. In contrast, the template method formed microparticles with narrow size distribution and drug distribution without apparent drug-rich domains. The template microparticles with a loading efficiency of 85% exhibited a zero-order release profile for 3 months after the initial burst release of 26.7%, and a steady surface erosion process as well. The same microparticles made by two different methods showed two distinguished drug release profiles. The two different methods can be supplementary with each other in optimization of drug formulation for achieving predetermined drug release patterns. Copyright © 2015 Elsevier B.V. All rights reserved.

Magnetization mechanisms in ordered arrays of polycrystalline Fe{sub 100−x}Co{sub x} nanowires

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

Viqueira, M. S.; Bajales, N.; Urreta, S. E.

2015-05-28

Magnetization reversal processes and coercivity mechanisms in polycrystalline Fe{sub 100−x}Co{sub x} nanowire arrays, resulting from an AC electrodeposition process, are investigated. The array coercivity is described on the basis of polarization reversal mechanisms operating in individual wires, under the effect of inter-wire dipolar interactions described by a mean field approximation. For individual wires, a reversal mechanism involving the nucleation and further expansion of domain-wall like spin configuration is considered. The wires have a mean grain size larger than both the nanowire diameter and the exchange length, so localized and non-cooperative nucleation modes are considered. As the Co content increases, themore » alloy saturation polarization gradually decreases, but the coercive field and the relative remanence of the arrays increase, indicating that they are not controlled by the shape anisotropy in all the composition range. The coercive field dependence on the angle between the applied field and the wire long axis is not well described by reversal mechanisms involving nucleation and further displacement of neither vortex nor transverse ideal domain walls. On the contrary, the angular dependence of the coercive field observed at room temperature is well predicted by a model considering nucleation of inverse domains by localized curling, in regions smaller than the grain size, exhibiting quite small aspect ratios as compared to those of the entire nanowire. In arrays with higher Co contents, a transition from an initial (small angle) localized curling nucleation mechanism to another one, involving localized coherent rotation is observed at about π/4.« less

Tuning the antiferromagnetic helical pitch length and nanoscale domain size in Fe3PO4O3 by magnetic dilution

NASA Astrophysics Data System (ADS)

Tarne, M. J.; Bordelon, M. M.; Calder, S.; Neilson, J. R.; Ross, K. A.

2017-12-01

The insulating magnetic material Fe3PO4O3 features a noncentrosymmetric lattice composed of Fe3 + triangular units. Frustration, due to competing near-neighbor (J1) and next-nearest-neighbor (J2) antiferromagnetic interactions, was recently suggested to be the origin of an antiferromagnetic helical ground state with unusual needlelike nanoscale magnetic domains in Fe3PO4O3 . Magnetic dilution is shown here to tune the ratio of these magnetic interactions, thus providing deeper insight into this unconventional antiferromagnet. Dilution of the Fe3 + lattice in Fe3PO4O3 was accomplished by substituting nonmagnetic Ga3 + to form the solid solution series Fe3-xGaxPO4O3 with x =0.012 , 0.06, 0.25, 0.5, 1.0, 1.5. Magnetic susceptibility and neutron powder diffraction data from this series are presented. A continuous decrease of both the helical pitch length and the domain size is observed with increasing dilution up to at least x =0.25 , while for x ≥0.5 , the compounds lack long-range magnetic order entirely. The decrease in the helical pitch length with increasing x can be qualitatively understood by reduction of the ratio of J2/J1 in the Heisenberg model, consistent with mean-field considerations. Intriguingly, the magnetic correlation length in the a b plane remains nearly equal to the pitch length for each value of x ≤0.25 , showing that the two quantities are intrinsically connected in this unusual antiferromagnet.

Wavelet-based 3-D inversion for frequency-domain airborne EM data

NASA Astrophysics Data System (ADS)

Liu, Yunhe; Farquharson, Colin G.; Yin, Changchun; Baranwal, Vikas C.

2018-04-01

In this paper, we propose a new wavelet-based 3-D inversion method for frequency-domain airborne electromagnetic (FDAEM) data. Instead of inverting the model in the space domain using a smoothing constraint, this new method recovers the model in the wavelet domain based on a sparsity constraint. In the wavelet domain, the model is represented by two types of coefficients, which contain both large- and fine-scale informations of the model, meaning the wavelet-domain inversion has inherent multiresolution. In order to accomplish a sparsity constraint, we minimize an L1-norm measure in the wavelet domain that mostly gives a sparse solution. The final inversion system is solved by an iteratively reweighted least-squares method. We investigate different orders of Daubechies wavelets to accomplish our inversion algorithm, and test them on synthetic frequency-domain AEM data set. The results show that higher order wavelets having larger vanishing moments and regularity can deliver a more stable inversion process and give better local resolution, while the lower order wavelets are simpler and less smooth, and thus capable of recovering sharp discontinuities if the model is simple. At last, we test this new inversion algorithm on a frequency-domain helicopter EM (HEM) field data set acquired in Byneset, Norway. Wavelet-based 3-D inversion of HEM data is compared to L2-norm-based 3-D inversion's result to further investigate the features of the new method.

Irreversible transformation of ferromagnetic ordered stripe domains in single-shot infrared-pump/resonant-x-ray-scattering-probe experiments

NASA Astrophysics Data System (ADS)

Bergeard, Nicolas; Schaffert, Stefan; López-Flores, Víctor; Jaouen, Nicolas; Geilhufe, Jan; Günther, Christian M.; Schneider, Michael; Graves, Catherine; Wang, Tianhan; Wu, Benny; Scherz, Andreas; Baumier, Cédric; Delaunay, Renaud; Fortuna, Franck; Tortarolo, Marina; Tudu, Bharati; Krupin, Oleg; Minitti, Michael P.; Robinson, Joe; Schlotter, William F.; Turner, Joshua J.; Lüning, Jan; Eisebitt, Stefan; Boeglin, Christine

2015-02-01

The evolution of a magnetic domain structure upon excitation by an intense, femtosecond infrared (IR) laser pulse has been investigated using single-shot based time-resolved resonant x-ray scattering at the x-ray free electron laser LCLS. A well-ordered stripe domain pattern as present in a thin CoPd alloy film has been used as a prototype magnetic domain structure for this study. The fluence of the IR laser pump pulse was sufficient to lead to an almost complete quenching of the magnetization within the ultrafast demagnetization process taking place within the first few hundreds of femtoseconds following the IR laser pump pulse excitation. On longer time scales this excitation gave rise to subsequent irreversible transformations of the magnetic domain structure. Under our specific experimental conditions, it took about 2 ns before the magnetization started to recover. After about 5 ns the previously ordered stripe domain structure had evolved into a disordered labyrinth domain structure. Surprisingly, we observe after about 7 ns the occurrence of a partially ordered stripe domain structure reoriented into a novel direction. It is this domain structure in which the sample's magnetization stabilizes as revealed by scattering patterns recorded long after the initial pump-probe cycle. Using micromagnetic simulations we can explain this observation based on changes of the magnetic anisotropy going along with heat dissipation in the film.

Regional climate model sensitivity to domain size

NASA Astrophysics Data System (ADS)

Leduc, Martin; Laprise, René

2009-05-01

Regional climate models are increasingly used to add small-scale features that are not present in their lateral boundary conditions (LBC). It is well known that the limited area over which a model is integrated must be large enough to allow the full development of small-scale features. On the other hand, integrations on very large domains have shown important departures from the driving data, unless large scale nudging is applied. The issue of domain size is studied here by using the “perfect model” approach. This method consists first of generating a high-resolution climatic simulation, nicknamed big brother (BB), over a large domain of integration. The next step is to degrade this dataset with a low-pass filter emulating the usual coarse-resolution LBC. The filtered nesting data (FBB) are hence used to drive a set of four simulations (LBs for Little Brothers), with the same model, but on progressively smaller domain sizes. The LB statistics for a climate sample of four winter months are compared with BB over a common region. The time average (stationary) and transient-eddy standard deviation patterns of the LB atmospheric fields generally improve in terms of spatial correlation with the reference (BB) when domain gets smaller. The extraction of the small-scale features by using a spectral filter allows detecting important underestimations of the transient-eddy variability in the vicinity of the inflow boundary, which can penalize the use of small domains (less than 100 × 100 grid points). The permanent “spatial spin-up” corresponds to the characteristic distance that the large-scale flow needs to travel before developing small-scale features. The spin-up distance tends to grow in size at higher levels in the atmosphere.

The formation of topological defects in phase transitions

NASA Technical Reports Server (NTRS)

Hodges, Hardy M.

1989-01-01

It was argued, and fought through numerical work that the results of non-dynamical Monte Carlo computer simulations cannot be applied to describe the formation of topological defects when the correlation length at the Ginzburg temperature is significantly smaller than the horizon size. To test the current hypothesis that infinite strings at formation are essentially described by Brownian walks of size the correlation length at the Ginzburg temperature, fields at the Ginzburg temperature were equilibrated. Infinite structure do not exist in equilibrium for reasonable definitions of the Ginzburg temperature, and horizons must be included in a proper treatment. A phase transition, from small-scale to large-scale string or domain wall structure, is found to occur very close to the Ginzburg temperature, in agreement with recent work. The formation process of domain walls and global strings were investigated through the breaking of initially ordered states. To mimic conditions in the early Universe, cooling times are chosen so that horizons exist in the sample volume when topological structure formation occurs. The classical fields are evolved in real-time by the numerical solution of Langevin equations of motion on a three dimensional spatial lattice. The results indicate that it is possible for most of the string energy to be in small loops, rather than in long strings, at formation.

Monomeric CH3: A Small, Stable Antibody Domain with Therapeutic Promise | Poster

Cancer.gov

By Ashley DeVine, Staff Writer Antibody domains are emerging as promising biopharmaceuticals because of their relatively small size compared to full-sized antibodies, which are too large to effectively penetrate tumors and bind to sterically restricted therapeutic targets. In an article published in The Journal of Biological Chemistry, Tianlei Ying, Ph.D., Dimiter Dimitrov, Ph.D., and their colleagues in the Protein Interactions Group, Cancer and Inflammation Program, Center for Cancer Research, reported their design of a novel antibody domain, monomeric CH3 (mCH3).

Hydration shell parameters of aqueous alcohols: THz excess absorption and packing density.

PubMed

Matvejev, V; Zizi, M; Stiens, J

2012-12-06

Solvation in water requires minimizing the perturbations in its hydrogen bonded network. Hence solutes distort water molecular motions in a surrounding domain, forming a molecule-specific hydration shell. The properties of those hydration shells impact the structure and function of the solubilized molecules, both at the single molecule and at higher order levels. The size of the hydration shell and the picoseconds time-scale water dynamics retardation are revealed by terahertz (THz) absorption coefficient measurements. Room-temperature absorption coefficient at f = 0.28 [THz] is measured as a function of alcohol concentration in aqueous methanol, ethanol, 1,2-propanol, and 1-butanol solutions. Highly diluted alcohol measurements and enhanced overall measurement accuracy are achieved with a THz absorption measurement technique of nL-volume liquids in a capillary tube. In the absorption analysis, bulk and interfacial molecular domains of water and alcohol are considered. THz ideal and excess absorption coefficients are defined in accordance with thermodynamics mixing formulations. The parameter extraction method is developed based on a THz excess absorption model and hydrated solute molecule packing density representation. First, the hydration shell size is deduced from the hydrated solute packing densities at two specific THz excess absorption nonlinearity points: at infinite alcohol dilution (IAD) and at the THz excess absorption extremum (EAE). Consequently, interfacial water and alcohol molecular domain absorptions are deduced from the THz excess absorption model. The hydration shell sizes obtained at the THz excess absorption extremum are in excellent agreement with other reports. The hydration shells of methanol, ethanol, 1- and 2-propanol consist of 13.97, 22.94, 22.99, and 31.10 water molecules, respectively. The hydration shell water absorption is on average 0.774 ± 0.028 times the bulk water absorption. The hydration shell parameters might shed light on hydration dynamics of biomolecules.

Direct Numerical Simulation of Automobile Cavity Tones

NASA Technical Reports Server (NTRS)

Kurbatskii, Konstantin; Tam, Christopher K. W.

2000-01-01

The Navier Stokes equation is solved computationally by the Dispersion-Relation-Preserving (DRP) scheme for the flow and acoustic fields associated with a laminar boundary layer flow over an automobile door cavity. In this work, the flow Reynolds number is restricted to R(sub delta*) < 3400; the range of Reynolds number for which laminar flow may be maintained. This investigation focuses on two aspects of the problem, namely, the effect of boundary layer thickness on the cavity tone frequency and intensity and the effect of the size of the computation domain on the accuracy of the numerical simulation. It is found that the tone frequency decreases with an increase in boundary layer thickness. When the boundary layer is thicker than a certain critical value, depending on the flow speed, no tone is emitted by the cavity. Computationally, solutions of aeroacoustics problems are known to be sensitive to the size of the computation domain. Numerical experiments indicate that the use of a small domain could result in normal mode type acoustic oscillations in the entire computation domain leading to an increase in tone frequency and intensity. When the computation domain is expanded so that the boundaries are at least one wavelength away from the noise source, the computed tone frequency and intensity are found to be computation domain size independent.

A Short Note on Rules and Higher Order Rules.

ERIC Educational Resources Information Center

Scandura, Joseph M.

This brief paper argues that structural analysis--an extended form of cognitive task analysis--demonstrates that both domain dependent and domain independent knowledge can be derived from specific content domains. It is noted that the major difference between the two is that lower order rules (specific knowledge) are derived directly from specific…

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

Paranin, V. D.

In work we investigated yttrium iron garnet epitaxial films with a thickness of 10 µm and 55 µm which were grown on the surface of garnet substrate. Using the polarizing microscopy method the branching domain structure of films was shown with the period of domains 21.5 µm and 42.5 µm. Disappearance of domains at presence of an external magnetic field up to 100 Oe was noted. The optical transmission of films for the polarized beam of HeNe laser is investigated and zero diffraction order and odd diffraction rings orders were shown. Interconnection of the period of chaotically oriented domains with angles of axially symmetricmore » diffraction rings orders was shown. Diffraction patterns at various longitudinal magnetic fields are investigated. Disappearance of odd diffraction orders and increasing in intensity of zero diffraction order were fixed. Optical transmission of epitaxial films was measured in range of 500 - 900 nm.« less

Oxygen reduction reaction on highly-durable Pt/nanographene fuel cell catalyst synthesized employing in-liquid plasma

NASA Astrophysics Data System (ADS)

Amano, Tomoki; Kondo, Hiroki; Takeda, Keigo; Ishikawa, Kenji; Kano, Hiroyuki; Hiramatsu, Mineo; Sekine, Makoto; Hori, Masaru

2016-09-01

We recently have established ultrahigh-speed synthesis method of nanographene materials employing in-liquid plasma, and reported high durability of Pt/nanographene composites as a fuel cell catalyst. Crystallinity and domain size of nanographene materials were essential to their durability. However, their mechanism is not clarified yet. In this study, we investigated the oxygen reduction reaction using three-types of nanographene materials with different crystallinity and domain sizes, which were synthesized using ethanol, 1-propanol and 1-butanol, respectively. According to our previous studies, the nanographene material synthesized using the lower molecular weight alcohol has the higher crystallinity and larger domain size. Pt nanoparticles were supported on the nanographene surfaces by reducing 8 wt% H2PtCl6 diluted with H2O. Oxygen reduction current densities at a potential of 0.2 V vs. RHE were 5.43, 5.19 and 3.69 mA/cm2 for the samples synthesized using ethanol, 1-propanol and 1-butanol, respectively. This means that the higher crystallinity nanographene showed the larger oxygen reduction current density. The controls of crystallinity and domain size of nanographene materials are essential to not only their durability but also highly efficiency as catalyst electrodes.

Are normative sonographic values of kidney size in children valid and reliable? A systematic review of the methodological quality of ultrasound studies using the Anatomical Quality Assessment (AQUA) tool.

PubMed

Chhapola, Viswas; Tiwari, Soumya; Deepthi, Bobbity; Henry, Brandon Michael; Brar, Rekha; Kanwal, Sandeep Kumar

2018-06-01

A plethora of research is available on ultrasonographic kidney size standards. We performed a systematic review of methodological quality of ultrasound studies aimed at developing normative renal parameters in healthy children, by evaluating the risk of bias (ROB) using the 'Anatomical Quality Assessment (AQUA)' tool. We searched Medline, Scopus, CINAHL, and Google Scholar on June 04 2018, and observational studies measuring kidney size by ultrasonography in healthy children (0-18 years) were included. The ROB of each study was evaluated in five domains using a 20 item coding scheme based on AQUA tool framework. Fifty-four studies were included. Domain 1 (subject characteristics) had a high ROB in 63% of studies due to the unclear description of age, sex, and ethnicity. The performance in Domain 2 (study design) was the best with 85% of studies having a prospective design. Methodological characterization (Domain 3) was poor across the studies (< 10% compliance), with suboptimal performance in the description of patient positioning, operator experience, and assessment of intra/inter-observer reliability. About three-fourth of the studies had a low ROB in Domain 4 (descriptive anatomy). Domain 5 (reporting of results) had a high ROB in approximately half of the studies, the majority reporting results in the form of central tendency measures. Significant deficiencies and heterogeneity were observed in the methodological quality of USG studies performed to-date for measurement of kidney size in children. We hereby provide a framework for the conducting such studies in future. PROSPERO (CRD42017071601).

Role of initial correlation in coarsening of a ferromagnet

NASA Astrophysics Data System (ADS)

Chakraborty, Saikat; Das, Subir K.

2015-06-01

We study the dynamics of ordering in ferromagnets via Monte Carlo simulations of the Ising model, employing the Glauber spin-flip mechanism, in space dimensions d = 2 and 3, on square and simple cubic lattices. Results for the persistence probability and the domain growth are discussed for quenches to various temperatures (Tf) below the critical one (Tc), from different initial temperatures Ti ≥ Tc. In long time limit, for Ti>Tc, the persistence probability exhibits power-law decay with exponents θ ≃ 0.22 and ≃ 0.18 in d = 2 and 3, respectively. For finite Ti, the early time behavior is a different power-law whose life-time diverges and exponent decreases as Ti → Tc. The two steps are connected via power-law as a function of domain length and the crossover to the second step occurs when this characteristic length exceeds the equilibrium correlation length at T = Ti. Ti = Tc is expected to provide a new universality class for which we obtain θ ≡ θc ≃ 0.035 in d = 2 and ≃0.105 in d = 3. The time dependence of the average domain size ℓ, however, is observed to be rather insensitive to the choice of Ti.

Mesoscale organization of domains in the plasma membrane - beyond the lipid raft.

PubMed

Lu, Stella M; Fairn, Gregory D

2018-04-01

The plasma membrane is compartmentalized into several distinct regions or domains, which show a broad diversity in both size and lifetime. The segregation of lipids and membrane proteins is thought to be driven by the lipid composition itself, lipid-protein interactions and diffusional barriers. With regards to the lipid composition, the immiscibility of certain classes of lipids underlies the "lipid raft" concept of plasmalemmal compartmentalization. Historically, lipid rafts have been described as cholesterol and (glyco)sphingolipid-rich regions of the plasma membrane that exist as a liquid-ordered phase that are resistant to extraction with non-ionic detergents. Over the years the interest in lipid rafts grew as did the challenges with studying these nanodomains. The term lipid raft has fallen out of favor with many scientists and instead the terms "membrane raft" or "membrane nanodomain" are preferred as they connote the heterogeneity and dynamic nature of the lipid-protein assemblies. In this article, we will discuss the classical lipid raft hypothesis and its limitations. This review will also discuss alternative models of lipid-protein interactions, annular lipid shells, and larger membrane clusters. We will also discuss the mesoscale organization of plasmalemmal domains including visible structures such as clathrin-coated pits and caveolae.

Stable multi-domain spectral penalty methods for fractional partial differential equations

NASA Astrophysics Data System (ADS)

Xu, Qinwu; Hesthaven, Jan S.

2014-01-01

We propose stable multi-domain spectral penalty methods suitable for solving fractional partial differential equations with fractional derivatives of any order. First, a high order discretization is proposed to approximate fractional derivatives of any order on any given grids based on orthogonal polynomials. The approximation order is analyzed and verified through numerical examples. Based on the discrete fractional derivative, we introduce stable multi-domain spectral penalty methods for solving fractional advection and diffusion equations. The equations are discretized in each sub-domain separately and the global schemes are obtained by weakly imposed boundary and interface conditions through a penalty term. Stability of the schemes are analyzed and numerical examples based on both uniform and nonuniform grids are considered to highlight the flexibility and high accuracy of the proposed schemes.

On the maximum principle for complete second-order elliptic operators in general domains

NASA Astrophysics Data System (ADS)

Vitolo, Antonio

This paper is concerned with the maximum principle for second-order linear elliptic equations in a wide generality. By means of a geometric condition previously stressed by Berestycki-Nirenberg-Varadhan, Cabré was very able to improve the classical ABP estimate obtaining the maximum principle also in unbounded domains, such as infinite strips and open connected cones with closure different from the whole space. Now we introduce a new geometric condition that extends the result to a more general class of domains including the complements of hypersurfaces, as for instance the cut plane. The methods developed here allow us to deal with complete second-order equations, where the admissible first-order term, forced to be zero in a preceding result with Cafagna, depends on the geometry of the domain.

A boundary-value problem for a first-order hyperbolic system in a two-dimensional domain

NASA Astrophysics Data System (ADS)

Zhura, N. A.; Soldatov, A. P.

2017-06-01

We consider a strictly hyperbolic first-order system of three equations with constant coefficients in a bounded piecewise-smooth domain. The boundary of the domain is assumed to consist of six smooth non-characteristic arcs. A boundary-value problem in this domain is posed by alternately prescribing one or two linear combinations of the components of the solution on these arcs. We show that this problem has a unique solution under certain additional conditions on the coefficients of these combinations, the boundary of the domain and the behaviour of the solution near the characteristics passing through the corner points of the domain.

A nanomagnetic study of phase transition in manganite thin films and ballistic magnetoresistance in magnetic nanocontacts

NASA Astrophysics Data System (ADS)

Chung, Seok-Hwan

This work focuses on two largely unexplored phenomena in micromagnetics: the temperature-driven paramagnetic insulator to ferromagnetic (FM) metallic phase transition in perovskite manganite and ballistic magnetoresistance in spin-polarized nanocontacts. To investigate the phase transition, an off-the-shelf commercial scanning force microscope was redesigned for operation at temperatures from 350 K to 100 K. This adaptation is elaborated in this thesis. Using this system, both ferromagnetic and charge-ordered domain structures of (La 1-xPrx)0.67Ca0.33MnO3 thin film were observed by magnetic force microscopy (MFM) and electric force microscopy (EFM) operated in the vicinity of the peak resistance temperature (Tp). Predominantly in-plane oriented FM domains of sub-micrometer size emerge below Tp and their local magnetic moment increased as the temperature is reduced. Charge-ordered insulating regions show a strong electrostatic interaction with an EFM tip at a few degrees above Tp and the interaction correlates well with the temperature dependence of resistivity of the film. Cross-correlation analysis between topography and magnetic structure on several substrates indicates FM domains form on the flat regions of the surface, while charge ordering occurs at surface protrusions. In the investigation of ballistic magnetoresistance, new results on half-metallic ferromagnets formed by atomic or nanometer contacts of CrO2-CrO 2 and CrO2-Ni are presented showing magnetoconductance as high as 400%. Analysis of the magnetoconductance versus conductance data for all materials known to exhibit so-called ballistic magnetoresistance strongly suggests that magnetoconductance of nanocontacts follows a universal mechanism. If the maximum magnetoconductance is normalized to unity and the conductance is scaled with the resistivity of the material, then all data points fall onto a universal curve independent of the contact material and the transport mechanism. The analysis has been applied to all available magnetoconductance data of magnetic nanocontacts in the literature. The results are in agreement with a theory that takes into account only the spin-scattering within a magnetic domain wall and are independent of whether the transport is ballistic or diffusive.

A Note on Substructuring Preconditioning for Nonconforming Finite Element Approximations of Second Order Elliptic Problems

NASA Technical Reports Server (NTRS)

Maliassov, Serguei

1996-01-01

In this paper an algebraic substructuring preconditioner is considered for nonconforming finite element approximations of second order elliptic problems in 3D domains with a piecewise constant diffusion coefficient. Using a substructuring idea and a block Gauss elimination, part of the unknowns is eliminated and the Schur complement obtained is preconditioned by a spectrally equivalent very sparse matrix. In the case of quasiuniform tetrahedral mesh an appropriate algebraic multigrid solver can be used to solve the problem with this matrix. Explicit estimates of condition numbers and implementation algorithms are established for the constructed preconditioner. It is shown that the condition number of the preconditioned matrix does not depend on either the mesh step size or the jump of the coefficient. Finally, numerical experiments are presented to illustrate the theory being developed.

A General Sparse Tensor Framework for Electronic Structure Theory

DOE PAGES

Manzer, Samuel; Epifanovsky, Evgeny; Krylov, Anna I.; ...

2017-01-24

Linear-scaling algorithms must be developed in order to extend the domain of applicability of electronic structure theory to molecules of any desired size. But, the increasing complexity of modern linear-scaling methods makes code development and maintenance a significant challenge. A major contributor to this difficulty is the lack of robust software abstractions for handling block-sparse tensor operations. We therefore report the development of a highly efficient symbolic block-sparse tensor library in order to provide access to high-level software constructs to treat such problems. Our implementation supports arbitrary multi-dimensional sparsity in all input and output tensors. We then avoid cumbersome machine-generatedmore » code by implementing all functionality as a high-level symbolic C++ language library and demonstrate that our implementation attains very high performance for linear-scaling sparse tensor contractions.« less

Self-Assembly of Ordered Hybrid Materials with over 100 nm Domain Spacings and up to 15 nm Nanoparticles using Bottle Brush Block Copolymers

NASA Astrophysics Data System (ADS)

Song, Dongpo; Lin, Ying; Qian, Gang; Wang, Xinyu; Liu, Xiaohui; Li, Cheng; Watkins, James

2014-03-01

The preparation of well-ordered nanocomposites using block copolymers and nanoparticles (NPs) with precise control over their spatial organization at different length scales remains challenging, especially for NP cores up to 10 nm in diameter and for domain spacings greater than 100 nm. In this work, these challenges have been overcome using amphiphilic bottle brush block copolymers as templates for the self-assembly of ordered, periodic hybrid materials with domain spacings more than 130 nm using functionalized NPs with core diameters up to 15 nm. CdSe NPs of 10 nm or gold NPs of 15 nm bearing 11-mercaptoundecyl-hydroquinone or poly(4-vinylphenol) ligands were selectively incorporated within (polynorbornene-g-polystyrene)-b- (polynorbornene-g-polyethylene oxide) copolymers by taking advantage of hydrogen bonding between the ligand and PEO domain. Well-ordered composites with cylindrical and lamellar morphologies and NP loadings of up to 30 wt% in the target domains were achieved. This strategy provides a simple and robust means to create ordered hybrid materials of large domain spacings allowing for relatively large functional nanoparticles. This work was supported by the NSF Center for Hierarchical Manufacturing at the University of Massachusetts (CMMI-1025020).

Influence of computational domain size on the pattern formation of the phase field crystals

NASA Astrophysics Data System (ADS)

Starodumov, Ilya; Galenko, Peter; Alexandrov, Dmitri; Kropotin, Nikolai

2017-04-01

Modeling of crystallization process by the phase field crystal method (PFC) represents one of the important directions of modern computational materials science. This method makes it possible to research the formation of stable or metastable crystal structures. In this paper, we study the effect of computational domain size on the crystal pattern formation obtained as a result of computer simulation by the PFC method. In the current report, we show that if the size of a computational domain is changed, the result of modeling may be a structure in metastable phase instead of pure stable state. The authors present a possible theoretical justification for the observed effect and provide explanations on the possible modification of the PFC method to account for this phenomenon.

Factor Structure of the Quality of Life Scale for Mental Disorders in Patients With Schizophrenia.

PubMed

Chiu, En-Chi; Lee, Shu-Chun

2018-06-01

The Quality of Life for Mental Disorders (QOLMD) scale was designed to measure health-related quality of life (HRQOL) in patients with mental illness, especially schizophrenia. The QOLMD contains 45 items, which are divided into eight domains. However, the factor structure of the QOLMD has not been evaluated, which restricts the interpretations of the results of this scale. The purpose of this study was to evaluate the factor structures (i.e., unidimensionality, eight-factor structure, and second-order model) of the QOLMD in patients with schizophrenia. Two hundred thirty-eight outpatients with schizophrenia participated. We first conducted confirmatory factor analysis to evaluate the unidimensionality of each domain. After the unidimensionality of the eight individual domains was supported, we examined the eight-factor structure and second-order model. The results of unidimensionality showed sufficient model fit in all of the domains with the exception of the autonomy domain. A good model fit was confirmed for the autonomy domain after deleting two of the original items. The eight-factor structure for the 43-item QOLMD showed an acceptable model fit, although the second-order model showed poor model fit. Our results supported the unidimensionality and eight-factor structure of the 43-item QOLMD. The sum score for each of the domains may be used to reflect its domain-specific function. We recommend using the 43-item QOLMD to capture the multiple domains of HRQOL. However, the second-order model showed an unsatisfactory model fit. Furthermore, caution is advised when interpreting overall HRQOL using the total score for the eight domains.

Plasmonic Antennas for Optical Nanocrystallography and Femtosecond Spatio-Temporal Control

NASA Astrophysics Data System (ADS)

Berweger, Samuel

Controlling optical fields on nanometer length scales has been a long standing problem in optics, driven by the desire to image spatial inhomogeneities of condensed matter on the natural length scales of molecular, electronic, or lattice correlations. The concept of optical antennas based on plasmon resonant nanostructures has emerged as an attractive solution for concentrating and confining light to the nanoscale with a high degree of spatial confinement achieved in the evanescent field. This dissertation focuses on the fundamental characteristics of the antenna properties of plasmonic metal tips and their application for nanometer-resolved optical scanning probe spectroscopy and imaging. First this work demonstrates the extension of tip-enhanced Raman scattering (TERS) to optical nanocrystallography in order to study ferroelectric domain order by using the symmetry selective Raman selection rules for polar phonon modes in combination with the polarization-dependent TERS enhancement. After the derivation of the polar phonon TERS selection rules, ferroelectric domains arising from finite size effects within individual BaTiO3 nanorods are imaged. The second part of this work explores the fundamental characteristics and applications of adiabatic surface plasmon polariton (SPP) nanofocusing as an optical antenna for far- to near-field mode transformation. This process, resulting from the radius-dependent index of refraction experienced by SPP's propagating on tapered waveguides, is shown to result in a nanoconfined optical excitation at the apex of Au tips 10's of nm in size. To demonstrate the general application for background-free spectroscopy, adiabatic nanofocusing TERS is shown to improve contrast and sensitivity, and enables the extension to the near-IR spectral range. Lastly, due to the phase, wavelength, and amplitude independent nanofocusing mechanism, the independent and simultaneous nanometer-femtosecond spatio-temporal control of ultrafast pulses is possible. Combining the frequency domain shaping of optical transients with nanofocusing, we demonstrate the deterministic control of pulses as short as 16 fs and the generation of arbitrary waveforms at the tip apex. These results demonstrate the capability of these plasmonic optical antennas to not only generate enhanced optical fields for the study of matter on the nanoscale, but also to control ultrafast nano-optical excitations with applications for imaging and spectroscopy.

Perceptıon scale of barrıers to contraceptıve use: a methodologıcal study.

PubMed

Sen, Selma; Cetinkaya, Aynur; Cavuslar, Aysel

2017-01-01

The objective of this study was to design and develop the Perception Scale of Barriers to Contraceptive Use (PSBCU) as a measurement tool for the qualitative assessment of the barriers and obstacles women perceived with regard to contraceptive use or low rates of contraceptive use in women using family planning services. The data for this methodological study were collected using the face-to-face interview technique from 320 married women between the ages of 15-49 who were attending clinics at the Hafsa Sultan Hospital, CBU. The data collection tools used in the study, which was carried out from May to September 2014, were the "Introductory Information Form" and the "Perception Scale of Barriers to Contraceptive Use". Language validity and construct validity (explanatory factor analysis) were applied in order to test the validity of the Perception Scale of Barriers to Contraceptive Use. Kaiser Meier Olkin (KMO) analysis was performed to determine the availability of the scale for the size of participants. The sample adequacy calculated as the KMO value was 0.916 and the Bartlett's Test of Sphericity (X 2  = 6721.793 p  < 0.000) sample size analysis value was found to be sufficient for factor analysis. The total Cronbach's Alpha coefficient of 34 items which included three factors explaining 54.95% of the variance after Varimax rotation was calculated to be 0.95. The largest factor was the "cognitive domain" explaining 18.89% of the variance, followed by the "emotional domain" explaining 18.05% of the variance, and finally the "social domain" explaining 18.01% of the variance. Item-total score correlation coefficients of scale items were found to be between 0.54 and 0.83. The study demonstrateded that the "Perception Scale of Barriers to Contraceptive Use" was valid and reliable. We believe that the scale is suitable for use by women in a family planning education and training programs in order to evaluate their situation. It should also be assessed for validity and reliability for different groups (adolescents, men, etc.).

Metastability in the formation of Condon domains

NASA Astrophysics Data System (ADS)

Bakaleinikov, L. A.; Gordon, A.

2018-05-01

Metastability effects in the formation of Condon non-spin magnetic domains are considered. A possibility for the first-order phase transition occurrence in a three-dimensional electron gas is described in the case of two-frequency de-Haas-van Alphen magnetization oscillations originating from two extremal cross sections of the Fermi surface. The appearance of two additional domains is shown in the metastable region in aluminum. The phase diagram temperature-magnetic field exhibits the presence of second-order and first- order phase transitions in the two-frequency case.

Step by Step: Biology Undergraduates’ Problem-Solving Procedures during Multiple-Choice Assessment

PubMed Central

Prevost, Luanna B.; Lemons, Paula P.

2016-01-01

This study uses the theoretical framework of domain-specific problem solving to explore the procedures students use to solve multiple-choice problems about biology concepts. We designed several multiple-choice problems and administered them on four exams. We trained students to produce written descriptions of how they solved the problem, and this allowed us to systematically investigate their problem-solving procedures. We identified a range of procedures and organized them as domain general, domain specific, or hybrid. We also identified domain-general and domain-specific errors made by students during problem solving. We found that students use domain-general and hybrid procedures more frequently when solving lower-order problems than higher-order problems, while they use domain-specific procedures more frequently when solving higher-order problems. Additionally, the more domain-specific procedures students used, the higher the likelihood that they would answer the problem correctly, up to five procedures. However, if students used just one domain-general procedure, they were as likely to answer the problem correctly as if they had used two to five domain-general procedures. Our findings provide a categorization scheme and framework for additional research on biology problem solving and suggest several important implications for researchers and instructors. PMID:27909021

An automatic generation of non-uniform mesh for CFD analyses of image-based multiscale human airway models

NASA Astrophysics Data System (ADS)

Miyawaki, Shinjiro; Tawhai, Merryn H.; Hoffman, Eric A.; Lin, Ching-Long

2014-11-01

The authors have developed a method to automatically generate non-uniform CFD mesh for image-based human airway models. The sizes of generated tetrahedral elements vary in both radial and longitudinal directions to account for boundary layer and multiscale nature of pulmonary airflow. The proposed method takes advantage of our previously developed centerline-based geometry reconstruction method. In order to generate the mesh branch by branch in parallel, we used the open-source programs Gmsh and TetGen for surface and volume meshes, respectively. Both programs can specify element sizes by means of background mesh. The size of an arbitrary element in the domain is a function of wall distance, element size on the wall, and element size at the center of airway lumen. The element sizes on the wall are computed based on local flow rate and airway diameter. The total number of elements in the non-uniform mesh (10 M) was about half of that in the uniform mesh, although the computational time for the non-uniform mesh was about twice longer (170 min). The proposed method generates CFD meshes with fine elements near the wall and smooth variation of element size in longitudinal direction, which are required, e.g., for simulations with high flow rate. NIH Grants R01-HL094315, U01-HL114494, and S10-RR022421. Computer time provided by XSEDE.

Numerical solution of the wave equation with variable wave speed on nonconforming domains by high-order difference potentials

NASA Astrophysics Data System (ADS)

Britt, S.; Tsynkov, S.; Turkel, E.

2018-02-01

We solve the wave equation with variable wave speed on nonconforming domains with fourth order accuracy in both space and time. This is accomplished using an implicit finite difference (FD) scheme for the wave equation and solving an elliptic (modified Helmholtz) equation at each time step with fourth order spatial accuracy by the method of difference potentials (MDP). High-order MDP utilizes compact FD schemes on regular structured grids to efficiently solve problems on nonconforming domains while maintaining the design convergence rate of the underlying FD scheme. Asymptotically, the computational complexity of high-order MDP scales the same as that for FD.

Fluorescence correlation spectroscopy diffusion laws in the presence of moving nanodomains

NASA Astrophysics Data System (ADS)

Šachl, Radek; Bergstrand, Jan; Widengren, Jerker; Hof, Martin

2016-03-01

It has been shown by means of simulations that spot variation fluorescence correlation spectroscopy (sv-FCS) can be used for the identification and, to some extent, also characterization of immobile lipid nanodomains in model as well as cellular plasma membranes. However, in these simulations, the nanodomains were assumed to be stationary, whereas they actually tend to move like the surrounding lipids. In the present study, we investigated how such domain movement influences the diffusion time/spot-size dependence observed in FCS experiments, usually referred to as ‘diffusion law’ analysis. We show that domain movement might mask the effects of the ‘anomalous’ diffusion characteristics of membrane lipids or proteins predicted for stationary domains, making it difficult to identify such moving nanodomains by sv-FCS. More specifically, our simulations indicate that (i) for domains moving up to a factor of 2.25 slower than the surrounding lipids, such impeded diffusion cannot be observed and the diffusion behaviour of the proteins or lipids is indistinguishable from that of freely diffusing molecules, i.e. nanodomains are not detected; (ii) impeded protein/lipid diffusion behaviour can be observed in experiments where the radii of the detection volume are similar in size to the domain radii, the domain diffusion is about 10 times slower than that of the lipids, and the probes show a high affinity to the domains; and (iii) presence of nanodomains can only be reliably detected by diffraction limited sv-FCS when the domains move very slowly (about 200 times slower than the lipid diffusion). As nanodomains are expected to be in the range of tens of nanometres and most probes show low affinities to such domains, sv-FCS is limited to stationary domains and/or STED-FCS. However, even for that latter technique, diffusing domains smaller than 50 nm in radius are hardly detectable by FCS diffusion time/spot-size dependencies.

Atomic model of a cell-wall cross-linking enzyme in complex with an intact bacterial peptidoglycan.

PubMed

Schanda, Paul; Triboulet, Sébastien; Laguri, Cédric; Bougault, Catherine M; Ayala, Isabel; Callon, Morgane; Arthur, Michel; Simorre, Jean-Pierre

2014-12-24

The maintenance of bacterial cell shape and integrity is largely attributed to peptidoglycan, a highly cross-linked biopolymer. The transpeptidases that perform this cross-linking are important targets for antibiotics. Despite this biomedical importance, to date no structure of a protein in complex with an intact bacterial peptidoglycan has been resolved, primarily due to the large size and flexibility of peptidoglycan sacculi. Here we use solid-state NMR spectroscopy to derive for the first time an atomic model of an l,d-transpeptidase from Bacillus subtilis bound to its natural substrate, the intact B. subtilis peptidoglycan. Importantly, the model obtained from protein chemical shift perturbation data shows that both domains-the catalytic domain as well as the proposed peptidoglycan recognition domain-are important for the interaction and reveals a novel binding motif that involves residues outside of the classical enzymatic pocket. Experiments on mutants and truncated protein constructs independently confirm the binding site and the implication of both domains. Through measurements of dipolar-coupling derived order parameters of bond motion we show that protein binding reduces the flexibility of peptidoglycan. This first report of an atomic model of a protein-peptidoglycan complex paves the way for the design of new antibiotic drugs targeting l,d-transpeptidases. The strategy developed here can be extended to the study of a large variety of enzymes involved in peptidoglycan morphogenesis.

Can ferroelectric polarization explain the high performance of hybrid halide perovskite solar cells?

PubMed

Sherkar, Tejas S; Koster, L Jan Anton

2016-01-07

The power conversion efficiency of photovoltaic cells based on the use of hybrid halide perovskites, CH3NH3PbX3 (X = Cl, Br, I), now exceeds 20%. Recently, it was suggested that this high performance originates from the presence of ferroelectricity in the perovskite, which is hypothesized to lower charge recombination in the device. Here, we investigate and quantify the influence of mesoscale ferroelectric polarization on the device performance of perovskite solar cells. We implement a 3D drift diffusion model to describe the solar cell operation. To account for the mesoscale ferroelectricity, we incorporate domains defined by polarization strength, P, in 3D space, forming different polarization landscapes or microstructures. Study of microstructures with highly-ordered polarized domains shows that charge transport and recombination in the solar cell depends significantly on the polarization landscape viz. the orientation of domain boundaries and the size of domains. In the case of the microstructure with random correlated polarization, a realistic scenario, we find indication of the existence of channels for efficient charge transport in the device which leads to lowering of charge recombination, as evidenced by the high fill factor (FF). However, the high open-circuit voltage (VOC), which is typical of high performance perovskite solar cells, is unlikely to be explained by the presence of ferroelectric polarization in the perovskite.

Understanding effects in reviews of implementation interventions using the Theoretical Domains Framework.

PubMed

Little, Elizabeth A; Presseau, Justin; Eccles, Martin P

2015-06-17

Behavioural theory can be used to better understand the effects of behaviour change interventions targeting healthcare professional behaviour to improve quality of care. However, the explicit use of theory is rarely reported despite interventions inevitably involving at least an implicit idea of what factors to target to implement change. There is a quality of care gap in the post-fracture investigation (bone mineral density (BMD) scanning) and management (bisphosphonate prescription) of patients at risk of osteoporosis. We aimed to use the Theoretical Domains Framework (TDF) within a systematic review of interventions to improve quality of care in post-fracture investigation. Our objectives were to explore which theoretical factors the interventions in the review may have been targeting and how this might be related to the size of the effect on rates of BMD scanning and osteoporosis treatment with bisphosphonate medication. A behavioural scientist and a clinician independently coded TDF domains in intervention and control groups. Quantitative analyses explored the relationship between intervention effect size and total number of domains targeted, and as number of different domains targeted. Nine randomised controlled trials (RCTs) (10 interventions) were analysed. The five theoretical domains most frequently coded as being targeted by the interventions in the review included "memory, attention and decision processes", "knowledge", "environmental context and resources", "social influences" and "beliefs about consequences". Each intervention targeted a combination of at least four of these five domains. Analyses identified an inverse relationship between both number of times and number of different domains coded and the effect size for BMD scanning but not for bisphosphonate prescription, suggesting that the more domains the intervention targeted, the lower the observed effect size. When explicit use of theory to inform interventions is absent, it is possible to retrospectively identify the likely targeted factors using theoretical frameworks such as the TDF. In osteoporosis management, this suggested that several likely determinants of healthcare professional behaviour appear not yet to have been considered in implementation interventions. This approach may serve as a useful basis for using theory-based frameworks such as the TDF to retrospectively identify targeted factors within systematic reviews of implementation interventions in other implementation contexts.

A meta-analysis of work-family conflict and various outcomes with a special emphasis on cross-domain versus matching-domain relations.

PubMed

Amstad, Fabienne T; Meier, Laurenz L; Fasel, Ursula; Elfering, Achim; Semmer, Norbert K

2011-04-01

A literature review of studies analyzing work-family conflict and its consequences was conducted, and 427 effect sizes were analyzed meta-analytically. Work-family conflict was analyzed bidirectionally in terms of work interference with family (WIF) and family interference with work (FIW). We assessed 3 categories of potential outcomes: work-related outcomes, family-related outcomes, and domain-unspecific outcomes. Results show that WIF and FIW are consistently related to all 3 types of outcomes. Both types of interrole conflict showed stronger relationships to same-domain outcomes than to cross-domain outcomes. Thus, WIF was more strongly associated with work-related than with family-related outcomes, and FIW was more strongly associated with family-related than with work-related outcomes. In moderator analyses, parenthood could not explain variability in effect sizes. However, time spent at work did moderate the relationships between WIF and family-related outcomes, as well as FIW and domain-unspecific outcomes.

TOPICAL REVIEW: Progress in engineering high strain lead-free piezoelectric ceramics

NASA Astrophysics Data System (ADS)

Leontsev, Serhiy O.; Eitel, Richard E.

2010-08-01

Environmental concerns are strongly driving the need to replace the lead-based piezoelectric materials currently employed as multilayer actuators. The current review describes both compositional and structural engineering approaches to achieve enhanced piezoelectric properties in lead-free materials. The review of the compositional engineering approach focuses on compositional tuning of the properties and phase behavior in three promising families of lead-free perovskite ferroelectrics: the titanate, alkaline niobate and bismuth perovskites and their solid solutions. The 'structural engineering' approaches focus instead on optimization of microstructural features including grain size, grain orientation or texture, ferroelectric domain size and electrical bias field as potential paths to induce large piezoelectric properties in lead-free piezoceramics. It is suggested that a combination of both compositional and novel structural engineering approaches will be required in order to realize viable lead-free alternatives to current lead-based materials for piezoelectric actuator applications.

Progress in engineering high strain lead-free piezoelectric ceramics

PubMed Central

Leontsev, Serhiy O; Eitel, Richard E

2010-01-01

Environmental concerns are strongly driving the need to replace the lead-based piezoelectric materials currently employed as multilayer actuators. The current review describes both compositional and structural engineering approaches to achieve enhanced piezoelectric properties in lead-free materials. The review of the compositional engineering approach focuses on compositional tuning of the properties and phase behavior in three promising families of lead-free perovskite ferroelectrics: the titanate, alkaline niobate and bismuth perovskites and their solid solutions. The ‘structural engineering’ approaches focus instead on optimization of microstructural features including grain size, grain orientation or texture, ferroelectric domain size and electrical bias field as potential paths to induce large piezoelectric properties in lead-free piezoceramics. It is suggested that a combination of both compositional and novel structural engineering approaches will be required in order to realize viable lead-free alternatives to current lead-based materials for piezoelectric actuator applications. PMID:27877343

Controlling the Topological Sector of Magnetic Solitons in Exfoliated Cr 1 / 3 NbS 2 Crystals

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

Wang, Lin; Chepiga, N.; Ki, D. -K.

Here, we investigate manifestations of topological order in monoaxial helimagnet Cr 1/3NbS 2 by performing transport measurements on ultrathin crystals. Upon sweeping the magnetic field perpendicularly to the helical axis, crystals thicker than one helix pitch (48 nm) but much thinner than the magnetic domain size (similar to 1 mu m) are found to exhibit sharp and hysteretic resistance jumps. We also show that these phenomena originate from transitions between topological sectors with a different number of magnetic solitons. This is confirmed by measurements on crystals thinner than 48 nm-in which the topological sector cannot change-that do not exhibit anymore » jump or hysteresis. These results show the ability to deterministically control the topological sector of finite-size Cr 1/3NbS 2 and to detect intersector transitions by transport measurements.« less

Controlling the Topological Sector of Magnetic Solitons in Exfoliated Cr 1 / 3 NbS 2 Crystals

DOE PAGES

Wang, Lin; Chepiga, N.; Ki, D. -K.; ...

2017-06-23

Here, we investigate manifestations of topological order in monoaxial helimagnet Cr 1/3NbS 2 by performing transport measurements on ultrathin crystals. Upon sweeping the magnetic field perpendicularly to the helical axis, crystals thicker than one helix pitch (48 nm) but much thinner than the magnetic domain size (similar to 1 mu m) are found to exhibit sharp and hysteretic resistance jumps. We also show that these phenomena originate from transitions between topological sectors with a different number of magnetic solitons. This is confirmed by measurements on crystals thinner than 48 nm-in which the topological sector cannot change-that do not exhibit anymore » jump or hysteresis. These results show the ability to deterministically control the topological sector of finite-size Cr 1/3NbS 2 and to detect intersector transitions by transport measurements.« less

Domain size and structure in exchange coupled [Co/Pt]/NiO/[Co/Pt] multilayers.

PubMed

Baruth, A; Adenwalla, S

2011-09-21

We investigate the competing effects of interlayer exchange coupling and magnetostatic coupling in the magnetic heterostructure ([Co/Pt]/NiO/[Co/Pt]) with perpendicular magnetic anisotropy (PMA). This particular heterostructure is unique among coupled materials with PMA in directly exhibiting both ferromagnetic and antiferromagnetic coupling, oscillating between the two as a function of spacer layer thickness. By systematically tuning the coupling interactions via a wedge-shaped NiO spacer layer, we explore the energetics that dictate magnetic domain formation using high resolution magnetic force microscopy coupled with the magneto-optical Kerr effect. This technique probes the microscopic and macroscopic magnetic behavior as a continuous function of thickness and the interlayer exchange coupling, including the regions where interlayer coupling goes through zero. We see significant changes in domain structure based on the sign of coupling, and also show that magnetic domain size is directly related to the magnitude of the interlayer exchange coupling energy, which generally dominates over the magnetostatic interactions. When magnetostatic interactions become comparable to the interlayer exchange coupling, a delicate interplay between the differing energy contributions is apparent and energy scales are extracted. The results are of intense interest to the magnetic recording industry and also illustrate a relatively new avenue of undiscovered physics, primarily dealing with the delicate balance of energies in the formation of magnetic domains for coupled systems with PMA, defining limits on domain size as well as the interplay between roughness, domains and magnetic coupling.

On the role of the grain size in the magnetic behavior of sintered permanent magnets

NASA Astrophysics Data System (ADS)

Efthimiadis, K. G.; Ntallis, N.

2018-02-01

In this work the finite elements method is used to simulate, by micromagnetic modeling, the magnetic behavior of sintered anisotropic magnets. Hysteresis loops were simulated for different grain sizes in an oriented multigrain sample. By keeping out other parameters that contribute to the magnetic microstructure, such as the sample size, the grain morphology and the grain boundaries mismatch, it has been found that the grain size affects the magnetic properties only if the grains are exchange-decoupled. In this case, as the grain size decreases, a decrease in the nucleation field of a reverse magnetic domain is observed and an increase in the coercive field due to the pinning of the magnetic domain walls at the grain boundaries.

Tailoring magnetic domains in Gd-Fe thin films

NASA Astrophysics Data System (ADS)

Talapatra, A.; Chelvane, J. Arout; Mohanty, J.

2018-05-01

This paper presents the global modification of magnetic domains and magnetic properties in amorphous Gd19Fe81 thin films with rapid thermal processing at two distinct temperatures (250oC and 450oC), and with different time intervals viz., 2, 5, 10 and 20 minutes. 100 nm thick as-prepared films display nano-scale meandering stripe domains with high magnetic phase contrast which is the signature of perpendicular magnetic anisotropy. The films processed at 250oC for various time intervals show successive reduction in magnetic phase contrast and domain size. The domain pattern completely disappeared, and topography dominated mixed magnetic phase has been obtained for the films processed at 450oC for time intervals greater than 2 minutes. The magnetization measurements indicate the reduction in perpendicular magnetic anisotropy with increase in saturation magnetization for all the rapid thermal processed films. The experimental outputs have been used to simulate the domain pattern. Reduction in uniaxial anisotropy along with the increase in saturation magnetization successfully explain the experimental trend of decrease in domain size and magnetic contrast.

Deformations of a pre-stretched elastic membrane driven by non-uniform electroosmotic flow

NASA Astrophysics Data System (ADS)

Bercovici, Moran; Boyko, Evgeniy; Gat, Amir

2016-11-01

We study viscous-elastic dynamics of fluid confined between a rigid plate and a pre-stretched elastic membrane subjected to non-uniform electroosmotic flow, and focus on the case of a finite-size membrane clamped at its boundaries. Considering small deformations of a strongly pre-stretched membrane, and applying the lubrication approximation for the flow, we derive a linearized leading-order non-homogenous 4th order diffusion equation governing the deformation and pressure fields. We derive a time-dependent Green's function for a rectangular domain, and use it to obtain several basic solutions for the cases of constant and time varying electric fields. In addition, defining an asymptotic expansion where the small parameter is the ratio of the induced to prescribed tension, we obtain a set of four one-way coupled equations providing a first order correction for the deformation field. Funded by the European Research Council (ERC) under the Horizon 2020 Research and Innovation Programme, Grant agreement No. 678734 (MetamorphChip).

Dynamics of the quantum search and quench-induced first-order phase transitions.

PubMed

Coulamy, Ivan B; Saguia, Andreia; Sarandy, Marcelo S

2017-02-01

We investigate the excitation dynamics at a first-order quantum phase transition (QPT). More specifically, we consider the quench-induced QPT in the quantum search algorithm, which aims at finding out a marked element in an unstructured list. We begin by deriving the exact dynamics of the model, which is shown to obey a Riccati differential equation. Then, we discuss the probabilities of success by adopting either global or local adiabaticity strategies. Moreover, we determine the disturbance of the quantum criticality as a function of the system size. In particular, we show that the critical point exponentially converges to its thermodynamic limit even in a fast evolution regime, which is characterized by both entanglement QPT estimators and the Schmidt gap. The excitation pattern is manifested in terms of quantum domain walls separated by kinks. The kink density is then shown to follow an exponential scaling as a function of the evolution speed, which can be interpreted as a Kibble-Zurek mechanism for first-order QPTs.

A mesh partitioning algorithm for preserving spatial locality in arbitrary geometries

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

Nivarti, Girish V., E-mail: g.nivarti@alumni.ubc.ca; Salehi, M. Mahdi; Bushe, W. Kendal

2015-01-15

Highlights: •An algorithm for partitioning computational meshes is proposed. •The Morton order space-filling curve is modified to achieve improved locality. •A spatial locality metric is defined to compare results with existing approaches. •Results indicate improved performance of the algorithm in complex geometries. -- Abstract: A space-filling curve (SFC) is a proximity preserving linear mapping of any multi-dimensional space and is widely used as a clustering tool. Equi-sized partitioning of an SFC ignores the loss in clustering quality that occurs due to inaccuracies in the mapping. Often, this results in poor locality within partitions, especially for the conceptually simple, Morton ordermore » curves. We present a heuristic that improves partition locality in arbitrary geometries by slicing a Morton order curve at points where spatial locality is sacrificed. In addition, we develop algorithms that evenly distribute points to the extent possible while maintaining spatial locality. A metric is defined to estimate relative inter-partition contact as an indicator of communication in parallel computing architectures. Domain partitioning tests have been conducted on geometries relevant to turbulent reactive flow simulations. The results obtained highlight the performance of our method as an unsupervised and computationally inexpensive domain partitioning tool.« less

Spanwise vorticity and wall normal velocity structure in the inertial region of turbulent boundary layers

NASA Astrophysics Data System (ADS)

Cuevas Bautista, Juan Carlos; Morrill-Winter, Caleb; White, Christopher; Chini, Gregory; Klewicki, Joseph

2017-11-01

The Reynolds shear stress gradient is a leading order mechanism on the inertial domain of turbulent wall-flows. This quantity can be described relative to the sum of two velocity-vorticity correlations, vωz and wωy . Recent studies suggest that the first of these correlates with the step-like structure of the instantaneous streamwise velocity profile on the inertial layer. This structure is comprised of large zones of uniform momentum segregated by slender regions of concentrated vorticity. In this talk we study the contributions of the v and ωz motions to the vorticity transport (vωz) mechanism through the use of experimental data at large friction Reynolds numbers, δ+. The primary contributions to v and ωz were estimated by identifying the peak wavelengths of their streamwise spectra. The magnitudes of these peaks are of the same order, and are shown to exhibit a weak δ+ dependence. The peak wavelengths of v, however, exhibit a strong wall-distance (y) dependence, while the peak wavelengths of ωz show only a weak y dependence, and remain almost O (√{δ+}) in size throughout the inertial domain. This research was partially supported by the National Science Foundation and partially supported by the Australian Research Council.

Submillisecond-response IR spatial light modulators with polymer network liquid crystal

NASA Astrophysics Data System (ADS)

Sun, Jie; Chen, Yuan; Wu, Shin-Tson

2013-03-01

Polymer network liquid crystal (PNLC) is attractive for many photonic applications because of its fast response time and large phase modulation. However, the voltage-on state light scattering caused by multi-domains of LC molecules hinders its applications in the visible and near infrared regions. To reduce domain sizes and eliminate scattering for λ=1.06 μm and 1.55 μm, we studied the effect of LC viscosity on domain sizes. PNLCs based on five different LC hosts were prepared. The LC host was first mixed with 6% reactive mesogen and then filled into a 12-μm cell with homogeneous alignment. After UV curing, we measured the on-state transmission spectra of these five PNLCs. By fitting the transmission spectra with Rayleigh-Gans-Debye model, we can estimate the average domain sizes. We found that the domain sizes of PNLC are inversely proportional to the rotational viscosity of the LC host. This finding can be explained by the Stokes-Einstein equation. As a result, PNLC with a slower diffusion rate would cause smaller domain sizes, which in turn lead to faster response time. To achieve a slower diffusion rate, we cured the PNLC samples at a lower temperature. By selecting a high viscosity and high Δɛ LC host, we demonstrate a scattering-free (<3%) 2π phase modulator at λ=1.06 μm and λ=1.55 μm. Temperature affects the PNLC performance significantly. As the operation temperature increases from 25oC to 70oC, the response time drops from 220 μs to 30 μs. 2π operating voltage for λ=1.06 μm slightly increases from 65V to 85V. Meanwhile, hysteresis decreases from 7.7% to 2%. For λ=1.55μm, operating voltage is 100V. If reflective mode is employed, operating voltage can be reduced to 55V.

Detailed analysis of the effects of stencil spatial variations with arbitrary high-order finite-difference Maxwell solver

DOE PAGES

Vincenti, H.; Vay, J. -L.

2015-11-22

Due to discretization effects and truncation to finite domains, many electromagnetic simulations present non-physical modifications of Maxwell's equations in space that may generate spurious signals affecting the overall accuracy of the result. Such modifications for instance occur when Perfectly Matched Layers (PMLs) are used at simulation domain boundaries to simulate open media. Another example is the use of arbitrary order Maxwell solver with domain decomposition technique that may under some condition involve stencil truncations at subdomain boundaries, resulting in small spurious errors that do eventually build up. In each case, a careful evaluation of the characteristics and magnitude of themore » errors resulting from these approximations, and their impact at any frequency and angle, requires detailed analytical and numerical studies. To this end, we present a general analytical approach that enables the evaluation of numerical discretization errors of fully three-dimensional arbitrary order finite-difference Maxwell solver, with arbitrary modification of the local stencil in the simulation domain. The analytical model is validated against simulations of domain decomposition technique and PMLs, when these are used with very high-order Maxwell solver, as well as in the infinite order limit of pseudo-spectral solvers. Results confirm that the new analytical approach enables exact predictions in each case. It also confirms that the domain decomposition technique can be used with very high-order Maxwell solver and a reasonably low number of guard cells with negligible effects on the whole accuracy of the simulation.« less

Large Diversity of Nonstandard Genes and Dynamic Evolution of Chloroplast Genomes in Siphonous Green Algae (Bryopsidales, Chlorophyta)

PubMed Central

Leliaert, Frederik; Marcelino, Vanessa R

2018-01-01

Abstract Chloroplast genomes have undergone tremendous alterations through the evolutionary history of the green algae (Chloroplastida). This study focuses on the evolution of chloroplast genomes in the siphonous green algae (order Bryopsidales). We present five new chloroplast genomes, which along with existing sequences, yield a data set representing all but one families of the order. Using comparative phylogenetic methods, we investigated the evolutionary dynamics of genomic features in the order. Our results show extensive variation in chloroplast genome architecture and intron content. Variation in genome size is accounted for by the amount of intergenic space and freestanding open reading frames that do not show significant homology to standard plastid genes. We show the diversity of these nonstandard genes based on their conserved protein domains, which are often associated with mobile functions (reverse transcriptase/intron maturase, integrases, phage- or plasmid-DNA primases, transposases, integrases, ligases). Investigation of the introns showed proliferation of group II introns in the early evolution of the order and their subsequent loss in the core Halimedineae, possibly through RT-mediated intron loss. PMID:29635329

A pilot study to evaluate multi-dimensional effects of dance for people with Parkinson's disease.

PubMed

Ventura, Maria I; Barnes, Deborah E; Ross, Jessica M; Lanni, Kimberly E; Sigvardt, Karen A; Disbrow, Elizabeth A

2016-11-01

Parkinson's disease (PD) is a progressive neurodegenerative disease associated with deficits in motor, cognitive, and emotion/quality of life (QOL) domains, yet most pharmacologic and behavioral interventions focus only on motor function. Our goal was to perform a pilot study of Dance for Parkinson's-a community-based program that is growing in popularity-in order to compare effect sizes across multiple outcomes and to inform selection of primary and secondary outcomes for a larger trial. Study participants were people with PD who self-enrolled in either Dance for Parkinson's classes (intervention group, N=8) or PD support groups (control group, N=7). Assessments of motor function (Timed-Up-and-Go, Gait Speed, Standing Balance Test), cognitive function (Test of Everyday Attention, Verbal Fluency, Alternate Uses, Digit Span Forward and Backward), and emotion/QOL (Geriatric Depression Scale, Falls Efficacy Scale-International, Parkinson's Disease Questionnaire-39 (total score and Activities of Daily Living subscale)) were performed in both groups at baseline and follow-up. Standardized effect sizes were calculated within each group and between groups for all 12 measures. Effect sizes were positive (suggesting improvement) for all 12 measures within the intervention group and 7 of 12 measures within the control group. The largest between-group differences were observed for the Test of Everyday Attention (a measure of cognitive switching), gait speed and falls efficacy. Our findings suggest that dance has potential to improve multiple outcomes in people with PD. Future trials should consider co-primary outcomes given potential benefits in motor, cognitive and emotion/QOL domains. Copyright © 2016 Elsevier Inc. All rights reserved.

A pilot study to evaluate multi-dimensional effects of dance for people with Parkinson’s disease

PubMed Central

Ventura, Maria I.; Barnes, Deborah E.; Ross, Jessica M.; Lanni, Kimberly E.; Sigvardt, Karen A.; Disbrow, Elizabeth A.

2016-01-01

Parkinson’s disease (PD) is a progressive neurodegenerative disease associated with deficits in motor, cognitive, and emotion/quality of life (QOL) domains, yet most pharmacologic and behavioral interventions focus only on motor function. Our goal was to perform a pilot study of Dance for Parkinson’s—a community-based program that is growing in popularity—in order to compare effect sizes across multiple outcomes and to inform selection of primary and secondary outcomes for a larger trial. Study participants were people with PD who self-enrolled in either Dance for Parkinson’s classes (intervention group, N=8) or PD support groups (control group, N=7). Assessments of motor function (Timed-Up-and-Go, Gait Speed, Standing Balance Test), cognitive function (Test of Everyday Attention, Verbal Fluency, Alternate Uses, Digit Span Forward and Backward), and emotion/QOL (Geriatric Depression Scale, Falls Efficacy Scale-International, Parkinson’s Disease Questionnaire-39 (total score and Activities of Daily Living subscale)) were performed in both groups at baseline and follow-up. Standardized effect sizes were calculated within each group and between groups for all 12 measures. Effect sizes were positive (suggesting improvement) for all 12 measures within the intervention group and 7 of 12 measures within the control group. The largest between-group differences were observed for the Test of Everyday Attention (a measure of cognitive switching), gait speed and falls efficacy. Our findings suggest that dance has potential to improve multiple outcomes in people with PD. Future trials should consider co-primary outcomes given potential benefits in motor, cognitive and emotion/QOL domains. PMID:27765693

Supporting Semantic Annotation of Educational Content by Automatic Extraction of Hierarchical Domain Relationships

ERIC Educational Resources Information Center

Vrablecová, Petra; Šimko, Marián

2016-01-01

The domain model is an essential part of an adaptive learning system. For each educational course, it involves educational content and semantics, which is also viewed as a form of conceptual metadata about educational content. Due to the size of a domain model, manual domain model creation is a challenging and demanding task for teachers or…

Applied Routh approximation

NASA Technical Reports Server (NTRS)

Merrill, W. C.

1978-01-01

The Routh approximation technique for reducing the complexity of system models was applied in the frequency domain to a 16th order, state variable model of the F100 engine and to a 43d order, transfer function model of a launch vehicle boost pump pressure regulator. The results motivate extending the frequency domain formulation of the Routh method to the time domain in order to handle the state variable formulation directly. The time domain formulation was derived and a characterization that specifies all possible Routh similarity transformations was given. The characterization was computed by solving two eigenvalue-eigenvector problems. The application of the time domain Routh technique to the state variable engine model is described, and some results are given. Additional computational problems are discussed, including an optimization procedure that can improve the approximation accuracy by taking advantage of the transformation characterization.

An arbitrary boundary with ghost particles incorporated in coupled FEM-SPH model for FSI problems

NASA Astrophysics Data System (ADS)

Long, Ting; Hu, Dean; Wan, Detao; Zhuang, Chen; Yang, Gang

2017-12-01

It is important to treat the arbitrary boundary of Fluid-Structure Interaction (FSI) problems in computational mechanics. In order to ensure complete support condition and restore the first-order consistency near the boundary of Smoothed Particle Hydrodynamics (SPH) method for coupling Finite Element Method (FEM) with SPH model, a new ghost particle method is proposed by dividing the interceptive area of kernel support domain into subareas corresponding to boundary segments of structure. The ghost particles are produced automatically for every fluid particle at each time step, and the properties of ghost particles, such as density, mass and velocity, are defined by using the subareas to satisfy the boundary condition. In the coupled FEM-SPH model, the normal and shear forces from a boundary segment of structure to a fluid particle are calculated through the corresponding ghost particles, and its opposite forces are exerted on the corresponding boundary segment, then the momentum of the present method is conservation and there is no matching requirements between the size of elements and the size of particles. The performance of the present method is discussed and validated by several FSI problems with complex geometry boundary and moving boundary.

On the importance of collective excitations for thermal transport in graphene

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

Gill-Comeau, Maxime; Lewis, Laurent J., E-mail: Laurent.Lewis@UMontreal.CA

2015-05-11

We use equilibrium molecular dynamics (MD) simulations to study heat transport in bulk single-layer graphene. Through a modal analysis of the MD trajectories employing a time-domain formulation, we find that collective excitations involving flexural acoustic (ZA) phonons, which have been neglected in the previous MD studies, actually dominate the heat flow, generating as much as 78% of the flux. These collective excitations are, however, much less significant if the atomic displacements are constrained in the lattice plane. Although relaxation is slow, we find graphene to be a regular (non-anomalous) heat conductor for sample sizes of order 40 μm and more.

Nanoscale control of stripe-ordered magnetic domain walls by vertical spin transfer torque in La0.67Sr0.33MnO3 film

NASA Astrophysics Data System (ADS)

Wang, Jing; Wu, Shizhe; Ma, Ji; Xie, Lishan; Wang, Chuanshou; Malik, Iftikhar Ahmed; Zhang, Yuelin; Xia, Ke; Nan, Ce-Wen; Zhang, Jinxing

2018-02-01

Stripe-ordered domains with perpendicular magnetic anisotropy have been intensively investigated due to their potential applications in high-density magnetic data-storage devices. However, the conventional control methods (e.g., epitaxial strain, local heating, magnetic field, and magnetoelectric effect) of the stripe-ordered domain walls either cannot meet the demands for miniaturization and low power consumption of spintronic devices or require high strength of the electric field due to the small value of the magnetoelectric effect at room temperature. Here, a domain-wall resistive effect of 0.1% was clarified in La0.67Sr0.33MnO3 thin films between the configurations of current in the plane and perpendicular to the plane of walls. Furthermore, a reversible nanoscale control of the domain-wall re-orientation by vertical spin transfer torque across the probe/film interface was achieved, where a probe voltage of 0.1 V was applied on a manganite-based capacitor. We also demonstrated that the stripe-ordered magnetic domain-wall re-orientation strongly depends on the AC frequency of the scanning probe voltage which was applied on the capacitor.

Turbulent thermal superstructures in Rayleigh-Bénard convection

NASA Astrophysics Data System (ADS)

Stevens, Richard J. A. M.; Blass, Alexander; Zhu, Xiaojue; Verzicco, Roberto; Lohse, Detlef

2018-04-01

We report the observation of superstructures, i.e., very large-scale and long living coherent structures in highly turbulent Rayleigh-Bénard convection up to Rayleigh Ra=109 . We perform direct numerical simulations in horizontally periodic domains with aspect ratios up to Γ =128 . In the considered Ra number regime the thermal superstructures have a horizontal extend of six to seven times the height of the domain and their size is independent of Ra. Many laboratory experiments and numerical simulations have focused on small aspect ratio cells in order to achieve the highest possible Ra. However, here we show that for very high Ra integral quantities such as the Nusselt number and volume averaged Reynolds number only converge to the large aspect ratio limit around Γ ≈4 , while horizontally averaged statistics such as standard deviation and kurtosis converge around Γ ≈8 , the integral scale converges around Γ ≈32 , and the peak position of the temperature variance and turbulent kinetic energy spectra only converge around Γ ≈64 .

Neutron and proton electric dipole moments from N f=2+1 domain-wall fermion lattice QCD

DOE PAGES

Shintani, Eigo; Blum, Thomas; Izubuchi, Taku; ...

2016-05-05

We present a lattice calculation of the neutron and proton electric dipole moments (EDM’s) with N f = 2 + 1 flavors of domain-wall fermions. The neutron and proton EDM form factors are extracted from three-point functions at the next-to-leading order in the θ vacuum of QCD. In this computation, we use pion masses 330 and 420 MeV and 2.7 fm 3 lattices with Iwasaki gauge action and a 170 MeV pion and 4.6 fm 3 lattice with I-DSDR gauge action, all generated by the RBC and UKQCD collaborations. The all-mode-averaging technique enables an efficient, high statistics calculation; however themore » statistical errors on our results are still relatively large, so we investigate a new direction to reduce them, reweighting with the local topological charge density which appears promising. Furthermore, we discuss the chiral behavior and finite size effects of the EDM’s in the context of baryon chiral perturbation theory.« less

Giant strain with ultra-low hysteresis and high temperature stability in grain oriented lead-free K0.5Bi0.5TiO3-BaTiO3-Na0.5Bi0.5TiO3 piezoelectric materials

PubMed Central

Maurya, Deepam; Zhou, Yuan; Wang, Yaojin; Yan, Yongke; Li, Jiefang; Viehland, Dwight; Priya, Shashank

2015-01-01

We synthesized grain-oriented lead-free piezoelectric materials in (K0.5Bi0.5TiO3-BaTiO3-xNa0.5Bi0.5TiO3 (KBT-BT-NBT) system with high degree of texturing along the [001]c (c-cubic) crystallographic orientation. We demonstrate giant field induced strain (~0.48%) with an ultra-low hysteresis along with enhanced piezoelectric response (d33 ~ 190pC/N) and high temperature stability (~160°C). Transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) results demonstrate smaller size highly ordered domain structure in grain-oriented specimen relative to the conventional polycrystalline ceramics. The grain oriented specimens exhibited a high degree of non-180° domain switching, in comparison to the randomly axed ones. These results indicate the effective solution to the lead-free piezoelectric materials. PMID:25716551

Numerical investigation of flow parameters for solid rigid spheroidal particle in a pulsatile pipe flow

NASA Astrophysics Data System (ADS)

Varghese, Joffin; Jayakumar, J. S.

2017-09-01

Quantifying, forecasting and analysing the displacement rates of suspended particles are essential while discussing about blood flow analysis. Because blood is one of the major organs in the body, which enables transport phenomena, comprising of numerous blood cells. In order to model the blood flow, a flow domain was created and numerically simulated. Flow field velocity in the stream is solved utilizing Finite Volume Method utilizing FVM unstructured solver. In pulsatile flow, the effect of parameters such as average Reynolds number, tube radius, particle size and Womersley number are taken into account. In this study spheroidal particle trajectory in axial direction is simulated at different values of pulsating frequency including 1.2 Hz, 3.33 Hz and 4.00 Hz and various densities including 1005 kg/m3 and 1025 kg/m3 for the flow domain. The analysis accomplishes the interaction study of blood constituents for different flow situations which have applications in diagnosis and treatment of cardio vascular related diseases.

Giant strain with ultra-low hysteresis and high temperature stability in grain oriented lead-free K₀̣₅Bi₀̣₅TiO₃-BaTiO₃-Na₀̣₅Bi₀̣₅TiO₃ piezoelectric materials

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

Maurya, Deepam; Zhou, Yuan; Wang, Yaojin

2015-02-26

We synthesized grain-oriented lead-free piezoelectric materials in (K₀̣₅Bi₀̣₅TiO₃-BaTiO₃-xNa₀̣₅Bi₀̣₅TiO₃ (KBT-BT-NBT) system with high degree of texturing along the [001]c (c-cubic) crystallographic orientation. We demonstrate giant field induced strain (~0.48%) with an ultra-low hysteresis along with enhanced piezoelectric response (d₃₃ ~ 190pC/N) and high temperature stability (~160°C). Transmission electron microscopy (TEM) and piezoresponse force microscopy (PFM) results demonstrate smaller size highly ordered domain structure in grain-oriented specimen relative to the conventional polycrystalline ceramics. The grain oriented specimens exhibited a high degree of non-180° domain switching, in comparison to the randomly axed ones. These results indicate the effective solution to the lead-free piezoelectricmore » materials.« less

Multifocus image fusion scheme based on the multiscale curvature in nonsubsampled contourlet transform domain

NASA Astrophysics Data System (ADS)

Li, Xiaosong; Li, Huafeng; Yu, Zhengtao; Kong, Yingchun

2015-07-01

An efficient multifocus image fusion scheme in nonsubsampled contourlet transform (NSCT) domain is proposed. Based on the property of optical imaging and the theory of defocused image, we present a selection principle for lowpass frequency coefficients and also investigate the connection between a low-frequency image and the defocused image. Generally, the NSCT algorithm decomposes detail image information indwells in different scales and different directions in the bandpass subband coefficient. In order to correctly pick out the prefused bandpass directional coefficients, we introduce multiscale curvature, which not only inherits the advantages of windows with different sizes, but also correctly recognizes the focused pixels from source images, and then develop a new fusion scheme of the bandpass subband coefficients. The fused image can be obtained by inverse NSCT with the different fused coefficients. Several multifocus image fusion methods are compared with the proposed scheme. The experimental results clearly indicate the validity and superiority of the proposed scheme in terms of both the visual qualities and the quantitative evaluation.

Simulations of incompressible Navier Stokes equations on curved surfaces using discrete exterior calculus

NASA Astrophysics Data System (ADS)

Samtaney, Ravi; Mohamed, Mamdouh; Hirani, Anil

2015-11-01

We present examples of numerical solutions of incompressible flow on 2D curved domains. The Navier-Stokes equations are first rewritten using the exterior calculus notation, replacing vector calculus differential operators by the exterior derivative, Hodge star and wedge product operators. A conservative discretization of Navier-Stokes equations on simplicial meshes is developed based on discrete exterior calculus (DEC). The discretization is then carried out by substituting the corresponding discrete operators based on the DEC framework. By construction, the method is conservative in that both the discrete divergence and circulation are conserved up to machine precision. The relative error in kinetic energy for inviscid flow test cases converges in a second order fashion with both the mesh size and the time step. Numerical examples include Taylor vortices on a sphere, Stuart vortices on a sphere, and flow past a cylinder on domains with varying curvature. Supported by the KAUST Office of Competitive Research Funds under Award No. URF/1/1401-01.

Cooperative rearrangements leading to long range order in monolayers of supramolecular polymers.

PubMed

Vonau, F; Aubel, D; Bouteiller, L; Reiter, G; Simon, L

2007-08-24

Using scanning tunneling microscopy (STM), we followed the self-organization process of a supramolecular polymer monolayer deposited on a gold surface. During the growth of ordered domains from small to large scales, the molecule-molecule interactions were found to overrule the coupling to the substrate, causing a reorientation of the monolayer. The flexibility at the molecular level, due to reversible hydrogen bonds, was directly visualized by STM. The supramolecules were able to slide and insert between neighboring molecules, allowing the annihilation of domain boundaries and improving long range order. Large domains were found to cross monoatomic steps on the substrate without perturbation of their order.

Statistics of opinion domains of the majority-vote model on a square lattice

NASA Astrophysics Data System (ADS)

Peres, Lucas R.; Fontanari, José F.

2010-10-01

The existence of juxtaposed regions of distinct cultures in spite of the fact that people’s beliefs have a tendency to become more similar to each other’s as the individuals interact repeatedly is a puzzling phenomenon in the social sciences. Here we study an extreme version of the frequency-dependent bias model of social influence in which an individual adopts the opinion shared by the majority of the members of its extended neighborhood, which includes the individual itself. This is a variant of the majority-vote model in which the individual retains its opinion in case there is a tie among the neighbors’ opinions. We assume that the individuals are fixed in the sites of a square lattice of linear size L and that they interact with their nearest neighbors only. Within a mean-field framework, we derive the equations of motion for the density of individuals adopting a particular opinion in the single-site and pair approximations. Although the single-site approximation predicts a single opinion domain that takes over the entire lattice, the pair approximation yields a qualitatively correct picture with the coexistence of different opinion domains and a strong dependence on the initial conditions. Extensive Monte Carlo simulations indicate the existence of a rich distribution of opinion domains or clusters, the number of which grows with L2 whereas the size of the largest cluster grows with lnL2 . The analysis of the sizes of the opinion domains shows that they obey a power-law distribution for not too large sizes but that they are exponentially distributed in the limit of very large clusters. In addition, similarly to other well-known social influence model—Axelrod’s model—we found that these opinion domains are unstable to the effect of a thermal-like noise.

The critical domain size of stochastic population models.

PubMed

Reimer, Jody R; Bonsall, Michael B; Maini, Philip K

2017-02-01

Identifying the critical domain size necessary for a population to persist is an important question in ecology. Both demographic and environmental stochasticity impact a population's ability to persist. Here we explore ways of including this variability. We study populations with distinct dispersal and sedentary stages, which have traditionally been modelled using a deterministic integrodifference equation (IDE) framework. Individual-based models (IBMs) are the most intuitive stochastic analogues to IDEs but yield few analytic insights. We explore two alternate approaches; one is a scaling up to the population level using the Central Limit Theorem, and the other a variation on both Galton-Watson branching processes and branching processes in random environments. These branching process models closely approximate the IBM and yield insight into the factors determining the critical domain size for a given population subject to stochasticity.

Submillisecond-response and scattering-free infrared liquid crystal phase modulators.

PubMed

Sun, Jie; Chen, Yuan; Wu, Shin-Tson

2012-08-27

We demonstrate a submillisecond-response and scattering-free infrared phase modulator using a polymer network liquid crystal (PNLC). The required voltage for achieving 2π phase change at λ = 1.06 µm is 70V (or 5.8 V/μm) and the measured response time is ~200 µs at 25°C and 30 µs at 70°C. Opposite to our conventional understanding, a high viscosity LC helps to achieve small domain size during polymerization process, which in turn reduces the response time and light scattering. We use Rayleigh-Gans-Debye scattering model to analyze the voltage-on state transmission spectra. When the domain size is comparable to the wavelength, the model fits with experimental results well. But when the domain size is smaller than the wavelength, the simple Rayleigh model works well.

Simulations of Cyclone Sidr in the Bay of Bengal with a High-Resolution Model: Sensitivity to Large-Scale Boundary Forcing

NASA Technical Reports Server (NTRS)

Kumar, Anil; Done, James; Dudhia, Jimy; Niyogi, Dev

2011-01-01

The predictability of Cyclone Sidr in the Bay of Bengal was explored in terms of track and intensity using the Advanced Research Hurricane Weather Research Forecast (AHW) model. This constitutes the first application of the AHW over an area that lies outside the region of the North Atlantic for which this model was developed and tested. Several experiments were conducted to understand the possible contributing factors that affected Sidr s intensity and track simulation by varying the initial start time and domain size. Results show that Sidr s track was strongly controlled by the synoptic flow at the 500-hPa level, seen especially due to the strong mid-latitude westerly over north-central India. A 96-h forecast produced westerly winds over north-central India at the 500-hPa level that were notably weaker; this likely caused the modeled cyclone track to drift from the observed actual track. Reducing the model domain size reduced model error in the synoptic-scale winds at 500 hPa and produced an improved cyclone track. Specifically, the cyclone track appeared to be sensitive to the upstream synoptic flow, and was, therefore, sensitive to the location of the western boundary of the domain. However, cyclone intensity remained largely unaffected by this synoptic wind error at the 500-hPa level. Comparison of the high resolution, moving nested domain with a single coarser resolution domain showed little difference in tracks, but resulted in significantly different intensities. Experiments on the domain size with regard to the total precipitation simulated by the model showed that precipitation patterns and 10-m surface winds were also different. This was mainly due to the mid-latitude westerly flow across the west side of the model domain. The analysis also suggested that the total precipitation pattern and track was unchanged when the domain was extended toward the east, north, and south. Furthermore, this highlights our conclusion that Sidr was influenced from the west side of the domain. The displacement error was significantly reduced after the domain size from the western model boundary was decreased. Study results demonstrate the capability and need of a high-resolution mesoscale modeling framework for simulating the complex interactions that contribute to the formation of tropical cyclones over the Bay of Bengal region

Parameterized Radiative Convective Equilibrium Across a Range of Domains: A Unifying Tool for General Circulation Models and High Resolution Models

NASA Astrophysics Data System (ADS)

Silvers, L. G.; Stevens, B. B.; Mauritsen, T.; Marco, G. A.

2015-12-01

The characteristics of clouds in General Circulation Models (GCMs) need to be constrained in a consistent manner with theory, observations, and high resolution models (HRMs). One way forward is to base improvements of parameterizations on high resolution studies which resolve more of the important dynamical motions and allow for less parameterizations. This is difficult because of the numerous differences between GCMs and HRMs, both technical and theoretical. Century long simulations at resolutions of 20-250 km on a global domain are typical of GCMs while HRMs often simulate hours at resolutions of 0.1km-5km on domains the size of a single GCM grid cell. The recently developed mode ICON provides a flexible framework which allows many of these difficulties to be overcome. This study uses the ICON model to compute SST perturbation simulations on multiple domains in a state of Radiative Convective Equilibrium (RCE) with parameterized convection. The domains used range from roughly the size of Texas to nearly half of Earth's surface area. All simulations use a doubly periodic domain with an effective distance between cell centers of 13 km and are integrated to a state of statistical stationarity. The primary analysis examines the mean characteristics of the cloud related fields and the feedback parameter of the simulations. It is shown that the simulated atmosphere of a GCM in RCE is sufficiently similar across a range of domain sizes to justify the use of RCE to study both a GCM and a HRM on the same domain with the goal of improved constraints on the parameterized clouds. The simulated atmospheres are comparable to what could be expected at midday in a typical region of Earth's tropics under calm conditions. In particular, the differences between the domains are smaller than differences which result from choosing different physics schemes. Significant convective organization is present on all domain sizes with a relatively high subsidence fraction. Notwithstanding the overall qualitative similarities of the simulations, quantitative differences lead to a surprisingly large sensitivity of the feedback parameter. This range of the feedback parameter is more than a factor of two and is similar to the range of feedbacks which were obtained by the CMIP5 models.

Phylogenetic Tracings of Proteome Size Support the Gradual Accretion of Protein Structural Domains and the Early Origin of Viruses from Primordial Cells

PubMed Central

Nasir, Arshan; Kim, Kyung Mo; Caetano-Anollés, Gustavo

2017-01-01

Untangling the origin and evolution of viruses remains a challenging proposition. We recently studied the global distribution of protein domain structures in thousands of completely sequenced viral and cellular proteomes with comparative genomics, phylogenomics, and multidimensional scaling methods. A tree of life describing the evolution of proteomes revealed viruses emerging from the base of the tree as a fourth supergroup of life. A tree of domains indicated an early origin of modern viral lineages from ancient cells that co-existed with the cellular ancestors. However, it was recently argued that the rooting of our trees and the basal placement of viruses was artifactually induced by small genome (proteome) size. Here we show that these claims arise from misunderstanding and misinterpretations of cladistic methodology. Trees are reconstructed unrooted, and thus, their topologies cannot be distorted a posteriori by the rooting methodology. Tracing proteome size in trees and multidimensional views of evolutionary relationships as well as tests of leaf stability and exclusion/inclusion of taxa demonstrated that the smallest proteomes were neither attracted toward the root nor caused any topological distortions of the trees. Simulations confirmed that taxa clustering patterns were independent of proteome size and were determined by the presence of known evolutionary relatives in data matrices, highlighting the need for broader taxon sampling in phylogeny reconstruction. Instead, phylogenetic tracings of proteome size revealed a slowdown in innovation of the structural domain vocabulary and four regimes of allometric scaling that reflected a Heaps law. These regimes explained increasing economies of scale in the evolutionary growth and accretion of kernel proteome repertoires of viruses and cellular organisms that resemble growth of human languages with limited vocabulary sizes. Results reconcile dynamic and static views of domain frequency distributions that are consistent with the axiom of spatiotemporal continuity that is tenet of evolutionary thinking. PMID:28690608

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

Vincenti, H.; Vay, J. -L.

Due to discretization effects and truncation to finite domains, many electromagnetic simulations present non-physical modifications of Maxwell's equations in space that may generate spurious signals affecting the overall accuracy of the result. Such modifications for instance occur when Perfectly Matched Layers (PMLs) are used at simulation domain boundaries to simulate open media. Another example is the use of arbitrary order Maxwell solver with domain decomposition technique that may under some condition involve stencil truncations at subdomain boundaries, resulting in small spurious errors that do eventually build up. In each case, a careful evaluation of the characteristics and magnitude of themore » errors resulting from these approximations, and their impact at any frequency and angle, requires detailed analytical and numerical studies. To this end, we present a general analytical approach that enables the evaluation of numerical discretization errors of fully three-dimensional arbitrary order finite-difference Maxwell solver, with arbitrary modification of the local stencil in the simulation domain. The analytical model is validated against simulations of domain decomposition technique and PMLs, when these are used with very high-order Maxwell solver, as well as in the infinite order limit of pseudo-spectral solvers. Results confirm that the new analytical approach enables exact predictions in each case. It also confirms that the domain decomposition technique can be used with very high-order Maxwell solver and a reasonably low number of guard cells with negligible effects on the whole accuracy of the simulation.« less

Beneath the Surface: Understanding Patterns of Intra-Domain Orientational Order

NASA Astrophysics Data System (ADS)

Prasad, Ishan; Seo, Youngmi; Hall, Lisa; Grason, Gregory

Block copolymers (BCP) self assemble into a rich spectrum of ordered phases due to asymmetry in copolymer architecture. Despite extensive study of spatially-ordered composition patterns of BCP, knowledge of orientational order of chain segments that underlie these spatial patterns is evidently missing. We show using self consistent field (SCF) theory and coarse-grained molecular dynamics (MD) simulations that, even without explicit orientational interactions between segments, BCP exhibit generic patterns of intra-domain segment orientation, which vary both within a given morphology and from morphology to morphology. We find that segment alignment is usually both normal and parallel to the interface within different local regions of a BCP sub-domain. We describe principles that control relative strength and directionality of alignment in different morphologies and report a surprising yet generic emergence of biaxial segment order in morphologies with anisotropic curved interfaces, such as cylinders and gyroid phases. Finally, we focus our study on cholesteric textures that pervade mesochiral BCP morphologies, specifically alternating double gyroid (aDG) and helical cylinder (H*) phases, and analyze patterns of twisted (nematic and polar) segment order within these domains.

Wafer Scale Fabrication of Dense and High Aspect Ratio Sub-50 nm Nanopillars from Phase Separation of Cross-Linkable Polysiloxane/Polystyrene Blend.

PubMed

Li, Yang; Hao, Yuli; Huang, Chunyu; Chen, Xingyao; Chen, Xinyu; Cui, Yushuang; Yuan, Changsheng; Qiu, Kai; Ge, Haixiong; Chen, Yanfeng

2017-04-19

We demonstrated a simple and effective approach to fabricate dense and high aspect ratio sub-50 nm pillars based on phase separation of a polymer blend composed of a cross-linkable polysiloxane and polystyrene (PS). In order to obtain the phase-separated domains with nanoscale size, a liquid prepolymer of cross-linkable polysiloxane was employed as one moiety for increasing the miscibility of the polymer blend. After phase separation via spin-coating, the dispersed domains of liquid polysiloxane with sub-50 nm size could be solidified by UV exposure. The solidified polysiloxane domains took the role of etching mask for formation of high aspect ratio nanopillars by O 2 reactive ion etching (RIE). The aspect ratio of the nanopillars could be further amplified by introduction of a polymer transfer layer underneath the polymer blend film. The effects of spin speeds, the weight ratio of the polysiloxane/PS blend, and the concentration of polysiloxane/PS blend in toluene on the characters of the nanopillars were investigated. The gold-coated nanopillar arrays exhibited a high Raman scattering enhancement factor in the range of 10 8 -10 9 with high uniformity across over the wafer scale sample. A superhydrophobic surface could be realized by coating a self-assembled monolayers (SAM) of fluoroalkyltrichlorosilane on the nanopillar arrays. Sub-50 nm silicon nanowires (SiNWs) with high aspect ratio of about 1000 were achieved by using the nanopillars as etching mask through a metal-assisted chemical etching process. They showed an ultralow reflectance of approximately 0.1% for wavelengths ranging from 200 to 800 nm.

Three is much more than two in coarsening dynamics of cyclic competitions

NASA Astrophysics Data System (ADS)

Mitarai, Namiko; Gunnarson, Ivar; Pedersen, Buster Niels; Rosiek, Christian Anker; Sneppen, Kim

2016-04-01

The classical game of rock-paper-scissors has inspired experiments and spatial model systems that address the robustness of biological diversity. In particular, the game nicely illustrates that cyclic interactions allow multiple strategies to coexist for long-time intervals. When formulated in terms of a one-dimensional cellular automata, the spatial distribution of strategies exhibits coarsening with algebraically growing domain size over time, while the two-dimensional version allows domains to break and thereby opens the possibility for long-time coexistence. We consider a quasi-one-dimensional implementation of the cyclic competition, and study the long-term dynamics as a function of rare invasions between parallel linear ecosystems. We find that increasing the complexity from two to three parallel subsystems allows a transition from complete coarsening to an active steady state where the domain size stays finite. We further find that this transition happens irrespective of whether the update is done in parallel for all sites simultaneously or done randomly in sequential order. In both cases, the active state is characterized by localized bursts of dislocations, followed by longer periods of coarsening. In the case of the parallel dynamics, we find that there is another phase transition between the active steady state and the coarsening state within the three-line system when the invasion rate between the subsystems is varied. We identify the critical parameter for this transition and show that the density of active boundaries has critical exponents that are consistent with the directed percolation universality class. On the other hand, numerical simulations with the random sequential dynamics suggest that the system may exhibit an active steady state as long as the invasion rate is finite.

Growth Of Organic Semiconductor Thin Films with Multi-Micron Domain Size and Fabrication of Organic Transistors Using a Stencil Nanosieve.

PubMed

Fesenko, Pavlo; Flauraud, Valentin; Xie, Shenqi; Kang, Enpu; Uemura, Takafumi; Brugger, Jürgen; Genoe, Jan; Heremans, Paul; Rolin, Cédric

2017-07-19

To grow small molecule semiconductor thin films with domain size larger than modern-day device sizes, we evaporate the material through a dense array of small apertures, called a stencil nanosieve. The aperture size of 0.5 μm results in low nucleation density, whereas the aperture-to-aperture distance of 0.5 μm provides sufficient crosstalk between neighboring apertures through the diffusion of adsorbed molecules. By integrating the nanosieve in the channel area of a thin-film transistor mask, we show a route for patterning both the organic semiconductor and the metal contacts of thin-film transistors using one mask only and without mask realignment.

Multifunctional two-photon active silica-coated Au@MnO Janus particles for selective dual functionalization and imaging.

PubMed

Schick, Isabel; Lorenz, Steffen; Gehrig, Dominik; Schilmann, Anna-Maria; Bauer, Heiko; Panthöfer, Martin; Fischer, Karl; Strand, Dennis; Laquai, Frédéric; Tremel, Wolfgang

2014-02-12

Monodisperse multifunctional and nontoxic Au@MnO Janus particles with different sizes and morphologies were prepared by a seed-mediated nucleation and growth technique with precise control over domain sizes, surface functionalization, and dye labeling. The metal oxide domain could be coated selectively with a thin silica layer, leaving the metal domain untouched. In particular, size and morphology of the individual (metal and metal oxide) domains could be controlled by adjustment of the synthetic parameters. The SiO2 coating of the oxide domain allows biomolecule conjugation (e.g., antibodies, proteins) in a single step for converting the photoluminescent and superparamagnetic Janus nanoparticles into multifunctional efficient vehicles for theranostics. The Au@MnO@SiO2 Janus particles were characterized using high-resolution transmission electron microscopy (HR-)TEM, powder X-ray diffraction (PXRD), optical (UV-vis) spectroscopy, confocal laser fluorescence scanning microscopy (CLSM), and dynamic light scattering (DLS). The functionalized nanoparticles were stable in buffer solution or serum, showing no indication of aggregation. Biocompatibility and potential biomedical applications of the Au@MnO@SiO2 Janus particles were assayed by a cell viability analysis by coincubating the Au@MnO@SiO2 Janus particles with Caki 1 and HeLa cells. Time-resolved fluorescence spectroscopy in combination with CLSM revealed the silica-coated Au@MnO@SiO2 Janus particles to be highly two-photon active; no indication for an electronic interaction between the dye molecules incorporated in the silica shell surrounding the MnO domains and the attached Au domains was found; fluorescence quenching was observed when dye molecules were bound directly to the Au domains.

Compositional Tuning, Crystal Growth, and Magnetic Properties of Iron Phosphate Oxide

NASA Astrophysics Data System (ADS)

Tarne, Michael

Iron phosphate oxide, Fe3PO4O 3, is a crystalline solid featuring magnetic Fe3+ ions on a complex lattice composed of closely-spaced triangles. Previous work from our research group on this compound has proposed a helical magnetic structure below T = 163 K attributed to J1 - J2 competing interactions between nearest-neighbor and next-nearest-neighbor iron atoms. This was based on neutron powder diffraction featuring unique broad, flat-topped magnetic reflections due to needle-like magnetic domains. In order to confirm the magnetic structure and origins of frustration, this thesis will expand upon the research focused on this compound. The first chapter focuses on single crystal growth of Fe3PO 4O3. While neutron powder diffraction provides insight to the magnetic structure, powder and domain averaging obfuscate a conclusive structure for Fe3PO4O3 and single crystal neutron scattering is necessary. Due to the incongruency of melting, single crystal growth has proven challenging. A number of techniques including flux growth, slow cooling, and optical floating zone growth were attempted and success has been achieved via heterogenous chemical vapor transport from FePO 4 using ZrCl4 as a transport agent. These crystals are of sufficient size for single crystal measurements on modern neutron diffractometers. Dilution of the magnetic sublattice in frustrated magnets can also provide insight into the nature of competing spin interactions. Dilution of the Fe 3+ lattice in Fe3PO4O3 is accomplished by substituting non-magnetic Ga3+ to form the solid solution series Fe3-xGaxPO4O3 with x = 0, 0.012, 0.06, 0.25, 0.5, 1.0, 1.5. The magnetic susceptibility and neutron powder diffraction data of these compounds are presented. A dramatic decrease of the both the helical pitch length and the domain size is observed with increasing x; for x > 0.5, the compounds lack long range magnetic order. The phases that do exhibit magnetic order show a decrease in helical pitch with increasing x as determined from the magnitude of the magnetic propagation vector. This trend can be qualitatively reproduced by increasing the ratio of J2/ J1 in the Heisenberg model. Intriguingly, the domain size extracted from peak broadening of the magnetic reflections is nearly equal to the pitch length for each value of x, which suggests that the two qualities are linked in this unusual antiferromagnet. The last chapter focuses on the oxyfluoride Fe3PO7-x Fx. Through fluorination using low-temperature chimie douce reactions with polytetrafluoroethylene, the magnetic properties show changes in the magnetic susceptibility, isothermal magnetization, and neutron powder diffraction. The magnetic susceptibility shows a peak near T = 13 K and a zero field cooled/field cooled splitting at T = 78 K. The broad, flat-topped magnetic reflections in the powder neutron diffraction exhibit a decrease in width and increase in intensity. The changes in the neutron powder diffraction suggest an increase in correlation length in the ab plane of the fluorinated compound. Iron phosphate oxide is a unique lattice showing a rich magnetic phase diagram in both the gallium-substituted and fluorinated species. While mean-field interactions are sufficient to describe interactions in the solid solution series Fe3-xGaxPO4O3, the additional magnetic transitions in Fe3PO7-xFx suggest a more complicated set of interactions.

Deposition and growth of domains in one dimension

NASA Astrophysics Data System (ADS)

Rodgers, G. J.; Tavassoli, Z.

1998-09-01

A model of deposition and growth in one dimension is studied in which finite sized domains are deposited by the random sequential adsorption process. The domains then grow with a time dependent growth rate. When the initial deposited domains are monomers and dimers the coverage is found exactly for a number of different growth rates. A continuum version of this model is also considered.

Angular-domain scattering interferometry.

PubMed

Shipp, Dustin W; Qian, Ruobing; Berger, Andrew J

2013-11-15

We present an angular-scattering optical method that is capable of measuring the mean size of scatterers in static ensembles within a field of view less than 20 μm in diameter. Using interferometry, the method overcomes the inability of intensity-based models to tolerate the large speckle grains associated with such small illumination areas. By first estimating each scatterer's location, the method can model between-scatterer interference as well as traditional single-particle Mie scattering. Direct angular-domain measurements provide finer angular resolution than digitally transformed image-plane recordings. This increases sensitivity to size-dependent scattering features, enabling more robust size estimates. The sensitivity of these angular-scattering measurements to various sizes of polystyrene beads is demonstrated. Interferometry also allows recovery of the full complex scattered field, including a size-dependent phase profile in the angular-scattering pattern.

Object size determines the spatial spread of visual time

PubMed Central

McGraw, Paul V.; Roach, Neil W.; Whitaker, David

2016-01-01

A key question for temporal processing research is how the nervous system extracts event duration, despite a notable lack of neural structures dedicated to duration encoding. This is in stark contrast with the orderly arrangement of neurons tasked with spatial processing. In this study, we examine the linkage between the spatial and temporal domains. We use sensory adaptation techniques to generate after-effects where perceived duration is either compressed or expanded in the opposite direction to the adapting stimulus' duration. Our results indicate that these after-effects are broadly tuned, extending over an area approximately five times the size of the stimulus. This region is directly related to the size of the adapting stimulus—the larger the adapting stimulus the greater the spatial spread of the after-effect. We construct a simple model to test predictions based on overlapping adapted versus non-adapted neuronal populations and show that our effects cannot be explained by any single, fixed-scale neural filtering. Rather, our effects are best explained by a self-scaled mechanism underpinned by duration selective neurons that also pool spatial information across earlier stages of visual processing. PMID:27466452

Structure of the mixed-metal carbonate KAgCO₃ revisited: order-disorder (OD) polytypism and allotwinning.

PubMed

Hans, Philipp; Stöger, Berthold; Weil, Matthias; Zobetz, Erich

2015-04-01

Crystals of KAgCO3 belong to an order-disorder (OD) family of structures composed of layers of two kinds. There are two polytypes with a maximum degree of order [MDO1: Pccb; MDO2: Ibca, doubled a-axis compared with MDO1], which are both realised to a different extent in two crystals under investigation [volume fraction MDO1:MDO2 in crystal (I): 0.0216:0.9784 (3) and in crystal (II): 0.9657:0.0343 (3)]. Sharp diffraction spots and the absence of diffuse scattering indicate highly ordered macroscopic domains. The structure of KAgCO3 was refined concurrently against all reflections using an allotwin model (addition of the intensities of both domains). It is shown that a disorder model refined against reflections of only one domain can lead to a significant overestimation of the volume fraction of this domain.

Ordered CdSe nanoparticles within self-assembled block copolymer domains on surfaces.

PubMed

Zou, Shan; Hong, Rui; Emrick, Todd; Walker, Gilbert C

2007-02-13

Hierarchical, high-density, ordered patterns were fabricated on Si substrates by self-assembly of CdSe nanoparticles within approximately 20-nm-thick diblock copolymer films in a controlled manner. Surface-modified CdSe nanoparticles formed well-defined structures within microphase-separated polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) domains. Trioctylphosphine oxide (TOPO)-coated CdSe nanoparticles were incorporated into PS domains and polyethylene glycol-coated CdSe nanoparticles were located primarily in the P2VP domains. Nearly close-packed CdSe nanoparticles were clearly identified within the highly ordered patterns on Si substrates by scanning electron microscopy (SEM). Contact angle measurements together with SEM results indicate that TOPO-CdSe nanoparticles were partially placed at the air/copolymer interface.

A Reaction-Diffusion Model for Synapse Growth and Long-Term Memory

NASA Astrophysics Data System (ADS)

Liu, Kang; Lisman, John; Hagan, Michael

Memory storage involves strengthening of synaptic transmission known as long-term potentiation (LTP). The late phase of LTP is associated with structural processes that enlarge the synapse. Yet, synapses must be stable, despite continual subunit turnover, over the lifetime of an encoded memory. These considerations suggest that synapses are variable-size stable structure (VSSS), meaning they can switch between multiple metastable structures with different sizes. The mechanisms underlying VSSS are poorly understood. While experiments and theory have suggested that the interplay between diffusion and receptor-scaffold interactions can lead to a preferred stable size for synaptic domains, such a mechanism cannot explain how synapses adopt widely different sizes. Here we develop a minimal reaction-diffusion model of VSSS for synapse growth, incorporating the recent observation from super-resolution microscopy that neural activity can build compositional heterogeneities within synaptic domains. We find that introducing such heterogeneities can change the stable domain size in a controlled manner. We discuss a potential connection between this model and experimental data on synapse sizes, and how it provides a possible mechanism to structurally encode graded long-term memory. We acknowledge the support from NSF INSPIRE Award number IOS-1526941 (KL, MFH, JL) and the Brandeis Center for Bioinspired Soft Materials, an NSF MRSEC, DMR- 1420382 (MFH).

Confined diffusion of transmembrane proteins and lipids induced by the same actin meshwork lining the plasma membrane

PubMed Central

Fujiwara, Takahiro K.; Iwasawa, Kokoro; Kalay, Ziya; Tsunoyama, Taka A.; Watanabe, Yusuke; Umemura, Yasuhiro M.; Murakoshi, Hideji; Suzuki, Kenichi G. N.; Nemoto, Yuri L.; Morone, Nobuhiro; Kusumi, Akihiro

2016-01-01

The mechanisms by which the diffusion rate in the plasma membrane (PM) is regulated remain unresolved, despite their importance in spatially regulating the reaction rates in the PM. Proposed models include entrapment in nanoscale noncontiguous domains found in PtK2 cells, slow diffusion due to crowding, and actin-induced compartmentalization. Here, by applying single-particle tracking at high time resolutions, mainly to the PtK2-cell PM, we found confined diffusion plus hop movements (termed “hop diffusion”) for both a nonraft phospholipid and a transmembrane protein, transferrin receptor, and equal compartment sizes for these two molecules in all five of the cell lines used here (actual sizes were cell dependent), even after treatment with actin-modulating drugs. The cross-section size and the cytoplasmic domain size both affected the hop frequency. Electron tomography identified the actin-based membrane skeleton (MSK) located within 8.8 nm from the PM cytoplasmic surface of PtK2 cells and demonstrated that the MSK mesh size was the same as the compartment size for PM molecular diffusion. The extracellular matrix and extracellular domains of membrane proteins were not involved in hop diffusion. These results support a model of anchored TM-protein pickets lining actin-based MSK as a major mechanism for regulating diffusion. PMID:26864625

Magnitude of cognitive dysfunction in adults with type 2 diabetes: a meta-analysis of six cognitive domains and the most frequently reported neuropsychological tests within domains.

PubMed

Palta, Priya; Schneider, Andrea L C; Biessels, Geert Jan; Touradji, Pegah; Hill-Briggs, Felicia

2014-03-01

The objectives were to conduct a meta-analysis in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) standards to determine effect sizes (Cohen's d) for cognitive dysfunction in adults with type 2 diabetes, relative to nondiabetic controls, and to obtain effect sizes for the most commonly reported neuropsychological tests within domains. Twenty-four studies, totaling 26,137 patients (n = 3351 with diabetes), met study inclusion criteria. Small to moderate effect sizes were obtained for five of six domains: motor function (3 studies, n = 2374; d = -0.36), executive function (12 studies, n = 1784; d = -0.33), processing speed (16 studies, n = 3076; d = -0.33), verbal memory (15 studies, n = 4,608; d = -0.28), and visual memory (6 studies, n = 1754; d = -0.26). Effect size was smallest for attention/concentration (14 studies, n = 23,143; d = -0.19). The following tests demonstrated the most notable performance decrements in diabetes samples: Grooved Pegboard (dominant hand) (d = -0.60), Rey Auditory Verbal Learning Test (immediate) (d = -0.40), Trails B (d = -0.39), Rey-Osterreith Complex Figure (delayed) (d = -0.38), Trails A (d = -0.34), and Stroop Part I (d = -0.28). This study provides effect sizes to power future epidemiological and clinical diabetes research studies examining cognitive function and to help inform the selection of neuropsychological tests.

Textural domain walls in superfluid 3He-B

NASA Astrophysics Data System (ADS)

Mizushima, Takeshi

Owing to the richness of symmetry, the superfluid 3He serves as a rich repository of topological quantum phenomena. This includes the emergence of surface Majorana fermions and their quantum mass acquisition at the topological critical point. Furthermore, the marriage of the prototype topological superfluid with nanofabrication techniques brings about a rich variety of spontaneous symmetry breaking, such as the formation of the stripe order and nontrivial domain walls. In this work, we examine the possible formation of textural domain walls in the superfluid 3He-B confined to a thin slab with a sub-micron thickness. When an applied magnetic field is much higher than the dipolar field, two nearly degenerate ground states appear, which are characterized by the Ising order associated with the spontaneous breaking of a magnetic order-two symmetry, lcirc;z = + 1 and - 1 . We here discuss the structure of the textural domain wall formed by the spatial modulation of the Ising order, such as low-lying quasiparticle excitations and spontaneous spin current. We also report bosonic modes bound to the textural domain wall.

Moving Computational Domain Method and Its Application to Flow Around a High-Speed Car Passing Through a Hairpin Curve

NASA Astrophysics Data System (ADS)

Watanabe, Koji; Matsuno, Kenichi

This paper presents a new method for simulating flows driven by a body traveling with neither restriction on motion nor a limit of a region size. In the present method named 'Moving Computational Domain Method', the whole of the computational domain including bodies inside moves in the physical space without the limit of region size. Since the whole of the grid of the computational domain moves according to the movement of the body, a flow solver of the method has to be constructed on the moving grid system and it is important for the flow solver to satisfy physical and geometric conservation laws simultaneously on moving grid. For this issue, the Moving-Grid Finite-Volume Method is employed as the flow solver. The present Moving Computational Domain Method makes it possible to simulate flow driven by any kind of motion of the body in any size of the region with satisfying physical and geometric conservation laws simultaneously. In this paper, the method is applied to the flow around a high-speed car passing through a hairpin curve. The distinctive flow field driven by the car at the hairpin curve has been demonstrated in detail. The results show the promising feature of the method.

Magnesium hydroxide extracted from a magnesium-rich mineral for CO2 sequestration in a gas-solid system.

PubMed

Lin, Pao-Chung; Huang, Cheng-Wei; Hsiao, Ching-Ta; Teng, Hsisheng

2008-04-15

Magnesium hydroxide extracted from magnesium-bearing minerals is considered a promising agent for binding CO2 as a carbonate mineral in a gas-solid reaction. An efficient extraction route consisting of hydrothermal treatment on serpentine in HCl followed by NaOH titration for Mg(OH)2 precipitation was demonstrated. The extracted Mg(OH)2 powder had a mean crystal domain size as small as 12 nm and an apparent surface area of 54 m2/g. Under one atmosphere of 10 vol% CO2/N2, carbonation of the serpentine-derived Mg(OH)2 to 26% of the stoichiometric limit was achieved at 325 degrees C in 2 h; while carbonation of a commercially available Mg(OH)2, with a mean crystal domain size of 33 nm and an apparent surface area of 3.5 m2/g, reached only 9% of the stoichiometric limit. The amount of CO2 fixation was found to be inversely proportional to the crystal domain size of the Mg(OH)2 specimens. The experimental data strongly suggested that only a monolayer of carbonates was formed on the crystal domain boundary in the gas-solid reaction, with little penetration of the carbonates into the crystal domain.

A first line of stress defense: small heat shock proteins and their function in protein homeostasis.

PubMed

Haslbeck, Martin; Vierling, Elizabeth

2015-04-10

Small heat shock proteins (sHsps) are virtually ubiquitous molecular chaperones that can prevent the irreversible aggregation of denaturing proteins. sHsps complex with a variety of non-native proteins in an ATP-independent manner and, in the context of the stress response, form a first line of defense against protein aggregation in order to maintain protein homeostasis. In vertebrates, they act to maintain the clarity of the eye lens, and in humans, sHsp mutations are linked to myopathies and neuropathies. Although found in all domains of life, sHsps are quite diverse and have evolved independently in metazoans, plants and fungi. sHsp monomers range in size from approximately 12 to 42kDa and are defined by a conserved β-sandwich α-crystallin domain, flanked by variable N- and C-terminal sequences. Most sHsps form large oligomeric ensembles with a broad distribution of different, sphere- or barrel-like oligomers, with the size and structure of the oligomers dictated by features of the N- and C-termini. The activity of sHsps is regulated by mechanisms that change the equilibrium distribution in tertiary features and/or quaternary structure of the sHsp ensembles. Cooperation and/or co-assembly between different sHsps in the same cellular compartment add an underexplored level of complexity to sHsp structure and function. Copyright © 2015 Elsevier Ltd. All rights reserved.

Wettability Patterning for Enhanced Dropwise Condensation

NASA Astrophysics Data System (ADS)

Ghosh, Aritra; Ganguly, Ranjan; Megaridis, Constantine

2014-11-01

Dropwise condensation (DwC), in order to be sustainable, requires removal of the condensate droplets. This removal is frequently facilitated by gravity. The rate of DwC heat transfer depends strongly on the maximum departing droplet diameter. Based on wettability patterning, we present a facile technique designed to control the maximum droplet size in DwC within vapor/air atmospheres, and demonstrate how this approach can be used to enhance the corresponding heat transfer rate. We examine various hydrophilic-superhydrophilic patterns, which, respectively sustain DwC and filmwise (FwC) condensation on the substrate. The fabrication method does notemploy any hydrophobizing agent. By juxtaposing parallel lines of hydrophilic (CA ~ 78°) and superhydrophilic (CA ~ 0°) regions on the condensing surface, we create alternating domains of DwC and FwC. The average droplet size on the DwC domain is reduced by ~ 60% compared to the theoretical maximum, which corresponds to the line width. We compare heat transfer rate between unpatternend DwC surfaces and patterned DwC surfaces. Even after sacrificing 40% of condensing area, we achieve up to 20% improvement in condensate collection rate using an interdigitated superhydrophilic pattern, inspired by the vein network of plant leaves. The bioinspired interdigitated pattern is found to outperform the straight hydrophilic-superhydrophilic pattern, particularly under higher vapor loadings in an air/vapor ambient atmosphere. NSF STTR Grant 1331817 via NBD Nano.

Accelerating solutions of one-dimensional unsteady PDEs with GPU-based swept time-space decomposition

NASA Astrophysics Data System (ADS)

Magee, Daniel J.; Niemeyer, Kyle E.

2018-03-01

The expedient design of precision components in aerospace and other high-tech industries requires simulations of physical phenomena often described by partial differential equations (PDEs) without exact solutions. Modern design problems require simulations with a level of resolution difficult to achieve in reasonable amounts of time-even in effectively parallelized solvers. Though the scale of the problem relative to available computing power is the greatest impediment to accelerating these applications, significant performance gains can be achieved through careful attention to the details of memory communication and access. The swept time-space decomposition rule reduces communication between sub-domains by exhausting the domain of influence before communicating boundary values. Here we present a GPU implementation of the swept rule, which modifies the algorithm for improved performance on this processing architecture by prioritizing use of private (shared) memory, avoiding interblock communication, and overwriting unnecessary values. It shows significant improvement in the execution time of finite-difference solvers for one-dimensional unsteady PDEs, producing speedups of 2 - 9 × for a range of problem sizes, respectively, compared with simple GPU versions and 7 - 300 × compared with parallel CPU versions. However, for a more sophisticated one-dimensional system of equations discretized with a second-order finite-volume scheme, the swept rule performs 1.2 - 1.9 × worse than a standard implementation for all problem sizes.

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

Gamblin, T; de Supinski, B R; Schulz, M

Good load balance is crucial on very large parallel systems, but the most sophisticated algorithms introduce dynamic imbalances through adaptation in domain decomposition or use of adaptive solvers. To observe and diagnose imbalance, developers need system-wide, temporally-ordered measurements from full-scale runs. This potentially requires data collection from multiple code regions on all processors over the entire execution. Doing this instrumentation naively can, in combination with the application itself, exceed available I/O bandwidth and storage capacity, and can induce severe behavioral perturbations. We present and evaluate a novel technique for scalable, low-error load balance measurement. This uses a parallel wavelet transformmore » and other parallel encoding methods. We show that our technique collects and reconstructs system-wide measurements with low error. Compression time scales sublinearly with system size and data volume is several orders of magnitude smaller than the raw data. The overhead is low enough for online use in a production environment.« less

Optimum allocation for a dual-frame telephone survey.

PubMed

Wolter, Kirk M; Tao, Xian; Montgomery, Robert; Smith, Philip J

2015-12-01

Careful design of a dual-frame random digit dial (RDD) telephone survey requires selecting from among many options that have varying impacts on cost, precision, and coverage in order to obtain the best possible implementation of the study goals. One such consideration is whether to screen cell-phone households in order to interview cell-phone only (CPO) households and exclude dual-user household, or to take all interviews obtained via the cell-phone sample. We present a framework in which to consider the tradeoffs between these two options and a method to select the optimal design. We derive and discuss the optimum allocation of sample size between the two sampling frames and explore the choice of optimum p , the mixing parameter for the dual-user domain. We illustrate our methods using the National Immunization Survey , sponsored by the Centers for Disease Control and Prevention.

Continuous-Variable Instantaneous Quantum Computing is Hard to Sample.

PubMed

Douce, T; Markham, D; Kashefi, E; Diamanti, E; Coudreau, T; Milman, P; van Loock, P; Ferrini, G

2017-02-17

Instantaneous quantum computing is a subuniversal quantum complexity class, whose circuits have proven to be hard to simulate classically in the discrete-variable realm. We extend this proof to the continuous-variable (CV) domain by using squeezed states and homodyne detection, and by exploring the properties of postselected circuits. In order to treat postselection in CVs, we consider finitely resolved homodyne detectors, corresponding to a realistic scheme based on discrete probability distributions of the measurement outcomes. The unavoidable errors stemming from the use of finitely squeezed states are suppressed through a qubit-into-oscillator Gottesman-Kitaev-Preskill encoding of quantum information, which was previously shown to enable fault-tolerant CV quantum computation. Finally, we show that, in order to render postselected computational classes in CVs meaningful, a logarithmic scaling of the squeezing parameter with the circuit size is necessary, translating into a polynomial scaling of the input energy.

Cobalt ferrite nanocrystals: out-performing magnetotactic bacteria.

PubMed

Prozorov, Tanya; Palo, Pierre; Wang, Lijun; Nilsen-Hamilton, Marit; Jones, DeAnna; Orr, Daniel; Mallapragada, Surya K; Narasimhan, Balaji; Canfield, Paul C; Prozorov, Ruslan

2007-10-01

Magnetotactic bacteria produce exquisitely ordered chains of uniform magnetite (Fe(3)O(4)) nanocrystals, and the use of the bacterial mms6 protein allows for the shape-selective synthesis of Fe(3)O(4) nanocrystals. Cobalt ferrite (CoFe(2)O(4)) nanoparticles, on the other hand, are not known to occur in living organisms. Here we report on the use of the recombinant mms6 protein in a templated synthesis of CoFe(2)O(4) nanocrystals in vitro. We have covalently attached the full-length mms6 protein and a synthetic C-terminal domain of mms6 protein to self-assembling polymers in order to template hierarchical CoFe(2)O(4) nanostructures. This new synthesis pathway enables facile room-temperature shape-specific synthesis of complex magnetic crystalline nanomaterials with particle sizes in the range of 40-100 nm that are difficult to produce using conventional techniques.

UV missile-plume signature model

NASA Astrophysics Data System (ADS)

Roblin, Antoine; Baudoux, Pierre E.; Chervet, Patrick

2002-08-01

A new 3D radiative code is used to solve the radiative transfer equation in the UV spectral domain for a nonequilibrium and axisymmetric media such as a rocket plume composed of hot reactive gases and metallic oxide particles like alumina. Calculations take into account the dominant chemiluminescence radiation mechanism and multiple scattering effects produced by alumina particles. Plume radiative properties are studied by using a simple cylindrical media of finite length, deduced from different aerothermochemical real rocket plume afterburning zones. Assumed a log-normal size distribution of alumina particles, optical properties are calculated by using Mie theory. Due to large uncertainties of particles properties, systematic tests have been performed in order to evaluate the influence of the different input data (refractive index, particle mean geometric radius) upon the radiance field. These computations will help us to define the set of parameters which need to be known accurately in order to compare computations with radiance measurements obtained during field experiments.

Poly(cyclohexylethylene)- block-poly(ethylene oxide) block polymers for metal oxide templating

DOE PAGES

Schulze, Morgan W.; Sinturel, Christophe; Hillmyer, Marc A.

2015-09-01

A series of poly(cyclohexylethylene)- block-poly(ethylene oxide) (CEO) diblock copolymers were synthesized through tandem anionic polymerizations and heterogeneous catalytic hydrogenation. Solvent-annealed CEO diblock films were used to template dense arrays of inorganic oxide nanodots via simple spin coating of an inorganic precursor solution atop the ordered film. The substantial chemical dissimilarity of the two blocks enables (i) selective inclusion of the inorganic precursor within the PEO domain and (ii) the formation of exceptionally small feature sizes due to a relatively large interaction parameter estimated from mean-field analysis of the order–disorder transition temperatures of compositionally symmetric samples. UV/ozone treatment following incorporation producesmore » an ordered arrangement of oxide nanodots and simultaneously removes the block polymer template. However, we report the smallest particles (6 ± 1 nm) templated from a selective precursor insertion method to date using a block polymer scaffold.« less

Topologically Diverse Human Membrane Proteins Partition to Liquid-Disordered Domains in Phase-Separated Lipid Vesicles.

PubMed

Schlebach, Jonathan P; Barrett, Paul J; Day, Charles A; Kim, Ji Hun; Kenworthy, Anne K; Sanders, Charles R

2016-02-23

The integration of membrane proteins into "lipid raft" membrane domains influences many biochemical processes. The intrinsic structural properties of membrane proteins are thought to mediate their partitioning between membrane domains. However, whether membrane topology influences the targeting of proteins to rafts remains unclear. To address this question, we examined the domain preference of three putative raft-associated membrane proteins with widely different topologies: human caveolin-3, C99 (the 99 residue C-terminal domain of the amyloid precursor protein), and peripheral myelin protein 22. We find that each of these proteins are excluded from the ordered domains of giant unilamellar vesicles containing coexisting liquid-ordered and liquid-disordered phases. Thus, the intrinsic structural properties of these three topologically distinct disease-linked proteins are insufficient to confer affinity for synthetic raft-like domains.

Interactions between lipids and proteins are critical for organization of plasma membrane-ordered domains in tobacco BY-2 cells.

PubMed

Grosjean, Kevin; Der, Christophe; Robert, Franck; Thomas, Dominique; Mongrand, Sébastien; Simon-Plas, Françoise; Gerbeau-Pissot, Patricia

2018-06-27

The laterally heterogeneous plant plasma membrane (PM) is organized into finely controlled specialized areas that include membrane-ordered domains. Recently, the spatial distribution of such domains within the PM has been identified as playing a key role in cell responses to environmental challenges. To examine membrane order at a local level, BY-2 tobacco suspension cell PMs were labelled with an environment-sensitive probe (di-4-ANEPPDHQ). Four experimental models were compared to identify mechanisms and cell components involved in short-term (1 h) maintenance of the ordered domain organization in steady-state cell PMs: modulation of the cytoskeleton or the cell wall integrity of tobacco BY-2 cells; and formation of giant vesicles using either a lipid mixture of tobacco BY-2 cell PMs or the original lipid and protein combinations of the tobacco BY-2 cell PM. Whilst inhibiting phosphorylation or disrupting either the cytoskeleton or the cell wall had no observable effects, we found that lipids and proteins significantly modified both the abundance and spatial distribution of ordered domains. This indicates the involvement of intrinsic membrane components in the local physical state of the plant PM. Our findings support a major role for the 'lipid raft' model, defined as the sterol-dependent ordered assemblies of specific lipids and proteins in plant PM organization.

Correlational effect size benchmarks.

PubMed

Bosco, Frank A; Aguinis, Herman; Singh, Kulraj; Field, James G; Pierce, Charles A

2015-03-01

Effect size information is essential for the scientific enterprise and plays an increasingly central role in the scientific process. We extracted 147,328 correlations and developed a hierarchical taxonomy of variables reported in Journal of Applied Psychology and Personnel Psychology from 1980 to 2010 to produce empirical effect size benchmarks at the omnibus level, for 20 common research domains, and for an even finer grained level of generality. Results indicate that the usual interpretation and classification of effect sizes as small, medium, and large bear almost no resemblance to findings in the field, because distributions of effect sizes exhibit tertile partitions at values approximately one-half to one-third those intuited by Cohen (1988). Our results offer information that can be used for research planning and design purposes, such as producing better informed non-nil hypotheses and estimating statistical power and planning sample size accordingly. We also offer information useful for understanding the relative importance of the effect sizes found in a particular study in relationship to others and which research domains have advanced more or less, given that larger effect sizes indicate a better understanding of a phenomenon. Also, our study offers information about research domains for which the investigation of moderating effects may be more fruitful and provide information that is likely to facilitate the implementation of Bayesian analysis. Finally, our study offers information that practitioners can use to evaluate the relative effectiveness of various types of interventions. PsycINFO Database Record (c) 2015 APA, all rights reserved.

Library of electrocatalytic sites in nano-structured domains: electrocatalysis of hydrogen peroxide.

PubMed

Pandey, Prem C; Singh, Bhupendra

2008-12-01

Electrochemical detection of hydrogen peroxide at eight types of ormosil-modified electrodes, referred as hexacyanoferrate-system; Prussian blue systems (PB-1, PB-2, and PB-3), palladium (Pd-) system, graphite (Gr-) system, gold nanoparticle (AuNPs) system and palladium-gold nanoparticle (Pd-AuNPs) system were studied. The results on electrochemical detection suggested that hydrogen peroxide does not undergo homogeneous electrochemical mediation; however, the presence of redox mediator within nano-structured domains facilitates the electro-analysis of the same via redox electrocatalysis. Four approaches causing manipulation in nano-structured domains are described: (a) increase in the molecular size of the components generating nano-structured domains; (b) modulation via chemical reactivity; (c) modulation by non-reactive moieties and known nanoparticles; and (d) modulation by mixed approaches (a-c), all leading to decrease in a nano-structured domains. The results demonstrated that an increase in the size of nano-structured domains or decrease in micro-porous geometry increases the efficiency of electrocatalysis. The basic reaction protocol adopted in generating nano-structured domains, followed by manipulation protocols, supported the introduction of a library for creating electrocatalytic sites with varying electrocatalytic efficiency within the same basic nano-structured platform.

Computational study of scattering of a zero-order Bessel beam by large nonspherical homogeneous particles with the multilevel fast multipole algorithm

NASA Astrophysics Data System (ADS)

Yang, Minglin; Wu, Yueqian; Sheng, Xinqing; Ren, Kuan Fang

2017-12-01

Computation of scattering of shaped beams by large nonspherical particles is a challenge in both optics and electromagnetics domains since it concerns many research fields. In this paper, we report our new progress in the numerical computation of the scattering diagrams. Our algorithm permits to calculate the scattering of a particle of size as large as 110 wavelengths or 700 in size parameter. The particle can be transparent or absorbing of arbitrary shape, smooth or with a sharp surface, such as the Chebyshev particles or ice crystals. To illustrate the capacity of the algorithm, a zero order Bessel beam is taken as the incident beam, and the scattering of ellipsoidal particles and Chebyshev particles are taken as examples. Some special phenomena have been revealed and examined. The scattering problem is formulated with the combined tangential formulation and solved iteratively with the aid of the multilevel fast multipole algorithm, which is well parallelized with the message passing interface on the distributed memory computer platform using the hybrid partitioning strategy. The numerical predictions are compared with the results of the rigorous method for a spherical particle to validate the accuracy of the approach. The scattering diagrams of large ellipsoidal particles with various parameters are examined. The effect of aspect ratios, as well as half-cone angle of the incident zero-order Bessel beam and the off-axis distance on scattered intensity, is studied. Scattering by asymmetry Chebyshev particle with size parameter larger than 700 is also given to show the capability of the method for computing scattering by arbitrary shaped particles.

Aperiodic topological order in the domain configurations of functional materials

NASA Astrophysics Data System (ADS)

Huang, Fei-Ting; Cheong, Sang-Wook

2017-03-01

In numerous functional materials, such as steels, ferroelectrics and magnets, new functionalities can be achieved through the engineering of the domain structures, which are associated with the ordering of certain parameters within the material. The recent progress in technologies that enable imaging at atomic-scale spatial resolution has transformed our understanding of domain topology, revealing that, along with simple stripe-like or irregularly shaped domains, intriguing vortex-type topological domain configurations also exist. In this Review, we present a new classification scheme of 'Zm Zn domains with Zl vortices' for 2D macroscopic domain structures with m directional variants and n translational antiphases. This classification, together with the concepts of topological protection and topological charge conservation, can be applied to a wide range of materials, such as multiferroics, improper ferroelectrics, layered transition metal dichalcogenides and magnetic superconductors, as we discuss using selected examples. The resulting topological considerations provide a new basis for the understanding of the formation, kinetics, manipulation and property optimization of domains and domain boundaries in functional materials.

Symmetry based assembly of a 2 dimensional protein lattice

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

Poulos, Sandra; Agah, Sayeh; Jallah, Nikardi

2017-04-18

The design of proteins that self-assemble into higher order architectures is of great interest due to their potential application in nanotechnology. Specifically, the self-assembly of proteins into ordered lattices is of special interest to the field of structural biology. Here we designed a 2 dimensional (2D) protein lattice using a fusion of a tandem repeat of three TelSAM domains (TTT) to the Ferric uptake regulator (FUR) domain. We determined the structure of the designed (TTT-FUR) fusion protein to 2.3 Å by X-ray crystallographic methods. In agreement with the design, a 2D lattice composed of TelSAM fibers interdigitated by the FURmore » domain was observed. As expected, the fusion of a tandem repeat of three TelSAM domains formed 21 screw axis, and the self-assembly of the ordered oligomer was under pH control. We demonstrated that the fusion of TTT to a domain having a 2-fold symmetry, such as the FUR domain, can produce an ordered 2D lattice. The TTT-FUR system combines features from the rotational symmetry matching approach with the oligomer driven crystallization method. This TTT-FUR fusion was amenable to X-ray crystallographic methods, and is a promising crystallization chaperone.« less

Dynamical Downscaling of Typhoon Vera (1959) and related Storm Surge based on JRA-55 Reanalysis

NASA Astrophysics Data System (ADS)

Ninomiya, J.; Takemi, T.; Mori, N.; Shibutani, Y.; Kim, S.

2015-12-01

Typhoon Vera in 1959 is historical extreme typhoon that caused severest typhoon damage mainly due to the storm surge up to 389 cm in Japan. Vera developed 895 hPa on offshore and landed with 929.2 hPa. There are many studies of the dynamical downscaling of Vera but it is difficult to simulate accurately because of the lack of the accuracy of global reanalysis data. This study carried out dynamical downscaling experiment of Vera using WRF downscaling forced by JRA-55 that are latest atmospheric model and reanalysis data. In this study, the reproducibility of five global reanalysis data for Typhoon Vera were compered. Comparison shows that reanalysis data doesn't have strong typhoon information except for JRA-55, so that downscaling with conventional reanalysis data goes wrong. The dynamical downscaling method for storm surge is studied very much (e.g. choice of physical model, nudging, 4D-VAR, bogus and so on). In this study, domain size and resolution of the coarse domain were considered. The coarse domain size influences the typhoon route and central pressure, and larger domain restrains the typhoon strength. The results of simulations with different domain size show that the threshold of developing restrain is whether the coarse domain fully includes the area of wind speed more than 15 m/s around the typhoon. The results of simulations with different resolution show that the resolution doesn't affect the typhoon route, and higher resolution gives stronger typhoon simulation.

Problematic Peer Functioning in Girls with ADHD: A Systematic Literature Review.

PubMed

Kok, Francien M; Groen, Yvonne; Fuermaier, Anselm B M; Tucha, Oliver

2016-01-01

Children with attention deficit hyperactivity disorder (ADHD) experience many peer interaction problems and are at risk of peer rejection and victimisation. Although many studies have investigated problematic peer functioning in children with ADHD, this research has predominantly focused on boys and studies investigating girls are scant. Those studies that did examine girls, often used a male comparison sample, disregarding the inherent gender differences between girls and boys. Previous studies have highlighted this limitation and recommended the need for comparisons between ADHD females and typical females, in order to elucidate the picture of female ADHD with regards to problematic peer functioning. The aim of this literature review was to gain insight into peer functioning difficulties in school-aged girls with ADHD. PsychINFO, PubMed, and Web of Knowledge were searched for relevant literature comparing school-aged girls with ADHD to typically developing girls (TDs) in relation to peer functioning. The peer relationship domains were grouped into 'friendship', 'peer status', 'social skills/competence', and 'peer victimisation and bullying'. In total, thirteen studies were included in the review. All of the thirteen studies included reported that girls with ADHD, compared to TD girls, demonstrated increased difficulties in the domains of friendship, peer interaction, social skills and functioning, peer victimization and externalising behaviour. Studies consistently showed small to medium effects for lower rates of friendship participation and stability in girls with ADHD relative to TD girls. Higher levels of peer rejection with small to large effect sizes were reported in all studies, which were predicted by girls' conduct problems. Peer rejection in turn predicted poor social adjustment and a host of problem behaviours. Very high levels of peer victimisation were present in girls with ADHD with large effect sizes. Further, very high levels of social impairment and social skills deficits, with large effect sizes, were found across all studies. Levels of pro-social behaviour varied across studies, but were mostly lower in girls with ADHD, with small to large effect sizes. Overall, social disability was significantly higher among girls with ADHD than among TD girls. Congruous evidence was found for peer functioning difficulties in the peer relationship domains of friendship, peer status, social skills/competence, and peer victimisation and bullying in girls with ADHD.

Problematic Peer Functioning in Girls with ADHD: A Systematic Literature Review

PubMed Central

Groen, Yvonne; Fuermaier, Anselm B. M.; Tucha, Oliver

2016-01-01

Objective Children with attention deficit hyperactivity disorder (ADHD) experience many peer interaction problems and are at risk of peer rejection and victimisation. Although many studies have investigated problematic peer functioning in children with ADHD, this research has predominantly focused on boys and studies investigating girls are scant. Those studies that did examine girls, often used a male comparison sample, disregarding the inherent gender differences between girls and boys. Previous studies have highlighted this limitation and recommended the need for comparisons between ADHD females and typical females, in order to elucidate the picture of female ADHD with regards to problematic peer functioning. The aim of this literature review was to gain insight into peer functioning difficulties in school-aged girls with ADHD. Methods PsychINFO, PubMed, and Web of Knowledge were searched for relevant literature comparing school-aged girls with ADHD to typically developing girls (TDs) in relation to peer functioning. The peer relationship domains were grouped into ‘friendship’, ‘peer status’, ‘social skills/competence’, and ‘peer victimisation and bullying’. In total, thirteen studies were included in the review. Results All of the thirteen studies included reported that girls with ADHD, compared to TD girls, demonstrated increased difficulties in the domains of friendship, peer interaction, social skills and functioning, peer victimization and externalising behaviour. Studies consistently showed small to medium effects for lower rates of friendship participation and stability in girls with ADHD relative to TD girls. Higher levels of peer rejection with small to large effect sizes were reported in all studies, which were predicted by girls’ conduct problems. Peer rejection in turn predicted poor social adjustment and a host of problem behaviours. Very high levels of peer victimisation were present in girls with ADHD with large effect sizes. Further, very high levels of social impairment and social skills deficits, with large effect sizes, were found across all studies. Levels of pro-social behaviour varied across studies, but were mostly lower in girls with ADHD, with small to large effect sizes. Overall, social disability was significantly higher among girls with ADHD than among TD girls. Conclusion Congruous evidence was found for peer functioning difficulties in the peer relationship domains of friendship, peer status, social skills/competence, and peer victimisation and bullying in girls with ADHD. PMID:27870862

Frequency and time-domain inspiral templates for comparable mass compact binaries in eccentric orbits

NASA Astrophysics Data System (ADS)

Tanay, Sashwat; Haney, Maria; Gopakumar, Achamveedu

2016-03-01

Inspiraling compact binaries with non-negligible orbital eccentricities are plausible gravitational wave (GW) sources for the upcoming network of GW observatories. In this paper, we present two prescriptions to compute post-Newtonian (PN) accurate inspiral templates for such binaries. First, we adapt and extend the postcircular scheme of Yunes et al. [Phys. Rev. D 80, 084001 (2009)] to obtain a Fourier-domain inspiral approximant that incorporates the effects of PN-accurate orbital eccentricity evolution. This results in a fully analytic frequency-domain inspiral waveform with Newtonian amplitude and 2PN-order Fourier phase while incorporating eccentricity effects up to sixth order at each PN order. The importance of incorporating eccentricity evolution contributions to the Fourier phase in a PN-consistent manner is also demonstrated. Second, we present an accurate and efficient prescription to incorporate orbital eccentricity into the quasicircular time-domain TaylorT4 approximant at 2PN order. New features include the use of rational functions in orbital eccentricity to implement the 1.5PN-order tail contributions to the far-zone fluxes. This leads to closed form PN-accurate differential equations for evolving eccentric orbits, and the resulting time-domain approximant is accurate and efficient to handle initial orbital eccentricities ≤0.9 . Preliminary GW data analysis implications are probed using match estimates.

Monte Carlo simulation of ferroelectric domain growth

NASA Astrophysics Data System (ADS)

Li, B. L.; Liu, X. P.; Fang, F.; Zhu, J. L.; Liu, J.-M.

2006-01-01

The kinetics of two-dimensional isothermal domain growth in a quenched ferroelectric system is investigated using Monte Carlo simulation based on a realistic Ginzburg-Landau ferroelectric model with cubic-tetragonal (square-rectangle) phase transitions. The evolution of the domain pattern and domain size with annealing time is simulated, and the stability of trijunctions and tetrajunctions of domain walls is analyzed. It is found that in this much realistic model with strong dipole alignment anisotropy and long-range Coulomb interaction, the powerlaw for normal domain growth still stands applicable. Towards the late stage of domain growth, both the average domain area and reciprocal density of domain wall junctions increase linearly with time, and the one-parameter dynamic scaling of the domain growth is demonstrated.

Predicting detection performance with model observers: Fourier domain or spatial domain?

PubMed

Chen, Baiyu; Yu, Lifeng; Leng, Shuai; Kofler, James; Favazza, Christopher; Vrieze, Thomas; McCollough, Cynthia

2016-02-27

The use of Fourier domain model observer is challenged by iterative reconstruction (IR), because IR algorithms are nonlinear and IR images have noise texture different from that of FBP. A modified Fourier domain model observer, which incorporates nonlinear noise and resolution properties, has been proposed for IR and needs to be validated with human detection performance. On the other hand, the spatial domain model observer is theoretically applicable to IR, but more computationally intensive than the Fourier domain method. The purpose of this study is to compare the modified Fourier domain model observer to the spatial domain model observer with both FBP and IR images, using human detection performance as the gold standard. A phantom with inserts of various low contrast levels and sizes was repeatedly scanned 100 times on a third-generation, dual-source CT scanner at 5 dose levels and reconstructed using FBP and IR algorithms. The human detection performance of the inserts was measured via a 2-alternative-forced-choice (2AFC) test. In addition, two model observer performances were calculated, including a Fourier domain non-prewhitening model observer and a spatial domain channelized Hotelling observer. The performance of these two mode observers was compared in terms of how well they correlated with human observer performance. Our results demonstrated that the spatial domain model observer correlated well with human observers across various dose levels, object contrast levels, and object sizes. The Fourier domain observer correlated well with human observers using FBP images, but overestimated the detection performance using IR images.

Predicting detection performance with model observers: Fourier domain or spatial domain?

PubMed Central

Chen, Baiyu; Yu, Lifeng; Leng, Shuai; Kofler, James; Favazza, Christopher; Vrieze, Thomas; McCollough, Cynthia

2016-01-01

The use of Fourier domain model observer is challenged by iterative reconstruction (IR), because IR algorithms are nonlinear and IR images have noise texture different from that of FBP. A modified Fourier domain model observer, which incorporates nonlinear noise and resolution properties, has been proposed for IR and needs to be validated with human detection performance. On the other hand, the spatial domain model observer is theoretically applicable to IR, but more computationally intensive than the Fourier domain method. The purpose of this study is to compare the modified Fourier domain model observer to the spatial domain model observer with both FBP and IR images, using human detection performance as the gold standard. A phantom with inserts of various low contrast levels and sizes was repeatedly scanned 100 times on a third-generation, dual-source CT scanner at 5 dose levels and reconstructed using FBP and IR algorithms. The human detection performance of the inserts was measured via a 2-alternative-forced-choice (2AFC) test. In addition, two model observer performances were calculated, including a Fourier domain non-prewhitening model observer and a spatial domain channelized Hotelling observer. The performance of these two mode observers was compared in terms of how well they correlated with human observer performance. Our results demonstrated that the spatial domain model observer correlated well with human observers across various dose levels, object contrast levels, and object sizes. The Fourier domain observer correlated well with human observers using FBP images, but overestimated the detection performance using IR images. PMID:27239086

Optimizing Sampling Efficiency for Biomass Estimation Across NEON Domains

NASA Astrophysics Data System (ADS)

Abercrombie, H. H.; Meier, C. L.; Spencer, J. J.

2013-12-01

Over the course of 30 years, the National Ecological Observatory Network (NEON) will measure plant biomass and productivity across the U.S. to enable an understanding of terrestrial carbon cycle responses to ecosystem change drivers. Over the next several years, prior to operational sampling at a site, NEON will complete construction and characterization phases during which a limited amount of sampling will be done at each site to inform sampling designs, and guide standardization of data collection across all sites. Sampling biomass in 60+ sites distributed among 20 different eco-climatic domains poses major logistical and budgetary challenges. Traditional biomass sampling methods such as clip harvesting and direct measurements of Leaf Area Index (LAI) involve collecting and processing plant samples, and are time and labor intensive. Possible alternatives include using indirect sampling methods for estimating LAI such as digital hemispherical photography (DHP) or using a LI-COR 2200 Plant Canopy Analyzer. These LAI estimations can then be used as a proxy for biomass. The biomass estimates calculated can then inform the clip harvest sampling design during NEON operations, optimizing both sample size and number so that standardized uncertainty limits can be achieved with a minimum amount of sampling effort. In 2011, LAI and clip harvest data were collected from co-located sampling points at the Central Plains Experimental Range located in northern Colorado, a short grass steppe ecosystem that is the NEON Domain 10 core site. LAI was measured with a LI-COR 2200 Plant Canopy Analyzer. The layout of the sampling design included four, 300 meter transects, with clip harvests plots spaced every 50m, and LAI sub-transects spaced every 10m. LAI was measured at four points along 6m sub-transects running perpendicular to the 300m transect. Clip harvest plots were co-located 4m from corresponding LAI transects, and had dimensions of 0.1m by 2m. We conducted regression analyses with LAI and clip harvest data to determine whether LAI can be used as a suitable proxy for aboveground standing biomass. We also compared optimal sample sizes derived from LAI data, and clip-harvest data from two different size clip harvest areas (0.1m by 1m vs. 0.1m by 2m). Sample sizes were calculated in order to estimate the mean to within a standardized level of uncertainty that will be used to guide sampling effort across all vegetation types (i.e. estimated within × 10% with 95% confidence). Finally, we employed a Semivariogram approach to determine optimal sample size and spacing.

Crystallization of micrometer-sized particles with molecular contours.

PubMed

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

2013-11-12

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

Size and Temperature Dependence of Electron Transfer between CdSe Quantum Dots and a TiO 2 Nanobelt

DOE PAGES

Tafen, De Nyago; Prezhdo, Oleg V.

2015-02-24

Understanding charge transfer reactions between quantum dots (QD) and metal oxides is fundamental for improving photocatalytic, photovoltaic and electronic devices. The complexity of these processes makes it difficult to find an optimum QD size with rapid charge injection and low recombination. We combine time-domain density functional theory with nonadiabatic molecular dynamics to investigate the size and temperature dependence of the experimentally studied electron transfer and charge recombination at CdSe QD-TiO 2 nanobelt (NB) interfaces. The electron injection rate shows strong dependence on the QD size, increasing for small QDs. The rate exhibits Arrhenius temperature dependence, with the activation energy ofmore » the order of millielectronvolts. The charge recombination process occurs due to coupling of the electronic subsystem to vibrational modes of the TiO 2 NB. Inelastic electron-phonon scattering happens on a picosecond time scale, with strong dependence on the QD size. Our simulations demonstrate that the electron-hole recombination rate decreases significantly as the QD size increases, in excellent agreement with experiments. The temperature dependence of the charge recombination rates can be successfully modeled within the framework of the Marcus theory through optimization of the electronic coupling and the reorganization energy. Our simulations indicate that by varying the QD size, one can modulate the photoinduced charge separation and charge recombination, fundamental aspects of the design principles for high efficiency devices.« less

Determination of magnetic domain state of carbon coated iron nanoparticles via 57Fe zero-external-field NMR

NASA Astrophysics Data System (ADS)

Manjunatha, M.; Kumar, Rajeev; Sahoo, Balaram; Damle, Ramakrishna; Ramesh, K. P.

2018-05-01

The magnetic domain state of carbon coated iron nanopowder (Fe@C) was studied by the internal field nuclear magnetic resonance (IFNMR) at 77 K using the spin echo technique. The structure and magnetic properties of the sample were further characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Mössbauer spectroscopy, vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA) and Raman Spectroscopy. The obtained IFNMR results of Fe@C powder were compared with that of micron sized carbonyl iron (CI) and electrolytic iron (EI) powders. The calculated critical size of the single domain iron particles in Fe@C is ∼ 16 nm. A higher enhancement in echo amplitude was observed due to better response of the domain walls of multidomain particles in comparison to the single domain particles. The echo signal of CI and EI particles exhibit a single narrow intense peak corresponding to the domain walls, whereas Fe@C exhibits two low amplitude peaks at two different frequencies: a low frequency (46.6 MHz) peak corresponds to the response of the domain walls of the multidomain particles and the other high frequency (47.2 MHz) signal (a shoulder) corresponding to the response of the magnetic nuclei inside the domain. Our results help in determining the domain state of iron-based magnetic particles using 57Fe-IFNMR.

Inverted electro-mechanical behaviour induced by the irreversible domain configuration transformation in (K,Na)NbO3-based ceramics

PubMed Central

Huan, Yu; Wang, Xiaohui; Koruza, Jurij; Wang, Ke; Webber, Kyle G.; Hao, Yanan; Li, Longtu

2016-01-01

Miniaturization of domains to the nanometer scale has been previously reported in many piezoelectrics with two-phase coexistence. Despite the observation of nanoscale domain configuration near the polymorphic phase transition (PPT) regionin virgin (K0.5Na0.5)NbO3 (KNN) based ceramics, it remains unclear how this domain state responds to external loads and influences the macroscopic electro-mechanical properties. To this end, the electric-field-induced and stress-induced strain curves of KNN-based ceramics over a wide compositional range across PPT were characterized. It was found that the coercive field of the virgin samples was highest in PPT region, which was related to the inhibited domain wall motion due to the presence of nanodomains. However, the coercive field was found to be the lowest in the PPT region after electrical poling. This was related to the irreversible transformation of the nanodomains into micron-sized domains during the poling process. With the similar micron-sized domain configuration for all poled ceramics, the domains in the PPT region move more easily due to the additional polarization vectors. The results demonstrate that the poling process can give rise to the irreversible domain configuration transformation and then account for the inverted macroscopic piezoelectricity in the PPT region of KNN-based ceramics. PMID:26915972

Cohesiveness tunes assembly and morphology of FG nucleoporin domain meshworks – Implications for nuclear pore permeability

PubMed Central

Eisele, Nico B.; Labokha, Aksana A.; Frey, Steffen; Görlich, Dirk; Richter, Ralf P.

2013-01-01

Nuclear pore complexes control the exchange of macromolecules between the cytoplasm and the nucleus. A selective permeability barrier that arises from a supramolecular assembly of intrinsically unfolded nucleoporin domains rich in phenylalanine-glycine dipeptides (FG domains) fills the nuclear pore. There is increasing evidence that selective transport requires cohesive FG domain interactions. To understand the functional roles of cohesive interactions, we studied monolayers of end-grafted FG domains as a bottom-up nanoscale model system of the permeability barrier. Based on detailed physicochemical analysis of the model films and comparison of the data with polymer theory, we propose that cohesiveness is tuned to promote rapid assembly of the permeability barrier and to generate a stable and compact pore-filling meshwork with a small mesh size. Our results highlight the functional importance of weak interactions, typically a few kBT per chain, and contribute important information to understand the mechanism of size-selective transport. PMID:24138862

Fast marching methods for the continuous traveling salesman problem.

PubMed

Andrews, June; Sethian, J A

2007-01-23

We consider a problem in which we are given a domain, a cost function which depends on position at each point in the domain, and a subset of points ("cities") in the domain. The goal is to determine the cheapest closed path that visits each city in the domain once. This can be thought of as a version of the traveling salesman problem, in which an underlying known metric determines the cost of moving through each point of the domain, but in which the actual shortest path between cities is unknown at the outset. We describe algorithms for both a heuristic and an optimal solution to this problem. The complexity of the heuristic algorithm is at worst case M.N log N, where M is the number of cities, and N the size of the computational mesh used to approximate the solutions to the shortest paths problems. The average runtime of the heuristic algorithm is linear in the number of cities and O(N log N) in the size N of the mesh.

Replication domains are self-interacting structural chromatin units of human chromosomes

NASA Astrophysics Data System (ADS)

Arneodo, Alain

2011-03-01

In higher eukaryotes, the absence of specific sequence motifs marking the origins of replication has been a serious hindrance to the understanding of the mechanisms that regulate the initiation and the maintenance of the replication program in different cell types. In silico analysis of nucleotide compositional skew has predicted the existence, in the germline, of replication N-domains bordered by putative replication origins and where the skew decreases rather linearly as the signature of a progressive inversion of the average fork polarity. Here, from the demonstration that the average fork polarity can be directly extracted from the derivative of replication timing profiles, we develop a wavelet-based pattern recognition methodology to delineate replication U-domains where the replication timing profile is shaped as a U and its derivative as a N. Replication U-domains are robustly found in seven cell lines as covering a significant portion (40-50%) of the human genome where the replication timing data actually displays some plasticity between cell lines. The early replication initiation zones at U-domains borders are found to be hypersensitive to DNase I cleavage, to be associated with transcriptional activity and to present a significant enrichment in insular-binding proteins CTCF, the hallmark of an open chromatin structure. A comparative analysis of genome-wide chromatin interaction (HiC) data shows that replication-U domains correspond to self-interacting structural high order chromatin units of megabase characteristic size. Taken together, these findings provide evidence that the epigenetic compartmentalization of the human genome into autonomous replication U-domains comes along with an extensive remodelling of the threedimensional chromosome architecture during development or in specific diseases. The observed cell specific conservation of the replication timing between the human and mouse genomes strongly suggests that this chromosome organization into self-interacting structural and functional units is a general feature of mammalian organisms.

Mapping cis-Regulatory Domains in the Human Genome UsingMulti-Species Conservation of Synteny

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

Ahituv, Nadav; Prabhakar, Shyam; Poulin, Francis

2005-06-13

Our inability to associate distant regulatory elements with the genes that they regulate has largely precluded their examination for sequence alterations contributing to human disease. One major obstacle is the large genomic space surrounding targeted genes in which such elements could potentially reside. In order to delineate gene regulatory boundaries we used whole-genome human-mouse-chicken (HMC) and human-mouse-frog (HMF) multiple alignments to compile conserved blocks of synteny (CBS), under the hypothesis that these blocks have been kept intact throughout evolution at least in part by the requirement of regulatory elements to stay linked to the genes that they regulate. A totalmore » of 2,116 and 1,942 CBS>200 kb were assembled for HMC and HMF respectively, encompassing 1.53 and 0.86 Gb of human sequence. To support the existence of complex long-range regulatory domains within these CBS we analyzed the prevalence and distribution of chromosomal aberrations leading to position effects (disruption of a genes regulatory environment), observing a clear bias not only for mapping onto CBS but also for longer CBS size. Our results provide a genome wide data set characterizing the regulatory domains of genes and the conserved regulatory elements within them.« less

Mesostructure of Ordered Corneal Nano-nipple Arrays: The Role of 5-7 Coordination Defects

NASA Astrophysics Data System (ADS)

Lee, Ken C.; Yu, Qi; Erb, Uwe

2016-06-01

Corneal nano-nipple structures consisting of hexagonally arranged protrusions with diameters around 200 nm have long been known for their antireflection capability and have served as biological blueprint for solar cell, optical lens and other surface designs. However, little is known about the global arrangement of these nipples on the ommatidial surface and their growth during the eye development. This study provides new insights based on the analysis of nano-nipple arrangements on the mesoscale across entire ommatidia, which has never been done before. The most important feature in the nipple structures are topological 5- and 7-fold coordination defects, which align to form dislocations and interconnected networks of grain boundaries that divide the ommatidia into crystalline domains in different orientations. Furthermore, the domain size distribution might be log-normal, and the domains demonstrate no preference in crystal orientation. Both observations suggest that the nipple growth process may be similar to the nucleation and growth mechanisms during the formation of other crystal structures. Our results are also consistent with the most recently proposed Turing-type reaction-diffusion process. In fact, we were able to produce the key structural characteristics of the nipple arrangements using Turing analysis from the nucleation to the final structure development.

Does neuropsychological performance in OCD relate to different symptoms? A meta-analysis comparing the symmetry and obsessing dimensions.

PubMed

Bragdon, Laura B; Gibb, Brandon E; Coles, Meredith E

2018-06-19

Investigations of neuropsychological functioning in obsessive-compulsive disorder (OCD) have produced mixed results for deficits in executive functioning (EF), attention, and memory. One potential explanation for varied findings may relate to the heterogeneity of symptom presentations, and different clinical or neurobiological characteristics may underlie these different symptoms. We investigated differences in neuropsychological functioning between two symptoms groups, obsessing/checking (O/C) and symmetry/ordering (S/O), based on data suggesting an association with different motivations: harm avoidance and incompleteness, respectively. Ten studies (with 628 patients) were included and each investigation assessed at least one of 14 neuropsychological domains. The S/O domain demonstrated small, negative correlations with overall neuropsychological functioning, performance in EF, memory, visuospatial ability, cognitive flexibility, and verbal working memory. O/C symptoms demonstrated small, negative correlations with memory and verbal memory performance. A comparison of functioning between symptom groups identified large effect sizes showing that the S/O dimension was more strongly related to poorer neuropsychological performance overall, and in the domains of attention, visuospatial ability, and the subdomain of verbal working memory. Findings support existing evidence suggesting that different OCD symptoms, and their associated core motivations, relate to unique patterns of neuropsychological functioning, and, potentially dysfunction in different neural circuits. © 2018 Wiley Periodicals, Inc.

Spatiotemporal Domain Decomposition for Massive Parallel Computation of Space-Time Kernel Density

NASA Astrophysics Data System (ADS)

Hohl, A.; Delmelle, E. M.; Tang, W.

2015-07-01

Accelerated processing capabilities are deemed critical when conducting analysis on spatiotemporal datasets of increasing size, diversity and availability. High-performance parallel computing offers the capacity to solve computationally demanding problems in a limited timeframe, but likewise poses the challenge of preventing processing inefficiency due to workload imbalance between computing resources. Therefore, when designing new algorithms capable of implementing parallel strategies, careful spatiotemporal domain decomposition is necessary to account for heterogeneity in the data. In this study, we perform octtree-based adaptive decomposition of the spatiotemporal domain for parallel computation of space-time kernel density. In order to avoid edge effects near subdomain boundaries, we establish spatiotemporal buffers to include adjacent data-points that are within the spatial and temporal kernel bandwidths. Then, we quantify computational intensity of each subdomain to balance workloads among processors. We illustrate the benefits of our methodology using a space-time epidemiological dataset of Dengue fever, an infectious vector-borne disease that poses a severe threat to communities in tropical climates. Our parallel implementation of kernel density reaches substantial speedup compared to sequential processing, and achieves high levels of workload balance among processors due to great accuracy in quantifying computational intensity. Our approach is portable of other space-time analytical tests.

Stabilization, Characterization, and Selective Removal of Cystatin C Amyloid Oligomers*

PubMed Central

Östner, Gustav; Lindström, Veronica; Hjort Christensen, Per; Kozak, Maciej; Abrahamson, Magnus; Grubb, Anders

2013-01-01

The pathophysiological process in amyloid disorders usually involves the transformation of a functional monomeric protein via potentially toxic oligomers into amyloid fibrils. The structure and properties of the intermediary oligomers have been difficult to study due to their instability and dynamic equilibrium with smaller and larger species. In hereditary cystatin C amyloid angiopathy, a cystatin C variant is deposited in arterial walls and cause brain hemorrhage in young adults. In the present investigation, we use redox experiments of monomeric cystatin C, stabilized against domain swapping by an intramolecular disulfide bond, to generate stable oligomers (dimers, trimers, tetramers, decamers, and high molecular weight oligomers). These oligomers were characterized concerning size by gel filtration, polyacrylamide gel electrophoresis, and mass spectrometry, shape by electron and atomic force microscopy, and, function by assays of their capacity to inhibit proteases. The results showed the oligomers to be highly ordered, domain-swapped assemblies of cystatin C and that the oligomers could not build larger oligomers, or fibrils, without domain swapping. The stabilized oligomers were used to induce antibody formation in rabbits. After immunosorption, using immobilized monomeric cystatin C, and elution from columns with immobilized cystatin C oligomers, oligomer-specific antibodies were obtained. These could be used to selectively remove cystatin C dimers from biological fluids containing both dimers and monomers. PMID:23629649

Development of the morphology during functional stack build-up of P3HT:PCBM bulk heterojunction solar cells with inverted geometry.

PubMed

Wang, Weijia; Pröller, Stephan; Niedermeier, Martin A; Körstgens, Volker; Philipp, Martine; Su, Bo; Moseguí González, Daniel; Yu, Shun; Roth, Stephan V; Müller-Buschbaum, Peter

2015-01-14

Highly efficient poly(3-hexylthiophene-2,5-diyl) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction solar cells are achieved by using an inverted geometry. The development of the morphology is investigated as a function of the multilayer stack assembling during the inverted solar cell preparation. Atomic force microscopy is used to reveal the surface morphology of each stack, and the inner structure is probed with grazing incidence small-angle X-ray scattering. It is found that the smallest domain size of P3HT is introduced by replicating the fluorine-doped tin oxide structure underneath. The structure sizes of the P3HT:PCBM active layer are further optimized after thermal annealing. Compared to devices with standard geometry, the P3HT:PCBM layer in the inverted solar cells shows smaller domain sizes, which are much closer to the exciton diffusion length in the polymer. The decrease in domain sizes is identified as the main reason for the improvement of the device performance.

Coarsening of protein clusters on subcellular drops exhibits strong and sudden size selectivity

NASA Astrophysics Data System (ADS)

Brown, Aidan; Rutenberg, Andrew

2015-03-01

Autophagy is an important process for the degradation of cellular components, with receptor proteins targeting substrates to downstream autophagy machinery. An important question is how receptor protein interactions lead to their selective accumulation on autophagy substrates. Receptor proteins have recently been observed in clusters, raising the possibility that clustering could affect autophagy selectivity. We investigate the clustering dynamics of the autophagy receptor protein NBR1. In addition to standard receptor protein domains, NBR1 has a ``J'' domain that anchors it to membranes, and a coiled-coil domain that enhances self-interaction. We model coarsening clusters of NBR1 on the surfaces of a polydisperse collection of drops, representing organelles. Despite the disconnected nature of the drop surfaces, we recover dynamical scaling of cluster sizes. Significantly, we find that at a well-defined time after coarsening begins, clusters evaporate from smaller drops and grow on larger drops. Thus, coarsening-driven size selection will localize protein clusters to larger substrates, leaving smaller substrates without clusters. This provides a possible physical mechanism for autophagy selectivity, and can explain reports of size selection during peroxisome degradation.

Current-controlled unidirectional edge-meron motion

NASA Astrophysics Data System (ADS)

Xing, Xiangjun; Pong, Philip W. T.; Zhou, Yan

2016-11-01

In order to address many of the challenges and bottlenecks currently experienced by traditional charge-based technologies, various alternatives are being actively explored to provide potential solutions of device miniaturization and scaling in the post-Moore's-law era. Amongst these alternatives, spintronic physics and devices have recently attracted rapidly increasing interest by exploiting the additional degree of electrons-spin. For example, magnetic domain-wall racetrack-memory and logic devices have been realized via manipulating domain-wall motion. As compared to domain-wall-based devices, magnetic skyrmions have the advantages of ultrasmall size (typically 5-100 nm in diameter), facile current-driven motion, topological stability, and peculiar emergent electrodynamics, promising for next-generation electronics applications in the post-Moore's-law regime. Here, a magnetic meron device, which behaves similarly to a PN-junction diode, is demonstrated for the first time, by tailoring the current-controlled unidirectional motion of edge-merons (i.e., fractional skyrmions) in a nanotrack with interfacial Dzyaloshinskii-Moriya interaction. The working principles of the meron device, theoretically predicted from the Thiele equation for topological magnetic objects, are further verified using micromagnetic simulations. The present study has revealed the topology-independent transport property of different magnetic objects and is expected to open the vista toward integrated composite circuitry (with unified data storage and processing) based on a single magnetic chip, as the meron device can be used, either as a building block to develop complex logic components or as a signal controller to interconnect skyrmion, domain-wall, and even spin-wave devices.

Frequency-domain optical tomographic image reconstruction algorithm with the simplified spherical harmonics (SP3) light propagation model.

PubMed

Kim, Hyun Keol; Montejo, Ludguier D; Jia, Jingfei; Hielscher, Andreas H

2017-06-01

We introduce here the finite volume formulation of the frequency-domain simplified spherical harmonics model with n -th order absorption coefficients (FD-SP N ) that approximates the frequency-domain equation of radiative transfer (FD-ERT). We then present the FD-SP N based reconstruction algorithm that recovers absorption and scattering coefficients in biological tissue. The FD-SP N model with 3 rd order absorption coefficient (i.e., FD-SP 3 ) is used as a forward model to solve the inverse problem. The FD-SP 3 is discretized with a node-centered finite volume scheme and solved with a restarted generalized minimum residual (GMRES) algorithm. The absorption and scattering coefficients are retrieved using a limited-memory Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm. Finally, the forward and inverse algorithms are evaluated using numerical phantoms with optical properties and size that mimic small-volume tissue such as finger joints and small animals. The forward results show that the FD-SP 3 model approximates the FD-ERT (S 12 ) solution within relatively high accuracy; the average error in the phase (<3.7%) and the amplitude (<7.1%) of the partial current at the boundary are reported. From the inverse results we find that the absorption and scattering coefficient maps are more accurately reconstructed with the SP 3 model than those with the SP 1 model. Therefore, this work shows that the FD-SP 3 is an efficient model for optical tomographic imaging of small-volume media with non-diffuse properties both in terms of computational time and accuracy as it requires significantly lower CPU time than the FD-ERT (S 12 ) and also it is more accurate than the FD-SP 1 .

The organization of domains in proteins obeys Menzerath-Altmann's law of language.

PubMed

Shahzad, Khuram; Mittenthal, Jay E; Caetano-Anollés, Gustavo

2015-08-11

The combination of domains in multidomain proteins enhances their function and structure but lengthens the molecules and increases their cost at cellular level. The dependence of domain length on the number of domains a protein holds was surveyed for a set of 60 proteomes representing free-living organisms from all kingdoms of life. Distributions were fitted using non-linear functions and fitted parameters interpreted with a formulation of decreasing returns. We find that domain length decreases with increasing number of domains in proteins, following the Menzerath-Altmann (MA) law of language. Highly significant negative correlations exist for the set of proteomes examined. Mathematically, the MA law expresses as a power law relationship that unfolds when molecular persistence P is a function of domain accretion. P holds two terms, one reflecting the matter-energy cost of adding domains and extending their length, the other reflecting how domain length and number impinges on information and biophysics. The pattern of diminishing returns can therefore be explained as a frustrated interplay between the strategies of economy, flexibility and robustness, matching previously observed trade-offs in the domain makeup of proteomes. Proteomes of Archaea, Fungi and to a lesser degree Plants show the largest push towards molecular economy, each at their own economic stratum. Fungi increase domain size in single domain proteins while reinforcing the pattern of diminishing returns. In contrast, Metazoa, and to lesser degrees Protista and Bacteria, relax economy. Metazoa achieves maximum flexibility and robustness by harboring compact molecules and complex domain organization, offering a new functional vocabulary for molecular biology. The tendency of parts to decrease their size when systems enlarge is universal for language and music, and now for parts of macromolecules, extending the MA law to natural systems.

General practitioner views on the determinants of test ordering: a theory-based qualitative approach to the development of an intervention to improve immunoglobulin requests in primary care.

PubMed

Cadogan, S L; McHugh, S M; Bradley, C P; Browne, J P; Cahill, M R

2016-07-19

Research suggests that variation in laboratory requesting patterns may indicate unnecessary test use. Requesting patterns for serum immunoglobulins vary significantly between general practitioners (GPs). This study aims to explore GP's views on testing to identify the determinants of behaviour and recommend feasible intervention strategies for improving immunoglobulin test use in primary care. Qualitative semi-structured interviews were conducted with GPs requesting laboratory tests at Cork University Hospital or University Hospital Kerry in the South of Ireland. GPs were identified using a Health Service Executive laboratory list of GPs in the Cork-Kerry region. A random sample of GPs (stratified by GP requesting patterns) was generated from this list. GPs were purposively sampled based on the criteria of location (urban/rural); length of time qualified; and practice size (single-handed/group). Interviews were carried out between December 2014 and February 2015. Interviews were transcribed verbatim using NVivo 10 software and analysed using the framework analysis method. Emerging themes were mapped to the theoretical domains framework (TDF), which outlines 12 domains that can enable or inhibit behaviour change. The behaviour change wheel and behaviour change technique (BCT) taxonomy were then used to identify potential intervention strategies. Sixteen GPs were interviewed (ten males and six females). Findings suggest that intervention strategies should specifically target the key barriers to effective test ordering, while considering the context of primary care practice. Seven domains from the TDF were perceived to influence immunoglobulin test ordering behaviours and were identified as 'mechanisms for change' (knowledge, environmental context and resources, social/professional role and identity, beliefs about capabilities, beliefs about consequences, memory, attention and decision-making processes and behavioural regulation). Using these TDF domains, seven BCTs emerged as feasible 'intervention content' for targeting GPs' ordering behaviour. These included instructions on how to effectively request the test (how to perform behaviour), information on GPs' use of the test (feedback on behaviour), information about patient consequences resulting from not doing the test (information about health consequences), laboratory/consultant-based advice/education (credible source), altering the test ordering form (restructuring the physical environment), providing guidelines (prompts/cues) and adding interpretive comments to the results (adding objects to the environment). These BCTs aligned to four intervention functions: education, persuasion, environmental restructuring and enablement. This study has effectively applied behaviour change theory to identify feasible strategies for improving immunoglobulin test use in primary care using the TDF, 'behaviour change wheel' and BCT taxonomy. The identified BCTs will form the basis of a theory-based intervention to improve the use of immunoglobulin tests among GPs. Future research will involve the development and evaluation of this intervention.

Nanoscale organization of {beta}{sub 2}-adrenergic receptor-Venus fusion protein domains on the surface of mammalian cells

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

Vobornik, Dusan; Rouleau, Yanouchka; Haley, Jennifer

2009-04-24

Adrenergic receptors are a key component of nanoscale multiprotein complexes that are responsible for controlling the beat rate in a mammalian heart. We demonstrate the ability of near-field scanning optical microscopy (NSOM) to visualize {beta}{sub 2}-adrenergic receptors ({beta}{sub 2}AR) fused to the GFP analogue Venus at the nanoscale on HEK293 cells. The expression of the {beta}{sub 2}AR-Venus fusion protein was tightly controlled using a tetracycline-induced promoter. Both the size and density of the observed nanoscale domains are dependent on the level of induction and thus the level of protein expression. At concentrations between 100 and 700 ng/ml of inducer doxycycline,more » the size of domains containing the {beta}{sub 2}AR-Venus fusion protein appears to remain roughly constant, but the number of domains per cell increase. At 700 ng/ml doxycycline the functional receptors are organized into domains with an average diameter of 150 nm with a density similar to that observed for the native protein on primary murine cells. By contrast, larger micron-sized domains of {beta}{sub 2}AR are observed in the membrane of the HEK293 cells that stably overexpress {beta}{sub 2}AR-GFP and {beta}{sub 2}AR-eYFP. We conclude that precise chemical control of gene expression is highly advantageous for the use {beta}{sub 2}AR-Venus fusion proteins as models for {beta}{sub 2}AR function. These observations are critical for designing future cell models and assays based on {beta}{sub 2}AR, since the receptor biology is consistent with a relatively low density of nanoscale receptor domains.« less

A hybrid algorithm for parallel molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Mangiardi, Chris M.; Meyer, R.

2017-10-01

This article describes algorithms for the hybrid parallelization and SIMD vectorization of molecular dynamics simulations with short-range forces. The parallelization method combines domain decomposition with a thread-based parallelization approach. The goal of the work is to enable efficient simulations of very large (tens of millions of atoms) and inhomogeneous systems on many-core processors with hundreds or thousands of cores and SIMD units with large vector sizes. In order to test the efficiency of the method, simulations of a variety of configurations with up to 74 million atoms have been performed. Results are shown that were obtained on multi-core systems with Sandy Bridge and Haswell processors as well as systems with Xeon Phi many-core processors.

Mesostructured Block Copolymer Nanoparticles: Versatile Templates for Hybrid Inorganic/Organic Nanostructures

PubMed Central

Connal, Luke A.; Lynd, Nathaniel A.; Robb, Maxwell J.; See, Kimberly A.; Jang, Se Gyu; Spruell, Jason M.

2012-01-01

We present a versatile strategy to prepare a range of nanostructured poly(styrene)-block-poly(2-vinyl pyridine) copolymer particles with tunable interior morphology and controlled size by a simple solvent exchange procedure. A key feature of this strategy is the use of functional block copolymers incorporating reactive pyridyl moieties which allow the absorption of metal salts and other inorganic precursors to be directed. Upon reduction of the metal salts, well-defined hybrid metal nanoparticle arrays could be prepared, while the use of oxide precursors followed by calcination permits the synthesis of silica and titania particles. In both cases, ordered morphologies templated by the original block copolymer domains were obtained. PMID:23335837

Asymptotic boundary conditions for dissipative waves: General theory

NASA Technical Reports Server (NTRS)

Hagstrom, Thomas

1990-01-01

An outstanding issue in the computational analysis of time dependent problems is the imposition of appropriate radiation boundary conditions at artificial boundaries. Accurate conditions are developed which are based on the asymptotic analysis of wave propagation over long ranges. Employing the method of steepest descents, dominant wave groups are identified and simple approximations to the dispersion relation are considered in order to derive local boundary operators. The existence of a small number of dominant wave groups may be expected for systems with dissipation. Estimates of the error as a function of domain size are derived under general hypotheses, leading to convergence results. Some practical aspects of the numerical construction of the asymptotic boundary operators are also discussed.

Hysteresis heating based induction bonding of composite materials

NASA Astrophysics Data System (ADS)

Suwanwatana, Witchuda

The viability of using magnetic particulate susceptor materials for induction heating during bonding of polymer matrix composites is well established in this work. The unique ability to offer localized heating, geometric flexibility, and self-controlled temperature is the major advantage of this technique. Hysteresis heating is tailored through careful design of the microstructure of nickel particulate polymer films (Ni/PSU). An excellent heating rate can be attained in the frequency range of 1 to 10 MHz for particle volume fraction below percolation of 0.26. The diameter of nickel particle should be kept between 65 nm to 10 mum to ensure multi-domain heating, Curie temperature control, negligible shielding effect, minimum eddy current, and slight particle oxidation. The hysteresis heating behavior of the Ni/PSU films is found to be volumetric in nature and proportional to the cube of applied magnetic field. On the other hand, heat generation is inversely proportional to the size of the multi-domain particles. The frequency effect; however, provide maximum heat generation at the domain wall resonance frequency. Curie temperature control is observed when sufficiently high magnetic fields (˜138 Oe) are applied. The master curves of AC heat generation in Ni/PSU films are established and show a strong particle size effect. Hysteresis fusion bonding of glass/polyphenylene sulfide thermoplastic composites using a magnetic film as the thermoplastic adhesive shows that the bond strength of hysteresis-welded materials is comparable to that of autoclave-welded materials while offering an order of magnitude reduction in cycle time. The relative contribution of the intimate contact and healing mechanisms to the fusion bonding process indicates that hysteresis bonding is controlled by intimate contact. The macroscopic failure modes vary from mostly adhesive composite/film (low bond strength) to a combination of adhesive composite/film, cohesive film, cohesive composite and mostly cohesive composite (high bond strength). Inspection of the microscopic failure at the nickel particle/polymer interface in the film indicates quasi-brittle failure mode. The amount of adhesive failure increases with decreasing particle size and increasing particle volume fraction. The XPS peaks confirm nickel oxide in the form of NiO on the failure surface of particle/polymer debonding of hysteresis susceptor film.

Phase behavior and orientational ordering in block copolymers doped with anisotropic nanoparticles

NASA Astrophysics Data System (ADS)

Osipov, M. A.; Gorkunov, M. V.; Berezkin, A. V.; Kudryavtsev, Y. V.

2018-04-01

A molecular field theory and coarse-grained computer simulations with dissipative particle dynamics have been used to study the spontaneous orientational ordering of anisotropic nanoparticles in the lamellar and hexagonal phases of diblock copolymers and the effect of nanoparticles on the phase behavior of these systems. Both the molecular theory and computer simulations indicate that strongly anisotropic nanoparticles are ordered orientationally mainly in the boundary region between the domains and the nematic order parameter possesses opposite signs in adjacent domains. The orientational order is induced by the boundary and by the interaction between nanoparticles and the monomer units in different domains. In simulations, sufficiently long and strongly selective nanoparticles are ordered also inside the domains. The nematic order parameter and local concentration profiles of nanoparticles have been calculated numerically using the model of a nanoparticle with two interaction centers and also determined using the results of computer simulations. A number of phase diagrams have been obtained which illustrate the effect of nanoparticle selectivity and molar fraction of the stability ranges of various phases. Different morphologies have been identified by analyzing the static structure factor and a phase diagram has been constructed in coordinates' nanoparticle concentration-copolymer composition. Orientational ordering of even a small fraction of nanoparticles may result in a significant increase of the dielectric anisotropy of a polymer nanocomposite, which is important for various applications.

Item usage in a multidimensional computerized adaptive test (MCAT) measuring health-related quality of life.

PubMed

Paap, Muirne C S; Kroeze, Karel A; Terwee, Caroline B; van der Palen, Job; Veldkamp, Bernard P

2017-11-01

Examining item usage is an important step in evaluating the performance of a computerized adaptive test (CAT). We study item usage for a newly developed multidimensional CAT which draws items from three PROMIS domains, as well as a disease-specific one. The multidimensional item bank used in the current study contained 194 items from four domains: the PROMIS domains fatigue, physical function, and ability to participate in social roles and activities, and a disease-specific domain (the COPD-SIB). The item bank was calibrated using the multidimensional graded response model and data of 795 patients with chronic obstructive pulmonary disease. To evaluate the item usage rates of all individual items in our item bank, CAT simulations were performed on responses generated based on a multivariate uniform distribution. The outcome variables included active bank size and item overuse (usage rate larger than the expected item usage rate). For average θ-values, the overall active bank size was 9-10%; this number quickly increased as θ-values became more extreme. For values of -2 and +2, the overall active bank size equaled 39-40%. There was 78% overlap between overused items and active bank size for average θ-values. For more extreme θ-values, the overused items made up a much smaller part of the active bank size: here the overlap was only 35%. Our results strengthen the claim that relatively short item banks may suffice when using polytomous items (and no content constraints/exposure control mechanisms), especially when using MCAT.

The DEP domain-containing protein TOE-2 promotes apoptosis in the Q lineage of C. elegans through two distinct mechanisms

PubMed Central

Gurling, Mark; Talavera, Karla; Garriga, Gian

2014-01-01

Neuroblast divisions in the nematode Caenorhabditis elegans often give rise to a larger neuron and a smaller cell that dies. We have previously identified genes that, when mutated, result in neuroblast divisions that generate daughter cells that are more equivalent in size. This effect correlates with the survival of daughter cells that would normally die. We now describe a role for the DEP domain-containing protein TOE-2 in promoting the apoptotic fate in the Q lineage. TOE-2 localized at the plasma membrane and accumulated in the cleavage furrow of the Q.a and Q.p neuroblasts, suggesting that TOE-2 might position the cleavage furrow asymmetrically to generate daughter cells of different sizes. This appears to be the case for Q.a divisions where loss of TOE-2 led to a more symmetric division and to survival of the smaller Q.a daughter. Localization of TOE-2 to the membrane is required for this asymmetry, but, surprisingly, the DEP domain is dispensable. By contrast, loss of TOE-2 led to loss of the apoptotic fate in the smaller Q.p daughter but did not affect the size asymmetry of the Q.p daughters. This function of TOE-2 required the DEP domain but not localization to the membrane. We propose that TOE-2 ensures an apoptotic fate for the small Q.a daughter by promoting asymmetry in the daughter cell sizes of the Q.a neuroblast division but by a mechanism that is independent of cell size in the Q.p division. PMID:24961802

Time domain reflectometry waveform analysis with second order bounded mean oscillation

USDA-ARS?s Scientific Manuscript database

Tangent-line methods and adaptive waveform interpretation with Gaussian filtering (AWIGF) have been proposed for determining reflection positions of time domain reflectometry (TDR) waveforms. However, the accuracy of those methods is limited for short probe TDR sensors. Second order bounded mean osc...

PLATSIM: An efficient linear simulation and analysis package for large-order flexible systems

NASA Technical Reports Server (NTRS)

Maghami, Periman; Kenny, Sean P.; Giesy, Daniel P.

1995-01-01

PLATSIM is a software package designed to provide efficient time and frequency domain analysis of large-order generic space platforms implemented with any linear time-invariant control system. Time domain analysis provides simulations of the overall spacecraft response levels due to either onboard or external disturbances. The time domain results can then be processed by the jitter analysis module to assess the spacecraft's pointing performance in a computationally efficient manner. The resulting jitter analysis algorithms have produced an increase in speed of several orders of magnitude over the brute force approach of sweeping minima and maxima. Frequency domain analysis produces frequency response functions for uncontrolled and controlled platform configurations. The latter represents an enabling technology for large-order flexible systems. PLATSIM uses a sparse matrix formulation for the spacecraft dynamics model which makes both the time and frequency domain operations quite efficient, particularly when a large number of modes are required to capture the true dynamics of the spacecraft. The package is written in MATLAB script language. A graphical user interface (GUI) is included in the PLATSIM software package. This GUI uses MATLAB's Handle graphics to provide a convenient way for setting simulation and analysis parameters.

Light control of orbital domains: case of the prototypical manganite La0.5Sr1.5MnO4

NASA Astrophysics Data System (ADS)

Miller, Timothy; Gensch, Michael; Wall, Simon

2016-12-01

Control of electronic and structural ordering in correlated materials on the ultrafast timescale with light is a new and emerging approach to disentangle the complex interplay of the charge, spin, orbital and structural degree of freedom. In this paper we present an overview of how orbital order and orbital domains can be controlled by near IR and THz radiation in the layered manganite La0.5Sr1.5MnO4. We show how near-IR pumping can efficiently and rapidly melt orbital ordering. However, the nanoscale domain structure recovers unchanged demonstrating the importance of structural defects for the orbital domain formation. On the contrary, we show that pulsed THz fields can be used to effectively orientate the domains. In this case the alignment depends on the in-plane electric field polarisation and is induced by an energy penalty that arises from THz field induced hopping of the localised charges.

Time-Reversal Symmetry Breaking and Consequent Physical Responses Induced by All-In-All-Out Type Magnetic Order on the Pyrochlore Lattice

NASA Astrophysics Data System (ADS)

Arima, Taka-Hisa

2014-03-01

Pyrochlore-type 5d transition-metal oxide compounds Cd2Os2O7 and R2Ir2O7 (R =rare earth) undergo a metal-insulator transition accompanied by a magnetic transition. Recently, the magnetic structures of Cd2Os2O7 and Eu2Ir2O7 were investigated by means of resonant x-ray magnetic scattering. The x-ray data indicated the all-in/all-out type magnetic order. The all-in/all-out order breaks the time-reversal symmetry, while the spontaneous magnetization is essentially absent. The magnetic order can be viewed as ferroic magnetic octupolar order. The magnetic order is expected to provide several unique physical properties like quadratic magnetization. linear magneto-capacitance, linear magneto-resistance, linear magneto-mechanical coupling and so on. The symmetry breaking results in two non-equivalent domains, ``all-in/all-out'' and ``all-out/all-in.'' Interestingly, some theoretical works predict that a peculiar metallic state would appear on the domain wall. The observation and control of the domain distribution are essential for studying verious exotic physical responses. We have developed an x-ray technique for domain imaging and started studying the effects of external stimuli on the domain distribution. This work was performed in collaboration with S. Tardif, S. Takeshita, H. Ohsumi, D. Uematsu, H. Sagayama, J. J. Ishikawa, S. Nakatsuji, J. Yamaura, and Z. Hiroi.

Dynamics and Size of Cross-Linking-Induced Lipid Nanodomains in Model Membranes

PubMed Central

Štefl, Martin; Šachl, Radek; Humpolíčková, Jana; Cebecauer, Marek; Macháň, Radek; Kolářová, Marie; Johansson, Lennart B.-Å.; Hof, Martin

2012-01-01

Changes of membrane organization upon cross-linking of its components trigger cell signaling response to various exogenous factors. Cross-linking of raft gangliosides GM1 with cholera toxin (CTxB) was shown to cause microscopic phase separation in model membranes, and the CTxB-GM1 complexes forming a minimal lipid raft unit are the subject of ongoing cell membrane research. Yet, those subdiffraction sized rafts have never been described in terms of size and dynamics. By means of two-color z-scan fluorescence correlation spectroscopy, we show that the nanosized domains are formed in model membranes at lower sphingomyelin (Sph) content than needed for the large-scale phase separation and that the CTxB-GM1 complexes are confined in the domains poorly stabilized with Sph. Förster resonance energy transfer together with Monte Carlo modeling of the donor decay response reveal the domain radius of ∼8 nm, which increases at higher Sph content. We observed two types of domains behaving differently, which suggests a dual role of the cross-linker: first, local transient condensation of the GM1 molecules compensating for a lack of Sph and second, coalescence of existing nanodomains ending in large-scale phase separation. PMID:22824274

Crossover in growth laws for phase-separating binary fluids: molecular dynamics simulations.

PubMed

Ahmad, Shaista; Das, Subir K; Puri, Sanjay

2012-03-01

Pattern and dynamics during phase separation in a symmetrical binary (A+B) Lennard-Jones fluid are studied via molecular dynamics simulations after quenching homogeneously mixed critical (50:50) systems to temperatures below the critical one. The morphology of the domains, rich in A or B particles, is observed to be bicontinuous. The early-time growth of the average domain size is found to be consistent with the Lifshitz-Slyozov law for diffusive domain coarsening. After a characteristic time, dependent on the temperature, we find a clear crossover to an extended viscous hydrodynamic regime where the domains grow linearly with time. Pattern formation in the present system is compared with that in solid binary mixtures, as a function of temperature. Important results for the finite-size and temperature effects on the small-wave-vector behavior of the scattering function are also presented.

Radiation-damage-assisted ferroelectric domain structuring in magnesium-doped lithium niobate

NASA Astrophysics Data System (ADS)

Jentjens, L.; Peithmann, K.; Maier, K.; Steigerwald, H.; Jungk, T.

2009-06-01

Irradiation of 5% magnesium-doped lithium niobate crystals (LiNbO3:Mg) with high-energy, low-mass 3He ions, which are transmitted through the crystal, changes the domain reversal properties of the material. This enables easier domain engineering compared to non-irradiated material and assists the formation of small-sized periodically poled domains in LiNbO3:Mg. Periodic domain structures exhibiting a width of ≈520 nm are obtained in radiation-damaged sections of the crystals. The ferroelectric poling behavior between irradiated and non-treated material is compared.

Prefrontal contributions to domain-general executive control processes during temporal context retrieval.

PubMed

Rajah, M Natasha; Ames, Blaine; D'Esposito, Mark

2008-03-07

Neuroimaging studies have reported increased prefrontal cortex (PFC) activity during temporal context retrieval versus recognition memory. However, it remains unclear if these activations reflect PFC contributions to domain-general executive control processes or domain-specific retrieval processes. To gain a better understanding of the functional roles of these various PFC regions during temporal context retrieval we propose it is necessary to examine PFC activity across tasks from different domains, in which parallel manipulations are included targeting specific cognitive processes. In the current fMRI study, we examined domain-general and domain-specific PFC contributions to temporal context retrieval by increasing stimulus (but maintaining response number) and increasing response number (but maintaining stimulus number) across temporal context memory and ordering control tasks, for faces. The control task required subjects to order faces from youngest to oldest. Our behavioral results indicate that the combination of increased stimulus and response numbers significantly increased task difficulty for temporal context retrieval and ordering tasks. Across domains, increasing stimulus number, while maintaining response numbers, caused greater right lateral premotor cortex (BA 6/8) activity; whereas increasing response number, while maintaining stimulus number, caused greater domain-general left DLPFC (BA 9) and VLPFC (BA 44/45) activity. In addition, we found domain-specific right DLPFC (BA 9) activity only during retrieval events. These results highlight the functional heterogeneity of frontal cortex, and suggest its involvement in temporal context retrieval is related to its role in various cognitive control processes.

The Errors Sources Affect to the Results of One-Way Nested Ocean Regional Circulation Model

NASA Astrophysics Data System (ADS)

Pham, S. V.

2016-02-01

Pham-Van Sy1, Jin Hwan Hwang2 and Hyeyun Ku3 Dept. of Civil & Environmental Engineering, Seoul National University, KoreaEmail: 1phamsymt@gmail.com (Corresponding author) Email: 2jinhwang@snu.ac.krEmail: 3hyeyun.ku@gmail.comAbstractThe Oceanic Regional Circulation Model (ORCM) is an essential tool in resolving highly a regional scale through downscaling dynamically the results from the roughly revolved global model. However, when dynamic downscaling from a coarse resolution of the global model or observations to the small scale, errors are generated due to the different sizes of resolution and lateral updating frequency. This research evaluated the effect of four main sources on the results of the ocean regional circulation model (ORCMs) during downscaling and nesting the output data from the ocean global circulation model (OGCMs). Representative four error sources should be the way of the LBC formulation, the spatial resolution difference between driving and driven data, the frequency for up-dating LBCs and domain size. Errors which are contributed from each error source to the results of the ORCMs are investigated separately by applying the Big-Brother Experiment (BBE). Within resolution of 3km grid point of the ORCMs imposing in the BBE framework, it clearly exposes that the simulation results of the ORCMs significantly depend on the domain size and specially the spatial and temporal resolution of lateral boundary conditions (LBCs). The ratio resolution of spatial resolution between driving data and driven model could be up to 3, the updating frequency of the LBCs can be up to every 6 hours per day. The optimal domain size of the ORCMs could be smaller than the OGCMs' domain size around 2 to 10 times. Key words: ORCMs, error source, lateral boundary conditions, domain size Acknowledgement: This research was supported by grants from the Korean Ministry of Oceans and Fisheries entitled as "Developing total management system for the Keum river estuary and coast" and "Development of Technology for CO2 Marine Geological Storage". We also thank to the administrative supports of the Integrated Research Institute of Construction and Environmental Engineering of the Seoul National University.

Anesthesiologists' and surgeons' perceptions about routine pre-operative testing in low-risk patients: application of the Theoretical Domains Framework (TDF) to identify factors that influence physicians' decisions to order pre-operative tests.

PubMed

Patey, Andrea M; Islam, Rafat; Francis, Jill J; Bryson, Gregory L; Grimshaw, Jeremy M

2012-06-09

Routine pre-operative tests for anesthesia management are often ordered by both anesthesiologists and surgeons for healthy patients undergoing low-risk surgery. The Theoretical Domains Framework (TDF) was developed to investigate determinants of behaviour and identify potential behaviour change interventions. In this study, the TDF is used to explore anaesthesiologists' and surgeons' perceptions of ordering routine tests for healthy patients undergoing low-risk surgery. Sixteen clinicians (eleven anesthesiologists and five surgeons) throughout Ontario were recruited. An interview guide based on the TDF was developed to identify beliefs about pre-operative testing practices. Content analysis of physicians' statements into the relevant theoretical domains was performed. Specific beliefs were identified by grouping similar utterances of the interview participants. Relevant domains were identified by noting the frequencies of the beliefs reported, presence of conflicting beliefs, and perceived influence on the performance of the behaviour under investigation. Seven of the twelve domains were identified as likely relevant to changing clinicians' behaviour about pre-operative test ordering for anesthesia management. Key beliefs were identified within these domains including: conflicting comments about who was responsible for the test-ordering (Social/professional role and identity); inability to cancel tests ordered by fellow physicians (Beliefs about capabilities and social influences); and the problem with tests being completed before the anesthesiologists see the patient (Beliefs about capabilities and Environmental context and resources). Often, tests were ordered by an anesthesiologist based on who may be the attending anesthesiologist on the day of surgery while surgeons ordered tests they thought anesthesiologists may need (Social influences). There were also conflicting comments about the potential consequences associated with reducing testing, from negative (delay or cancel patients' surgeries), to indifference (little or no change in patient outcomes), to positive (save money, avoid unnecessary investigations) (Beliefs about consequences). Further, while most agreed that they are motivated to reduce ordering unnecessary tests (Motivation and goals), there was still a report of a gap between their motivation and practice (Behavioural regulation). We identified key factors that anesthesiologists and surgeons believe influence whether they order pre-operative tests routinely for anesthesia management for a healthy adults undergoing low-risk surgery. These beliefs identify potential individual, team, and organisation targets for behaviour change interventions to reduce unnecessary routine test ordering.

Step by Step: Biology Undergraduates' Problem-Solving Procedures during Multiple-Choice Assessment.

PubMed

Prevost, Luanna B; Lemons, Paula P

2016-01-01

This study uses the theoretical framework of domain-specific problem solving to explore the procedures students use to solve multiple-choice problems about biology concepts. We designed several multiple-choice problems and administered them on four exams. We trained students to produce written descriptions of how they solved the problem, and this allowed us to systematically investigate their problem-solving procedures. We identified a range of procedures and organized them as domain general, domain specific, or hybrid. We also identified domain-general and domain-specific errors made by students during problem solving. We found that students use domain-general and hybrid procedures more frequently when solving lower-order problems than higher-order problems, while they use domain-specific procedures more frequently when solving higher-order problems. Additionally, the more domain-specific procedures students used, the higher the likelihood that they would answer the problem correctly, up to five procedures. However, if students used just one domain-general procedure, they were as likely to answer the problem correctly as if they had used two to five domain-general procedures. Our findings provide a categorization scheme and framework for additional research on biology problem solving and suggest several important implications for researchers and instructors. © 2016 L. B. Prevost and P. P. Lemons. CBE—Life Sciences Education © 2016 The American Society for Cell Biology. This article is distributed by The American Society for Cell Biology under license from the author(s). It is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

Effects of Aperture Size on Q factor and Shielding Effectiveness of a Cubic Resonator

NASA Astrophysics Data System (ADS)

Parr, Stefan; Chromy, Stephan; Dickmann, Stefan; Schaarschmidt, Martin

2017-09-01

The EMC properties of a cubic metallic shield are highly affected by its resonances. At the resonant frequencies, the shielding effectiveness (SE) collapses, which results in high field strengths inside the cavity. This can cause failure or even breakdown of electronic devices inside the shield. The resonant behaviour is mainly determined by the quality or Q factor of the shield. In this paper, the effects of the aperture size on the Q factor and the SE of an electrically large, cubic shield are analysed. At first, a method is developed in order to determine the Q factor based on the resonance behaviour of the shield in time domain. Only the first resonance of the shield is considered therefore. The results are evaluated for different aperture diameters and compared with theory for the Q factor. The dominant coupling mechanism of electromagnetic energy into the shield is thus identified. Then the effect of aperture size on the SE is analysed. The excitation of resonances is very probable if the interfering signal is an ultrawideband (UWB) pulse, which constitutes a typical intentional electromagnetic interference (IEMI) scenario. Therefore, the relation between aperture size and SE is analysed using the theory of the transient SE for a broadband signal with a constant spectral density distribution. The results show, that a worst case aperture size exists, where the SE has its minimum.

A novel potential/viscous flow coupling technique for computing helicopter flow fields

NASA Technical Reports Server (NTRS)

Summa, J. Michael; Strash, Daniel J.; Yoo, Sungyul

1993-01-01

The primary objective of this work was to demonstrate the feasibility of a new potential/viscous flow coupling procedure for reducing computational effort while maintaining solution accuracy. This closed-loop, overlapped velocity-coupling concept has been developed in a new two-dimensional code, ZAP2D (Zonal Aerodynamics Program - 2D), a three-dimensional code for wing analysis, ZAP3D (Zonal Aerodynamics Program - 3D), and a three-dimensional code for isolated helicopter rotors in hover, ZAPR3D (Zonal Aerodynamics Program for Rotors - 3D). Comparisons with large domain ARC3D solutions and with experimental data for a NACA 0012 airfoil have shown that the required domain size can be reduced to a few tenths of a percent chord for the low Mach and low angle of attack cases and to less than 2-5 chords for the high Mach and high angle of attack cases while maintaining solution accuracies to within a few percent. This represents CPU time reductions by a factor of 2-4 compared with ARC2D. The current ZAP3D calculation for a rectangular plan-form wing of aspect ratio 5 with an outer domain radius of about 1.2 chords represents a speed-up in CPU time over the ARC3D large domain calculation by about a factor of 2.5 while maintaining solution accuracies to within a few percent. A ZAPR3D simulation for a two-bladed rotor in hover with a reduced grid domain of about two chord lengths was able to capture the wake effects and compared accurately with the experimental pressure data. Further development is required in order to substantiate the promise of computational improvements due to the ZAPR3D coupling concept.

Domain-averaged snow depth over complex terrain from flat field measurements

NASA Astrophysics Data System (ADS)

Helbig, Nora; van Herwijnen, Alec

2017-04-01

Snow depth is an important parameter for a variety of coarse-scale models and applications, such as hydrological forecasting. Since high-resolution snow cover models are computational expensive, simplified snow models are often used. Ground measured snow depth at single stations provide a chance for snow depth data assimilation to improve coarse-scale model forecasts. Snow depth is however commonly recorded at so-called flat fields, often in large measurement networks. While these ground measurement networks provide a wealth of information, various studies questioned the representativity of such flat field snow depth measurements for the surrounding topography. We developed two parameterizations to compute domain-averaged snow depth for coarse model grid cells over complex topography using easy to derive topographic parameters. To derive the two parameterizations we performed a scale dependent analysis for domain sizes ranging from 50m to 3km using highly-resolved snow depth maps at the peak of winter from two distinct climatic regions in Switzerland and in the Spanish Pyrenees. The first, simpler parameterization uses a commonly applied linear lapse rate. For the second parameterization, we first removed the obvious elevation gradient in mean snow depth, which revealed an additional correlation with the subgrid sky view factor. We evaluated domain-averaged snow depth derived with both parameterizations using flat field measurements nearby with the domain-averaged highly-resolved snow depth. This revealed an overall improved performance for the parameterization combining a power law elevation trend scaled with the subgrid parameterized sky view factor. We therefore suggest the parameterization could be used to assimilate flat field snow depth into coarse-scale snow model frameworks in order to improve coarse-scale snow depth estimates over complex topography.

Size-dependent magnetic properties of FeGaB/Al2O3 multilayer micro-islands

NASA Astrophysics Data System (ADS)

Wang, X.; Gao, Y.; Chen, H.; Chen, Y.; Liang, X.; Lin, W.; Sun, N. X.

2018-06-01

Recently, micrometer-size patterned magnetic materials have been widely used in MEMS devices. However, the self-demagnetizing action is significantly influencing the performance of the magnetic materials in many MEMS devices. Here, we report an experimental study on the magnetic properties of the patterned micro-scale FeGaB/Al2O3 multilayers. Ferromagnetic hysteresis loop, ferromagnetic resonance (FMR), permeability and domain behavior have been demonstrated by complementary techniques. Magnetic annealing was used to enhance the performance of magnetic multilayers. The comparisons among micro-islands with different sizes in the range of 200 μm ∼ 500 μm as well as full film show a marked influence of size-effect, the exchange coupling effect, and the different domain structures inside the islands.

Analysis of spatial distribution of land cover maps accuracy

NASA Astrophysics Data System (ADS)

Khatami, R.; Mountrakis, G.; Stehman, S. V.

2017-12-01

Land cover maps have become one of the most important products of remote sensing science. However, classification errors will exist in any classified map and affect the reliability of subsequent map usage. Moreover, classification accuracy often varies over different regions of a classified map. These variations of accuracy will affect the reliability of subsequent analyses of different regions based on the classified maps. The traditional approach of map accuracy assessment based on an error matrix does not capture the spatial variation in classification accuracy. Here, per-pixel accuracy prediction methods are proposed based on interpolating accuracy values from a test sample to produce wall-to-wall accuracy maps. Different accuracy prediction methods were developed based on four factors: predictive domain (spatial versus spectral), interpolation function (constant, linear, Gaussian, and logistic), incorporation of class information (interpolating each class separately versus grouping them together), and sample size. Incorporation of spectral domain as explanatory feature spaces of classification accuracy interpolation was done for the first time in this research. Performance of the prediction methods was evaluated using 26 test blocks, with 10 km × 10 km dimensions, dispersed throughout the United States. The performance of the predictions was evaluated using the area under the curve (AUC) of the receiver operating characteristic. Relative to existing accuracy prediction methods, our proposed methods resulted in improvements of AUC of 0.15 or greater. Evaluation of the four factors comprising the accuracy prediction methods demonstrated that: i) interpolations should be done separately for each class instead of grouping all classes together; ii) if an all-classes approach is used, the spectral domain will result in substantially greater AUC than the spatial domain; iii) for the smaller sample size and per-class predictions, the spectral and spatial domain yielded similar AUC; iv) for the larger sample size (i.e., very dense spatial sample) and per-class predictions, the spatial domain yielded larger AUC; v) increasing the sample size improved accuracy predictions with a greater benefit accruing to the spatial domain; and vi) the function used for interpolation had the smallest effect on AUC.

Magnetic hysteresis in small-grained CoxPd1-x nanowire arrays

NASA Astrophysics Data System (ADS)

Viqueira, M. S.; Pozo-López, G.; Urreta, S. E.; Condó, A. M.; Cornejo, D. R.; Fabietti, L. M.

2015-11-01

Co-Pd nanowires with small grain size are fabricated by AC electrodeposition into hexagonally ordered alumina pores, 20-35 nm in diameter and about 1 μm long. The effects of the alloy composition, the nanowire diameter and the grain size on the hysteresis properties are considered. X-ray diffraction indicates that the nanowires are single phase, a fcc Co-Pd solid solution; electron microscopy results show that they are polycrystalline, with randomly oriented grains (7-12 nm), smaller than the wire diameter. Nanowire arrays are ferromagnetic, with an easy magnetization axis parallel to the nanowire long axis. Both, the coercive field and the loop squareness monotonously increase with the Co content and with the grain size, but no clear correlation with the wire diameter is found. The Co and Co-rich nanowire arrays exhibit coercive fields and reduced remanence values quite insensitive to temperature in the range 4 K-300 K; on the contrary, in Pd-rich nanowires both magnitudes are smaller and they largely increase during cooling below 100 K. These behaviors are systematized by considering the strong dependences displayed by the magneto-crystalline anisotropy and the saturation magnetostriction on composition and temperature. At low temperatures the effective anisotropy value and the domain-wall width to grain size ratio drastically change, promoting less cooperative and harder nucleation modes.

Two-dimensional self-organization of an ordered Au silicide nanowire network on a Si(110)-16 x 2 surface.

PubMed

Hong, Ie-Hong; Yen, Shang-Chieh; Lin, Fu-Shiang

2009-08-17

A well-ordered two-dimensional (2D) network consisting of two crossed Au silicide nanowire (NW) arrays is self-organized on a Si(110)-16 x 2 surface by the direct-current heating of approximately 1.5 monolayers of Au on the surface at 1100 K. Such a highly regular crossbar nanomesh exhibits both a perfect long-range spatial order and a high integration density over a mesoscopic area, and these two self-ordering crossed arrays of parallel-aligned NWs have distinctly different sizes and conductivities. NWs are fabricated with widths and pitches as small as approximately 2 and approximately 5 nm, respectively. The difference in the conductivities of two crossed-NW arrays opens up the possibility for their utilization in nanodevices of crossbar architecture. Scanning tunneling microscopy/spectroscopy studies show that the 2D self-organization of this perfect Au silicide nanomesh can be achieved through two different directional electromigrations of Au silicide NWs along different orientations of two nonorthogonal 16 x 2 domains, which are driven by the electrical field of direct-current heating. Prospects for this Au silicide nanomesh are also discussed.

Graphene prepared by thermal reduction–exfoliation of graphite oxide: Effect of raw graphite particle size on the properties of graphite oxide and graphene

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

Dao, Trung Dung; Jeong, Han Mo, E-mail: hmjeong@mail.ulsan.ac.kr

Highlights: • Effect of raw graphite particle size on properties of GO and graphene is reported. • Size of raw graphite affects oxidation degree and chemical structure of GO. • Highly oxidized GO results in small-sized but well-exfoliated graphene. • GO properties affect reduction degree, structure, and conductivity of graphene. - Abstract: We report the effect of raw graphite size on the properties of graphite oxide and graphene prepared by thermal reduction–exfoliation of graphite oxide. Transmission electron microscope analysis shows that the lateral size of graphene becomes smaller when smaller size graphite is used. X-ray diffraction analysis confirms that graphitemore » with smaller size is more effectively oxidized, resulting in a more effective subsequent exfoliation of the obtained graphite oxide toward graphene. X-ray photoelectron spectroscopy demonstrates that reduction of the graphite oxide derived from smaller size graphite into graphene is more efficient. However, Raman analysis suggests that the average size of the in-plane sp{sup 2}-carbon domains on graphene is smaller when smaller size graphite is used. The enhanced reduction degree and the reduced size of sp{sup 2}-carbon domains contribute contradictively to the electrical conductivity of graphene when the particle size of raw graphite reduces.« less

Effect of surface hydrophobicity on the function of the immobilized biomineralization protein Mms6

DOE PAGES

Liu, Xunpei; Zhang, Honghu; Nayak, Srikanth; ...

2015-08-13

Magnetotactic bacteria produce magnetic nanocrystals with uniform shapes and sizes in nature, which has inspired in vitro synthesis of uniformly sized magnetite nanocrystals under mild conditions. Mms6, a biomineralization protein from magnetotactic bacteria with a hydrophobic N-terminal domain and a hydrophilic C-terminal domain, can promote formation of magnetite nanocrystals in vitro with well-defined shape and size in gels under mild conditions. Here we investigate the role of surface hydrophobicity on the ability of Mms6 to template magnetite nanoparticle formation on surfaces. Our results confirmed that Mms6 can form a protein network structure on a monolayer of hydrophobic octadecanethiol (ODT)-coated goldmore » surfaces and facilitate magnetite nanocrystal formation with uniform sizes close to those seen in nature, in contrast to its behavior on more hydrophilic surfaces. We propose that this hydrophobicity effect might be due to the amphiphilic nature of the Mms6 protein and its tendency to incorporate the hydrophobic N-terminal domain into the hydrophobic lipid bilayer environment of the magnetosome membrane, exposing the hydrophilic C-terminal domain that promotes biomineralization. Supporting this hypothesis, the larger and well-formed magnetite nanoparticles were found to be preferentially located on ODT surfaces covered with Mms6 as compared to control samples, as characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and atomic force microscopy studies. A C-terminal domain mutant of this protein did not form the same network structure as wild-type Mms6, suggesting that the network structure is important for the magnetite nanocrystal formation. This article provides valuable insights into the role of surface hydrophilicity on the action of the biomineralization protein Mms6 to synthesize magnetic nanocrystals and provides a facile route to controlling bioinspired nanocrystal synthesis in vitro.« less

A randomised controlled trial of adjunctive yoga and adjunctive physical exercise training for cognitive dysfunction in schizophrenia.

PubMed

Bhatia, Triptish; Mazumdar, Sati; Wood, Joel; He, Fanyin; Gur, Raquel E; Gur, Ruben C; Nimgaonkar, Vishwajit L; Deshpande, Smita N

2017-04-01

Yoga and physical exercise have been used as adjunctive intervention for cognitive dysfunction in schizophrenia (SZ), but controlled comparisons are lacking. Aims A single-blind randomised controlled trial was designed to evaluate whether yoga training or physical exercise training enhance cognitive functions in SZ, based on a prior pilot study. Consenting, clinically stable, adult outpatients with SZ (n=286) completed baseline assessments and were randomised to treatment as usual (TAU), supervised yoga training with TAU (YT) or supervised physical exercise training with TAU (PE). Based on the pilot study, the primary outcome measure was speed index for the cognitive domain of 'attention' in the Penn computerised neurocognitive battery. Using mixed models and contrasts, cognitive functions at baseline, 21 days (end of training), 3 and 6 months post-training were evaluated with intention-to-treat paradigm. Speed index of attention domain in the YT group showed greater improvement than PE at 6 months follow-up (p<0.036, effect size 0.51). In the PE group, 'accuracy index of attention domain showed greater improvement than TAU alone at 6-month follow-up (p<0.025, effect size 0.61). For several other cognitive domains, significant improvements were observed with YT or PE compared with TAU alone (p<0.05, effect sizes 0.30-1.97). Both YT and PE improved attention and additional cognitive domains well past the training period, supporting our prior reported beneficial effect of YT on speed index of attention domain. As adjuncts, YT or PE can benefit individuals with SZ.

Lower Sensitivity to Happy and Angry Facial Emotions in Young Adults with Psychiatric Problems

PubMed Central

Vrijen, Charlotte; Hartman, Catharina A.; Lodder, Gerine M. A.; Verhagen, Maaike; de Jonge, Peter; Oldehinkel, Albertine J.

2016-01-01

Many psychiatric problem domains have been associated with emotion-specific biases or general deficiencies in facial emotion identification. However, both within and between psychiatric problem domains, large variability exists in the types of emotion identification problems that were reported. Moreover, since the domain-specificity of the findings was often not addressed, it remains unclear whether patterns found for specific problem domains can be better explained by co-occurrence of other psychiatric problems or by more generic characteristics of psychopathology, for example, problem severity. In this study, we aimed to investigate associations between emotion identification biases and five psychiatric problem domains, and to determine the domain-specificity of these biases. Data were collected as part of the ‘No Fun No Glory’ study and involved 2,577 young adults. The study participants completed a dynamic facial emotion identification task involving happy, sad, angry, and fearful faces, and filled in the Adult Self-Report Questionnaire, of which we used the scales depressive problems, anxiety problems, avoidance problems, Attention-Deficit Hyperactivity Disorder (ADHD) problems and antisocial problems. Our results suggest that participants with antisocial problems were significantly less sensitive to happy facial emotions, participants with ADHD problems were less sensitive to angry emotions, and participants with avoidance problems were less sensitive to both angry and happy emotions. These effects could not be fully explained by co-occurring psychiatric problems. Whereas this seems to indicate domain-specificity, inspection of the overall pattern of effect sizes regardless of statistical significance reveals generic patterns as well, in that for all psychiatric problem domains the effect sizes for happy and angry emotions were larger than the effect sizes for sad and fearful emotions. As happy and angry emotions are strongly associated with approach and avoidance mechanisms in social interaction, these mechanisms may hold the key to understanding the associations between facial emotion identification and a wide range of psychiatric problems. PMID:27920735

Systematic biochemical characterization of the SAM domains in Eph receptor family from Mus Musculus.

PubMed

Wang, Yue; Li, Qingxia; Zheng, Yunhua; Li, Gang; Liu, Wei

2016-05-13

The Eph receptor family is the largest subfamily of receptor tyrosine kinases and well-known for their pivotal roles in axon guidance, synaptogenesis, artery/venous differentiation and tumorigenesis, etc. Activation of the Eph receptor needs multimerization of the receptors. The intracellular C-terminal SAM domain of Eph receptor was reported to mediate self-association of Eph receptors via the homo SAM-SAM interaction. In this study, we systematically expressed and purified the SAM domain proteins of all fourteen Eph receptors of Mus musculus in Escherichia coli. The FPLC (fast protein liquid chromatography) results showed the recombinant SAM domains were highly homogeneous. Using CD (circular dichroism) spectrometry, we found that the secondary structure of all the SAM domains was typically alpha helical folded and remarkably similar. The thermo-stability tests showed that they were quite stable in solution. SEC-MALS (size exclusion chromatography coupled with multiple angle light scattering) results illustrated 200 μM Eph SAM domains behaved as good monomers in the size-exclusion chromatography. More importantly, DLS (dynamic light scattering) results revealed the overwhelming majority of SAM domains was not multimerized in solution either at 200 μM or 2000 μM protein concentration, which indicating the SAM domain alone was not sufficient to mediate the polymerization of Eph receptor. In summary, our studies provided the systematic biochemical characterizations of the Eph receptor SAM domains and implied their roles in Eph receptor mediated signaling pathways. Copyright © 2016 Elsevier Inc. All rights reserved.