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Sample records for particle growing mechanisms

  1. Extreme Mechanics of Growing Matter

    NASA Astrophysics Data System (ADS)

    Kuhl, Ellen

    2013-03-01

    Growth is a distinguishing feature of all living things. Unlike standard materials, living matter can autonomously respond to alterations in its environment. As a result of a continuous ultrastructural turnover and renewal of cells and extracellular matrix, living matter can undergo extreme changes in composition, size, and shape within the order of months, weeks, or days. While hard matter typically adapts by increasing its density to grow strong, soft matter adapts by increasing its volume to grow large. Here we provide a state-of-the-art review of growing matter, and compare existing mathematical models for growth and remodeling of living systems. Applications are plentiful ranging from plant growth to tumor growth, from asthma in the lungs to restenosis in the vasculature, from plastic to reconstructive surgery, and from skeletal muscle adaptation to heart failure. Using these examples, we discuss current challenges and potential future directions. We hope to initiate critical discussions around the biophysical modeling of growing matter as a powerful tool to better understand biological systems in health and disease. This research has been supported by the NSF CAREER award CMMI 0952021.

  2. 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.

  3. Particles Growing in Solutions: Depletion Forces and Instability of Homogeneous Particle Distribution

    NASA Technical Reports Server (NTRS)

    Chernov, A. A.

    2004-01-01

    Crystallites, droplets and amorphous precipitates growing from supersaturated solution are surrounded by zones, which are depleted with respect to the molecules they are built of. If two such particles of colloidal size are separated by a distance comparable to their diameters, then the depletion within the gap between particles is deeper than that at the outer portion of the particles. This will cause depletion attraction between the particles should appear. It may cause particle coagulation and decay of the originally homogeneous particle distribution into a system of clouds within which the particle number density is higher, separated by the region of the lower number density. Stability criterion, Q = 4 pi R(exp 3)c/3 >> 1, was analytically found along with typical particle density distribution wavevector q = (Q/I)(exp 1/2)(a/R)(exp 1/4). Here, R and a are the particle and molecular radii, respectively, c is the average molecular number density in solution and I is the squared diffusion length covered by a molecule during a typical time characterizing decay of molecular concentration in solution due to consumption of the molecules by the growing particles.

  4. Mechanical Stress Induces Remodeling of Vascular Networks in Growing Leaves

    PubMed Central

    Bar-Sinai, Yohai; Julien, Jean-Daniel; Sharon, Eran; Armon, Shahaf; Nakayama, Naomi; Adda-Bedia, Mokhtar; Boudaoud, Arezki

    2016-01-01

    Differentiation into well-defined patterns and tissue growth are recognized as key processes in organismal development. However, it is unclear whether patterns are passively, homogeneously dilated by growth or whether they remodel during tissue expansion. Leaf vascular networks are well-fitted to investigate this issue, since leaves are approximately two-dimensional and grow manyfold in size. Here we study experimentally and computationally how vein patterns affect growth. We first model the growing vasculature as a network of viscoelastic rods and consider its response to external mechanical stress. We use the so-called texture tensor to quantify the local network geometry and reveal that growth is heterogeneous, resembling non-affine deformations in composite materials. We then apply mechanical forces to growing leaves after veins have differentiated, which respond by anisotropic growth and reorientation of the network in the direction of external stress. External mechanical stress appears to make growth more homogeneous, in contrast with the model with viscoelastic rods. However, we reconcile the model with experimental data by incorporating randomness in rod thickness and a threshold in the rod growth law, making the rods viscoelastoplastic. Altogether, we show that the higher stiffness of veins leads to their reorientation along external forces, along with a reduction in growth heterogeneity. This process may lead to the reinforcement of leaves against mechanical stress. More generally, our work contributes to a framework whereby growth and patterns are coordinated through the differences in mechanical properties between cell types. PMID:27074136

  5. Growing Characteristics of Fine Ice Particles in Surfactant Solution

    NASA Astrophysics Data System (ADS)

    Suzuki, Hiroshi; Nakayama, Kosuke; Komoda, Yoshiyuki; Usui, Hiromoto; Okada, Kazuto; Fujisawa, Ryo

    Time variation characteristics of ice particles in a surfactant solution have been investigated. The effect of surfactants on corrosion characteristics was also studied. The results were compared with those treated with poly(vinyl alcohol). From the results, the present surfactant, cetyl dimethyl betaine was not found to be effective on preventing Ostward ripening of ice particles as poly(vinyl alcohol) showed. Then, it was concluded some effective technology has to be installed with surfactants when this surfactant treatment is realized. On the corrosion characteristics, it was found that the present surfactant shows the same level as tap water.

  6. Particle Suspension Mechanisms - Supplemental Material

    SciTech Connect

    Dillon, M B

    2011-03-03

    This supplemental material provides a brief introduction to particle suspension mechanisms that cause exfoliated skin cells to become and remain airborne. The material presented here provides additional context to the primary manuscript and serves as background for designing possible future studies to assess the impact of skin cells as a source of infectious aerosols. This introduction is not intended to be comprehensive and interested readers are encouraged to consult the references cited.

  7. On the mechanics of growing thin biological membranes

    PubMed Central

    Rausch, Manuel K.; Kuhl, Ellen

    2013-01-01

    Despite their seemingly delicate appearance, thin biological membranes fulfill various crucial roles in the human body and can sustain substantial mechanical loads. Unlike engineering structures, biological membranes are able to grow and adapt to changes in their mechanical environment. Finite element modeling of biological growth holds the potential to better understand the interplay of membrane form and function and to reliably predict the effects of disease or medical intervention. However, standard continuum elements typically fail to represent thin biological membranes efficiently, accurately, and robustly. Moreover, continuum models are typically cumbersome to generate from surface-based medical imaging data. Here we propose a computational model for finite membrane growth using a classical midsurface representation compatible with standard shell elements. By assuming elastic incompressibility and membrane-only growth, the model a priori satisfies the zero-normal stress condition. To demonstrate its modular nature, we implement the membrane growth model into the general-purpose non-linear finite element package Abaqus/Standard using the concept of user subroutines. To probe efficiently and robustness, we simulate selected benchmark examples of growing biological membranes under different loading conditions. To demonstrate the clinical potential, we simulate the functional adaptation of a heart valve leaflet in ischemic cardiomyopathy. We believe that our novel approach will be widely applicable to simulate the adaptive chronic growth of thin biological structures including skin membranes, mucous membranes, fetal membranes, tympanic membranes, corneoscleral membranes, and heart valve membranes. Ultimately, our model can be used to identify diseased states, predict disease evolution, and guide the design of interventional or pharmaceutic therapies to arrest or revert disease progression. PMID:24563551

  8. On the mechanics of growing thin biological membranes

    NASA Astrophysics Data System (ADS)

    Rausch, Manuel K.; Kuhl, Ellen

    2014-02-01

    Despite their seemingly delicate appearance, thin biological membranes fulfill various crucial roles in the human body and can sustain substantial mechanical loads. Unlike engineering structures, biological membranes are able to grow and adapt to changes in their mechanical environment. Finite element modeling of biological growth holds the potential to better understand the interplay of membrane form and function and to reliably predict the effects of disease or medical intervention. However, standard continuum elements typically fail to represent thin biological membranes efficiently, accurately, and robustly. Moreover, continuum models are typically cumbersome to generate from surface-based medical imaging data. Here we propose a computational model for finite membrane growth using a classical midsurface representation compatible with standard shell elements. By assuming elastic incompressibility and membrane-only growth, the model a priori satisfies the zero-normal stress condition. To demonstrate its modular nature, we implement the membrane growth model into the general-purpose non-linear finite element package Abaqus/Standard using the concept of user subroutines. To probe efficiently and robustness, we simulate selected benchmark examples of growing biological membranes under different loading conditions. To demonstrate the clinical potential, we simulate the functional adaptation of a heart valve leaflet in ischemic cardiomyopathy. We believe that our novel approach will be widely applicable to simulate the adaptive chronic growth of thin biological structures including skin membranes, mucous membranes, fetal membranes, tympanic membranes, corneoscleral membranes, and heart valve membranes. Ultimately, our model can be used to identify diseased states, predict disease evolution, and guide the design of interventional or pharmaceutic therapies to arrest or revert disease progression.

  9. Research on improved mechanism for particle filter

    NASA Astrophysics Data System (ADS)

    Yu, Jinxia; Xu, Jingmin; Tang, Yongli; Zhao, Qian

    2013-03-01

    Based on the analysis of particle filter algorithm, two improved mechanism are studied so as to improve the performance of particle filter. Firstly, hybrid proposal distribution with annealing parameter is studied in order to use current information of the latest observed measurement to optimize particle filter. Then, resampling step in particle filter is improved by two methods which are based on partial stratified resampling (PSR). One is that it uses the optimal idea to improve the weights after implementing PSR, and the other is that it uses the optimal idea to improve the weights before implementing PSR and uses adaptive mutation operation for all particles so as to assure the diversity of particle sets after PSR. At last, the simulations based on single object tracking are implemented, and the performances of the improved mechanism for particle filter are estimated.

  10. Formation mechanisms and aggregation behavior of borohydride reduced silver particles

    SciTech Connect

    Hyning, D.L. van; Zukoski, C.F.

    1998-11-24

    In this work, the authors examine the formation mechanisms of nanoscale silver particles produced by the reduction of silver perchlorate with sodium borohydride. Evidence is presented that the reaction pathway does not follow classical nucleation and growth theory, but is dominated by colloidal interactions. Upon injection of silver into a sodium borohydride solution, a molecular species absorbing at 220 nm is produced in less than 1 s. The authors suggest that this species contains borohydride nd small particles of reduced silver. The reaction mixture is initially dark as the result of the aggregation of the small silver particles into larger particles which have broad absorption spectra. During an intermediate stage, transmission electron microscopy and absorbance data show that even larger ({approximately}6--10 nm) particles grow at the expense of the monomeric silver particles. Later in the reaction, electrochemical potential measurements show that the borohydride concentration suddenly decreases. Direct measurement of interparticle forces demonstrate that this change in the solution conditions drives the particle surface potential toward zero and results in increased adhesive forces. The resulting aggregation manifests itself in a darkening of the solution temperatures, the increase is minimal. This effect can be linked to the number of monomeric silver particles remaining during the final transition.

  11. Dynamic wormholes with particle creation mechanism

    NASA Astrophysics Data System (ADS)

    Pan, Supriya; Chakraborty, Subenoy

    2015-01-01

    The present work deals with a spherically symmetric space-time which is asymptotically (at spatial infinity) FRW space-time and represents wormhole configuration: The matter component is divided into two parts—(a) dissipative but homogeneous and isotropic fluid, and (b) an inhomogeneous and anisotropic barotropic fluid. Evolving wormhole solutions are obtained when isotropic fluid is phantom in nature and there is a big rip singularity at the end. Here the dissipative phenomena is due to the particle creation mechanism in non-equilibrium thermodynamics. Using the process to be adiabatic, the dissipative pressure is expressed linearly to the particle creation rate. For two choices of the particle creation rate as a function of the Hubble parameter, the equation of state parameter of the isotropic fluid is constrained to be in the phantom domain, except in one choice, it is possible to have wormhole configuration with normal isotropic fluid.

  12. QCD mechanisms for heavy particle production

    SciTech Connect

    Brodsky, S.J.

    1985-09-01

    For very large pair mass, the production of heavy quarks and supersymmetric particles is expected to be governed by ACD fusion subprocesses. At lower mass scales other QCD mechanisms such as prebinding distortion and intrinsic heavy particle Fock states can become important, possibly accounting for the anomalies observed for charm hadroproduction. We emphasize the importance of final-state Coulomb interactions at low relative velocity in QCD and predict the existence of heavy narrow four quark resonances (c c-bar u u-bar) and (cc c-bar c-bar) in ..gamma gamma.. reactions. Coherent QCD contributions are discussed as a contribution to the non-additivity of nuclear structure functions and heavy particle production cross sections. We also predict a new type of amplitude zero for exclusive heavy meson pair production which follows from the tree-graph structure of QCD. 35 refs., 8 figs., 1 tab.

  13. Dynamics and mechanics of tracer particles

    NASA Astrophysics Data System (ADS)

    Phillips, C. B.; Jerolmack, D. J.

    2014-06-01

    Understanding the mechanics of bed load at the flood scale is necessary to link hydrology to landscape evolution. Here we report on observations of the transport of coarse sediment tracer particles in a cobble-bedded alluvial river and a step-pool tributary, at the individual flood and multi-annual timescales. Tracer particle data for each survey are composed of measured displacement lengths for individual particles, and the number of tagged particles mobilized. For single floods we find that: measured tracer particle displacement lengths are exponentially distributed; the number of mobile particles increases linearly with peak flood Shields stress, indicating partial bed load transport for all observed floods; and modal displacement lengths scale linearly with excess shear velocity. These findings provide quantitative field support for a recently proposed modelling framework based on momentum conservation at the grain scale. Tracer displacement shows a weak correlation with particle size at the individual flood scale, however cumulative travel distance begins to show an inverse relation to grain size when measured over many transport events. The observed spatial sorting of tracers approaches that of the river bed, and is consistent with size-selective deposition models and laboratory experiments. Tracer displacement data for the step-pool and alluvial channels collapse onto a single curve - despite more than an order of magnitude difference in channel slope - when variations of critical Shields stress and flow resistance between the two are accounted for. Results show how bed load dynamics may be predicted from a record of river stage, providing a direct link between climate and sediment transport.

  14. Particle aggregation mechanisms in ionic liquids.

    PubMed

    Szilagyi, Istvan; Szabo, Tamas; Desert, Anthony; Trefalt, Gregor; Oncsik, Tamas; Borkovec, Michal

    2014-05-28

    Aggregation of sub-micron and nano-sized polystyrene latex particles was studied in room temperature ionic liquids (ILs) and in their water mixtures by time-resolved light scattering. The aggregation rates were found to vary with the IL-to-water molar ratio in a systematic way. At the water side, the aggregation rate is initially small, but increases rapidly with increasing IL content, and reaches a plateau value. This behaviour resembles simple salts, and can be rationalized by the competition of double-layer and van der Waals forces as surmised by the classical theory of Derjaguin, Landau, Verwey, and Overbeek (DLVO). At the IL side, aggregation slows down again. Two generic mechanisms could be identified to be responsible for the stabilization in ILs, namely viscous stabilization and solvation stabilization. Viscous stabilization is important in highly viscous ILs, as it originates from the slowdown of the diffusion controlled aggregation due to the hindrance of the diffusion in a viscous liquid. The solvation stabilization mechanism is system specific, but can lead to a dramatic slowdown of the aggregation rate in ILs. This mechanism is related to repulsive solvation forces that are operational in ILs due to the layering of the ILs close to the surfaces. These two stabilization mechanisms are suspected to be generic, as they both occur in different ILs, and for particles differing in surface functionalities and size. PMID:24727976

  15. Interaction between high protein supplement and copper oxide wire particles to control gastrointestinal nematodes in growing goats

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective was to investigate the interaction between high protein supplementation and copper oxide wire particles (COWP) to control gastrointestinal nematodes (GIN) in growing female goats. Haemonchus contortus is the primary GIN during summer months on this farm. In early August 2006, Boer an...

  16. On the mechanics of continua with boundary energies and growing surfaces.

    PubMed

    Papastavrou, Areti; Steinmann, Paul; Kuhl, Ellen

    2013-06-01

    Many biological systems are coated by thin films for protection, selective absorption, or transmembrane transport. A typical example is the mucous membrane covering the airways, the esophagus, and the intestine. Biological surfaces typically display a distinct mechanical behavior from the bulk; in particular, they may grow at different rates. Growth, morphological instabilities, and buckling of biological surfaces have been studied intensely by approximating the surface as a layer of finite thickness; however, growth has never been attributed to the surface itself. Here, we establish a theory of continua with boundary energies and growing surfaces of zero thickness in which the surface is equipped with its own potential energy and is allowed to grow independently of the bulk. In complete analogy to the kinematic equations, the balance equations, and the constitutive equations of a growing solid body, we derive the governing equations for a growing surface. We illustrate their spatial discretization using the finite element method, and discuss their consistent algorithmic linearization. To demonstrate the conceptual differences between volume and surface growth, we simulate the constrained growth of the inner layer of a cylindrical tube. Our novel approach towards continua with growing surfaces is capable of predicting extreme growth of the inner cylindrical surface, which more than doubles its initial area. The underlying algorithmic framework is robust and stable; it allows to predict morphological changes due to surface growth during the onset of buckling and beyond. The modeling of surface growth has immediate biomedical applications in the diagnosis and treatment of asthma, gastritis, obstructive sleep apnoea, and tumor invasion. Beyond biomedical applications, the scientific understanding of growth-induced morphological instabilities and surface wrinkling has important implications in material sciences, manufacturing, and microfabrication, with applications in

  17. On the mechanics of continua with boundary energies and growing surfaces

    NASA Astrophysics Data System (ADS)

    Papastavrou, Areti; Steinmann, Paul; Kuhl, Ellen

    2013-06-01

    Many biological systems are coated by thin films for protection, selective absorption, or transmembrane transport. A typical example is the mucous membrane covering the airways, the esophagus, and the intestine. Biological surfaces typically display a distinct mechanical behavior from the bulk; in particular, they may grow at different rates. Growth, morphological instabilities, and buckling of biological surfaces have been studied intensely by approximating the surface as a layer of finite thickness; however, growth has never been attributed to the surface itself. Here, we establish a theory of continua with boundary energies and growing surfaces of zero thickness in which the surface is equipped with its own potential energy and is allowed to grow independently of the bulk. In complete analogy to the kinematic equations, the balance equations, and the constitutive equations of a growing solid body, we derive the governing equations for a growing surface. We illustrate their spatial discretization using the finite element method, and discuss their consistent algorithmic linearization. To demonstrate the conceptual differences between volume and surface growth, we simulate the constrained growth of the inner layer of a cylindrical tube. Our novel approach toward continua with growing surfaces is capable of predicting extreme growth of the inner cylindrical surface, which more than doubles its initial area. The underlying algorithmic framework is robust and stable; it allows to predict morphological changes due to surface growth during the onset of buckling and beyond. The modeling of surface growth has immediate biomedical applications in the diagnosis and treatment of asthma, gastritis, obstructive sleep apnoea, and tumor invasion. Beyond biomedical applications, the scientific understanding of growth-induced morphological instabilities and surface wrinkling has important implications in material sciences, manufacturing, and microfabrication, with applications in

  18. Investigation of the Mechanisms by Which Listeria monocytogenes Grows in Porcine Gallbladder Bile▿ †

    PubMed Central

    Dowd, Georgina C.; Joyce, Susan A.; Hill, Colin; Gahan, Cormac G. M.

    2011-01-01

    The food-borne pathogen Listeria monocytogenes is known to colonize the lumen of the gallbladder in infected mice and to grow rapidly in this environment (J. Hardy et al., Science 303:851-853, 2004). However, relatively little is known about the mechanisms utilized by the pathogen to survive and grow in this location. We utilized gallbladder bile (GB bile) isolated directly from porcine gallbladders as an ex vivo model of gallbladder growth. We demonstrate that GB bile is generally nontoxic for bacteria and can readily support growth of a variety of bacterial species including L. monocytogenes, Lactococcus lactis, Salmonella enterica serovar Typhimurium, and Escherichia coli. Significantly, L. monocytogenes grew at the same rate as the nonpathogenic species Listeria innocua, indicating that the pathogen does not possess specialized mechanisms that enable growth in this environment. However, when we reduced the pH of GB bile to pH 5.5 in order to mimic the release of bile within the small intestine, the toxicity of GB bile increased significantly and specific resistance mechanisms (Sigma B, BSH, and BilE) were essential for survival of the pathogen under these conditions. In order to identify genetic loci that are necessary for growth of L. monocytogenes in the gallbladder, a mariner transposon bank was created and screened for mutants unable to replicate in GB bile. This led to the identification of mutants in six loci, including genes encoding enzymes involved in purine metabolism, amino acid biosynthesis, and biotin uptake. Although GB bile does not represent a significant impediment to bacterial growth, specific metabolic processes are required by L. monocytogenes in order to grow in this environment. PMID:20937762

  19. Molelcular dynamics, smooth particle applied mechanics and Clausius` inequality

    SciTech Connect

    Hoover, W.G.

    1996-03-01

    Recent developments in molecular dynamics furnish new interconnections among three classical fields: particle mechanics, continuum mechanics, and thermodynamics. The resulting links clarify the importance of Lyapunov instability to irreversibility.

  20. Elucidating the Locking Mechanism of Peptides onto Growing Amyloid Fibrils through Transition Path Sampling

    PubMed Central

    Schor, Marieke; Vreede, Jocelyne; Bolhuis, Peter G.

    2012-01-01

    We investigate the molecular mechanism of monomer addition to a growing amyloid fibril composed of the main amyloidogenic region from the insulin peptide hormone, the LVEALYLLVEALYL heptapeptide. Applying transition path sampling in combination with reaction coordinate analysis reveals that the transition from a docked peptide to a locked, fully incorporated peptide can occur in two ways. Both routes involve the formation of backbone hydrogen bonds between the three central amino acids of the attaching peptide and the fibril, as well as a reorientation of the central Glu side chain of the locking peptide toward the interface between two β-sheets forming the fibril. The mechanisms differ in the sequence of events. We also conclude that proper docking is important for correct alignment of the peptide with the fibril, as alternative pathways result in misfolding. PMID:22995502

  1. Effects of a 1-wk spaceflight on morphological and mechanical properties of growing bone

    NASA Technical Reports Server (NTRS)

    Shaw, S. R.; Vailas, A. C.; Grindeland, R. E.; Zernicke, R. F.

    1988-01-01

    The morphological and mechanical responses of tibia and humerus were assessed in growing male rats after a 1-wk spaceflight aboard NASA Spacelab 3. In contrast to flights of longer duration, changes in middiaphysial cross-sectional morphology were minimal. Inhibition of longitudinal growth was not found in the tibia but was apparent in the humerus. The normal age-related increase in tibial middiaphysial density was not observed in the flight animals. Three-point bending tests indicated that a 1-wk spaceflight impeded the maturation of bone strength and stiffness, with the effects more pronounced in the tibia than in the humerus. Material property alterations in bone thus overshadowed morphological factors in determining the bone's mechanical response. It is likely that deprivation of normal weight-bearing loads was a major factor contributing to the observed changes, but endocrine and other local factors must also be considered.

  2. Growth of new particle in less and highly polluted atmosphere: Implication for an important role of NH4NO3 in growing new particles to CCN size

    NASA Astrophysics Data System (ADS)

    Zhu, Y.; Gao, H.; Duan, Z. Q.; Evans, G. J.; Yao, X.

    2013-12-01

    When new particles formed in the atmosphere grow over 50-80 nm, they will activate as cloud condensation nuclei (CCN) and lead to an increase of cloud albedo. Knowledge gaps still existed, e.g., 1) new particles under which conditions can grow to CCN size? 2) which chemicals determine the growth of new particles to CCN size? In this study, new particle formation (NPF) events were investigated at two urban sites, in Qingdao during 23 April and 31 May, 2010, and in Toronto during 1 May and 31 May, 2009, using two identical Fast Mobility Particle Sizer (FMPS). Based on the satellite column densities of air pollutants and the particulate chemical concentration in PM2.5, the site in Qingdao suffered severe air pollution while the site in Toronto is less polluted. NPF events were observed in 16 days out of 39 sampling days in Qingdao and 13 days out of 31 sampling days in Toronto. The occurrence frequency of NPF events between Qingdao (41%) and Toronto (42%) was comparable to each other. In Qingdao, the geometric mean diameter of grown nucleated particles (Dpg,i) in 15 days grew to larger than 40 nm except in one day when the growth of new particles terminated at ~20 nm. In addition, the Dpg,i in 8 days out of the 15 days grew over 50 nm and it reached ~100 nm in two days. Two-phase growth of new particles was generally observed in these NPF events of Qingdao. The first-phase growth occurred in daytime and the CMAQ modeling results showed that formation of secondary organics was likely an important cause for the growth. The second-phase growth was observed at night and was associated with the increased concentrations of NH4+ and NO3-, implying that NH4NO3 condensation played an important role in the growth. In Toronto, NPF events in 4 days followed with the growth of new particles <~20 nm while new particles grew up to ~40 nm in the remaining NPF events. A slight growth of new particles at night was observed only in 3-day NPF events when the increased concentrations of

  3. Nonequilibrium flows with smooth particle applied mechanics

    SciTech Connect

    Kum, O.

    1995-07-01

    Smooth particle methods are relatively new methods for simulating solid and fluid flows through they have a 20-year history of solving complex hydrodynamic problems in astrophysics, such as colliding planets and stars, for which correct answers are unknown. The results presented in this thesis evaluate the adaptability or fitness of the method for typical hydrocode production problems. For finite hydrodynamic systems, boundary conditions are important. A reflective boundary condition with image particles is a good way to prevent a density anomaly at the boundary and to keep the fluxes continuous there. Boundary values of temperature and velocity can be separately controlled. The gradient algorithm, based on differentiating the smooth particle expression for (u{rho}) and (T{rho}), does not show numerical instabilities for the stress tensor and heat flux vector quantities which require second derivatives in space when Fourier`s heat-flow law and Newton`s viscous force law are used. Smooth particle methods show an interesting parallel linking to them to molecular dynamics. For the inviscid Euler equation, with an isentropic ideal gas equation of state, the smooth particle algorithm generates trajectories isomorphic to those generated by molecular dynamics. The shear moduli were evaluated based on molecular dynamics calculations for the three weighting functions, B spline, Lucy, and Cusp functions. The accuracy and applicability of the methods were estimated by comparing a set of smooth particle Rayleigh-Benard problems, all in the laminar regime, to corresponding highly-accurate grid-based numerical solutions of continuum equations. Both transient and stationary smooth particle solutions reproduce the grid-based data with velocity errors on the order of 5%. The smooth particle method still provides robust solutions at high Rayleigh number where grid-based methods fails.

  4. Single-particle mechanism of magnetostriction in magnetoactive elastomers

    NASA Astrophysics Data System (ADS)

    Kalita, Viktor M.; Snarskii, Andrei A.; Zorinets, Denis; Shamonin, Mikhail

    2016-06-01

    Magnetoactive elastomers (MAEs) are composite materials comprised of micrometer-sized ferromagnetic particles in a nonmagnetic elastomer matrix. A single-particle mechanism of magnetostriction in MAEs, assuming the rotation of a soft magnetic, mechanically rigid particle with uniaxial magnetic anisotropy in magnetic fields is identified and considered theoretically within the framework of an alternative model. In this mechanism, the total magnetic anisotropy energy of the filling particles in the matrix is the sum over single particles. Matrix displacements in the vicinity of the particle and the resulting direction of the magnetization vector are calculated. The effect of matrix deformation is pronounced well if the magnetic anisotropy coefficient K is much larger than the shear modulus µ of the elastic matrix. The feasibility of the proposed magnetostriction mechanism in soft magnetoactive elastomers and gels is elucidated. The magnetic-field-induced internal stresses in the matrix lead to effects of magnetodeformation and may increase the elastic moduli of these composite materials.

  5. Fluid bed porosity mathematical model for an inverse fluidized bed bioreactor with particles growing biofilm.

    PubMed

    Campos-Díaz, K E; Bandala-González, E R; Limas-Ballesteros, R

    2012-08-15

    A new mathematic model to estimate bed porosity as a function of Reynolds and Archimedes numbers was developed based in experimental data. Experiments were performed using an inverse fluidized bed bioreactor filled with polypropylene particles, Lactobacillus acidophillus as the immobilized strain and fluidized with a Man-Rogosa-Sharpe culture medium under controlled temperature and pH conditions. Bed porosity was measured at different flow rates, starting from 0.95 to 9.5 LPM. The new model has several advantages when compared with previously reported. Among them, advantages such as standard deviation values ≤ 1% between experimental and calculated bed porosity, its applicability in traditional and inverse fluidization, wall effects do not take account, it gives excellent agreement with spherical particles with or without biofilm, and inertial drag coefficient allow extend the new model a non-spherical particles. PMID:22484706

  6. Water regime of mechanical-biological pretreated waste materials under fast-growing trees.

    PubMed

    Rüth, Björn; Lennartz, Bernd; Kahle, Petra

    2007-10-01

    In this study mechanical-biological pre-treated waste material (MBP) was tested for suitability to serve as an alternative surface layer in combination with fast-growing and water-consumptive trees for final covers at landfill sites. The aim was to quantify evapotranspiration and seepage losses by numerical model simulations for two sites in Germany. In addition, the leaf area index (LAI) of six tree species over the growing season as the driving parameter for transpiration calculations was determined experimentally. The maximum LAI varied between 3.8 and 6.1 m2 m(-2) for poplar and willow clones, respectively. The evapotranspiration calculations revealed that the use of MBP waste material for re-cultivation enhanced evapotranspiration by 40 mm year(-1) (10%) over an 11 year calculation period compared to a standard mineral soil. Between 82% (for LAI(max) = 3.8) and 87% (for LAI(max) = 6.1) of the average annual precipitation (506 mm) could be retained from the surface layer assuming eastern German climate conditions, compared with a retention efficiency between 79 and 82% for a mineral soil. Although a MBP layer in conjunction with water-consumptive trees can reduce vertical water losses as compared to mineral substrates, the effect is not sufficient to meet legal regulations. PMID:17985666

  7. Enhancing the mechanical properties of cement paste by growing in-situ fiber reinforcement during hydration

    NASA Astrophysics Data System (ADS)

    Constantinides, Margarita

    Efforts to improve the mechanical properties of concrete by modifying the cement paste matrix have focused entirely on strength enhancement. But the intrinsic brittleness of the cement paste matrix limits the possible improvement in the mechanical properties of concrete, and in particular the toughness of the material. Increasing the toughness of the cement paste matrix could lead to a reduction in flaw sensitivity by delaying unstable crack propagation. Consequently, the resistance of the material to cracking due to drying shrinkage, thermal shrinkage, expansive deterioration processes, and applied loads could increase considerably. The goal of this study was to grow in-situ fiber reinforcement in cement paste, a technique never before applied to cement-based materials, to enhance the toughness of the material. Ettringite, an existing, fiber-like hydration product was selected as the fiber reinforcement. Ettringite met all the necessary criteria to act as reinforcement in cement paste: adequate distribution in the matrix; adjustable volume fraction, aspect ratio and size; high stiffness along the fiber length; and finally compatibility with existing hydration products. Alkali-free accelerators were selected as the admixtures used to grow the ettringite in the cement paste. X-ray diffraction and scanning electron microscopy experiments were performed to study the volume fraction, distribution, size, and morphology of the ettringite crystals in the cement paste matrix (both plain and accelerator-containing). Mechanical tests (compression, splitting tension, flexural, compact tension) were used to evaluate the effect of the accelerators on the strength and toughness of cement paste. Microindentations on the surface of the cement paste matrix were performed to study the morphology of the cracks and the toughening mechanisms taking place. Through the characterization tests we identified that while more ettringite forms with the addition of the alkali-free accelerators

  8. Growth mechanism for spherical carbon particles in a dc methane plasma

    SciTech Connect

    Nagai, Tatsuzo; Feng Zongbao; Kono, Akihiko; Shoji, Fumiya

    2008-05-15

    The growth mechanism for spherical carbon particles of micron sizes observed in a vertically excited CH{sub 4}/Ar columnar plasma [F. Shoji, Z. Feng, A. Kono, and T. Nagai, Appl. Phys. Lett. 89, 171504 (2006)] is investigated theoretically, based on a model in which the particles are negatively charged in the plasma sheath region where they grow by capturing graphite onions with a diameter of ca. 10 nm and a positive charge. A balance of gravity and electric force keeps the particles in the sheath region during their growth. It is found that the particle radius initially increases linearly with time and then approaches a saturation radius, and that the center of gravity of the particle executes a simple harmonic oscillation about its balance position with a characteristic frequency of the order of 10 Hz determined by its specific charge, gravity, and sheath structure.

  9. Foreign Particle Promoted Crystalline Nucleation for Growing High-Quality Ultrathin Rubrene Films.

    PubMed

    Hu, Xiaorong; Wang, Zi; Zhu, Xiaofei; Zhu, Tao; Zhang, Xiaodong; Dong, Bin; Huang, Lizhen; Chi, Lifeng

    2016-08-01

    Introducing foreign particles or agents as nucleator is an efficient way to promote crystallization in the crystal growth field, with the advantage to speed up the crystallizing rate and control the growth process. However, in the field of organic crystalline film growth, where the crystallization and morphology modulation are of significant importance in optoelectronics, this method has rarely been utilized. Particularly, some potential high-performance materials such as rubrene face the problem of crystallization during film formation. Here a strategy is reported to promote the crystallization of rubrene films in the initial stage assisted by foreign particles. Highly ordered thin film from the sub-monolayer stage can be achieved. Efficient charge transport and high mobility up to 2.95 cm(2) V(-1) s(-1) are achieved on thus ultrathin crystalline films. Such a method enables the well controlling of the film growth from the very early stage and produces uniform crystalline films with good reproducibility, thus highly promising to yield desired optoelectrical properties and applications. PMID:27335247

  10. Mechanisms and implications of air pollution particle associations with chemokines

    SciTech Connect

    Seagrave, JeanClare

    2008-11-01

    Inflammation induced by inhalation of air pollutant particles has been implicated as a mechanism for the adverse health effects associated with exposure to air pollution. The inflammatory response is associated with upregulation of various pro-inflammatory cytokines and chemokines. We have previously shown that diesel exhaust particles (DEP), a significant constituent of air pollution particulate matter in many urban areas, bind and concentrate IL-8, an important human neutrophil-attracting chemokine, and that the chemokine remains biologically active. In this report, we examine possible mechanisms of this association and the effects on clearance of the chemokine. The binding appears to be the result of ionic interactions between negatively charged particles and positively charged chemokine molecules, possibly combined with intercalation into small pores in the particles. The association is not limited to diesel exhaust particles and IL-8: several other particle types also adsorb the chemokine and several other cytokines are adsorbed onto the diesel particles. However, there are wide ranges in the effectiveness of various particle types and various cytokines. Finally, male Fisher 344 rats were intratracheally instilled with chemokine alone or combined with diesel exhaust or silica particles under isofluorane anesthesia. In contrast to silica particles, which do not bind the chemokine, the presence of diesel exhaust particles, which bind the chemokine, prolonged the retention of the chemokine.

  11. Morphological and Chemical Mechanisms of Elongated Mineral Particle Toxicities

    EPA Science Inventory

    Much of our understanding regarding the mechanisms for induction of disease following inhalation of respirable elongated mineral particles (REMPs) is based on studies involving the biological effects of asbestos fibers. The factors governing the disease potential of an exposure i...

  12. Quantum mechanics emerging from stochastic dynamics of virtual particles

    NASA Astrophysics Data System (ADS)

    Tsekov, Roumen

    2016-03-01

    It is shown how quantum mechanics emerges from the stochastic dynamics of force carriers. It is demonstrated that the Moyal equation corresponds to dynamic correlations between the real particle momentum and the virtual particle position, which are not present in classical mechanics. This new concept throws light on the physical meaning of quantum theory, showing that the Planck constant square is a second-second position-momentum cross-cumulant.

  13. Dietary restriction does not adversely affect bone geometry and mechanics in rapidly growing male wistar rats.

    PubMed

    Lambert, Jennifer; Lamothe, Jeremy M; Zernicke, Ronald F; Auer, Roland N; Reimer, Raylene A

    2005-02-01

    The present study assessed the effects of dietary restriction on tibial and vertebral mechanical and geometrical properties in 2-mo-old male Wistar rats. Two-month-old male Wistar rats were randomized to the ad libitum (n=8) or the 35% diet-restricted (DR) feeding group (n=9) for 5 mo. Tibiae and L6 vertebrae were dissected out for microcomputed tomography (microCT) scanning and subsequently fractured in biomechanical testing to determine geometrical and mechanical properties. The DR group had significantly lower mean tibial length, mass, area, and cross-sectional moment of inertia, as well as vertebral energy to maximal load. After adjustment for body mass, however, DR tibial mean maximal load and stiffness, and DR vertebral area, height, volume, and maximal load were significantly greater, relative to ad libitum means. No significant differences were found between the DR and ad libitum mineral ash fractions. Because the material properties of the tibiae between the two groups were not significantly different, presumably the material integrity of the bones was not adversely affected as a consequence of DR. The similar material characteristics were consistent with mineral ash fractions that were not different between the two groups. Vertebral maximal load and stiffness were not significant between the DR and ad libitum animals. Importantly, we show that a level of dietary restriction (35%) that is less severe than many studies (40%), and without micronutrient compensation does not adversely affect tibial and vertebral mechanical properties in young growing male rats when normalized for body mass. PMID:15585686

  14. Analyses of the involvement of PKA regulation mechanism in meiotic incompetence of porcine growing oocytes.

    PubMed

    Nishimura, Takanori; Fujii, Wataru; Kano, Kiyoshi; Sugiura, Koji; Naito, Kunihiko

    2012-09-01

    Mammalian growing oocytes (GOs) lack the ability to resume meiosis, although the molecular mechanism of this limitation is not fully understood. In the present study, we cloned cDNAs of cAMP-dependent protein-kinase (PKA) subunits from porcine oocytes and analyzed the involvement of the PKA regulation mechanism in the meiotic incompetence of GOs at the molecular level. We found a cAMP-independent high PKA activity in GOs throughout the in vitro culture using a porcine PKA assay system we established, and inhibition of the activity by injection of the antisense RNA of the PKA catalytic subunit (PKA-C) induced meiotic resumption in GOs. Then we examined the possibility that the amount of the PKA regulatory subunit (PKA-R), which can bind and inhibit PKA-C, was insufficient to suppress PKA activity in GOs because of the overexpression of two PKA-Rs, PRKAR1A and PRKAR2A. We found that neither of them affected PKA activity and induced meiotic resumption in GO although PRKAR2A could inhibit PKA activity and induce meiosis in cAMP-treated full-grown oocytes (FGOs). Finally, we analyzed the subcellular localization of PKA subunits and found that all the subunits were localized in the cytoplasm during meiotic arrest and that PKA-C and PRKAR2A, but not PRKAR1A, entered into the nucleus just before meiotic resumption in FGOs, whereas all of them remained in the cytoplasm in GOs throughout the culture period. Our findings suggest that the continuous high PKA activity is a primary cause of the meiotic incompetence of porcine GOs and that this PKA activity is not simply caused by an insufficient expression level of PKA-R, but can be attributed to more complex spatial-temporal regulation mechanisms. PMID:22674394

  15. Adaptation and detoxification mechanisms of Vetiver grass (Chrysopogon zizanioides) growing on gold mine tailings.

    PubMed

    Melato, F A; Mokgalaka, N S; McCrindle, R I

    2016-01-01

    Vetiver grass (Chrysopogon zizanioides) was investigated for its potential use in the rehabilitation of gold mine tailings, its ability to extract and accumulate toxic metals from the tailings and its metal tolerant strategies. Vetiver grass was grown on gold mine tailings soil, in a hothouse, and monitored for sixteen weeks. The mine tailings were highly acidic and had high electrical conductivity. Vetiver grass was able to grow and adapt well on gold mine tailings. The results showed that Vetiver grass accumulated large amounts of metals in the roots and restricted their translocation to the shoots. This was confirmed by the bioconcentration factor of Zn, Cu, and Ni of >1 and the translocation factor of <1 for all the metals. This study revealed the defense mechanisms employed by Vetiver grass against metal stress that include: chelation of toxic metals by phenolics, glutathione S-tranferase, and low molecular weight thiols; sequestration and accumulation of metals within the cell wall that was revealed by the scanning electron microscopy that showed closure of stomata and thickened cell wall and was confirmed by high content of cell wall bound phenolics. Metal induced reactive oxygen species are reduced or eliminated by catalase, superoxide dismutase and peroxidase dismutase. PMID:26588814

  16. Bioaccumulation of Cu-complex reactive dye by growing pellets of Penicillium oxalicum and its mechanism.

    PubMed

    Xin, Baoping; Chen, Gang; Zheng, Wenchai

    2010-06-01

    In this paper bioaccumulation of Cu-complex reactive dye by growing pellets of Penicillium oxalicum and its mechanism was investigated. Shaking flasks experiment showed that 99.7% of dye removal at 400 mg/l was attained after 48 h contact. Column reactor experiment showed that air lift ferment tower was a suitable reactor for both pellets formation and dye bioaccumulation. Repeated inoculation of the dye-loaded pellets accelerated dye bioaccumulation, leading to complete dye removal within 12 h. Dye initially was adsorbed on surface of cell, followed by penetration into cytoplasm. During bioaccumulation, mycelium expanded unevenly and thickened locally in diameter, generating a chain of spindles along the mycelium. In addition, the cell walls grew loose and thickened remarkably, being 4-5 folds as thick as the control one. The loose cell wall may offer both dye accumulation space and route way for dye to enter cytoplasm. There were certain unknown active matters in cytoplasm, which played an important role in dye accumulation. Desorption experiments suggested that electrostatic attraction was mainly attributed to the dye bioaccumulation. PMID:20421123

  17. Novel electrodynamic trapping mechanism for neutral, polar particles

    NASA Astrophysics Data System (ADS)

    Blümel, R.

    2011-09-01

    A conceptually new trapping mechanism for neutral, polar particles is introduced and discussed. Unlike existing mechanisms that are based on oscillating saddle-point potentials or rotating electric dipole fields, the new mechanism is based on a superposition of ac and dc electric monopolefields that dynamically generate a minimum of the effective ponderomotive potential in which the particles are trapped. Extensive numerical simulations of the dynamics and the stability properties of trapped HC17N molecules and ferroelectric rods (made of barium titanate or croconic acid crystals) prove the validity of the new mechanism. The examples show that the same mechanism is applicable to the trapping of macroscopic as well as microscopic particles. The numerical results are backed by a physical pseudo-potential picture and an analytical stability analysis that provide physical insight into why and how the new mechanism works. A semi-quantum, Born-Oppenheimer-type calculation that treats the intrinsic rotational degree of freedom of HC17N quantum mechanically is also presented. A detailed discussion of engineering aspects shows that laboratory implementation of the new mechanism is within current technological reach.

  18. Particle-surface interactions in chemical mechanical polishing

    SciTech Connect

    Dugger, M.T.; Adkins, C.L.J.; Resnick, P.J.; Jeon, J.S.; Raghavan, S.

    1996-10-01

    Material removal in chemical mechanical polishing (CMP) occurs by a pressure accentuated chemical attack of the surface. The polishing slurry typically consists of abrasive particles and reactive chemicals that may or may not include an oxidant. Post-CMP cleaning processes must remove both the ionic contaminants and any remaining polishing slurry particles. Central to the effectiveness of a clean is the use of conditions that will minimize the binding force between the residual particles and the wafer surface. The morphology and composition of the particle, the surface from which it must be removed, and the environment surrounding the wafer will determine the magnitude of forces that hold a particle to the wafer surface. At the Sandia/SEMATECH Center for Contamination Free Manufacturing, two techniques--atomic force microscopy (AFM) and electrokinetic deposition--are being used to explore these interactions for CMP of both oxide and tungsten surfaces. A basic understanding of particle-surface interaction forces and how they are affected by the chemical/physical environment of the particle and surface is the objective of this task. Modification of the binding forces between particles and wafer surfaces may be used to maximize post-CMP cleaning effectiveness.

  19. Particle interaction of lubricated or unlubricated binary mixtures according to their particle size and densification mechanism.

    PubMed

    Di Martino, Piera; Joiris, Etienne; Martelli, Sante

    2004-09-01

    The aim of this study is to assess an experimental approach for technological development of a direct compression formulation. A simple formula was considered composed by an active ingredient, a diluent and a lubricant. The active ingredient and diluent were selected as an example according to their typical densification mechanism: the nitrofurantoine, a fragmenting material, and the cellulose microcrystalline (Vivapur), which is a typical visco-elastic material, equally displaying good bind and disintegrant properties. For each ingredient, samples of different particle size distribution were selected. Initially, tabletability of pure materials was studied by a rotary press without magnesium stearate. Vivapur tabletability decreases with increase in particle size. The addition of magnesium stearate as lubricant decreases tabletability of Vivapur of greater particle size, while it kept unmodified that of Vivapur of lower particle size. Differences in tabletability can be related to differences in particle-particle interactions; for Vivapur of higher particle size (Vivapur 200, 102 and 101), the lower surface area develops lower surface available for bonds, while for Vivapur of lower particle size (99 and 105) the greater surface area allows high particle proximity favouring particle cohesivity. Nitrofurantoine shows great differences in compression behaviour according to its particle size distribution. Large crystals show poorer tabletability than fine crystals, further decreased by lubricant addition. The large crystals poor tabletability is due to their poor compactibility, in spite of high compressibility and plastic intrinsic deformability; in fact, in spite of the high densification tendency, the nature of the involved bonds is very weak. Nitrofurantoine samples were then mixed with Vivapurs in different proportions. Compression behaviour of binary mixes (tabletability and compressibility) was then evaluated according to diluents proportion in the mixes. The

  20. Lagrangian dynamics for classical, Brownian, and quantum mechanical particles

    NASA Astrophysics Data System (ADS)

    Pavon, Michele

    1996-07-01

    In the framework of Nelson's stochastic mechanics [E. Nelson, Dynamical Theories of Brownian Motion (Princeton University, Princeton, 1967); F. Guerra, Phys. Rep. 77, 263 (1981); E. Nelson, Quantum Fluctuations (Princeton University, Princeton, 1985)] we seek to develop the particle counterpart of the hydrodynamic results of M. Pavon [J. Math. Phys. 36, 6774 (1995); Phys. Lett. A 209, 143 (1995)]. In particular, a first form of Hamilton's principle is established. We show that this variational principle leads to the correct equations of motion for the classical particle, the Brownian particle in thermodynamical equilibrium, and the quantum particle. In the latter case, the critical process q satisfies a stochastic Newton law. We then introduce the momentum process p, and show that the pair (q,p) satisfies canonical-like equations.

  1. Mechanical Stability and Reversible Fracture of Vault Particles

    PubMed Central

    Llauró, Aida; Guerra, Pablo; Irigoyen, Nerea; Rodríguez, José F.; Verdaguer, Núria; de Pablo, Pedro J.

    2014-01-01

    Vaults are the largest ribonucleoprotein particles found in eukaryotic cells, with an unclear cellular function and promising applications as vehicles for drug delivery. In this article, we examine the local stiffness of individual vaults and probe their structural stability with atomic force microscopy under physiological conditions. Our data show that the barrel, the central part of the vault, governs both the stiffness and mechanical strength of these particles. In addition, we induce single-protein fractures in the barrel shell and monitor their temporal evolution. Our high-resolution atomic force microscopy topographies show that these fractures occur along the contacts between two major vault proteins and disappear over time. This unprecedented systematic self-healing mechanism, which enables these particles to reversibly adapt to certain geometric constraints, might help vaults safely pass through the nuclear pore complex and potentiate their role as self-reparable nanocontainers. PMID:24507609

  2. Relativistic wave and particle mechanics formulated without classical mass

    SciTech Connect

    Fry, J.L.; Musielak, Z.E.; Chang, Trei-wen

    2011-08-15

    Highlights: > Formal derivation of the Klein-Gordon equation with an invariant frequency. > Formal derivation of the relativistic version of Newton's equation. > The classical mass is replaced by the invariant frequency. > The invariant frequencies for selected elementary particles are deduced. > The choice of natural units resulting from the developed theories is discussed. - Abstract: The fact that the concept of classical mass plays an important role in formulating relativistic theories of waves and particles is well-known. However, recent studies show that Galilean invariant theories of waves and particles can be formulated with the so-called 'wave mass', which replaces the classical mass and allows attaining higher accuracy of performing calculations [J.L. Fry and Z.E. Musielak, Ann. Phys. 325 (2010) 1194]. The main purpose of this paper is to generalize these results and formulate fundamental (Poincare invariant) relativistic theories of waves and particles without the classical mass. In the presented approach, the classical mass is replaced by an invariant frequency that only involves units of time. The invariant frequencies for various elementary particles are deduced from experiments and their relationship to the corresponding classical and wave mass for each particle is described. It is shown that relativistic wave mechanics with the invariant frequency is independent of the Planck constant, and that such theory can attain higher accuracy of performing calculations. The choice of natural units resulting from the developed theories of waves and particles is also discussed.

  3. Double Higgs mechanisms, supermassive stable particles and the vacuum energy

    NASA Astrophysics Data System (ADS)

    Santillán, Osvaldo P.; Gabbanelli, Luciano

    2016-07-01

    In the present work, a hidden scenario which cast a long-lived superheavy particle A0 and simultaneously an extremely light particle a with mass ma ˜ 10‑32-10‑33 eV is presented. The potential energy V (a) of the particle a models the vacuum energy density of the universe ρc ≃ 10‑47GeV4. On the other hand, the A0 particle may act as superheavy dark matter at present times and the products of its decay may be observed in high energy cosmic ray events. The hidden sector proposed here include light fermions with masses near the neutrino mass mν ˜ 10‑2 eV and superheavy ones with masses of the order of the GUT scale, interacting through a hidden SU(2)L interaction which also affects the ordinary sector. The construction of such combined scenario is nontrivial since the presence of light particles may spoil the stability of the heavy particle A0. However, double Higgs mechanisms may be helpful for overcoming this problem. In this context, the stability of the superheavy particle A0 is ensured due to chiral symmetry arguments elaborated in the text.

  4. Investigation of the Profile Control Mechanisms of Dispersed Particle Gel

    PubMed Central

    Zhao, Guang; Dai, Caili; Zhao, Mingwei

    2014-01-01

    Dispersed particle gel (DPG) particles of nano- to micron- to mm-size have been prepared successfully and will be used for profile control treatment in mature oilfields. The profile control and enhanced oil recovery mechanisms of DPG particles have been investigated using core flow tests and visual simulation experiments. Core flow test results show that DPG particles can easily be injected into deep formations and can effectively plug the high permeability zones. The high profile improvement rate improves reservoir heterogeneity and diverts fluid into the low permeability zone. Both water and oil permeability were reduced when DPG particles were injected, but the disproportionate permeability reduction effect was significant. Water permeability decreases more than the oil permeability to ensure that oil flows in its own pathways and can easily be driven out. Visual simulation experiments demonstrate that DPG particles can pass directly or by deformation through porous media and enter deep formations. By retention, adsorption, trapping and bridging, DPG particles can effectively reduce the permeability of porous media in high permeability zones and divert fluid into a low permeability zone, thus improving formation profiles and enhancing oil recovery. PMID:24950174

  5. Fractal dimension and mechanism of aggregation of apple juice particles.

    PubMed

    Benítez, E I; Lozano, J E; Genovese, D B

    2010-04-01

    Turbidity of freshly squeezed apple juice is produced by a polydisperse suspension of particles coming from the cellular tissue. After precipitation of coarse particles by gravity, only fine-colloidal particles remain in suspension. Aggregation of colloidal particles leads to the formation of fractal structures. The fractal dimension is a measure of the internal density of these aggregates and depends on their mechanism of aggregation. Digitized images of primary particles and aggregates of depectinized, diafiltered cloudy apple juice were obtained by scanning electron microscopy (SEM). Average radius of the primary particles was found to be a = 40 ± 11 nm. Maximum radius of the aggregates, R(L), ranged between 250 and 7750 nm. Fractal dimension of the aggregates was determined by analyzing SEM images with the variogram method, obtaining an average value of D(f) = 2.3 ± 0.1. This value is typical of aggregates formed by rapid flocculation or diffusion limited aggregation. Diafiltration process was found to reduce the average size and polydispersity of the aggregates, determined by photon correlation spectroscopy. Average gyration radius of the aggregates before juice diafiltration was found to be R(g) = 629 ± 87 nm. Average number of primary particles per aggregate was calculated to be N = 1174. PMID:21339133

  6. Empirical Research of College Students' Alternative Frameworks of Particle Mechanics

    ERIC Educational Resources Information Center

    Wang, Hongmei

    2010-01-01

    Based on the constructive theory, about 300 college students of grade 05 of the electronic information specialty of Dezhou University are surveyed for their alternative frameworks of particle mechanics in college physics in this article. In the survey, the questionnaires are used to find out college students' alternative frameworks, and the…

  7. Undergraduate Students' Preferences of Knowledge to Solve Particle Mechanics Problems

    ERIC Educational Resources Information Center

    Luneta, Kakoma; Makonye, Judah P.

    2011-01-01

    This study explores the nature of undergraduate students' errors and misconceptions in particle mechanics. This paper provides in-depth descriptions of the errors presented by students and accounts for them in terms of students' procedural or conceptual knowledge. Specifically, this study analyses students' written responses to questions on…

  8. Molecular Mechanisms of Particle Ration Induced Apoptosis in Lymphocyte

    NASA Astrophysics Data System (ADS)

    Shi, Yufang

    Space radiation, composed of high-energy charged nuclei (HZE particles) and protons, has been previously shown to severely impact immune homeostasis in mice. To determine the molecular mechanisms that mediate acute lymphocyte depletion following exposure to HZE particle radiation mice were exposed to particle radiation beams at Brookhaven National Laboratory. We found that mice given whole body 5 6Fe particle irradiation (1GeV /n) had dose-dependent losses in total lymphocyte numbers in the spleen and thymus (using 200, 100 and 50 cGy), with thymocytes being more sensitive than splenocytes. All phenotypic subsets were reduced in number. In general, T cells and B cells were equally sensitive, while CD8+ T cells were more senstive than CD4+ T cells. In the thymus, immature CD4+CD8+ double-positive thymocytes were exquisitely sensitive to radiation-induced losses, single-positive CD4 or CD8 cells were less sensitive, and the least mature double negative cells were resistant. Irradiation of mice deficient in genes encoding essential apoptosis-inducing proteins revealed that the mechanism of lymphocyte depletion is independent of Fas ligand and TRAIL (TNF-ralated apoptosis-inducing ligand), in contrast to γ-radiation-induced lymphocyte losses which require the Fas-FasL pathway. Using inhibitors in vitro, lymphocyte apoptosis induced by HZE particle radiation was found to be caspase dependent, and not involve nitric oxide or oxygen free radicals.

  9. Saltating Snow Mechanics: High Frequency Particle Response to Mountain Wind

    NASA Astrophysics Data System (ADS)

    Aksamit, N. O.; Pomeroy, J. W.

    2015-12-01

    Blowing snow transport theory is currently limited by its dependency on the coupling of time-averaged measurements of particle saltation and suspension and wind speed. Details of the stochastic process of particle transport and complex bed interactions in the saltation layer, along with the influence of boundary-layer turbulence are unobservable with classic measurement techniques. In contrast, recent advances in two-phase sand transport understanding have been spurred by development of high-frequency wind and particle velocity measurement techniques. To advance the understanding of blowing snow, laser illuminated high-speed videography and ultrasonic anemometry were deployed in a mountain environment to examine saltation of snow over a natural snowpack in detail. A saltating snow measurement site was established at the Fortress Mountain Snow Laboratory, Alberta, Canada and instrumented with two Campbell CSAT3 ultrasonic anemometers, four Campbell SR50 ultrasonic snow depth sounders and a two dimensional Particle Tracking Velocimetry (PTV) system. Measurements were collected during nighttime blowing snow events, quantifying snow particle response to high frequency wind gusts. This novel approach permits PTV to step beyond mean statistics of snow transport by identifying sub-species of saltation motion in the first 20 mm above the surface, as well as previously overlooked initiation processes, such as tumbling aggregate snow crystals ejecting smaller grains, then eventually disintegrating and bouncing into entrainment. Spectral characteristics of snow particle ejection and saltation dynamics were also investigated. These unique observations are starting to inform novel conceptualizations of saltating snow transport mechanisms.

  10. Freestanding 3D supramolecular particle bridges: fabrication and mechanical behavior.

    PubMed

    Ling, Xing Yi; Phang, In Yee; Schönherr, Holger; Reinhoudt, David N; Vancso, G Julius; Huskens, Jurriaan

    2009-06-01

    Freestanding particle bridges with controlled composition and macroscopic robustness are demonstrated by the use of supramolecular nanoparticle assembly. Self-assembly of nanoparticles, templating, and supramolecular glue infiltration are combined to form stable and ordered three-dimensional polystyrene particle composites on a polydimethylsiloxane stamp. Freestanding hybrid polystyrene nanoparticle bridges are obtained by transfer printing of the hybrid structures onto topographically patterned substrates via host-guest interactions. The mechanical robustness and rigidity of the particle bridges can be controlled by manipulating the layer-by-layer cycles of supramolecular glues of gold nanoparticles and dendrimers. Atomic force microscopy-based microbending results, in particular the location and force-dependent deflection behavior, confirm that the particle bridge fulfills the classical supported-beam characteristics. As estimated from classical beam theory, the bending moduli of the particle bridges vary between 0.8 and 1.1 GPa, depending on the degree of filling by the supramolecular glues. Failure analysis on the particle structure indicates linear elastic behavior and a plastic deformation upon failure. PMID:19373830

  11. Mechanisms of Particle Charging by Surfactants in Nonpolar Dispersions.

    PubMed

    Lee, Joohyung; Zhou, Zhang-Lin; Alas, Guillermo; Behrens, Sven Holger

    2015-11-10

    Electric charging of colloidal particles in nonpolar solvents plays a crucial role for many industrial applications and products, including rubbers, engine oils, toners, or electronic displays. Although disfavored by the low solvent permittivity, particle charging can be induced by added surfactants, even nonionic ones, but the underlying mechanism is poorly understood, and neither the magnitude nor the sign of charge can generally be predicted from the particle and surfactant properties. The conclusiveness of scientific studies has been limited partly by a traditional focus on few surfactant types with many differences in their chemical structure and often poorly defined composition. Here we investigate the surface charging of poly(methyl methacrylate) particles dispersed in hexane-based solutions of three purified polyisobutylene succinimide polyamine surfactants with "subtle" structural variations. We precisely vary the surfactant chemistry by replacing only a single electronegative atom located at a fixed position within the polar headgroup. Electrophoresis reveals that these small differences between the surfactants lead to qualitatively different particle charging. In the respective particle-free surfactant solutions we also find potentially telling differences in the size of the surfactant aggregates (inverse micelles), the residual water content, and the electric solution conductivity as well as indications for a significant size difference between oppositely charged inverse micelles of the most hygroscopic surfactant. An analysis that accounts for the acid/base properties of all constituents suggests that the observed particle charging is better described by asymmetric adsorption of charged inverse micelles from the liquid bulk than by charge creation at the particle surface. Intramicellar acid-base interaction and intermicellar surfactant exchange help rationalize the formation of micellar ions pairs with size asymmetry. PMID:26484617

  12. Dynamics and mechanics of bed-load tracer particles

    NASA Astrophysics Data System (ADS)

    Phillips, C. B.; Jerolmack, D. J.

    2014-12-01

    Understanding the mechanics of bed load at the flood scale is necessary to link hydrology to landscape evolution. Here we report on observations of the transport of coarse sediment tracer particles in a cobble-bedded alluvial river and a step-pool bedrock tributary, at the individual flood and multi-annual timescales. Tracer particle data for each survey are composed of measured displacement lengths for individual particles, and the number of tagged particles mobilized. For single floods we find that measured tracer particle displacement lengths are exponentially distributed; the number of mobile particles increases linearly with peak flood Shields stress, indicating partial bed load transport for all observed floods; and modal displacement distances scale linearly with excess shear velocity. These findings provide quantitative field support for a recently proposed modeling framework based on momentum conservation at the grain scale. Tracer displacement is weakly negatively correlated with particle size at the individual flood scale; however cumulative travel distance begins to show a stronger inverse relation to grain size when measured over many transport events. The observed spatial sorting of tracers approaches that of the river bed, and is consistent with size-selective deposition models and laboratory experiments. Tracer displacement data for the bedrock and alluvial channels collapse onto a single curve - despite more than an order of magnitude difference in channel slope - when variations of critical Shields stress and flow resistance between the two are accounted for. Results show how bed load dynamics may be predicted from a record of river stage, providing a direct link between climate and sediment transport.

  13. Unstable particles in non-relativistic quantum mechanics?

    SciTech Connect

    Hernandez-Coronado, H.

    2011-10-14

    The Schroedinger equation is up-to-a-phase invariant under the Galilei group. This phase leads to the Bargmann's superselection rule, which forbids the existence of the superposition of states with different mass and implies that unstable particles cannot be described consistently in non-relativistic quantum mechanics (NRQM). In this paper we claim that Bargmann's rule neglects physical effects and that a proper description of non-relativistic quantum mechanics requires to take into account this phase through the Extended Galilei group and the definition of its action on spacetime coordinates.

  14. Spacetime alternatives in the quantum mechanics of a relativistic particle

    SciTech Connect

    Whelan, J.T. Isaac Newton Institute for Mathematical Sciences, 20 Clarkson Road, Cambridge, CB3 0EH )

    1994-11-15

    Hartle's generalized quantum mechanics formalism is used to examine spacetime coarse grainings, i.e., sets of alternatives defined with respect to a region extended in time as well as space, in the quantum mechanics of a free relativistic particle. For a simple coarse graining and suitable initial conditions, tractable formulas are found for branch wave functions. Despite the nonlocality of the positive-definite version of the Klein-Gordon inner product, which means that nonoverlapping branches are not sufficient to imply decoherence, some initial conditions are found to give decoherence and allow the consistent assignment of probabilities.

  15. Particle Size Concentration Distribution and Influences on Exhaled Breath Particles in Mechanically Ventilated Patients

    PubMed Central

    Chen, Yi-Fang; Huang, Sheng-Hsiu; Wang, Yu-Ling; Chen, Chun-Wan

    2014-01-01

    Humans produce exhaled breath particles (EBPs) during various breath activities, such as normal breathing, coughing, talking, and sneezing. Airborne transmission risk exists when EBPs have attached pathogens. Until recently, few investigations had evaluated the size and concentration distributions of EBPs from mechanically ventilated patients with different ventilation mode settings. This study thus broke new ground by not only evaluating the size concentration distributions of EBPs in mechanically ventilated patients, but also investigating the relationship between EBP level and positive expiratory end airway pressure (PEEP), tidal volume, and pneumonia. This investigation recruited mechanically ventilated patients, with and without pneumonia, aged 20 years old and above, from the respiratory intensive care unit of a medical center. Concentration distributions of EBPs from mechanically ventilated patients were analyzed with an optical particle analyzer. This study finds that EBP concentrations from mechanically ventilated patients during normal breathing were in the range 0.47–2,554.04 particles/breath (0.001–4.644 particles/mL). EBP concentrations did not differ significantly between the volume control and pressure control modes of the ventilation settings in the mechanically ventilated patients. The patient EBPs were sized below 5 µm, and 80% of them ranged from 0.3 to 1.0 µm. The EBPs concentrations in patients with high PEEP (> 5 cmH2O) clearly exceeded those in patients with low PEEP (≤ 5 cmH2O). Additionally, a significant negative association existed between pneumonia duration and EBPs concentration. However, tidal volume was not related to EBPs concentration. PMID:24475230

  16. Fluid Mechanics of Inertial Particle-Laden Flow

    NASA Astrophysics Data System (ADS)

    Gharaghieh, Hamed Haddadi

    This work addresses the role of particle scale inertia on the motion of hard spherical particles suspended in a Newtonian fluid. We have utilized lattice-Boltzmann method to solve for the motion of particles in the fluid. The particles in the suspension are neutrally buoyant; therefore, a same level of inertia is carried by solid and liquid phase. In the first phase, the microstructure and rheological properties of suspensions are studied. The suspensions are subjected to simple shear flow and the properties are studied as a function of Reynolds number. The flow-induced microstructure is studied using the pair distribution function. Different stress mechanisms, including those due to surface tractions (stresslet), acceleration, and the Reynolds stress due to velocity fluctuations are computed and their influence on the first and second normal stress differences, the particle pressure and the viscosity of the suspensions are detailed. The probability density functions of linear and angular accelerations are also presented. Next, we present our results on the topology of particle pair trajectories. The pair relative trajectory is studied both for pairs which are isolated and for pairs in suspension of large solid fractions. For the suspension, the average trajectory and aspects of its dispersion are considered. The pair trajectories in a dilute inertial suspension have the same basic features as the streamlines around an isolated particle at similar Re, with reversing, in-plane and off-plane spiraling, and open but fore-aft asymmetric trajectories. The origin of the off-plane spirals is examined in detail, and the zone of these spirals is found to become smaller with increasing Re. The average pair trajectory space in a suspension of finite volume fraction is found to be qualitatively similar to the dilute suspension pair trajectories, as the spiraling and reversing zones are retained; the influence of volume fraction and Re on the extension of the different zones is

  17. Mechanics of invagination and folding: Hybridized instabilities when one soft tissue grows on another

    NASA Astrophysics Data System (ADS)

    Tallinen, Tuomas; Biggins, John S.

    2015-08-01

    We address the folding induced by differential growth in soft layered solids via an elementary model that consists of a soft growing neo-Hookean elastic layer adhered to a deep elastic substrate. As the layer-to-substrate modulus ratio is varied from above unity toward zero, we find a first transition from supercritical smooth folding followed by cusping of the valleys to direct subcritical cusped folding, then another to supercritical cusped folding. Beyond threshold, the high-amplitude fold spacing converges to about four layer thicknesses for many modulus ratios. In three dimensions, the instability gives rise to a wide variety of morphologies, including almost degenerate zigzag and triple-junction patterns that can coexist when the layer and substrate are of comparable softness. Our study unifies these results providing understanding for the complex and diverse fold morphologies found in biology, including the zigzag precursors to intestinal villi, and disordered zigzags and triple junctions in mammalian cortex.

  18. In-situ characterisation of the dynamics of a growing dust particle cloud in a direct-current argon glow discharge

    NASA Astrophysics Data System (ADS)

    Barbosa, S.; Couëdel, L.; Arnas, C.; Kishor Kumar, K.; Pardanaud, C.; Onofri, F. R. A.

    2016-02-01

    The growth and the dynamics of a tungsten nanoparticle cloud were investigated in a direct-current low pressure argon glow discharge. Real-time analyses of the dust particle size and number concentration were performed in-situ by light extinction spectrometry, while spatial dynamics of the cloud was investigated with the laser light-sheet scattering method. Additional off-line electron microscopy and Raman spectroscopy measurements were also performed for comparison purpose. This experimental work reveals the existence of an agglomeration phase followed by the appearance of a new dust particle generation. While growing, the dust cloud is pushed towards the anode and the discharge edge. Afterwards, a new dust particle generation can grow in the space freed by the first generation of nanoparticles. The continuous growth, below the light extinction spectrometry scanning positions, explains the apparent dissimilarities observed between the in-line optical and the off-line electron microscopy analyses.

  19. Morphological and Chemical Mechanisms of Elongated Mineral Particle Toxicities

    PubMed Central

    Aust, Ann E.; Cook, Philip M.; Dodson, Ronald F.

    2011-01-01

    Much of our understanding regarding the mechanisms for induction of disease following inhalation of respirable elongated mineral particles (REMP) is based on studies involving the biological effects of asbestos fibers. The factors governing the disease potential of an exposure include duration and frequency of exposures; tissue-specific dose over time; impacts on dose persistence from in vivo REMP dissolution, comminution, and clearance; individual susceptibility; and the mineral type and surface characteristics. The mechanisms associated with asbestos particle toxicity involve two facets for each particle's contribution: (1) the physical features of the inhaled REMP, which include width, length, aspect ratio, and effective surface area available for cell contact; and (2) the surface chemical composition and reactivity of the individual fiber/elongated particle. Studies in cell-free systems and with cultured cells suggest an important way in which REMP from asbestos damage cellular molecules or influence cellular processes. This may involve an unfortunate combination of the ability of REMP to chemically generate potentially damaging reactive oxygen species, through surface iron, and the interaction of the unique surfaces with cell membranes to trigger membrane receptor activation. Together these events appear to lead to a cascade of cellular events, including the production of damaging reactive nitrogen species, which may contribute to the disease process. Thus, there is a need to be more cognizant of the potential impact that the total surface area of REMP contributes to the generation of events resulting in pathological changes in biological systems. The information presented has applicability to inhaled dusts, in general, and specifically to respirable elongated mineral particles. PMID:21534085

  20. Particle-production mechanism in relativistic heavy-ion collisions

    SciTech Connect

    Bush, B.W.; Nix, J.R.

    1994-07-01

    We discuss the production of particles in relativistic heavy-ion collisions through the mechanism of massive bremsstrahlung, in which massive mesons are emitted during rapid nucleon acceleration. This mechanism is described within the framework of classical hadrodynamics for extended nucleons, corresponding to nucleons of finite size interacting with massive meson fields. This new theory provides a natural covariant microscopic approach to relativistic heavy-ion collisions that includes automatically spacetime nonlocality and retardation, nonequilibrium phenomena, interactions among all nucleons, and particle production. Inclusion of the finite nucleon size cures the difficulties with preacceleration and runaway solutions that have plagued the classical theory of self-interacting point particles. For the soft reactions that dominate nucleon-nucleon collisions, a significant fraction of the incident center-of-mass energy is radiated through massive bremsstrahlung. In the present version of the theory, this radiated energy is in the form of neutral scalar ({sigma}) and neutral vector ({omega}) mesons, which subsequently decay primarily into pions with some photons also. Additional meson fields that are known to be important from nucleon-nucleon scattering experiments should be incorporated in the future, in which case the radiated energy would also contain isovector pseudoscalar ({pi}{sup +}, {pi}{sup {minus}}, {pi}{sup 0}), isovector scalar ({delta}{sup +}, {delta}{sup {minus}}, {delta}{sup 0}), isovector vector ({rho}{sup +}, {rho}{sup {minus}}, {rho}{sup 0}), and neutral pseudoscalar ({eta}) mesons.

  1. Effect of Particle Shape on Mechanical Behaviors of Rocks: A Numerical Study Using Clumped Particle Model

    PubMed Central

    Rong, Guan; Liu, Guang; Zhou, Chuang-bing

    2013-01-01

    Since rocks are aggregates of mineral particles, the effect of mineral microstructure on macroscopic mechanical behaviors of rocks is inneglectable. Rock samples of four different particle shapes are established in this study based on clumped particle model, and a sphericity index is used to quantify particle shape. Model parameters for simulation in PFC are obtained by triaxial compression test of quartz sandstone, and simulation of triaxial compression test is then conducted on four rock samples with different particle shapes. It is seen from the results that stress thresholds of rock samples such as crack initiation stress, crack damage stress, and peak stress decrease with the increasing of the sphericity index. The increase of sphericity leads to a drop of elastic modulus and a rise in Poisson ratio, while the decreasing sphericity usually results in the increase of cohesion and internal friction angle. Based on volume change of rock samples during simulation of triaxial compression test, variation of dilation angle with plastic strain is also studied. PMID:23997677

  2. Fluctuating Nonlinear Spring Model of Mechanical Deformation of Biological Particles.

    PubMed

    Kononova, Olga; Snijder, Joost; Kholodov, Yaroslav; Marx, Kenneth A; Wuite, Gijs J L; Roos, Wouter H; Barsegov, Valeri

    2016-01-01

    The mechanical properties of virus capsids correlate with local conformational dynamics in the capsid structure. They also reflect the required stability needed to withstand high internal pressures generated upon genome loading and contribute to the success of important events in viral infectivity, such as capsid maturation, genome uncoating and receptor binding. The mechanical properties of biological nanoparticles are often determined from monitoring their dynamic deformations in Atomic Force Microscopy nanoindentation experiments; but a comprehensive theory describing the full range of observed deformation behaviors has not previously been described. We present a new theory for modeling dynamic deformations of biological nanoparticles, which considers the non-linear Hertzian deformation, resulting from an indenter-particle physical contact, and the bending of curved elements (beams) modeling the particle structure. The beams' deformation beyond the critical point triggers a dynamic transition of the particle to the collapsed state. This extreme event is accompanied by a catastrophic force drop as observed in the experimental or simulated force (F)-deformation (X) spectra. The theory interprets fine features of the spectra, including the nonlinear components of the FX-curves, in terms of the Young's moduli for Hertzian and bending deformations, and the structural damage dependent beams' survival probability, in terms of the maximum strength and the cooperativity parameter. The theory is exemplified by successfully describing the deformation dynamics of natural nanoparticles through comparing theoretical curves with experimental force-deformation spectra for several virus particles. This approach provides a comprehensive description of the dynamic structural transitions in biological and artificial nanoparticles, which is essential for their optimal use in nanotechnology and nanomedicine applications. PMID:26821264

  3. Fluctuating Nonlinear Spring Model of Mechanical Deformation of Biological Particles

    PubMed Central

    Kononova, Olga; Snijder, Joost; Kholodov, Yaroslav; Marx, Kenneth A.; Wuite, Gijs J. L.; Roos, Wouter H.; Barsegov, Valeri

    2016-01-01

    The mechanical properties of virus capsids correlate with local conformational dynamics in the capsid structure. They also reflect the required stability needed to withstand high internal pressures generated upon genome loading and contribute to the success of important events in viral infectivity, such as capsid maturation, genome uncoating and receptor binding. The mechanical properties of biological nanoparticles are often determined from monitoring their dynamic deformations in Atomic Force Microscopy nanoindentation experiments; but a comprehensive theory describing the full range of observed deformation behaviors has not previously been described. We present a new theory for modeling dynamic deformations of biological nanoparticles, which considers the non-linear Hertzian deformation, resulting from an indenter-particle physical contact, and the bending of curved elements (beams) modeling the particle structure. The beams’ deformation beyond the critical point triggers a dynamic transition of the particle to the collapsed state. This extreme event is accompanied by a catastrophic force drop as observed in the experimental or simulated force (F)-deformation (X) spectra. The theory interprets fine features of the spectra, including the nonlinear components of the FX-curves, in terms of the Young’s moduli for Hertzian and bending deformations, and the structural damage dependent beams’ survival probability, in terms of the maximum strength and the cooperativity parameter. The theory is exemplified by successfully describing the deformation dynamics of natural nanoparticles through comparing theoretical curves with experimental force-deformation spectra for several virus particles. This approach provides a comprehensive description of the dynamic structural transitions in biological and artificial nanoparticles, which is essential for their optimal use in nanotechnology and nanomedicine applications. PMID:26821264

  4. Mechanical Properties of Murine Leukemia Virus Particles: Effect of Maturation

    PubMed Central

    Kol, Nitzan; Gladnikoff, Micha; Barlam, David; Shneck, Roni Z.; Rein, Alan; Rousso, Itay

    2006-01-01

    After budding from the host cell, retroviruses undergo a process of internal reorganization called maturation, which is prerequisite to infectivity. Viral maturation is accompanied by dramatic morphological changes, which are poorly understood in physical/mechanistic terms. Here, we study the mechanical properties of live mature and immature murine leukemia virus particles by indentation-type experiments conducted with an atomic force microscope tip. We find that both mature and immature particles have an elastic shell. Strikingly, the virus shell is twofold stiffer in the immature (0.68 N/m) than the mature (0.31 N/m) form. However, finite-element simulation shows that the average Young's modulus of the immature form is more than fourfold lower than that of the mature form. This finding suggests that per length unit, the protein-protein interactions in the mature shell are stronger than those in the immature shell. We also show that the mature virus shell is brittle, since it can be broken by application of large loading forces, by firm attachment to a substrate, or by repeated application of force. Our results are the first analysis of the mechanical properties of an animal virus, and demonstrate a linkage between virus morphology and mechanical properties. PMID:16632508

  5. Ambient particle inhalation and the cardiovascular system: potential mechanisms.

    PubMed Central

    Donaldson, K; Stone, V; Seaton, A; MacNee, W

    2001-01-01

    Well-documented air pollution episodes throughout recent history have led to deaths among individuals with cardiovascular and respiratory disease. Although the components of air pollution that cause the adverse health effects in these individuals are unknown, a small proportion by mass but a large proportion by number of the ambient air particles are ultrafine, i.e., less than 100 nm in diameter. This ultrafine component of particulate matter with a mass median aerodynamic diameter less than 10 microm (PM(10) may mediate some of the adverse health effects reported in epidemiologic studies and for which there is toxicologic evidence to support this contention. The exact mechanism by which ultrafine particles have adverse effects is unknown, but these particles have recently been shown to enhance calcium influx on contact with macrophages. Oxidative stress is also to be anticipated at the huge particle surface; this can be augmented by oxidants generated by recruited inflammatory leukocytes. Atheromatous plaques form in the coronary arteries and are major causes of morbidity and death associated epidemiologically with particulate air pollution. In populations exposed to air pollution episodes, blood viscosity, fibrinogen, and C-reactive protein (CRP) were higher. More recently, increases in heart rate in response to rising air pollution have been described and are most marked in individuals who have high blood viscosity. In our study of elderly individuals, there were significant rises in CRP, an index of inflammation. In this present review, we consider the likely interactions between the ultrafine particles the acute phase response and cardiovascular disease. PMID:11544157

  6. Mechanical properties of growing melanocytic nevi and the progression to melanoma

    NASA Astrophysics Data System (ADS)

    Taloni, Alessandro; Alemi, Alexander; Ciusani, Emilio; Sethna, James P.; Zapperi, Stefano; La Porta, Caterina A. M.; National Research Council Of Italy Team; Lassp, Department Of Physics, Cornell University Team; Istituto Neurologico Carlo Besta Collaboration; Department Of Biosciences, University Of Milano Team

    2015-03-01

    Melanocytic nevi are benign proliferations that sometimes turn into malignant melanoma in a way that is still unclear from the biochemical and genetic point of view. Diagnostic and prognostic tools are then mostly based on dermoscopic examination and morphological analysis of histological tissues. To investigate the role of mechanics and geometry in the morpholgical dynamics of melanocytic nevi, we present a computational model for cell proliferation in a layered non-linear elastic tissue. Our simulations show that the morphology of the nevus is correlated to the initial location of the proliferating cell starting the growth process and to the mechanical properties of the tissue. We also demonstrate that melanocytes are subject to compressive stresses that fluctuate widely in the nevus and depend on the growth stage. Numerical simulations of cells in the epidermis releasing matrix metalloproteinases display an accelerated invasion of the dermis by destroying the basal membrane. Moreover, we show experimentally that osmotic stress and collagen inhibit growth in primary melanoma cells while the effect is much weaker in metastatic cells.

  7. Chaos in the test particle eccentric Kozai-Lidov mechanism

    SciTech Connect

    Li, Gongjie; Naoz, Smadar; Holman, Matt; Loeb, Abraham

    2014-08-20

    The Kozai-Lidov mechanism can be applied to a vast variety of astrophysical systems involving hierarchical three-body systems. Here, we study the Kozai-Lidov mechanism systematically in the test particle limit at the octupole level of approximation. We investigate the chaotic and quasi-periodic orbital evolution by studying the surfaces of section and the Lyapunov exponents. We find that the resonances introduced by the octupole level of approximation cause orbits to flip from prograde to retrograde and back as well as cause significant eccentricity excitation, and chaotic behavior occurs when the mutual inclination between the inner and the outer binary is high. We characterize the parameter space that allows large amplitude oscillations in eccentricity and inclination.

  8. A signed particle formulation of non-relativistic quantum mechanics

    SciTech Connect

    Sellier, Jean Michel

    2015-09-15

    A formulation of non-relativistic quantum mechanics in terms of Newtonian particles is presented in the shape of a set of three postulates. In this new theory, quantum systems are described by ensembles of signed particles which behave as field-less classical objects which carry a negative or positive sign and interact with an external potential by means of creation and annihilation events only. This approach is shown to be a generalization of the signed particle Wigner Monte Carlo method which reconstructs the time-dependent Wigner quasi-distribution function of a system and, therefore, the corresponding Schrödinger time-dependent wave-function. Its classical limit is discussed and a physical interpretation, based on experimental evidences coming from quantum tomography, is suggested. Moreover, in order to show the advantages brought by this novel formulation, a straightforward extension to relativistic effects is discussed. To conclude, quantum tunnelling numerical experiments are performed to show the validity of the suggested approach.

  9. Biophysical mechanisms of trichloroethene uptake and loss in baldcypress growing in shallow contaminated groundwater

    USGS Publications Warehouse

    Nietch, C.T.; Morris, J.T.; Vroblesky, D.A.

    1999-01-01

    Wetland vegetation may be useful in the remediation of shallow contaminated aquifers. Mesocosm experiments were conducted to describe the regulatory mechanisms affecting trichloroethene (TCE) removal rates from groundwater by flood-adapted wetland trees at a contaminated site. TCE flux through baldcypress [Taxodium distichum (L) Rich] seedlings grown in glass- carboys decreased from day to night and from August to December. The diel fluctuation coincided with changes in leaf-level physiology, as the daytime flux was significantly correlated with net photosynthesis but not with respiration at night. A decrease in seedling water use from summer to winter explained the large seasonal difference in TCE flux. A simple model that simulates gas-phase diffusion through aerenchyma tested the importance of diffusion of TCE vapor from roots to the stem. The modeled diffusive flux was within 64% of the observed value during the winter but could only explain 8% of the summer flux. Seedling water use was a good estimator of flux during the summer. Hence, evapotranspiration (ET) in the summer may serve as a good predictor for the potential of TCE removal by baldcypress trees, while diffusive flux may better approximate potential contaminant loss in the winter.Wetland vegetation may be useful in the remediation of shallow contaminated aquifers. Mesocosm experiments were conducted to describe the regulatory mechanisms affecting trichloroethene (TCE) removal rates from groundwater by flood-adapted wetland trees at a contaminated site. TCE flux through baldcypress [Taxodium distichum (L) Rich] seedlings grown in glass-carboys decreased from day to night and from August to December. The diel fluctuation coincided with changes in leaf-level physiology, as the daytime flux was significantly correlated with net photosynthesis but not with respiration at night. A decrease in seedling water use from summer to winter explained the large seasonal difference in TCE flux. A simple model that

  10. Self-assembled light lanthanide oxalate architecture with controlled morphology, characterization, growing mechanism and optical property

    SciTech Connect

    He, Hongmei; Zhang, Youjin; Zhu, Wei; Zheng, Ao

    2011-10-15

    Highlights: {yields} Flower-like Sm{sub 2}(C{sub 2}O{sub 4}){sub 3}.10H{sub 2}O was gained with Na{sub 3}Cit assisted precipitation method. {yields} The mechanism of the flower-like Sm{sub 2}(C{sub 2}O{sub 4}){sub 3}.10H{sub 2}O formation was proposed. {yields} The Sm{sub 2}(C{sub 2}O{sub 4}){sub 3}.10H{sub 2}O and Sm{sub 2}O{sub 3} samples exhibited obviously different PL spectra. {yields} Ln{sub 2}(C{sub 2}O{sub 4}){sub 3}.nH{sub 2}O (Ln = Gd, Dy, Lu, Y) also were achieved by the simple method. -- Abstract: Flower-like Sm{sub 2}(C{sub 2}O{sub 4}){sub 3}.10H{sub 2}O had been synthesized by a facile complex agent assisted precipitation method. The flower-like Sm{sub 2}(C{sub 2}O{sub 4}){sub 3}.10H{sub 2}O was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, thermogravimetry-differential thermal analysis and photoluminescence. The possible growth mechanism of the flower-like Sm{sub 2}(C{sub 2}O{sub 4}){sub 3}.10H{sub 2}O was proposed. To extend this method, other Ln{sub 2}(C{sub 2}O{sub 4}){sub 3}.nH{sub 2}O (Ln = Gd, Dy, Lu, Y) with different morphologies also had been prepared by adjusting different rare earth precursors. Further studies revealed that besides the reaction conditions and the additive amount of complex agents, the morphologies of the as-synthesised lanthanide oxalates were also determined by the rare earth ions. The Sm{sub 2}(C{sub 2}O{sub 4}){sub 3}.10H{sub 2}O and Sm{sub 2}O{sub 3} samples exhibited different photoluminescence spectra, which was relevant to Sm{sup 3+} energy level structure of 4f electrons. The method may be applied in the synthesis of other lanthanide compounds, and the work could explore the potential optical materials.

  11. Hydrodynamic mechanisms of cell and particle trapping in microfluidics

    PubMed Central

    Karimi, A.; Yazdi, S.; Ardekani, A. M.

    2013-01-01

    Focusing and sorting cells and particles utilizing microfluidic phenomena have been flourishing areas of development in recent years. These processes are largely beneficial in biomedical applications and fundamental studies of cell biology as they provide cost-effective and point-of-care miniaturized diagnostic devices and rare cell enrichment techniques. Due to inherent problems of isolation methods based on the biomarkers and antigens, separation approaches exploiting physical characteristics of cells of interest, such as size, deformability, and electric and magnetic properties, have gained currency in many medical assays. Here, we present an overview of the cell/particle sorting techniques by harnessing intrinsic hydrodynamic effects in microchannels. Our emphasis is on the underlying fluid dynamical mechanisms causing cross stream migration of objects in shear and vortical flows. We also highlight the advantages and drawbacks of each method in terms of throughput, separation efficiency, and cell viability. Finally, we discuss the future research areas for extending the scope of hydrodynamic mechanisms and exploring new physical directions for microfluidic applications. PMID:24404005

  12. Alveolar macrophage cytokine response to air pollution particles: Oxidant mechanisms

    SciTech Connect

    Imrich, Amy; Ning Yaoyu; Lawrence, Joy; Coull, Brent; Gitin, Elena; Knutson, Mitchell; Kobzik, Lester . E-mail: lkobzik@hsph.harvard.edu

    2007-02-01

    Alveolar macrophages (AMs) primed with LPS and treated with concentrated ambient air particles (CAPs) showed enhanced release of tumor necrosis factor (TNF) and provide an in vitro model for the amplified effects of air pollution particles seen in people with preexisting lung disease. To investigate the mechanism(s) by which CAPs mediate TNF release in primed rat AMs, we first tested the effect of a panel of antioxidants. N-Acetyl-L-cysteine (20 mM), dimethyl thiourea (20 mM) and catalase (5 {mu}M) significantly inhibited TNF release by primed AMs incubated with CAPs. Conversely, when LPS-primed AMs were treated with CAPs in the presence of exogenous oxidants (H{sub 2}O{sub 2} generated by glucose oxidase, 10 {mu}M/h), TNF release and cell toxicity was significantly increased. The soluble fraction of CAPs suspensions caused most of the increased bioactivity in the presence of exogenous H{sub 2}O{sub 2}. The metal chelator deferoxamine (DFO) strongly inhibited the interaction of the soluble fraction with H{sub 2}O{sub 2} but had no effect on the bioactivity of the insoluble CAPs fraction. We conclude that CAPs can mediate their effects in primed AMs by acting on oxidant-sensitive cytokine release in at least two distinct ways. In the primed cell, insoluble components of PM mediate enhanced TNF production that is H{sub 2}O{sub 2}-dependent (catalase-sensitive) yet independent of iron (DFO-insensitive). In the presence of exogenous H{sub 2}O{sub 2} released by AMs, PMNs, or other lung cells within an inflamed alveolar milieu, soluble iron released from air particles can also mediate cytokine release and cell toxicity.

  13. Alveolar macrophage cytokine response to air pollution particles: oxidant mechanisms

    PubMed Central

    Imrich, Amy; Ning, YaoYu; Lawrence, Joy; Coull, Brent; Gitin, Elena; Knutson, Mitchell; Kobzik, Lester

    2007-01-01

    Alveolar macrophages (AMs) primed with LPS and treated with concentrated ambient air particles (CAPs) showed enhanced release of tumor necrosis factor (TNF) and provide an in vitro model for the amplified effects of air pollution particles seen in people with preexisting lung disease. To investigate the mechanism(s) by which CAPs mediate TNF release in primed rat AMs, we first tested the effect of a panel of antioxidants. N-acetyl cysteine (20mM), dimethyl thiourea (20 mM) and catalase (5 uM) significantly inhibited TNF release by primed AMs incubated with CAPs. Conversely, when LPS-primed AMs were treated with CAPs in the presence of exogenous oxidants (H2O2 generated by glucose oxidase, 10 uM/hr), TNF release and cell toxicity was significantly increased. The soluble fraction of CAPs suspensions caused most of the increased bioactivity in the presence of exogenous H2O2. The metal chelator deferoxamine (DFO) strongly inhibited the interaction of the soluble fraction with H2O2 but had no effect on the bioactivity of the insoluble CAPs fraction. We conclude that CAPs can mediate their effects in primed AMs by acting on oxidant-sensitive cytokine release in at least two distinct ways. In the primed cell, insoluble components of PM mediate enhanced TNF production that is H2O2-dependent (catalase-sensitive) yet independent of iron (DFO-insensitive). In the presence of exogenous H2O2 released by AMs, PMNs, or other lung cells within an inflamed alveolar milieu, soluble iron released from air particles can also mediate cytokine release and cell toxicity. PMID:17222881

  14. Why Cells Grow and Divide? General Growth Mechanism and How it Defines Cells’ Growth, Reproduction and Metabolic Properties

    NASA Astrophysics Data System (ADS)

    Shestopaloff, Yuri K.

    2015-02-01

    We consider a general growth mechanism, which acts at cellular level and above (organs, systems and whole organisms). Using its mathematical representation, the growth equation, we study the growth and division mechanisms of amoeba and fission yeast Schizosaccharomyces pombe. We show how this mechanism, together with biomolecular machinery, governs growth and reproduction of cells, and these organisms in particular. This mechanism provides revealing answers to fundamental questions of biology, like why cells grow and divide, why and when cells’ growth stops. It also sheds light on questions like why and how life originated and developed. Solving the growth equation, we obtain analytical expression for the growth curve of fission yeast as a function of geometrical characteristics and nutrient influxes for RNA and protein synthesis, and compare the computed growth curves with 85 experiments. Statistical evaluation shows that these growth curves correspond to experimental data significantly better than all previous approximations. Also, using the general growth mechanism, we show how metabolic characteristics of cells, their size and evolutionary traits relate, considering fission yeast. In particular, we found that fission yeast S. pombe consumes about 16-18 times more nutrients for maintenance needs than for biomass synthesis.

  15. Monitoring the regulation of gene expression in a growing organ using a fluid mechanics formalism

    PubMed Central

    2010-01-01

    Background Technological advances have enabled the accurate quantification of gene expression, even within single cell types. While transcriptome analyses are routinely performed, most experimental designs only provide snapshots of gene expression. Molecular mechanisms underlying cell fate or positional signalling have been revealed through these discontinuous datasets. However, in developing multicellular structures, temporal and spatial cues, known to directly influence transcriptional networks, get entangled as the cells are displaced and expand. Access to an unbiased view of the spatiotemporal regulation of gene expression occurring during development requires a specific framework that properly quantifies the rate of change of a property in a moving and expanding element, such as a cell or an organ segment. Results We show how the rate of change in gene expression can be quantified by combining kinematics and real-time polymerase chain reaction data in a mechanistic model which considers any organ as a continuum. This framework was applied in order to assess the developmental regulation of the two reference genes Actin11 and Elongation Factor 1-β in the apex of poplar root. The growth field was determined by time-lapse photography and transcript density was obtained at high spatial resolution. The net accumulation rates of the transcripts of the two genes were found to display highly contrasted developmental profiles. Actin11 showed pulses of up and down regulation in the accelerating and decelerating parts of the growth zone while the dynamic of EF1β were much slower. This framework provides key information about gene regulation in a developing organ, such as the location, the duration and the intensity of gene induction/repression. Conclusions We demonstrated that gene expression patterns can be monitored using the continuity equation without using mutants or reporter constructions. Given the rise of imaging technologies, this framework in our view opens a

  16. Low-Level Mechanical Vibrations can Reduce Bone Resorption and Enhance Bone Formation in the Growing Skeleton

    SciTech Connect

    Xie,L.; Jacobsen, J.; Busa, B.; Donahue, L.; Miller, L.; Rubin, C.; Judex, S.

    2006-01-01

    Short durations of extremely small magnitude, high-frequency, mechanical stimuli can promote anabolic activity in the adult skeleton. Here, it is determined if such signals can influence trabecular and cortical formative and resorptive activity in the growing skeleton, if the newly formed bone is of high quality, and if the insertion of rest periods during the loading phase would enhance the efficacy of the mechanical regimen. Eight-week-old female BALB/cByJ mice were divided into four groups, baseline control (n = 8), age-matched control (n = 10), whole-body vibration (WBV) at 45 Hz (0.3 g) for 15 min day{sup -1} (n = 10), and WBV that were interrupted every second by 10 of rest (WBV-R, n = 10). In vivo strain gaging of two additional mice indicated that the mechanical signal induced strain oscillations of approximately 10 microstrain on the periosteal surface of the proximal tibia. After 3 weeks of WBV, applied for 15 min each day, osteoclastic activity in the trabecular metaphysis and epiphysis of the tibia was 33% and 31% lower (P < 0.05) than in age-matched controls. Bone formation rates (BFR{center_dot}BS{sup -1}) on the endocortical surface of the metaphysis were 30% greater (P < 0.05) in WBV than in age-matched control mice but trabecular and middiaphyseal BFR were not significantly altered. The insertion of rest periods (WBV-R) failed to potentiate the cellular effects. Three weeks of either WBV or WBV-R did not negatively influence body mass, bone length, or chemical bone matrix properties of the tibia. These data indicate that in the growing skeleton, short daily periods of extremely small, high-frequency mechanical signals can inhibit trabecular bone resorption, site specifically attenuate the declining levels of bone formation, and maintain a high level of matrix quality. If WBV prove to be efficacious in the growing human skeleton, they may be able to provide the basis for a non-pharmacological and safe means to increase peak bone mass and, ultimately

  17. Probing the Mechanical Strength of an Armored Bubble and Its Implication to Particle-Stabilized Foams

    NASA Astrophysics Data System (ADS)

    Taccoen, Nicolas; Lequeux, François; Gunes, Deniz Z.; Baroud, Charles N.

    2016-01-01

    Bubbles are dynamic objects that grow and rise or shrink and disappear, often on the scale of seconds. This conflicts with their uses in foams where they serve to modify the properties of the material in which they are embedded. Coating the bubble surface with solid particles has been demonstrated to strongly enhance the foam stability, although the mechanisms for such stabilization remain mysterious. In this paper, we reduce the problem of foam stability to the study of the behavior of a single spherical bubble coated with a monolayer of solid particles. The behavior of this armored bubble is monitored while the ambient pressure around it is varied, in order to simulate the dissolution stress resulting from the surrounding foam. We find that above a critical stress, localized dislocations appear on the armor and lead to a global loss of the mechanical stability. Once these dislocations appear, the armor is unable to prevent the dissolution of the gas into the surrounding liquid, which translates into a continued reduction of the bubble volume, even for a fixed overpressure. The observed route to the armor failure therefore begins from localized dislocations that lead to large-scale deformations of the shell until the bubble completely dissolves. The critical value of the ambient pressure that leads to the failure depends on the bubble radius, with a scaling of Δ Pcollapse∝R-1 , but does not depend on the particle diameter. These results disagree with the generally used elastic models to describe particle-covered interfaces. Instead, the experimental measurements are accounted for by an original theoretical description that equilibrates the energy gained from the gas dissolution with the capillary energy cost of displacing the individual particles. The model recovers the short-wavelength instability, the scaling of the collapse pressure with bubble radius, and the insensitivity to particle diameter. Finally, we use this new microscopic understanding to predict

  18. Carbonaceous Matter in Growing Nanoparticles

    NASA Astrophysics Data System (ADS)

    Johnston, M. V.; Stangl, C. M.; Horan, A. J.

    2015-12-01

    Atmospheric nanoparticles constitute the greatest portion of ambient aerosol loading by number. A major source of atmospheric nanoparticles is new particle formation (NPF), a gas to particle conversion process whereby clusters nucleate from gas phase precursors to form clusters on the order of one or a few nanometers and then grow rapidly to climatically relevant sizes. A substantial fraction of cloud condensation nuclei (CCN) are thought to arise from NPF. In order to better predict the frequency, growth rates, and climatic impacts of NPF, knowledge of the chemical mechanisms by which nucleated nanoparticles grow is needed. The two main contributors to particle growth are (neutralized) sulfate and carbonaceous matter. Particle growth by sulfuric acid condensation is generally well understood, though uncertainty remains about the extent of base neutralization and the relative roles of ammonia and amines. Much less is known about carbonaceous matter, and field measurements suggest that nitrogen-containing species are important. In this presentation, recent work by our group will be described that uses a combination of ambient measurements, laboratory experiments and computational work to study carbonaceous matter in growing nanoparticles. These studies span a range of particle sizes from the initial adsorption of molecules onto a nanometer-size ammonium bisulfate seed cluster to reactions in particles that are large enough to support condensed-phase chemistry.

  19. Design of sustained release fine particles using two-step mechanical powder processing: particle shape modification of drug crystals and dry particle coating with polymer nanoparticle agglomerate.

    PubMed

    Kondo, Keita; Ito, Natsuki; Niwa, Toshiyuki; Danjo, Kazumi

    2013-09-10

    We attempted to prepare sustained release fine particles using a two-step mechanical powder processing method; particle-shape modification and dry particle coating. First, particle shape of bulk drug was modified by mechanical treatment to yield drug crystals suitable for the coating process. Drug crystals became more rounded with increasing rotation speed, which demonstrates that powerful mechanical stress yields spherical drug crystals with narrow size distribution. This process is the result of destruction, granulation and refinement of drug crystals. Second, the modified drug particles and polymer coating powder were mechanically treated to prepare composite particles. Polymer nanoparticle agglomerate obtained by drying poly(meth)acrylate aqueous dispersion was used as a coating powder. The porous nanoparticle agglomerate has superior coating performance, because it is completely deagglomerated under mechanical stress to form fine fragments that act as guest particles. As a result, spherical drug crystals treated with porous agglomerate were effectively coated by poly(meth)acrylate powder, showing sustained release after curing. From these findings, particle-shape modification of drug crystals and dry particle coating with nanoparticle agglomerate using a mechanical powder processor is expected as an innovative technique for preparing controlled-release coated particles having high drug content and size smaller than 100 μm. PMID:23796831

  20. Nondiffusive mechanisms enhance protein uptake rates in ion exchange particles

    PubMed Central

    Dziennik, S. R.; Belcher, E. B.; Barker, G. A.; DeBergalis, M. J.; Fernandez, S. E.; Lenhoff, A. M.

    2003-01-01

    Scanning confocal fluorescence microscopy and multiphoton fluorescence microscopy were used to image the uptake of the protein lysozyme into individual ion exchange chromatography particles in a packed bed in real time. Self-sharpening concentration fronts penetrating into the particles were observed at low salt concentrations in all of the adsorbents studied, but persisted to 100 mM ionic strength only in some materials. In other adsorbents, diffuse profiles were seen at these higher salt concentrations, with the transition region exhibiting a pronounced fluorescence peak at the front at intermediate salt concentrations. These patterns in the uptake profiles are accompanied by significant increases in protein uptake rates that are also seen macroscopically in batch uptake experiments. The fluorescence peak appears to be a concentration overshoot that may develop, in part, from an electrokinetic contribution to transport that also enhances the uptake rate. Further evidence for an electrokinetic origin is that the effect is correlated with high adsorbent surface charge densities. Predictions of a mathematical model incorporating the electrokinetic effect are in qualitative agreement with the observations. These findings indicate that mechanisms other than diffusion contribute to protein transport in oppositely charged porous materials and may be exploited to achieve rapid uptake in process chromatography. PMID:12522150

  1. Growth mechanisms of iron oxide particles of differing morphologies from the forced hydrolysis of ferric chloride solutions

    SciTech Connect

    Bailey, J.K.; Brinker, C.J. ); MeCartney, M.L. )

    1993-04-01

    To determine the growth mechanisms responsible for the different morphologies, the authors used time resolved transmission electron microscopy to follow the growth of iron oxide particles produced by the forced hydrolysis of ferric chloride solutions. The growth of three different hematite particle morphologies were investigated: cubes, spheres, and so-called double ellipsoids. The morphology of the particles depends on the concentration of FeCl[sub 3], the pH, and the temperature of aging. All solutions were seen to first produce rod-like particles of akaganeite ([beta]-FeOOH) which would then transform to hematite ([alpha]-Fe[sub 2]O[sub 3]), leading under different conditions to spheres, cubes, or double ellipsoids. For all solutions, the initially produced akaganeite rods form by homogeneous nucleation and subsequent growth. The hematite particles are produced by dissolution of the akaganeite rods and reprecipitation as hematite. For the double-ellipsoid-producing solution, the akaganeite rods remain unaggregated in solution. Hematite heterogeneously nucleates on these rods. In addition to growing outward, the hematite particle uses the rod as a template, and a collar forms, which grows along the rod, producing the double-ellipsoid shape. For a sphere-producing solution, the [beta]-FeOOH rods also remain unaggregated in solution but the akaganeite rods which are formed are shorter and dissolve before the growing hematite particles can use the rods as templates. For the cube-producing solution, the initially produced akaganeite rods aggregate into rafts. These rafts, formed from rods of similar length, have a cubic shape that they impart to the hematite which nucleates on the akaganeite raft. The findings indicate that the concentrations of starting compounds not only influence the kinetics of the reaction, but also influence the colloidal behavior.

  2. Growth mechanism of ultrafine tellurium particles produced by the gas evaporation method

    NASA Astrophysics Data System (ADS)

    Kaito, Chihiro; Saito, Yoshio; Watanabe, Tsuyoshi; Ohtsuka, Kazushi; Chen, Fangyu; Nakamura, Masahiko

    1994-06-01

    Ultrafine particles of tellurium have been produced by evaporating tellurium powder from a quartz boat using the atmospheric temperature. Particles of 20-200 nm in size grew under low vapor pressure of tellurium. The shapes of the particles were sphere and hexagonal rod. Spherical amorphous particles also grew in the smoke. Hollow hexagonal rod particles grew under high vapor pressure of tellurium. The growth mechanism of these particles is discussed on the basis of atmospheric temperature and the vapor pressure of tellurium.

  3. Growing TiO2 nanowires by solid-liquid-solid mechanism including two factors (Ti and O)

    NASA Astrophysics Data System (ADS)

    Pishekloo, S. Piri; Dariani, R. S.

    2016-04-01

    Identifying the growth factors of nanowires helps in controlling their structure and morphology and determining their optimal growth conditions. This study investigates the effect of titanium substrate in growing TiO2 nanowires (NWs) with evaporation method. It reveals that the titanium in substrate is indeed the main source of growth. Using the substrate as the only source of growth with regulated amount of accessible oxygen in the furnace, NWs with lengths ranging from 1 to 70 µm were obtained. The results of the experiments show that the nanowires' growth is mainly controlled by diffusion of titanium atoms from the substrate through TiO2 grain boundaries and surface diffusion toward NWs' tips rather than adsorption from vapor phase. The solid-liquid-solid mechanism including two factors (Ti and O) is proposed and discussed for growth of TiO2 NWs.

  4. The role of mechanical forces in the planar-to-bulk transition in growing Escherichia coli microcolonies

    PubMed Central

    Grant, Matthew A. A.; Wacław, Bartłomiej; Allen, Rosalind J.; Cicuta, Pietro

    2014-01-01

    Mechanical forces are obviously important in the assembly of three-dimensional multicellular structures, but their detailed role is often unclear. We have used growing microcolonies of the bacterium Escherichia coli to investigate the role of mechanical forces in the transition from two-dimensional growth (on the interface between a hard surface and a soft agarose pad) to three-dimensional growth (invasion of the agarose). We measure the position within the colony where the invasion transition happens, the cell density within the colony and the colony size at the transition as functions of the concentration of the agarose. We use a phenomenological theory, combined with individual-based computer simulations, to show how mechanical forces acting between the bacterial cells, and between the bacteria and the surrounding matrix, lead to the complex phenomena observed in our experiments—in particular the observation that agarose concentration non-trivially affects the colony size at transition. Matching these approaches leads to a prediction for how the friction between the bacteria and the agarose should vary with agarose concentration. Our experimental conditions mimic numerous clinical and environmental scenarios in which bacteria invade soft matrices, as well as shedding more general light on the transition between two- and three-dimensional growth in multicellular assemblies. PMID:24920113

  5. The role of mechanical forces in the planar-to-bulk transition in growing Escherichia coli microcolonies.

    PubMed

    Grant, Matthew A A; Wacław, Bartłomiej; Allen, Rosalind J; Cicuta, Pietro

    2014-08-01

    Mechanical forces are obviously important in the assembly of three-dimensional multicellular structures, but their detailed role is often unclear. We have used growing microcolonies of the bacterium Escherichia coli to investigate the role of mechanical forces in the transition from two-dimensional growth (on the interface between a hard surface and a soft agarose pad) to three-dimensional growth (invasion of the agarose). We measure the position within the colony where the invasion transition happens, the cell density within the colony and the colony size at the transition as functions of the concentration of the agarose. We use a phenomenological theory, combined with individual-based computer simulations, to show how mechanical forces acting between the bacterial cells, and between the bacteria and the surrounding matrix, lead to the complex phenomena observed in our experiments-in particular the observation that agarose concentration non-trivially affects the colony size at transition. Matching these approaches leads to a prediction for how the friction between the bacteria and the agarose should vary with agarose concentration. Our experimental conditions mimic numerous clinical and environmental scenarios in which bacteria invade soft matrices, as well as shedding more general light on the transition between two- and three-dimensional growth in multicellular assemblies. PMID:24920113

  6. Augmented Lagrangian Particle Swarm Optimization in Mechanism Design

    NASA Astrophysics Data System (ADS)

    Sedlaczek, Kai; Eberhard, Peter

    The problem of optimizing nonlinear multibody systems is in general nonlinear and nonconvex. This is especially true for the dimensional synthesis process of rigid body mechanisms, where often only local solutions might be found with gradient-based optimization methods. An attractive alternative for solving such multimodal optimization problems is the Particle Swarm Optimization (PSO) algorithm. This stochastic solution technique allows a derivative-free search for a global solution without the need for any initial design. In this work, we present an extension to the basic PSO algorithm in order to solve the problem of dimensional synthesis with nonlinear equality and inequality constraints. It utilizes the Augmented Lagrange Multiplier Method in combination with an advanced non-stationary penalty function approach that does not rely on excessively large penalty factors for sufficiently accurate solutions. Although the PSO method is even able to solve nonsmooth and discrete problems, this augmented algorithm can additionally calculate accurate Lagrange multiplier estimates for differentiable formulations, which are helpful in the analysis process of the optimization results. We demonstrate this method and show its very promising applicability to the constrained dimensional synthesis process of rigid body mechanisms.

  7. Formation mechanism of uniform CdS particles from condensed Cd(OH){sub 2} suspension

    SciTech Connect

    Sugimoto, Tadao; Dirige, G.E.; Muramatsu, Atsushi

    1995-12-15

    The formation mechanism of uniform cadmium sulfide particles obtained in large quantities from condensed Cd(OH){sub 2} suspension in the presence of thioacetamide (TAA), gelatin and NH{sub 3}-NH{sub 4}{sup +} buffer system was investigated. Basically, the reaction proceeded through rapid dissolution of Cd(OH){sub 2} particles induced by the reaction of Cd{sup 2+} ions with S{sup 2{minus}} ions liberated from TAA in the solution phase. It was finished in ca. 1 min under the standard conditions, 0.5 mol/dm{sup 3} in Cd(OH){sub 2}, 0.55 mol/dm{sup 3} in TAA, 1 wt% in deionized gelatin, and 1.0 mol/dm{sup 3} NH{sub 4}NO{sub 3} at 20 C and at pH 8.50 adjusted with NH{sub 3}. The resulting uniform and nearly spherical particles of CdS prepared under the standard conditions were 40 nm in mean diameter and were polycrystalline particles consisting of randomly oriented much smaller subcrystals (8.60 nm). Besides using the NH{sub 3}--NH{sub 4}{sup +} system in generating uniform CdS particles, employing borax/NaOH buffer system in the formation of spherical CdS particles was also possible. It was also found that S{sup 2{minus}} ions were furnished through a reaction, CH{sub 3}CSNH{sub 2} {yields} CH{sub 3}CN + 2H{sup +} + S{sup 2{minus}}. This reaction was excessively accelerated by the rapid consumption of S{sup 2{minus}} ions so that it is thought to be a reversible reaction. The reaction was virtually stoichiometric and the contribution of hydrolysis of TAA was not observed. The uniform growth of the CdS particles was achieved by the controlled dissolution of the Cd(OH){sub 2} without aggregation of the growing CdS particles after an instantaneous nucleation.

  8. Condensation of HNO3 on falling ice particles - Mechanism for denitrification of the polar stratosphere

    NASA Technical Reports Server (NTRS)

    Wofsy, S. C.; Salawitch, R. J.; Yatteau, J. H.; Mcelroy, M. B.; Gandrud, B. W.

    1990-01-01

    Ice particles created in polar stratospheric cooling events are predicted to descend into Type I PSCs and accrete a coating of nitric acid trihydrate (NAT) that inhibits evaporation. Coated particles efficiently strip HNO3 from the atmosphere, providing a mechanism for denitrification without significant dehydration. Coatings that disintegrate may release large particles of NAT that influence subsequent particle growth.

  9. Titanate cathodes with enhanced electrical properties achieved via growing surface Ni particles toward efficient carbon dioxide electrolysis.

    PubMed

    Gan, Lizhen; Ye, Lingting; Tao, Shanwen; Xie, Kui

    2016-01-28

    Ionic conduction in perovskite oxide is commonly tailored by element doping in lattices to create charge carriers, while few studies have been focused on ionic conduction enhancement through tailoring microstructures. In this work, remarkable enhancement of ionic conduction in titanate has been achieved via in situ growing active nickel nanoparticles on an oxide surface by controlling the oxide material nonstoichiometry. The combined use of XRD, SEM, XPS and EDS indicates that the exsolution/dissolution of the nickel nanoparticles is completely reversible in redox cycles. With the synergetic effect of enhanced ionic conduction of titanate and the presence of catalytic active Ni nanocatalysts, significant improvement of electrocatalytic performances of the titanate cathode is demonstrated. A current density of 0.3 A cm(-2) with a Faradic efficiency of 90% has been achieved for direct carbon dioxide electrolysis in a 2 mm-thick YSZ-supported solid oxide electrolyzer with the modified titanate cathode at 2 V and 1073 K. PMID:26743799

  10. Mechanisms for nano particle removal in brush scrubber cleaning

    NASA Astrophysics Data System (ADS)

    Huang, Yating; Guo, Dan; Lu, Xinchun; Luo, Jianbin

    2011-01-01

    A model describing the nano particle (<100 nm) removal behavior in brush scrubber cleaning is presented based on experiment results and theoretical analysis. The forces on the particles in different situations are analyzed and discussed. The adhesion forces of the van der Waals force, the electrostatic force, the brush load and the static friction between the particle and the wafer are calculated. The contact elastic force, hydrodynamic drag force and friction between the brush and the particle are considered as removal forces and are evaluated. The porous structure and roughness surface of brush material are considered in the hydrodynamic model to describe the brush deformation and the flow field in the cleaning process. The porous structure will result in decrease of hydrodynamic drag force. There are four situations of the particles relative to the brush roughness asperities for which the forces on the particle are different. When the particle is in contact with a brush asperity or on the wafer surface and in a semi-infinite fluid flow field, the particle may be removed by hydrodynamic force and elastic force in the presence of surfactant. When the particle is embedded in the brush asperity, the remove will realized when the friction caused by adhesion between the brush and the particle overcome the adhesion force between particle and wafer surface. The removed particles will be in the flow field or adhered on the brush surface and may redeposit on the wafer surface.

  11. Impact of distillers dried grains with solubles particle size on nutrient digestibility, DE and ME content, and flowability in diets for growing pigs.

    PubMed

    Liu, P; Souza, L W O; Baidoo, S K; Shurson, G C

    2012-12-01

    A study was conducted to determine the effect of particle size of distillers dried grains with solubles (DDGS) on DE and ME content, diet DM, energy, N, P digestibility, and diet flowability for growing pigs. One DDGS source was processed through an Urshel Commitrol mill or a hammer mill to achieve mean particle sizes of 818, 595, and 308 μm. The basal control diet consisted of 96.8% corn with supplemental minerals and vitamins. Three experimental diets were formulated by replacing 30% of corn from the basal diet with DDGS of different particle sizes. Thirty-six growing pigs (initial BW of 40 ± 1.13 kg) were assigned to 1 of 4 treatments in a randomized complete block design according to their BW block and housed in individual metabolic crates for a 9-d adaptation period followed by a 4-d total collection of feces and urine. Pigs were provided ad libitum access to water and fed an amount of their respective experimental diets equivalent to 3% of the initial BW of each pig. Feed, feces, and urine samples were analyzed for DM, GE, N, and P and used to calculate diet apparent total tract digestibility (ATTD). Gross energy was also used to calculate DE and ME of diets as well as the DE and ME content of corn and DDGS with different particle sizes. Diet drained and poured angles of repose were measured using a modified Hele-Shaw cell method to evaluate the diet flowability. Inclusion of 30% DDGS with an average particle size of 308 μm improved (P < 0.05) dietary ATTD of DM and GE as well as DE (4,006 vs. 3,783 kcal/kg DM) and ME (3,861 vs. 3,583 kcal/kg DM) compared with 818 μm DDGS. No differences (P > 0.05) were found in N and P digestibility among the 3 DDGS diets. The DDGS particle size of 595 μm had greater (P < 0.05) DE but not ME compared with 818 μm DDGS, and DE and ME were not different between 308 and 595 μm. Compared with a 595 or 818 μm DDGS, grinding DDGS to 308 μm reduced diet flowability as indicated by a greater (P < 0.05) drained angle of

  12. Model Fe-Al Steel with Exceptional Resistance to High Temperature Coarsening. Part I: Coarsening Mechanism and Particle Pinning Effects

    NASA Astrophysics Data System (ADS)

    Zhou, Tihe; Zurob, Hatem S.; O'Malley, Ronald J.; Rehman, Kashif

    2015-01-01

    The mechanism by which austenite particles coarsen in a delta-ferrite matrix was investigated in a model Al-containing steel. Special emphasis was placed on the effect of volume fraction on the coarsening kinetics as well as the ability of the particles to pin the growth of delta-ferrite grains. The specimens were heated to temperatures in the range of 1123 K to 1583 K (850 °C to 1305 °C) in the austenite plus delta-ferrite two-phase region and held for times between 5 minutes and 288 hours, followed by water quenching. When the reheating temperature was higher than 1473 K (1200 °C), the coarsening of austenite particles was found to evolve as t 1/3, which is typical of volume diffusion-controlled behavior. For lower temperatures, the particle coarsening behavior followed t 1/4 kinetics which is consistent with a grain boundary diffusion-controlled process. The observations were interpreted in terms of the modified Lifshitz-Slyozov-Wanger theory by considering multi-component diffusion, particle volume fraction, and the fact that this two-phase material is a non-ideal solid solution. Three types of interaction between particle coarsening and grain growth were observed. Grain growth was completely pinned when the particle pinning force was much larger than the driving force for grain growth. When the particle pinning force was comparable to the driving force for grain growth, the delta-ferrite grains were observed to grow at a rate which is controlled by the kinetics of coarsening of the austenite particles. Finally, when the particle pinning force was smaller than the driving force for grain growth, significant grain growth occurred but its rate was lower than that expected in the absence of particle pinning. The results point to an effective approach for controlling grain growth at high temperatures.

  13. Inferring Growth Control Mechanisms in Growing Multi-cellular Spheroids of NSCLC Cells from Spatial-Temporal Image Data

    PubMed Central

    Müller, Margareta; Vignon-Clementel, Irene E.; Drasdo, Dirk

    2016-01-01

    We develop a quantitative single cell-based mathematical model for multi-cellular tumor spheroids (MCTS) of SK-MES-1 cells, a non-small cell lung cancer (NSCLC) cell line, growing under various nutrient conditions: we confront the simulations performed with this model with data on the growth kinetics and spatial labeling patterns for cell proliferation, extracellular matrix (ECM), cell distribution and cell death. We start with a simple model capturing part of the experimental observations. We then show, by performing a sensitivity analysis at each development stage of the model that its complexity needs to be stepwise increased to account for further experimental growth conditions. We thus ultimately arrive at a model that mimics the MCTS growth under multiple conditions to a great extent. Interestingly, the final model, is a minimal model capable of explaining all data simultaneously in the sense, that the number of mechanisms it contains is sufficient to explain the data and missing out any of its mechanisms did not permit fit between all data and the model within physiological parameter ranges. Nevertheless, compared to earlier models it is quite complex i.e., it includes a wide range of mechanisms discussed in biological literature. In this model, the cells lacking oxygen switch from aerobe to anaerobe glycolysis and produce lactate. Too high concentrations of lactate or too low concentrations of ATP promote cell death. Only if the extracellular matrix density overcomes a certain threshold, cells are able to enter the cell cycle. Dying cells produce a diffusive growth inhibitor. Missing out the spatial information would not permit to infer the mechanisms at work. Our findings suggest that this iterative data integration together with intermediate model sensitivity analysis at each model development stage, provide a promising strategy to infer predictive yet minimal (in the above sense) quantitative models of tumor growth, as prospectively of other tissue

  14. Inferring Growth Control Mechanisms in Growing Multi-cellular Spheroids of NSCLC Cells from Spatial-Temporal Image Data.

    PubMed

    Jagiella, Nick; Müller, Benedikt; Müller, Margareta; Vignon-Clementel, Irene E; Drasdo, Dirk

    2016-02-01

    We develop a quantitative single cell-based mathematical model for multi-cellular tumor spheroids (MCTS) of SK-MES-1 cells, a non-small cell lung cancer (NSCLC) cell line, growing under various nutrient conditions: we confront the simulations performed with this model with data on the growth kinetics and spatial labeling patterns for cell proliferation, extracellular matrix (ECM), cell distribution and cell death. We start with a simple model capturing part of the experimental observations. We then show, by performing a sensitivity analysis at each development stage of the model that its complexity needs to be stepwise increased to account for further experimental growth conditions. We thus ultimately arrive at a model that mimics the MCTS growth under multiple conditions to a great extent. Interestingly, the final model, is a minimal model capable of explaining all data simultaneously in the sense, that the number of mechanisms it contains is sufficient to explain the data and missing out any of its mechanisms did not permit fit between all data and the model within physiological parameter ranges. Nevertheless, compared to earlier models it is quite complex i.e., it includes a wide range of mechanisms discussed in biological literature. In this model, the cells lacking oxygen switch from aerobe to anaerobe glycolysis and produce lactate. Too high concentrations of lactate or too low concentrations of ATP promote cell death. Only if the extracellular matrix density overcomes a certain threshold, cells are able to enter the cell cycle. Dying cells produce a diffusive growth inhibitor. Missing out the spatial information would not permit to infer the mechanisms at work. Our findings suggest that this iterative data integration together with intermediate model sensitivity analysis at each model development stage, provide a promising strategy to infer predictive yet minimal (in the above sense) quantitative models of tumor growth, as prospectively of other tissue

  15. Mechanism of vibration-induced repulsion force on a particle in a viscous fluid cell.

    PubMed

    Saadatmand, Mehrrad; Kawaji, Masahiro

    2013-08-01

    Space platforms such as the Space Shuttle and International Space Station have been considered an ideal environment for production of protein and semiconductor crystals of superior quality due to the negligible gravity-induced convection. Although it was believed that under microgravity environment diffusive mass transport would dominate the growth of the crystals, some related experiments have not shown satisfactory results possibly due to the movement of the growing crystals in fluid cells caused by small vibrations present in the space platforms called g-jitter. In ground-based experiments, there have been clear observations of attraction and repulsion of a solid particle with respect to a nearby wall of the fluid cell due to small vibrations. The present work is a numerical investigation on the physical mechanisms responsible for the repulsion force, which has been predicted to increase with the cell vibration frequency and amplitude, as well as the fluid viscosity. Moreover, the simulations have revealed that the repulsion force occurs mostly due to the increased pressure in the narrow gap between the particle and the nearest wall. PMID:24032936

  16. Mechanism of vibration-induced repulsion force on a particle in a viscous fluid cell

    NASA Astrophysics Data System (ADS)

    Saadatmand, Mehrrad; Kawaji, Masahiro

    2013-08-01

    Space platforms such as the Space Shuttle and International Space Station have been considered an ideal environment for production of protein and semiconductor crystals of superior quality due to the negligible gravity-induced convection. Although it was believed that under microgravity environment diffusive mass transport would dominate the growth of the crystals, some related experiments have not shown satisfactory results possibly due to the movement of the growing crystals in fluid cells caused by small vibrations present in the space platforms called g-jitter. In ground-based experiments, there have been clear observations of attraction and repulsion of a solid particle with respect to a nearby wall of the fluid cell due to small vibrations. The present work is a numerical investigation on the physical mechanisms responsible for the repulsion force, which has been predicted to increase with the cell vibration frequency and amplitude, as well as the fluid viscosity. Moreover, the simulations have revealed that the repulsion force occurs mostly due to the increased pressure in the narrow gap between the particle and the nearest wall.

  17. Alp7/TACC-Alp14/TOG generates long-lived, fast-growing MTs by an unconventional mechanism

    PubMed Central

    Hussmann, Frauke; Drummond, Douglas R.; Peet, Daniel R.; Martin, Douglas S.; Cross, Robert A.

    2016-01-01

    Alp14 is a TOG-family microtubule polymerase from S. pombe that tracks plus ends and accelerates their growth. To interrogate its mechanism, we reconstituted dynamically unstable single isoform S. pombe microtubules with full length Alp14/TOG and Alp7, the TACC-family binding partner of Alp14. We find that Alp14 can drive microtubule plus end growth at GTP-tubulin concentrations at least 10-fold below the usual critical concentration, at the expense of increased catastrophe. This reveals Alp14 to be a highly unusual enzyme that biases the equilibrium for the reaction that it catalyses. Alp7/TACC enhances the effectiveness of Alp14, by increasing its occupancy. Consistent with this, we show in live cells that Alp7 deletion produces very similar MT dynamics defects to Alp14 deletion. The ability of Alp7/14 to accelerate and bias GTP-tubulin exchange at microtubule plus ends allows it to generate long-lived, fast-growing microtubules at very low cellular free tubulin concentrations. PMID:26864000

  18. Minimal mechanisms for school formation in self-propelled particles

    NASA Astrophysics Data System (ADS)

    Li, Yue-Xian; Lukeman, Ryan; Edelstein-Keshet, Leah

    2008-05-01

    In the context of social organisms, a school refers to a cohesive group of organisms that share a common speed and direction of motion, as well as a common axis of body alignment or polarization. Schools are also noted for the relatively fixed nearest-neighbour distances between individuals. The rules of interaction that lead to the formation and maintenance of a school structure have been explored experimentally, analytically, and by simulation. Interest in biological examples, and non-biological “self-propelled particles” such as robots, vehicles, or autonomous agents leads to the question of what are the simplest possible sets of rules that can assure the formation and the stability of the “perfect school”: an aggregate in which the nearest-neighbour distances and speeds are identical. Here we explore mechanisms that lead to a perfect school structure in one and two dimensions. We consider distance-detection as well as velocity-detection between the interacting pairs of self-propelled particles. We construct interaction forces and formulate schooling equations. In the simplest cases, these equations have analytic solutions. In many cases, the stability of the perfect school can be explored. We then investigate how these structures form and evolve over time from various initial configurations using simulations. We study the relationship between the assumed interaction forces and the school patterns that emerge. While true biological schools are far from perfect, the insights gained from this investigation can help to understand some properties of real schools, and to suggest the appropriate properties of artificial schools where coordinated motion is desired.

  19. Attachment Mechanisms Between Cotton Fibers and Foreign-matter Particles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In order to develop a fundamental understanding of the requirements for removing foreign matter from bulk cotton fiber, a video microscope was used to collect images of foreign-matter particles in lint from smooth-leaf and hairy-leaf cottons. A method is given for categorizing the particles accordin...

  20. ALTERED IRON HOMEOSTATIS AND THE MECHANISM OF BIOLOGIC EFFECT BY PARTICLES

    EPA Science Inventory

    Several features of the clinical presentation and changes in physiology and pathology following exposure to many diverse ambient air pollution particles are comparable, suggesting a common mechanism for their biological effect. We propose that a mechanism of biological effect com...

  1. Note: Evaluation of slurry particle size analyzers for chemical mechanical planarization process.

    PubMed

    Jang, Sunjae; Kulkarni, Atul; Qin, Hongyi; Kim, Taesung

    2016-04-01

    In the chemical mechanical planarization (CMP) process, slurry particle size is important because large particles can cause defects. Hence, selection of an appropriate particle measuring system is necessary in the CMP process. In this study, a scanning mobility particle sizer (SMPS) and dynamic light scattering (DLS) were compared for particle size distribution (PSD) measurements. In addition, the actual particle size and shape were confirmed by transmission electron microscope (TEM) results. SMPS classifies the particle size according to the electrical mobility, and measures the particle concentration (single particle measurement). On the other hand, the DLS measures the particle size distribution by analyzing scattered light from multiple particles (multiple particle measurement). For the slurry particles selected for evaluation, it is observed that SMPS shows bi-modal particle sizes 30 nm and 80 nm, which closely matches with the TEM measurements, whereas DLS shows only single mode distribution in the range of 90 nm to 100 nm and showing incapability of measuring small particles. Hence, SMPS can be a better choice for the evaluation of CMP slurry particle size and concentration measurements. PMID:27131717

  2. Note: Evaluation of slurry particle size analyzers for chemical mechanical planarization process

    NASA Astrophysics Data System (ADS)

    Jang, Sunjae; Kulkarni, Atul; Qin, Hongyi; Kim, Taesung

    2016-04-01

    In the chemical mechanical planarization (CMP) process, slurry particle size is important because large particles can cause defects. Hence, selection of an appropriate particle measuring system is necessary in the CMP process. In this study, a scanning mobility particle sizer (SMPS) and dynamic light scattering (DLS) were compared for particle size distribution (PSD) measurements. In addition, the actual particle size and shape were confirmed by transmission electron microscope (TEM) results. SMPS classifies the particle size according to the electrical mobility, and measures the particle concentration (single particle measurement). On the other hand, the DLS measures the particle size distribution by analyzing scattered light from multiple particles (multiple particle measurement). For the slurry particles selected for evaluation, it is observed that SMPS shows bi-modal particle sizes 30 nm and 80 nm, which closely matches with the TEM measurements, whereas DLS shows only single mode distribution in the range of 90 nm to 100 nm and showing incapability of measuring small particles. Hence, SMPS can be a better choice for the evaluation of CMP slurry particle size and concentration measurements.

  3. Embryonic stem cells growing in 3-dimensions shift from reliance on the substrate to each other for mechanical support.

    PubMed

    Teo, Ailing; Lim, Mayasari; Weihs, Daphne

    2015-07-16

    Embryonic stem cells (ESCs) grow into three-dimensional (3D) spheroid structures en-route to tissue growth. In vitro spheroids can be controllably induced on a two-dimensional (2D) substrate with high viability. Here we use a method for inducing pluripotent embryoid body (EB) formation on flat polyacrylamide gels while simultaneously evaluating the dynamic changes in the mechano-biology of the growing 3D spheroids. During colony growth in 3D, pluripotency is conserved while the spheroid-substrate interactions change significantly. We correlate colony-size, cell-applied traction-forces, and expressions of cell-surface molecules indicating cell-cell and cell-substrate interactions, while verifying pluripotency. We show that as the colony size increases with time, the stresses applied by the spheroid to the gel decrease in the 3D growing EBs; control cells growing in 2D-monolayers maintain unvarying forces. Concurrently, focal-adhesion mediated cell-substrate interactions give way to E-cadherin cell-cell connections, while pluripotency. The mechano-biological changes occurring in the growing embryoid body are required for stabilization of the growing pluripotent 3D-structure, and can affect its potential uses including differentiation. This could enable development of more effective expansion, differentiation, and separation approaches for clinical purposes. PMID:26050958

  4. Effect of particle incorporation on mechanical properties of carbon fiber textile composites

    NASA Astrophysics Data System (ADS)

    Kobayashi, Satoshi; Kitagawa, Jun; Tokyo Metropolitan University Collaboration

    2014-03-01

    In this study, the effect of mechanical properties and fracture behavior due to the inclusion of the fine particles was investigated. The tensile and flexural properties of CFRPs with rubber or Al2O3 particle modified matrix were characterized as a function of particle loading. Tensile strength of particle incorporated CFRP were nearly equal to that of neat matrix CFRP. Flexural strength of CFRP composites were influenced by both matrix modulus and toughness. It is found that higher flexural strength for 5wt.% rubber particle incorporated specimen largely depends on matrix toughness, although lower flexural strength for 10wt.% rubber particle incorporated specimen depends on matrix flexural modulus. In case of Al2O3 particle incorporated specimen, particle content of 10wt.% had a maximum flexural strength. However, further particle addition up to 20wt.%, decreased the flexural strength due to the worse formability.

  5. Texture formation in iron particles using mechanical milling with graphite as a milling aid

    SciTech Connect

    Motozuka, S.; Hayashi, K.; Tagaya, M.; Morinaga, M.

    2015-09-15

    Crystallographically anisotropic platelet iron particles were successfully prepared using a conventional ball mill with addition of graphite (Gp) particles. The morphological and structural changes resulting from the milling were investigated using scanning electron microscopy and X-ray diffraction. The spherical iron particles were plastically deformed into platelet shapes during the milling. Simultaneously, it is suggested that the size of the Gp particles decreased and adhered as nanoparticles on the surface of the iron particles. The adhered Gp particles affected the plastic deformation behavior of the iron particles: the (001) planes of α-iron were oriented parallel to the particle face, and no preferred in-plane orientation was observed. This study not only details the preparation of soft magnetic metal particles that crystallographically oriented to enhance their magnetic properties but also provides new insight into the activities of the well-established and extensively studied mechanical milling method.

  6. Roller compactor: The effect of mechanical properties of primary particles.

    PubMed

    Al-Asady, Riyadh B; Osborne, James D; Hounslow, Michael J; Salman, Agba D

    2015-12-30

    In this study, the nano-indentation hardness of a single primary particle was measured for six different materials; microcrystalline cellulose, hydroxypropyl methylcellulose, maltodextrin, lactose, sodium carbonate and calcium carbonate. This was linked to the properties of the ribbons produced by roller compactor at different hydraulic pressures in the range of 30-230 bar. The main investigated ribbon properties were strength, porosity and width. For the range of materials that were tested, it was found that the lower the nano-indentation hardness of the powder particles, the higher the strength, width and lower the ribbon porosity. This is because the applied pressure by the rollers was enough to plastically deform the particles and create bonds between them. A method was suggested to predict the workability of the powder in roller compactor by using the data of nano-indentation for three materials. PMID:26024822

  7. HIGH SPEED PARTICLE BEAM GENERATION: SIMPLE FOCUSING MECHANISMS. (R823980)

    EPA Science Inventory

    Modern chemical characterization instruments employ an aerosol inlet that transmits atmospheric aerosols to the low pressure source region of a time-of-flight mass spectrometer, where particles are ablated and ionized using high energy irradiation. The ions when analyzed in the m...

  8. Particles detection and analysis of hard disk substrate after cleaning of post chemical mechanical polishing

    NASA Astrophysics Data System (ADS)

    Huang, Yating; Lu, Xinchun; Pan, Guoshun; Lee, Bill; Luo, Jianbin

    2009-08-01

    Scrub, ultrasonic and megasonic are widely used in industry as post-CMP (chemical mechanical polishing/planarization) cleaning procedure. In this paper experiments and results are described to analyze the particle contaminations of hard disk substrate after each process of post-CMP cleaning. A scatter spot method has been exploited to detect the location and characteristics of the particles. SEM with EDX is used to observe and analyze the particles' shape and size as well as the elements. The results indicate that brush scrub process can remove 99% contaminations after CMP but not that efficient for submicron particle. Megasonic is a refined method for cleaning nano-particles. However, contaminations like metallic particles and bacteria from the equipment may cause pollution. The abrasive particles embedded in the plating pits cannot be removed by mechanical force. Pollution in the dryer is also discussed.

  9. Particle size and surfactant effects on chemical mechanical polishing of glass using silica-based slurry

    SciTech Connect

    Zhang Zefang; Liu Weili; Song Zhitang

    2010-10-01

    This study explores the effect of particle size and surfactant on the chemical mechanical polishing (CMP) of glass using colloidal silica-based slurry. It was found that the material removal rate strongly depends on the particle size and the types of surfactants and that the rms roughness was independent of particle size and correlated to surfactants. On the basis of polishing results, it was concluded that the main polishing mechanism was changed from indentation mechanism to surface-area mechanism, with the variation of particle size. In addition, the molecular structure, charge type, and lubricating effect of the surfactants play an important role in the dispersion of abrasive particles and in the CMP performance.

  10. ULTRAFINE PARTICLE CELL INTERACTIONS IN VITRO: MOLECULAR MECHANISMS LEADING TO ALTERED GENE EXPRESSION IN RELATION TO PARTICLE COMPOSITION

    EPA Science Inventory

    The results of these in vitro studies will identify specific mechanisms that are triggered following particle cell contact in a cell specific context and identify markers of cellular response. We predict that many of the subsequent physiologic effects in vivo are...

  11. A one-dimensional lattice model for a quantum mechanical free particle

    NASA Astrophysics Data System (ADS)

    de La Torre, A. C.; Daleo, A.

    2000-01-01

    Two types of particles, A and B with their corresponding antiparticles, are defined in a onedimensional cyclic lattice with an odd number of sites. In each step of time evolution, each particle acts as a source for the polarization field of the other type of particle with nonlocal action but with an effect decreasing with the distance: A to \\cdots bar BBbar BBbar B \\cdots ;B to \\cdots Abar AAbar AA \\cdots . It is shown that the combined distribution of these particles obeys the time evolution of a free particle as given by quantum mechanics.

  12. Mechanisms underlying the redistribution of particles among the lung's alveolar macrophages during alveolar phase clearance

    SciTech Connect

    Lehnert, B.E.; Oritz, J.B.; Steinkamp, J.A.; Tietjen, G.L.; Sebring, R.J. ); Oberdorster, G. )

    1991-01-01

    In order to obtain information about the particle redistribution phenomenon following the deposition of inhaled particles, as well as to obtain information about some of the mechanisms that may be operable in the redistribution of particles, lavaged lung free cell analyses and transmission electron microscopic (TEM) analyses of lung tissue and were performed using lungs from rats after they were subchronically exposed to aerosolized dioxide (TiO{sub 2}). TEM analyses indicated that the in situ autolysis of particle-containing Alveolar Macropages (AM) is one important mechanism involved in the redistribution of particles. Evidence was also obtained that indicated that the engulfment of one particle-containing phagocyte by another phagocyte also occurs. Another prominent mechanism of the particle redistribution phenomenon may be the in situ proliferation of particle-laden AM. We used the macrophage cell line J774A.1 as a surrogate for AM to investigate how different particulate loads in macrophages may affect their abilities to proliferate. These in vitro investigations indicated that the normal rate of proliferation of macrophages is essentially unaffected by the containment of relatively high particulate burdens. Overall, the results of our investigations suggest that in situ autolysis of particle-containing AM and the rephagocytosis of freed particles by other phagocytes, the phagocytosis of effete and disintegrating particle-containing phagocytes by other AM, and the in situ division of particle-containing AM are likely mechanisms that underlie the post-depositional redistribution of particles among the lung's AM during alveolar phase clearance. 19 refs., 8 figs., 2 tabs.

  13. Biogeochemical Mechanisms Controlling Reduced Radionuclide Particle Properties and Stability

    SciTech Connect

    Jim K. Fredrickson; John M. Zachara; Matthew J. Marshall; Alex S. Beliaev

    2006-06-01

    Uranium and Technetium are the major risk-driving contaminants at Hanford and other DOE sites. These radionuclides have been shown to be reduced by dissimilatory metal reducing bacteria (DMRB) under anoxic conditions. Laboratory studies have demonstrated that reduction results in the formation of poorly soluble hydrous oxides, UO2(s) and TcO2n?H2O(s), that are believed to limit mobility in the environment. The mechanisms of microbial reduction of U and Tc have been the focus of considerable research in the Environmental Remediation Sciences Program (ERSP). In spite of equal or greater importance in terms of controlling the environmental fate of the contaminants relatively little is known regarding the precipitation mechanism(s), reactivity, persistence, and transport of biogenic UO2(s) and TcO2(s).

  14. An assessment of 'shuffle algorithm' collision mechanics for particle simulations

    NASA Technical Reports Server (NTRS)

    Feiereisen, William J.; Boyd, Iain D.

    1991-01-01

    Among the algorithms for collision mechanics used at present, the 'shuffle algorithm' of Baganoff (McDonald and Baganoff, 1988; Baganoff and McDonald, 1990) not only allows efficient vectorization, but also discretizes the possible outcomes of a collision. To assess the applicability of the shuffle algorithm, a simulation was performed of flows in monoatomic gases and the calculated characteristics of shock waves was compared with those obtained using a commonly employed isotropic scattering law. It is shown that, in general, the shuffle algorithm adequately represents the collision mechanics in cases when the goal of calculations are mean profiles of density and temperature.

  15. Relativistic wave mechanics of spinless particles in a curved space-time.

    NASA Astrophysics Data System (ADS)

    Cognola, G.; Vanzo, L.; Zerbini, S.

    1986-09-01

    Starting from the Klein-Gordon equation, the single-particle approximation for a reiativistic scalar particle in the presence of external electromagnetic and gravitational fields is performed. The nonrelativistic limit is obtained by a Foldy-Wouthuysen transformation on a Schrödinger-type equation. The results are then compared with those obtained in classical mechanics.

  16. MECHANISMS OF ACTION OF INHALED FIBERS, PARTICLES AND NANOPARTICLES IN LUNG AND CARDIOVASCULAR DISEASES

    EPA Science Inventory

    ABSTRACT: A symposium on the mechanisms of action of inhaled airborne particulate matter (PM),pathogenic particles and fibers such as silica and asbestos, and nanomaterials, defined as synthetic particles or fibers less than 100 nm in diameter, was held on October 27 and 28,
    ...

  17. EFFECTS OF TEMPERATURE AND PRESSURE ON PARTICLE COLLECTION MECHANISMS: EXPERIMENTAL PROGRAM

    EPA Science Inventory

    The report gives results of a theoretical and experimental investigation of the effects of high temperatures and high pressures (HTPs) on fundamental particle collection mechanisms. It gives experimental results of inertial impaction, cyclone separation, Brownian diffusion, and e...

  18. Submicron particle removal in post-oxide chemical-mechanical planarization (CMP) cleaning

    NASA Astrophysics Data System (ADS)

    Zhang, F.; Busnaina, A.

    Particle removal models for soft-pad buffing (the second-step polishing with DI water) and mechanical brush-cleaning processes are proposed and the removal forces are evaluated and compared with the average particle adhesion force to the oxide wafer surface resulting from the primary polishing (the first-step polishing with slurry). The hydrodynamic force due to the fluid flow is too small to remove slurry particles by itself and particles are most likely removed from the surfaces by the pad or brush asperity contact forces and the hydrodynamic drag force together. This conclusion is consistent with the experimental observations.

  19. The experimental investigation of the ignition petrol mechanism at high temperature metal single particles

    NASA Astrophysics Data System (ADS)

    Zakharevich, Arkadiy V.; Osotova, Diana S.

    2015-01-01

    The flammable substance by single "hot" metallic particle ignition mechanism are experimentally investigated. On the basis experimental data it is established that the gasoline ignition occurs only with interaction of the mixture of its vapors with air and "hot" particle with the vapors concentrations, which correspond to the evaporating the gasoline conditions at room temperatures. The probability of gasoline vapors mixture with air igniting rapidly is reduced in proportion to their withdrawal from the evaporation surface. Ignition occurs neither in the vapor phase nor on the gasoline surface, even if particle is immersed in it in full or in partly, if the particle temperature is lower than the critical.

  20. From Mechanical Motion to Brownian Motion, Thermodynamics and Particle Transport Theory

    ERIC Educational Resources Information Center

    Bringuier, E.

    2008-01-01

    The motion of a particle in a medium is dealt with either as a problem of mechanics or as a transport process in non-equilibrium statistical physics. The two kinds of approach are often unrelated as they are taught in different textbooks. The aim of this paper is to highlight the link between the mechanical and statistical treatments of particle…

  1. Interfacial wave theory for dendritic structure of a growing needle crystal. I - Local instability mechanism. II - Wave-emission mechanism at the turning point

    NASA Technical Reports Server (NTRS)

    Xu, Jian-Jun

    1989-01-01

    The complicated dendritic structure of a growing needle crystal is studied on the basis of global interfacial wave theory. The local dispersion relation for normal modes is derived in a paraboloidal coordinate system using the multiple-variable-expansion method. It is shown that the global solution in a dendrite growth process incorporates the morphological instability factor and the traveling wave factor.

  2. Diffuse reflectance infrared spectroscopic identification of dispersant/particle bonding mechanisms in functional inks.

    PubMed

    Deiner, L Jay; Farjami, Elaheh

    2015-01-01

    In additive manufacturing, or 3D printing, material is deposited drop by drop, to create micron to macroscale layers. A typical inkjet ink is a colloidal dispersion containing approximately ten components including solvent, the nano to micron scale particles which will comprise the printed layer, polymeric dispersants to stabilize the particles, and polymers to tune layer strength, surface tension and viscosity. To rationally and efficiently formulate such an ink, it is crucial to know how the components interact. Specifically, which polymers bond to the particle surfaces and how are they attached? Answering this question requires an experimental procedure that discriminates between polymer adsorbed on the particles and free polymer. Further, the method must provide details about how the functional groups of the polymer interact with the particle. In this protocol, we show how to employ centrifugation to separate particles with adsorbed polymer from the rest of the ink, prepare the separated samples for spectroscopic measurement, and use Diffuse Reflectance Fourier Transform Infrared Spectroscopy (DRIFTS) for accurate determination of dispersant/particle bonding mechanisms. A significant advantage of this methodology is that it provides high level mechanistic detail using only simple, commonly available laboratory equipment. This makes crucial data available to almost any formulation laboratory. The method is most useful for inks composed of metal, ceramic, and metal oxide particles in the range of 100 nm or greater. Because of the density and particle size of these inks, they are readily separable with centrifugation. Further, the spectroscopic signatures of such particles are easy to distinguish from absorbed polymer. The primary limitation of this technique is that the spectroscopy is performed ex-situ on the separated and dried particles as opposed to the particles in dispersion. However, results from attenuated total reflectance spectra of the wet separated

  3. An integrated acoustic and dielectrophoretic particle manipulation in a microfluidic device for particle wash and separation fabricated by mechanical machining.

    PubMed

    Çetin, Barbaros; Özer, Mehmet Bülent; Çağatay, Erdem; Büyükkoçak, Süleyman

    2016-01-01

    In this study, acoustophoresis and dielectrophoresis are utilized in an integrated manner to combine the two different operations on a single polydimethylsiloxane (PDMS) chip in sequential manner, namely, particle wash (buffer exchange) and particle separation. In the washing step, particles are washed with buffer solution with low conductivity for dielectrophoretic based separation to avoid the adverse effects of Joule heating. Acoustic waves generated by piezoelectric material are utilized for washing, which creates standing waves along the whole width of the channel. Coupled electro-mechanical acoustic 3D multi-physics analysis showed that the position and orientation of the piezoelectric actuators are critical for successful operation. A unique mold is designed for the precise alignment of the piezoelectric materials and 3D side-wall electrodes for a highly reproducible fabrication. To achieve the throughput matching of acoustophoresis and dielectrophoresis in the integration, 3D side-wall electrodes are used. The integrated device is fabricated by PDMS molding. The mold of the integrated device is fabricated using high-precision mechanical machining. With a unique mold design, the placements of the two piezoelectric materials and the 3D sidewall electrodes are accomplished during the molding process. It is shown that the proposed device can handle the wash and dielectrophoretic separation successfully. PMID:26865905

  4. Mechanical stimulation and intermittent parathyroid hormone treatment induce disproportional osteogenic, geometric, and biomechanical effects in growing mouse bone

    PubMed Central

    McAteer, Maureen E.; Niziolek, Paul J.; Ellis, Shana N.; Alge, Daniel L.; Robling, Alexander G.

    2011-01-01

    Mechanical loading and intermittent parathyroid (iPTH) treatment are both osteoanabolic stimuli, and are regulated by partially overlapping cellular signaling pathways. iPTH has been shown clinically to be effective in increasing bone mass and reducing fracture risk. Likewise, mechanical stimulation can significantly enhance bone apposition and prevent bone loss, but its clinical effects on fracture susceptibility are less certain. Many of the osteogenic effects of iPTH are localized to biomechanically suboptimal bone surfaces, whereas mechanical loading directs new bone formation to high-stress areas and not to strain-neutral areas. These differences in localization in new tissue, resulting from load-induced vs iPTH-induced bone accumulation, should affect the relation between bone mass and bone strength, or “tissue economy.” We investigated the changes in bone mass and strength induced by 6 wks mechanical loading, and compared them to changes induced by 6 wks iPTH treatment. Loading and iPTH both increased ulnar bone accrual, as measured by bone mineral density and content, and fluorochrome-derived bone formation. iPTH induced a significantly greater increase in bone mass than loading, but ulnar bone strength was increased approximately the same amount by both treatments. Mechanical loading during growth can spatially optimize new bone formation to improve structural integrity with a minimal increase in mass, thereby increasing tissue economy i.e., the amount of strength returned per unit bone mass added. Furthermore, exercise studies in which only small changes in bone mass are detected might be more beneficial to bone health and fracture resistance than has commonly been presumed. PMID:20306026

  5. Morphological Variations of Explosive Residue Particles and Implications for Understanding Detonation Mechanisms.

    PubMed

    Abdul-Karim, Nadia; Blackman, Christopher S; Gill, Philip P; Morgan, Ruth M; Matjacic, Lidija; Webb, Roger; Ng, Wing H

    2016-04-01

    The possibility of recovering undetonated explosive residues following detonation events is well-known; however, the morphology and chemical identity of these condensed phase postblast particles remains undetermined. An understanding of the postblast explosive particle morphology would provide vital information during forensic examinations, allowing rapid initial indication of the explosive material to be microscopically determined prior to any chemical analyses and thereby saving time and resources at the crucial stage of an investigation. In this study, condensed phase particles collected from around the detonations of aluminized ammonium nitrate and RDX-based explosive charges were collected in a novel manner utilizing SEM stubs. By incorporating the use of a focused ion beam during analysis, for the first time it is possible to determine that such particles have characteristic shapes, sizes, and internal structures depending on the explosive and the distance from the detonation at which the particles are recovered. Spheroidal particles (10-210 μm) with microsurface features recovered following inorganic charge detonations were dissimilar to the irregularly shaped particles (5-100 μm) recovered following organic charge firings. Confirmatory analysis to conclude that the particles were indeed explosive included HPLC-MS, Raman spectroscopy, and mega-electron volt-secondary ionization mass spectrometry. These results may impact not only forensic investigations but also the theoretical constructs that govern detonation theory by indicating the potential mechanisms by which these particles survive and how they vary between the different explosive types. PMID:26938055

  6. Mechanism of formation of composite CdS-ZnS ultrafine particles in reverse micelles

    SciTech Connect

    Sato, Hiroshi; Hirai, Takayuki; Komasawa, Isao

    1995-07-01

    The mechanism of formation of composite cadmium sulfide and zinc sulfide ultrafine particles (Cd{sub 1{minus}x}Zn{sub x}S) by simultaneous precipitation of cadmium sulfide and zinc sulfide in sodium bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane reverse micelles has been studied. The particle formation process was followed by the change in UV-visible absorption spectra. The effects of the reactant concentration, the molar ratio of cadmium to zinc ions, and the water content on the particle formation process were investigated. The resultant particles were richer in CdS than the feed composition of the cadmium to zinc ions in the reaction solution. The particle composition was found to be controlled by the solubility of the CdS and ZnS ultrafine particles. The particle coagulation process was analyzed on the basis of a statistical distribution of particles among the reverse micelles. The coagulation rate constant was controlled by the composition and the size of the particles and by the size of the reverse micelles.

  7. Fluid flow and particle transport in mechanically ventilated airways. Part II: particle transport.

    PubMed

    Alzahrany, Mohammed; Van Rhein, Timothy; Banerjee, Arindam; Salzman, Gary

    2016-07-01

    The flow mechanisms that play a role on aerosol deposition were identified and presented in a companion paper (Timothy et al. in Med Biol Eng Comput. doi: 10.1007/s11517-015-1407-3 , 2015). In the current paper, the effects of invasive conventional mechanical ventilation waveforms and endotracheal tube (ETT) on the aerosol transport were investigated. In addition to the enhanced deposition seen at the carinas of the airway bifurcations, enhanced deposition was also seen in the right main bronchus due to impaction and turbulent dispersion resulting from the fluid structures created by jet caused by the ETT. The orientation of the ETT toward right bronchus resulted in a substantial deposition inside right lung compared to left lung. The deposition inside right lung was ~12-fold higher than left lung for all considered cases, except for the case of using pressure-controlled sinusoidal waveform where a reduction of this ratio by ~50 % was found. The total deposition during pressure constant, volume ramp, and ascending ramp waveforms was similar and ~1.44 times higher than deposition fraction when using pressure sinusoidal waveform. Varying respiratory waveform demonstrated a significant role on the deposition enhancement factors and give evidence of drug aerosol concentrations in key deposition sites, which may be significant for drugs with negative side effects in high concentrations. These observations are thought to be important for ventilation treatment strategy. PMID:26541600

  8. Experimental investigation of particle deposition mechanisms in the lung acinus using microfluidic models.

    NASA Astrophysics Data System (ADS)

    Fishler, Rami; Mulligan, Molly; Dubowski, Yael; Sznitman, Josue; Sznitman Lab-department of Biomedical Engineering Team; Dubowski Lab-faculty of Civil; Environmental Engineering Team

    2014-11-01

    In order to experimentally investigate particle deposition mechanisms in the deep alveolated regions of the lungs, we have developed a novel microfluidic device mimicking breathing acinar flow conditions directly at the physiological scale. The model features an anatomically-inspired acinar geometry with five dichotomously branching airway generations lined with periodically expanding and contracting alveoli. Deposition patterns of airborne polystyrene microspheres (spanning 0.1 μm to 2 μm in diameter) inside the airway tree network compare well with CFD simulations and reveal the roles of gravity and Brownian motion on particle deposition sites. Furthermore, measured trajectories of incense particles (0.1-1 μm) inside the breathing device show a critical role for Brownian diffusion in determining the fate of inhaled sub-micron particles by enabling particles to cross from the acinar ducts into alveolar cavities, especially during the short time lag between inhalation and exhalation phases.

  9. By Different Cellular Mechanisms, Lymphatic Vessels Sprout by Endothelial Cell Recruitment Whereas Blood Vessels Grow by Vascular Expansion

    NASA Technical Reports Server (NTRS)

    Parsons-Wingerter, Patricia; McKay, Terri L.; Leontiev, Dmitry; Condrich, Terence K.; DiCorleto, Paul E.

    2005-01-01

    The development of effective vascular therapies requires the understanding of all modes of vessel formation contributing to vasculogenesis, angiogenesis (here termed hemangiogenesis) and lymphangiogenesis. We show that lymphangiogenesis proceeds by blind-ended vessel sprouting via recruitment of isolated endothelial progenitor cells to the tips of growing vessels, whereas hemangiogenesis occurs by non-sprouting vessel expansion from the capillary network, during middevelopment in the quail chorioallantoic membrane (CAM). Blood vessels expanded out of capillaries that displayed transient expression of alpha smooth muscle actin (alphaSMA), accompanied by mural recruitment of migratory progenitor cells expressing SMA. Lymphatics and blood vessels were identified by confocal/fluorescence microscopy of vascular endothelial growth factor (VEGF) receptors VEGFR-1 and VEGFR-2, alphaSMA (expressed on CAM blood vessels but not on lymphatics), homeobox transcription factor Prox-1 (specific to CAM lymphatic endothelium), and the quail hematopoetic/vascular marker, QH-1. Expression of VEGFR-1 was highly restricted to blood vessels (primarily capillaries). VEGFR-2 was expressed intensely in isolated hematopoietic cells, lymphatic vessels and moderately in blood vessels. Prox-1 was absent from endothelial progenitor cells prior to lymphatic recruitment. Although vascular endothelial growth factor-165 (VEGF(sub 165)) is a key regulator of numerous cellular processes in hemangiogenesis and vasculogenesis, the role of VEGF(sub 165) in lymphangiogenesis is less clear. Exogenous VEGF(sub 165) increased blood vessel density without changing endogenous modes of vascular/lymphatic vessel formation or marker expression patterns. However, VEGF(sub 165) did increase the frequency of blood vascular anastomoses and strongly induced the antimaturational dissociation of lymphatics from blood vessels, with frequent formation of homogeneous lymphatic networks.

  10. Mechanism for Particle Transport and Size Sorting via Low-Frequency Vibrations

    NASA Technical Reports Server (NTRS)

    Sherrit, Stewart; Scott, James S.; Bar-Cohen, Yoseph; Badescu, Mircea; Bao, Xiaoqi

    2010-01-01

    There is a need for effective sample handling tools to deliver and sort particles for analytical instruments that are planned for use in future NASA missions. Specifically, a need exists for a compact mechanism that allows transporting and sieving particle sizes of powdered cuttings and soil grains that may be acquired by sampling tools such as a robotic scoop or drill. The required tool needs to be low mass and compact to operate from such platforms as a lander or rover. This technology also would be applicable to sample handling when transporting samples to analyzers and sorting particles by size.

  11. The pedagogical value of the four-dimensional picture: I. Relativistic mechanics of point particles

    NASA Astrophysics Data System (ADS)

    Kosyakov, B. P.

    2014-03-01

    In this paper we outline two subjects of relativistic mechanics: (i) the set of allowable world lines, and (ii) the origin of the relativistic law of dynamics governing point particles. We show that: (i) allowable world lines in the classical theory of particles and fields are quite simple geometric objects as opposed to their associated three-dimensional trajectories; and (ii) Newton’s second law requires neither modification nor generalization, it should only be smoothly embedded in the four-dimensional geometry of Minkowski spacetime to yield the dynamical law for relativistic particles.

  12. Airborne particle generation for optical tweezers by thermo-mechanical membrane actuators

    NASA Astrophysics Data System (ADS)

    Polster, T.; Leopold, S.; Hoffmann, M.

    2011-06-01

    This article presents a new approach for airborne particle generation for optical tweezers. The used element is a 500 nm thin aluminum nitride membrane with an integrated heating element. Thus the membrane works as thermo-mechanical actor. The membrane device is characterized concerning their mechanical and thermal behavior. Successful airborne particle generation is demonstrated with 10 μm silicon dioxide spheres. They are lifted up some 10th of μm from the membrane surface. The development and test of this device serves as starting point for experiments with optical tweezers in air.

  13. Particle Disease: A Current Review of the Biological Mechanisms in Periprosthetic Osteolysis After Hip Arthroplasty

    PubMed Central

    Sukur, Erhan; Akman, Yunus Emre; Ozturkmen, Yusuf; Kucukdurmaz, Fatih

    2016-01-01

    Background: Inflammatory responses to wear debris cause osteolysis that leads to aseptic prosthesis loosening and hip arthroplasty failure. Although osteolysis is usually associated with aseptic loosening, it is rarely seen around stable implants. Aseptic implant loosening is a simple radiologic phenomenon, but a complex immunological process. Particulate debris produced by implants most commonly causes osteolysis, and this is called particle-associated periprosthetic osteolysis (PPO). Objective: The objective of this review is to outline the features of particle-associated periprosthetic osteolysis to allow the physician to recognise this condition and commence early treatment, thereby optimizing patient outcome. Methods: A thorough literature search was performed using available databases, including Pubmed, to cover important research published covering particle-associated PPO. Results: Although osteolysis causes bone resorption, clinical, animal, and in vitro studies of particle bioreactivity suggest that particle-associated PPO represents the culmination of several biological reactions of many cell types, rather than being caused solely by the osteoclasts. The biological activity is highly dependent on the characteristics and quantity of the wear particles. Conclusion: Despite advances in total hip arthroplasty (THA), particle-associated PPO and aseptic loosening continue to be major factors that affect prosthetic joint longevity. Biomarkers could be exploited as easy and objective diagnostic and prognostic targets that would enable testing for osteolysis after THA. Further research is needed to identify new biomarkers in PPO. A comprehensive understanding of the underlying biological mechanisms is crucial for developing new therapeutic interventions to reverse or suppress biological responses to wear particles. PMID:27499822

  14. Effect of Thermal Treatment of Fast Growing Wood Fibers on Physical and Mechanical Properties of Light Medium Density Fiberboard

    NASA Astrophysics Data System (ADS)

    Jarusombuti, Songklod; Ayrilmis, Nadir; Fueangvivat, Vallayuth; Bauchongkol, Piyawade

    2011-06-01

    This study investigated physical and mechanical properties of the light medium density fiberboard (MDF) panels made from thermally treated wood fibers of eucalyptus camaldulensis at three different temperatures (393 K, 423 K or 453 K) for 30 or 60 min in a laboratory autoclave. The average thickness swelling of the panels decreased by 16-54% depending on the treatment temperature and time. However, the modulus of rupture, modulus of elasticity, and internal bond strength decreased by 16-37%, 9-25% and 10-39%, respectively. Based on the findings obtained from the present study, it may be said that wood fibers of E. camaldulensis treated at 453 K - 30 min can be used in the light MDF manufacture for use in humid conditions, such as kitchen and bathroom furniture requiring improved dimensional stability.

  15. A mass spectrometric study of the simultaneous reaction mechanism of TMIn and PH3 to grow InP

    NASA Technical Reports Server (NTRS)

    Buchan, N. I.; Larsen, C. A.; Stringfellow, G. B.

    1988-01-01

    The reaction mechanisms for the growth of InP from various mixtures of trimethyl indium (TMIn) and PH3 by OMVPE were investigated using mass spectrometry and a D2 ambient for isotopic labeling of the reaction products. It was found that, whereas TMIn alone pyrolyzes homogeneously, forming CH3D, and PH3 alone pyrolyzes heterogeneously, producing H2, the pyrolysis reactions of TMIn and PH3 together are completely different. The pyrolysis temperatures of both TMIn and PH3 are reduced (by 50 C for TMIn and 225 C for PH3), and the sole product is CH4 at high values of the PH3/TMIn ratio. The pyrolysis reaction is shown to be coupled (as evidenced by the equal depletion of TMIn and PH3 from the vapor) and, at temperatures below 400 C, heterogeneous.

  16. Scaling of volume to surface ratio and doubling time in growing unicellular organisms: Do cells appear quantum-mechanical systems?

    NASA Astrophysics Data System (ADS)

    Atanasov, Atanas Todorov

    2014-10-01

    The scaling of physical and biological characteristics of the living organisms is a basic method for searching of new biophysical laws. In series of previous studies the author showed that in Poikilotherms, Mammals and Aves, the volume to surface ratio V×S-1 (m) of organisms is proportional to their generation time Tgt(s) via growth rate v (m s-1): V×S-1 = vgr×Tr. The power and the correlation coefficients are near to 1.0. Aim of this study is: i) to prove with experimental data the validity of the above equation for Unicellular organisms and ii) to show that perhaps, the cells are quantum-mechanical systems. The data for body mass M (kg), density ρ (kg/m3), minimum and maximum doubling time Tdt (s) for 50 unicellular organisms are assembled from scientific sources, and the computer program `Statistics' is used for calculations. In result i) the analytical relationship from type: V×S-1 = 4.46ṡ10-11×Tdt was found, where vgr = 4.46×10-11 m/s and ii) it is shown that the products between cell mass M, cell length expressed by V/S ratio and growth rate vgr satisfied the Heisenberg uncertainty principle i.e. the inequalities V/S×M×vgr>h/2π and Tdt×M×vgr2>h/2π are valid, where h= 6.626×10-34 Jṡs is the Planck constant. This rise the question: do cells appear quantum-mechanical systems?

  17. Scaling of volume to surface ratio and doubling time in growing unicellular organisms: Do cells appear quantum-mechanical systems?

    SciTech Connect

    Atanasov, Atanas Todorov

    2014-10-06

    The scaling of physical and biological characteristics of the living organisms is a basic method for searching of new biophysical laws. In series of previous studies the author showed that in Poikilotherms, Mammals and Aves, the volume to surface ratio V×S{sup −1} (m) of organisms is proportional to their generation time T{sub gt}(s) via growth rate v (m s{sup −1}): V×S{sup −1} = v{sub gr}×T{sup r}. The power and the correlation coefficients are near to 1.0. Aim of this study is: i) to prove with experimental data the validity of the above equation for Unicellular organisms and ii) to show that perhaps, the cells are quantum-mechanical systems. The data for body mass M (kg), density ρ (kg/m{sup 3}), minimum and maximum doubling time T{sub dt} (s) for 50 unicellular organisms are assembled from scientific sources, and the computer program ‘Statistics’ is used for calculations. In result i) the analytical relationship from type: V×S{sup −1} = 4.46⋅10{sup −11}×T{sub dt} was found, where v{sub gr} = 4.46×10{sup −11} m/s and ii) it is shown that the products between cell mass M, cell length expressed by V/S ratio and growth rate v{sub gr} satisfied the Heisenberg uncertainty principle i.e. the inequalities V/S×M×v{sub gr}>h/2π and T{sub dt}×M×v{sub gr}{sup 2}>h/2π are valid, where h= 6.626×10{sup −34} J⋅s is the Planck constant. This rise the question: do cells appear quantum-mechanical systems?.

  18. COMPARATIVE IN VITRO CARDIAC TOXICITY OF PRIMARY COMBUSTION PARTICLES: IDENTIFICATION OF CAUSAL CONSTITUENTS AND MECHANISMS OF INJURY

    EPA Science Inventory

    Identification of causal particle characteristics and mechanisms of injury would allow linkage of particulate air pollution adverse health effects to sources. Research has examined the direct cardiovascular effects of air pollution particle constituents since previous studies dem...

  19. Self-Propulsion Mechanism of Active Janus Particles in Near-Critical Binary Mixtures

    NASA Astrophysics Data System (ADS)

    Samin, Sela; van Roij, René

    2015-10-01

    Gold-capped Janus particles immersed in a near-critical binary mixture can be propelled using illumination. We employ a nonisothermal diffuse interface approach to investigate the self-propulsion mechanism of a single colloid. We attribute the motion to body forces at the edges of a micronsized droplet that nucleates around the particle. Thus, the often-used concept of a surface velocity cannot account for the self-propulsion. The particle's swimming velocity is related to the droplet shape and size, which is determined by a so-called critical isotherm. Two distinct swimming regimes exist, depending on whether the droplet partially or completely covers the particle. Interestingly, the dependence of the swimming velocity on temperature is nonmonotonic in both regimes.

  20. Chemo-Mechanical Characteristics of Mud Formed from Environmental Dust Particles in Humid Ambient Air

    PubMed Central

    Hassan, Ghassan; Yilbas, B. S.; Said, Syed A. M.; Al-Aqeeli, N.; Matin, Asif

    2016-01-01

    Mud formed from environmental dust particles in humid ambient air significantly influences the performance of solar harvesting devices. This study examines the characterization of environmental dust particles and the chemo-mechanics of dry mud formed from dust particles. Analytical tools, including scanning electron microscopy, atomic force microscopy, energy dispersive spectroscopy, particle sizing, and X-ray diffraction, are used to characterize dry mud and dust particles. A micro/nano tribometer is used to measure the tangential force and friction coefficient while tensile tests are carried out to assess the binding forces of dry mud pellets. After dry mud is removed, mud residuals on the glass surface are examined and the optical transmittance of the glass is measured. Dust particles include alkaline compounds, which dissolve in water condensate and form a mud solution with high pH (pH = 7.5). The mud solution forms a thin liquid film at the interface of dust particles and surface. Crystals form as the mud solution dries, thus, increasing the adhesion work required to remove dry mud from the surface. Optical transmittance of the glass is reduced after dry mud is removed due to the dry mud residue on the surface. PMID:27445272

  1. Chemo-Mechanical Characteristics of Mud Formed from Environmental Dust Particles in Humid Ambient Air

    NASA Astrophysics Data System (ADS)

    Hassan, Ghassan; Yilbas, B. S.; Said, Syed A. M.; Al-Aqeeli, N.; Matin, Asif

    2016-07-01

    Mud formed from environmental dust particles in humid ambient air significantly influences the performance of solar harvesting devices. This study examines the characterization of environmental dust particles and the chemo-mechanics of dry mud formed from dust particles. Analytical tools, including scanning electron microscopy, atomic force microscopy, energy dispersive spectroscopy, particle sizing, and X-ray diffraction, are used to characterize dry mud and dust particles. A micro/nano tribometer is used to measure the tangential force and friction coefficient while tensile tests are carried out to assess the binding forces of dry mud pellets. After dry mud is removed, mud residuals on the glass surface are examined and the optical transmittance of the glass is measured. Dust particles include alkaline compounds, which dissolve in water condensate and form a mud solution with high pH (pH = 7.5). The mud solution forms a thin liquid film at the interface of dust particles and surface. Crystals form as the mud solution dries, thus, increasing the adhesion work required to remove dry mud from the surface. Optical transmittance of the glass is reduced after dry mud is removed due to the dry mud residue on the surface.

  2. Chemo-Mechanical Characteristics of Mud Formed from Environmental Dust Particles in Humid Ambient Air.

    PubMed

    Hassan, Ghassan; Yilbas, B S; Said, Syed A M; Al-Aqeeli, N; Matin, Asif

    2016-01-01

    Mud formed from environmental dust particles in humid ambient air significantly influences the performance of solar harvesting devices. This study examines the characterization of environmental dust particles and the chemo-mechanics of dry mud formed from dust particles. Analytical tools, including scanning electron microscopy, atomic force microscopy, energy dispersive spectroscopy, particle sizing, and X-ray diffraction, are used to characterize dry mud and dust particles. A micro/nano tribometer is used to measure the tangential force and friction coefficient while tensile tests are carried out to assess the binding forces of dry mud pellets. After dry mud is removed, mud residuals on the glass surface are examined and the optical transmittance of the glass is measured. Dust particles include alkaline compounds, which dissolve in water condensate and form a mud solution with high pH (pH = 7.5). The mud solution forms a thin liquid film at the interface of dust particles and surface. Crystals form as the mud solution dries, thus, increasing the adhesion work required to remove dry mud from the surface. Optical transmittance of the glass is reduced after dry mud is removed due to the dry mud residue on the surface. PMID:27445272

  3. Simple One-Dimensional Quantum-Mechanical Model for a Particle Attached to a Surface

    ERIC Educational Resources Information Center

    Fernandez, Francisco M.

    2010-01-01

    We present a simple one-dimensional quantum-mechanical model for a particle attached to a surface. It leads to the Schrodinger equation for a harmonic oscillator bounded on one side that we solve in terms of Weber functions and discuss the behaviour of the eigenvalues and eigenfunctions. We derive the virial theorem and other exact relationships…

  4. EFFECTS OF TEMPERATURE AND PRESSURE ON PARTICLE COLLECTION MECHANISMS: THEORETICAL REVIEW

    EPA Science Inventory

    The report is a critical review and evaluation of the mechanics of aerosols at high temperatures and pressures. It discusses equations and models used to predict particle behavior at normal conditions, with regard to their applicability at high temperatures and pressures. It disc...

  5. SIGNALING MECHANISMS IN HUMAN AIRWAY EPITHELIAL CELLS EXPOSED TO CARBON ULTRAFINE PARTICLES

    EPA Science Inventory

    SIGNALING MECHANISMS IN HUMAN AIRWAY EPITHELIAL CELLS EXPOSED TO CARBON ULTRAFINE PARTICLES
    Y.M. Kim, A.G. Lenz, R. Silbajoris, I. Jaspers and J.M. Samet. Department of Environmental Sciences and Engineering and Center for Environmental Medicine, University of North Carolina, ...

  6. Cyclic Polyynes as Examples of the Quantum Mechanical Particle on a Ring

    ERIC Educational Resources Information Center

    Anderson, Bruce D.

    2012-01-01

    Many quantum mechanical models are discussed as part of the undergraduate physical chemistry course to help students understand the connection between eigenvalue expressions and spectroscopy. Typical examples covered include the particle in a box, the harmonic oscillator, the rigid rotor, and the hydrogen atom. This article demonstrates that…

  7. A generalized mass transfer law unifying various particle transport mechanisms in dilute dispersions

    NASA Astrophysics Data System (ADS)

    Guha, Abhijit

    2008-09-01

    A generalized mass transfer law for dilute dispersion of particles (or droplets) of any sizes suspended in a fluid has been described, which can be applied to turbulent or laminar flow. The generalized law reduces to the Fick’s law of diffusion in the limit of very small particles. Thus the study shows how the well-known and much-used Fick’s law of diffusion fits into the broader context of particle transport. The general expression for particle flux comprises a diffusive flux due to Brownian motion and turbulent fluctuation, a diffusive flux due to temperature gradient (thermophoresis plus stressphoresis) and a convective flux that arises primarily due to the interaction of particle inertia and the inhomogeneity of the fluid turbulence field (turbophoresis). Shear-induced lift force, electrical force, gravity, etc. also contribute to the convective flux. The present study includes the effects of surface roughness, and the calculations show that the presence of small surface roughness even in the hydraulically smooth regime significantly enhances deposition especially of small particles. Thermophoresis can have equally strong effects, even with a modest temperature difference between the wall and the bulk fluid. For particles of the intermediate size range, turbophoresis, thermophoresis and roughness are all important contributors to the overall deposition rate. The paper includes a parametric study of the effects of electrostatic forces due to mirror charging. The present work provides a unified framework to determine the combined effect of various particle transport mechanisms on mass transfer rate and the inclusion of other mechanisms not considered in this paper is possible.

  8. Optimum selection of mechanism type for heavy manipulators based on particle swarm optimization method

    NASA Astrophysics Data System (ADS)

    Zhao, Yong; Chen, Genliang; Wang, Hao; Lin, Zhongqin

    2013-07-01

    The mechanism type plays a decisive role in the mechanical performance of robotic manipulators. Feasible mechanism types can be obtained by applying appropriate type synthesis theory, but there is still a lack of effective and efficient methods for the optimum selection among different types of mechanism candidates. This paper presents a new strategy for the purpose of optimum mechanism type selection based on the modified particle swarm optimization method. The concept of sub-swarm is introduced to represent the different mechanisms generated by the type synthesis, and a competitive mechanism is employed between the sub-swarms to reassign their population size according to the relative performances of the mechanism candidates to implement the optimization. Combining with a modular modeling approach for fast calculation of the performance index of the potential candidates, the proposed method is applied to determine the optimum mechanism type among the potential candidates for the desired manipulator. The effectiveness and efficiency of the proposed method is demonstrated through a case study on the optimum selection of mechanism type of a heavy manipulator where six feasible candidates are considered with force capability as the specific performance index. The optimization result shows that the fitness of the optimum mechanism type for the considered heavy manipulator can be up to 0.578 5. This research provides the instruction in optimum selection of mechanism types for robotic manipulators.

  9. Ultrafine particles cross cellular membranes by nonphagocytic mechanisms in lungs and in cultured cells.

    PubMed

    Geiser, Marianne; Rothen-Rutishauser, Barbara; Kapp, Nadine; Schürch, Samuel; Kreyling, Wolfgang; Schulz, Holger; Semmler, Manuela; Im Hof, Vinzenz; Heyder, Joachim; Gehr, Peter

    2005-11-01

    High concentrations of airborne particles have been associated with increased pulmonary and cardiovascular mortality, with indications of a specific toxicologic role for ultrafine particles (UFPs; particles < 0.1 microm). Within hours after the respiratory system is exposed to UFPs, the UFPs may appear in many compartments of the body, including the liver, heart, and nervous system. To date, the mechanisms by which UFPs penetrate boundary membranes and the distribution of UFPs within tissue compartments of their primary and secondary target organs are largely unknown. We combined different experimental approaches to study the distribution of UFPs in lungs and their uptake by cells. In the in vivo experiments, rats inhaled an ultrafine titanium dioxide aerosol of 22 nm count median diameter. The intrapulmonary distribution of particles was analyzed 1 hr or 24 hr after the end of exposure, using energy-filtering transmission electron microscopy for elemental microanalysis of individual particles. In an in vitro study, we exposed pulmonary macrophages and red blood cells to fluorescent polystyrene microspheres (1, 0.2, and 0.078 microm) and assessed particle uptake by confocal laser scanning microscopy. Inhaled ultrafine titanium dioxide particles were found on the luminal side of airways and alveoli, in all major lung tissue compartments and cells, and within capillaries. Particle uptake in vitro into cells did not occur by any of the expected endocytic processes, but rather by diffusion or adhesive interactions. Particles within cells are not membrane bound and hence have direct access to intracellular proteins, organelles, and DNA, which may greatly enhance their toxic potential. PMID:16263511

  10. Silicon-based elementary particle tracking system: Materials science and mechanical engineering design

    SciTech Connect

    Miller, W.O.; Gamble, M.T.; Thompson, T.C.; Hanlon, J.A.

    1993-01-01

    Research and development of the mechanical, cooling, and structural design aspects of a silicon detector-based elementary particle tracking system has been performed. Achieving stringent system precision, stability, and mass requirements necessitated the use of graphite fiber-reinforced cyanate-ester (C-E) resins. Mechanical test results of the effects of butane, ionizing radiation, and a combination of both on the mechanical properties of these materials are presented, as well as progress on developing compression molding of an ultralightweight graphite composite ring structure and TV holography-based noninvasive evaluation.

  11. Silicon-based elementary particle tracking system: Materials science and mechanical engineering design

    SciTech Connect

    Miller, W.O.; Gamble, M.T.; Thompson, T.C.; Hanlon, J.A.

    1993-05-01

    Research and development of the mechanical, cooling, and structural design aspects of a silicon detector-based elementary particle tracking system has been performed. Achieving stringent system precision, stability, and mass requirements necessitated the use of graphite fiber-reinforced cyanate-ester (C-E) resins. Mechanical test results of the effects of butane, ionizing radiation, and a combination of both on the mechanical properties of these materials are presented, as well as progress on developing compression molding of an ultralightweight graphite composite ring structure and TV holography-based noninvasive evaluation.

  12. Correlation between erythropoietic activity and body growth rate in hypertransfused polycythemic growing rats as the result of an erythropoietin-dependent operating mechanism

    SciTech Connect

    Bozzini, C.E.; Alippi, R.M.; Barcelo, A.C.; Caro, J.

    1989-02-01

    The established relationship between erythropoietic activity and body growth rate in the polycythemic growing rat could be the result of either an erythropoietin (EPO)-dependent or an EPO-independent operating mechanism. The present study was thus undertaken to elucidate the nature of the aforementioned mechanism by assessing the ratio between plasma immunoreactive EPO (iEPO) concentration and erythropoietic activity in young hypertransfused rats for different body growth rates. Red blood cell (RBC)-59Fe uptake was about 75% in 21-day-old rats; it rapidly decreased with time when the animals were placed on a protein-free diet, approaching a level of about 1% by the 10th day of protein starvation. Over the same period plasma iEPO decreased from 55 mU/ml to 7 mU/ml. Body growth rate was 0. Following this ''protein depletion period'' the rats received diets containing different amounts of casein (''protein repletion period'') added isocalorically to the protein-free diet to elicit a rise in body growth rate. Statistically significant relationships (p less than 0.001) were found between dietary casein concentration and body growth rate (r = 0.991), dietary casein concentration and RBC-59Fe uptake (r = 0.991), dietary casein concentration and plasma iEPO level (r = 0.992), body growth rate and RBC-59Fe (r = 0.986), and body growth rate and plasma iEPO level (r = 0.994) in hypertransfused polycythemic rats during the protein repletion period. These findings suggest that the correlation between erythropoietic activity and growth rate in the growing rat is the result of an erythropoietin-dependent operating mechanism, which appears to be independent of the ratio tissue oxygen supply/tissue oxygen demand.

  13. Macromolecular crystal growing system

    NASA Technical Reports Server (NTRS)

    Snyder, Robert S. (Inventor); Herren, Blair J. (Inventor); Carter, Daniel C. (Inventor); Yost, Vaughn H. (Inventor); Bugg, Charles E. (Inventor); Delucas, Lawrence J. (Inventor); Suddath, Fred L. (Inventor)

    1991-01-01

    A macromolecular crystal growing system especially designed for growing crystals in the low gravity of space as well as the gravity of earth includes at least one tray assembly, a carrier assembly which receives the tray, and a refrigeration-incubation module in which the carrier assembly is received. The tray assembly includes a plurality of sealed chambers with a plastic syringe and a plug means for the double tip of the syringe provided therein. Ganging mechanisms operate the syringes and plugs simultaneously in a precise and smooth operation. Preferably, the tray assemblies are mounted on ball bearing slides for smooth operation in inserting and removing the tray assemblies into the carrier assembly. The plugging mechanism also includes a loading control mechanism. A mechanism for leaving a syringe unplugged is also provided.

  14. Nonequilibrium statistical mechanics of mixtures of particles in contact with different thermostats

    NASA Astrophysics Data System (ADS)

    Grosberg, A. Y.; Joanny, J.-F.

    2015-09-01

    We introduce a novel type of locally driven systems made of two types of particles (or a polymer with two types of monomers) subject to a chaotic drive with approximately white noise spectrum, but different intensity; in other words, particles of different types are in contact with thermostats at different temperatures. We present complete systematic statistical mechanics treatment starting from first principles. Although we consider only corrections to the dilute limit due to pairwise collisions between particles, meaning we study a nonequilibrium analog of the second virial approximation, we find that the system exhibits a surprisingly rich behavior. In particular, pair correlation function of particles has an unusual quasi-Boltzmann structure governed by an effective temperature distinct from that of any of the two thermostats. We also show that at sufficiently strong drive the uniformly mixed system becomes unstable with respect to steady states consisting of phases enriched with different types of particles. In the second virial approximation, we define nonequilibrium "chemical potentials" whose gradients govern diffusion fluxes and a nonequilibrium "osmotic pressure," which governs the mechanical stability of the interface.

  15. Mechanisms governing the interaction of metallic particles with nanosecond laser pulses.

    PubMed

    Demos, Stavros G; Negres, Raluca A; Raman, Rajesh N; Shen, Nan; Rubenchik, Alexander M; Matthews, Manyalibo J

    2016-04-01

    The interaction of nanosecond laser pulses at 1064- and 355-nm with micro-scale, nominally spherical metallic particles is investigated in order to elucidate the governing interaction mechanisms as a function of material and laser parameters. The experimental model used involves the irradiation of metal particles located on the surface of transparent plates combined with time-resolved imaging capable of capturing the dynamics of particle ejection, plume formation and expansion along with the kinetics of the dispersed material from the liquefied layer of the particle. The mechanisms investigated in this work are informative and relevant across a multitude of materials and irradiation geometries suitable for the description of a wide range of specific applications. The experimental results were interpreted using physical models incorporating specific processes to assess their contribution to the overall observed behaviors. Analysis of the experimental results suggests that the induced kinetic properties of the particle can be adequately described using the concept of momentum coupling introduced to explain the interaction of plane metal targets to large-aperture laser beams. The results also suggest that laser energy deposition on the formed plasma affects the energy partitioning and the material modifications to the substrate. PMID:27137063

  16. Nonequilibrium statistical mechanics of mixtures of particles in contact with different thermostats.

    PubMed

    Grosberg, A Y; Joanny, J-F

    2015-09-01

    We introduce a novel type of locally driven systems made of two types of particles (or a polymer with two types of monomers) subject to a chaotic drive with approximately white noise spectrum, but different intensity; in other words, particles of different types are in contact with thermostats at different temperatures. We present complete systematic statistical mechanics treatment starting from first principles. Although we consider only corrections to the dilute limit due to pairwise collisions between particles, meaning we study a nonequilibrium analog of the second virial approximation, we find that the system exhibits a surprisingly rich behavior. In particular, pair correlation function of particles has an unusual quasi-Boltzmann structure governed by an effective temperature distinct from that of any of the two thermostats. We also show that at sufficiently strong drive the uniformly mixed system becomes unstable with respect to steady states consisting of phases enriched with different types of particles. In the second virial approximation, we define nonequilibrium "chemical potentials" whose gradients govern diffusion fluxes and a nonequilibrium "osmotic pressure," which governs the mechanical stability of the interface. PMID:26465437

  17. Effect of the mechanical activation on size reduction of crystalline acetaminophen drug particles.

    PubMed

    Biazar, Esmaeil; Beitollahi, Ali; Rezayat, S Mehdi; Forati, Tahmineh; Asefnejad, Azadeh; Rahimi, Mehdi; Zeinali, Reza; Ardeshir, Mahmoud; Hatamjafari, Farhad; Sahebalzamani, Ali; Heidari, Majid

    2009-01-01

    The decrease in particle size may offer new properties to drugs. In this study, we investigated the size reduction influence of the acetaminophen (C(8)H(9)O(2)N) particles by mechanical activation using a dry ball mill. The activated samples with the average size of 1 microm were then investigated in different time periods with the infrared (IR), inductively coupled plasma (ICP), atomic force microscopy (AFM), and X-ray diffraction (XRD) methods. The results of the IR and XRD images showed no change in the drug structure after the mechanical activation of all samples. With the peak height at full width at half maximum from XRD and the Scherrer equation, the size of the activated crystallite samples illustrated that the AFM images were in sound agreement with the Scherrer equation. According to the peaks of the AFM images, the average size of the particles in 30 hours of activation was 24 nm with a normal particle distribution. The ICP analysis demonstrated the presence of tungsten carbide particle impurities after activation from the powder sample impacting with the ball and jar. The greatest reduction in size was after milling for 30 hours. PMID:20054432

  18. Testing of the coalescence mechanism in high energy heavy ion collisions using two-particle correlations with identified particle trigger

    NASA Astrophysics Data System (ADS)

    Choudhury, Subikash; Sarkar, Debojit; Chattopadhyay, Subhasis

    2016-05-01

    In central Au-Au collisions at top RHIC energy, two-particle correlation measurements with identified hadron trigger have shown attenuation of near-side proton triggered jetlike yield at intermediate transverse momentum (p T ),2

    mechanism of hadronization. Baryon enhancement was also observed at LHC in the single inclusive spectra. We study the consequence of such an enhancement on two-particle correlations at LHC energy within the framework of a multiphase transport (AMPT) model that implements quark coalescence as a mode of hadronization. In this paper we have calculated the proton over pion ratio and the near side per trigger yield associated with pion and proton triggers at intermediate p T from the string melting (SM) version of AMPT. Results obtained are contrasted with the AMPT default (Def.) which does not include coalescence. Baryon enhancement was observed in AMPT SM at intermediate p T . Near-side jetlike correlated yield associated with baryon (proton) trigger in the momentum region where baryon generation is enhanced is found to be suppressed as compared to the corresponding yields for the meson (pion) trigger in most central Pb-Pb events. No such effect was found in the default version of AMPT.

  19. Contrasting macrophage activation by fine and ultrafine titanium dioxide particles is associated with different uptake mechanisms

    PubMed Central

    2011-01-01

    Inhalation of (nano)particles may lead to pulmonary inflammation. However, the precise mechanisms of particle uptake and generation of inflammatory mediators by alveolar macrophages (AM) are still poorly understood. The aim of this study was to investigate the interactions between particles and AM and their associated pro-inflammatory effects in relation to particle size and physico-chemical properties. NR8383 rat lung AM were treated with ultrafine (uf), fine (f) TiO2 or fine crystalline silica (DQ12 quartz). Physico-chemical particle properties were investigated by transmission electron microscopy, elemental analysis and thermogravimetry. Aggregation and agglomeration tendency of the particles were determined in assay-specific suspensions by means of dynamic light scattering. All three particle types were rapidly taken up by AM. DQ12 and ufTiO2 , but not fTiO2 , caused increased extracellular reactive oxygen species (ROS), heme oxygenase 1 (HO-1) mRNA expression and tumor necrosis factor (TNF)-α release. Inducible nitric oxide synthase (iNOS) mRNA expression was increased most strongly by ufTiO2 , while DQ12 exclusively triggered interleukin (IL) 1β release. However, oscillations of intracellular calcium concentration and increased intracellular ROS were observed with all three samples. Uptake inhibition experiments with cytochalasin D, chlorpromazine and a Fcγ receptor II (FcγRII) antibody revealed that the endocytosis of fTiO2 by the macrophages involves actin-dependent phagocytosis and macropinocytosis as well as clathrin-coated pit formation, whereas the uptake of ufTiO2 was dominated by FcγIIR. The uptake of DQ12 was found to be significantly reduced by all three inhibitors. Our findings suggest that the contrasting AM responses to fTiO2 , ufTiO2 and DQ12 relate to differences in the involvement of specific uptake mechanisms. PMID:21995556

  20. Another Mechanism which Can Prevent Infinite Collision Energy via Black Hole as Particle Accelerators

    NASA Astrophysics Data System (ADS)

    Ding, Chikun; Lin, Siyuan; Li, Junfeng; Wang, Peng; Li, Qian; Zhang, Binqing

    2013-03-01

    It has recently been pointed out that infinite center of mass energies for the colliding particles can be attained when the black hole is exactly extremal and only at infinite time and on the horizon of the black hole. In this letter, we show that it cannot occur when the spacetime noncommutative effect is considered, i.e. the quantum effect of gravity is an other preventing mechanism. Additionally, the bigger of the black hole's mass is, the higher of center of mass energy that the particles obtain.

  1. Quantum-mechanical description of spin-1 particles with electric dipole moments

    NASA Astrophysics Data System (ADS)

    Silenko, Alexander J.

    2013-04-01

    The Proca-Corben-Schwinger equations for a spin-1 particle with an anomalous magnetic moment are added by a term describing an electric dipole moment, then they are reduced to a Hamiltonian form, and finally they are brought to the Foldy-Wouthuysen representation. Relativistic equations of motion are derived. The needed agreement between quantum-mechanical and classical relativistic equations of motion is proved. The scalar and tensor electric and magnetic polarizabilities of pointlike spin-1 particles (W bosons) are calculated for the first time.

  2. Bihydrogel particles as free-standing mechanical pH microsensors

    NASA Astrophysics Data System (ADS)

    Tsou, Tsung-Yen; Chen, Hsien-Yeh; Hsieh, Chih-Chen

    2013-01-01

    We propose a bihydrogel mechanical microsensor made from two hydrogels with different sensitivity to the environment. The idea was used to create pH microsensors consisting of two parallel phases of crosslinked hydrogel in which only one phase is pH-sensitive. Working similarly to a bimetallic strip, the bihydrogel particle bends depending on the environmental pH. These freestanding bihydrogel particles are low-cost and easy to manufacture. They are particularly suitable for use in confined environment where most microsensors are unable to fit in. The same principle can also be used to create sensors for temperature, ionic strength, and other environmental parameters.

  3. Impact of controlled particle size nanofillers on the mechanical properties of segmented polyurethane nanocomposites

    SciTech Connect

    Finnigan, Bradley; Casey, Phil; Cookson, David; Halley, Peter; Jack, Kevin; Truss, Rowan; Martin, Darren

    2008-04-02

    The impact of average layered silicate particle size on the mechanical properties of thermoplastic polyurethane (TPU) nanocomposites has been investigated. At fixed addition levels (3 wt% organosilicate), an increase in average particle size resulted in an increase in stiffness. Negligible stiffening was observed for the smallest particles (30 nm) due to reduced long-range intercalation and molecular confinement, as well as ineffective stress transfer from matrix to filler. At low strain ({le}100%), an increase in filler particle size was associated with an increase in the rate of stress relaxation, tensile hysteresis, and permanent set. At high strain (1200%), two coexisting relaxation processes were observed. The rate of the slower (long-term) relaxation process, which is believed to primarily involve the hard segment rich structures, decreased on addition of particles with an average diameter of 200 nm or less. At high strain the tensile hysteresis was less sensitive to particle size, however the addition of particles with an average size of 200 nm or more caused a significant increase in permanent set. This was attributed to slippage of temporary bonds at the polymer-filler interface, and to the formation of voids at the sites of unaligned tactoids. Relative to the host TPU, the addition of particles with an average size of 30 nm caused a reduction in permanent set. This is a significant result because the addition of fillers to elastomers has long been associated with an increase in hysteresis and permanent set. At high strain, well dispersed and aligned layered silicates with relatively small interparticle distances and favourable surface interactions are capable of imparting a resistance to molecular slippage throughout the TPU matrix.

  4. Silver (Ag) Transport Mechanisms in TRISO Coated Particles: A Critical Review

    SciTech Connect

    IJ van Rooyen; ML Dunzik-Gougar; PM van Rooyen

    2014-05-01

    Transport of 110mAg in the intact SiC layer of TRISO coated particles has been studied for approximately 30 years without arriving at a satisfactory explanation of the transport mechanism. In this paper the possible mechanisms postulated in previous experimental studies, both in-reactor and out-of reactor research environment studies are critically reviewed and of particular interest are relevance to very high temperature gas reactor operating and accident conditions. Among the factors thought to influence Ag transport are grain boundary stoichiometry, SiC grain size and shape, the presence of free silicon, nano-cracks, thermal decomposition, palladium attack, transmutation products, layer thinning and coated particle shape. Additionally new insight to nature and location of fission products has been gained via recent post irradiation electron microscopy examination of TRISO coated particles from the DOE’s fuel development program. The combined effect of critical review and new analyses indicates a direction for investigating possible the Ag transport mechanism including the confidence level with which these mechanisms may be experimentally verified.

  5. Silver (Ag) Transport Mechanisms in TRISO coated particles: A Critical Review

    SciTech Connect

    I J van Rooyen; J H Neethling; J A A Engelbrecht; P M van Rooyen; G Strydom

    2012-10-01

    Transport of 110mAg in the intact SiC layer of TRISO coated particles has been studied for approximately 30 years without arriving at a satisfactory explanation of the transport mechanism. In this paper the possible mechanisms postulated in previous experimental studies, both in-reactor and out-of reactor research environment studies are critically reviewed and of particular interest are relevance to very high temperature gas reactor operating and accident conditions. Among the factors thought to influence Ag transport are grain boundary stoichiometry, SiC grain size and shape, the presence of free silicon, nano-cracks, thermal decomposition, palladium attack, transmutation products, layer thinning and coated particle shape. Additionally new insight to nature and location of fission products has been gained via recent post irradiation electron microscopy examination of TRISO coated particles from the DOE’s fuel development program. The combined effect of critical review and new analyses indicates a direction for investigating possible the Ag transport mechanism including the confidence level with which these mechanisms may be experimentally verified.

  6. Wave-Particle Interactions As a Driving Mechanism for the Solar Wind

    NASA Technical Reports Server (NTRS)

    Wagner, William J.

    2004-01-01

    Our research has been focusing on a highly experimentally relevant issue: intermittency of the fluctuating fields in outflowing plasmas. We have contributed to both the theoretical and experimental research of the topic. In particular, we have developed a theoretical model and data analyzing programs to examine the issue of intermittency in space plasma outflows, including the solar wind. As fluctuating electric fields in the solar wind are likely to provide a heating and acceleration mechanism for the ions, our studies of the intermittency in turbulence in space plasma outflows help us toward achieving the goal of comparing major physical mechanisms that contribute to the driving of the fast solar wind. Our new theoretical model extends the utilities of our global hybrid model, which has allowed us to follow the kinetic evolution of the particle distributions along an inhomogeneous field line while the particles are subjected to various physical mechanisms. The physical effects that were considered in the global hybrid model included wave-particle interactions, an ambipolar electric field that was consistent with the particle distributions themselves, and Coulomb collisions. With an earlier version of the global hybrid model, we examined the overall impact on the solar wind flow due to the combination of these physical effects. In particular, we studied the combined effects of two major mechanisms that had been proposed as the drivers of the fast solar wind: (1) velocity filtration effect due to suprathermal electrons; (2) ion cyclotron resonance. Since the approval of this research grant, we have updated the model such that the effects due to these two driving mechanisms can be examined separately, thereby allowing us to compare their contributions to the acceleration of the solar wind. In the next section, we shall demonstrate that the velocity filtration effect is rather insignificant in comparison with that due to ion cyclotron resonance.

  7. The Reaction Mechanism of Decomposing Chloroform by Bi-Metal Nano-Metallic Particles of Fe/Ni

    SciTech Connect

    Hsieh, Su-Hwei; Horng, Jao-Jia

    2004-03-31

    By adding Ni into the production of Fe/Ni nano-metallic particles, the acceleration of reduction ability of particles to decompose Chloroform is observed. The addition also could inhibit the shielding effect of pure iron compounds. This research studied the production and properties of the nano-particle metallic compounds of Fe and Ni, the decomposition of Chloroform by the particles and the mechanism of the decomposition processes. The experimental results indicated effective and rapid decomposition of chloroform by the Fe/Ni nano-particles on aluminum oxides, comparing to nano particles of iron in other researches. The reaction mechanism of Fe/Ni particles was pseudo first order with the half life about 0.7 hour, which was much shorter than the nano-Fe particles.

  8. Pre-activation of ice nucleating particles by the pore condensation and freezing mechanism

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Kiselev, A.; Möhler, O.; Saathoff, H.; Steinke, I.

    2015-10-01

    In spite of the resurgence in ice nucleation research a comparatively small number of studies deal with the phenomenon of pre-activation in heterogeneous ice nucleation. Already fifty years ago, it was shown that various mineral dust and volcanic ash particles can be pre-activated to become nuclei for ice crystal formation even at temperatures as high as 270-271 K. Pre-activation was achieved under ice subsaturated conditions without any preceding macroscopic ice growth by just temporarily cooling the particles to temperatures below 228 K. A two-step mechanism involving capillary condensation of supercooled water and subsequent homogeneous freezing was proposed to account for the particles' enhanced ice nucleation ability at high temperatures. This work reinvestigates the efficiency of the proposed pre-activation mechanism in temperature-cycling experiments performed in a large cloud chamber with suspended particles. We find the efficiency to be highest for the clay mineral illite as well as for highly porous materials like zeolite and diatomaceous earth, whereas most aerosols generated from desert dust surface samples did not reveal a measurable pre-activation ability. The pre-activation efficiency is linked to particle pores in a certain size range. As estimated by model calculations, only pores with diameters between about 5 and 8 nm contribute to pre-activation under ice subsaturated conditions. In contrast to the early study, pre-activation is only observed for temperatures below 260 K. Above that threshold, the particles' improved ice nucleation ability disappears due to the melting of ice in the pores.

  9. Pre-activation of ice-nucleating particles by the pore condensation and freezing mechanism

    NASA Astrophysics Data System (ADS)

    Wagner, Robert; Kiselev, Alexei; Möhler, Ottmar; Saathoff, Harald; Steinke, Isabelle

    2016-02-01

    In spite of the resurgence in ice nucleation research a comparatively small number of studies deal with the phenomenon of pre-activation in heterogeneous ice nucleation. Fifty years ago, it was shown that various mineral dust and volcanic ash particles can be pre-activated to become nuclei for ice crystal formation even at temperatures as high as 270-271 K. Pre-activation was achieved under ice-subsaturated conditions without any preceding macroscopic ice growth by just temporarily cooling the particles to temperatures below 228 K. A two-step mechanism involving capillary condensation of supercooled water and subsequent homogeneous freezing was proposed to account for the particles' enhanced ice nucleation ability at high temperatures. This work reinvestigates the efficiency of the proposed pre-activation mechanism in temperature-cycling experiments performed in a large cloud chamber with suspended particles. We find the efficiency to be highest for the clay mineral illite as well as for highly porous materials like zeolite and diatomaceous earth, whereas most aerosols generated from desert dust surface samples did not reveal a measurable pre-activation ability. The pre-activation efficiency is linked to particle pores in a certain size range. As estimated by model calculations, only pores with diameters between about 5 and 8 nm contribute to pre-activation under ice-subsaturated conditions. This range is set by a combination of requirements from the negative Kelvin effect for condensation and a critical size of ice embryos for ice nucleation and melting. In contrast to the early study, pre-activation is only observed for temperatures below 260 K. Above that threshold, the particles' improved ice nucleation ability disappears due to the melting of ice in the pores.

  10. A micromanipulation particle tester for agglomeration contact mechanism studies in a controlled environment

    NASA Astrophysics Data System (ADS)

    Haider, C. I.; Althaus, T.; Niederreiter, G.; Hounslow, M. J.; Palzer, S.; Salman, A. D.

    2012-10-01

    Pressure agglomeration of powders is widely applied in various industries and an increasing interest lies in the identification and description of contact mechanisms between particles, which are responsible for the compaction product properties. In this paper, the design and development of a novel micromanipulation particle tester (MPT) is presented. This device makes it possible to measure the deformation kinetics and resulting adhesion of two individual particles in contact under load, which are strongly influenced by the applied process conditions. The MPT set-up is, therefore, designed to offer a unique control over the process conditions most relevant to the compaction of powders: external stress, dwell or holding time at constant deformation, compression velocity as well as relative humidity and temperature determining the physical state and mechanical characteristics of hygrosensitive amorphous particles. The latter are often part of powder formulations, e.g. in the food industry, and have been used for force and contact-zone development studies with the MPT. The experimental results on the microscale level will deliver valuable quantitative information for an improved tailoring of pressure agglomeration process conditions of bulk solids.

  11. Mechanochemical mechanism for reaction of aluminium nano- and micrometre-scale particles.

    PubMed

    Levitas, Valery I

    2013-11-28

    A recently suggested melt-dispersion mechanism (MDM) for fast reaction of aluminium (Al) nano- and a few micrometre-scale particles during fast heating is reviewed. Volume expansion of 6% during Al melting produces pressure of several GPa in a core and tensile hoop stresses of 10 GPa in an oxide shell. Such stresses cause dynamic fracture and spallation of the shell. After spallation, an unloading wave propagates to the centre of the particle and creates a tensile pressure of 3-8 GPa. Such a tensile pressure exceeds the cavitation strength of liquid Al and disperses the melt into small, bare clusters (fragments) that fly at a high velocity. Reaction of the clusters is not limited by diffusion through a pre-existing oxide shell. Some theoretical and experimental results related to the MDM are presented. Various theoretical predictions based on the MDM are in good qualitative and quantitative agreement with experiments, which resolves some basic puzzles in combustion of Al particles. Methods to control and improve reactivity of Al particles are formulated, which are exactly opposite to the current trends based on diffusion mechanism. Some of these suggestions have experimental confirmation. PMID:24146008

  12. Rotating magnetic field induced oscillation of magnetic particles for in vivo mechanical destruction of malignant glioma.

    PubMed

    Cheng, Yu; Muroski, Megan E; Petit, Dorothée C M C; Mansell, Rhodri; Vemulkar, Tarun; Morshed, Ramin A; Han, Yu; Balyasnikova, Irina V; Horbinski, Craig M; Huang, Xinlei; Zhang, Lingjiao; Cowburn, Russell P; Lesniak, Maciej S

    2016-02-10

    Magnetic particles that can be precisely controlled under a magnetic field and transduce energy from the applied field open the way for innovative cancer treatment. Although these particles represent an area of active development for drug delivery and magnetic hyperthermia, the in vivo anti-tumor effect under a low-frequency magnetic field using magnetic particles has not yet been demonstrated. To-date, induced cancer cell death via the oscillation of nanoparticles under a low-frequency magnetic field has only been observed in vitro. In this report, we demonstrate the successful use of spin-vortex, disk-shaped permalloy magnetic particles in a low-frequency, rotating magnetic field for the in vitro and in vivo destruction of glioma cells. The internalized nanomagnets align themselves to the plane of the rotating magnetic field, creating a strong mechanical force which damages the cancer cell structure inducing programmed cell death. In vivo, the magnetic field treatment successfully reduces brain tumor size and increases the survival rate of mice bearing intracranial glioma xenografts, without adverse side effects. This study demonstrates a novel approach of controlling magnetic particles for treating malignant glioma that should be applicable to treat a wide range of cancers. PMID:26708022

  13. Mechanics of semiflexible chains formed by poly(ethylene glycol)-linked paramagnetic particles.

    PubMed

    Biswal, Sibani Lisa; Gast, Alice P

    2003-08-01

    Magnetorheological particles, permanently linked into chains, provide a magnetically actuated means to manipulate microscopic fluid flow. Paramagnetic colloidal particles form reversible chains by acquiring dipole moments in the presence of an external magnetic field. By chemically connecting paramagnetic colloidal particles, flexible magnetoresponsive chains can be created. We link the paramagnetic microspheres using streptavidin-biotin binding. Streptavidin coated microspheres are placed in a flow cell and a magnetic field is applied, causing the particles to form chains. Then a solution of polymeric linkers of bis-biotin-poly(ethylene glycol) molecules is added in the presence of the field. These linked chains remain responsive to a magnetic field; however, in the absence of an external magnetic field these chains bend and flex due to thermal motion. The chain flexibility is determined by the length of the spacer molecule between particles and is quantified by the flexural rigidity or bending stiffness. To understand the mechanical properties of the chains, we use a variety of optical trapping experiments to measure the flexural rigidity. Increasing the length of the poly(ethylene glycol) chain in the linker increases the flexibility of the chains. PMID:14524968

  14. Exocytosis of Alphaherpesvirus Virions, Light Particles, and Glycoproteins Uses Constitutive Secretory Mechanisms

    PubMed Central

    Hogue, Ian B.; Scherer, Julian

    2016-01-01

    ABSTRACT Many molecular and cell biological details of the alphaherpesvirus assembly and egress pathway remain unclear. Recently we developed a live-cell fluorescence microscopy assay of pseudorabies virus (PRV) exocytosis, based on total internal reflection fluorescence (TIRF) microscopy and a virus-encoded pH-sensitive fluorescent probe. Here, we use this assay to distinguish three classes of viral exocytosis in a nonpolarized cell type: (i) trafficking of viral glycoproteins to the plasma membrane, (ii) exocytosis of viral light particles, and (iii) exocytosis of virions. We find that viral glycoproteins traffic to the cell surface in association with constitutive secretory Rab GTPases and exhibit free diffusion into the plasma membrane after exocytosis. Similarly, both virions and light particles use these same constitutive secretory mechanisms for egress from infected cells. Furthermore, we show that viral light particles are distinct from cellular exosomes. Together, these observations shed light on viral glycoprotein trafficking steps that precede virus particle assembly and reinforce the idea that virions and light particles share a biogenesis and trafficking pathway. PMID:27273828

  15. Structure and biodegradation mechanism of milled B.mori silk particles

    PubMed Central

    Rajkhowa, Rangam; Hu, Xiao; Tsuzuki, Takuya; Kaplan, David L; Wang, Xungai

    2013-01-01

    Silk particles with a volume median d(0.5) of about 6 μm were prepared using a chemical free and efficient wet milling-spray drying process. Milling reduced the intermolecular stacking forces within the β-sheet crystallites without changing the intramolecular binding energy of the β-sheets. The rough morphology and the ultrafine size of the particles were responsible for significant surface modulated protease XIV degradation, about a three-fold increase compared to silk fibres. Fracture of brittle and porous enzyme hydrolysed particles produced a 72% fall in d(0.5) within the in-vitro experimental conditions. Of note, upon biodegradation, the thermal degradation temperature of silk increased, which was attributed to the formation of tight aggregates by the hydrolysed residual fibroin macromolecules. A model of the biodegradation mechanism of silk particles was developed based on these data. The model explains the process of disintegration of β-sheets within the microstructure, supported by quantitative secondary structural analysis and microscopic images. This study is useful to engineer silk particles for targeted biomedical applications and also in understating structural remodeling of debris if generated from silk-based implants. PMID:22746375

  16. Mechanism of Methylene Blue adsorption on hybrid laponite-multi-walled carbon nanotube particles.

    PubMed

    Manilo, Maryna; Lebovka, Nikolai; Barany, Sandor

    2016-04-01

    The kinetics of adsorption and parameters of equilibrium adsorption of Methylene Blue (MB) on hybrid laponite-multi-walled carbon nanotube (NT) particles in aqueous suspensions were determined. The laponite platelets were used in order to facilitate disaggregation of NTs in aqueous suspensions and enhance the adsorption capacity of hybrid particles for MB. Experiments were performed at room temperature (298K), and the laponite/NT ratio (Xl) was varied in the range of 0-0.5. For elucidation of the mechanism of MB adsorption on hybrid particles, the electrical conductivity of the system as well as the electrokinetic potential of laponite-NT hybrid particles were measured. Three different stages in the kinetics of adsorption of MB on the surface of NTs or hybrid laponite-NT particles were discovered to be a fast initial stage I (adsorption time t=0-10min), a slower intermediate stage II (up to t=120min) and a long-lasting final stage III (up to t=24hr). The presence of these stages was explained accounting for different types of interactions between MB and adsorbent particles, as well as for the changes in the structure of aggregates of NT particles and the long-range processes of restructuring of laponite platelets on the surface of NTs. The analysis of experimental data on specific surface area versus the value of Xl evidenced in favor of the model with linear contacts between rigid laponite platelets and NTs. It was also concluded that electrostatic interactions control the first stage of adsorption at low MB concentrations. PMID:27090704

  17. Quantum-Mechanical Contributions to Numerical Simulations of Charged Particle Transport at the DNA Scale

    NASA Astrophysics Data System (ADS)

    Champion, Christophe; Galassi, Mariel E.; Weck, Philippe F.; Fojón, Omar; Hanssen, Jocelyn; Rivarola, Roberto D.

    Two quantum mechanical models (CB1 and CDW-EIS) are here presented to provide accurate multiple differential and total cross sections for describing the two most important ionizing processes, namely, ionization and capture induced by heavy charged particles in targets of biological interest. Water and DNA bases are then successively investigated by reporting in particular a detailed study of the influence of the target description on the cross section calculations.

  18. Structural properties of composites of polyvinylidene fluoride and mechanically activated BaTiO3 particles

    NASA Astrophysics Data System (ADS)

    Pavlović, V. P.; Pavlović, V. B.; Vlahović, B.; Božanić, D. K.; Pajović, J. D.; Dojčilović, R.; Djoković, V.

    2013-11-01

    Nanocomposites of electroactive ceramics and ferroelectric polymers exploit favorable features of the matrix polymer and the nanostructured filler to produce new functional materials for pressure and IR sensors. In this study, the influence of mechanical activation of barium titanate (BaTiO3) particles on the structural properties of BaTiO3/polyvinylidene fluoride (PVDF) nanocomposites was investigated. Nanocomposite films were prepared by the solution casting method and characterized by scanning electron microscopy, x-ray diffraction and Raman spectroscopy. It was found that mechanically activated fillers promote the formation of a ferroelectric β-phase during crystallization of PVDF.

  19. Mechanical characteristics of SiC coating layer in TRISO fuel particles

    SciTech Connect

    Hosemann, Peter; Martos, J. N.; Frazer, D.; Vasudevamurthy, Gokul; Byun, Thak Sang; Hunn, John D; Jolly, Brian C; Terrani, Kurt A; Okuniewski, Maria A.

    2013-01-01

    Tristructural isotropic (TRISO) particles are considered as advanced fuel forms for a variety of fission platforms. While these fuel structures have been tested and deployed in reactors, the mechanical properties of these structures as a function of production parameters need to be investigated in order to ensure their reliability during service. Nanoindentation techniques, indentation crack testing, and half sphere crush testing were utilized in order to evaluate the integrity of the SiC coating layer that is meant to prevent fission product release in the coated particle fuel form. The results are complimented by scanning electron microscopy (SEM) of the grain structure that is subject to change as a function of processing parameters and can alter the mechanical properties such as hardness, elastic modulus, fracture toughness and fracture strength. Through utilization of these advanced techniques, subtle differences in mechanical properties that can be important for in-pile fuel performance can be distinguished and optimized in iteration with processing science of coated fuel particle production.

  20. Mechanical Characteristics of SiC Coating Layer in TRISO Fuel Particles

    SciTech Connect

    P. Hosemann; J. N. Martos; D. Frazer; G. Vasudevamurthy; T. S. Byun; J. D. Hunn; B. C. Jolly; K. Terrani; M. Okuniewski

    2013-11-01

    Tristructural isotropic (TRISO) particles are considered as advanced fuel forms for a variety of fission platforms. While these fuel structures have been tested and deployed in reactors, the mechanical properties of these structures as a function of production parameters need to be investigated in order to ensure their reliability during service. Nanoindentation techniques, indentation crack testing, and half sphere crush testing were utilized in order to evaluate the integrity of the SiC coating layer that is meant to prevent fission product release in the coated particle fuel form. The results are complimented by scanning electron microscopy (SEM) of the grain structure that is subject to change as a function of processing parameters and can alter the mechanical properties such as hardness, elastic modulus, fracture toughness and fracture strength. Through utilization of these advanced techniques, subtle differences in mechanical properties that can be important for in-pile fuel performance can be distinguished and optimized in iteration with processing science of coated fuel particle production.

  1. Thermo-Mechanical Analysis of Coated Particle Fuel Experiencing a Fast Control Rod Ejection Transient

    SciTech Connect

    Ortensi, J.; Brian Boer; Abderrafi M. Ougouag

    2010-10-01

    A rapid increase of the temperature and the mechanical stress is expected in TRISO coated particle fuel that experiences a fast Total Control Rod Ejection (CRE) transient event. During this event the reactor power in the pebble bed core increases significantly for a short time interval. The power is deposited instantly and locally in the fuel kernel. This could result in a rapid increase of the pressure in the buffer layer of the coated fuel particle and, consequently, in an increase of the coating stresses. These stresses determine the mechanical failure probability of the coatings, which serve as the containment of radioactive fission products in the Pebble Bed Reactor (PBR). A new calculation procedure has been implemented at the Idaho National Laboratory (INL), which analyzes the transient fuel performance behavior of TRISO fuel particles in PBRs. This early capability can easily be extended to prismatic designs, given the availability of neutronic and thermal-fluid solvers. The full-core coupled neutronic and thermal-fluid analysis has been modeled with CYNOD-THERMIX. The temperature fields for the fuel kernel and the particle coatings, as well as the gas pressures in the buffer layer, are calculated with the THETRIS module explicitly during the transient calculation. Results from this module are part of the feedback loop within the neutronic-thermal fluid iterations performed for each time step. The temperature and internal pressure values for each pebble type in each region of the core are then input to the PArticle STress Analysis (PASTA) code, which determines the particle coating stresses and the fraction of failed particles. This paper presents an investigation of a Total Control Rod Ejection (TCRE) incident in the 400 MWth Pebble Bed Modular reactor design using the above described calculation procedure. The transient corresponds to a reactivity insertion of $3 (~2000 pcm) reaching 35 times the nominal power in 0.5 seconds. For each position in the core

  2. The size-dependent charge fraction of sub-3-nm particles as a key diagnostic of competitive nucleation mechanisms under atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Yu, F.; Turco, R.

    2011-04-01

    A clear physical understanding of atmospheric particle nucleation mechanisms is critical in assessing the influences of aerosols on climate and climate variability. Currently, several mechanisms have been proposed and are being employed to interpret field observations of nucleation events. Roughly speaking, the two most likely candidates are neutral cluster nucleation (NCN) and ion-mediated nucleation (IMN). Detailed nucleation event data has been obtained in boreal forests. In one set of analyses of these measurements, NCN was suggested as the dominant formation mode, while in another, it was IMN. Obviously, information on the electrical charge distribution carried by the nucleating clusters themselves is the key to identifying the relative contributions of neutral and ion-mediated processes under various conditions. Fortunately, ground-breaking measurements of the charged states or fractions of ambient nanometer-sized particles soon after undergoing nucleation are now available to help resolve the main pathway. In the present study, the size-dependent "apparent" formation rates and fractions of charged and neutral particles are simulated with a detailed kinetic model. We show that the predicted "apparent" formation rates of charged and neutral particles at 2 nm agree well with the corresponding values derived from the boreal forest data, but the "apparent" contribution of ion-based nucleation increases by up to ~ one order of magnitude as the size of particles decreases from 2 nm to ~1.5 nm. It appears that most of the neutral particles detected at sizes around 2 nm are in reality initially formed on ionic cores that are neutralized before the particles grow to this size. Thus, although the apparent rate of formation of neutral 2-nm particles might seem to be dominated by a neutral clustering process, in fact those particles are largely the result of an ion-induced nucleation mechanism. This point is clarified when the formation rates of smaller particles (e

  3. The size-dependent charge fraction of sub-3-nm particles as a key diagnostic of competitive nucleation mechanisms under atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Yu, F.; Turco, R. P.

    2011-09-01

    A clear physical understanding of atmospheric particle nucleation mechanisms is critical in assessing the influences of aerosols on climate and climate variability. Currently, several mechanisms have been proposed and are being employed to interpret field observations of nucleation events. Roughly speaking, the two most likely candidates are neutral cluster nucleation (NCN) and ion-mediated nucleation (IMN). Detailed nucleation event data has been obtained in boreal forests. In one set of analyses of these measurements, NCN was suggested as the dominant formation mode, while in another, it was IMN. Information on the electrical charge distribution carried by the nucleating clusters is one key for identifying the relative contributions of neutral and ion-mediated processes under various conditions. Fortunately, ground-breaking measurements of the charged states or fractions of ambient nanometer-sized particles soon after undergoing nucleation are now available to help resolve the main pathways. In the present study, the size-dependent "apparent" formation rates and fractions of charged and neutral particles in a boreal forest setting are simulated with a detailed kinetic model. We show that the predicted "apparent" formation rates of charged and neutral particles at 2 nm for eight representative case study days agree well with the corresponding values based on observations. In the simulations, the "apparent" contribution of ion-based nucleation increases by up to ~one order of magnitude as the size of "sampled" particles is decreased from 2 nm to ~1.5 nm. These results suggest that most of the neutral particles sampled in the field at sizes around 2 nm are in reality initially formed on ionic cores that are neutralized before the particles grow to this size. Thus, although the apparent rate of formation of neutral 2-nm particles might seem to be dominated by a neutral clustering process, in fact those particles may be largely the result of an ion-induced nucleation

  4. Primary Surface Particle Motion as a Mechanism for YORP-Driven Binary Asteroid Evolution

    NASA Astrophysics Data System (ADS)

    Fahnestock, Eugene G.; Scheeres, D. J.

    2008-09-01

    Within the largest class of binary asteroid systems -- asynchronous binaries typified by 1999 KW4 -- we hypothesize continued YORP spin-up of the rapidly rotating primary leads to recurring episodic lofting motion of primary equator regolith. We theorize this is a mechanism for transporting YORP-injected angular momentum from primary spin into the mutual orbit. This both enables binary primaries to continue to spin at near surface fission rates and produces continued orbit expansion on time scales several times faster than expansion predicted by tidal dissipation alone. This is distinct from the Binary Yorp (BYORP) phenomenon, not studied in this work but to be added to it later. We evaluate our hypotheses using a combination of techniques for an example binary system. First high-fidelity dynamic simulation of surface-originating particles in the full-detail gravity field of the binary components, themselves propagated according to the full two body problem, gives particle final disposition (return impact, transfer impact, escape). Trajectory end states found for regolith lofted at different initial primary spin rates and relative poses are collected into probability matrices, allowing probabilistic propagation of surface particles for long durations at low computational cost. We track changes to mass, inertia dyad, rotation state, and centroid position and velocity for each component in response to this mapped particle motion. This allows tracking of primary, secondary, and mutual orbit angular momenta over time, clearly demonstrating the angular momentum transfer mechanism and validating our hypotheses. We present current orbit expansion rates and estimated orbit size doubling times consistent with this mechanism, for a few binary systems. We also discuss ramifications of this type of rapid binary evolution towards separation, including the frequency with which "divorced binaries" on similar heliocentric orbits are produced, formation of triple systems such as

  5. On the mechanism for the clustering of inertial particles in the inertial range of isotropic turbulence

    NASA Astrophysics Data System (ADS)

    Collins, Lance; Bragg, Andrew; Ireland, Peter

    2014-11-01

    In this talk, we consider the physical mechanism for the clustering of inertial particles in the inertial range of turbulence. By comparisons with DNS data we demonstrate that the mechanism in the theory of Zaichik et al. (Phys. Fluids 19, 113308, 2007) quantitatively describes the clustering of particles in the inertial range. We then analyze the theory for isotropic turbulence in the limit Reλ --> ∞ . For arbitrary St (Stokes number), there exists a separation in the inertial range beyond which Str << 1 , where Str is the Stokes number based on the eddy turnover timescale at separation r. The inertial-range clustering in this limit can be understood to be due to the preferential sampling of the coarse-grained velocity gradient tensor at that scale. At smaller separations, there may be transitions to Str ~ 1 , where a path history symmetry breaking effect dominates the clustering mechanism, and in some cases Str >> 1 , which implies ballistic behavior and a flat RDF. The scaling for each of these regimes is derived and compared to DNS, where applicable. Finally, we compare the results with the ``sweep-stick'' mechanism by Coleman and Vassilicos (Phys. Fluids 21, 113301, 2009) and discuss the similarities and differences between the two theories.

  6. The Schr{umlt o}dinger and Dirac free particle equations without quantum mechanics

    SciTech Connect

    Ord, G.N.

    1996-08-01

    Einstein{close_quote}s theory of Brownian Movement has provided a well accepted microscopic model of diffusion for many years. Until recently the relationship between this model and Quantum Mechanics has been completely formal. Brownian motion provides a microscopic model for diffusion, but quantum mechanics and diffusion are related by a formal analytic continuation, so the relationship between Brownian motion and Quantum Mechanics has been correspondingly vague. Some recent work has changed this picture somewhat and here we show that a random walk model of Brownian motion produces the diffusion equation or the telegraph equations as a descriptions of particle densities, while at the same time the correlations in the space-time geometry of these same Brownian particles obey the Schr{umlt o}dinger and Dirac equations respectively. This is of interest because the equations of Quantum Mechanics appear here naturally in a classical context without the problems of interpretation they have in the usual context. {copyright} 1996 Academic Press, Inc.

  7. On the mechanisms controlling the formation and properties of volatile particles in aircraft wakes

    NASA Astrophysics Data System (ADS)

    Yu, Fangqun; Turco, Richard P.; Kärcher, Bernd; Schröder, Franz P.

    New observations taken in aircraft wakes, including the DLR ATTAS, provide strong constraints on models of aircraft plume aerosols. Using a comprehensive microphysics code, we have performed sensitivity studies to identify the key microphysical mechanisms acting in such plumes. Analysis of these simulations reveals that the largest volatile plume particles—those most likely to contribute to the background abundance of condensation nuclei—are dominated by ion-mode particles when chemiions are included. Moreover, such modeling demonstrates that standard treatments of plume microphysics—in the absence of chemiions—fails to explain field measurements. The principal factor controlling the population of ultrafine plume particles is the number of chemiions emitted by the aircraft engines. Since the ions are a byproduct of the combustion itself, and their abundance in the exhaust stream is controlled by ion-ion recombination, the initial ion concentrations—and so the eventual emission indices for ion-mode particles—are expected to be relatively invariant. Our results indicate that reductions in fuel sulfur content, while not likely to lower the total number of volatile particles emitted, would decrease the size of the ion-mode particles in fresh aircraft wakes, reducing their atmospheric lifetimes and potential environmental effects.

  8. Overview of continuum and particle dynamics methods for mechanical modeling of contractional geologic structures

    NASA Astrophysics Data System (ADS)

    Gray, Gary G.; Morgan, Julia K.; Sanz, Pablo F.

    2014-02-01

    Mechanically-based numerical modeling is a powerful tool for investigating fundamental processes associated with the formation and evolution of both large and small-scale geologic structures. Such methods are complementary with traditional geometrically-based cross-section analysis tools, as they enable mechanical validation of geometric interpretations. A variety of numerical methods are now widely used, and readily accessible to both expert and novice. We provide an overview of the two main classes of methods used for geologic studies: continuum methods (finite element, finite difference, boundary element), which divide the model into elements to calculate a system of equations to solve for both stress and strain behavior; and particle dynamics methods, which rely on the interactions between discrete particles to define the aggregate behavior of the system. The complex constitutive behaviors, large displacements, and prevalence of discontinuities in geologic systems, pose unique challenges for the modeler. The two classes of methods address these issues differently; e.g., continuum methods allow the user to input prescribed constitutive laws for the modeled materials, whereas the constitutive behavior 'emerges' from particle dynamics methods. Sample rheologies, case studies and comparative models are presented to demonstrate the methodologies and opportunities for future modelers.

  9. Entropy increase in confined free expansions via molecular dynamics and smooth-particle applied mechanics

    SciTech Connect

    Hoover, W.G.

    1999-02-01

    The eventual entropy increase of an ideal gas undergoing free expansion, {Delta}S=k&hthinsp;ln(V{sub fin}/V{sub 0}), requires a {open_quotes}coarse-grained{close_quotes} hydrodynamic description because Gibbs{close_quote} fine-grained entropy is unchanged in such a process. Smooth particle applied mechanics (SPAM) is well suited to the simulation and study of such problems because the particles in SPAM simulations can be of any size, from microscopic to macroscopic. SPAM furnishes a natural interpolation, or bridge, linking microscopic molecular dynamics to macroscopic continuum mechanics. We analyze particle-based simulations of ideal-gas free expansions from both the microscopic and the macroscopic points of view, comparing several dynamical estimates for the time development of the system entropy. Most of the entropy increase occurs rapidly, within a single sound traversal time. A local comoving version of turbulent hydrodynamics provides the most useful viewpoint for describing flows of this kind. {copyright} {ital 1999} {ital The American Physical Society}

  10. Do not drop: mechanical shock in vials causes cavitation, protein aggregation, and particle formation.

    PubMed

    Randolph, Theodore W; Schiltz, Elise; Sederstrom, Donn; Steinmann, Daniel; Mozziconacci, Olivier; Schöneich, Christian; Freund, Erwin; Ricci, Margaret S; Carpenter, John F; Lengsfeld, Corrine S

    2015-02-01

    Industry experience suggests that g-forces sustained when vials containing protein formulations are accidentally dropped can cause aggregation and particle formation. To study this phenomenon, a shock tower was used to apply controlled g-forces to glass vials containing formulations of two monoclonal antibodies and recombinant human growth hormone (rhGH). High-speed video analysis showed cavitation bubbles forming within 30 μs and subsequently collapsing in the formulations. As a result of echoing shock waves, bubbles collapsed and reappeared periodically over a millisecond time course. Fluid mechanics simulations showed low-pressure regions within the fluid where cavitation would be favored. A hydroxyphenylfluorescein assay determined that cavitation produced hydroxyl radicals. When mechanical shock was applied to vials containing protein formulations, gelatinous particles appeared on the vial walls. Size-exclusion chromatographic analysis of the formulations after shock did not detect changes in monomer or soluble aggregate concentrations. However, subvisible particle counts determined by microflow image analysis increased. The mass of protein attached to the vial walls increased with increasing drop height. Both protein in bulk solution and protein that became attached to the vial walls after shock were analyzed by mass spectrometry. rhGH recovered from the vial walls in some samples revealed oxidation of Met and/or Trp residues. PMID:25418950

  11. DO NOT DROP: MECHANICAL SHOCK IN VIALS CAUSES CAVITATION, PROTEIN AGGREGATION AND PARTICLE FORMATION

    PubMed Central

    Randolph, Theodore W.; Schiltz, Elise; Sederstrom, Donn; Steinmann, Daniel; Mozziconacci, Olivier; Schöneich, Christian; Freund, Erwin; Ricci, Margaret S.; Carpenter, John F.; Lengsfeld, Corrine S.

    2014-01-01

    Industry experience suggests that g-forces sustained when vials containing protein formulations are accidentally dropped can cause aggregation and particle formation. To study this phenomenon, a shock tower was used to apply controlled g-forces to glass vials containing formulations of two monoclonal antibodies and recombinant human growth hormone (rhGH). High-speed video analysis showed cavitation bubbles forming within 30 μs and subsequently collapsing in the formulations. As a result of echoing shock waves, bubbles collapsed and reappeared periodically over a millisecond timecourse. Fluid mechanics simulations showed low-pressure regions within the fluid where cavitation would be favored. A hydroxyphenylfluorescein assay determined that cavitation produced hydroxyl radicals. When mechanical shock was applied to vials containing protein formulations, gelatinous particles appeared on the vial walls. Size exclusion chromatographic analysis of the formulations after shock did not detect changes in monomer or soluble aggregate concentrations. However, subvisible particle counts determined by microflow image analysis increased. The mass of protein attached to the vial walls increased with increasing drop height. Both protein in bulk solution and protein that became attached to the vial walls after shock were analyzed by mass spectrometry. rhGH recovered from the vial walls in some samples revealed oxidation of Met and/or Trp residues. PMID:25418950

  12. Quantum-mechanical description of Lense-Thirring effect for relativistic scalar particles

    NASA Astrophysics Data System (ADS)

    Silenko, A. J.

    2013-12-01

    Exact expression for the Foldy-Wouthuysen Hamiltonian of scalar particles is used for a quantum-mechanical description of the relativistic Lense-Thirring effect. The exact evolution of the angular momentum operator in the Kerr field approximated by a spatially isotropic metric is found. The quantummechanical description of the full Lense-Thirring effect based on the Laplace-Runge-Lenz vector is given in the nonrelativistic and weak-field approximation. Relativistic quantum-mechanical equations for the velocity and acceleration operators are obtained. The equation for the acceleration defines the Coriolis-like and centrifugal-like accelerations and presents the quantum-mechanical description of the frame-dragging effect.

  13. The effect of mechanical vibration on the dust particle kinetic temperature measurement

    NASA Astrophysics Data System (ADS)

    Kong, Jie; Qiao, Ke; Matthews, Lorin; Hyde, Truell

    2015-11-01

    An important parameter in governing the self-assembly of structures in a complex (dusty) plasma is the coupling parameter Γ, the ratio of the electrostatic energy of the charged dust to the dust thermal energy. In a GEC rf reference cell, the dust thermal energy can come from collisions with the neutral gas, fluctuations of the confining electric field or changes in the charge on the dust particle itself. Experimentally, the kinetic energy of the dust can be determined using the Gaussian thermal velocity probability distribution. However, recent measurements of the dust particle velocity probability distribution function have shown that external mechanical vibrations of the plasma chamber can have a significant effect on the result. This investigation compares measurements of the dust kinetic temperature with and without external vibrations to the GEC cell. Support from the NSF and the DOE (award numbers PHY-1262031 and PHY-1414523) is gratefully acknowledged.

  14. Probing phase-space noncommutativity through quantum mechanics and thermodynamics of free particles and quantum rotors

    NASA Astrophysics Data System (ADS)

    Santos, Jonas F. G.; Bernardini, Alex E.; Bastos, Catarina

    2015-11-01

    Novel quantization properties related to the state vectors and the energy spectrum of a two-dimensional system of free particles are obtained in the framework of noncommutative (NC) quantum mechanics (QM) supported by the Weyl-Wigner formalism. Besides reproducing the magnetic field aspect of a Zeeman-like effect, the momentum space NC parameter introduces mutual information properties quantified by the quantum purity related to the relevant coordinates of the corresponding Hilbert space. Supported by the QM in the phase-space, the thermodynamic limit is obtained, and the results are extended to three-dimensional systems. The noncommutativity imprints on the thermodynamic variables related to free particles are identified and, after introducing some suitable constraints to fix an axial symmetry, the analysis is extended to two- and- three dimensional quantum rotor systems, for which the quantization aspects and the deviation from standard QM results are verified.

  15. Understanding the adsorption mechanism of chitosan onto poly(lactide-co-glycolide) particles

    PubMed Central

    Guo, Chunqiang; Gemeinhart, Richard A.

    2008-01-01

    Polyelectrolyte-coated nanoparticles or microparticles interact with bioactive molecules (peptides, proteins or nucleic acids) and have been proposed as delivery systems for these molecules. However, the mechanism of adsorption of polyelectrolyte onto particles remains unsolved. In this study, cationic poly(lactide-co-glycolide) (PLGA) nanoparticles were fabricated by adsorption of various concentrations of a biodegradable polysaccharide, chitosan (0–2.4 g/L), using oil-in-water emulsion and solvent evaporation techniques. The particle diameter, zeta-potential, and chitosan adsorption of chitosan coated PLGA nanoparticles confirmed the increase of polyelectrolyte adsorption. Five adsorption isotherm models (Langmuir, Freundlich, Halsey, Henderson and Smith) were applied to the experimental data in order to better understand the mechanism of adsorption. Both particle diameter and chitosan adsorption increased with chitosan concentration during adsorption. A good correlation was obtained between PLGA-chitosan nanoparticle size and adsorbed chitosan on the surface, suggesting the increased particle size was primarily due to the increased chitosan adsorption. The zeta-potential of chitosan-coated PLGA nanoparticles was positive and increased with chitosan adsorbed until a maximum value (+55 mV) was reached at approximately 0.4–0.6 g/L; PLGA nanoparticles had a negative zeta-potential (−20 mV) prior to chitosan adsorption. Chitosan adsorption on PLGA nanoparticles followed a multilayer adsorption behavior, although the Langmuir monolayer equation held at low concentrations of chitosan. The underlying reasons for adsorption of chitosan on PLGA nanoparticles were thought to be the cationic nature of chitosan, high surface energy and microporous non-uniform surface of PLGA nanoparticles. PMID:18602994

  16. The Philosophy of Fields and Particles in Classical and Quantum Mechanics, Including the Problem of Renormalisation.

    NASA Astrophysics Data System (ADS)

    Huggett, Nick

    1995-01-01

    This work first explicates the philosophy of classical and quantum fields and particles. I am interested in determining how science can have a metaphysical dimension, and then with the claim that the quantum revolution has an important metaphysical component. I argue that the metaphysical implications of a theory are properties of its models, as classical mechanics determines properties of atomic diversity and temporal continuity with its representations of distinct, continuous trajectories. It is often suggested that classical statistical physics requires that many particle states be represented so that permuting properties leads to distinct states; this implies that individuals can be reidentified across possible worlds in a non-qualitative way. I show there is no evidence for this conclusion, an important result, for it is claimed that quantum particles are not individuals. This claim is based on the misconception about classical statistics, but also on a conflation of notions of identity; I show that, while transworld identity is incompatible with quantum mechanics, other classical notions may be consistently ascribed. I also give a field-particle distinction that applies usefully in both quantum and classical domains. In the former the distinction helps defeat claims of underdetermined by data, in the latter it helps provide a minimal field metaphysics. Next I tackle renormalisation: I show how divergences occur in approximate, perturbative calculations, and demonstrate how finite, empirically verified, answers are obtained. These techniques seem to show that the predictions are not logical consequences of the exact theory. I use the techniques of the renormalisation group to establish that perturbative renormalised quantum field theory does indeed approximate the consequences of field theory. Finally, I discuss the idea (Cao and Schweber, 1994) that renormalisation proves that there can be no quantum theory of everything, only a patchwork of effective

  17. A discrete mesoscopic particle model of the mechanics of a multi-constituent arterial wall.

    PubMed

    Witthoft, Alexandra; Yazdani, Alireza; Peng, Zhangli; Bellini, Chiara; Humphrey, Jay D; Karniadakis, George Em

    2016-01-01

    Blood vessels have unique properties that allow them to function together within a complex, self-regulating network. The contractile capacity of the wall combined with complex mechanical properties of the extracellular matrix enables vessels to adapt to changes in haemodynamic loading. Homogenized phenomenological and multi-constituent, structurally motivated continuum models have successfully captured these mechanical properties, but truly describing intricate microstructural details of the arterial wall may require a discrete framework. Such an approach would facilitate modelling interactions between or the separation of layers of the wall and would offer the advantage of seamless integration with discrete models of complex blood flow. We present a discrete particle model of a multi-constituent, nonlinearly elastic, anisotropic arterial wall, which we develop using the dissipative particle dynamics method. Mimicking basic features of the microstructure of the arterial wall, the model comprises an elastin matrix having isotropic nonlinear elastic properties plus anisotropic fibre reinforcement that represents the stiffer collagen fibres of the wall. These collagen fibres are distributed evenly and are oriented in four directions, symmetric to the vessel axis. Experimental results from biaxial mechanical tests of an artery are used for model validation, and a delamination test is simulated to demonstrate the new capabilities of the model. PMID:26790998

  18. Theory of self-resonance after inflation. II. Quantum mechanics and particle-antiparticle asymmetry

    NASA Astrophysics Data System (ADS)

    Hertzberg, Mark P.; Karouby, Johanna; Spitzer, William G.; Becerra, Juana C.; Li, Lanqing

    2014-12-01

    We further develop a theory of self-resonance after inflation in a large class of models involving multiple scalar fields. We concentrate on inflaton potentials that carry an internal symmetry, but also analyze weak breaking of this symmetry. This is the second part of a two-part series of papers. Here in Part 2 we develop an understanding of the resonance structure from the underlying many-particle quantum mechanics. We begin with a small-amplitude analysis, which obtains the central resonant wave numbers, and relate it to perturbative processes. We show that the dominant resonance structure is determined by (i) the nonrelativistic scattering of many quantum particles and (ii) the application of Bose-Einstein statistics to the adiabatic and isocurvature modes, as introduced in Part 1 [M. P. Hertzberg et al., Phys. Rev. D 90, 123528 (2014)]. Other resonance structures are understood in terms of annihilations and decays. We set up Bunch-Davies vacuum initial conditions during inflation and track the evolution of modes including Hubble expansion. In the case of a complex inflaton carrying an internal U(1) symmetry, we show that when the isocurvature instability is active, the inflaton fragments into separate regions of ϕ -particles and anti-ϕ -particles. We then introduce a weak breaking of the U(1) symmetry; this can lead to baryogenesis, as shown by some of us recently [M. P. Hertzberg and J. Karouby, Phys. Lett. B 737, 34 (2014); Phys. Rev. D 89, 063523 (2014)]. Then using our results, we compute corrections to the particle-antiparticle asymmetry from this preheating era.

  19. Quantum mechanical and semi-classical treatment of quantum excitations due to the passage of a particle

    NASA Astrophysics Data System (ADS)

    van Dijk, W.; Kiers, K. A.; Nogami, Y.; Platt, A.; Spyksma, K.

    2003-05-01

    We examine the validity of the approximation in which an alpha particle interacting with an atom is treated classically. In order to analyse such interactions, we perform a model simulation in which the alpha particle is considered as a particle in one dimension, and the atom as a quantum two-level system. The particle impinges on and excites the two-level system. We treat the particle in two ways: as a quantum mechanical wave packet, and as a classical particle. The classical particle may be a point or may have an extended structure. In each case we calculate the excitation probability P21(t) as a function of time t. We focus on the situation in which the kinetic energy of the incident particle well exceeds the excitation energy of the two-level system. Although the finite-time behaviour of P21(t) varies, P21(infty) is remarkably insensitive to the size and shape of the incident wave packet in the quantum mechanical treatment. In the classical treatment, in contrast, we find that P21(infty) is sensitive to the size of the particle. The classical point particle, however, yields nearly the same values of P21(infty) as the quantum wave packet. Implications of the results on the interaction between an alpha particle and an atom are discussed.

  20. Quantum mechanics of a constrained particle on an ellipsoid: Bein formalism and Geometric momentum

    NASA Astrophysics Data System (ADS)

    Panahi, H.; Jahangiri, L.

    2016-09-01

    In this work we apply the Dirac method in order to obtain the classical relations for a particle on an ellipsoid. We also determine the quantum mechanical form of these relations by using Dirac quantization. Then by considering the canonical commutation relations between the position and momentum operators in terms of curved coordinates, we try to propose the suitable representations for momentum operator that satisfy the obtained commutators between position and momentum in Euclidean space. We see that our representations for momentum operators are the same as geometric one.

  1. A thermo-mechanical analysis of a particle impact during thermal spraying

    NASA Astrophysics Data System (ADS)

    Danouni, Samir; Abdellah El-hadj, Abdellah; Zirari, Mounir; Belharizi, Mohamed

    2016-05-01

    The present study discusses the development of a simulation model of transient impact between a particle and a substrate. The equations for structural behavior are coupled with those of heat transfer, wherein material properties are taken as temperature dependent. The set of equations is solved with Ansys program using a direct coupling method. At first, structural model is solved without heat transfer. Then, coupled thermo-mechanical model is solved with and without thermoelastic effects. Computational results indicate that thermal consideration has significant effects on contact problem. In addition, it is shown that, themoelasticity consideration is crucial for simulating these problems to determine the structural and thermal parameters.

  2. Magnetomotive optical coherence elastography using magnetic particles to induce mechanical waves

    PubMed Central

    Ahmad, Adeel; Kim, Jongsik; Sobh, Nahil A.; Shemonski, Nathan D.; Boppart, Stephen A.

    2014-01-01

    Magnetic particles are versatile imaging agents that have found wide spread applicability in diagnostic, therapeutic, and rheology applications. In this study, we demonstrate that mechanical waves generated by a localized inclusion of magnetic nanoparticles can be used for assessment of the tissue viscoelastic properties using magnetomotive optical coherence elastography. We show these capabilities in tissue mimicking elastic and viscoelastic phantoms and in biological tissues by measuring the shear wave speed under magnetomotive excitation. Furthermore, we demonstrate the extraction of the complex shear modulus by measuring the shear wave speed at different frequencies and fitting to a Kelvin-Voigt model. PMID:25071969

  3. ULTRAFINE CARBON PARTICLES INDUCE IL-8 EXPRESSION IN HUMAN AIRWAY EPITHELIAL CELLS THROUGH A POST-TRANSCRIPTIONAL MECHANISM

    EPA Science Inventory

    Ultrafine carbon particles induce IL-8 expression in human airway
    epithelial cells through a post-transcritpional mechanism
    Epidemiological studies suggest that ultrafine particles contribute to
    particulate matter (PM) - induced adverse health effects. IL-8 is an
    i...

  4. Influence of protein hydrolysis on the mechanical properties of natural rubber composites reinforced with soy protein particles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    For natural rubber applications, the reinforcing fillers are used to improve the mechanical properties of the rubber. Soy protein particles have been shown to reinforce natural rubber. The hydrolysis conditions of soy protein are studied to understand its effect on the particle size and size distrib...

  5. Preparation and formation mechanism of wood-block-like calcite particles

    SciTech Connect

    Guo Hua; Yu Jiaguo . E-mail: jiaguoyu@yahoo.com; Cheng Bei

    2006-08-15

    Pure calcite crystal with different morphologies such as wood-block and spherical aggregates were prepared by a precipitation reaction in the presence of citric acid. The as-prepared products were characterized with scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that citric acid obviously influenced the formation of precipitates and the morphology of final products. The formation mechanism of wood-block-like particles was proposed according to theoretical deduction and the proposed growth mode. - Graphical abstract: Pure calcite crystal with different morphologies such as wood-block and spherical aggregates were prepared by a simple precipitation reaction in the presence of citric acid and the formation mechanism was proposed.

  6. Protein adsorption onto nanoparticles induces conformational changes: Particle size dependency, kinetics, and mechanisms

    PubMed Central

    Satzer, Peter; Svec, Frantisek; Sekot, Gerhard

    2015-01-01

    The use of nanomaterials in bioapplications demands a detailed understanding of protein–nanoparticle interactions. Proteins can undergo conformational changes while adsorbing onto nanoparticles, but studies on the impact of particle size on conformational changes are scarce. We have shown that conformational changes happening upon adsorption of myoglobin and BSA are dependent on the size of the nanoparticle they are adsorbing to. Out of eight initially investigated model proteins, two (BSA and myoglobin) showed conformational changes, and in both cases this conformational change was dependent on the size of the nanoparticle. Nanoparticle sizes ranged from 30 to 1000 nm and, in contrast to previous studies, we attempted to use a continuous progression of sizes in the range found in live viruses, which is an interesting size of nanoparticles for the potential use as drug delivery vehicles. Conformational changes were only visible for particles of 200 nm and bigger. Using an optimized circular dichroism protocol allowed us to follow this conformational change with regard to the nanoparticle size and, thanks to the excellent temporal resolution also in time. We uncovered significant differences between the unfolding kinetics of myoglobin and BSA. In this study, we also evaluated the plausibility of commonly used explanations for the phenomenon of nanoparticle size‐dependent conformational change. Currently proposed mechanisms are mostly based on studies done with relatively small particles, and fall short in explaining the behavior seen in our studies.

  7. Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering

    PubMed Central

    Çınar, Simge; Tevis, Ian D.; Chen, Jiahao; Thuo, Martin

    2016-01-01

    Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate (‘/’ = physisorbed, ‘-’ = chemisorbed), from molten Field’s metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity. PMID:26902483

  8. Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering.

    PubMed

    Çınar, Simge; Tevis, Ian D; Chen, Jiahao; Thuo, Martin

    2016-01-01

    Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate ('/' = physisorbed, '-' = chemisorbed), from molten Field's metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity. PMID:26902483

  9. Algebraic roots of Newtonian mechanics: correlated dynamics of particles on a unique worldline

    NASA Astrophysics Data System (ADS)

    Kassandrov, Vladimir V.; Khasanov, Ildus Sh

    2013-05-01

    In the development of the old ideas of Stueckelberg-Wheeler-Feynman on the ‘one-electron Universe’, we study the purely algebraic dynamics of the ensemble of (two kinds of) identical point-like particles. These are represented by the (real and complex conjugate) roots of a generic polynomial system of equations that implicitly defines a single ‘worldline’. The dynamics includes events of ‘merging’ of a pair of particles modelling the annihilation/creation processes. Correlations in the location and motion of the particles-roots relate, in particular, to the Vieta formulas. After a special choice of the inertial-like reference frame, the linear Vieta formulas guarantee that, for any worldline, the law of (non-relativistic) momentum conservation is identically satisfied. Thus, the general structure of Newtonian mechanics follows from the algebraic properties of a worldline alone. A simple example of, unexpectedly rich, ‘polynomial dynamics’ is retraced in detail and illustrated via an animation (available from stacks.iop.org/JPhysA/46/175206/mmedia).

  10. Kinetics and proposed mechanism of the reaction of an immunoinhibition, particle-enhanced immunoassay.

    PubMed

    Thompson, J C; Craig, A R; Davey, C L; Newman, D J; Lonsdale, M L; Bucher, W J; Nagle, P D; Price, C P

    1997-12-01

    We report kinetic studies on the reaction of a latex agglutination immunoassay used to quantify phenytoin in serum. In this assay, polystyrene particles with a covalently attached analog of phenytoin react with an antiphenytoin monoclonal antibody to form light-scattering aggregates, with the rate of this reaction being decreased by addition of phenytoin from sample. In the absence of free (sample) phenytoin, this reaction did not exhibit a maximum rate of agglutination in the presence of excess antibody, i.e., an equivalence point. Furthermore, agglutination was inhibitable by free phenytoin even when the latter was added after agglutination of particles with antibody had begun. Most significantly, the immunoagglutination proceeded in an identical fashion with monovalent F(ab) fragment. These data are consistent with low-affinity immunospecific particle-antibody complexation, which then induces colloidal aggregation, without requiring immunospecific bridging by antibody molecules. The described mechanism is not generalizable to all latex agglutination immunoassays, although disturbance of colloidal stability may be a component in most assays. PMID:9439458

  11. Mechanical Fracturing of Core-Shell Undercooled Metal Particles for Heat-Free Soldering

    NASA Astrophysics Data System (ADS)

    Çınar, Simge; Tevis, Ian D.; Chen, Jiahao; Thuo, Martin

    2016-02-01

    Phase-change materials, such as meta-stable undercooled (supercooled) liquids, have been widely recognized as a suitable route for complex fabrication and engineering. Despite comprehensive studies on the undercooling phenomenon, little progress has been made in the use of undercooled metals, primarily due to low yields and poor stability. This paper reports the use of an extension of droplet emulsion technique (SLICE) to produce undercooled core-shell particles of structure; metal/oxide shell-acetate (‘/’ = physisorbed, ‘-’ = chemisorbed), from molten Field’s metal (Bi-In-Sn) and Bi-Sn alloys. These particles exhibit stability against solidification at ambient conditions. Besides synthesis, we report the use of these undercooled metal, liquid core-shell, particles for heat free joining and manufacturing at ambient conditions. Our approach incorporates gentle etching and/or fracturing of outer oxide-acetate layers through mechanical stressing or shearing, thus initiating a cascade entailing fluid flow with concomitant deformation, combination/alloying, shaping, and solidification. This simple and low cost technique for soldering and fabrication enables formation of complex shapes and joining at the meso- and micro-scale at ambient conditions without heat or electricity.

  12. Aging behavior and mechanical properties of maraging steels in the presence of submicrocrystalline Laves phase particles

    SciTech Connect

    Mahmoudi, A.; Ghavidel, M.R. Zamanzad; Nedjad, S. Hossein; Heidarzadeh, A.; Ahmadabadi, M. Nili

    2011-10-15

    Cold rolling and annealing of homogenized Fe-Ni-Mn-Mo-Ti-Cr maraging steels resulted in the formation of submicrocrystalline Fe{sub 2}(Mo,Ti) Laves phase particles. Optical and scanning electron microscopy, X-ray diffraction, tensile and hardness tests were used to study the microstructure, aging behavior and mechanical properties of the annealed steels. The annealed microstructures showed age hardenability during subsequent isothermal aging at 753 K. Ultrahigh fracture stress but poor tensile ductility was obtained after substantial age hardening in the specimens with 2% and 4% chromium. Increasing chromium addition up to 6% toughened the aged microstructure at the expense of the fracture stress by increasing the volume fraction of retained austenite. The Laves phase particles acted as crack nucleation sites during tensile deformation. - Highlights: {yields} Laves phases dispersed in a BCC iron matrix by annealing of cold rolled samples. {yields} The samples showed age hardenability during subsequent isothermal aging at 753 K. {yields} Ultrahigh fracture stress but poor ductility was obtained after age hardening. {yields} Increasing chromium addition toughened the aged microstructure. {yields} Laves phase particles acting as crack nucleation sites during tensile deformation.

  13. Laboratory evidence for particle mobilization as a mechanism for permeability enhancement via dynamic stressing

    NASA Astrophysics Data System (ADS)

    Candela, Thibault; Brodsky, Emily E.; Marone, Chris; Elsworth, Derek

    2014-04-01

    It is well-established that seismic waves can increase the permeability in natural systems, yet the mechanism remains poorly understood. We investigate the underlying mechanics by generating well-controlled, repeatable permeability enhancement in laboratory experiments. Pore pressure oscillations, simulating dynamic stresses, were applied to intact and fractured Berea sandstone samples under confining stresses of tens of MPa. Dynamic stressing produces an immediate permeability enhancement ranging from 1 to 60%, which scales with the amplitude of the dynamic strain (7×10-7 to 7×10-6) followed by a gradual permeability recovery. We investigated the mechanism by: (1) recording deformation of samples both before and after fracturing during the experiment, (2) varying the chemistry of the water and therefore particle mobility, (3) evaluating the dependence of permeability enhancement and recovery on dynamic stress amplitude, and (4) examining micro-scale pore textures of the rock samples before and after experiments. We find that dynamic stressing does not produce permanent deformation in our samples. Water chemistry has a pronounced effect on the sensitivity to dynamic stressing, with the magnitude of permeability enhancement and the rate of permeability recovery varying with ionic strength of the pore fluid. Permeability recovery rates generally correlate with the permeability enhancement sensitivity. Microstructural observations of our samples show clearing of clay particulates from fracture surfaces during the experiment. From these four lines of evidence, we conclude that a flow-dependent mechanism associated with mobilization of fines controls both the magnitude of the permeability enhancement and the recovery rate in our experiments. We also find that permeability sensitivity to dynamic stressing increases after fracturing, which is a process that generates abundant particulate matter in situ. Our results suggest that fluid permeability in many areas of the

  14. Evolution of the morphology of diamond particles and mechanism of their growth during the synthesis by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Feoktistov, N. A.; Grudinkin, S. A.; Golubev, V. G.; Baranov, M. A.; Bogdanov, K. V.; Kukushkin, S. A.

    2015-11-01

    The evolution of the surface morphology of diamond particles synthesized by chemical vapor deposition (CVD) on silicon substrates has been investigated. It has been found that, when the diamond particles reach a critical size of less than 800 nm, the surface of the diamond faces is transformed. Particles with sizes of no more than 100-300 nm have a well-faceted surface covered by the {100} and {111} faces. An increase in the size of diamond particles leads to a change in the structure of their surface. The surface is covered by the {100} faces surrounded by a disordered phase. With a further increase in the particle size (up to ˜2000 nm), the {100} faces disappear and the diamond particles are covered by high-index faces. A model explaining the evolution of the surface morphology of diamond particles has been proposed. According to this model, during the evolution of diamond particles with an increase in their size, the mechanism of layer-bylayer growth changes to normal growth, which leads to a significant transformation of the entire surface of the diamond particles. The critical size of a two-dimensional nucleus formed on the {100} and {111} faces, at which the change in the growth mechanism begins to occur, has been calculated. A method has been proposed for controlling the morphology of diamond particles during their synthesis.

  15. Evidence for particle mobilization as a mechanism for permeability enhancement via dynamic stressing

    NASA Astrophysics Data System (ADS)

    Candela, T.; Brodsky, E. E.; Marone, C.; Elsworth, D.

    2013-12-01

    Dynamic permeability change by seismic waves is a well-established natural phenomenon yet the mechanism remains poorly understood. We investigate the mechanism by generating well-controlled repeatable permeability enhancement in a laboratory experiment. Each experiment proceeded as: (1) pore pressure oscillations, simulating dynamic stresses, were applied at one end of intact Berea sandstone samples under triaxial stresses of tens of megapascals, (2) samples were fractured within the apparatus, and (3) pore pressure oscillations resumed post-fracturing. In this way, both the fracture and porous media response to the dynamic stresses were investigated. In addition, we controled the mobility of fine particles by adjusting the pore fluid chemistry (deionized water, and brines of: NaCl 5%, NaCl 35%, CaCl2 5%). Our results are consistent with natural observations. Dynamic stressing produces an immediate permeability enhancement ranging from 1-60%, which scales with the amplitude of the dynamic strain, 7*10^-7 to 7*10^-6, followed by a progressive permeability recovery. In our experiments a flow-dependent mechanism associated with mobilization of fines appears to control both the magnitude of the permeability enhancement and the recovery rate. Both processes operate at two time scales, i.e., fast flushing/unclogging of the fines during the pore pressure oscillations and progressive clogging of the pore throats by particle migration, and were influenced by the fluid chemistry. The dynamic permeability changes were not associated with permanent deformation. We show that: 1) injection of unequilibrated fluids favors particle mobilization, and 2) transient permeability change results from the migration of fines which in turn results from dynamic stressing. Our results suggest that areas where pore fluids are in disequilibrium should be more sensitive to dynamic stressing. Interestingly, early observations of dynamic earthquake-triggering revealed preferential triggering in

  16. Does Moss Grow on a Rolling Stone? The Influence of Precipitation Phase on Streamflow Characteristics, Bed Particle Transport and Periphyton Development in 18 Mountain Channels, Central Idaho

    NASA Astrophysics Data System (ADS)

    Tennant, C.; Crosby, B. T.; Baxter, C.

    2012-12-01

    It has been suggested that linked ecological and geomorphological systems exhibit complex and non-linear response to disturbance. However, quantifying the response of these systems is complicated by identifying the relevant linkages between system components and by variability in time scale adjustments. To help elucidate some of these complexities we characterized the influence of streamflow and bed-substrate mobility on periphyton assemblage development. Study catchments are subdivided into 3 categories based on the fraction of precipitation that fell as rain vs. snow. The categories are rain-dominated (RD), mixed rain-snow (MRS) and snow-dominated (SD). Three water years of streamflow data demonstrate that RD catchments experienced the largest inter-regime and inter-annual variability in streamflow conditions. RD sites were characterized by flashy responses to frequent precipitation events during wet winter and spring months and experienced channel drying during the summer. Runoff in MRS and SD catchments was characterized by much higher magnitude, longer duration flow events in early and mid-summer. Hydrologic results suggest that RD watersheds limit periphyton mass because of drought conditions and that MRS and SD channels control the temporal scale of periphyton development via long duration, high magnitude flood events that transport bed sediments and disrupt primary production. Results from our rock-tracing experiment indicate that assessments of biological disturbance based on hydrologic metrics alone miss important details of the characteristics of physical disturbance within channels. Channels within RD catchments appear to be in disequilibrium because of variability in the frequency and consistency of hydrologic events capable of mobilizing bed particles. Wet winters resulted in frequent and flashy streamflow events that likely caused bedload transport, whereas drier winters caused few streamflow events and subsequently little to no bedload transport

  17. Dynamic mechanism of the velocity splitting of ablated particles produced by pulsed-laser deposition in an inert gas

    NASA Astrophysics Data System (ADS)

    Ding, X. C.; Wang, Y. L.; Chu, L. Z.; Deng, Z. C.; Liang, W. H.; Galalaldeen, I. I. A.; Fu, G. S.

    2011-12-01

    The transport dynamics of ablated particles produced by pulsed-laser deposition in an inert gas is investigated via the Monte Carlo simulation method. The splitting mechanism of ablated particles is discussed by tracking every ablated particle with their forces, velocities and locations. The force analysis demonstrates that whether the splitting appears or not is decided by the releasing way of the driving force acting on the ablated particles. The "average" drag force, which is related to the mass and radius of the ambient gas, determines the releasing way of the driving force. Our simulated results are approximately in agreement with the previous experimental data.

  18. Detecting Both the Mass and Position of an Accreted Particle by a Micro/Nano-Mechanical Resonator Sensor

    PubMed Central

    Zhang, Yin; Liu, Yun

    2014-01-01

    In the application of a micro-/nano-mechanical resonator, the position of an accreted particle and the resonant frequencies are measured by two different physical systems. Detecting the particle position sometimes can be extremely difficult or even impossible, especially when the particle is as small as an atom or a molecule. Using the resonant frequencies to determine the mass and position of an accreted particle formulates an inverse problem. The Dirac delta function and Galerkin method are used to model and formulate an eigenvalue problem of a beam with an accreted particle. An approximate method is proposed by ignoring the off-diagonal elements of the eigenvalue matrix. Based on the approximate method, the mass and position of an accreted particle can be decoupled and uniquely determined by measuring at most three resonant frequencies. The approximate method is demonstrated to be very accurate when the particle mass is small, which is the application scenario for much of the mass sensing of micro-/nano-mechanical resonators. By solving the inverse problem, the position measurement becomes unnecessary, which is of some help to the mass sensing application of a micro-/nano-mechanical resonator by reducing two measurement systems to one. How to apply the method to the general scenario of multiple accreted particles is also discussed. PMID:25184493

  19. Growing scheme for topologically ordered states in interacting systems

    NASA Astrophysics Data System (ADS)

    Letscher, Fabian; Grusdt, Fabian; Fleischhauer, Michael

    2015-05-01

    We present a protocol for growing states with topological order in interacting many-body systems. The basic ingredients are explained using the superlattice Bose-Hubbard model as a simple toy model. Firstly, a topologically protected Thouless pump is used to create a local quasi-hole excitation. Secondly, a coherent pump refills the quasi-hole excitation with a single particle by making use of a blockade mechanism due to the repulsive interaction between the particles. In finite systems with dispersive bands, we discuss extensions to the protocol to maintain a high efficiency. The scheme can be used to grow the highly correlated Laughlin state in the fractional quantum Hall effect. We use an effective model based on the composite fermion description to simulate large lattice systems with many particles.

  20. Growing Galaxies Gently

    NASA Astrophysics Data System (ADS)

    2010-10-01

    New observations from ESO's Very Large Telescope have, for the first time, provided direct evidence that young galaxies can grow by sucking in the cool gas around them and using it as fuel for the formation of many new stars. In the first few billion years after the Big Bang the mass of a typical galaxy increased dramatically and understanding why this happened is one of the hottest problems in modern astrophysics. The results appear in the 14 October issue of the journal Nature. The first galaxies formed well before the Universe was one billion years old and were much smaller than the giant systems - including the Milky Way - that we see today. So somehow the average galaxy size has increased as the Universe has evolved. Galaxies often collide and then merge to form larger systems and this process is certainly an important growth mechanism. However, an additional, gentler way has been proposed. A European team of astronomers has used ESO's Very Large Telescope to test this very different idea - that young galaxies can also grow by sucking in cool streams of the hydrogen and helium gas that filled the early Universe and forming new stars from this primitive material. Just as a commercial company can expand either by merging with other companies, or by hiring more staff, young galaxies could perhaps also grow in two different ways - by merging with other galaxies or by accreting material. The team leader, Giovanni Cresci (Osservatorio Astrofisico di Arcetri) says: "The new results from the VLT are the first direct evidence that the accretion of pristine gas really happened and was enough to fuel vigorous star formation and the growth of massive galaxies in the young Universe." The discovery will have a major impact on our understanding of the evolution of the Universe from the Big Bang to the present day. Theories of galaxy formation and evolution may have to be re-written. The group began by selecting three very distant galaxies to see if they could find evidence

  1. Growing Galaxies Gently

    NASA Astrophysics Data System (ADS)

    2010-10-01

    New observations from ESO's Very Large Telescope have, for the first time, provided direct evidence that young galaxies can grow by sucking in the cool gas around them and using it as fuel for the formation of many new stars. In the first few billion years after the Big Bang the mass of a typical galaxy increased dramatically and understanding why this happened is one of the hottest problems in modern astrophysics. The results appear in the 14 October issue of the journal Nature. The first galaxies formed well before the Universe was one billion years old and were much smaller than the giant systems - including the Milky Way - that we see today. So somehow the average galaxy size has increased as the Universe has evolved. Galaxies often collide and then merge to form larger systems and this process is certainly an important growth mechanism. However, an additional, gentler way has been proposed. A European team of astronomers has used ESO's Very Large Telescope to test this very different idea - that young galaxies can also grow by sucking in cool streams of the hydrogen and helium gas that filled the early Universe and forming new stars from this primitive material. Just as a commercial company can expand either by merging with other companies, or by hiring more staff, young galaxies could perhaps also grow in two different ways - by merging with other galaxies or by accreting material. The team leader, Giovanni Cresci (Osservatorio Astrofisico di Arcetri) says: "The new results from the VLT are the first direct evidence that the accretion of pristine gas really happened and was enough to fuel vigorous star formation and the growth of massive galaxies in the young Universe." The discovery will have a major impact on our understanding of the evolution of the Universe from the Big Bang to the present day. Theories of galaxy formation and evolution may have to be re-written. The group began by selecting three very distant galaxies to see if they could find evidence

  2. Growing and Growing: Promoting Functional Thinking with Geometric Growing Patterns

    ERIC Educational Resources Information Center

    Markworth, Kimberly A.

    2010-01-01

    Design research methodology is used in this study to develop an empirically-substantiated instruction theory about students' development of functional thinking in the context of geometric growing patterns. The two research questions are: (1) How does students' functional thinking develop in the context of geometric growing patterns? (2) What are…

  3. Mechanical Evolution and Dynamics of Decollement Slip in Contractional Systems: Correlating Macro- and Micro-Scale Processes in Particle Dynamics Simulation

    NASA Astrophysics Data System (ADS)

    Morgan, J. K.

    2014-12-01

    Particle-based numerical simulations allow detailed investigations of small-scale processes and mechanisms associated with fault initiation and slip, which emerge naturally in such models. This study investigates the evolving mechanical conditions and associated micro-mechanisms during transient slip on a weak decollement propagating beneath a growing contractional wedge (e.g., accretionary prism, fold and thrust belt). The models serve as analogs of the seismic cycle, although lacking full earthquake dynamics. Nonetheless, the mechanical evolution of both decollement and upper plate can be monitored, and correlated with the particle-scale physical and contact properties, providing insights into changes that accompany such stick-slip behavior. In this study, particle assemblages consolidated under gravity and bonded to impart cohesion, are pushed at a constant velocity above a weak, unbonded decollement surface. Forward propagation of decollement slip occurs in discrete pulses, modulated by heterogeneous stress conditions (e.g., roughness, contact bridging) along the fault. Passage of decollement slip resets the stress along this horizon, producing distinct patterns: shear stress is enhanced in front of the slipped decollement due to local contact bridging and fault locking; shear stress minima occur immediately above the tip, denoting local stress release and contact reorganization following slip; more mature portions of the fault exhibit intermediate shear stress, reflecting more stable contact force distributions and magnitudes. This pattern of shear stress pre-conditions the decollement for future slip events, which must overcome the high stresses at the fault tip. Long-term slip along the basal decollement induces upper plate contraction. When upper plate stresses reach critical strength conditions, new thrust faults break through the upper plate, relieving stresses and accommodating horizontal shortening. Decollement activity retreats back to the newly formed

  4. Particle morphology influence on mechanical and biocompatibility properties of injection molded Ti alloy powder.

    PubMed

    Gülsoy, H Özkan; Gülsoy, Nagihan; Calışıcı, Rahmi

    2014-01-01

    Titanium and Titanium alloys exhibits properties that are excellent for various bio-applications. Metal injection molding is a processing route that offers reduction in costs, with the added advantage of near net-shape components. Different physical properties of Titanium alloy powders, shaped and processed via injection molding can achieve high complexity of part geometry with mechanical and bioactivity properties, similar or superior to wrought material. This study describes that the effect of particle morphology on the microstructural, mechanical and biocompatibility properties of injection molded Ti-6Al-4V (Ti64) alloy powder for biomaterials applications. Ti64 powders irregular and spherical in shape were injection molded with wax based binder. Binder debinding was performed in solvent and thermal method. After debinding the samples were sintered under high vacuum. Metallographic studies were determined to densification and the corresponding microstructural changes. Sintered samples were immersed in a simulated body fluid (SBF) with elemental concentrations that were comparable to those of human blood plasma for a total period of 15 days. Both materials were implanted in fibroblast culture for biocompatibility evaluations were carried out. The results show that spherical and irregular powder could be sintered to a maximum theoretical density. Maximum tensile strength was obtained for spherical shape powder sintered. The tensile strength of the irregular shape powder sintered at the same temperature was lower due to higher porosity. Finally, mechanical tests show that the irregular shape powder has lower mechanical properties than spherical shape powder. The sintered irregular Ti64 powder exhibited better biocompatibility than sintered spherical Ti64 powder. Results of study showed that sintered spherical and irregular Ti64 powders exhibited high mechanical properties and good biocompatibility properties. PMID:25201399

  5. Nonlinear elastic behavior and failure mechanism of polyhedral graphite particles undergoing uniaxial compression

    NASA Astrophysics Data System (ADS)

    Li, B.; Zhang, P.; Fu, Q. Q.; Li, X. F.; Zhao, X.; Song, X. L.

    2014-08-01

    Load-displacement responses and ultimate strength of polyhedral graphite particles (PGPs) undergoing in situ nano-compression at ambient temperature have been studied. The dynamic responses of PGPs to uniaxial loads exhibit a typical nonlinear elastic behavior for graphitic nanomaterials. Based on the analysis of stress-strain relationship, the intrinsic strength is slightly larger than actual ultimate strength, indicating the mechanical properties influenced by the initial defects in PGPs. For a given case, compressive Young's modulus E and third-order elastic modulus D achieve to 12.8 GPa and -13.9 GPa, respectively. Weibull probability analysis confirmed its broad range of structural defects inside PGPs and mechanical properties are sensitive to initial defects. The values of ultimate strength of tested PGPs with diameter of 150-400 nm fall within 2-4.5 GPa, which are in the range between shear elastic modulus C44 of turbo-g (minimum) and C44 of hex-g (maximum) in the literature. The deformation and failure mechanisms are discussed and rationalized in terms of structural factors and elastic moduli of perfect graphite crystals.

  6. Aggravation of inflammatory response by costimulation with titanium particles and mechanical perturbations in osteoblast- and macrophage-like cells.

    PubMed

    Lee, Heon Goo; Hsu, Anny; Goto, Hana; Nizami, Saqib; Lee, Jonathan H; Cadet, Edwin R; Tang, Peter; Shaji, Roya; Chandhanayinyong, Chandhanarat; Kweon, Seok Hyun; Oh, Daniel S; Tawfeek, Hesham; Lee, Francis Y

    2013-03-01

    The interface between bone tissue and metal implants undergoes various types of mechanical loading, such as strain, compression, fluid pressure, and shear stress, from daily activities. Such mechanical perturbations create suboptimal environments at the host bone-implant junction, causing an accumulation of wear particles and debilitating osseous integration, potentially leading to implant failure. While many studies have focused on the effect of particles on macrophages or osteoprogenitor cells, differential and combined effects of mechanical perturbations and particles on such cell types have not been extensively studied. In this study, macrophages and osteoprogenitor cells were subjected to physiological and superphysiological mechanical stimuli in the presence and absence of Ti particles with the aim of simulating various microenvironments of the host bone-implant junction. Macrophages and osteoprogenitor cells were capable of engulfing Ti particles through actin remodeling and also exhibited changes in mRNA levels of proinflammatory cytokines under certain conditions. In osteoprogenitor cells, superphysiological strain increased proinflammatory gene expression; in macrophages, such mechanical perturbations did not affect gene expression. We confirmed that this phenomenon in osteoprogenitor cells occurred via activation of the ERK1/2 signaling pathway as a result of damage to the cytoplasmic membrane. Furthermore, AZD6244, a clinically relevant inhibitor of the ERK1/2 pathway, mitigated particle-induced inflammatory gene expression in osteoprogenitor cells and macrophages. This study provides evidence of more inflammatory responses under mechanical strains in osteoprogenitor cells than macrophages. Phagocytosis of particles and mechanical perturbation costimulate the ERK1/2 pathway, leading to expression of proinflammatory genes. PMID:23255578

  7. The eikonal function: the commom concept in ray optics and particle mechanics

    NASA Astrophysics Data System (ADS)

    Krautter, Martin

    1993-04-01

    The habit of teaching the movements of masses first, and propagation of light later, as an electromagnetic phenomenon was widespread. Looking further back into the history of physics, however, we see earlier the concepts for understanding light rays, and later their successful application to particle trajectories, leading to the highly developed celestial mechanics towards the end of the 19th century. And then, 1905, Karl Schwarzschild transferred the technique of `canonical coordinates,' named so by C.G.J. Jacobi in 1837, back to light rays in imaging systems. I would like to point to the chief steps in the evolution. The learning process for handling both particle and wave propagation aspects continues up to our time: Richard Feynman 1918 - 1988. We may judge each contribution: whether it opens our mind to a unifying theory, or whether it hardens partial understanding. And we can notice where the understanding of light propagation led the evolution, and how the theory for movement of masses caught up.

  8. Antimicrobial, Mechanical and Thermal Studies of Silver Particle-Loaded Polyurethane

    PubMed Central

    Paul, Deepen; Paul, Sharmistha; Roohpour, Nima; Wilks, Mark; Vadgama, Pankaj

    2013-01-01

    Silver-particle-incorporated polyurethane films were evaluated for antimicrobial activity towards two different bacteria: Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Distributed silver particles sourced from silver nitrate, silver lactate and preformed silver nanoparticles were mixed with polyurethane (PU) and variously characterized by field emission scanning electron microscopy (FESEM), fourier transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD) and contact angle measurement. Antibacterial activity against E.coli was confirmed for films loaded with 10% (w/w) AgNO3, 1% and 10% (w/w) Ag lactate and preformed Ag nanoparticles. All were active against S. aureus, but Ag nanoparticles loaded with PU had a minor effect. The apparent antibacterial performance of Ag lactate-loaded PU is better than other Ag ion-loaded films, revealed from the zone of inhibition study. The better performance of silver lactate-loaded PU was the likely result of a porous PU structure. FESEM and FTIR indicated direct interaction of silver with the PU backbone, and XRD patterns confirmed that face-centred cubic-type silver, representative of Ag metal, was present. Young’s modulus, tensile strength and the hardness of silver containing PU films were not adversely affected and possibly marginally increased with silver incorporation. Dynamic mechanical analysis (DMA) indicated greater thermal stability. PMID:24956194

  9. On a theory of two-beam mechanisms of charged particle acceleration in electrodynamic structures

    SciTech Connect

    Ostrovsky, A.O.

    1993-09-01

    This work is devoted to the theoretical studies of two-beam mechanisms of charged particle acceleration in electronic structures. The first section continues the outline of results of theoretical studies commenced in the intermediate report and considers the two-beam scheme of acceleration in the plasma waveguide. According to this scheme the strong current relativistic electron beam (REB) excites the intensive plasma waves accelerating the electrons of the second beam. The driving beam is assumed to be density-modulated. The preliminary modulation of the driving REB is shown to enhance substantially the acceleration efficiency of relativistic electrons of the driven beam. The second section deals with the two-beam acceleration in the vacuum corrugated waveguide. According to this scheme the excitation of electromagnetic waves and acceleration of driven beam electrons by them is accomplished under different Cherenkov resonances between the particles of beams and the corrugated waveguide field. The electromagnetic field in the periodic structure is known to be the superposition of spatial harmonics. With the small depth of the periodic nonuniformity the amplitudes of these harmonics decrease fast with their number increasing. Therefore, if the driving beam is in the Cherenkov resonance with the first spatial harmonic and the driven beam is in resonance with the zero space harmonic then the force accelerating the driven beam would be considerably bigger than the force decelerating the driving beam electrons.

  10. Fluid flow and particle transport in mechanically ventilated airways. Part I. Fluid flow structures.

    PubMed

    Van Rhein, Timothy; Alzahrany, Mohammed; Banerjee, Arindam; Salzman, Gary

    2016-07-01

    A large eddy simulation-based computational study of fluid flow and particle transport in upper tracheobronchial airways is carried out to investigate the effect of ventilation parameters on pulmonary fluid flow. Respiratory waveforms commonly used by commercial mechanical ventilators are used to study the effect of ventilation parameters and ventilation circuit on pulmonary fluid dynamics. A companion paper (Alzahrany et al. in Med Biol Eng Comput, 2014) reports our findings on the effect of the ventilation parameters and circuit on particle transport and aerosolized drug delivery. The endotracheal tube (ETT) was found to be an important geometric feature and resulted in a fluid jet that caused an increase in turbulence and created a recirculation zone with high wall shear stress in the main bronchi. Stronger turbulence was found in lower airways than would be found under normal breathing conditions due to the presence of the jet caused by the ETT. The pressure-controlled sinusoidal waveform induced the lowest wall shear stress on the airways wall. PMID:26563199

  11. Smooth-particle applied mechanics: Conservation of angular momentum with tensile stability and velocity averaging.

    PubMed

    Hoover, Wm G; Hoover, Carol G; Merritt, Elizabeth C

    2004-01-01

    Smooth-particle applied mechanics (SPAM) provides several approaches to approximate solutions of the continuum equations for both fluids and solids. Though many of the usual formulations conserve mass, (linear) momentum, and energy, the angular momentum is typically not conserved by SPAM. A second difficulty with the usual formulations is that tensile stress states often exhibit an exponentially fast high-frequency short-wavelength instability, "tensile instability." We discuss these twin defects of SPAM and illustrate them for a rotating elastic body. We formulate ways to conserve angular momentum while at the same time delaying the symptoms of tensile instability for many sound-traversal times. These ideas should prove useful in more general situations. PMID:14995750

  12. Newtonian mechanics of a many-particle assembly coupled to an external body potential

    NASA Technical Reports Server (NTRS)

    Salvino, R. E.

    1990-01-01

    The Newtonian mechanics of a many-particle system evolving in time under the influence of an external body potential, that is, an external potential that couples to the center of mass only, is examined. The lack of any other external fields allows the complete separation of the center-of-mass (or external-field-dependent) equations from the internal (or external-field-independent) dynamics. The complete solution of the center-of-mass motion then allows an analytical evaluation of the external body potential contributions to the thermophysical properties of the system. The phenomena of field-induced heating, Taylor-Aris hydrodynamic form for the diffusion tensor, and an analogous hydrodynamic form for the viscosity tensor are derived from microscopic principles. A brief and model-dependent description of equilibrium phenomena is also presented.

  13. Self-consistent particle-in-cell simulations of fundamental and harmonic radio plasma emission mechanisms

    NASA Astrophysics Data System (ADS)

    Tsiklauri, D.; Thurgood, J. O.

    2015-12-01

    first co-author Jonathan O. Thurgood (QMUL) The simulation of three-wave interaction based plasma emission, an underlying mechanism for type III solar radio bursts, is a challenging task requiring fully-kinetic, multi-dimensional models. This paper aims to resolve a contradiction in past attempts, whereby some authors report that no such processes occur and others draw conflicting conclusions, by using 2D, fully kinetic, particle-in-cell simulations of relaxing electron beams. Here we present the results of particle-in-cell simulations which for different physical parameters permit or prohibit the plasma emission. We show that the possibility of plasma emission is contingent upon the frequency of the initial electrostatic waves generated by the bump-in-tail instability, and that these waves may be prohibited from participating in the necessary three-wave interactions due to the frequency beat requirements. We caution against simulating astrophysical radio bursts using unrealistically dense beams (a common approach which reduces run time), as the resulting non-Langmuir characteristics of the initial wave modes significantly suppresses the emission. Comparison of our results indicates that, contrary to the suggestions of previous authors, a plasma emission mechanism based on two counter-propagating beams is unnecessary in astrophysical context. Finally, we also consider the action of the Weibel instability, which generates an electromagnetic beam mode. As this provides a stronger contribution to electromagnetic energy than the emission, we stress that evidence of plasma emission in simulations must disentangle the two contributions and not simply interpret changes in total electromagnetic energy as the evidence of plasma emission. In summary, we present the first self-consistent demonstration of fundamental and harmonic plasma emission from a single-beam system via fully kinetic numerical simulation. Pre-print can be found at http://astro.qmul.ac.uk/~tsiklauri/jtdt1

  14. Particle Image Velocimetry Analysis in Micromodels to Investigate Two-Phase Flow Mechanisms

    NASA Astrophysics Data System (ADS)

    Roman, S.; Soulaine, C.; Kovscek, A. R.

    2014-12-01

    The inherent instabilities in two-phase displacements play a key role in the process of carbon dioxide sequestration. Thus, a fundamental understanding of two-phase unstable flows in porous media across a range of length and time scales is essential. However, the dynamics at the pore scale remains relatively unknown and influences macroscale behaviors. In that context, experiments in simplified porous media were performed in order to investigate pore scale mechanisms. The dynamics of fluid displacement in porous media were captured with Particle Image Velocimetry (PIV).The experimental apparatus includes 2D etched micromodels connected to a syringe pump and placed under a microscope for flow visualization. The micromodels contain an etched flow pattern composed of circular grains homogeneously distributed or composed of a sandstone replica pattern. The fluids under study are seeded with polymer microparticles and image sequences of the flow are recorded. The motion of the seeding particles is used to calculate the velocity field of the flow with PIV algortithms.The PIV measurements were first validated for single phase flow. For that purpose, experiments were performed where water and microparticles flowed through the micromodels. The PIV measurements were compared to 2D direct numerical simulations of the flow through the different geometries under consideration. Experiments and numerical simulations show a good agreement. PIV measurements are quantitatively validated to investigate flow mechanisms at the pore scale. Then, the feasibility of PIV measurements for two-phase flow in micromodels has been demonstrated and we can now use this technique with confidence to investigate multiphase flow dynamics. Experiments in micromodels will henceforth allow the validation of two-phase flow simulation, in fact no reliable numerical works have been published at this scale for multiphase flows.

  15. Room temperature deformation mechanisms of alumina particles observed from in situ micro-compression and atomistic simulations.

    SciTech Connect

    Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay D.; Mook, William M.; Bufford, Daniel Charles; Boyce, Brad L.; Hattar, Khalid Mikhiel; Kotula, Paul G.; Hall, Aaron Christopher

    2015-09-22

    Aerosol deposition (AD) is a solid-state deposition technology that has been developed to fabricate ceramic coatings nominally at room temperature. Sub-micron ceramic particles accelerated by pressurized gas impact, deform, and consolidate on substrates under vacuum. Ceramic particle consolidation in AD coatings is highly dependent on particle deformation and bonding; these behaviors are not well understood. In this work, atomistic simulations and in situ micro-compressions in the scanning electron microscope, and the transmission electron microscope (TEM) were utilized to investigate fundamental mechanisms responsible for plastic deformation/fracture of particles under applied compression. Results showed that highly defective micron-sized alumina particles, initially containing numerous dislocations or a grain boundary, exhibited no observable shape change before fracture/fragmentation. Simulations and experimental results indicated that particles containing a grain boundary only accommodate low strain energy per unit volume before crack nucleation and propagation. In contrast, nearly defect-free, sub-micron, single crystal alumina particles exhibited plastic deformation and fracture without fragmentation. Dislocation nucleation/motion, significant plastic deformation, and shape change were observed. Simulation and TEM in situ micro-compression results indicated that nearly defect-free particles accommodate high strain energy per unit volume associated with dislocation plasticity before fracture. As a result, the identified deformation mechanisms provide insight into feedstock design for AD.

  16. Room temperature deformation mechanisms of alumina particles observed from in situ micro-compression and atomistic simulations.

    DOE PAGESBeta

    Sarobol, Pylin; Chandross, Michael E.; Carroll, Jay D.; Mook, William M.; Bufford, Daniel Charles; Boyce, Brad L.; Hattar, Khalid Mikhiel; Kotula, Paul G.; Hall, Aaron Christopher

    2015-09-22

    Aerosol deposition (AD) is a solid-state deposition technology that has been developed to fabricate ceramic coatings nominally at room temperature. Sub-micron ceramic particles accelerated by pressurized gas impact, deform, and consolidate on substrates under vacuum. Ceramic particle consolidation in AD coatings is highly dependent on particle deformation and bonding; these behaviors are not well understood. In this work, atomistic simulations and in situ micro-compressions in the scanning electron microscope, and the transmission electron microscope (TEM) were utilized to investigate fundamental mechanisms responsible for plastic deformation/fracture of particles under applied compression. Results showed that highly defective micron-sized alumina particles, initially containingmore » numerous dislocations or a grain boundary, exhibited no observable shape change before fracture/fragmentation. Simulations and experimental results indicated that particles containing a grain boundary only accommodate low strain energy per unit volume before crack nucleation and propagation. In contrast, nearly defect-free, sub-micron, single crystal alumina particles exhibited plastic deformation and fracture without fragmentation. Dislocation nucleation/motion, significant plastic deformation, and shape change were observed. Simulation and TEM in situ micro-compression results indicated that nearly defect-free particles accommodate high strain energy per unit volume associated with dislocation plasticity before fracture. As a result, the identified deformation mechanisms provide insight into feedstock design for AD.« less

  17. Room Temperature Deformation Mechanisms of Alumina Particles Observed from In Situ Micro-compression and Atomistic Simulations

    NASA Astrophysics Data System (ADS)

    Sarobol, Pylin; Chandross, Michael; Carroll, Jay D.; Mook, William M.; Bufford, Daniel C.; Boyce, Brad L.; Hattar, Khalid; Kotula, Paul G.; Hall, Aaron C.

    2016-01-01

    Aerosol deposition (AD) is a solid-state deposition technology that has been developed to fabricate ceramic coatings nominally at room temperature. Sub-micron ceramic particles accelerated by pressurized gas impact, deform, and consolidate on substrates under vacuum. Ceramic particle consolidation in AD coatings is highly dependent on particle deformation and bonding; these behaviors are not well understood. In this work, atomistic simulations and in situ micro-compressions in the scanning electron microscope, and the transmission electron microscope (TEM) were utilized to investigate fundamental mechanisms responsible for plastic deformation/fracture of particles under applied compression. Results showed that highly defective micron-sized alumina particles, initially containing numerous dislocations or a grain boundary, exhibited no observable shape change before fracture/fragmentation. Simulations and experimental results indicated that particles containing a grain boundary only accommodate low strain energy per unit volume before crack nucleation and propagation. In contrast, nearly defect-free, sub-micron, single crystal alumina particles exhibited plastic deformation and fracture without fragmentation. Dislocation nucleation/motion, significant plastic deformation, and shape change were observed. Simulation and TEM in situ micro-compression results indicated that nearly defect-free particles accommodate high strain energy per unit volume associated with dislocation plasticity before fracture. The identified deformation mechanisms provide insight into feedstock design for AD.

  18. Insights into secondary organic aerosol formation mechanisms from measured gas/particle partitioning of specific organic tracer compounds.

    PubMed

    Zhao, Yunliang; Kreisberg, Nathan M; Worton, David R; Isaacman, Gabriel; Weber, Robin J; Liu, Shang; Day, Douglas A; Russell, Lynn M; Markovic, Milos Z; VandenBoer, Trevor C; Murphy, Jennifer G; Hering, Susanne V; Goldstein, Allen H

    2013-04-16

    In situ measurements of organic compounds in both gas and particle phases were made with a thermal desorption aerosol gas chromatography (TAG) instrument. The gas/particle partitioning of phthalic acid, pinonaldehyde, and 6,10,14-trimethyl-2-pentadecanone is discussed in detail to explore secondary organic aerosol (SOA) formation mechanisms. Measured fractions in the particle phase (f(part)) of 6,10,14-trimethyl-2-pentadecanone were similar to those expected from the absorptive gas/particle partitioning theory, suggesting that its partitioning is dominated by absorption processes. However, f(part) of phthalic acid and pinonaldehyde were substantially higher than predicted. The formation of low-volatility products from reactions of phthalic acid with ammonia is proposed as one possible mechanism to explain the high f(part) of phthalic acid. The observations of particle-phase pinonaldehyde when inorganic acids were fully neutralized indicate that inorganic acids are not required for the occurrence of reactive uptake of pinonaldehyde on particles. The observed relationship between f(part) of pinonaldehyde and relative humidity suggests that the aerosol water plays a significant role in the formation of particle-phase pinonaldehyde. Our results clearly show it is necessary to include multiple gas/particle partitioning pathways in models to predict SOA and multiple SOA tracers in source apportionment models to reconstruct SOA. PMID:23448102

  19. A unified sweep-stick mechanism to explain particle clustering in two- and three-dimensional homogeneous, isotropic turbulence

    NASA Astrophysics Data System (ADS)

    Coleman, S. W.; Vassilicos, J. C.

    2009-11-01

    Our work focuses on the sweep-stick mechanism of particle clustering in turbulent flows introduced by Chen et al. [L. Chen, S. Goto, and J. C. Vassilicos, "Turbulent clustering of stagnation points and inertial particles," J. Fluid Mech. 553, 143 (2006)] for two-dimensional (2D) inverse cascading homogeneous, isotropic turbulence (HIT), whereby heavy particles cluster in a way that mimics the clustering of zero-acceleration points. We extend this phenomenology to three-dimensional (3D) HIT, where it was previously reported that zero-acceleration points were extremely rare. Having obtained a unified mechanism we quantify the Stokes number dependency of the probability of the heavy particles to be at zero-acceleration points and show that in the inertial range of Stokes numbers, the sweep-stick mechanism is dominant over the conventionally proposed mechanism of heavy particles being centrifuged from high vorticity regions to high strain regions. Finally, having a clustering coincidence between particles and zero-acceleration points, both in 2D and 3D HIT, motivates us to demonstrate the sweep and stick parts of the mechanism in both dimensions. The sweeping of regions of low acceleration regions by the local fluid velocity in both flows is demonstrated by introducing a velocity of the acceleration field. Finally, the stick part is demonstrated by showing that heavy particles statistically move with the same velocity as zero-acceleration points, while moving away from any nonzero-acceleration region, irrespective of their Stokes number. These results explain the clustering of inertial particles given the clustering of zero-acceleration points.

  20. Studies of near-surface phenomena and erosion mechanisms in metallic alloys using single- and multi-particle impacts

    SciTech Connect

    Rao, M.; Keiser, J.R.

    1992-03-01

    An experimental study of the effects of material properties on erosion mechanisms was conducted by subjecting targets to single as well as multiple impacts of spherical particles at various velocities. A mechanical properties microprobe was used to monitor the hardening due to the impacts. Initial studies on several engineering alloys showed that work hardening was associated with single impacts, and the results suggested that the capacity to distribute the impact energy over large volumes improved a material's erosion resistance. Studies also showed that the alloys work hardened significantly under multiple-particle impacts. Single-particle impact studies were found to correlate well with results from low-velocity, multiple-particle erosion experiments. (VC)

  1. Ceramic Nano-particle/Substrate Interface Bonding Formation Derived from Dynamic Mechanical Force at Room Temperature: HRTEM Examination

    NASA Astrophysics Data System (ADS)

    Yao, Hai-Long; Yang, Guan-Jun; Fan, Sheng-Qiang; Li, Cheng-Xin; Li, Chang-Jiu

    2015-04-01

    The bonding of TiO2 nano-particle/substrate is a critical factor influencing the performance of dye-sensitized solar cells. In order to reveal the bonding properties at TiO2 nano-particle/substrate interface, high-resolution transmission electron microscopy (HRTEM) analysis was adopted to TiO2 coatings prepared by three different approaches. In the HRTEM analysis, the effective bonding mode is allowed to distinguish from the false image overlapping. Results show that large areas of effective bonding between nano-TiO2 particles and the substrate surface formed in the room temperature cold sprayed coating and mechanically pressed coating, while only limited interface areas with the effective bonding were observed in the coating deposited by non-pressed method. These results confirm that both high impact pressure during the room temperature cold spraying and mechanical pressure contribute to the bonding formation at the particle/substrate interface.

  2. Damage mechanism involved in the solid particle erosion of CVD diamond

    NASA Astrophysics Data System (ADS)

    Davies, Alun R.; Field, John E.

    2001-09-01

    Sophisticated electro-optic sensors are employed on aircraft and missiles, and it is essential to protect them from relatively high-speed impacts with airborne dust particles. A loss in transmission caused by such an event can impair guidance, and catastrophic failure may occur. Protection is afforded by the installation of a hard cover that is transparent in the relevant regime. Diamond is potentially by far the most attractive window material due to excellent optical and mechanical properties, but it is difficult to shape. Chemical vapor deposited (CVD) diamond is a polycrystalline synthetic with properties that approach those of single crystal diamond, and it can be more easily shaped. The aims of the present research were to quantify the erosion and transmission losses, and to understand the material removal mechanisms involved. Steady-state erosion rates were obtained for CVD diamond of different grain sizes, using 300-600 micrometers quartz erodent at velocities between 60 and 140 m/s. Images of CVD diamond at various stages of erosion, obtained using an optical microscope and an environmental scanning electron microscope (ESEM), reveal that erosion initially occurs at grain boundaries and that so-called micro-features also have some influence on erosion.

  3. The role of colloid particles in the albumin-lanthanides interaction: The study of aggregation mechanisms.

    PubMed

    Tikhonova, Tatiana N; Shirshin, Evgeny A; Romanchuk, Anna Yu; Fadeev, Victor V

    2016-10-01

    We studied the interaction between bovine serum albumin (BSA) and lanthanide ions in aqueous solution in the 4.0÷9.5pH range. A strong increase of the solution turbidity was observed at pH values exceeding 6, which corresponds to the formation of Ln(OH)3 nanoparticles, while no changes were observed near the isoelectric point of BSA (pH 4.7). The results of the dynamic light scattering and protein adsorption measurements clearly demonstrated that the observed turbidity enhancement was caused by albumin sorption on the surface of Ln(OH)3 and colloid particles bridging via adsorbed protein molecules. Upon pH increase from 4.5 to 6.5, albumin adsorption on lanthanide colloids was observed, while the following increase of pH from 6.5 to 9.5 led to protein desorption. The predominant role of the electrostatic interactions in the adsorption and desorption processes were revealed in the zeta-potential measurements. No reversibility was observed upon decreasing pH from 9.5 to 4.5 that was suggested to be due to the other interaction mechanisms present in the system. It was shown that while for all lanthanide ions the interaction mechanism with BSA was similar, its manifestation in the optical properties of the system was significantly different. This was interpreted as a consequence of the differences in lanthanides hydrolysis constants. PMID:27419645

  4. Transport Mechanism of Coumarin 6 Nanocrystals with Two Particle Sizes in MDCKII Monolayer and Larval Zebrafish.

    PubMed

    Miao, Xiaoqing; Li, Ye; Wang, Xueqing; Lee, Simon Ming-Yuen; Zheng, Ying

    2016-05-25

    Nanocrystals (NCs) were utilized as oral formulations in commercial products to deliver lipophilic drug, but their transport mechanisms are not fully understood. This study aimed to explore the transport mechanism of NCs using in vitro Madin-Darby canine kidney II (MDCK II) cells and in vivo larval zebrafish models. Coumarin 6 (C6) was formulated into NCs with particle size of 67.5 ± 5.2 and 190 ± 9.2 nm. In vitro studies showed that 70 nm NCs accumulated in lysosome and endoplasmic reticulum (ER) as destinations. Lipid raft pathways mediated the endocytosis, while lipid raft, ER/Golgi, and Golgi/plasma membrane pathways were involved in exocytosis and transcytosis process. However, 200 nm NCs accumulated more in a lysosome, where lipid raft pathways were also involved in the endocytosis process. In vivo studies in larval zebrafish model further confirmed that the above network plays an important role in the absorption and distribution of C6-NCs. PMID:27159431

  5. Mechanism of amorphous silica particles precipitation: simulation approach compared to experimental results

    NASA Astrophysics Data System (ADS)

    Noguera, Claudine; Fritz, Bertrand; Clement, Alain

    2015-04-01

    Despite its importance in numerous industrial and natural processes, many unsolved questions remain regarding the mechanism of silica precipitation in aqueous solutions: order of the reaction, role of silica oligomers, existence of an induction time and characteristics of the particle population. Beyond empirical approaches used in the past, we demonstrate that the classical nucleation theory associated to a size dependent growth law, as embedded in the NANOKIN code (1-3), allows a quantitative description of precipitation occurring under largely different experimental conditions : preexisting initial supersaturation in a large domain of temperature (5-150°C) and chemical composition (4), supersaturation reached by neutralization of a high pH silica solution (5) or by fast cooling (6). In that way, the mechanism of silica precipitation can be unraveled. We are able to discard the hypothesis of an induction time as an explanation for the plateaus observed in the saturation curves in these experiments. We challenge the role of oligomer incorporation at the growth stage to account for the observed rate laws and we stress the difference between the order of the growth law and the order of the total reaction rate. We also demonstrate that the characteristics of the particle population are strongly dependent on the way supersaturation is reached (7). Such a microscopic approach thus proves to be well suited to elucidate the mechanism of nanoparticle formation in natural and industrial contexts, involving silica, but also other mineral phases produced as nanoparticles (8). (1) Noguera C., Fritz B., Clément A. and Barronet A., J. Cryst. Growth, 2006, 297, 180. (2) Noguera C., Fritz B., Clément A. and Barronet A., J. Cryst. Growth, 2006, 297, 187. (3) Fritz B., Clément A., Amal Y. and Noguera C., Geochim. Cosmochim. Acta, 2009, 73, 1340. (4) Rothbaum, H.P. and Rohde A.G., J. Colloid Interf. Sci., 1979,71, 533. (5) Tobler D.J., Shaw S. and Benning L.G., Geochim

  6. Microstructure and strain rate effects on the mechanical behavior of particle reinforced epoxy-based reactive materials

    NASA Astrophysics Data System (ADS)

    White, Bradley William

    The effects of reactive metal particles on the microstructure and mechanical properties of epoxy-based composites is investigated in this work. Particle reinforced polymer composites show promise as structural energetic materials that can provide structural strength while simultaneously being capable of releasing large amounts of chemical energy through highly exothermic reactions occurring between the particles and with the matrix. This advanced class of materials is advantageous due to the decreased amount of high density inert casings needed for typical energetic materials and for their ability to increase payload expectancy and decrease collateral damage. Structural energetic materials can be comprised of reactive particles that undergo thermite or intermetallic reactions. In this work nickel (Ni) and aluminum (Al) particles were chosen as reinforcing constituents due to their well characterized mechanical and energetic properties. Although, the reactivity of nickel and aluminum is well characterized, the effects of their particle size, volume fractions, and spatial distribution on the mechanical behavior of the epoxy matrix and composite, across a large range of strain rates, are not well understood. To examine these effects castings of epoxy reinforced with 20--40 vol.% Al and 0--10 vol.% Ni were prepared, while varying the aluminum nominal particle size from 5 to 50 mum and holding the nickel nominal particle size constant at 50 mum. Through these variations eight composite materials were produced, possessing unique microstructures exhibiting different particle spatial distributions and constituent makeup. In order to correlate the microstructure to the constitutive response of the composites, techniques such as nearest-neighbor distances, and multiscale analysis of area fractions (MSAAF) were used to quantitatively characterize the microstructures. The composites were investigated under quasi-static and dynamic compressive loading conditions to characterize

  7. The Prediction and Simulation for the Mechanical Properties of Ceramic-Based Composites Reinforced with Nano-Micro Particles

    SciTech Connect

    Luo Dongmei; Hu Jinshan; Yang Hong; Zhou Yinglong

    2010-05-21

    The global-local homogenization method with precise period boundary conditions is applied to predict and simulate the mechanical properties of ceramic composites reinforced by spherical nano-micro particles with enwrapping and nesting arrays. The numerical simulation is performed with different size ratios of nano-micro particles, and different configurations for representative volume element. The results show that the low radius ratios of nano-micro particles produce a larger effective Young's modulus for its more uniform dispersion, and the hexagon RVE with nesting array can make an overestimation for effective elastic modulus of ceramic composites, and the interfacial damage between nano-microscopic particles and matrix degenerates the effective elastic modulus. It shows in this paper that it is significant to improve the mechanical properties of ceramic materials by mixing some nano- and micro-particles into the matrix with good designed array methods from the viewpoints of nano-microscopic crystal structure, and a rational interfacial damage model should be further proposed to investigate the toughening mechanism of ceramic-composites reinforced with nano-micro particles.

  8. Particle-Based Geometric and Mechanical Modelling of Woven Technical Textiles and Reinforcements for Composites

    NASA Astrophysics Data System (ADS)

    Samadi, Reza

    affecting the textile geometry and constitutive behaviour under evolving loading; 5) validating simulation results with experimental trials; and 6) demonstrating the applicability of the simulation procedure to textile reinforcements featuring large numbers of small fibres as used in PMCs. As a starting point, the effects of reinforcement configuration on the in-plane permeability of textile reinforcements, through-thickness thermal conductivity of PMCs and in-plane stiffness of unidirectional and bidirectional PMCs were quantified systematically and correlated with specific geometric parameters. Variability was quantified for each property at a constant fibre volume fraction. It was observed that variability differed strongly between properties; as such, the simulated behaviour can be related to variability levels seen in experimental measurements. The effects of the geometry of textile reinforcements on the aforementioned processing and performance properties of the textiles and PMCs made from these textiles was demonstrated and validated, but only for simple cases as thorough and credible geometric models were not available at the onset of this work. Outcomes of this work were published in a peer-reviewed journal [101]. Through this thesis it was demonstrated that predicting changes in textile geometry prior and during loading is feasible using the proposed particle-based modelling method. The particle-based modelling method relies on discrete mechanics and offers an alternative to more traditional methods based on continuum mechanics. Specifically it alleviates issues caused by large strains and management of intricate, evolving contact present in finite element simulations. The particle-based modelling method enables credible, intricate modelling of the geometry of textiles at the mesoscopic scale as well as faithful mechanical modelling under load. Changes to textile geometry and configuration due to the normal compaction pressure, stress relaxation, in-plane shear

  9. Distinct mechanisms of the inhibition of vasculogenesis by different species of ionizing particles

    PubMed Central

    Grabham, Peter; Sharma, Preety; Bigelow, Alan; Geard, Charles

    2014-01-01

    dynamic microtubules showed a 65% decrease when exposed to high-energy protons but not with the same dose of high-energy Fe ions. Since protein kinase C (PKC) has long been known to stimulate angiogenesis, we hypothesized that rescue of the capillary phenotype after proton exposure would be possible by stimulating PKC before irradiation. One-day-old vessel cultures were treated with 30 and 60 nM phorbol ester (PMA) 15 min before irradiation. Stimulation of PKC restored capillary formation in proton-treated cultures but not in Fe ion-treated cultures. More specifically, stimulation of PKC by PMA was able to restore the tip motility that was inhibited by low LET ions [ 1]. Further studies with various charged particles showed that low LET ion particles (Proton and He ions) with an LET lower or equal to 1 keV/μm inhibit vasculogenesis in the same way as protons. Higher LET charged particles (Silicon 1GeV, Oxygen 250 MeV and 1 GeV and Carbon 290 MeV and 1 GeV) with an LET ≥8 keV/μm inhibit vasculogenesis in the same way as Fe ions. In conclusion, we have shown that low and high LET ions inhibit the formation of brain capillaries by different mechanisms. For low LET ions, inhibition involves regulation of PKC-dependent motile tips leading to a failure of cellular processes to migrate through the matrix and meet up with other processes. For high LET ions, the cells fail to complete angiogenesis by not migrating and forming tubular structures. This complexity of response opens up possibilities of greater control over angiogenesis and the resulting pathologies during coincident exposure or therapy. For exposure in space, knowledge of these mechanisms will enable more precise risk assessment and mitigation strategies. For radiotherapy, treatment could be manipulated to utilize the radiation effectively.

  10. Mechanism and kinetics of organic matter degradation based on particle structure variation during pig manure aerobic composting.

    PubMed

    Ge, Jinyi; Huang, Guangqun; Huang, Jing; Zeng, Jianfei; Han, Lujia

    2015-07-15

    Characterization of the dynamic structure of composting particles may facilitate our understanding of the mechanisms of organic matter degradation during pig manure-wheat straw aerobic composting. In this study, changes in the size, shape, pores, chemical compositions, and crystal structures of pig manure particles during composting were investigated. The results showed that the median diameter (D50) decreased exponentially, while the particle aspect ratio and sphericity were unchanged, suggesting that particles were degraded uniformly along different radial directions. Pores had a mean diameter of 15-30 μm and were elliptical. The particle porosity increased linearly mainly because of hemicellulose degradation. Furthermore, the influence of particle structure variation on the first order rate constant (k) of organic matter degradation was corrected, which may facilitate the optimization of operation conditions. The k value was proportional to the reciprocal of D50 according to the specific surface area of particles, and it decreased with increased porosity due to the stabilized chemical compositions and crystal structures of particles. However, the applicability of these data to other composting materials should be verified. PMID:25781372

  11. Growing Unculturable Bacteria

    PubMed Central

    2012-01-01

    The bacteria that can be grown in the laboratory are only a small fraction of the total diversity that exists in nature. At all levels of bacterial phylogeny, uncultured clades that do not grow on standard media are playing critical roles in cycling carbon, nitrogen, and other elements, synthesizing novel natural products, and impacting the surrounding organisms and environment. While molecular techniques, such as metagenomic sequencing, can provide some information independent of our ability to culture these organisms, it is essentially impossible to learn new gene and pathway functions from pure sequence data. A true understanding of the physiology of these bacteria and their roles in ecology, host health, and natural product production requires their cultivation in the laboratory. Recent advances in growing these species include coculture with other bacteria, recreating the environment in the laboratory, and combining these approaches with microcultivation technology to increase throughput and access rare species. These studies are unraveling the molecular mechanisms of unculturability and are identifying growth factors that promote the growth of previously unculturable organisms. This minireview summarizes the recent discoveries in this area and discusses the potential future of the field. PMID:22661685

  12. Nonlinear growing neutrino cosmology

    NASA Astrophysics Data System (ADS)

    Ayaita, Youness; Baldi, Marco; Führer, Florian; Puchwein, Ewald; Wetterich, Christof

    2016-03-01

    The energy scale of dark energy, ˜2 ×10-3 eV , is a long way off compared to all known fundamental scales—except for the neutrino masses. If dark energy is dynamical and couples to neutrinos, this is no longer a coincidence. The time at which dark energy starts to behave as an effective cosmological constant can be linked to the time at which the cosmic neutrinos become nonrelativistic. This naturally places the onset of the Universe's accelerated expansion in recent cosmic history, addressing the why-now problem of dark energy. We show that these mechanisms indeed work in the growing neutrino quintessence model—even if the fully nonlinear structure formation and backreaction are taken into account, which were previously suspected of spoiling the cosmological evolution. The attractive force between neutrinos arising from their coupling to dark energy grows as large as 106 times the gravitational strength. This induces very rapid dynamics of neutrino fluctuations which are nonlinear at redshift z ≈2 . Nevertheless, a nonlinear stabilization phenomenon ensures only mildly nonlinear oscillating neutrino overdensities with a large-scale gravitational potential substantially smaller than that of cold dark matter perturbations. Depending on model parameters, the signals of large-scale neutrino lumps may render the cosmic neutrino background observable.

  13. A "TEST OF CONCEPT" COMPARISON OF AERODYNAMIC AND MECHANICAL RESUSPENSION MECHANISMS FOR PARTICLES DEPOSITED ON FIELD RYE GRASS (SECALE CERCELE). PART I. RELATIVE PARTICLE FLUX RATES

    EPA Science Inventory

    Resuspension of uniform latex micro spheres deposited on a single seed pod of field rye grass stalk and head was investigated experimentally in a wind tunnel. The experiment was designed to distinguish aerodynamic (viscous and turbulent) mechanisms from mechanical resuspension re...

  14. Mechanism of fault friction variations associated with rolling of non-spherical particles

    NASA Astrophysics Data System (ADS)

    Dyskin, Arcady; Pasternak, Elena

    2013-04-01

    Friction resisting the fault sliding is known to be rate and path-dependent, which is often related to the movement of the gouge particles. This movement includes particle rotation which can be modelled either using the Cosserat-type models or by direct computer simulation using a discrete element method. These models are however based on the notion that the gouge particles are spherical (circular in 2D) tacitly assuming that the real non-spherical shapes of the particles create quantities effects, which can be accounted for by introducing proper correction factors. We show that non-spherical particles behave qualitatively different. This is a result of the fact that the normal force applied to the non-spherical particle can create a moment whose resistance to the particle rolling changes with the angle - a phenomenon not possible in a spherical (circular) particle due to symmetry. If rolling of a particle is caused by macroscopic shear stress, the normal stress will resist or assist the rolling depending on the angle. As a result the effective friction coefficient associated with a single particle can be reduced to zero in the process of its rolling and then restore its initial value. This leads to the oscillatory behaviour of the friction coefficient as a function of displacement. When sliding involves the rolling of (very) many particles the random variations in their sizes and initial positions cause the friction coefficient to oscillate with decreasing amplitude; the characteristic displacement of this decrease can be an order of magnitude greater than the average particle size. If the gouge layer is sufficiently thick, the friction variations can be associated with rotating clusters of particles. The size of the clusters exceeds the particle size by a factor of the order of the ratio of the effective modulus of the particulate material to the acting shear stress. Thus the clusters may be significantly larger than the original particles and hence the

  15. Understanding the mechanisms of sickle cell disease by simulations with a discrete particle model

    NASA Astrophysics Data System (ADS)

    Hui, Katrina; Lin, Guang; Pan, Wenxiao

    2013-01-01

    Sickle cell disease (SCD) is an inherited blood disorder characterized by rigid, sickle-shaped red blood cells (RBCs). Because of their rigidity and shape, sickle cells can get stuck in smaller blood vessels, causing blockages and depriving oxygen to tissues. This study develops and applies mathematical models to better understand the mechanism of SCD. Two-dimensional models of RBCs and blood vessels have been constructed by representing them as discrete particles interacting with different forces. The nonlinear, elastic property of healthy RBCs could be adequately reproduced using a cosine angle bending force and a worm-like chain spring force. With the ability to deform, RBCs can squeeze through narrow blood vessels. In modeling sickle cells as rigid bodies and applying repelling and friction forces from the blood vessel, this study shows that geometrical factors (dimensions of the sickle cell and blood vessels) as well as rigidity and adhesiveness of the sickle cell all play an important role in determining how, and if, sickle cells become trapped within narrow blood capillaries. With lack of data to validate the model, this study primarily provides a sensitivity analysis of factors influencing sickle cell occlusion and identified critical data to support future modeling.

  16. Mapping dynamic mechanical remodeling in 3D tumor models via particle tracking microrheology

    NASA Astrophysics Data System (ADS)

    Jones, Dustin P.; Hanna, William; Celli, Jonathan P.

    2015-03-01

    Particle tracking microrheology (PTM) has recently been employed as a non-destructive way to longitudinally track physical changes in 3D pancreatic tumor co-culture models concomitant with tumor growth and invasion into the extracellular matrix (ECM). While the primary goal of PTM is to quantify local viscoelasticity via the Generalized Stokes-Einstein Relation (GSER), a more simplified way of describing local tissue mechanics lies in the tabulation and subsequent visualization of the spread of probe displacements in a given field of view. Proper analysis of this largely untapped byproduct of standard PTM has the potential to yield valuable insight into the structure and integrity of the ECM. Here, we use clustering algorithms in R to analyze the trajectories of probes in 3D pancreatic tumor/fibroblast co-culture models in an attempt to differentiate between probes that are effectively constrained by the ECM and/or contractile traction forces, and those that exhibit uninhibited mobility in local water-filled pores. We also discuss the potential pitfalls of this method. Accurately and reproducibly quantifying the boundary between these two categories of probe behavior could result in an effective method for measuring the average pore size in a given region of ECM. Such a tool could prove useful for studying stromal depletion, physical impedance to drug delivery, and degradation due to cellular invasion.

  17. Formation mechanism of chalcogenide nanocrystals confined inside genetically engineered virus-like particles

    NASA Astrophysics Data System (ADS)

    Zhou, Ziyou; Bedwell, Gregory J.; Li, Rui; Prevelige, Peter E.; Gupta, Arunava

    2014-01-01

    Engineered virus-like particles (VLP) are attractive for fabricating nanostructured materials for applications in diverse areas such as catalysis, drug delivery, biomedicine, composites, etc. Basic understanding of the interaction between the inorganic guest and biomolecular host is thus important for the controlled synthesis of inorganic nanoparticles inside VLP and rational assembly of ordered VLP-based hierarchical nanostructures. We have investigated in detail the formation mechanism and growth kinetics of semiconducting nanocrystals confined inside genetically engineered bacteriophage P22 VLP using semiconducting CdS as a prototypical example. The selective nucleation and growth of CdS at the engineered sites is found to be uniform during the early stage, followed by a more stochastic growth process. Furthermore, kinetic studies reveal that the presence of an engineered biotemplate helps in significantly retarding the reaction rate. These findings provide guidance for the controlled synthesis of a wide range of other inorganic materials confined inside VLP, and are of practical importance for the rational design of VLP-based hierarchical nanostuctures.

  18. Particle-in-Cell Modeling of Magnetized Argon Plasma Flow Through Small Mechanical Apertures

    SciTech Connect

    Adam B. Sefkow and Samuel A. Cohen

    2009-04-09

    Motivated by observations of supersonic argon-ion flow generated by linear helicon-heated plasma devices, a three-dimensional particle-in-cell (PIC) code is used to study whether stationary electrostatic layers form near mechanical apertures intersecting the flow of magnetized plasma. By self-consistently evaluating the temporal evolution of the plasma in the vicinity of the aperture, the PIC simulations characterize the roles of the imposed aperture and applied magnetic field on ion acceleration. The PIC model includes ionization of a background neutral-argon population by thermal and superthermal electrons, the latter found upstream of the aperture. Near the aperture, a transition from a collisional to a collisionless regime occurs. Perturbations of density and potential, with mm wavelengths and consistent with ion acoustic waves, propagate axially. An ion acceleration region of length ~ 200-300 λD,e forms at the location of the aperture and is found to be an electrostatic double layer, with axially-separated regions of net positive and negative charge. Reducing the aperture diameter or increasing its length increases the double layer strength.

  19. Observation of plasma instabilities related to dust particle growth mechanisms in electron cyclotron resonance plasmas

    SciTech Connect

    Drenik, A.; CNRS, LAPLACE, 31062 Toulouse Yuryev, P.; Clergereaux, R.; Margot, J.

    2013-10-15

    Instabilities are observed in the self-bias voltage measured on a probe immersed in microwave plasma excited at Electron Cyclotron Resonance (ECR). Observed in the MHz range, they were systematically measured in dust-free or dusty plasmas (obtained for different conditions of applied microwave powers and acetylene flow rates). Two characteristic frequencies, well described as lower hybrid oscillations, can be defined. The first one, in the 60–70 MHz range, appears as a sharp peak in the frequency spectra and is observed in every case. Attributed to ions, its position shift observed with the output power highlights that nucleation process takes place in the dusty plasma. Attributed to lower hybrid oscillation of powders, the second broad peak in the 10–20 MHz range leads to the characterization of dust particles growth mechanisms: in the same way as in capacitively coupled plasmas, accumulation of nucleus confined near the probe in the magnetic field followed by aggregation takes place. Then, the measure of electrical instabilities on the self-bias voltage allows characterizing the discharge as well as the chemical processes that take place in the magnetic field region and their kinetics.

  20. Interaction mechanism of in-situ nano-TiN-AlN particles and solid/liquid interface during solidification.

    PubMed

    Cui, Chunxiang; Li, Yanchun; Shen, Yutian; Sun, Jibing; Wang, Ru

    2003-10-01

    This paper deals with the interaction mechanism between in situ nanometer-grade TiN-AlN particles and the solid/liquid (S/L) interface during the solidification of an in situ TiN-AlN/Al composite. According to the setting of a force balance for the particles in front of the S/L interface during solidification, F = F(buoyant) + F(repulsive) + F(viscous). We obtained the relationship between the critical cooling velocity of the liquid composite, Vr, and the size of the ceramic particle, rp. By this relationship formula, we can know that the S/L interface engulfs particles or pushes them to the crystal grain boundary during the solidification of a TiN-AlN/Al composite. It is found that Vr is proportional to the radius of ceramic particles by transmission electron microscope (TEM) observation. The TEM test indicates that the smaller the particle is, the more easily the S/L interface engulfs particles. PMID:14733152

  1. RELATIONSHIP OF FORAGE FIBER CONTENT AND MECHANICAL STRENGTH TO PARTICLE SIZE REDUCTION DURING INGESTIVE MASTICATION BY STEERS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Forage fiber content and mechanical toughness have been proposed as factors that limit particle size reduction and feed intake of ruminants. Three coarsely chopped forages were available ad lib to six mature rumen- fistulated steers. The oaten and mature alfalfa hays were similar in NDF concentratio...

  2. Consequences of Growing Up Poor.

    ERIC Educational Resources Information Center

    Duncan, Greg J., Ed.; Brooks-Gunn, Jeanne, Ed.

    The consequences and correlates of growing up poor as well as the mechanisms through which poverty influences children are explored. This book is organized with a primary focus on research findings and a secondary concern with policy implications. The chapters are: (1) "Poor Families, Poor Outcomes: The Well-Being of Children and Youth" (Jeanne…

  3. Photoluminescence mechanism model for oxidized porous silicon and nanoscale-silicon-particle-embedded silicon oxide

    NASA Astrophysics Data System (ADS)

    Qin, G. G.; Li, Y. J.

    2003-08-01

    There is much debate about the photoluminescence (PL) mechanisms of the nanoscale Si/Si oxide systems containing oxidized porous silicon and a nanoscale-Si-particle (NSP)—embedded Si oxide deposited by chemical vapor deposition, sputtering, or Si-ion implanting into Si oxide. In this paper, we suggest that two competitive processes, namely, the quantum confinement (QC) process and the quantum confinement-luminescence center (QCLC) process, take place in the PL. The photoexcitation occurs in the NSPs for both of the processes, while the photoemission occurs either in the NSPs for the QC process or in the luminescence centers (LCs) in Si oxide adjacent to the NSPs for the QCLC process. The rates of the two processes are compared quantitatively. Which process plays the major role in PL is determined by the capture cross section, the luminescence efficiency, and the density of the LCs, and the sizes of the NSPs. For a nanoscale Si/Si oxide system with the LCs having certain capture cross-section and luminescence efficiency, the higher the LC density and the larger the sizes of NSPs, the more beneficial for the QCLC process to surpass the QC process, and vice versa. For certain LC parameters, there is a critical most probable size for the NSPs. When the most probable size of the NSPs is larger than the critical one, the QCLC process dominates the PL, and when the most probable size of the NSPs is smaller than the critical one, the QC process dominates the PL. When the most probable size of the NSPs is close to the critical one, both the QC and QCLC processes should be taken into account. We have used this model to discuss PL experimental results reported for some nanoscale Si/Si oxide systems.

  4. Self-consistent particle-in-cell simulations of fundamental and harmonic plasma radio emission mechanisms

    NASA Astrophysics Data System (ADS)

    Thurgood, J. O.; Tsiklauri, D.

    2015-12-01

    Aims: The simulation of three-wave interaction based plasma emission, thought to be the underlying mechanism for Type III solar radio bursts, is a challenging task requiring fully-kinetic, multi-dimensional models. This paper aims to resolve a contradiction in past attempts, whereby some studies indicate that no such processes occur. Methods: We self-consistently simulate three-wave based plasma emission through all stages by using 2D, fully kinetic, electromagnetic particle-in-cell simulations of relaxing electron beams using the EPOCH2D code. Results: Here we present the results of two simulations; Run 1 (nb/n0 = 0.0057, vb/ Δvb = vb/Ve = 16) and Run 2 (nb/n0 = 0.05, vb/ Δvb = vb/Ve = 8), which we find to permit and prohibit plasma emission respectively. We show that the possibility of plasma emission is contingent upon the frequency of the initial electrostatic waves generated by the bump-in-tail instability, and that these waves may be prohibited from participating in the necessary three-wave interactions due to frequency conservation requirements. In resolving this apparent contradiction through a comprehensive analysis, in this paper we present the first self-consistent demonstration of fundamental and harmonic plasma emission from a single-beam system via fully kinetic numerical simulation. We caution against simulating astrophysical radio bursts using unrealistically dense beams (a common approach which reduces run time), as the resulting non-Langmuir characteristics of the initial wave modes significantly suppresses emission. Comparison of our results also indicates that, contrary to the suggestions of previous authors, an alternative plasma emission mechanism based on two counter-propagating beams is unnecessary in an astrophysical context. Finally, we also consider the action of the Weibel instability which generates an electromagnetic beam mode. As this provides a stronger contribution to electromagnetic energy than the emission, we stress that

  5. Nano-particle precipitation in mechanically alloyed and annealed precursor powders of legacy PM2000 ODS alloy

    NASA Astrophysics Data System (ADS)

    Dawson, Karl; Haigh, Sarah J.; Tatlock, Gordon J.; Jones, Andy R.

    2015-09-01

    The early stages of nano-particulate formation in mechanically alloyed and annealed, precursor powders used to manufacture the legacy commercial oxide dispersion strengthened alloy PM2000, formerly produced by Plansee GmbH, have been investigated. Powders were analysed in both the as-mechanically-alloyed condition and after annealing over the temperature range 923-1423 K. The nucleation and growth of coherent nano-particles in the partially recovered, fine grained, ferritic matrix of powders annealed at temperatures as low as 923 K has been confirmed. Powders annealed for 1 h at temperatures of 1123 K and 1223 K were partially recrystallised and contained high number densities (NV > 1023 m-3) of coherent 2 nm yttrium-aluminium-oxygen rich nano-particles. The identification of particle free zones in recrystallised grains, adjacent to recrystallising interfaces, plus the identical orientation relationships between nano-particles and the matrices in both unrecrystallised and recrystallised grains, indicates that the Y-Al-O nano-particles, first formed in fine grained regions, are dissolved during recrystallisation and re-precipitated subsequently in recrystallised grains.

  6. MECHANISMS BY WHICH ULTRAFINE, FINE, AND COARSE PARTICLES CAUSE ADVERSE HEALTH EFFECTS

    EPA Science Inventory

    A small number of recent studies suggest that different size particles may cause different health effects. There are clearly differences in the chemical makeup of coarse, fine, and ultrafine particles, and this different chemistry may well drive different health responses. The ...

  7. The mechanism of particles transport induced by electrostatic perturbation in tokamak

    SciTech Connect

    Feng, Zhichen; Qiu, Zhiyong; Sheng, Zhengmao

    2013-12-15

    Particle transport in tokamak devices due to wave-particle resonance induced diffusion is studied. The diffusion coefficient is derived both analytically using quasilinear theory, and numerically using a test particle code, and the obtained diffusion coefficient agrees with each other in its validity regime. Dependence of the diffusion coefficient on turbulence intensity, turbulence radial mode structures, and particle energy is investigated. It is found that the diffusion coefficient is proportional to the turbulence intensity, and the diffusion is maximized for E{sub t}≃T{sub i}, and k{sub r}Δ{sub 0}≃1. Here, E{sub t} is the test particle energy, T{sub i} is the thermal ion temperature, Δ{sub 0} is the distance between neighboring mode rational surfaces, and 1/k{sub r} is the half width of the fine radial mode structure on each rational surface.

  8. Detailed Structural and Mechanical Response of Wet Foam to the Settling Particle.

    PubMed

    Jing, Zefeng; Wang, Shuzhong; Wang, Zhiguo

    2016-03-15

    Liquid foam, as a complex fluid, provides an observable prototype for studying a discrete fluid system. In this work, a numerical study on the settling behavior of a round particle in wet polydisperse foam has been conducted on the bubble scale. The local and nonuniform distribution of bubble pressure, as well as the localized plastic events, is presented. It shows a foam region of higher pressure in front of the settling particle due to the extrusion deformation of the bubbles applied by the particle. Additionally, the forces exerted on the particle by the disordered wet foam are measured during the sedimentation. It exhibits in particular a power-law dependence of the drag force caused by the bubble as a function of the foam quality. Moreover, sedimentation experiments are demonstrated to verify this power-law relation. The evolution of the components of drag force is demonstrated when a plastic event occurs in front of the settling particle. The result shows that both the contributions of the pulling force of foam films and the bubble pressure to the drag force decrease in that case. Likewise, the variation of both these contributions to the drag force is illustrated as well when a bubble in the wake detaches from the particle. These results assist in understanding the mesoscopic response of wet foam to a settling particle. PMID:26898137

  9. The mechanisms of fine particle generation and electrification during Mount St. Helens volcanic eruption

    NASA Technical Reports Server (NTRS)

    Cheng, R. J.

    1982-01-01

    Microscopical investigation of volcanic ash collected from ground stations during Mount St. Helens eruptions reveal a distinctive bimodel size distribution with high concentrations of particle ranges at (1) 200-100 microns and (2) 20-0.1 microns. Close examination of individual particles shows that most larger ones are solidified magma particles of porous pumice with numerous gas bubbles in the interior and the smaller ones are all glassy fragments without any detectable gas bubbles. Elemental analysis demonstrates that the fine fragments all have a composition similar to that of the larger pumice particles. Laboratory experiments suggest that the formation of the fine fragments is by bursting of glassy bubbles from a partially solidified surface of a crystallizing molten magma particle. The production of gas bubbles is due to the release of absorbed gases in molten magma particles when solubility decreases during phase transition. Diffusion cloud chamber experiments strongly indicate that sub-micron volcanic fragments are highly hygroscopic and extremely active as cloud condensation nuclei. Ice crystals also are evidently formed on those fragments in a supercooled (-20 C) cloud chamber. It has been reported that charge generation from ocean volcanic eruptions is due to contact of molten lava with sea water. This seems to be insufficient to explain the observed rapid and intense lightning activities over Mount St. Helens eruptions. Therefore, a hypothesis is presented here that highly electrically charged fine solid fragments are ejected by bursting of gas bubbles from the surface of a crystallizing molten magma particles.

  10. Quantum mechanical tunneling of composite particle systems: Linkage to sub-barrier nuclear reactions

    SciTech Connect

    Shotter, A. C.; Shotter, M. D.

    2011-05-15

    A variety of physical phenomena have at their foundation the quantum tunneling of particles through potential barriers. Many of these phenomena can be associated with the tunneling of single inert particles. The tunneling of composite systems is more complex than for single particles due to the coupling of the tunneling coordinate with the internal degrees of freedom of the tunneling system. Reported here are the results of a study for the tunneling of a two-component projectile incident on a potential energy system which differs for the two components. A specific linkage is made to sub-Coulomb nuclear reactions.

  11. Nonequilibrium statistical mechanics of the heat bath for two Brownian particles.

    PubMed

    De Bacco, Caterina; Baldovin, Fulvio; Orlandini, Enzo; Sekimoto, Ken

    2014-05-01

    We propose a new look at the heat bath for two Brownian particles, in which the heat bath as a "system" is both perturbed and sensed by the Brownian particles. Nonlocal thermal fluctuations give rise to bath-mediated static forces between the particles. Based on the general sum rule of the linear response theory, we derive an explicit relation linking these forces to the friction kernel describing the particles' dynamics. The relation is analytically confirmed in the case of two solvable models and could be experimentally challenged. Our results point out that the inclusion of the environment as a part of the whole system is important for micron- or nanoscale physics. PMID:24856686

  12. MECHANISMS OF NANODIAMOND PARTICLE INDUCED IL-8 EXPRESSION IN HUMAN AIRWAY EPITHELIAL CELLS

    EPA Science Inventory

    Nanodiamond particles (NDP) prepared by detonation under confined conditions have a number of industrial and analytical applications. Previous in vitro studies have reported NDP to be biologically inert with negligible cytotoxicity, implying that they are potentially suitable for...

  13. Nanodiamond particles induce IL-8 expression through a transcript stabilization mechanism in human airway epithelial cells

    EPA Science Inventory

    Nanodiamond particles (NDP) prepared by detonational processes have a number of industrial and analytical applications. Previous in vitro studies have reported NDP to be biologically inert with negligible cytotoxicity, implying that they are potentially suitable for biomedical ap...

  14. Charging Mechanism for Polymer Particles in Nonpolar Surfactant Solutions: Influence of Polymer Type and Surface Functionality.

    PubMed

    Lee, Joohyung; Zhou, Zhang-Lin; Behrens, Sven Holger

    2016-05-17

    Surface charging phenomena in nonpolar dispersions are exploited in a wide range of industrial applications, but their mechanistic understanding lags far behind. We investigate the surface charging of a variety of polymer particles with different surface functionality in alkane solutions of a custom-synthesized and purified polyisobutylene succinimide (PIBS) polyamine surfactant and a related commercial surfactant mixture commonly used to control particle charge. We find that the observed electrophoretic particle mobility cannot be explained exclusively by donor-acceptor interactions between surface functional groups and surfactant polar moieties. Our results instead suggest an interplay of multiple charging pathways, which likely include the competitive adsorption of ions generated among inverse micelles in the solution bulk. We discuss possible factors affecting the competitive adsorption of micellar ions, such as the chemical nature of the particle bulk material and the size asymmetry between inverse micelles of opposite charge. PMID:27135950

  15. DIESEL EXHAUST PARTICLES INDUCE ABERRANT ALVEOLAR EPITHELIAL DIRECTED CELL MOVEMENT BY DISRUPTION OF POLARITY MECHANISMS

    EPA Science Inventory

    Disruption of the respiratory epithelium contributes to the progression of a variety of respiratory diseases that are aggravated by exposure to air pollutants, specifically traffic-based pollutants such as diesel exhaust particles (DEP). Recognizing that lung repair following inj...

  16. Phase-space quantum mechanics study of two identical particles in an external oscillatory potential

    NASA Technical Reports Server (NTRS)

    Nieto, Luis M.; Gadella, Manuel

    1993-01-01

    This simple example is used to show how the formalism of Moyal works when it is applied to systems of identical particles. The symmetric and antisymmetric Moyal propagators are evaluated for this case; from them, the correct energy levels of energy are obtained, as well as the Wigner functions for the symmetric and antisymmetric states of the two identical particle system. Finally, the solution of the Bloch equation is straightforwardly obtained from the expressions of the Moyal propagators.

  17. Jetting mechanisms of particles under shock wave acceleration: the role of force chains

    NASA Astrophysics Data System (ADS)

    Xue, Kun

    The particle jetting phenomenon is widely observed in many problems associated with blast/shock dispersal of granular materials, although its origin is still unidentified. We carried out discrete element simulations of the shock dispersal of two-dimensional particle rings in order to extract the particle-scale evolution of the shocked rings in terms of the velocity profile and the force-chain networks. Initially the force chains distribute uniformly along the circumference, but after several dozens of microseconds, they disseminate into a handful of blobs which mainly consist of long linear or branched chains align with the radial direction. These blobs are separated by zones featuring relatively sparse force chains which take forms of short chains or small compact polygons. The radial-like force chains in blobs serves as the channels transferring the momentum from the inner layers to outer layers, resulting in fast moving blocks without appreciable velocity differences. By contrast, the shock energy in the zones with short force chains is largely dissipated among the particle collision. Thus particles in these zones lag behind those bound by strong force chains. The resultant heterogeneous velocity profile acts as the precursor of the ensuing particle jetting.

  18. Synthesis and new structure shaping mechanism of silica particles formed at high pH

    SciTech Connect

    Zhang, Henan; Zhao, Yu; Akins, Daniel L.

    2012-10-15

    For the sol-gel synthesis of silica particles under high pH catalytic conditions (pH>12) in water/ethanol solvent, we have deduced that the competing dynamics of chemical etching and sol-gel process can explain the types of silica particles formed and their morphologies. We have demonstrated that emulsion droplets that are generated by adding tetraethyl orthosilicate (TEOS) to a water-ethanol solution serve as soft templates for hollow spherical silica (1-2 {mu}m). And if the emulsion is converted by the sol-gel process, one finds that suspended solid silica spheres of diameter of {approx}900 nm are formed. Moreover, several other factors are found to play fundamental roles in determining the final morphologies of silica particles, such as by variation of the pH (in our case, using OH{sup -}) to a level where condensation dominates; by changing the volume ratios of water/ethanol; and using an emulsifier (specifically, CTAB) - Graphical abstract: 'Local chemical etching' and sol-gel process have been proposed to interpret the control of morphologies of silica particles through varying initial pHs in syntheses. Highlights: Black-Right-Pointing-Pointer Different initial pHs in our syntheses provides morphological control of silica particles. Black-Right-Pointing-Pointer 'Local chemical etching' and sol-gel process describes the formation of silica spheres. Black-Right-Pointing-Pointer The formation of emulsions generates hollow silica particles.

  19. Development of an ash particle deposition model considering build-up and removal mechanisms

    SciTech Connect

    Kjell Strandstroem; Christian Muellera; Mikko Hupa

    2007-12-15

    Slagging and fouling on heat exchanger surfaces in power boilers fired with fossil fuels and fuel mixtures has a significant influence on boiler efficiency and availability. Mathematical modelling has long been considered a suitable method to assist boiler operators to determine optimized operating conditions for an existing furnace. The ultimate goal in ash deposition prediction is hereby the determination of the total amount of material deposited and hence the determination of the total reduction in efficiency. Depending on the fuels fired the total deposited mass is a combination of ash particle deposition and ash particle erosion due to non-sticky particles. The novel ash particle deposition model presented in this work considers deposition of sticky ash particles, cleansing of deposit by non-sticky sand particles and sticking of sand due to contact with sticky ash. The steady-state modelling results for the total amount of ash deposited on the deposition probe of an entrained flow reactor presented in this work agree well with the experimental data. Only at very high fractions of sand added as non-sticky material, a significant influence of the sand on the overall mass deposited was found. Since the model considers sticking of non-sticking sand due to contact with sticky ash, the fraction of sand deposited on the probe was especially studied. Using a correction factor to consider the influence of operating time on the steady-state simulations led to good agreement between simulations and experimental data. 12 refs., 10 figs.

  20. Effect of crumb-rubber particle size on mechanical response of polyurethane foam composites

    NASA Astrophysics Data System (ADS)

    Sanjay, Omer Sheik

    The compression properties of foam are governed by by three factors: i) cell edge bending ii) compression of cell fluid iii) membrane stresses in the cell faces. The effect of reinforcement, granular form of scrap tire rubber on contribution of each of these effects along with the physical properties of polyurethane foam is investigated. It is seen that the addition of crumb-rubber hinders the formation of cell membranes during the foaming process. Four different sizes of particles were chosen to closely study the effect of particle size on the physical properties of the foam composite. There is a definite pattern seen in each of the physical property of the composite with change in the particle size. Addition of crumb-rubber decreases the compressive strength but in turn increases the elastic modulus of the composite. The rubber particles act as the sites for stress concentration and hence the inclusion of rubber particles induces the capability to transfer the axial load laterally along the surface of the foam. Also, the filler material induces porosity into the foam, which is seen in the SEM images, and hence the addition of rubber particles induces brittleness, which makes the foam composites extensively applicable for structural application in sandwich components. The lightweight composite therefore is a potential substitute to the heavier metal foams and honeycombs as a protective layer.

  1. Growing for different ends.

    PubMed

    Catts, Oron; Zurr, Ionat

    2014-11-01

    Tissue engineering and regenerative biology are usually discussed in relation to biomedical research and applications. However, hand in hand with developments of this field in the biomedical context, other approaches and uses for non-medical ends have been explored. There is a growing interest in exploring spin off tissue engineering and regenerative biology technologies in areas such as consumer products, art and design. This paper outlines developments regarding in vitro meat and leather, actuators and bio-mechanic interfaces, speculative design and contemporary artistic practices. The authors draw on their extensive experience of using tissue engineering for non-medical ends to speculate about what lead to these applications and their possible future development and uses. Avoiding utopian and dystopian postures and using the notion of the contestable, this paper also mentions some philosophical and ethical consideration stemming from the use of non-medical approaches to tissue constructs. This article is part of a directed issue entitled: Regenerative Medicine: the challenge of translation. PMID:25286303

  2. Heat generation in an elastic binder system with embedded discrete energetic particles due to high-frequency, periodic mechanical excitation

    NASA Astrophysics Data System (ADS)

    Mares, J. O.; Miller, J. K.; Gunduz, I. E.; Rhoads, J. F.; Son, S. F.

    2014-11-01

    High-frequency mechanical excitation can induce heating within energetic materials and may lead to advances in explosives detection and defeat. In order to examine the nature of this mechanically induced heating, samples of an elastic binder (Sylgard 184) were embedded with inert and energetic particles placed in a fixed spatial pattern and were subsequently excited with an ultrasonic transducer at discrete frequencies from 100 kHz to 20 MHz. The temperature and velocity responses of the sample surfaces suggest that heating due to frictional effects occurred near the particles at excitation frequencies near the transducer resonance of 215 kHz. An analytical solution involving a heat point source was used to estimate heating rates and temperatures at the particle locations in this frequency region. Heating located near the sample surface at frequencies near and above 1 MHz was attributed to viscoelastic effects related to the surface motion of the samples. At elevated excitation parameters near the transducer resonance frequency, embedded particles of ammonium perchlorate and cyclotetramethylene-tetranitramine were driven to chemical decomposition.

  3. Effect of Particle Size on the Mechanical Properties of Semi-Solid, Powder-Rolled AA7050 Strips

    NASA Astrophysics Data System (ADS)

    Luo, Xia; Liu, Yunzhong

    2016-07-01

    The AA7050 alloy strips can be successfully prepared by semi-solid powder rolling. The effect and factors of particle size on the microstructure, relative density, and mechanical properties were discussed. The results show that coarse starting powders require less liquid to achieve high relative density, and the formed strips have lower elongation compared with that prepared with the fine starting powders. The strength is more related to defects, whereas elongation partially depends on the grain size. Additionally, the fracture mechanism of strips prepared with fine powders is the ductile fracture because many dimples are observed. For relative density, when the initial liquid fraction is lower than 10%, the difference of deformation degree is the main factor. When the liquid fraction is higher than 10-20%, premature solidification and more particle interfaces are the two main factors.

  4. Effects of diesel exhaust particles on microRNA-21 in human bronchial epithelial cells and potential carcinogenic mechanisms.

    PubMed

    Zhou, Fang; Li, Suli; Jia, Wenliang; Lv, Gang; Song, Chonglin; Kang, Chunsheng; Zhang, Qingyu

    2015-08-01

    Air pollution plays a role in cancer risk, particularly in lung cancer, which is the leading cause of cancer-related mortality worldwide. Diesel exhaust particles (DEPs), a component of diesel exhaust products, is a complex mixture of particle compounds that include a large number of known and suspected human carcinogens. Historically, lung cancer, which is associated with DEPs, has been the focus of attention as a health risk in human and animal studies. However, the mechanism by which DEPs cause lung cancer remains unclear. The present study reports that DEPs increased miR-21 expression and then activated the PTEN/PI3K/AKT pathway in human bronchial epithelial (HBE) cells, which may serve as an important carcinogenic mechanism. However, the data revealed that short-term exposure to a high DEP concentration did not cause evident cell carcinogenesis in HBE cells. PMID:25901472

  5. Molecular Dynamics Study on the Particle Dispersion Mechanism of Polyamide-imide/Silica Nano-composite Materials

    NASA Astrophysics Data System (ADS)

    Kikuchi, Hideyuki; Iwasaki, Tomio; Hanawa, Hidehito; Honda, Yuki

    We studied the particle dispersion mechanism of polyamide-imide/silica nano-composite material by using molecular-dynamics simulation technique based on Newtonian dynamics and quantum mechanics. In simulations, adhesive fracture energies at the interfaces between silica and solvents were calculated, and Brownian motions of silica particles were simulated to clarify dispersion properties. The simulation results showed that the colloidal state of silica was maintained by covering the silica surface with a new low hygroscopicity solvent and that the chemical structure of polymer contributed to the dispersion of silica. It is found that the results obtained from molecular dynamics agree well with those obtained by experiments, and that molecular-dynamics simulation technique will become very useful for the development of nano-composite materials in the future.

  6. Microstructure and Mechanical Properties of Cr-SiC Particles-Reinforced Fe-Based Alloy Coating

    NASA Astrophysics Data System (ADS)

    Wang, Fu-cheng; Du, Xiao-dong; Zhan, Ma-ji; Lang, Jing-wei; Zhou, Dan; Liu, Guang-fu; Shen, Jian

    2015-12-01

    In this study, SiC particles were first coated with Cr to form a layer that can protect the SiC particles from dissolution in the molten pool. Then, the Cr-SiC powder was injected into the tail of molten pool during plasma-transferred arc welding process (PTAW), where the temperature was relatively low, to prepare Cr-SiC particles reinforced Fe-based alloy coating. The microstructure and phase composition of the powder and surface coatings were analyzed, and the element distribution and hardness at the interfacial region were also evaluated. The protective layer consists of Cr3Si, Cr7C3, and Cr23C6, which play an important role in the microstructure and mechanical properties. The protective layer is dissolved in the molten pool forming a flocculent region and a transition region between the SiC particles and the matrix. The tribological performance of the coating was also assessed using a ring-block sliding wear tester with GGr15 grinding ring under 490 and 980 N load. Cr-SiC particles-reinforced coating has a lower wear rate than the unreinforced coating.

  7. The Effect of SiC Particle Addition During FSW on Microstructure and Mechanical Properties of AZ31 Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Abbasi, M.; Abdollahzadeh, A.; Bagheri, B.; Omidvar, H.

    2015-12-01

    Welding and joining of magnesium alloys exert a profound effect on magnesium application expansion, especially in ground and air transportations where large-size, complex components are required. Due to specific physical properties of magnesium, its welding requires great control. In general, the solid-state nature of friction stir welding (FSW) process has been found to produce a low concentration of defects. In the current research, specimens from AZ31 magnesium alloy were welded together using the friction stir process with previously inserted SiC powder particles in the nugget zone. In other words, during the FSW process, the pre-placed SiC particles were stirred throughout the nugget zone of the weld. The results indicated that proper values of rotation and translation speeds led to good appearance of weld zone and suitable distribution of SiC particles producing increased weld strength. The comparison of the microstructures and mechanical properties of FS-welded AZ31 with those of FS-welded one using pre-placed SiC particles showed that the addition of SiC particles decreased the grain size and increased the strength and the formability index.

  8. Mechanism of Cluster DNA Damage Repair in Response to High-Atomic Number and Energy Particles Radiation

    PubMed Central

    Asaithamby, Aroumougame; Chen, David J.

    2012-01-01

    Low-linear energy transfer (LET) radiation (i.e., γ- and X-rays) induces DNA double-strand breaks (DSBs) that are rapidly repaired (rejoined). In contrast, DNA damage induced by the dense ionizing track of high-atomic number and energy (HZE) particles are slowly repaired or are irreparable. These unrepaired and/or misrepaired DNA lesions may contribute to the observed higher relative biological effectiveness for cell killing, chromosomal aberrations, mutagenesis, and carcinogenesis in HZE particle irradiated cells compared to those treated with low-LET radiation. The types of DNA lesions induced by HZE particles have been characterized in vitro and usually consist of two or more closely spaced strand breaks, abasic sites, or oxidized bases on opposing strands. It is unclear why these lesions are difficult to repair. In this review, we highlight the potential of a new technology allowing direct visualization of different types of DNA lesions in human cells and document the emerging significance of live-cell imaging for elucidation of the spatio-temporal characterization of complex DNA damage. We focus on the recent insights into the molecular pathways that participate in the repair of HZE particle-induced DSBs. We also discuss recent advances in our understanding of how different end-processing nucleases aid in repair of DSBs with complicated ends generated by HZE particles. Understanding the mechanism underlying the repair of DNA damage induced by HZE particles will have important implications for estimating the risks to human health associated with HZE particle exposure. PMID:21126526

  9. Physical and mechanical properties of LoVAR: a new lightweight particle-reinforced Fe-36Ni alloy

    NASA Astrophysics Data System (ADS)

    Stephenson, Timothy; Tricker, David; Tarrant, Andrew; Michel, Robert; Clune, Jason

    2015-09-01

    Fe-36Ni is an alloy of choice for low thermal expansion coefficient (CTE) for optical, instrument and electrical applications in particular where dimensional stability is critical. This paper outlines the development of a particle-reinforced Fe-36Ni alloy that offers reduced density and lower CTE compared to the matrix alloy. A summary of processing capability will be given relating the composition and microstructure to mechanical and physical properties.

  10. Physical and Mechanical Properties of LoVAR: A New Lightweight Particle-Reinforced Fe-36Ni Alloy

    NASA Technical Reports Server (NTRS)

    Stephenson, Timothy; Tricker, David; Tarrant, Andrew; Michel, Robert; Clune, Jason

    2015-01-01

    Fe-36Ni is an alloy of choice for low thermal expansion coefficient (CTE) for optical, instrument and electrical applications in particular where dimensional stability is critical. This paper outlines the development of a particle-reinforced Fe-36Ni alloy that offers reduced density and lower CTE compared to the matrix alloy. A summary of processing capability will be given relating the composition and microstructure to mechanical and physical properties.

  11. Effects of Compressive Force, Particle Size and Moisture Content on Mechanical Properties of Biomass Grinds

    SciTech Connect

    Mani, Sudhagar; Tabil, Lope Jr.; Sokhansanj, Shahabaddine

    2006-03-01

    Chemical composition, moisture content, bulk and particle densities, and geometric mean particle size were determined to characterize grinds from wheat and barley straws, corn stover and switchgrass. The biomass grinds were compressed for five levels of compressive forces (1000, 2000, 3000, 4000, 4400 N) and three levels of particle sizes (3.2, 1.6 and 0.8 mm) at two levels of moisture contents (12% and 15% (wb) to establish the compression and relaxation data. Corn stover grind produced the highest compact density at low pressure during compression. Compressive force, particle size and moisture content of grinds significantly affected the compact density of barley straw, corn stover and switchgrass grinds. However, different particle sizes of wheat straw grind did not produce any significant difference on compact density. Barley straw grind had the highest asymptotic modulus among all other biomass grinds indicating that compact from barley straw grind were more rigid than those of other compacts. Asymptotic modulus increased with an increase in maximum compressive pressure. The trend of increase in asymptotic modulus (EA) with the maximum compressive pressure ( 0) was fitted to a second order polynomial equation. Keywords: Biomass grinds, chemical composition, compact density and asymptotic modulus

  12. Revealing deposition mechanism of colloid particles on human serum albumin monolayers.

    PubMed

    Nattich-Rak, Małgorzata; Adamczyk, Zbigniew; Kujda, Marta

    2016-01-01

    Colloid particle deposition was applied in order to characterize human serum albumin (HSA) monolayers on mica adsorbed under diffusion transport at pH 3.5. The surface concentration of HSA was determined by a direct AFM imaging of single molecules. The electrokinetic characteristics of the monolayers for various ionic strength were done by in situ streaming potential measurements. In this way the mean-field zeta potential of monolayers was determined. It was shown that the initially negative potential changed its sign for HSA surface concentrations above 2800μm(-2) that was interpreted as overcharging effect. The monolayers were also characterized by the colloid deposition method where negatively charged polystyrene particles, 810nm in diameter were used. The kinetics of particle deposition and their maximum coverage were determined as a function of the HSA monolayer surface concentration. An anomalous deposition of particles on substrates exhibiting a negative zeta potential was observed, which contradicts the mean-field theoretical predictions. This effect was quantitatively interpreted in terms of the random site sequential adsorption model. It was shown that efficient immobilization of particles only occurs at adsorption sites formed by three and more closely adsorbed HSA molecules. These results can be exploited as useful reference data for the analysis of deposition phenomena of bioparticles at protein monolayers that has practical significance for the regulation of the bioadhesive properties of surfaces. PMID:26272241

  13. Growing Pains (For Parents)

    MedlinePlus

    ... Joints affected by more serious diseases are swollen, red, tender, or warm — the joints of kids having growing pains look normal. Although growing pains often strike in late afternoon or early evening before bed, pain can sometimes wake a sleeping child. The ...

  14. An investigation of the microstructure and mechanical properties of electrochemically coated Ag(4)Sn dental alloy particles condensed in vitro

    NASA Astrophysics Data System (ADS)

    Marquez, Jose Antonio

    As part of the ongoing scientific effort to develop a new amalgam-like material without mercury, a team of metallurgists and electrochemists at the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland, announced in 1993 the development of a new Ag-Sn dental alloy system without mercury that sought to replace conventional dental amalgams. They used spherical Ag3Sn and Ag4Sn intermetallic dental alloy particles, commonly used in conventional dental alloys, and coated them with electrodeposited silver with newly-developed electrolytic and immersion techniques. The particles had relatively pure silver coatings that were closely adherent to the intermetalfic cores. These silver-coated particles, due to silver's plasticity at room temperature, were condensed into PlexiglasRTM molds with the aid of an acidic surface activating solution (HBF4) and a mechanical condensing device, producing a metal-matrix composite with Ag3,4Sn filler particles surrounded by a cold-welded silver matrix. Since silver strain hardens rather easily, the layers had to be condensed in less than 0.5 mm increments to obtain a dense structure. Mechanical testing at NIST produced compressive strength values equal to or greater than those of conventional dental amalgams. Because of its potential for eliminating mercury as a constituent in dental amalgam, this material created a stir in dental circles when first developed and conceivably could prove to be a major breakthrough in the field of dental restoratives. To date, the chief impediments to its approval for human clinical applications by the Food and Drug Administration are the potentially-toxic surface activating solution used for oxide reduction, and the high condensation pressures needed for cold welding because of the tendency for silver to strain harden. In this related study, the author, who has practiced general dentistry for 25 years, evaluates some of the mechanical and microstructural properties of these

  15. Three-body collisions as a particle formation mechanism in silver nanoparticle synthesis.

    PubMed

    Lehtinen, Kari E J; Backman, Ulrika; Jokiniemi, Jorma K; Kulmala, Markku

    2004-06-15

    Silver nanoparticles were prepared in a tubular flow reactor using an evaporation-condensation technique. The size distribution of the particles was measured using standard aerosol instruments and electron microscopy. A comparison with results obtained by a discrete population balance model with molecule-by-molecule resolution suggest that the particles probably nucleate kinetically through a dimerization process instead of a thermodynamic pathway over a free energy barrier, as is typically described by classical nucleation theory. Furthermore, the kinetic rate of dimerization seems to be accompanied by a correction term, associated with the requirement of energy and momentum conservation in molecule-molecule collisions. This energy conservation requires the presence of three-body collisions at the very initial step of particle formation. PMID:15144825

  16. The mechanism of polyelectrolyte-assisted retention of TiO2 filler particles during paper formation.

    PubMed

    Gesenhues, Ulrich

    2011-02-17

    The mechanism of the retention of TiO(2) filler particles on cellulose fibers has been under discussion for several decades; the diverse models, and the properties of the components relevant to retention, are critically reviewed in the first part of this study. In addition, two new quantitative models of detachment of polyelectrolyte-bonded colloidal particles from the fiber are also examined; one of these is based on DLVO theory for description of the influence of particle charge and polyelectrolyte amount, and should hold true at low shear rates and high bond strengths. The other model applies Kolmogorov's theory of isotropic turbulence in order to relate the work necessary for particle detachment to the turbulent energy of pulp in paper machines, i.e., under high shear rate and low bond-strength conditions. The second model is based on analysis of fluid dynamics in paper machines, and is formulated here for laboratory tests using the Dynamic Drainage Jar (DDJ). A series of laboratory-prepared TiO(2) fillers covering a range of isoelectric points (ieps) from pH 4.4 to pH 7.5, additionally with poly-(aminoamide)-epichlorohydrin (PAE) and polyethyleneimine (PEI) as retention aids, and commercially milled cellulose, were used in the experimental part of the study. The retention-aid demand of fillers and cellulose for surface neutralization was determined using electrokinetic methods. Filler retention on cellulose was measured in the DDJ for various stirrer speeds and amounts of retention aid, with the amount of filler not exceeding that for a monolayer on the fiber. Without retention aids, neutral filler particles are accordingly completely retained on the negative fiber, whereas negatively charged particles are not. The retention of the latter can, however, be steadily improved by increasing polyelectrolyte concentration. Retention of colloidal particles in paper manufacturing is therefore determined by a delicate balance between H-bridging and van der Waals forces

  17. The classical and quantum mechanics of a particle on a knot

    SciTech Connect

    Sreedhar, V.V.

    2015-08-15

    A free particle is constrained to move on a knot obtained by winding around a putative torus. The classical equations of motion for this system are solved in a closed form. The exact energy eigenspectrum, in the thin torus limit, is obtained by mapping the time-independent Schrödinger equation to the Mathieu equation. In the general case, the eigenvalue problem is described by the Hill equation. Finite-thickness corrections are incorporated perturbatively by truncating the Hill equation. Comparisons and contrasts between this problem and the well-studied problem of a particle on a circle (planar rigid rotor) are performed throughout.

  18. The classical and quantum mechanics of a particle on a knot

    NASA Astrophysics Data System (ADS)

    Sreedhar, V. V.

    2015-08-01

    A free particle is constrained to move on a knot obtained by winding around a putative torus. The classical equations of motion for this system are solved in a closed form. The exact energy eigenspectrum, in the thin torus limit, is obtained by mapping the time-independent Schrödinger equation to the Mathieu equation. In the general case, the eigenvalue problem is described by the Hill equation. Finite-thickness corrections are incorporated perturbatively by truncating the Hill equation. Comparisons and contrasts between this problem and the well-studied problem of a particle on a circle (planar rigid rotor) are performed throughout.

  19. Seepage erosion mechanisms of bank collapse: three-dimensional seepage particle mobilization and undercutting

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seepage flow initiates undercutting, similar to development and headward migration of internal gullies, by liquefaction of soil particles, followed by mass wasting of the bank. Although seepage erosion has three-dimensional characteristics, two-dimensional lysimeters have been used in previous resea...

  20. MECHANISMS OF INORGANIC PARTICLE FORMATION DURING SUSPENSION HEATING OF SIMULATED AQEOUS WASTES

    EPA Science Inventory

    The paper gives results of measurements of metal partitioning between the fine condensation aerosol and the larger particles produced during rapid heating of polydisperse droplet streams of aqueous solutions containing nitrates of Cd, Pb, and Ni in a laboratory scale furnace. rim...

  1. Particle film mechanisms of action that reduce environmental stress in 'Empire' apple

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heat stress is a limiting factor of plant productivity throughout the world, and kaolin-based particle films (PF) have demonstrated that the reflective nature of the resulting plant surface can increase plant productivity primarily by reducing temperature in fruit, leaf, and canopy. The purpose of ...

  2. Progress in Solving the Elusive Ag Transport Mechanism in TRISO Coated Particles: What is new?

    SciTech Connect

    Isabella Van Rooyen

    2014-10-01

    The TRISO particle for HTRs has been developed to an advanced state where the coating withstands internal gas pressures and retains fission products during irradiation and under postulated accidents. However, one exception is Ag that has been found to be released from high quality TRISO coated particles when irradiated and can also during high temperature accident heating tests. Although out- of- pile laboratory tests have never hither to been able to demonstrate a diffusion process of Ag in SiC, effective diffusion coefficients have been derived to successfully reproduce measured Ag-110m releases from irradiated HTR fuel elements, compacts and TRISO particles It was found that silver transport through SiC does not proceed via bulk volume diffusion. Presently grain boundary diffusion that may be irradiation enhanced either by neutron bombardment or by the presence of fission products such as Pd, are being investigated. Recent studies of irradiated AGR-1 TRISO fuel using scanning transmission electron microscopy (STEM), transmission kukuchi diffraction (TKD) patterns and high resolution transmission electron microscopy (HRTEM) have been used to further the understanding of Ag transport through TRISO particles. No silver was observed in SiC grains, but Ag was identified at triple-points and grain boundaries of the SiC layer in the TRISO particle. Cadmium was also found in some of the very same triple junctions, but this could be related to silver behavior as Ag-110m decays to Cd-110. Palladium was identified as the main constituent of micron-sized precipitates present at the SiC grain boundaries and in most SiC grain boundaries and the potential role of Pd in the transport of Ag will be discussed.

  3. Interfacial Microstructure and Enhanced Mechanical Properties of Carbon Fiber Composites Caused by Growing Generation 1-4 Dendritic Poly(amidoamine) on a Fiber Surface.

    PubMed

    Gao, Bo; Zhang, Ruliang; Gao, Fucheng; He, Maoshuai; Wang, Chengguo; Liu, Lei; Zhao, Lifen; Cui, Hongzhi

    2016-08-23

    In an attempt to improve the mechanical properties of carbon fiber composites, propagation of poly(amidoamine) (PAMAM) dendrimers by in situ polymerization on a carbon fiber surface was performed. During polymerization processes, PAMAM was grafted on carbon fiber by repeated Michael addition and amidation reactions. The changes in surface microstructure and the chemical composition of carbon fibers before and after modification were investigated by atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. All the results indicated that PAMAM was successfully grown on the carbon fiber surface. Such propagation could significantly increase the surface roughness and introduce sufficient polar groups onto the carbon fiber surface, enhancing the surface wettability of carbon fiber. The fractured surface of carbon fiber-reinforced composites showed a great enhancement of interfacial adhesion. Compared with those of desized fiber composites, the interlaminar shear strength and interfacial shear strength of PAMAM/fiber-reinforced composites showed increases of 55.49 and 110.94%, respectively. PMID:27472250

  4. Control of adhesion force between ceria particles and polishing pad in shallow trench isolation chemical mechanical planarization.

    PubMed

    Seo, Jihoon; Moon, Jinok; Bae, Jae-Young; Yoon, Kwang Seob; Sigmund, Wolfgang; Paik, Ungyu

    2014-06-01

    The adhesion force between ceria and polyurethane (PU) pad was controlled to remove the step height from cell region to peripheral region during Shallow Trench Isolation Chemical Mechanical Planarization (STI-CMP) for NAND flash. Picolinic acid was found to be adsorbed on ceria particles at pH 4.5 following a Langmuir isotherm with the maximum adsorbed amount of 0.36 mg/m2. The ceria suspension with full surface coverage of picolinic acid showed a threefold increase in the number of adhered ceria particles on the PU pad over non-coated ceria particles. It was shown that the coverage percent of picolinic acid on ceria corresponds well with the amount percent of adsorbed ceria on PU pad. The change in adsorbed particles was directly reflected in the CMP polishing process where significant improvements were achieved. Particularly, convex areas on the chip experienced higher friction force from the attached abrasives on the PU pad than concave areas. As a result, the convex areas have increased removal rate of step height compared to the ceria suspension without picolinic acid. The changing profiles of convex areas are reported during the step height reduction as a function of polishing time. PMID:24738395

  5. A laboratory study of particle ploughing and pore-pressure feedback: A velocity-weakening mechanism for soft glacier beds

    USGS Publications Warehouse

    Thomason, J.F.; Iverson, N.R.

    2008-01-01

    If basal-water discharge and pressure are sufficiently high, a soft-bedded glacier will slip over its bed by ploughing, the process in which particles that span the ice-bed interface are dragged across the bed surface. Results of laboratory experiments indicate that resistance to ploughing can decrease with increasing ploughing velocity (velocity weakening). During ploughing at various velocities (15-400 ma-1), till was compacted in front of idealized particles, causing pore pressures there that were orders of magnitude higher than the ambient value. This excess pore pressure locally weakened the till in shear, thereby decreasing ploughing resistance by a factor of 3.0-6.6 with a six-fold increase in ploughing velocity. Characteristic timescales of pore-pressure diffusion and compaction down-glacier from ploughing particles depend on till diffusivity, ploughing velocity and sizes of ploughing particles. These timescales accurately predict the ranges of these variables over which excess pore pressure and velocity weakening occurred. Existing ploughing models do not account for velocity weakening. A new ploughing model with no adjustable parameters predicts ploughing resistance to no worse than 38% but requires that excess pore pressures be measured. Velocity weakening by this mechanism may affect fast glacier flow, sediment transport by bed deformation and basal seismicity.

  6. The influence of particle shape on structure, mechanics, and transport in granular materials

    NASA Astrophysics Data System (ADS)

    Smith, Kyle C.

    The development of materials with tailored transport properties is essential to energy conversion and storage applications. Utilization of heterogeneous composite materials composed of discrete particles (i.e., granular materials) represents a promising approach to sustainable, scalable materials production. The so-called jamming point, which represents the transition between fluid-like and solid-like regimes of granular materials, has been the subject of recent fundamental studies. Prior studies have incorporated highly simplified grain shapes that do not reflect the diversity commonly observed in advanced composite materials (e.g., nanomaterials). In the present work, the coupling of heat and charge transport to the level of order in jammed microstructures composed of faceted 3D grains is explored. The systems investigated include lithium ion battery cathodes composed of LiFePO4 nanoparticles, solid state H2 storage in packed beds composed of metal hydride particles, and the Platonic solids. Empirical and theoretical representations of particle shape are determined with single crystal growth models, statistical geometric models, and experimental measurements. An energy-based structural optimization method for the jamming of such arbitrary polyhedral grains is developed to model the mesoscopic structure of heterogeneous materials. Diffusion through the resulting microstructures is simulated with the finite volume method. In LiFePO4 systems a strong dependence of jamming on particle shapes is observed, in which columnar structures aligned with the [010] direction inhibit diffusion along [010] in anisotropic LiFePO4. Transport limitations are induced by [010] columnar order and lead to catastrophic performance degradation in anisotropic LiFePO4 cathodes. Further, judicious mixing of nanoplatelets with additive nanoparticles can frustrate columnar ordering and thereby enhance the rate capability of LiFePO4 electrodes by nearly an order of magnitude. In contrast

  7. How Your Baby Grows

    MedlinePlus

    ... brain, the heart and lungs, are forming. The placenta grows in your uterus and supplies the baby ... like alcohol, cigarette smoke and drugs through the placenta, too. So don’t drink alcohol , smoke , use ...

  8. Apparatus for growing crystals

    NASA Technical Reports Server (NTRS)

    Jasinski, Thomas J. (Inventor); Witt, August F. (Inventor)

    1986-01-01

    An improved apparatus and method for growing crystals from a melt employing a heat pipe, consisting of one or more sections, each section serving to control temperature and thermal gradients in the crystal as it forms inside the pipe.

  9. Direct path from microscopic mechanics to Debye shielding, Landau damping and wave-particle interaction

    NASA Astrophysics Data System (ADS)

    Escande, D. F.; Elskens, Yves; Doveil, F.

    2015-02-01

    The derivation of Debye shielding and Landau damping from the N-body description of plasmas is performed directly by using Newton’s second law for the N-body system. This is done in a few steps with elementary calculations using standard tools of calculus and no probabilistic setting. Unexpectedly, Debye shielding is encountered together with Landau damping. This approach is shown to be justified in the one-dimensional case when the number of particles in a Debye sphere becomes large. The theory is extended to accommodate a correct description of trapping and chaos due to Langmuir waves. On top of their well-known production of collisional transport, the repulsive deflections of electrons are shown to produce shielding, in such a way that each particle is shielded by all other ones, while keeping in uninterrupted motion.

  10. Quantum Mechanics in Noninertial Frames with a Multitemporal Quantization Scheme II:. Nonrelativistic Particles

    NASA Astrophysics Data System (ADS)

    Alba, David

    The nonrelativistic version of the multitemporal quantization scheme of relativistic particles in a family of noninertial frames (see Ref. 1) is defined. At the classical level the description of a family of nonrigid noninertial frames, containing the standard rigidly linear accelerated and rotating ones, is given in the framework of parametrized Galilei theories. Then the multitemporal quantization, in which the gauge variables, describing the noninertial effects, are not quantized but considered as c-number generalized times, is applied to nonrelativistic particles. It is shown that with a suitable ordering there is unitary evolution in all times and that, after the separation of the center-of-mass, it is still possible to identify the inertial bound states. The few existing results of quantization in rigid noninertial frames are recovered as special cases.

  11. A new look at reaction mechanisms with 4. pi. charged-particle and neutron multiplicity measurements

    SciTech Connect

    Sarantites, D.G.; Semkow, T.M.; Sobotka, L.G.; Abenante, V.; Li, Z.; Majka, Z.; Nicolis, N.G.; Stracener, D.W.; Hensley, D.C.; Beene, J.R.

    1987-01-01

    We have studied the excitation of target-like fragments produced in the reactions of 331.9 MeV /sup 28/Si + /sup 181/Ta. The light charged particles and intermediate mass fragments were detected in a small, highly segmented 4..pi.. phoswich detector system placed inside the spin spectrometer, a 4..pi.. NaI array which served as a neutron and ..gamma..-ray detector. All target emissions indicate that excitation ceases to increase with decreasing projectile-like fragment energy, as it should if the primary reaction is binary. Non-equilibrium neutron, proton and ..cap alpha..-particle emission and projectile fragmentation conspire and limit the conversion of kinetic energy into target excitation. This effect is more pronounced for PLF away from the injection point and for the largest kinetic energy losses. 8 refs., 10 figs.

  12. Mechanical properties of concrete containing a high volume of tire-rubber particles.

    PubMed

    Khaloo, Ali R; Dehestani, M; Rahmatabadi, P

    2008-12-01

    Due to the increasingly serious environmental problems presented by waste tires, the feasibility of using elastic and flexible tire-rubber particles as aggregate in concrete is investigated in this study. Tire-rubber particles composed of tire chips, crumb rubber, and a combination of tire chips and crumb rubber, were used to replace mineral aggregates in concrete. These particles were used to replace 12.5%, 25%, 37.5%, and 50% of the total mineral aggregate's volume in concrete. Cylindrical shape concrete specimens 15 cm in diameter and 30 cm in height were fabricated and cured. The fresh rubberized concrete exhibited lower unit weight and acceptable workability compared to plain concrete. The results of a uniaxial compressive strain control test conducted on hardened concrete specimens indicate large reductions in the strength and tangential modulus of elasticity. A significant decrease in the brittle behavior of concrete with increasing rubber content is also demonstrated using nonlinearity indices. The maximum toughness index, indicating the post failure strength of concrete, occurs in concretes with 25% rubber content. Unlike plain concrete, the failure state in rubberized concrete occurs gently and uniformly, and does not cause any separation in the specimen. Crack width and its propagation velocity in rubberized concrete are lower than those of plain concrete. Ultrasonic analysis reveals large reductions in the ultrasonic modulus and high sound absorption for tire-rubber concrete. PMID:18372166

  13. Particle-scale CO2 adsorption kinetics modeling considering three reaction mechanisms

    SciTech Connect

    Suh, Dong-Myung; Sun, Xin

    2013-09-01

    In the presence of water (H2O), dry and wet adsorptions of carbon dioxide (CO2) and physical adsorption of H2O happen concurrently in a sorbent particle. The three reactions depend on each other and have a complicated, but important, effect on CO2 capturing via a solid sorbent. In this study, transport phenomena in the sorbent were modeled, including the tree reactions, and a numerical solving procedure for the model also was explained. The reaction variable distribution in the sorbent and their average values were calculated, and simulation results were compared with experimental data to validate the proposed model. Some differences, caused by thermodynamic parameters, were observed between them. However, the developed model reasonably simulated the adsorption behaviors of a sorbent. The weight gained by each adsorbed species, CO2 and H2O, is difficult to determine experimentally. It is known that more CO2 can be captured in the presence of water. Still, it is not yet known quantitatively how much more CO2 the sorbent can capture, nor is it known how much dry and wet adsorptions separately account for CO2 capture. This study addresses those questions by modeling CO2 adsorption in a particle and simulating the adsorption process using the model. As adsorption temperature changed into several values, the adsorbed amount of each species was calculated. The captured CO2 in the sorbent particle was compared quantitatively between dry and wet conditions. As the adsorption temperature decreased, wet adsorption increased. However, dry adsorption was reduced.

  14. Process for preparation of large-particle-size monodisperse latexes

    NASA Technical Reports Server (NTRS)

    Vanderhoff, J. W.; Micale, F. J.; El-Aasser, M. S.; Kornfeld, D. M. (Inventor)

    1981-01-01

    Monodisperse latexes having a particle size in the range of 2 to 40 microns are prepared by seeded emulsion polymerization in microgravity. A reaction mixture containing smaller monodisperse latex seed particles, predetermined amounts of monomer, emulsifier, initiator, inhibitor and water is placed in a microgravity environment, and polymerization is initiated by heating. The reaction is allowed to continue until the seed particles grow to a predetermined size, and the resulting enlarged particles are then recovered. A plurality of particle-growing steps can be used to reach larger sizes within the stated range, with enlarge particles from the previous steps being used as seed particles for the succeeding steps. Microgravity enables preparation of particles in the stated size range by avoiding gravity related problems of creaming and settling, and flocculation induced by mechanical shear that have precluded their preparation in a normal gravity environment.

  15. Influence of jet milling and particle size on the composition, physicochemical and mechanical properties of barley and rye flours.

    PubMed

    Drakos, Antonios; Kyriakakis, Georgios; Evageliou, Vasiliki; Protonotariou, Styliani; Mandala, Ioanna; Ritzoulis, Christos

    2017-01-15

    Finer barley and rye flours were produced by jet milling at two feed rates. The effect of reduced particle size on composition and several physicochemical and mechanical properties of all flours were evaluated. Moisture content decreased as the size of the granules decreased. Differences on ash and protein contents were observed. Jet milling increased the amount of damaged starch in both rye and barley flours. True density increased with decreased particle size whereas porosity and bulk density increased. The solvent retention capacity profile was also affected by jet milling. Barley was richer in phenolics and had greater antioxidant activity than rye. Regarding colour, both rye and barley flours when subjected to jet milling became brighter, whereas their yellowness was not altered significantly. The minimum gelation concentration for all flours was 16%w/v. Barley flour gels were stronger, firmer and more elastic than the rye ones. PMID:27542482

  16. Characterization and modeling of illite crystal particles and growth mechanisms in a zoned hydrothermal deposit, Lake City, Colorado

    USGS Publications Warehouse

    Bove, D.J.; Eberl, D.D.; McCarty, D.K.; Meeker, G.P.

    2002-01-01

    Mean thickness measurements and crystal-thickness distributions (CTDs) of illite particles vary systematically with changes in hydrothermal alteration type, fracture density, and attendant mineralization in a large acid-sulfate/Mo-porphyry hydrothermal system at Red Mountain, near Lake City, Colorado. The hydrothermal illites characterize an extensive zone of quartz-sericite-pyrite alteration beneath two deeply rooted bodies of magmatic-related, quartz-alunite altered rock. Nineteen illites from a 3000 ft vertical drill hole were analyzed by XRD using the PVP-10 intercalation method and the computer program MudMaster (Bertaut-Warren-Averbach technique). Mean crystallite thicknesses, as determined from 001 reflections, range from 5-7 nanometers (nm) at depths from 0-1700 ft, then sharply increase to 10-16 nm at depths between 1800-2100 ft, and decrease again to 4-5 nm below this level. The interval of largest particle thickness correlates strongly with the zone of most intense quartz-sericite-pyrite alteration (QSP) and attendant high-density stockwork fracturing, and with the highest concentrations of Mo within the drill core. CTD shapes for the illite particles fall into two main categories: asymptotic and lognormal. The shapes of the CTDs are dependent on conditions of illite formation. The asymptotic CTDs correspond to a nucleation and growth mechanism, whereas surface-controlled growth was the dominant mechanism for the lognormal CTDs. Lognormal CTDs coincide with major through-going fractures or stockwork zones, whereas asymptotic CTDs are present in wallrock distal to these intense fracture zones. The increase in illite particle size and the associated zone of intense QSP alteration and stockwork veining was related by proximity to the dacitic magma(s), which supplied both reactants and heat to the hydrothermal system. However, no changes in illite polytype, which in other studies reflect temperature transitions, were observed within this interval.

  17. Toxicity of Mineral Dusts and a Proposed Mechanism for the Pathogenesis of Particle-Induced Lung Diseases

    NASA Technical Reports Server (NTRS)

    Lam, C.-W.; Zeidler-Erdely, P.; Scully, R.R.; Meyers, V.; Wallace, W.; Hunter, R.; Renne, R.; McCluskey, R.; Castranova, V.; Barger, M.; Meighan, T.; James, J.T.

    2015-01-01

    Humans will set foot on the moon again. The lunar surface has been bombarded for 4 billion years by micrometeoroids and cosmic radiation, creating a layer of fine dust having a potentially reactive particle surface. To investigate the impact of surface reactivity (SR) on the toxicity of particles, and in particular, lunar dust (LD), we ground 2 Apollo 14 LD samples to increase their SR and compare their toxicity with those of unground LD, TiO2 and quartz. Intratracheally instilled at 0, 1, 2.5, or 7.5 mg/rat, all dusts caused dose-dependent increases in pulmonary lesions, and enhancement of biomarkers of toxicity assessed in bronchoalveolar lavage fluids (BALF). The toxicity of LD was greater than that of TiO2 but less than that of quartz. Three LDs differed 14-fold in SR but were equally toxic; quartz had the lowest SR but was most toxic. These results show no correlation between particle SR and toxicity. Often pulmonary toxicity of a dust can be attributed to oxidative stress (OS). We further observed dose-dependent and dustcytotoxicity- dependent increases in neutrophils. The oxidative content per BALF cell was also directly proportional to both the dose and cytotoxicity of the dusts. Because neutrophils are short-lived and release of oxidative contents after they die could initiate and promote a spectrum of lesions, we postulate a general mechanism for the pathogenesis of particle-induced diseases in the lung that involves chiefly neutrophils, the source of persistent endogenous OS. This mechanism explains why one dust (e.g., quartz or nanoparticles) is more toxic than another (e.g., micrometer-sized TiO2), why dust-induced lesions progress with time, and why lung cancer occurs in rats but not in mice and hamsters exposed to the same duration and concentration of dust.

  18. Isostructural solid-solid phase transition in monolayers of soft core-shell particles at fluid interfaces: structure and mechanics.

    PubMed

    Rey, Marcel; Fernández-Rodríguez, Miguel Ángel; Steinacher, Mathias; Scheidegger, Laura; Geisel, Karen; Richtering, Walter; Squires, Todd M; Isa, Lucio

    2016-04-13

    We have studied the complete two-dimensional phase diagram of a core-shell microgel-laden fluid interface by synchronizing its compression with the deposition of the interfacial monolayer. Applying a new protocol, different positions on the substrate correspond to different values of the monolayer surface pressure and specific area. Analyzing the microstructure of the deposited monolayers, we discovered an isostructural solid-solid phase transition between two crystalline phases with the same hexagonal symmetry, but with two different lattice constants. The two phases corresponded to shell-shell and core-core inter-particle contacts, respectively; with increasing surface pressure the former mechanically failed enabling the particle cores to come into contact. In the phase-transition region, clusters of particles in core-core contacts nucleate, melting the surrounding shell-shell crystal, until the whole monolayer moves into the second phase. We furthermore measured the interfacial rheology of the monolayers as a function of the surface pressure using an interfacial microdisk rheometer. The interfaces always showed a strong elastic response, with a dip in the shear elastic modulus in correspondence with the melting of the shell-shell phase, followed by a steep increase upon the formation of a percolating network of the core-core contacts. These results demonstrate that the core-shell nature of the particles leads to a rich mechanical and structural behavior that can be externally tuned by compressing the interface, indicating new routes for applications, e.g. in surface patterning or emulsion stabilization. PMID:26948023

  19. Mechanical alignment of particles for use in fabricating superconducting and permanent magnetic materials

    DOEpatents

    Nellis, William J.; Maple, M. Brian

    1992-01-01

    A method for mechanically aligning oriented superconducting or permanently magnetic materials for further processing into constructs. This pretreatment optimizes the final crystallographic orientation and, thus, properties in these constructs. Such materials as superconducting fibers, needles and platelets are utilized.

  20. High Extracellular Levels of Mycobacterium tuberculosis Glutamine Synthetase and Superoxide Dismutase in Actively Growing Cultures Are Due to High Expression and Extracellular Stability Rather than to a Protein-Specific Export Mechanism

    PubMed Central

    Tullius, Michael V.; Harth, Günter; Horwitz, Marcus A.

    2001-01-01

    Glutamine synthetase (GS) and superoxide dismutase (SOD), large multimeric enzymes that are thought to play important roles in the pathogenicity of Mycobacterium tuberculosis, are among the bacterium's major culture filtrate proteins in actively growing cultures. Although these proteins lack a leader peptide, their presence in the extracellular medium during early stages of growth suggested that they might be actively secreted. To understand their mechanism of export, we cloned the homologous genes (glnA1 and sodA) from the rapid-growing, nonpathogenic Mycobacterium smegmatis, generated glnA1 and sodA mutants of M. smegmatis by allelic exchange, and quantitated expression and export of both mycobacterial and nonmycobacterial GSs and SODs in these mutants. We also quantitated expression and export of homologous and heterologous SODs from M. tuberculosis. When each of the genes was expressed from a multicopy plasmid, M. smegmatis exported comparable proportions of both the M. tuberculosis and M. smegmatis GSs (in the glnA1 strain) or SODs (in the sodA strain), in contrast to previous observations in wild-type strains. Surprisingly, recombinant M. smegmatis and M. tuberculosis strains even exported nonmycobacterial SODs. To determine the extent to which export of these large, leaderless proteins is expression dependent, we constructed a recombinant M. tuberculosis strain expressing green fluorescent protein (GFP) at high levels and a recombinant M. smegmatis strain coexpressing the M. smegmatis GS, M. smegmatis SOD, and M. tuberculosis BfrB (bacterioferritin) at high levels. The recombinant M. tuberculosis strain exported GFP even in early stages of growth and at proportions very similar to those of the endogenous M. tuberculosis GS and SOD. Similarly, the recombinant M. smegmatis strain exported bacterioferritin, a large (∼500-kDa), leaderless, multimeric protein, in proportions comparable to GS and SOD. In contrast, high-level expression of the large, leaderless

  1. Studies on supercritical hydrothermal syntheses of uranium and lanthanide oxide particles and their reaction mechanisms

    NASA Astrophysics Data System (ADS)

    Hwang, DongKi; Tsukahara, Takehiko; Tanaka, Kosuke; Osaka, Masahiko; Ikeda, Yasuhisa

    2015-11-01

    In order to develop preparation method of raw metal oxide particles for low decontaminated MOX fuels by supercritical hydrothermal (SH) treatments, we have investigated behavior of aqueous solutions dissolving U(VI), Ln(III) (Ln: lanthanide = Ce, Pr, Nd, Sm, Tb), Cs(I), and Sr(II) nitrate or chloride compounds under SH conditions (temperature = 400-500 °C, pressure = 30-40 MPa). As a result, it was found that Ln(NO3)3 (Ln = Ce, Pr, Tb) compounds produce LnO2, that Ln(NO3)3 (Ln = Nd, Sm) compounds are hardly converted to their oxides, and that LnCl3 (Ln = Ce, Pr, Nd, Sm, Tb), CsNO3, and Sr(NO3)2 do not form their oxide compounds. Furthermore, HNO2 species were detected in the liquid phase obtained after treating HNO3 aqueous solutions containing Ln(NO3)3 (Ln = Ce, Pr, Tb) under SH conditions, and also NO2 and NO compounds were found to be produced by decomposition of HNO3. From these results, it was proposed that the Ln oxide (LnO2) particles are directly formed with oxidation of Ln(III) to Ln(IV) by HNO3 and HNO2 species in the SH systems. Moreover, the uranyl ions were found to form U3O8 and UO3 depending on the concentration of HNO3. From these results, it is expected that the raw metal oxide particles for low decontaminated MOX fuels are efficiently prepared by the SH method.

  2. Quantum mechanics of lattice gas automata: One-particle plane waves and potentials

    SciTech Connect

    Meyer, D.A.

    1997-05-01

    Classical lattice gas automata effectively simulate physical processes, such as diffusion and fluid flow (in certain parameter regimes), despite their simplicity at the microscale. Motivated by current interest in quantum computation we recently defined {ital quantum} lattice gas automata; in this paper we initiate a project to analyze which physical processes these models can effectively simulate. Studying the single particle sector of a one-dimensional quantum lattice gas we find discrete analogs of plane waves and wave packets, and then investigate their behavior in the presence of inhomogeneous potentials. {copyright} {ital 1997} {ital The American Physical Society}

  3. A damage mechanics of a particle-reinforced ductile matrix composite with progressive partial debonding

    SciTech Connect

    Zhao, Y.H.; Weng, G.J.

    1995-12-31

    A micromechanical damage theory is developed to determine the overall elastoplastic stress-strain behavior of a ductile composite containing homogeneously dispersed prolate inclusions which, under the action of external tension, experience debonding on the top and bottom of the interface. The debonding process is described by Weibull`s probability function in terms of the tensile stress of the inclusions. Qiu and Weng`s energy approach is also used here to determine the internal stress state of the damaged composite. The initial two-phase system gradually turns into a three-phase one as the debonded inclusions lose their load-carrying capacity partially. The stress-strain responses are then derived as a function of volume concentrations of still bonded particles and already debonded ones, and of the shape of inclusions and the average interfacial strength. It is shown that the stress-strain curve of the system always starts out with that of perfectly a bonded composite, then deviates from it, and finally approaches a state parallel to that of a porous material containing similarly aligned voids. A detail comparison is provided with the results from Mochida, Taya, and Obata`s rigid particle theory with an elastic matrix and Togho and Weng`s completely debonding theory with an elastoplastic matrix. It is found that the behavior of a partially debonded composite always lies between the two.

  4. Quantum-mechanical Brayton engine working with a particle in a one-dimensional harmonic trap

    NASA Astrophysics Data System (ADS)

    Wang, H.

    2013-05-01

    Based on the quantum version of thermodynamic processes, a quantum-mechanical Brayton engine model has been established. Expressions for the power output and efficiency of the engine are derived. Some fundamental optimal relations and general performance characteristic curves of the cycle are obtained. Furthermore, we note that it is possible to resist the reduction in efficiency, caused by compression of the adiabatic process, by decreasing the amount of energy levels of the quantum system. The results obtained here will provide theoretical guidance for the design of some new quantum-mechanical engines.

  5. High-throughput inertial particle focusing in a curved microchannel: Insights into the flow-rate regulation mechanism and process model.

    PubMed

    Xiang, Nan; Yi, Hong; Chen, Ke; Sun, Dongke; Jiang, Di; Dai, Qing; Ni, Zhonghua

    2013-01-01

    In this work, we design and fabricate a miniaturized spiral-shaped microchannel device which can be used for high-throughput particle/cell ordering, enrichment, and purification. To probe into the flow rate regulation mechanism, an experimental investigation is carried out on the focusing behaviors of particles with significantly different sizes in this device. A complete picture of the focusing position shifting process is unfolded to clarify the confusing results obtained from flow regimes with different dominant forces in past research. Specifically, with the increase of the flow rate, particles are observed to first move towards the inner wall under the dominant inertial migration, then stabilize at a specific position and finally shift away from the inner wall due to the alternation of the dominant force. Novel phenomena of focusing instability, co-focusing, and focusing position interchange of differently sized particles are also observed and investigated. Based on the obtained experimental data, we develop and validate, for the first time, a five-stage model of the particle focusing process with increasing flow rate for interpreting particle behaviors in terms of the competition between inertial lift and Dean drag forces. These new experimental findings and the proposed process model provide an important supplement to the existing mechanism of inertial particle flow and enable more flexible and precise particle manipulation. Additionally, we examine the focusing behaviors of bioparticles with a polydisperse size distribution to validate the explored mechanisms and thus help realize efficient enrichment and purification of these particles. PMID:24404049

  6. Optimisation of full-toroidal continuously variable transmission in conjunction with fixed ratio mechanism using particle swarm optimisation

    NASA Astrophysics Data System (ADS)

    Delkhosh, Mojtaba; Saadat Foumani, Mahmoud

    2013-05-01

    The aim of this research is the optimisation of full-toroidal continuously variable transmission (CVT) in conjunction with the fixed ratio (FR) mechanism, while the optimisation objective is to minimise fuel consumption (FC) of the vehicle in the new European driving cycle. After the dynamic analysis of the power train, a computer model is developed to simulate contact between CVT elements and consequently calculate its efficiency. Then an algorithm is presented to calculate FC of the vehicle in the driving cycle. Then, an optimisation using particle swarm optimisation on the CVT geometry and FR mechanism (which is embedded between CVT and final drive) is carried out to minimise FC. It is found that by utilisation of the optimised CVT; FC will be about 11% and 8% lower, compared with the application of a five-speed manual transmission and conventional CVT, respectively. Finally, effects of the roller tilt angle and oil temperature on the FC are investigated.

  7. Investigation of Polar Stratospheric Cloud Solid Particle Formation Mechanisms Using ILAS and AVHRR Observations in the Arctic

    NASA Technical Reports Server (NTRS)

    Irie, H.; Pagan, K. L.; Tabazadeh, A.; Legg, M. J.; Sugita, T.

    2004-01-01

    Satellite observations of denitrification and ice clouds in the Arctic lower stratosphere in February 1997 are used with Lagrangian microphysical box model calculations to evaluate nucleation mechanisms of solid polar stratospheric cloud (PSC) particles. The occurrences of ice clouds are not correlated in time and space with the locations of back trajectories of denitrified air masses, indicating that ice particle surfaces are not always a prerequisite for the formation of solid PSCs that lead to denitrification. In contrast, the model calculations incorporating a pseudoheterogeneous freezing process occurring at the vapor-liquid interface can quantitatively explain most of the observed denitrification when the nucleation activation free energy for nitric acid dihydrate formation is raised by only approx.10% relative to the current published values. Once nucleated, the conversion of nitric acid dihydrate to the stable trihydrate phase brings the computed levels of denitrification closer to the measurements. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0320 Atmospheric Composition and SblctureC: loud physics and chemistry; 0340 Atmospheric Composition and Structure: Middle atmosphere-composition and chemistry

  8. Non-thermal electron acceleration in low Mach number collisionless shocks. I. Particle energy spectra and acceleration mechanism

    SciTech Connect

    Guo, Xinyi; Narayan, Ramesh; Sironi, Lorenzo

    2014-10-20

    Electron acceleration to non-thermal energies in low Mach number (M{sub s} ≲ 5) shocks is revealed by radio and X-ray observations of galaxy clusters and solar flares, but the electron acceleration mechanism remains poorly understood. Diffusive shock acceleration, also known as first-order Fermi acceleration, cannot be directly invoked to explain the acceleration of electrons. Rather, an additional mechanism is required to pre-accelerate the electrons from thermal to supra-thermal energies, so they can then participate in the Fermi process. In this work, we use two- and three-dimensional particle-in-cell plasma simulations to study electron acceleration in low Mach number shocks. We focus on the particle energy spectra and the acceleration mechanism in a reference run with M{sub s} = 3 and a quasi-perpendicular pre-shock magnetic field. We find that about 15% of the electrons can be efficiently accelerated, forming a non-thermal power-law tail in the energy spectrum with a slope of p ≅ 2.4. Initially, thermal electrons are energized at the shock front via shock drift acceleration (SDA). The accelerated electrons are then reflected back upstream where their interaction with the incoming flow generates magnetic waves. In turn, the waves scatter the electrons propagating upstream back toward the shock for further energization via SDA. In summary, the self-generated waves allow for repeated cycles of SDA, similarly to a sustained Fermi-like process. This mechanism offers a natural solution to the conflict between the bright radio synchrotron emission observed from the outskirts of galaxy clusters and the low electron acceleration efficiency usually expected in low Mach number shocks.

  9. Geometry and mechanics of thin growing bilayers.

    PubMed

    Pezzulla, Matteo; Smith, Gabriel P; Nardinocchi, Paola; Holmes, Douglas P

    2016-05-11

    We investigate how thin sheets of arbitrary shapes morph under the isotropic in-plane expansion of their top surface, which may represent several stimuli such as nonuniform heating, local swelling and differential growth. Inspired by geometry, an analytical model is presented that rationalizes how the shape of the disk influences morphing, from the initial spherical bending to the final isometric limit. We introduce a new measure of slenderness that describes a sheet in terms of both thickness and plate shape. We find that the mean curvature of the isometric state is three fourths the natural curvature, which we verify by numerics and experiments. We finally investigate the emergence of a preferred direction of bending in the isometric state, guided by numerical analyses. The scalability of our model suggests that it is suitable to describe the morphing of sheets spanning several orders of magnitude. PMID:27098344

  10. Geometry and Mechanics of Thin Growing Bilayers

    NASA Astrophysics Data System (ADS)

    Pezzulla, Matteo; Smith, Gabriel; Nardinocchi, Paola; Holmes, Douglas

    We investigate how thin sheets of arbitrary shapes morph under the isotropic in-plane expansion of their top surface, which may represent several stimuli such as nonuniform heating, local swelling and differential growth. Inspired by geometry, an analytical model is presented that rationalizes how the shape of the disk influences morphing, from the initial spherical bending to the final isometric limit. We introduce a new measure of slenderness that describes a sheet in terms of both thickness and plate shape. We find that the mean curvature of the isometric state is three fourth's the natural curvature, which we verify by numerics and experiments. We finally investigate the emergence of a preferred direction of bending in the isometric state, guided by numerical analyses. The scalability of our model suggests that it is suitable to describe the morphing of sheets spanning several orders of magnitude. NSF Grant CMMI-1300860.

  11. To Grow or not to Grow?

    PubMed

    Bassel, George W

    2016-06-01

    The seed to seedling transition in plants is initiated following the termination of seed dormancy. Here, I present a simplified developmental framework describing the events underlying this transition. I discuss putative mechanisms of signal integration and their relation to a global developmental fate switch in seeds within this framework. I delineate the events that occur before and after the flipping of this switch, marking an important distinction between these different developmental states. To end, I propose that the final fate switch resides within the embryo, and is informed by the endosperm in arabidopsis (Arabidopsis thaliana). This framework can serve as a template to focus future research in seed science. PMID:26934952

  12. Growing Up with "1984."

    ERIC Educational Resources Information Center

    Franza, August

    1983-01-01

    Relates changing student reaction to George Orwell's "1984" over 20 years of teaching. Finds present high school students' acceptance of Orwell's bleak world vision both a sign of student honesty and a frightening indication of the growing reality of the book. (MM)

  13. Growing through Literature.

    ERIC Educational Resources Information Center

    Thomas, Barbara J.

    "Growing through Literature" is a curriculum using Joan M. and Erik H. Erikson's theory of the Life Cycle as a structure for selecting and teaching literature to inner-city high school students at Brighton High School in Massachusetts. The program consists of four component parts: Journals, Selected Stories, Discussion, and Autobiography. By…

  14. GROWING SEEDS, TEACHER'S GUIDE.

    ERIC Educational Resources Information Center

    Elementary Science Study, Newton, MA.

    THIS TEACHER'S GUIDE IS DESIGNED FOR USE WITH AN ELEMENTARY SCIENCE STUDY UNIT, "GROWING SEEDS," IN WHICH SUCH BASIC SCIENCE SKILLS AND PROCESSES AS MEASUREMENT, OBSERVATION, AND HYPOTHESIS FORMATION ARE INTRODUCED THROUGH STUDENT ACTIVITIES INVOLVING SEEDS, GERMINATION, AND SEEDLING GROWTH. THE MATERIALS WERE DEVELOPED FOR USE IN ELEMENTARY…

  15. Growing Up In Appalachia.

    ERIC Educational Resources Information Center

    Reed, Judith

    1981-01-01

    Offers a glimpse of a Smithsonian Institution Traveling Exhibition of 80 photographs and selected writings by first through eighth grade children growing up in Letcher County, Kentucky. Children were guided by an artist-in-residence sponsored by the Kentucky Arts Commission and Appalshop, a multimedia cooperative. (Author/RH)

  16. Growing Backyard Textiles

    ERIC Educational Resources Information Center

    Nelson, Eleanor Hall

    1975-01-01

    For those involved in creative work with textiles, the degree of control possible in texture, finish, and color of fiber by growing and processing one's own (perhaps with students' help) can make the experience rewarding. The author describes the processes for flax and nettles and gives tips on necessary equipment. (Author/AJ)

  17. Growing Plants in School.

    ERIC Educational Resources Information Center

    Salt, Bernard

    1990-01-01

    Background information on the methods and varieties used to demonstrate the cultivation of plants without the use of chemical pesticides is provided. Discussed are species and variety selection, growing plants from seed and from seedlings, soil preparation, using cuttings, useful crops, and pest control. (CW)

  18. Growing a Nurturing Classroom

    ERIC Educational Resources Information Center

    Boorn, Clare; Dunn, Paula Hopkins; Page, Claire

    2010-01-01

    "Growing a nurturing classroom" is an awareness training programme presented by educational psychologists in Leicestershire for professionals working in primary schools with the aim of promoting an optimal environment for learning and emotional well-being. The training helps primary school staff to take a holistic approach to education; see…

  19. Watching single gold nanorods grow.

    PubMed

    Wei, Zhongqing; Qi, Hua; Li, Min; Tang, Bochong; Zhang, Zhengzheng; Han, Ruiling; Wang, Jiaojiao; Zhao, Yuliang

    2012-05-01

    The consecutive evolution process of single gold nanorods is monitored using atomic force microscopy (AFM). The single-crystal gold nanorods investigated are grown directly on surfaces to which gold seed particles are covalently linked. The growth kinetics for single nanorods is derived from the 3D information recorded by AFM. A better understanding of the seed-mediated growth mechanism may ultimately lead to the direct growth of aligned nanorods on surfaces. PMID:22378704

  20. A mechanism for the abundance enhancements of heavy nuclei in solar flare particle events

    NASA Technical Reports Server (NTRS)

    Cartwright, B. G.; Mogro-Campero, A.

    1973-01-01

    A mechanism is proposed to account for the recently reported abundance enhancements of heavy nuclei in solar flares. The mechanism requires two acceleration stages for its operation: First, fully stripped ions are accelerated to suprathermal energies, and subsequently, a fraction of these ions are Fermi accelerated to higher energies. It is shown that because injection into Fermi acceleration is rigidity dependent and the ions may pick up electrons during transport to the Fermi acceleration region, an enhancement of the abundances of heavy nuclei can occur. The degree of the enhancement depends on a number of factors particular to each flare, so that the degree of enhancement may be variable from flare to flare, or may be a function of time within a given flare. In some flares, conditions may be such that no enhancement would be expected.

  1. HIV-1 Infection of DC: Evidence for the Acquisition of Virus Particles from Infected T Cells by Antigen Uptake Mechanism

    PubMed Central

    Venkatachari, Narasimhan J.; Alber, Sean; Watkins, Simon C.; Ayyavoo, Velpandi

    2009-01-01

    Dendritic cells (DC) play a pivotal role in transmission and dissemination of HIV-1. Earlier studies reported that DC present at the site of infection trap virus particles via DC-SIGN and transfer the virus to the interacting naïve T cells. This prompted us to ask the question whether DC could acquire virus from infected T cells during DC-T cell interaction. To address this, we investigated the likely transfer of virus from HIV-1 infected T cells to DC and the underlying mechanisms involved. Results indicate that DC acquire virus from infected T cells via antigen uptake mechanism and this results in infection of DC with expression of proteins directed by viral DNA. Further studies with HIV-1 lacking the Env protein also resulted in infection of DC. The use of antibodies against DC-SIGN and DC-SIGN-R ruled out a role for receptor in the infection of DC. Additional data show that DC infection is directly correlated with the ability of DC to take up antigen from infected T cells. Overall, these studies provide evidence to suggest that HIV-1, besides infecting immune cells, also utilizes immunological mechanism(s) to acquire and disseminate virus. PMID:19829715

  2. Dynamics of classical particles in oval or elliptic billiards with a dispersing mechanism.

    PubMed

    da Costa, Diogo Ricardo; Dettmann, Carl P; de Oliveira, Juliano A; Leonel, Edson D

    2015-03-01

    Some dynamical properties for an oval billiard with a scatterer in its interior are studied. The dynamics consists of a classical particle colliding between an inner circle and an external boundary given by an oval, elliptical, or circle shapes, exploring for the first time some natural generalizations. The billiard is indeed a generalization of the annular billiard, which is of strong interest for understanding marginally unstable periodic orbits and their role in the boundary between regular and chaotic regions in both classical and quantum (including experimental) systems. For the oval billiard, which has a mixed phase space, the presence of an obstacle is an interesting addition. We demonstrate, with details, how to obtain the equations of the mapping, and the changes in the phase space are discussed. We study the linear stability of some fixed points and show both analytically and numerically the occurrence of direct and inverse parabolic bifurcations. Lyapunov exponents and generalized bifurcation diagrams are obtained. Moreover, histograms of the number of successive iterations for orbits that stay in a cusp are studied. These histograms are shown to be scaling invariant when changing the radius of the scatterer, and they have a power law slope around -3. The results here can be generalized to other kinds of external boundaries. PMID:25833431

  3. Dynamics of classical particles in oval or elliptic billiards with a dispersing mechanism

    SciTech Connect

    Costa, Diogo Ricardo da; Dettmann, Carl P.; Oliveira, Juliano A. de; Leonel, Edson D.

    2015-03-15

    Some dynamical properties for an oval billiard with a scatterer in its interior are studied. The dynamics consists of a classical particle colliding between an inner circle and an external boundary given by an oval, elliptical, or circle shapes, exploring for the first time some natural generalizations. The billiard is indeed a generalization of the annular billiard, which is of strong interest for understanding marginally unstable periodic orbits and their role in the boundary between regular and chaotic regions in both classical and quantum (including experimental) systems. For the oval billiard, which has a mixed phase space, the presence of an obstacle is an interesting addition. We demonstrate, with details, how to obtain the equations of the mapping, and the changes in the phase space are discussed. We study the linear stability of some fixed points and show both analytically and numerically the occurrence of direct and inverse parabolic bifurcations. Lyapunov exponents and generalized bifurcation diagrams are obtained. Moreover, histograms of the number of successive iterations for orbits that stay in a cusp are studied. These histograms are shown to be scaling invariant when changing the radius of the scatterer, and they have a power law slope around −3. The results here can be generalized to other kinds of external boundaries.

  4. Solid lipid particles for oral delivery of peptide and protein drugs I--elucidating the release mechanism of lysozyme during lipolysis.

    PubMed

    Christophersen, P C; Zhang, L; Yang, M; Nielsen, H Mørck; Müllertz, A; Mu, H

    2013-11-01

    The mechanism of protein release from solid lipid particles was investigated by a new lipolysis model in a biorelevant medium containing both bile salts and phospholipids. Lysozyme, a model protein, was formulated into solid lipid particles using four different types of lipids, two triglycerides with different chain-length of fatty acyl groups i.e. trimyristin (TG14) and tristearin (TG18), and two lipid blends dominated by diglycerides and monoglycerides, respectively. The release of lysozyme from the solid lipid particles and the lipid hydrolysis process were assessed in the lipolysis model, while the change in particle surface during the lipolysis process was evaluated using scanning electron microscopy. The lysozyme release profiles from TG14 and TG18 as well as diglyceride particles correlated well with the release of free fatty acids from the lipid particles during the lipolysis and therefore exhibited a lipase-mediated degradation-based release mechanism. The release of lysozyme from monoglyceride particles was independent on lipase degradation due to the instability of the lipid matrix in the lipolysis medium. In conclusion, the established lipolysis model is successfully used to elucidate the drug release mechanism from solid lipid particles and can potentially be used in rational selection of lipid excipients for oral delivery of peptide/protein drugs. PMID:23911434

  5. Structure, phase content and mechanical properties of aluminium with hard particles after shock-wave compaction

    NASA Astrophysics Data System (ADS)

    Kulkov, S.; Vorozhtsov, S.; Turuntaev, I.

    2015-04-01

    The possibilities to combine metal and metal oxide powders in various compositions open a broad range of mechanical and thermal behavior. When using in nanostructured components the resulting materials might exhibit even more interesting properties, like product effectiveness, tensile strength, wear resistance, endurance and corrosion resistance. Intermetallics like TiAl could be obtained as TiAlx in a quality similar to that obtained from melting where only eutectic mixture can be produced. Similar effects are possible when compacting nanoceramic powders whereas these can be combined with intermetallics. Currently, it is very difficult to produce wires and special shaped parts from high temperature superconducting materials. The compacting by explosives could solve this problem.The present paper uses explosion compacting of Al nanoparticles to create nanocomposite with increased physico-mechanical properties. Russian civil explosive Uglenit was chosen as high energy material (HEM) for shock-wave compaction. The different schemes and conditions were suggested to run the explosion process. Al nanoparticles as produced by electric wire explosion contain 8-10% of aluminum oxide. That aluminum oxide can serve as strengthening material in the final nanocomposite which may be generated in various compositions by explosive compacting. Further modifications of nanocomposites were obtained when including nanodiamonds into the mixture with aluminum nanoparticles with different percentages. The addition of nanodiamonds results in a substantial strengthening effect. The experiments with compacting aluminum nanoparticles by explosives are described in detail including the process variations and conditions. The physico-mechanical properties of the nanocomposites are determined and discussed by considering the applied conditions. Especially, microstructure and phases of the obtained nanocomposites are analyzed by X-ray diffraction.

  6. Mechanical strain induced valley-dependent quantum magnetotransport of Dirac particles in graphene

    NASA Astrophysics Data System (ADS)

    Ma, Ning; Zhang, Shengli; Liu, Daqing; Wang, Vei

    2015-12-01

    We have explored the mechanical strain effects on the magnetotransport in graphene with a 1D electrostatic periodic potential in the presence of a perpendicular magnetic field. We find that, in a strong magnetic field regime, the conductivity exhibits a superposition of the Shubnikov-de Haas and Weiss oscillations in each valley due to the electrical modulation. Especially, the strain removes the valley degeneracy of Landau levels in inversion symmetric Dirac cones. Accordingly, this causes the valley-dependence of the conductivity. These phenomena, absent in a freestanding graphene, are a consequence of the anomalous spectrum of carriers in a fully stained graphene.

  7. Effects of Thermal and Mechanical Processing on Microstructures and Desired Properties of Particle-Strengthened Cu-Cr-Nb Alloys

    NASA Technical Reports Server (NTRS)

    Anderson, Kenneth Reed

    2000-01-01

    Ternary Cu-Cr-Nb alloys, particularly Cu-8 Cr-4 Nb (in at.%), have demonstrated good thermal stability as well as high strength and conductivity at elevated temperatures. The initial powder material has a bimodal size distribution of Cr2Nb precipitates. Primary Cr2Nb precipitates are approx. 1 micron, and secondary Cr2Nb particles are 30-200 nm. The particle coarsening was analyzed and found to follow LSW-type behavior, This study provides a detailed examination of the stability and strengthening effects of Cr2Nb particles. This investigation also revealed that the primary particles provide direct grain boundary pinning and indirect grain boundary strengthening but virtually no Orowan strengthening. The secondary particles found within grains do provide Orowan strengthening. For extruded material, grain bound-ary strengthening (Hall-Petch effect) accounts for two-thirds of the strength with Orowan effects contributing the remainder. The proven advantages of Cu-Cr-Nb were the motivation to improve these attributes via microstructural refinement. Mechanical milling (MM) of Cu- 4 Cr-2 Nb and Cu-8 Cr-2 Nb produced an increase in hot pressed Vickers hardness of 122% and 96%, respectively. The increase in hardness was more due to Cu grain-size refinement than to Cr,,Nb refinement. This study also demonstrated enhanced stability of MM Cu-4 Cr-2 Nb. Hot pressed 4 h milled Cu-4 Cr-2 Nb experienced only a 22% drop in hardness when annealed at 1273 K for 50 h versus a 30% drop for extruded Cu-8 Cr-4 Nb. The goal of improving the strength and stability of Cu-4 Cr-2 Nb to better than such properties for as- extruded Cu-8 Cr-4 Nb has been met. In addition, a figure-of-merit (FOM) coupling hardness and thermal conductivity was maximized for the case of 4 h milled Cu-4 Cr-2 Nb material. Overall, Cu-Cr-Nb alloys not only possess high strength, conductivity and thermal stability but also can be further developed to improve strength and stability.

  8. How to grow tomatoes.

    PubMed

    Kimura, Seisuke; Sinha, Neelima

    2008-01-01

    INTRODUCTIONTomatoes can be easily grown in a field, in a greenhouse, or in a growth cabinet. They need acidic soil (pH 6.0-6.8), a lot of light, and water. The optimum temperature for growing tomato plants and fruit is 18°C-24°C. This protocol describes how to germinate tomato seeds, cultivate adult plants, and harvest seeds from fruit. PMID:21356721

  9. Growing up with Retinoblastoma

    ERIC Educational Resources Information Center

    Maley, Tom

    2005-01-01

    An account is given of growing up as a child blinded as a result of a cancer of the eye known as retinoblastoma. The role of his mother is brought out, variously as a source of objective knowledge, of one's personal worth, and of the worth of other people in one's community. The strengths and weaknesses of his first school in his home area and…

  10. High-resolution chemical analysis by STEM-EELS of nanosized oxide particles in a mechanically-alloyed FeCrAl intermetallic

    SciTech Connect

    Morris, D.G. Muñoz-Morris, M.A.

    2015-05-15

    The chemical composition of nanosized oxides has been analysed in a mechanically-alloyed (MA) iron–chromium–aluminium intermetallic containing yttria additions using an aberration-corrected, high-resolution scanning transmission electron microscope (STEM). The oxide particles are seen to contain yttrium and oxygen only, but very little of the matrix metallic elements, while the matrix in the immediate vicinity shows a very low iron content. Possible reasons for the change of matrix composition outside the particle-matrix interface are discussed. - Highlights: • High-resolution chemical analysis of oxide particles was performed using STEM-EELS. • Oxide particles contain Y and O but essentially no elements from the Fe–Cr–Al matrix. • The matrix immediately outside the particles appears to be depleted in Fe. • Diffusion of Y during particle growth possibly transports vacancies to the interface.

  11. Particle removal in a novel sequential mechanical filter system loaded with blackwater.

    PubMed

    Todt, Daniel; Jenssen, Petter D

    2015-01-01

    A novel sequential mechanical filter system was developed as an alternative primary treatment method for onsite wastewater treatment. The filter combines traditional screening with a novel type of counter-flow filter using wood-shavings as a biodegradable filter matrix. This study tested the system in a batch loading regime simulating high frequency toilet flushing using blackwater from a student dormitory. The filter removed 78-85% of suspended solids, 60-80% of chemical oxygen demand, and 42-57% of total-P in blackwater, giving a retentate with a dry matter content of 13-20%. Data analysis clearly indicated a tendency towards higher removal performance with high inlet concentrations, hence, the system seems to be most applicable to blackwater or other types of wastewater with a high content of suspended solids. PMID:25945859

  12. Theoretical and Observational Analysis of Particle Acceleration Mechanisms at Astrophysical Shocks

    NASA Astrophysics Data System (ADS)

    Lever, Edward Lawrence

    We analytically and numerically investigate the viability of Shock Surfing as a pre-injection mechanism for Diffusive Shock Acceleration, believed to be responsible for the production of Cosmic Rays. We demonstrate mathematically and from computer simulations that four critical conditions must be satisfied for Shock Surfing to function; the shock ramp must be narrow, the shock front must be smooth, the magnetic field angle must be very nearly perpendicular and, finally, these conditions must persist without interruption over substantial time periods and spatial scales. We quantify these necessary conditions, exhibit predictive functions for velocity maxima and accelerated ion fluxes based on observable shock parameters, and show unequivocally from current observational evidence that all of these necessary conditions are violated at shocks within the heliosphere, at the heliospheric Termination Shock, and also at Supernovae.

  13. Interferon-induced HERC5 is evolving under positive selection and inhibits HIV-1 particle production by a novel mechanism targeting Rev/RRE-dependent RNA nuclear export

    PubMed Central

    2014-01-01

    Background Type I interferon (IFN) inhibits virus replication by activating multiple antiviral mechanisms and pathways. It has long been recognized that type I IFNs can potently block HIV-1 replication in vitro; as such, HIV-1 has been used as a system to identify and characterize IFN-induced antiviral proteins responsible for this block. IFN-induced HERC5 contains an amino-terminal Regulator of Chromosome Condensation 1 (RCC1)-like domain and a carboxyl-terminal Homologous to the E6-AP Carboxyl Terminus (HECT) domain. HERC5 is the main cellular E3 ligase that conjugates the IFN-induced protein ISG15 to proteins. This E3 ligase activity was previously shown to inhibit the replication of evolutionarily diverse viruses, including HIV-1. The contribution of the RCC1-like domain to the antiviral activity of HERC5 was previously unknown. Results In this study, we showed that HERC5 inhibits HIV-1 particle production by a second distinct mechanism that targets the nuclear export of Rev/RRE-dependent RNA. Unexpectedly, the E3 ligase activity of HERC5 was not required for this inhibition. Instead, this activity required the amino-terminal RCC1-like domain of HERC5. Inhibition correlated with a reduction in intracellular RanGTP protein levels and/or the ability of RanGTP to interact with RanBP1. Inhibition also correlated with altered subcellular localization of HIV-1 Rev. In addition, we demonstrated that positive evolutionary selection is operating on HERC5. We identified a region in the RCC1-like domain that exhibits an exceptionally high probability of having evolved under positive selection and showed that this region is required for HERC5-mediated inhibition of nuclear export. Conclusions We have identified a second distinct mechanism by which HERC5 inhibits HIV-1 replication and demonstrate that HERC5 is evolving under strong positive selection. Together, our findings contribute to a growing body of evidence suggesting that HERC5 is a novel host restriction factor

  14. Mechanical Disruption of Tumors by Iron Particles and Magnetic Field Application Results in Increased Anti-Tumor Immune Responses

    PubMed Central

    Bouchlaka, Myriam N.; Sckisel, Gail D.; Wilkins, Danice; Maverakis, Emanual; Monjazeb, Arta M.; Fung, Maxwell; Welniak, Lisbeth; Redelman, Doug; Fuchs, Alan; Evrensel, Cahit A.; Murphy, William J.

    2012-01-01

    The primary tumor represents a potential source of antigens for priming immune responses for disseminated disease. Current means of debulking tumors involves the use of cytoreductive conditioning that impairs immune cells or removal by surgery. We hypothesized that activation of the immune system could occur through the localized release of tumor antigens and induction of tumor death due to physical disruption of tumor architecture and destruction of the primary tumor in situ. This was accomplished by intratumor injection of magneto-rheological fluid (MRF) consisting of iron microparticles, in Balb/c mice bearing orthotopic 4T1 breast cancer, followed by local application of a magnetic field resulting in immediate coalescence of the particles, tumor cell death, slower growth of primary tumors as well as decreased tumor progression in distant sites and metastatic spread. This treatment was associated with increased activation of DCs in the draining lymph nodes and recruitment of both DCs and CD8(+)T cells to the tumor. The particles remained within the tumor and no toxicities were observed. The immune induction observed was significantly greater compared to cryoablation. Further anti-tumor effects were observed when MRF/magnet therapy was combined with systemic low dose immunotherapy. Thus, mechanical disruption of the primary tumor with MRF/magnetic field application represents a novel means to induce systemic immune activation in cancer. PMID:23133545

  15. Particle-in-cell simulations of the excitation mechanism for fusion-product-driven ion cyclotron emission from tokamaks

    NASA Astrophysics Data System (ADS)

    Dendy, Richard; Cook, James; Chapman, Sandra

    2009-11-01

    Suprathermal ion cyclotron emission (ICE) was the first collective radiative instability, driven by fusion products, observed on JET and TFTR. Strong emission occurs at sequential cyclotron harmonics of the energetic ion population at the outer mid-plane. Its intensity scales linearly with fusion reactivity, including its time evolution during a discharge. The emission mechanism is probably the magnetoacoustic cyclotron instability (MCI), involving resonance between: fast Alfv'en waves; cyclotron harmonic waves supported by the energetic particle population and by the background thermal plasma; and a subset of the centrally born fusion products, just inside the trapped-passing boundary, whose drift orbits make large radial excursions. The linear growth rate of the MCI has been intensively studied analytically, and yields good agreement with several key observational features of ICE. To address outstanding issues in the nonlinear ICE regime, we have developed a particle-in-cell code which self-consistently evolves electron and multi-species ion macroparticles and the electromagnetic field. We focus on the growth rate of the MCI, as it evolves from the linear into the nonlinear regime for JET-like parameters.

  16. Role of channel coupling and deuteron-exchange mechanisms in anomalous alpha-particle scattering on {sup 6}Li

    SciTech Connect

    Sakuta, S. B.; Artemov, S.V.; Burtebaev, N.; Kerimkulov, Zh.; Novatsky, B. G.; Stepanov, D.N.; Yarmukhamedov, R.

    2009-12-15

    A unified description of existing experimental data on alpha-particle scattering by {sup 6}Li over the broad energy range from 18 to 166 MeV was obtained with allowance for channel-coupling effects and mechanisms involving the exchange of a deuteron cluster. Angular distributions were analyzed on the basis of the optical model and the coupled reaction channels method. It was shown that the inclusion of channel coupling and the contributions from one- and two-step exchangemechanismsmakes it possible to describe special features of the behavior of differential cross sections for both elastic and inelastic scattering in a full energy range. Optimum values found for the parameters of optical potentials agree with the parameters of the global potential proposed previously for nuclei in the mass region A > 12.

  17. Effect of Y2O3 and TiC Reinforcement Particles on Intermetallic Formation and Hardness of Al6061 Composites via Mechanical Alloying and Sintering

    NASA Astrophysics Data System (ADS)

    Chen, Chun-Liang; Lin, Chen-Han

    2015-08-01

    Al6061-based composites reinforced with 2 wt pctY2O3 and 2 wt pctTiC particles produced by mechanical alloying were investigated. The reinforced particles play important roles in the microstructural development and in determining the properties of the alloys. High-energy ball milling can facilitate a solid-state reaction between reinforced particles and the Al matrix, and the reaction kinetics of atomic diffusion can be accelerated enormously by subsequent sintering processing. As a result, complex intermetallic compounds and oxide particles can be formed in the alloy. In this study, the effect of reinforcement on phase formation and mechanical properties of Al6061-based composites has been examined. The results suggest that nano-Y2O3 particles can act as nucleation sites to facilitate formation of Al-Si-Y-O-based oxide particles. The addition of TiC particles can effectively refine the grain structure and encourage formation of iron-rich intermetallic compounds. Nanoindentation was used to understand the local variations in mechanical properties of the Al6061-based composites.

  18. The mechanisms of plant stress mitigation by kaolin-based particle films and its applications in horticultural and agricultural crops

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Kaolin-based particle films have utility in reducing insect, heat, light, and uv stress in plants due to the reflective nature of the particles. Particle films with a residue density of 1 to 3 g/ square meter have been evaluated in a range of crops and agricultural environments. The particle film ...

  19. Studies of near-surface phenomena and erosion mechanisms in metallic alloys using single- and multi-particle impacts. Fossil Energy Program

    SciTech Connect

    Rao, M.; Keiser, J.R.

    1992-03-01

    An experimental study of the effects of material properties on erosion mechanisms was conducted by subjecting targets to single as well as multiple impacts of spherical particles at various velocities. A mechanical properties microprobe was used to monitor the hardening due to the impacts. Initial studies on several engineering alloys showed that work hardening was associated with single impacts, and the results suggested that the capacity to distribute the impact energy over large volumes improved a material`s erosion resistance. Studies also showed that the alloys work hardened significantly under multiple-particle impacts. Single-particle impact studies were found to correlate well with results from low-velocity, multiple-particle erosion experiments. (VC)

  20. Experimental investigations on the fluid-mechanics of an electrospun heart valve by means of particle image velocimetry.

    PubMed

    Del Gaudio, Costantino; Gasbarroni, Pier Luca; Romano, Giovanni Paolo

    2016-12-01

    End-stage failing heart valves are currently replaced by mechanical or biological prostheses. Both types positively contribute to restore the physiological function of native valves, but a number of drawbacks limits the expected performances. In order to improve the outcome, tissue engineering can offer an alternative approach to design and fabricate innovative heart valves capable to support the requested function and to promote the formation of a novel, viable and correctly operating physiological structure. This potential result is particularly critical if referred to the aortic valve, being the one mainly exposed to structural and functional degeneration. In this regard, the here proposed study presents the fabrication and in vitro characterization of a bioresorbable electrospun heart valve prosthesis using the particle image velocimetry technique either in physiological and pathological fluid dynamic conditions. The scaffold was designed to reproduce the aortic valve geometry, also mimicking the fibrous structure of the natural extracellular matrix. To evaluate its performances for possible implantation, the flow fields downstream the valve were accurately investigated and compared. The experimental results showed a correct functionality of the device, supported by the formation of vortex structures at the edge of the three cusps, with Reynolds stress values below the threshold for the risk of hemolysis (which can be comprised in the range 400-4000N/m(2) depending on the exposure period), and a good structural resistance to the mechanical loads generated by the driving pressure difference. PMID:27521817

  1. Influences of Substrate Adhesion and Particle Size on the Shape Memory Effect of Polystyrene Particles.

    PubMed

    Cox, Lewis M; Killgore, Jason P; Li, Zhengwei; Long, Rong; Sanders, Aric W; Xiao, Jianliang; Ding, Yifu

    2016-04-19

    Formulations and applications of micro- and nanoscale polymer particles have proliferated rapidly in recent years, yet knowledge of their mechanical behavior has not grown accordingly. In this study, we examine the ways that compressive strain, substrate surface energy, and particle size influence the shape memory cycle of polystyrene particles. Using nanoimprint lithography, differently sized particles are programmed into highly deformed, temporary shapes in contact with substrates of differing surface energies. Atomic force microscopy is used to obtain in situ measurements of particle shape recovery kinetics, and scanning electron microscopy is employed to assess differences in the profiles of particles at the conclusion of the shape memory cycle. Finally, finite element models are used to investigate the growing impact of surface energies at smaller length scales. Results reveal that the influence of substrate adhesion on particle recovery is size-dependent and can become dominating at submicron length scales. PMID:27023181

  2. Computational modeling of lava domes using particle dynamics to investigate the effect of conduit flow mechanics on flow patterns

    NASA Astrophysics Data System (ADS)

    Husain, Taha Murtuza

    Large (1--4 x 106 m3) to major (> 4 x 106 m3) dome collapses for andesitic lava domes such as Soufriere Hills Volcano, Montserrat are observed for elevated magma discharge rates (6--13 m3/s). The gas rich magma pulses lead to pressure build up in the lava dome that result in structural failure of the over steepened canyon-like walls which may lead to rockfall or pyroclastic flow. This indicates that dome collapse intimately related to magma extrusion rate. Variation in magma extrusion rate for open-system magma chambers is observed to follow alternating periods of high and low activity. Periodic behavior of magma exhibits a rich diversity in the nature of its eruptive history due to variation in magma chamber size, total crystal content, linear crystal growth rate and magma replenishment rate. Distinguished patterns of growth were observed at different magma flow rates ranging from endogenous to exogenous dome growth for magma with varying strengths. Determining the key parameters that control the transition in flow pattern of the magma during its lava dome building eruption is the main focus. This dissertation examines the mechanical effects on the morphology of the evolving lava dome on the extrusion of magma from a central vent using a 2D particle dynamics model. The particle dynamics model is coupled with a conduit flow model that incorporates the kinetics of crystallization and rheological stiffening to investigate important mechanisms during lava dome building eruptions. Chapter I of this dissertation explores lava dome growth and failure mechanics using a two-dimensional particle-dynamics model. The model follows the evolution of fractured lava, with solidification driven by degassing induced crystallization of magma. The particle-dynamics model emulates the natural development of dome growth and rearrangement of the lava dome which is difficult in mesh-based analyses due to mesh entanglement effects. The deformable talus evolves naturally as a frictional

  3. Effect of additive particles on mechanical, thermal, and cell functioning properties of poly(methyl methacrylate) cement

    PubMed Central

    Khandaker, Morshed; Vaughan, Melville B; Morris, Tracy L; White, Jeremiah J; Meng, Zhaotong

    2014-01-01

    The most common bone cement material used clinically today for orthopedic surgery is poly(methyl methacrylate) (PMMA). Conventional PMMA bone cement has several mechanical, thermal, and biological disadvantages. To overcome these problems, researchers have investigated combinations of PMMA bone cement and several bioactive particles (micrometers to nanometers in size), such as magnesium oxide, hydroxyapatite, chitosan, barium sulfate, and silica. A study comparing the effect of these individual additives on the mechanical, thermal, and cell functional properties of PMMA would be important to enable selection of suitable additives and design improved PMMA cement for orthopedic applications. Therefore, the goal of this study was to determine the effect of inclusion of magnesium oxide, hydroxyapatite, chitosan, barium sulfate, and silica additives in PMMA on the mechanical, thermal, and cell functional performance of PMMA. American Society for Testing and Materials standard three-point bend flexural and fracture tests were conducted to determine the flexural strength, flexural modulus, and fracture toughness of the different PMMA samples. A custom-made temperature measurement system was used to determine maximum curing temperature and the time needed for each PMMA sample to reach its maximum curing temperature. Osteoblast adhesion and proliferation experiments were performed to determine cell viability using the different PMMA cements. We found that flexural strength and fracture toughness were significantly greater for PMMA specimens that incorporated silica than for the other specimens. All additives prolonged the time taken to reach maximum curing temperature and significantly improved cell adhesion of the PMMA samples. The results of this study could be useful for improving the union of implant-PMMA or bone-PMMA interfaces by incorporating nanoparticles into PMMA cement for orthopedic and orthodontic applications. PMID:24920906

  4. Effect of additive particles on mechanical, thermal, and cell functioning properties of poly(methyl methacrylate) cement.

    PubMed

    Khandaker, Morshed; Vaughan, Melville B; Morris, Tracy L; White, Jeremiah J; Meng, Zhaotong

    2014-01-01

    The most common bone cement material used clinically today for orthopedic surgery is poly(methyl methacrylate) (PMMA). Conventional PMMA bone cement has several mechanical, thermal, and biological disadvantages. To overcome these problems, researchers have investigated combinations of PMMA bone cement and several bioactive particles (micrometers to nanometers in size), such as magnesium oxide, hydroxyapatite, chitosan, barium sulfate, and silica. A study comparing the effect of these individual additives on the mechanical, thermal, and cell functional properties of PMMA would be important to enable selection of suitable additives and design improved PMMA cement for orthopedic applications. Therefore, the goal of this study was to determine the effect of inclusion of magnesium oxide, hydroxyapatite, chitosan, barium sulfate, and silica additives in PMMA on the mechanical, thermal, and cell functional performance of PMMA. American Society for Testing and Materials standard three-point bend flexural and fracture tests were conducted to determine the flexural strength, flexural modulus, and fracture toughness of the different PMMA samples. A custom-made temperature measurement system was used to determine maximum curing temperature and the time needed for each PMMA sample to reach its maximum curing temperature. Osteoblast adhesion and proliferation experiments were performed to determine cell viability using the different PMMA cements. We found that flexural strength and fracture toughness were significantly greater for PMMA specimens that incorporated silica than for the other specimens. All additives prolonged the time taken to reach maximum curing temperature and significantly improved cell adhesion of the PMMA samples. The results of this study could be useful for improving the union of implant-PMMA or bone-PMMA interfaces by incorporating nanoparticles into PMMA cement for orthopedic and orthodontic applications. PMID:24920906

  5. Growing a market economy

    SciTech Connect

    Basu, N.; Pryor, R.J.

    1997-09-01

    This report presents a microsimulation model of a transition economy. Transition is defined as the process of moving from a state-enterprise economy to a market economy. The emphasis is on growing a market economy starting from basic microprinciples. The model described in this report extends and modifies the capabilities of Aspen, a new agent-based model that is being developed at Sandia National Laboratories on a massively parallel Paragon computer. Aspen is significantly different from traditional models of the economy. Aspen`s emphasis on disequilibrium growth paths, its analysis based on evolution and emergent behavior rather than on a mechanistic view of society, and its use of learning algorithms to simulate the behavior of some agents rather than an assumption of perfect rationality make this model well-suited for analyzing economic variables of interest from transition economies. Preliminary results from several runs of the model are included.

  6. From laser particle acceleration to the synthesis of extremely neutron rich isotopes via the novel fission-fusion mechanism

    NASA Astrophysics Data System (ADS)

    Thirolf, P. G.

    2015-02-01

    High-power, short pulse lasers have emerged in the last decade as attractive tools for accelerating charged particles (electrons, ions) to high energies over mm-scale acceleration lengths, thus promising to rival conventional acceleration techniques in the years ahead. In the first part of the article, the principles of laser-plasma interaction as well as the techniques and the current status of the acceleration of electron and ion beams will be briefly introduced. In particular with the upcoming next generation of multi-PW class laser systems, such as the one under construction for the ELI-Nuclear Physics project in Bucharest (ELI-NP), very efficient acceleration mechanisms for brilliant ion beams like radiation pressure acceleration (RPA) come into reach. Here, ultra-dense ion beams reaching solid-state density can be accelerated from thin target foils, exceeding the density of conventionally accelerated ion beams by about 14 orders of magnitude. This unique property of laser-accelerated ion beams can be exploited to explore the scenario of a new reaction mechanism called `fission-fusion', which will be introduced in the second part of the article. Accelerating fissile species (e.g. 232Th ) towards a second layer of the same material will lead to fission both of the beam-like and target-like particles. Due to the close to solid-state density of the accelerated ion bunches, fusion may occur between neutron-rich (light) fission products. This may open an access path towards extremely neutron-rich nuclides in the vicinity of the N=126 waiting point of the astrophysical r process. `Waiting points' at closed nucleon shells play a crucial role in controlling the reaction rates. However, since most of the pathway of heavy-element formation via the rapid-neutron capture process (r-process) runs in `terra incognita' of the nuclear landscape, in particular the waiting point at N=126 is yet unexplored and will remain largely inaccessible to conventional nuclear reaction

  7. From laser particle acceleration to the synthesis of extremely neutron rich isotopes via the novel fission-fusion mechanism

    SciTech Connect

    Thirolf, P. G.

    2015-02-24

    High-power, short pulse lasers have emerged in the last decade as attractive tools for accelerating charged particles (electrons, ions) to high energies over mm-scale acceleration lengths, thus promising to rival conventional acceleration techniques in the years ahead. In the first part of the article, the principles of laser-plasma interaction as well as the techniques and the current status of the acceleration of electron and ion beams will be briefly introduced. In particular with the upcoming next generation of multi-PW class laser systems, such as the one under construction for the ELI-Nuclear Physics project in Bucharest (ELI-NP), very efficient acceleration mechanisms for brilliant ion beams like radiation pressure acceleration (RPA) come into reach. Here, ultra-dense ion beams reaching solid-state density can be accelerated from thin target foils, exceeding the density of conventionally accelerated ion beams by about 14 orders of magnitude. This unique property of laser-accelerated ion beams can be exploited to explore the scenario of a new reaction mechanism called ‘fission-fusion’, which will be introduced in the second part of the article. Accelerating fissile species (e.g. {sup 232}Th) towards a second layer of the same material will lead to fission both of the beam-like and target-like particles. Due to the close to solid-state density of the accelerated ion bunches, fusion may occur between neutron-rich (light) fission products. This may open an access path towards extremely neutron-rich nuclides in the vicinity of the N=126 waiting point of the astrophysical r process. ‘Waiting points’ at closed nucleon shells play a crucial role in controlling the reaction rates. However, since most of the pathway of heavy-element formation via the rapid-neutron capture process (r-process) runs in ‘terra incognita’ of the nuclear landscape, in particular the waiting point at N=126 is yet unexplored and will remain largely inaccessible to conventional

  8. Growing vortex patches

    NASA Astrophysics Data System (ADS)

    Crowdy, Darren; Marshall, Jonathan

    2004-08-01

    This paper demonstrates that two well-known equilibrium solutions of the Euler equations—the corotating point vortex pair and the Rankine vortex—are connected by a continuous branch of exact solutions. The central idea is to "grow" new vortex patches at two stagnation points that exist in the frame of reference of the corotating point vortex pair. This is done by generalizing a mathematical technique for constructing vortex equilibria first presented by Crowdy [D. G. Crowdy, "A class of exact multipolar vortices," Phys. Fluids 11, 2556 (1999)]. The solutions exhibit several interesting features, including the merging of two separate vortex patches via the development of touching cusps. Numerical contour dynamics methods are used to verify the mathematical solutions and reveal them to be robust structures. The general issue of how simple vortex equilibria can be continued continuously to more complicated ones with very different vortical topologies is discussed. The solutions are examples of exact solutions of the Euler equations involving multiple interacting vortex patches.

  9. How Do Galaxies Grow?

    NASA Astrophysics Data System (ADS)

    2008-08-01

    Astronomers have caught multiple massive galaxies in the act of merging about 4 billion years ago. This discovery, made possible by combining the power of the best ground- and space-based telescopes, uniquely supports the favoured theory of how galaxies form. ESO PR Photo 24/08 ESO PR Photo 24/08 Merging Galaxies in Groups How do galaxies form? The most widely accepted answer to this fundamental question is the model of 'hierarchical formation', a step-wise process in which small galaxies merge to build larger ones. One can think of the galaxies forming in a similar way to how streams merge to form rivers, and how these rivers, in turn, merge to form an even larger river. This theoretical model predicts that massive galaxies grow through many merging events in their lifetime. But when did their cosmological growth spurts finish? When did the most massive galaxies get most of their mass? To answer these questions, astronomers study massive galaxies in clusters, the cosmological equivalent of cities filled with galaxies. "Whether the brightest galaxies in clusters grew substantially in the last few billion years is intensely debated. Our observations show that in this time, these galaxies have increased their mass by 50%," says Kim-Vy Tran from the University of Zürich, Switzerland, who led the research. The astronomers made use of a large ensemble of telescopes and instruments, including ESO's Very Large Telescope (VLT) and the Hubble Space Telescope, to study in great detail galaxies located 4 billion light-years away. These galaxies lie in an extraordinary system made of four galaxy groups that will assemble into a cluster. In particular, the team took images with VIMOS and spectra with FORS2, both instruments on the VLT. From these and other observations, the astronomers could identify a total of 198 galaxies belonging to these four groups. The brightest galaxies in each group contain between 100 and 1000 billion of stars, a property that makes them comparable

  10. Explanation of the Quantum-Mechanical Particle-Wave Duality through the Emission of Watt-Less Gravitational Waves by the Dirac Equation

    NASA Astrophysics Data System (ADS)

    Winterberg, Friedwardt

    2016-01-01

    An explanation of the quantum-mechanical particle-wave duality is given by the watt-less emission of gravitational waves from a particle described by the Dirac equation. This explanation is possible through the existence of negative energy, and hence negative mass solutions of Einstein's gravitational field equations. They permit to understand the Dirac equation as the equation for a gravitationally bound positive-negative mass (pole-dipole particle) two-body configuration, with the mass of the Dirac particle equal to the positive mass of the gravitational field binding the positive with the negative mass particle, and with the mass particles making a luminal "Zitterbewegung" (quivering motion), emitting a watt-less oscillating positive-negative space curvature wave. It is shown that this thusly produced "Zitterbewegung" reproduces the quantum potential of the Madelung-transformed Schrödinger equation. The watt-less gravitational wave emitted by the quivering particles is conjectured to be de Broglie's pilot wave. The hypothesised connection of the Dirac equation to gravitational wave physics could, with the failure to detect gravitational waves by the LIGO antennas and pulsar timing arrays, give a clue to extended theories of gravity, or a correction of astrophysical models for the generation of such waves.

  11. Growing a Forest for the Trees.

    ERIC Educational Resources Information Center

    Growing Ideas, 2001

    2001-01-01

    Describes a tree studies program in a fourth-grade classroom. Students collected local tree seeds and seeds from supermarket fruits, researched growing conditions, and grew seeds under various conditions. Students kept journals on local trees, observing seed dispersal mechanisms and examining rings on trunk slices. Inquiry-based tree studies…

  12. Influence of particle velocity and molten phase on the chemical and mechanical properties of HVOF-sprayed structural coatings of alloy 316L

    SciTech Connect

    Voggenreiter, H.; Huber, H.; Beyer, S.; Spies, H.J.

    1995-12-31

    The HP/HVOF spraying process allows the production of oxide-low, thick coatings with low porosity. This fact implies the feasibility of load-bearing HP/HVOF-sprayed structures. Optimum mechanical properties are required for structural applications of HP/HVOF-sprayed iron base alloy 316L. Process-parameter-dependent particle properties like temperature and velocity strongly influence the microstructure and the chemical and mechanical properties of HP/HVOF-sprayed alloy 316L. Results of metallographical and chemical analysis and laser-optic-aided particle velocity measurement lead to a new understanding of particle oxidation based on a high volume fraction of liquid phase and high particle impact velocity. The volume fraction of oxides greatly affects the mechanical properties of homogenized HP/HVOF-316 L. Optimum process parameters result in reduced oxide content less than 0.9% and consequently in strength and elongation comparable to that of wrought alloy 316L. Additionally to these excellent mechanical properties, a low porosity level of about 0.1 to 0.2% is achieved. These fundamental results were transferred successfully to a new type of combustion chamber for hypersonic aircraft with reduced complexity and weight.

  13. Direct observation of solid-phase adsorbate concentration profile in powdered activated carbon particle to elucidate mechanism of high adsorption capacity on super-powdered activated carbon.

    PubMed

    Ando, Naoya; Matsui, Yoshihiko; Matsushita, Taku; Ohno, Koichi

    2011-01-01

    Decreasing the particle size of powdered activated carbon (PAC) by pulverization increases its adsorption capacities for natural organic matter (NOM) and polystyrene sulfonate (PSS, which is used as a model adsorbate). A shell adsorption mechanism in which NOM and PSS molecules do not completely penetrate the adsorbent particle and instead preferentially adsorb near the outer surface of the particle has been proposed as an explanation for this adsorption capacity increase. In this report, we present direct evidence to support the shell adsorption mechanism. PAC particles containing adsorbed PSS were sectioned with a focused ion beam, and the solid-phase PSS concentration profiles of the particle cross-sections were directly observed by means of field emission-scanning electron microscopy/energy-dispersive X-ray spectrometry (FE-SEM/EDXS). X-ray emission from sulfur, an index of PSS concentration, was higher in the shell region than in the inner region of the particles. The X-ray emission profile observed by EDXS did not agree completely with the solid-phase PSS concentration profile predicted by shell adsorption model analysis of the PSS isotherm data, but the observed and predicted profiles were not inconsistent when the analytical errors were considered. These EDXS results provide the first direct evidence that PSS is adsorbed mainly in the vicinity of the external surface of the PAC particles, and thus the results support the proposition that the increase in NOM and PSS adsorption capacity with decreasing particle size is due to the increase in external surface area on which the molecules can be adsorbed. PMID:20851447

  14. Growing quantum states with topological order

    NASA Astrophysics Data System (ADS)

    Letscher, Fabian; Grusdt, Fabian; Fleischhauer, Michael

    2015-05-01

    We discuss a protocol for growing states with topological order in interacting many-body systems using a sequence of flux quanta and particle insertion. We first consider a simple toy model, the superlattice Bose-Hubbard model, to explain all required ingredients. Our protocol is then applied to fractional quantum Hall systems in both, continuum and lattice. We investigate in particular how the fidelity, with which a topologically ordered state can be grown, scales with increasing particle number N . For small systems, exact diagonalization methods are used. To treat large systems with many particles, we introduce an effective model based on the composite fermion description of the fractional quantum Hall effect. This model also allows to take into account the effects of dispersive bands and edges in the system, which will be discussed in detail.

  15. Particle-image velocimetry investigation of the fluid-structure interaction mechanisms of a natural owl wing.

    PubMed

    Winzen, A; Roidl, B; Schröder, W

    2015-10-01

    The increasing interest in the development of small flying air vehicles has given rise to a strong need to thoroughly understand low-speed aerodynamics. The barn owl is a well-known example of a biological system that possesses a high level of adaptation to its habitat and as such can inspire future small-scale air vehicle design. The combination of the owl-specific wing geometry and plumage adaptations with the flexibility of the wing structure yields a highly complex flow field, still enabling the owl to perform stable and at the same time silent low-speed gliding flight. To investigate the effects leading to such a characteristic flight, time-resolved stereoscopic particle-image velocimetry (TR-SPIV) measurements are performed on a prepared natural owl wing in a range of angles of attack 0° ≤ α ≤ 6° and Reynolds numbers 40,000 ≤ Re(c) ≤ 120,000 based on the chord length at a position located at 30% of the halfspan from the owl's body. The flow field does not show any flow separation on the suction side, whereas flow separation is found on the pressure side for all investigated cases. The flow field on the pressure side is characterized by large-scale vortices which interact with the flexible wing structure. The good agreement of the shedding frequency of the pressure side vortices with the frequency of the trailing-edge deflection indicates that the structural deformation is induced by the flow field on the pressure side. Additionally, the reduction of the time-averaged mean wing curvature at high Reynolds numbers indicates a passive lift-control mechanism that provides constant lift in the entire flight envelope of the owl. PMID:26372422

  16. Effects of MgO Nano Particles on Microstructural and Mechanical Properties of Aluminum Matrix Composite prepared via Powder Metallurgy Route

    NASA Astrophysics Data System (ADS)

    Baghchesara, Mohammad Amin; Abdizadeh, Hossein; Baharvandi, Hamid Reza

    The objective of the present investigation was to evaluate the microstructural and mechanical properties of Al/nano MgO composite prepared via powder metallurgy method. Pure atomized aluminum powder with an average particle size of 1μm and MgO particulate with an average particle size between 60 to 80 nm were used. Composites containing 1.5, 2.5 and 5 percent of volume fraction of MgO were prepared by powder metallurgy method. The specimens were pressed by Cold Isostatic Press machine (CIP), subsequently were sintered at 575, 600 and 625°C. After sintering and preparing the samples, mechanical properties were measured. The results of microstructure, compression and hardness tests indicated that addition of MgO particulates to aluminum matrix composites improves the mechanical properties.

  17. Study on the synthesis and formation mechanism of Cu{sub 2}ZnSnS{sub 4} particles by microwave irradiation

    SciTech Connect

    Wang, Wei; Shen, Honglie He, Xiancong

    2013-09-01

    Graphical abstract: - Highlights: • Cu{sub 2}ZnSnS{sub 4} microparticles were fabricated by low-cost chemical method. • The ball cactus-like shaped microparticles are with a diameter about 250 nm. • The optical band energy of Cu{sub 2}ZnSnS{sub 4} microparticles is obtained to be about 1.5 eV. • The CuS nuclei firstly form, and serve as the growth point for Cu{sub 2}ZnSnS{sub 4}. - Abstract: Cu{sub 2}ZnSnS{sub 4} (CZTS) particles were successfully synthesized by microwave assisted solvothermal method. The structure, shape, composition, and optical properties of these particles were investigated with X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy dispersive spectrometer, and UV–vis-NIR spectroscopy. The results show that the as-prepared particles had single phase, stoichiometric composition, and a ball cactus-like shape with a diameter about 250 nm, when reaction time is 10 min. The formation mechanism of the CZTS particles was investigated by evaluation of samples prepared with different reaction time. According to the proposed growth mechanism of CZTS particles, the copper sulfide nuclei firstly forms, and serves as the starting point for the nucleation and growth of CZTS.

  18. Low-solubility particles and a Trojan-horse type mechanism of toxicity: the case of cobalt oxide on human lung cells

    PubMed Central

    2014-01-01

    Background The mechanisms of toxicity of metal oxide particles towards lung cells are far from being understood. In particular, the relative contribution of intracellular particulate versus solubilized fractions is rarely considered as it is very challenging to assess, especially for low-solubility particles such as cobalt oxide (Co3O4). Methods This study was possible owing to two highly sensitive, independent, analytical techniques, based on single-cell analysis, using ion beam microanalysis, and on bulk analysis of cell lysates, using mass spectrometry. Results Our study shows that cobalt oxide particles, of very low solubility in the culture medium, are readily incorporated by BEAS-2B human lung cells through endocytosis via the clathrin-dependent pathway. They are partially solubilized at low pH within lysosomes, leading to cobalt ions release. Solubilized cobalt was detected within the cytoplasm and the nucleus. As expected from these low-solubility particles, the intracellular solubilized cobalt content is small compared with the intracellular particulate cobalt content, in the parts-per-thousand range or below. However, we were able to demonstrate that this minute fraction of intracellular solubilized cobalt is responsible for the overall toxicity. Conclusions Cobalt oxide particles are readily internalized by pulmonary cells via the endo-lysosomal pathway and can lead, through a Trojan-horse mechanism, to intracellular release of toxic metal ions over long periods of time, involving specific toxicity. PMID:24669904

  19. Simplified mechanism for new particle formation from methanesulfonic acid, amines, and water via experiments and ab initio calculations

    PubMed Central

    Dawson, Matthew L.; Varner, Mychel E.; Perraud, Véronique; Ezell, Michael J.; Gerber, R. Benny; Finlayson-Pitts, Barbara J.

    2012-01-01

    Airborne particles affect human health and significantly influence visibility and climate. A major fraction of these particles result from the reactions of gaseous precursors to generate low-volatility products such as sulfuric acid and high-molecular weight organics that nucleate to form new particles. Ammonia and, more recently, amines, both of which are ubiquitous in the environment, have also been recognized as important contributors. However, accurately predicting new particle formation in both laboratory systems and in air has been problematic. During the oxidation of organosulfur compounds, gas-phase methanesulfonic acid is formed simultaneously with sulfuric acid, and both are found in particles in coastal regions as well as inland. We show here that: (i) Amines form particles on reaction with methanesulfonic acid, (ii) water vapor is required, and (iii) particle formation can be quantitatively reproduced by a semiempirical kinetics model supported by insights from quantum chemical calculations of likely intermediate clusters. Such an approach may be more broadly applicable in models of outdoor, indoor, and industrial settings where particles are formed, and where accurate modeling is essential for predicting their impact on health, visibility, and climate. PMID:23090988

  20. A STUDY OF THE MECHANISMS BY WHICH AMBIENT PARTICLES ENTER AND ARE TRANSPORTED WITHIN THE INDOOR ENVIRONMENT

    EPA Science Inventory

    Recent studies have indicated significant health effects associated with exposure to increases in fine particles in the ambient. While these studies were very persuasive towards the dangers of breathing fine particles, it should be noted that the victims of highest risk were larg...

  1. Effect of Mechanical Actions on Cotton Fiber Quality and Foreign-Matter Particle Attachment to Cotton Fibers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The effects of various machine-fiber interactions during harvesting and ginning on fiber quality and attachment between foreign-matter particles and fibers were studied to develop new and less damaging methods for removing foreign-matter particles from cotton fiber. In total, the study involved 75 s...

  2. Simplified mechanism for new particle formation from methanesulfonic acid, amines, and water via experiments and ab initio calculations.

    PubMed

    Dawson, Matthew L; Varner, Mychel E; Perraud, Véronique; Ezell, Michael J; Gerber, R Benny; Finlayson-Pitts, Barbara J

    2012-11-13

    Airborne particles affect human health and significantly influence visibility and climate. A major fraction of these particles result from the reactions of gaseous precursors to generate low-volatility products such as sulfuric acid and high-molecular weight organics that nucleate to form new particles. Ammonia and, more recently, amines, both of which are ubiquitous in the environment, have also been recognized as important contributors. However, accurately predicting new particle formation in both laboratory systems and in air has been problematic. During the oxidation of organosulfur compounds, gas-phase methanesulfonic acid is formed simultaneously with sulfuric acid, and both are found in particles in coastal regions as well as inland. We show here that: (i) Amines form particles on reaction with methanesulfonic acid, (ii) water vapor is required, and (iii) particle formation can be quantitatively reproduced by a semiempirical kinetics model supported by insights from quantum chemical calculations of likely intermediate clusters. Such an approach may be more broadly applicable in models of outdoor, indoor, and industrial settings where particles are formed, and where accurate modeling is essential for predicting their impact on health, visibility, and climate. PMID:23090988

  3. Particle astrophysics

    NASA Astrophysics Data System (ADS)

    Sadoulet, Bernard; Cronin, James; Aprile, Elena; Barish, Barry C.; Beier, Eugene W.; Brandenberger, Robert; Cabrera, Blas; Caldwell, David; Cassiday, George; Cline, David B.

    The following scientific areas are reviewed: (1) cosmology and particle physics (particle physics and the early universe, dark matter, and other relics); (2) stellar physics and particles (solar neutrinos, supernovae, and unconventional particle physics); (3) high energy gamma ray and neutrino astronomy; (4) cosmic rays (space and ground observations). Highest scientific priorities for the next decade include implementation of the current program, new initiatives, and longer-term programs. Essential technological developments, such as cryogenic detectors of particles, new solar neutrino techniques, and new extensive air shower detectors, are discussed. Also a certain number of institutional issues (the funding of particle astrophysics, recommended funding mechanisms, recommended facilities, international collaborations, and education and technology) which will become critical in the coming decade are presented.

  4. Particle astrophysics

    NASA Technical Reports Server (NTRS)

    Sadoulet, Bernard; Cronin, James; Aprile, Elena; Barish, Barry C.; Beier, Eugene W.; Brandenberger, Robert; Cabrera, Blas; Caldwell, David; Cassiday, George; Cline, David B.

    1991-01-01

    The following scientific areas are reviewed: (1) cosmology and particle physics (particle physics and the early universe, dark matter, and other relics); (2) stellar physics and particles (solar neutrinos, supernovae, and unconventional particle physics); (3) high energy gamma ray and neutrino astronomy; (4) cosmic rays (space and ground observations). Highest scientific priorities for the next decade include implementation of the current program, new initiatives, and longer-term programs. Essential technological developments, such as cryogenic detectors of particles, new solar neutrino techniques, and new extensive air shower detectors, are discussed. Also a certain number of institutional issues (the funding of particle astrophysics, recommended funding mechanisms, recommended facilities, international collaborations, and education and technology) which will become critical in the coming decade are presented.

  5. In situ Measurements of Gas- and Particle-Phase Organic Compounds: Insights for SOA Formation Mechanisms and Contributions of SOA to Organic Aerosol

    NASA Astrophysics Data System (ADS)

    Zhao, Y.; Kreisberg, N. M.; Worton, D. R.; Isaacman, G. A.; Weber, R.; Liu, S.; Day, D. A.; Markovic, M. Z.; VandenBoer, T. C.; Russell, L. M.; Murphy, J. G.; Hering, S. V.; Goldstein, A. H.

    2011-12-01

    To investigate formation of secondary organic aerosol (SOA) and the contribution of SOA to organic aerosols, semi-volatile and intermediate-volatile organic compounds (SVOCs/IVOCs) in both gas and particle phases were measured using a modified Thermal Desorption Gas Chromatograph (TAG) instrument in Bakersfield, CA during the CALifornia at the NEXus between air quality and climate (CALNEX) campaign from 31 May through 27 June, 2010. More than 150 organic compounds were identified, spanning a wide range of volatility and functionality. Quantified compounds included organic tracers for primary and secondary organic sources, such as alkanes, PAHs, acids, hopanes and ketones. Hourly gas/particle partitioning was determined by a denuder difference method where the sample flow alternated every other sample through an active charcoal multi-channel denuder that efficiently removed gas-phase components. Gas/particle partitioning of three SOA tracers (phthalic acid, pinonaldehyde and 6, 10, 14-trimethyl-2-pentadecanone) was investigated to understand the formation mechanisms of SOA for different functional group classes in the ambient atmosphere. Comparison with Pankow gas/particle partitioning theory, observed particle-phase phthalic acid and pinonaldehyde, suggests formation by other mechanisms than gas-to-particle condensation. Source attribution is performed using Positive Matrix Factorization (PMF) analysis of speciated particle-phase TAG data along with total submicron organic aerosol (OA) measured by an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS). SOA accounts for a major component of OA and the contribution of biogenic SOA to total SOA is comparable to anthropogenic SOA during nights.

  6. Effect of reinforcing particle type on morphology and age-hardening behavior of Al–4.5 wt.% Cu based nanocomposites synthesized through mechanical milling

    SciTech Connect

    Mostaed, A.; Saghafian, H.; Mostaed, E.; Shokuhfar, A.; Rezaie, H.R.

    2013-02-15

    The effects of reinforcing particle type (SiC and TiC) on morphology and precipitation hardening behavior of Al–4.5%Cu based nanocomposites synthesized via mechanical milling were investigated in the current work. In order to study the microstructure and morphology of mechanically milled powder, X-ray diffraction technique, scanning electron microscopy and high resolution transmission electron microscopy were utilized. Results revealed that at the early stages of mechanical milling, when reinforcing particles are polycrystal, the alloying process is enhanced more in the case of using the TiC particles as reinforcement. But, at the final stages of mechanical milling, when reinforcing particles are single crystal, the alloying process is enhanced more in the case of using the SiC ones. Transmission electron microscopy results demonstrated that Al–4.5 wt.%Cu based nanocomposite powders were synthesized and confirmed that the mutual diffusion of aluminum and copper occurs through the interfacial plane of (200). The hardness results showed that not only does introducing 4 vol.% of reinforcing particles (SiC or TiC) considerably decrease the porosity of the bulk composite samples, but also it approximately doubles the hardness of Al–4.5 wt.%Cu alloy (53.4 HB). Finally, apart from TEM and scanning electron microscopy observation which are localized, a decline in hardness in the TiC and SiC contained samples, respectively, after 1.5 and 2 h aging time at 473 K proves the fact that the size of SiC particles is smaller than the size of the TiC ones. - Highlights: ► HRTEM results show mutual diffusion of Al and Cu occurs through the (200) planes. ► TiC particles enhance alloying process more than the SiC ones at the early stages of MM. ► SiC particles enhance alloying process more than the TiC ones at the final stages of MM.

  7. Reactivity of NaCl with Secondary Organic Acids: An Important Mechanism of the Chloride Depletion in Sea Salt Particles Mixed with Organic Materials

    NASA Astrophysics Data System (ADS)

    Wang, B.; Laskin, A.; Kelly, S.; Gilles, M. K.; Shilling, J. E.; Zelenyuk, A.; Wilson, J. M.; Tivanski, A.

    2012-12-01

    Sea salt particles, one of the major sources of atmospheric aerosols, undergo complex multi-phase reactions and have profound consequences on their physical and chemical properties, thus on climate. Depletion of chloride in sea salt particles was reported in previous field studies and was attributed to the acid displacement of sea salt chlorides with inorganic acids, such as nitric and sulfuric acids. Some studies have also showed that the chloride deficit cannot be fully compensated for this mechanism. We present an important pathway contributing to this chloride depletion: reactions of weak organic acids with sea salt particles. NaCl particles internally mixed with secondary organic materials generated from the reactions of limonene and alpha-pinene with ozone served as surrogates for sea salt particles mixed with organic materials. Chemical imaging analysis of these particles was conducted using complementary techniques including computer controlled scanning electron microscopy with energy dispersive analysis of X-rays (CCSEM/EDX), scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS), and micro-fourier transform infrared spectroscopy (micro-FTIR). Substantial chloride depletion and formation of organic salts were observed along with distinctive changes in particle morphology after hydration/dehydration processes. The results indicate that secondary organic acids can effectively react with NaCl particles resulting in displacement of chloride and release of gaseous HCl. This is consistent with a recent field study showing chloride depletion in sea salt particles mixed with organic materials which cannot be fully compensated by inorganic acid displacement. Although the formation of the organic salts is not thermodynamically favored in bulk aqueous solution, these reactions are driven by the high volatility and evaporation of gaseous HCl in particles, especially during hydration/dehydration processes. The

  8. Decreasing effect and mechanism of FeSO4 seed particles on secondary organic aerosol in α-pinene photooxidation.

    PubMed

    Chu, Biwu; Liu, Yongchun; Li, Junhua; Takekawa, Hideto; Liggio, John; Li, Shao-Meng; Jiang, Jingkun; Hao, Jiming; He, Hong

    2014-10-01

    α-Pinene/NOx and α-pinene/HONO photooxidation experiments at varying humidity were conducted in smog chambers in the presence or absence of FeSO4 seed particles. FeSO4 seed particles decrease SOA mass as long as water was present on the seed particle surface, but FeSO4 seed particles have no decreasing effect on SOA under dryer conditions at 12% relative humidity (RH). The decreasing effect of FeSO4 seed particles on the SOA mass is proposed to be related to oxidation processes in the surface layer of water on the seed particles. Free radicals, including OH, can be formed from catalytic cycling of Fe(2+) and Fe(3+) in the aqueous phase. These radicals can react further with the organic products of α-pinene oxidation on the seed particles. The oxidation may lead to formation of smaller molecules which have higher saturation vapor pressures and favor repartitioning to the gas phase, and therefore, reduces SOA mass. PMID:25014016

  9. Esophageal malignancy: A growing concern

    PubMed Central

    Chai, Jianyuan; Jamal, M Mazen

    2012-01-01

    Esophageal cancer is mainly found in Asia and east Africa and is one of the deadliest cancers in the world. However, it has not garnered much attention in the Western world due to its low incidence rate. An increasing amount of data indicate that esophageal cancer, particularly esophageal adenocarcinoma, has been rising by 6-fold annually and is now becoming the fastest growing cancer in the United States. This rise has been associated with the increase of the obese population, as abdominal fat puts extra pressure on the stomach and causes gastroesophageal reflux disease (GERD). Long standing GERD can induce esophagitis and metaplasia and, ultimately, leads to adenocarcinoma. Acid suppression has been the main strategy to treat GERD; however, it has not been proven to control esophageal malignancy effectively. In fact, its side effects have triggered multiple warnings from regulatory agencies. The high mortality and fast growth of esophageal cancer demand more vigorous efforts to look into its deeper mechanisms and come up with better therapeutic options. PMID:23236223

  10. Airborne particulate matter and human health: toxicological assessment and importance of size and composition of particles for oxidative damage and carcinogenic mechanisms.

    PubMed

    Valavanidis, Athanasios; Fiotakis, Konstantinos; Vlachogianni, Thomais

    2008-01-01

    Air pollution has been considered a hazard to human health. In the past decades, many studies highlighted the role of ambient airborne particulate matter (PM) as an important environmental pollutant for many different cardiopulmonary diseases and lung cancer. Numerous epidemiological studies in the past 30 years found a strong exposure-response relationship between PM for short-term effects (premature mortality, hospital admissions) and long-term or cumulative health effects (morbidity, lung cancer, cardiovascular and cardiopulmonary diseases, etc). Current research on airborne particle-induced health effects investigates the critical characteristics of particulate matter that determine their biological effects. Several independent groups of investigators have shown that the size of the airborne particles and their surface area determine the potential to elicit inflammatory injury, oxidative damage, and other biological effects. These effects are stronger for fine and ultrafine particles because they can penetrate deeper into the airways of the respiratory tract and can reach the alveoli in which 50% are retained in the lung parenchyma. Composition of the PM varies greatly and depends on many factors. The major components of PM are transition metals, ions (sulfate, nitrate), organic compound, quinoid stable radicals of carbonaceous material, minerals, reactive gases, and materials of biologic origin. Results from toxicological research have shown that PM have several mechanisms of adverse cellular effects, such as cytotoxicity through oxidative stress mechanisms, oxygen-free radical-generating activity, DNA oxidative damage, mutagenicity, and stimulation of proinflammatory factors. In this review, the results of the most recent epidemiological and toxicological studies are summarized. In general, the evaluation of most of these studies shows that the smaller the size of PM the higher the toxicity through mechanisms of oxidative stress and inflammation. Some studies

  11. A possible mechanism for the capture of microparticles by the earth and other planets of the solar system. [planetary gravitation effects on cosmic dust particles

    NASA Technical Reports Server (NTRS)

    Dibenedetto, F.

    1973-01-01

    By application of Lyttleton's theory for the formation of comets, it is shown that a possible mechanism for the origin and formation of a concentration of cosmic particles around the earth and the other planets of the solar system exists. In the vicinity of the neutral point, where the velocity of colliding particles is not greater than 6 km/s, it is found that if the solid particles after collision must remain in a solid state, there can be no possibility of accretion for Mercury, Mars, and the Moon, where the maximum value of the distance of the center of the planet to the asymptotic trajectory is less than the radius of the planet. On the other hand, the capture radii of microparticles in solid form varies from a minimum of 2.95 planetary radii for Venus and 3.47 for the Earth, to about 986 for Jupiter.

  12. Effect of mechanical milling on particle size, magnetic susceptibility and dielectric of synthetic toner colorant magnetite extracted from Indonesian iron sand

    NASA Astrophysics Data System (ADS)

    Zulaikah, S.; Mufti, N.; Fuad, A.; Dwi, L. D.

    2014-09-01

    As a colorant and additive substance for toner, magnetite (Fe3O4) has become main mineral that can produce electrical charge on printing process. In this research, we reports the effect of mechanical milling time to magnetic susceptibility, morphology and dielectric properties of synthetic toner The standard of the grain size of toner including of magnetite dissolved, are ranged from 2 to 10 micron or less, depending on the kind of toner. The results of this research show that the average of particle size decreases from 15μm to 5 μm by milling time between 6 hour to 9 hour and almost constant up to 12 hour. The magnetic susceptibility of the sample decreases as decreasing particle size, while the dielectric constant increases as decreasing particle size.

  13. Evaluating the Role of the Air-Solution Interface on the Mechanism of Subvisible Particle Formation Caused by Mechanical Agitation for an IgG1 mAb.

    PubMed

    Ghazvini, Saba; Kalonia, Cavan; Volkin, David B; Dhar, Prajnaparamita

    2016-05-01

    Mechanical agitation of monoclonal antibody (mAb) solutions often leads to protein particle formation. In this study, various formulations of an immunoglobulin G (IgG) 1 mAb were subjected to different controlled interfacial stresses using a Langmuir trough, and protein particles formed at the interface and measured in bulk solution were characterized using atomic force microscopy and flow digital imaging. Results were compared to mAb solutions agitated in glass vials and unstressed controls. At lower pH, mAb solutions exhibited larger hysteresis in their surface pressure versus area isotherms and increased number of particles in bulk solution, when subjected to interfacial stresses. mAb samples subjected to 750-1000 interfacial compression-expansion cycles in 6 h contained high particle numbers in bulk solution, and displayed similar particulation trends when agitated in vials. At compression rates of 50 cycles in 6 h, however, particle levels in mAb solutions were comparable to unstressed controls, despite protein aggregates being present at the air-solution interface. These results suggest that while the air-solution interface serves as a nucleation site for initiating protein aggregation, the number of protein particles measured in bulk mAb solutions depends on the total number of compression cycles that proteins at the air-solution interface are subjected to within a fixed time. PMID:27025981

  14. Growing local likelihood network: Emergence of communities

    NASA Astrophysics Data System (ADS)

    Chen, S.; Small, M.

    2015-10-01

    In many real situations, networks grow only via local interactions. New nodes are added to the growing network with information only pertaining to a small subset of existing nodes. Multilevel marketing, social networks, and disease models can all be depicted as growing networks based on local (network path-length) distance information. In these examples, all nodes whose distance from a chosen center is less than d form a subgraph. Hence, we grow networks with information only from these subgraphs. Moreover, we use a likelihood-based method, where at each step we modify the networks by changing their likelihood to be closer to the expected degree distribution. Combining the local information and the likelihood method, we grow networks that exhibit novel features. We discover that the likelihood method, over certain parameter ranges, can generate networks with highly modulated communities, even when global information is not available. Communities and clusters are abundant in real-life networks, and the method proposed here provides a natural mechanism for the emergence of communities in scale-free networks. In addition, the algorithmic implementation of network growth via local information is substantially faster than global methods and allows for the exploration of much larger networks.

  15. Pattern formation in a growing bacterial colony facilitated by extra-cellular polymeric substances

    NASA Astrophysics Data System (ADS)

    Ghosh, Pushpita; Mondal, Jagannath; Ben-Jacob, Eshel; Levine, Herbert

    2015-03-01

    Self-organization in bacterial colony is quite pervasive and diverse phenomena. Bacteria are known to self-organize into multicellular communities, commonly known as biofilms, in which microbial cells live in close association with a solid surface and are embedded in a self-produced extracellular polymeric substances(EPS). In such dense systems mechanical interactions among the structural components can be expected to significantly contribute to the morphological properties. By a simple particle-based simulation model of nonmotile rod-shaped bacterial cells and EPS secreted in a growing colony, we investigate how the combined mechanical effects can give rise naturally spatial heterogeneity observed in a biofilm. In our individual-based simulation model all the components interact mechanically via repulsive forces by pushing each other away as bacterial cells grow and divide consuming diffusing nutrient and produce EPS. We show that mechanical interactions control the collective behavior of the system, particularly, we show that the presence of non-adsorbing EPS leads spontaneous aggregation of bacterial cells by depletion attraction and generates phase separated patterns in a nonequilibrium growing colony.

  16. Growth mechanism, distribution characteristics and reinforcing behavior of (Ti, Nb)C particle in laser cladded Fe-based composite coating

    NASA Astrophysics Data System (ADS)

    Li, Qingtang; Lei, Yongping; Fu, Hanguang

    2014-10-01

    Over the past decade, researchers have demonstrated much interest in laser cladded metal matrix composite coatings for its good wear resistance, corrosion resistance, and high temperature properties. In this paper, in-situ (Ti, Nb)C particle reinforced Fe-based composite coatings were produced by laser cladding. The effects of Ti/Nb(atomic ratio) in the cladding powder on the formation mechanism and distribution characteristics of multiple particle were investigated. The results showed that when Ti/Nb > 1, Ti had a stronger ability to bond with C compared with Nb. (Ti, Nb)C multiple particles with TiC core formed in the molten pool. With the decrease of Ti/Nb, core-shell structure disappeared, the structure of particle got close to that of NbC gradually. It is found that the amount, area ratio and distribution of the reinforced particle in the coating containing Ti and Nb elements were improved, compared with these in the coating containing equal Nb element. When Ti/Nb = 1, the effects above-mentioned is most prominent, and the wear resistance of the coating is promoted obviously.

  17. TOF-SIMS Analysis of Sea Salt Particles: Imaging and Depth Profiling in the Discovery of an Unrecognized Mechanism for pH Buffering

    SciTech Connect

    Gaspar, Dan J.; Laskin, Alexander; Wang, Weihong; Hunt, Sherri W.; Finlayson-Pitts, Barbara J.

    2004-06-15

    As part of a broader effort at understanding the chemistry of sea salt particles, we have performed time-of-flight secondary ion mass spectroscopy (TOF-SIMS) analysis of individual sea salt particles deposited on a transmission electron microscopy (TEM) grid. Environmental scanning electron microscopy (ESEM) and TOF-SIMS analysis have, in conjunction with OH exposure studies, led to the discovery of an unrecognized buffering mechanism in the uptake and oxidation of SO2 in sea salt particles in the marine boundary layer. This chemistry may resolve several discrepancies in the atmospheric chemistry literature. Several challenges during the acquisition and interpretation of both imaging and depth profiling data on specific particles on the TEM grid identified by the ESEM were overcome. A description of the analysis challenges and the solutions ultimately developed to them is presented here, along with an account of how the TOF-SIMS data were incorporated into the overall research effort. Several issues unique to the analysis of high aspect ratio particles are addressed.[1

  18. TOF-SIMS Analysis of Sea Salt Particles: Imaging and Depth Profiling in the Discovery of an Unrecogized Mechanism for pH Buffering

    SciTech Connect

    Gaspar, Dan J.; Laskin, Alexander; Wang, Weihong; Hunt, Sherri W.; Finlayson-Pitts, Barbara J.

    2004-06-15

    As part of a broader effort at understanding the chemistry of sea salt particles, we have performed time-of-flight secondary ion mass spectroscopy (TOF-SIMS) analysis of individual sea salt particles deposited on a transmission electron microscopy (TEM) grid. Environmental scanning electron microscopy (ESEM) and TOF-SIMS analysis have, in conjunction with OH exposure studies, led to the discovery of an unrecognised buffering mechanism in the uptake and oxidation of SO2 in sea salt particles in the marine boundary layer. This chemistry may resolve several discrepancies in the atmospheric chemistry literature. Several challenges during the acquisition and interpretation of both imaging and depth profiling data on specific particles on the TEM grid identified by the ESEM were overcome. A description of the analysis challenges and the solutions ultimately developed to them is presented here, along with an account of how the TOF-SIMS data were incorporated into the overall research effort. Several issues unique to the analysis of high aspect ratio particles are addressed.[1

  19. Nano polypeptide particles reinforced polymer composite fibers.

    PubMed

    Li, Jiashen; Li, Yi; Zhang, Jing; Li, Gang; Liu, Xuan; Li, Zhi; Liu, Xuqing; Han, Yanxia; Zhao, Zheng

    2015-02-25

    Because of the intensified competition of land resources for growing food and natural textile fibers, there is an urgent need to reuse and recycle the consumed/wasted natural fibers as regenerated green materials. Although polypeptide was extracted from wool by alkaline hydrolysis, the size of the polypeptide fragments could be reduced to nanoscale. The wool polypeptide particles were fragile and could be crushed down to nano size again and dispersed evenly among polymer matrix under melt extrusion condition. The nano polypeptide particles could reinforce antiultraviolet capability, moisture regain, and mechanical properties of the polymer-polypeptide composite fibers. PMID:25647481

  20. Thermo-Mechanical Response of a TRISO Fuel Particle in a Fusion/Fission Engine for Incineration of Weapons Grade Plutonium

    SciTech Connect

    Caro, M; DeMange, P; Marian, J; Caro, A

    2009-12-08

    The Laser Inertial Fusion-based (LIFE) engine is an advanced energy concept under development at Lawrence Livermore National Laboratory (LLNL). LIFE engine could be used to drive a subcritical fission blanket with fertile or fissile fuel. Current LIFE engine designs envisages fuel in pebble bed form with TRISO (tristructural isotropic) particles embedded in a graphite matrix, and pebbles flowing in molten salt Flibe (2LiF+BeF{sub 2}) coolant at T {approx} 700C. Weapons-grade plutonium (WGPu) fuel is an attractive option for LIFE engine involving the achievement of high fractional burnups in a short lifetime frame. However, WGPu LIFE engine operating conditions of high neutron fast fluence, high radiation damage, and high Helium and Hydrogen production pose severe challenges for typical TRISO particles. The thermo-mechanical fuel performance code HUPPCO (High burn-Up fuel Pebble Performance COde) currently under development accounts for spatial and time dependence of the material elastic properties, temperature, and irradiation swelling and creep mechanisms. In this work, some aspects of the thermo-mechanical response of TRISO particles used for incineration of weapons grade fuel in LIFE engine are analyzed. Preliminary results show the importance of developing reliable high-fidelity models of the performance of these new fuel designs and the need of new experimental data relevant to WGPu LIFE conditions.

  1. In situ observations of new particle formation in the tropical upper troposphere: the role of clouds and the nucleation mechanism

    NASA Astrophysics Data System (ADS)

    Weigel, R.; Borrmann, S.; Kazil, J.; Minikin, A.; Stohl, A.; Wilson, J. C.; Reeves, J. M.; Kunkel, D.; de Reus, M.; Frey, W.; Lovejoy, E. R.; Volk, C. M.; Viciani, S.; D'Amato, F.; Schiller, C.; Peter, T.; Schlager, H.; Cairo, F.; Law, K. S.; Shur, G. N.; Belyaev, G. V.; Curtius, J.

    2011-09-01

    New particle formation (NPF), which generates nucleation mode aerosol, was observed in the tropical Upper Troposphere (UT) and Tropical Tropopause Layer (TTL) by in situ airborne measurements over South America (January-March 2005), Australia (November-December 2005), West Africa (August 2006) and Central America (2004-2007). Particularly intense NPF was found at the bottom of the TTL. Measurements with a set of condensation particle counters (CPCs) with different dp50 (50% lower size detection efficiency diameter or "cut-off diameter") were conducted on board the M-55 Geophysica in the altitude range of 12.0-20.5 km and on board the DLR Falcon-20 at up to 11.5 km altitude. On board the NASA WB-57F size distributions were measured over Central America in the 4 to 1000 nm diameter range with a system of nucleation mode aerosol spectrometers. Nucleation mode particle concentrations (NNM) were derived from these measurements which allow for identifying many NPF events with NNM in the range of thousands of particles per cm3. Over Australia and West Africa, we identified NPF in the outflow of tropical convection, in particular of a Mesoscale Convective System (MCS). Newly formed particles with NNM > 1000 cm-3 were found to coexist with ice cloud particles (dp > 2 μm) as long as cloud particle concentrations remained below 2 cm-3. The occurrence of NPF within the upper troposphere and the TTL was generally confined within 340 K to 380 K potential temperature, but NPF was of particular strength between 350 K and 370 K (i.e. ~1-4 km below the cold point tropopause). Analyses of the aerosol volatility (at 250 °C) show that in the TTL on average 75-90% of the particles were volatile, compared to typically only 50% in the extra-tropical UT, indicative for the particles to mainly consist of H2SO4-H2O and possibly organic compounds. Along two flight segments over Central and South America (24 February 2005 and 7 August 2006, at 12.5 km altitude) in cloud free air, above thin

  2. Application of porous titanium in prosthesis production using a moldless process: Evaluation of physical and mechanical properties with various particle sizes, shapes, and mixing ratios.

    PubMed

    Prananingrum, Widyasri; Tomotake, Yoritoki; Naito, Yoshihito; Bae, Jiyoung; Sekine, Kazumitsu; Hamada, Kenichi; Ichikawa, Tetsuo

    2016-08-01

    The prosthetic applications of titanium have been challenging because titanium does not possess suitable properties for the conventional casting method using the lost wax technique. We have developed a production method for biomedical application of porous titanium using a moldless process. This study aimed to evaluate the physical and mechanical properties of porous titanium using various particle sizes, shapes, and mixing ratio of titanium powder to wax binder for use in prosthesis production. CP Ti powders with different particle sizes, shapes, and mixing ratios were divided into five groups. A 90:10wt% mixture of titanium powder and wax binder was prepared manually at 70°C. After debinding at 380°C, the specimen was sintered in Ar at 1100°C without a mold for 1h. The linear shrinkage ratio of sintered specimens ranged from 2.5% to 14.2%. The linear shrinkage ratio increased with decreasing particle size. While the linear shrinkage ratio of Groups 3, 4, and 5 were approximately 2%, Group 1 showed the highest shrinkage of all. The bending strength ranged from 106 to 428MPa under the influence of porosity. Groups 1 and 2 presented low porosity followed by higher strength. The shear bond strength ranged from 32 to 100MPa. The shear bond strength was also particle-size dependent. The decrease in the porosity increased the linear shrinkage ratio and bending strength. Shrinkage and mechanical strength required for prostheses were dependent on the particle size and shape of titanium powders. These findings suggested that this production method can be applied to the prosthetic framework by selecting the material design. PMID:27148637

  3. Growing matter: a review of growth in living systems.

    PubMed

    Kuhl, Ellen

    2014-01-01

    Living systems can grow, develop, adapt, and evolve. These phenomena are non-intuitive to traditional engineers and often difficult to understand. Yet, classical engineering tools can provide valuable insight into the mechanisms of growth in health and disease. Within the past decade, the concept of incompatible configurations has evolved as a powerful tool to model growing systems within the framework of nonlinear continuum mechanics. However, there is still a substantial disconnect between the individual disciplines, which explore the phenomenon of growth from different angles. Here we show that the nonlinear field theories of mechanics provide a unified concept to model finite growth by means of a single tensorial internal variable, the second order growth tensor. We review the literature and categorize existing growth models by means of two criteria: the microstructural appearance of growth, either isotropic or anisotropic; and the microenvironmental cues that drive the growth process, either chemical or mechanical. We demonstrate that this generic concept is applicable to a broad range of phenomena such as growing arteries, growing tumors, growing skin, growing airway walls, growing heart valve leaflets, growing skeletal muscle, growing plant stems, growing heart valve annuli, and growing cardiac muscle. The proposed approach has important biological and clinical applications in atherosclerosis, in-stent restenosis, tumor invasion, tissue expansion, chronic bronchitis, mitral regurgitation, limb lengthening, tendon tear, plant physiology, dilated and hypertrophic cardiomyopathy, and heart failure. Understanding the mechanisms of growth in these chronic conditions may open new avenues in medical device design and personalized medicine to surgically or pharmacologically manipulate development and alter, control, or revert disease progression. PMID:24239171

  4. Effect of processing methods on the mechanical properties of natural rubber filled with stearic acid modified soy protein particles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Natural rubber was reinforced with stearic acid modified soy protein particles prepared with a microfluidizing and ball milling process. Longer ball milling time tends to increase tensile strength of the rubber composites. Elastic modulus of the composites increased with the increasing filler concen...

  5. Self-Assembled Colloidal Particle Clusters from In Situ Pickering-Like Emulsion Polymerization via Single Electron Transfer Mechanism.

    PubMed

    Yuan, Jinfeng; Zhao, Weiting; Pan, Mingwang; Zhu, Lei

    2016-08-01

    A simple route is reported to synthesize colloidal particle clusters (CPCs) from self-assembly of in situ poly(vinylidene fluoride)/poly(styrene-co-tert-butyl acrylate) [PVDF/P(St-co-tBA)] Janus particles through one-pot seeded emulsion single electron transfer radical polymerization. In the in situ Pickering-like emulsion polymerization, the tBA/St/PVDF feed ratio and polymerization temperature are important for the formation of well-defined CPCs. When the tBA/St/PVDF feed ratio is 0.75 g/2.5 g/0.5 g and the reaction temperature is 35 °C, relatively uniform raspberry-like CPCs are obtained. The hydrophobicity of the P(St-co-tBA) domains and the affinity of PVDF to the aqueous environment are considered to be the driving force for the self-assembly of the in situ formed PVDF/P(St-co-tBA) Janus particles. The resultant raspberry-like CPCs with PVDF particles protruding outward may be promising for superhydrophobic smart coatings. PMID:27226331

  6. Sociology: The growing climate divide

    NASA Astrophysics Data System (ADS)

    Hoffman, Andrew J.

    2011-07-01

    Climate change has reached the level of a 'scientific consensus', but is not yet a 'social consensus'. New analysis highlights that a growing divide between liberals and conservatives in the American public is a major obstacle to achieving this end.

  7. Birth of space plant growing

    NASA Technical Reports Server (NTRS)

    Mashinskiy, A.; Nechitaylo, G.

    1983-01-01

    The attempts, and successes, to grow plants in space, and get them to fully develop, bloom and produce seeds using orchids are presented. The psychological advantages of the presence of plants onboard space vehicles and space stations is indicated.

  8. Reaction of oleic acid particles with NO3 radicals: Products, mechanism, and implications for radical-initiated organic aerosol oxidation.

    PubMed

    Docherty, Kenneth S; Ziemann, Paul J

    2006-03-16

    The heterogeneous reaction of liquid oleic acid aerosol particles with NO3 radicals in the presence of NO2, N2O5, and O2 was investigated in an environmental chamber using a combination of on-line and off-line mass spectrometric techniques. The results indicate that the major reaction products, which are all carboxylic acids, consist of hydroxy nitrates, carbonyl nitrates, dinitrates, hydroxydinitrates, and possibly more highly nitrated products. The key intermediate in the reaction is the nitrooxyalkylperoxy radical, which is formed by the addition of NO3 to the carbon-carbon double bond and subsequent addition of O2. The nitrooxyalkylperoxy radicals undergo self-reactions to form hydroxy nitrates and carbonyl nitrates, and may also react with NO2 to form nitrooxy peroxynitrates. The latter compounds are unstable and decompose to carbonyl nitrates and dinitrates. It is noteworthy that in this reaction nitrooxyalkoxy radicals appear not to be formed, as indicated by the absence of the expected products of decomposition or isomerization of these species. This is different from gas-phase alkene-NO3 reactions, in which a large fraction of the products are formed through these pathways. The results may indicate that, for liquid organic aerosol particles in low NOx environments, the major products of the radical-initiated oxidation (including by OH radicals) of unsaturated and saturated organic compounds will be substituted forms of the parent compound rather than smaller decomposition products. These compounds will remain in the particle and can potentially enhance particle hygroscopicity and the ability of particles to act as cloud condensation nuclei. PMID:16526637

  9. Quantum grow--A quantum dynamics sampling approach for growing potential energy surfaces and nonadiabatic couplings

    SciTech Connect

    Godsi, Oded; Peskin, Uri; Collins, Michael A.

    2010-03-28

    A quantum sampling algorithm for the interpolation of diabatic potential energy matrices by the Grow method is introduced. The new procedure benefits from penetration of the wave packet into classically forbidden regions, and the accurate quantum mechanical description of nonadiabatic transitions. The increased complexity associated with running quantum dynamics is reduced by using approximate low order expansions of the nuclear wave function within a Multi-configuration time-dependent Hartree scheme during the Grow process. The sampling algorithm is formulated and applied for three representative test cases, demonstrating the recovery of analytic potentials by the interpolated ones, and the convergence of a dynamic observable.

  10. The Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) yo-yo despin and solar array deployment mechanism

    NASA Technical Reports Server (NTRS)

    Kellogg, James W.

    1993-01-01

    The SAMPEX spacecraft, successfully launched in July 1992, carried a yo-yo despin system and deployable solar arrays. The despin and solar array mechanisms formed an integral system as the yo-yo cables held the solar array release mechanism in place. The SAMPEX design philosophy was to minimize size and weight through the use of a predominantly single string system. The design challenge was to build a system in a limited space, which was reliable with minimal redundancy. This paper covers the design and development of the SAMPEX yo-yo despin and solar array deployment mechanisms. The problems encountered during development and testing will also be discussed.

  11. Study of applied magnetic field magnetoplasmadynamic thrusters with particle-in-cell and Monte Carlo collision. II. Investigation of acceleration mechanisms

    NASA Astrophysics Data System (ADS)

    Tang, Hai-Bin; Cheng, Jiao; Liu, Chang; York, Thomas M.

    2012-07-01

    The particle-in-cell method previously described in paper (I) has been applied to the investigation of acceleration mechanisms in applied-field magnetoplasmadynamic thrusters. This new approach is an alternative to magnetohydrodynamics models and allows nonlocal dynamic effects of particles and improved transport properties. It was used to model a 100 kW, steady-state, applied-field, argon magnetoplasmadynamic thruster to study the physical acceleration processes with discharge currents of 1000-1500 A, mass flow rates of 0.025-0.1 g/s and applied magnetic field strengths of 0.034-0.102 T. The total thrust calculations were used to verify the theoretical approach by comparison with experimental data. Investigations of the acceleration model offer an underlying understanding of applied-field magnetoplasmadynamic thrusters, including the following conclusions: (1) swirl acceleration mechanism is the dominant contributor to the plasma acceleration, and self-magnetic, Hall, gas-dynamic, and swirl acceleration mechanisms are in an approximate ratio of 1:10:10:100; (2) the Hall acceleration produced mainly by electron swirl is insensitive to the change of externally applied magnetic field and shows only slight increases when the current is raised; (3) self-magnetic acceleration is normally negligible for all cases, while the gas-dynamic acceleration contribution increases with increasing applied magnetic field strength, discharge current, and mass flow rate.

  12. Study of applied magnetic field magnetoplasmadynamic thrusters with particle-in-cell and Monte Carlo collision. II. Investigation of acceleration mechanisms

    SciTech Connect

    Tang Haibin; Cheng Jiao; Liu Chang; York, Thomas M.

    2012-07-15

    The particle-in-cell method previously described in paper (I) has been applied to the investigation of acceleration mechanisms in applied-field magnetoplasmadynamic thrusters. This new approach is an alternative to magnetohydrodynamics models and allows nonlocal dynamic effects of particles and improved transport properties. It was used to model a 100 kW, steady-state, applied-field, argon magnetoplasmadynamic thruster to study the physical acceleration processes with discharge currents of 1000-1500 A, mass flow rates of 0.025-0.1 g/s and applied magnetic field strengths of 0.034-0.102 T. The total thrust calculations were used to verify the theoretical approach by comparison with experimental data. Investigations of the acceleration model offer an underlying understanding of applied-field magnetoplasmadynamic thrusters, including the following conclusions: (1) swirl acceleration mechanism is the dominant contributor to the plasma acceleration, and self-magnetic, Hall, gas-dynamic, and swirl acceleration mechanisms are in an approximate ratio of 1:10:10:100; (2) the Hall acceleration produced mainly by electron swirl is insensitive to the change of externally applied magnetic field and shows only slight increases when the current is raised; (3) self-magnetic acceleration is normally negligible for all cases, while the gas-dynamic acceleration contribution increases with increasing applied magnetic field strength, discharge current, and mass flow rate.

  13. Morphological instability of a thermophoretically growing deposit

    NASA Technical Reports Server (NTRS)

    Castillo, Jose L.; Garcia-Ybarra, Pedro L.; Rosner, Daniel E.

    1992-01-01

    The stability of the planar interface of a structureless solid growing from a depositing component dilute in a carrier fluid is studied when the main solute transport mechanism is thermal (Soret) diffusion. A linear stability analysis, carried out in the limit of low growth Peclet number, leads to a dispersion relation which shows that the planar front is unstable either when the thermal diffusion factor of the condensing component is positive and the latent heat release is small or when the thermal diffusion factor is negative and the solid grows over a thermally-insulating substrate. Furthermore, the influence of interfacial energy effects and constitutional supersaturation in the vicinity of the moving interface is analyzed in the limit of very small Schmidt numbers (small solute Fickian diffusion). The analysis is relevant to physical vapor deposition of very massive species on cold surfaces, as in recent experiments of organic solid film growth under microgravity conditions.

  14. Understanding of the mechanical and structural changes induced by alpha particles and heavy ions in the French simulated nuclear waste glass

    NASA Astrophysics Data System (ADS)

    Karakurt, G.; Abdelouas, A.; Guin, J.-P.; Nivard, M.; Sauvage, T.; Paris, M.; Bardeau, J.-F.

    2016-07-01

    Borosilicate glasses are considered for the long-term confinement of high-level nuclear wastes. External irradiations with 1 MeV He+ ions and 7 MeV Au5+ ions were performed to simulate effects produced by alpha particles and by recoil nuclei in the simulated SON68 nuclear waste glass. To better understand the structural modifications, irradiations were also carried out on a 6-oxides borosilicate glass, a simplified version of the SON68 glass (ISG glass). The mechanical and macroscopic properties of the glasses were studied as function of the deposited electronic and nuclear energies. Alpha particles and gold ions induced a volume change up to -0.7% and -2.7%, respectively, depending on the glass composition. Nano-indentations tests were used to determine the mechanical properties of the irradiated glasses. A decrease of about -22% to -38% of the hardness and a decrease of the reduced Young's modulus by -8% were measured after irradiations. The evolution of the glass structure was studied by Raman spectroscopy, and also 11B and 27Al Nuclear Magnetic Resonance (MAS-NMR) on a 20 MeV Kr irradiated ISG glass powder. A decrease of the silica network connectivity after irradiation with alpha particles and gold ions is deduced from the structural changes observations. NMR spectra revealed a partial conversion of BO4 to BO3 units but also a formation of AlO5 and AlO6 species after irradiation with Kr ions. The relationships between the mechanical and structural changes are also discussed.

  15. Scene segmentation through region growing

    NASA Technical Reports Server (NTRS)

    Latty, R. S.

    1984-01-01

    A computer algorithm to segment Landsat Thematic Mapper (TM) images into areas representing surface features is described. The algorithm is based on a region growing approach and uses edge elements and edge element orientation to define the limits of the surface features. Adjacent regions which are not separated by edges are linked to form larger regions. Some of the advantages of scene segmentation over conventional TM image extraction algorithms are discussed, including surface feature analysis on a pixel-by-pixel basis, and faster identification of the pixels in each region. A detailed flow diagram of region growing algorithm is provided.

  16. Rotating Vessels for Growing Protein Crystals

    NASA Technical Reports Server (NTRS)

    Cottingham, Paul

    2005-01-01

    Rotating vessels have been proposed as means of growing larger, more nearly uniform protein crystals than would otherwise be possible in the presence of normal Earth gravitation. Heretofore, nonrotating vessels have been used. It is difficult to grow high-quality protein crystals in the terrestrial gravitational field because of convection plumes created by the interaction between gravitation and density gradients in protein-solution depletion layers around growing crystals. The density gradients and the associated convection plumes cause the surfaces of growing crystals to be exposed to nonuniform solution densities, thereby causing the crystals to form in irregular shapes. The microgravitational environment of outer space has been utilized to eliminate gravitation-induced convection, but this approach is generally not favorable because of the high cost and limited availability of space flight. The use of a rotating vessel according to the proposal is intended to ameliorate the effects of gravitation and the resultant convection, relative to the corresponding effects in a non-rotating vessel. The rotation would exert an averaging effect over time, distributing the convective force on the depletion layer. Therefore, the depletion layer would be more nearly uniform and, as a result, the growing crystal would be more nearly perfect. The proposal admits of variations (see figure), including the following: The growing crystal could be rotated about its own central axis or an external axis. The crystal-growth vessel could be of any of various shapes, including cylindrical, hemispherical, conical, and combinations thereof. The crystal-growth vessel could be suspended in a viscous fluid in an outer vessel to isolate the growing crystal from both ambient vibrations and vibrations induced by a mechanism that drives the rotation. The rotation could be coupled to the crystal-growth vessel by viscous or magnetic means. The crystal-growth vessel could be supported within the

  17. The effects of microgravity on protein crystallization: evidence for concentration gradients around growing crystals

    NASA Astrophysics Data System (ADS)

    McPherson, Alexander; Malkin, Alexander J.; Kuznetsov, Yurii G.; Koszelak, Stan; Wells, Mark; Jenkins, Greg; Howard, Jeff; Lawson, Greg

    1999-01-01

    Atomic force microscopy (AFM) investigations have revealed that macromolecular crystals, during their growth, incorporate an extensive array of impurities. These vary from individual molecules to large particles, and microcrystals in the micron size range. AFM, along with X-ray topology, has further shown that the density of defects and faults in most macromolecular crystals is very high in comparison with conventional crystals. The high defect density is a consequence of the incorporation of impurities, misoriented nutrient molecules, and aggregates of molecules. High defect and impurity density, contributes to a deterioration of both the mechanical and the diffraction properties of crystals. In microgravity, access by impurities and aggregates to growing crystal surfaces is restricted due to altered fluid transport properties. We designed, and have now constructed an instrument, the observable protein crystal growth apparatus (OPCGA) that employs a fused optics, phase shift, Mach-Zehnder interferometer to analyze the fluid environment around growing crystals. Using this device, which will ultimately be employed on the international space station, we have, in thin cells on earth, succeeded in directly visualizing concentration gradients around growing protein crystals. This provides the first direct evidence that quasi-stable depletion zones formed around growing crystals in space may explain the improved quality of macromolecular crystals grown in microgravity. Further application of the interferometric technique will allow us to quantitatively describe the shapes, extent, and magnitudes of the concentration gradients and to evaluate their degree of stability.

  18. The Impact of Oil Consumption Mechanisms on Diesel Exhaust Particle Size Distributions and Detailed Exhaust Chemical Composition

    SciTech Connect

    Stetter, J; Forster, N; Ghandhi, J; Foster, D

    2003-08-24

    Detailed exhaust emission data have been taken from a Cummins N-14 single cylinder research engine in which the oil consumption was varied by different engine modifications. Low sulfur fuel was used, and oil consumption was varied by modifying the intake valve stem seals, the exhaust valve stem seals, the oil control ring and combinations of these modifications. Detailed measurements of exhaust gas particle size distributions and chemical composition were made for the various oil consumption configurations for a range of engine loads and speeds. The particulate mass was measured with TEOM and traditional gravimetric filter methods. Filter data for EC/OC, sulfates and trace metals have been taken and analyzed. The trace metals in the particulate mass serve as the basis for assessing oil consumption at the different operating conditions. The data indicate that the oil consumption for the steady state testing done here was approximately an order of magnitude below oil consumption values cited in the literature. We did measure changes in the details of the chemical composition of the particulate for the different engine operating conditions, but it did not correlate with changes in the oil consumption. Furthermore, the data indicate that the particle size distribution is not strongly impacted by low level oil consumption variations observed in this work.

  19. Growing Ideas, 1990-1993.

    ERIC Educational Resources Information Center

    Pranis, Eve, Ed.

    1993-01-01

    This series of journals includes volumes 1-4 of "Growing Ideas," a journal of garden-based learning. Each issue provides instructional ideas, horticultural information and a forum for exchange among teachers using classroom gardening to stimulate learning. Ideas in each issue are separated into three sections. The "Green Tips" section presents…

  20. Exploring Classroom Hydroponics. Growing Ideas.

    ERIC Educational Resources Information Center

    National Gardening Association, Burlington, VT.

    Growing Ideas, the National Gardening Association's series for elementary, middle, and junior high school educators, helps teachers engage students in using plants and gardens as contexts for developing a deeper, richer understanding of the world around them. This volume's focus is on hydroponics. It presents basic hydroponics information along…

  1. Growing an Emerging Research University

    ERIC Educational Resources Information Center

    Birx, Donald L.; Anderson-Fletcher, Elizabeth; Whitney, Elizabeth

    2013-01-01

    The emerging research college or university is one of the most formidable resources a region has to reinvent and grow its economy. This paper is the first of two that outlines a process of building research universities that enhance regional technology development and facilitate flexible networks of collaboration and resource sharing. Although the…

  2. Growing Patterns: Seeing beyond Counting

    ERIC Educational Resources Information Center

    Markworth, Kimberly A.

    2012-01-01

    Over the past two decades, mathematical patterns have been acknowledged as important early components of children's development of algebraic reasoning (NCTM 2000). In particular, growing patterns have attracted significant attention as a context that helps students develop an understanding of functional relationships (Lee and Freiman 2006; Moss et…

  3. Growing Your Own: Minority Teachers

    ERIC Educational Resources Information Center

    Singh, Delar K.; Stoloff, David L.

    2007-01-01

    In the USA, the number of school age children who represent minority backgrounds is rapidly growing. However, despite several efforts, the teaching force remains primarily White. The purpose of this paper is to describe a residential future teachers program in Connecticut which recruits minority rising juniors and seniors from high schools across…

  4. How Does Your Garlic Grow?

    ERIC Educational Resources Information Center

    Shimabukuro, Mary A.; Fearing, Vickie

    1993-01-01

    Garlic is an ideal plant for the elementary classroom. It grows rapidly in water without aeration for several weeks and remains relatively free of microbial contamination. Simple experiments with garlic purchased at grocery stores can illustrate various aspects of plant growth. (PR)

  5. Colleges' Earmarks Grow, Amid Criticism

    ERIC Educational Resources Information Center

    Brainard, Jeffrey; Hermes, J. J.

    2008-01-01

    A record-breaking number of Congressional pork-barrel projects this year has loaded college and university plates with more earmarks than ever before, despite growing worries that the noncompetitive grants undermine the American scientific enterprise, and in spite of promises by some lawmakers to cut back. An analysis by "The Chronicle" shows that…

  6. How the pilidium larva grows

    PubMed Central

    2014-01-01

    Background For animal cells, ciliation and mitosis appear to be mutually exclusive. While uniciliated cells can resorb their cilium to undergo mitosis, multiciliated cells apparently can never divide again. Nevertheless, many multiciliated epithelia in animals must grow or undergo renewal. The larval epidermis in a number of marine invertebrate larvae, such as those of annelids, mollusks and nemerteans, consists wholly or in part of multiciliated epithelial cells, generally organized into a swimming and feeding apparatus. Many of these larvae must grow substantially to reach metamorphosis. Do individual epithelial cells simply expand to accommodate an increase in body size, or are there dividing cells amongst them? If some cells divide, where are they located? Results We show that the nemertean pilidium larva, which is almost entirely composed of multiciliated cells, retains pockets of proliferative cells in certain regions of the body. Most of these are found near the larval ciliated band in the recesses between the larval lobes and lappets, which we refer to as axils. Cells in the axils contribute both to the growing larval body and to the imaginal discs that form the juvenile worm inside the pilidium. Conclusions Our findings not only explain how the almost-entirely multiciliated pilidium can grow, but also demonstrate direct coupling of larval and juvenile growth in a maximally-indirect life history. PMID:24690541

  7. Growing Crystals on the Ceiling.

    ERIC Educational Resources Information Center

    Christman, Robert A.

    1980-01-01

    Described is a method of studying growing crystals in a classroom utilizing a carrousel projector standing vertically. A saturated salt solution is placed on a slide on the lens of the projector and the heat from the projector causes the water to evaporate and salt to crystalize. (Author/DS)

  8. Organization of growing random networks

    SciTech Connect

    Krapivsky, P. L.; Redner, S.

    2001-06-01

    The organizational development of growing random networks is investigated. These growing networks are built by adding nodes successively, and linking each to an earlier node of degree k with an attachment probability A{sub k}. When A{sub k} grows more slowly than linearly with k, the number of nodes with k links, N{sub k}(t), decays faster than a power law in k, while for A{sub k} growing faster than linearly in k, a single node emerges which connects to nearly all other nodes. When A{sub k} is asymptotically linear, N{sub k}(t){similar_to}tk{sup {minus}{nu}}, with {nu} dependent on details of the attachment probability, but in the range 2{lt}{nu}{lt}{infinity}. The combined age and degree distribution of nodes shows that old nodes typically have a large degree. There is also a significant correlation in the degrees of neighboring nodes, so that nodes of similar degree are more likely to be connected. The size distributions of the in and out components of the network with respect to a given node{emdash}namely, its {open_quotes}descendants{close_quotes} and {open_quotes}ancestors{close_quotes}{emdash}are also determined. The in component exhibits a robust s{sup {minus}2} power-law tail, where s is the component size. The out component has a typical size of order lnt, and it provides basic insights into the genealogy of the network.

  9. Factors affecting the microstructure and mechanical properties of Ti-Al3Ti core-shell-structured particle-reinforced Al matrix composites

    NASA Astrophysics Data System (ADS)

    Guo, Baisong; Yi, Jianhong; Ni, Song; Shen, Rujuan; Song, Min

    2016-04-01

    This work studied the effects of matrix powder and sintering temperature on the microstructure and mechanical properties of in situ formed Ti-Al3Ti core-shell-structured particle-reinforced pure Al-based composites. It has been shown that both factors have significant effects on the morphology of the reinforcements and densification behaviour of the composites. Due to the strong interfacial bonding and the limitation of the crack propagation in the intermetallic shell during deformation by soft Al matrix and Ti core, the composite fabricated using fine spherical-shaped Al powder and sintered at 570 °C for 5 h has the optimal combination of the overall mechanical properties. The study provides a direction for the optimum combination of high strength and ductility of the composites by adjusting the fabrication parameters.

  10. 7 CFR 319.37-8 - Growing media.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... growing, storing, and shipping in compliance with 7 CFR 319.37-8(f); and (6) If the accompanying... affecting § 319.37-8, see the List of CFR Sections Affected, which appears in the Finding Aids section of... inorganic fibers, peat, perlite, phenol formaldehyde, plastic particles, polyethylene, polymer...

  11. Degradation mechanisms of Platinum Nanoparticle Catalysts in Proton Exchange Membrane Fuel Cells: The Role of Particle Size

    SciTech Connect

    Yu, Kang; Groom, Daniel J.; Wang, Xiaoping; Yang, Zhiwei; Gummalla, Mallika; Ball, Sarah C.; Myers, Deborah J.; Ferreira, Paulo J.

    2014-10-14

    Five membrane-electrode assemblies (MEAs) with different average sizes of platinum (Pt) nanoparticles (2.2, 3.5, 5.0, 6.7, and 11.3 nm) in the cathode were analyzed before and after potential cycling (0.6 to 1.0 V, 50 mV/s) by transmission electron microscopy. Cathodes loaded with 2.2 nm and 3.5 nm catalyst nanoparticles exhibit the following changes during electrochemical cycling: (i) substantial broadening of the size distribution relative to the initial size distribution, (ii) presence of coalesced particles within the electrode, and (iii) precipitation of sub-micron-sized particles with complex shapes within the membrane. In contrast, cathodes loaded with 5.0 nm, 6.7 nm and 11.3 nm size catalyst nanoparticles are significantly less prone to the aforementioned effects. As a result, the electrochemically-active surface area (ECA) of MEA cathodes loaded with 2.2 nm and 3.5 nm nanoparticle catalysts degrades dramatically within 1,000 cycles of operation, while the electrochemically-active surface area of MEA cathodes loaded with 5.0 nm, 6.7 nm and 11.3 nm nanoparticle catalysts appears to be stable even after 10,000 cycles. The loss in MEA performance for cathodes loaded with 2.2 nm and 3.5 nm nanoparticle catalysts appears to be due to the loss in electrochemically-active surface area concomitant with the observed morphological changes in these nanoparticle catalysts

  12. Competing source and loss mechanisms due to wave-particle interactions in Earth's outer radiation belt during the 30 September to 3 October 2012 geomagnetic storm

    NASA Astrophysics Data System (ADS)

    Turner, D. L.; Angelopoulos, V.; Li, W.; Bortnik, J.; Ni, B.; Ma, Q.; Thorne, R. M.; Morley, S. K.; Henderson, M. G.; Reeves, G. D.; Usanova, M.; Mann, I. R.; Claudepierre, S. G.; Blake, J. B.; Baker, D. N.; Huang, C.-L.; Spence, H.; Kurth, W.; Kletzing, C.; Rodriguez, J. V.

    2014-03-01

    Drastic variations of Earth's outer radiation belt electrons ultimately result from various competing source, loss, and transport processes, to which wave-particle interactions are critically important. Using 15 spacecraft including NASA's Van Allen Probes, THEMIS, and SAMPEX missions and NOAA's GOES and POES constellations, we investigated the evolution of the outer belt during the strong geomagnetic storm of 30 September to 3 October 2012. This storm's main phase dropout exhibited enhanced losses to the atmosphere at L* < 4, where the phase space density (PSD) of multi-MeV electrons dropped by over an order of magnitude in <4 h. Based on POES observations of precipitating >1 MeV electrons and energetic protons, SAMPEX >1 MeV electrons, and ground observations of band-limited Pc1-2 wave activity, we show that this sudden loss was consistent with pitch angle scattering by electromagnetic ion cyclotron waves in the dusk magnetic local time sector at 3 < L* < 4. At 4 < L* < 5, local acceleration was also active during the main and early recovery phases, when growing peaks in electron PSD were observed by both Van Allen Probes and THEMIS. This acceleration corresponded to the period when IMF Bz was southward, the AE index was >300 nT, and energetic electron injections and whistler-mode chorus waves were observed throughout the inner magnetosphere for >12 h. After this period, Bz turned northward, and injections, chorus activity, and enhancements in PSD ceased. Overall, the outer belt was depleted by this storm. From the unprecedented level of observations available, we show direct evidence of the competitive nature of different wave-particle interactions controlling relativistic electron fluxes in the outer radiation belt.

  13. How faceted liquid droplets grow tails

    PubMed Central

    Guttman, Shani; Sapir, Zvi; Schultz, Moty; Butenko, Alexander V.; Ocko, Benjamin M.; Deutsch, Moshe; Sloutskin, Eli

    2016-01-01

    Liquid droplets, widely encountered in everyday life, have no flat facets. Here we show that water-dispersed oil droplets can be reversibly temperature-tuned to icosahedral and other faceted shapes, hitherto unreported for liquid droplets. These shape changes are shown to originate in the interplay between interfacial tension and the elasticity of the droplet’s 2-nm-thick interfacial monolayer, which crystallizes at some T = Ts above the oil’s melting point, with the droplet’s bulk remaining liquid. Strikingly, at still-lower temperatures, this interfacial freezing (IF) effect also causes droplets to deform, split, and grow tails. Our findings provide deep insights into molecular-scale elasticity and allow formation of emulsions of tunable stability for directed self-assembly of complex-shaped particles and other future technologies. PMID:26733673

  14. How faceted liquid droplets grow tails.

    PubMed

    Guttman, Shani; Sapir, Zvi; Schultz, Moty; Butenko, Alexander V; Ocko, Benjamin M; Deutsch, Moshe; Sloutskin, Eli

    2016-01-19

    Liquid droplets, widely encountered in everyday life, have no flat facets. Here we show that water-dispersed oil droplets can be reversibly temperature-tuned to icosahedral and other faceted shapes, hitherto unreported for liquid droplets. These shape changes are shown to originate in the interplay between interfacial tension and the elasticity of the droplet's 2-nm-thick interfacial monolayer, which crystallizes at some T = Ts above the oil's melting point, with the droplet's bulk remaining liquid. Strikingly, at still-lower temperatures, this interfacial freezing (IF) effect also causes droplets to deform, split, and grow tails. Our findings provide deep insights into molecular-scale elasticity and allow formation of emulsions of tunable stability for directed self-assembly of complex-shaped particles and other future technologies. PMID:26733673

  15. Mobilization of iron from coal fly ash was dependent upon the particle size and source of coal: analysis of rates and mechanisms.

    PubMed

    Veranth, J M; Smith, K R; Hu, A A; Lighty, J S; Aust, A E

    2000-05-01

    The observed iron mobilization rate from size-fractionated coal fly ash is consistent with the model predictions for a limiting case of mass transfer where the dominant resistance is diffusion through a layer of depleted solid between the surface of spherical particles and a shrinking core of unreacted material. The rate of mobilization of iron from coal fly ash under physiologically relevant conditions in vitro was previously shown to depend on the size of the ash particles and on the source of the coal, and these in vitro measurements have been shown to correlate with indirect measurements of excess iron in cultured cells. Existing iron mobilization data were compared to mathematical models for mass transfer and chemical reaction in solid-liquid heterogeneous systems. Liquid-phase diffusion resistance can be ruled out as the rate-limiting mechanism for iron mobilization as the model predictions for this case are clearly inconsistent with the measurements. Other plausible hypotheses, such as a rate limited by a heterogeneous surface reaction, cannot be conclusively ruled out by the available data. These mathematical analysis methods are applicable to the design of future experiments to determine the rate-limiting mechanism for the mobilization of iron and of other transition metals from both ambient air samples and surrogates for major sources of particulate air pollution. PMID:10813655

  16. Mechanics

    NASA Astrophysics Data System (ADS)

    Cox, John

    2014-05-01

    Part 1. The Winning of the Principles: 1. Introduction; 2. The beginnings of statics. Archimedes. Problem of the lever and of the centre of gravity; 2. Experimental verification and applications of the principle of the lever; 3. The centre of gravity; 4. The balance; 5. Stevinus of Bruges. The principle of the inclined plane; 6. The parallelogram of forces; 7. The principle of virtual work; 8. Review of the principles of statics; 9. The beginnings of dynamics. Galileo. The problem of falling bodies; 10. Huyghens. The problem of uniform motion in a circle. 'Centrifugal force'; 11. Final statement of the principles of dynamics. Extension to the motions of the heavenly bodies. The law of universal gravitation. Newton; Part II. Mathematical Statement of the Principles: Introduction; 12. Kinematics; 13. Kinetics of a particle moving in a straight line. The laws of motion; 14. Experimental verification of the laws of motion. Atwood's machine; 15. Work and energy; 16. The parallelogram law; 17. The composition and resolution of forces. Resultant. Component. Equilibrium; 18. Forces in one plane; 19. Friction; Part III. Application to Various Problems: 20. Motion on an inclined plane. Brachistochrones; 21. Projectiles; 22. Simple harmonic motion; 23. The simple pendulum; 24. Central forces. The law of gravitation; 25. Impact and impulsive forces; Part IV. The Elements of Rigid Dynamics: 26. The compound pendulum. Huyghens' solution; 27. D'alembert's principle; 28. Moment of inertia; 29. Experimental determination of moments of inertia; 30. Determination of the value of gravity by Kater's pendulum; 31. The constant of gravitation, or weighing the Earth. The Cavendish experiment; Answers to the examples; Index.

  17. Glucocorticoid-induced osteoporosis in growing rats.

    PubMed

    Lin, Sien; Huang, Jianping; Zheng, Liang; Liu, Yanzhi; Liu, Guihua; Li, Nan; Wang, Kuixing; Zou, Liyi; Wu, Tie; Qin, Ling; Cui, Liao; Li, Gang

    2014-10-01

    This study evaluated whether growing rats were appropriate animal models of glucocorticoid-induced osteoporosis. The 3-month-old male rats were treated with either vehicle or prednisone acetate at 1.5, 3.0, and 6.0 mg/kg/day by oral gavage, respectively. All rats were injected with tetracycline and calcein before sacrificed for the purpose of double in vivo labeling. Biochemistry, histomorphometry, mechanical test, densitometry, micro-CT, histology, and component analysis were performed. We found that prednisone treatments dose dependently decreased body weight, serum biomarkers, biomechanical markers, bone formation, and bone resorption parameters in both tibial and femoral trabecular bone without trabecular bone loss. We also found that significant bone loss happened in femoral cortical bone in the glucocorticoid-treated rats. The results suggested that prednisone not only inhibited bone formation, but also inhibited bone resorption which resulted in poor bone strength but with no cancellous bone loss in growing rats. These data also suggested that the effects of glucocorticoid on bone metabolism were different between cortical bone and trabecular bone, and different between tibia and femur. Growing rats may be a glucocorticoid-induced osteoporosis animal model when evaluated the effects of drugs upon juvenile patients exposed to GC for a long time. PMID:25086673

  18. Mechanical Behavior of Brittle Rock-Like Specimens with Pre-existing Fissures Under Uniaxial Loading: Experimental Studies and Particle Mechanics Approach

    NASA Astrophysics Data System (ADS)

    Cao, Ri-hong; Cao, Ping; Lin, Hang; Pu, Cheng-zhi; Ou, Ke

    2016-03-01

    Joints and fissures with similar orientation or characteristics are common in natural rocks; the inclination and density of the fissures affect the mechanical properties and failure mechanism of the rock mass. However, the strength, crack coalescence pattern, and failure mode of rock specimens containing multi-fissures have not been studied comprehensively. In this paper, combining similar material testing and discrete element numerical method (PFC2D), the peak strength and failure characteristics of rock-like materials with multi-fissures are explored. Rock-like specimens were made of cement and sand and pre-existing fissures created by inserting steel shims into cement mortar paste and removing them during curing. The peak strength of multi-fissure specimens depends on the fissure angle α (which is measured counterclockwise from horizontal) and fissure number ( N f). Under uniaxial compressional loading, the peak strength increased with increasing α. The material strength was lowest for α = 25°, and highest for α = 90°. The influence of N f on the peak strength depended on α. For α = 25° and 45°, N f had a strong effect on the peak strength, while for higher α values, especially for the 90° sample, there were no obvious changes in peak strength with different N f. Under uniaxial compression, the coalescence modes between the fissures can be classified into three categories: S-mode, T-mode, and M-mode. Moreover, the failure mode can be classified into four categories: mixed failure, shear failure, stepped path failure, and intact failure. The failure mode of the specimen depends on α and N f. The peak strength and failure modes in the numerically simulated and experimental results are in good agreement.

  19. Direct mechanical energy measures of hammer mill comminution of switchgrass, wheat straw, and corn stover and analysis of their particle size distributions

    SciTech Connect

    Bitra, V.S.P; Womac, A.R.; Chevanan, Nehru; Miu, P.I.; Smith, D.R.; Igathinathane, C.; Sokhansanj, Shahabaddine

    2009-07-01

    Biomass particle size impacts handling, storage, conversion, and dust control systems. Size reduction mechanical energy was directly measured for switchgrass (Panicum virgatum L.), wheat straw (Triticum aestivum L.), and corn stover (Zea mays L.) in an instrumented hammer mill. Direct energy inputs were determined for hammer mill operating speeds from 2000 to 3600 rpm for 3.2 mm integral classifying screen and mass input rate of 2.5 kg/min with 90 - and 30 -hammers. Overall accuracy of specific energy measurement was calculated as 0.072 MJ/Mg. Particle size distributions created by hammer mill were determined for mill operating factors using ISO sieve sizes from 4.75 to 0.02 mm in conjunction with Ro-Tap sieve analyzer. A wide range of analytical descriptors were examined to mathematically represent the range of particle sizes in the distributions. Total specific energy (MJ/Mg) was defined as size reduction energy to operate the hammer mill plus that imparted to biomass. Effective specific energy was defined as energy imparted to biomass. Total specific energy for switchgrass, wheat straw, and corn stover grinding increased by 37, 30, and 45% from 114.4, 125.1, and 103.7 MJ/Mg, respectively, with an increase in hammer mill speed from 2000 to 3600 rpm for 90 -hammers. Corresponding total specific energy per unit size reduction was 14.9, 19.7, and 13.5 MJ/Mg mm, respectively. Effective specific energy of 90 -hammers decreased marginally for switchgrass and considerably for wheat straw and it increased for corn stover with an increase in speed from 2000 to 3600 rpm. However, effective specific energy increased with speed to a certain extent and then decreased for 30 -hammers. Rosin Rammler equation fitted the size distribution data with R2 > 0.995. Mass relative span was greater than 1, which indicated a wide distribution of particle sizes. Hammer milling of switchgrass, wheat straw, and corn stover with 3.2 mm screen resulted in well-graded fine-skewed mesokurtic

  20. Silicone Granulomas, a Growing Problem?

    PubMed

    Park, Michelle E; Curreri, Alexis T; Taylor, Gina A; Burris, Katy

    2016-05-01

    The formation of granulomas is known to be a possible adverse effect of liquid silicone administration, used for soft tissue augmentation. Its plumping effects provide enhancement of certain body parts, such as the lips, hips, and buttocks. The desire for enhancement, perhaps influenced by popular culture and an unrealistic standard of beauty, leads individuals to seek silicone injections. There is a growing population of women and men receiving injections by unlicensed, unskilled "practitioners" not related to the healthcare profession. Complications under such circumstances are not uncommon, particularly the emergence of silicone granulomas, and the authors' medical center has seen an increase in such cases. In this case report, the authors illustrate a young patient with significant complications from her silicone injections, review current therapies for silicone granulomas, and discuss this growing medical problem. PMID:27386046

  1. A rapidly growing lid lump

    PubMed Central

    Koay, Su-Yin; Lee, Richard M H; Hugkulstone, Charles; Rodrigues, Ian Aureliano Stephen

    2014-01-01

    A 97-year-old woman presented with a 5-month history of a rapidly growing, painless, left upper eyelid lesion. Examination revealed a large vascularised, ulcerated nodule on the left upper lid, causing significant ptosis. Wide local excision of the lesion was performed and the wound was left to heal by secondary intention. Histology and immunohistochemistry of the lesion confirmed a diagnosis of Merkel cell carcinoma, a rare primary malignancy of the eyelid which has significant morbidity and mortality. Although uncommon, this diagnosis should always be considered in any patient with a rapidly growing lid lump. In view of the patient's age, known dementia and family wishes, the patient was managed conservatively, with no further investigations performed. She was due to be followed up in clinic on a regular basis, but has since died from other causes. PMID:25123568

  2. Silicone Granulomas, a Growing Problem?

    PubMed Central

    Curreri, Alexis T.; Taylor, Gina A.; Burris, Katy

    2016-01-01

    The formation of granulomas is known to be a possible adverse effect of liquid silicone administration, used for soft tissue augmentation. Its plumping effects provide enhancement of certain body parts, such as the lips, hips, and buttocks. The desire for enhancement, perhaps influenced by popular culture and an unrealistic standard of beauty, leads individuals to seek silicone injections. There is a growing population of women and men receiving injections by unlicensed, unskilled “practitioners” not related to the healthcare profession. Complications under such circumstances are not uncommon, particularly the emergence of silicone granulomas, and the authors’ medical center has seen an increase in such cases. In this case report, the authors illustrate a young patient with significant complications from her silicone injections, review current therapies for silicone granulomas, and discuss this growing medical problem. PMID:27386046

  3. Growing a miracle in Kenya.

    PubMed

    Farruggia, Michael J

    2013-01-01

    A Kenyan woman, a retired nurse, and a nurse executive in America are miraculously led together to start a library in Kima, Kenya. Small beginnings grow into the Heather May-MashoodAbiola Children's Resource Centre (HEMAMA). Named after two infant children lost by the Kenyan woman and the nurse executive, HEMAMA is making a difference in the lives of children in the Kima, Kenya community. PMID:24282879

  4. Growing Yeast into Cylindrical Colonies

    PubMed Central

    Vulin, Clément; Di Meglio, Jean-Marc; Lindner, Ariel B.; Daerr, Adrian; Murray, Andrew; Hersen, Pascal

    2014-01-01

    Microorganisms often form complex multicellular assemblies such as biofilms and colonies. Understanding the interplay between assembly expansion, metabolic yield, and nutrient diffusion within a freely growing colony remains a challenge. Most available data on microorganisms are from planktonic cultures, due to the lack of experimental tools to control the growth of multicellular assemblies. Here, we propose a method to constrain the growth of yeast colonies into simple geometric shapes such as cylinders. To this end, we designed a simple, versatile culture system to control the location of nutrient delivery below a growing colony. Under such culture conditions, yeast colonies grow vertically and only at the locations where nutrients are delivered. Colonies increase in height at a steady growth rate that is inversely proportional to the cylinder radius. We show that the vertical growth rate of cylindrical colonies is not defined by the single-cell division rate, but rather by the colony metabolic yield. This contrasts with cells in liquid culture, in which the single-cell division rate is the only parameter that defines the population growth rate. This method also provides a direct, simple method to estimate the metabolic yield of a colony. Our study further demonstrates the importance of the shape of colonies on setting their expansion. We anticipate that our approach will be a starting point for elaborate studies of the population dynamics, evolution, and ecology of microbial colonies in complex landscapes. PMID:24853750

  5. Mechanical stability analysis of carrageenan-based polymer gel for magnetic resonance imaging liver phantom with lesion particles.

    PubMed

    In, Eunji; Naguib, Hani; Haider, Masoom

    2014-10-01

    Medical imaging is an effective technique used to detect and prevent disease in cancer research. To optimize medical imaging, a calibration medium or phantom with tissue-mimicking properties is required. Although the feasibility of various polymer gel materials has previously been studied, the stability of the gels' properties has not been investigated. In this study, we fabricated carrageenan-based polymer gel to examine the stability of its properties such as density, conductivity, permittivity, elastic modulus, and [Formula: see text] and [Formula: see text] relaxation times over six weeks. We fabricated eight samples with different carrageenan and agar concentrations and found that the density, elastic modulus, and compressive strength fluctuated with no specific pattern. The elastic modulus in sample 4 with 3 wt. % carrageenan and 1.5 wt. % agar fluctuated from 0.51 to 0.64 MPa in five weeks. The [Formula: see text] and [Formula: see text] relaxation times also varied by 23% to 29%. We believe that the fluctuation of these properties is related to the change in water content of the sample due to cycles of water expulsion and absorption in their containers. The fluctuation of the properties should be minimized to achieve accurate calibration over the shelf life of the phantom and to serve as the standard for quality assurance. Furthermore, a full liver phantom with spherical lesion particles was fabricated to demonstrate the potential for phantom production. PMID:26158073

  6. Characteristics and mechanisms of the bystander response in monolayer cell cultures exposed to very low fluences of alpha particles

    NASA Astrophysics Data System (ADS)

    Little, John B.; Azzam, Edouard I.; de Toledo, Sonia M.; Nagasawa, Hatsumi

    2005-02-01

    When confluent cultures of mammalian cells are irradiated with very low fluences of alpha particles whereby only occasional cells receive any radiation exposure, genetic changes are observed in the non-irradiated ("bystander") cells. Upregulation of the p53 damage-response pathway as well as activation of proteins in the MAPK family occurred in bystander cells; p53 was phosphorylated on the serine 15 residue suggesting that the upregulation of p53 was a consequence of DNA damage. Damage signals were transmitted to bystander cells through gap junctions, as confirmed by the use of genetically manipulated cells including connexin43 knockouts. Expression of connexin43 was markedly enhanced by irradiation. A moderate bystander effect was observed for specific gene mutations and chromosomal aberrations. This effect was markedly enhanced in cells defective in the non-homologous end joining DNA repair pathway. Finally, an upregulation of oxidative metabolism occurred in bystander cells; the increased levels of reactive oxygen species appeared to be derived from flavine-containing oxidase enzymes. We hypothesize that genetic effects observed in non-irradiated bystander cells are a consequence of oxidative base damage; >90% of mutations in bystander cells were point mutations. When bystander cells cannot repair DNA double strand breaks, they become much more sensitive to the induction of chromosomal aberrations and mutations, the latter consisting primarily of deletion mutants. While we propose that the genetic effects occurring in bystander cells are a consequence of oxidative stress, the nature of the signal that initiates this process remains to be determined.

  7. Mechanical stability analysis of carrageenan-based polymer gel for magnetic resonance imaging liver phantom with lesion particles

    PubMed Central

    In, Eunji; Naguib, Hani; Haider, Masoom

    2014-01-01

    Abstract. Medical imaging is an effective technique used to detect and prevent disease in cancer research. To optimize medical imaging, a calibration medium or phantom with tissue-mimicking properties is required. Although the feasibility of various polymer gel materials has previously been studied, the stability of the gels’ properties has not been investigated. In this study, we fabricated carrageenan-based polymer gel to examine the stability of its properties such as density, conductivity, permittivity, elastic modulus, and T1 and T2 relaxation times over six weeks. We fabricated eight samples with different carrageenan and agar concentrations and found that the density, elastic modulus, and compressive strength fluctuated with no specific pattern. The elastic modulus in sample 4 with 3 wt. % carrageenan and 1.5 wt. % agar fluctuated from 0.51 to 0.64 MPa in five weeks. The T1 and T2 relaxation times also varied by 23% to 29%. We believe that the fluctuation of these properties is related to the change in water content of the sample due to cycles of water expulsion and absorption in their containers. The fluctuation of the properties should be minimized to achieve accurate calibration over the shelf life of the phantom and to serve as the standard for quality assurance. Furthermore, a full liver phantom with spherical lesion particles was fabricated to demonstrate the potential for phantom production. PMID:26158073

  8. Structure of the hepatitis E virus-like particle suggests mechanisms for virus assembly and receptor binding

    SciTech Connect

    Guu, Tom S.Y.; Liu, Zheng; Ye, Qiaozhen; Mata, Douglas A.; Li, Kunpeng; Yin, Changcheng; Zhang, Jingqiang; Tao, Yizhi Jane

    2009-08-25

    Hepatitis E virus (HEV), a small, non-enveloped RNA virus in the family Hepeviridae, is associated with endemic and epidemic acute viral hepatitis in developing countries. Our 3.5-{angstrom} structure of a HEV-like particle (VLP) shows that each capsid protein contains 3 linear domains that form distinct structural elements: S, the continuous capsid; P1, 3-fold protrusions; and P2, 2-fold spikes. The S domain adopts a jelly-roll fold commonly observed in small RNA viruses. The P1 and P2 domains both adopt {beta}-barrel folds. Each domain possesses a potential polysaccharide-binding site that may function in cell-receptor binding. Sugar binding to P1 at the capsid protein interface may lead to capsid disassembly and cell entry. Structural modeling indicates that native T = 3 capsid contains flat dimers, with less curvature than those of T = 1 VLP. Our findings significantly advance the understanding of HEV molecular biology and have application to the development of vaccines and antiviral medications.

  9. Numerical Modeling of Plasmas in which Nanoparticles Nucleate and Grow

    NASA Astrophysics Data System (ADS)

    Agarwal, Pulkit

    Dusty plasmas refer to a broad category of plasmas. Plasmas such as argon-silane plasmas in which particles nucleate and grow are widely used in semiconductor processing and nanoparticle manufacturing. In such dusty plasmas, the plasma and the dust particles are strongly coupled to each other. This means that the presence of dust particles significantly affects the plasma properties and vice versa. Therefore such plasmas are highly complex and they involve several interesting phenomena like nucleation, growth, coagulation, charging and transport. Dusty plasma afterglow is equally complex and important. Especially, residual charge on dust particles carries special significance in several industrial and laboratory situations and it has not been well understood. A 1D numerical model was developed of a low-pressure capacitively-coupled plasma in which nanoparticles nucleate and grow. Polydispersity of particle size distributions can be important in such plasmas. Sectional method, which is well known in aerosol literature, was used to model the evolving particle size and charge distribution. The numerical model is transient and one-dimensional and self consistently accounts for nucleation, growth, coagulation, charging and transport of dust particles and their effect on plasma properties. Nucleation and surface growth rates were treated as input parameters. Results were presented in terms of particle size and charge distribution with an emphasis on importance of polydispersity in particle growth and dynamics. Results of numerical model were compared with experimental measurements of light scattering and light emission from plasma. Reasonable qualitative agreement was found with some discrepancies. Pulsed dusty plasma can be important for controlling particle production and/or unwanted particle deposition. In this case, it is important to understand the behavior of the particle cloud during the afterglow following plasma turn-off. Numerical model was modified to self

  10. Biochar as a growing media additive and peat substitute

    NASA Astrophysics Data System (ADS)

    Steiner, C.; Harttung, T.

    2014-09-01

    Environmental concerns raised the demand for alternative growing media substituting Sphagnum peat. However growing media formulations still depend on peat and alternatives are limited. Biochar is carbonized plant material and could be an appropriate additive or even substitute for Sphagnum peat. Freshly produced, it is free from pathogens, has a low nutrient content (if produced from nutrient-poor feedstock), a very high structural stability and likely other favourable properties such as air capacity and water-holding capacity. Preliminary tests were conducted to compare biochar with other growing media and growing media additives. The growth of a miniature sunflower, pH and electrical conductivity (EC) was measured in different growing media such as biochar, perlite, clay granules, Sphagnum peat and peat mixed with biochar in the ratios 1 : 4, 1 : 1 and 4 : 1 (25, 50 and 75%, by volume). Fresh biochar has a similar EC to peat which is even lower after rinsing with water. Due to the relatively high pH of biochar, it could be added to peat instead of lime in a concentration of up to 75%. The growth of the sunflower was similar in all growing media. Only the plant weight was slightly higher of plants that grew in perlite or peat. There is a large potential for optimization such as selection of particle size and feedstock for biochar production and growing media formulations for specific plant requirements.

  11. Biochar as growing media additive and peat substitute

    NASA Astrophysics Data System (ADS)

    Steiner, C.; Harttung, T.

    2014-04-01

    Environmental concerns raised the demand for alternative growing media substituting sphagnum peat. However growing media formulations still depend on peat and alternatives are limited. Biochar is carbonized plant material and could be an appropriate additive or even substitute for sphagnum peat. Freshly produced, it is free from pathogens, has a low nutrient content (if produced from nutrient poor feedstock), a very high structural stability and likely other favourable properties such as air capacity and water holding capacity. Preliminary tests were conducted to compare biochar with other growing media and growing media additives. The growth of a miniature sunflower, pH and electrical conductivity (EC) was measured in different growing media such as biochar, perlite, clay granules, sphagnum peat and peat mixed with biochar in the ratios 1 : 4, 1 : 1 and 4 : 1 (25, 50 and 75%, by volume). Fresh biochar has a similar EC than peat which is even lower after rinsing with water. Due to the relatively high pH of biochar, it could be added to peat instead of lime in a concentration of up to 75%. The growth of the sunflower was similar in all growing media. Only the plant weight was slightly higher of plants that grew in perlite or peat. There is a large potential for optimization such as selection of particle size and feedstock for biochar production and growing media formulations for specific plant requirements.

  12. The mechanical stability of precipitated austenite in 9Ni steel

    NASA Astrophysics Data System (ADS)

    Fultz, B.; Morris, J. W.

    1985-12-01

    The strains inherent to the martensitic transformation of austenite particles in 9Ni steel create dislocation structures in the tempered martensite. These dislocation structures were studied by the complementary techniques of X-ray line profile analysis and transmission electron microscopy. The energy required to form these dislocation structures affects the thermodynamics of the transformation. We propose that changes in these dislocation structures reduce the “mechanical stability” of the austenite particles as they grow larger during isothermal tempering.

  13. Qualitative analysis of response caused by growing plane waves by underdetermined system theory

    NASA Astrophysics Data System (ADS)

    Sano, Yukio

    1991-03-01

    A qualitative analysis of the mechanical response of rate-dependent media caused by one-dimensional plane smooth- and continuous-wave fronts with the growing peaks of strain, particle velocity, and stress is performed by an underdetermined system of nonlinear partial differential equations. The response found by the analysis reveals that strain, particle velocity, and stress profiles in the smooth-wave front are not similar and that the front is composed of five partial waves having different properties. The property is represented by the set of strain rate, acceleration, and stress rate as in a previous study. The front of the wave front is necessarily a contraction wave in which strain, particle velocity, and stress increase with time. The second partial wave is another contraction wave. We call the wave a vice-contraction wave. The rear is assumed to be a rarefaction wave where they all decrease with time. Between these two partial waves there are two remaining partial waves. We call these waves mesorarefaction waves I and II. Wave II is a wave in which particle velocity and stress increase, notwithstanding the decrease in strain with time. It is followed by wave I in which the increase in stress with time occurs in spite of the decrease in strain and particle velocity. The continuous-wave front, which has discontinuous-movement velocities at the continuous, but nonsmooth, positions in the profiles of strain, particle velocity, and stress, is composed of five independent waves. These waves are a contraction wave, a vice-contraction wave, evolutional rarefaction waves II and I, and a rarefaction wave which possess the same properties as the corresponding partial waves in the smooth-wave front mentioned above. Both in the smooth-growing-wave front and in the continuous one the peak precedence is in the order of the strain, particle velocity, and stress peaks. The stress-strain path and stress-particle velocity path at a position in a rate-dependent medium which is

  14. Effect of modified starch and nanoclay particles on biodegradability and mechanical properties of cross-linked poly lactic acid.

    PubMed

    Shayan, M; Azizi, H; Ghasemi, I; Karrabi, M

    2015-06-25

    Mechanical properties and biodegradation of cross-linked poly(lactic acid) (PLA)/maleated thermoplastic starch (MTPS)/montmorillonite (MMT) nanocomposite were studied. Crosslinking was carried out by adding di-cumyl peroxide (DCP) in the presence of triallyl isocyanurate (TAIC) as coagent. At first, MTPS was prepared by grafting maleic anhydride (MA) to thermoplastic starch in internal mixer. Experimental design was performed by using Box-Behnken method at three variables: MTPS, nanoclay and TAIC at three levels. Results showed that increasing TAIC amount substantially increased the gel fraction, enhanced tensile strength, and caused a decrease in elongation at break. Biodegradation was prevented by increasing TAIC amount in nanocomposite. Increasing MTPS amount caused a slight increase in gel fraction and decreased the tensile strength of nanocomposite. Also, MTPS could increase the elongation at break of nanocomposite and improve the biodegradation. Nanoclay had no effect on the gel fraction, but it improved tensile strength. PMID:25839817

  15. The role of fine material and grain size distribution on excess pore pressure dissipation and particle support mechanisms in granular deposits based in large-scale physical experiments

    NASA Astrophysics Data System (ADS)

    Palucis, M. C.; Kaitna, R.; Tewoldebrhan, B.; Hill, K. M.; Dietrich, W. E.

    2011-12-01

    The dominant mechanisms behind sustained mobilization in granular debris flows are poorly understood, and experiments are needed to determine the conditions under which the fluid can fully support the coarse fraction. However, field-scale studies are difficult to instrument and constrain and laboratory studies suffer from scaling issues. A 4-m rotating drum located at UC Berkeley's Richmond Field Station allowed us to perform reproducible experiments with materials similar to those in the field to explore mechanisms relevant to slow pore fluid pressure dissipation. Specifically, we performed a series of experiments to assess the role of fines and grain size distribution on the rate of pore fluid pressure dissipation upon deposition of a granular mass. For each experiment we kept the total mass of the gravel particles constant and varied the amount of fines (from no fines to amounts found in an actual debris flow deposit) and the gravel particle size distribution (from a single grain size to a range found in natural flows). We first rotated each mixture in the drum, during which we monitored fluid pressures at the base of the flows (near the wall of the drum and at the center). Then we stopped the drum and continued to monitor the fluid pressures. Immediately upon stopping, the pore fluid pressure was nearly hydrostatic for the gravel-water flows, and any elevated pore pressure quickly dissipated. On the other hand, the mixtures with fines contents close to those found in actual debris flows had elevated pore pressures indicating they were almost fully liquefied. Furthermore, the rate of pore pressure dissipation was an order of magnitude slower than when no fines were present; the grain size distribution of the coarse fraction did not strongly influence the dissipation rates in either case. We also placed a cobble upon a fines-rich mixture after cessation of motion above the center pressure sensor, and observed that the pore fluid pressure rose instantly, bearing

  16. Particle acceleration

    NASA Technical Reports Server (NTRS)

    Vlahos, L.; Machado, M. E.; Ramaty, R.; Murphy, R. J.; Alissandrakis, C.; Bai, T.; Batchelor, D.; Benz, A. O.; Chupp, E.; Ellison, D.

    1986-01-01

    Data is compiled from Solar Maximum Mission and Hinothori satellites, particle detectors in several satellites, ground based instruments, and balloon flights in order to answer fundamental questions relating to: (1) the requirements for the coronal magnetic field structure in the vicinity of the energization source; (2) the height (above the photosphere) of the energization source; (3) the time of energization; (4) transistion between coronal heating and flares; (5) evidence for purely thermal, purely nonthermal and hybrid type flares; (6) the time characteristics of the energization source; (7) whether every flare accelerates protons; (8) the location of the interaction site of the ions and relativistic electrons; (9) the energy spectra for ions and relativistic electrons; (10) the relationship between particles at the Sun and interplanetary space; (11) evidence for more than one acceleration mechanism; (12) whether there is single mechanism that will accelerate particles to all energies and also heat the plasma; and (13) how fast the existing mechanisms accelerate electrons up to several MeV and ions to 1 GeV.

  17. Anatomy of Particle Diffusion

    ERIC Educational Resources Information Center

    Bringuier, E.

    2009-01-01

    The paper analyses particle diffusion from a thermodynamic standpoint. The main goal of the paper is to highlight the conceptual connection between particle diffusion, which belongs to non-equilibrium statistical physics, and mechanics, which deals with particle motion, at the level of third-year university courses. We start out from the fact…

  18. Growing Hemorrhagic Choroidal Fissure Cyst

    PubMed Central

    Gelal, Fazıl; Gurkan, Gokhan; Feran, Hamit

    2016-01-01

    Choroidal fissure cysts are often incidentally discovered. They are usually asymptomatic. The authors report a case of growing and hemorrhagic choroidal fissure cyst which was treated surgically. A 22-year-old female presented with headache. Cranial MRI showed a left-sided choroidal fissure cyst. Follow-up MRI showed that the size of the cyst had increased gradually. Twenty months later, the patient was admitted to our emergency department with severe headache. MRI and CT showed an intracystic hematoma. Although such cysts usually have a benign course without symptoms and progression, they may rarely present with intracystic hemorrhage, enlargement of the cyst and increasing symptomatology. PMID:26962426

  19. Thermal oxidation of medical Ti6Al4V blasted with ceramic particles: Effects on the microstructure, residual stresses and mechanical properties.

    PubMed

    Lieblich, M; Barriuso, S; Multigner, M; González-Doncel, G; González-Carrasco, J L

    2016-02-01

    Roughening of Ti6Al4V by blasting with alumina or zirconia particles improves the mechanical fixation of implants by increasing the surface area available for bone/implant apposition. Additional thermal oxidation treatments of the blasted alloy have already shown to be a complementary low-cost solution to enhancing the in vitro biocompatibility and corrosion resistance of the alloy. In this work, the effects of oxidation treatment on a grit blasted Ti6Al4V biomedical alloy have been analysed in order to understand the net effect of the combined treatments on the alloy fatigue properties. Synchrotron radiation diffraction experiments have been performed to measure residual stresses before and after the treatments and microstructural and hardness changes have been determined. Although blasting of Ti6Al4V with small spherical zirconia particles increases the alloy fatigue resistance with respect to unblasted specimens, fatigue strength after oxidation decreases below the unblasted value, irrespective of the type of particle used for blasting. Moreover, at 700°C the as-blasted compressive residual stresses (700MPa) are not only fully relaxed but even moderate tensile residual stresses, of about 120MPa, are found beneath the blasted surfaces. Contrary to expectations, a moderate increase in hardness occurs towards the blasted surface after oxidation treatments. This can be attributed to the fact that grit blasting modifies the crystallographic texture of the Ti6Al4V shifting it to a random texture, which affects the hardness values as shown by additional experiments on cold rolled samples. The results indicate that the oxidation treatment performed to improve biocompatibility and corrosion resistance of grit blasted Ti6Al4V should be carried out with caution since the alloy fatigue strength can be critically diminished below the value required for high load-bearing components. PMID:26458115

  20. Elucidation of the mechanisms of action of Bacteriophage K/nano-emulsion formulations against S. aureus via measurement of particle size and zeta potential.

    PubMed

    Esteban, Patricia Perez; Jenkins, A Toby A; Arnot, Tom C

    2016-03-01

    In earlier work we have demonstrated the effect that nano-emulsions have on bacterial growth, and most importantly the enhanced bacteriophage infectivity against Staphylococcus aureus in planktonic culture when phage are carried in nano-emulsions. However, the mechanisms of enhancement of the bacteriophage killing effect are not specifically understood. This work focuses on the investigation of the possible interactions between emulsion droplets and bacterial cells, between emulsion droplets and bacteriophages, and finally interactions between all three components: nano-emulsion droplets, bacteria, and bacteriophages. The first approach consists of simple calculations to determine the spatial distribution of the components, based on measurements of particle size. It was found that nano-emulsion droplets are much more numerous than bacteria or bacteriophage, and due to their size and surface area they must be covering the surface of both cells and bacteriophage particles. Stabilisation of bacteriophages due to electrostatic forces and interaction with nano-emulsion droplets is suspected, since bacteriophages may be protected against inactivation due to 'charge shielding'. Zeta potential was measured for the individual components in the system, and for all of them combined. It was concluded that the presence of nano-emulsions could be reducing electrostatic repulsion between bacterial cells and bacteriophage, both of which are very negatively 'charged'. Moreover, nano-emulsions lead to more favourable interaction between bacteriophages and bacteria, enhancing the anti-microbial or killing effect. These findings are relevant since the physicochemical properties of nano-emulsions (i.e. particle size distribution and zeta potential) are key in determining the efficacy of the formulation against infection in the context of responsive burn wound dressings-which is the main target for this work. PMID:26700237

  1. The Contradiction Between the Measurement Theory of Quantum Mechanics and the Theory that the Velocity of Any Particle Can Not be Larger than the Velocity of Light

    NASA Technical Reports Server (NTRS)

    Shen, Y.; Shen, Z. J.; Shen, G. T.; Yang, B. C.

    1996-01-01

    By the measurement theory of quantum mechanics and the method of Fourier transform,we proved that the wave function psi(x,y,z,t)= (8/((2(pi)(2L(exp (1/2)))(exp 3))(Phi(L,t,x)Phi(L,t,y)Phi(L,t,z)). According to the theory that the velocity of any particle can not be larger than the velocity of light and the Born interpretation, when absolute value of delta greater than (ct+ L),Phi(L,t,delta) = 0. But according to the calculation, we proved that for some delta, even if absolute value of delta is greater than (ct+L), Phi(L,t,delta) is not equal to 0.

  2. Enhancing the recovery of tiger nut (Cyperus esculentus) oil by mechanical pressing: Moisture content, particle size, high pressure and enzymatic pre-treatment effects.

    PubMed

    Ezeh, Onyinye; Gordon, Michael H; Niranjan, Keshavan

    2016-03-01

    Tiger nut (Cyperus esculentus) tuber contains oil that is high in monounsaturated fatty acids, and this oil makes up about 23% of the tuber. The study aimed at evaluating the impact of several factors and enzymatic pre-treatment on the recovery of pressed tiger nut oil. Smaller particles were more favourable for pressing. High pressure pre-treatment did not increase oil recovery but enzymatic treatment did. The highest yield obtained by enzymatic treatment prior to mechanical extraction was 33% on a dry defatted basis, which represents a recovery of 90% of the oil. Tiger nut oil consists mainly of oleic acid; its acid and peroxide values reflect the high stability of the oil. PMID:26471565

  3. Mechanism insights into enhanced trichloroethylene removal using xanthan gum-modified microscale zero-valent iron particles.

    PubMed

    Xin, Jia; Han, Jun; Zheng, Xilai; Shao, Haibing; Kolditz, Olaf

    2015-03-01

    This report focuses on the enhancement in trichloroethylene (TCE) removal from contaminated groundwater using xanthan gum (XG)-modified, microscale, zero-valent iron (mZVI). Compared with bare mZVI, XG-coated mZVI increased the TCE removal efficiency by 30.37% over a 480-h experimental period. Because the TCE removal is attributed to both sorption and reduction processes, the contributions from sorption and reduction were separately investigated to determine the mechanism of XG on TCE removal using mZVI. The results showed that the TCE sorption capacity of mZVI was lower in the presence of XG, whereas the TCE reduction capacity was significantly increased. The FTIR spectra confirmed that XG, which is rich in hydrophilic functional groups, was adsorbed onto the iron surface through intermolecular hydrogen bonds, which competitively repelled the sorption and mass transfer of TCE toward reactive sites. The variations in the pH, Eh, and Fe(2+) concentration as functions of the reaction time were recorded and indicated that XG buffered the solution pH, inhibited surface passivation, and promoted TCE reduction by mZVI. Overall, the XG-modified mZVI was considered to be potentially effective for the in-situ remediation of TCE contaminated groundwater due to its high stability and dechlorination reactivity. PMID:25556871

  4. The use of mechanical alloying for the preparation of palladized magnesium bimetallic particles for the remediation of PCBs.

    PubMed

    Coutts, Janelle L; Devor, Robert W; Aitken, Brian; Hampton, Michael D; Quinn, Jacqueline W; Clausen, Christian A; Geiger, Cherie L

    2011-09-15

    The kinetic rate of dechlorination of a polychlorinated biphenyl (PCB-151) by mechanically alloyed Mg/Pd was studied for optimization of the bimetallic system. Bimetal production was first carried out in a small-scale environment using a SPEX 8000M high-energy ball mill with 4-μm-magnesium and palladium impregnated on graphite, with optimized parameters including milling time and Pd-loading. A 5.57-g sample of bimetal containing 0.1257% Pd and ball milled for 3 min resulted in a degradation rate of 0.00176 min(-1)g(-1) catalyst as the most reactive bimetal. The process was then scaled-up, using a Red Devil 5400 Twin-Arm Paint Shaker, fitted with custom plates to hold milling canisters. Optimization parameters tested included milling time, number of ball bearings used, Pd-loading, and total bimetal mass milled. An 85-g sample of bimetal containing 0.1059% Pd and ball-milled for 23 min with 16 ball bearings yielded the most reactive bimetal with a degradation rate of 0.00122 min(-1)g(-1) catalyst. Further testing showed adsorption did not hinder extraction efficiency and that dechlorination products were only seen when using the bimetallic system, as opposed to any of its single components. The bimetallic system was also tested for its ability to degrade a second PCB congener, PCB-45, and a PCB mixture (Arochlor 1254); both contaminants were seen to degrade successfully. PMID:21807459

  5. What a Pain! Kids and Growing Pains

    MedlinePlus

    ... Here's Help White House Lunch Recipes What a Pain! Kids and Growing Pains KidsHealth > For Kids > What a Pain! Kids and ... something doctors call growing pains . What Are Growing Pains? Growing pains aren't a disease. You probably ...

  6. Reaction Mechanism for Direct Propylene Epoxidation by Alumina-Supported Silver Aggregates. The Role of the Particle / Support Interface

    SciTech Connect

    Cheng, Lei; Yin, Chunrong; Mehmood, Faisal; Liu, Bin; Greeley, Jeffrey P.; Lee, Sungsik; Lee, Byeongdu; Seifert, Soenke; Winans, R. E.; Teschner, D.; Schlogl, Robert; Vajda, S.; Curtiss, Larry A.

    2013-11-21

    Sub-nanometer Ag aggregates on alumina supports have been found to be active toward direct propylene epoxidation to propylene oxide by molecular oxygen at low temperatures, with a negligible amount of carbon dioxide formation (Science 328, p. 224, 2010). In this work, we computationally and experimentally investigate the origin of the high reactivity of the sub-nanometer Ag aggregates. Computationally, we study O2 dissociation and propylene epoxidation on unsupported Ag19 and Ag20 clusters, as well as alumina-supported Ag19. The O2 dissociation and propylene epoxidation apparent barriers at the interface between the Ag aggregate and the alumina support are calculated to be 0.2 and 0.2~0.4 eV, respectively. These barriers are somewhat lower than those on sites away from the interface. The mechanism at the interface is similar to what was previously found for the silver trimer on alumina and can account for the high activity observed for the direct oxidation of propylene on the Ag aggregates. The barriers for oxygen dissociation on these model systems both at the interface and on the surfaces are small compared to crystalline surfaces, indicating that availability of oxygen will not be a rate limiting step for the aggregates, as in the case of the crystalline surfaces. Experimentally, we investigate Ultrananocrystalline Diamond (UNCD)-supported silver aggregates under reactive conditions of propylene partial oxidation. The UNCD-supported Ag clusters are found to be not measurably active toward propylene oxidation, in contrast to the alumina supported Ag clusters. This suggests that the lack of metal-oxide interfacial sites of the Ag-UNCD catalyst, limits the epoxidation catalytic activity. This combined computational and experimental study shows the importance of the metal-oxide interface as well as the non-crystalline nature of the alumina-supported sub-nanometer Ag aggregate catalysts for propylene epoxidation.

  7. Classical confined particles

    NASA Technical Reports Server (NTRS)

    Horzela, Andrzej; Kapuscik, Edward

    1993-01-01

    An alternative picture of classical many body mechanics is proposed. In this picture particles possess individual kinematics but are deprived from individual dynamics. Dynamics exists only for the many particle system as a whole. The theory is complete and allows to determine the trajectories of each particle. It is proposed to use our picture as a classical prototype for a realistic theory of confined particles.

  8. Effects fo sulfuric acid aerosol on respiratory mechanics and mucociliary particle clearance in healthy and asthmatic adults

    SciTech Connect

    Leikauf, G.D.

    1981-01-01

    The effects of submicrometer sulfuric acid (H/sub 2/SO/sub 4/) aerosol on human pulmonary physiology were investigated. Eighteen healthy and 10 asthmatic subjects inhaled H/sub 2/SO/sub 4/ via nasal mask for 1 hour at concentrations of 0, 100, 300 and 1000 ..mu..g/m/sup 3/ in a random sequence. The aerosol size (0.5 ..mu..m) and lower exposure level (100 ..mu..g/m/sup 3/) were selected to simulate peak ambient conditions, while the upper exposure concentration (1000 ..mu..g/m/sup 3/) is comparable to the current occupational limit for chronic exposure. Bronchial mucociliary clearance was markedly altered in all but one of the healthy subjects following one or more of the H/sub 2/SO/sub 4/ inhalations. The mucus was tagged by having each subject inhale either a 7.6 or 4.2 ..mu..m radiolabeled Fe/sub 2/O/sub 3/ aerosol. Exposure to 1000 ..mu..g/m/sup 3/ H/sub 2/SO/sub 4/ produced a delay in clearance which lasted longer in the group of eight inhaling the smaller 4.2 ..mu..m Fe/sub 2/O/sub 3/ aerosol than in the group of ten inhaling 7.6 ..mu..m Fe/sub 2/O/sub 3/. At 100 ..mu..g/m/sup 3/, the groups differed to a greater extent with clearance of the more centrally deposited larger aerosol being stimulated and that of the distally deposited smaller aerosol being transiently inhibited. Tracheal clearance remained unchanged in both groups. These findings, along with calculations of the various aerosols' deposition patterns, indicate that H/sub 2/SO/sub 4/ exerted a greater effect in the distal airways than in the proximal airways. Slight changes in ventilatory mechanics were noted in the asthmatic subjects following the 1000 ..mu..g/m/sup 3/ H/sub 2/SO/sub 4/ exposure, an effect not observed in the healthy subjects. However, the results obtained in the asthmatic group for tests of mucociliary clearance failed to reach significance, possible due to the large variability of such measurements in groups with respiratory disease.

  9. Features and heterogeneities in growing network models

    NASA Astrophysics Data System (ADS)

    Ferretti, Luca; Cortelezzi, Michele; Yang, Bin; Marmorini, Giacomo; Bianconi, Ginestra

    2012-06-01

    Many complex networks from the World Wide Web to biological networks grow taking into account the heterogeneous features of the nodes. The feature of a node might be a discrete quantity such as a classification of a URL document such as personal page, thematic website, news, blog, search engine, social network, etc., or the classification of a gene in a functional module. Moreover the feature of a node can be a continuous variable such as the position of a node in the embedding space. In order to account for these properties, in this paper we provide a generalization of growing network models with preferential attachment that includes the effect of heterogeneous features of the nodes. The main effect of heterogeneity is the emergence of an “effective fitness” for each class of nodes, determining the rate at which nodes acquire new links. The degree distribution exhibits a multiscaling behavior analogous to the the fitness model. This property is robust with respect to variations in the model, as long as links are assigned through effective preferential attachment. Beyond the degree distribution, in this paper we give a full characterization of the other relevant properties of the model. We evaluate the clustering coefficient and show that it disappears for large network size, a property shared with the Barabási-Albert model. Negative degree correlations are also present in this class of models, along with nontrivial mixing patterns among features. We therefore conclude that both small clustering coefficients and disassortative mixing are outcomes of the preferential attachment mechanism in general growing networks.

  10. Growing Vertical in the Flatland.

    PubMed

    Robinson, Joshua A

    2016-01-26

    The world of two-dimensional (2D) heterostructures continues to expand at a rate much greater than anyone could have predicted 10 years ago, but if we are to make the leap from science to technology, many materials challenges must still be overcome. Recent advances, such as those by Liu et al. in this issue of ACS Nano, demonstrate that it is possible to grow rotationally commensurate 2D heterostructures, which could pave the way toward single crystal van der Waals solids. In this Perspective, I provide some insight into a few of the challenges associated with growth of heterostructures, and discuss some of the recent works that help us better understand synthetic realization of 2D heterostructures. PMID:26762232

  11. How to grow great leaders.

    PubMed

    Ready, Douglas A

    2004-12-01

    Few leaders excel at both the unit and enterprise levels. More than ever, though, corporations need people capable of running business units, functions, or regions and focusing on broader company goals. It's up to organizations to develop leaders who can manage the inherent tensions between unit and enterprise priorities. Take the example of RBC Financial Group, one of the largest, most profitable companies in Canada. In the mid-1990's, RBC revamped its competitive strategy in a couple of ways. After the government announced that the Big Six banks in Canada could neither merge with nor acquire one another, RBC decided to grow through cross-border acquisitions. Additionally, because customers were starting to seek bundled products and services, RBC reached across its traditional stand-alone businesses to offer integrated solutions. These changes in strategy didn't elicit immediate companywide support. Instinctively, employees reacted against what would amount to a delicate balancing act: They would have to lift their focus out of their silos while continuing to meet unit goals. However, by communicating extensively with staff members, cross-fertilizing talent across unit boundaries, and targeting rewards to shape performance, RBC was able to cultivate rising leaders with the unit expertise and the enterprise vision to help the company fulfill its new aims. Growing such well-rounded leaders takes sustained effort because unit-enterprise tensions are quite real. Three common conditions reinforce these tensions. First, most organizational structures foster silo thinking and unimaginative career paths. Second, most companies lack venues for airing and resolving conflicts that arise when there are competing priorities. Third, many have misguided reward systems that pit unit performance against enterprise considerations. Such long-established patterns of organizational behavior are tough to break. Fortunately, as RBC discovered, people can be trained to think and work

  12. Shape dynamics of growing cell walls.

    PubMed

    Banerjee, Shiladitya; Scherer, Norbert F; Dinner, Aaron R

    2016-04-14

    We introduce a general theoretical framework to study the shape dynamics of actively growing and remodeling surfaces. Using this framework we develop a physical model for growing bacterial cell walls and study the interplay of cell shape with the dynamics of growth and constriction. The model allows us to derive constraints on cell wall mechanical energy based on the observed dynamics of cell shape. We predict that exponential growth in cell size requires a constant amount of cell wall energy to be dissipated per unit volume. We use the model to understand and contrast growth in bacteria with different shapes such as spherical, ellipsoidal, cylindrical and toroidal morphologies. Coupling growth to cell wall constriction, we predict a discontinuous shape transformation, from partial constriction to cell division, as a function of the chemical potential driving cell wall synthesis. Our model for cell wall energy and shape dynamics relates growth kinetics with cell geometry, and provides a unified framework to describe the interplay between shape, growth and division in bacterial cells. PMID:26953519

  13. How do normal faults grow?

    NASA Astrophysics Data System (ADS)

    Jackson, Christopher; Bell, Rebecca; Rotevatn, Atle; Tvedt, Anette

    2016-04-01

    Normal faulting accommodates stretching of the Earth's crust, and it is arguably the most fundamental tectonic process leading to continent rupture and oceanic crust emplacement. Furthermore, the incremental and finite geometries associated with normal faulting dictate landscape evolution, sediment dispersal and hydrocarbon systems development in rifts. Displacement-length scaling relationships compiled from global datasets suggest normal faults grow via a sympathetic increase in these two parameters (the 'isolated fault model'). This model has dominated the structural geology literature for >20 years and underpins the structural and tectono-stratigraphic models developed for active rifts. However, relatively recent analysis of high-quality 3D seismic reflection data suggests faults may grow by rapid establishment of their near-final length prior to significant displacement accumulation (the 'coherent fault model'). The isolated and coherent fault models make very different predictions regarding the tectono-stratigraphic evolution of rift basin, thus assessing their applicability is important. To-date, however, very few studies have explicitly set out to critically test the coherent fault model thus, it may be argued, it has yet to be widely accepted in the structural geology community. Displacement backstripping is a simple graphical technique typically used to determine how faults lengthen and accumulate displacement; this technique should therefore allow us to test the competing fault models. However, in this talk we use several subsurface case studies to show that the most commonly used backstripping methods (the 'original' and 'modified' methods) are, however, of limited value, because application of one over the other requires an a priori assumption of the model most applicable to any given fault; we argue this is illogical given that the style of growth is exactly what the analysis is attempting to determine. We then revisit our case studies and demonstrate

  14. Growing plants on atoll soils

    SciTech Connect

    Stone, E L; Migvar, L; Robison, W L

    2000-02-16

    Many years ago people living on atolls depended entirely on foods gathered from the sea and reefs and grown on land. Only a few plants, such as coconut (ni), Pandanus (bob), and arrowroot (mok-mok), could be grown on the lower rainfall atolls, although adequate groundwater conditions also allowed taro (iaraj, kotak, wot) to be cultivated. On higher rainfall atolls, breadfruit (ma) was a major food source, and banana (binana, kepran), lime (laim), and taros (iaraj, kotak, wot) could be grown. The early atoll populations were experts in growing plants that were vital to sustaining their nutrition requirements and to providing materials for thatch, basketry, cordage, canoe construction, flowers, and medicine. They knew which varieties of food plants grew well or poorly on their atolls, how to propagate them, and where on their atoll they grew best. They knew the uses of most native plants and what the various woods were well suited for. Many varieties of Pandanus (bob) and breadfruit (ma) grew well with high rainfall, but only a few produced well on drier atolls. Such information had been passed down through the generations although some of it has been lost in the last century. Today there are new plants and new varieties of existing plants that can be grown on atolls. There are also new materials and information on how to grow both the old and new plants more effectively. However, there are also introduced weeds and pests to control. Today, there is also an acute need to grow more of the useful plants adapted to atolls. Increasing numbers of people living on an atoll without an equal increase in income or food production stretches the available food supplies. Much has been written about the poor conditions for plant growth on atolls. As compared with many places in the world where crops are grown, however, atolls can provide some highly favorable conditions. For instance, the driving force for plant growth is sunlight, and on atolls light is abundant throughout the

  15. Growing and evolving soft robots.

    PubMed

    Rieffel, John; Knox, Davis; Smith, Schuyler; Trimmer, Barry

    2014-01-01

    Completely soft and flexible robots offer to revolutionize fields ranging from search and rescue to endoscopic surgery. One of the outstanding challenges in this burgeoning field is the chicken-and-egg problem of body-brain design: Development of locomotion requires the preexistence of a locomotion-capable body, and development of a location-capable body requires the preexistence of a locomotive gait. This problem is compounded by the high degree of coupling between the material properties of a soft body (such as stiffness or damping coefficients) and the effectiveness of a gait. This article synthesizes four years of research into soft robotics, in particular describing three approaches to the co-discovery of soft robot morphology and control. In the first, muscle placement and firing patterns are coevolved for a fixed body shape with fixed material properties. In the second, the material properties of a simulated soft body coevolve alongside locomotive gaits, with body shape and muscle placement fixed. In the third, a developmental encoding is used to scalably grow elaborate soft body shapes from a small seed structure. Considerations of the simulation time and the challenges of physically implementing soft robots in the real world are discussed. PMID:23373976

  16. [Growing old differently: Transdisciplinary perspective].

    PubMed

    Zimmermann, H-P

    2015-04-01

    Growing old differently: the phrase is intended to call something other to mind than merely the fact that images and forms of old age and aging have multiplied and diversified to an enormous extent. The suggestion put forward here is that otherness (as opposed to mere differences) should be positively reinforced. In other words, it is not just a matter of noting different forms of old age and aging but more than this, of seeking out opportunities for aging differently. In order to explore this, the article follows an older strand of theory, which has recently come to be frequently quoted in gerontology: the phenomenology of difference as reasoned analytically by Lévinas and Sartre and applied to gerontology by Améry and de Beauvoir. Here, opportunities for aging crucially depend on the way we look at it, how we observe and describe it and not least, how gerontology frames it. A distinction is made between two perspectives and their associated consequences for old age: alienation and alterity. Alienation means looking at old age above all as a disconcerting "other", as a perplexing, problematic deviation from the norm of vitality. Alterity, by contrast, refers to different options for living life in old age: options to be explored and opened up in contradistinction to cultural or academic alienation. Not least, the article appeals for diversity in scholarly approaches and for cross-disciplinary perspectives. PMID:25801518

  17. Fighting Back, Bedbugs Grow a Thicker Skin

    MedlinePlus

    ... Grow a Thicker Skin It helps protect against pesticides and may explain why population is growing worldwide, ... developing thicker "skins" that help them resist common pesticides, a new study suggests. This might explain why ...

  18. How High Do Sandbars Grow?

    NASA Astrophysics Data System (ADS)

    Alexander, J. S.; McElroy, B. J.

    2015-12-01

    Bar forms in wide sandy rivers store sediment, control channel hydraulics, and are fundamental units of riverine ecosystems. Bar form height is often used as a measure of channel depth in ancient fluvial deposits and is also a crucially important measure of habitat quality in modern rivers. In the Great Plains of North America, priority bird species use emergent bars to nest, and sandbar heights are a direct predictor of flood hazard for bird nests. Our current understanding of controls on bar height are limited to few datasets and ad hoc observations from specific settings. We here examine a new dataset of bar heights and explore models of bar growth. We present bar a height dataset from the Platte and Niobrara Rivers in Nebraska, and an unchannelized reach of the Missouri River along the Nebraska-South Dakota border. Bar height data are normalized by flow frequency, and we examine parsimonious statistical models between expected controls (depth, stage, discharge, flow duration, work etc.) and maximum bar heights. From this we generate empirical-statistical models of maximum bar height for wide, sand-bedded rivers in the Great Plains of the United States and rivers of similar morphology elsewhere. Migration of bar forms is driven by downstream slip-face additions of sediment sourced from their stoss sides, but bars also sequester sediment and grow vertically and longitudinally. We explore our empirical data with a geometric-kinematic model of bar growth driven by sediment transport from smaller-scale bedforms. Our goal is to understand physical limitations on bar growth and geometry, with implications for interpreting the rock record and predicting physically-driven riverine habitat variables.

  19. Atmospheric Aerosol Nucleation: Formation of Sub-3 nm Particles and Their Subsequent Growth

    NASA Astrophysics Data System (ADS)

    Lee, S.

    2012-12-01

    Aerosol nucleation is an important step in the chain reaction that lead to cloud formation but the nucleation mechanisms are poorly understand. Most of the previous aerosol nucleation studies were based on measurements of particles, typically larger than 3 nm, so it was unclear how gas phase molecules nucleate to form clusters and how they further grow to become aerosol particles. In this presentation, we will show recent results of aerosol nucleation based on direct measurements of sub-3 nm particles. We will show laboratory studies of multicomponent nucleation involving sulfuric acid, ammonia, and organic amines and atmospheric observations made in various atmospheric conditions (biogenic, marine, and less polluted continental atmosphere).

  20. Distinct kinetics and mechanisms of mZVI particles aging in saline and fresh groundwater: H2 Evolution and surface passivation

    NASA Astrophysics Data System (ADS)

    Xin, Jia; Tang, Fenglin; Zheng, Xilai

    2016-04-01

    Application of microscale zero-valent iron (mZVI) is a promising technology for in-situ contaminated groundwater remediation. However, its longevity would be negatively impacted by surface passivation, especially in saline groundwater. In this study, the aging behaviors of mZVI particles were investigated in three media (milli-Q water, fresh groundwater and saline groundwater) using batch experiments to evaluate their potential corrosion and passivation performance in different field conditions. The results indicated that mZVI was reactive between 0-7 days exposure to water and then gradually lost reactivity over the next few hundred days. The patterns of kinetic curve were analogous among the three different media. In comparison, during the early phase (0-7 d), mZVI in saline groundwater showed a faster corrosion rate with a k value of 1.357, which was relatively higher than k values in milli-Q water and fresh groundwater. However, as the corrosion process further developed, the fastest corrosion rate was observed in milli-Q water followed with fresh groundwater and saline groundwater. These changes in reactivity provided evidence for different patterns and formation mechanisms of passive layers on mZVI in three media. The SEM-EDS analysis demonstrated that in the saline groundwater, a compact and even oxide film of carbonate green rust or Fe oxide (hydroxyl) species was formed immediately on the surface due to the high concentration and widely distributed bicarbonate and hardness, whereas in the fresh groundwater and milli-Q water, the passive layer was composed of loosely and unevenly distributed precipitates which much slowly formed as the iron corrosion proceeded. These findings provide insight into the molecular-scale mechanism of mZVI passivation by inorganic salts with particular implications in saline groundwater.

  1. A Growing and Expanding Earth is no Longer Questionable

    NASA Astrophysics Data System (ADS)

    Myers, L. S.

    2008-05-01

    The young age of today's oceans is absolute proof that the Earth has been growing and expanding for the past 250 million years. Today, these young oceans now cover approximately 71% of Earth's surface and have added about 40% to its size. That fact, alone, is proof that Kant's nebular hypothesis is false, and that the Earth has been increasing in size and mass for the past 250 million years. Growth and expansion of the Earth can no longer be refuted. Ocean sediments cored from basaltic basement floors by the Deep Sea Drilling Program (DSDP) and its successors confirm that all of today's oceans are relatively young and could not have been present when the planet was first created, as postulated by Kant's nebular hypothesis (1755), modified by Laplace in 1796, which holds that the Earth and other planets were created approximately 4.6 billion years ago with their present sizes and chemical composition. The nebular hypothesis has no evidence to support it and is easily disproved. This discovery has immense consequences for current scientific beliefs, primarily the concepts of plate tectonics and subduction to maintain a static Earth diameter. Plate tectonics philosophy is basically correct, but its mechanism of subduction will prove to be the most avoidable and egregious error in the history of geophysics. A new cosmological concept called Accreation (creation by accretion) is offered to replace Kant's false philosophy of creation of the Earth and Solar System. Accreation, fundamentally, is based on the known daily influx of large tonnages of meteorites, particles and dust from outer space. An age for the Earth is impossible to estimate because a plausible starting point cannot be determined. Scientists of the world must face up to other erroneous hypotheses generated by Kant's false philosophy and recognize that a paradigm shift equal to that wrought by Copernicus is now in order. The benefits to scientific knowledge are inestimable, and science will henceforth be

  2. Hydrothermal synthesis and dielectric properties of chrysanthemum-like ZnO particles

    NASA Astrophysics Data System (ADS)

    Yan, Jun-Feng; Zhang, Zhi-Yong; You, Tian-Gui; Zhao, Wu; Yun, Jiang-Ni

    2009-09-01

    By orthogonal design theory, technological parameters of chrysanthemum-like ZnO particles prepared in a hydrothermal process are optimized. This paper reports a set of technological parameters for growing chrysanthemum-like ZnO particles on a large scale. It investigates the morphologies and crystalline structures of the as-synthesized three-dimensional ZnO particles with a scanning electron microscope, x-ray diffractometer and transmission electron microscope, and the possible growth mechanism on the three-dimensional ZnO particles. The experimental results indicate that the values of in', in″ and tan δe gradually increase in the X band with the improvement of the developmental level of chrysanthemum-like ZnO particles, implying that the electromagnetic wave absorbing property depends on the morphologies of three-dimensional ZnO particles.

  3. How Crystals Nucleate and Grow in Aqueous NaCl Solution.

    PubMed

    Chakraborty, Debashree; Patey, G N

    2013-02-21

    Large-scale molecular dynamics simulations (64 000 particles) are used to examine the microscopic mechanism of crystal nucleation and growth in a slightly supersaturated solution of NaCl in water at 300 K and 1 atm. Early-stage nucleation is observed, and the growth of a single crystal is followed for ∼140 ns. It is shown that the nucleation and growth process is better described by Ostwald's rule of stages than by classical nucleation theory. Crystal nucleation originates in a region where the local salt concentration exceeds that of the bulk solution. The early-stage nucleus is a loosely ordered arrangement of ions that retains a significant amount of water. The residual water is slowly removed as the crystal grows and evolves toward its stable anhydrous state. PMID:26281868

  4. Particle-Based Multidimensional Multispecies Biofilm Model

    PubMed Central

    Picioreanu, Cristian; Kreft, Jan-Ulrich; van Loosdrecht, Mark C. M.

    2004-01-01

    In this paper we describe a spatially multidimensional (two-dimensional [2-D] and three-dimensional [3-D]) particle-based approach for modeling the dynamics of multispecies biofilms growing on multiple substrates. The model is based on diffusion-reaction mass balances for chemical species coupled with microbial growth and spreading of biomass represented by hard spherical particles. Effectively, this is a scaled-up version of a previously proposed individual-based biofilm model. Predictions of this new particle-based model were quantitatively compared with those obtained with an established one-dimensional (1-D) multispecies model for equivalent problems. A nitrifying biofilm containing aerobic ammonium and nitrite oxidizers, anaerobic ammonium oxidizers, and inert biomass was chosen as an example. The 2-D and 3-D models generally gave the same results. If only the average flux of nutrients needs to be known, 2-D and 1-D models are very similar. However, the behavior of intermediates, which are produced and consumed in different locations within the biofilm, is better described in 2-D and 3-D models because of the multidirectional concentration gradients. The predictions of 2-D or 3-D models are also different from those of 1-D models for slowly growing or minority species in the biofilm. This aspect is related to the mechanism of biomass spreading or advection implemented in the models and should receive more attention in future experimental studies. PMID:15128564

  5. Investigating the Effects of Surface-Initiated Polymerization of ε-Caprolactone to Bioactive Glass Particles on the Mechanical Properties of Settable Polymer/Ceramic Composites

    PubMed Central

    Harmata, Andrew J.; Ward, Catherine L.; Zienkiewicz, Katarzyna J.; Wenke, Joseph C.

    2015-01-01

    Injectable bone grafts with strength exceeding that of trabecular bone could improve the management of a number of orthopaedic conditions. Ceramic/polymer composites have been investigated as weight-bearing bone grafts, but they are typically weaker than trabecular bone due to poor interfacial bonding. We hypothesized that entrapment of surface-initiated poly(ε-caprolactone) (PCL) chains on 45S5 bioactive glass (BG) particles within an in situ-formed polymer network would enhance the mechanical properties of reactive BG/polymer composites. When the surface-initiated PCL molecular weight exceeded the molecular weight between crosslinks of the network, the compressive strength of the composites increased 6- to 10-fold. The torsional strength of the composites exceeded that of human trabecular bone by a factor of two. When injected into femoral condyle defects in rats, the composites supported new bone formation at 8 weeks. The initial bone-like strength of BG/polymer composites and their ability to remodel in vivo highlight their potential for development as injectable grafts for repair of weight-bearing bone defects. PMID:25798027

  6. Distinct kinetics and mechanisms of mZVI particles aging in saline and fresh groundwater: H2 evolution and surface passivation.

    PubMed

    Xin, Jia; Tang, Fenglin; Zheng, Xilai; Shao, Haibing; Kolditz, Olaf; Lu, Xin

    2016-09-01

    Application of microscale zero-valent iron (mZVI) is a promising technology for in-situ contaminated groundwater remediation; however, its longevity is negatively impacted by surface passivation, especially in saline groundwater. In this study, the aging behavior of mZVI particles was investigated in three media (milli-Q water, fresh groundwater and saline groundwater) using batch experiments to evaluate their potential corrosion and passivation performance under different field conditions. The results indicated that mZVI was reactive for 0-7 days of exposure to water and then gradually lost H2-generating capacity over the next hundred days in all of the tested media. In comparison, mZVI in saline groundwater exhibited the fastest corrosion rate during the early phase (0-7 d), followed by the sharpest kinetic constant decline in the latter phases. The SEM-EDS and XPS analyses demonstrated that in the saline groundwater, a thin and compact oxide film was immediately formed on the surface and significantly shielded the iron reactive site. Nevertheless, in fresh groundwater and milli-Q water, a passive layer composed of loosely and unevenly distributed precipitates slowly formed, with abundant reactive sites available to support continuous iron corrosion. These findings provide insight into the molecular-scale mechanism that governs mZVI passivation and provide implications for long-term mZVI application in saline contaminated groundwater. PMID:27179595

  7. Mechanism of the formation and growth of fine particles clustered polymer microspheres by simple one-step polymerization in aqueous alcohol system

    NASA Astrophysics Data System (ADS)

    Mao, Hui; Wen, Chao; Wu, Shuyao; Liu, Daliang; Zhang, Yu; Song, Xi-Ming

    2016-02-01

    By using the one-step copolymerization of styrene (St) and 1-vinyl-3-ethylimidazolium bromide (VEIB), fine particles clustered (FPC) poly(St-co-VEIB) microspheres have been successfully prepared in the present of sodium dodecylsulfonate (SDS) in aqueous alcohol system. The FPC poly(St-co-VEIB) microspheres are composed of small poly(St-co-VEIB) nanospheres with the average diameter of 40 nm. The formation mechanism of FPC poly(St-co-VEIB) microspheres is proposed by investigating the influence of reaction conditions on their morphologies and observing their growth process. It can be well convinced that VEIB not only acted as a kind of monomers, which participated in the polymerization and provided electropositivity for FPC poly(St-co-VEIB) microspheres, but also acted as emulsifier and reactive stabilizer. The FPC poly(St-co-VEI[SO3CF3]) microspheres, which were obtained by anion-exchange between -SO3CF3 of HSO3CF3 and Br- in FPC poly(St-co-VEIB) microspheres due to the existence of imidazolium groups with electropositivity, showed higher catalytic efficiency for hydration of 1,2-epoxypropane with H2O and esterification between acetic acid and ethanol than that of H2SO4.

  8. SBA-15-incorporated nanoscale zero-valent iron particles for chromium(VI) removal from groundwater: mechanism, effect of pH, humic acid and sustained reactivity.

    PubMed

    Sun, Xia; Yan, Yubo; Li, Jiansheng; Han, Weiqing; Wang, Lianjun

    2014-02-15

    Nanoscale zero-valent iron particles (NZVIs) were incorporated inside the channels of SBA-15 rods by a "two solvents" reduction technique and used to remove Cr(VI) from groundwater. The resulting NZVIs/SBA-15 composites before and after reaction were characterized by N2 adsorption/desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Results helped to propose the mechanism of Cr(VI) removal by NZVIs/SBA-15, where Cr(VI) in aqueous was firstly impregnated into the channels of the silica, then adsorbed on the surfaces of the incorporated NZVIs and reduced to Cr(III) directly in the inner pores of the silica. Corrosion products included Fe2O3, FeO(OH), Fe3O4 and Cr2FeO4. Batch experiments revealed that Cr(VI) removal decreased from 99.7% to 92.8% when the initial solution pH increased from 5.5 to 9.0, accompanied by the decrease of the kobs from 0.600 to 0.024 min(-1). Humic acid (HA) had a little effect on the removal efficiency of Cr(VI) by NZVIs/SBA-15 but could decrease the reduction rate. The stable reduction of NZVIs/SBA-15 was observed within six cycles. NZVIs/SBA-15 composites offer a promising alternative material to remove heavy metals from groundwater. PMID:24374562

  9. El Nino Continues to Grow

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The latest image from NASA's Jason oceanography satellite, taken during a 10-day collection cycle ending December 2, 2002, shows the Pacific dominated by two significant areas of higher-than-normal sealevel (warmer ocean temperatures). In the central equatorial Pacific, the large area of higher than normal sea surface heights(warmer than normal sea surface temperatures) associated with growing El Nino conditions has recently migrated eastward toward the coast of South America. Meanwhile, the influence of the 20- to 30-year larger than El Nino/La Nina pattern called the Pacific Decadal Oscillation continues to create warm, higher-than-normal sea-surface heights in the north Pacific that are connected in a warm horseshoe pattern with the western and southern Pacific. Sea-surface heights are a measure of how much heat is stored in the ocean below. This heat influences both present weather and future planetary climate events.

    The image shows red areas in the north Pacific and at the equator that are about 10 centimeters (4 inches) above normal; white areas indicate sea surface heights between 14 and 32 centimeters (6 to 13 inches) above normal. These regions contrast with the western tropical Pacific, where lower-than-normal sea levels (blue areas) have developed that are between 5 and 13 centimeters (2 and 5 inches) below normal, while purple areas range from 14 to 18 centimeters (6 to 7 inches) below normal. Along the equator, the red sea surface heights equate to sea surface temperature departures greater than one degree Celsius (two degrees Fahrenheit) and the white sea surface heights are sea surface temperatures 1.5 to 2.5 degrees Celsius(three to five degrees Fahrenheit) above normal.

    The U.S. portion of the Jason mission is managed by JPL for NASA's Earth Science Enterprise, Washington, D.C. Research on Earth's oceans using Jason and other space-based capabilities is conducted by NASA's Earth Science Enterprise to better understand and protect our

  10. Growing multiplex networks with arbitrary number of layers

    NASA Astrophysics Data System (ADS)

    Momeni, Naghmeh; Fotouhi, Babak

    2015-12-01

    This paper focuses on the problem of growing multiplex networks. Currently, the results on the joint degree distribution of growing multiplex networks present in the literature pertain to the case of two layers and are confined to the special case of homogeneous growth and are limited to the state state (that is, the limit of infinite size). In the present paper, we first obtain closed-form solutions for the joint degree distribution of heterogeneously growing multiplex networks with arbitrary number of layers in the steady state. Heterogeneous growth means that each incoming node establishes different numbers of links in different layers. We consider both uniform and preferential growth. We then extend the analysis of the uniform growth mechanism to arbitrary times. We obtain a closed-form solution for the time-dependent joint degree distribution of a growing multiplex network with arbitrary initial conditions. Throughout, theoretical findings are corroborated with Monte Carlo simulations. The results shed light on the effects of the initial network on the transient dynamics of growing multiplex networks and takes a step towards characterizing the temporal variations of the connectivity of growing multiplex networks, as well as predicting their future structural properties.

  11. Diffusion Rate Limitations in Actin-Based Propulsion of Hard and Deformable Particles

    PubMed Central

    Dickinson, Richard B.; Purich, Daniel L.

    2006-01-01

    The mechanism by which actin polymerization propels intracellular vesicles and invasive microorganisms remains an open question. Several recent quantitative studies have examined propulsion of biomimetic particles such as polystyrene microspheres, phospholipid vesicles, and oil droplets. In addition to allowing quantitative measurement of parameters such as the dependence of particle speed on its size, these systems have also revealed characteristic behaviors such a saltatory motion of hard particles and oscillatory deformation of soft particles. Such measurements and observations provide tests for proposed mechanisms of actin-based motility. In the actoclampin filament end-tracking motor model, particle-surface-bound filament end-tracking proteins are involved in load-insensitive processive insertion of actin subunits onto elongating filament plus-ends that are persistently tethered to the surface. In contrast, the tethered-ratchet model assumes working filaments are untethered and the free-ended filaments grow as thermal ratchets in a load-sensitive manner. This article presents a model for the diffusion and consumption of actin monomers during actin-based particle propulsion to predict the monomer concentration field around motile particles. The results suggest that the various behaviors of biomimetic particles, including dynamic saltatory motion of hard particles and oscillatory vesicle deformations, can be quantitatively and self-consistently explained by load-insensitive, diffusion-limited elongation of (+)-end-tethered actin filaments, consistent with predictions of the actoclampin filament-end tracking mechanism. PMID:16731556

  12. Electromagnetic Particle-in-Cell Simulations of the Solar Wind Interaction with Lunar Magnetic Anomalies: Interaction Mechanisms Under Varying Solar Wind Conditions.

    NASA Astrophysics Data System (ADS)

    Deca, Jan; Divin, Andrey; Lapenta, Giovanni; Lembège, Bertrand; Markidis, Stefano; Horányi, Mihály

    2015-04-01

    We present three-dimensional fully kinetic and electromagnetic simulations of the solar wind interaction with lunar crustal magnetic anomalies (LMAs). Using the implicit particle-in-cell code iPic3D, we confirm that LMAs may indeed be strong enough to stand off the solar wind from directly impacting the lunar surface forming a mini-magnetosphere, as suggested by spacecraft observations and theory. In contrast to earlier MHD and hybrid simulations, the fully kinetic nature of iPic3D allows to investigate the space charge effects and in particular the electron dynamics dominating the near-surface lunar plasma environment. We describe the general picture of the interaction of a dipole model centered just below the lunar surface under various solar wind and plasma conditions, and focus afterwards on the ion and electron kinetic behavior of the system. It is shown that the configuration is dominated by electron motion, because the LMA scale size is small with respect to the gyroradius of the solar wind ions. We identify a population of backstreaming ions, the deflection of magnetized electrons via the ExB-drift motion and the subsequent formation of a halo region of elevated density around the dipole source. Finally, it is shown that the presence and efficiency of the latter mechanisms are heavily impacted by the upstream plasma conditions and, on their turn, influence the overall structure and evolution of the LMA system. Our work opens new frontiers of research toward a deeper understanding of LMAs and is ideally suited to be compared with field or particle observations from spacecraft such as Kaguya (SELENE), Lunar Prospector or ARTEMIS. The ability to evaluate the implications for future lunar exploration as well as lunar science in general hinges on a better understanding of LMAs. This research has received funding from the European Commission's FP7 Program with the grant agreement SWIFF (project 2633430, swiff.eu) and EHEROES (project 284461, www.eheroes.eu). The

  13. The growing world of expansins

    NASA Technical Reports Server (NTRS)

    Cosgrove, Daniel J.; Li, Lian Chao; Cho, Hyung-Taeg; Hoffmann-Benning, Susanne; Moore, Richard C.; Blecker, Douglas

    2002-01-01

    Expansins are cell wall proteins that induce pH-dependent wall extension and stress relaxation in a characteristic and unique manner. Two families of expansins are known, named alpha- and beta-expansins, and they comprise large multigene families whose members show diverse organ-, tissue- and cell-specific expression patterns. Other genes that bear distant sequence similarity to expansins are also represented in the sequence databases, but their biological and biochemical functions have not yet been uncovered. Expansin appears to weaken glucan-glucan binding, but its detailed mechanism of action is not well established. The biological roles of expansins are diverse, but can be related to the action of expansins to loosen cell walls, for example during cell enlargement, fruit softening, pollen tube and root hair growth, and abscission. Expansin-like proteins have also been identified in bacteria and fungi, where they may aid microbial invasion of the plant body.

  14. Mechanics/heat-transfer relation for particulate materials. [Measure of particle pressure generated in a bed of FCC catalyst that is undergoing particulate fluidization

    SciTech Connect

    Campbell, C.S.

    1991-07-01

    The major emphasis this quarter has been in two areas. The first is to continue working the bugs out of the new particle pressure transducer. The second was to try and measure the particle pressures generated in a bed of FCC catalyst that is undergoing particulate fluidization. The results indicate that the stabilization of fluidized beds in that regime cannot be explained in terms of particle pressure generation. Instead, consistent with other recent observations,the observations can be explained by a material is that not completely fluidized but, instead, retains much of the properties of a solid and, in particular, can transmit particle pressure like a solid. 2 figs.

  15. Recovering from "amnesia" brought about by radiation. Verification of the "Over the air" (OTA) application software update mechanism On-Board Solar Orbiter's Energetic Particle Detector

    NASA Astrophysics Data System (ADS)

    Da Silva, Antonio; Sánchez Prieto, Sebastián; Rodriguez Polo, Oscar; Parra Espada, Pablo

    Computer memories are not supposed to forget, but they do. Because of the proximity of the Sun, from the Solar Orbiter boot software perspective, it is mandatory to look out for permanent memory errors resulting from (SEL) latch-up failures in application binaries stored in EEPROM and its SDRAM deployment areas. In this situation, the last line in defense established by FDIR mechanisms is the capability of the boot software to provide an accurate report of the memories’ damages and to perform an application software update, that avoid the harmed locations by flashing EEPROM with a new binary. This paper describes the OTA EEPROM firmware update procedure verification of the boot software that will run in the Instrument Control Unit (ICU) of the Energetic Particle Detector (EPD) on-board Solar Orbiter. Since the maximum number of rewrites on real EEPROM is limited and permanent memory faults cannot be friendly emulated in real hardware, the verification has been accomplished by the use of a LEON2 Virtual Platform (Leon2ViP) with fault injection capabilities and real SpaceWire interfaces developed by the Space Research Group (SRG) of the University of Alcalá. This way it is possible to run the exact same target binary software as if was run on the real ICU platform. Furthermore, the use of this virtual hardware-in-the-loop (VHIL) approach makes it possible to communicate with Electrical Ground Support Equipment (EGSE) through real SpaceWire interfaces in an agile, controlled and deterministic environment.

  16. Rapid degradation of phenol by ultrasound-dispersed nano-metallic particles (NMPs) in the presence of hydrogen peroxide: A possible mechanism for phenol degradation in water.

    PubMed

    Singh, Jiwan; Yang, Jae-Kyu; Chang, Yoon-Young

    2016-06-15

    The present study was carried out to investigate the degradation of phenol by ultrasonically dispersed nano-metallic particles (NMPs) in an aqueous solution of phenol. Leaching liquor from automobile shredder residue (ASR) was used to obtain the NMPs. The prepared NMPs were analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and by X-ray diffraction (XRD). The SEM images show that the diameters of the NMPs were less than 50 nm. An SEM-EDX elemental analysis reveals that Fe was the most commonly found element (weight %) in the NMPs. The FTIR and XRD peaks indicate the presence of metals oxides on the surfaces of the NMPs. The results of the XPS analysis indicate that various elements (e.g., C, O, Zn, Cu, Mn, Fe) are present on the surfaces of the NMPs. The effects of the NMP dose, the initial solution pH, and of different concentrations of phenol and H2O2 on the phenol degradation characteristics were evaluated. The results of this study demonstrate that phenol degradation can be improved by increasing the amount of NMPs, whereas it is reduced with an increase in the phenol concentration. The degradation of phenol by ultrasonically dispersed NMPs followed the pseudo-first-order kinetics. The probable mechanism of phenol degradation by ultrasonically dispersed NMPs was the oxidation of phenol caused by the hydroxyl radicals produced during the reaction between H2O2 and the NMPs during the ultrasonication process. PMID:27038433

  17. NEW ASPECTS OF A LID-REMOVAL MECHANISM IN THE ONSET OF AN ERUPTION SEQUENCE THAT PRODUCED A LARGE SOLAR ENERGETIC PARTICLE (SEP) EVENT

    SciTech Connect

    Sterling, Alphonse C.; Moore, Ronald L.; Falconer, David A.; Knox, Javon M. E-mail: ron.moore@nasa.gov

    2014-06-20

    We examine a sequence of two ejective eruptions from a single active region on 2012 January 23, using magnetograms and EUV images from the Solar Dynamics Observatory's (SDO) Helioseismic and Magnetic Imager (HMI) and Atmospheric and Imaging Assembly (AIA), and EUV images from STEREO/EUVI. This sequence produced two coronal mass ejections (CMEs) and a strong solar energetic particle event (SEP); here we focus on the magnetic onset of this important space weather episode. Cheng et al. showed that the first eruption's ({sup E}ruption 1{sup )} flux rope was apparent only in ''hotter'' AIA channels, and that it removed overlying field that allowed the second eruption ({sup E}ruption 2{sup )} to begin via ideal MHD instability; here we say that Eruption 2 began via a ''lid removal'' mechanism. We show that during Eruption 1's onset, its flux rope underwent a ''tether weakening'' (TW) reconnection with field that arched from the eruption-source active region to an adjacent active region. Standard flare loops from Eruption 1 developed over Eruption 2's flux rope and enclosed filament, but these overarching new loops were unable to confine that flux rope/filament. Eruption 1's flare loops, from both TW reconnection and standard-flare-model internal reconnection, were much cooler than Eruption 2's flare loops (GOES thermal temperatures of ∼7.5 MK and 9 MK, compared to ∼14 MK). The corresponding three sequential GOES flares were, respectively, due to TW reconnection plus earlier phase Eruption 1 tether-cutting reconnection, Eruption 1 later-phase tether-cutting reconnection, and Eruption 2 tether-cutting reconnection.

  18. Effect of hinge gap width of a St. Jude medical bileaflet mechanical heart valve on blood damage potential--an in vitro micro particle image velocimetry study.

    PubMed

    Jun, Brian H; Saikrishnan, Neelakantan; Arjunon, Sivakkumar; Yun, B Min; Yoganathan, Ajit P

    2014-09-01

    The hinge regions of the bileaflet mechanical heart valve (BMHV) can cause blood element damage due to nonphysiological shear stress levels and regions of flow stasis. Recently, a micro particle image velocimetry (μPIV) system was developed to study whole flow fields within BMHV hinge regions with enhanced spatial resolution under steady leakage flow conditions. However, global velocity maps under pulsatile conditions are still necessary to fully understand the blood damage potential of these valves. The current study hypothesized that the hinge gap width will affect flow fields in the hinge region. Accordingly, the blood damage potential of three St. Jude Medical (SJM) BMHVs with different hinge gap widths was investigated under pulsatile flow conditions, using a μPIV system. The results demonstrated that the hinge gap width had a significant influence during the leakage flow phase in terms of washout and shear stress characteristics. During the leakage flow, the largest hinge gap generated the highest Reynolds shear stress (RSS) magnitudes (~1000 N/m²) among the three valves at the ventricular side of the hinge. At this location, all three valves indicated viscous shear stresses (VSS) greater than 30 N/m². The smallest hinge gap exhibited the lowest level of shear stress values, but had the poorest washout flow characteristics among the three valves, demonstrating propensity for flow stasis and associated activated platelet accumulation potential. The results from this study indicate that the hinge is a critical component of the BMHV design, which needs to be optimized to find the appropriate balance between reduction in fluid shear stresses and enhanced washout during leakage flow, to ensure minimal thrombotic complications. PMID:24976188

  19. The Least Particle Theory

    NASA Astrophysics Data System (ADS)

    Hartsock, Robert

    2011-10-01

    The Least Particle Theory states that the universe was cast as a great sea of energy. MaX Planck declared a quantum of energy to be the least value in the universe. We declare the quantum of energy to be the least particle in the universe. Stephen Hawking declared quantum mechanics to be of no value in todays gross mechanics. That's like saying the number 1 has no place in mathematics.

  20. Particle size effect on microwave absorbing of La0.67Ba0.33Mn0.94Ti0.06O3 powders prepared by mechanical alloying with the assistance of ultrasonic irradiation

    NASA Astrophysics Data System (ADS)

    Saptari, Sitti Ahmiatri; Manaf, Azwar; Kurniawan, Budhy

    2016-03-01

    Doped manganites have attracted substantial interest due to their unique chemical and physics properties, which makes it possible to be used for microwave absorbing materials. In this paper we report synthesizes and characterization of La0.67Ba0.33Mn0.94Ti0.06O3 powders prepared by mechanical alloying with the assistance of a high power ultrasonic treatment. After solid state reaction, the presence of single phase was confirmed by X-ray Diffraction (XRD). Refinement results showed that samples are single phase with monoclinic structure. It was found that powder materials derived from mechanical alloying results in large variation in the particle size. A significant improvement was obtained upon subjecting the mechanically milled powder materials to an ultrasonication treatment for a relatively short period of time. As determined by particle size analyzer (PSA), the mean particle size gradually decreased from the original size of 5.02 µm to 0.36 µm. Magnetic properties were characterized by VSM, and hysteresis loops results showed that samples are soft magnetic. It was found that when the mean particle size decreases, saturation was increases and coersitivity was decreases. Microwave absorption properties were investigated in the frequency range of 8-12 GHz using vector network analyzer. An optimal reflection loss of 24.44 dB is reached at 11.4 GHz.