Sample records for directed random polymer

  1. Directed random polymers via nested contour integrals

    Borodin, Alexei; Bufetov, Alexey; Corwin, Ivan


    We study the partition function of two versions of the continuum directed polymer in 1 + 1 dimension. In the full-space version, the polymer starts at the origin and is free to move transversally in R, and in the half-space version, the polymer starts at the origin but is reflected at the origin and stays in R-. The partition functions solve the stochastic heat equation in full-space or half-space with mixed boundary condition at the origin; or equivalently the free energy satisfies the Kardar-Parisi-Zhang equation. We derive exact formulas for the Laplace transforms of the partition functions. In the full-space this is expressed as a Fredholm determinant while in the half-space this is expressed as a Fredholm Pfaffian. Taking long-time asymptotics we show that the limiting free energy fluctuations scale with exponent 1 / 3 and are given by the GUE and GSE Tracy-Widom distributions. These formulas come from summing divergent moment generating functions, hence are not mathematically justified. The primary purpose of this work is to present a mathematical perspective on the polymer replica method which is used to derive these results. In contrast to other replica method work, we do not appeal directly to the Bethe ansatz for the Lieb-Liniger model but rather utilize nested contour integral formulas for moments as well as their residue expansions.

  2. Directed polymers in random environment with heavy tails

    Auffinger, Antonio


    We study the model of Directed Polymers in Random Environment in 1+1 dimensions, where the distribution at a site has a tail which decays regularly polynomially with power \\alpha, where \\alpha \\in (0,2). After proper scaling of temperature \\beta^{-1}, we show strong localization of the polymer to a favorable region in the environment where energy and entropy are best balanced. We prove that this region has a weak limit under linear scaling and identify the limiting distribution as an (\\alpha, \\beta)-indexed family of measures on Lipschitz curves lying inside the 45-degrees-rotated square with unit diagonal. In particular, this shows order n transversal fluctuations of the polymer. If, and only if, \\alpha is small enough, we find that there exists a random critical temperature below which, but not above, the effect of the environment is macroscopic. The results carry over to d+1 dimensions for d>1 with minor modifications.

  3. Mean field theory of directed polymers with random complex weights

    Derrida, B.; Evans, M. R.; Speer, E. R.


    We show that for the problem of directed polymers on a tree with i.i.d. random complex weights on each bond, three possible phases can exist; the phase of a particular system is determined by the distribution ρ of the random weights. For each of these three phases, we give the expression of the free energy per unit length in the limit of infinitely long polymers. Our proofs require several hypotheses on the distribution ρ, most importantly, that the amplitude and the phase of each complex weight be statistically independent. The main steps of our proofs use bounds on noninteger moments of the partition function and self averaging properties of the free energy. We illustrate our results by some examples and discuss possible generalizations to a larger class of distributions, to Random Energy Models, and to the finite dimensional case. We note that our results are not in agreement with the predictions of a recent replica approach to a similar problem.

  4. Free energy fluctuations for directed polymers in random media in 1+1 dimension

    Borodin, Alexei; Ferrari, Patrik


    We consider two models for directed polymers in space-time independent random media (the O'Connell-Yor semi-discrete directed polymer and the continuum directed random polymer) at positive temperature and prove their KPZ universality via asymptotic analysis of exact Fredholm determinant formulas for the Laplace transform of their partition functions. In particular, we show that for large time tau, the probability distributions for the free energy fluctuations, when rescaled by tau^{1/3}, converges to the GUE Tracy-Widom distribution. We also consider the effect of boundary perturbations to the quenched random media on the limiting free energy statistics. For the semi-discrete directed polymer, when the drifts of a finite number of the Brownian motions forming the quenched random media are critically tuned, the statistics are instead governed by the limiting Baik-Ben Arous-Peche distributions from spiked random matrix theory. For the continuum polymer, the boundary perturbations correspond to choosing the init...

  5. Determinantal Structures in the O'Connell-Yor Directed Random Polymer Model

    Imamura, Takashi; Sasamoto, Tomohiro


    We study the semi-discrete directed random polymer model introduced by O'Connell and Yor. We obtain a representation for the moment generating function of the polymer partition function in terms of a determinantal measure. This measure is an extension of the probability measure of the eigenvalues for the Gaussian unitary ensemble in random matrix theory. To establish the relation, we introduce another determinantal measure on larger degrees of freedom and consider its few properties, from which the representation above follows immediately.

  6. On the genealogy of branching random walks and of directed polymers

    Derrida, Bernard; Mottishaw, Peter


    It is well known that the mean-field theory of directed polymers in a random medium exhibits replica symmetry breaking with a distribution of overlaps which consists of two delta functions. Here we show that the leading finite-size correction to this distribution of overlaps has a universal character which can be computed explicitly. Our results can also be interpreted as genealogical properties of branching Brownian motion or of branching random walks.

  7. Directed polymer in random media, in two dimensions: numerical study of the aging dynamics

    Barrat, A.


    Following a recent work by Yoshino, we study the aging dynamics of a directed polymer in random media, in 1+1 dimensions. Through temperature quench, and temperature cycling numerical experiments similar to the experiments on real spin glasses, we show that the observed behaviour is comparable to the one of a well known mean field spin glass model. The observation of various quantities (correlation function, ``clonation'' overlap function) leads to an analysis of the phase space landscape.

  8. Probability distribution of the free energy of a directed polymer in a random medium

    Brunet, Éric; Derrida, Bernard


    We calculate exactly the first cumulants of the free energy of a directed polymer in a random medium for the geometry of a cylinder. By using the fact that the nth moment of the partition function is given by the ground-state energy of a quantum problem of n interacting particles on a ring of length L, we write an integral equation allowing to expand these moments in powers of the strength of the disorder γ or in powers of n. For n small and n~(Lγ)-1/2, the moments take a scaling form which allows us to describe all the fluctuations of order 1/L of the free energy per unit length of the directed polymer. The distribution of these fluctuations is the same as the one found recently in the asymmetric exclusion process, indicating that it is characteristic of all the systems described by the Kardar-Parisi-Zhang equation in 1+1 dimensions.

  9. Probability distributions for directed polymers in random media with correlated noise

    Chu, Sherry; Kardar, Mehran


    The probability distribution for the free energy of directed polymers in random media (DPRM) with uncorrelated noise in d =1 +1 dimensions satisfies the Tracy-Widom distribution. We inquire if and how this universal distribution is modified in the presence of spatially correlated noise. The width of the distribution scales as the DPRM length to an exponent β , in good (but not full) agreement with previous renormalization group and numerical results. The scaled probability is well described by the Tracy-Widom form for uncorrelated noise, but becomes symmetric with increasing correlation exponent. We thus find a class of distributions that continuously interpolates between Tracy-Widom and Gaussian forms.

  10. Finite-temperature perturbation theory for the random directed polymer problem

    Korshunov, S. E., E-mail: [Russian Academy of Sciences, Landau Institute for Theoretical Physics (Russian Federation); Geshkenbein, V. B.; Blatter, G. [Theoretische Physik (Switzerland)


    We study the random directed polymer problem-the short-scale behavior of an elastic string (or polymer) in one transverse dimension subject to a disorder potential and finite temperature fluctuations. We are interested in the polymer short-scale wandering expressed through the displacement correlator Left-Pointing-Angle-Bracket [{delta}u(X)]{sup 2} Right-Pointing-Angle-Bracket , with {delta}u(X) being the difference in the displacements at two points separated by a distance X. While this object can be calculated at short scales using the perturbation theory in higher dimensions d > 2, this approach becomes ill-defined and the problem turns out to be nonperturbative in the lower dimensions and for an infinite-length polymer. In order to make progress, we redefine the task and analyze the wandering of a string of a finite length L. At zero temperature, we find that the displacement fluctuations Left-Pointing-Angle-Bracket [{delta}u(X)]{sup 2} Right-Pointing-Angle-Bracket {proportional_to} LX{sup 2} depend on L and scale with the square of the segment length X, which differs from a straightforward Larkin-type scaling. The result is best understood in terms of a typical squared angle Left-Pointing-Angle-Bracket {alpha}{sup 2} Right-Pointing-Angle-Bracket {proportional_to} L, where {alpha} = {partial_derivative}{sub x}u, from which the displacement scaling for the segment X follows naturally, Left-Pointing-Angle-Bracket [{delta}u(X)]{sup 2} Right-Pointing-Angle-Bracket {proportional_to} Left-Pointing-Angle-Bracket {alpha}{sup 2} Right-Pointing-Angle-Bracket X{sup 2}. At high temperatures, thermal fluctuations smear the disorder potential and the lowest-order results for disorder-induced fluctuations in both the displacement field and the angle vanish in the thermodynamic limit L {yields} {infinity}. The calculation up to the second order allows us to identify the regime of validity of the perturbative approach and provides a finite expression for the displacement

  11. Polymer Directed Protein Assemblies

    Patrick van Rijn


    Full Text Available Protein aggregation and protein self-assembly is an important occurrence in natural systems, and is in some form or other dictated by biopolymers. Very obvious influences of biopolymers on protein assemblies are, e.g., virus particles. Viruses are a multi-protein assembly of which the morphology is dictated by poly-nucleotides namely RNA or DNA. This “biopolymer” directs the proteins and imposes limitations on the structure like the length or diameter of the particle. Not only do these bionanoparticles use polymer-directed self-assembly, also processes like amyloid formation are in a way a result of directed protein assembly by partial unfolded/misfolded biopolymers namely, polypeptides. The combination of proteins and synthetic polymers, inspired by the natural processes, are therefore regarded as a highly promising area of research. Directed protein assembly is versatile with respect to the possible interactions which brings together the protein and polymer, e.g., electrostatic, v.d. Waals forces or covalent conjugation, and possible combinations are numerous due to the large amounts of different polymers and proteins available. The protein-polymer interacting behavior and overall morphology is envisioned to aid in clarifying protein-protein interactions and are thought to entail some interesting new functions and properties which will ultimately lead to novel bio-hybrid materials.

  12. Statistical mechanics of fuzzy random polymer networks



    A statistical mechanics framework of fuzzy random polymer networks is established based on the theories of fuzzy systems. The entanglement effect is manifested quantitatively by introducing an entanglement tensor and membership function and the amorphous structure is treated as the fuzzy random network made up of macromolecular coils entangled randomly. A random tetrahedral entangled-crosslinked cell is chosen as an average representative unit of the fuzzy random polymer network structure. By making use of the theory of fuzzy probability and statistical mechanics, the expression for the free energy of deformation is given, which fits well with the experimental data on rubber elasticity under various deformation modes. Both classical statistical theory and Mooney-Rivlin equation can be taken as its special cases.

  13. Direct Photopatterning of Electrochromic Polymers

    Jensen, Jacob; Dyer, Aubrey L.; Shen, D. Eric


    Propylenedioxythiophene (ProDOT) polymers are synthesized using an oxidative polymerization route that results in methacrylate substituted poly(ProDOTs) having a Mn of 10–20 kDa wherein the methacrylate functionality constitutes from 6 to 60% of the total monomer units. Solutions of these polymer...

  14. Conformation and intramolecular relaxation dynamics of semiflexible randomly hyperbranched polymers

    Kumar, Amit; Rai, Gobind Ji; Biswas, Parbati


    The conformational and dynamic properties of semiflexible randomly hyperbranched polymers are investigated in dilute solutions within the framework of optimized Rouse-Zimm formalism. Semiflexibility is incorporated by restricting the directions and orientations of the respective bond vectors, while hydrodynamic interactions are modeled through the preaveraged Oseen tensor. The effect of semiflexibility is typically reflected in the intermediate frequency regime of the viscoelastic relaxation moduli where the bond orientation angle restores the characteristic power-law scaling in fractal structures, as in randomly hyperbranched polymers. Despite the absence of this power-law scaling regime in flexible randomly hyperbranched polymers and in earlier models of semiflexible randomly branched polymers due to weak disorder [C. von Ferber and A. Blumen, J. Chem. Phys. 116, 8616 (2002)], 10.1063/1.1470198, this power-law behavior may be reinstated by explicitly modeling hyperbranched polymers as a Vicsek fractals. The length of this power-law zone in the intermediate frequency region is a combined function of the number of monomers and the degree of semiflexibility. A clear conformational transition from compact to open structures is facilitated by changing the bond orientation angle, where the compressed conformations are compact, while the expanded ones are relatively non-compact. The extent of compactness in the compressed conformations are much less compared to the semiflexible dendrimers, which resemble hard spheres. The fractal dimensions of the compressed and expanded conformations calculated from the Porod's scaling law vary as a function of the bond orientation angle, spanning the entire range of three distinct scaling regimes of linear polymers in three-dimensions. The results confirm that semiflexibility exactly accounts for the excluded volume interactions which are expected to be significant for such polymers with complex topologies.

  15. On the Long-Range Directed Polymer Model

    Wei, Ran


    We study the long-range directed polymer model on Z in a random environment, where the underlying random walk lies in the domain of attraction of an α -stable process for some α in (0,2]. Similar to the more classic nearest-neighbor directed polymer model, as the inverse temperature β increases, the model undergoes a transition from a weak disorder regime to a strong disorder regime. We extend most of the important results known for the nearest-neighbor directed polymer model on Z^d to the long-range model on Z. More precisely, we show that in the entire weak disorder regime, the polymer satisfies an analogue of invariance principle, while in the so-called very strong disorder regime, the polymer end point distribution contains macroscopic atoms and under some mild conditions, the polymer has a super-α -stable motion. Furthermore, for α in (1,2], we show that the model is in the very strong disorder regime whenever β >0, and we give explicit bounds on the free energy.

  16. Barium titanate-polymer composites produced via directional freezing.

    Gorzkowski, Edward P; Pan, Ming-Jen


    In this study, we use a freeze casting technique to construct ceramic-polymer composites in which the 2 phases are arranged in an electrically parallel configuration. By doing so, the composites exhibit dielectric constant (K) up to 2 orders of magnitude higher than that of composites with ceramic particles randomly dispersed in a polymer matrix. In this technique, an aqueous ceramic slurry was frozen unidirectionally to form ice platelets and ceramic aggregates that were aligned in the temperature gradient direction. Upon freeze-drying, the ice platelets sublimed and left the lamellar ceramic structure intact. The green ceramic body was fired to retain the microstructure, and then the space between ceramic lamellae was infiltrated with a polymer material. The finished composites exhibit the high dielectric constant (1000) of ferroelectric ceramics while maintaining the unique properties of polymer materials such as graceful failure, low dielectric loss, and high dielectric breakdown.

  17. Universality for directed polymers in thin rectangles

    Auffinger, Antonio; Corwin, Ivan


    We consider the fluctuations of the free energy of positive temperature directed polymers in thin rectangles (N,N^{\\alpha}), \\alpha < 3/14. For general weight distributions with finite fourth moment we prove that the distribution of these fluctuations converges as N goes to infinity to the GUE Tracy-Widom distribution.

  18. Compositions for directed alignment of conjugated polymers

    Kim, Jinsang; Kim, Bong-Gi; Jeong, Eun Jeong


    Conjugated polymers (CPs) achieve directed alignment along an applied flow field and a dichroic ratio of as high as 16.67 in emission from well-aligned thin films and fully realized anisotropic optoelectronic properties of CPs in field-effect transistor (FET).

  19. Polymer-directed crystallization of atorvastatin.

    Choi, Hyemin; Lee, Hyeseung; Lee, Min Kyung; Lee, Jonghwi


    Living organisms secrete minerals composed of peptides and proteins, resulting in "mesocrystals" of three-dimensional-assembled composite structures. Recently, this biomimetic polymer-directed crystallization technique has been widely applied to inorganic materials, although it has seldom been used with drugs. In this study, the technique was applied to the drowning-out crystallization of atorvastatin using various polymers. Nucleation and growth at optimized conditions successfully produced composite crystals with significant polymer contents and unusual characteristics. Atorvastatin composite crystals containing polyethylene glycol, polyacrylic acid, polyethylene imine, and chitosan showed a markedly decreased melting point and heat of fusion, improved stability, and sustained-release patterns. The use of hydroxypropyl cellulose yielded a unique combination of enhanced in vitro release and improved drug stability under a forced degradation condition. The formation hypothesis of unique mesocrystal structures was strongly supported by an X-ray diffraction pattern and substantial melting point reduction. This polymer-directed crystallization technique offers a novel and effective way, different from the solid dispersion approach, to engineer the release, stability, and processability of drug crystals.

  20. Direct dialling of Haar random unitary matrices

    Russell, Nicholas J.; Chakhmakhchyan, Levon; O’Brien, Jeremy L.; Laing, Anthony


    Random unitary matrices find a number of applications in quantum information science, and are central to the recently defined boson sampling algorithm for photons in linear optics. We describe an operationally simple method to directly implement Haar random unitary matrices in optical circuits, with no requirement for prior or explicit matrix calculations. Our physically motivated and compact representation directly maps independent probability density functions for parameters in Haar random unitary matrices, to optical circuit components. We go on to extend the results to the case of random unitaries for qubits.

  1. On a directionally reinforced random walk

    Ghosh, Arka; Roitershtein, Alexander


    We consider a generalized version of a directionally reinforced random walk, which was originally introduced by Mauldin, Monticino, and von Weizs\\"{a}cker in \\cite{drw}. Our main result is a stable limit theorem for the position of the random walk in higher dimensions. This extends a result of Horv\\'{a}th and Shao \\cite{limits} that was previously obtained in dimension one only (however, in a more stringent functional form).

  2. From chromosome crumpling to the interacting randomly branched polymers

    Everaers, Ralf

    The conformational statistics of ring polymers in melts or dense solutions is strongly affected by their quenched microscopic topological state. The effect is particularly strong for non-concatenated unknotted rings, which are known to crumple and segregate and which have been implicated as models for the generic behavior of interphase chromosomes. In we have used a computationally efficient multi-scale approach to identify the subtle physics underlying their behavior, where we combine massive Molecular Dynamics simulations on the fiber level with Monte Carlo simulations of a wide range of lattice models for the large scale structure. This allowed us to show that ring melts can be quantitatively mapped to coarse-grained melts of interacting randomly branched primitive paths. To elucidate the behavior of interacting branched polymers, we use a combination of scaling arguments and computer simulations. The simulations are carried out for different statistical ensembles: ideal randomly branching polymers, melts of interacting randomly branching polymers, and self-avoiding trees with annealed and quenched connectivities. In all cases, we perform a detailed analysis of the tree connectivities and conformations. We find that the scaling behaviour of average properties is very well described by the Flory theory of Gutin et al. [Macromolecules 26, 1293 (1993)]. A detailed study of the corresponding distribution functions allows us to propose a coherent framework of the behavior of interacting trees, including generalised Fisher-Pincus relationships and the detailed analysis of contacts statistics.

  3. Laser Direct Writing of Thick Hybrid Polymers for Microfluidic Chips

    Akanksha Singh; Gianmario Scotti; Tiina Sikanen; Ville Jokinen; Sami Franssila


    This work presents patterning of thick (10–50 µm) hybrid polymer structures of ORMOCER® by laser direct writing. ORMOCER® combine polymer-like fabrication processes with glass-like surface chemistry that is beneficial for many bio-microfluidic applications. ORMOCER® is liquid before exposure, so patterning is done by contact-free lithography, such as proximity exposure. With laser direct writing, we obtained higher resolution patterns, with smaller radius of curvature (~2–4 µm), compared to p...

  4. Stiff directed lines in random media.

    Boltz, Horst-Holger; Kierfeld, Jan


    We investigate the localization of stiff directed lines with bending energy by a short-range random potential. We apply perturbative arguments, Flory scaling arguments, a variational replica calculation, and functional renormalization to show that a stiff directed line in 1+d dimensions undergoes a localization transition with increasing disorder for d>2/3. We demonstrate that this transition is accessible by numerical transfer matrix calculations in 1+1 dimensions and analyze the properties of the disorder-dominated phase in detail. On the basis of the two-replica problem, we propose a relation between the localization of stiff directed lines in 1+d dimensions and of directed lines under tension in 1+3d dimensions, which is strongly supported by identical free-energy distributions. This shows that pair interactions in the replicated Hamiltonian determine the nature of directed line localization transitions with consequences for the critical behavior of the Kardar-Parisi-Zhang equation. We support the proposed relation to directed lines via multifractal analysis, revealing an analogous Anderson transition-like scenario and a matching correlation length exponent. Furthermore, we quantify how the persistence length of the stiff directed line is reduced by disorder.

  5. Exploring the randomness of Directed Acyclic Networks

    Goñi, Joaquín; Solé, Ricard V; Rodríguez-Caso, Carlos


    The feed-forward relationship naturally observed in time-dependent processes and in a diverse number of real systems -such as some food-webs and electronic and neural wiring- can be described in terms of so-called directed acyclic graphs (DAGs). An important ingredient of the analysis of such networks is a proper comparison of their observed architecture against an ensemble of randomized graphs, thereby quantifying the {\\em randomness} of the real systems with respect to suitable null models. This approximation is particularly relevant when the finite size and/or large connectivity of real systems make inadequate a comparison with the predictions obtained from the so-called {\\em configuration model}. In this paper we analyze four methods of DAG randomization as defined by the desired combination of topological invariants (directed and undirected degree sequence and component distributions) aimed to be preserved. A highly ordered DAG, called \\textit{snake}-graph and a Erd\\:os-R\\'enyi DAG were used to validate ...

  6. Computer simulations of melts of randomly branching polymers

    Rosa, Angelo; Everaers, Ralf


    Randomly branching polymers with annealed connectivity are model systems for ring polymers and chromosomes. In this context, the branched structure represents transient folding induced by topological constraints. Here we present computer simulations of melts of annealed randomly branching polymers of 3 ≤ N ≤ 1800 segments in d = 2 and d = 3 dimensions. In all cases, we perform a detailed analysis of the observed tree connectivities and spatial conformations. Our results are in excellent agreement with an asymptotic scaling of the average tree size of R ˜ N1/d, suggesting that the trees behave as compact, territorial fractals. The observed swelling relative to the size of ideal trees, R ˜ N1/4, demonstrates that excluded volume interactions are only partially screened in melts of annealed trees. Overall, our results are in good qualitative agreement with the predictions of Flory theory. In particular, we find that the trees swell by the combination of modified branching and path stretching. However, the former effect is subdominant and difficult to detect in d = 3 dimensions.

  7. Agreement dynamics on directed random graphs

    Lipowski, Adam; Ferreira, Antonio L


    When agreement-dynamics models are placed on a directed random graph, a fraction of sites $\\exp(-z)$, where $z$ is the average degree, becomes permanently fixed or flickering. In the Voter model, which has no surface tension, such zealots or flickers freely spread their opinions and that makes the system disordered. For models with a surface tension, like the Ising model or the Naming Game model, their role is limited and such systems are ordered at large~$z$. However, when $z$ decreases, the density of zealots or flickers increases, and below a certain threshold ($z\\sim 1.9-2.0$) the system becomes disordered. Our results show that the agreement dynamics on directed networks is much different from their undirected analogues.

  8. Direct dimethyl ether high temperature polymer electrolyte membrane fuel cells

    Vassiliev, Anton; Jensen, Jens Oluf; Li, Qingfeng

    and suffers from low DME solubility in water. When the DME - water mixture is fed as vapour miscibility is no longer a problem. The increased temperature is more beneficial for the kinetics of the direct oxidation of DME than of methanol. The Open Circuit Voltage (OCV) with DME operation was 50 to 100 m......A high temperature polybenzimidazole (PBI) polymer fuel cell was fed with dimethyl ether (DME) and water vapour mixture on the anode at ambient pressure with air as oxidant. A peak power density of 79 mW/cm2 was achieved at 200°C. A conventional polymer based direct DME fuel cell is liquid fed...

  9. Random walks in directed modular networks

    Comin, Cesar H.; Viana, Mateus P.; Antiqueira, Lucas; Costa, Luciano da F.


    Because diffusion typically involves symmetric interactions, scant attention has been focused on studying asymmetric cases. However, important networked systems underlain by diffusion (e.g. cortical networks and WWW) are inherently directed. In the case of undirected diffusion, it can be shown that the steady-state probability of the random walk dynamics is fully correlated with the degree, which no longer holds for directed networks. We investigate the relationship between such probability and the inward node degree, which we call efficiency, in modular networks. Our findings show that the efficiency of a given community depends mostly on the balance between its ingoing and outgoing connections. In addition, we derive analytical expressions to show that the internal degree of the nodes does not play a crucial role in their efficiency, when considering the Erdős-Rényi and Barabási-Albert models. The results are illustrated with respect to the macaque cortical network, providing subsidies for improving transportation and communication systems.

  10. Heterogeneous Directional Mobility in the Early Stages of Polymer Crystallization

    Lacevic, N; Fried, L E; Gee, R H


    Recently we demonstrated via large large-scale molecular dynamics simulations a 'coexistence period' in polymer melt ordering before crystallization, where nucleation and growth mechanisms coexist with a phase phase-separation mechanism. Here we present an extension of this work, where we analyze the directional displacements as a measure of the mobility of monomers as they order during crystallization over more than 100 ns of simulation time. It is found that the polymer melt, after quenching, rapidly separates into many ordered hexagonal domains separated by amorphous regions, where surprisingly, the magnitude of the monomer's displacement in the ordered state, parallel to the domain axial direction, is similar to its magnitude in the melt. T. The monomer he displacements in the domain's lateral direction are found to decrease during the time of the simulation. The ordered hexagonal domains do not align into uniform lamellar structures during the timescales of our simulations.




    Using a scanning force microscope, direct imaging of the metal/polymer interface was achieved for the first time by removing the evaporated metal film from the deposited polymer and imaging the side that was exposed to the polymer, This technique allows direct sight of the metal/polymer interface an

  12. Transition for Optimal Paths in Bimodal Directed Polymers

    WANG Xiao-Hong


    @@ The problem for optimal paths in bimodal directed polymers is studied. It is shown that the distribution of the thermal average position of the endpoints of the optimal paths is discontinuous below the threshold p < pc. The origin is that there is a finite possibility that only one endpoint takes the global minimum energy for p < pc. Our results suggest that the percolation threshold for directed percolation is also the critical point of the transition for the possibility that the optimal paths converge to one endpoint.

  13. Random Lasers for Broadband Directional Emission

    Schönhuber, Sebastian; Hisch, Thomas; Deutsch, Christoph; Krall, Michael; Detz, Hermann; Strasser, Gottfried; Rotter, Stefan; Unterrainer, Karl


    Broadband coherent light sources are becoming increasingly important for sensing and spectroscopic applications, especially in the mid-infrared and terahertz (THz) spectral regions, where the unique absorption characteristics of a whole host of molecules are located. The desire to miniaturize such light emitters has recently lead to spectacular advances with compact on-chip lasers that cover both of these spectral regions. The long wavelength and the small size of the sources result in a strongly diverging laser beam that is difficult to focus on the target that one aims to perform spectroscopy with. Here, we introduce an unconventional solution to this vexing problem relying on a random laser to produce coherent broadband THz radiation as well as an almost diffraction limited far-field emission profile. Our random lasers do not require any fine-tuning and thus constitute a promising example of practical device applications for random lasing.

  14. Novel Random Mutagenesis Method for Directed Evolution.

    Feng, Hong; Wang, Hai-Yan; Zhao, Hong-Yan


    Directed evolution is a powerful strategy for gene mutagenesis, and has been used for protein engineering both in scientific research and in the biotechnology industry. The routine method for directed evolution was developed by Stemmer in 1994 (Stemmer, Proc Natl Acad Sci USA 91, 10747-10751, 1994; Stemmer, Nature 370, 389-391, 1994). Since then, various methods have been introduced, each of which has advantages and limitations depending upon the targeted genes and procedure. In this chapter, a novel alternative directed evolution method which combines mutagenesis PCR with dITP and fragmentation by endonuclease V is described. The kanamycin resistance gene is used as a reporter gene to verify the novel method for directed evolution. This method for directed evolution has been demonstrated to be efficient, reproducible, and easy to manipulate in practice.

  15. Exact solution for a random walk in a time-dependent 1D random environment: the point-to-point Beta polymer

    Thiery, Thimothée; Le Doussal, Pierre


    We consider the Beta polymer, an exactly solvable model of directed polymer on the square lattice, introduced by Barraquand and Corwin (BC) (2016 Probab. Theory Relat. Fields 1-16). We study the statistical properties of its point to point partition sum. The problem is equivalent to a model of a random walk in a time-dependent (and in general biased) 1D random environment. In this formulation, we study the sample to sample fluctuations of the transition probability distribution function (PDF) of the random walk. Using the Bethe ansatz we obtain exact formulas for the integer moments, and Fredholm determinant formulas for the Laplace transform of the directed polymer partition sum/random walk transition probability. The asymptotic analysis of these formulas at large time t is performed both (i) in a diffusive vicinity, x˜ {{t}1/2} , of the optimal direction (in space-time) chosen by the random walk, where the fluctuations of the PDF are found to be Gamma distributed; (ii) in the large deviations regime, x˜ t , of the random walk, where the fluctuations of the logarithm of the PDF are found to grow with time as t 1/3 and to be distributed according to the Tracy-Widom GUE distribution. Our exact results complement those of BC for the cumulative distribution function of the random walk in regime (ii), and in regime (i) they unveil a novel fluctuation behavior. We also discuss the crossover regime between (i) and (ii), identified as x˜ {{t}3/4} . Our results are confronted to extensive numerical simulations of the model.

  16. Ferritin nanocontainers that self-direct in synthetic polymer systems

    Sengonul, Merih C.

    Currently, there are many approaches to introduce functionality into synthetic polymers. Among these, for example, are copolymerization, grafting, and blending methods. However, modifications made by such methods also change the thermodynamics and rheological properties of the polymer system of interest, and each new modification often requires a costly reoptimization of polymer processing. Such a reoptimalization would not be necessary if new functionality could be introduced via a container whose external surface is chemically and physically tuned to interact with the parent polymer. The contents of the container could then be changed without changing other important properties of the parent polymer. In this context this thesis project explores an innovative nanocontainer platform which can be introduced into phase-separating homopolymer blends. Ferritin is a naturally existing nanocontainer that can be used synthetically to package and selectively transport functional moieties to a particular phase that is either in the bulk or on the surface of a homopolymer blend system. The principal focus of this work centers on modifying the surface of wild ferritin to: (1) render modified ferritin soluble in a non-aqueous solvent; and (2) impart it with self-directing properties when exposed to a homopolymer blend surface or incorporated into the bulk of a homopolymer blend. Wild ferritin is water soluble, and this research project successfully modified wild ferritin by grafting either amine-functional poly(ethylene glycol) (PEG) or short-chain alkanes to carbodiimide activated carboxylate groups on ferritin's surface. Such modified ferritin is soluble in dichloromethane (DCM). Modification was confirmed by ion-exchange chromatography, zeta-potential measurements, and electrospray mass spectroscopy. FT-IR was used to quantify the extent of PEGylation of the reaction products through area ratios of the -C-O-C asymmetric stretching vibration of the grafted PEG chains to the

  17. Laser Direct Writing of Thick Hybrid Polymers for Microfluidic Chips

    Akanksha Singh


    Full Text Available This work presents patterning of thick (10–50 µm hybrid polymer structures of ORMOCER® by laser direct writing. ORMOCER® combine polymer-like fabrication processes with glass-like surface chemistry that is beneficial for many bio-microfluidic applications. ORMOCER® is liquid before exposure, so patterning is done by contact-free lithography, such as proximity exposure. With laser direct writing, we obtained higher resolution patterns, with smaller radius of curvature (~2–4 µm, compared to proximity exposure (~10–20 µm. Process parameters were studied to find the optimal dose for different exposure conditions and ORMOCER® layer thicknesses. Two fluidic devices were successfully fabricated: a directional wetting device (fluidic diode and an electrophoresis chip. The fluidic diode chip operation depends on the sharp corner geometry and water contact angle, and both have been successfully tailored to obtain diodicity. Electrophoresis chips were used to separate of two fluorescent dyes, rhodamine 123 and fluorescein. The electrophoresis chip also made use of ORMOCER® to ORMOCER® bonding.

  18. Directed colloidal assembly and characterization of PZT-polymer composites

    Smay, James Earl

    Lead zirconate titanate (PZT)-based layers and 3-D structures were directly assembled using two colloidal routes: (1) tape casting and (2) a layer-by-layer robotic deposition technique, known as robocasting. First, concentrated (φsolids > 0.45) suspensions of PZT-5H and a latex emulsion were tape cast with the aid of viscosifier and surfactant additions. Drying stress evolved to a maximum at φ PZT ˜ 0.49, followed by a reduction and a secondary stress rise attributed to latex coalescence. Dielectric and piezoelectric properties of sintered PZT multilayer laminates exhibited good agreement with those for isostatically pressed and sintered samples. Concentrated, weakly gelled suspensions of PZT 95/5 and poly(ethylene) (PE) latices, a fugitive species, were developed as inks for the robotic deposition of monolithic and tri-layered composite structures. Monoliths, with densities of 93.6% and 96.1%, and composites with a 96.1% dense layer between 93.6% regions were fabricated. The structures displayed equivalent electrical properties to cold isostatically pressed parts. The composites withstood repeated saturation polarization switching as well as a 500 MPa hydrostatic pressure-induced poled ferroelectric (FE) to antiferroelectric (AFE) phase transformation. Concentrated (φPZT = 0.47) PZT-5H gels were developed as inks for the robotic deposition of 3-D, mesoscale periodic structures with self-supporting features such as lattices of rod-like elements and v-shaped test structures. The gels exhibited pH dependent viscoelastic properties and Hershel-Bulkley flow behavior. The deflection of as-deposited spanning elements was measured using laser profilometry. Flow modeling and shape evolution data indicated a core-shell architecture as the ink exited the deposition nozzle, which simultaneously provided strength to form spanning elements and good bonding between layers. The core grew rapidly (˜1s) due to the quick recovery of gel structure in these inks. 3-X type PZT-polymer

  19. Study of charge transport in highly conducting polymers based on a random resistor network

    Zhou Liping [Department of Physics, Suzhou University, Suzhou 215006 (China)]. E-mail:; Liu Bo [Department of Physics, Suzhou University, Suzhou 215006 (China); Department of Physics, Jiangsu Teachers University of Technology, Changzhou 213001 (China); Li Zhenya [CCAST (World Laboratory), P.O. Box 8730, Beijing 100080 (China) and Department of Physics, Suzhou University, Suzhou 215006 (China)]. E-mail:


    Based on a random resistor network (RRN), we study the unusual ac conductivity {sigma}({omega}) of highly conducting polymer such as PF{sub 6} doped polypyrrole. The system is modeled as a composite medium consisting of metallic regions randomly distributed in the amorphous parts. Within the metallic regions, the polymer chains are regularly and densely packed, outside which the poorly arranged chains form amorphous host. The metallic grains are connected by resonance quantum tunneling, which occurs through the strongly localized states in the amorphous media. {sigma}({omega}), calculated from this model, reproduces the main experimental features associated with the metal-insulator transition in these polymers.

  20. Polymers on disordered hierarchical lattices: A nonlinear combination of random variables

    Cook, J. (Commissariat a l' Energie Atomique, Gif-sur-Yvette (France) Univ. of Edinburgh (England)); Derrida, B. (Commissariat a l' Energie Atomique, Gif-sur-Yvette (France))


    The problem of directed polymers on disordered hierarchical and hypercubic lattices is considered. For the hierarchical lattices the problem can be reduced to the study of the stable laws for combining random variables in a nonlinear way. The authors present the results of numerical simulations of two hierarchical lattices, finding evidence of a phase transition in one case. For a limiting case they extend the perturbation theory developed by Derrida and Griffiths to nonzero temperature and to higher order and use this approach to calculate thermal and geometrical properties (overlaps) of the model. In this limit they obtain an interpolation formula, allowing one to obtain the noninteger moments of the partition function from the integer moments. They obtain bounds for the transition temperature for hierarchical and hypercubic lattices, and some similarities between the problem on the two different types of lattice are discussed.

  1. Search for Directed Networks by Different Random Walk Strategies

    ZHU Zi-Qi; JIN Xiao-Ling; HUANG Zhi-Long


    A comparative study is carried out on the effciency of five different random walk strategies searching on directed networks constructed based on several typical complex networks.Due to the difference in search effciency of the strategies rooted in network clustering,the clustering coeFfcient in a random walker's eye on directed networks is defined and computed to be half of the corresponding undirected networks.The search processes are performed on the directed networks based on Erd(o)s-Rényi model,Watts-Strogatz model,Barabási-Albert model and clustered scale-free network model.It is found that self-avoiding random walk strategy is the best search strategy for such directed networks.Compared to unrestricted random walk strategy,path-iteration-avoiding random walks can also make the search process much more effcient. However,no-triangle-loop and no-quadrangle-loop random walks do not improve the search effciency as expected,which is different from those on undirected networks since the clustering coefficient of directed networks are smaller than that of undirected networks.

  2. Liquid immersion thermal crosslinking of 3D polymer nanopatterns for direct carbonisation with high structural integrity

    Da-Young Kang; Cheolho Kim; Gyurim Park; Jun Hyuk Moon


    The direct pyrolytic carbonisation of polymer patterns has attracted interest for its use in obtaining carbon materials. In the case of carbonisation of nanopatterned polymers, the polymer flow and subsequent pattern change may occur in order to relieve their high surface energies. Here, we demonstrated that liquid immersion thermal crosslinking of polymer nanopatterns effectively enhanced the thermal resistance and maintained the structure integrity during the heat treatment. We employed the...

  3. Multifunctional polymer-metal nanocomposites via direct chemical reduction by conjugated polymers.

    Xu, Ping; Han, Xijiang; Zhang, Bin; Du, Yunchen; Wang, Hsing-Lin


    Noble metal nanoparticles (MNPs) have attracted continuous attention due to their promising applications in chemistry, physics, bioscience, medicine and materials science. As an alternative to conventional solution chemistry routes, MNPs can be directly synthesized through a conjugated polymer (CP) mediated technique utilizing the redox chemistry of CPs to chemically reduce the metal ions and modulate the size, morphology, and structure of the MNPs. The as-prepared multifunctional CP-MNP nanocomposites have shown application potentials as highly sensitive surface enhanced Raman spectroscopy (SERS) substrates, effective heterogeneous catalysts for organic synthesis and electrochemistry, and key components for electronic and sensing devices. In this tutorial review, we begin with a brief introduction to the chemical nature and redox properties of CPs that enable the spontaneous reduction of noble metal ions to form MNPs. We then focus on recent progress in control over the size, morphology and structure of MNPs during the conjugated polymer mediated syntheses of CP-MNP nanocomposites. Finally, we highlight the multifunctional CP-MNP nanocomposites toward their applications in sensing, catalysis, and electronic devices.

  4. On random flights with non-uniformly distributed directions

    De Gregorio, Alessandro


    This paper deals with a new class of random flights $\\underline{\\bf X}_d(t),t>0,$ defined in the real space $\\mathbb{R}^d, d\\geq 2,$ characterized by non-uniform probability distributions on the multidimensional sphere. These random motions differ from similar models appeared in literature which take directions according to the uniform law. The family of angular probability distributions introduced in this paper depends on a parameter $\

  5. Randomized clinical trial comparing abluminal biodegradable polymer sirolimus-eluting stents with durable polymer sirolimus-eluting stents

    Zhang, Haijun; Wang, Xiangfei; Deng, Wei; Wang, Shenguo; Ge, Junbo; Toft, Egon


    Abstract Background: The biodegradable polymer drug-eluting stents (DES) were developed to improve vascular healing. However, further data and longer-term follow-up are needed to confirm safety and efficacy of these stents. This randomized clinical trial aimed to compare safety and efficacy of 2 sirolimus-eluting stents (SES): Cordimax—a novel abluminal biodegradable polymer SES and Cypher Select—a durable polymer SES, at 9 months angiographic and 5-year clinical follow-up. Methods: We randomized 402 patients with coronary artery disease to percutaneous coronary intervention with Cordimax (n = 202) or Cypher select (n = 200). Angiographic follow-up was performed at 9 months after the index procedure and clinical follow-up annually up to 5 years. The primary endpoint was angiographic in-stent late luminal loss (LLL). Secondary endpoints included angiographic restenosis rate, target vessel revascularization (TVR), and major adverse cardiac events (MACEs; defined as cardiac death, myocardial infarction, or TVR) at 5-year follow-up. Results: Cordimax was noninferior to Cypher select for in-stent LLL (0.25 ± 0.47 vs 0.18 ± 0.49 mm; P = 0.587) and in-stent mean diameter stenosis (22.19 ± 12.21% vs 19.89 ± 10.79%; P = 0.064) at 9 months angiographic follow-up. The MACE rates were not different at 1 year (5.9% vs 4.0%, P = 0.376); however, MACE rates from 2 to 5 years were lower in the Cordimax group (6.8% vs 13.1%; P = 0.039). Conclusion: Abluminal biodegradable polymer SES is noninferior to durable polymer SES at 9-month angiographic and 1-year clinical follow-up. However, MACE rates from 2 to 5 years were less in the abluminal biodegradable polymer group. PMID:27661023

  6. Direct measurement of the microscale conductivity of conjugated polymer monolayers

    Bøggild, Peter; Grey, Francois; Hassenkam, T.;


    The in-plane conductivity of conjugated polymer monolayers is mapped here for the first time on the microscale using a novel scanning micro four-point probe (see Figure). The probe allows the source, drain, and voltage electrodes to be positioned within the same domain and the mapping results...... demonstrate how microscopic ordering in the polymer domains controls the conductivity....

  7. Design directed self-assembly of donor-acceptor polymers.

    Marszalek, Tomasz; Li, Mengmeng; Pisula, Wojciech


    Donor-acceptor polymers with an alternating array of donor and acceptor moieties have gained particular attention during recent years as active components of organic electronics. By implementation of suitable subunits within the conjugated backbone, these polymers can be made either electron-deficient or -rich. Additionally, their band gap and light absorption can be precisely tuned for improved light-harvesting in solar cells. On the other hand, the polymer design can also be modified to encode the desired supramolecular self-assembly in the solid-state that is essential for an unhindered transport of charge carriers. This review focuses on three major factors playing a role in the assembly of donor-acceptor polymers on surfaces which are (1) nature, geometry and substitution position of solubilizing alkyl side chains, (2) shape of the conjugated polymer defined by the backbone curvature, and (3) molecular weight which determines the conjugation length of the polymer. These factors adjust the fine balance between attractive and repulsive forces and ensure a close polymer packing important for an efficient charge hopping between neighboring chains. On the microscopic scale, an appropriate domain formation with a low density of structural defects in the solution deposited thin film is crucial for the charge transport. The charge carrier transport through such thin films is characterized by field-effect transistors as basic electronic elements.

  8. Recent progress toward the templated synthesis and directed evolution of sequence-defined synthetic polymers.

    Brudno, Yevgeny; Liu, David R


    Biological polymers such as nucleic acids and proteins are ubiquitous in living systems, but their ability to address problems beyond those found in nature is constrained by factors such as chemical or biological instability, limited building-block functionality, bioavailability, and immunogenicity. In principle, sequence-defined synthetic polymers based on nonbiological monomers and backbones might overcome these constraints; however, identifying the sequence of a synthetic polymer that possesses a specific desired functional property remains a major challenge. Molecular evolution can rapidly generate functional polymers but requires a means of translating amplifiable templates such as nucleic acids into the polymer being evolved. This review covers recent advances in the enzymatic and nonenzymatic templated polymerization of nonnatural polymers and their potential applications in the directed evolution of sequence-defined synthetic polymers.

  9. Dynamics of comb-of-comb-network polymers in random layered flows

    Katyal, Divya; Kant, Rama


    We analyze the dynamics of comb-of-comb-network polymers in the presence of external random flows. The dynamics of such structures is evaluated through relevant physical quantities, viz., average square displacement (ASD) and the velocity autocorrelation function (VACF). We focus on comparing the dynamics of the comb-of-comb network with the linear polymer. The present work displays an anomalous diffusive behavior of this flexible network in the random layered flows. The effect of the polymer topology on the dynamics is analyzed by varying the number of generations and branch lengths in these networks. In addition, we investigate the influence of external flow on the dynamics by varying flow parameters, like the flow exponent α and flow strength Wα. Our analysis highlights two anomalous power-law regimes, viz., subdiffusive (intermediate-time polymer stretching and flow-induced diffusion) and superdiffusive (long-time flow-induced diffusion). The anomalous long-time dynamics is governed by the temporal exponent ν of ASD, viz., ν =2 -α /2 . Compared to a linear polymer, the comb-of-comb network shows a shorter crossover time (from the subdiffusive to superdiffusive regime) but a reduced magnitude of ASD. Our theory displays an anomalous VACF in the random layered flows that scales as t-α /2. We show that the network with greater total mass moves faster.

  10. Dynamics of comb-of-comb-network polymers in random layered flows.

    Katyal, Divya; Kant, Rama


    We analyze the dynamics of comb-of-comb-network polymers in the presence of external random flows. The dynamics of such structures is evaluated through relevant physical quantities, viz., average square displacement (ASD) and the velocity autocorrelation function (VACF). We focus on comparing the dynamics of the comb-of-comb network with the linear polymer. The present work displays an anomalous diffusive behavior of this flexible network in the random layered flows. The effect of the polymer topology on the dynamics is analyzed by varying the number of generations and branch lengths in these networks. In addition, we investigate the influence of external flow on the dynamics by varying flow parameters, like the flow exponent α and flow strength W_{α}. Our analysis highlights two anomalous power-law regimes, viz., subdiffusive (intermediate-time polymer stretching and flow-induced diffusion) and superdiffusive (long-time flow-induced diffusion). The anomalous long-time dynamics is governed by the temporal exponent ν of ASD, viz., ν=2-α/2. Compared to a linear polymer, the comb-of-comb network shows a shorter crossover time (from the subdiffusive to superdiffusive regime) but a reduced magnitude of ASD. Our theory displays an anomalous VACF in the random layered flows that scales as t^{-α/2}. We show that the network with greater total mass moves faster.

  11. Random lasing and coherent back scattering study in rhodamine 6G doped polymer optical fiber (POF) particles

    C, Sreechandralijith K.; Peter, Jaison; Thankappan, Aparna; Nampoori, V. P. N.; Radhakrishnan, P.


    We demonstrate coherent back scattering and random lasing from an active random media of Rhodamine 6G doped polymer optical fiber particles on different sizes. Narrow emission modes are observed experimentally over a broad range of scattering strengths without requiring optical cavities. The particle-size dependence of transport mean free path, which measured from coherent backscattering measurements. Since the scattering mean free path is less than the emission wavelength, recurrent light scattering arises and provides coherent feedback for lasing. Laser emission from the sample observed in all directions. This observation also provides direct evidence for the existence of recurrent scattering of light. The lasing threshold intensity depends on the excitation volume, also the decrease of the lasing threshold at large particle size. The feedback for lasing originates mainly from backscattering of particles near the boundaries of the pumped region. Here, the lasing threshold depends strongly on the size distribution, dye concentration and intensity of excitation in the ensemble.

  12. Switchable random laser from dye-doped polymer dispersed liquid crystal waveguides

    Xiao, Shumin; Song, Qinghai; Wang, Feng; Liu, Liying; Liu, Jianhua; Xu, Lei


    A dye-doped polymer-dispersed liquid crystal (PDLC) film has been fabricated for random lasing action. In this PDLC film, the sizes of most liquid crystal (LC) droplets ranged from 200 to 500 nm. When the sample is optically pumped, ultrahigh Q (>10 000) lasing modes and a collimated laser beam can

  13. Polyketone polymer: a new support for direct enzyme immobilization.

    Agostinelli, E; Belli, F; Tempera, G; Mura, A; Floris, G; Toniolo, L; Vavasori, A; Fabris, S; Momo, F; Stevanato, R


    Polyketone polymer -[-CO-CH(2)-CH(2)-](n)-, obtained by copolymerization of ethene and carbon monoxide, is utilized for immobilization of three different enzymes, one peroxidase from horseradish (HRP) and two amine oxidases, from bovine serum (BSAO) and lentil seedlings (LSAO). The easy immobilization procedure is carried out in diluted buffer, at pH 7.0 and 3 degrees C, gently mixing the proteins with the polymer. No bifunctional reagents and spacer arms are required for the immobilization, which occurs exclusively via a large number of hydrogen bonds between the carbonyl groups of the polymer and the -NH groups of the polypeptidic chain. Experiments demonstrate a high linking capacity of polymer for BSAO and an extraordinary strong linkage for LSAO. Moreover, activity measurements demonstrate that immobilized LSAO totally retains the catalytic characteristics of the free enzyme, where only a limited increase of K(M) value is observed. Finally, the HRP-activated polymer is successfully used as active packed bed of an enzymatic reactor for continuous flow conversion and flow injection analysis of hydrogen peroxide containing solutions.

  14. Anisotropy of the monomer random walk in a polymer melt: local-order and connectivity effects

    Bernini, S.; Leporini, D.


    The random walk of a bonded monomer in a polymer melt is anisotropic due to local order and bond connectivity. We investigate both effects by molecular-dynamics simulations on melts of fully-flexible linear chains ranging from dimers (M  =  2) up to entangled polymers (M  =  200). The corresponding atomic liquid is also considered a reference system. To disentangle the influence of the local geometry and the bond arrangements, and to reveal their interplay, we define suitable measures of the anisotropy emphasising either the former or the latter aspect. Connectivity anisotropy, as measured by the correlation between the initial bond orientation and the direction of the subsequent monomer displacement, shows a slight enhancement due to the local order at times shorter than the structural relaxation time. At intermediate times—when the monomer displacement is comparable to the bond length—a pronounced peak and then decays slowly as t -1/2, becoming negligible when the displacement is as large as about five bond lengths, i.e. about four monomer diameters or three Kuhn lengths. Local-geometry anisotropy, as measured by the correlation between the initial orientation of a characteristic axis of the Voronoi cell and the subsequent monomer dynamics, is affected at shorter times than the structural relaxation time by the cage shape with antagonistic disturbance by the connectivity. Differently, at longer times, the connectivity favours the persistence of the local-geometry anisotropy, which vanishes when the monomer displacement exceeds the bond length. Our results strongly suggest that the sole consideration of the local order is not enough to understand the microscopic origin of the rattling amplitude of the trapped monomer in the cage of the neighbours.

  15. Computer simulation of randomly cross-linked polymer networks

    Williams, T P


    In this work, Monte Carlo and Stochastic Dynamics computer simulations of mesoscale model randomly cross-linked networks were undertaken. Task parallel implementations of the lattice Monte Carlo Bond Fluctuation model and Kremer-Grest Stochastic Dynamics bead-spring continuum model were designed and used for this purpose. Lattice and continuum precursor melt systems were prepared and then cross-linked to varying degrees. The resultant networks were used to study structural changes during deformation and relaxation dynamics. The effects of a random network topology featuring a polydisperse distribution of strand lengths and an abundance of pendant chain ends, were qualitatively compared to recent published work. A preliminary investigation into the effects of temperature on the structural and dynamical properties was also undertaken. Structural changes during isotropic swelling and uniaxial deformation, revealed a pronounced non-affine deformation dependant on the degree of cross-linking. Fractal heterogeneiti...

  16. Random lasing in dye-doped polymer dispersed liquid crystal film

    Wu, Rina; Shi, Rui-xin; Wu, Xiaojiao; Wu, Jie; Dai, Qin


    A dye-doped polymer-dispersed liquid crystal film was designed and fabricated, and random lasing action was studied. A mixture of laser dye, nematic liquid crystal, chiral dopant, and PVA was used to prepare the dye-doped polymer-dispersed liquid crystal film by means of microcapsules. Scanning electron microscopy analysis showed that most liquid crystal droplets in the polymer matrix ranged from 30 μm to 40 μm, the size of the liquid crystal droplets was small. Under frequency doubled 532 nm Nd:YAG laser-pumped optical excitation, a plurality of discrete and sharp random laser radiation peaks could be measured in the range of 575-590 nm. The line-width of the lasing peak was 0.2 nm and the threshold of the random lasing was 9 mJ. Under heating, the emission peaks of random lasing disappeared. By detecting the emission light spot energy distribution, the mechanism of radiation was found to be random lasing. The random lasing radiation mechanism was then analyzed and discussed. Experimental results indicated that the size of the liquid crystal droplets is the decisive factor that influences the lasing mechanism. The surface anchor role can be ignored when the size of the liquid crystal droplets in the polymer matrix is small, which is beneficial to form multiple scattering. The transmission path of photons is similar to that in a ring cavity, providing feedback to obtain random lasing output. Project supported by the National Natural Science Foundation of China (Grant No. 61378042), the Colleges and Universities in Liaoning Province Outstanding Young Scholars Growth Plans, China (Grant No. LJQ2015093), and Shenyang Ligong University Laser and Optical Information of Liaoning Province Key Laboratory Open Funds, China.

  17. Sulfamides and sulfamide polymers directly from sulfur dioxide.

    Leontiev, Alexander V; Dias, H V Rasika; Rudkevich, Dmitry M


    SO2 gas is effectively used for the preparation of N,N'-diarylsulfamides and shape-persistent sulfamide polymers, which utilize a network of intermolecular N-H...O=S hydrogen bonds to self-assemble into soft porous materials.

  18. Polymer-Derived In- Situ Metal Matrix Composites Created by Direct Injection of a Liquid Polymer into Molten Magnesium

    Sudarshan; Terauds, Kalvis; Anilchandra, A. R.; Raj, Rishi


    We show that a liquid organic precursor can be injected directly into molten magnesium to produce nanoscale ceramic dispersions within the melt. The castings made in this way possess good resistance to tensile deformation at 673 K (400 °C), confirming the non-coarsening nature of these dispersions. Direct liquid injection into molten metals is a significant step toward inserting different chemistries of liquid precursors to generate a variety of polymer-derived metal matrix composites.

  19. Analysis of diverse direct arylation polymerization (DArP) conditions toward the efficient synthesis of polymers converging with stille polymers in organic solar cells

    Livi, Francesco; Gobalasingham, Nemal S.; Thompson, Barry C.


    Despite the emergence of direct arylation polymerization (DArP) as an alternative method to traditional cross-coupling routes like Stille polymerization, the exploration of DArP polymers in practical applications like polymer solar cells (PSCs) is limited. DArP polymers tend to have a reputation...

  20. Novel polymorphic form of adefovir dipivoxil derived from polymer-directed crystallization.

    Lee, Min Kyung; Lee, Hyeseung; Kim, Il Won; Lee, Jonghwi


    Crystallization is an essential step in pharmaceutical processing. The discovery of a non-classical crystallization pathway would be a promising strategy to engineer the properties of drug crystalline particles for specific delivery conditions. Herein, polymer-directed crystallization was successfully employed to modify the characteristics of a model drug, adefovir dipivoxil (AD). Polyacrylic acid (PAA), ethyl cellulose (EC), and hydroxypropyl cellulose were added as active polymers to control the crystallization pathway of AD. Changes in crystal habit were observed in all cases. A novel polymorph was found after the addition of PAA and EC, and was confirmed by XRD and DSC results. In FTIR investigations, the crystals derived from PAA-directed crystallization showed strong interactions between PAA and AD. The polymer content in polymer-directed crystallization-derived powders varied from 7 to 24 wt%, and the presence of polymers lead to sustained release of AD. These results make polymer-directed crystallization a simple and efficient technique to engineer the physical and chemical properties of drug crystals.

  1. Cryogenic EBSD reveals structure of directionally solidified ice–polymer composite

    Donius, Amalie E., E-mail: [Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 (United States); Department of Materials Science and Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Obbard, Rachel W., E-mail: [Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 (United States); Burger, Joan N., E-mail: [Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 (United States); Department of Materials Science and Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Hunger, Philipp M., E-mail: [Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 (United States); Department of Materials Science and Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Baker, Ian, E-mail: [Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 (United States); Doherty, Roger D., E-mail: [Department of Materials Science and Engineering, Drexel University, 3141 Chestnut Street, Philadelphia, PA 19104 (United States); Wegst, Ulrike G.K., E-mail: [Thayer School of Engineering, Dartmouth College, 14 Engineering Drive, Hanover, NH 03755 (United States)


    Despite considerable research efforts on directionally solidified or freeze-cast materials in recent years, little fundamental knowledge has been gained that links model with experiment. In this contribution, the cryogenic characterization of directionally solidified polymer solutions illustrates, how powerful cryo-scanning electron microscopy combined with electron backscatter diffraction is for the structural characterization of ice–polymer composite materials. Under controlled sublimation, the freeze-cast polymer scaffold structure is revealed and imaged with secondary electrons. Electron backscatter diffraction fabric analysis shows that the ice crystals, which template the polymer scaffold and create the lamellar structure, have a-axes oriented parallel to the direction of solidification and the c-axes perpendicular to it. These results indicate the great potential of both cryo-scanning electron microscopy and cryo-electron backscatter diffraction in gaining fundamental knowledge of structure–property–processing correlations. - Highlights: • Cryo-SEM of freeze-cast polymer solution reveals an ice-templated structure. • Cryo-EBSD reveals the ice crystal a-axis to parallel the solidification direction. • The honeycomb-like polymer phase favors columnar ridges only on one side. • Combining cryo-SEM with EBSD links solidification theory with experiment.

  2. Surface segregation of fluorinated moieties on random copolymer films controlled by random-coil conformation of polymer chains in solution.

    Xue, Dongwu; Wang, Xinping; Ni, Huagang; Zhang, Wei; Xue, Gi


    The relationship between solution properties, film-forming methods, and the solid surface structures of random copolymers composed of butyl methacrylate and dodecafluorheptyl methylacrylate (DFHMA) was investigated by contact angle measurements, X-ray photoelectron spectroscopy, sum frequency generation vibrational spectroscopy, and surface tension measurements. The results, based on thermodynamic considerations, demonstrated that the random copolymer chain conformation at the solution/air interface greatly affected the surface structure of the resulting film, thereby determining the surface segregation of fluorinated moieties on films obtained by various film-forming techniques. When the fluorinated monomer content of the copolymer solution was low, entropic forces dominated the interfacial structure, with the perfluoroalkyl groups unable to migrate to the solution/air interface and thus becoming buried in a random-coil chain conformation. When employing this copolymer solution for film preparation by spin-coating, the copolymer chains in solution were likely extended due to centrifugal forces, thereby weakening the entropy effect of the polymer chains. Consequently, this resulted in the segregation of the fluorinated moieties on the film surface. For the films prepared by casting, the perfluoroalkyl groups were, similar to those in solution, incapable of segregating at the film surface and were thus buried in the random-coil chains. When the copolymers contained a high content of DFHMA, the migration of perfluoroalkyl groups at the solution/air interface was controlled by enthalpic forces, and the perfluoroalkyl groups segregated at the surface of the film regardless of the film-forming technique. The aim of the present work was to obtain an enhanced understanding of the formation mechanism of the chemical structure on the surface of the polymer film, while demonstrating that film-forming methods may be used in practice to promote the segregation of fluorinated

  3. Statistical mechanics of directed models of polymers in the square lattice

    Rensburg, J V


    Directed square lattice models of polymers and vesicles have received considerable attention in the recent mathematical and physical sciences literature. These are idealized geometric directed lattice models introduced to study phase behaviour in polymers, and include Dyck paths, partially directed paths, directed trees and directed vesicles models. Directed models are closely related to models studied in the combinatorics literature (and are often exactly solvable). They are also simplified versions of a number of statistical mechanics models, including the self-avoiding walk, lattice animals and lattice vesicles. The exchange of approaches and ideas between statistical mechanics and combinatorics have considerably advanced the description and understanding of directed lattice models, and this will be explored in this review. The combinatorial nature of directed lattice path models makes a study using generating function approaches most natural. In contrast, the statistical mechanics approach would introduce...

  4. Direct Imaging of Deformation and Disorder in Extended-Chain Polymer Fibers


    Lenhert, T. J. Resch, and W. W. Adams, "Molecular Packing and Crystalline Order in Polybenzobisoxazole and Polybenzobisthiazole Fibers ", in...WL-TR-91-4011 AiAh 1A0 DIRECT IMAGING OF DEFORMATION AND DISORDER IN EXTENDED-CHAIN POLYMER FIBERS David C. Martin Department of Polymer Science and...Deformation and Disorder in Extended-Chain Polymer Fibers 12. PERSONAL AUTHOR(S) David C. Martin 13a. TYPE OF REPORT 13b. TIME COVERED 14. DATE OF REPORT (Year

  5. Direct numerical simulations of statistically steady, homogeneous, isotropic fluid turbulence with polymer additives

    Perlekar, Prasad; Pandit, Rahul


    We carry out a direct numerical simulation (DNS) study that reveals the effects of polymers on statistically steady, forced, homogeneous, isotropic fluid turbulence. We find clear manifestations of dissipation-reduction phenomena: On the addition of polymers to the turbulent fluid, we obtain a reduction in the energy dissipation rate, a significant modification of the fluid energy spectrum, especially in the deep-dissipation range, a suppression of small-scale intermittency, and a decrease in small-scale vorticity filaments. We also compare our results with recent experiments and earlier DNS studies of decaying fluid turbulence with polymer additives.

  6. Direct formation of gold nanorods on surfaces using polymer-immobilised gold seeds

    Abyaneh, Majid K; Pietro Parisse; Loredana Casalis


    Herein, we present the formation of gold nanorods (GNRs) on novel gold–poly(methyl methacrylate) (Au–PMMA) nanocomposite substrates with unprecedented growth control through the polymer molecular weight (Mw) and gold-salt-to-polymer weight ratio. For the first time, GNRs have been produced by seed-mediated direct growth on surfaces that were pre-coated with polymer-immobilised gold seeds. A Au–PMMA nanocomposite formed by UV photoreduction has been used as the gold seed. The influence of poly...

  7. Exploring a direct injection method for microfluidic generation of polymer microgels.

    Wang, Yihe; Tumarkin, Ethan; Velasco, Diego; Abolhasani, Milad; Lau, Willie; Kumacheva, Eugenia


    Microfluidics (MFs) offers a promising method for the preparation of polymer microgels with exquisite control over their dimensions, shapes and morphologies. A challenging task in this process is the generation of droplets (precursors for microgels) from highly viscous polymer solutions. Spatial separation of MF emulsification and gelation of the precursor droplets on chip can address this challenge. In the present work, we explored the application of the "direct injection" method for the preparation of microgels by adding a highly concentrated polymer solution or a gelling agent directly into the precursor droplets. In the first system, primary droplets were generated from a dilute aqueous solution of agarose, followed by the injection of the concentrated agarose solution directly in the primary droplets. The secondary droplets served as precursors for microgels. In the second system, primary droplets were generated from the low-viscous solution of methyl-β-cyclodextrin and poly(ethylene glycol) end-terminated with octadecyl hydrophobic groups. Addition of surfactant directly into the primary droplets led to the binding of methyl-β-cyclodextrin to the surfactant, thereby releasing hydrophobized poly(ethylene glycol) to form polymer microgels. Our results show that, when optimized, the direct injection method can be used for microgel preparation from highly viscous liquids and thus this method expands the range of polymers used for MF generation of microgels.

  8. Optimization of polymer electrolyte fuel cell cathode catalyst layers via direct numerical simulation modeling

    Wang, Guoqing; Mukherjee, Partha P.; Wang, Chao-Yang [Electrochemical Engine Center (ECEC), Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)


    The cathode catalyst layer (CL), due to sluggish oxygen reduction reaction and several transport losses therein, plays an important role in the overall performance of polymer electrolyte fuel cells (PEFCs). The relative volume fractions of the constituent phases, i.e. the electronic, electrolyte and void phases, of the cathode CL need to be selected appropriately in order to achieve an optimal balance between oxygen diffusion and proton conduction. In this work, the influence of electrolyte and void phase fractions of the cathode CL on the cell performance is investigated based on a pore-level description of species and charge transport through a random CL microstructure via the direct numerical simulation (DNS) model. Additionally, the effects of inlet relative humidity and net water transport from the anode on the cathode performance have been studied which indicate the interdependence between the CL composition and the cell operating conditions. The results indicate that the low humidity operation benefits the performance by enhancing the oxygen transport especially under high current densities. Finally, the DNS model predicts the volume fractions of 0.4 and 0.26 for the void and electrolyte phases, respectively, as the optimal composition of the catalyst layer for the best performance. (author)

  9. Direct passivation of hydride-terminated silicon (100) surfaces by free-radically tethered polymer brushes.

    Moran, Isaac W; Carter, Kenneth R


    A simple and effective means for passivating crystalline silicon is reported by the use of free-radical polymerization (FRP) to directly graft polymer chains to a hydride-terminated surface (Si-H). Complete surface coverage and passivation was achieved in approximately 24 h at 60 degrees C or 30 min at 90 degrees C. Mechanistic studies determined that chain attachment followed a hydride-transfer-based grafting-to mechanism. The grafting process is compatible with a variety of monomers and was used to assemble polymer brush layers (2-12 nm thick), with grafting densities ranging from 0.02 to 0.65 chains/nm2 rivaling densities typically obtained by grafting-from scenarios. This new passivation route provides a uniquely accessible means to covalently anchor dense polymer brushes to silicon surfaces without the need for functionalization of the polymer chain ends or the substrate.

  10. Direct observation of ultrafast long-range charge separation at polymer:fullerene heterojunctions

    Silva, Carlos


    In polymeric semiconductors, charge carriers are polarons, which means that the excess charge deforms the molecular structure of the polymer chain that hosts it. This effect results in distinctive signatures in the vibrational modes of the polymer. We probe polaron photogeneration dynamics at polymer:fullerene heterojunctions by monitoring its time-resolved resonance-Raman spectrum following ultrafast photoexcitation. We conclude that polarons emerge within 200 fs, which is nearly two orders of magnitude faster than exciton localisation in the neat polymer film. Surprisingly, further vibrational evolution on polarons is not significantly different from that in equilibrium. This suggests that charges are free from their mutual Coulomb potential, under which vibrational dynamics would report charge-pair relaxation. Our work addresses current debates on the photocarrier generation mechanism at organic semiconductor heterojunctions, and is, to our knowledge, the first direct probe of molecular conformation dynamics during this fundamentally important process in these materials.

  11. Direct observation of ultrafast long-range charge separation at polymer-fullerene heterojunctions

    Provencher, Françoise; Bérubé, Nicolas; Parker, Anthony W.; Greetham, Gregory M.; Towrie, Michael; Hellmann, Christoph; Côté, Michel; Stingelin, Natalie; Silva, Carlos; Hayes, Sophia C.


    In polymeric semiconductors, charge carriers are polarons, which means that the excess charge deforms the molecular structure of the polymer chain that hosts it. This results in distinctive signatures in the vibrational modes of the polymer. Here, we probe polaron photogeneration dynamics at polymer:fullerene heterojunctions by monitoring its time-resolved resonance-Raman spectrum following ultrafast photoexcitation. We conclude that polarons emerge within 300 fs. Surprisingly, further structural evolution on ≲50-ps timescales is modest, indicating that the polymer conformation hosting nascent polarons is not significantly different from that near equilibrium. We interpret this as suggestive that charges are free from their mutual Coulomb potential because we would expect rich vibrational dynamics associated with charge-pair relaxation. We address current debates on the photocarrier generation mechanism at molecular heterojunctions, and our work is, to our knowledge, the first direct probe of molecular conformation dynamics during this fundamentally important process in these materials.

  12. Liquid immersion thermal crosslinking of 3D polymer nanopatterns for direct carbonisation with high structural integrity

    Kang, Da-Young; Kim, Cheolho; Park, Gyurim; Moon, Jun Hyuk


    The direct pyrolytic carbonisation of polymer patterns has attracted interest for its use in obtaining carbon materials. In the case of carbonisation of nanopatterned polymers, the polymer flow and subsequent pattern change may occur in order to relieve their high surface energies. Here, we demonstrated that liquid immersion thermal crosslinking of polymer nanopatterns effectively enhanced the thermal resistance and maintained the structure integrity during the heat treatment. We employed the liquid immersion thermal crosslinking for 3D porous SU8 photoresist nanopatterns and successfully converted them to carbon nanopatterns while maintaining their porous features. The thermal crosslinking reaction and carbonisation of SU8 nanopatterns were characterised. The micro-crystallinity of the SU8-derived carbon nanopatterns was also characterised. The liquid immersion heat treatment can be extended to the carbonisation of various polymer or photoresist nanopatterns and also provide a facile way to control the surface energy of polymer nanopatterns for various purposes, for example, to block copolymer or surfactant self-assemblies.

  13. Final Report for Grant "Direct Writing via Novel Aromatic Ladder Polymer Precursors"

    C. B. Gorman


    This report describes activities and findings under the above entitled grant. These pertain to the development of new synthetic routes to novel precursor polymers and oligomers that are applicable for conversion from electrical insulators to electrical conductors under the application of light (e.g. direct photolithographic writing)

  14. Characterization of polymer blends PES/SPSf and PES/SPEEK for direct methanol fuel cells

    Manea, G.C.; Mulder, M.H.V.


    Existing polymer electrolyte membranes (PEMs) applied for hydrogen fuel cells are frequently not suitable for direct methanol fuel cells due to the high methanol permeability. Therefore, new materials are required and in order to avoid laborious fuel cell experiments with a so-called membrane–electr

  15. Direct simulation of liquid water dynamics in the gas channel of a polymer electrolyte fuel cell

    Qin, C.; Rensink, D.; Hassanizadeh, S.M.; Fell, S.


    For better water management in gas channels (GCs) of polymer electrolyte fuel cells (PEFCs), a profound understanding of the liquid water dynamics is needed. In this study, we propose a novel geometrical setup to conduct a series of direct simulations of the liquid water dynamics in a GC. The conduc

  16. Directions for Development of the Field of Electroactive Polymer (EAP)

    Bar-Cohen, Yoseph


    In last few years, the rate of development and advances in the field of EAP has accelerated significantly and it is increasingly getting closer to the point of finding them used in commercial products. Substantial development has been reported in the understanding of their drive mechanisms and the parameters that control their electro-activation behavior. Further, efforts are being made to develop mass production techniques with greatly improved actuation capability and operation durability. The recent efforts to develop energy harvesting techniques, haptic interfacing (including refreshable braille displays), and toys are further increasing the likelihood of finding niches for these materials. In this paper, the author sought to examine the potential directions for the future development of the field of EAP in relation to the state-of-the-art.

  17. Thermodynamic properties of direct methanol polymer electrolyte fuel cell

    Seong, Ji Yun; Bae, Young Chan [Division of Chemical Engineering and Molecular Thermodynamics Laboratory, Hanyang University, Sungdonggu Haengdangdong 17, Seoul 133-791 (Korea, Republic of); Sun, Yang Kook [Division of Chemical Engineering and Center for Information and Communication, Materials, Hanyang University, Seoul 133-791 (Korea, Republic of)


    A new semi-empirical model is established to describe the cell voltage of a direct methanol fuel cell (DMFC) as a function of current density. The model equation is validated experimental data over a wide range of a methanol concentration and temperatures. A number of existing models are semi-empirical. They, however, have a serious mathematical defect. When the current density, j, becomes zero, the equation should reduce to the open circuit voltage, E{sub 0}. These models, however, do not meet the mathematical boundary condition. The proposed model focuses on very unfavorable conditions for the cell operation, i.e. low methanol solution concentrations and relatively low cell temperatures. A newly developed semi-empirical equation with reasonable boundary conditions includes the methanol crossover effect that plays a major role in determining the cell voltage of DMFC. Also, it contains methanol activity based on thermodynamic functions to represent methanol crossover effect. (author)

  18. Economics of Direct Hydrogen Polymer Electrolyte Membrane Fuel Cell Systems

    Mahadevan, Kathyayani


    Battelle's Economic Analysis of PEM Fuel Cell Systems project was initiated in 2003 to evaluate the technology and markets that are near-term and potentially could support the transition to fuel cells in automotive markets. The objective of Battelle?s project was to assist the DOE in developing fuel cell systems for pre-automotive applications by analyzing the technical, economic, and market drivers of direct hydrogen PEM fuel cell adoption. The project was executed over a 6-year period (2003 to 2010) and a variety of analyses were completed in that period. The analyses presented in the final report include: Commercialization scenarios for stationary generation through 2015 (2004); Stakeholder feedback on technology status and performance status of fuel cell systems (2004); Development of manufacturing costs of stationary PEM fuel cell systems for backup power markets (2004); Identification of near-term and mid-term markets for PEM fuel cells (2006); Development of the value proposition and market opportunity of PEM fuel cells in near-term markets by assessing the lifecycle cost of PEM fuel cells as compared to conventional alternatives used in the marketplace and modeling market penetration (2006); Development of the value proposition of PEM fuel cells in government markets (2007); Development of the value proposition and opportunity for large fuel cell system application at data centers and wastewater treatment plants (2008); Update of the manufacturing costs of PEM fuel cells for backup power applications (2009).

  19. A quasi-direct methanol fuel cell system based on blend polymer membrane electrolytes

    Li, Qingfeng; Hjuler, Hans Aage; Hasiotis, C.


    , compared to less than 100 ppm CO for the Nafion-based technology at 80degrees C. The high CO tolerance makes it possible to use the reformed hydrogen directly from a simple methanol reformer without further CO removal. That both the fuel cell and the methanol reformer operate at temperatures around 200......On the basis of blend polymer electrolytes of polybenzimidazole and sulfonated polysulfone, a polymer electrolyte membrane fuel cell was developed with an operational temperature up to 200degrees C. Due to the high operational temperature, the fuel cell can tolerate 1.0-3.0 vol % CO in the fuel...

  20. Local direct and indirect reduction of electrografted aryldiazonium/gold surfaces for polymer brushes patterning

    Hauquier, Fanny; Matrab, Tarik; Kanoufi, Frederic [Laboratoire Environnement et Chimie Analytique, CNRS UMR7121, ESPCI, 10 rue Vauquelin, 75231 Paris Cedex 05 (France); Combellas, Catherine [Laboratoire Environnement et Chimie Analytique, CNRS UMR7121, ESPCI, 10 rue Vauquelin, 75231 Paris Cedex 05 (France)], E-mail:


    The patterning of conductive substrates by polymer brushes may be achieved by using successively scanning electrochemical microscopy (SECM) and atom transfer radical polymerization (ATRP). After the surface functionalization by a brominated aryldiazonium initiator, SECM allows the local reduction at the micrometer scale of the initiator grafted layer. Different channels sizes involved in charge transport within the initiator layers are evidenced by combining SECM, CV and observation of the aryl-grafted layer transformation. ATRP is performed on the SECM patterned substrate. Inside the pattern, the lower density of initiator decreases the polymer thickness. The pattern resolution is enhanced when the direct mode of the SECM is used instead of the mediated indirect mode.

  1. Direct measurement of the intermolecular forces confining a single molecule in an entangled polymer solution.

    Robertson, Rae M; Smith, Douglas E


    We use optical tweezers to directly measure the intermolecular forces acting on a single polymer imposed by surrounding entangled polymers (115 kbp DNA, 1 mg/ml). A tubelike confining field was measured in accord with the key assumption of reptation models. A time-dependent harmonic potential opposed transverse displacement, in accord with recent simulation findings. A tube radius of 0.8 microm was determined, close to the predicted value (0.5 microm). Three relaxation modes (approximately 0.4, 5, and 34 s) were measured following transverse displacement, consistent with predicted relaxation mechanisms.

  2. Direct formation of gold nanorods on surfaces using polymer-immobilised gold seeds

    Majid K. Abyaneh


    Full Text Available Herein, we present the formation of gold nanorods (GNRs on novel gold–poly(methyl methacrylate (Au–PMMA nanocomposite substrates with unprecedented growth control through the polymer molecular weight (Mw and gold-salt-to-polymer weight ratio. For the first time, GNRs have been produced by seed-mediated direct growth on surfaces that were pre-coated with polymer-immobilised gold seeds. A Au–PMMA nanocomposite formed by UV photoreduction has been used as the gold seed. The influence of polymer Mw and gold concentration on the formation of GNRs has been investigated and discussed. The polymer nanocomposite formed with a lower Mw PMMA and 20 wt % gold salt provides a suitable medium for growing well-dispersed GNRs. In this sample, the average dimension of produced GNRs is 200 nm in length with aspect ratios up to 10 and a distribution of GNRs to nanoparticles of nearly 22%. Suitable characterization techniques such as AFM and SEM have been used to support concept of the proposed growth method.

  3. Direct formation of gold nanorods on surfaces using polymer-immobilised gold seeds.

    Abyaneh, Majid K; Parisse, Pietro; Casalis, Loredana


    Herein, we present the formation of gold nanorods (GNRs) on novel gold-poly(methyl methacrylate) (Au-PMMA) nanocomposite substrates with unprecedented growth control through the polymer molecular weight (M w) and gold-salt-to-polymer weight ratio. For the first time, GNRs have been produced by seed-mediated direct growth on surfaces that were pre-coated with polymer-immobilised gold seeds. A Au-PMMA nanocomposite formed by UV photoreduction has been used as the gold seed. The influence of polymer M w and gold concentration on the formation of GNRs has been investigated and discussed. The polymer nanocomposite formed with a lower M w PMMA and 20 wt % gold salt provides a suitable medium for growing well-dispersed GNRs. In this sample, the average dimension of produced GNRs is 200 nm in length with aspect ratios up to 10 and a distribution of GNRs to nanoparticles of nearly 22%. Suitable characterization techniques such as AFM and SEM have been used to support concept of the proposed growth method.

  4. Improving the functional expression of a Bacillus licheniformis laccase by random and site-directed mutagenesis

    Schmid Rolf D


    Full Text Available Abstract Background Laccases have huge potential for biotechnological applications due to their broad substrate spectrum and wide range of reactions they are able to catalyze. These include, for example, the formation and degradation of dimers, oligomers, polymers, and ring cleavage as well as oxidation of aromatic compounds. Potential applications of laccases include detoxification of industrial effluents, decolorization of textile dyes and the synthesis of natural products by, for instance, dimerization of phenolic acids. We have recently published a report on the cloning and characterization of a CotA Bacillus licheniformis laccase, an enzyme that catalyzes dimerization of phenolic acids. However, the broad application of this laccase is limited by its low expression level of 26 mg l-1 that was achieved in Escherichia coli. To counteract this shortcoming, random and site-directed mutagenesis have been combined in order to improve functional expression and activity of CotA. Results A CotA double mutant, K316N/D500G, was constructed by combining random and site-directed mutagenesis. It can be functionally expressed at an 11.4-fold higher level than the wild-type enzyme. In addition, it is able to convert ferulic acid much faster than the wild-type enzyme (21% vs. 14% and is far more efficient in decolorizing a range of industrial dyes. The investigation of the effects of the mutations K316N and D500G showed that amino acid at position 316 had a major influence on enzyme activity and position 500 had a major influence on the expression of the laccase. Conclusion The constructed double mutant K316N/D500G of the Bacillus licheniformis CotA laccase is an appropriate candidate for biotechnological applications due to its high expression level and high activity in dimerization of phenolic acids and decolorization of industrial dyes.

  5. Thermal desorption characterisation of molecularly imprinted polymers. Part I: A novel study using direct-probe GC-MS analysis.

    Cummins, Wayne; Duggan, Patrick; McLoughlin, Peter


    A novel thermal desorption technique using a direct-probe device (Chromatoprobe) attached to a gas chromatograph-mass spectrometer is presented for the thermal pretreatment, characterisation and analysis of molecularly imprinted polymers. The technique is demonstrated as effective for the removal of volatile materials, including template and unreacted monomers, from methacrylic acid-ethylene glycol dimethacrylate copolymers imprinted with 2-aminopyridine. Mass spectrometry is a powerful technique for polymer bleed characterisation. Thermal desorption studies on reloaded template and related compounds are reported as a means of assessing polymer morphology, specific binding by imprinted polymers compared with reference non-imprinted polymers and selective binding by an imprinted polymer for its template. Calibration studies on the thermal desorption technique using an internal standard are presented with R(2) > 0.999. The technique provides a novel method for assessment of polymer thermal stability, composition and morphology.

  6. Diffractive devices fabricated on azobenezene polymer by polarization laser direct-writing

    Hao, Peng; Duan, Shiyuan; Cao, Zhaolou; Wu, Shuo; Wang, Keyi; Yan, Peizheng


    Polarization laser direct-writing system was designed and the recording and research using the azobenzence polymer film on the system was investigated. Only single laser beam was used, and move the laser focal spot on the sample film pointto- point. By composite control of the optical power density, polarization direction and exposure time of the inscribing laser, a special phase-delay distribution graph which have different etching depth in different point can be achieved. Diffractive devices, such as grating and zone plate, have been inscribed. The anisotropy and surface topography was measured by polarizing optical microscopy (POM) and profilometer. Some qualitative analysis was made. Using the red light which is insensitivity to the azo polymer film, the diffractive devices' focal spots were collected by CCD. Compared with the holographic interference method, the method is more flexible, undemanding for the experimental environment and any two-dimension distribution graph can be written in theory. It may get extensive application.

  7. Direct Writing of Fiber Bragg Grating in Microstructured Polymer Optical Fiber

    Stefani, Alessio; Stecher, Matthias; Town, G. E.


    We report point-by-point laser direct writing of a 1520-nm fiber Bragg grating in a microstructured polymer optical fiber (mPOF). The mPOF is specially designed such that the microstructure does not obstruct the writing beam when properly aligned. A fourth-order grating is inscribed in the mPOF w......POF with only a 2.5-s writing time....

  8. Direct Uniaxial Alignment of a Donor-Acceptor Semiconducting Polymer Using Single-Step Solution Shearing.

    Shaw, Leo; Hayoz, Pascal; Diao, Ying; Reinspach, Julia Antonia; To, John W F; Toney, Michael F; Weitz, R Thomas; Bao, Zhenan


    The alignment of organic semiconductors (OSCs) in the active layers of electronic devices can confer desirable properties, such as enhanced charge transport properties due to better ordering, charge transport anisotropy for reduced device cross-talk, and polarized light emission or absorption. The solution-based deposition of highly aligned small molecule OSCs has been widely demonstrated, but the alignment of polymeric OSCs in thin films deposited directly from solution has typically required surface templating or complex pre- or postdeposition processing. Therefore, single-step solution processing and the charge transport enhancement afforded by alignment continue to be attractive. We report here the use of solution shearing to tune the degree of alignment in poly(diketopyrrolopyrrole-terthiophene) thin films by controlling the coating speed. A maximum dichroic ratio of ∼7 was achieved on unpatterned substrates without any additional pre- or postdeposition processing. The degree of polymer alignment was found to be a competition between the shear alignment of polymer chains in solution and the complex thin film drying process. Contrary to previous reports, no charge transport anisotropy was observed because of the small crystallite size relative to the channel length, a meshlike morphology, and the likelihood of increased grain boundaries in the direction transverse to coating. In fact, the lack of aligned morphological structures, coupled with observed anisotropy in X-ray diffraction data, suggests the alignment of polymer molecules in both the crystalline and the amorphous regions of the films. The shear speed at which maximum dichroism is achieved can be controlled by altering deposition parameters such as temperature and substrate treatment. Modest changes in molecular weight showed negligible effects on alignment, while longer polymer alkyl side chains were found to reduce the degree of alignment. This work demonstrates that solution shearing can be used

  9. A Review on the Fabrication of Electrospun Polymer Electrolyte Membrane for Direct Methanol Fuel Cell

    Hazlina Junoh


    Full Text Available Proton exchange membrane (PEM is an electrolyte which behaves as important indicator for fuel cell’s performance. Research and development (R&D on fabrication of desirable PEM have burgeoned year by year, especially for direct methanol fuel cell (DMFC. However, most of the R&Ds only focus on the parent polymer electrolyte rather than polymer inorganic composites. This might be due to the difficulties faced in producing good dispersion of inorganic filler within the polymer matrix, which would consequently reduce the DMFC’s performance. Electrospinning is a promising technique to cater for this arising problem owing to its more widespread dispersion of inorganic filler within the polymer matrix, which can reduce the size of the filler up to nanoscale. There has been a huge development on fabricating electrolyte nanocomposite membrane, regardless of the effect of electrospun nanocomposite membrane on the fuel cell’s performance. In this present paper, issues regarding the R&D on electrospun sulfonated poly (ether ether ketone (SPEEK/inorganic nanocomposite fiber are addressed.

  10. Polymer tensiometers with ceramic cones: direct observations of matric pressures in drying soils

    M. J. van der Ploeg


    Full Text Available Measuring soil water potentials is crucial to characterize vadose zone processes. Conventional tensiometers only measure until approximately −0.09 MPa, and indirect methods may suffer from the non-uniqueness in the relationship between matric potential and measured properties. Recently developed polymer tensiometers (POTs are able to directly measure soil matric potentials until the theoretical wilting point (−1.6 MPa. By minimizing the volume of polymer solution inside the POT while maximizing the ceramic area in contact with that polymer solution, response times drop to acceptable ranges for laboratory and field conditions. Contact with the soil is drastically improved with the use of cone-shaped solid ceramics instead of flat ceramics. The comparison between measured potentials by polymer tensiometers and indirectly obtained potentials with time domain reflectometry highlights the risk of using the latter method at low water contents. By combining POT and time domain reflectometry readings in situ moisture retention curves can be measured over the range permitted by the measurement range of both POT and time domain reflectometry.

  11. Microwave synthesis of polymer-embedded Pt-Ru catalyst for direct methanol fuel cell.

    Bensebaa, Farid; Farah, Abdiaziz A; Wang, Dashan; Bock, Christina; Du, Xiaomei; Kung, Judy; Le Page, Yvon


    Platinum-ruthenium nanoparticles stabilized within a conductive polymer matrix are prepared using microwave heating. Polypyrrole di(2-ethylhexyl) sulfosuccinate, or PPyDEHS, has been chosen for its known electrical conductivity, thermal stability, and solubility in polar organic solvents. A scalable and quick two-step process is proposed to fabricate alloyed nanoparticles dispersed in PPyDEHS. First a mixture of PPyDEHS and metallic precursors is heated in a microwave under reflux conditions. Then the nanoparticles are extracted by centrifugation. Physical characterization by TEM shows that crystalline and monodisperse alloyed nanoparticles with an average size of 2.8 nm are obtained. Diffraction data show that crystallite size is around 2.0 nm. Methanol electro-oxidation data allow us to propose these novel materials as potential candidates for direct methanol fuel cells (DMFC) application. The observed decrease in sulfur content in the polymer upon incorporation of PtRu nanoparticles may have adversely affected the measured catalytic activity by decreasing the conductivity of PPyDEHS. Higher concentration of polymer leads to lower catalyst activity. Design and synthesis of novel conductive polymers is needed at this point to enhance the catalytic properties of these hybrid materials.

  12. Carbazole-based copolymers via direct arylation polymerization (DArP) for Suzuki-convergent polymer solar cell performance

    Gobalasingham, Nemal S.; Ekiz, Seyma; Pankow, Robert M.


    Although direct arylation polymerization (DArP) has recently emerged as an alternative to traditional cross-coupling methods like Suzuki polymerization, the evaluation of DArP polymers in practical applications like polymer solar cells (PSCs) is limited. Because even the presence of minute quanti...

  13. 10-Gb/s direct modulation of polymer-based tunable external cavity lasers.

    Choi, Byung-Seok; Oh, Su Hwan; Kim, Ki Soo; Yoon, Ki-Hong; Kim, Hyun Soo; Park, Mi-Ran; Jeong, Jong Sool; Kwon, O-Kyun; Seo, Jun-Kyu; Lee, Hak-Kyu; Chung, Yun C


    We demonstrate a directly-modulated 10-Gb/s tunable external cavity laser (ECL) fabricated by using a polymer Bragg reflector and a high-speed superluminescent diode (SLD). The tuning range and output power of this ECL are measured to be >11 nm and 2.6 mW (@ 100 mA), respectively. We directly modulate this laser at 10 Gb/s and transmit the modulated signal over 20 km of standard single-mode fiber. The power penalty is measured to be <2.8 dB at the bit-error rate (BER) of 10(-10).

  14. Polymer-directed synthesis of metal oxide-containing nanomaterials for electrochemical energy storage.

    Mai, Yiyong; Zhang, Fan; Feng, Xinliang


    Metal oxide-containing nanomaterials (MOCNMs) of controllable structures at the nano-scale have attracted considerable interest because of their great potential applications in electrochemical energy storage devices, such as lithium-ion batteries (LIBs) and supercapacitors. Among many structure-directing agents, polymers and macromolecules, including block copolymers (BCPs) and graphene, exhibit distinct advantages in the template-assisted synthesis of MOCNMs. In this feature article, we introduce the controlled preparation of MOCNMs employing BCPs and graphene as structure-directing agents. Typical synthetic strategies are presented for the control of structures and sizes as well as the improvement of physical properties and electrochemical performance of MOCNMs in LIBs and supercapacitors.

  15. Stereoselectivity in metallocene-catalyzed coordination polymerization of renewable methylene butyrolactones: From stereo-random to stereo-perfect polymers

    Chen, Xia


    Coordination polymerization of renewable α-methylene-γ-(methyl) butyrolactones by chiral C 2-symmetric zirconocene catalysts produces stereo-random, highly stereo-regular, or perfectly stereo-regular polymers, depending on the monomer and catalyst structures. Computational studies yield a fundamental understanding of the stereocontrol mechanism governing these new polymerization reactions mediated by chiral metallocenium catalysts. © 2012 American Chemical Society.

  16. Chemical and Spectroscopic Aspects of Polymer Ablation-Special Features and Novel Directions-

    Lippert, Thomas


    Laser ablation of polymers has become an established technique in the electronic industry and the large number of studies published annually indicates that this is still an attractive area of research. Several new approaches with new techniques and materials have given new insights in the ablation process. One of these approaches is the development of polymers designed specifically for laser ablation which are a unique tool for probing the ablation mechanisms as well as for improving ablation properties. These novel polymers exhibit very low thresholds of ablation, with high ablation rates (even at low fluences), and excellent ablation quality. New commercial applications will require improved ablation rates and control of undesirable surface effects, such as debris. The complexity of the interactions between polymers and laser photons are illustrated by the various processes associated with different irradiation conditions. i) Photothermal-photochemical laser ablation under excimer laser irradiation. ii) Dopant-induced laser ablation. iii) Photo-oxidative etching with lamps in an oxidizing atmosphere. iv) VUV etching in the absence of oxidizing conditions. v) Photokinetic etching with CW UV lasers. vi) Ultrafast laser ablation, affected by pulse length, wavelength, and possibly shock waves. vii) Shock assisted photothermal ablation on picosecond time scales. viii) VUV laser ablation: purely photochemical? ix) Synchrotron structuring. x) Mid-IR ablation (FEL and CO2 laser), the influence of exciting various functional groups. Several of these new approaches and processes will be discussed to emphasize the importance of different approaches but also to review some fundamental processes. The combination of various experimental techniques (new approaches and 'well-known') with materials made to measure has given new insights in the ablation mechanisms, but has also shown new possible future directions of laser polymer ablation.

  17. Surface modification of polyacrylonitrile co-polymer membranes using pulsed direct current nitrogen plasma

    Pal, Dipankar; Neogi, Sudarsan; De, Sirshendu, E-mail:


    Low temperature plasma treatment using pulsed direct current discharge of nitrogen gas was employed to enhance hydrophilicity of the polyacrylonitrile co-polymer membranes. The membranes were characterized in terms of morphology, structure, hydrophilicity, and membrane performance. Properties and functional groups on the surface of polyacrylonitrile co-polymer membranes were investigated by contact angle, scanning electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopy. Effects of plasma conditions, namely, pulsed voltage, duty cycle and treatment time on increase in membrane hydrophilicity were studied. Permeability of treated membrane was increased by 47% and it was retained up to 70 days. Surface etching due to plasma treatment was confirmed by weight loss of the treated membranes. Due to surface etching, average pore size increased and rejection of 200 kDa polyethylene glycol decreased to about 70% for the treated membrane. Oxygen and nitrogen functional groups were responsible for surface hydrophilicity. - Highlights: • Surface modification of polyacrylonitrile co-polymer membranes by pulsed direct current nitrogen plasma • Hydrophilic functional groups incorporated on the membrane surface • Significant enhancement of the permeability and wettability of the membranes • Water contact angle increased with storage time and finally stabilized.

  18. Comparative Studies of the Adsorption of Direct Dye on Activated Carbon and Conducting Polymer Composite

    J. Raffiea Baseri


    Full Text Available This study analyses the feasibility of removing Direct Blue 71 from aqueous solution by different adsorbents such as activated carbon (TPAC and Poly pyrrole polymer composite (PPC prepared from Thevetia Peruviana. Batch mode adsorption was performed to investigate the adsorption capacities of these adsorbents by varying initial dye concentration, temperature, agitation time and pH. The performance of TPAC was compared with PPC. Among the adsorbents, PPC had more adsorption capacity (88.24% than TPAC (58.82% at an initial concentration of 50 mg/L and at 30°C. The experimental data best fitted with pseudo second order kinetic model. The adsorption data fitted well for Langmuir adsorption isotherm. Thermodynamic parameters for the adsorbents were also evaluated. The carbon embedded in conducting polymers matrix show better adsorptive properties than activated carbon.

  19. Spatially isolated palladium in porous organic polymers by direct knitting for versatile organic transformations

    Wang, Xinbo


    We report here a direct knitting Method for preparation of highly robust, effective while air- and moisture-tolerant, and readily recyclable three-dimensional (3D) porous polymer-Pd network (PPPd) from the widely used Pd(PPh3)4. Electro-beam induced Pd atom crystallization was observed for the first time in organic polymer and revealed the ultrafine dispersion of palladium atoms. Challenging types of Suzuki-Miyaura couplings, reductive coupling of aryl halides and oxidative coupling of arylboronic acid were successively catalyzed by PPPd in aqueous media. Also catalytically selective CH functionalization reactions were achieved with orders of magnitude more efficient than conventional Pd homogeneous catalysts. The strategy developed here provides a practical method for easy-to-make yet highly efficient heterogeneous catalysis.

  20. Hybrid optics for three-dimensional microstructuring of polymers via direct laser writing

    Burmeister, Frank; Zeitner, Uwe D.; Nolte, Stefan; Tünnermann, Andreas


    We present an immersion hybrid optics specially designed for focusing ultrashort laser pulses into a polymer for direct laser writing via two-photon polymerization. The hybrid optics enables well corrected focusing over a working distance range of 577 μm with a numerical aperture (NA) of 1.33 thereby causing low internal dispersion. We combine the concepts of an aplanatic solid immersion lens (ASIL) for achieving a high NA with the correction of aberrations with a diffractive optical element (DOE). To demonstrate the improvements for volume structuring of the polymer, we compare achievable feature sizes of structures written with our optics and a commercial available oil immersion objective (100x, NA=1.4).

  1. Polymer Directed Self-Assembly of pH-Responsive Antioxidant Nanoparticles

    Tang, Christina; Amin, Devang; Messersmith, Phillip B.; Anthony, John E.; Prud’homme, Robert K.


    We have developed pH-responsive, multifunctional nanoparticles based on encapsulation of an antioxidant, tannic acid (TA), using Flash NanoPrecipitation, a polymer directed self-assembly method. Formation of insoluble coordination complexes of tannic acid and iron during mixing drives nanoparticle assembly. Tuning the core material to polymer ratio, the size of the nanoparticles can be readily tuned between 50 and 265 nm. The resulting nanoparticle is pH-responsive, i.e. stable at pH 7.4 and soluble under acidic conditions due to the nature of the coordination complex. Further, the coordination complex can be coprecipitated with other hydrophobic materials such as therapeutics or imaging agents. For example, coprecipitation with a hydrophobic fluorescent dye creates fluorescent nanoparticles. In vitro, the nanoparticles have low cytotoxicity show antioxidant activity. Therefore, these particles may facilitate intracellular delivery of antioxidants. PMID:25760226

  2. Direct immobilization of antibodies on a new polymer film for fabricating an electrochemical impedance immunosensor.

    Zhang, Xiangyang; Shen, Guangyu; Shen, Youming; Yin, Dan; Zhang, Chunxiang


    A new polymer bearing aldehyde groups was designed and synthesized by grafting 4-pyridinecarboxaldehyde onto poly(epichlorohydrin). Antibodies can be directly immobilized on the surface of the polymer film through the covalent bonding of aldehyde groups of the film with amino groups of antibodies. In this study, human immunoglobulin G (IgG) was used as a model analyte for the fabrication of an electrochemical impedance immunosensor. Using the proposed immunosensor, IgG in the range from 0.1 to 80 ng ml(-1) was detected with a detection limit of 0.07 ng ml(-1) (signal/noise [S/N]=3). In addition, the electrochemical impedance immunosensor displays good stability and reproducibility.

  3. Hierarchy in directed random networks: analytical and numerical results

    Mones, Enys


    In recent years, the theory and application of complex networks has been quickly developing in a markable way due to the increasing amount of data from real systems and to the fruitful application of powerful methods used in statistical physics. Many important characteristics of social or biological systems can be described by the study of their underlying structure of interactions. Hierarchy is one of these features that can be formulated in the language of networks. In this paper we present the analytic results on the hierarchical properties of random network models with zero correlations and also investigate the effects of different type of correlations. The behavior of hierarchy is different in the absence and the presence of the giant components. We show that the hierarchical structure can be drastically different if there are one-point correlations in the network. We also show numerical results suggesting that hierarchy does not change monotonously with the correlations and there is an optimal level of ...




    In this contribution, the general concepts of force microscopy will be presented together with its application to polymer surfaces (Ref.1). Several examples will be presented to illustrate that force microscopy is a powerful and promising tool for investigation of (polymer) surfaces, such as the ima

  5. Direct-written polymer field-effect transistors operating at 20 MHz

    Perinot, Andrea; Kshirsagar, Prakash; Malvindi, Maria Ada; Pompa, Pier Paolo; Fiammengo, Roberto; Caironi, Mario


    Printed polymer electronics has held for long the promise of revolutionizing technology by delivering distributed, flexible, lightweight and cost-effective applications for wearables, healthcare, diagnostic, automation and portable devices. While impressive progresses have been registered in terms of organic semiconductors mobility, field-effect transistors (FETs), the basic building block of any circuit, are still showing limited speed of operation, thus limiting their real applicability. So far, attempts with organic FETs to achieve the tens of MHz regime, a threshold for many applications comprising the driving of high resolution displays, have relied on the adoption of sophisticated lithographic techniques and/or complex architectures, undermining the whole concept. In this work we demonstrate polymer FETs which can operate up to 20 MHz and are fabricated by means only of scalable printing techniques and direct-writing methods with a completely mask-less procedure. This is achieved by combining a fs-laser process for the sintering of high resolution metal electrodes, thus easily achieving micron-scale channels with reduced parasitism down to 0.19 pF mm‑1, and a large area coating technique of a high mobility polymer semiconductor, according to a simple and scalable process flow.

  6. Direct characterization of polymer encapsulated CdSe/CdS/ZnS quantum dots

    Zorn, Gilad; Dave, Shivang R.; Weidner, Tobias; Gao, Xiaohu; Castner, David G.


    Surface engineering advances of semiconductor quantum dots (QDs) have enabled their application to molecular labeling, disease diagnostics and tumor imaging. For biological applications, hydrophobic core/shell QDs are transferred into aqueous solutions through the incorporation of water-solubility imparting moieties, typically achieved via direct exchange of the native surface passivating ligands or indirectly through the adsorption of polymers. Although polymeric encapsulation has gained wide acceptance, there are few reports addressing the characterization of the adsorbed polymers and existing theoretical analyses are typically based on simple geometric models. In this work, we experimentally characterize and quantify water-soluble QDs prepared by adsorption of amphiphilic poly(maleic anhydride-alt-1-tetradecene) (PMAT, MW ~ 9000) onto commercially available CdSe/CdS/ZnS (CdSe/CdS/ZnS-PMAT). Using X-ray photoelectron spectroscopy (XPS) we determined that ~ 15 PMAT molecules are adsorbed onto each QD and sum frequency generation (SFG) vibrational spectra were utilized to investigate the mechanism of interaction between PMAT molecules and the QD surface. Importantly, when employed together, these techniques constitute a platform with which to investigate any polymer-nanoparticle complex in general.

  7. Directed alignment of conjugated polymers for enhanced long-range photocurrent collection

    Li, Anton; Bilby, David; Dong, Ban; Kim, Jinsang; Green, Peter


    To realize the full potential of conjugated polymers, possessing anisotropic structure and properties, it is often desirable to extend their organization to larger length scales. An epitaxy-directing solvent additive 1,3,5-trichlorobenzene was combined with an off-center spin-casting technique to produce poly(3-hexylthiophene) (P3HT) fibers with uniaxial in-plane alignment on the centimeter scale, which were incorporated into planar heterojunction solar cells with PCBM acceptor. Topography and photocurrent were mapped by photoconductive AFM; in devices with aligned P3HT, local photocurrent measured on fibers was over 4 times higher than in control devices with unaligned polymer. Even at large distances (>200 μm) between laser spot (carrier excitation) and conductive probe (charge extraction), significant long-range photocurrent was measured in the aligned devices, especially when the separation was oriented parallel to the fiber alignment. Complementary TFT measurements of neat P3HT fibers revealed that the anisotropy of in-plane carrier mobilities was greater than a factor of 3. Together, these findings highlight the importance of conjugated polymer alignment for improving carrier transport and ultimately the performance of solar cells and other devices.

  8. Modelling of solid polymer and direct methanol fuel cells: Phenomenological equations and analytical solutions

    Kauranen, P. S.


    In the solid state concept of a direct methanol fuel cell (DMFC), methanol is directly oxidized at the anode of a solid polymer electrolyte fuel cell (SPEFC). Mathematical modelling of the transport and reaction phenomena within the electrodes and the electrolyte membrane is needed in order to get a closer insight into the operation of the fuel cell. In the work, macro-homogenous porous electrode and dilute solution theories are used to derive the phenomenological equations describing the transport and reaction mechanisms in a SPEFC single cell. The equations are first derived for a conventional H2/air SPEFC, and then extended for a DMFC. The basic model is derived in a one dimensional form in which it is assumed that species transport take place only in the direction crossing the cell sandwich. In addition, two dimensional descriptions of the catalyst layer are reviewed.

  9. A molecular design principle of lyotropic liquid-crystalline conjugated polymers with directed alignment capability for plastic electronics.

    Kim, Bong-Gi; Jeong, Eun Jeong; Chung, Jong Won; Seo, Sungbaek; Koo, Bonwon; Kim, Jinsang


    Conjugated polymers with a one-dimensional p-orbital overlap exhibit optoelectronic anisotropy. Their unique anisotropic properties can be fully realized in device applications only when the conjugated chains are aligned. Here, we report a molecular design principle of conjugated polymers to achieve concentration-regulated chain planarization, self-assembly, liquid-crystal-like good mobility and non-interdigitated side chains. As a consequence of these intra- and intermolecular attributes, chain alignment along an applied flow field occurs. This liquid-crystalline conjugated polymer was realized by incorporating intramolecular sulphur-fluorine interactions and bulky side chains linked to a tetrahedral carbon having a large form factor. By optimizing the polymer concentration and the flow field, we could achieve a high dichroic ratio of 16.67 in emission from conducting conjugated polymer films. Two-dimensional grazing-incidence X-ray diffraction was performed to analyse a well-defined conjugated polymer alignment. Thin-film transistors built on highly aligned conjugated polymer films showed more than three orders of magnitude faster carrier mobility along the conjugated polymer alignment direction than the perpendicular direction.

  10. Effect of Methanol Crossover in a Liquid-FeedPolymer-Electrolyte Direct Methanol Fuel Cell

    Ravikumar, MK; Shukla, AK


    The performance of a liquid-feed direct methanol fuel cell employing a proton-exchange membrane electrolyte with Pt-Ru/C as anode and Pt/C as cathode is reported. The fuel cell can deliver a power density of ca. 0.2 $W/cm^2$ at 95°C, sufficient to suggest that the stack construction is well worthwhile.Methanol crossover across the polymer electrolyte at concentrations beyond 2 M methanol affects the performance of the cell which appreciates with increasing operating temperature.

  11. Directed Self-Assembly of Block Copolymers for High Breakdown Strength Polymer Film Capacitors

    Samant, Saumil P.; Grabowski, Christopher A.; Kisslinger, Kim; Yager, Kevin G.; Yuan, Guangcui; Satija, Sushil K.; Durstock, Michael F.; Raghavan, Dharmaraj; Karim, Alamgir


    Emerging needs for fast charge/discharge yet high-power, lightweight, and flexible electronics requires the use of polymer-film-based solid-state capacitors with high energy densities. Fast charge/discharge rates of film capacitors on the order of microseconds are not achievable with slower charging conventional batteries, supercapacitors and related hybrid technologies. However, the current energy densities of polymer film capacitors fall short of rising demand, and could be significantly enhanced by increasing the breakdown strength (EBD) and dielectric permittivity (εr) of the polymer films. Co-extruded two-homopolymer component multilayered films have demonstrated much promise in this regard showing higher EBD over that of component polymers. Multilayered films can also help incorporate functional features besides energy storage, such as enhanced optical, mechanical, thermal and barrier properties. In this work, we report accomplishing multilayer, multicomponent block copolymer dielectric films (BCDF) with soft-shear driven highly oriented self-assembled lamellar diblock copolymers (BCP) as a novel application of this important class of self-assembling materials. Results of a model PS-b-PMMA system show ~50% enhancement in EBD of self-assembled multilayer lamellar BCP films compared to unordered as-cast films, indicating that the breakdown is highly sensitive to the nanostructure of the BCP. The enhancement in EBD is attributed to the “barrier effect”, where the multiple interfaces between the lamellae block components act as barriers to the dielectric breakdown through the film. The increase in EBD corresponds to more than doubling the energy storage capacity using a straightforward directed self-assembly strategy. This approach opens a new nanomaterial paradigm for designing high energy density dielectric materials.

  12. Direct observation of the ultrafast electron transfer process in a polymer/fullerene blend. : Section Title: Physical Properties of Synthetic High Polymers

    Brabec, Ch J.; Zerza, G.; Sariciftci, N. S.; Cerullo, G.; Lanzani, G.; De Silvestri, S.; Hummelen, J. C.


    Optical studies on conjugated polymer-fullerene blends are performed with sub-10-fs temporal resoln. The photoinduced electron transfer process is directly monitored in the time domain, obtaining a forward electron transfer time const. of 45 fs. [on SciFinder(R)

  13. Direct observation of the ultrafast electron transfer process in a polymer/fullerene blend. : Section Title: Physical Properties of Synthetic High Polymers

    Brabec, Ch J.; Zerza, G.; Sariciftci, N. S.; Cerullo, G.; Lanzani, G.; De Silvestri, S.; Hummelen, J. C.


    Optical studies on conjugated polymer-fullerene blends are performed with sub-10-fs temporal resoln. The photoinduced electron transfer process is directly monitored in the time domain, obtaining a forward electron transfer time const. of 45 fs. [on SciFinder(R)

  14. Improved performance of traveling wave directional coupler modulator based on electro-optic polymer

    Zhang, Xingyu; Lin, Che-yun; Wang, Alan X; Hosseini, Amir; Lin, Xiaohui; Chen, Ray T


    Polymer based electro-optic modulators have shown great potentials in high frequency analog optical links. Existing commercial LiNibO3 Mach-Zehnder modulators have intrinsic drawbacks in linearity to provide high fidelity communication. In this paper, we present the design, fabrication and characterization of a traveling wave directional coupler modulator based on electro-optic polymer, which is able to provide high linearity, high speed, and low optical insertion loss. A silver ground electrode is used to reduce waveguide sidewall roughness due to the scattering of UV light in photolithography process in addition to suppressing the RF loss. A 1-to-2 multi-mode interference 3dB-splitter, a photobleached refractive index taper and a quasi-vertical taper are used to reduce the optical insertion loss of the device. The symmetric waveguide structure of the MMI-fed directional coupler is intrinsically bias-free, and the modulation is obtained at the 3-dB point regardless of the ambient temperature. By achieving lo...

  15. Midpoint Distribution of Directed Polymers in the Stationary Regime: Exact Result Through Linear Response

    Maes, Christian; Thiery, Thimothée


    We obtain an exact result for the midpoint probability distribution function (pdf) of the stationary continuum directed polymer, when averaged over the disorder. It is obtained by relating that pdf to the linear response of the stochastic Burgers field to some perturbation. From the symmetries of the stochastic Burgers equation we derive a fluctuation-dissipation relation so that the pdf gets given by the stationary two space-time points correlation function of the Burgers field. An analytical expression for the latter was obtained by Imamura and Sasamoto (J Stat Phys 150:908-939, 2013), thereby rendering our result explicit. In the large length limit that implies that the pdf is nothing but the scaling function f_{KPZ}(y) introduced by Prähofer and Spohn (J Stat Phys 115(1):255-279, 2004). Using the KPZ-universality paradigm, we find that this function can therefore also be interpreted as the pdf of the position y of the maximum of the Airy process minus a parabola and a two-sided Brownian motion. We provide a direct numerical test of the result through simulations of the Log-Gamma polymer.

  16. Dynamic-template-directed multiscale assembly for large-area coating of highly-aligned conjugated polymer thin films

    Mohammadi, Erfan; Zhao, Chuankai; Meng, Yifei; Qu, Ge; Zhang, Fengjiao; Zhao, Xikang; Mei, Jianguo; Zuo, Jian-Min; Shukla, Diwakar; Diao, Ying


    Solution processable semiconducting polymers have been under intense investigations due to their diverse applications from printed electronics to biomedical devices. However, controlling the macromolecular assembly across length scales during solution coating remains a key challenge, largely due to the disparity in timescales of polymer assembly and high-throughput printing/coating. Herein we propose the concept of dynamic templating to expedite polymer nucleation and the ensuing assembly process, inspired by biomineralization templates capable of surface reconfiguration. Molecular dynamic simulations reveal that surface reconfigurability is key to promoting template-polymer interactions, thereby lowering polymer nucleation barrier. Employing ionic-liquid-based dynamic template during meniscus-guided coating results in highly aligned, highly crystalline donor-acceptor polymer thin films over large area (>1 cm2) and promoted charge transport along both the polymer backbone and the π-π stacking direction in field-effect transistors. We further demonstrate that the charge transport anisotropy can be reversed by tuning the degree of polymer backbone alignment.

  17. Nonequilibrium phase transition in directed small-world-Voronoi-Delaunay random lattices

    Lima, F. W. S.


    On directed small-world-Voronoi-Delaunay random lattices in two dimensions with quenched connectivity disorder we study the critical properties of the dynamics evolution of public opinion in social influence networks using a simple spin-like model. The system is treated by applying Monte Carlo simulations. We show that directed links on these random lattices may lead to phase diagram with first- and second-order social phase transitions out of equilibrium.

  18. Pd-catalysed direct arylation polymerisation for synthesis of low-bandgap conjugated polymers and photovoltaic performance.

    Chang, Shu-Wei; Waters, Huw; Kettle, Jeff; Kuo, Zi-Rui; Li, Chun-Han; Yu, Chin-Yang; Horie, Masaki


    Low-bandgap conjugated copolymers based on a donor-acceptor structure have been synthesised via palladium-complex catalysed direct arylation polymerisation. Initially, we report the optimisation of the synthesis of poly(cyclopentadithiophene-alt-benzothiadiazole) (PCPDTBT) formed between cyclopentadithiophene and dibromobenzothiadiazole units. The polymerisation condition has been optimised, which affords high-molecular-weight polymers of up to M(n) = 70 k using N-methylpyrrolidone as a solvent. The polymers are used to fabricate organic photovoltaic devices and the best performing PCPDTBT device exhibits a moderate improvement over devices fabricated using the related polymer via Suzuki coupling. Similar polymerisation conditions have also been applied for other monomer units.

  19. A Directed Continuous Time Random Walk Model with Jump Length Depending on Waiting Time

    Long Shi


    Full Text Available In continuum one-dimensional space, a coupled directed continuous time random walk model is proposed, where the random walker jumps toward one direction and the waiting time between jumps affects the subsequent jump. In the proposed model, the Laplace-Laplace transform of the probability density function P(x,t of finding the walker at position x at time t is completely determined by the Laplace transform of the probability density function φ(t of the waiting time. In terms of the probability density function of the waiting time in the Laplace domain, the limit distribution of the random process and the corresponding evolving equations are derived.

  20. Molecular template-directed synthesis of microporous polymer networks for highly selective CO2 capture.

    Shi, Yao-Qi; Zhu, Jing; Liu, Xiao-Qin; Geng, Jian-Cheng; Sun, Lin-Bing


    Porous polymer networks have great potential in various applications including carbon capture. However, complex monomers and/or expensive catalysts are commonly used for their synthesis, which makes the process complicated, costly, and hard to scale up. Herein, we develop a molecular template strategy to fabricate new porous polymer networks by a simple nucleophilic substitution reaction of two low-cost monomers (i.e., chloromethylbenzene and ethylene diamine). The polymerization reactions can take place under mild conditions in the absence of any catalysts. The resultant materials are interconnected with secondary amines and show well-defined micropores due to the structure-directing role of solvent molecules. These properties make our materials highly efficient for selective CO2 capture, and unusually high CO2/N2 and CO2/CH4 selectivities are obtained. Furthermore, the adsorbents can be completely regenerated under mild conditions. Our materials may provide promising candidates for selective capture of CO2 from mixtures such as flue gas and natural gas.

  1. Mussel-Inspired Polymer Carpets: Direct Photografting of Polymer Brushes on Polydopamine Nanosheets for Controlled Cell Adhesion.

    Hafner, Daniel; Ziegler, Lisa; Ichwan, Muhammad; Zhang, Tao; Schneider, Maximilian; Schiffmann, Michael; Thomas, Claudia; Hinrichs, Karsten; Jordan, Rainer; Amin, Ihsan


    2D mussel-inspired polydopamine (PDA) nanosheets are prepared and exploited as a functional surface for grafting various polymer brushes. The PDA nanosheet and its polymer-brush derivatives show lateral integrity and are robust; therefore, they can be detached from their substrates. Cell-adhesion tests show that the PDA nanosheet promotes cell growth and attachment, while a PDA-based poly(3-sulfopropyl methacrylate) carpet exhibits nonfouling behavior. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Robust fabrication of electrospun-like polymer mats to direct cell behaviour.

    Ballester-Beltrán, José; Lebourg, Myriam; Capella, Hector; Diaz Lantada, Andres; Salmerón-Sánchez, Manuel


    Currently, cell culture systems that include nanoscale topography are widely used in order to provide cells additional cues closer to the in vivo environment, seeking to mimic the natural extracellular matrix. Electrospinning is one of the most common techniques to produce nanofiber mats. However, since many sensitive parameters play an important role in the process, a lack of reproducibility is a major drawback. Here we present a simple and robust methodology to prepare reproducible electrospun-like samples. It consists of a polydimethylsiloxane mold reproducing the fiber pattern to solvent-cast a polymer solution and obtain the final sample. To validate this methodology, poly(L-lactic) acid (PLLA) samples were obtained and, after characterisation, bioactivity and ability to direct cell response were assessed. C2C12 myoblasts developed focal adhesions on the electrospun-like fibers and, when cultured under myogenic differentiation conditions, similar differentiation levels to electrospun PLLA fibers were obtained.

  3. Fabrication of Ag nanowire/polymer composite nanocables via direct electrospinning

    Han, Ming-Chu; He, Hong-Wei; Zhang, Bin; Wang, Xiao-Xiong; Zhang, Jun; You, Ming-Hao; Yan, Shi-Ying; Long, Yun-Ze


    1D nanocables consisting of metal core with high conductivity and protective polymer shell are promising for electronic devices. In this paper, silver nanowire/polyvinylidene fluoride (AgNW/PVDF) composite nanocables with excellent thermal stability were successfully fabricated by facile direct electrospinning (e-spinning), in which a slurry of AgNWs were uniformly dispersed into N,N-dimethylformamide/acetone solution containing 20% PVDF to form the e-spinning precursor solution. The decomposed temperature of resultant AgNW/PVDF nanocables is up to 460 °C. Interestingly, the as-spun nanocables exhibit more β phase of PVDF than that of pure PVDF nanofibers. The as-spun AgNW/PVDF nanocables could be applied in fields of antibacterial, ultrathin cables and optoelectronic devices.

  4. Surface Wettability Modification of Cyclic Olefin Polymer by Direct Femtosecond Laser Irradiation

    Bing Wang


    Full Text Available The effect of laser irradiation on surface wettability of cyclic olefin polymer (COP was investigated. Under different laser parameters, a superhydrophilic or a superhydrophobic COP surface with a water contact angle (WCA of almost 0° or 163°, respectively, could be achieved by direct femtosecond laser irradiation. The laser power deposition rate (PDR was found to be a key factor on the wettability of the laser-treated COP surface. The surface roughness and surface chemistry of the laser-irradiated samples were characterized by surface profilometer and X-ray photoelectron spectroscopy, respectively; they were found to be responsible for the changes of the laser-induced surface wettability. The mechanisms involved in the laser surface wettability modification process were discussed.

  5. A mixed-reactants solid-polymer-electrolyte direct methanol fuel cell

    Scott, K.; Shukla, A. K.; Jackson, C. L.; Meuleman, W. R. A.

    Mixed-reactants solid-polymer-electrolyte direct methanol fuel cells (SPE-DMFCs) with a PtRu/C anode and a methanol-tolerant oxygen-reduction cathode catalyst have been assembled and have been subjected to galvanostatic polarisation studies. The oxygen-reduction cathode was either of the FeTMPP/C, CoTMPP/C, FeCoTMPP/C and RuSe/C. It was found that the SPE-DMFC with the RuSe/C cathode yielded the best performance. It has been possible to achieve power densities of approximately 50 and 20 mW/cm 2 while operating a mixed-reactants SPE-DMFC at 90 °C with oxygen and air fed cathodes, respectively. Interestingly, these SPE-DMFCs exhibit no parasitic oxidation of methanol with oxygen.

  6. How to qualify and quantify directional dependencies in spatial random fields: Direction-dependent asymmetry

    Hörning, Sebastian; Bárdossy, András


    Traditional geostatistical analysis is mainly based on variograms and/or covariance functions. A more advanced investigation of spatially distributed variables can be performed using rank order geostatistical methods. For example the rank correlation function in combination with the asymmetry function gives a more detailed insight in the spatial dependence structure of the data of interest. However, many physical processes, for example advection of solute in porous media, can lead to asymmetries that exhibit a certain direction, i.e. they lead to irreversibility in a spatial context. Reversibility is well known in time series analysis; however it is hardly utilized in geostatistics. Spatial reversibility or directional dependencies can neither be covered by the rank correlation function nor by the classical asymmetry function. Therefore, a statistical test based on a chi-squared test on empirical directional copulas will be introduced that enables testing for spatial reversibility. In order to quantify the strength of directional dependencies a new direction-dependent asymmetry function is introduced. Different examples, ranging from synthetical flow and transport experiments to real-world precipitation data, will be used to demonstrate the applicability of the test and the new measure. The difference to classical anisotropy will be shown and the chi-squared test will also be used to test for significance.

  7. The electrolyte challenge for a direct methanol-air polymer electrolyte fuel cell operating at temperatures up to 200 C

    Savinell, Robert; Yeager, Ernest; Tryk, Donald; Landau, Uziel; Wainright, Jesse; Gervasio, Dominic; Cahan, Boris; Litt, Morton; Rogers, Charles; Scherson, Daniel


    Novel polymer electrolytes are being evaluated for use in a direct methanol-air fuel cell operating at temperatures in excess of 100 C. The evaluation includes tests of thermal stability, ionic conductivity, and vapor transport characteristics. The preliminary results obtained to date indicate that a high temperature polymer electrolyte fuel cell is feasible. For example, Nafion 117 when equilibrated with phosphoric acid has a conductivity of at least 0.4 Omega(exp -1)cm(exp -1) at temperatures up to 200 C in the presence of 400 torr of water vapor and methanol vapor cross over equivalent to 1 mA/cm(exp 2) under a one atmosphere methanol pressure differential at 135 C. Novel polymers are also showing similar encouraging results. The flexibility to modify and optimize the properties by custom synthesis of these novel polymers presents an exciting opportunity to develop an efficient and compact methanol fuel cell.

  8. Scalable-manufactured randomized glass-polymer hybrid metamaterial for daytime radiative cooling

    Zhai, Yao; Ma, Yaoguang; David, Sabrina N.; Zhao, Dongliang; Lou, Runnan; Tan, Gang; Yang, Ronggui; Yin, Xiaobo


    Passive radiative cooling draws heat from surfaces and radiates it into space as infrared radiation to which the atmosphere is transparent. However, the energy density mismatch between solar irradiance and the low infrared radiation flux from a near-ambient-temperature surface requires materials that strongly emit thermal energy and barely absorb sunlight. We embedded resonant polar dielectric microspheres randomly in a polymeric matrix, resulting in a metamaterial that is fully transparent to the solar spectrum while having an infrared emissivity greater than 0.93 across the atmospheric window. When backed with a silver coating, the metamaterial shows a noontime radiative cooling power of 93 watts per square meter under direct sunshine. More critically, we demonstrated high-throughput, economical roll-to-roll manufacturing of the metamaterial, which is vital for promoting radiative cooling as a viable energy technology.

  9. Laser direct synthesis and patterning of silver nano/microstructures on a polymer substrate.

    Liu, Yi-Kai; Lee, Ming-Tsang


    This study presents a novel approach for the rapid fabrication of conductive nano/microscale metal structures on flexible polymer substrate (polyimide). Silver film is simultaneously synthesized and patterned on the polyimide substrate using an advanced continuous wave (CW) laser direct writing technology and a transparent, particle-free reactive silver ion ink. The location and shape of the resulting silver patterns are written by a laser beam from a digitally controlled micromirror array device. The silver patterns fabricated by this laser direct synthesis and patterning (LDSP) process exhibit the remarkably low electrical resistivity of 2.1 μΩ cm, which is compatible to the electrical resistivity of bulk silver. This novel LDSP process requires no vacuum chamber or photomasks, and the steps needed for preparation of the modified reactive silver ink are simple and straightforward. There is none of the complexity and instability associated with the synthesis of the nanoparticles that are encountered for the conventional laser direct writing technology which involves nanoparticle sintering process. This LDSP technology is an advanced method of nano/microscale selective metal patterning on flexible substrates that is fast and environmentally benign and shows potential as a feasible process for the roll-to-roll manufacturing of large area flexible electronic devices.

  10. Polymers as directing agents for motions of chemical and biological species

    Tanyeri, Nihan Yonet

    This thesis involves descriptions of solid surface modifications with various polymeric materials which were used as a guiding agent for motion of chemical and biological species. Quasi-two dimensional poly(oligoethylene glycol) acrylate polymer brush based molecular conduits have been designed with the goal of regulating and controlling the diffusive transport of molecular, e.g. organic dyes, and ionic species, e.g. AuCl4-, and Cu2+ ions, along predefined 2-D pathways. The transport of these chemical species has been examined by both fluorescence and dark field microscopy. The polymer brushes were formed through microcontact printing of an initiator, followed by surface-initiated Atom Transfer Radical Polymerization (SI-ATRP). SI-ATRP enables both 2-D patterning with a resolution of about 1 micrometer, and control over the resultant polymer brush thickness (which was varied from 10-100 nm). A hydrophilic poly(oligoethylene glycol) acrylate brushe was selected because of its potential to dissolve a wide range of hydrophilic species. The transport of fluorescent species can be directly followed. A non-lithographic fabrication method was developed for mufluidic devices used in the diffusion studies. Singular channel mufluidic device was utilized to study the directed organic dye diffusion. The AuCl4-, and Cu 2+ ion transport was studied by designing molecular devices with two mufluidic channels. We have demonstrated that the various species of interest diffuse much more rapidly along the predefined pathway than along the bare (polymer brush free) regions of the substrate, demonstrating that diffusive conduits for molecular transport can indeed be formed. The protein resistance of poly(N-isopropylacrylamide) (PNIPAM) brushes grafted from silicon wafers was investigated as a function of the chain molecular weight, grafting density, and temperature. Above the lower critical solution temperature (LCST) of 32°C, the collapse of the water swollen chains, determined by

  11. A direct-staining method to evaluate the mucoadhesion of polymers from aqueous dispersion.

    Kockisch, S; Rees, G D; Young, S A; Tsibouklis, J; Smart, J D


    A novel technique to evaluate polymer adhesion to human buccal cells following exposure to aqueous polymer dispersion, both in vitro and in vivo, is described. Adhering polymer has been visualised by staining with 0.1% (w/v) of either Alcian blue (60 min) or Eosin (10 min) solution, uncomplexed dye being removed by 0.25 M sucrose washings. The extent of polymer adhesion was quantified by measuring the relative staining intensity of control and polymer-treated cells by image analysis. In vitro, Carbopol 974P, polycarbophil (Noveon AA-1) and chitosan (CL 113) were found to adhere to human buccal cells from 0.10% (w/w) aqueous dispersions of these polymers. Following in vivo administration as a mouthwash, these polymers persisted upon the human buccal mucosa for at least 1 h.

  12. Colloids and polymers in random colloidal matrices: Demixing under good-solvent conditions

    Annunziata, Mario Alberto; Pelissetto, Andrea


    We consider a simplified coarse-grained model for colloid-polymer mixtures, in which polymers are represented as monoatomic molecules interacting by means of pair potentials. We use it to study polymer-colloid segregation in the presence of a quenched matrix of colloidal hard spheres. We fix the polymer-to-colloid size ratio to 0.8 and consider matrices such that the fraction f of the volume that is not accessible to the colloids due to the matrix is equal to 40%. As in the Asakura-Oosawa-Vrij (AOV) case, we find that binodal curves in the polymer and colloid volume-fraction plane have a small dependence on disorder. As for the position of the critical point, the behavior differs from that observed in the AOV case: While the critical colloid volume fraction is essentially the same in the bulk and in the presence of the matrix, the polymer volume fraction at criticality increases as f increases. At variance with the AOV case, no capillary colloid condensation or evaporation is generically observed.

  13. Random Walks on Directed Networks: Inference and Respondent-driven Sampling

    Malmros, Jens; Britton, Tom


    Respondent driven sampling (RDS) is a method often used to estimate population properties (e.g. sexual risk behavior) in hard-to-reach populations. It combines an effective modified snowball sampling methodology with an estimation procedure that yields unbiased population estimates under the assumption that the sampling process behaves like a random walk on the social network of the population. Current RDS estimation methodology assumes that the social network is undirected, i.e. that all edges are reciprocal. However, empirical social networks in general also have non-reciprocated edges. To account for this fact, we develop a new estimation method for RDS in the presence of directed edges on the basis of random walks on directed networks. We distinguish directed and undirected edges and consider the possibility that the random walk returns to its current position in two steps through an undirected edge. We derive estimators of the selection probabilities of individuals as a function of the number of outgoing...

  14. Clinical outcomes of biodegradable polymer drug-eluting stents for percutaneous coronary intervention: an updated meta-analysis of randomized controlled trials.

    Kwong, Joey S W; Yu, Cheuk-Man


    Biodegradable polymer drug-eluting stents (DES) are innovative concepts in the era of percutaneous coronary intervention. We systematically reviewed the latest randomized evidence on the efficacy and safety of biodegradable polymer DES as compared to durable polymer DES. MEDLINE, Embase, and the Cochrane database were searched in August 2013 for eligible randomized controlled trials (RCTs) comparing biodegradable polymer DES with durable polymer DES. Clinical outcomes of interest were mortality, myocardial infarction (MI), target lesion revascularization (TLR), target vessel revascularization (TVR), and stent thrombosis. A total of 20 RCTs randomizing 20 021 participants were included, of whom 11 045 were allocated to biodegradable polymer DES and 8976 to durable polymer DES. Treatment of biodegradable polymer DES was not associated with a significant reduction of any of the clinical outcomes (all-cause mortality, odds ratio [OR]: 0.94, 95% confidence interval [CI]: 0.80 to 1.10, P = 0.42; cardiovascular mortality, OR: 0.97, 95% CI: 0.79 to 1.19, P = 0.74; MI, OR: 1.07, 95% CI: 0.91 to 1.26, P = 0.41; TLR, OR: 0.87, 95% CI: 0.69 to 1.08, P = 0.20; TVR, OR: 1.05, 95% CI: 0.85 to 1.28, P = 0.67; definite/probable stent thrombosis, OR: 0.80, 95% CI: 0.59 to 1.07, P = 0.14). Current randomized data indicate that clinical efficacy and safety profiles of biodegradable polymer DES are comparable to those of durable polymer DES. Findings from large-scale studies with rigorous methodology and long follow-up duration are needed.

  15. Photogenerating Silver Nanoparticles and Polymer Nanocomposites by Direct Activation in the Near Infrared

    Lavinia Balan


    Full Text Available This work reports on an improvement of the photochemically assisted synthesis of silver nanoparticles by direct photoreduction of AgNO3 with a laser source emitting in the near infrared range (NIR. For this, polymethine dyes were used as the photoactive agents. Both the effects of central chain structure and activation intensity were investigated. The reduction kinetics was followed up by UV-Vis spectroscopy, and the particles size was evaluated by transmission electron microscopy. The results showed that light intensity affects both the average size and size distribution of Ag nanoparticles generated through this process. The particles can also be generated in situ in a photopolymerizable formulation so that metal/polymer nanocomposites become available through a one-step photoassisted process on the basis of NIR activation. The process described herein is very fast (seconds to a few minutes, and it readily lends itself to automatization for mass production of micro-optical elements implemented directly onto integrated NIR sources.

  16. Biocompatible 3D printed polymers via fused deposition modelling direct C2C12 cellular phenotype in vitro.

    Rimington, Rowan P; Capel, Andrew J; Christie, Steven D R; Lewis, Mark P


    The capability to 3D print bespoke biologically receptive parts within short time periods has driven the growing prevalence of additive manufacture (AM) technology within biological settings, however limited research concerning cellular interaction with 3D printed polymers has been undertaken. In this work, we used skeletal muscle C2C12 cell line in order to ascertain critical evidence of cellular behaviour in response to multiple bio-receptive candidate polymers; polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), polyethylene terephthalate (PET) and polycarbonate (PC) 3D printed via fused deposition modelling (FDM). The extrusion based nature of FDM elicited polymer specific topographies, within which C2C12 cells exhibited reduced metabolic activity when compared to optimised surfaces of tissue culture plastic, however assay viability readings remained high across polymers outlining viable phenotypes. C2C12 cells exhibited consistently high levels of morphological alignment across polymers, however differential myotube widths and levels of transcriptional myogenin expression appeared to demonstrate response specific thresholds at which varying polymer selection potentiates cellular differentiation, elicits pre-mature early myotube formation and directs subsequent morphological phenotype. Here we observed biocompatible AM polymers manufactured via FDM, which also appear to hold the potential to simultaneously manipulate the desired biological phenotype and enhance the biomimicry of skeletal muscle cells in vitro via AM polymer choice and careful selection of machine processing parameters. When considered in combination with the associated design freedom of AM, this may provide the opportunity to not only enhance the efficiency of creating biomimetic models, but also to precisely control the biological output within such scaffolds.

  17. Characterization of polymer blends of polyethersulfone/sulfonated polysulfone and polyethersulfone/sulfonated polyetheretherketone for direct methanol fuel cell applications

    Manea, Carmen; Mulder, Marcel


    Existing polymer electrolyte membranes (PEMs) applied for hydrogen fuel cells are frequently not suitable for direct methanol fuel cells due to the high methanol permeability. Therefore, new materials are required and in order to avoid laborious fuel cell experiments with a so-called membrane–electr

  18. The random co-polymer glatiramer acetate rapidly kills primary human leukocytes through sialic-acid-dependent cell membrane damage

    Christiansen, Stig Hill; Zhang, Xianwei; Juul-Madsen, Kristian;


    The formulation glatiramer acetate (GA) is widely used in therapy of multiple sclerosis. GA consists of random copolymers of four amino acids, in ratios that produce a predominantly positive charge and an amphipathic character. With the extraordinary complexity of the drug, several pharmacological...... contacts, which is critical for the lytic properties. In our study, SAXS showed that GA also forms this type of contacts. Taken together, our study offers new insight on the immunomodulatory mode-of-action of positively charged co-polymers. The comparison of LL-37 and GA highlights a consistent requirement...

  19. Biased versus unbiased randomness in homo-polymers and copolymers of amino acids in the prebiotic world.

    Mosqueira, Fernando G; Negron, Alicia; Ramos, Sergio; Polanco, Carlos


    The polymerization of amino acids under anhydrous prebiotic conditions was first studied several decades ago. Here we use a stochastic model stressing the relevant role of the polarity of amino acids in the formation of oligopeptides in a prebiotic milieu. Our goal is to outline the predominance of co-polypeptides over homo-polypeptides, resulting not only from the randomness, but also from polarity properties of amino acids. Our results conclude that there was a higher probability of the formation of co-polypeptides than of homo-polymers. Besides, we may hypothesize that the former would have a more ample spectrum of possible chemical functions than homo-polypeptides.

  20. First-in-man randomized comparison of BuMA Supreme biodegradable polymer sirolimus-eluting versus durable polymer zotarolimus-eluting coronary stents: The PIONEER trial.

    von Birgelen, Clemens; Asano, Taku; Amoroso, Giovanni; Aminian, Adel; Brugaletta, Salvatore; Vrolix, Mathias; Hernandez-Antolín, Rosana; van de Harst, Pim; Iñiguez, Andres; Janssens, Luc; Smits, Pieter C; Wykrzykowska, Joanna J; Ribeiro, Vasco Gama; Periera, Helder; Canas da Silva, Pedro; Piek, Jan J; Onuma, Yoshinobu; Serruys, Patrick W; Sabaté, Manel


    A second iteration of a sirolimus-eluting stent (SES) that has a biodegradable PLGA-polymer coating with electrografting base layer on a thin-strut (80µm) cobalt-chromium platform (BuMA Supreme; SINOMED, Tianjin, China) has been developed. This first-in-man trial assessed the efficacy and safety of the novel device. This randomized, multi-center, single-blinded, non-inferiority trial compared BuMA Supreme SES versus contemporary durable polymer zotarolimus-eluting stents (ZES) in terms of angiographic in-stent late lumen loss (LLL) at 9-months follow-up as the primary endpoint. A total of 170 patients were randomly allocated to treatment with SES (n=83) or ZES (n=87). At 9-month angiographic follow-up, in-stent LLL was 0.29±0.33mm in SES and 0.14±0.37mm in ZES (Pnon-inferiority=0.45). The in-stent percent diameter stenosis and the binary restenosis rate of the two treatment arms were similar (19.2±12.0% vs. 16.1±12.6%, p=0.09, and 3.3% vs. 4.4%, P=1.00, respectively). At 12-month clinical follow-up, there was no difference between treatment arms with regard to a device-oriented composite clinical endpoint (4.9% vs. 5.7%; p=0.72). The PIONEER trial did not meet its primary endpoint in terms of in-stent LLL at 9-month follow-up. However, this result did not translate into any increase in restenosis rate or impairment in 12-month clinical outcomes.

  1. Eigentime identities for random walks on a family of treelike networks and polymer networks

    Dai, Meifeng; Wang, Xiaoqian; Sun, Yanqiu; Sun, Yu; Su, Weiyi


    In this paper, we investigate the eigentime identities quantifying as the sum of reciprocals of all nonzero normalized Laplacian eigenvalues on a family of treelike networks and the polymer networks. Firstly, for a family of treelike networks, it is shown that all their eigenvalues can be obtained by computing the roots of several small-degree polynomials defined recursively. We obtain the scalings of the eigentime identity on a family of treelike with network size Nn is Nn lnNn. Then, for the polymer networks, we apply the spectral decimation approach to determine analytically all the eigenvalues and their corresponding multiplicities. Using the relationship between the generation and the next generation of eigenvalues we obtain the scalings of the eigentime identity on the polymer networks with network size Nn is Nn lnNn. By comparing the eigentime identities on these two kinds of networks, their scalings with network size Nn are all Nn lnNn.

  2. Highly robust crystalsome via directed polymer crystallization at curved liquid/liquid interface

    Wang, Wenda; Qi, Hao; Zhou, Tian; Mei, Shan; Han, Lin; Higuchi, Takeshi; Jinnai, Hiroshi; Li, Christopher Y


    ... is incommensurate with crystals having three-dimensional translational symmetry. Herein, we report using a miniemulsion crystallization method to grow nanosized, polymer single-crystal-like capsules...

  3. Thioamides: versatile bonds to induce directional and cooperative hydrogen bonding in supramolecular polymers.

    Mes, Tristan; Cantekin, Seda; Balkenende, Dirk W R; Frissen, Martijn M M; Gillissen, Martijn A J; De Waal, Bas F M; Voets, Ilja K; Meijer, E W; Palmans, Anja R A


    The amide bond is a versatile functional group and its directional hydrogen-bonding capabilities are widely applied in, for example, supramolecular chemistry. The potential of the thioamide bond, in contrast, is virtually unexplored as a structuring moiety in hydrogen-bonding-based self-assembling systems. We report herein the synthesis and characterisation of a new self-assembling motif comprising thioamides to induce directional hydrogen bonding. N,N',N''-Trialkylbenzene-1,3,5-tris(carbothioamide)s (thioBTAs) with either achiral or chiral side-chains have been readily obtained by treating their amide-based precursors with P2S5. The thioBTAs showed thermotropic liquid crystalline behaviour and a columnar mesophase was assigned. IR spectroscopy revealed that strong, three-fold, intermolecular hydrogen-bonding interactions stabilise the columnar structures. In apolar alkane solutions, thioBTAs self-assemble into one-dimensional, helical supramolecular polymers stabilised by three-fold hydrogen bonding. Concentration- and temperature-dependent self-assembly studies performed by using a combination of UV and CD spectroscopy demonstrated a cooperative supramolecular polymerisation mechanism and a strong amplification of supramolecular chirality. The high dipole moment of the thioamide bond in combination with the anisotropic shape of the resulting cylindrical aggregate gives rise to sufficiently strong depolarised light scattering to enable depolarised dynamic light scattering (DDLS) experiments in dilute alkane solution. The rotational and translational diffusion coefficients, D(trans) and D(rot), were obtained from the DDLS measurements, and the average length, L, and diameter, d, of the thioBTA aggregates were derived (L = 490 nm and d = 3.6 nm). These measured values are in good agreement with the value L(w) = 755 nm obtained from fitting the temperature-dependent CD data by using a recently developed equilibrium model. This experimental verification

  4. Complex microstructures of ABC triblock copolymer thin films directed by polymer brushes based on self-consistent field theory.

    Jiang, Zhibin; Xu, Chang; Qiu, Yu Dong; Wang, Xiaoliang; Zhou, Dongshan; Xue, Gi


    The morphology and the phase diagram of ABC triblock copolymer thin film directed by polymer brushes are investigated by the self-consistent field theory in three dimensions. The polymer brushes coated on the substrate can be used as a good soft template to tailor the morphology of the block copolymer thin films compared with those on the hard substrates. The polymer brush is identical with the middle block B. By continuously changing the composition of the block copolymer, the phase diagrams are constructed for three cases with the fixed film thickness and the brush density: identical interaction parameters, frustrated and non-frustrated cases. Some ordered complex morphologies are observed: parallel lamellar phase with hexagonally packed pores at surfaces (LAM3 (ll) -HFs), perpendicular lamellar phase with cylinders at the interface (LAM(⊥)-CI), and perpendicular hexagonally packed cylinders phase with rings at the interface (C2 (⊥)-RI). A desired direction (perpendicular or parallel to the coated surfaces) of lamellar phases or cylindrical phases can be obtained by varying the composition and the interactions between different blocks. The phase diagram of ABC triblock copolymer thin film wetted between the polymer brush-coated surfaces is very useful in designing the directed pattern of ABC triblock copolymer thin film.

  5. Direct induction of molecular alignment in liquid crystal polymer network film by photopolymerization

    Hisano, K.; Aizawa, M.; Ishizu, M.; Kurata, Y.; Shishido, A.


    Liquid crystal (LC) is the promising material for the fabrication of high-performance soft, flexible devices. The fascinating and useful properties arise from their cooperative effect that inherently allows the macroscopic integration and control of molecular alignment through various external stimuli. To date, light-matter interaction is the most attractive stimuli and researchers developed photoalignment through photochemical or photophysical reactions triggered by linearly polarized light. Here we show the new choice based on molecular diffusion by photopolymerization. We found that photopolymerization of a LC monomer and a crosslinker through a photomask enables to direct molecular alignment in the resultant LC polymer network film. The key generating the molecular alignment is molecular diffusion due to the difference of chemical potentials between irradiated and unirradiated regions. This concept is applicable to various shapes of photomask and two-dimensional molecular alignments can be fabricated depending on the spatial design of photomask. By virtue of the inherent versatility of molecular diffusion in materials, the process would shed light on the fabrication of various high-performance flexible materials with molecular alignment having controlled patterns.

  6. Polymer optical fibers integrated directly into 3D orthogonal woven composites for sensing

    Hamouda, Tamer; Seyam, Abdel-Fattah M.; Peters, Kara


    This study demonstrates that standard polymer optical fibers (POF) can be directly integrated into composites from 3D orthogonal woven preforms during the weaving process and then serve as in-situ sensors to detect damage due to bending or impact loads. Different composite samples with embedded POF were fabricated of 3D orthogonal woven composites with different parameters namely number of y-/x-layers and x-yarn density. The signal of POF was not affected significantly by the preform structure. During application of resin using VARTM technique, significant drop in backscattering level was observed due to pressure caused by vacuum on the embedded POF. Measurements of POF signal while in the final composites after resin cure indicated that the backscattering level almost returned to the original level of un-embedded POF. The POF responded to application of bending and impact loads to the composite with a reduction in the backscattering level. The backscattering level almost returned back to its original level after removing the bending load until damage was present in the composite. Similar behavior occurred due to impact events. As the POF itself is used as the sensor and can be integrated throughout the composite, large sections of future 3D woven composite structures could be monitored without the need for specialized sensors or complex instrumentation.

  7. Directed evolution of artificial enzymes (XNAzymes) from diverse repertoires of synthetic genetic polymers.

    Taylor, Alexander I; Holliger, Philipp


    This protocol describes the directed evolution of artificial endonuclease and ligase enzymes composed of synthetic genetic polymers (XNAzymes), using 'cross-chemistry selective enrichment by exponential amplification' (X-SELEX). The protocol is analogous to (deoxy)ribozyme selections, but it enables the development of fully substituted catalysts. X-SELEX is initiated by the synthesis of diverse repertoires (here 10(14) different sequences), using xeno nucleic acid (XNA) polymerases, on DNA templates primed with DNA, RNA or XNA oligonucleotides that double as substrates, allowing selection for XNA-catalyzed cleavage or ligation. XNAzymes are reverse-transcribed into cDNA using XNA-dependent DNA polymerases, and then PCR-amplified to generate templates for subsequent rounds or deep sequencing. We describe methods developed for four XNA chemistries, arabino nucleic acids (ANAs), 2'-fluoroarabino nucleic acids (FANAs), hexitol nucleic acids (HNAs) and cyclohexene nucleic acids (CeNAs), which require ∼1 week per round, and typically 10-20 rounds; in principle, these methods are scalable and applicable to a wide range of novel XNAzyme chemistries, substrates and reactions.

  8. Continuous-Time Classical and Quantum Random Walk on Direct Product of Cayley Graphs

    S. Salimi; M.A. Jafarizadeh


    In this paper we define direct product of graphs and give a recipe for obtaining probability of observing particle on vertices in the continuous-time classical and quantum random walk. In the recipe, the probability of observing particle on direct product of graph is obtained by multiplication of probability on the corresponding to sub-graphs, where this method is useful to determining probability of walk on complicated graphs. Using this method, we calculate the probability of continuous-time classical and quantum random walks on many of finite direct product Cayley graphs (complete cycle, complete Kn, charter and n-cube). Also, we inquire that the classical state the stationary uniform distribution is reached as t→∞ but for quantum state is not always satisfied.

  9. Electrical stimulation via a biocompatible conductive polymer directs retinal progenitor cell differentiation.

    Saigal, Rajiv; Cimetta, Elisa; Tandon, Nina; Zhou, Jing; Langer, Robert; Young, Michael; Vunjak-Novakovic, Gordana; Redenti, Stephen


    The goal of this study was to simulate in vitro the spontaneous electrical wave activity associated with retinal development and investigate if such biometrically designed signals can enhance differentiation of mouse retinal progenitor cells (mRPC). To this end, we cultured cells on an electroconductive transplantable polymer, polypyrrole (PPy) and measured gene expression and morphology of the cells. Custom-made 8-well cell culture chambers were designed to accommodate PPy deposited onto indium tin oxide-coated (ITO) glass slides, with precise control of the PPy film thickness. mRPCs were isolated from post-natal day 1 (P1) green fluorescent protein positive (GFP+) mice, expanded, seeded onto PPY films, allowed to adhere for 24 hours, and then subjected to electrical stimulation (100 µA pulse trains, 5 s in duration, once per minute) for 4 days. Cultured cells and non-stimulated controls were processed for immunostaining and confocal analysis, and for RNA extraction and quantitative PCR. Stimulated cells expressed significantly higher levels of the early photoreceptor marker cone-rod homebox (CRX, the earliest known marker of photoreceptor identity), and protein kinase-C (PKC), and significantly lower levels of the glial fibrillary acidic protein (GFAP). Consistently, stimulated cells developed pronounced neuronal morphologies with significantly longer dendritic processes and larger cell bodies than non-stimulated controls. Taken together, the experimental evidence shows that the application of an electrical stimulation designed based on retinal development can be implemented to direct and enhance retinal differentiation of mRPCs, suggesting a role for biomimetic electrical stimulation in directing progenitor cells toward neural fates.

  10. Direct fiber strengthening in three dimensional random-oriented short-fiber composites

    Zhu, Y.T.; Blumenthal, W.R.


    A theory for direct fiber strengthening in random-oriented short-fiber composites is developed. It adopts a maximum load composite failure criterion and takes into account the fiber orientation effect on the probability of a fiber being intercepted by a specimen cross-section. The strain and load of short fibers with different inclination angles with respect to the loading direction were first calculated, and their contribution in carrying load toward the composite load direction was integrated to give the total load. The fibers with smaller inclination angles bear greater stress and break first. This load is then transferred to fibers with larger inclination angles. Direct fiber strengthening component of the composite strength was calculated from the maximum total load these short fibers can carry. The present theory predicts a much greater direct short-fiber strengthening than does previous theories, and provides useful information for composite design and strength assessment.

  11. Fluid-fluid demixing curves for colloid-polymer mixtures in a random colloidal matrix

    Annunziata, Mario Alberto; Pelissetto, Andrea


    We study fluid-fluid phase separation in a colloid-polymer mixture adsorbed in a colloidal porous matrix close to the θ point. For this purpose we consider the Asakura-Oosawa model in the presence of a quenched matrix of colloidal hard spheres. We study the dependence of the demixing curve on the parameters that characterize the quenched matrix, fixing the polymer-to-colloid size ratio to 0.8. We find that, to a large extent, demixing curves depend only on a single parameter f, which represents the volume fraction which is unavailable to the colloids. We perform Monte Carlo simulations for volume fractions f equal to 40% and 70%, finding that the binodal curves in the polymer and colloid packing-fraction plane have a small dependence on disorder. The critical point instead changes significantly: for instance, the colloid packing fraction at criticality increases with increasing f. Finally, we observe for some values of the parameters capillary condensation of the colloids: a bulk colloid-poor phase is in chemical equilibrium with a colloid-rich phase in the matrix.

  12. Implementation of the direct evaluation of strains using a phase analysis code for random patterns

    Molimard, Jérôme


    A new approach for decoding directly strains from surfaces encoded with random patterns has been developed and validated. It is based on phase analysis of small region of interest. Here we adapt to random patterns new concepts proposed by Badulescu (2009) on the grid method. First metrological results are encouraging: resolution is proportional to strain level, being 9% of the nominal value, for a spatial resolution of 9 pixels (ZOI 64 \\times 64 pixels2). Random noise has to be carefully controlled. A numerical example shows the relevance of the approach. Then, first application on a carbon fiber reinforced composite is developed. Fabric intertwining is studied using a tensile test. Over-strains are clearly visible, and results connect well with the previous studies

  13. Direct observation of localized conduction pathways in photocross-linkable polymer memory

    Kwan, Wei Lek; Lei, Bao; Shao, Yue; Prikhodko, Sergey V.; Bodzin, Noah; Yang, Yang


    Resistive switching in photocross-linkable polymer memory devices was found to occur in localized areas of the device. In order to elucidate the reason behind the switching, we used focused ion-beam to prepare a cross-section of the device. It was found that after the device was switched to the high conductive state, in certain parts of the device, the electrodes were only about 5 nm apart. This was probably caused by a combination of high electric field and metal injection into the polymer film. Gold injection into the polymer film by locally enhanced electric field was confirmed by transmission electron microscope-energy dispersive x-ray analysis. This model was in agreement with both the temperature dependent and transient behavior of our device. We conclude that the non-uniformities at the nanoscale interface of the electrode dominated the device characteristics while the polymer played only a secondary role.

  14. Directly patternable, highly conducting polymers for broad applications in organic electronics.

    Yoo, Joung Eun; Lee, Kwang Seok; Garcia, Andres; Tarver, Jacob; Gomez, Enrique D; Baldwin, Kimberly; Sun, Yangming; Meng, Hong; Nguyen, Thuc-Quyen; Loo, Yueh-Lin


    Postdeposition solvent annealing of water-dispersible conducting polymers induces dramatic structural rearrangement and improves electrical conductivities by more than two orders of magnitude. We attain electrical conductivities in excess of 50 S/cm when polyaniline films are exposed to dichloroacetic acid. Subjecting commercially available poly(ethylene dioxythiophene) to the same treatment yields a conductivity as high as 250 S/cm. This process has enabled the wide incorporation of conducting polymers in organic electronics; conducting polymers that are not typically processable can now be deposited from solution and their conductivities subsequently enhanced to practical levels via a simple and straightforward solvent annealing process. The treated conducting polymers are thus promising alternatives for metals as source and drain electrodes in organic thin-film transistors as well as for transparent metal oxide conductors as anodes in organic solar cells and light-emitting diodes.

  15. Direct observation of the ultrafast electron transfer process in a polymer/fullerene blend

    Cerullo, G.; Lanzani, G.; Silvestri, S. De; Brabec, Ch.J.; Zerza, G.; Sariciftci, N.S.; Hummelen, J.C.


    Photoinduced electron transfer in organic molecules is an extensively investigated topic both because of fundamental interest in the photophysics and for applications to artificial photosynthesis. Highly efficient ultrafast electron transfer from photoexcited conjugated polymers to C60 has been

  16. Direct correlation of single-molecule properties with bulk mechanical performance for the biomimetic design of polymers.

    Chung, Jaeyoon; Kushner, Aaron M; Weisman, Adam C; Guan, Zhibin


    For rational design of advanced polymeric materials, it is critical to establish a clear mechanistic link between the molecular structure of a polymer and the emergent bulk mechanical properties. Despite progress towards this goal, it remains a major challenge to directly correlate the bulk mechanical performance to the nanomechanical properties of individual constituent macromolecules. Here, we show a direct correlation between the single-molecule nanomechanical properties of a biomimetic modular polymer and the mechanical characteristics of the resulting bulk material. The multi-cyclic single-molecule force spectroscopy (SMFS) data enabled quantitative derivation of the asymmetric potential energy profile of individual module rupture and re-folding, in which a steep dissociative pathway accounted for the high plateau modulus, while a shallow associative well explained the energy-dissipative hysteresis and dynamic, adaptive recovery. These results demonstrate the potential for SMFS to serve as a guide for future rational design of advanced multifunctional materials.

  17. Phase Behavior of the Ternary Solution Involving Rodlike and Random Coil Polymers


    The present paper covers the phase behavior of poly(p-benzamide)(PBA)/Nylon 6/H2SO4 and poly(p-phenylene terephthalamide) (PPTA)/Nylon 6/H2SO4 systems. The transition temperatures detected by the Depolarized Light Intensity measurements were used to construct the phase diagram in which the influence of temperature was shown. The enhanced depolarized light intensity observed in the ternary system suggests that the coil polymer chains may tend to be extended and contribute to the overall anisotropy of the liquid crystal phase.

  18. A multi-directional rapidly exploring random graph (mRRG) for protein folding

    Nath, Shuvra Kanti


    Modeling large-scale protein motions, such as those involved in folding and binding interactions, is crucial to better understanding not only how proteins move and interact with other molecules but also how proteins misfold, thus causing many devastating diseases. Robotic motion planning algorithms, such as Rapidly Exploring Random Trees (RRTs), have been successful in simulating protein folding pathways. Here, we propose a new multi-directional Rapidly Exploring Random Graph (mRRG) specifically tailored for proteins. Unlike traditional RRGs which only expand a parent conformation in a single direction, our strategy expands the parent conformation in multiple directions to generate new samples. Resulting samples are connected to the parent conformation and its nearest neighbors. By leveraging multiple directions, mRRG can model the protein motion landscape with reduced computational time compared to several other robotics-based methods for small to moderate-sized proteins. Our results on several proteins agree with experimental hydrogen out-exchange, pulse-labeling, and F-value analysis. We also show that mRRG covers the conformation space better as compared to the other computation methods. Copyright © 2012 ACM.

  19. A direct product theorem for bounded-round public-coin randomized communication complexity

    Jain, Rahul; Yao, Penghui


    In this paper, we show a direct product theorm in the model of two-party bounded-round public-coin randomized communication complexity. For a relation f subset of X times Y times Z (X,Y,Z are finite sets), let R^{(t), pub}_e (f) denote the two-party t-message public-coin communication complexity of f with worst case error e. We show that for any relation f and positive integer k: R^{(t), pub}_{1 - 2^{-Omega(k/t^2)}}(f^k) = Omega(k/t (R^{(t), pub}_{1/3}(f) - O(t^2))) . In particular, it implies a strong direct product theorem for the two-party constant-message public-coin randomized communication complexity of all relations f. Our result for example implies a strong direct product theorem for the pointer chasing problem. This problem has been well studied for understanding round v/s communication trade-offs in both classical and quantum communication protocols. We show our result using information theoretic arguments. Our arguments and techniques build on the ones used in [Jain 2011], where a strong direct pro...

  20. The shape effect of Au particles on random laser action in disordered media of Rh6G dye doped with PMMA polymer

    Yin, Jiajia; Feng, Guoying; Zhou, Shouhuan; Zhang, Hong; Wang, Shutong; Zhang, Hua


    Random laser actions in a disordered media based on polymethyl methacrylate (PMMA) polymer doped with Rh6G dye and Au nanoparticles have been demonstrated. It was observed that the shape of Au nanoparticles can tune the spectral central position of the random laser action. It was also seen that the shape of Au nanoparticles strongly affects the pump threshold. Comparing nanosphere- and nanorod-based systems, the nanorod-based one exhibited a lower threshold.

  1. Emergence of the giant weak component in directed random graphs with arbitrary degree distributions

    Kryven, Ivan


    The weak component generalizes the idea of connected components to directed graphs. In this paper, an exact criterion for the existence of the giant weak component is derived for directed graphs with arbitrary bivariate degree distributions. In addition, we consider a random process for evolving directed graphs with bounded degrees. The bounds are not the same for different vertices but satisfy a predefined distribution. The analytic expression obtained for the evolving degree distribution is then combined with the weak-component criterion to obtain the exact time of the phase transition. The phase-transition time is obtained as a function of the distribution that bounds the degrees. Remarkably, when viewed from the step-polymerization formalism, the new results yield Flory-Stockmayer gelation theory and generalize it to a broader scope.

  2. Mathematical Modeling of Transport Phenomena in Polymer Electrolyte and Direct Methanol Fuel Cells

    Birgersson, Erik


    This thesis deals with modeling of two types of fuel cells: the polymer electrolyte fuel cell (PEFC) and the direct methanol fuel cell (DMFC), for which we address four major issues: a) mass transport limitations; b) water management (PEFC); c) gas management (DMFC); d) thermal management. Four models have been derived and studied for the PEFC, focusing on the cathode. The first exploits the slenderness of the cathode for a two-dimensional geometry, leading to a reduced model, where several non dimensional parameters capture the behavior of the cathode. The model was extended to three dimensions, where four different flow distributors were studied for the cathode. A quantitative comparison shows that the interdigitated channels can sustain the highest current densities. These two models, comprising isothermal gas phase flow, limit the studies to (a). Returning to a two-dimensional geometry of the PEFC, the liquid phase was introduced via a separate flow model approach for the cathode. In addition to conservation of mass, momentum and species, the model was extended to consider simultaneous charge and heat transfer for the whole cell. Different thermal, flow fields, and hydrodynamic conditions were studied, addressing (a), (b) and (d). A scale analysis allowed for predictions of the cell performance prior to any computations. Good agreement between experiments with a segmented cell and the model was obtained. A liquid-phase model, comprising conservation of mass, momentum and species, was derived and analyzed for the anode of the DMFC. The impact of hydrodynamic, electrochemical and geometrical features on the fuel cell performance were studied, mainly focusing on (a). The slenderness of the anode allows the use of a narrow-gap approximation, leading to a reduced model, with benefits such as reduced computational cost and understanding of the physical trends prior to any numerical computations. Adding the gas-phase via a multiphase mixture approach, the gas

  3. Chemically selective polymer substrate based direct isotope dilution alpha spectrometry of Pu.

    Paul, Sumana; Pandey, Ashok K; Shah, R V; Aggarwal, S K


    Quantification of actinides in the complex environmental, biological, process and waste streams samples requires multiple steps like selective preconcentration and matrix elimination, solid source preparations generally by evaporation or electrodeposition, and finally alpha spectrometry. To minimize the sample manipulation steps, a membrane based isotope dilution alpha spectrometry method was developed for the determination of plutonium concentrations in the complex aqueous solutions. The advantages of this method are that it is Pu(IV) selective at 3M HNO3, high preconcentration factor can be achieved, and obviates the need of solid source preparation. For this, a thin phosphate-sulfate bifunctional polymer layer was anchored on the surface of microporous poly(ethersulfone) membrane by UV induced surface grafting. The thickness of the bifunctional layer on one surface of the poly(ethersulfone) membrane was optimized. The thickness, physical and chemical structures of the bifunctional layer were studied by secondary ionization mass spectrometry (SIMS), scanning electron microscopy (SEM) and SEM-EDS (energy-dispersive spectroscopy). The optimized membrane was used for preconcentration of Pu(IV) from aqueous solutions having 3-4M HNO3, followed by direct quantification of the preconcentrated Pu(IV) by isotope dilution alpha spectrometry using (238)Pu spike. The chemical recovery efficiency of Pu(IV) was found to be 86±3% below Pu(IV) loading capacity (1.08 μg in 2×1 cm(2)) of the membrane sample. The experiments with single representative actinides indicated that Am(III) did not sorb to significant extent (7%) but U(VI) sorbed with 78±3% efficiency from the solutions having 3M HNO3 concentration. However, Pu(IV) chemical recovery in the membrane remained unaffected from the solution containing 1:1000 wt. proportion of Pu(IV) to U(VI). Pu concentrations in the (U, Pu)C samples and in the irradiated fuel dissolver solutions were determined. The results thus obtained

  4. The direct link model for polymer rings using topological field theory and the second topological moment in dense systems

    Otto, Matthias [Institut fuer Theoretische Physik, Universitaet Goettingen, Goettingen (Germany)


    Polymer rings in solution are either permanently entangled or are not. Permanent topological restrictions give rise to additional entropic interactions apart from the ones arising due to mere chain flexibility or excluded volume. Conversely, entangled polymer rings systems may be formed by closing randomly entangled flexible linear chains. The dependence of linking numbers between randomly entangled rings on the chain length, more specifically the second topological moment , i.e. the average squared linking number, may be determined. In this paper, an approach recently discussed in mathematical physics and called Abelian BF theory, is presented which allows one to express the linking constraint in its simplest form, the Gauss integral, in terms of two gauge fields. The model of Brereton and Shah for a single ring entangled with many other surrounding rings is rederived. The latter model is finally used to calculate the second topological moment, in agreement with a recent result by Ferrari, Kleinert, and Lazzizzera obtained using n-component {phi}{sup 4} theory for the limit n{yields}0. (author)

  5. Inference of biological networks using Bi-directional Random Forest Granger causality.

    Furqan, Mohammad Shaheryar; Siyal, Mohammad Yakoob


    The standard ordinary least squares based Granger causality is one of the widely used methods for detecting causal interactions between time series data. However, recent developments in technology limit the utilization of some existing implementations due to the availability of high dimensional data. In this paper, we are proposing a technique called Bi-directional Random Forest Granger causality. This technique uses the random forest regularization together with the idea of reusing the time series data by reversing the time stamp to extract more causal information. We have demonstrated the effectiveness of our proposed method by applying it to simulated data and then applied it to two real biological datasets, i.e., fMRI and HeLa cell. fMRI data was used to map brain network involved in deductive reasoning while HeLa cell dataset was used to map gene network involved in cancer.

  6. The effects of noise due to random undetected tilts and paleosecular variation on regional paleomagnetic directions

    Calderone, G.J.; Butler, R.F.


    Random tilting of a single paleomagnetic vector produces a distribution of vectors which is not rotationally symmetric about the original vector and therefore not Fisherian. Monte Carlo simulations were performed on two types of vector distributions: 1) distributions of vectors formed by perturbing a single original vector with a Fisher distribution of bedding poles (each defining a tilt correction) and 2) standard Fisher distributions. These simulations demonstrate that inclinations of vectors drawn from both distributions are biased toward shallow inclinations. The Fisher mean direction of the distribution of vectors formed by perturbing a single vector with random undetected tilts is biased toward shallow inclinations, but this bias is insignificant for angular dispersions of bedding poles less than 20??. -from Authors

  7. Direct covalent coupling of proteins to nanostructured plasma polymers: a route to tunable cell adhesion

    Melnichuk, Iurii, E-mail: [Charles University in Prague, Faculty of Mathematics and Physics, Department of Macromolecular Physics, Prague 18000 (Czech Republic); Choukourov, Andrei, E-mail: [Charles University in Prague, Faculty of Mathematics and Physics, Department of Macromolecular Physics, Prague 18000 (Czech Republic); Bilek, Marcela, E-mail: [Charles University in Prague, Faculty of Mathematics and Physics, Department of Macromolecular Physics, Prague 18000 (Czech Republic); School of Physics, University of Sydney, NSW 2006 (Australia); Weiss, Anthony, E-mail: [School of Molecular Bioscience, University of Sydney, NSW 2006 (Australia); Vandrovcová, Marta, E-mail: [Institute of Physiology of Czech Academy of Science, Prague 14220 (Czech Republic); Bačáková, Lucie, E-mail: [Institute of Physiology of Czech Academy of Science, Prague 14220 (Czech Republic); Hanuš, Jan, E-mail: [Charles University in Prague, Faculty of Mathematics and Physics, Department of Macromolecular Physics, Prague 18000 (Czech Republic); Kousal, Jaroslav, E-mail: [Charles University in Prague, Faculty of Mathematics and Physics, Department of Macromolecular Physics, Prague 18000 (Czech Republic); Shelemin, Artem, E-mail: [Charles University in Prague, Faculty of Mathematics and Physics, Department of Macromolecular Physics, Prague 18000 (Czech Republic); Solař, Pavel, E-mail: [Charles University in Prague, Faculty of Mathematics and Physics, Department of Macromolecular Physics, Prague 18000 (Czech Republic); and others


    Highlights: • Flat and nanostructured interfaces were overcoated by hydrocarbon plasma polymer. • Linker-free covalent attachment of proteins to resultant surfaces was validated. • Ultra-thin hydrocarbon overcoat (<2 nm) secured prolonged effective binding. • Pre-adsorbed tropoelastin promoted proliferation of osteoblast-like MG-63 cells. • Nanostructured films were multi-affine and impeded cell adhesion. - Abstract: Flat and nanostructured thin films were fabricated by deposition of ultra-thin (<2 nm) layer of hydrocarbon plasma polymer over polished silicon and over a pattern of 8 nm-thick poly(ethylene) islands on silicon. Linker-free radical-based covalent binding of bovine serum albumin and tropoelastin was confirmed for both types of films. The binding capability of albumin was found to be stable over many days of ambient air storage time. Tropoelastin-mediated flat plasma polymers favored adhesion and proliferation of osteoblast-like MG-63 cells. Nanostructured plasma polymers were multi-affine and their hierarchical surface represented an additional barrier for cell attachment.

  8. Direct measurement of gas solubilities in polymers with a high-pressure microbalance

    von Solms, Nicolas; Nielsen, Johannes Kristoffer; Hassager, Ole


    for methane, for which negative deviations from Henry's law behavior were observed. The diffusion coefficients for each of the gases in the polymer were also measured with the balance, although the uncertainty was greater than for the solubility measurements. (C) 2003 Wiley Periodicals, Inc. J Appl Polyrn Sci...

  9. Effective conductivity of particulate polymer composite electrolytes using random resistor network method

    Kalnaus, Sergiy [ORNL; Sabau, Adrian S [ORNL; Newman, Sarah M [ORNL; Tenhaeff, Wyatt E [ORNL; Daniel, Claus [ORNL; Dudney, Nancy J [ORNL


    The effective DC conductivity of particulate composite electrolytes was obtained by solving electrostatics equations using random resistors network method in three dimensions. The composite structure was considered to consist of three phases: matrix, particulate filler, and conductive shell that surrounded each particle; each phase possessing a different conductivity. Different particle size distributions were generated using Monte Carlo simulations. Unlike effective medium formulations, it was shown that the random resistors network method was able to predict percolation thresholds for the effective composite conductivity. It was found that the mean particle radius has a higher influence on the effective composite conductivity compared to the effect of type of the particle size distributions that were considered. The effect of the shell thickness on the composite conductivity has been investigated. It was found that the conductivity enhancement due to the presence of the conductive shell phase becomes less evident as the shell thickness increases.

  10. Continuum quasiparticle random phase approximation for astrophysical direct neutron capture reaction of neutron-rich nuclei

    Matsuo, Masayuki


    We formulate a many-body theory to calculate the cross section of direct radiative neutron capture reaction by means of the Hartree-Fock-Bogoliubov mean-field model and the continuum quasiparticle random phase approximation (QRPA). A focus is put on very neutron-rich nuclei and low-energy neutron kinetic energy in the range of O(1 keV) - O(1 MeV), relevant for the rapid neutron-capture process of nucleosynthesis. We begin with the photo-absorption cross section and the E1 strength function, t...

  11. Impact of biodegradable versus durable polymer drug-eluting stents on clinical outcomes in patients with coronary artery disease: a meta-analysis of 15 randomized trials

    Zhang Yaojun; Tian Nailiang; Dong Shengjie; Ye Fei; Li Minghui; Christos V.Bourantas; Javaid Iqbal


    Background Drug eluting stents (DESs) made with biodegradable polymer have been developed in an attempt to improve clinical outcomes.However,the impact of biodegradable polymers on clinical events and stent thrombosis (ST) remains controversial.Methods We searched Medline,the Cochrane Library and other internet sources,without language or date restrictions for articles comparing clinical outcomes between biodegradable polymer DES and durable polymer DES.Safety endpoints were ST (definite,definite/probable),mortality,and myocardial infarction (MI).Efficacy endpoints were major adverse cardiac event (MACE) and target lesion revascularization (TLR).Results We identified 15 randomized controlled trials (n=17 068) with a weighted mean follow-up of 20.6 months.There was no statistical difference in the incidence of definite/probable ST between durable polymer-and biodegradable polymerDES; relative risk (RR) 0.83; 95% confidence interval (CI) 0.62-1.11; P=0.22.Biodegradable polymer DES had similar rates of definite ST (RR 0.94,95% CI 0.66-1.33,P=0.72),mortality (RR 0.94,95% C/0.82-1.09,P=0.43),MI (RR 1.08,95% CI 0.92-1.26.P=0.35),MACE (RR 0.99,95% CI 0.91-1.09,P=0.85),and TLR (RR,0.94,95% CI 0.83-1.06,P=0.30) compared with durable polymer DES.Based on the stratified analysis of the included trials,the treatment effect on definite ST was different at different follow-up times:≤1 year favoring durable polymer DES and >1 year favoring biodegradable polymer DES.Conclusions Biodegradable polymer DES has similar safety and efficacy for treating patients with coronary artery disease compared with durable polymer DES.Further data with longer term follow-up are warranted to confirm the potential benefits of biodegradable polymer DES.

  12. Direct versus Indirect Treatment for Preschool Children who Stutter: The RESTART Randomized Trial.

    Caroline de Sonneville-Koedoot

    Full Text Available Stuttering is a common childhood disorder. There is limited high quality evidence regarding options for best treatment. The aim of the study was to compare the effectiveness of direct treatment with indirect treatment in preschool children who stutter.In this multicenter randomized controlled trial with an 18 month follow-up, preschool children who stutter who were referred for treatment were randomized to direct treatment (Lidcombe Program; n = 99 or indirect treatment (RESTART-DCM treatment; n = 100. Main inclusion criteria were age 3-6 years, ≥3% syllables stuttered (%SS, and time since onset ≥6 months. The primary outcome was the percentage of non-stuttering children at 18 months. Secondary outcomes included stuttering frequency (%SS, stuttering severity ratings by the parents and therapist, severity rating by the child, health-related quality of life, emotional and behavioral problems, and speech attitude.Percentage of non-stuttering children for direct treatment was 76.5% (65/85 versus 71.4% (65/91 for indirect treatment (Odds Ratio (OR, 0.6; 95% CI, 0.1-2.4, p = .42. At 3 months, children treated by direct treatment showed a greater decline in %SS (significant interaction time x therapy: β = -1.89; t(282.82 = -2.807, p = .005. At 18 months, stuttering frequency was 1.2% (SD 2.1 for direct treatment and 1.5% (SD 2.1 for indirect treatment. Direct treatment had slightly better scores on most other secondary outcome measures, but no differences between treatment approaches were significant.Direct treatment decreased stuttering more quickly during the first three months of treatment. At 18 months, however, clinical outcomes for direct and indirect treatment were comparable. These results imply that at 18 months post treatment onset, both treatments are roughly equal in treating developmental stuttering in ways that surpass expectations of natural recovery. Follow-up data are needed to confirm these findings in the longer term

  13. Monte Carlo simulation and self-consistent integral equation theory for polymers in quenched random media.

    Sung, Bong June; Yethiraj, Arun


    The conformational properties and static structure of freely jointed hard-sphere chains in matrices composed of stationary hard spheres are studied using Monte Carlo simulations and integral equation theory. The simulations show that the chain size is a nonmonotonic function of the matrix density when the matrix spheres are the same size as the monomers. When the matrix spheres are of the order of the chain size the chain size decreases monotonically with increasing matrix volume fraction. The simulations are used to test the replica-symmetric polymer reference interaction site model (RSP) integral equation theory. When the simulation results for the intramolecular correlation functions are input into the theory, the agreement between theoretical predictions and simulation results for the pair-correlation functions is quantitative only at the highest fluid volume fractions and for small matrix sphere sizes. The RSP theory is also implemented in a self-consistent fashion, i.e., the intramolecular and intermolecular correlation functions are calculated self-consistently by combining a field theory with the integral equations. The theory captures qualitative trends observed in the simulations, such as the nonmonotonic dependence of the chain size on media fraction.

  14. Nonlinear random resistor diode networks and fractal dimensions of directed percolation clusters.

    Stenull, O; Janssen, H K


    We study nonlinear random resistor diode networks at the transition from the nonpercolating to the directed percolating phase. The resistor-like bonds and the diode-like bonds under forward bias voltage obey a generalized Ohm's law V approximately I(r). Based on general grounds such as symmetries and relevance we develop a field theoretic model. We focus on the average two-port resistance, which is governed at the transition by the resistance exponent straight phi(r). By employing renormalization group methods we calculate straight phi(r) for arbitrary r to one-loop order. Then we address the fractal dimensions characterizing directed percolation clusters. Via considering distinct values of the nonlinearity r, we determine the dimension of the red bonds, the chemical path, and the backbone to two-loop order.

  15. An Application of Direct Ritz Method for Random Seismic Responses of Jacket Platforms

    HAN Xiao-shuang; MA Jun; ZHAO De-you; ZHOU Bo


    In this paper, the jacket platform is simulated by a non-uniform cantilever beam subjected to axial force. Based on the Hamilton theory, the equation of bending motion is developed and solved by the classical Ritz method combined with the pseudo-excitation method for random responses with non-classical damping. Usually, random responses of this continuous structure are obtained by orthogonality of modes, and some normal modes of the structure are needed, causing inconvenience for the analysis of the non-uniform beam whose normal modes are not easy to be obtained. However, if the pseudo-excitation method is extended to calculate random responses by combining it with the classical Ritz method, the responses of a non-uniform beam, such as auto-PSD function, cross-PSD and higher spectral moments, can be solved directly avoiding the calculation of normal modes. The numerical results show that the present method is effective and useful in aseismic design of platforms.

  16. Collapsed polymer-directed synthesis of multicomponent coaxial-like nanostructures

    Huang, Zhiqi


    Multicomponent colloidal nanostructures (MCNs) exhibit intriguing topologically dependent chemical and physical properties. However, there remain significant challenges in the synthesis of MCNs with high-order complexity. Here we show the development of a general yet scalable approach for the rational design and synthesis of MCNs with unique coaxial-like construction. The site-preferential growth in this synthesis relies on the selective protection of seed nanoparticle surfaces with locally defined domains of collapsed polymers. By using this approach, we produce a gallery of coaxial-like MCNs comprising a shaped Au core surrounded by a tubular metal or metal oxide shell. This synthesis is robust and not prone to variations in kinetic factors of the synthetic process. The essential role of collapsed polymers in achieving anisotropic growth makes our approach fundamentally distinct from others. We further demonstrate that this coaxial-like construction can lead to excellent photocatalytic performance over conventional core–shell-type MCNs.

  17. Collapsed polymer-directed synthesis of multicomponent coaxial-like nanostructures.

    Huang, Zhiqi; Liu, Yijing; Zhang, Qian; Chang, Xiaoxia; Li, Ang; Deng, Lin; Yi, Chenglin; Yang, Yang; Khashab, Niveen M; Gong, Jinlong; Nie, Zhihong


    Multicomponent colloidal nanostructures (MCNs) exhibit intriguing topologically dependent chemical and physical properties. However, there remain significant challenges in the synthesis of MCNs with high-order complexity. Here we show the development of a general yet scalable approach for the rational design and synthesis of MCNs with unique coaxial-like construction. The site-preferential growth in this synthesis relies on the selective protection of seed nanoparticle surfaces with locally defined domains of collapsed polymers. By using this approach, we produce a gallery of coaxial-like MCNs comprising a shaped Au core surrounded by a tubular metal or metal oxide shell. This synthesis is robust and not prone to variations in kinetic factors of the synthetic process. The essential role of collapsed polymers in achieving anisotropic growth makes our approach fundamentally distinct from others. We further demonstrate that this coaxial-like construction can lead to excellent photocatalytic performance over conventional core-shell-type MCNs.

  18. Nanoparticle-Directed Metal-Organic Framework/Porous Organic Polymer Monolithic Supports for Flow-Based Applications.

    Darder, María Del Mar; Salehinia, Shima; Parra, José B; Herrero-Martinez, José M; Svec, Frantisek; Cerdà, Víctor; Turnes Palomino, Gemma; Maya, Fernando


    A two-step nanoparticle-directed route for the preparation of macroporous polymer monoliths for which the pore surface is covered with a metal-organic framework (MOF) coating has been developed to facilitate the use of MOFs in flow-based applications. The flow-through monolithic matrix was prepared in a column format from a polymerization mixture containing ZnO-nanoparticles. These nanoparticles embedded in the precursor monolith were converted to MOF coatings via the dissolution-precipitation equilibrium after filling the pores of the monolith with a solution of the organic linker. Pore surface coverage with the microporous zeolitic imidazolate framework ZIF-8 resulted in an increase in surface area from 72 to 273 m(2) g(-1). Monolithic polymer containing ZIF-8 coating was implemented as a microreactor catalyzing the Knoevenagel condensation reaction and also in extraction column format enabling the preconcentration of trace levels of toxic chlorophenols in environmental waters. Our approach can be readily adapted to other polymers and MOFs thus enabling development of systems for flow-based MOF applications.

  19. Wavelength-scale light concentrator made by direct 3D laser writing of polymer metamaterials

    Moughames, J.; Jradi, S.; Chan, T. M.; Akil, S.; Battie, Y.; Naciri, A. En; Herro, Z.; Guenneau, S.; Enoch, S.; Joly, L.; Cousin, J.; Bruyant, A.


    We report on the realization of functional infrared light concentrators based on a thick layer of air-polymer metamaterial with controlled pore size gradients. The design features an optimum gradient index profile leading to light focusing in the Fresnel zone of the structures for two selected operating wavelength domains near 5.6 and 10.4 μm. The metamaterial which consists in a thick polymer containing air holes with diameters ranging from λ/20 to λ/8 is made using a 3D lithography technique based on the two-photon polymerization of a homemade photopolymer. Infrared imaging of the structures reveals a tight focusing for both structures with a maximum local intensity increase by a factor of 2.5 for a concentrator volume of 1.5 λ3, slightly limited by the residual absorption of the selected polymer. Such porous and flat metamaterial structures offer interesting perspectives to increase infrared detector performance at the pixel level for imaging or sensing applications.

  20. Wavelength-scale light concentrator made by direct 3D laser writing of polymer metamaterials

    Moughames, J.; Jradi, S.; Chan, T. M.; Akil, S.; Battie, Y.; Naciri, A. En; Herro, Z.; Guenneau, S.; Enoch, S.; Joly, L.; Cousin, J.; Bruyant, A.


    We report on the realization of functional infrared light concentrators based on a thick layer of air-polymer metamaterial with controlled pore size gradients. The design features an optimum gradient index profile leading to light focusing in the Fresnel zone of the structures for two selected operating wavelength domains near 5.6 and 10.4 μm. The metamaterial which consists in a thick polymer containing air holes with diameters ranging from λ/20 to λ/8 is made using a 3D lithography technique based on the two-photon polymerization of a homemade photopolymer. Infrared imaging of the structures reveals a tight focusing for both structures with a maximum local intensity increase by a factor of 2.5 for a concentrator volume of 1.5 λ3, slightly limited by the residual absorption of the selected polymer. Such porous and flat metamaterial structures offer interesting perspectives to increase infrared detector performance at the pixel level for imaging or sensing applications. PMID:27698476

  1. Random and Directed Walk-Based Top-  Queries in Wireless Sensor Networks

    Jun-Song Fu


    Full Text Available In wireless sensor networks, filter-based top-  query approaches are the state-of-the-art solutions and have been extensively researched in the literature, however, they are very sensitive to the network parameters, including the size of the network, dynamics of the sensors’ readings and declines in the overall range of all the readings. In this work, a random walk-based top-  query approach called RWTQ and a directed walk-based top-  query approach called DWTQ are proposed. At the beginning of a top-  query, one or several tokens are sent to the specific node(s in the network by the base station. Then, each token walks in the network independently to record and process the readings in a random or directed way. A strategy of choosing the “right” way in DWTQ is carefully designed for the token(s to arrive at the high-value regions as soon as possible. When designing the walking strategy for DWTQ, the spatial correlations of the readings are also considered. Theoretical analysis and simulation results indicate that RWTQ and DWTQ both are very robust against these parameters discussed previously. In addition, DWTQ outperforms TAG, FILA and EXTOK in transmission cost, energy consumption and network lifetime.

  2. Random resistor-diode networks and the crossover from isotropic to directed percolation

    Janssen; Stenull


    By employing the methods of renormalized field theory, we show that the percolation behavior of random resistor-diode networks near the multicritical line belongs to the universality class of isotropic percolation. We construct a mesoscopic model from the general epidemic process by including a relevant isotropy-breaking perturbation. We present a two-loop calculation of the crossover exponent straight phi. Upon blending the varepsilon-expansion result with the exact value straight phi=1 for one dimension by a rational approximation, we obtain straight phi=1.29+/-0.05 for two dimensions. This value is in agreement with the recent simulations of a two-dimensional random diode network by Inui, et al. [Phys. Rev. E 59, 6513 (1999)], who found an order parameter exponent beta different from those of isotropic and directed percolation. Furthermore, we reconsider the theory of the full crossover from isotropic to directed percolation by Frey, Tauber, and Schwabl [Europhys. Lett. 26, 413 (1994); Phys. Rev. E 49, 5058 (1994)], and clear up some minor shortcomings.

  3. Performance of SuSi: a method for generating atomistic models of amorphous polymers based on a random search of energy minima.

    Curcó, David; Alemán, Carlos


    The performance of a recently developed method to generate representative atomistic models of amorphous polymers has been investigated. This method, which is denoted SuSi, can be defined as a random generator of energy minima. The effects produced by different parameters used to define the size of the system and the characteristics of the generation algorithm have been examined. Calculations have been performed on poly(L,D-lactic) acid (rho = 1.25 g/cm3) and nylon 6 (rho = 1.084 g/cm(3)), which are important commercial polymers.

  4. Randomized comparison of a polymer-free sirolimus-eluting stent versus a polymer-based paclitaxel-eluting stent in patients with diabetes mellitus: the LIPSIA Yukon trial.

    Desch, Steffen; Schloma, Denis; Möbius-Winkler, Sven; Erbs, Sandra; Gielen, Stephan; Linke, Axel; Yu, Jiangtao; Lauer, Bernward; Kleinertz, Klaus; Dänschel, Wilfried; Schuler, Gerhard; Thiele, Holger


    The objective of the study was to assess noninferiority of the polymer-free sirolimus-eluting Yukon Choice stent (Translumina GmbH, Hechingen, Germany) compared with the polymer-based Taxus Liberté stent (Boston Scientific, Natick, Massachusetts) with regard to the primary endpoint, in-stent late lumen loss, at 9 months in patients with diabetes mellitus. The Yukon Choice stent has been evaluated in several randomized controlled trials before, albeit to date, there has been no trial that exclusively enrolled patients with diabetes mellitus. Patients with diabetes mellitus undergoing percutaneous coronary intervention for clinically significant de novo coronary artery stenosis were randomized 1:1 to receive either the polymer-free sirolimus-eluting Yukon Choice stent or the polymer-based paclitaxel-eluting Taxus Liberté stent. A total of 240 patients were randomized. Quantitative coronary angiography was available for 79% of patients. Mean in-stent late lumen loss was 0.63 ± 0.62 mm for the Yukon Choice stent and 0.45 ± 0.60 mm for the Taxus Liberté stent. Based on the pre-specified margin, the Yukon Choice stent failed to show noninferiority for the primary endpoint. During follow-up, there were no significant differences between groups regarding death, myocardial infarction, stent thrombosis, target lesion revascularization, target vessel revascularization, or nontarget vessel revascularization. Compared with the Taxus Liberté stent, the polymer-free sirolimus-eluting Yukon Choice stent failed to show noninferiority with regard to the primary endpoint, in-stent late lumen loss, in patients with diabetes mellitus after 9-month follow-up. Both stents showed comparable clinical efficacy and safety. (Yukon Choice Versus Taxus Liberté in Diabetes Mellitus; NCT00368953). Copyright © 2011 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

  5. Random noise de-noising and direct wave eliminating based on SVD method for ground penetrating radar signals

    Liu, Cai; Song, Chao; Lu, Qi


    In this paper, we present a method using singular value decomposition (SVD) which aims at eliminating the random noise and direct wave from ground penetrating radar (GPR) signals. To demonstrate the validity and high efficiency of the SVD method in eliminating random noise, we compare the SVD de-noising method with wavelet threshold de-noising method and bandpass filtering method on both noisy synthetic data and field data. After that, we compare the SVD method with the mean trace deleting in eliminating direct wave on synthetic data and field data. We set general and quantitative criteria on choosing singular values to carry out the random noise de-noising and direct wave eliminating process. We find that by choosing appropriate singular values, SVD method can eliminate the random noise and direct wave in the GPR data validly and efficiently to improve the signal-to-noise ratio (SNR) of the GPR profiles and make effective reflection signals clearer.

  6. Polymer-Assisted Direct Deposition of Uniform Carbon Nanotube Bundle Networks for High Performance Transparent Electrodes

    Hellstrom, Sondra L.


    Flexible transparent electrodes are crucial for touch screen, flat panel display, and solar cell technologies. While carbon nanotube network electrodes show promise, characteristically poor dispersion properties have limited their practicality. We report that addition of small amounts of conjugated polymer to nanotube dispersions enables straightforward fabrication of uniform network electrodes by spin-coating and simultaneous tuning of parameters such as bundle size and density. After treatment in thionyl chloride, electrodes have sheet resistances competitive with other reported carbon nanotube based transparent electrodes to date. © 2009 American Chemical Society.

  7. Conduction mechanisms in some graphite - polymer composites: the effect of a direct-current electric field

    Celzard, A.; McRae, E.; Furdin, G.; Marêché, J. F.


    This paper deals with the possible conduction mechanisms in highly anisotropic composites comprising 0 - 10 vol% graphite flakes within a polymer host. Conductivity measurements as a function of DC electric field have been made. In most cases, a non-linear behaviour of the current - voltage relationships is observed. A number of theoretical models are considered and we show that none of them is, by itself, able to explain our results. We further develop several arguments which lead us to consider the existence of a combined tunnelling effect and ionic conduction mechanism.

  8. The influence of the directional energy distribution on the nonlinear dispersion relation in a random gravity wave field

    Huang, N. E.; Tung, C.-C.


    The influence of the directional distribution of wave energy on the dispersion relation is calculated numerically using various directional wave spectrum models. The results indicate that the dispersion relation varies both as a function of the directional energy distribution and the direction of propagation of the wave component under consideration. Furthermore, both the mean deviation and the random scatter from the linear approximation increase as the energy spreading decreases. Limited observational data are compared with the theoretical results. The agreement is favorable.

  9. Bichromatic coherent random lasing from dye-doped polymer stabilized blue phase liquid crystals controlled by pump light polarization

    Wang, Lei; Wang, Meng; Yang, Mingchao; Shi, Li-Jie; Deng, Luogen; Yang, Huai


    In this paper, we investigate the bichromatic coherent random lasing actions from the dye-doped polymer stabilized blue phase liquid crystals. Two groups of lasing peaks, of which the full widith at half maximum is about 0.3 nm, are clearly observed. The shorter- and longer-wavelength modes are associated with the excitation of the single laser dye (DCM) monomers and dimers respectively. The experimental results show that the competition between the two groups of the lasing peaks can be controlled by varying the polarization of the pump light. When the polarization of the pump light is rotated from 0° to 90°, the intensity of the shorter-wavelength lasing peak group reduces while the intensity of the longer-wavelength lasing peak group increases. In addition, a red shift of the longer-wavelength modes is also observed and the physical mechanisms behind the red-shift phenomenon are discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 11474021 and 51333001), the Key Program for International S&T Cooperation Projects of China (Grant No. 2013DFB50340), the Issues of Priority Development Areas of the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20120001130005), and the Key (Key Grant) Project of Chinese Ministry of Education (Grant No. 313002).

  10. Diffusion of flexible random-coil dextran polymers measured in anisotropic brain extracellular space by integrative optical imaging.

    Xiao, Fanrong; Nicholson, Charles; Hrabe, Jan; Hrabetová, Sabina


    There are a limited number of methods available to quantify the extracellular diffusion of macromolecules in an anisotropic brain region, e.g., an area containing numerous aligned fibers where diffusion is faster along the fibers than across. We applied the integrative optical imaging method to measure diffusion of the fluorophore Alexa Fluor 488 (molecular weight (MW) 547) and fluorophore-labeled flexible random-coil dextran polymers (dex3, MW 3000; dex75, MW 75,000; dex282, MW 282,000; dex525, MW 525,000) in the extracellular space (ECS) of the anisotropic molecular layer of the isolated turtle cerebellum. For all molecules, two-dimensional images acquired an elliptical shape with major and minor axes oriented along and across, respectively, the unmyelinated parallel fibers. The effective diffusion coefficients, D*(major) and D*(minor), decreased with molecular size. The diffusion anisotropy ratio (DAR = D*(major)/D*(minor)) increased for Alexa Fluor 488 through dex75 but then unexpectedly reached a plateau. We argue that dex282 and dex525 approach the ECS width and deform to diffuse. In support of this concept, scaling theory shows the diffusion behavior of dex282 and dex525 to be consistent with transition to a reptation regime, and estimates the average ECS width at approximately 31 nm. These findings have implications for the interstitial transport of molecules and drugs, and for modeling neurotransmitter diffusion during ectopic release and spillover.

  11. Femtosecond laser direct-write of optofluidics in polymer-coated optical fiber

    Joseph, Kevin A. J.; Haque, Moez; Ho, Stephen; Aitchison, J. Stewart; Herman, Peter R.


    Multifunctional lab in fiber technology seeks to translate the accomplishments of optofluidic, lab on chip devices into silica fibers. a robust, flexible, and ubiquitous optical communication platform that can underpin the `Internet of Things' with distributed sensors, or enable lab on chip functions deep inside our bodies. Femtosecond lasers have driven significant advances in three-dimensional processing, enabling optical circuits, microfluidics, and micro-mechanical structures to be formed around the core of the fiber. However, such processing typically requires the stripping and recoating of the polymer buffer or jacket, increasing processing time and mechanically weakening the device. This paper reports on a comprehensive assessment of laser damage in urethane-acrylate-coated fiber. The results show a sufficient processing window is available for femtosecond laser processing of the fiber without damaging the polymer jacket. The fiber core, cladding, and buffer could be simultaneously processed without removal of the buffer jacket. Three-dimensional lab in fiber devices were successfully fabricated by distortion-free immersionlens focusing, presenting fiber-cladding optical circuits and progress towards chemically-etched channels, microfluidic cavities, and MEMS structure inside buffer-coated fiber.

  12. Directed assembly of conducting polymers on sub-micron templates by electrical fields

    Shen, Jia; Wei, Ming [National Science Foundation (NSF) Nanoscale Science and Engineering Center for High-Rate Nanomanufacturing, University of Massachusetts Lowell, Lowell, MA 01854 (United States); Busnaina, Ahmed [National Science Foundation (NSF) Nanoscale Science and Engineering Center for High-Rate Nanomanufacturing, Northeastern University, Boston, MA 02115 (United States); Barry, Carol [National Science Foundation (NSF) Nanoscale Science and Engineering Center for High-Rate Nanomanufacturing, University of Massachusetts Lowell, Lowell, MA 01854 (United States); Mead, Joey, E-mail: [National Science Foundation (NSF) Nanoscale Science and Engineering Center for High-Rate Nanomanufacturing, University of Massachusetts Lowell, Lowell, MA 01854 (United States)


    Highlights: Black-Right-Pointing-Pointer Nanoscale patterns with dimensions of assembled PANi down to 100 nm were fabricated. Black-Right-Pointing-Pointer We use electrophoretic and dielectrophoretic assembly to deposit PANi. Black-Right-Pointing-Pointer Electrophoretic and dielectrophoretic assembly of PANi finished in less than 1 min. Black-Right-Pointing-Pointer Effect of process parameters on assembly of PANi onto nanoscale pattern was studied. Black-Right-Pointing-Pointer The assembled PANi can be transferred to other flexible substrates. - Abstract: Patterning of conducting polymer into sub-micron patterns over large areas at high rate and low cost is significant for commercial manufacturing of novel devices. Electrophoretic and dielectrophoretic assembly provide an easily scaled approach with high fabrication rates. In this work, electrophoretic and dielectrophoretic assembly were used to assemble polyaniline (PANi) into multiscale sub-micron size patterns in less than 1 min. The process was controlled by assembly time, amplitude, and frequency of the electric field. Dielectrophoretic assembly is preferable for manufacturing as it reduces damage to the templates used to control the assembly. Using this method, sub-micron patterns with dimensions of the assembled PANi down to 100 nm were fabricated over large areas in short times. The assembled PANi was further transferred to other flexible polymer substrates by a thermoforming process, providing a fast, easily controlled and promising approach for fabrication of nanoscale devices.

  13. Delta-Bar-Delta and directed random search algorithms to study capacitor banks switching overvoltages

    Sadeghkhani Iman


    Full Text Available This paper introduces an approach to analyse transient overvoltages during capacitor banks switching based on artificial neural networks (ANN. Three learning algorithms, delta-bar-delta (DBD, extended delta-bar-delta (EDBD and directed random search (DRS were used to train the ANNs. The ANN training is based on equivalent parameters of the network and therefore, a trained ANN is applicable to every studied system. The developed ANN is trained with extensive simulated results and tested for typical cases. The new algorithms are presented and demonstrated for a partial 39-bus New England test system. The simulated results show the proposed technique can accurately estimate the peak values of switching overvoltages.

  14. Transcranial direct current stimulation in post-stroke dysphagia: a systematic review of randomized controlled trials

    Kavian Ghandehari


    Full Text Available Introduction: The aim of this research was to systematically review all the randomized controlled trials that have evaluated the effect of transcranial direct current stimulation (tDCS on post-stroke dysphagia. Methods: Three electronic databases were searched for relevant articles that were uploaded from their inception to March 2015: PubMed, Cochrane Library (Cochrane Central Register of Controlled Trials, and Scopus. All data was that was related to the location of the cerebrovascular accident (CVA, the parameters of tDCS, post-stroke time to commencement of tDCS, the stimulated hemisphere, stimulation dose, any outcome measurements, and follow-up duration were extracted and assessed. Finally, a number of observations were generated through a qualitative synthesis of the extracted data.Result: Three eligible randomized controlled trials were included in the systematic review. All three trials reported that, in comparison to a placebo, tDCS had a statistically significant effect on post-stroke dysphagia.Discussion: The results of our systematic review suggest that tDCS may represent a promising novel treatment for post-stroke dysphagia. However, to date, little is known about the optimal parameters of tDCS for relieving post-stroke dysphagia. Further studies are warranted to refine this promising intervention by exploring the optimal parameters of tDCS.Conclusion: Since brainstem swallowing centers have bilateral cortical innervations, measures that enhance cortical input and sensorimotor control of brainstem swallowing may facilitate recovery from dysphagia.

  15. Direct-to-consumer marketing of psychological treatments: A randomized controlled trial.

    Gallo, Kaitlin P; Comer, Jonathan S; Barlow, David H; Clarke, Roberta N; Antony, Martin M


    Although direct-to-consumer (DTC) marketing of pharmacologic interventions is effective and common, similar approaches have yet to be evaluated in the promotion of psychological treatments (PTs). This is the first randomized controlled trial evaluating the potential of DTC marketing of PTs. Participants (N = 344; 75.0% female, mean age = 18.6 years, 48.5% non-Hispanic White) were randomly assigned to consume one of four extended commercial campaigns embedded within unrelated programming across 3 weeks. The four campaign conditions were a PT campaign, a PT informing about medication side effects campaign, a medication campaign, and a neutral campaign. Attitudes about and intention to seek psychological treatment were assessed prior to campaign exposure (T1), 1 week following the final week of campaign exposure (T2), and at a 3-month follow-up evaluation (T3). The percentage of participants who newly intended psychological treatment at T2 or T3 differed by condition, with those assigned to the PT campaign slightly more likely to have intended to receive psychological treatment at T2 or T3 than those in other conditions. Baseline reports of emotional symptoms moderated the effect of condition on attitudes toward PT and perceived likelihood of seeking treatment in the future. Findings support the preliminary utility of DTC marketing of psychological treatments. Increasing consumer knowledge of PTs may be a worthwhile complement to current dissemination and implementation efforts aimed at promoting the uptake of PTs in mental health care. (c) 2015 APA, all rights reserved).

  16. All-Direction Random Routing for Source-Location Privacy Protecting against Parasitic Sensor Networks.

    Wang, Na; Zeng, Jiwen


    Wireless sensor networks are deployed to monitor the surrounding physical environments and they also act as the physical environments of parasitic sensor networks, whose purpose is analyzing the contextual privacy and obtaining valuable information from the original wireless sensor networks. Recently, contextual privacy issues associated with wireless communication in open spaces have not been thoroughly addressed and one of the most important challenges is protecting the source locations of the valuable packages. In this paper, we design an all-direction random routing algorithm (ARR) for source-location protecting against parasitic sensor networks. For each package, the routing process of ARR is divided into three stages, i.e., selecting a proper agent node, delivering the package to the agent node from the source node, and sending it to the final destination from the agent node. In ARR, the agent nodes are randomly chosen in all directions by the source nodes using only local decisions, rather than knowing the whole topology of the networks. ARR can control the distributions of the routing paths in a very flexible way and it can guarantee that the routing paths with the same source and destination are totally different from each other. Therefore, it is extremely difficult for the parasitic sensor nodes to trace the packages back to the source nodes. Simulation results illustrate that ARR perfectly confuses the parasitic nodes and obviously outperforms traditional routing-based schemes in protecting source-location privacy, with a marginal increase in the communication overhead and energy consumption. In addition, ARR also requires much less energy than the cloud-based source-location privacy protection schemes.

  17. All-Direction Random Routing for Source-Location Privacy Protecting against Parasitic Sensor Networks

    Wang, Na; Zeng, Jiwen


    Wireless sensor networks are deployed to monitor the surrounding physical environments and they also act as the physical environments of parasitic sensor networks, whose purpose is analyzing the contextual privacy and obtaining valuable information from the original wireless sensor networks. Recently, contextual privacy issues associated with wireless communication in open spaces have not been thoroughly addressed and one of the most important challenges is protecting the source locations of the valuable packages. In this paper, we design an all-direction random routing algorithm (ARR) for source-location protecting against parasitic sensor networks. For each package, the routing process of ARR is divided into three stages, i.e., selecting a proper agent node, delivering the package to the agent node from the source node, and sending it to the final destination from the agent node. In ARR, the agent nodes are randomly chosen in all directions by the source nodes using only local decisions, rather than knowing the whole topology of the networks. ARR can control the distributions of the routing paths in a very flexible way and it can guarantee that the routing paths with the same source and destination are totally different from each other. Therefore, it is extremely difficult for the parasitic sensor nodes to trace the packages back to the source nodes. Simulation results illustrate that ARR perfectly confuses the parasitic nodes and obviously outperforms traditional routing-based schemes in protecting source-location privacy, with a marginal increase in the communication overhead and energy consumption. In addition, ARR also requires much less energy than the cloud-based source-location privacy protection schemes. PMID:28304367

  18. p16 Immunohistochemistry in Colposcope-Directed and Random Cervical Biopsies of CIN2 and CIN3.

    Arvizo, Cynthia; Chen, Qing; Du, Hui; Wang, Chun; Tang, Jinlong; Yang, Bin; Pretorius, Robert G; Wu, Ruifang; Belinson, Jerome Leslie


    The aim of this study was to determine if there is a different p16 expression pattern between colposcope-directed and random (colposcope-undetectable) biopsies of cervical intraepithelial neoplasia (CIN2) and CIN3. Cervical biopsies that were positive for CIN2 or CIN3 were selected from a database of samples acquired during a large population-based clinical trial in Guangdong Province in China (Shenzhen Cervical Cancer Screening Study II). Blocks were recut, reread, and then immunostained for p16. Biopsies were categorized as either colposcope-directed or random biopsies. Diffuse staining was considered p16 positive, whereas focal or no staining was considered p16 negative. Differences were determined by the Fisher exact test. Among the patients with CIN3, there were 232 individual biopsies of CIN3. Sixty were randomly collected, and 172 were colposcopy directed. p16 positivity for the colposcope-directed and random biopsies was 97.7% and 91.7%, respectively (p = 0.052). Like the CIN3 biopsies, colposcope-directed and random CIN2 samples expressed p16 similarly (86.8% [46/53] and 82.6% [19/23], p = .73, respectively). Based on our data, even small colposcope-undetectable biopsies of CIN3 are significant. Random biopsies of CIN2 or CIN3 demonstrate similar p16 positivity as visible lesions and therefore might be expected to have a similar natural history.

  19. Comparisons of treatment optimization directly incorporating random patient setup uncertainty with a margin-based approach.

    Moore, Joseph A; Gordon, John J; Anscher, Mitchell S; Siebers, Jeffrey V


    The purpose of this study is to incorporate the dosimetric effect of random patient positioning uncertainties directly into a commercial treatment planning system's IMRT plan optimization algorithm through probabilistic treatment planning (PTP) and compare coverage of this method with margin-based planning. In this work, PTP eliminates explicit margins and optimizes directly on the estimated integral treatment dose to determine optimal patient dose in the presence of setup uncertainties. Twenty-eight prostate patient plans adhering to the RTOG-0126 criteria are optimized using both margin-based and PTP methods. Only random errors are considered. For margin-based plans, the planning target volume is created by expanding the clinical target volume (CTV) by 2.1 mm to accommodate the simulated 3 mm random setup uncertainty. Random setup uncertainties are incorporated into IMRT dose evaluation by convolving each beam's incident fluence with a sigma = 3 mm Gaussian prior to dose calculation. PTP optimization uses the convolved fluence to estimate dose to ensure CTV coverage during plan optimization. PTP-based plans are compared to margin-based plans with equal CTV coverage in the presence of setup errors based on dose-volume metrics. The sensitivity of the optimized plans to patient-specific setup uncertainty variations is assessed by evaluating dose metrics for dose distributions corresponding to halving and doubling of the random setup uncertainty used in the optimization. Margin-based and PTP-based plans show similar target coverage. A physician review shows that PTP is preferred for 21 patients, margin-based plans are preferred in 2 patients, no preference is expressed for 1 patient, and both autogenerated plans are rejected for 4 patients. For the PTP-based plans, the average CTV receiving the prescription dose decreases by 0.5%, while the mean dose to the CTV increases by 0.7%. The CTV tumor control probability (TCP) is the same for both methods with the exception

  20. Enhancement of dynamic wetting properties by direct fabrication on robust micro-micro hierarchical polymer surfaces

    Chu, Donghui; Nemoto, Akihiko; Ito, Hiroshi


    Understanding evaporation phenomena on hierarchical surfaces is of crucial importance for the design of robust superhydrophobic polymer structures for various applications. This fabrication method enables precise control of the dimensions to elucidate the dynamic wetting behavior affected by geometric parameters. That behavior exhibits three distinct evaporation modes: a constant contact line (CCL), a constant contact angle (CCA), and mixed mode during the droplet evaporation. The droplet evaporation results show that the sticky CCL mode and the Cassie-Wenzel transition can be prevented by engineering hierarchy integration. Moreover, the CCL-CCA transition point time scale exhibits remarkable dependence on surface dimensions such as the area fraction and solid-liquid contact line. Finally, the fabricated hierarchical structures indicate remarkable superhydrophobic properties, static contact angle above 160° and low sliding angle under 10°, with good durability in terms of aging effect and mechanical robustness for 2 months.

  1. Direct detection of photoinduced charge transfer complexes in polymer fullerene blends

    Behrends, Jan; Sperlich, Andreas; Schnegg, Alexander; Biskup, Till; Teutloff, Christian; Lips, Klaus; Dyakonov, Vladimir; Bittl, Robert


    We report transient electron paramagnetic resonance (trEPR) measurements with submicrosecond time resolution performed on a polymer:fullerene blend consisting of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) at low temperatures. The trEPR spectrum immediately following photoexcitation reveals signatures of spin-correlated polaron pairs. The pair partners (positive polarons in P3HT and negative polarons in PCBM) can be identified by their characteristic g values. The fact that the polaron pair states exhibit strong non-Boltzmann population unambiguously shows that the constituents of each pair are geminate, i.e., originate from one exciton. We demonstrate that coupled polaron pairs are present even several microseconds after charge transfer and suggest that they embody the intermediate charge transfer complexes that form at the donor/acceptor interface and mediate the conversion from excitons into free charge carriers.

  2. Dual Imprinted Polymer Thin Films via Pattern Directed Self-Organization.

    Grolman, Danielle; Bandyopadhyay, Diya; Al-Enizi, Abdullah; Elzatahry, Ahmed; Karim, Alamgir


    Synthetic topographically patterned films and coatings are typically contoured on one side, yet many of nature's surfaces have distinct textures on different surfaces of the same object. Common examples are the top and bottom sides of the butterfly wing or lotus leaf, onion shells, and the inside versus outside of the stem of a flower. Inspired by nature, we create dual (top and bottom) channel patterned polymer films. To this end, we first develop a novel fabrication method to create ceramic line channel relief structures by converting the oligomeric residue of stamped poly(dimethylsiloxane) (PDMS) nanopatterns on silicon substrates to glass (SiOx, silica) by ultraviolet-ozone (UVO) exposure. These silica patterned substrates are flow coated with polystyrene (PS) films and confined within an identically patterned top confining soft PDMS elastomer film. Annealing of the sandwich structures drives the PS to rapidly mold fill the top PDMS pattern in conjunction with a dewetting tendency of the PS on the silica pattern. Varying the film thickness h, from less than to greater than the pattern height, and varying the relative angle between the top-down and bottom-up patterned confinement surfaces create interesting uniform and nonuniform digitized defects in PS channel patterns, as also a defect-free channel regime. Our dual patterned polymer channels provide a novel fabrication route to topographically imprinted Moiré patterns (whose applications range from security encrypting holograms to sensitive strain gauges), and their basic laser light diffractions properties are illustrated and compared to graphical simulations and 2D-FFT of real-space AFM channel patterns. While traditional "geometrical" and "fringe" Moiré patterns function by superposition of two misaligned optical patterned transmittance gratings, our topographic pattern gratings are quite distinct and may allow for more unique holographic optical characteristics with further development.

  3. Randomized controlled split-mouth clinical trial of direct laminate veneers with two micro-hybrid resin composites

    Gresnigt, Marco M. M.; Kalk, Warner; Ozcan, M.; Ozcan, Mutlu

    Objectives: This randomized, split-mouth clinical study evaluated the survival rate of direct laminate veneers made of two resin-composite materials. Methods: A total of 23 patients (mean age: 52.4 years old) received 96 direct composite laminate veneers using two micro-hybrid composites in

  4. Randomized controlled split-mouth clinical trial of direct laminate veneers with two micro-hybrid resin composites

    Gresnigt, Marco M. M.; Kalk, Warner; Ozcan, M.; Ozcan, Mutlu


    Objectives: This randomized, split-mouth clinical study evaluated the survival rate of direct laminate veneers made of two resin-composite materials. Methods: A total of 23 patients (mean age: 52.4 years old) received 96 direct composite laminate veneers using two micro-hybrid composites in combinat

  5. Bi-directional triplexer with butterfly MMI coupler using SU-8 polymer waveguides

    Mareš, David; Jeřábek, Vítězslav; Prajzler, Václav


    We report about a design of a bi-directional planar optical multiplex/demultiplex filter (triplexer) for the optical part of planar hybrid WDM bi-directional transceiver in fiber-to-the-home (FTTH) PON applications. The triplex lightwave circuit is based on the Epoxy Novolak Resin SU-8 waveguides on the silica-on-silicon substrate with Polymethylmethacrylate cladding layer. The triplexer is comprised of a linear butterfly concept of multimode interference (MMI) coupler separating downstream optical signals of 1490 nm and 1550 nm. For the upstream channel of 1310 nm, an additional directional coupler (DC) is used to add optical signal of 1310 nm propagating in opposite direction. The optical triplexer was designed and optimized using beam propagation method. The insertion losses, crosstalk attenuation, and extinction ratio for all three inputs/outputs were investigated. The intended triplexer was designed using the parameters of the separated DC and MMI filter to approximate the idealized direct connection of both devices.

  6. An Investigation of Micro and Nanomanufactured Polymer Substrates to Direct Stem Cell Response for Biomedical Applications

    Rodgers, John W.

    The development of high aspect ratio large feature density polymer microarrays requires the synergistic optimization of design, material, mold tooling, and processing. A conventional mold base with steel inserts and controllable resistance heating was assembled to incorporate interchangeable inserts with microfeatured silicon inlays. Ultraviolet (UV) lithography with dry etching was used to impart microfeatures into silicon wafers with a variety of different geometries containing aspect ratios ranging from 0.92 to 6. Multiple polymer resins, including polystyrene (PS), low density polyethylene (LDPE), cyclic olefin copolymer (COC), and thermoplastic polyurethane (TPU), were used to test replication and cellular response to materials with different bulk stiffness and topography-modified surface stiffness. The maximum achieved microfeature aspect ratio was 9.3 (high impact polystyrene), owed to tensile stretching during part ejection. For non-stretched substrates, the maximum molded aspect ratio was 4.5 (LDPE) and highest replication quotient (RQ = feature height / tooling feature depth) was 0.97 (COC). The maximum aspect ratio molded with consistent features across the entire surface was 2.1 (TPU). Parameters shown to enhance replication were mold temperature (T mold = Tg was a critical replication transition point), injection velocity at higher mold temperatures, holding time, holding pressure, and nozzle temperature. The importance of certain parameters was material dependent, but mold temperature consistently had a relatively large impact. A concern that was addressed for a high density array of microfeatures was the consistency of replication, which is vital for the intended application and seldom address in published literature. Increased consistency was attained through strategic placement of temperature control, modification of the main cavity design, and optimized silicon tooling with reduced microcavity nanoroughness. Silicon tooling was fabricated with the

  7. Insights into the effect of structure-directing agents on structural properties of mesoporous carbon for polymer electrolyte fuel cells

    A Arunchander; K G Nishanth; K K Tintula; S Gouse Peera; A K Sahu


    Synthesis of mesoporous carbon (MC) with well-defined morphologies and, wide range of surface area and pore size, is reported by organic–organic interaction between thermally decomposable surfactants (structure-directing agents) and the cost-effective carbon precursors, such as phloroglucinol and formaldehyde. Selected surfactants based on tri-block co-polymer, non-ionic and ionic, are used for synthesis of MCs with wide variation in their physical properties. The present method could be applied to large-scale production of porous carbon with desired surface area and pore morphology and would practically be relevant to many emerging technologies including electrochemical power sources such as super-capacitors and fuel cells. In the present study, we have successfully used MCs as gas-diffusion layers in fuel cell electrodes and established proper balance between air permeability and water management. The porous carbon contributes significantly to reduce mass transfer existing at high current density region resulting in improved performance of the polymer electrolyte fuel cells.

  8. Extremes of N vicious walkers for large N: application to the directed polymer and KPZ interfaces

    Schehr, Gregory


    We compute the joint probability distribution function (jpdf) P_N(M, \\tau_M) of the maximum M and its position \\tau_M for N non-intersecting Brownian excursions, on the unit time interval, in the large N limit. For N \\to \\infty, this jpdf is peaked around M = \\sqrt{2N} and \\tau_M = 1/2, while the typical fluctuations behave for large N like M - \\sqrt{2N} \\propto s N^{-1/6} and \\tau_M - 1/2 \\propto w N^{-1/3} where s and w are correlated random variables. One obtains an explicit expression of the limiting jpdf P(s,w) in terms of the Tracy-Widom distribution for the Gaussian Orthogonal Ensemble (GOE) of Random Matrix Theory and the psi-function for the Hastings-McLeod solution to the Painlev\\'e II equation. Our result yields, up to a rescaling of the random variables s and w, an expression for the jpdf of the maximum and its position for the Airy_2 process minus a parabola. This latter describes the fluctuations in many different physical systems belonging to the Kardar-Parisi-Zhang (KPZ) universality class in ...

  9. Microring resonator based modulator made by direct photodefinition of an electro-optic polymer

    Balakrishnan, M; Faccini, M.; Diemeer, M.B.J.; Klein, E.J.; Sengo, G.; Driessen, A.; Verboom, W.; Reinhoudt, D.N.


    A laterally coupled microring resonator was fabricated by direct photodefinition of negative photoresist SU8, containing tricyanovinylidenediphenylaminobenzene chromophore, by exploiting the low ultraviolet absorption window of this chromophore. The ring resonator was first photodefined by slight cr

  10. Safety and feasibility of transcranial direct current stimulation in pediatric hemiparesis: randomized controlled preliminary study.

    Gillick, Bernadette T; Feyma, Tim; Menk, Jeremiah; Usset, Michelle; Vaith, Amy; Wood, Teddi Jean; Worthington, Rebecca; Krach, Linda E


    Transcranial direct current stimulation (tDCS) is a form of noninvasive brain stimulation that has shown improved adult stroke outcomes. Applying tDCS in children with congenital hemiparesis has not yet been explored. The primary objective of this study was to explore the safety and feasibility of single-session tDCS through an adverse events profile and symptom assessment within a double-blind, randomized placebo-controlled preliminary study in children with congenital hemiparesis. A secondary objective was to assess the stability of hand and cognitive function. A double-blind, randomized placebo-controlled pretest/posttest/follow-up study was conducted. The study was conducted in a university pediatric research laboratory. Thirteen children, ages 7 to 18 years, with congenital hemiparesis participated. Adverse events/safety assessment and hand function were measured. Participants were randomly assigned to either an intervention group or a control group, with safety and functional assessments at pretest, at posttest on the same day, and at a 1-week follow-up session. An intervention of 10 minutes of 0.7 mA tDCS was applied to bilateral primary motor cortices. The tDCS intervention was considered safe if there was no individual decline of 25% or group decline of 2 standard deviations for motor evoked potentials (MEPs) and behavioral data and no report of adverse events. No major adverse events were found, including no seizures. Two participants did not complete the study due to lack of MEP and discomfort. For the 11 participants who completed the study, group differences in MEPs and behavioral data did not exceed 2 standard deviations in those who received the tDCS (n=5) and those in the control group (n=6). The study was completed without the need for stopping per medical monitor and biostatisticial analysis. A limitation of the study was the small sample size, with data available for 11 participants. Based on the results of this study, tDCS appears to be safe

  11. Highly Efficient Electrocatalysts for Oxygen Reduction Reaction Based on 1D Ternary Doped Porous Carbons Derived from Carbon Nanotube Directed Conjugated Microporous Polymers

    He, Yafei


    © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.One-dimensional (1D) porous materials have shown great potential for gas storage and separation, sensing, energy storage, and conversion. However, the controlled approach for preparation of 1D porous materials, especially porous organic materials, still remains a great challenge due to the poor dispersibility and solution processability of the porous materials. Here, carbon nanotube (CNT) templated 1D conjugated microporous polymers (CMPs) are prepared using a layer-by-layer method. As-prepared CMPs possess high specific surface areas of up to 623 m2 g-1 and exhibit strong electronic interactions between p-type CMPs and n-type CNTs. The CMPs are used as precursors to produce heteroatom-doped 1D porous carbons through direct pyrolysis. As-produced ternary heteroatom-doped (B/N/S) 1D porous carbons possess high specific surface areas of up to 750 m2 g-1, hierarchical porous structures, and excellent electrochemical-catalytic performance for oxygen reduction reaction. Both of the diffusion-limited current density (4.4 mA cm-2) and electron transfer number (n = 3.8) for three-layered 1D porous carbons are superior to those for random 1D porous carbon. These results demonstrate that layered and core-shell type 1D CMPs and related heteroatom-doped 1D porous carbons can be rationally designed and controlled prepared for high performance energy-related applications.

  12. Generation of 3-Dimensional Polymer Structures in Liquid Crystalline Devices using Direct Laser Writing

    Tartan, CC; Salter, PS; Wilkinson, TD; Booth, M; Morris, S.; Elston, SJ


    Direct laser writing is a powerful nonlinear fabrication technique that provides high intensities in the focal plane of a sample to engineer multidimensional structures with submicron feature sizes. Dielectrically and optically anisotropic soft matter is of particular interest when considering a host medium in which exotic topological characteristics may be generated. In this manuscript, we adopt a novel approach for direct laser writing of polymeric structures, whereby the photo-sensitive re...

  13. Polymer Vesicles as Robust Scaffolds for the Directed Assembly of Highly Crystalline Nanocrystals †

    Wang, Mingfeng


    We report the incorporation of various inorganic nanoparticles (NPs) (PbS, LaOF, LaF3, and TiO2, each capped by oleic acid, and CdSe/ZnS core/shell QDs capped by trioctylphosphine oxide) into vesicles (d = 70-150 nm) formed by a sample of poly(styrene-b-acrylic acid) (PS4o4-b-PAA 62, where the subscripts refer to the degree of polymerization) in mixtures of tetrahydrofuran (THF), dioxane, and water. The block copolymer formed mixtures of crew-cut micelles and vesicles with some enhancement of the vesicle population when the NPs were present. The vesicle fraction could be isolated by selective sedimentation via centrifugation, followed by redispersion in water. The NPs appeared to be incorporated into the PAA layers on the internal and external walls of the vesicles (strongly favoring the former). NPs on the exterior surface of the vesicles could be removed completely by treating the samples with a solution of ethylenediaminetetraacetate (EDTA) in water. The triangular nanoplatelets of LaF3 behaved differently. Stacks of these platelets were incorporated into solid colloidal entities, similar in size to the empty vesicles that accompanied them, during the coassembly as water was added to the polymer/LaF3/THF/ dioxane mixture. © 2009 American Chemical Society.

  14. A concept for direct deposition of thin film batteries on flexible polymer substrate

    Glenneberg, Jens; Andre, Felix; Bardenhagen, Ingo; Langer, Frederieke; Schwenzel, Julian; Kun, Robert


    In this paper, the preparation and characteristics of all-solid-state thin film batteries (TFB) are described. In contrast to the state-of-the-art TFB preparation processes, only room temperature processes are used. The cathode is based on amorphous molybdenum(VI) oxide (MoO3), for the electrolyte lithium phosphorus oxynitride (LiPON) is employed and lithium metal acts as anode active material. The cycling stability and rate performance were examined and are discussed. The material set shows a very high cycling stability and excellent rate capability. Performing 550 full cycles at a current density of 202.5 μA cm-2 (10C) a discharge capacity fade of around 15% could be observed. Furthermore, at higher current densities of 2 μA cm-2 (145C) about one third of the initial discharge capacity remained. Using the proposed technology a shift from inorganic rigid substrates, such as glass to flexible polymer substrates is enabled. The performance of the MoO3/LiPON/Li TFBs on glass and flexible polyimide substrates were tested and are discussed within this paper.

  15. Effect of polymer additives on characteristics of direct-current motor with liquid dielectric filler

    Ivanov, V. I.; Bashkatova, S. T.; Lubsanova, A. A.; Tokarev, S. B.; Zadaroshnaya, G. N.; Pastukhova, I. N.


    In d.c. motors filled with dielectric of the hydrocarbon kind hydrodynamic losses can constitute up to 40% of the total losses. Consequently, a study was made to determine the proper additive and amount to reduce the hydraulic drag without dehomogenizing the liquid filler over long operating periods. Two polymethacrylates, never before used for this application were selected. Two motors of different size, a 0.8 kW DPK and a 6 kW DPK, were tested in kerosene with 0.005-1.0 wt% of these additives. An evaluation of the data, including the hydraulic drag coefficient as a function of the Reynolds number and the temperature rise at critical motor components (armature winding in slots, armature endturns on drive side, armature teeth, liquid in interpolar space, field winding, pole pieces) with or without additive, has yielded the optimum range of additive concentration for each motor size. An evaluation of the heat transfer at critical surfaces, with the aid of dimensional analysis, has yielded the semiempirical relation Nu=CRe0.65Pr0.4Km (C- constant factor different for each surface, Km- constant factor with exponent different for each additive polymer materials). The results can be extended to transformer oil and diesel oil as liquid motor-filling medium.

  16. Direct chemical-analysis of uv laser-ablation products of organic polymers by using selective ion monitoring mode in gas-chromatography mass-spectrometry

    Cho, Yirang; Lee, H.W.; Fountain, S.T.; Lubman, D.M.


    Trace quantities of laser ablated organic polymers were analyzed by using commercial capillary column gas chromatography/mass spectrometry; the instrument was modified so that the laser ablation products could be introduced into the capillary column directly and the constituents of each peak in the chromatogram were identified by using a mass spectrometer. The present study takes advantage of the selective ion monitoring mode for significantly improving the sensitivity of the mass spectrometer as a detector, which is critical in analyzing the trace quantities and confirming the presence or absence of the species of interest in laser ablated polymers. The initial composition of the laser ablated polymers was obtained by using an electron impact reflectron time-of-flight mass spectrometer and the possible structure of the fragments observed in the spectra was proposed based on the structure of the polymers.

  17. Endotracheal Intubation Using a Direct Laryngoscope and the Protective Performances of Respirators: A Randomized Trial

    Taeho Lim


    Full Text Available Purpose. Emergency physicians are at risk for infection during invasive procedures, and the respirators can reduce this risk. This study aimed to determine whether endotracheal intubation using direct laryngoscopes affected protection performances of respirators. Methods. A randomized crossover study of 24 emergency physicians was performed. We performed quantitative fit tests using respirators (cup type, fold type without a valve, and fold type with a valve before and during intubation. The primary outcome was respirators’ fit factors (FF, and secondary outcomes were acceptable protection (percentage of scores above 100 FF [FF%]. Results. 24 pieces of data were analyzed. Compared to fold-type respirator without a valve, FF and FF% values were lower when participants wore a cup-type respirator (200 FF [200-200] versus 200 FF [102.75–200], 100% [78.61–100] versus 74.16% [36.1–98.9]; all P<0.05 or fold-type respirator with a valve (200 FF [200-200] versus 142.5 FF [63.50–200], 100% [76.10–100] versus 62.50% [8.13–100]; all P<0.05. There were no significant differences in intubation time and success rate according to respirator types. Conclusions. Motion during endotracheal intubation using direct laryngoscopes influenced the protective performance of some respirators. Therefore, emergency physicians should identify and wear respirators that provide the best personalized fit for intended tasks.

  18. Rapid evaluation of the electrooxidation of fuel compounds with a multiple-electrode setup for direct polymer electrolyte fuel cells

    Fujiwara, Naoko; Siroma, Zyun; Ioroi, Tsutomu; Yasuda, Kazuaki

    Electrochemical oxidation of fuel compounds in acidic media was examined on eight electrodes (Pt, Ru, PtRu, Rh, Ir, Pd, Au, and glassy carbon) simultaneously by multiple cyclic voltammetry (CV) with an electrochemical cell equipped with an eight-electrode configuration. Direct-type polymer electrolyte fuel cells (PEFCs), in which aqueous solutions of the fuel compounds are directly supplied to the anode, were also evaluated. The performances of direct PEFCs with various anode catalysts could be roughly estimated from the results obtained with multiple CV. This multiple evaluation may be useful for identifying novel fuels or electrocatalysts. Methanol, ethanol, ethylene glycol, 2-propanol, and D-glucose were oxidized selectively on Pt or PtRu, as reported previously. However, several compounds that are often used as reducing agents show electrochemical oxidation with unique characteristics. Large current was obtained for the oxidation of formic acid, hypophosphorous acid, and phosphorous acid on a Pd electrode. L-Ascorbic acid and sulfurous acid were oxidized on all of the electrodes used in the present study.

  19. Direct strain energy harvesting in automobile tires using piezoelectric PZT–polymer composites

    Van den Ende, D.A.; Van de Wiel, H.J.; Groen, W.A.; Van der Zwaag, S.


    Direct piezoelectric strain energy harvesting can be used to power wireless autonomous sensors in environments where low frequency, high strains are present, such as in automobile tires during operation. However, these high strains place stringent demands on the materials with respect to mechanical

  20. Direct strain energy harvesting in automobile tires using piezoelectric PZT-polymer composites

    Ende, D.A. van den; Wiel, H.J. van de; Groen, W.A.; Zwaag, S. van der


    Direct piezoelectric strain energy harvesting can be used to power wireless autonomous sensors in environments where low frequency, high strains are present, such as in automobile tires during operation. However, these high strains place stringent demands on the materials with respect to mechanical

  1. Direct dimethyl ether fueling of a high temperature polymer fuel cell

    Jensen, Jens Oluf; Vassiliev, Anton; Olsen, M.I.


    Direct dimethyl ether (DME) fuel cells suffer from poor DME–water miscibility and so far peak powers of only 20–40 mW cm−2 have been reported. Based on available literature on solubility of dimethyl ether (DME) in water at ambient pressure it was estimated that the maximum concentration of DME at...

  2. A Graphite Oxide Paper Polymer Electrolyte for Direct Methanol Fuel Cells

    Ravi Kumar


    Full Text Available A flow directed assembly of graphite oxide solution was used in the formation of free-standing graphene oxide paper of approximate thickness of 100 μm. The GO papers were characterised by XRD and SEM. Electrochemical characterization of the GO paper membrane electrode assembly revealed proton conductivities of 4.1 × 10−2 S cm−1 to 8.2 × 10−2 S cm−1 at temperatures of 25–90°C. A direct methanol fuel cell, at 60°C, gave a peak power density of 8 mW cm−2 at a current density of 35 mA cm−2.

  3. Direct-write/cure conductive polymer nanocomposites for 3D structural electronics

    Lu, Yanfeng; Vatani, Morteza; Choi, Jae Won [The University of Akron, Akron, Ohio (United States)


    The use of direct-write (DW) in the fabrication of conductive structures offers dramatic benefits over traditional technologies in terms of low-cost, print-on-demand conformal manufacturing. This DW process can be combined with direct-cure (DC) process as one-step manufacturing of conducting elements, whereas conventional methods need a manufacturing process of conducting elements followed by a relatively long time post-curing/baking process. A hybrid technology combined with direct-write/cure (DWC) and projection microstereolithography (PμSL) is presented in this work. Carbon nanotubes (CNTs) were dispersed in a photopolymer solution to introduce conductivity. The developed PμSL was used to create 3D structures, and DWC of conductive photopolymers with CNTs was utilized to produce conductive paths. To show the capabilities of the developed system and materials, a 3D structure with embedded conductive paths was designed and fabricated. Based on the experiments, it is thought that the suggested manufacturing process and materials are promising to produce 3D structural electronics.

  4. Five-year clinical follow-up of a randomized comparison of a polymer-free sirolimus-eluting stent versus a polymer-based paclitaxel-eluting stent in patients with diabetes mellitus (LIPSIA Yukon trial).

    Stiermaier, Thomas; Heinz, Anja; Schloma, Denis; Kleinertz, Klaus; Dänschel, Wilfried; Erbs, Sandra; Linke, Axel; Boudriot, Enno; Lauer, Bernward; Schuler, Gerhard; Thiele, Holger; Desch, Steffen


    The long-term performance of polymer-free stent systems in patients with diabetes mellitus has not been investigated extensively. This study reports long-term results of the LIPSIA Yukon trial which compared the polymer-free sirolimus-eluting Yukon Choice stent with the polymer-based paclitaxel-eluting Taxus Liberté stent in this subpopulation. At 9 months, the Yukon Choice stent failed to show non-inferiority in terms of the primary end point late lumen loss, while no significant difference in clinical outcome was detected. The LIPSIA Yukon trial randomized 240 patients with diabetes mellitus to a polymer-free sirolimus eluting stent (Yukon Choice, Translumina) versus a polymer-based paclitaxel-eluting stent (Taxus Liberté, Boston Scientific). Clinical follow-up was conducted with a standardized telephone follow-up and all events were centrally adjudicated. Follow-up was available for 98.3% of patients after a median of 5.0 years. The incidence of all-cause death (16.9% versus 14.0%, P = 0.67), respectively definite or presumed cardiovascular death (7.6% versus 8.8%, P = 0.94) were similar in the Yukon Choice and the Taxus Liberté group. There were no significant differences in the rates of myocardial infarction (9.3% versus 7.9%, P = 0.88), definite stent thrombosis (0.8% versus 0.9%, P = 1.0), target lesion revascularization (15.3% versus 15.8%, P = 1.0), target vessel revascularization (18.6% versus 23.7%, P = 0.44), non-target vessel revascularization (18.6% versus 26.3%, P = 0.21), and stroke (3.4% versus 4.4%, P = 0.96) between patients assigned to the Yukon Choice and the Taxus Liberté stent. At 5 years of follow-up, clinical outcome was similar between the polymer-free sirolimus-eluting Yukon Choice stent and the polymer-based paclitaxel-eluting Taxus Liberté stent. Copyright © 2013 Wiley Periodicals, Inc.

  5. Random polyfluorene co-polymers designed for a better optical absorption coverage of the visible region of the electromagnetic spectrum

    D. A. Gedefaw


    Full Text Available Two alternating polyfluorenes (APFO15-F8BT and APFO3-F8BT with full absorption of the visible region of the electromagnetic radiation were designed and synthesized for bulk-heterojunction solar cell devices. The optical and electrochemical properties of the two polymers were studied. The two polymers exhibited strong absorption in the visible region with no significant valley over the visible region extending up to 650 nm. Deep HOMO and ideally situated LUMO energy levels were the characteristics of the two polymers as revealed from the square wave voltammogram study: desired properties for extracting high open circuit voltage and for a facile charge transfer to the acceptor component in devices to take place, respectively. Photovoltaic devices were fabricated by blending the two polymers with PCBM[70] and up to ~2% power conversion efficiency were obtained. DOI:

  6. A randomized multicenter comparison of hybrid sirolimus-eluting stents with bioresorbable polymer versus everolimus-eluting stents with durable polymer in total coronary occlusion: rationale and design of the Primary Stenting of Occluded Native Coronary Arteries IV study

    Teeuwen Koen


    Full Text Available Abstract Background Percutaneous recanalization of total coronary occlusion (TCO was historically hampered by high rates of restenosis and reocclusions. The PRISON II trial demonstrated a significant restenosis reduction in patients treated with sirolimus-eluting stents compared with bare metal stents for TCO. Similar reductions in restenosis were observed with the second-generation zotarolimus-eluting stent and everolimus-eluting stent. Despite favorable anti-restenotic efficacy, safety concerns evolved after identifying an increased rate of very late stent thrombosis (VLST with drug-eluting stents (DES for the treatment of TCO. Late malapposition caused by hypersensitivity reactions and chronic inflammation was suggested as a probable cause of these VLST. New DES with bioresorbable polymer coatings were developed to address these safety concerns. No randomized trials have evaluated the efficacy and safety of the new-generation DES with bioresorbable polymers in patients treated for TCO. Methods/Design The prospective, randomized, single-blinded, multicenter, non-inferiority PRISON IV trial was designed to evaluate the safety, efficacy, and angiographic outcome of hybrid sirolimus-eluting stents with bioresorbable polymers (Orsiro; Biotronik, Berlin, Germany compared with everolimus-eluting stents with durable polymers (Xience Prime/Xpedition; Abbott Vascular, Santa Clara, CA, USA in patients with successfully recanalized TCOs. In total, 330 patients have been randomly allocated to each treatment arm. Patients are eligible with estimated duration of TCO ≥4 weeks with evidence of ischemia in the supply area of the TCO. The primary endpoint is in-segment late luminal loss at 9-month follow-up angiography. Secondary angiographic endpoints include in-stent late luminal loss, minimal luminal diameter, percentage of diameter stenosis, in-stent and in-segment binary restenosis and reocclusions at 9-month follow-up. Additionally, optical coherence

  7. Synthesis of indolo[3,2-b]carbazole-based random copolymers for polymer solar cell applications

    Chan, Li-Hsin, E-mail: [Department of Applied Materials and Optoelectronic Engineering, National Chi Nan University, Nantou, Taiwan 54561, ROC (China); Lin, Lu-Chi; Yao, Chi-Han [Department of Applied Materials and Optoelectronic Engineering, National Chi Nan University, Nantou, Taiwan 54561, ROC (China); Liu, You-Ren; Jiang, Zong-Jhih [Department of Applied Chemistry, National Chi Nan University, Nantou, Taiwan 54561, ROC (China); Cho, Ting-Yu [Department of Applied Materials and Optoelectronic Engineering, National Chi Nan University, Nantou, Taiwan 54561, ROC (China)


    In addition to preparing two indolocarbazole-based random copolymers (named as r-PICTBT1 and r-PICTBT2), this work investigated their feasibility for bulk heterojunction polymer solar cells (PSCs). These copolymers consisted of commercially available 3,9-dibromo-5,11-dioctyl-5,11-dihydroindole[3,2-b]carbazole, 2,5-bis(trimethylstannyl) thiophene and dibromobenzo[c][1,2,5]thiadiazole by varying the feed in ratios via Stille cross-coupling reactions. The photophysical and electrochemical properties of the resulting copolymers could be fine-modulated easily by adjusting the feed ratios of monomers. Both copolymers in the thin film state exhibited two obvious peaks and a vibronic shoulder in the absorption spectra. Electrochemical experiments indicated that the highest occupied molecular orbital energy levels were − 4.95, − 5.00 eV; meanwhile, the lowest unoccupied molecular orbital energy levels were − 3.38, − 3.54 eV for r-PICTBT1 and r-PICTBT2, respectively. Bulk heterojunction PSCs composed of an electron-donor copolymer blended with an electron acceptor [6,6]-phenyl-C61-butyric acid methyl ester (PC{sub 61}BM) or [6,6]-phenyl-C71-butyric acid methyl ester (PC{sub 71}BM) at a weight ratio of 1:1 or 1:3 were investigated. Moreover, the r-PICTBT2/PC{sub 71}BM-based (w/w = 1:1) PSC performed the best with an open-circuit voltage of 0.54 V, short-circuit current of 6.83 mA/cm{sup 2}, fill factor of 0.44, and power conversion efficiency of 1.63%. - Highlights: • We report two indolocarbazole-based copolymers for photovoltaic applications. • Two copolymers exhibited excellent thermal stability. • Energy levels of copolymers can be modulated by varying the monomers ratios. • Increasing of planar monomer content leads to a relatively smooth morphology. • The optimal device performance reached a power conversion efficiency of 1.63%.

  8. An Investigation of Mechanically Tunable and Nanostructured Polymer Scaffolds for Directing Human Mesenchymal Stem Cell Development

    Jaafar, Israd Hakim

    This work investigated the use of biomedically relevant, polymer substrates for in vitro human mesenchymal stem cell (hMSC)-substrate surface interaction. Two materials were identified: (i) Poly(glycerol-sebacate) (PGS), a novel biocompatible and biodegradable thermosetting rubber-like elastomer, and (ii) injection molded polystyrene (PS). PGS was selected because it has tunable mechanical properties within the range of biological tissue, and thus provides a useful model to determine the types of substrate mechanical cues that would elicit specific hMSC lineage specification and possible differentiation outcomes. PS is a relevant material for in vitro cell-substrate surface interaction analysis since it is typically the base material of cell culture dishes. Both these materials have also shown micro to nanoscale molding capabilities. Hence these materials would also serve as a model in determining topographical properties (and related mechanical properties) at the dimension-scale of the extracellular environment that modulates hMSC state and fate. The work characterized, designed, and manufactured substrates made of these materials, for in vitro hMSC culture. Micro/nanoscale PGS and PS surface features were manufactured using silicon (Si) based tooling technology. The response of hMSCs to PGS substrates of various Young.s moduli was examined. hMSC response to a nanoscale array of PS pegs was also investigated. PGS was observed to be a semi-crystalline thermosetting elastomer that is fully amorphous above 35°C. The material acquired increasing stiffness and density of photoresist-coated with increasing levels of curing temperature and duration of cure. hMSCs were observed to respond differently on PGS with elastic modulii of 0.11, 1.11, and 2.30 MPa. The cells spread and proliferate more, and develop a stretched cytoskeleton on the stiffer substrates. On the softest substrate (0.11 MPa) the cells developed a branched and filopodia-rich morphology with a diffused

  9. A randomized direct comparison of the pharmacokinetics and pharmacodynamics of apixaban and rivaroxaban

    Frost C


    Full Text Available Charles Frost,1 Yan Song,1 Yu Chen Barrett,1 Jessie Wang,2 Janice Pursley,3 Rebecca A Boyd,4 Frank LaCreta1 1Exploratory Clinical and Translational Research, 2Exploratory Development Global Biometric Sciences, 3Analytical and Bioanalytical Development, Bristol-Myers Squibb Company, Princeton, NJ, USA; 4Global Innovative Pharma Business Clinical Pharmacology, Pfizer Inc., Groton, CT, USA Background: Currently, there are no direct comparisons of apixaban and rivaroxaban, two new oral direct factor Xa inhibitors approved for management of thromboembolic disorders. Objective: Compare the pharmacokinetics and anti-factor Xa activity (AXA of apixaban and rivaroxaban. Methods: In this randomized, open-label, two-period, two-treatment crossover study, healthy subjects (N=14 received apixaban 2.5 mg twice daily (BID and rivaroxaban 10 mg once daily (QD for 4 days with a ≥4.5-day washout. Plasma samples were obtained for pharmacokinetic and AXA assessments; parameters were calculated using noncompartmental methods. Results: Median time-to-maximum concentration was 2 hours for both compounds, and the mean half-life was 8.7 and 7.9 hours for apixaban and rivaroxaban, respectively. Daily exposure, the area under the curve (AUC(0–24, appeared similar for rivaroxaban (1,094 ng · h/mL and apixaban (935 ng · h/mL, whereas mean peak-to-trough plasma concentration ratio was 3.6-fold greater for rivaroxaban (16.9 than apixaban (4.7. Coefficient of variation for exposure parameters (AUC0–24, Cmax, Cmin was 20%–24% for apixaban versus 29%–46% for rivaroxaban. Peak AXA, AXA AUC(0–24, and AXA fluctuation were ~2.5-, 1.3-, and 3.5-fold higher for rivaroxaban than apixaban, respectively. Trough concentrations and AXA were lower for rivaroxaban (10 ng/mL and 0.17 IU/mL vs 17 ng/mL and 0.24 IU/mL for apixaban, respectively. Rivaroxaban exhibited a steeper concentration–AXA response (slope: 0.0172 IU/ng vs 0.0134 IU/ng for apixaban, P<0.0001. Conclusion

  10. Fabrication of conjugated polymers nanostructures via direct near-field optical lithography

    Cacialli, F.; Riehn, Robert; Downes, A.; Latini, G.; Charas, Ana; Morgado, Jorge


    We report our investigations into the fabrication of nanostructures of poly(p-phenylene vinylene) via direct scanning near-field lithography of its soluble precursor. Our technique is based on the spatially selective inhibition of the precursor solubility by exposure to the ultraviolet optical field present at the apex of commercially available, Au-coated near-field probes with aperture diameters between 40 and 80 nm ({+-}5 nm). After development in methanol and thermal conversion under vacuum we obtain features with a minimum dimension of 160 nm. We analyse our results via tapping-mode atomic force microscopy, and find a clear phase contrast between the core and the centre of the lithographed features, corroborating the hypothesis that hard, fully insolubilised regions are surrounded by a gel-like phase, which we estimate of the order of 110-130 nm for the smallest features, by comparing our experiments with simulations carried out using a Bethe-Bouwkamp model. Use of such model also allows us to discuss the influence of probe size, tip-sample distance, and film thickness on the resolution of the lithographic process. We demonstrate the use of the technique for the direct writing of two-dimensional periodic structures with intentional defects and a periodicity relevant to applications in the visible range.

  11. Direct electrospray ionization mass spectrometry quantitative analysis of sebacic and terephthalic acids in biodegradable polymers.

    Rizzarelli, Paola; Zampino, Daniela; Ferreri, Loredana; Impallomeni, Giuseppe


    A direct, rapid, and easy electrospray ionization mass spectrometry (ESI-MS) method to determine concentrations of sebacic acid (SA) and terephthalic acid (TA) residues in biodegradable copolymers was developed. Copolyester samples were synthesized from 1,4-butanediol and sebacic and terephthalic acids by melt polymerization. Extraction of monomers was performed in methanol. Their concentrations were determined by direct infusion ESI-MS, without chromatographic separation, using 1,12-dodecanedioic acid (DDA) as an internal standard. Calibration curves were obtained by plotting the ratio of the areas of the peaks relative to monomers and DDA standard as a function of their concentration ratio. We validated the method by determining the concentration of TA residue using both the ESI-MS protocol and high-performance liquid chromatography (HPLC) analysis with UV detection. The linearity range and the detection limit of this assay were 0.1-5.0 and 0.01 ppm for SA and 0.1-6.0 and 0.03 ppm for TA. This assay represents a useful alternative to conventional methods currently employed for acid quantification, resulting advantageous for its speed and high sensitivity.

  12. Polymer Electrolyte Fuel Cells Membrane Hydration by Direct Liquid Water Contact

    Wilson, M.S.; Zawodzinski, C.; Gottesfeld, S.


    An effective means of providing direct liquid hydration of the membrane tends to improve performance particularly of cells with thicker membranes or at elevated temperatures. Supplying the water to the membrane from the anode flow-field through the anode backing via wicks would appear to have advantages over delivering the water through the thickness of the membrane with regards to the uniformity and stability of the supply and the use of off-the-shelf membranes or MEAs. In addition to improving cell performance, an important contribution of direct liquid hydration approaches may be that the overall fuel cell system becomes simpler and more effective. The next steps in the evolution of this approach are a demonstration of the effectiveness of this technique with larger active area cells as well as the implementation of an internal flow-field water reservoir (to eliminate the injection method). Scale-up to larger cell sizes and the use of separate water channels within the anode flow-field is described.

  13. Novel high band gap pendant-borylated carbazole polymers with deep HOMO levels through direct +N=B- interaction for organic photovoltaics

    Brandt, Rasmus G.; Sveegaard, Steffen G.; Xiao, Manjun


    In this communication, we investigate the direct and still conjugated intramolecular +N=B- interactions in novel high band gap borylated carbazole containing polymers, namely, poly(3,6-(N-di(2,4,6-trimethyl)-phenylboryl-carbazole)-alt- 4,8-di(5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b: 4,5-b'] di...

  14. A Parent-Directed Language Intervention for Children of Low Socioeconomic Status: A Randomized Controlled Pilot Study

    Suskind, Dana L.; Leffel, Kristin R.; Graf, Eileen; Hernandez, Marc W.; Gunderson, Elizabeth A.; Sapolich, Shannon G.; Suskind, Elizabeth; Leininger, Lindsey; Goldin-Meadow, Susan; Levine, Susan C.


    We designed a parent-directed home-visiting intervention targeting socioeconomic status (SES) disparities in children's early language environments. A randomized controlled trial was used to evaluate whether the intervention improved parents' knowledge of child language development and increased the amount and diversity of parent talk.…

  15. Capabilities and limitations of direct analysis in real time orbitrap mass spectrometry and tandem mass spectrometry for the analysis of synthetic and natural polymers.

    Bridoux, Maxime C; Machuron-Mandard, Xavier


    Despite the widespread use of direct analysis in real time mass spectrometry (DART-MS), its capabilities in terms of accessible mass range and the types of polymers that can be analysed are not well known. The goal of this work was to evaluate the capabilities and limitations of this ionization technique combined with orbitrap mass spectrometry and tandem mass spectrometry, for the characterization (structural and polydispersity metrics) of various synthetic and natural polymers. The capabilities and limitations of DART-MS (and -MS(2)), using an orbitrap mass spectrometer, for polymer analysis were evaluated using various industrial synthetic polymers and biopolymers. Stainless steel mesh screens secured on a movable rail were used as the sampling surface, onto which 5 μL of various polymers dissolved in tetrahydrofuran were added. Assignment of spectral features and calculation of molecular weight and polydispersity metrics were performed using Polymerix™ software and the results were compared with those obtained by gel-permeation chromatography (GPC). Protonated oligomers and ammonium adducts were instantaneously detected as the major ionisation products in positive ion mode. Only perfluoropolyethers (PFPEs) were ionised in negative mode and detected as [M](-·) ions. Only singly charged molecular species were observed for all oligomers under study, allowing for a rapid determination of the molecular weight and polydispersity metrics of polymers. At elevated DART gas temperatures (400-500°C) the molecular weight and polydispersity metrics compared fairly well with those obtained by GPC, with polymers whose masses ranged from 200 g x mol(-1) to 4000 g x mol(-1). DART-MS allowed the direct and rapid analysis (mass spectra and tandem mass spectra of all the polymers were acquired in seconds) based on the exact masses of their [M+H](+) and [M+NH4](+) ions (in the positive mode) or [M](-·) ions (for polymers having a high sensitivity toward electron

  16. TOPICAL REVIEW: Micromachined polymer electrolyte membrane and direct methanol fuel cells—a review

    Nguyen, Nam-Trung; Chan, Siew Hwa


    This review reports recent progress of the development of micromachined membrane-based fuel cells. The review first discusses the scaling law applied to this type of fuel cell. Impacts of miniaturization on the performance of membrane-based fuel cells are highlighted. This review includes only the two most common micro fuel cell types: proton exchange membrane micro fuel cells (PEMµFC) and direct methanol micro fuel cells (DMµFC). Furthermore, we only consider fuel cells with the active area of a single cell less than 1 square inch. Since the working principles of these fuel cell types are well known, the review only focuses on the choice of material and the design consideration of the components in the miniature fuel cell. Next, we compare and discuss the performance of different micro fuel cells published recently in the literature. Finally, this review gives an outlook on possible future development of micro fuel cell research.

  17. Treatment of deep caries lesions in adults: randomized clinical trials comparing stepwise vs. direct complete excavation, and direct pulp capping vs. partial pulpotomy.

    Bjørndal, Lars; Reit, Claes; Bruun, Gitte; Markvart, Merete; Kjaeldgaard, Marianne; Näsman, Peggy; Thordrup, Marianne; Dige, Irene; Nyvad, Bente; Fransson, Helena; Lager, Anders; Ericson, Dan; Petersson, Kerstin; Olsson, Jadranka; Santimano, Eva M; Wennström, Anette; Winkel, Per; Gluud, Christian


    Less invasive excavation methods have been suggested for deep caries lesions. We tested the effects of stepwise vs. direct complete excavation, 1 yr after the procedure had been carried out, in 314 adults (from six centres) who had received treatment of a tooth with deep caries. The teeth had caries lesions involving 75% or more of the dentin and were centrally randomized to stepwise or direct complete excavation. Stepwise excavation resulted in fewer pulp exposures compared with direct complete excavation [difference: 11.4%, 95% confidence interval (CI) (1.2; 21.3)]. At 1 yr of follow-up, there was a statistically significantly higher success rate with stepwise excavation, with success being defined as an unexposed pulp with sustained pulp vitality without apical radiolucency [difference: 11.7%, 95% CI (0.5; 22.5)]. In a subsequent nested trial, 58 patients with exposed pulps were randomized to direct capping or partial pulpotomy. We found no significant difference in pulp vitality without apical radiolucency between the two capping procedures after more than 1 yr [31.8% and 34.5%; difference: 2.7%, 95% CI (-22.7; 26.6)]. In conclusion, stepwise excavation decreases the risk of pulp exposure compared with direct complete excavation. In view of the poor prognosis of vital pulp treatment, a stepwise excavation approach for managing deep caries lesions is recommended.

  18. Development of Polymer Electrolyte Mambrane (PEM) from Bisphonol S for Direct Methanol Fuel Cell (DMFC)

    Changkhamchom, Sairung


    The currently used Proton Exchange Membrane (PEM) in a Direct Methanol Fuel Cell (DMFC) is Nafion^, an excellent proton conductor in a fully hydrated membrane. However, it has major drawbacks, such as very high cost, and loss of conductivity at elevated temperature and low humidity. In this work, a novel PEM based on sulfonated poly(ether ether ketone) (S-PEEK). Poly(ether ether ketone) (PEEK) was synthesized by the nucleophilic aromatic substitution polycondensation of Bisphonol-S and 4,4'-difluorobenzophenone for system A, and Bisphenol S and 4,4'-dichlorobenzophenone for system B. Bisphenol-S helps to increase the thermal stability due to its high melting point (245^oC). The post-sulfonation reaction was performed by using concentrated sulfuric acid. Sulfonated poly(ether ether ketone) (S-PEEK) samples were characterized by FTIR and ^1H-NMR to confirm the chemical structure of the S-PEEK, and by TGA to investigate the thermal property.

  19. Direct and charge transfer state mediated photogeneration in polymer-fullerene bulk heterojunction solar cells

    Mingebach, M.; Walter, S.; Dyakonov, V.; Deibel, C.


    We investigated photogeneration yield and recombination dynamics in blends of poly(3-hexyl thiophene) (P3HT) and poly[2-methoxy-5 -(3',7'-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) with [6,6]-phenyl-C61butyric acid methyl ester (PC61BM) by means of temperature dependent time delayed collection field measurements. In MDMO-PPV:PC61BM, we find a strongly field dependent polaron pair dissociation which can be attributed to geminate recombination in the device. Our findings are in good agreement with field dependent photoluminescence measurements published before, supporting a scenario of polaron pair dissociation via an intermediate charge transfer state. In contrast, polaron pair dissociation in P3HT:PC61BM shows only a very weak field dependence, indicating an almost field independent polaron pair dissociation or a direct photogeneration. Furthermore, we found Langevin recombination for MDMO-PPV:PC61BM and strongly reduced Langevin recombination for P3HT:PC61BM.

  20. Direct simulation of electron transfer using ring polymer molecular dynamics: comparison with semiclassical instanton theory and exact quantum methods.

    Menzeleev, Artur R; Ananth, Nandini; Miller, Thomas F


    The use of ring polymer molecular dynamics (RPMD) for the direct simulation of electron transfer (ET) reaction dynamics is analyzed in the context of Marcus theory, semiclassical instanton theory, and exact quantum dynamics approaches. For both fully atomistic and system-bath representations of condensed-phase ET, we demonstrate that RPMD accurately predicts both ET reaction rates and mechanisms throughout the normal and activationless regimes of the thermodynamic driving force. Analysis of the ensemble of reactive RPMD trajectories reveals the solvent reorganization mechanism for ET that is anticipated in the Marcus rate theory, and the accuracy of the RPMD rate calculation is understood in terms of its exact description of statistical fluctuations and its formal connection to semiclassical instanton theory for deep-tunneling processes. In the inverted regime of the thermodynamic driving force, neither RPMD nor a related formulation of semiclassical instanton theory capture the characteristic turnover in the reaction rate; comparison with exact quantum dynamics simulations reveals that these methods provide inadequate quantization of the real-time electronic-state dynamics in the inverted regime.

  1. MoO3 Thickness, Thermal Annealing and Solvent Annealing Effects on Inverted and Direct Polymer Photovoltaic Solar Cells

    Guillaume Wantz


    Full Text Available Several parameters of the fabrication process of inverted polymer bulk heterojunction solar cells based on titanium oxide as an electron selective layer and molybdenum oxide as a hole selective layer were tested in order to achieve efficient organic photovoltaic solar cells. Thermal annealing treatment is a common process to achieve optimum morphology, but it proved to be damageable for the performance of this kind of inverted solar cells. We demonstrate using Auger analysis combined with argon etching that diffusion of species occurs from the MoO3/Ag top layers into the active layer upon thermal annealing. In order to achieve efficient devices, the morphology of the bulk heterojunction was then manipulated using the solvent annealing technique as an alternative to thermal annealing. The influence of the MoO3 thickness was studied on inverted, as well as direct, structure. It appeared that only 1 nm-thick MoO3 is enough to exhibit highly efficient devices (PCE = 3.8% and that increasing the thickness up to 15 nm does not change the device performance. 

  2. Electrochemical impedance spectroscopy analysis of a thin polymer film-based micro-direct methanol fuel cell

    Schulz, Tobias; Weinmueller, Christian; Nabavi, Majid; Poulikakos, Dimos [Department of Mechanical and Process Engineering, Laboratory of Thermodynamics in Emerging Technologies, Institute of Energy Technology, ETH Zurich, CH-8092 Zurich (Switzerland)


    A single cell micro-direct methanol fuel cell (micro-DMFC) was investigated using electrochemical impedance spectroscopy. The electrodes consisted of thin, flexible polymer (SU8) film microchannel structures fabricated in-house using microfabrication techniques. AC impedance spectroscopy was used to separate contributions to the overall cell polarization from the anode, cathode and membrane. A clear distinction between the different electrochemical phenomena occurring in the micro-DMFC, especially the distinction between double layer charging and Faradaic reactions was shown. The effect of fuel flow rate, temperature, and anode flow channel structure on the impedance of the electrode reactions and membrane/electrode double layer charging were investigated. Analysis of impedance data revealed that the performance of the test cell was largely limited by the presence of intermediate carbon monoxide in the anode reaction. Higher temperatures increase cell performance by enabling intermediate CO to be oxidized at much higher rates. The results also revealed that serpentine anode flow microchannels show a lower tendency to intermediate CO coverage and a more stable cell behavior than parallel microchannels. (author)




    Full Text Available Theoretical evidence is presented in this review that architectural aspects can play an important role, not only in the bulk but also in confined geometries by using our recursive lattice theory, which is equally applicable to fixed architectures (regularly branched polymers, stars, dendrimers, brushes, linear chains, etc. and variable architectures, i.e. randomly branched structures. Linear chains possess an inversion symmetry (IS of a magnetic system (see text, whose presence or absence determines the bulk phase diagram. Fixed architectures possess the IS and yield a standard bulk phase diagram in which there exists a theta point at which two critical lines C and C' meet and the second virial coefficient A2 vanishes. The critical line C appears only for infinitely large polymers, and an order parameter is identified for this criticality. The critical line C' exists for polymers of all sizes and represents phase separation criticality. Variable architectures, which do not possess the IS, give rise to a topologically different phase diagram with no theta point in general. In confined regions next to surfaces, it is not the IS but branching and monodispersity, which becomes important in the surface regions. We show that branching plays no important role for polydisperse systems, but become important for monodisperse systems. Stars and linear chains behave differently near a surface.

  4. Sterilization of propylene/ethylene random copolymers: Annealing effects on crystalline structure and transparency as influenced by polymer structure and nucleation


    Full Text Available An extensive investigation of three different series of isotactic ethylene/propylene (EP random copolymers was performed to understand the factors influencing the change in optical properties in the steam sterilization of extrusion cast films from such materials. Different analytical methods (differential scanning calorimetry (DSC, X-ray diffraction and electron microscopy were employed to elucidate structural changes determining film optics, and in addition to the polymer structure parameters also nucleation and processing effects were studied. The findings clearly show that a combination of homogeneously randomized comonomer distribution and nucleation can partly inhibit lamellar thickening in sterilization, thus preserving high transparency even after a heat treatment. In detail, attention has to be paid to the combined effects of primary and secondary post-crystallization, which both are affected by the chain regularity.

  5. Investigation of the adhesion properties of direct 3D printing of polymers and nanocomposites on textiles: Effect of FDM printing process parameters

    Hashemi Sanatgar, Razieh; Campagne, Christine; Nierstrasz, Vincent


    In this paper, 3D printing as a novel printing process was considered for deposition of polymers on synthetic fabrics to introduce more flexible, resource-efficient and cost effective textile functionalization processes than conventional printing process like screen and inkjet printing. The aim is to develop an integrated or tailored production process for smart and functional textiles which avoid unnecessary use of water, energy, chemicals and minimize the waste to improve ecological footprint and productivity. Adhesion of polymer and nanocomposite layers which were 3D printed directly onto the textile fabrics using fused deposition modeling (FDM) technique was investigated. Different variables which may affect the adhesion properties including 3D printing process parameters, fabric type and filler type incorporated in polymer were considered. A rectangular shape according to the peeling standard was designed as 3D computer-aided design (CAD) to find out the effect of the different variables. The polymers were printed in different series of experimental design: nylon on polyamide 66 (PA66) fabrics, polylactic acid (PLA) on PA66 fabric, PLA on PLA fabric, and finally nanosize carbon black/PLA (CB/PLA) and multi-wall carbon nanotubes/PLA (CNT/PLA) nanocomposites on PLA fabrics. The adhesion forces were quantified using the innovative sample preparing method combining with the peeling standard method. Results showed that different variables of 3D printing process like extruder temperature, platform temperature and printing speed can have significant effect on adhesion force of polymers to fabrics while direct 3D printing. A model was proposed specifically for deposition of a commercial 3D printer Nylon filament on PA66 fabrics. In the following, among the printed polymers, PLA and its composites had high adhesion force to PLA fabrics.

  6. Thermal desorption characterisation of molecularly imprinted polymers. Part II: Use of direct probe GC-MS analysis to study crosslinking effects.

    Holland, Niamh; Duggan, Patrick; Owens, Eleanor; Cummins, Wayne; Frisby, June; Hughes, Helen; McLoughlin, Peter


    A powerful method utilising direct probe thermal desorption GC-MS is presented for the study of molecularly imprinted polymers (MIPs). A series of 2-aminopyridine (2-apy)-imprinted methacrylic acid-ethyleneglycol dimethacrylate (MAA-EGDMA) copolymers were prepared under identical conditions but with varying amounts of EGDMA (crosslinking monomer). The use of appropriate temperature programmes permitted template removal, and the subsequent assessment of polymer affinity and specificity, all of which were found to be dependent on polymer composition and morphology. The system was sufficiently sensitive to identify a specific response of imprinted polymers over nonimprinted counterparts. Correlations were found to exist between thermal desorption analysis and solution phase binding, which was assessed by UV spectroscopy, where specificity was found to diminish with decreasing EGDMA concentration. This was attributed to the increased number of free carboxyl groups in those polymers containing a lower percentage of EGDMA. Thermal desorption profiles obtained for the analyte were found to be unaffected by the physical and chemical properties of the solvent used for analyte reloading.

  7. Meta-analysis of randomized controlled trials on risk of myocardial infarction from the use of oral direct thrombin inhibitors

    Artang, Ramin; Rome, Eric; Nielsen, Jørn Dalsgaard;


    . To address these questions, we systematically searched MEDLINE and performed a meta-analysis on randomized trials that compared oral DTIs with warfarin for any indication with end point of MIs after randomization. We furthermore performed a secondary meta-analysis on atrial fibrillation stroke prevention......Dabigatran has been associated with greater risk of myocardial infarction (MI) than warfarin. It is unknown whether the increased risk is unique to dabigatran, an adverse effect shared by other oral direct thrombin inhibitors (DTIs), or the result of a protective effect of warfarin against MI...... trials with alternative anticoagulants compared with warfarin with end point of MIs after randomization. A total of 11 trials (39,357 patients) that compared warfarin to DTIs (dabigatran, ximelagatran, and AZD0837) were identified. In these trials, patients treated with oral DTIs were more likely...

  8. Phase transitions within the isolated polymer molecule: Coupling of the polymer threading a membrane transition to the helix-random coil, the collapse, the adsorption, and the equilibrium polymerization transitions

    Di Marzio, Edmund A.; Kasianowicz, John J.


    The polymer threading a membrane transition (PTM), which is a first-order thermodynamic phase transition for an isolated linear polymer in the limit of infinite molecular weight, is coupled to the other four phase transitions of the isolated polymer molecule. They are (1) the helix-random coil (HR) phase transition which can be diffuse (polypeptides), second-order (DNA) or first-order (collagen) depending on the number of strands, (2) the collapse (C) transition which is usually second-order but can be first-order for polymeric solvents, (3) adsorption onto a surface (SA) which is second-order, (4) a model of equilibrium polymerization (P) which is first-order. In each case an exact expression for the partition function of the coupled pair is given as a one-dimensional summation over products of the individual partition functions corresponding to sides 1 and 2. Using a procedure analogous to evaluation of the grand canonical ensemble the summation can be performed and the character of the transition elucidated in the limit of infinite molecular weight. Given that the solutions on either side are sufficiently diverse there are 15 possible translocation pair couplings. They are PTM-PTM, HR-HR, C-C, SA-SA, P-P, PTM-HR, PTM-C, PTM-SA, PTM-P, HR-C, HR-SA, HR-P, C-SA, C-P, SA-P. The PTM-P coupling is most interesting because one can create polymer in the PTM side even though the P side is in the depolymerization regime. For HR-HR there are eight possible translocation modes. For example, as we raise the temperature we can have H1→H2→R1→R2 in obvious notation. These exact model solutions provide a thermodynamic base for the study of the kinetics of significant technological problems such as the translocation of DNA through pores imbedded in membranes. They also throw light on the nature of polymer-membrane-pore interactions in living cells and viruses.

  9. Time scales and mechanisms of relaxation in the energy landscape of polymer glass under deformation: direct atomistic modeling.

    Lyulin, Alexey V; Michels, M A J


    Molecular-dynamics simulation is used to explore the influence of thermal and mechanical history of typical glassy polymers on their deformation. Polymer stress-strain and energy-strain developments have been followed for different deformation velocities, also in closed extension-recompression loops. The latter simulate for the first time the experimentally observed mechanical rejuvenation and overaging of polymers, and energy partitioning reveals essential differences between mechanical and thermal rejuvenation. All results can be qualitatively interpreted by considering the ratios of the relevant time scales: for cooling down, for deformation, and for segmental relaxation.

  10. Exact solutions for social and biological contagion models on mixed directed and undirected, degree-correlated random networks

    Payne, Joshua L; Dodds, Peter Sheridan


    We derive analytic expressions for the probability and expected size of global spreading events starting from a single infected seed for a broad collection of contagion processes acting on random networks with both directed and undirected edges and arbitrary degree-degree correlations. Our work extends previous theoretical developments for the undirected case, and we provide numerical support for our findings by investigating an example class of networks for which we are able to obtain closed-form expressions.

  11. Direct Numerical Simulation of Fracture Behaviour for Random Short Wood Fibres Reinforced Composites, Comparison with Digital Image Correlation Experiments

    Shen, M.; Touchard, F.; Bezine, G.; Brillaud, J.


    The work is to predict fracture behaviour of bio-composites from the tensile properties of its components. In this work, we have realized a direct numerical simulation of fracture behaviour for random short spruce fibers reinforced composites. For calculations, wood fibers have been considered as linear elastic bodies, polypropylene matrix as an elastic-plastic material. Then, numerical results have been compared with experimental results that have been obtained by digital image correlation. This comparison indicates that random fiber FE model of random short spruce fibers reinforced composites can be able to fairly reflect the influence of random fibers microstructure in the composite on its fracture behavior. The calculation of both random fiber and homogeneous FE model and their comparison with experiments show that the average values of J-integral in a region in the front of the crack tip from both numerical FE models are in good agreement with the average J value of DIC experiment in the same region when the numerical and experimental CT specimens of the short spruce fiber reinforced composite are subjected to the same extension at their loading point.

  12. Direct Numerical Simulation of Fracture Behaviour for Random Short Wood Fibres Reinforced Composites, Comparison with Digital Image Correlation Experiments

    Brillaud J.


    Full Text Available The work is to predict fracture behaviour of bio-composites from the tensile properties of its components. In this work, we have realized a direct numerical simulation of fracture behaviour for random short spruce fibers reinforced composites. For calculations, wood fibers have been considered as linear elastic bodies, polypropylene matrix as an elastic-plastic material. Then, numerical results have been compared with experimental results that have been obtained by digital image correlation. This comparison indicates that random fiber FE model of random short spruce fibers reinforced composites can be able to fairly reflect the influence of random fibers microstructure in the composite on its fracture behavior. The calculation of both random fiber and homogeneous FE model and their comparison with experiments show that the average values of J-integral in a region in the front of the crack tip from both numerical FE models are in good agreement with the average J value of DIC experiment in the same region when the numerical and experimental CT specimens of the short spruce fiber reinforced composite are subjected to the same extension at their loading point.

  13. Polymer Directed Protein Assemblies

    van Rijn, Patrick


    Protein aggregation and protein self-assembly is an important occurrence in natural systems, and is in some form or other dictated by biopolymers. Very obvious influences of biopolymers on protein assemblies are, e. g., virus particles. Viruses are a multi-protein assembly of which the morphology is

  14. Polymer Directed Protein Assemblies

    van Rijn, Patrick

    Protein aggregation and protein self-assembly is an important occurrence in natural systems, and is in some form or other dictated by biopolymers. Very obvious influences of biopolymers on protein assemblies are, e. g., virus particles. Viruses are a multi-protein assembly of which the morphology is

  15. Multi-directional random wave interaction with an array of cylinders

    Ji, Xinran; Liu, Shuxue; Bingham, Harry B.;


    . The biggest transverse force is found to occur on the rear cylinder rather than the front one. This is quite different from the results in unidirectional waves and should be paid much more attention in the design of offshore structures. At last, the possibility of the near-trapping under the multi......Based on the linear theory of wave interaction with an array of circular bottom-mounted vertical cylinders, systematic calculations are made to investigate the effects of the wave directionality on wave loads in short-crested seas. The multi-directional waves are specified using a discrete form...... of the Mitsuyasu-type spreading function. The time series of multi-directional wave loads, including both the wave run-up and wave force, can be simulated. The effect of wave directionality on the wave run-up and wave loading on the cylinders is investigated. For multi-directional waves, as the distribution...

  16. A Binational Multicenter Pilot Feasibility Randomized Controlled Trial of Early Goal-Directed Mobilization in the ICU.

    Hodgson, Carol L; Bailey, Michael; Bellomo, Rinaldo; Berney, Susan; Buhr, Heidi; Denehy, Linda; Gabbe, Belinda; Harrold, Megan; Higgins, Alisa; Iwashyna, Theodore J; Papworth, Rebecca; Parke, Rachael; Patman, Shane; Presneill, Jeffrey; Saxena, Manoj; Skinner, Elizabeth; Tipping, Claire; Young, Paul; Webb, Steven


    To determine if the early goal-directed mobilization intervention could be delivered to patients receiving mechanical ventilation with increased maximal levels of activity compared with standard care. A pilot randomized controlled trial. Five ICUs in Australia and New Zealand. Fifty critically ill adults mechanically ventilated for greater than 24 hours. Patients were randomly assigned to either early goal-directed mobilization (intervention) or to standard care (control). Early goal-directed mobilization comprised functional rehabilitation treatment conducted at the highest level of activity possible for that patient assessed by the ICU mobility scale while receiving mechanical ventilation. The ICU mobility scale, strength, ventilation duration, ICU and hospital length of stay, and total inpatient (acute and rehabilitation) stay as well as 6-month post-ICU discharge health-related quality of life, activities of daily living, and anxiety and depression were recorded. The mean age was 61 years and 60% were men. The highest level of activity (ICU mobility scale) recorded during the ICU stay between the intervention and control groups was mean (95% CI) 7.3 (6.3-8.3) versus 5.9 (4.9-6.9), p = 0.05. The proportion of patients who walked in ICU was almost doubled with early goal-directed mobilization (intervention n = 19 [66%] vs control n = 8 [38%]; p = 0.05). There was no difference in total inpatient stay (d) between the intervention versus control groups (20 [15-35] vs 34 [18-43]; p = 0.37). There were no adverse events. Key Practice Points: Delivery of early goal-directed mobilization within a randomized controlled trial was feasible, safe and resulted in increased duration and level of active exercises.

  17. A solid-polymer-electrolyte direct methanol fuel cell (DMFC) with Pt-Ru nanoparticles supported onto poly(3,4-ethylenedioxythiophene) and polystyrene sulphonic acid polymer composite as anode

    K K Tintula; S Pitchumani; P Sridhar; A K Shukla


    Nano-sized Pt-Ru supported onto a mixed-conducting polymer composite comprising poly(3,4-ethylenedioxythiophene)-polystyrene sulphonic acid (PEDOT-PSSA) is employed as anode in a solid-polymer-electrolyte direct methanol fuel cell (SPE-DMFC) and its performance compared with the SPE-DMFC employing conventional Vulcan XC-72R carbon supported Pt-Ru anode. Physical characterization of the catalyst is conducted by Fourier-transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray analysis (EDAX) in conjunction with cyclic voltammetry and chronoamperometry. The study suggests that PEDOT-PSSA to be a promising alternative catalyst-support-material for SPE-DMFCs.

  18. Oblique and Multi-Directional Random Wave Loads on Vertical Breakwaters

    俞聿修; 李本霞; 张宁川


    Extensive 3-D model tests have been performed to study the effects of wave obliquity and multi-directionality on the wave loads acting on vertical breakwaters. The variation of horizontal and uplift forces acting on an unit length of a breakwater with wave direction, the longitudinal distribution of wave forces, as well as the longitudinal load reduction are analyzed. Some empirical formulae of the longitudinal distribution coefficient and the longitudinal load reduction factor are presented for practical use.

  19. Modeling of ionic transport in solid polymer electrolytes

    Cheang, P L; Teo, L L; Lim, T L, E-mail: [Centre for Foundation Studies and Extension Education, Multimedia University, Jln Ayer Keroh Lama, 75450 Melaka (Malaysia)


    A Monte Carlo model describing the ionic trans port in solid polyme relectrolyte is developed. Single cation simulation is carried out using hopping rate to study the transport mechanism of a thermally activated ion in solid polymer electrolyte. In our model, the ion is able to hop along a polymer chain and to jump between different chains, surmounting energy barriers that consist of polymer's activation energy and the externally applied electric field. The model is able to trace the motion of ion across polymer electrolyte. The mean hopping distance is calculated based on the available open bond in the next nearest side. Random numbers are used to determine the hopping distances, free flight times, final energy and direction of the cation after successful hop. Drift velocity and energy of cation are simulated in our work. The model is expected to be able to simulate the lithium-polymer battery in future.

  20. Couple relationship education: A randomized controlled trial of professional contact and self-directed tools.

    Zemp, Martina; Merz, Corina A; Nussbeck, Fridtjof W; Halford, W Kim; Schaer Gmelch, Marcel; Bodenmann, Guy


    The aim of this randomized controlled trial was to examine the efficacy of an evidence-based relationship distress prevention program, the Couples Coping Enhancement Training (CCET), in dual well-earning couples and to investigate whether effects vary by (a) hours of professional contact and (b) mode of delivery (face to face vs. self-learning DVD). N = 159 couples were randomly assigned to 1 of 4 intervention conditions: (1) standard CCET (15 hours face to face), (2) compact CCET (12 hr face to face), (3) short CCET (self-learning DVD + 8 hr face to face), or (4) wait-list control group. Relationship satisfaction and dyadic coping skills were assessed by means of questionnaires completed prior to and 2 weeks after completion of the treatment, at 3-month follow-up, and at 6-month follow-up. Baseline latent change models for 2 factors showed that the CCET enhanced relationship satisfaction and dyadic coping skills in couples relative to the wait-list control group, albeit effects were small. The standard format of the CCET was not more effective than the compact or the short format indicating that reduced amount of professional contact did not decrease the treatment's efficacy and that the self-learning DVD successfully replaced the psycho-educational part of the program. Since dual earner couples usually face multiple stressors, it is a promising finding that they can strengthen their relationship with a relatively short time investment. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  1. Time and direction of arrival detection and filtering for imaging in strongly scattering random media

    Borcea, Liliana; Tsogka, Chrysoula


    We study detection and imaging of small reflectors in heavy clutter, using an array of transducers that emits and receives sound waves. Heavy clutter means that multiple scattering of the waves in the heterogeneous host medium is strong and overwhelms the arrivals from the small reflectors. Building on the adaptive time-frequency filter of [1], we propose a robust method for detecting the direction of arrival of the direct echoes from the small reflectors, and suppressing the unwanted clutter backscatter. This improves the resolution of imaging. We illustrate the performance of the method with realistic numerical simulations in a non-destructive testing setup.

  2. Direct observation of asperity deformation of specimens with random rough surfaces in upsetting and indentation processes

    Azushima, A.; Kuba, S.; Tani, S.


    The trapping behavior of liquid lubricant and contact behavior of asperities at the workpiece-tool interface during upsetting and indentation are observed directly using a compression subpress which consists of a transparent die made of sapphire, a microscope with a CCD camera and a video system...

  3. Direct versus indirect treatment for preschool children who stutter: The RESTART randomized trial

    C. de Sonneville (Caroline); E.A. Stolk (Elly); Rietveld, T. (Toni); M.-C. Franken (Marie-Christine)


    textabstractObjective Stuttering is a common childhood disorder. There is limited high quality evidence regarding options for best treatment. The aim of the study was to compare the effectiveness of direct treatment with indirect treatment in preschool children who stutter. Methods In this multicent

  4. Direct Observation of Asperity Deformation of Specimen with Random Rough Surface in Upsetting Process

    Azushima, A.; Kuba, S.; Tani, S.


    The trapping behavior of liquid lubricant and contact behavior of asperities at the workpiece-tool interface during upsetting and indentation are observed directly using a compression subpress which consists of a transparent die made of sapphire, a microscope with a CCD camera and a video system....

  5. Direct Observation of Asperity Deformation of Specimen with Random Rough Surface in Upsetting Process

    Azushima, A.; Kuba, S.; Tani, S.


    The trapping behavior of liquid lubricant and contact behavior of asperities at the workpiece-tool interface during upsetting and indentation are observed directly using a compression subpress which consists of a transparent die made of sapphire, a microscope with a CCD camera and a video system...

  6. Direct versus indirect treatment for preschool children who stutter: The RESTART randomized trial

    C. de Sonneville (Caroline); E.A. Stolk (Elly); T. Rietveld (Toni); M.-C. Franken (Marie-Christine)


    textabstractObjective Stuttering is a common childhood disorder. There is limited high quality evidence regarding options for best treatment. The aim of the study was to compare the effectiveness of direct treatment with indirect treatment in preschool children who stutter. Methods In this

  7. Glatiramer Acetate in Treatment of Multiple Sclerosis: A Toolbox of Random Co-Polymers for Targeting Inflammatory Mechanisms of both the Innate and Adaptive Immune System?

    Thomas Vorup-Jensen


    Full Text Available Multiple sclerosis is a disease of the central nervous system, resulting in the demyelination of neurons, causing mild to severe symptoms. Several anti-inflammatory treatments now play a significant role in ameliorating the disease. Glatiramer acetate (GA is a formulation of random polypeptide copolymers for the treatment of relapsing-remitting MS by limiting the frequency of attacks. While evidence suggests the influence of GA on inflammatory responses, the targeted molecular mechanisms remain poorly understood. Here, we review the multiple pharmacological modes-of-actions of glatiramer acetate in treatment of multiple sclerosis. We discuss in particular a newly discovered interaction between the leukocyte-expressed integrin αMβ2 (also called Mac-1, complement receptor 3, or CD11b/CD18 and perspectives on the GA co-polymers as an influence on the function of the innate immune system.

  8. A polymer, random walk model for the size-distribution of large DNA fragments after high linear energy transfer radiation

    Ponomarev, A. L.; Brenner, D.; Hlatky, L. R.; Sachs, R. K.


    DNA double-strand breaks (DSBs) produced by densely ionizing radiation are not located randomly in the genome: recent data indicate DSB clustering along chromosomes. Stochastic DSB clustering at large scales, from > 100 Mbp down to energy transfer (LET) radiation, are obtained. They are found to be non-linear when the dose becomes so large that there is a significant probability of overlapping or close juxtaposition, along one chromosome, for different DSB clusters from different tracks. The non-linearity is more evident for large fragments than for small. The DNAbreak results furnish an example of the RLC (randomly located clusters) analytic formalism, which generalizes the broken-stick fragment-size distribution of the random-breakage model that is often applied to low-LET data.

  9. Efficient one-pot synthesis of hydrophilic and fluorescent molecularly imprinted polymer nanoparticles for direct drug quantification in real biological samples.

    Niu, Hui; Yang, Yaqiong; Zhang, Huiqi


    Efficient one-pot synthesis of hydrophilic and fluorescent molecularly imprinted polymer (MIP) nanoparticles and their application as optical chemosensor for direct drug quantification in real, undiluted biological samples are described. The general principle was demonstrated by preparing tetracycline (Tc, a broad-spectrum antibiotic)-imprinted fluorescent polymer nanoparticles bearing hydrophilic polymer brushes via poly(2-hydroxyethyl methacrylate) (PHEMA) macromolecular chain transfer agent-mediated reversible addition-fragmentation chain transfer (RAFT) precipitation polymerization in the presence of a fluorescent monomer. The introduction of hydrophilic PHEMA brushes and fluorescence labeling onto/into the MIP nanoparticles proved to not only significantly improve their surface hydrophilicity and lead to their obvious specific binding and high selectivity toward Tc in the undiluted bovine serum, but also impart them with strong fluorescent properties. In particular, significant fluorescence quenching was observed upon their binding with Tc in such complex biological milieu, which makes these Tc-MIP nanoparticles useful optical chemosensor with a detection limit of 0.26 μM. Furthermore, such advanced functional MIP nanoparticles-based chemosensor was also successfully utilized for the direct, sensitive, and accurate determination of Tc in another biological medium (i.e., the undiluted pig serum) with average recoveries ranging from 98% to 102%, even in the presence of several interfering drugs.

  10. Dielectric Electro Active Polymer Incremental Actuator Driven by Multiple High-Voltage Bi-directional DC-DC Converters

    Thummala, Prasanth; Zhang, Zhe; Andersen, Michael A. E.


    This paper presents driving circuit for a recently invented dielectric electro active polymer (DEAP) incremental actuator. The basic operation of such an actuator is bioinspired from the movement of an inchworm. The actuator consists of three electrically isolated, and mechanically connected....... The experimental results and efficiency measurements are shown....

  11. Additive Manufacturing of a Photo-Cross-Linkable Polymer via Direct Melt Electrospinning Writing for Producing High Strength Structures.

    Chen, Fei; Hochleitner, Gernot; Woodfield, Tim; Groll, Juergen; Dalton, Paul D; Amsden, Brian G


    Melt electrospinning writing (MEW) is an emerging additive manufacturing technique that enables the design and fabrication of micrometer-thin fibrous scaffolds made of biocompatible and biodegradable polymers. By using a computer-aided deposition process, a unique control over pore size and interconnectivity of the resulting scaffolds is achieved, features highly interesting for tissue engineering applications. However, MEW has been mainly used to process low melting point thermoplastics such as poly(ε-caprolactone). Since this polymer exhibits creep and a reduction in modulus upon hydration, we manufactured scaffolds of poly(L-lactide-co-ε-caprolactone-co-acryloyl carbonate) (poly(LLA-ε-CL-AC)), a photo-cross-linkable and biodegradable polymer, for the first time. We show that the stiffness of the scaffolds increases significantly (up to ∼10-fold) after cross-linking by UV irradiation at room temperature, compared with un-cross-linked microfiber scaffolds. The preservation of stiffness and high average fiber modulus (370 ± 166 MPa) within the cross-linked hydrated scaffolds upon repetitive loading (10% strain at 1 Hz up to 200,000 cycles) suggests that the prepared scaffolds may be of potential interest for soft connective tissue engineering applications. Moreover, the approach can be readily adapted through manipulation of polymer properties and scaffold geometry to prepare structures with mechanical properties suitable for other tissue engineering applications.

  12. The random co-polymer glatiramer acetate rapidly kills primary human leukocytes through sialic-acid-dependent cell membrane damage

    Christiansen, Stig Hill; Zhang, Xianwei; Juul-Madsen, Kristian;


    The formulation glatiramer acetate (GA) is widely used in therapy of multiple sclerosis. GA consists of random copolymers of four amino acids, in ratios that produce a predominantly positive charge and an amphipathic character. With the extraordinary complexity of the drug, several pharmacological...

  13. Spectral evolution of weakly nonlinear random waves: kinetic description vs direct numerical simulations

    Annenkov, Sergei; Shrira, Victor


    We study numerically the long-term evolution of water wave spectra without wind forcing, using three different models, aiming at understanding the role of different sets of assumptions. The first model is the classical Hasselmann kinetic equation (KE). We employ the WRT code kindly provided by G. van Vledder. Two other models are new. As the second model, we use the generalised kinetic equation (gKE), derived without the assumption of quasi-stationarity. Thus, unlike the KE, the gKE is valid in the cases when a wave spectrum is changing rapidly (e.g. at the initial stage of evolution of a narrow spectrum). However, the gKE employs the same statistical closure as the KE. The third model is based on the Zakharov integrodifferential equation for water waves and does not depend on any statistical assumptions. Since the Zakharov equation plays the role of the primitive equation of the theory of wave turbulence, we refer to this model as direct numerical simulation of spectral evolution (DNS-ZE). For initial conditions, we choose two narrow-banded spectra with the same frequency distribution (a JONSWAP spectrum with high peakedness γ = 6) and different degrees of directionality. These spectra are from the set of observations collected in a directional wave tank by Onorato et al (2009). Spectrum A is very narrow in angle (corresponding to N = 840 in the cosN directional model). Spectrum B is initially wider in angle (corresponds to N = 24). Short-term evolution of both spectra (O(102) wave periods) has been studied numerically by Xiao et al (2013) using two other approaches (broad-band modified nonlinear Schrödinger equation and direct numerical simulation based on the high-order spectral method). We use these results to verify the initial stage of our DNS-ZE simulations. However, the advantage of the DNS-ZE method is that it allows to study long-term spectral evolution (up to O(104) periods), which was previously possible only with the KE. In the short-term evolution

  14. Directed random walks and constraint programming reveal active pathways in hepatocyte growth factor signaling.

    Kittas, Aristotelis; Delobelle, Aurélien; Schmitt, Sabrina; Breuhahn, Kai; Guziolowski, Carito; Grabe, Niels


    An effective means to analyze mRNA expression data is to take advantage of established knowledge from pathway databases, using methods such as pathway-enrichment analyses. However, pathway databases are not case-specific and expression data could be used to infer gene-regulation patterns in the context of specific pathways. In addition, canonical pathways may not always describe the signaling mechanisms properly, because interactions can frequently occur between genes in different pathways. Relatively few methods have been proposed to date for generating and analyzing such networks, preserving the causality between gene interactions and reasoning over the qualitative logic of regulatory effects. We present an algorithm (MCWalk) integrated with a logic programming approach, to discover subgraphs in large-scale signaling networks by random walks in a fully automated pipeline. As an exemplary application, we uncover the signal transduction mechanisms in a gene interaction network describing hepatocyte growth factor-stimulated cell migration and proliferation from gene-expression measured with microarray and RT-qPCR using in-house perturbation experiments in a keratinocyte-fibroblast co-culture. The resulting subgraphs illustrate possible associations of hepatocyte growth factor receptor c-Met nodes, differentially expressed genes and cellular states. Using perturbation experiments and Answer Set programming, we are able to select those which are more consistent with the experimental data. We discover key regulator nodes by measuring the frequency with which they are traversed when connecting signaling between receptors and significantly regulated genes and predict their expression-shift consistently with the measured data. The Java implementation of MCWalk is publicly available under the MIT license at:

  15. Packing by random sequential addition of small blocks: pressure effects, orientational correlations and application to graphitic fillers in polymer matrices

    Sergi, Danilo; Scocchi, Giulio; Ortona, Alberto


    Packing is a complex phenomenon of prominence in many natural and industrial processes (liquid crystals, granular materials, infiltration, melting, flow, sintering, segregation, sedimentation, compaction, etc.). A variety of computational methods is available in particular for spheroid particles. Our aim is to develop strategies devised to fill free space in 3D by random hard blocks of varying size and orientation in order to reproduce the observed arrangement of graphitic assemblies into polymeric matrices. Random packing is improved by applying an external pressure implemented with a drifted diffusive motion of the fillers. Attention is also paid to the emergence of structural and orientational order. Interestingly, mixtures of fillers of irregular shapes can be dealt with efficiently using the proposed algorithm.

  16. PREFACE: Polymers and Complex Matter

    von Ferber, Christian


    This special issue, in honour of Lothar Schäfer on the occasion of his 60th birthday, focuses on polymers and complex matter and covers a broad range of topics both in terms of subject matter and methods applied. This reflects the wide and open minded interests of the honoree. Lothar Schäfer began his career in Heidelberg working on theoretical nuclear physics with H A Weidenmüller. Following a stay at the CEN Saclay in 1974, he turned to the field of critical phenomena. He made fundamental contributions to the subject of disordered systems, in particular on Goldstone modes with F J Wegner and on Anderson localization with A U Pruisken. With T A Witten he formulated a truly field theoretic description of general polymer solutions. Polymers in solution and the renormalization group approach to their experimentally accessible properties have, since 1980 in Hannover and 1983 in Essen, been his primary field of research summarized in his book Excluded Volume Effects in Polymer Solutions as Explained by the Renormalization Group covering `all you ought to know' on the subject. This work is complemented by analytical studies of polymer dynamics. The subjects contained in this special issue encompass soft matter and its rheology, polymers in confinement and their role in short- and long-range colloidal interactions: discussing lenses, dumbbells, rods and dendrimers. Special topics are short chains, directed molecules and gas permeation through polymers. Applications of polymer theory to biological systems include the interactions between DNA molecules and between DNA and proteins and the polymerization of the actin skeleton. Work on random matrix theory, functional renormalization and ageing is devoted to the implications of disorder. Finally, more general aspects of the field theory of polymers and complex matter are discussed, like the Hubbard-Stratonovich transformation, renormalization of polymer field theory, exact renormalization group equations, percolation and

  17. Rapid and direct micro-machining/patterning of polymer materials by oxygen MeV ion beam irradiation through masks

    Brun, S., E-mail: [Institut des Microtechnologies Appliquees, Eplatures-Grise 17, 2300 La Chaux-de-Fonds (Switzerland); Guibert, G. [Institut des Microtechnologies Appliquees, Eplatures-Grise 17, 2300 La Chaux-de-Fonds (Switzerland); Meunier, C. [Universite de Franche Comte, Institut FEMTO-ST, UMR 6174 CNRS, 4 Place Tharradin, BP 71427, 25211 Montbeliard (France); Guibert, E.; Keppner, H.; Mikhailov, S. [Institut des Microtechnologies Appliquees, Eplatures-Grise 17, 2300 La Chaux-de-Fonds (Switzerland)


    PTFE (PolyTetraFluoroEthylene), often called Teflon, is a well-known polymer for being a non-stick material with good thermal properties. Moreover, PTFE is biocompatible and especially it is a cyto-compatible polymer. To enable bonding, a chemical etching based on sodium solutions is generally used to modify surfaces. In this paper we study the etching of PTFE using an oxygen ion beam in the MeV energy range. We present micro-patterning of PTFE through masks with two fluences of 5 x 10{sup 15} and 1 x 10{sup 16} ion cm{sup -2}. As is demonstrated the use of a mask allows structuring of large areas while maintaining a distance between the mask and sample makes industrial applications possible.

  18. Femtosecond laser direct writing of single mode polymer micro ring laser with high stability and low pumping threshold.

    Parsanasab, Gholam-Mohammad; Moshkani, Mojtaba; Gharavi, Alireza


    We have demonstrated an optically pumped polymer microring laser fabricated by two photon polymerization (TPP) of SU-8. The gain medium is an organic dye (Rhodamine B) doped in SU-8, and the laser cavity is a double coupled microring structure. Single mode lasing was obtained from the two coupled rings each with 30 µm and 29 µm radii using Vernier effect. Low laser threshold of 0.4 µJ/mm(2) is achieved using 1 µm wide polymer waveguides and the quality factor is greater than 10(4) at 612.4 nm wavelength. The lasing remained stable with pump energies from threshold to energies as high as 125 times the threshold.

  19. Direct Replacement of Antibodies with Molecularly Imprinted Polymer Nanoparticles in ELISA-Development of a Novel Assay for Vancomycin

    Chianella, Iva; Guerreiro, Antonio; Moczko, Ewa; Caygill, J. Sarah; Piletska, Elena V.; Perez De Vargas Sansalvador, Isabel M.; Whitcombe, Michael J.; Piletsky, Sergey A.


    A simple and straightforward technique for coating microplate wells with molecularly imprinted polymer nanoparticles (nanoMIPs) to develop ELISA type assays is presented here for the first time. NanoMIPs were synthesized by a solid phase approach with immobilized vancomycin (template) and characterized using Biacore 3000, dynamic light scattering and electron microscopy. Immobilization, blocking and washing conditions were optimized in microplate format. The detection of vancomycin was achiev...

  20. Proton-conducting Membranes Based on PVA-PAMPS Semi-interpenetrating Polymer Networks for Low Temperature Direct Methanol Fuel Cells

    Jinli Qiao; Tatsuhiro Okada


    @@ 1Introduction In direct methanol fuel cells (DMFCs) the methanol crossover from anode to cathode through the polymer electrolyte membrane is a major isue, because this not only causes loss of fuel, but also reduces the performance at the cathode due to the mixed reaction of methanol oxidation with oxygen reduction reaction. Membranes that show high proton conductivity, and at the same time, low methanol permeability are strongly desired but difficult to attain, because of trade-off relations between these parameters. We here report a new type of cost-effective polymer blend membranes based on chemically cross-linked poly(vinyl alcohol) (PVA)and 2-acrylamido-2-methyl-1-propanesulfonic acid (PAMPS) which is called semi-interpenetrating polymer networks (semi-IPNs). The membrane structure is finished by cross-linking the hydroxyl groups of poly (vinyl alchol) (PVA) main chain with acetal ring formation using glutaraldehyde (GA) cross-linker. For improving the flexibility of the membranes, we reported "binary chemcial cross-linking", "hydrophobicizer" and "stabilizer"effect[1-3], respectively, in our recent work.

  1. Direct spectroscopic evidence of ultrafast electron transfer from a low band gap polymer to CdSe quantum dots in hybrid photovoltaic thin films.

    Couderc, Elsa; Greaney, Matthew J; Brutchey, Richard L; Bradforth, Stephen E


    Ultrafast transient absorption spectroscopy is used to study charge transfer dynamics in hybrid films composed of the low band gap polymer PCPDTBT and CdSe quantum dots capped with tert-butylthiol ligands. By selectively exciting the polymer, a spectral signature for electrons on the quantum dots appears on ultrafast time scales (≲ 65 fs), which indicates ultrafast electron transfer. From this time scale, the coupling between the polymer chains and the quantum dots is estimated to be J ≳ 17 meV. The reduced quantum dot acceptors exhibit an unambiguous spectral bleach signature, whose amplitude allows for the first direct calculation of the absolute electron transfer yield in a hybrid solar cell (82 ± 5%). We also show that a limitation of the hybrid system is rapid and measurable geminate recombination due to the small separation of the initial charge pair. The fast recombination is consistent with the internal quantum efficiency of the corresponding solar cell. We therefore have identified and quantified a main loss mechanism in this type of third generation solar cell.

  2. Template-Directed Copolymerization, Random Walks along Disordered Tracks, and Fractals

    Gaspard, Pierre


    In biology, template-directed copolymerization is the fundamental mechanism responsible for the synthesis of DNA, RNA, and proteins. More than 50 years have passed since the discovery of DNA structure and its role in coding genetic information. Yet, the kinetics and thermodynamics of information processing in DNA replication, transcription, and translation remain poorly understood. Challenging issues are the facts that DNA or RNA sequences constitute disordered media for the motion of polymerases or ribosomes while errors occur in copying the template. Here, it is shown that these issues can be addressed and sequence heterogeneity effects can be quantitatively understood within a framework revealing universal aspects of information processing at the molecular scale. In steady growth regimes, the local velocities of polymerases or ribosomes along the template are distributed as the continuous or fractal invariant set of a so-called iterated function system, which determines the copying error probabilities. The growth may become sublinear in time with a scaling exponent that can also be deduced from the iterated function system.

  3. Enhancing the chroma of pigmented polymers using antireflective surface structures

    Clausen, Jeppe Sandvik; Christiansen, Alexander Bruun; Kristensen, Anders;


    In this paper we investigate how the color of a pigmented polymer is affected by reduction of the reflectance at the air-polymer interface. Both theoretical and experimental investigations show modified diffuse-direct reflectance spectra when the reflectance of the surface is lowered. Specifically...... it is found that the color change is manifested as an increase in chroma, leading to a clearer color experience. The experimental implementation is done using random tapered surface structures replicated in polymer from silicon masters using hot embossing....

  4. Polymer nanocomposites: polymer and particle dynamics

    Kim, Daniel


    Polymer nanocomposites containing nanoparticles smaller than the random coil size of their host polymer chains are known to exhibit unique properties, such as lower viscosity and glass transition temperature relative to the neat polymer melt. It has been hypothesized that these unusual properties result from fast diffusion of the nanostructures in the host polymer, which facilitates polymer chain relaxation by constraint release and other processes. In this study, the effects of addition of sterically stabilized inorganic nanoparticles to entangled cis-1,4-polyisoprene and polydimethylsiloxane on the overall rheology of nanocomposites are discussed. In addition, insights about the relaxation of the host polymer chains and transport properties of nanoparticles in entangled polymer nanocomposites are presented. The nanoparticles are found to act as effective plasticizers for their entangled linear hosts, and below a critical, chemistry and molecular-weight dependent particle volume fraction, lead to reduced viscosity, glass transition temperature, number of entanglements, and polymer relaxation time. We also find that the particle motions in the polymer host are hyperdiffusive and at the nanoparticle length scale, the polymer host acts like a simple, ideal fluid and the composites\\' viscosity rises with increasing particle concentration. © 2012 The Royal Society of Chemistry.




    Suppose that Z1,Z2…,Zn are independent normal random variables with common mean μ and variance σ2. Then S2=∑n n=1 (zi-z)2/σ2 and T =(n-1的平方根)-Z/(S2/n的平方根) have x2n-1 distribution and tn-1 distribution respectively. If the normal assumption fails, there will be the remainders of the distribution functions and density functions. This paper gives the direct expansions of distribution functions and density functions of S2 and T up to o(n-1). They are more intuitive and convenient than usual Edgeworth expansions.

  6. Directed assembly of gold nanowires on silicon via reorganization and simultaneous fusion of randomly distributed gold nanoparticles.

    Reinhardt, Hendrik M; Bücker, Kerstin; Hampp, Norbert A


    Laser-induced reorganization and simultaneous fusion of nanoparticles is introduced as a versatile concept for pattern formation on surfaces. The process takes advantage of a phenomenon called laser-induced periodic surface structures (LIPSS) which originates from periodically alternating photonic fringe patterns in the near-field of solids. Associated photonic fringe patterns are shown to reorganize randomly distributed gold nanoparticles on a silicon wafer into periodic gold nanostructures. Concomitant melting due to optical heating facilitates the formation of continuous structures such as periodic gold nanowire arrays. Generated patterns can be converted into secondary structures using directed assembly or self-organization. This includes for example the rotation of gold nanowire arrays by arbitrary angles or their fragmentation into arrays of aligned gold nanoparticles.

  7. Virtual fabrication using directed self-assembly for process optimization in a 14-nm dynamic random access memory

    Kamon, Mattan; Akbulut, Mustafa; Yan, Yiguang; Faken, Daniel; Pap, Andras; Allampalli, Vasanth; Greiner, Ken; Fried, David


    For directed self-assembly (DSA) to be deployed in advanced semiconductor technologies, it must reliably integrate into a full process flow. We present a methodology for using virtual fabrication software, including predictive DSA process models, to develop and analyze the replacement of self-aligned quadruple patterning with Liu-Nealey chemoepitaxy on a 14-nm dynamic random access memory (DRAM) process. To quantify the impact of this module replacement, we investigated a key process yield metric for DRAM, interface area between the capacitor contacts and transistor source/drain. Additionally, we demonstrate virtual fabrication of the DRAM cell's hexagonally packed capacitors patterned with an array of diblock copolymer cylinders in place of fourfold litho-etch (LE4) patterning.

  8. A family of enhanced Lehmer random number generators, with hyperplane suppression, and direct support for certain physical applications

    Dyadkin, Iosif G.; Hamilton, Kenneth G.


    Over two hundred congruential pseudorandom number generators, each with a different multiplier, are built into a single assembler routine that returns 32-bit integer and floating-point values. This gives a Monte Carlo user the opportunity of selecting a combination of sequences, so as to provide a greater appearance of chaos. The software makes use of extended 64-bit arithmetic on Intel 386/387 (or higher) chips, thus attaining a period of 2 62 for each of the individual generators. The routine also features entry points that more directly support certain applications, such as well logging in nuclear geophysics. In addition to the customary uniform (0,1) "white noise" generator, the package provides values distributed according to the exponential and Gaussian distributions, random unit vectors in two and three dimensions, as well as Klein-Nishina and neutron scattering distributions.

  9. Effects of the addition of transcranial direct current stimulation to virtual reality therapy after stroke: a pilot randomized controlled trial.

    Viana, R T; Laurentino, G E C; Souza, R J P; Fonseca, J B; Silva Filho, E M; Dias, S N; Teixeira-Salmela, L F; Monte-Silva, K K


    Upper limb (UL) impairment is the most common disabling deficit following a stroke. Previous studies have suggested that transcranial direct current stimulation (tDCS) enhances the effect of conventional therapies. This pilot double-blind randomized control trial aimed to determine whether or not tDCS, combined with Wii virtual reality therapy (VRT), would be superior to Wii therapy alone in improving upper limb function and quality of life in chronic stroke individuals. Twenty participants were randomly assigned either to an experimental group that received VRT and tDCS, or a control group that received VRT and sham tDCS. The therapy was delivered over 15 sessions with 13 minutes of active or sham anodal tDCS, and one hour of virtual reality therapy. The outcomes included were determined using the Fugl-Meyer scale, the Wolf motor function test, the modified Ashworth scale (MAS), grip strength, and the stroke specific quality of life scale (SSQOL). Minimal clinically important differences (MCID) were observed when assessing outcome data. Both groups demonstrated gains in all evaluated areas, except for the SSQOL-UL domain. Differences between groups were only observed in wrist spasticity levels in the experimental group, where more than 50% of the participants achieved the MCID. These findings support that tDCS, combined with VRT therapy, should be investigated and clarified further.

  10. Effects of transcranial direct current stimulation (tDCS) on cognition, symptoms, and smoking in schizophrenia: A randomized controlled study.

    Smith, Robert C; Boules, Sylvia; Mattiuz, Sanela; Youssef, Mary; Tobe, Russell H; Sershen, Henry; Lajtha, Abel; Nolan, Karen; Amiaz, Revital; Davis, John M


    Schizophrenia is characterized by cognitive deficits which persist after acute symptoms have been treated or resolved. Transcranial direct current stimulation (tDCS) has been reported to improve cognition and reduce smoking craving in healthy subjects but has not been as carefully evaluated in a randomized controlled study for these effects in schizophrenia. We conducted a randomized double-blind, sham-controlled study of the effects of 5 sessions of tDCS (2 milliamps for 20minutes) on cognition, psychiatric symptoms, and smoking and cigarette craving in 37 outpatients with schizophrenia or schizoaffective disorder who were current smokers. Thirty subjects provided evaluable data on the MATRICS Consensus Cognitive Battery (MCCB), with the primary outcome measure, the MCCB Composite score. Active compared to sham tDCS subjects showed significant improvements after the fifth tDCS session in MCCB Composite score (p=0.008) and on the MCCB Working Memory (p=0.002) and Attention-Vigilance (p=0.027) domain scores, with large effect sizes. MCCB Composite and Working Memory domain scores remained significant at Benjamini-Hochberg corrected significance levels (α=0.05). There were no statistically significant effects on secondary outcome measures of psychiatric symptoms (PANSS scores), hallucinations, cigarette craving, or cigarettes smoked. The positive effects of tDCS on cognitive performance suggest a potential efficacious treatment for cognitive deficits in partially recovered chronic schizophrenia outpatients that should be further investigated.

  11. Evolution of a Directional Wave Spectrum in a 3D Marginal Ice Zone with Random Floe Size Distribution

    Montiel, F.; Squire, V. A.


    A new ocean wave/sea-ice interaction model is proposed that simulates how a directional wave spectrum evolves as it travels through a realistic marginal ice zone (MIZ), where wave/ice dynamics are entirely governed by coherent conservative wave scattering effects. Field experiments conducted by Wadhams et al. (1986) in the Greenland Sea generated important data on wave attenuation in the MIZ and, particularly, on whether the wave spectrum spreads directionally or collimates with distance from the ice edge. The data suggest that angular isotropy, arising from multiple scattering by ice floes, occurs close to the edge and thenceforth dominates wave propagation throughout the MIZ. Although several attempts have been made to replicate this finding theoretically, including by the use of numerical models, none have confronted this problem in a 3D MIZ with fully randomised floe distribution properties. We construct such a model by subdividing the discontinuous ice cover into adjacent infinite slabs of finite width parallel to the ice edge. Each slab contains an arbitrary (but finite) number of circular ice floes with randomly distributed properties. Ice floes are modeled as thin elastic plates with uniform thickness and finite draught. We consider a directional wave spectrum with harmonic time dependence incident on the MIZ from the open ocean, defined as a continuous superposition of plane waves traveling at different angles. The scattering problem within each slab is then solved using Graf's interaction theory for an arbitrary incident directional plane wave spectrum. Using an appropriate integral representation of the Hankel function of the first kind (see Cincotti et al., 1993), we map the outgoing circular wave field from each floe on the slab boundaries into a directional spectrum of plane waves, which characterizes the slab reflected and transmitted fields. Discretizing the angular spectrum, we can obtain a scattering matrix for each slab. Standard recursive

  12. A comparison of King Vision video laryngoscopy and direct laryngoscopy as performed by residents: a randomized controlled trial.

    Valencia, Jose A; Pimienta, Katherine; Cohen, Darwin; Benitez, Daniel; Romero, David; Amaya, Oswaldo; Arango, Enrique


    For more than 40 years, direct laryngoscopy (DL) has been used to assure the airway during endotracheal intubation. The King Vision video laryngoscope is one of the latest devices introduced for endotracheal intubation. We hypothesize that, relative to direct laryngoscopy, it improves the intubation success rate with fewer intubation attempts and no difference in intubation time or complications. This randomized controlled clinical trial included. The operating room and postanesthesia care unit of an academic hospital. Eighty-eight patients with American Society of Anesthesiologists status I to II and aged ≥18 years who were scheduled for elective surgery under general anesthesia and had no predictors of difficult airway. Patients were randomized (44 per group) to undergo intubation using either DL or King Vision video laryngoscopy (KVVL) performed by first year residents in anesthesia and intensive care. During endotracheal intubation by residents, measurements were success rate, number of attempts, time to intubation, visualization of the glottis, and presence of complications. Both groups had a 100% success rate. A greater frequency of grade 1 laryngoscopy was reported with KVVL (86.4%) relative to DL (59.1%) (P intubation or the number of attempts between the groups (P = .75 and P = .91, respectively). Complications after intubation were low and included oral trauma, esophageal intubation, and sore throat. The use of KVVL by residents with less than 1 year of training (considered nonexperts) significantly improves visualization of the glottis in patients without predictors of difficult airway. The incidence of complications was too low to draw conclusions. Copyright © 2016. Published by Elsevier Inc.

  13. One-pot synthesis of quantum dot-labeled hydrophilic molecularly imprinted polymer nanoparticles for direct optosensing of folic acid in real, undiluted biological samples.

    Yang, Yaqiong; Wang, Zhengzheng; Niu, Hui; Zhang, Huiqi


    A facile and efficient one-pot approach for the synthesis of quantum dot (QD)-labeled hydrophilic molecularly imprinted polymer (MIP) nanoparticles for direct optosensing of folic acid (FA) in the undiluted bovine and porcine serums is described. Hydrophilic macromolecular chain transfer agent-mediated reversible addition-fragmentation chain transfer (RAFT) precipitation polymerization was used to implement the molecular imprinting of FA in the presence of CdTe quantum dots (QDs). The resulting FA-imprinted polymer nanoparticles with surface-grafted hydrophilic poly(glyceryl monomethacrylate) brushes and QDs labeling not only showed outstanding specific molecular recognition toward FA in biological samples, but also exhibited good photostability, rapid binding kinetics, and obvious template binding-induced fluorescence quenching. These characteristics make them a useful fluorescent chemosensor for directly and selectively optosensing FA in the undiluted bovine and porcine serums, with its limit of detection being 0.025μM and average recoveries ranging from 98% to 102%, even in the presence of several interfering compounds. This advanced fluorescent MIP chemosensor is highly promising for rapid quantification of FA in such applications as clinical diagnostics and food analysis.

  14. Modeling and fabrication of lithium polymer ion batteries designed for wireless sensor network applications and printed directly on device

    Steingart, Daniel Artemis

    Microfabrication has enabled devices that were unimaginable just a century ago. The ability to create structured channels of metal and ceramic within the confines of half a micron took four decades to perfect but the reward has created cheap, reliable, and small computer devices, some of which communicate with no wires to the rest of the world. Conversely, electrochemical energy cells, or batteries, were well known to the scientific community one hundred years ago, and a 19th century chemist would be hard pressed to find a radical difference in the size, structure and performance of most batteries. While materials have been purified, and new chemistries have been implemented, modern batteries only offer, at most, an order of magnitude improvement in energy and power density over their original counter parts. Moore's "Law" [1] regarding integrated circuits only applies to semiconductor devices for a very simple reason: energy storage capacity is directly related to size. While transistor performance increases as size decreases, battery performance in terms of deliverable power and not. Though some performance gain can be made by modifying the battery chemistry or microstructure, more mass will always provide more capacity. With the advent of the "smart dust" class computers a critical point was reached. The devices became significantly smaller than the batteries required to do useful work, inspiring a new kind of battery, the microbattery, or a battery of a size of less than a few cubic millimeters and capable of delivering a continuous current of roughly 50 to 100 muA at 1 to 4 V. The pioneering microbatteries created by Bates [2] were promising in that they (1) used common microfabrication techniques and (2) were completely solid state. These cells are only now beginning to see commercialization, and are beset by a variety of problems. Though some are related to manufacturing control, others are inherent to the nature of the production processes. Sputtering and

  15. Ratios of partition functions for the log-gamma polymer

    Georgiou, Nicos; Rassoul-Agha, Firas; Seppalainen, Timo; Yilmaz, Atilla


    The Annals of Probability 2015, Vol. 43, No. 5, 2282–2331 DOI: 10.1214/14-AOP933 © Institute of Mathematical Statistics, 2015 RATIOS OF PARTITION FUNCTIONS FOR THE LOG-GAMMA POLYMER BY NICOS GEORGIOU1, FIRAS RASSOUL-AGHA1, TIMO SEPPÄLÄINEN2 AND ATILLA YILMAZ3 University of Sussex, University of Utah, University of Wisconsin–Madison and Bo˘gaziçi University We introduce a random walk in random environment associated to an underlying directed polymer model in 1 ...

  16. The sensitivity of random polymer brush-lamellar polystyrene-b-polymethylmethacrylate block copolymer systems to process conditions.

    Borah, Dipu; Rasappa, Sozaraj; Senthamaraikannan, Ramsankar; Shaw, Matthew T; Holmes, Justin D; Morris, Michael A


    The use of random copolymer brushes (polystyrene-r-polymethylmethacrylate--PS-r-PMMA) to 'neutralise' substrate surfaces and ordain perpendicular orientation of the microphase separated lamellae in symmetric polystyrene-b-polymethylmethacrylate (PS-b-PMMA) block copolymers (BCPs) is well known. However, less well known is how the brushes interact with both the substrate and the BCP, and how this might change during thermal processing. A detailed study of changes in these films for different brush and diblock PS-b-PMMA molecular weights is reported here. In general, self-assembly and pattern formation is altered little, and a range of brush molecular weights are seen to be effective. However, on extended anneal times, the microphase separated films can undergo dimension changes and loss of order. This process is not related to any complex microphase separation dynamics but rather a degradation of methacrylate components in the film. The data suggest that care must be taken in interpretation of structural changes in these systems as being due to BCP only effects.

  17. Parent-directed intervention for children with cancer-related neurobehavioral late effects: a randomized pilot study.

    Patel, Sunita K; Ross, Paula; Cuevas, Michelle; Turk, Anne; Kim, Heeyoung; Lo, Tracy T Y; Wong, Lennie F; Bhatia, Smita


    OBJECTIVE : To evaluate feasibility and preliminary efficacy of an intervention directed at parents of childhood cancer survivors (CCSs) with neurobehavioral late effects to improve targeted parenting skills, and thus to indirectly benefit the child's educational functioning.  METHODS : 44 CCSs and their parents were randomized. Intervention-arm parents participated in eight individual training sessions augmented by a 3-month telephone support period. Pre- and postparent measures and child performance on Wechsler Individual Achievement Test-II and School Motivation and Learning Strategies Inventory assessed intervention effects.  RESULTS : 90% of intervention parents completed the program with high adherence/perceived benefit. Between-group effect sizes ranged from d = 0.77 to d = 1.45 for parent knowledge, efficacy, frequency of pro-learning behaviors, and d = 0.21 to d = 0.76 for child academic scores. Parental time spent in intervention activities was associated with academic change.  CONCLUSIONS : A parent-directed intervention to indirectly promote academic functioning in CCSs appears feasible and effective in improving targeted parenting outcomes and for selected child academic outcomes.

  18. How to get an exact sample from a generic Markov chain and sample a random spanning tree from a directed graph, both within the cover time

    Wilson, D.B.; Propp, J.G.


    This paper shows how to obtain unbiased samples from an unknown Markov chain by observing it for O(T{sub c}) steps, where T{sub c} is the cover time. This algorithm improves on several previous algorithms, and there is a matching lower bound. Using the techniques from the sampling algorithm, we also show how to sample random directed spanning trees from a weighted directed graph, with arcs directed to a root, and probability proportional to the product of the edge weights. This tree sampling algorithm runs within 18 cover times of the associated random walk, and is more generally applicable than the algorithm of Broder and Aldous.

  19. A randomized, open-label clinical trial using optical coherence tomography to compare two sirolimus-eluting stents, one with a biodegradable polymer and the other with a permanent polymer.

    Tian, Feng; Chen, Yundai; Liu, Changfu; Jin, Qinhua; Chen, Lian; Sun, Zhijun; Liu, Hongbin; Guo, Jun; Gai, Luyue


    Intimal hyperplasia appears to differ after implanting a drug-eluting stent (DES) with a biodegradable or a permanent polymer. The aim of the present study was to compare biodegradable with permanent polymer DES, since the available data are limited. One hundred patients with de novo coronary artery stenosis were included in this study. The patients were classified into 2 groups: DES with a biodegradable polymer (n=50) and DES with a permanent polymer (n=50). Optical coherence tomography (OCT) examination was performed before and after stent implantation. A follow‑up OCT, performed 1 year after stent implantation, compared the morphologies of intimal hyperplasia in the 2 groups. The frequencies of uncovered stent struts (2.27 vs. 1.87%, P=0.145) and stent strut malapposition (1.9 vs. 2.02%, P=0.655) upon the first-year follow-up were not significantly different. Average neointimal thickness was lower in the biodegradable compared with the permanent polymer group (106.12±80.65 vs. 181.20±146.96 µm, Pbiodegradable compared with the permanent polymer group (62.1 vs. 35.9%, Pbiodegradable compared with the permanent polymer group (57.7±24.6 vs. 67.6±22.4 µm, Pbiodegradable polymer DES resulted in significantly lower intimal hyperplasia and had well-proportioned intimal coverage compared with permanent polymer DES.

  20. Gas adsorption/separation properties of metal directed self-assembly of two coordination polymers with 5-nitroisophthalate

    Arıcı, Mürsel [Department of Chemistry, Faculty of Arts and Sciences, Eskişehir Osmangazi University, 26480 Eskişehir (Turkey); Yeşilel, Okan Zafer, E-mail: [Department of Chemistry, Faculty of Arts and Sciences, Eskişehir Osmangazi University, 26480 Eskişehir (Turkey); Keskin, Seda [Department of Chemical and Biological Engineering, Koç University, İstanbul (Turkey); Şahin, Onur [Scientific and Technological Research Application and Research Center, Sinop University, 57010 Sinop (Turkey)


    Two new coordination polymers, namely, [Co(µ-nip)(µ-bpe)]{sub n} (1) and [Zn(µ-nip)(µ-bpe)]{sub n} (2) (nip: 5-nitroisophthalate, bpe: 1,2-bis(4-pyridyl)ethane) were hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction, IR spectroscopy, elemental analysis and thermal analysis. Moreover, atomically detailed simulation studies of complex 2 for CO{sub 2}/CH{sub 4} adsorption and separation were performed. Complex 1 consists of two dimensional (2D) (4,4) grid networks with the point symbol of 4{sup 4}.6{sup 2}. Complex 2 exhibits a 3-fold interpenetrating 3D framework with 6{sup 5}.8-dmp topology. Thermal properties of the complexes showed that both complexes were stable over 320 °C. Simulation studies demonstrated that complex 2 can separate CO{sub 2} from CH{sub 4} at low pressures at 273 K. - Graphical abstract: In this study, two new coordination polymers, namely, [Co(µ-nip)(µ-bpe)]{sub n} (1) and [Zn(µ-nip)(µ-bpe)]{sub n} (2) (nip: 5-nitroisophthalate, bpe: 1,2-bis(4-pyridyl)ethane) were hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction, IR spectroscopy, elemental analysis and thermal analysis. Moreover, atomically detailed simulation studies of complex 2 for CO{sub 2}/CH{sub 4} adsorption and separation were performed. Complex 1 consists of two dimensional (2D) (4,4) grid networks with the point symbol of 4{sup 4}.6{sup 2}. Complex 2 exhibits a 3-fold interpenetrating 3D framework with 6{sup 5}.8-dmp topology. Simulation studies demonstrated that complex 2 can separate CO{sub 2} from CH{sub 4} at low pressures at 273 K. Display Omitted - Highlights: • Two new coordination polymers with 5-nitroisophthalate and 1,2-bis(4-pyridyl)ethane. • Atomically detailed simulation studies of the complexes. • Complex 2 can be proposed as molecular sieve to separate CO{sub 2} from CH{sub 4} at low pressures.

  1. Reactive polymer fused deposition manufacturing

    Kunc, Vlastimil; Rios, Orlando; Love, Lonnie J.; Duty, Chad E.; Johs, Alexander


    Methods and compositions for additive manufacturing that include reactive or thermosetting polymers, such as urethanes and epoxies. The polymers are melted, partially cross-linked prior to the depositing, deposited to form a component object, solidified, and fully cross-linked. These polymers form networks of chemical bonds that span the deposited layers. Application of a directional electromagnetic field can be applied to aromatic polymers after deposition to align the polymers for improved bonding between the deposited layers.

  2. Direct-Access Online Care for the Management of Atopic Dermatitis: A Randomized Clinical Trial Examining Patient Quality of Life.

    Kornmehl, Heather; Singh, Sanminder; Johnson, Mary Ann; Armstrong, April W


    Atopic dermatitis (AD) is a chronic disease requiring regular follow-up. To increase access to dermatological care, online management of AD is being studied. However, a critical knowledge gap exists in determining AD patients' quality of life in direct-to-patient online models. In this study, we examined quality of life in AD patients managed through a direct-access online model. We randomized 156 patients to receiving care through a direct-access online platform or in person. Patients were seen for six visits over 12 months. At each visit, the patients completed Dermatology Life Quality Index/Children's Dermatology Life Quality Index (DLQI/CDLQI), and Short Form (SF-12). Between baseline and 12 months, the mean (standard deviation, SD) within-group difference in DLQI score in the online group was 4.1 (±2.3); for the in-person group, the within-group difference was 4.8 (±2.7). The mean (SD) within-group difference in CDLQI score in the online group was 4.7 (±2.8); for the in-person group, the within-group difference was 4.9 (±3.1). The mean (SD) within-group difference in physical component score (PCS) and mental component score (MCS) SF-12 scores in the online group was 6.5 (±3.8) and 8.6 (±4.3); for the in-person group, it was 6.8 (±3.2) and 9.1(±3.8), respectively. The difference in the change in DLQI, CDLQI, SF-12 PCS, and SF-12 MCS scores between the two groups was 0.72 (95% confidence interval [90% CI], -0.97 to 2.41), 0.23 (90% CI, -2.21 to 2.67), 0.34 (90% CI, -1.16 to 1.84), and 0.51 (90% CI, -1.11 to 2.13), respectively. All differences were contained within their equivalence margins. Adult and pediatric AD patients receiving direct-access online care had equivalent quality of life outcomes as those see in person. The direct-access online model has the potential to increase access to care for patients with chronic skin diseases.

  3. Polymer membrane based electrolytic cell and process for the direct generation of hydrogen peroxide in liquid streams

    White, James H. (Inventor); Schwartz, Michael (Inventor); Sammells, Anthony F. (Inventor)


    An electrolytic cell for generating hydrogen peroxide is provided including a cathode containing a catalyst for the reduction of oxygen, and an anode containing a catalyst for the oxidation of water. A polymer membrane, semipermeable to either protons or hydroxide ions is also included and has a first face interfacing to the cathode and a second face interfacing to the anode so that when a stream of water containing dissolved oxygen or oxygen bubbles is passed over the cathode and a stream of water is passed over the anode, and an electric current is passed between the anode and the cathode, hydrogen peroxide is generated at the cathode and oxygen is generated at the anode.

  4. SiC fibers with controllable thickness of carbon layer prepared directly by preceramic polymer pyrolysis routes

    Hu Tianjiao, E-mail: [College of Science, National University of Defense Technology, Changsha 410073 (China); Li Xiaodong; Li Gongyi [College of Science, National University of Defense Technology, Changsha 410073 (China); Wang Yingde; Wang Jun [State Key Laboratory of Advanced Ceramic Fibers and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, Changsha 410073 (China)


    Continuous SiC fibers with different thickness of carbon layer were prepared through three preceramic polymer pyrolysis routes. To make the carbon layer thickness controllable, a simple improvement by using a ceramic bushing was adopted to retard the deposition of the pyrolytic carbons. Auger electron spectroscopy (AES) analysis reveals that the carbon layer thickness varies from less than 5 nm to 40 nm. The specific resistivity of the fibers increases by 5 orders of magnitude as the carbon layer thickness decreases. All of the fibers exhibit a tensile strength of around 1.8 GPa which is independent of the carbon layer thickness. The formation process of the carbon layer is discussed in three steps: the decomposition, the carbonization and the deposition. The as-received fibers have a potential application as the reinforcement of functional materials.

  5. Fabrication of composite polymer foam films at the liquid/liquid interface through emulsion-directed assembly and adsorption processes.

    Geng, Yuanyuan; Liu, Mei; Tong, Kun; Xu, Jian; Lee, Yong-Ill; Hao, Jingcheng; Liu, Hong-Guo


    The foam films of polystyrene-b-poly(acrylic acid)-b-polystyrene (PS-b-PAA-b-PS) doped with Cd(II) or Pb(II) species were fabricated at the planar liquid/liquid interfaces between a DMF/chloroform (v/v: 1/1) solution of the polymer and aqueous solutions containing cadmium acetate or lead acetate at ambient temperature. Optical microscopic observation shows the thin film is uniform on a larger length scale. Transmission electron microscopic (TEM) investigations reveal that the foam films are made up of microcapsules with the size of several hundreds of nanometers to micrometers. The walls of the microcapsules have a layered structure decorating with nanofibers and hollow nanospheres, where numerous inorganic fine nanoparticles are dispersed homogeneously. The film formation is a result of emulsion droplet-templated assembly and adsorption of the formed microcapsules at the planar liquid/liquid interface. Because of the miscibility of DMF with chloroform and water, DMF migrates to the aqueous phase while water migrates to the organic phase across the interface, resulting in the formation of a W/O emulsion, as revealed by optical microscopic observation, freeze fracture transmission electron microscopic (FF-TEM) observation, and dynamic laser scattering (DLS) investigation. The triblock copolymer molecules and the inorganic species adsorb and self-assemble around the emulsion drops, leading to the formation of the composite microcapsules. X-ray photoelectron spectroscopic (XPS) and FTIR spectroscopic results indicate that two kinds of Cd(II) or Pb(II) species, metal oxide or hydroxide, resulting from the hydrolysis of the metal ions and the coordinated metal ions to the carboxyl groups coexist in the formed thin films, which transform to metal sulfide completely after treating with hydrogen sulfide to get metal sulfide nanoparticle-doped polymer thin films.

  6. A Randomized, Double-Blind, Sham-Controlled Trial of Transcranial Direct Current Stimulation in Attention-Deficit/Hyperactivity Disorder.

    Camila Cosmo

    Full Text Available Current standardized treatments for cognitive impairment in attention-deficit/hyperactivity disorder remain limited and their efficacy restricted. Transcranial direct current stimulation (tDCS is a promising tool for enhancing cognitive performance in several neuropsychiatric disorders. Nevertheless, the effects of tDCS in reducing cognitive impairment in patients with attention-deficit/hyperactivity disorder (ADHD have not yet been investigated.A parallel, randomized, double-blind, sham-controlled trial was conducted to examine the efficacy of tDCS on the modulation of inhibitory control in adults with ADHD. Thirty patients were randomly allocated to each group and performed a go/no-go task before and after a single session of either anodal stimulation (1 mA over the left dorsolateral prefrontal cortex or sham stimulation.A nonparametric two-sample Wilcoxon rank-sum (Mann-Whitney test revealed no significant differences between the two groups of individuals with ADHD (tDCS vs. sham in regard to behavioral performance in the go/no go tasks. Furthermore, the effect sizes of group differences after treatment for the primary outcome measures-correct responses, impulsivity and omission errors--were small. No adverse events resulting from stimulation were reported.According to these findings, there is no evidence in support of the use of anodal stimulation over the left dorsolateral prefrontal cortex as an approach for improving inhibitory control in ADHD patients. To the best of our knowledge, this is the first clinical study to assess the cognitive effects of tDCS in individuals with ADHD. Further research is needed to assess the clinical efficacy of tDCS in this NCT01968512.

  7. People-centered tuberculosis care versus standard directly observed therapy: study protocol for a cluster randomized controlled trial.

    Khachadourian, Vahe; Truzyan, Nune; Harutyunyan, Arusyak; Thompson, Michael E; Harutyunyan, Tsovinar; Petrosyan, Varduhi


    Tuberculosis is a major public health concern resulting in high rates of morbidity and mortality worldwide, particularly in low- and middle-income countries. Tuberculosis requires a long and intensive course of treatment. Thus, various approaches, including patient empowerment, education and counselling sessions, and involvement of family members and community workers, have been suggested for improving treatment adherence and outcome. The current randomized controlled trial aims to evaluate the effectiveness over usual care of an innovative multicomponent people-centered tuberculosis-care strategy in Armenia. Innovative Approach to Tuberculosis care in Armenia is an open-label, stratified cluster randomized controlled trial with two parallel arms. Tuberculosis outpatient centers are the clusters assigned to intervention and control arms. Drug-sensitive tuberculosis patients in the continuation phase of treatment in the intervention arm and their family members participate in a short educational and counselling session to raise their knowledge, decrease tuberculosis-related stigma, and enhance treatment adherence. Patients receive the required medications for one week during the weekly visits to the tuberculosis outpatient centers. Additionally, patients receive daily Short Message Service (SMS) reminders to take their medications and daily phone calls to assure adherence and monitoring of treatment potential side effects. Control-arm patients follow the World Health Organization--recommended directly observed treatment strategy, including daily visits to tuberculosis outpatient centers for drug-intake. The primary outcome is physician-reported treatment outcome. Patients' knowledge, depression, quality of life, within-family tuberculosis-related stigma, family social support, and self-reported adherence to tuberculosis treatment are secondary outcomes. Improved adherence and tuberculosis treatment outcomes can strengthen tuberculosis control and thereby forestall

  8. Polymer films

    Granick, Steve; Sukhishvili, Svetlana A.


    A film contains a first polymer having a plurality of hydrogen bond donating moieties, and a second polymer having a plurality of hydrogen bond accepting moieties. The second polymer is hydrogen bonded to the first polymer.

  9. Polymer films

    Granick, Steve; Sukhishvili, Svetlana A.


    A film contains a first polymer having a plurality of hydrogen bond donating moieties, and a second polymer having a plurality of hydrogen bond accepting moieties. The second polymer is hydrogen bonded to the first polymer.

  10. Catalysts from synthetic genetic polymers.

    Taylor, Alexander I; Pinheiro, Vitor B; Smola, Matthew J; Morgunov, Alexey S; Peak-Chew, Sew; Cozens, Christopher; Weeks, Kevin M; Herdewijn, Piet; Holliger, Philipp


    The emergence of catalysis in early genetic polymers such as RNA is considered a key transition in the origin of life, pre-dating the appearance of protein enzymes. DNA also demonstrates the capacity to fold into three-dimensional structures and form catalysts in vitro. However, to what degree these natural biopolymers comprise functionally privileged chemical scaffolds for folding or the evolution of catalysis is not known. The ability of synthetic genetic polymers (XNAs) with alternative backbone chemistries not found in nature to fold into defined structures and bind ligands raises the possibility that these too might be capable of forming catalysts (XNAzymes). Here we report the discovery of such XNAzymes, elaborated in four different chemistries (arabino nucleic acids, ANA; 2'-fluoroarabino nucleic acids, FANA; hexitol nucleic acids, HNA; and cyclohexene nucleic acids, CeNA) directly from random XNA oligomer pools, exhibiting in trans RNA endonuclease and ligase activities. We also describe an XNA-XNA ligase metalloenzyme in the FANA framework, establishing catalysis in an entirely synthetic system and enabling the synthesis of FANA oligomers and an active RNA endonuclease FANAzyme from its constituent parts. These results extend catalysis beyond biopolymers and establish technologies for the discovery of catalysts in a wide range of polymer scaffolds not found in nature. Evolution of catalysis independent of any natural polymer has implications for the definition of chemical boundary conditions for the emergence of life on Earth and elsewhere in the Universe.

  11. Secondary ligand-directed assembly of Co(II) coordination polymers based on a pyridine carboxylate ligand

    Cao, Ke-Li; Zhang, Yi-Ping; Cai, Yi-Ni; Xu, Xiao-Wei; Feng, Yun-Long, E-mail:


    To investigate the influence of hydrogen bonds and secondary ligands on the structures and properties of the resulting frameworks, five new Co(II) compounds have been synthesized by the reactions of Co(II) salts and 3,5-bis(pyridin-4-ylmethoxy)benzoic acid (HL) with four rationally selected dicarboxylic acid ligands. Without secondary ligand, we got one compound [CoL{sub 2}(H{sub 2}O){sub 2}]{sub n}·2nH{sub 2}O (1), which possesses a 1D chain structure. In the presence of ancillary ligands, namely, 1,3-adamantanedicarboxylic acid (H{sub 2}adbc), terephthalic acid (H{sub 2}tpa), thiophene-2,5-dicarboxylic acid (H{sub 2}tdc) and 1,4-benzenedithioacetic acid (H{sub 2}bdtc), four 3D structures [Co{sub 2}L{sub 2}(adbc)]{sub n}·nH{sub 2}O (2), [Co{sub 2}L{sub 2}(tpa)]{sub n} (3), [Co{sub 2}L{sub 2}(tdc)]{sub n} (4), [Co{sub 2}L{sub 2}(bdtc)(H{sub 2}O)]{sub n} (5) were obtained, respectively. It can be observed from the architectures of 1–5 that hydrogen bonds and secondary ligands both have great effects on the spatial connective fashions, resulting in the formation of various dimensional compounds. The XRPD, TGA data of title polymers and the magnetic properties for 2 and 5 have also been investigated. - Graphical abstract: The structural differences show that the ancillary ligands have great effects on the spatial connective fashions, resulting in the formation of various dimensional compounds. - Highlights: • Five new Co(II) coordination polymers have been synthesized by solvothermal reactions based on 3,5-bis(pyridin-4-ylmethoxy)benzoic acid (HL). • The long-flexible ligand (HL) is a good candidate to produce interpenetrating architectures. • The secondary dicarboxylic acid ligands play important roles in the spatial connective fashions and the formation of various dimensional compounds. • The magnetism studies show that both 2 and 5 exhibit antiferromagnetic interactions.

  12. Reduction of chronic abdominal pain in patients with inflammatory bowel disease through transcranial direct current stimulation: a randomized controlled trial.

    Volz, Magdalena S; Farmer, Annabelle; Siegmund, Britta


    Inflammatory bowel disease (IBD) is frequently associated with chronic abdominal pain (CAP). Transcranial direct current stimulation (tDCS) has been proven to reduce chronic pain. This study aimed to investigate the effects of tDCS in patients with CAP due to IBD. This randomized, sham-controlled, double blind, parallel-designed study included 20 patients with either Crohn disease or ulcerative colitis with CAP (≥3/10 on the visual analog scale (VAS) in 3/6 months). Anodal or sham tDCS was applied over the primary motor cortex for 5 consecutive days (2 mA, 20 minutes). Assessments included VAS, pressure pain threshold, inflammatory markers, and questionnaires on quality of life, functional and disease specific symptoms (Irritable Bowel Syndrome-Severity Scoring System [IBS-SSS]), disease activity, and pain catastrophizing. Follow-up data were collected 1 week after the end of the stimulation. Statistical analyses were performed using analysis of variance and t tests. There was a significant reduction of abdominal pain in the anodal tDCS group compared with sham tDCS. This effect was evident in changes in VAS and pressure pain threshold on the left and right sides of the abdomen. In addition, 1 week after stimulation, pain reduction remained significantly decreased in the right side of the abdomen. There was also a significant reduction in scores on pain catastrophizing and on IBS-SSS when comparing both groups. Inflammatory markers and disease activity did not differ significantly between groups throughout the experiment. Transcranial direct current stimulation proved to be an effective and clinically relevant therapeutic strategy for CAP in IBD. The analgesic effects observed are unrelated to inflammation and disease activity, which emphasizes central pain mechanisms in CAP.

  13. Turbulent drag reduction by polymers

    Bonn, Daniel [Van der Waals-Zeeman Instituut, University of Amsterdam, Valckenierstraat 65 1018, XE Amsterdam (Netherlands); Amarouchene, Yacine [CPMOH, Universite Bordeaux 1, 351 Cours de la Liberation, 33405 Talence cedex (France); Wagner, Christian [Institut fuer Experimentalphysik, Universitaet des Saarlandes, Saarbruecken (Germany); Douady, Stephane [Laboratoire de Physique Statistique de l' ENS, 24 rue Lhomond, 75231 Paris cedex 05 (France); Cadot, Olivier [ENSTA, Chemin de la Huniere, 91761 Palaiseau cedex (France)


    The reduction of turbulent energy dissipation by addition of polymers is studied experimentally. We first address the question of where the action of the polymers is taking place. Subsequently, we show that there is a direct correlation of drag reduction with the elongational viscosity of the polymers. For this, the reduction of turbulent energy dissipation by addition of the biopolymer DNA is studied. These results open the way for a direct visualization study of the polymer conformation in a turbulent boundary layer.

  14. Polymer physics

    Gedde, Ulf W


    This book is the result of my teaching efforts during the last ten years at the Royal Institute of Technology. The purpose is to present the subject of polymer physics for undergraduate and graduate students, to focus the fundamental aspects of the subject and to show the link between experiments and theory. The intention is not to present a compilation of the currently available literature on the subject. Very few reference citations have thus been made. Each chapter has essentially the same structure: starling with an introduction, continuing with the actual subject, summarizing the chapter in 30D-500 words, and finally presenting problems and a list of relevant references for the reader. The solutions to the problems presented in Chapters 1-12 are given in Chapter 13. The theme of the book is essentially polymer science, with the exclusion of that part dealing directly with chemical reactions. The fundamentals in polymer science, including some basic polymer chemistry, are presented as an introduction in t...

  15. Direct oral anticoagulants in atrial fibrillation: can data from randomized clinical trials be safely transferred to the general population? No.

    Marietta, Marco


    Direct oral anticoagulants (DOAC) represent an innovative and relevant treatment for the prevention of cardiac embolism in patients with atrial fibrillation (AF). Their introduction has been followed by an ample debate on their appropriate use, considering that they can offer an effective treatment for the many patients with AF, which are not taking any effective anticoagulant treatment, even though they have a substantial thromboembolic risk (1). On the other hand, DOAC are much less tested in everyday clinical practice and much more expensive than anti-vitamin k anticoagulants (AVKs). Starting from the quite favorable results of the available randomized controlled trials (RCTs)--showing that DOAC are at least non-inferior to AVK and that may be even better for some outcomes--this article discusses their transferability to the majority of AF patients. In summary, the body of evidence supports the efficacy and safety of DOAC in patients carrying demographic and clinical characteristics similar to subjects included in RCT, but their use in less well-characterized subpopulations requires particular caution, while waiting for more reliable data from the real world.

  16. Visual presentations of efficacy data in direct-to-consumer prescription drug print and television advertisements: A randomized study.

    Sullivan, Helen W; O'Donoghue, Amie C; Aikin, Kathryn J; Chowdhury, Dhuly; Moultrie, Rebecca R; Rupert, Douglas J


    To determine whether visual aids help people recall quantitative efficacy information in direct-to-consumer (DTC) prescription drug advertisements, and if so, which types of visual aids are most helpful. Individuals diagnosed with high cholesterol (n=2504) were randomized to view a fictional DTC print or television advertisement with no visual aid or one of four visual aids (pie chart, bar chart, table, or pictograph) depicting drug efficacy. We measured drug efficacy and risk recall, drug perceptions and attitudes, and behavioral intentions. For print advertisements, a bar chart or table, compared with no visual aid, elicited more accurate drug efficacy recall. The bar chart was better at this than the pictograph and the table was better than the pie chart. For television advertisements, any visual aid, compared with no visual aid, elicited more accurate drug efficacy recall. The bar chart was better at this than the pictograph or the table. Visual aids depicting quantitative efficacy information in DTC print and television advertisements increased drug efficacy recall, which may help people make informed decisions about prescription drugs. Adding visual aids to DTC advertising may increase the public's knowledge of how well prescription drugs work. Published by Elsevier Ireland Ltd.

  17. Enhancement of couples' communication and dyadic coping by a self-directed approach: a randomized controlled trial.

    Bodenmann, Guy; Hilpert, Peter; Nussbeck, Fridtjof W; Bradbury, Thomas N


    Although prevention of relationship distress and dissolution has potential to strengthen the well-being of partners and any children they are raising, dissemination of prevention programs can be limited because couples face many barriers to in-person participation. An alternative strategy, providing couples with an instructional DVD, is tested in the present study, in which 330 Caucasian couples (N = 660 participants; mean age: men 41.4 years, women 40.0 years) were randomly assigned to a DVD group without any further support, a DVD group with technical telephone coaching, or a wait-list control group. Couples completed questionnaires at pretest, posttest, and 3 and 6 months after completion of the intervention. Self-report measures of dyadic coping, communication quality, ineffective arguing, and relationship satisfaction were used to test whether the intervention groups improved in comparison with the control group. Women in both intervention groups increased in dyadic coping, reduced conflict behavior, and were more satisfied with their relationship 6 months after the intervention. Effects for men were mixed. Participants with poorer skills reported stronger improvement. Intimate relationships can, within limits, be positively influenced by a self-directed approach. Effective dissemination of principles underlying successful relationships can be facilitated through the use of emerging low-cost tools and technologies.

  18. Direct replacement of antibodies with molecularly imprinted polymer nanoparticles in ELISA--development of a novel assay for vancomycin.

    Chianella, Iva; Guerreiro, Antonio; Moczko, Ewa; Caygill, J Sarah; Piletska, Elena V; De Vargas Sansalvador, Isabel M Perez; Whitcombe, Michael J; Piletsky, Sergey A


    A simple and straightforward technique for coating microplate wells with molecularly imprinted polymer nanoparticles (nanoMIPs) to develop assays similar to the enzyme-linked immunosorbent assay (ELISA) is presented here for the first time. NanoMIPs were synthesized by a solid-phase approach with an immobilized vancomycin (template) and characterized using Biacore 3000, dynamic light scattering, and electron microscopy. Immobilization, blocking, and washing conditions were optimized in microplate format. The detection of vancomycin was achieved in competitive binding experiments with a horseradish peroxidase-vancomycin conjugate. The assay was capable of measuring vancomycin in buffer and in blood plasma within the range of 0.001-70 nM with a detection limit of 0.0025 nM (2.5 pM). The sensitivity of the assay was 3 orders of magnitude better than a previously described ELISA based on antibodies. In these experiments, nanoMIPs have shown high affinity and minimal interference from blood plasma components. Immobilized nanoMIPs were stored for 1 month at room temperature without any detrimental effects to their binding properties. The high affinity of nanoMIPs and the lack of a requirement for cold chain logistics make them an attractive alternative to traditional antibodies used in ELISA.

  19. Genetically encoded synthesis of protein-based polymers with precisely specified molecular weight and sequence by recursive directional ligation: examples from the elastin-like polypeptide system.

    Meyer, Dan E; Chilkoti, Ashutosh


    We report a new strategy for the synthesis of genes encoding repetitive, protein-based polymers of specified sequence, chain length, and architecture. In this stepwise approach, which we term "recursive directional ligation" (RDL), short gene segments are seamlessly combined in tandem using recombinant DNA techniques. The resulting larger genes can then be recursively combined until a gene of a desired length is obtained. This approach is modular and can be used to combine genes encoding different polypeptide sequences. We used this method to synthesize three different libraries of elastin-like polypeptides (ELPs); each library encodes a unique ELP sequence with systematically varied molecular weights. We also combined two of these sequences to produce a block copolymer. Because the thermal properties of ELPs depend on their sequence and chain length, the synthesis of these polypeptides provides an example of the importance of precise control over these parameters that is afforded by RDL.

  20. Encapsulation of Polymer Colloids in a Sol-Gel Matrix. Direct-Writing of Coassembling Organic-Inorganic Hybrid Photonic Crystals.

    Mikosch, Annabel; Kuehne, Alexander J C


    The spontaneous self-assembly of polymer colloids into ordered arrangements provides a facile strategy for the creation of photonic crystals. However, these structures often suffer from defects and insufficient cohesion, which result in flaking and delamination from the substrate. A coassembly process has been developed for convective assembly, resulting in large-area encapsulated colloidal crystals. However, to generate patterns or discrete deposits in designated places, convective assembly is not suitable. Here we experimentally develop conditions for direct-writing of coassembling monodisperse dye-doped polystyrene particles with a sol-gel precursor to form solid encapsulated photonic crystals. In a simple procedure the colloids are formulated in a sol-gel precursor solution, drop-cast on a flat substrate, and dried. We here establish the optimal parameters to form reproducible highly ordered photonic crystals with good optical performance. The obtained photonic crystals interact with light in the visible spectrum with a narrow optical stop-gap.

  1. Direct modification of hydrogen/deuterium-terminated diamond particles with polymers to form reversed and strong cation exchange solid phase extraction sorbents.

    Yang, Li; Jensen, David S; Vail, Michael A; Dadson, Andrew; Linford, Matthew R


    We describe direct polymer attachment to hydrogen and deuterium-terminated diamond (HTD and DTD) surfaces using a radical initiator (di-tert-amyl peroxide, DTAP), a reactive monomer (styrene) and a crosslinking agent (divinylbenzene, DVB) to create polystyrene encapsulated diamond. Chemisorbed polystyrene is sulfonated with sulfuric acid in acetic acid. Surface changes were followed by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and diffuse reflectance Fourier transform infrared spectroscopy (DRIFT). Finally, both polystyrene-modified DTD and sulfonated styrene-modified DTD were used in solid phase extraction (SPE). Percent recovery and column capacity were investigated for both phenyl (polystyrene) and sulfonic acid treated polystyrene SPE columns. These diamond-based SPE supports are stable under basic conditions, which is not the case for silica-based SPE supports.

  2. Causal relationship between obesity and vitamin D status: bi-directional Mendelian randomization analysis of multiple cohorts.

    Karani S Vimaleswaran

    Full Text Available Obesity is associated with vitamin D deficiency, and both are areas of active public health concern. We explored the causality and direction of the relationship between body mass index (BMI and 25-hydroxyvitamin D [25(OHD] using genetic markers as instrumental variables (IVs in bi-directional Mendelian randomization (MR analysis.We used information from 21 adult cohorts (up to 42,024 participants with 12 BMI-related SNPs (combined in an allelic score to produce an instrument for BMI and four SNPs associated with 25(OHD (combined in two allelic scores, separately for genes encoding its synthesis or metabolism as an instrument for vitamin D. Regression estimates for the IVs (allele scores were generated within-study and pooled by meta-analysis to generate summary effects. Associations between vitamin D scores and BMI were confirmed in the Genetic Investigation of Anthropometric Traits (GIANT consortium (n = 123,864. Each 1 kg/m(2 higher BMI was associated with 1.15% lower 25(OHD (p = 6.52×10⁻²⁷. The BMI allele score was associated both with BMI (p = 6.30×10⁻⁶² and 25(OHD (-0.06% [95% CI -0.10 to -0.02], p = 0.004 in the cohorts that underwent meta-analysis. The two vitamin D allele scores were strongly associated with 25(OHD (p≤8.07×10⁻⁵⁷ for both scores but not with BMI (synthesis score, p = 0.88; metabolism score, p = 0.08 in the meta-analysis. A 10% higher genetically instrumented BMI was associated with 4.2% lower 25(OHD concentrations (IV ratio: -4.2 [95% CI -7.1 to -1.3], p = 0.005. No association was seen for genetically instrumented 25(OHD with BMI, a finding that was confirmed using data from the GIANT consortium (p≥0.57 for both vitamin D scores.On the basis of a bi-directional genetic approach that limits confounding, our study suggests that a higher BMI leads to lower 25(OHD, while any effects of lower 25(OHD increasing BMI are likely to be small. Population level interventions to

  3. The effects of a psychological intervention directed at optimizing immune function: study protocol for a randomized controlled trial.

    Schakel, Lemmy; Veldhuijzen, Dieuwke S; van Middendorp, Henriët; Prins, Corine; Joosten, Simone A; Ottenhoff, Tom H M; Visser, Leo G; Evers, Andrea W M


    Previous research has provided evidence for the link between psychological processes and psychophysiological health outcomes. Psychological interventions, such as face-to-face or online cognitive behavioral therapy (CBT) and serious games aimed at improving health, have shown promising results in promoting health outcomes. Few studies so far, however, have examined whether Internet-based CBT combined with serious gaming elements is effective in modulating health outcomes. Moreover, studies often did not incorporate psychophysiological or immunological challenges in order to gain insight into physiological responses to real-life challenges after psychological interventions. The overall aim of this study is to investigate the effects of a psychological intervention on self-reported and physiological health outcomes in response to immune and psychophysiological challenges. In a randomized controlled trial, 60 healthy men are randomly assigned to either an experimental condition, receiving guided Internet-based (e-health) CBT combined with health-related serious gaming elements for 6 weeks, or a control condition receiving no intervention. After the psychological intervention, self-reported vitality is measured, and participants are given an immunological challenge in the form of a Mycobacterium bovis Bacillus Calmette-Guérin (BCG) vaccination. One day after the vaccination, participants are asked to perform several psychophysiological tasks in order to explore the effects of the psychological intervention on participants' stress response following the immune challenge. To assess the delayed effects of vaccination on self-reported and physiological health outcomes, a follow-up visit is planned 4 weeks later. Total study duration is approximately 14 weeks. The primary outcome measure is self-reported vitality measured directly after the intervention. Secondary outcome measures include inflammatory and endocrine markers, as well as psychophysiological measures of

  4. Adherence and success in long-term weight loss diets: the dietary intervention randomized controlled trial (DIRECT).

    Greenberg, Ilana; Stampfer, Meir J; Schwarzfuchs, Dan; Shai, Iris


    Data are limited as to whether participants in diet trials truly adhere to their assigned diet and the factors that affect their adherence. We evaluated success and adherence in a two-year dietary intervention randomized controlled trial (DIRECT) in which 322 moderately obese participants (mean age 52 yrs, mean body-mass-index (BMI) 31 kg/m(2), 86% men) were randomized to one of three groups: low-fat, Mediterranean, or low-carbohydrate diets. Overall compliance at month-24 was 85%, with 90% in low-fat, 85% in Mediterranean, and 78% in low-carbohydrate diet (p = .042 between groups). Attrition was higher in women (29% vs. 14% men, p = .001) and current smokers (25% vs. 14% among maintainers, p = 0.04). In a multivariate model, independent predictors of dropping-out were: higher baseline BMI (OR = 1.11; CI: 1.03-1.21) and less weight loss at month-6 (OR = 1.20; CI: 1.1-1.3). In a multivariate model, greater weight loss achieved at month-6 was the main predictor associated with success in weight loss (> 5%) over 2 years (OR = 1.5; CI: 1.35-1.67). Self-reported complete adherence score to diet was greater on low-carbohydrate diet (p low-fat) until month-6, but dropped overall from 81% at month-1 to 57% at month-24. Holidays were a trigger to a significant decrease in adherence followed by a partial rebound. Changes in diet composition from month-1 to month-12 were more pronounced in the multi-stage low-carbohydrate diet-group (p < .05). Generally, the most irresistible restricted food items were cookies (45% of dieters) and fruits (30%). Among the physically active (n = 107), 44% reported a tendency to eat less after exercising compared to 10% who tended to eat more. Initial 6-month reduction in weight is the main predictor of both long-term retention and success in weight loss. Special attention is needed for women, current smokers, and during holidays. Physical activity is associated with subsequent reduction in energy intake.

  5. A Randomized Double-Blind Sham-Controlled Study of Transcranial Direct Current Stimulation for Treatment-Resistant Major Depression

    Daniel eBlumberger


    Full Text Available Objectives: Transcranial direct current stimulation (tDCS has demonstrated some efficacy in treatment-resistant major depression (TRD. The majority of previous controlled studies have used anodal stimulation to the left dorsolateral prefrontal cortex (DLPFC and a control location such as the supraorbital region on for the cathode. Several open label studies have suggested effectiveness from anodal stimulation to the left DLPFC combined with cathodal stimulation to the right DLPFC. Thus, this study evaluated the efficacy of tDCS using anodal stimulation to the left DLPFC and cathodal stimulation to the right DLPFC compared to sham tDCS. Methods: Subjects between the ages of 18 and 65 were recruited from a tertiary care university hospital. Twenty-four subjects with TRD and a 17-item Hamilton Depression Rating Scale (HDRS greater than 21 were randomized to receive tDCS or sham tDCS. The rates of remission were compared between the two treatment groups.Results: The remission rates did not differ significantly between the two groups using an intention to treat analysis. More subjects in the active tDCS group had failed a course of electroconvulsive therapy in the current depressive episode. Side effects did not differ between the two groups and in general the treatment was very well tolerated. Conclusion: Anodal stimulation to the left DLPFC and cathodal stimulation to the right DLPFC was not efficacious in TRD. However, a number of methodological limitations warrant caution in generalizing from this study. Ongoing, controlled studies should provide further clarification on the efficacy of this stimulation configuration in TRD.

  6. Goal-directed intraoperative fluid therapy guided by stroke volume and its variation in high-risk surgical patients : a prospective randomized multicentre study

    Scheeren, Thomas W. L.; Wiesenack, Christoph; Gerlach, Herwig; Marx, Gernot


    Perioperative hemodynamic optimisation improves postoperative outcome for patients undergoing high-risk surgery (HRS). In this prospective randomized multicentre study we studied the effects of an individualized, goal-directed fluid management based on continuous stroke volume variation (SVV) and st

  7. Machinability study of Carbon Fiber Reinforced Polymer in the longitudinal and transverse direction and optimization of process parameters using PSO–GSA

    K. Shunmugesh


    Full Text Available Carbon Fiber Reinforced Polymer (CFRP composites are widely used in aerospace industry in lieu of its high strength to weight ratio. This study is an attempt to evaluate the machinability of Bi-Directional Carbon Fiber–Epoxy composite and optimize the process parameters of cutting speed, feed rate and drill tool material. Machining trials were carried using drill bits made of high speed steel, TiN and TiAlN at different cutting speeds and feed rates. Output parameters of thrust force and torque were monitored using Kistler multicomponent dynamometer 9257B and vibrations occurring during machining normal to the work surface were measured by a vibration sensor (Dytran 3055B. Linear regression analysis was carried out by using Response Surface Methodology (RSM, to correlate the input and output parameters in drilling of the composite in the longitudinal and transverse directions. The optimization of process parameters were attempted using Genetic Algorithm (GA and Particle Swarm Optimization–Gravitational Search Algorithm (PSO–GSA techniques.

  8. Hybrid nanoparticle architecture for cellular uptake and bioimaging: direct crystallization of a polymer immobilized with magnetic nanoparticles on carbon nanotubes.

    Depan, D; Misra, R D K


    We describe here the success of an innovative approach of direct immobilization of magnetic nanoparticles (MNPs) onto carbon nanotubes (CNTs). The approach involved functionalization of magnetic nanoparticles and consequent covalent linkage to a copolymer (PE-b-PEG). Next, the immobilized magnetic nanoparticles on the copolymer were directly crystallized on the long axis of CNTs, where the interfacial adhesion comes from electrostatic and van der Waals interaction. The intracellular trafficking of a hybrid nanoparticle system [(PE-b-PEG)-MNP-CNT-FITC] in HeLa cells was monitored using a fluorescent marker, FITC, conjugated to the nanoparticle system. The distribution of the nanoparticle system inside cells was studied by fluorescence microscopy in a time and dose dependent manner, and it was observed that the nanoparticles are located in the cytoplasm and no apparent cell death was observed at the concentration studied. Also, the effect of an externally applied magnetic field on actin cytoskeleton, cell morphology and intracellular uptake of iron was studied. The approach described here is promising for simultaneous imaging and monitoring intracellular uptake.

  9. CO2 -Responsive polymers.

    Lin, Shaojian; Theato, Patrick


    This Review focuses on the recent progress in the area of CO2 -responsive polymers and provides detailed descriptions of these existing examples. CO2 -responsive polymers can be categorized into three types based on their CO2 -responsive groups: amidine, amine, and carboxyl groups. Compared with traditional temperature, pH, or light stimuli-responsive polymers, CO2 -responsive polymers provide the advantage to use CO2 as a "green" trigger as well as to capture CO2 directly from air. In addition, the current challenges of CO2 -responsive polymers are discussed and the different solution methods are compared. Noteworthy, CO2 -responsive polymers are considered to have a prosperous future in various scientific areas.

  10. Effects of AFM tip-based direct and vibration assisted scratching methods on nanogrooves fabrication on a polymer resist

    Geng, Yanquan [The State Key Laboratory of Robotics and Systems, Robotics Institute, Harbin Institute of Technology, Harbin, Heilongjiang 150080 (China); Center for Precision Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001 (China); Yan, Yongda, E-mail: [The State Key Laboratory of Robotics and Systems, Robotics Institute, Harbin Institute of Technology, Harbin, Heilongjiang 150080 (China); Center for Precision Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001 (China); Zhuang, Yun; Hu, Zhenjiang [Center for Precision Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001 (China)


    Graphical abstract: - Highlights: • The comparison of three different atomic force microscope (AFM) tip-based material processing techniques to generate nano-grooves on polymethylmethacrylate (PMMA) thin film is presented. • The machined depths of the nano-grooves machined by these three methods are analyzed. • Nano-groove with the machined depth closed to the thickness of the thin-film resist is achieved. - Abstract: This study proposes two atomic force microscope (AFM) tip-based direct nanoscratching methods including single-pass scratching and multi-pass scratching compared with a vibration-assisted scratching method to fabricate nano-grooves on the surface of the polymethylmethacrylate (PMMA) thin-film resist. In order to protect the AFM tip from wearing and optimize the subsequent etching process, the machined depth is expected slightly less than the PMMA thickness to prevent the tip directly contacting with the silicon substrate and obtain better process results. First, single-pass scratching tests are performed on films with different thickness employing varied normal loads. Results show that the machined depths of the grooves cannot be obtained slightly less than the thickness of the film very easily when scratching with single-pass method, 50–120 nm in the present study, which may not be very suitable for the following etching process. Multi-pass and vibration-assisted methods are then utilized to solve this limitation of the machined depth in single-pass process. The machined depths using the multi-pass method are dependent on scratching times and the applied normal loads. Moreover, the depth closed to the thickness of the film can be obtained by enlarging the number of the scratching cycles. However, with a longer scratching time, large tip wear can be found. For vibration assisted method, the machined depths are controlled by the vibration amplitude and the applied normal load. With the vibration in z direction increasing, the machined depth can

  11. Parallel input parallel output high voltage bi-directional converters for driving dielectric electro active polymer actuators

    Thummala, Prasanth; Zhang, Zhe; Andersen, Michael A. E.;


    is to design and implement driving circuits for the DEAP actuators for their use in various applications. This paper presents implementation of parallel input, parallel output, high voltage (~2.5 kV) bi-directional DC-DC converters for driving the DEAP actuators. The topology is a bidirectional flyback DC......-DC converter incorporating commercially available high voltage MOSFETs (4 kV) and high voltage diodes (5 kV). Although the average current of the aforementioned devices is limited to 300 mA and 150 mA, respectively, connecting the outputs of multiple converters in parallel can provide a scalable design....... This enables operating the DEAP actuators in various static and dynamic applications e.g. positioning, vibration generation or damping, and pumps. The proposed idea is experimentally verified by connecting three high voltage converters in parallel to operate a single DEAP actuator. The experimental results...

  12. Polymer fractionation

    Hadermann, A. F.


    Soluble polymers are fractionated according to molecular weight by cryogenically comminuting the polymer and introducing the polymer particles, while still in the active state induced by cryogenic grinding, into a liquid having a solvent power selected to produce a coacervate fraction containing high molecular weight polymer species and a dilute polymer solution containing lower molecular weight polymer species. The coacervate may be physically separated from the solution and finds use in the production of antimisting jet fuels and the like.

  13. Biodegradable Polymers

    Isabelle Vroman; Lan Tighzert


    Biodegradable materials are used in packaging, agriculture, medicine and other areas. In recent years there has been an increase in interest in biodegradable polymers. Two classes of biodegradable polymers can be distinguished: synthetic or natural polymers. There are polymers produced from feedstocks derived either from petroleum resources (non renewable resources) or from biological resources (renewable resources). In general natural polymers offer fewer advantages than synthetic polymers. ...

  14. Fire-safe polymers and polymer composites

    Zhang, Huiqing

    The intrinsic relationships between polymer structure, composition and fire behavior have been explored to develop new fire-safe polymeric materials. Different experimental techniques, especially three milligram-scale methods---pyrolysis-combustion flow calorimetry (PCFC), simultaneous thermal analysis (STA) and pyrolysis GC/MS---have been combined to fully characterize the thermal decomposition and flammability of polymers and polymer composites. Thermal stability, mass loss rate, char yield and properties of decomposition volatiles were found to be the most important parameters in determining polymer flammability. Most polymers decompose by either an unzipping or a random chain scission mechanism with an endothermic decomposition of 100--900 J/g. Aromatic or heteroaromatic rings, conjugated double or triple bonds and heteroatoms such as halogens, N, O, S, P and Si are the basic structural units for fire-resistant polymers. The flammability of polymers can also be successfully estimated by combining pyrolysis GC/MS results or chemical structures with TGA results. The thermal decomposition and flammability of two groups of inherently fire-resistant polymers---poly(hydroxyamide) (PHA) and its derivatives, and bisphenol C (BPC II) polyarylates---have been systematically studied. PHA and most of its derivatives have extremely low heat release rates and very high char yields upon combustion. PHA and its halogen derivatives can completely cyclize into quasi-polybenzoxazole (PBO) structures at low temperatures. However, the methoxy and phosphate derivatives show a very different behavior during decomposition and combustion. Molecular modeling shows that the formation of an enol intermediate is the rate-determining step in the thermal cyclization of PHA. BPC II-polyarylate is another extremely flame-resistant polymer. It can be used as an efficient flame-retardant agent in copolymers and blends. From PCFC results, the total heat of combustion of these copolymers or blends

  15. Resonant soft X-ray reflectivity of ultrathin polymer films at the C-edge: A direct approach

    Alain Gibaud


    Full Text Available The use of resonant soft X-ray reflectivity (RSXRR in s-polarization is presented with the aim to show how far it is possible to go in the understanding the evolution of the refractive index n(E=1−δ(E−iβ(E of a ultrathin polystyrene film when the RSXRR is measured through the C-edge. We evidence that a direct fit to the data provides a very good estimation of δ(E and β(E in a large range of energies. Nevertheless, at some specific energy close to C-edge we observe that it is not possible to obtain a satisfactory fit to the data though the same formalism is applied to calculate the reflectivity. We show that even though we take into account the energy resolution of the incident beam, we still end up with a poor fit at these energies. Incorporating the strong contribution of 2nd order photons appeared near C-edge we could not eliminate the discrepancy. Probably the data normalisations have some impacts on such discrepancies at some specific energies.

  16. Resonant soft X-ray reflectivity of ultrathin polymer films at the C-edge: A direct approach

    Gibaud, Alain; Bal, Jayanta Kumar; Gullikson, Eric M.; Wang, Cheng; Vignaud, Guillaume


    The use of resonant soft X-ray reflectivity (RSXRR) in s-polarization is presented with the aim to show how far it is possible to go in the understanding the evolution of the refractive index n (E ) =1 -δ (E ) -i β (E ) of a ultrathin polystyrene film when the RSXRR is measured through the C-edge. We evidence that a direct fit to the data provides a very good estimation of δ (E ) and β (E ) in a large range of energies. Nevertheless, at some specific energy close to C-edge we observe that it is not possible to obtain a satisfactory fit to the data though the same formalism is applied to calculate the reflectivity. We show that even though we take into account the energy resolution of the incident beam, we still end up with a poor fit at these energies. Incorporating the strong contribution of 2nd order photons appeared near C-edge we could not eliminate the discrepancy. Probably the data normalisations have some impacts on such discrepancies at some specific energies.

  17. Surface-Directed Assembly of Sequence-Defined Synthetic Polymers into Networks of Hexagonally Patterned Nanoribbons with Controlled Functionalities

    Chen, Chun-Long; Zuckermann, Ronald N.; DeYoreo, James J.


    The exquisite self-assembly of proteins and peptides in nature into highly ordered functional materials has inspired innovative approaches to biomimetic materials design and synthesis. Here we report the assembly of peptoids—a class of highly stable sequence-defined synthetic polymers—into biomimetic materials on mica surfaces. The assembling 12-mer peptoid contains alternating acidic and aromatic residues, and the presence of Ca2+ cations creates peptoid-peptoid and peptoid-mica interactions that drive assembly. In situ atomic force microscopy (AFM) shows that peptoids first assemble into discrete nanoparticles, these particles then transform into hexagonally-patterned nanoribbons on mica surfaces. AFM-based dynamic force spectroscopy (DFS) studies show that peptoid-mica interactions are much stronger than peptoidpeptoid interactions in the presence of Ca2+, illuminating the physical parameters that drive peptoid assembly. We further demonstrate the display of functional groups at the N-terminus of assembling peptoid sequence to produce biomimetic materials with similar hierarchical structures. This research demonstrates that surface-directed peptoid assembly can be used as a robust platform to develop biomimetic coating materials for applications.

  18. Platinum and palladium nano-structured catalysts for polymer electrolyte fuel cells and direct methanol fuel cells.

    Long, Nguyen Viet; Thi, Cao Minh; Yong, Yang; Nogami, Masayuki; Ohtaki, Michitaka


    In this review, we present the synthesis and characterization of Pt, Pd, Pt based bimetallic and multi-metallic nanoparticles with mixture, alloy and core-shell structure for nano-catalysis, energy conversion, and fuel cells. Here, Pt and Pd nanoparticles with modified nanostructures can be controllably synthesized via chemistry and physics for their uses as electro-catalysts. The cheap base metal catalysts can be studied in the relationship of crystal structure, size, morphology, shape, and composition for new catalysts with low cost. Thus, Pt based alloy and core-shell catalysts can be prepared with the thin Pt and Pt-Pd shell, which are proposed in low and high temperature proton exchange membrane fuel cells (PEMFCs), and direct methanol fuel cells (DMFCs). We also present the survey of the preparation of Pt and Pd based catalysts for the better catalytic activity, high durability, and stability. The structural transformations, quantum-size effects, and characterization of Pt and Pd based catalysts in the size ranges of 30 nm (1-30 nm) are presented in electro-catalysis. In the size range of 10 nm (1-10 nm), the pure Pt catalyst shows very large surface area for electro-catalysis. To achieve homogeneous size distribution, the shaped synthesis of the polyhedral Pt nanoparticles is presented. The new concept of shaping specific shapes and morphologies in the entire nano-scale from nano to micro, such as polyhedral, cube, octahedra, tetrahedra, bar, rod, and others of the nanoparticles is proposed, especially for noble and cheap metals. The uniform Pt based nanosystems of surface structure, internal structure, shape, and morphology in the nanosized ranges are very crucial to next fuel cells. Finally, the modifications of Pt and Pd based catalysts of alloy, core-shell, and mixture structures lead to find high catalytic activity, durability, and stability for nano-catalysis, energy conversion, fuel cells, especially the next large-scale commercialization of next

  19. Quenched Free Energy and Large Deviations for Random Walks in Random Potentials

    Rassoul-Agha, Firas; Yilmaz, Atilla


    We study quenched distributions on random walks in a random potential on integer lattices of arbitrary dimension and with an arbitrary finite set of admissible steps. The potential can be unbounded and can depend on a few steps of the walk. Directed, undirected and stretched polymers, as well as random walk in random environment, are covered. The restriction needed is on the moment of the potential, in relation to the degree of mixing of the ergodic environment. We derive two variational formulas for the limiting quenched free energy and prove a process-level quenched large deviation principle for the empirical measure. As a corollary we obtain LDPs for types of random walk in random environment not covered by earlier results.

  20. Delocalization in polymer models

    Jitomirskaya, S Yu; Stolz, G


    A polymer model is a one-dimensional Schroedinger operator composed of two finite building blocks. If the two associated transfer matrices commute, the corresponding energy is called critical. Such critical energies appear in physical models, an example being the widely studied random dimer model. Although the random models are known to have pure-point spectrum with exponentially localized eigenstates for almost every configuration of the polymers, the spreading of an initially localized wave packet is here proven to be at least diffusive for every configuration.

  1. Highly efficient direct aerobic oxidative esterification of cinnamyl alcohol with alkyl alcohols catalysed by gold nanoparticles incarcerated in a nanoporous polymer matrix: a tool for investigating the role of the polymer host.

    Buonerba, Antonio; Noschese, Annarita; Grassi, Alfonso


    The selective aerobic oxidation of cinnamyl alcohol to cinnamaldehyde, as well as direct oxidative esterification of this alcohol with primary and secondary aliphatic alcohols, were achieved with high chemoselectivity by using gold nanoparticles supported in a nanoporous semicrystalline multi-block copolymer matrix, which consisted of syndiotactic polystyrene-co-cis-1,4-polybutadiene. The cascade reaction that leads to the alkyl cinnamates occurs through two oxidation steps: the selective oxidation of cinnamyl alcohol to cinnamaldehyde, followed by oxidation of the hemiacetal that results from the base-catalysed reaction of cinnamaldehyde with an aliphatic alcohol. The rate constants for the two steps were evaluated in the temperature range 10-45 °C. The cinnamyl alcohol oxidation is faster than the oxidative esterification of cinnamaldehyde with methanol, ethanol, 2-propanol, 1-butanol, 1-hexanol or 1-octanol. The rate constants of the latter reaction are pseudo-zero order with respect to the aliphatic alcohol and decrease as the bulkiness of the alcohol is increased. The activation energy (Ea) for the two oxidation steps was calculated for esterification of cinnamyl alcohol with 1-butanol (Ea = 57.8±11.5 and 62.7±16.7 kJ mol(-1) for the first and second step, respectively). The oxidative esterification of cinnamyl alcohol with 2-phenylethanol follows pseudo-first-order kinetics with respect to 2-phenylethanol and is faster than observed for other alcohols because of fast diffusion of the aromatic alcohol in the crystalline phase of the support. The kinetic investigation allowed us to assess the role of the polymer support in the determination of both high activity and selectivity in the title reaction.

  2. Performance comparison of portable direct methanol fuel cell mini-stacks based on a low-cost fluorine-free polymer electrolyte and Nafion membrane

    Baglio, V., E-mail: baglio@itae.cnr.i [CNR-ITAE, Via Salita S. Lucia sopra Contesse 5, 98126 Messina (Italy); Stassi, A.; Modica, E.; Antonucci, V.; Arico, A.S. [CNR-ITAE, Via Salita S. Lucia sopra Contesse 5, 98126 Messina (Italy); Caracino, P.; Ballabio, O.; Colombo, M.; Kopnin, E. [Pirelli Labs, Viale Sarca, 222, 20126 Milano (Italy)


    A low-cost fluorine-free proton conducting polymer electrolyte was investigated for application in direct methanol fuel cell (DMFC) mini-stacks. The membrane consisted of a sulfonated polystyrene grafted onto a polyethylene backbone. DMFC operating conditions specifically addressing portable applications, i.e. passive mode, air breathing, high methanol concentration, room temperature, were selected. The device consisted of a passive DMFC monopolar three-cell stack. Two designs for flow-fields/current collectors based on open-flow or grid-like geometry were investigated. An optimization of the mini-stack structure was necessary to improve utilization of the fluorine-free membrane. Titanium-grid current collectors with proper mechanical stiffness allowed a significant increase of the performance by reducing contact resistance even in the case of significant swelling. A single cell maximum power density of about 18 mW cm{sup -2} was achieved with the fluorine-free membrane at room temperature under passive mode. As a comparison, the performance obtained with Nafion 117 membrane and Ti grids was 31 mW cm{sup -2}. Despite the lower performance, the fluorine-free membrane showed good characteristics for application in portable DMFCs especially with regard to the perspectives of significant cost reduction.

  3. The current-voltage characteristics of polymer/C60 diodes in the dark: A direct way to assess photovoltaic devices efficiency parameters

    Koehler, M.; Yamamoto, N. A. D.; Macedo, A. G.; Grodniski, D. Z.; Roman, L. S.; da Luz, M. G. E.


    A general description of dark transport properties in bi-layer organic photovoltaic devices formed by a heterojunction of a semiconducting co-polymer and fullerene (C60) is presented. The copolymers are composed of thiophene, phenylene, and fluorene units, where the thiophene content is kept constant while the fluorene/phenylene ratio is varied. Measurements show that the j × V characteristics display typical diode behavior (exponential increasing) at low and are space-charge limited at high voltages. Extending a theoretical analysis by Koehler et al. [J. Appl. Phys. 92, 5575 (2002)], a model which assumes a space-charge dependent inner series resistance—attributed to molecular and morphological aspects of the materials—is proposed. It turns out to be general and able to nicely fit the experimental curves for all the studied samples. Furthermore, the model quantifies relevant parameters (the effective mobility and the diode reverse saturation current j0) which will determine the systems efficiency. The framework hence allows to foremost the devices functioning under illumination from direct experiments of the active material in the dark.

  4. Direct-write fabrication of 4D active shape-changing behavior based on a shape memory polymer and its nanocomposite (Conference Presentation)

    Wei, Hongqiu; Zhang, Qiwei; Yao, Yongtao; Liu, Liwu; Liu, Yanju; Leng, Jinsong


    Shape memory polymers (SMPs), a typical class of smart materials, have been witnessed significant advances in the past decades. Based on the unique performance to recover the initial shape after going through a shape deformation, the applications of SMPs have aroused growing interests. However, most of the researches are hindered by traditional processing technologies which limit the design space of SMPs-based structures. Three-dimension (3D) printing as an emerging technology endows design freedom to manufacture materials with complex structures. In present article, we show that by employing direct-write printing method; one can realize the printing of SMPs to achieve 4D active shape-changing structures. We first fabricated a kind of 3D printable polylactide (PLA)-based SMPs and characterized the overall properties of such materials. Results demonstrated the prepared PLA-based SMPs presenting excellent shape memory effect. In what follows, the rheological properties of such PLA-based SMP ink during printing process were discussed in detail. Finally, we designed and printed several 3D configurations for investigation. By combining 3D printing with shape memory behavior, these printed structures achieve 4D active shape-changing performance under heat stimuli. This research presents a high flexible method to realize the fabrication of SMP-based 4D active shape-changing structures, which opens the way for further developments and improvements of high-tech fields like 4D printing, soft robotics, micro-systems and biomedical devices.

  5. Porous rod-like MgO complex membrane with good anti-bacterial activity directed by conjugated linolenic acid polymer

    Wang, Hua-Jie, E-mail:; Chen, Meng [Henan Normal University, College of Chemistry and Chemical Engineering (China); Mi, Li-Wei, E-mail: [Zhongyuan University of Technology, Center for Advanced Materials Research (China); Shi, Li-Hua [Anyang 101 Education Center (China); Cao, Ying, E-mail: [Zhongyuan University of Technology, Center for Advanced Materials Research (China)


    The problem of infection in the tissue engineering substitutes is driving us to seek new coating materials. We previously found that conjugated linolenic acid (CLnA) has well biocompatibility and excellent membrane-forming property. The objective of this study is to endow the anti-bacterial activity to CLnA membra ne by linking with MgO. The results showed that the CLnA polymer membrane can be loaded with porous rod-like MgO and such complex membrane showed anti-bacterial sensitivity against gram-positive bacteria (Staphylococcus aureus) even at the low concentration (0.15 μg/mm{sup 2}). In the present study, the best zone of inhibition got to 18.2 ± 0.8 mm when the amount of MgO reach 2.42 ± 0.58 μg/mm{sup 2}. It was deduced that the porous rod-like structure of MgO was directed by CLnA in its polymerization process. Such CLnA/MgO complex membrane can be helpful in the tissue engineering, medicine, food engineering, food preservation, etc. on the basis of its good anti-bacterial activity.

  6. Estimating the prevalence of sensitive behaviour and cheating with a dual design for direct questioning and randomized reponse.

    Van den Hout, A.D.L.; Bockenholt, U.; Van der Heijden, P.G.M.


    Randomized response is a misclassification design to estimate the prevalence of sensitive behaviour.Respondents who do not followthe instructions of the design are considered to be cheating. A mixture model is proposed to estimate the prevalence of sensitive behaviour and cheating in the case of a d

  7. Evaluation of laryngoscopic view, intubation difficulty and sympathetic response during direct laryngoscopy in sniffing position and simple head extension: a prospective and randomized comparative study

    Rashmi Pal; Sangeeta Chauhan; Bhanu Kumar Ved; Shankar Rao Lad


    Background: Airway management is critical to the care of patients and direct laryngoscopy is the mainstay of airway management. Despite the proliferation of difficult airway devices, sniffing position for laryngoscopy remains the gold standard and ideal position. This prospective, randomized and single-blind study was done to evaluate and compare the laryngoscopic view, complexity of intubation and sympathetic response during laryngoscopy in sniffing position and simple head extension. Met...

  8. A double-blind randomized clinical trial on the efficacy of cortical direct current stimulation for the treatment of Alzheimer’s disease

    Khedr, Eman M.


    Background: The purpose of this study was to investigate the long-term efficacy of transcranial direct current stimulation (tDCS) in the neurorehabilitation of Alzheimer’s disease (AD). Methods: 34 AD patients were randomly assigned to three groups: anodal, cathodal and sham tDCS. Stimulation was applied over the left dorsolateral prefrontal cortex (DLPFC) for 25 minutes at 2mA, daily for 10 days. Each patient was submitted to the following psychometric assessments: Minimental State Examinat...

  9. Transcranial Direct Current Stimulation Combined with Aerobic Exercise to Optimize Analgesic Responses in Fibromyalgia: A Randomized Placebo-Controlled Clinical Trial

    Mendonca, Mariana E.; Simis, Marcel; Grecco, Luanda C.; Battistella, Linamara R.; Baptista, Abrahão F; Fregni, Felipe


    Fibromyalgia is a chronic pain syndrome that is associated with maladaptive plasticity in neural central circuits. One of the neural circuits that are involved in pain in fibromyalgia is the primary motor cortex. We tested a combination intervention that aimed to modulate the motor system: transcranial direct current stimulation (tDCS) of the primary motor cortex (M1) and aerobic exercise (AE). In this phase II, sham-controlled randomized clinical trial, 45 subjects were assigned to 1 of 3 gr...

  10. Biodegradable Polymers

    Isabelle Vroman


    Full Text Available Biodegradable materials are used in packaging, agriculture, medicine and other areas. In recent years there has been an increase in interest in biodegradable polymers. Two classes of biodegradable polymers can be distinguished: synthetic or natural polymers. There are polymers produced from feedstocks derived either from petroleum resources (non renewable resources or from biological resources (renewable resources. In general natural polymers offer fewer advantages than synthetic polymers. The following review presents an overview of the different biodegradable polymers that are currently being used and their properties, as well as new developments in their synthesis and applications.

  11. Polymer electronics

    Hsin-Fei, Meng


    Polymer semiconductor is the only semiconductor that can be processed in solution. Electronics made by these flexible materials have many advantages such as large-area solution process, low cost, and high performance. Researchers and companies are increasingly dedicating time and money in polymer electronics. This book focuses on the fundamental materials and device physics of polymer electronics. It describes polymer light-emitting diodes, polymer field-effect transistors, organic vertical transistors, polymer solar cells, and many applications based on polymer electronics. The book also disc

  12. Self-Directed Interactive Video-Based Instruction Versus Instructor-Led Teaching for Myanmar House Surgeons: A Randomized, Noninferiority Trial.

    Lwin, Albert Thein; Lwin, Thein; Naing, Phyu; Oo, Yee; Kidd, David; Cerullo, Marcelo; Posen, Joshua; Hlaing, Kyaw; Yenokyan, Gayane; Thinn, Kyi Kyi; Soe, Zaw Wai; Stevens, Kent A


    To compare self-directed interactive video-based instruction (IVBI) with instructor-led teaching in the acquisition of basic surgical skills by House Surgeons at University of Medicine 1, Yangon. A prospective, 1:1 randomized controlled trial was conducted. Participants were randomized into 2 teaching arms: (1) self-directed IVBI or (2) instructor-led teaching. Self-directed IVBI participants were provided with a portable DVD player that could play, fast forward, rewind, and skip through skills modules. Participants in the instructor-led teaching group were taught in small groups by standardized instructors. Pretesting and posttesting of 1-handed knot tie, 2-handed knot tie, vertical mattress suture, and instrument tie was performed using the Objective Structured Assessment of Technical Skills (OSATS). Students randomized to self-directed IVBI completed an exit survey to assess satisfaction. Demographic data were collected of all participants. University of Medicine 1, Yangon, Myanmar. Fifty participants were randomly selected from 78 eligible House Surgeons who were enrolled in their basic surgery rotation. Demographic characteristics and baseline skills were comparable in participants randomized to IVBI and instructor-led teaching. Mean OSATS score increased from pretest to posttest in both groups (p < 0.001). The mean posttest OSATS score of the IVBI group was 0.72 points below that of the instructor-led teaching group (90% CI: -3.8 to 5.2), with the 90% CI falling below the a priori noninferiority margin, satisfying criteria for noninferiority. More than 90% of students marked either "agree" or "strongly agree" to the following statements on the exit survey: further expansion of IVBI into other skills modules and integration of IVBI into training curriculum. IVBI is noninferior to instructor-led teaching of surgical skills based on OSATS scores. House Surgeons highly rated self-directed IVBI. Self-directed IVBI has the potential to significantly reduce the

  13. TAXUS VI 2-year follow-up: randomized comparison of polymer-based paclitaxel-eluting with bare metal stents for treatment of long, complex lesions

    Grube, Eberhard; Dawkins, Keith D; Guagliumi, Giulio;


    AIMS: Drug-eluting stents (DESs) have shown to be effective in reducing in-stent restenosis, although data relating to long-term experience in treating more complex lesion subsets are limited. In order to assess the long-term safety and clinical efficacy of the polymer-based moderate release (MR)...

  14. High Temperature, Low Relative Humidity, Polymer-type Membranes Based on Disulfonated Poly(arylene ether) Block and Random Copolymers Optionally Incorporating Protonic Conducting Layered Water insoluble Zirconium Fillers

    McGrath, James E.; Baird, Donald G.


    Our research group has been engaged in the past few years in the synthesis of biphenol based partially disulfonated poly(arylene ether sulfone) random copolymers as potential PEMs. This series of polymers are named as BPSH-xx, where BP stands for biphenol, S stands for sulfonated, H stands for acidified and xx represents the degree of disulfonation. All of these sulfonated copolymers phase separate to form nano scale hydrophilic and hydrophobic morphological domains. The hydrophilic phase containing the sulfonic acid moieties causes the copolymer to absorb water. Water confined in hydrophilic pores in concert with the sulfonic acid groups serve the critical function of proton (ion) conduction and water transport in these systems. Both Nafion and BPSH show high proton conductivity at fully hydrated conditions. However proton transport is especially limited at low hydration level for the BPSH random copolymer. It has been observed that the diffusion coefficients of both water and protons change with the water content of the pore. This change in proton and water transport mechanisms with hydration level has been attributed to the solvation of the acid groups and the amount of bound and bulk-like water within a pore. At low hydration levels most of the water is tightly associated with sulfonic groups and has a low diffusion coefficient. This tends to encourage isolated domain morphology. Thus, although there may be significant concentrations of protons, the transport is limited by the discontinuous morphological structure. Hence the challenge lies in how to modify the chemistry of the polymers to obtain significant protonic conductivity at low hydration levels. This may be possible if one can alter the chemical structure to synthesize nanophase separated ion containing block copolymers. Unlike the BPSH copolymers, where the sulfonic acid groups are randomly distributed along the chain, the multiblock copolymers will feature an ordered sequence of hydrophilic and

  15. A randomized controlled study of the use of ProRoot mineral trioxide aggregate and Endocem as direct pulp capping materials.

    Song, Minju; Kang, Minji; Kim, Hyeon-Cheol; Kim, Euiseong


    The purpose of the present study was to evaluate and compare the short-term clinical outcomes of direct pulp capping using ProRoot MTA (Dentsply, Tulsa, OK) or Endocem (Maruchi, Wonju, Korea) as capping materials in a prospective randomized controlled study. This study was conducted with subjects who were recruited from the pool of patients from the Department of Conservative Dentistry at the Dental College of Yonsei University, Seoul, Korea, between January and May 2013. Of the 48 teeth confirmed to be eligible for direct pulp capping, a total of 46 teeth were randomly assigned to either the ProRoot MTA or the Endocem group (23 teeth per group). Direct pulp capping was performed using these 2 materials, and clinical and radiographic evaluations were performed at 1, 2, 4, and 12 weeks after the treatments. Teeth with no response to pulp vitality test and those exhibiting clinical or radiographic signs and/or symptoms of irreversible pulpitis or pulp necrosis were considered to be failures. Thirty-two patients (43 teeth) were examined at the 3-month follow-up (patient recall rate = 91.4%); 22 of these teeth were in the ProRoot MTA group, and 21 were in the Endocem group. The overall success rate was 93%, and the success rates in the ProRoot MTA and Endocem groups were 95.5% (21/22 teeth) and 90.5% (19/21 teeth), respectively. Statistical analyses of these success rates did not reveal any significant difference between the groups (P = .522). In this randomized controlled study, no significant difference in the short-term clinical outcomes of direct pulp capping using ProRoot MTA or Endocem as the capping material was found. Furthermore, the favorable short-term outcome success rate of 93% indicates that direct pulp capping may be a reliable treatment for pulp exposure in adult teeth. Copyright © 2015 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  16. Treatment of deep caries lesions in adults: randomized clinical trials comparing stepwise vs. direct complete excavation, and direct pulp capping vs. partial pulpotomy

    Bjørndal, Lars; Reit, Claes; Bruun, Gitte Hoffmann


    Less invasive excavation methods have been suggested for deep caries lesions. We tested the effects of stepwise vs. direct complete excavation, 1 yr after the procedure had been carried out, in 314 adults (from six centres) who had received treatment of a tooth with deep caries. The teeth had...... capping or partial pulpotomy. We found no significant difference in pulp vitality without apical radiolucency between the two capping procedures after more than 1 yr [31.8% and 34.5%; difference: 2.7%, 95% CI (-22.7; 26.6)]. In conclusion, stepwise excavation decreases the risk of pulp exposure compared...

  17. Dutch randomized trial comparing standard catheter-directed thrombolysis versus Ultrasound-accElerated Thrombolysis for thromboembolic infrainguinal disease (DUET: design and rationale

    Fioole Bram


    Full Text Available Abstract Background The use of thrombolytic therapy in the treatment of thrombosed infrainguinal native arteries and bypass grafts has increased over the years. Main limitation of this treatment modality, however, is the occurrence of bleeding complications. Low intensity ultrasound (US has been shown to accelerate enzymatic thrombolysis, thereby reducing therapy time. So far, no randomized trials have investigated the application of US-accelerated thrombolysis in the treatment of thrombosed infra-inguinal native arteries or bypass grafts. The DUET study (Dutch randomized trial comparing standard catheter-directed thrombolysis versus Ultrasound-accElerated Thrombolysis for thrombo-embolic infrainguinal disease is designed to assess whether US-accelerated thrombolysis will reduce therapy time significantly compared with standard catheter-directed thrombolysis. Methods/design Sixty adult patients with recently (between 1 and 7 weeks thrombosed infrainguinal native arteries or bypass grafts with acute limb ischemia class I or IIa, according to the Rutherford classification for acute ischemia, will be randomly allocated to either standard thrombolysis (group A or US-accelerated thrombolysis (group B. Patients will be recruited from 5 teaching hospitals in the Netherlands during a 2-year period. The primary endpoint is the duration of catheter-directed thrombolysis needed for uninterrupted flow in the thrombosed infrainguinal native artery or bypass graft, with outflow through at least 1 crural artery. Discussion The DUET study is a randomized controlled trial that will provide evidence of whether US-accelerated thrombolysis will significantly reduce therapy time in patients with recently thrombosed infrainguinal native arteries or bypass grafts, without an increase in complications. Trial registration Current Controlled Trials ISRCTN72676102

  18. General and Robust Strategies for Multifunctional Organic-Inorganic Nanocompositesvia Direct Growth of Monodisperse Nanocrystals Intimately and Permanently Connected with Polymers


    amphiphilic copolymer brushes: Poly( ethylene oxide )-graft-polystyrene. J. Polym. Sci. Part A: Polym. Chem. 44, 4361-4371 (2006). 2. Mora-Pale, M., Meli, L...results are summarized as follows. Recent research has witnessed tremendous advances in isotropic nanomaterials synthesis , which has provided access...nanocrystals of both fundamental and practical interest.(12, 13) Current emerging synthesis approaches, including template-assisted synthesis ,(14-16

  19. Fe₃O₄@rGO doped molecularly imprinted polymer membrane based on magnetic field directed self-assembly for the determination of amaranth.

    Han, Qing; Wang, Xi; Yang, Zaiyue; Zhu, Wanying; Zhou, Xuemin; Jiang, Huijun


    Based on magnetic field directed self-assembly (MDSA) of Fe3O4@rGO composites, a novel magnetic molecularly imprinted electrochemical sensor (MIES) was fabricated and developed for the determination of the azo dye amaranth. Fe3O4@rGO composites were obtained by a one-step approach involving the initial intercalating of iron ions between the graphene oxide layers via the electrostatic interaction, followed by the reduction with hydrazine hydrate to deposit Fe3O4 nanoparticles onto the reduced oxide graphene nanosheets. In molecular imprinting, the complex including the function monomer of aniline, the template of amaranth and Fe3O4@rGO was pre-assembled through π-π stacking and hydrogen bonding interactions, and then was self-assembled on the surface of magnetic glassy carbon electrode (MGCE) with the help of magnetic field induction before electropolymerization. The structures and morphologies of Fe3O4@rGO and the doped molecularly imprinted polymers (MIPs) were investigated by Fourier transform infrared spectrometer (FT-IR), Raman spectra and scanning electron microscope (SEM). Besides, the characterization by differential pulse voltammetry (DPV) showed that Fe3O4@rGO composites promoted the electrical conductivity of the imprinted sensors when doped into the MIPs. The adsorption isotherms and adsorption kinetics were employed to evaluate the performances of MIES. The detection of amaranth was achieved via the redox probe K3[Fe(CN)6] by blocking the imprinted cavities, which avoided the interferences of oxidation products and analogs of amaranth. Furthermore, the prepared MIES exhibited good sensitivity, selectivity, reproducibility and efficiency for detecting amaranth in fruit drinks. The average recoveries were 93.15-100.81% with the RSD <3.0%.

  20. Enhancement of Li Ion Conductivity by Electrospun Polymer Fibers and Direct Fabrication of Solvent-Free Separator Membranes for Li Ion Batteries.

    Freitag, Katharina M; Kirchhain, Holger; Wüllen, Leo van; Nilges, Tom


    Poly(ethylene oxide) (PEO)-based polymer fibers, containing different amounts of the conductive salt LiBF4 and the plasticizer succinonitrile, were prepared by an electrospinning process. This process resulted in fiber membranes of several square centimeters area and an overall thickness of ∼100 μm. All membranes are characterized by scanning electron microscopy, differential scanning calorimetry, X-ray diffraction, impedance spectroscopy, cyclic voltammetry (CV), and solid-state NMR spectroscopy, to evaluate the influence of the preparation process and the composition on the conductivity of the materials. Impedance spectroscopy was used to measure the conductivities and activation barriers for the different membranes. The highest conductivity of 2 × 10(-4) S/cm at room temperature and 9 × 10(-4) S/cm at 328 K is reached for a PEO/SN/LiBF4 (36:8:1) membrane, featuring an activation energy of 31 kJ/mol. Li mobilities, as deduced from the evaluation of the temperature dependence of the (7)Li NMR line width and the overall electrochemical performance, are found to be distinctively superior to nonspun samples, synthesized via conventional solution casting. The same trend was found for the conductivities. NMR spectroscopy clearly substantiated that the mobility of the PEO segments drastically increases with the addition of succinonitrile pushing the conductivity to reasonable high values. In CV experiments the reversible Li transport through the dry membrane was evaluated and proved. This study shows that electrospinning provides a direct synthesis of solvent-free solid-state electrolyte membranes, ready to use in electrochemical applications.

  1. Positive parenting program (triple P) for families of adolescents with type 1 diabetes: a randomized controlled trial of self-directed teen triple P.

    Doherty, Francesca M; Calam, Rachel; Sanders, Matthew R


    Adolescents with type 1 diabetes (T1D) have shown improvements in glycemic control and family relations, via clinic-based family interventions. However, reach and clinician availability may be limited. We evaluated a self-directed intervention for this purpose. Recruitment for a randomized controlled trial (RCT) occurred through national advertising with diabetes charities and conducted with online data collection. Parents of 11-17-year-olds with diabetes were randomized to usual care (n = 37) or intervention (n = 42) using computerized block randomization. The 10-week intervention comprised the Self-directed Teen Triple P workbook (10 × 1 hr modules) plus chronic illness tip sheet. Primary outcomes of diabetes-related family conflict and parenting stress were assessed pre and post-intervention. Intention-to-treat analyses (n = 79) identified significantly improved diabetes-related conflict, but not parental stress, compared with usual care. The preliminary findings suggest that this could be a useful way to expand intervention reach for this population.

  2. The perceived visual direction of monocular objects in random-dot stereograms is influenced by perceived depth and allelotropia.

    Hariharan-Vilupuru, Srividhya; Bedell, Harold E


    The proposed influence of objects that are visible to both eyes on the perceived direction of an object that is seen by only one eye is known as the "capture of binocular visual direction". The purpose of this study was to evaluate whether stereoscopic depth perception is necessary for the "capture of binocular visual direction" to occur. In one pair of experiments, perceived alignment between two nearby monocular lines changed systematically with the magnitude and direction of horizontal but not vertical disparity. In four of the five observers, the effect of horizontal disparity on perceived alignment depended on which eye viewed the monocular lines. In additional experiments, the perceived alignment between the monocular lines changed systematically with the magnitude and direction of both horizontal and vertical disparities when the monocular line separation was increased from 1.1 degrees to 3.3 degrees . These results indicate that binocular capture depends on the perceived depth that results from horizontal retinal image disparity as well as allelotropia, or the averaging of local-sign information. Our data suggest that, during averaging, different weights are afforded to the local-sign information in the two eyes, depending on whether the separation between binocularly viewed targets is horizontal or vertical.

  3. Facile and controllable one-step fabrication of molecularly imprinted polymer membrane by magnetic field directed self-assembly for electrochemical sensing of glutathione

    Zhu, Wanying; Jiang, Guoyi; Xu, Lei; Li, Bingzhi; Cai, Qizhi; Jiang, Huijun; Zhou, Xuemin, E-mail:


    Based on magnetic field directed self-assembly (MDSA) of the ternary Fe{sub 3}O{sub 4}@PANI/rGO nanocomposites, a facile and controllable molecularly imprinted electrochemical sensor (MIES) was fabricated through a one-step approach for detection of glutathione (GSH). The ternary Fe{sub 3}O{sub 4}@PANI/rGO nanocomposites were obtained by chemical oxidative polymerization and intercalation of Fe{sub 3}O{sub 4}@PANI into the graphene oxide layers via π–π stacking interaction, followed by reduction of graphene oxide in the presence of hydrazine hydrate. In molecular imprinting process, the pre-polymers, including GSH as template molecule, Fe{sub 3}O{sub 4}@PANI/rGO nanocomposites as functional monomers and pyrrole as both cross-linker and co-monomer, was assembled through N–H hydrogen bonds and the electrostatic interaction, and then was rapidly oriented onto the surface of MGCE under the magnetic field induction. Subsequently, the electrochemical GSH sensor was formed by electropolymerization. In this work, the ternary Fe{sub 3}O{sub 4}@PANI/rGO nanocomposites could not only provide available functionalized sites in the matrix to form hydrogen bond and electrostatic interaction with GSH, but also afford a promoting network for electron transfer. Moreover, the biomimetic sensing membrane could be controlled more conveniently and effectively by adjusting the magnetic field strength. The as-prepared controllable sensor showed good stability and reproducibility for the determination of GSH with the detection limit reaching 3 nmol L{sup −1} (S/N = 3). In addition, the highly sensitive and selective biomimetic sensor has been successfully used for the clinical determination of GSH in biological samples. - Highlights: • The ternary composites exhibited great conductivity and electrocatalytical activity. • By magnetic field induction, the orderly film was fabricated on the surface of MGCE. • The microstructure of the sensing membrane could be controlled


    J. Reece Roth; Z.Y. Chen; Peter P.- Y. Tsai


    Direct exposure of samples to the active species of air generated by a One AtmosphereUniform Glow Discharge Plasma (OA UGDP) has been used to etch and to increasethe surface energy of metallic surfaces, photoresist, polymer films, and nonwoven fab-rics. The OAUGDP is a non-thermal plasma with the classical characteristics of aDC normal glow discharge that operates in air (and other gases) at atmospheric pres-sure. Neither a vacuum system nor batch processing is necessary. A wide range ofapplications to metals, photoresist, films, fabrics, and polymeric webs can be accom-modated by direct exposure of the workpiece to the plasma in parallel-plate reactors.This technology is simple, it produces effects that can be obtained in no other way atone atmosphere; it generates minimal pollutants or unwanted by-products; and it issuitable for individual sample or online treatment of metallic surfaces, wafers, films.and fabrics.``Early exposures of solid materials to the OA UGDP required minutes to produce rela-tively small increases of surface energy. These durations appeared too long for com-mercial application to fast-moving webs. Recent improvements in OA UGDP gas com-position, power density, plasma quality, recirculating gas flow, and impedance match-ing of the power supply to the parallel plate plasma reactor have made it possible toraise the surface energy ofa variety of polymeric webs (PP, PET, PE, etc.) to levels of60 to 70 dynes/crn with one second of exposure. In air plasmas, the high surface ener-gies are not durable, and fall to 50 dynes/em after periods of weeks to months. Here.we report the exposure of metallic surfaces, photoresist, polymeric films, and nonwo-ven fabrics made of PP and PET to an impedance matched parallel plate OA UGDPfor durations ranging from one second to several tens of seconds. Data will be re-ported on the surface energy, wettability, wickability, and aging effect of polymericfilms and fabrics as functions of time of exposure, and time

  5. Impact of parent-directed education on parental use of pain treatments during routine infant vaccinations: a cluster randomized trial.

    Taddio, Anna; Parikh, Chaitya; Yoon, Eugene W; Sgro, Michael; Singh, Harvinder; Habtom, Erita; Ilersich, Andrew F; Pillai Riddell, Rebecca; Shah, Vibhuti


    Educating parents about ways to minimize pain during routine infant vaccine injections at the point of care may positively impact on pain management practices. The objective of this cluster randomized trial was to determine the impact of educating parents about pain in outpatient pediatric clinics on their use of pain treatments during routine infant vaccinations. Four hospital-based pediatric clinics were randomized to intervention or control groups. Parents of 2- to 4-month-old infants attending the intervention clinics reviewed a pamphlet and a video about vaccination pain management on the day of vaccination, whereas those in the control clinics did not. Parent use of specific pain treatments (breastfeeding, sugar water, topical anesthetics, and/or holding of infants) on the education day and at subsequent routine vaccinations 2 months later was the primary outcome. Altogether, 160 parent-infant dyads (80 per group) participated between November 2012 and February 2014; follow-up data were available for 126 (79%). Demographics did not differ between groups (P > 0.05). On the education day and at follow-up vaccinations, use of pain interventions during vaccinations was higher in the intervention group (80% vs 26% and 68% vs 32%, respectively; P vaccinations.

  6. Active Polymer Gel Actuators

    Shuji Hashimoto; Ryo Yoshida; Yusuke Hara; Shingo Maeda


    Many kinds of stimuli-responsive polymer and gels have been developed and applied to biomimetic actuators or artificial muscles. Electroactive polymers that change shape when stimulated electrically seem to be particularly promising. In all cases, however, the mechanical motion is driven by external stimuli, for example, reversing the direction of electric field. On the other hand, many living organisms can generate an autonomous motion without external driving stimuli like self-beating of he...

  7. GlideScope videolaryngoscope vs. Macintosh direct laryngoscope for intubation of morbidly obese patients: a randomized trial

    Andersen, L H; Rovsing, Marie Louise; Olsen, K S


    Morbidly obese patients are at increased risk of hypoxemia during tracheal intubation because of increased frequency of difficult and impossible intubation and a decreased apnea tolerance. In this study, intubation with the GlideScope videolaryngoscope (GS) was compared with the Macintosh direct...


    Morichere, D; Malliaras, G.G; Krasnikov, V.V.; Bolink, H.J; Hadziioannou, G


    The use of polymers as photorefractive materials offers many advantages : flexibility in synthesis, doping, processing and low cost. The required functionalities responsible for photorefractivity, namely charge generation, transport, trapping and linear electrooptic effect are given in the polymer w


    Morichere, D; Malliaras, G.G; Krasnikov, V.V.; Bolink, H.J; Hadziioannou, G


    The use of polymers as photorefractive materials offers many advantages : flexibility in synthesis, doping, processing and low cost. The required functionalities responsible for photorefractivity, namely charge generation, transport, trapping and linear electrooptic effect are given in the polymer w

  10. Magnesium(II) polyporphine: The first electron-conducting polymer with directly linked unsubstituted porphyrin units obtained by electrooxidation at a very low potential

    Vorotyntsev, Mikhail A., E-mail: mv@u-bourgogne.f [Institut de Chimie Moleculaire de l' Universite de Bourgogne, Universite de Bourgogne, CNRS UMR 5260, 21078 Dijon (France); Konev, Dmitry V. [Institut de Chimie Moleculaire de l' Universite de Bourgogne, Universite de Bourgogne, CNRS UMR 5260, 21078 Dijon (France); Devillers, Charles H., E-mail: charles.devillers@u-bourgogne.f [Institut de Chimie Moleculaire de l' Universite de Bourgogne, Universite de Bourgogne, CNRS UMR 5260, 21078 Dijon (France); Bezverkhyy, Igor; Heintz, Olivier [Institut Carnot de Bourgogne, Universite de Bourgogne, CNRS UMR 5209, 21078 Dijon (France)


    Electrooxidation of magnesium(II) porphine, a totally unsubstituted porphyrin, in acetonitrile solution under potentiostatic or potentiodynamic regime leads to a polymer film at the electrode surface. Polymer deposition takes place at extremely low potential, several hundred mV less positive even compared to the deposition potential for pyrrole or EDOT (at identical monomer concentrations) in the same solvent. Film thickness can be controlled by the passed deposition charge. This material and its THF-soluble fraction have been characterized by various electrochemical methods as well as by UV-visible and IR spectroscopies, XPS, XRD and MALDI-TOF techniques. This analysis has allowed us to conclude that the polymer film is composed by chains of Mg porphine building blocks, with single bonds between the neighboring units. In the course of the potential sweep, this polymer film demonstrates a redox response resembling that of polythiophene-coated electrodes. Namely, the film is electroactive and electronically conducting in two potential ranges (p- and n-doping), which are separated by a broad interval where the film possesses a much higher resistance. The polymer may be switched between all these redox states repeatedly by the change of the potential. The film capacitance in the electroactive potential intervals is proportional to the deposition charge.

  11. Polymer Brushes

    Vos, de W.M.; Kleijn, J.M.; Keizer, de A.; Cosgrove, T.; Cohen Stuart, M.A.


    A polymer brush can be defined as a dense array of polymers end-attached to an interface that stretch out into the surrounding medium. Polymer brushes have been investigated for the past 30 years and have shown to be an extremely useful tool to control interfacial properties. This review is intended

  12. Transcranial direct current stimulation as a memory enhancer in patients with Alzheimer’s disease: a randomized, placebo-controlled trial

    Bystad, Martin; Grønli, Ole; Rasmussen, Ingrid Daae; Gundersen, Nina; Nordvang, Lene; Wang-Iversen, Henrik; Aslaksen, Per M


    Background The purpose of this study was to assess the efficacy of transcranial direct current stimulation (tDCS) on verbal memory function in patients with Alzheimer’s disease. Methods We conducted a randomized, placebo-controlled clinical trial in which tDCS was applied in six 30-minute sessions for 10 days. tDCS was delivered to the left temporal cortex with 2-mA intensity. A total of 25 patients with Alzheimer’s disease were enrolled in the study. All of the patients were diagnosed accord...

  13. Amplitude-phase retrieval attack free cryptosystem based on direct attack to phase-truncated Fourier-transform-based encryption using a random amplitude mask.

    Wang, Xiaogang; Zhao, Daomu


    We propose a simple amplitude-phase retrieval attack free cryptosystem based on direct attack to phase-truncated Fourier-transform-based encryption using a random amplitude mask (RAM). The RAM that is not saved during the encryption provides extremely high security for the two private keys, and no iterative calculations are involved in the nonlinear encryption process. Lack of enough constraints makes the specific attack based on iterative amplitude-phase retrieval algorithms unusable. Numerical simulation results are given for testing the validity and security of the proposed approach.

  14. New amphiphilic glycopolymers by click functionalization of random copolymers – application to the colloidal stabilisation of polymer nanoparticles and their interaction with concanavalin A lectin

    Otman Otman


    Full Text Available Glycopolymers with mannose units were readily prepared by click chemistry of an azido mannopyranoside derivative and a poly(propargyl acrylate-co-N-vinyl pyrrolidone. These glycopolymers were used as polymer surfactants, in order to obtain glycosylated polycaprolactone nanoparticles. Optimum stabilization for long time storage was achieved by using a mixture of glycopolymers and the non-ionic triblock copolymer Pluronic® F-68. The mannose moieties are accessible at the surface of nanoparticles and available for molecular recognition by concanavalin A lectin. Interaction of mannose units with the lectin were evaluated by measuring the changes in nanoparticles size by dynamic light scattering in dilute media.

  15. Directed self assembly of block copolymers using chemical patterns with sidewall guiding lines, backfilled with random copolymer brushes.

    Pandav, Gunja; Durand, William J; Ellison, Christopher J; Willson, C Grant; Ganesan, Venkat


    Recently, alignment of block copolymer domains has been achieved using a topographically patterned substrate with a sidewall preferential to one of the blocks. This strategy has been suggested as an option to overcome the patterning resolution challenges facing chemoepitaxy strategies, which utilize chemical stripes with a width of about half the period of block copolymer to orient the equilibrium morphologies. In this work, single chain in mean field simulation methodology was used to study the self assembly of symmetric block copolymers on topographically patterned substrates with sidewall interactions. Random copolymer brushes grafted to the background region (space between patterns) were modeled explicitly. The effects of changes in pattern width, film thicknesses and strength of sidewall interaction on the resulting morphologies were examined and the conditions which led to perpendicular morphologies required for lithographic applications were identified. A number of density multiplication schemes were studied in order to gauge the efficiency with which the sidewall pattern can guide the self assembly of block copolymers. The results indicate that such a patterning technique can potentially utilize pattern widths of the order of one-two times the period of block copolymer and still be able to guide ordering of the block copolymer domains up to 8X density multiplication.

  16. Comparison of an alternative schedule of extended care contacts to a self-directed control: a randomized trial of weight loss maintenance.

    Dutton, Gareth R; Gowey, Marissa A; Tan, Fei; Zhou, Dali; Ard, Jamy; Perri, Michael G; Lewis, Cora E


    Behavioral interventions for obesity produce clinically meaningful weight loss, but weight regain following treatment is common. Extended care programs attenuate weight regain and improve weight loss maintenance. However, less is known about the most effective ways to deliver extended care, including contact schedules. We compared the 12-month weight regain of an extended care program utilizing a non-conventional, clustered campaign treatment schedule and a self-directed program among individuals who previously achieved ≥5% weight reductions. Participants (N = 108; mean age = 51.6 years; mean weight = 92.6 kg; 52% African American; 95% female) who achieved ≥5% weight loss during an initial 16-week behavioral obesity treatment were randomized into a 2-arm, 12-month extended care trial. A clustered campaign condition included 12 group-based visits delivered in three, 4-week clusters. A self-directed condition included provision of the same printed intervention materials but no additional treatment visits. The study was conducted in a U.S. academic medical center from 2011 to 2015. Prior to randomization, participants lost an average of -7.55 ± 3.04 kg. Participants randomized to the 12-month clustered campaign program regained significantly less weight (0.35 ± 4.62 kg) than self-directed participants (2.40 ± 3.99 kg), which represented a significant between-group difference of 2.28 kg (p = 0.0154) after covariate adjustments. This corresponded to maintaining 87% and 64% of lost weight in the clustered campaign and self-directed conditions, respectively, which was a significant between-group difference of 29% maintenance of lost weight after covariate adjustments, p = 0.0396. In this initial test of a clustered campaign treatment schedule, this novel approach effectively promoted 12-month maintenance of lost weight. Future trials should directly compare the clustered campaigns with conventional (e.g., monthly) extended care schedules

  17. Rapid Polymer Sequencer

    Stolc, Viktor (Inventor); Brock, Matthew W (Inventor)


    Method and system for rapid and accurate determination of each of a sequence of unknown polymer components, such as nucleic acid components. A self-assembling monolayer of a selected substance is optionally provided on an interior surface of a pipette tip, and the interior surface is immersed in a selected liquid. A selected electrical field is impressed in a longitudinal direction, or in a transverse direction, in the tip region, a polymer sequence is passed through the tip region, and a change in an electrical current signal is measured as each polymer component passes through the tip region. Each of the measured changes in electrical current signals is compared with a database of reference electrical change signals, with each reference signal corresponding to an identified polymer component, to identify the unknown polymer component with a reference polymer component. The nanopore preferably has a pore inner diameter of no more than about 40 nm and is prepared by heating and pulling a very small section of a glass tubing.

  18. An array of ordered pillars with retentive properties for pressure-driven liquid chromatography fabricated directly from an unmodified cyclo olefin polymer

    Illa, Xavi; Malsche, de Wim; Bomer, Johan; Gardeniers, Han; Eijkel, Jan; Morante, Joan Ramon; Romano-Rodriguez, Albert; Desmet, Gert


    The current paper describes the development and characterization of a pillar array chip that is constructed out of a sandwich of cyclo olefin polymer (COP) sheets. The silicon master of a 5 cm long pillar array was embossed into the COP, yielding 4.3 µm deep pillars of 15.3 µm diameter with an exter

  19. Distributed Consensus for Discrete-Time Directed Networks of Multiagents with Time-Delays and Random Communication Links

    Yurong Liu


    Full Text Available This paper is concerned with the leader-following consensus problem in mean-square for a class of discrete-time multiagent systems. The multiagent systems under consideration are the directed and contain arbitrary discrete time-delays. The communication links are assumed to be time-varying and stochastic. It is also assumed that some agents in the network are well informed and act as leaders, and the others are followers. By introducing novel Lyapunov functionals and employing some new analytical techniques, sufficient conditions are derived to guarantee the leader-following consensus in mean-square for the concerned multiagent systems, so that all the agents are steered to an anticipated state target. A numerical example is presented to illustrate the main results.

  20. Direction of the J-tip of the guidewire, in seldinger technique, is a significant factor in misplacement of subclavian vein catheter: a randomized, controlled study.

    Tripathi, Mukesh; Dubey, Prakash K; Ambesh, Sushil P


    Misplacement of central venous catheters, predisposing to poor functioning including inability to aspirate blood, is common with the subclavian approach. In this prospective study we sought to determine whether the direction of the guidewire J-tip influenced the catheter tip placement during right subclavian catheterization. In this randomized, double-blind clinical study, we observed the placement of catheters via the right subclavian vein while keeping the J-tip directed either caudad in Group 1 (n=147) or cephalad in Group 2 (n=148) patients. The majority of catheters (97% and 57%) in Groups 1 and 2 respectively entered the superior vena cava/right atrium (P <0.05). The incidence of catheter misplacement into the ipsilateral internal jugular vein was 2% and 40% in Groups 1 and 2, respectively (P = <0.01). Subsequent experimental study confirmed that the direction of the J-tip was retained inside a model of vascular tubes and its tip led the guidewire into the tubing on the same side even at the acute angulation formed between tubings representing the subclavian, internal jugular, and superior vena cava junction complex. The authors conclude that the simple measure of keeping the guidewire J-tip directed caudad increased correct placement of central venous catheters towards the right atrium during right subclavian catheterization.

  1. Shape-memory polymers

    Marc Behl


    Full Text Available Shape-memory polymers are an emerging class of active polymers that have dual-shape capability. They can change their shape in a predefined way from shape A to shape B when exposed to an appropriate stimulus. While shape B is given by the initial processing step, shape A is determined by applying a process called programming. We review fundamental aspects of the molecular design of suitable polymer architectures, tailored programming and recovery processes, and the quantification of the shape-memory effect. Shape-memory research was initially founded on the thermally induced dual-shape effect. This concept has been extended to other stimuli by either indirect thermal actuation or direct actuation by addressing stimuli-sensitive groups on the molecular level. Finally, polymers are introduced that can be multifunctional. Besides their dual-shape capability, these active materials are biofunctional or biodegradable. Potential applications for such materials as active medical devices are highlighted.

  2. Polymer crowding and shape distributions in polymer-nanoparticle mixtures

    Lim, Wei Kang; Denton, Alan R., E-mail: [Department of Physics, North Dakota State University, Fargo, North Dakota 58108-6050 (United States)


    Macromolecular crowding can influence polymer shapes, which is important for understanding the thermodynamic stability of polymer solutions and the structure and function of biopolymers (proteins, RNA, DNA) under confinement. We explore the influence of nanoparticle crowding on polymer shapes via Monte Carlo simulations and free-volume theory of a coarse-grained model of polymer-nanoparticle mixtures. Exploiting the geometry of random walks, we model polymer coils as effective penetrable ellipsoids, whose shapes fluctuate according to the probability distributions of the eigenvalues of the gyration tensor. Accounting for the entropic cost of a nanoparticle penetrating a larger polymer coil, we compute the crowding-induced shift in the shape distributions, radius of gyration, and asphericity of ideal polymers in a theta solvent. With increased nanoparticle crowding, we find that polymers become more compact (smaller, more spherical), in agreement with predictions of free-volume theory. Our approach can be easily extended to nonideal polymers in good solvents and used to model conformations of biopolymers in crowded environments.

  3. Skin cancer texture analysis of OCT images based on Haralick, fractal dimension, Markov random field features, and the complex directional field features

    Raupov, Dmitry S.; Myakinin, Oleg O.; Bratchenko, Ivan A.; Zakharov, Valery P.; Khramov, Alexander G.


    In this paper, we propose a report about our examining of the validity of OCT in identifying changes using a skin cancer texture analysis compiled from Haralick texture features, fractal dimension, Markov random field method and the complex directional features from different tissues. Described features have been used to detect specific spatial characteristics, which can differentiate healthy tissue from diverse skin cancers in cross-section OCT images (B- and/or C-scans). In this work, we used an interval type-II fuzzy anisotropic diffusion algorithm for speckle noise reduction in OCT images. The Haralick texture features as contrast, correlation, energy, and homogeneity have been calculated in various directions. A box-counting method is performed to evaluate fractal dimension of skin probes. Markov random field have been used for the quality enhancing of the classifying. Additionally, we used the complex directional field calculated by the local gradient methodology to increase of the assessment quality of the diagnosis method. Our results demonstrate that these texture features may present helpful information to discriminate tumor from healthy tissue. The experimental data set contains 488 OCT-images with normal skin and tumors as Basal Cell Carcinoma (BCC), Malignant Melanoma (MM) and Nevus. All images were acquired from our laboratory SD-OCT setup based on broadband light source, delivering an output power of 20 mW at the central wavelength of 840 nm with a bandwidth of 25 nm. We obtained sensitivity about 97% and specificity about 73% for a task of discrimination between MM and Nevus.

  4. Longstanding neuropathic pain after spinal cord injury is refractory to transcranial direct current stimulation: a randomized controlled trial.

    Wrigley, Paul J; Gustin, Sylvia M; McIndoe, Leigh N; Chakiath, Rosemary J; Henderson, Luke A; Siddall, Philip J


    Neuropathic pain remains one of the most difficult consequences of spinal cord injury (SCI) to manage. It is a major cause of suffering and adds to the physical, emotional, and societal impact of the injury. Despite the use of the best available treatments, two thirds of people experiencing neuropathic pain after SCI do not achieve satisfactory pain relief. This study was undertaken in response to a recent clinical trial reporting short-term, clinically significant reductions in neuropathic SCI pain with primary motor cortex transcranial direct current stimulation (tDCS). In this investigation, we aimed to build on this previous clinical trial by extending the assessment period to determine the short-, medium-, and long-term efficacy of tDCS for the treatment of neuropathic pain after SCI. We found that, contrary to previous reports, after 5 tDCS treatment periods, mean pain intensity and unpleasantness rating were not significantly different from initial assessment. That is, in this trial tDCS did not provide any pain relief in subjects with neuropathic SCI pain (n=10). A similar lack of effect was also seen after sham treatment. Because the injury duration in this study was significantly greater than that of previous investigations, it is possible that tDCS is an effective analgesic only in individuals with relatively recent injuries and pain. Future investigations comparing a range of injury durations are required if we are to determine whether this is indeed the case. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

  5. Stepped Care Versus Direct Face-to-Face Cognitive Behavior Therapy for Social Anxiety Disorder and Panic Disorder: A Randomized Effectiveness Trial.

    Nordgreen, Tine; Haug, Thomas; Öst, Lars-Göran; Andersson, Gerhard; Carlbring, Per; Kvale, Gerd; Tangen, Tone; Heiervang, Einar; Havik, Odd E


    The aim of this study was to assess the effectiveness of a cognitive behavioral therapy (CBT) stepped care model (psychoeducation, guided Internet treatment, and face-to-face CBT) compared with direct face-to-face (FtF) CBT. Patients with panic disorder or social anxiety disorder were randomized to either stepped care (n=85) or direct FtF CBT (n=88). Recovery was defined as meeting two of the following three criteria: loss of diagnosis, below cut-off for self-reported symptoms, and functional improvement. No significant differences in intention-to-treat recovery rates were identified between stepped care (40.0%) and direct FtF CBT (43.2%). The majority of the patients who recovered in the stepped care did so at the less therapist-demanding steps (26/34, 76.5%). Moderate to large within-groups effect sizes were identified at posttreatment and 1-year follow-up. The attrition rates were high: 41.2% in the stepped care condition and 27.3% in the direct FtF CBT condition. These findings indicate that the outcome of a stepped care model for anxiety disorders is comparable to that of direct FtF CBT. The rates of improvement at the two less therapist-demanding steps indicate that stepped care models might be useful for increasing patients' access to evidence-based psychological treatments for anxiety disorders. However, attrition in the stepped care condition was high, and research regarding the factors that can improve adherence should be prioritized. Copyright © 2015. Published by Elsevier Ltd.


    Ch. von Ferber; Yu.Holovatch


    It is our great pleasure to present a collection of papers devoted to theoretical, numerical, and experimental studies in the field of star polymers. Since its introduction in the early 80-ies, this field has attracted increasing interest and has become an important part of contemporary polymer physics. While research papers in this field appear regularly in different physical and chemical journals, the present collection is an attempt to join together the studies of star polymers showing the...

  7. Direct observation of electronic and nuclear ground state splitting in external magnetic field by inelastic neutron scattering on oxidized ferrocene and ferrocene containing polymers

    Appel Markus


    Full Text Available The quantum mechanical splitting of states by interaction of a magnetic moment with an external magnetic field is well known, e.g., as Zeeman effect in optical transitions, and is also often seen in magnetic neutron scattering. We report excitations observed in inelastic neutron spectroscopy on the redox-responsive polymer poly(vinylferrocene. They are interpreted as splitting of the electronic ground state in the organometallic ferrocene units attached to the polymer chain where a magnetic moment is created by oxidation. In a second experiment using high resolution neutron backscattering spectroscopy we observe the hyperfine splitting, i.e., interaction of nuclear magnetic moments with external magnetic fields leading to sub-μeV excitations observable in incoherent neutron spin-flip scattering on hydrogen and vanadium nuclei.

  8. Preparation and degradation mechanisms of biodegradable polymer: a review

    Zeng, S. H.; Duan, P. P.; Shen, M. X.; Xue, Y. J.; Wang, Z. Y.


    Polymers are difficult to degrade completely in Nature, and their catabolites may pollute the environment. In recent years, biodegradable polymers have become the hot topic in people's daily life with increasing interest, and a controllable polymer biodegradation is one of the most important directions for future polymer science. This article presents the main preparation methods for biodegradable polymers and discusses their degradation mechanisms, the biodegradable factors, recent researches and their applications. The future researches of biodegradable polymers are also put forward.

  9. Polymer Chemistry

    Williams, Martha; Roberson, Luke; Caraccio, Anne


    This viewgraph presentation describes new technologies in polymer and material chemistry that benefits NASA programs and missions. The topics include: 1) What are Polymers?; 2) History of Polymer Chemistry; 3) Composites/Materials Development at KSC; 4) Why Wiring; 5) Next Generation Wiring Materials; 6) Wire System Materials and Integration; 7) Self-Healing Wire Repair; 8) Smart Wiring Summary; 9) Fire and Polymers; 10) Aerogel Technology; 11) Aerogel Composites; 12) Aerogels for Oil Remediation; 13) KSC's Solution; 14) Chemochromic Hydrogen Sensors; 15) STS-130 and 131 Operations; 16) HyperPigment; 17) Antimicrobial Materials; 18) Conductive Inks Formulations for Multiple Applications; and 19) Testing and Processing Equipment.

  10. Catalytic roles of lysines (K9, K27, K31) in the N-terminal domain in human adenylate kinase by random site-directed mutagenesis.

    Ayabe, T; Park, S K; Takenaka, H; Sumida, M; Uesugi, S; Takenaka, O; Hamada, M


    To elucidate lysine residues in the N-terminal domain of human cytosolic adenylate kinase (hAK1, EC, random site-directed mutagenesis of K9, K27, and K31 residues was performed, and six mutants were analyzed by steady-state kinetics. K9 residue may play an important role in catalysis by interacting with AMP2-. K27 and K31 residues appear to play a functional role in catalysis by interacting with MgATP2-. In human AK, the epsilon-amino group in the side chain of these lysine residues would be essential for phosphoryl transfer between MgATP2- and AMP2- during transition state.

  11. Human Pulp Response to Direct Pulp Capping and Miniature Pulpotomy with MTA after Application of Topical Dexamethasone: A Randomized Clinical Trial

    Mousavi, Seyed Amir; Ghoddusi, Jamileh; Mohtasham, Nooshin; Shahnaseri, Shirin; Paymanpour, Payam; Kinoshita, Jun-Ichiro


    Introduction: The aim of this randomized clinical trial was to compare the histologic pulp tissue response to one-step direct pulp capping (DPC) and miniature pulpotomy (MP) with mineral trioxide aggregate (MTA) after application of dexamethasone in healthy human premolars. Methods and Materials: Forty intact premolars from 10 orthodontic patients, were randomly chosen for DPC (n=20) or MP (n=20). In 10 teeth from each group, after exposure of the buccal pulp horn, topical dexamethasone was applied over the pulp. In all teeth the exposed/miniaturely resected pulp tissue was covered with MTA and cavities were restored with glass ionomer. Teeth vitality was evaluated during the next 7, 21, 42, and 60 days. Signs and/or symptoms of irreversible pulpitis or pulp necrosis were considered as failure. According to the orthodontic schedule, after 60 days the teeth were extracted and submitted for histological examination. The Kruskal-Wallis and Fisher’s exact tests were used for statistical analysis of the data (P=0.05). Results: Although dexamethasone specimens showed less inflammation, calcified bridge, pulpal blood vasculature, collagen fibers and granulation tissue formation were not significantly different between the groups (P>0.05). Conclusion: Topical dexamethasone did not hindered pulp healing but reduced the amount of underlying pulpal tissue inflammation after DPC and MP in healthy human premolars. PMID:27141213

  12. A prospective, randomized crossover study comparing direct inspection by light microscopy versus projected images for teaching of hematopathology to medical students.

    Carlson, Aaron M; McPhail, Ellen D; Rodriguez, Vilmarie; Schroeder, Georgene; Wolanskyj, Alexandra P


    Instruction in hematopathology at Mayo Medical School has evolved from instructor-guided direct inspection under the light microscope (laboratory method), to photomicrographs of glass slides with classroom projection (projection method). These methods have not been compared directly to date. Forty-one second-year medical students participated in this pilot study, a prospective, randomized, crossover study measuring educational performance during a hematology pathophysiology course. The students were randomized to one of two groups. All students received the same didactic lectures in the classroom and subsequent case-based review of peripheral blood smears using either laboratory or projection methods, on day one with a crossover to the other method on day two. Pre- and post-test examinations centered on morphology recognition measured educational performance on each day, followed by a questionnaire identifying the student's favored method. There was no significant difference in the pre-test and post-test scores between the two teaching methods (rank-sum P = 0.43). Students overwhelmingly preferred the projection method and perceived it as superior (76%), although post-test scores were not significantly different. Student's recommended method was split with 50% favoring the projection method, 43% favoring a combined approach, and 23% noting logistical challenges to the laboratory. In this study, the laboratory and projection method were equivalent in terms of educational performance for hematopathology among medicals students. A classroom-based approach such as the projection method is favored, given the large class sizes in undergraduate medical education, as well as the ergonomic challenges and additional resources required for large group instruction in a laboratory setting.

  13. Effect of a single session of transcranial direct-current stimulation on balance and spatiotemporal gait variables in children with cerebral palsy: A randomized sham-controlled study

    Luanda A. C. Grecco


    Full Text Available Background: Transcranial direct-current stimulation (tDCS has been widely studied with the aim of enhancing local synaptic efficacy and modulating the electrical activity of the cortex in patients with neurological disorders. Objective: The purpose of the present study was to determine the effect of a single session of tDCS regarding immediate changes in spatiotemporal gait and oscillations of the center of pressure (30 seconds in children with cerebral palsy (CP. Method: A randomized controlled trial with a blinded evaluator was conducted involving 20 children with CP between six and ten years of age. Gait and balance were evaluated three times: Evaluation 1 (before the stimulation, Evaluation 2 (immediately after stimulation, and Evaluation 3 (20 minutes after the stimulation. The protocol consisted of a 20-minute session of tDCS applied to the primary motor cortex at an intensity of 1 mA. The participants were randomly allocated to two groups: experimental group - anodal stimulation of the primary motor cortex; and control group - placebo transcranial stimulation. Results: Significant reductions were found in the experimental group regarding oscillations during standing in the anteroposterior and mediolateral directions with eyes open and eyes closed in comparison with the control group (p<0.05. In the intra-group analysis, the experimental group exhibited significant improvements in gait velocity, cadence, and oscillation in the center of pressure during standing (p<0.05. No significant differences were found in the control group among the different evaluations. Conclusion: A single session of tDCS applied to the primary motor cortex promotes positive changes in static balance and gait velocity in children with cerebral palsy.

  14. Effect of transcranial direct-current stimulation combined with treadmill training on balance and functional performance in children with cerebral palsy: a double-blind randomized controlled trial.

    Natália de Almeida Carvalho Duarte

    Full Text Available BACKGROUND: Cerebral palsy refers to permanent, mutable motor development disorders stemming from a primary brain lesion, causing secondary musculoskeletal problems and limitations in activities of daily living. The aim of the present study was to determine the effects of gait training combined with transcranial direct-current stimulation over the primary motor cortex on balance and functional performance in children with cerebral palsy. METHODS: A double-blind randomized controlled study was carried out with 24 children aged five to 12 years with cerebral palsy randomly allocated to two intervention groups (blocks of six and stratified based on GMFCS level (levels I-II or level III.The experimental group (12 children was submitted to treadmill training and anodal stimulation of the primary motor cortex. The control group (12 children was submitted to treadmill training and placebo transcranial direct-current stimulation. Training was performed in five weekly sessions for 2 weeks. Evaluations consisted of stabilometric analysis as well as the administration of the Pediatric Balance Scale and Pediatric Evaluation of Disability Inventory one week before the intervention, one week after the completion of the intervention and one month after the completion of the intervention. All patients and two examiners were blinded to the allocation of the children to the different groups. RESULTS: The experimental group exhibited better results in comparison to the control group with regard to anteroposterior sway (eyes open and closed; p<0.05, mediolateral sway (eyes closed; p<0.05 and the Pediatric Balance Scale both one week and one month after the completion of the protocol. CONCLUSION: Gait training on a treadmill combined with anodal stimulation of the primary motor cortex led to improvements in static balance and functional performance in children with cerebral palsy. TRIAL REGISTRATION:

  15. Scaling Behaviors of Branched Polymers

    Aoki, H; Kawai, H; Kitazawa, Y; Aoki, Hajime; Iso, Satoshi; Kawai, Hikaru; Kitazawa, Yoshihisa


    We study the thermodynamic behavior of branched polymers. We first study random walks in order to clarify the thermodynamic relation between the canonical ensemble and the grand canonical ensemble. We then show that correlation functions for branched polymers are given by those for $\\phi^3$ theory with a single mass insertion, not those for the $\\phi^3$ theory themselves. In particular, the two-point function behaves as $1/p^4$, not as $1/p^2$, in the scaling region. This behavior is consistent with the fact that the Hausdorff dimension of the branched polymer is four.

  16. Accelerated Characterization of Polymer Properties

    R. Wroczynski; l. Brewer; D. Buckley; M. Burrell; R. Potyrailo


    This report describes the efforts to develop a suite of microanalysis techniques that can rapidly measure a variety of polymer properties of industrial importance, including thermal, photo-oxidative, and color stability; as well as ductility, viscosity, and mechanical and antistatic properties. Additional goals of the project were to direct the development of these techniques toward simultaneous measurements of multiple polymer samples of small size in real time using non-destructive and/or parallel or rapid sequential measurements, to develop microcompounding techniques for preparing polymers with additives, and to demonstrate that samples prepared in the microcompounder could be analyzed directly or used in rapid off-line measurements. These enabling technologies are the crucial precursors to the development of high-throughput screening (HTS) methodologies for the polymer additives industry whereby the rate of development of new additives and polymer formulations can be greatly accelerated.

  17. Patient directed self management of pain (PaDSMaP compared to treatment as usual following total knee replacement: study protocol for a randomized controlled trial

    Donell Simon


    Full Text Available Abstract Background In 2009, 665 patients underwent total knee replacements (TKRs at the Norfolk and Norwich University Hospitals NHS Foundation Trust (NNUH, representing nearly 1% of the national total. Pain control following the operation can be poor, and this can cause poor mobilization and potential long-term adverse events. Although high levels of pain are not associated with patient dissatisfaction, brief periods of pain may lead to neuronal remodeling and sensitization. Patient controlled oral analgesia (PCOA may improve pain relief; however, the evidence to date has been inconclusive. Patient directed self management of pain (PaDSMaP is a single center randomized controlled trial, which aims to establish if patient self-medication improves, or is equivalent to, treatment as usual and to create an educational package to allow implementation elsewhere. Methods/design Patients eligible for a TKR will be recruited and randomized in the outpatient clinic. All patients will undergo their operations according to normal clinical practice but will be randomized into two groups. Once oral medication has commenced, one group will have pain relief administered by nursing staff in the usual way (treatment as usual; TAU, whilst the second group will self manage their pain medication (patient directed self management of pain; PaDSMaP. Those recruited for self-medication will undergo a training program to teach the use of oral analgesics according to the World Health Organization (WHO pain cascade and how to complete the study documentation. The primary endpoint of the trial is the visual analogue scale (VAS pain score at 3 days or discharge, whichever is sooner. The follow-up time is 6 weeks with a planned trial period of 3 years. The secondary objectives are satisfaction with the management of patient pain post-operatively whilst an inpatient after primary TKR; overall pain levels and pain on mobilization; satisfaction with pain management information

  18. Polymers & People

    Lentz, Linda; Robinson, Thomas; Martin, Elizabeth; Miller, Mary; Ashburn, Norma


    Each Tuesday during the fall of 2002, teams of high school students from three South Carolina counties conducted a four-hour polymer institute for their peers. In less than two months, over 300 students visited the Charleston County Public Library in Charleston, South Carolina, to explore DNA, nylon, rubber, gluep, and other polymers. Teams of…

  19. Effectiveness of the Gaze Direction Recognition Task for Chronic Neck Pain and Cervical Range of Motion: A Randomized Controlled Pilot Study

    Satoshi Nobusako


    Full Text Available We developed a mental task with gaze direction recognition (GDR by which subjects observed neck rotation of another individual from behind and attempted to recognize the direction of gaze. A randomized controlled trial was performed in test (=9 and control (=8 groups of subjects with chronic neck pain undergoing physical therapy either with or without the GDR task carried out over 12 sessions during a three-week period. Primary outcome measures were defined as the active range of motion and pain on rotation of the neck. Secondary outcome measures were reaction time (RT and response accuracy in the GDR task group. ANOVA indicated a main effect for task session and group, and interaction of session. Post hoc testing showed that the GDR task group exhibited a significant simple main effect upon session, and significant sequential improvement of neck motion and relief of neck pain. Rapid effectiveness was significant in both groups. The GDR task group had a significant session-to-session reduction of RTs in correct responses. In conclusion, the GDR task we developed provides a promising rehabilitation measure for chronic neck pain.

  20. Driving High-Performance n- and p-type Organic Transistors with Carbon Nanotube/Conjugated Polymer Composite Electrodes Patterned Directly from Solution

    Hellstrom, Sondra L.


    We report patterned deposition of carbon nanotube/conjugated polymer composites from solution with high nanotube densities and excellent feature resolution. Such composites are suited for use as electrodes in high-performance transistors of pentacene and C60, with bottom-contact mobilities of ?0.5 and ?1 cm2 V-1 s-1, respectively. This represents a clear step towards development of inexpensive, high-performance all-organic circuits. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Effects of Intravenous and Catheter Directed Thrombolytic Therapy with Recombinant Tissue Plasminogen Activator (Alteplase in Non-Traumatic Acute Limb Ischemia; A Randomized Double-Blind Clinical Trial

    Abbas Saroukhani


    Full Text Available Objective: To evaluate the efficacy and safety of intravenous and catheter directed thrombolysis by recombinant tissue plasminogen activator (Alteplase in the patients with non-traumatic acute limb ischemia (ALI. Methods: This was a randomized clinical trial being performed between 2009 and 2011 in Mashhad University of Medical Sciences. We included those patients who were<75 years, with symptoms of less than 14 days duration, ALI of grade IIa and IIb (according to Rutherford classification and absence of distal run off. Baseline assessment of peripheral circulation performed in all the patients. Patients were randomly assigned to undergo intravenous (n=18 or catheter directed thrombolysis (n=20 with Alteplase. The primary endpoint of the study was improvement of clinical status measured by Rutherford classification, ankle brachial index (ABI, visual analogue scale (VAS score measured at 1, 3 and 6 months. The secondary endpoint of the study was complete or near complete recanalization of the occluded artery. Results: A total number of 38 patients with mean age of 54.13±13.5 years were included in the study. There were 23 (60.5% men and 15 (39.5% women among the patients. Overall 3 (7.9% patients had upper and 35 (92.1% lower extremity ischemia. There was no significant difference between two study groups. None of the patients experienced major therapeutic side effects. Both ABI and VAS score improved in patients who have received first dose of t-PA within 24-hourof ALI. There was no significant difference between two study groups regarding the 6-month clinical grade ( p=0.088, VAS score ( p=0.316 and ABI ( p=0.360. The angiographic improvement was significantly higher in CDT group ( p<0.001. Conclusion: Intravenous and catheter directed thrombolysis with t-PA is a safe and effective method in treatment of acute arteriolar ischemia of extremities. However there both intravenous thrombolysis and CDT are comparable regarding the clinical outcome

  2. Low-temperature Preparation of Photocatalytic TiO2 Thin Films on Polymer Substrates by Direct Deposition from Anatase Sol


    Anatase TiO2 sol was synthesized under mild conditions (75C and ambient pressure) by hydrolysis of titaniumn-butoxide in abundant acidic aqueous solution and subsequent reflux to enhance crystallization. At room temperature and in ambient atmosphere, crystalline TiO2 thin films were deposited on polymethylmethacrylate (PMMA), SiO2-coated PMMA and SiO2-coated silicone rubber substrates from the as-prepared TiO2 sol by a dip-coating process. SiO2 layers prior to TiO2 thin films on polymer substrates could not only protect the substrates from the photocatalytic decomposition of the TiO2 thin films but also enhance the adhesion of the TiO2 thin films to the substrates. Field-emission type scanning electron microscope (FE-SEM) investigations revealed that the average particle sizes of the nanoparticles composing the TiO2 thin films were about 35~47 nm. The TiO2 thin films exhibited high photocatalytic activities in the degradation of reactive brilliant red dye X-3B in aqueous solution under aerated conditions. The preparation process of photocatalytic TiO2 thin films on the polymer substrates was quite simple and a low temperature route.

  3. Active Polymer Gel Actuators

    Shuji Hashimoto


    Full Text Available Many kinds of stimuli-responsive polymer and gels have been developed and applied to biomimetic actuators or artificial muscles. Electroactive polymers that change shape when stimulated electrically seem to be particularly promising. In all cases, however, the mechanical motion is driven by external stimuli, for example, reversing the direction of electric field. On the other hand, many living organisms can generate an autonomous motion without external driving stimuli like self-beating of heart muscles. Here we show a novel biomimetic gel actuator that can walk spontaneously with a wormlike motion without switching of external stimuli. The self-oscillating motion is produced by dissipating chemical energy of oscillating reaction. Although the gel is completely composed of synthetic polymer, it shows autonomous motion as if it were alive.

  4. Polymer flexibility and turbulent drag reduction

    Gillissen, J.J.J.


    Polymer-induced drag reduction is the phenomenon by which the friction factor of a turbulent flow is reduced by the addition of small amounts of high-molecular-weight linear polymers, which conformation in solution at rest can vary between randomly coiled and rodlike. It is well known that drag redu

  5. A pilot randomized controlled trial of the feasibility of a self-directed coping skills intervention for couples facing prostate cancer: Rationale and design

    Lambert Sylvie D


    Full Text Available Abstract Background Although it is known both patients’ and partners’ reactions to a prostate cancer diagnosis include fear, uncertainty, anxiety and depression with patients’ partners’ reactions mutually determining how they cope with and adjust to the illness, few psychosocial interventions target couples. Those that are available tend to be led by highly trained professionals, limiting their accessibility and long-term sustainability. In addition, it is recognised that patients who might benefit from conventional face-to-face psychosocial interventions do not access these, either by preference or because of geographical or mobility barriers. Self-directed interventions can overcome some of these limitations and have been shown to contribute to patient well-being. This study will examine the feasibility of a self-directed, coping skills intervention for couples affected by cancer, called Coping-Together, and begin to explore its potential impact on couples’ illness adjustment. The pilot version of Coping-Together includes a series of four booklets, a DVD, and a relaxation audio CD. Methods/design In this double-blind, two-group, parallel, randomized controlled trial, 70 couples will be recruited within 4 months of a prostate cancer diagnosis through urology private practices and randomized to: 1 Coping-Together or 2 a minimal ethical care condition. Minimal ethical care condition couples will be mailed information booklets available at the Cancer Council New South Wales and a brochure for the Cancer Council Helpline. The primary outcome (anxiety and additional secondary outcomes (distress, depression, dyadic adjustment, quality of life, illness or caregiving appraisal, self-efficacy, and dyadic and individual coping will be assessed at baseline (before receiving study material and 2 months post-baseline. Intention-to-treat and per protocol analysis will be conducted. Discussion As partners’ distress rates exceed not only population

  6. 3D technology of Sony Bloggie has no advantage in decision-making of tennis serve direction: A randomized placebo-controlled study.

    Liu, Sicong; Ritchie, Jason; Sáenz-Moncaleano, Camilo; Ward, Savanna K; Paulsen, Cody; Klein, Tyler; Gutierrez, Oscar; Tenenbaum, Gershon


    This study aimed at exploring whether 3D technology enhances tennis decision-making under the conceptual framework of human performance model. A 3 (skill-level: varsity, club, recreational) × 3 (experimental condition: placebo, weak 3D [W3D], strong 3D [S3D]) between-participant design was used. Allocated to experimental conditions by a skill-level stratified randomization, 105 tennis players judged tennis serve direction from video scenarios and rated their perceptions of enjoyment, flow, and presence during task performance. Results showed that varsity players made more accurate decisions than less skilled ones. Additionally, applying 3D technology to typical video displays reduced tennis players' decision-making accuracy, although wearing the 3D glasses led to a placebo effect that shortened the decision-making reaction time. The unexpected negative effect of 3D technology on decision-making was possibly due to participants being more familiar to W3D than to S3D, and relatedly, a suboptimal task-technology match. Future directions for advancing this area of research are offered. Highlights 3D technology augments binocular depth cues to tradition video displays, and thus results in the attainment of more authentic visual representation. This process enhances task fidelity in researching perceptual-cognitive skills in sports. The paper clarified both conceptual and methodological difficulties in testing 3D technology in sports settings. Namely, the nomenclature of video footage (with/without 3D technology) and the possible placebo effect (arising from wearing glasses of 3D technology) merit researchers' attention. Participants varying in level of domain-specific expertise were randomized into viewing conditions using a placebo-controlled design. Measurement consisted of both participants' subjective experience (i.e., presence, flow, and enjoyment) and objective performance (i.e., accuracy and reaction time) in a decision-making task. Findings revealed that

  7. Selection of IgG variants with increased FcRn binding using random and directed mutagenesis: impact on effector functions

    Céline eMonnet


    Full Text Available Despite the reasonably long half-life of IgGs, market pressure for higher patient convenience while conserving efficacy continues to drive IgG half-life improvement. IgG half-life is dependent on the neonatal Fc receptor FcRn, which amongst other functions, protects IgG from catabolism. FcRn binds the Fc domain of IgG at an acidic pH ensuring that endocytosed IgG will not be degraded in lysosomal compartments and will then be released into the bloodstream. Consistent with this mechanism of action, several Fc engineered IgG with increased FcRn affinity and conserved pH-dependency were designed and resulted in longer half-life in vivo in human FcRn transgenic mice (hFcRn, cynomolgus monkeys and recently in healthy humans. These IgG variants were usually obtained by in silico approaches or directed mutagenesis in the FcRn binding site. Using random mutagenesis, combined with a pH-dependent phage display selection process, we isolated IgG variants with improved FcRn-binding which exhibited longer in vivo half-life in hFcRn mice. Interestingly, many mutations enhancing Fc/FcRn interaction were located at a distance from the FcRn binding site validating our random molecular approach. Directed mutagenesis was then applied to generate new variants to further characterize our IgG variants and the effect of the mutations selected. Since these mutations are distributed over the whole Fc sequence, binding to other Fc effectors, such as complement C1q and FcgRs, was dramatically modified, even by mutations distant from these effectors’ binding sites. Hence, we obtained numerous IgG variants with increased FcRn binding and different binding patterns to other Fc effectors, including variants without any effector function, providing distinct fit-for-purpose Fc molecules. We therefore provide evidence that half-life and effector functions should be optimized simultaneously as mutations can have unexpected effects on all Fc receptors that are critical for Ig

  8. A Randomized Controlled Trial Comparing the McKenzie Method to Motor Control Exercises in People With Chronic Low Back Pain and a Directional Preference.

    Halliday, Mark H; Pappas, Evangelos; Hancock, Mark J; Clare, Helen A; Pinto, Rafael Z; Robertson, Gavin; Ferreira, Paulo H


    Study Design Randomized clinical trial. Background Motor control exercises are believed to improve coordination of the trunk muscles. It is unclear whether increases in trunk muscle thickness can be facilitated by approaches such as the McKenzie method. Furthermore, it is unclear which approach may have superior clinical outcomes. Objectives The primary aim was to compare the effects of the McKenzie method and motor control exercises on trunk muscle recruitment in people with chronic low back pain classified with a directional preference. The secondary aim was to conduct a between-group comparison of outcomes for pain, function, and global perceived effect. Methods Seventy people with chronic low back pain who demonstrated a directional preference using the McKenzie assessment were randomized to receive 12 treatments over 8 weeks with the McKenzie method or with motor control approaches. All outcomes were collected at baseline and at 8-week follow-up by blinded assessors. Results No significant between-group difference was found for trunk muscle thickness of the transversus abdominis (-5.8%; 95% confidence interval [CI]: -15.2%, 3.7%), obliquus internus (-0.7%; 95% CI: -6.6%, 5.2%), and obliquus externus (1.2%; 95% CI: -4.3%, 6.8%). Perceived recovery was slightly superior in the McKenzie group (-0.8; 95% CI: -1.5, -0.1) on a -5 to +5 scale. No significant between-group differences were found for pain or function (P = .99 and P = .26, respectively). Conclusion We found no significant effect of treatment group for trunk muscle thickness. Participants reported a slightly greater sense of perceived recovery with the McKenzie method than with the motor control approach. Level of Evidence Therapy, level 1b-. Registered September 7, 2011 at (ACTRN12611000971932). J Orthop Sports Phys Ther 2016;46(7):514-522. Epub 12 May 2016. doi:10.2519/jospt.2016.6379.

  9. Performance of inverted polymer solar cells with randomly oriented ZnO nanorods coupled with atomic layer deposited ZnO

    Zafar, Muhammad; Yun, Ju-Young; Kim, Do-Heyoung


    Nanostructuring of the electron transport layer (ETL) in organic photovoltaic cells (OPV) is of great interest because it increases the surface area of the cell and electron transport. In this work, hydrothermally grown, randomly oriented, and low areal density ZnO nanorods (NRs) have been adopted as the ETL, and the effect of adding atomic layer deposited (ALD) ZnO on the ZnO NRs on the inverted organic solar cell performance has been investigated. The fabricated inverted organic solar cell with 5-nm-thick ALD-ZnO grown on the ZnO NRs showed the highest power conversion efficiency (PCE) of 3.08%, which is an enhancement of 85% from that of the cell without ALD-ZnO (PCE = 1.67%). The ultrathin ALD-ZnO was found to act as a curing layer of the surface defects on the hydrothermally grown ZnO NRs, resulting in an improvement in photovoltaic performance.

  10. Dual responsive polymeric nanoparticles prepared by direct functionalization of polylactic acid-based polymers via graft-from ring opening metathesis polymerization.

    Veccharelli, Kate M; Tong, Venus K; Young, Jennifer L; Yang, Jerry; Gianneschi, Nathan C


    Polylactic acid (PLA) has found widespread use in plastics and in biomedical applications due to its biodegradability into natural benign products. However, PLA-based materials remain limited in usefulness due to difficulty of incorporating functional groups into the polymer backbone. In this paper, we report a strategy for PLA functionalization that establishes the preparation of highly derivatized materials in which ring opening metathesis polymerization (ROMP) is employed as a graft-from polymerization technique utilizing a norbornene-modified handle incorporated into the PLA backbone. As a demonstration of this new synthetic methodology, a PLA-derived nanoparticle bearing imidazole units protected with a photolabile group was prepared. The morphology of this material could be controllably altered in response to exposure of UV light or acidic pH as a stimulus. We anticipate that this graft-from approach to derivatization of PLA could find broad use in the development of modified, biodegradable PLA-based materials.

  11. Metal ions directed assembly of two coordination polymers based on an organic phosphonate anion and a multidentate N-donor ligand

    Kan, Wei-Qiu; Xu, Ji-Ming; Wen, Shi-Zheng; Yang, Lin


    Two new coordination polymers [Cd(4,4‧-tmbpt)(HL)(H2O)] (1) and [Cu(4,4‧-tmbpt)(HL)]·H2O (2) (H3L = 2‧-carboxybiphenyl-4-ylmethylphosphonic and 4,4‧-tmbpt = 1-((1H-1,2,4-triazol-1-yl)methyl)-3,5-bis(4-pyridyl)-1,2,4-triazole) have been synthesized hydrothermally. The two compounds have the same metal to ligand ratio, but different metal ions. As a result, the two compounds display different 2D layer structures, which is mainly caused by the different coordination numbers of the different metal ions. The effects of the metal ions on the structures, the optical band gaps and photoluminescent and photocatalytic properties of the compounds have been studied.

  12. Organometallic Polymers.

    Carraher, Charles E., Jr.


    Reactions utilized to incorporate a metal-containing moiety into a polymer chain (addition, condensation, and coordination) are considered, emphasizing that these reactions also apply to smaller molecules. (JN)

  13. Coordination-directed one-dimensional coordination polymers generated from a new oxadiazole bridging ligand and HgX2 (X=Cl, Br and I).

    Yang, Rui; Ma, Jian Ping; Huang, Ru Qi; Dong, Yu Bin


    A new 1,3,4-oxadiazole bridging bent organic ligand, 2,5-bis{5-methyl-2-[(4-pyridyl)methoxy]phenyl}-1,3,4-oxadiazole, C(28)H(24)N(4)O(3), L, has been used to create three novel one-dimensional isomorphic coordination polymers, viz. catena-poly[[[dichloridomercury(II)]-μ-2,5-bis{5-methyl-2-[(4-pyridyl)methoxy]phenyl}-1,3,4-oxadiazole] methanol monosolvate], {[HgCl(2)(C(28)H(24)N(4)O(3))]·CH(3)OH}(n), catena-poly[[[dibromidomercury(II)]-μ-2,5-bis{5-methyl-2-[(4-pyridyl)methoxy]phenyl}-1,3,4-oxadiazole] methanol monosolvate], {[HgBr(2)(C(28)H(24)N(4)O(3))]·CH(3)OH}(n), and catena-poly[[[diiodidomercury(II)]-μ-2,5-bis{5-methyl-2-[(4-pyridyl)methoxy]phenyl}-1,3,4-oxadiazole] methanol monosolvate], {[HgI(2)(C(28)H(24)N(4)O(3))]·CH(3)OH}(n). The free L ligand itself adopts a cis conformation, with the two terminal pyridine rings and the central oxadiazole ring almost coplanar [dihedral angles = 5.994 (7) and 9.560 (6)°]. In the Hg(II) complexes, however, one of the flexible pyridylmethyl arms of ligand L is markedly bent and helical chains are obtained. The Hg(II) atom lies in a distorted tetrahedral geometry defined by two pyridine N-atom donors from two L ligands and two halide ligands. The helical chains stack together via interchain π-π interactions that expand the dimensionality of the structure from one to two. The methanol solvent molecules link to the complex polymers through O-H···N and O-H···O hydrogen bonds. © 2011 International Union of Crystallography

  14. Polymers All Around You!

    Gertz, Susan

    Background information on natural polymers, synthetic polymers, and the properties of polymers is presented as an introduction to this curriculum guide. Details are provided on the use of polymer products in consumer goods, polymer recycling, polymer densities, the making of a polymer such as GLUEP, polyvinyl alcohol, dissolving plastics, polymers…

  15. Phase stability and dynamics of entangled polymer-nanoparticle composites.

    Mangal, Rahul


    Nanoparticle-polymer composites, or polymer-nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host.

  16. Synthesis and properties of optically active nanostructured polymers bearing amino acid moieties by direct polycondensation of 4,4'-thiobis(2-tert-butyl-5-methylphenol) with chiral diacids.

    Mallakpour, Shadpour; Soltanian, Samaneh


    Four derivatives of N-trimellitylimido-L-amino acid (4a-4d) were prepared by the reaction of trimellitic anhydride (1) with the L-amino acids (2a-2d) in acetic acid as diacid monomers and were used with the aim to obtain a new family of amino acid based poly(ester-imide)s (PEI)s. The polymerization was performed by direct polycondensation of chiral diacids (4a-4d) with 4,4'-thiobis(2-tert-butyl-5-methylphenol) (5) in the presence of tosyl chloride (TsCl), pyridine and N,N-dimethyl formamide (DMF). Step-growth polymerization was carried out by varying the time of heating and the molar ratio of TsCl/diacid and the optimum conditions were achieved. The synthesized polymers were characterized by means of specific rotation experiments, FT-IR, 1H-NMR, X-ray diffraction techniques and elemental analysis. The surface morphology of the obtained polymers was studied by field emission scanning electron microscopy. The result showed nanostructure morphology of the resulting polymers. The obtained PEIs were soluble in polar aprotic solvents such as DMF, N,N-dimethyl acetamide, dimethyl sulfoxide, N-methyl-2-pyrrolidone and protic solvents such as sulfuric acid. Thermal stability and the weight-loss behavior of the PEIs were studied by thermal gravimetric analysis (TGA) techniques. TGA showed that the 10% weight loss temperature in a nitrogen atmosphere was more than 402°C, therefore they had useful levels of thermal stability associated with excellent solubility.

  17. A randomized controlled trial comparing traditional training in cardiopulmonary resuscitation (CPR) to self-directed CPR learning in first year medical students: The two-person CPR study.

    Roppolo, Lynn P; Heymann, Rahm; Pepe, Paul; Wagner, James; Commons, Bradford; Miller, Ronna; Allen, Emilie; Horne, Leyla; Wainscott, Michael P; Idris, Ahamed H


    The primary purpose of this study was to compare two, shorter, self-directed methods of cardiopulmonary resuscitation (CPR) education for healthcare professionals (HCP) to traditional training with a focus on the trainee's ability to perform two-person CPR. First-year medical students with either no prior CPR for HCP experience or prior training greater than 5 years were randomized to complete one of three courses: 1) HeartCode BLS System, 2) BLS Anytime, or 3) Traditional training. Only data from the adult CPR skills testing station was reviewed via video recording by certified CPR instructors and the Laerdal PC Skill Reporter software program (Laerdal Medical, Stavanger, Norway). There were 180 first-year medical students who met inclusion criteria: 68 were HeartCode BLS System, 53 BLS Anytime group, and 59 traditional group Regarding two-person CPR, 57 (84%) of Heartcode BLS students and 43 (81%) of BLS Anytime students were able to initiate the switch compared to 39 (66%) of traditional course students (p = 0.04). There were no significant differences in the quality of chest compressions or ventilations between the three groups. There was a trend for a much higher CPR skills testing pass rate for the traditional course students. However, failure to "clear to analyze or shock" while using the AED was the most common reason for failure in all groups. The self-directed learning groups not only had a high level of success in initiating the "switch" to two-person CPR, but were not significantly different from students who completed traditional training. Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.

  18. Functional mapping of the fission yeast DNA polymerase δ B-subunit Cdc1 by site-directed and random pentapeptide insertion mutagenesis

    Gray Fiona C


    Full Text Available Abstract Background DNA polymerase δ plays an essential role in chromosomal DNA replication in eukaryotic cells, being responsible for synthesising the bulk of the lagging strand. In fission yeast, Pol δ is a heterotetrameric enzyme comprising four evolutionarily well-conserved proteins: the catalytic subunit Pol3 and three smaller subunits Cdc1, Cdc27 and Cdm1. Pol3 binds directly to the B-subunit, Cdc1, which in turn binds the C-subunit, Cdc27. Human Pol δ comprises the same four subunits, and the crystal structure was recently reported of a complex of human p50 and the N-terminal domain of p66, the human orthologues of Cdc1 and Cdc27, respectively. Results To gain insights into the structure and function of Cdc1, random and directed mutagenesis techniques were used to create a collection of thirty alleles encoding mutant Cdc1 proteins. Each allele was tested for function in fission yeast and for binding of the altered protein to Pol3 and Cdc27 using the two-hybrid system. Additionally, the locations of the amino acid changes in each protein were mapped onto the three-dimensional structure of human p50. The results obtained from these studies identify amino acid residues and regions within the Cdc1 protein that are essential for interaction with Pol3 and Cdc27 and for in vivo function. Mutations specifically defective in Pol3-Cdc1 interactions allow the identification of a possible Pol3 binding surface on Cdc1. Conclusion In the absence of a three-dimensional structure of the entire Pol δ complex, the results of this study highlight regions in Cdc1 that are vital for protein function in vivo and provide valuable clues to possible protein-protein interaction surfaces on the Cdc1 protein that will be important targets for further study.

  19. Segmented conjugated polymers

    G Padmanaban; S Ramakrishnan


    Segmented conjugated polymers, wherein the conjugation is randomly truncated by varying lengths of non-conjugated segments, form an interesting class of polymers as they not only represent systems of varying stiffness, but also ones where the backbone can be construed as being made up of chromophores of varying excitation energies. The latter feature, especially when the chromophores are fluorescent, like in MEHPPV, makes these systems particularly interesting from the photophysics point of view. Segmented MEHPPV- samples, where x represents the mole fraction of conjugated segments, were prepared by a novel approach that utilizes a suitable precursor wherein selective elimination of one of the two eliminatable groups is affected; the uneliminated units serve as conjugation truncations. Control of the composition x of the precursor therefore permits one to prepare segmented MEHPPV- samples with varying levels of conjugation (elimination). Using fluorescence spectroscopy, we have seen that even in single isolated polymer chains, energy migration from the shorter (higher energy) chromophores to longer (lower energy) ones occurs – the extent of which depends on the level of conjugation. Further, by varying the solvent composition, it is seen that the extent of energy transfer and the formation of poorly emissive inter-chromophore excitons are greatly enhanced with increasing amounts of non-solvent. A typical S-shaped curve represents the variation of emission yields as a function of composition suggestive of a cooperative collapse of the polymer coil, reminiscent of conformational transitions seen in biological macromolecules.

  20. Comparison of the operation of polymer/fullerene, polymer/polymer, and polymer/nanocrystal solar cells: a transient photocurrent and photovoltage study

    Li, Zhe; Gao, Feng; Greenham, Neil C.; McNeill, Christopher R. [Cavendish Laboratory, University of Cambridge, J J Thomson Ave, Cambridge, CB3 0HE (United Kingdom)


    We utilize transient techniques to directly compare the operation of polymer/fullerene, polymer/nanocrystal, and polymer/polymer bulk heterojunction solar cells. For all devices, poly(3-hexylthiophene) (P3HT) is used as the electron donating polymer, in combination with either the fullerene derivative phenyl-C{sub 61}-butyric acid methyl ester (PCBM) in polymer/fullerene cells, CdSe nanoparticles in polymer/nanocrystal cells, or the polyfluorene copolymer poly((9,9-dioctylfluorene)-2,7-diyl-alt-[4,7-bis(3-hexylthien-5-yl)-2,1,3-benzothiadiazole]-2,2-diyl) (F8TBT) in polymer/polymer cells. Transient photocurrent and photovoltage measurements are used to probe the dynamics of charge-separated carriers, with vastly different dynamic behavior observed for polymer/fullerene, polymer/polymer, and polymer/nanocrystal devices on the microsecond to millisecond timescale. Furthermore, by employing transient photocurrent analysis with different applied voltages we are also able to probe the dynamics behavior of these cells from short circuit to open circuit. P3HT/F8TBT and P3HT/CdSe devices are characterized by poor charge extraction of the long-lived carriers attributed to charge trapping. P3HT/PCBM devices, in contrast, show relatively trap-free operation with the variation in the photocurrent decay kinetics with applied bias at low intensity, consistent with the drift of free charges under a uniform electric field. Under solar conditions at the maximum power point, we see direct evidence of bimolecular recombination in the P3HT/PCBM device competing with charge extraction. Transient photovoltage measurements reveal that, at open circuit, photogenerated charges have similar lifetimes in all device types, and hence, the extraction of these long-lived charges is a limiting process in polymer/nanocrystal and polymer/polymer devices. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Bihemispheric Motor Cortex Transcranial Direct Current Stimulation Improves Force Steadiness in Post-Stroke Hemiparetic Patients: A Randomized Crossover Controlled Trial

    Montenegro, Rafael A.; Midgley, Adrian; Massaferri, Renato; Bernardes, Wendell; Okano, Alexandre H.; Farinatti, Paulo


    Post-stroke patients usually exhibit reduced peak muscular torque (PT) and/or force steadiness during submaximal exercise. Brain stimulation techniques have been proposed to improve neural plasticity and help to restore motor performance in post-stroke patients. The present study compared the effects of bihemispheric motor cortex transcranial direct current stimulation (tDCS) on PT and force steadiness during maximal and submaximal resistance exercise performed by post-stroke patients vs. healthy controls. A double-blind randomized crossover controlled trial (identification number: TCTR20151112001; URL: was conducted involving nine healthy and 10 post-stroke hemiparetic individuals who received either tDCS (2 mA) or sham stimulus upon the motor cortex for 20 min. PT and force steadiness (reflected by the coefficient of variation (CV) of muscular torque) were assessed during unilateral knee extension and flexion at maximal and submaximal workloads (1 set of 3 repetitions at 100% PT and 2 sets of 10 repetitions at 50% PT, respectively). No significant change in PT was observed in post-stroke and healthy subjects. Force steadiness during knee extension (~25–35%, P knee extension (~13–27%, P < 0.001) in healthy controls. These results suggest that tDCS may improve force steadiness, but not PT in post-stroke hemiparetic patients, which might be relevant in the context of motor rehabilitation programs. PMID:27601988

  2. Differential effects of primary motor cortex and cerebellar transcranial direct current stimulation on motor learning in healthy individuals: A randomized double-blind sham-controlled study.

    Ehsani, F; Bakhtiary, A H; Jaberzadeh, S; Talimkhani, A; Hajihasani, A


    The purpose of study was to compare the effect of primary motor cortex (M1) and cerebellar anodal transcranial direct current stimulation (a-tDCS) on online and offline motor learning in healthy individuals. Fifty-nine healthy volunteers were randomly divided into three groups (n=20 in two experimental groups and n=19 in sham-control group). One experimental group received M1a-tDCSand another received cerebellar a-tDCS. The main outcome measure were response time (RT) and number of errors during serial response time test (SRTT) which were assessed prior, 35min and 48h after the interventions. Reduction of response time (RT) and error numbers at last block of the test compared to the first block was considered online learning. Comparison of assessments during retention tests was considered as short-term and long-term offline learning. Online RT reduction was not different among groups (P>0.05), while online error reduction was significantly greater in cerebellar a-tDCS than sham-control group (Plearning as compared to sham tDCS (Pgroup (Plearning and M1a-tDCS has more effect on short-term offline learning, both M1 and cerebellar a-tDCS can be used as a boosting technique for improvement of offline motor learning in healthy individuals. Crown Copyright © 2016. Published by Elsevier Ireland Ltd. All rights reserved.

  3. Constraint-Induced Movement Therapy Combined with Transcranial Direct Current Stimulation over Premotor Cortex Improves Motor Function in Severe Stroke: A Pilot Randomized Controlled Trial

    Batista, Larissa M.; Nogueira, Lídia L. R. F.; de Oliveira, Eliane A.; de Carvalho, Antonio G. C.; Lima, Soriano S.; Santana, Jordânia R. M.; de Lima, Emerson C. C.; Fernández-Calvo, Bernardino


    Objective. We compared the effects of transcranial direct current stimulation at different cortical sites (premotor and motor primary cortex) combined with constraint-induced movement therapy for treatment of stroke patients. Design. Sixty patients were randomly distributed into 3 groups: Group A, anodal stimulation on premotor cortex and constraint-induced movement therapy; Group B, anodal stimulation on primary motor cortex and constraint-induced movement therapy; Group C, sham stimulation and constraint-induced movement therapy. Evaluations involved analysis of functional independence, motor recovery, spasticity, gross motor function, and muscle strength. Results. A significant improvement in primary outcome (functional independence) after treatment in the premotor group followed by primary motor group and sham group was observed. The same pattern of improvement was highlighted among all secondary outcome measures regarding the superior performance of the premotor group over primary motor and sham groups. Conclusions. Premotor cortex can contribute to motor function in patients with severe functional disabilities in early stages of stroke. This study was registered in database (NCT 02628561). PMID:28250992

  4. Constraint-Induced Movement Therapy Combined with Transcranial Direct Current Stimulation over Premotor Cortex Improves Motor Function in Severe Stroke: A Pilot Randomized Controlled Trial.

    Andrade, Suellen M; Batista, Larissa M; Nogueira, Lídia L R F; de Oliveira, Eliane A; de Carvalho, Antonio G C; Lima, Soriano S; Santana, Jordânia R M; de Lima, Emerson C C; Fernández-Calvo, Bernardino


    Objective. We compared the effects of transcranial direct current stimulation at different cortical sites (premotor and motor primary cortex) combined with constraint-induced movement therapy for treatment of stroke patients. Design. Sixty patients were randomly distributed into 3 groups: Group A, anodal stimulation on premotor cortex and constraint-induced movement therapy; Group B, anodal stimulation on primary motor cortex and constraint-induced movement therapy; Group C, sham stimulation and constraint-induced movement therapy. Evaluations involved analysis of functional independence, motor recovery, spasticity, gross motor function, and muscle strength. Results. A significant improvement in primary outcome (functional independence) after treatment in the premotor group followed by primary motor group and sham group was observed. The same pattern of improvement was highlighted among all secondary outcome measures regarding the superior performance of the premotor group over primary motor and sham groups. Conclusions. Premotor cortex can contribute to motor function in patients with severe functional disabilities in early stages of stroke. This study was registered in database (NCT 02628561).

  5. Bihemispheric Motor Cortex Transcranial Direct Current Stimulation Improves Force Steadiness in Post-Stroke Hemiparetic Patients: A Randomized Crossover Controlled Trial.

    Montenegro, Rafael A; Midgley, Adrian; Massaferri, Renato; Bernardes, Wendell; Okano, Alexandre H; Farinatti, Paulo


    Post-stroke patients usually exhibit reduced peak muscular torque (PT) and/or force steadiness during submaximal exercise. Brain stimulation techniques have been proposed to improve neural plasticity and help to restore motor performance in post-stroke patients. The present study compared the effects of bihemispheric motor cortex transcranial direct current stimulation (tDCS) on PT and force steadiness during maximal and submaximal resistance exercise performed by post-stroke patients vs. healthy controls. A double-blind randomized crossover controlled trial (identification number: TCTR20151112001; URL: was conducted involving nine healthy and 10 post-stroke hemiparetic individuals who received either tDCS (2 mA) or sham stimulus upon the motor cortex for 20 min. PT and force steadiness (reflected by the coefficient of variation (CV) of muscular torque) were assessed during unilateral knee extension and flexion at maximal and submaximal workloads (1 set of 3 repetitions at 100% PT and 2 sets of 10 repetitions at 50% PT, respectively). No significant change in PT was observed in post-stroke and healthy subjects. Force steadiness during knee extension (~25-35%, P stroke patients, but improved only during knee extension (~13-27%, P stroke hemiparetic patients, which might be relevant in the context of motor rehabilitation programs.

  6. Enhancement of the catalytic activity of ferulic acid decarboxylase from Enterobacter sp. Px6-4 through random and site-directed mutagenesis.

    Lee, Hyunji; Park, Jiyoung; Jung, Chaewon; Han, Dongfei; Seo, Jiyoung; Ahn, Joong-Hoon; Chong, Youhoon; Hur, Hor-Gil


    The enzyme ferulic acid decarboxylase (FADase) from Enterobacter sp. Px6-4 catalyzes the decarboxylation reaction of lignin monomers and phenolic compounds such as p-coumaric acid, caffeic acid, and ferulic acid into their corresponding 4-vinyl derivatives, that is, 4-vinylphenol, 4-vinylcatechol, and 4-vinylguaiacol, respectively. Among various ferulic acid decarboxylase enzymes, we chose the FADase from Enterobacter sp. Px6-4, whose crystal structure is known, and produced mutants to enhance its catalytic activity by random and site-directed mutagenesis. After three rounds of sequential mutations, FADase(F95L/D112N/V151I) showed approximately 34-fold higher catalytic activity than wild-type for the production of 4-vinylguaiacol from ferulic acid. Docking analyses suggested that the increased activity of FADase(F95L/D112N/V151I) could be due to formation of compact active site compared with that of the wild-type FADase. Considering the amount of phenolic compounds such as lignin monomers in the biomass components, successfully bioengineered FADase(F95L/D112N/V151I) from Enterobacter sp. Px6-4 could provide an ecofriendly biocatalytic tool for producing diverse styrene derivatives from biomass.

  7. Constraint-Induced Movement Therapy Combined with Transcranial Direct Current Stimulation over Premotor Cortex Improves Motor Function in Severe Stroke: A Pilot Randomized Controlled Trial

    Suellen M. Andrade


    Full Text Available Objective. We compared the effects of transcranial direct current stimulation at different cortical sites (premotor and motor primary cortex combined with constraint-induced movement therapy for treatment of stroke patients. Design. Sixty patients were randomly distributed into 3 groups: Group A, anodal stimulation on premotor cortex and constraint-induced movement therapy; Group B, anodal stimulation on primary motor cortex and constraint-induced movement therapy; Group C, sham stimulation and constraint-induced movement therapy. Evaluations involved analysis of functional independence, motor recovery, spasticity, gross motor function, and muscle strength. Results. A significant improvement in primary outcome (functional independence after treatment in the premotor group followed by primary motor group and sham group was observed. The same pattern of improvement was highlighted among all secondary outcome measures regarding the superior performance of the premotor group over primary motor and sham groups. Conclusions. Premotor cortex can contribute to motor function in patients with severe functional disabilities in early stages of stroke. This study was registered in database (NCT 02628561.

  8. Combined transcranial direct current stimulation and home-based occupational therapy for upper limb motor impairment following intracerebral hemorrhage: a double-blind randomized controlled trial.

    Mortensen, Jesper; Figlewski, Krystian; Andersen, Henning


    To investigate the combined effect of transcranial direct current stimulation (tDCS) and home-based occupational therapy on activities of daily living (ADL) and grip strength, in patients with upper limb motor impairment following intracerebral hemorrhage (ICH). A double-blind randomized controlled trial with one-week follow-up. Patients received five consecutive days of occupational therapy at home, combined with either anodal (n = 8) or sham (n = 7) tDCS. The primary outcome was ADL performance, which was assessed with the Jebsen-Taylor test (JTT). Both groups improved JTT over time (p occupational therapy provided greater improvements in grip strength compared with occupational therapy alone. tDCS is a promising add-on intervention regarding training of upper limb motor impairment. It is well tolerated by patients and can easily be applied for home-based training. Larger studies with long-term follow-up are needed to further explore possible effects of tDCS in patients with ICH. Five consecutive days of tDCS combined with occupational therapy provided greater improvements in grip strength compared with occupational therapy alone. tDCS is well tolerated by patients and can easily be applied for home-based rehabilitation.

  9. A double-blind randomized clinical trial on the efficacy of cortical direct current stimulation for the treatment of Alzheimer’s disease

    Eman M Khedr


    Full Text Available Background: The purpose of this study was to investigate the long-term efficacy of transcranial direct current stimulation (tDCS in the neurorehabilitation of Alzheimer’s disease (AD. Methods: 34 AD patients were randomly assigned to three groups: anodal, cathodal and sham tDCS. Stimulation was applied over the left dorsolateral prefrontal cortex (DLPFC for 25 minutes at 2mA, daily for 10 days. Each patient was submitted to the following psychometric assessments: Minimental State Examination (MMSE and Wechsler adult intelligence scale - third edition (WAIS-III at base line, at the end of the 10th sessions and then at 1 and 2 months after the end of the sessions. Motor cortical excitability and the P300 event related potential were assessed at baseline and after the last tDCS session.Results: Significant TREATMENT GROUP x TIME interactions were observed for the MMSE and performance IQ of the WAIS-III. Post hoc comparisons showed that both anodal and cathodal tDCS improved MMSE in contrast to sham tDCS. whereas this was only true for cathodal tDCS in the performance IQ. Remarkably, tDCS also reduced the P300 latency, but had no effect on motor cortex excitability. Conclusion: Our findings reveal that repeated sessions of tDCS could not only improve cognitive function but also reduce the P300 latency, which is known to be pathologically increased in AD.

  10. The Research of Biomedical Intelligent Polymer Materials

    ZHANG Zhi-bin; CHEN Yuan-wei; TANG Chang-wei; QIU Kai; LUO Juan; XU Cheng-yin; WAN Chang-xiu


    The properties of biomedical intelligent polymer materials can be changed obviously when there is a little physical or chemical change caused by external condition. They are in the forms of solids, solutions and the polymers on the surface of carrier, and include water solution of hydrophilic polymers, cross-linking hydrophilic polymers(i.e. hydrogels) and the polymers on the surface of carrier. The environmental stimulating factors are temperature, pH value, composition of solution, ionic intention, light intention, electric field, stress field and magnetic field etc.. The properties of intelligent polymer are those of phase, photics, mechanics, electric field, surface energy,reaction ratio, penetrating ratio and recognition etc..Stimulation-response of intelligent water-soluble polymerWater-soluble intelligent polymer can be separated out from solution under special external condition. It can be used as the switch of temperature or pH indicator. When water-soluble intelligent polymer is mixed with soluble-enzyme matter or cell suspension, the polymer can bring phase separation and react with soluble-enzyme matter or cell membrane through accepting some external stimulation. Other water-soluble intelligent polymer is that can make the main chemical group of some natural biomolecular recognition sequence section to arrange on skeleton of polymer at random. It is the same ratio as natural biomolecules.Stimulation-response of intelligent polymer of carrier surface Intelligent polymer can be fixed on the surface of solid polymer carrier through chemical grafting or physical adsorption. When the external conditions are changed, the thickness, humidity and electric field of the surface layer will be changed. Intelligent polymer can be preparated the permanence switch by precipitating into the hole of porous surface, and it can control on-off state of the hole. When protein or cell interacts with intelligent polymer surface to be placed in to open or close, they can be

  11. Entanglement probabilities of polymers: a white noise functional approach

    Bernido, Christopher C; Carpio-Bernido, M Victoria [Research Center for Theoretical Physics, Central Visayan Institute Foundation, Jagna, Bohol 6308 (Philippines)


    The entanglement probabilities for a highly flexible polymer to wind n times around a straight polymer are evaluated using white noise analysis. To introduce the white noise functional approach, the one-dimensional random walk problem is taken as an example. The polymer entanglement scenario, viewed as a random walk on a plane, is then treated and the entanglement probabilities are obtained for a magnetic flux confined along the straight polymer, and a case where an entangled polymer is subjected to the potential V = f-dot(s){theta}. In the absence of the magnetic flux and the potential V, the entanglement probabilities reduce to a result obtained by Wiegel.

  12. Recent developments in intelligent biomedical polymers


    Intelligent polymers or stimuli-responsive polymers may exhibit distinct transitions in physical-chemical properties, including conformation, polarity, phase structure and chemical composition in response to changes in environmental stimuli. Due to their unique ’intelligent’ characteristics, stimuli-sensitive polymers have found a wide variety of applications in biomedical and nanotechnological fields. This review focuses on the recent developments in biomedical application of intelligent polymer systems, such as intelligent hydrogel systems, intelligent drug delivery systems and intelligent molecular recognition systems. Also, the possible future directions for the application of these intelligent polymer systems in the biomedical field are presented.

  13. Recent developments in intelligent biomedical polymers

    XIAO ChunSheng; TIAN HuaYu; ZHUANG XiuLi; CHEN XueSi; JING XiaBin


    Intelligent polymers or stimuli-responsive polymers may exhibit distinct transitions in physical-chemical properties, including conformation, polarity, phase structure and chemical composition in response to changes in environmental stimuli. Due to their unique 'intelligent' characteristics, stimuli-sensitive polymers have found a wide variety of applications in biomedical and nanotechnological fields. This review focuses on the recent developments in biomedical application of intelligent polymer systems, such as intelligent hydrogel systems, intelligent drug delivery systems and intelligent molecular recognition systems. Also, the possible future directions for the application of these intelligent polymer systems in the biomedical field are presented.

  14. Randomized controlled ferret study to assess the direct impact of 2008-09 trivalent inactivated influenza vaccine on A(H1N1pdm09 disease risk.

    Danuta M Skowronski

    Full Text Available During spring-summer 2009, several observational studies from Canada showed increased risk of medically-attended, laboratory-confirmed A(H1N1pdm09 illness among prior recipients of 2008-09 trivalent inactivated influenza vaccine (TIV. Explanatory hypotheses included direct and indirect vaccine effects. In a randomized placebo-controlled ferret study, we tested whether prior receipt of 2008-09 TIV may have directly influenced A(H1N1pdm09 illness. Thirty-two ferrets (16/group received 0.5 mL intra-muscular injections of the Canadian-manufactured, commercially-available, non-adjuvanted, split 2008-09 Fluviral or PBS placebo on days 0 and 28. On day 49 all animals were challenged (Ch0 with A(H1N1pdm09. Four ferrets per group were randomly selected for sacrifice at day 5 post-challenge (Ch+5 and the rest followed until Ch+14. Sera were tested for antibody to vaccine antigens and A(H1N1pdm09 by hemagglutination inhibition (HI, microneutralization (MN, nucleoprotein-based ELISA and HA1-based microarray assays. Clinical characteristics and nasal virus titers were recorded pre-challenge then post-challenge until sacrifice when lung virus titers, cytokines and inflammatory scores were determined. Baseline characteristics were similar between the two groups of influenza-naïve animals. Antibody rise to vaccine antigens was evident by ELISA and HA1-based microarray but not by HI or MN assays; virus challenge raised antibody to A(H1N1pdm09 by all assays in both groups. Beginning at Ch+2, vaccinated animals experienced greater loss of appetite and weight than placebo animals, reaching the greatest between-group difference in weight loss relative to baseline at Ch+5 (7.4% vs. 5.2%; p = 0.01. At Ch+5 vaccinated animals had higher lung virus titers (log-mean 4.96 vs. 4.23pfu/mL, respectively; p = 0.01, lung inflammatory scores (5.8 vs. 2.1, respectively; p = 0.051 and cytokine levels (p>0.05. At Ch+14, both groups had recovered. Findings in influenza

  15. Functionalised Polymers by Surface Modification

    Jon-Paul Griffiths; M. G. Moloney


    @@ 1Introduction Surface-active polymers are of substantial importance in many diverse aspects of modern technology, with applications ranging from solid phase chemical synthesis related to drug discovery and chemical catalysis to biocompatible/bioactive medical implants and prostheses, and to surface-modified fabrics. Whilst there are a number of existing physical (e. g. corona or plasma discharge, ion beam irradiation[1] ) and chemical (e. g.silanisation, oxidation, chlorination, acylation and quaternisation[2-4]) methods for the surface modification of polymers, the frequent requirement for significant infrastructure, harsh reaction conditions, and limitation to specific polymer types (e. g. polybutadiene[5] ), which must possess suitable chemical functionality capable of direct modification, led us to consider alternative chemical methods. Desirable was an alternative that would be amenable to a large range of polymers, permitting direct chemical modification under mild conditions and using inexpensive reagents.

  16. Incorporation of a lauric acid-conjugated GRGDS peptide directly into the matrix of a poly(carbonate-urea)urethane polymer for use in cardiovascular bypass graft applications.

    Kidane, Asmeret G; Punshon, Geoffrey; Salacinski, Henryk J; Ramesh, Bala; Dooley, Audrey; Olbrich, Michael; Heitz, Johannes; Hamilton, George; Seifalian, Alexander M


    Gly-Arg-Gly-Asp-Ser (GRGDS) was modified by conjugation to lauric acid (LA) to facilitate incorporation into the matrix of a poly(carbonate-urea)urethane (PCU) used in vascular bypass grafts. GRGDS and LA-GRGDS were synthesized using solid phase Fmoc chemistry and characterized by high performance liquid chromatography and Fourier transform infrared spectroscopy. LA-GRGDS was passively coated and incorporated as nanoparticle dispersion on the PCU films. Biocompatibility of the modified surfaces was investigated. Endothelial cells seeded on LA-GRGDS coated and incorporated PCU showed after 48 h and 72 h a significant (p < 0.05) increase in metabolism compared with unmodified PCU. The platelet adhesion and hemolysis studies showed that the modification of PCU had no adverse effect. In conclusion, LA-conjugated RGD derivatives, such as LA-GRGDS, that permit solubility into solvents used in solvent casting methodologies should have wide applicability in polymer development for use in coronary, vascular, and dialysis bypass grafts, and furthermore scaffolds utilized for tissue regeneration and tissue engineering.

  17. Turbulence in dilute polymer solutions

    Liberzon, A.; Guala, M.; Lüthi, B.; Kinzelbach, W.; Tsinober, A.


    The work reported below is a comparative study of the properties of turbulence with weak mean flow in a Newtonian fluid and in a dilute polymer solution with an emphasis on the small scale phenomena. The main tool used is a three-dimensional particle tracking system allowing to measure and follow in a Lagrangian manner the field of velocities, as well as velocity derivatives, and thus vorticity, strain, and a variety of related and dynamically significant quantities. The comparison of data from the two flows allows to directly observe the influence of polymers on these quantities as well as the evolution of material elements in the presence of polymers.

  18. Distribution of levels in high-dimensional random landscapes

    Kabluchko, Zakhar


    We prove empirical central limit theorems for the distribution of levels of various random fields defined on high-dimensional discrete structures as the dimension of the structure goes to $\\infty$. The random fields considered include costs of assignments, lengths of Hamiltonian cycles and spanning trees, energies of directed polymers, locations of particles in the branching random walk, as well as energies in the Sherrington--Kirkpatrick and Edwards--Anderson models. The distribution of levels in all models listed above is shown to be essentially the same as in a stationary Gaussian process with regularly varying non-summable covariance function. This type of behavior is different from the Brownian bridge-type limit known for independent or stationary weakly dependent sequences of random variables.

  19. Optimizing Rehabilitation for Phantom Limb Pain Using Mirror Therapy and Transcranial Direct Current Stimulation: A Randomized, Double-Blind Clinical Trial Study Protocol.

    Pinto, Camila Bonin; Saleh Velez, Faddi Ghassan; Bolognini, Nadia; Crandell, David; Merabet, Lotfi B; Fregni, Felipe


    Despite the multiple available pharmacological and behavioral therapies for the management of chronic phantom limb pain (PLP) in lower limb amputees, treatment for this condition is still a major challenge and the results are mixed. Given that PLP is associated with maladaptive brain plasticity, interventions that promote cortical reorganization such as non-invasive brain stimulation and behavioral methods including transcranial direct current stimulation (tDCS) and mirror therapy (MT), respectively, may prove to be beneficial to control pain in PLP. Due to its complementary effects, a combination of tDCS and MT may result in synergistic effects in PLP. The objective of this study is to evaluate the efficacy of tDCS and MT as a rehabilitative tool for the management of PLP in unilateral lower limb amputees. A prospective, randomized, placebo-controlled, double-blind, factorial, superiority clinical trial will be carried out. Participants will be eligible if they meet the following inclusion criteria: lower limb unilateral traumatic amputees that present PLP for at least 3 months after the amputated limb has completely healed. Participants (N=132) will be randomly allocated to the following groups: (1) active tDCS and active MT, (2) sham tDCS and active MT, (3) active tDCS and sham MT, and (4) sham tDCS and sham MT. tDCS will be applied with the anodal electrode placed over the primary motor cortex (M1) contralateral to the amputation side and the cathode over the contralateral supraorbital area. Stimulation will be applied at the same time of the MT protocol with the parameters 2 mA for 20 minutes. Pain outcome assessments will be performed at baseline, before and after each intervention session, at the end of MT, and in 2 follow-up visits. In order to assess cortical reorganization and correlate with clinical outcomes, participants will undergo functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) before and after the

  20. Complaint-Directed Mini-Interventions for Depressive Complaints: A Randomized Controlled Trial of Unguided Web-Based Self-Help Interventions

    Sommers-Spijkerman, Marion; van der Poel, Agnes; Smit, Filip; Boon, Brigitte


    Background Prevention of depression is important due to the substantial burden of disease associated with it. To this end, we developed a novel, brief, and low-threshold Web-based self-help approach for depressive complaints called complaint-directed mini-interventions (CDMIs). These CDMIs focus on highly prevalent complaints that are demonstrably associated with depression and have a substantial economic impact: stress, sleep problems, and worry. Objective The aim was to evaluate the effectiveness of the Web-based self-help CDMIs in a sample of adults with mild-to-moderate depressive symptoms compared to a wait-list control group. Methods A two-armed randomized controlled trial was conducted. An open recruitment strategy was used. Participants were randomized to either the Web-based CDMIs or the no-intervention wait-list control group. The CDMIs are online, unguided, self-help interventions, largely based on cognitive behavioral techniques, which consist of 3 to 4 modules with up to 6 exercises per module. Participants are free to choose between the modules and exercises. Assessments, using self-report questionnaires, took place at baseline and at 3 and 6 months after baseline. The control group was given access to the intervention following the 3-month assessment. The primary goal of the CDMIs is to reduce depressive complaints. The primary outcome of the study was a reduction in depressive complaints as measured by the Inventory of Depressive Symptomatology Self-Report (IDS-SR). Secondary outcomes included reductions in stress, worry, sleep problems, and anxiety complaints, and improvements in well-being. Data were analyzed using linear mixed models. Results In total, 329 participants enrolled in the trial, of which 165 were randomized to the intervention group and 164 to the control group. Approximately three-quarters of the intervention group actually created an account. Of these participants, 91.3% (116/127) logged into their chosen CDMI at least once during

  1. Antimocrobial Polymer

    McDonald, William F. (Utica, OH); Huang, Zhi-Heng (Walnut Creek, CA); Wright, Stacy C. (Columbus, GA)


    A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The composition comprises a crosslinked chemical combination of (i) a polymer having amino group-containing side chains along a backbone forming the polymer, (ii) an antimicrobial agent selected from quaternary ammonium compounds, gentian violet compounds, substituted or unsubstituted phenols, biguanide compounds, iodine compounds, and mixtures thereof, and (iii) a crosslinking agent containing functional groups capable of reacting with the amino groups. In one embodiment, the polymer is a polyamide formed from a maleic anhydride or maleic acid ester monomer and alkylamines thereby producing a polyamide having amino substituted alkyl chains on one side of the polyamide backbone; the crosslinking agent is a phosphine having the general formula (A)3P wherein A is hydroxyalkyl; and the antimicrobial agent is chlorhexidine, dimethylchlorophenol, cetyl pyridinium chloride, gentian violet, triclosan, thymol, iodine, and mixtures thereof.

  2. Polymer inflation

    Hassan, Syed Moeez; Seahra, Sanjeev S


    We consider the semi-classical dynamics of a free massive scalar field in a homogeneous and isotropic cosmological spacetime. The scalar field is quantized using the polymer quantization method assuming that it is described by a gaussian coherent state. For quadratic potentials, the semi-classical equations of motion yield a universe that has an early "polymer inflation" phase which is generic and almost exactly de Sitter, followed by a epoch of slow-roll inflation. We compute polymer corrections to the slow roll formalism, and discuss the probability of inflation in this model using a physical Hamiltonian arising from time gauge fixing. These results show the extent to which a quantum gravity motivated quantization method affects early universe dynamics.

  3. Neuroplastic effects of transcranial direct current stimulation on painful symptoms reduction in chronic Hepatitis C: a phase II randomized, double blind, sham controlled trial

    Aline Patricia Brietzke


    Full Text Available Introduction: Pegylated Interferon Alpha (Peg-IFN in combination with other drugs is the standard treatment for chronic hepatitis C infection (HCV and is related to severe painful symptoms. The aim of this study was access the efficacy of transcranial direct current stimulation (tDCS in controlling the painful symptoms related to Peg-IFN side effects. Material and Methods: In this phase II double-blind trial, twenty eight (n=28 HCV subjects were randomized to receive either five consecutive days of active tDCS (n=14 or sham (n=14 during five consecutive days with anodal stimulation over the primary motor cortex region using 2 mA for 20 minutes. The primary outcomes were visual analogue scale (VAS pain and brain-derived neurotrophic factor (BDNF serum levels. Secondary outcomes were the pressure-pain threshold (PPT, the Brazilian Profile of Chronic Pain: Screen (B-PCP:S and drug analgesics use. Results: tDCS reduced the VAS scores (P<0.003, with a mean pain drop of 56% (p<0.001. Furthermore, tDCS was able to enhance BDNF levels (p<0.01. The mean increase was 37.48% in the active group. Finally, tDCS raised PPT (p<0.001 and reduced the B-PCP:S scores and analgesic use (p<0.05. Conclusions: Five sessions of tDCS were effective in reducing the painful symptoms in HCV patients undergoing Peg-IFN treatment. These findings support the efficacy of tDCS as a promising therapeutic tool to improve the tolerance of the side effects related to the use of Peg-IFN. Future larger studies (phase III and IV trials are needed to confirm the clinical use of the therapeutic effects of tDCS in such condition. Trial registration: Brazilian Human Health Regulator for Research with the approval number CAAE 07802012.0.0000.5327

  4. Comparison of the Laryngeal Mask Airway (CTrachTM and Direct Coupled Interface-Video Laryngoscope for Endotracheal Intubation: a Prospective, Randomized, Clinical Study

    Kamil Toker


    Full Text Available Objective: Video laryngoscopy was developed to facilitate tracheal intubation of difficult airways. We aimed to compare the efficacy of CTrach™ (CT and Direct Coupled Interface-Videolaryngoscope (DCI-VL in patients with normal airways. Material and Methods: Sixty ASA I–II (American Society of Anesthesiologists adult patients admitted for elective surgery were enrolled in this prospective study. The patients were randomly assigned to two groups, where intubation was performed via CT or DCI-VL. Time to obtain a good glottic view, total intubation time, success rates and the number of patients who required maneuvers for a good glottic view were recorded.Results: The mean time to obtaining a good glottic view was significantly longer with CT than with DCI-VL (29.4±20.3 seconds vs. 12.8±1.9 seconds, respectively; p=0.01. Intubation was achieved on the first attempt in 28 patients in the CT group (93.3% and in 24 in the DCI-VL group (80% (p=0.77. The total intubation time for CT was significantly longer compared to DCI-VL (99.9±36.0 seconds vs. 39.2±21.4 seconds, respectively; p=0.01. Optimization maneuvers were required in eight and two patients in the CT and DCI-VL groups, respectively (p=0.03.Conclusion: Although the normal airway endotracheal intubation success rates were similar in both groups, the time to obtain a good glottic view and the total intubation time were significantly shorter with DCI-VL.

  5. Study design for the fostering eating after stroke with transcranial direct current stimulation trial: a randomized controlled intervention for improving Dysphagia after acute ischemic stroke.

    Marchina, Sarah; Schlaug, Gottfried; Kumar, Sandeep


    Dysphagia is a major stroke complication but lacks effective therapy that can promote recovery. Noninvasive brain stimulation with and without peripheral sensorimotor activities may be an attractive treatment option for swallowing recovery but has not been systematically investigated in the stroke population. This article describes the study design of the first prospective, single-center, double-blinded trial of anodal versus sham transcranial direct current stimulation (tDCS) used in combination with swallowing exercises in patients with dysphagia from an acute ischemic stroke. The aim of this study is to gather safety data on cumulative sessions of tDCS in acute-subacute phases of stroke, obtain information about effects of this intervention on important physiologic and clinically relevant swallowing parameters, and examine possible dose effects. Ninety-nine consecutive patients with dysphagia from an acute unilateral hemispheric infarction with a Penetration and Aspiration Scale (PAS) score of 4 or more and without other confounding reasons for dysphagia will be enrolled at a single tertiary care center. Subjects will be randomized to either a high or low dose tDCS or a sham group and will undergo 10 sessions over 5 consecutive days concomitantly with effortful swallowing maneuvers. The main efficacy measures are a change in the PAS score before and after treatment; the main safety measures are mortality, seizures, neurologic, motor, and swallowing deterioration. The knowledge gained from this study will help plan a larger confirmatory trial for treating stroke-related dysphagia and advance our understanding of important covariates influencing swallowing recovery and response to the proposed intervention. Copyright © 2015 National Stroke Association. Published by Elsevier Inc. All rights reserved.

  6. Comparative Effects of Direct Renin Inhibitor and Angiotensin Receptor Blocker on Albuminuria in Hypertensive Patients with Type 2 Diabetes. A Randomized Controlled Trial

    Uzu, Takashi; Araki, Shin-ichi; Kashiwagi, Atsunori; Haneda, Masakazu; Koya, Daisuke; Yokoyama, Hiroki; Kida, Yasuo; Ikebuchi, Motoyoshi; Nakamura, Takaaki; Nishimura, Masataka; Takahara, Noriko; Obata, Toshiyuki; Omichi, Nobuyuki; Sakamoto, Katsuhiko; Shingu, Ryosuke; Taki, Hideki; Nagai, Yoshio; Tokuda, Hiroaki; Kitada, Munehiro; Misawa, Miwa; Nishiyama, Akira; Kobori, Hiroyuki; Maegawa, Hiroshi


    Background In patients with diabetes, albuminuria is a risk marker of end-stage renal disease and cardiovascular events. An increased renin-angiotensin system activity has been reported to play an important role in the pathological processes in these conditions. We compared the effect of aliskiren, a direct renin inhibitor (DRI), with that of angiotensin receptor blockers (ARBs) on albuminuria and urinary excretion of angiotensinogen, a marker of intrarenal renin-angiotensin system activity. Methods We randomly assigned 237 type 2 diabetic patients with high-normal albuminuria (10 to <30 mg/g of albumin-to-creatinine ratio) or microalbuminuria (30 to <300 mg/g) to the DRI group or ARB group (any ARB) with a target blood pressure of <130/80 mmHg. The primary endpoint was a reduction in albuminuria. Results Twelve patients dropped out during the observation period, and a total of 225 patients were analyzed. During the study period, the systolic and diastolic blood pressures were not different between the groups. The changes in the urinary albumin-to-creatinine ratio from baseline to the end of the treatment period in the DRI and ARB groups were similar (-5.5% and -6.7%, respectively). In contrast, a significant reduction in the urinary excretion of angiotensinogen was observed in the ARB group but not in the DRI group. In the subgroup analysis, a significant reduction in the albuminuria was observed in the ARB group but not in the DRI group among high-normal albuminuria patients. Conclusion DRI and ARB reduced albuminuria in hypertensive patients with type 2 diabetes. In addition, ARB, but not DRI, reduced albuminuria even in patients with normal albuminuria. DRI is not superior to ARB in the reduction of urinary excretion of albumin and angiotensinogen. PMID:28033332

  7. Transcranial direct current stimulation combined with aerobic exercise to optimize analgesic responses in fibromyalgia: A randomized placebo-controlled clinical trial

    Mariana Emerenciano Mendonça


    Full Text Available Fibromyalgia is a chronic pain syndrome that is associated with maladaptive plasticity in neural central circuits. One of the neural circuits that are involved in pain in fibromyalgia is the primary motor cortex. We tested a combination intervention that aimed to modulate the motor system: transcranial direct current stimulation (tDCS of the primary motor cortex (M1 and aerobic exercise (AE. In this phase II, sham-controlled randomized clinical trial, 45 subjects were assigned to 1 of 3 groups: tDCS + AE, AE only, and tDCS only. The following outcomes were assessed: intensity of pain, level of anxiety, quality of life, mood, pressure pain threshold, and cortical plasticity, as indexed by transcranial magnetic stimulation. There was a significant effect for the group-time interaction for intensity of pain, demonstrating that tDCS/AE was superior to AE (F(13,364=2.25, p=0.007 and tDCS (F(13.364=2.33, p=0.0056 alone. Post hoc adjusted analysis showed a difference between tDCS/AE and tDCS group after the first week of stimulation and after one month intervention period (p=0.02 and p=0.03, respectively. Further, after treatment there was a significant difference between groups in anxiety and mood levels. The combination treatment effected the greatest response. The three groups had no differences regarding responses in motor cortex plasticity, as assessed by TMS. The combination of tDCS with aerobic exercise is superior compared with each individual intervention (cohen’s d effect sizes > 0.55. The combination intervention had a significant effect on pain, anxiety and mood. Based on the similar effects on cortical plasticity outcomes, the combination intervention might have affected other neural circuits, such as those that control the affective-emotional aspects of pain.

  8. Bihemispheric motor cortex transcranial direct current stimulation improves force steadiness in post-stroke hemiparetic patients: a randomized crossover controlled trial

    Rafael Ayres Montenegro


    Full Text Available Post-stroke patients usually exhibit reduced peak muscular torque (PT and/or force steadiness during submaximal exercise. Brain stimulation techniques have been proposed to improve neural plasticity and help to restore motor performance in post-stroke patients. The present study compared the effects of bihemispheric motor cortex transcranial direct current stimulation (tDCS on PT and force steadiness during maximal and submaximal resistance exercise performed by post-stroke patients vs. healthy controls. A double-blind randomized crossover controlled trial (identification number: TCTR20151112001; URL: was conducted involving nine healthy and ten post-stroke hemiparetic individuals who received either tDCS (2 mA or sham stimulus upon motor cortex for 20 min. PT and force steadiness (reflected by the coefficient of variation of muscular torque were assessed during unilateral knee extension and flexion at maximal and submaximal workloads (1 set of 3 reps at 100% PT and 2 sets of 10 repetitions at 50% PT, respectively. No significant change in PT was observed in post-stroke and healthy subjects. Force steadiness during knee extension (~25-35%, P<0.001 and flexion (~22-33%, P<0.001 improved after tDCS compared to the sham condition in post-stroke patients, but improved only during knee extension (~13-27%, P<0.001 in healthy controls. These results suggest that tDCS may improve force steadiness, but not PT in post-stroke hemiparetic patients, which might be relevant in the context of motor rehabilitation programs.

  9. Photogenerating work from polymers

    Hilmar Koerner; White, Timothy J.; Nelson V. Tabiryan; Timothy J. Bunning; Vaia, Richard A.


    The ability to control the creation of mechanical work remotely, with high speed and spatial precision, over long distances, offers many intriguing possibilities. Recent developments in photoresponsive polymers and nanocomposite concepts are at the heart of these future devices. Whether driving direct conformational changes, initiating reversible chemical reactions to release stored strain, or converting a photon to a local temperature increase, combinations of photoactive units, nanoparticle...

  10. Polymer electronics

    Geoghegan, Mark


    Polymer electronics is the science behind many important new developments in technology, such as the flexible electronic display (e-ink) and many new developments in transistor technology. Solar cells, light-emitting diodes, and transistors are all areas where plastic electronics is likely to, or is already having, a serious impact on our daily lives. With polymer transistors and light-emitting diodes now being commercialised, there is a clear need for a pedagogic text thatdiscusses the subject in a clear and concise fashion suitable for senior undergraduate and graduate students. The content

  11. Primordial polymer perturbations

    Seahra, Sanjeev S.; Husain, Viqar [Department of Mathematics and Statistics, University of New Brunswick, Fredericton, NB, E3B 5A3 (Canada); Brown, Iain A. [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, N-0315 Oslo (Norway); Hossain, Golam Mortuza, E-mail:, E-mail:, E-mail:, E-mail: [Department of Physical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur Campus, P.O. Krishi Viswavidyalaya, Nadia 741 252, WB (India)


    We study the generation of primordial fluctuations in pure de Sitter inflation where the quantum scalar field dynamics are governed by polymer (not Schroedinger) quantization. This quantization scheme is related to, but distinct from, the structures employed in Loop Quantum Gravity; and it modifies standard results above a polymer energy scale M{sub *}. We recover the scale invariant Harrison Zel'dovich spectrum for modes that have wavelengths bigger than M{sub *}{sup −1} at the start of inflation. The primordial spectrum for modes with initial wavelengths smaller than M{sub *}{sup −1} exhibits oscillations superimposed on the standard result. The amplitude of these oscillations is proportional to the ratio of the inflationary Hubble parameter H to the polymer energy scale. For reasonable choices of M{sub *}, we find that polymer effects are likely unobservable in CMB angular power spectra due to cosmic variance uncertainty, but future probes of baryon acoustic oscillations may be able to directly constrain the ratio H/M{sub *}.

  12. Antimicrobial polymers.

    Jain, Anjali; Duvvuri, L Sailaja; Farah, Shady; Beyth, Nurit; Domb, Abraham J; Khan, Wahid


    Better health is basic requirement of human being, but the rapid growth of harmful pathogens and their serious health effects pose a significant challenge to modern science. Infections by pathogenic microorganisms are of great concern in many fields such as medical devices, drugs, hospital surfaces/furniture, dental restoration, surgery equipment, health care products, and hygienic applications (e.g., water purification systems, textiles, food packaging and storage, major or domestic appliances etc.) Antimicrobial polymers are the materials having the capability to kill/inhibit the growth of microbes on their surface or surrounding environment. Recently, they gained considerable interest for both academic research and industry and were found to be better than their small molecular counterparts in terms of enhanced efficacy, reduced toxicity, minimized environmental problems, resistance, and prolonged lifetime. Hence, efforts have focused on the development of antimicrobial polymers with all desired characters for optimum activity. In this Review, an overview of different antimicrobial polymers, their mechanism of action, factors affecting antimicrobial activity, and application in various fields are given. Recent advances and the current clinical status of these polymers are also discussed.

  13. Programmable disorder in random DNA tilings

    Tikhomirov, Grigory; Petersen, Philip; Qian, Lulu


    Scaling up the complexity and diversity of synthetic molecular structures will require strategies that exploit the inherent stochasticity of molecular systems in a controlled fashion. Here we demonstrate a framework for programming random DNA tilings and show how to control the properties of global patterns through simple, local rules. We constructed three general forms of planar network—random loops, mazes and trees—on the surface of self-assembled DNA origami arrays on the micrometre scale with nanometre resolution. Using simple molecular building blocks and robust experimental conditions, we demonstrate control of a wide range of properties of the random networks, including the branching rules, the growth directions, the proximity between adjacent networks and the size distribution. Much as combinatorial approaches for generating random one-dimensional chains of polymers have been used to revolutionize chemical synthesis and the selection of functional nucleic acids, our strategy extends these principles to random two-dimensional networks of molecules and creates new opportunities for fabricating more complex molecular devices that are organized by DNA nanostructures.

  14. Mechanisms of Morphology Development and Control in Polymer- Polymer Blends

    Macosko, Christopher W.


    Polymer-polymer blends continue to be the most important method for achieving optimization of properties in plastics products. Over 30 percent of all plastics are blends. While miscible blends generally give average properties between the components, immiscible blends offer synergistic possibilities such as high modulus with high toughness; high flow with high impact strength or diffusion barriers with good mechanical properties and low cost. The key to performance of these immiscible blends is their morphology. There are several important types of morphology which can lead to valuable property improvement: emulsion - small polymer spheres well dispersed in a polymer matrix. double emulsion - spheres inside spheres which are dispersed in another matrix. microlayer - thin, parallel layers of one polymer in a matrix. cocontinuous - two (or more) continuous, interpenetrating polymer phases. To be economical it is desirable to create these morphologies via melt mixing of powder or pellets in conventional compounding equipment. The melting stage during compounding is very important for morphology development. This presentation will demonstrate the role of melting or softening of each phase as well as their viscosity, elasticity and interfacial tension in morphology development. Interfacial modification with premade block copolymers or reactively formed copolymers can greatly alter morphology formation and stability. Experimental results will be presented which quantify the role of these additives. References to recent work in this area by our group are listed below: DeBrule, M. B., L. Levitt and C.W. Macosko, "The Rheology and Morphology of Layered Polymer Melts in Shear," Soc. Plastics Eng. Tech Papers (ANTEC), 84-89 (1996). Guegan, P., C. W. Macosko, T. Ishizone, A. Hirao and S. Nakahama, "Kinetics of Chain Coupling at Melt Interfaces, Macromol. 27, 4993-4997 (1994). Lee, M. S., T.P. Lodge, and C. W. Macosko, "Can Random Copolymers Serve as Effective Polymeric

  15. A comparison of laser ablation-inductively coupled plasma-mass spectrometry and high-resolution continuum source graphite furnace molecular absorption spectrometry for the direct determination of bromine in polymers

    de Gois, Jefferson S.; Van Malderen, Stijn J. M.; Cadorim, Heloisa R.; Welz, Bernhard; Vanhaecke, Frank


    This work describes the development and comparison of two methods for the direct determination of Br in polymer samples via solid sampling, one using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) and the other using high-resolution continuum source graphite furnace molecular absorption spectrometry with direct solid sample analysis (HR-CS SS-GF MAS). The methods were optimized and their accuracy was evaluated by comparing the results obtained for 6 polymeric certified reference materials (CRMs) with the corresponding certified values. For Br determination with LA-ICP-MS, the 79Br+ signal could be monitored interference-free. For Br determination via HR-CS SS-GF MAS, the CaBr molecule was monitored at 625.315 nm with integration of the central pixel ± 1. Bromine quantification by LA-ICP-MS was performed via external calibration against a single CRM while using the 12C+ signal as an internal standard. With HR-CS SS-GF MAS, Br quantification could be accomplished using external calibration against aqueous standard solutions. Except for one LA-ICP-MS result, the concentrations obtained with both techniques were in agreement with the certified values within the experimental uncertainty as evidenced using a t-test (95% confidence level). The limit of quantification was determined to be 100 μg g- 1 Br for LA-ICP-MS and 10 μg g- 1 Br for HR-CS SS-GF MAS.


    蒋淇忠; 马紫峰; Oumarou Savadogo


    A new membrane electrolyte assembly (MEA) preparation method for polymer electrolyte membrane fuel cell (PEMFC) was developed by applying the directly printing catalyst on membrane technique. This method was simple and easy to be controlled as verified by repetition experiment. When the membrane with catalyst prepared by the new technique and the electrode with diffusion layer was only sandwiched but not hot pressed, this kind of MEA was called not-hot-press MEA (NPMEA) and its fuel cell performance was better than that of MEA which was hot pressed (HPMEA). The effects of 6 different kinds of solvents in catalyst mixture ink on the performance of fuel cell were assessed. It was discovered that iso-propanol was the best solvent in catalyst mixture ink and showed the best performance of fuel cell. Finally several MEAs prepared by different ways were tested on fuel cell station and it was reported that the performance of MEA prepared by the directly printing catalyst on membrane technique was the best in the whole voltage region.

  17. Polymer electronic devices and materials.

    Schubert, William Kent; Baca, Paul Martin; Dirk, Shawn M.; Anderson, G. Ronald; Wheeler, David Roger


    Polymer electronic devices and materials have vast potential for future microsystems and could have many advantages over conventional inorganic semiconductor based systems, including ease of manufacturing, cost, weight, flexibility, and the ability to integrate a wide variety of functions on a single platform. Starting materials and substrates are relatively inexpensive and amenable to mass manufacturing methods. This project attempted to plant the seeds for a new core competency in polymer electronics at Sandia National Laboratories. As part of this effort a wide variety of polymer components and devices, ranging from simple resistors to infrared sensitive devices, were fabricated and characterized. Ink jet printing capabilities were established. In addition to promising results on prototype devices the project highlighted the directions where future investments must be made to establish a viable polymer electronics competency.

  18. Conjugated Polymers for Energy Production

    Livi, Francesco

    arylation (DAr) and direct arylation polymerization (DArP) have been applied to the preparation of PPDTBT, making this polymer readily available in only 4 synthetic steps and thus easily transferable to a large scale-production setup. DArP avoids organometallic species and therefore is an appealing......This dissertation is aimed at developing materials for flexible, large area, ITO-free polymer solar cells (PSCs) fully printed under ambient conditions. A large screening of conjugated polymers, both novel and well-known materials, has been carried out in order to find suitable candidates...... for scalable PSCs fully printed under ambient conditions [Adv. Energy Mater. 2015, 5, 1402186]. PPDTBT resulted to be the conjugated polymer with the best photovoltaic performance within the 104 synthesized macromolecules. Therefore, further studies have been done on such material. The impact of side chain...

  19. Sedimentation of Knotted Polymers

    Piili, Joonas; Kaski, Kimmo; Linna, Riku


    We investigate the sedimentation of knotted polymers by means of the stochastic rotation dynamics, a molecular dynamics algorithm which takes hydrodynamics fully into account. We show that the sedimentation coefficient s, related to the terminal velocity of the knotted polymers, increases linearly with the average crossing number n_c of the corresponding ideal knot. To the best of our knowledge, this provides the first direct computational confirmation of this relation, postulated on the basis of experiments in "The effect of ionic conditions on the conformations of supercoiled DNA. I. sedimentation analysis" by Rybenkov et al., for the case of sedimentation. Such a relation was previously shown to hold with simulations for knot electrophoresis. We also show that there is an accurate linear dependence of s on the inverse of the radius of gyration R_g^-1, more specifically with the inverse of the R_g component that is perpendicular to the direction along which the polymer sediments. Intriguingly, the linear de...

  20. Transition of polymers from rubbery elastic state to fluid state

    Renyuan QIAN; Yansheng YU


    On increasing the temperature of a polymer,the transition of the polymer from a rubbery elastic state to a fluid state could occur. The transition temperature is termed the fluid temperature of the polymer, Tf, which has a direct relationship with the polymer molecular weight.As one of polymer parameters, Tf is as important as the glass transition temperature of a polymer, Tg. Moreover,special attention to Tf should be paid for polymer processing. In research on the transition of a polymer from a rubbery elastic state to a fluid state, the concept of Tfwould be more reasonable and more effective than the concept of T1,1 because it is neglected in the concept of T1,1in that the molecular weight of a polymer may affect the transition of the polymer. In this paper the discussion on the fluid temperature involves the characters of polymers,such as the deformation-temperature curve, the tempera-ture range of the rubbery state and the shear viscosity of polymer melt. From the viewpoint of the cohesional state of polymers, the transition of a polymer from a rubbery elastic state to a fluid state responds to destruction and construction of the cohesional entanglement network in the polymer. The relaxing network of polymer melt would be worthy to be considered as an object of study.

  1. Random walks, random fields, and disordered systems

    Černý, Jiří; Kotecký, Roman


    Focusing on the mathematics that lies at the intersection of probability theory, statistical physics, combinatorics and computer science, this volume collects together lecture notes on recent developments in the area. The common ground of these subjects is perhaps best described by the three terms in the title: Random Walks, Random Fields and Disordered Systems. The specific topics covered include a study of Branching Brownian Motion from the perspective of disordered (spin-glass) systems, a detailed analysis of weakly self-avoiding random walks in four spatial dimensions via methods of field theory and the renormalization group, a study of phase transitions in disordered discrete structures using a rigorous version of the cavity method, a survey of recent work on interacting polymers in the ballisticity regime and, finally, a treatise on two-dimensional loop-soup models and their connection to conformally invariant systems and the Gaussian Free Field. The notes are aimed at early graduate students with a mod...

  2. Wave propagation and scattering in random media

    Ishimaru, Akira


    Wave Propagation and Scattering in Random Media, Volume 2, presents the fundamental formulations of wave propagation and scattering in random media in a unified and systematic manner. The topics covered in this book may be grouped into three categories: waves in random scatterers, waves in random continua, and rough surface scattering. Random scatterers are random distributions of many particles. Examples are rain, fog, smog, hail, ocean particles, red blood cells, polymers, and other particles in a state of Brownian motion. Random continua are the media whose characteristics vary randomly an

  3. Optimal paths as correlated random walks

    Perlsman, E.; Havlin, S.


    A numerical study of optimal paths in the directed polymer model shows that the paths are similar to correlated random walks. It is shown that when a directed optimal path of length t is divided into 3 segments whose length is t/3, the correlation between the transversal movements along the first and last path segments is independent of the path length t. It is also shown that the transversal correlations along optimal paths decrease as the paths approach their endpoints. The numerical results obtained for optimal paths in 1+4 dimensions are qualitatively similar to those obtained for optimal paths in lower dimensions, and the data supplies a strong numerical indication that 1+4 is not the upper critical dimension of this model, and of the associated KPZ equation.

  4. Syntheses and characterization of two novel 1D Pb(II) Halide supramolecular polymers possessing incomplete Cubane subunit directed by -conjugated Dication templates

    Chengjie Ma; Mei Liu; Wenli Zhang; Haijuan Du; Yao Li; Chaohai Wang; Yunyin Niu


    Two novel cation-templated complexes, {(1, 4-PMBP)[Pb4I10]·DMF} n(1) {(DBBP)2[Pb5I8Br6]} n(2), (1,4-PMBP·2Br =1,1”-[1,4-phenylene-bis(methylene)]bis-4,4’-bipyridinium dibromide; DBBP·2Br = N, N’-dibenzyl- 4, 4’-bipyridinium dibromide) have been synthesized via the self-assembly reaction in solution. X-ray crystallography showed that compounds 1 and 2 can be regarded as 1D iodoplumbate examples which contain incomplete cubane subunit directed by -conjugated dication templates. It is the H-bonds and electrostatic interactions between the organic counter cations and inorganic moieties that contribute the crystal packing. These compounds have been further characterized by IR spectroscopy, UV-Vis spectra, elemental analysis and thermostability properties.

  5. Photogenerating work from polymers

    Hilmar Koerner


    Full Text Available The ability to control the creation of mechanical work remotely, with high speed and spatial precision, over long distances, offers many intriguing possibilities. Recent developments in photoresponsive polymers and nanocomposite concepts are at the heart of these future devices. Whether driving direct conformational changes, initiating reversible chemical reactions to release stored strain, or converting a photon to a local temperature increase, combinations of photoactive units, nanoparticles, ordered mesophases, and polymeric networks are providing an expansive array of photoresponsive polymer options for mechanical devices. Framing the typically geometry-specific observations into an applied engineering vocabulary will ultimately define the role of these materials in future actuator applications, ranging from microfluidic valves in medical devices to optically controlled mirrors in displays.

  6. Polymer blends

    Allen, Scott D.; Naik, Sanjeev


    The present invention provides, among other things, extruded blends of aliphatic polycarbonates and polyolefins. In one aspect, provided blends comprise aliphatic polycarbonates such as poly(propylene carbonate) and a lesser amount of a crystalline or semicrystalline polymer. In certain embodiments, provided blends are characterized in that they exhibit unexpected improvements in their elongation properties. In another aspect, the invention provides methods of making such materials and applications of the materials in applications such as the manufacture of consumer packaging materials.

  7. Dynamic liquid-liquid-solid microextraction based on molecularly imprinted polymer filaments on-line coupling to high performance liquid chromatography for direct analysis of estrogens in complex samples.

    Zhong, Qisheng; Hu, Yufei; Hu, Yuling; Li, Gongke


    A novel sample preparation technique termed dynamic liquid-liquid-solid microextraction (DLLSME) was developed and on-line coupled to high performance liquid chromatography (HPLC) for direct extraction, desorption, and analysis of trace estrogens in complex samples. The DLLSME consists of the aqueous donor phase, the organic medium phase and the molecularly imprinted polymer filaments (MIPFs) as solid acceptor phase. The organic solvent with lesser density was directly added on top of the aqueous sample, and the dynamic extraction was performed by circulating the organic solvent through the MIPFs inserted into a PEEK tube which served as an extraction and desorption chamber. Afterwards, the extracted analytes on the MIPFs were on-line desorbed and then introduced into the HPLC for analysis. To evaluate the feasibility of the on-line system, a new DLLSME-HPLC method was developed for the analysis of five estrogens in aqueous samples by using 17β-estradiol MIPFs as the solid phase. Under the optimized conditions, the enrichment factors of 51-70, limits of detection of 0.08-0.25 μg/L and precision within 4.5-6.9% were achieved. Furthermore, the proposed method was applied to the analysis of real samples including urine, milk and skin toner, satisfactory recovery (81.9-99.8%) and reproducibility (4.1-7.9%) were obtained. Especially, 0.59 μg/L of 17β-estradiol was determined in female urine sample. The DLLSME offers an attractive alternative for direct analysis of trace analytes in aqueous samples and could potentially be extended to other adsorptive materials.

  8. Polymer network stretching during electrospinning

    Greenfeld, Israel; Arinstein, Arkadii; Fezzaa, Kamel; Rafailovich, Miriam; Zussman, Eyal


    Fast X-ray phase contrast imaging is used to observe the flow of a semi-dilute polyethylene oxide solution during electrospinning. Micron-size glass particles mixed in the polymer solution allow viewing of the jet flow field, and reveal a high-gradient flow that has both longitudinal and radial components that grow rapidly along the jet. The resulting hydrodynamic forces cause substantial longitudinal stretching and transversal contraction of the polymer network within the jet, as confirmed by random walk simulation and theoretical modeling. The polymer network therefore concentrates towards the jet center, and its conformation may transform from a free state to a fully-stretched state within a short distance from the jet start. We acknowledge the financial support of the United States - Israel Bi-National Science Foundation (grant 2006061).

  9. Creation of Superheterojunction Polymers via Direct Polycondensation: Segregated and Bicontinuous Donor-Acceptor π-Columnar Arrays in Covalent Organic Frameworks for Long-Lived Charge Separation.

    Jin, Shangbin; Supur, Mustafa; Addicoat, Matthew; Furukawa, Ko; Chen, Long; Nakamura, Toshikazu; Fukuzumi, Shunichi; Irle, Stephan; Jiang, Donglin


    By developing metallophthalocyanines and diimides as electron-donating and -accepting building blocks, herein, we report the construction of new electron donor-acceptor covalent organic frameworks (COFs) with periodically ordered electron donor and acceptor π-columnar arrays via direct polycondensation reactions. X-ray diffraction measurements in conjunction with structural simulations resolved that the resulting frameworks consist of metallophthalocyanine and diimide columns, which are ordered in a segregated yet bicontinuous manner to form built-in periodic π-arrays. In the frameworks, each metallophthalocyanine donor and diimide acceptor units are exactly linked and interfaced, leading to the generation of superheterojunctions-a new type of heterojunction machinery, for photoinduced electron transfer and charge separation. We show that this polycondensation method is widely applicable to various metallophthalocyanines and diimides as demonstrated by the combination of copper, nickel, and zinc phthalocyanine donors with pyrommellitic diimide, naphthalene diimide, and perylene diimide acceptors. By using time-resolved transient absorption spectroscopy and electron spin resonance, we demonstrated that the COFs enable long-lived charge separation, whereas the metal species, the class of acceptors, and the local geometry between donor and acceptor units play roles in determining the photochemical dynamics. The results provide insights into photoelectric COFs and demonstrate their enormous potential for charge separation and photoenergy conversions.

  10. Detection of oligonucleotide hybridization on a single microparticle by time-resolved fluorometry: hybridization assays on polymer particles obtained by direct solid phase assembly of the oligonucleotide probes.

    Hakala, H; Heinonen, P; Iitiä, A; Lönnberg, H


    Oligodeoxyribonucleotides were assembled by conventional phosphoramidite chemistry on uniformly sized (50 microns) porous glycidyl methacrylate/ethylene dimethacrylate (SINTEF) and compact polystyrene (Dynosphere) particles, the aminoalkyl side chains of which were further derivatized with DMTrO-acetyl groups. The linker was completely resistant toward ammonolytic deprotection of the base moieties. The quality of oligonucleotides was assessed by repeating the synthesis on the same particles derivatized with a cleavable ester linker. The ability of the oligonucleotide-coated particles to bind complementary sequences via hybridization was examined by following the attachment of oligonucleotides bearing a photoluminescent europium(III) chelate to the particles. The fluorescence emission was measured directly on a single particle. The effects of the following factors on the kinetics and efficiency of hybridization were studied: number of particles in a given volume of the assay solution, loading of oligonucleotide on the particle, concentration of the target oligonucleotide in solution, length of the hybridizing sequence, presence of noncomplementary sequences, and ionic strength. The fluorescence signal measured on a single particle after hybridization was observed to be proportional to the concentration of the target oligonucleotide in solution over a concentration range of 5 orders of magnitude.

  11. Ultrathin, bioresorbable polymer sirolimus-eluting stents versus thin, durable polymer everolimus-eluting stents in patients undergoing coronary revascularisation (BIOFLOW V): a randomised trial.

    Kandzari, David E; Mauri, Laura; Koolen, Jacques J; Massaro, Joseph M; Doros, Gheorghe; Garcia-Garcia, Hector M; Bennett, Johan; Roguin, Ariel; Gharib, Elie G; Cutlip, Donald E; Waksman, Ron


    The development of coronary drug-eluting stents has included use of new metal alloys, changes in stent architecture, and use of bioresorbable polymers. Whether these advancements improve clinical safety and efficacy has not been shown in previous randomised trials. We aimed to examine the clinical outcomes of a bioresorbable polymer sirolimus-eluting stent compared with a durable polymer everolimus-eluting stent in a broad patient population undergoing percutaneous coronary intervention. BIOFLOW V was an international, randomised trial done in patients undergoing elective and urgent percutaneous coronary intervention in 90 hospitals in 13 countries (Australia, Belgium, Canada, Denmark, Germany, Hungary, Israel, the Netherlands, New Zealand, South Korea, Spain, Switzerland, and the USA). Eligible patients were those aged 18 years or older with ischaemic heart disease undergoing planned stent implantation in de-novo, native coronary lesions. Patients were randomly assigned (2:1) to either an ultrathin strut (60 μm) bioresorbable polymer sirolimus-eluting stent or to a durable polymer everolimus-eluting stent. Randomisation was via a central web-based data capture system (mixed blocks of 3 and 6), and stratified by study site. The primary endpoint was 12-month target lesion failure. The primary non-inferiority comparison combined these data from two additional randomised trials of bioresorbable polymer sirolimus-eluting stent and durable polymer everolimus-eluting stent with Bayesian methods. Analysis was by intention to treat. The trial is registered with, number NCT02389946. Between May 8, 2015, and March 31, 2016, 4772 patients were recruited into the study. 1334 patients met inclusion criteria and were randomly assigned to treatment with bioresorbable polymer sirolimus-eluting stents (n=884) or durable polymer everolimus-eluting stents (n=450). 52 (6%) of 883 patients in the bioresorbable polymer sirolimus-eluting stent group and 41 (10%) of

  12. Limit theorems for multi-indexed sums of random variables

    Klesov, Oleg


    Presenting the first unified treatment of limit theorems for multiple sums of independent random variables, this volume fills an important gap in the field. Several new results are introduced, even in the classical setting, as well as some new approaches that are simpler than those already established in the literature. In particular, new proofs of the strong law of large numbers and the Hajek-Renyi inequality are detailed. Applications of the described theory include Gibbs fields, spin glasses, polymer models, image analysis and random shapes. Limit theorems form the backbone of probability theory and statistical theory alike. The theory of multiple sums of random variables is a direct generalization of the classical study of limit theorems, whose importance and wide application in science is unquestionable. However, to date, the subject of multiple sums has only been treated in journals. The results described in this book will be of interest to advanced undergraduates, graduate students and researchers who ...

  13. Polymer/Solvent and Polymer/Polymer Interaction Studies


    DCM and ATS are completely miscible. The sorption data described 1 2Jones, E. G., Pedrick , D. L., and Benadum, P. A., Polymer Characteri- zation Using...Encyclopedia of Polymer Science and Technology, Vol. 11, Wiley-Interscience, N.Y. (1969), p. 447. 12. Jones, E.G., Pedrick , D.L., and Benadum, P.A., Polymer

  14. Studies on the direct methanol fuel cell: Characterization of proton conducting polymer membranes and investigations of current distribution at the cathode

    Saarinen, V.


    Novel proton conducting membranes for the direct methanol fuel cell (DMFC) are characterized widely by combining methods of physical chemistry, electrochemistry and material science. This work mainly concentrates on the sulphonated poly(ethylene-alt-tetrafluoroethylene) (ETFE-SA) membrane. Other investigated membranes are poly(vinylidene fluoride)-graft-poly(styrene sulphonic acid) (PVDF-g-PSSA), sulphonated poly(phenylene sulphone) (sPSO{sub 2}) and the commercial Nafion membrane as a reference material. The swelling properties of the membranes are investigated in different alcohol - water and H2SO{sub 4} - water mixtures. Clear trends are observed for the water / alcohol selectivity: preferential water uptake (alcohol rejection) correlates with high ion exchange capacity (IEC) and low solvent uptake (swelling). The total swelling significantly decreases in the presence of H2SO{sub 4} indicating that osmosis is a major driving force in the swelling process. The membrane properties are characterized with sophisticated microscopic techniques (AFM, SEM and EDX, SECM) and many benefits of the extensive characterization are demonstrated. The surface hydrophobicity is investigated by water contact angle (CA) measurement. During the measurements, the surface properties of the different membranes are found to differ significantly from each other and the properties of the ETFE-SA membrane to vary also as a function of the manufacturing parameters. Also, the ETFE-SA membrane has exceptionally low water uptake, high water selectivity against methanol and good chemical and mechanical stability. Methanol permeability through the membranes is investigated both with a diffusion cell and under actual DMFC conditions. The membranes are investigated in a laboratory-scale DMFC system and the connections between different operation parameters are clarified in detail. The main observation is that durability of ETFE-SA is sufficient for DMFC applications at low temperatures (T < 80 +-C

  15. Highly sensitive biosensors based on water-soluble conjugated polymers

    XU Hui; WU Haiping; FAN Chunhai; LI Wenxin; ZHANG Zhizhou; HE Lin


    Conjugated, conductive polymers are a kind of important organic macromolecules, which has found applications in a variety of areas. The application of conjugated polymers in developing fluorescent biosensors represents the merge of polymer sciences and biological sciences. Conjugated polymers are very good light harvesters as well as fluorescent polymers, and they are also "molecular wires". Through elaborate designs, these important features, i.e. efficient light harvesting and electron/energy transfer, can be used as signal amplification in fluorescent biosensors. This might significantly improve the sensitivity of conjugated polymer-based biosensors. In this article, we reviewed the application of conjugated polymers, via either electron transfer or energy transfer, to detections of gene targets, antibodies or enzymes. We also reviewed recent efforts in conjugated polymer-based solid-state sensor designs as well as chip-based multiple target detection. Possible directions in this conjugated polymer-based biosensor area are also discussed.

  16. Mechanical characterization of fiber reinforced Polymer Concrete

    João Marciano Laredo dos Reis


    Full Text Available A comparative study between epoxy Polymer Concrete plain, reinforced with carbon and glass fibers and commercial concrete mixes was made. The fibers are 6 mm long and the fiber content was 2% and 1%, respectively, in mass. Compressive tests were performed at room temperature and load vs. displacement curves were plotted up to failure. The carbon and glass fibers reinforcement were randomly dispersed into the matrix of polymer concrete. An increase in compressive properties was observed as function of reinforcement. The comparison also showed that Polymer Concrete, plain and reinforced, has a better performance than regular market concrete, suggesting that PC is a reliable alternative for construction industry.

  17. Synthetic Random Copolymers as a Molecular Platform To Mimic Host-Defense Antimicrobial Peptides.

    Takahashi, Haruko; Caputo, Gregory A; Vemparala, Satyavani; Kuroda, Kenichi


    Synthetic polymers have been used as a molecular platform to develop host-defense antimicrobial peptide (AMP) mimetics which are effective in killing drug-resistant bacteria. In this topical review, we will discuss the AMP-mimetic design and chemical optimization strategies as well as the biological and biophysical implications of AMP mimicry by synthetic polymers. Traditionally, synthetic polymers have been used as a chemical means to replicate the chemical functionalities and physicochemical properties of AMPs (e.g., cationic charge, hydrophobicity) to recapitulate their mode of action. However, we propose a new perception that AMP-mimetic polymers are an inherently bioactive platform as whole molecules, which mimic more than the side chain functionalities of AMPs. The tunable nature and chemical simplicity of synthetic random polymers facilitate the development of potent, cost-effective, broad-spectrum antimicrobials. The polymer-based approach offers the potential for many antimicrobial applications to be used directly in solution or attached to surfaces to fight against drug-resistant bacteria.


    WAN Meixiang; LI Suzhen; LI Junchao; DONG Haiou


    The infrared emissivity of conducting polymers in 8-20μm and at 50-150℃ in the direction of normal line has been measured as a function of wavelength, conductivity at room temperature,counterion, doping levels, measuring temperature and thickness of sample.

  19. Anisotropic piezoresistivity characteristics of aligned carbon nanotube-polymer nanocomposites

    Sengezer, Engin C.; Seidel, Gary D.; Bodnar, Robert J.


    Dielectrophoresis under the application of AC electric fields is one of the primary fabrication techniques for obtaining aligned carbon nanotube (CNT)-polymer nanocomposites, and is used here to generate long range alignment of CNTs at the structural level. The degree of alignment of CNTs within this long range architecture is observed via polarized Raman spectroscopy so that its influence on the electrical conductivity and piezoresistive response in both the alignment and transverse to alignment directions can be assessed. Nanocomposite samples consisting of randomly oriented, well dispersed single-wall carbon nanotubes (SWCNTs) and of long range electric field aligned SWCNTs in a photopolymerizable monomer blend (urethane dimethacrylate and 1,6-hexanediol dimethacrylate) are quantitatively and qualitatively evaluated. Piezoresistive sensitivities in form of gauge factors were measured for randomly oriented, well dispersed specimens with 0.03, 0.1 and 0.5 wt% SWCNTs and compared with gauge factors in both the axial and transverse to SWCNT alignment directions for electric field aligned 0.03 wt% specimens under both quasi-static monotonic and cyclic tensile loading. Gauge factors in the axial direction were observed to be on the order of 2, while gauge factors in the transverse direction demonstrated a 5 fold increase with values on the order of 10 for aligned specimens. Based on Raman analysis, it is believed the higher sensitivity of the transverse direction is related to architectural evolution of misaligned bridging structures which connect alignment structures under load due to Poisson’s contraction.

  20. Randomization tests

    Edgington, Eugene


    Statistical Tests That Do Not Require Random Sampling Randomization Tests Numerical Examples Randomization Tests and Nonrandom Samples The Prevalence of Nonrandom Samples in Experiments The Irrelevance of Random Samples for the Typical Experiment Generalizing from Nonrandom Samples Intelligibility Respect for the Validity of Randomization Tests Versatility Practicality Precursors of Randomization Tests Other Applications of Permutation Tests Questions and Exercises Notes References Randomized Experiments Unique Benefits of Experiments Experimentation without Mani

  1. Statistics at the tip of a branching random walk and the delay of traveling waves

    Brunet, É.; Derrida, B.


    We study the limiting distribution of particles at the frontier of a branching random walk. The positions of these particles can be viewed as the lowest energies of a directed polymer in a random medium in the mean-field case. We show that the average distances between these leading particles can be computed as the delay of a traveling wave evolving according to the Fisher-KPP front equation. These average distances exhibit universal behaviors, different from those of the probability cascades studied recently in the context of mean-field spin-glasses.

  2. Fast switching water processable electrochromic polymers.

    Shi, Pengjie; Amb, Chad M; Dyer, Aubrey L; Reynolds, John R


    This paper describes the synthesis of two new blue to transmissive donor-acceptor electrochromic polymers: a polymer synthesized using an alternating copolymerization route (ECP-Blue-A) and a polymer synthesized using a random copolymerization (ECP-Blue-R) by Stille polymerization. These polymers utilize side chains with four ester groups per donor moiety, allowing organic solubility in the ester form, and water solubility upon saponification to their carboxylate salt form. We demonstrate that the saponified polymer salts of ECP-Blue-A and ECP-Blue-R (WS-ECP-Blue-A and WS-ECP-Blue-R) can be processed from aqueous solutions into thin films by spray-casting. Upon the subsequent neutralization of the thin films, the resulting polymer acid films are solvent resistant and can be electrochemically switched between their colored state and a transmissive state in a KNO(3)/water electrolyte solution. The polymer acids, WS-ECP-Blue-A-acid and WS-ECP-Blue-R-acid, show electrochromic contrast Δ%T of 38% at 655 nm and 39% at 555 nm for a 0.5 s switch, demonstrating the advantage of an aqueous compatible electrochrome switchable in high ionic conductivity aqueous electrolytes. The results of the electrochromic properties study indicate that these polymers are promising candidates for aqueous processable and aqueous switching electrochromic materials and devices as desired for applications where environmental impact is of importance.

  3. Cationic polymers and porous materials

    Han, Yu


    According to one or more embodiments, cationic polymers may be produced which include one or more monomers containing cations. Such cationic polymers may be utilized as structure directing agents to form mesoporous zeolites. The mesoporous zeolites may include micropores as well as mesopores, and may have a surface area of greater than 350 m2/g and a pore volume of greater than 0.3 cm3/g. Also described are core/shell zeolites, where at least the shell portion includes a mesoporous zeolite material.

  4. Polymer electrolytes, problems, prospects, and promises

    Nagasubramanian, G.; Boone, D.


    Ionically conducting polymer electrolytes have generated, in recent years, wide-spread interest as candidate materials for a number of applications including high energy density and power lithium batteries. In the early 70s the first measurements of ionic conductivity in polyethylene oxide (PEO)-salt complexes were carried out. However, Armand was the first one to realize potential of these complexes (polymer-salt complexes) as practical ionically conducting materials for use as electrolytes in lithium batteries. Subsequent research efforts identified the limitations and constraints of the polymer electrolytes. These limitations include poor ionic conductivity at RT (< 10{sup {minus}8} S/cm), low cation transport number (<0.2) etc. Several different approaches have been made to improving the ionic conductivity of the polymer electrolytes while retaining the flexibility, processibility, ease of handling and relatively low impact on the environment that polymers inherently possess. This paper- reviews evolution of polymer electrolytes from conventional PEO-LiX slat complexes to the more conducting polyphosphazene and copolymers, gelled electrolytes etc. We also review the various chemical approaches including modifying PEO to synthesizing complicated polymer architecture. In addition, we discuss effect of various lithium salts on the conductivity of PEO-based polymers. Charge/discharge and cycle life data of polymer cells containing oxide and chalcogenide cathodes and lithium (Li) anode are reviewed. Finally, future research directions to improve the electrolyte properties are discussed.

  5. Randomized controlled ferret study to assess the direct impact of 2008-09 trivalent inactivated influenza vaccine on A(H1N1)pdm09 disease risk

    D.M. Skowronski (Danuta); M.E. Hamelin (Marie Ève); G. de Serres (Gaston); N.Z. Janjua (Naveed); G. Li (Guiyun); S. Sabaiduc (Suzana); X. Bouhy (Xavier); C. Couture (Christian); A. Leung (Anders); D. Kobasa (Darwyn); C. Embury-Hyatt (Carissa); E.I. de Bruin (Esther); R. Balshaw (Robert); S. Lavigne (Sophie); M. Petric (Martin); M.P.G. Koopmans D.V.M. (Marion); G. Boivin (Guy)


    textabstractDuring spring-summer 2009, several observational studies from Canada showed increased risk of medically-attended, laboratory-confirmed A(H1N1)pdm09 illness among prior recipients of 2008-09 trivalent inactivated influenza vaccine (TIV). Explanatory hypotheses included direct and indirect

  6. Randomized controlled ferret study to assess the direct impact of 2008-09 trivalent inactivated influenza vaccine on A(H1N1)pdm09 disease risk

    D.M. Skowronski (Danuta); M.E. Hamelin (Marie Ève); G. de Serres (Gaston); N.Z. Janjua (Naveed); G. Li (Guiyun); S. Sabaiduc (Suzana); X. Bouhy (Xavier); C. Couture (Christian); A. Leung (Anders); D. Kobasa (Darwyn); C. Embury-Hyatt (Carissa); E.I. de Bruin (Esther); R. Balshaw (Robert); S. Lavigne (Sophie); M. Petric (Martin); M.P.G. Koopmans D.V.M. (Marion); G. Boivin (Guy)


    textabstractDuring spring-summer 2009, several observational studies from Canada showed increased risk of medically-attended, laboratory-confirmed A(H1N1)pdm09 illness among prior recipients of 2008-09 trivalent inactivated influenza vaccine (TIV). Explanatory hypotheses included direct and indirect

  7. Goal-directed fluid management based on stroke volume variation and stroke volume optimization during high-risk surgery : a pilot multicentre randomized controlled trial

    Scheeren, Thomas; Wiesenack, Christoph; Gerlach, H.; Marx, G.


    Introduction: Perioperative hemodynamic optimization has been shown to be useful to improve the postoperative outcome of patients undergoing major surgery. We designed a pilot study in patients undergoing major abdominal, urologic or vascular surgery to investigate the effects of a goal-directed (GD

  8. Linear side chains in benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c] pyrrole-4,6-dione polymers direct self-assembly and solar cell performance

    Cabanetos, Clement


    While varying the size and branching of solubilizing side chains in π-conjugated polymers impacts their self-assembling properties in thin-film devices, these structural changes remain difficult to anticipate. This report emphasizes the determining role that linear side-chain substituents play in poly(benzo[1,2-b:4,5-b′]dithiophene-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymers for bulk heterojunction (BHJ) solar cell applications. We show that replacing branched side chains by linear ones in the BDT motifs induces a critical change in polymer self-assembly and backbone orientation in thin films that correlates with a dramatic drop in solar cell efficiency. In contrast, we show that for polymers with branched alkyl-substituted BDT motifs, controlling the number of aliphatic carbons in the linear N-alkyl-substituted TPD motifs is a major contributor to improved material performance. With this approach, PBDTTPD polymers were found to reach power conversion efficiencies of 8.5% and open-circuit voltages of 0.97 V in BHJ devices with PC71BM, making PBDTTPD one of the best polymer donors for use in the high-band-gap cell of tandem solar cells. © 2013 American Chemical Society.

  9. Shape memory polymers

    Wilson, Thomas S.; Bearinger, Jane P.


    New shape memory polymer compositions, methods for synthesizing new shape memory polymers, and apparatus comprising an actuator and a shape memory polymer wherein the shape memory polymer comprises at least a portion of the actuator. A shape memory polymer comprising a polymer composition which physically forms a network structure wherein the polymer composition has shape-memory behavior and can be formed into a permanent primary shape, re-formed into a stable secondary shape, and controllably actuated to recover the permanent primary shape. Polymers have optimal aliphatic network structures due to minimization of dangling chains by using monomers that are symmetrical and that have matching amine and hydroxl groups providing polymers and polymer foams with clarity, tight (narrow temperature range) single transitions, and high shape recovery and recovery force that are especially useful for implanting in the human body.

  10. Shape memory polymers

    Wilson, Thomas S.; Bearinger, Jane P.


    New shape memory polymer compositions, methods for synthesizing new shape memory polymers, and apparatus comprising an actuator and a shape memory polymer wherein the shape memory polymer comprises at least a portion of the actuator. A shape memory polymer comprising a polymer composition which physically forms a network structure wherein the polymer composition has shape-memory behavior and can be formed into a permanent primary shape, re-formed into a stable secondary shape, and controllably actuated to recover the permanent primary shape. Polymers have optimal aliphatic network structures due to minimization of dangling chains by using monomers that are symmetrical and that have matching amine and hydroxyl groups providing polymers and polymer foams with clarity, tight (narrow temperature range) single transitions, and high shape recovery and recovery force that are especially useful for implanting in the human body.

  11. Direct drug-eluting stenting to reduce stent restenosis : a randomized comparison of direct stent implantation to conventional stenting with pre-dilation or provisional stenting in elective PCI patients

    Remkes, Wouter S; Somi, Samer; Roolvink, Vincent; Rasoul, Saman; Ottervanger, Jan Paul; Gosselink, A T Marcel; Hoorntje, Jan C A; Dambrink, Jan-Henk E; de Boer, Menko-Jan; Suryapranata, Harry; van 't Hof, Arnoud W J


    OBJECTIVES: The aim was to investigate whether a strategy of direct drug-eluting stent (DES) implantation without pre-dilation is associated with a reduced incidence of restenosis compared with CS with pre-dilation or provisional stenting (PS). BACKGROUND: Previous studies were performed comparing d

  12. Liquid Crystal Alignment Control Using Polymer Filament and Polymer Layers Coated on Substrates

    Murashige, Takeshi; Fujikake, Hideo; Sato, Hiroto; Kikuchi, Hiroshi; Kurita, Taiichiro; Sato, Fumio


    We investigated liquid crystal (LC) alignment in LC cells containing an aligned cellulose filament sandwiched by thin polymer layers coated on substrates. Three types of polymer material, namely polystyrene (PS), polyvinyl alcohol (PVA) and polyimide (PI), were used as polymer layers. LC alignment areas induced on both sides of the filament were large in the order of PS, PVA and PI. In the case of the PS layer, the average LC alignment area reached approximately 100 μm in the direction perpendicular to the polymer filament. The molecular interaction between the LC and the PS layer is thought to be weak and it does not disturb the LC alignment due to the polymer filament. On the other hand, rubbed PS layers were used as polymer layers of the LC cell, where the LC alignment direction induced by the rubbed PS layer was perpendicular to the polymer filament. It was found that the LC alignment near the polymer filament gradually bent in the cell plane. The result suggests that various three-dimensional LC alignments can be realized by the combination of the polymer filament and substrate surface.

  13. Emulsification-Induced Homohelicity in Racemic Helical Polymer for Preparing Optically Active Helical Polymer Nanoparticles.

    Zhao, Biao; Deng, Jinrui; Deng, Jianping


    Optically active nano- and microparticles have constituted a significant category of advanced functional materials. However, constructing optically active particles derived from synthetic helical polymers still remains as a big challenge. In the present study, it is attempted to induce a racemic helical polymer (containing right- and left-handed helices in equal amount) to prefer one predominant helicity in aqueous media by using emulsifier in the presence of chiral additive (emulsification process). Excitingly, the emulsification process promotes the racemic helical polymer to unify the helicity and directly provides optically active nanoparticles constructed by chirally helical polymer. A possible mechanism is proposed to explain the emulsification-induced homohelicity effect. The present study establishes a novel strategy for preparing chirally helical polymer-derived optically active nanoparticles based on racemic helical polymers.

  14. Soft matter beats hard matter: rupturing of thin metallic films induced by mass transport in photosensitive polymer films.

    Yadavalli, Nataraja Sekhar; Linde, Felix; Kopyshev, Alexey; Santer, Svetlana


    The interface between thin films of metal and polymer materials play a significant role in modern flexible microelectronics viz., metal contacts on polymer substrates, printed electronics and prosthetic devices. The major emphasis in metal-polymer interface is on studying how the externally applied stress in the polymer substrate leads to the deformation and cracks in metal film and vice versa. Usually, the deformation process involves strains varying over large lateral dimensions because of excessive stress at local imperfections. Here we show that the seemingly random phenomena at macroscopic scales can be rendered rather controllable at submicrometer length scales. Recently, we have created a metal-polymer interface system with strains varying over periods of several hundred nanometers. This was achieved by exploiting the formation of surface relief grating (SRG) within the azobenzene containing photosensitive polymer film upon irradiation with light interference pattern. Up to a thickness of 60 nm, the adsorbed metal film adapts neatly to the forming relief, until it ultimately ruptures into an array of stripes by formation of highly regular and uniform cracks along the maxima and minima of the polymer topography. This surprising phenomenon has far-reaching implications. This is the first time a direct probe is available to estimate the forces emerging in SRG formation in glassy polymers. Furthermore, crack formation in thin metal films can be studied literally in slow motion, which could lead to substantial improvements in the design process of flexible electronics. Finally, cracks are produced uniformly and at high density, contrary to common sense. This could offer new strategies for precise nanofabrication procedures mechanical in character.

  15. Thermal Spray Formation of Polymer Coatings

    Coquill, Scott; Galbraith, Stephen L.; Tuss. Darren L.; Ivosevic, Milan


    This innovation forms a sprayable polymer film using powdered precursor materials and an in-process heating method. This device directly applies a powdered polymer onto a substrate to form an adherent, mechanically-sound, and thickness-regulated film. The process can be used to lay down both fully dense and porous, e.g., foam, coatings. This system is field-deployable and includes power distribution, heater controls, polymer constituent material bins, flow controls, material transportation functions, and a thermal spray apparatus. The only thing required for operation in the field is a power source. Because this method does not require solvents, it does not release the toxic, volatile organic compounds of previous methods. Also, the sprayed polymer material is not degraded because this method does not use hot combustion gas or hot plasma gas. This keeps the polymer from becoming rough, porous, or poorly bonded.

  16. The Short-Term Effects of Transcranial Direct Current Stimulation on Electroencephalography in Children with Autism: A Randomized Crossover Controlled Trial

    Anuwat Amatachaya


    Full Text Available Abnormal synaptic maturation and connectivity are possible etiologies of autism. Previous studies showed significantly less alpha activity in autism than normal children. Therefore, we studied the effects of anodal tDCS on peak alpha frequency (PAF related to autism treatment evaluation checklist (ATEC. Twenty male children with autism were randomly assigned in a crossover design to receive a single session of both active and sham tDCS stimulation (11 mA over F3 (left dorsolateral prefrontal cortex. Pre- to postsession changes in a measure of cortical activity impacted by tDCS (PAF and ATEC were compared between groups. We also examined the associations between pre- and postsession changes in the PAF and ATEC. The results show significant pre- to postsession improvements in two domains of ATEC (social and health/behavior domains following active tDCS, relative to sham treatment. PAF also significantly increased at the stimulation site, and an increase in PAF was significantly associated with improvements in the two domains of ATEC impacted by tDCS. The findings suggest that a single session of anodal tDCS over the F3 may have clinical benefits in children with autism and that those benefits may be related to an increase in PAF.

  17. Evaluation of fit and efficiency of CAD/CAM fabricated all-ceramic restorations based on direct and indirect digitalization: a double-blinded, randomized clinical trial.

    Ahrberg, Danush; Lauer, Hans Christoph; Ahrberg, Martin; Weigl, Paul


    The aim of this clinical trial was to evaluate the marginal and internal fit of CAD/CAM fabricated zirconia crowns and three-unit fixed dental prostheses (FDPs) resulting from direct versus indirect digitalization. The efficiency of both methods was analyzed. In 25 patients, 17 single crowns and eight three-unit FDPs were fabricated with all-ceramic zirconia using CAD/CAM technology. Each patient underwent two different impression methods; a computer-aided impression with Lava C.O.S. (CAI) and a conventional polyether impression with Impregum pent soft (CI). The working time for each group was recorded. Before insertion, the marginal and internal fit was recorded using silicone replicas of the frameworks. Each sample was cut into four sections and evaluated at four sites (marginal gap, mid-axial wall, axio-occlusal transition, centro-occlusal site) under ×64 magnification. The Mann-Whitney U test was used to detect significant differences between the two groups in terms of marginal and internal fit (α = 0.05). The mean for the marginal gap was 61.08 μm (±24.77 μm) for CAI compared with 70.40 μm (±28.87 μm) for CI, which was a statistically significant difference. The other mean values for CAI and CI, respectively, were as follows in micrometers (± standard deviation): 88.27 (±41.49) and 92.13 (±49.87) at the mid-axial wall; 144.78 (±46.23) and 155.60 (±55.77) at the axio-occlusal transition; and 155.57 (49.85) and 171.51 (±60.98) at the centro-occlusal site. The CAI group showed significantly lower values of internal fit at the centro-occlusal site. A quadrant scan with a computer-aided impression was 5 min 6 s more time efficient when compared with a conventional impression, and a full-arch scan was 1 min 34 s more efficient. Although both direct and indirect digitalization facilitate the fabrication of single crowns and three-unit FDPs with clinically acceptable marginal fit, a significantly better marginal fit was noted with direct

  18. Synthesis and photocurrent response of porphyrin-containing conjugated polymers

    ZHAO Jinling; LI Binsong; BO Zhishan


    Porphyrin-containing conjugated polymers with fluorene or carbazole as spacer groups were prepared by Sonogashira cross-coupling reactions. The polymers were of high molecular weight and the flexible alkyl chains on fluorene or carbazole units made the conjugated polymers soluble in common organic solvents, such as THF and methylene chloride. The polymers could form high quality durable films from solution casting. Their optical and photocurrent responsive properties were investigated. It was found that the photocurrent response was directly proportional to the content of porphyrin. The incorporation of carbazole units into the polymer chains also gave positive contribution to the photocurrent generation in some extent.

  19. Long polymers near wedges and cones

    Hammer, Yosi; Kantor, Yacov


    We perform a Monte Carlo study of N -step self-avoiding walks, attached to the corner of an impenetrable wedge in two dimensions (d =2 ), or the tip of an impenetrable cone in d =3 , of sizes ranging up to N =106 steps. We find that the critical exponent γα, which determines the dependence of the number of available conformations on N for a cone or wedge with opening angle α , is in good agreement with the theory for d =2 . We study the end-point distribution of the walks in the allowed space and find similarities to the known behavior of random walks (ideal polymers) in the same geometry. For example, the ratio between the mean square end-to-end distances of a polymer near the cone or wedge and a polymer in free space depends linearly on γα, as is known for ideal polymers. We show that the end-point distribution of polymers attached to a wedge does not separate into a product of angular and radial functions, as it does for ideal polymers in the same geometry. The angular dependence of the end position of polymers near the wedge differs from theoretical predictions.

  20. MOLECULAR IMPRINTED POLYMERS--Novel Polymer Adsorbents

    LI Haitao; XU Mancai; SHI Zuoqing; HE Binglin


    Molecular imprinted polymers (MIPs) are novel functional polymer materials and known as specific adsorbents for the template molecules. These novel functional polymers have promised potential applications in racemic resolution, sensor, chromatography, adsorptive separation and other fields. This review exhibits the approach for preparing MIPs, the features of MIPs obtained by different routes and the characteristics of adsorptive separations with MIPs. The molecular recognition mechanism and the idea of the present possibilities and limitations of molecular imprinting polymerization are discussed as well.