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Sample records for constitutive polymers biological

  1. A constitutive law for degrading bioresorbable polymers.

    PubMed

    Samami, Hassan; Pan, Jingzhe

    2016-06-01

    This paper presents a constitutive law that predicts the changes in elastic moduli, Poisson's ratio and ultimate tensile strength of bioresorbable polymers due to biodegradation. During biodegradation, long polymer chains are cleaved by hydrolysis reaction. For semi-crystalline polymers, the chain scissions also lead to crystallisation. Treating each scission as a cavity and each new crystal as a solid inclusion, a degrading semi-crystalline polymer can be modelled as a continuum solid containing randomly distributed cavities and crystal inclusions. The effective elastic properties of a degrading polymer are calculated using existing theories for such solid and the tensile strength of the degrading polymer is predicted using scaling relations that were developed for porous materials. The theoretical model for elastic properties and the scaling law for strength form a complete constitutive relation for the degrading polymers. It is shown that the constitutive law can capture the trend of the experimental data in the literature for a range of biodegradable polymers fairly well. PMID:26971070

  2. Constitutive equations for an electroactive polymer

    NASA Astrophysics Data System (ADS)

    Tixier, Mireille; Pouget, Joël

    2016-07-01

    Ionic electroactive polymers can be used as sensors or actuators. For this purpose, a thin film of polyelectrolyte is saturated with a solvent and sandwiched between two platinum electrodes. The solvent causes a complete dissociation of the polymer and the release of small cations. The application of an electric field across the thickness results in the bending of the strip and vice versa. The material is modeled by a two-phase continuous medium. The solid phase, constituted by the polymer backbone inlaid with anions, is depicted as a deformable porous media. The liquid phase is composed of the free cations and the solvent (usually water). We used a coarse grain model. The conservation laws of this system have been established in a previous work. The entropy balance law and the thermodynamic relations are first written for each phase and then for the complete material using a statistical average technique and the material derivative concept. One deduces the entropy production. Identifying generalized forces and fluxes provides the constitutive equations of the whole system: the stress-strain relations which satisfy a Kelvin-Voigt model, generalized Fourier's and Darcy's laws and the Nernst-Planck equation.

  3. Multiscale constitutive modeling of polymer materials

    NASA Astrophysics Data System (ADS)

    Valavala, Pavan Kumar

    Materials are inherently multi-scale in nature consisting of distinct characteristics at various length scales from atoms to bulk material. There are no widely accepted predictive multi-scale modeling techniques that span from atomic level to bulk relating the effects of the structure at the nanometer (10-9 meter) on macro-scale properties. Traditional engineering deals with treating matter as continuous with no internal structure. In contrast to engineers, physicists have dealt with matter in its discrete structure at small length scales to understand fundamental behavior of materials. Multiscale modeling is of great scientific and technical importance as it can aid in designing novel materials that will enable us to tailor properties specific to an application like multi-functional materials. Polymer nanocomposite materials have the potential to provide significant increases in mechanical properties relative to current polymers used for structural applications. The nanoscale reinforcements have the potential to increase the effective interface between the reinforcement and the matrix by orders of magnitude for a given reinforcement volume fraction as relative to traditional micro- or macro-scale reinforcements. To facilitate the development of polymer nanocomposite materials, constitutive relationships must be established that predict the bulk mechanical properties of the materials as a function of the molecular structure. A computational hierarchical multiscale modeling technique is developed to study the bulk-level constitutive behavior of polymeric materials as a function of its molecular chemistry. Various parameters and modeling techniques from computational chemistry to continuum mechanics are utilized for the current modeling method. The cause and effect relationship of the parameters are studied to establish an efficient modeling framework. The proposed methodology is applied to three different polymers and validated using experimental data available in

  4. Constitutive Modeling of Piezoelectric Polymer Composites

    NASA Technical Reports Server (NTRS)

    Odegard, Gregory M.; Gates, Tom (Technical Monitor)

    2003-01-01

    A new modeling approach is proposed for predicting the bulk electromechanical properties of piezoelectric composites. The proposed model offers the same level of convenience as the well-known Mori-Tanaka method. In addition, it is shown to yield predicted properties that are, in most cases, more accurate or equally as accurate as the Mori-Tanaka scheme. In particular, the proposed method is used to determine the electromechanical properties of four piezoelectric polymer composite materials as a function of inclusion volume fraction. The predicted properties are compared to those calculated using the Mori-Tanaka and finite element methods.

  5. Constitutive Modeling of Nanotube-Reinforced Polymer Composite Systems

    NASA Technical Reports Server (NTRS)

    Odegard, Gregory M.; Harik, Vasyl M.; Wise, Kristopher E.; Gates, Thomas S.

    2001-01-01

    In this study, a technique has been proposed for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Since the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local molecular structure and bonding. At these small length scales, the lattice structures of the nanotube and polymer chains cannot be considered continuous, and the bulk mechanical properties of the SWNT/polymer composites can no longer be determined through traditional micromechanical approaches that are formulated using continuum mechanics. It is proposed herein that the nanotube, the local polymer near the nanotube, and the nanotube/polymer interface can be modeled as an effective continuum fiber using an equivalent-continuum modeling method. The effective fiber retains the local molecular structure and bonding information and serves as a means for incorporating micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composites with various nanotube sizes and orientations. As an example, the proposed approach is used for the constitutive modeling of two SWNT/polyethylene composite systems, one with continuous and aligned SWNT and the other with discontinuous and randomly aligned nanotubes.

  6. Constitutive Modeling of Nanotube-Reinforced Polymer Composite Systems

    NASA Technical Reports Server (NTRS)

    Odegard, Gregory M.; Harik, Vasyl M.; Wise, Kristopher E.; Gates, Thomas S.

    2004-01-01

    In this study, a technique has been proposed for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Since the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local molecular structure and bonding. At these small length scales, the lattice structures of the nanotube and polymer chains cannot be considered continuous, and the bulk mechanical properties of the SWNT/polymer composites can no longer be determined through traditional micromechanical approaches that are formulated using continuum mechanics. It is proposed herein that the nanotube, the local polymer near the nanotube, and the nanotube/polymer interface can be modeled as an effective continuum fiber using an equivalent-continuum modeling method. The effective fiber retains the local molecular structure and bonding information and serves as a means for incorporating micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composites with various nanotube sizes and orientations. As an example, the proposed approach is used for the constitutive modeling of two SWNT/polyethylene composite systems, one with continuous and aligned SWNT and the other with discontinuous and randomly aligned nanotubes.

  7. Solid Rocket Fuel Constitutive Theory and Polymer Cure

    NASA Technical Reports Server (NTRS)

    Ream, Robert

    2006-01-01

    Solid Rocket Fuel is a complex composite material for which no general constitutive theory, based on first principles, has been developed. One of the principles such a relation would depend on is the morphology of the binder. A theory of polymer curing is required to determine this morphology. During work on such a theory an algorithm was developed for counting the number of ways a polymer chain could assemble. The methods used to develop and check this algorithm led to an analytic solution to the problem. This solution is used in a probability distribution function which characterizes the morphology of the polymer.

  8. Constitutive Modeling of Nanotube-Reinforced Polymer Composites

    NASA Technical Reports Server (NTRS)

    Odegard, G. M.; Gates, T. S.; Wise, K. E.; Park, C.; Siochi, E. J.; Bushnell, Dennis M. (Technical Monitor)

    2002-01-01

    In this study, a technique is presented for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Because the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local molecular structure and bonding. At these small length scales, the lattice structures of the nanotube and polymer chains cannot be considered continuous, and the bulk mechanical properties can no longer be determined through traditional micromechanical approaches that are formulated by using continuum mechanics. It is proposed herein that the nanotube, the local polymer near the nanotube, and the nanotube/polymer interface can be modeled as an effective continuum fiber using an equivalent-continuum modeling method. The effective fiber serves as a means for incorporating micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composites with various nanotube lengths, concentrations, and orientations. As an example, the proposed approach is used for the constitutive modeling of two SWNT/polyimide composite systems.

  9. Constitutive Modeling of Nanotube-Reinforced Polymer Composites

    NASA Technical Reports Server (NTRS)

    Odegard, G. M.; Gates, T. S.; Wise, K. E.

    2002-01-01

    In this study, a technique is presented for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT). Because the polymer molecules are on the same size scale as the nanotubes, the interaction at the polymer/nanotube interface is highly dependent on the local molecular structure and bonding. At these small length scales, the lattice structures of the nanotube and polymer chains cannot be considered continuous, and the bulk mechanical properties can no longer be determined through traditional micromechanical approaches that are formulated by using continuum mechanics. It is proposed herein that the nanotube, the local polymer near the nanotube, and the nanotube/polymer interface can be modeled as an effective continuum fiber using an equivalent-continuum modeling method. The effective fiber serves as a means for incorporating micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composites with various nanotube shapes, sizes, concentrations, and orientations. As an example, the proposed approach is used for the constitutive modeling of two SWNT/LaRC-SI (with a PmPV interface) composite systems, one with aligned SWNTs and the other with three-dimensionally randomly oriented SWNTs. The Young's modulus and shear modulus have been calculated for the two systems for various nanotube lengths and volume fractions.

  10. Constitutive Equation for Polymer Networks with Phonon Fluctuations

    NASA Astrophysics Data System (ADS)

    Hansen, Rasmus; Hassager, Ole; Skov, Anne Ladegaard

    2008-07-01

    Recent research by Xing et al. [Phys. Rev. Lett. 98, 075502, 2007] has provided an expression for the Helmholtz free energy related to phonon fluctuations in polymer networks. We extend this result by constructing the corresponding nonlinear constitutive equation, usable for entirely general, volume conserving deformation fields. Constitutive equations for the sliplink and the tube model are applied. The three models are examined by comparison with each other and with data from Xu and Mark [Rubber Chem. Technol. 63, 276, 1990] and Wang and Mark [J. Polym. Sci. Part B: Polym. Phys. 30, 801, 1992] on end-linked polydimethylsiloxane networks. Elastic moduli are derived for the three models and compared with the moduli determined from the chemical stoichiometry. We conclude that the sliplink model and the phonon fluctuation model are relatively consistent with each other and also with the data. The tube model seems consistent neither with the other models nor with the data.

  11. Biological activity of ionene polymers

    NASA Technical Reports Server (NTRS)

    Rembaum, A.

    1973-01-01

    Ionene polymers are polyammonium salts with positive nitrogens in the backbone, resulting from the polycondensation of diamines with dihalides or from the polycondensation of halo amines. The mechanism of formation of ionene polymers of different structures and their biological activity is reviewed. The antimicrobial and antifungal properties are compared with low molecular weight ammonium salts. Ionenes were found to combine with DNA by means of ionic bonds to yield similar complexes to those obtained with polyamines (spermine and spermidine). They also combine with nerve cell receptors and exercise a more powerful and longer duration ganglionic blocking action than their monomeric analogs. The antiheparin activity of ionenes and the thromboresistance of elastomeric ionene heparin coatings is described. The enhanced biological activity of ionenes as compared with low molecular weight compounds is attributed to a cooperative effect of a large number of positive charges on the polymeric chains.

  12. Mechanics of biological polymer composites

    NASA Astrophysics Data System (ADS)

    Lomakin, Joseph

    2009-12-01

    displayed a darker coloration and significantly increased n of 0.0470.004, suggesting both cuticles to be less cross-linked, a finding consistent with reduced beta-alanine metabolism. Suppression of the tanning enzyme laccase2 (TcLac2) resulted in a pale cuticle with an n of 0.043+/-0.005, implicating laccases in the formation of both pigments and cross-links during sclerotization. Cuticular cross-linking was increased and n decreased with decreased expression of structural proteins, CP10 and CP20. This work establishes n as an important novel parameter for confirming metabolic pathways within load bearing tissues and for understanding structure function relationships within biological polymer composites. Additionally, Tribolium castaneum elytral indentation modulus (800+/-200 MPa) was determined by nanoindentation and a 4nm regular hexagonal pattern on the dorsal side of elytra investigated via scanning, transmission and atomic microscopy. Based on studied biological materials, the combination of rigid macromolecules immersed in a ductile matrix was found to be significant in achieving exceptional mechanical performance. Inspired by this biological design principle, the synthesis, properties and structure of Poly(ethylene glycol) diacrylate/agarose semi-interpenetrating network hydrogels were explored. The resulting novel composite materials were 9x stiffer than agarose and 5x tougher than PEGDA alone and showed good biocompatibility, suggesting promise as a scaffold material for tissue engineering constructs for cartilage regeneration.

  13. Rate constitutive theories for ordered thermoviscoelastic fluids: polymers

    NASA Astrophysics Data System (ADS)

    Surana, K. S.; Nunez, D.; Reddy, J. N.; Romkes, A.

    2014-03-01

    This paper presents development of rate constitutive theories for compressible as well as in incompressible ordered thermoviscoelastic fluids, i.e., polymeric fluids in Eulerian description. The polymeric fluids in this paper are considered as ordered thermoviscoelastic fluids in which the stress rate of a desired order, i.e., the convected time derivative of a desired order ` m' of the chosen deviatoric Cauchy stress tensor, and the heat vector are functions of density, temperature, temperature gradient, convected time derivatives of the chosen strain tensor up to any desired order ` n' and the convected time derivative of up to orders ` m-1' of the chosen deviatoric Cauchy stress tensor. The development of the constitutive theories is presented in contravariant and covariant bases, as well as using Jaumann rates. The polymeric fluids described by these constitutive theories will be referred to as ordered thermoviscoelastic fluids due to the fact that the constitutive theories are dependent on the orders ` m' and ` n' of the convected time derivatives of the deviatoric Cauchy stress and conjugate strain tensors. The highest orders of the convected time derivative of the deviatoric Cauchy stress and strain tensors define the orders of the polymeric fluid. The admissibility requirement necessitates that the constitutive theories for the stress tensor and heat vector satisfy conservation laws, hence, in addition to conservation of mass, balance of momenta, and conservation of energy, the second law of thermodynamics, i.e., Clausius-Duhem inequality must also be satisfied by the constitutive theories or be used in their derivations. If we decompose the total Cauchy stress tensor into equilibrium and deviatoric components, then Clausius-Duhem inequality and Helmholtz free-energy density can be used to determine the equilibrium stress in terms of thermodynamic pressure for compressible fluids and in terms of mechanical pressure for incompressible fluids, but the second

  14. Polymer constitutive properties and adhesive effects at the nanoscale

    NASA Astrophysics Data System (ADS)

    Palacio, Manuel Luis Ballelos

    The development of new materials and devices depend on accurately determining its mechanical properties. As the length scale of device components decreases, nanoindentation is evolving into a desirable metrology tool due to its load and displacement resolution. This dissertation examines models for evaluating the elastic modulus (E), hardness (H), yield strength (sigmays) and adhesion energy (G) of glassy and rubbery polymers. Two types of glassy polymer films were examined---fully dense and porous. These films are of interest due to their potential as low dielectric constant ("low-k") materials for microelectronic systems. Quasi-static and creep indentation techniques were employed to determine the modulus, and results from the latter appear to give more reliable results as it accounts for viscoelastic effects. Hardness was also determined, and its relationship with the yield strength at the nanoscale follows the prediction of a model valid for macroscale testing, implying length scale connectivity. The same test methods were applied to films with 10, 20 and 35% porosity, where the observed 45 percent drop of the E and sigma ys with increasing porosity was described using a model that assumes the pores are closed cell systems. Temperature effects on yielding were also examined from 24 to 140°C, where the hardness was found to follow Eyring's rate theory. Another glassy polymer, polyethersulfone, was studied to determine the effect of arsenic ion implantation on surface mechanical properties. Implantation enhances the hardness only up to a certain threshold ion dose, beyond which it decreases due to sputtering of material from the surface. The adhesion energy of acrylic pressure sensitive adhesive-like networks was determined by nanoindentation. These rubbery polymers have been studied in the past using the JKR apparatus, which measures self-adhesion at the microscale. An unloading rate dependence analogous to the crack propagation rate behavior was observed for

  15. Constitutive Modeling of Nanotube/Polymer Composites with Various Nanotube Orientations

    NASA Technical Reports Server (NTRS)

    Odegard, Gregory M.; Gates, Thomas S.

    2002-01-01

    In this study, a technique has been proposed for developing constitutive models for polymer composite systems reinforced with single-walled carbon nanotubes (SWNT) with various orientations with respect to the bulk material coordinates. A nanotube, the local polymer adjacent to the nanotube, and the nanotube/polymer interface have been modeled as an equivalent-continuum fiber by using an equivalent-continuum modeling method. The equivalent-continuum fiber accounts for the local molecular structure and bonding information and serves as a means for incorporating micromechanical analyses for the prediction of bulk mechanical properties of SWNT/polymer composite. As an example, the proposed approach is used for the constitutive modeling of a SWNT/LaRC-SI (with a PmPV interface) composite system, with aligned nanotubes, three-dimensionally randomly oriented nanotubes, and nanotubes oriented with varying degrees of axisymmetry. It is shown that the Young s modulus is highly dependent on the SWNT orientation distribution.

  16. High Strain Rate Deformation Modeling of a Polymer Matrix Composite. Part 1; Matrix Constitutive Equations

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Stouffer, Donald C.

    1998-01-01

    Recently applications have exposed polymer matrix composite materials to very high strain rate loading conditions, requiring an ability to understand and predict the material behavior under these extreme conditions. In this first paper of a two part report, background information is presented, along with the constitutive equations which will be used to model the rate dependent nonlinear deformation response of the polymer matrix. Strain rate dependent inelastic constitutive models which were originally developed to model the viscoplastic deformation of metals have been adapted to model the nonlinear viscoelastic deformation of polymers. The modified equations were correlated by analyzing the tensile/ compressive response of both 977-2 toughened epoxy matrix and PEEK thermoplastic matrix over a variety of strain rates. For the cases examined, the modified constitutive equations appear to do an adequate job of modeling the polymer deformation response. A second follow-up paper will describe the implementation of the polymer deformation model into a composite micromechanical model, to allow for the modeling of the nonlinear, rate dependent deformation response of polymer matrix composites.

  17. Nanostructure Control of Biologically Inspired Polymers

    NASA Astrophysics Data System (ADS)

    Rosales, Adrianne Marie

    Biological polymers, such as polypeptides, are responsible for many of life's most sophisticated functions due to precisely evolved hierarchical structures. These protein structures are the result of monodisperse sequences of amino acids that fold into well-defined chain shapes and tertiary structures. Recently, there has been much interest in the design of such sequence-specific polymers for materials applications in fields ranging from biotechnology to separations membranes. Non-natural polymers offer the stability and robustness necessary for materials applications; however, our ability to control monomer sequence in non-natural polymers has traditionally operated on a much simpler level. In addition, the relationship between monomer sequence and self-assembly is not well understood for biological molecules, much less synthetic polymers. Thus, there is a need to explore self-assembly phase space with sequence using a model system. Polypeptoids are non-natural, sequence-specific polymers that offer the opportunity to probe the effect of sequence on self-assembly. A variety of monomer interactions have an impact on polymer properties, such as chirality, hydrophobicity, and electrostatic interactions. Thus, a necessary starting point for this project was to investigate monomer sequence effects on the bulk properties of polypeptoid homopolymers. It was found that several polypeptoids have experimentally accessible melting transitions that are dependent on the choice of side chains, and it was shown that this transition is tuned by the incorporation of "defects" or a comonomer. The polypeptoid chain shape is also controlled with the choice of monomer and monomer sequence. By using at least 50% monomers with bulky, chiral side chains, the polypeptoid backbone is sterically twisted into a helix, and as found for the first time in this work, the persistence length is increased. However, this persistence length, which is a measure of the stiffness of the polymer, is

  18. Biologically Inspired Technology Using Electroactive Polymers (EAP)

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph

    2006-01-01

    Evolution allowed nature to introduce highly effective biological mechanisms that are incredible inspiration for innovation. Humans have always made efforts to imitate nature's inventions and we are increasingly making advances that it becomes significantly easier to imitate, copy, and adapt biological methods, processes and systems. This brought us to the ability to create technology that is far beyond the simple mimicking of nature. Having better tools to understand and to implement nature's principles we are now equipped like never before to be inspired by nature and to employ our tools in far superior ways. Effectively, by bio-inspiration we can have a better view and value of nature capability while studying its models to learn what can be extracted, copied or adapted. Using electroactive polymers (EAP) as artificial muscles is adding an important element to the development of biologically inspired technologies.

  19. A Micromechanical Constitutive Model of Progressive Crushing in Random Carbon Fiber Polymer Matrix Composites

    SciTech Connect

    Lee, H.K.; Simunovic, S.

    1999-09-01

    A micromechanical damage constitutive model is presented to predict the overall elastoplastic behavior and damage evolution in random carbon fiber polymer matrix composites (RFPCs).To estimate the overall elastoplastic damage responses,an effective yield criterion is derived based on the ensemble-volume averaging process and first-order effects of eigenstrains due to the existence of spheroidal (prolate) fibers.The proposed effective yield criterion,to ether with the assumed overall associative plastic flow rule and hardening law, constitutes the analytical foundation for the estimation of effective elastoplastic behavior of ductile matrix composites.First,an effective elastoplastic constitutive dama e model for aligned fiber-reinforced composites is proposed.A micromechanical damage constitutive model for RFPCs is then developed.The average process over all orientations upon overning constitutive field equations and overall yield function for aligned fiber-reinforced composites i s performed to obtain the constitutive relations and effective yield function of RFPCs.The discrete numerical integration algorithms and the continuum tan ent operator are also presented to implement the proposed dama e constitutive model.The dama e constitutive model forms the basis for the pro ressive crushing in composite structures under impact loading.

  20. A comparative study of viscoelastic planar contraction flow for polymer melts using molecular constitutive models

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Wang, Xuanping; Hu, Changxu

    2014-11-01

    The benchmark problem of planar contraction flow is often used to evaluate the stability of numerical algorithms and the predictability of viscoelastic constitutive models in predicting the rheological behavior of polymer fluids. In this paper, for the simulation of planar contraction flow, the single/simplified modified double convected Pom-Pom (S-MDCPP) model recently proposed is adopted, and in the frame of iterative stabilized fractional step algorithm, the discrete elastic viscous stress splitting (DEVSS) technique in combination with the streamline upwind Petrov-Galerkin (SUPG) method is taken to serve as a stable numerical solution scheme for the viscoelastic flow, where the equal low-order interpolations are applied to the independent solution variables by virtue of stabilized form of mass conservation equation constructed based-on the finite incremental calculus method. The comparison of rheological behaviors by S-MDCPP model with those by experiment results and DCPP model is taken on the aspects of the material functions of shear viscosities and uniaxial elongation viscosities, stresses fields through the way of flow induced birefringence in the planar contraction flow, with the aim of assessing the constitutive models. In addition, the effects of the constitutive parameters of the S-MDCPP model and Weissenberg number on the rheological behaviors of polymer melts are discussed, with the flow field responses such as velocity, pressure, stress components, and backbone stretch included. Through these comparative studies, the capabilities of the S-MDCPP constitutive model are justified for the applications in branched polymer melts characterizations and numerical modeling.

  1. Constitutive Modeling and Testing of Polymer Matrix Composites Incorporating Physical Aging at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Veazie, David R.

    1998-01-01

    Advanced polymer matrix composites (PMC's) are desirable for structural materials in diverse applications such as aircraft, civil infrastructure and biomedical implants because of their improved strength-to-weight and stiffness-to-weight ratios. For example, the next generation military and commercial aircraft requires applications for high strength, low weight structural components subjected to elevated temperatures. A possible disadvantage of polymer-based composites is that the physical and mechanical properties of the matrix often change significantly over time due to the exposure of elevated temperatures and environmental factors. For design, long term exposure (i.e. aging) of PMC's must be accounted for through constitutive models in order to accurately assess the effects of aging on performance, crack initiation and remaining life. One particular aspect of this aging process, physical aging, is considered in this research.

  2. The anisotropic mechanical behaviour of electro-spun biodegradable polymer scaffolds: Experimental characterisation and constitutive formulation.

    PubMed

    Limbert, Georges; Omar, Rodaina; Krynauw, Hugo; Bezuidenhout, Deon; Franz, Thomas

    2016-01-01

    Electro-spun biodegradable polymer fibrous structures exhibit anisotropic mechanical properties dependent on the degree of fibre alignment. Degradation and mechanical anisotropy need to be captured in a constitutive formulation when computational modelling is used in the development and design optimisation of such scaffolds. Biodegradable polyester-urethane scaffolds were electro-spun and underwent uniaxial tensile testing in and transverse to the direction of predominant fibre alignment before and after in vitro degradation of up to 28 days. A microstructurally-based transversely isotropic hyperelastic continuum constitutive formulation was developed and its parameters were identified from the experimental stress-strain data of the scaffolds at various stages of degradation. During scaffold degradation, maximum stress and strain in circumferential direction decreased from 1.02 ± 0.23 MPa to 0.38 ± 0.004 MPa and from 46 ± 11 % to 12 ± 2 %, respectively. In longitudinal direction, maximum stress and strain decreased from 0.071 ± 0.016 MPa to 0.010 ± 0.007 MPa and from 69 ± 24 % to 8 ± 2 %, respectively. The constitutive parameters were identified for both directions of the non-degraded and degraded scaffold for strain range varying between 0% and 16% with coefficients of determination r(2)>0.871. The six-parameter constitutive formulation proved versatile enough to capture the varying non-linear transversely isotropic behaviour of the fibrous scaffold throughout various stages of degradation.

  3. High-temperature viscoelastic creep constitutive equations for polymer composites: Homogenization theory and experiments

    SciTech Connect

    Skontorp, A.; Wang, S.S.; Shibuya, Y.

    1994-12-31

    In this paper, a homogenization theory is developed to determine high-temperature effective viscoelastic constitutive equations for fiber-reinforced polymer composites. The homogenization theory approximates the microstructure of a fiber composite, and determine simultaneously effective macroscopic constitutive properties of the composite and the associated microscopic strain and stress in the heterogeneous material. The time-temperature dependent homogenization theory requires that the viscoelastic constituent properties of the matrix phase at elevated temperatures, the governing equations for the composites, and the boundary conditions of the problem be Laplace transformed to a conjugate problem. The homogenized effective properties in the transformed domain are determined, using a two-scale asymptotic expansion of field variables and an averaging procedure. Field solutions in the unit cell are determined from basic and first-order governing equations with the aid of a boundary integral method (BIM). Effective viscoelastic constitutive properties of the composite at elevated temperatures are determined by an inverse transformation, as are the microscopic stress and deformation in the composite. Using this method, interactions among fibers and between the fibers and the matrix can be evaluated explicitly, resulting in accurate solutions for composites with high-volume fraction of reinforcing fibers. Examples are given for the case of a carbon-fiber reinforced thermoplastic polyamide composite in an elevated temperature environment. The homogenization predictions are in good agreement with experimental data available for the composite.

  4. A multi-branch finite deformation constitutive model for a shape memory polymer based syntactic foam

    NASA Astrophysics Data System (ADS)

    Gu, Jianping; Sun, Huiyu; Fang, Changqing

    2015-02-01

    A multi-branch thermoviscoelastic-themoviscoplastic finite deformation constitutive model incorporated with structural and stress relaxation is developed for a thermally activated shape memory polymer (SMP) based syntactic foam. In this paper, the total mechanical deformation of the foam is divided into the components of the SMP and the elastic glass microballoons by using the mixture rule. The nonlinear Adam-Gibbs model is used to describe the structural relaxation of the SMP as the temperature crosses the glass transition temperature (Tg). Further, a multi-branch model combined with the modified Eying model of viscous flow is used to capture the multitude of relaxation processes of the SMP. The deformation of the glass microballoons could be split into elastic and inelastic components. In addition, the phenomenological evolution rule is implemented in order to further characterize the macroscopic post-yield strain softening behaviors of the syntactic foam. A comparison between the numerical simulation and the thermomechanical experiment shows an acceptable agreement. Moreover, a parametric study is conducted to examine the predictability of the model and to provide guidance for reasonable design of the syntactic foam.

  5. How Discourses of Biology Textbooks Work to Constitute Subjectivity: From the Ethical to the Colonial

    NASA Astrophysics Data System (ADS)

    Bazzul, Jesse

    This thesis examines how discourses of biology textbooks can work to constitute various kinds of subjectivities. Using a Foucauldian archaeological approach to discourse analysis I examine how four Ontario secondary school biology textbooks discursively delimit what can be thought and acted upon, and in the process work to partially constitute students/teachers as sex/gendered; neocolonial; neoliberal (and a subject of work), and ethical subjects and subjectivities. This thesis engages the topic of how discourse can constitute subjectivity in science in three basic ways: First, on a theoretical level, in terms of working out an understanding of subject constitution/interpellation that would also be useful when engaging with other sociopolitical and ethical questions in science education. Secondly, in terms of an empirically based critical discourse analysis that examines how various statements within these four textbooks could set limits on what is possible for students to think and act upon in relation to themselves, science, and the world. Thirdly, this thesis represents a narrative of scholarly development that moves from an engagement of my personal experiences in science education and current science education literature towards the general politico-philosophical topic of subjectivity and biopolitics. This thesis begins with a discussion of my experiences as a science teacher, a review of relevant science education literature, and considerations of subjectivity that relate specifically ii to the specific methodological approach I employ when examining these textbooks. After this I present five chapters, each of which can be thought of as a somewhat separate analysis concerning how the discourses of these textbooks can work to constitute specific subjectivities (each involving different theoretical/methodological considerations). I conclude with a reflection/synthesis chapter and a call to see science education as a site for biopolitical struggle.

  6. Bioinspired polymer vesicles and membranes for biological and medical applications.

    PubMed

    Palivan, Cornelia G; Goers, Roland; Najer, Adrian; Zhang, Xiaoyan; Car, Anja; Meier, Wolfgang

    2016-01-21

    Biological membranes play an essential role in living organisms by providing stable and functional compartments, preserving cell architecture, whilst supporting signalling and selective transport that are mediated by a variety of proteins embedded in the membrane. However, mimicking cell membranes - to be applied in artificial systems - is very challenging because of the vast complexity of biological structures. In this respect a highly promising strategy to designing multifunctional hybrid materials/systems is to combine biological molecules with polymer membranes or to design membranes with intrinsic stimuli-responsive properties. Here we present supramolecular polymer assemblies resulting from self-assembly of mostly amphiphilic copolymers either as 3D compartments (polymersomes, PICsomes, peptosomes), or as planar membranes (free-standing films, solid-supported membranes, membrane-mimetic brushes). In a bioinspired strategy, such synthetic assemblies decorated with biomolecules by insertion/encapsulation/attachment, serve for development of multifunctional systems. In addition, when the assemblies are stimuli-responsive, their architecture and properties change in the presence of stimuli, and release a cargo or allow "on demand" a specific in situ reaction. Relevant examples are included for an overview of bioinspired polymer compartments with nanometre sizes and membranes as candidates in applications ranging from drug delivery systems, up to artificial organelles, or active surfaces. Both the advantages of using polymer supramolecular assemblies and their present limitations are included to serve as a basis for future improvements. PMID:26563574

  7. Logarithmic rate based elasto-viscoplastic cyclic constitutive model for soft biological tissues.

    PubMed

    Zhu, Yilin; Kang, Guozheng; Yu, Chao; Poh, Leong Hien

    2016-08-01

    Based on the logarithmic rate and piecewise linearization theory, a thermodynamically consistent elasto-viscoplastic constitutive model is developed in the framework of finite deformations to describe the nonlinear time-dependent biomechanical performances of soft biological tissues, such as nonlinear anisotropic monotonic stress-strain responses, stress relaxation, creep and ratchetting. In the proposed model, the soft biological tissue is assumed as a typical composites consisting of an isotropic matrix and anisotropic fiber aggregation. Accordingly, the free energy function and stress tensor are divided into two parts related to the matrix and fiber aggregation, respectively. The nonlinear biomechanical responses of the tissues are described by the piecewise linearization theory with hypo-elastic relations of fiber aggregation. The evolution equations of viscoplasticity are formulated from the dissipation inequalities by the co-directionality hypotheses. The anisotropy is considered in the hypo-elastic relations and viscoplastic flow rules by introducing some material parameters dependent on the loading direction. Then the capability of the proposed model to describe the nonlinear time-dependent deformation of soft biological tissues is verified by comparing the predictions with the corresponding experimental results of three tissues. It is seen that the predicted monotonic stress-strain responses, stress relaxation, creep and ratchetting of soft biological tissues are in good agreement with the corresponding experimental ones. PMID:27108349

  8. Logarithmic rate based elasto-viscoplastic cyclic constitutive model for soft biological tissues.

    PubMed

    Zhu, Yilin; Kang, Guozheng; Yu, Chao; Poh, Leong Hien

    2016-08-01

    Based on the logarithmic rate and piecewise linearization theory, a thermodynamically consistent elasto-viscoplastic constitutive model is developed in the framework of finite deformations to describe the nonlinear time-dependent biomechanical performances of soft biological tissues, such as nonlinear anisotropic monotonic stress-strain responses, stress relaxation, creep and ratchetting. In the proposed model, the soft biological tissue is assumed as a typical composites consisting of an isotropic matrix and anisotropic fiber aggregation. Accordingly, the free energy function and stress tensor are divided into two parts related to the matrix and fiber aggregation, respectively. The nonlinear biomechanical responses of the tissues are described by the piecewise linearization theory with hypo-elastic relations of fiber aggregation. The evolution equations of viscoplasticity are formulated from the dissipation inequalities by the co-directionality hypotheses. The anisotropy is considered in the hypo-elastic relations and viscoplastic flow rules by introducing some material parameters dependent on the loading direction. Then the capability of the proposed model to describe the nonlinear time-dependent deformation of soft biological tissues is verified by comparing the predictions with the corresponding experimental results of three tissues. It is seen that the predicted monotonic stress-strain responses, stress relaxation, creep and ratchetting of soft biological tissues are in good agreement with the corresponding experimental ones.

  9. Controlled polymer synthesis--from biomimicry towards synthetic biology.

    PubMed

    Pasparakis, George; Krasnogor, Natalio; Cronin, Leroy; Davis, Benjamin G; Alexander, Cameron

    2010-01-01

    The controlled assembly of synthetic polymer structures is now possible with an unprecedented range of functional groups and molecular architectures. In this critical review we consider how the ability to create artificial materials over lengthscales ranging from a few nm to several microns is generating systems that not only begin to mimic those in nature but also may lead to exciting applications in synthetic biology (139 references).

  10. The effect of heat developed during high strain rate deformation on the constitutive modeling of amorphous polymers

    NASA Astrophysics Data System (ADS)

    Safari, Keivan H.; Zamani, Jamal; Guedes, Rui M.; Ferreira, Fernando J.

    2016-02-01

    An adiabatic constitutive model is proposed for large strain deformation of polycarbonate (PC) at high strain rates. When the strain rate is sufficiently high such that the heat generated does not have time to transfer to the surroundings, temperature of material rises. The high strain rate deformation behavior of polymers is significantly affected by temperature-dependent constants and thermal softening. Based on the isothermal model which first was introduced by Mulliken and Boyce et al. (Int. J. Solids Struct. 43:1331-1356, 2006), an adiabatic model is proposed to predict the yield and post-yield behavior of glassy polymers at high strain rates. When calculating the heat generated and the temperature changes during the step by step simulation of the deformation, temperature-dependent elastic constants are incorporated to the constitutive equations. Moreover, better prediction of softening phenomena is achieved by the new definition for softening parameters of the proposed model. The constitutive model has been implemented numerically into a commercial finite element code through a user material subroutine (VUMAT). The experimental results, obtained using a split Hopkinson pressure bar, are supported by dynamic mechanical thermal analysis (DMTA) and Decompose/Shift/Reconstruct (DSR) method. Comparison of adiabatic model predictions with experimental data demonstrates the ability of the model to capture the characteristic features of stress-strain curve of the material at very high strain rates.

  11. Peptidomimetic Star Polymers for Targeting Biological Ion Channels

    PubMed Central

    Chen, Rong; Lu, Derong; Xie, Zili; Feng, Jing; Jia, Zhongfan; Ho, Junming; Coote, Michelle L.; Wu, Yingliang; Monteiro, Michael J.; Chung, Shin-Ho

    2016-01-01

    Four end-functionalized star polymers that could attenuate the flow of ionic currents across biological ion channels were first de novo designed computationally, then synthesized and tested experimentally on mammalian K+ channels. The 4-arm ethylene glycol conjugate star polymers with lysine or a tripeptide attached to the end of each arm were specifically designed to mimic the action of scorpion toxins on K+ channels. Molecular dynamics simulations showed that the lysine side chain of the polymers physically occludes the pore of Kv1.3, a target for immuno-suppression therapy. Two of the compounds tested were potent inhibitors of Kv1.3. The dissociation constants of these two compounds were computed to be 0.1 μM and 0.7 μM, respectively, within 3-fold to the values derived from subsequent experiments. These results demonstrate the power of computational methods in molecular design and the potential of star polymers as a new infinitely modifiable platform for ion channel drug discovery. PMID:27007701

  12. Peptidomimetic Star Polymers for Targeting Biological Ion Channels.

    PubMed

    Chen, Rong; Lu, Derong; Xie, Zili; Feng, Jing; Jia, Zhongfan; Ho, Junming; Coote, Michelle L; Wu, Yingliang; Monteiro, Michael J; Chung, Shin-Ho

    2016-01-01

    Four end-functionalized star polymers that could attenuate the flow of ionic currents across biological ion channels were first de novo designed computationally, then synthesized and tested experimentally on mammalian K+ channels. The 4-arm ethylene glycol conjugate star polymers with lysine or a tripeptide attached to the end of each arm were specifically designed to mimic the action of scorpion toxins on K+ channels. Molecular dynamics simulations showed that the lysine side chain of the polymers physically occludes the pore of Kv1.3, a target for immuno-suppression therapy. Two of the compounds tested were potent inhibitors of Kv1.3. The dissociation constants of these two compounds were computed to be 0.1 μM and 0.7 μM, respectively, within 3-fold to the values derived from subsequent experiments. These results demonstrate the power of computational methods in molecular design and the potential of star polymers as a new infinitely modifiable platform for ion channel drug discovery.

  13. Solid-State Constitutive Modelling of Glassy Polymers: Coupling the Rolie-Poly Equations for Melts with Anisotropic Viscoplastic Flow

    SciTech Connect

    De Focatiis, Davide S. A.; Buckley, C. Paul; Embery, John

    2008-07-07

    This paper investigates the behaviour of a well-characterised monodisperse grade of entangled atactic polystyrene across a very wide temperature and strain rate range through linear and non-linear melt rheology and solid-state deformation. In an effort to construct a constitutive model for large deformations able to describe rheological response right across this wide timescale, two well-established rheological models are combined: the well known RoliePoly (RP) conformational melt model and the Oxford glass-rubber constitutive model for glassy polymers. Comparisons between experimental data and simulations from a numerical implementation of the model illustrate that the model can cope well with the range of deformations in which orientation is limited to length-scales longer than an entanglement length. One approach in which the model can be expanded to incorporate the effects of orientation on shorter length scales using anisotropic viscoplastic flow is briefly discussed.

  14. pH-responsive fluorescence chemical sensor constituted by conjugated polymers containing pyridine rings.

    PubMed

    Adachi, Naoya; Kaneko, Yuki; Sekiguchi, Kazuki; Sugiyama, Hiroki; Sugeno, Masafumi

    2015-12-01

    Poly(p-pyridinium phenylene ethynylene)s (PPyPE) functionalized with alternating donor-acceptor repeat units were synthesized by a Pd-catalyzed Sonogashira coupling reaction between diethynyl monomer and di-iodopyridine for use as a pH-responsive fluorescence chemical sensor. The synthesized PPyPE, containing pyridine units, was characterized by FT-IR, (1)H and (13)C NMR, UV-visible and fluorescence spectroscopies. We investigated the relationship between changes of optical properties and protonation/deprotonation of PPyPE containing pyridine units in solution. Addition of HCl decreased and red-shifted the fluorescence intensity of the conjugated polymers that contained pyridine rings; fluorescence intensity of the polymers increased upon addition of NaOH solution. The synthesized PPyPE was found to be an effective and reusable chemical sensor for pH sensing.

  15. Constitutive modeling of large inelastic deformation of amorphous polymers: Free volume and shear transformation zone dynamics

    NASA Astrophysics Data System (ADS)

    Voyiadjis, George Z.; Samadi-Dooki, Aref

    2016-06-01

    Due to the lack of the long-range order in their molecular structure, amorphous polymers possess a considerable free volume content in their inter-molecular space. During finite deformation, these free volume holes serve as the potential sites for localized permanent plastic deformation inclusions which are called shear transformation zones (STZs). While the free volume content has been experimentally shown to increase during the course of plastic straining in glassy polymers, thermal analysis of stored energy due to the deformation shows that the STZ nucleation energy decreases at large plastic strains. The evolution of the free volume, and the STZs number density and nucleation energy during the finite straining are formulated in this paper in order to investigate the uniaxial post-yield softening-hardening behavior of the glassy polymers. This study shows that the reduction of the STZ nucleation energy, which is correlated with the free volume increase, brings about the post-yield primary softening of the amorphous polymers up to the steady-state strain value; and the secondary hardening is a result of the increased number density of the STZs, which is required for large plastic strains, while their nucleation energy is stabilized beyond the steady-state strain. The evolutions of the free volume content and STZ nucleation energy are also used to demonstrate the effect of the strain rate, temperature, and thermal history of the sample on its post-yield behavior. The obtained results from the model are compared with the experimental observations on poly(methyl methacrylate) which show a satisfactory consonance.

  16. Polymer biomaterial constructs for regenerative medicine and functional biological systems

    NASA Astrophysics Data System (ADS)

    Meng, Linghui

    The use of collagen as a biomaterial is currently undergoing a renaissance in the tissue engineering field. The excellent biocompatibility and safety due to its biological characteristics, such as biodegradability and weak antigenicity, make collagen a primary material resource in medical applications. Described herein is work towards the development of novel collagen-based matrices, with additional multi-functionality imparted through a novel in-situ crosslinking approach. The process of electrospinning has become a widely used technique for the creation of fibrous scaffolds for tissue engineering applications due to its ability to rapidly create structures composed of nano-scale polymer fibers closely resembling the architecture of the extracellular matrix (ECM). Collagen-PCL sheath-core bicomponent fibrous scaffolds were fabricated using a novel variation on traditional electrospinning, known as co-axial electrospinning. The results showed that the addition of a synthetic polymer core into collagen nanofibers remarkably increased the mechanical strength of collagen matrices spun from the benign solvent system. A novel single-step, in-situ collagen crosslink approach was developed in order to solve the problems dominating traditional collagen crosslinking methods, such as dimensional shrinking and loss of porous morphology, and to simplify the crosslinking procedure for electrospun collagen scaffolds. The excess amount of NHS present in the crosslinking mixture was found to delay the EDC/collagen coupling reaction in a controlled fashion. Fundamental investigations into the development and characterization of in-situ crosslinked collagen matrices such as fibrous scaffolds, gels and sponges, as well as their biomedical applications including cell culture substrates, wound dressings, drug delivery matrices and bone regeneration substitutes, were performed. The preliminary mice studies indicated that the in-situ crosslinked collagen matrices could be good candidates

  17. Conducting polymers on microelectronic devices as tools for biological analyses.

    PubMed

    Livache, T; Bazin, H; Mathis, G

    1998-12-01

    In the field of biological analysis, the need for multiparametric analysis has prompted the development of supports bearing a series of biomolecules linked to a support in a precise location (addressed). To reach a high information density, miniaturization of this kind of support has to be carried out. We describe in this paper an approach involving the use of electro-conducting polymers such as polypyrrole. This technology is based on an electro-directed copolymerization of pyrrole and oligodeoxynucleotides (ODN) linked to a pyrrole residue. The process allows the grafting of the selected ODN at the surface of the successively addressed microelectrodes. In this way, the syntheses are carried out on 50 microm electrodes on passive chips or on active (multiplexed) chips bearing 48 or 128 gold microelectrodes, respectively. The detection of biological targets recognized by the biochip is carried out by using fluorescent tracers. This technology, involving prepurified materials precisely addressed, allows better reproducibility of the biochip preparation and, then, an easy interpretation of the fluorescence results. The versatility of this technology is illustrated by ODN or peptide copolymerizations leading to DNA chips or peptide chips, respectively. This would open the field for other biological interaction studies.

  18. Combinatorial synthesis and screening of non-biological polymers

    DOEpatents

    Schultz, Peter G.; Xiang, Xiao-Dong; Goldwasser, Isy; Briceno, Gabriel; Sun, Xiao-Dong; Wang, Kai-An

    2006-04-25

    Methods and apparatus for the preparation and use of a substrate having an array of diverse materials in predefined regions thereon. A substrate having an array of diverse materials thereon is generally prepared by delivering components of materials to predefined regions on a substrate, and simultaneously reacting the components to form at least two materials. Materials which can be prepared using the methods and apparatus of the present invention include, for example, covalent network solids, ionic solids and molecular solids. More particularly, materials which can be prepared using the methods and apparatus of the present invention include, for example, inorganic materials, intermetallic materials, metal alloys, ceramic materials, organic materials, organometallic materials, non-biological organic polymers, composite materials (e.g., inorganic composites, organic composites, or combinations thereof), etc. Once prepared, these materials can be screened for useful properties including, for example, electrical, thermal, mechanical, morphological, optical, magnetic, chemical, or other properties. Thus, the present invention provides methods for the parallel synthesis and analysis of novel materials having useful properties.

  19. Research Programs Constituting U.S. Participation in the International Biological Program.

    ERIC Educational Resources Information Center

    National Academy of Sciences--National Research Council, Washington, DC. Div. of Biology and Agriculture.

    The United States contribution to the International Biological Program, which aims to understand more clearly the interrelationships within ecosystems, is centered on multidisciplinary research programs investigating the biological basis of ecological productivity and human welfare. Integrated research programs have been established for the…

  20. The constitutional protection of trade secrets and patents under the Biologics Price Competition and Innovation Act of 2009.

    PubMed

    Epstein, Richard A

    2011-01-01

    The Biologics Price Competition and Innovation Act of 2009 ("Biosimilars Act") is for the field of pharmaceutical products the single most important legislative development since passage of the Drug Price Competition and Patent Term Restoration Act of 1984 ("Hatch-Waxman Act"), on which portions of the Biosimilars Act are clearly patterned. Congress revised section 351 of the Public Health Service Act (PHSA) to create a pathway for FDA approval of "biosimilar" biological products. Each biosimilar applicant is required to cite in its application a "reference product" that was approved on the basis of a full application containing testing data and manufacturing information, which is owned and was submitted by another company and much of which constitutes trade secret information subject to constitutional protection. Because the Biosimilars Act authorizes biosimilar applicants to cite these previously approved applications, the implementation of the new legislative scheme raises critical issues under the Fifth Amendment of the Constitution, pursuant to which private property--trade secrets included--may not be taken for public use, without "just compensation." FDA must confront those issues as it implements the scheme set out in the Biosimilars Act. This article will discuss these issues, after providing a brief overview of the Biosimilars Act and a more detailed examination of the law of trade secrets.

  1. Constitutive expression of tdTomato protein as a cytotoxicity and proliferation marker for space radiation biology.

    PubMed

    Chishti, Arif A; Hellweg, Christine E; Berger, Thomas; Baumstark-Khan, Christa; Feles, Sebastian; Kätzel, Thorben; Reitz, Günther

    2015-01-01

    The radiation risk assessment for long-term space missions requires knowledge on the biological effectiveness of different space radiation components, e.g. heavy ions, on the interaction of radiation and other space environmental factors such as microgravity, and on the physical and biological dose distribution in the human body. Space experiments and ground-based experiments at heavy ion accelerators require fast and reliable test systems with an easy readout for different endpoints. In order to determine the effect of different radiation qualities on cellular proliferation and the biological depth dose distribution after heavy ion exposure, a stable human cell line expressing a novel fluorescent protein was established and characterized. tdTomato, a red fluorescent protein of the new generation with fast maturation and high fluorescence intensity, was selected as reporter of cell proliferation. Human embryonic kidney (HEK/293) cells were stably transfected with a plasmid encoding tdTomato under the control of the constitutively active cytomegalovirus (CMV) promoter (ptdTomato-N1). The stably transfected cell line was named HEK-ptdTomato-N1 8. This cytotoxicity biosensor was tested by ionizing radiation (X-rays and accelerated heavy ions) exposure. As biological endpoints, the proliferation kinetics and the cell density reached 100 h after irradiation reflected by constitutive expression of the tdTomato were investigated. Both were reduced dose-dependently after radiation exposure. Finally, the cell line was used for biological weighting of heavy ions of different linear energy transfer (LET) as space-relevant radiation quality. The relative biological effectiveness of accelerated heavy ions in reducing cellular proliferation peaked at an LET of 91 keV/μm. The results of this study demonstrate that the HEK-ptdTomato-N1 reporter cell line can be used as a fast and reliable biosensor system for detection of cytotoxic damage caused by ionizing radiation.

  2. Constitutive expression of tdTomato protein as a cytotoxicity and proliferation marker for space radiation biology

    NASA Astrophysics Data System (ADS)

    Chishti, Arif A.; Hellweg, Christine E.; Berger, Thomas; Baumstark-Khan, Christa; Feles, Sebastian; Kätzel, Thorben; Reitz, Günther

    2015-01-01

    The radiation risk assessment for long-term space missions requires knowledge on the biological effectiveness of different space radiation components, e.g. heavy ions, on the interaction of radiation and other space environmental factors such as microgravity, and on the physical and biological dose distribution in the human body. Space experiments and ground-based experiments at heavy ion accelerators require fast and reliable test systems with an easy readout for different endpoints. In order to determine the effect of different radiation qualities on cellular proliferation and the biological depth dose distribution after heavy ion exposure, a stable human cell line expressing a novel fluorescent protein was established and characterized. tdTomato, a red fluorescent protein of the new generation with fast maturation and high fluorescence intensity, was selected as reporter of cell proliferation. Human embryonic kidney (HEK/293) cells were stably transfected with a plasmid encoding tdTomato under the control of the constitutively active cytomegalovirus (CMV) promoter (ptdTomato-N1). The stably transfected cell line was named HEK-ptdTomato-N1 8. This cytotoxicity biosensor was tested by ionizing radiation (X-rays and accelerated heavy ions) exposure. As biological endpoints, the proliferation kinetics and the cell density reached 100 h after irradiation reflected by constitutive expression of the tdTomato were investigated. Both were reduced dose-dependently after radiation exposure. Finally, the cell line was used for biological weighting of heavy ions of different linear energy transfer (LET) as space-relevant radiation quality. The relative biological effectiveness of accelerated heavy ions in reducing cellular proliferation peaked at an LET of 91 keV/μm. The results of this study demonstrate that the HEK-ptdTomato-N1 reporter cell line can be used as a fast and reliable biosensor system for detection of cytotoxic damage caused by ionizing radiation.

  3. Nanoengineered Templated Polymer Particles: Navigating the Biological Realm.

    PubMed

    Cui, Jiwei; Richardson, Joseph J; Björnmalm, Mattias; Faria, Matthew; Caruso, Frank

    2016-06-21

    Nanoengineered materials offer tremendous promise for developing the next generation of therapeutics. We are transitioning from simple research questions, such as "can this particle eradicate cancer cells?" to more sophisticated ones like "can we design a particle to preferentially deliver cargo to a specific cancer cell type?" These developments are poised to usher in a new era of nanoengineered drug delivery systems. We primarily work with templating methods for engineering polymer particles and investigate their biological interactions. Templates are scaffolds that facilitate the formation of particles with well-controlled size, shape, structure, stiffness, stability, and surface chemistry. In the past decade, breakthroughs in engineering new templates, combined with advances in coating techniques, including layer-by-layer (LbL) assembly, surface polymerization, and metal-phenolic network (MPN) coordination chemistry, have enabled particles with specific physicochemical properties to be engineered. While materials science offers an ever-growing number of new synthesis techniques, a central challenge of therapeutic delivery has become understanding how nanoengineered materials interact with biological systems. Increased collaboration between chemists, biologists, and clinicians has resulted in a vast research output on bio-nano interactions. Our understanding of cell-particle interactions has grown considerably, but conventional in vitro experimentation provides limited information, and understanding how to bridge the in vitro/in vivo gap is a continuing challenge. As has been demonstrated in other fields, there is now a growing interest in applying computational approaches to advance this area. A considerable knowledge base is now emerging, and with it comes new and exciting opportunities that are already being capitalized on through the translation of materials into the clinic. In this Account, we outline our perspectives gained from a decade of work at the

  4. The Porosity of Autonomy: Social and Biological Constitution of the Patient in Biomedicine.

    PubMed

    Beever, Jonathan; Morar, Nicolae

    2016-01-01

    The nature and role of the patient in biomedicine comprise issues central to bioethical inquiry. Given its developmental history grounded firmly in a backlash against 20th-century cases of egregious human subjects abuse, contemporary medical bioethics has come to rely on a fundamental assumption: the unit of care (and the unit of value) is the autonomous self-directing patient. In this article we examine first the structure of the feminist social critique of autonomy. Then we show that a parallel argument can be made against relational autonomy as well, demonstrating how this second concept of autonomy fails to take sufficiently into account an array of biological determinants, particularly those from microbial biology. Finally, in light of this biological critique, we question whether or to what extent any relevant and meaningful view of autonomy can be recovered in the contemporary landscape of bioethics.

  5. The Porosity of Autonomy: Social and Biological Constitution of the Patient in Biomedicine.

    PubMed

    Beever, Jonathan; Morar, Nicolae

    2016-01-01

    The nature and role of the patient in biomedicine comprise issues central to bioethical inquiry. Given its developmental history grounded firmly in a backlash against 20th-century cases of egregious human subjects abuse, contemporary medical bioethics has come to rely on a fundamental assumption: the unit of care (and the unit of value) is the autonomous self-directing patient. In this article we examine first the structure of the feminist social critique of autonomy. Then we show that a parallel argument can be made against relational autonomy as well, demonstrating how this second concept of autonomy fails to take sufficiently into account an array of biological determinants, particularly those from microbial biology. Finally, in light of this biological critique, we question whether or to what extent any relevant and meaningful view of autonomy can be recovered in the contemporary landscape of bioethics. PMID:26832092

  6. Teleology and its constitutive role for biology as the science of organized systems in nature.

    PubMed

    Toepfer, Georg

    2012-03-01

    'Nothing in biology makes sense, except in the light of teleology'. This could be the first sentence in a textbook about the methodology of biology. The fundamental concepts in biology, e.g. 'organism' and 'ecosystem', are only intelligible given a teleological framework. Since early modern times, teleology has often been considered methodologically unscientific. With the acceptance of evolutionary theory, one popular strategy for accommodating teleological reasoning was to explain it by reference to selection in the past: functions were reconstructed as 'selected effects'. But the theory of evolution obviously presupposes the existence of organisms as organized and regulated, i.e. functional systems. Therefore, evolutionary theory cannot provide the foundation for teleology. The underlying reason for the central methodological role of teleology in biology is not its potential to offer particular forms of (evolutionary) explanations for the presence of parts, but rather an ontological one: organisms and other basic biological entities do not exist as physical bodies do, as amounts of matter with a definite form. Rather, they are dynamic systems in stable equilibrium; despite changes of their matter and form (in metabolism and metamorphosis) they maintain their identity. What remains constant in these kinds of systems is their 'organization', i.e. the causal pattern of interdependence of parts with certain effects of each part being relevant for the working of the system. Teleological analysis consists in the identification of these system-relevant effects and at the same time of the system as a whole. Therefore, the identity of biological systems cannot be specified without teleological reasoning. PMID:22326080

  7. Teleology and its constitutive role for biology as the science of organized systems in nature.

    PubMed

    Toepfer, Georg

    2012-03-01

    'Nothing in biology makes sense, except in the light of teleology'. This could be the first sentence in a textbook about the methodology of biology. The fundamental concepts in biology, e.g. 'organism' and 'ecosystem', are only intelligible given a teleological framework. Since early modern times, teleology has often been considered methodologically unscientific. With the acceptance of evolutionary theory, one popular strategy for accommodating teleological reasoning was to explain it by reference to selection in the past: functions were reconstructed as 'selected effects'. But the theory of evolution obviously presupposes the existence of organisms as organized and regulated, i.e. functional systems. Therefore, evolutionary theory cannot provide the foundation for teleology. The underlying reason for the central methodological role of teleology in biology is not its potential to offer particular forms of (evolutionary) explanations for the presence of parts, but rather an ontological one: organisms and other basic biological entities do not exist as physical bodies do, as amounts of matter with a definite form. Rather, they are dynamic systems in stable equilibrium; despite changes of their matter and form (in metabolism and metamorphosis) they maintain their identity. What remains constant in these kinds of systems is their 'organization', i.e. the causal pattern of interdependence of parts with certain effects of each part being relevant for the working of the system. Teleological analysis consists in the identification of these system-relevant effects and at the same time of the system as a whole. Therefore, the identity of biological systems cannot be specified without teleological reasoning.

  8. [Kinetic model of enhanced biological phosphorus removal with mixed acetic and propionic acids as carbon sources. (I): Model constitution].

    PubMed

    Zhang, Chao; Chen, Yin-Guang

    2013-03-01

    Based on activated sludge model No. 2 (ASM2), the anaerobic/aerobic kinetic model of phosphorus-accumulating organisms (PAO) was established with mixed short-chain fatty acids (SCFAs) as the base substance in enhanced biological phosphorus removal process. The characteristic of the PAO model was that the anaerobic metabolism rates of glycogen degradation, poly-beta-hydroxyalkanoates synthesis and polyphosphate hydrolysis were expressed by SCFAs uptake equation, and the effects of anaerobic maintenance on kinetics and stoichiometry were considered. The PAO kinetic model was composed of 3 soluble components, 4 particulate components and a pH parameter, which constituted the matrix of stoichiometric coefficients. On the basis of PAO model, the GAO kinetic model was established, which included 7 processes, and phosphorus content influenced the aerobic metabolism only.

  9. Multicolor Conjugated Polymer Dots for Biological Fluorescence Imaging

    PubMed Central

    Wu, Changfeng; Bull, Barbara; Szymanski, Craig; Christensen, Kenneth; McNeill, Jason

    2009-01-01

    Highly fluorescent conjugated polymer dots were developed for demanding applications such as fluorescence imaging in live cells. These nanoparticles exhibit small particle diameters, extraordinary fluorescence brightness, and excellent photostability. Single particle fluorescence imaging and kinetic studies indicate much higher emission rates (∼108 s-1) and little or no blinking of the nanoparticles as compared to typical results for single dye molecules and quantum dots. Analysis of single particle photobleaching trajectories reveals excellent photostability — as many as 109 or more photons emitted per nanoparticle prior to irreversible photobleaching. The superior figures of merit of these new fluorescent probes, together with the demonstration of cellular imaging, indicate their enormous potential for demanding fluorescence-based imaging and sensing applications such as high speed super-resolution single molecule/particle tracking and highly sensitive assays. PMID:19206410

  10. Multifunctionalized polymer microcapsules: novel tools for biological and pharmacological applications.

    PubMed

    Sukhorukov, Gleb B; Rogach, Andrey L; Garstka, Malgorzata; Springer, Sebastian; Parak, Wolfgang J; Muñoz-Javier, Almudena; Kreft, Oliver; Skirtach, Andre G; Susha, Andrei S; Ramaye, Yannic; Palankar, Raghavendra; Winterhalter, Mathias

    2007-06-01

    We describe recent developments with multifunctional nanoengineered polymer capsules. In addition to their obvious use as a delivery system, multifunctional nanocontainers find wide application in enzymatic catalysis, controlled release, and directed drug delivery in medicine. The multifunctionality is provided by the following components: 1) Luminescent semiconductor nanocrystals (quantum dots) that facilitate imaging and identification of different capsules, 2) superparamagnetic nanoparticles that allow manipulation of the capsules in a magnetic field, 3) surface coatings, which target the capsules to desired cells, 4) metallic nanoparticles in the capsule wall that act as an absorbing antenna for electromagnetic fields and provide heat for controlled release, and 5) enzymes and pharmaceutical agents that allow specific reactions. The unique advantage of multifunctional microcapsules in comparison to other systems is that they can be simultaneously loaded/functionalized with the above components, allowing for the combination of their properties in a single object. PMID:17487898

  11. Identification of Novel Activators of Constitutive Androstane Receptor from FDA-approved Drugs by Integrated Computational and Biological Approaches

    PubMed Central

    Lynch, Caitlin; Pan, Yongmei; Li, Linhao; Ferguson, Stephen S.; Xia, Menghang; Swaan, Peter W.; Wang, Hongbing

    2012-01-01

    Purpose The constitutive androstane receptor (CAR, NR1I3) is a xenobiotic sensor governing the transcription of numerous hepatic genes associated with drug metabolism and clearance. Recent evidence suggests that CAR also modulates energy homeostasis and cancer development. Thus, identification of novel human (h) CAR activators is of both clinical importance and scientific interest. Methods Docking and ligand-based structure-activity models were used for virtual screening of a database containing over 2000 FDA-approved drugs. Identified lead compounds were evaluated in cell-based reporter assays to determine hCAR activation. Potential activators were further tested in human primary hepatocytes (HPHs) for the expression of the prototypical hCAR target gene CYP2B6. Results Nineteen lead compounds with optimal modeling parameters were selected for biological evaluation. Seven of the 19 leads exhibited moderate to potent activation of hCAR. Five out of the seven compounds translocated hCAR from the cytoplasm to the nucleus of HPHs in a concentration-dependent manner. These compounds also induce the expression of CYP2B6 in HPHs with rank-order of efficacies closely resembling that of hCAR activation. Conclusion These results indicate that our strategically integrated approaches are effective in the identification of novel hCAR modulators, which may function as valuable research tools or potential therapeutic molecules. PMID:23090669

  12. The biological response to nanometre-sized polymer particles.

    PubMed

    Liu, Aiqin; Richards, Laura; Bladen, Catherine L; Ingham, Eileen; Fisher, John; Tipper, Joanne L

    2015-09-01

    Recently, nanometre-sized UHMWPE particles generated from hip and knee replacements have been identified in vitro and in vivo. UHMWPE particles in the 0.1-1.0μm size range have been shown to be more biologically active than larger particles, provoking an inflammatory response implicated in late aseptic loosening of total joint replacements. The biological activity of nanometre-sized particles has not previously been studied. The biological response to clinically-relevant UHMWPE wear particles including nanometre-sized and micrometre-sized, along with polystyrene particles (FluoSpheres 20nm, 60nm, 200nm and 1.0μm), and nanometre-sized model polyethylene particles (Ceridust 3615®), was determined in terms of osteolytic cytokine release from primary human peripheral blood mononuclear cells (PBMNCs). Nanometre-sized UHMWPE wear particles, nanometre-sized Ceridust 3615® and 20nm FluoSpheres had no significant effect on TNF-α, IL-1β, IL-6 and IL-8 release from PBMNCs at a concentration of 100μm(3) particles per cell after 12 and 24h. The micrometre-size UHMWPE wear particles (0.1-1.0μm) and 60nm, 200nm and 1.0μm FluoSpheres caused significantly elevated osteolytic cytokine release from PBMNCs. These results indicated that particles below circa 50nm fail to activate PBMNCs and that particle size, composition and morphology played a crucial role in cytokine release by particle stimulated macrophages. PMID:26004221

  13. The biological response to nanometre-sized polymer particles

    PubMed Central

    Liu, Aiqin; Richards, Laura; Bladen, Catherine L.; Ingham, Eileen; Fisher, John; Tipper, Joanne L.

    2015-01-01

    Recently, nanometre-sized UHMWPE particles generated from hip and knee replacements have been identified in vitro and in vivo. UHMWPE particles in the 0.1–1.0 μm size range have been shown to be more biologically active than larger particles, provoking an inflammatory response implicated in late aseptic loosening of total joint replacements. The biological activity of nanometre-sized particles has not previously been studied. The biological response to clinically-relevant UHMWPE wear particles including nanometre-sized and micrometre-sized, along with polystyrene particles (FluoSpheres 20 nm, 60 nm, 200 nm and 1.0 μm), and nanometre-sized model polyethylene particles (Ceridust 3615®), was determined in terms of osteolytic cytokine release from primary human peripheral blood mononuclear cells (PBMNCs). Nanometre-sized UHMWPE wear particles, nanometre-sized Ceridust 3615® and 20 nm FluoSpheres had no significant effect on TNF-α, IL-1β, IL-6 and IL-8 release from PBMNCs at a concentration of 100 μm3 particles per cell after 12 and 24 h. The micrometre-size UHMWPE wear particles (0.1–1.0 μm) and 60 nm, 200 nm and 1.0 μm FluoSpheres caused significantly elevated osteolytic cytokine release from PBMNCs. These results indicated that particles below circa 50 nm fail to activate PBMNCs and that particle size, composition and morphology played a crucial role in cytokine release by particle stimulated macrophages. PMID:26004221

  14. Advantages of a 3-parameter reduced constitutive model for the measurement of polymers elastic modulus using tensile tests

    NASA Astrophysics Data System (ADS)

    Blaise, A.; André, S.; Delobelle, P.; Meshaka, Y.; Cunat, C.

    2016-04-01

    Exact measurements of the rheological parameters of time-dependent materials are crucial to improve our understanding of their intimate relation to the internal bulk microstructure. Concerning solid polymers and the apparently simple determination of Young's modulus in tensile tests, international standards rely on basic protocols that are known to lead to erroneous values. This paper describes an approach allowing a correct measurement of the instantaneous elastic modulus of polymers by a tensile test. It is based on the use of an appropriate reduced model to describe the behavior of the material up to great strains, together with well-established principles of parameter estimation in engineering science. These principles are objective tools that are used to determine which parameters of a model can be correctly identified according to the informational content of a given data set. The assessment of the methodology and of the measurements is accomplished by comparing the results with those obtained from two other physical experiments, probing the material response at small temporal and length scales, namely, ultrasound measurements with excitation at 5 MHz and modulated nanoindentation tests over a few nanometers of amplitude.

  15. Development of a Systems Computational Model to Investigate Early Biological Events in Hepatic Activation of Constitutive Androstane Receptor (CAR) by Phenobarbital

    EPA Science Inventory

    Activation of the nuclear receptor CAR (constitutive active/androstane receptor) is implicated in the control several key biological events such as metabolic pathways. Here, we combined data from literature with information obtained from in vitro assays in the US EPA ToxCast dat...

  16. An irreversible constitutive model for fibrous soft biological tissue: a 3-D microfiber approach with demonstrative application to abdominal aortic aneurysms.

    PubMed

    Christian Gasser, T

    2011-06-01

    Understanding the failure and damage mechanisms of soft biological tissue is critical to a sensitive and specific characterization of tissue injury tolerance and its relation to biological responses. Despite increasing experimental and analytical efforts, failure-related irreversible effects of soft biological tissue are still poorly understood. There is still no clear definition of what "damage" of a soft biological material is, and conventional macroscopic indicators, as known from damage of engineering materials for example, may not identify the tissue's tolerance to injury appropriately. To account for the complex three-dimensional arrangement of collagen, a microfiber model approach is applied, where constitutive relations for collagen fibers are integrated over the unit sphere, which in turn defines the tissue's macroscopic properties. A collagen fiber is represented by a bundle of proteoglycan cross-linked collagen fibrils that undergoes irreversible deformations when exceeding its elastic tensile limit. The proposed constitutive model is able to predict strain stiffening at physiological strain levels and does not exhibit a clear macroscopic elastic limit, two typical features known from soft biological tissue testing. An elastic-predictor/plastic-corrector implementation of the model is followed and constitutive parameters are estimated from in vitro test data from a particular abdominal aortic aneurysm (AAA). Damage-based structural instabilities of the AAA under different inflation conditions are investigated, where the collagen orientation density has been estimated from its in vivo stress state. PMID:21338718

  17. A two-phase hyperelastic-viscoplastic constitutive model for semi-crystalline polymers: application to polyethylene materials with a variable range of crystal fractions.

    PubMed

    Abdul-Hameed, H; Messager, T; Ayoub, G; Zaïri, F; Naït-Abdelaziz, M; Qu, Z; Zaïri, F

    2014-09-01

    Polyethylene-based polymers as biomedical materials can contribute to a wide range of biomechanical applications. Therefore, it is important to identify, analyse, and predict with precision their mechanical behaviour. Polyethylene materials are semi-crystalline systems consisting of both amorphous and crystalline phases interacting in a rather complex manner. When the amorphous phase is in the rubbery state, the mechanical behaviour is strongly dependent on the crystal fraction, therefore leading to essentially thermoplastic or elastomeric responses. In this study, the finite deformation stress-strain response of polyethylene materials is modelled by considering these semi-crystalline polymers as two-phase heterogeneous media in order to provide insight into the role of crystalline and amorphous phases on the macro-behaviour and on the material deformation resistances, i.e. intermolecular and network resistances. A hyperelastic-viscoplastic model is developed in contemplation of representing the overall mechanical response of polyethylene materials under large deformation. An evolutionary optimization procedure based on a genetic algorithm is developed to identify the model parameters at different strain rates. The identification results show good agreement with experimental data, demonstrating the usefulness of the proposed approach: the constitutive model, with only one set of identified parameters, allows reproducing the stress-strain behaviour of polyethylene materials exhibiting a wide range of crystallinities, the crystal content becoming the only variable of the model.

  18. Optical diagnostics of biological tissue cells during their cultivation in polymers

    NASA Astrophysics Data System (ADS)

    Letuta, S. N.; Maryakhina, V. S.; Rakhmatullin, R. R.

    2011-04-01

    The specific features of long-term luminescence of exogenous molecular probes in cells of pathogenic and normal biological tissues, cultivated on a solid nutrient medium, have been investigated by laser kinetic fluorimetry. It is proposed to use the Hyamatrix biopolymer as a nutrient medium. This polymer is formed on the basis of native, chemically unmodified hyaluronic acid and contains amino acids, microelements, vitamins, and other components. The possibility of using the obtained results to develop an alternative method of fluorescent diagnostics of biological tissues is discussed.

  19. Optical diagnostics of biological tissue cells during their cultivation in polymers

    SciTech Connect

    Letuta, S N; Maryakhina, V S; Rakhmatullin, R R

    2011-04-30

    The specific features of long-term luminescence of exogenous molecular probes in cells of pathogenic and normal biological tissues, cultivated on a solid nutrient medium, have been investigated by laser kinetic fluorimetry. It is proposed to use the Hyamatrix biopolymer as a nutrient medium. This polymer is formed on the basis of native, chemically unmodified hyaluronic acid and contains amino acids, microelements, vitamins, and other components. The possibility of using the obtained results to develop an alternative method of fluorescent diagnostics of biological tissues is discussed. (optical technologies in biophysics and medicine)

  20. Synthesis of surface nano-molecularly imprinted polymers for sensitive baicalin detection from biological samples

    PubMed Central

    Gu, Xiaoli; He, Hongliang; Wang, Chong-Zhi; Gao, Yankun; Zhang, Hongjuan; Hong, Junli; Du, Shuhu; Chen, Lina; Yuan, Chun-Su

    2015-01-01

    Surface molecularly imprinted polymers (MIP@SBA-15) imprinted on the surface of hybrid nanostructured organic/inorganic materials (SBA-15) were prepared for the selective extraction and detection of baicalin (BA) from biological samples. The surface morphologies and characteristics of the imprinted and non-imprinted polymers were characterized by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermo–gravimetric analysis (TGA) and nitrogen adsorption–desorption isotherms. The results indicated that the polymers were successfully grafted on the surface of SBA-15 and possessed a highly ordered mesoporous structure. In binding tests, MIP@SBA-15 reached saturated adsorption within 80 min and exhibited significant specific recognition toward BA with large adsorption capacity. Meanwhile, the prepared MIP@SBA-15 was used as a selective sorbent for solid-phase extraction of BA from biological samples. Recoveries of BA from the liver and spleen ranged from 90.6% to 90.9% with RSD < 3.7%. All these results reveal that this method is simple, rapid and sensitive for effectively extracting and detecting trace BA in biological samples. PMID:26257892

  1. Combined X-ray and neutron fibre diffraction studies of biological and synthetic polymers.

    SciTech Connect

    Parrot, I. M.; Urban, Volker S; Gardner, K. H.; Forsyth, V. T.

    2005-04-01

    The fibrous state is a natural one for polymer molecules which tend to assume regular helical conformations rather than the globular structures characteristic of many proteins. Fibre diffraction therefore has broad application to the study of a wide range of biological and synthetic polymers. The purpose of this paper is to illustrate the general scope of the method and in particular to demonstrate the impact of a combined approach involving both X-ray and neutron diffraction methods. While the flux of modern X-ray synchrotron radiation sources allows high quality datasets to be recorded with good resolution within a very short space of time, neutron studies can provide unique information through the ability to locate hydrogen or deuterium atoms that are often difficult or impossible to locate using X-ray methods. Furthermore, neutron fibre diffraction methods can, through the ability to selectively label specific parts of a structure, be used to highlight novel aspects of polymer structure that can not be studied using X-rays. Two examples are given. The first describes X-ray and neutron diffraction studies of conformational transitions in DNA. The second describes structural studies of the synthetic high-performance polymer poly(p-phenylene terephthalamide) (PPTA), known commercially as Kevlar{reg_sign} or Twaron{reg_sign}.

  2. Protein-polymer nano-machines. Towards synthetic control of biological processes

    PubMed Central

    Pennadam, Sivanand S; Firman, Keith; Alexander, Cameron; Górecki, Dariusz C

    2004-01-01

    The exploitation of nature's machinery at length scales below the dimensions of a cell is an exciting challenge for biologists, chemists and physicists, while advances in our understanding of these biological motifs are now providing an opportunity to develop real single molecule devices for technological applications. Single molecule studies are already well advanced and biological molecular motors are being used to guide the design of nano-scale machines. However, controlling the specific functions of these devices in biological systems under changing conditions is difficult. In this review we describe the principles underlying the development of a molecular motor with numerous potential applications in nanotechnology and the use of specific synthetic polymers as prototypic molecular switches for control of the motor function. The molecular motor is a derivative of a TypeI Restriction-Modification (R-M) enzyme and the synthetic polymer is drawn from the class of materials that exhibit a temperature-dependent phase transition. The potential exploitation of single molecules as functional devices has been heralded as the dawn of new era in biotechnology and medicine. It is not surprising, therefore, that the efforts of numerous multidisciplinary teams [1,2]. have been focused in attempts to develop these systems. as machines capable of functioning at the low sub-micron and nanometre length-scales [3]. However, one of the obstacles for the practical application of single molecule devices is the lack of functional control methods in biological media, under changing conditions. In this review we describe the conceptual basis for a molecular motor (a derivative of a TypeI Restriction-Modification enzyme) with numerous potential applications in nanotechnology and the use of specific synthetic polymers as prototypic molecular switches for controlling the motor function [4]. PMID:15350203

  3. Protein-polymer nano-machines. Towards synthetic control of biological processes.

    PubMed

    Pennadam, Sivanand S; Firman, Keith; Alexander, Cameron; Górecki, Dariusz C

    2004-09-01

    The exploitation of nature's machinery at length scales below the dimensions of a cell is an exciting challenge for biologists, chemists and physicists, while advances in our understanding of these biological motifs are now providing an opportunity to develop real single molecule devices for technological applications. Single molecule studies are already well advanced and biological molecular motors are being used to guide the design of nano-scale machines. However, controlling the specific functions of these devices in biological systems under changing conditions is difficult. In this review we describe the principles underlying the development of a molecular motor with numerous potential applications in nanotechnology and the use of specific synthetic polymers as prototypic molecular switches for control of the motor function. The molecular motor is a derivative of a TypeI Restriction-Modification (R-M) enzyme and the synthetic polymer is drawn from the class of materials that exhibit a temperature-dependent phase transition.The potential exploitation of single molecules as functional devices has been heralded as the dawn of new era in biotechnology and medicine. It is not surprising, therefore, that the efforts of numerous multidisciplinary teams 12. have been focused in attempts to develop these systems. as machines capable of functioning at the low sub-micron and nanometre length-scales 3. However, one of the obstacles for the practical application of single molecule devices is the lack of functional control methods in biological media, under changing conditions. In this review we describe the conceptual basis for a molecular motor (a derivative of a TypeI Restriction-Modification enzyme) with numerous potential applications in nanotechnology and the use of specific synthetic polymers as prototypic molecular switches for controlling the motor function 4. PMID:15350203

  4. Path-Integration Computation of the Transport Properties of Polymers Nanoparticles and Complex Biological Structures

    NASA Astrophysics Data System (ADS)

    Douglas, Jack

    2014-03-01

    finite cross-section, DNA, nanoparticles with grafted chain layers and knotted polymers. The path-integration method, which grew up from research in Karl Freed's group, is evidently a powerful tool for computing basic transport properties of complex-shaped objects and should find increasing application in polymer science, nanotechnological applications and biology.

  5. Prediction of intracellular storage polymers using quantitative image analysis in enhanced biological phosphorus removal systems.

    PubMed

    Mesquita, Daniela P; Leal, Cristiano; Cunha, Jorge R; Oehmen, Adrian; Amaral, A Luís; Reis, Maria A M; Ferreira, Eugénio C

    2013-04-01

    The present study focuses on predicting the concentration of intracellular storage polymers in enhanced biological phosphorus removal (EBPR) systems. For that purpose, quantitative image analysis techniques were developed for determining the intracellular concentrations of PHA (PHB and PHV) with Nile blue and glycogen with aniline blue staining. Partial least squares (PLS) were used to predict the standard analytical values of these polymers by the proposed methodology. Identification of the aerobic and anaerobic stages proved to be crucial for improving the assessment of PHA, PHB and PHV intracellular concentrations. Current Nile blue based methodology can be seen as a feasible starting point for further enhancement. Glycogen detection based on the developed aniline blue staining methodology combined with the image analysis data proved to be a promising technique, toward the elimination of the need for analytical off-line measurements.

  6. Terbium-based coordination polymer nanoparticles for detection of ciprofloxacin in tablets and biological fluids.

    PubMed

    Tan, Hongliang; Zhang, Li; Ma, Chanjiao; Song, Yonghai; Xu, Fugang; Chen, Shouhui; Wang, Li

    2013-11-27

    The metal-organic coordination polymers with tunable structures and properties have been rapidly emerging as very important functional materials. In this work, we prepared terbium (Tb(3+))-based coordination polymer nanoparticles (CPNPs) by employing adenine (Ad) as bridging ligands. The CPNPs was further used as a receptor reagent for ciprofloxacin (CF) detection in aqueous solution. Addition of CF induces a typical emission of Tb(3+) due to the formation of Ad/Tb-CF complex and the sensitization of CF. The fluorescent intensity of Tb(3+) was enhanced linearly with increasing the CF concentration from 60 nM to 14 μM. The detection limit for CF in aqueous solution is 60 nM. The Ad/Tb CPNPs was successfully applied to detect CF in tablet and urine samples and showed a satisfactory result. Compared with other methods, the proposed method is advantageous because that it provides a very simple strategy for CF detection, which does not require complicated sample pretreatment processes or special reaction media. The proposed strategy could be contributed to expand the potential applications of lanthanide coordination polymers in biological and environmental fields.

  7. [Refusal of the biological proof practice and the harm of the law to effective judicial guardianship in constitutional jurisprudence].

    PubMed

    Herrán Ortiz, Ana Isabel

    2007-01-01

    The Spanish Constitution protects the free investigation of the paternity on its 39.2 the article, in which is granted that possibility. This right is not absolute, it has limits, but those limits will have to be interpreted in a restrictive way due to the principles based on it, such as the legal equality of children, and the integral protection of them. In view of this, the sentences are a very valuable element to delimit the aplication of this right, and establish its limitations.

  8. Biological performance of functionalized biomedical polymers for potential applications as intraocular lens.

    PubMed

    Zheng, Zhiwen; Wang, Yingjun; Jiao, Yan; Zhai, Zhichen

    2016-08-01

    To study the biological performance of surface-modified biomedical polymer materials, a model of the functional mechanism of nonspecific adsorption resistance was constructed. Cell behavior on the surface and in vivo transplantation features of intraocular lens (IOL) materials, such as hydrophobic acrylic ester and polymethyl methacrylate (PMMA), were investigated. The results of cell adhesion and proliferation studies showed that the addition of hirudin can significantly resist epithelial cell adhesion, better than the pure amination process, and thereby inhibit excessive proliferation on the surface. Experiments on the eyes of rabbits indicated that the IOL surfaces with hirudin modification reduced the incidence of cell aggregation and inflammation. Combined with a study of protein-resistant layer construction with recombinant hirudin on the material surface, the mechanism of surface functionalization was determined. The biological performance indicated that nonspecific adsorption is greatly decreased due to the existence of amphiphilic ions or hydration layers, which lead to stability and long-term resistance to nonspecific adsorption. These results offer a theoretical basis for the use of traditional biomedical polymer materials in long-term clinical applications. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1961-1967, 2016.

  9. Polymers.

    ERIC Educational Resources Information Center

    Tucker, David C.

    1986-01-01

    Presents an open-ended experiment which has students exploring polymer chemistry and reverse osmosis. This activity involves construction of a polymer membrane, use of it in a simple osmosis experiment, and application of its principles in solving a science-technology-society problem. (ML)

  10. Tuning the biological activity profile of antibacterial polymers via subunit substitution pattern.

    PubMed

    Liu, Runhui; Chen, Xinyu; Chakraborty, Saswata; Lemke, Justin J; Hayouka, Zvi; Chow, Clara; Welch, Rodney A; Weisblum, Bernard; Masters, Kristyn S; Gellman, Samuel H

    2014-03-19

    Binary nylon-3 copolymers containing cationic and hydrophobic subunits can mimic the biological properties of host-defense peptides, but relationships between composition and activity are not yet well understood for these materials. Hydrophobic subunits in previously studied examples have been limited mostly to cycloalkane-derived structures, with cyclohexyl proving to be particularly promising. The present study evaluates alternative hydrophobic subunits that are isomeric or nearly isomeric with the cyclohexyl example; each has four sp(3) carbons in the side chains. The results show that varying the substitution pattern of the hydrophobic subunit leads to relatively small changes in antibacterial activity but causes significant changes in hemolytic activity. We hypothesize that these differences in biological activity profile arise, at least in part, from variations among the conformational propensities of the hydrophobic subunits. The α,α,β,β-tetramethyl unit is optimal among the subunits we have examined, providing copolymers with potent antibacterial activity and excellent prokaryote vs eukaryote selectivity. Bacteria do not readily develop resistance to the new antibacterial nylon-3 copolymers. These findings suggest that variation in subunit conformational properties could be generally valuable in the development of synthetic polymers for biological applications. PMID:24601599

  11. Dynamics of intracellular polymers in enhanced biological phosphorus removal processes under different organic carbon concentrations.

    PubMed

    Xing, Lizhen; Ren, Li; Tang, Bo; Wu, Guangxue; Guan, Yuntao

    2013-01-01

    Enhanced biological phosphorus removal (EBPR) may deteriorate or fail during low organic carbon loading periods. Polyphosphate accumulating organisms (PAOs) in EBPR were acclimated under both high and low organic carbon conditions, and then dynamics of polymers in typical cycles, anaerobic conditions with excess organic carbons, and endogenous respiration conditions were examined. After long-term acclimation, it was found that organic loading rates did not affect the yield of PAOs and the applied low organic carbon concentrations were advantageous for the enrichment of PAOs. A low influent organic carbon concentration induced a high production of extracellular carbohydrate. During both anaerobic and aerobic endogenous respirations, when glycogen decreased to around 80 ± 10 mg C per gram of volatile suspended solids, PAOs began to utilize polyphosphate significantly. Regressed by the first-order reaction model, glycogen possessed the highest degradation rate and then was followed by polyphosphate, while biomass decay had the lowest degradation rate.

  12. Biologic and immunohistochemical analysis of interleukin-6 expression in vivo. Constitutive and induced expression in murine polymorphonuclear and mononuclear phagocytes.

    PubMed Central

    Terebuh, P. D.; Otterness, I. G.; Strieter, R. M.; Lincoln, P. M.; Danforth, J. M.; Kunkel, S. L.; Chensue, S. W.

    1992-01-01

    Interleukin-6 (IL-6) is considered an important multifunctional cytokine involved in the regulation of a variety of cellular responses, including the induction of acute-phase protein synthesis, lymphocyte activation, and hematopoiesis. In vitro studies have identified many cells that can produce IL-6, but the cellular sources under physiologic conditions have yet to be identified. Using immunoaffinity purified goat anti-murine IL-6, the authors performed immunohistochemical studies to localize cells expressing IL-6 in selected organs of normal and endotoxin challenged NIH-Swiss outbred mice. In the blood, findings were correlated with cell-associated bioactivity using the standard B9 cell proliferation assay. In normal mice, constitutive expression was seen in granulocytes, monocytes and their precursors as well as in bone marrow and splenic stromal macrophages. Hepatic macrophages were negative, as were lymphocytes, megakaryocytes, erythroid precursors, and endothelial cells. In the absence of significant serum levels of IL-6, cell-associated IL-6 bioactivity was detected in circulating polymorphonuclear leukocytes (PMNs), but not lymphocytes. After endotoxin challenge, there was a threefold increase in PMN IL-6 content from 1 to 3 hours followed by almost complete depletion at 6 hours. This correlated well with a threefold increase of IL-6 mRNA in the bone marrow followed by a decrease at 6 hours. This pattern also correlated with serum levels of IL-6, which peaked at 3 hours and dropped significantly by 6 hours. By 24 hours, cell-associated IL-6 showed recovery with no increase in serum levels. In vivo findings showing IL-6 expression in bone marrow macrophages support in vitro studies suggesting a role for IL-6 in hematopoiesis. Furthermore, PMNs as well as macrophages are likely important sources of IL-6 during inflammatory and septic states. Images Figure 1 Figure 5 PMID:1372159

  13. Heterogeneity of intracellular polymer storage states in enhanced biological phosphorus removal (EBPR)--observation and modeling.

    PubMed

    Bucci, Vanni; Majed, Nehreen; Hellweger, Ferdi L; Gu, April Z

    2012-03-20

    A number of agent-based models (ABMs) for biological wastewater treatment processes have been developed, but their skill in predicting heterogeneity of intracellular storage states has not been tested against observations due to the lack of analytical methods for measuring single-cell intracellular properties. Further, several mechanisms can produce and maintain heterogeneity (e.g., different histories, uneven division) and their relative importance has not been explored. This article presents an ABM for the enhanced biological phosphorus removal (EBPR) treatment process that resolves heterogeneity in three intracellular polymer storage compounds (i.e., polyphosphate, polyhydroxybutyrate, and glycogen) in three functional microbial populations (i.e., polyphosphate-accumulating, glycogen-accumulating, and ordinary heterotrophic organisms). Model predicted distributions were compared to those based on single-cell estimates obtained using a Raman microscopy method for a laboratory-scale sequencing batch reactor (SBR) system. The model can reproduce many features of the observed heterogeneity. Two methods for introducing heterogeneity were evaluated. First, biological variability in individual cell behavior was simulated by randomizing model parameters (e.g., maximum acetate uptake rate) at division. This method produced the best fit to the data. An optimization algorithm was used to determine the best variability (i.e., coefficient of variance) for each parameter, which suggests large variability in acetate uptake. Second, biological variability in individual cell states was simulated by randomizing state variables (e.g., internal nutrient) at division, which was not able to maintain heterogeneity because the memory in the internal states is too short. These results demonstrate the ability of ABM to predict heterogeneity and provide insights into the factors that contribute to it. Comparison of the ABM with an equivalent population-level model illustrates the effect

  14. Heterogeneity of intracellular polymer storage states in enhanced biological phosphorus removal (EBPR)--observation and modeling.

    PubMed

    Bucci, Vanni; Majed, Nehreen; Hellweger, Ferdi L; Gu, April Z

    2012-03-20

    A number of agent-based models (ABMs) for biological wastewater treatment processes have been developed, but their skill in predicting heterogeneity of intracellular storage states has not been tested against observations due to the lack of analytical methods for measuring single-cell intracellular properties. Further, several mechanisms can produce and maintain heterogeneity (e.g., different histories, uneven division) and their relative importance has not been explored. This article presents an ABM for the enhanced biological phosphorus removal (EBPR) treatment process that resolves heterogeneity in three intracellular polymer storage compounds (i.e., polyphosphate, polyhydroxybutyrate, and glycogen) in three functional microbial populations (i.e., polyphosphate-accumulating, glycogen-accumulating, and ordinary heterotrophic organisms). Model predicted distributions were compared to those based on single-cell estimates obtained using a Raman microscopy method for a laboratory-scale sequencing batch reactor (SBR) system. The model can reproduce many features of the observed heterogeneity. Two methods for introducing heterogeneity were evaluated. First, biological variability in individual cell behavior was simulated by randomizing model parameters (e.g., maximum acetate uptake rate) at division. This method produced the best fit to the data. An optimization algorithm was used to determine the best variability (i.e., coefficient of variance) for each parameter, which suggests large variability in acetate uptake. Second, biological variability in individual cell states was simulated by randomizing state variables (e.g., internal nutrient) at division, which was not able to maintain heterogeneity because the memory in the internal states is too short. These results demonstrate the ability of ABM to predict heterogeneity and provide insights into the factors that contribute to it. Comparison of the ABM with an equivalent population-level model illustrates the effect

  15. Enhancement in biological response of Ag-nano composite polymer membranes using plasma treatment for fabrication of efficient bio materials

    NASA Astrophysics Data System (ADS)

    Agrawal, Narendra Kumar; Sharma, Tamanna Kumari; Chauhan, Manish; Agarwal, Ravi; Vijay, Y. K.; Swami, K. C.

    2016-05-01

    Biomaterials are nonviable material used in medical devices, intended to interact with biological systems, which are becoming necessary for the development of artificial material for biological systems such as artificial skin diaphragm, valves for heart and kidney, lenses for eye etc. Polymers having novel properties like antibacterial, antimicrobial, high adhesion, blood compatibility and wettability are most suitable for synthesis of biomaterial, but all of these properties does not exist in any natural or artificial polymeric material. Nano particles and plasma treatment can offer these properties to the polymers. Hence a new nano-biomaterial has been developed by modifying the surface and chemical properties of Ag nanocomposite polymer membranes (NCPM) by Argon ion plasma treatment. These membranes were characterized using different techniques for surface and chemical modifications occurred. Bacterial adhesion and wettability were also tested for these membranes, to show direct use of this new class of nano-biomaterial for biomedical applications.

  16. Micro-processing of polymers and biological materials using high repetition rate femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Ding, Li

    High repetition rate femtosecond laser micro-processing has been applied to ophthalmological hydrogel polymers and ocular tissues to create novel refractive and diffractive structures. Through the optimization of laser irradiation conditions and material properties, this technology has become feasible for future industrial applications and clinical practices. A femtosecond laser micro-processing workstation has been designed and developed. Different experimental parameters of the workstation such as laser pulse duration, focusing lens, and translational stages have been described and discussed. Diffractive gratings and three-dimensional waveguides have been fabricated and characterized in hydrogel polymers, and refractive index modifications as large as + 0.06 have been observed within the laser-irradiated region. Raman spectroscopic studies have shown that our femtosecond laser micro-processing induces significant thermal accumulation, resulting in a densification of the polymer network and increasing the localized refractive index of polymers within the laser irradiated region. Different kinds of dye chromophores have been doped in hydrogel polymers to enhance the two-photon absorption during femtosecond laser micro-processing. As the result, laser scanning speed can be greatly increased while the large refractive index modifications remain. Femtosecond laser wavelength and pulse energy as well as water and dye concentration of the hydrogels are optimized. Lightly fixed ocular tissues such as corneas and lenses have been micro-processed by focused femtosecond laser pulses, and refractive index modifications without any tissue-breakdown are observed within the stromal layer of the corneas and the cortex of the lenses. Living corneas are doped with Sodium Fluorescein to increase the two-photon absorption during the laser micro-processing, and laser scanning speed can be greatly increased while inducing large refractive index modifications. No evidence of cell death

  17. From Biological Cilia to Artificial Flow Sensors: Biomimetic Soft Polymer Nanosensors with High Sensing Performance.

    PubMed

    Asadnia, Mohsen; Kottapalli, Ajay Giri Prakash; Karavitaki, K Domenica; Warkiani, Majid Ebrahimi; Miao, Jianmin; Corey, David P; Triantafyllou, Michael

    2016-01-01

    We report the development of a new class of miniature all-polymer flow sensors that closely mimic the intricate morphology of the mechanosensory ciliary bundles in biological hair cells. An artificial ciliary bundle is achieved by fabricating bundled polydimethylsiloxane (PDMS) micro-pillars with graded heights and electrospinning polyvinylidenefluoride (PVDF) piezoelectric nanofiber tip links. The piezoelectric nature of a single nanofiber tip link is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Rheology and nanoindentation experiments are used to ensure that the viscous properties of the hyaluronic acid (HA)-based hydrogel are close to the biological cupula. A dome-shaped HA hydrogel cupula that encapsulates the artificial hair cell bundle is formed through precision drop-casting and swelling processes. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. Functioning with principles analogous to the hair bundles, the sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively. These self-powered, sensitive, flexible, biocompatibale and miniaturized sensors can find extensive applications in navigation and maneuvering of underwater robots, artificial hearing systems, biomedical and microfluidic devices. PMID:27622466

  18. From Biological Cilia to Artificial Flow Sensors: Biomimetic Soft Polymer Nanosensors with High Sensing Performance.

    PubMed

    Asadnia, Mohsen; Kottapalli, Ajay Giri Prakash; Karavitaki, K Domenica; Warkiani, Majid Ebrahimi; Miao, Jianmin; Corey, David P; Triantafyllou, Michael

    2016-09-13

    We report the development of a new class of miniature all-polymer flow sensors that closely mimic the intricate morphology of the mechanosensory ciliary bundles in biological hair cells. An artificial ciliary bundle is achieved by fabricating bundled polydimethylsiloxane (PDMS) micro-pillars with graded heights and electrospinning polyvinylidenefluoride (PVDF) piezoelectric nanofiber tip links. The piezoelectric nature of a single nanofiber tip link is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Rheology and nanoindentation experiments are used to ensure that the viscous properties of the hyaluronic acid (HA)-based hydrogel are close to the biological cupula. A dome-shaped HA hydrogel cupula that encapsulates the artificial hair cell bundle is formed through precision drop-casting and swelling processes. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. Functioning with principles analogous to the hair bundles, the sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively. These self-powered, sensitive, flexible, biocompatibale and miniaturized sensors can find extensive applications in navigation and maneuvering of underwater robots, artificial hearing systems, biomedical and microfluidic devices.

  19. From Biological Cilia to Artificial Flow Sensors: Biomimetic Soft Polymer Nanosensors with High Sensing Performance

    NASA Astrophysics Data System (ADS)

    Asadnia, Mohsen; Kottapalli, Ajay Giri Prakash; Karavitaki, K. Domenica; Warkiani, Majid Ebrahimi; Miao, Jianmin; Corey, David P.; Triantafyllou, Michael

    2016-09-01

    We report the development of a new class of miniature all-polymer flow sensors that closely mimic the intricate morphology of the mechanosensory ciliary bundles in biological hair cells. An artificial ciliary bundle is achieved by fabricating bundled polydimethylsiloxane (PDMS) micro-pillars with graded heights and electrospinning polyvinylidenefluoride (PVDF) piezoelectric nanofiber tip links. The piezoelectric nature of a single nanofiber tip link is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Rheology and nanoindentation experiments are used to ensure that the viscous properties of the hyaluronic acid (HA)-based hydrogel are close to the biological cupula. A dome-shaped HA hydrogel cupula that encapsulates the artificial hair cell bundle is formed through precision drop-casting and swelling processes. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. Functioning with principles analogous to the hair bundles, the sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively. These self-powered, sensitive, flexible, biocompatibale and miniaturized sensors can find extensive applications in navigation and maneuvering of underwater robots, artificial hearing systems, biomedical and microfluidic devices.

  20. From Biological Cilia to Artificial Flow Sensors: Biomimetic Soft Polymer Nanosensors with High Sensing Performance

    PubMed Central

    Asadnia, Mohsen; Kottapalli, Ajay Giri Prakash; Karavitaki, K. Domenica; Warkiani, Majid Ebrahimi; Miao, Jianmin; Corey, David P.; Triantafyllou, Michael

    2016-01-01

    We report the development of a new class of miniature all-polymer flow sensors that closely mimic the intricate morphology of the mechanosensory ciliary bundles in biological hair cells. An artificial ciliary bundle is achieved by fabricating bundled polydimethylsiloxane (PDMS) micro-pillars with graded heights and electrospinning polyvinylidenefluoride (PVDF) piezoelectric nanofiber tip links. The piezoelectric nature of a single nanofiber tip link is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Rheology and nanoindentation experiments are used to ensure that the viscous properties of the hyaluronic acid (HA)-based hydrogel are close to the biological cupula. A dome-shaped HA hydrogel cupula that encapsulates the artificial hair cell bundle is formed through precision drop-casting and swelling processes. Fluid drag force actuates the hydrogel cupula and deflects the micro-pillar bundle, stretching the nanofibers and generating electric charges. Functioning with principles analogous to the hair bundles, the sensors achieve a sensitivity and threshold detection limit of 300 mV/(m/s) and 8 μm/s, respectively. These self-powered, sensitive, flexible, biocompatibale and miniaturized sensors can find extensive applications in navigation and maneuvering of underwater robots, artificial hearing systems, biomedical and microfluidic devices. PMID:27622466

  1. Conformational assembly and biological properties of collagen mimetic peptides and their thermally responsive polymer conjugates

    NASA Astrophysics Data System (ADS)

    Krishna, Ohm Divyam

    2011-12-01

    Collagens are one of the most abundant proteins found in body tissues and organs, endowing structural integrity, mechanical strength, and multiple biological functions. Destabilized collagen inside human body leads to various degenerative diseases (ex. osteoarthritis) and ageing. This has continued to motivate the design of synthetic peptides and bio-synthetic polypeptides to closely mimic the native collagens in terms of triple helix structure and stability, potential for higher order assembly, and biological properties. However, the widespread application of de novo collagens has been limited in part by the need for hydroxylated proline in the formation of stable triple helical structures. To address this continued need, a hydroxyproline-free, thermally stable collagen-mimetic peptide (CLP-Cys) was rationally designed via the incorporation of electrostatically stabilized amino acid triplets. CLP-Cys was synthesized via solid phase peptide synthesis. The formation and stability of the triple helical structure were indicated via circular dichroism (CD) experiments and confirmed via differential scanning calorimetry (DSC) results. CLP-Cys also self-assembled into nano-rods and micro-fibrils, as evidenced via a combination of dynamic light scattering and transmission electron microscopy. Given the high thermal stability and its propensity for higher-order assembly, CLP-Cys was further functionalized at both the ends with a thermally responsive polymer, poly(diethylene glycol methyl ether methacrylate), (PDEGMEMA) to synthesize a biohybrid triblock copolymer. The CD results indicated that the triple helical form is retained, the thermal unfolding is sustained and helix to coil transition is reversible in the triblock hybrid context. The LCST of PDEGMEMA homopolymer (26 °C) is increased (to 35 °C) upon conjugation to the hydrophilic collagen peptide domain. Further, a combination of static light scattering, Cryo-SEM, TEM and confocal microscopy elucidated that the

  2. Development and testing of new biologically-based polymers as advanced biocompatible contact lenses

    SciTech Connect

    Bertozzi, Carolyn R.

    2000-06-01

    Nature has evolved complex and elegant materials well suited to fulfill a myriad of functions. Lubricants, structural scaffolds and protective sheaths can all be found in nature, and these provide a rich source of inspiration for the rational design of materials for biomedical applications. Many biological materials are based in some fashion on hydrogels, the crosslinked polymers that absorb and hold water. Biological hydrogels contribute to processes as diverse as mineral nucleation during bone growth and protection and hydration of the cell surface. The carbohydrate layer that coats all living cells, often referred to as the glycocalyx, has hydrogel-like properties that keep cell surfaces well hydrated, segregated from neighboring cells, and resistant to non-specific protein deposition. With the molecular details of cell surface carbohydrates now in hand, adaptation of these structural motifs to synthetic materials is an appealing strategy for improving biocompatibility. The goal of this collaborative project between Prof. Bertozzi's research group, the Center for Advanced Materials at Lawrence Berkeley National Laboratory and Sunsoft Corporation was the design, synthesis and characterization of novel hydrogel polymers for improved soft contact lens materials. Our efforts were motivated by the urgent need for improved materials that allow extended wear, and essential feature for those whose occupation requires the use of contact lenses rather than traditional spectacles. Our strategy was to transplant the chemical features of cell surface molecules into contact lens materials so that they more closely resemble the tissue in which they reside. Specifically, we integrated carbohydrate molecules similar to those found on cell surfaces, and sulfoxide materials inspired by the properties of the carbohydrates, into hydrogels composed of biocompatible and manufacturable substrates. The new materials were characterized with respect to surface and bulk hydrophilicity, and

  3. The force generated by biological membranes on a polymer rod and its response: Statics and dynamics

    NASA Astrophysics Data System (ADS)

    Daniels, D. R.; Turner, M. S.

    2004-10-01

    We propose a theory for the force exerted by a fluctuating membrane on a polymer rod tip. Using statistical mechanical methods, the expression for the generated force is written in terms of the distance of the rod tip from the membrane "frame." We apply the theory in calculating the stall force and membrane displacement required to cease the growth of a growing fiber induced by membrane fluctuations, as well as the membrane force and membrane displacement required for rod/fiber buckling. We also consider the dynamics of a growing fiber tip under the influence of a fluctuation-induced membrane force. We discuss the importance of our results in various biological contexts. Finally, we present a method to simultaneously extract both the rigidity of the semiflexible rod and the force applied by, e.g., the membrane from the measurements of the bending fluctuations of the rod. Such a measurement of the force would give information about the thermodynamics of the rod polymerization that involves the usual Brownian ratchet mechanism.

  4. Stem-loop oligonucleotide beacons as switches for amplifying-fluorescent-polymer-based biological warfare sensors

    NASA Astrophysics Data System (ADS)

    Clinkenbeard, Kenneth D.; Ramachandran, Akhilesh; Malayer, Jerry R.; Moon, Joong Ho; Hancock, Lawrence F.

    2003-09-01

    Sensors that are exceptionally sensitive with real-time outputs and minimal consumption of reagents are needed to continuously monitor air and water against bioterrorist incidents. Amplifying fluorescent polymers (AFP) provide exceptionally sensitive real-time reagentless sensor platforms as applied to detection of nitroaromatic explosives. This platform technology has the potential to be adapted to detect biological warfare (BW) agents by covalently attaching the 5" end of stem-loop molecular beacons to AFP as DNA hybridization signal transduction switches. Molecular beacons with loop sequences specific for sequence signatures of a target BW agent are configured with a quencher on the end of the 3" arm of the stem-loop. The AFP is quenched in the absence of target DNA, but upon hybridization with target the stem is melted, the duplex loop extended, and the AFP dequenched. This signal transduction is reversible upon removal of the target sequence with the molecular beacon reforming the stem-loop conformation. Proof-of-concept research has demonstrated that molecular beacons for signature sequences of Francisella tularensis result in correct identification of the presence of this agent in samples, but no false positives were seen with Escherichia coli.

  5. Biological fate of a polydisperse acrylate polymer in anaerobic sand-medium transport.

    PubMed

    Rittmann, B E; Henry, B; Odencrantz, J E; Sutfin, J A

    Soluble polyacrylate (PA), a polydisperse mixture of polyacrylate polymers, is strongly adsorbed and biodegradable. Biotic fate studies were carried out with once-through columns containing sand colonized with anaerobic biomass previously grown in a methanogenic fluidized bed. A fraction of soluble PA having a weight-average molecular weight of 16,700 and a range of molecular weight from 10(3) to 10(5) was biologically removed and mineralized to CO2. Due to its polydisperse nature, the breakthrough curve had a gradual increase to an apparent steady-state removal of approximately 60% near one day when the liquid detention time was 21 minutes. Modeling successfully explained the observed breakthrough result when the fraction was divided into components having a wide range of retardation factors (R): about 25% was strongly adsorbed (R = 200 and 500), 45% was moderately adsorbed (R = 50 and 100), and 30% was weakly adsorbed (R = 1-10). In this study, in which active biomass already was present from utilization of a primary substrate (glucose here), equilibrium adsorption increased the time to breakthrough, which also reduced the exiting concentration by increasing the substrate contact time.

  6. Impact of HydroPolymers on the soil biological components in mediterranean drylands

    NASA Astrophysics Data System (ADS)

    Dvořáčková, Helena; Hueso González, Paloma; Záhora, Jaroslav; Mikajlo, Irina; Damián Ruiz Sinoga, Jose

    2016-04-01

    Soil degradation affects more than 52 million ha of land in counties of the European Union. This problem is particularly serious in Mediterranean areas, where the effects of anthropogenic activities (tillage on slopes, deforestation, and pasture production) add to problems caused by prolonged periods of drought and intense and irregular rainfall. Soil microbiota can be used as an indicator of the soil healthy in degraded areas. This is because soil microbiota participates in the cycle elements and in the organic matter decomposition. All this helps to the young plants establishment and in long term protect the soils against the erosion. During dry periods in the Mediterranean areas, the lack of water entering the soil matrix leads to a loss of soil microbiological activity and it turns into a lower soil production capabilities. Under these conditions, the aim of this study was to evaluate the positive effect on soil biological components produced by an hydro absorbent polymer (Terracottem). The aim of the experiment was to evaluate the impact assessment of an hydropolymer (Terracottem) on the soil biological components. An experimental flowerpot layout was established in June 2015 and 12 variants with different amount of Terracottem were applied as follow: i) 3.0 kg.m3 ; ii) 1.5 kg.m3 and; iii) 0 kg.m3. In all the variants were tested the further additives: a) 1% of glucose, b) 50 kg N.ha-1 of Mineral nitrogen, c) 1% of Glucose + 50 kg N.ha-1 of Mineral nitrogen d) control (no additive). According to natural conditions, humidity have been kept at 15% in all the variants. During four weeks, mineral nitrogen leaching and soil respiration have been measured in each flowerplot. Respiration has been quantified four times every time while moistening containers and alkaline soda lime has been used as a sorbent. The amount of CO2 increase has been measured with the sorbent. Leaching of mineral nitrogen has been quantified by ion exchange resins (IER). IER pouches have been

  7. Synthesis, Characterization and Biological Studies of New Linear Thermally Stable Schiff Base Polymers with Flexible Spacers.

    PubMed

    Qureshi, Farah; Khuhawar, Muhammad Yar; Jahangir, Taj Muhammad; Channar, Abdul Hamid

    2016-01-01

    Five new linear Schiff base polymers having azomethine structures, ether linkages and extended aliphatic chain lengths with flexible spacers were synthesized by polycondensation of dialdehyde (monomer) with aliphatic and aromatic diamines. The formation yields of monomer and polymers were obtained within 75-92%. The polymers with flexible spacers of n-hexane were somewhat soluble in acetone, chloroform, THF, DMF and DMSO on heating. The monomer and polymers were characterized by melting point, elemental microanalysis, FT-IR, (1)HNMR, UV-Vis spectroscopy, thermogravimetry (TG), differential thermal analysis (DTA), fluorescence emission, scanning electron microscopy (SEM) and viscosities and thermodynamic parameters measurements of their dilute solutions. The studies supported formation of the monomer and polymers and on the basis of these studies their structures have been assigned. The synthesized polymers were tested for their antibacterial and antifungal activities.

  8. Synthesis, Characterization and Biological Studies of New Linear Thermally Stable Schiff Base Polymers with Flexible Spacers.

    PubMed

    Qureshi, Farah; Khuhawar, Muhammad Yar; Jahangir, Taj Muhammad; Channar, Abdul Hamid

    2016-01-01

    Five new linear Schiff base polymers having azomethine structures, ether linkages and extended aliphatic chain lengths with flexible spacers were synthesized by polycondensation of dialdehyde (monomer) with aliphatic and aromatic diamines. The formation yields of monomer and polymers were obtained within 75-92%. The polymers with flexible spacers of n-hexane were somewhat soluble in acetone, chloroform, THF, DMF and DMSO on heating. The monomer and polymers were characterized by melting point, elemental microanalysis, FT-IR, (1)HNMR, UV-Vis spectroscopy, thermogravimetry (TG), differential thermal analysis (DTA), fluorescence emission, scanning electron microscopy (SEM) and viscosities and thermodynamic parameters measurements of their dilute solutions. The studies supported formation of the monomer and polymers and on the basis of these studies their structures have been assigned. The synthesized polymers were tested for their antibacterial and antifungal activities. PMID:26970795

  9. Cell compatible arginine containing cationic polymer: one-pot synthesis and preliminary biological assessment.

    PubMed

    Zavradashvili, Nino; Memanishvili, Tamar; Kupatadze, Nino; Baldi, Lucia; Shen, Xiao; Tugushi, David; Wandrey, Christine; Katsarava, Ramaz

    2014-01-01

    Synthetic cationic polymers are of interest as both nonviral vectors for intracellular gene delivery and antimicrobial agents. For both applications synthetic polymers containing guanidine groups are of special interest since such kind of organic compounds/polymers show a high transfection potential along with antibacterial activity. It is important that the delocalization of the positive charge of the cationic group in guanidine significantly decreases the toxicity compared to the ammonium functionality. One of the most convenient ways for incorporating guanidine groups is the synthesis of polymers composed of the amino acid arginine (Arg) via either application of Arg-based monomers or chemical modification of polymers with derivatives of Arg. It is also important to have biodegradable cationic polymers that will be cleared from the body after their function as transfection or antimicrobial agent is fulfilled. This chapter deals with a two-step/one-pot synthesis of a new biodegradable cationic polymer-poly(ethylene malamide) containing L-arginine methyl ester covalently attached to the macrochains in β-position of the malamide residue via the α-amino group. The goal cationic polymer was synthesized by in situ interaction of arginine methyl ester dihydrochloride with intermediary poly(ethylene epoxy succinimide) formed by polycondensation of di-p-nitrophenyl-trans-epoxy succinate with ethylenediamine. The cell compatibility study with Chinese hamster ovary (CHO) and insect Schneider 2 cells (S2) within the concentration range of 0.02-500 mg/mL revealed that the new polymer is not cytotoxic. It formed nanocomplexes with pDNA (120-180 nm in size) at low polymer/DNA weight ratios (WR = 5-10). A preliminarily transfection efficiency of the Arg-containing new cationic polymer was assessed using CHO, S2, H5, and Sf9 cells.

  10. Additives-biological activities of tin-containing polymers bonded to noncarbons

    SciTech Connect

    Carraher, C.; Butler, C.; Foster, V.; Pandya, B.; Sterling, D.

    1993-12-31

    Organotin-containing polymers serve as effective additives to a silicon-based sealant, latex coating and talc exhibiting inhibition to tested bacteria and fungi. These polymers are candidates for uses a paint additives, sealant and caulk additives and within talc as an epidermal treatment.

  11. Polymer gel dosimetry for neutron beam in the Neutron Exposure Accelerator System for Biological Effect Experiments (NASBEE)

    NASA Astrophysics Data System (ADS)

    Kawamura, H.; Sato, H.; Hamano, T.; Suda, M.; Yoshii, H.

    2015-01-01

    This study aimed to investigate whether gel dosimetry could be used to measure neutron beams. We irradiated a BANG3-type polymer gel dosimeter using neutron beams in the Neutron exposure Accelerator System for Biological Effect Experiments (NASBEE) at the National Institute of Radiological Sciences (NIRS) in Japan. First, the polymer gels were irradiated from 0 to 7.0 Gy to investigate the dose-R2 responses. Irradiated gels were evaluated using 1.5-T magnetic resonance R2 images. Second, the polymer gels were irradiated to 1.0, 3.0, and 5.0 Gy to acquire a depth-R2 response curve. The dose-R2 response curve was linear up to approximately 7 Gy, with a slope of 1.25 Gy-1·s-1. Additionally, compared with the photon- irradiated gels, the neutron-irradiated gels had lower R2 values. The acquired depth-R2 curves of the central axis from the 3.0- and 5.0-Gy neutron dose-irradiated gels exhibited an initial build-up. Although, a detailed investigation is needed, polymer gel dosimetry is effective for measuring the dose-related R2 linearity and depth-R2 relationships of neutron beams.

  12. WILL FLUOROTELOMER ALCOHOL BASED POLYMER FORMULATIONS BIODEGRADE DURING AEROBIC BIOLOGICAL WASTEWATER TREATMENT?

    EPA Science Inventory

    The release of fluorotelomer alcohol (FTOH) based polymer formulations (PFs) to wastewater treatment plants (WWTPs) may be an important source of the perfluoroalkyl carboxylic acids (PFCAs) observed in many environmental matrices. Working with the Office of Pollution, Prevention,...

  13. Exploiting the Physicochemical Properties of Dendritic Polymers for Environmental and Biological Applications

    SciTech Connect

    Bhattacharya, Priyanka; Geitner, Nicholas K.; Sarupria, Sapna; Ke, Pu Chun

    2013-04-07

    In this Perspective we first examine the rich physicochemical properties of dendritic polymers for hosting cations, anions, and polyaromatic hydrocarbons. We then extrapolate these conceptual discussions to the use of dendritic polymers for humic acid antifouling, oil dispersion, copper sensing, and fullerenol remediation. In addition, we review the state-of-the-art of dendrimer research and elaborate on their 10 implications for water purification, environmental remediation, nanomedicine, and energy harvesting.

  14. Graphene-polymer hybrid nanostructure-based bioenergy storage device for real-time control of biological motor activity.

    PubMed

    Byun, Kyung-Eun; Choi, Dong Shin; Kim, Eunji; Seo, David H; Yang, Heejun; Seo, Sunae; Hong, Seunghun

    2011-11-22

    We report a graphene-polymer hybrid nanostructure-based bioenergy storage device to turn on and off biomotor activity in real-time. In this strategy, graphene was functionalized with amine groups and utilized as a transparent electrode supporting the motility of biomotors. Conducting polymer patterns doped with adenosine triphosphate (ATP) were fabricated on the graphene and utilized for the fast release of ATP by electrical stimuli through the graphene. The controlled release of biomotor fuel, ATP, allowed us to control the actin filament transportation propelled by the biomotor in real-time. This strategy should enable the integrated nanodevices for the real-time control of biological motors, which can be a significant stepping stone toward hybrid nanomechanical systems based on motor proteins.

  15. Biological materials: (Part A): Temperature-responsive polymers and drug delivery, and, (Part B): Polymer modification of fish scale and their nano-mechanical properties

    NASA Astrophysics Data System (ADS)

    Xiang, Xu

    This research has three parts. Two parts deal with novel nanoparticle assemblies for drug delivery, and are described in Part A, while the third part looks at properties of fish scales, an abundant and little-used waste resource, that can be modified to have value in medical and other areas. Part A describes fundamental research into the affects of block sequence of amphiphilic block copolymers prepared from on a new and versatile class of monomers, oligo(ethylene glycol) methyl ether acrylate (OEGA) and the more hydrophobic di(ethylene glycol) methyl ether methacrylate (DEGMA). Polymers from these monomers are biologically safe and give polymers with thermoresponsive properties that can be manipulated over a broader temperature range than the more researched N-isopropylacrylamide polymers. Using RAFT polymerization and different Chain Transfer Agents (CTAs) amphiphilic block copolymers were prepared to study the effect of block sequence (hydrophilic OEGA and more hydrophobic DEGMA) on their thermo-responsive properties. Pairing hydrophilic chain ends to a hydrophobic DEGMA block and hydrophobic chain ends to hydrophilic blocks ("mis-matched polarity") significantly affected thermoresponsive properties for linear and star diblock copolymers, but little affected symmetric triblock copolymers. Specifically matching polarity in diblock copolymers yielded nanoparticles with higher cloud points (CP), narrow temperature ranges for coil collapse above CP, and smaller hydrodynamic diameter than mis-matched polarity. Using this knowledge two linear OEGA/DEGMA diblock copolymers were prepared with thiol end groups and assembled into hybrid nanoparticles with a gold nanoparticle core (GNP-polymer hybrids). This design was made using the hypothesis that a hybrid polymer drug carrier with a high CP (50-60 °C) and a diblock structure could be designed with low levels of drug release below 37 °C (body temperature) allowing the drug carrier to reach a target (tumor) site with

  16. Understanding the interactions between porphyrin-containing photosensitizers and polymer-coated nanoparticles in model biological environments.

    PubMed

    Jenkins, Samir V; Srivatsan, Avinash; Reynolds, Kimberly Y; Gao, Feng; Zhang, Yongbin; Heyes, Colin D; Pandey, Ravindra K; Chen, Jingyi

    2016-01-01

    Non-covalent incorporation of hydrophobic drugs into polymeric systems is a commonly-used strategy for drug delivery because non-covalent interactions minimize modification of the drug molecules whose efficacy is retained upon release. The behaviors of the drug-polymer delivery system in the biological environments it encounters will affect the efficacy of treatment. In this report, we have investigated the interaction between a hydrophobic drug and its encapsulating polymer in model biological environments using a photosensitizer encapsulated in a polymer-coated nanoparticle system. The photosensitizer, 3-(1'-hexyloxyethyl)-3-devinylpyropheophorbide-a (HPPH), was non-covalently incorporated to the poly(ethylene glycol) (PEG) layer coated on Au nanocages (AuNCs) to yield AuNC-HPPH complexes. The non-covalent binding was characterized by Scatchard analysis, fluorescence lifetime, and Raman experiments. The dissociation constant between PEG and HPPH was found to be ∼35 μM with a maximum loading of ∼2.5×10(5) HPPHs/AuNC. The release was studied in serum-mimetic environment and in vesicles that model human cell membranes. The rate of protein-mediated drug release decreased when using a negatively-charged or cross-linked terminus of the surface-modified PEG. Furthermore, the photothermal effect of AuNCs can initiate burst release, and thus allow control of the release kinetics, demonstrating on-demand drug release. This study provides insights regarding the actions and release kinetics of non-covalent drug delivery systems in biological environments. PMID:26402781

  17. Molecular bioengineering of biomaterials in the 1990s and beyond: a growing liaison of polymers with molecular biology.

    PubMed

    Hoffman, A S

    1992-02-01

    An important trend in biomaterials research and development is the synthesis of polymers that combine capabilities of biologic recognition (biomimetic) with special physicochemical properties of the synthetic polymer system. Another important trend in such "molecular bioengineering" is to develop, perhaps via computer-aided molecular design, new artificial biomimetic systems by exact placement of functional groups on rigid polymer backbones, cross-linked structures, or macromolecular assemblies. In this way, biocatalytic functioning or biorecognition similar to enzymes and antibodies can be achieved without the inherent instability often encountered with the native biomolecules or assemblies. Perhaps the most exciting trend in biomaterials research and development is the availability of new biomolecules, e.g., via protein engineering and of hardy cells with specific biofunctions and bioresponses that can be tailored to specific medical or biotechnological needs. The wide variety of ways that such biomolecules and cells can be combined with polymeric biomaterials provides tremendously exciting opportunities for the biomaterials scientists and engineers. In addition to these synthetic approaches, new and exciting analytical tools, such as the scanning tunneling microscope and the atomic force microscope, are permitting study on a molecular scale of individual and small clusters of proteins and other biomolecular assemblies on surfaces. Cell attachments and spreading may also be visualized at various depths within the cell using the confocal laser microscope. Such analytical techniques can lead to important new knowledge about biologic interactions with biomaterials and, therefore, to development of even more biocompatible implants and devices. This paper overviews the present state of polymeric biomaterials and highlights the important and exciting opportunities generated by the liaison of these materials with molecular biology.

  18. Extension of in vivo half-life of biologically active peptides via chemical conjugation to XTEN protein polymer.

    PubMed

    Podust, Vladimir N; Sim, Bee-Cheng; Kothari, Dharti; Henthorn, Lana; Gu, Chen; Wang, Chia-wei; McLaughlin, Bryant; Schellenberger, Volker

    2013-11-01

    XTEN, unstructured biodegradable proteins, have been used to extend the in vivo half-life of genetically fused therapeutic proteins and peptides. To expand the applications of XTEN technology to half-life extension of other classes of molecules, XTEN protein polymers and methods for chemical XTENylation were developed. Two XTEN precursors were engineered to contain enzymatically removable purification tags. The proteins were readily expressed in bacteria and purified to homogeneity by chromatography techniques. As proof-of-principle, GLP2-2G peptide was chemically conjugated to each of the two XTEN protein polymers using maleimide-thiol chemistry. The monodisperse nature of XTEN protein polymer enabled reaction monitoring as well as the detection of peptide modifications in the conjugated state using reverse phase-high performance liquid chromatography (RP-HPLC) and electrospray ionization mass spectrometry. The resulting GLP2-2G-XTEN conjugates were purified by preparative RP-HPLC to homogeneity. In comparison with recombinantly fused GLP2-2G-XTEN, chemically conjugated GLP2-2G-XTEN molecules exhibited comparable in vitro activity, in vitro plasma stability and pharmacokinetics in rats. These data suggest that chemical XTENylation could effectively extend the half-life of a wide spectrum of biologically active molecules, therefore broadening its applicability.

  19. Polymer Fluid Dynamics.

    ERIC Educational Resources Information Center

    Bird, R. Byron

    1980-01-01

    Problems in polymer fluid dynamics are described, including development of constitutive equations, rheometry, kinetic theory, flow visualization, heat transfer studies, flows with phase change, two-phase flow, polymer unit operations, and drag reduction. (JN)

  20. Polymer adhesion at surfaces: biological adhesive proteins and their synthetic mimics

    NASA Astrophysics Data System (ADS)

    Messersmith, Phillip

    2008-03-01

    Mussels are famous for their ability to permanently adhere to a wide variety of wet surfaces, such as rocks, metal and polymer ship hulls, and wood structures. They accomplish this through specialized proteins collectively referred to as mussel adhesive proteins (MAPs). The biophysical aspects of MAP adhesion is being revealed through the use of single molecule force measurements. The results provide insight into the adhesive roles of key amino acids found in these proteins, including the magnitude of adhesive forces, cooperative effects, and their self-healing properties. This molecular-level information is being incorporated into designs of biomimetic polymer coatings for a variety of applications. Our biomimetic approach to polymer design will be illustrated by a few examples where adhesive constituents found in MAPs are exploited to make wet-adhesive polymer coatings. In addition, small molecule analogs of MAPs can be used to apply thin functional films onto virtually any material surface using a facile approach. These coatings have a variety of potential uses in microelectronics, water treatment, prevention of environmental biofouling, and for control of biointerfacial phenomena at the surfaces of medical/diagnostic devices.

  1. Physics in Cell Biology: Actin as a Model System for Polymer Physics

    NASA Astrophysics Data System (ADS)

    Frey, Erwin

    Living cells are soft bodies of a characteristic form, but endowed with a capacity for a steady turnover of their structures. Both of these material properties, i.e. recovery of the shape after an external stress has been imposed and dynamic structural reorganization, are essential for many cellular phenomena. The structural element responsible for the extraordinary mechanical and dynamical properties of eukaryotic cells is a three-dimensional assembly of protein fibers, the cytoskeleton. These fibers are semiflexible polymers with a stiffness intermediate between rigid rods and freely jointed chains. We discuss the statistical mechanics of individual semiflexible polymers and analyze the viscoelastic properties of solutions and cross linked networks of these biopolymers.

  2. Biomaterials-Based Electronics: Polymers and Interfaces for Biology and Medicine

    PubMed Central

    Muskovich, Meredith; Bettinger, Christopher J.

    2012-01-01

    Advanced polymeric biomaterials continue to serve as a cornerstone of new medical technologies and therapies. The vast majority of these materials, both natural and synthetic, interact with biological matter without direct electronic communication. However, biological systems have evolved to synthesize and employ naturally-derived materials for the generation and modulation of electrical potentials, voltage gradients, and ion flows. Bioelectric phenomena can be interpreted as potent signaling cues for intra- and inter-cellular communication. These cues can serve as a gateway to link synthetic devices with biological systems. This progress report will provide an update on advances in the application of electronically active biomaterials for use in organic electronics and bio-interfaces. Specific focus will be granted to the use of natural and synthetic biological materials as integral components in technologies such as thin film electronics, in vitro cell culture models, and implantable medical devices. Future perspectives and emerging challenges will also be highlighted. PMID:23184740

  3. Biomaterials-based electronics: polymers and interfaces for biology and medicine.

    PubMed

    Muskovich, Meredith; Bettinger, Christopher J

    2012-05-01

    Advanced polymeric biomaterials continue to serve as a cornerstone for new medical technologies and therapies. The vast majority of these materials, both natural and synthetic, interact with biological matter in the absence of direct electronic communication. However, biological systems have evolved to synthesize and utilize naturally-derived materials for the generation and modulation of electrical potentials, voltage gradients, and ion flows. Bioelectric phenomena can be translated into potent signaling cues for intra- and inter-cellular communication. These cues can serve as a gateway to link synthetic devices with biological systems. This progress report will provide an update on advances in the application of electronically active biomaterials for use in organic electronics and bio-interfaces. Specific focus will be granted to covering technologies where natural and synthetic biological materials serve as integral components such as thin film electronics, in vitro cell culture models, and implantable medical devices. Future perspectives and emerging challenges will also be highlighted.

  4. Biological and physicochemical properties of carbon-graphite fibre-reinforced polymers intended for implant suprastructures.

    PubMed

    Segerström, Susanna; Sandborgh-Englund, Gunilla; Ruyter, Eystein I

    2011-06-01

    The aim of this study was to determine water sorption, water solubility, dimensional change caused by water storage, residual monomers, and possible cytotoxic effects of heat-polymerized carbon-graphite fibre-reinforced composites with different fibre loadings based on methyl methacrylate/poly(methyl methacrylate) (MMA/PMMA) and the copolymer poly (vinyl chloride-co-vinyl acetate). Two different resin systems were used. Resin A contained ethylene glycol dimethacrylate (EGDMA) and 1,4-butanediol dimethacrylate (1,4-BDMA); the cross-linker in Resin B was diethylene glycol dimethacrylate (DEGDMA). The resin mixtures were reinforced with 24, 36 and 47 wt% surface-treated carbon-graphite fibres. In addition, polymer B was reinforced with 58 wt% fibres. Water sorption was equal to or below 3.34±1.18 wt%, except for the 58 wt% fibre loading of polymer B (5.27±1.22 wt%). Water solubility was below 0.36±0.015 wt%, except for polymer B with 47 and 58 wt% fibres. For all composites, the volumetric increase was below 0.01±0.005 vol%. Residual MMA monomer was equal to or below 0.68±0.05 wt% for the fibre composites. The filter diffusion test and the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) (MTT) assay demonstrated no cytotoxicity for the carbon-graphite fibre-reinforced composites, and residual cross-linking agents and vinyl chloride were not detectable by high-performance liquid chromatography (HPLC) analysis.

  5. Development of Voltammetric Double-Polymer-Modified Electrodes for Nanomolar Ion Detection for Environmental and Biological Applications

    NASA Astrophysics Data System (ADS)

    Kim, Yushin

    Qualitative and quantitative electrochemical methods for trace ion analysis of organic and inorganic species with environmental and biological attention have been developed and reported during past decades. The development of fast and accurate electrochemical methods is critical for field applications with various blocking contaminants. Voltammetric method is attractive not only to analyze selective ion species due to its characteristic based on ion lipophilicity, but also to lower the limit of detection by combining with stripping analysis. In my PhD work, I have developed and studied a highly selective and sensitive electrochemical method that can be used to characterize fundamental transport dynamics and to develop electrochemical sensors at liquid/liquid interfaces based on electrochemically-controlled ion transfer and recognition. The understanding of the kinetic and thermodynamic properties of the voltammetric ion transfer through polymer-modified ion-selective electrodes leads to realize the highly selective and sensitive analytical method. The ultrathin polymer membrane is used to maximize a current response by complete exhaustion of preconcentrated ions. Therefore, nanomolar detection is achieved and confirmed by a thermodynamic mechanism that controls the detection limit. It was also demonstrated experimentally and theoretically that more lipophilic ionic species gives a significantly lower detection limit. The voltammetric method was expanded into inexpensive and disposable applications based on pencil lead modified with the thin polymer membrane. In the other hand, micropipet/nanopipet voltammetry as an artificial cell membrane was used to study the interface between two immiscible solutions for environmental and biomedical applications. It is very useful to get quantitative kinetic and thermodynamic information by studying numerical simulations of ion transfer and diffusion. Molecular recognition and transport of heparin and low

  6. Creating Biological Membranes on the Micron Scale: Forming Patterned Lipid Bilayers Using a Polymer Lift-Off Technique

    PubMed Central

    Orth, R. N.; Kameoka, J.; Zipfel, W. R.; Ilic, B.; Webb, W. W.; Clark, T. G.; Craighead, H. G.

    2003-01-01

    We present a new method for creating patches of fluid lipid bilayers with conjugated biotin and other compounds down to 1 μm resolution using a photolithographically patterned polymer lift-off technique. The patterns are realized as the polymer is mechanically peeled away in one contiguous piece in solution. The functionality of these surfaces is verified with binding of antibodies and avidin on these uniform micron-scale platforms. The biomaterial patches, measuring 1 μm–76 μm on edge, provide a synthetic biological substrate for biochemical analysis that is ∼100× smaller in width than commercial printing technologies. 100 nm unilamellar lipid vesicles spread to form a supported fluid lipid bilayer on oxidized silicon surface as confirmed by fluorescence photobleaching recovery. Fluorescence photobleaching recovery measurements of DiI (1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiIC18(3))) stained bilayer patches yielded an average diffusion coefficient of 7.54 ± 1.25 μm2 s−1, equal to or slightly faster than typically found in DiI stained cells. This diffusion rate is ∼3× faster than previous values for bilayers on glass. This method provides a new means to form functionalized fluid lipid bilayers as micron-scale platforms to immobilize biomaterials, capture antibodies and biotinylated reagents from solution, and form antigenic stimuli for cell stimulation. PMID:14581207

  7. Quinoxaline-Based Polymer Dots with Ultrabright Red to Near-Infrared Fluorescence for In Vivo Biological Imaging.

    PubMed

    Liu, Hong-Yi; Wu, Pei-Jing; Kuo, Shih-Yu; Chen, Chuan-Pin; Chang, En-Hao; Wu, Chang-Yi; Chan, Yang-Hsiang

    2015-08-19

    This article describes the design and synthesis of quinoxaline-based semiconducting polymer dots (Pdots) that exhibit near-infrared fluorescence, ultrahigh brightness, large Stokes shifts, and excellent cellular targeting capability. We also introduced fluorine atoms and long alkyl chains into polymer backbones and systematically investigated their effect on the fluorescence quantum yields of Pdots. These new series of quinoxaline-based Pdots have a fluorescence quantum yield as high as 47% with a Stokes shift larger than 150 nm. Single-particle analysis reveals that the average per-particle brightness of the Pdots is at least 6 times higher than that of the commercially available quantum dots. We further demonstrated the use of this new class of quinoxaline-based Pdots for effective and specific cellular and subcellular labeling without any noticeable nonspecific binding. Moreover, the cytotoxicity of Pdots were evaluated on HeLa cells and zebrafish embryos to demonstrate their great biocompatibility. By taking advantage of their extreme brightness and minimal cytotoxicity, we performed, for the first time, in vivo microangiography imaging on living zebrafish embryos using Pdots. These quinoxaline-based NIR-fluorescent Pdots are anticipated to find broad use in a variety of in vitro and in vivo biological research.

  8. Preparation of 17β-estradiol surface molecularly imprinted polymers and their application to the analysis of biological samples.

    PubMed

    Zhang, Jing; Wang, Lingling; Han, Yanting

    2013-11-01

    17β-Estradiol (E2) surface molecularly imprinted polymers have been prepared using functionalized monodispersed poly(glycidyl methacrylate-co-ethylene dimethacrylate) beads as a support. The resulting polymers were found to be uniform in size (5 μm), and the surfaces of the microspheres possessed large pore-like structures. A chromatographic experiment demonstrated that the resulting microspheres exhibited high levels of recognition and selectivity toward the target molecule. The particles were employed as a novel sorbent in a molecularly imprinted SPE protocol. A method was then developed involving the combination of the pretreatment with HPLC to determine the levels of estrogen secreted from Michigan Cancer Foundation-7 cells. The obtained results revealed that the extraction recoveries of E2 from real samples were in the range of 73.0-97.5% with RSDs of < 7.5% (n = 3). Calibration curves were established with R values > 0.9996 for concentrations in the range of 0.50-100.00 ng/mL. The LOD of this new method was 0.14 ng/mL. Compared with traditional C18 SPE agents, the particles showed high selectivity and extraction efficiency for E2 in the pretreatment process. The particles could therefore be used to determine trace estrogen in biological samples with a UV detector only.

  9. Mind your P's and Q's: the coming of age of semiconducting polymer dots and semiconductor quantum dots in biological applications.

    PubMed

    Massey, Melissa; Wu, Miao; Conroy, Erin M; Algar, W Russ

    2015-08-01

    Semiconductor quantum dots (QDs) and semiconducting polymer nanoparticles (Pdots) are brightly emissive materials that offer many advantages for bioanalysis and bioimaging, and are complementary to revolutionary advances in fluorescence technology. Within the context of biological applications, this review compares the evolution and different stages of development of these two types of nanoparticle, and addresses current perceptions about QDs. Although neither material is a wholesale replacement for fluorescent dyes, recent trends have demonstrated that both types of nanoparticle can excel in applications that are often too demanding for fluorescent dyes alone. Examples discussed in this review include single particle tracking and imaging, multicolor imaging and multiplexed detection, biosensing, point-of-care diagnostics, in vivo imaging and drug delivery.

  10. Comparison between polyethylene glycol and zwitterionic polymers as antifouling coatings on wearable devices for selective antigen capture from biological tissue.

    PubMed

    Robinson, Kye J; Coffey, Jacob W; Muller, David A; Young, Paul R; Kendall, Mark A F; Thurecht, Kristofer J; Grøndahl, Lisbeth; Corrie, Simon R

    2015-01-01

    Selective capture of disease-related proteins in complex biological fluids and tissues is an important aim in developing sensitive protein biosensors for in vivo applications. Microprojection arrays are biomedical devices whose mechanical and chemical properties can be tuned to allow efficient penetration of skin, coupled with highly selective biomarker capture from the complex biological environment of skin tissue. Herein, the authors describe an improved surface modification strategy to produce amine-modified polycarbonate arrays, followed by the attachment of an antifouling poly(sulfobetaine-methacrylate) (pSBMA) polymer or a linear polyethylene glycol (PEG) polymer of comparative molecular weight and hydrodynamic radius. Using a "grafting to" approach, pSBMA and linear PEG coatings yielded comparative antifouling behavior in single protein solutions, diluted plasma, or when applied to mouse flank skin penetrating into the vascularized dermal tissue. Interestingly, the density of immobilized immunoglobulin G (IgG) or bovine serum albumin protein on pSBMA surfaces was significantly higher than that on the PEG surfaces, while the nonspecific adsorption was comparable for each protein. When incubated in buffer or plasma solutions containing dengue non-structural protein 1 (NS1), anti-NS1-IgG-coated pSBMA surfaces captured significantly more NS1 in comparison to PEG-coated devices. Similarly, when wearable microprojection arrays were applied to the skin of dengue-infected mice using the same coatings, the pSBMA-coated devices showed significantly higher capture efficiency (>2-fold increase in signal) than the PEG-coated substrates, which showed comparative signal when applied to naïve mice. In conclusion, zwitterionic pSBMA polymers (of equivalent hydrodynamic radii to PEG) allowed detection of dengue NS1 disease biomarker in a preclinical model of dengue infection, showing significantly higher signal-to-noise ratio in comparison to the PEG controls. The results of

  11. Rheological properties of a biological thermo-responsive hydrogel produced from soybean oil polymers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The rheological properties of a newly developed biological thermo-hydrogel made from vegetable oil were investigated. The material named HPSO-HG is a hydrolytic product of polymerized soybean oil (PSO). HPSO-HG is a thermo-responsive gel, and it exhibited viscoelastic behavior above 2% (wt.%) at roo...

  12. Star Polymers.

    PubMed

    Ren, Jing M; McKenzie, Thomas G; Fu, Qiang; Wong, Edgar H H; Xu, Jiangtao; An, Zesheng; Shanmugam, Sivaprakash; Davis, Thomas P; Boyer, Cyrille; Qiao, Greg G

    2016-06-22

    Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.

  13. Molecularly imprinted polymer on a SiO2 -coated graphene oxide surface for the fast and selective dispersive solid-phase extraction of Carbamazepine from biological samples.

    PubMed

    Khalilian, Faezeh; Ahmadian, Setareh

    2016-04-01

    A surface carbamazepine-imprinted polymer was grafted and synthesized on the SiO2 /graphene oxide surface. Firstly SiO2 was coated on synthesized graphene oxide sheet using the sol-gel technique. Prior to polymerization, the vinyl group was incorporated on to the surface of SiO2 /graphene oxide to direct selective polymerization on the surface. Methacrylic acid, ethylene glycol dimethacrylate and ethanol were used as monomer, cross-linker and porogen, respectively. Nonimprinted polymer was also prepared for comparison. The properties of the molecularly imprinted polymer were characterized using field-emission scanning electron microscopy and Fourier-transform infrared spectroscopy. The surface molecularly imprinted polymer was utilized as an adsorbent of dispersive solid-phase extraction for separation and preconcentration of carbamazepine. The effects of the different parameters influencing the extraction efficiency, such as sample pH were investigated and optimized. The specificity of the molecular imprinted polymer over the nonimprinted polymer was examined in absence and presence of competitive drugs. The carbamazepine calibration curve showed linearity in the ranges 0.5-500 μg/L. The limits of detection and quantification under the optimized conditions were 0.1 and 0.3 μg/L, respectively. The within-day and between-day relative standard deviations (n = 3) were 3.6 and 4.3%, respectively. Furthermore, the relative recoveries for spiked biological samples were above 85%. PMID:26899307

  14. “Turn-on” fluorescence probe integrated polymer nanoparticles for sensing biological thiol molecules

    PubMed Central

    Ang, Chung Yen; Tan, Si Yu; Lu, Yunpeng; Bai, Linyi; Li, Menghuan; Li, Peizhou; Zhang, Quan; Selvan, Subramanian Tamil; Zhao, Yanli

    2014-01-01

    A “turn-on” thiol-responsive fluorescence probe was synthesized and integrated into polymeric nanoparticles for sensing intracellular thiols. There is a photo-induced electron transfer process in the off state of the probe, and this process is terminated upon the reaction with thiol compounds. Configuration interaction singles (CIS) calculation was performed to confirm the mechanism of this process. A series of sensing studies were carried out, showing that the probe-integrated nanoparticles were highly selective towards biological thiol compounds over non-thiolated amino acids. Kinetic studies were also performed to investigate the relative reaction rate between the probe and the thiolated amino acids. Subsequently, the Gibbs free energy of the reactions was explored by means of the electrochemical method. Finally, the detection system was employed for sensing intracellular thiols in cancer cells, and the sensing selectivity could be further enhanced with the use of a cancer cell-targeting ligand in the nanoparticles. This development paves a path for the sensing and detection of biological thiols, serving as a potential diagnostic tool in the future. PMID:25394758

  15. NMR Studies of Polymer-Nanoparticle Interfaces in Biological and Synthetic Nanocomposites

    NASA Astrophysics Data System (ADS)

    Schmidt-Rohr, Klaus

    2010-03-01

    Nuclear magnetic resonance (NMR) provides unique capabilities for studying buried interfaces in organic-inorganic (specifically phosphate-based) nanocomposites, in terms of local composition as well as distances between, and mobility of, structural units near the interface. The organic-inorganic interface is crucial for the mechanical coupling between the polymer and the inorganic nanoparticles. We have studied the organic-inorganic nanocomposite in bone and characterized the interface between the organic matrix (the triple-helical fibrous polypeptide collagen) and the inorganic, reinforcing bioapatite (a calcium phosphate) that accounts for 45 vol% of the material and is present as ˜3-nm thick nanocrystals. By solid-state ^13C^31P NMR, we can obtain selective spectra of the collagen residues at the interface; ionic and hydroxyproline C-OH groups of significant mobility are dominant. ^1H-^31P and ^1H-^13C NMR prove that water with isotropic mobility, which accounts for about 7% of the total volume, forms a monomolecular interfacial layer between apatite and collagen. Its rotational correlation time is about five orders of magnitude longer than that of liquid water. We propose that this water layer can be considered as ``viscous glue'' that holds the components of the nanocomposite together. It would avoid stress concentration and, by virtue of its flexible H-bonding, reduce the requirement of matched lock-and-key binding sites for collagen sidegroups on the apatite surface. In nanocomposites of phosphate glass with polyamides, ^1H-^13C NMR reveals a reduced crystallinity of the polyamide near the inorganic particles.[4pt] Coauthors: Yan-Yan Hu, Aditya Rawal (Ames Laboratory), Joshua Otaigbe (University of Southern Mississippi)

  16. Controlling potassium selectivity and proton blocking in a hybrid biological/solid-state polymer nanoporous membrane.

    PubMed

    Balme, Sébastien; Picaud, Fabien; Kraszewski, Sebastian; Déjardin, Philippe; Janot, Jean Marc; Lepoitevin, Mathilde; Capomanes, Jhon; Ramseyer, Christophe; Henn, François

    2013-05-01

    Specific separations of protons and cations are usually performed by electromembrane processes, which require external electric energy. An easier process would be using a membrane able to separate both entities by passive diffusion. Presently, such synthetic nanoporous membranes do not exist. Here, we report the production of a robust hybrid biological/artificial solid-state membrane, which allows selective permeation of alkali metal cations without competing or concurrent permeation of protons. This membrane is simple to prepare and is based on the hydrophobic nature of the polymeric pore walls, and the confined gramicidin A molecules within. This work opens a new route for separation in the domain of nanobiofiltration, especially for tunable nanodevices based on differential ion conduction, with a fundamental understanding of the confinement mechanism.

  17. Controlling potassium selectivity and proton blocking in a hybrid biological/solid-state polymer nanoporous membrane

    NASA Astrophysics Data System (ADS)

    Balme, Sébastien; Picaud, Fabien; Kraszewski, Sebastian; Déjardin, Philippe; Janot, Jean Marc; Lepoitevin, Mathilde; Capomanes, Jhon; Ramseyer, Christophe; Henn, François

    2013-04-01

    Specific separations of protons and cations are usually performed by electromembrane processes, which require external electric energy. An easier process would be using a membrane able to separate both entities by passive diffusion. Presently, such synthetic nanoporous membranes do not exist. Here, we report the production of a robust hybrid biological/artificial solid-state membrane, which allows selective permeation of alkali metal cations without competing or concurrent permeation of protons. This membrane is simple to prepare and is based on the hydrophobic nature of the polymeric pore walls, and the confined gramicidin A molecules within. This work opens a new route for separation in the domain of nanobiofiltration, especially for tunable nanodevices based on differential ion conduction, with a fundamental understanding of the confinement mechanism.Specific separations of protons and cations are usually performed by electromembrane processes, which require external electric energy. An easier process would be using a membrane able to separate both entities by passive diffusion. Presently, such synthetic nanoporous membranes do not exist. Here, we report the production of a robust hybrid biological/artificial solid-state membrane, which allows selective permeation of alkali metal cations without competing or concurrent permeation of protons. This membrane is simple to prepare and is based on the hydrophobic nature of the polymeric pore walls, and the confined gramicidin A molecules within. This work opens a new route for separation in the domain of nanobiofiltration, especially for tunable nanodevices based on differential ion conduction, with a fundamental understanding of the confinement mechanism. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00564j

  18. The Constitutional Amendment Process

    ERIC Educational Resources Information Center

    Chism, Kahlil

    2005-01-01

    This article discusses the constitutional amendment process. Although the process is not described in great detail, Article V of the United States Constitution allows for and provides instruction on amending the Constitution. While the amendment process currently consists of six steps, the Constitution is nevertheless quite difficult to change.…

  19. Biologically Derived Soft Conducting Hydrogels Using Heparin-Doped Polymer Networks

    PubMed Central

    2015-01-01

    The emergence of flexible and stretchable electronic components expands the range of applications of electronic devices. Flexible devices are ideally suited for electronic biointerfaces because of mechanically permissive structures that conform to curvilinear structures found in native tissue. Most electronic materials used in these applications exhibit elastic moduli on the order of 0.1–1 MPa. However, many electronically excitable tissues exhibit elasticities in the range of 1–10 kPa, several orders of magnitude smaller than existing components used in flexible devices. This work describes the use of biologically derived heparins as scaffold materials for fabricating networks with hybrid electronic/ionic conductivity and ultracompliant mechanical properties. Photo-cross-linkable heparin–methacrylate hydrogels serve as templates to control the microstructure and doping of in situ polymerized polyaniline structures. Macroscopic heparin-doped polyaniline hydrogel dual networks exhibit impedances as low as Z = 4.17 Ω at 1 kHz and storage moduli of G′ = 900 ± 100 Pa. The conductivity of heparin/polyaniline networks depends on the oxidation state and microstructure of secondary polyaniline networks. Furthermore, heparin/polyaniline networks support the attachment, proliferation, and differentiation of murine myoblasts without any surface treatments. Taken together, these results suggest that heparin/polyaniline hydrogel networks exhibit suitable physical properties as an electronically active biointerface material that can match the mechanical properties of soft tissues composed of excitable cells. PMID:24738911

  20. Facile synthesis of AIE-active amphiphilic polymers: Self-assembly and biological imaging applications.

    PubMed

    Long, Zi; Liu, Meiying; Wang, Ke; Deng, Fengjie; Xu, Dazhuang; Liu, Liangji; Wan, Yiqun; Zhang, Xiaoyong; Wei, Yen

    2016-09-01

    In this work, we reported a rather facile method for fabrication of ultrabright, well dispersible and biocompatible fluorescent organic nanoparticles (FONs) with aggregation-induced emission (AIE) properties through combination of esterification and ring-opening reaction. The hydroxyl groups of Pluronic F127 was first reacted with the chloride of trimellitic anhydride chloride (TMAC), and its anhydride groups were further reacted with the amino groups of amino-terminated AIE dye (PhNH2) through ring-opening reaction. The optical properties, biocompatibility as well as cell uptake behavior of these obtained AIE-active nanoparticles (F127-TMAC-PhNH2 FONs) were examined by a series of characterization techniques and assays. We demonstrated that uniform organic nanoparticles with high water dispersibility, strong luminescence and desirable biocompatibility can be facilely obtained, which are promising for biological imaging applications. More importantly, a number of carboxyl groups were introduced into these AIE-active nanoparticles, which can be further utilized for further conjugation reaction and carrying anticancer drugs such as cisplatin. Therefore, the strategy of described in this work should be a simple and useful route for fabrication of multifunctional AIE-active luminescent nanotheranostic systems. PMID:27207057

  1. Ligand stimulation of ErbB4 and a constitutively-active ErbB4 mutant result in different biological responses in human pancreatic tumor cell lines

    SciTech Connect

    Mill, Christopher P.; Gettinger, Kathleen L.; Riese, David J.

    2011-02-15

    Pancreatic cancer is the fourth leading cause of cancer death in the United States. Indeed, it has been estimated that 37,000 Americans will die from this disease in 2010. Late diagnosis, chemoresistance, and radioresistance of these tumors are major reasons for poor patient outcome, spurring the search for pancreatic cancer early diagnostic and therapeutic targets. ErbB4 (HER4) is a member of the ErbB family of receptor tyrosine kinases (RTKs), a family that also includes the Epidermal Growth Factor Receptor (EGFR/ErbB1/HER1), Neu/ErbB2/HER2, and ErbB3/HER3. These RTKs play central roles in many human malignancies by regulating cell proliferation, survival, differentiation, invasiveness, motility, and apoptosis. In this report we demonstrate that human pancreatic tumor cell lines exhibit minimal ErbB4 expression; in contrast, these cell lines exhibit varied and in some cases abundant expression and basal tyrosine phosphorylation of EGFR, ErbB2, and ErbB3. Expression of a constitutively-dimerized and -active ErbB4 mutant inhibits clonogenic proliferation of CaPan-1, HPAC, MIA PaCa-2, and PANC-1 pancreatic tumor cell lines. In contrast, expression of wild-type ErbB4 in pancreatic tumor cell lines potentiates stimulation of anchorage-independent colony formation by the ErbB4 ligand Neuregulin 1{beta}. These results illustrate the multiple roles that ErbB4 may be playing in pancreatic tumorigenesis and tumor progression.

  2. In Situ Functionalized Polymers for siRNA Delivery.

    PubMed

    Priegue, Juan M; Crisan, Daniel N; Martínez-Costas, José; Granja, Juan R; Fernandez-Trillo, Francisco; Montenegro, Javier

    2016-06-20

    A new method is reported herein for screening the biological activity of functional polymers across a consistent degree of polymerization and in situ, that is, under aqueous conditions and without purification/isolation of candidate polymers. In brief, the chemical functionality of a poly(acryloyl hydrazide) scaffold was activated under aqueous conditions using readily available aldehydes to obtain amphiphilic polymers. The transport activity of the resulting polymers can be evaluated in situ using model membranes and living cells without the need for tedious isolation and purification steps. This technology allowed the rapid identification of a supramolecular polymeric vector with excellent efficiency and reproducibility for the delivery of siRNA into human cells (HeLa-EGFP). The reported method constitutes a blueprint for the high-throughput screening and future discovery of new polymeric functional materials with important biological applications.

  3. In Situ Functionalized Polymers for siRNA Delivery.

    PubMed

    Priegue, Juan M; Crisan, Daniel N; Martínez-Costas, José; Granja, Juan R; Fernandez-Trillo, Francisco; Montenegro, Javier

    2016-06-20

    A new method is reported herein for screening the biological activity of functional polymers across a consistent degree of polymerization and in situ, that is, under aqueous conditions and without purification/isolation of candidate polymers. In brief, the chemical functionality of a poly(acryloyl hydrazide) scaffold was activated under aqueous conditions using readily available aldehydes to obtain amphiphilic polymers. The transport activity of the resulting polymers can be evaluated in situ using model membranes and living cells without the need for tedious isolation and purification steps. This technology allowed the rapid identification of a supramolecular polymeric vector with excellent efficiency and reproducibility for the delivery of siRNA into human cells (HeLa-EGFP). The reported method constitutes a blueprint for the high-throughput screening and future discovery of new polymeric functional materials with important biological applications. PMID:27100572

  4. Three distinct clades of cultured heterocystous cyanobacteria constitute the dominant N2-fixing members of biological soil crusts of the Colorado Plateau, USA

    USGS Publications Warehouse

    Yeager, C.M.; Kornosky, J.L.; Morgan, R.E.; Cain, E.C.; Garcia-Pichel, F.; Housman, D.C.; Belnap, J.; Kuske, C.R.

    2007-01-01

    The identity of the numerically dominant N2-fixing bacteria in biological soil crusts of the Colorado Plateau region and two outlying areas was determined using multiple approaches, to link the environmental diversity of nifH gene sequences to cultured bacterial isolates from the regions. Of the nifH sequence-types detected in soil crusts of the Colorado Plateau, 89% (421/473) were most closely related to nifH signature sequences from cyanobacteria of the order Nostocales. N2-fixing cyanobacterial strains were cultured from crusts and their morphotypes, 16S rRNA gene and nifH gene sequences were characterized. The numerically dominant diazotrophs in the Colorado Plateau crusts fell within three clades of heterocystous cyanobacteria. Two clades are well-represented by phylogenetically and morphologically coherent strains, corresponding to the descriptions of Nostoc commune and Scytonema hyalinum, which are widely recognized as important N2-fixing components of soil crusts. A third, previously-overlooked clade was represented by a phylogenetically coherent but morphologically diverse group of strains that encompass the morphogenera Tolypothrix and Spirirestis. Many of the strains in each of these groups contained at least two nifH copies that represent different clusters in the nifH environmental survey. ?? 2007 Federation of European Microbiological Societies.

  5. β-Cyclodextrin/thermosensitive containing polymer brushes grafted onto magnetite nano-particles for extraction and determination of venlafaxine in biological and pharmaceutical samples.

    PubMed

    Ahmad Panahi, Homayon; Alaei, Haniyeh Sadat

    2014-12-10

    In this paper, a novel nano-sorbent is fabricated by the surface grafting of poly[β-CD/allylamine-co-N-isopropylacrylamide] onto modified magnetite nano-particles by 3-mercaptopropyltrimethoxysilane. The polymer grafted magnetite nano-particles was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, elemental analysis, scanning electron microscopy, and transmission electron microscopy. The feasibility of employing this nano-sorbent for extraction of trace venlafaxine in pharmaceutical samples and human biological fluids are investigated. The effect of various parameters such as pH, reaction temperature, and contact time was evaluated. The result revealed that the best sorption of venlafaxine by the magnetite nano-sorbent occurred at 35 °C at an optimum pH of 5. The kinetics of the venlafaxine shows accessibility of active sites in the grafted polymer onto the drug. The equilibrium data of venlafaxine by grafted magnetite nano-sorbent are well represented by the Langmuir and Freundlich isotherm models. The adsorption capacity of venlafaxine is found 142.8 mg g(-1) and indicated the homogeneous sites onto polymer grafted magnetite nano-sorbent surface. Nearly 80% of venlafaxine was released in simulated intestinal fluid, pH 7.4, in 30 h and 90% in simulated gastric fluid, pH 1.2, in 1 h. The venlafaxine loaded-polymer grafted magnetite nano-particles were successfully applied for the extraction in urine and pharmaceutical samples.

  6. Identification of functionally relevant populations in enhanced biological phosphorus removal processes based on intracellular polymers profiles and insights into the metabolic diversity and heterogeneity.

    PubMed

    Majed, Nehreen; Chernenko, Tatyana; Diem, Max; Gu, April Z

    2012-05-01

    This study proposed and demonstrated the application of a new Raman microscopy-based method for metabolic state-based identification and quantification of functionally relevant populations, namely polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs), in enhanced biological phosphorus removal (EBPR) system via simultaneous detection of multiple intracellular polymers including polyphosphate (polyP), glycogen, and polyhydroxybutyrate (PHB). The unique Raman spectrum of different combinations of intracellular polymers within a cell at a given stage of the EBPR cycle allowed for its identification as PAO, GAO, or neither. The abundance of total PAOs and GAOs determined by Raman method were consistent with those obtained with polyP staining and fluorescence in situ hybridization (FISH). Different combinations and quantities of intracellular polymer inclusions observed in single cells revealed the distribution of different sub-PAOs groups among the total PAO populations, which exhibit phenotypic and metabolic heterogeneity and diversity. These results also provided evidence for the hypothesis that different PAOs may employ different extents of combination of glycolysis and TCA cycle pathways for anaerobic reducing power and energy generation and it is possible that some PAOs may rely on TCA cycle solely without glycolysis. Sum of cellular level quantification of the internal polymers associated with different population groups showed differentiated and distributed trends of glycogen and PHB level between PAOs and GAOs, which could not be elucidated before with conventional bulk measurements of EBPR mixed cultures.

  7. Identification of functionally relevant populations in enhanced biological phosphorus removal processes based on intracellular polymers profiles and insights into the metabolic diversity and heterogeneity.

    PubMed

    Majed, Nehreen; Chernenko, Tatyana; Diem, Max; Gu, April Z

    2012-05-01

    This study proposed and demonstrated the application of a new Raman microscopy-based method for metabolic state-based identification and quantification of functionally relevant populations, namely polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs), in enhanced biological phosphorus removal (EBPR) system via simultaneous detection of multiple intracellular polymers including polyphosphate (polyP), glycogen, and polyhydroxybutyrate (PHB). The unique Raman spectrum of different combinations of intracellular polymers within a cell at a given stage of the EBPR cycle allowed for its identification as PAO, GAO, or neither. The abundance of total PAOs and GAOs determined by Raman method were consistent with those obtained with polyP staining and fluorescence in situ hybridization (FISH). Different combinations and quantities of intracellular polymer inclusions observed in single cells revealed the distribution of different sub-PAOs groups among the total PAO populations, which exhibit phenotypic and metabolic heterogeneity and diversity. These results also provided evidence for the hypothesis that different PAOs may employ different extents of combination of glycolysis and TCA cycle pathways for anaerobic reducing power and energy generation and it is possible that some PAOs may rely on TCA cycle solely without glycolysis. Sum of cellular level quantification of the internal polymers associated with different population groups showed differentiated and distributed trends of glycogen and PHB level between PAOs and GAOs, which could not be elucidated before with conventional bulk measurements of EBPR mixed cultures. PMID:22471394

  8. Virus Outbreaks in Chemical and Biological Sensors

    PubMed Central

    Hwang, Inseong

    2014-01-01

    Filamentous bacteriophages have successfully been used to detect chemical and biological analytes with increased selectivity and sensitivity. The enhancement largely originates not only from the ability of viruses to provide a platform for the surface display of a wide range of biological ligands, but also from the geometric morphologies of the viruses that constitute biomimetic structures with larger surface area-to-volume ratio. This review will appraise the mechanism of multivalent display of the viruses that enables surface modification of virions either by chemical or biological methods. The accommodation of functionalized virions to various materials, including polymers, proteins, metals, nanoparticles, and electrodes for sensor applications will also be discussed. PMID:25068866

  9. The nanocrystalline coordination polymer of AMT-Ag for an effective detection of ciprofloxacin hydrochloride in pharmaceutical formulation and biological fluid.

    PubMed

    Tiwari, Madhu; Kumar, Ashish; Shankar, Uma; Prakash, Rajiv

    2016-11-15

    The present report highlights a cost effective and portable AMT-Ag nanocrystalline coordination polymer (NCCP) based electrochemical sensor for an efficient sensing of biologically active drug molecule ciprofloxacin hydrochloride (CFX). The AMT-Ag NCCP, is synthesized using an easily accessible organic ligand 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) with silver nitrate. In the infinite polymer array of AMT-Ag, silver (I) centers are bridged by tecton AMT through the exocyclic thiol and amino linkage. A successful ultra‒trace detection of CFX has been achieved due to the prominent electron channeling through the pores of polymeric nano-crystallites. The efficient charge transfer arises at the interface of electrolyte and AMT-Ag nano-crystals anchored electrode through hydrophobic interaction and π-π electron coupling. The voltammogram reveals the critical redox features of CFX and provides a clear representation about the steps involved in the AMT-Ag assisted oxidation of CFX. This specific signature further applied in the voltammetric assay of CFX in pharmaceutical formulation (eye drops) and biological fluid (urine) by a significantly high sensitivity (0.002µA/µM and 0.007µA/µM) and detection limit (22nM and 60nM) respectively without any interference. Therefore, the developed AMT-Ag NCCP could serve as a highly valuable platform for the fabrication of high-performance electrochemical sensors for the detection of biologically important drug molecules.

  10. The nanocrystalline coordination polymer of AMT-Ag for an effective detection of ciprofloxacin hydrochloride in pharmaceutical formulation and biological fluid.

    PubMed

    Tiwari, Madhu; Kumar, Ashish; Shankar, Uma; Prakash, Rajiv

    2016-11-15

    The present report highlights a cost effective and portable AMT-Ag nanocrystalline coordination polymer (NCCP) based electrochemical sensor for an efficient sensing of biologically active drug molecule ciprofloxacin hydrochloride (CFX). The AMT-Ag NCCP, is synthesized using an easily accessible organic ligand 2-amino-5-mercapto-1,3,4-thiadiazole (AMT) with silver nitrate. In the infinite polymer array of AMT-Ag, silver (I) centers are bridged by tecton AMT through the exocyclic thiol and amino linkage. A successful ultra‒trace detection of CFX has been achieved due to the prominent electron channeling through the pores of polymeric nano-crystallites. The efficient charge transfer arises at the interface of electrolyte and AMT-Ag nano-crystals anchored electrode through hydrophobic interaction and π-π electron coupling. The voltammogram reveals the critical redox features of CFX and provides a clear representation about the steps involved in the AMT-Ag assisted oxidation of CFX. This specific signature further applied in the voltammetric assay of CFX in pharmaceutical formulation (eye drops) and biological fluid (urine) by a significantly high sensitivity (0.002µA/µM and 0.007µA/µM) and detection limit (22nM and 60nM) respectively without any interference. Therefore, the developed AMT-Ag NCCP could serve as a highly valuable platform for the fabrication of high-performance electrochemical sensors for the detection of biologically important drug molecules. PMID:27236138

  11. Melons are Branched Polymers

    NASA Astrophysics Data System (ADS)

    Gurau, Razvan; Ryan, James P.

    2014-11-01

    Melonic graphs constitute the family of graphs arising at leading order in the 1/N expansion of tensor models. They were shown to lead to a continuum phase, reminiscent of branched polymers. We show here that they are in fact precisely branched polymers, that is, they possess Hausdorff dimension 2 and spectral dimension 4/3.

  12. The Constitution by Cell

    ERIC Educational Resources Information Center

    Greenhut, Stephanie; Jones, Megan

    2010-01-01

    On their visit to the National Archives Experience in Washington, D.C., students in Jenni Ashley and Gay Brock's U.S. history classes at the Potomac School in McLean, Virginia, participated in a pilot program called "The Constitution by Cell." Armed with their cell phones, a basic understanding of the Constitution, and a willingness to participate…

  13. Interpreting the Constitution.

    ERIC Educational Resources Information Center

    Brennan, William J., Jr.

    1987-01-01

    Discusses constitutional interpretations relating to capital punishment and protection of human dignity. Points out the document's effectiveness in creating a new society by adapting its principles to current problems and needs. Considers two views of the Constitution that lead to controversy over the legitimacy of judicial decisions. (PS)

  14. Teaching the Constitution.

    ERIC Educational Resources Information Center

    Weatherman, Donald V.

    1987-01-01

    Courses on the Constitution must focus on the principles of government. Those principles and how the understanding of those principles shaped the document are appropriate subjects for consideration. The best sources for an examination of the Constitution are "The Records of the Federal Convention of 1787" and "The Federalist." (MLW)

  15. Preparation, spectral and biological investigation of formaldehyde-based ligand containing piperazine moiety and its various polymer metal complexes.

    PubMed

    Khan, Shamim Ahmad; Nishat, Nahid; Parveen, Shadma; Rasool, Raza

    2011-10-15

    A novel tetradentate salicylic acid-formaldehyde ligand containing piperazine moiety (SFP) was synthesized by condensation of salicylic acid, formaldehyde and piperazine in presence of base catalyst, which was subjected for the preparation of coordination polymers with metal ions like manganese(II), cobalt(II), copper(II), nickel(II) and zinc(II). All the synthesized polymeric compounds were characterized by elemental analysis, IR, (1)H NMR and electronic spectral studies. The thermal stability was determined by thermogravimetric analysis and thermal data revealed that all the polymer metal complexes show good thermal stability than their parent ligand. Electronic spectral data and magnetic moment values revealed that polymer metal complexes of Mn(II), Co(II) and Ni(II) show an octahedral geometry while Cu(II) and Zn(II) show distorted octahedral and tetrahedral geometry respectively. The antimicrobial screening of the ligand and coordination polymers was done by using Agar well diffusion method against various bacteria and fungi. It was evident from the data that antibacterial and antifungal activity increased on chelation and all the polymer metal complexes show excellent antimicrobial activity than their parent ligand. PMID:21757398

  16. Preparation, spectral and biological investigation of formaldehyde-based ligand containing piperazine moiety and its various polymer metal complexes

    NASA Astrophysics Data System (ADS)

    Khan, Shamim Ahmad; Nishat, Nahid; Parveen, Shadma; Rasool, Raza

    2011-10-01

    A novel tetradentate salicylic acid-formaldehyde ligand containing piperazine moiety (SFP) was synthesized by condensation of salicylic acid, formaldehyde and piperazine in presence of base catalyst, which was subjected for the preparation of coordination polymers with metal ions like manganese(II), cobalt(II), copper(II), nickel(II) and zinc(II). All the synthesized polymeric compounds were characterized by elemental analysis, IR, 1H NMR and electronic spectral studies. The thermal stability was determined by thermogravimetric analysis and thermal data revealed that all the polymer metal complexes show good thermal stability than their parent ligand. Electronic spectral data and magnetic moment values revealed that polymer metal complexes of Mn(II), Co(II) and Ni(II) show an octahedral geometry while Cu(II) and Zn(II) show distorted octahedral and tetrahedral geometry respectively. The antimicrobial screening of the ligand and coordination polymers was done by using Agar well diffusion method against various bacteria and fungi. It was evident from the data that antibacterial and antifungal activity increased on chelation and all the polymer metal complexes show excellent antimicrobial activity than their parent ligand.

  17. From Commodity Polymers to Functional Polymers

    PubMed Central

    Xiang, Tao; Wang, Ling-Ren; Ma, Lang; Han, Zhi-Yuan; Wang, Rui; Cheng, Chong; Xia, Yi; Qin, Hui; Zhao, Chang-Sheng

    2014-01-01

    Functional polymers bear specified chemical groups, and have specified physical, chemical, biological, pharmacological, or other uses. To adjust the properties while keeping material usage low, a method for direct synthesis of functional polymers is indispensable. Here we show that various functional polymers can be synthesized by in situ cross-linked polymerization/copolymerization. We demonstrate that the polymers synthesized by the facile method using different functional monomers own outstanding pH-sensitivity and pH-reversibility, antifouling property, antibacterial, and anticoagulant property. Our study opens a route for the functionalization of commodity polymers, which lead to important advances in polymeric materials applications. PMID:24710333

  18. From Commodity Polymers to Functional Polymers

    NASA Astrophysics Data System (ADS)

    Xiang, Tao; Wang, Ling-Ren; Ma, Lang; Han, Zhi-Yuan; Wang, Rui; Cheng, Chong; Xia, Yi; Qin, Hui; Zhao, Chang-Sheng

    2014-04-01

    Functional polymers bear specified chemical groups, and have specified physical, chemical, biological, pharmacological, or other uses. To adjust the properties while keeping material usage low, a method for direct synthesis of functional polymers is indispensable. Here we show that various functional polymers can be synthesized by in situ cross-linked polymerization/copolymerization. We demonstrate that the polymers synthesized by the facile method using different functional monomers own outstanding pH-sensitivity and pH-reversibility, antifouling property, antibacterial, and anticoagulant property. Our study opens a route for the functionalization of commodity polymers, which lead to important advances in polymeric materials applications.

  19. Probing the Biomimetic Ice Nucleation Inhibition Activity of Poly(vinyl alcohol) and Comparison to Synthetic and Biological Polymers

    PubMed Central

    2015-01-01

    Nature has evolved many elegant solutions to enable life to flourish at low temperatures by either allowing (tolerance) or preventing (avoidance) ice formation. These processes are typically controlled by ice nucleating proteins or antifreeze proteins, which act to either promote nucleation, prevent nucleation or inhibit ice growth depending on the specific need, respectively. These proteins can be expensive and their mechanisms of action are not understood, limiting their translation, especially into biomedical cryopreservation applications. Here well-defined poly(vinyl alcohol), synthesized by RAFT/MADIX polymerization, is investigated for its ice nucleation inhibition (INI) activity, in contrast to its established ice growth inhibitory properties and compared to other synthetic polymers. It is shown that ice nucleation inhibition activity of PVA has a strong molecular weight dependence; polymers with a degree of polymerization below 200 being an effective inhibitor at just 1 mg.mL–1. Other synthetic and natural polymers, both with and without hydroxyl-functional side chains, showed negligible activity, highlighting the unique ice/water interacting properties of PVA. These findings both aid our understanding of ice nucleation but demonstrate the potential of engineering synthetic polymers as new biomimetics to control ice formation/growth processes PMID:26258729

  20. Probing the Biomimetic Ice Nucleation Inhibition Activity of Poly(vinyl alcohol) and Comparison to Synthetic and Biological Polymers.

    PubMed

    Congdon, Thomas; Dean, Bethany T; Kasperczak-Wright, James; Biggs, Caroline I; Notman, Rebecca; Gibson, Matthew I

    2015-09-14

    Nature has evolved many elegant solutions to enable life to flourish at low temperatures by either allowing (tolerance) or preventing (avoidance) ice formation. These processes are typically controlled by ice nucleating proteins or antifreeze proteins, which act to either promote nucleation, prevent nucleation or inhibit ice growth depending on the specific need, respectively. These proteins can be expensive and their mechanisms of action are not understood, limiting their translation, especially into biomedical cryopreservation applications. Here well-defined poly(vinyl alcohol), synthesized by RAFT/MADIX polymerization, is investigated for its ice nucleation inhibition (INI) activity, in contrast to its established ice growth inhibitory properties and compared to other synthetic polymers. It is shown that ice nucleation inhibition activity of PVA has a strong molecular weight dependence; polymers with a degree of polymerization below 200 being an effective inhibitor at just 1 mg.mL(-1). Other synthetic and natural polymers, both with and without hydroxyl-functional side chains, showed negligible activity, highlighting the unique ice/water interacting properties of PVA. These findings both aid our understanding of ice nucleation but demonstrate the potential of engineering synthetic polymers as new biomimetics to control ice formation/growth processes.

  1. Probing the Biomimetic Ice Nucleation Inhibition Activity of Poly(vinyl alcohol) and Comparison to Synthetic and Biological Polymers.

    PubMed

    Congdon, Thomas; Dean, Bethany T; Kasperczak-Wright, James; Biggs, Caroline I; Notman, Rebecca; Gibson, Matthew I

    2015-09-14

    Nature has evolved many elegant solutions to enable life to flourish at low temperatures by either allowing (tolerance) or preventing (avoidance) ice formation. These processes are typically controlled by ice nucleating proteins or antifreeze proteins, which act to either promote nucleation, prevent nucleation or inhibit ice growth depending on the specific need, respectively. These proteins can be expensive and their mechanisms of action are not understood, limiting their translation, especially into biomedical cryopreservation applications. Here well-defined poly(vinyl alcohol), synthesized by RAFT/MADIX polymerization, is investigated for its ice nucleation inhibition (INI) activity, in contrast to its established ice growth inhibitory properties and compared to other synthetic polymers. It is shown that ice nucleation inhibition activity of PVA has a strong molecular weight dependence; polymers with a degree of polymerization below 200 being an effective inhibitor at just 1 mg.mL(-1). Other synthetic and natural polymers, both with and without hydroxyl-functional side chains, showed negligible activity, highlighting the unique ice/water interacting properties of PVA. These findings both aid our understanding of ice nucleation but demonstrate the potential of engineering synthetic polymers as new biomimetics to control ice formation/growth processes. PMID:26258729

  2. Preparation and biological evaluation of synthetic and polymer-encapsulated congeners of the antitumor agent pactamycin: Insight into functional group effects and biological activity

    PubMed Central

    Sharpe, Robert J.; Malinowski, Justin T.; Sorana, Federico; Luft, J. Christopher; Bowerman, Charles J.; DeSimone, Joseph M.; Johnson, Jeffrey S.

    2015-01-01

    The synthesis and biological analysis of a number of novel congeners of the aminocyclopentitol pactamycin is described. Specific attention was paid to the preparation of derivatives at crucial synthetic branch points of the parent structure, and biological assays revealed a number of insights into the source of pactamycin’s biological activity. Additionally, the encapsulation of pactamycin and select derivatives into the PRINT© nanoparticle technology was investigated as a proof-of-concept, and evidence of bioactivity modulation through nanoparticle delivery is demonstrated. This work has provided heretofore unrealized access to a large number of novel compounds for further evaluation. PMID:25792144

  3. Preparation and biological evaluation of synthetic and polymer-encapsulated congeners of the antitumor agent pactamycin: insight into functional group effects and biological activity.

    PubMed

    Sharpe, Robert J; Malinowski, Justin T; Sorana, Federico; Luft, J Christopher; Bowerman, Charles J; DeSimone, Joseph M; Johnson, Jeffrey S

    2015-04-15

    The synthesis and biological analysis of a number of novel congeners of the aminocyclopentitol pactamycin is described. Specific attention was paid to the preparation of derivatives at crucial synthetic branch points of the parent structure, and biological assays revealed a number of insights into the source of pactamycin's biological activity. Additionally, the encapsulation of pactamycin and select derivatives into the PRINT© nanoparticle technology was investigated as a proof-of-concept, and evidence of bioactivity modulation through nanoparticle delivery is demonstrated. This work has provided heretofore unrealized access to a large number of novel compounds for further evaluation. PMID:25792144

  4. - and Post-Workshop Assessment of Teachers and Students Attending the Scientific Workshop ``FROM Educational to Scientific Perspectives: Sugar Polymers in Biology and Their Applications''

    NASA Astrophysics Data System (ADS)

    Ufondu, Chuck; Ali, Nawab; Stapleton, Carl; Taylor, Loria; Barker, Linda; Tarasenko, Olga

    2011-06-01

    During summer 2010, a two-week-long scientific workshop "From educational to scientific perspectives: sugar polymers in biology and their applications" was offered for high school teachers and students at the University of Arkansas at Little Rock's Department of Biology. Teacher and student participants took part in science, technology, engineering, and mathematics (STEM) activities in order to improve math and science skills. Participants were taught various laboratory techniques, computer skills, Public Medical library searches, individual research project, PowerPoint presentation preparation, and a final oral presentation. Each participant was given pre- and post-workshop questionnaires, to gage initial and acquired knowledge. From the questionnaires, it was determined that there was a significant gain in knowledge of basic scientific concepts related to sugar polymers and their applications. It was found that 100% of participants—five teachers and seven students—reported their overall STEM experience as favorable. Furthermore, participants reported that the research project, computer techniques, and PowerPoint presentations were useful. This research experience provides knowledge about basic scientific concepts and is an excellent method to bridge the gap between high school and post-secondary education for both teachers and students.

  5. Constitution and Bylaws.

    ERIC Educational Resources Information Center

    Journal of Dental Education, 1981

    1981-01-01

    Constitutions and bylaws of the American Association of Dental Schools are presented, covering organization name, statement of purpose, administrative organization, offices, membership, legislative and administrative bodies, elected and appointed officers, regular and special sessions, sections, publications, election, and finance. (MSE)

  6. A Tailor-Made Synthetic Polymer for Cell Encapsulation: Design Rationale, Synthesis, Chemical-Physics and Biological Characterizations.

    PubMed

    Gerges, Irini; Tamplenizza, Margherita; Rossi, Eleonora; Tocchio, Alessandro; Martello, Federico; Recordati, Camilla; Kumar, Deepak; Forsyth, Nicholas R; Liu, Yang; Lenardi, Cristina

    2016-06-01

    This study presents a custom-made in situ gelling polymeric precursor for cell encapsulation. Composed of poly((2-hydroxyethyl)methacrylate-co-(3-aminopropyl)methacrylamide) (P(HEMA-co-APM) mother backbone and RGD-mimicking poly(amidoamine) (PAA) moiteis, the comb-like structured polymeric precursor is tailored to gather the advantages of the two families of synthetic polymers, i.e., the good mechanical integrity of PHEMA-based polymers and the biocompatibility and biodegradability of PAAs. The role of P(HEMA-co-APM) in the regulation of the chemico-physical properties of P(HEMA-co-APM)/PAA hydrogels is thoroughly investigated. On the basis of obtained results, namely the capability of maintaining vital NIH3T3 cell line in vitro for 2 d in a 3D cell culture, the in vivo biocompatibility in murine model for 16 d, and the ability of finely tuning mechanical properties and degradation kinetics, it can be assessed that P(HEMA-co-APM)/PAAs offer a cost-effective valid alternative to the so far studied natural polymer-based systems for cell encapsulation.

  7. High-Resolution Size-Discrimination of Single Nonionic Synthetic Polymers with a Highly Charged Biological Nanopore.

    PubMed

    Baaken, Gerhard; Halimeh, Ibrahim; Bacri, Laurent; Pelta, Juan; Oukhaled, Abdelghani; Behrends, Jan C

    2015-06-23

    Electrophysiological studies of the interaction of polymers with pores formed by bacterial toxins (1) provide a window on single molecule interaction with proteins in real time, (2) report on the behavior of macromolecules in confinement, and (3) enable label-free single molecule sensing. Using pores formed by the staphylococcal toxin α-hemolysin (aHL), a particularly pertinent observation was that, under high salt conditions (3-4 M KCl), the current through the pore is blocked for periods of hundreds of microseconds to milliseconds by poly(ethylene glycol) (PEG) oligomers (degree of polymerization approximately 10-60). Notably, this block showed monomeric sensitivity on the degree of polymerization of individual oligomers, allowing the construction of size or mass spectra from the residual current values. Here, we show that the current through the pore formed by aerolysin (AeL) from Aeromonas hydrophila is also blocked by PEG but with drastic differences in the voltage-dependence of the interaction. In contrast to aHL, AeL strongly binds PEG at high transmembrane voltages. This fact, which is likely related to AeL's highly charged pore wall, allows discrimination of polymer sizes with particularly high resolution. Multiple applications are now conceivable with this pore to screen various nonionic or charged polymers. PMID:26028280

  8. Core-double-shell Fe3O4@carbon@poly(In(III)-carboxylate) microspheres: cycloaddition of CO2 and epoxides on coordination polymer shells constituted by imidazolium-derived Al(III)-Salen bifunctional catalysts.

    PubMed

    An, Qiao; Li, Zifeng; Graff, Robert; Guo, Jia; Gao, Haifeng; Wang, Changchun

    2015-03-01

    A hydrid microsphere Fe3O4@carbon@poly(In(III)-carboxylate) consisting of a cluster of Fe3O4 nanoparticles as the core, a carbon layer as the inner shell and a porous In(III)-carboxylate coordination polymer as the outer shell was prepared and applied as a recyclable catalyst for the cycloaddition reaction of CO2 and epoxides. Construction of this hybrid microsphere was achieved in the two steps, including (1) the one-pot solvothermal synthesis of Fe3O4@C particles with the abundant carboxylic groups on the carbon surface and (2) the subsequent growth of the outer shell polymers based on the precipitation coordination polymerization. Imidazolium-substituted Salen ligands were synthesized and chelated with the In(III) ions using the terminal carboxylic groups. The coordination polymer shell was formed on the Fe3O4@C particles, and the structures including shell thickness, surface area and porosity could be varied by tuning the feeding ratios of the In(III) ions and the ligands. The optimal structure of the coordination polymers showed a shell thickness of ca. 45 nm with ∼5 nm of mesopore, 174.7 m(2)/g of surface area and 0.2175 cm(3)/g of pore volume. In light of gas uptake capability, catalytic activity and magnetic susceptibility, cycloaddition of CO2 with a series of epoxides were studied by using Al-complexed Fe3O4@C@In(III)-[IL-Salen] microspheres. The results validated that the self-supporting catalytic layer with high surface area was of remarkable advantages, which were attributed from great increment of effective active sites and combination of nucleophilic/electrophilic synergistic property and CO2 uptake capability. Therefore, these hybrid microspheres provided excellent catalytic activity, prominent selectivity to cyclic carbonates and outstanding recyclability with the assistance of an applied magnetic field.

  9. Constitution, 15 August 1982.

    PubMed

    1987-01-01

    This document reprints major provisions of the 1982 Constitution of Equatorial Guinea. The Constitution calls for protection of the family as the basic building block of society. Foreigners are afforded the same civil rights as citizens and may seek asylum but may not exercise political rights. The Constitution guarantees equality before the law and prohibits discrimination based on ethnic background, race, sex, language, religion, filiation, political or other views, social origin, economic position, or birth. Women are afforded the same rights as men regardless of their marital status. The Constitution also guarantees citizens freedom to travel nationally and internationally and to choose a place of residence. Equatoguineans are also entitled to a standard of living that insures health, nutrition, education, clothing, housing, medical care, and necessary social services. The family policy contained in the Constitution protects all types of legal marriages equally and recognizes nonattachable and inalienable family patrimony. Children are protected from the time of conception, and all inhabitants are guaranteed a basic state education which is compulsory and free. Efforts are also being made to eradicate illiteracy. Women are insured training and promotion for their integration into the active life and development of the country, and farmers are guaranteed traditional ownership of the lands they possess, although the state retains the right of eminent domain. PMID:12346662

  10. Poly(ADP-ribose)--a unique natural polymer structural features, biological role and approaches to the chemical synthesis.

    PubMed

    Drenichev, Mikhail S; Mikhailov, Sergey N

    2015-01-01

    Poly(ADP-ribose) (PAR) is a natural polymer, taking part in numerous important cellular processes. Several enzymes are involved in biosynthesis and degradation of PAR. One of them, poly(ADP-ribose)polymerase-1 (PARP-1) is considered to be a perspective target for the design of new drugs, affecting PAR metabolism. The structure of PAR was established by enzymatic hydrolysis and further analysis of the products, but total chemical synthesis of PAR hasn't been described yet. Several approaches have been developed on the way to chemical synthesis of this unique biopolymer.

  11. Crushed Salt Constitutive Model

    SciTech Connect

    Callahan, G.D.

    1999-02-01

    The constitutive model used to describe the deformation of crushed salt is presented in this report. Two mechanisms -- dislocation creep and grain boundary diffusional pressure solution -- are combined to form the basis for the constitutive model governing the deformation of crushed salt. The constitutive model is generalized to represent three-dimensional states of stress. Upon complete consolidation, the crushed-salt model reproduces the Multimechanism Deformation (M-D) model typically used for the Waste Isolation Pilot Plant (WIPP) host geological formation salt. New shear consolidation tests are combined with an existing database that includes hydrostatic consolidation and shear consolidation tests conducted on WIPP and southeastern New Mexico salt. Nonlinear least-squares model fitting to the database produced two sets of material parameter values for the model -- one for the shear consolidation tests and one for a combination of the shear and hydrostatic consolidation tests. Using the parameter values determined from the fitted database, the constitutive model is validated against constant strain-rate tests. Shaft seal problems are analyzed to demonstrate model-predicted consolidation of the shaft seal crushed-salt component. Based on the fitting statistics, the ability of the model to predict the test data, and the ability of the model to predict load paths and test data outside of the fitted database, the model appears to capture the creep consolidation behavior of crushed salt reasonably well.

  12. South Africa's Constitutional Change.

    ERIC Educational Resources Information Center

    Getman, Thomas

    1987-01-01

    Describes the striking dichotomy of South Africa's beauty and the squalor resulting from the apartheid policies of the government. Reviews reactions of black South Africans to recent constitutional changes and details efforts to secure more sweeping reform. Includes stories of several individuals who have taken actions which oppose the system of…

  13. Sexuality and the Constitution.

    ERIC Educational Resources Information Center

    Copelon, Rhonda

    1987-01-01

    Argues for abortion rights and protection of intimate decisions and relationships. Describes the role and position of women in eighteenth century American society as a means of exposing the fallacy of the anti-abortion movement's insistence on adherence to constitutional text. Discusses the recent attempts to overturn the Roe v. Wade ruling. (PS)

  14. The Constitution in Action

    ERIC Educational Resources Information Center

    Potter, Lee Ann

    2007-01-01

    In this article, the author describes the experiences middle school students on a field trip to the new Constitution in Action Learning Lab in the Boeing Learning Center at the National Archives can expect. There, middle school students take on the roles of archivists and researchers collecting and analyzing primary sources from the holdings of…

  15. Instabilities and constitutive modelling.

    PubMed

    Wilson, Helen J

    2006-12-15

    The plastics industry today sees huge wastage through product defects caused by unstable flows during the manufacturing process. In addition, many production lines are throughput-limited by a flow speed threshold above which the process becomes unstable. Therefore, it is critically important to understand the mechanisms behind these instabilities. In order to investigate the flow of a molten plastic, the first step is a model of the liquid itself, a relation between its current stress and its flow history called a constitutive relation. These are derived in many ways and tested on several benchmark flows, but rarely is the stability of the model used as a criterion for selection. The relationship between the constitutive model and the stability properties of even simple flows is not yet well understood. We show that in one case a small change to the model, which does not affect the steady flow behaviour, entirely removes a known instability. In another, a change that makes a qualitative difference to the steady flow makes only tiny changes to the stability.The long-term vision of this research is to exactly quantify what are the important properties of a constitutive relation as far as stability is concerned. If we could understand that, not only could very simple stability experiments be used to choose the best constitutive models for a particular material, but our ability to predict and avoid wasteful industrial instabilities would also be vastly improved.

  16. The Constitutional Heritage.

    ERIC Educational Resources Information Center

    Baxter, Maurice

    Changing political, social, economic, and intellectual conditions over the past two hundred years have demanded innovation and adjustment of legal doctrine, thus giving the United States Constitution a character which the framers of the document could not have predicted. Historically, one must not only understand developments since 1787 but also…

  17. Preconcentration and Determination of Mefenamic Acid in Pharmaceutical and Biological Fluid Samples by Polymer-grafted Silica Gel Solid-phase Extraction Following High Performance Liquid Chromatography

    PubMed Central

    Bagheri Sadeghi, Hayedeh; Panahi, Homayon Ahmad; Mahabadi, Mahsa; Moniri, Elham

    2015-01-01

    Mefenamic acid is a nonsteroidal anti-inflammatory drug (NSAID) that has analgesic, anti-infammatory and antipyretic actions. It is used to relieve mild to moderate pains. Solid-phase extraction of mefenamic acid by a polymer grafted to silica gel is reported. Poly allyl glycidyl ether/iminodiacetic acid-co-N, N-dimethylacrylamide was synthesized and grafted to silica gel and was used as an adsorbent for extraction of trace mefenamic acid in pharmaceutical and biological samples. Different factors affecting the extraction method were investigated and optimum conditions were obtained. The optimum pH value for sorption of mefenamic acid was 4.0. The sorption capacity of grafted adsorbent was 7.0 mg/g. The best eluent solvent was found to be trifluoroacetic acid-acetic acid in methanol with a recovery of 99.6%. The equilibrium adsorption data of mefenamic acid by grafted silica gel was analyzed by Langmuir model. The conformation of obtained data to Langmuir isotherm model reveals the homogeneous binding sites of grafted silica gel surface. Kinetic study of the mefenamic acid sorption by grafted silica gel indicates the good accessibility of the active sites in the grafted polymer. The sorption rate of the investigated mefenamic acid on the grafted silica gel was less than 5 min. This novel synthesized adsorbent can be successfully applied for the extraction of trace mefenamic acid in human plasma, urine and pharmaceutical samples. PMID:26330865

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

    PubMed

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

    2016-12-15

    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. PMID:27453986

  19. Two-photon excited quantum dots with compact surface coatings of polymer ligands used as an upconversion luminescent probe for dopamine detection in biological fluids.

    PubMed

    Jin, Hui; Gui, Rijun; Wang, Zonghua; Zhang, Feifei; Xia, Jianfei; Yang, Min; Bi, Sai; Xia, Yanzhi

    2015-03-21

    Water-soluble multidentate polymer coated CdTe quantum dots (QDs) were prepared via a stepwise addition of raw materials in a one-pot aqueous solution under ambient conditions. Just by adjusting the compositions of raw materials, different sized CdTe QDs were achieved within a short time. The as-prepared QDs showed compact surface coating (1.6-1.8 nm) of polymer ligands and photoluminescence (PL) emitted at 533-567 nm, as well as high colloidal/photo-stability and quantum yields (58-67%). Moreover, these QDs exhibited significant upconversion luminescence (UCL) upon excitation using an 800 nm femtosecond laser. Experimental results confirm that the UCL was ascribed to the two-photon assisted process via a virtual energy state. Then, the two-photon excited QDs were further developed as a novel UCL probe of dopamine (DA) due to self-assembled binding of DA molecules with QDs via non-covalent bonding. As a receptor, the DA attached onto the QD surface induced an electron transfer from QDs to DA, triggering UCL quenching of QDs. This UCL probe of DA presented a low limit of detection (ca. 5.4 nM), and high selectivity and sensitivity in the presence of potential interferences. In particular, it was favorably applied to the detection of DA in biological fluids, with quantitative recoveries (96.0-102.6%). PMID:25684191

  20. Bringing an "old" biological buffer to coordination chemistry: new 1D and 3D coordination polymers with [Cu(4)(Hbes)(4)] cores for mild hydrocarboxylation of alkanes.

    PubMed

    Kirillov, Alexander M; Coelho, Jaime A S; Kirillova, Marina V; da Silva, M Fátima C Guedes; Nesterov, Dmytro S; Gruenwald, Katrin R; Haukka, Matti; Pombeiro, Armando J L

    2010-07-19

    New water-soluble 1D and 3D Cu(II)/Na coordination polymers 1-3 bearing unprecedented [Cu(4)(Hbes)(4)] cores have been easily generated by aqueous-medium self-assembly and fully characterized, thus opening up the use of the common biological buffer H(3)bes, (HO(3)SCH(2)CH(2))N(CH(2)CH(2)OH)(2), in synthetic coordination chemistry. Apart from representing the first isolated and structurally characterized coordination compounds derived from H(3)bes, 1-3 show a remarkable promoting effect in the mild aqueous-medium hydrocarboxylation, by CO and H(2)O, of gaseous alkanes (C(3)H(8) and n-C(4)H(10)) to the corresponding carboxylic acids, which are obtained in up to 95% yields based on the alkane.

  1. Biological preconcentrator

    DOEpatents

    Manginell, Ronald P.; Bunker, Bruce C.; Huber, Dale L.

    2008-09-09

    A biological preconcentrator comprises a stimulus-responsive active film on a stimulus-producing microfabricated platform. The active film can comprise a thermally switchable polymer film that can be used to selectively absorb and desorb proteins from a protein mixture. The biological microfabricated platform can comprise a thin membrane suspended on a substrate with an integral resistive heater and/or thermoelectric cooler for thermal switching of the active polymer film disposed on the membrane. The active polymer film can comprise hydrogel-like polymers, such as poly(ethylene oxide) or poly(n-isopropylacrylamide), that are tethered to the membrane. The biological preconcentrator can be fabricated with semiconductor materials and technologies.

  2. Fabrication of a Selective and Sensitive Sensor Based on Molecularly Imprinted Polymer/Acetylene Black for the Determination of Azithromycin in Pharmaceuticals and Biological Samples

    PubMed Central

    Zhou, Tingting; Tao, Yun; Jin, Hua; Song, Bin; Jing, Tao; Luo, Dan; Zhou, Yusun; Zhou, Yikai; Lee, Yong-Ill; Mei, Surong

    2016-01-01

    A new selective and sensitive sensor based on molecularly imprinted polymer/acetylene black (MIP/AB) was developed for the determination of azithromycin (AZM) in pharmaceuticals and biological samples. The MIP of AZM was synthesized by precipitation polymerization. MIP and AB were then respectively introduced as selective and sensitive elements for the preparation of MIP/AB-modified carbon paste (MIP/ABP) electrode. The performance of the obtained sensor was estimated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. Compared with non-molecularly imprinted polymer (NIP) electrodes, NIP/ABP electrodes, and MIP-modified carbon paste electrodes, MIP/ABP electrode exhibited excellent current response toward AZM. The prepared sensor also exhibited good selectivity for AZM in comparison with structurally similar compounds. The effect of electrode composition, extraction parameters, and electrolyte conditions on the current response of the sensor was investigated. Under the optimized conditions, the prepared sensor showed two dynamic linear ranges of 1.0 × 10−7 mol L−1 to 2.0 × 10−6 mol L−1 and 2.0 × 10−6 mol L−1 to 2.0 × 10−5 mol L−1, with a limit of detection of 1.1 × 10−8 mol L−1. These predominant properties ensured that the sensor exhibits excellent reliability for detecting AZM in pharmaceuticals and biological fluids without the assistance of any separation techniques. The results were validated by the high-performance liquid chromatography–tandem mass spectrometry method. PMID:26820753

  3. A new magnetic ion-imprinted polymer as a highly selective sorbent for determination of cobalt in biological and environmental samples.

    PubMed

    Khoddami, Nafiseh; Shemirani, Farzaneh

    2016-01-01

    A magnetic ion-imprinted polymer (Fe3O4@TiO2@SiO2-IIP) functionalized with -NH groups for the selective determination of Co(II) ions from environmental and biological samples is presented. This sorbent was synthesized by surface imprinting technique combined with sol-gel process using 3-(2-aminoethylamino) propyltrimethoxysilane (AAPTS) as a functional ligand, tetraethyl orthosilicate as across-linking agent, and Co(II) ion as the template. The prepared magnetic ion-imprinted polymer was characterized by infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), dynamic light scattering (DLS), and X-ray diffraction (XRD). Fe3O4@TiO2@SiO2-IIP showed higher capacity and selectivity than that of Fe3O4@TiO2@SiO2-NIP. The important parameters influencing the recovery such as pH, the volume and eluent concentration, contact time, and the amount of sorbent on extraction percentage of Fe3O4@TiO2@SiO2-IIP were studied and optimized. The linear range (LR), relative standard deviation(RSD) and limit of detection (LOD=3 S(b)/m) for flame atomic absorption spectrometric determination of Co(II) ion, after its selective extraction by the prepared IIP polymer, were evaluated as 1-130 µg L(-1), 1.22% and 0.15 µg L(-1), respectively. The maximum capacity of Fe3O4@TiO2@SiO2-IIP and Fe3O4@TiO2@SiO2-NIP is 35.21 mg g(-1) and 10.34 mg g(-1), respectively. The separation factor of Fe3O4@TiO2@SiO2-IIP for Co(II)/Pb(II), Co(II)/Ni(II), and Co(II)/Cd(II) are 41.17, 79.74, and 56.48, respectively. In addition, the spent magnetic ion-imprinted polymer can be refreshed by simply washing with an aqueous HNO3 solution, and there is no significant decrease in adsorption capacity after a test of upto seven cycles, demonstrating that the Fe3O4@ TiO2@SiO2-IIP is stable and reusable. PMID:26695259

  4. A new magnetic ion-imprinted polymer as a highly selective sorbent for determination of cobalt in biological and environmental samples.

    PubMed

    Khoddami, Nafiseh; Shemirani, Farzaneh

    2016-01-01

    A magnetic ion-imprinted polymer (Fe3O4@TiO2@SiO2-IIP) functionalized with -NH groups for the selective determination of Co(II) ions from environmental and biological samples is presented. This sorbent was synthesized by surface imprinting technique combined with sol-gel process using 3-(2-aminoethylamino) propyltrimethoxysilane (AAPTS) as a functional ligand, tetraethyl orthosilicate as across-linking agent, and Co(II) ion as the template. The prepared magnetic ion-imprinted polymer was characterized by infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), dynamic light scattering (DLS), and X-ray diffraction (XRD). Fe3O4@TiO2@SiO2-IIP showed higher capacity and selectivity than that of Fe3O4@TiO2@SiO2-NIP. The important parameters influencing the recovery such as pH, the volume and eluent concentration, contact time, and the amount of sorbent on extraction percentage of Fe3O4@TiO2@SiO2-IIP were studied and optimized. The linear range (LR), relative standard deviation(RSD) and limit of detection (LOD=3 S(b)/m) for flame atomic absorption spectrometric determination of Co(II) ion, after its selective extraction by the prepared IIP polymer, were evaluated as 1-130 µg L(-1), 1.22% and 0.15 µg L(-1), respectively. The maximum capacity of Fe3O4@TiO2@SiO2-IIP and Fe3O4@TiO2@SiO2-NIP is 35.21 mg g(-1) and 10.34 mg g(-1), respectively. The separation factor of Fe3O4@TiO2@SiO2-IIP for Co(II)/Pb(II), Co(II)/Ni(II), and Co(II)/Cd(II) are 41.17, 79.74, and 56.48, respectively. In addition, the spent magnetic ion-imprinted polymer can be refreshed by simply washing with an aqueous HNO3 solution, and there is no significant decrease in adsorption capacity after a test of upto seven cycles, demonstrating that the Fe3O4@ TiO2@SiO2-IIP is stable and reusable.

  5. Elucidation of molecular structures at buried polymer interfaces and biological interfaces using sum frequency generation vibrational spectroscopy

    PubMed Central

    Zhang, Chi; Myers, John; Chen, Zhan

    2013-01-01

    Sum frequency generation (SFG) vibrational spectroscopy has been developed into an important technique to study surfaces and interfaces. It can probe buried interfaces in situ and provide molecular level structural information such as the presence of various chemical moieties, quantitative molecular functional group orientation, and time dependent kinetics or dynamics at such interfaces. This paper focuses on these three most important advantages of SFG and reviews some of the recent progress in SFG studies on interfaces related to polymer materials and biomolecules. The results discussed here demonstrate that SFG can provide important molecular structural information of buried interfaces in situ and in real time, which is difficult to obtain by other surface sensitive analytical techniques. PMID:23710244

  6. Protein-style dynamical transition in a non-biological polymer and a non-aqueous solvent

    DOE PAGESBeta

    Mamontov, E.; Sharma, V. K.; Borreguero, J. M.; Tyagi, M.

    2016-03-15

    Using neutron scattering and molecular dynamics simulation, techniques most often associated with protein dynamical transition studies, we have investigated the microscopic dynamics of one of the most common polymers, polystyrene, which was exposed to toluene vapor, mimicking the process of protein hydration from water vapor. Polystyrene with adsorbed toluene is an example of a solvent-solute system, which, unlike biopolymers, is anhydrous and lacks hydrogen bonding. Nevertheless, it exhibits the essential traits of the dynamical transition in biomolecules, such as a specific dependence of the microscopic dynamics of both solvent and host on the temperature and the amount of solvent adsorbed.more » Ultimately, we conclude that the protein dynamical transition is a manifestation of a universal solvent-solute dynamical relationship, which is not specific to either biomolecules as solute, or aqueous media as solvent, or even a particular type of interactions between solvent and solute.« less

  7. Polymer monolithic capillary microextraction combined on-line with inductively coupled plasma MS for the determination of trace rare earth elements in biological samples.

    PubMed

    Zhang, Lin; Chen, Beibei; He, Man; Hu, Bin

    2013-07-01

    A rapid and sensitive method based on polymer monolithic capillary microextraction combined on-line with microconcentric nebulization inductively coupled plasma MS has been developed for the determination of trace/ultratrace rare earth elements in biological samples. For this purpose, the iminodiacetic acid modified poly(glycidyl methacrylate-trimethylolpropane trimethacrylate) monolithic capillary was prepared and characterized by SEM and FTIR spectroscopy. Factors affecting the extraction efficiency, such as sample pH, sample flow rate, sample/eluent volume, and coexisting ions were investigated in detail. Under the optimal conditions, the LODs for rare earth elements were in the range of 0.08 (Er) to 0.97 ng/L (Nd) with a sampling frequency of 8.5 h(-1), and the RSDs were between 1.5% (Sm) and 7.4% (Nd) (c = 20 ng/L, n = 7). The proposed method was successfully applied to the analysis of trace/ultratrace rare earth elements in human urine and serum samples, and the recoveries for the spiked samples were in the range of 82-105%. The developed method was simple, rapid, sensitive, and favorable for the analysis of trace/ultratrace rare earth elements in biological samples with limited sample volume.

  8. Dual-emissive Polymer Dots for Rapid Detection of Fluoride in Pure Water and Biological Systems with Improved Reliability and Accuracy

    PubMed Central

    Zhao, Qiang; Zhang, Chuanqi; Liu, Shujuan; Liu, Yahong; Zhang, Kenneth Yin; Zhou, Xiaobo; Jiang, Jiayang; Xu, Wenjuan; Yang, Tianshe; Huang, Wei

    2015-01-01

    It is of paramount importance to develop new probes that can selectively, sensitively, accurately and rapidly detect fluoride in aqueous media and biological systems, because F- is found to be closely related to many health and environmental concerns. Herein, a dual-emissive conjugated polyelectrolyte P1 containing phosphorescent iridium(III) complex was designed and synthesized, which can form ultrasmall polymer dots (Pdots) in aqueous media. The F--responsive tert-butyldiphenylsilyl moiety was introduced into iridium(III) complex as the signaling unit for sensing F− with the quenched phosphorescence. Thus, the dual-emissive Pdots can rapidly and accurately detect F− in aqueous media and live cells as a ratiometric probe by measuring the change in the ratio of the F−-sensitive red phosphorescence from iridium(III) complex to the F−-insensitive blue fluorescence from polyfluorene. Moreover, the interaction of Pdots with F− also changes its emission lifetime, and the lifetime-based detection of F− in live cells has been realized through photoluminescence lifetime imaging microscopy for the first time. Both the ratiometric luminescence and lifetime imaging have been demonstrated to be resistant to external influences, such as the probe’s concentration and excitation power. This study provides a new perspective for the design of promising Pdots-based probes for biological applications. PMID:26552859

  9. Dual-emissive Polymer Dots for Rapid Detection of Fluoride in Pure Water and Biological Systems with Improved Reliability and Accuracy.

    PubMed

    Zhao, Qiang; Zhang, Chuanqi; Liu, Shujuan; Liu, Yahong; Zhang, Kenneth Yin; Zhou, Xiaobo; Jiang, Jiayang; Xu, Wenjuan; Yang, Tianshe; Huang, Wei

    2015-11-10

    It is of paramount importance to develop new probes that can selectively, sensitively, accurately and rapidly detect fluoride in aqueous media and biological systems, because F(-) is found to be closely related to many health and environmental concerns. Herein, a dual-emissive conjugated polyelectrolyte P1 containing phosphorescent iridium(III) complex was designed and synthesized, which can form ultrasmall polymer dots (Pdots) in aqueous media. The F(-)-responsive tert-butyldiphenylsilyl moiety was introduced into iridium(III) complex as the signaling unit for sensing F(-) with the quenched phosphorescence. Thus, the dual-emissive Pdots can rapidly and accurately detect F(-) in aqueous media and live cells as a ratiometric probe by measuring the change in the ratio of the F(-)-sensitive red phosphorescence from iridium(III) complex to the F(-)-insensitive blue fluorescence from polyfluorene. Moreover, the interaction of Pdots with F(-) also changes its emission lifetime, and the lifetime-based detection of F(-) in live cells has been realized through photoluminescence lifetime imaging microscopy for the first time. Both the ratiometric luminescence and lifetime imaging have been demonstrated to be resistant to external influences, such as the probe's concentration and excitation power. This study provides a new perspective for the design of promising Pdots-based probes for biological applications.

  10. Dual-emissive Polymer Dots for Rapid Detection of Fluoride in Pure Water and Biological Systems with Improved Reliability and Accuracy

    NASA Astrophysics Data System (ADS)

    Zhao, Qiang; Zhang, Chuanqi; Liu, Shujuan; Liu, Yahong; Zhang, Kenneth Yin; Zhou, Xiaobo; Jiang, Jiayang; Xu, Wenjuan; Yang, Tianshe; Huang, Wei

    2015-11-01

    It is of paramount importance to develop new probes that can selectively, sensitively, accurately and rapidly detect fluoride in aqueous media and biological systems, because F- is found to be closely related to many health and environmental concerns. Herein, a dual-emissive conjugated polyelectrolyte P1 containing phosphorescent iridium(III) complex was designed and synthesized, which can form ultrasmall polymer dots (Pdots) in aqueous media. The F--responsive tert-butyldiphenylsilyl moiety was introduced into iridium(III) complex as the signaling unit for sensing F- with the quenched phosphorescence. Thus, the dual-emissive Pdots can rapidly and accurately detect F- in aqueous media and live cells as a ratiometric probe by measuring the change in the ratio of the F--sensitive red phosphorescence from iridium(III) complex to the F--insensitive blue fluorescence from polyfluorene. Moreover, the interaction of Pdots with F- also changes its emission lifetime, and the lifetime-based detection of F- in live cells has been realized through photoluminescence lifetime imaging microscopy for the first time. Both the ratiometric luminescence and lifetime imaging have been demonstrated to be resistant to external influences, such as the probe’s concentration and excitation power. This study provides a new perspective for the design of promising Pdots-based probes for biological applications.

  11. Dual-emissive Polymer Dots for Rapid Detection of Fluoride in Pure Water and Biological Systems with Improved Reliability and Accuracy.

    PubMed

    Zhao, Qiang; Zhang, Chuanqi; Liu, Shujuan; Liu, Yahong; Zhang, Kenneth Yin; Zhou, Xiaobo; Jiang, Jiayang; Xu, Wenjuan; Yang, Tianshe; Huang, Wei

    2015-01-01

    It is of paramount importance to develop new probes that can selectively, sensitively, accurately and rapidly detect fluoride in aqueous media and biological systems, because F(-) is found to be closely related to many health and environmental concerns. Herein, a dual-emissive conjugated polyelectrolyte P1 containing phosphorescent iridium(III) complex was designed and synthesized, which can form ultrasmall polymer dots (Pdots) in aqueous media. The F(-)-responsive tert-butyldiphenylsilyl moiety was introduced into iridium(III) complex as the signaling unit for sensing F(-) with the quenched phosphorescence. Thus, the dual-emissive Pdots can rapidly and accurately detect F(-) in aqueous media and live cells as a ratiometric probe by measuring the change in the ratio of the F(-)-sensitive red phosphorescence from iridium(III) complex to the F(-)-insensitive blue fluorescence from polyfluorene. Moreover, the interaction of Pdots with F(-) also changes its emission lifetime, and the lifetime-based detection of F(-) in live cells has been realized through photoluminescence lifetime imaging microscopy for the first time. Both the ratiometric luminescence and lifetime imaging have been demonstrated to be resistant to external influences, such as the probe's concentration and excitation power. This study provides a new perspective for the design of promising Pdots-based probes for biological applications. PMID:26552859

  12. Thomas Jefferson and the Constitution.

    ERIC Educational Resources Information Center

    Peterson, Merrill D.

    1987-01-01

    Examines Thomas Jefferson's role in the making and interpretation of the United States Constitution. Discusses the dominant features of Jefferson's constitutional theory; the character of Jefferson's presidency; and Jefferson's ongoing concern about constitutional preservation and change. Lists important dates in the history of the constitution.…

  13. The Constitution in Other Lands.

    ERIC Educational Resources Information Center

    Bill of Rights in Action, 1987

    1987-01-01

    Designed for classroom teaching, this document contains articles on the new constitutions of Japan, South Korea, and the Philippine Islands which were modeled in part on the U.S. Constitution. These countries' experiences with constitutional government are examined, and whether or not the U.S. Constitution can be a suitable model for other…

  14. Comparison between Monte Carlo simulation and measurement with a 3D polymer gel dosimeter for dose distributions in biological samples.

    PubMed

    Furuta, T; Maeyama, T; Ishikawa, K L; Fukunishi, N; Fukasaku, K; Takagi, S; Noda, S; Himeno, R; Hayashi, S

    2015-08-21

    In this research, we used a 135 MeV/nucleon carbon-ion beam to irradiate a biological sample composed of fresh chicken meat and bones, which was placed in front of a PAGAT gel dosimeter, and compared the measured and simulated transverse-relaxation-rate (R2) distributions in the gel dosimeter. We experimentally measured the three-dimensional R2 distribution, which records the dose induced by particles penetrating the sample, by using magnetic resonance imaging. The obtained R2 distribution reflected the heterogeneity of the biological sample. We also conducted Monte Carlo simulations using the PHITS code by reconstructing the elemental composition of the biological sample from its computed tomography images while taking into account the dependence of the gel response on the linear energy transfer. The simulation reproduced the experimental distal edge structure of the R2 distribution with an accuracy under about 2 mm, which is approximately the same as the voxel size currently used in treatment planning. PMID:26266894

  15. Comparison between Monte Carlo simulation and measurement with a 3D polymer gel dosimeter for dose distributions in biological samples

    NASA Astrophysics Data System (ADS)

    Furuta, T.; Maeyama, T.; Ishikawa, K. L.; Fukunishi, N.; Fukasaku, K.; Takagi, S.; Noda, S.; Himeno, R.; Hayashi, S.

    2015-08-01

    In this research, we used a 135 MeV/nucleon carbon-ion beam to irradiate a biological sample composed of fresh chicken meat and bones, which was placed in front of a PAGAT gel dosimeter, and compared the measured and simulated transverse-relaxation-rate (R2) distributions in the gel dosimeter. We experimentally measured the three-dimensional R2 distribution, which records the dose induced by particles penetrating the sample, by using magnetic resonance imaging. The obtained R2 distribution reflected the heterogeneity of the biological sample. We also conducted Monte Carlo simulations using the PHITS code by reconstructing the elemental composition of the biological sample from its computed tomography images while taking into account the dependence of the gel response on the linear energy transfer. The simulation reproduced the experimental distal edge structure of the R2 distribution with an accuracy under about 2 mm, which is approximately the same as the voxel size currently used in treatment planning.

  16. Protein-Style Dynamical Transition in a Non-Biological Polymer and a Non-Aqueous Solvent.

    PubMed

    Mamontov, E; Sharma, V K; Borreguero, J M; Tyagi, M

    2016-03-31

    Temperature-dependent onset of apparent anharmonicity in the microscopic dynamics of hydrated proteins and other biomolecules has been known as protein dynamical transition for the last quarter of a century. Using neutron scattering and molecular dynamics simulation, techniques most often associated with protein dynamical transition studies, we have investigated the microscopic dynamics of one of the most common polymers, polystyrene, which was exposed to toluene vapor, mimicking the process of protein hydration from water vapor. Polystyrene with adsorbed toluene is an example of a solvent-solute system, which, unlike biopolymers, is anhydrous and lacks hydrogen bonding. Nevertheless, it exhibits the essential traits of the dynamical transition in biomolecules, such as a specific dependence of the microscopic dynamics of both solvent and host on the temperature and the amount of solvent adsorbed. We conclude that the protein dynamical transition is a manifestation of a universal solvent-solute dynamical relationship, which is not specific to either biomolecules as solute, or aqueous media as solvent, or even a particular type of interactions between solvent and solute.

  17. Constitution, 30 September 1987.

    PubMed

    1987-01-01

    This document reprints provisions of Suriname's 1987 Constitution relating to freedom of movement, equality of the sexes, the right to life, the right to physical integrity, equal opportunity in employment, the family, children, maternity benefits, the right to health care, parental responsibilities, free and compulsory education, illiteracy, and housing. All citizens enjoy freedom of movement within the bounds of the law. All people within the territory may claim protection of their person and property, and discrimination is forbidden on the basis of birth, sex, race, language, religion, education, political beliefs, economic position, or other status. Torture or inhuman treatment and punishment is banned, and the right to life is protected by the law. The state guarantees the right to work, and all employees have the right to equal remuneration for equal work, safe working conditions, and sufficient rest and recreation. The family is protected, and husbands and wives are equal before the law. Children have the right to protection, and working women are entitled to paid maternity leave. The state promotes the right to good health by systematic improvements in living and working conditions and dissemination of health education. The right to education is protected by the provision of free general primary education and efforts of the state to enable all citizens to achieve the highest educational levels possible. The Constitution also calls for the institution of a plan to allow the state to create public housing.

  18. Ethics and constitutional government.

    PubMed

    Albright, James A

    2007-01-01

    The term ethics refers to a set of principles that govern acceptable, proper conduct. Attacks on the Constitution of the United States pose the most serious breach of ethics today. Our country was founded as a republic, not as a democracy. Our Founding Fathers' main concern was to protect citizens from the power of the federal government, so constitutionally, the central government has little or no authority over individual citizens except on federal property. One of the major problems today is the fact that we now have professional politicians. This is due in large part to the lure of financial gain from countless special interest groups. This would change under constitutional law because the federal budget would decrease drastically. Article 1 states that all legislative power is vested in Congress. Congress has only 18 enumerated powers, and almost half of these pertain to defense of the country. Many of our current problems are due to regulatory agencies that have become independent fiefdoms with unconstitutional legislative, as well as executive and judicial, powers. The regulatory agency most relevant to medicine, both clinical care and research, is the FDA. It is now obvious that its basic structure needs to be changed or abolished because its actions are identical to those inherent in authoritarian systems. Constructive change could come from Congress, but it would be most desirable if the Supreme Court would take the lead and reestablish the authority of the Constitution as the Supreme Law of the Land. The FDA's function could be limited to the determination of safety, but preferably its mission would be altered to that of product certification. Defenders of the current system claim that such a drastic change would be too dangerous and their prime example is thalidomide. But it is now known that the market has already solved that problem prior to the government-imposed sanctions. Realistically, market forces and their ramifications, including our legal

  19. Ethics and constitutional government.

    PubMed

    Albright, James A

    2007-01-01

    The term ethics refers to a set of principles that govern acceptable, proper conduct. Attacks on the Constitution of the United States pose the most serious breach of ethics today. Our country was founded as a republic, not as a democracy. Our Founding Fathers' main concern was to protect citizens from the power of the federal government, so constitutionally, the central government has little or no authority over individual citizens except on federal property. One of the major problems today is the fact that we now have professional politicians. This is due in large part to the lure of financial gain from countless special interest groups. This would change under constitutional law because the federal budget would decrease drastically. Article 1 states that all legislative power is vested in Congress. Congress has only 18 enumerated powers, and almost half of these pertain to defense of the country. Many of our current problems are due to regulatory agencies that have become independent fiefdoms with unconstitutional legislative, as well as executive and judicial, powers. The regulatory agency most relevant to medicine, both clinical care and research, is the FDA. It is now obvious that its basic structure needs to be changed or abolished because its actions are identical to those inherent in authoritarian systems. Constructive change could come from Congress, but it would be most desirable if the Supreme Court would take the lead and reestablish the authority of the Constitution as the Supreme Law of the Land. The FDA's function could be limited to the determination of safety, but preferably its mission would be altered to that of product certification. Defenders of the current system claim that such a drastic change would be too dangerous and their prime example is thalidomide. But it is now known that the market has already solved that problem prior to the government-imposed sanctions. Realistically, market forces and their ramifications, including our legal

  20. Constitutive equations of ageing polymeric materials

    NASA Technical Reports Server (NTRS)

    Peng, S. T. J.

    1985-01-01

    The constitutive equation for the relaxation behavior of time-dependent, chemically unstable materials developed by Valanis and Peng (1983), which used the irreversible thermodynamics of internal variables in Eyring's absolute reaction theory and yielded a theoretical expression for the effect of chemical crosslink density on the relaxation rate, is presently applied to the creep behavior of a network polymer which is undergoing a scission process. In particular, two equations are derived which may for the first time show the relations between mechanical models and internal variables in the creep expressions, using a three-element model with a Maxwell element.

  1. Polymer films

    DOEpatents

    Granick, Steve; Sukhishvili, Svetlana A.

    2008-12-30

    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.

  2. Polymer films

    DOEpatents

    Granick, Steve; Sukhishvili, Svetlana A.

    2004-05-25

    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.

  3. Constitution, 5 May 1989.

    PubMed

    1989-01-01

    This document contains provisions of Cambodia's Constitution of May 5, 1989. Article 7 gives men and women equal rights in marriage and the family, calls for monogamous marriages, and affords social protection to mothers and children. Article 8 guides parent-child relationships. The 14th article defines state property, and the 15th gives citizens full rights to own, use, and inherit land. The use of agricultural and forested land can only be changed with permission. Article 22 assigns educational responsibilities to the state, including free elementary education and a gradual expansion of higher education. Adult literacy classes are also promoted. Article 26 guarantees free medical consultations, and article 27 gives women a 90-day paid maternity leave. Breast-feeding women are also given special privileges. Article 33 guarantees the right to pay equity and to social security benefits. Article 36 grants the freedom to travel, the inviolability of homes, and privacy in correspondence of all types.

  4. Constitution, 5 October 1988.

    PubMed

    1989-01-01

    This document contains major provisions of the constitution adopted by Brazil on 5 October 1988. This constitution seeks to promote the welfare of all citizens without discrimination. The equality of all citizens is guaranteed, and the equal rights of women are specifically mentioned. Property rights are also guaranteed and defined. Female inmates are granted the right to remain with their children while breast feeding. Workers are guaranteed a minimum wage, a family allowance for dependents, maternity/paternity leave, specific incentives to protect the labor market for women, retirement benefits, free day care for preschool-age children, pay equity, and equal rights between tenured and sporadically employed workers. Agrarian reform provisions are given, including the authority to expropriate land. Social and economic policies to promote health are called for, and public health services are to be decentralized, to be integrated, and to foster community participation. Pension plan and social assistance provisions are outlined as are duties of the state in regard to education. The amount of money to be dedicated to education is set out, and a national educational plan is called for to achieve such goals as the eradication of illiteracy, the universalization of school attendance, the improvement of instruction, and the provision of vocational training. Specific measures are set out to protect and preserve the environment. Family policy deals with issues of marriage, the definition of a family, divorce, the right to family planning services, and the deterrence of domestic violence. Social protection provisions cover mothers and children, handicapped persons, and protection of minors. Finally, the customs and rights of Indians are protected, with special provisions given to protect land tenure and to protect the rights of Indians in water resource development and prospecting and mining activities. PMID:12344286

  5. Constitution, 5 October 1988.

    PubMed

    1989-01-01

    This document contains major provisions of the constitution adopted by Brazil on 5 October 1988. This constitution seeks to promote the welfare of all citizens without discrimination. The equality of all citizens is guaranteed, and the equal rights of women are specifically mentioned. Property rights are also guaranteed and defined. Female inmates are granted the right to remain with their children while breast feeding. Workers are guaranteed a minimum wage, a family allowance for dependents, maternity/paternity leave, specific incentives to protect the labor market for women, retirement benefits, free day care for preschool-age children, pay equity, and equal rights between tenured and sporadically employed workers. Agrarian reform provisions are given, including the authority to expropriate land. Social and economic policies to promote health are called for, and public health services are to be decentralized, to be integrated, and to foster community participation. Pension plan and social assistance provisions are outlined as are duties of the state in regard to education. The amount of money to be dedicated to education is set out, and a national educational plan is called for to achieve such goals as the eradication of illiteracy, the universalization of school attendance, the improvement of instruction, and the provision of vocational training. Specific measures are set out to protect and preserve the environment. Family policy deals with issues of marriage, the definition of a family, divorce, the right to family planning services, and the deterrence of domestic violence. Social protection provisions cover mothers and children, handicapped persons, and protection of minors. Finally, the customs and rights of Indians are protected, with special provisions given to protect land tenure and to protect the rights of Indians in water resource development and prospecting and mining activities.

  6. Synthesis, physical characterization, and biological performance of sequential homointerpenetrating polymer network sponges based on poly(2-hydroxyethyl methacrylate).

    PubMed

    Lou, X; Vijayasekaran, S; Chirila, T V; Maley, M A; Hicks, C R; Constable, I J

    1999-12-01

    A limitation in the use of hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) sponges as implantable devices is their inherently poor mechanical strength. This precludes proper surgical manipulation, especially in the eye where the size of the implant is usually small. In this study a new method was developed to produce mechanically stronger PHEMA sponges. Sequential homointerpenetrating polymer network (homo-IPN) sponges were made by using HEMA as the precursor for generating both the first network and the successive interpenetrated networks. Following the formation of network I, the sponge was squeezed to remove the interstitial water, soaked in the second monomer (also HEMA), and squeezed again to remove the excess monomer from the pores before being subjected to the second polymerization leading to the formation of network II. Two two-component IPN sponges (K2 and K4) with increasing HEMA content in the network II and a three-component IPN sponge (K3) were produced, and their properties were compared to those of a homopolymer PHEMA sponge (control). Apart from elongation, the tensile properties were all significantly enhanced in the IPN sponges; the water content was the same as in the control sponge, except for sponge K4, which was lower. Light microscopy revealed similar pore morphologies of the control and IPN sponges K2 and K3, and the majority of the pores were around 25 microm. Sponge K4 displayed smaller pores of around 10 microm. Cellular invasion into the sponges was examined in vitro (incubation with 3T3 fibroblasts) and in vivo (implantation in rabbit corneas). Although the in vitro assay detected a change in the cell behavior in the early stage of invasion, which was probably due to the formation of IPNs, such changes were not reflected in the longer term in vivo experiment. There was a proper integration of sponges K2 and K3 with the corneal stroma, but much less cellular invasion and no neovascularization in sponge K4. We concluded that IPN

  7. Modeling semiflexible polymer networks

    NASA Astrophysics Data System (ADS)

    Broedersz, C. P.; MacKintosh, F. C.

    2014-07-01

    This is an overview of theoretical approaches to semiflexible polymers and their networks. Such semiflexible polymers have large bending rigidities that can compete with the entropic tendency of a chain to crumple up into a random coil. Many studies on semiflexible polymers and their assemblies have been motivated by their importance in biology. Indeed, cross-linked networks of semiflexible polymers form a major structural component of tissue and living cells. Reconstituted networks of such biopolymers have emerged as a new class of biological soft matter systems with remarkable material properties, which have spurred many of the theoretical developments discussed here. Starting from the mechanics and dynamics of individual semiflexible polymers, the physics of semiflexible bundles, entangled solutions, and disordered cross-linked networks are reviewed. Finally, recent developments on marginally stable fibrous networks, which exhibit critical behavior similar to other marginal systems such as jammed soft matter, are discussed.

  8. Polymers with pendant ferrocenes.

    PubMed

    Pietschnig, Rudolf

    2016-10-01

    The tailoring of smart material properties is one of the challenges in materials science. The unique features of polymers with pendant ferrocene units, either as ferrocenyl or ferrocenediyl groups, provide electrochemical, electronic, optoelectronic, catalytic, and biological properties with potential for applications as smart materials. The possibility to tune or to switch the properties of such materials relies mostly on the redox activity of the ferrocene/ferricenium couple. By switching the redox state of ferrocenyl units - separately or in a cooperative fashion - charge, polarity, color (UV-vis range) and hydrophilicity of polymers, polymer functionalized surfaces and polymer derived networks (sol-gel) may be controlled. In turn, also the vicinity of such polymers influences the redox behavior of the pendant ferrocenyl units allowing for sensing applications by using polymer bound enzymes as triggering units. In this review the focus is set mainly on the literature of the past five years.

  9. Constitutive models in LAME.

    SciTech Connect

    Hammerand, Daniel Carl; Scherzinger, William Mark

    2007-09-01

    The Library of Advanced Materials for Engineering (LAME) provides a common repository for constitutive models that can be used in computational solid mechanics codes. A number of models including both hypoelastic (rate) and hyperelastic (total strain) constitutive forms have been implemented in LAME. The structure and testing of LAME is described in Scherzinger and Hammerand ([3] and [4]). The purpose of the present report is to describe the material models which have already been implemented into LAME. The descriptions are designed to give useful information to both analysts and code developers. Thus far, 33 non-ITAR/non-CRADA protected material models have been incorporated. These include everything from the simple isotropic linear elastic models to a number of elastic-plastic models for metals to models for honeycomb, foams, potting epoxies and rubber. A complete description of each model is outside the scope of the current report. Rather, the aim here is to delineate the properties, state variables, functions, and methods for each model. However, a brief description of some of the constitutive details is provided for a number of the material models. Where appropriate, the SAND reports available for each model have been cited. Many models have state variable aliases for some or all of their state variables. These alias names can be used for outputting desired quantities. The state variable aliases available for results output have been listed in this report. However, not all models use these aliases. For those models, no state variable names are listed. Nevertheless, the number of state variables employed by each model is always given. Currently, there are four possible functions for a material model. This report lists which of these four methods are employed in each material model. As far as analysts are concerned, this information is included only for the awareness purposes. The analyst can take confidence in the fact that model has been properly implemented

  10. How Democratic Is the Constitution?

    ERIC Educational Resources Information Center

    Goldwin, Robert A., Ed.; Schambra, William A., Ed.

    Designed to help prepare the nation for a thoughtful observance of the Constitutional bicentennial, this publication contains seven essays on the topic of democracy and the Constitution. "Democracy and the Constitution" (Gordon S. Wood) looks at the popular and democratic rhetoric used to justify the federalist system in the late 1700's. "Decent,…

  11. Constitution, 3 February 1987.

    PubMed

    1987-01-01

    This document contains provisions of the 1987 Constitution of the Philippines. The state policies reprinted from Article 2 note that the state recognizes the sanctity of family life and protects the life of the mother and of the unborn from conception. Women and men are afforded equality before the law. The state prioritizes education, science and technology, arts, culture, and sports and promotes comprehensive rural development and agrarian reform. Provisions reprinted from Article 13 (Social Justice and Human Rights) cover agrarian and natural resources reform, urban land reform and housing, health, and protection of women in the workforce. Sections from Article 14 (Education, Science and Technology, Arts, Culture, and Sports) set forth the state's duty to make quality education accessible to all citizens through a compulsory system of free public education, provision of incentives to deserving students, encouragement of informal education, and provision of adult education. Article 15, on the family, recognizes the family as the foundation of the nation and marriage as the foundation of the family. Spouses have the right to found a family, children have the right to appropriate care, the family has the right to a living wage and income, families or family associations have the right to participate in the planning and implementation of policies and programs that affect them, and the family has the duty to care for its elderly.

  12. Amendment to the Constitution.

    PubMed

    1988-01-01

    This Amendment rewrites Clause 4 of Article 10 of the Chinese Constitution to permit the right of land use to be transferred by lease in accordance with the law. In December 1988, the Government also enacted legislation amending the Land Management Law so as to allow for the transfer of Land. See Renmin Ribao (Beijing), 31 December 1988, p. 4; Foreign Broadcast Information Service, FBIS-CHI-89-003, 5 January 1989, pp. 38-39. Provisional Regulations on the Land Use Tax in Urban Areas were promulgated on 27 September 1988. See Xinhua Domestic Service (Beijing), 4 October 1988, Foreign Broadcast Information Service, FBIS-CHI-88-197, 12 October 1988, pp. 26-27, and Xinhua (Beijing), 4 October 1988, FBIS-CHI-88-193, 5 October 1988, pp. 20. Provisional Tax Regulations on Farmland Occupation and Use were proclaimed on 1 April 1987. See Xinhua Domestic Service (Beijing), 19 April 1987; Joint Publications Research Service, China, 22 April 1987, pp. K33-K35. PMID:12289449

  13. Constitution, 1989. [Selected provisions].

    PubMed

    1989-01-01

    Chapter XII of the Hungarian Constitution, 1989, details the Fundamental Rights and Duties of Citizens. Everyone lawfully within the territory of Hungary has the right to liberty of movement and the freedom to choose his or her residence, except when restricted by law, including the right to leave his or her residence or county. The Republic of Hungary grants asylum to foreign citizens who were persecuted for racial, religious ethnic, linguistic, or political reasons. Men and women shall equally enjoy all civil, political, economic, social and political rights. Mothers are entitled to special care and protection before and after childbirth; women and juveniles are protected at work by special regulations. Every child has the right to special care an assistance from his or her family, the State, and society, for appropriate physical, spiritual, and moral development. Parents shall decide the kind of education their children receive. Hungary grants equal rights to all person within its territories, without regard to race, color, sex, language, religion, political, or other opinion, national, and social origin, property, birth and other status. Prejudicial discrimination shall be severely punished. Everyone has the right to work, to the free choice of employment and profession and to equal pay for equal work. Citizens have the right to social security, including social services necessary in old age, sickness, disability, widowhood, orphanhood an unemployment through no fault of their own. Hungary guarantees the right to culture for its citizens and realized this right by free and compulsory elementary education, by secondary and higher education which is accessible to all on the basis of capacity, and by the financial support of those receiving an education.

  14. Essential Medicines in National Constitutions

    PubMed Central

    Toebes, Brigit; Hogerzeil, Hans

    2016-01-01

    Abstract A constitutional guarantee of access to essential medicines has been identified as an important indicator of government commitment to the progressive realization of the right to the highest attainable standard of health. The objective of this study was to evaluate provisions on access to essential medicines in national constitutions, to identify comprehensive examples of constitutional text on medicines that can be used as a model for other countries, and to evaluate the evolution of constitutional medicines-related rights since 2008. Relevant articles were selected from an inventory of constitutional texts from WHO member states. References to states’ legal obligations under international human rights law were evaluated. Twenty-two constitutions worldwide now oblige governments to protect and/or to fulfill accessibility of, availability of, and/or quality of medicines. Since 2008, state responsibilities to fulfill access to essential medicines have expanded in five constitutions, been maintained in four constitutions, and have regressed in one constitution. Government commitments to essential medicines are an important foundation of health system equity and are included increasingly in state constitutions. PMID:27781006

  15. Ion-exchange polymer artificial muscle and actuating system

    NASA Astrophysics Data System (ADS)

    Vial, Dominique; Tondu, Bertrand; Lopez, Pierre; Aurelle, Yves; Ricard, Alain

    1996-04-01

    Chemomechanical transformations are used to produce a mechanical force from a reversible chemical reaction in order to generate artificial muscular contraction, on the model of the biological muscle. The design and experimentation of an original artificial muscle using an ion-exchange polymer which reacts inside a soft envelope, derived from research on pneumatic artificial McKibben muscle, is presented. Then a chemomechanical actuator constituted of two artificial muscles has been conceived: first results are shown on position control in open-loop mode.

  16. Constitutional Issues--Watergate and the Constitution. Teaching with Documents.

    ERIC Educational Resources Information Center

    National Archives and Records Administration, Washington, DC.

    When U.S. President Richard Nixon resigned in 1974 in the wake of the Watergate scandal, it was only the second time that impeachment of a president had been considered. Although the U.S. Constitution has provisions for a person removed from office to be indicted, there are no guidelines in the Constitution about a President who has resigned. The…

  17. Supramolecular Polymers in Aqueous Media.

    PubMed

    Krieg, Elisha; Bastings, Maartje M C; Besenius, Pol; Rybtchinski, Boris

    2016-02-24

    This review discusses one-dimensional supramolecular polymers that form in aqueous media. First, naturally occurring supramolecular polymers are described, in particular, amyloid fibrils, actin filaments, and microtubules. Their structural, thermodynamic, kinetic, and nanomechanical properties are highlighted, as well as their importance for the advancement of biologically inspired supramolecular polymer materials. Second, five classes of synthetic supramolecular polymers are described: systems based on (1) hydrogen-bond motifs, (2) large π-conjugated surfaces, (3) host-guest interactions, (4) peptides, and (5) DNA. We focus on recent studies that address key challenges in the field, providing mechanistic understanding, rational polymer design, important functionality, robustness, or unusual thermodynamic and kinetic properties. PMID:26727633

  18. Directed Assembly of Biological Polymers

    NASA Astrophysics Data System (ADS)

    Miller, Aline

    2009-03-01

    The self-assembly of polypeptides into beta-sheet rich nanofibrils has attracted considerable attention in recent years to both understand amyloidgenesis and for their potential biomaterials applications. This self-assembly process is generic to all proteins where fibrillation is typically induced under harsh conditions of low pH and/or high temperature, which are of course not suitable for biomaterials applications. Here we will outline the method developed in our laboratory to create thermo-reversible fibrillar hydrogels from aqueous solutions of a series of proteins by adding a reductant. Proteins studied include beta-lactoglobulin, ovalbimum, lysozyme and bovine serum albimum; all contain an increasing number of disulfide bridges that are disrupted by the reductant. Such disruption destabilises the native state of the protein and this allows us to form transparent, self-supporting hydrogels under physiological conditions. The potential to control and manipulate the gel properties, including mechanical strength and structure (fibre diameter and mesh size of hydrogel) has been explored by varying the protein (consequently the number of disulfide bridges), protein concentration, reductant concentration and ionic strength of the matrix. Our results will be presented here and similarities and differences highlighted. Furthermore we will present both our 2- and 3-dimensional cell culture experiments that show the gel matrix promotes both fibroblast and chondrocyte cell spreading, attachment and proliferation; indicating our hydrogels gels are biocompatible and they can provide a viable support for different cell types.

  19. Dynamic Ordering and Phase Segregation in Hydrogen-Bonded Polymers.

    PubMed

    Chen, Senbin; Binder, Wolfgang H

    2016-07-19

    Hydrogen bonds (H-bonds) constitute highly relevant structural units of molecular self-assembly. They bridge biological and synthetic sciences, implementing dynamic properties into materials and molecules, not achieved via purely covalent bonds. Phase segregation on the other hand represents another important assembly principle, responsible for, e.g., cell compartimentation, membrane-formation, and microphase segregation in polymers. Yet, despite the expanding elegant synthetic strategies of supramolecular polymers, the investigation of phase behavior of macromolecules driven by H-bonding forces still remains in its infancy. Compared to phase segregation arising from covalently linked block copolymers, the generation of phase segregated nanostructures via supramolecular polymers facilitates the design of novel functional materials, such as those with stimuli-responsive, self-healing, and erasable-material properties. We here discuss the phase segregation of H-bonding polymers in both the solution and solid state, wherein the molecular recognition elements are based on multiple H-bonding moieties, such as thymine/2,6-diamino-pyridine (THY/DAP), thymine/diamino triazine (THY/DAT), and barbiturate/Hamilton wedge (Ba/HW) elements. The specific aggregation of a series of different H-bonding polymers in solution, both linear and dendritic polymers, bearing heterocomplementary H-bonding moieties are described, in particular focusing on the issue of phase segregation. The exploitation of H-bonded supramolecular dendrons with segregating polymer chains leads to the formation of three-phase segregated hierarchical micelles in solution, purely linking the components via H-bonds, in turn displaying a versatile spectrum of segregated morphologies. We also focus on segregation effects of H-bonded amorphous and crystalline polymers: thus the formation of nanostructures, such as disordered micelles and well-ordered body centered cubic (BCC) packed spheres from telechelic polymers

  20. Dynamic Ordering and Phase Segregation in Hydrogen-Bonded Polymers.

    PubMed

    Chen, Senbin; Binder, Wolfgang H

    2016-07-19

    Hydrogen bonds (H-bonds) constitute highly relevant structural units of molecular self-assembly. They bridge biological and synthetic sciences, implementing dynamic properties into materials and molecules, not achieved via purely covalent bonds. Phase segregation on the other hand represents another important assembly principle, responsible for, e.g., cell compartimentation, membrane-formation, and microphase segregation in polymers. Yet, despite the expanding elegant synthetic strategies of supramolecular polymers, the investigation of phase behavior of macromolecules driven by H-bonding forces still remains in its infancy. Compared to phase segregation arising from covalently linked block copolymers, the generation of phase segregated nanostructures via supramolecular polymers facilitates the design of novel functional materials, such as those with stimuli-responsive, self-healing, and erasable-material properties. We here discuss the phase segregation of H-bonding polymers in both the solution and solid state, wherein the molecular recognition elements are based on multiple H-bonding moieties, such as thymine/2,6-diamino-pyridine (THY/DAP), thymine/diamino triazine (THY/DAT), and barbiturate/Hamilton wedge (Ba/HW) elements. The specific aggregation of a series of different H-bonding polymers in solution, both linear and dendritic polymers, bearing heterocomplementary H-bonding moieties are described, in particular focusing on the issue of phase segregation. The exploitation of H-bonded supramolecular dendrons with segregating polymer chains leads to the formation of three-phase segregated hierarchical micelles in solution, purely linking the components via H-bonds, in turn displaying a versatile spectrum of segregated morphologies. We also focus on segregation effects of H-bonded amorphous and crystalline polymers: thus the formation of nanostructures, such as disordered micelles and well-ordered body centered cubic (BCC) packed spheres from telechelic polymers

  1. The Origins of the Constitution.

    ERIC Educational Resources Information Center

    Grindle, Diane

    1987-01-01

    Maintains that there were three forces operating in colonial American culture which led to the drafting of the Constitution. These were: English law and tradition, the lifestyle of the colonies, and the Enlightenment. Provides examples of how these forces were expressed in the events surrounding the birth of the United States Constitution. (JDH)

  2. Constitution And Bylaws: 2004 Edition

    ERIC Educational Resources Information Center

    Distance Education and Training Council, 2004

    2004-01-01

    This document contains the constitution and bylaws of the Distance Education and Training Council. The constitution and bylaws include 13 articles. Sections include: Name; Mission and Goals; Administration of the Council; Membership; Meetings; The Commission; Terms of Office; Officers; Committees; Compensation; Dues and Assessments; Miscellaneous…

  3. The Constitution and Its Critics

    ERIC Educational Resources Information Center

    Main, Thomas J.

    2011-01-01

    In planning a freshman undergraduate curriculum with colleagues recently, the question arose as to what type of understanding educators wanted to impart to their students about the Constitution. The alleged defects of the Constitution that these books point to are wide-ranging and can be classified into various categories. Some problems--such as…

  4. The Constitution and American Radicalism.

    ERIC Educational Resources Information Center

    Lobel, Jules

    1987-01-01

    Discusses the history of the following movements' attitudes towards the Constitution: (1) abolition; (2) feminism; (3) trade unions; (4) socialism and communism; and (5) civil rights and anti-war. Maintains that the tensions in these movements' towards the Constitution represent basic contradictions in the document itself. (PS)

  5. Constitutional Change: A Case Study.

    ERIC Educational Resources Information Center

    Christofferson, Walter D.; Pergande, Donald J.

    1987-01-01

    Presents a lesson for secondary students which teaches that the U.S. Constitution has changed in a variety of ways and that it has a direct effect upon the lives of citizens. Provides a worksheet and a lecture outline covering three methods of constitutional change and Supreme Court cases such as Dred Scott and Brown vs. Board of Education. (GEA)

  6. Microgravity Polymers

    NASA Technical Reports Server (NTRS)

    1986-01-01

    A one-day, interactive workshop considering the effects of gravity on polymer materials science was held in Cleveland, Ohio, on May 9, 1985. Selected programmatic and technical issues were reviewed to introduce the field to workshop participants. Parallel discussions were conducted in three disciplinary working groups: polymer chemistry, polymer physics, and polymer engineering. This proceedings presents summaries of the workshop discussions and conclusions.

  7. Remarks on turbulent constitutive relations

    NASA Technical Reports Server (NTRS)

    Shih, Tsan-Hsing; Lumley, John L.

    1993-01-01

    The paper demonstrates that the concept of turbulent constitutive relations can be used to construct general models for various turbulent correlations. Some of the Generalized Cayley-Hamilton formulas for relating tensor products of higher extension to tensor products of lower extension are introduced. The combination of dimensional analysis and invariant theory can lead to 'turbulent constitutive relations' (or general turbulence models) for, in principle, any turbulent correlations. As examples, the constitutive relations for Reynolds stresses and scalar fluxes are derived. The results are consistent with ones from Renormalization Group (RNG) theory and two-scale Direct-Interaction Approximation (DIA) method, but with a more general form.

  8. Polymers for Drug Delivery Systems

    PubMed Central

    Liechty, William B.; Kryscio, David R.; Slaughter, Brandon V.; Peppas, Nicholas A.

    2012-01-01

    Polymers have played an integral role in the advancement of drug delivery technology by providing controlled release of therapeutic agents in constant doses over long periods, cyclic dosage, and tunable release of both hydrophilic and hydrophobic drugs. From early beginnings using off-the-shelf materials, the field has grown tremendously, driven in part by the innovations of chemical engineers. Modern advances in drug delivery are now predicated upon the rational design of polymers tailored for specific cargo and engineered to exert distinct biological functions. In this review, we highlight the fundamental drug delivery systems and their mathematical foundations and discuss the physiological barriers to drug delivery. We review the origins and applications of stimuli-responsive polymer systems and polymer therapeutics such as polymer-protein and polymer-drug conjugates. The latest developments in polymers capable of molecular recognition or directing intracellular delivery are surveyed to illustrate areas of research advancing the frontiers of drug delivery. PMID:22432577

  9. Abnormal human sex chromosome constitutions

    SciTech Connect

    1993-12-31

    Chapter 22, discusses abnormal human sex chromosome constitution. Aneuploidy of X chromosomes with a female phenotype, sex chromosome aneuploidy with a male phenotype, and various abnormalities in X chromosome behavior are described. 31 refs., 2 figs.

  10. The Constitution's Prescription for Freedom.

    ERIC Educational Resources Information Center

    Peach, Lucinda

    1986-01-01

    Examines how the framers of the Constitution came to choose our system of government, how that system was designed to function, and how the separation of powers has served to maintain our democracy despite attempts to violate it. (JDH)

  11. Constitutive modeling for isotropic materials

    NASA Technical Reports Server (NTRS)

    Ramaswamy, V. G.; Vanstone, R. H.; Dame, L. T.; Laflen, J. H.

    1984-01-01

    The unified constitutive theories for application to typical isotropic cast nickel base supperalloys used for air-cooled turbine blades were evaluated. The specific modeling aspects evaluated were: uniaxial, monotonic, cyclic, creep, relaxation, multiaxial, notch, and thermomechanical behavior. Further development of the constitutive theories to model thermal history effects, refinement of the material test procedures, evaluation of coating effects, and verification of the models in an alternate material will be accomplished in a follow-on for this base program.

  12. Molecular dynamics modeling the synthetic and biological polymers interactions pre-studied via docking: anchors modified polyanions interference with the HIV-1 fusion mediator.

    PubMed

    Tsvetkov, Vladimir B; Serbin, Alexander V

    2014-06-01

    In previous works we reported the design, synthesis and in vitro evaluations of synthetic anionic polymers modified by alicyclic pendant groups (hydrophobic anchors), as a novel class of inhibitors of the human immunodeficiency virus type 1 (HIV-1) entry into human cells. Recently, these synthetic polymers interactions with key mediator of HIV-1 entry-fusion, the tri-helix core of the first heptad repeat regions [HR1]3 of viral envelope protein gp41, were pre-studied via docking in terms of newly formulated algorithm for stepwise approximation from fragments of polymeric backbone and side-group models toward real polymeric chains. In the present article the docking results were verified under molecular dynamics (MD) modeling. In contrast with limited capabilities of the docking, the MD allowed of using much more large models of the polymeric ligands, considering flexibility of both ligand and target simultaneously. Among the synthesized polymers the dinorbornen anchors containing alternating copolymers of maleic acid were selected as the most representative ligands (possessing the top anti-HIV activity in vitro in correlation with the highest binding energy in the docking). To verify the probability of binding of the polymers with the [HR1]3 in the sites defined via docking, various starting positions of polymer chains were tried. The MD simulations confirmed the main docking-predicted priority for binding sites, and possibilities for axial and belting modes of the ligands-target interactions. Some newly MD-discovered aspects of the ligand's backbone and anchor units dynamic cooperation in binding the viral target clarify mechanisms of the synthetic polymers anti-HIV activity and drug resistance prevention.

  13. Functional Supramolecular Polymers*

    PubMed Central

    Aida, T.; Meijer, E.W.; Stupp, S.I.

    2012-01-01

    Supramolecular polymers can be random and entangled coils with the mechanical properties of plastics and elastomers, but with great capacity for processability, recycling, and self-healing due to their reversible monomer-to-polymer transitions. At the other extreme, supramolecular polymers can be formed by self-assembly among designed subunits to yield shape-persistent and highly ordered filaments. The use of strong and directional interactions among molecular subunits can achieve not only rich dynamic behavior but also high degrees of internal order that are not known in ordinary polymers. They can resemble, for example, the ordered and dynamic one-dimensional supramolecular assemblies of the cell cytoskeleton, and possess useful biological and electronic functions. PMID:22344437

  14. A phenomenological constitutive model for low density polyurethane foams

    SciTech Connect

    Neilsen, M.K.; Morgan, H.S.; Krieg, R.D.

    1987-04-01

    Results from a series of hydrostatic and triaxial compression tests which were performed on polyurethane foams are presented in this report. These tests indicate that the volumetric and deviatoric parts of the foam behavior are strongly coupled. This coupling behavior could not be captured with any of several commonly used plasticity models. Thus, a new constitutive model was developed. This new model was based on a decomposition of the foam response into two parts: (1) response of the polymer skeleton, and (2) response of the air inside the cells. The air contribution was completely volumetric. The new constitutive model was implemented in two finite element codes, SANCHO and PRONTO. Results from a series of analyses completed with these codes indicated that the new constitutive model captured all of the foam behaviors that had been observed in the experiments. Finally, a typical dynamic problem was analyzed using the new constitutive model and other constitutive models to demonstrate differences between the models. Results from this series of analyses indicated that the new constitutive model generated displacement and acceleration predictions that were between predictions obtained using the other models. This result was expected. 9 refs., 45 figs., 4 tabs.

  15. Immigration, naturalization and the Constitution.

    PubMed

    Vecoli, R J

    1987-03-01

    This essay focuses upon major decisions made by the US government affecting aliens and the constitutional bases for them. These include: 1) the admission and exclusion of aliens, 2) the deportation of aliens, 3) the rights of aliens within the US, and 4) naturalization and denaturalization. The recourse to the extra-constitutional doctrine of sovereignty by the Supreme Court was the source of the plenary power of the Congress over immigration, thus denying the authority of the judiciary to extend the guarantees of due process of law and the equal protection of the law to aliens. The courts in the last 2 decades have assumed a more activist posture with respect to the rights of aliens, extending a greater degree of constitutional protection to the security of acquired citizenship and to the rights of due process and equal protection of foreigners, even to undocumented aliens.

  16. Micromechanical model for isolated polymer-colloid clusters under tension

    NASA Astrophysics Data System (ADS)

    Dargazany, Roozbeh; Lin, Jiaqi; Khalili, Leila; Itskov, Mikhail; Chen, Hsieh; Alexander-Katz, Alfredo

    2016-10-01

    Binary polymer-colloid (PC) composites form the majority of biological load-bearing materials. Due to the abundance of the polymer and particles, and their simple aggregation process, PC clusters are used broadly by nature to create biomaterials with a variety of functions. However, our understanding of the mechanical features of the clusters and their load transfer mechanism is limited. Our main focus in this paper is the elastic behavior of close-packed PC clusters formed in the presence of polymer linkers. Therefore, a micromechanical model is proposed to predict the constitutive behavior of isolated polymer-colloid clusters under tension. The mechanical response of a cluster is considered to be governed by a backbone chain, which is the stress path that transfers most of the applied load. The developed model can reproduce the mean behavior of the clusters and is not dependent on their local geometry. The model utilizes four geometrical parameters for defining six shape descriptor functions which can affect the geometrical change of the clusters in the course of deformation. The predictions of the model are benchmarked against an extensive set of simulations by coarse-grained-Brownian dynamics, where clusters with different shapes and sizes were considered. The model exhibits good agreement with these simulations, which, besides its relative simplicity, makes the model an excellent add-on module for implementation into multiscale models of nanocomposites.

  17. Piezoelectric Polymers

    NASA Technical Reports Server (NTRS)

    Harrison, J. S.; Ounaies, Z.; Bushnell, Dennis M. (Technical Monitor)

    2001-01-01

    The purpose of this review is to detail the current theoretical understanding of the origin of piezoelectric and ferroelectric phenomena in polymers; to present the state-of-the-art in piezoelectric polymers and emerging material systems that exhibit promising properties; and to discuss key characterization methods, fundamental modeling approaches, and applications of piezoelectric polymers. Piezoelectric polymers have been known to exist for more than forty years, but in recent years they have gained notoriety as a valuable class of smart materials.

  18. Constitutional Reform of School Finance.

    ERIC Educational Resources Information Center

    Alexander, Kern, Ed.; Jordan, K. Forbis, Ed.

    This book contains conference papers by experts in educational administration, law, and economics. Six of the papers are devoted to a legal analysis of fiscal inequality among school attendance units, school districts, and States. These contributions are: (1) K. Forbis Jordan and Kern Alexander, "Constitutional Methods of Financing Public…

  19. Civil Liberties under State Constitutions.

    ERIC Educational Resources Information Center

    Tarr, G. Alan

    1988-01-01

    Discusses "new judicial federalism" as the rediscovery of state bills of rights for protecting civil liberties. Analyzes the differences in protection under state and federal bills of rights. Recommends that the growing importance of state constitutions be included in the political science curriculum and suggests bibliographic sources to be used.…

  20. Take Advantage of Constitution Day

    ERIC Educational Resources Information Center

    McCune, Bonnie F.

    2008-01-01

    The announcement of the mandate for Constitution and Citizenship Day shortly before September, 2005, probably led to groans of dismay. Not another "must-do" for teachers and schools already stressed by federal and state requirements for standardized tests, increasingly rigid curricula, and scrutiny from the public and officials. But the idea and…

  1. Lazy Elephants and the Constitution.

    ERIC Educational Resources Information Center

    Hantula, James

    1989-01-01

    Depicts an eighth grade unit utilizing the production of a newspaper to teach U.S. history, 1787 to 1791, in a combined social studies and language arts class at Malcolm Price Laboratory School (Iowa). Two teachers used both large- and small-group instruction to focus on the development of the U.S. Constitution. (LS)

  2. Photoaddressable Polymers

    NASA Astrophysics Data System (ADS)

    Bieringer, T.

    Polymers are the perfect materials for a variety of applications in almost every field of technical as well as human life. Because of their macromolecular architecture there are a lot of degrees of freedom in the synthesis of polymers. Owing to the change of their functional composition, they can be tailored even for quite difficult demands. Since a whole industry deals with the processing of polymers, cheap production lines have been developed for almost every polymer. This is the reason why not only the molecular composition but even the price of polymers has been optimized. Therefore these materials can be considered as encouraging components even in highly sophisticated areas of applications.

  3. Conjugated Polymer-Based Hybrid Nanoparticles with Two-Photon Excitation and Near-Infrared Emission Features for Fluorescence Bioimaging within the Biological Window.

    PubMed

    Lv, Yanlin; Liu, Peng; Ding, Hui; Wu, Yishi; Yan, Yongli; Liu, Heng; Wang, Xuefei; Huang, Fei; Zhao, Yongsheng; Tian, Zhiyuan

    2015-09-23

    Hybrid fluorescent nanoparticles (NPs) capable of fluorescing near-infrared (NIR) light (centered ∼730 nm) upon excitation of 800 nm laser light were constructed. A new type of conjugated polymer with two-photon excited fluorescence (TPEF) feature, P-F8-DPSB, was used as the NIR-light harvesting component and the energy donor while a NIR fluorescent dye, DPA-PR-PDI, was used as the energy acceptor and the NIR-light emitting component for the construction of the fluorescent NPs. The hybrid NPs possess δ value up to 2.3 × 10(6) GM per particle upon excitation of 800 nm pulse laser. The excellent two-photon absorption (TPA) property of the conjugated polymer component, together with its high fluorescence quantum yield (ϕ) up to 45% and the efficient energy transfer from the conjugated polymer to NIR-emitting fluorophore with efficiency up to 90%, imparted the hybrid NPs with TPEF-based NIR-input-NIR-output fluorescence imaging ability with penetration depth up to 1200 μm. The practicability of the hybrid NPs for fluorescence imaging in Hela cells was validated. PMID:26340609

  4. Antifouling Polymer Brushes Displaying Antithrombogenic Surface Properties.

    PubMed

    de los Santos Pereira, Andres; Sheikh, Sonia; Blaszykowski, Christophe; Pop-Georgievski, Ognen; Fedorov, Kiril; Thompson, Michael; Rodriguez-Emmenegger, Cesar

    2016-03-14

    The contact of blood with artificial materials generally leads to immediate protein adsorption (fouling), which mediates subsequent biological processes such as platelet adhesion and activation leading to thrombosis. Recent progress in the preparation of surfaces able to prevent protein fouling offers a potential avenue to mitigate this undesirable effect. In the present contribution, we have prepared several types of state-of-the-art antifouling polymer brushes on polycarbonate plastic substrate, and investigated their ability to prevent platelet adhesion and thrombus formation under dynamic flow conditions using human blood. Moreover, we compared the ability of such brushes--grafted on quartz via an adlayer analogous to that used on polycarbonate--to prevent protein adsorption from human blood plasma, assessed for the first time by means of an ultrahigh frequency acoustic wave sensor. Results show that the prevention of such a phenomenon constitutes one promising route toward enhanced resistance to thrombus formation, and suggest that antifouling polymer brushes could be of service in biomedical applications requiring extensive blood-material surface contact.

  5. Sex Differences in Constitutive Autophagy

    PubMed Central

    Oliván, Sara; Calvo, Ana Cristina; Manzano, Raquel; Zaragoza, Pilar

    2014-01-01

    Sex bias has been described nowadays in biomedical research on animal models, although sexual dimorphism has been confirmed widely under pathological and physiological conditions. The main objective of our work was to study the sex differences in constitutive autophagy in spinal cord and skeletal muscle tissue from wild type mice. To examine the influence of sex on autophagy, mRNA and proteins were extracted from male and female mice tissues. The expressions of microtubule-associated protein 1 light chain 3 (LC3) and sequestosome 1 (p62), markers to monitor autophagy, were analyzed at 40, 60, 90, and 120 days of age. We found significant sex differences in the expression of LC3 and p62 in both tissues at these ages. The results indicated that sex and tissue specific differences exist in constitutive autophagy. These data underlined the need to include both sexes in the experimental groups to minimize any sex bias. PMID:24719882

  6. [Women, gender, and the Constitution].

    PubMed

    1993-12-01

    Although all the constitutions of Latin America directly or indirectly acknowledge the juridical equality of the sexes, these patriarchal societies continue to maintain institutional power in male hands and to neutralize legal actions favoring women. International instruments such as the Convention on Elimination of All Forms of Discrimination Against Women, approved by the UN in 1979, have given a firmer basis to policies and actions to improve the status of women. Obstacles to full equality of Latin American women are rooted in economic and sociopolitical factors, but lack of true political will also plays a significant role. A number of new laws in the past several years as well as the new Constitution have improved the legal position of Colombian women. The new Constitution recognizes fundamental rights that may be claimed directly before a judge, and social, economic, and collective rights requiring legislative development. Article 43 of the new Constitution states that women will not be subjected to any form of discrimination. Another norm states that women will enjoy special assistance and protection before and after childbirth, in recognition of the social functions of maternity. Article 43 also states that women who are heads of households will receive special assistance, but the corresponding regulations have not yet been promulgated. The mechanism of tutelage has become an important recourse that has been used in several cases in which fundamental rights of women have been violated or threatened because of their sex. The order of tutelage has been used in cases of adolescents expelled from school for pregnancy and of abused wives, as well as to force recognition of the social and economic contributions of housework.

  7. [Women, gender, and the Constitution].

    PubMed

    1993-12-01

    Although all the constitutions of Latin America directly or indirectly acknowledge the juridical equality of the sexes, these patriarchal societies continue to maintain institutional power in male hands and to neutralize legal actions favoring women. International instruments such as the Convention on Elimination of All Forms of Discrimination Against Women, approved by the UN in 1979, have given a firmer basis to policies and actions to improve the status of women. Obstacles to full equality of Latin American women are rooted in economic and sociopolitical factors, but lack of true political will also plays a significant role. A number of new laws in the past several years as well as the new Constitution have improved the legal position of Colombian women. The new Constitution recognizes fundamental rights that may be claimed directly before a judge, and social, economic, and collective rights requiring legislative development. Article 43 of the new Constitution states that women will not be subjected to any form of discrimination. Another norm states that women will enjoy special assistance and protection before and after childbirth, in recognition of the social functions of maternity. Article 43 also states that women who are heads of households will receive special assistance, but the corresponding regulations have not yet been promulgated. The mechanism of tutelage has become an important recourse that has been used in several cases in which fundamental rights of women have been violated or threatened because of their sex. The order of tutelage has been used in cases of adolescents expelled from school for pregnancy and of abused wives, as well as to force recognition of the social and economic contributions of housework. PMID:12287889

  8. Simulations of Polymer Translocation

    NASA Astrophysics Data System (ADS)

    Vocks, H.

    2008-07-01

    Transport of molecules across membranes is an essential mechanism for life processes. These molecules are often long, and the pores in the membranes are too narrow for the molecules to pass through as a single unit. In such circumstances, the molecules have to squeeze -- i.e., translocate -- themselves through the pores. DNA, RNA and proteins are such naturally occuring long molecules in a variety of biological processes. Understandably, the process of translocation has been an active topic of current research: not only because it is a cornerstone of many biological processes, but also due to its relevance for practical applications. Translocation is a complicated process in living organisms -- the presence of chaperone molecules, pH, chemical potential gradients, and assisting molecular motors strongly influence its dynamics. Consequently, the translocation process has been empirically studied in great variety in biological literature. Study of translocation as a biophysical process is more recent. Herein, the polymer is simplified to a sequentially connected string of N monomers as it passes through a narrow pore on a membrane. The quantities of interest are the typical time scale for the polymer to leave a confining cell (the ``escape of a polymer from a vesicle'' time scale), and the typical time scale the polymer spends in the pore (the ``dwell'' time scale) as a function of N and other parameters like membrane thickness, membrane adsorption, electrochemical potential gradient, etc. Our research is focused on computer simulations of translocation. Since our main interest is in the scaling properties, we use a highly simplified description of the translocation process. The polymer is described as a self-avoiding walk on a lattice, and its dynamics consists of single-monomer jumps from one lattice site to another neighboring one. Since we have a very efficient program to simulate such polymer dynamics, which we decribe in Chapter 2, we can perform long

  9. Constitutive modeling for isotropic materials

    NASA Technical Reports Server (NTRS)

    Chan, K. S.; Lindholm, U. S.; Bodner, S. R.

    1988-01-01

    The third and fourth years of a 4-year research program, part of the NASA HOST Program, are described. The program goals were: (1) to develop and validate unified constitutive models for isotropic materials, and (2) to demonstrate their usefulness for structural analysis of hot section components of gas turbine engines. The unified models selected for development and evaluation were those of Bodner-Partom and of Walker. The unified approach for elastic-viscoplastic constitutive equations is a viable method for representing and predicting material response characteristics in the range where strain rate and temperature dependent inelastic deformations are experienced. This conclusion is reached by extensive comparison of model calculations against the experimental results of a test program of two high temperature Ni-base alloys, B1900+Hf and Mar-M247, over a wide temperature range for a variety of deformation and thermal histories including uniaxial, multiaxial, and thermomechanical loading paths. The applicability of the Bodner-Partom and the Walker models for structural applications has been demonstrated by implementing these models into the MARC finite element code and by performing a number of analyses including thermomechanical histories on components of hot sections of gas turbine engines and benchmark notch tensile specimens. The results of the 4-year program have been published in four annual reports. The results of the base program are summarized in this report. The tasks covered include: (1) development of material test procedures, (2) thermal history effects, and (3) verification of the constitutive model for an alternative material.

  10. A constitutive model of nanocomposite hydrogels with nanoparticle crosslinkers

    NASA Astrophysics Data System (ADS)

    Wang, Qiming; Gao, Zheming

    2016-09-01

    Nanocomposite hydrogels with only nanoparticle crosslinkers exhibit extraordinarily higher stretchability and toughness than the conventional organically crosslinked hydrogels, thus showing great potential in the applications of artificial muscles and cartilages. Despite their potential, the microscopic mechanics details underlying their mechanical performance have remained largely elusive. Here, we develop a constitutive model of the nanoparticle hydrogels to elucidate the microscopic mechanics behaviors, including the microarchitecture and evolution of the nanoparticle crosslinked polymer chains during the mechanical deformation. The constitutive model enables us to understand the Mullins effect of the nanocomposite hydrogels, and the effects of nanoparticle concentrations and sizes on their cyclic stress-strain behaviors. The theory is quantitatively validated by the tensile tests on a nanocomposite hydrogel with nanosilica crosslinkers. The theory can also be extended to explain the mechanical behaviors of existing hydrogels with nanoclay crosslinkers, and the necking instability of the composite hydrogels with both nanoparticle crosslinkers and organic crosslinkers. We expect that this constitutive model can be further exploited to reveal mechanics behaviors of novel particle-polymer chain interactions, and to design unprecedented hydrogels with both high stretchability and toughness.

  11. Synthetic Polymers from Readily Available Monosaccharides

    NASA Astrophysics Data System (ADS)

    Galbis, J. A.; García-Martín, M. G.

    The low degradability of petroleum-based polymers and the massive use of these materials constitute a serious problem because of the environmental pollution that they can cause. Thus, sustained efforts have been extensively devoted to produce new polymers based on natural renewing resources and with higher degradability. Of the different natural sources, carbohydrates stand out as highly convenient raw materials because they are inexpensive, readily available, and provide great stereochemical diversity. New polymers, analogous to the more accredited technical polymers, but based on chiral monomers, have been synthesized from natural and available sugars. This chapter describes the potential of sugar-based monomers as precursors to a wide variety of macromolecular materials.

  12. Synthetic polymers from readily available monosaccharides.

    PubMed

    Galbis, J A; García-Martín, M G

    2010-01-01

    The low degradability of petroleum-based polymers and the massive use of these materials constitute a serious problem because of the environmental pollution that they can cause. Thus, sustained efforts have been extensively devoted to produce new polymers based on natural renewing resources and with higher degradability. Of the different natural sources, carbohydrates stand out as highly convenient raw materials because they are inexpensive, readily available, and provide great stereochemical diversity. New polymers, analogous to the more accredited technical polymers, but based on chiral monomers, have been synthesized from natural and available sugars. This chapter describes the potential of sugar-based monomers as precursors to a wide variety of macromolecular materials.

  13. Polymer flexibility and turbulent drag reduction.

    PubMed

    Gillissen, J J J

    2008-10-01

    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 reduction is positively correlated to viscous stresses, which are generated by extended polymers. Rodlike polymers always assume this favorable conformation, while randomly coiling chains need to be unraveled by fluid strain rate in order to become effective. The coiling and stretching of flexible polymers in turbulent flow produce an additional elastic component in the polymer stress. The effect of the elastic stresses on drag reduction is unclear. To study this issue, we compare direct numerical simulations of turbulent drag reduction in channel flow using constitutive equations describing solutions of rigid and flexible polymers. When compared at constant phi r2, both simulations predict the same amount of drag reduction. Here phi is the polymer volume fraction and r is the polymer aspect ratio, which for flexible polymers is based on average polymer extension at the channel wall. This demonstrates that polymer elasticity plays a marginal role in the mechanism for drag reduction.

  14. Polymer adsorption

    NASA Astrophysics Data System (ADS)

    Joanny, Jean-Francois

    2008-03-01

    The aim of this talk is to review Pierre-Gilles deGennes' work on polymer adsorption and the impact that it has now in our understanding of this problem. We will first present the self-consistent mean-field theory and its applications to adsorption and depletion. De Gennes most important contribution is probably the derivation of the self-similar power law density profile for adsorbed polymer layers that we will present next, emphasizing the differences between the tail sections and the loop sections of the adsorbed polymers. We will then discuss the kinetics of polymer adsorption and the penetration of a new polymer chain in an adsobed layer that DeGennes described very elegantly in analogy with a quantum tunneling problem. Finally, we will discuss the role of polymer adsorption for colloid stabilization.

  15. The Constitution: Perspectives on Contemporary American Democracy.

    ERIC Educational Resources Information Center

    Close Up Foundation, Arlington, VA.

    Four articles expressing the views of nine prominent United States citizens about the Constitution provide a context for reflecting on the meaning of the Constitution in present-day America. In "Why Has the Constitution Endured So Long?" Don Edwards, chairman of the House Civil and Constitutional Rights Subcommittee, discusses why the Constitution…

  16. Strongly anisotropic polymer networks

    NASA Astrophysics Data System (ADS)

    Ulrich, Stephan; Zippelius, Annette; Benetatos, Panayotis

    2011-03-01

    We investigate a network of worm-like chains, which are strongly oriented along a preferred direction due to an external field, boundary conditions, or a nematic environment. We discuss the effects of random permanent cross-links, whose density may follow an arbitrary distribution along the alignment direction. We show that the tilt modulus is unaffected by cross-links. As the cross-link density is increased beyond the gel point, the network develops a stiffness to in-plane shear deformations. Results for the shear elasticity and fluctuations of the polymer chains are presented. The case of cross-linking the chains on one end only is highlighted, it constitutes a simple model for polymer brushes. Moreover force-extension curves are presented for a toy model that consists of two cross-linked chains.

  17. Three-dimensional polymer nanostructures for applications in cell biology generated by high-repetition rate sub-15 fs near-infrared laser pulses

    NASA Astrophysics Data System (ADS)

    Licht, Martin; Straub, Martin; König, Karsten; Afshar, Maziar; Feili, Dara; Seidel, Helmut

    2011-03-01

    In recent years two-photon photopolymerization has emerged as a novel and extremely powerful technique of three-dimensional nanostructure formation. Complex-shaped structures can be generated using appropriate beam steering or nanopositioning systems. Here, we report on the fabrication of three-dimensional arrangements made of biocompatible polymer material, which can be used as templates for cell growth. Using three-dimensional cell cages as cell culture substrates is advantageous, as cells may develop in a more natural environment as compared to conventional planar growth methods. The two-photon fabrication experiments were carried out on a commercial microscope setup. Sub-15 fs pulsed Ti:Sapphire laser light (centre wavelength 800 nm, bandwidth 120 nm, repetition rate 85 MHz) was focused into the polymer material by a high-numerical aperture oil immersion objective. Due to the high peak intensities picojoule pulse energies in the focal spot are sufficient to polymerize the material at sub-100 nm structural element dimensions. Therefore, cell cages of sophisticated architecture can be constructed involving very fine features which take into account the specific needs of various types of cells. Ultimately, our research aims at three-dimensional assemblies of photopolymerized structural elements involving sub-100 nm features, which provide cell culture substrates far superior to those currently existing.

  18. Polymer Chemistry

    NASA Technical Reports Server (NTRS)

    Williams, Martha; Roberson, Luke; Caraccio, Anne

    2010-01-01

    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.

  19. Constitutive equations for solid propellants

    SciTech Connect

    Oezuepek, S.; Becker, E.B.

    1997-04-01

    Mechanical behavior of the Space Shuttle redesigned solid rocket motor (RSRM) propellant is studied from a phenomenological point of view. Motivated by the study of the experimental data three initially isotropic constitutive models have been developed. All models represent the effect of strain rate, superimposed hydrostatic pressure, and cyclic loading on the stress and dilatation response of the material. A particular emphasis is given to the prediction of volume dilatation. The model resulting in the best representation of the available data is calibrated using only a few tests. The predictions of the model are compared with experiments for several loading conditions not used in the calibration.

  20. Macromolecular recognition: Recognition of polymer side chains by cyclodextrin

    NASA Astrophysics Data System (ADS)

    Hashidzume, Akihito; Harada, Akira

    2015-12-01

    The interaction of cyclodextrins (CD) with water soluble polymers possessing guest residues has been investigated as model systems in biological molecular recognition. The selectivity of interaction of CD with polymer-carrying guest residues is controlled by polymer chains, i.e., the steric effect of polymer main chain, the conformational effect of polymer main chain, and multi-site interaction. Macroscopic assemblies have been also realized based on molecular recognition using polyacrylamide-based gels possessing CD and guest residues.

  1. Constitutive modeling for isotropic materials

    NASA Technical Reports Server (NTRS)

    Lindholm, Ulric S.; Chan, Kwai S.

    1986-01-01

    The objective of the program is to evaluate and develop existing constitutive models for use in finite-element structural analysis of turbine engine hot section components. The class of constitutive equation studied is considered unified in that all inelastic deformation including plasticity, creep, and stress relaxation are treated in a single term rather than a classical separation of plasticity (time independent) and creep (time dependent) behavior. The unified theories employed also do not utilize the classical yield surface or plastic potential concept. The models are constructed from an appropriate flow law, a scalar kinetic relation between strain rate, temperature and stress, and evolutionary equations for internal variables describing strain or work hardening, both isotropic and directional (kinematic). This and other studies have shown that the unified approach is particularly suited for determining the cyclic behavior of superalloy type blade and vane materials and is entirely compatible with three-dimensional inelastic finite-element formulations. The behavior was examined of a second nickel-base alloy, MAR-M247, and compared it with the Bodner-Partom model, further examined procedures for determining the material-specific constants in the models, and exercised the MARC code for a turbine blade under simulated flight spectrum loading. Results are summarized.

  2. A novel one-dimensional manganese(II) coordination polymer containing both dicyanamide and pyrazinamide ligands: Synthesis, spectroscopic investigations, X-ray studies and evaluation of biological activities

    NASA Astrophysics Data System (ADS)

    Tabrizi, Leila; Chiniforoshan, Hossein; McArdle, Patrick

    2015-03-01

    A novel 1D coordination polymer {[Mn(μ1,5-dca)2(PZA)2](PZA)2}n, 1, has been synthesized and characterized by single crystal X-ray crystallography. The coordination mode of dicyanamide (dca) and pyrazinamide (PZA) ligands was inferred by IR spectroscopy. The compound 1 was evaluated for in vitro antimycobacterial and antitumor activities. It demonstrated better in vitro activity against Mycobacterium tuberculosis than pyrazinamide and its MIC value was determined. Complex 1 was also screened for its in vitro antitumor activity towards LM3 and LP07 murine cancer cell lines. In addition, the antibacterial activity of complex 1 has been tested against Gram(+) and Gram(-) bacteria and it has shown promising broad range anti-bacterial activity.

  3. Effects of cholesterol incorporation on the physicochemical, colloidal, and biological characteristics of pH-sensitive AB₂ miktoarm polymer-based polymersomes.

    PubMed

    Yin, Haiqing; Kang, Han Chang; Huh, Kang Moo; Bae, You Han

    2014-04-01

    In our previous study, a histidine-based AB2 miktoarm polymer, methoxy poly(ethylene glycol)-b-poly(l-histidine)2 (mPEG-b-(PolyHis)2), was designed to construct pH-sensitive polymersomes that transform in acidic pH; the polymer self-assembles into a structure that mimics phospholipids. In this study, the polymersomes further imitated liposomes due to the incorporation of cholesterol (CL). The hydrodynamic radii of the polymersomes increased with increasing CLwt% (e.g., 70 nm for 0 wt% vs. 91 nm for 1 wt%), resulting in an increased capacity for encapsulating hydrophilic drugs (e.g., 0.92 μL/mg for 0 wt% vs. 1.42 μL/mg for 1 wt%). The CL incorporation enhanced the colloidal stability of the polymersomes in the presence of serum protein and retarded their payload release. However, CL-incorporating polymersomes still demonstrated accelerated release of a hydrophilic dye (e.g., 5(6)-carboxyfluorescein (CF)) below pH 6.8 without losing their desirable pH sensitivity. CF-loaded CL-incorporating polymersomes showed better cellular internalization than the hydrophilic CF, whereas doxorubicin (DOX)-loaded CL-incorporating polymersomes presented similar or somewhat lower anti-tumor effects than free hydrophobic DOX. The findings suggest that CL-incorporating mPEG-b-(PolyHis)2-based polymersomes may have potential for intracellular drug delivery of chemical drugs due to their improved colloidal stability, lower drug loss during circulation, acidic pH-induced drug release, and endosomal disruption.

  4. Effects of Cholesterol Incorporation on the Physicochemical, Colloidal, and Biological Characteristics of pH-sensitive AB2 Miktoarm Polymer-Based Polymersomes

    PubMed Central

    Yin, Haiqing; Kang, Han Chang; Huh, Kang Moo; Bae, You Han

    2014-01-01

    In our previous study, a histidine-based AB2 miktoarm polymer, methoxy poly(ethylene glycol)-b-poly(l-histidine)2 (mPEG-b-(PolyHis)2), was designed to construct pH-sensitive polymersomes that transform in acidic pH; the polymer self-assembles into a structure that mimics phospholipids. In this study, the polymersomes further imitated liposomes due to the incorporation of cholesterol (CL). The hydrodynamic radii of the polymersomes increased with increasing CL wt% (e.g., 70 nm for 0 wt% vs. 91 nm for 1 wt%), resulting in an increased capacity for encapsulating hydrophilic drugs (e.g., 0.92 µL/mg for 0 wt% vs. 1.42 µL/mg for 1 wt%). The CL incorporation enhanced the colloidal stability of the polymersomes in the presence of serum protein and retarded their payload release. However, CL-incorporating polymersomes still demonstrated accelerated release of a hydrophilic dye (e.g., 5(6)-carboxyfluorescein (CF)) below pH 6.8 without losing their desirable pH sensitivity. CF-loaded CL-incorporating polymersomes showed better cellular internalization than the hydrophilic CF, whereas doxorubicin (DOX)-loaded CL-incorporating polymersomes presented similar or somewhat lower anti-tumor effects than free hydrophobic DOX. The findings suggest that CL-incorporating mPEG-b-(PolyHis)2-based polymersomes may have potential for intracellular drug delivery of chemical drugs due to their improved colloidal stability, lower drug loss during circulation, acidic pH-induced drug release, and endosomal disruption. PMID:24463148

  5. A novel solid fluorescence method for the fast determination of quercetin in biological samples based on the quercetin-Al(III) complex imprinted polymer

    NASA Astrophysics Data System (ADS)

    Hu, Yufei; Feng, Ting; Li, Gongke

    2014-01-01

    In this work, a novel solid fluorescence method was proposed and applied to the fast determination of quercetin in urine and onion skin samples by using metal coordination imprinted polymer membrane, which was regarded as a recognition element. The quercetin-Al(III) imprinted polymer was immobilized in the microporous polypropylene fiber membrane via consecutive in situ polymerization. The CIP membrane had the porous, loose and layer upon layer structure. The CIP membrane was characterized by electron microscope photographs, infrared spectra, thermogravimetric analysis and solvent-resistant investigation. The extraction conditions including extraction solvent, extraction time, desorption solvent were optimized. Compared with MIP and NIP membrane, CIP membrane had been proved to be peculiar selective for quercetin even in presence of the structurally similar compounds such as kaempferol, rutin, naringenin and alpinetin. The CIP membrane was characteristic of high selectivity, stable and sensitive response to quercetin in polar environment. Under the optimum condition, there was a linear relationship between the state fluorescent response and the concentration of quercetin. The linear calibration range was over 0.02 mg L-1-0.80 mg L-1 with a detection limit of 5 μg L-1. The method was characteristic of flexible and good repeatability with relative standard deviation (RSD) of 4.1%. The proposed method was also successfully applied for the determination of quercetin in urine and onion skin samples without complicated pretreatment. The recoveries were 84.0-112.4% and RSDs varied from 1.5% to 6.8%. The results obtained by the proposed method agreed well with those obtained by HPLC method.

  6. Polymers & People

    ERIC Educational Resources Information Center

    Lentz, Linda; Robinson, Thomas; Martin, Elizabeth; Miller, Mary; Ashburn, Norma

    2004-01-01

    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…

  7. Unborn children as constitutional persons.

    PubMed

    Roden, Gregory J

    2010-01-01

    In Roe v. Wade, the state of Texas argued that "the fetus is a 'person' within the language and meaning of the Fourteenth Amendment." To which Justice Harry Blackmun responded, "If this suggestion of personhood is established, the appellant's case, of course, collapses, for the fetus' right to life would then be guaranteed specifically by the Amendment." However, Justice Blackmun then came to the conclusion "that the word 'person,' as used in the Fourteenth Amendment, does not include the unborn." In this article, it is argued that unborn children are indeed "persons" within the language and meaning of the Fourteenth and Fifth Amendments. As there is no constitutional text explicitly holding unborn children to be, or not to be, "persons," this argument will be based on the "historical understanding and practice, the structure of the Constitution, and thejurisprudence of [the Supreme] Court." Specifically, it is argued that the Constitution does not confer upon the federal government a specifically enumerated power to grant or deny "personhood" under the Fourteenth Amendment. Rather, the power to recognize or deny unborn children as the holders of rights and duties has been historically exercised by the states. The Roe opinion and other Supreme Court cases implicitly recognize this function of state sovereignty. The states did exercise this power and held unborn children to be persons under the property, tort, and criminal law of the several states at the time Roe was decided. As an effect of the unanimity of the states in holding unborn children to be persons under criminal, tort, and property law, the text of the Equal Protection Clause of the Fourteenth Amendment compels federal protection of unborn persons. Furthermore, to the extent Justice Blackmun examined the substantive law in these disciplines, his findings are clearly erroneous and as a whole amount to judicial error. Moreover, as a matter of procedure, according to the due process standards recognized in

  8. New constitutionalism and the social reproduction of caring institutions.

    PubMed

    Gill, Stephen; Bakker, Isabella

    2006-01-01

    This essay analyzes neo-liberal economic agreements and legal and political frameworks or what has been called the "new constitutionalism," a governance framework that empowers market forces to reshape economic and social development worldwide. The article highlights some consequences of new constitutionalism for caring institutions specifically, and for what feminists call social reproduction more generally: the biological reproduction of the species; the reproduction of labor power; and the reproduction of social institutions and processes associated with the creation and maintenance of communities. New constitutional governance frameworks fundamentally reshape conditions under which the care of human beings takes place. Caring institutions once governed by enabling professions geared to universal care are now determined increasingly by market values and private forces, and driven directly by the profit motive. This is one of the reasons why neo-liberalism is increasingly contested in both the North and the global South. PMID:16532302

  9. New constitutionalism and the social reproduction of caring institutions.

    PubMed

    Gill, Stephen; Bakker, Isabella

    2006-01-01

    This essay analyzes neo-liberal economic agreements and legal and political frameworks or what has been called the "new constitutionalism," a governance framework that empowers market forces to reshape economic and social development worldwide. The article highlights some consequences of new constitutionalism for caring institutions specifically, and for what feminists call social reproduction more generally: the biological reproduction of the species; the reproduction of labor power; and the reproduction of social institutions and processes associated with the creation and maintenance of communities. New constitutional governance frameworks fundamentally reshape conditions under which the care of human beings takes place. Caring institutions once governed by enabling professions geared to universal care are now determined increasingly by market values and private forces, and driven directly by the profit motive. This is one of the reasons why neo-liberalism is increasingly contested in both the North and the global South.

  10. Simulating the flow of entangled polymers.

    PubMed

    Masubuchi, Yuichi

    2014-01-01

    To optimize automation for polymer processing, attempts have been made to simulate the flow of entangled polymers. In industry, fluid dynamics simulations with phenomenological constitutive equations have been practically established. However, to account for molecular characteristics, a method to obtain the constitutive relationship from the molecular structure is required. Molecular dynamics simulations with atomic description are not practical for this purpose; accordingly, coarse-grained models with reduced degrees of freedom have been developed. Although the modeling of entanglement is still a challenge, mesoscopic models with a priori settings to reproduce entangled polymer dynamics, such as tube models, have achieved remarkable success. To use the mesoscopic models as staging posts between atomistic and fluid dynamics simulations, studies have been undertaken to establish links from the coarse-grained model to the atomistic and macroscopic simulations. Consequently, integrated simulations from materials chemistry to predict the macroscopic flow in polymer processing are forthcoming.

  11. Written Constitution or None: Which Works Better?

    ERIC Educational Resources Information Center

    Cowen, Zelman

    1987-01-01

    Explores the differences between the U.S. Constitution and British constitutional law. Specifically examines the concept of the U.S. Bill of Rights in relation to the United Kingdom common law doctrine of parliamentary sovereignty. (BSR)

  12. Polymer nanolithography

    NASA Astrophysics Data System (ADS)

    Vance, Jennifer M.

    Nanolithography involves making patterns of materials with at least one dimension less than 100 nanometers. Surprisingly, writable CDs can provide polymer nanostructures for pennies a piece. Building on work previously done in the Drain lab, with an inherited home-built oven press, this research will explore the relationships between polymer chemical reactivity, polymer printing, and material surface energies. In addition, a relatively inexpensive entry point into high school and undergraduate education in nanolithography is presented. The ability to pattern cheaply at the nanoscale and microscale is necessary and attractive for many technologies towards biosensors, organic light emitting diodes, identification tags, layered devices, and transistors.

  13. A Self-Assembled Aggregate Composed of a Fatty Acid Membrane and the Building Blocks of Biological Polymers Provides a First Step in the Emergence of Protocells.

    PubMed

    Black, Roy A; Blosser, Matthew C

    2016-01-01

    We propose that the first step in the origin of cellular life on Earth was the self-assembly of fatty acids with the building blocks of RNA and protein, resulting in a stable aggregate. This scheme provides explanations for the selection and concentration of the prebiotic components of cells; the stabilization and growth of early membranes; the catalysis of biopolymer synthesis; and the co-localization of membranes, RNA and protein. In this article, we review the evidence and rationale for the formation of the proposed aggregate: (i) the well-established phenomenon of self-assembly of fatty acids to form vesicles; (ii) our published evidence that nucleobases and sugars bind to and stabilize such vesicles; and (iii) the reasons why amino acids likely do so as well. We then explain how the conformational constraints and altered chemical environment due to binding of the components to the membrane could facilitate the formation of nucleosides, oligonucleotides and peptides. We conclude by discussing how the resulting oligomers, even if short and random, could have increased vesicle stability and growth more than their building blocks did, and how competition among these vesicles could have led to longer polymers with complex functions. PMID:27529283

  14. Monolithic molecular imprinted polymer fiber for recognition and solid phase microextraction of ephedrine and pseudoephedrine in biological samples prior to capillary electrophoresis analysis.

    PubMed

    Deng, Dong-Li; Zhang, Ji-You; Chen, Chen; Hou, Xiao-Ling; Su, Ying-Ying; Wu, Lan

    2012-01-01

    A novel capillary electrophoresis (CE) method coupled with monolithic molecular imprinted polymer (MIP) fiber based solid phase microextraction (SPME) was developed for selective and sensitive determination of ephedrine (E) and pseudoephedrine (PE). With in situ polymerization in a silica capillary mold and E as template, the MIP fibers could be produced in batch reproducibly and each fiber was available for 50 extraction cycles without significant decrease in extraction ability. Using the MIP fiber under optimized extraction conditions, CE detection limits of E and PE were greatly lowered from 0.20 to 0.00096 μg/mL and 0.12 to 0.0011 μg/mL, respectively. Analysis of urine and serum samples by the MIP-SPME-CE method was also performed, with results indicating that E and PE could be selectively extracted. The recoveries and relative standard deviations (RSDs) for sample analysis were found in the range of 91-104% and 3.8-9.1%, respectively.

  15. A Self-Assembled Aggregate Composed of a Fatty Acid Membrane and the Building Blocks of Biological Polymers Provides a First Step in the Emergence of Protocells

    PubMed Central

    Black, Roy A.; Blosser, Matthew C.

    2016-01-01

    We propose that the first step in the origin of cellular life on Earth was the self-assembly of fatty acids with the building blocks of RNA and protein, resulting in a stable aggregate. This scheme provides explanations for the selection and concentration of the prebiotic components of cells; the stabilization and growth of early membranes; the catalysis of biopolymer synthesis; and the co-localization of membranes, RNA and protein. In this article, we review the evidence and rationale for the formation of the proposed aggregate: (i) the well-established phenomenon of self-assembly of fatty acids to form vesicles; (ii) our published evidence that nucleobases and sugars bind to and stabilize such vesicles; and (iii) the reasons why amino acids likely do so as well. We then explain how the conformational constraints and altered chemical environment due to binding of the components to the membrane could facilitate the formation of nucleosides, oligonucleotides and peptides. We conclude by discussing how the resulting oligomers, even if short and random, could have increased vesicle stability and growth more than their building blocks did, and how competition among these vesicles could have led to longer polymers with complex functions. PMID:27529283

  16. Theoretical Issues of the Constitutional Regulation Mechanism

    ERIC Educational Resources Information Center

    Zhussupova, Guldaray B.; Zhailyaubayev, Rassul T.; Ukin, Symbat K.; Shunayeva, Sylu M.; Nurmagambetov, Rachit G.

    2016-01-01

    The purpose of this research is to define the concept of "constitutional regulation mechanism." The definition of the concept of "constitutional regulation mechanism" will give jurists and legislators a theoretical framework for developing legal sciences, such as the constitutional law and the theory of state and law. The…

  17. Antithetical Ethics: Kenneth Burke and the Constitution.

    ERIC Educational Resources Information Center

    Anderson, Virginia

    1995-01-01

    Shows how the textuality of the United States Constitution, the most venerable of classic democratic icons, might be exploited to nurture postmodern ethics. Shows how Kenneth Burke's reading of the Constitution accords with and augments the postmodern theories of J.-F. Lyotard and S. Jarratt. Discusses a postmodern Constitution and the…

  18. About Our Constitution: 1787-1987.

    ERIC Educational Resources Information Center

    National Council for the Social Studies, Washington, DC.

    Designed to assist elementary school teachers, these materials present a series of lessons about the United States Constitution. Ten lesson plans and appropriate work sheets are included for grades K-3. The topics covered include the age of the Constitution, a constitutional convention, elected representatives, majority rule, voting, law making,…

  19. 32 CFR 536.42 - Constitutional torts.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY CLAIMS AND ACCOUNTS CLAIMS AGAINST THE UNITED STATES Investigation and Processing of Claims § 536.42 Constitutional torts. A claim for violation of the U.S. Constitution does not constitute a state tort and is not cognizable...

  20. 32 CFR 536.42 - Constitutional torts.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY CLAIMS AND ACCOUNTS CLAIMS AGAINST THE UNITED STATES Investigation and Processing of Claims § 536.42 Constitutional torts. A claim for violation of the U.S. Constitution does not constitute a state tort and is not cognizable...

  1. 32 CFR 536.42 - Constitutional torts.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY CLAIMS AND ACCOUNTS CLAIMS AGAINST THE UNITED STATES Investigation and Processing of Claims § 536.42 Constitutional torts. A claim for violation of the U.S. Constitution does not constitute a state tort and is not cognizable...

  2. 32 CFR 536.42 - Constitutional torts.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY CLAIMS AND ACCOUNTS CLAIMS AGAINST THE UNITED STATES Investigation and Processing of Claims § 536.42 Constitutional torts. A claim for violation of the U.S. Constitution does not constitute a state tort and is not cognizable...

  3. 7 CFR 718.201 - Farm constitution.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 7 2011-01-01 2011-01-01 false Farm constitution. 718.201 Section 718.201 Agriculture... Reconstitution of Farms, Allotments, Quotas, and Bases § 718.201 Farm constitution. (a) In order to implement... this section. The constitution and identification of land as a farm for the first time and...

  4. 7 CFR 718.201 - Farm constitution.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 7 2014-01-01 2014-01-01 false Farm constitution. 718.201 Section 718.201 Agriculture... Reconstitution of Farms, Allotments, Quotas, and Bases § 718.201 Farm constitution. (a) In order to implement... this section. The constitution and identification of land as a farm for the first time and...

  5. 29 CFR 452.18 - Constitutional officers.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... officer refers to a person holding a position identified as an officer by the constitution and bylaws of... constitution identifies the holder of such a position as an officer. On the other hand, legislative representatives who are required to be elected by the constitution and bylaws of a labor organization are...

  6. 29 CFR 452.18 - Constitutional officers.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... officer refers to a person holding a position identified as an officer by the constitution and bylaws of... constitution identifies the holder of such a position as an officer. On the other hand, legislative representatives who are required to be elected by the constitution and bylaws of a labor organization are...

  7. 7 CFR 718.201 - Farm constitution.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 7 2013-01-01 2013-01-01 false Farm constitution. 718.201 Section 718.201 Agriculture... Reconstitution of Farms, Allotments, Quotas, and Bases § 718.201 Farm constitution. (a) In order to implement... this section. The constitution and identification of land as a farm for the first time and...

  8. 29 CFR 452.18 - Constitutional officers.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... officer refers to a person holding a position identified as an officer by the constitution and bylaws of... constitution identifies the holder of such a position as an officer. On the other hand, legislative representatives who are required to be elected by the constitution and bylaws of a labor organization are...

  9. 7 CFR 718.201 - Farm constitution.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 7 2012-01-01 2012-01-01 false Farm constitution. 718.201 Section 718.201 Agriculture... Reconstitution of Farms, Allotments, Quotas, and Bases § 718.201 Farm constitution. (a) In order to implement... this section. The constitution and identification of land as a farm for the first time and...

  10. American Focus on World Constitutions. Teacher's Guide.

    ERIC Educational Resources Information Center

    Holmes, Stanley T., III

    This curriculum project was designed to familiarize high school students with their own constitutional roots while gaining a better understanding of governmental systems developed by other nations. The project uses the U.S. Constitution as a baseline for analyzing the constitutions of other nations, and is intended to supplement courses in such…

  11. Organometallic Polymers.

    ERIC Educational Resources Information Center

    Carraher, Charles E., Jr.

    1981-01-01

    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)

  12. Polymers All Around You!

    ERIC Educational Resources Information Center

    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…

  13. Multifunctional and biologically active matrices from multicomponent polymeric solutions

    NASA Technical Reports Server (NTRS)

    Kiick, Kristi L. (Inventor); Yamaguchi, Nori (Inventor); Rabolt, John (Inventor); Casper, Cheryl (Inventor)

    2012-01-01

    A functionalized electrospun matrix for the controlled-release of biologically active agents, such as growth factors, is presented. The functionalized matrix comprises a matrix polymer, a compatibilizing polymer and a biomolecule or other small functioning molecule. In certain aspects the electrospun polymer fibers comprise at least one biologically active molecule functionalized with low molecular weight heparin.

  14. 78 FR 39721 - Constitution Pipeline Company, LLC; Notice of Application

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-02

    ... Energy Regulatory Commission Constitution Pipeline Company, LLC; Notice of Application Take notice that on June 13, 2013, Constitution Pipeline Company, LLC (Constitution), having its principal place of...\\ Constitution further requests that the Commission grant Constitution a blanket certificate...

  15. Nanoscale Study of Polymer Dynamics.

    PubMed

    Keshavarz, Masoumeh; Engelkamp, Hans; Xu, Jialiang; Braeken, Els; Otten, Matthijs B J; Uji-I, Hiroshi; Schwartz, Erik; Koepf, Matthieu; Vananroye, Anja; Vermant, Jan; Nolte, Roeland J M; De Schryver, Frans; Maan, Jan C; Hofkens, Johan; Christianen, Peter C M; Rowan, Alan E

    2016-01-26

    The thermal motion of polymer chains in a crowded environment is anisotropic and highly confined. Whereas theoretical and experimental progress has been made, typically only indirect evidence of polymer dynamics is obtained either from scattering or mechanical response. Toward a complete understanding of the complicated polymer dynamics in crowded media such as biological cells, it is of great importance to unravel the role of heterogeneity and molecular individualism. In the present work, we investigate the dynamics of synthetic polymers and the tube-like motion of individual chains using time-resolved fluorescence microscopy. A single fluorescently labeled polymer molecule is observed in a sea of unlabeled polymers, giving access to not only the dynamics of the probe chain itself but also to that of the surrounding network. We demonstrate that it is possible to extract the characteristic time constants and length scales in one experiment, providing a detailed understanding of polymer dynamics at the single chain level. The quantitative agreement with bulk rheology measurements is promising for using local probes to study heterogeneity in complex, crowded systems.

  16. Nanoscale Study of Polymer Dynamics.

    PubMed

    Keshavarz, Masoumeh; Engelkamp, Hans; Xu, Jialiang; Braeken, Els; Otten, Matthijs B J; Uji-I, Hiroshi; Schwartz, Erik; Koepf, Matthieu; Vananroye, Anja; Vermant, Jan; Nolte, Roeland J M; De Schryver, Frans; Maan, Jan C; Hofkens, Johan; Christianen, Peter C M; Rowan, Alan E

    2016-01-26

    The thermal motion of polymer chains in a crowded environment is anisotropic and highly confined. Whereas theoretical and experimental progress has been made, typically only indirect evidence of polymer dynamics is obtained either from scattering or mechanical response. Toward a complete understanding of the complicated polymer dynamics in crowded media such as biological cells, it is of great importance to unravel the role of heterogeneity and molecular individualism. In the present work, we investigate the dynamics of synthetic polymers and the tube-like motion of individual chains using time-resolved fluorescence microscopy. A single fluorescently labeled polymer molecule is observed in a sea of unlabeled polymers, giving access to not only the dynamics of the probe chain itself but also to that of the surrounding network. We demonstrate that it is possible to extract the characteristic time constants and length scales in one experiment, providing a detailed understanding of polymer dynamics at the single chain level. The quantitative agreement with bulk rheology measurements is promising for using local probes to study heterogeneity in complex, crowded systems. PMID:26688072

  17. More Than Just a Polymer

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Triton atomic Oxygen Resistant polymers TOR(TM), were developed by Chelmsford, Massachusetts-based Triton Systems, Inc., through a Small Business Innovation Research (SBIR) contract from NASA's Langley Research Center. The new family of polymers comes from a Langley-developed polymer technology, which marks a new class of aerospace materials that resist the extreme effects of low Earth orbit (LEO). When applied to spacecraft surfaces, TOR polymers protect against erosion caused by the atomic oxygen and radiation present in space. Other polymers, such as Teflon(R) and Kapton(R), are subject to degradation from atomic oxygen and ultraviolet radiation, but TOR polymers use atomic oxygen to their advantage. A long-lasting protective barrier means major savings in the cost of spacecraft maintenance and the time spent performing repairs. While the obvious application of this material lies with the aerospace industry, an underlying benefit is found in the field of electronics. TOR polymers can be made electrically conductive, and then utilized in the creation of sensors that react to the presence of chemical and biological agents by exhibiting a detectable change in electrical conductivity. These sensors have applications in the defense, medical, and industrial sectors.

  18. 3 CFR 8562 - Proclamation 8562 of September 16, 2010. Constitution Day and Citizenship Day, Constitution Week...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    .... Constitution Day and Citizenship Day, Constitution Week, 2010 8562 Proclamation 8562 Presidential Documents Proclamations Proclamation 8562 of September 16, 2010 Proc. 8562 Constitution Day and Citizenship Day... the States, the Framers advanced our national journey. On Constitution Day and Citizenship Day,...

  19. 75 FR 57835 - Constitution Day and Citizenship Day, Constitution Week, 2010

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-22

    ... two hundred and thirty-fifth. (Presidential Sig.) [FR Doc. 2010-23898 Filed 9-21-10; 11:15 am] Billing... Proclamation 8562--Constitution Day and Citizenship Day, Constitution Week, 2010 Proclamation 8563--National... President ] Proclamation 8562 of September 16, 2010 Constitution Day and Citizenship Day, Constitution...

  20. Constitutional and Non-Constitutional Governments...Similarities and Differences throughout History. Resource Packet.

    ERIC Educational Resources Information Center

    Pallasch, Brian Thomas

    This civic education resource packet is designed to provide teachers, community leaders, and other civic educators with an understanding of the differences between constitutional and non-constitutional governments. Six papers discussing the topic are included: "The Differences bewteen Constitutional and Non-Constitutional Governments" (John…

  1. Mesoscale Polymer Assemblies

    NASA Astrophysics Data System (ADS)

    Choudhary, Satyan; Pham, Jonathan; Crosby, Alfred

    2015-03-01

    Materials encompassing structural hierarchy and multi-functionality allow for remarkable physical properties across different length scales. Mesoscale Polymer (MSP) assemblies provide a critical link, from nanometer to centimeter scales, in the definition of such hierarchical structures. Recent focus has been on exploiting these MSP assemblies for optical, electronic, photonics and biological applications. We demonstrate a novel fabrication method for MSP assemblies. Current fabrication methods restrict the length scale and volume of such assemblies. A new method developed uses a simple piezo-actuated motion for de-pinning of a polymer solution trapped by capillary forces between a flexible blade and a rigid substrate. The advantages of new method include ability to make MSP of monodisperse length and to fabricate sufficient volumes of MSP to study their physical properties and functionality in liquid dispersions. We demonstrate the application of MSP as filler for soft materials, providing rheological studies of the MSP with surrounding matrices.

  2. Detoxification of olive mill wastewater using superabsorbent polymers.

    PubMed

    Davies, L C; Novais, J M; Martins-Dias, S

    2004-01-01

    The detoxification of agro-industrial effluents using superabsorbent polymers is a new and innovative process. Olive mill wastewater constitutes a major environmental problem in Mediterranean countries due to the large volumes generated, the seasonality of the industry, and the high content of polyphenols and organic matter. The application of superabsorbent polymers allows olive mill wastewater to be used as a fertilizer, as it is immobilized, increasing the biological activity that decreases its phytotoxicity, thus making its water, organic matter and mineral content usable for plant nutrition. Various parameters that characterise olive mill wastewater were evaluated after absorption in 2 different superabsorbent polymers (SAP1 and SAP2). The organic matter was equally distributed in both phases, while there was a concentration of protein and sodium in solution. The K:Na ratio decreased from 70:1 to 2:1. The polyphenol desorption from the gel into solution was found to follow Fick's law. The mass transfer coefficients were 0.147 min(-1) and 0.0085 min(-1) for SAP1 and SAP2, respectively. Phytotoxicity tests were carried out with SAP2. Olive mill wastewater in SAP2 with polyphenol concentrations up to 200 mg l(-1) revealed no phytotoxicity, and even stimulated Lepidium sativum growth, while olive mill wastewater without superabsorbent polymer revealed growth inhibition for all concentrations tested. Caffeic acid degradation by the immobilised biomass followed zero order kinetics. Degradation constants of 0.087 mg l(-1) min(-1) gSAP2(-1) and 1.156 mg l(-1) min(-1) gSAP2(-1) were found. Fungi that developed in the plant growth medium were identified as Aspergillus sp. and Penicillium sp. PMID:15027653

  3. Solubility properties in polymers and biological media. 7. An analysis of toxicant properties that influence inhibition of bioluminescence in photobacterium phosphoreum (the Microtox test)

    SciTech Connect

    Kamlet, M.J.; Doherty, R.M.; Veith, G.D.; Taft, R.W.; Abraham, M.H.

    1986-07-01

    Inhibition of bioluminescence in Photobacterium phosphoreum (the Microtox test) has been proposed as a cost-effective prescreening procedure to eliminate the relatively more innocuous chemicals from testing programs for toxicities of organic chemicals to fish. The biological response, as a function of toxicant properties, is given by log EC/sub 50/ (in ..mu..molL) = 7.61 - 4.11 anti V100 - 1.54 ..pi..* + 3.94..beta.. - 1.51..cap alpha../sub m/ n = 38, r = 0.987, SD = 0.28 where anti V is the solute molar volume and ..pi..*, ..beta.., and ..cap alpha../sub m/ are the solvatochromic parameters that measure dipolaritypolarizability, hydrogen-bond acceptor basicity, and hydrogen-bond donor acidity of the solute (toxicant). The above equation applies to compounds that act by a nonreactive toxicity mechanism, and it is suggested that for certain compounds, which are outliers relative to the above equation, reactive toxicity properties mask the effects of the nonreactive mechanism. The above equation is compared with a correlation of log EC/sub 50/ with octanolwater partition coefficients. 25 references, 2 figures, 2 tables.

  4. Mechanistic Constitutive Models for Rubber Elasticity and Viscoelasticity

    SciTech Connect

    Puso, M

    2003-01-21

    Physically based models which describe the finite strain behavior of vulcanized rubber are developed. Constitutive laws for elasticity and viscoelasticity are derived by integrating over orientation space the forces due to each individual polymer chain. A novel scheme is presented which effectively approximates these integrals in terms of strain and strain invariants. In addition, the details involving the implementation of such models into a quasi-static large strain finite element formulation are provided. In order to account for the finite extensibility of a molecular chain, Langevin statistics is used to model the chain response. The classical statistical model of rubber assumes that polymer chains interact only at the chemical crosslinks. It is shown that such model when fitted for uniaxial tension data cannot fit compression or equibiaxial data. A model which incorporates the entanglement interactions of surrounding chains, in addition to the finite extensibility of the chains, is shown to give better predictions than the classical model. The technique used for approximating the orientation space integral was applied to both the classical and entanglement models. A viscoelasticity model based on the force equilibration process as described by Doi and Edwards is developed. An assumed form for the transient force in the chain is postulated. The resulting stress tensor is composed of an elastic and a viscoelastic portion with the elastic stress given by the proposed entanglement model. In order to improve the simulation of experimental data, it was found necessary to include the effect of unattached or dangling polymer chains in the viscoelasticity model. The viscoelastic effect of such chains is the manifestation of a disengagement process. This disengagement model for unattached polymer chains motivated an empirical model which was very successful in simulating the experimental results considered.

  5. Antimocrobial Polymer

    DOEpatents

    McDonald, William F.; Huang, Zhi-Heng; Wright, Stacy C.

    2005-09-06

    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.

  6. Antimicrobial Polymer

    DOEpatents

    McDonald, William F.; Wright, Stacy C.; Taylor, Andrew C.

    2004-09-28

    A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The polymeric 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 metals, metal alloys, metal salts, metal complexes and mixtures thereof, and (iii) a crosslinking agent containing functional groups capable of reacting with the amino groups. In one example 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).sub.3 P wherein A is hydroxyalkyl; and the metallic antimicrobial agent is selected from chelated silver ions, silver metal, chelated copper ions, copper metal, chelated zinc ions, zinc metal and mixtures thereof.

  7. Defining the criteria for identifying constitutional epimutations.

    PubMed

    Sloane, Mathew A; Ward, Robyn L; Hesson, Luke B

    2016-01-01

    In the January 2016 issue of Clinical Epigenetics, Quiñonez-Silva et al. (Clin Epigenetics 8:1, 2016) described a possible constitutional epimutation of the RB1 gene as a cause of hereditary predisposition to retinoblastoma. The term constitutional epimutation describes an epigenetic aberration in normal tissues that predisposes to disease. The data presented by Quiñonez-Silva et al. are interesting, but further analysis is required to demonstrate a constitutional epimutation in this family. Here, we define the criteria and describe the experimental approach necessary to identify an epigenetic aberration as a constitutional epimutation. PMID:27096027

  8. Testing of constitutive models in LAME.

    SciTech Connect

    Hammerand, Daniel Carl; Scherzinger, William Mark

    2007-09-01

    Constitutive models for computational solid mechanics codes are in LAME--the Library of Advanced Materials for Engineering. These models describe complex material behavior and are used in our finite deformation solid mechanics codes. To ensure the correct implementation of these models, regression tests have been created for constitutive models in LAME. A selection of these tests is documented here. Constitutive models are an important part of any solid mechanics code. If an analysis code is meant to provide accurate results, the constitutive models that describe the material behavior need to be implemented correctly. Ensuring the correct implementation of constitutive models is the goal of a testing procedure that is used with the Library of Advanced Materials for Engineering (LAME) (see [1] and [2]). A test suite for constitutive models can serve three purposes. First, the test problems provide the constitutive model developer a means to test the model implementation. This is an activity that is always done by any responsible constitutive model developer. Retaining the test problem in a repository where the problem can be run periodically is an excellent means of ensuring that the model continues to behave correctly. A second purpose of a test suite for constitutive models is that it gives application code developers confidence that the constitutive models work correctly. This is extremely important since any analyst that uses an application code for an engineering analysis will associate a constitutive model in LAME with the application code, not LAME. Therefore, ensuring the correct implementation of constitutive models is essential for application code teams. A third purpose of a constitutive model test suite is that it provides analysts with example problems that they can look at to understand the behavior of a specific model. Since the choice of a constitutive model, and the properties that are used in that model, have an enormous effect on the results of an

  9. Molecularly imprinted polymers for biomedical and biotechnological applications

    NASA Astrophysics Data System (ADS)

    Dmitrienko, E. V.; Pyshnaya, I. A.; Martyanov, O. N.; Pyshnyi, D. V.

    2016-05-01

    This survey covers main advances in the preparation and application of molecularly imprinted polymers which are capable of specific recognition of biologically active compounds. The principles underlying the production of highly efficient and template-specific molecularly imprinted polymers are discussed. The focus is on the imprinting of highly structured macromolecular and supramolecular templates. The existing and potential applications of molecularly imprinted polymers in various fields of chemistry and molecular biology are considered. The bibliography includes 261 references.

  10. Electrochemical Sensors Based on Organic Conjugated Polymers

    PubMed Central

    Rahman, Md. Aminur; Kumar, Pankaj; Park, Deog-Su; Shim, Yoon-Bo

    2008-01-01

    Organic conjugated polymers (conducting polymers) have emerged as potential candidates for electrochemical sensors. Due to their straightforward preparation methods, unique properties, and stability in air, conducting polymers have been applied to energy storage, electrochemical devices, memory devices, chemical sensors, and electrocatalysts. Conducting polymers are also known to be compatible with biological molecules in a neutral aqueous solution. Thus, these are extensively used in the fabrication of accurate, fast, and inexpensive devices, such as biosensors and chemical sensors in the medical diagnostic laboratories. Conducting polymer-based electrochemical sensors and biosensors play an important role in the improvement of public health and environment because rapid detection, high sensitivity, small size, and specificity are achievable for environmental monitoring and clinical diagnostics. In this review, we summarized the recent advances in conducting polymer-based electrochemical sensors, which covers chemical sensors (potentiometric, voltammetric, amperometric) and biosensors (enzyme based biosensors, immunosensors, DNA sensors).

  11. Polymer brushes: Tools for surface design

    NASA Astrophysics Data System (ADS)

    Ober, Christopher

    2011-03-01

    Polymers brushes are ideal materials for interfacing with biological systems as they share many of the same molecular components and properties. Polymer brushes provide remarkable screening power in shielding a substrate from the environment through both steric and charge interactions. However, the majority of biomolecular species will still non-specifically bind to polymer brush surfaces unless some care is given to molecular design. Several polymer brush systems are described to control interaction of biomacromolecules and cells by design of specific and non-specific interactions in polymer brush architectures. ``Grown from'' and block copolymer brushes are described, both of which provide excellent substrates for study of brush surfaces. Examples of polymer brushes used for sensor creation and for investigation of cellular interaction are given. Brushes used in non-fouling coatings tailored for marine applications and in which amphiphilic structures play an important role are also described. Support from both NSF and ONR is gratefully acknowledged.

  12. Polymer Science.

    ERIC Educational Resources Information Center

    Frank, Curtis W.

    1979-01-01

    Described is a series of four graduate level courses in polymer science, offered or currently in preparation, at Stanford University. Course descriptions and a list of required and recommended texts are included. Detailed course outlines for two of the courses are presented. (BT)

  13. Functional polymers

    SciTech Connect

    Wegner, G.

    2000-01-01

    Improving the existing polymer materials and the designing of model polymers need fundamental insights into the structure and dynamics over a large range of length and time scales. Consequently, a host of quite different methods needs to be applied to gain insights into the molecular and supramolecular structures and interactions that determine the performance of these materials. Supramolecular structures derived from shape persistent (stiff) macromolecules are used as examples to demonstrate the correlation between chemical structure, order phenomena and performance in applications concerning advanced or developing technologies: organic light emitting diodes (OLEDs) and separator membranes in lithium based batteries and fuel cells. Polymers are also important as additives in the manufacture and the processing of other materials. The design of block copolymers to control the nucleation and growth of inorganic particles precipitating from aqueous solutions (mineralization) is discussed as well as the use of block copolymers to optimize the processing of ceramic pieces and objects. Finally, the modification of surfaces by polymers including aspects of biocompatibility is discussed. Some remarks concerning the importance of recent developments and advances in synthesis of macromolecular materials are also given.

  14. Polymer solutions

    DOEpatents

    Krawczyk, Gerhard Erich; Miller, Kevin Michael

    2011-07-26

    There is provided a method of making a polymer solution comprising polymerizing one or more monomer in a solvent, wherein said monomer comprises one or more ethylenically unsaturated monomer that is a multi-functional Michael donor, and wherein said solvent comprises 40% or more by weight, based on the weight of said solvent, one or more multi-functional Michael donor.

  15. The United States and the Indian Constitution.

    ERIC Educational Resources Information Center

    Weil, Jonathan S.

    India, a huge land with the second largest population in the world, socially and economically poor, and culturally and linguistically diverse, became the largest democracy in the world on November 26, 1949 with the adoption of the Indian Constitution. The goals of that constitution are: (1) the achievement of national unity and stability; (2) the…

  16. From Confederation to Constitution: 1781-1789.

    ERIC Educational Resources Information Center

    Urofsky, Melvin I.; Cox, Nancy

    Students should achieve a higher level of understanding and appreciation of the evolving nature of the U.S. Constitution and its relevance to contemporary societal issues by studying historical documents from the period of time between the Articles of Confederation and the Constitution. This document begins with a history of that period and of the…

  17. The Constitution in the Twentieth Century.

    ERIC Educational Resources Information Center

    Murphy, Paul L.

    1987-01-01

    Investigates the development of the United States Constitution in the twentieth century up to and including the Burger Court. Contends that interpreting the Constitution is an important issue of our times. Consequently argues that we should teach students about the development of this document. (RKM)

  18. 32 CFR 536.42 - Constitutional torts.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 32 National Defense 3 2010-07-01 2010-07-01 true Constitutional torts. 536.42 Section 536.42 National Defense Department of Defense (Continued) DEPARTMENT OF THE ARMY CLAIMS AND ACCOUNTS CLAIMS AGAINST THE UNITED STATES Investigation and Processing of Claims § 536.42 Constitutional torts. A...

  19. Liberty, Power, and the American Constitutional Heritage.

    ERIC Educational Resources Information Center

    Madison, James H.

    The principles, values, and issues of our constitutional heritage that should be emphasized in citizenship education are based on the concepts of liberty and power. The Constitution is not a sacred icon formulated by immortals, but rather a changing and controversial framework guided by a diverse group of practical politicians, sensitive to their…

  20. An Internet Guide to Teaching the Constitution

    ERIC Educational Resources Information Center

    Risinger, C. Frederick

    2005-01-01

    In 2004, Congress passed and President Bush signed legislation designating every September 17 as Constitution Day and suggesting that all schools teach about the Constitution on that day. There are innumerable websites, countless lesson plans and a multitude of other teaching resources on the topic. Teachers were inundated with brochures,…

  1. Depletion-induced forces and crowding in polymer-nanoparticle mixtures: Role of polymer shape fluctuations and penetrability.

    PubMed

    Lim, Wei Kang; Denton, Alan R

    2016-01-14

    Depletion forces and macromolecular crowding govern the structure and function of biopolymers in biological cells and the properties of polymer nanocomposite materials. To isolate and analyze the influence of polymer shape fluctuations and penetrability on depletion-induced interactions and crowding by nanoparticles, we model polymers as effective penetrable ellipsoids, whose shapes fluctuate according to the probability distributions of the eigenvalues of the gyration tensor of an ideal random walk. Within this model, we apply Monte Carlo simulation methods to compute the depletion-induced potential of mean force between hard nanospheres and crowding-induced shape distributions of polymers in the protein limit, in which polymer coils can be easily penetrated by smaller nanospheres. By comparing depletion potentials from simulations of ellipsoidal and spherical polymer models with predictions of polymer field theory and free-volume theory, we show that polymer depletion-induced interactions and crowding depend sensitively on polymer shapes and penetrability, with important implications for bulk thermodynamic phase behavior.

  2. 3 CFR 8418 - Proclamation 8418 of September 16, 2009. Constitution Day and Citizenship Day, Constitution Week...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    .... Constitution Day and Citizenship Day, Constitution Week, 2009 8418 Proclamation 8418 Presidential Documents Proclamations Proclamation 8418 of September 16, 2009 Proc. 8418 Constitution Day and Citizenship Day... citizenship, the Congress, by joint resolution of February 29, 1952 (36 U.S.C. 106), designated September...

  3. 77 FR 57981 - Constitution Day and Citizenship Day, Constitution Week, 2012

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-09-18

    ... of the United States of America the two hundred and thirty- seventh. (Presidential Sig.) [FR Doc... September 18, 2012 Part VI The President Proclamation 8862--Constitution Day and Citizenship Day... ] Proclamation 8862 of September 13, 2012 Constitution Day and Citizenship Day, Constitution Week, 2012 By...

  4. 3 CFR 8714 - Proclamation 8714 of September 16, 2011. Constitution Day and Citizenship Day, Constitution Week...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    .... Constitution Day and Citizenship Day, Constitution Week, 2011 8714 Proclamation 8714 Presidential Documents Proclamations Proclamation 8714 of September 16, 2011 Proc. 8714 Constitution Day and Citizenship Day... because they believed in what our country stands for. Every year, thousands of candidates for...

  5. 78 FR 57777 - Constitution Day and Citizenship Day, Constitution Week, 2013

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-19

    .... (Presidential Sig.) [FR Doc. 2013-23014 Filed 9-18-13; 11:15 am] Billing code 3295-F3 ... September 19, 2013 Part IV The President Proclamation 9019--Constitution Day and Citizenship Day... September 16, 2013 Constitution Day and Citizenship Day, Constitution Week, 2013 By the President of...

  6. 3 CFR 8862 - Proclamation 8862 of September 13, 2012. Constitution Day and Citizenship Day, Constitution Week...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    .... Constitution Day and Citizenship Day, Constitution Week, 2012 8862 Proclamation 8862 Presidential Documents Proclamations Proclamation 8862 of September 13, 2012 Proc. 8862 Constitution Day and Citizenship Day... candidates for citizenship who will commemorate this day by joining our American family. For more than...

  7. Constitutive Modeling and Numerical Simulation of Frp Confined Concrete Specimens

    NASA Astrophysics Data System (ADS)

    Smitha, Gopinath; Ramachandramurthy, Avadhanam; Nagesh, Ranganatha Iyer; Shahulhameed, Eduvammal Kunhimoideen

    2014-09-01

    Fiber-reinforced polymer (FRP) composites are generally used for the seismic retrofit of concrete members to enhance their strength and ductility. In the present work, the confining effect of Carbon Fiber-Reinforced Polymer (CFRP) composite layers has been investigated by numerical simulation. The numerical simulation has been carried out using nonlinear finite element analysis (FEA) to predict the response behaviour of CFRP-wrapped concrete cylinders. The nonlinear behaviour of concrete in compression and the linear elastic behaviour of CFRP has been modeled using an appropriate constitutive relationship. A cohesive model has been developed for modeling the interface between the concrete and CFRP. The interaction and damage failure criteria between the concrete to the cohesive element and the cohesive element to the CFRP has also been accounted for in the modeling. The response behaviour of the wrapped concrete specimen has been compared with the proposed interface model and with a perfectly bonded condition. The results obtained from the present study showed good agreement with the experimental load-displacement response and the failure pattern in the literature. Further, a sensitivity analysis has been carried out to study the effect of the number of layers of CFRP on the concrete specimens. It has been observed that wrapping with two layers was found to be the optimum, beyond which the response becomes flexible but with a higher load-carrying capacity

  8. Phthalocyanine polymers

    NASA Technical Reports Server (NTRS)

    Achar, B. N.; Fohlen, G. M.; Parker, J. A. (Inventor)

    1985-01-01

    A method of forming 4,4',4'',4''' -tetraamino phthalocyanines involves reducing 4,4',4'',4''' -tetranitro phthalocyanines, polymerizing the metal tetraamino phthalocyanines with a tetracarboxylic dianhydride (preferably aromatic) or copolymerizing with a tetracarboxylic dianhydride and a diamine (preferably also aromatic) to produce amic acids which are then dehydrocyclized to imides. Thermally and oxidatively stable polymers result which form tough, flexible films, varnishes, adhesives, and fibers.

  9. Small-molecule modulators of the constitutive androstane receptor

    PubMed Central

    Cherian, Milu T.; Chai, Sergio C.; Chen, Taosheng

    2015-01-01

    Introduction The constitutive androstane receptor (CAR) induces drug-metabolizing enzymes for xenobiotic metabolism. Areas covered This review covers recent advances in elucidating the biological functions of CAR and its modulation by a growing number of agonists and inhibitors. Expert opinion Extrapolation of animal CAR function to that of humans should be carefully scrutinized, particularly when rodents are used in evaluating the metabolic profile and carcinogenic properties of clinical drugs and environmental chemicals. Continuous efforts are needed to discover novel CAR inhibitors, with extensive understanding of their inhibitory mechanism, species selectivity, and discriminating power against other xenobiotic sensors. PMID:25979168

  10. Periodic Polymers

    NASA Astrophysics Data System (ADS)

    Thomas, Edwin

    2013-03-01

    Periodic polymers can be made by self assembly, directed self assembly and by photolithography. Such materials provide a versatile platform for 1, 2 and 3D periodic nano-micro scale composites with either dielectric or impedance contrast or both, and these can serve for example, as photonic and or phononic crystals for electromagnetic and elastic waves as well as mechanical frames/trusses. Compared to electromagnetic waves, elastic waves are both less complex (longitudinal modes in fluids) and more complex (longitudinal, transverse in-plane and transverse out-of-plane modes in solids). Engineering of the dispersion relation between wave frequency w and wave vector, k enables the opening of band gaps in the density of modes and detailed shaping of w(k). Band gaps can be opened by Bragg scattering, anti-crossing of bands and discrete shape resonances. Current interest is in our group focuses using design - modeling, fabrication and measurement of polymer-based periodic materials for applications as tunable optics and control of phonon flow. Several examples will be described including the design of structures for multispectral band gaps for elastic waves to alter the phonon density of states, the creation of block polymer and bicontinuous metal-carbon nanoframes for structures that are robust against ballistic projectiles and quasi-crystalline solid/fluid structures that can steer shock waves.

  11. Conductive Polymers

    SciTech Connect

    Bohnert, G.W.

    2002-11-22

    Electroluminescent devices such as light-emitting diodes (LED) and high-energy density batteries. These new polymers offer cost savings, weight reduction, ease of processing, and inherent rugged design compared to conventional semiconductor materials. The photovoltaic industry has grown more than 30% during the past three years. Lightweight, flexible solar modules are being used by the U.S. Army and Marine Corps for field power units. LEDs historically used for indicator lights are now being investigated for general lighting to replace fluorescent and incandescent lights. These so-called solid-state lights are becoming more prevalent across the country since they produce efficient lighting with little heat generation. Conductive polymers are being sought for battery development as well. Considerable weight savings over conventional cathode materials used in secondary storage batteries make portable devices easier to carry and electric cars more efficient and nimble. Secondary battery sales represent an $8 billion industry annually. The purpose of the project was to synthesize and characterize conductive polymers. TRACE Photonics Inc. has researched critical issues which affect conductivity. Much of their work has focused on production of substituted poly(phenylenevinylene) compounds. These compounds exhibit greater solubility over the parent polyphenylenevinylene, making them easier to process. Alkoxy substituted groups evaluated during this study included: methoxy, propoxy, and heptyloxy. Synthesis routes for production of alkoxy-substituted poly phenylenevinylene were developed. Considerable emphasis was placed on final product yield and purity.

  12. The Constitution and the Black Experiences

    ERIC Educational Resources Information Center

    Miles, E. W.

    1973-01-01

    A review of the constitutional promises to black people, early congressional efforts to fulfill these promises, early court cases construing the Fourteenth Amendment and the impact of these decisions along with their subsequent overruling. (Author/JB)

  13. Biomedical Applications of Biodegradable Polymers

    PubMed Central

    Ulery, Bret D.; Nair, Lakshmi S.; Laurencin, Cato T.

    2011-01-01

    Utilization of polymers as biomaterials has greatly impacted the advancement of modern medicine. Specifically, polymeric biomaterials that are biodegradable provide the significant advantage of being able to be broken down and removed after they have served their function. Applications are wide ranging with degradable polymers being used clinically as surgical sutures and implants. In order to fit functional demand, materials with desired physical, chemical, biological, biomechanical and degradation properties must be selected. Fortunately, a wide range of natural and synthetic degradable polymers has been investigated for biomedical applications with novel materials constantly being developed to meet new challenges. This review summarizes the most recent advances in the field over the past 4 years, specifically highlighting new and interesting discoveries in tissue engineering and drug delivery applications. PMID:21769165

  14. Electrospinning of Bioinspired Polymer Scaffolds.

    PubMed

    Araujo, Jose V; Carvalho, Pedro P; Best, Serena M

    2015-01-01

    Electrospinning is a technique used in the production of polymer nanofibre meshes. The use of biodegradable and biocompatible polymers to produce nanofibres that closely mimic the extracellular matrix (ECM) of different tissues has opened a wide range of possibilities for the application of electrospinning in Tissue Engineering. It is believed that nano-features (such as voids and surface cues) present in nanofibre mesh scaffolds, combined with the chemical composition of the fibres, can stimulate cell attachment, growth and differentiation. Despite the widespread use of electrospun nanofibres in tissue engineering, the present chapter will focus on the advances made in the utilisation of these materials in bone, cartilage and tooth related applications. Several aspects will be taken into consideration, namely the choice of polymers, the surface modification of the nanofibres in order to achieve mineralisation, and also the biological application of such materials. PMID:26545743

  15. Electrospinning of Bioinspired Polymer Scaffolds.

    PubMed

    Araujo, Jose V; Carvalho, Pedro P; Best, Serena M

    2015-01-01

    Electrospinning is a technique used in the production of polymer nanofibre meshes. The use of biodegradable and biocompatible polymers to produce nanofibres that closely mimic the extracellular matrix (ECM) of different tissues has opened a wide range of possibilities for the application of electrospinning in Tissue Engineering. It is believed that nano-features (such as voids and surface cues) present in nanofibre mesh scaffolds, combined with the chemical composition of the fibres, can stimulate cell attachment, growth and differentiation. Despite the widespread use of electrospun nanofibres in tissue engineering, the present chapter will focus on the advances made in the utilisation of these materials in bone, cartilage and tooth related applications. Several aspects will be taken into consideration, namely the choice of polymers, the surface modification of the nanofibres in order to achieve mineralisation, and also the biological application of such materials.

  16. Polymer Electronics: Power from Polymers

    SciTech Connect

    Venkataraman, D.; Russell, Thomas P.

    2012-06-19

    We review polymer-based electronics and photovoltaics to provide the reader with a sense of how the field has developed, where we stand at present, and what possibilities are looming in the future. Expertise in areas ranging from synthesis to morphology to device design was sought to achieve this end. While these reviews cannot be exhaustive, they do provide a snapshot of the field at present and give some sense of where the key impediments are.

  17. South African court rejects country's new constitution.

    PubMed

    1996-09-20

    Fundamental principles designed to ensure that South Africa's new constitution upholds a wide range of individual rights and freedoms and establishes a responsive government with a balanced separation of powers, including recognition of the role of traditional tribal leadership, were adopted into the current interim constitution shortly before the 1994 free elections which brought Nelson Mandela and the African National Congress to power. In a judgement issued on September 6, 1996, South Africa's Constitutional Court rejected the country's new draft constitution, arguing that it failed to meet the standards of nine of the 34 principles established at the Kempton Park negotiations. The Constitutional Assembly is comprised of a joint meeting of the National Assembly and Senate. One of the court's major objections to the constitution concerned the proposed structure of rule, which was seen to give inadequate power to South Africa's nine provinces as compared with the national government. However, the bill of rights was almost entirely upheld. The bill would create a favorable environment for legalized abortion and guarantee a universal right of access to health care, including reproductive health services

  18. Computational systems chemical biology.

    PubMed

    Oprea, Tudor I; May, Elebeoba E; Leitão, Andrei; Tropsha, Alexander

    2011-01-01

    There is a critical need for improving the level of chemistry awareness in systems biology. The data and information related to modulation of genes and proteins by small molecules continue to accumulate at the same time as simulation tools in systems biology and whole body physiologically based pharmacokinetics (PBPK) continue to evolve. We called this emerging area at the interface between chemical biology and systems biology systems chemical biology (SCB) (Nat Chem Biol 3: 447-450, 2007).The overarching goal of computational SCB is to develop tools for integrated chemical-biological data acquisition, filtering and processing, by taking into account relevant information related to interactions between proteins and small molecules, possible metabolic transformations of small molecules, as well as associated information related to genes, networks, small molecules, and, where applicable, mutants and variants of those proteins. There is yet an unmet need to develop an integrated in silico pharmacology/systems biology continuum that embeds drug-target-clinical outcome (DTCO) triplets, a capability that is vital to the future of chemical biology, pharmacology, and systems biology. Through the development of the SCB approach, scientists will be able to start addressing, in an integrated simulation environment, questions that make the best use of our ever-growing chemical and biological data repositories at the system-wide level. This chapter reviews some of the major research concepts and describes key components that constitute the emerging area of computational systems chemical biology.

  19. Polymers influencing transportability profile of drug

    PubMed Central

    Gaikwad, Vinod L.; Bhatia, Manish S.

    2013-01-01

    Drug release from various polymers is generally governed by the type of polymer/s incorporated in the formulation and mechanism of drug release from polymer/s. A single polymer may show one or more mechanisms of drug release out of which one mechanism is majorly followed for drug release. Some of the common mechanisms of drug release from polymers were, diffusion, swelling, matrix release, leaching of drug, etc. Mechanism or rate of drug release from a polymer or a combination of polymers can be predicted by using different computational methods or models. These models were capable of predicting drug release from its dosage form in advance without actual formulation and testing of drug release from dosage form. Quantitative structure–property relationship (QSPR) is an important tool used in the prediction of various physicochemical properties of actives as well as inactives. Since last several decades QSPR has been applied in new drug development for reducing the total number of drugs to be synthesized, as it involves a selection of the most desirable compound of interest. This technique was also applied in predicting in vivo performance of drug/s for various parameters. QSPR serves as a predictive tool to correlate structural descriptors of molecules with biological as well as physicochemical properties. Several researchers have contributed at different extents in this area to modify various properties of pharmaceuticals. The present review is focused on a study of different polymers that influence the transportability profiles of drugs along with the application of QSPR either to study different properties of polymers that regulate drug release or in predicting drug transportability from different polymer systems used in formulations. PMID:24227951

  20. Molecular Mechanisms of Failure in Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Gersappe, Dilip

    2002-07-01

    Molecular dynamics simulations of polymers reinforced with nanoscopic filler particles reveal the mechanisms by which nanofillers improve the toughness of the material. We find that the mobility of the nanofiller particle, rather than its surface area, controls its ability to dissipate energy. Our results show similarities between the toughening mechanisms observed in polymer nanocomposites and those postulated for biological structural materials such as spider silk and abalone adhesive.

  1. Health care law versus constitutional law.

    PubMed

    Hall, Mark A

    2013-04-01

    National Federation of Independent Business v. Sebelius, the Supreme Court's ruling on the Patient Protection and Affordable Care Act, is a landmark decision - both for constitutional law and for health care law and policy. Others will study its implications for constitutional limits on a range of federal powers beyond health care. This article considers to what extent the decision is also about health care law, properly conceived. Under one view, health care law is the subdiscipline that inquires how courts and government actors take account of the special features of medicine that make legal or policy issues especially problematic - rather than regarding health care delivery and finance more generically, like most any other economic or social enterprise. Viewed this way, the opinions from the Court's conservative justices are mainly about general constitutional law principles. In contrast, Justice Ruth Bader Ginsburg's dissenting opinion for the four more liberal justices is just as much about health care law as it is about constitutional law. Her opinion gives detailed attention to the unique features of health care finance and delivery in order to inform her analysis of constitutional precedents and principles. Thus, the Court's multiple opinions give a vivid depiction of the compelling contrasts between communal versus individualistic conceptions of caring for those in need, and between health care and health insurance as ordinary commodities versus ones that merit special economic, social, and legal status.

  2. A constitutive theory of reacting electrolyte mixtures

    NASA Astrophysics Data System (ADS)

    Costa Reis, Martina; Wang, Yongqi; Bono Maurizio Sacchi Bassi, Adalberto

    2013-11-01

    A constitutive theory of reacting electrolyte mixtures is formulated. The intermolecular interactions among the constituents of the mixture are accounted for through additional freedom degrees to each constituent of the mixture. Balance equations for polar reacting continuum mixtures are accordingly formulated and a proper set of constitutive equations is derived with basis in the Müller-Liu formulation of the second law of thermodynamics. Moreover, the non-equilibrium and equilibrium responses of the reacting mixture are investigated in detail by emphasizing the inner and reactive structures of the medium. From the balance laws and constitutive relations, the effects of molecular structure of constituents upon the fluid flow are studied. It is also demonstrated that the local thermodynamic equilibrium state can be reached without imposing that the set of independent constitutive variables is time independent, neither spatially homogeneous nor null. The resulting constitutive relations presented throughout this work are of relevance to many practical applications, such as swelling of clays, developing of bio and polymeric membranes, and use of electrorheological fluids in industrial processes. The first author acknowledges financial support from National Counsel of Technological and Scientific Development (CNPq) and German Academic Exchange Service (DAAD).

  3. Interpretations of Polymer-Polymer Miscibility.

    ERIC Educational Resources Information Center

    Olabisi, Olagoke

    1981-01-01

    Discusses various aspects of polymeric mixtures, mixtures of structurally different homopolymers, copolymers, terpolymers, and the like. Defines concepts of polymer-polymer miscibility from practical and theoretical viewpoints, and ways of predicting such miscibility. (JN)

  4. Unexpected power-law stress relaxation of entangled ring polymers

    NASA Astrophysics Data System (ADS)

    Kapnistos, M.; Lang, M.; Vlassopoulos, D.; Pyckhout-Hintzen, W.; Richter, D.; Cho, D.; Chang, T.; Rubinstein, M.

    2008-12-01

    After many years of intense research, most aspects of the motion of entangled polymers have been understood. Long linear and branched polymers have a characteristic entanglement plateau and their stress relaxes by chain reptation or branch retraction, respectively. In both mechanisms, the presence of chain ends is essential. But how do entangled polymers without ends relax their stress? Using properly purified high-molar-mass ring polymers, we demonstrate that these materials exhibit self-similar dynamics, yielding a power-law stress relaxation. However, trace amounts of linear chains at a concentration almost two decades below their overlap cause an enhanced mechanical response. An entanglement plateau is recovered at higher concentrations of linear chains. These results constitute an important step towards solving an outstanding problem of polymer science and are useful for manipulating properties of materials ranging from DNA to polycarbonate. They also provide possible directions for tuning the rheology of entangled polymers.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    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.

  6. Unified constitutive equations of foam materials

    SciTech Connect

    Chang, Fu S.; Song, Y.; Lu, D.X.; DeSilva, C.N.

    1998-07-01

    Foam materials, because of their energy absorbing and recovery behavior during impact as well as lightweight and moldable characteristics, have found more and more applications in the automotive industry. A unified constitutive equation with the effect of compression strain rate, tension strain, and shear strain for foam materials with very low Poisson`s ratio has been developed. The mathematical derivation of the constitutive equation is described in detail. The effect of each parameter in the constitutive equation is studied. Numerical formula and procedure are also included in the paper. The test data of two types of energy absorbing foam materials are used for correlation study: polyurethane foam, which was tested at five compressive strain rates, and polypropylene foam, which was tested for quasi-static compression, tension, and shear. Good correlations have been concluded for both cases.

  7. Acoustomechanical constitutive theory for soft materials

    NASA Astrophysics Data System (ADS)

    Xin, Fengxian; Lu, Tian Jian

    2016-07-01

    Acoustic wave propagation from surrounding medium into a soft material can generate acoustic radiation stress due to acoustic momentum transfer inside the medium and material, as well as at the interface between the two. To analyze acoustic-induced deformation of soft materials, we establish an acoustomechanical constitutive theory by combining the acoustic radiation stress theory and the nonlinear elasticity theory for soft materials. The acoustic radiation stress tensor is formulated by time averaging the momentum equation of particle motion, which is then introduced into the nonlinear elasticity constitutive relation to construct the acoustomechanical constitutive theory for soft materials. Considering a specified case of soft material sheet subjected to two counter-propagating acoustic waves, we demonstrate the nonlinear large deformation of the soft material and analyze the interaction between acoustic waves and material deformation under the conditions of total reflection, acoustic transparency, and acoustic mismatch.

  8. Thermoelastic constitutive equations for chemically hardening materials

    NASA Technical Reports Server (NTRS)

    Shaffer, B. W.; Levitsky, M.

    1974-01-01

    Thermoelastic constitutive equations are derived for a material undergoing solidification or hardening as the result of a chemical reaction. The derivation is based upon a two component model whose composition is determined by the degree of hardening, and makes use of strain-energy considerations. Constitutive equations take the form of stress rate-strain rate relations, in which the coefficients are time-dependent functions of the composition. Specific results are developed for the case of a material of constant bulk modulus which undergoes a transition from an initial liquidlike state into an isotropic elastic solid. Potential applications are discussed.

  9. Composites comprising biologically-synthesized nanomaterials

    DOEpatents

    Curran, Seamus; Dias, Sampath; Blau, Werner; Wang, Jun; Oremland, Ronald S; Baesman, Shaun

    2013-04-30

    The present disclosure describes composite materials containing a polymer material and a nanoscale material dispersed in the polymer material. The nanoscale materials may be biologically synthesized, such as tellurium nanorods synthesized by Bacillus selenitireducens. Composite materials of the present disclosure may have optical limiting properties and find use in optical limiting devices.

  10. Protein-polymer nanoreactors for medical applications.

    PubMed

    Palivan, Cornelia G; Fischer-Onaca, Ozana; Delcea, Mihaela; Itel, Fabian; Meier, Wolfgang

    2012-04-01

    Major challenges that confront nanoscience in medicine today include the development of efficacious therapies with minimum side effects, diagnostic methods featuring significantly higher sensitivities and selectivities, and personalized diagnostics and therapeutics for theragnostic approaches. With these goals in mind, combining biological molecules and synthetic carriers/templates, such as polymer supramolecular assemblies, represents a very promising strategy. In this critical review, we present protein-polymer systems as reaction spaces at the nano-scale in which the enzymatic reactions take place inside polymer supramolecular assembly, at its interface with the environment or in a combination of both. The location of the protein(s) with respect to the polymer assembly generates a diversity of systems ranging from nanoreactors to active enzymatic polymer surfaces. We describe these both in terms of general modelling and addressing the specific conditions and requirements related to the medical domain. We will particularly present protein-polymer nanoreactors that provide protected spaces for enzymatic reactions. We also show how polymer supramolecular structures, such as micelles, capsules, dendrimers and vesicles, can accommodate sensitive biomolecules to mimic natural systems and functions, and to serve as avenues for new medical approaches. Even though not yet on the market, we will emphasize possible applications of protein-polymer systems that generate reaction nanospaces-as novel ways to advanced medicine (264 references).

  11. Rate Dependent Deformation and Strength Analysis of Polymer Matrix Composites

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Stouffer, Donald C.

    1999-01-01

    A research program is being undertaken to develop rate dependent deformation and failure models for the analysis of polymer matrix composite materials. In previous work in this program, strain-rate dependent inelastic constitutive equations used to analyze polymers have been implemented into a mechanics of materials based composite micromechanics method. In the current work, modifications to the micromechanics model have been implemented to improve the calculation of the effective inelastic strain. Additionally, modifications to the polymer constitutive model are discussed in which pressure dependence is incorporated into the equations in order to improve the calculation of constituent and composite shear stresses. The Hashin failure criterion is implemented into the analysis method to allow for the calculation of ply level failure stresses. The deformation response and failure stresses for two representative uniaxial polymer matrix composites, IM7/977-2 and AS4-PEEK, are predicted for varying strain rates and fiber orientations. The predicted results compare favorably to experimentally obtained values.

  12. Biologically inspired toys using artificial muscles

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Y.

    2001-01-01

    Recent developments in electroactive polymers, so-called artificial muscles, could one day be used to make bionics possible. Meanwhile, as this technology evolves novel mechanisms are expected to emerge that are biologically inspired.

  13. Nanotribology of charged polymer brushes

    NASA Astrophysics Data System (ADS)

    Klein, Jacob

    Polymers at surfaces, whose modern understanding may be traced back to early work by Sam Edwards1, have become a paradigm for modification of surface properties, both as steric stabilizers and as remarkable boundary lubricants2. Charged polymer brushes are of particular interest, with both technological implications and especially biological relevance where most macromolecules are charged. In the context of biolubrication, relevant in areas from dry eye syndrome to osteoarthritis, charged polymer surface phases and their complexes with other macromolecules may play a central role. The hydration lubrication paradigm, where tenaciously-held yet fluid hydration shells surrounding ions or zwitterions serve as highly-efficient friction-reducing elements, has been invoked to understand the excellent lubrication provided both by ionized3 and by zwitterionic4 brushes. In this talk we describe recent advances in our understanding of the nanotribology of such charged brush systems. We consider interactions between charged end-grafted polymers, and how one may disentangle the steric from the electrostatic surface forces5. We examine the limits of lubrication by ionized brushes, both synthetic and of biological origins, and how highly-hydrated zwitterionic chains may provide extremely effective boundary lubrication6. Finally we describe how the lubrication of articular cartilage in the major joints, a tribosystem presenting some of the greatest challenges and opportunities, may be understood in terms of a supramolecular synergy between charged surface-attached polymers and zwitterionic groups7. Work supported by European Research Council (HydrationLube), Israel Science Foundation (ISF), Petroleum Research Fund of the American Chemical Society, ISF-NSF China Joint Program.

  14. 3 CFR 9019 - Proclamation 9019 of September 16, 2013. Constitution Day and Citizenship Day, Constitution Week...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ..., Constitution Week, 2013By the President of the United States of America A Proclamation In May of 1787... each year as “Constitution Week.” NOW, THEREFORE, I, BARACK OBAMA, President of the United States of... September, in the year of our Lord two thousand thirteen, and of the Independence of the......

  15. The constitutive equation for membrane tether extraction.

    PubMed

    Chen, Yong; Yao, Da-Kang; Shao, Jin-Yu

    2010-12-01

    Membrane tethers or nanotubes play a critical role in a variety of cellular and subcellular processes such as leukocyte rolling and intercellular mass transport. The current constitutive equations that describe the relationship between the pulling force and the tether velocity during tether extraction have serious limitations. In this article, we propose a new phenomenological constitutive equation that captures all known characteristics of nanotube formation, including nonlinearity, nonzero threshold force, and possible negative tether velocity. We used tether extraction from endothelial cells as a prototype to illustrate how to obtain the material constants in the constitutive equation. With the micropipette aspiration technique, we measured tether pulling forces at both positive and negative tether velocities. We also determined the threshold force of 55 pN experimentally for the first time. This new constitutive equation unites two established ones and provides us a unified platform to better understand not only the physiological role of tether extraction during leukocyte rolling and intercellular or intracellular transport, but also the physics of membrane tether growth or retraction.

  16. Celebrating the Constitution: A Bicentennial Retrospective.

    ERIC Educational Resources Information Center

    Walch, Timothy G., Ed.

    1988-01-01

    This commemorative document was published to celebrate the Bicentennial of the signing of the U.S. Constitution and to pay tribute to the bicentennial celebration efforts of the U.S. National Archives and Records Administration staff. The included articles are: (1) "Introduction: A Celebration at the National Archives" (F. Burke); (2) "The Odyssey…

  17. James Madison and the Constitutional Convention.

    ERIC Educational Resources Information Center

    Scanlon, Thomas M.

    1987-01-01

    Part 1 of this three-part article traces James Madison's life and focuses primarily on those events that prepared him for leadership in the U.S. Constitutional Convention of 1787. It describes his early love of learning, education, and public service efforts. Part 2 chronicles Madison's devotion to study and preparation prior to the Constitutional…

  18. Crushed-salt constitutive model update

    SciTech Connect

    Callahan, G.D.; Loken, M.C.; Mellegard, K.D.

    1998-01-01

    Modifications to the constitutive model used to describe the deformation of crushed salt are presented in this report. Two mechanisms--dislocation creep and grain boundary diffusional pressure solutioning--defined previously but used separately are combined to form the basis for the constitutive model governing the deformation of crushed salt. The constitutive model is generalized to represent three-dimensional states of stress. New creep consolidation tests are combined with an existing database that includes hydrostatic consolidation and shear consolidation tests conducted on Waste Isolation Pilot Plant and southeastern New Mexico salt to determine material parameters for the constitutive model. Nonlinear least-squares model fitting to data from the shear consolidation tests and a combination of the shear and hydrostatic consolidation tests produced two sets of material parameter values for the model. The change in material parameter values from test group to test group indicates the empirical nature of the model but demonstrates improvement over earlier work with the previous models. Key improvements are the ability to capture lateral strain reversal and better resolve parameter values. To demonstrate the predictive capability of the model, each parameter value set was used to predict each of the tests in the database. Based on the fitting statistics and the ability of the model to predict the test data, the model appears to capture the creep consolidation behavior of crushed salt quite well.

  19. Censorship of Obscenity: The Developing Constitutional Standards.

    ERIC Educational Resources Information Center

    Lockhart, William B.; McClure, Robert C.

    1960-01-01

    To demonstrate that substantial protection has been given to published material dealing with sex, an analysis of the constitutional criteria governing recent Supreme Court decisions in the area of obscenity censorship is presented. It is found that the Supreme Court uses "hard core pornography" as the foundation of a "constant" concept of…

  20. Student Perspectives on Behaviors That Constitute Cheating

    ERIC Educational Resources Information Center

    Higbee, Jeanne L.; Schultz, Jennifer L.; Sanford, Thomas

    2011-01-01

    A previous study conducted a decade ago determined that there can be considerable disagreement--not only between students and faculty, but also among students and among faculty--regarding behaviors that constitute cheating. This article reports the results of a research study that replicated the student survey administered for the previous study,…

  1. School Choice and State Constitutions' Religion Clauses

    ERIC Educational Resources Information Center

    Komer, Richard D.

    2009-01-01

    After the U.S. Supreme Court's decision in "Zelman v. Simmons-Harris," only state religion clauses represent a potential constitutional bar to the inclusion of religious options in properly designed school choice programs. The two most significant are compelled support clauses and Blaine Amendments. Both are frequently misinterpreted by state…

  2. Rapping the 27 Amendments to the Constitution

    ERIC Educational Resources Information Center

    Knaresborough, Adam

    2009-01-01

    Early in the year, the students of history and government at Mountain View High School in Stafford, Virginia, began to devise hand motions to help memorize the 27 amendments to the Constitution for government class. Three students in the school who are interested in hip hop music then suggested composing a rap song about the topic. Working with…

  3. The Search for Constitutional School Choice.

    ERIC Educational Resources Information Center

    Bauknight, Suzanne H.

    1998-01-01

    Addresses the constitutionality of tuition-voucher programs that provide access to private, parochial schools. Surveys Establishment Clause jurisprudence of the United States Supreme Court. Examines the Cleveland, Ohio, and Milwaukee, Wisconsin, tuition-voucher programs, currently being litigated in the respective state courts, in an attempt to…

  4. 7 CFR 718.201 - Farm constitution.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... land after the last constitution or reconstitution and as a result of such change the farm does not... agency programs and monitor farmer compliance with regulations, the agency must have records on what land is being farmed by a particular producer. This is accomplished by a determination of what land...

  5. Chemical and Biological Kinetics

    NASA Astrophysics Data System (ADS)

    Emanuel', N. M.

    1981-10-01

    Examples of the application of the methods and ideas of chemical kinetics in various branches of chemistry and biology are considered and the results of studies on the kinetics and mechanisms of autoxidation and inhibited and catalysed oxidation of organic substances in the liquid phase are surveyed. Problems of the kinetics of the ageing of polymers and the principles of their stabilisation are discussed and certain trends in biological kinetics (kinetics of tumour growth, kinetic criteria of the effectiveness of chemotherapy, problems of gerontology, etc.) are considered. The bibliography includes 281 references.

  6. Multifunctional and biologically active matrices from multicomponent polymeric solutions

    NASA Technical Reports Server (NTRS)

    Kiick, Kristi L. (Inventor); Yamaguchi, Nori (Inventor)

    2010-01-01

    The present invention relates to a biologically active functionalized electrospun matrix to permit immobilization and long-term delivery of biologically active agents. In particular the invention relates to a functionalized polymer matrix comprising a matrix polymer, a compatibilizing polymer and a biomolecule or other small functioning molecule. In certain aspects the electrospun polymer fibers comprise at least one biologically active molecule functionalized with low molecular weight heparin. Examples of active molecules that may be used with the multicomponent polymer of the invention include, for example, a drug, a biopolymer, for example a growth factor, a protein, a peptide, a nucleotide, a polysaccharide, a biological macromolecule or the like. The invention is further directed to the formation of functionalized crosslinked matrices, such as hydrogels, that include at least one functionalized compatibilizing polymer capable of assembly.

  7. Shape memory polymers

    SciTech Connect

    Wilson, Thomas S.; Bearinger, Jane P.

    2015-06-09

    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.

  8. Thermoelectric Polymers and their Elastic Aerogels.

    PubMed

    Khan, Zia Ullah; Edberg, Jesper; Hamedi, Mahiar Max; Gabrielsson, Roger; Granberg, Hjalmar; Wågberg, Lars; Engquist, Isak; Berggren, Magnus; Crispin, Xavier

    2016-06-01

    Electronically conducting polymers constitute an emerging class of materials for novel electronics, such as printed electronics and flexible electronics. Their properties have been further diversified to introduce elasticity, which has opened new possibility for "stretchable" electronics. Recent discoveries demonstrate that conducting polymers have thermoelectric properties with a low thermal conductivity, as well as tunable Seebeck coefficients - which is achieved by modulating their electrical conductivity via simple redox reactions. Using these thermoelectric properties, all-organic flexible thermoelectric devices, such as temperature sensors, heat flux sensors, and thermoelectric generators, are being developed. In this article we discuss the combination of the two emerging fields: stretchable electronics and polymer thermoelectrics. The combination of elastic and thermoelectric properties seems to be unique for conducting polymers, and difficult to achieve with inorganic thermoelectric materials. We introduce the basic concepts, and state of the art knowledge, about the thermoelectric properties of conducting polymers, and illustrate the use of elastic thermoelectric conducting polymer aerogels that could be employed as temperature and pressure sensors in an electronic-skin.

  9. Optically responsive supramolecular polymer glasses

    NASA Astrophysics Data System (ADS)

    Balkenende, Diederik W. R.; Monnier, Christophe A.; Fiore, Gina L.; Weder, Christoph

    2016-03-01

    The reversible and dynamic nature of non-covalent interactions between the constituting building blocks renders many supramolecular polymers stimuli-responsive. This was previously exploited to create thermally and optically healable polymers, but it proved challenging to achieve high stiffness and good healability. Here we present a glass-forming supramolecular material that is based on a trifunctional low-molecular-weight monomer ((UPyU)3TMP). Carrying three ureido-4-pyrimidinone (UPy) groups, (UPyU)3TMP forms a dynamic supramolecular polymer network, whose properties are governed by its cross-linked architecture and the large content of the binding motif. This design promotes the formation of a disordered glass, which, in spite of the low molecular weight of the building block, displays typical polymeric behaviour. The material exhibits a high stiffness and offers excellent coating and adhesive properties. On account of reversible dissociation and the formation of a low-viscosity liquid upon irradiation with ultraviolet light, rapid optical healing as well as (de)bonding on demand is possible.

  10. Optically responsive supramolecular polymer glasses.

    PubMed

    Balkenende, Diederik W R; Monnier, Christophe A; Fiore, Gina L; Weder, Christoph

    2016-01-01

    The reversible and dynamic nature of non-covalent interactions between the constituting building blocks renders many supramolecular polymers stimuli-responsive. This was previously exploited to create thermally and optically healable polymers, but it proved challenging to achieve high stiffness and good healability. Here we present a glass-forming supramolecular material that is based on a trifunctional low-molecular-weight monomer ((UPyU)3TMP). Carrying three ureido-4-pyrimidinone (UPy) groups, (UPyU)3TMP forms a dynamic supramolecular polymer network, whose properties are governed by its cross-linked architecture and the large content of the binding motif. This design promotes the formation of a disordered glass, which, in spite of the low molecular weight of the building block, displays typical polymeric behaviour. The material exhibits a high stiffness and offers excellent coating and adhesive properties. On account of reversible dissociation and the formation of a low-viscosity liquid upon irradiation with ultraviolet light, rapid optical healing as well as (de)bonding on demand is possible. PMID:26983805

  11. Optically responsive supramolecular polymer glasses

    PubMed Central

    Balkenende, Diederik W. R.; Monnier, Christophe A.; Fiore, Gina L.; Weder, Christoph

    2016-01-01

    The reversible and dynamic nature of non-covalent interactions between the constituting building blocks renders many supramolecular polymers stimuli-responsive. This was previously exploited to create thermally and optically healable polymers, but it proved challenging to achieve high stiffness and good healability. Here we present a glass-forming supramolecular material that is based on a trifunctional low-molecular-weight monomer ((UPyU)3TMP). Carrying three ureido-4-pyrimidinone (UPy) groups, (UPyU)3TMP forms a dynamic supramolecular polymer network, whose properties are governed by its cross-linked architecture and the large content of the binding motif. This design promotes the formation of a disordered glass, which, in spite of the low molecular weight of the building block, displays typical polymeric behaviour. The material exhibits a high stiffness and offers excellent coating and adhesive properties. On account of reversible dissociation and the formation of a low-viscosity liquid upon irradiation with ultraviolet light, rapid optical healing as well as (de)bonding on demand is possible. PMID:26983805

  12. Materials comprising polydienes and hydrophilic polymers and related methods

    SciTech Connect

    Mays, Jimmy W.; Deng, Suxiang; Mauritz, Kenneth A.; Hassan, Mohammad K.; Gido, Samuel P.

    2011-11-22

    Materials prepared from polydienes, such as poly(cyclohexadiene), and hydrophilic polymers, such as poly(alkylene oxide), are described. Methods of making the materials and their use in fuel cell membranes, batteries, breathable chemical-biological protective materials, and templates for sol-gel polymerization are also provided. The materials can be crosslinked and sulfonated, and can include copolymers and polymer blends.

  13. Biological Threats

    MedlinePlus

    ... Thunderstorms & Lightning Tornadoes Tsunamis Volcanoes Wildfires Main Content Biological Threats Biological agents are organisms or toxins that ... Centers for Disease Control and Prevention . Before a Biological Threat Unlike an explosion, a biological attack may ...

  14. Polymers in the gut compress the colonic mucus hydrogel.

    PubMed

    Datta, Sujit S; Preska Steinberg, Asher; Ismagilov, Rustem F

    2016-06-28

    Colonic mucus is a key biological hydrogel that protects the gut from infection and physical damage and mediates host-microbe interactions and drug delivery. However, little is known about how its structure is influenced by materials it comes into contact with regularly. For example, the gut abounds in polymers such as dietary fibers or administered therapeutics, yet whether such polymers interact with the mucus hydrogel, and if so, how, remains unclear. Although several biological processes have been identified as potential regulators of mucus structure, the polymeric composition of the gut environment has been ignored. Here, we demonstrate that gut polymers do in fact regulate mucus hydrogel structure, and that polymer-mucus interactions can be described using a thermodynamic model based on Flory-Huggins solution theory. We found that both dietary and therapeutic polymers dramatically compressed murine colonic mucus ex vivo and in vivo. This behavior depended strongly on both polymer concentration and molecular weight, in agreement with the predictions of our thermodynamic model. Moreover, exposure to polymer-rich luminal fluid from germ-free mice strongly compressed the mucus hydrogel, whereas exposure to luminal fluid from specific-pathogen-free mice-whose microbiota degrade gut polymers-did not; this suggests that gut microbes modulate mucus structure by degrading polymers. These findings highlight the role of mucus as a responsive biomaterial, and reveal a mechanism of mucus restructuring that must be integrated into the design and interpretation of studies involving therapeutic polymers, dietary fibers, and fiber-degrading gut microbes.

  15. Constitutive response and mechanical properties of PFSA membranes in liquid water

    NASA Astrophysics Data System (ADS)

    Kusoglu, Ahmet; Tang, Yaliang; Lugo, Melissa; Karlsson, Anette M.; Santare, Michael H.; Cleghorn, Simon; Johnson, William B.

    The mechanical properties and swelling behavior of perfluorosulfonic acid (PFSA) membranes in liquid water have been investigated using a custom-built, temperature-controlled water bath. Interestingly, the theoretical models of Mooney-Rivlin and Ogden for rubber elasticity are shown to reproduce the major features of the experimentally obtained stress-strain relationships. In addition, stress relaxation of the membrane subjected to a fixed strain at room temperature fits time-dependent constitutive models used to describe nonlinear rubber elasticity. Thus, the experimental results suggest that even though PFSA is not an elastomer, the constitutive models developed for rubber-like behavior can be used for describing the ex situ constitutive response of PFSA membranes with high water content. This response is in contrast to the constitutive behavior of PFSA membranes swollen in water vapor (e.g. humid air and consequently lower water absorption in the membrane) where studies have suggested constitutive behavior corresponding to that of semicrystalline polymers, including distinct features such as a linear regime followed by onset of nonlinearity.

  16. Polymer Composites Corrosive Degradation: A Computational Simulation

    NASA Technical Reports Server (NTRS)

    Chamis, Christos C.; Minnetyan, Levon

    2007-01-01

    A computational simulation of polymer composites corrosive durability is presented. The corrosive environment is assumed to manage the polymer composite degradation on a ply-by-ply basis. The degradation is correlated with a measured pH factor and is represented by voids, temperature and moisture which vary parabolically for voids and linearly for temperature and moisture through the laminate thickness. The simulation is performed by a computational composite mechanics computer code which includes micro, macro, combined stress failure and laminate theories. This accounts for starting the simulation from constitutive material properties and up to the laminate scale which exposes the laminate to the corrosive environment. Results obtained for one laminate indicate that the ply-by-ply degradation degrades the laminate to the last one or the last several plies. Results also demonstrate that the simulation is applicable to other polymer composite systems as well.

  17. Polymer antidotes for toxin sequestration.

    PubMed

    Weisman, Adam; Chou, Beverly; O'Brien, Jeffrey; Shea, Kenneth J

    2015-08-01

    Toxins delivered by envenomation, secreted by microorganisms, or unintentionally ingested can pose an immediate threat to life. Rapid intervention coupled with the appropriate antidote is required to mitigate the threat. Many antidotes are biological products and their cost, methods of production, potential for eliciting immunogenic responses, the time needed to generate them, and stability issues contribute to their limited availability and effectiveness. These factors exacerbate a world-wide challenge for providing treatment. In this review we evaluate a number of polymer constructs that may serve as alternative antidotes. The range of toxins investigated includes those from sources such as plants, animals and bacteria. The development of polymeric heavy metal sequestrants for use as antidotes to heavy metal poisoning faces similar challenges, thus recent findings in this area have also been included. Two general strategies have emerged for the development of polymeric antidotes. In one, the polymer acts as a scaffold for the presentation of ligands with a known affinity for the toxin. A second strategy is to generate polymers with an intrinsic affinity, and in some cases selectivity, to a range of toxins. Importantly, in vivo efficacy has been demonstrated for each of these strategies, which suggests that these approaches hold promise as an alternative to biological or small molecule based treatments.

  18. Biaxial constitutive equation development for single crystals

    NASA Technical Reports Server (NTRS)

    Jordan, E. H.

    1984-01-01

    Current gas turbine engines utilize large single crystal superalloy components in the hot section. Structural analysis of these components requires a valid stress strain temperature constitutive equation. The goal of the program described is to create one or more models and verify these models. A constitutive equation based on an assumed slip behavior of a single slip system was formulated, programmed, and debugged. Specifically, the basic theory for a model based on aggravating slip behavior on individual slip systems was formulated and programmed and some simulations were run using assumed values of constants. In addition, a formulation allowing strain controlled simulations was completed. An approach to structural analysis of the specimen was developed. This approach uses long tube consistancy conditions and finite elements specially formulated to take advantage of the symmetry of 100 oriented specimens.

  19. In quest of constitutional principles of "neurolaw".

    PubMed

    Pizzetti, Federico Gustavo

    2011-01-01

    The growing use of brain imaging technology and the developing of cognitive neuroscience pose unaccustomed challenges to legal systems. Until now, the fields of Law much affected are the civil and criminal law and procedure, but the constitutional dimension of "neurolaw" cannot be easily underestimated. As the capacity to investigate and to trace brain mechanisms and functional neural activities increases, it becomes urgent the recognition and definition of the unalienable rights and fundamental values in respect of this new techno-scientific power, that must be protected and safeguard at "constitutional level" of norms such as: human dignity, personal identity, authenticity and the pursuit of individual "happiness". As the same as for the law regulating research and experimentation on human genome adopted in the past years, one may also argue if the above mentioned fundamental principles of "neurolaw" must be fixed and disciplined also at European and International level. PMID:23057208

  20. Constitutive Modeling of Crosslinked Nanotube Materials

    NASA Technical Reports Server (NTRS)

    Odegard, G. M.; Frankland, S. J. V.; Herzog, M. N.; Gates, T. S.; Fay, C. C.

    2004-01-01

    A non-linear, continuum-based constitutive model is developed for carbon nanotube materials in which bundles of aligned carbon nanotubes have varying amounts of crosslinks between the nanotubes. The model accounts for the non-linear elastic constitutive behavior of the material in terms of strain, and is developed using a thermodynamic energy approach. The model is used to examine the effect of the crosslinking on the overall mechanical properties of variations of the crosslinked carbon nanotube material with varying degrees of crosslinking. It is shown that the presence of the crosslinks has significant effects on the mechanical properties of the carbon nanotube materials. An increase in the transverse shear properties is observed when the nanotubes are crosslinked. However, this increase is accompanied by a decrease in axial mechanical properties of the nanotube material upon crosslinking.

  1. In quest of constitutional principles of "neurolaw".

    PubMed

    Pizzetti, Federico Gustavo

    2011-01-01

    The growing use of brain imaging technology and the developing of cognitive neuroscience pose unaccustomed challenges to legal systems. Until now, the fields of Law much affected are the civil and criminal law and procedure, but the constitutional dimension of "neurolaw" cannot be easily underestimated. As the capacity to investigate and to trace brain mechanisms and functional neural activities increases, it becomes urgent the recognition and definition of the unalienable rights and fundamental values in respect of this new techno-scientific power, that must be protected and safeguard at "constitutional level" of norms such as: human dignity, personal identity, authenticity and the pursuit of individual "happiness". As the same as for the law regulating research and experimentation on human genome adopted in the past years, one may also argue if the above mentioned fundamental principles of "neurolaw" must be fixed and disciplined also at European and International level.

  2. The role of anticipation in the constitution of the subject

    NASA Astrophysics Data System (ADS)

    Van de Vijver, Gertrudis

    2000-05-01

    The aim of this paper is to explore some aspects of anticipation from a dynamic structuralist, and more specifically, Lacanian point of view. Against the background of Lucan's article on «Logical Time and the Assertion of Anticipated Certainty. A New Sophism» (1) a dynamical structuralist viewpoint on psychic systems is laid out, in which the emergence of psychic systems is conceived of in continuation with the emergence of biological forms of organization, and in which the mechanism of psychic closure, interpreted in terms of identification, plays a crucial role. The constitution of the subject, considered as the emergence of a specific psychic organization, is subjected to a specific logic, in which anticipation plays a crucial role.

  3. Comparison of two laryngeal tissue fiber constitutive models

    NASA Astrophysics Data System (ADS)

    Hunter, Eric J.; Palaparthi, Anil Kumar Reddy; Siegmund, Thomas; Chan, Roger W.

    2014-02-01

    Biological tissues are complex time-dependent materials, and the best choice of the appropriate time-dependent constitutive description is not evident. This report reviews two constitutive models (a modified Kelvin model and a two-network Ogden-Boyce model) in the characterization of the passive stress-strain properties of laryngeal tissue under tensile deformation. The two models are compared, as are the automated methods for parameterization of tissue stress-strain data (a brute force vs. a common optimization method). Sensitivity (error curves) of parameters from both models and the optimized parameter set are calculated and contrast by optimizing to the same tissue stress-strain data. Both models adequately characterized empirical stress-strain datasets and could be used to recreate a good likeness of the data. Nevertheless, parameters in both models were sensitive to measurement errors or uncertainties in stress-strain, which would greatly hinder the confidence in those parameters. The modified Kelvin model emerges as a potential better choice for phonation models which use a tissue model as one component, or for general comparisons of the mechanical properties of one type of tissue to another (e.g., axial stress nonlinearity). In contrast, the Ogden-Boyce model would be more appropriate to provide a basic understanding of the tissue's mechanical response with better insights into the tissue's physical characteristics in terms of standard engineering metrics such as shear modulus and viscosity.

  4. Association of Sasang Constitutional Type with Sarcopenia

    PubMed Central

    Lee, Seung Ku; Yoon, Dae Wui; Choi, Kyung-Mee; Lee, Si Woo; Kim, Jong Yeol; Kim, Jin Kwan; Shin, Chol

    2015-01-01

    Sasang constitutional medicine (SCM) is a unique Korean traditional medicine that classifies human beings as four distinct types named Sasang constitutional types (SCTs), based on physiologic, physical, and psychological traits. Accumulating evidence has demonstrated that specific constitutional types are associated with chronic diseases, but no study has investigated the relationship between SCTs and sarcopenia. The aim of this study was to examine the association in a large population-based study. Data from 1,204 participants who completed questionnaires for life style, anthropometric evaluation, and biochemical analysis were analyzed. Classification of the SCTs was done using an integrated diagnostic method. Sarcopenia was defined as appendicular skeletal muscle mass/height2 less than one standard deviation below the gender-specific normal mean of a younger group. Dual-energy X-ray absorptiometry was used to assess whole body composition. The prevalence of sarcopenia was 8.6% in the Tae-eum (TE) type, 44.7% in the So-eum (SE) type, and 20.7% in the So-yang (SY) type. Multivariate analysis revealed that the SE and SY types had 9.22 (5.06–16.81; P < 0.0001) and 2.90 (1.76–4.76; P < 0.0001) greater odds of sarcopenia compared to the TE type, respectively. Our results show that the SE and SY types are significantly associated with increased prevalence of sarcopenia. PMID:26649062

  5. A constitutive theory for rigid polyurethane foam

    SciTech Connect

    Neilsen, M.K.; Krieg, R.D.; Schreyer, H.L.

    1992-12-31

    Rigid, closed-cell, polyurethane foam consists of interconnected polyurethane plates which form cells. When this foam is compressed, it exhibits an initial elastic regime which is followed by a plateau regime in which the load required to compress the foam remains nearly constant. In the plateau regime, cell walls are damaged and large permanent volume changes are generated. As additional load is applied, cell walls are compressed against neighboring cell walls, and the stiffness of the foam increases and approaches a value equal to that of solid polyurethane. When the foam is loaded in tension, the cell walls are damaged and the foam fractures. A constitutive theory for rigid polyurethane foam has been developed. This theory is based on a decomposition of the foam into two parts: a skeleton and a nonlinear elastic continuum in parallel. The skeleton accounts for the foam behavior in the elastic and plateau regimes and is described using a coupled plasticity with continuum damage theory. The nonlinear elastic continuum accounts for the lock-up of the foam due to internal gas pressure and cell wall interactions. This new constitutive theory has been implemented in both static and dynamic finite element codes. Numerical simulations performed using the new constitutive theory are presented.

  6. Implicit constitutive relations for nonlinear magnetoelastic bodies

    PubMed Central

    Bustamante, R.; Rajagopal, K. R.

    2015-01-01

    Implicit constitutive relations that characterize the response of elastic bodies have greatly enhanced the arsenal available at the disposal of the analyst working in the field of elasticity. This class of models were recently extended to describe electroelastic bodies by the present authors. In this paper, we extend the development of implicit constitutive relations to describe the behaviour of elastic bodies that respond to magnetic stimuli. The models that are developed provide a rational way to describe phenomena that have hitherto not been adequately described by the classical models that are in place. After developing implicit constitutive relations for magnetoelastic bodies undergoing large deformations, we consider the linearization of the models within the context of small displacement gradients. We then use the linearized model to describe experimentally observed phenomena which the classical linearized magnetoelastic models are incapable of doing. We also solve several boundary value problems within the context of the models that are developed: extension and shear of a slab, and radial inflation and extension of a cylinder. PMID:25792968

  7. Constitutive modeling for isotropic materials (HOST)

    NASA Technical Reports Server (NTRS)

    Lindholm, Ulric S.; Chan, Kwai S.; Bodner, S. R.; Weber, R. M.; Walker, K. P.; Cassenti, B. N.

    1984-01-01

    The results of the first year of work on a program to validate unified constitutive models for isotropic materials utilized in high temperature regions of gas turbine engines and to demonstrate their usefulness in computing stress-strain-time-temperature histories in complex three-dimensional structural components. The unified theories combine all inelastic strain-rate components in a single term avoiding, for example, treating plasticity and creep as separate response phenomena. An extensive review of existing unified theories is given and numerical methods for integrating these stiff time-temperature-dependent constitutive equations are discussed. Two particular models, those developed by Bodner and Partom and by Walker, were selected for more detailed development and evaluation against experimental tensile, creep and cyclic strain tests on specimens of a cast nickel base alloy, B19000+Hf. Initial results comparing computed and test results for tensile and cyclic straining for temperature from ambient to 982 C and strain rates from 10(exp-7) 10(exp-3) s(exp-1) are given. Some preliminary date correlations are presented also for highly non-proportional biaxial loading which demonstrate an increase in biaxial cyclic hardening rate over uniaxial or proportional loading conditions. Initial work has begun on the implementation of both constitutive models in the MARC finite element computer code.

  8. Rapid implementation of advanced constitutive models

    NASA Astrophysics Data System (ADS)

    Starman, Bojan; Halilovič, Miroslav; Vrh, Marko; Štok, Boris

    2013-12-01

    This paper presents a methodology based on the NICE integration scheme [1, 2] for simple and rapid numerical implementation of a class of plasticity constitutive models. In this regard, an algorithm is purposely developed for the implementation of newly developed advanced constitutive models into explicit finite element framework. The methodology follows the organization of the problem state variables into an extended form, which allows the constitutive models' equations to be organized in such a way, that the algorithm can be optionally extended with minimal effort to integrate also evolution equations related to a description of other specific phenomena, such as damage, distortional hardening, phase transitions, degradation etc. To confirm simplicity of the program implementation, computational robustness, effectiveness and improved accuracy of the implemented integration algorithm, a deep drawing simulation of the cylindrical cup is considered as the case study, performed in ABAQUS/Explicit. As a fairly complex considered model, the YLD2004-18p model [3, 4] is first implemented via external subroutine VUMAT. Further, to give additional proof of the simplicity of the proposed methodology, a combination of the YLD2004-18p model and Gurson-Tvergaard-Needleman model (GTN) is considered. As demonstrated, the implementation is really obtained in a very simple way.

  9. Controlling segregation speed of entangled polymers by the shapes: A simple model for eukaryotic chromosome segregation

    NASA Astrophysics Data System (ADS)

    Sakai, Yuji; Tachikawa, Masashi; Mochizuki, Atsushi

    2016-10-01

    We report molecular dynamics simulations of the segregation of two overlapping polymers motivated by chromosome segregation in biological cells. We investigate the relationship between polymer shapes and segregation dynamics and show that elongation and compaction make entangled polymers segregate rapidly. This result suggests that eukaryotic chromosomes take such a characteristic rod-shaped structure, which is induced by condensins, to achieve rapid segregation.

  10. Conducting polymer actuators: From basic concepts to proprioceptive systems

    NASA Astrophysics Data System (ADS)

    Martinez Gil, Jose Gabriel

    Designers and engineers have been dreaming for decades of motors sensing, by themselves, working and surrounding conditions, as biological muscles do originating proprioception. Here bilayer full polymeric artificial muscles were checked up to very high cathodic potential limits (-2.5 V) in aqueous solution by cyclic voltammetry. The electrochemical driven exchange of ions from the conducting polymer film, and the concomitant Faradaic bending movement of the muscle, takes place in the full studied potential range. The presence of trapped counterion after deep reduction was corroborated by EDX determinations giving quite high electronic conductivity to the device. The large bending movement was used as a tool to quantify the amount of water exchanged per reaction unit (exchanged electron or ion). The potential evolutions of self-supported films of conducting polymers or conducting polymers (polypyrrole, polyaniline) coating different microfibers, during its oxidation/reduction senses working mechanical, thermal, chemical or electrical variables. The evolution of the muscle potential from electrochemical artificial muscles based on electroactive materials such as intrinsically conducting polymers and driven by constant currents senses, while working, any variation of the mechanical (trailed mass, obstacles, pressure, strain or stress), thermal or chemical conditions of work. One physically uniform artificial muscle includes one electrochemical motor and several sensors working simultaneously under the same driving reaction. Actuating (current and charge) and sensing (potential and energy) magnitudes are present, simultaneously, in the only two connecting wires and can be read by the computer at any time. From basic polymeric, mechanical and electrochemical principles a physicochemical equation describing artificial proprioception has been developed. It includes and describes, simultaneously, the evolution of the muscle potential during actuation as a function of the

  11. Multicomponent polymer materials

    SciTech Connect

    Paul, D.R.; Sperling, L.H.

    1986-01-01

    Interpenetrating polymer networks are discussed, taking into account interpenetrating polymer networks based on polybutadiene and polystyrene, polyurethane-polysiloxane simultaneous interpenetrating polymer networks, extraction studies and morphology of physical-chemical interpenetrating polymer networks based on block polymer and polystyrene, twoand three-component interpenetrating polymer networks, and poly(acrylourethane)-polyepoxide semiinterpenetrating networks formed by electron-beam curing. Other topics studied are related to the characterization of polymer blends, the characterization of block copolymers, the mechanical behavior, and rheology and applications. Attention is given to a new silicone flame-retardant system for thermoplastics, recent developments in interpenetrating polymer networks and related materials, miscibility in random copolymer blends, crystallization and melting in compatible polymer blends, and fatigue in rubber-modified epoxies and other polyblends.

  12. All-polymer photonic crystal slab sensor.

    PubMed

    Hermannsson, Pétur G; Sørensen, Kristian T; Vannahme, Christoph; Smith, Cameron L C; Klein, Jan J; Russew, Maria-Melanie; Grützner, Gabi; Kristensen, Anders

    2015-06-29

    An all-polymer photonic crystal slab sensor is presented, and shown to exhibit narrow resonant reflection with a FWHM of less than 1 nm and a sensitivity of 31 nm/RIU when sensing media with refractive indices around that of water. This results in a detection limit of 4.5 × 10(-6) RIU when measured in conjunction with a spectrometer of 12 pm/pixel resolution. The device is a two-layer structure, composed of a low refractive index polymer with a periodically modulated surface height, covered with a smooth upper-surface high refractive index inorganic-organic hybrid polymer modified with ZrO2based nanoparticles. Furthermore, it is fabricated using inexpensive vacuum-less techniques involving only UV nanoreplication and polymer spin-casting, and is thus well suited for single-use biological and refractive index sensing applications. PMID:26191664

  13. Polymer scaffold degradation control via chemical control

    DOEpatents

    Hedberg-Dirk, Elizabeth L.; Dirk, Shawn; Cicotte, Kirsten

    2016-01-05

    A variety of polymers and copolymers suitable for use as biologically compatible constructs and, as a non-limiting specific example, in the formation of degradable tissue scaffolds as well methods for synthesizing these polymers and copolymers are described. The polymers and copolymers have degradation rates that are substantially faster than those of previously described polymers suitable for the same uses. Copolymers having a synthesis route which enables one to fine tune the degradation rate by selecting the specific stoichiometry of the monomers in the resulting copolymer are also described. The disclosure also provides a novel synthesis route for maleoyl chloride which yields monomers suitable for use in the copolymer synthesis methods described herein.

  14. Functional supramolecular polymers for biomedical applications.

    PubMed

    Dong, Ruijiao; Zhou, Yongfeng; Huang, Xiaohua; Zhu, Xinyuan; Lu, Yunfeng; Shen, Jian

    2015-01-21

    As a novel class of dynamic and non-covalent polymers, supramolecular polymers not only display specific structural and physicochemical properties, but also have the ability to undergo reversible changes of structure, shape, and function in response to diverse external stimuli, making them promising candidates for widespread applications ranging from academic research to industrial fields. By an elegant combination of dynamic/reversible structures with exceptional functions, functional supramolecular polymers are attracting increasing attention in various fields. In particular, functional supramolecular polymers offer several unique advantages, including inherent degradable polymer backbones, smart responsiveness to various biological stimuli, and the ease for the incorporation of multiple biofunctionalities (e.g., targeting and bioactivity), thereby showing great potential for a wide range of applications in the biomedical field. In this Review, the trends and representative achievements in the design and synthesis of supramolecular polymers with specific functions are summarized, as well as their wide-ranging biomedical applications such as drug delivery, gene transfection, protein delivery, bio-imaging and diagnosis, tissue engineering, and biomimetic chemistry. These achievements further inspire persistent efforts in an emerging interdisciplin-ary research area of supramolecular chemistry, polymer science, material science, biomedical engineering, and nanotechnology.

  15. Exploring 'new' bioactivities of polymers at the nano-bio interface.

    PubMed

    Wang, Chunming; Dong, Lei

    2015-01-01

    A biological system is essentially an elegant assembly of polymeric nanostructures. The polymers in the body, biomacromolecules, are both building blocks and versatile messengers. We propose that non-biologically derived polymers can be potential therapeutic candidates with unique advantages. Emerging findings about polycations, polysaccharides, immobilised multivalent ligands, and biomolecular coronas provide evidence that polymers are activated at the nano-bio interface, while emphasising the current theoretical and practical challenges. Our increasing understanding of the nano-bio interface and evolving approaches to establish the therapeutic potential of polymers enable the development of polymer drugs with high specificities for broad applications.

  16. Lipid-absorbing Polymers

    NASA Technical Reports Server (NTRS)

    Marsh, H. E., Jr.; Wallace, C. J.

    1973-01-01

    The removal of bile acids and cholesterol by polymeric absorption is discussed in terms of micelle-polymer interaction. The results obtained with a polymer composed of 75 parts PEO and 25 parts PB plus curing ingredients show an absorption of 305 to 309%, based on original polymer weight. Particle size effects on absorption rate are analyzed. It is concluded that crosslinked polyethylene oxide polymers will absorb water, crosslinked polybutadiene polymers will absorb lipids; neither polymer will absorb appreciable amounts of lipids from micellar solutions of lipids in water.

  17. A toolbox of oligopeptide-modified polymers for tailored elastomers.

    PubMed

    Croisier, Emmanuel; Liang, Su; Schweizer, Thomas; Balog, Sandor; Mionić, Marijana; Snellings, Ruben; Cugnoni, Joël; Michaud, Véronique; Frauenrath, Holger

    2014-01-01

    Biomaterials are constructed from limited sets of building blocks but exhibit extraordinary and versatile properties, because hierarchical structure formation lets them employ identical supramolecular motifs for different purposes. Here we exert a similar degree of structural control in synthetic supramolecular elastomers and thus tailor them for a broad range of thermomechanical properties. We show that oligopeptide-terminated polymers selectively self-assemble into small aggregates or nanofibrils, depending on the length of the oligopeptides. This process is self-sorting if differently long oligopeptides are combined so that different nanostructures coexist in bulk mixtures. Blends of polymers with oligopeptides matching in length furnish reinforced elastomers that exhibit shear moduli one order of magnitude higher than the parent polymers. By contrast, novel interpenetrating supramolecular networks that display excellent vibration damping properties are obtained from blends comprising non-matching oligopeptides or unmodified polymers. Hence, blends of oligopeptide-modified polymers constitute a toolbox for tailored elastomers with versatile properties. PMID:25198134

  18. Coating carbon nanotubes with a polystyrene-based polymer protects against pulmonary toxicity

    PubMed Central

    2011-01-01

    Background carbon nanotubes (CNT) can have adverse effects on health. Therefore, minimizing the risk associated with CNT exposure is of crucial importance. The aim of this work was to evaluate if coating multi-walled CNT (MWCNT) with polymers could modify their toxicity, thus representing a useful strategy to decrease adverse health effects of CNT. We used industrially-produced MWCNT uncoated (NT1) or coated (50/50 wt%) with acid-based (NT2) or polystyrene-based (NT3) polymer, and exposed murine macrophages (RAW 264.7 cell line) or Balb/c mice by intratracheal administration. Biological experiments were performed both in vitro and in vivo, examining time- and dose-dependent effects of CNT, in terms of cytotoxicity, expression of genes and proteins related to oxidative stress, inflammation and tissue remodeling, cell and lung tissue morphology (optical and transmission electron microscopy), and bronchoalveolar lavage fluid content analysis. Results extensive physico-chemical characterization of MWCNT was performed, and showed, although similar dimensions for the 3 MWCNT, a much smaller specific surface area for NT2 and NT3 as compared to NT1 (54.1, 34 and 227.54 m2/g respectively), along with different surface characteristics. MWCNT-induced cytotoxicity, oxidative stress, and inflammation were increased by acid-based and decreased by polystyrene-based polymer coating both in vitro in murine macrophages and in vivo in lung of mice monitored for 6 months. Conclusions these results demonstrate that coating CNT with polymers, without affecting their intrinsic structure, may constitute a useful strategy for decreasing CNT toxicity, and may hold promise for improving occupational safety and that of general the user. PMID:21255417

  19. The Economics of the U.S. Constitution.

    ERIC Educational Resources Information Center

    Schug, Mark C., Ed.

    1986-01-01

    In conjunction with the United States Constitution's Bicentennial, this issue is devoted to the contributions the Constitution has made in shaping the U.S. economic system. The main article, "The Economics of the Constitution," provides important insights on how the Constitution influences the economic system through answers to the following…

  20. Power: Constitutional Update. Bar/School Partnership Programs Series.

    ERIC Educational Resources Information Center

    American Bar Association, Chicago, IL. Special Committee on Youth Education for Citizenship.

    The fourth in a special series of handbooks dealing with constitutional themes, this document looks at power in the context of the U.S. Constitution. "The Constitution's Prescription for Freedom" (L. Peach) examines the separation of powers provided for in the Constitution. "The Concept of Power" (C. Roach) is a series of strategies, some using…

  1. 29 CFR 402.1 - Labor organization constitution and bylaws.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 2 2010-07-01 2010-07-01 false Labor organization constitution and bylaws. 402.1 Section... constitution and bylaws. Every labor organization shall adopt a constitution and bylaws consistent with the... a constitution and bylaws which it has previously adopted and under which it is operating when...

  2. 29 CFR 402.1 - Labor organization constitution and bylaws.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 2 2012-07-01 2012-07-01 false Labor organization constitution and bylaws. 402.1 Section... constitution and bylaws. Every labor organization shall adopt a constitution and bylaws consistent with the... a constitution and bylaws which it has previously adopted and under which it is operating when...

  3. 29 CFR 402.1 - Labor organization constitution and bylaws.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 2 2014-07-01 2014-07-01 false Labor organization constitution and bylaws. 402.1 Section... constitution and bylaws. Every labor organization shall adopt a constitution and bylaws consistent with the... a constitution and bylaws which it has previously adopted and under which it is operating when...

  4. 29 CFR 402.1 - Labor organization constitution and bylaws.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 2 2013-07-01 2013-07-01 false Labor organization constitution and bylaws. 402.1 Section... constitution and bylaws. Every labor organization shall adopt a constitution and bylaws consistent with the... a constitution and bylaws which it has previously adopted and under which it is operating when...

  5. 29 CFR 402.1 - Labor organization constitution and bylaws.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 2 2011-07-01 2011-07-01 false Labor organization constitution and bylaws. 402.1 Section... constitution and bylaws. Every labor organization shall adopt a constitution and bylaws consistent with the... a constitution and bylaws which it has previously adopted and under which it is operating when...

  6. Electron transfer in biology

    NASA Astrophysics Data System (ADS)

    Williams, R. J. P.

    Electron transfer is one of the key reactions of biology not just in catalysis of oxidation/reduction reactions but in the conversion of sources of energy such as light to usable form for chemical transformations. There are then two intriguing problems. What is the nature of the matrix in which electrons flow in a biological cell after the initial charge separation due for example to the absorption of light. Here we are examining biological structures similar to man's electronic wires and the construction must be of low resistance in what are apparently insulators - organic polymers. It has been found that the electronic conduction system is largely made from metallo-proteins associated with lipid membranes. We understand much about these biological wires today. The second problem concerns the conversion of the energy captured from the light into usable chemical form. The major synthetic step in the production of biological polymers, including proteins, DNA, RNA, polysaccharides and fats, is condensation, i.e. the removal of water in the formation of amides, esters and so on. Now these condensation reactions are driven in biology by using a drying agent in water, namely the anhydride, pyrophosphate, in a special compound ATP, adenosine triphosphate. The central problem is to discover exactly how the flow of electrons can be related to the synthesis of (bound) pyrophosphate. (In a thermodynamic sense pyrophosphate is a water soluble kinetically stable drying agent comparable with solid P2O5.) In the biological systems the connection between these different classes of reaction, electron transfer and condensation, is known to be via the production of an energized gradient of protons across the biological membrane which arises from the flow of electrons across the same membrane in the electron transport wires of biology. However we do not understand thoroughly the steps which lead from electron flow in a membrane to proton gradients in that membrane, i.e. electron

  7. MathBench Biology Modules: Web-Based Math for All Biology Undergraduates

    ERIC Educational Resources Information Center

    Nelson, Karen C.; Marbach-Ad, Gili; Schneider, Katie; Thompson, Katerina V.; Shields, Patricia A.; Fagan, William F.

    2009-01-01

    Historically, biology has not been a heavily quantitative science, but this is changing rapidly (Ewing 2002; Gross 2000; Hastings and palmer 2003; Jungck 2005; Steen 2005). Quantitative approaches now constitute a key tool for modern biologists, yet undergraduate biology courses remain largely qualitative and descriptive. Although biology majors…

  8. Constitutive modeling for isotropic materials (HOST)

    NASA Technical Reports Server (NTRS)

    Chan, Kwai S.; Lindholm, Ulric S.; Bodner, S. R.; Hill, Jeff T.; Weber, R. M.; Meyer, T. G.

    1986-01-01

    The results of the third year of work on a program which is part of the NASA Hot Section Technology program (HOST) are presented. The goals of this program are: (1) the development of unified constitutive models for rate dependent isotropic materials; and (2) the demonstration of the use of unified models in structural analyses of hot section components of gas turbine engines. The unified models selected for development and evaluation are those of Bodner-Partom and of Walker. A test procedure was developed for assisting the generation of a data base for the Bodner-Partom model using a relatively small number of specimens. This test procedure involved performing a tensile test at a temperature of interest that involves a succession of strain-rate changes. The results for B1900+Hf indicate that material constants related to hardening and thermal recovery can be obtained on the basis of such a procedure. Strain aging, thermal recovery, and unexpected material variations, however, preluded an accurate determination of the strain-rate sensitivity parameter is this exercise. The effects of casting grain size on the constitutive behavior of B1900+Hf were studied and no particular grain size effect was observed. A systematic procedure was also developed for determining the material constants in the Bodner-Partom model. Both the new test procedure and the method for determining material constants were applied to the alternate material, Mar-M247 . Test data including tensile, creep, cyclic and nonproportional biaxial (tension/torsion) loading were collected. Good correlations were obtained between the Bodner-Partom model and experiments. A literature survey was conducted to assess the effects of thermal history on the constitutive behavior of metals. Thermal history effects are expected to be present at temperature regimes where strain aging and change of microstructure are important. Possible modifications to the Bodner-Partom model to account for these effects are outlined

  9. Numerically abnormal chromosome constitutions in humans

    SciTech Connect

    1993-12-31

    Chapter 24, discusses numerically abnormal chromosome constitutions in humans. This involves abnormalities of human chromosome number, including polyploidy (when the number of sets of chromosomes increases) and aneuploidy (when the number of individual normal chromosomes changes). Chapter sections discuss the following chromosomal abnormalities: human triploids, imprinting and uniparental disomy, human tetraploids, hydatidiform moles, anomalies caused by chromosomal imbalance, 13 trisomy (D{sub 1} trisomy, Patau syndrome), 21 trisomy (Down syndrome), 18 trisomy syndrome (Edwards syndrome), other autosomal aneuploidy syndromes, and spontaneous abortions. The chapter concludes with remarks on the nonrandom participation of chromosomes in trisomy. 69 refs., 3 figs., 4 tabs.

  10. Evaluation of constitutive models for crushed salt

    SciTech Connect

    Callahan, G.D.; Loken, M.C. [RE Hurtado, L.D.; Hansen, F.D.

    1996-05-01

    Three constitutive models are recommended as candidates for describing the deformation of crushed salt. These models are generalized to three-dimensional states of stress to include the effects of mean and deviatoric stress and modified to include effects of temperature, grain size, and moisture content. A database including hydrostatic consolidation and shear consolidation tests conducted on Waste Isolation Pilot Plant (WIPP) and southeastern New Mexico salt is used to determine material parameters for the models. To evaluate the capability of the models, parameter values obtained from fitting the complete database are used to predict the individual tests. Finite element calculations of a WIPP shaft with emplaced crushed salt demonstrate the model predictions.

  11. Photoreceptor cells constitutively express functional TLR4

    PubMed Central

    Tu, Zhidan; Portillo, Jose-Andres; Howell, Scott; Bu, Hong; Subauste, Carlos S.; Al-Ubaidi, Muayyad R; Pearlman, Eric; Lin, Feng

    2010-01-01

    Toll-like receptor 4 (TLR4) is expressed on a number of cells including neurons in the brain. However, it has yet to be determined if TLR4 is expressed on photoreceptor cells in the retina. In this report, we examined primary photoreceptor cells and an established photoreceptor cell line (661W). We found that functional TLR4 is constitutively expressed on photoreceptor cells, and can be activated by LPS. We conclude that TLR4 on photoreceptor cells could directly contribute to retinal inflammatory diseases and photoreceptor cell survival. PMID:20801528

  12. Constitutive parameter measurements of lossy materials

    NASA Technical Reports Server (NTRS)

    Dominek, A.; Park, A.

    1989-01-01

    The electrical constitutive parameters of lossy materials are considered. A discussion of the NRL arch for lossy coatings is presented involving analytical analyses of the reflected field using the geometrical theory of diffraction (GTD) and physical optics (PO). The actual values for these parameters can be obtained through a traditional transmission technique which is examined from an error analysis standpoint. Alternate sample geometries are suggested for this technique to reduce sample tolerance requirements for accurate parameter determination. The performance for one alternate geometry is given.

  13. Civil and Constitutional Rights of Adjudicated Youth.

    PubMed

    Landess, Jacqueline

    2016-01-01

    Mental health clinicians serving child and adolescent patients are frequently asked to evaluate youth who have been arrested for various offenses or who are otherwise involved with the juvenile justice system. To help orient clinicians and other stakeholders involved with such cases, this article describes the evolution of the juvenile justice system and summarizes the history and current status of the civil and constitutional rights of youth involved in the adjudicatory process. This article also points out key areas in which due process rights are still evolving, particularly in the case of status offenders.

  14. Introduction to Polymer Chemistry.

    ERIC Educational Resources Information Center

    Harris, Frank W.

    1981-01-01

    Reviews the physical and chemical properties of polymers and the two major methods of polymer synthesis: addition (chain, chain-growth, or chain-reaction), and condensation (step-growth or step-reaction) polymerization. (JN)

  15. Polymer composites containing nanotubes

    NASA Technical Reports Server (NTRS)

    Bley, Richard A. (Inventor)

    2008-01-01

    The present invention relates to polymer composite materials containing carbon nanotubes, particularly to those containing singled-walled nanotubes. The invention provides a polymer composite comprising one or more base polymers, one or more functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers and carbon nanotubes. The invention also relates to functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers, particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having side chain functionalization, and more particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having olefin side chains and alkyl epoxy side chains. The invention further relates to methods of making polymer composites comprising carbon nanotubes.

  16. Mechanical Properties of Polymers.

    ERIC Educational Resources Information Center

    Aklonis, J. J.

    1981-01-01

    Mechanical properties (stress-strain relationships) of polymers are reviewed, taking into account both time and temperature factors. Topics include modulus-temperature behavior of polymers, time dependence, time-temperature correspondence, and mechanical models. (JN)

  17. Anion exchange polymer electrolytes

    SciTech Connect

    Kim, Yu Seung; Kim, Dae Sik

    2015-06-02

    Anion exchange polymer electrolytes that include guanidinium functionalized polymers may be used as membranes and binders for electrocatalysts in preparation of anodes for electrochemical cells such as solid alkaline fuel cells.

  18. Playing with Polymers.

    ERIC Educational Resources Information Center

    Chemecology, 1997

    1997-01-01

    Presents an activity that enables students to gain a better understanding of the importance of polymers. Students perform an experiment in which polymer chains of polyvinyl acetate form crosslinks. Includes background information and discussion questions. (DDR)

  19. Polymer physics experiments with single DNA molecules

    NASA Astrophysics Data System (ADS)

    Smith, Douglas E.

    1999-11-01

    Bacteriophage DNA molecules were taken as a model flexible polymer chain for the experimental study of polymer dynamics at the single molecule level. Video fluorescence microscopy was used to directly observe the conformational dynamics of fluorescently labeled molecules, optical tweezers were used to manipulate individual molecules, and micro-fabricated flow cells were used to apply controlled hydrodynamic strain to molecules. These techniques constitute a powerful new experimental approach in the study of basic polymer physics questions. I have used these techniques to study the diffusion and relaxation of isolated and entangled polymer molecules and the hydrodynamic deformation of polymers in elongational and shear flows. These studies revealed a rich, and previously unobserved, ``molecular individualism'' in the dynamical behavior of single molecules. Individual measurements on ensembles of identical molecules allowed the average conformation to be determined as well as the underlying probability distributions for molecular conformation. Scaling laws, that predict the dependence of properties on chain length and concentration, were also tested. The basic assumptions of the reptation model were directly confirmed by visualizing the dynamics of entangled chains.

  20. Dendritic polyurea polymers.

    PubMed

    Tuerp, David; Bruchmann, Bernd

    2015-01-01

    Dendritic polymers, subsuming dendrimers as well as hyperbranched or highly branched polymers are well established in the field of polymer chemistry. This review article focuses on urea based dendritic polymers and summarizes their synthetic routes through both isocyanate and isocyanate-free processes. Furthermore, this article highlights applications where dendritic polyureas show their specific chemical and physical potential. For these purposes scientific publications as well as patent literature are investigated to generate a comprehensive overview on this topic.

  1. Relationships among certain joint constitutive models.

    SciTech Connect

    Segalman, Daniel Joseph; Starr, Michael James

    2004-09-01

    In a recent paper, Starr and Segalman demonstrated that any Masing model can be represented as a parallel-series Iwan model. A preponderance of the constitutive models that have been suggested for simulating mechanical joints are Masing models, and the purpose of this discussion is to demonstrate how the Iwan representation of those models can yield insight into their character. In particular, this approach can facilitate a critical comparison among numerous plausible constitutive models. It is explicitly shown that three-parameter models such as Smallwood's (Ramberg-Osgood) calculate parameters in such a manner that macro-slip is not an independent parameter, yet the model admits macro-slip. The introduction of a fourth parameter is therefore required. It is shown that when a macro-slip force is specified for the Smallwood model the result is a special case of the Segalman four-parameter model. Both of these models admit a slope discontinuity at the inception of macro-slip. A five-parameter model that has the beneficial features of Segalman's four-parameter model is proposed. This model manifests a force-displacement curve having a continuous first derivative.

  2. Space shuttle propellant constitutive law verification tests

    NASA Technical Reports Server (NTRS)

    Thompson, James R.

    1995-01-01

    As part of the Propellants Task (Task 2.0) on the Solid Propulsion Integrity Program (SPIP), a database of material properties was generated for the Space Shuttle Redesigned Solid Rocket Motor (RSRM) PBAN-based propellant. A parallel effort on the Propellants Task was the generation of an improved constitutive theory for the PBAN propellant suitable for use in a finite element analysis (FEA) of the RSRM. The outcome of an analysis with the improved constitutive theory would be more reliable prediction of structural margins of safety. The work described in this report was performed by Materials Laboratory personnel at Thiokol Corporation/Huntsville Division under NASA contract NAS8-39619, Mod. 3. The report documents the test procedures for the refinement and verification tests for the improved Space Shuttle RSRM propellant material model, and summarizes the resulting test data. TP-H1148 propellant obtained from mix E660411 (manufactured February 1989) which had experienced ambient igloo storage in Huntsville, Alabama since January 1990, was used for these tests.

  3. Constitutive modeling for isotropic materials (HOST)

    NASA Technical Reports Server (NTRS)

    Lindholm, U. S.; Chan, K. S.; Bodner, S. R.; Weber, R. M.; Walker, K. P.; Cassenti, B. N.

    1985-01-01

    This report presents the results of the second year of work on a problem which is part of the NASA HOST Program. Its goals are: (1) to develop and validate unified constitutive models for isotropic materials, and (2) to demonstrate their usefulness for structural analyses of hot section components of gas turbine engines. The unified models selected for development and evaluation are that of Bodner-Partom and Walker. For model evaluation purposes, a large constitutive data base is generated for a B1900 + Hf alloy by performing uniaxial tensile, creep, cyclic, stress relation, and thermomechanical fatigue (TMF) tests as well as biaxial (tension/torsion) tests under proportional and nonproportional loading over a wide range of strain rates and temperatures. Systematic approaches for evaluating material constants from a small subset of the data base are developed. Correlations of the uniaxial and biaxial tests data with the theories of Bodner-Partom and Walker are performed to establish the accuracy, range of applicability, and integability of the models. Both models are implemented in the MARC finite element computer code and used for TMF analyses. Benchmark notch round experiments are conducted and the results compared with finite-element analyses using the MARC code and the Walker model.

  4. Molecular simulation guided constitutive modeling on finite strain viscoelasticity of elastomers

    NASA Astrophysics Data System (ADS)

    Li, Ying; Tang, Shan; Kröger, Martin; Liu, Wing Kam

    2016-03-01

    Viscoelasticity characterizes the most important mechanical behavior of elastomers. Understanding the viscoelasticity, especially finite strain viscoelasticity, of elastomers is the key for continuation of their dedicated use in industrial applications. In this work, we present a mechanistic and physics-based constitutive model to describe and design the finite strain viscoelastic behavior of elastomers. Mathematically, the viscoelasticity of elastomers has been decomposed into hyperelastic and viscous parts, which are attributed to the nonlinear deformation of the cross-linked polymer network and the diffusion of free chains, respectively. The hyperelastic deformation of a cross-linked polymer network is governed by the cross-linking density, the molecular weight of the polymer strands between cross-linkages, and the amount of entanglements between different chains, which we observe through large scale molecular dynamics (MD) simulations. Moreover, a recently developed non-affine network model (Davidson and Goulbourne, 2013) is confirmed in the current work to be able to capture these key physical mechanisms using MD simulation. The energy dissipation during a loading and unloading process of elastomers is governed by the diffusion of free chains, which can be understood through their reptation dynamics. The viscous stress can be formulated using the classical tube model (Doi and Edwards, 1986); however, it cannot be used to capture the energy dissipation during finite deformation. By considering the tube deformation during this process, as observed from the MD simulations, we propose a modified tube model to account for the finite deformation behavior of free chains. Combing the non-affine network model for hyperelasticity and modified tube model for viscosity, both understood by molecular simulations, we develop a mechanism-based constitutive model for finite strain viscoelasticity of elastomers. All the parameters in the proposed constitutive model have

  5. Metal-containing and related polymers for biomedical applications.

    PubMed

    Yan, Yi; Zhang, Jiuyang; Ren, Lixia; Tang, Chuanbing

    2016-10-01

    A survey of the most recent progress in the biomedical applications of metal-containing polymers is given. Due to the unique optical, electrochemical, and magnetic properties, at least 30 different metal elements, most of them transition metals, are introduced into polymeric frameworks for interactions with biology-relevant substrates via various means. Inspired by the advance of metal-containing small molecular drugs and promoted by the great progress in polymer chemistry, metal-containing polymers have gained momentum during recent decades. According to their different applications, this review summarizes the following biomedical applications: (1) metal-containing polymers as drug delivery vehicles; (2) metal-containing polymeric drugs and biocides, including antimicrobial and antiviral agents, anticancer drugs, photodynamic therapy agents, radiotherapy agents and biocides; (3) metal-containing polymers as biosensors, and (4) metal-containing polymers in bioimaging.

  6. Polymer-mediated growth of crystals and mesocrystals.

    PubMed

    Cölfen, Helmut

    2013-01-01

    Polymers are important additives for the control of mineralization reactions in both biological and bioinspired mineralization. The reason is that they allow for a number of interactions with the growing crystals and even amorphous minerals. These can substantially influence the way the mineral grows on several levels. Already in the prenucleation phase, polymers can control the formation of prenucleation clusters and subsequently the nucleation event. Also, polymers can control whether the further crystallization follows a classical or nonclassical particle-mediated growth path. In this chapter, the main ways in which polymers can be used to control a crystallization reaction will be highlighted. In addition, polymers that are useful for this purpose and the experimental conditions suitable for directing a crystallization reaction into the desired direction through the use of polymers will be described.

  7. Noise spectroscopy of polymer transistors

    NASA Astrophysics Data System (ADS)

    Harsh, Rishav; Narayan, K. S.

    2015-11-01

    Noise studies constitute an important approach to study polymer based field effect transistors (FETs) from the perspective of disorder physics as well as device application. The current fluctuations in an all organic solution-processable FET in different regimes of operation (I-V) are measured and analyzed. The intrinsic transport noise is sizable and readily observed in the current time series measurements. The ensuing current spectrum (SI(f)) exhibits a typical 1/f characteristics. It is observed that this noise amplitude scales with respect to current bias and indicative of mobility as well as number fluctuations at dielectric-semiconductor interface. FETs with leakage (lossy) dielectric layer indicate characteristic noise spectrum features which can serve as a diagnostic tool to monitor device stability.

  8. A Viscoelastic Constitutive Law For FRP Materials

    NASA Astrophysics Data System (ADS)

    Ascione, Luigi; Berardi, Valentino Paolo; D'Aponte, Anna

    2011-09-01

    The present study deals with the long-term behavior of fiber-reinforced polymer (FRP) materials in civil engineering. More specifically, the authors propose a mechanical model capable of predicting the viscoelastic behavior of FRP laminates in the field of linear viscoelasticity, starting from that of the matrix material and fiber. The model is closely connected with the low FRP stress levels in civil engineering applications. The model is based on a micromechanical approach which assumes that there is a perfect adhesion between the matrix and fiber. The long-term behavior of the phases is described through a four-parameter rheological law. A validation of the model has also been developed by matching the predicted behavior with an experimental one available in the literature.

  9. EDITORIAL: Electroactive polymer materials

    NASA Astrophysics Data System (ADS)

    Bar-Cohen, Yoseph; Kim, Kwang J.; Ryeol Choi, Hyouk; Madden, John D. W.

    2007-04-01

    years, a series of new materials have emerged that exhibit large displacement in response to electrical stimulation. This capability is making them highly attractive as actuators for their operational similarity to biological muscles, particularly their resilience, quiet operation, damage tolerance and ability to induce large actuation strains (stretching, contracting or bending). The application of these materials as actuators involves multi-disciplines including materials, electromechanics, chemistry, computers and electronics. Even though the force of actuation of existing EAP materials and their robustness requires further improvement, there has already been a series of reported successes in the development of EAP-actuated mechanisms. Using EAP to replace existing actuators may be a difficult challenge and therefore it is highly desirable to identify a niche application where EAP materials would not need to compete with existing technologies. EAP materials can be divided into two major groups based on their activation mechanism: ionic or electronic. Electronic EAPs, such as electrostrictive, electrostatic, piezoelectric and ferroelectric, are driven by Coulomb forces. These types of EAP material can be made to hold the induced displacement while activated under a DC voltage, allowing them to be considered for robotic applications. These materials have high mechanical energy density and they can be operated in air with no major constraints. However, electronic EAPs require high activation fields (>10 V/μm) that are close to the breakdown level. In contrast to electronic EAPs, ionic EAPs are materials that involve the transport of ions and they consist of two electrodes and an electrolyte. The activation of ionic EAPs can be achieved by voltages as low as 1-2 volts. Examples of ionic EAPs include gels, polymer-metal composites, conducting polymers and carbon nanotubes. Their disadvantages are a need to maintain wetness and their low electromechanical coupling

  10. Fire-safe polymers and polymer composites

    NASA Astrophysics Data System (ADS)

    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

  11. [Functional type of the constitution (systematic analysis of individual-typological characteristics of an organism)].

    PubMed

    Kolpakov, V V; Bespalova, T V; Tomolova, E A; Shtork, T E; Mamchits, E V; Lar'kina, N Iu; Tkachuk, A A

    2011-01-01

    Analysis of the statistical distribution of feature based chi2 and lambda criteria and average data somatometric, functional and psycho-physiological indices in the total sample of individuals with low, medium and high habitual physical activity (LHPA, M H PA and HHP A) at different stages of ontogenesis (the older preschool and early school children, boys and girls) has identified a fairly wide area of different quality and physiological individuality in a healthy population and the feasibility of allocating the three typological groups--functional constitution types (FTC-1 - LHPA, FTC-2 - MHPA, FTC-3 - HHPA). Set model parameters of the first and second order for each FTC, as well as performance tests of the third order, describing the current functional state. For the full specifications of the constitutional membership (synthetic constitution) of individuals with low, medium and high-held PDA integral assessment of their properties by using the principles polythetic (multidimensional) classification. Obtained by means of multivariate statistical methods results confirmed the postulate of the concept of typological variability of physiological individuality real different quality of healthy human population on the morphofunctional and psycho-physiological grounds and conducted a comprehensive physiological and statistical analysis of results allowed us to scientifically justify the selection of three functional types of constitution (PTC-1, FTC-2, FTC-3), corresponding to three types of synthetic constitutive (K 0-1, K 00, K 01). The data obtained show that the system (constitutional) approach to the evaluation of individual-typological characteristics of the organism confirms the high information private constitution(PTC-1, FTC-2, FTC-3) in human biological organization, and the selected feature set can adequately differentiate the synthetic constitutional types in a formal basis.

  12. [Body composition and constitution: a constitutional syndrome (1st of 2 parts)].

    PubMed

    Terán Díaz, E

    1999-04-01

    Constitutional syndrome alters body constitution modifying (usually decreasing) two of its dimensions--weight and perimeters--by changing the composition of one, several or every body levels. Apart of the cause, the basic physiopathological process that characterizes this new syndrome is the amino acid mobilization from the muscle (proteolysis). As soon as fat loss has no consequence to the organism, proteolysis reduces the muscle mass and life is in danger. Actually, there is no effective treatment to improve the nitrogen balance by medication or hormones in speed catabolic states but it can also approach us to more proper therapeutics for these so frequent processes in clinic.

  13. Nanoporous polymer electrolyte

    DOEpatents

    Elliott, Brian; Nguyen, Vinh

    2012-04-24

    A nanoporous polymer electrolyte and methods for making the polymer electrolyte are disclosed. The polymer electrolyte comprises a crosslinked self-assembly of a polymerizable salt surfactant, wherein the crosslinked self-assembly includes nanopores and wherein the crosslinked self-assembly has a conductivity of at least 1.0.times.10.sup.-6 S/cm at 25.degree. C. The method of making a polymer electrolyte comprises providing a polymerizable salt surfactant. The method further comprises crosslinking the polymerizable salt surfactant to form a nanoporous polymer electrolyte.

  14. Using Polymer Conformation to Control Architecture in Semiconducting Polymer/Viral Capsid Assemblies

    PubMed Central

    Ng, Benny C.; Chan, Stephanie T.; Lin, Jason; Tolbert, Sarah H.

    2011-01-01

    Cowpea Chlorotic Mottle Virus is a single-stranded RNA plant virus with a diameter of 28 nm. The proteins comprising the capsid of this virus can be purified and reassembled either by themselves to form hollow structures, or with polyanions like double-stranded DNA or single-stranded RNA. Depending on pH and ionic strength, a diverse range of structures and shapes can form. The work presented here focuses on using these proteins to encapsulate a fluorescent polyanionic semiconducting polymer, MPS-PPV (poly-2-methoxy-5-propyloxy sulfonate phenylene vinlyene), in order to obtain optically active virus-like particles. After encapsulation, fluorescence from MPS-PPV shows two distinct peaks, which suggests the polymer may be in two conformations. A combination of TEM, fluorescence anisotropy, and sucrose gradient separation indicate that the blue peak arises from polymer encapsulated into spherical particles, while the redder peak corresponds to polymers contained in rod-like cages. Ionic strength during assembly can be used to tune the propensity to form rods or spheres. The results illustrate the synergy of hybrid synthetic/biological system – polymer conformation drives the structure of this composite material, which in turn modifies the polymer optical properties. This synergy could be useful for the future development of synthetic/biological hybrid materials with designated functionality. PMID:21942298

  15. Hydroxycinnamic acid-derived polymers constitute the polyaromatic domain of suberin

    NASA Technical Reports Server (NTRS)

    Bernards, M. A.; Lopez, M. L.; Zajicek, J.; Lewis, N. G.

    1995-01-01

    Suberin is an abundant, complex, intractable, plant cell wall polymeric network that forms both protective and wound-healing layers. Its function is, therefore, critical to the survival of all vascular plants. Its chemical structure and biosynthesis are poorly defined, although it is known to consist of both aromatic and aliphatic domains. While the composition of the aliphatic component has been fairly well characterized, that of the phenolic component has not. Using a combination of specific carbon-13 labeling techniques, and in situ solid state 13C NMR spectroscopic analysis, we now provide the first direct evidence for the nature of the phenolic domain of suberin and report here that it is almost exclusively comprised of a covalently linked, hydroxycinnamic acid-derived polymeric matrix.

  16. Methodology to study polymers interaction by surface plasmon resonance imaging.

    PubMed

    Vollmer, N; Trombini, F; Hely, M; Bellon, S; Mercier, K; Cazeneuve, C

    2015-01-01

    The surface plasmon resonance (SPR) technique has been primarily used in the field of biology, in particular for the study of antibody-antigen interactions. Recently, polymers were introduced to form inclusion complexes. We describe here, a methodology based on surface plasmon resonance imaging to study water-resistant and reversible inclusion complexes using systems which are compatible with a cosmetic use. The purpose of this study is to follow in real time the interaction between two polymers. To carry out this study: •A biochip based on a covalent binding of one "host polymer" on a gold-activated surface was developed.•The binding of the host polymer to a guest polymer was monitored.•The presence of interactions between the β-cyclodextrins groups of the host polymer and the adamantyl functional groups of the guest polymer and the possibility of dissociating the complex were established. This technique allowed carrying out parallel assays for optimizing the amount of complexes formed, the host polymer being spotted at five concentrations. It was then possible to study the influence of the concentration in host system for two concentrations of the guest polymer. The concentration in the host polymer yielding the highest immobilization of the guest system was further determined. PMID:26150967

  17. Drug delivery's quest for polymers: Where are the frontiers?

    PubMed

    Merkle, Hans P

    2015-11-01

    Since the legendary 1964 article of Folkman and Long entitled "The use of silicone rubber as a carrier for prolonged drug therapy" the role of polymers in controlled drug delivery has come a long way. Today it is evident that polymers play a crucial if not the prime role in this field. The latest boost owes to the interest in drug delivery for the purpose of tissue engineering in regenerative medicine. The focus of this commentary is on a selection of general and personal observations that are characteristic for the current state of polymer therapeutics and carriers. It briefly highlights selected examples for the long march of synthetic polymer-drug conjugates from bench to bedside, comments on the ambivalence of selected polymers as inert excipients versus biological response modifiers, and on the yet unsolved dilemma of cationic polymers for the delivery of nucleic acid therapeutics. Further subjects are the complex design of multifunctional polymeric carriers including recent concepts towards functional supramolecular polymers, as well as observations on stimuli-sensitive polymers and the currently ongoing trend towards natural and naturally-derived biopolymers. The final topic is the discovery and early development of a novel type of biodegradable polyesters for parenteral use. Altogether, it is not the basic and applied research in polymer therapeutics and carriers, but the translational process that is the key hurdle to proceed towards an authoritative approval of new polymer therapeutics and carriers.

  18. Drug delivery's quest for polymers: Where are the frontiers?

    PubMed

    Merkle, Hans P

    2015-11-01

    Since the legendary 1964 article of Folkman and Long entitled "The use of silicone rubber as a carrier for prolonged drug therapy" the role of polymers in controlled drug delivery has come a long way. Today it is evident that polymers play a crucial if not the prime role in this field. The latest boost owes to the interest in drug delivery for the purpose of tissue engineering in regenerative medicine. The focus of this commentary is on a selection of general and personal observations that are characteristic for the current state of polymer therapeutics and carriers. It briefly highlights selected examples for the long march of synthetic polymer-drug conjugates from bench to bedside, comments on the ambivalence of selected polymers as inert excipients versus biological response modifiers, and on the yet unsolved dilemma of cationic polymers for the delivery of nucleic acid therapeutics. Further subjects are the complex design of multifunctional polymeric carriers including recent concepts towards functional supramolecular polymers, as well as observations on stimuli-sensitive polymers and the currently ongoing trend towards natural and naturally-derived biopolymers. The final topic is the discovery and early development of a novel type of biodegradable polyesters for parenteral use. Altogether, it is not the basic and applied research in polymer therapeutics and carriers, but the translational process that is the key hurdle to proceed towards an authoritative approval of new polymer therapeutics and carriers. PMID:26614554

  19. Sequence Programmable Peptoid Polymers for Diverse Materials Applications.

    PubMed

    Knight, Abigail S; Zhou, Effie Y; Francis, Matthew B; Zuckermann, Ronald N

    2015-10-14

    Polymer sequence programmability is required for the diverse structures and complex properties that are achieved by native biological polymers, but efforts towards controlling the sequence of synthetic polymers are, by comparison, still in their infancy. Traditional polymers provide robust and chemically diverse materials, but synthetic control over their monomer sequences is limited. The modular and step-wise synthesis of peptoid polymers, on the other hand, allows for precise control over the monomer sequences, affording opportunities for these chains to fold into well-defined nanostructures. Hundreds of different side chains have been incorporated into peptoid polymers using efficient reaction chemistry, allowing for a seemingly infinite variety of possible synthetically accessible polymer sequences. Combinatorial discovery techniques have allowed the identification of functional polymers within large libraries of peptoids, and newly developed theoretical modeling tools specifically adapted for peptoids enable the future design of polymers with desired functions. Work towards controlling the three-dimensional structure of peptoids, from the conformation of the amide bond to the formation of protein-like tertiary structure, has and will continue to enable the construction of tunable and innovative nanomaterials that bridge the gap between natural and synthetic polymers.

  20. Rotational and constitutional dynamics of caged supramolecules

    PubMed Central

    Kühne, Dirk; Klappenberger, Florian; Krenner, Wolfgang; Klyatskaya, Svetlana; Ruben, Mario; Barth, Johannes V.

    2010-01-01

    The confinement of molecular species in nanoscale environments leads to intriguing dynamic phenomena. Notably, the organization and rotational motions of individual molecules were controlled by carefully designed, fully supramolecular host architectures. Here we use an open 2D coordination network on a smooth metal surface to steer the self-assembly of discrete trimeric guest units, identified as noncovalently bound dynamers. Each caged chiral supramolecule performs concerted, chirality-preserving rotary motions within the template honeycomb pore, which are visualized and quantitatively analyzed using temperature-controlled scanning tunneling microscopy. Furthermore, with higher thermal energies, a constitutional system dynamics appears, which is revealed by monitoring repetitive switching events of the confined supramolecules’ chirality signature, reflecting decay and reassembly of the caged units. PMID:21098303

  1. [Constitutions and generalities in traditional Tibetan medicine].

    PubMed

    Rovere, P M

    1986-04-28

    The present work is the result of a preliminary study promoted by C.I.S.ME.T. (the International Tibetan Medicine Study Centre) and aims to unify the diagnostic and therapeutic language of various medical cultures. In line with the spirit of the W.H.O. aimed at safeguarding the cultural heritage represented by popular and traditional medicine, encouraged by the Tibetan Medical Centre and under the auspices of His Holiness the Dalai Lama a terminological and conceptual integration of the basic elements of traditional Tibetan medicine is proposed. The Rlung, Bad Kan, Mkris Pa constitution is correlated with embryological anatomy. The 5 exhalations, 5 biles and 5 phlegbs are analysed from a tissue viewpoint with a search for parallels with embryological tissues.

  2. Constituting objectivity: Transcendental perspectives on modern physics

    NASA Astrophysics Data System (ADS)

    Everett, Jonathan

    2012-05-01

    There is increasing interest in exploring Kantian approaches in the study of the history and philosophy of physics. The most well-known examples of this trend-Friedman's (2001), Ryckman's (2005) and DiSalle's (2006)-focus on Kantianism in the context of the development of the general theory of relativity. The edited collection Constituting Objectivity seeks to develop key Kantian insights-in the most part-in the context of later developments in physics: as well as discussing relativity the volume also provides Kantian interpretations of Bohr's development of quantum theory and continues to provide Kantian insight from later interpretations of quantum mechanics all the way through to considering noncommutative geometry and loop quantum gravity. The volume contains papers on a wide variety of subjects and offers an essential introduction to the breadth of Kantian trends in modern physics.

  3. Laboratory constitutive characterization of cellular concrete.

    SciTech Connect

    Hardy, Robert Douglas; Lee, Moo Yul; Bronowski, David R.

    2004-03-01

    To establish mechanical material properties of cellular concrete mixes, a series of quasi-static, compression and tension tests have been completed. This report summarizes the test methods, set-up, relevant observations, and results from the constitutive experimental efforts. Results from the uniaxial and triaxial compression tests established failure criteria for the cellular concrete in terms of stress invariants I{sub 1} and J{sub 2}. {radical}J{sub 2} (MPa) = 297.2 - 278.7 exp{sup -0.000455 I}{sub 1}{sup (MPa)} for the 90-pcf concrete {radical}J{sub 2} (MPa) = 211.4 - 204.2 exp {sup -0.000628 I}{sub 1}{sup (MPa)} for the 60-pcf concrete

  4. Constitutive Models for Shape Memory Alloy Polycrystals

    NASA Technical Reports Server (NTRS)

    Comstock, R. J., Jr.; Somerday, M.; Wert, J. A.

    1996-01-01

    Shape memory alloys (SMA) exhibiting the superelastic or one-way effects can produce large recoverable strains upon application of a stress. In single crystals this stress and resulting strain are very orientation dependent. We show experimental stress/strain curves for a Ni-Al single crystal for various loading orientations. Also shown are model predictions; the open and closed circles indicate recoverable strains obtained at various stages in the transformation process. Because of the strong orientation dependence of shape memory properties, crystallographic texture can be expected to play an important role in the mechanical behavior of polycrystalline SMA. It is desirable to formulate a constitutive model to better understand and exploit the unique properties of SMA.

  5. The influence of polymer topology on pharmacokinetics: differences between cyclic and linear PEGylated poly(acrylic acid) comb polymers.

    PubMed

    Chen, Bo; Jerger, Katherine; Fréchet, Jean M J; Szoka, Francis C

    2009-12-16

    Water-soluble polymers for the delivery of chemotherapeutic drugs passively target solid tumors as a consequence of reduced renal clearance and the enhanced permeation and retention (EPR) effect. Elimination of the polymers in the kidney occurs due to filtration through biological nanopores with a hydrodynamic diameter comparable to the polymer. Therefore we have investigated chemical features that may broadly be grouped as "molecular architecture" such as: molecular weight, chain flexibility, number of chain ends and branching, to learn how they impact polymer elimination. In this report we describe the synthesis of four pairs of similar molecular weight cyclic and linear polyacrylic acid polymers grafted with polyethylene glycol (23, 32, 65, 114 kDa) with low polydispersities using ATRP and "click" chemistry. The polymers were radiolabeled with (125)I and their pharmacokinetics and tissue distribution after intravenous injection were determined in normal and C26 adenocarcinoma tumored BALB/c mice. Cyclic polymers above the renal threshold of 30 kDa had a significantly longer elimination time (between 10 and 33% longer) than did the comparable linear polymer (for the 66 kDa cyclic polymer, t(1/2,beta)=35+/-2 h) and a greater area under the serum concentration versus time curve. This resulted in a greater tumor accumulation of the cyclic polymer than the linear polymer counterpart. Thus water-soluble cyclic comb polymers join a growing list of polymer topologies that show greatly extended circulation times compared to their linear counterparts and provide alternative polymer architecture for use as drug carriers.

  6. Multiscale mechanical modeling of soft biological tissues

    NASA Astrophysics Data System (ADS)

    Stylianopoulos, Triantafyllos

    2008-10-01

    Soft biological tissues include both native and artificial tissues. In the human body, tissues like the articular cartilage, arterial wall, and heart valve leaflets are examples of structures composed of an underlying network of collagen fibers, cells, proteins and molecules. Artificial tissues are less complex than native tissues and mainly consist of a fiber polymer network with the intent of replacing lost or damaged tissue. Understanding of the mechanical function of these materials is essential for many clinical treatments (e.g. arterial clamping, angioplasty), diseases (e.g. arteriosclerosis) and tissue engineering applications (e.g. engineered blood vessels or heart valves). This thesis presents the derivation and application of a multiscale methodology to describe the macroscopic mechanical function of soft biological tissues incorporating directly their structural architecture. The model, which is based on volume averaging theory, accounts for structural parameters such as the network volume fraction and orientation, the realignment of the fibers in response to strain, the interactions among the fibers and the interactions between the fibers and the interstitial fluid in order to predict the overall tissue behavior. Therefore, instead of using a constitutive equation to relate strain to stress, the tissue microstructure is modeled within a representative volume element (RVE) and the macroscopic response at any point in the tissue is determined by solving a micromechanics problem in the RVE. The model was applied successfully to acellular collagen gels, native blood vessels, and electrospun polyurethane scaffolds and provided accurate predictions for permeability calculations in isotropic and oriented fiber networks. The agreement of model predictions with experimentally determined mechanical properties provided insights into the mechanics of tissues and tissue constructs, while discrepancies revealed limitations of the model framework.

  7. Nanoscale glucan polymer network causes pathogen resistance

    PubMed Central

    Eggert, Dennis; Naumann, Marcel; Reimer, Rudolph; Voigt, Christian A.

    2014-01-01

    Successful defence of plants against colonisation by fungal pathogens depends on the ability to prevent initial penetration of the plant cell wall. Here we report that the pathogen-induced (1,3)-β-glucan cell wall polymer callose, which is deposited at sites of attempted penetration, directly interacts with the most prominent cell wall polymer, the (1,4)-β-glucan cellulose, to form a three-dimensional network at sites of attempted fungal penetration. Localisation microscopy, a super-resolution microscopy technique based on the precise localisation of single fluorescent molecules, facilitated discrimination between single polymer fibrils in this network. Overexpression of the pathogen-induced callose synthase PMR4 in the model plant Arabidopsis thaliana not only enlarged focal callose deposition and polymer network formation but also resulted in the exposition of a callose layer on the surface of the pre-existing cellulosic cell wall facing the invading pathogen. The importance of this previously unknown polymeric defence network is to prevent cell wall hydrolysis and penetration by the fungus. We anticipate our study to promote nanoscale analysis of plant-microbe interactions with a special focus on polymer rearrangements in and at the cell wall. Moreover, the general applicability of localisation microscopy in visualising polymers beyond plant research will help elucidate their biological function in complex networks. PMID:24561766

  8. Statics and dynamics of softly confined polymers

    NASA Astrophysics Data System (ADS)

    Scagliarini, Andrea; Sbragaglia, Mauro; Sega, Marcello

    2015-03-01

    A variety of biological and technological problems where long chain molecules are constrained in spaces small compared to the molecule size (like membrane nanopores or nanofluidic slits) motivated recently a growing effort to understand the dynamics and structural scaling properties of polymers confined by solid walls. Our focus is, instead, on polymers confined in different geometries by soft interfaces, mimicking, e.g., DNA packaging inside cell nuclei or, mutatis mutandis, viral capsids. Soft-confinement is achieved by a proper choice of the solvation energies such that the polymer is trapped in one of the two phases of a binary mixture of immiscible liquids. We perform Molecular Dynamics simulations of polymers coupled with a fluctuating lattice Boltzmann method for the embedding matrix. Slab and droplet configurations are considered. In the former case we address the transition among various regimes of size scaling at changing the slab width. Under shear, the droplet is distorted from its equilibrium spherical shape and we explore how the transition from an isotropic geometry to a quasi-tube-like one affects polymer size scaling and knotting degree. Finally, we show how the feedback on the solvent induces viscoelastic rheology that can be related to polymer entanglement.

  9. High performance polymer development

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M.

    1991-01-01

    The term high performance as applied to polymers is generally associated with polymers that operate at high temperatures. High performance is used to describe polymers that perform at temperatures of 177 C or higher. In addition to temperature, other factors obviously influence the performance of polymers such as thermal cycling, stress level, and environmental effects. Some recent developments at NASA Langley in polyimides, poly(arylene ethers), and acetylenic terminated materials are discussed. The high performance/high temperature polymers discussed are representative of the type of work underway at NASA Langley Research Center. Further improvement in these materials as well as the development of new polymers will provide technology to help meet NASA future needs in high performance/high temperature applications. In addition, because of the combination of properties offered by many of these polymers, they should find use in many other applications.

  10. Therapeutic cloning and the constitution--a Canadian perspective.

    PubMed

    Muscati, S A

    2001-08-01

    Recent developments in the field of therapeutic cloning have been welcomed by many in the medical community as important breakthroughs that may help provide a better understanding of a variety of human diseases. Nevertheless, research in this field appears to have struck a sensitive nerve in society. A large amount of social debate has been generated regarding the validity of therapeutic cloning, and there are many seeking legislation to have the practice restricted. It is unclear, however, whether such restrictions can be legally justified. Analysing cloning in such a social and legal context raises a number of questions. What scientific procedures are behind therapeutic cloning? What is the legal status of the cultured or unimplanted embryo? Can cloning be considered an aspect of reproductive liberty as protected by the constitution? What medical advances might therapeutic cloning further? What social benefits and harms might arise from its promotion or restriction? Such questions, and the broader debate surrounding human therapeutic cloning, are addressed in this paper in three parts. Part 1 presents an overview of the basic biological principles behind cloning and the science behind the therapeutic cloning of specific cells and tissues. Part 2 analyses ss. 7, 2, 15(1) and 1 of the Canadian Charter of Rights and Freedoms and how they may be implicated by legal incursions into the field of human cloning. Several Charter-based arguments, both for and against the practice, are presented. Finally, Part 3 assesses some recent scientific developments in cloning technology, and how they affect the debate over the constitutionality of human therapeutic cloning.

  11. Protein-Polymer Functionalized Nanopatterned Surfaces

    NASA Astrophysics Data System (ADS)

    Wang, Haoyu; Akcora, Pinar

    2015-03-01

    Understanding and controlling the protein interactions with surfaces for biosensors and biomedical implants is a fundamental problem for biocompatible nanomaterial design. Proteins attached in ordered nanopores can exhibit superior biological activities compared to smooth microstructured surfaces. We developed heterogeneous and nanopatterned surfaces decorated with polymer brushes and proteins to control protein fates through elasticity. The heterogeneity of surfaces is controlled with well-defined chemistry, pattern size and geometry, stiffness of polymers and protein types. We will present our recent nanoindentation results on nanopatterned and biofunctionalized flat surfaces and discuss the pattern size effect on protein activity, hence conformation.

  12. Advances in inherently conducting polymers

    SciTech Connect

    Aldissi, M.

    1987-09-01

    The discovery of polyacetylene as the prototype material led to extensive research on its synythesis and characterization. The techniques that emerged as the most important and promising ones are those that dealt with molecular orientation and that resulted in conductivities almost as high as that of copper. The study of dozens of other materials followed. Interest in conducting polymers stems from their nonclassical optical and electronic properties as well as their potential technological applications. However, some of the factors currently limiting their use are the lack of long-term stability and the need to develop conventional low-cost techniques for easy processing. Therefore, research was extended toward solving these problems, and progress has been recently made in that direction. The synthesis of new materials such as stable and easily processable alkylthiophenes, water-soluble polymers, and multicomponent systems, including copolymers and composites, constitutes an important step forward in the area of synthetic metals. However, a full understanding of materials chemistry and properties requires more work in the years to come. Although, few small-scale applications have proven to be successful, long-term stability and applicability tests are needed before their commercial use becomes reality.

  13. Biological Technicians

    MedlinePlus

    ... Biological technicians typically need a bachelor’s degree in biology or a closely related field. It is important ... Biological technicians typically need a bachelor’s degree in biology or a closely related field. It is important ...

  14. Private Higher Education and the Constitutions; Constitutionality of State Aid to Private Higher Education.

    ERIC Educational Resources Information Center

    Thomas, Ann Van Wynen; Thomas, A. J., Jr.

    This report discusses the constitutionality of state aid to church-related institutions of higher education. The introduction deals with the important role that private institutions play in the total system of higher education, the seriousness of their financial plight, and the necessity for increased state aid to these institutions. Sections 2…

  15. Pinning down the Constitution: Interactively Teaching Congress's Power, Federalism, and Constitutional Interpretation

    ERIC Educational Resources Information Center

    Emenaker, Ryan

    2014-01-01

    "Pin-the-Tail-on-the-Constitution" is an engaged-learning activity that has been conducted in 26 classes over the past four years. The activity teaches multiple themes commonly included in a variety of courses on American politics such as federalism, congressional powers, the role of the federal courts, and the relevance of the commerce…

  16. Implementing the Equal Access Act and State Constitutional Provisions.

    ERIC Educational Resources Information Center

    Bjorklun, Eugene C.

    1992-01-01

    Examines the issue of whether implementation of the Equal Access Act would violate the constitutions of some states that require a stricter separation of church and state than the federal Constitution. (MLF)

  17. Close view of the south facade on Constitution Avenue to ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Close view of the south facade on Constitution Avenue to show main entrance - United States Department of Justice, Constitution Avenue between Ninth & Tenth Streets, Northwest, Washington, District of Columbia, DC

  18. Perspective view looking along the Constitution Avenue facade, showing the ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Perspective view looking along the Constitution Avenue facade, showing the twenty-seven bays and the three central arches that mark the entrance to the building - Internal Revenue Service Headquarters Building, 1111 Constitution Avenue Northwest, Washington, District of Columbia, DC

  19. Close view of the Constitution Avenue elevation to show arched ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Close view of the Constitution Avenue elevation to show arched gateways and pedimented pavilion ("Commerce and Communication" sculpted pediment) - Interstate Commerce Commission, Constitution Avenue between Twelfth and Fourteenth streets, Washington, District of Columbia, DC

  20. Endotoxin hitchhiking on polymer nanoparticles

    NASA Astrophysics Data System (ADS)

    Donnell, Mason L.; Lyon, Andrew J.; Mormile, Melanie R.; Barua, Sutapa

    2016-07-01

    The control of microbial infections is critical for the preparation of biological media including water to prevent lethal septic shock. Sepsis is one of the leading causes of death in the United States. More than half a million patients suffer from sepsis every year. Both gram-positive and gram-negative bacteria are responsible for septic infection by the most common organisms i.e., Escherichia coli and Pseuodomonas aeruginosa. The bacterial cell membrane releases negatively charged endotoxins upon death and enzymatic destruction, which stimulate antigenic response in humans to gram-negative infections. Several methods including distillation, ethylene oxide treatment, filtration and irradiation have been employed to remove endotoxins from contaminated samples, however, the reduction efficiency remains low, and presents a challenge. Polymer nanoparticles can be used to overcome the current inability to effectively sequester endotoxins from water. This process is termed endotoxin hitchhiking. The binding of endotoxin on polymer nanoparticles via electrostatic and hydrophobic interactions offers efficient removal from water. However, the effect of polymer nanoparticles and its surface areas has not been investigated for removal of endotoxins. Poly(ε-caprolactone) (PCL) polymer was tested for its ability to effectively bind and remove endotoxins from water. By employing a simple one-step phase separation technique, we were able to synthesize PCL nanoparticles of 398.3 ± 95.13 nm size and a polydispersity index of 0.2. PCL nanoparticles showed ∼78.8% endotoxin removal efficiency, the equivalent of 3.9 × 105 endotoxin units (EU) per ml. This is 8.34-fold more effective than that reported for commercially available membranes. Transmission electron microscopic images confirmed binding of multiple endotoxins to the nanoparticle surface. The concept of using nanoparticles may be applicable not only to eliminate gram-negative bacteria, but also for any gram

  1. Endotoxin hitchhiking on polymer nanoparticles.

    PubMed

    Donnell, Mason L; Lyon, Andrew J; Mormile, Melanie R; Barua, Sutapa

    2016-07-15

    The control of microbial infections is critical for the preparation of biological media including water to prevent lethal septic shock. Sepsis is one of the leading causes of death in the United States. More than half a million patients suffer from sepsis every year. Both gram-positive and gram-negative bacteria are responsible for septic infection by the most common organisms i.e., Escherichia coli and Pseuodomonas aeruginosa. The bacterial cell membrane releases negatively charged endotoxins upon death and enzymatic destruction, which stimulate antigenic response in humans to gram-negative infections. Several methods including distillation, ethylene oxide treatment, filtration and irradiation have been employed to remove endotoxins from contaminated samples, however, the reduction efficiency remains low, and presents a challenge. Polymer nanoparticles can be used to overcome the current inability to effectively sequester endotoxins from water. This process is termed endotoxin hitchhiking. The binding of endotoxin on polymer nanoparticles via electrostatic and hydrophobic interactions offers efficient removal from water. However, the effect of polymer nanoparticles and its surface areas has not been investigated for removal of endotoxins. Poly(ε-caprolactone) (PCL) polymer was tested for its ability to effectively bind and remove endotoxins from water. By employing a simple one-step phase separation technique, we were able to synthesize PCL nanoparticles of 398.3 ± 95.13 nm size and a polydispersity index of 0.2. PCL nanoparticles showed ∼78.8% endotoxin removal efficiency, the equivalent of 3.9 × 10(5) endotoxin units (EU) per ml. This is 8.34-fold more effective than that reported for commercially available membranes. Transmission electron microscopic images confirmed binding of multiple endotoxins to the nanoparticle surface. The concept of using nanoparticles may be applicable not only to eliminate gram-negative bacteria, but also for any gram

  2. Endotoxin hitchhiking on polymer nanoparticles.

    PubMed

    Donnell, Mason L; Lyon, Andrew J; Mormile, Melanie R; Barua, Sutapa

    2016-07-15

    The control of microbial infections is critical for the preparation of biological media including water to prevent lethal septic shock. Sepsis is one of the leading causes of death in the United States. More than half a million patients suffer from sepsis every year. Both gram-positive and gram-negative bacteria are responsible for septic infection by the most common organisms i.e., Escherichia coli and Pseuodomonas aeruginosa. The bacterial cell membrane releases negatively charged endotoxins upon death and enzymatic destruction, which stimulate antigenic response in humans to gram-negative infections. Several methods including distillation, ethylene oxide treatment, filtration and irradiation have been employed to remove endotoxins from contaminated samples, however, the reduction efficiency remains low, and presents a challenge. Polymer nanoparticles can be used to overcome the current inability to effectively sequester endotoxins from water. This process is termed endotoxin hitchhiking. The binding of endotoxin on polymer nanoparticles via electrostatic and hydrophobic interactions offers efficient removal from water. However, the effect of polymer nanoparticles and its surface areas has not been investigated for removal of endotoxins. Poly(ε-caprolactone) (PCL) polymer was tested for its ability to effectively bind and remove endotoxins from water. By employing a simple one-step phase separation technique, we were able to synthesize PCL nanoparticles of 398.3 ± 95.13 nm size and a polydispersity index of 0.2. PCL nanoparticles showed ∼78.8% endotoxin removal efficiency, the equivalent of 3.9 × 10(5) endotoxin units (EU) per ml. This is 8.34-fold more effective than that reported for commercially available membranes. Transmission electron microscopic images confirmed binding of multiple endotoxins to the nanoparticle surface. The concept of using nanoparticles may be applicable not only to eliminate gram-negative bacteria, but also for any gram

  3. Advanced Developments in Cyclic Polymers: Synthesis, Applications, and Perspectives

    PubMed Central

    Zhu, Yinghuai; Hosmane, Narayan S

    2015-01-01

    Due to the topological effect, cyclic polymers demonstrate different and unique physical and biological properties in comparison with linear counterparts having the same molecular-weight range. With advanced synthetic and analytic technologies, cyclic polymers with different topologies, e.g. multicyclic polymers, have been reported and well characterized. For example, various cyclic DNA and related structures, such as cyclic duplexes, have been prepared conveniently by click chemistry. These types of DNA have increased resistance to enzymatic degradation and have high thermodynamic stability, and thus, have potential therapeutic applications. In addition, cyclic polymers have also been used to prepare organic–inorganic hybrids for applications in catalysis, e.g. catalyst supports. Due to developments in synthetic technology, highly pure cyclic polymers could now be produced in large scale. Therefore, we anticipate discovering more applications in the near future. Despite their promise, cyclic polymers are still less explored than linear polymers like polyolefins and polycarbonates, which are widely used in daily life. Some critical issues, including controlling the molecular weight and finding suitable applications, remain big challenges in the cyclic-polymer field. This review briefly summarizes the commonly used synthetic methodologies and focuses more on the attractive functional materials and their biological properties and potential applications. PMID:26478835

  4. Biologically active LIL proteins built with minimal chemical diversity

    PubMed Central

    Heim, Erin N.; Marston, Jez L.; Federman, Ross S.; Edwards, Anne P. B.; Karabadzhak, Alexander G.; Petti, Lisa M.; Engelman, Donald M.; DiMaio, Daniel

    2015-01-01

    We have constructed 26-amino acid transmembrane proteins that specifically transform cells but consist of only two different amino acids. Most proteins are long polymers of amino acids with 20 or more chemically distinct side-chains. The artificial transmembrane proteins reported here are the simplest known proteins with specific biological activity, consisting solely of an initiating methionine followed by specific sequences of leucines and isoleucines, two hydrophobic amino acids that differ only by the position of a methyl group. We designate these proteins containing leucine (L) and isoleucine (I) as LIL proteins. These proteins functionally interact with the transmembrane domain of the platelet-derived growth factor β-receptor and specifically activate the receptor to transform cells. Complete mutagenesis of these proteins identified individual amino acids required for activity, and a protein consisting solely of leucines, except for a single isoleucine at a particular position, transformed cells. These surprisingly simple proteins define the minimal chemical diversity sufficient to construct proteins with specific biological activity and change our view of what can constitute an active protein in a cellular context. PMID:26261320

  5. Experiments to find constitutive relation for materials undergoing large deformation

    NASA Astrophysics Data System (ADS)

    Hariharaputhiran, H.; Saravanan, U.

    2010-03-01

    In this article, details about state of art custom built experimental set up to perform biaxial tests on thin sheets made of polymers or soft biological tissues is presented. This displacement controlled set up can apply and measure loads ranging from 0.01 N to 100 N. Then, the uniform or non-uniform surface deformation is determined from tracking a set of markers in 3D space using 2 CCD cameras. Using this setup both elastic and viscoelastic properties of the material could be characterized and the assumption of incompressibility verified. Following Rivlin and Saunders,1 the stored energy corresponding to vulcanized rubber, for stretch ratios less than 1.5, is found by systematically varying one of the variables in the stored energy function. This is achieved by performing biaxial extension tests in which the stretch ratio along one direction is held constant but varied between protocols and the stretch ratio in the perpendicular direction is increased gradually from 1 to 1.5. Then, the predictive capability of the stored energy function is examined by comparing its prediction for the uniaxial extension test with the actual experimental results. However, unlike Rivlin and Saunders, the stored energy is allowed to be either a function of the invariants of left Cauchy-Green stretch tensor (Rivlin2) or the invariants of Hencky strain (Criscione et al3) or the principal stretch ratios (Ogden4). None of the stored energy functions evaluated in this study is able to consistently predict the available experimental data.

  6. Experiments to find constitutive relation for materials undergoing large deformation

    NASA Astrophysics Data System (ADS)

    Hariharaputhiran, H.; Saravanan, U.

    2009-12-01

    In this article, details about state of art custom built experimental set up to perform biaxial tests on thin sheets made of polymers or soft biological tissues is presented. This displacement controlled set up can apply and measure loads ranging from 0.01 N to 100 N. Then, the uniform or non-uniform surface deformation is determined from tracking a set of markers in 3D space using 2 CCD cameras. Using this setup both elastic and viscoelastic properties of the material could be characterized and the assumption of incompressibility verified. Following Rivlin and Saunders,1 the stored energy corresponding to vulcanized rubber, for stretch ratios less than 1.5, is found by systematically varying one of the variables in the stored energy function. This is achieved by performing biaxial extension tests in which the stretch ratio along one direction is held constant but varied between protocols and the stretch ratio in the perpendicular direction is increased gradually from 1 to 1.5. Then, the predictive capability of the stored energy function is examined by comparing its prediction for the uniaxial extension test with the actual experimental results. However, unlike Rivlin and Saunders, the stored energy is allowed to be either a function of the invariants of left Cauchy-Green stretch tensor (Rivlin2) or the invariants of Hencky strain (Criscione et al3) or the principal stretch ratios (Ogden4). None of the stored energy functions evaluated in this study is able to consistently predict the available experimental data.

  7. Constitutive Theory Developed for Monolithic Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Janosik, Lesley A.

    1998-01-01

    With the increasing use of advanced ceramic materials in high-temperature structural applications such as advanced heat engine components, the need arises to accurately predict thermomechanical behavior that is inherently time-dependent and that is hereditary in the sense that the current behavior depends not only on current conditions but also on the material's thermomechanical history. Most current analytical life prediction methods for both subcritical crack growth and creep models use elastic stress fields to predict the time-dependent reliability response of components subjected to elevated service temperatures. Inelastic response at high temperatures has been well documented in the materials science literature for these material systems, but this issue has been ignored by the engineering design community. From a design engineer's perspective, it is imperative to emphasize that accurate predictions of time-dependent reliability demand accurate stress field information. Ceramic materials exhibit different time-dependent behavior in tension and compression. Thus, inelastic deformation models for ceramics must be constructed in a fashion that admits both sensitivity to hydrostatic stress and differing behavior in tension and compression. A number of constitutive theories for materials that exhibit sensitivity to the hydrostatic component of stress have been proposed that characterize deformation using time-independent classical plasticity as a foundation. However, none of these theories allow different behavior in tension and compression. In addition, these theories are somewhat lacking in that they are unable to capture the creep, relaxation, and rate-sensitive phenomena exhibited by ceramic materials at high temperatures. The objective of this effort at the NASA Lewis Research Center has been to formulate a macroscopic continuum theory that captures these time-dependent phenomena. Specifically, the effort has focused on inelastic deformation behavior associated

  8. Frederick Douglass Changed My Mind about the Constitution

    ERIC Educational Resources Information Center

    Oakes, James

    2008-01-01

    Frederick Douglass dramatically and publicly changed his own mind about the Constitution. Like Frederick Douglass, the author had originally viewed the Constitution as pro-slavery. Yet a close look at Douglass's writings revealed a Constitution that empowered the federal government to abolish slavery.

  9. Resolution and Letter to Congress from the Constitutional Convention

    ERIC Educational Resources Information Center

    Potter, Lee Ann

    2005-01-01

    This article explores the drafting of the United States Constitution. The United States Constitution is the longest-lasting written national constitution in the world. Its four parchment pages serve as the blueprint for a government under which more than 290 million Americans live. It holds great significance for the American people and for others…

  10. The Separation of Church and State. Exploring the Constitution Series.

    ERIC Educational Resources Information Center

    McWhirter, Darien A.

    This textbook on the separation of church and state continues the "Exploring the Constitution Series," which introduces important areas of constitutional law. Intended to serve either as a reference work, a supplement to a standard textbook, or as the textbook for a course, this volume covers the constitutional issues of prayer in public schools,…

  11. 42 CFR 23.28 - What events constitute default?

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false What events constitute default? 23.28 Section 23.28... SERVICE CORPS Private Practice Special Loans for Former Corps Members § 23.28 What events constitute default? The following events will constitute defaults of the loan agreement: (a) Failure to make...

  12. 42 CFR 23.28 - What events constitute default?

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false What events constitute default? 23.28 Section 23.28... SERVICE CORPS Private Practice Special Loans for Former Corps Members § 23.28 What events constitute default? The following events will constitute defaults of the loan agreement: (a) Failure to make...

  13. 42 CFR 23.28 - What events constitute default?

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false What events constitute default? 23.28 Section 23.28... SERVICE CORPS Private Practice Special Loans for Former Corps Members § 23.28 What events constitute default? The following events will constitute defaults of the loan agreement: (a) Failure to make...

  14. 42 CFR 23.28 - What events constitute default?

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false What events constitute default? 23.28 Section 23.28... SERVICE CORPS Private Practice Special Loans for Former Corps Members § 23.28 What events constitute default? The following events will constitute defaults of the loan agreement: (a) Failure to make...

  15. 42 CFR 23.28 - What events constitute default?

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false What events constitute default? 23.28 Section 23.28... SERVICE CORPS Private Practice Special Loans for Former Corps Members § 23.28 What events constitute default? The following events will constitute defaults of the loan agreement: (a) Failure to make...

  16. Constitution Day: Start the School Year with Civics

    ERIC Educational Resources Information Center

    Lesser, Eli J.

    2006-01-01

    The celebration and recognition of Constitution Day on September 17th is now required by federal law. The new law, known colloquially as the Byrd Amendment, requires all schools receiving any federal assistance, from kindergarten to higher education, to teach students about the Constitution on Constitution Day. The concept of a school's civic…

  17. 29 CFR 452.3 - Interpretations of constitution and bylaws.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 2 2013-07-01 2013-07-01 false Interpretations of constitution and bylaws. 452.3 Section... REPORTING AND DISCLOSURE ACT OF 1959 General Considerations § 452.3 Interpretations of constitution and bylaws. The interpretation consistently placed on a union's constitution by the responsible...

  18. 29 CFR 452.3 - Interpretations of constitution and bylaws.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 2 2014-07-01 2014-07-01 false Interpretations of constitution and bylaws. 452.3 Section... REPORTING AND DISCLOSURE ACT OF 1959 General Considerations § 452.3 Interpretations of constitution and bylaws. The interpretation consistently placed on a union's constitution by the responsible...

  19. 29 CFR 452.3 - Interpretations of constitution and bylaws.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 2 2012-07-01 2012-07-01 false Interpretations of constitution and bylaws. 452.3 Section... REPORTING AND DISCLOSURE ACT OF 1959 General Considerations § 452.3 Interpretations of constitution and bylaws. The interpretation consistently placed on a union's constitution by the responsible...

  20. 29 CFR 452.3 - Interpretations of constitution and bylaws.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 2 2011-07-01 2011-07-01 false Interpretations of constitution and bylaws. 452.3 Section... REPORTING AND DISCLOSURE ACT OF 1959 General Considerations § 452.3 Interpretations of constitution and bylaws. The interpretation consistently placed on a union's constitution by the responsible...

  1. 29 CFR 452.3 - Interpretations of constitution and bylaws.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 2 2010-07-01 2010-07-01 false Interpretations of constitution and bylaws. 452.3 Section... REPORTING AND DISCLOSURE ACT OF 1959 General Considerations § 452.3 Interpretations of constitution and bylaws. The interpretation consistently placed on a union's constitution by the responsible...

  2. Blood Clotting Inspired Polymer Physics

    NASA Astrophysics Data System (ADS)

    Sing, Charles Edward

    The blood clotting process is one of the human body's masterpieces in targeted molecular manipulation, as it requires the activation of the clotting cascade at a specific place and a specific time. Recent research in the biological sciences have discovered that one of the protein molecules involved in the initial stages of the clotting response, von Willebrand Factor (vWF), exhibits counterintuitive and technologically useful properties that are driven in part by the physical environment in the bloodstream at the site of a wound. In this thesis, we take inspiration from initial observations of the vWF in experiments, and aim to describe the behaviors observed in this process within the context of polymer physics. By understanding these physical principles, we hope to harness nature's ability to both direct molecules in both spatial and conformational coordinates. This thesis is presented in three complementary sections. After an initial introduction describing the systems of interest, we first describe the behavior of collapsed Lennard-Jones polymers in the presence of an infinite medium. It has been shown that simple bead-spring homopolymer models describe vWF quite well in vitro. We build upon this previous work to first describe the behavior of a collapsed homopolymer in an elongational fluid flow. Through a nucleation-protrusion mechanism, scaling relationships can be developed to provide a clear picture of a first-order globule-stretch transition and its ramifications in dilute-solution rheology. The implications of this behavior and its relation to the current literature provides qualitative explanations for the physiological process of vasoconstriction. In an effort to generalize these observations, we present an entire theory on the behavior of polymer globules under influence of any local fluid flow. Finally, we investigate the internal dynamics of these globules by probing their pulling response in an analogous fashion to force spectroscopy. We elucidate

  3. Biology and biotechnology of hyaluronan.

    PubMed

    Viola, Manuela; Vigetti, Davide; Karousou, Evgenia; D'Angelo, Maria Luisa; Caon, Ilaria; Moretto, Paola; De Luca, Giancarlo; Passi, Alberto

    2015-05-01

    The hyaluronan (HA) polymer is a critical component of extracellular matrix with a remarkable structure: is a linear and unbranched polymer without sulphate or phosphate groups. It is ubiquitous in mammals showing several biological functions, ranging from cell proliferation and migration to angiogenesis and inflammation. For its critical biological functions the amount of HA in tissues is carefully controlled by different mechanisms including covalent modification of the synthetic enzymes and epigenetic control of their gene expression. The concentration of HA is also critical in several pathologies including cancer, diabetes and inflammation. Beside these biological roles, the structural properties of HA allow it to take advantage of its capacity to form gels even at concentration of 1 % producing scaffolds with very promising applications in regenerative medicine as biocompatible material for advanced therapeutic uses. In this review we highlight the biological aspects of HA addressing the mechanisms controlling the HA content in tissues as well as its role in important human pathologies. In the second part of the review we highlight the different use of HA polymers in the modern biotechnology.

  4. Health care for Micronesians and constitutional rights.

    PubMed

    Shek, Dina; Yamada, Seiji

    2011-11-01

    Under the Compacts of Free Association (COFA), people from the Freely Associated States--the Republic of Palau (ROP), the Republic of the Marshall Islands (RMI), and the Federated States of Micronesia (FSM)--have been migrating to the United States in increasing numbers. In 1996, Congress passed broad welfare reform (Personal Responsibility and Work Opportunity Reconciliation Act) which limited certain federal benefits previously available to COFA migrants, including Medicaid benefits. Prior to July 2010, the State of Hawai'i had continued to include COFA migrants under its state-funded Medicaid program. In the face of budget constraints, the State removed these people from its Medicaid rolls. A challenge on the legal basis of the denial of equal protection of the laws, ie, the Fourteenth Amendment to the US Constitution, was successful in reinstating health care to the COFA migrants in December 2010. From the health worker's perspective, regardless of various social justice arguments that may have been marshaled in favor of delivering health care to the people, it was an appeal to the judicial system that succeeded. From the attorney's perspective, the legal victories are potentially limited to the four walls of the courtroom without community involvement and related social justice movements. Together, the authors propose that in order to better address the issue of health care access for Micronesian peoples, we must work together, as health and legal advocates, to define a more robust vision of both systems that includes reconciliation and community engagement. PMID:22235150

  5. Improvements to constitutive material model for fabrics

    NASA Astrophysics Data System (ADS)

    Morea, Mihai I.

    2011-12-01

    The high strength to weight ratio of woven fabric offers a cost effective solution to be used in a containment system for aircraft propulsion engines. Currently, Kevlar is the only Federal Aviation Administration (FAA) approved fabric for usage in systems intended to mitigate fan blade-out events. This research builds on an earlier constitutive model of Kevlar 49 fabric developed at Arizona State University (ASU) with the addition of new and improved modeling details. Latest stress strain experiments provided new and valuable data used to modify the material model post peak behavior. These changes reveal an overall improvement of the Finite Element (FE) model's ability to predict experimental results. First, the steel projectile is modeled using Johnson-Cook material model and provides a more realistic behavior in the FE ballistic models. This is particularly noticeable when comparing FE models with laboratory tests where large deformations in projectiles are observed. Second, follow-up analysis of the results obtained through the new picture frame tests conducted at ASU provides new values for the shear moduli and corresponding strains. The new approach for analysis of data from picture frame tests combines digital image analysis and a two-level factorial optimization formulation. Finally, an additional improvement in the material model for Kevlar involves checking the convergence at variation of mesh density of fabrics. The study performed and described herein shows the converging trend, therefore validating the FE model.

  6. Constitutive Autophagy and Nucleophagy during Epidermal Differentiation.

    PubMed

    Akinduro, Olufolake; Sully, Katherine; Patel, Ankit; Robinson, Deborah J; Chikh, Anissa; McPhail, Graham; Braun, Kristin M; Philpott, Michael P; Harwood, Catherine A; Byrne, Carolyn; O'Shaughnessy, Ryan F L; Bergamaschi, Daniele

    2016-07-01

    Epidermal keratinocytes migrate through the epidermis up to the granular layer where, on terminal differentiation, they progressively lose organelles and convert into anucleate cells or corneocytes. Our report explores the role of autophagy in ensuring epidermal function providing the first comprehensive profile of autophagy marker expression in developing epidermis. We show that autophagy is constitutively active in the epidermal granular layer where by electron microscopy we identified double-membrane autophagosomes. We demonstrate that differentiating keratinocytes undergo a selective form of nucleophagy characterized by accumulation of microtubule-associated protein light chain 3/lysosomal-associated membrane protein 2/p62 positive autolysosomes. These perinuclear vesicles displayed positivity for histone interacting protein, heterochromatin protein 1α, and localize in proximity with Lamin A and B1 accumulation, whereas in newborn mice and adult human skin, we report LC3 puncta coincident with misshaped nuclei within the granular layer. This process relies on autophagy integrity as confirmed by lack of nucleophagy in differentiating keratinocytes depleted from WD repeat domain phosphoinositide interacting 1 or Unc-51 like autophagy activating kinase 1. Final validation into a skin disease model showed that impaired autophagy contributes to the pathogenesis of psoriasis. Lack of LC3 expression in psoriatic skin lesions correlates with parakeratosis and deregulated expression or location of most of the autophagic markers. Our findings may have implications and improve treatment options for patients with epidermal barrier defects. PMID:27021405

  7. Health Care for Micronesians and Constitutional Rights

    PubMed Central

    Shek, Dina

    2011-01-01

    Under the Compacts of Free Association (COFA), people from the Freely Associated States — the Republic of Palau (ROP), the Republic of the Marshall Islands (RMI), and the Federated States of Micronesia (FSM) — have been migrating to the United States in increasing numbers. In 1996, Congress passed broad welfare reform (Personal Responsibility and Work Opportunity Reconciliation Act) which limited certain federal benefits previously available to COFA migrants, including Medicaid benefits. Prior to July 2010, the State of Hawai‘i had continued to include COFA migrants under its state-funded Medicaid program. In the face of budget constraints, the State removed these people from its Medicaid rolls. A challenge on the legal basis of the denial of equal protection of the laws, ie, the Fourteenth Amendment to the US Constitution, was successful in reinstating health care to the COFA migrants in December 2010. From the health worker's perspective, regardless of various social justice arguments that may have been marshaled in favor of delivering health care to the people, it was an appeal to the judicial system that succeeded. From the attorney's perspective, the legal victories are potentially limited to the four walls of the courtroom without community involvement and related social justice movements. Together, the authors propose that in order to better address the issue of health care access for Micronesian peoples, we must work together, as health and legal advocates, to define a more robust vision of both systems that includes reconciliation and community engagement. PMID:22235150

  8. A Constitutive Equation for Stratospheric Balloon Materials

    NASA Technical Reports Server (NTRS)

    Rand, J. L.; Sterling, W. J.

    2004-01-01

    The selection of a suitable material for use as a reliable stratospheric balloon gas barrier and structural component is based on a variety of properties. Due to a more desirable combination of properties, the low density polyethylene that has been used for the last half century has been replaced during the last decade by linear low density polyethylene (LLDPE). This paper describes the effort to characterize the time dependent properties of a 38 micron coextrusion of LLDPE. The nonlinear viscoelastic constitutive equation presented may be used to accurately describe the creep and/or relaxation of this film when subjected to a biaxial state of stress, such as might be required for an extended balloon flight. Recent laboratory data have been used to mod@ an existing model of LLDPE to account for differences caused by the coextrusion process. The new model will facilitate structural design optimization and reliability assessment, and may be further utilized as a predictive tool to benefit in-flight operations. Current structural analysis tech&ques based on linear elastic properties have predicted stresses in excess of those which would actually exist.

  9. Constitutive Modeling of Magnesium Alloy Sheets

    SciTech Connect

    Lee, M. G.; Piao, K.; Wagoner, R. H.; Lee, J. K.; Chung, K.; Kim, H. Y.

    2007-05-17

    Magnesium alloy sheets have unique mechanical properties: high in-plane anisotropy/asymmetry of yield stress and hardening response, which have not been thoroughly studied. The unusual mechanical behavior of magnesium alloys has been understood by the limited symmetry crystal structure of h.c.p metals and thus by deformation twinning. In this paper, the phenomenological continuum plasticity models considering the unusual plastic behavior of magnesium alloy sheet were developed for a finite element analysis. A new hardening law based on two-surface model was developed to consider the general stress-strain response of metal sheets such as Bauschinger effect, transient behavior and the unusual asymmetry. Three deformation modes observed during the continuous tension/compression tests were mathematically formulated with simplified relations between the state of deformation and their histories. In terms of the anisotropy and asymmetry of the initial yield stress, the Drucker-Prager's pressure dependent yield surface was modified to include the anisotropy of magnesium alloys. Also, characterization procedures of material parameters for the constitutive equations were presented and finally the correlation of simulation with measurements was performed to validate the proposed theory.

  10. Covariant constitutive relations and relativistic inhomogeneous plasmas

    SciTech Connect

    Gratus, J.; Tucker, R. W.

    2011-04-15

    The notion of a 2-point susceptibility kernel used to describe linear electromagnetic responses of dispersive continuous media in nonrelativistic phenomena is generalized to accommodate the constraints required of a causal formulation in spacetimes with background gravitational fields. In particular the concepts of spatial material inhomogeneity and temporal nonstationarity are formulated within a fully covariant spacetime framework. This framework is illustrated by recasting the Maxwell-Vlasov equations for a collisionless plasma in a form that exposes a 2-point electromagnetic susceptibility kernel in spacetime. This permits the establishment of a perturbative scheme for nonstationary inhomogeneous plasma configurations. Explicit formulae for the perturbed kernel are derived in both the presence and absence of gravitation using the general solution to the relativistic equations of motion of the plasma constituents. In the absence of gravitation this permits an analysis of collisionless damping in terms of a system of integral equations that reduce to standard Landau damping of Langmuir modes when the perturbation refers to a homogeneous stationary plasma configuration. It is concluded that constitutive modeling in terms of a 2-point susceptibility kernel in a covariant spacetime framework offers a natural extension of standard nonrelativistic descriptions of simple media and that its use for describing linear responses of more general dispersive media has wide applicability in relativistic plasma modeling.

  11. Mechanics of light-activated network polymers

    NASA Astrophysics Data System (ADS)

    Long, Kevin Nicholas

    Mechanically responsive, environmentally activated polymers can undergo large, complex deformation in response to external stimuli such as thermal, luminous, and chemical changes to the environment. Light as a stimulus provides unique application potential because it allows for remote, rapid, and isothermal activation of the material with precise spatial control via existing optical technologies. While certain systems have received considerable attention, the state of the art of most light-activated polymers is limited to basic characterization and demonstrations. To make such materials available to the engineering and scientific communities, physically based theoretical and computational tools are required to guide experimental and design efforts that capitalize on their complex photo-mechanical couplings. The central objective of this thesis is to develop a multi-physics constitutive modeling framework to simulate the continuum scale, photo mechanical behavior of light-activated polymers and implement it into a finite element analysis setting. This framework is independent of specific underlying photo-stimulation mechanisms and is discussed in the context of photo-activated shape memory polymers and network rearranging polymers. Next, the framework is applied to the light-activated network rearranging polymer system, which is relaxed of stress upon irradiation with UV light, and a suite of characterization and application oriented experiments are carried out to calibrate and validate the model's predictive capabilities. The calibrated model is used to investigate several applications such as photo-activated stress relaxation of notched specimens, bending actuation, creep, the buckling of equi-biaxially deformed and irradiated films, and photomechanically formed 1D channels and ridges. Modeling creep involves additional complexity through simultaneous deformation and irradiation, and so the model framework is extended to cover such scenarios. Experiments, finite

  12. Hybrid polymer photonic crystal fiber with integrated chalcogenide glass nanofilms

    NASA Astrophysics Data System (ADS)

    Markos, Christos; Kubat, Irnis; Bang, Ole

    2014-08-01

    The combination of chalcogenide glasses with polymer photonic crystal fibers (PCFs) is a difficult and challenging task due to their different thermo-mechanical material properties. Here we report the first experimental realization of a hybrid polymer-chalcogenide PCF with integrated As2S3 glass nanofilms at the inner surface of the air-channels of a poly-methyl-methacrylate (PMMA) PCF. The integrated high refractive index glass films introduce distinct antiresonant transmission bands in the 480-900 nm wavelength region. We demonstrate that the ultra-high Kerr nonlinearity of the chalcogenide glass makes the polymer PCF nonlinear and provides a possibility to shift the transmission band edges as much as 17 nm by changing the intensity. The proposed fabrication technique constitutes a new highway towards all-fiber nonlinear tunable devices based on polymer PCFs, which at the moment is not possible with any other fabrication method.

  13. On Eulerian constitutive equations for modeling growth and residual stresses in arteries.

    PubMed

    Volokh, K Y

    2005-06-01

    Recently Volokh and Lev (2005) argued that residual stresses could appear in growing arteries because of the arterial anisotropy. This conclusion emerged from a continuum mechanics theory of growth of soft biological tissues proposed by the authors. This theory included Lagrangian constitutive equations, which were formulated directly with respect to the reference configuration. Alternatively, it is possible to formulate Eulerian constitutive equations with respect to the current configuration and to 'pull them back' to the reference configuration. Such possibility is examined in the present work. The Eulerian formulation of the constitutive equations is used for a study of arterial growth. It is shown, particularly, that bending resultants are developed in the ring cross-section of the artery. These resultants may cause the ring opening or closing after cutting the artery in vitro as it is observed in experiments. It is remarkable that the results of the present study, based on the Eulerian constitutive equations, are very similar to the results of Volokh and Lev (2005), based on the Lagrangian constitutive equations. This strengthens the authors' argument that anisotropy is a possible reason for accumulation of residual stresses in arteries. This argument appears to be invariant with respect to the mathematical description.

  14. The diversification of developmental biology.

    PubMed

    Crowe, Nathan; Dietrich, Michael R; Alomepe, Beverly S; Antrim, Amelia F; ByrneSim, Bay Lauris; He, Yi

    2015-10-01

    In the 1960s, "developmental biology" became the dominant term to describe some of the research that had previously been included under the rubrics of embryology, growth, morphology, and physiology. As scientific societies formed under this new label, a new discipline took shape. Historians, however, have a number of different perspectives on what changes led to this new field of developmental biology and how the field itself was constituted during this period. Using the General Embryological Information Service, a global index of post-World War II development-related research, we have documented and visualized significant changes in the kinds of research that occurred as this new field formed. In particular, our analysis supports the claim that the transition toward developmental biology was marked by a growth in new topics and forms of research. Although many historians privilege the role of molecular biology and/or the molecularization of biology in general during this formative period, we have found that the influence of molecular biology is not sufficient to account for the wide range of new research that constituted developmental biology at the time. Overall, our work creates a robust characterization of the changes that occurred with regard to research on growth and development in the decades following World War II and provides a context for future work on the specific drivers of those changes.

  15. CO2 -Responsive polymers.

    PubMed

    Lin, Shaojian; Theato, Patrick

    2013-07-25

    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.

  16. Micromechanics and constitutive models for soft active materials with phase evolution

    NASA Astrophysics Data System (ADS)

    Wang, Binglian

    Soft active materials, such as shape memory polymers, liquid crystal elastomers, soft tissues, gels etc., are materials that can deform largely in response to external stimuli. Micromechanics analysis of heterogeneous materials based on finite element method is a typically numerical way to study the thermal-mechanical behaviors of soft active materials with phase evolution. While the constitutive models that can precisely describe the stress and strain fields of materials in the process of phase evolution can not be found in the databases of some commercial finite element analysis (FEA) tools such as ANSYS or Abaqus, even the specific constitutive behavior for each individual phase either the new formed one or the original one has already been well-known. So developing a computationally efficient and general three dimensional (3D) thermal-mechanical constitutive model for soft active materials with phase evolution which can be implemented into FEA is eagerly demanded. This paper first solved this problem theoretically by recording the deformation history of each individual phase in the phase evolution process, and adopted the idea of effectiveness by regarding all the new formed phase as an effective phase with an effective deformation to make this theory computationally efficient. A user material subroutine (UMAT) code based on this theoretical constitutive model has been finished in this work which can be added into the material database in Abaqus or ANSYS and can be easily used for most soft active materials with phase evolution. Model validation also has been done through comparison between micromechanical FEA and experiments on a particular composite material, shape memory elastomeric composite (SMEC) which consisted of an elastomeric matrix and the crystallizable fibre. Results show that the micromechanics and the constitutive models developed in this paper for soft active materials with phase evolution are completely relied on.

  17. Biomimetic Gradient Polymers with Enhanced Damping Capacities.

    PubMed

    Wang, Dong; Zhang, Huan; Guo, Jing; Cheng, Beichen; Cao, Yuan; Lu, Shengjun; Zhao, Ning; Xu, Jian

    2016-04-01

    Designing gradient structures, mimicking biological materials, such as pummelo peels and tendon, is a promising strategy for developing advanced materials with superior energy damping capacities. Here a facile and effective approach for fabricating polymers with composition gradients at millimeter length scale is presented. The gradient thiol-ene polymers (TEPs) are created by the use of density difference of ternary thiol-ene-ene precursors and the subsequent photo-crosslinking via thiol-ene reaction. The compositional gradients are analyzed via differential scanning calorimeter (DSC), compressive modulus testing, atomic force microscopy (AFM) indentation, and swelling measurements. In contrast to homogeneous TEPs networks, the resultant gradient polymer shows a broader effective damping temperature range combining with good mechanical properties. The present result provides an effective route toward high damping materials by the fabrication of gradient structures. PMID:26776353

  18. Do biological medicinal products pose a risk to the environment?: a current view on ecopharmacovigilance.

    PubMed

    Kühler, Thomas C; Andersson, Mikael; Carlin, Gunnar; Johnsson, Ann; Akerblom, Lennart

    2009-01-01

    The occurrence of active pharmaceutical substances in the environment is of growing concern. The vast majority of the compounds in question are of low molecular weight, intended for oral use and designed to tolerate, for example, the digestive enzymes in the upper alimentary tract, the harsh milieus found in the acidic stomach, or the microbe rich intestine. Accordingly, these xenobiotic compounds may, due to their inherent biological activity, constitute a risk to the environment. Biological medicinal products, for example recombinant human insulin or monoclonal antibodies, however, are different. They are primarily made up of oligomers or polymers of amino acids, sugars or nucleotides and are thus readily metabolized. They are therefore generally not considered to pose any risk to the environment. Certain classes of biological medicinal products, however, are associated with specific safety issues. Genetically modified organisms as vectors in vaccines or in gene therapy products have attracted much attention in this regard. Issues include the degree of attenuation of the live recombinant vaccine, replication restrictions of the vaccine vector, alteration of the host and tissue tropism of the vector, the possibility of reversion to virulence, and risk to the ecosystem. In this review we discuss the fate and the potential environmental impact of biological medicinal products following clinical use from an ecopharmacovigilance point of view, and review relevant policy documents and regulatory statements. PMID:19810773

  19. Preparation and characterization of gradient polymer films

    SciTech Connect

    Smith, S.C.

    1987-01-01

    Gradient polymers are multicomponent polymers whose chemical constitution varies with depth in the sample. Although these polymers may possess unique mechanical, optical, and barrier properties they remain relatively unexplored. This work is a study of the preparation of gradient polymers by sequential exposure of films to a diffusing monomer followed by electron beam irradiation. Initial experiments involved immersion of poly(vinyl chloride) (PVC) films in styrene or n-butyl methacrylate (BMA) for various time periods followed by irradiation with 1 or 10 megarads of accelerated electrons. A significant amount of poly(n-butyl methacrylate) (PBMA) formed in PVC/BMA systems, but little polystyrene could be found in the PVC/styrene films. A second set of experiments involved immersion of PVC and polyethylene (PE) films in BMA for 20, 40, 60, and 720 minutes followed by irradiation with 10 megarads of electrons. These films were then characterized using optical microscopy, quantitative transmission Fourier transform infrared spectroscopy (FTIR), and a depth profiling procedure based on quantitative attenuated total reflection (ATR) FTIR. It was concluded that the mechanism of PBMA formation in the polyethylene films was a result of events immediately following irradiation. Atmospheric oxygen diffusing into irradiated films trapped free radicals at the film surfaces. This was followed by storage in an evacuated desiccator where unintentional exposure to BMA vapor took place. This BMA reacted with free radicals that remained within the film cores, polymerizing to PBMA.

  20. Modelling Polymer Deformation during 3D Printing

    NASA Astrophysics Data System (ADS)

    McIlroy, Claire; Olmsted, Peter

    Three-dimensional printing has the potential to transform manufacturing processes, yet improving the strength of printed parts, to equal that of traditionally-manufactured parts, remains an underlying issue. The fused deposition modelling technique involves melting a thermoplastic, followed by layer-by-layer extrusion to fabricate an object. The key to ensuring strength at the weld between layers is successful inter-diffusion. However, prior to welding, both the extrusion process and the cooling temperature profile can significantly deform the polymer micro-structure and, consequently, how well the polymers are able to ``re-entangle'' across the weld. In particular, polymer alignment in the flow can cause de-bonding of the layers and create defects. We have developed a simple model of the non-isothermal extrusion process to explore the effects that typical printing conditions and material rheology have on the conformation of a polymer melt. In particular, we incorporate both stretch and orientation using the Rolie-Poly constitutive equation to examine the melt structure as it flows through the nozzle, the subsequent alignment with the build plate and the resulting deformation due to the fixed nozzle height, which is typically less than the nozzle radius.

  1. High Performance Polymers

    NASA Technical Reports Server (NTRS)

    Venumbaka, Sreenivasulu R.; Cassidy, Patrick E.

    2003-01-01

    This report summarizes results from research on high performance polymers. The research areas proposed in this report include: 1) Effort to improve the synthesis and to understand and replicate the dielectric behavior of 6HC17-PEK; 2) Continue preparation and evaluation of flexible, low dielectric silicon- and fluorine- containing polymers with improved toughness; and 3) Synthesis and characterization of high performance polymers containing the spirodilactam moiety.

  2. Thermally conductive polymers

    NASA Technical Reports Server (NTRS)

    Byrd, N. R.; Jenkins, R. K.; Lister, J. L. (Inventor)

    1971-01-01

    A thermally conductive polymer is provided having physical and chemical properties suited to use as a medium for potting electrical components. The polymer is prepared from hydroquinone, phenol, and formaldehyde, by conventional procedures employed for the preparation of phenol-formaldehyde resins. While the proportions of the monomers can be varied, a preferred polymer is formed from the monomers in a 1:1:2.4 molar or ratio of hydroquinone:phenol:formaldehyde.

  3. Predictive aging of polymers

    NASA Technical Reports Server (NTRS)

    Cuddihy, Edward F. (Inventor); Willis, Paul B. (Inventor)

    1989-01-01

    A method of predicting aging of polymers operates by heating a polymer in the outdoors to an elevated temperature until a change of property is induced. The test is conducted at a plurality of temperatures to establish a linear Arrhenius plot which is extrapolated to predict the induction period for failure of the polymer at ambient temperature. An Outdoor Photo Thermal Aging Reactor (OPTAR) is also described including a heatable platen for receiving a sheet of polymer, means to heat the platen, and switching means such as a photoelectric switch for turning off the heater during dark periods.

  4. Predictive aging of polymers

    NASA Technical Reports Server (NTRS)

    Cuddihy, Edward F. (Inventor); Willis, Paul B. (Inventor)

    1990-01-01

    A method of predicting aging of polymers operates by heating a polymer in the outdoors to an elevated temperature until a change of property is induced. The test is conducted at a plurality of temperatures to establish a linear Arrhenius plot which is extrapolated to predict the induction period for failure of the polymer at ambient temperature. An Outdoor Photo Thermal Aging Reactor (OPTAR) is also described including a heatable platen for receiving a sheet of polymer, means to heat the platen and switching means such as a photoelectric switch for turning off the heater during dark periods.

  5. Polymers for engineering applications

    SciTech Connect

    Seymour, R.B.

    1987-01-01

    This book provides an introduction to the world of engineering plastics. It discusses the polymers, their properties strengths and limitations. There are 11 chapters, organized so that each chapter builds on the knowledge of the previous material. Coverage includes important polymer concepts, such as molecular structure, bonding, morphology and molecular weight, and polymer properties, such as thermal expansion, thermal transition, electrical properties and viscoelasticity. Details are provided on methods of processing fabrication and on specific families of polymers. The general-purpose polymers are discussed, such as natural and synthetic rubbers, rayon, acrylic and alkyd coatings, polyethylene, polystyrene and polyvinyl chloride (PVC). There's information on high-performance polymers - fibers, elastomers, and coatings. A thorough explanation of the characteristics and qualities of nylons, polyesters, polyimides, neoprene, silicones, polyurethanes and other polymers is given in the same section. Functional polymers with special properties, such as photoconductivity, electric conductivity, piezoelectricity, light sensitivity, and ion exchange; and polymers that are superior to general-purpose plastics, such as ABS, filled polypropylene, and glass-reinforced plastics, are also covered.

  6. Polymer-coated long-circulating microparticulate pharmaceuticals.

    PubMed

    Torchilin, V P

    1998-01-01

    The field of long-circulating microparticulate drug carriers is reviewed. The protective effect of certain polymers including poly(ethylene glycol) on nanoparticulate carriers (liposomes, nanoparticles, micelles) is considered in terms of statistical behaviour of macromolecules in solution. Using liposomes as an example, the mechanism is discussed assuming that surface-grafted chains of flexible and hydrophilic polymers form dense 'conformational clouds' preventing other macromolecules from interaction with the surface even at low concentrations of the protecting polymer. The scale of the protective effect is interpreted as the balance between the energy of the hydrophobic anchor interaction with the liposome membrane core or with the particle surface and the energy of the polymer chain free motion in solution. The possibility of using protecting polymers other than poly(ethylene glycol) is analysed, and examples of such polymers are given, based on polymer-coated liposome biodistribution data. General requirements for protecting polymers are formulated. Sterically protected nanoparticles and micelles are considered, and differences in steric protection of liposomes and particles are discussed. The problem of the preparation of drug carriers combining longevity and targetability is analysed. The biological consequences of steric protection of drug carriers with surface-grafted polymers are discussed, and possible clinical applications for long-circulating pharmaceutical carriers are considered.

  7. How Does Astronomy Constitute A Learning Community?

    NASA Astrophysics Data System (ADS)

    Dogan, Yasemin; Sengul, R.; Unat, O.; Aknil, A.; Gurel, Z.

    2010-01-01

    This study was conducted in Turkey within an interdisciplinary project called "From a windowless home to a skyscraper: Let's build a home". It was realized through collaboration between a public university and a private high school. Researchers from Physics Education Department and volunteer teachers from high school, each studying on a different discipline, and volunteer high school students, all from an urban area of the country, conducted the project in a rural small town with resident secondary school students. It was implemented on the basis of history, through the use of different fields such as science, mathematics, geography, art, handcraft, architecture, engineering and astronomy in August 2008. The purpose of this study was to present the effect of the astronomical activities involved in the project. These implementations constructed a scientific and social base for the framework of astronomical activities of IYA2009, including building an amateur observatory. Since today's people are not so much acquainted with the issues of space and astronomy as much as the people of Antiquity, we attached special importance to the efforts in this field. The project, proceeded by a preparatory and informative period, involved night sky observation, initially with naked eye, followed by observation through telescope. Not only the students but also countless people, old or young, participated in our work in the field of astronomy. It provided a chance for all the people participating in or connected to the project to discover the sky. Astronomical activities aroused curiosity among students and the community and made a difference by inducing an awareness of the sky. The participants of the study had completely different social and cultural backgrounds, and this study removed all these differences bringing them together under the overarching astronomical and historical aspect. Moreover the community revealed all the characteristics that constitute a learning community.

  8. How Does Astronomy Constitute a Learning Community?

    NASA Astrophysics Data System (ADS)

    Dogan, Yasemin; Sengul, R.; Unat, O.; Aknil, A.; Gurel, Z.

    2009-05-01

    This study was conducted in Turkey within an interdisciplinary project called "From a windowless home to a skyscraper: Let's build a home". It was realized through collaboration between a public university and a private high school. Researchers from Physics Education Department and volunteer teachers from high school, each studying on a different discipline, and volunteer high school students, all from an urban area of the country, conducted the project in a rural small town with resident secondary school students. It was implemented on the basis of history, through the use of different fields such as science, mathematics, geography, art, handcraft, architecture, engineering and astronomy in August 2008. The purpose of this study was to present the effect of the astronomical activities involved in the project. Since today's people are not so much acquainted with the issues of space and astronomy as much as the people of Antiquity, we attached special importance to the efforts in this field. The project, proceeded by a preparatory and informative period, involved night sky observation, initially with naked eye, followed by observation through a telescope. Not only the students but also countless people, old or young, participated in our work in the field of astronomy. It provided a chance for all the people participating in or connected to the project to discover the sky. Astronomical activities aroused curiosity among students and the community and made a difference by inducing an awareness of the sky. The participants of the study had completely different social and cultural backgrounds, and this study removed all these differences bringing them together under the overarching astronomical and historical aspect. Moreover the community revealed all the characteristics that constitute a learning community.

  9. The normative constitution of professional power.

    PubMed

    Frankford, D M

    1997-02-01

    This article concerns the manner in which we think and talk about power in health care policy and regulation, and the political and social practices allied with that discourse. I assert that in health care policy and practice we speak of and live within the era of countervailing power. In this language and practice power is a force exercised by one actor to enforce its will against another actor against whom power is exerted. I contend that this language inculcates an individual and social passivity in which citizens rely upon various types of representatives to constitute health care for them in a manner in which they do not and cannot participate. However, this language of power and the political and social practice with which it is associated is merely a contingent, historical product. I claim that an alternative discourse of power is possible, in which power consists of the social interactions in which all of us mutually participate but no one of us can control. Power in this sense is participatory by nature, and because no one is in control, it makes no sense to relegate tasks to specialized, nonparticipatory domains. This alternative discourse of power, therefore, might call forth participatory practices in health care and a concomitant diminution of specialization and expansion of the public sphere. The result would be to blur the lines separating politics from everyday interaction, politics from economy, professionals from patients, and insurers from insureds. Participation would mean much more than casting a vote or writing a check but would also include the mutual sharing of time and energy in the tasks that need to be done: long-term and short-term care, practices of prevention, caring for the chronically ill, and monitoring bureaucratic and professional activities. PMID:9057126

  10. Biological Filters.

    ERIC Educational Resources Information Center

    Klemetson, S. L.

    1978-01-01

    Presents the 1978 literature review of wastewater treatment. The review is concerned with biological filters, and it covers: (1) trickling filters; (2) rotating biological contractors; and (3) miscellaneous reactors. A list of 14 references is also presented. (HM)

  11. Biological Agents

    MedlinePlus

    ... to Z Index Contact Us FAQs What's New Biological Agents This page requires that javascript be enabled ... and Health Topics A-Z Index What's New Biological agents include bacteria, viruses, fungi, other microorganisms and ...

  12. Modelling of electrokinetic phenomena involving confined polymers: Applications to DNA separation and electroosmotic flow control

    NASA Astrophysics Data System (ADS)

    Tessier, Frederic

    Microfluidic and nanofluidic technology is revolutionizing experimental practices in analytical chemistry, molecular biology and medicine. Indeed, the development of systems of small dimensions for the processing of fluids heralds the miniaturization of traditional, cumbersome laboratory equipment onto robust, portable and efficient microchip devices (similar to the electronic microchips found in computers). Moreover, the conjunction of scale between the smallest man-made device and the largest macromolecules evolved by Nature is fertile ground for the blooming of our knowledge about the key processes of life. In fact, the conjunction is threefold, because modern computational resources also allow us to contemplate a rather explicit modelling of physical systems between the nanoscale and the microscale. In the five articles comprising this thesis, we present the results of computer simulations that address specific questions concerning the operation of two different model systems relevant to the development of small-scale fluidic devices for the manipulation and analysis of biomolecules. First, we use a Bond-Fluctuation Monte Carlo approach to study the electrophoretic drift of macromolecules across an entropic trap array built for the length separation of long, double-stranded DNA molecules. We show that the motion of the molecules is consistent with a simple balance between electric and entropic forces, in terms of a single characteristic parameter. We also extract detailed information on polymer deformation during migration, predict the separation of topoisomers, and investigate innovative ratchet driving regimes. Secondly, we present theoretical derivations, numerical calculations and Molecular Dynamics simulation results for an electrolyte confined in a capillary of nanoscopic dimensions. In particular, we study the effectiveness of neutral grafted polymer chains in reducing the magnitude of electroosmotic flow (fluid flow induced by an external electric field

  13. Prediction of multiaxial mechanical behavior for conventional and highly crosslinked UHMWPE using a hybrid constitutive model.

    PubMed

    Bergström, J S; Rimnac, C M; Kurtz, S M

    2003-04-01

    The development of theoretical failure, fatigue, and wear models for ultra-high molecular weight polyethylene (UHMWPE) used in joint replacements has been hindered by the lack of a validated constitutive model that can accurately predict large deformation mechanical behavior under clinically relevant, multiaxial loading conditions. Recently, a new Hybrid constitutive model for unirradiated UHMWPE was developed Bergström et al., (Biomaterials 23 (2002) 2329) based on a physics-motivated framework which incorporates the governing micro-mechanisms of polymers into an effective and accurate continuum representation. The goal of the present study was to compare the predictive capability of the new Hybrid model with the J(2)-plasticity model for four conventional and highly crosslinked UHMWPE materials during multiaxial loading. After calibration under uniaxial loading, the predictive capabilities of the J(2)-plasticity and Hybrid model were tested by comparing the load-displacement curves from experimental multiaxial (small punch) tests with simulated load-displacement curves calculated using a finite element model of the experimental apparatus. The quality of the model predictions was quantified using the coefficient of determination (r(2)). The results of the study demonstrate that the Hybrid model outperforms the J(2)-plasticity model both for combined uniaxial tension and compression predictions and for simulating multiaxial large deformation mechanical behavior produced by the small punch test. The results further suggest that the parameters of the HM may be generalizable for a wide range of conventional, highly crosslinked, and thermally treated UHMWPE materials, based on the characterization of four material properties related to the elastic modulus, yield stress, rate of strain hardening, and locking stretch of the polymer chains. Most importantly, from a practical perspective, these four key material properties for the Hybrid constitutive model can be measured

  14. Molecularly Imprinted Polymers: Present and Future Prospective

    PubMed Central

    Vasapollo, Giuseppe; Sole, Roberta Del; Mergola, Lucia; Lazzoi, Maria Rosaria; Scardino, Anna; Scorrano, Sonia; Mele, Giuseppe

    2011-01-01

    Molecular Imprinting Technology (MIT) is a technique to design artificial receptors with a predetermined selectivity and specificity for a given analyte, which can be used as ideal materials in various application fields. Molecularly Imprinted Polymers (MIPs), the polymeric matrices obtained using the imprinting technology, are robust molecular recognition elements able to mimic natural recognition entities, such as antibodies and biological receptors, useful to separate and analyze complicated samples such as biological fluids and environmental samples. The scope of this review is to provide a general overview on MIPs field discussing first general aspects in MIP preparation and then dealing with various application aspects. This review aims to outline the molecularly imprinted process and present a summary of principal application fields of molecularly imprinted polymers, focusing on chemical sensing, separation science, drug delivery and catalysis. Some significant aspects about preparation and application of the molecular imprinting polymers with examples taken from the recent literature will be discussed. Theoretical and experimental parameters for MIPs design in terms of the interaction between template and polymer functionalities will be considered and synthesis methods for the improvement of MIP recognition properties will also be presented. PMID:22016636

  15. Binary Polymer Brushes of Strongly Immiscible Polymers.

    PubMed

    Chu, Elza; Babar, Tashnia; Bruist, Michael F; Sidorenko, Alexander

    2015-06-17

    The phenomenon of microphase separation is an example of self-assembly in soft matter and has been observed in block copolymers (BCPs) and similar materials (i.e., supramolecular assemblies (SMAs) and homo/block copolymer blends (HBCs)). In this study, we use microphase separation to construct responsive polymer brushes that collapse to generate periodic surfaces. This is achieved by a chemical reaction between the minor block (10%, poly(4-vinylpyridine)) of the block copolymer and a substrate. The major block of polystyrene (PS) forms mosaic-like arrays of grafted patches that are 10-20 nm in size. Depending on the nature of the assembly (SMA, HBC, or neat BCP) and annealing method (exposure to vapors of different solvents or heating above the glass transition temperature), a range of "mosaic" brushes with different parameters can be obtained. Successive grafting of a secondary polymer (polyacrylamide, PAAm) results in the fabrication of binary polymer brushes (BPBs). Upon being exposed to specific selective solvents, BPBs may adopt different conformations. The surface tension and adhesion of the binary brush are governed by the polymer occupying the top stratum. The "mosaic" brush approach allows for a combination of strongly immiscible polymers in one brush. This facilitates substantial contrast in the surface properties upon switching, previously only possible for substrates composed of predetermined nanostructures. We also demonstrate a possible application of such PS/PAAm brushes in a tunable bioadhesion-bioadhesive (PS on top) or nonbioadhesive (PAAm on top) surface as revealed by Escherichia coli bacterial seeding.

  16. A Method for the Construction of Hereditary Constitutive Equations of Laminates Bases on a Hereditary Constitutive Equation for a Layer

    NASA Astrophysics Data System (ADS)

    Dumansky, Alexander M.; Tairova, Lyudmila P.

    2008-09-01

    A method for the construction of hereditary constitutive equation is proposed for the laminate on the basis of hereditary constitutive equations of a layer. The method is developed from the assumption that in the directions of axes of orthotropy the layer follows elastic behavior, and obeys hereditary constitutive equations under shear. The constitutive equations of the laminate are constructed on the basis of classical laminate theory and algebra of resolvent operators. Effective matrix algorithm and relationships of operator algebra are used to derive visco-elastic stiffness and compliance of the laminate. The example of construction of hereditary constitutive equations of cross-ply carbon fiber-reinforced plastic is presented.

  17. Polymers in Space: Applications in the NASA Life Support and Habitation Program

    NASA Technical Reports Server (NTRS)

    Campbell, Paul D.

    2005-01-01

    Outline of Content to be Presented: Session 1: Background on Human Space Flight, NASA Human Space Flight Programs: Apollo, Shuttle, ISS, U.S. Vision for Space Exploration, Goals of Human Spaceflight. Session. 2: Use of Polymers in NASA Technology Development, Life Support & Habitation Program, Spacecraft and Space Suit Requirements and Constraints Applications - Past, Current, Future Technologies in Development. Session 3: NASA Materials Database, Classes of Useful Polymers and Composites, Unique Requirements on Polymers in Space Applications of Synthetic and Biological Polymers. Session 4: Design of Polymer Parts for a Lunar Space Suit, Sample Activities for Teachers to Use in High School Classrooms.

  18. Triclosan antimicrobial polymers

    PubMed Central

    Petersen, Richard C.

    2016-01-01

    Triclosan antimicrobial molecular fluctuating energies of nonbonding electron pairs for the oxygen atom by ether bond rotations are reviewed with conformational computational chemistry analyses. Subsequent understanding of triclosan alternating ether bond rotations is able to help explain several material properties in Polymer Science. Unique bond rotation entanglements between triclosan and the polymer chains increase both the mechanical properties of polymer toughness and strength that are enhanced even better through secondary bonding relationships. Further, polymer blend compatibilization is considered due to similar molecular relationships and polarities. With compatibilization of triclosan in polymers a more uniform stability for nonpolar triclosan in the polymer solid state is retained by the antimicrobial for extremely low release with minimum solubility into aqueous solution. As a result, triclosan is projected for long extended lifetimes as an antimicrobial polymer additive. Further, triclosan rapid alternating ether bond rotations disrupt secondary bonding between chain monomers in the resin state to reduce viscosity and enhance polymer blending. Thus, triclosan is considered for a polymer additive with multiple properties to be an antimicrobial with additional benefits as a nonpolar toughening agent and a hydrophobic wetting agent. The triclosan material relationships with alternating ether bond rotations are described through a complete different form of medium by comparisons with known antimicrobial properties that upset bacterial cell membranes through rapid fluctuating mechanomolecular energies. Also, triclosan bond entanglements with secondary bonding can produce structural defects in weak bacterial lipid membranes requiring pliability that can then interfere with cell division. Regarding applications with polymers, triclosan can be incorporated by mixing into a resin system before cure, melt mixed with thermoplastic polymers that set on cooling

  19. Applications of conducting polymers: robotic fins and other devices

    NASA Astrophysics Data System (ADS)

    Tangorra, James L.; Anquetil, Patrick A.; Weideman, Nathan S.; Fofonoff, Timothy; Hunter, Ian W.

    2007-04-01

    Conducting polymers are becoming viable engineering materials and are gradually being integrated into a wide range of devices. Parallel efforts conducted to characterize their electromechanical behavior, understand the factors that affect actuation performance, mechanically process films, and address the engineering obstacles that must be overcome to generate the forces and displacements required in real-world applications have made it possible to begin using conducting polymers in devices that cannot be made optimal using traditional actuators and materials. The use of conducting polymers has allowed us to take better advantage of biological architectures for robotic applications and has enabled us to pursue the development of novel sensors, motors, and medical diagnostic technologies. This paper uses the application of conducting polymer actuators to a biorobotic fin for unmanned undersea vehicles (UUVs) as a vehicle for discussing the efforts in our laboratory to develop conducting polymers into a suite of useful actuators and engineering components.

  20. 77 FR 63309 - Constitution Pipeline Company, LLC; Notice of Public Scoping Meeting and Extension of Scoping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-16

    ... Energy Regulatory Commission Constitution Pipeline Company, LLC; Notice of Public Scoping Meeting and Extension of Scoping Period for the Planned Constitution Pipeline Project On October 24, 2012, the Federal... Constitution Pipeline Company's (Constitution) Constitution Pipeline Project. This notice also extends...