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Sample records for microphase separation induced

  1. Reticulated Nanoporous Polymers by Controlled Polymerization-Induced Microphase Separation

    SciTech Connect

    Seo, Myungeun; Hillmyer, Marc A.

    2013-04-08

    Materials with percolating mesopores are attractive for applications such as catalysis, nanotemplating, and separations. Polymeric frameworks are particularly appealing because the chemical composition and the surface chemistry are readily tunable. We report on the preparation of robust nanoporous polymers with percolating pores in the 4- to 8-nanometer range from a microphase-separated bicontinuous precursor. We combined polymerization-induced phase separation with in situ block polymer formation from a mixture of multifunctional monomers and a chemically etchable polymer containing a terminal chain transfer agent. This marriage results in microphase separation of the mixture into continuous domains of the etchable polymer and the emergent cross-linked polymer. Precise control over pore size distribution and mechanical integrity renders these materials particularly suited for various advanced applications.

  2. Anhydrous Proton Conducting Polymer Electrolyte Membranes via Polymerization-Induced Microphase Separation.

    PubMed

    Chopade, Sujay A; So, Soonyong; Hillmyer, Marc A; Lodge, Timothy P

    2016-03-01

    Solid-state polymer electrolyte membranes (PEMs) exhibiting high ionic conductivity coupled with mechanical robustness and high thermal stability are vital for the design of next-generation lithium-ion batteries and high-temperature fuel cells. We present the in situ preparation of nanostructured PEMs incorporating a protic ionic liquid (IL) into one of the domains of a microphase-separated block copolymer created via polymerization-induced microphase separation. This facile, one-pot synthetic strategy transforms a homogeneous liquid precursor consisting of a poly(ethylene oxide) (PEO) macro-chain-transfer agent, styrene and divinylbenzene monomers, and protic IL into a robust and transparent monolith. The resulting PEMs exhibit a bicontinuous morphology comprising PEO/protic IL conducting pathways and highly cross-linked polystyrene (PS) domains. The cross-linked PS mechanical scaffold imparts thermal and mechanical stability to the PEMs, with an elastic modulus approaching 10 MPa at 180 °C, without sacrificing the ionic conductivity of the system. Crucially, the long-range continuity of the PEO/protic IL conducting nanochannels results in an outstanding ionic conductivity of 14 mS/cm at 180 °C. We posit that proton conduction in the protic IL occurs via the vehicular mechanism and the PEMs exhibit an average proton transference number of 0.7. This approach is very promising for the development of high-temperature, robust PEMs with excellent proton conductivities. PMID:26927732

  3. Proton conducting, high modulus polymer electrolyte membranes by polymerization-induced microphase separation

    NASA Astrophysics Data System (ADS)

    Chopade, Sujay; Hillmyer, Marc; Lodge, Timothy

    Robust solid-state polymer electrolyte membranes (PEMs) are vital for designing next-generation lithium-ion batteries and high-temperature fuel cells. However, the performance of diblock polymer electrolytes is generally limited by poor mechanical stability and network defects in the conducting pathways. We present the in-situ preparation of robust cross-linked PEMs via polymerization-induced microphase separation, and incorporation of protic ionic liquid (IL) into one of the microphase separated domains. The facile design strategy involves a delicate balance between the controlled growth of polystyrene from a poly(ethylene oxide) macro-chain transfer agent (PEO-CTA) and simultaneous chemical cross-linking by divinylbenzene in the presence of IL. Small angle X-ray scattering and transmission electron microscopy confirmed the formation of a disordered structure with bicontinuous morphology and a characteristic domain size of order 20 nm. The long-range continuity of the PEO/protic IL conducting nanochannels and cross-linked polystyrene domains imparts high thermal and mechanical stability to the PEMs, with elastic modulus approaching 10 MPa and a high ionic conductivity of 15 mS/cm at 180 °C.

  4. Protonation-Induced Microphase Separation in Thin Films of a Polyelectrolyte-Hydrophilic Diblock Copolymer

    PubMed Central

    2015-01-01

    Block copolymers composed of poly(oligo ethylene glycol methyl ether methacrylate) and poly(2-vinylpyridine) are disordered in the neat state but can be induced to order by protonation of the P2VP block, demonstrating a tunable and responsive method for triggering assembly in thin films. Comparison of protonation with the addition of salts shows that microphase separation is due to selective protonation of the P2VP block. Increasing acid incorporation and increasing 2-vinylpyridine content for P2VP minority copolymers both promote increasingly phase-separated morphologies, consistent with protonation increasing the effective strength of segregation between the two blocks. The self-assembled nanostructures formed after casting from acidic solutions may be tuned based on the amount and type of acid incorporation as well as the annealing treatment applied after casting, where both aqueous and polar organic solvents are shown to be effective. Therefore, POEGMA-b-P2VP is a novel ion-containing block copolymer whose morphologies can be facilely tuned during casting and processing by controlling its exposure to acid. PMID:24910809

  5. Microphase separation induced in the melt of Pluronic copolymers by blending with a hydrogen bonding urea-urethane end-capped supramolecular polymer.

    PubMed

    Hermida-Merino, Daniel; Newby, Gemma E; Hamley, Ian W; Hayes, Wayne; Slark, Andrew

    2015-08-01

    Blending with a hydrogen-bonding supramolecular polymer is shown to be a successful novel strategy to induce microphase-separation in the melt of a Pluronic polyether block copolymer. The supramolecular polymer is a polybutadiene derivative with urea-urethane end caps. Microphase separation is analysed using small-angle X-ray scattering and its influence on the macroscopic rheological properties is analysed. FTIR spectroscopy provides a detailed picture of the inter-molecular interactions between the polymer chains that induces conformational changes leading to microphase separation. PMID:26151722

  6. Development of Self-Assembled Nanoscale Templates via Microphase Separation Induced by Polymer Brushes

    NASA Astrophysics Data System (ADS)

    Chu, Elza

    Phase separation in soft matter has been the crucial element in generating hybrid materials, such as polymer blends and mixed polymer brushes. This dissertation discusses two methods of developing self-assembled nanoscale templates via microphase separation induced by polymer brush synthesis. This work introduces a novel soft substrate approach with renewable grafting sites where polyacrylamide is "grafted through" chitosan soft substrates. The mechanism of grafting leads to ordered arrays of filament-like nanostructures spanning the chitosan-air interface. Additionally, the chemical composition of the filaments allows for post-chemical modification to change the physical properties of the filaments, and subsequently tailor surfaces for specific application. Unlike traditional materials, multi-functional or "smart" materials, such as binary polymer brushes (BPB) are capable of spontaneously changing the spatial distribution of functional groups and morphology at the surface upon external stimuli. Although promising in principle, the limited range of available complementary polymers with common non-selective solvents confines the diversity of usable materials and restricts any further advancement in the field. This dissertation also covers the fabrication and characterization of responsive nanoscale polystyrene templates or "mosaic" brushes that are capable of changing interfacial composition upon exposure to varying solvent qualities. Using a "mosaic" brush template is a unique approach that allows the fabrication of strongly immiscible polymer BPB without the need for a common solvent. The synthesis of such BPB is exemplified by two strongly immiscible polymers, i.e. polystyrene (polar) and polyacrylamide (non-polar), where polyacrylamide brush is "graft through" a Si-substrate modified with the polystyrene collapsed "mosaic" brush. The surface exhibits solvent-triggered responses, as well as application potential for anti-biofouling.

  7. An effective strategy to increase hydroxide-ion conductivity through microphase separation induced by hydrophobic-side chains

    NASA Astrophysics Data System (ADS)

    Zeng, L.; Zhao, T. S.

    2016-01-01

    A highly conductive and durable anion exchange membrane (AEM) is an essential component for alkaline electrochemical conversion and storage systems. Contrary to the conventional wisdom that the ionic conductivity can be improved by increasing the ion exchange capacity (IEC) through a cross-linking process, in this work, a new approach to improve the ionic conductivity by enhancing the ionic mobility is adopted. The microstructure of quaternary ammonia poly (2, 6-dimethyl-1, 4-phenylene oxide) (QAPPO) is manipulated through grafting with hydrophobic side chains, which will drive the well-established hydrophilic/hydrophobic domains and nano-phase separated, well-connected ionic channels. As a result, the local hydroxide concentration is enhanced by the novel microstructure, thereby improving the ionic conductivity of the as-prepared ionomers. The as-prepared ionomers, denoted as self-aggregated QAPPO-CF, with an intermediate IEC value achieved an ionic conductivity of 65 mS cm-1 at 80 °C, outperforming the QAPPO with an even higher IEC value. This result suggests that the microphase separation is an effective approach to enhance the ionic conductivity.

  8. Patterned silica films using microphase separation of a block copolymer

    NASA Astrophysics Data System (ADS)

    Kataoka, Sho; Takeuchi, Yasutaka; Endo, Akira

    2014-11-01

    Block copolymers exhibit various nanoscale ordered morphologies induced by microphase separation. Here, we present a method for providing two types of patterned silica films on Si wafer substrates simply by shifting the phase equilibrium of a block copolymer, polystyrene-block-poly(4-vinylpyridine) (PS-P4VP). In this method, siloxane is adsorbed onto poly(4-vinylpyridine) blocks of PS-P4VP whose structure varies with solvent polarity and is calcined to remove the block copolymer. Siloxane is in a dispersed phase with toluene as a solvent resulting in silica nanoparticle arrays, while siloxane is in a continuous phase with N, N-dimethylformamide (DMF) resulting in silica films with ordered mesopores. Since the pore size of silica films prepared in DMF is approximately 20 nm, the film has the ability to serve as a support for enzymes such as laccase.

  9. Microphase separation in graphite-adsorbed paraffin solid solutions

    SciTech Connect

    Gilbert, E.P.; Reynolds, P.A.; White, J.W.

    1996-11-14

    Using time-resolved small-angle neutron scattering (SANS), the time-dependent microphase separation occurring in metastable, quenched binary paraffin mixtures C{sub 30}H(D){sub 62}/C{sub 36}D(H){sub 74} doped into porous graphite has been observed. In the presence of graphite, microphase formation is enhanced compared to the bulk mixtures and the isotopic dependence of the demixing process reported for these systems when quenched to 20{degree}C is not apparent. We relate the enhanced microphase separation to an elevation of the eutectic temperature relative to the critical temperature, due to stabilization of the paraffins at the graphite basal plane. For 1:1 mixtures, the microphase forms an alternating lamellar structure, while the 1:4 and 4:1 mixtures exhibit an increase in scattering at lower angles associated with significantly longer repeat-spacings. An increase in quench temperature from 20 to 27{degree}C increases the strength of the microphase scattering over the time period studied, but quenching to 35{degree}C results in a significant reduction in this signal. On aging, additional weaker peaks are observed, which for 1:1 mixtures, are consistent with the formation of alternating lamellae. For all mixtures, except 1:4 C{sub 30}H{sub 62}/C{sub 36}D{sub 74}, there is a constant offset in Q between the strong and weak peaks. The scattering can be understood to rise from a mixed lamellar system in which incommensurate deviations from the mean structure occur. 56 refs., 14 figs., 9 tabs.

  10. Direct observations of transition dynamics from macro- to micro-phase separation in asymmetric lipid bilayers induced by externally added glycolipids

    NASA Astrophysics Data System (ADS)

    Shimobayashi, Shunsuke F.; Ichikawa, Masatoshi; Taniguchi, Takashi

    2016-03-01

    We present the first direct observations of morphological transitions from macro- to micro-phase separation using micrometer-sized asymmetric lipid vesicles exposed to externally added glycolipids (GM1:monosialotetrahexosylganglioside). The transition occurs via an intermediate stripe morphology state. During the transition, monodisperse micro-domains emerge through repeated scission events of the stripe domains. Moreover, we numerically confirmed such transitions using a time-dependent Ginzburg-Landau model, which describes both the intramembrane phase separation and the bending elastic membrane. The experimental and simulation results are in quantitative agreement.

  11. Self-doped microphase separated block copolymer electrolyte

    DOEpatents

    Mayes, Anne M.; Sadoway, Donald R.; Banerjee, Pallab; Soo, Philip; Huang, Biying

    2002-01-01

    A polymer electrolyte includes a self-doped microphase separated block copolymer including at least one ionically conductive block and at least one second block that is immiscible in the ionically conductive block, an anion immobilized on the polymer electrolyte and a cationic species. The ionically conductive block provides a continuous ionically conductive pathway through the electrolyte. The electrolyte may be used as an electrolyte in an electrochemical cell.

  12. Structure and dynamics of microphase separated polymers containing strong associations

    NASA Astrophysics Data System (ADS)

    Colbert, Rachel Sarah

    The morphology and dynamics of microphase separated polymers containing strong associations (i.e., ionic associations and hydrogen bonding) are investigated in this dissertation. The microphase separated domains in these polymers act as physical crosslinks and are expected to strongly influence molecular dynamics. Small-angle X-ray scattering (SAXS) is utilized to quantify microphase separation characteristics and broadband dielectric relaxation spectroscopy reveals the sensitivity of polymer dynamics to the presence of microphase segregation in the polymers studied. A model ionomer, sulfonated polystyrene (SPS) is chosen to probe the effect of ionic aggregation. The microphase separation and dynamics in polyurethanes and polyureas, containing strongly hydrogen bonded hard domains, are also examined. The role of ion associations on aggregate morphology and polymer dynamics of SPS is investigated via the systematic variation of sulfonation level, neutralization, and ion type. Evidence of acid group aggregation was found at 3.5, 6.7 and 9.5 mol% sulfonation. Upon neutralization, spherical aggregates ˜2 nm in diameter are revealed from SAXS and scanning transmission electron microscopy. Aggregate size is found to be independent of degree of sulfonation and neutralization level, however, aggregate composition becomes increasingly ionic with increasing neutralization. The polymer segmental relaxation process is highly sensitive to changes in ion content, neutralization and ion type. The relaxation time of this process slows with increasing ion content as the number density of ionic aggregates increases, similar to the effect of chemical crosslinking. The breadth of this process is sensitive to the interaction strength of the neutralizing ion type. For SPS neutralized with Zn2+, two distinct segmental relaxations are observed, a matrix segmental relaxation and a slow segmental process, the strength of which correlates with an increase in volume fraction of the region of

  13. Macro- and microphase separation in multifunctional supramolecular polymer networks

    NASA Astrophysics Data System (ADS)

    Mester, Zoltan; Mohan, Aruna; Fredrickson, Glenn

    2011-03-01

    We develop a field-based model for a binary melt of multifunctional polymers that can reversibly bond to form copolymer networks. The mean-field phase separation behavior of several model networks with heterogeneous bonding is calculated via the random phase approximation (RPA). The extent of bonding between polymers is controlled by specified bond energies. The phase boundary calculated via RPA is the stability limit of the homogeneous disordered phase to coexisting homogeneous macrophases, for low bond strengths, and to microphases, for high bond strengths. An isotropic Lifshitz point separates these two regions along the spindodal boundary. It is demonstrated that higher functionality and higher bond strength suppresses macrophase separation due to greater connectivity between unlike species. Gelation first occurs at a bond strength higher than the Lifshitz point for tri- or higher functional polymer components.

  14. Microphase Separation within Disk Shaped Aggregates of Triblock Bottlebrushes.

    PubMed

    Long, Meiling; Shi, Yi; Zhang, Ke; Chen, Yongming

    2016-04-01

    Well-defined AbBA triblock bottlebrush with poly(N,N-dimethyl acrylamide) (PAm) as A block and polyacrylate, densely grafted with poly(tert-butyl acrylate)-block-polystyrene (PBA-b-PS), as brush bB block is prepared by controlled radical polymerization and click chemistry. The triblock copolymer with a composition of PAm200 -b-b(PBA14 -b-PS47 )167 -b-PAm200 is obtained and is further transformed into PAm200 -b-b(PAA14 -b-PS47 )167 -b-PAm200 by hydrolysis of the PBA segment into poly(acrylic acid) (PAA). In a mixture of N,N-dimethylformamide (DMF) and methanol, a poor solvent of bB block, PAm200 -b-b(PAA14 -b-PS47 )167 -b-PAm200 self-assembled into disk-like platelets, which have an internal lamellar structure by further microphase-separation of PAA-b-PS branches in 2D. Moreover, Ag nanoparticles are aligned by PAA segments along the disk to form a pattern. PMID:26866716

  15. Kinetics of Microphase Separation in Crosslinked Polymer Blend

    SciTech Connect

    Bettachy, A.; Benhamou, M.; Derouiche, A.; Fazni, A.

    2009-04-19

    The solvent effect on the early kinetics of the microphase separation (MPS) in binary crosslinked polymer was studied. In the presence of a good solvent, calculations were done using first the random phase approximation method and second an extended blob model, where a crosslinked chain is viewed as a sequence having blobs as new units. Kinetics were studied through the variation of the relaxation rate, {tau}{sub q}, upon the wave number, q, in the region around the spinodal temperature. When the temperature is changed from an initial value, T{sub i}, toward the final value, T{sub f}, very close to the critical point, the only motion allowed to the crosslinked chains is of Rouse type because of the presence of the crosslinks. The swelling effect on the MPS leads to a multiplicative renormalization of critical parameters of the molten state by factors as power of the overall monomer volume fraction, {phi}. The characteristic frequency, {omega}{sub (q)}, inverse of {tau}{sub q}, scales as {omega}(q) congruent with q{sup 6}{epsilon}{sup 3}, where {epsilon} stands for the traditional screening length. The study of kinetics of MPS is then extended in the presence of a theta solvent.

  16. Microphase separation in thin films of lamellar forming polydisperse di-block copolymers

    SciTech Connect

    Kumar, Rajeev; Lokitz, Bradley S.; Sides, Scott W.; Chen, Jihua; Heller, William T.; Ankner, John F.; Browning, James F.; Kilbey, II, S. Michael; Sumpter, Bobby G.

    2015-02-03

    Despite the ubiquity of polydispersity in chain lengths of di-block copolymers, its effects on microphase separation in thin films have eluded a clear understanding. In this paper, we have studied effects of polydispersity on the microphase separation in thin films of lamellar forming di-block copolymers using self-consistent field theory (SCFT) and neutron reflectivity experiments. Di-block copolymers containing a polydisperse block of poly(glycidylmethacrylate) (PGMA) connected to a near-monodisperse block poly(2-vinyl-4,4-dimethyl-d6 azlactone) (PVDMA-d6) are considered in this work. Effects of chain length polydispersity, film thickness, substrate–monomer and monomer–monomer interactions on the microphase segregation are studied using SCFT. The theoretical study reveals that in comparison to a film created with monodisperse di-block copolymers, an increase in polydispersity tends to decrease the number of lamellar strata that can be packed in a film of given thickness. This is a direct consequence of an increase in lamellar domain spacing with an increase in polydispersity index. Furthermore, it is shown that polydispersity induces conformational asymmetry and an increase in the polydispersity index leads to an increase in the effective Kuhn segment length of the polydisperse blocks. It is shown that the conformational asymmetry effects, which are entropic in origin and of increasing importance as film thickness decreases, drive the polydisperse blocks to the middle of the films despite favorable substrate interactions. These predictions are verified by results from neutron reflectivity experiments on thin films made from moderately polydisperse PGMA-PVDMA-d6 di-block copolymer deposited on silicon substrates. In conclusion, results from SCFT are used to predict neutron reflectivity profiles, providing a facile and robust route to obtain useful physical insights into the structure of polydisperse diblock copolymers at

  17. Microphase separation in thin films of lamellar forming polydisperse di-block copolymers

    DOE PAGESBeta

    Kumar, Rajeev; Lokitz, Bradley S.; Sides, Scott W.; Chen, Jihua; Heller, William T.; Ankner, John F.; Browning, James F.; Kilbey, II, S. Michael; Sumpter, Bobby G.

    2015-02-03

    Despite the ubiquity of polydispersity in chain lengths of di-block copolymers, its effects on microphase separation in thin films have eluded a clear understanding. In this paper, we have studied effects of polydispersity on the microphase separation in thin films of lamellar forming di-block copolymers using self-consistent field theory (SCFT) and neutron reflectivity experiments. Di-block copolymers containing a polydisperse block of poly(glycidylmethacrylate) (PGMA) connected to a near-monodisperse block poly(2-vinyl-4,4-dimethyl-d6 azlactone) (PVDMA-d6) are considered in this work. Effects of chain length polydispersity, film thickness, substrate–monomer and monomer–monomer interactions on the microphase segregation are studied using SCFT. The theoretical study reveals thatmore » in comparison to a film created with monodisperse di-block copolymers, an increase in polydispersity tends to decrease the number of lamellar strata that can be packed in a film of given thickness. This is a direct consequence of an increase in lamellar domain spacing with an increase in polydispersity index. Furthermore, it is shown that polydispersity induces conformational asymmetry and an increase in the polydispersity index leads to an increase in the effective Kuhn segment length of the polydisperse blocks. It is shown that the conformational asymmetry effects, which are entropic in origin and of increasing importance as film thickness decreases, drive the polydisperse blocks to the middle of the films despite favorable substrate interactions. These predictions are verified by results from neutron reflectivity experiments on thin films made from moderately polydisperse PGMA-PVDMA-d6 di-block copolymer deposited on silicon substrates. In conclusion, results from SCFT are used to predict neutron reflectivity profiles, providing a facile and robust route to obtain useful physical insights into the structure of polydisperse diblock copolymers at interfaces.« less

  18. Micro-phase Separation via Spinodal-like Decomposition in Hexamethylynediisocyanate (HDI)-polyurea

    SciTech Connect

    Kulkarni, Amit S.; Beaucage, Gregory; Wilkes, Garth L.; Das, Sudipto; Yilgor, Iskander

    2012-04-03

    We found that micro-phase separation in hexamethylynediisocyanate-polyurea was studied using small-angle X-ray scattering and infrared absorption. Moreover, it was found that phase separation in this system followed spinodal-like decomposition on a 3–4 nm size scale with phase separation occuring on a time scale of days.

  19. Structural Formation Process of Microphase Separated Films with Liquid Crystalline Phase Transition

    NASA Astrophysics Data System (ADS)

    Komura, Motonori; Iyoda, Tomokazu

    2008-03-01

    Ordered nanostructures arising from the microphase separation of block copolymers have driven one to fabricate nanofunctional materials as fundamental technology of the coming electronic and photonic materials. Thin films of a series of newly designed amphiphilic block copolymer consisting of hydrophilic polyethylene oxide (PEO) and hydrophobic polymethacrylate with azobenzene-mesogen in side-chain (PMA(Az)) show highly ordered microphase separation with PEO cylinders perpendicularly oriented to the film surface. In the present report, we investigated a structural formation process of the microphase separated films by temperature controlled atomic force microscopy (AFM) and grazing incidence small angle X-ray scattering (GISAXS). These measurements revealed that homeotropic alignments of Az liquid crystalline layers predominated the cylinder orientation, which corresponded to a <110> direction of body centered cubic structure under annealing condition, in disagreement with cylinder orientation of order-order transition of traditional block copolymers.

  20. Controlling Solution Self-assembly and Non-Solvent Induced Microphase Separation of Triblock Terpolymers to Generate Nanofiltration Membranes with Chemically-Tailored Pore Walls

    NASA Astrophysics Data System (ADS)

    Boudouris, Bryan; Mulvenna, Ryan; Weidman, Jacob; Phillip, William

    2014-03-01

    Block polymer-based templates have been utilized in a number of membrane applications; however, there has yet to be a demonstration of a nanoporous block polymer thin film that can achieve high flux and high selectivity simultaneously while also allowing for the facile tuning of the pore wall chemistry. Here, we demonstrate that by synthesizing and controlling the solution self-assembly of a triblock terpolymer, polyisoprene- b-polystyrene- b-poly(N, N-dimethylacrylamide) (PI-PS-PDMA), and precisely inducing non-solvent induced phase separation during the self-assembly process allows for the creation of an asymmetric nanoporous membrane with PDMA-lined pore walls. This PDMA functionality is then converted to any number of side chain functionalities through simple chemistry in the solid state. In this way, we are able to show a highly selectivity membrane that can separate analytes of interest based both on size and chemical composition at a high solution flux. In fact, this high fidelity structure has a very narrow distribution of pore sizes (<10% variation in diameter) over large areas (>500 cm2) . This has allowed for the separation of particles with hydrodynamic radii as low as 0.8 nm, which is the smallest separation achieved using a block polymer-based membrane to date.

  1. Equilibrium microphase separation in the two-leaflet model of lipid membranes

    NASA Astrophysics Data System (ADS)

    Reigada, Ramon; Mikhailov, Alexander S.

    2016-01-01

    Because of the coupling between local lipid composition and the thickness of the membrane, microphase separation in two-component lipid membranes can take place; such effects may underlie the formation of equilibrium nanoscale rafts. Using a kinetic description, this phenomenon is analytically and numerically investigated. The phase diagram is constructed through the stability analysis for linearized kinetic equations, and conditions for microphase separation are discussed. Simulations of the full kinetic model reveal the development of equilibrium membrane nanostructures with various morphologies from the initial uniform state.

  2. Microphase separation in thin films of lamellar forming poydisperse di-block copolymers

    DOE PAGESBeta

    Kumar, Rajeev; Kilbey, II, S Michael; Ankner, John Francis; Heller, William T; Chen, Jihua; Sides, Scott; Browning, Jim; Lokitz, Bradley S; Sumpter, Bobby G

    2015-01-01

    Microphase separation in thin films of lamellar forming polydisperse di-block copolymers is studied using self-consistent field theory (SCFT) and neutron reflectivity experiments. Diblock copolymers containing a polydisperse block (poly(glycidylmethacrylate) (PGMA)) connected to a near monodisperse block (poly(4,4-dimethyl-d6-2-vinylazlactone) (PVDMA-d6)) are considered in this work. Effects of chain length polydispersity, film thickness, substrate monomer and monomer-monomer interactions on the microphase segregation are studied using SCFT. The theoretical study reveals that an increase in polydispersity tends to decrease the number of lamellar strata that can be packed in a film of given thickness, in comparison to a film created with monodisperse di-block copolymers.more » This is a direct consequence of an increase in lamellar domain spacing with an increase in polydispersity index. These predictions are verified by comparison with neutron reflectity experiments done on thin films made from moderately polydisperse PGMA-b-PVDMA-d6 di-block copolymer deposited on silicon substrates. Furthermore, it is shown that polydispersity induces conformational asymmetry and an increase in the polydispersity index makes the polydisperse blocks less flexible in comparison with monodisperse blocks. It is shown that conformational asymmetry effects, which are entropic in origin and of increasing importance as film thickness descreases, drive the polydisperse blocks to the middle of the films despite favorable substrate interactions. Prediction of neutron reflectivity profiles using the SCFT provides a facile and robust route for model verification and leads to useful physical insights into behavior of di-block copolymers near interfaces.« less

  3. Microphase separated structures of block copolymer thin film with non-volatile selective solvent

    NASA Astrophysics Data System (ADS)

    Yamamoto, Katsuhiro; Umegaki, Naoya; Matsutani, Taito; Takagi, Hideaki; Ito, Eri; Sakurai, Shinichi

    2010-11-01

    Microphase separated structures of block copolymer, polystyrene-b-polyisoprene (PS-b-PI, phiPS = 14%) including non-volatile selective solvent thin films were investigated using grazing incidence small angle X-ray scattering technique. The diethyl phthalate (DEP) was used as a non-volatile selective solvent which solves PS only. The DEP swelled PS phase selectively and the microphase separated structure transited from the PS spherical domain to the lamellar domain with an increase in DEP content in the bulk state. Similarly, the phase separated structure in the thin film prepared by spin cast on a silicon wafer from the mixture of toluene/DEP and block copolymer changed according to the initial DPE concentration. However, the morphologies developed in the thin film were shifted to the structures at lower DEP concentration than that expected from the initial concentration. Moreover, the cylindrical and lamellar domains were aligned parallel and perpendicularly to the substrate, respectively.

  4. Cation-containing Polymers with Co-continuous Microphase-Separated Morphologies for Rapid Transport Membranes

    NASA Astrophysics Data System (ADS)

    Beyer, Frederick; Price, Samuel; Savage, Alice; Ren, Xiaoming; Pomerantz, Natalie; Zukas, Walter

    2015-03-01

    Cation-containing polymer membranes are the subject of renewed research for their potential to enable the use of alkaline fuel cells, and are also of interest for their water vapor transport properties. Charge and water vapor transport are both heavily dependent on membrane morphology and the development of hydrophilic channels throughout the material. Reaction induced phase separation has been shown to create such morphologies when used with uncharged copolymers and crosslinking monomers. Here we have applied this same technique but used ion-containing block copolymers of 4-vinylbenzyltrimethylammonium chloride and styrene to create a cation-containing polymer membrane having a microphase-separated, co-continuous morphology, as characterized by small-angle X-ray scattering (SAXS) and high-angle annular dark field scanning transmission electron microscopy (HAADF STEM). These materials show excellent charge transport behavior and water vapor transport properties, surpassing commercially available materials. These results and efforts to improve other important physical characteristics for membrane applications will be presented.

  5. Ionic Aggregation and Microphase Separation in Sulfonated Polyester Multiblock Copolymers and Ionomers

    NASA Astrophysics Data System (ADS)

    O'Reilly, Michael; Tudryn, Gregory; Colby, Ralph; Winey, Karen

    2011-03-01

    Polyethylene oxide (PEO) has been copolymerized with polytetramethylene oxide (PTMO) using a sulfonated phthalate ionic linker between blocks. The product is a linear multiblock copolymer, which is neutralized with lithium and sodium. We used X-ray scattering to investigate the morphology from 25°C to 200°C. The results show that this copolymer exhibits three distinct morphology characteristics. First, microphase separation exists between the PEO and PTMO phases. Second, ionic aggregates occur in the PEO microdomains. Finally, the appearance of better defined ionic aggregates occurs in the PTMO microdomains. Ion aggregation and microphase separation are studied as functions of temperature and copolymer molar composition. DRS analysis confirms that ionic aggregation is independent of copolymer composition.

  6. Control of Crystallization to Promote Microphase Separation in Fully Conjugated Block Copolymers

    NASA Astrophysics Data System (ADS)

    Lee, Youngmin; Le, Thinh P.; Seibers, Zach; Kilbey, S. Michael, II; Wang, Qing; Gomez, Enrique D.

    Donor -acceptor fully conjugated block copolymers, where donor and acceptor conjugated polymers are covalently bonded together, are interesting as single-component active-layer materials for photovoltaics because it can adopt mesoscale microphase separated structures with length scales comparable to the exciton diffusion length. Nevertheless, due to the strong crystallization of poly(3-hexylthiophene-2,5-diyl) (P3HT), morphologies of fully conjugated block copolymers containing P3HT are predominantly driven by crystallization as opposed to microphase separation. We control the crystallization in block copolymers to promote microphase separation in fully conjugated block copolymers through the addition of small amounts of 3-octylthiophene to the polymerization of P3HT. Poly(3-hexylthiophene-2,5-diyl- r-3-octylthiophene-2,5-diyl)-block-poly((9,9-dioctylfluorene-2,7-diyl)-alt-(4,7-di(thiophene-2-yl)-2,1,3-benzothiadiazole)-5',5''-diyl) (P3HT- b-PFTBT) copolymers were prepared by Grignard metathesis for the alkylthiophene block followed by chain extension through a Suzuki-Miyaura polycondensation. We compare the crystallization, self-assembly and performance in devices of P3HT-b-PFTBT with a few mole percent of 3-octylthiophene in the P3HT block. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831.

  7. Molecular Dynamics Simulations of Penetrants in Microphase Separated Tapered Diblock Copolymers

    NASA Astrophysics Data System (ADS)

    Seo, Youngmi; Brown, Jonathan R.; Hall, Lisa M.

    Tapered AB diblock copolymers contain pure A and B monomer blocks on the ends with a tapered midblock of intermediate composition, providing taper length as an additional tuning parameter to control microphase separation and interfacial behavior. We model the midblock as a statistical linear gradient from pure A to pure B. Recent experiments with salt dissolved in one of microphases show that a certain length of taper increases ion conductivity while the same length of inverse taper lowers conductivity. We perform coarse-grained molecular dynamics simulations of tapered copolymers with monomer sized penetrants, which have preferential interactions with one microphase, to better understand this observation and the general effects of tapering on dynamics. We calculate penetrant diffusion, polymer relaxation times, and other quantities over the range from 0% (diblock) to 100% (full gradient) taper length, with the taper direction either normal or inverse (with the A side of the taper connected to the pure B block). Normal taper results typically lie between those of diblocks and full gradients, while inverse tapers show strong nonmonotonic behavior as a function of taper length. For intermediate length inverse tapers, penetrant and monomer dynamics are significantly slower than those of diblocks or normal tapers, and this relates to the folding of the inverse chains back and forth across the interface. To provide further insight, we also compare to the dynamics of random copolymers of various compositions. Based upon work supported by NSF Grant 1454343.

  8. From Phase to Microphase Separation in Flocking Models: The Essential Role of Nonequilibrium Fluctuations

    NASA Astrophysics Data System (ADS)

    Solon, Alexandre P.; Chaté, Hugues; Tailleur, Julien

    2015-02-01

    We show that the flocking transition in the Vicsek model is best understood as a liquid-gas transition, rather than an order-disorder one. The full phase separation observed in flocking models with Z2 rotational symmetry is, however, replaced by a microphase separation leading to a smectic arrangement of traveling ordered bands. Remarkably, continuous deterministic descriptions do not account for this difference, which is only recovered at the fluctuating hydrodynamics level. Scalar and vectorial order parameters indeed produce different types of number fluctuations, which we show to be essential in selecting the inhomogeneous patterns. This highlights an unexpected role of fluctuations in the selection of flock shapes.

  9. Microphase separations of the fluids with spherically symmetric competing interactions.

    PubMed

    Kim, Soon-Chul; Suh, Soong-Hyuck; Seong, Baek-Seok

    2012-09-21

    A density functional perturbation theory has been developed for studying the phase behaviors of a competing system in the spherical pores. The pore size as well as the intensity of competing interactions exerts a strong influence on the vapor-liquid, vapor-cluster, and cluster-liquid transitions of a competing system. The microdomain spacing (D) of the cluster is commensurate with the periodicity of modulation in the particle density distributions of a competing system in a spherical pore with the pore radius (R). For the cluster phase, we find that the multi-vaporlike void is formed depending on the periodicity of modulation by finite-size artifacts. For R < D, the competing system only shows the vapor-liquid transition at a high amplitude. For R > D, the vapor-cluster and cluster-liquid transitions are found at a high amplitude, whereas at a low amplitude, the cluster-liquid transition only occurs. The competing system exhibits two tricritical points, which are joined to one another by the line of second-order transitions at the low and high densities. A comparison with the result of a slit pore shows that (i) the tricritical points in a spherical pore, which has the highest symmetry, occur at a low amplitude compared with that of a slit pore because of the geometrical properties of the pores, and that (ii) the slit pore relatively shows the wide vapor-cluster and cluster-liquid coexistence regions compared with that of a spherical pore: the geometrical symmetry of a pore results in a weaker tendency for phase separation. PMID:22998277

  10. Lamellar, micro-phase separated blends of methyl cellulose and dendritic polyethylene glycol, POSS-PEG.

    PubMed

    Chinnam, Parameswara Rao; Mantravadi, Ramya; Jimenez, Jayvic C; Dikin, Dmitriy A; Wunder, Stephanie L

    2016-01-20

    Blends of methyl cellulose (MC) and liquid pegylated polyoctahedralsilsesquioxane (POSS-PEG) were prepared from non-gelled, aqueous solutions at room temperature (RT), which was below their gel temperatures (Tm). Lamellar, fibrillated films (pure MC) and increasingly micro-porous morphologies with increasing POSS-PEG content were formed, which had RT moduli between 1 and 5GPa. Evidence of distinct micro-phase separated MC and POSS-PEG domains was indicated by the persistence of the MC and POSS-PEG (at 77K) crystal structures in the X-ray diffraction data, and scanning transmission electron images. Mixing of MC and POSS-PEG in the interface region was indicated by suppression of crystallinity in the POSS-PEG, and increases/decreases in the glass transition temperatures (Tg) of POSS-PEG/MC in the blends compared with the pure components. These interface interactions may serve as cross-link sites between the micro-phase separated domains that permit incorporation of high amounts of POSS-PEG in the blends, prevent macro-phase separation and result in rubbery material properties (at high POSS-PEG content). Above Tg/Tm of POSS-PEG, the moduli of the blends increase with MC content as expected. However, below Tg/Tm of POSS-PEG, the moduli are greater for blends with high POSS-PEG content, suggesting that it behaves like semi-crystalline polyethylene oxide reinforced with silica (SiO1.5). PMID:26572324

  11. Microphase separation patterns in diblock copolymers on curved surfaces using a nonlocal Cahn-Hilliard equation.

    PubMed

    Jeong, Darae; Kim, Junseok

    2015-11-01

    We investigate microphase separation patterns on curved surfaces in three-dimensional space by numerically solving a nonlocal Cahn-Hilliard equation for diblock copolymers. In our model, a curved surface is implicitly represented as the zero level set of a signed distance function. We employ a discrete narrow band grid that neighbors the curved surface. Using the closest point method, we apply a pseudo-Neumann boundary at the boundary of the computational domain. The boundary treatment allows us to replace the Laplace-Beltrami operator by the standard Laplacian operator. In particular, we can apply standard finite difference schemes in order to approximate the nonlocal Cahn-Hilliard equation in the discrete narrow band domain. We employ a type of unconditionally stable scheme, which was introduced by Eyre, and use the Jacobi iterative to solve the resulting implicit discrete system of equations. In addition, we use the minimum number of grid points for the discrete narrow band domain. Therefore, the algorithm is simple and fast. Numerous computational experiments are provided to study microphase separation patterns for diblock copolymers on curved surfaces in three-dimensional space. PMID:26577816

  12. The interactions between microphase separation and crystallization in block copolymers containing polyethylene

    NASA Astrophysics Data System (ADS)

    Quiram, Daniel Jonathan

    The interactions between microphase separation and crystallization were examined in block copolymers containing polyethylene of varying chemistry, composition (fsb{E} = 0.26-0.88, where fsb{E} is weight fraction polyethylene), and molecular weight. Block copolymer compositions were altered to explore crystallization from three distinct melt morphologies: body-centered cubic spheres, hexagonally-packed cylinders, and alternating lamellae. Polymer morphology was investigated on a size-scale ranging from angstroms to microns, employing wide-angle and small-angle x-ray scattering (WAXS and SAXS), small-angle light scattering, and differential scanning calorimetry. The primary series of diblock copolymers investigated were polyethylene-b-poly(3-methyl-1-butene) (E/MB, where MB is an olefinic rubber; fsb{E} = 0.26-0.27). This composition led to a cylindrical morphology when the melt microphase separated. Molecular weights were varied to obtain differing degrees of melt incompatibility, ranging from disordered to strongly segregated. Crystallization from strongly segregated melts was confined to the cylindrical microdomains, essentially independent of thermal history. In contrast, the morphology produced by crystallization from weakly segregated melts was highly dependent upon thermal history. Several block copolymers with microphase-separated melts containing an E block and either polystyrene (glass transition temperature, Tsb{g}≈ 100sp°C) or poly(vinylcyclohexane) (Tsb{g}≈ 135sp°C) were investigated to determine the effect of a vitreous component on crystallization. SAXS experiments showed that vitrification of the amorphous material effectively confined E crystallization to its melt domain phase: cylinders in a glassy matrix, lamellae, and matrices surrounding both glassy cylinders and spheres. Crystalline chain orientation within cylinders was examined through WAXS. The chains aligned preferentially and this orientation varied depending on chain diffusion during

  13. Microphase-separated structures within randomly end-linked copolymer networks

    NASA Astrophysics Data System (ADS)

    Zeng, Di; Hayward, Ryan

    Self-assembly within randomly cross-linked or end-linked copolymer networks provides a robust method to generate co-continuous nanometer-scale structures. Here, we investigate self-assembly within copolymer networks prepared by end linking of several different pairs of telechelic polymers in a common solvent. For sufficiently high levels of immiscibility between the constituent polymers, removal of solvent leads to microphase separation into disordered nanoscale structures. Using a variety of characterization methods, including transmission electron microscopy, small-angle X-ray scattering, differential scanning calorimetry, and dynamic mechanical analysis, we find that these networks exhibit co-continuous morphologies over a wide range of volume fraction of the two components, with a characteristic length scale that can be tuned by adjusting the molecular weight of the starting polymers.

  14. Microphase separation in copolymers of hydrophilic PEG blocks and hydrophobic tyrosine-derived segments using simultaneous SAXS/WAXS/DSC

    SciTech Connect

    Murthy, N.S.; Wang, W.; Kohn, J.

    2010-10-22

    Hydration- and temperature-induced microphase separations were investigated by simultaneous small- and wide-angle X-ray scattering (SAXS and WAXS) and differential scanning calorimetry (DSC) in a family of copolymers in which hydrophilic poly(ethylene glycol) (PEG) blocks are inserted randomly into a hydrophobic polymer made of either desaminotyrosyl-tyrosine ethyl ester (DTE) or iodinated I{sub 2}DTE segments. Iodination of the tyrosine rings in I{sub 2}DTE increased the X-ray contrast between the hydrophobic and hydrophilic segments in addition to facilitating the study of the effect of iodination on microphase separation. The formation of phase-separated, hydrated PEG domains is of considerable significance as it profoundly affects the polymer properties. The copolymers of DTE (or I{sub 2}DTE) and PEG are a useful model system, and the findings presented here may be applicable to other PEG-containing random copolymers. In copolymers of PEG and DTE and I{sub 2}DTE, the presence of PEG depressed the glass transition temperature (T{sub g}) of the copolymer relative to the homopolymer, poly(DTE carbonate), and the DTE/I{sub 2}DTE segments hindered the crystallization of the PEG segments. In the dry state, at large PEG fractions (>70 vol%), the PEG domains self-assembled into an ordered structure with 14-18 nm distance between the domains. These domains gave rise to a SAXS peak at all temperatures in the iodinated polymers, but only above the T{sub g} in non-iodinated polymers, due to the unexpected contrast-match between the crystalline PEG domains and the glassy DTE segments. Irrespective of whether PEG was crystalline or not, immersion of these copolymers in water resulted in the formation of hydrated PEG domains that were 10-20 nm apart. Since both water and the polymer chains must be mobile for the phase separation to occur, the PEG domains disappeared when the water froze, and reappeared as the ice began to melt. This transformation was reversible, and showed

  15. Microphase separation in copolymers of hydrophilic PEG blocks and hydrophobic tyrosine-derived segments using simultaneous SAXS/WAXS/DSC.

    PubMed

    Murthy, N S; Wang, W; Kohn, J

    2010-08-01

    Hydration- and temperature-induced microphase separations were investigated by simultaneous small- and wide-angle X-ray scattering (SAXS and WAXS) and differential scanning calorimetry (DSC) in a family of copolymers in which hydrophilic poly(ethylene glycol) (PEG) blocks are inserted randomly into a hydrophobic polymer made of either desaminotyrosyl-tyrosine ethyl ester (DTE) or iodinated I(2)DTE segments. Iodination of the tyrosine rings in I(2)DTE increased the X-ray contrast between the hydrophobic and hydrophilic segments in addition to facilitating the study of the effect of iodination on microphase separation. The formation of phase-separated, hydrated PEG domains is of considerable significance as it profoundly affects the polymer properties. The copolymers of DTE (or I(2)DTE) and PEG are a useful model system and the findings presented here may be applicable to other PEG-containing random copolymers as well. In copolymers of PEG and DTE and I(2)DTE, the presence of PEG depressed the glass transition temperature (T(g)) of the copolymer relative to the homopolymer, poly(DTE carbonate), and the DTE/ I(2)DTE segments hindered the crystallization of the PEG segments. In the dry state, at large PEG fractions (> 70 vol%), the PEG domains self-assembled into an ordered structure with 14-18 nm distance between the domains. These domains gave rise to a SAXS peak at all temperatures in the iodinated polymers, but only above the T(g) in non-iodinated polymers, due to the unexpected contrast- match between the crystalline PEG domains and the glassy DTE segments. Irrespective of whether PEG was crystalline or not, immersion of these copolymers in water resulted in the formation of hydrated PEG domains that were 10-20 nm apart. Since both water and the polymer chains must be mobile for the phase separation to occur, the PEG domains disappeared when the water froze, and reappeared as the ice began to melt. This transformation was reversible, and showed hysteresis as did

  16. Microphase Separation Controlled beta-Sheet Crystallization Kinetics in Fibrous Proteins

    SciTech Connect

    Hu, X.; Lu, Q; Kaplan, D; Cebe, P

    2009-01-01

    Silk is a naturally occurring fibrous protein with a multiblock chain architecture. As such, it has many similarities with synthetic block copolymers, including the possibility for e-sheet crystallization restricted within the crystallizable blocks. The mechanism of isothermal crystallization kinetics of e-sheet crystals in silk multiblock fibrous proteins is reported in this study. Kinetics theories, such as Avrami analysis which was established for studies of synthetic polymer crystal growth, are for the first time extended to investigate protein self-assembly in e-sheet rich Bombyx mori silk fibroin samples, using time-resolved Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and synchrotron real-time wide-angle X-ray scattering (WAXS). The Avrami exponent, n, was close to 2 for all methods and crystallization temperatures, indicating formation of e-sheet crystals in silk proteins is different from the 3-D spherulitic crystal growth found in synthetic polymers. Observations by scanning electron microscopy support the view that the protein structures vary during the different stages of crystal growth, and show a microphase separation pattern after chymotrypsin enzyme biodegradation. We present a model to explain the crystallization of the multiblock silk fibroin protein, by analogy to block copolymers: crystallization of e-sheets occurs under conditions of geometrical restriction caused by phase separation of the crystallizable and uncrystallizable blocks. This crystallization model could be widely applicable in other proteins with multiblock (i.e., crystallizable and noncrystallizable) domains.

  17. Microphase-Separated PE/PEO Thin Films Prepared by Plasma-Assisted Vapor Phase Deposition.

    PubMed

    Choukourov, Andrei; Gordeev, Ivan; Ponti, Jessica; Uboldi, Chiara; Melnichuk, Iurii; Vaidulych, Mykhailo; Kousal, Jaroslav; Nikitin, Daniil; Hanyková, Lenka; Krakovský, Ivan; Slavínská, Danka; Biederman, Hynek

    2016-03-01

    Immiscible polymer blends tend to undergo phase separation with the formation of nanoscale architecture which can be used in a variety of applications. Different wet-chemistry techniques already exist to fix the resultant polymeric structure in predictable manner. In this work, an all-dry and plasma-based strategy is proposed to fabricate thin films of microphase-separated polyolefin/polyether blends. This is achieved by directing (-CH2-)100 and (-CH2-CH2-O-)25 oligomer fluxes produced by vacuum thermal decomposition of poly(ethylene) and poly(ethylene oxide) onto silicon substrates through the zone of the glow discharge. The strategy enables mixing of thermodynamically incompatible macromolecules at the molecular level, whereas electron-impact-initiated radicals serve as cross-linkers to arrest the subsequent phase separation at the nanoscale. The mechanism of the phase separation as well as the morphology of the films is found to depend on the ratio between the oligomeric fluxes. For polyolefin-rich mixtures, polyether molecules self-organize by nucleation and growth into spherical domains with average height of 22 nm and average diameter of 170 nm. For equinumerous fluxes and for mixtures with the prevalence of polyethers, spinodal decomposition is detected that results in the formation of bicontinuous structures with the characteristic domain size and spacing ranging between 5 × 10(1) -7 × 10(1) nm and 3 × 10(2)-4 × 10(2) nm, respectively. The method is shown to produce films with tunable wettability and biologically nonfouling properties. PMID:26953817

  18. Superhydrophobic film fabricated by controlled microphase separation of PEO-PLA mixture and its transparence property

    NASA Astrophysics Data System (ADS)

    Pi, Pihui; Mu, Wei; Fei, George; Deng, Yulin

    2013-05-01

    Instead of block copolymers that have been widely used in controlling thin film morphology, a mixture of two homopolymers has been used in this study to create desired nano- to microporous structure. By further modifying the nano-sized porous structured surface, a superhydrophobic surface was obtained. Experimentally, a chloroform solution containing a mixture of polylactic acid (PLA) and polyethylene oxide (PEO) was first coated on glass slides. Because of the dissimilarity of PLA and PEO, a microphase separation happened and the PEO formed microdomains in the coating layer during the film drying. Because PEO is water soluble but PLA is water-insoluble, the PEO microdomains could be washed out with water but PLA remained, resulted in a porous and rough PLA film. By two or three layer coating and washing, nano-sized roughness was obtained. A thin layer of fluorinated acrylic resin was further deposited on the rough surface. Because of the synergistic effect of surface roughness and hydrophobic, a superhydrophobicicity layer was obtained.

  19. Chemical Interactions and Their Role in the Microphase Separation of Block Copolymer Thin Films

    PubMed Central

    Farrell, Richard A.; Fitzgerald, Thomas G.; Borah, Dipu; Holmes, Justin D.; Morris, Michael A.

    2009-01-01

    The thermodynamics of self-assembling systems are discussed in terms of the chemical interactions and the intermolecular forces between species. It is clear that there are both theoretical and practical limitations on the dimensions and the structural regularity of these systems. These considerations are made with reference to the microphase separation that occurs in block copolymer (BCP) systems. BCP systems self-assemble via a thermodynamic driven process where chemical dis-affinity between the blocks driving them part is balanced by a restorative force deriving from the chemical bond between the blocks. These systems are attracting much interest because of their possible role in nanoelectronic fabrication. This form of self-assembly can obtain highly regular nanopatterns in certain circumstances where the orientation and alignment of chemically distinct blocks can be guided through molecular interactions between the polymer and the surrounding interfaces. However, for this to be possible, great care must be taken to properly engineer the interactions between the surfaces and the polymer blocks. The optimum methods of structure directing are chemical pre-patterning (defining regions on the substrate of different chemistry) and graphoepitaxy (topographical alignment) but both centre on generating alignment through favourable chemical interactions. As in all self-assembling systems, the problems of defect formation must be considered and the origin of defects in these systems is explored. It is argued that in these nanostructures equilibrium defects are relatively few and largely originate from kinetic effects arising during film growth. Many defects also arise from the confinement of the systems when they are ‘directed’ by topography. The potential applications of these materials in electronics are discussed. PMID:19865513

  20. Structural organization, micro-phase separation and polyamorphism of liquid MgSiO3 under compression

    NASA Astrophysics Data System (ADS)

    San, Luyen Thi; Van Hong, Nguyen; Iitaka, Toshiaki; Hung, Pham Khac

    2016-03-01

    The structure, structural change and micro-phase separation in liquid MgSiO3 under pressure are studied by molecular dynamics simulation with pair-wise potentials. Models consisting of 5000 atoms are constructed at 3500 K in the 0-30 GPa pressure range. The structural organization and structural phase transition under compression as well as network topology of liquid MgSiO3 are clarified through analysis and visualization of molecular dynamics simulation data. The short-range structure, intermediate-range structure and the degree of polymerization as well as structural, compositional and dynamical heterogeneities are also discussed in detail.

  1. Sporadic Nucleation and Growth in the Microphase Separation Process of an I2S Miktoarm Star Block Copolymer and its Blends with Homopolymer

    NASA Astrophysics Data System (ADS)

    Yang, Lizhang; Pochan, Darrin J.; Gido, Samuel P.; Pispas, Stergios; Hong, Kunlun; Mays, Jimmy W.

    2000-03-01

    A selective solvent and annealing study was done to investigate the morphology behavior of an I2S miktoarm star block copolymer and its blends with homopolyisoprene. Casting from cyclohexane, a selective solvent for polyisoprene, the neat star shaped I2S block copolymer only partially microphase separated, and formed a unique layered morphology inside a homogeneous media. During annealing, the layered phase and the homogeneous phase both transformed into a randomly oriented worm morphology. The path of this transformation is different depending on whether the starting state is layered or homogenous. The I2S/homopolyisoprene blend formed a mostly homogeneous phase after casting from cyclohexane. Annealing produced slow microphase separation which was observed at various stages by TEM. Based on these observations, a sporadic nucleation process of microphase separation is proposed.

  2. Theory of microphase separation on side-chain liquid-crystalline polymers with flexible spacers.

    PubMed

    Hernández-Jiménez, M; Westfahl, H

    2007-05-01

    We model a melt of monodisperse side-chain liquid-crystalline polymers as a melt of comb copolymers in which the side groups are rod-coil diblock copolymers. We consider both excluded-volume and Maier-Saupe interactions. The first acts among any pair of segments while the latter acts only between rods. Using a free-energy functional calculated from this microscopic model, we study the spinodal stability of the isotropic phase against density and orientational fluctuations. The phase diagram obtained in this way predicts nematic and smectic instabilities as well as the existence of microphases or phases with modulated wave vector but without nematic ordering. Such microphases are the result of the competition between the incompatibility among the blocks and the connectivity constraints imposed by the spacer and the backbone. Also the effects of the polymerization degree and structural conformation of the monomeric units on the phase behavior of the side-chain liquid-crystalline polymers are studied. PMID:17541501

  3. Phase Equilibria, Morphologies of Microphase Separation, and Interfacial Structures of Polymer Systems Studied by Equations of State

    NASA Astrophysics Data System (ADS)

    Liu, Honglai; Xu, Hui; Chen, Houyang; Peng, Changjun; Hu, Ying

    Polymer blends or copolymers have multiscale complex structures that can be used as templates to prepare various complex materials. To regulate the mesoscale structures of these polymer blends or copolymers, there are three fun damental problems: What is the physical condition of the microphase separation needed to form materials with desired compositions and mesoscale structures in dif ferent domains? How do these compositions and mesoscale structures evolve during the preparation period? How does the morphology change in the interfacial region? Many experimental measurements, computer simulation methods, and theories have been developed. However, most of them are only suitable for individual tasks. In re cent years, we have developed theoretical methods based on equations of state that can be used comprehensively to study the multiscale structure of polymer systems, including the phase diagrams, the morphologies and evolution of microphase sepa ration, the densities and composition profiles in different domains, and the molecular configurations in the interfacial region. The molecular parameters of the equation of state or the Helmholtz function model can be determined from the pressure, volume, temperature, and miscibility data of polymers, which ensures the practical applica bility of the methods.

  4. Solution-Processed Ambipolar Organic Thin-Film Transistors by Blending p- and n-Type Semiconductors: Solid Solution versus Microphase Separation.

    PubMed

    Xu, Xiaomin; Xiao, Ting; Gu, Xiao; Yang, Xuejin; Kershaw, Stephen V; Zhao, Ni; Xu, Jianbin; Miao, Qian

    2015-12-30

    Here, we report solid solution of p- and n-type organic semiconductors as a new type of p-n blend for solution-processed ambipolar organic thin film transistors (OTFTs). This study compares the solid-solution films of silylethynylated tetraazapentacene 1 (acceptor) and silylethynylated pentacene 2 (donor) with the microphase-separated films of 1 and 3, a heptagon-embedded analogue of 2. It is found that the solid solutions of (1)x(2)1-x function as ambipolar semiconductors, whose hole and electron mobilities are tunable by varying the ratio of 1 and 2 in the solid solution. The OTFTs of (1)0.5(2)0.5 exhibit relatively balanced hole and electron mobilities comparable to the highest values as reported for ambipolar OTFTs of stoichiometric donor-acceptor cocrystals and microphase-separated p-n bulk heterojunctions. The solid solution of (1)0.5(2)0.5 and the microphase-separated blend of 1:3 (0.5:0.5) in OTFTs exhibit different responses to light in terms of absorption and photoeffect of OTFTs because the donor and acceptor are mixed at molecular level with π-π stacking in the solid solution. PMID:25886029

  5. The Relationship between the Hydrophilicity and Surface Chemical Composition Microphase Separation Structure of Multicomponent Silicone Hydrogels.

    PubMed

    Zhao, Zheng-Bai; An, Shuang-Shuang; Xie, Hai-Jiao; Han, Xue-Lian; Wang, Fu-He; Jiang, Yong

    2015-07-30

    Three series of multicomponent silicone hydrogels were prepared by the copolymerization of two hydrophobic silicon monomers bis(trimethylsilyloxy) methylsilylpropyl glycerol methacrylate (SiMA) and tris(trimethylsiloxy) 3-methacryloxypropylsilane (TRIS) with three hydrophilic monomers. The surface hydrophilicity of the silicone hydrogels was characterized by contact angle measurements, and an interesting phenomenon was found that the silicone hydrogels made from less hydrophobic monomer SiMA possess more hydrophobic surfaces than those made from TRIS. The surface properties such as morphology and elemental composition of the silicone hydrogels were explored by scanning electron microscopy (SEM) imaging and energy dispersive spectrometry (EDS) analysis, and their relationships with the surface hydrophilicity were investigated in details. The results show neither the surface morphology nor the elemental composition has obvious impact on the surface hydrophilicity. Atomic force microscopy (AFM) imaging revealed that SiMA hydrogel had a more significant phase separation structure, which also made its surface uneven: a lot of tiny holes were observed on the surface. This surface phase separation structure made SiMA hydrogel more difficult to be wetted by water or PBS buffer, i.e., more hydrophobic than TRIS hydrogel. On the basis of these results, we propose that the phase separation structure as well as the nature of silicon monomers might be the fundamental reasons of surface hydrophilicity. These results could help to design a silicone hydrogel with better surface properties and wider application. PMID:26125331

  6. Polystyrene/methacrylate microphase separated semi-interpenetrating polymer networks with controlled morphology

    SciTech Connect

    Moeller, M.; Graaf, L.A. de

    1993-12-31

    Semi-interpenetrating polymer networks with on forehand controllable morphology could be obtained using a three-step process, separating morphology formation and polymerization/crosslinking. This is opposite to conventional synthesis routes, where morphology is formed due to polymerization and crosslinking. Morphology was formed by spinodal liquid/liquid demixing of a solution of atactic polystyrene in a methacrylate monomer, which was arrested by thermoreversible gelation (vitrification) of the polymer-rich phase at a desired stage. After low-temperature UV-polymerization and crosslinking of the methacrylate, the phase separated structure was preserved at room temperature. The morphology was found to be determined by the viscosity of the solution (polymer molecular weight and concentration) and by the efficiency of quenching (quench temperature, sample geometry). Domains of 0.03-0.06 m could be achieved, due to vitrification of the summits of concentration fluctuations of spinodal demixing in its initial stage. Thereby, domains were separated a distance (n times) the wavelength of spinodal demixing.

  7. A solid-state NMR investigation into microphase separation in polyurethane thermoplastic elastomers

    SciTech Connect

    Meltzer, A.D.; Lantman, C.W.; Steppan, S.; Seneker, S.; Wehrle, B.

    1993-12-31

    A combination of {sup 13}C-CP-MAS and static {sup 2}H-NMR techniques were used to study phase separation in polyurethane thermoplastic elastomers. The segmented polymers were prepared from hard segments comprised of 4,4{prime}-dicyclohexylmethane diisocyanate (DCHDI) chain extended with 1,4-butanediol, and soft segments of either poly(propylene glycol) or poly(butylene adipate). The DCHDI was prepared so as to contain different levels of the various geometric isomers, i.e., the cis,cis, cis,trans and trans,trans isomers, in order to monitor the influence of the trans,trans content on segmental mobility and phase separation. Lineshape analysis of static {sup 2}H-NMR spectra of samples selectively labelled in the chain extender indicate the trans,trans isomer constrains motion much more effectively than the other isomers of DCHDI at temperatures above the dynamic glass transition temperature of the soft phase and below the melting point of the hard domains. This is confirmed both by {sup 1}H-spin diffusion and t{sub 1{rho}} relaxation data. The data also indicate that the samples prepared with less trans-trans DCHDI have a much more significant interphase region than when DCHDI with a higher trans,trans content was employed, or that the higher trans-trans content allows for better hard domain formation. This insinuates that a relatively small amount of the trans,trans isomer of the DCHDI is more effective in allowing for the formation of physical cross-links than a larger amount of a statistical distribution of the diisocyanate, as corroborated by DSC and DMTA.

  8. Microphase Separation and Shear Alignment of Gradient Copolymers: Melt Rheology and Small-Angle X-Ray Scattering Analysis

    SciTech Connect

    Mok, Michelle M.; Pujari, Saswati; Burghardt, Wesley R.; Dettmer, Christine M.; Nguyen, SonBinh T.; Ellison, Christopher J.; Torkelson, John M.

    2008-10-24

    The degree of microphase or nanophase segregation in gradient copolymers with compositions varying across the whole copolymer backbone is studied via low-amplitude oscillatory shear (LAOS) measurements and small-angle X-ray scattering (SAXS). Studies are done as a function of comonomer segregation strength, molecular weight (MW), gradient architecture and temperature. Controlled radical polymerization is used to synthesize strongly segregating styrene/4-acetoxystyrene (S/AS) and the more weakly segregating S/n-butyl acrylate (S/nBA) gradient copolymers. Results are compared to those from S/AS and S/nBA random and block copolymers. The higher MW S/AS gradient copolymer exhibits LAOS behavior similar to the highly microphase segregated S/AS block copolymer, while the lower MW S/AS gradient copolymer exhibits complex, nonterminal behavior indicative of a lower degree of microphase segregation. The S/nBA gradient copolymers demonstrate more liquidlike behavior, with the lower MW sample exhibiting near-Newtonian behavior, indicative of a weakly segregating structure, while the higher MW, steeper gradient sample shows behavior ranging from solidlike to more liquidlike with increasing temperature. With the exception of the lower MW S/nBA case, the gradient copolymers exhibit temperature-dependent LAOS behavior over a wide temperature range, reflecting their temperature-dependent nanodomain composition amplitudes. The S/AS samples have SAXS results consistent with the degree of microphase segregation observed via rheology. Shear alignment studies are done on the higher MW S/AS gradient copolymer, which is the most highly microphase segregated gradient copolymer. Rheology and SAXS provide evidence of shear alignment, despite the gradual variation in composition profile across the nanodomains of such gradient copolymers. A short review of the nomenclature and behavior of linear copolymer architectures is also provided.

  9. Ordered, microphase-separated, noncharged-charged diblock copolymers via the sequential ATRP of styrene and styrenic imidazolium monomers

    SciTech Connect

    Shi, ZX; Newell, BS; Bailey, TS; Gin, DL

    2014-12-15

    A series of imidazolium-based noncharged-charged diblock copolymers (1) was synthesized by the direct, sequential ATRP of styrene and styrenic imidazolium bis(trifluoromethyl)sulfonamide monomers with methyl, n-butyl, and n-decyl side-chains. Small-angle X-ray scattering studies on initial examples of 1 with a total of 50 repeat units and styrene:imidazolium-styrene repeat unit ratios of 25:25, 20:30, and 15:35 showed that their ability to form ordered nanostructures (i.e., sphere and cylinder phases) in their neat states depends on both the block ratio and the length of the alkyl side-chain on the imidazolium monomer. To our knowledge, the synthesis of imidazolium-based BCPs that form ordered, phase-separated nanostructures via direct ATRP of immiscible co-monomers is unprecedented. (C) 2014 Elsevier Ltd. All rights reserved.

  10. Photochemical control of microphase structure in biocompatible polyester membranes generated by ultraviolet irradiation.

    PubMed

    Li, Rui; Pang, Wenmin; Tian, Liming; Nie, Kangming

    2016-04-13

    The morphologies of PEMA-RB/PHEMA semi-interpenetrating polymeric network (semi-IPN) blended membranes prepared via ultraviolet (UV) promoted in situ photopolymerization were investigated using laser scanning confocal fluorescence microscopy (LSCFM). The results show that the semi-IPN morphology generated through UV light irradiation-induced microphase separation is considerably dependent on the relative rates of the photochemical reaction and microphase separation in the reactive precursor mixtures, which are determined by reactive dynamic factors. Changing the dynamic conditions, such as the UV light intensity, content of cross-linker and concentration of HEMA photopolymerization monomer resulted in a corresponding alteration of the morphological structure in the semi-IPN membranes. The hierarchical morphology appearing in the PEMA-RB/PHEMA semi-IPN should be related to the inhomogeneous photoreaction dynamics of the mixed system. Desired morphologies of the semi-IPN blend membranes can be obtained by controlling the corresponding dynamic conditions of both the photochemical reaction and microphase separation. PMID:26968035

  11. Microphase separation in a model graft copolymer

    SciTech Connect

    Dozier, W.D.; Thiyagarajan, P.; Peiffer, D.G.

    1993-10-01

    We present a preliminary overview of our work on a series of graft copolymers having poly(ethyl acrylate) backbones with pendant chains of polystyrene (PS). The copolymer system appeared to be in the strong segregation limit and exhibited evidence of ordered structures. The morphology of these structures can apparently be very different from what would be expected. For instance, we observed a lamellar structure in a material containing 28 wt.% PS grafts. Samples under uniaxial strain showed either conventional (i.e., affine deformation) and anomalous ({open_quotes}butterfly{close_quotes} isointensity patterns) behavior in small-angle neutron scattering.

  12. Microphase formation at a 2D solid-gas phase transition.

    PubMed

    Schuman, Adam W; Bsaibes, Thomas S; Schlossman, Mark L

    2014-10-01

    Density modulated micro-separated phases (microphases) occur at 2D liquid interfaces in the form of alternating regions of high and low density domains. Brewster angle microscopy (BAM) images demonstrate the existence of microphases in cluster, stripe, and mosaic morphologies at the buried interface between hexane and water with fluoro-alkanol surfactant dissolved in the bulk hexane. At high temperature, the surfactant assembles at the interface in a 2D gaseous state. As the system is cooled additional surfactants condense onto the interface, which undergoes a 2D gas-solid phase transition. Microphase structure is observed within a few degrees of this transition in the form of clusters and labyrinthine stripes. Microphases have been observed previously in a number of other systems; nevertheless, we demonstrate that adsorption transitions at the liquid-liquid interface provide a convenient way to observe a full sequence of temperature-dependent 2D phases, from gas to cluster to stripe to mosaic to inverted stripe phases, as well as coexistence between some of these microphases. Cracking and fracture of the clusters reveal that they are a solid microphase. Theories of microphases often predict a single length scale for cluster and stripe phases as a result of the competition between an attractive and a repulsive interaction. Our observation that two characteristic length scales are required to describe clusters whose diameter is much larger than the stripe period, combined with the solid nature of the clusters, suggests that a long-range elastic interaction is relevant. These results complement earlier X-ray measurements on the same system. PMID:25088351

  13. Equilibrium Phase Behavior of a Continuous-Space Microphase Former

    NASA Astrophysics Data System (ADS)

    Zhuang, Yuan; Zhang, Kai; Charbonneau, Patrick

    2016-03-01

    Periodic microphases universally emerge in systems for which short-range interparticle attraction is frustrated by long-range repulsion. The morphological richness of these phases makes them desirable material targets, but our relatively coarse understanding of even simple models hinders controlling their assembly. We report here the solution of the equilibrium phase behavior of a microscopic microphase former through specialized Monte Carlo simulations. The results for cluster crystal, cylindrical, double gyroid, and lamellar ordering qualitatively agree with a Landau-type free energy description and reveal the nontrivial interplay between cluster, gel, and microphase formation.

  14. Free-surface wave-induced separation

    SciTech Connect

    Zhang, Z.J.; Stern, F.

    1996-09-01

    Free-surface wave-induced separation is studied for a surface-piercing NACA 0024 foil over a range of Froude numbers (0, .2, .37, .55) through computational fluid dynamics of the unsteady Reynolds-averaged Navier-Stokes and the continuity equations with the Baldwin-Lomax turbulence model, exact nonlinear kinematic and approximate dynamic free-surface boundary conditions, and a body/free-surface conforming grid. The flow conditions and uncertainty analysis are discussed. A topological rule for a surface-piercing body is derived and verified. Steady-flow results are presented and analyzed with regard to the wave and viscous flow and the nature of the separation.

  15. Shock Induced Separating Flows in Scramjet Intakes

    NASA Astrophysics Data System (ADS)

    Yao, Yufeng; Rincon, Daniel; Zheng, Yao

    Shock induced separating flows in a scramjet intake has been studied by using a computational fluid dynamics approach. A configuration of scramjet intake geometry consisting of two exterior compression ramps, followed by a subsequent inlet and interior isolator/diffuser assembly, is chosen. The flow conditions are incoming Mach 7 with free-stream static temperature of 46.3K and wall temperature of 300K, respectively. Consequently, oblique shock wave will be formed and its interaction with viscous boundary layers will lead to flow separation that is responsible for the loss of mass flow, total pressure and several other effects. Simulations confirmed that it is necessary to include the cowl wedge in order to predict wall pressure distributions along the lower surface of the intake walls. It is also shown that mesh topology has some influences on prediction results with structured mesh gives better predictions than that of hybrid mesh. A total of eight turbulence models have been applied and results have shown reasonably good agreement with the experimental measurements and other numerical predictions, with small differences occur in localized regions particularly after shock reflection inside the intake channel. Not surprisingly, shock induced flow separation occurs and it correlates well with higher wall pressure and heating downstream. This phenomenon will have significant impact on deteriorating boundary layer property and consequently the engine performance.

  16. Does dynamic vulcanization induce phase separation?

    PubMed

    Abolhasani, Mohammad Mahdi; Zarejousheghani, Fatemeh; Naebe, Minoo; Guo, Qipeng

    2014-08-14

    Immiscible and miscible blends of poly(vinylidene fluoride) (PVDF) and acrylic rubber (ACM) were subjected to dynamic vulcanization to investigate the effect of crosslinking on phase separation. As a result of different processability, mixing torque behavior of miscible and immiscible blends was significantly different from one another. Scanning electron microscopy (SEM) was used to investigate the morphology of the system. After dynamic vulcanization, submicron ACM droplets were observed in the samples near the binodal curve of the system under mixing conditions. Small angle X-ray scattering (SAXS) and differential scanning calorimetry (DSC) analysis were used to investigate the effect of dynamic vulcanization on the lamellar structure of the system. It was shown that for samples near the boundary of phase separation, increasing the crosslink density led to a decrease in the lamellar long period (L) as a sign of increment of crosslink density induced phase decomposition. Effects of shear rate on the final morphology of the system were investigated by changing the mixing temperature and by comparing the results of dynamic vulcanization at one phase and two phase regions. PMID:24957793

  17. Microphase Ordering in Melts of Randomly Grafted Copolymers

    SciTech Connect

    Qi, S.; Chakraborty, A.K.; Wang, H.; Lefebvre, A.A.; Balsara, N.P.; Shakhnovich, E.I.; Xenidou, M.; Hadjichristidis, N.

    1999-04-01

    Using optical birefringence, small-angle neutron scattering, and field-theoretic methods, we study the effects of frustrating quenched randomness and connectivity on microphase ordering in copolymer melts. Our results show that randomly grafted copolymers are good model systems to examine these effects, and we find that these materials exhibit behavior different from that observed heretofore for other types of molten polymers. {copyright} {ital 1999} {ital The American Physical Society}

  18. Equilibrium Phase Behavior of the Square-Well Linear Microphase-Forming Model.

    PubMed

    Zhuang, Yuan; Charbonneau, Patrick

    2016-07-01

    We have recently developed a simulation approach to calculate the equilibrium phase diagram of particle-based microphase formers. Here, this approach is used to calculate the phase behavior of the square-well linear model for different strengths and ranges of the linear long-range repulsive component. The results are compared with various theoretical predictions for microphase formation. The analysis further allows us to better understand the mechanism for microphase formation in colloidal suspensions. PMID:27117230

  19. Thermocapillary-Induced Phase Separation with Coalescence

    NASA Technical Reports Server (NTRS)

    Davis, Robert H.

    2003-01-01

    Research has been undertaken on interactions of two or more deformable drops (or bubbles) in a viscous fluid and subject to a temperature, gravitational, or flow field. An asymptotic theory for nearly spherical drops shows that small deformations reduce the coalescence and phase separation rates. Boundary-integral simulations for large deformations show that bubbles experience alignment and enhanced coalescence, whereas more viscous drops may break as a result of hydrodynamic interactions. Experiments for buoyancy motion confirm these observations. Simulations of the sedimentation of many drops show clustering phenomena due to deformations, which lead to enhanced phase separation rates, and simulations of sheared emulsions show that deformations cause a reduction in the effective viscosity.

  20. Recent Advances in the Theory and Simulation of Model Colloidal Microphase Formers.

    PubMed

    Zhuang, Yuan; Charbonneau, Patrick

    2016-08-18

    This mini-review synthesizes our understanding of the equilibrium behavior of particle-based models with short-range attractive and long-range repulsive (SALR) interactions. These models, which can form stable periodic microphases, aim to reproduce the essence of colloidal suspensions with competing interparticle interactions. Ordered structures, however, have yet to be obtained in experiments. In order to better understand the hurdles to periodic microphase assembly, marked theoretical and simulation advances have been made over the past few years. Here, we present recent progress in the study of microphases in models with SALR interactions using liquid-state theory and density-functional theory as well as numerical simulations. Combining these various approaches provides a description of periodic microphases, and gives insights into the rich phenomenology of the surrounding disordered regime. Ongoing research directions in the thermodynamics of models with SALR interactions are also presented. PMID:27466702

  1. Polymerization-Induced Phase Separation in Vinyl Ester Resins

    NASA Astrophysics Data System (ADS)

    Ganglani, Manisha; Torkelson, John; Carr, Stephen

    2000-03-01

    In certain multi-component, crosslinking polymer systems, phase separation is induced by polymerization, a process call polymerization-induced phase separation (PIPS) in which there exists a competition between reaction rate and phase separation rate. The final morphology and properties of a system that experiences PIPS depend on the outcome of this competition. Thus, by controlling these rates, it would be possible to control end properties. In fact, this theory has been applied for the creation of polymer-dispersed liquid crystals (PDLCs) where cure occurs via condensation reactions or via free radical polymerization initiated by UV light. This research examines PIPS in the vinyl ester (VE) resins, which are popular as matrix materials in polymer composites. Cure of the VE resins is more complicated because it uses initiators and therefore requires more time and offers less control than cure by photopolymerization. To better understand the PIPS process in the VE resins, this research separates the two competitive effects and examines each one in turn. Initial experiments use a model system to focus on the effect of PIPS in the absence of crosslinking.

  2. Nanoparticle-Mediated, Light-Induced Phase Separations.

    PubMed

    Neumann, Oara; Neumann, Albert D; Silva, Edgar; Ayala-Orozco, Ciceron; Tian, Shu; Nordlander, Peter; Halas, Naomi J

    2015-12-01

    Nanoparticles that both absorb and scatter light, when dispersed in a liquid, absorb optical energy and heat a reduced fluid volume due to the combination of multiple scattering and optical absorption. This can induce a localized liquid-vapor phase change within the reduced volume without the requirement of heating the entire fluid. For binary liquid mixtures, this process results in vaporization of the more volatile component of the mixture. When subsequently condensed, these two steps of vaporization and condensation constitute a distillation process mediated by nanoparticles and driven by optical illumination. Because it does not require the heating of a large volume of fluid, this process requires substantially less energy than traditional distillation using thermal sources. We investigated nanoparticle-mediated, light-induced distillation of ethanol-H2O and 1-propanol-H2O mixtures, using Au-SiO2 nanoshells as the absorber-scatterer nanoparticle and nanoparticle-resonant laser irradiation to drive the process. For ethanol-H2O mixtures, the mole fraction of ethanol obtained in the light-induced process is substantially higher than that obtained by conventional thermal distillation, essentially removing the ethanol-H2O azeotrope that limits conventional distillation. In contrast, for 1-propanol-H2O mixtures the distillate properties resulting from light-induced distillation were very similar to those obtained by thermal distillation. In the 1-propanol-H2O system, a nanoparticle-mediated, light-induced liquid-liquid phase separation was also observed. PMID:26535465

  3. Silk fibroin gelation via non-solvent induced phase separation.

    PubMed

    Kasoju, Naresh; Hawkins, Nicholas; Pop-Georgievski, Ognen; Kubies, Dana; Vollrath, Fritz

    2016-03-01

    Tissue engineering benefits from novel materials with precisely tunable physical, chemical and mechanical properties over a broad range. Here we report a practical approach to prepare Bombyx mori silk fibroin hydrogels using the principle of non-solvent induced phase separation (NIPS). A combination of reconstituted silk fibroin (RSF) and methanol (non-solvent), with a final concentration of 2.5% w/v and 12.5% v/v respectively, maintained at 22 °C temperature turned into a hydrogel within 10 hours. Freeze-drying of this gel gave a foam with a porosity of 88%, a water uptake capacity of 89% and a swelling index of 8.6. The gelation kinetics and the loss tangent of the gels were investigated by rheometry. The changes in the morphology of the porous foams were visualized by SEM. The changes in RSF chemical composition and the relative fraction of its secondary structural elements were analyzed by ATR-FTIR along with Fourier self-deconvolution. And, the changes in the glass transition temperature, specific heat capacity and the relative fraction of crystallinity of RSF were determined by TM-DSC. Data suggested that RSF-water-methanol behaved as a polymer-solvent-non-solvent ternary phase system, wherein the demixing of the water-methanol phases altered the thermodynamic equilibrium of RSF-water phases and resulted in the desolvation and eventual separation of the RSF phase. Systematic analysis revealed that both gelation time and the properties of hydrogels and porous foams could be controlled by the ratios of RSF and non-solvent concentration as well as by the type of non-solvent and incubation temperature. Due to the unique properties we envisage that the herein prepared NIPS induced RSF hydrogels and porous foams can possibly be used for the encapsulation of cells and/or for the controlled release of both hydrophilic and hydrophobic drugs. PMID:26730413

  4. An Optimized Nanoparticle Separator Enabled by Electron Beam Induced Deposition

    SciTech Connect

    Fowlkes, Jason Davidson; Doktycz, Mitchel John; Rack, P. D.

    2010-01-01

    Size based separations technologies will inevitably benefit from advances in nanotechnology. Direct write nanofabrication provides a useful mechanism to deposit/etch nanoscale elements in environments otherwise inaccessible to conventional nanofabrication techniques. Here, electron beam induced deposition (EBID) was used to deposit an array of nanoscale features in a 3D environment with minimal material proximity effects outside the beam interaction region (BIR). Specifically, the membrane component of a nanoparticle separator was fabricated by depositing a linear array of sharply tipped nanopillars, with a singular pitch, designed for sub 50nm nanoparticle permeability. The nanopillar membrane was used in a dual capacity to control the flow of nanoparticles in the transaxial direction of the array while facilitating the sealing of the cellular sized compartment in the paraxial direction. An optimized growth recipe resulted which (1) maximized the growth efficiency of the membrane (which minimizes proximity effects), (2) preserved the fidelity of spacing between nanopillars (which maximizes the size based gating quality of the membrane) while (3) maintaining sharp nanopillar apexes for impaling an optically transparent polymeric lid critical for device sealing.

  5. An optimized nanoparticle separator enabled by electron beam induced deposition.

    PubMed

    Fowlkes, J D; Doktycz, M J; Rack, P D

    2010-04-23

    Size-based separations technologies will inevitably benefit from advances in nanotechnology. Direct-write nanofabrication provides a useful mechanism for depositing/etching nanoscale elements in environments otherwise inaccessible to conventional nanofabrication techniques. Here, electron beam induced deposition was used to deposit an array of nanoscale features in a 3D environment with minimal material proximity effects outside the beam-interaction region. Specifically, the membrane component of a nanoparticle separator was fabricated by depositing a linear array of sharply tipped nanopillars, with a singular pitch, designed for sub-50 nm nanoparticle permeability. The nanopillar membrane was used in a dual capacity to control the flow of nanoparticles in the transaxial direction of the array while facilitating the sealing of the cellular-sized compartment in the paraxial direction. An optimized growth recipe resulted which (1) maximized the growth efficiency of the membrane (which minimizes proximity effects) and (2) preserved the fidelity of the spacing between nanopillars (which maximizes the size-based gating quality of the membrane) while (3) maintaining sharp nanopillar apexes for impaling an optically transparent polymeric lid critical for device sealing. PMID:20351412

  6. Aluminum-matrix electrotechnical composite alloys hardened by endogenous nano- and microphases

    NASA Astrophysics Data System (ADS)

    Babkin, V. G.; Terent'ev, N. A.; Cherepanov, A. I.

    2014-09-01

    A method is developed to manufacture aluminum-matrix composite alloys hardened by endogenous nano- and microphases. The formation of the structure and properties of the composite materials is studied. The experimental results demonstrate that the developed alloys are promising to produce electro-technical wire rods and other electrotechnical products.

  7. Prediction of fluctuating pressure environments associated with plume-induced separated flow fields

    NASA Technical Reports Server (NTRS)

    Plotkin, K. J.

    1973-01-01

    The separated flow environment induced by underexpanded rocket plumes during boost phase of rocket vehicles has been investigated. A simple semi-empirical model for predicting the extent of separation was developed. This model offers considerable computational economy as compared to other schemes reported in the literature, and has been shown to be in good agreement with limited flight data. The unsteady pressure field in plume-induced separated regions was investigated. It was found that fluctuations differed from those for a rigid flare only at low frequencies. The major difference between plume-induced separation and flare-induced separation was shown to be an increase in shock oscillation distance for the plume case. The prediction schemes were applied to PRR shuttle launch configuration. It was found that fluctuating pressures from plume-induced separation are not as severe as for other fluctuating environments at the critical flight condition of maximum dynamic pressure.

  8. EGF Induced Centrosome Separation Promotes Mitotic Progression and Cell Survival

    PubMed Central

    Mardin, Balca R.; Isokane, Mayumi; Cosenza, Marco R.; Krämer, Alwin; Ellenberg, Jan; Fry, Andrew M.; Schiebel, Elmar

    2014-01-01

    Summary Timely and accurate assembly of the mitotic spindle is critical for the faithful segregation of chromosomes and centrosome separation is a key step in this process. The timing of centrosome separation varies dramatically between cell types; however, the mechanisms responsible for these differences and its significance are unclear. Here, we show that activation of epidermal growth factor receptor (EGFR) signaling determines the timing of centrosome separation. Premature separation of centrosomes decreases the requirement for the major mitotic kinesin Eg5 for spindle assembly, accelerates mitosis and decreases the rate of chromosome missegregation. Importantly, EGF stimulation impacts upon centrosome separation and mitotic progression to different degrees in different cell lines. Cells with high EGFR levels fail to arrest in mitosis upon Eg5 inhibition. This has important implications for cancer therapy since cells with high centrosomal response to EGF are more susceptible to combinatorial inhibition of EGFR and Eg5. PMID:23643362

  9. Controlling sub-microdomain structure in microphase-ordered block copolymers and their nanocomposites

    NASA Astrophysics Data System (ADS)

    Bowman, Michelle Kathleen

    Block copolymers exhibit a wealth of morphologies that continue to find ubiquitous use in a diverse variety of mature and emergent (nano)technologies, such as photonic crystals, integrated circuits, pharmaceutical encapsulents, fuel cells and separation membranes. While numerous studies have explored the effects of molecular confinement on such copolymers, relatively few have examined the sub-microdomain structure that develops upon modification of copolymer molecular architecture or physical incorporation of nanoscale objects. This work will address two relevant topics in this vein: (i) bidisperse brushes formed by single block copolymer molecules and (ii) copolymer nanocomposites formed by addition of molecular or nanoscale additives. In the first case, an isomorphic series of asymmetric poly(styrene-b -isoprene-b-styrene) (S1IS2) triblock copolymers of systematically varied chain length has been synthesized from a parent SI diblock copolymer. Small-angle x-ray scattering, coupled with dynamic rheology and self-consistent field theory (SCFT), reveals that the progressively grown S2 block initially resides in the I-rich matrix and effectively reduces the copolymer incompatibility until a critical length is reached. At this length, the S2 block co-locates with the S1 block so that the two blocks generate a bidisperse brush (insofar as the S1 and S2 lengths differ). This single-molecule analog to binary block copolymer blends affords unique opportunities for materials design at sub-microdomain length scales and provides insight into the transition from diblock to triblock copolymer (and thermoplastic elastomeric nature). In the second case, I explore the distribution of molecular and nanoscale additives in microphase-ordered block copolymers and demonstrate via SCFT that an interfacial excess, which depends strongly on additive concentration, selectivity and relative size, develops. These predictions are in agreement with experimental findings. Moreover, using a

  10. Micro-phase measuring profilometry: Its sensitivity analysis and phase unwrapping

    NASA Astrophysics Data System (ADS)

    Tang, Suming; Zhang, Xu; Tu, Dawei

    2015-09-01

    Global illumination affects shape measurement accuracy, and phase unwrapping is an important problem in phase measuring profilometry. In this paper, a micro-phase measuring profilometry is proposed to reduce the effects of global illumination. The wrapped phase error level of the proposed method is lower than that of the traditional micro-phase shifting method. First, a frequency selection rule is developed in combination with the micro-phase rule to design the frequencies of the proposed phase measuring profilometry. The frequency rule is obtained by analysing the uncertainty of the wrapped phase caused by intensity noise. Then, phase unwrapping is regarded as a congruence problem, and the closed-form robust Chinese remainder theorem algorithm is adopted to determine the correspondence. Finally, the comparative experiments are conducted on a projector-camera system. Experimental results show that the effects of global illumination can be effectively reduced with the proposed phase measuring profilometry, and the proposed frequency selection rule is valid. In addition, the performance of the robust Chinese remainder theorem in addressing the phase error is better than that of traditional Chinese remainder theorem. Furthermore, the unwrapping accuracy can nearly reach 100% if the frequency selection rule is satisfied. Otherwise, the performance degrades.

  11. Effect of Hydrogen-Bonding Junctions on Microphase Separation in Block Copolymers

    NASA Astrophysics Data System (ADS)

    Stone, Greg; Hedrick, Jim; Nederberg, Fredrik; Balsara, Nitash

    2008-03-01

    The morphology of poly(styrene-block- trimethylene carbonate) (PS-PTMC) copolymers with and without thiourea groups at the junction between the blocks was studied by a combination of small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). The thiourea groups are known to exhibit inter-molecular hydrogen bonding. We demonstrate that the presence of thiourea groups results in increased segregation between PS and PTMC blocks. We focus on symmetric systems with total molecular weights in the 5 kg/mol range. In conventional block copolymers without hydrogen bonding groups it is difficult to obtain strong segregation in low molecular weight systems because the product chi*N controls segregation (chi is the Flory-Huggins interaction parameter and N is the number of monomers per chain). The incorporation of hydrogen bonding groups may provide a route for the generation of patterns with small, sharply defined features using block copolymers.

  12. Microphase separation of short wormlike diblock copolymers with a finite interaction range.

    PubMed

    Jiang, Ying; Zhang, Xinghua; Miao, Bing; Yan, Dadong; Chen, Jeff Z Y

    2016-02-17

    We investigate several structural properties of low-molecular weight AB diblock copolymer melts, focusing on a number of features that substantially deviate from those of high-molecular weight copolymer melts. The study is based on the wormlike chain formalism aided by random phase approximation and self-consistent field theory. We examine the effects that stemmed from both the finite molecular weight and the finite interaction range between unlike AB monomers. The latter yields profound effects on systems consisting of short wormlike block copolymers. The noticeable shift of the order-disorder transition point is discussed. Attention is also paid to the strong-segregation regime, where low molecular weight polymers are subject to finite stretchability. PMID:26822622

  13. A Comparative Study of Microphase Separation of Polyurethane Multiblock Copolymers with Different Soft Segment Chemistries.

    NASA Astrophysics Data System (ADS)

    Hernandez, Rebeca; Choi, Taeyi; Weksler, Jadwiga; Padsalgikar, Ajay; Xu, Lichong; Siedlecki, Christopher; Runt, James

    2008-03-01

    We focus in this study on three series of chemically well-defined polyurethanes (PUs) with the same hard segments (MDI-BDO) but different soft segment chemistries of interest in biomedical applications: 1000 g/mol aliphatic polycarbonate, polytetramethylenoxide and a mixed macrodiol of polydimethylsiloxane (PDMS) and polyhexamethylenoxide. Using quantitative small-angle X-ray scattering we demonstrate that the degree of hard/soft segment demixing varies greatly between the materials. For example, the PDMS-based copolymers exhibit a three phase, core-shell morphology, while the other copolymers exhibit a typical two phase structure. Additional analysis was conducted with a number of experimental probes including FTIR to assess inter- and intracomponent hydrogen bonding, and tapping mode AFM to characterize the nanoscale morphology.

  14. Injection Induced Mixing in Flows Separating From Smooth Surfaces

    NASA Technical Reports Server (NTRS)

    Adamczyk, John J. (Technical Monitor); Wundrow, David W.

    2004-01-01

    An analytic model for predicting the effect of unsteady local surface injection on the flow separating from a streamlined body at angle of attack is proposed. The model uses the premise that separation control results from enhanced mixing along the shear layer that develops between the main stream and the fluid in the underlying recirculation zone. High-Reynolds-number asymptotic methods are used to connect the unsteady surface injection to an instability wave propagating on the separating shear layer and then to the large-scale coherent structures that produce the increased mixing. The results is a tool that can guide the choice of fluid-actuator parameters to maximize flow-control effectiveness and may also facilitate computer-based numerical experiments.

  15. Shape-induced separation of nanospheres and aligned nanorods.

    PubMed

    Ahmad, I; Zandvliet, H J W; Kooij, E S

    2014-07-15

    We studied the phase separation and spatial arrangement of gold nanorods and nanospheres after evaporative self-assembly from aqueous suspension. Depending on the position relative to the contact line of the drying droplet, spheres and rods separate into various liquid-crystalline phases. Nanorods exhibit a strong preference for side-by-side alignment, giving rise to smectic phases; spheres in solution are forced out of these regions and form close-packed arrays. We discuss this self-separation into nanorod- and sphere-rich phases in terms of various interactions, including electrostatic, van der Waals, and deplection interactions forces. The experimental results are compared to quantitative calculations of the colloidal interaction energies. We also describe and discuss the role of the surfactant on the different crystal facets of the nanorods on the assembly process. PMID:24959664

  16. Activity induced phase separation in particles and (bio)polymers

    NASA Astrophysics Data System (ADS)

    Grosberg, Alexander

    It was recently shown that the non-equilibrium steady state of the mixture of two types of particles exposed to two different thermostats can phase separate (A.Y.Grosberg, J.-F.Joanny, PRE, v. 91, 032118, 2015). similar result is valid also in the case when particles in question are monomers of two different polymer chains, or blocks of a co-polymer. We discuss the implications of these results for the physics of chromatin.

  17. Apparatus for heat induced separation of hydrocarbon constituents from coal

    SciTech Connect

    Pine, M.; Johnson, J.R.; Moss, R.E.; Sandoval, R.A.

    1984-09-25

    A method and apparatus is provided for accomplishing thermal separation of various hydrocarbons and other compounds from coal, a hydrocarbon rendering module is provided for the continuous agitation and circulation of coal during the rendering period and utilizes thermal trays having stationary and revolving apparatus to improve heat transfer to coal particles and minimize rendering time. Portions of the rendered hydrocarbon products are recycled to the mechanism as an energy source for continuous operation.

  18. Simulation of Reaction-Induced Phase Separation in Surface Alloy

    NASA Astrophysics Data System (ADS)

    Zvejnieks, G.; Tornau, E. E.

    2008-03-01

    Using kinetic Monte Carlo method we simulate the dynamics of biatomic Au0.3Ni0.7 surface alloy separation on Ni(111) due to Ni(CO)4 out-reaction. The experiment of Vestergaard et al. is modeled by counterbalancing dynamical processes and interactions between reactants. The simulations demonstrate step flow rate increase with CO coverage, cCO, in qualitative agreement with the experiment only for cCO ≲ 0.45 monolayer. Moreover, we demonstrate both CO influence on reaction process and Au domain formation.

  19. Light-induced charge separation across bio-inorganic interface.

    SciTech Connect

    Dimitrijevic, N. M.; Rajh, T.; De La Garza, L.; Valdosta State Univ.

    2009-01-01

    Rational design of hybrid biomolecule - nanoparticulate semiconductor conjugates enables coupling of functionality of biomolecules with the capability of semiconductors for solar energy capture, that can have potential application in energy conversion, sensing and catalysis. The particular challenge is to obtain efficient charge separation analogous to the natural photosynthesis process. The synthesis of axially anisotropic TiO{sub 2} nano-objects such as tubes, rods and bricks, as well as spherical and faceted nanoparticles has been developed in our laboratory. Depending on their size and shape, these nanostructures exhibit different domains of crystallinity, surface areas and aspect ratios. Moreover, in order to accommodate for high curvature in nanoscale regime, the surfaces of TiO{sub 2} nano-objects reconstructs resulting in changes in the coordination of surface Ti atoms from octahedral (D{sub 2d}) to square pyramidal structures (C{sub 4v}). The formation of these coordinatively unsaturated Ti atoms, thus depends strongly on the size and shape of nanocrystallites and affects trapping and reactivity of photogenerated charges. We have exploited these coordinatively unsaturated Ti atoms to coupe electron-donating (such as dopamine) and electron-accepting (pyrroloquinoline quinone) conductive linkers that allow wiring of biomolecules and proteins resulting in enhanced charge separation which increases the yield of ensuing chemical transformations.

  20. Light-Induced Charge Separation across Bio-Inorganic Interface

    NASA Astrophysics Data System (ADS)

    Dimitrijevic, Nada M.; de La Garza, Linda; Rajh, Tijana

    Rational design of hybrid biomolecule — nanoparticulate semiconductor conjugates enables coupling of functionality of biomolecules with the capability of semiconductors for solar energy capture, that can have potential application in energy conversion, sensing and catalysis. The particular challenge is to obtain efficient charge separation analogous to the natural photosynthesis process. The synthesis of axially anisotropic TiO2 nano-objects such as tubes, rods and bricks, as well as spherical and faceted nanoparticles has been developed in our laboratory. Depending on their size and shape, these nanostructures exhibit different domains of crystallinity, surface areas and aspect ratios. Moreover, in order to accommodate for high curvature in nanoscale regime, the surfaces of TiO2 nano-objects reconstructs resulting in changes in the coordination of surface Ti atoms from octahedral (D2d) to square pyramidal structures (C4v). The formation of these coordinatively unsaturated Ti atoms, thus depends strongly on the size and shape of nanocrystallites and affects trapping and reactivity of photogenerated charges. We have exploited these coordinatively unsaturated Ti atoms to coupe electron-donating (such as dopamine) and electron-accepting (pyrroloquinoline quinone) conductive linkers that allow wiring of biomolecules and proteins resulting in enhanced charge separation which increases the yield of ensuing chemical transformations.

  1. Rheological monitoring of phase separation induced by chemical reaction in thermoplastic-modified epoxy

    SciTech Connect

    Vinh-Tung, C.; Lachenal, G.; Chabert, B.

    1996-12-31

    The phase separation induced by chemical reaction in blends of tetraglycidyl-diaminodiphenylmethane epoxy resin with an aromatic diamine hardener and a thermoplastic was monitored. Rheological measurements and morphologies are described.

  2. Deuterium separation by infrared-induced addition reaction

    DOEpatents

    Marling, John B.

    1977-01-01

    A method for deuterium enrichment by the infrared-induced addition reaction of a deuterium halide with an unsaturated aliphatic compound. A gaseous mixture of a hydrogen halide feedstock and an unsaturated aliphatic compound, particularly an olefin, is irradiated to selectively vibrationally excite the deuterium halide contained therein. The excited deuterium halide preferentially reacts with the unsaturated aliphatic compound to produce a deuterated addition product which is removed from the reaction mixture.

  3. Weakly Charged Cationic Nanoparticles Induce DNA Bending and Strand Separation

    SciTech Connect

    Railsback, Justin; Singh, Abhishek; Pearce, Ryan; McKnight, Timothy E; Collazo, Ramon; Sitar, Zlatko; Yingling, Yaroslava; Melechko, Anatoli Vasilievich

    2012-01-01

    The understanding of interactions between double stranded (ds) DNA and charged nanoparticles will have a broad bearing on many important applications from drug delivery [ 1 4 ] to DNAtemplated metallization. [ 5 , 6 ] Cationic nanoparticles (NPs) can bind to DNA, a negatively charged molecule, through a combination of electrostatic attraction, groove binding, and intercalation. Such binding events induce changes in the conformation of a DNA strand. In nature, DNA wraps around a cylindrical protein assembly (diameter and height of 6 nm) [ 7 ] with an 220 positive charge, [ 8 ] creating the complex known as chromatin. Wrapping and bending of DNA has also been achieved in the laboratory through the binding of highly charged species such as molecular assemblies, [ 9 , 10 ] cationic dendrimers, [ 11 , 12 ] and nanoparticles. [ 13 15 ] The charge of a nanoparticle plays a crucial role in its ability to induce DNA structural changes. If a nanoparticle has a highly positive surface charge density, the DNA is likely to wrap and bend upon binding to the nanoparticle [ 13 ] (as in the case of chromatin). On the other hand, if a nanoparticle is weakly charged it will not induce dsDNA compaction. [ 9 , 10 , 15 ] Consequently, there is a transition zone from extended to compact DNA conformations which depends on the chemical nature of the nanoparticle and occurs for polycations with charges between 5 and 10. [ 9 ] While the interactions between highly charged NPs and DNA have been extensively studied, the processes that occur within the transition zone are less explored.

  4. Ethnic Variations in the Connection between Work-Induced Family Separation and Turnover Intent

    ERIC Educational Resources Information Center

    Behnke, Andrew O.; MacDermid, Shelley M.; Anderson, James C.; Weiss, Howard M.

    2010-01-01

    Using conservation of resources theory, this study examines the role of resources in the relationship between work-induced family separation and workers' intentions to leave their employment and how these relationships vary across ethnic groups. Analyses of a large representative sample of military members reveal that family separation is…

  5. Short environmental enrichment in adulthood reverses anxiety and basolateral amygdala hypertrophy induced by maternal separation

    PubMed Central

    Koe, A S; Ashokan, A; Mitra, R

    2016-01-01

    Maternal separation during early childhood results in greater sensitivity to stressors later in adult life. This is reflected as greater propensity to develop stress-related disorders in humans and animal models, including anxiety and depression. Environmental enrichment (EE) reverses some of the damaging effects of maternal separation in rodent models when provided during peripubescent life, temporally proximal to the separation. It is presently unknown if EE provided outside this critical window can still rescue separation-induced anxiety and neural plasticity. In this report we use a rat model to demonstrate that a single short episode of EE in adulthood reduced anxiety-like behaviour in maternally separated rats. We further show that maternal separation resulted in hypertrophy of dendrites and increase in spine density of basolateral amygdala neurons in adulthood, long after initial stress treatment. This is congruent with prior observations showing centrality of basolateral amygdala hypertrophy in anxiety induced by stress during adulthood. In line with the ability of the adult enrichment to rescue stress-induced anxiety, we show that enrichment renormalized stress-induced structural expansion of the amygdala neurons. These observations argue that behavioural plasticity induced by early adversity can be rescued by environmental interventions much later in life, likely mediated by ameliorating effects of enrichment on basolateral amygdala plasticity. PMID:26836417

  6. Entropy-induced separation of star polymers in porous media

    NASA Astrophysics Data System (ADS)

    Blavats'Ka, V.; von Ferber, C.; Holovatch, Yu.

    2006-09-01

    We present a quantitative picture of the separation of star polymers in a solution where part of the volume is influenced by a porous medium. To this end, we study the impact of long-range-correlated quenched disorder on the entropy and scaling properties of f -arm star polymers in a good solvent. We assume that the disorder is correlated on the polymer length scale with a power-law decay of the pair correlation function g(r)˜r-a . Applying the field-theoretical renormalization group approach we show in a double expansion in ɛ=4-d and δ=4-a that there is a range of correlation strengths δ for which the disorder changes the scaling behavior of star polymers. In a second approach we calculate for fixed space dimension d=3 and different values of the correlation parameter a the corresponding scaling exponents γf that govern entropic effects. We find that γf-1 , the deviation of γf from its mean field value is amplified by the disorder once we increase δ beyond a threshold. The consequences for a solution of diluted chain and star polymers of equal molecular weight inside a porous medium are that star polymers exert a higher osmotic pressure than chain polymers and in general higher branched star polymers are expelled more strongly from the correlated porous medium. Surprisingly, polymer chains will prefer a stronger correlated medium to a less or uncorrelated medium of the same density while the opposite is the case for star polymers.

  7. Entropy-induced separation of star polymers in porous media

    SciTech Connect

    Blavats'ka, V.; Ferber, C. von; Holovatch, Yu.

    2006-09-15

    We present a quantitative picture of the separation of star polymers in a solution where part of the volume is influenced by a porous medium. To this end, we study the impact of long-range-correlated quenched disorder on the entropy and scaling properties of f-arm star polymers in a good solvent. We assume that the disorder is correlated on the polymer length scale with a power-law decay of the pair correlation function g(r){approx}r{sup -a}. Applying the field-theoretical renormalization group approach we show in a double expansion in {epsilon}=4-d and {delta}=4-a that there is a range of correlation strengths {delta} for which the disorder changes the scaling behavior of star polymers. In a second approach we calculate for fixed space dimension d=3 and different values of the correlation parameter a the corresponding scaling exponents {gamma}{sub f} that govern entropic effects. We find that {gamma}{sub f}-1, the deviation of {gamma}{sub f} from its mean field value is amplified by the disorder once we increase {delta} beyond a threshold. The consequences for a solution of diluted chain and star polymers of equal molecular weight inside a porous medium are that star polymers exert a higher osmotic pressure than chain polymers and in general higher branched star polymers are expelled more strongly from the correlated porous medium. Surprisingly, polymer chains will prefer a stronger correlated medium to a less or uncorrelated medium of the same density while the opposite is the case for star polymers.

  8. Injection slot location for boundary-layer control in shock-induced separation

    NASA Technical Reports Server (NTRS)

    Viswanath, P. R.; Sankaran, L.; Sagdeo, P. M.; Narasimha, R.; Prabhu, A.

    1978-01-01

    An experimental investigation of the effect of tangential air injection, when the injection slot is located inside of what would otherwise have been the dead air zone in a separated flow, in controlling shock-induced turbulent boundary layer separation is presented. The experiments were carried out at a free-stream Mach number of 2.5 in the separated flow induced by a compression corner with a 20 deg angle. The observations made were wall static pressures, pitot profiles, and schlieren visualizations of the flow. The results show that the present location for injection is more effective in suppressing boundary-layer separation than the more conventional one, where the slot is located upstream of where separation would occur in the absence of injection.

  9. Influence of Soft Segment Composition on Phase Separated Microstructure of PDMS-Based Multiblock Polyurethane Copolymers.

    NASA Astrophysics Data System (ADS)

    Choi, Taeyi; Weksler, Jadwiga; Padsalgikar, Ajay; Runt, James

    2008-03-01

    Multiblock polyurethane (PU) copolymers with polydimethylsiloxane (PDMS) based soft segments possess intriguing microphase separation behavior and excellent biocompatibility. In this study we investigate the microphase-separated structure of PDMS-PUs with various well-defined soft segment compositions, which is closely connected to the structural and surface properties of these copolymers. The PDMS-PUs are shown to exhibit a three phase, core-shell like morphology. Intra- and intercomponent hydrogen bonding was explored using FTIR spectroscopy and quantitative analysis of hard/soft segment mixing was determined by small-angle X-ray scattering. The presentation will focus on the latest findings, particularly the role of PDMS in controlling the details of the microphase-separated texture.

  10. Control of Shock-Induced Boundary Layer Separation by using Pulsed Plasma Jets

    NASA Astrophysics Data System (ADS)

    Greene, Benton R.; Clemens, Noel T.; Micka, Daniel

    2012-11-01

    Shock-induced turbulent boundary layer separation can have many detrimental effects in supersonic flow including flow instability, fatigue of structural panels, and unstart in supersonic inlets. Pulsed plasma jets (or ``spark jets''), which are characterized by high bandwidth and the ability to direct momentum into the flow, are one promising method of reducing shock-induced separation. The current study is focused on investigating the efficacy of plasma jets to reduce the separated flow induced by a compression ramp in a Mach 3 flow. Three different 3-jet actuator configurations are tested: 20° pitched, 45° pitched, and 22° pitched and 45° skewed. The jets are pulsed at frequencies between 2 kHz and 4 kHz with duty cycles between 5 and 15%. The shock wave is generated using a 20° compression ramp, and the location of the shock-induced separation is visualized using surface oil streak visualization as well as particle image velocimetry. The results of the study show that of the three configurations, the plasma jets pitched at 20° from the streamwise direction cause the greatest reduction in separation, and when pulsed at a frequency of 3.2 kHz and 12% duty cycle can reduce the size of the separation region by up to 40%. This work is supported by AFRL under SBIR contract.

  11. Solidification Behavior of Polymer Solution during Membrane Preparation by Thermally Induced Phase Separation

    PubMed Central

    Ishigami, Toru; Nii, Yoko; Ohmukai, Yoshikage; Rajabzadeh, Saeid; Matsuyama, Hideto

    2014-01-01

    The solidification behavior of poly(vinylidene fluoride) (PVDF) solution during membrane preparation by thermally induced phase separation (TIPS) was investigated. Apparatus newly developed in our laboratory was used to quantitatively measure membrane stiffness during phase separation. In this apparatus, a cooling polymer solution, placed on a stage, is moved upwards and the surface of the polymer solution contacts a sphere attached to the tip of a needle. The displacement of a blade spring attached to the needle is then measured by a laser displacement sensor. Different phase separation modes, such as liquid-liquid (L-L) phase separation and solid-liquid (S-L) phase separation (polymer crystallization) were investigated. In the case of S-L phase separation, the stiffness of the solution surface began to increase significantly just before termination of crystallization. In contrast, L-L phase separation delayed solidification of the solution. This was because mutual contact of the spherulites was obstructed by droplets of polymer-lean phase formed during L-L phase separation. Thus, the solidification rate was slower for the L-L phase separation system than for the S-L phase separation system. PMID:24957124

  12. Active Vector Separation Using Induced Charge Electro-osmosis with Polarizable Obstacle Arrays

    NASA Astrophysics Data System (ADS)

    Sugioka, Hideyuki

    2016-09-01

    Vector separation using obstacle post arrays is promising for various microfluidic applications. Here, we propose a novel active sieve using induced charge electro-osmosis (ICEO). By the multi-physics simulation technique based on the boundary element method combined with a thin electric double-layer approximation, we find that the active sieve having a polarizable post array shows excellent vector separation with dynamic size selectivity owing to the hydrodynamic interactions between the polarizable post array and the target particle. We consider that our separation device is useful for realizing innovative high-throughput biomedical systems with a simple structure.

  13. Shock-induced separation of adiabatic turbulent boundary layers in supersonic axially symmetric internal flow

    NASA Technical Reports Server (NTRS)

    Page, R. J.; Childs, M. E.

    1974-01-01

    An experimental investigation at Mach 4 of shock-induced turbulent boundary layer separation at the walls of axially symmetric flow passages is discussed, with particular emphasis placed on determining the shock strengths required for incipient separation. The shock waves were produced by interchangeable sting-mounted cones placed on the axes of the flow passages and aligned with the freestream flow. The interactions under study simulate those encountered in axially symmetric engine inlets of supersonic aircraft. Knowledges of the shock strengths required for boundary layer separation in inlets is important since for shocks of somewhat greater strength rather drastic alterations in the inlet flow field may occur.

  14. Photo-induced cataphoretic isotope separation. Final report, June 15, 1976-June 15, 1981

    SciTech Connect

    Carruthers, J A

    1981-03-01

    The original studies were undertaken to study the feasibility of radiation-induced cataphoretic separation. This part of the work is concerned with laser-induced cataphoretic separation in neon using a He-Ne 6328A laser. The basic concept of radiation-induced caphoretic isotope separation is based on the preferential excitation of one isotope with the result that one isotope is more readily ionized, and relatively more of its ions move toward the cathode in the dc discharge. For the later part of the work a second radiation source was added, a helical Ne/sup 20/ radiation lamp. Radiation-induced cataphoretic isotope separation has not been observed. Selective excitation has been achieved by both the He-Ne/sup 20/ 6328A laser and the Ne/sup 20/ helical radiation lamp in spite of the fact that the isotope shift is comprable with Doppler-broadened linewidths. Collisional excitation exchange between the Ne/sup 20/ and Ne/sup 22/ atoms does not appear to be a problem for the neon partial pressure range involved. The population of the 3S/sub 2/ and 2p/sub 4/ laser levels (6328A) are apparently too low to offer reasonable expectation of inducing observable cataphoretic isotope separation by means of the 6328A laser radiation, even with the high detection sensitivity of the scanning Fabry-Perot spectrometer sytem. The use of the additional radiation source in the form of a helical Ne/sup 20/ radiation lamp has not improved the effectiveness of the laser 6328A laser. It has become clear from these experiments, however, that for isotope separation in neon it is well to concentrate on using radiation sources that interact mainly with the ls population.

  15. Microphase-contrast x-ray computed tomography for basic biomedical study at SPring-8

    NASA Astrophysics Data System (ADS)

    Wu, Jin; Takeda, Tohoru; Lwin, Thet-Thet; Koyama, Ichiro; Momose, Atsushi; Fujii, Akiko; Hamaishi, Yoshitaka; Kuroe, Taichi; Yuasa, Tetsuya; Suzuki, Yoshio; Akatsuka, Takao

    2004-10-01

    Micro-phase-contrast X-ray computed tomography with an X-ray interferometer (micro-phase-contrast CT) is in operation to obtain high spatial resolution images of less than 0.01 mm at the undulator beam-line 20XU of SPring-8, Japan, and we applied micro-phase-contrast CT to observe the organs of rats and hamsters. The excised kidney and spleen fixed by formalin were imaged. The fine inner-structures such as vessels, glomeruli of kidney and white and red pulps of spleen were visualized clearly about 0.01-mm spatial resolutions without using contrast agent or staining procedure. The results were very similar to those by optical microscopic images with 20-fold magnification. These results suggest that the micro-phase tomography might be a useful tool for various biomedical researches.

  16. Magnetic microphases in chrome-spinels from alpine-type ultramafic rocks, Central Urals

    NASA Astrophysics Data System (ADS)

    Sherendo, T. A.; Mitrofanov, V. Ya.; Martyshko, P. S.; Vazhenin, V. A.; Pamyatnykh, L. A.; Alekseev, A. V.

    2014-05-01

    The ore and accessory chrome-spinels from metamorphosed dunites of the Cr-bearing Klyuchevskoi alpine-type ultramafic massif are studied. As a result of use of thermomagnetic analysis in the range of 4-900 K, magnetic resonance spectroscopy, and magnetic-force microscopy, secondary magnetic Fe3+-enriched microphases chaotically distributed in the primary nonmagnetic mineral were revealed for the first time in accessory chrome-spinels. It was established that the metamorphosed accessory chrome-spinels produce the magnetic properties of the host rocks and the primary nonmagnetic chrome-spinels forming ore bodies remains almost unaltered. This originates the contrast of magnetic properties between the ore body and host rocks and provides the geomagnetic anomaly in the ore-hosting zone.

  17. An unconstrained DFT approach to microphase formation and application to binary Gaussian mixtures.

    PubMed

    Pini, Davide; Parola, Alberto; Reatto, Luciano

    2015-07-21

    The formation of microphases in systems of particles interacting by repulsive, bounded potentials is studied by means of density-functional theory (DFT) using a simple, mean-field-like form for the free energy which has already been proven accurate for this class of soft interactions. In an effort not to constrain the configurations available to the system, we do not make any assumption on the functional form of the density profile ρ(r), save for its being periodic. We sample ρ(r) at a large number of points in the unit cell and minimize the free energy with respect to both the values assumed by ρ(r) at these points and the lattice vectors which identify the Bravais lattice. After checking the accuracy of the method by applying it to a one-component generalized exponential model (GEM) fluid with pair potential ϵexp[ - (r/R)(4)], for which extensive DFT and simulation results are already available, we turn to a binary mixture of Gaussian particles which some time ago was shown to support microphase formation [A. J. Archer, C. N. Likos, and R. Evans, J. Phys.: Condens. Matter 16, L297 (2004)], but has not yet been investigated in detail. The phase diagram which we obtain, that supersedes the tentative one proposed by us in a former study [M. Carta, D. Pini, A. Parola, and L. Reatto, J. Phys.: Condens. Matter 24, 284106 (2012)], displays cluster, tubular, and bicontinuous phases similar to those observed in block copolymers or oil/water/surfactant mixtures. Remarkably, bicontinuous phases occupy a rather large portion of the phase diagram. We also find two non-cubic phases, in both of which one species is preferentially located inside the channels left available by the other, forming helices of alternating chirality. The features of cluster formation in this mixture and in GEM potentials are also compared. PMID:26203044

  18. An unconstrained DFT approach to microphase formation and application to binary Gaussian mixtures

    NASA Astrophysics Data System (ADS)

    Pini, Davide; Parola, Alberto; Reatto, Luciano

    2015-07-01

    The formation of microphases in systems of particles interacting by repulsive, bounded potentials is studied by means of density-functional theory (DFT) using a simple, mean-field-like form for the free energy which has already been proven accurate for this class of soft interactions. In an effort not to constrain the configurations available to the system, we do not make any assumption on the functional form of the density profile ρ(r), save for its being periodic. We sample ρ(r) at a large number of points in the unit cell and minimize the free energy with respect to both the values assumed by ρ(r) at these points and the lattice vectors which identify the Bravais lattice. After checking the accuracy of the method by applying it to a one-component generalized exponential model (GEM) fluid with pair potential ɛexp[ - (r/R)4], for which extensive DFT and simulation results are already available, we turn to a binary mixture of Gaussian particles which some time ago was shown to support microphase formation [A. J. Archer, C. N. Likos, and R. Evans, J. Phys.: Condens. Matter 16, L297 (2004)], but has not yet been investigated in detail. The phase diagram which we obtain, that supersedes the tentative one proposed by us in a former study [M. Carta, D. Pini, A. Parola, and L. Reatto, J. Phys.: Condens. Matter 24, 284106 (2012)], displays cluster, tubular, and bicontinuous phases similar to those observed in block copolymers or oil/water/surfactant mixtures. Remarkably, bicontinuous phases occupy a rather large portion of the phase diagram. We also find two non-cubic phases, in both of which one species is preferentially located inside the channels left available by the other, forming helices of alternating chirality. The features of cluster formation in this mixture and in GEM potentials are also compared.

  19. A review of the use of vortex generators for mitigating shock-induced separation

    NASA Astrophysics Data System (ADS)

    Titchener, Neil; Babinsky, Holger

    2015-09-01

    This article reviews research into the potential of vortex generators to mitigate shock-induced separation. Studies ranging from those conducted in the early post-war era to those performed recently are discussed. On the basis of the investigations described in this report, it is clear that vortex generators can alleviate shock-induced boundary layer separation. Yet, it will be shown that their potential and efficiency varies considerably in practical applications. Much more success is reported in transonic test cases compared to separation induced in purely supersonic interactions. Under a variety of flow conditions, the best performance is achieved with vortex generators with a height of roughly half the boundary layer thickness and a shape similar to a swept vane. Notwithstanding this, vortex generator performance is not as consistent as it is in low-speed applications. Further work is required before vortex generators can be implemented into the design process for eliminating shock-induced separation on transonic wings and in supersonic inlets.

  20. Coping Repertoires of Families Adapting to Prolonged War-Induced Separations

    ERIC Educational Resources Information Center

    McCubbin, Hamilton I.; And Others

    1976-01-01

    Coping with husband absence, an enigma of family life in the military, stimulated questions as to how wives endure hardships engendered by war-induced separations. The investigators studied the adjustment of 47 families of servicemen missing in action. Findings are explained in terms of psychological and sociological theories of coping. (Author)

  1. Prednisolone-induced predisposition to femoral head separation and the accompanying plasma protein changes in chickens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Femoral head separation (FHS) is an idiopathic bone problem that causes lameness and production losses in commercial poultry. In a model of prednisolone induced susceptibility to FHS, the changes in plasma proteins and peptides were analyzed to find possible biomarkers. Plasma from control and FHS-s...

  2. Phase separation induced molecular fractionation of gum arabic--sugar beet pectin systems.

    PubMed

    Mao, Peng; Zhao, Meng; Zhang, Fan; Fang, Yapeng; Phillips, Glyn O; Nishinari, Katsuyoshi; Jiang, Fatang

    2013-10-15

    This paper investigates the phase separation and phase separation-induced fractionation of gum arabic (GA)/sugar beet pectin (SBP) mixed solutions. A phase diagram, including cloud and binodal curves, was established by visual observation and phase composition analysis. The deviation of the binodal curve from the cloud curve was a result of phase separation-induced fractionation of polydisperse GA and SBP molecules. Fractionation of GA increased the content of arabinogalactan-protein complex (AGP) from ca. 13% to 27%. The fractionated GA (FGA) showed improved emulsifying functionality, whereas the fractionated SBP (FSBP) had a reduced emulsifying functionality. The changes in emulsifying efficiency can be explained by interfacial adsorption behaviors at the oil-water interface as indicated by interfacial tension measurements. PMID:23987401

  3. Separation and characterization of rat kidney isometallothioneins induced by exposure to inorganic mercury.

    PubMed

    Morcillo, M A; Santamaría, J

    1993-11-26

    High-performance liquid chromatography (HPLC) was applied to the separation of metallothionein (MT) isoforms from different tissues from a variety of eukaryotic species. Recently we reported an analytical method for 203Hg-metallothionein, which detects the radioisotope bound to each iso-MT after separation by HPLC on a size-exclusion column coupled with on-line radioactivity flow detection. The MTs can be separated as distinct isoprotein peaks by elution with alkaline buffer solution owing to cation-exchange chromatographic action. In the present work, renal MT from rats exposed to inorganic mercury was separated into four peaks by UV and 203Hg detection. Moreover, it was resolved into four components by non-denaturing polyacrylamide gel electrophoresis. The two major components correspond to MT-1 and MT-2, which were characterized by amino acid analysis. Finally, Hg induces and binds to both iso-MTs. PMID:8308096

  4. Laser-induced separation of hydrogen isotopes in the liquid phase

    DOEpatents

    Freund, Samuel M.; Maier, II, William B.; Beattie, Willard H.; Holland, Redus F.

    1980-01-01

    Hydrogen isotope separation is achieved by either (a) dissolving a hydrogen-bearing feedstock compound in a liquid solvent, or (b) liquefying a hydrogen-bearing feedstock compound, the liquid phase thus resulting being kept at a temperature at which spectral features of the feedstock relating to a particular hydrogen isotope are resolved, i.e., a clear-cut isotope shift is delineated, irradiating the liquid phase with monochromatic radiation of a wavelength which at least preferentially excites those molecules of the feedstock containing a first hydrogen isotope, inducing photochemical reaction in the excited molecules, and separating the reaction product containing the first isotope from the liquid phase.

  5. Separation of radiation induced and process induced lateral non-uniformities

    NASA Astrophysics Data System (ADS)

    Xapsos, M. A.; Freitag, R. K.; Dozier, C. M.; Brown, D. B.; Summers, G. P.

    1990-12-01

    Fast measurements of channel current versus gate voltage (I-V) were performed on irradiated MOSFETs as a function of time and temperature after pulsed proton irradiation. Stretchout of the I-V curves due to lateral nonuniformities (LNUs) in the hole distribution in the oxide is shown to be experimentally separable from stretchout due to interface traps. The stretchout due to LNUs is then shown to consist of two experimentally separable components-one due to the random production of holes by the radiation, and one due to the random distribution of hole traps in the oxide. This suggests an entirely new approach for evaluating the quality of oxides in terms of the microscopic uniformity of the processing.

  6. CO-laser-induced photochemical reaction of UF6 with HCl for the isotope separation of uranium hexafluoride

    NASA Astrophysics Data System (ADS)

    Ding, Hong-Bin; Shen, Z. Y.; Zhang, Cun H.

    1993-05-01

    In this paper, we report the results of CO-laser induced photochemical reaction of UF6 with HCl for the isotope separation of uranium hexafluoride, we also discussed that the molecular collision inducing V-T, V-V relaxation process affects on the selectivity of the isotope separation. The obtained quantum coefficiency of the reaction is about 0.34.

  7. Synthesis of semicrystalline nanocapsular structures obtained by Thermally Induced Phase Separation in nanoconfinement

    PubMed Central

    Torino, Enza; Aruta, Rosaria; Sibillano, Teresa; Giannini, Cinzia; Netti, Paolo A.

    2016-01-01

    Phase separation of a polymer solution exhibits a peculiar behavior when induced in a nanoconfinement. The energetic constraints introduce additional interactions between the polymer segments that reduce the number of available configurations. In our work, this effect is exploited in a one-step strategy called nanoconfined-Thermally Induced Phase Separation (nc-TIPS) to promote the crystallization of polymer chains into nanocapsular structures of controlled size and shell thickness. This is accomplished by performing a quench step of a low-concentrated PLLA-dioxane-water solution included in emulsions of mean droplet size <500 nm acting as nanodomains. The control of nanoconfinement conditions enables not only the production of nanocapsules with a minimum mean particle diameter of 70 nm but also the tunability of shell thickness and its crystallinity degree. The specific properties of the developed nanocapsular architectures have important implications on release mechanism and loading capability of hydrophilic and lipophilic payload compounds. PMID:27604818

  8. Synthesis of semicrystalline nanocapsular structures obtained by Thermally Induced Phase Separation in nanoconfinement.

    PubMed

    Torino, Enza; Aruta, Rosaria; Sibillano, Teresa; Giannini, Cinzia; Netti, Paolo A

    2016-01-01

    Phase separation of a polymer solution exhibits a peculiar behavior when induced in a nanoconfinement. The energetic constraints introduce additional interactions between the polymer segments that reduce the number of available configurations. In our work, this effect is exploited in a one-step strategy called nanoconfined-Thermally Induced Phase Separation (nc-TIPS) to promote the crystallization of polymer chains into nanocapsular structures of controlled size and shell thickness. This is accomplished by performing a quench step of a low-concentrated PLLA-dioxane-water solution included in emulsions of mean droplet size <500 nm acting as nanodomains. The control of nanoconfinement conditions enables not only the production of nanocapsules with a minimum mean particle diameter of 70 nm but also the tunability of shell thickness and its crystallinity degree. The specific properties of the developed nanocapsular architectures have important implications on release mechanism and loading capability of hydrophilic and lipophilic payload compounds. PMID:27604818

  9. Site-selective nanoscale-polymerization of pyrrole on gold nanoparticles via plasmon induced charge separation

    NASA Astrophysics Data System (ADS)

    Takahashi, Y.; Furukawa, Y.; Ishida, T.; Yamada, S.

    2016-04-01

    We proposed a nanoscale oxidative polymerization method which enables site-selective deposition on the surface of gold nanoparticles (AuNPs) combined with TiO2 by using plasmon induced charge separation (PICS) under visible-to-near infrared (IR) light irradiation. The method also revealed that the anodic site of PICS was located at the surface of AuNPs.We proposed a nanoscale oxidative polymerization method which enables site-selective deposition on the surface of gold nanoparticles (AuNPs) combined with TiO2 by using plasmon induced charge separation (PICS) under visible-to-near infrared (IR) light irradiation. The method also revealed that the anodic site of PICS was located at the surface of AuNPs. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01531j

  10. Phase separation of polymer mixtures induced by light and heat: a comparative study by light scattering

    NASA Astrophysics Data System (ADS)

    Ochi, Yuki; Kawakubo, Rie; Van-Pham, Dan-Thuy; Kitamura, Yuki; Nakanishi, Hideyuki; Norisuye, Tomohisa; Tran-Cong-Miyata, Qui

    2015-12-01

    Phase separation of binary blends composed of a polystyrene derivative (PS) and poly (vinyl methyl ether) (PVME) with a lower critical solution temperature (LCST) was experimentally induced by two different methods: heating and UV light irradiation. Using laser light scattering combined with the temperature jump (T-jump) technique, it was demonstrated that in the case of heating, the mixture undergoes phase separation via the nucleation-and-growth (NG) and the spinodal decomposition (SN) processes under shallow and deep quenches, respectively. Particularly, the crossover from the spinodal decomposition to the nucleation-and-growth process was observed at long time under a deep T-jump by light-scattering experiments. On the other hand, in the photo-crosslink case, the PS/PVME blends undergo a nucleation-and-growth process upon irradiation with weak light intensity, whereas the mixture exhibits the spinodal decomposition under irradiation with strong light intensity. From the analysis of the light-scattering data obtained for the blends under the photo-crosslink, the kinetic data reveal the suppression of morphologies having large characteristic length scales. This feature clearly differs from the phase separation induced by heating where no mode-suppression process was observed. It was also found that distribution of the characteristic length scales (the regularity) of the morphology becomes narrow as the phase separation proceeds for reacting blends, whereas it becomes broader as the phase separation proceeds by heating, revealing the important roles of reaction in the suppression of fluctuations with long wavelengths. These experimental results establish a method to control the length scales and the regularity of the morphology of polymer blends by chemical reaction.

  11. Milk Thistle Extract and Silymarin Inhibit Lipopolysaccharide Induced Lamellar Separation of Hoof Explants in Vitro

    PubMed Central

    Reisinger, Nicole; Schaumberger, Simone; Nagl, Veronika; Hessenberger, Sabine; Schatzmayr, Gerd

    2014-01-01

    The pathogenesis of laminitis is not completely identified and the role of endotoxins (lipopolysaccharides, LPS) in this process remains unclear. Phytogenic substances, like milk thistle (MT) and silymarin, are known for their anti-inflammatory and antioxidant properties and might therefore have the potential to counteract endotoxin induced effects on the hoof lamellar tissue. The aim of our study was to investigate the influence of endotoxins on lamellar tissue integrity and to test if MT and silymarin are capable of inhibiting LPS-induced effects in an in vitro/ex vivo model. In preliminary tests, LPS neutralization efficiency of these phytogenics was determined in an in vitro neutralization assay. Furthermore, tissue explants gained from hooves of slaughter horses were tested for lamellar separation after incubation with different concentrations of LPS. By combined incubation of explants with LPS and either Polymyxin B (PMB; positive control), MT or silymarin, the influence of these substances on LPS-induced effects was assessed. In the in vitro neutralization assay, MT and silymarin reduced LPS concentrations by 64% and 75%, respectively, in comparison PMB reduced 98% of the LPS concentration. In hoof explants, LPS led to a concentration dependent separation. Accordantly, separation force was significantly decreased by 10 µg/mL LPS. PMB, MT and silymarin could significantly improve tissue integrity of explants incubated with 10 µg/mL LPS. This study showed that LPS had a negative influence on the structure of hoof explants in vitro. MT and silymarin reduced endotoxin activity and inhibited LPS-induced effects on the lamellar tissue. Hence, MT and silymarin might be used to support the prevention of laminitis and should be further evaluated for this application. PMID:25290524

  12. Milk thistle extract and silymarin inhibit lipopolysaccharide induced lamellar separation of hoof explants in vitro.

    PubMed

    Reisinger, Nicole; Schaumberger, Simone; Nagl, Veronika; Hessenberger, Sabine; Schatzmayr, Gerd

    2014-10-01

    The pathogenesis of laminitis is not completely identified and the role of endotoxins (lipopolysaccharides, LPS) in this process remains unclear. Phytogenic substances, like milk thistle (MT) and silymarin, are known for their anti-inflammatory and antioxidant properties and might therefore have the potential to counteract endotoxin induced effects on the hoof lamellar tissue. The aim of our study was to investigate the influence of endotoxins on lamellar tissue integrity and to test if MT and silymarin are capable of inhibiting LPS-induced effects in an in vitro/ex vivo model. In preliminary tests, LPS neutralization efficiency of these phytogenics was determined in an in vitro neutralization assay. Furthermore, tissue explants gained from hooves of slaughter horses were tested for lamellar separation after incubation with different concentrations of LPS. By combined incubation of explants with LPS and either Polymyxin B (PMB; positive control), MT or silymarin, the influence of these substances on LPS-induced effects was assessed. In the in vitro neutralization assay, MT and silymarin reduced LPS concentrations by 64% and 75%, respectively, in comparison PMB reduced 98% of the LPS concentration. In hoof explants, LPS led to a concentration dependent separation. Accordantly, separation force was significantly decreased by 10 µg/mL LPS. PMB, MT and silymarin could significantly improve tissue integrity of explants incubated with 10 µg/mL LPS. This study showed that LPS had a negative influence on the structure of hoof explants in vitro. MT and silymarin reduced endotoxin activity and inhibited LPS-induced effects on the lamellar tissue. Hence, MT and silymarin might be used to support the prevention of laminitis and should be further evaluated for this application. PMID:25290524

  13. Maternal separation fails to render animals more susceptible to methamphetamine-induced conditioned place preference.

    PubMed

    Faure, Jacqueline; Stein, Dan J; Daniels, William

    2009-12-01

    The maternal separation (MS) paradigm is an animal model that has been successfully used to study the long term effects of child abuse and neglect. Experiments showed that animals subjected to trauma and stress early in life display behavioural, endocrinological and growth factor abnormalities at a later stage in life, results that mirrored clinical conditions. It is apparent that adverse events early in life may affect the development and maturation of the brain negatively. The purpose of the present study was to investigate whether the abnormal brain development occurring in separated animals would also enhance the development of a preference for psychostimulant drug usage. Rats were subjected to maternal deprivation and further exposed to methamphetamine-induced conditioned place preference (CPP) which primarily measures drug reward (ventral striatum) learning and memory. Apomorphine-induced locomotor activity was also assessed to investigate the effects of methamphetamine on the dorsal (primarily locomotor activity) striatal dopaminergic system. We found that four consecutive injections of methamphetamine resulted in CPP behaviour 24 h after the 4th injection. A further four injections yielded similar CPP results and this effect lasted for at least 7 days until the third CPP assessment. These animals also had decreased ACTH and corticosterone secretions, but the prolactin levels were increased. Prior exposure to maternal separation did not have any effect on the CPP test. The ACTH and corticosterone secretions were also similarly reduced. However maternal separation decreased the release of prolactin and this reduction was not evident in the separated group that received methamphetamine. There was no significant difference in the apomorphine-induced locomotor activity of normally reared animals whether they received methamphetamine or saline. Interestingly there was a significant difference in locomotor activity between the two groups of animals that were

  14. Facile synthesis of gradient mesoporous carbon monolith based on polymerization-induced phase separation

    NASA Astrophysics Data System (ADS)

    Xu, Shunjian; Luo, Yufeng; Zhong, Wei; Xiao, Zonghu; Luo, Yongping; Ou, Hui; Zhao, Xing-Zhong

    2014-06-01

    In this paper, a gradient mesoporous carbon (GMC) monolith derived from the mixtures of phenolic resin (PF) and ethylene glycol (EG) was prepared by a facile route based on polymerization-induced phase separation under temperature gradient (TG). A graded biphasic structure of PF-rich and EG-rich phases was first formed in preform under a TG, and then the preform was pyrolyzed to obtain the GMC monolith. The TG is mainly induced by the thermal resistance of the preferential phase separation layer at high temperature region. The pore structure of the monolith changes gradually along the TG direction. When the TG varies from 58°C to 29°C, the pore size, apparent porosity and specific surface area of the monolith range respectively from 18 nm to 83 nm, from 32% to 39% and from 140.5 m2/g to 515.3 m2/g. The gradient porous structure of the monolith is inherited from that of the preform, which depends on phase separation under TG in the resin mixtures. The pyrolysis mainly brings about the contraction of the pore size and wall thickness as well as the transformation of polymerized PF into glassy carbon.

  15. Chiral separation of benzoporphyrin derivative mono- and diacids by laser induced fluorescence-capillary electrophoresis.

    PubMed

    Peng, Xuejun; Sternberg, Ethan; Dolphin, David

    2002-01-01

    A method for the separation of benzoporphyrin derivative mono- and diacid (BPDMA, BPDDA) enantiomers by laser induced fluorescence-capillary electrophoresis (LIF-CE) has been developed. By using 300 mM borate buffer, pH 9.2, 25 mM sodium cholate and 10% acetronitrile as electrolyte, +10 kV electrokinetic sampling injection of 2 s and an applied +20 kV voltage across the ends of a 37 cm capillary (30 cm to the detector, 50 microm ID), all six BPD stereoisomers were baseline-separated within 20 min. Formation constants, free electrophoretic and complexation mobilities with borate and cholate were determined based on dynamic complexation capillary electrophoresis theory. The BPD enantiomers can be quantitatively determined in the range of 10(-2)-10(-5) mg mL(-1). The correlation coefficients (r2) of the least-squares linear regression analysis of the BPD enantiomers are in the range of 0.9914-0.9997. Their limits of detection are 2.18-3.5 x 10(-3) mg mL(-1). The relative standard deviations for the separation were 2.90-4.64% (n = 10). In comparison with high-performance liquid chromatography (HPLC), CE has better resolution and efficiency. This separation method was successfully applied to the BPD enantiomers obtained from a matrix of bovine serum and from liposomally formulated material as well as from studies with rat, dog and human microsomes. PMID:11824627

  16. Chronic Exposure to Particulate Chromate Induces Premature Centrosome Separation and Centriole Disengagement in Human Lung Cells.

    PubMed

    Martino, Julieta; Holmes, Amie L; Xie, Hong; Wise, Sandra S; Wise, John Pierce

    2015-10-01

    Particulate hexavalent chromium (Cr(VI)) is a well-established human lung carcinogen. Lung tumors are characterized by structural and numerical chromosome instability. Centrosome amplification is a phenotype commonly found in solid tumors, including lung tumors, which strongly correlates with chromosome instability. Human lung cells exposed to Cr(VI) exhibit centrosome amplification but the underlying phenotypes and mechanisms remain unknown. In this study, we further characterize the phenotypes of Cr(VI)-induced centrosome abnormalities. We show that Cr(VI)-induced centrosome amplification correlates with numerical chromosome instability. We also show chronic exposure to particulate Cr(VI) induces centrosomes with supernumerary centrioles and acentriolar centrosomes in human lung cells. Moreover, chronic exposure to particulate Cr(VI) affects the timing of important centriolar events. Specifically, chronic exposure to particulate Cr(VI) causes premature centriole disengagement in S and G2 phase cells. It also induces premature centrosome separation in interphase. Altogether, our data suggest that chronic exposure to particulate Cr(VI) targets the protein linkers that hold centrioles together. These centriolar linkers are important for key events of the centrosome cycle and their premature disruption might underlie Cr(VI)-induced centrosome amplification. PMID:26293554

  17. Soft-shear induced phase-separated nanoparticle string-structures in polymer thin films.

    PubMed

    Zhang, Ren; Lee, Bongjoon; Bockstaller, Michael R; Al-Enizi, Abdullah M; Elzatahry, Ahmed; Berry, Brian C; Karim, Alamgir

    2016-04-12

    Application of shear stress has been shown to unidirectionally orient the microstructures of block copolymers and polymer blends. In the present work, we study the phase separation of a novel nanoparticle (NP)-polymer blend thin film system under shear using a soft-shear dynamic zone annealing (DZA-SS) method. The nanoparticles are densely grafted with polymer chains of chemically dissimilar composition from the matrix polymer, which induces phase separation upon thermal annealing into concentrated nanoparticle domains. We systematically examine the influence of DZA-SS translation speed and thus the effective shear rate on nanoparticle domain elongation and compare this with the counterpart binary polymer blend behavior. Unidirectionally aligned nanoparticle string-domains are fabricated in the presence of soft-shear in confined thin film geometry. We expect this DZA-SS method to be applicable to various NP-polymer blends towards unidirectionally aligned nanoparticle structures, which are important to functional nanoparticle structure fabrication. PMID:26814827

  18. Separation of photo-induced radical pair in cryptochrome to a functionally critical distance

    NASA Astrophysics Data System (ADS)

    Solov'yov, Ilia A.; Domratcheva, Tatiana; Schulten, Klaus

    2014-01-01

    Cryptochrome is a blue light receptor that acts as a sensor for the geomagnetic field and assists many animals in long-range navigation. The magnetoreceptor function arises from light-induced formation of a radical pair through electron transfer between a flavin cofactor (FAD) and a triad of tryptophan residues. Here, this electron transfer is investigated by quantum chemical and classical molecular dynamics calculations. The results reveal how sequential electron transfer, assisted by rearrangement of polar side groups in the cryptochrome interior, can yield a FAD-Trp radical pair state with the FAD and Trp partners separated beyond a critical distance. The large radical pair separation reached establishes cryptochrome's sensitivity to the geomagnetic field through weakening of distance-dependent exchange and dipole-dipole interactions. It is estimated that the key secondary electron transfer step can overcome in speed both recombination (electron back-transfer) and proton transfer involving the radical pair reached after primary electron transfer.

  19. Fabrication of triple layered vascular scaffolds by combining electrospinning, braiding, and thermally induced phase separation

    NASA Astrophysics Data System (ADS)

    Mi, Hao-Yang; Jing, Xin; Yu, Emily; McNulty, Jason; Turng, Lih-Sheng

    2015-12-01

    Triple layered small diameter vascular scaffolds, which consisted of thermoplastic polyurethane (TPU) and silk, were fabricated in this study for the first time by combining electrospinning, braiding, and thermally induced phase separation methods. These novel vascular scaffolds, which possess three layers of different structures (nanofibrous inner layer, woven silk filament middle layer, and porous outer layer) have a desired toe region in the tensile test and sufficient suture retention and burst pressure for vascular graft applications. The endothelia cell culture tests showed that a cell layer could form on the inner surface of a scaffold with high cell viability. Furthermore, the cells showed favorable morphology on the scaffold.

  20. High-purity separation of cancer cells by optically induced dielectrophoresis.

    PubMed

    Chen, Hsiu-Hsiang; Lin, Mai-Wei; Tien, Wan-Ting; Lai, Chin-Pen; Weng, Kuo-Yao; Ko, Ching-Huai; Lin, Chun-Chuan; Chen, Jyh-Chern; Tiao, Kuo-Tung; Chen, Tse-Ching; Chen, Shin-Cheh; Yeh, Ta-Sen; Cheng, Chieh-Fang

    2014-04-01

    Detecting and concentrating cancer cells in peripheral blood is of great importance for cancer diagnosis and prognosis. Optically induced dielectrophoresis (ODEP) can achieve high resolution and low optical intensities, and the electrode pattern can be dynamically changed by varied light patterns. By changing the projected light pattern, it is demonstrated to separate high-purity gastric cancer cell lines. Traditionally, the purity of cancer cell isolation by negative selection is 0.9% to 10%; by positive selection it is 50% to 62%. An ODEP technology is proposed to enhance the purity of cancer cell isolation to about 77%. PMID:24723112

  1. Continuous particle separation using pressure-driven flow-induced miniaturizing free-flow electrophoresis (PDF-induced μ-FFE).

    PubMed

    Jeon, Hyungkook; Kim, Youngkyu; Lim, Geunbae

    2016-01-01

    In this paper, we introduce pressure-driven flow-induced miniaturizing free-flow electrophoresis (PDF-induced μ-FFE), a novel continuous separation method. In our separation system, the external flow and electric field are applied to particles, such that particle movement is affected by pressure-driven flow, electroosmosis, and electrophoresis. We then analyzed the hydrodynamic drag force and electrophoretic force applied to the particles in opposite directions. Based on this analysis, micro- and nano-sized particles were separated according to their electrophoretic mobilities with high separation efficiency. Because the separation can be achieved in a simple T-shaped microchannel, without the use of internal electrodes, it offers the advantages of low-cost, simple device fabrication and bubble-free operation, compared with conventional μ-FFE methods. Therefore, we expect the proposed separation method to have a wide range of filtering/separation applications in biochemical analysis. PMID:26819221

  2. Continuous particle separation using pressure-driven flow-induced miniaturizing free-flow electrophoresis (PDF-induced μ-FFE)

    PubMed Central

    Jeon, Hyungkook; Kim, Youngkyu; Lim, Geunbae

    2016-01-01

    In this paper, we introduce pressure-driven flow-induced miniaturizing free-flow electrophoresis (PDF-induced μ-FFE), a novel continuous separation method. In our separation system, the external flow and electric field are applied to particles, such that particle movement is affected by pressure-driven flow, electroosmosis, and electrophoresis. We then analyzed the hydrodynamic drag force and electrophoretic force applied to the particles in opposite directions. Based on this analysis, micro- and nano-sized particles were separated according to their electrophoretic mobilities with high separation efficiency. Because the separation can be achieved in a simple T-shaped microchannel, without the use of internal electrodes, it offers the advantages of low-cost, simple device fabrication and bubble-free operation, compared with conventional μ-FFE methods. Therefore, we expect the proposed separation method to have a wide range of filtering/separation applications in biochemical analysis. PMID:26819221

  3. Continuous particle separation using pressure-driven flow-induced miniaturizing free-flow electrophoresis (PDF-induced μ-FFE)

    NASA Astrophysics Data System (ADS)

    Jeon, Hyungkook; Kim, Youngkyu; Lim, Geunbae

    2016-01-01

    In this paper, we introduce pressure-driven flow-induced miniaturizing free-flow electrophoresis (PDF-induced μ-FFE), a novel continuous separation method. In our separation system, the external flow and electric field are applied to particles, such that particle movement is affected by pressure-driven flow, electroosmosis, and electrophoresis. We then analyzed the hydrodynamic drag force and electrophoretic force applied to the particles in opposite directions. Based on this analysis, micro- and nano-sized particles were separated according to their electrophoretic mobilities with high separation efficiency. Because the separation can be achieved in a simple T-shaped microchannel, without the use of internal electrodes, it offers the advantages of low-cost, simple device fabrication and bubble-free operation, compared with conventional μ-FFE methods. Therefore, we expect the proposed separation method to have a wide range of filtering/separation applications in biochemical analysis.

  4. Evidence for photo-induced charge separation between dye molecules adsorbed to aluminium oxide surfaces

    PubMed Central

    Cappel, Ute B.; Moia, Davide; Bruno, Annalisa; Vaissier, Valerie; Haque, Saif A.; Barnes, Piers R. F.

    2016-01-01

    Excited state dynamics and photo-induced charge transfer of dye molecules have been widely studied due to their relevance for organic and dye-sensitised solar cells. Herein, we present a femtosecond transient absorption spectroscopy study of the indolene dye D131 when adsorbed to inert Al2O3 substrates for different surface concentration of the dye. Surprisingly, we find that at high surface concentrations, the first singlet excited state of the dye is converted into a new state with an efficiency of about 80%. We assign the absorption features of this state to the oxidised dye and discuss the possibility of photo-induced charge separation between neighboring dye molecules. Our study is the first to show that this process can be highly efficient without the use of donor and acceptor molecules of different chemical structures. PMID:26891851

  5. Evidence for photo-induced charge separation between dye molecules adsorbed to aluminium oxide surfaces

    NASA Astrophysics Data System (ADS)

    Cappel, Ute B.; Moia, Davide; Bruno, Annalisa; Vaissier, Valerie; Haque, Saif A.; Barnes, Piers R. F.

    2016-02-01

    Excited state dynamics and photo-induced charge transfer of dye molecules have been widely studied due to their relevance for organic and dye-sensitised solar cells. Herein, we present a femtosecond transient absorption spectroscopy study of the indolene dye D131 when adsorbed to inert Al2O3 substrates for different surface concentration of the dye. Surprisingly, we find that at high surface concentrations, the first singlet excited state of the dye is converted into a new state with an efficiency of about 80%. We assign the absorption features of this state to the oxidised dye and discuss the possibility of photo-induced charge separation between neighboring dye molecules. Our study is the first to show that this process can be highly efficient without the use of donor and acceptor molecules of different chemical structures.

  6. Pattern Polymerization-Induced Phase Separation in a Polymer-Dispersed Liquid Crystal System

    NASA Astrophysics Data System (ADS)

    Kyu, Thein

    2002-03-01

    Liquid crystal (LC)/polymer composite films have gained attention increasingly due to their applications in flat panel displays and shutters. Photopolymerization is a preferred method to produce LC/polymer composite films from mixtures of reactive monomers and LCs. On the basis of the combined Flory-Huggins free energy for isotropic mixing and Maier-Saupe free energy for nematic ordering along with the elastic free energy of the network, phase diagrams have been established by solving self-consistently. A theoretical simulation has been modeled by incorporating the kinetics of crosslinking reaction into the time-dependent Ginzburg-Landau (TDGL-model C) equations to elucidate the emergence of nematic domains during photopolymerization induced phase separation in electrically switchable holographic polymer-dispersed liquid crystals (H-PDLC). The simulated morphological patterns in the concentration and orientation order parameter fields show discrete layers of liquid crystal droplets alternating periodically with polymer network-rich layers. Furthermore, we recognized the potential for producing electrically tunable microlens from PDLC systems through pattern-photopolymerization-induced phase separation by means of the interference of two horizontal waves and two vertical waves. Our simulation revealed that the emerged LC microlens are of the order of a few hundred nanometers. These LC microlens are not only uniformed in size, but also form in regular arrays, reminiscence of the compound eyes found in flies, ants, and wasps. Supported by ALCOM, NSF DMR 99-03519, and OBR.

  7. Properties of triple shape memory composites prepared via polymerization-induced phase separation.

    PubMed

    Torbati, Amir H; Nejad, Hossein Birjandi; Ponce, Mileysa; Sutton, James P; Mather, Patrick T

    2014-05-01

    Research in the field of shape memory polymers has recently witnessed the introduction of increasing complexity of material response, including such phenomena as triple/multishape behavior, temperature memory, and reversible actuation. Ordinarily, such complexity in physical behaviour is achieved through comparable complexity in material composition and synthesis. Seeking to achieve a triple shape behaviour with a simple route to materials synthesis, we introduce here a method that utilizes polymerization induced phase separation (PIPS) to yield the requisite combination of microstructure and composition. Thus, two blends incorporating epoxy and poly(ε-caprolactone) were developed using commercially available reactants, one featuring a semicrystalline epoxy and the other featuring an amorphous epoxy. We show that both blends exhibited distinct transition temperatures and three modulus-temperature plateaus needed for triple shape behaviour. Despite these similarities, their physical character at room temperature is vastly different: the semicrystalline epoxy material is elastomeric and the amorphous epoxy material is highly stiff. Characterization of the triple shape behaviour revealed an ability of both systems to fix two separate deformations independently, one by PCL crystallization and a second one by epoxy crystallization or vitrification, and recover both programmed shapes separately upon heating. Given the simplicity of fabrication, we envision application as multi-shape coatings, adhesives, and films. PMID:24695693

  8. Reprint of: self-assembly of nanoparticles employing polymerization-induced phase separation.

    PubMed

    Williams, Roberto J J; Hoppe, Cristina E; Zucchi, Ileana A; Romeo, Hernán E; dell'Erba, Ignacio E; Gómez, María L; Puig, Julieta; Leonardi, Agustina B

    2015-06-01

    Nanoparticles (NPs) may be homogeneously dispersed in the precursors of a polymer (reactive solvent) by an adequate selection of their stabilizing ligands. However, the dispersion can become metastable or unstable in the course of polymerization. If this happens, NP-rich domains can be segregated by a process called polymerization-induced phase separation (PIPS). This occurs mainly due to the decrease in the entropic contribution of the reactive solvent to the free energy of mixing (increase in its average size) and, for a reactive solvent generating a cross-linked polymer, the additional contribution of the elastic energy in the post-gel stage. The extent of PIPS will depend on the competition between phase separation and polymerization rates. It can be completely avoided, limited to a local scale or conveyed to generate different types of NPs' aggregates such as crystalline platelets, self-assembled structures with a hierarchical order and partitioning at the interface, and bidimensional patterns of NPs at the film surface. The use of a third component in the initial formulation such as a linear polymer or a block copolymer, provides the possibility of generating an internal template for the preferential location and self-assembly of phase-separated NPs. Some illustrative examples of morphologies generated by PIPS in solutions of NPs in reactive solvents, are analyzed in this feature article. PMID:25736431

  9. Self-assembly of nanoparticles employing polymerization-induced phase separation.

    PubMed

    Williams, Roberto J J; Hoppe, Cristina E; Zucchi, Ileana A; Romeo, Hernán E; dell'Erba, Ignacio E; Gómez, María L; Puig, Julieta; Leonardi, Agustina B

    2014-10-01

    Nanoparticles (NPs) may be homogeneously dispersed in the precursors of a polymer (reactive solvent) by an adequate selection of their stabilizing ligands. However, the dispersion can become metastable or unstable in the course of polymerization. If this happens, NP-rich domains can be segregated by a process called polymerization-induced phase separation (PIPS). This occurs mainly due to the decrease in the entropic contribution of the reactive solvent to the free energy of mixing (increase in its average size) and, for a reactive solvent generating a cross-linked polymer, the additional contribution of the elastic energy in the post-gel stage. The extent of PIPS will depend on the competition between phase separation and polymerization rates. It can be completely avoided, limited to a local scale or conveyed to generate different types of NPs' aggregates such as crystalline platelets, self-assembled structures with a hierarchical order and partitioning at the interface, and bidimensional patterns of NPs at the film surface. The use of a third component in the initial formulation such as a linear polymer or a block copolymer, provides the possibility of generating an internal template for the preferential location and self-assembly of phase-separated NPs. Some illustrative examples of morphologies generated by PIPS in solutions of NPs in reactive solvents, are analyzed in this feature article. PMID:25014172

  10. Photopolymerization-induced crystallization and phase separation in poly(ethylene oxide)/triacrylate blends

    SciTech Connect

    Park, Soo Jeoung; Kyu, Thein

    2008-12-28

    The present article describes experimental and theoretical investigations of miscibility and crystallization behavior of blends of poly(ethylene oxide) (PEO) and triacrylate monomer (TA) using differential scanning calorimetry and optical microscopy. The PEO/TA blends manifested a single T{sub g} varying systematically with composition suggestive of a miscible character in their amorphous states. Moreover, there occurs melting point depression of PEO crystals with increasing TA. A phase diagram was subsequently established that exhibited a solid+liquid coexistence region bound by the liquidus and solidus lines, followed by an upper critical solution temperature (UCST) at a lower temperature. The emerging phase morphology was investigated to verify the coexistence regions. Upon photopolymerization in the isotropic melt above the melting point depression curve, both the UCST and the melting temperatures move upward and eventually surpass the reaction temperature, resulting in phase separation as well as crystallization of PEO driven by the changing supercooling, i.e., the thermodynamic driving force. Of particular interest is the interplay between photopolymerization-induced phase separation and crystallization, which eventually determines the final phase morphology of the PEO/TA blend such as crystalline lamellae, sheaf, or spherulites in isotropic liquid, phase separated domains, and viscous fingering liquids.

  11. Microfluidic Production of Semipermeable Microcapsules by Polymerization-Induced Phase Separation.

    PubMed

    Kim, Bomi; Jeon, Tae Yoon; Oh, You-Kwan; Kim, Shin-Hyun

    2015-06-01

    Semipermeable microcapsules are appealing for controlled release of drugs, study of cell-to-cell communication, and isolation of enzymes or artificial catalysts. Here, we report a microfluidic strategy for creating monodisperse microcapsules with size-selective permeability using polymerization-induced phase separation. Monodisperse water-in-oil-in-water (W/O/W) double-emulsion drops, whose ultrathin middle layer is composed of photocurable resin and inert oil, are generated in a capillary microfluidic device, and irradiated by UV light. Upon UV illumination, the monomers are photopolymerized, which leads to phase separation between the polymerized resin and the oil within the ultrathin shell. Subsequent dissolution of the oil leaves behind regular pores in the polymerized membrane that interconnect the interior and exterior of the microcapsules, thereby providing size-selective permeability. The degree of phase separation can be further tuned by adjusting the fraction of oil in the shell or the affinity of the oil to the monomers, thereby enabling the control of the cutoff value of permeation. High mechanical stability and chemical resistance of the microcapsules, as well as controllable permeability and high encapsulation efficiency, will provide new opportunity in a wide range of applications. PMID:26020458

  12. Microbially induced separation of quartz from hematite using sulfate reducing bacteria.

    PubMed

    Prakasan, M R Sabari; Natarajan, K A

    2010-07-01

    Cells and metabolic products of Desulfovibrio desulfuricans were successfully used to separate quartz from hematite through environmentally benign microbially induced flotation. Bacterial metabolic products such as extracellular proteins and polysaccharides were isolated from both unadapted and mineral-adapted bacterial metabolite and their basic characteristics were studied in order to get insight into the changes brought about on bioreagents during adaptation. Interaction between bacterial cells and metabolites with minerals like hematite and quartz brought about significant surface-chemical changes on both the minerals. Quartz was rendered more hydrophobic, while hematite became more hydrophilic after biotreatment. The predominance of bacterial polysaccharides on interacted hematite and of proteins on quartz was responsible for the above surface-chemical changes, as attested through adsorption studies. Surface-chemical changes were also observed on bacterial cells after adaptation to the above minerals. Selective separation of quartz from hematite was achieved through interaction with quartz-adapted bacterial cells and metabolite. Mineral-specific proteins secreted by quartz-adapted cells were responsible for conferment of hydrophobicity on quartz resulting in enhanced separation from hematite through flotation. PMID:20347277

  13. On the comparisons between dissipative particle dynamics simulations and self-consistent field calculations of diblock copolymer microphase separation

    NASA Astrophysics Data System (ADS)

    Sandhu, Paramvir; Zong, Jing; Yang, Delian; Wang, Qiang

    2013-05-01

    To highlight the importance of quantitative and parameter-fitting-free comparisons among different models/methods, we revisited the comparisons made by Groot and Madden [J. Chem. Phys. 108, 8713 (1998), 10.1063/1.476300] and Chen et al. [J. Chem. Phys. 122, 104907 (2005), 10.1063/1.1860351] between their dissipative particle dynamics (DPD) simulations of the DPD model and the self-consistent field (SCF) calculations of the "standard" model done by Matsen and Bates [Macromolecules 29, 1091 (1996), 10.1021/ma951138i] for diblock copolymer (DBC) A-B melts. The small values of the invariant degree of polymerization used in the DPD simulations do not justify the use of the fluctuation theory of Fredrickson and Helfand [J. Chem. Phys. 87, 697 (1987), 10.1063/1.453566] by Groot and Madden, and their fitting between the DPD interaction parameters and the Flory-Huggins χ parameter in the "standard" model also has no rigorous basis. Even with their use of the fluctuation theory and the parameter-fitting, we do not find the "quantitative match" for the order-disorder transition of symmetric DBC claimed by Groot and Madden. For lamellar and cylindrical structures, we find that the system fluctuations/correlations decrease the bulk period and greatly suppress the large depletion of the total segmental density at the A-B interfaces as well as its oscillations in A- and B-domains predicted by our SCF calculations of the DPD model. At all values of the A-block volume fractions in the copolymer f (which are integer multiples of 0.1), our SCF calculations give the same sequence of phase transitions with varying χN as the "standard" model, where N denotes the number of segments on each DBC chain. All phase boundaries, however, are shifted to higher χN due to the finite interaction range in the DPD model, except at f = 0.1 (and 0.9), where χN at the transition between the disordered phase and the spheres arranged on a body-centered cubic lattice is lower due to N = 10 in the DPD model. Finally, in 11 of the total 20 cases (f-χN combinations) studied in the DPD simulations, a morphology different from the SCF prediction was obtained due to the differences between these two methods.

  14. Preparation and dielectric analysis of microphase-separated poly(acrylonitrile-co-acrylamide-co-acrylic acid) hydrogels

    SciTech Connect

    Hu, D.Shiaw-Guang; Lin, Yow-Shi

    1993-12-31

    The acidic hydrolysis of polyacrylonitrile was carried out to yield a variety of terpolymers made up of nitriles, amides and acids. The formation of block structure was shown to follow a ripper mechanism occurring to acrylamide groups, that is more pronounced for a certain range of acrylamide content, evidenced by the composition analysis using {sup 1}H-NMR and base titration. The rates of formation of acrylamide fraction and acid fraction in the consecutive mode are approximately the same, yielding the content of ionic groups from 0.8 to 2.2. mole percent, dependent on the time of hydrolysis. The dielectric relaxation measurement on swollen gels shows three relaxation transitions, {alpha}, {beta}, {gamma}, over -150{degrees}C to 0{degrees}C, as influenced by the chemical composition and water absorption. The {beta} and {gamma} are associated with the polymer-water interaction and short-range motion of polymers and water.

  15. Design and characterization of materials with microphase-separated surface patterns for screening osteoblast response to adhesion

    NASA Astrophysics Data System (ADS)

    Wingkono, Gracy A.

    Combinatorial techniques have changed the paradigm of materials research by allowing efficient screening of complex materials problems with large, multidimensional parameter spaces. The focus of this thesis is to demonstrate combinatorial methods (CM) and high-throughput methods (HTM) applied to biomaterials design, characterization, and screening. In particular, this work focuses on screening the effects of biomaterial surface features on adherent bone cell cultures. Polymeric biomaterials were prepared on two-dimensional combinatorial libraries that systematically varied the size and shape of chemically-distinct microstructural patterns. These libraries were generated from blends of biodegradable polyurethanes and polyesters prepared with thickness, composition and temperature gradient techniques. Characterization and screening were performed with high-throughput optical and fluorescence microscopy. A unique advance of this work is the application of data mining techniques to identify the controlling structural features that affect cell behavior from among the myriad variety of metrics from the microscope images. Libraries were designed to exhibit chemically-distinct cell-adhesive versus non-adhesive microstructural domains that improve library performance compared to previous implementations that had employed only modest chemical differences. Improving adhesive contrast should minimize combination of effects of chemistry and physical structure, making data interpretation simpler. To accomplish this, a method of blending and crosslinking cell-non-adhesive poly(ethylene glycol) (PEG) with cell-adhesive poly(·-caprolactone) (PCL) was developed. The behavior of MC3T3-E1 osteoblast cells cultured on the PCL-PEG libraries were observed, equivalent to thousands of distinct chemistries and microstructures. Cell spreading area, shape, and density upon adhesion on surface patterns are observed in this study. Characterization of the surface library and screening of surface physical properties via HTM and PCA show that cell density is sensitive to the physical distribution, shape, solidity, and orientation of the PCL and PEG domains. Correlation is shown between surface pattern descriptors and the subsequent cellular adhesion responses. Certain spacing and shapes in surface pattern are preferred to others for distinct cellular states; circular pattern favors apoptotic cells, while elongated patterns favor viable cells---for both cases, cells preferred anchoring themselves to surface patterns. However, the effect of surface pattern's solidity and area did not show any conclusive trend in this dataset. This might be due to the existence of correlation between solidity and eccentricity as described in Chapter 1. Further improvement in the surface pattern library generation is necessary for future studies. The results from this study demonstrated the potentials of CM/HTS to be applied to exploratory studies involving complex systems in life sciences. This study accomplishes the goal to demonstrate the efficient screening and exploration of vast and complex dataset, extracting important and meaningful information to narrow down the future path of study in this field. Further study aimed to tuning cellular responses via signals from surface cues will be necessary to examine the causal relationships beyond the observed correlations shown in this exploratory study. It is recommended for further studies to narrow down the range for surface patterning around each of the three 'activation' ranges found in this study: apoptotic, viable, and one unknown state to be studied further. Different cellular-function staining methods will be necessary to be used in cellular imaging techniques in order to explore this unknown state further.

  16. On the comparisons between dissipative particle dynamics simulations and self-consistent field calculations of diblock copolymer microphase separation.

    PubMed

    Sandhu, Paramvir; Zong, Jing; Yang, Delian; Wang, Qiang

    2013-05-21

    To highlight the importance of quantitative and parameter-fitting-free comparisons among different models/methods, we revisited the comparisons made by Groot and Madden [J. Chem. Phys. 108, 8713 (1998)] and Chen et al. [J. Chem. Phys. 122, 104907 (2005)] between their dissipative particle dynamics (DPD) simulations of the DPD model and the self-consistent field (SCF) calculations of the "standard" model done by Matsen and Bates [Macromolecules 29, 1091 (1996)] for diblock copolymer (DBC) A-B melts. The small values of the invariant degree of polymerization used in the DPD simulations do not justify the use of the fluctuation theory of Fredrickson and Helfand [J. Chem. Phys. 87, 697 (1987)] by Groot and Madden, and their fitting between the DPD interaction parameters and the Flory-Huggins χ parameter in the "standard" model also has no rigorous basis. Even with their use of the fluctuation theory and the parameter-fitting, we do not find the "quantitative match" for the order-disorder transition of symmetric DBC claimed by Groot and Madden. For lamellar and cylindrical structures, we find that the system fluctuations/correlations decrease the bulk period and greatly suppress the large depletion of the total segmental density at the A-B interfaces as well as its oscillations in A- and B-domains predicted by our SCF calculations of the DPD model. At all values of the A-block volume fractions in the copolymer f (which are integer multiples of 0.1), our SCF calculations give the same sequence of phase transitions with varying χN as the "standard" model, where N denotes the number of segments on each DBC chain. All phase boundaries, however, are shifted to higher χN due to the finite interaction range in the DPD model, except at f = 0.1 (and 0.9), where χN at the transition between the disordered phase and the spheres arranged on a body-centered cubic lattice is lower due to N = 10 in the DPD model. Finally, in 11 of the total 20 cases (f-χN combinations) studied in the DPD simulations, a morphology different from the SCF prediction was obtained due to the differences between these two methods. PMID:23697438

  17. Ordered three- and five-ply nanocomposites from ABC block terpolymer microphase separation with niobia and aluminosilicate sols

    PubMed Central

    Stefik, Morgan; Mahajan, Surbhi; Sai, Hiroaki; Epps, Thomas H.; Bates, Frank S.; Gruner, Sol M; DiSalvo, Francis J.; Wiesner, Ulrich

    2009-01-01

    We report the first use of a non-frustrated block terpolymer for the synthesis of highly ordered oxide nanocomposites containing multiple plies. The morphological behavior of 15 ISO-oxide nanocomposites was investigated spanning a large range of compositions along the ƒI=ƒS isopleth using aluminosilicate and niobia sols. Morphologies were determined by TEM and SAXS measurements. Four morphologies were identified, including core-shell hexagonal, core-shell double gyroid, three-domain lamellae, and core-shell inverse-hexagonal, in order of increasing O+oxide vol fraction. All of the resulting nanocomposites had three- or five-ply morphologies containing domains that were continuous in one, two, or three dimensions. The five-ply core-shell double gyroid phase was only found to be stable when the O+oxide domain was a minority. Removal of the polymer enabled simple and direct synthesis of mesoporous oxide materials while retaining the ordered network structure. We believe that advances in the synthesis of multi-ply nanocomposites will lead to advanced materials and devices containing multiple plies of functional materials. PMID:20209023

  18. Separation of the sperm agglutinin and the acrosome reaction-inducing substance in egg jelly of starfish.

    PubMed

    Uno, Y; Hoshi, M

    1978-04-01

    The egg jelly of the starfish Asterias amurensis was separated into the fractions J1, J2, and J3 on a Sephadex G-100 column. The Jl fraction induced the acrosome reaction and J2 induced sperm agglutination. Chemical analysis and chromatography revealed that sperm agglutinin is similar to asterosaponin A. PMID:17847329

  19. Distress, support, and relationship satisfaction during military-induced separations: a longitudinal study among spouses of Dutch deployed military personnel.

    PubMed

    Andres, Manon

    2014-02-01

    The aim of this study was to examine (a) how life stress, work-family conflict, social support, psychological distress, and relationship satisfaction develop over the course of military-induced separations; (b) what best predicts relationship satisfaction after being separated for several months; and (c) whether the effects were mediated by spousal interaction. Longitudinal data were collected among 153 spouses of Dutch military personnel before, during, and after military-induced separations. Analyses demonstrated a significant decrease in relationship satisfaction, psychological distress, and social support over time. Controlling for predeployment levels of relationship satisfaction, work-family conflict, social support, psychological distress, and spousal interaction made significant contributions to the explanation of relationship satisfaction after military-induced separations. However, the effects on relationships varied for each stage of the work-related spousal separation. Hence, clinical implications for psychological service delivery suggested by these findings are impacted by the stage of the work-related spousal separation. Specifically, before the separation, services might focus upon balancing work and family demands; during the separation, services that facilitate building networks are important; and finally, communication remains the key service focus upon reunion. PMID:24564440

  20. Exploiting the wall-induced non-inertial lift in electrokinetic flow for a continuous particle separation by size.

    PubMed

    Lu, Xinyu; Hsu, Jyh-Ping; Xuan, Xiangchun

    2015-01-01

    Separating particles from a heterogeneous mixture is important and necessary in many engineering and biomedical applications. Electrokinetic flow-based continuous particle separation has thus far been realized primarily by the use of particle dielectrophoresis induced in constricted and/or curved microchannels. We develop in this work a new electrokinetic method that exploits the wall-induced non-inertial lift in a straight uniform microchannel to continuously separate particles by intrinsic properties (e.g., size and surface charge). Such an electrically originated lift force arises from the asymmetric electric field distribution around a particle nearby a planar dielectric wall. We demonstrate this method through separating both a binary and ternary mixture of dispersed polystyrene microspheres by size in a T-shaped microchannel. A semi-analytical model is also developed to simulate and understand the particle separation process. The predicted particle trajectories in the entire microchannel agree reasonably well with the experimental measurements. PMID:25521509

  1. Magnetic-field-induced nematic-nematic phase separation and droplet formation in colloidal goethite.

    PubMed

    van den Pol, E; Verhoeff, A A; Lupascu, A; Diaconeasa, M A; Davidson, P; Dozov, I; Kuipers, B W M; Thies-Weesie, D M E; Vroege, G J

    2011-05-18

    We demonstrate the suitability of polarization microscopy to study the recently discovered (parallel) nematic-(perpendicular) nematic phase separation. This novel type of phase transition is induced by applying an external magnetic field to a nematic liquid crystal of boardlike colloidal goethite and is due to an interplay between the intrinsic magnetic properties of goethite and the collective effect of liquid crystal formation. It is shown that the intense ochre colour of goethite does not preclude the use of polarization microscopy and interference colours, and that dichroism can give valuable qualitative information on the nature of the phases, their anchoring and their sedimentation and order parameter profiles. We also apply these techniques to study 'nematic-nematic tactoids': nematic droplets sedimenting within a nematic medium with mutually perpendicular orientations. PMID:21525548

  2. Polymeric scaffolds prepared via Thermally Induced Phase Separation (TIPS): tuning of structure and morphology

    NASA Astrophysics Data System (ADS)

    Pavia, F. Carfı; La Carrubba, V.; Brucato, V.; Piccarolo, S.

    2007-04-01

    Scaffolds suitable for tissue engineering applications were prepared by Thermally Induced Phase Separation (TIPS) starting from a ternary solution PLLA/dioxane/water. The experimental protocol consisted of three consecutive steps, a first quench from the homogeneous solution to an appropriate demixing temperature (within the metastable region), a holding stage for a given residence time and a final quench from the demixing temperature to a low temperature (within the unstable region). A large variety of morphologies, in terms of average pore size and interconnection, were obtained upon modifying the demixing time and temperature, owing to the interplay of nucleation and growth processes during the residence in the metastable state. An interesting combination of micro and macro-porosity was observed for long residence times in the metastable state (above 30 min at 35°C).

  3. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs

    SciTech Connect

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; Luetkens, Hubertus; Amato, Alex; Biswas, Pabitra K.; Ruegg, Christian; Susner, Michael A.; Sefat, Athena S.; Zhigadlo, Nikolai D.; Morenzoni, Elvezio

    2015-09-08

    We report that the recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p ≃ 3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p ≃ 7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc ≃ 1.2 K which decreases upon increasing the pressure. In the intermediate pressure region (3.5≲ p ≲ 7 kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with Tc3.2 as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs.

  4. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs.

    PubMed

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; Luetkens, Hubertus; Amato, Alex; Biswas, Pabitra K; Rüegg, Christian; Susner, Michael A; Sefat, Athena S; Zhigadlo, Nikolai D; Morenzoni, Elvezio

    2015-01-01

    The recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p ≃ 3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p ≃ 7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc ≃ 1.2 K which decreases upon increasing the pressure. In the intermediate pressure region (3.5 < or ~  p < or ~ 7 kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with Tc(3.2) as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs. PMID:26346548

  5. Investigating the three-dimensional flow separation induced by a model vocal fold polyp.

    PubMed

    Stewart, Kelley C; Erath, Byron D; Plesniak, Michael W

    2014-01-01

    The fluid-structure energy exchange process for normal speech has been studied extensively, but it is not well understood for pathological conditions. Polyps and nodules, which are geometric abnormalities that form on the medial surface of the vocal folds, can disrupt vocal fold dynamics and thus can have devastating consequences on a patient's ability to communicate. Our laboratory has reported particle image velocimetry (PIV) measurements, within an investigation of a model polyp located on the medial surface of an in vitro driven vocal fold model, which show that such a geometric abnormality considerably disrupts the glottal jet behavior. This flow field adjustment is a likely reason for the severe degradation of the vocal quality in patients with polyps. A more complete understanding of the formation and propagation of vortical structures from a geometric protuberance, such as a vocal fold polyp, and the resulting influence on the aerodynamic loadings that drive the vocal fold dynamics, is necessary for advancing the treatment of this pathological condition. The present investigation concerns the three-dimensional flow separation induced by a wall-mounted prolate hemispheroid with a 2:1 aspect ratio in cross flow, i.e. a model vocal fold polyp, using an oil-film visualization technique. Unsteady, three-dimensional flow separation and its impact of the wall pressure loading are examined using skin friction line visualization and wall pressure measurements. PMID:24513707

  6. Membrane nanotubes induced by aqueous phase separation and stabilized by spontaneous curvature

    PubMed Central

    Li, Yanhong; Lipowsky, Reinhard; Dimova, Rumiana

    2011-01-01

    Tubular membrane structures are widespread in eukaryotic cells, but the mechanisms underlying their formation and stability are not well understood. Previous work has focused on tube extrusion from cells and model membranes under the application of external forces. Here, we present novel membrane/polymer systems, where stable tubes form in the absence of externally applied forces. Solutions of two water-soluble polymers, polyethylene glycol and dextran, were encapsulated in giant lipid vesicles, cell-size model systems. Hypertonic deflation induced phase separation of the enclosed solution. The excess membrane area created during the deflation process was stored in a large number of membrane nanotubes inside the vesicle. The tubes had a diameter below optical resolution and became visible only when fluorescently labeled. The tubes were rather stable: In the absence of external forces, they existed for several days. A theoretical analysis of the shapes of the deflated vesicles reveals that these shapes would be unstable if the membranes had no spontaneous curvature. Using the large separation of length scales between the tube diameter and the overall size of the vesicles, the spontaneous curvature can be calculated and is found to be about -1/(240 nm) for a certain range of polymer concentrations. The nanotubes could also be retracted back into the mother vesicle by increasing the membrane tension via micropipette aspiration of the vesicle. Membrane tubes, which can form and be retracted easily, should be relevant for lipid storage in cells. PMID:21383120

  7. Investigating the Three-dimensional Flow Separation Induced by a Model Vocal Fold Polyp

    PubMed Central

    Stewart, Kelley C.; Erath, Byron D.; Plesniak, Michael W.

    2014-01-01

    The fluid-structure energy exchange process for normal speech has been studied extensively, but it is not well understood for pathological conditions. Polyps and nodules, which are geometric abnormalities that form on the medial surface of the vocal folds, can disrupt vocal fold dynamics and thus can have devastating consequences on a patient's ability to communicate. Our laboratory has reported particle image velocimetry (PIV) measurements, within an investigation of a model polyp located on the medial surface of an in vitro driven vocal fold model, which show that such a geometric abnormality considerably disrupts the glottal jet behavior. This flow field adjustment is a likely reason for the severe degradation of the vocal quality in patients with polyps. A more complete understanding of the formation and propagation of vortical structures from a geometric protuberance, such as a vocal fold polyp, and the resulting influence on the aerodynamic loadings that drive the vocal fold dynamics, is necessary for advancing the treatment of this pathological condition. The present investigation concerns the three-dimensional flow separation induced by a wall-mounted prolate hemispheroid with a 2:1 aspect ratio in cross flow, i.e. a model vocal fold polyp, using an oil-film visualization technique. Unsteady, three-dimensional flow separation and its impact of the wall pressure loading are examined using skin friction line visualization and wall pressure measurements. PMID:24513707

  8. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs

    DOE PAGESBeta

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; Luetkens, Hubertus; Amato, Alex; Biswas, Pabitra K.; Ruegg, Christian; Susner, Michael A.; Sefat, Athena S.; Zhigadlo, Nikolai D.; et al

    2015-09-08

    We report that the recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p ≃ 3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p ≃ 7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc ≃ 1.2 K which decreasesmore » upon increasing the pressure. In the intermediate pressure region (3.5≲ p ≲ 7 kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with Tc3.2 as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs.« less

  9. Three-Dimensional Flow Separation Induced by a Model Vocal Fold Polyp

    NASA Astrophysics Data System (ADS)

    Stewart, Kelley C.; Erath, Byron D.; Plesniak, Michael W.

    2012-11-01

    The fluid-structure energy exchange process for normal speech has been studied extensively, but it is not well understood for pathological conditions. Polyps and nodules, which are geometric abnormalities that form on the medial surface of the vocal folds, can disrupt vocal fold dynamics and thus can have devastating consequences on a patient's ability to communicate. A recent in-vitro investigation of a model polyp in a driven vocal fold apparatus demonstrated that such a geometric abnormality considerably disrupts the glottal jet behavior and that this flow field adjustment was a likely reason for the severe degradation of the vocal quality in patients. Understanding of the formation and propagation of vortical structures from a geometric protuberance, and their subsequent impact on the aerodynamic loadings that drive vocal fold dynamic, is a critical component in advancing the treatment of this pathological condition. The present investigation concerns the three-dimensional flow separation induced by a wall-mounted prolate hemispheroid with a 2:1 aspect ratio in cross flow, i.e. a model vocal fold polyp. Unsteady three-dimensional flow separation and its impact of the wall pressure loading are examined using skin friction line visualization and wall pressure measurements. Supported by the National Science Foundation, Grant No. CBET-1236351 and GW Center for Biomimetics and Bioinspired Engineering (COBRE).

  10. Polyurethane/poly(lactic-co-glycolic) acid composite scaffolds fabricated by thermally induced phase separation.

    PubMed

    Rowlands, A S; Lim, S A; Martin, D; Cooper-White, J J

    2007-04-01

    In this study, we present a novel composite scaffold fabricated using a thermally induced phase separation (TIPS) process from poly(lactic-co-glycolic) (PLGA) and biomedical polyurethane (PU). This processing method has been tuned to allow intimate (molecular) mixing of these two very different polymers, giving rise to a unique morphology that can be manipulated by controlling the phase separation behaviour of an initially homogenous polymer solution. Pure PLGA scaffolds possessed a smooth, directional fibrous sheet-like structure with pore sizes of 0.1-200mum, a porous Young's modulus of 93.5kPa and were relatively brittle to touch. Pure PU scaffolds had an isotropic emulsion-like structure, a porous Young's modulus of 15.7kPa and were much more elastic than the PLGA scaffolds. The composite PLGA/PU scaffold exhibits advantageous morphological, mechanical and cell adhesion and growth supporting properties, when compared with scaffolds fabricated from PLGA or PU alone. This novel method provides a mechanism for the formation of tailored bioactive scaffolds from nominally incompatible polymers, representing a significant step forward in scaffold processing for tissue-engineering applications. PMID:17258315

  11. Pressure-induced electronic phase separation of magnetism and superconductivity in CrAs

    PubMed Central

    Khasanov, Rustem; Guguchia, Zurab; Eremin, Ilya; Luetkens, Hubertus; Amato, Alex; Biswas, Pabitra K.; Rüegg, Christian; Susner, Michael A.; Sefat, Athena S.; Zhigadlo, Nikolai D.; Morenzoni, Elvezio

    2015-01-01

    The recent discovery of pressure (p) induced superconductivity in the binary helimagnet CrAs has raised questions on how superconductivity emerges from the magnetic state and on the mechanism of the superconducting pairing. In the present work the suppression of magnetism and the occurrence of superconductivity in CrAs were studied by means of muon spin rotation. The magnetism remains bulk up to p  3.5 kbar while its volume fraction gradually decreases with increasing pressure until it vanishes at p  7 kbar. At 3.5 kbar superconductivity abruptly appears with its maximum Tc  1.2 K which decreases upon increasing the pressure. In the intermediate pressure region (3.5  p  7 kbar) the superconducting and the magnetic volume fractions are spatially phase separated and compete for phase volume. Our results indicate that the less conductive magnetic phase provides additional carriers (doping) to the superconducting parts of the CrAs sample thus leading to an increase of the transition temperature (Tc) and of the superfluid density (ρs). A scaling of ρs with as well as the phase separation between magnetism and superconductivity point to a conventional mechanism of the Cooper-pairing in CrAs. PMID:26346548

  12. Effect of alkaline earth oxides on the formation of surface microphases that protect strontium titanate from reduction

    SciTech Connect

    Aksenova, L.A.; Kostikov, Yu.P.; Leonov, A.I.; Rotenberg, B.A.; Strykanov, V.S.

    1986-08-20

    The authors studied the effect of addition of strontium oxide, barium oxide, and calcium oxide on the formation of surface microphases and the reduction of strontium titanate. The materials were strontium carbonate, barium carbonate, and calcium carbonate (analytical grade) and titanium dioxide (pure grade). X-ray diffraction analysis was carried out on a DRON-2.0 diffractometer (CuK/sub ..cap alpha../, Ni filter). The surface layers were studies in an electron spectrometer by ESCA (exciting irradiation Al/sub K..cap alpha../; bond energy in standard gold sample Au/sub 4/f/sub 1/2/ = 84.1 eV; depth of layer 8 nm). Samplers were prepared according to the usual ceramic technology. It was found that protection from reduction of strontium titanate that is doped with calcium, strontium, or barium oxide is related to the formation of surface microphases that are close to M/sub 2/TiO/sub 4/ in composition and do not undergo reduction when calcined in a medium at low partial pressure of oxygen.

  13. Carbon nanotubes reinforced poly(L-lactide) scaffolds fabricated by thermally induced phase separation.

    PubMed

    Ma, Haiyun; Xue, Li

    2015-01-16

    In tissue engineering, porous nanocomposite scaffolds can potentially mimic aspects of the nanoscale architecture of the extra-cellular matrix, as well as enhance the mechanical properties required for successful weight-bearing implants. In this paper, we demonstrate that highly porous thermoplastic poly(L-lactide) nanocomposite scaffolds containing different types of functionalized multi-walled carbon nanotubes (CNTs). The nanocomposite scaffolds were manufactured by a thermally induced phase separation method. This experiment produced an uniform distribution of CNTs throughout the scaffold without obvious aggregations for funtionalized CNTs filled scaffolds by scanning electron microscope observation. The CNTs were frequently located on the pore surface, forming rough, hairy nano-textures. The pore size was reduced with the increasing of CNT loading. Parts of PLLA matrix was induced into nanofibrous structures from solid-walled state, which reduced the crystallinity of the PLLA characterized by DSC measurement. The CNT incorporation significantly improved the compression modulus of the nanocomposite scaffolds, especially the functionalized CNTs. The capacity of protein adsorption is significantly improved when the concentration of the CNTs was higher than 1.0 wt.% and the cell attachment was also enhanced by the addition of CNTs, especially N-CNT. PMID:25525708

  14. Carbon nanotubes reinforced poly(L-lactide) scaffolds fabricated by thermally induced phase separation

    NASA Astrophysics Data System (ADS)

    Ma, Haiyun; Xue, Li

    2015-01-01

    In tissue engineering, porous nanocomposite scaffolds can potentially mimic aspects of the nanoscale architecture of the extra-cellular matrix, as well as enhance the mechanical properties required for successful weight-bearing implants. In this paper, we demonstrate that highly porous thermoplastic poly(L-lactide) nanocomposite scaffolds containing different types of functionalized multi-walled carbon nanotubes (CNTs). The nanocomposite scaffolds were manufactured by a thermally induced phase separation method. This experiment produced an uniform distribution of CNTs throughout the scaffold without obvious aggregations for funtionalized CNTs filled scaffolds by scanning electron microscope observation. The CNTs were frequently located on the pore surface, forming rough, hairy nano-textures. The pore size was reduced with the increasing of CNT loading. Parts of PLLA matrix was induced into nanofibrous structures from solid-walled state, which reduced the crystallinity of the PLLA characterized by DSC measurement. The CNT incorporation significantly improved the compression modulus of the nanocomposite scaffolds, especially the functionalized CNTs. The capacity of protein adsorption is significantly improved when the concentration of the CNTs was higher than 1.0 wt.% and the cell attachment was also enhanced by the addition of CNTs, especially N-CNT.

  15. Charge-separated atmospheric neutrino-induced muons in the MINOS far detector

    SciTech Connect

    Adamson, P.; Andreopoulos, Constantinos V.; Arms, Kregg E.; Armstrong, Stephen Randolph; Auty, D.J.; Avvakumov, S.; Ayres, David S.; Baller, Bruce R.; Barish, Barry C.; Barnes, P.D., Jr.; Barr, Giles David; /Oxford U. /Western Washington U.

    2007-01-01

    We found 140 neutrino-induced muons in 854.24 live days in the MINOS far detector, which has an acceptance for neutrino-induced muons of 6.91 x 10{sup 6} cm{sup 2} sr. We looked for evidence of neutrino disappearance in this data set by computing the ratio of the number of low momentum muons to the sum of the number of high momentum and unknown momentum muons for both data and Monte Carlo expectation in the absence of neutrino oscillations. The ratio of data and Monte Carlo ratios, R, is R = 0.65{sub 0.12}{sup +0.15}(stat) {+-} 0.09(syst), a result that is consistent with an oscillation signal. A fit to the data for the oscillation parameters sin{sup 2} 2{theta}{sub 23} and {Delta}m{sub 23}{sup 2} excludes the null oscillation hypothesis at the 94% confidence level. We separated the muons into {mu}{sup -} and {mu}{sup +} in both the data and Monte Carlo events and found the ratio of the total number of {mu}{sup -} to {mu}{sup +} in both samples. The ratio of those ratios, {cflx R}{sub CPT}, is a test of CPT conservation. The result {cflx R}{sub CPT} = 0.72{sub -0.18}{sup +0.24}(stat){sub -0.04}{sup +0.08}(syst), is consistent with CPT conservation.

  16. High Reynolds number tests of a C-141A aircraft semispan model to investigate shock-induced separation. [boundary layer separation

    NASA Technical Reports Server (NTRS)

    Blackerby, W. T.; Cahill, J. F.

    1975-01-01

    Results from a high Reynolds number transonic wind tunnel investigation are presented. Wing chordwise pressure distributions were measured over a matrix of Mach numbers and angles-of-attack for which shock-induced separations are known to exist. The range of Reynolds number covered by these data nearly spanned the gap between previously available wind tunnel and flight test data. The results are compared with both flight and low Reynolds number data, and show that use of the semispan test technique produced good correlation with the prior data at both ends of the Reynolds number range, but indicated strong sensitivity to details of the test setup.

  17. The role of shock induced trailing-edge separation in limit cycle oscillations

    NASA Technical Reports Server (NTRS)

    Cunningham, Atlee M., Jr.

    1989-01-01

    The potential role of shock induced trailing edge separation (SITES) in limit cycle oscillations (LCO) was established. It was shown that the flip-flop characteristics of transition to and from SITES as well as its hysteresis could couple with wing modes with torsional motion and low damping. This connection led to the formulation of a very simple nonlinear math model using the linear equations of motion with a nonlinear step forcing function with hysteresis. A finite difference solution with time was developed and calculations were made for the F-111 TACT were used to determine the step forcing function due to SITES transition. Since no data were available for the hysteresis, a parameter study was conducted allowing the hysteresis effect to vary. Very small hysteresis effects, which were within expected bounds, were required to obtain reasonable response levels that essentially agreed with flight test results. Also in agreement with wind tunnel tests, LCO calculations for the 1/6 scale F-111 model showed that the model should have not experienced LCO.

  18. Kirromycin-induced modifications facilitate the separation of EF-Tu species and reveal intermolecular interactions.

    PubMed

    Anborgh, P H; Swart, G W; Parmeggiani, A

    1991-11-01

    A simplified method for the separation of a kirromycin-sensitive tufB-encoded elongation factor Tu (EF-TuBs) from a kirromycin-resistant tufA product (EF-TuAr) was obtained by exploiting the specific increase of negative [corrected] charges induced by the antibiotic, resulting in a retarded elution of kirromycin-bound EF-TuBs on ionic chromatography. The kirromycin-free EF-TuBs is active in poly(Phe) synthesis and shows similar properties to EF-TuAsBs. As expected for these two distinct species, the dissociation of the EF-TuArBs.GTP complex in the presence of kirromycin shows a biphasic curve; in contrast, a monophasic GTP dissociation rate was found for a combination of two mutated EF-Tu species, EF-TuArBo, revealing the existence of intermolecular interactions. These observations prove for the first time the existence of cooperative phenomena between EF-Tu species in vitro, as suggested earlier by in vivo experiments. PMID:1959611

  19. USM3D Simulations of Saturn V Plume Induced Flow Separation

    NASA Technical Reports Server (NTRS)

    Deere, Karen; Elmlilgui, Alaa; Abdol-Hamid, K. S.

    2011-01-01

    The NASA Constellation Program included the Ares V heavy lift cargo vehicle. During the design stage, engineers questioned if the Plume Induced Flow Separation (PIFS) that occurred along Saturn V rocket during moon missions at some flight conditions, would also plague the newly proposed rocket. Computational fluid dynamics (CFD) was offered as a tool for initiating the investigation of PIFS along the Ares V rocket. However, CFD best practice guidelines were not available for such an investigation. In an effort to establish a CFD process and define guidelines for Ares V powered simulations, the Saturn V vehicle was used because PIFS flight data existed. The ideal gas, computational flow solver USM3D was evaluated for its viability in computing PIFS along the Saturn V vehicle with F-1 engines firing. Solutions were computed at supersonic freestream conditions, zero degree angle of attack, zero degree sideslip, and at flight Reynolds numbers. The effects of solution sensitivity to grid refinement, turbulence models, and the engine boundary conditions on the predicted PIFS distance along the Saturn V were discussed and compared to flight data from the Apollo 11 mission AS-506.

  20. Structure and surface nanomechanics of poly(L-lactide) from thermally induced phase separation process

    NASA Astrophysics Data System (ADS)

    Shao, Jundong; Chen, Cong; Wang, Yingjun; Chen, Xiaofeng; Du, Chang

    2012-06-01

    The surface morphology, crystalline structure and nanomechanical properties of poly(L-lactide) (PLLA) samples prepared via thermally induced phase separation (TIPS) process have been investigated by scanning electron microscopy (SEM), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), wide-angle X-ray diffraction (WAXD), atomic force microscopy (AFM), force spectroscopy and nanoindentation. Typical nanofibrous scaffold was obtained at -24 °C (NF sample) while a denser matrix with some plateletlike structure was obtained at 15 °C (PL sample). The NF sample has a higher crystallinity with α'-form crystals while the PL sample has α-form crystals embedded in a largely amorphous matrix. The two kinds of samples have differences in the chain conformation with a more restricted backbone vibration and stiffened segmental motion in NF samples. The NF samples have a higher adhesion force although both samples showed a heterogeneous distribution of adhesion force on the surface based on force spectroscopy analysis. The alternating distribution of domains with higher and lower adhesion force exhibited a banded pattern on PLLA nanofibre. This pattern is proposed to reflect the distribution of crystal-rich and amorphous-rich domains in the semicrystalline samples. AFM-based nanoindentation test indicated that the nanofibrous NF samples can have more significant plastic deformation and creep than the largely amorphous PL samples. The sliding of the crystal-rich domains along the fibrils would account for this increased plasticity of the nanofiber.

  1. Preparation of porous microsphere-scaffolds by electrohydrodynamic forming and thermally induced phase separation.

    PubMed

    Ghanbar, Hanif; Luo, C J; Bakhshi, Poonam; Day, Richard; Edirisinghe, Mohan

    2013-07-01

    The availability of forming technologies able to mass produce porous polymeric microspheres with diameters ranging from 150 to 300 μm is significant for some biomedical applications where tissue augmentation is required. Moreover, appropriate assembly of microspheres into scaffolds is an important challenge to enable direct usage of the as-formed structures in treatments. This work reports the production of poly (glycolic-co-lactic acid) and poly (ε-caprolactone) microspheres under ambient conditions using one-step electrohydrodynamic jetting (traditionally known as atomisation) and thermally induced phase separation (TIPS). To ensure robust production for practical uses, this work presents 12 comprehensive parametric mode mappings of the diameter distribution profiles of the microspheres obtained over a broad range of key processing parameters and correlating of this with the material parameters of 5 different polymer solutions of various concentrations. Poly (glycolic-co-lactic acid) (PLGA) in Dimethyl carbonate (DMC), a low toxicity solvent with moderate conductivity and low dielectric constant, generated microspheres within the targeted diameter range of 150-300 μm. The fabrication of the microspheres suitable for formation of the scaffold structure is achieved by changing the collection method from distilled water to liquid nitrogen and lyophilisation in a freeze dryer. PMID:23623059

  2. High Modulus, High Conductivity Nanostructured Polymer Electrolyte Membranes via Polymerization-Induced Phase Separation

    NASA Astrophysics Data System (ADS)

    McIntosh, Lucas; Schulze, Morgan; Hillmyer, Marc; Lodge, Timothy

    2014-03-01

    Solvent-free, solid-state polymer electrolyte membranes (PEMs) will play a vital role in next-generation electrochemical devices such as Li-metal batteries and high- T fuel cells. The primary challenge is that these applications require PEMs with substantial mechanical robustness, as well as high ionic conductivity. The key to optimizing orthogonal macroscopic properties is to use a heterogeneous composite with well-defined nanoscopic morphology--specifically, long-range co-continuity of high modulus and ion transport domains, which has proven difficult to achieve in commonly-studied diblock copolymer-based electrolytes. We report a simple synthetic strategy to generate PEMs via polymerization-induced phase separation, where the delicate balance between controlled addition of styrene onto a poly(ethylene oxide) macro-chain transfer agent and simultaneous chemical crosslinking by divinylbenzene results in a disordered structure with domain size of order 10 nm. Crucially, both domains exhibit long-range continuity, which results in PEMs that are glassy solids (modulus ~ 1 GPa) owing to the isotropic network of stiff, crosslinked polystyrene, and are highly conductive (> 1 mS/cm at 70 °C) because ions migrate in channels of low Tg poly(ethylene oxide).

  3. Early maternal separation affects ethanol-induced conditioning in a nor-BNI insensitive manner, but does not alter ethanol-induced locomotor activity.

    PubMed

    Pautassi, Ricardo Marcos; Nizhnikov, Michael E; Fabio, Ma Carolina; Spear, Norman E

    2012-01-01

    Early environmental stress significantly affects the development of offspring. This stress has been modeled in rats through the maternal separation (MS) paradigm, which alters the functioning of the HPA axis and can enhance ethanol intake at adulthood. Infant rats are sensitive to ethanol's reinforcing effects, which modulate ethanol seeking and intake. Little is known about the impact of MS on sensitivity to ethanol's appetitive and aversive effects during infancy. The present study assessed ethanol-induced conditioned place preference established through second-order conditioning (SOC), spontaneous or ethanol-induced locomotor activity and ethanol intake in preweanling rats that experienced normal animal facility rearing (AFR) or daily episodes of maternal separation (MS) during postnatal days 1-13 (PDs 1-13). Low-ethanol dose (0.5 g/kg) induced appetitive conditioned place preference (via SOC) in control rats given conventional rearing but not in rats given maternal separation in early infancy, whereas 2.0 g/kg ethanol induced aversive conditioned place preference in the former but not the latter. The administration of a kappa antagonist at PD 1 or immediately before testing did not alter ethanol-induced reinforcement. High (i.e., 2.5 and 2.0 g/kg) but not low (i.e., 0.5 g/kg) ethanol dose induced reliable motor stimulation, which was independent of early maternal separation. Ethanol intake and blood alcohol levels during conditioning were unaffected by rearing conditions. Pups given early maternal separation had lower body weights than controls and showed an altered pattern of exploration when placed in an open field. These results indicate that, when assessed in infant rats, earlier maternal separation alters the balance between the appetitive and aversive motivational effects of ethanol but has no effect on the motor activating effects of the drug. PMID:22108648

  4. New considerations on scale extrapolation of wing pressure distributions affected by transonic shock-induced separations

    NASA Technical Reports Server (NTRS)

    Kahn, M. M. S.; Cahill, J. F.

    1983-01-01

    Use of this analytical parameter, it is shown, highlights the distinction between cases which are dominated by trailing-edge separation, and those for which separation at the shock foot is dominant. Use of the analytical parameter and the distinction noted above greatly improves the correlation of separation data and the extrapolation of wind tunnel data to flight conditions.

  5. Protein formulation and lyophilization cycle design: prevention of damage due to freeze-concentration induced phase separation.

    PubMed

    Heller, M C; Carpenter, J F; Randolph, T W

    1999-04-20

    Hemoglobin has been previously shown to unfold during freeze drying when lyophilized from formulations that undergo freeze-concentration induced phase separation (Heller et al. 1997. Biotechnol Prog 13:590-596). In this report, we show that such damage may be avoided using kinetic strategies to arrest the phase separation. By rapidly cooling samples during liquid nitrogen spray-freeze drying, the time that the formulation spends in temperature regimes (ca. -3 to -23 degrees C) in which phase separation is both thermodynamically favorable and kinetically realizable is minimized. Increased protein damage with decreasing cooling rates and/or longer annealing periods at -7 degrees C is observed by FTIR spectroscopy. Phase separation and concomitant protein damage may also be avoided by addition of mannitol at concentrations sufficient to cause crystallization. Mannitol crystals segregate the freeze concentrated solution into microscopic domains that block propagation and nucleation of phase separating events. Addition of noncrystallizing sugars, such as sucrose and trehalose, or nonionic surfactants, such as Tween 80 and Triton X-100, has little protective effect against phase separation induced damage during freezing drying. PMID:10099593

  6. Use of single crystal and soft piezoceramics for alleviation of flow separation induced vibration in a smart helicopter rotor

    NASA Astrophysics Data System (ADS)

    Thakkar, Dipali; Ganguli, Ranjan

    2006-04-01

    Dynamic stall and flow separation induced vibration alleviation is investigated using single crystal and soft piezoceramic-induced shear actuation. PZT-5H performs well to reduce vibration at cruise speed (about 50%) but fails to achieve a substantial vibration reduction (about 20%) at high speed forward flight because dynamic stall and flow separation require a larger stroke for vibration reduction. {\\mathrm {PZN\\mbox {-}8%PT}}\\langle 111\\rangle -induced shear actuation is found to generate a larger stroke and eventually a higher vibration reduction (about 60-70%) at both cruise and high speed flight. It is observed that the controller performs satisfactorily up to a noise level of 20% in the sensed data. Optimum placement of actuators along the span, as well as the eventualities of actuator failure and degradation are also addressed.

  7. Gentamicin-induced ototoxicity and nephrotoxicity vary with circadian time of treatment and entail separate mechanisms.

    PubMed

    Blunston, Mary A; Yonovitz, Al; Woodahl, Erica L; Smolensky, Michael H

    2015-01-01

    The aminoglycoside antibiotic gentamicin can cause both ototoxicity and nephrotoxicity, the severity of which varies with circadian time of daily treatment. However, it is not yet resolved if such drug-induced adverse effects are independent or interdependent phenomena. Two groups of 9 female Sprague-Dawley rats (200-250 g), each housed separately and entrained to a 12 h light (06:00-18:00 h) - 12 h dark cycle, received a daily subcutaneous injection of 100 mg/kg gentamicin. One group was treated at the beginning of the activity span, 2 Hours After Lights On (HALO), and the other at the beginning of the rest span, 14 HALO. Global toxicity was gauged by both body weight loss relative to the pre-treatment baseline and number of deaths. Ototoxicity, i.e., hearing loss, was assessed by changes in auditory brainstem response (ABR) for pure tone stimuli of 8, 16, 24, and 32 kHz before and after 2 and 4 weeks of gentamicin treatment. Renal toxicity was evaluated by changes in urinary N-acetyl-β-glucosaminidase (NAG)/creatinine (CR) concentration ratio before and after each week of treatment. In a complementary substudy of separate but comparable 2 and 14 HALO groups of rats, blood samples were obtained before and 30, 60, 120, and 240 min post-subcutaneous injection of 100 mg/kg gentamicin. Number of animal deaths was greater in the 2 (4 deaths) than 14 HALO (1 death) group, mirroring more severe initial (first two weeks of treatment) body weight losses from baseline, being more than 2-fold greater in animals of the 2 than 14 HALO group. Ototoxicity progressively worsened during the treatment; although, the extent of hearing loss varied according to circadian time of treatment across all frequencies (p < 0.05), particularly the 24 and 32 kHz ones (both p < 0.005), both at the 2 and 4 week assessments. At 32 kHz after 4 weeks of gentamicin dosing, the 2 HALO group showed an average 42 dB hearing loss, while the 14 HALO group exhibited only an

  8. Inducing Planar Orientation in Side-Chain Liquid-Crystalline Polymer Systems via Interfacial Control.

    PubMed

    Nagano, Shusaku

    2016-02-01

    For efficient photoresponses of liquid-crystal (LC) azobenzene (Az) polymer systems, planar LC orientation of the Az mesogenic group is required because the light irradiation process usually occurs with normal incidence to the film surface. However, LC molecules with a rodlike shape tend to orient perpendicularly to the film surface according to the excluded volume effect theory. This review introduces new approaches for inducing planar orientation in side-chain LC Az polymer films via interface and surface molecular designs. The planar orientation offers efficient in-plane photoalignment and photoswitching to hierarchical LC architectures from molecular LC mesogens and LC phases to mesoscopic microphase-separated structures. These approaches are expected to provide new concepts and possibilities in new LC polymer devices. PMID:26775770

  9. Properties and Detection Limits of Planetary Caustic Perturbation Induced by a Wide-separation Planet

    NASA Astrophysics Data System (ADS)

    Ryu, Yoon-Hyun; Chung, Sun-Ju; Lee, Ki-Won; Kim, Han-Seek; Han, Du-Hwan

    2016-03-01

    Microlensing experiments are entering a next generation of survey types to monitor a wide field of view continuously with a frequent sampling. The theoretically predicted sensitivity of a planet detection on the lensing parameters can be used for the establishment of observational strategies for maximal planet detections. Hence, we investigate the detection condition of planetary signals caused by the planetary caustic. We calculate the deviation area induced by the planetary caustic for various lensing parameters and find that the deviation area generally increases according to the increase of the source radius. However, after the normalized source radius approaches a certain value the deviation area rapidly decreases and disappears at the same normalized source radius, regardless of the mass ratio and the separation between the planet and its host star. We find a simple relation between the normalized source radius and the deviation threshold for the largest and smallest deviation areas. From this relation we also find an analytic condition for the detection limit of the planetary signal as the function of the source radius and the deviation threshold. In addition, we compare the deviation areas and the light curves between the planetary caustic perturbation and a free-floating planet. We find that the planetary caustic perturbation can be approximated by the single-lensing light curve of the planet itself perturbed by the planetary caustic. Finally, we can expect to find a low-mass planet with the Earth’s mass or even that of the Earth's moon from the detection condition and conclude that our findings may help for maximal planet detections considering the source type and the photometric accuracy.

  10. Rapid and Label-Free Separation of Burkitt's Lymphoma Cells from Red Blood Cells by Optically-Induced Electrokinetics

    PubMed Central

    Liang, Wenfeng; Zhao, Yuliang; Liu, Lianqing; Wang, Yuechao; Dong, Zaili; Li, Wen Jung; Lee, Gwo-Bin; Xiao, Xiubin; Zhang, Weijing

    2014-01-01

    Early stage detection of lymphoma cells is invaluable for providing reliable prognosis to patients. However, the purity of lymphoma cells in extracted samples from human patients' marrow is typically low. To address this issue, we report here our work on using optically-induced dielectrophoresis (ODEP) force to rapidly purify Raji cells' (a type of Burkitt's lymphoma cell) sample from red blood cells (RBCs) with a label-free process. This method utilizes dynamically moving virtual electrodes to induce negative ODEP force of varying magnitudes on the Raji cells and RBCs in an optically-induced electrokinetics (OEK) chip. Polarization models for the two types of cells that reflect their discriminate electrical properties were established. Then, the cells' differential velocities caused by a specific ODEP force field were obtained by a finite element simulation model, thereby established the theoretical basis that the two types of cells could be separated using an ODEP force field. To ensure that the ODEP force dominated the separation process, a comparison of the ODEP force with other significant electrokinetics forces was conducted using numerical results. Furthermore, the performance of the ODEP-based approach for separating Raji cells from RBCs was experimentally investigated. The results showed that these two types of cells, with different concentration ratios, could be separated rapidly using externally-applied electrical field at a driven frequency of 50 kHz at 20 Vpp. In addition, we have found that in order to facilitate ODEP-based cell separation, Raji cells' adhesion to the OEK chip's substrate should be minimized. This paper also presents our experimental results of finding the appropriate bovine serum albumin concentration in an isotonic solution to reduce cell adhesion, while maintaining suitable medium conductivity for electrokinetics-based cell separation. In short, we have demonstrated that OEK technology could be a promising tool for efficient and

  11. Rapid and label-free separation of Burkitt's lymphoma cells from red blood cells by optically-induced electrokinetics.

    PubMed

    Liang, Wenfeng; Zhao, Yuliang; Liu, Lianqing; Wang, Yuechao; Dong, Zaili; Li, Wen Jung; Lee, Gwo-Bin; Xiao, Xiubin; Zhang, Weijing

    2014-01-01

    Early stage detection of lymphoma cells is invaluable for providing reliable prognosis to patients. However, the purity of lymphoma cells in extracted samples from human patients' marrow is typically low. To address this issue, we report here our work on using optically-induced dielectrophoresis (ODEP) force to rapidly purify Raji cells' (a type of Burkitt's lymphoma cell) sample from red blood cells (RBCs) with a label-free process. This method utilizes dynamically moving virtual electrodes to induce negative ODEP force of varying magnitudes on the Raji cells and RBCs in an optically-induced electrokinetics (OEK) chip. Polarization models for the two types of cells that reflect their discriminate electrical properties were established. Then, the cells' differential velocities caused by a specific ODEP force field were obtained by a finite element simulation model, thereby established the theoretical basis that the two types of cells could be separated using an ODEP force field. To ensure that the ODEP force dominated the separation process, a comparison of the ODEP force with other significant electrokinetics forces was conducted using numerical results. Furthermore, the performance of the ODEP-based approach for separating Raji cells from RBCs was experimentally investigated. The results showed that these two types of cells, with different concentration ratios, could be separated rapidly using externally-applied electrical field at a driven frequency of 50 kHz at 20 Vpp. In addition, we have found that in order to facilitate ODEP-based cell separation, Raji cells' adhesion to the OEK chip's substrate should be minimized. This paper also presents our experimental results of finding the appropriate bovine serum albumin concentration in an isotonic solution to reduce cell adhesion, while maintaining suitable medium conductivity for electrokinetics-based cell separation. In short, we have demonstrated that OEK technology could be a promising tool for efficient and

  12. Modification of linear prepolymers to tailor heterogeneous network formation through photo-initiated Polymerization-Induced Phase Separation

    PubMed Central

    Szczepanski, Caroline R.; Stansbury, Jeffrey W.

    2015-01-01

    Polymerization-induced phase separation (PIPS) was studied in ambient photopolymerizations of triethylene glycol dimethacrylate (TEGDMA) modified by poly(methyl methacrylate) (PMMA). The molecular weight of PMMA and the rate of network formation (through incident UV-irradiation) were varied to influence both the promotion of phase separation through increases in overall free energy, as well as the extent to which phase development occurs during polymerization through diffusion prior to network gelation. The overall free energy of the polymerizing system increases with PMMA molecular weight, such that PIPS is promoted thermodynamically at low loading levels (5 wt%) of a higher molecular weight PMMA (120 kDa), while a higher loading level (20 wt%) is needed to induce PIPS with lower PMMA molecular weight (11 kDa), and phase separation was not promoted at any loading level tested of the lowest molecular weight PMMA (1 kDa). Due to these differences in overall free energy, systems modified by PMMA (11 kDa) underwent phase separation via Nucleation and Growth, and systems modified by PMMA (120 kDa), followed the Spinodal Decomposition mechanism. Despite differences in phase structure, all materials form a continuous phase rich in TEGDMA homopolymer. At high irradiation intensity (Io=20mW/cm2), the rate of network formation prohibited significant phase separation, even when thermodynamically preferred. A staged curing approach, which utilizes low intensity irradiation (Io=300µW/cm2) for the first ~50% of reaction to allow phase separation via diffusion, followed by a high intensity flood-cure to achieve a high degree of conversion, was employed to form phase-separated networks with reduced polymerization stress yet equivalent final conversion and modulus. PMID:26190865

  13. A study of a plume induced separation shock wave, including effects of periodic plume unsteadiness

    NASA Technical Reports Server (NTRS)

    Doughty, J. O.

    1976-01-01

    A wind tunnel investigation was conducted to study the flow field in which separation is caused by an expanding plume, with emphasis on effects associated with periodic unsteadiness in the plume. The separation shock was photographed with high speed motion pictures, from which mean shock position and excursion data were reported. Pressure fluctuations were measured beneath the separation shock. A response of the separation shock to plume periodic unsteadiness was identified, and the magnitude of a corresponding transfer function was defined. Small harmonic effects in plume response to periodic unsteadiness were noted. The stabilizing effect of a lateral surface protuberance near the separation shock wave was investigated. The protuberance configuration was a lateral circular cylinder, and various diameters, all less than the boundary layer thickness, were employed.

  14. Gravitational sedimentation induced blood delamination for continuous plasma separation on a microfluidics chip.

    PubMed

    Zhang, Xian-Bo; Wu, Zeng-Qiang; Wang, Kang; Zhu, Jie; Xu, Jing-Juan; Xia, Xing-Hua; Chen, Hong-Yuan

    2012-04-17

    Continuous plasma separation will be greatly helpful for dynamic metabolite monitoring in kinetics research and drug development. In this work, we proposed a continuous on-chip plasma separation method based on the natural aggregating and sedimentation behavior of red blood cells at low shear rate. In this approach, a glass capillary was first used to realize quick and obvious delamination of blood cells from plasma. A novel "dual-elbow" connector was designed to change the direction of delamination. The blood was finally separated by laminar flow and bifurcation on the microchip. Results demonstrated that the present device can efficiently and stably separate plasma from blood in a continuous means, e.g., in a 4 h separation we did not observe clogging or a trend of clogging. In addition, the present approach can avoid the damage to cells which usually occurs in separation with high shear rate in a microchannel and possible contaminants to plasma. The proposed microchip device is robust, simple, and inexpensive for long time plasma separation with high plasma recovery and less sample consumption. The present work provides an effective tool for metabolite monitoring in pharmacokinetics research and drug development. PMID:22449121

  15. Separation of porphyrin-based photosensitizer isomers by laser-induced fluorescence capillary electrophoresis.

    PubMed

    Peng, Xuejun; Sternberg, Ethan; Dolphin, David

    2005-10-01

    Methods for the separation of photosensitizer isomers, such as benzoporphyrin derivative monoacid, benzoporphyrin ethyl monoacid, 2-[1-hexyloxyethyl]-2-devinylpyropheophorbide-a, diethyleneglycol diester benzoporphyrin derivative, tin ethyl etiopurpurin, and phthalocyanine tetrasulfonate, have been systematically developed by CE. Detection was accomplished by UV absorption at 214 nm or by LIF with excitation at 442/488 nm and emission at 690 nm. The effects of three major experimental parameters of buffer types, organic solvents, and surfactant additives are described. The optimized separation conditions were determined so as to provide satisfactory separation efficiency and analysis time. The methods are shown to be suitable for the separation and determination of porphyrin and phthalocyanines regioisomers, diastereoisomers, and enantiomers. PMID:16231398

  16. Phase separation between conductive and insulative materials induced by the electric field

    NASA Astrophysics Data System (ADS)

    Nagamine, Yuko

    2016-07-01

    To demonstrate that phase separation is a main mechanism of pattern formation for one of the spatiotemporal patterns emerging in the Ag and Sb electrodeposition system, I performed numerical simulations to model the mixed system of conductive and insulative materials under a steady electric field. For such a dissipative system, I derived the extended Cahn-Hilliard equation using Onsager's variational principle. My results demonstrate that conductive and insulative materials phase separate spatially under the constant-current mode.

  17. Phase separation between conductive and insulative materials induced by the electric field.

    PubMed

    Nagamine, Yuko

    2016-07-01

    To demonstrate that phase separation is a main mechanism of pattern formation for one of the spatiotemporal patterns emerging in the Ag and Sb electrodeposition system, I performed numerical simulations to model the mixed system of conductive and insulative materials under a steady electric field. For such a dissipative system, I derived the extended Cahn-Hilliard equation using Onsager's variational principle. My results demonstrate that conductive and insulative materials phase separate spatially under the constant-current mode. PMID:27575064

  18. The project of the mass separator of atomic nuclei produced in heavy ion induced reactions

    NASA Astrophysics Data System (ADS)

    Oganessian, Yu. Ts.; Shchepunov, V. A.; Dmitriev, S. N.; Itkis, M. G.; Gulbekyan, G. G.; Khabarov, M. V.; Bekhterev, V. V.; Bogomolov, S. L.; Efremov, A. A.; Pashenko, S. V.; Stepantsov, S. V.; Yeremin, A. V.; Yavor, M. I.; Kalimov, A. G.

    2003-05-01

    A new separator and mass analyzer, named MASHA (mass analyzer of super heavy atoms), has been designed at the Flerov Laboratory JINR Dubna to separate and measure masses of nuclei and molecules with precision better than 10 -3. The set up can work in the wide mass range from A≈20 to A≈500, its mass acceptance is as large as ±2.8%. In particular, it allows unambiguous mass identification of super heavy nuclei with a resolution better than 1 amu at the level of 300 amu. Synthesized in nuclear reactions nuclides are emitted from an ECR ion source at energy E=40 kV and charge state Q=+1. Then they pass the following steps of separation and analysis: the first section of rough separation, the second section of separation and mass analysis and the final section of separation with a 90° electrostatic deflector. In the focal plane of the device, a focal plane detector determines positions (masses) of studied nuclei. Ion optics of the analyzer, optimized up to the second order, is considered. Description of its elements and subsystems is given.

  19. Smart Fiber Membrane for pH-Induced Oil/Water Separation.

    PubMed

    Li, Jin-Jin; Zhou, Yin-Ning; Luo, Zheng-Hong

    2015-09-01

    Wastewater contaminated with oil or organic compounds poses threats to the environment and humans. Efficient separation of oil and water are highly desired yet still challenging. This paper reports the fabrication of a smart fiber membrane by depositing pH-responsive copolymer fibers on a stainless steel mesh through electrospinning. The cost-effective precursor material poly(methyl methacrylate)-block-poly(4-vinylpyridine) (PMMA-b-P4VP) was synthesized using copper(0)-mediated reversible-deactivation radical polymerization. The pH-responsive P4VP and the underwater oleophilic/hydrophilic PMMA confer the as-prepared membrane with switchable surface wettability toward water and oil. The three-dimensional network structure of the fibers considerably strengthens the oil/water wetting property of the membrane, which is highly desirable in the separation of oil and water mixtures. The as-prepared fiber membrane accomplishes gravity-driven pH-controllable oil/water separations. Oil selectively passes through the membrane, whereas water remains at the initial state; after the membrane is wetted with acidic water (pH 3), a reverse separation is realized. Both separations are highly efficient, and the membrane also exhibits switchable wettability after numerous cycles of the separation process. This cost-effective and easily mass-produced smart fiber membrane with excellent oil-fouling repellency has significant potential in practical applications, such as water purification and oil recovery. PMID:26293145

  20. Beta transition and stress-induced phase separation in the spinning of spider dragline silk.

    PubMed

    Knight, D P; Knight, M M; Vollrath, F

    2000-06-13

    Spider dragline silk is formed as the result of a remarkable transformation in which an aqueous dope solution is rapidly converted into an insoluble protein filament with outstanding mechanical properties. Microscopy on the spinning duct in Nephila edulis spiders suggests that this transformation involves a stress-induced formation of anti-parallel beta-sheets induced by extensional flow. Measurements of draw stress at different draw rates during silking confirm that a stress-induced phase transition occurs. PMID:10828366

  1. Effects of the positive feedback loop in polymerization on the reaction-induced phase separation of polymer mixturesa)

    NASA Astrophysics Data System (ADS)

    Furubayashi, Y.; Kawakubo, R.; Nakanishi, H.; Norisuye, T.; Tran-Cong-Miyata, Q.

    2015-06-01

    Phase separation of mixtures composed of a guest polymer dissolved in monomer of a host polymer was induced by photopolymerization. From the polymerization kinetics, it was found that for the host polymer with the glass transition temperature (Tg) higher than the experimental temperature, the Trommsdorff-Norrish effect emerges, providing a method to terminate the phase separation at various intermediate stages of the process and thereby a variety of morphologies can be constructed. For the host polymers with (Tg) lower than the experimental temperature, the freezing process of morphology is not complete, leading to the secondary phase separation inside the domains already generated by the primary process. The kinetics of this secondary phase separation indicates that the peculiar morphology like "sunny-side-up egg"-like structures was generated via spinodal decomposition. The experimental results obtained in this study show that the competition between photopolymerization and phase separation can provide a useful method of materials design in the micro- and sub-micrometer scales.

  2. Selective Metal Deposition on a Phase-Separated Polymer Blend Surface

    NASA Astrophysics Data System (ADS)

    Tsujioka, Tsuyoshi; Yamaguchi, Koji

    2013-07-01

    We report selective metal deposition on a phase-separated polymer blend surface. A polymer blend film consisting of polystyrene (PS) and a polystyrene-block-polybutadiene copolymer (PS-BR) was annealed, and a micro-phase-separated film was obtained. Pb was evaporated onto the phase-separated surface without an evaporation mask and was selectively deposited on the PS phase but not on the PS-BR phase. We achieved fine metal patterns corresponding to the microphase separation. This result suggests a novel method of preparing fine metal patterns for electronics and photonics.

  3. Electric Double-Layer Effects Induce Separation of Aqueous Metal Ions.

    PubMed

    Ji, Qinghua; An, Xiaoqiang; Liu, Huijuan; Guo, Lin; Qu, Jiuhui

    2015-11-24

    Metal ion separation is crucial to environmental decontamination, chromatography, and metal recovery and recycling. Theoretical studies have suggested that the ion distributions in the electric double-layer (EDL) region depend on the nature of the ions and the characteristics of the charged electrode surface. We believe that rational design of the electrode material and device structure will enable EDL-based devices to be utilized in the separation of aqueous metal ions. On the basis of this concept, we fabricate an EDL separation (EDLS) device based on sandwich-structured N-functionalized graphene sheets (CN-GS) for selective separation of aqueous toxic heavy metal ions. We demonstrate that the EDLS enables randomly distributed soluble ions to form a coordination-driven layer and electrostatic-driven layer in the interfacial region of the CN-GS/solution. Through tuning the surface potential of the CN-GS, the effective separation of heavy metal ions (coordination-driven layer) from alkali or alkaline earth metal ions (electrostatic-driven layer) can be achieved. PMID:26481603

  4. Photochemically induced charge separation occurring in bacteriorhodopsin. Detection by time-resolved dielectric loss.

    PubMed Central

    McIntosh, A R; Boucher, F

    1991-01-01

    Time-resolved dielectric loss (TRDL) measurements are reported for the photochemical excitation of bacteriorhodopsin (bR) in solid films of Halobacterium halobium purple membranes. These measurements provide an independent confirmation for the existence of an important component of charge separation in these membranes after photochemical excitation. The separation of charge is detected by the absorption of microwave energy by the multilayer films of purple membranes in a microwave cavity during flash photolysis experiments. The TRDL method has the advantage of being sensitive to charge separation occurring in both oriented and unoriented films of purple membranes. One disadvantage is that the water content of the samples must be minimized, however, there is some absorbed water present in our electrodeposited solid film samples. To the best of our knowledge, TRDL measurements have not been reported previously for photochemical charge separation in biological membranes. It is significant that an early decay component of TRDL in the 20-microseconds time domain corresponds to the relaxation of the negative charge displacement photocurrent in oriented samples of purple membranes. In addition, a component of charge separation persists during the first several hundred microseconds of the bR photocycle. PMID:1883930

  5. Control of unsteady shock-induced turbulent boundary layer separation upstream of blunt fins

    NASA Technical Reports Server (NTRS)

    Kleifges, K.; Dolling, D. S.

    1993-01-01

    Fluctuating wall pressure measurements have been made on centerline upstream of blunt fins in a Mach 5 turbulent boundary layer. Standard time series analysis and conditional sampling algorithms have been used to examine the effects of leading edge sweepback, leading edge shape, and fin root modifications on the fluctuating pressures. Leading edge sweep considerably reduces the mean and rms pressure loading at the fin root, the extent of the region of unsteady separation shock motion, and the separation length. The frequency of pressure fluctuations in the intermittent region increases with leading edge sweepback, while the spectral content of pressure fluctuations in the separated region is virtually unchanged by leading edge sweep. A swept hemicylindrically blunted root fillet reduces the centerline upstream influence and intermittent region length by 50 percent, and reduces the mean and rms pressure loading at the fin root by about 75 percent and 95 percent respectively. Experiments using hemicylindrical, wedge shaped and flat leading edges show that while separated flow scales increase with increasing 'bluntness', intermittent region length and root loading decrease, and separation shock frequency increases.

  6. Stable suspension and dispersion-induced transitions from repulsive Casimir forces between fluid separated eccentric cylinders

    SciTech Connect

    Dalvit, Diego A1; Rodriguez, Alejandro W; Munday, J N; Joannopoulos, J D

    2008-01-01

    Using accurate numerical methods for finite-size nonplanar objects, we demonstrate a stable mechanical suspension of a silica cylinder within a metallic cylinder separated by ethanol, via a repulsive Casimir force between the silica and the metal. We investigate cylinders with both circular and square cross sections, and show that the latter exhibit a stable orientation as well as a stable position, employing a new method to accurately compute Casimir torques for finite objects. Furthermore, the stable orientation of the square cylinder is shown to undergo an unusual 45 transition as a function of the separation lengthscale, and this transition is explained as a consequence of material dispersion.

  7. Large-angular separation of particles induced by cascaded deflection angles in optical sorting

    PubMed Central

    Yuan, X.-C.; Zhu, S. W.; Bu, J.; Sun, Y. Y.; Lin, J.; Gao, Bruce Z.

    2013-01-01

    A composite microlens array (MLA) with two cascaded guiding axes has been fabricated to achieve a large lateral separation of an object with different refractive indices or sizes. The MLA projects a composite pattern formed by its focal spots into a microchamber for optical sorting in a microscopic system. This approach enables passive, high power, efficient, and continuous microfluidic sorting without requiring complicated optical assembly. Separation of particles with different refractive indices to a lateral angle of 40° is experimentally demonstrated with moderate laser power. PMID:23997243

  8. Micro-phase assembly of active sites in a coarse-grained model of chromatin by Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Zhang, Yang; Heermann, Dieter; Farmer, Barry; Pandey, Ras

    2011-03-01

    A coarse-grained model is used to study the self-assembly of active sites in a DNA (chromatin) chain. The chromosome is described by a bond-fluctuating chain of two types of nodes A (interacting) and B (non-interacting), distributed randomly with concentration C and 1 - C respectively. Active nodes interact with a Lennard-Jones (LJ) potential and execute their stochastic motion with the Metropolis algorithm. The depth of the LJ potential (f) , a measure of interaction strength and the concentration (C) of the active sites are varied. A number of local and global physical quantities are studied such as mobility (Mn) profile of each node, their local structural profile, root mean square (RMS) displacement (R) , radius of gyration (Rg) , and structure factor S (q) . We find that the chain segments assemble into microphase of blobs which requires higher concentration of active sites at weaker interaction. These findings are consistent with that of a dynamic loop model of chromatin on global (large) scale but differ at small scales. This work is supported in part by the Alexander von Humboldt foundation and AFRL.

  9. Investigation of Shock-Induced Laminar Separation Bubble in a Supersonic Boundary Layer

    NASA Astrophysics Data System (ADS)

    Sivasubramanian, Jayahar; Fasel, Hermann

    2015-11-01

    The interaction between an impinging oblique shock and a laminar boundary-layer on a flat plate is investigated using DNS. In particular, the two-dimensional separation bubble resulting from the shock/boundary-layer interaction (SBLI) at freestream Mach number of 2.0 is investigated in detail. The flow parameters used for the present investigation match the laboratory conditions in the experiments by Hakkinen et al. The skin friction and pressure distribution from the simulations are compared to the experimental measurements and numerical results available in the literature. Our results confirm the asymmetric nature of the separation bubble as reported in the literature. In addition to the steady flow field calculations, the response to low-amplitude disturbances is investigated in order to study the linear stability behavior of the separation bubble. For comparison, both the development of two-dimensional and three-dimensional (oblique) disturbances are studied with and without the impinging oblique shock. Furthermore, the effects of the shock incidence angle and Reynolds number are also investigated. Finally, three-dimensional simulations were performed in order to explore the laminar-turbulent transition process in the presence of a laminar separation bubble. Funded by the Air Force Office of Scientific Research under grant FA9550-14-1-0195.

  10. Traction–separation relationships for hydrogen induced grain boundary embrittlement in nickel via molecular dynamics simulations

    SciTech Connect

    Barrows, Wesley; Dingreville, Rémi; Spearot, Douglas

    2015-10-19

    A statistical approach combined with molecular dynamics simulations is used to study the influence of hydrogen on intergranular decohesion. This methodology is applied to a Ni Σ3(112)[11¯0] symmetric tilt grain boundary. Hydrogenated grain boundaries with different H concentrations are constructed using an energy minimization technique with initial H atom positions guided by Monte Carlo simulation results. Decohesion behavior is assessed through extraction of a traction–separation relationship during steady-state crack propagation in a statistically meaningful approach, building upon prior work employing atomistic cohesive zone volume elements (CZVEs). A sensitivity analysis is performed on the numerical approach used to extract the traction–separation relationships, clarifying the role of CZVE size, threshold parameters necessary to differentiate elastic and decohesion responses, and the numerical averaging technique. Results show that increasing H coverage at the Ni Σ3(112)[11¯0] grain boundary asymmetrically influences the crack tip velocity during propagation, leads to a general decrease in the work of separation required for crack propagation, and provides a reduction in the peak stress in the extracted traction–separation relationship. Furthermore the present framework offers a meaningful vehicle to pass atomistically derived interfacial behavior to higher length scale formulations for intergranular fracture.

  11. A Classroom Demonstration of Water-Induced Phase Separation of Alcohol-Gasoline Biofuel Blends

    ERIC Educational Resources Information Center

    Mueller, Sherry A.; Anderson, James E.; Wallington, Timothy J.

    2009-01-01

    A significant issue associated with ethanol-gasoline blends is the phase separation that occurs with the addition of small volumes of water, producing an ethanol-deficient gasoline layer and an ethanol-rich aqueous layer. The gasoline layer may have a lower-than-desired octane rating due to the decrease in ethanol content, resulting in engine…

  12. A new approach to network heterogeneity: Polymerization Induced Phase Separation in photo-initiated, free-radical methacrylic systems.

    PubMed

    Szczepanski, Caroline R; Pfeifer, Carmem S; Stansbury, Jeffrey W

    2012-09-28

    Non-reactive, thermoplastic prepolymers (poly- methyl, ethyl and butyl methacrylate) were added to a model homopolymer matrix composed of triethylene glycol dimethacrylate (TEGDMA) to form heterogeneous networks via polymerization induced phase separation (PIPS). PIPS creates networks with distinct phase structure that can partially compensate for volumetric shrinkage during polymerization through localized internal volume expansion. This investigation utilizes purely photo-initiated, free-radical systems, broadening the scope of applications for PIPS since these processing conditions have not been studied previously.The introduction of prepolymer into TEGDMA monomer resulted in stable, homogeneous monomer formulations, most of which underwent PIPS upon photo-irradiation, creating heterogeneous networks. During polymerization the presence of prepolymer enhanced autoacceleration, allowing for a more extensive ambient cure of the material. Phase separation, as characterized by dynamic changes in sample turbidity, was monitored simultaneously with monomer conversion and either preceded or was coincident with network gelation. Dynamic mechanical analysis shows a broadening of the tan delta peak and secondary peak formation, characteristic of phase-separated materials, indicating one phase rich in prepolymer and another depleted form upon phase separation. In certain cases, PIPS leads to an enhanced physical reduction of volumetric shrinkage, which is attractive for many applications including dental composite materials. PMID:23109733

  13. Structure of the wall pressure fluctuations in a shock-induced separated turbulent flow

    NASA Technical Reports Server (NTRS)

    Muck, K. C.; Bogdonoff, S. M.; Dussauge, J.-P.

    1985-01-01

    This paper presents the results of an experimental study of the unsteady nature of a shock wave/turbulent boundary layer interaction. The interaction was generated using an unswept compression ramp. The incoming freestream Mach number was 2.9 and the flow was separated at the corner. An array of flush mounted miniature high frequency pressure transducers was used to make multi-channel measurements of the fluctuating wall pressure within the interaction. From the present results, an overall picture of the instantaneous structure of the unsteady shock system (as inferred from the wall pressure signals) can be constructed. The flow ahead of the corner can be considered as composed of two regions, namely the 'intermittent' region where there is essentially a single leading shock which exhibits significant streamwise 'flapping' and spanwise 'rippling', and the separated region where the flow experiences continuous compression.

  14. Ramsey's method of separated oscillating fields and its application to gravitationally induced quantum phase shifts

    SciTech Connect

    Abele, H.; Jenke, T.; Leeb, H.; Schmiedmayer, J.

    2010-03-15

    We propose to apply Ramsey's method of separated oscillating fields to the spectroscopy of the quantum states in the gravity potential above a horizontal mirror. This method allows a precise measurement of quantum mechanical phaseshifts of a Schroedinger wave packet bouncing off a hard surface in the gravitational field of the Earth. Measurements with ultracold neutrons will offer a sensitivity to Newton's law or hypothetical short-ranged interactions, which is about 21 orders of magnitude below the energy scale of electromagnetism.

  15. Traction–separation relationships for hydrogen induced grain boundary embrittlement in nickel via molecular dynamics simulations

    DOE PAGESBeta

    Barrows, Wesley; Dingreville, Rémi; Spearot, Douglas

    2015-10-19

    A statistical approach combined with molecular dynamics simulations is used to study the influence of hydrogen on intergranular decohesion. This methodology is applied to a Ni Σ3(112)[11¯0] symmetric tilt grain boundary. Hydrogenated grain boundaries with different H concentrations are constructed using an energy minimization technique with initial H atom positions guided by Monte Carlo simulation results. Decohesion behavior is assessed through extraction of a traction–separation relationship during steady-state crack propagation in a statistically meaningful approach, building upon prior work employing atomistic cohesive zone volume elements (CZVEs). A sensitivity analysis is performed on the numerical approach used to extract the traction–separationmore » relationships, clarifying the role of CZVE size, threshold parameters necessary to differentiate elastic and decohesion responses, and the numerical averaging technique. Results show that increasing H coverage at the Ni Σ3(112)[11¯0] grain boundary asymmetrically influences the crack tip velocity during propagation, leads to a general decrease in the work of separation required for crack propagation, and provides a reduction in the peak stress in the extracted traction–separation relationship. Furthermore the present framework offers a meaningful vehicle to pass atomistically derived interfacial behavior to higher length scale formulations for intergranular fracture.« less

  16. New influence factor inducing difficulty in selective flotation separation of Cu-Zn mixed sulfide minerals

    NASA Astrophysics Data System (ADS)

    Deng, Jiu-shuai; Mao, Ying-bo; Wen, Shu-ming; Liu, Jian; Xian, Yong-jun; Feng, Qi-cheng

    2015-02-01

    Selective flotation separation of Cu-Zn mixed sulfides has been proven to be difficult. Thus far, researchers have found no satisfactory way to separate Cu-Zn mixed sulfides by selective flotation, mainly because of the complex surface and interface interaction mechanisms in the flotation solution. Undesired activation occurs between copper ions and the sphalerite surfaces. In addition to recycled water and mineral dissolution, ancient fluids in the minerals are observed to be a new source of metal ions. In this study, significant amounts of ancient fluids were found to exist in Cu-Zn sulfide and gangue minerals, mostly as gas-liquid fluid inclusions. The concentration of copper ions released from the ancient fluids reached 1.02 × 10-6 mol/L, whereas, in the cases of sphalerite and quartz, this concentration was 0.62 × 10-6 mol/L and 0.44 × 10-6 mol/L, respectively. As a result, the ancient fluid is a significant source of copper ions compared to mineral dissolution under the same experimental conditions, which promotes the unwanted activation of sphalerite. Therefore, the ancient fluid is considered to be a new factor that affects the selective flotation separation of Cu-Zn mixed sulfide ores.

  17. Fluorine-Free Superhydrophobic Coatings with pH-induced Wettability Transition for Controllable Oil-Water Separation.

    PubMed

    Xu, Zhiguang; Zhao, Yan; Wang, Hongxia; Zhou, Hua; Qin, Chuanxiang; Wang, Xungai; Lin, Tong

    2016-03-01

    We present a simple, environmentally friendly approach to fabricating superhydrophobic coatings with pH-induced wettability transition. The coatings are prepared from a mixture of silica nanoparticles and decanoic acid-modified TiO2. When the coating is applied on cotton fabric, the fabric turns superhydrophobic in air but superoleophilic in neutral aqueous environment. It is permeable to oil fluids but impermeable to water. However, when the coated fabric is placed in basic aqueous solution or ammonia vapor, it turns hydrophilic but underwater superoleophobic, thus allowing water to penetrate through but blocking oil. Therefore, such a unique, selective water/oil permeation feature makes the treated fabric have capability to separate either oil or water from a water-oil mixture. It may be useful for development of smart oil-water separators, microfluidic valves, and lab-on-a-chip devices. PMID:26837794

  18. Vortex generators for control of shock-induced separation. Part 3: Examples of applications of vortex generators to aircraft

    NASA Astrophysics Data System (ADS)

    1993-12-01

    ESDU 93026 illustrates by case studies the use of the information in Parts 1 and 2 on the use of vortex generators to control shock-induced separation. The examples are the control of internal noise by the application of vortex generators on the forward cabin roof of a business aircraft (Gulfstream III), the control of separation associated with a three-shock pattern near the tip of a highly swept and tapered model wing in a wind-tunnel, and the improvement of the buffet maneuver boundary on a straight wing interceptor aircraft of the fifties. In each case the geometric details of the arrays of vortex generators tested are provided, the results obtained are described, and the aerodynamic principles involved that influence those results are assessed.

  19. Polymer induced flocculation and separation of particulates from extracts of lignocellulosic materials.

    PubMed

    Duarte, G V; Ramarao, B V; Amidon, T E

    2010-11-01

    Biofuels from lignocellulosic materials like wood are renewable and sustainable alternatives to petroleum and other fossil fuels. Wood can be grown and harvested without adding to the carbon load of the atmosphere and thus can be part of the solution to the problem posed by global climate changes. Recently much interest has developed on the concept of the forest product biorefinery, where wood is hydrolyzed prior to conventional pulping and papermaking processes and the hydrolyzate consisting of hemicellulose sugars are to be used as a feedstock for biofuels or bioplastics. The purification of the hydrolyzate stream and the separation of fermentable sugars from it thus constitutes an important step in biorefinery processes. The separation of particulate material from wood hydrolyzates is considered in this paper. Sugar maple hardwood was extracted with hot water at 160 degrees C. The extracts contain hemicelluloses (primarily xylooligomers, xylose and xylan), acetic acid and smaller amounts of lignin. The colloidal stability of the extracts plays a critical role in the separation and purification of the wood extracts. Here, we report the size and charge of the particles in the extract measured using standard instruments based on light scattering and microelectrophoresis. Particles were found to be in the size range from approximately 220nm to 270nm. Zeta potential measurements showed them to be negatively charged. By treating the extracts with a cationic flocculating agent poly-DADMAC, it was possible to preferentially precipitate out the colloidal fraction containing lignin and lignin derived compounds. Upon the addition of poly-DADMAC the turbidity of the suspension reduced from 920 NTU to 4 NTU in a 24 h period and particulates sedimented from the extract. The lignin concentration was reduced in the supernatant, while the sugar content remained unchanged. The addition of an indifferent electrolyte hindered the effectiveness of the polyelectrolyte. The optimum p

  20. High-pressure light scattering apparatus to study pressure-induced phase separation in polymer solutions

    NASA Astrophysics Data System (ADS)

    Xiong, Yan; Kiran, Erdogan

    1998-03-01

    A new high-pressure time- and angle-resolved light scattering apparatus has been developed to study the kinetics of phase separation in polymer solutions and other fluid mixtures under pressure at near- and supercritical conditions. The system consists of a high-pressure polymer loading chamber, a solvent charge line, a variable-volume scattering cell (with a built-in movable piston connected to a pressure generator, and an expansion rod driven by an air-actuated diaphragm), and a recirculation pump which are all housed in a temperature-controlled oven. The system is operable at pressures up to 70 MPa, and temperatures up to 473 K. The scattering cell is a short path-length cell made of two flat sapphire windows that are separated by 250 μm. It is designed to permit measurements of transmitted and scattered light intensities over an angle range from 0° to 30°. A linear image sensor with 256 elements is used to monitor the time evolution of the scattered light intensities at different angles. With this sensor, the angle range from 2° to 13° is scanned at a sampling rate of 3.2 ms/scan. The pressure quenches are achieved by movement of the air-actuated movable expansion rod, or by the movement of the piston with the aid of the pressure generator to bring about either rapid (at rates approaching 2000 MPa/s) or slow pressure changes in the system. Quench depth is also adjustable, and very deep (70 MPa) or very shallow (as low as 0.1 MPa) pressure quenches are readily achievable. The temperature and the pressure of the solution in the scattering cell, and the transmitted and scattered light intensities at different angles are recorded in real time through a computerized data acquisition system before and during phase separation. The experimental system is especially suited to follow the kinetics of phase separation in polymer solutions and to assess the metastable and unstable regions where phase separation proceeds by the nucleation and growth, and the spinodal

  1. Oxidation Ability of Plasmon-Induced Charge Separation Evaluated on the Basis of Surface Hydroxylation of Gold Nanoparticles.

    PubMed

    Nishi, Hiroyasu; Tatsuma, Tetsu

    2016-08-26

    The oxidation ability of plasmonic photocatalysts, which has its origins in plasmon-induced charge separation and has not yet been studied quantitatively and systematically, is important for designing practical photocatalytic systems. Oxidation ability was investigated on the basis of surface hydroxylation of Au nanoparticles on TiO2 at various irradiation wavelengths and electrolyte pH values. The reaction proceeds only when the sum of the flat band potential of TiO2 and the irradiated photon energy is close to, or more positive than, the theoretical potential for the reaction. PMID:27505255

  2. The Energetics of the Primary Proton Transfer in Bacteriorhodopsin Revisited: It is a Sequential Light Induced Charge Separation After All

    PubMed Central

    Braun-Sand, Sonja; Sharma, Pankaz K.; Chu, Zhen T.; Pisliakov, Andrei V.; Warshel, Arieh

    2008-01-01

    The light induced proton transport in bacteriorhodopsin has been considered as a model for other light-induced proton pumps. However, the exact nature of this process is still unclear. For example, it is not entirely clear what the driving force of the initial proton transfer is and, in particular, whether it reflects electrostatic forces or other effects. The present work simulates the primary proton transfer (PT) by a specialized combination of the EVB and the QCFF/PI methods. This combination allows us to obtain sufficient sampling and a quantitative free energy profile for the PT at different protein configurations. The calculated profiles provide new insight about energetics of the primary PT and its coupling to the protein conformational changes. The present finding confirms the tentative analysis of our early work [1] and determines that the overall PT process is driven by the energetics of the charge separation between the Schiff base and its counterion Asp85. Apparently, the light-induced relaxation of the steric energy of the chromophore leads to an increase in the ion-pair distance, and this drives the PT process. Our use of the linear response approximation allows us to estimate the change in the protein conformational energy and provides the first computational description of the coupling between the protein structural changes and the PT process. It is also found that the PT is not driven by twist-modulated changes of the Schiff base’s pKa, changes in the hydrogen bond directionality, or other non-electrostatic effects. Overall, based on a consistent use of structural information as the starting point for converging free-energy calculations, we conclude that the primary event should be described as a light-induced formation of an unstable ground state, whose relaxation leads to charge separation and to the destabilization of the ion-pair state. This provides the driving force for the subsequent PT steps. PMID:18387356

  3. From matrix nano- and micro-phase tougheners to composite macro-properties.

    PubMed

    Kinloch, A J; Taylor, A C; Techapaitoon, M; Teo, W S; Sprenger, S

    2016-07-13

    In this paper, firstly, the morphology and toughness of a range of bulk epoxy polymers, which incorporate a second phase of well-dispersed silica nanoparticles and/or rubber microparticles, have been determined. Secondly, the macro-properties of natural-fibre reinforced-plastic (NFRP) composites based upon these epoxy polymers have been ascertained, using (i) unidirectional flax fibres or (ii) regenerated-cellulose fibres in the architecture of a plain-woven fabric. Thirdly, the toughening mechanisms which are induced in these materials by the presence of the silica nanoparticles, the rubber microparticles and the natural fibres have been identified. Finally, the values of the toughness of the bulk epoxy polymers and corresponding NFRPs have been quantitatively modelled. The increased toughness recorded for the bulk epoxy polymer due to the presence of the silica nanoparticles and/or rubber microparticles was indeed typically transferred to the NFRP composites when using such epoxies as the matrices for the fibres. Thus, the important role that may be played by modifications to the epoxy matrices in order to increase the toughness of the composites was very clearly demonstrated by these results. However, notwithstanding, the toughening mechanisms induced by the fibres were essentially responsible for the very high toughnesses of the NFRP composites, compared with the bulk epoxy polymers. The modelling studies successfully predicted the values of toughness of the bulk epoxy polymers and of the NFRP composites. These studies also quantified the extent to which each toughening mechanism, induced by the second-phase nano- and microparticles and the natural fibres, contributed to the overall values of toughness of the materials. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'. PMID:27242298

  4. Light-Induced Charge Separation in Densely Packed Donor-Acceptor Coordination Cages.

    PubMed

    Frank, Marina; Ahrens, Jennifer; Bejenke, Isabel; Krick, Marcel; Schwarzer, Dirk; Clever, Guido H

    2016-07-01

    Photon-powered charge separation is achieved in a supramolecular architecture based on the dense packing of functional building blocks. Therefore, self-assembled dimers of interpenetrated coordination cages consisting of redoxactive chromophors were synthesized in a single assembly step starting from easily accessible ligands and Pd(II) cations. Two backbones consisting of electron rich phenothiazine (PTZ) and electron deficient anthraquinone (ANQ) were used to assemble either homo-octameric or mixed-ligand double cages. The electrochemical and spectroscopic properties of the pure cages, mixtures of donor and acceptor cages and the mixed-ligand cages were compared by steady-state UV-vis and transient absorption spectroscopy, supported by cyclic voltammetry and spectroelectrochemistry. Only the mixed-ligand cages, allowing close intra-assembly communication between the donors and acceptors, showed the evolution of characteristic PTZ radical cation and ANQ radical anion features upon excitation in the transient spectra. In contrast, excitation of the mixtures of the homo-octameric donor and acceptor cages in solution did not lead to any signs of electron transfer. Densely packed photo- and redox-functional self-assemblies promise molecular-level control over the morphology of the charge separation layer in future photovoltaic applications. PMID:27258549

  5. Interaction Mechanisms of Cavitation Bubbles Induced by Spatially and Temporally Separated fs-Laser Pulses

    PubMed Central

    Tinne, Nadine; Kaune, Brigitte; Krüger, Alexander; Ripken, Tammo

    2014-01-01

    The emerging use of femtosecond lasers with high repetition rates in the MHz regime together with limited scan speed implies possible mutual optical and dynamical interaction effects of the individual cutting spots. In order to get more insight into the dynamics a time-resolved photographic analysis of the interaction of cavitation bubbles is presented. Particularly, we investigated the influence of fs-laser pulses and their resulting bubble dynamics with various spatial as well as temporal separations. Different time courses of characteristic interaction effects between the cavitation bubbles were observed depending on pulse energy and spatio-temporal pulse separation. These ranged from merely no interaction to the phenomena of strong water jet formation. Afterwards, the mechanisms are discussed regarding their impact on the medical application of effective tissue cutting lateral to the laser beam direction with best possible axial precision: the mechanical forces of photodisruption as well as the occurring water jet should have low axial extend and a preferably lateral priority. Furthermore, the overall efficiency of energy conversion into controlled mechanical impact should be maximized compared to the transmitted pulse energy and unwanted long range mechanical side effects, e.g. shock waves, axial jet components. In conclusion, these experimental results are of great importance for the prospective optimization of the ophthalmic surgical process with high-repetition rate fs-lasers. PMID:25502697

  6. Efficient UV-induced charge separation and recombination in an 8-oxoguanine-containing dinucleotide.

    PubMed

    Zhang, Yuyuan; Dood, Jordan; Beckstead, Ashley A; Li, Xi-Bo; Nguyen, Khiem V; Burrows, Cynthia J; Improta, Roberto; Kohler, Bern

    2014-08-12

    During the early evolution of life, 8-oxo-7,8-dihydro-2'-deoxyguanosine (O) may have functioned as a proto-flavin capable of repairing cyclobutane pyrimidine dimers in DNA or RNA by photoinduced electron transfer using longer wavelength UVB radiation. To investigate the ability of O to act as an excited-state electron donor, a dinucleotide mimic of the FADH2 cofactor containing O at the 5'-end and 2'-deoxyadenosine at the 3'-end was studied by femtosecond transient absorption spectroscopy in aqueous solution. Following excitation with a UV pulse, a broadband mid-IR pulse probed vibrational modes of ground-state and electronically excited molecules in the double-bond stretching region. Global analysis of time- and frequency-resolved transient absorption data coupled with ab initio quantum mechanical calculations reveal vibrational marker bands of nucleobase radical ions formed by electron transfer from O to 2'-deoxyadenosine. The quantum yield of charge separation is 0.4 at 265 nm, but decreases to 0.1 at 295 nm. Charge recombination occurs in 60 ps before the O radical cation can lose a deuteron to water. Kinetic and thermodynamic considerations strongly suggest that all nucleobases can undergo ultrafast charge separation when π-stacked in DNA or RNA. Interbase charge transfer is proposed to be a major decay pathway for UV excited states of nucleic acids of great importance for photostability as well as photoredox activity. PMID:25071180

  7. Liquid filament instability due to stretch-induced phase separation in polymer solutions

    NASA Astrophysics Data System (ADS)

    Arinstein, Arkadii; Kulichikhin, Valery; Malkin, Alexander; Technion-Israel Institute of Technology Collaboration; Institute of Petrochemical Synthesis, Russian Academy of Sciences Team

    2015-03-01

    The instability in a jet of a viscoelastic semi-dilute entangled polymer solution under high stretching is discussed. Initially, the variation in osmotic pressure can compensate for decrease in the capillary force, and the jet is stable. The further evolution of the polymer solution along the jet results in formation of a filament in the jet center and of a near-surface solvent layer. Such a redistribution of polymer seems like a ``phase separation'', but it is related to stretching of the jet. The viscous liquid shell demonstrates Raleigh-type instability resulting in the formation of individual droplets on the oriented filament. Experimental observations showed that this separation is starting during few first seconds, and continues of about 10 -15 seconds. The modeling shows that a jet stretching results in a radial gradient in the polymer distribution: the polymer is concentrated in the jet center, whereas the solvent is remaining near the surface. The key point of this model is that a large longitudinal stretching of a polymer network results in its lateral contraction, so a solvent is pressed out of this polymer network because of the decrease in its volume. V.K. and A.M. acknowledge the financial support of the Russian Scientific Foundation (Grant 4-23-00003).

  8. Separation of retinoid-induced epidermal and dermal thickening from skin irritation

    PubMed Central

    Fligiel, Helene; Zhang, Jian; Aslam, Muhammad Nadeem; Lu, Yi; Dehne, Lindsay A.; Keller, Evan T.

    2010-01-01

    The ability of the synthetic retinoid MDI-301, in which the carboxylic acid of 9-cis-retinoic acid (9-cis-RA) is replaced with an ester linkage, to induce epidermal and dermal thickening and skin irritation (erythema and flaking) in hairless (rhino) mice following its topical application was investigated in comparison with that of 14-all-trans-retinoic acid (14-all-trans-RA) and 9-cis-RA. MDI-301 induced epidermal proliferation leading to a thickened epidermis. Treated animals also demonstrated a prominent band of organized connective tissue immediately below the epidermis. In its ability to induce epidermal thickening, MDI-301 was quantitatively similar to 14-all-trans-RA and 9-cis-RA. However, unlike 14-all-trans-RA and 9-cis-RA, which produced skin irritation associated with a perivascular influx of mononuclear leukocytes into the dermis, there was no evidence of irritation with MDI-301 and little leukocyte infiltration. Intraperitoneal injection of either 14-all-trans-RA or MDI-301 also resulted in epidermal and dermal thickening. Irritation of skin was not observed in these animals but splenomegaly was prominent in animals treated with either agent. PMID:14564458

  9. Synthesis of nanofibrous gelatin/silica bioglass composite microspheres using emulsion coupled with thermally induced phase separation.

    PubMed

    Noh, Da-Young; An, Young-Hyeon; Jo, In-Hwan; Koh, Young-Hag; Kim, Hyoun-Ee

    2016-05-01

    This study proposes an innovative way of synthesizing porous gelatin/silica bioglass composite microspheres with a nanofibrous structure using emulsion coupled with thermally induced phase separation (TIPS). In particular, a mixture of the solvent (water) and non-solvent (ethanol) was used to induce a unique phase separation of gelatin/silica mixtures (i.e. gelatin/silica hybrid-rich and liquid-rich phases) at -70 °C for the creation of a nanofibrous structure. All the composite microspheres synthesized with silica contents of 10 wt.%, 15 wt.%, and 20 wt.% had well-defined spherical shapes between 124 and 136 μm in size. In addition, they were comprised of nanofibrous gelatin/silica composite walls (several tens of nanometers in thickness), where the sol-gel derived silica bioglass phase was uniformly distributed throughout the gelatin matrix. The in vitro apatite-forming ability and biocompatibility of the nanofibrous gelatin/silica bioglass composite microspheres was significantly enhanced with an increase in silica content, demonstrating their great potential for the promotion of bone tissue regeneration. PMID:26952472

  10. Endosomal Sorting Complex Required for Transport (ESCRT) Complexes Induce Phase-separated Microdomains in Supported Lipid Bilayers*

    PubMed Central

    Boura, Evzen; Ivanov, Vassili; Carlson, Lars-Anders; Mizuuchi, Kiyoshi; Hurley, James H.

    2012-01-01

    The endosomal sorting complex required for transport (ESCRT) system traffics ubiquitinated cargo to lysosomes via an unusual membrane budding reaction that is directed away from the cytosol. Here, we show that human ESCRT-II self-assembles into clusters of 10–100 molecules on supported lipid bilayers. The ESCRT-II clusters are functional in that they bind to ubiquitin and the ESCRT-III subunit VPS20 at nanomolar concentrations on membranes with the same stoichiometries observed in solution and in crystals. The clusters only form when cholesterol is included in the lipid mixture at >10 mol %. The clusters induce the formation of ordered membrane domains that exclude the dye 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindodicarbo-cyanine perchlorate. These results show that ESCRT complexes are capable of inducing lateral lipid phase separation under conditions where the lipids themselves do not spontaneously phase-separate. This property could facilitate ESCRT-mediated membrane budding. PMID:22718754

  11. Hepatitis C Virus E1 and E2 Proteins Used as Separate Immunogens Induce Neutralizing Antibodies with Additive Properties

    PubMed Central

    Beaumont, Elodie; Roch, Emmanuelle; Chopin, Lucie; Roingeard, Philippe

    2016-01-01

    Various strategies involving the use of hepatitis C virus (HCV) E1 and E2 envelope glycoproteins as immunogens have been developed for prophylactic vaccination against HCV. However, the ideal mode of processing and presenting these immunogens for effective vaccination has yet to be determined. We used our recently described vaccine candidate based on full-length HCV E1 or E2 glycoproteins fused to the heterologous hepatitis B virus S envelope protein to compare the use of the E1 and E2 proteins as separate immunogens with their use as the E1E2 heterodimer, in terms of immunogenetic potential and the capacity to induce neutralizing antibodies. The specific anti-E1 and anti-E2 antibody responses induced in animals immunized with vaccine particles harboring the heterodimer were profoundly impaired with respect to those in animals immunized with particles harboring E1 and E2 separately. Moreover, the anti-E1 and anti-E2 antibodies had additive neutralizing properties that increase the cross-neutralization of heterologous strains of various HCV genotypes, highlighting the importance of including both E1 and E2 in the vaccine for an effective vaccination strategy. Our study has important implications for the optimization of HCV vaccination strategies based on HCV envelope proteins, regardless of the platform used to present these proteins to the immune system. PMID:26966906

  12. Influence of acid-induced conformational variability on protein separation in reversed phase high performance liquid chromatography.

    PubMed

    Bobály, Balázs; Tóth, Eszter; Drahos, László; Zsila, Ferenc; Visy, Júlia; Fekete, Jenő; Vékey, Károly

    2014-01-17

    Influence of acid concentration in the mobile phase on protein separation was studied in a wide concentration range using trifluoroacetic acid (TFA) and formic acid (FA). At low, 0.001-0.01 (v/v%) TFA concentration and appropriate solvent strength proteins elute before the column's dead time. This is explained by the proteins having a structured, but relatively extended conformation in the eluent; and are excluded from the pores of the stationary phase. Above ca. 0.01-0.05 (v/v%) TFA concentration proteins undergo further conformational change, leading to a compact, molten globule-like structure, likely stabilized by ion pairing. Proteins in this conformation enter the pores and are retained on the column. The results suggest a pore exclusion induced separation related to protein conformation. This effect is influenced by the pH and type of acid used, and is likely to involve ion-pair formation. The TFA concentration needed to result in protein folding (and therefore to observe retention on the column) depends on the protein; and therefore can be utilized to improve chromatographic performance. Conformation change was monitored by circular dichroism spectroscopy and mass spectrometry; and it was shown that not only TFA but FA can also induce molten globule formation. PMID:24373532

  13. Oscillatory phase separation in giant lipid vesicles induced by transmembrane osmotic differentials.

    PubMed

    Oglęcka, Kamila; Rangamani, Padmini; Liedberg, Bo; Kraut, Rachel S; Parikh, Atul N

    2014-01-01

    Giant lipid vesicles are closed compartments consisting of semi-permeable shells, which isolate femto- to pico-liter quantities of aqueous core from the bulk. Although water permeates readily across vesicular walls, passive permeation of solutes is hindered. In this study, we show that, when subject to a hypotonic bath, giant vesicles consisting of phase separating lipid mixtures undergo osmotic relaxation exhibiting damped oscillations in phase behavior, which is synchronized with swell-burst lytic cycles: in the swelled state, osmotic pressure and elevated membrane tension due to the influx of water promote domain formation. During bursting, solute leakage through transient pores relaxes the pressure and tension, replacing the domain texture by a uniform one. This isothermal phase transition--resulting from a well-coordinated sequence of mechanochemical events--suggests a complex emergent behavior allowing synthetic vesicles produced from simple components, namely, water, osmolytes, and lipids to sense and regulate their micro-environment. PMID:25318069

  14. Strategies towards controlling strain-induced mesoscopic phase separation in manganite thin films

    NASA Astrophysics Data System (ADS)

    Habermeier, H.-U.

    2008-10-01

    Complex oxides represent a class of materials with a plethora of fascinating intrinsic physical functionalities. The intriguing interplay of charge, spin and orbital ordering in these systems superimposed by lattice effects opens a scientifically rewarding playground for both fundamental as well as application oriented research. The existence of nanoscale electronic phase separation in correlated complex oxides is one of the areas in this field whose impact on the current understanding of their physics and potential applications is not yet clear. In this paper this issue is treated from the point of view of complex oxide thin film technology. Commenting on aspects of complex oxide thin film growth gives an insight into the complexity of a reliable thin film technology for these materials. Exploring fundamentals of interfacial strain generation and strain accommodation paves the way to intentionally manipulate thin film properties. Furthermore, examples are given for an extrinsic continuous tuning of intrinsic electronic inhomogeneities in perovskite-type complex oxide thin films.

  15. A Transient Model of Induced Natural Circulation Thermal Cycling for Hydrogen Isotope Separation

    SciTech Connect

    SHADDAY, MARTIN

    2005-07-12

    The property of selective temperature dependence of adsorption and desorption of hydrogen isotopes by palladium is used for isotope separation. A proposal to use natural circulation of nitrogen to alternately heat and cool a packed bed of palladium coated beads is under active investigation, and a device consisting of two interlocking natural convection loops is being designed. A transient numerical model of the device has been developed to aid the design process. It is a one-dimensional finite-difference model, using the Boussinesq approximation. The thermal inertia of the pipe walls and other heat structures as well as the heater control logic is included in the model. Two system configurations were modeled and results are compared.

  16. Poly(ethylene glycol)-induced and temperature-dependent phase separation in fluid binary phospholipid membranes.

    PubMed Central

    Lehtonen, J. Y.; Kinnunen, P. K.

    1995-01-01

    Exclusion of the strongly hygroscopic polymer, poly(ethylene glycol) (PEG), from the surface of phosphatidylcholine liposomes results in an osmotic imbalance between the hydration layer of the liposome surface and the bulk polymer solution, thus causing a partial dehydration of the phospholipid polar headgroups. PEG (average molecular weight of 6000 and in concentrations ranging from 5 to 20%, w/w) was added to the outside of large unilamellar liposomes (LUVs). This leads to, in addition to the dehydration of the outer monolayer, an osmotically driven water outflow and shrinkage of liposomes. Under these conditions phase separation of the fluorescent lipid 1-palmitoyl-2[6-(pyren-1-yl)]decanoyl-sn-glycero-3-phosphocholine (PPDPC) embedded in various phosphatidylcholine matrices was observed, evident as an increase in the excimer-to-monomer fluorescence intensity ratio (IE/IM). Enhanced segregation of the fluorescent lipid was seen upon increasing and equal concentrations of PEG both inside and outside of the LUVs, revealing that osmotic gradient across the membrane is not required, and phase separation results from the dehydration of the lipid. Importantly, phase separation of PPDPC could be induced by PEG also in binary mixtures with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (SOPC), and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), for which temperature-induced phase segregation of the fluorescent lipid below Tm was otherwise not achieved. In the different lipid matrices the segregation of PPDPC caused by PEG was abolished above characteristic temperatures T0 well above their respective main phase transition temperatures Tm. For 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), DMPC, SOPC, and POPC, T0 was observed at approximately 50, 32, 24, and 20 degrees C, respectively. Notably, the observed phase separation of PPDPC cannot be accounted for the 1 degree C increase in Tm for DMPC or for the

  17. Structure of salts solution in polar dielectric liquids and electrically induced separation of solvated ions

    NASA Astrophysics Data System (ADS)

    Shamanin, Igor V.; Kazaryan, Mishik A.; Sachkov, Victor I.

    2015-12-01

    The aim of study is to demonstrate that separation of solvated ions in solution of mix of salts under the action of external periodic electric field happens because of around ions there are formed clusters consisting of molecules of solvent and the sizes of such clusters have dimensions ~ 0.1 μm. In investigations the sizes of clusters theoretically were defined and experimentally value of frequency of external electric field which action excites the effect of separation of the solvated ions was defined. Experiments were done in the Technical Physics Chair of the National Research Tomsk Polytechnic University. At theoretical determination of the dimensions of clusters Poisson's equation was solved and was considered that polar molecules of solvent are oriented under the action of electric field of an ion. The chemical composition of samples of solutions was determined by means of the spectrophotometry and he X-ray excited fluorescent radiation analysis method. Theoretical estimates and results of experiments confirmed the assumption that clusters which are formed around ions in solutions have the dimensions ~ 0.1 μm. Results of investigation testify that placing of volume distributed electric charge of ion in dielectric liquid is accompanied by formation of the supramolecular particles, which we called "clusters", linear sizes of which is significantly more than first and second radiuses of solvation (~ 1 Angstrom) and reach size ~ 0.1 μm. At such sizes inertial properties of clusters and their natural frequencies give the chance to operate their movement by means of action of external electric field on solution.

  18. Shock tunnel measurements of surface pressures in shock induced separated flow field using MEMS sensor array

    NASA Astrophysics Data System (ADS)

    Sriram, R.; Ram, S. N.; Hegde, G. M.; Nayak, M. M.; Jagadeesh, G.

    2015-09-01

    Characterized not just by high Mach numbers, but also high flow total enthalpies—often accompanied by dissociation and ionization of flowing gas itself—the experimental simulation of hypersonic flows requires impulse facilities like shock tunnels. However, shock tunnel simulation imposes challenges and restrictions on the flow diagnostics, not just because of the possible extreme flow conditions, but also the short run times—typically around 1 ms. The development, calibration and application of fast response MEMS sensors for surface pressure measurements in IISc hypersonic shock tunnel HST-2, with a typical test time of 600 μs, for the complex flow field of strong (impinging) shock boundary layer interaction with separation close to the leading edge, is delineated in this paper. For Mach numbers 5.96 (total enthalpy 1.3 MJ kg-1) and 8.67 (total enthalpy 1.6 MJ kg-1), surface pressures ranging from around 200 Pa to 50 000 Pa, in various regions of the flow field, are measured using the MEMS sensors. The measurements are found to compare well with the measurements using commercial sensors. It was possible to resolve important regions of the flow field involving significant spatial gradients of pressure, with a resolution of 5 data points within 12 mm in each MEMS array, which cannot be achieved with the other commercial sensors. In particular, MEMS sensors enabled the measurement of separation pressure (at Mach 8.67) near the leading edge and the sharply varying pressure in the reattachment zone.

  19. Initial Droplet Size Impacts pH-Induced Structural Changes in Phase-Separated Polymer Dispersions.

    PubMed

    Thongkaew, Chutima; Zeeb, Benjamin; Gibis, Monika; Hinrichs, Jörg; Weiss, Jochen

    2016-05-01

    The effect of pH change on the morphology of whey protein isolate (WPI)-pectin dispersions obtained from phase-separated systems after mild shear was studied. The purpose of this study was to examine the impact of mixing speed on the initial particle size of biopolymer complexes and their structure morphology after sequentially changing the pH. Therefore, solutions of WPI and pectin were combined at pH 6.1, allowed to phase separate and were then mildly homogenized at 50, 100, and 150 rpm, respectively, to form a dispersion containing differently sized WPI droplets in a surrounding pectin-rich phase. Each dispersion was then subjected to a pH change, such as 6.1 to 5.2 and 3.2, by slowly adding hydrochloric acid. The systems morphology, size, appearance, rheology, and storage stability was then characterized by optical microscopy, static light scattering, visual inspections, and steady shear rheometry to gain insights into the structural rearrangements. Results indicated substantial changes in the structure of the dispersion when the pH was changed. Formation of core-shell structures from the WPI droplets was observed at an intermediate pH. There, initial droplet size was found to affect structures formed, that is, core-shell type particles would only form if droplets were large (>1.5 μm) prior to pH change. Insights gained may be of importance to food manufacturers intending to create new structures from mixtures of proteins and carbohydrates. PMID:27061600

  20. Protective Effects of Diallyl Sulfide and Curcumin Separately against Thallium-Induced Toxicity in Rats

    PubMed Central

    Abdel-Daim, Mohamed M.; Abdou, Rania H.

    2015-01-01

    Thallium acetate (TI) is a cumulative poison intimately accompanied by an increase in reactive oxygen species (ROS) formation that represents an important risk factor for tissue injury and malfunction. This study aims to determine the possible hepatoprotective and antioxidant effects of diallyl sulfide (DAS) from garlic and curcumin from turmeric against TI-induced liver injury and oxidative stress (OS) in rats. This in vivo animal study divided rats into six groups of 8 rats per group. The first group received saline and served as the control group. The second and third groups received DAS or curcumin only at a dose of 200 mg/kg. The fourth group received TI at a dose of 6.4 mg/kg for 5 consecutive days. The fifth and sixth groups received DAS or curcumin orally 1 hour before TI intoxication at the same dose as the second and third groups. Liver integrity serum enzymes aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), and γ-glutamyltransferase (γ-GT) were evaluated. Serum and liver tissue homogenate lipid peroxidation and OS biomarkers were measured. The data were analyzed by one-way ANOVA followed by Duncan’s multiple range test for post hoc analysis using SPSS version 16. TI induced marked oxidative liver damage as shown by significantly (P≤0.05) elevated serum AST, ALT, ALP, LDH and γ-GT levels. There were significant (P≤0.05) increases in serum and hepatic malondialdehyde (MDA) and serum nitric oxide (NO) as well as decreased hepatic glutathione (GSH) and catalase (CAT) activities. There were significantly (P≤0.05) less serum and hepatic superoxide dismutase (SOD) and total antioxidant capacity (TAC). Pre-treatment with DAS or curcumin ameliorated the changes in most studied biochemical parameters. DAS and curcumin effectively reduced TI-induced liver toxicity. PMID:26199917

  1. Sex Determination in Honeybees: Two Separate Mechanisms Induce and Maintain the Female Pathway

    PubMed Central

    Gempe, Tanja; Hasselmann, Martin; Schiøtt, Morten; Hause, Gerd; Otte, Marianne; Beye, Martin

    2009-01-01

    Organisms have evolved a bewildering diversity of mechanisms to generate the two sexes. The honeybee (Apis mellifera) employs an interesting system in which sex is determined by heterozygosity at a single locus (the Sex Determination Locus) harbouring the complementary sex determiner (csd) gene. Bees heterozygous at Sex Determination Locus are females, whereas bees homozygous or hemizygous are males. Little is known, however, about the regulation that links sex determination to sexual differentiation. To investigate the control of sexual development in honeybees, we analyzed the functions and the regulatory interactions of genes involved in the sex determination pathway. We show that heterozygous csd is only required to induce the female pathway, while the feminizer (fem) gene maintains this decision throughout development. By RNAi induced knockdown we show that the fem gene is essential for entire female development and that the csd gene exclusively processes the heterozygous state. Fem activity is also required to maintain the female determined pathway throughout development, which we show by mosaic structures in fem-repressed intersexuals. We use expression of Fem protein in males to demonstrate that the female maintenance mechanism is controlled by a positive feedback splicing loop in which Fem proteins mediate their own synthesis by directing female fem mRNA splicing. The csd gene is only necessary to induce this positive feedback loop in early embryogenesis by directing splicing of fem mRNAs. Finally, fem also controls the splicing of Am-doublesex transcripts encoding conserved male- and female-specific transcription factors involved in sexual differentiation. Our findings reveal how the sex determination process is realized in honeybees differing from Drosophila melanogaster. PMID:19841734

  2. Cellular Immune Responses in Humans Induced by Two Serogroup B Meningococcal Outer Membrane Vesicle Vaccines Given Separately and in Combination.

    PubMed

    Oftung, Fredrik; Korsvold, Gro Ellen; Aase, Audun; Næss, Lisbeth M

    2016-04-01

    MenBvac and MeNZB are safe and efficacious outer membrane vesicle (OMV) vaccines against serogroup B meningococcal disease. Antibody responses have previously been investigated in a clinical trial with these two OMV vaccines given separately (25 μg/dose) or in combination (12.5 and 12.5 μg/dose) in three doses administered at 6-week intervals. Here, we report the results from analyzing cellular immune responses against MenBvac and MeNZB OMVs in terms of antigen-specific CD4(+)T cell proliferation and secretion of cytokines. The proliferative CD4(+)T cell responses to the combined vaccine were of the same magnitude as the homologous responses observed for each individual vaccine. The results also showed cross-reactivity in the sense that both vaccine groups receiving separate vaccines responded to both homologous and heterologous OMV antigen when assayed for antigen-specific cellular proliferation. In addition, a multiplex bead array assay was used to analyze the presence of Th1 and Th2 cytokines in cell culture supernatants. The results showed that gamma interferon, interleukin-4 (IL-4), and IL-10 responses could be detected as a result of vaccination with both the MenBvac and the MeNZB vaccines given separately, as well as when given in combination. With respect to cross-reactivity, the cytokine results paralleled the observations made for proliferation. In conclusion, the results demonstrate that cross-reactive cellular immune responses involving both Th1 and Th2 cytokines can be induced to the same extent by different tailor-made OMV vaccines given either separately or in combination with half the dose of each vaccine. PMID:26865595

  3. The Effects of Damage on Hydrogen-Implant-Induced Thin-Film Separation from Bulk Silicon Carbide

    SciTech Connect

    Gregory, R.B.; Holland, O.W.; Thomas, D.K.; Wetteroth, T.A.; Wilson, S.R.

    1999-04-05

    Exfoliation of Sic by hydrogen implantation and subsequent annealing forms the basis for a thin-film separation process which, when combined with hydrophilic wafer bonding, can be exploited to produce silicon-carbide-on-insulator, SiCOI. Sic thin films produced by this process exhibit unacceptably high resistivity because defects generated by the implant neutralize electrical carriers. Separation occurs because of chemical interaction of hydrogen with dangling bonds within microvoids created by the implant, and physical stresses due to gas-pressure effects during post-implant anneal. Experimental results show that exfoliation of Sic is dependent upon the concentration of implanted hydrogen, but the damage generated by the implant approaches a point when exfoliation is, in fact, retarded. This is attributed to excessive damage at the projected range of the implant which inhibits physical processes of implant-induced cleaving. Damage is controlled independently of hydrogen dosage by elevating the temperature of the SiC during implant in order to promote dynamic annealing. The resulting decrease in damage is thought to promote growth of micro-cracks which form a continuous cleave. Channeled H{sup +} implantation enhances the cleaving process while simultaneously minimizing residual damage within the separated film. It is shown that high-temperature irradiation and channeling each reduces the hydrogen fluence required to affect separation of a thin film and results in a lower concentration of defects. This increases the potential for producing SiC01 which is sufficiently free of defects and, thus, more easily electrically activated.

  4. Maternal separation enhances object location memory and prevents exercise-induced MAPK/ERK signalling in adult Sprague-Dawley rats.

    PubMed

    Makena, Nokuthula; Bugarith, Kishor; Russell, Vivienne A

    2012-09-01

    Early life stress increases the risk of developing psychopathology accompanied by reduced cognitive function in later life. Maternal separation induces anxiety-like behaviours and is associated with impaired memory. On the other hand, exercise has been shown to diminish anxiety-like behaviours and improve cognitive function. The effects of maternal separation and exercise on anxiety, memory and hippocampal proteins were investigated in male Sprague-Dawley rats. Maternal separation produced anxiety-like behaviours which were reversed by exercise. Maternal separation also enhanced object location memory which was not affected by exercise. Exercise did, however, increase synaptophysin and phospho-extracellular signal-regulated kinase (p-ERK) in the hippocampus of non-separated rats and this effect was not observed in maternally separated rats. These findings show that maternal separation selectively enhanced n memory and prevented activation of the MAPK/ERK signalling pathway in the adult rat hippocampus. PMID:22476924

  5. Selective Stabilization of the Fddd Diblock Copolymer Microphase in an Applied Electric Field

    NASA Astrophysics Data System (ADS)

    Martin, Jonathan; Li, Wei; Delaney, Kris; Fredrickson, Glenn

    Using self-consistent field theory, we explore the phase behavior of AB diblock copolymer melts in a uniform applied electric field. We assign an isotropic polarizability to each monomer type, such that the electric field selectively destabilizes AB interfaces that are perpendicular to the applied field. Under the mean-field approximation of the present model, lamellar and cylindrical structures align such that their AB interfaces are parallel to the electric field, and their relative stability with respect to the disordered phase is unchanged. Sphere and network phases do not have an axis of uniformity, so the preferred orientation for each of these phases must be identified by simulation. Small distortions in morphology are induced by the electric field for these phases, such that the free energy response includes non-harmonic terms. We compute the phase diagram for a melt in an applied electric field by comparing free energies of each morphology at its preferred orientation. We find that the stability regions for the sphere and network phases shrink with increasing electric field strength. Moreover, the double gyroid phase is relatively destabilized against the Fddd phase, extending the stability region for the Fddd phase to larger segregation strengths.

  6. Light-induced charge separation and storage in titanium oxide gels

    SciTech Connect

    Kuznetsov, A.I.; Kameneva, O.; Alexandrov, A.; Bityurin, N.; Marteau, Ph.; Chhor, K.; Kanaev, A.; Sanchez, C.

    2005-02-01

    We report on the interaction of light with a particular class of media--wet gels, which in contrast to sols of nanoparticles possess a macroscopic bulk structure, and which differ from conventional solids by the existence of the internal liquid-solid interface. We show, taking an absorption cross section of trapped electrons from Safrany, Gao, and Rabani [J. Phys. Chem. B 104, 5848 (2000)], that a separation of charges with quantum efficiency as high as 46% appears under the band-gap irradiation of titanium oxide gels: electrons are stored in the gel network as Ti{sup 3+} centers, whereas holes are stored in the liquid phase. Under a prolonged UV-laser irradiation, more than 14% of Ti{sup 4+} centers can be converted into Ti{sup 3+}. Their lifetime can be extremely long and exceeds months at room temperature. The trapped electrons are responsible for a 'dark' absorption continuum covering the spectral range from 350 nm to 2.5 {mu}m.

  7. Calculations on Isotope Separation by Laser Induced Photodissociation of Polyatomic Molecules. Final Report

    DOE R&D Accomplishments Database

    Lamb, W. E. Jr.

    1978-11-01

    This report describes research on the theory of isotope separation produced by the illumination of polyatomic molecules by intense infrared laser radiation. Newton`s equations of motion were integrated for the atoms of the SF{sub 6} molecule including the laser field interaction. The first year`s work has been largely dedicated to obtaining a suitable interatomic potential valid for arbitrary configurations of the seven particles. This potential gives the correct symmetry of the molecule, the equilibrium configuration, the frequencies of the six distinct normal modes of oscillation and the correct (or assumed) value of the total potential energy of the molecule. Other conditions can easily be imposed in order to obtain a more refined potential energy function, for example, by making allowance for anharmonicity data. A suitable expression was also obtained for the interaction energy between a laser field and the polyatomic molecule. The electromagnetic field is treated classically, and it would be easily possible to treat the cases of time dependent pulses, frequency modulation and noise.

  8. Oscillatory phase separation in giant lipid vesicles induced by transmembrane osmotic differentials

    PubMed Central

    Oglęcka, Kamila; Rangamani, Padmini; Liedberg, Bo; Kraut, Rachel S; Parikh, Atul N

    2014-01-01

    Giant lipid vesicles are closed compartments consisting of semi-permeable shells, which isolate femto- to pico-liter quantities of aqueous core from the bulk. Although water permeates readily across vesicular walls, passive permeation of solutes is hindered. In this study, we show that, when subject to a hypotonic bath, giant vesicles consisting of phase separating lipid mixtures undergo osmotic relaxation exhibiting damped oscillations in phase behavior, which is synchronized with swell–burst lytic cycles: in the swelled state, osmotic pressure and elevated membrane tension due to the influx of water promote domain formation. During bursting, solute leakage through transient pores relaxes the pressure and tension, replacing the domain texture by a uniform one. This isothermal phase transition—resulting from a well-coordinated sequence of mechanochemical events—suggests a complex emergent behavior allowing synthetic vesicles produced from simple components, namely, water, osmolytes, and lipids to sense and regulate their micro-environment. DOI: http://dx.doi.org/10.7554/eLife.03695.001 PMID:25318069

  9. Hydration-Induced Phase Separation in Amphiphilic Polymer Matrices and its Influence on Voclosporin Release

    PubMed Central

    Khan, I. John; Murthy, N. Sanjeeva; Kohn, Joachim

    2012-01-01

    Voclosporin is a highly potent, new cyclosporine-A derivative that is currently in Phase 3 clinical trials in the USA as a potential treatment for inflammatory diseases of the eye. Voclosporin represents a number of very sparingly soluble drugs that are difficult to administer. We therefore selected it as a model drug that is dispersed within amphiphilic polymer matrices, and investigated the changing morphology of the matrices using neutron and x-ray scattering during voclosporin release and polymer resorption. The hydrophobic segments of the amphiphilic polymer chain are comprised of desaminotyrosyl-tyrosine ethyl ester (DTE) and desaminotyrosyl-tyrosine (DT), and the hydrophilic component is poly(ethylene glycol) (PEG). Water uptake in these matrices resulted in the phase separation of hydrophobic and hydrophilic domains that are a few hundred Angstroms apart. These water-driven morphological changes influenced the release profile of voclosporin and facilitated a burst-free release from the polymer. No such morphological reorganization was observed in poly(lactide-co-glycolide) (PLGA), which exhibits an extended lag period, followed by a burst-like release of voclosporin when the polymer was degraded. An understanding of the effect of polymer composition on the hydration behavior is central to understanding and controlling the phase behavior and resorption characteristics of the matrix for achieving long-term controlled release of hydrophobic drugs such as voclosporin. PMID:24955746

  10. Depletion induced isotropic-isotropic phase separation in suspensions of rod-like colloids.

    PubMed

    Jungblut, S; Tuinier, R; Binder, K; Schilling, T

    2007-12-28

    When non-adsorbing polymers are added to an isotropic suspension of rod-like colloids, the colloids effectively attract each other via depletion forces. We performed Monte Carlo simulations to study the phase diagram of such rod-polymer mixture. The colloidal rods were modeled as hard spherocylinders; the polymers were described as spheres of the same diameter as the rods. The polymers may overlap with no energy cost, while the overlap of polymers and rods is forbidden. Large amounts of depletant cause phase separation of the mixture. We estimated the phase boundaries of isotropic-isotropic coexistence both in the bulk and in confinement. To determine the phase boundaries we applied the grand canonical ensemble using successive umbrella sampling [J. Chem. Phys. 120, 10925 (2004)], and we performed a finite size scaling analysis to estimate the location of the critical point. The results are compared with predictions of the free volume theory developed by Lekkerkerker and Stroobants [Nuovo Cimento D 16, 949 (1994)]. We also give estimates for the interfacial tension between the coexisting isotropic phases and analyze its power-law behavior on the approach of the critical point. PMID:18163708

  11. Fumonisin B₁ (FB₁) Induces Lamellar Separation and Alters Sphingolipid Metabolism of In Vitro Cultured Hoof Explants.

    PubMed

    Reisinger, Nicole; Dohnal, Ilse; Nagl, Veronika; Schaumberger, Simone; Schatzmayr, Gerd; Mayer, Elisabeth

    2016-04-01

    One of the most important hoof diseases is laminitis. Yet, the pathology of laminitis is not fully understood. Different bacterial toxins, e.g. endotoxins or exotoxins, seem to play an important role. Additionally, ingestion of mycotoxins, toxic secondary metabolites of fungi, might contribute to the onset of laminitis. In this respect, fumonsins are of special interest since horses are regarded as species most susceptible to this group of mycotoxins. The aim of our study was to investigate the influence of fumonisin B₁ (FB₁) on primary isolated epidermal and dermal hoof cells, as well as on the lamellar tissue integrity and sphingolipid metabolism of hoof explants in vitro. There was no effect of FB₁ at any concentration on dermal or epidermal cells. However, FB₁ significantly reduced the separation force of explants after 24 h of incubation. The Sa/So ratio was significantly increased in supernatants of explants incubated with FB₁ (2.5-10 µg/mL) after 24 h. Observed effects on Sa/So ratio were linked to significantly increased sphinganine concentrations. Our study showed that FB₁ impairs the sphingolipid metabolism of explants and reduces lamellar integrity at non-cytotoxic concentrations. FB₁ might, therefore, affect hoof health. Further in vitro and in vivo studies are necessary to elucidate the effects of FB₁ on the equine hoof in more detail. PMID:27023602

  12. Phase separation predicted to induce water-rich channels in fuel cell membranes

    NASA Astrophysics Data System (ADS)

    Herbst, Daniel; Witten, Thomas; Tsai, Tsung-Han; Coughlin, Bryan; Maes, Ashley; Herring, Andrew

    2015-03-01

    Fuel cells are a promising alternative energy technology that convert chemical fuel directly into electric power. One important fundamental property is exactly how and where water is absorbed in the polyelectrolyte membrane. Previous theoretical studies have used idealized parameters. In this talk, I show how we made a rigorous connection to experiment to make parameter-free predictions of the water-swelling behavior, using self-consistent field theory. The model block co-polymers we studied form alternating hydrophilic/hydrophobic lamellar domains that absorb water in humid air. I will show how simple measurements of the hydrophilic portion in solution lead to predictions of non-uniform water distribution in the membrane, and compare the results to x-ray scattering. The results suggest locally near-uniform water distributions. In special cases, however, each hydrophilic lamella phase-separates, forming an additional water-rich lamella down the center, a beneficial arrangement for ion conductivity. A small amount of water enhances conductivity most when it is partitioned into such channels, improving fuel-cell performance. MURI #W911NF-10-1-0520.

  13. Hydration-Induced Phase Separation in Amphiphilic Polymer Matrices and its Influence on Voclosporin Release

    SciTech Connect

    Khan, I. John; Murthy, N. Sanjeeva; Kohn, Joachim

    2015-10-30

    Voclosporin is a highly potent, new cyclosporine -- a derivative that is currently in Phase 3 clinical trials in the USA as a potential treatment for inflammatory diseases of the eye. Voclosporin represents a number of very sparingly soluble drugs that are difficult to administer. It was selected as a model drug that is dispersed within amphiphilic polymer matrices, and investigated the changing morphology of the matrices using neutron and x-ray scattering during voclosporin release and polymer resorption. The hydrophobic segments of the amphiphilic polymer chain are comprised of desaminotyrosyl-tyrosine ethyl ester (DTE) and desaminotyrosyl-tyrosine (DT), and the hydrophilic component is poly(ethylene glycol) (PEG). Water uptake in these matrices resulted in the phase separation of hydrophobic and hydrophilic domains that are a few hundred Angstroms apart. These water-driven morphological changes influenced the release profile of voclosporin and facilitated a burst-free release from the polymer. No such morphological reorganization was observed in poly(lactide-co-glycolide) (PLGA), which exhibits an extended lag period, followed by a burst-like release of voclosporin when the polymer was degraded. An understanding of the effect of polymer composition on the hydration behavior is central to understanding and controlling the phase behavior and resorption characteristics of the matrix for achieving long-term controlled release of hydrophobic drugs such as voclosporin.

  14. Haloing in bimodal magnetic colloids: the role of field-induced phase separation.

    PubMed

    Magnet, C; Kuzhir, P; Bossis, G; Meunier, A; Suloeva, L; Zubarev, A

    2012-07-01

    If a suspension of magnetic micrometer-sized and nanosized particles is subjected to a homogeneous magnetic field, the nanoparticles are attracted to the microparticles and form thick anisotropic halos (clouds) around them. Such clouds can hinder the approach of microparticles and result in effective repulsion between them [M. T. López-López, A. Yu. Zubarev, and G. Bossis, Soft Matter 6, 4346 (2010)]. In this paper, we present detailed experimental and theoretical studies of nanoparticle concentration profiles and of the equilibrium shapes of nanoparticle clouds around a single magnetized microsphere, taking into account interactions between nanoparticles. We show that at a strong enough magnetic field, the ensemble of nanoparticles experiences a gas-liquid phase transition such that a dense liquid phase is condensed around the magnetic poles of a microsphere while a dilute gas phase occupies the rest of the suspension volume. Nanoparticle accumulation around a microsphere is governed by two dimensionless parameters--the initial nanoparticle concentration (φ(0)) and the magnetic-to-thermal energy ratio (α)--and the three accumulation regimes are mapped onto a α-φ(0) phase diagram. Our local thermodynamic equilibrium approach gives a semiquantitative agreement with the experiments on the equilibrium shapes of nanoparticle clouds. The results of this work could be useful for the development of the bimodal magnetorheological fluids and of the magnetic separation technologies used in bioanalysis and water purification systems. PMID:23005414

  15. Separate fractions of mRNA from Torpedo electric organ induce chloride channels and acetylcholine receptors in Xenopus oocytes.

    PubMed Central

    Sumikawa, K; Parker, I; Amano, T; Miledi, R

    1984-01-01

    Poly(A)+ mRNA extracted from the electric organ of Torpedo was fractionated by sucrose density gradient centrifugation. After injection into Xenopus oocytes one mRNA fraction induced the appearance of chloride channels in the oocyte membrane. Many of these channels were normally open, and the ensuing chloride current kept the resting potential of injected oocytes close to the chloride equilibrium potential. When the membrane was hyperpolarized, the chloride current was reduced. A separate fraction of mRNA induced the incorporation of acetylcholine receptors into the oocyte membrane. When translated in a cell-free system this fraction directed the synthesis of the alpha, beta, gamma, and delta subunits of the acetylcholine receptor. In contrast, the mRNA fraction that induced the chloride channels caused the synthesis of the delta subunit, a very small amount of alpha, and no detectable beta or gamma subunits. This suggests that the size of the mRNA coding for the chloride channel is similar to the preponderant species of mRNA coding for the delta subunit of the acetylcholine receptor. Images Fig. 1. PMID:6094179

  16. Genetic and anatomical basis of the barrier separating wakefulness and anesthetic-induced unresponsiveness.

    PubMed

    Joiner, William J; Friedman, Eliot B; Hung, Hsiao-Tung; Koh, Kyunghee; Sowcik, Mallory; Sehgal, Amita; Kelz, Max B

    2013-01-01

    A robust, bistable switch regulates the fluctuations between wakefulness and natural sleep as well as those between wakefulness and anesthetic-induced unresponsiveness. We previously provided experimental evidence for the existence of a behavioral barrier to transitions between these states of arousal, which we call neural inertia. Here we show that neural inertia is controlled by processes that contribute to sleep homeostasis and requires four genes involved in electrical excitability: Sh, sss, na and unc79. Although loss of function mutations in these genes can increase or decrease sensitivity to anesthesia induction, surprisingly, they all collapse neural inertia. These effects are genetically selective: neural inertia is not perturbed by loss-of-function mutations in all genes required for the sleep/wake cycle. These effects are also anatomically selective: sss acts in different neurons to influence arousal-promoting and arousal-suppressing processes underlying neural inertia. Supporting the idea that anesthesia and sleep share some, but not all, genetic and anatomical arousal-regulating pathways, we demonstrate that increasing homeostatic sleep drive widens the neural inertial barrier. We propose that processes selectively contributing to sleep homeostasis and neural inertia may be impaired in pathophysiological conditions such as coma and persistent vegetative states. PMID:24039590

  17. Genetic and Anatomical Basis of the Barrier Separating Wakefulness and Anesthetic-Induced Unresponsiveness

    PubMed Central

    Hung, Hsiao-Tung; Koh, Kyunghee; Sowcik, Mallory; Sehgal, Amita; Kelz, Max B.

    2013-01-01

    A robust, bistable switch regulates the fluctuations between wakefulness and natural sleep as well as those between wakefulness and anesthetic-induced unresponsiveness. We previously provided experimental evidence for the existence of a behavioral barrier to transitions between these states of arousal, which we call neural inertia. Here we show that neural inertia is controlled by processes that contribute to sleep homeostasis and requires four genes involved in electrical excitability: Sh, sss, na and unc79. Although loss of function mutations in these genes can increase or decrease sensitivity to anesthesia induction, surprisingly, they all collapse neural inertia. These effects are genetically selective: neural inertia is not perturbed by loss-of-function mutations in all genes required for the sleep/wake cycle. These effects are also anatomically selective: sss acts in different neurons to influence arousal-promoting and arousal-suppressing processes underlying neural inertia. Supporting the idea that anesthesia and sleep share some, but not all, genetic and anatomical arousal-regulating pathways, we demonstrate that increasing homeostatic sleep drive widens the neural inertial barrier. We propose that processes selectively contributing to sleep homeostasis and neural inertia may be impaired in pathophysiological conditions such as coma and persistent vegetative states. PMID:24039590

  18. Quantitative evaluation of colloidal stability of antibody solutions using PEG-induced liquid-liquid phase separation.

    PubMed

    Wang, Ying; Latypov, Ramil F; Lomakin, Aleksey; Meyer, Julie A; Kerwin, Bruce A; Vunnum, Suresh; Benedek, George B

    2014-05-01

    Colloidal stability of antibody solutions, i.e., the propensity of the folded protein to precipitate, is an important consideration in formulation development of therapeutic monoclonal antibodies. In a protein solution, different pathways including crystallization, colloidal aggregation, and liquid-liquid phase separation (LLPS) can lead to the formation of precipitates. The kinetics of crystallization and aggregation are often slow and vary from protein to protein. Due to the diverse mechanisms of these protein condensation processes, it is a challenge to develop a standardized test for an early evaluation of the colloidal stability of antibody solutions. LLPS would normally occur in antibody solutions at sufficiently low temperature, provided that it is not preempted by freezing of the solution. Poly(ethylene glycol) (PEG) can be used to induce LLPS at temperatures above the freezing point. Here, we propose a colloidal stability test based on inducing LLPS in antibody solutions and measuring the antibody concentration of the dilute phase. We demonstrate experimentally that such a PEG-induced LLPS test can be used to compare colloidal stability of different antibodies in different solution conditions and can be readily applied to high-throughput screening. We have derived an equation for the effects of PEG concentration and molecular weight on the results of the LLPS test. Finally, this equation defines a binding energy in the condensed phase, which can be determined in the PEG-induced LLPS test. This binding energy is a measure of attractive interactions between antibody molecules and can be used for quantitative characterization of the colloidal stability of antibody solutions. PMID:24679215

  19. Poly lactic acid based foams prepared via thermally induced phase separation (TIPS): A method to tune the crystallinity

    NASA Astrophysics Data System (ADS)

    Pavia, Francesco Carfı; La Carrubba, Vincenzo; Brucato, Valerio

    2012-07-01

    Blends of Poly-L-Lactic Acid (PLLA) with two Poly-Lactic Acid (PLA) in different proportions (90/10 and 70/30) were utilized in order to produce biodegradable and biocompatible scaffolds for soft tissue engineering applications. The scaffolds were produced via thermally induced phase separation (TIPS) starting from ternary systems where dioxane was the solvent and water the non-solvent. Morphology was evaluated by Scanning Electron Microscopy (average pore size and interconnection). Moreover a DSC analysis was carried out on the as-obtained scaffold in order to obtain information about theirs thermal properties (enthalpy of melt and crystallization). The results showed that is possible to prepare scaffolds of PLLA/PLA via TIPS. Moreover, the PLA seems to influences the TIPS process in terms of demixing temperatures. The data confirm that the morphology and the mechanical properties of the scaffold can be tuned, starting from PLLA blends and using PLA with different molecular weights.

  20. Susceptibility to ozone-induced inflammation. II. Separate loci control responses to acute and subacute exposures

    SciTech Connect

    Kleeberger, S.R.; Levitt, R.C.; Zhang, L.Y. )

    1993-01-01

    We demonstrated previously that inbred strains of mice are differentially susceptible to acute (3 h) and subacute (48 h) exposures to 2 parts per million (ppm) ozone (O3) and 0.30 ppm O3, respectively. Genetic studies with O3-resistant C3H/HeJ and O3-susceptible C57BL/6J strains have indicated that susceptibility to each of these O3 exposures is under Mendelian (single gene) control. In the present study, we hypothesized that the same gene controls susceptibility to the airway inflammatory responses to 2 ppm and 0.30 ppm O3 exposures. To test this hypothesis, airway inflammation was induced in 10 BXH and 16 BXD recombinant inbred (RI) strains of mice by acute as well as subacute O3 exposures. Airway inflammation was assessed by counting the number of polymorphonuclear leukocytes (PMNs) in bronchoalveolar lavage (BAL) returns obtained immediately after 48-h subacute exposure to 0.30 ppm O3, or 6 h after 3 h acute exposure to 2 ppm O3. Each RI strain was classified as susceptible or resistant to each exposure, based on a comparison of mean numbers of PMNs with those of the respective progenitor strains. For each RI set, a phenotypic strain distribution pattern (SDP) was thus derived for each exposure regimen, and the SDPs were then compared for concordance. Among the BXH RI strains, 4 of 10 responded discordantly to the two exposures: 3 were susceptible to acute exposure and resistant to subacute exposure, whereas 1 was conversely susceptible. Among the BXD RI strains, 4 of 16 were discordant: 1 was susceptible to acute exposure, and resistant to subacute exposure, whereas 3 were conversely susceptible.

  1. Effect of low-level laser therapy on dental pain induced by separator force in orthodontic treatment

    PubMed Central

    Abtahi, Seyed Mostafa; Mousavi, Seyed Amir; Shafaee, Hooman; Tanbakuchi, Behrad

    2013-01-01

    Background: Patients undergoing orthodontic treatment experience varying degrees of pain with separator insertion. A survey of patients’ attitude towards orthodontic treatment revealed that pain was the most discouraging factor related to their treatment. Moreover, it was the highest ranking reason for wanting to discontinue care. The purpose of this study was to determine the effect of low-level laser irradiation on dental pain induced by forces from separators in orthodontic treatment. Materials and Methods: This study was an experimental clinical trial. Twenty-nine patients were recruited for this research. Low-level laser irradiation was applied on one half of the maxillary and mandibular arches for 5 days. The opposite half of the arches was considered the control group. Laser irradiation was applied for 30 seconds in the alveolar bone between the second premolars, first molars, and second molars. Pain perception was evaluated with a standardized questionnaire that was answered by patients before and after laser irradiation. Data was analyzed by Wilcoxon and Friedman test. P value ≤0.05 was considered significant. Results: The highest pain level was reported at day 1 following separator placement and decreased gradually until day 5. At day 4 and 5, the pain intensity was lower in the laser group than in the control group; however, this finding was not statistically significant. At day 1 and 3, the pain intensity was higher in the laser group than in the control group; however, it was not statistically significant. At day 2, the pain intensity was lower in the laser group than in the control group and was statistically significant. Conclusion: Our findings suggest that there is no statistically significant difference in pain by using low-level laser irradiation. PMID:24348624

  2. Alcohol-induced drying of carbon nanotubes and its implications for alcohol/water separation: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Tian, Xingling; Yang, Zaixing; Zhou, Bo; Xiu, Peng; Tu, Yusong

    2013-05-01

    Alcohols are important products in chemical industry, but separating them from their aqueous solutions is very difficult due to the hydrophilic nature of alcohols. Based on molecular dynamics simulations, we observe a striking nanoscale drying phenomenon and suggest an energy-saving and efficient approach toward alcohol/water separation by using single-walled carbon nanotubes (SWNTs). We use various common linear alcohols including C1-C6 1-alcohols and glycerol for demonstration (the phenol is also used as comparison). Our simulations show that when SWNTs are immersed in aqueous alcohols solutions, although the alcohols concentration is low (1 M), all kinds of alcohols can induce dehydration (drying) of nanotubes and accumulate inside wide [(13, 13)] and narrow [(6, 6) or (7, 7)] SWNTs. In particular, most kinds of alcohols inside the narrow SWNTs form nearly uniform 1D molecular wires. Detailed energetic analyses reveal that the preferential adsorption of alcohols over water inside nanotubes is attributed to the stronger dispersion interactions of alcohols with SWNTs than water. Interestingly, we find that for the wide SWNT, the selectivity for 1-alcohols increases with the number of alcohol's carbon atoms (Ncarbon) and exhibits an exponential law with respect to Ncarbon for C1-C5 1-alcohols; for narrow SWNTs, the selectivity for 1-alcohols is very high for methanol, ethanol, and propanol, and reaches a maximum when Ncarbon = 3. The underlying physical mechanisms and the implications of these observations for alcohol/water separation are discussed. Our findings provide the possibility for efficient dehydration of aqueous alcohols (and other hydrophilic organic molecules) by using SWNT bundles/membranes.

  3. EphrinB/EphB Signaling Controls Embryonic Germ Layer Separation by Contact-Induced Cell Detachment

    PubMed Central

    Rohani, Nazanin; Canty, Laura; Luu, Olivia

    2011-01-01

    Background The primordial organization of the metazoan body is achieved during gastrulation by the establishment of the germ layers. Adhesion differences between ectoderm, mesoderm, and endoderm cells could in principle be sufficient to maintain germ layer integrity and prevent intermixing. However, in organisms as diverse as fly, fish, or amphibian, the ectoderm-mesoderm boundary not only keeps these germ layers separated, but the ectoderm also serves as substratum for mesoderm migration, and the boundary must be compatible with repeated cell attachment and detachment. Principal Findings We show that localized detachment resulting from contact-induced signals at the boundary is at the core of ectoderm-mesoderm segregation. Cells alternate between adhesion and detachment, and detachment requires ephrinB/EphB signaling. Multiple ephrinB ligands and EphB receptors are expressed on each side of the boundary, and tissue separation depends on forward signaling across the boundary in both directions, involving partially redundant ligands and receptors and activation of Rac and RhoA. Conclusion This mechanism differs from a simple differential adhesion process of germ layer formation. Instead, it involves localized responses to signals exchanged at the tissue boundary and an attachment/detachment cycle which allows for cell migration across a cellular substratum. PMID:21390298

  4. Separation and purification of the tonoplast ATPase and pyrophosphatase from plants with constitutive and inducible Crassulacean acid metabolism.

    PubMed

    Bremberger, C; Haschke, H P; Lüttge, U

    1988-10-01

    Tonoplast vesicles were isolated from Kalanchoe daigremontiana Hamet et Pierrer de la Bâthie and Mesembryanthemum crystallinum L., exhibiting constitutive and inducible crassulacean acid metabolism (CAM), respectively. Membrane-bound proteins were detergent-solubilized with 2% of Triton X-100. During CAM induction in M. crystallinum, ATPase activity increases four-fold, whereas pyrophosphatase activity decreases somewhat. With all plants, ATPase and pyrophosphatase could be separated by size-exclusion chromatography (SEC, Sephacryl S 400), and the ATPase was further purified by diethylaminoethyl-ion-exchange chromatography. Sodium-dodecyl-sulfate electrophoresis of the SEC fractions from K. daigremontiana containing maximum ATPase activity separates several protein bands, indicating subunits of 72, 56, 48, 42, 28, and 16 kDa. Purified ATPase from M. crystallinum in the C3 and CAM states shows a somewhat different protein pattern. With M. crystallinum, an increase in ATP-hydrolysis and changes in the subunit composition of the native enzyme indicate that the change from the C3 to the CAM state is accompanied by de-novo synthesis and by structural changes of the tonoplast ATPase. PMID:24221927

  5. Giant Electric-Field-Induced Strain in PVDF-Based Battery Separator Membranes Probed by Electrochemical Strain Microscopy.

    PubMed

    Romanyuk, Konstantin; Costa, Carlos M; Luchkin, Sergey Yu; Kholkin, Andrei L; Lanceros-Méndez, Senentxu

    2016-05-31

    Efficiency of lithium-ion batteries largely relies on the performance of battery separator membrane as it controls the mobility and concentration of Li-ions between the anode and cathode electrodes. Recent advances in electrochemical strain microscopy (ESM) prompted the study of Li diffusion and transport at the nanoscale via electromechanical strain developed under an application of inhomogeneous electric field applied via the sharp ESM tip. In this work, we observed unexpectedly high electromechanical strain developed in polymer membranes based on porous poly(vinylidene fluoride) (PVDF) and poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) and, using it, could study a dynamics of electroosmotic flow of electrolyte inside the pores. We show that, independently of the separator membrane, electric field-induced deformation observed by ESM on wetted membrane surfaces can reach up to 10 nm under a moderate bias of 1 V (i.e., more than an order of magnitude higher than that in best piezoceramics). Such a high strain is explained by the electroosmotic flow in a porous media composed of PVDF. It is shown that the strain-based ESM method can be used to extract valuable information such as average pore size, porosity, elasticity of membrane in electrolyte solvent, and membrane-electrolyte affinity expressed in terms of zeta potential. Besides, such systems can, in principle, serve as actuators even in the absence of apparent piezoelectricity in amorphous PVDF. PMID:27142946

  6. Polymer composites and porous materials prepared by thermally induced phase separation and polymer-metal hybrid methods

    NASA Astrophysics Data System (ADS)

    Yoon, Joonsung

    The primary objective of this research is to investigate the morphological and mechanical properties of composite materials and porous materials prepared by thermally induced phase separation. High melting crystallizable diluents were mixed with polymers so that the phase separation would be induced by the solidification of the diluents upon cooling. Theoretical phase diagrams were calculated using Flory-Huggins solution thermodynamics which show good agreement with the experimental results. Porous materials were prepared by the extraction of the crystallized diluents after cooling the mixtures (hexamethylbenzene/polyethylene and pyrene/polyethylene). Anisotropic structures show strong dependence on the identity of the diluents and the composition of the mixtures. Anisotropic crystal growth of the diluents was studied in terms of thermodynamics and kinetics using DSC, optical microscopy and SEM. Microstructures of the porous materials were explained in terms of supercooling and dendritic solidification. Dual functionality of the crystallizable diluents for composite materials was evaluated using isotactic polypropylene (iPP) and compatible diluents that crystallize upon cooling. The selected diluents form homogeneous mixtures with iPP at high temperature and lower the viscosity (improved processability), which undergo phase separation upon cooling to form solid particles that function as a toughening agent at room temperature. Tensile properties and morphology of the composites showed that organic crystalline particles have the similar effect as rigid particles to increase toughness; de-wetting between the particle and iPP matrix occurs at the early stage of deformation, followed by unhindered plastic flow that consumes significant amount of fracture energy. The effect of the diluents, however, strongly depends on the identity of the diluents that interact with the iPP during solidification step, which was demonstrated by comparing tetrabromobisphenol-A and

  7. Characterization of induced struvite formation from source-separated urine using seawater and brine as magnesium sources.

    PubMed

    Liu, Bianxia; Giannis, Apostolos; Zhang, Jiefeng; Chang, Victor W-C; Wang, Jing-Yuan

    2013-11-01

    Struvite (MgNH4PO4·6H2O) precipitation is widely used for nutrient recovery from source-separated urine in view of limited natural resources. Spontaneous struvite formation depletes the magnesium in hydrolyzed urine so that additional magnesium source is required to produce induced struvite for P-recovery. The present study investigated the morphology and purity of induced struvite crystals obtained from hydrolyzed urine by using seawater and desalination brine as low cost magnesium sources. The results demonstrated that both seawater and brine were effective magnesium sources to recover phosphorus from hydrolyzed urine. Crystals obtained from synthetic and real urine were revealed that the morphology was feather and coffin shape, respectively. Structural characterization of the precipitates confirmed that crystallized struvite was the main product. However, co-precipitates magnesium calcite and calcite were observed when seawater was added into synthetic and real urine, respectively. It was found that the presence of calcium in the magnesium sources could compromise struvite purity. Higher struvite purity could be obtained with higher Mg/Ca ratio in the magnesium source. Comparative analysis indicated that seawater and brine had similar effect on the crystallized struvite purity. PMID:24134888

  8. 1,2-propanediol-induced premature centromere separation in mouse oocytes and aneuploidy in one-cell zygotes.

    PubMed

    Mailhes, J B; Young, D; London, S N

    1997-07-01

    Aneuploidy in germ cells results in reproductive failure and mental and physical disorders in humans. Unfortunately, little is known about the causes and mechanisms of aneuploidy induction. The objective of this study was to test the hypothesis that propylene glycol (1,2-propanediol; PG) induces cytogenetic aberrations in mouse metaphase II (MII) oocytes that predispose zygotes to aneuploidy. Female ICR mice received 7.5 IU eCG and 5.0 IU hCG 48 h later. PG doses of 1300, 2600, and 5200 mg/kg body weight were given 3 h post-hCG; controls received the solvent deionized water. Ovulated oocytes were collected 16 h after administration of PG and processed for cytogenetic analysis. For the one-cell zygote cytogenetic study, females were given PG and paired (1:1) with ICR males for 16 h. Females that mated were given 2 x 10(-3) M colchicine 22 h post-PG, and zygotes were collected 18 h later. PG significantly (p < 0.05) increased both the proportion of MII oocytes with premature centromere separation (PCS) and the proportion of aneuploid one-cell zygotes. These results support the hypothesis that PG-induced PCS in MII oocytes predisposes zygotes to aneuploidy. PMID:9209085

  9. Developmental Changes in Desensitisation of c-Fos Expression Induced by Repeated Maternal Separation in Pre-Weaned Mice

    PubMed Central

    Horii-Hayashi, N; Sasagawa, T; Matsunaga, W; Matsusue, Y; Azuma, C; Nishi, M

    2013-01-01

    Early-life stress has long-lasting effects on neuroendocrine and behaviour in adulthood. Maternal separation (MS) is used as a model of early-life stress and daily repeated MS (RMS) for 3 h during the first two postnatal weeks is widely used in rodent studies. However, it is not fully understood whether early-life animals desensitise/habituate to repeated stress. In the present study, we investigated the effects of daily RMS for 3 h and acute/single time MS (SMS) for 3 h on the plasma corticosterone level and c-Fos expression in the brain in mice at different postnatal ages. Mice were subjected to: (i) RMS from postnatal day (PND) 1 to 14 (RMS14); (ii) RMS from PND14 to 21 (RMS21); (iii) SMS on PND14 (SMS14); and (iv) SMS on PND21 (SMS21). Plasma corticosterone and c-Fos expression were examined on the final day in each experiment. The basal corticosterone levels in RMS14 and RMS21 were equal to those in respective age-matched controls. After the final separation, the levels were significantly increased and were comparable with those after SMS14 and SMS21, respectively. Histological analysis indicated that c-Fos expression significantly increased in many brain regions, including the paraventricular nucleus, prefrontal cortex, hippocampus, and basolateral and medial amygdale in both SMS14 and SMS21 mice. However, c-Fos expression in RMS14 mice significantly increased in many regions, whereas such increases were hardly seen in RMS21 mice. These results indicate that repeated early-life stress neither increases basal corticosterone, nor decreases the magnitude of the corticosterone response during the first three postnatal weeks, although desensitisation of c-Fos expression induced by repeated stress is changed during postnatal development. PMID:22913644

  10. Enzymatic hydrolysis of penicillin and in situ product separation in thermally induced reversible phase-separation of ionic liquids/water mixture.

    PubMed

    Mai, Ngoc Lan; Koo, Yoon-Mo

    2014-09-01

    Enzymatic hydrolysis of penicillin G to produce 6-aminopenicillanic acid, key intermediate for the production of semisynthetic β-lactam antibiotics, is one of the most relevant example of industrial implementation of biocatalysts. The hydrolysis reaction is traditionally carried out in aqueous buffer at pH 7.5-8. However, the aqueous rout exhibits several drawbacks in enzyme stability and product recovery. In this study, several ionic liquids (ILs) have been used as media for enzymatic hydrolysis of penicillin G. The results indicated that hydrophobic ILs/water two-phase system were good media for the reaction. In addition, a novel aqueous two-phase system based on the lower critical solution temperature type phase changes of amino acid based ILs/water mixture was developed for in situ penicillin G hydrolysis and product separation. For instance, hydrolysis yield of 87.13% was obtained in system containing 30 wt% [TBP][Tf-ILe] with pH control (pH 7.6). Since the phase-separation of this medium system can be reversible switched from single to two phases by slightly changing the solution temperature, enzymatic hydrolytic reaction and product recovery were more efficient than those of aqueous system. In addition, the ILs could be reused for at least 5 cycles without significant loss in hydrolysis efficiency. PMID:25039057