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Sample records for membrane curvature controls

  1. Myosin IIA interacts with the spectrin-actin membrane skeleton to control red blood cell membrane curvature and deformability.

    Science.gov (United States)

    Smith, Alyson S; Nowak, Roberta B; Zhou, Sitong; Giannetto, Michael; Gokhin, David S; Papoin, Julien; Ghiran, Ionita C; Blanc, Lionel; Wan, Jiandi; Fowler, Velia M

    2018-05-08

    The biconcave disk shape and deformability of mammalian RBCs rely on the membrane skeleton, a viscoelastic network of short, membrane-associated actin filaments (F-actin) cross-linked by long, flexible spectrin tetramers. Nonmuscle myosin II (NMII) motors exert force on diverse F-actin networks to control cell shapes, but a function for NMII contractility in the 2D spectrin-F-actin network of RBCs has not been tested. Here, we show that RBCs contain membrane skeleton-associated NMIIA puncta, identified as bipolar filaments by superresolution fluorescence microscopy. MgATP disrupts NMIIA association with the membrane skeleton, consistent with NMIIA motor domains binding to membrane skeleton F-actin and contributing to membrane mechanical properties. In addition, the phosphorylation of the RBC NMIIA heavy and light chains in vivo indicates active regulation of NMIIA motor activity and filament assembly, while reduced heavy chain phosphorylation of membrane skeleton-associated NMIIA indicates assembly of stable filaments at the membrane. Treatment of RBCs with blebbistatin, an inhibitor of NMII motor activity, decreases the number of NMIIA filaments associated with the membrane and enhances local, nanoscale membrane oscillations, suggesting decreased membrane tension. Blebbistatin-treated RBCs also exhibit elongated shapes, loss of membrane curvature, and enhanced deformability, indicating a role for NMIIA contractility in promoting membrane stiffness and maintaining RBC biconcave disk cell shape. As structures similar to the RBC membrane skeleton exist in many metazoan cell types, these data demonstrate a general function for NMII in controlling specialized membrane morphology and mechanical properties through contractile interactions with short F-actin in spectrin-F-actin networks.

  2. A Theoretical Characterization of Curvature Controlled Adhesive Properties of Bio-Inspired Membranes

    DEFF Research Database (Denmark)

    Afferante, Luciano; Heepe, Lars; Casdorff, Kirstin

    2016-01-01

    Some biological systems, such as the tree frog, Litoria caerulea, and the bush-cricket, Tettigonia viridissima, have developed the ability to control adhesion by changing the curvature of their pads. Active control systems of adhesion inspired by these biological models can be very attractive...

  3. CURVATURE-DRIVEN MOLECULAR FLOW ON MEMBRANE SURFACE.

    Science.gov (United States)

    Mikucki, Michael; Zhou, Y C

    2017-01-01

    This work presents a mathematical model for the localization of multiple species of diffusion molecules on membrane surfaces. Morphological change of bilayer membrane in vivo is generally modulated by proteins. Most of these modulations are associated with the localization of related proteins in the crowded lipid environments. We start with the energetic description of the distributions of molecules on curved membrane surface, and define the spontaneous curvature of bilayer membrane as a function of the molecule concentrations on membrane surfaces. A drift-diffusion equation governs the gradient flow of the surface molecule concentrations. We recast the energetic formulation and the related governing equations by using an Eulerian phase field description to define membrane morphology. Computational simulations with the proposed mathematical model and related numerical techniques predict (i) the molecular localization on static membrane surfaces at locations with preferred mean curvatures, and (ii) the generation of preferred mean curvature which in turn drives the molecular localization.

  4. Curvature-Controlled Topological Defects

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    Luka Mesarec

    2017-05-01

    Full Text Available Effectively, two-dimensional (2D closed films exhibiting in-plane orientational ordering (ordered shells might be instrumental for the realization of scaled crystals. In them, ordered shells are expected to play the role of atoms. Furthermore, topological defects (TDs within them would determine their valence. Namely, bonding among shells within an isotropic liquid matrix could be established via appropriate nano-binders (i.e., linkers which tend to be attached to the cores of TDs exploiting the defect core replacement mechanism. Consequently, by varying configurations of TDs one could nucleate growth of scaled crystals displaying different symmetries. For this purpose, it is of interest to develop a simple and robust mechanism via which one could control the position and number of TDs in such atoms. In this paper, we use a minimal mesoscopic model, where variational parameters are the 2D curvature tensor and the 2D orientational tensor order parameter. We demonstrate numerically the efficiency of the effective topological defect cancellation mechanism to predict positional assembling of TDs in ordered films characterized by spatially nonhomogeneous Gaussian curvature. Furthermore, we show how one could efficiently switch among qualitatively different structures by using a relative volume v of ordered shells, which represents a relatively simple naturally accessible control parameter.

  5. Novel tilt-curvature coupling in lipid membranes

    Science.gov (United States)

    Terzi, M. Mert; Deserno, Markus

    2017-08-01

    On mesoscopic scales, lipid membranes are well described by continuum theories whose main ingredients are the curvature of a membrane's reference surface and the tilt of its lipid constituents. In particular, Hamm and Kozlov [Eur. Phys. J. E 3, 323 (2000)] have shown how to systematically derive such a tilt-curvature Hamiltonian based on the elementary assumption of a thin fluid elastic sheet experiencing internal lateral pre-stress. Performing a dimensional reduction, they not only derive the basic form of the effective surface Hamiltonian but also express its emergent elastic couplings as trans-membrane moments of lower-level material parameters. In the present paper, we argue, though, that their derivation unfortunately missed a coupling term between curvature and tilt. This term arises because, as one moves along the membrane, the curvature-induced change of transverse distances contributes to the area strain—an effect that was believed to be small but nevertheless ends up contributing at the same (quadratic) order as all other terms in their Hamiltonian. We illustrate the consequences of this amendment by deriving the monolayer and bilayer Euler-Lagrange equations for the tilt, as well as the power spectra of shape, tilt, and director fluctuations. A particularly curious aspect of our new term is that its associated coupling constant is the second moment of the lipid monolayer's lateral stress profile—which within this framework is equal to the monolayer Gaussian curvature modulus, κ¯ m. On the one hand, this implies that many theoretical predictions now contain a parameter that is poorly known (because the Gauss-Bonnet theorem limits access to the integrated Gaussian curvature); on the other hand, the appearance of κ¯ m outside of its Gaussian curvature provenance opens opportunities for measuring it by more conventional means, for instance by monitoring a membrane's undulation spectrum at short scales.

  6. Supported lipid bilayers with controlled curvature via colloidal lithography

    DEFF Research Database (Denmark)

    Sundh, Maria; Manandhar, Michal; Svedhem, Sofia

    2011-01-01

    Supported lipid bilayers (SLBs) at surfaces provide a route to quantitatively study molecular interactions with and at lipid membranes via different surface-based analytical techniques. Here, a method to fabricate SLBs with controlled curvatures, in the nanometer regime over large areas, is prese...

  7. Membrane curvature enables N-Ras lipid anchor sorting to liquid-ordered membrane phases

    DEFF Research Database (Denmark)

    Larsen, Jannik Bruun; Jensen, Martin Borch; Bhatia, Vikram Kjøller

    2015-01-01

    Trafficking and sorting of membrane-anchored Ras GTPases are regulated by partitioning between distinct membrane domains. Here, in vitro experiments and microscopic molecular theory reveal membrane curvature as a new modulator of N-Ras lipid anchor and palmitoyl chain partitioning. Membrane...

  8. Annexin A4 and A6 induce membrane curvature and constriction during cell membrane repair

    DEFF Research Database (Denmark)

    Boye, Theresa Louise; Maeda, Kenji; Pezeshkian, Weria

    2017-01-01

    Efficient cell membrane repair mechanisms are essential for maintaining membrane integrity and thus for cell life. Here we show that the Ca2+- and phospholipid-binding proteins annexin A4 and A6 are involved in plasma membrane repair and needed for rapid closure of micron-size holes. We demonstrate...... that annexin A4 binds to artificial membranes and generates curvature force initiated from free edges, whereas annexin A6 induces constriction force. In cells, plasma membrane injury and Ca2+ influx recruit annexin A4 to the vicinity of membrane wound edges where its homo-trimerization leads to membrane...... that induction of curvature force around wound edges is an early key event in cell membrane repair....

  9. Manipulating lipid membrane architecture by liquid crystal-analog curvature elasticity (Presentation Recording)

    Science.gov (United States)

    Lee, Sin-Doo

    2015-10-01

    Soft matters such as liquid crystals and biological molecules exhibit a variety of interesting physical phenomena as well as new applications. Recently, in mimicking biological systems that have the ability to sense, regulate, grow, react, and regenerate in a highly responsive and self-adaptive manner, the significance of the liquid crystal order in living organisms, for example, a biological membrane possessing the lamellar order, is widely recognized from the viewpoints of physics and chemistry of interfaces and membrane biophysics. Lipid bilayers, resembling cell membranes, provide primary functions for the transport of biological components of ions and molecules in various cellular activities, including vesicle budding and membrane fusion, through lateral organization of the membrane components such as proteins. In this lecture, I will describe how the liquid crystal-analog curvature elasticity of a lipid bilayer plays a critical role in developing a new platform for understanding diverse biological functions at a cellular level. The key concept is to manipulate the local curvature at an interface between a solid substrate and a model membrane. Two representative examples will be demonstrated: one of them is the topographic control of lipid rafts in a combinatorial array where the ligand-receptor binding event occurs and the other concerns the reconstitution of a ring-type lipid raft in bud-mimicking architecture within the framework of the curvature elasticity.

  10. A unifying mechanism accounts for sensing of membrane curvature by BAR domains, amphipathic helices and membrane-anchored proteins

    DEFF Research Database (Denmark)

    Bhatia, Vikram Kjøller; Hatzakis, Nikos; Stamou, Dimitrios

    2010-01-01

    itself. We thus anticipate that membrane curvature will promote the redistribution of proteins that are anchored in membranes through any type of hydrophobic moiety, a thesis that broadens tremendously the implications of membrane curvature for protein sorting, trafficking and signaling in cell biology....

  11. Membrane Stored Curvature Elastic Stress Modulates Recruitment of Maintenance Proteins PspA and Vipp1.

    Science.gov (United States)

    McDonald, Christopher; Jovanovic, Goran; Ces, Oscar; Buck, Martin

    2015-09-01

    Phage shock protein A (PspA), which is responsible for maintaining inner membrane integrity under stress in enterobacteria, and vesicle-inducting protein in plastids 1 (Vipp1), which functions for membrane maintenance and thylakoid biogenesis in cyanobacteria and plants, are similar peripheral membrane-binding proteins. Their homologous N-terminal amphipathic helices are required for membrane binding; however, the membrane features recognized and required for expressing their functionalities have remained largely uncharacterized. Rigorously controlled, in vitro methodologies with lipid vesicles and purified proteins were used in this study and provided the first biochemical and biophysical characterizations of membrane binding by PspA and Vipp1. Both proteins are found to sense stored curvature elastic (SCE) stress and anionic lipids within the membrane. PspA has an enhanced sensitivity for SCE stress and a higher affinity for the membrane than Vipp1. These variations in binding may be crucial for some of the proteins' differing roles in vivo. Assays probing the transcriptional regulatory function of PspA in the presence of vesicles showed that a relief of transcription inhibition occurs in an SCE stress-specific manner. This in vitro recapitulation of membrane stress-dependent transcription control suggests that the Psp response may be mounted in vivo when a cell's inner membrane experiences increased SCE stress. All cell types maintain the integrity of their membrane systems. One widely distributed membrane stress response system in bacteria is the phage shock protein (Psp) system. The central component, peripheral membrane protein PspA, which mitigates inner membrane stress in bacteria, has a counterpart, Vipp1, which functions for membrane maintenance and thylakoid biogenesis in plants and photosynthetic bacteria. Membrane association of both these proteins is accepted as playing a pivotal role in their functions. Here we show that direct membrane binding by

  12. Amphipathic motifs in BAR domains are essential for membrane curvature sensing

    DEFF Research Database (Denmark)

    Bhatia, Vikram K; Madsen, Kenneth L; Bolinger, Pierre-Yves

    2009-01-01

    BAR (Bin/Amphiphysin/Rvs) domains and amphipathic alpha-helices (AHs) are believed to be sensors of membrane curvature thus facilitating the assembly of protein complexes on curved membranes. Here, we used quantitative fluorescence microscopy to compare the binding of both motifs on single...... nanosized liposomes of different diameters and therefore membrane curvature. Characterization of members of the three BAR domain families showed surprisingly that the crescent-shaped BAR dimer with its positively charged concave face is not able to sense membrane curvature. Mutagenesis on BAR domains showed...... that membrane curvature sensing critically depends on the N-terminal AH and furthermore that BAR domains sense membrane curvature through hydrophobic insertion in lipid packing defects and not through electrostatics. Consequently, amphipathic motifs, such as AHs, that are often associated with BAR domains...

  13. Protein shape and crowding drive domain formation and curvature in biological membranes

    NARCIS (Netherlands)

    Frese, R.N.; Pamies, Josep C.; Olsen, John D.; Bahatyrova, S.; van der Weij-de Wit, Chantal D.; Aartsma, Thijs J.; Otto, Cornelis; Hunter, C. Neil; Frenkel, Daan; van Grondelle, Rienk

    2007-01-01

    Folding, curvature, and domain formation are characteristics of many biological membranes. Yet the mechanisms that drive both curvature and the formation of specialized domains enriched in particular protein complexes are unknown. For this reason, studies in membranes whose shape and organization

  14. Curvature of double-membrane organelles generated by changes in membrane size and composition.

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    Roland L Knorr

    Full Text Available Transient double-membrane organelles are key players in cellular processes such as autophagy, reproduction, and viral infection. These organelles are formed by the bending and closure of flat, double-membrane sheets. Proteins are believed to be important in these morphological transitions but the underlying mechanism of curvature generation is poorly understood. Here, we describe a novel mechanism for this curvature generation which depends primarily on three membrane properties: the lateral size of the double-membrane sheets, the molecular composition of their highly curved rims, and a possible asymmetry between the two flat faces of the sheets. This mechanism is evolutionary advantageous since it does not require active processes and is readily available even when resources within the cell are restricted as during starvation, which can induce autophagy and sporulation. We identify pathways for protein-assisted regulation of curvature generation, organelle size, direction of bending, and morphology. Our theory also provides a mechanism for the stabilization of large double-membrane sheet-like structures found in the endoplasmic reticulum and in the Golgi cisternae.

  15. Membrane curvature stress and antibacterial activity of lactoferricin derivatives.

    Science.gov (United States)

    Zweytick, Dagmar; Tumer, Sabine; Blondelle, Sylvie E; Lohner, Karl

    2008-05-02

    We have studied correlation of non-lamellar phase formation and antimicrobial activity of two cationic amphipathic peptides, termed VS1-13 and VS1-24 derived from a fragment (LF11) of human lactoferricin on Escherichia coli total lipid extracts. Compared to LF11, VS1-13 exhibits minor, but VS1-24 significantly higher antimicrobial activity. X-ray experiments demonstrated that only VS1-24 decreased the onset of cubic phase formation of dispersions of E. coli lipid extracts, significantly, down to physiological relevant temperatures. Cubic structures were identified to belong to the space groups Pn3m and Im3m. Formation of latter is enhanced in the presence of VS1-24. Additionally, the presence of this peptide caused membrane thinning in the fluid phase, which may promote cubic phase formation. VS1-24 containing a larger hydrophobic volume at the N-terminus than its less active counterpart VS1-13 seems to increase curvature stress in the bilayer and alter the behaviour of the membrane significantly enhancing disruption.

  16. Single Lipid Molecule Dynamics on Supported Lipid Bilayers with Membrane Curvature

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    Philip P. Cheney

    2017-03-01

    Full Text Available The plasma membrane is a highly compartmentalized, dynamic material and this organization is essential for a wide variety of cellular processes. Nanoscale domains allow proteins to organize for cell signaling, endo- and exocytosis, and other essential processes. Even in the absence of proteins, lipids have the ability to organize into domains as a result of a variety of chemical and physical interactions. One feature of membranes that affects lipid domain formation is membrane curvature. To directly test the role of curvature in lipid sorting, we measured the accumulation of two similar lipids, 1,2-Dihexadecanoyl-sn-glycero-3-phosphoethanolamine (DHPE and hexadecanoic acid (HDA, using a supported lipid bilayer that was assembled over a nanopatterned surface to obtain regions of membrane curvature. Both lipids studied contain 16 carbon, saturated tails and a head group tag for fluorescence microscopy measurements. The accumulation of lipids at curvatures ranging from 28 nm to 55 nm radii was measured and fluorescein labeled DHPE accumulated more than fluorescein labeled HDA at regions of membrane curvature. We then tested whether single biotinylated DHPE molecules sense curvature using single particle tracking methods. Similar to groups of fluorescein labeled DHPE accumulating at curvature, the dynamics of single molecules of biotinylated DHPE was also affected by membrane curvature and highly confined motion was observed.

  17. Measuring the composition-curvature coupling in binary lipid membranes by computer simulations

    Energy Technology Data Exchange (ETDEWEB)

    Barragán Vidal, I. A., E-mail: vidal@theorie.physik.uni-goettingen.de; Müller, M., E-mail: mmueller@theorie.physik.uni-goettingen.de [Institut für Theoretische Physik, Georg-August-Universität, Friedrich-Hund-Platz 1, 37077 Göttingen (Germany); Rosetti, C. M., E-mail: carla@dqb.fcq.unc.edu.ar [Centro de Investigaciones en Química Biológica de Córdoba, Departamento de Química Biológica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, Córdoba (Argentina); Pastorino, C., E-mail: pastor@cnea.gov.ar [Departamento de Física de la Materia Condensada, Centro Atómico Constituyentes, CNEA/CONICET, Av. Gral. Paz 1499, 1650 Pcia. de Buenos Aires (Argentina)

    2014-11-21

    The coupling between local composition fluctuations in binary lipid membranes and curvature affects the lateral membrane structure. We propose an efficient method to compute the composition-curvature coupling in molecular simulations and apply it to two coarse-grained membrane models—a minimal, implicit-solvent model and the MARTINI model. Both the weak-curvature behavior that is typical for thermal fluctuations of planar bilayer membranes as well as the strong-curvature regime corresponding to narrow cylindrical membrane tubes are studied by molecular dynamics simulation. The simulation results are analyzed by using a phenomenological model of the thermodynamics of curved, mixed bilayer membranes that accounts for the change of the monolayer area upon bending. Additionally the role of thermodynamic characteristics such as the incompatibility between the two lipid species and asymmetry of composition are investigated.

  18. Measuring the composition-curvature coupling in binary lipid membranes by computer simulations

    International Nuclear Information System (INIS)

    Barragán Vidal, I. A.; Müller, M.; Rosetti, C. M.; Pastorino, C.

    2014-01-01

    The coupling between local composition fluctuations in binary lipid membranes and curvature affects the lateral membrane structure. We propose an efficient method to compute the composition-curvature coupling in molecular simulations and apply it to two coarse-grained membrane models—a minimal, implicit-solvent model and the MARTINI model. Both the weak-curvature behavior that is typical for thermal fluctuations of planar bilayer membranes as well as the strong-curvature regime corresponding to narrow cylindrical membrane tubes are studied by molecular dynamics simulation. The simulation results are analyzed by using a phenomenological model of the thermodynamics of curved, mixed bilayer membranes that accounts for the change of the monolayer area upon bending. Additionally the role of thermodynamic characteristics such as the incompatibility between the two lipid species and asymmetry of composition are investigated

  19. Bacterial cell curvature through mechanical control of cell growth

    DEFF Research Database (Denmark)

    Cabeen, M.; Charbon, Godefroid; Vollmer, W.

    2009-01-01

    The cytoskeleton is a key regulator of cell morphogenesis. Crescentin, a bacterial intermediate filament-like protein, is required for the curved shape of Caulobacter crescentus and localizes to the inner cell curvature. Here, we show that crescentin forms a single filamentous structure...... that collapses into a helix when detached from the cell membrane, suggesting that it is normally maintained in a stretched configuration. Crescentin causes an elongation rate gradient around the circumference of the sidewall, creating a longitudinal cell length differential and hence curvature. Such curvature...... can be produced by physical force alone when cells are grown in circular microchambers. Production of crescentin in Escherichia coli is sufficient to generate cell curvature. Our data argue for a model in which physical strain borne by the crescentin structure anisotropically alters the kinetics...

  20. Curvature controlled wetting in two dimensions

    DEFF Research Database (Denmark)

    Gil, Tamir; Mikheev, Lev V.

    1995-01-01

    . As the radius of the substrate r0→∞, the leading effect of the curvature is adding the Laplace pressure ΠL∝r0-1 to the pressure balance in the film. At temperatures and pressures under which the wetting is complete in planar geometry, Laplace pressure suppresses divergence of the mean thickness of the wetting...... term reduces the thickness by the amount proportional to r0-1/3...

  1. BAR domains, amphipathic helices and membrane-anchored proteins use the same mechanism to sense membrane curvature

    DEFF Research Database (Denmark)

    Madsen, Kenneth Lindegaard; Bhatia, V K; Gether, U

    2010-01-01

    /ensemble liposome samples of different mean diameter. Next, we describe two different MCS protein motifs (amphipathic helices and BAR domains) and suggest that in both cases curvature sensitive membrane binding results from asymmetric insertion of hydrophobic amino acids in the lipid membrane. This mechanism can...

  2. The homeodomain derived peptide Penetratin induces curvature of fluid membrane domains.

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    Antonin Lamazière

    Full Text Available BACKGROUND: Protein membrane transduction domains that are able to cross the plasma membrane are present in several transcription factors, such as the homeodomain proteins and the viral proteins such as Tat of HIV-1. Their discovery resulted in both new concepts on the cell communication during development, and the conception of cell penetrating peptide vectors for internalisation of active molecules into cells. A promising cell penetrating peptide is Penetratin, which crosses the cell membranes by a receptor and metabolic energy-independent mechanism. Recent works have claimed that Penetratin and similar peptides are internalized by endocytosis, but other endocytosis-independent mechanisms have been proposed. Endosomes or plasma membranes crossing mechanisms are not well understood. Previously, we have shown that basic peptides induce membrane invaginations suggesting a new mechanism for uptake, "physical endocytosis". METHODOLOGY/PRINCIPAL FINDINGS: Herein, we investigate the role of membrane lipid phases on Penetratin induced membrane deformations (liquid ordered such as in "raft" microdomains versus disordered fluid "non-raft" domains in membrane models. Experimental data show that zwitterionic lipid headgroups take part in the interaction with Penetratin suggesting that the external leaflet lipids of cells plasma membrane are competent for peptide interaction in the absence of net negative charges. NMR and X-ray diffraction data show that the membrane perturbations (tubulation and vesiculation are associated with an increase in membrane negative curvature. These effects on curvature were observed in the liquid disordered but not in the liquid ordered (raft-like membrane domains. CONCLUSIONS/SIGNIFICANCE: The better understanding of the internalisation mechanisms of protein transduction domains will help both the understanding of the mechanisms of cell communication and the development of potential therapeutic molecular vectors. Here we

  3. The Role of Membrane Curvature in Nanoscale Topography-Induced Intracellular Signaling.

    Science.gov (United States)

    Lou, Hsin-Ya; Zhao, Wenting; Zeng, Yongpeng; Cui, Bianxiao

    2018-05-15

    Over the past decade, there has been growing interest in developing biosensors and devices with nanoscale and vertical topography. Vertical nanostructures induce spontaneous cell engulfment, which enhances the cell-probe coupling efficiency and the sensitivity of biosensors. Although local membranes in contact with the nanostructures are found to be fully fluidic for lipid and membrane protein diffusions, cells appear to actively sense and respond to the surface topography presented by vertical nanostructures. For future development of biodevices, it is important to understand how cells interact with these nanostructures and how their presence modulates cellular function and activities. How cells recognize nanoscale surface topography has been an area of active research for two decades before the recent biosensor works. Extensive studies show that surface topographies in the range of tens to hundreds of nanometers can significantly affect cell functions, behaviors, and ultimately the cell fate. For example, titanium implants having rough surfaces are better for osteoblast attachment and host-implant integration than those with smooth surfaces. At the cellular level, nanoscale surface topography has been shown by a large number of studies to modulate cell attachment, activity, and differentiation. However, a mechanistic understanding of how cells interact and respond to nanoscale topographic features is still lacking. In this Account, we focus on some recent studies that support a new mechanism that local membrane curvature induced by nanoscale topography directly acts as a biochemical signal to induce intracellular signaling, which we refer to as the curvature hypothesis. The curvature hypothesis proposes that some intracellular proteins can recognize membrane curvatures of a certain range at the cell-to-material interface. These proteins then recruit and activate downstream components to modulate cell signaling and behavior. We discuss current technologies

  4. Influence of Global and Local Membrane Curvature on Mechanosensitive Ion Channels: A Finite Element Approach

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    Omid Bavi

    2016-02-01

    Full Text Available Mechanosensitive (MS channels are ubiquitous molecular force sensors that respond to a number of different mechanical stimuli including tensile, compressive and shear stress. MS channels are also proposed to be molecular curvature sensors gating in response to bending in their local environment. One of the main mechanisms to functionally study these channels is the patch clamp technique. However, the patch of membrane surveyed using this methodology is far from physiological. Here we use continuum mechanics to probe the question of how curvature, in a standard patch clamp experiment, at different length scales (global and local affects a model MS channel. Firstly, to increase the accuracy of the Laplace’s equation in tension estimation in a patch membrane and to be able to more precisely describe the transient phenomena happening during patch clamping, we propose a modified Laplace’s equation. Most importantly, we unambiguously show that the global curvature of a patch, which is visible under the microscope during patch clamp experiments, is of negligible energetic consequence for activation of an MS channel in a model membrane. However, the local curvature (RL < 50 and the direction of bending are able to cause considerable changes in the stress distribution through the thickness of the membrane. Not only does local bending, in the order of physiologically relevant curvatures, cause a substantial change in the pressure profile but it also significantly modifies the stress distribution in response to force application. Understanding these stress variations in regions of high local bending is essential for a complete understanding of the effects of curvature on MS channels.

  5. On ripples and rafts: Curvature induced nanoscale structures in lipid membranes

    International Nuclear Information System (INIS)

    Schmid, Friederike; Dolezel, Stefan; Meinhardt, Sebastian; Lenz, Olaf

    2014-01-01

    We develop an elastic theory that predicts the spontaneous formation of nanoscale structures in lipid bilayers which locally phase separate between two phases with different spontaneous monolayer curvature. The theory rationalizes in a unified manner the observation of a variety of nanoscale structures in lipid membranes: Rippled states in one-component membranes, lipid rafts in multicomponent membranes. Furthermore, we report on recent observations of rippled states and rafts in simulations of a simple coarse-grained model for lipid bilayers, which are compatible with experimental observations and with our elastic model

  6. Mesoscale computational studies of membrane bilayer remodeling by curvature-inducing proteins

    Science.gov (United States)

    Ramakrishnan, N.; Sunil Kumar, P. B.; Radhakrishnan, Ravi

    2014-01-01

    Biological membranes constitute boundaries of cells and cell organelles. These membranes are soft fluid interfaces whose thermodynamic states are dictated by bending moduli, induced curvature fields, and thermal fluctuations. Recently, there has been a flood of experimental evidence highlighting active roles for these structures in many cellular processes ranging from trafficking of cargo to cell motility. It is believed that the local membrane curvature, which is continuously altered due to its interactions with myriad proteins and other macromolecules attached to its surface, holds the key to the emergent functionality in these cellular processes. Mechanisms at the atomic scale are dictated by protein-lipid interaction strength, lipid composition, lipid distribution in the vicinity of the protein, shape and amino acid composition of the protein, and its amino acid contents. The specificity of molecular interactions together with the cooperativity of multiple proteins induce and stabilize complex membrane shapes at the mesoscale. These shapes span a wide spectrum ranging from the spherical plasma membrane to the complex cisternae of the Golgi apparatus. Mapping the relation between the protein-induced deformations at the molecular scale and the resulting mesoscale morphologies is key to bridging cellular experiments across the various length scales. In this review, we focus on the theoretical and computational methods used to understand the phenomenology underlying protein-driven membrane remodeling. Interactions at the molecular scale can be computationally probed by all atom and coarse grained molecular dynamics (MD, CGMD), as well as dissipative particle dynamics (DPD) simulations, which we only describe in passing. We choose to focus on several continuum approaches extending the Canham - Helfrich elastic energy model for membranes to include the effect of curvature-inducing proteins and explore the conformational phase space of such systems. In this

  7. Mesoscale computational studies of membrane bilayer remodeling by curvature-inducing proteins

    Energy Technology Data Exchange (ETDEWEB)

    Ramakrishnan, N., E-mail: ramn@seas.upenn.edu [Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA-19104 (United States); Department of Bioengineering, University of Pennsylvania, Philadelphia, PA-19104 (United States); Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA-19104 (United States); Sunil Kumar, P.B., E-mail: sunil@physics.iitm.ac.in [Department of Physics, Indian Institute of Technology Madras, Chennai, 600036 (India); Radhakrishnan, Ravi, E-mail: rradhak@seas.upenn.edu [Department of Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, PA-19104 (United States); Department of Bioengineering, University of Pennsylvania, Philadelphia, PA-19104 (United States); Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA-19104 (United States)

    2014-10-01

    Biological membranes constitute boundaries of cells and cell organelles. These membranes are soft fluid interfaces whose thermodynamic states are dictated by bending moduli, induced curvature fields, and thermal fluctuations. Recently, there has been a flood of experimental evidence highlighting active roles for these structures in many cellular processes ranging from trafficking of cargo to cell motility. It is believed that the local membrane curvature, which is continuously altered due to its interactions with myriad proteins and other macromolecules attached to its surface, holds the key to the emergent functionality in these cellular processes. Mechanisms at the atomic scale are dictated by protein–lipid interaction strength, lipid composition, lipid distribution in the vicinity of the protein, shape and amino acid composition of the protein, and its amino acid contents. The specificity of molecular interactions together with the cooperativity of multiple proteins induce and stabilize complex membrane shapes at the mesoscale. These shapes span a wide spectrum ranging from the spherical plasma membrane to the complex cisternae of the Golgi apparatus. Mapping the relation between the protein-induced deformations at the molecular scale and the resulting mesoscale morphologies is key to bridging cellular experiments across various length scales. In this review, we focus on the theoretical and computational methods used to understand the phenomenology underlying protein-driven membrane remodeling. Interactions at the molecular scale can be computationally probed by all atom and coarse grained molecular dynamics (MD, CGMD), as well as dissipative particle dynamics (DPD) simulations, which we only describe in passing. We choose to focus on several continuum approaches extending the Canham–Helfrich elastic energy model for membranes to include the effect of curvature-inducing proteins and explore the conformational phase space of such systems. In this description

  8. Mesoscale computational studies of membrane bilayer remodeling by curvature-inducing proteins

    International Nuclear Information System (INIS)

    Ramakrishnan, N.; Sunil Kumar, P.B.; Radhakrishnan, Ravi

    2014-01-01

    Biological membranes constitute boundaries of cells and cell organelles. These membranes are soft fluid interfaces whose thermodynamic states are dictated by bending moduli, induced curvature fields, and thermal fluctuations. Recently, there has been a flood of experimental evidence highlighting active roles for these structures in many cellular processes ranging from trafficking of cargo to cell motility. It is believed that the local membrane curvature, which is continuously altered due to its interactions with myriad proteins and other macromolecules attached to its surface, holds the key to the emergent functionality in these cellular processes. Mechanisms at the atomic scale are dictated by protein–lipid interaction strength, lipid composition, lipid distribution in the vicinity of the protein, shape and amino acid composition of the protein, and its amino acid contents. The specificity of molecular interactions together with the cooperativity of multiple proteins induce and stabilize complex membrane shapes at the mesoscale. These shapes span a wide spectrum ranging from the spherical plasma membrane to the complex cisternae of the Golgi apparatus. Mapping the relation between the protein-induced deformations at the molecular scale and the resulting mesoscale morphologies is key to bridging cellular experiments across various length scales. In this review, we focus on the theoretical and computational methods used to understand the phenomenology underlying protein-driven membrane remodeling. Interactions at the molecular scale can be computationally probed by all atom and coarse grained molecular dynamics (MD, CGMD), as well as dissipative particle dynamics (DPD) simulations, which we only describe in passing. We choose to focus on several continuum approaches extending the Canham–Helfrich elastic energy model for membranes to include the effect of curvature-inducing proteins and explore the conformational phase space of such systems. In this description

  9. Mesoscale computational studies of membrane bilayer remodeling by curvature-inducing proteins.

    Science.gov (United States)

    Ramakrishnan, N; Sunil Kumar, P B; Radhakrishnan, Ravi

    2014-10-01

    Biological membranes constitute boundaries of cells and cell organelles. These membranes are soft fluid interfaces whose thermodynamic states are dictated by bending moduli, induced curvature fields, and thermal fluctuations. Recently, there has been a flood of experimental evidence highlighting active roles for these structures in many cellular processes ranging from trafficking of cargo to cell motility. It is believed that the local membrane curvature, which is continuously altered due to its interactions with myriad proteins and other macromolecules attached to its surface, holds the key to the emergent functionality in these cellular processes. Mechanisms at the atomic scale are dictated by protein-lipid interaction strength, lipid composition, lipid distribution in the vicinity of the protein, shape and amino acid composition of the protein, and its amino acid contents. The specificity of molecular interactions together with the cooperativity of multiple proteins induce and stabilize complex membrane shapes at the mesoscale. These shapes span a wide spectrum ranging from the spherical plasma membrane to the complex cisternae of the Golgi apparatus. Mapping the relation between the protein-induced deformations at the molecular scale and the resulting mesoscale morphologies is key to bridging cellular experiments across the various length scales. In this review, we focus on the theoretical and computational methods used to understand the phenomenology underlying protein-driven membrane remodeling. Interactions at the molecular scale can be computationally probed by all atom and coarse grained molecular dynamics (MD, CGMD), as well as dissipative particle dynamics (DPD) simulations, which we only describe in passing. We choose to focus on several continuum approaches extending the Canham - Helfrich elastic energy model for membranes to include the effect of curvature-inducing proteins and explore the conformational phase space of such systems. In this

  10. Towards understanding of Nipah virus attachment protein assembly and the role of protein affinity and crowding for membrane curvature events.

    Energy Technology Data Exchange (ETDEWEB)

    Stachowiak, Jeanne C.; Hayden, Carl C.; Negrete, Oscar.; Davis, Ryan Wesley; Sasaki, Darryl Y

    2013-10-01

    Pathogenic viruses are a primary threat to our national security and to the health and economy of our world. Effective defense strategies to combat viral infection and spread require the development of understanding of the mechanisms that these pathogens use to invade the host cell. We present in this report results of our research into viral particle recognition and fusion to cell membranes and the role that protein affinity and confinement in lipid domains plays in membrane curvature in cellular fusion and fission events. Herein, we describe 1) the assembly of the G attachment protein of Nipah virus using point mutation studies to define its role in viral particle fusion to the cell membrane, 2) how lateral pressure of membrane bound proteins induce curvature in model membrane systems, and 3) the role of membrane curvature in the selective partitioning of molecular receptors and specific affinity of associated proteins.

  11. Lipid clustering correlates with membrane curvature as revealed by molecular simulations of complex lipid bilayers.

    Directory of Open Access Journals (Sweden)

    Heidi Koldsø

    2014-10-01

    Full Text Available Cell membranes are complex multicomponent systems, which are highly heterogeneous in the lipid distribution and composition. To date, most molecular simulations have focussed on relatively simple lipid compositions, helping to inform our understanding of in vitro experimental studies. Here we describe on simulations of complex asymmetric plasma membrane model, which contains seven different lipids species including the glycolipid GM3 in the outer leaflet and the anionic lipid, phosphatidylinositol 4,5-bisphophate (PIP2, in the inner leaflet. Plasma membrane models consisting of 1500 lipids and resembling the in vivo composition were constructed and simulations were run for 5 µs. In these simulations the most striking feature was the formation of nano-clusters of GM3 within the outer leaflet. In simulations of protein interactions within a plasma membrane model, GM3, PIP2, and cholesterol all formed favorable interactions with the model α-helical protein. A larger scale simulation of a model plasma membrane containing 6000 lipid molecules revealed correlations between curvature of the bilayer surface and clustering of lipid molecules. In particular, the concave (when viewed from the extracellular side regions of the bilayer surface were locally enriched in GM3. In summary, these simulations explore the nanoscale dynamics of model bilayers which mimic the in vivo lipid composition of mammalian plasma membranes, revealing emergent nanoscale membrane organization which may be coupled both to fluctuations in local membrane geometry and to interactions with proteins.

  12. NMR Determination of Protein Partitioning into Membrane Domains with Different Curvatures and Application to the Influenza M2 Peptide

    Science.gov (United States)

    Wang, Tuo; Cady, Sarah D.; Hong, Mei

    2012-01-01

    The M2 protein of the influenza A virus acts both as a drug-sensitive proton channel and mediates virus budding through membrane scission. The segment responsible for causing membrane curvature is an amphipathic helix in the cytoplasmic domain of the protein. Here, we use 31P and 13C solid-state NMR to examine M2-induced membrane curvature. M2(22–46), which includes only the transmembrane (TM) helix, and M2(21–61), which contains an additional amphipathic helix, are studied. 31P chemical shift lineshapes indicate that M2(21–61) causes a high-curvature isotropic phase to both cholesterol-rich virus-mimetic membranes and 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayers, whereas M2(22–46) has minimal effect. The lamellar and isotropic domains have distinct 31P isotropic chemical shifts, indicating perturbation of the lipid headgroup conformation by the amphipathic helix. 31P- and 13C-detected 1H T2 relaxation and two-dimensional peptide-lipid correlation spectra show that M2(21–61) preferentially binds to the high-curvature domain. 31P linewidths indicate that the isotropic vesicles induced by M2(21–61) are 10–35 nm in diameter, and the virus-mimetic vesicles are smaller than the 1,2-dimyristoyl-sn-glycero-3-phosphocholine vesicles. A strong correlation is found between high membrane curvature and weak drug-binding ability of the TM helix. Thus, the M2 amphipathic helix causes membrane curvature, which in turn perturbs the TM helix conformation, abolishing drug binding. These NMR experiments are applicable to other curvature-inducing membrane proteins such as fusion proteins and antimicrobial peptides. PMID:22385849

  13. The effect of curvature on the undulation spectrum of Red Blood Cell membranes

    Science.gov (United States)

    Kuriabova, Tatiana; Henle, Mark L.; Levine, Alex J.

    2009-03-01

    The human red blood cell (RBC) membrane has a composite structure of a fluid lipid bilayer tethered to an elastic 2D spectrin network. The study of the mechanical properties of RBCs is crucial to our understanding of their ability withstand large amplitude deformations during their passage through the microvasculature. The linear mechanical response of this composite membrane can be measured by observing its undulatory dynamics in thermal equilibrium, i.e. microrheology. Previous models of these dynamics postulated an effective surface tension. In this talk, we show that surface tension is not necessary. Rather, the coupling of membrane bending to spectrin network compression by curvature can account for the observed dynamics. We use a simplified theoretical model to describe the undulatory dynamics of RBCs, measured experimentally by the Popescu group.ootnotetextG. Popescu et al. ``Imaging red blood cell dynamics by quantitative phase microscopy, Blood Cells, Molecules, and Diseases, (2008), in print'' Analyzing their data using our model, we observe dramatic changes in RBC membrane elasticity associated with cells' morphological transition from discocytes to echinocyte to spherocyte.

  14. The N-terminal amphipathic helix of the topological specificity factor MinE is associated with shaping membrane curvature.

    Directory of Open Access Journals (Sweden)

    Yu-Ling Shih

    Full Text Available Pole-to-pole oscillations of the Min proteins in Escherichia coli are required for the proper placement of the division septum. Direct interaction of MinE with the cell membrane is critical for the dynamic behavior of the Min system. In vitro, this MinE-membrane interaction led to membrane deformation; however, the underlying mechanism remained unclear. Here we report that MinE-induced membrane deformation involves the formation of an amphipathic helix of MinE(2-9, which, together with the adjacent basic residues, function as membrane anchors. Biochemical evidence suggested that the membrane association induces formation of the helix, with the helical face, consisting of A2, L3, and F6, inserted into the membrane. Insertion of this helix into the cell membrane can influence local membrane curvature and lead to drastic changes in membrane topology. Accordingly, MinE showed characteristic features of protein-induced membrane tubulation and lipid clustering in in vitro reconstituted systems. In conclusion, MinE shares common protein signatures with a group of membrane trafficking proteins in eukaryotic cells. These MinE signatures appear to affect membrane curvature.

  15. DNA release from lipoplexes by anionic lipids: correlation with lipid mesomorphism, interfacial curvature, and membrane fusion

    Energy Technology Data Exchange (ETDEWEB)

    Tarahovsky, Yury S.; Koynova, Rumiana; MacDonald, Robert C. (Northwestern)

    2010-01-18

    DNA release from lipoplexes is an essential step during lipofection and is probably a result of charge neutralization by cellular anionic lipids. As a model system to test this possibility, fluorescence resonance energy transfer between DNA and lipid covalently labeled with Cy3 and BODIPY, respectively, was used to monitor the release of DNA from lipid surfaces induced by anionic liposomes. The separation of DNA from lipid measured this way was considerably slower and less complete than that estimated with noncovalently labeled DNA, and depends on the lipid composition of both lipoplexes and anionic liposomes. This result was confirmed by centrifugal separation of released DNA and lipid. X-ray diffraction revealed a clear correlation of the DNA release capacity of the anionic lipids with the interfacial curvature of the mesomorphic structures developed when the anionic and cationic liposomes were mixed. DNA release also correlated with the rate of fusion of anionic liposomes with lipoplexes. It is concluded that the tendency to fuse and the phase preference of the mixed lipid membranes are key factors for the rate and extent of DNA release. The approach presented emphasizes the importance of the lipid composition of both lipoplexes and target membranes and suggests optimal transfection may be obtained by tailoring lipoplex composition to the lipid composition of target cells.

  16. MreB filaments align along greatest principal membrane curvature to orient cell wall synthesis

    Science.gov (United States)

    Szwedziak, Piotr; Wong, Felix; Schaefer, Kaitlin; Izoré, Thierry; Renner, Lars D; Holmes, Matthew J; Sun, Yingjie; Bisson-Filho, Alexandre W; Walker, Suzanne; Amir, Ariel; Löwe, Jan

    2018-01-01

    MreB is essential for rod shape in many bacteria. Membrane-associated MreB filaments move around the rod circumference, helping to insert cell wall in the radial direction to reinforce rod shape. To understand how oriented MreB motion arises, we altered the shape of Bacillus subtilis. MreB motion is isotropic in round cells, and orientation is restored when rod shape is externally imposed. Stationary filaments orient within protoplasts, and purified MreB tubulates liposomes in vitro, orienting within tubes. Together, this demonstrates MreB orients along the greatest principal membrane curvature, a conclusion supported with biophysical modeling. We observed that spherical cells regenerate into rods in a local, self-reinforcing manner: rapidly propagating rods emerge from small bulges, exhibiting oriented MreB motion. We propose that the coupling of MreB filament alignment to shape-reinforcing peptidoglycan synthesis creates a locally-acting, self-organizing mechanism allowing the rapid establishment and stable maintenance of emergent rod shape. PMID:29469806

  17. A major QTL controls susceptibility to spinal curvature in the curveback guppy

    Directory of Open Access Journals (Sweden)

    Dreyer Christine

    2011-01-01

    Full Text Available Abstract Background Understanding the genetic basis of heritable spinal curvature would benefit medicine and aquaculture. Heritable spinal curvature among otherwise healthy children (i.e. Idiopathic Scoliosis and Scheuermann kyphosis accounts for more than 80% of all spinal curvatures and imposes a substantial healthcare cost through bracing, hospitalizations, surgery, and chronic back pain. In aquaculture, the prevalence of heritable spinal curvature can reach as high as 80% of a stock, and thus imposes a substantial cost through production losses. The genetic basis of heritable spinal curvature is unknown and so the objective of this work is to identify quantitative trait loci (QTL affecting heritable spinal curvature in the curveback guppy. Prior work with curveback has demonstrated phenotypic parallels to human idiopathic-type scoliosis, suggesting shared biological pathways for the deformity. Results A major effect QTL that acts in a recessive manner and accounts for curve susceptibility was detected in an initial mapping cross on LG 14. In a second cross, we confirmed this susceptibility locus and fine mapped it to a 5 cM region that explains 82.6% of the total phenotypic variance. Conclusions We identify a major QTL that controls susceptibility to curvature. This locus contains over 100 genes, including MTNR1B, a candidate gene for human idiopathic scoliosis. The identification of genes associated with heritable spinal curvature in the curveback guppy has the potential to elucidate the biological basis of spinal curvature among humans and economically important teleosts.

  18. An Amphipathic Helix Directs Cellular Membrane Curvature Sensing and Function of the BAR Domain Protein PICK1.

    Science.gov (United States)

    Herlo, Rasmus; Lund, Viktor K; Lycas, Matthew D; Jansen, Anna M; Khelashvili, George; Andersen, Rita C; Bhatia, Vikram; Pedersen, Thomas S; Albornoz, Pedro B C; Johner, Niklaus; Ammendrup-Johnsen, Ina; Christensen, Nikolaj R; Erlendsson, Simon; Stoklund, Mikkel; Larsen, Jannik B; Weinstein, Harel; Kjærulff, Ole; Stamou, Dimitrios; Gether, Ulrik; Madsen, Kenneth L

    2018-05-15

    BAR domains are dimeric protein modules that sense, induce, and stabilize lipid membrane curvature. Here, we show that membrane curvature sensing (MCS) directs cellular localization and function of the BAR domain protein PICK1. In PICK1, and the homologous proteins ICA69 and arfaptin2, we identify an amphipathic helix N-terminal to the BAR domain that mediates MCS. Mutational disruption of the helix in PICK1 impaired MCS without affecting membrane binding per se. In insulin-producing INS-1E cells, super-resolution microscopy revealed that disruption of the helix selectively compromised PICK1 density on insulin granules of high curvature during their maturation. This was accompanied by reduced hormone storage in the INS-1E cells. In Drosophila, disruption of the helix compromised growth regulation. By demonstrating size-dependent binding on insulin granules, our finding highlights the function of MCS for BAR domain proteins in a biological context distinct from their function, e.g., at the plasma membrane during endocytosis. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

  19. Magnetically controlled permeability membranes

    KAUST Repository

    Kosel, Jurgen

    2013-10-31

    A bioactive material delivery system can include a thermoresponsive polymer membrane and nanowires distributed within the thermoresponsive polymer membrane. Magnetic activation of a thermoresponsive polymer membrane can take place via altering the magnetization or dimensions of nanowires dispersed or ordered within the membrane matrix.

  20. Magnetically controlled permeability membranes

    KAUST Repository

    Kosel, Jü rgen; Khashab, Niveen M.; Zaher, Amir

    2013-01-01

    A bioactive material delivery system can include a thermoresponsive polymer membrane and nanowires distributed within the thermoresponsive polymer membrane. Magnetic activation of a thermoresponsive polymer membrane can take place via altering the magnetization or dimensions of nanowires dispersed or ordered within the membrane matrix.

  1. Salt Bridge Formation between the I-BAR Domain and Lipids Increases Lipid Density and Membrane Curvature.

    Science.gov (United States)

    Takemura, Kazuhiro; Hanawa-Suetsugu, Kyoko; Suetsugu, Shiro; Kitao, Akio

    2017-07-28

    The BAR domain superfamily proteins sense or induce curvature in membranes. The inverse-BAR domain (I-BAR) is a BAR domain that forms a straight "zeppelin-shaped" dimer. The mechanisms by which IRSp53 I-BAR binds to and deforms a lipid membrane are investigated here by all-atom molecular dynamics simulation (MD), binding energy analysis, and the effects of mutation experiments on filopodia on HeLa cells. I-BAR adopts a curved structure when crystallized, but adopts a flatter shape in MD. The binding of I-BAR to membrane was stabilized by ~30 salt bridges, consistent with experiments showing that point mutations of the interface residues have little effect on the binding affinity whereas multiple mutations have considerable effect. Salt bridge formation increases the local density of lipids and deforms the membrane into a concave shape. In addition, the point mutations that break key intra-molecular salt bridges within I-BAR reduce the binding affinity; this was confirmed by expressing these mutants in HeLa cells and observing their effects. The results indicate that the stiffness of I-BAR is important for membrane deformation, although I-BAR does not act as a completely rigid template.

  2. 2,2'-Bis(monoacylglycero) PO4 (BMP), but Not 3,1'-BMP, increases membrane curvature stress to enhance α-tocopherol transfer protein binding to membranes.

    Science.gov (United States)

    Baptist, Matilda; Panagabko, Candace; Nickels, Jonathan D; Katsaras, John; Atkinson, Jeffrey

    2015-03-01

    Previous work revealed that α-tocopherol transfer protein (α-TTP) co-localizes with bis(monoacylglycero)phosphate (BMP) in late endosomes. BMP is a lipid unique to late endosomes and is believed to induce membrane curvature and support the multivesicular nature of this organelle. We examined the effect of BMP on α-TTP binding to membranes using dual polarization interferometry and vesicle-binding assay. α-TTP binding to membranes is increased by the curvature-inducing lipid BMP. α-TTP binds to membranes with greater affinity when they contain the 2,2'-BMP versus 3,1'-BMP isomers.

  3. Membrane curvature, lipid segregation, and structural transitions for phospholipids under dual-solvent stress

    International Nuclear Information System (INIS)

    Rand, R.P.; Fuller, N.L.; Gruner, S.M.; Parsegian, V.A.

    1990-01-01

    Amphiphiles respond both to polar and to nonpolar solvents. In this paper X-ray diffraction and osmotic stress have been used to examine the phase behavior, the structural dimensions, and the work of deforming the monolayer-lined aqueous cavities formed by mixtures of dioleoylphosphatidylethanolamine (DOPE) and dioleoylphosphatidylcholine (DOPC) as a function of the concentration of two solvents, water and tetradecane (td). In the absence of td, most PE/PC mixtures show only lamellar phases in excess water; all of these become single reverse hexagonal (H II ) phases with addition of excess td. The spontaneous radius of curvature R 0 of lipid monolayers, as expressed in these H II phases, is allowed by the relief of hydrocarbon chain stress by td; R 0 increases with the ratio DOPC/DOPE. Single H II phases stressed by limited water or td show several responses. (a) the molecular area is compressed at the polar end of the molecule and expanded at the hydrocarbon ends. (b) For circularly symmetrical water cylinders, the degrees of hydrocarbon chain splaying and polar group compression are different for molecules aligned in different directions around the water cylinder. (c) A pivotal position exists along the length of the phospholipid molecule where little area change occurs as the monolayer is bent to increasing curvatures. (d) By defining R 0 at the pivotal position, the authors find that measured energies are well fit by a quadratic bending energy. (e) For lipid mixtures, enforced deviation of the H II monolayer from R 0 is sufficiently powerful to cause demixing of the phospholipids in a way suggesting that the DOPE/DOPC ratio self-adjusts so that its R 0 matches the amount of td or water available, i.e., that curvature energy is minimized

  4. Membrane Curvature and Lipid Composition Synergize To Regulate N-Ras Anchor Recruitment

    DEFF Research Database (Denmark)

    Larsen, Jannik B.; Kennard, Celeste; Pedersen, Søren L.

    2017-01-01

    Proteins anchored to membranes through covalently linked fatty acids and/or isoprenoid groups play crucial roles in all forms of life. Sorting and trafficking of lipidated proteins has traditionally been discussed in the context of partitioning to membrane domains of different lipid composition. We...

  5. Controllable soliton propagation based on phase-front curvature in asymmetrical nonlocal media

    Science.gov (United States)

    Zhang, Huafeng; Lü, Hua; Luo, Jianghua; Sun, Lihui

    2016-08-01

    The influence of phase-front curvature on the dynamical behavior of the fundamental mode soliton during its transmission in asymmetrical nonlocal media is studied in detail and the phase-front curvature can be imposed on the fundamental mode soliton by reshaping or phase imprinting technologies. By changing the phase-front curvature or its imposed position, controllable soliton propagation in asymmetrical nonlocal media can be achieved. Project supported by the National Natural Science Foundation of China (Grants Nos. 11547007 and 11304024), the Innovation Personnel Training Plan for Excellent Youth of Guangdong University Project (Grant No. 2013LYM_0023), and the Yangtze Fund for Youth Teams of Science and Technology Innovation (Grant No. 2015cqt03).

  6. Membrane Curvature Induced by Aggregates of LH2s and Monomeric LH1s

    OpenAIRE

    Chandler, Danielle E.; Gumbart, James; Stack, John D.; Chipot, Christophe; Schulten, Klaus

    2009-01-01

    The photosynthetic apparatus of purple bacteria is contained within organelles called chromatophores, which form as extensions of the cytoplasmic membrane. The shape of these chromatophores can be spherical (as in Rhodobacter sphaeroides), lamellar (as in Rhodopseudomonas acidophila and Phaeospirillum molischianum), or tubular (as in certain Rb. sphaeroides mutants). Chromatophore shape is thought to be influenced by the integral membrane proteins Light Harvesting Complexes I and II (LH1 and ...

  7. Membrane curvature induction and tubulation are common features of synucleins and apolipoproteins

    DEFF Research Database (Denmark)

    Varkey, Jobin; Isas, Jose Mario; Mizuno, Naoko

    2010-01-01

    Synucleins and apolipoproteins have been implicated in a number of membrane and lipid trafficking events. Lipid interaction for both types of proteins is mediated by 11 amino acid repeats that form amphipathic helices. This similarity suggests that synucleins and apolipoproteins might have...... of amphipathic helices alone. Moreover, we frequently observed that a-synuclein caused membrane structures that had the appearance of nascent budding vesicles. The ability to function as a minimal machinery for vesicle budding agrees well with recent findings that a-synuclein plays a role in vesicle trafficking...

  8. Nanoengineered membranes for controlled transport

    Science.gov (United States)

    Doktycz, Mitchel J [Oak Ridge, TN; Simpson, Michael L [Knoxville, TN; McKnight, Timothy E [Greenback, TN; Melechko, Anatoli V [Oak Ridge, TN; Lowndes, Douglas H [Knoxville, TN; Guillorn, Michael A [Knoxville, TN; Merkulov, Vladimir I [Oak Ridge, TN

    2010-01-05

    A nanoengineered membrane for controlling material transport (e.g., molecular transport) is disclosed. The membrane includes a substrate, a cover definining a material transport channel between the substrate and the cover, and a plurality of fibers positioned in the channel and connected to an extending away from a surface of the substrate. The fibers are aligned perpendicular to the surface of the substrate, and have a width of 100 nanometers or less. The diffusion limits for material transport are controlled by the separation of the fibers. In one embodiment, chemical derivitization of carbon fibers may be undertaken to further affect the diffusion limits or affect selective permeability or facilitated transport. For example, a coating can be applied to at least a portion of the fibers. In another embodiment, individually addressable carbon nanofibers can be integrated with the membrane to provide an electrical driving force for material transport.

  9. Effects of membrane curvature and pH on proton pumping activity of single cytochrome bo3 enzymes

    DEFF Research Database (Denmark)

    Li, Mengqiu; Khan, Sanobar; Rong, Honglin

    2017-01-01

    The molecular mechanism of proton pumping by heme-copper oxidases (HCO) has intrigued the scientific community since it was first proposed. We have recently reported a novel technology that enables the continuous characterisation of proton transport activity of a HCO and ubiquinol oxidase from...... Escherichia coli, cytochrome bo3, for hundreds of seconds on the single enzyme level (Li et al. J Am Chem Soc 137 (2015) 16055–16063). Here, we have extended these studies by additional experiments and analyses of the proton transfer rate as a function of proteoliposome size and pH at the N- and P......-side of single HCOs. Proton transport activity of cytochrome bo3 was found to decrease with increased curvature of the membrane. Furthermore, proton uptake at the N-side (proton entrance) was insensitive to pH between pH 6.4–8.4, while proton release at the P-side had an optimum pH of ~ 7.4, suggesting...

  10. Trans-membrane area asymmetry controls the shape of cellular organelles

    NARCIS (Netherlands)

    Beznoussenko, Galina V; Pilyugin, Sergei S; Geerts, Willie J C; Kozlov, Michael M; Burger, Koert N J; Luini, Alberto; Derganc, Jure; Mironov, Alexander A

    2015-01-01

    Membrane organelles often have complicated shapes and differ in their volume, surface area and membrane curvature. The ratio between the surface area of the cytosolic and luminal leaflets (trans-membrane area asymmetry (TAA)) determines the membrane curvature within different sites of the organelle.

  11. Fabrication of miniature elastomer lenses with programmable liquid mold for smartphone microscopy: curing polydimethylsiloxane with in situ curvature control

    Science.gov (United States)

    Karunakaran, Bhuvaneshwari; Tharion, Joseph; Dhawangale, Arvind Ramrao; Paul, Debjani; Mukherji, Soumyo

    2018-02-01

    Miniature lenses can transform commercial imaging systems, e.g., smartphones and webcams, into powerful, low-cost, handheld microscopes. To date, the reproducible fabrication of polymer lenses is still a challenge as they require controlled dispensing of viscous liquid. This paper reports a reproducible lens fabrication technique using liquid mold with programmable curvature and off-the-shelf materials. The lens curvature is controlled during fabrication by tuning the curvature of an interface of two immiscible liquids [polydimethylsiloxane (PDMS) and glycerol]. The curvature control is implemented using a visual feedback system, which includes a software-based guiding system to produce lenses of desired curvature. The technique allows PDMS lens fabrication of a wide range of sizes and focal lengths, within 20 min. The fabrication of two lens diameters: 1 and 5 mm with focal lengths ranging between 1.2 and 11 mm are demonstrated. The lens surface and bulk quality check performed using X-ray microtomography and atomic force microscopy reveal that the lenses are suitable for optical imaging. Furthermore, a smartphone microscope with ˜1.4-μm resolution is developed using a self-assembly of a single high power fabricated lens and microaperture. The lenses have various potential applications, e.g., optofluidics, diagnostics, forensics, and surveillance.

  12. Small RNAs controlling outer membrane porins

    DEFF Research Database (Denmark)

    Valentin-Hansen, Poul; Johansen, Jesper; Rasmussen, Anders A

    2007-01-01

    are key regulators of environmental stress. Recent work has revealed an intimate interplay between small RNA regulation of outer membrane proteins and the stress-induced sigmaE-signalling system, which has an essential role in the maintenance of the integrity of the outer membrane.......Gene regulation by small non-coding RNAs has been recognized as an important post-transcriptional regulatory mechanism for several years. In Gram-negative bacteria such as Escherichia coli and Salmonella, these RNAs control stress response and translation of outer membrane proteins and therefore...

  13. Curvature and bottlenecks control molecular transport in inverse bicontinuous cubic phases

    Science.gov (United States)

    Assenza, Salvatore; Mezzenga, Raffaele

    2018-02-01

    We perform a simulation study of the diffusion of small solutes in the confined domains imposed by inverse bicontinuous cubic phases for the primitive, diamond, and gyroid symmetries common to many lipid/water mesophase systems employed in experiments. For large diffusing domains, the long-time diffusion coefficient shows universal features when the size of the confining domain is renormalized by the Gaussian curvature of the triply periodic minimal surface. When bottlenecks are widely present, they become the most relevant factor for transport, regardless of the connectivity of the cubic phase.

  14. Controlling the shape of membrane protein polyhedra

    Science.gov (United States)

    Li, Di; Kahraman, Osman; Haselwandter, Christoph A.

    2017-03-01

    Membrane proteins and lipids can self-assemble into membrane protein polyhedral nanoparticles (MPPNs). MPPNs have a closed spherical surface and a polyhedral protein arrangement, and may offer a new route for structure determination of membrane proteins and targeted drug delivery. We develop here a general analytic model of how MPPN self-assembly depends on bilayer-protein interactions and lipid bilayer mechanical properties. We find that the bilayer-protein hydrophobic thickness mismatch is a key molecular control parameter for MPPN shape that can be used to bias MPPN self-assembly towards highly symmetric and uniform MPPN shapes. Our results suggest strategies for optimizing MPPN shape for structural studies of membrane proteins and targeted drug delivery.

  15. Control of distributed heat transfer mechanisms in membrane distillation plants

    KAUST Repository

    Laleg-Kirati, Taous-Meriem; Eleiwi, Fadi; Karam, Ayman M.

    2017-01-01

    Various examples are provided that are related to boundary control in membrane distillation (MD) processes. In one example, a system includes a membrane distillation (MD) process comprising a feed side and a permeate side separated by a membrane

  16. Chemically triggered ejection of membrane tubules controlled by intermonolayer friction.

    Science.gov (United States)

    Fournier, J-B; Khalifat, N; Puff, N; Angelova, M I

    2009-01-09

    We report a chemically driven membrane shape instability that triggers the ejection of a tubule growing exponentially toward a chemical source. The instability is initiated by a dilation of the exposed monolayer, which is coupled to the membrane spontaneous curvature and slowed down by intermonolayer friction. Our experiments are performed by local delivery of a basic pH solution to a giant vesicle. Quantitative fits of the data give an intermonolayer friction coefficient b approximately 2x10;{9} J s/m;{4}. The exponential growth of the tubule may be explained by a Marangoni stress yielding a pulling force proportional to its length.

  17. Curvature Entropy for Curved Profile Generation

    OpenAIRE

    Ujiie, Yoshiki; Kato, Takeo; Sato, Koichiro; Matsuoka, Yoshiyuki

    2012-01-01

    In a curved surface design, the overall shape features that emerge from combinations of shape elements are important. However, controlling the features of the overall shape in curved profiles is difficult using conventional microscopic shape information such as dimension. Herein two types of macroscopic shape information, curvature entropy and quadrature curvature entropy, quantitatively represent the features of the overall shape. The curvature entropy is calculated by the curvature distribu...

  18. Membrane dynamics

    DEFF Research Database (Denmark)

    Bendix, Pól Martin

    2015-01-01

    Current topics include membrane-protein interactions with regard to membrane deformation or curvature sensing by BAR domains. Also, we study the dynamics of membrane tubes of both cells and simple model membrane tubes. Finally, we study membrane phase behavior which has important implications...... for the lateral organization of membranes as wells as for physical properties like bending, permeability and elasticity...

  19. Studying biomolecule localization by engineering bacterial cell wall curvature.

    Directory of Open Access Journals (Sweden)

    Lars D Renner

    Full Text Available In this article we describe two techniques for exploring the relationship between bacterial cell shape and the intracellular organization of proteins. First, we created microchannels in a layer of agarose to reshape live bacterial cells and predictably control their mean cell wall curvature, and quantified the influence of curvature on the localization and distribution of proteins in vivo. Second, we used agarose microchambers to reshape bacteria whose cell wall had been chemically and enzymatically removed. By combining microstructures with different geometries and fluorescence microscopy, we determined the relationship between bacterial shape and the localization for two different membrane-associated proteins: i the cell-shape related protein MreB of Escherichia coli, which is positioned along the long axis of the rod-shaped cell; and ii the negative curvature-sensing cell division protein DivIVA of Bacillus subtilis, which is positioned primarily at cell division sites. Our studies of intracellular organization in live cells of E. coli and B. subtilis demonstrate that MreB is largely excluded from areas of high negative curvature, whereas DivIVA localizes preferentially to regions of high negative curvature. These studies highlight a unique approach for studying the relationship between cell shape and intracellular organization in intact, live bacteria.

  20. Curvature Entropy for Curved Profile Generation

    Directory of Open Access Journals (Sweden)

    Koichiro Sato

    2012-03-01

    Full Text Available In a curved surface design, the overall shape features that emerge from combinations of shape elements are important. However, controlling the features of the overall shape in curved profiles is difficult using conventional microscopic shape information such as dimension. Herein two types of macroscopic shape information, curvature entropy and quadrature curvature entropy, quantitatively represent the features of the overall shape. The curvature entropy is calculated by the curvature distribution, and represents the complexity of a shape (one of the overall shape features. The quadrature curvature entropy is an improvement of the curvature entropy by introducing a Markov process to evaluate the continuity of a curvature and to approximate human cognition of the shape. Additionally, a shape generation method using a genetic algorithm as a calculator and the entropy as a shape generation index is presented. Finally, the applicability of the proposed method is demonstrated using the side view of an automobile as a design example.

  1. Cholera toxin B subunit induces local curvature on lipid bilayers

    DEFF Research Database (Denmark)

    Pezeshkian, Weria; Nåbo, Lina J.; Ipsen, John H.

    2017-01-01

    B induces a local membrane curvature that is essential for its clathrin-independent uptake. Using all-atom molecular dynamics, we show that CTxB induces local curvature, with the radius of curvature around 36 nm. The main feature of the CTxB molecular structure that causes membrane bending is the protruding...... alpha helices in the middle of the protein. Our study points to a generic protein design principle for generating local membrane curvature through specific binding to their lipid anchors....

  2. Control of distributed heat transfer mechanisms in membrane distillation plants

    KAUST Repository

    Laleg-Kirati, Taous-Meriem

    2017-01-05

    Various examples are provided that are related to boundary control in membrane distillation (MD) processes. In one example, a system includes a membrane distillation (MD) process comprising a feed side and a permeate side separated by a membrane boundary layer; and processing circuitry configured to control a water production rate of the MD process based at least in part upon a distributed heat transfer across the membrane boundary layer. In another example, a method includes determining a plurality of estimated temperature states of a membrane boundary layer separating a feed side and a permeate side of a membrane distillation (MD) process; and adjusting inlet flow rate or inlet temperature of at least one of the feed side or the permeate side to maintain a difference temperature along the membrane boundary layer about a defined reference temperature based at least in part upon the plurality of estimated temperature states.

  3. The curvature coordinate system

    DEFF Research Database (Denmark)

    Almegaard, Henrik

    2007-01-01

    The paper describes a concept for a curvature coordinate system on regular curved surfaces from which faceted surfaces with plane quadrangular facets can be designed. The lines of curvature are used as parametric lines for the curvature coordinate system on the surface. A new conjugate set of lin...

  4. Effect of a kneeling chair on lumbar curvature in patients with low back pain and healthy controls: A pilot study

    NARCIS (Netherlands)

    Vaucher, M.; Isner-Horobeti, M.E.; Demattei, C.; Alonso, S.; Herisson, C.; Kouyoumdijan, P.; van Dieen, J.H.; Dupeyron, A.

    2015-01-01

    Background: The concept of an ideal sitting posture is often used in practice but lacks a basis in evidence. Objective: We designed a cross-sectional, comparative, matched study to determine the effects of chair and posture on lumbar curvature in 10 patients with chronic non-specific low back pain

  5. Does Chlorination of Seawater Reverse Osmosis Membranes Control Biofouling?

    KAUST Repository

    Khan, Muhammad Tariq; Hong, Pei-Ying; Nada, Nabil; Croue, Jean Philippe

    2015-01-01

    Biofouling is the major problem of reverse osmosis (RO) membranes used for desalting seawater (SW). The use of chlorine is a conventional and common practice to control/prevent biofouling. Unlike polyamide RO membranes, cellulose triacetate (CTA) RO membranes display a high chlorine tolerance. Due to this characteristic, CTA membranes are used in most of the RO plants located in the Middle East region where the elevated seawater temperature and water quality promote the risk of membrane biofouling. However, there is no detailed study on the investigation/characterization of CTA-RO membrane fouling. In this investigation, the fouling profile of a full–scale SWRO desalination plant operating with not only continuous chlorination of raw seawater but also intermittent chlorination of CTA-RO membranes was studied. Detailed water quality and membrane fouling analyses were conducted. Profiles of microbiological, inorganic, and organic constituents of analysed fouling layers were extensively discussed. Our results clearly identified biofilm development on these membranes. The incapability of chlorination on preventing biofilm formation on SWRO membranes could be assigned to its failure in effectively reaching throughout the different regions of the permeators. This failure could have occurred due to three main factors: plugging of membrane fibers, chlorine consumption by organics accumulated on the front side fibers, or chlorine adaptation of certain bacterial populations.

  6. Does Chlorination of Seawater Reverse Osmosis Membranes Control Biofouling?

    KAUST Repository

    Khan, Muhammad Tariq

    2015-04-01

    Biofouling is the major problem of reverse osmosis (RO) membranes used for desalting seawater (SW). The use of chlorine is a conventional and common practice to control/prevent biofouling. Unlike polyamide RO membranes, cellulose triacetate (CTA) RO membranes display a high chlorine tolerance. Due to this characteristic, CTA membranes are used in most of the RO plants located in the Middle East region where the elevated seawater temperature and water quality promote the risk of membrane biofouling. However, there is no detailed study on the investigation/characterization of CTA-RO membrane fouling. In this investigation, the fouling profile of a full–scale SWRO desalination plant operating with not only continuous chlorination of raw seawater but also intermittent chlorination of CTA-RO membranes was studied. Detailed water quality and membrane fouling analyses were conducted. Profiles of microbiological, inorganic, and organic constituents of analysed fouling layers were extensively discussed. Our results clearly identified biofilm development on these membranes. The incapability of chlorination on preventing biofilm formation on SWRO membranes could be assigned to its failure in effectively reaching throughout the different regions of the permeators. This failure could have occurred due to three main factors: plugging of membrane fibers, chlorine consumption by organics accumulated on the front side fibers, or chlorine adaptation of certain bacterial populations.

  7. Controls of structural inheritance on orogenic curvature and foreland basin sedimentation: Insights from the Przemyśl area, Western Carpathians

    Science.gov (United States)

    Szaniawski, Rafał; Mazzoli, Stefano; Jankowski, Leszek

    2017-10-01

    Orogenic curvatures can have various origins and are widely debated worldwide. In the Poland-Ukraine border area, the Outer Western Carpathians are characterized by a marked curvature. The origin of this curvature was analysed by integrating stratigraphic information with structural constraints and anisotropy of the magnetic susceptibility (AMS) data. Hangingwall frontal ramp domains are characterized by a relatively simple deformation dominated by layer-parallel shortening and folding around a regional NW-SE trending axis, recorded by an AMS lineation with a similar trend. On the other hand, the N-S trending hangingwall oblique ramp domain is characterized by maximum AMS axes recording transpressional strain either dominated by simple shear (sub-horizontal AMS lineation) or pure shear (steeply plunging AMS lineation) components. Early Miocene basin inversion with two distinct depocentres created a number of different detachment surfaces and thickness variations for the sedimentary successions involved in thrusting. The main depocentre of the Lower-Middle Miocene foredeep was originally located in the recess area of the curved Carpathian front. On the other hand, the occurrence of a salient to the west resulted in the axial zone of the foreland flexure being filled with allochthonous units, thereby dramatically reducing the accommodation space for foredeep sediments in this area. Our results suggest that thrust-belt geometry was controlled by the inherited Mesozoic extensional basin architecture.

  8. Curvature-Induced Instabilities of Shells

    Science.gov (United States)

    Pezzulla, Matteo; Stoop, Norbert; Steranka, Mark P.; Bade, Abdikhalaq J.; Holmes, Douglas P.

    2018-01-01

    Induced by proteins within the cell membrane or by differential growth, heating, or swelling, spontaneous curvatures can drastically affect the morphology of thin bodies and induce mechanical instabilities. Yet, the interaction of spontaneous curvature and geometric frustration in curved shells remains poorly understood. Via a combination of precision experiments on elastomeric spherical shells, simulations, and theory, we show how a spontaneous curvature induces a rotational symmetry-breaking buckling as well as a snapping instability reminiscent of the Venus fly trap closure mechanism. The instabilities, and their dependence on geometry, are rationalized by reducing the spontaneous curvature to an effective mechanical load. This formulation reveals a combined pressurelike term in the bulk and a torquelike term in the boundary, allowing scaling predictions for the instabilities that are in excellent agreement with experiments and simulations. Moreover, the effective pressure analogy suggests a curvature-induced subcritical buckling in closed shells. We determine the critical buckling curvature via a linear stability analysis that accounts for the combination of residual membrane and bending stresses. The prominent role of geometry in our findings suggests the applicability of the results over a wide range of scales.

  9. Implementing quantum Ricci curvature

    Science.gov (United States)

    Klitgaard, N.; Loll, R.

    2018-05-01

    Quantum Ricci curvature has been introduced recently as a new, geometric observable characterizing the curvature properties of metric spaces, without the need for a smooth structure. Besides coordinate invariance, its key features are scalability, computability, and robustness. We demonstrate that these properties continue to hold in the context of nonperturbative quantum gravity, by evaluating the quantum Ricci curvature numerically in two-dimensional Euclidean quantum gravity, defined in terms of dynamical triangulations. Despite the well-known, highly nonclassical properties of the underlying quantum geometry, its Ricci curvature can be matched well to that of a five-dimensional round sphere.

  10. Controlled release of curcumin from poly(HEMA-MAPA) membrane.

    Science.gov (United States)

    Caka, Müşerref; Türkcan, Ceren; Aktaş Uygun, Deniz; Uygun, Murat; Akgöl, Sinan; Denizli, Adil

    2017-05-01

    In this work, poly(HEMA-MAPA) membranes were prepared by UV-polymerization technique. These membranes were characterized by SEM, FTIR, and swelling studies. Synthesized membranes had high porous structure. These membranes were used for controlled release of curcumin which is already used as folk remedy and used as drug for some certain diseases and cancers. Curcumin release was investigated for various pHs and temperatures. Optimum drug release yield was found to be as 70% at pH 7.4 and 37 °C within 2 h period. Time-depended release of curcumin was also investigated and its slow release from the membrane demonstrated within 48 h.

  11. Nanomaterials for membrane fouling control: accomplishments and challenges.

    Science.gov (United States)

    Yang, Qian; Mi, Baoxia

    2013-11-01

    We report a review of recent research efforts on incorporating nanomaterials-including metal/metal oxide nanoparticles, carbon-based nanomaterials, and polymeric nanomaterials-into/onto membranes to improve membrane antifouling properties in biomedical or potentially medical-related applications. In general, nanomaterials can be incorporated into/onto a membrane by blending them into membrane fabricating materials or by attaching them to membrane surfaces via physical or chemical approaches. Overall, the fascinating, multifaceted properties (eg, high hydrophilicity, superparamagnetic properties, antibacterial properties, amenable functionality, strong hydration capability) of nanomaterials provide numerous novel strategies and unprecedented opportunities to fully mitigate membrane fouling. However, there are still challenges in achieving a broader adoption of nanomaterials in the membrane processes used for biomedical applications. Most of these challenges arise from the concerns over their long-term antifouling performance, hemocompatibility, and toxicity toward humans. Therefore, rigorous investigation is still needed before the adoption of some of these nanomaterials in biomedical applications, especially for those nanomaterials proposed to be used in the human body or in contact with living tissue/body fluids for a long period of time. Nevertheless, it is reasonable to predict that the service lifetime of membrane-based biomedical devices and implants will be prolonged significantly with the adoption of appropriate fouling control strategies. Copyright © 2013 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

  12. Hydrogen concentration control utilizing a hydrogen permeable membrane

    International Nuclear Information System (INIS)

    Keating, S.J. Jr.

    1976-01-01

    The concentration of hydrogen in a fluid mixture is controlled to a desired concentration by flowing the fluid through one chamber of a diffusion cell separated into two chambers by a hydrogen permeable membrane. A gradient of hydrogen partial pressure is maintained across the membrane to cause diffusion of hydrogen through the membrane to maintain the concentration of hydrogen in the fluid mixture at the predetermined level. The invention has particular utility for the purpose of injecting into and/or separating hydrogen from the reactor coolant of a nuclear reactor system

  13. Introducing quantum Ricci curvature

    Science.gov (United States)

    Klitgaard, N.; Loll, R.

    2018-02-01

    Motivated by the search for geometric observables in nonperturbative quantum gravity, we define a notion of coarse-grained Ricci curvature. It is based on a particular way of extracting the local Ricci curvature of a smooth Riemannian manifold by comparing the distance between pairs of spheres with that of their centers. The quantum Ricci curvature is designed for use on non-smooth and discrete metric spaces, and to satisfy the key criteria of scalability and computability. We test the prescription on a variety of regular and random piecewise flat spaces, mostly in two dimensions. This enables us to quantify its behavior for short lattices distances and compare its large-scale behavior with that of constantly curved model spaces. On the triangulated spaces considered, the quantum Ricci curvature has good averaging properties and reproduces classical characteristics on scales large compared to the discretization scale.

  14. Quantifying the Relationship Between Curvature and Electric Potential in Lipid Bilayers

    DEFF Research Database (Denmark)

    Bruhn, Dennis Skjøth; Lomholt, Michael Andersen; Khandelia, Himanshu

    2016-01-01

    Cellular membranes mediate vital cellular processes by being subject to curvature and transmembrane electrical potentials. Here we build upon the existing theory for flexoelectricity in liquid crystals to quantify the coupling between lipid bilayer curvature and membrane potentials. Using molecular...... dynamics simulations, we show that head group dipole moments, the lateral pressure profile across the bilayer and spontaneous curvature all systematically change with increasing membrane potentials. In particu- lar, there is a linear dependence between the bending moment (the product of bending rigidity...

  15. Modeling curvature-dependent subcellular localization of a small sporulation protein in Bacillus subtilis

    Science.gov (United States)

    Wasnik, Vaibhav; Wingreen, Ned; Mukhopadhyay, Ranjan

    2012-02-01

    Recent experiments suggest that in the bacterium, B. subtilis, the cue for the localization of small sporulation protein, SpoVM, that plays a central role in spore coat formation, is curvature of the bacterial plasma membrane. This curvature-dependent localization is puzzling given the orders of magnitude difference in lengthscale of an individual protein and radius of curvature of the membrane. Here we develop a minimal model to study the relationship between curvature-dependent membrane absorption of SpoVM and clustering of membrane-associated SpoVM and compare our results with experiments.

  16. Glass Membrane For Controlled Diffusion Of Gases

    Science.gov (United States)

    Shelby, James E.; Kenyon, Brian E.

    2001-05-15

    A glass structure for controlled permeability of gases includes a glass vessel. The glass vessel has walls and a hollow center for receiving a gas. The glass vessel contains a metal oxide dopant formed with at least one metal selected from the group consisting of transition metals and rare earth metals for controlling diffusion of the gas through the walls of the glass vessel. The vessel releases the gas through its walls upon exposure to a radiation source.

  17. Ultrasonic control of ceramic membrane fouling: Effect of particle characteristics.

    Science.gov (United States)

    Chen, Dong; Weavers, Linda K; Walker, Harold W

    2006-02-01

    In this study, the effect of particle characteristics on the ultrasonic control of membrane fouling was investigated. Ultrasound at 20 kHz was applied to a cross-flow filtration system with gamma-alumina membranes in the presence of colloidal silica particles. Experimental results indicated that particle concentration affected the ability of ultrasound to control membrane fouling, with less effective control of fouling at higher particle concentrations. Measurements of sound wave intensity and images of the cavitation region indicated that particles induced additional cavitation bubbles near the ultrasonic source, which resulted in less turbulence reaching the membrane surface and subsequently less effective control of fouling. When silica particles were modified to be hydrophobic, greater inducement of cavitation bubbles near the ultrasonic source occurred for a fixed concentration, also resulting in less effective control of fouling. Particle size influenced the cleaning ability of ultrasound, with better permeate recovery observed with larger particles. Particle size did not affect sound wave intensity, suggesting that the more effective control of fouling by large particles was due to greater lift and cross-flow drag forces on larger particles compared to smaller particles.

  18. Periplasmic quality control in biogenesis of outer membrane proteins.

    Science.gov (United States)

    Lyu, Zhi Xin; Zhao, Xin Sheng

    2015-04-01

    The β-barrel outer membrane proteins (OMPs) are integral membrane proteins that reside in the outer membrane of Gram-negative bacteria and perform a diverse range of biological functions. Synthesized in the cytoplasm, OMPs must be transported across the inner membrane and through the periplasmic space before they are assembled in the outer membrane. In Escherichia coli, Skp, SurA and DegP are the most prominent factors identified to guide OMPs across the periplasm and to play the role of quality control. Although extensive genetic and biochemical analyses have revealed many basic functions of these periplasmic proteins, the mechanism of their collaboration in assisting the folding and insertion of OMPs is much less understood. Recently, biophysical approaches have shed light on the identification of the intricate network. In the present review, we summarize recent advances in the characterization of these key factors, with a special emphasis on the multifunctional protein DegP. In addition, we present our proposed model on the periplasmic quality control in biogenesis of OMPs.

  19. PH-triggered micellar membrane for controlled release microchips

    KAUST Repository

    Yang, Xiaoqiang; Moosa, Basem; Deng, Lin; Zhao, Lan; Khashab, Niveen M.

    2011-01-01

    A pH-responsive membrane based on polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer was developed on a model glass microchip as a promising controlled polymer delivery system. The PS-b-P4VP copolymer assembles into spherical and

  20. Biological control of biofilms on membranes by metazoans.

    Science.gov (United States)

    Klein, Theresa; Zihlmann, David; Derlon, Nicolas; Isaacson, Carl; Szivak, Ilona; Weissbrodt, David G; Pronk, Wouter

    2016-01-01

    Traditionally, chemical and physical methods have been used to control biofouling on membranes by inactivating and removing the biofouling layer. Alternatively, the permeability can be increased using biological methods while accepting the presence of the biofouling layer. We have investigated two different types of metazoans for this purpose, the oligochaete Aelosoma hemprichi and the nematode Plectus aquatilis. The addition of these grazing metazoans in biofilm-controlled membrane systems resulted in a flux increase of 50% in presence of the oligochaetes (Aelosoma hemprichi), and a flux increase of 119-164% in presence of the nematodes (Plectus aquatilis) in comparison to the control system operated without metazoans. The change in flux resulted from (1) a change in the biofilm structure, from a homogeneous, cake-like biofilm to a more heterogeneous, porous structure and (2) a significant reduction in the thickness of the basal layer. Pyrosequencing data showed that due to the addition of the predators, also the community composition of the biofilm in terms of protists and bacteria was strongly affected. The results have implications for a range of membrane processes, including ultrafiltration for potable water production, membrane bioreactors and reverse osmosis. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Advanced Curvature Deformable Mirrors

    Science.gov (United States)

    2010-09-01

    ORGANIZATION NAME(S) AND ADDRESS(ES) University of Hawaii ,Institute for Astronomy,640 North A‘ohoku Place, #209 , Hilo ,HI,96720-2700 8. PERFORMING...Advanced Curvature Deformable Mirrors Christ Ftaclas1,2, Aglae Kellerer2 and Mark Chun2 Institute for Astronomy, University of Hawaii

  2. Vesicle fusion with bilayer lipid membrane controlled by electrostatic interaction

    Directory of Open Access Journals (Sweden)

    Azusa Oshima

    2017-09-01

    Full Text Available The fusion of proteoliposomes is a promising approach for incorporating membrane proteins in artificial lipid membranes. In this study, we employed an electrostatic interaction between vesicles and supported bilayer lipid membranes (s-BLMs to control the fusion process. We combined large unilamellar vesicles (LUVs containing anionic lipids, which we used instead of proteoliposomes, and s-BLMs containing cationic lipids to control electrostatic interaction. Anionic LUVs were never adsorbed or ruptured on the SiO2 substrate with a slight negative charge, and selectively fused with cationic s-BLMs. The LUVs can be fused effectively to the target position. Furthermore, as the vesicle fusion proceeds and some of the positive charges are neutralized, the attractive interaction weakens and finally the vesicle fusion saturates. In other words, we can control the number of LUVs fused with s-BLMs by controlling the concentration of the cationic lipids in the s-BLMs. The fluidity of the s-BLMs after vesicle fusion was confirmed to be sufficiently high. This indicates that the LUVs attached to the s-BLMs were almost completely fused, and there were few intermediate state vesicles in the fusion process. We could control the position and amount of vesicle fusion with the s-BLMs by employing an electrostatic interaction.

  3. Control of membrane fouling during hyperhaline municipal wastewater treatment using a pilot-scale anoxic/aerobic-membrane bioreactor system

    Institute of Scientific and Technical Information of China (English)

    Jingmei Sun; Jiangxiu Rong; Lifeng Dai; Baoshan Liu; Wenting Zhu

    2011-01-01

    Membrane fouling limits the effects of long-term stable operation of membrane bioreactor (MBR).Control of membrane foulin can extend the membrane life and reduce water treatment cost effectively.A pilot scale anoxic/aerobic-membrane bioreactor (A/O MBR,40 L/hr) was used to treat the hyperhaline municipal sewage from a processing zone of Tianjin,China.Impact factors including mixed liquid sludge suspension (MLSS),sludge viscosity (μ),microorganisms,extracellular polymeric substances (EPS),aeration intensity and suction/suspended time on membrane fouling and pollution control were studied.The relationships among various factors associated with membrane fouling were analyzed.Results showed that there was a positive correlation among MLSS,sludge viscosity and trans-membrane pressure (TMP).Considering water treatment efficiency and stable operation of the membrane module,MLSS of 5 g/L was suggested for the process.There was a same trend among EPS,sludge viscosity and TMP.Numbers and species of microorganisms affected membrane fouling.Either too high or too low aeration intensity was not conducive to membrane fouling control.Aeration intensity of 1.0 m3/hr (gas/water ratio of 25:1) is suggested for the process.A long suction time caused a rapid increase in membrane resistance.However,long suspended time cannot prevent the increase of membrane resistance effectively even though a suspended time was necessary for scale off particles from the membrane surface.The suction/suspended time of 12 min/3 min was selected for the process.The interaction of various environmental factors and operation conditions must be considered synthetically.

  4. PH-triggered micellar membrane for controlled release microchips

    KAUST Repository

    Yang, Xiaoqiang

    2011-01-01

    A pH-responsive membrane based on polystyrene-b-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer was developed on a model glass microchip as a promising controlled polymer delivery system. The PS-b-P4VP copolymer assembles into spherical and/or worm-like micelles with styrene block cores and pyridine coronas in selective solvents. The self-assembled worm-like morphology exhibited pH-responsive behaviour due to the protonation of the P4VP block at low pH and it\\'s deprotonation at high pH and thus constituting a switchable "off/on" system. Doxorubicin (Dox) was used as cargo to test the PS-b-P4VP membrane. Luminescence experiments indicated that the membrane was able to store Dox molecules within its micellar structure at neutral pH and then release them as soon as the pH was raised to 8.0. The performance of the cast membrane was predictable and most importantly reproducible. The physiochemical and biological properties were also investigated carefully in terms of morphology, cell viability and cell uptake. This journal is © The Royal Society of Chemistry.

  5. Regularized strings with extrinsic curvature

    International Nuclear Information System (INIS)

    Ambjoern, J.; Durhuus, B.

    1987-07-01

    We analyze models of discretized string theories, where the path integral over world sheet variables is regularized by summing over triangulated surfaces. The inclusion of curvature in the action is a necessity for the scaling of the string tension. We discuss the physical properties of models with extrinsic curvature terms in the action and show that the string tension vanishes at the critical point where the bare extrinsic curvature coupling tends to infinity. Similar results are derived for models with intrinsic curvature. (orig.)

  6. The effect of increasing membrane curvature on the phase transition and mixing behavior of a dimyristoyl-sn-glycero-3-phosphatidylcholine/distearoyl-sn-glycero-3-phosphatidylcholine lipid mixture as studied by Fourier transform infrared spectroscopy and differential scanning calorimetry

    DEFF Research Database (Denmark)

    Brumm, T.; Jørgensen, Kent; Mouritsen, Ole G.

    1996-01-01

    The phase transition behavior of a lipid bilayer of dimyristoyl-sn-glycero-3-phosphalidylcholine/distearoyl-sn- glycero-3-phosphatidylcholine (DMPC-d54/DSPC) (1:1) on a solid support with varying curvatures was investigated with differential scanning calorimetry, infrared spectroscopy, and model...... of the liquidus point can be understood as a reduction of the lateral pressure in the bilayer with increasing curvature. The shift of the solidus line is interpreted as a result of the increased demixing of the two components in the two-phase region with increasing curvature due to lowering of the lateral...

  7. Brane cosmology with curvature corrections

    International Nuclear Information System (INIS)

    Kofinas, Georgios; Maartens, Roy; Papantonopoulos, Eleftherios

    2003-01-01

    We study the cosmology of the Randall-Sundrum brane-world where the Einstein-Hilbert action is modified by curvature correction terms: a four-dimensional scalar curvature from induced gravity on the brane, and a five-dimensional Gauss-Bonnet curvature term. The combined effect of these curvature corrections to the action removes the infinite-density big bang singularity, although the curvature can still diverge for some parameter values. A radiation brane undergoes accelerated expansion near the minimal scale factor, for a range of parameters. This acceleration is driven by the geometric effects, without an inflation field or negative pressures. At late times, conventional cosmology is recovered. (author)

  8. Attosecond control of electron beams at dielectric and absorbing membranes

    Science.gov (United States)

    Morimoto, Yuya; Baum, Peter

    2018-03-01

    Ultrashort electron pulses are crucial for time-resolved electron diffraction and microscopy of the fundamental light-matter interaction. In this work, we study experimentally and theoretically the generation and characterization of attosecond electron pulses by optical-field-driven compression and streaking at dielectric or absorbing interaction elements. The achievable acceleration and deflection gradient depends on the laser-electron angle, the laser's electric and magnetic field directions, and the foil orientation. Electric and magnetic fields have similar contributions to the final effect and both need to be considered. Experiments and theory agree well and reveal the optimum conditions for highly efficient, velocity-matched electron-field interactions in the longitudinal or transverse direction. We find that metallic membranes are optimum for light-electron control at mid-infrared or terahertz wavelengths, but dielectric membranes are excellent in the visible and near-infrared regimes and are therefore ideal for the formation of attosecond electron pulses.

  9. Controlled change of transport properties of poly(ethylene terephthalate) track membranes by plasma method

    International Nuclear Information System (INIS)

    Kravets, L I; Dmitriev, S N; Drachev, A I; Gilman, A B; Lazea, A; Dinescu, G

    2007-01-01

    A process of plasma polymerization of dimethylaniline and acrylic acid vapours on the surface of poly(ethylene terephthalate) track membranes has been investigated. The surface and hydrodynamic properties of the composite membranes produced in this case have been studied. It is shown that the water permeability of the obtained polymeric membranes can be controlled by changing the filtrate pH. Membranes with such properties can be used for controllable drug delivery and in sensor control

  10. Combination of Electrochemical Processes with Membrane Bioreactors for Wastewater Treatment and Fouling Control: A Review

    OpenAIRE

    Ensano, Benny M. B.; Borea, Laura; Naddeo, Vincenzo; Belgiorno, Vincenzo; de Luna, Mark D. G.; Ballesteros, Florencio C.

    2016-01-01

    This paper provides a critical review about the integration of electrochemical processes into membrane bioreactors (MBR) in order to understand the influence of these processes on wastewater treatment performance and membrane fouling control. The integration can be realized either in an internal or an external configuration. Electrically enhanced membrane bioreactors or electro membrane bioreactors (eMBRs) combine biodegradation, electrochemical and membrane filtration processes into one syst...

  11. Combination of electrochemical processes with membrane bioreactors for wastewater treatment and fouling control: A review

    OpenAIRE

    Benny Marie B. Ensano; Laura Borea; Vincenzo Naddeo; Vincenzo Belgiorno; Mark Daniel G. de Luna; Mark Daniel G. de Luna; Florencio C. Ballesteros, Jr.; Florencio C. Ballesteros, Jr.

    2016-01-01

    This paper provides a critical review about the integration of electrochemical processes into membrane bioreactors (MBR) in order to understand the influence of these processes on wastewater treatment performance and membrane fouling control. The integration can be realized either in an internal or an external configuration. Electrically enhanced membrane bioreactors or electro membrane bioreactors (eMBRs) combine biodegradation, electrochemical and membrane filtration processes into one syst...

  12. Alkali-assisted membrane cleaning for fouling control of anaerobic ceramic membrane bioreactor.

    Science.gov (United States)

    Mei, Xiaojie; Quek, Pei Jun; Wang, Zhiwei; Ng, How Yong

    2017-09-01

    In this study, a chemically enhanced backflush (CEB) cleaning method using NaOH solution was proposed for fouling mitigation in anaerobic membrane bioreactors (AnMBRs). Ex-situ cleaning tests revealed that NaOH dosages ranging from 0.05 to 1.30mmol/L had positive impacts on anaerobic biomass, while higher dosages (>1.30mmol/L) showed inhibition and/or toxic impacts. In-situ cleaning tests showed that anaerobic biomass could tolerate much higher NaOH concentrations due to the alkali consumption by anaerobic process and/or the buffering role of mixed liquor. More importantly, 10-20mmol-NaOH/L could significantly reduce membrane fouling rates (4-5.5 times over the AnMBR with deionized water backflush) and slightly improve methanogenic activities. COD removal efficiencies were over 87% and peaked at 20mmol-NaOH/L. However, extremely high NaOH concentration had adverse effects on filtration and treatment performance. Economic analysis indicated that 12mmol/L of NaOH was the cost-efficient and optimal fouling-control dosage for the CEB cleaning. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Filtration behavior of casein glycomacropeptide (CGMP) in an enzymatic membrane reactor: fouling control by membrane selection and threshold flux operation

    DEFF Research Database (Denmark)

    Luo, Jianquan; Morthensen, Sofie Thage; Meyer, Anne S.

    2014-01-01

    . In this study, the filtration performance and fouling behavior during ultrafiltration (UF) of CGMP for the enzymatic production of 3′-sialyllactose were investigated. A 5kDa regenerated cellulose membrane with high anti-fouling performance, could retain CGMP well, permeate 3′-sialyllactose, and was found...... to be the most suitable membrane for this application. Low pH increased CGMP retention but produced more fouling. Higher agitation and lower CGMP concentration induced larger permeate flux and higher CGMP retention. Adsorption fouling and pore blocking by CGMP in/on membranes could be controlled by selecting...... a highly hydrophilic membrane with appropriate pore size. Operating under threshold flux could minimize the concentration polarization and cake/gel/scaling layers, but might not avoid irreversible fouling caused by adsorption and pore blocking. The effects of membrane properties, pH, agitation and CGMP...

  14. On Gauss-Bonnet Curvatures

    Directory of Open Access Journals (Sweden)

    Mohammed Larbi Labbi

    2007-12-01

    Full Text Available The $(2k$-th Gauss-Bonnet curvature is a generalization to higher dimensions of the $(2k$-dimensional Gauss-Bonnet integrand, it coincides with the usual scalar curvature for $k = 1$. The Gauss-Bonnet curvatures are used in theoretical physics to describe gravity in higher dimensional space times where they are known as the Lagrangian of Lovelock gravity, Gauss-Bonnet Gravity and Lanczos gravity. In this paper we present various aspects of these curvature invariants and review their variational properties. In particular, we discuss natural generalizations of the Yamabe problem, Einstein metrics and minimal submanifolds.

  15. The role of internal limiting membrane peeling in epiretinal membrane surgery: a randomised controlled trial.

    Science.gov (United States)

    Tranos, Paris; Koukoula, Stavrenia; Charteris, Davic G; Perganda, Georgia; Vakalis, Athanasios; Asteriadis, Solon; Georgalas, Ilias; Petrou, Petros

    2017-06-01

    To compare the anatomical and functional outcomes after primary idiopathic epiretinal membrane (ERM) peeling with or without internal limiting membrane (ILM) peeling. A two-centre randomised, controlled clinical trial with 12 months of follow-up. One hundred and two eyes of 102 patients were included in the analysis and were randomised into two groups (ILM peeling (P) and non-ILM peeling (NP) group). Inclusion criteria were: Idiopathic ERM confirmed on optical coherence tomography, age ≥18 years, binocular distortion, best-corrected visual acuity (BCVA) ≤90 ETDRS letters, intraocular pressure ≤23 mm Hg and informed consent. The primary outcome measure was the mean change in the ETDRS distance BCVA at 12 months' follow-up for each group. The mean change in distance BCVA at 12 months was 0.30±0.24 logMAR (15 ETDRS letters) in the P group and 0.31±0.23 logMAR (14 ETDRS letters) in the NP group, a change that was not statistically significant (p=0.84). No statistically significant differences were observed when comparing the changes in distance BCVA, the changes in metamorphopsia (Amsler grid) and the changes in central retinal thickness between the two groups at any of the time points studied. Our analysis suggests that ILM peeling in idiopathic ERM surgery does not result in better visual improvement. The more frequent presence of an uninterrupted interdigitation zone in the P group did not result in a better functional outcome of our patients. No recurrent ERMs were noted in either group. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

  16. Manifolds of positive scalar curvature

    Energy Technology Data Exchange (ETDEWEB)

    Stolz, S [Department of Mathematics, University of Notre Dame, Notre Dame (United States)

    2002-08-15

    This lecture gives an survey on the problem of finding a positive scalar curvature metric on a closed manifold. The Gromov-Lawson-Rosenberg conjecture and its relation to the Baum-Connes conjecture are discussed and the problem of finding a positive Ricci curvature metric on a closed manifold is explained.

  17. Investigation of humidity control via membrane separation for advanced Extravehicular Mobility Unit (EMU) application

    Science.gov (United States)

    Newbold, D. D.; Ray, R. J.; Pledger, W. A.; Mccray, S. B.; Brown, M. F.

    1989-01-01

    This paper describes the development of a membrane-based process for dehumidifying the Extravehicular Mobility Unit (EMU). The membrane process promises to be smaller, lighter, and more energy efficient than the other technologies for dehumidification. The dehydration membranes were tested for 90 days at conditions expected to be present in the EMU. The results of these tests indicate that membrane-based technology can effectively control humidity in the EMU.

  18. Some Inequalities for the -Curvature Image

    Directory of Open Access Journals (Sweden)

    Daijun Wei

    2009-01-01

    Full Text Available Lutwak introduced the notion of -curvature image and proved an inequality for the volumes of convex body and its -curvature image. In this paper, we first give an monotonic property of -curvature image. Further, we establish two inequalities for the -curvature image and its polar, respectively. Finally, an inequality for the volumes of -projection body and -curvature image is obtained.

  19. Pedal claw curvature in birds, lizards and mesozoic dinosaurs--complicated categories and compensating for mass-specific and phylogenetic control.

    Directory of Open Access Journals (Sweden)

    Aleksandra V Birn-Jeffery

    Full Text Available Pedal claw geometry can be used to predict behaviour in extant tetrapods and has frequently been used as an indicator of lifestyle and ecology in Mesozoic birds and other fossil reptiles, sometimes without acknowledgement of the caveat that data from other aspects of morphology and proportions also need to be considered. Variation in styles of measurement (both inner and outer claw curvature angles has made it difficult to compare results across studies, as have over-simplified ecological categories. We sought to increase sample size in a new analysis devised to test claw geometry against ecological niche. We found that taxa from different behavioural categories overlapped extensively in claw geometry. Whilst most taxa plotted as predicted, some fossil taxa were recovered in unexpected positions. Inner and outer claw curvatures were statistically correlated, and both correlated with relative claw robusticity (mid-point claw height. We corrected for mass and phylogeny, as both likely influence claw morphology. We conclude that there is no strong mass-specific effect on claw curvature; furthermore, correlations between claw geometry and behaviour are consistent across disparate clades. By using independent contrasts to correct for phylogeny, we found little significant relationship between claw geometry and behaviour. 'Ground-dweller' claws are less curved and relatively dorsoventrally deep relative to those of other behavioural categories; beyond this it is difficult to assign an explicit category to a claw based purely on geometry.

  20. Lectures on mean curvature flows

    CERN Document Server

    Zhu, Xi-Ping

    2002-01-01

    "Mean curvature flow" is a term that is used to describe the evolution of a hypersurface whose normal velocity is given by the mean curvature. In the simplest case of a convex closed curve on the plane, the properties of the mean curvature flow are described by Gage-Hamilton's theorem. This theorem states that under the mean curvature flow, the curve collapses to a point, and if the flow is diluted so that the enclosed area equals \\pi, the curve tends to the unit circle. In this book, the author gives a comprehensive account of fundamental results on singularities and the asymptotic behavior of mean curvature flows in higher dimensions. Among other topics, he considers in detail Huisken's theorem (a generalization of Gage-Hamilton's theorem to higher dimension), evolution of non-convex curves and hypersurfaces, and the classification of singularities of the mean curvature flow. Because of the importance of the mean curvature flow and its numerous applications in differential geometry and partial differential ...

  1. Ion Transport through Diffusion Layer Controlled by Charge Mosaic Membrane

    Directory of Open Access Journals (Sweden)

    Akira Yamauchi

    2012-01-01

    Full Text Available The kinetic transport behaviors in near interface of the membranes were studied using commercial anion and cation exchange membrane and charge mosaic membrane. Current-voltage curve gave the limiting current density that indicates the ceiling of conventional flux. From chronopotentiometry above the limiting current density, the transition time was estimated. The thickness of boundary layer was derived with conjunction with the conventional limiting current density and the transition time from steady state flux. On the other hand, the charge mosaic membrane was introduced in order to examine the ion transport on the membrane surface in detail. The concentration profile was discussed by the kinetic transport number with regard to the water dissociation (splitting on the membrane surface.

  2. Phase separation in artificial vesicles driven by light and curvature

    Science.gov (United States)

    Rinaldin, Melissa; Pomp, Wim; Schmidt, Thomas; Giomi, Luca; Kraft, Daniela; Physics of Life Processes Team; Soft; Bio Mechanics Collaboration; Self-Assembly in Soft Matter Systems Collaboration

    The role of phase-demixing in living cells, leading to the lipid-raft hypothesis, has been extensively studied. Lipid domains of higher lipid chain order are proposed to regulate protein spatial organization. Giant Unilamellar Vesicles provide an artificial model to study phase separation. So far temperature was used to initiate the process. Here we introduce a new methodology based on the induction of phase separation by light. To this aim, the composition of the lipid membrane is varied by photo-oxidation of lipids. The control of the process gained by using light allowed us to observe vesicle shape fluctuations during phase-demixing. The presence of fluctuations near the critical mixing point resembles features of a critical process. We quantitatively analyze these fluctuations using a 2d elastic model, from which we can estimate the material parameters such as bending rigidity and surface tension, demonstrating the non-equilibrium critical behaviour. Finally, I will describe recent attempts toward tuning the membrane composition by controlling the vesicle curvature.

  3. Fine-Tuning of Photosynthesis Requires CURVATURE THYLAKOID1-Mediated Thylakoid Plasticity

    DEFF Research Database (Denmark)

    Pribil, Mathias; Sandoval Ibáñez, Omar Alejandro; Xu, Wenteng

    2018-01-01

    ultrastructure in Arabidopsis (Arabidopsis thaliana) reduces photosynthetic efficiency and plant fitness under adverse, controlled, and natural light conditions. Plants that lack CURT1 show less adjustment of grana diameter, which compromises regulatory mechanisms like the photosystem II repair cycle and state...... transitions. Interestingly, CURT1A suffices to induce thylakoid membrane curvature in planta and thylakoid hyperbending in plants overexpressing CURT1A. We suggest that CURT1 oligomerization is regulated at the posttranslational level in a light-dependent fashion and that CURT1-mediated thylakoid plasticity...

  4. Environmental influences on DNA curvature

    DEFF Research Database (Denmark)

    Ussery, David; Higgins, C.F.; Bolshoy, A.

    1999-01-01

    DNA curvature plays an important role in many biological processes. To study environmentalinfluences on DNA curvature we compared the anomalous migration on polyacrylamide gels ofligation ladders of 11 specifically-designed oligonucleotides. At low temperatures (25 degreesC and below) most......, whilst spermine enhanced theanomalous migration of a different set of sequences. Sequences with a GGC motif exhibitedgreater curvature than predicted by the presently-used angles for the nearest-neighbour wedgemodel and are especially sensitive to Mg2+. The data have implications for models...... for DNAcurvature and for environmentally-sensitive DNA conformations in the regulation of geneexpression....

  5. Curvature force and dark energy

    International Nuclear Information System (INIS)

    Balakin, Alexander B; Pavon, Diego; Schwarz, Dominik J; Zimdahl, Winfried

    2003-01-01

    A curvature self-interaction of the cosmic gas is shown to mimic a cosmological constant or other forms of dark energy, such as a rolling tachyon condensate or a Chaplygin gas. Any given Hubble rate and deceleration parameter can be traced back to the action of an effective curvature force on the gas particles. This force self-consistently reacts back on the cosmological dynamics. The links between an imperfect fluid description, a kinetic description with effective antifriction forces and curvature forces, which represent a non-minimal coupling of gravity to matter, are established

  6. G-protein signaling leverages subunit-dependent membrane affinity to differentially control βγ translocation to intracellular membranes.

    Science.gov (United States)

    O'Neill, Patrick R; Karunarathne, W K Ajith; Kalyanaraman, Vani; Silvius, John R; Gautam, N

    2012-12-18

    Activation of G-protein heterotrimers by receptors at the plasma membrane stimulates βγ-complex dissociation from the α-subunit and translocation to internal membranes. This intermembrane movement of lipid-modified proteins is a fundamental but poorly understood feature of cell signaling. The differential translocation of G-protein βγ-subunit types provides a valuable experimental model to examine the movement of signaling proteins between membranes in a living cell. We used live cell imaging, mathematical modeling, and in vitro measurements of lipidated fluorescent peptide dissociation from vesicles to determine the mechanistic basis of the intermembrane movement and identify the interactions responsible for differential translocation kinetics in this family of evolutionarily conserved proteins. We found that the reversible translocation is mediated by the limited affinity of the βγ-subunits for membranes. The differential kinetics of the βγ-subunit types are determined by variations among a set of basic and hydrophobic residues in the γ-subunit types. G-protein signaling thus leverages the wide variation in membrane dissociation rates among different γ-subunit types to differentially control βγ-translocation kinetics in response to receptor activation. The conservation of primary structures of γ-subunits across mammalian species suggests that there can be evolutionary selection for primary structures that confer specific membrane-binding affinities and consequent rates of intermembrane movement.

  7. Cell volume and membrane stretch independently control K+ channel activity

    DEFF Research Database (Denmark)

    Bomholtz, Sofia Hammami; Willumsen, Niels J; Olsen, Hervør L

    2009-01-01

    A number of potassium channels including members of the KCNQ family and the Ca(2+) activated IK and SK, but not BK, are strongly and reversibly regulated by small changes in cell volume. It has been argued that this general regulation is mediated through sensitivity to changes in membrane stretch...... was not affected by membrane stretch. The results indicate that (1) activation of BK channels by local membrane stretch is not mimicked by membrane stress induced by cell swelling, and (2) activation of KCNQ1 channels by cell volume increase is not mediated by local tension in the cell membrane. We conclude....... To test this hypothesis we have studied the regulation of KCNQ1 and BK channels after expression in Xenopus oocytes. Results from cell-attached patch clamp studies (approximately 50 microm(2) macropatches) in oocytes expressing BK channels demonstrate that the macroscopic volume-insensitive BK current...

  8. Haptic perception of object curvature in Parkinson's disease.

    Directory of Open Access Journals (Sweden)

    Jürgen Konczak

    2008-07-01

    Full Text Available The haptic perception of the curvature of an object is essential for adequate object manipulation and critical for our guidance of actions. This study investigated how the ability to perceive the curvature of an object is altered by Parkinson's disease (PD.Eight healthy subjects and 11 patients with mild to moderate PD had to judge, without vision, the curvature of a virtual "box" created by a robotic manipulandum. Their hands were either moved passively along a defined curved path or they actively explored the curved curvature of a virtual wall. The curvature was either concave or convex (bulging to the left or right and was judged in two locations of the hand workspace--a left workspace location, where the curved hand path was associated with curved shoulder and elbow joint paths, and a right workspace location in which these joint paths were nearly linear. After exploring the curvature of the virtual object, subjects had to judge whether the curvature was concave or convex. Based on these data, thresholds for curvature sensitivity were established. The main findings of the study are: First, 9 out 11 PD patients (82% showed elevated thresholds for detecting convex curvatures in at least one test condition. The respective median threshold for the PD group was increased by 343% when compared to the control group. Second, when distal hand paths became less associated with proximal joint paths (right workspace, haptic acuity was reduced substantially in both groups. Third, sensitivity to hand trajectory curvature was not improved during active exploration in either group.Our data demonstrate that PD is associated with a decreased acuity of the haptic sense, which may occur already at an early stage of the disease.

  9. Coating of reverse osmosis membranes with amphiphilic copolymers for biofouling control

    KAUST Repository

    Bucs, Szilard

    2017-05-30

    Surface coating of membranes may be a promising option to control biofilm development and biofouling impact on membrane performance of spiral-wound reverse osmosis (RO) systems. The objective of this study was to investigate the impact of an amphiphilic copolymer coating on biofilm formation and biofouling control. The coating was composed of both hydrophilic and hydrophobic monomers hydroxyethyl methacrylate (HEMA) and perfluorodecyl acrylate (PFA), respectively. Commercial RO membranes were coated with HEMA-PFA copolymer film. Long and short term biofouling studies with coated and uncoated membranes and feed spacer were performed using membrane fouling simulators (MFSs) operated in parallel, fed with water containing nutrients. For the long-term studies pressure drop development in time was monitored and after eight days the MFSs were opened and the accumulated biofilm on the membrane and spacer sheets was quantified and characterized. The presence of the membrane coating was determined using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Results showed that the amphiphilic coating (i) delayed biofouling (a lower pressure drop increase by a factor of 3 and a lower accumulated active biomass amount by a factor of 6), (ii) influenced the biofilm composition (23% lower polysaccharides and 132% higher protein content) and (iii) was still completely present on the membrane at the end of the biofouling study, showing that the coating was strongly attached to the membrane surface. Using coated membranes and feed spacers in combination with advanced cleaning strategies may be a suitable way to control biofouling.

  10. Coating of reverse osmosis membranes with amphiphilic copolymers for biofouling control

    KAUST Repository

    Bucs, Szilard; Valladares Linares, Rodrigo; Siddiqui, Amber; Matin, Asif; Khan, Zafarullah; van Loosdrecht, Mark C.M.; Yang, Rong; Wang, Minghui; Gleason, Karen K.; Kruithof, Joop C.; Vrouwenvelder, Johannes S.

    2017-01-01

    Surface coating of membranes may be a promising option to control biofilm development and biofouling impact on membrane performance of spiral-wound reverse osmosis (RO) systems. The objective of this study was to investigate the impact of an amphiphilic copolymer coating on biofilm formation and biofouling control. The coating was composed of both hydrophilic and hydrophobic monomers hydroxyethyl methacrylate (HEMA) and perfluorodecyl acrylate (PFA), respectively. Commercial RO membranes were coated with HEMA-PFA copolymer film. Long and short term biofouling studies with coated and uncoated membranes and feed spacer were performed using membrane fouling simulators (MFSs) operated in parallel, fed with water containing nutrients. For the long-term studies pressure drop development in time was monitored and after eight days the MFSs were opened and the accumulated biofilm on the membrane and spacer sheets was quantified and characterized. The presence of the membrane coating was determined using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). Results showed that the amphiphilic coating (i) delayed biofouling (a lower pressure drop increase by a factor of 3 and a lower accumulated active biomass amount by a factor of 6), (ii) influenced the biofilm composition (23% lower polysaccharides and 132% higher protein content) and (iii) was still completely present on the membrane at the end of the biofouling study, showing that the coating was strongly attached to the membrane surface. Using coated membranes and feed spacers in combination with advanced cleaning strategies may be a suitable way to control biofouling.

  11. Design and simulation of the surface shape control system for membrane mirror

    Science.gov (United States)

    Zhang, Gengsheng; Tang, Minxue

    2009-11-01

    The surface shape control is one of the key technologies for the manufacture of membrane mirror. This paper presents a design of membrane mirror's surface shape control system on the basis of fuzzy logic control. The system contains such function modules as surface shape design, surface shape control, surface shape analysis, and etc. The system functions are realized by using hybrid programming technology of Visual C# and MATLAB. The finite element method is adopted to simulate the surface shape control of membrane mirror. The finite element analysis model is established through ANSYS Parametric Design Language (APDL). ANSYS software kernel is called by the system in background running mode when doing the simulation. The controller is designed by means of controlling the sag of the mirror's central crosssection. The surface shape of the membrane mirror and its optical aberration are obtained by applying Zernike polynomial fitting. The analysis of surface shape control and the simulation of disturbance response are performed for a membrane mirror with 300mm aperture and F/2.7. The result of the simulation shows that by using the designed control system, the RMS wavefront error of the mirror can reach to 142λ (λ=632.8nm), which is consistent to the surface accuracy of the membrane mirror obtained by the large deformation theory of membrane under the same condition.

  12. How membrane lipids control the 3D structure and function of receptors

    Directory of Open Access Journals (Sweden)

    Jacques Fantini

    2018-02-01

    Full Text Available The cohabitation of lipids and proteins in the plasma membrane of mammalian cells is controlled by specific biochemical and biophysical rules. Lipids may be either constitutively tightly bound to cell-surface receptors (non-annular lipids or less tightly attached to the external surface of the protein (annular lipids. The latter are exchangeable with surrounding bulk membrane lipids on a faster time scale than that of non-annular lipids. Not only do non-annular lipids bind to membrane proteins through stereoselective mechanisms, they can also help membrane receptors acquire (or maintain a functional 3D structure. Cholesterol is the prototype of membrane lipids that finely controls the 3D structure and function of receptors. However, several other lipids such as sphingolipids may also modulate the function of membrane proteins though conformational adjustments. All these concepts are discussed in this review in the light of representative examples taken from the literature.

  13. Discrete Curvature Theories and Applications

    KAUST Repository

    Sun, Xiang

    2016-08-25

    Discrete Di erential Geometry (DDG) concerns discrete counterparts of notions and methods in di erential geometry. This thesis deals with a core subject in DDG, discrete curvature theories on various types of polyhedral surfaces that are practically important for free-form architecture, sunlight-redirecting shading systems, and face recognition. Modeled as polyhedral surfaces, the shapes of free-form structures may have to satisfy di erent geometric or physical constraints. We study a combination of geometry and physics { the discrete surfaces that can stand on their own, as well as having proper shapes for the manufacture. These proper shapes, known as circular and conical meshes, are closely related to discrete principal curvatures. We study curvature theories that make such surfaces possible. Shading systems of freeform building skins are new types of energy-saving structures that can re-direct the sunlight. From these systems, discrete line congruences across polyhedral surfaces can be abstracted. We develop a new curvature theory for polyhedral surfaces equipped with normal congruences { a particular type of congruences de ned by linear interpolation of vertex normals. The main results are a discussion of various de nitions of normality, a detailed study of the geometry of such congruences, and a concept of curvatures and shape operators associated with the faces of a triangle mesh. These curvatures are compatible with both normal congruences and the Steiner formula. In addition to architecture, we consider the role of discrete curvatures in face recognition. We use geometric measure theory to introduce the notion of asymptotic cones associated with a singular subspace of a Riemannian manifold, which is an extension of the classical notion of asymptotic directions. We get a simple expression of these cones for polyhedral surfaces, as well as convergence and approximation theorems. We use the asymptotic cones as facial descriptors and demonstrate the

  14. Biofouling Control in Spiral-Wound Membrane Systems: Impact of Feed Spacer Modification and Biocides

    KAUST Repository

    Siddiqui, Amber

    2016-12-01

    High-quality drinking water can be produced with membrane-based filtration processes like reverse osmosis and nanofiltration. One of the major problems in these membrane systems is biofouling that reduces the membrane performance, increasing operational costs. Current biofouling control strategies such as pre-treatment, membrane modification, and chemical cleaning are not sufficient in all cases. Feed spacers are thin (0.8 mm), complex geometry meshes that separate membranes in a module. The main objective of this research was to evaluate whether feed spacer modification is a suitable strategy to control biofouling. Membrane fouling simulator studies with six feed spacers showed differences in biofouled spacer performance, concluding that (i) spacer geometry influences biofouling impact and (ii) biofouling studies are essential for evaluation of spacer biofouling impact. Computed tomography (CT) was found as a suitable technique to obtain three-dimensional (3D) measurements of spacers, enabling more representative mathematical modeling of hydraulic behavior of spacers in membrane systems. A strategy for developing, characterizing, and testing of spacers by numerical modeling, 3D printing of spacers and experimental membrane fouling simulator studies was developed. The combination of modeling and experimental testing of 3D printed spacers is a promising strategy to develop advanced spacers aiming to reduce the impact of biofilm formation on membrane performance and to improve the cleanability of spiral-wound membrane systems.

  15. How membrane lipids control the 3D structure and function of receptors

    OpenAIRE

    Jacques Fantini; Francisco J. Barrantes

    2018-01-01

    The cohabitation of lipids and proteins in the plasma membrane of mammalian cells is controlled by specific biochemical and biophysical rules. Lipids may be either constitutively tightly bound to cell-surface receptors (non-annular lipids) or less tightly attached to the external surface of the protein (annular lipids). The latter are exchangeable with surrounding bulk membrane lipids on a faster time scale than that of non-annular lipids. Not only do non-annular lipids bind to membrane prote...

  16. System and method for air temperature control in an oxygen transport membrane based reactor

    Science.gov (United States)

    Kelly, Sean M

    2016-09-27

    A system and method for air temperature control in an oxygen transport membrane based reactor is provided. The system and method involves introducing a specific quantity of cooling air or trim air in between stages in a multistage oxygen transport membrane based reactor or furnace to maintain generally consistent surface temperatures of the oxygen transport membrane elements and associated reactors. The associated reactors may include reforming reactors, boilers or process gas heaters.

  17. Dynamic curvature sensing employing ionic-polymer–metal composite sensors

    International Nuclear Information System (INIS)

    Bahramzadeh, Yousef; Shahinpoor, Mohsen

    2011-01-01

    A dynamic curvature sensor is presented based on ionic-polymer–metal composite (IPMC) for curvature monitoring of deployable/inflatable dynamic space structures. Monitoring the curvature variation is of high importance in various engineering structures including shape monitoring of deployable/inflatable space structures in which the structural boundaries undergo a dynamic deployment process. The high sensitivity of IPMCs to the applied deformations as well as its flexibility make IPMCs a promising candidate for sensing of dynamic curvature changes. Herein, we explore the dynamic response of an IPMC sensor strip with respect to controlled curvature deformations subjected to different forms of input functions. Using a specially designed experimental setup, the voltage recovery effect, phase delay, and rate dependency of the output voltage signal of an IPMC curvature sensor are analyzed. Experimental results show that the IPMC sensor maintains the linearity, sensitivity, and repeatability required for curvature sensing. Besides, in order to describe the dynamic phenomena such as the rate dependency of the IPMC sensor, a chemo-electro-mechanical model based on the Poisson–Nernst–Planck (PNP) equation for the kinetics of ion diffusion is presented. By solving the governing partial differential equations the frequency response of the IPMC sensor is derived. The physical model is able to describe the dynamic properties of the IPMC sensor and the dependency of the signal on rate of excitations

  18. Clinical Assessment of Lamina Cribrosa Curvature in Eyes with Primary Open-Angle Glaucoma.

    Directory of Open Access Journals (Sweden)

    Yong Woo Kim

    Full Text Available Quantitative evaluation of lamina cribrosa (LC posterior bowing in primary open-angle glaucoma (POAG eyes using swept-source optical coherence tomography.Patients with POAG (n = 123 eyes and healthy individuals of a similar age (n = 92 eyes were prospectively recruited. Anterior laminar insertion depth (ALID was defined as the vertical distance between the anterior laminar insertion and a reference plane connecting the Bruch's membrane openings (BMO. The mean LC depth (mLCD was approximated by dividing the area enclosed by the anterior LC, the BMO reference plane, and the two vertical lines for ALID measurement by the length between those two vertical lines. The LC curvature index was defined as the difference between the mLCD and the ALID. The factors influencing the LC curvature index were evaluated.The ALID and mLCD were significantly larger in POAG eyes than in healthy controls (P -6 dB and moderate-to-advanced glaucoma (MD < -6 dB, P = 0.95.LC posterior bowing was increased in POAG eyes, and was significantly associated with structural optic nerve head (ONH changes but not with functional glaucoma severity. Quantitative evaluation of LC curvature can facilitate assessment of glaucomatous ONH change.

  19. Curvature bound from gravitational catalysis

    Science.gov (United States)

    Gies, Holger; Martini, Riccardo

    2018-04-01

    We determine bounds on the curvature of local patches of spacetime from the requirement of intact long-range chiral symmetry. The bounds arise from a scale-dependent analysis of gravitational catalysis and its influence on the effective potential for the chiral order parameter, as induced by fermionic fluctuations on a curved spacetime with local hyperbolic properties. The bound is expressed in terms of the local curvature scalar measured in units of a gauge-invariant coarse-graining scale. We argue that any effective field theory of quantum gravity obeying this curvature bound is safe from chiral symmetry breaking through gravitational catalysis and thus compatible with the simultaneous existence of chiral fermions in the low-energy spectrum. With increasing number of dimensions, the curvature bound in terms of the hyperbolic scale parameter becomes stronger. Applying the curvature bound to the asymptotic safety scenario for quantum gravity in four spacetime dimensions translates into bounds on the matter content of particle physics models.

  20. Cationic membranes complexed with oppositely charged microtubules: hierarchical self-assembly leading to bio-nanotubes

    International Nuclear Information System (INIS)

    Raviv, Uri; Needleman, Daniel J; Safinya, Cyrus R

    2006-01-01

    The self-assembly of microtubules and charged membranes has been studied, using x-ray diffraction and electron microscopy. Polyelectrolyte lipid complexes usually form structures templated by the lipid phase, when the polyelectrolyte curvature is much larger than the membrane spontaneous curvature. When the polyelectrolyte curvature approaches the membrane spontaneous curvature, as in microtubules, two types of new structures emerge. Depending on the conditions, vesicles either adsorb onto the microtubule, forming a 'beads on a rod' structure, or coat the microtubule, which now forms the template. Tubulin oligomers then coat the external lipid layer, forming a lipid protein nanotube. The tubulin oligomer coverage at the external layer is determined by the membrane charge density. The energy barrier between the beads on a rod and the lipid-protein nanotube states depends on the membrane bending rigidity and membrane charge density. By controlling the lipid/tubulin stoichiometry we can switch between lipid-protein nanotubes with open ends to lipid-protein nanotubes with closed end with lipid cups. This forms the basis for controlled drug encapsulation and release

  1. Inefficacy of osmotic backwash induced by sodium chloride salt solution in controlling SWRO membrane fouling

    Science.gov (United States)

    Farooque, A. Mohammed; Al-Jeshi, Subhi; Saeed, Mohamed O.; Alreweli, Ali

    2014-12-01

    A study was conducted to evaluate the efficacy of osmotic backwash induced by high salt (NaCl) concentration solution on feed side of seawater reverse osmosis (SWRO) membranes, online and offline, in controlling membrane fouling and therefore minimizing/eliminating the need for chemical cleaning. SWRO membranes were deliberately fouled by feeding seawater from an open intake located on the Arabian Gulf Coast without dosing chemicals. The fouled membranes were subjected to offline cleaning with the salt solution of up to 25 % concentration. Despite the partial removal of foulants from the membrane surface, SWRO membrane performance could not be restored, indicating the ineffectiveness of osmotic backwash in aiding offline salt cleaning. Similarly, online osmotic backwash was found to be not only ineffective in removing foulants from membrane surfaces but actually increased the fouling rate, as indicated by faster fouling rates compared to other cases. Although the driving force required for the osmotic backwash existed, the generated back flow proved to be insufficient to detach foulants from membrane surfaces. During the study period, the average SWRO membrane flux was maintained between 19 and 23 LMH, whereas the average generated back flow flux by high salt concentration solution was only 11 LMH, which was not adequate to remove foulants from membrane surfaces. Moreover, it seems that the membrane configuration as well as inherent microstructure of SWRO membrane places certain constraints on the osmotic backwash process and renders osmotic backwash ineffective in tackling SWRO membrane fouling. Hence, chemical cleaning is essential to restore SWRO membrane performance whenever fouling occurs, and the use of highly concentrated salt solution does not have any significant benefit. Membrane autopsy revealed only an insignificant accumulation of biofouling layer despite the absence of disinfection. However, it was shown that culturable biofilm bacteria species

  2. Folding DNA into a Lipid-Conjugated Nanobarrel for Controlled Reconstitution of Membrane Proteins.

    Science.gov (United States)

    Dong, Yuanchen; Chen, Shuobing; Zhang, Shijian; Sodroski, Joseph; Yang, Zhongqiang; Liu, Dongsheng; Mao, Youdong

    2018-02-19

    Building upon DNA origami technology, we introduce a method to reconstitute a single membrane protein into a self-assembled DNA nanobarrel that scaffolds a nanodisc-like lipid environment. Compared with the membrane-scaffolding-protein nanodisc technique, our approach gives rise to defined stoichiometry, controlled sizes, as well as enhanced stability and homogeneity in membrane protein reconstitution. We further demonstrate potential applications of the DNA nanobarrels in the structural analysis of membrane proteins. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Feed gas contaminant control in ion transport membrane systems

    Science.gov (United States)

    Carolan, Michael Francis [Allentown, PA; Minford, Eric [Laurys Station, PA; Waldron, William Emil [Whitehall, PA

    2009-07-07

    Ion transport membrane oxidation system comprising an enclosure having an interior and an interior surface, inlet piping having an internal surface and adapted to introduce a heated feed gas into the interior of the enclosure, and outlet piping adapted to withdraw a product gas from the interior of the enclosure; one or more planar ion transport membrane modules disposed in the interior of the enclosure, each membrane module comprising mixed metal oxide material; and a preheater adapted to heat a feed gas to provide the heated feed gas to the inlet piping, wherein the preheater comprises an interior surface. Any of the interior surfaces of the enclosure, the inlet piping, and the preheater may be lined with a copper-containing metal lining. Alternatively, any of the interior surfaces of the inlet piping and the preheater may be lined with a copper-containing metal lining and the enclosure may comprise copper.

  4. The role of curvature in silica mesoporous crystals

    KAUST Repository

    Miyasaka, Keiichi; Bennett, Alfonso Garcia; Han, Lu; Han, Yu; Xiao, Changhong; Fujita, Nobuhisa; Castle, Toen; Sakamoto, Yasuhiro; Che, Shunai; Terasaki, Osamu

    2012-01-01

    Silica mesoporous crystals (SMCs) offer a unique opportunity to study micellar mesophases. Replication of non-equilibrium mesophases into porous silica structures allows the characterization of surfactant phases under a variety of chemical and physical perturbations, through methods not typically accessible to liquid crystal chemists. A poignant example is the use of electron microscopy and crystallography, as discussed herein, for the purpose of determining the fundamental role of amphiphile curvature, namely mean curvature and Gaussian curvature, which have been extensively studied in various fields such as polymer, liquid crystal, biological membrane, etc. The present work aims to highlight some current studies devoted to the interface curvature on SMCs, in which electron microscopy and electron crystallography (EC) are used to understand the geometry of silica wall surface in bicontinuous and cage-type mesostructures through the investigation of electrostatic potential maps. Additionally, we show that by altering the synthesis conditions during the preparation of SMCs, it is possible to isolate particles during micellar mesophase transformations in the cubic bicontinuous system, allowing us to view and study epitaxial relations under the specific synthesis conditions. By studying the relationship between mesoporous structure, interface curvature and micellar mesophases using electron microscopy and EC, we hope to bring new insights into the formation mechanism of these unique materials but also contribute a new way of understanding periodic liquid crystal systems. © 2012 The Royal Society.

  5. The role of curvature in silica mesoporous crystals

    KAUST Repository

    Miyasaka, Keiichi

    2012-02-08

    Silica mesoporous crystals (SMCs) offer a unique opportunity to study micellar mesophases. Replication of non-equilibrium mesophases into porous silica structures allows the characterization of surfactant phases under a variety of chemical and physical perturbations, through methods not typically accessible to liquid crystal chemists. A poignant example is the use of electron microscopy and crystallography, as discussed herein, for the purpose of determining the fundamental role of amphiphile curvature, namely mean curvature and Gaussian curvature, which have been extensively studied in various fields such as polymer, liquid crystal, biological membrane, etc. The present work aims to highlight some current studies devoted to the interface curvature on SMCs, in which electron microscopy and electron crystallography (EC) are used to understand the geometry of silica wall surface in bicontinuous and cage-type mesostructures through the investigation of electrostatic potential maps. Additionally, we show that by altering the synthesis conditions during the preparation of SMCs, it is possible to isolate particles during micellar mesophase transformations in the cubic bicontinuous system, allowing us to view and study epitaxial relations under the specific synthesis conditions. By studying the relationship between mesoporous structure, interface curvature and micellar mesophases using electron microscopy and EC, we hope to bring new insights into the formation mechanism of these unique materials but also contribute a new way of understanding periodic liquid crystal systems. © 2012 The Royal Society.

  6. Current research and development of controlling membrane fouling ...

    African Journals Online (AJOL)

    Fouling is a major problem influencing the operational performance, stability and cost of a membrane bioreactor (MBR). The composition of wastewater and biomass grown in the MBR are directly related to fouling. Many factors including operational parameters can affect the fouling process. The extent of fouling can be ...

  7. Surface meshing with curvature convergence

    KAUST Repository

    Li, Huibin; Zeng, Wei; Morvan, Jean-Marie; Chen, Liming; Gu, Xianfengdavid

    2014-01-01

    Surface meshing plays a fundamental role in graphics and visualization. Many geometric processing tasks involve solving geometric PDEs on meshes. The numerical stability, convergence rates and approximation errors are largely determined by the mesh qualities. In practice, Delaunay refinement algorithms offer satisfactory solutions to high quality mesh generations. The theoretical proofs for volume based and surface based Delaunay refinement algorithms have been established, but those for conformal parameterization based ones remain wide open. This work focuses on the curvature measure convergence for the conformal parameterization based Delaunay refinement algorithms. Given a metric surface, the proposed approach triangulates its conformal uniformization domain by the planar Delaunay refinement algorithms, and produces a high quality mesh. We give explicit estimates for the Hausdorff distance, the normal deviation, and the differences in curvature measures between the surface and the mesh. In contrast to the conventional results based on volumetric Delaunay refinement, our stronger estimates are independent of the mesh structure and directly guarantee the convergence of curvature measures. Meanwhile, our result on Gaussian curvature measure is intrinsic to the Riemannian metric and independent of the embedding. In practice, our meshing algorithm is much easier to implement and much more efficient. The experimental results verified our theoretical results and demonstrated the efficiency of the meshing algorithm. © 2014 IEEE.

  8. Surface meshing with curvature convergence

    KAUST Repository

    Li, Huibin

    2014-06-01

    Surface meshing plays a fundamental role in graphics and visualization. Many geometric processing tasks involve solving geometric PDEs on meshes. The numerical stability, convergence rates and approximation errors are largely determined by the mesh qualities. In practice, Delaunay refinement algorithms offer satisfactory solutions to high quality mesh generations. The theoretical proofs for volume based and surface based Delaunay refinement algorithms have been established, but those for conformal parameterization based ones remain wide open. This work focuses on the curvature measure convergence for the conformal parameterization based Delaunay refinement algorithms. Given a metric surface, the proposed approach triangulates its conformal uniformization domain by the planar Delaunay refinement algorithms, and produces a high quality mesh. We give explicit estimates for the Hausdorff distance, the normal deviation, and the differences in curvature measures between the surface and the mesh. In contrast to the conventional results based on volumetric Delaunay refinement, our stronger estimates are independent of the mesh structure and directly guarantee the convergence of curvature measures. Meanwhile, our result on Gaussian curvature measure is intrinsic to the Riemannian metric and independent of the embedding. In practice, our meshing algorithm is much easier to implement and much more efficient. The experimental results verified our theoretical results and demonstrated the efficiency of the meshing algorithm. © 2014 IEEE.

  9. A prescribing geodesic curvature problem

    International Nuclear Information System (INIS)

    Chang, K.C.; Liu, J.Q.

    1993-09-01

    Let D be the unit disk and k be a function on S 1 = δD. Find a flat metric which is pointwise conformal to the standard metric and has k as the geodesic curvature of S 1 . A sufficient condition for the existence of such a metric is that the harmonic extension of k in D has saddle points. (author). 11 refs

  10. Nonlinear Lyapunov-based boundary control of distributed heat transfer mechanisms in membrane distillation plant

    KAUST Repository

    Eleiwi, Fadi; Laleg-Kirati, Taous-Meriem

    2015-01-01

    This paper presents a nonlinear Lyapunov-based boundary control for the temperature difference of a membrane distillation boundary layers. The heat transfer mechanisms inside the process are modeled with a 2D advection-diffusion equation. The model

  11. Application of electrochemical processes to membrane bioreactors for improving nutrient removal and fouling control.

    Science.gov (United States)

    Borea, Laura; Naddeo, Vincenzo; Belgiorno, Vincenzo

    2017-01-01

    Membrane bioreactor (MBR) technology is becoming increasingly popular as wastewater treatment due to the unique advantages it offers. However, membrane fouling is being given a great deal of attention so as to improve the performance of this type of technology. Recent studies have proven that the application of electrochemical processes to MBR represents a promising technological approach for membrane fouling control. In this work, two intermittent voltage gradients of 1 and 3 V/cm were applied between two cylindrical perforated electrodes, immersed around a membrane module, at laboratory scale with the aim of investigating the treatment performance and membrane fouling formation. For comparison purposes, the reactor also operated as a conventional MBR. Mechanisms of nutrient removal were studied and membrane fouling formation evaluated in terms of transmembrane pressure variation over time and sludge relative hydrophobicity. Furthermore, the impact of electrochemical processes on transparent exopolymeric particles (TEP), proposed as a new membrane fouling precursor, was investigated in addition to conventional fouling precursors such as bound extracellular polymeric substances (bEPS) and soluble microbial products (SMP). All the results indicate that the integration of electrochemical processes into a MBR has the advantage of improving the treatment performance especially in terms of nutrient removal, with an enhancement of orthophosphate (PO 4 -P) and ammonia nitrogen (NH 4 -N) removal efficiencies up to 96.06 and 69.34 %, respectively. A reduction of membrane fouling was also observed with an increase of floc hydrophobicity to 71.72 %, a decrease of membrane fouling precursor concentrations, and, thus, of membrane fouling rates up to 54.33 %. The relationship found between TEP concentration and membrane fouling rate after the application of electrochemical processes confirms the applicability of this parameter as a new membrane fouling indicator.

  12. Structural Changes of PVDF Membranes by Phase Separation Control

    International Nuclear Information System (INIS)

    Lee, Semin; Kim, Sung Soo

    2016-01-01

    Thermally induced phase separation (TIPS) and nonsolvent induced phase separation (NIPS) were simultaneously induced for the preparation of flat PVDF membranes. N-methyl-2-pyrrolidone (NMP) was used as a solvent and dibutyl-phthlate (DBP) was used as a diluent for PVDF. When PVDF was melt blended with NMP and DBP, crystallization temperature was lowered for TIPS and unstable region was expanded for NIPS. Ratio of solvent to diluent changed the phase separation mechanism to obtain the various membrane structures. Contact mode of dope solution with nonsolvent determined the dominant phase separation behavior. Since heat transfer rate was greater than mass transfer rate, surface structure was formed by NIPS and inner structure was by TIPS. Quenching temperature of dope solution also affected the phase separation mechanism and phase separation rate to result in the variation of structure

  13. Controlled growth of CNT in mesoporous AAO through optimized conditions for membrane preparation and CVD operation

    Energy Technology Data Exchange (ETDEWEB)

    Ciambelli, P; Sarno, M; Leone, C; Sannino, D [Department of Chemical and Food Engineering, University of Salerno, I-84084 Fisciano (Italy); Arurault, L; Fontorbes, S; Datas, L; Lenormand, P; Le Blond Du Plouy, S, E-mail: msarno@unisa.it, E-mail: arurault@chimie.ups-tlse.fr [Universite de Toulouse, CIRIMAT, UPS/INPT/CNRS, LCMIE, F-31062 Toulouse Cedex 9 (France)

    2011-07-01

    Anodic aluminium oxide (RAAO) membranes with a mesoporous structure were prepared under strictly controlling experimental process conditions, and physically and chemically characterized by a wide range of experimental techniques. Commercial anodic aluminium oxide (CAAO) membranes were also investigated for comparison. We demonstrated that RAAO membranes have lower content of both water and phosphorus and showed better porosity shape than CAAO. The RAAO membranes were used for template growth of carbon nanotubes (CNT) inside its pores by ethylene chemical vapour deposition (CVD) in the absence of a catalyst. A composite material, containing one nanotube for each channel, having the same length as the membrane thickness and an external diameter close to the diameter of the membrane holes, was obtained. Yield, selectivity and quality of CNTs in terms of diameter, length and arrangement (i.e. number of tubes for each channel) were optimized by investigating the effect of changing the experimental conditions for the CVD process. We showed that upon thermal treatment RAAO membranes were made up of crystallized allotropic alumina phases, which govern the subsequent CNT growth, because of their catalytic activity, likely due to their Lewis acidity. The strict control of experimental conditions for membrane preparation and CNT growth allowed us to enhance the carbon structural order, which is a critical requisite for CNT application as a substitute for copper in novel nano-interconnects.

  14. Air dehumidification by membrane with cold water for manned spacecraft environmental control

    Directory of Open Access Journals (Sweden)

    Shang Yonghong

    2017-01-01

    Full Text Available The traditional condensation dehumidification method requires additional gas-liquid separation and water recovery process in the manned spacecraft humidity control system, which would increase weight and complexity of systems. A new membrane dehumidification with cold water is proposed, which uses water vapor partial pressure difference to promote water vapor transmembrane mass transfer for dehumidification. The permeability of the membrane was measured and the experimental results agree well with the theoretical calculations. Based on the simulation of dehumidification process of cold water-membrane, the influence of module structure and working condition on dehumidification performance was analyzed, which provided reference for the design of membrane module construct. It can be seen from the simulation and experiments that the cold water-membrane dehumidification can effectively reduce the thermal load of the manned spacecraft.

  15. Mass transfer rate through liquid membranes: interfacial chemical reactions and diffusion as simultaneous permeability controlling factors

    International Nuclear Information System (INIS)

    Danesi, P.R.; Horwitz, E.P.; Vandegrift, G.F.; Chiarizia, R.

    1981-01-01

    Equations describing the permeability of a liquid membrane to metal cations have been derived taking into account aqueous diffusion, membrane diffusion, and interfacial chemical reactions as simultaneous permeability controlling factors. Diffusion and chemical reactions have been coupled by a simple model analogous to the one previously described by us to represent liquid-liquid extraction kinetics. The derived equations, which make use of experimentally determined interfacial reaction mechanisms, qualitatively fit unexplained literature data regarding Cu 2+ transfer through liquid membranes. Their use to predict and optimize membrane permeability in practical separation processes by setting the appropriate concentration of the membrane carrier [LIX 64 (General Mills), a commercial β-hydroxy-oxime] and the pH of the aqueous copper feed solution is briefly discussed. 4 figures

  16. Membrane tension controls adhesion positioning at the leading edge of cells.

    Science.gov (United States)

    Pontes, Bruno; Monzo, Pascale; Gole, Laurent; Le Roux, Anabel-Lise; Kosmalska, Anita Joanna; Tam, Zhi Yang; Luo, Weiwei; Kan, Sophie; Viasnoff, Virgile; Roca-Cusachs, Pere; Tucker-Kellogg, Lisa; Gauthier, Nils C

    2017-09-04

    Cell migration is dependent on adhesion dynamics and actin cytoskeleton remodeling at the leading edge. These events may be physically constrained by the plasma membrane. Here, we show that the mechanical signal produced by an increase in plasma membrane tension triggers the positioning of new rows of adhesions at the leading edge. During protrusion, as membrane tension increases, velocity slows, and the lamellipodium buckles upward in a myosin II-independent manner. The buckling occurs between the front of the lamellipodium, where nascent adhesions are positioned in rows, and the base of the lamellipodium, where a vinculin-dependent clutch couples actin to previously positioned adhesions. As membrane tension decreases, protrusion resumes and buckling disappears, until the next cycle. We propose that the mechanical signal of membrane tension exerts upstream control in mechanotransduction by periodically compressing and relaxing the lamellipodium, leading to the positioning of adhesions at the leading edge of cells. © 2017 Pontes et al.

  17. Cosmic curvature tested directly from observations

    Science.gov (United States)

    Denissenya, Mikhail; Linder, Eric V.; Shafieloo, Arman

    2018-03-01

    Cosmic spatial curvature is a fundamental geometric quantity of the Universe. We investigate a model independent, geometric approach to measure spatial curvature directly from observations, without any derivatives of data. This employs strong lensing time delays and supernova distance measurements to measure the curvature itself, rather than just testing consistency with flatness. We define two curvature estimators, with differing error propagation characteristics, that can crosscheck each other, and also show how they can be used to map the curvature in redshift slices, to test constancy of curvature as required by the Robertson-Walker metric. Simulating realizations of redshift distributions and distance measurements of lenses and sources, we estimate uncertainties on the curvature enabled by next generation measurements. The results indicate that the model independent methods, using only geometry without assuming forms for the energy density constituents, can determine the curvature at the ~6×10‑3 level.

  18. Mechanical Characterization of Anion Exchange Membranes Under Controlled Environmental Conditions

    Science.gov (United States)

    2015-05-11

    little market penetration has been achieved. Proton exchange membrane fuel cells ( PEMFC ) have struggled primarily due to high cost, driven by the use...and requirements for Pt, Pt-alloy, and non-Pt oxygen reduction catalysts for PEMFCs , Appl. Catal. B Environ. 56 (2005) 9–35. doi:10.1016/j.apcatb...resins for PEMFCs , Electrochim. Acta. 50 (2004) 571–575. doi:10.1016/j.electacta.2004.01.133. [89] S. Bhadra, N.H. Kim, J.S. Choi, K.Y. Rhee, J.H. Lee

  19. A remark about the mean curvature

    International Nuclear Information System (INIS)

    Zhang Weitao.

    1992-11-01

    In this paper, we give an integral identity about the mean curvature in Sobolev space H 0 1 (Ω) intersection H 2 (Ω). Suppose the mean curvature on Γ=δΩ is positive, we prove some inequalities of the positive mean curvature and propose some open problems. (author). 4 refs

  20. The dark side of curvature

    International Nuclear Information System (INIS)

    Barenboim, Gabriela; Martínez, Enrique Fernández; Mena, Olga; Verde, Licia

    2010-01-01

    Geometrical tests such as the combination of the Hubble parameter H(z) and the angular diameter distance d A (z) can, in principle, break the degeneracy between the dark energy equation of state parameter w(z), and the spatial curvature Ω k in a direct, model-independent way. In practice, constraints on these quantities achievable from realistic experiments, such as those to be provided by Baryon Acoustic Oscillation (BAO) galaxy surveys in combination with CMB data, can resolve the cosmic confusion between the dark energy equation of state parameter and curvature only statistically and within a parameterized model for w(z). Combining measurements of both H(z) and d A (z) up to sufficiently high redshifts z ∼ 2 and employing a parameterization of the redshift evolution of the dark energy equation of state are the keys to resolve the w(z)−Ω k degeneracy

  1. Modern approaches to discrete curvature

    CERN Document Server

    Romon, Pascal

    2017-01-01

     This book provides a valuable glimpse into discrete curvature, a rich new field of research which blends discrete mathematics, differential geometry, probability and computer graphics. It includes a vast collection of ideas and tools which will offer something new to all interested readers. Discrete geometry has arisen as much as a theoretical development as in response to unforeseen challenges coming from applications. Discrete and continuous geometries have turned out to be intimately connected. Discrete curvature is the key concept connecting them through many bridges in numerous fields: metric spaces, Riemannian and Euclidean geometries, geometric measure theory, topology, partial differential equations, calculus of variations, gradient flows, asymptotic analysis, probability, harmonic analysis, graph theory, etc. In spite of its crucial importance both in theoretical mathematics and in applications, up to now, almost no books have provided a coherent outlook on this emerging field.

  2. Impact of feed spacer and membrane modification by hydrophilic, bactericidal and biocidal coating on biofouling control

    KAUST Repository

    Araújo, Paula A.

    2012-06-01

    The influence of polydopamine- and polydopamine-. graft-poly(ethylene glycol)-coated feed spacers and membranes, copper-coated feed spacers, and commercially-available biostatic feed spacers on biofouling has been studied in membrane fouling simulators. Feed spacers and membranes applied in practical membrane filtration systems were used; biofouling development was monitored by feed channel pressure drop increase and biomass accumulation. Polydopamine and polydopamine-. g-PEG are hydrophilic surface modification agents expected to resist protein and bacterial adhesion, while copper feed spacer coatings and biocides infused in feed spacers are expected to restrict biological growth. Our studies showed that polydopamine and polydopamine-. g-PEG coatings on feed spacers and membranes, copper coatings on feed spacers, and a commercial biostatic feed spacer did not have a significant impact on feed channel pressure drop increase and biofilm accumulation as measured by ATP and TOC content. The studied spacer and membrane modifications were not effective for biofouling control; it is doubtful that feed spacer and membrane modification, in general, may be effective for biofouling control regardless of the type of applied coating. © 2012 Elsevier B.V.

  3. Membrane morphology and topology for fouling control in Reverse Osmosis filtration systems

    Science.gov (United States)

    Ling, Bowen; Battiato, Ilenia

    2017-11-01

    Reverse Osmosis Membrane (ROM) filtration systems are widely utilized in waste-water recovery, seawater desalination, landfill water treatment, etc. During filtration, the system performance is dramatically affected by membrane fouling which causes a significant decrease in permeate flux as well as an increase in the energy input required to operate the system. Design and optimization of ROM filtration systems aim at reducing membrane fouling by studying the coupling between membrane structure, local flow field and foulant adsorption patterns. Yet, current studies focus exclusively on oversimplified steady-state models that ignore any dynamic coupling between fluid flow and transport through the membrane. In this work, we develop a customized solver (SUMembraneFoam) under OpenFOAM to solve the transient equations. The simulation results not only predict macroscopic quantities (e.g. permeate flux, pressure drop, etc.) but also show an excellent agreement with the fouling patterns observed in experiments. It is observed that foulant deposition is strongly controlled by the local shear stress on the membrane, and channel morphology or membrane topology can be modified to control the shear stress distribution and reduce fouling. Finally, we identify optimal regimes for design.

  4. Exact boundary controllability for a series of membranes elastically connected

    Directory of Open Access Journals (Sweden)

    Waldemar D. Bastos

    2017-01-01

    Full Text Available In this article we study the exact controllability with Neumann boundary controls for a system of linear wave equations coupled in parallel by lower order terms on piecewise smooth domains of the plane. We obtain square integrable controls for initial state with finite energy and time of controllability near the optimal value.

  5. Nanoporous gold membranes: From morphological control to fuel cell catalysis

    Science.gov (United States)

    Ding, Yi

    Porous noble metals are particularly attractive for scientific research and industrial applications such as catalysis, sensing, and filtration. In this thesis, I will discuss the fabrication, characterization, and application of a new class of porous metals, called nanoporous metals (NPM). NPM is made during selective dissolution (also called dealloying) of reactive components (e.g., silver) from multi-component alloys (e.g., Ag/Au alloy). Commercially available white gold leaf (Ag65Au35) can, for example, be etched into nanoporous gold (NPG) membrane by simply floating the leaf on concentrated nitric acid for periods of a few minutes. NPG leaf adopts a single crystal porous structure within individual grains. The microstructure of NPG, such as the pore size, is tunable between a few nanometers to sub-micron length scale by either thermal annealing or post-treatment in nitric acid for extended period of time. A new gas-liquid-solid interface electroless plating technique is developed to uniformly cover the NPG surface with other metals, such as silver and platinum. This technique allows new opportunities of making functionalized nanostructures. We show that a combination of silver plating and dealloying can be used to make multimodal porous metals, which are expected to have application in sensing field. Electroless platinum plating onto NPG shows very usual growth mode. TEM observation indicates that the platinum layer on NPG surface takes a novel form of layer-islanding growth (Stranski-Krastanov growth). Annealing the Pt/NPG composite smoothens the Pt islands and forms a 1 nm coherent Pt layer on the NPG backbone, possibly with dislocation formation at the Pt/Au interface. Furthermore, it was found that we could dissolve the gold away in aqueous gold etchant, leaving behind the 1 nm-thick Pt shell, a structure we call nanotubular mesoporous platinum (NMP). Pt plated NPG has a series of unique structural properties, such as high active surface area, thermally

  6. Graphene oxide enrichment of collagen membranes improves DPSCs differentiation and controls inflammation occurrence.

    Science.gov (United States)

    Radunovic, Milena; De Colli, Marianna; De Marco, Patrizia; Di Nisio, Chiara; Fontana, Antonella; Piattelli, Adriano; Cataldi, Amelia; Zara, Susi

    2017-08-01

    Collagen membranes are used in oral surgery for bone defects treatment acting as a barrier that does not allow the invasion of soft tissue into the growing bone. To improve biocompatibility collagen membranes were coated with graphene oxide (GO), a graphene derivative. The aim of this study was to investigate the biocompatibility of GO coated collagen membranes on human dental pulp stem cells (DPSCs) focusing on biomaterial cytotoxicity, ability to promote DPSCs differentiation process and to control inflammation event induction. DPSCs were cultured on uncoated membranes and on both 2 and 10 μg mL -1 GO coated membranes up to 28 days. Alamar blue and LDH cytotocicity assay, PGE2 ELISA assay, real time RT-PCR for RUNX2, BMP2, SP7, TNFα and COX2 genes expression were performed. Proliferation is higher on GO coated membranes at days 14 and 28. LDH assay evidences no cytotoxicity. BMP2 and RUNX2 expression is higher on coated membranes, BMP2 at early and RUNX2 and SP7 at late experimental times. PGE2 levels are lower on GO coated membranes at days 14 and 28, both TNFα and COX2 expression is significantly decreased when GO is applied. GO coated membranes are not toxic for DPSCs, induce a faster DPSCs differentiation into odontoblasts/osteoblasts and may represent good alternative to conventional membranes thus ensuring more efficient bone formation and improving the clinical performance. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2312-2320, 2017. © 2017 Wiley Periodicals, Inc.

  7. Spinal curvature and characteristics of postural change in pregnant women.

    Science.gov (United States)

    Okanishi, Natsuko; Kito, Nobuhiro; Akiyama, Mitoshi; Yamamoto, Masako

    2012-07-01

    Pregnant women often report complaints due to physiological and postural changes. Postural changes during pregnancy may cause low back pain and pelvic girdle pain. This study aimed to compare the characteristics of postural changes in pregnant compared with non-pregnant women. Prospective case-control study. Pregnancy care center. Fifteen women at 17-34 weeks pregnancy comprised the study group, while 10 non-pregnant female volunteers comprised the control group. Standing posture was evaluated in the sagittal plane with static digital pictures. Two angles were measured by image analysis software: (1) between the trunk and pelvis; and (2) between the trunk and lower extremity. Spinal curvature was measured with Spinal Mouse® to calculate the means of sacral inclination, thoracic and lumbar curvature and inclination. The principal components were calculated until eigenvalues surpassed 1. Three distinct factors with eigenvalues of 1.00-2.49 were identified, consistent with lumbosacral spinal curvature and inclination, thoracic spine curvature, and inclination of the body. These factors accounted for 77.2% of the total variance in posture variables. Eleven pregnant women showed postural characteristics of lumbar kyphosis and sacral posterior inclination. Body inclination showed a variety of patterns compared with those in healthy women. Spinal curvature demonstrated a tendency for lumbar kyphosis in pregnant women. Pregnancy may cause changes in spinal curvature and posture, which may in turn lead to relevant symptoms. Our data provide a basis for investigating the effects of spinal curvature and postural changes on symptoms during pregnancy. © 2012 The Authors Acta Obstetricia et Gynecologica Scandinavica© 2012 Nordic Federation of Societies of Obstetrics and Gynecology.

  8. Biofouling of Water Treatment Membranes: A Review of the Underlying Causes, Monitoring Techniques and Control Measures

    Directory of Open Access Journals (Sweden)

    Felicity A. Roddick

    2012-11-01

    Full Text Available Biofouling is a critical issue in membrane water and wastewater treatment as it greatly compromises the efficiency of the treatment processes. It is difficult to control, and significant economic resources have been dedicated to the development of effective biofouling monitoring and control strategies. This paper highlights the underlying causes of membrane biofouling and provides a review on recent developments of potential monitoring and control methods in water and wastewater treatment with the aim of identifying the remaining issues and challenges in this area.

  9. Numerical and Theoretical Investigations Concerning the Continuous-Surface-Curvature Effect in Compressor Blades

    Directory of Open Access Journals (Sweden)

    Yin Song

    2014-12-01

    Full Text Available Though the importance of curvature continuity on compressor blade performances has been realized, there are two major questions that need to be solved, i.e., the respective effects of curvature continuity at the leading-edge blend point and the main surface, and the contradiction between the traditional theory and experimental observations in the effect of those novel leading-edge shapes with smaller curvature discontinuity and sharper nose. In this paper, an optimization method to design continuous-curvature blade profiles which deviate little from datum blades is proposed, and numerical and theoretical analysis is carried out to investigate the continuous-curvature effect on blade performances. The results show that the curvature continuity at the leading-edge blend point helps to eliminate the separation bubble, thus improving the blade performance. The main-surface curvature continuity is also beneficial, although its effects are much smaller than those of the blend-point curvature continuity. Furthermore, it is observed that there exist two factors controlling the leading-edge spike, i.e., the curvature discontinuity at the blend point which dominates at small incidences, and the nose curvature which dominates at large incidences. To the authors’ knowledge, such mechanisms have not been reported before, and they can help to solve the sharp-leading-edge paradox.

  10. A balance between membrane elasticity and polymerization energy sets the shape of spherical clathrin coats

    Science.gov (United States)

    Saleem, Mohammed; Morlot, Sandrine; Hohendahl, Annika; Manzi, John; Lenz, Martin; Roux, Aurélien

    2015-02-01

    In endocytosis, scaffolding is one of the mechanisms to create membrane curvature by moulding the membrane into the spherical shape of the clathrin cage. However, the impact of membrane elastic parameters on the assembly and shape of clathrin lattices has never been experimentally evaluated. Here, we show that membrane tension opposes clathrin polymerization. We reconstitute clathrin budding in vitro with giant unilamellar vesicles (GUVs), purified adaptors and clathrin. By changing the osmotic conditions, we find that clathrin coats cause extensive budding of GUVs under low membrane tension while polymerizing into shallow pits under moderate tension. High tension fully inhibits polymerization. Theoretically, we predict the tension values for which transitions between different clathrin coat shapes occur. We measure the changes in membrane tension during clathrin polymerization, and use our theoretical framework to estimate the polymerization energy from these data. Our results show that membrane tension controls clathrin-mediated budding by varying the membrane budding energy.

  11. Membrane shape modulates transmembrane protein distribution.

    Science.gov (United States)

    Aimon, Sophie; Callan-Jones, Andrew; Berthaud, Alice; Pinot, Mathieu; Toombes, Gilman E S; Bassereau, Patricia

    2014-01-27

    Although membrane shape varies greatly throughout the cell, the contribution of membrane curvature to transmembrane protein targeting is unknown because of the numerous sorting mechanisms that take place concurrently in cells. To isolate the effect of membrane shape, we used cell-sized giant unilamellar vesicles (GUVs) containing either the potassium channel KvAP or the water channel AQP0 to form membrane nanotubes with controlled radii. Whereas the AQP0 concentrations in flat and curved membranes were indistinguishable, KvAP was enriched in the tubes, with greater enrichment in more highly curved membranes. Fluorescence recovery after photobleaching measurements showed that both proteins could freely diffuse through the neck between the tube and GUV, and the effect of each protein on membrane shape and stiffness was characterized using a thermodynamic sorting model. This study establishes the importance of membrane shape for targeting transmembrane proteins and provides a method for determining the effective shape and flexibility of membrane proteins. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Combination of electrochemical processes with membrane bioreactors for wastewater treatment and fouling control: A review

    Directory of Open Access Journals (Sweden)

    Benny Marie B. Ensano

    2016-08-01

    Full Text Available This paper provides a critical review about the integration of electrochemical processes into membrane bioreactors (MBR in order to understand the influence of these processes on wastewater treatment performance and membrane fouling control. The integration can be realized either in an internal or an external configuration. Electrically enhanced membrane bioreactors or electro membrane bioreactors (eMBRs combine biodegradation, electrochemical and membrane filtration processes into one system providing higher effluent quality as compared to conventional MBRs and activated sludge plants. Furthermore, electrochemical processes, such as electrocoagulation, electrophoresis and electroosmosis, help to mitigate deposition of foulants into the membrane and enhance sludge dewaterability by controlling the morphological properties and mobility of the colloidal particles and bulk liquid. Intermittent application of minute electric field has proven to reduce energy consumption and operational cost as well as minimize the negative effect of direct current field on microbial activity which are some of the main concerns in eMBR technology. The present review discusses important design considerations of eMBR, its advantages as well as its applications to different types of wastewater. It also presents several challenges that need to be addressed for future development of this hybrid technology which include treatment of high strength industrial wastewater and removal of emerging contaminants, optimization study, cost benefit analysis and the possible combination with microbial electrolysis cell for biohydrogen production.

  13. On controllability of an integrated bioreactor and periodically operated membrane separation process

    DEFF Research Database (Denmark)

    Prado Rubio, Oscar Andres; Jørgensen, Sten Bay; Jonsson, Gunnar Eigil

    the influence of membrane fouling. Previously, the REED and fermentation processes have been modeled and investigated separately (Prado- Rubio et al., 2011a; Boonmee, 2003). Additionally, a simple quasi-sequential strategy for integrated process design and control structure development has been proposed (Prado...... to understand the controlled operation of the integrated process, it is convenient to use a model based approach supported by experimental evidence. Recently, an integrated bioreactor and electrically driven membrane separation process (Reverse Electro- Enhanced Dialysis - REED) has been proposed as a method...... at a certain lactate concentration level. Hence, productivity can be enhanced by the in situ lactate removal from the cultivation broth during pH controlled fermentation. This can be done by means of ion exchange membranes and electrical potential gradients. The novelty of the integrated process lies...

  14. Dynamic Double Curvature Mould System

    DEFF Research Database (Denmark)

    Jepsen, Christian Raun; Kristensen, Mathias Kræmmergaard; Kirkegaard, Poul Henning

    2011-01-01

    The present paper describes a concept for a reconfigurable mould surface which is designed to fit the needs of contemporary architecture. The core of the concept presented is a dynamic surface manipulated into a given shape using a digital signal created directly from the CAD drawing of the design....... This happens fast, automatic and without production of waste, and the manipulated surface is fair and robust, eliminating the need for additional, manual treatment. Limitations to the possibilities of the flexible form are limited curvature and limited level of detail, making it especially suited for larger...

  15. Control-oriented model of a membrane humidifier for fuel cell applications

    International Nuclear Information System (INIS)

    Solsona, Miguel; Kunusch, Cristian; Ocampo-Martinez, Carlos

    2017-01-01

    Highlights: • A control-oriented model of a Nafion® membrane gas humidifier has been developed. • The control-oriented model has been experimentally validated. • A non-linear control strategy has been used to test its suitability for control purposes. - Abstract: Improving the humidification of polymer electrolyte membrane fuel-cells (PEMFC) is essential to optimize its performance and stability. Therefore, this paper presents an experimentally validated model of a low temperature PEMFC cathode humidifier for control/observation design purposes. A multi-input/multi-output non-linear fourth order model is derived, based on the mass and heat dynamics of circulating air. In order to validate the proposed model and methodology, experimental results are provided. Finally, a non-linear control strategy based on second order sliding mode is designed and analyzed in order to show suitability and usefulness of the approach.

  16. Nonlinear Lyapunov-based boundary control of distributed heat transfer mechanisms in membrane distillation plant

    KAUST Repository

    Eleiwi, Fadi

    2015-07-01

    This paper presents a nonlinear Lyapunov-based boundary control for the temperature difference of a membrane distillation boundary layers. The heat transfer mechanisms inside the process are modeled with a 2D advection-diffusion equation. The model is semi-descretized in space, and a nonlinear state-space representation is provided. The control is designed to force the temperature difference along the membrane sides to track a desired reference asymptotically, and hence a desired flux would be generated. Certain constraints are put on the control law inputs to be within an economic range of energy supplies. The effect of the controller gain is discussed. Simulations with real process parameters for the model, and the controller are provided. © 2015 American Automatic Control Council.

  17. Natural material-decorated mesoporous silica nanoparticle container for multifunctional membrane-controlled targeted drug delivery

    Directory of Open Access Journals (Sweden)

    Hu Y

    2017-11-01

    Full Text Available Yan Hu,1 Lei Ke,2 Hao Chen,1 Ma Zhuo,1 Xinzhou Yang,1 Dan Zhao,1 Suying Zeng,1 Xincai Xiao1 1Department of Pharmaceutics, School of Pharmaceutical Science, South-Central University for Nationalities, 2Department of Medicinal Chemistry, School of Pharmacy, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People’s Republic of China Abstract: To avoid the side effects caused by nonspecific targeting, premature release, weak selectivity, and poor therapeutic efficacy of current nanoparticle-based systems used for drug delivery, we fabricated natural material-decorated nanoparticles as a multifunctional, membrane-controlled targeted drug delivery system. The nanocomposite material coated with a membrane was biocompatible and integrated both specific tumor targeting and responsiveness to stimulation, which improved transmission efficacy and controlled drug release. Mesoporous silica nanoparticles (MSNs, which are known for their biocompatibility and high drug-loading capacity, were selected as a model drug container and carrier. The membrane was established by the polyelectrolyte composite method from chitosan (CS which was sensitive to the acidic tumor microenvironment, folic acid-modified CS which recognizes the folate receptor expressed on the tumor cell surface, and a CD44 receptor-targeted polysaccharide hyaluronic acid. We characterized the structure of the nanocomposite as well as the drug release behavior under the control of the pH-sensitive membrane switch and evaluated the antitumor efficacy of the system in vitro. Our results provide a basis for the design and fabrication of novel membrane-controlled nanoparticles with improved tumor-targeting therapy. Keywords: multifunctional, membrane-controlled, natural materials, mesoporous silica nanoparticles, targeted drug delivery

  18. Control of biofouling on reverse osmosis polyamide membranes modified with biocidal nanoparticles and antifouling polymer brushes

    KAUST Repository

    Rahaman, Md. Saifur

    2014-01-01

    Thin-film composite (TFC) polyamide reverse osmosis (RO) membranes are prone to biofouling due to their inherent physicochemical surface properties. In order to address the biofouling problem, we have developed novel surface coatings functionalized with biocidal silver nanoparticles (AgNPs) and antifouling polymer brushes via polyelectrolyte layer-by-layer (LBL) self-assembly. The novel surface coating was prepared with polyelectrolyte LBL films containing poly(acrylic acid) (PAA) and poly(ethylene imine) (PEI), with the latter being either pure PEI or silver nanoparticles coated with PEI (Ag-PEI). The coatings were further functionalized by grafting of polymer brushes, using either hydrophilic poly(sulfobetaine) or low surface energy poly(dimethylsiloxane) (PDMS). The presence of both LBL films and sulfobetaine polymer brushes at the interface significantly increased the hydrophilicity of the membrane surface, while PDMS brushes lowered the membrane surface energy. Overall, all surface modifications resulted in significant reduction of irreversible bacterial cell adhesion. In microbial adhesion tests with E. coli bacteria, a normalized cell adhesion in the range of only 4 to 16% on the modified membrane surfaces was observed. Modified surfaces containing silver nanoparticles also exhibited strong antimicrobial activity. Membranes coated with LBL films of PAA/Ag-PEI achieved over 95% inactivation of bacteria attached to the surface within 1 hour of contact time. Both the antifouling and antimicrobial results suggest the potential of using these novel surface coatings in controlling the fouling of RO membranes. © The Royal Society of Chemistry 2014.

  19. A link between mitotic entry and membrane growth suggests a novel model for cell size control.

    Science.gov (United States)

    Anastasia, Steph D; Nguyen, Duy Linh; Thai, Vu; Meloy, Melissa; MacDonough, Tracy; Kellogg, Douglas R

    2012-04-02

    Addition of new membrane to the cell surface by membrane trafficking is necessary for cell growth. In this paper, we report that blocking membrane traffic causes a mitotic checkpoint arrest via Wee1-dependent inhibitory phosphorylation of Cdk1. Checkpoint signals are relayed by the Rho1 GTPase, protein kinase C (Pkc1), and a specific form of protein phosphatase 2A (PP2A(Cdc55)). Signaling via this pathway is dependent on membrane traffic and appears to increase gradually during polar bud growth. We hypothesize that delivery of vesicles to the site of bud growth generates a signal that is proportional to the extent of polarized membrane growth and that the strength of the signal is read by downstream components to determine when sufficient growth has occurred for initiation of mitosis. Growth-dependent signaling could explain how membrane growth is integrated with cell cycle progression. It could also control both cell size and morphogenesis, thereby reconciling divergent models for mitotic checkpoint function.

  20. Dimensional and Structural Control of Silica Aerogel Membranes for Miniaturized Motionless Gas Pumps.

    Science.gov (United States)

    Zhao, Shanyu; Jiang, Bo; Maeder, Thomas; Muralt, Paul; Kim, Nayoung; Matam, Santhosh Kumar; Jeong, Eunho; Han, Yen-Lin; Koebel, Matthias M

    2015-08-26

    With growing public interest in portable electronics such as micro fuel cells, micro gas total analysis systems, and portable medical devices, the need for miniaturized air pumps with minimal electrical power consumption is on the rise. Thus, the development and downsizing of next-generation thermal transpiration gas pumps has been investigated intensively during the last decades. Such a system relies on a mesoporous membrane that generates a thermomolecular pressure gradient under the action of an applied temperature bias. However, the development of highly miniaturized active membrane materials with tailored porosity and optimized pumping performance remains a major challenge. Here we report a systematic study on the manufacturing of aerogel membranes using an optimized, minimal-shrinkage sol-gel process, leading to low thermal conductivity and high air conductance. This combination of properties results in superior performance for miniaturized thermomolecular air pump applications. The engineering of such aerogel membranes, which implies pore structure control and chemical surface modification, requires both chemical processing know-how and a detailed understanding of the influence of the material properties on the spatial flow rate density. Optimal pumping performance was found for devices with integrated membranes with a density of 0.062 g cm(-3) and an average pore size of 142.0 nm. Benchmarking of such low-density hydrophobic active aerogel membranes gave an air flow rate density of 3.85 sccm·cm(-2) at an operating temperature of 400 °C. Such a silica aerogel membrane based system has shown more than 50% higher pumping performance when compared to conventional transpiration pump membrane materials as well as the ability to withstand higher operating temperatures (up to 440 °C). This study highlights new perspectives for the development of miniaturized thermal transpiration air pumps while offering insights into the fundamentals of molecular pumping in

  1. Electrospun Gelatin/poly(Glycerol Sebacate Membrane with Controlled Release of Antibiotics for Wound Dressing

    Directory of Open Access Journals (Sweden)

    Parisa Shirazaki

    2017-01-01

    Full Text Available Background: The most important risk that threatens the skin wounds is infections. Therefore, fabrication of a membrane as a wound dressing with the ability of antibiotic delivery in a proper delivery rate is especially important. Materials and Methods: Poly(glycerol sebacate (PGS was prepared from sebacic acid and glycerol with 1:1 ratio; then, it was added to gelatin in the 1:3 ratio and was dissolved in 80% (v/v acetic acid, and finally, ciprofloxacin was added in 10% (w/v of polymer solution. The gelatin/PGS membrane was fabricated using an electrospinning method. The membrane was cross-linked using ethyl-3-(3-dimethylaminopropyl carbodiimide ethyl-3-(3-dimethylaminopropylcarbodiim (EDC and N-hydroxysuccinimide (NHS in different time periods to achieve a proper drug release rate. Fourier-transform infrared (FTIR spectroscopy was being used to manifest the peaks of polymers and drug in the membrane. Scanning electron microscopy (SEM was used to evaluate the morphology, fibers diameter, pore size, and porosity before and after crosslinking process. Ultraviolet (UV-visible spectrophotometry was used to show the ciprofloxacin release from the cross-linked membrane. Results: FTIR analysis showed the characteristic peaks of gelatin, PGS, and ciprofloxacin without any added peaks after the crosslinking process. SEM images revealed that nanofibers' size increased during the crosslinking process and porosity was higher than 80% before and after crosslinking process. UV-visible spectrophotometry showed the proper rate of ciprofloxacin release occurred from cross-linked membrane that remaining in EDC/NHS ethanol solution for 120 min. Conclusion: The obtained results suggest that this recently developed gelatin/PGS membrane with controlled release of ciprofloxacin could be a promising biodegradable membrane for wound dressing.

  2. Nitric oxide treatment for the control of reverse osmosis membrane biofouling.

    Science.gov (United States)

    Barnes, Robert J; Low, Jiun Hui; Bandi, Ratnaharika R; Tay, Martin; Chua, Felicia; Aung, Theingi; Fane, Anthony G; Kjelleberg, Staffan; Rice, Scott A

    2015-04-01

    Biofouling remains a key challenge for membrane-based water treatment systems. This study investigated the dispersal potential of the nitric oxide (NO) donor compound, PROLI NONOate, on single- and mixed-species biofilms formed by bacteria isolated from industrial membrane bioreactor and reverse osmosis (RO) membranes. The potential of PROLI NONOate to control RO membrane biofouling was also examined. Confocal microscopy revealed that PROLI NONOate exposure induced biofilm dispersal in all but two of the bacteria tested and successfully dispersed mixed-species biofilms. The addition of 40 μM PROLI NONOate at 24-h intervals to a laboratory-scale RO system led to a 92% reduction in the rate of biofouling (pressure rise over a given period) by a bacterial community cultured from an industrial RO membrane. Confocal microscopy and extracellular polymeric substances (EPS) extraction revealed that PROLI NONOate treatment led to a 48% reduction in polysaccharides, a 66% reduction in proteins, and a 29% reduction in microbial cells compared to the untreated control. A reduction in biofilm surface coverage (59% compared to 98%, treated compared to control) and average thickness (20 μm compared to 26 μm, treated compared to control) was also observed. The addition of PROLI NONOate led to a 22% increase in the time required for the RO module to reach its maximum transmembrane pressure (TMP), further indicating that NO treatment delayed fouling. Pyrosequencing analysis revealed that the NO treatment did not significantly alter the microbial community composition of the membrane biofilm. These results present strong evidence for the application of PROLI NONOate for prevention of RO biofouling. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  3. Ion sieving in graphene oxide membranes via cationic control of interlayer spacing

    Science.gov (United States)

    Chen, Liang; Shi, Guosheng; Shen, Jie; Peng, Bingquan; Zhang, Bowu; Wang, Yuzhu; Bian, Fenggang; Wang, Jiajun; Li, Deyuan; Qian, Zhe; Xu, Gang; Liu, Gongping; Zeng, Jianrong; Zhang, Lijuan; Yang, Yizhou; Zhou, Guoquan; Wu, Minghong; Jin, Wanqin; Li, Jingye; Fang, Haiping

    2017-10-01

    Graphene oxide membranes—partially oxidized, stacked sheets of graphene—can provide ultrathin, high-flux and energy-efficient membranes for precise ionic and molecular sieving in aqueous solution. These materials have shown potential in a variety of applications, including water desalination and purification, gas and ion separation, biosensors, proton conductors, lithium-based batteries and super-capacitors. Unlike the pores of carbon nanotube membranes, which have fixed sizes, the pores of graphene oxide membranes—that is, the interlayer spacing between graphene oxide sheets (a sheet is a single flake inside the membrane)—are of variable size. Furthermore, it is difficult to reduce the interlayer spacing sufficiently to exclude small ions and to maintain this spacing against the tendency of graphene oxide membranes to swell when immersed in aqueous solution. These challenges hinder the potential ion filtration applications of graphene oxide membranes. Here we demonstrate cationic control of the interlayer spacing of graphene oxide membranes with ångström precision using K+, Na+, Ca2+, Li+ or Mg2+ ions. Moreover, membrane spacings controlled by one type of cation can efficiently and selectively exclude other cations that have larger hydrated volumes. First-principles calculations and ultraviolet absorption spectroscopy reveal that the location of the most stable cation adsorption is where oxide groups and aromatic rings coexist. Previous density functional theory computations show that other cations (Fe2+, Co2+, Cu2+, Cd2+, Cr2+ and Pb2+) should have a much stronger cation-π interaction with the graphene sheet than Na+ has, suggesting that other ions could be used to produce a wider range of interlayer spacings.

  4. The Drosophila inner-membrane protein PMI controls crista biogenesis and mitochondrial diameter.

    Science.gov (United States)

    Macchi, Marc; El Fissi, Najla; Tufi, Roberta; Bentobji, Mélanie; Liévens, Jean-Charles; Martins, L Miguel; Royet, Julien; Rival, Thomas

    2013-02-01

    Cristae are mitochondrial inner-membrane structures that concentrate respiratory chain complexes and hence regulate ATP production. Mechanisms controlling crista morphogenesis are poorly understood and few crista determinants have been identified. Among them are the Mitofilins that are required to establish crista junctions and ATP-synthase subunits that bend the membrane at the tips of the cristae. We report here the phenotypic consequences associated with the in vivo inactivation of the inner-membrane protein Pantagruelian Mitochondrion I (PMI) both at the scale of the whole organism, and at the level of mitochondrial ultrastructure and function. We show that flies in which PMI is genetically inactivated experience synaptic defects and have a reduced life span. Electron microscopy analysis of the inner-membrane morphology demonstrates that loss of PMI function increases the average length of mitochondrial cristae in embryonic cells. This phenotype is exacerbated in adult neurons in which cristae form a dense tangle of elongated membranes. Conversely, we show that PMI overexpression is sufficient to reduce crista length in vivo. Finally, these crista defects are associated with impaired respiratory chain activity and increases in the level of reactive oxygen species. Since PMI and its human orthologue TMEM11 are regulators of mitochondrial morphology, our data suggest that, by controlling crista length, PMI influences mitochondrial diameter and tubular shape.

  5. Higher curvature supergravity and cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Ferrara, Sergio [Th-Ph Department, CERN, Geneva (Switzerland); U.C.L.A., Los Angeles, CA (United States); INFN - LNF, Frascati (Italy); Sagnotti, Augusto [Scuola Normale Superiore, Pisa (Italy); INFN, Pisa (Italy)

    2016-04-15

    In this contribution we describe dual higher-derivative formulations of some cosmological models based on supergravity. Work in this direction started with the R + R{sup 2} Starobinsky model, whose supersymmetric extension was derived in the late 80's and was recently revived in view of new CMB data. Models dual to higher-derivative theories are subject to more restrictions than their bosonic counterparts or standard supergravity. The three sections are devoted to a brief description of R + R{sup 2} supergravity, to a scale invariant R{sup 2} supergravity and to theories with a nilpotent curvature, whose duals describe non-linear realizations (in the form of a Volkov-Akulov constrained superfield) coupled to supergravity. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  6. SLED phenomenology: curvature vs. volume

    International Nuclear Information System (INIS)

    Niedermann, Florian; Schneider, Robert

    2016-01-01

    We assess the question whether the SLED (Supersymmetric Large Extra Dimensions) model admits phenomenologically viable solutions with 4D maximal symmetry. We take into account a finite brane width and a scale invariance (SI) breaking dilaton-brane coupling, both of which should be included in a realistic setup. Provided that the brane tension and the microscopic size of the brane take generic values set by the fundamental bulk Planck scale, we find that either the 4D curvature or the size of the extra dimensions is unacceptably large. Since this result is independent of the dilaton-brane couplings, it provides the biggest challenge to the SLED program. In addition, to quantify its potential with respect to the cosmological constant problem, we infer the amount of tuning on model parameters required to obtain a sufficiently small 4D curvature. A first answer was recently given in http://dx.doi.org/10.1007/JHEP02(2016)025, showing that 4D flat solutions are only ensured in the SI case by imposing a tuning relation, even if a brane-localized flux is included. In this companion paper, we find that the tuning can in fact be avoided for certain SI breaking brane-dilaton couplings, but only at the price of worsening the phenomenological problem. Our results are obtained by solving the full coupled Einstein-dilaton system in a completely consistent way. The brane width is implemented using a well-known ring regularization. In passing, we note that for the couplings considered here the results of http://dx.doi.org/10.1007/JHEP02(2016)025 (which only treated infinitely thin branes) are all consistently recovered in the thin brane limit, and how this can be reconciled with the concerns about their correctness, recently brought up in http://dx.doi.org/10.1007/JHEP01(2016)017.

  7. Ultra-thin and strong formvar-based membranes with controlled porosity for micro- and nano-scale systems

    Science.gov (United States)

    Auchter, Eric; Marquez, Justin; Stevens, Garrison; Silva, Rebecca; Mcculloch, Quinn; Guengerich, Quintessa; Blair, Andrew; Litchfield, Sebastian; Li, Nan; Sheehan, Chris; Chamberlin, Rebecca; Yarbro, Stephen L.; Dervishi, Enkeleda

    2018-05-01

    We present a methodology for developing ultra-thin and strong formvar-based membranes with controlled morphologies. Formvar is a thin hydrophilic and oleophilic polymer inert to most chemicals and resistant to radiation. The formvar-based membranes are viable materials as support structures in micro- and macro-scale systems depending on thinness and porosity control. Tunable sub-micron thick porous membranes with 20%–65% porosity were synthesized by controlling the ratios of formvar, glycerol, and chloroform. This synthesis process does not require complex separation or handling methods and allows for the production of strong, thin, and porous formvar-based membranes. An expansive array of these membrane characterizations including chemical compatibility, mechanical responses, wettability, as well as the mathematical simulations as a function of porosity has been presented. The wide range of chemical compatibility allows for membrane applications in various environments, where other polymers would not be suitable. Our formvar-based membranes were found to have an elastic modulus of 7.8 GPa, a surface free energy of 50 mN m‑1 and an average thickness of 125 nm. Stochastic model simulations indicate that formvar with the porosity of ∼50% is the optimal membrane formulation, allowing the most material transfer across the membrane while also withstanding the highest simulated pressure loadings before tearing. Development of novel, resilient and versatile membranes with controlled porosity offers a wide range of exciting applications in the fields of nanoscience, microfluidics, and MEMS.

  8. The application of nitric oxide to control biofouling of membrane bioreactors.

    Science.gov (United States)

    Luo, Jinxue; Zhang, Jinsong; Barnes, Robert J; Tan, Xiaohui; McDougald, Diane; Fane, Anthony G; Zhuang, Guoqiang; Kjelleberg, Staffan; Cohen, Yehuda; Rice, Scott A

    2015-05-01

    A novel strategy to control membrane bioreactor (MBR) biofouling using the nitric oxide (NO) donor compound PROLI NONOate was examined. When the biofilm was pre-established on membranes at transmembrane pressure (TMP) of 88-90 kPa, backwashing of the membrane module with 80 μM PROLI NONOate for 45 min once daily for 37 days reduced the fouling resistance (Rf ) by 56%. Similarly, a daily, 1 h exposure of the membrane to 80 μM PROLI NONOate from the commencement of MBR operation for 85 days resulted in reduction of the TMP and Rf by 32.3% and 28.2%. The microbial community in the control MBR was observed to change from days 71 to 85, which correlates with the rapid TMP increase. Interestingly, NO-treated biofilms at 85 days had a higher similarity with the control biofilms at 71 days relative to the control biofilms at 85 days, indicating that the NO treatment delayed the development of biofilm bacterial community. Despite this difference, sequence analysis indicated that NO treatment did not result in a significant shift in the dominant fouling species. Confocal microscopy revealed that the biomass of biopolymers and microorganisms in biofilms were all reduced on the PROLI NONOate-treated membranes, where there were reductions of 37.7% for proteins and 66.7% for microbial cells, which correlates with the reduction in TMP. These results suggest that NO treatment could be a promising strategy to control biofouling in MBRs. © 2015 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

  9. Dynamic water management of polymer electrolyte membrane fuel cells using intermittent RH control

    KAUST Repository

    Hussaini, I.S.

    2010-06-01

    A novel method of water management of polymer electrolyte membrane (PEM) fuel cells using intermittent humidification is presented in this study. The goal is to maintain the membrane close to full humidification, while eliminating channel flooding. The entire cycle is divided into four stages: saturation and de-saturation of the gas diffusion layer followed by de-hydration and hydration of membrane. By controlling the duration of dry and humid flows, it is shown that the cell voltage can be maintained within a narrow band. The technique is applied on experimental test cells using both plain and hydrophobic materials for the gas diffusion layer and an improvement in performance as compared to steady humidification is demonstrated. Duration of dry and humid flows is determined experimentally for several operating conditions. © 2010 Elsevier B.V. All rights reserved.

  10. Control of directed cell migration in vivo by membrane-to-cortex attachment.

    Directory of Open Access Journals (Sweden)

    Alba Diz-Muñoz

    2010-11-01

    Full Text Available Cell shape and motility are primarily controlled by cellular mechanics. The attachment of the plasma membrane to the underlying actomyosin cortex has been proposed to be important for cellular processes involving membrane deformation. However, little is known about the actual function of membrane-to-cortex attachment (MCA in cell protrusion formation and migration, in particular in the context of the developing embryo. Here, we use a multidisciplinary approach to study MCA in zebrafish mesoderm and endoderm (mesendoderm germ layer progenitor cells, which migrate using a combination of different protrusion types, namely, lamellipodia, filopodia, and blebs, during zebrafish gastrulation. By interfering with the activity of molecules linking the cortex to the membrane and measuring resulting changes in MCA by atomic force microscopy, we show that reducing MCA in mesendoderm progenitors increases the proportion of cellular blebs and reduces the directionality of cell migration. We propose that MCA is a key parameter controlling the relative proportions of different cell protrusion types in mesendoderm progenitors, and thus is key in controlling directed migration during gastrulation.

  11. Controllable synthesis of single-walled carbon nanotube framework membranes and capsules.

    Science.gov (United States)

    Song, Changsik; Kwon, Taeyun; Han, Jae-Hee; Shandell, Mia; Strano, Michael S

    2009-12-01

    Controlling the morphology of membrane components at the nanometer scale is central to many next-generation technologies in water purification, gas separation, fuel cell, and nanofiltration applications. Toward this end, we report the covalent assembly of single-walled carbon nanotubes (SWNTs) into three-dimensional framework materials with intertube pores controllable by adjusting the size of organic linker molecules. The frameworks are fashioned into multilayer membranes possessing linker spacings from 1.7 to 3.0 nm, and the resulting framework films were characterized, including transport properties. Nanoindentation measurements by atomic force microscopy show that the spring constant of the SWNT framework film (22.6 +/- 1.2 N/m) increased by a factor of 2 from the control value (10.4 +/- 0.1 N/m). The flux ratio comparison in a membrane-permeation experiment showed that larger spacer sizes resulted in larger pore structures. This synthetic method was equally efficient on silica microspheres, which could then be etched to create all-SWNT framework, hollow capsules approximately 5 mum in diameter. These hollow capsules are permeable to organic and inorganic reagents, allowing one to form inorganic nanoparticles, for example, that become entrapped within the capsule. The ability to encapsulate functional nanomaterials inside perm-selective SWNT cages and membranes may find applications in new adsorbents, novel catalysts, and drug delivery vehicles.

  12. Curvature recognition and force generation in phagocytosis

    Directory of Open Access Journals (Sweden)

    Prassler Jana

    2010-12-01

    Full Text Available Abstract Background The uptake of particles by actin-powered invagination of the plasma membrane is common to protozoa and to phagocytes involved in the immune response of higher organisms. The question addressed here is how a phagocyte may use geometric cues to optimize force generation for the uptake of a particle. We survey mechanisms that enable a phagocyte to remodel actin organization in response to particles of complex shape. Results Using particles that consist of two lobes separated by a neck, we found that Dictyostelium cells transmit signals concerning the curvature of a surface to the actin system underlying the plasma membrane. Force applied to a concave region can divide a particle in two, allowing engulfment of the portion first encountered. The phagosome membrane that is bent around the concave region is marked by a protein containing an inverse Bin-Amphiphysin-Rvs (I-BAR domain in combination with an Src homology (SH3 domain, similar to mammalian insulin receptor tyrosine kinase substrate p53. Regulatory proteins enable the phagocyte to switch activities within seconds in response to particle shape. Ras, an inducer of actin polymerization, is activated along the cup surface. Coronin, which limits the lifetime of actin structures, is reversibly recruited to the cup, reflecting a program of actin depolymerization. The various forms of myosin-I are candidate motor proteins for force generation in particle uptake, whereas myosin-II is engaged only in retracting a phagocytic cup after a switch to particle release. Thus, the constriction of a phagocytic cup differs from the contraction of a cleavage furrow in mitosis. Conclusions Phagocytes scan a particle surface for convex and concave regions. By modulating the spatiotemporal pattern of actin organization, they are capable of switching between different modes of interaction with a particle, either arresting at a concave region and applying force in an attempt to sever the particle

  13. Nitric oxide partitioning into mitochondrial membranes and the control of respiration at cytochrome c oxidase

    Science.gov (United States)

    Shiva, Sruti; Brookes, Paul S.; Patel, Rakesh P.; Anderson, Peter G.; Darley-Usmar, Victor M.

    2001-06-01

    An emerging and important site of action for nitric oxide (NO) within cells is the mitochondrial inner membrane, where NO binds to and inhibits members of the electron transport chain, complex III and cytochrome c oxidase. Although it is known that inhibition of cytochrome c oxidase by NO is competitive with O2, the mechanisms that underlie this phenomenon remain unclear, and the impact of both NO and O2 partitioning into biological membranes has not been considered. These properties are particularly interesting because physiological O2 tensions can vary widely, with NO having a greater inhibitory effect at low O2 tensions (mitochondrial membranes in the absence of substrate, in a nonsaturable process that is O2 dependent. This consumption modulates inhibition of cytochrome c oxidase by NO and is enhanced by the addition of exogenous membranes. From these data, it is evident that the partition of NO into mitochondrial membranes has a major impact on the ability of NO to control mitochondrial respiration. The implications of this conclusion are discussed in the context of mitochondrial lipid:protein ratios and the importance of NO as a regulator of respiration in pathophysiology.

  14. Detection and quantification through a lipid membrane using the molecularly controlled semiconductor resistor.

    Science.gov (United States)

    Bavli, Danny; Tkachev, Maria; Piwonski, Hubert; Capua, Eyal; de Albuquerque, Ian; Bensimon, David; Haran, Gilad; Naaman, Ron

    2012-01-10

    The detection of covalent and noncovalent binding events between molecules and biomembranes is a fundamental goal of contemporary biochemistry and analytical chemistry. Currently, such studies are performed routinely using fluorescence methods, surface-plasmon resonance spectroscopy, and electrochemical methods. However, there is still a need for novel sensitive miniaturizable detection methods where the sample does not have to be transferred to the sensor, but the sensor can be brought into contact with the sample studied. We present a novel approach for detection and quantification of processes occurring on the surface of a lipid bilayer membrane, by monitoring the current change through the n-type GaAs-based molecularly controlled semiconductor resistor (MOCSER), on which the membrane is adsorbed. Since GaAs is susceptible to etching in an aqueous environment, a protective thin film of methoxysilane was deposited on the device. The system was found to be sensitive enough to allow monitoring changes in pH and in the concentration of amino acids in aqueous solution on top of the membrane. When biotinylated lipids were incorporated into the membrane, it was possible to monitor the binding of streptavidin or avidin. The device modified with biotin-streptavidin complex was capable of detecting the binding of streptavidin antibodies to immobilized streptavidin with high sensitivity and selectivity. The response depends on the charge on the analyte. These results open the way to facile electrical detection of protein-membrane interactions.

  15. Fluorescent in situ folding control for rapid optimization of cell-free membrane protein synthesis.

    Directory of Open Access Journals (Sweden)

    Annika Müller-Lucks

    Full Text Available Cell-free synthesis is an open and powerful tool for high-yield protein production in small reaction volumes predestined for high-throughput structural and functional analysis. Membrane proteins require addition of detergents for solubilization, liposomes, or nanodiscs. Hence, the number of parameters to be tested is significantly higher than with soluble proteins. Optimization is commonly done with respect to protein yield, yet without knowledge of the protein folding status. This approach contains a large inherent risk of ending up with non-functional protein. We show that fluorophore formation in C-terminal fusions with green fluorescent protein (GFP indicates the folding state of a membrane protein in situ, i.e. within the cell-free reaction mixture, as confirmed by circular dichroism (CD, proteoliposome reconstitution and functional assays. Quantification of protein yield and in-gel fluorescence intensity imply suitability of the method for membrane proteins of bacterial, protozoan, plant, and mammalian origin, representing vacuolar and plasma membrane localization, as well as intra- and extracellular positioning of the C-terminus. We conclude that GFP-fusions provide an extension to cell-free protein synthesis systems eliminating the need for experimental folding control and, thus, enabling rapid optimization towards membrane protein quality.

  16. Nonlinear observer-based Lyapunov boundary control of distributed heat transfer mechanisms for membrane distillation plant

    KAUST Repository

    Eleiwi, Fadi

    2016-09-19

    This paper presents a nonlinear observer-based Lyapunov control for a membrane distillation (MD) process. The control considers the inlet temperatures of the feed and the permeate solutions as inputs, transforming it to boundary control process, and seeks to maintain the temperature difference along the membrane boundaries around a sufficient level to promote water production. MD process is modeled with advection diffusion equation model in two dimensions, where the diffusion and convection heat transfer mechanisms are best described. Model analysis, effective order reduction and parameters physical interpretation, are provided. Moreover, a nonlinear observer has been designed to provide the control with estimates of the temperature evolution at each time instant. In addition, physical constraints are imposed on the control to have an acceptable range of feasible inputs, and consequently, better energy consumption. Numerical simulations for the complete process with real membrane parameter values are provided, in addition to detailed explanations for the role of the controller and the observer. (C) 2016 Elsevier Ltd. All rights reserved.

  17. Optimal design and control of solar driven air gap membrane distillation desalination systems

    International Nuclear Information System (INIS)

    Chen, Yih-Hang; Li, Yu-Wei; Chang, Hsuan

    2012-01-01

    Highlights: ► Air gap membrane distillation unit was used in the desalination plants. ► Aspen Custom Molder was used to simulate each unit of desalination plants. ► Design parameters were investigated to obtain the minimum total annual cost. ► The control structure was proposed to operate desalination plants all day long. -- Abstract: A solar heated membrane distillation desalination system is constructed of solar collectors and membrane distillation devices for increasing pure water productivity. This technically and economically feasible system is designed to use indirect solar heat to drive membrane distillation processes to overcome the unstable supply of solar radiation from sunrise to sunset. The solar heated membrane distillation desalination system in the present study consisted of hot water storage devices, heat exchangers, air gap membrane distillation units, and solar collectors. Aspen Custom Molder (ACM) software was used to model and simulate each unit and establish the cost function of a desalination plant. From Design degree of freedom (DOF) analysis, ten design parameters were investigated to obtain the minimum total annual cost (TAC) with fixed pure water production rate. For a given solar energy density profile of typical summer weather, the minimal TAC per 1 m 3 pure water production can be found at 500 W/m 2 by varying the solar energy intensity. Therefore, we proposed two modes for controlling the optimal design condition of the desalination plant; day and night. In order to widen the operability range of the plant, the sensitivity analysis was used to retrofit the original design point to lower the effluent temperature from the solar collector by increasing the hot water recycled stream. The simulation results show that the pure water production can be maintained at a very stable level whether in sunny or cloudy weather.

  18. Ion-Exchanged SAPO-34 Membranes for Krypton-Xenon Separation: Control of Permeation Properties and Fabrication of Hollow Fiber Membranes.

    Science.gov (United States)

    Kwon, Yeon Hye; Min, Byunghyun; Yang, Shaowei; Koh, Dong-Yeun; Bhave, Ramesh R; Nair, Sankar

    2018-02-21

    Separation of radioisotope 85 Kr from 136 Xe is of importance in used nuclear fuel reprocessing. Membrane separation based on zeolite molecular sieves such as chabazite SAPO-34 is an attractive alternative to energy-intensive cryogenic distillation. We report the synthesis of SAPO-34 membranes with considerably enhanced performance via thickness reduction based upon control of a steam-assisted vapor-solid conversion technique followed by ion exchange with alkali metal cations. The reduction of membrane thickness leads to a large increase in Kr permeance from 7.5 to 26.3 gas permeation units (GPU) with ideal Kr/Xe selectivities >20 at 298 K. Cation-exchanged membranes show large (>50%) increases in selectivity at ambient or slight subambient conditions. The adsorption, diffusion, and permeation characteristics of ion-exchanged SAPO-34 materials and membranes are investigated in detail, with potassium-exchanged SAPO-34 membranes showing particularly attractive performance. We then demonstrate the fabrication of selective SAPO-34 membranes on α-alumina hollow fibers.

  19. Effect of Graphene and Fullerene Nanofillers on Controlling the Pore Size and Physicochemical Properties of Chitosan Nanocomposite Mesoporous Membranes

    Directory of Open Access Journals (Sweden)

    Irene S. Fahim

    2015-01-01

    Full Text Available Chitosan (CS nanocomposite mesoporous membranes were fabricated by mixing CS with graphene (G and fullerene (F nanofillers, and the diffusion properties through CS membranes were studied. In addition, in order to enhance the binding between the internal CS chains, physical cross-linking of CS by sodium tripolyphosphate (TPP was carried out. F and G with different weight percentages (0.1, 0.5, and 1 wt.% were added on physically cross-linked chitosan (CLCS and non-cross-linked chitosan (NCLCS membranes by wet mixing. Permeability and diffusion time of CLCS and NCLCS membranes at different temperatures were investigated. The results revealed that the pore size of all fabricated CS membranes is in the mesoporous range (i.e., 2–50 nm. Moreover, the addition of G and F nanofillers to CLCS and NCLCS solutions aided in controlling the CS membranes’ pore size and was found to enhance the barrier effect of the CS membranes either by blocking the internal pores or decreasing the pore size. These results illustrate the significant possibility of controlling the pore size of CS membranes by cross-linking and more importantly the careful selection of nanofillers and their percentage within the CS membranes. Controlling the pore size of CS membranes is a fundamental factor in packaging applications and membrane technology.

  20. Weyl tensors for asymmetric complex curvatures

    International Nuclear Information System (INIS)

    Oliveira, C.G.

    Considering a second rank Hermitian field tensor and a general Hermitian connection the associated complex curvature tensor is constructed. The Weyl tensor that corresponds to this complex curvature is determined. The formalism is applied to the Weyl unitary field theory and to the Moffat gravitational theory. (Author) [pt

  1. The curvature function in general relativity

    International Nuclear Information System (INIS)

    Hall, G S; MacNay, Lucy

    2006-01-01

    A function, here called the curvature function, is defined and which is constructed explicitly from the type (0, 4) curvature tensor. Although such a function may be defined for any manifold admitting a metric, attention is here concentrated on this function on a spacetime. Some properties of this function are explored and compared with a previous discussion of it given by Petrov

  2. Directable weathering of concave rock using curvature estimation.

    Science.gov (United States)

    Jones, Michael D; Farley, McKay; Butler, Joseph; Beardall, Matthew

    2010-01-01

    We address the problem of directable weathering of exposed concave rock for use in computer-generated animation or games. Previous weathering models that admit concave surfaces are computationally inefficient and difficult to control. In nature, the spheroidal and cavernous weathering rates depend on the surface curvature. Spheroidal weathering is fastest in areas with large positive mean curvature and cavernous weathering is fastest in areas with large negative mean curvature. We simulate both processes using an approximation of mean curvature on a voxel grid. Both weathering rates are also influenced by rock durability. The user controls rock durability by editing a durability graph before and during weathering simulation. Simulations of rockfall and colluvium deposition further improve realism. The profile of the final weathered rock matches the shape of the durability graph up to the effects of weathering and colluvium deposition. We demonstrate the top-down directability and visual plausibility of the resulting model through a series of screenshots and rendered images. The results include the weathering of a cube into a sphere and of a sheltered inside corner into a cavern as predicted by the underlying geomorphological models.

  3. Membrane-bound organelles versus membrane-less compartments and their control of anabolic pathways in Drosophila

    NARCIS (Netherlands)

    Aguilera-Gomez, Angelica; Rabouille, Catherine

    2017-01-01

    Classically, we think of cell compartmentalization as being achieved by membrane-bound organelles. It has nevertheless emerged that membrane-less assemblies also largely contribute to this compartmentalization. Here, we compare the characteristics of both types of compartmentalization in term of

  4. Zeta potential control in decontamination with inorganic membranes and inorganic adsorbents

    Energy Technology Data Exchange (ETDEWEB)

    Andalaft, E; Vega, R; Correa, M; Araya, R; Loyola, P [Comision Chilena de Energia Nuclear, Santiago (Chile)

    1997-02-01

    The application of some advanced separation processes such as microfiltration and ultrafiltration, electroosmosis and electrodialysis for treating nuclear waste from different aqueous streams is under examination at the Chilean Commission for Nuclear Energy. The application of these techniques can be extended to regular industrial wastes when economically advisable. This report deals mainly with electrodialysis, electroosmosis and adsorption with inorganic materials. Special attention is paid to zeta potential control as a driving factor to electroosmosis. For radioactive contaminants that are present in the form of cations, anions, non-ionic solutions, colloids and suspended matter, appropriate combination of the processes may considerably increase the efficiency of processes used. As an example, colloids and suspended particles may be retained in porous ceramic membranes by nanofiltration, ultrafiltration or microfiltration depending on the particle size of the particles. The control of zeta potential by acting in the solid phase or else on the liquid phase has been studied; a mathematical model to predict electrodialysis data has been developed, and finally, the use of a home-made inorganic adsorbent illustrated. The effect of gamma irradiation on the membranes has also been studied. Properties such as salt retention, water flux and pore size diameter determined on both organic and inorganic membranes before and after irradiation indicate deterioration of the organic membrane. (author). 13 refs, 15 figs, 2 tabs.

  5. Light-activated control of protein channel assembly mediated by membrane mechanics

    Science.gov (United States)

    Miller, David M.; Findlay, Heather E.; Ces, Oscar; Templer, Richard H.; Booth, Paula J.

    2016-12-01

    Photochemical processes provide versatile triggers of chemical reactions. Here, we use a photoactivated lipid switch to modulate the folding and assembly of a protein channel within a model biological membrane. In contrast to the information rich field of water-soluble protein folding, there is only a limited understanding of the assembly of proteins that are integral to biological membranes. It is however possible to exploit the foreboding hydrophobic lipid environment and control membrane protein folding via lipid bilayer mechanics. Mechanical properties such as lipid chain lateral pressure influence the insertion and folding of proteins in membranes, with different stages of folding having contrasting sensitivities to the bilayer properties. Studies to date have relied on altering bilayer properties through lipid compositional changes made at equilibrium, and thus can only be made before or after folding. We show that light-activation of photoisomerisable di-(5-[[4-(4-butylphenyl)azo]phenoxy]pentyl)phosphate (4-Azo-5P) lipids influences the folding and assembly of the pentameric bacterial mechanosensitive channel MscL. The use of a photochemical reaction enables the bilayer properties to be altered during folding, which is unprecedented. This mechanical manipulation during folding, allows for optimisation of different stages of the component insertion, folding and assembly steps within the same lipid system. The photochemical approach offers the potential to control channel assembly when generating synthetic devices that exploit the mechanosensitive protein as a nanovalve.

  6. BSM-MBR: a benchmark simulation model to compare control and operational strategies for membrane bioreactors.

    Science.gov (United States)

    Maere, Thomas; Verrecht, Bart; Moerenhout, Stefanie; Judd, Simon; Nopens, Ingmar

    2011-03-01

    A benchmark simulation model for membrane bioreactors (BSM-MBR) was developed to evaluate operational and control strategies in terms of effluent quality and operational costs. The configuration of the existing BSM1 for conventional wastewater treatment plants was adapted using reactor volumes, pumped sludge flows and membrane filtration for the water-sludge separation. The BSM1 performance criteria were extended for an MBR taking into account additional pumping requirements for permeate production and aeration requirements for membrane fouling prevention. To incorporate the effects of elevated sludge concentrations on aeration efficiency and costs a dedicated aeration model was adopted. Steady-state and dynamic simulations revealed BSM-MBR, as expected, to out-perform BSM1 for effluent quality, mainly due to complete retention of solids and improved ammonium removal from extensive aeration combined with higher biomass levels. However, this was at the expense of significantly higher operational costs. A comparison with three large-scale MBRs showed BSM-MBR energy costs to be realistic. The membrane aeration costs for the open loop simulations were rather high, attributed to non-optimization of BSM-MBR. As proof of concept two closed loop simulations were run to demonstrate the usefulness of BSM-MBR for identifying control strategies to lower operational costs without compromising effluent quality. Copyright © 2011 Elsevier Ltd. All rights reserved.

  7. Zeta potential control in decontamination with inorganic membranes and inorganic adsorbents

    International Nuclear Information System (INIS)

    Andalaft, E.; Vega, R.; Correa, M.; Araya, R.; Loyola, P.

    1997-01-01

    The application of some advanced separation processes such as microfiltration and ultrafiltration, electroosmosis and electrodialysis for treating nuclear waste from different aqueous streams is under examination at the Chilean Commission for Nuclear Energy. The application of these techniques can be extended to regular industrial wastes when economically advisable. This report deals mainly with electrodialysis, electroosmosis and adsorption with inorganic materials. Special attention is paid to zeta potential control as a driving factor to electroosmosis. For radioactive contaminants that are present in the form of cations, anions, non-ionic solutions, colloids and suspended matter, appropriate combination of the processes may considerably increase the efficiency of processes used. As an example, colloids and suspended particles may be retained in porous ceramic membranes by nanofiltration, ultrafiltration or microfiltration depending on the particle size of the particles. The control of zeta potential by acting in the solid phase or else on the liquid phase has been studied; a mathematical model to predict electrodialysis data has been developed, and finally, the use of a home-made inorganic adsorbent illustrated. The effect of gamma irradiation on the membranes has also been studied. Properties such as salt retention, water flux and pore size diameter determined on both organic and inorganic membranes before and after irradiation indicate deterioration of the organic membrane. (author). 13 refs, 15 figs, 2 tabs

  8. Integrating 3D seismic curvature and curvature gradient attributes for fracture characterization: Methodologies and interpretational implications

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Dengliang

    2013-03-01

    In 3D seismic interpretation, curvature is a popular attribute that depicts the geometry of seismic reflectors and has been widely used to detect faults in the subsurface; however, it provides only part of the solutions to subsurface structure analysis. This study extends the curvature algorithm to a new curvature gradient algorithm, and integrates both algorithms for fracture detection using a 3D seismic test data set over Teapot Dome (Wyoming). In fractured reservoirs at Teapot Dome known to be formed by tectonic folding and faulting, curvature helps define the crestal portion of the reservoirs that is associated with strong seismic amplitude and high oil productivity. In contrast, curvature gradient helps better define the regional northwest-trending and the cross-regional northeast-trending lineaments that are associated with weak seismic amplitude and low oil productivity. In concert with previous reports from image logs, cores, and outcrops, the current study based on an integrated seismic curvature and curvature gradient analysis suggests that curvature might help define areas of enhanced potential to form tensile fractures, whereas curvature gradient might help define zones of enhanced potential to develop shear fractures. In certain fractured reservoirs such as at Teapot Dome where faulting and fault-related folding contribute dominantly to the formation and evolution of fractures, curvature and curvature gradient attributes can be potentially applied to differentiate fracture mode, to predict fracture intensity and orientation, to detect fracture volume and connectivity, and to model fracture networks.

  9. Superhydrophilic Thin-Film Composite Forward Osmosis Membranes for Organic Fouling Control: Fouling Behavior and Antifouling Mechanisms

    KAUST Repository

    Tiraferri, Alberto

    2012-10-16

    This study investigates the fouling behavior and fouling resistance of superhydrophilic thin-film composite forward osmosis membranes functionalized with surface-tailored nanoparticles. Fouling experiments in both forward osmosis and reverse osmosis modes are performed with three model organic foulants: alginate, bovine serum albumin, and Suwannee river natural organic matter. A solution comprising monovalent and divalent salts is employed to simulate the solution chemistry of typical wastewater effluents. Reduced fouling is consistently observed for the superhydrophilic membranes compared to control thin-film composite polyamide membranes, in both reverse and forward osmosis modes. The fouling resistance and cleaning efficiency of the functionalized membranes is particularly outstanding in forward osmosis mode where the driving force for water flux is an osmotic pressure difference. To understand the mechanism of fouling, the intermolecular interactions between the foulants and the membrane surface are analyzed by direct force measurement using atomic force microscopy. Lower adhesion forces are observed for the superhydrophilic membranes compared to the control thin-film composite polyamide membranes. The magnitude and distribution of adhesion forces for the different membrane surfaces suggest that the antifouling properties of the superhydrophilic membranes originate from the barrier provided by the tightly bound hydration layer at their surface, as well as from the neutralization of the native carboxyl groups of thin-film composite polyamide membranes. © 2012 American Chemical Society.

  10. Superhydrophilic thin-film composite forward osmosis membranes for organic fouling control: fouling behavior and antifouling mechanisms.

    Science.gov (United States)

    Tiraferri, Alberto; Kang, Yan; Giannelis, Emmanuel P; Elimelech, Menachem

    2012-10-16

    This study investigates the fouling behavior and fouling resistance of superhydrophilic thin-film composite forward osmosis membranes functionalized with surface-tailored nanoparticles. Fouling experiments in both forward osmosis and reverse osmosis modes are performed with three model organic foulants: alginate, bovine serum albumin, and Suwannee river natural organic matter. A solution comprising monovalent and divalent salts is employed to simulate the solution chemistry of typical wastewater effluents. Reduced fouling is consistently observed for the superhydrophilic membranes compared to control thin-film composite polyamide membranes, in both reverse and forward osmosis modes. The fouling resistance and cleaning efficiency of the functionalized membranes is particularly outstanding in forward osmosis mode where the driving force for water flux is an osmotic pressure difference. To understand the mechanism of fouling, the intermolecular interactions between the foulants and the membrane surface are analyzed by direct force measurement using atomic force microscopy. Lower adhesion forces are observed for the superhydrophilic membranes compared to the control thin-film composite polyamide membranes. The magnitude and distribution of adhesion forces for the different membrane surfaces suggest that the antifouling properties of the superhydrophilic membranes originate from the barrier provided by the tightly bound hydration layer at their surface, as well as from the neutralization of the native carboxyl groups of thin-film composite polyamide membranes.

  11. Osmotically driven drug delivery through remote-controlled magnetic nanocomposite membranes

    KAUST Repository

    Zaher, A.

    2015-09-29

    Implantable drug delivery systems can provide long-term reliability, controllability, and biocompatibility, and have been used in many applications, including cancer pain and non-malignant pain treatment. However, many of the available systems are limited to zero-order, inconsistent, or single burst event drug release. To address these limitations, we demonstrate prototypes of a remotely operated drug delivery device that offers controllability of drug release profiles, using osmotic pumping as a pressure source and magnetically triggered membranes as switchable on-demand valves. The membranes are made of either ethyl cellulose, or the proposed stronger cellulose acetate polymer, mixed with thermosensitive poly(N-isopropylacrylamide) hydrogel and superparamagnetic iron oxide particles. The prototype devices\\' drug diffusion rates are on the order of 0.5–2 μg/h for higher release rate designs, and 12–40 ng/h for lower release rates, with maximum release ratios of 4.2 and 3.2, respectively. The devices exhibit increased drug delivery rates with higher osmotic pumping rates or with magnetically increased membrane porosity. Furthermore, by vapor deposition of a cyanoacrylate layer, a drastic reduction of the drug delivery rate from micrograms down to tens of nanograms per hour is achieved. By utilizing magnetic membranes as the valve-control mechanism, triggered remotely by means of induction heating, the demonstrated drug delivery devices benefit from having the power source external to the system, eliminating the need for a battery. These designs multiply the potential approaches towards increasing the on-demand controllability and customizability of drug delivery profiles in the expanding field of implantable drug delivery systems, with the future possibility of remotely controlling the pressure source.

  12. Osmotically driven drug delivery through remote-controlled magnetic nanocomposite membranes

    KAUST Repository

    Zaher, Amir; Li, S.; Wolf, K. T.; Pirmoradi, F. N.; Yassine, Omar; Lin, L.; Khashab, Niveen M.; Kosel, Jü rgen

    2015-01-01

    Implantable drug delivery systems can provide long-term reliability, controllability, and biocompatibility, and have been used in many applications, including cancer pain and non-malignant pain treatment. However, many of the available systems are limited to zero-order, inconsistent, or single burst event drug release. To address these limitations, we demonstrate prototypes of a remotely operated drug delivery device that offers controllability of drug release profiles, using osmotic pumping as a pressure source and magnetically triggered membranes as switchable on-demand valves. The membranes are made of either ethyl cellulose, or the proposed stronger cellulose acetate polymer, mixed with thermosensitive poly(N-isopropylacrylamide) hydrogel and superparamagnetic iron oxide particles. The prototype devices' drug diffusion rates are on the order of 0.5–2 μg/h for higher release rate designs, and 12–40 ng/h for lower release rates, with maximum release ratios of 4.2 and 3.2, respectively. The devices exhibit increased drug delivery rates with higher osmotic pumping rates or with magnetically increased membrane porosity. Furthermore, by vapor deposition of a cyanoacrylate layer, a drastic reduction of the drug delivery rate from micrograms down to tens of nanograms per hour is achieved. By utilizing magnetic membranes as the valve-control mechanism, triggered remotely by means of induction heating, the demonstrated drug delivery devices benefit from having the power source external to the system, eliminating the need for a battery. These designs multiply the potential approaches towards increasing the on-demand controllability and customizability of drug delivery profiles in the expanding field of implantable drug delivery systems, with the future possibility of remotely controlling the pressure source.

  13. Mechanical collapse of confined fluid membrane vesicles.

    Science.gov (United States)

    Rim, Jee E; Purohit, Prashant K; Klug, William S

    2014-11-01

    Compact cylindrical and spherical invaginations are common structural motifs found in cellular and developmental biology. To understand the basic physical mechanisms that produce and maintain such structures, we present here a simple model of vesicles in confinement, in which mechanical equilibrium configurations are computed by energy minimization, balancing the effects of curvature elasticity, contact of the membrane with itself and the confining geometry, and adhesion. For cylindrical confinement, the shape equations are solved both analytically and numerically by finite element analysis. For spherical confinement, axisymmetric configurations are obtained numerically. We find that the geometry of invaginations is controlled by a dimensionless ratio of the adhesion strength to the bending energy of an equal area spherical vesicle. Larger adhesion produces more concentrated curvatures, which are mainly localized to the "neck" region where the invagination breaks away from its confining container. Under spherical confinement, axisymmetric invaginations are approximately spherical. For extreme confinement, multiple invaginations may form, bifurcating along multiple equilibrium branches. The results of the model are useful for understanding the physical mechanisms controlling the structure of lipid membranes of cells and their organelles, and developing tissue membranes.

  14. Curvature function and coarse graining

    International Nuclear Information System (INIS)

    Diaz-Marin, Homero; Zapata, Jose A.

    2010-01-01

    A classic theorem in the theory of connections on principal fiber bundles states that the evaluation of all holonomy functions gives enough information to characterize the bundle structure (among those sharing the same structure group and base manifold) and the connection up to a bundle equivalence map. This result and other important properties of holonomy functions have encouraged their use as the primary ingredient for the construction of families of quantum gauge theories. However, in these applications often the set of holonomy functions used is a discrete proper subset of the set of holonomy functions needed for the characterization theorem to hold. We show that the evaluation of a discrete set of holonomy functions does not characterize the bundle and does not constrain the connection modulo gauge appropriately. We exhibit a discrete set of functions of the connection and prove that in the abelian case their evaluation characterizes the bundle structure (up to equivalence), and constrains the connection modulo gauge up to ''local details'' ignored when working at a given scale. The main ingredient is the Lie algebra valued curvature function F S (A) defined below. It covers the holonomy function in the sense that expF S (A)=Hol(l=∂S,A).

  15. Intracellular magnetophoresis of amyloplasts and induction of root curvature

    Science.gov (United States)

    Kuznetsov, O. A.; Hasenstein, K. H.

    1996-01-01

    High-gradient magnetic fields (HGMFs) were used to induce intracellular magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the gap edge between two permanent magnets. In the vicinity of the tip of the wedge the dynamic factor of the magnetic field, delta(H2/2), was about 10(9) Oe2.cm-1, which subjected the amyloplasts to a force comparable to that of gravity. When roots of 2-d-old seedlings of flax (Linum usitatissimum L.) were positioned vertically and exposed to an HGMF, curvature away from the wedge was transient and lasted approximately 1 h. Average curvature obtained after placing magnets, wedge and seedlings on a 1-rpm clinostat for 2 h was 33 +/- 5 degrees. Roots of horizontally placed control seedlings without rotation curved about 47 +/- 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. Microscopy showed displacement of amyloplasts in vitro and in vivo. Studies with Arabidopsis thaliana (L.) Heynh. showed that the wild type responded to HGMFs but the starchless mutant TC7 did not. The data indicate that a magnetic force can be used to study the gravisensing and response system of roots.

  16. Performance of diagonal control structures at different operating conditions for polymer electrolyte membrane fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Serra, Maria; Husar, Attila; Feroldi, Diego; Riera, Jordi [Institut de Robotica i Informatica Industrial, Universitat Politecnica de Catalunya, Consejo Superior de Investigaciones Cientificas, C. Llorens i Artigas 4, 08028 Barcelona (Spain)

    2006-08-25

    This work is focused on the selection of operating conditions in polymer electrolyte membrane fuel cells. It analyses efficiency and controllability aspects, which change from one operating point to another. Specifically, several operating points that deliver the same amount of net power are compared, and the comparison is done at different net power levels. The study is based on a complex non-linear model, which has been linearised at the selected operating points. Different linear analysis tools are applied to the linear models and results show important controllability differences between operating points. The performance of diagonal control structures with PI controllers at different operating points is also studied. A method for the tuning of the controllers is proposed and applied. The behaviour of the controlled system is simulated with the non-linear model. Conclusions indicate a possible trade-off between controllability and optimisation of hydrogen consumption. (author)

  17. Microfluidic Device for Controllable Chemical Release via Field-Actuated Membrane Incorporating Nanoparticles

    Directory of Open Access Journals (Sweden)

    Xiang Wang

    2013-01-01

    Full Text Available We report a robust magnetic-membrane-based microfluidic platform for controllable chemical release. The magnetic membrane was prepared by mixing polydimethylsiloxane (PDMS and carbonyl-iron nanoparticles together to obtain a flexible thin film. With combined, simultaneous regulation of magnetic stimulus and mechanical pumping, the desired chemical release rate can easily be realized. For example, the dose release experimental data was well fitted by a mathematical sigmoidal model, exhibiting a typical dose-response relationship, which shows promise in providing significant guidance for on-demand drug delivery. To test the platform’s feasibility, our microfluidic device was employed in an experiment involving Escherichia coli culture under controlled antibiotic ciprofloxacin exposure, and the expected outcomes were successfully obtained. Our experimental results indicate that such a microfluidic device, with high accuracy and easy manipulation properties, can legitimately be characterized as active chemical release system.

  18. Microfluidic Device for Controllable Chemical Release via Field-Actuated Membrane Incorporating Nanoparticles

    KAUST Repository

    Wang, Xiang; Li, Shunbo; Wang, Limu; Yi, Xin; Hui, Yu Sanna; Qin, Jianhua; Wen, Weijia

    2013-01-01

    We report a robust magnetic-membrane-based microfluidic platform for controllable chemical release. The magnetic membrane was prepared by mixing polydimethylsiloxane (PDMS) and carbonyl-iron nanoparticles together to obtain a flexible thin film. With combined, simultaneous regulation of magnetic stimulus and mechanical pumping, the desired chemical release rate can easily be realized. For example, the dose release experimental data was well fitted by a mathematical sigmoidal model, exhibiting a typical dose-response relationship, which shows promise in providing significant guidance for on-demand drug delivery. To test the platform’s feasibility, our microfluidic device was employed in an experiment involving Escherichia coli culture under controlled antibiotic ciprofloxacin exposure, and the expected outcomes were successfully obtained. Our experimental results indicate that such a microfluidic device, with high accuracy and easy manipulation properties, can legitimately be characterized as active chemical release system.

  19. Self-ordered, controlled structure nanoporous membranes using constant current anodization.

    Science.gov (United States)

    Lee, Kwan; Tang, Yun; Ouyang, Min

    2008-12-01

    We report a constant current (CC) based anodization technique to fabricate and control structure of mechanically stable anodic aluminum oxide (AAO) membranes with a long-range ordered hexagonal nanopore pattern. For the first time we show that interpore distance (Dint) of a self-ordered nanopore feature can be continuously tuned over a broad range with CC anodization and is uniquely defined by the conductivity of sulfuric acid as electrolyte. We further demonstrate that this technique can offer new degrees of freedom for engineering planar nanopore structures by fine tailoring the CC based anodization process. Our results not only facilitate further understanding of self-ordering mechanism of alumina membranes but also provide a fast, simple (without requirement of prepatterning or preoxide layer), and flexible methodology for controlling complex nanoporous structures, thus offering promising practical applications in nanotechnology.

  20. Microfluidic Device for Controllable Chemical Release via Field-Actuated Membrane Incorporating Nanoparticles

    KAUST Repository

    Wang, Xiang

    2013-01-01

    We report a robust magnetic-membrane-based microfluidic platform for controllable chemical release. The magnetic membrane was prepared by mixing polydimethylsiloxane (PDMS) and carbonyl-iron nanoparticles together to obtain a flexible thin film. With combined, simultaneous regulation of magnetic stimulus and mechanical pumping, the desired chemical release rate can easily be realized. For example, the dose release experimental data was well fitted by a mathematical sigmoidal model, exhibiting a typical dose-response relationship, which shows promise in providing significant guidance for on-demand drug delivery. To test the platform’s feasibility, our microfluidic device was employed in an experiment involving Escherichia coli culture under controlled antibiotic ciprofloxacin exposure, and the expected outcomes were successfully obtained. Our experimental results indicate that such a microfluidic device, with high accuracy and easy manipulation properties, can legitimately be characterized as active chemical release system.

  1. Flow restrictor silicon membrane microvalve actuated by optically controlled paraffin phase transition

    International Nuclear Information System (INIS)

    Kolari, K; Havia, T; Stuns, I; Hjort, K

    2014-01-01

    Restrictor valves allow proportional control of fluid flow but are rarely integrated in microfluidic systems. In this study, an optically actuated silicon membrane restrictor microvalve is demonstrated. Its actuation is based on the phase transition of paraffin, using a paraffin wax mixed with a suitable concentration of optically absorbing nanographite particles. Backing up the membrane with oil (the melted paraffin) allows for a compliant yet strong contact to the valve seat, which enables handling of high pressures. At flow rates up to 30 µL min −1 and at a pressure of 2 bars, the valve can successfully be closed and control the flow level by restriction. The use of this paraffin composite as an adhesive layer sandwiched between the silicon valve and glass eases fabrication. This type of restrictor valve is best suited for high pressure, low volume flow silicon-based nanofluidic systems. (paper)

  2. Curvature and torsion in growing actin networks

    International Nuclear Information System (INIS)

    Shaevitz, Joshua W; Fletcher, Daniel A

    2008-01-01

    Intracellular pathogens such as Listeria monocytogenes and Rickettsia rickettsii move within a host cell by polymerizing a comet-tail of actin fibers that ultimately pushes the cell forward. This dense network of cross-linked actin polymers typically exhibits a striking curvature that causes bacteria to move in gently looping paths. Theoretically, tail curvature has been linked to details of motility by considering force and torque balances from a finite number of polymerizing filaments. Here we track beads coated with a prokaryotic activator of actin polymerization in three dimensions to directly quantify the curvature and torsion of bead motility paths. We find that bead paths are more likely to have low rather than high curvature at any given time. Furthermore, path curvature changes very slowly in time, with an autocorrelation decay time of 200 s. Paths with a small radius of curvature, therefore, remain so for an extended period resulting in loops when confined to two dimensions. When allowed to explore a three-dimensional (3D) space, path loops are less evident. Finally, we quantify the torsion in the bead paths and show that beads do not exhibit a significant left- or right-handed bias to their motion in 3D. These results suggest that paths of actin-propelled objects may be attributed to slow changes in curvature, possibly associated with filament debranching, rather than a fixed torque

  3. Clustering on Membranes

    DEFF Research Database (Denmark)

    Johannes, Ludger; Pezeshkian, Weria; Ipsen, John H

    2018-01-01

    Clustering of extracellular ligands and proteins on the plasma membrane is required to perform specific cellular functions, such as signaling and endocytosis. Attractive forces that originate in perturbations of the membrane's physical properties contribute to this clustering, in addition to direct...... protein-protein interactions. However, these membrane-mediated forces have not all been equally considered, despite their importance. In this review, we describe how line tension, lipid depletion, and membrane curvature contribute to membrane-mediated clustering. Additional attractive forces that arise...... from protein-induced perturbation of a membrane's fluctuations are also described. This review aims to provide a survey of the current understanding of membrane-mediated clustering and how this supports precise biological functions....

  4. Right thoracic curvature in the normal spine

    Directory of Open Access Journals (Sweden)

    Masuda Keigo

    2011-01-01

    Full Text Available Abstract Background Trunk asymmetry and vertebral rotation, at times observed in the normal spine, resemble the characteristics of adolescent idiopathic scoliosis (AIS. Right thoracic curvature has also been reported in the normal spine. If it is determined that the features of right thoracic side curvature in the normal spine are the same as those observed in AIS, these findings might provide a basis for elucidating the etiology of this condition. For this reason, we investigated right thoracic curvature in the normal spine. Methods For normal spinal measurements, 1,200 patients who underwent a posteroanterior chest radiographs were evaluated. These consisted of 400 children (ages 4-9, 400 adolescents (ages 10-19 and 400 adults (ages 20-29, with each group comprised of both genders. The exclusion criteria were obvious chest and spinal diseases. As side curvature is minimal in normal spines and the range at which curvature is measured is difficult to ascertain, first the typical curvature range in scoliosis patients was determined and then the Cobb angle in normal spines was measured using the same range as the scoliosis curve, from T5 to T12. Right thoracic curvature was given a positive value. The curve pattern was organized in each collective three groups: neutral (from -1 degree to 1 degree, right (> +1 degree, and left ( Results In child group, Cobb angle in left was 120, in neutral was 125 and in right was 155. In adolescent group, Cobb angle in left was 70, in neutral was 114 and in right was 216. In adult group, Cobb angle in left was 46, in neutral was 102 and in right was 252. The curvature pattern shifts to the right side in the adolescent group (p Conclusions Based on standing chest radiographic measurements, a right thoracic curvature was observed in normal spines after adolescence.

  5. [Characteristics of nitrogen and phosphorus removal and control of membrane fouling in MBR and SMBR].

    Science.gov (United States)

    Guo, Xiao-Ma; Zhao, Yan; Wang, Kai-Yan; Zhao Yang-Guo

    2015-03-01

    To improve the efficiency and running stability of wastewater advanced treatment, a sequencing membrane bioreactor (SMBR) and a traditional membrane bioreactor (MBR) were used to investigate the characteristics of nitrogen and phosphorus removal, and the effect of anoxic time on treatment systems and membrane fouling. Simultaneously, molecular biology techniques were applied to analyze the composition of microbial community and the structure of suspended sludge. The results showed that SMBR had higher efficiency in removing TN than MBR, which indicated that intermittent aeration could enhance the ability of nitrogen removal. SMBR and MBR had a similar removal efficiency of NH4(+)-N, TP, COD, and turbidity with the removal rates of 94%, 78%, 80%, and 97%, respectively. Extension of SMBR anoxic time had no effect on COD, NH4(+) -N removal but decreased TN and TP removal rate, dropping from 61% and 74% to 46% and 52%, respectively. Intermittent aeration and powder activated carbon (PAC) could both mitigate membrane fouling. The analysis on microbial community indicated that there was no difference in the composition and structure of microbial community between SMBR and MBR. Nitrospira and Dechloromonas were both highly abundant functional groups, which provided the basis for highly efficient control of bioreactors.

  6. Effects of ethylene on the kinetics of curvature and auxin redistribution in gravistimulated roots of Zea mays

    Science.gov (United States)

    Lee, J. S.; Evans, M. L.

    1990-01-01

    We tested the involvement of ethylene in maize (Zea mays L.) root gravitropism by measuring the kinetics of curvature and lateral auxin movement in roots treated with ethylene, inhibitors of ethylene synthesis, or inhibitors of ethylene action. In the presence of ethylene the latent period of gravitropic curvature appeared to be increased somewhat. However, ethylene-treated roots continued to curve after control roots had reached their final angle of curvature. Consequently, maximum curvature in the presence of ethylene was much greater in ethylene-treated roots than in controls. Inhibitors of ethylene biosynthesis or action had effects on the kinetics of curvature opposite to that of ethylene, i.e. the latent period appeared to be shortened somewhat while total curvature was reduced relative to that of controls. Label from applied 3H-indole-3-acetic acid was preferentially transported toward the lower side of stimulated roots. In parallel with effects on curvature, ethylene treatment delayed the development of gravity-induced asymmetric auxin movement across the root but extended its duration once initiated. The auxin transport inhibitor, 1-N-naphthylphthalamic acid reduced both gravitropic curvature and the effect of ethylene on curvature. Since neither ethylene nor inhibitors of ethylene biosynthesis or action prevented curvature, we conclude that ethylene does not mediate the primary differential growth response causing curvature. Because ethylene affects curvature and auxin transport in parallel, we suggest that ethylene modifies curvature by affecting gravity-induced lateral transport of auxin, perhaps by interfering with adaptation of the auxin transport system to the gravistimulus.

  7. Pointlike Inclusion Interactions in Tubular Membranes

    NARCIS (Netherlands)

    Vahid Belarghou, A.; Idema, T.

    2016-01-01

    Membrane tubes and tubular networks are ubiquitous in living cells. Inclusions like proteins are vital for both the stability and the dynamics of such networks. These inclusions interact via the curvature deformations they impose on the membrane. We analytically study the resulting membrane

  8. Integrated Wireless Monitoring and Control System in Reverse Osmosis Membrane Desalination Plants

    Directory of Open Access Journals (Sweden)

    Al Haji Ahmad

    2015-01-01

    Full Text Available The operational processes of the Reverse Osmosis (RO membrane desalination plants require continuous monitoring through the constant attendance of operators to ensure proper productivity and minimize downtime and prevent membrane failure. Therefore, the plant must be equipped with a control system that monitors and controls the operational variables. Monitoring and controlling the affecting parameters are critical to the evaluation of the performance of the desalination plant, which will help the operator find and resolve problems immediately. Therefore, this paper was aimed at developing an RO unit by utilizing a wireless sensor network (WSN system. Hence, an RO pilot plant with a feed capacity of 1.2 m3/h was utilized, commissioned, and tested in Kuwait to assess and verify the performance of the integrated WSN in RO membrane desalination system. The investigated system allowed the operators to remotely monitor the operational process of the RO system. The operational data were smoothly recorded and monitored. Furthermore, the technical problems were immediately determined, which reduced the time and effort in rectifying the technical problems relevant to the RO performance. The manpower requirements of such treatment system were dramatically reduced by about 50%. Based on a comparison between manual and wireless monitoring operational processes, the availability of the integrated RO unit with a wireless monitoring was increased by 10%

  9. Vertical melting of a stack of membranes

    Science.gov (United States)

    Borelli, M. E. S.; Kleinert, H.; Schakel, A. M. J.

    2001-02-01

    A stack of tensionless membranes with nonlinear curvature energy and vertical harmonic interaction is studied. At low temperatures, the system forms a lamellar phase. At a critical temperature, the stack disorders vertically in a melting-like transition.

  10. Curvature distribution within hillslopes and catchments and its effect on the hydrological response

    NARCIS (Netherlands)

    Bogaart, P.W.; Troch, P.A.A.

    2006-01-01

    Topographic convergence and divergence are first order controls on the hillslope and catchment hydrological response, as evidenced by similarity parameter analyses. Hydrological models often do not take convergence as measured by contour curvature directly into account; instead they use comparable

  11. Discrete Curvatures and Discrete Minimal Surfaces

    KAUST Repository

    Sun, Xiang

    2012-01-01

    This thesis presents an overview of some approaches to compute Gaussian and mean curvature on discrete surfaces and discusses discrete minimal surfaces. The variety of applications of differential geometry in visualization and shape design leads

  12. Higher Curvature Supergravity, Supersymmetry Breaking and Inflation

    CERN Document Server

    Ferrara, Sergio

    2017-01-01

    In these lectures, after a short introduction to cosmology, we discuss the supergravity embedding of higher curvature models of inflation. The supergravity description of such models is presented for the two different formulations of minimal supergravity.

  13. Curvature of Indoor Sensor Network: Clustering Coefficient

    Directory of Open Access Journals (Sweden)

    2009-03-01

    Full Text Available We investigate the geometric properties of the communication graph in realistic low-power wireless networks. In particular, we explore the concept of the curvature of a wireless network via the clustering coefficient. Clustering coefficient analysis is a computationally simplified, semilocal approach, which nevertheless captures such a large-scale feature as congestion in the underlying network. The clustering coefficient concept is applied to three cases of indoor sensor networks, under varying thresholds on the link packet reception rate (PRR. A transition from positive curvature (“meshed” network to negative curvature (“core concentric” network is observed by increasing the threshold. Even though this paper deals with network curvature per se, we nevertheless expand on the underlying congestion motivation, propose several new concepts (network inertia and centroid, and finally we argue that greedy routing on a virtual positively curved network achieves load balancing on the physical network.

  14. The spinning particle with extrinsic curvature

    International Nuclear Information System (INIS)

    Dhar, A.

    1988-01-01

    We construct and analyse an action for the spinning particle which contains an extrinsic curvature term. A possible generalization of this construction to the case of the spinning string is also discussed. (orig.)

  15. Feedback control for distributed heat transfer mechanisms in direct-contact membrane distillation system

    KAUST Repository

    Eleiwi, Fadi; N'Doye, Ibrahima; Laleg-Kirati, Taous-Meriem

    2015-01-01

    In this paper, the problem of stabilization and production rate reference tracking for a Direct-Contact Membrane Distillation (DCMD) system is addressed. Sufficient conditions for the asymptotic and exponential stabilization for DCMD system are presented using the Gronwall-Bellman lemma and Linear Matrix Inequalities (LMIs) approaches, respectively. A nonlinear observer is then proposed to estimate the temperature distribution among the DCMD domain. This contributes to propose a reference production rate control design for the DCMD process via observer-based output control approach. Finally, numerical simulations are given to show the effectiveness of the proposed methods.

  16. Feedback control for distributed heat transfer mechanisms in direct-contact membrane distillation system

    KAUST Repository

    Eleiwi, Fadi

    2015-09-21

    In this paper, the problem of stabilization and production rate reference tracking for a Direct-Contact Membrane Distillation (DCMD) system is addressed. Sufficient conditions for the asymptotic and exponential stabilization for DCMD system are presented using the Gronwall-Bellman lemma and Linear Matrix Inequalities (LMIs) approaches, respectively. A nonlinear observer is then proposed to estimate the temperature distribution among the DCMD domain. This contributes to propose a reference production rate control design for the DCMD process via observer-based output control approach. Finally, numerical simulations are given to show the effectiveness of the proposed methods.

  17. Development and Optimization of Osmotically Controlled Asymmetric Membrane Capsules for Delivery of Solid Dispersion of Lycopene

    Directory of Open Access Journals (Sweden)

    Nitin Jain

    2014-01-01

    Full Text Available The aim of the present investigation is to develop and statistically optimize the osmotically controlled asymmetric membrane capsules of solid dispersion of lycopene. Solid dispersions of lycopene with β-cyclodextrin in different ratios were prepared using solvent evaporation method. Solubility studies showed that the solid dispersion with 1 : 5 (lycopene : β-cyclodextrin exhibited optimum solubility (56.25 mg/mL for osmotic controlled delivery. Asymmetric membrane capsules (AMCs were prepared on glass mold pins via dip coating method. Membrane characterization by scanning electron microscopy showed inner porous region and outer dense region. Central composite design response surface methodology was applied for the optimization of AMCs. The independent variables were ethyl cellulose (X1, glycerol (X2, and NaCl (X3 which were varied at different levels to analyze the effect on dependent variables (percentage of cumulative drug release (Y1 and correlation coefficient of drug release (Y2. The effect of independent variables on the response was significantly influential. The F18 was selected as optimized formulation based on percentage of CDR (cumulative drug release of 85.63% and correlation coefficient of 0.9994. The optimized formulation was subjected to analyze the effect of osmotic pressure and agitational intensity on percentage of CDR. The drug release was independent of agitational intensity but was dependent on osmotic pressure of dissolution medium.

  18. GDP growth and the yield curvature

    DEFF Research Database (Denmark)

    Møller, Stig Vinther

    2014-01-01

    This paper examines the forecastability of GDP growth using information from the term structure of yields. In contrast to previous studies, the paper shows that the curvature of the yield curve contributes with much more forecasting power than the slope of yield curve. The yield curvature also...... predicts bond returns, implying a common element to time-variation in expected bond returns and expected GDP growth....

  19. Straight-line string with curvature

    International Nuclear Information System (INIS)

    Solov'ev, L.D.

    1995-01-01

    Classical and quantum solutions for the relativistic straight-line string with arbitrary dependence on the world surface curvature are obtained. They differ from the case of the usual Nambu-Goto interaction by the behaviour of the Regge trajectory which in general can be non-linear. A regularization of the action is considered and a comparison with relativistic point with curvature is made. 5 refs

  20. Controlled in meso phase crystallization--a method for the structural investigation of membrane proteins.

    Directory of Open Access Journals (Sweden)

    Jan Kubicek

    Full Text Available We investigated in meso crystallization of membrane proteins to develop a fast screening technology which combines features of the well established classical vapor diffusion experiment with the batch meso phase crystallization, but without premixing of protein and monoolein. It inherits the advantages of both methods, namely (i the stabilization of membrane proteins in the meso phase, (ii the control of hydration level and additive concentration by vapor diffusion. The new technology (iii significantly simplifies in meso crystallization experiments and allows the use of standard liquid handling robots suitable for 96 well formats. CIMP crystallization furthermore allows (iv direct monitoring of phase transformation and crystallization events. Bacteriorhodopsin (BR crystals of high quality and diffraction up to 1.3 Å resolution have been obtained in this approach. CIMP and the developed consumables and protocols have been successfully applied to obtain crystals of sensory rhodopsin II (SRII from Halobacterium salinarum for the first time.

  1. The effect of spontaneous curvature on a two-phase vesicle

    International Nuclear Information System (INIS)

    Cox, Geoffrey; Lowengrub, John

    2015-01-01

    Vesicles are membrane-bound structures commonly known for their roles in cellular transport and the shape of a vesicle is determined by its surrounding membrane (lipid bilayer). When the membrane is composed of different lipids, it is natural for the lipids of similar molecular structure to migrate towards one another (via spinodal decomposition), creating a multi-phase vesicle. In this article, we consider a two-phase vesicle model which is driven by nature's propensity to maintain a minimal state of elastic energy. The model assumes a continuum limit, thereby treating the membrane as a closed three-dimensional surface. The main purpose of this study is to reveal the complexity of the Helfrich two-phase vesicle model with non-zero spontaneous curvature and provide further evidence to support the relevance of spontaneous curvature as a modelling parameter. In this paper, we illustrate the complexity of the Helfrich two-phase model by providing multiple examples of undocumented solutions and energy hysteresis. We also investigate the influence of spontaneous curvature on morphological effects and membrane phenomena such as budding and fusion. (paper)

  2. Convective mass transfer in helical pipes: effect of curvature and torsion

    Energy Technology Data Exchange (ETDEWEB)

    Litster, S.; Djilali, N. [University of Victoria, Department of Mechanical Engineering, Victoria, BC (Canada); Pharoah, J.G. [University of Victoria, Department of Mechanical Engineering, Victoria, BC (Canada); Queen' s University at Kingston, Department of Mechanical Engineering, Kingston, ON (Canada)

    2006-03-01

    A 3D numerical analysis of the flow and mass transfer in helical pipes is presented. The interpretation of the flow patterns and their impact on mass transfer is shown to require a non-orthogonal pseudo-stream function based visualization. The strong coupling between torsion and curvature effects, and the resulting secondary flow regimes are well characterized by a parameter combining both the Dean (Dn) and Germano numbers (Gn). For membrane separation applications, helical modules combining high curvature with low torsion would alleviate concentration polarization and yield appreciable flux improvement. (orig.)

  3. Improved performance of single-chamber microbial fuel cells through control of membrane deformation

    KAUST Repository

    Zhang, Xiaoyuan; Cheng, Shaoan; Huang, Xia; Logan, Bruce E.

    2010-01-01

    , but in initial experiments we observed the opposite using a membrane electrode assembly MFC. The reason was identified to be membrane deformation, which resulted in water and gas trapped between the membrane and cathode. To correct this, stainless steel mesh

  4. A strain-controlled C2N monolayer membrane for gas separation in PEMFC application

    Science.gov (United States)

    Deng, Shengwei; Hu, Hui; Zhuang, Guilin; Zhong, Xing; Wang, Jianguo

    2018-05-01

    Ultrathin membranes with controllable pore sizes have great potential to realize high-selectivity gas separation at low energy cost, especially for those mixtures with narrow size distributions. Using a combination of van der Waals-corrected density functional theory (DFT) calculations and molecular dynamics (MD) simulation, we examine the separation ability of biaxial stretched monolayer C2N nanosheets which is applied to the O2 separation from CO/CO2/O2 mixtures in the cathode of proton exchange membrane fuel cells (PEMFC). The DFT calculations show that the diffusion energy barrier for molecules passing through the membrane followed by CO, CO2 and O2 in descending order, and an overall decrease of energy barriers due to the widen the pore size is observed with the increase of applied strains. Furthermore, MD results show that the nanosheet can effectively purify O2 from CO2 and CO with a strain from 8% to 10%. It confirms that the selectivity is determined by the electronic structure related interaction in addition to the kinetic diameter of individual molecules. The O2 permeability is improved progressively with further increase of strain, and small amount of CO2 begins to permeate through the nanosheet at relatively large strain, while the excellent CO isolation is not compromised until the theoretical maximum strain.

  5. Analysis of plasma membrane Ca(2+)-ATPase expression in control and SV40-transformed human fibroblasts.

    Science.gov (United States)

    Reisner, P D; Brandt, P C; Vanaman, T C

    1997-01-01

    It has been long known that neoplastic transformation is accompanied by a lowered requirement for extracellular Ca2+ for growth. The studies presented here demonstrate that human fibroblastic cell lines produce the two commonly found 'housekeeping' isoforms of the plasma membrane Ca(2+)-ATPase (PMCA), PMCA1b and 4b, and at the expression of both is demonstrably lower in cell lines neoplastically transformed by SV40 than in the corresponding parental cell lines. Western blot analyses of lysates from control (GM00037) and SV40-transformed (GM00637) skin fibroblasts revealed a 138 kDa PMCA whose level was significantly lower in the SV40-transformed cells relative to either total cellular protein or alpha-tubulin. Similar analyses of plasma membrane preparations from control WI-38) and SV40-transformed (WI-38VA13) lung fibroblasts revealed 3-4-fold lower levels of PMCA in the SV40-transformed cells. Competitive ELISAs performed on detergent solubilized plasma membrane preparations indicated at least 3-4-fold lower levels of PMCA in the SV40-transformed cell lines compared to controls. Reverse transcriptase coupled-PCR analyses showed that PMCA1b and PMCA4b were the only isoforms expressed in all four cell lines. The PMCA4b mRNA level detected by Northern analysis also was substantially lower in SV40 transformed skin fibroblasts than in non-transformed fibroblasts. Quantitative RT-PCR analyses showed levels of PMCA1b and 4b mRNAs to be 5 and 10-fold lower, respectively, in GM00637 than in GM00037 when the levels of PCR products were normalized to glyceraldehyde-3-phosphate dehydrogenase (G3PDH) mRNA. These results demonstrate that the expression of these distinct PMCA genes is substantially lower in SV40 transformed human skin and lung fibroblasts and may be coordinately regulated in these cells.

  6. Dynamic Modeling and Control of Distributed Heat Transfer Mechanisms: Application to a Membrane Distillation Module

    KAUST Repository

    Eleiwi, Fadi

    2015-12-01

    Sustainable desalination technologies are the smart solution for producing fresh water and preserve the environment and energy by using sustainable renewable energy sources. Membrane distillation (MD) is an emerging technology which can be driven by renewable energy. It is an innovative method for desalinating seawater and brackish water with high quality production, and the gratitude is to its interesting potentials. MD includes a transfer of water vapor from a feed solution to a permeate solution through a micro-porous hydrophobic membrane, rejecting other non-volatile constituents present in the influent water. The process is driven by the temperature difference along the membrane boundaries. Different control applications and supervision techniques would improve the performance and the efficiency of the MD process, however controlling the MD process requires comprehensive mathematical model for the distributed heat transfer mechanisms inside the process. Our objective is to propose a dynamic mathematical model that accounts for the time evolution of the involved heat transfer mechanisms in the process, and to be capable of hosting intermittent energy supplies, besides managing the production rate of the process, and optimizing its energy consumption. Therefore, we propose the 2D Advection-Diffusion Equation model to account for the heat diffusion and the heat convection mechanisms inside the process. Furthermore, experimental validations have proved high agreement between model simulations and experiments with less than 5% relative error. Enhancing the MD production is an anticipated goal, therefore, two main control strategies are proposed. Consequently, we propose a nonlinear controller for a semi-discretized version of the dynamic model to achieve an asymptotic tracking for a desired temperature difference. Similarly, an observer-based feedback control is used to track sufficient temperature difference for better productivity. The second control strategy

  7. A PtdIns(4)P-driven electrostatic field controls cell membrane identity and signalling in plants.

    Science.gov (United States)

    Simon, Mathilde Laetitia Audrey; Platre, Matthieu Pierre; Marquès-Bueno, Maria Mar; Armengot, Laia; Stanislas, Thomas; Bayle, Vincent; Caillaud, Marie-Cécile; Jaillais, Yvon

    2016-06-20

    Many signalling proteins permanently or transiently localize to specific organelles. It is well established that certain lipids act as biochemical landmarks to specify compartment identity. However, they also influence membrane biophysical properties, which emerge as important features in specifying cellular territories. Such parameters include the membrane inner surface potential, which varies according to the lipid composition of each organelle. Here, we found that the plant plasma membrane (PM) and the cell plate of dividing cells have a unique electrostatic signature controlled by phosphatidylinositol-4-phosphate (PtdIns(4)P). Our results further reveal that, contrarily to other eukaryotes, PtdIns(4)P massively accumulates at the PM, establishing it as a critical hallmark of this membrane in plants. Membrane surface charges control the PM localization and function of the polar auxin transport regulator PINOID as well as proteins from the BRI1 KINASE INHIBITOR1 (BKI1)/MEMBRANE ASSOCIATED KINASE REGULATOR (MAKR) family, which are involved in brassinosteroid and receptor-like kinase signalling. We anticipate that this PtdIns(4)P-driven physical membrane property will control the localization and function of many proteins involved in development, reproduction, immunity and nutrition.

  8. Electrically-controlled permeation of vapors through carbon nanotube network-based membranes

    Czech Academy of Sciences Publication Activity Database

    Slobodian, P.; Říha, Pavel; Olejník, R.

    2018-01-01

    Roč. 17, č. 2 (2018), s. 332-337 ISSN 1536-125X R&D Projects: GA MŠk ED2.1.00/19.0409 Grant - others:Ministerstvo školství, mládeže a tělovýchovy (MŠMT)(CZ) LO1504 Institutional research plan: CEZ:AV0Z20600510 Keywords : carbon nanotubes * electrically controlled membranes * permeation of chemical vapors Impact factor: 2.485, year: 2016

  9. New type of chitosan/2-hydroxypropyl-β-cyclodextrin composite membrane for gallic acid encapsulation and controlled release.

    Science.gov (United States)

    Paun, Gabriela; Neagu, Elena; Tache, Andreia; Radu, G L

    2014-01-01

    A new type of chitosan/2-hydroxypropyl-β-cyclodextrin composite membrane have been developed for the encapsulation and controlled release of gallic acid. The morphology of the composite membrane was investigated by infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM), whereas swelling gallic acid and release properties were investigated by UV-visible spectroscopy. The release behavior with pH changes was also explored. The composite membrane based on chitosan/2-hydroxypropyl-β-cyclodextrin with gallic acid included showed improved antioxidant capacities compared to plain chitosan membrane. The information obtained in this study will facilitate the design and preparation of composite membrane based on chitosan and could open a wide range of applications, particularly its use as an antioxidant in food, food packaging, biomedical (biodegradable soft porous scaffolds for enhance the surrounding tissue regeneration), pharmaceutical and cosmetics industries.

  10. Interaction between bacterial outer membrane proteins and periplasmic quality control factors: a kinetic partitioning mechanism.

    Science.gov (United States)

    Wu, Si; Ge, Xi; Lv, Zhixin; Zhi, Zeyong; Chang, Zengyi; Zhao, Xin Sheng

    2011-09-15

    The OMPs (outer membrane proteins) of Gram-negative bacteria have to be translocated through the periplasmic space before reaching their final destination. The aqueous environment of the periplasmic space and high permeability of the outer membrane engender such a translocation process inevitably challenging. In Escherichia coli, although SurA, Skp and DegP have been identified to function in translocating OMPs across the periplasm, their precise roles and their relationship remain to be elucidated. In the present paper, by using fluorescence resonance energy transfer and single-molecule detection, we have studied the interaction between the OMP OmpC and these periplasmic quality control factors. The results of the present study reveal that the binding rate of OmpC to SurA or Skp is much faster than that to DegP, which may lead to sequential interaction between OMPs and different quality control factors. Such a kinetic partitioning mechanism for the chaperone-substrate interaction may be essential for the quality control of the biogenesis of OMPs.

  11. A Highly Controllable Electrochemical Anodization Process to Fabricate Porous Anodic Aluminum Oxide Membranes

    Science.gov (United States)

    Lin, Yuanjing; Lin, Qingfeng; Liu, Xue; Gao, Yuan; He, Jin; Wang, Wenli; Fan, Zhiyong

    2015-12-01

    Due to the broad applications of porous alumina nanostructures, research on fabrication of anodized aluminum oxide (AAO) with nanoporous structure has triggered enormous attention. While fabrication of highly ordered nanoporous AAO with tunable geometric features has been widely reported, it is known that its growth rate can be easily affected by the fluctuation of process conditions such as acid concentration and temperature during electrochemical anodization process. To fabricate AAO with various geometric parameters, particularly, to realize precise control over pore depth for scientific research and commercial applications, a controllable fabrication process is essential. In this work, we revealed a linear correlation between the integrated electric charge flow throughout the circuit in the stable anodization process and the growth thickness of AAO membranes. With this understanding, we developed a facile approach to precisely control the growth process of the membranes. It was found that this approach is applicable in a large voltage range, and it may be extended to anodization of other metal materials such as Ti as well.

  12. Preliminary analysis of a membrane-based atmosphere-control subsystem

    Science.gov (United States)

    Mccray, Scott B.; Newbold, David D.; Ray, Rod; Ogle, Kathryn

    1993-01-01

    Controlled ecological life supprot systems will require subsystems for maintaining the consentrations of atmospheric gases within acceptable ranges in human habitat chambers and plant growth chambers. The goal of this work was to develop a membrane-based atmosphere comntrol (MBAC) subsystem that allows the controlled exchange of atmospheric componets (e.g., oxygen, carbon dioxide, and water vapor) between these chambers. The MBAC subsystem promises to offer a simple, nonenergy intensive method to separate, store and exchange atmospheric components, producing optimal concentrations of components in each chamber. In this paper, the results of a preliminary analysis of the MBAC subsystem for control of oxygen and nitrogen are presented. Additionally, the MBAC subsystem and its operation are described.

  13. Curvature constraints from the causal entropic principle

    International Nuclear Information System (INIS)

    Bozek, Brandon; Albrecht, Andreas; Phillips, Daniel

    2009-01-01

    Current cosmological observations indicate a preference for a cosmological constant that is drastically smaller than what can be explained by conventional particle physics. The causal entropic principle (Bousso et al.) provides an alternative approach to anthropic attempts to predict our observed value of the cosmological constant by calculating the entropy created within a causal diamond. We have extended this work to use the causal entropic principle to predict the preferred curvature within the 'multiverse'. We have found that values larger than ρ k =40ρ m are disfavored by more than 99.99% peak value at ρ Λ =7.9x10 -123 and ρ k =4.3ρ m for open universes. For universes that allow only positive curvature or both positive and negative curvature, we find a correlation between curvature and dark energy that leads to an extended region of preferred values. Our universe is found to be disfavored to an extent depending on the priors on curvature. We also provide a comparison to previous anthropic constraints on open universes and discuss future directions for this work.

  14. Effective tension and fluctuations in active membranes.

    Science.gov (United States)

    Loubet, Bastien; Seifert, Udo; Lomholt, Michael Andersen

    2012-03-01

    We calculate the fluctuation spectrum of the shape of a lipid vesicle or cell exposed to a nonthermal source of noise. In particular, we take constraints on the membrane area and the volume of fluid that it encapsulates into account when obtaining expressions for the dependency of the membrane tension on the noise. We then investigate three possible origins of the nonthermal noise taken from the literature: A direct force, which models an external medium pushing on the membrane, a curvature force, which models a fluctuating spontaneous curvature, and a permeation force coming from an active transport of fluid through the membrane. For the direct force and curvature force cases, we compare our results to existing experiments on active membranes.

  15. Study of Hydrogen Consumption by Control System in Proton Exchange Membrane Fuel Cell

    International Nuclear Information System (INIS)

    Ros Emilia Rosli; Edy Herianto Majlan; Siti Afiqah Abd Hamid; Wan Ramli Wan Daud; Ramizi Mohamed; Dedi Rohendi

    2016-01-01

    Efficient operation results from a proper control strategy. In the operation and performance of a Proton Exchange Membrane Fuel Cell (PEMFC), the hydrogen gas flow rate is one of the most essential control parameter in addition to operating pressure, water management, temperature and humidity. This is because of the high cost and amount of energy are required to produce the purity hydrogen gas. In this paper, a Proportional Integral Derivative (PID) feedback control system is used to control the hydrogen flow rate. A strategy is adapted to balance the hydrogen use based on the loading requirements, especially during start-ups and sudden power demands. This system is implemented using National Instrument (NI) devices powered by the LabVIEW program. This is due to its simplicity and customization flexibility for measuring, processing and recording data. Designed structure allows the real-time implementation of a robust control law that is able to address the related nonlinearities and uncertainties without incurring a heavy computational load for the controller algorithm. While it facilitating a fast sampling rate according to the needs of the power system. Test results from the controller show that the new fuel control system provides good performance by reducing the amount of wasted hydrogen gas compared with that of the previous open loop system by 30 % to over 80 % saved by the varied load. This improvement is beneficial for any PEMFC that experiences fluctuating power demand, especially for vehicle applications. (author)

  16. Some Inequalities for the Lp-Curvature Image

    Directory of Open Access Journals (Sweden)

    Xiang Yu

    2009-01-01

    Full Text Available Lutwak introduced the notion of Lp-curvature image and proved an inequality for the volumes of convex body and its Lp-curvature image. In this paper, we first give an monotonic property of Lp-curvature image. Further, we establish two inequalities for the Lp-curvature image and its polar, respectively. Finally, an inequality for the volumes of Lp-projection body and Lp-curvature image is obtained.

  17. Superpermeable membrane for particle control in divertor: the effect of impurity deposition

    International Nuclear Information System (INIS)

    Nakahara, Y.; Nakamura, Y.; Ohyabu, N.; Suzuki, H.; Busnyuk, A.; Alimov, V.

    2000-01-01

    The effect of impurity (stainless steel (SS) components, carbon) deposition onto niobium membrane surface on the membrane permeability to hydrogen particles is investigated with a plasma device. The deposition of SS components onto the upstream surface of the membrane at the membrane temperature (T M ) M M ≥800 deg. C. It appears to be due to the dissolution of the impurities deposited onto the upstream surface into the membrane bulk within the measurements

  18. Integrated pyrolucite fluidized bed-membrane hybrid process for improved iron and manganese control in drinking water.

    Science.gov (United States)

    Dashtban Kenari, Seyedeh Laleh; Barbeau, Benoit

    2017-04-15

    Newly developed ceramic membrane technologies offer numerous advantages over the conventional polymeric membranes. This work proposes a new configuration, an integrated pyrolucite fluidized bed (PFB)-ceramic MF/UF hybrid process, for improved iron and manganese control in drinking water. A pilot-scale study was undertaken to evaluate the performance of this process with respect to iron and manganese control as well as membrane fouling. In addition, the fouling of commercially available ceramic membranes in conventional preoxidation-MF/UF process was compared with the hybrid process configuration. In this regard, a series of experiments were conducted under different influent water quality and operating conditions. Fouling mechanisms and reversibility were analyzed using blocking law and resistance-in-series models. The results evidenced that the flux rate and the concentration of calcium and humic acids in the feed water have a substantial impact on the filtration behavior of both membranes. The model for constant flux compressible cake formation well described the rise in transmembrane pressure. The compressibility of the filter cake substantially increased in the presence of 2 mg/L humic acids. The presence of calcium ions caused significant aggregation of manganese dioxide and humic acid which severely impacted the extent of membrane fouling. The PFB pretreatment properly alleviated membrane fouling by removing more than 75% and 95% of iron and manganese, respectively. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Extrinsic and intrinsic curvatures in thermodynamic geometry

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini Mansoori, Seyed Ali, E-mail: shossein@bu.edu [Department of Physics, Boston University, 590 Commonwealth Ave., Boston, MA 02215 (United States); Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Mirza, Behrouz, E-mail: b.mirza@cc.iut.ac.ir [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Sharifian, Elham, E-mail: e.sharifian@ph.iut.ac.ir [Department of Physics, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2016-08-10

    We investigate the intrinsic and extrinsic curvatures of a certain hypersurface in thermodynamic geometry of a physical system and show that they contain useful thermodynamic information. For an anti-Reissner–Nordström-(A)de Sitter black hole (Phantom), the extrinsic curvature of a constant Q hypersurface has the same sign as the heat capacity around the phase transition points. The intrinsic curvature of the hypersurface can also be divergent at the critical points but has no information about the sign of the heat capacity. Our study explains the consistent relationship holding between the thermodynamic geometry of the KN-AdS black holes and those of the RN (J-zero hypersurface) and Kerr black holes (Q-zero hypersurface) ones [1]. This approach can easily be generalized to an arbitrary thermodynamic system.

  20. Extrinsic and intrinsic curvatures in thermodynamic geometry

    International Nuclear Information System (INIS)

    Hosseini Mansoori, Seyed Ali; Mirza, Behrouz; Sharifian, Elham

    2016-01-01

    We investigate the intrinsic and extrinsic curvatures of a certain hypersurface in thermodynamic geometry of a physical system and show that they contain useful thermodynamic information. For an anti-Reissner–Nordström-(A)de Sitter black hole (Phantom), the extrinsic curvature of a constant Q hypersurface has the same sign as the heat capacity around the phase transition points. The intrinsic curvature of the hypersurface can also be divergent at the critical points but has no information about the sign of the heat capacity. Our study explains the consistent relationship holding between the thermodynamic geometry of the KN-AdS black holes and those of the RN (J-zero hypersurface) and Kerr black holes (Q-zero hypersurface) ones [1]. This approach can easily be generalized to an arbitrary thermodynamic system.

  1. Substrate curvature gradient drives rapid droplet motion.

    Science.gov (United States)

    Lv, Cunjing; Chen, Chao; Chuang, Yin-Chuan; Tseng, Fan-Gang; Yin, Yajun; Grey, Francois; Zheng, Quanshui

    2014-07-11

    Making small liquid droplets move spontaneously on solid surfaces is a key challenge in lab-on-chip and heat exchanger technologies. Here, we report that a substrate curvature gradient can accelerate micro- and nanodroplets to high speeds on both hydrophilic and hydrophobic substrates. Experiments for microscale water droplets on tapered surfaces show a maximum speed of 0.42  m/s, 2 orders of magnitude higher than with a wettability gradient. We show that the total free energy and driving force exerted on a droplet are determined by the substrate curvature and substrate curvature gradient, respectively. Using molecular dynamics simulations, we predict nanoscale droplets moving spontaneously at over 100  m/s on tapered surfaces.

  2. Cosmic curvature from de Sitter equilibrium cosmology.

    Science.gov (United States)

    Albrecht, Andreas

    2011-10-07

    I show that the de Sitter equilibrium cosmology generically predicts observable levels of curvature in the Universe today. The predicted value of the curvature, Ω(k), depends only on the ratio of the density of nonrelativistic matter to cosmological constant density ρ(m)(0)/ρ(Λ) and the value of the curvature from the initial bubble that starts the inflation, Ω(k)(B). The result is independent of the scale of inflation, the shape of the potential during inflation, and many other details of the cosmology. Future cosmological measurements of ρ(m)(0)/ρ(Λ) and Ω(k) will open up a window on the very beginning of our Universe and offer an opportunity to support or falsify the de Sitter equilibrium cosmology.

  3. Radion stabilization in higher curvature warped spacetime

    Energy Technology Data Exchange (ETDEWEB)

    Das, Ashmita [Indian Institute of Technology, Department of Physics, Guwahati, Assam (India); Mukherjee, Hiya; Paul, Tanmoy; SenGupta, Soumitra [Indian Association for the Cultivation of Science, Department of Theoretical Physics, Kolkata (India)

    2018-02-15

    We consider a five dimensional AdS spacetime in presence of higher curvature term like F(R) = R + αR{sup 2} in the bulk. In this model, we examine the possibility of modulus stabilization from the scalar degrees of freedom of higher curvature gravity free of ghosts. Our result reveals that the model stabilizes itself and the mechanism of modulus stabilization can be argued from a geometric point of view. We determine the region of the parametric space for which the modulus (or radion) can to be stabilized. We also show how the mass and coupling parameters of radion field are modified due to higher curvature term leading to modifications of its phenomenological implications on the visible 3-brane. (orig.)

  4. Roentgenographic findings in hyaline membrane disease treated with exogenous surfactant: comparison with control group

    International Nuclear Information System (INIS)

    Lee, Sun Kyoung; Lim, Chae Ha; Lim, Woo Young; Kim, Young Sook; Byen, Ju Nam; Oh, Jae Hee; Kim, Young Chul

    1997-01-01

    To compare, with the use of chest radiographic findings, improvement and complications in newborns treated with exogenous surfactant for hyaline membrane disease (HMD), and an untreated control group. Thirty-six patients with HMD were randomly assigned to a control group (n=18) or surfactant treated group (n=18). As part of an initial evaluation of their pulmonary status, we then performed a retrospective statistical analysis of chest radiographic findings obtained in exogenous surfactant treated and untreated infants within the first 90 minutes of life. Subsequent examinations were performed at less than 24 hours of age. Chest radiograph before treatment showed no significant differences between the two groups, but significant improvement was noted in the surfactant treated group, in contrast to the control group. The most common chest radiographic finding after surfactant administration was uniform (n=15) or disproportionate (n=2) improvement of pulmonary aeration. Patent ductus arteriosus developed in three treated neonates and in four cases in the control group. Air leak occurred in three cases in the treated group and in five cases in the control group. In one treated patient pulmonary hemorrhage developed and intracranial hemorrhage occurred in three treated neonates and in four cases in the control group. Bronchopulmonary dysplasia was developed in 6 cases of treated group and 3 cases of control group. A chest radiograph is considered to be helpful in the evaluation of improvement and complications of HMD in infants treated with surfactant

  5. MPK-1 ERK controls membrane organization in C. elegans oogenesis via a sex-determination module.

    Science.gov (United States)

    Arur, Swathi; Ohmachi, Mitsue; Berkseth, Matt; Nayak, Sudhir; Hansen, David; Zarkower, David; Schedl, Tim

    2011-05-17

    Tissues that generate specialized cell types in a production line must coordinate developmental mechanisms with physiological demand, although how this occurs is largely unknown. In the Caenorhabditis elegans hermaphrodite, the developmental sex-determination cascade specifies gamete sex in the distal germline, while physiological sperm signaling activates MPK-1/ERK in the proximal germline to control plasma membrane biogenesis and organization during oogenesis. We discovered repeated utilization of a self-contained negative regulatory module, consisting of NOS-3 translational repressor, FEM-CUL-2 (E3 ubiquitin ligase), and TRA-1 (Gli transcriptional repressor), which acts both in sex determination and in physiological demand control of oogenesis, coordinating these processes. In the distal germline, where MPK-1 is not activated, TRA-1 represses the male fate as NOS-3 functions in translational repression leading to inactivation of the FEM-CUL-2 ubiquitin ligase. In the proximal germline, sperm-dependent physiological MPK-1 activation results in phosphorylation-based inactivation of NOS-3, FEM-CUL-2-mediated degradation of TRA-1 and the promotion of membrane organization during oogenesis. Copyright © 2011 Elsevier Inc. All rights reserved.

  6. Shipment of a photodynamic therapy agent into model membrane and its controlled release: A photophysical approach.

    Science.gov (United States)

    Karar, Monaj; Paul, Suvendu; Mallick, Arabinda; Majumdar, Tapas

    2018-01-01

    Harmine, an efficient cancer cell photosensitizer (PS), emits intense violet color when it is incorporated in well established self assembly based drug carrier formed by cationic surfactants of identical positive charge of head group but varying chain length, namely, dodecyltrimethylammonium bromide (DTAB), tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB). Micelle entrapped drug emits in the UV region when it interacts with non-toxic β-cyclodextrin (β-CD). Inspired by these unique fluorescence/structural switching properties of the anticancer drug, in the present work we have monitored the interplay of the drug between micelles and non-toxic β-CDs. We have observed that the model membranes formed by micelles differing in their hydrophobic chain length interact with the drug differently. Variation in the surfactant chain length plays an important role for structural switching i.e. in choosing a particular structural form of the drug that will be finally presented to their targets. The present study shows that in case of necessity, the bound drug molecule can be removed from its binding site in a controlled manner by the use of non-toxic β-CD and it is exploited to serve a significant purpose for the removal of excess/unused adsorbed drugs from the model cell membranes. We believe this kind of β-CD driven translocation of drugs monitored by fluorescence switching may find possible applications in controlled release of the drug inside cells. Copyright © 2017 Elsevier B.V. All rights reserved.

  7. Control and experimental characterization of a methanol reformer for a 350W high temperature polymer electrolyte membrane fuel cell system

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen; Jensen, Hans-Christian Becker

    suited for reformer systems, where high CO tolerance is required. This enables the use fuels based on e.g. liquid alcohols. This work presents the control strategies of a methanol refoermer for a 350W HTPEM FC system. The system examined is the Serenergy H3-350 Mobile Battery Charger, an integrated......High temperature polymer electrolyte membrane(HTPEM) fuel cells offer many advantages due to their increased operating tempera-tures compared to similar Nafion-based membrane tech-nologies, that rely on the conductive abilities of liquid water. The polybenzimidazole (PBI) membranes are especially...

  8. Electrodiffusion of Lipids on Membrane Surfaces

    OpenAIRE

    Zhou, Y. C.

    2011-01-01

    Random lateral translocation of lipids and proteins is a universal process on membrane surfaces. Local aggregation or organization of lipids and proteins can be induced when this lateral random diffusion is mediated by the electrostatic interactions and membrane curvature. Though the lateral diffusion rates of lipids on membrane of various compositions are measured and the electrostatic free energies of predetermined protein-membrane-lipid systems can be computed, the process of the aggregati...

  9. Longitudinal surface curvature effect in magnetohydrodynamics

    International Nuclear Information System (INIS)

    Bodas, N.G.

    1975-01-01

    The two-dimensional motion of an incompressible and electrically conducting fluid past an electrically insulated body surface (having curvature) is studied for a given O(1) basic flow and magnetic field, when (i) the applied magnetic field is aligned with the velocity in the basic flow, and (ii) the applied magnetic field is within the body surface. 01 and 0(Re sup(1/2)) mean the first and second order approximations respectively in an exansion scheme in powers of Resup(-1/2), Re being the Reynolds number). The technique of matched asymptotic expansions is used to solve the problem. The governing partial differential equations to 0(Resup(-1/2)) boundary layer approximation are found to give similarity solutions for a family of surface curvature and pressure gradient distributions in case (i), and for uniform basic flow with analytic surface curvature distributions in case (ii). The equations are solved numerically. In case (i) it is seen that the effect of the magnetic field on the skin-friction- correction due to the curvature is very small. Also the magnetic field at the wall is reduced by the curvature on the convex side. In case (ii) the magnetic field significantly increases the skin-friction-correction due to the curvature. The effect of the magnetic field on the O(1) and O(Resup(-1/2)) skin friction coefficients increases with the increase of the electrical conductivity of the fluid. Also, at higher values of the magnetic pressure, moderate changes in the electrical conductivity do not influence the correction to the skin-friction significantly. (Auth.)

  10. Generic Properties of Curvature Sensing through Vision and Touch

    Directory of Open Access Journals (Sweden)

    Birgitta Dresp-Langley

    2013-01-01

    Full Text Available Generic properties of curvature representations formed on the basis of vision and touch were examined as a function of mathematical properties of curved objects. Virtual representations of the curves were shown on a computer screen for visual scaling by sighted observers (experiment 1. Their physical counterparts were placed in the two hands of blindfolded and congenitally blind observers for tactile scaling. The psychophysical data show that curvature representations in congenitally blind individuals, who never had any visual experience, and in sighted observers, who rely on vision most of the time, are statistically linked to the same mathematical properties of the curves. The perceived magnitude of object curvature, sensed through either vision or touch, is related by a mathematical power law, with similar exponents for the two sensory modalities, to the aspect ratio of the curves, a scale invariant geometric property. This finding supports biologically motivated models of sensory integration suggesting a universal power law for the adaptive brain control and balance of motor responses to environmental stimuli from any sensory modality.

  11. Connections and curvatures on complex Riemannian manifolds

    International Nuclear Information System (INIS)

    Ganchev, G.; Ivanov, S.

    1991-05-01

    Characteristic connection and characteristic holomorphic sectional curvatures are introduced on a complex Riemannian manifold (not necessarily with holomorphic metric). For the class of complex Riemannian manifolds with holomorphic characteristic connection a classification of the manifolds with (pointwise) constant holomorphic characteristic curvature is given. It is shown that the conformal geometry of complex analytic Riemannian manifolds can be naturally developed on the class of locally conformal holomorphic Riemannian manifolds. Complex Riemannian manifolds locally conformal to the complex Euclidean space are characterized with zero conformal fundamental tensor and zero conformal characteristic tensor. (author). 12 refs

  12. Study on antilock brake system with elastic membrane vibration generated by controlled solenoid excitation

    International Nuclear Information System (INIS)

    Wibowo,; Zakaria,; Lambang, Lullus; Triyono,; Muhayat, Nurul

    2016-01-01

    The most effective chassis control system for improving vehicle safety during severe braking is anti-lock braking system (ABS). Antilock effect can be gained by vibrate the pad brake at 7 to 20 cycle per second. The aim of this study is to design a new method of antilock braking system with membrane elastic vibrated by solenoid. The influence of the pressure fluctuations of brake fluid is investigated. Vibration data is collected using a small portable accelerometer-slam stick. The experiment results that the vibration of brake pad caused by controlled solenoid excitation at 10 Hz is obtained by our new method. The result of measurements can be altered by varying brake fluid pressure.

  13. Study on antilock brake system with elastic membrane vibration generated by controlled solenoid excitation

    Energy Technology Data Exchange (ETDEWEB)

    Wibowo,, E-mail: wibowo-uns@yahoo.com; Zakaria,, E-mail: zakaaria27@gmail.com; Lambang, Lullus, E-mail: lulus-l@yahoo.com; Triyono,, E-mail: tyon-bila@yahoo.co.id; Muhayat, Nurul, E-mail: nurulmuhayat@ymail.com [Mechanical Engineering Department, Sebelas Maret University, Surakarta 57128 (Indonesia)

    2016-03-29

    The most effective chassis control system for improving vehicle safety during severe braking is anti-lock braking system (ABS). Antilock effect can be gained by vibrate the pad brake at 7 to 20 cycle per second. The aim of this study is to design a new method of antilock braking system with membrane elastic vibrated by solenoid. The influence of the pressure fluctuations of brake fluid is investigated. Vibration data is collected using a small portable accelerometer-slam stick. The experiment results that the vibration of brake pad caused by controlled solenoid excitation at 10 Hz is obtained by our new method. The result of measurements can be altered by varying brake fluid pressure.

  14. Controlled Patterning of Plasmonic Dimers by Using an Ultrathin Nanoporous Alumina Membrane as a Shadow Mask.

    Science.gov (United States)

    Hao, Qi; Huang, Hao; Fan, Xingce; Yin, Yin; Wang, Jiawei; Li, Wan; Qiu, Teng; Ma, Libo; Chu, Paul K; Schmidt, Oliver G

    2017-10-18

    We report on design and fabrication of patterned plasmonic dimer arrays by using an ultrathin anodic aluminum oxide (AAO) membrane as a shadow mask. This strategy allows for controllable fabrication of plasmonic dimers where the location, size, and orientation of each particle in the dimer pairs can be independently tuned. Particularly, plasmonic dimers with ultrasmall nanogaps down to the sub-10 nm scale as well as a large dimer density up to 1.0 × 10 10 cm -2 are fabricated over a centimeter-sized area. The plasmonic dimers exhibit significant surface-enhanced Raman scattering (SERS) enhancement with a polarization-dependent behavior, which is well interpreted by finite-difference time-domain (FDTD) simulations. Our results reveal a facile approach for controllable fabrication of large-area dimer arrays, which is of fundamental interest for plasmon-based applications in surface-enhanced spectroscopy, biochemical sensing, and optoelectronics.

  15. Curvature effects on the electronic and transport properties of semiconductor films

    Science.gov (United States)

    Batista, F. F.; Chaves, Andrey; da Costa, D. R.; Farias, G. A.

    2018-05-01

    Within the effective mass approximation, we study the curvature effects on the electronic and transport properties of semiconductor films. We investigate how the geometry-induced potential resulting exclusively from periodic ripples in the film induces electronic confinement and a superlattice band structure. For fixed curvature parameters, such a confinement can be easily tuned by an external electric field, hence features of the superlattice band structure such as its energy gaps and band curvature can be controlled by an external parameter. We also show that, for some values of curvature and electric field, it is possible to obtain massless Dirac bands for a smooth curved structure. Moreover, we use a wave packet propagation method to demonstrate that the ripples are responsible for a significant inter-sub-band transition, specially for moderate values of the ripple height.

  16. Dynamic water management of polymer electrolyte membrane fuel cells using intermittent RH control

    KAUST Repository

    Hussaini, I.S.; Wang, C.Y.

    2010-01-01

    A novel method of water management of polymer electrolyte membrane (PEM) fuel cells using intermittent humidification is presented in this study. The goal is to maintain the membrane close to full humidification, while eliminating channel flooding

  17. Control of Target Molecular Recognition in a Small Pore Space with Biomolecule-Recognition Gating Membrane.

    Science.gov (United States)

    Okuyama, Hiroto; Oshiba, Yuhei; Ohashi, Hidenori; Yamaguchi, Takeo

    2018-05-01

    A biomolecule-recognition gating membrane, which introduces thermosensitive graft polymer including molecular recognition receptor into porous membrane substrate, can close its pores by recognizing target biomolecule. The present study reports strategies for improving both versatility and sensitivity of the gating membrane. First, the membrane is fabricated by introducing the receptor via a selectively reactive click reaction improving the versatility. Second, the sensitivity of the membrane is enhanced via an active delivering method of the target molecules into the pores. In the method, the tiny signal of the target biomolecule is amplified as obvious pressure change. Furthermore, this offers 15 times higher sensitivity compared to the previously reported passive delivering method (membrane immersion to sample solution) with significantly shorter recognition time. The improvement will aid in applying the gating membrane to membrane sensors in medical fields. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Application of DBNPA dosage for biofouling control in spiral wound membrane systems

    KAUST Repository

    Siddiqui, Amber

    2017-05-30

    Biocides may be used to control biofouling in spiral-wound reverse osmosis (RO) and nanofiltration (NF) systems. The objective of this study was to investigate the effect of biocide 2,2-dibromo-3-ni-trilopropionamide (DBNPA) dosage on biofouling control. Preventive biofouling control was studied applying a continuous dosage of substrate (0.5 mg/L) and DBNPA (1 mg/L). Curative biofouling control was studied on pre-grown biofilms, once again applying a continuous dosage of substrate (0.5 mg acetate C/L) and DBNPA (1 and 20 mg/L). Biofouling studies were performed in membrane fouling simulators (MFSs) supplied with biodegradable substrate and DBNPA. The pressure drop was monitored in time and at the end of the study, the accumulated biomass in MFS was quantified by adenosine triphosphate (ATP) and total organic carbon (TOC) analysis. Continuous dosage of DBNPA (1 mg/L) prevented pressure drop increase and biofilm accumulation in the MFSs during a run time of 7 d, showing that biofouling can be managed by preventive DBNPA dosage. For biofouled systems, continuous dosage of DBNPA (1 and 20 mg/L) inactivated the accumulated biomass but did not restore the original pressure drop and did not remove the accumulated inactive cells and extracellular polymeric substances (EPS), indicating DBNPA dosage is not suitable for curative biofouling control.

  19. Zero curvature conditions and conformal covariance

    International Nuclear Information System (INIS)

    Akemann, G.; Grimm, R.

    1992-05-01

    Two-dimensional zero curvature conditions were investigated in detail, with special emphasis on conformal properties, and the appearance of covariant higher order differential operators constructed in terms of a projective connection was elucidated. The analysis is based on the Kostant decomposition of simple Lie algebras in terms of representations with respect to their 'principal' SL(2) subalgebra. (author) 27 refs

  20. Norm of the Riemannian Curvature Tensor

    Indian Academy of Sciences (India)

    We consider the Riemannian functional R p ( g ) = ∫ M | R ( g ) | p d v g defined on the space of Riemannian metrics with unit volume on a closed smooth manifold where R ( g ) and d v g denote the corresponding Riemannian curvature tensor and volume form and p ∈ ( 0 , ∞ ) . First we prove that the Riemannian metrics ...

  1. Constraining inverse curvature gravity with supernovae

    Energy Technology Data Exchange (ETDEWEB)

    Mena, Olga; Santiago, Jose; /Fermilab; Weller, Jochen; /University Coll., London /Fermilab

    2005-10-01

    We show that the current accelerated expansion of the Universe can be explained without resorting to dark energy. Models of generalized modified gravity, with inverse powers of the curvature can have late time accelerating attractors without conflicting with solar system experiments. We have solved the Friedman equations for the full dynamical range of the evolution of the Universe. This allows us to perform a detailed analysis of Supernovae data in the context of such models that results in an excellent fit. Hence, inverse curvature gravity models represent an example of phenomenologically viable models in which the current acceleration of the Universe is driven by curvature instead of dark energy. If we further include constraints on the current expansion rate of the Universe from the Hubble Space Telescope and on the age of the Universe from globular clusters, we obtain that the matter content of the Universe is 0.07 {le} {omega}{sub m} {le} 0.21 (95% Confidence). Hence the inverse curvature gravity models considered can not explain the dynamics of the Universe just with a baryonic matter component.

  2. On Mass, Spacetime Curvature, and Gravity

    Science.gov (United States)

    Janis, Allen I.

    2018-01-01

    The frequently used analogy of a massive ball distorting an elastic sheet, which is used to illustrate why mass causes spacetime curvature and gravitational attraction, is criticized in this article. A different analogy that draws on the students' previous knowledge of spacetime diagrams in special relativity is suggested.

  3. Curvature tensor copies in affine geometry

    International Nuclear Information System (INIS)

    Srivastava, P.P.

    1981-01-01

    The sets of space-time and spin-connections which give rise to the same curvature tensor are constructed. The corresponding geometries are compared. Results are illustrated by an explicit calculation and comment on the copies in Einstein-Cartan and Weyl-Cartan geometries. (Author) [pt

  4. Gaussian curvature on hyperelliptic Riemann surfaces

    Indian Academy of Sciences (India)

    Indian Acad. Sci. (Math. Sci.) Vol. 124, No. 2, May 2014, pp. 155–167. c Indian Academy of Sciences. Gaussian curvature on hyperelliptic Riemann surfaces. ABEL CASTORENA. Centro de Ciencias Matemáticas (Universidad Nacional Autónoma de México,. Campus Morelia) Apdo. Postal 61-3 Xangari, C.P. 58089 Morelia,.

  5. Resolving curvature singularities in holomorphic gravity

    NARCIS (Netherlands)

    Mantz, C.L.M.; Prokopec, T.

    2011-01-01

    We formulate a holomorphic theory of gravity and study how the holomorphy symmetry alters the two most important singular solutions of general relativity: black holes and cosmology. We show that typical observers (freely) falling into a holomorphic black hole do not encounter a curvature

  6. Curvature driven instabilities in toroidal plasmas

    International Nuclear Information System (INIS)

    Andersson, P.

    1986-11-01

    The electromagnetic ballooning mode, the curvature driven trapped electron mode and the toroidally induced ion temperature gradient mode have been studies. Eigenvalue equations have been derived and solved both numerically and analytically. For electromagnetic ballooning modes the effects of convective damping, finite Larmor radius, higher order curvature terms, and temperature gradients have been investigated. A fully toroidal fluid ion model has been developed. It is shown that a necessary and sufficient condition for an instability below the MHD limit is the presence of an ion temperature gradient. Analytical dispersion relations giving results in good agreement with numerical solutions are also presented. The curvature driven trapped electron modes are found to be unstable for virtually all parameters with growth rates of the order of the diamagnetic drift frequency. Studies have been made, using both a gyrokinetic ion description and the fully toroidal ion model. Both analytical and numerical results are presented and are found to be in good agreement. The toroidally induced ion temperature gradients modes are found to have a behavior similar to that of the curvature driven trapped electron modes and can in the electrostatic limit be described by a simple quadratic dispersion equation. (author)

  7. Random paths with curvature dependent action

    International Nuclear Information System (INIS)

    Ambjoern, J.; Durhuus, B.

    1986-11-01

    We study discretized random paths with a curvature dependent action. The scaling limits of the corresponding statistical mechanical models can be constructed explicitly and are either usual Brownian motion or a theory where the correlations of tangents are nonzero and described by diffusion on the unit sphere. In the latter case the two point function has an anomalous dimension η = 1. (orig.)

  8. Apical membrane P2Y4 purinergic receptor controls K+ secretion by strial marginal cell epithelium

    Directory of Open Access Journals (Sweden)

    Scofield Margaret A

    2005-11-01

    Full Text Available Abstract Background It was previously shown that K+ secretion by strial marginal cell epithelium is under the control of G-protein coupled receptors of the P2Y family in the apical membrane. Receptor activation by uracil nucleotides (P2Y2, P2Y4 or P2Y6 leads to a decrease in the electrogenic K+ secretion. The present study was conducted to determine the subtype of the functional purinergic receptor in gerbil stria vascularis, to test if receptor activation leads to elevation of intracellular [Ca2+] and to test if the response to these receptors undergoes desensitization. Results The transepithelial short circuit current (Isc represents electrogenic K+ secretion and was found to be decreased by uridine 5'-triphosphate (UTP, adenosine 5'-triphosphate (ATP and diadenosine tetraphosphate (Ap4A but not uridine 5'-diphosphate (UDP at the apical membrane of marginal cells of the gerbil stria vascularis. The potencies of these agonists were consistent with rodent P2Y4 and P2Y2 but not P2Y6 receptors. Activation caused a biphasic increase in intracellular [Ca2+] that could be partially blocked by 2-aminoethoxy-diphenyl borate (2-APB, an inhibitor of the IP3 receptor and store-operated channels. Suramin (100 μM did not inhibit the effect of UTP (1 μM. The ineffectiveness of suramin at the concentration used was consistent with P2Y4 but not P2Y2. Transcripts for both P2Y2 and P2Y4 were found in the stria vascularis. Sustained exposure to ATP or UTP for 15 min caused a depression of Isc that appeared to have two components but with apparently no chronic desensitization. Conclusion The results support the conclusion that regulation of K+ secretion across strial marginal cell epithelium occurs by P2Y4 receptors at the apical membrane. The apparent lack of desensitization of the response is consistent with two processes: a rapid-onset phosphorylation of KCNE1 channel subunit and a slower-onset of regulation by depletion of plasma membrane PIP2.

  9. Continued Advancement of Supported Liquid Membranes for Carbon Dioxide Control in Extravehicular Activity Applications

    Science.gov (United States)

    Wickham, David T.; Gleason, Kevin J.; Engel, Jeffrey R.; Cowley, Scott W.; Chullen, Cinda

    2015-01-01

    The Development of a new, robust, portable life support system (PLSS) is currently a high NASA priority in order to support longer and safer extravehicular activity (EVA) missions that will be necessary as space travel extends to near-Earth asteroids and eventually Mars. One of the critical PLSS functions is maintaining the carbon dioxide (CO2) concentration in the suit at acceptable levels. The Metal Oxide (MetOx) canister has a finite CO2 adsorption capacity and therefore in order to extend mission times, the unit would have to be larger and heavier, which is undesirable; therefore new CO2 control technologies must be developed. While recent work has centered on the use of alternating sorbent beds that can be regenerated during the EVA, this strategy increases the system complexity and power consumption. A simpler approach is to use a membrane that vents CO2 to space but retains oxygen(O2). A membrane has many advantages over current technology: it is a continuous system with no theoretical capacity limit, it requires no consumables, and it requires no hardware for switching beds between absorption and regeneration. Conventional gas separation membranes do not have adequate selectivity for use in the PLSS, but the required performance could be obtained with a supported liquid membrane (SLM), which consists of a microporous film filled with a liquid that selectively reacts with CO2 over oxygen (O2). In a recently completed Phase II Small Business Innovative Research project, Reaction Systems developed a new reactive liquid that has effectively zero vapor pressure, making it an ideal candidate for use in an SLM. Results obtained with the SLM in a flat sheet configuration with representative pressures of CO2, O2, and water (H2O) have shown that the CO2 permeation rate and CO2/O2 selectivity requirements have been met. In addition, the SLM vents moisture to space very effectively. The SLM has also been prepared and tested in a hollow fiber form, which will be

  10. Polyamines control of cation transport across plant membranes: implications for ion homeostasis and abiotic stress signaling.

    Science.gov (United States)

    Pottosin, Igor; Shabala, Sergey

    2014-01-01

    Polyamines are unique polycationic metabolites, controlling a variety of vital functions in plants, including growth and stress responses. Over the last two decades a bulk of data was accumulated providing explicit evidence that polyamines play an essential role in regulating plant membrane transport. The most straightforward example is a blockage of the two major vacuolar cation channels, namely slow (SV) and fast (FV) activating ones, by the micromolar concentrations of polyamines. This effect is direct and fully reversible, with a potency descending in a sequence Spm(4+) > Spd(3+) > Put(2+). On the contrary, effects of polyamines on the plasma membrane (PM) cation and K(+)-selective channels are hardly dependent on polyamine species, display a relatively low affinity, and are likely to be indirect. Polyamines also affect vacuolar and PM H(+) pumps and Ca(2+) pump of the PM. On the other hand, catabolization of polyamines generates H2O2 and other reactive oxygen species (ROS), including hydroxyl radicals. Export of polyamines to the apoplast and their oxidation there by available amine oxidases results in the induction of a novel ion conductance and confers Ca(2+) influx across the PM. This mechanism, initially established for plant responses to pathogen attack (including a hypersensitive response), has been recently shown to mediate plant responses to a variety of abiotic stresses. In this review we summarize the effects of polyamines and their catabolites on cation transport in plants and discuss the implications of these effects for ion homeostasis, signaling, and plant adaptive responses to environment.

  11. Electrostatic control by lipids upon the membrane-bound (Na+ + K+)-ATPase.

    Science.gov (United States)

    Ahrens, M L

    1981-04-06

    In this paper, the membrane-bound (Na+ + K+)-ATPase from bovine brain is shown to be controlled by electrostatic alterations of the charged lipids surrounding the enzyme. The properties under investigation are the enzymatic activity, activation energy and the response of the enzymatic system to temperature. Arrhenius plots of the ATPase activity are biphasic with a break at temperature Ti. The temperature Ti, the activation energies at temperatures above and below Ti, and the enzymatic activity at any constant temperature have been shown to depend upon the concentrations of alkali and alkaline-earth metal ions in the solution. These electrolyte dependencies are ascribed to changes of electrostatic conditions at the lipids surrounding the ATPase. If the higher electrostatic screening ability of divalent ions is taken into account, the results in the presence of mono- and divalent ions become virtually the same. As a result of this work, it is concluded that electrostatic alterations are transmitted to the ATPase from the lipids of the membrane in which the enzyme is embedded. Inhibition and activation of the enzyme by mono-and divalent metal ions may thus be explained without any auxiliary hypothesis, particularly without postulating specific binding sites for the different ionic species at the protein. In addition, the specific lipid requirement of the ATPase may be understood better in the light of this interpretation.

  12. Surfactant-controlled etching of ion track nanopores and its practical applications in membrane technology

    International Nuclear Information System (INIS)

    Apel, P.Yu.; Blonskaya, I.V.; Dmitriev, S.N.; Mamonova, T.I.; Orelovitch, O.L.; Sartowska, B.; Yamauchi, Yu.

    2008-01-01

    The effect of surfactants on chemical development of ion tracks in polymers has been studied. It has been shown that surface-active agents added to an alkaline etching solution adsorb on the polymer surface at the pore entrances. This reduces the etch rate, which leads to the formation of pores tapered toward the surface. Self-assembly of surfactant molecules at the pore entrance creates a barrier for their penetration into the etched-out nanopores, whereas hydroxide ions diffuse freely. Due to this, the internal pore volume grows faster than the pore surface diameter. The ability to control pore shape is demonstrated with the fabrication of profiled nano- and micropores in polyethylene terephthalate, polycarbonate. Some earlier published data on small track-etched pores in polycarbonate (in particular, the pore diameter vs. etching time curves measured conductometrically) have been revised in light of the above findings. Adding surfactants to chemical etchants makes it possible to optimize the structure of track membranes, thus improving their retention and permeation properties. Asymmetric membranes with thin skin retention layers have been produced and their performance studied

  13. Controlling the porosity of a polyethersulfone membrane surface with an XeCl laser

    International Nuclear Information System (INIS)

    Pazokian, Hedieh; Mehrabadi, Adeleh H P; Mollabashi, Mahmoud; Barzin, Jalal

    2016-01-01

    Pure and polyvinyl pyrrolidone blend polyethersulfone (PES) membranes were irradiated by an XeCl laser with various numbers of pulses at different fluences to investigate the changes in the surface morphology and the porosity. The results show that the membrane pore size and distribution on the surface can be modified following irradiation dependent on the laser fluence, the number of pulses and the membrane composition. These changes are very attractive for improving the membrane surface in filtration processes and biological applications. (paper)

  14. A Coincidence Detection Mechanism Controls PX-BAR Domain-Mediated Endocytic Membrane Remodeling via an Allosteric Structural Switch.

    Science.gov (United States)

    Lo, Wen-Ting; Vujičić Žagar, Andreja; Gerth, Fabian; Lehmann, Martin; Puchkov, Dymtro; Krylova, Oxana; Freund, Christian; Scapozza, Leonardo; Vadas, Oscar; Haucke, Volker

    2017-11-20

    Clathrin-mediated endocytosis occurs by bending and remodeling of the membrane underneath the coat. Bin-amphiphysin-rvs (BAR) domain proteins are crucial for endocytic membrane remodeling, but how their activity is spatiotemporally controlled is largely unknown. We demonstrate that the membrane remodeling activity of sorting nexin 9 (SNX9), a late-acting endocytic PX-BAR domain protein required for constriction of U-shaped endocytic intermediates, is controlled by an allosteric structural switch involving coincident detection of the clathrin adaptor AP2 and phosphatidylinositol-3,4-bisphosphate (PI(3,4)P 2 ) at endocytic sites. Structural, biochemical, and cell biological data show that SNX9 is autoinhibited in solution. Binding to PI(3,4)P 2 via its PX-BAR domain, and concomitant association with AP2 via sequences in the linker region, releases SNX9 autoinhibitory contacts to enable membrane constriction. Our results reveal a mechanism for restricting the latent membrane remodeling activity of BAR domain proteins to allow spatiotemporal coupling of membrane constriction to the progression of the endocytic pathway. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Potentiometric determination of trypsin using a polymeric membrane polycation-sensitive electrode based on current-controlled reagent delivery.

    Science.gov (United States)

    Chen, Yan; Ding, Jiawang; Qin, Wei

    2012-12-01

    A potentiometric biosensor for the determination of trypsin is described based on current-controlled reagent delivery. A polymeric membrane protamine-sensitive electrode with dinonylnaphthalene sulfonate as cation exchanger is used for in situ generation of protamine. Diffusion of protamine across the polymeric membrane can be controlled precisely by applying an external current. The hydrolysis catalyzed with trypsin in sample solution decreases the concentration of free protamine released at the sample-membrane interface and facilitates the stripping of protamine out of the membrane surface via the ion-exchange process with sodium ions from the sample solution, thus decreasing the membrane potential, by which the protease can be sensed potentiometrically. The influences of anodic current amplitude, current pulse duration and protamine concentration in the inner filling solution on the membrane potential response have been studied. Under optimum conditions, the proposed protamine-sensitive electrode is useful for continuous and reversible detection of trypsin over the concentration range of 0.5-5UmL(-1) with a detection limit of 0.3UmL(-1). The proposed detection strategy provides a rapid and reagentless way for the detection of protease activities and offers great potential in the homogeneous immunoassays using proteases as labels. Copyright © 2012 Elsevier B.V. All rights reserved.

  16. Control and experimental characterization of a methanol reformer for a 350 W high temperature polymer electrolyte membrane fuel cell system

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen; Sahlin, Simon Lennart

    2013-01-01

    is the water and methanol mixture fuel flow and the burner fuel/air ratio and combined flow. An experimental setup is presented capable of testing the methanol reformer used in the Serenergy H3 350 Mobile Battery Charger; a high temperature polymer electrolyte membrane (HTPEM) fuel cell system......This work presents a control strategy for controlling the methanol reformer temperature of a 350 W high temperature polymer electrolyte membrane fuel cell system, by using a cascade control structure for reliable system operation. The primary states affecting the methanol catalyst bed temperature....... The experimental system consists of a fuel evaporator utilizing the high temperature waste gas from the cathode air cooled 45 cell HTPEM fuel cell stack. The fuel cells used are BASF P1000 MEAs which use phosphoric acid doped polybenzimidazole membranes. The resulting reformate gas output of the reformer system...

  17. A review of fault tolerant control strategies applied to proton exchange membrane fuel cell systems

    Science.gov (United States)

    Dijoux, Etienne; Steiner, Nadia Yousfi; Benne, Michel; Péra, Marie-Cécile; Pérez, Brigitte Grondin

    2017-08-01

    Fuel cells are powerful systems for power generation. They have a good efficiency and do not generate greenhouse gases. This technology involves a lot of scientific fields, which leads to the appearance of strongly inter-dependent parameters. This makes the system particularly hard to control and increases fault's occurrence frequency. These two issues call for the necessity to maintain the system performance at the expected level, even in faulty operating conditions. It is called "fault tolerant control" (FTC). The present paper aims to give the state of the art of FTC applied to the proton exchange membrane fuel cell (PEMFC). The FTC approach is composed of two parts. First, a diagnosis part allows the identification and the isolation of a fault; it requires a good a priori knowledge of all the possible faults. Then, a control part allows an optimal control strategy to find the best operating point to recover/mitigate the fault; it requires the knowledge of the degradation phenomena and their mitigation strategies.

  18. Shaping of parabolic cylindrical membrane reflectors for the Dart Precision Test Bed

    Science.gov (United States)

    Morgan, R.; Agnes, Gregory S.; Dragovan, M.; Barber, D.; Marcin, M.; White, C.; Dooley, J.; Hatheway, A.

    2004-01-01

    The DART is a new telescope architecture consisting of a single aperture formed from two cylindrical parabolic reflectors. The system is ideally suited to using tensioned membranes for the reflective surfaces, owing to the zero Gaussian curvature of a cylindrical parabola. In this paper, we present experimental measurements for shaping the membranes by using curved boundary elements to achieve coarse shaping, and a pair of precision rails shaped by moments and forces at the ends, and lightly pushed into the surface, to provide fine shape control.

  19. Photocuring of stimulus responsive membranes for controlled-release of drugs having different molecular weights

    International Nuclear Information System (INIS)

    Ng, Loo-Teck; Nakayama, Hiroshi; Kaetsu, Isao; Uchida, Kumao

    2005-01-01

    Intelligent drug delivery membranes were prepared by photocuring poly(acrylic acid) coatings onto poly(2-hydroxyethyl methacrylate) membranes each with model drugs of different molecular weights being incorporated. pH-responsive release behaviours of the model drugs which included sodium salicylate, nicotinamide, nicotinic acid, methylene blue, brilliant green and crystal violet were investigated. Only the membrane with methylene blue incorporated showed a clear pH-responsive release and other drug-incorporated membranes showed no intelligent behaviour. These phenomena were explained in terms of the difference in diffusivity of drugs through polymer matrices of the membranes attributable to the difference in the molecular weights of drugs

  20. Photocuring of stimulus responsive membranes for controlled-release of drugs having different molecular weights

    Energy Technology Data Exchange (ETDEWEB)

    Ng, Loo-Teck [School of Science, Food and Horticulture, University of Western Sydney, Locked bag 1797, Penrith South DC, NSW 1797 (Australia)]. E-mail: l.ng@uws.edu.au; Nakayama, Hiroshi [Department of Nuclear Engineering, Faculty of Science and technology, Kinki University, Kowakae, 3-4-1, Higashi-Osaka 577-8502 (Japan); Kaetsu, Isao [Department of Nuclear Engineering, Faculty of Science and technology, Kinki University, Kowakae, 3-4-1, Higashi-Osaka 577-8502 (Japan)]. E-mail: kaetsu@ned.kindai.ac.jp; Uchida, Kumao [Department of Nuclear Engineering, Faculty of Science and technology, Kinki University, Kowakae, 3-4-1, Higashi-Osaka 577-8502 (Japan)

    2005-06-01

    Intelligent drug delivery membranes were prepared by photocuring poly(acrylic acid) coatings onto poly(2-hydroxyethyl methacrylate) membranes each with model drugs of different molecular weights being incorporated. pH-responsive release behaviours of the model drugs which included sodium salicylate, nicotinamide, nicotinic acid, methylene blue, brilliant green and crystal violet were investigated. Only the membrane with methylene blue incorporated showed a clear pH-responsive release and other drug-incorporated membranes showed no intelligent behaviour. These phenomena were explained in terms of the difference in diffusivity of drugs through polymer matrices of the membranes attributable to the difference in the molecular weights of drugs.

  1. A Japanese Stretching Intervention Can Modify Lumbar Lordosis Curvature.

    Science.gov (United States)

    Kadono, Norio; Tsuchiya, Kazushi; Uematsu, Azusa; Kamoshita, Hiroshi; Kiryu, Kazunori; Hortobágyi, Tibor; Suzuki, Shuji

    2017-08-01

    Eighteen healthy male adults were assigned to either an intervention or control group. Isogai dynamic therapy (IDT) is one of Japanese stretching interventions and has been practiced for over 70 years. However, its scientific quantitative evidence remains unestablished. The objective of this study was to determine whether IDT could modify lumbar curvature in healthy young adults compared with stretching exercises used currently in clinical practice. None of previous studies have provided data that conventional stretching interventions could modify spinal curvatures. However, this study provides the first evidence that a specific form of a Japanese stretching intervention can acutely modify the spinal curvatures. We compared the effects of IDT, a Japanese stretching intervention (n=9 males), with a conventional stretching routine (n=9 males) used widely in clinics to modify pelvic tilt and lumbar lordosis (LL) angle. We measured thoracic kyphosis (TK) and LL angles 3 times during erect standing using the Spinal Mouse before and after each intervention. IDT consisted of: (1) hip joint correction, (2) pelvic tilt correction, (3) lumbar alignment correction, and (4) squat exercise stretch. The control group performed hamstring stretches while (1) standing and (2) sitting. IDT increased LL angle to 25.1 degrees (±5.9) from 21.2 degrees (±6.9) (P=0.047) without changing TK angle (pretest: 36.8 degrees [±6.9]; posttest: 36.1 degrees [±6.5]) (P=0.572). The control group showed no changes in TK (P=0.819) and LL angles (P=0.744). IDT can thus be effective for increasing LL angle, hence anterior pelvic tilt. Such modifications could ameliorate low back pain and improve mobility in old adults with an unfavorable pelvic position.

  2. Gaussian curvature elasticity determined from global shape transformations and local stress distributions : a comparative study using the MARTINI model

    NARCIS (Netherlands)

    Hu, Mingyang; de Jong, Djurre H.; Marrink, Siewert J.; Deserno, Markus

    2013-01-01

    We calculate the Gaussian curvature modulus (k) over bar of a systematically coarse-grained (CG) one-component lipid membrane by applying the method recently proposed by Hu et al. [Biophys. J., 2012, 102, 1403] to the MARTINI representation of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). We

  3. Sensitive zone parameters and curvature radius evaluation for polymer optical fiber curvature sensors

    Science.gov (United States)

    Leal-Junior, Arnaldo G.; Frizera, Anselmo; José Pontes, Maria

    2018-03-01

    Polymer optical fibers (POFs) are suitable for applications such as curvature sensors, strain, temperature, liquid level, among others. However, for enhancing sensitivity, many polymer optical fiber curvature sensors based on intensity variation require a lateral section. Lateral section length, depth, and surface roughness have great influence on the sensor sensitivity, hysteresis, and linearity. Moreover, the sensor curvature radius increase the stress on the fiber, which leads on variation of the sensor behavior. This paper presents the analysis relating the curvature radius and lateral section length, depth and surface roughness with the sensor sensitivity, hysteresis and linearity for a POF curvature sensor. Results show a strong correlation between the decision parameters behavior and the performance for sensor applications based on intensity variation. Furthermore, there is a trade-off among the sensitive zone length, depth, surface roughness, and curvature radius with the sensor desired performance parameters, which are minimum hysteresis, maximum sensitivity, and maximum linearity. The optimization of these parameters is applied to obtain a sensor with sensitivity of 20.9 mV/°, linearity of 0.9992 and hysteresis below 1%, which represent a better performance of the sensor when compared with the sensor without the optimization.

  4. Hemocompatible control of sulfobetaine-grafted polypropylene fibrous membranes in human whole blood via plasma-induced surface zwitterionization.

    Science.gov (United States)

    Chen, Sheng-Han; Chang, Yung; Lee, Kueir-Rarn; Wei, Ta-Chin; Higuchi, Akon; Ho, Feng-Ming; Tsou, Chia-Chun; Ho, Hsin-Tsung; Lai, Juin-Yih

    2012-12-21

    In this work, the hemocompatibility of zwitterionic polypropylene (PP) fibrous membranes with varying grafting coverage of poly(sulfobetaine methacrylate) (PSBMA) via plasma-induced surface polymerization was studied. Charge neutrality of PSBMA-grafted layers on PP membrane surfaces was controlled by the low-pressure and atmospheric plasma treatment in this study. The effects of grafting composition, surface hydrophilicity, and hydration capability on blood compatibility of the membranes were determined. Protein adsorption onto the different PSBMA-grafted PP membranes from human fibrinogen solutions was measured by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. Blood platelet adhesion and plasma clotting time measurements from a recalcified platelet-rich plasma solution were used to determine if platelet activation depends on the charge bias of the grafted PSBMA layer. The charge bias of PSBMA layer deviated from the electrical balance of positively and negatively charged moieties can be well-controlled via atmospheric plasma-induced interfacial zwitterionization and was further tested with human whole blood. The optimized PSBMA surface graft layer in overall charge neutrality has a high hydration capability and keeps its original blood-inert property of antifouling, anticoagulant, and antithrmbogenic activities when it comes into contact with human blood. This work suggests that the hemocompatible nature of grafted PSBMA polymers by controlling grafting quality via atmospheric plasma treatment gives a great potential in the surface zwitterionization of hydrophobic membranes for use in human whole blood.

  5. A curvature theory for discrete surfaces based on mesh parallelity

    KAUST Repository

    Bobenko, Alexander Ivanovich; Pottmann, Helmut; Wallner, Johannes

    2009-01-01

    We consider a general theory of curvatures of discrete surfaces equipped with edgewise parallel Gauss images, and where mean and Gaussian curvatures of faces are derived from the faces' areas and mixed areas. Remarkably these notions are capable

  6. Organizing membrane-curving proteins: the emerging dynamical picture.

    Science.gov (United States)

    Simunovic, Mijo; Bassereau, Patricia; Voth, Gregory A

    2018-03-30

    Lipid membranes play key roles in cells, such as in trafficking, division, infection, remodeling of organelles, among others. The key step in all these processes is creating membrane curvature, typically under the control of many anchored, adhered or included proteins. However, it has become clear that the membrane itself can mediate the interactions among proteins to produce highly ordered assemblies. Computer simulations are ideally suited to investigate protein organization and the dynamics of membrane remodeling at near-micron scales, something that is extremely challenging to tackle experimentally. We review recent computational efforts in modeling protein-caused membrane deformation mechanisms, specifically focusing on coarse-grained simulations. We highlight work that exposed the membrane-mediated ordering of proteins into lines, meshwork, spirals and other assemblies, in what seems to be a very generic mechanism driven by a combination of short and long-ranged forces. Modulating the mechanical properties of membranes is an underexplored signaling mechanism in various processes deserving of more attention in the near future. Copyright © 2018 Elsevier Ltd. All rights reserved.

  7. Correlations between gravitropic curvature and auxin movement across gravistimulated roots of Zea mays

    Science.gov (United States)

    Young, L. M.; Evans, M. L.; Hertel, R.

    1990-01-01

    We compared the kinetics of auxin redistribution across the caps of primary roots of 2-day-old maize (Zea mays, cv Merit) seedlings with the time course of gravitropic curvature. [3H] indoleacetic acid was applied to one side of the cap in an agar donor and radioactivity moving across the cap was collected in an agar receiver applied to the opposite side. Upon gravistimulation the roots first curved upward slightly, then returned to the horizontal and began curving downward, reaching a final angle of about 67 degrees. Movement of label across the caps of gravistimulated roots was asymmetric with preferential downward movement (ratio downward/upward = ca. 1.6, radioactivity collected during the 90 min following beginning of gravistimulation). There was a close correlation between the development of asymmetric auxin movement across the root cap and the rate of curvature, with both values increasing to a maximum and then declining as the roots approached the final angle of curvature. In roots preadapted to gravity (alternate brief stimulation on opposite flanks over a period of 1 hour) the initial phase of upward curvature was eliminated and downward bending began earlier than for controls. The correlation between asymmetric auxin movement and the kinetics of curvature also held in comparisons between control and preadapted roots. Both downward auxin transport asymmetry and downward curvature occurred earlier in preadapted roots than in controls. These findings are consistent with suggestions that the root cap is not only the site of perception but also the location of the initial redistribution of effectors that ultimately leads to curvature.

  8. Removal versus retention of cerclage in preterm premature rupture of membranes: a randomized controlled trial.

    Science.gov (United States)

    Galyean, Anna; Garite, Thomas J; Maurel, Kimberly; Abril, Diana; Adair, Charles D; Browne, Paul; Combs, C Andrew; How, Helen; Iriye, Brian K; Kominiarek, Michelle; Lu, George; Luthy, David; Miller, Hugh; Nageotte, Michael; Ozcan, Tulin; Porto, Manuel; Ramirez, Mildred; Sawai, Shirley; Sorokin, Yoram

    2014-10-01

    The decision of whether to retain or remove a previously placed cervical cerclage in women who subsequently rupture fetal membranes in a premature gestation is controversial and all studies to date are retrospective. We performed a multicenter randomized controlled trial of removal vs retention of cerclage in these patients to determine whether leaving the cerclage in place prolonged gestation and/or increased the risk of maternal or fetal infection. A prospective randomized multicenter trial of 27 hospitals was performed. Patients included were those with cerclage placement at ≤23 weeks 6 days in singleton or twin pregnancies, with subsequent spontaneous rupture of membranes between 22 weeks 0 days and 32 weeks 6 days. Patients were randomized to retention or removal of cerclage. Patients were then expectantly managed and delivered only for evidence of labor, chorioamnionitis, fetal distress, or other medical or obstetrical indications. Management after 34 weeks was at the clinician's discretion. The initial sample size calculation determined that a total of 142 patients should be included but after a second interim analysis, futility calculations determined that the conditional power for showing statistical significance after randomizing 142 patients for the primary outcome of prolonging pregnancy was 22.8%. Thus the study was terminated after a total of 56 subjects were randomized with complete data available for analysis, 32 to removal and 24 to retention of cerclage. There was no statistical significance in primary outcome of prolonging pregnancy by 1 week comparing the 2 groups (removal 18/32, 56.3%; retention 11/24, 45.8%) P = .59; or chorioamnionitis (removal 8/32, 25.0%; retention 10/24, 41.7%) P = .25, respectively. There was no statistical difference in composite neonatal outcomes (removal 16/33, 50%; retention 17/30, 56%), fetal/neonatal death (removal 4/33, 12%; retention 5/30, 16%); or gestational age at delivery (removal mean 200 days; retention

  9. Collineations of the curvature tensor in general relativity

    Indian Academy of Sciences (India)

    Curvature collineations for the curvature tensor, constructed from a fundamental Bianchi Type-V metric, are studied. We are concerned with a symmetry property of space-time which is called curvature collineation, and we briefly discuss the physical and kinematical properties of the models.

  10. Translating solitons to symplectic and Lagrangian mean curvature flows

    International Nuclear Information System (INIS)

    Han Xiaoli; Li Jiayu

    2007-05-01

    In this paper, we construct finite blow-up examples for symplectic mean curvature flows and we study symplectic translating solitons. We prove that there is no translating solitons with vertical bar α vertical bar ≤ α 0 to the symplectic mean curvature flow or to the almost calibrated Lagrangian mean curvature flow for some α 0 . (author)

  11. Integration of length and curvature in haptic perception

    NARCIS (Netherlands)

    Panday, V.; Bergmann Tiest, W.M.; Kappers, A.M.L.

    2014-01-01

    We investigated if and how length and curvature information are integrated when an object is explored in one hand. Subjects were asked to explore four types of objects between thumb and index finger. Objects differed in either length, curvature, both length and curvature correlated as in a circle,

  12. Weyl curvature tensor in static spherical sources

    International Nuclear Information System (INIS)

    Ponce de Leon, J.

    1988-01-01

    The role of the Weyl curvature tensor in static sources of the Schwarzschild field is studied. It is shown that in general the contribution from the Weyl curvature tensor (the ''purely gravitational field energy'') to the mass-energy inside the body may be positive, negative, or zero. It is proved that a positive (negative) contribution from the Weyl tensor tends to increase (decrease) the effective gravitational mass, the red-shift (from a point in the sphere to infinity), as well as the gravitational force which acts on a constituent matter element of a body. It is also proved that the contribution from the Weyl tensor always is negative in sources with surface gravitational potential larger than (4/9. It is pointed out that large negative contributions from the Weyl tensor could give rise to the phenomenon of gravitational repulsion. A simple example which illustrates the results is discussed

  13. Discrete Curvatures and Discrete Minimal Surfaces

    KAUST Repository

    Sun, Xiang

    2012-06-01

    This thesis presents an overview of some approaches to compute Gaussian and mean curvature on discrete surfaces and discusses discrete minimal surfaces. The variety of applications of differential geometry in visualization and shape design leads to great interest in studying discrete surfaces. With the rich smooth surface theory in hand, one would hope that this elegant theory can still be applied to the discrete counter part. Such a generalization, however, is not always successful. While discrete surfaces have the advantage of being finite dimensional, thus easier to treat, their geometric properties such as curvatures are not well defined in the classical sense. Furthermore, the powerful calculus tool can hardly be applied. The methods in this thesis, including angular defect formula, cotangent formula, parallel meshes, relative geometry etc. are approaches based on offset meshes or generalized offset meshes. As an important application, we discuss discrete minimal surfaces and discrete Koenigs meshes.

  14. On a curvature-statistics theorem

    International Nuclear Information System (INIS)

    Calixto, M; Aldaya, V

    2008-01-01

    The spin-statistics theorem in quantum field theory relates the spin of a particle to the statistics obeyed by that particle. Here we investigate an interesting correspondence or connection between curvature (κ = ±1) and quantum statistics (Fermi-Dirac and Bose-Einstein, respectively). The interrelation between both concepts is established through vacuum coherent configurations of zero modes in quantum field theory on the compact O(3) and noncompact O(2; 1) (spatial) isometry subgroups of de Sitter and Anti de Sitter spaces, respectively. The high frequency limit, is retrieved as a (zero curvature) group contraction to the Newton-Hooke (harmonic oscillator) group. We also make some comments on the physical significance of the vacuum energy density and the cosmological constant problem.

  15. On a curvature-statistics theorem

    Energy Technology Data Exchange (ETDEWEB)

    Calixto, M [Departamento de Matematica Aplicada y Estadistica, Universidad Politecnica de Cartagena, Paseo Alfonso XIII 56, 30203 Cartagena (Spain); Aldaya, V [Instituto de Astrofisica de Andalucia, Apartado Postal 3004, 18080 Granada (Spain)], E-mail: Manuel.Calixto@upct.es

    2008-08-15

    The spin-statistics theorem in quantum field theory relates the spin of a particle to the statistics obeyed by that particle. Here we investigate an interesting correspondence or connection between curvature ({kappa} = {+-}1) and quantum statistics (Fermi-Dirac and Bose-Einstein, respectively). The interrelation between both concepts is established through vacuum coherent configurations of zero modes in quantum field theory on the compact O(3) and noncompact O(2; 1) (spatial) isometry subgroups of de Sitter and Anti de Sitter spaces, respectively. The high frequency limit, is retrieved as a (zero curvature) group contraction to the Newton-Hooke (harmonic oscillator) group. We also make some comments on the physical significance of the vacuum energy density and the cosmological constant problem.

  16. Cosmological signatures of anisotropic spatial curvature

    International Nuclear Information System (INIS)

    Pereira, Thiago S.; Marugán, Guillermo A. Mena; Carneiro, Saulo

    2015-01-01

    If one is willing to give up the cherished hypothesis of spatial isotropy, many interesting cosmological models can be developed beyond the simple anisotropically expanding scenarios. One interesting possibility is presented by shear-free models in which the anisotropy emerges at the level of the curvature of the homogeneous spatial sections, whereas the expansion is dictated by a single scale factor. We show that such models represent viable alternatives to describe the large-scale structure of the inflationary universe, leading to a kinematically equivalent Sachs-Wolfe effect. Through the definition of a complete set of spatial eigenfunctions we compute the two-point correlation function of scalar perturbations in these models. In addition, we show how such scenarios would modify the spectrum of the CMB assuming that the observations take place in a small patch of a universe with anisotropic curvature

  17. Cosmological signatures of anisotropic spatial curvature

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, Thiago S. [Departamento de Física, Universidade Estadual de Londrina, 86057-970, Londrina – PR (Brazil); Marugán, Guillermo A. Mena [Instituto de Estructura de la Materia, IEM-CSIC, Serrano 121, 28006, Madrid (Spain); Carneiro, Saulo, E-mail: tspereira@uel.br, E-mail: mena@iem.cfmac.csic.es, E-mail: saulo.carneiro@pq.cnpq.br [Instituto de Física, Universidade Federal da Bahia, 40210-340, Salvador – BA (Brazil)

    2015-07-01

    If one is willing to give up the cherished hypothesis of spatial isotropy, many interesting cosmological models can be developed beyond the simple anisotropically expanding scenarios. One interesting possibility is presented by shear-free models in which the anisotropy emerges at the level of the curvature of the homogeneous spatial sections, whereas the expansion is dictated by a single scale factor. We show that such models represent viable alternatives to describe the large-scale structure of the inflationary universe, leading to a kinematically equivalent Sachs-Wolfe effect. Through the definition of a complete set of spatial eigenfunctions we compute the two-point correlation function of scalar perturbations in these models. In addition, we show how such scenarios would modify the spectrum of the CMB assuming that the observations take place in a small patch of a universe with anisotropic curvature.

  18. The Riemann-Lovelock curvature tensor

    International Nuclear Information System (INIS)

    Kastor, David

    2012-01-01

    In order to study the properties of Lovelock gravity theories in low dimensions, we define the kth-order Riemann-Lovelock tensor as a certain quantity having a total 4k-indices, which is kth order in the Riemann curvature tensor and shares its basic algebraic and differential properties. We show that the kth-order Riemann-Lovelock tensor is determined by its traces in dimensions 2k ≤ D < 4k. In D = 2k + 1 this identity implies that all solutions of pure kth-order Lovelock gravity are 'Riemann-Lovelock' flat. It is verified that the static, spherically symmetric solutions of these theories, which are missing solid angle spacetimes, indeed satisfy this flatness property. This generalizes results from Einstein gravity in D = 3, which corresponds to the k = 1 case. We speculate about some possible further consequences of Riemann-Lovelock curvature. (paper)

  19. Harmonic curvatures and generalized helices in En

    International Nuclear Information System (INIS)

    Camci, Cetin; Ilarslan, Kazim; Kula, Levent; Hacisalihoglu, H. Hilmi

    2009-01-01

    In n-dimensional Euclidean space E n , harmonic curvatures of a non-degenerate curve defined by Ozdamar and Hacisalihoglu [Ozdamar E, Hacisalihoglu HH. A characterization of Inclined curves in Euclidean n-space. Comm Fac Sci Univ Ankara, Ser A1 1975;24:15-23]. In this paper, we give some characterizations for a non-degenerate curve α to be a generalized helix by using its harmonic curvatures. Also we define the generalized Darboux vector D of a non-degenerate curve α in n-dimensional Euclidean space E n and we show that the generalized Darboux vector D lies in the kernel of Frenet matrix M(s) if and only if the curve α is a generalized helix in the sense of Hayden.

  20. Control of somatic membrane potential in nociceptive neurons and its implications for peripheral nociceptive transmission

    Science.gov (United States)

    Du, Xiaona; Hao, Han; Gigout, Sylvain; Huang, Dongyang; Yang, Yuehui; Li, Li; Wang, Caixue; Sundt, Danielle; Jaffe, David B.; Zhang, Hailin; Gamper, Nikita

    2014-01-01

    Peripheral sensory ganglia contain somata of afferent fibres conveying somatosensory inputs to the central nervous system. Growing evidence suggests that the somatic/perisomatic region of sensory neurons can influence peripheral sensory transmission. Control of resting membrane potential (Erest) is an important mechanism regulating excitability, but surprisingly little is known about how Erest is regulated in sensory neuron somata or how changes in somatic/perisomatic Erest affect peripheral sensory transmission. We first evaluated the influence of several major ion channels on Erest in cultured small-diameter, mostly capsaicin-sensitive (presumed nociceptive) dorsal root ganglion (DRG) neurons. The strongest and most prevalent effect on Erest was achieved by modulating M channels, K2P and 4-aminopiridine-sensitive KV channels, while hyperpolarization-activated cyclic nucleotide-gated, voltage-gated Na+, and T-type Ca2+ channels to a lesser extent also contributed to Erest. Second, we investigated how varying somatic/perisomatic membrane potential, by manipulating ion channels of sensory neurons within the DRG, affected peripheral nociceptive transmission in vivo. Acute focal application of M or KATP channel enhancers or a hyperpolarization-activated cyclic nucleotide-gated channel blocker to L5 DRG in vivo significantly alleviated pain induced by hind paw injection of bradykinin. Finally, we show with computational modelling how somatic/perisomatic hyperpolarization, in concert with the low-pass filtering properties of the t-junction within the DRG, can interfere with action potential propagation. Our study deciphers a complement of ion channels that sets the somatic Erest of nociceptive neurons and provides strong evidence for a robust filtering role of the somatic and perisomatic compartments of peripheral nociceptive neuron. PMID:25168672

  1. Use of cation selective membrane and acid addition for PH control in two-dimensional electrokinetic remediation of copper

    Energy Technology Data Exchange (ETDEWEB)

    Chan, M.S.M.; Lynch, R.J. [Cambridge Univ., Engineering Dept. (United Kingdom); Ilett, D.J. [AEA Technology, Harwell, Oxfordshire (United Kingdom)

    2001-07-01

    The feasibility of using a combination of a cation selective membrane and acid addition for pH control in electrokinetic remediation to toxic and heavy metals from low-permeability soil has been investigated. The high pH generated during the remediation process, as a result of surplus OH{sup -} ions, may cause metal ions to precipitate as hydroxides at or near the cathodes. This region of high pH is known to be associated with high electrical resistance, which limits the remediation efficiency by inhibiting current flow through the soil. One way to control pH is by adding acid to neutralize the OH{sup -} ions. However, preliminary work showed that addition of acid to the cathodic region was not effective in preventing the spread of the alkaline zone from cathodes toward anodes. Precipitates were formed before metal ions reached the cathodic region. Therefore, another method of pH control was investigated, using a cation selective membrane to enhance the electrokinetic process. The membrane was placed in front of the cathodes to contain the OH{sup -} ions generated, and confine the precipitates of metal hydroxide to a small cathodic region. The clean-up of a contaminated site was modelled in a rectangular tank, using silt as the low permeability soul and copper to simulate the contamination. The objective was to redistribute the contaminant so as to concentrate it into a small area. Three experiments were performed with the following methods of pH control: (1) acid addition, (2) use of a cation selective membrane and (3) a combination of acid addition and a cation selective membrane. Using the combined approach, it was found that 75% of the target clean-up section (bounded by the cation selective membrane and the anodes) had more than 40% of the initial copper removed. The general efficiency of remediation increased in the following order. (orig.)

  2. Gravitational curvature an introduction to Einstein's theory

    CERN Document Server

    Frankel, Theodore Thomas

    1979-01-01

    This classic text and reference monograph applies modern differential geometry to general relativity. A brief mathematical introduction to gravitational curvature, it emphasizes the subject's geometric essence, replacing the often-tedious analytical computations with geometric arguments. Clearly presented and physically motivated derivations express the deflection of light, Schwarzchild's exterior and interior solutions, and the Oppenheimer-Volkoff equations. A perfect choice for advanced students of mathematics, this volume will also appeal to mathematicians interested in physics. It stresses

  3. The Riemann-Lovelock Curvature Tensor

    OpenAIRE

    Kastor, David

    2012-01-01

    In order to study the properties of Lovelock gravity theories in low dimensions, we define the kth-order Riemann-Lovelock tensor as a certain quantity having a total 4k-indices, which is kth-order in the Riemann curvature tensor and shares its basic algebraic and differential properties. We show that the kth-order Riemann-Lovelock tensor is determined by its traces in dimensions 2k \\le D

  4. Development of nano-structure controlled polymer electrolyte fuel-cell membranes by high-energy heavy ion irradiation

    International Nuclear Information System (INIS)

    Yamaki, Tetsuya; Asano, Masaharu; Maekawa, Yasunari; Yoshida, Masaru; Kobayashi, Misaki; Nomura, Kumiko; Takagi, Shigeharu

    2008-01-01

    There is increasing interest in polymer electrolyte fuel cells (PEFCs) together with recent worldwide energy demand and environmental issues. In order to develop proton-conductive membranes for PEFCs, we have been using high-energy heavy ion beams from the cyclotron accelerator of Takasaki Ion Accelerators for Advanced Radiation Application (TIARA), JAEA. Our strategic focus is centered on using nano-scale controllability of the ion-beam processing; the membrane preparation involves (1) the irradiation of commercially-available base polymer films with MeV ions, (2) graft polymerization of vinyl monomers into electronically-excited parts along the ion trajectory, called latent tracks, and (3) sulfonation of the graft polymers. Interestingly, the resulting membranes exhibited anisotropic proton transport, i.e., higher conductivity in the thickness direction. According to microscopic observations, this is probably because the columnar electrolyte phase extended, with a width of tens-to-hundreds nanometers, through the membrane. Other excellent membrane properties, e.g., sufficient mechanical strength, high dimensional stability, and low gas permeability should be due to such a controlled structure. (author)

  5. Inflationary scenario from higher curvature warped spacetime

    International Nuclear Information System (INIS)

    Banerjee, Narayan; Paul, Tanmoy

    2017-01-01

    We consider a five dimensional warped spacetime, in presence of the higher curvature term like F(R) = R + αR 2 in the bulk, in the context of the two-brane model. Our universe is identified with the TeV scale brane and emerges as a four dimensional effective theory. From the perspective of this effective theory, we examine the possibility of ''inflationary scenario'' by considering the on-brane metric ansatz as an FRW one. Our results reveal that the higher curvature term in the five dimensional bulk spacetime generates a potential term for the radion field. Due to the presence of radion potential, the very early universe undergoes a stage of accelerated expansion and, moreover, the accelerating period of the universe terminates in a finite time. We also find the spectral index of curvature perturbation (n s ) and the tensor to scalar ratio (r) in the present context, which match with the observational results based on the observations of Planck (Astron. Astrophys. 594, A20, 2016). (orig.)

  6. Inflationary scenario from higher curvature warped spacetime

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Narayan [Indian Institute of Science Education and Research Kolkata, Department of Physical Sciences, Nadia, West Bengal (India); Paul, Tanmoy [Indian Association for the Cultivation of Science, Department of Theoretical Physics, Kolkata (India)

    2017-10-15

    We consider a five dimensional warped spacetime, in presence of the higher curvature term like F(R) = R + αR{sup 2} in the bulk, in the context of the two-brane model. Our universe is identified with the TeV scale brane and emerges as a four dimensional effective theory. From the perspective of this effective theory, we examine the possibility of ''inflationary scenario'' by considering the on-brane metric ansatz as an FRW one. Our results reveal that the higher curvature term in the five dimensional bulk spacetime generates a potential term for the radion field. Due to the presence of radion potential, the very early universe undergoes a stage of accelerated expansion and, moreover, the accelerating period of the universe terminates in a finite time. We also find the spectral index of curvature perturbation (n{sub s}) and the tensor to scalar ratio (r) in the present context, which match with the observational results based on the observations of Planck (Astron. Astrophys. 594, A20, 2016). (orig.)

  7. Codimension two branes and distributional curvature

    International Nuclear Information System (INIS)

    Traschen, Jennie

    2009-01-01

    In general relativity, there is a well-developed formalism for working with the approximation that a gravitational source is concentrated on a shell, or codimension one surface. In contrast, there are obstacles to concentrating sources on surfaces that have a higher codimension, for example, a string in a spacetime with a dimension greater than or equal to four. Here it is shown that, by giving up some of the generality of the codimension one case, curvature can be concentrated on submanifolds that have codimension two. A class of metrics is identified such that (1) the scalar curvature and Ricci densities exist as distributions with support on a codimension two submanifold, and (2) using the Einstein equation, the distributional curvature corresponds to a concentrated stress-energy with equation of state p = -ρ, where p is the isotropic pressure tangent to the submanifold, and ρ is the energy density. This is the appropriate stress-energy to describe a self-gravitating brane that is governed by an area action, or a braneworld deSitter cosmology. The possibility of having a different equation of state arise from a wider class of metrics is discussed.

  8. Using nanocomposite materials technology to understand and control reverse osmosis membrane compaction

    KAUST Repository

    Pendergast, Mary Theresa M.; Nygaard, Jodie M.; Ghosh, Asim K.; Hoek, Eric M.V.

    2010-01-01

    Composite reverse osmosis (RO) membranes were formed by interfacial polymerization of polyamide thin films over pure polysulfone and nanocomposite-polysulfone support membranes. Nanocomposite support membranes were formed from amorphous non-porous silica and crystalline microporous zeolite nanoparticles. For each hand-cast membrane, water flux and NaCl rejection were monitored over time at two different applied pressures. Nanocomposite-polysulfone supported RO membranes generally had higher initial permeability and experienced less flux decline due to compaction than pure polysulfone supported membranes. In addition, observed salt rejection tended to increase as flux declined from compaction. Crosssectional SEM images verified significant reduction in thickness of pure polysulfone supports, whereas nanocomposites better resisted compaction due to enhanced mechanical stability imparted by the nanoparticles. A conceptual model was proposed to explain the mechanistic relationship between support membrane compaction and observed changes in water flux and salt rejection. As the support membrane compacts, skin layer pore constriction increased the effective path length for diffusion through the composite membranes, which reduced both water and salt permeability identically. However, experimental salt permeability tended to decline to a greater extent than water permeability; hence, the observed changes in flux and rejection might also be related to structural changes in the polyamide thin film. © 2010 Elsevier B.V. All rights reserved.

  9. Using nanocomposite materials technology to understand and control reverse osmosis membrane compaction

    KAUST Repository

    Pendergast, Mary Theresa M.

    2010-10-01

    Composite reverse osmosis (RO) membranes were formed by interfacial polymerization of polyamide thin films over pure polysulfone and nanocomposite-polysulfone support membranes. Nanocomposite support membranes were formed from amorphous non-porous silica and crystalline microporous zeolite nanoparticles. For each hand-cast membrane, water flux and NaCl rejection were monitored over time at two different applied pressures. Nanocomposite-polysulfone supported RO membranes generally had higher initial permeability and experienced less flux decline due to compaction than pure polysulfone supported membranes. In addition, observed salt rejection tended to increase as flux declined from compaction. Crosssectional SEM images verified significant reduction in thickness of pure polysulfone supports, whereas nanocomposites better resisted compaction due to enhanced mechanical stability imparted by the nanoparticles. A conceptual model was proposed to explain the mechanistic relationship between support membrane compaction and observed changes in water flux and salt rejection. As the support membrane compacts, skin layer pore constriction increased the effective path length for diffusion through the composite membranes, which reduced both water and salt permeability identically. However, experimental salt permeability tended to decline to a greater extent than water permeability; hence, the observed changes in flux and rejection might also be related to structural changes in the polyamide thin film. © 2010 Elsevier B.V. All rights reserved.

  10. Control of recoil losses in nanomechanical SiN membrane resonators

    Science.gov (United States)

    Borrielli, A.; Marconi, L.; Marin, F.; Marino, F.; Morana, B.; Pandraud, G.; Pontin, A.; Prodi, G. A.; Sarro, P. M.; Serra, E.; Bonaldi, M.

    2016-09-01

    In the context of a recoil damping analysis, we have designed and produced a membrane resonator equipped with a specific on-chip structure working as a "loss shield" for a circular membrane. In this device the vibrations of the membrane, with a quality factor of 107, reach the limit set by the intrinsic dissipation in silicon nitride, for all the modes and regardless of the modal shape, also at low frequency. Guided by our theoretical model of the loss shield, we describe the design rationale of the device, which can be used as effective replacement of commercial membrane resonators in advanced optomechanical setups, also at cryogenic temperatures.

  11. Transabdominal amnioinfusion in preterm premature rupture of membranes: a randomised controlled trial.

    Science.gov (United States)

    Tranquilli, Andrea Luigi; Giannubilo, Stefano Raffaele; Bezzeccheri, Valeria; Scagnoli, Caterina

    2005-06-01

    To evaluate the role of transabdominal amnioinfusion in improving the perinatal outcomes of pregnancies complicated by preterm premature rupture of membranes (pPROM). A randomised controlled trial. A teaching hospital in Italy, obstetric unit. Population Women with singleton pregnancies complicated by pPROM, between 24 + 0 and 32 + 6 weeks of gestation. Patients were randomised 24 hours after admission to our referral hospital, to expectant management with transabdominal amnioinfusion or expectant management only. The effects of transabdominal amnioinfusion on pPROM-delivery interval and on perinatal outcomes. Of the 65 women with pPROM 34 met the inclusion criteria. Seventeen women were assigned to amnioinfusion (the amnioinfusion group) and the other 17 to expectant management. Compared with the control group (median: 8 days; range: 3-14), the pPROM-delivery period was significantly longer in women who underwent amnioinfusion (median: 21 days; range: 15-29) (P amnioinfusion were less likely to deliver within seven days since pPROM (RR: 0.18; range: 0.04-0.69 95% CI) or within two weeks (RR: 0.46; range: 0.21-1.02 95% CI). In the amnioinfusion group the neonatal survival was significantly higher at each gestational age (P amnioinfusion after pPROM resulted in significant prolongation of pregnancy and better neonatal outcomes.

  12. Integrated Microfluidic Membrane Transistor Utilizing Chemical Information for On-Chip Flow Control

    Science.gov (United States)

    Frank, Philipp; Schreiter, Joerg; Haefner, Sebastian; Paschew, Georgi; Voigt, Andreas; Richter, Andreas

    2016-01-01

    Microfluidics is a great enabling technology for biology, biotechnology, chemistry and general life sciences. Despite many promising predictions of its progress, microfluidics has not reached its full potential yet. To unleash this potential, we propose the use of intrinsically active hydrogels, which work as sensors and actuators at the same time, in microfluidic channel networks. These materials transfer a chemical input signal such as a substance concentration into a mechanical output. This way chemical information is processed and analyzed on the spot without the need for an external control unit. Inspired by the development electronics, our approach focuses on the development of single transistor-like components, which have the potential to be used in an integrated circuit technology. Here, we present membrane isolated chemical volume phase transition transistor (MIS-CVPT). The device is characterized in terms of the flow rate from source to drain, depending on the chemical concentration in the control channel, the source-drain pressure drop and the operating temperature. PMID:27571209

  13. Fuzzy control of the removal of estrogen in a membrane bioreactor

    International Nuclear Information System (INIS)

    Antonio Jose de Sucre (Venezuela, Bolivarian Republic of))" data-affiliation=" (Universidad Politecnica Salesiana Ecuador (Ecuador), E-mail: lsanchezb@ups.edu.ec); Torres Cruz, Ennodio (Universidad Experimental Politecnica Antonio Jose de Sucre (Venezuela, Bolivarian Republic of))" >Sanchez Barboza, Leadina

    2017-01-01

    The Membrane Bioreactor (MBR) has recently emerged as an important technology product for the treatment of wastewater containing estrogens and contaminants and is capable of transforming a residual water in a high quality effluent. Because of the recalcitrant nature of both natural and synthetic estrogens, one of the parameters that has been determined as influential to the removal of these substances is the Solids Retention Time (SRT), as this allows more time spent in the biomass in the reactor. The influence of the SRT in estrogen removal was simulated in the MATLAB Fuzzy Logic Toolbox using fuzzy control. For this purpose, the values measured or obtained by experts in laboratory scale experiments were fuzzified, and the fuzzy inference process was made on the basis of the previously designed inference rules. Finally the output is again desfuzzified for crisp value. The designed fuzzy control system produced very good results, with very small percentages of error for most cases, except for the removal of ethinylestradiol (EE2) in the reactor with long SRT. The performance of the simulation allows us to conclude that the Fuzzy Logic Toolbox is a good tool to get close to the results obtained by an actual experimental system. (author) [es

  14. Integrated Microfluidic Membrane Transistor Utilizing Chemical Information for On-Chip Flow Control.

    Science.gov (United States)

    Frank, Philipp; Schreiter, Joerg; Haefner, Sebastian; Paschew, Georgi; Voigt, Andreas; Richter, Andreas

    2016-01-01

    Microfluidics is a great enabling technology for biology, biotechnology, chemistry and general life sciences. Despite many promising predictions of its progress, microfluidics has not reached its full potential yet. To unleash this potential, we propose the use of intrinsically active hydrogels, which work as sensors and actuators at the same time, in microfluidic channel networks. These materials transfer a chemical input signal such as a substance concentration into a mechanical output. This way chemical information is processed and analyzed on the spot without the need for an external control unit. Inspired by the development electronics, our approach focuses on the development of single transistor-like components, which have the potential to be used in an integrated circuit technology. Here, we present membrane isolated chemical volume phase transition transistor (MIS-CVPT). The device is characterized in terms of the flow rate from source to drain, depending on the chemical concentration in the control channel, the source-drain pressure drop and the operating temperature.

  15. Cycle-time determination and process control of sequencing batch membrane bioreactors.

    Science.gov (United States)

    Krampe, J

    2013-01-01

    In this paper a method to determine the cycle time for sequencing batch membrane bioreactors (SBMBRs) is introduced. One of the advantages of SBMBRs is the simplicity of adapting them to varying wastewater composition. The benefit of this flexibility can only be fully utilised if the cycle times are optimised for the specific inlet load conditions. This requires either proactive and ongoing operator adjustment or active predictive instrument-based control. Determination of the cycle times for conventional sequencing batch reactor (SBR) plants is usually based on experience. Due to the higher mixed liquor suspended solids concentrations in SBMBRs and the limited experience with their application, a new approach to calculate the cycle time had to be developed. Based on results from a semi-technical pilot plant, the paper presents an approach for calculating the cycle time in relation to the influent concentration according to the Activated Sludge Model No. 1 and the German HSG (Hochschulgruppe) Approach. The approach presented in this paper considers the increased solid contents in the reactor and the resultant shortened reaction times. This allows for an exact calculation of the nitrification and denitrification cycles with a tolerance of only a few minutes. Ultimately the same approach can be used for a predictive control strategy and for conventional SBR plants.

  16. A knowledge-based control system for air-scour optimisation in membrane bioreactors.

    Science.gov (United States)

    Ferrero, G; Monclús, H; Sancho, L; Garrido, J M; Comas, J; Rodríguez-Roda, I

    2011-01-01

    Although membrane bioreactors (MBRs) technology is still a growing sector, its progressive implementation all over the world, together with great technical achievements, has allowed it to reach a mature degree, just comparable to other more conventional wastewater treatment technologies. With current energy requirements around 0.6-1.1 kWh/m3 of treated wastewater and investment costs similar to conventional treatment plants, main market niche for MBRs can be areas with very high restrictive discharge limits, where treatment plants have to be compact or where water reuse is necessary. Operational costs are higher than for conventional treatments; consequently there is still a need and possibilities for energy saving and optimisation. This paper presents the development of a knowledge-based decision support system (DSS) for the integrated operation and remote control of the biological and physical (filtration and backwashing or relaxation) processes in MBRs. The core of the DSS is a knowledge-based control module for air-scour consumption automation and energy consumption minimisation.

  17. Enhanced ferro-actuator with a porosity-controlled membrane using the sol-gel process and the HF etching method

    International Nuclear Information System (INIS)

    Kim, KiSu; Ko, Seong Young; Park, Jong-Oh; Park, Sukho

    2016-01-01

    In this paper, we propose a ferro-actuator using a porous polyvinylidene difluoride (PVDF) membrane. In detail, we fabricated the silica-embedded PVDF membrane using a sol-gel process with PVDF solution and tetraethyl orthosilicate (TEOS) solution, where the size of the silica was determined by the ratio of the PVDF and TEOS solutions. Using hydrofluoric acid (HF) etching, the silica were removed from the silica-embedded PVDF membrane, and porous PVDF membranes with different porosities were obtained. Finally, through absorption of a ferrofluid on the porous PVDF membrane, the proposed ferro-actuator using porous PVDF membranes with different porosities was fabricated. We executed the characterization and actuation test as follows. First, the silica size of the silica-embedded PVDF membrane and the pore size of the porous PVDF membrane were analyzed using scanning electron microscopy (SEM) imaging. Second, energy-dispersive x-ray spectroscopy analysis showed that the silica had clearly been removed from the silica-embedded PVDF membrane by HF etching. Third, through x-ray photoelectron spectroscopy and vibrating sample magnetometer (VSM) of the ferro-actuators, we found that more ferrofluids were absorbed by the porous PVDF membrane when the pore of the membrane was smaller and uniformly distributed. Finally, we executed tip displacement and a blocking force test of the proposed ferro-actuator using the porous PVDF membrane. Similar to the VSM result, the ferro-actuator that used a porous PVDF membrane with smaller pores exhibited better actuation performance. The ferro-actuator that used a porous PVDF membrane displayed a tip displacement that was about 7.2-fold better and a blocking force that was about 6.5-fold better than the ferro-actuator that used a pure PVDF membrane. Thus, we controlled the pore size of the porous PVDF membrane and enhanced the actuation performance of the ferro-actuator using a porous PVDF membrane. (technical note)

  18. Model-Based Control of a Continuous Coating Line for Proton Exchange Membrane Fuel Cell Electrode Assembly

    Directory of Open Access Journals (Sweden)

    Vikram Devaraj

    2015-01-01

    Full Text Available The most expensive component of a fuel cell is the membrane electrode assembly (MEA, which consists of an ionomer membrane coated with catalyst material. Best-performing MEAs are currently fabricated by depositing and drying liquid catalyst ink on the membrane; however, this process is limited to individual preparation by hand due to the membrane’s rapid water absorption that leads to shape deformation and coating defects. A continuous coating line can reduce the cost and time needed to fabricate the MEA, incentivizing the commercialization and widespread adoption of fuel cells. A pilot-scale membrane coating line was designed for such a task and is described in this paper. Accurate process control is necessary to prevent manufacturing defects from occurring in the coating line. A linear-quadratic-Gaussian (LQG controller was developed based on a physics-based model of the coating process to optimally control the temperature and humidity of the drying zones. The process controller was implemented in the pilot-scale coating line proving effective in preventing defects.

  19. Holonomy Attractor Connecting Spaces of Different Curvature Responsible for ``Anomalies''

    Science.gov (United States)

    Binder, Bernd

    2009-03-01

    In this lecture paper we derive Magic Angle Precession (MAP) from first geometric principles. MAP can arise in situations, where precession is multiply related to spin, linearly by time or distance (dynamic phase, rolling, Gauss law) and transcendentally by the holonomy loop path (geometric phase). With linear spin-precession coupling, gyroscopes can be spun up and down to very high frequencies via low frequency holonomy control induced by external accelerations, which provides for extreme coupling strengths or "anomalies" that can be tested by the powerball or gyrotwister device. Geometrically, a gyroscopic manifold with spherical metric is tangentially aligned to a precession wave channel with conic or hyperbolic metric (like the relativistic Thomas precession). Transporting triangular spin/precession vector relations across the tangential boundary of contact with SO(3) Lorentz symmetry, we get extreme vector currents near the attractor fixed points in precession phase space, where spin currents remain intact while crossing the contact boundaries between regions of different curvature signature (-1, 0, +1). The problem can be geometrically solved by considering a curvature invariant triangular condition, which holds on surfaces with different curvature that are in contact and locally parallel. In this case two out of three angles are identical, whereas the third angle is different due to holonomy. If we require that the side length ratio corresponding to these angles are invariant we get a geodesic chaotic attractor, which is a cosine map cos(x)˜Mx in parameter space providing for fixed points, limit cycle bifurcations, and singularities. The situation could be quite natural and common in the context of vector currents in curved spacetime and gauge theories. MAP could even be part of the electromagnetic interaction, where the electric charge is the geometric U(1) precession spin current and gauge potential with magnetic effects given by extra rotations under the

  20. Accurate control of oxygen level in cells during culture on silicone rubber membranes with application to stem cell differentiation.

    Science.gov (United States)

    Powers, Daryl E; Millman, Jeffrey R; Bonner-Weir, Susan; Rappel, Michael J; Colton, Clark K

    2010-01-01

    Oxygen level in mammalian cell culture is often controlled by placing culture vessels in humidified incubators with a defined gas phase partial pressure of oxygen (pO(2gas)). Because the cells are consuming oxygen supplied by diffusion, a difference between pO(2gas) and that experienced by the cells (pO(2cell)) arises, which is maximal when cells are cultured in vessels with little or no oxygen permeability. Here, we demonstrate theoretically that highly oxygen-permeable silicone rubber membranes can be used to control pO(2cell) during culture of cells in monolayers and aggregates much more accurately and can achieve more rapid transient response following a disturbance than on polystyrene and fluorinated ethylene-propylene copolymer membranes. Cell attachment on silicone rubber was achieved by physical adsorption of fibronectin or Matrigel. We use these membranes for the differentiation of mouse embryonic stem cells to cardiomyocytes and compare the results with culture on polystyrene or on silicone rubber on top of polystyrene. The fraction of cells that are cardiomyocyte-like increases with decreasing pO(2) only when using oxygen-permeable silicone membrane-based dishs, which contract on silicone rubber but not polystyrene. The high permeability of silicone rubber results in pO(2cell) being equal to pO(2gas) at the tissue-membrane interface. This, together with geometric information from histological sections, facilitates development of a model from which the pO(2) distribution within the resulting aggregates is computed. Silicone rubber membranes have significant advantages over polystyrene in controlling pO(2cell), and these results suggest they are a valuable tool for investigating pO(2) effects in many applications, such as stem cell differentiation. Copyright 2009 American Institute of Chemical Engineers

  1. Membrane remodeling by amyloidogenic and non-amyloidogenic proteins studied by EPR.

    Science.gov (United States)

    Varkey, Jobin; Langen, Ralf

    2017-07-01

    The advancement in site-directed spin labeling of proteins has enabled EPR studies to expand into newer research areas within the umbrella of protein-membrane interactions. Recently, membrane remodeling by amyloidogenic and non-amyloidogenic proteins has gained a substantial interest in relation to driving and controlling vital cellular processes such as endocytosis, exocytosis, shaping of organelles like endoplasmic reticulum, Golgi and mitochondria, intracellular vesicular trafficking, formation of filopedia and multivesicular bodies, mitochondrial fusion and fission, and synaptic vesicle fusion and recycling in neurotransmission. Misregulation in any of these processes due to an aberrant protein (mutation or misfolding) or alteration of lipid metabolism can be detrimental to the cell and cause disease. Dissection of the structural basis of membrane remodeling by proteins is thus quite necessary for an understanding of the underlying mechanisms, but it remains a formidable task due to the difficulties of various common biophysical tools in monitoring the dynamic process of membrane binding and bending by proteins. This is largely since membranes generally complicate protein structure analysis and this problem is amplified for structural analysis in the presence of different types of membrane curvatures. Recent EPR studies on membrane remodeling by proteins show that a significant structural information can be generated to delineate the role of different protein modules, domains and individual amino acids in the generation of membrane curvature. These studies also show how EPR can complement the data obtained by high resolution techniques such as X-ray and NMR. This perspective covers the application of EPR in recent studies for understanding membrane remodeling by amyloidogenic and non-amyloidogenic proteins that is useful for researchers interested in using or complimenting EPR to gain better understanding of membrane remodeling. We also discuss how a single

  2. Membrane remodeling by amyloidogenic and non-amyloidogenic proteins studied by EPR

    Science.gov (United States)

    Varkey, Jobin; Langen, Ralf

    2017-07-01

    The advancement in site-directed spin labeling of proteins has enabled EPR studies to expand into newer research areas within the umbrella of protein-membrane interactions. Recently, membrane remodeling by amyloidogenic and non-amyloidogenic proteins has gained a substantial interest in relation to driving and controlling vital cellular processes such as endocytosis, exocytosis, shaping of organelles like endoplasmic reticulum, Golgi and mitochondria, intracellular vesicular trafficking, formation of filopedia and multivesicular bodies, mitochondrial fusion and fission, and synaptic vesicle fusion and recycling in neurotransmission. Misregulation in any of these processes due to an aberrant protein (mutation or misfolding) or alteration of lipid metabolism can be detrimental to the cell and cause disease. Dissection of the structural basis of membrane remodeling by proteins is thus quite necessary for an understanding of the underlying mechanisms, but it remains a formidable task due to the difficulties of various common biophysical tools in monitoring the dynamic process of membrane binding and bending by proteins. This is largely since membranes generally complicate protein structure analysis and this problem is amplified for structural analysis in the presence of different types of membrane curvatures. Recent EPR studies on membrane remodeling by proteins show that a significant structural information can be generated to delineate the role of different protein modules, domains and individual amino acids in the generation of membrane curvature. These studies also show how EPR can complement the data obtained by high resolution techniques such as X-ray and NMR. This perspective covers the application of EPR in recent studies for understanding membrane remodeling by amyloidogenic and non-amyloidogenic proteins that is useful for researchers interested in using or complimenting EPR to gain better understanding of membrane remodeling. We also discuss how a single

  3. Distributed mean curvature on a discrete manifold for Regge calculus

    International Nuclear Information System (INIS)

    Conboye, Rory; Miller, Warner A; Ray, Shannon

    2015-01-01

    The integrated mean curvature of a simplicial manifold is well understood in both Regge Calculus and Discrete Differential Geometry. However, a well motivated pointwise definition of curvature requires a careful choice of the volume over which to uniformly distribute the local integrated curvature. We show that hybrid cells formed using both the simplicial lattice and its circumcentric dual emerge as a remarkably natural structure for the distribution of this local integrated curvature. These hybrid cells form a complete tessellation of the simplicial manifold, contain a geometric orthonormal basis, and are also shown to give a pointwise mean curvature with a natural interpretation as the fractional rate of change of the normal vector. (paper)

  4. Distributed mean curvature on a discrete manifold for Regge calculus

    Science.gov (United States)

    Conboye, Rory; Miller, Warner A.; Ray, Shannon

    2015-09-01

    The integrated mean curvature of a simplicial manifold is well understood in both Regge Calculus and Discrete Differential Geometry. However, a well motivated pointwise definition of curvature requires a careful choice of the volume over which to uniformly distribute the local integrated curvature. We show that hybrid cells formed using both the simplicial lattice and its circumcentric dual emerge as a remarkably natural structure for the distribution of this local integrated curvature. These hybrid cells form a complete tessellation of the simplicial manifold, contain a geometric orthonormal basis, and are also shown to give a pointwise mean curvature with a natural interpretation as the fractional rate of change of the normal vector.

  5. A curvature theory for discrete surfaces based on mesh parallelity

    KAUST Repository

    Bobenko, Alexander Ivanovich

    2009-12-18

    We consider a general theory of curvatures of discrete surfaces equipped with edgewise parallel Gauss images, and where mean and Gaussian curvatures of faces are derived from the faces\\' areas and mixed areas. Remarkably these notions are capable of unifying notable previously defined classes of surfaces, such as discrete isothermic minimal surfaces and surfaces of constant mean curvature. We discuss various types of natural Gauss images, the existence of principal curvatures, constant curvature surfaces, Christoffel duality, Koenigs nets, contact element nets, s-isothermic nets, and interesting special cases such as discrete Delaunay surfaces derived from elliptic billiards. © 2009 Springer-Verlag.

  6. Improved performance of single-chamber microbial fuel cells through control of membrane deformation.

    Science.gov (United States)

    Zhang, Xiaoyuan; Cheng, Shaoan; Huang, Xia; Logan, Bruce E

    2010-03-15

    Cation (CEMs) and anion exchange membrane (AEMs) are commonly used in microbial fuel cells (MFCs) to enhance Coulombic efficiencies (CEs) by reducing the flux of oxygen through the cathode to bacteria on the anode. AEMs typically work better than CEMs, but in initial experiments we observed the opposite using a membrane electrode assembly MFC. The reason was identified to be membrane deformation, which resulted in water and gas trapped between the membrane and cathode. To correct this, stainless steel mesh was used to press the membrane flat against the cathode. With the steel mesh, AEM performance increased to 46+/-4 W/m(3) in a single cathode MFC, and 98+/-14 W/m(3) in a double-cathode MFC. These power densities were higher than those using a CEM of 32+/-2 W/m(3) (single cathode) and 63+/-6 W/m(3) (double cathode). Higher pH gradients across the membrane and salt precipitation on the cathode were responsible for the reduced performance of the CEM compared to the AEM. CEs reached over 90% for both membranes at >2A/m(2). These results demonstrate the importance of avoiding water accumulation in thin films between membranes and electrodes, and explain additional reasons for poorer performance of CEMs compared to AEMs. (c) 2009 Elsevier B.V. All rights reserved.

  7. Improved performance of single-chamber microbial fuel cells through control of membrane deformation

    KAUST Repository

    Zhang, Xiaoyuan

    2010-03-01

    Cation (CEMs) and anion exchange membrane (AEMs) are commonly used in microbial fuel cells (MFCs) to enhance Coulombic efficiencies (CEs) by reducing thefluxof oxygen through the cathode to bacteriaonthe anode. AEMs typically work better than CEMs, but in initial experiments we observed the opposite using a membrane electrode assembly MFC. The reason was identified to be membrane deformation, which resulted in water and gas trapped between the membrane and cathode. To correct this, stainless steel mesh was used to press the membrane flat against the cathode. With the steel mesh, AEM performance increased to 46±4W/m3 in a single cathode MFC, and 98±14W/m3 in a double-cathode MFC. These power densities were higher than those using a CEM of 32±2W/m3 (single cathode) and 63±6W/m3 (double cathode). Higher pH gradients across the membrane and salt precipitation on the cathode were responsible for the reduced performance of the CEM compared to the AEM. CEs reached over 90% for both membranes at >2A/m2. These results demonstrate the importance of avoiding water accumulation in thin films between membranes and electrodes, and explain additional reasons for poorer performance of CEMs compared to AEMs. © 2009 Elsevier B.V.

  8. Controlled release of mitomycin C from PHEMAH-Cu(II) cryogel membranes.

    Science.gov (United States)

    Bakhshpour, Monireh; Yavuz, Handan; Denizli, Adil

    2018-02-19

    Molecular imprinting technique was used for the preparation of antibiotic and anti-neoplastic chemotherapy drug (mitomycin C) imprinted cryogel membranes (MMC-ICM). The membranes were synthezied by using metal ion coordination interactions with N-methacryloyl-(l)-histidine methyl ester (MAH) functional monomer and template molecules (i.e. MMC). The 2-hydroxyethyl methacrylate (HEMA) monomer and methylene bisacrylamide (MBAAm) crosslinker were used for the preparation of mitomycin C imprinted cryogel membranes by radical suspension polymerization technique. The imprinted cryogel membranes were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) and swelling degree measurements. Cytotoxicity of MMC-ICMs was investigated using mouse fibroblast cell line L929. Time-dependent release of MMC was demonstrated within 150 h from cryogel membranes. Cryogels demonstrated very high MMC loading efficiency (70-80%) and sustained MMC release over hours.

  9. EPA and DHA in blood cell membranes from acute coronary syndrome patients and controls.

    Science.gov (United States)

    Block, Robert C; Harris, William S; Reid, Kimberly J; Sands, Scott A; Spertus, John A

    2008-04-01

    Increased blood levels of the omega-3 fatty acids (FA) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been inversely associated with risk for sudden cardiac death, but their relationship with acute coronary syndromes (ACS) is unclear. We hypothesized that the EPA+DHA content of blood cell membranes, as a percent of total FAs, is reduced in ACS patients relative to matched controls. We measured the content of EPA+DHA in 768 ACS patients and 768 age-, sex- and race-matched controls. The association with ACS case status of blood cell EPA+DHA [both by a 1 unit change and by category (low, or =8%)] was assessed using multivariate conditional logistic regression models adjusting for matching variables and smoking status, alcohol use, diabetes, body mass index, serum lipids, education, family history of coronary artery disease, personal histories of myocardial infarction and hypertension, and statin, aspirin, and other antiplatelet drug use. The combined groups had a mean age of 61+/-12 years, 66% were male, and 92% were Caucasian. The EPA+DHA content was 20% lower in cases than controls (3.4+/-1.6 vs. 4.25+/-2.0%, pACS event was 0.58 (95% CI 0.42-0.80), in the intermediate EPA+DHA group and was 0.31 (95% CI 0.14-0.67; p for trend ACS case status increased incrementally as the EPA+DHA content decreased suggesting that low EPA+DHA may be associated with increased risk for ACS.

  10. Integration of length and curvature in haptic perception.

    Science.gov (United States)

    Panday, Virjanand; Tiest, Wouter M Bergmann; Kappers, Astrid M L

    2014-01-24

    We investigated if and how length and curvature information are integrated when an object is explored in one hand. Subjects were asked to explore four types of objects between thumb and index finger. Objects differed in either length, curvature, both length and curvature correlated as in a circle, or anti-correlated. We found that when both length and curvature are present, performance is significantly better than when only one of the two cues is available. Therefore, we conclude that there is integration of length and curvature. Moreover, if the two cues are correlated in a circular cross-section instead of in an anti-correlated way, performance is better than predicted by a combination of two independent cues. We conclude that integration of curvature and length is highly efficient when the cues in the object are combined as in a circle, which is the most common combination of curvature and length in daily life.

  11. Design and implementation of fixed-order robust controllers for a proton exchange membrane fuel cell system

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Fu-Cheng; Chen, Hsuan-Tsung [Department of Mechanical Engineering, National Taiwan University, No.1, Sec. 4, Roosevelt Road, 10617 Taipei (China)

    2009-03-15

    This paper applies fixed-order multivariable robust control strategies to a proton exchange membrane fuel cell (PEMFC) system, and implements the designed controllers on a microchip for system miniaturization. In previous studies, robust control was applied to guarantee system stability and to reduce hydrogen consumption for a PEMFC system. It was noted that for standard robust control design, the order of resulting H{sub {infinity}} controllers is dictated by the plants and weighting functions. However, for hardware implementation, controllers with lower orders are preferable in terms of computing efforts and cost. Therefore, in this paper the PEMFC is modeled as multivariable transfer matrices, then three fixed-order robust control algorithms are applied to design controllers with specified orders for a PEMFC. Finally, the designed controllers are implemented on a microchip to regulate the air and hydrogen flow rates. From the experimental results, fixed-order robust control is deemed effective in supplying steady power and reducing fuel consumption. (author)

  12. The establishment and application of direct coupled electrostatic-structural field model in electrostatically controlled deployable membrane antenna

    Science.gov (United States)

    Gu, Yongzhen; Duan, Baoyan; Du, Jingli

    2018-05-01

    The electrostatically controlled deployable membrane antenna (ECDMA) is a promising space structure due to its low weight, large aperture and high precision characteristics. However, it is an extreme challenge to describe the coupled field between electrostatic and membrane structure accurately. A direct coupled method is applied to solve the coupled problem in this paper. Firstly, the membrane structure and electrostatic field are uniformly described by energy, considering the coupled problem is an energy conservation phenomenon. Then the direct coupled electrostatic-structural field governing equilibrium equations are obtained by energy variation approach. Numerical results show that the direct coupled method improves the computing efficiency by 36% compared with the traditional indirect coupled method with the same level accuracy. Finally, the prototype has been manufactured and tested and the ECDMA finite element simulations show good agreement with the experiment results as the maximum surface error difference is 6%.

  13. Ocular dimensions, corneal thickness, and corneal curvature in quarter horses with hereditary equine regional dermal asthenia.

    Science.gov (United States)

    Badial, Peres R; Cisneros-Àlvarez, Luis Emiliano; Brandão, Cláudia Valéria S; Ranzani, José Joaquim T; Tomaz, Mayana A R V; Machado, Vania M; Borges, Alexandre S

    2015-09-01

    The aim of this study was to compare ocular dimensions, corneal curvature, and corneal thickness between horses affected with hereditary equine regional dermal asthenia (HERDA) and unaffected horses. Five HERDA-affected quarter horses and five healthy control quarter horses were used. Schirmer's tear test, tonometry, and corneal diameter measurements were performed in both eyes of all horses prior to ophthalmologic examinations. Ultrasonic pachymetry was performed to measure the central, temporal, nasal, dorsal, and ventral corneal thicknesses in all horses. B-mode ultrasound scanning was performed on both eyes of each horse to determine the dimensions of the ocular structures and to calculate the corneal curvature. Each corneal region examined in this study was thinner in the affected group compared with the healthy control group. However, significant differences in corneal thickness were only observed for the central and dorsal regions. HERDA-affected horses exhibited significant increases in corneal curvature and corneal diameter compared with unaffected animals. The ophthalmologic examinations revealed mild corneal opacity in one eye of one affected horse and in both eyes of three affected horses. No significant between-group differences were observed for Schirmer's tear test, intraocular pressure, or ocular dimensions. Hereditary equine regional dermal asthenia-affected horses exhibit decreased corneal thickness in several regions of the cornea, increased corneal curvature, increased corneal diameter, and mild corneal opacity. Additional research is required to determine whether the increased corneal curvature significantly impacts the visual accuracy of horses with HERDA. © 2014 American College of Veterinary Ophthalmologists.

  14. Distributed microscopic actuation analysis of paraboloidal membrane shells of different geometric parameters

    Science.gov (United States)

    Yue, Honghao; Lu, Yifan; Deng, Zongquan; Tzou, Hornsen

    2018-03-01

    Paraboloidal membrane shells of revolution are commonly used as key components for advanced aerospace structures and aviation mechanical systems. Due to their high flexibility and low damping property, active vibration control is of significant importance for these in-orbit membrane structures. To explore the dynamic control behavior of space flexible paraboloidal membrane shells, precision distributed actuation and control effectiveness of free-floating paraboloidal membrane shells with piezoelectric actuators are investigated. Governing equations of the shell structronic system are presented first. Then, distributed control forces and control actions are formulated. A transverse mode shape function of the paraboloidal shell based on the membrane approximation theory and specified boundary condition is assumed in the modal control force analysis. The actuator induced modal control forces on the paraboloidal shell are derived. The expressions of microscopic local modal control forces are obtained by shrinking the actuator area into infinitesimal and the four control components are investigated respectively to predict the spatial microscopic actuation behavior. Geometric parameter (height-radius ratio and shell thickness) effects on the modal actuation behavior are explored when evaluating the micro-control efficiency. Four different cases are discussed and the results reveal the fact that shallow (e.g., antennas/reflectors) and deep (e.g., rocket/missile fairing) paraboloidal shells exhibit totally different modal actuation behaviors due to their curvature differences. Analytical results in this paper can serve as guidelines for optimal actuator placement for vibration control of different paraboloidal structures.

  15. Controlling the Release of Indomethacin from Glass Solutions Layered with a Rate Controlling Membrane Using Fluid-Bed Processing. Part 1: Surface and Cross-Sectional Chemical Analysis.

    Science.gov (United States)

    Dereymaker, Aswin; Scurr, David J; Steer, Elisabeth D; Roberts, Clive J; Van den Mooter, Guy

    2017-04-03

    Fluid bed coating has been shown to be a suitable manufacturing technique to formulate poorly soluble drugs in glass solutions. Layering inert carriers with a drug-polymer mixture enables these beads to be immediately filled into capsules, thus avoiding additional, potentially destabilizing, downstream processing. In this study, fluid bed coating is proposed for the production of controlled release dosage forms of glass solutions by applying a second, rate controlling membrane on top of the glass solution. Adding a second coating layer adds to the physical and chemical complexity of the drug delivery system, so a thorough understanding of the physical structure and phase behavior of the different coating layers is needed. This study aimed to investigate the surface and cross-sectional characteristics (employing scanning electron microscopy (SEM) and time of flight secondary ion mass spectrometry (ToF-SIMS)) of an indomethacin-polyvinylpyrrolidone (PVP) glass solution, top-coated with a release rate controlling membrane consisting of either ethyl cellulose or Eudragit RL. The implications of the addition of a pore former (PVP) and the coating medium (ethanol or water) were also considered. In addition, polymer miscibility and the phase analysis of the underlying glass solution were investigated. Significant differences in surface and cross-sectional topography of the different rate controlling membranes or the way they are applied (solution vs dispersion) were observed. These observations can be linked to the polymer miscibility differences. The presence of PVP was observed in all rate controlling membranes, even if it is not part of the coating solution. This could be attributed to residual powder presence in the coating chamber. The distribution of PVP among the sample surfaces depends on the concentration and the rate controlling polymer used. Differences can again be linked to polymer miscibility. Finally, it was shown that the underlying glass solution layer

  16. Progestogens in singleton gestations with preterm prelabor rupture of membranes: a systematic review and metaanalysis of randomized controlled trials.

    Science.gov (United States)

    Quist-Nelson, Johanna; Parker, Pamela; Mokhtari, Neggin; Di Sarno, Rossana; Saccone, Gabriele; Berghella, Vincenzo

    2018-03-31

    Preterm prelabor rupture of membranes occurs in 3% of all pregnancies. Neonatal benefit is seen in uninfected women who do not deliver immediately after preterm prelabor rupture of membranes. The purpose of this study was to evaluate whether the administration of progestogens in singleton pregnancies prolongs pregnancy after preterm prelabor rupture of membranes. Searches were performed in MEDLINE, OVID, Scopus, EMBASE, ClinicalTrials.gov, and the Cochrane Central Register of Controlled Trials with the use of a combination of keywords and text words related to "progesterone," "progestogen," "prematurity," and "preterm premature rupture of membranes" from the inception of the databases until January 2018. We included all randomized controlled trials of singleton gestations after preterm prelabor rupture of membranes that were randomized to either progestogens or control (either placebo or no treatment). Exclusion criteria were trials that included women who had contraindications to expectant management after preterm prelabor rupture of membranes (ie, chorioamnionitis, severe preeclampsia, and nonreassuring fetal status) and trials on multiple gestations. We planned to include all progestogens, including but not limited to 17-α hydroxyprogesterone caproate, and natural progesterone. The primary outcome was latency from randomization to delivery. Metaanalysis was performed with the use of the random effects model of DerSimonian and Laird to produce relative risk with 95% confidence interval. Analysis was performed for each mode of progestogen administration separately. Six randomized controlled trials (n=545 participants) were included. Four of the included trials assessed the efficacy of 17-α hydroxyprogesterone caproate; 1 trial assessed rectal progestogen, and 1 trial had 3 arms that compared 17-α hydroxyprogesterone caproate, rectal progestogen, and placebo. The mean gestational age at time randomization was 26.9 weeks in the 17-α hydroxyprogesterone caproate

  17. Fouling on ion-exchange membranes: Classification, characterization and strategies of prevention and control.

    Science.gov (United States)

    Mikhaylin, Sergey; Bazinet, Laurent

    2016-03-01

    The environmentally friendly ion-exchange membrane (IEM) processes find more and more applications in the modern industries in order to demineralize, concentrate and modify products. Moreover, these processes may be applied for the energy conversion and storage. However, the main drawback of the IEM processes is a formation of fouling, which significantly decreases the process efficiency and increases the process cost. The present review is dedicated to the problematic of IEM fouling phenomena. Firstly, the major types of IEM fouling such as colloidal fouling, organic fouling, scaling and biofouling are discussed along with consideration of the main factors affecting fouling formation and development. Secondly, the review of the possible methods of IEM fouling characterization is provided. This section includes the methods of fouling visualization and characterization as well as methods allowing investigations of characteristics of the fouled IEMs. Eventually, the reader will find the conventional and modern strategies of prevention and control of different fouling types. Copyright © 2015 Elsevier B.V. All rights reserved.

  18. Controlled synthesis of N,N,N-trimethyl chitosan for modulated bioadhesion and nasal membrane permeability.

    Science.gov (United States)

    Pardeshi, Chandrakantsing V; Belgamwar, Veena S

    2016-01-01

    In an experiment to explore the bioadhesion, biocompatibility, and membrane permeation properties, the controlled synthesis of N,N,N-trimethyl chitosan (TMC) was carried out by two-step reductive methylation of chitosan (CHT). Methylation was confirmed by (1)H NMR (δ=3.1 ppm) and FTIR analysis (CH stretch at 1,485 cm(-1)). The TMC was further characterized by DSC, TGA, XRD, HR-TEM, SEM, and elemental analysis. Findings revealed improved solubility, enhanced viscosity, increased swelling index and higher molecular weight of TMC over CHT. Comparative evaluation validated increased bioadhesion potential, and improved ex vivo biocompatibility of TMC compared to CHT. Increased bioadhesion of TMC NPs over CHT NPs can be attributed to the strong electrostatic interactions between cationic amino groups with anionic sialic and sulfonic acid moieties contained in the mucin of the nasal mucus. Ex vivo biocompatibility studies suggested that the NP formulations of both biopolymers were biocompatible and could be applied safely on the nasal epithelium. Ex vivo permeation studies executed on excised cattle nasal mucosa illustrated improved permeability of TMC NPs over CHT NPs. In the author's opinion, two-step reductive methylation of CHT could be an attractive strategy to improve its solubility, bioadhesion, and permeation characteristics without affecting biocompatibility across the mucosal surfaces. Copyright © 2015 Elsevier B.V. All rights reserved.

  19. [Pollution prevention and control of aqueous extract of astragali radix processed with ZrO2 inorganic ceramic membrane micro-filtration].

    Science.gov (United States)

    Pan, Lin-Men; Huang, Min-Yan; Guo, Li-Wei

    2012-11-01

    To study the measures for preventing and controlling the pollution of aqueous extract of Astragali Radix proceeded with inorganic ceramic membrane micro-filtration, in order to find effective measures for preventing and controlling the membrane pollution. The resistance distribution, polymer removal and changes in physical and chemical parameters of the zirconium oxide film of different pore diameters were determined to analyze the state or location of pollutants as well as the regularity of formation. Meanwhile, recoil and ultrasonic physical measures were adopted to strengthen the membrane process, in order to explore the methods for preventing and controlling the membrane pollution. When 0.2 microm of ZrO2 micro-filtrated aqueous extract of Astragali Radix, the rate of pollution was as high as 44.9%. The hole blocking resistance and the concentration polarization resistance were the main filtration resistances, while the surface deposit resistance decreased with the increase in the membrane's hold diameter; after micro-filtration, the liquid turbidity significantly reduced, with slight changes in both pH and viscosity. The 0.2 microm ZrO2 micro-filtration membrane performed better than the 0.05 microm pore size membrane in terms of conductivity. The 0. 2 microm and 0.05 microm pore diameter membranes showed better performance in the removal of pectin. The ultrasonic measure to strengthen membranes is more suitable to this system, with a flux rate up by 41.7%. The membrane optimization process adopts appropriate measures for preventing and controlling the membrane pollution, in order to reduce the membrane pollution, recover membrane performance and increase filtration efficiency.

  20. A novel reverse osmosis membrane by ferrous sulfate assisted controlled oxidation of polyamide layer

    Science.gov (United States)

    Raval, Hiren D.; Raviya, Mayur R.; Gauswami, Maulik V.

    2017-11-01

    With growing desalination capacity, it is very important to evaluate the performance of thin film composite reverse osmosis (TFC RO) membrane in terms of energy consumption for desalination. There is a trade-off between salt rejection and water-flux of TFC RO membrane. This article presents a novel approach of analyzing the effect of mixture of an oxidizing agent sodium hypochlorite and a reducing agent ferrous sulfate on virgin TFC RO membrane. Experiments were carried out by varying the concentrations of both sodium hypochlorite and ferrous sulfate. The negative charge was induced on the membrane due to the treatment of combination of sodium hypochlorite and ferrous sulfate, thereby resulting in higher rejection of negative ions due to repulsive force. Membrane treated with 1000 mg l-1 sodium hypochlorite and 2000 mg l-1 ferrous sulfate showed the best salt rejection i.e. 96.23%. The characterization was carried out to understand the charge on the membrane surface by Zeta potential, morphology of membrane surface by scanning electron microscope (SEM), surface roughness features by atomic force microscope (AFM) and chemical structural changes by nuclear magnetic resonance (NMR) analysis.

  1. Characterization of phospholipid composition and its control in the plasma membrane of developing soybean root

    International Nuclear Information System (INIS)

    Whitman, C.E.

    1985-01-01

    The phospholipid composition of plasma membrane enriched fractions from developing soybean root and several mechanisms which may regulate it have been examined. Plasma membrane vesicles were isolated from meristematic and mature sections of four-day-old dark grown soybean roots (Glycine max [L.] Merr. Cult. Wells II). Analysis of lipid extracts revealed two major phospholipid classes: phosphatidylcholine and phosphatidylethanolamine. Minor phospholipid classes were phosphatidylinositol, phosphatidylserine, phosphatidylgylcerol and diphosphatidylgylcerol. Phospholipid composition was similar at each developmental stage. Fatty acids of phosphatidylcholine and phosphatidylethanolamine were 16:0, 18:0, 18:2, and 18:3. Fatty acid composition varied with both phospholipid class and the developmental stage of the root. The degradation of phosphatidylcholine by endogenous phospholipase D during membrane isolation indicated that this enzyme might be involved in phospholipid turnover within the membrane. Phospholipase D activity was heat labile and increasing the pH of the enzyme assay from 5.3 to 7.8 resulted in 90% inhibition of activity. The turnover of fatty acids within the phospholipids of the plasma membrane was studied. Mature root sections were incubated with [1- 14 C] acetate, 1 mM Na acetate and 50 μg/ml chloramphenicol. Membrane lipid extracts analyzed for phospholipid class and acyl chain composition revealed that the long incubation times did not alter the phospholipid composition of the plasma membrane enriched fraction

  2. A review on the use of membrane technology and fouling control for olive mill wastewater treatment.

    Science.gov (United States)

    Pulido, Javier Miguel Ochando

    2016-09-01

    Olive mill effluents (OME) by-produced have significantly increased in the last decades as a result of the boost of the olive oil agro-industrial sector and due to the conversion into continuous operation centrifugation technologies. In these effluents, the presence of phytotoxic recalcitrant pollutants makes them resistant to biological degradation and thus inhibits the efficiency of biological and conventional processes. Many reclamation treatments as well as integrated processes for OME have already been proposed and developed but not led to completely satisfactory and cost-effective results. Olive oil industries in its current status, typically small mills dispersed, cannot afford such high treatment costs. Furthermore, conventional treatments are not able to abate the significant dissolved monovalent and divalent ions concentration present in OME. Within this framework, membrane technology offers high efficiency and moderate investment and maintenance expenses. Wastewater treatment by membrane technologies is growing in the recent years. This trend is owed to the fact of the availability of new membrane materials, membrane designs, membrane module concepts and general know-how, which have promoted credibility among investors. However, fouling reduces the membrane performances in time and leads to premature substitution of the membrane modules, and this is a problem of cost efficiency since wastewater treatment must imply low operating costs. Appropriate fouling inhibition methods should assure this result, thus making membrane processes for wastewater stream treatment both technically and economically feasible. In this paper, the treatment of the effluents by-produced in olive mills, generally called olive mill wastewaters, will be addressed. Within this context, the state of the art of the different pretreatments and integral membrane processes proposed up to today will be gathered and discussed, with an insight in the problem of fouling. Copyright © 2015

  3. Zero curvature-surface driven small objects

    Science.gov (United States)

    Dou, Xiaoxiao; Li, Shanpeng; Liu, Jianlin

    2017-08-01

    In this study, we investigate the spontaneous migration of small objects driven by surface tension on a catenoid, formed by a layer of soap constrained by two rings. Although the average curvature of the catenoid is zero at each point, the small objects always migrate to the position near the ring. The force and energy analyses have been performed to uncover the mechanism, and it is found that the small objects distort the local shape of the liquid film, thus making the whole system energetically favorable. These findings provide some inspiration to design microfluidics, aquatic robotics, and miniature boats.

  4. Spacetime Curvature and Higgs Stability after Inflation.

    Science.gov (United States)

    Herranen, M; Markkanen, T; Nurmi, S; Rajantie, A

    2015-12-11

    We investigate the dynamics of the Higgs field at the end of inflation in the minimal scenario consisting of an inflaton field coupled to the standard model only through the nonminimal gravitational coupling ξ of the Higgs field. Such a coupling is required by renormalization of the standard model in curved space, and in the current scenario also by vacuum stability during high-scale inflation. We find that for ξ≳1, rapidly changing spacetime curvature at the end of inflation leads to significant production of Higgs particles, potentially triggering a transition to a negative-energy Planck scale vacuum state and causing an immediate collapse of the Universe.

  5. Constraining inverse-curvature gravity with supernovae.

    Science.gov (United States)

    Mena, Olga; Santiago, José; Weller, Jochen

    2006-02-03

    We show that models of generalized modified gravity, with inverse powers of the curvature, can explain the current accelerated expansion of the Universe without resorting to dark energy and without conflicting with solar system experiments. We have solved the Friedmann equations for the full dynamical range of the evolution of the Universe and performed a detailed analysis of supernovae data in the context of such models that results in an excellent fit. If we further include constraints on the current expansion of the Universe and on its age, we obtain that the matter content of the Universe is 0.07baryonic matter component.

  6. Amplification of curvature perturbations in cyclic cosmology

    International Nuclear Information System (INIS)

    Zhang Jun; Liu Zhiguo; Piao Yunsong

    2010-01-01

    We analytically and numerically show that through the cycles with nonsingular bounce, the amplitude of curvature perturbation on a large scale will be amplified and the power spectrum will redden. In some sense, this amplification will eventually destroy the homogeneity of the background, which will lead to the ultimate end of cycles of the global universe. We argue that for the model with increasing cycles, it might be possible that a fissiparous multiverse will emerge after one or several cycles, in which the cycles will continue only at corresponding local regions.

  7. Curvature, zero modes and quantum statistics

    Energy Technology Data Exchange (ETDEWEB)

    Calixto, M [Departamento de Matematica Aplicada y EstadIstica, Universidad Politecnica de Cartagena, Paseo Alfonso XIII 56, 30203 Cartagena (Spain); Aldaya, V [Instituto de AstrofIsica de AndalucIa, Apartado Postal 3004, 18080 Granada (Spain)

    2006-08-18

    We explore an intriguing connection between the Fermi-Dirac and Bose-Einstein statistics and the thermal baths obtained from a vacuum radiation of coherent states of zero modes in a second quantized (many-particle) theory on the compact O(3) and noncompact O(2, 1) isometry subgroups of the de Sitter and anti-de Sitter spaces, respectively. The high frequency limit is retrieved as a (zero-curvature) group contraction to the Newton-Hooke (harmonic oscillator) group. We also make some comments on the vacuum energy density and the cosmological constant problem. (letter to the editor)

  8. Differential geometry bundles, connections, metrics and curvature

    CERN Document Server

    Taubes, Clifford Henry

    2011-01-01

    Bundles, connections, metrics and curvature are the 'lingua franca' of modern differential geometry and theoretical physics. This book will supply a graduate student in mathematics or theoretical physics with the fundamentals of these objects. Many of the tools used in differential topology are introduced and the basic results about differentiable manifolds, smooth maps, differential forms, vector fields, Lie groups, and Grassmanians are all presented here. Other material covered includes the basic theorems about geodesics and Jacobi fields, the classification theorem for flat connections, the

  9. Curvature and temperature of complex networks.

    Science.gov (United States)

    Krioukov, Dmitri; Papadopoulos, Fragkiskos; Vahdat, Amin; Boguñá, Marián

    2009-09-01

    We show that heterogeneous degree distributions in observed scale-free topologies of complex networks can emerge as a consequence of the exponential expansion of hidden hyperbolic space. Fermi-Dirac statistics provides a physical interpretation of hyperbolic distances as energies of links. The hidden space curvature affects the heterogeneity of the degree distribution, while clustering is a function of temperature. We embed the internet into the hyperbolic plane and find a remarkable congruency between the embedding and our hyperbolic model. Besides proving our model realistic, this embedding may be used for routing with only local information, which holds significant promise for improving the performance of internet routing.

  10. Combination of cupric ion with hydroxylamine and hydrogen peroxide for the control of bacterial biofilms on RO membranes.

    Science.gov (United States)

    Lee, Hye-Jin; Kim, Hyung-Eun; Lee, Changha

    2017-03-01

    Combinations of Cu(II) with hydroxylamine (HA) and hydrogen peroxide (H 2 O 2 ) (i.e., Cu(II)/HA, Cu(II)/H 2 O 2 , and Cu(II)/HA/H 2 O 2 systems) were investigated for the control of P. aeruginosa biofilms on reverse osmosis (RO) membranes. These Cu(II)-based disinfection systems effectively inactivated P. aeruginosa cells, exhibiting different behaviors depending on the state of bacterial cells (planktonic or biofilm) and the condition of biofilm growth and treatment (normal or pressurized condition). The Cu(II)/HA and Cu(II)/HA/H 2 O 2 systems were the most effective reagents for the inactivation of planktonic cells. However, these systems were not effective in inactivating cells in biofilms on the RO membranes possibly due to the interactions of Cu(I) with extracellular polymeric substances (EPS), where biofilms were grown and treated in center for disease control (CDC) reactors. Different from the results using CDC reactors, in a pressurized cross-flow RO filtration unit, the Cu(II)/HA/H 2 O 2 treatment significantly inactivated biofilm cells formed on the RO membranes, successfully recovering the permeate flux reduced by the biofouling. The pretreatment of feed solutions by Cu(II)/HA and Cu(II)/HA/H 2 O 2 systems (applied before the biofilm formation) effectively mitigated the permeate flux decline by preventing the biofilm growth on the RO membranes. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. The membrane-topogenic vectorial behaviour of Nrf1 controls its post-translational modification and transactivation activity.

    Science.gov (United States)

    Zhang, Yiguo; Hayes, John D

    2013-01-01

    The integral membrane-bound Nrf1 transcription factor fulfils important functions in maintaining cellular homeostasis and organ integrity, but how it is controlled vectorially is unknown. Herein, creative use of Gal4-based reporter assays with protease protection assays (GRAPPA), and double fluorescence protease protection (dFPP), reveals that the membrane-topogenic vectorial behaviour of Nrf1 dictates its post-translational modification and transactivation activity. Nrf1 is integrated within endoplasmic reticulum (ER) membranes through its NHB1-associated TM1 in cooperation with other semihydrophobic amphipathic regions. The transactivation domains (TADs) of Nrf1, including its Asn/Ser/Thr-rich (NST) glycodomain, are transiently translocated into the ER lumen, where it is glycosylated in the presence of glucose to become a 120-kDa isoform. Thereafter, the NST-adjoining TADs are partially repartitioned out of membranes into the cyto/nucleoplasmic side, where Nrf1 is subject to deglycosylation and/or proteolysis to generate 95-kDa and 85-kDa isoforms. Therefore, the vectorial process of Nrf1 controls its target gene expression.

  12. Combined effects of coagulation and adsorption on ultrafiltration membrane fouling control and subsequent disinfection in drinking water treatment.

    Science.gov (United States)

    Xing, Jiajian; Liang, Heng; Cheng, Xiaoxiang; Yang, Haiyan; Xu, Daliang; Gan, Zhendong; Luo, Xinsheng; Zhu, Xuewu; Li, Guibai

    2018-06-02

    This study investigated the combined effects of coagulation and powdered activated carbon (PAC) adsorption on ultrafiltration (UF) membrane fouling control and subsequent disinfection efficiency through filtration performance, dissolved organic carbon (DOC) removal, fluorescence excitation-emission matrix (EEM) spectroscopy, and disinfectant curve. The fouling behavior of UF membrane was comprehensively analyzed especially in terms of pollutant removal and fouling reversibility to understand the mechanism of fouling accumulation and disinfectant dose reduction. Pre-coagulation with or without adsorption both achieved remarkable effect of fouling mitigation and disinfection dose reduction. The two pretreatments were effective in total fouling control and pre-coagulation combined with PAC adsorption even decreased hydraulically irreversible fouling notably. Besides, pre-coagulation decreased residual disinfectant decline due to the removal of hydrophobic components of natural organic matters (NOM). Pre-coagulation combined with adsorption had a synergistic effect on further disinfectant decline rate reduction and decreased total disinfectant consumption due to additional removal of hydrophilic NOM by PAC adsorption. The disinfectant demand was further reduced after membrane. These results show that membrane fouling and disinfectant dose can be reduced in UF coupled with pretreatment, which could lead to the avoidance of excessive operation cost disinfectant dose for drinking water supply.

  13. Receptor kinase-mediated control of primary active proton pumping at the plasma membrane

    DEFF Research Database (Denmark)

    Fuglsang, Anja Thoe; Kristensen, Astrid; Cuin, Tracey A.

    2014-01-01

    Acidification of the cell wall space outside the plasma membrane is required for plant growth and is the result of proton extrusion by the plasma membrane-localized H+-ATPases. Here we show that the major plasma membrane proton pumps in Arabidopsis, AHA1 and AHA2, interact directly in vitro...... and in planta with PSY1R, a receptor kinase of the plasma membrane that serves as a receptor for the peptide growth hormone PSY1. The intracellular protein kinase domain of PSY1R phosphorylates AHA2/AHA1 at Thr-881, situated in the autoinhibitory region I of the C-terminal domain. When expressed in a yeast...... heterologous expression system, the introduction of a negative charge at this position caused pump activation. Application of PSY1 to plant seedlings induced rapid in planta phosphorylation at Thr-881, concomitant with an instantaneous increase in proton efflux from roots. The direct interaction between AHA2...

  14. Nonlinear observer-based Lyapunov boundary control of distributed heat transfer mechanisms for membrane distillation plant

    KAUST Repository

    Eleiwi, Fadi; Laleg-Kirati, Taous-Meriem

    2016-01-01

    , and seeks to maintain the temperature difference along the membrane boundaries around a sufficient level to promote water production. MD process is modeled with advection diffusion equation model in two dimensions, where the diffusion and convection heat

  15. Stress-Matched RF and Thermal Control Coatings for Membrane Antennas, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The development of multi-meter diameter radiofrequency (RF) antennas for NASA and DoD will have a significant impact of future space programs. Polymer membrane...

  16. Controlling the rejection of protein during membrane filtration by adding selected polyelectrolytes

    DEFF Research Database (Denmark)

    Pinelo, Manuel; Ferrer Roca, Carme; Meyer, Anne S.

    2012-01-01

    Electrostatic interactions among the charged groups on proteins and/or between proteins and other solutes significantly affect the aggregation/deposition phenomena that induce fouling and decrease permeate flux during membrane purification of proteins. Such interactions can be turned...... help enhance the performance of membrane filtration for fractionation/purification of a target protein by significantly reducing fouling and modifying rejection/selectivity.......) changing the pH, on the permeate flux and membrane transmission of bovin serum albumina (BSA) through a PVDF membrane. The addition of PS-co-AA to the feed solution resulted in significant increases of the BSA transmission at pH 7.4 as compared to the transmission of a pure BSA solution (1g...

  17. Highly Reflecting, Broadband Deformable Membrane Mirror for Wavefront Control Applications, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Phase I STTR project will develop a highly reflecting, broadband, radiation resistant, low-stress and lightweight, membrane integrated into an electrostatically...

  18. Biofouling Control in Spiral-Wound Membrane Systems: Impact of Feed Spacer Modification and Biocides

    KAUST Repository

    Siddiqui, Amber

    2016-01-01

    was developed. The combination of modeling and experimental testing of 3D printed spacers is a promising strategy to develop advanced spacers aiming to reduce the impact of biofilm formation on membrane performance and to improve the cleanability of spiral

  19. ANALISIS PENGENDALIAN KUALITAS MEMBRAN DALAM PERVAPORASI ETANOL-AIR DENGAN MENGGUNAKAN METODE STATISTICAL QUALITY CONTROL

    Directory of Open Access Journals (Sweden)

    Miftahul Djana

    2018-01-01

    Full Text Available Pervaporation is an alternative separation process using membrane which allows separations of organic mixtures and dehydrates organic solvents with low energy consumption. The purpose of this experiment is to analyze the influence of operating parameters such as feed temperature, times, variation of feed ethanol water mixtures, variation of membranes on pervaporation performance shown by the flux and selectivity by using ceramic membranes with variation of diatomaceous earth and clay as separation. Pervaporation process performance is determined from permeate selectivity and flux. Increase of permeate selectivity and flux means also increasing performace of pervaporation. However, increasing product flux may contribute on decreasing selectivity. The research consists of membrane preparation, pervaporation process, and optimization. Feed of this research are ethanol-water mixture with temperature varying between 40-60oC and downstream pressure 0.5 mbar. Ceramic membrane is used and modification with 30,60,90% of diatomaceous earth. From the results, the membranes have successfully improved the flux of this research..The results showed that the operating conditions of 0,5mbar pressure of permeate, the variation in temperatures of 40ºC, 50ºC and º, th variation of membranes and times produces the flux increases and selectivity decreases.In these conditions the maximum temperature, 60ºC gives the flux of 0,1945 l/m2.hr and the selectivity of 1,7198. In these conditions produce fuel grade ethanol with purity levels reached 98% from 95% ethanol feed.The test results indicated the mean value of t = 31.400> t table = 2.00 and sig. =0,000 <α = 0.05, thus the average (mean of 1.806 issignificant. Thus the hypothesis that the level of damage membrane of the product significantly affect the processproduction is not proven.

  20. Mean cortical curvature reflects cytoarchitecture restructuring in mild traumatic brain injury

    Directory of Open Access Journals (Sweden)

    Jace B. King

    2016-01-01

    Full Text Available In the United States alone, the number of persons living with the enduring consequences of traumatic brain injuries is estimated to be between 3.2 and 5 million. This number does not include individuals serving in the United States military or seeking care at Veterans Affairs hospitals. The importance of understanding the neurobiological consequences of mild traumatic brain injury (mTBI has increased with the return of veterans from conflicts overseas, many of who have suffered this type of brain injury. However, identifying the neuroanatomical regions most affected by mTBI continues to prove challenging. The aim of this study was to assess the use of mean cortical curvature as a potential indicator of progressive tissue loss in a cross-sectional sample of 54 veterans with mTBI compared to 31 controls evaluated with MRI. It was hypothesized that mean cortical curvature would be increased in veterans with mTBI, relative to controls, due in part to cortical restructuring related to tissue volume loss. Mean cortical curvature was assessed in 60 bilateral regions (31 sulcal, 29 gyral. Of the 120 regions investigated, nearly 50% demonstrated significantly increased mean cortical curvature in mTBI relative to controls with 25% remaining significant following multiple comparison correction (all, pFDR < .05. These differences were most prominent in deep gray matter regions of the cortex. Additionally, significant relationships were found between mean cortical curvature and gray and white matter volumes (all, p < .05. These findings suggest potentially unique patterns of atrophy by region and indicate that changes in brain microstructure due to mTBI are sensitive to measures of mean curvature.

  1. Polarized curvature radiation in pulsar magnetosphere

    Science.gov (United States)

    Wang, P. F.; Wang, C.; Han, J. L.

    2014-07-01

    The propagation of polarized emission in pulsar magnetosphere is investigated in this paper. The polarized waves are generated through curvature radiation from the relativistic particles streaming along curved magnetic field lines and corotating with the pulsar magnetosphere. Within the 1/γ emission cone, the waves can be divided into two natural wave-mode components, the ordinary (O) mode and the extraordinary (X) mode, with comparable intensities. Both components propagate separately in magnetosphere, and are aligned within the cone by adiabatic walking. The refraction of O mode makes the two components separated and incoherent. The detectable emission at a given height and a given rotation phase consists of incoherent X-mode and O-mode components coming from discrete emission regions. For four particle-density models in the form of uniformity, cone, core and patches, we calculate the intensities for each mode numerically within the entire pulsar beam. If the corotation of relativistic particles with magnetosphere is not considered, the intensity distributions for the X-mode and O-mode components are quite similar within the pulsar beam, which causes serious depolarization. However, if the corotation of relativistic particles is considered, the intensity distributions of the two modes are very different, and the net polarization of outcoming emission should be significant. Our numerical results are compared with observations, and can naturally explain the orthogonal polarization modes of some pulsars. Strong linear polarizations of some parts of pulsar profile can be reproduced by curvature radiation and subsequent propagation effect.

  2. Emergent gravity in spaces of constant curvature

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, Orlando; Haddad, Matthew [Department of Physics, University of Miami,1320 Campo Sano Ave, Coral Gables, FL 33146 (United States)

    2017-03-07

    In physical theories where the energy (action) is localized near a submanifold of a constant curvature space, there is a universal expression for the energy (or the action). We derive a multipole expansion for the energy that has a finite number of terms, and depends on intrinsic geometric invariants of the submanifold and extrinsic invariants of the embedding of the submanifold. This is the second of a pair of articles in which we try to develop a theory of emergent gravity arising from the embedding of a submanifold into an ambient space equipped with a quantum field theory. Our theoretical method requires a generalization of a formula due to by Hermann Weyl. While the first paper discussed the framework in Euclidean (Minkowski) space, here we discuss how this framework generalizes to spaces of constant sectional curvature. We focus primarily on anti de Sitter space. We then discuss how such a theory can give rise to a cosmological constant and Planck mass that are within reasonable bounds of the experimental values.

  3. Lecture notes on mean curvature flow, barriers and singular perturbations

    CERN Document Server

    Bellettini, Giovanni

    2013-01-01

    The aim of the book is to study some aspects of geometric evolutions, such as mean curvature flow and anisotropic mean curvature flow of hypersurfaces. We analyze the origin of such flows and their geometric and variational nature. Some of the most important aspects of mean curvature flow are described, such as the comparison principle and its use in the definition of suitable weak solutions. The anisotropic evolutions, which can be considered as a generalization of mean curvature flow, are studied from the view point of Finsler geometry. Concerning singular perturbations, we discuss the convergence of the Allen–Cahn (or Ginsburg–Landau) type equations to (possibly anisotropic) mean curvature flow before the onset of singularities in the limit problem. We study such kinds of asymptotic problems also in the static case, showing convergence to prescribed curvature-type problems.

  4. The curvature calculation mechanism based on simple cell model.

    Science.gov (United States)

    Yu, Haiyang; Fan, Xingyu; Song, Aiqi

    2017-07-20

    A conclusion has not yet been reached on how exactly the human visual system detects curvature. This paper demonstrates how orientation-selective simple cells can be used to construct curvature-detecting neural units. Through fixed arrangements, multiple plurality cells were constructed to simulate curvature cells with a proportional output to their curvature. In addition, this paper offers a solution to the problem of narrow detection range under fixed resolution by selecting an output value under multiple resolution. Curvature cells can be treated as concrete models of an end-stopped mechanism, and they can be used to further understand "curvature-selective" characteristics and to explain basic psychophysical findings and perceptual phenomena in current studies.

  5. Root plasma membrane transporters controlling K+/Na+ homeostasis in salt-stressed bBarley1[C][W

    DEFF Research Database (Denmark)

    Chen, Zhonghua; Pottosin, Igor I.; Cuin, Tracey A.

    2007-01-01

    are well combined to withstand saline conditions. These mechanisms include: (1) better control of membrane voltage so retaining a more negative membrane potential; (2) intrinsically higher H1 pump activity; (3) better ability of root cells to pump Na1 from the cytosol to the external medium; and (4) higher......Plant salinity tolerance is a polygenic trait with contributions from genetic, developmental, and physiological interactions, in addition to interactions between the plant and its environment. In this study, we show that in salt-tolerant genotypes of barley (Hordeum vulgare), multiple mechanisms...... of the cytosolic K1-to-Na1 ratio being a key determinant of plant salinity tolerance, and suggest multiple pathways of controlling that important feature in salt-tolerant plants....

  6. MPK-1 ERK Controls Membrane Organization in C. elegans Oogenesis via a Sex-Determination Module

    OpenAIRE

    Arur, Swathi; Ohmachi, Mitsue; Berkseth, Matt; Nayak, Sudhir; Hansen, David; Zarkower, David; Schedl, Tim

    2011-01-01

    Tissues that generate specialized cell-types in a production line must coordinate developmental mechanisms with physiological demand, although how this occurs is largely unknown. In the C. elegans hermaphrodite, the developmental sex-determination cascade specifies gamete sex in the distal germline, while physiological sperm signaling activates MPK-1/ERK in the proximal germline to control plasma membrane biogenesis/organization during oogenesis. We discovered repeated utilization of a self-c...

  7. Reduced-Order Dynamic Modeling, Fouling Detection, and Optimal Control of Solar-Powered Direct Contact Membrane Distillation

    KAUST Repository

    Karam, Ayman M.

    2016-12-01

    Membrane Distillation (MD) is an emerging sustainable desalination technique. While MD has many advantages and can be powered by solar thermal energy, its main drawback is the low water production rate. However, the MD process has not been fully optimized in terms of its manipulated and controlled variables. This is largely due to the lack of adequate dynamic models to study and simulate the process. In addition, MD is prone to membrane fouling, which is a fault that degrades the performance of the MD process. This work has three contributions to address these challenges. First, we derive a mathematical model of Direct Contact Membrane Distillation (DCMD), which is the building block for the next parts. Then, the proposed model is extended to account for membrane fouling and an observer-based fouling detection method is developed. Finally, various control strategies are implemented to optimize the performance of the DCMD solar-powered process. In part one, a reduced-order dynamic model of DCMD is developed based on lumped capacitance method and electrical analogy to thermal systems. The result is an electrical equivalent thermal network to the DCMD process, which is modeled by a system of nonlinear differential algebraic equations (DAEs). This model predicts the water-vapor flux and the temperature distribution along the module length. Experimental data is collected to validate the steady-state and dynamic responses of the proposed model, with great agreement demonstrated in both. The second part proposes an extension of the model to account for membrane fouling. An adaptive observer for DAE systems is developed and convergence proof is presented. A method for membrane fouling detection is then proposed based on adaptive observers. Simulation results demonstrate the performance of the membrane fouling detection method. Finally, an optimization problem is formulated to maximize the process efficiency of a solar-powered DCMD. The adapted method is known as Extremum

  8. On Riemannian manifolds (Mn, g) of quasi-constant curvature

    International Nuclear Information System (INIS)

    Rahman, M.S.

    1995-07-01

    A Riemannian manifold (M n , g) of quasi-constant curvature is defined. It is shown that an (M n , g) in association with other class of manifolds gives rise, under certain conditions, to a manifold of quasi-constant curvature. Some observations on how a manifold of quasi-constant curvature accounts for a pseudo Ricci-symmetric manifold and quasi-umbilical hypersurface are made. (author). 10 refs

  9. Statistical mechanics of paths with curvature dependent action

    International Nuclear Information System (INIS)

    Ambjoern, J.; Durhuus, B.; Jonsson, T.

    1987-01-01

    We analyze the scaling limit of discretized random paths with curvature dependent action. For finite values of the curvature coupling constant the theory belongs to the universality class of simple random walk. It is possible to define a non-trivial scaling limit if the curvature coupling tends to infinity. We compute exactly the two point function in this limit and discuss the relevance of our results for random surfaces and string theories. (orig.)

  10. Controlled drug release from cross-linked κ-carrageenan/hyaluronic acid membranes.

    Science.gov (United States)

    El-Aassar, M R; El Fawal, G F; Kamoun, Elbadawy A; Fouda, Moustafa M G

    2015-01-01

    In this work, hydrogel membrane composed of; kappa carrageenan (κC) and hyaluronic acid (HA) crosslinked with epichlorohydrine is produced. The optimum condition has been established based on their water absorption properties. Tensile strength (TS) and elongation (E%) for the formed films are evaluated. The obtained films were characterized by FTIR, scanning electron microscopy (SEM) and thermal analysis. All membranes were loaded with l-carnosine as a drug model. The swelling properties and kinetics of the release of the model drug from the crosslinked hydrogel membrane were monitored in buffer medium at 37°C. The equilibrium swelling of films showed fair dependency on the high presence of HA in the hydrogel. Moreover, the cumulative release profile increased significantly and ranged from 28% to 93%, as HA increases. SEM explored that, the porosity increased by increasing HA content; consequently, drug release into the pores and channels of the membranes is facilitated. In addition, water uptake % increased as well. A slight change in TS occurred by increasing the HA% to κC, while the highest value of strain for κC membrane was 498.38% by using 3% HA. The thermal stability of the κC/HA was higher than that of HA. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. Plasma-deposited hybrid silica membranes with a controlled retention of organic bridges

    Energy Technology Data Exchange (ETDEWEB)

    Ngamou, P.H.T.; Creatore, M. [Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven (Netherlands); Overbeek, J.P.; Kreiter, R.; Van Veen, H.M.; Vente, J.F. [ECN, Energy research Centre of the Netherlands, Petten (Netherlands); Wienk, I.M.; Cuperus, P.F. [SolSep BV, Apeldoorn (Netherlands)

    2013-03-05

    Hybrid organically bridged silica membranes are suitable for energy-efficient molecular separations under harsh industrial conditions. Such membranes can be useful in organic solvent nanofiltration if they can be deposited on flexible, porous and large area supports. Here, we report the proof of concept for applying an expanding thermal plasma to the synthesis of perm-selective hybrid silica films from an organically bridged monomer, 1,2-bis(triethoxysilyl)ethane. This membrane is the first in its class to be produced by plasma enhanced chemical vapor deposition. By tuning the plasma and process parameters, the organic bridging groups could be retained in the separating layer. This way, a defect free film could be made with pervaporation performances of an n-butanol-water mixture comparable with those of conventional ceramic supported membranes made by sol-gel technology (i.e. a water flux of [similar]1.8 kg m'-{sup 2} h{sup -1}, a water concentration in the permeate higher than 98% and a separation factor of >1100). The obtained results show the suitability of expanding thermal plasma as a technology for the deposition of hybrid silica membranes for molecular separations.

  12. Evolution of the curvature perturbations during warm inflation

    International Nuclear Information System (INIS)

    Matsuda, Tomohiro

    2009-01-01

    This paper considers warm inflation as an interesting application of multi-field inflation. Delta-N formalism is used for the calculation of the evolution of the curvature perturbations during warm inflation. Although the perturbations considered in this paper are decaying after the horizon exit, the corrections to the curvature perturbations sourced by these perturbations can remain and dominate the curvature perturbations at large scales. In addition to the typical evolution of the curvature perturbations, inhomogeneous diffusion rate is considered for warm inflation, which may lead to significant non-Gaussianity of the spectrum

  13. 3D face recognition with asymptotic cones based principal curvatures

    KAUST Repository

    Tang, Yinhang; Sun, Xiang; Huang, Di; Morvan, Jean-Marie; Wang, Yunhong; Chen, Liming

    2015-01-01

    The classical curvatures of smooth surfaces (Gaussian, mean and principal curvatures) have been widely used in 3D face recognition (FR). However, facial surfaces resulting from 3D sensors are discrete meshes. In this paper, we present a general framework and define three principal curvatures on discrete surfaces for the purpose of 3D FR. These principal curvatures are derived from the construction of asymptotic cones associated to any Borel subset of the discrete surface. They describe the local geometry of the underlying mesh. First two of them correspond to the classical principal curvatures in the smooth case. We isolate the third principal curvature that carries out meaningful geometric shape information. The three principal curvatures in different Borel subsets scales give multi-scale local facial surface descriptors. We combine the proposed principal curvatures with the LNP-based facial descriptor and SRC for recognition. The identification and verification experiments demonstrate the practicability and accuracy of the third principal curvature and the fusion of multi-scale Borel subset descriptors on 3D face from FRGC v2.0.

  14. Robust estimation of adaptive tensors of curvature by tensor voting.

    Science.gov (United States)

    Tong, Wai-Shun; Tang, Chi-Keung

    2005-03-01

    Although curvature estimation from a given mesh or regularly sampled point set is a well-studied problem, it is still challenging when the input consists of a cloud of unstructured points corrupted by misalignment error and outlier noise. Such input is ubiquitous in computer vision. In this paper, we propose a three-pass tensor voting algorithm to robustly estimate curvature tensors, from which accurate principal curvatures and directions can be calculated. Our quantitative estimation is an improvement over the previous two-pass algorithm, where only qualitative curvature estimation (sign of Gaussian curvature) is performed. To overcome misalignment errors, our improved method automatically corrects input point locations at subvoxel precision, which also rejects outliers that are uncorrectable. To adapt to different scales locally, we define the RadiusHit of a curvature tensor to quantify estimation accuracy and applicability. Our curvature estimation algorithm has been proven with detailed quantitative experiments, performing better in a variety of standard error metrics (percentage error in curvature magnitudes, absolute angle difference in curvature direction) in the presence of a large amount of misalignment noise.

  15. 3D face recognition with asymptotic cones based principal curvatures

    KAUST Repository

    Tang, Yinhang

    2015-05-01

    The classical curvatures of smooth surfaces (Gaussian, mean and principal curvatures) have been widely used in 3D face recognition (FR). However, facial surfaces resulting from 3D sensors are discrete meshes. In this paper, we present a general framework and define three principal curvatures on discrete surfaces for the purpose of 3D FR. These principal curvatures are derived from the construction of asymptotic cones associated to any Borel subset of the discrete surface. They describe the local geometry of the underlying mesh. First two of them correspond to the classical principal curvatures in the smooth case. We isolate the third principal curvature that carries out meaningful geometric shape information. The three principal curvatures in different Borel subsets scales give multi-scale local facial surface descriptors. We combine the proposed principal curvatures with the LNP-based facial descriptor and SRC for recognition. The identification and verification experiments demonstrate the practicability and accuracy of the third principal curvature and the fusion of multi-scale Borel subset descriptors on 3D face from FRGC v2.0.

  16. Hair curvature: a natural dialectic and review.

    Science.gov (United States)

    Nissimov, Joseph N; Das Chaudhuri, Asit Baran

    2014-08-01

    Although hair forms (straight, curly, wavy, etc.) are present in apparently infinite variations, each fibre can be reduced to a finite sequence of tandem segments of just three types: straight, bent/curly, or twisted. Hair forms can thus be regarded as resulting from genetic pathways that induce, reverse or modulate these basic curvature modes. However, physical interconversions between twists and curls demonstrate that strict one-to-one correspondences between them and their genetic causes do not exist. Current hair-curvature theories do not distinguish between bending and twisting mechanisms. We here introduce a multiple papillary centres (MPC) model which is particularly suitable to explain twisting. The model combines previously known features of hair cross-sectional morphology with partially/completely separated dermal papillae within single follicles, and requires such papillae to induce differential growth rates of hair cortical material in their immediate neighbourhoods. The MPC model can further help to explain other, poorly understood, aspects of hair growth and morphology. Separate bending and twisting mechanisms would be preferentially affected at the major or minor ellipsoidal sides of fibres, respectively, and together they exhaust the possibilities for influencing hair-form phenotypes. As such they suggest dialectic for hair-curvature development. We define a natural-dialectic (ND) which could take advantage of speculative aspects of dialectic, but would verify its input data and results by experimental methods. We use this as a top-down approach to first define routes by which hair bending or twisting may be brought about and then review evidence in support of such routes. In particular we consider the wingless (Wnt) and mammalian target of rapamycin (mTOR) pathways as paradigm pathways for molecular hair bending and twisting mechanisms, respectively. In addition to the Wnt canonical pathway, the Wnt/Ca(2+) and planar cell polarity (PCP) pathways

  17. Ultrasonic control of ceramic membrane fouling by particles: effect of ultrasonic factors.

    Science.gov (United States)

    Chen, Dong; Weavers, Linda K; Walker, Harold W

    2006-07-01

    Ultrasound at 20 kHz was applied to a cross-flow ultrafiltration system with gamma-alumina membranes in the presence of colloidal silica particles to systematically investigate how ultrasonic factors affect membrane cleaning. Based on imaging of the ultrasonic cavitation region, optimal cleaning occurred when the membrane was outside but close to the cavitation region. Increasing the filtration pressure increased the compressive forces driving cavitation collapse and resulted in fewer cavitation bubbles absorbing and scattering sound waves and increasing sound wave penetration. However, an increased filtration pressure also resulted in greater permeation drag, and subsequently less improvement in permeate flux compared to low filtration pressure. Finally, pulsed ultrasound with short pulse intervals resulted in permeate flux improvement close to that of continuous sonication.

  18. Confinement of activating receptors at the plasma membrane controls natural killer cell tolerance.

    Science.gov (United States)

    Guia, Sophie; Jaeger, Baptiste N; Piatek, Stefan; Mailfert, Sébastien; Trombik, Tomasz; Fenis, Aurore; Chevrier, Nicolas; Walzer, Thierry; Kerdiles, Yann M; Marguet, Didier; Vivier, Eric; Ugolini, Sophie

    2011-04-05

    Natural killer (NK) cell tolerance to self is partly ensured by major histocompatibility complex (MHC) class I-specific inhibitory receptors on NK cells, which dampen their reactivity when engaged. However, NK cells that do not detect self MHC class I are not autoreactive. We used dynamic fluorescence correlation spectroscopy to show that MHC class I-independent NK cell tolerance in mice was associated with the presence of hyporesponsive NK cells in which both activating and inhibitory receptors were confined in an actin meshwork at the plasma membrane. In contrast, the recognition of self MHC class I by inhibitory receptors "educated" NK cells to become fully reactive, and activating NK cell receptors became dynamically compartmentalized in membrane nanodomains. We propose that the confinement of activating receptors at the plasma membrane is pivotal to ensuring the self-tolerance of NK cells.

  19. High Performance Platinum Group Metal Free Membrane Electrode Assemblies through Control of Interfacial Processes

    Energy Technology Data Exchange (ETDEWEB)

    Ayers, Katherine [Proton Energy Systems, Wallingford, CT (United States); Capuano, Christopher [Proton Energy Systems, Wallingford, CT (United States); Atanassov, Plamen [Univ. of New Mexico, Albuquerque, NM (United States); Mukerjee, Sanjeev [Northeastern Univ., Boston, MA (United States); Hickner, Michael [Pennsylvania State Univ., University Park, PA (United States)

    2017-11-29

    The quantitative goal of this project was to produce a high-performance anion exchange membrane water electrolyzer (AEM-WE) completely free of platinum group metals (PGMs), which could operate for at least 500 hours with less than 50 microV/hour degradation, at 500 mA/cm2. To achieve this goal, work focused on the optimization of electrocatalyst conductivity, with dispersion and utilization in the membrane electrode assembly (MEA) improved through refinement of deposition techniques. Critical factors were also explored with significant work undertaken by Northeastern University to further understand catalyst-membrane-ionomer interfaces and how they differ from liquid electrolyte. Water management and optimal cell operational parameters were established through the design, fabrication, and test of a new test station at Proton specific for AEM evaluation. Additionally, AEM material stability and robustness at high potentials and gas evolution conditions were advanced at Penn State.

  20. Hawking temperature of constant curvature black holes

    International Nuclear Information System (INIS)

    Cai Ronggen; Myung, Yun Soo

    2011-01-01

    The constant curvature (CC) black holes are higher dimensional generalizations of Banados-Teitelboim-Zanelli black holes. It is known that these black holes have the unusual topology of M D-1 xS 1 , where D is the spacetime dimension and M D-1 stands for a conformal Minkowski spacetime in D-1 dimensions. The unusual topology and time-dependence for the exterior of these black holes cause some difficulties to derive their thermodynamic quantities. In this work, by using a globally embedding approach, we obtain the Hawking temperature of the CC black holes. We find that the Hawking temperature takes the same form when using both the static and global coordinates. Also, it is identical to the Gibbons-Hawking temperature of the boundary de Sitter spaces of these CC black holes.

  1. Differential geometry connections, curvature, and characteristic classes

    CERN Document Server

    Tu, Loring W

    2017-01-01

    This text presents a graduate-level introduction to differential geometry for mathematics and physics students. The exposition follows the historical development of the concepts of connection and curvature with the goal of explaining the Chern–Weil theory of characteristic classes on a principal bundle. Along the way we encounter some of the high points in the history of differential geometry, for example, Gauss' Theorema Egregium and the Gauss–Bonnet theorem. Exercises throughout the book test the reader’s understanding of the material and sometimes illustrate extensions of the theory. Initially, the prerequisites for the reader include a passing familiarity with manifolds. After the first chapter, it becomes necessary to understand and manipulate differential forms. A knowledge of de Rham cohomology is required for the last third of the text. Prerequisite material is contained in author's text An Introduction to Manifolds, and can be learned in one semester. For the benefit of the reader and to establ...

  2. Curvature radiation by bunches of particles

    International Nuclear Information System (INIS)

    Saggion, A.

    1975-01-01

    A bunch of relativistic particles moving on a curved trajectory is considered. The coherent emission of curvature radiation is described with particular regard to the role played by the 'shape' of the bunch as a function of its dimensions. It is found that the length of the bunch strongly affects the spectrum of the radiation emitted, with no effect on its polarization. For wavelengths shorter than the length of the bunch, the emitted intensity as a function of frequency shows recurrent maxima and minima, the height of the maxima being proportional to νsup(-5/3). The bunch dimensions perpendicular to the plane of the orbit affect both the spectral intensity and the polarization of the radiation. (orig./BJ) [de

  3. Natural curvature for manifest T-duality

    International Nuclear Information System (INIS)

    Poláček, Martin; Siegel, Warren

    2014-01-01

    We reformulate the manifestly T-dual description of the massless sector of the closed bosonic string, directly from the geometry associated with the (left and right) affine Lie algebra of the coset space Poincaré/Lorentz. This construction initially doubles not only the (spacetime) coordinates for translations but also those for Lorentz transformations (and their “dual”). As a result, the Lorentz connection couples directly to the string (as does the vielbein), rather than being introduced ad hoc to the covariant derivative as previously. This not only reproduces the old definition of T-dual torsion, but automatically gives a general, covariant definition of T-dual curvature (but still with some undetermined connections)

  4. Nonminimal coupling of perfect fluids to curvature

    International Nuclear Information System (INIS)

    Bertolami, Orfeu; Lobo, Francisco S. N.; Paramos, Jorge

    2008-01-01

    In this work, we consider different forms of relativistic perfect fluid Lagrangian densities that yield the same gravitational field equations in general relativity (GR). A particularly intriguing example is the case with couplings of the form [1+f 2 (R)]L m , where R is the scalar curvature, which induces an extra force that depends on the form of the Lagrangian density. It has been found that, considering the Lagrangian density L m =p, where p is the pressure, the extra-force vanishes. We argue that this is not the unique choice for the matter Lagrangian density, and that more natural forms for L m do not imply the vanishing of the extra force. Particular attention is paid to the impact on the classical equivalence between different Lagrangian descriptions of a perfect fluid.

  5. Topological photonic crystals with zero Berry curvature

    Science.gov (United States)

    Liu, Feng; Deng, Hai-Yao; Wakabayashi, Katsunori

    2018-02-01

    Topological photonic crystals are designed based on the concept of Zak's phase rather than the topological invariants such as the Chern number and spin Chern number, which rely on the existence of a nonvanishing Berry curvature. Our photonic crystals (PCs) are made of pure dielectrics and sit on a square lattice obeying the C4 v point-group symmetry. Two varieties of PCs are considered: one closely resembles the electronic two-dimensional Su-Schrieffer-Heeger model, and the other continues as an extension of this analogy. In both cases, the topological transitions are induced by adjusting the lattice constants. Topological edge modes (TEMs) are shown to exist within the nontrivial photonic band gaps on the termination of those PCs. The high efficiency of these TEMs transferring electromagnetic energy against several types of disorders has been demonstrated using the finite-element method.

  6. A Field Theory with Curvature and Anticurvature

    Directory of Open Access Journals (Sweden)

    M. I. Wanas

    2014-01-01

    Full Text Available The present work is an attempt to construct a unified field theory in a space with curvature and anticurvature, the PAP-space. The theory is derived from an action principle and a Lagrangian density using a symmetric linear parameterized connection. Three different methods are used to explore physical contents of the theory obtained. Poisson’s equations for both material and charge distributions are obtained, as special cases, from the field equations of the theory. The theory is a pure geometric one in the sense that material distribution, charge distribution, gravitational and electromagnetic potentials, and other physical quantities are defined in terms of pure geometric objects of the structure used. In the case of pure gravity in free space, the spherical symmetric solution of the field equations gives the Schwarzschild exterior field. The weak equivalence principle is respected only in the case of pure gravity in free space; otherwise it is violated.

  7. Control and Experimental Characterization of a Methanol Reformer for a 350 W High Temperature Polymer Electrolyte Membrane Fuel Cell system

    DEFF Research Database (Denmark)

    Andreasen, Søren Juhl; Kær, Søren Knudsen; Jensen, Hans-Christian Becker

    , i.e. cathode and anode gas flows and temperature by using mass flow controllers and controlled heaters. Using this system the methanol reformer is characterized in its different operating points, both steady-state but also dynamically. Methanol steam reforming is a well known process, and provides...... and burner and the behaviour of the CO concentration of the reformate gas....... the high temperature waste gas from a cathode air cooled 45 cell HTPEM fuel cell stack. The MEAs used are BASF P2100 which use phosphoric acid doped polybenzimidazole type membranes; an MEA with high CO tolerance and no complex humidity requirements. The methanol reformer used is integrated into a compact...

  8. Membrane contactors in the beverage industry for controlling the water gas composition.

    Science.gov (United States)

    Criscuoli, Alessandra; Drioli, Enrico; Moretti, Ugo

    2003-03-01

    In the work described here, membrane contactors are used for coupling the removal of species (oxygen and hydrogen sulfide) present in the water with the water carbonation process. We include both experiments and a theoretical study devoted to the analysis of the transport phenomena that occur in the membrane contactor. The main resistance to mass transport was located at the liquid side. Correlations between Sherwood and Reynolds numbers on the shell side that are suitable for the membrane contactor used to carry out our experiments have been determined. In particular, for Re > 1.6, the expression proposed by Yang and Cussler in 1986: Sh = 0.90 Re(0.40) Sc(0.33) describes the behavior of the system; whereas, for Re between 0.03 and 0.3, a new expression is proposed: Sh = 0.435 Re(1.2)Sc(0.33). A comparison with traditional equipment is also furnished. Membrane contactors offer reduced size, CO(2) consumption, and capital costs.

  9. pH control structure design for a periodically operated membrane separation process

    DEFF Research Database (Denmark)

    Prado Rubio, Oscar Andres; Jørgensen, Sten Bay; Jonsson, Gunnar Eigil

    2012-01-01

    A bioreactor integrated with an electrically driven membrane separation process (Reverse Electro-Enhanced Dialysis – REED) is under investigation as potential technology for intensifying lactic acid bioproduction. In this contribution the pH regulation issue in the periodically operated REED module...

  10. Dual curvature acoustically damped concentrating collector. Semiannual technical progress report, June 1-December 1, 1978

    Energy Technology Data Exchange (ETDEWEB)

    None

    1978-12-01

    The project's first objective is to establish, analytically, the cost and performance of design choices within the boundaries of the basic proposed concept. With these cost and performance measures as a guide, the second project objective is to design a cost-effective Dual Curvature collector module and collector field array. The third objective is to establish technical and economic concept feasibility through prototype fabrication and test. The final objective is to define the Dual Curvature collector commercialization requirements. The Dual Curvature collector uses a unique reflector module consisting of a reflective film that is tensioned on a reflector support frame. The tensioned membrane (film) surface approximates a hyperbolic paraboloid that is capable of linear focusing when the surface tracks the sun's apparent motion in one axis. The reflective film can be backed by polystyrene foam with an air space between the film and the foam surfaces. This provides damping of the reflector surface to minimize the effect of wind gusts and physical impacts. The baseline collector is intended to operate at a concentration of ten (10) or greater with a nominal absorber temperature of 150/sup 0/C (300/sup 0/F). The Component Research and Analysis tasks which lead to the selection of a baseline collector configuration are discussed. Also, some preliminary results of the Collector Module Design task are presented.

  11. On harmonic curvatures of a Frenet curve in Lorentzian space

    International Nuclear Information System (INIS)

    Kuelahci, Mihriban; Bektas, Mehmet; Erguet, Mahmut

    2009-01-01

    In this paper, we consider curves of AW(k)-type, 1 ≤ k ≤ 3, in Lorentzian space. We give curvature conditions of these kind of curves. Furthermore, we study harmonic curvatures of curves of AW(k)-type. We investigate that under what conditions AW(k)-type curves are helix. Some related theorems and corollaries are also proved.

  12. The scalar curvature problem on the four dimensional half sphere

    CERN Document Server

    Ben-Ayed, M; El-Mehdi, K

    2003-01-01

    In this paper, we consider the problem of prescribing the scalar curvature under minimal boundary conditions on the standard four dimensional half sphere. We provide an Euler-Hopf type criterion for a given function to be a scalar curvature for some metric conformal to the standard one. Our proof involves the study of critical points at infinity of the associated variational problem.

  13. Statistical mechanics of surfaces with curvature dependent action

    International Nuclear Information System (INIS)

    Jonsson, T.

    1987-01-01

    We review recent results about discretized random surfaces whose action (energy) depends on the extrinsic curvature. The surface tension scales to zero at an appropriate critical point if the coupling constant of the curvature term is taken to infinity. At this critical point one expects to be able to construct a continuum theory of smooth surfaces. (orig.)

  14. Curvature of random walks and random polygons in confinement

    International Nuclear Information System (INIS)

    Diao, Y; Ernst, C; Montemayor, A; Ziegler, U

    2013-01-01

    The purpose of this paper is to study the curvature of equilateral random walks and polygons that are confined in a sphere. Curvature is one of several basic geometric properties that can be used to describe random walks and polygons. We show that confinement affects curvature quite strongly, and in the limit case where the confinement diameter equals the edge length the unconfined expected curvature value doubles from π/2 to π. To study curvature a simple model of an equilateral random walk in spherical confinement in dimensions 2 and 3 is introduced. For this simple model we derive explicit integral expressions for the expected value of the total curvature in both dimensions. These expressions are functions that depend only on the radius R of the confinement sphere. We then show that the values obtained by numeric integration of these expressions agrees with numerical average curvature estimates obtained from simulations of random walks. Finally, we compare the confinement effect on curvature of random walks with random polygons. (paper)

  15. Curvature collineations for the field of gravitational waves

    International Nuclear Information System (INIS)

    Singh, K.P.; Singh, Gulab

    1981-01-01

    It has been shown that the space-times formed from a plane-fronted gravity wave and from a plane sandwich wave with constant polarisation admit proper curvature collineation in general. The curvature collineation vectors have been determined explicitly. (author)

  16. Synthesis of Silicalite Membrane with an Aluminum-Containing Surface for Controlled Modification of Zeolitic Pore Entries for Enhanced Gas Separation

    Directory of Open Access Journals (Sweden)

    Shaowei Yang

    2018-02-01

    Full Text Available The separation of small molecule gases by membrane technologies can help performance enhancement and process intensification for emerging advanced fossil energy systems with CO2 capture capacity. This paper reports the demonstration of controlled modification of zeolitic channel size for the MFI-type zeolite membranes to enhance the separation of small molecule gases such as O2 and N2. Pure-silica MFI-type zeolite membranes were synthesized on porous α-alumina disc substrates with and without an aluminum-containing thin skin on the outer surface of zeolite membrane. The membranes were subsequently modified by on-stream catalytic cracking deposition (CCD of molecular silica to reduce the effective openings of the zeolitic channels. Such a pore modification caused the transition of gas permeation from the N2-selective gaseous diffusion mechanism in the pristine membrane to the O2-selective activated diffusion mechanism in the modified membrane. The experimental results indicated that the pore modification could be effectively limited within the aluminum-containing surface of the MFI zeolite membrane to minimize the mass transport resistance for O2 permeation while maintaining its selectivity. The implications of pore modification on the size-exclusion-enabled gas selectivity were discussed based on the kinetic molecular theory. In light of the theoretical analysis, experimental investigation was performed to further enhance the membrane separation selectivity by chemical liquid deposition of silica into the undesirable intercrystalline spaces.

  17. Robust modal curvature features for identifying multiple damage in beams

    Science.gov (United States)

    Ostachowicz, Wiesław; Xu, Wei; Bai, Runbo; Radzieński, Maciej; Cao, Maosen

    2014-03-01

    Curvature mode shape is an effective feature for damage detection in beams. However, it is susceptible to measurement noise, easily impairing its advantage of sensitivity to damage. To deal with this deficiency, this study formulates an improved curvature mode shape for multiple damage detection in beams based on integrating a wavelet transform (WT) and a Teager energy operator (TEO). The improved curvature mode shape, termed the WT - TEO curvature mode shape, has inherent capabilities of immunity to noise and sensitivity to damage. The proposed method is experimentally validated by identifying multiple cracks in cantilever steel beams with the mode shapes acquired using a scanning laser vibrometer. The results demonstrate that the improved curvature mode shape can identify multiple damage accurately and reliably, and it is fairly robust to measurement noise.

  18. Internal hydration of a metal-transporting ATPase is controlled by membrane lateral pressure

    Energy Technology Data Exchange (ETDEWEB)

    Fahmy, Karim [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Biophysics; Fischermeier, E. [Technische Univ. Dresden (Germany); Pospisil, P. [A.S.C. R., Prague (Czech Republic). J. Heyrovsky Inst. Physical Chemistry; Solioz, M. [Bern Univ. (Switzerland); Sayed, A.; Hof, M.

    2017-07-01

    The active transport of ions across biological mem branes requires their hydration shell to interact with the interior of membrane proteins. However, the influence of the external lipid phase on internal dielectric dynamics is hard to access by experiment. Using the octahelical transmembrane architecture of the copper-transporting P{sub 1B}-type ATPase from Legionella pneumophila (LpCopA) as a model structure, we have established the site-specific labeling of internal cysteines with a polarity-sensitive fluorophore. This enabled dipolar relaxation studies in a solubilized form of the protein and in its lipid-embedded state in nano-discs (NDs). Time-dependent fluorescence shifts revealed the site-specific hydration and dipole mobility around the conserved ion-binding motif. The spatial distribution of both features is shaped significantly and independently of each other by membrane lateral pressure.

  19. Internal hydration of a metal-transporting ATPase is controlled by membrane lateral pressure

    International Nuclear Information System (INIS)

    Fahmy, Karim; Pospisil, P.; Sayed, A.; Hof, M.

    2017-01-01

    The active transport of ions across biological mem branes requires their hydration shell to interact with the interior of membrane proteins. However, the influence of the external lipid phase on internal dielectric dynamics is hard to access by experiment. Using the octahelical transmembrane architecture of the copper-transporting P_1_B-type ATPase from Legionella pneumophila (LpCopA) as a model structure, we have established the site-specific labeling of internal cysteines with a polarity-sensitive fluorophore. This enabled dipolar relaxation studies in a solubilized form of the protein and in its lipid-embedded state in nano-discs (NDs). Time-dependent fluorescence shifts revealed the site-specific hydration and dipole mobility around the conserved ion-binding motif. The spatial distribution of both features is shaped significantly and independently of each other by membrane lateral pressure.

  20. INVESTIGATION OF CURVES SET BY CUBIC DISTRIBUTION OF CURVATURE

    Directory of Open Access Journals (Sweden)

    S. A. Ustenko

    2014-03-01

    Full Text Available Purpose. Further development of the geometric modeling of curvelinear contours of different objects based on the specified cubic curvature distribution and setpoints of curvature in the boundary points. Methodology. We investigate the flat section of the curvilinear contour generating under condition that cubic curvature distribution is set. Curve begins and ends at the given points, where angles of tangent slope and curvature are also determined. It was obtained the curvature equation of this curve, depending on the section length and coefficient c of cubic curvature distribution. The analysis of obtained equation was carried out. As well as, it was investigated the conditions, in which the inflection points of the curve are appearing. One should find such an interval of parameter change (depending on the input data and the section length, in order to place the inflection point of the curvature graph outside the curve section borders. It was determined the dependence of tangent slope of angle to the curve at its arbitrary point, as well as it was given the recommendations to solve a system of integral equations that allow finding the length of the curve section and the coefficient c of curvature cubic distribution. Findings. As the result of curves research, it is found that the criterion for their selection one can consider the absence of inflection points of the curvature on the observed section. Influence analysis of the parameter c on the graph of tangent slope angle to the curve showed that regardless of its value, it is provided the same rate of angle increase of tangent slope to the curve. Originality. It is improved the approach to geometric modeling of curves based on cubic curvature distribution with its given values at the boundary points by eliminating the inflection points from the observed section of curvilinear contours. Practical value. Curves obtained using the proposed method can be used for geometric modeling of curvilinear

  1. Assessment of the Hindlimb Membrane Musculature of Bats: Implications for Active Control of the Calcar.

    Science.gov (United States)

    Stanchak, Kathryn E; Santana, Sharlene E

    2018-03-01

    The striking postcranial anatomy of bats reflects their specialized ecology; they are the only mammals capable of powered flight. Bat postcranial adaptations include a series of membranes that connect highly-modified, or even novel, skeletal elements. While most studies of bat postcranial anatomy have focused on their wings, bat hindlimbs also contain many derived and functionally important, yet less studied, features. In this study, we investigate variation in the membrane and limb musculature associated with the calcar, a neomorphic skeletal structure found in the hindlimbs of most bats. We use diffusible iodine-based contrast-enhanced computed tomography and standard histological techniques to examine the calcars and hindlimb membranes of three bat species that vary ecologically (Myotis californicus, a slow-flying insectivore; Molossus molossus, a fast-flying insectivore; and Artibeus jamaicensis, a slow-flying frugivore). We also assess the level of mineralization of the calcar at muscle attachment sites to better understand how muscle contraction may enable calcar function. We found that the arrangement of the calcar musculature varies among the three bat species, as does the pattern of mineral content within the calcar. M. molossus and M. californicus exhibit more complex calcar and calcar musculature morphologies than A. jamaicensis, and the degree of calcar mineralization decreases toward the tip of the calcar in all species. These results are consistent with the idea that the calcar may have a functional role in flight maneuverability. Anat Rec, 301:441-448, 2018. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

  2. Enzymatic treatment for controlling irreversible membrane fouling in cross-flow humic acid-fed ultrafiltration

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Chien-Hwa [Department of Civil and Environment Engineering, Nanya Institute of Technology, Taoyuan, Taiwan (China); Fang, Lung-Chen; Lateef, Shaik Khaja [Graduate Institute of Environmental Engineering, National Taiwan University, Taipei, Taiwan (China); Wu, Chung-Hsin, E-mail: chunghsinwu@yahoo.com.tw [Department of Chemical and Materials Engineering, National Kaohsiung University of Applied Sciences, 415 Chien Kung Road, Kaohsiung 807, Taiwan (China); Lin, Cheng-Fang [Graduate Institute of Environmental Engineering, National Taiwan University, Taipei, Taiwan (China)

    2010-05-15

    Exploring reasonable ways to remove foulant is of great importance in order to allow sustainable operation of ultrafiltration (UF) membranes in water/wastewater treatment technology. Compounds of organic and inorganic origin largely contribute to irreversible fouling. This study attempted to remove problem of UF membrane fouling by using four different enzymes including {alpha}-amylase, lipase, cellulase and protease. This investigation showed that none of the above mentioned enzymes was found to be effective for the removal of foulant when used alone. However, when these enzymes were used in combination with NaOH and citric acid, about 90% cleaning was achieved. The addition of non-ionic surfactant to the enzymatic solution appears to increase the efficiency of flux recovery by reducing the adhesion of foulant species to the membrane surface through the decrease of contact angle. Field emission gun scanning electron microscopy, Fourier transform infrared spectroscopy and atomic force microscopy (AFM) techniques were employed to qualitatively illustrate the foulant characteristics. The surface roughness through AFM was used to explain the potential mechanism for the enzymatic cleaning.

  3. Enzymatic treatment for controlling irreversible membrane fouling in cross-flow humic acid-fed ultrafiltration

    International Nuclear Information System (INIS)

    Yu, Chien-Hwa; Fang, Lung-Chen; Lateef, Shaik Khaja; Wu, Chung-Hsin; Lin, Cheng-Fang

    2010-01-01

    Exploring reasonable ways to remove foulant is of great importance in order to allow sustainable operation of ultrafiltration (UF) membranes in water/wastewater treatment technology. Compounds of organic and inorganic origin largely contribute to irreversible fouling. This study attempted to remove problem of UF membrane fouling by using four different enzymes including α-amylase, lipase, cellulase and protease. This investigation showed that none of the above mentioned enzymes was found to be effective for the removal of foulant when used alone. However, when these enzymes were used in combination with NaOH and citric acid, about 90% cleaning was achieved. The addition of non-ionic surfactant to the enzymatic solution appears to increase the efficiency of flux recovery by reducing the adhesion of foulant species to the membrane surface through the decrease of contact angle. Field emission gun scanning electron microscopy, Fourier transform infrared spectroscopy and atomic force microscopy (AFM) techniques were employed to qualitatively illustrate the foulant characteristics. The surface roughness through AFM was used to explain the potential mechanism for the enzymatic cleaning.

  4. Facile Fabrication of Ordered Anodized Aluminum Oxide Membranes with Controlled Pore Size by Improved Hard Anodization.

    Science.gov (United States)

    Fan, Jiangxia; Zhu, Xinxin; Wang, Kunzhou; Chen, Xiaoyuan; Wang, Xinqing; Yan, Minhao; Ren, Yong

    2018-05-01

    We have fabricated highly ordered anodized aluminum oxide (AAO) membranes with different diameter through improved hard anodization (HA) at high temperature. This process can generate thick AAO membranes (30 μm) in a short anodizing time with high growth rate 20-60 μm h-1 which is much faster than that in traditional mild two-step anodization. We enlarged the AAO pore diameter by adjusting the voltage rise rate at the same time, which has a great influence on current density and temperature. The AAO pore diameter varies from 60-110 nm to 160-190 nm. The pore diameter (Dp) of the AAO prepared by this improved process is much larger than that prepared by HA (40-60 nm) when H2C2O4 as electrolyte. It can expand potential use of the AAO membranes such as for the template-based synthesis of nanowires or nanotubes with modulated diameters and also for practical separation technology. We also has used the AAO with different diameters prepared by this improved HA to fabricate Co nanowires and γ-Fe2O3 superparamagnetic nanorods.

  5. Kinetic models of controllable pore growth of anodic aluminum oxide membrane

    Science.gov (United States)

    Huang, Yan; Zeng, Hong-yan; Zhao, Ce; Qu, Ye-qing; Zhang, Pin

    2012-06-01

    An anodized Al2O3 (AAO) membrane with apertures about 72 nm in diameter was prepared by two-step anodic oxidation. The appearance and pore arrangement of the AAO membrane were characterized by energy dispersive x-ray spectroscopy and scanning electron microscopy. It was confirmed that the pores with high pore aspect ratio were parallel, well-ordered, and uniform. The kinetics of pores growth in the AAO membrane was derived, and the kinetic models showed that pores stopped developing when the pressure ( σ) trended to equal the surface tension at the end of anodic oxidation. During pore expansion, the effects of the oxalic acid concentration and expansion time on the pore size were investigated, and the kinetic behaviors were explained with two kinetic models derived in this study. They showed that the pore size increased with extended time ( r= G· t+ G'), but decreased with increased concentration ( r = - K·ln c- K') through the derived mathematic formula. Also, the values of G, G', K, and K' were derived from our experimental data.

  6. Control of Porosity and Pore Size of Metal Reinforced Carbon Nanotube Membranes

    Directory of Open Access Journals (Sweden)

    Stephen Gray

    2010-12-01

    Full Text Available Membranes are crucial in modern industry and both new technologies and materials need to be designed to achieve higher selectivity and performance. Exotic materials such as nanoparticles offer promising perspectives, and combining both their very high specific surface area and the possibility to incorporate them into macrostructures have already shown to substantially increase the membrane performance. In this paper we report on the fabrication and engineering of metal-reinforced carbon nanotube (CNT Bucky-Paper (BP composites with tuneable porosity and surface pore size. A BP is an entangled mesh non-woven like structure of nanotubes. Pure CNT BPs present both very high porosity (>90% and specific surface area (>400 m2/g. Furthermore, their pore size is generally between 20–50 nm making them promising candidates for various membrane and separation applications. Both electro-plating and electroless plating techniques were used to plate different series of BPs and offered various degrees of success. Here we will report mainly on electroless plated gold/CNT composites. The benefit of this method resides in the versatility of the plating and the opportunity to tune both average pore size and porosity of the structure with a high degree of reproducibility. The CNT BPs were first oxidized by short UV/O3 treatment, followed by successive immersion in different plating solutions. The morphology and properties of these samples has been investigated and their performance in air permeation and gas adsorption will be reported.

  7. Comparison of epithelial and fibroblastic cell behavior on nano/micro-topographic PCL membranes produced by crystallinity control.

    Science.gov (United States)

    Gümüşderelioğlu, Menemşe; Kaya, F Betül; Beşkardeş, Işıl Gerçek

    2011-06-15

    In this study, the relationship between the cellular morphology and the material surface topography was investigated. Poly(ε-caprolactone) (PCL) membranes were prepared in a wide range of surface wettabilities by means of crystallinity-controlled solvent casting process. Membrane surfaces were characterized by atomic force microscope (AFM), scanning electron microscope (SEM), and static/dynamic water contact angle measurements. It was found that solvent evaporation and non-solvent (methanol) addition to the solvent (THF) are the most decisive parameters to change the surface topography. The non-solvent addition and the decrease in solvent evaporation temperature from room temperature to -20 °C caused increased polymeric chain mobility and crystallization time. Such changes in crystallization parameters led to the formation of micro/nano-sized features on the membrane. Cell culture studies indicated that in contrast to Madin Darby kidney (MDBK) epithelial cells, L929 mouse fibroblast preferred rough and porous surfaces. Copyright © 2011 Elsevier Inc. All rights reserved.

  8. Controlled sulfonation of poly(ether sulfone using phthalic anhydride as catalyst and its membrane performance for fuel cell application

    Directory of Open Access Journals (Sweden)

    Seikh Jiyaur Rahaman

    2016-09-01

    Full Text Available Proton exchange membrane (PEM fuel cells are one of the most emerging alternative energy technologies under development. A novel proton exchange membrane sulfonated polyethersulfone (SPES was developed by homogeneous method using phthalic anhydride as catalyst and chlorosulfonic acid as sulfonating agent to control the sulfonation reaction. The method of sulfonation was optimized by varying the reaction time and concentration of the catalyst. The structure of the SPES was studied by 1H-Nuclear Magnetic Resonance, Fourier Transform Infra Red Spectroscopy and X-ray diffraction. The extent of sulfonation was determined by ion exchange capacity studies. The thermal and mechanical stabilities were studied using thermogravimetric analysis (TGA and Dynamic Mechanical Analysis (DMA respectively. DMA results show that the storage modulus increased with increase in degree of sulfonation (DS and water uptake of SPES increased with DS. The proton conductivity of SPES (34% DS measured by impedance spectroscopy was found to be 0.03S/cm at 80%RH and 100°C. Also, current-voltage polarization characteristics of SPES membranes offer a favourable alternative PEM due to the thermal stability and cost effective than perfluorinated ionomers.

  9. Kollidon VA64, a membrane-resealing agent, reduces histopathology and improves functional outcome after controlled cortical impact in mice.

    Science.gov (United States)

    Mbye, Lamin H; Keles, Eyup; Tao, Luyang; Zhang, Jimmy; Chung, Joonyong; Larvie, Mykol; Koppula, Rajani; Lo, Eng H; Whalen, Michael J

    2012-03-01

    Loss of plasma membrane integrity is a feature of acute cellular injury/death in vitro and in vivo. Plasmalemma-resealing agents are protective in acute central nervous system injury models, but their ability to reseal cell membranes in vivo has not been reported. Using a mouse controlled cortical impact (CCI) model, we found that propidium iodide-positive (PI+) cells pulse labeled at 6, 24, or 48 hours maintained a degenerative phenotype and disappeared from the injured brain by 7 days, suggesting that plasmalemma permeability is a biomarker of fatal cellular injury after CCI. Intravenous or intracerebroventricular administration of Kollidon VA64, poloxamer P188, or polyethylene glycol 8000 resealed injured cell membranes in vivo (P<0.05 versus vehicle or poloxamer P407). Kollidon VA64 (1 mmol/L, 500 μL) administered intravenously to mice 1  hour after CCI significantly reduced acute cellular degeneration, chronic brain tissue damage, brain edema, blood-brain barrier damage, and postinjury motor deficits (all P<0.05 versus vehicle). However, VA64 did not rescue pulse-labeled PI+ cells from eventual demise. We conclude that PI permeability within 48 hours of CCI is a biomarker of eventual cell death/loss. Kollidon VA64 reduces secondary damage after CCI by mechanisms other than or in addition to resealing permeable cells.

  10. Model cell membranes

    DEFF Research Database (Denmark)

    Günther-Pomorski, Thomas; Nylander, Tommy; Cardenas Gomez, Marite

    2014-01-01

    The high complexity of biological membranes has motivated the development and application of a wide range of model membrane systems to study biochemical and biophysical aspects of membranes in situ under well defined conditions. The aim is to provide fundamental understanding of processes control...

  11. FBAR syndapin 1 recognizes and stabilizes highly curved tubular membranes in a concentration dependent manner

    DEFF Research Database (Denmark)

    Ramesh, Pradeep; Baroji, Younes F.; Seyyed Reihani, Seyyed Nader

    2013-01-01

    Syndapin 1 FBAR, a member of the Bin-amphiphysin-Rvs (BAR) domain protein family, is known to induce membrane curvature and is an essential component in biological processes like endocytosis and formation and growth of neurites. We quantify the curvature sensing of FBAR on reconstituted porcine b...

  12. Magnetic vortices in nanocaps induced by curvature

    Science.gov (United States)

    Abdelgawad, Ahmed M.; Nambiar, Nikhil; Bapna, Mukund; Chen, Hao; Majetich, Sara A.

    2018-05-01

    Magnetic nanoparticles with room temperature remanent magnetic vortices stabilized by their curvature are very intriguing due to their potential use in biomedicine. In the present study, we investigate room temperature magnetic chirality in 100 nm diameter permalloy spherical caps with 10 nm and 30 nm thicknesses. Micromagnetic OOMMF simulations predict the equilibrium spin structure for these caps to form a vortex state. We fabricate the permalloy caps by sputtering permalloy on both close-packed and sparse arrays of polystyrene nanoparticles. Magnetic force microscopy scans show a clear signature of a vortex state in close-packed caps of both 10 nm and 30 nm thicknesses. Alternating gradient magnetometry measurements of the caps are consistent with a remnant vortex state in 30 nm thick caps and a transition to an onion state followed by a vortex state in 10 nm thick caps. Out-of-plane measurements supported by micromagnetic simulations shows that an out-of-plane field can stabilize a vortex state down to a diameter of 15 nm.

  13. Curvature-Continuous 3D Path-Planning Using QPMI Method

    Directory of Open Access Journals (Sweden)

    Seong-Ryong Chang

    2015-06-01

    Full Text Available It is impossible to achieve vertex movement and rapid velocity control in aerial robots and aerial vehicles because of momentum from the air. A continuous-curvature path ensures such robots and vehicles can fly with stable and continuous movements. General continuous path-planning methods use spline interpolation, for example B-spline and Bézier curves. However, these methods cannot be directly applied to continuous path planning in a 3D space. These methods use a subset of the waypoints to decide curvature and some waypoints are not included in the planned path. This paper proposes a method for constructing a curvature-continuous path in 3D space that includes every waypoint. The movements in each axis, x, y and z, are separated by the parameter u. Waypoint groups are formed, each with its own continuous path derived using quadratic polynomial interpolation. The membership function then combines each continuous path into one continuous path. The continuity of the path is verified and the curvature-continuous path is produced using the proposed method.

  14. Test of the FLRW Metric and Curvature with Strong Lens Time Delays

    Energy Technology Data Exchange (ETDEWEB)

    Liao, Kai [School of Science, Wuhan University of Technology, Wuhan 430070 (China); Li, Zhengxiang; Wang, Guo-Jian [Department of Astronomy, Beijing Normal University, Beijing 100875 (China); Fan, Xi-Long, E-mail: liaokai@whut.edu.cn, E-mail: xilong.fan@glasgow.ac.uk [Department of Physics and Mechanical and Electrical Engineering, Hubei University of Education, Wuhan 430205 (China)

    2017-04-20

    We present a new model-independent strategy for testing the Friedmann–Lemaître–Robertson–Walker (FLRW) metric and constraining cosmic curvature, based on future time-delay measurements of strongly lensed quasar-elliptical galaxy systems from the Large Synoptic Survey Telescope and supernova observations from the Dark Energy Survey. The test only relies on geometric optics. It is independent of the energy contents of the universe and the validity of the Einstein equation on cosmological scales. The study comprises two levels: testing the FLRW metric through the distance sum rule (DSR) and determining/constraining cosmic curvature. We propose an effective and efficient (redshift) evolution model for performing the former test, which allows us to concretely specify the violation criterion for the FLRW DSR. If the FLRW metric is consistent with the observations, then on the second level the cosmic curvature parameter will be constrained to ∼0.057 or ∼0.041 (1 σ ), depending on the availability of high-redshift supernovae, which is much more stringent than current model-independent techniques. We also show that the bias in the time-delay method might be well controlled, leading to robust results. The proposed method is a new independent tool for both testing the fundamental assumptions of homogeneity and isotropy in cosmology and for determining cosmic curvature. It is complementary to cosmic microwave background plus baryon acoustic oscillation analyses, which normally assume a cosmological model with dark energy domination in the late-time universe.

  15. Test of the FLRW Metric and Curvature with Strong Lens Time Delays

    International Nuclear Information System (INIS)

    Liao, Kai; Li, Zhengxiang; Wang, Guo-Jian; Fan, Xi-Long

    2017-01-01

    We present a new model-independent strategy for testing the Friedmann–Lemaître–Robertson–Walker (FLRW) metric and constraining cosmic curvature, based on future time-delay measurements of strongly lensed quasar-elliptical galaxy systems from the Large Synoptic Survey Telescope and supernova observations from the Dark Energy Survey. The test only relies on geometric optics. It is independent of the energy contents of the universe and the validity of the Einstein equation on cosmological scales. The study comprises two levels: testing the FLRW metric through the distance sum rule (DSR) and determining/constraining cosmic curvature. We propose an effective and efficient (redshift) evolution model for performing the former test, which allows us to concretely specify the violation criterion for the FLRW DSR. If the FLRW metric is consistent with the observations, then on the second level the cosmic curvature parameter will be constrained to ∼0.057 or ∼0.041 (1 σ ), depending on the availability of high-redshift supernovae, which is much more stringent than current model-independent techniques. We also show that the bias in the time-delay method might be well controlled, leading to robust results. The proposed method is a new independent tool for both testing the fundamental assumptions of homogeneity and isotropy in cosmology and for determining cosmic curvature. It is complementary to cosmic microwave background plus baryon acoustic oscillation analyses, which normally assume a cosmological model with dark energy domination in the late-time universe.

  16. Face recognition based on depth maps and surface curvature

    Science.gov (United States)

    Gordon, Gaile G.

    1991-09-01

    This paper explores the representation of the human face by features based on the curvature of the face surface. Curature captures many features necessary to accurately describe the face, such as the shape of the forehead, jawline, and cheeks, which are not easily detected from standard intensity images. Moreover, the value of curvature at a point on the surface is also viewpoint invariant. Until recently range data of high enough resolution and accuracy to perform useful curvature calculations on the scale of the human face had been unavailable. Although several researchers have worked on the problem of interpreting range data from curved (although usually highly geometrically structured) surfaces, the main approaches have centered on segmentation by signs of mean and Gaussian curvature which have not proved sufficient in themselves for the case of the human face. This paper details the calculation of principal curvature for a particular data set, the calculation of general surface descriptors based on curvature, and the calculation of face specific descriptors based both on curvature features and a priori knowledge about the structure of the face. These face specific descriptors can be incorporated into many different recognition strategies. A system that implements one such strategy, depth template comparison, giving recognition rates between 80% and 90% is described.

  17. Is the fluid mosaic (and the accompanying raft hypothesis a suitable model to describe fundamental features of biological membranes? What may be missing?

    Directory of Open Access Journals (Sweden)

    Luis Alberto Bagatolli

    2013-11-01

    Full Text Available The structure, dynamics, and stability of lipid bilayers are controlled by thermodynamic forces, leading to overall tensionless membranes with a distinct lateral organization and a conspicuous lateral pressure profile. Bilayers are also subject to built-in curvature-stress instabilities that may be released locally or globally in terms of morphological changes leading to the formation of non-lamellar and curved structures. A key controller of the bilayer’s propensity to form curved structures is the average molecular shape of the different lipid molecules. Via the curvature stress, molecular shape mediates a coupling to membrane-protein function and provides a set of physical mechanisms for formation of lipid domains and laterally differentiated regions in the plane of the membrane. Unfortunately, these relevant physical features of membranes are often ignored in the most popular models for biological membranes. Results from a number of experimental and theoretical studies emphasize the significance of these fundamental physical properties and call for a refinement of the fluid mosaic model (and the accompanying raft hypothesis.

  18. Thermodynamic analysis of effects of contact angle on interfacial interactions and its implications for membrane fouling control.

    Science.gov (United States)

    Chen, Jianrong; Shen, Liguo; Zhang, Meijia; Hong, Huachang; He, Yiming; Liao, Bao-Qiang; Lin, Hongjun

    2016-02-01

    Concept of hydrophobicity always fails to accurately assess the interfacial interaction and membrane fouling, which calls for reliable parameters for this purpose. In this study, effects of contact angle on interfacial interactions related to membrane fouling were investigated based on thermodynamic analysis. It was found that, total interaction energy between sludge foulants and membrane monotonically decreases and increases with water and glycerol contact angle, respectively, indicating that these two parameters can be reliable indicators predicting total interaction energy and membrane fouling. Membrane roughness decreases interaction strength for over 20 times, and effects of membrane roughness on membrane fouling should consider water and glycerol contact angle on membrane. It was revealed existence of a critical water and glycerol contact angle for a given membrane bioreactor. Meanwhile, diiodomethane contact angle has minor effect on the total interaction, and cannot be regarded as an effective indicator assessing interfacial interactions and membrane fouling. Copyright © 2015 Elsevier Ltd. All rights reserved.

  19. Short-term adhesion and long-term biofouling testing of polydopamine and poly(ethylene glycol) surface modifications of membranes and feed spacers for biofouling control

    KAUST Repository

    Miller, Daniel J.

    2012-08-01

    Ultrafiltration, nanofiltration membranes and feed spacers were hydrophilized with polydopamine and polydopamine- g-poly(ethylene glycol) surface coatings. The fouling propensity of modified and unmodified membranes was evaluated by short-term batch protein and bacterial adhesion tests. The fouling propensity of modified and unmodified membranes and spacers was evaluated by continuous biofouling experiments in a membrane fouling simulator. The goals of the study were: 1) to determine the effectiveness of polydopamine and polydopamine- g-poly(ethylene glycol) membrane coatings for biofouling control and 2) to compare techniques commonly used in assessment of membrane biofouling propensity with biofouling experiments under practical conditions. Short-term adhesion tests were carried out under static, no-flow conditions for 1 h using bovine serum albumin, a common model globular protein, and Pseudomonas aeruginosa, a common model Gram-negative bacterium. Biofouling tests were performed in a membrane fouling simulator (MFS) for several days under flow conditions similar to those encountered in industrial modules with the autochthonous drinking water population and acetate dosage as organic substrate. Polydopamine- and polydopamine- g-poly(ethylene glycol)-modified membranes showed significantly reduced adhesion of bovine serum albumin and P. aeruginosa in the short-term adhesion tests, but no reduction of biofouling was observed during longer biofouling experiments with modified membranes and spacers. These results demonstrate that short-term batch adhesion experiments using model proteins or bacteria under static conditions are not indicative of biofouling, while continuous biofouling experiments showed that membrane surface modification by polydopamine and polydopamine- g-poly(ethylene glycol) is not effective for biofouling control. © 2012 Elsevier Ltd.

  20. Peripheral Protein Unfolding Drives Membrane Bending.

    Science.gov (United States)

    Siaw, Hew Ming Helen; Raghunath, Gokul; Dyer, R Brian

    2018-06-20

    Dynamic modulation of lipid membrane curvature can be achieved by a number of peripheral protein binding mechanisms such as hy-drophobic insertion of amphipathic helices and membrane scaffolding. Recently, an alternative mechanism was proposed in which crowding of peripherally bound proteins induces membrane curvature through steric pressure generated by lateral collisions. This effect was enhanced using intrinsically disordered proteins that possess high hydrodynamic radii, prompting us to explore whether membrane bending can be triggered by the folding-unfolding transition of surface-bound proteins. We utilized histidine-tagged human serum albumin bound to Ni-NTA-DGS containing liposomes as our model system to test this hypothesis. We found that reduction of the disulfide bonds in the protein resulted in unfolding of HSA, which subsequently led to membrane tubule formation. The frequency of tubule formation was found to be significantly higher when the proteins were unfolded while being localized to a phase-separated domain as opposed to randomly distributed in fluid phase liposomes, indicating that the steric pressure generated from protein unfolding is directly responsible for membrane deformation. Our results are critical for the design of peripheral membrane protein-immobilization strategies and open new avenues for exploring mechanisms of membrane bending driven by conformational changes of peripheral membrane proteins.

  1. Interaction of Defensins with Model Cell Membranes

    Science.gov (United States)

    Sanders, Lori K.; Schmidt, Nathan W.; Yang, Lihua; Mishra, Abhijit; Gordon, Vernita D.; Selsted, Michael E.; Wong, Gerard C. L.

    2009-03-01

    Antimicrobial peptides (AMPs) comprise a key component of innate immunity for a wide range of multicellular organisms. For many AMPs, activity comes from their ability to selectively disrupt and lyse bacterial cell membranes. There are a number of proposed models for this action, but the detailed molecular mechanism of selective membrane permeation remains unclear. Theta defensins are circularized peptides with a high degree of selectivity. We investigate the interaction of model bacterial and eukaryotic cell membranes with theta defensins RTD-1, BTD-7, and compare them to protegrin PG-1, a prototypical AMP, using synchrotron small angle x-ray scattering (SAXS). The relationship between membrane composition and peptide induced changes in membrane curvature and topology is examined. By comparing the membrane phase behavior induced by these different peptides we will discuss the importance of amino acid composition and placement on membrane rearrangement.

  2. Profile Curvature Derivative Surface used to characterize the complexity of the seafloor around St. John, USVI

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Profile curvature was calculated from the bathymetry surface for each raster cell using the ArcGIS 3D Analyst "Curvature" Tool. Profile curvature describes the rate...

  3. Curvature Derivative Surface used to characterize the complexity of the seafloor around St. John, USVI

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Curvature was calculated from the bathymetry surface for each raster cell using the ArcGIS 3D Analyst "Curvature" Tool. Curvature describes the rate of change of...

  4. Research on Influence and Prediction Model of Urban Traffic Link Tunnel curvature on Fire Temperature Based on Pyrosim--SPSS Multiple Regression Analysis

    Science.gov (United States)

    Li, Xiao Ju; Yao, Kun; Dai, Jun Yu; Song, Yun Long

    2018-05-01

    The underground space, also known as the “fourth dimension” of the city, reflects the efficient use of urban development intensive. Urban traffic link tunnel is a typical underground limited-length space. Due to the geographical location, the special structure of space and the curvature of the tunnel, high-temperature smoke can easily form the phenomenon of “smoke turning” and the fire risk is extremely high. This paper takes an urban traffic link tunnel as an example to focus on the relationship between curvature and the temperature near the fire source, and use the pyrosim built different curvature fire model to analyze the influence of curvature on the temperature of the fire, then using SPSS Multivariate regression analysis simulate curvature of the tunnel and fire temperature data. Finally, a prediction model of urban traffic link tunnel curvature on fire temperature was proposed. The regression model analysis and test show that the curvature is negatively correlated with the tunnel temperature. This model is feasible and can provide a theoretical reference for the urban traffic link tunnel fire protection design and the preparation of the evacuation plan. And also, it provides some reference for other related curved tunnel curvature design and smoke control measures.

  5. Influence of Coanda surface curvature on performance of bladeless fan

    Science.gov (United States)

    Li, Guoqi; Hu, Yongjun; Jin, Yingzi; Setoguchi, Toshiaki; Kim, Heuy Dong

    2014-10-01

    The unique Coanda surface has a great influence on the performance of bladeless fan. However, there is few studies to explain the relationship between the performance and Coanda surface curvature at present. In order to gain a qualitative understanding of effect of the curvature on the performance of bladeless fan, numerical studies are performed in this paper. Firstly, three-dimensional numerical simulation is done by Fluent software. For the purpose to obtain detailed information of the flow field around the Coanda surface, two-dimensional numerical simulation is also conducted. Five types of Coanda surfaces with different curvature are designed, and the flow behaviour and the performance of them are analyzed and compared with those of the prototype. The analysis indicates that the curvature of Coanda surface is strongly related to blowing performance, It is found that there is an optimal curvature of Coanda surfaces among the studied models. Simulation result shows that there is a special low pressure region. With increasing curvature in Y direction, several low pressure regions gradually enlarged, then begin to merge slowly, and finally form a large area of low pressure. From the analyses of streamlines and velocity angle, it is found that the magnitude of the curvature affects the flow direction and reasonable curvature can induce fluid flow close to the wall. Thus, it leads to that the curvature of the streamlines is consistent with that of Coanda surface. Meanwhile, it also causes the fluid movement towards the most suitable direction. This study will provide useful information to performance improvements of bladeless fans.

  6. Yeast PAH1-encoded phosphatidate phosphatase controls the expression of CHO1-encoded phosphatidylserine synthase for membrane phospholipid synthesis.

    Science.gov (United States)

    Han, Gil-Soo; Carman, George M

    2017-08-11

    The PAH1 -encoded phosphatidate phosphatase (PAP), which catalyzes the committed step for the synthesis of triacylglycerol in Saccharomyces cerevisiae , exerts a negative regulatory effect on the level of phosphatidate used for the de novo synthesis of membrane phospholipids. This raises the question whether PAP thereby affects the expression and activity of enzymes involved in phospholipid synthesis. Here, we examined the PAP-mediated regulation of CHO1 -encoded phosphatidylserine synthase (PSS), which catalyzes the committed step for the synthesis of major phospholipids via the CDP-diacylglycerol pathway. The lack of PAP in the pah1 Δ mutant highly elevated PSS activity, exhibiting a growth-dependent up-regulation from the exponential to the stationary phase of growth. Immunoblot analysis showed that the elevation of PSS activity results from an increase in the level of the enzyme encoded by CHO1 Truncation analysis and site-directed mutagenesis of the CHO1 promoter indicated that Cho1 expression in the pah1 Δ mutant is induced through the inositol-sensitive upstream activation sequence (UAS INO ), a cis -acting element for the phosphatidate-controlled Henry (Ino2-Ino4/Opi1) regulatory circuit. The abrogation of Cho1 induction and PSS activity by a CHO1 UAS INO mutation suppressed pah1 Δ effects on lipid synthesis, nuclear/endoplasmic reticulum membrane morphology, and lipid droplet formation, but not on growth at elevated temperature. Loss of the DGK1 -encoded diacylglycerol kinase, which converts diacylglycerol to phosphatidate, partially suppressed the pah1 Δ-mediated induction of Cho1 and PSS activity. Collectively, these data showed that PAP activity controls the expression of PSS for membrane phospholipid synthesis. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

  7. Novel flower-shaped albumin particles as controlled-release carriers for drugs to penetrate the round-window membrane

    Directory of Open Access Journals (Sweden)

    Yu Z

    2014-07-01

    Full Text Available Zhan Yu,1,* Min Yu,2,* Zhimin Zhou,3 Zhibao Zhang,3 Bo Du,3 Qingqing Xiong3 1Second Artillery General Hospital, Beijing, 2Department of Cell Biology, Key Laboratory of Cell Biology, Ministry of Public Health, College of Basic Medicine, China Medical University, Shenyang, 3Institute of Biomedical Engineering, Chinese Academy of Medical Sciences, Peking Union Medical College, Key Laboratory of Biomedical Material of Tianjin, Tianjin, People’s Republic of China *These authors contributed equallyto this work Abstract: Controlled-release carriers for local drug delivery have attracted increasing attention for inner-ear treatment recently. In this paper, flower-shaped bovine serum albumin (FBSA particles were prepared by a modified desolvation method followed by glutaraldehyde or heat denaturation. The size of the FBSA particles varied from 10 µm to 100 µm, and most were 50–80 µm. Heat-denatured FBSA particles have good cytocompatibility with a prolonged survival time for L929 cells. The FBSA particles were utilized as carriers to investigate the release behaviors of the model drug – rhodamine B. Rhodamine B showed a sustained-release effect and penetrated the round-window membrane of guinea pigs. We also confirmed the attachment of FBSA particles onto the round-window membrane by microscopy. The FBSA particles, with good biocompatibility, drug-loading capacity, adhesive capability, and biodegradability, may have potential applications in the field of local drug delivery for inner-ear disease treatment. Keywords: bovine serum albumin (BSA, controlled release, local delivery, round-window membrane

  8. Positive spatial curvature does not falsify the landscape

    Science.gov (United States)

    Horn, B.

    2017-12-01

    We present a simple cosmological model where the quantum tunneling of a scalar field rearranges the energetics of the matter sector, sending a stable static ancestor vacuum with positive spatial curvature into an inating solution with positive curvature. This serves as a proof of principle that an observation of positive spatial curvature does not falsify the hypothesis that our current observer patch originated from false vacuum tunneling in a string or field theoretic landscape. This poster submission is a summary of the work, and was presented at the 3rd annual ICPPA held in Moscow from October 2 to 5, 2017, by Prof. Rostislav Konoplich on behalf of the author.

  9. Curvature perturbation and waterfall dynamics in hybrid inflation

    International Nuclear Information System (INIS)

    Abolhasani, Ali Akbar; Firouzjahi, Hassan; Sasaki, Misao

    2011-01-01

    We investigate the parameter spaces of hybrid inflation model with special attention paid to the dynamics of waterfall field and curvature perturbations induced from its quantum fluctuations. Depending on the inflaton field value at the time of phase transition and the sharpness of the phase transition inflation can have multiple extended stages. We find that for models with mild phase transition the induced curvature perturbation from the waterfall field is too large to satisfy the COBE normalization. We investigate the model parameter space where the curvature perturbations from the waterfall quantum fluctuations vary between the results of standard hybrid inflation and the results obtained here

  10. Curvature perturbation and waterfall dynamics in hybrid inflation

    Energy Technology Data Exchange (ETDEWEB)

    Abolhasani, Ali Akbar [Department of Physics, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Firouzjahi, Hassan [School of Physics, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Sasaki, Misao, E-mail: abolhasani@mail.ipm.ir, E-mail: firouz@mail.ipm.ir, E-mail: misao@yukawa.kyoto-u.ac.jp [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)

    2011-10-01

    We investigate the parameter spaces of hybrid inflation model with special attention paid to the dynamics of waterfall field and curvature perturbations induced from its quantum fluctuations. Depending on the inflaton field value at the time of phase transition and the sharpness of the phase transition inflation can have multiple extended stages. We find that for models with mild phase transition the induced curvature perturbation from the waterfall field is too large to satisfy the COBE normalization. We investigate the model parameter space where the curvature perturbations from the waterfall quantum fluctuations vary between the results of standard hybrid inflation and the results obtained here.

  11. Geometry-specific scaling of detonation parameters from front curvature

    International Nuclear Information System (INIS)

    Jackson, Scott I.; Short, Mark

    2011-01-01

    It has previously been asserted that classical detonation curvature theory predicts that the critical diameter and the diameter-effect curve of a cylindrical high-explosive charge should scale with twice the thickness of an analogous two-dimensional explosive slab. The varied agreement of experimental results with this expectation have led some to question the ability of curvature-based concepts to predict detonation propagation in non-ideal explosives. This study addresses such claims by showing that the expected scaling relationship (hereafter referred to d = 2w) is not consistent with curvature-based Detonation Shock Dynamics (DSD) theory.

  12. Numerical studies of transverse curvature effects on transonic flow stability

    Science.gov (United States)

    Macaraeg, M. G.; Daudpota, Q. I.

    1992-01-01

    A numerical study of transverse curvature effects on compressible flow temporal stability for transonic to low supersonic Mach numbers is presented for axisymmetric modes. The mean flows studied include a similar boundary-layer profile and a nonsimilar axisymmetric boundary-layer solution. The effect of neglecting curvature in the mean flow produces only small quantitative changes in the disturbance growth rate. For transonic Mach numbers (1-1.4) and aerodynamically relevant Reynolds numbers (5000-10,000 based on displacement thickness), the maximum growth rate is found to increase with curvature - the maximum occurring at a nondimensional radius (based on displacement thickness) between 30 and 100.

  13. Public and private space curvature in Robertson-Walker universes.

    Science.gov (United States)

    Rindler, W.

    1981-05-01

    The question is asked: what space curvature would a fundamental observer in an ideal Robertson-Walker universe obtain by direct local spatial measurements, i.e., without reference to the motion pattern of the other galaxies? The answer is that he obtains the curvatureK of his “private” space generated by all the geodesics orthogonal to his world line at the moment in question, and that ˜K is related to the usual curvatureK=k/R 2 of the “public” space of galaxies byK=K+H 2/c2, whereH is Hubble's parameter.

  14. Controlling the morphology and performance of FO membrane via adjusting the atmosphere humidity during casting procedure

    Science.gov (United States)

    Zuo, Hao-Ran; Cao, Gui-Ping; Wang, Meng; Zhang, Huan-Huan; Song, Chen-Chen; Fang, Xu; Wang, Tao

    2018-03-01

    Forward osmosis (FO) has received great interest for its considerable potential in a wide range of fields. In this work, the morphology and performance of FO membrane were regulated by adjusting the atmosphere humidity (HC) of casting procedure. The polysulfone support layer was casted under various atmosphere humidity levels ranging from 40% to 80%. By multi-techniques such as SEM, AFM, and XPS, it was proved that the atmosphere humidity had modified the surface morphology and thickness of the skin layer in support layer, which contributed up to 90% of the structure parameter, resulting in distinct morphology, thickness, and cross-linking degree of active layer. The active layer with sparse bead-like wrinkles on the smooth surface of support layer casted at HC = 65% showed the highest water permeability [26.9 (L/m2 h MPa)] and considerable low salt permeability [0.0390 (L/m2 h)]. It was found that the water flux of FO-65 was 27% and 46% higher than that of FO-80 in AL-DS and AL-FS mode, respectively, and the salt rejection was as high as 98%. Our work highlighted the importance of considering the effect of atmosphere humidity during casting when design an FO membrane for appropriate performance.

  15. Tetracaine – selective electrodes with polymer membranes and their application in pharmaceutical formulation control

    Directory of Open Access Journals (Sweden)

    Ahmed Khudhair Hassan

    2017-02-01

    Full Text Available The construction and electrochemical response characteristics of poly(vinyl chloride (PVC membrane electrodes for tetracaine hydrochloride (TCH are described. The sensing membranes incorporating ion-association complexes of tetracaine cation with phosphotungstic acid (PTA or phosphomolybdic acid (PMA or Sodium tetraphenyl borate (NaTPB as electroactive materials and di-n-butyl phthalate (DBPH or tri-n-butyl phosphate (TBP as a plasticizer in PVC matrixes were evaluated. The results obtained show the electrodes based on PTA or PMA as electroactive compounds and DBPH as plasticizer with a fast, stable and near-Nernstian response over a wide concentration range (1 × 10−5–5 × 10−2 M, with cationic slopes of 55.02 and 52.05 mV decade−1 over a pH range of (2.5–6.5. The electrodes show good discrimination of tetracaine from several inorganic cations and sugars. The electrodes were successfully applied for the determination of tetracaine in pharmaceutical formulations.

  16. A fluidic device for the controlled formation and real-time monitoring of soft membranes self-assembled at liquid interfaces.

    Science.gov (United States)

    Mendoza-Meinhardt, Arturo; Botto, Lorenzo; Mata, Alvaro

    2018-02-13

    Membrane materials formed at the interface between two liquids have found applications in a large variety of technologies, from sensors to drug-delivery and catalysis. However, studying the formation of these membranes in real-time presents considerable challenges, owing to the difficulty of prescribing the location and instant of formation of the membrane, the difficulty of observing time-dependent membrane shape and thickness, and the poor reproducibility of results obtained using conventional mixing procedures. Here we report a fluidic device that facilitates characterisation of the time-dependent thickness, morphology and mass transport properties of materials self-assembled at fluid-fluid interfaces. In the proposed device the membrane forms from the controlled coalescence of two liquid menisci in a linear open channel. The linear geometry and controlled mixing of the solutions facilitate real-time visualisation, manipulation and improve reproducibility. Because of its small dimensions, the device can be used in conjunction with standard microscopy methods and reduces the required volumes of potentially expensive reagents. As an example application to tissue engineering, we use the device to characterise interfacial membranes formed by supra-molecular self-assembly of peptide-amphiphiles with either an elastin-like-protein or hyaluronic acid. The device can be adapted to study self-assembling membranes for applications that extend beyond bioengineering.

  17. Lipid nanotechnologies for structural studies of membrane-associated proteins.

    Science.gov (United States)

    Stoilova-McPhie, Svetla; Grushin, Kirill; Dalm, Daniela; Miller, Jaimy

    2014-11-01

    We present a methodology of lipid nanotubes (LNT) and nanodisks technologies optimized in our laboratory for structural studies of membrane-associated proteins at close to physiological conditions. The application of these lipid nanotechnologies for structure determination by cryo-electron microscopy (cryo-EM) is fundamental for understanding and modulating their function. The LNTs in our studies are single bilayer galactosylceramide based nanotubes of ∼20 nm inner diameter and a few microns in length, that self-assemble in aqueous solutions. The lipid nanodisks (NDs) are self-assembled discoid lipid bilayers of ∼10 nm diameter, which are stabilized in aqueous solutions by a belt of amphipathic helical scaffold proteins. By combining LNT and ND technologies, we can examine structurally how the membrane curvature and lipid composition modulates the function of the membrane-associated proteins. As proof of principle, we have engineered these lipid nanotechnologies to mimic the activated platelet's phosphtaidylserine rich membrane and have successfully assembled functional membrane-bound coagulation factor VIII in vitro for structure determination by cryo-EM. The macromolecular organization of the proteins bound to ND and LNT are further defined by fitting the known atomic structures within the calculated three-dimensional maps. The combination of LNT and ND technologies offers a means to control the design and assembly of a wide range of functional membrane-associated proteins and complexes for structural studies by cryo-EM. The presented results confirm the suitability of the developed methodology for studying the functional structure of membrane-associated proteins, such as the coagulation factors, at a close to physiological environment. © 2014 Wiley Periodicals, Inc.

  18. Dual control of low concentration CO poisoning by anode air bleeding of low temperature polymer electrolyte membrane fuel cells

    Science.gov (United States)

    Klages, Merle; Tjønnås, Johannes; Zenith, Federico; Halvorsen, Ivar J.; Scholta, Joachim

    2016-12-01

    Fuel impurities, fed to a polymer electrolyte membrane fuel cell, can affect stack performance by poisoning of catalyst layers. This paper describes the dynamic behaviour of a stack, including state-of-the-art membrane electrode assemblies (MEA) of three different manufacturers, at different operating conditions. The voltage transients of the step responses to CO poisoning as well as air bleed recovery are compared, revealing differences in performance loss: slow poisoning versus fast recovery, incomplete recovery and voltage oscillation. The recorded behaviour is used to develop a model, based on Tafel equation and first order dynamic response, which can be calibrated to each MEA type. Using this model to predict voltage response, a controller is built with the aim of reducing the total amount of air bleed and monitoring upstream stack processes without the need of sensors measuring the poisoning level. Two controllers are implemented in order to show the concept from a heuristic, easy to implement, and a more technical side allowing more detailed analysis of the synthesis. The heuristic algorithm, based on periodic perturbations of the manipulated variable (air-bleed), is validated on a real stack, revealing a stabilized performance without the need of detailed stack properties knowledge.

  19. Performance of a sequencing-batch membrane bioreactor (SMBR) with an automatic control strategy treating high-strength swine wastewater.

    Science.gov (United States)

    Sui, Qianwen; Jiang, Chao; Yu, Dawei; Chen, Meixue; Zhang, Junya; Wang, Yawei; Wei, Yuansong

    2018-01-15

    Due to high-strength of organic matters, nutrients and pathogen, swine wastewater is a major source of pollution to rural environment and surface water. A sequencing-batch membrane bioreactor (SMBR) system with an automatic control strategy was developed for high-strength swine wastewater treatment. Short-cut nitrification and denitrification (SND) was achieved at nitrite accumulation rate of 83.6%, with removal rates of COD, NH 4 + -N and TN at 95%, 99% and 93%, respectively, at reduced HRT of 6.0 d and TN loading rate of 0.02kgN/(kgVSS d). With effective membrane separation, the reduction of total bacteria (TB) and putative pathogen were 2.77 logs and 1%, respectively. The shift of microbial community was well responded to controlling parameters. During the SND process, ammonia oxidizing bacteria (AOB) (Nitrosomonas, Nitrosospira) and nitrite oxidizing bacteria (NOB) (Nitrospira) were enriched by 52 times and reduced by 2 times, respectively. The denitrifiers (Thauera) were well enriched and the diversity was enhanced. Copyright © 2017. Published by Elsevier B.V.

  20. The influence of oscillating electromagnetic fields on membrane structure and function: Synthetic liposome and natural membrane bilayer systems with direct application to the controlled delivery of chemical agents

    International Nuclear Information System (INIS)

    Liburdy, R.P.; de Manincor, D.; Fingado, B.

    1989-09-01

    Investigations have been conducted to determine if an imposed electromagnetic field can influence membrane transport, and ion and drug permeability in both synthetic and natural cell membrane systems. Microwave fields enhance accumulation of sodium in the lymphocyte and induce protein shedding at Tc. Microwaves also trigger membrane permeability of liposome systems under specific field exposure conditions. Sensitivity varies in a defined way in bilayers displaying a membrane structural phase transition temperature, Tc; maximal release was observed at or near Tc. Significantly, liposome systems without a membrane phase transition were also found to experience permeability increases but, in contrast, this response was temperature independent. The above results indicate that field-enhanced drug release occurs in liposome vesicles that possess a Tc as well as non-Tc liposomes. Additional studies extend non-Tc liposome responses to the in vivo case in which microwaves trigger Gentamicin release from a liposome ''depot'' placed subcutaneously in the rat hind leg. In addition, evidence is provided that cell surface sequestered liposomes can be triggered by microwave fields to release drugs directly into target cells. 24 refs., 6 figs

  1. Cathepsin activities and membrane integrity of zebrafish (Danio rerio) oocytes after freezing to -196 degrees C using controlled slow cooling.

    Science.gov (United States)

    Zhang, T; Rawson, D M; Tosti, L; Carnevali, O

    2008-04-01

    This study investigated enzymatic activity of cathepsins and the membrane integrity of zebrafish (Danio rerio) oocytes after freezing to -196 degrees C using controlled slow cooling. Stage III oocytes (>0.5mm), obtained through dissection of anaesthetised female fish and desegregation of ovarian cumulus, were exposed to 2M methanol or 2M DMSO (both prepared in Hank's medium) for 30min at 22 degrees C before being loaded into 0.5ml plastic straws and placed into a programmable cooler. After controlled slow freezing, samples were plunged into liquid nitrogen (LN) and held for at least 10min, and thawed by immersing straws into a 27 degrees C water bath for 10s. Thawed oocytes were washed twice in Hank's medium. Cathepsin activity and membrane integrity of oocytes were assessed both after cryoprotectant treatment at 22 degrees C and after freezing in LN. Cathepsin B and L colorimetric analyses were performed using substrates Z-Arg-ArgNNap and Z-Phe-Arg-4MbetaNA-HCl, respectively, and 2-naphthylamine and 4-methoxy-2-naphthylamine were used as standards. Cathepsin D activity was performed by analysing the level of hydrolytic action on haemoglobin. Oocytes membrane integrity was assessed using 0.2% Trypan blue staining for 5min. Analysis of cathepsin activities showed that whilst the activity of cathepsin B and D was not affected by 2M DMSO treatment, their activity was lowered when treated with 2M methanol. Following freezing to -196 degrees C, the activity of all cathepsins (B, D and L) was significantly decreased in both 2M DMSO and 2M methanol. Trypan blue staining showed that 63.0+/-11.3% and 72.7+/-5.2% oocytes membrane stayed intact after DMSO and methanol treatment for 30min at 22 degrees C, respectively, whilst 14.9+/-2.6% and 1.4+/-0.8% stayed intact after freezing in DMSO and methanol to -196 degrees C. The results indicate that cryoprotectant treatment and freezing modified the activities of lysosomal enzymes involved in oocyte maturation and yolk

  2. Higher Curvature Gravity from Entanglement in Conformal Field Theories

    Science.gov (United States)

    Haehl, Felix M.; Hijano, Eliot; Parrikar, Onkar; Rabideau, Charles

    2018-05-01

    By generalizing different recent works to the context of higher curvature gravity, we provide a unifying framework for three related results: (i) If an asymptotically anti-de Sitter (AdS) spacetime computes the entanglement entropies of ball-shaped regions in a conformal field theory using a generalized Ryu-Takayanagi formula up to second order in state deformations around the vacuum, then the spacetime satisfies the correct gravitational equations of motion up to second order around the AdS background. (ii) The holographic dual of entanglement entropy in higher curvature theories of gravity is given by the Wald entropy plus a particular correction term involving extrinsic curvatures. (iii) Conformal field theory relative entropy is dual to gravitational canonical energy (also in higher curvature theories of gravity). Especially for the second point, our novel derivation of this previously known statement does not involve the Euclidean replica trick.

  3. On the projective curvature tensor of generalized Sasakian-space ...

    African Journals Online (AJOL)

    space-forms under some conditions regarding projective curvature tensor. All the results obtained in this paper are in the form of necessary and sufficient conditions. Keywords: Generalized Sasakian-space-forms; projectively flat; ...

  4. Inverse curvature flows in asymptotically Robertson Walker spaces

    Science.gov (United States)

    Kröner, Heiko

    2018-04-01

    In this paper we consider inverse curvature flows in a Lorentzian manifold N which is the topological product of the real numbers with a closed Riemannian manifold and equipped with a Lorentzian metric having a future singularity so that N is asymptotically Robertson Walker. The flow speeds are future directed and given by 1 / F where F is a homogeneous degree one curvature function of class (K*) of the principal curvatures, i.e. the n-th root of the Gauss curvature. We prove longtime existence of these flows and that the flow hypersurfaces converge to smooth functions when they are rescaled with a proper factor which results from the asymptotics of the metric.

  5. On a class of graphs with prescribed mean curvature

    International Nuclear Information System (INIS)

    Duong Minh Duc; Costa Salavessa, I.M. de

    1989-11-01

    We study a class of quasilinear elliptic equations on the unit ball of R n and apply these results to get the existence of graphs with prescribed mean curvature on n-hyperbolic spaces. (author). 18 refs

  6. Higher-order curvature terms and extended inflation

    International Nuclear Information System (INIS)

    Wang Yun

    1990-01-01

    We consider higher-order curvature terms in context of the Brans-Dicke theory of gravity, and investigate the effects of these terms on extended inflationary theories. We find that the higher-order curvature terms tend to speed up inflation, although the original extended-inflation solutions are stable when these terms are small. Analytical solutions are found for two extreme cases: when the higher-order curvature terms are small, and when they dominate. A conformal transformation is employed in solving the latter case, and some of the subtleties in this technique are discussed. We note that percolation is less likely to occur when the higher-order curvature terms are present. An upper bound on α is expected if we are to avoid excessive and inadequate percolation of true-vacuum bubbles

  7. Gauge and non-gauge curvature tensor copies

    International Nuclear Information System (INIS)

    Srivastava, P.P.

    1982-10-01

    A procedure for constructing curvature tensor copies is discussed using the anholonomic geometrical framework. The corresponding geometries are compared and the notion of gauge copy is elucidated. An explicit calculation is also made. (author)

  8. Constant scalar curvature hypersurfaces in extended Schwarzschild space-time

    International Nuclear Information System (INIS)

    Pareja, M. J.; Frauendiener, J.

    2006-01-01

    We present a class of spherically symmetric hypersurfaces in the Kruskal extension of the Schwarzschild space-time. The hypersurfaces have constant negative scalar curvature, so they are hyperboloidal in the regions of space-time which are asymptotically flat

  9. Translating Solitons of Mean Curvature Flow of Noncompact Submanifolds

    International Nuclear Information System (INIS)

    Li Guanghan; Tian Daping; Wu Chuanxi

    2011-01-01

    We prove the existence and asymptotic behavior of rotationally symmetric solitons of mean curvature flow for noncompact submanifolds in Euclidean and Minkowski spaces, which generalizes part of the corresponding results for hypersurfaces of Jian.

  10. Curvature and elasticity of substitution: what is the link?

    Czech Academy of Sciences Publication Activity Database

    Matveenko, Andrei; Matveenko, V.

    2014-01-01

    Roč. 10, č. 2 (2014), s. 7-20 ISSN 1800-5845 Grant - others:UK(CZ) GAUK 308214 Institutional support: PRVOUK-P23 Keywords : curvature * elasticity of substitution * production function Subject RIV: AH - Economics

  11. Cosmic censorship, persistent curvature and asymptotic causal pathology

    International Nuclear Information System (INIS)

    Newman, R.P.A.C.

    1984-01-01

    The paper examines cosmic censorship in general relativity theory. Conformally flat space-times; persistent curvature; weakly asymptotically simple and empty asymptotes; censorship conditions; and the censorship theorem; are all discussed. (U.K.)

  12. Hemocompatibility of poly(vinylidene fluoride) membrane grafted with network-like and brush-like antifouling layer controlled via plasma-induced surface PEGylation.

    Science.gov (United States)

    Chang, Yung; Shih, Yu-Ju; Ko, Chao-Yin; Jhong, Jheng-Fong; Liu, Ying-Ling; Wei, Ta-Chin

    2011-05-03

    In this work, the hemocompatibility of PEGylated poly(vinylidene fluoride) (PVDF) microporous membranes with varying grafting coverage and structures via plasma-induced surface PEGylation was studied. Network-like and brush-like PEGylated layers on PVDF membrane surfaces were achieved by low-pressure and atmospheric plasma treatment. The chemical composition, physical morphology, grafting structure, surface hydrophilicity, and hydration capability of prepared membranes were determined to illustrate the correlations between grafting qualities and hemocompatibility of PEGylated PVDF membranes in contact with human blood. Plasma protein adsorption onto different PEGylated PVDF membranes from single-protein solutions and the complex medium of 100% human plasma were measured by enzyme-linked immunosorbent assay (ELISA) with monoclonal antibodies. Hemocompatibility of the PEGylated membranes was evaluated by the antifouling property of platelet adhesion observed by scanning electron microscopy (SEM) and the anticoagulant activity of the blood coagulant determined by testing plasma-clotting time. The control of grafting structures of PEGylated layers highly regulates the PVDF membrane to resist the adsorption of plasma proteins, the adhesion of platelets, and the coagulation of human plasma. It was found that PVDF membranes grafted with brush-like PEGylated layers presented higher hydration capability with binding water molecules than with network-like PEGylated layers to improve the hemocompatible character of plasma protein and blood platelet resistance in human blood. This work suggests that the hemocompatible nature of grafted PEGylated polymers by controlling grafting structures gives them great potential in the molecular design of antithrombogenic membranes for use in human blood.

  13. Effect of IX dosing on polypropylene and PVDF membrane fouling control

    KAUST Repository

    Myat, Darli Theint

    2013-07-01

    The performance of ion exchange (IX) resin for organics removal from wastewater was assessed using advanced characterisation techniques for varying doses of IX. Organic characterisation using liquid chromatography with a photodiode array (PDA) and fluorescence spectroscopy (Method A), and UV254, organic carbon and organic nitrogen detectors (Method B), was undertaken on wastewater before and after magnetic IX treatment. Results showed partial removal of the biopolymer fraction at high IX doses. With increasing concentration of IX, evidence for nitrogen-containing compounds such as proteins and amino acids disappeared from the LC-OND chromatogram, complementary to the fluorescence response. A greater fluorescence response of tryptophan-like proteins (278nm/343nm) for low IX concentrations was consistent with aggregation of tryptophan-like compounds into larger aggregates, either by self-aggregation or with polysaccharides. Recycling of IX resin through multiple adsorption steps without regeneration maintained the high level of humics removal but there was no continued removal of biopolymer. Subsequent membrane filtration of the IX treated waters resulted in complex fouling trends. Filtration tests with either polypropylene (PP) or polyvinylidene fluoride (PVDF) membranes showed higher rates of initial fouling following treatment with high IX doses (10mL/L) compared to filtration of untreated water, while treatment with lower IX doses resulted in decreased fouling rates relative to the untreated water. However, at longer filtration times the rate of fouling of IX treated waters was lower than untreated water and the relative fouling rates corresponded to the amount of biopolymer material in the feed. It was proposed that the mode of fouling changed from pore constriction during the initial filtration period to filter cake build up at longer filtration times. The organic composition strongly influenced the rate of fouling during the initial filtration period due to

  14. A simple approach to uniform PdAg alloy membranes: Comparative study of conventional and silver concentration-controlled co-plating

    KAUST Repository

    Zeng, Gaofeng

    2014-03-01

    An Ag-controlled co-plating method was developed for the preparation of palladium/silver alloy membranes on porous tubular alumina supports. By controlling the feed rate of Ag to the Pd bath, the concentration of the silver in the plating bath was restricted during the course of plating. As a result, preferential deposition of silver at the beginning was suppressed and uniform dispersion of silver inside the membrane with silver composition in the desired range was achieved. Ultrathin (∼2.5 μm) PdAg alloy membranes with uniform silver composition of ∼25% were successfully obtained. The membrane showed a hydrogen permeance of 0.88 mol m-2 s-1 and pure-gas H2/N2 selectivity of 2140 at 823 K with ΔP = 100 kPa. Only one hydride phase existed in the studied temperature range from 373 to 823 K with ΔPH=100kPa. Direct comparisons with the conventional simply-mixed co-plating method showed that membranes made by the novel Ag-controlled co-plating method had much more uniform silver distribution, smoother surface, denser membrane structure, higher utilization rate of metal sources, and shorter alloying time. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

  15. A simple approach to uniform PdAg alloy membranes: Comparative study of conventional and silver concentration-controlled co-plating

    KAUST Repository

    Zeng, Gaofeng; Shi, Lei; Liu, Yunyang; Zhang, Yanfeng; Sun, Yuhan

    2014-01-01

    An Ag-controlled co-plating method was developed for the preparation of palladium/silver alloy membranes on porous tubular alumina supports. By controlling the feed rate of Ag to the Pd bath, the concentration of the silver in the plating bath was restricted during the course of plating. As a result, preferential deposition of silver at the beginning was suppressed and uniform dispersion of silver inside the membrane with silver composition in the desired range was achieved. Ultrathin (∼2.5 μm) PdAg alloy membranes with uniform silver composition of ∼25% were successfully obtained. The membrane showed a hydrogen permeance of 0.88 mol m-2 s-1 and pure-gas H2/N2 selectivity of 2140 at 823 K with ΔP = 100 kPa. Only one hydride phase existed in the studied temperature range from 373 to 823 K with ΔPH=100kPa. Direct comparisons with the conventional simply-mixed co-plating method showed that membranes made by the novel Ag-controlled co-plating method had much more uniform silver distribution, smoother surface, denser membrane structure, higher utilization rate of metal sources, and shorter alloying time. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

  16. No Large Scale Curvature Perturbations during Waterfall of Hybrid Inflation

    OpenAIRE

    Abolhasani, Ali Akbar; Firouzjahi, Hassan

    2010-01-01

    In this paper the possibility of generating large scale curvature perturbations induced from the entropic perturbations during the waterfall phase transition of standard hybrid inflation model is studied. We show that whether or not appreciable amounts of large scale curvature perturbations are produced during the waterfall phase transition depend crucially on the competition between the classical and the quantum mechanical back-reactions to terminate inflation. If one considers only the clas...

  17. Existence of conformal metrics on spheres with prescribed Paneitz curvature

    International Nuclear Information System (INIS)

    Ben Ayed, Mohamed; El Mehdi, Khalil

    2003-07-01

    In this paper we study the problem of prescribing a fourth order conformal invariant (the Paneitz curvature) on the n-spheres, with n ≥ 5. Using tools from the theory of critical points at infinity, we provide some topological conditions on the level sets of a given function defined on the sphere, under which we prove the existence of conformal metric with prescribed Paneitz curvature. (author)

  18. Inflation in a shear-or curvature-dominated universe

    International Nuclear Information System (INIS)

    Steigman, G.; Turner, M.S.

    1983-01-01

    We show that new inflation occurs even if the universe is shear-or (negative) curvature-dominated when the phase transition begins. In such situations the size of a causally coherent region, after inflation, is only slightly smaller (by powers, but not by exponential factors) than the usual result. The creation and evolution of density perturbations is unaffected. This result is marked contrast to 'old' inflation, where shear- or curvature-domination could quench inflation. (orig.)

  19. Curvature-driven acceleration: a utopia or a reality?

    International Nuclear Information System (INIS)

    Das, Sudipta; Banerjee, Narayan; Dadhich, Naresh

    2006-01-01

    The present work shows that a combination of nonlinear contributions from the Ricci curvature in Einstein field equations can drive a late time acceleration of expansion of the universe. The transit from the decelerated to the accelerated phase of expansion takes place smoothly without having to resort to a study of asymptotic behaviour. This result emphasizes the need for thorough and critical examination of models with nonlinear contribution from the curvature

  20. Curvature-driven acceleration: a utopia or a reality?

    Energy Technology Data Exchange (ETDEWEB)

    Das, Sudipta [Relativity and Cosmology Research Centre, Department of Physics, Jadavpur University, Calcutta-700 032 (India); Banerjee, Narayan [Relativity and Cosmology Research Centre, Department of Physics, Jadavpur University, Calcutta-700 032 (India); Dadhich, Naresh [Inter University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411 007 (India)

    2006-06-21

    The present work shows that a combination of nonlinear contributions from the Ricci curvature in Einstein field equations can drive a late time acceleration of expansion of the universe. The transit from the decelerated to the accelerated phase of expansion takes place smoothly without having to resort to a study of asymptotic behaviour. This result emphasizes the need for thorough and critical examination of models with nonlinear contribution from the curvature.

  1. Existence of conformal metrics on spheres with prescribed Paneitz curvature

    CERN Document Server

    Ben-Ayed, M

    2003-01-01

    In this paper we study the problem of prescribing a fourth order conformal invariant (the Paneitz curvature) on the n-spheres, with n >= 5. Using tools from the theory of critical points at infinity, we provide some topological conditions on the level sets of a given function defined on the sphere, under which we prove the existence of conformal metric with prescribed Paneitz curvature.

  2. Curvature effects in carbon nanomaterials: Exohedral versus endohedral supercapacitors

    OpenAIRE

    Huang, Jingsong; Bobby,; Sumpter, Bobby G.; Meunier, Vincent; Yushin, Gleb; Portet, Cristelle; Gogotsi, Yury

    2010-01-01

    Capacitive energy storage mechanisms in nanoporous carbon supercapacitors hinge on endohedral interactions in carbon materials with macro-, meso-, and micropores that have negative surface curvature. In this article, we show that because of the positive curvature found in zero-dimensional carbon onions or one-dimensional carbon nanotube arrays, exohedral interactions cause the normalized capacitance to increase with decreasing particle size or tube diameter, in sharp contrast to the behavior ...

  3. Atomic fine structure in a space of constant curvature

    International Nuclear Information System (INIS)

    Bessis, N.; Bessis, G.; Shamseddine, R.

    1982-01-01

    As a contribution to a tentative formulation of atomic physics in a curved space, the determination of atomic fine structure energies in a space of constant curvature is investigated. Starting from the Dirac equation in a curved space-time, the analogue of the Pauli equation in a general coordinate system is derived. The theoretical curvature induced shifts and splittings of the fine structure energy levels are put in evidence and examined for the particular case of the hydrogenic n=2 levels. (author)

  4. On $L_p$ Affine Surface Area and Curvature Measures

    OpenAIRE

    Zhao, Yiming

    2015-01-01

    The relationship between $L_p$ affine surface area and curvature measures is investigated. As a result, a new representation of the existing notion of $L_p$ affine surface area depending only on curvature measures is derived. Direct proofs of the equivalence between this new representation and those previously known are provided. The proofs show that the new representation is, in a sense, "polar" to that of Lutwak's and "dual" to that of Sch\\"utt & Werner's.

  5. Curvature reduces bending strains in the quokka femur

    Directory of Open Access Journals (Sweden)

    Kyle McCabe

    2017-03-01

    Full Text Available This study explores how curvature in the quokka femur may help to reduce bending strain during locomotion. The quokka is a small wallaby, but the curvature of the femur and the muscles active during stance phase are similar to most quadrupedal mammals. Our hypothesis is that the action of hip extensor and ankle plantarflexor muscles during stance phase place cranial bending strains that act to reduce the caudal curvature of the femur. Knee extensors and biarticular muscles that span the femur longitudinally create caudal bending strains in the caudally curved (concave caudal side bone. These opposing strains can balance each other and result in less strain on the bone. We test this idea by comparing the performance of a normally curved finite element model of the quokka femur to a digitally straightened version of the same bone. The normally curved model is indeed less strained than the straightened version. To further examine the relationship between curvature and the strains in the femoral models, we also tested an extra-curved and a reverse-curved version with the same loads. There appears to be a linear relationship between the curvature and the strains experienced by the models. These results demonstrate that longitudinal curvature in bones may be a manipulable mechanism whereby bone can induce a strain gradient to oppose strains induced by habitual loading.

  6. Separation membrane development

    Energy Technology Data Exchange (ETDEWEB)

    Lee, M.W. [Savannah River Technology Center, Aiken, SC (United States)

    1998-08-01

    A ceramic membrane has been developed to separate hydrogen from other gases. The method used is a sol-gel process. A thin layer of dense ceramic material is coated on a coarse ceramic filter substrate. The pore size distribution in the thin layer is controlled by a densification of the coating materials by heat treatment. The membrane has been tested by permeation measurement of the hydrogen and other gases. Selectivity of the membrane has been achieved to separate hydrogen from carbon monoxide. The permeation rate of hydrogen through the ceramic membrane was about 20 times larger than Pd-Ag membrane.

  7. Observer-Based Perturbation Extremum Seeking Control with Input Constraints for Direct-Contact Membrane Distillation Process

    KAUST Repository

    Eleiwi, Fadi

    2017-05-08

    An Observer-based Perturbation Extremum Seeking Control (PESC) is proposed for a Direct-Contact Membrane Distillation (DCMD) process. The process is described with a dynamic model that is based on a 2D Advection-Diffusion Equation (ADE) model which has pump flow rates as process inputs. The objective of the controller is to optimize the trade-off between the permeate mass flux and the energy consumption by the pumps inside the process. Cases of single and multiple control inputs are considered through the use of only the feed pump flow rate or both the feed and the permeate pump flow rates. A nonlinear Lyapunov-based observer is designed to provide an estimation for the temperature distribution all over the designated domain of the DCMD process. Moreover, control inputs are constrained with an anti-windup technique to be within feasible and physical ranges. Performance of the proposed structure is analyzed, and simulations based on real DCMD process parameters for each control input are provided.

  8. Observer-based perturbation extremum seeking control with input constraints for direct-contact membrane distillation process

    Science.gov (United States)

    Eleiwi, Fadi; Laleg-Kirati, Taous Meriem

    2018-06-01

    An observer-based perturbation extremum seeking control is proposed for a direct-contact membrane distillation (DCMD) process. The process is described with a dynamic model that is based on a 2D advection-diffusion equation model which has pump flow rates as process inputs. The objective of the controller is to optimise the trade-off between the permeate mass flux and the energy consumption by the pumps inside the process. Cases of single and multiple control inputs are considered through the use of only the feed pump flow rate or both the feed and the permeate pump flow rates. A nonlinear Lyapunov-based observer is designed to provide an estimation for the temperature distribution all over the designated domain of the DCMD process. Moreover, control inputs are constrained with an anti-windup technique to be within feasible and physical ranges. Performance of the proposed structure is analysed, and simulations based on real DCMD process parameters for each control input are provided.

  9. Development of the novel control algorithm for the small proton exchange membrane fuel cell stack without external humidification

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tae-Hoon; Kim, Sang-Hyun; Kim, Wook; Lee, Jong-Hak; Cho, Kwan-Seok; Choi, Woojin [Department of Electrical Engineering, Soongsil University, 1-1 Sangdo-dong, Dongjak-gu, Seoul 156-743 (Korea); Park, Kyung-Won [Department of Chemical/Environmental Engineering, Soongsil University, 1-1 Sangdo-dong, Dongjak-gu, Seoul 156-743 (Korea)

    2010-09-15

    Small PEM (proton exchange membrane) fuel cell systems do not require humidification and have great commercialization possibilities. However, methods for controlling small PEM fuel cell stacks have not been clearly established. In this paper, a control method for small PEM fuel cell systems using a dual closed loop with a static feed-forward structure is defined and realized using a microcontroller. The fundamental elements that need to be controlled in fuel cell systems include the supply of air and hydrogen, water management inside the stack, and heat management of the stack. For small PEM fuel cell stacks operated without a separate humidifier, fans are essential for air supply, heat management, and water management of the stack. A purge valve discharges surplus water from the stack. The proposed method controls the fan using a dual closed loop with a static feed-forward structure, thereby improving system efficiency and operation stability. The validity of the proposed method is confirmed by experiments using a 150-W PEM fuel cell stack. We expect the proposed algorithm to be widely used for controlling small PEM fuel cell stacks. (author)

  10. The V-ATPase membrane domain is a sensor of granular pH that controls the exocytotic machinery.

    Science.gov (United States)

    Poëa-Guyon, Sandrine; Ammar, Mohamed Raafet; Erard, Marie; Amar, Muriel; Moreau, Alexandre W; Fossier, Philippe; Gleize, Vincent; Vitale, Nicolas; Morel, Nicolas

    2013-10-28

    Several studies have suggested that the V0 domain of the vacuolar-type H(+)-adenosine triphosphatase (V-ATPase) is directly implicated in secretory vesicle exocytosis through a role in membrane fusion. We report in this paper that there was a rapid decrease in neurotransmitter release after acute photoinactivation of the V0 a1-I subunit in neuronal pairs. Likewise, inactivation of the V0 a1-I subunit in chromaffin cells resulted in a decreased frequency and prolonged kinetics of amperometric spikes induced by depolarization, with shortening of the fusion pore open time. Dissipation of the granular pH gradient was associated with an inhibition of exocytosis and correlated with the V1-V0 association status in secretory granules. We thus conclude that V0 serves as a sensor of intragranular pH that controls exocytosis and synaptic transmission via the reversible dissociation of V1 at acidic pH. Hence, the V-ATPase membrane domain would allow the exocytotic machinery to discriminate fully loaded and acidified vesicles from vesicles undergoing neurotransmitter reloading.

  11. Novel flower-shaped albumin particles as controlled-release carriers for drugs to penetrate the round-window membrane.

    Science.gov (United States)

    Yu, Zhan; Yu, Min; Zhou, Zhimin; Zhang, Zhibao; Du, Bo; Xiong, Qingqing

    2014-01-01

    Controlled-release carriers for local drug delivery have attracted increasing attention for inner-ear treatment recently. In this paper, flower-shaped bovine serum albumin (FBSA) particles were prepared by a modified desolvation method followed by glutaraldehyde or heat denaturation. The size of the FBSA particles varied from 10 μm to 100 μm, and most were 50-80 μm. Heat-denatured FBSA particles have good cytocompatibility with a prolonged survival time for L929 cells. The FBSA particles were utilized as carriers to investigate the release behaviors of the model drug - rhodamine B. Rhodamine B showed a sustained-release effect and penetrated the round-window membrane of guinea pigs. We also confirmed the attachment of FBSA particles onto the round-window membrane by microscopy. The FBSA particles, with good biocompatibility, drug-loading capacity, adhesive capability, and biodegradability, may have potential applications in the field of local drug delivery for inner-ear disease treatment.

  12. Evaluation of plasma membrane calcium/calmodulin-dependent ATPase isoform 4 as a potential target for fertility control.

    Science.gov (United States)

    Cartwright, Elizabeth J; Neyses, Ludwig

    2010-01-01

    The array of contraceptives currently available is clearly inadequate and does not meet consumer demands since it is estimated that up to a quarter of all pregnancies worldwide are unintended. There is, therefore, an overwhelming global need to develop new effective, safe, ideally non-hormonal contraceptives for both male and female use. The contraceptive field, unlike other areas such as cancer, has a dearth of new targets. We have addressed this issue and propose that isoform 4 of the plasma membrane calcium ATPase is a potentially exciting novel target for fertility control. The plasma membrane calcium ATPase is a ubiquitously expressed calcium pump whose primary function in the majority of cells is to extrude calcium to the extracellular milieu. Two isoforms of this gene family, PMCA1 and PMCA4, are expressed in spermatozoa, with PMCA4 being the predominant isoform. Although this gene is ubiquitously expressed, its function is highly tissue-specific. Genetic deletion of PMCA4, in PMCA4 knockout mice, led to 100% infertility specifically in the male mutant mice due to a selective defect in sperm motility. It is important to note that the gene deletion did not affect normal mating characteristics in these mice. This phenotype was mimicked in wild-type sperm treated with the non-specific PMCA inhibitor 5-(and 6-) carboxyeosin diacetate succinimidyl ester; a proof-of-principle that inhibition of PMCA4 has potential importance in the control of fertility. This review outlines the potential for PMCA4 to be a novel target for fertility control by acting to inhibit sperm motility. It will outline the characteristics that make this target drugable and will describe methodologies to identify and validate novel inhibitors of this target.

  13. Efficacy of bacterial cellulose membrane for the treatment of lower limbs chronic varicose ulcers: a randomized and controlled trial.

    Science.gov (United States)

    Cavalcanti, Luciana Marins; Pinto, Flávia Cristina Morone; Oliveira, Glícia Maria DE; Lima, Salvador Vilar Correia; Aguiar, José Lamartine DE Andrade; Lins, Esdras Marques

    2017-01-01

    to evaluate the efficacy of Bacterial Cellulose (BC) membrane dressings in the treatment of lower limb venous ulcers. we carried out a prospective, randomized, controlled study of 25 patients with chronic venous ulcer disease in the lower limbs from the Angiology and Vascular Surgery Service of the Federal University of Pernambuco Hospital and from the Salgado Polyclinic of the County Health Department, Caruaru, Pernambuco. We randomly assigned patients to two groups: control group, receiving dressings with triglyceride oil (11 patients) and experimental group, treated with BC membrane (14 patients). We followed the patients for a period of 120 days. There was a reduction in the wound area in both groups. There were no infections or reactions to the product in any of the groups. Patients in the BC group showed decreased pain and earlier discontinuation of analgesic use. BC membrane can be used as a dressing for the treatment of varicose ulcers of the lower limbs. avaliar a eficácia de curativos com membrana de Celulose Bacteriana (CB) no tratamento de úlceras venosas de membros inferiores. estudo prospectivo, randomizado e controlado de 25 pacientes com úlceras decorrentes de doença venosa crônica nos membros inferiores provenientes do Serviço de Angiologia e Cirurgia Vascular do Hospital de Clínicas da Universidade Federal de Pernambuco e da Policlínica do Salgado da Secretaria Municipal de Saúde, Caruaru, Pernambuco. Os pacientes foram distribuídos aleatoriamente em dois grupos: grupo controle, que recebeu curativos com óleo de triglicerídeos (11 pacientes) e grupo experimental, tratado com membrana de CB (14 pacientes). Os pacientes foram acompanhados por um período de 120 dias. houve uma redução na área de ferida em ambos os grupos. Não houve infecção ou reações ao produto em nenhum dos grupos. Pacientes do grupo CB mostraram diminuição da dor e interrupção mais precoce do uso de analgésicos. a membrana de CB pode ser usada como

  14. Genital infections and risk of premature rupture of membranes in Mulago Hospital, Uganda: a case control study.

    Science.gov (United States)

    Nakubulwa, Sarah; Kaye, Dan K; Bwanga, Freddie; Tumwesigye, Nazarius Mbona; Mirembe, Florence M

    2015-10-16

    Inflammatory mediators that weaken and cause membrane rupture are released during the course of genital infections among pregnant women. We set out to determine the association of common genital infections (Trichomonas vaginalis, syphilis, Neisseria gonorrhea, Chlamydia trachomatis, Group B Streptococcus, Bacterial vaginosis, Herpes Simplex Virus Type 2 and candidiasis) and premature rupture of membranes in Mulago hospital, Uganda. We conducted an unmatched case-control study among women who were in the third trimester of pregnancy at New Mulago hospital, Uganda. The cases had PROM and the controls had intact membranes during latent phase of labour in the labour ward. We used interviewer-administered questionnaires to collect data on socio-demographic characteristics, obstetric and medical history. Laboratory tests were conducted to identify T. vaginalis, syphilis, N. gonorrhea, C. trachomatis, Group B Streptococcus, Bacterial vaginosis, Herpes Simplex Virus Type 2 (HSV-2) and candidiasis. Logistic regression models were used to estimate the odds ratios (OR) and 95% CI of the association between genital infections and PROM. There was an association between PROM and abnormal vaginal discharge (OR = 2.02, 95% CI 1.10-3.70 and AOR = 2.30, 95% CI 1.18-4.47), presence of candidiasis (OR = 0.27, 95% CI 0.14-0.52 and AOR = 0.22, 95% CI 0.10-0.46) and T. vaginalis (OR = 2.98, 95% CI 1.18-7.56 and AOR = 4.22, 95% CI 1.51-11.80). However, there was no association between PROM and presence of C. trachomatis (OR = 2.05, 95% CI 0.37-11.49) and HSV-2 serostatus (OR = 1.15, 95% CI 0.63-2.09). Few or no patients with Bacterial vaginosis, Neisseria gonorrhoea, Group B streptococcus or syphilis were identified among the cases and controls. Co-infection of Trichomoniasis and candidiasis was not associated with PROM (AOR = 1.34, 95% CI 0.16-11.10). Co infection with T. vaginalis and C. trachomatis was associated with PROM (OR = 3.09, 95% CI 1.21-7.84 and AOR = 4.22, 95% CI 1

  15. Effective tension and fluctuations in active membranes

    OpenAIRE

    Loubet, Bastien; Seifert, Udo; Lomholt, Michael Andersen

    2011-01-01

    We calculate the fluctuation spectrum of the shape of a lipid vesicle or cell exposed to a nonthermal source of noise. In particular we take into account constraints on the membrane area and the volume of fluid that it encapsulates when obtaining expressions for the dependency of the membrane tension on the noise. We then investigate three possible origins of the non-thermal noise taken from the literature: A direct force, which models an external medium pushing on the membrane. A curvature f...

  16. Improved glycaemic control decreases inner mitochondrial membrane leak in type 2 diabetes

    DEFF Research Database (Denmark)

    Rabøl, R; Højberg, P M V; Almdal, T

    2009-01-01

    AIM: Several mechanisms have been targeted as culprits of weight gain during antihyperglycaemic treatment in type 2 diabetes (T2DM). These include reductions in glucosuria, increased food intake from fear of hypoglycaemia, the anabolic effect of insulin, decreased metabolic rate and increased eff...... to reductions in inner mitochondrial membrane leak and increased efficiency of mitochondria. This change in mitochondrial physiology could contribute to the weight gain seen with antihyperglycaemic treatment....... efficiency in fuel usage. The purpose of the study was to test the hypothesis that mitochondrial efficiency increases as a result of insulin treatment in patients with type 2 diabetes. METHODS: We included ten patients with T2DM (eight males) on oral antidiabetic treatment, median age: 51.5 years (range: 39......-67) and body mass index (BMI): 30.1 +/- 1.2 kg/m2 (mean +/- s.e.). Muscle biopsies from m. vastus lateralis and m. deltoideus were obtained before and after seven weeks of intensive insulin treatment, and mitochondrial respiration was measured using high-resolution respirometry. State 3 respiration...

  17. Controlled Bulk Properties of Composite Polymeric Solutions for Extensive Structural Order of Honeycomb Polysulfone Membranes.

    Science.gov (United States)

    Gugliuzza, Annarosa; Perrotta, Maria Luisa; Drioli, Enrico

    2016-05-16

    This work provides additional insights into the identification of operating conditions necessary to overcome a current limitation to the scale-up of the breath figure method, which is regarded as an outstanding manufacturing approach for structurally ordered porous films. The major restriction concerns, indeed, uncontrolled touching droplets at the boundary. Herein, the bulk of polymeric solutions are properly managed to generate honeycomb membranes with a long-range structurally ordered texture. Water uptake and dynamics are explored as chemical environments are changed with the intent to modify the hydrophilic/hydrophobic balance and local water floatation. In this context, a model surfactant such as the polyoxyethylene sorbitan monolaurate is used in combination with alcohols at different chain length extents and a traditional polymer such as the polyethersufone. Changes in the interfacial tension and kinematic viscosity taking place in the bulk of composite solutions are explored and examined in relation to competitive droplet nucleation and growth rate. As a result, extensive structurally ordered honeycomb textures are obtained with the rising content of the surfactant while a broad range of well-sized pores is targeted as a function of the hydrophilic-hydrophobic balance and viscosity of the composite polymeric mixture. The experimental findings confirm the consistency of the approach and are expected to give propulsion to the commercially production of breath figures films shortly.

  18. Controlled Bulk Properties of Composite Polymeric Solutions for Extensive Structural Order of Honeycomb Polysulfone Membranes

    Directory of Open Access Journals (Sweden)

    Annarosa Gugliuzza

    2016-05-01

    Full Text Available This work provides additional insights into the identification of operating conditions necessary to overcome a current limitation to the scale-up of the breath figure method, which is regarded as an outstanding manufacturing approach for structurally ordered porous films. The major restriction concerns, indeed, uncontrolled touching droplets at the boundary. Herein, the bulk of polymeric solutions are properly managed to generate honeycomb membranes with a long-range structurally ordered texture. Water uptake and dynamics are explored as chemical environments are changed with the intent to modify the hydrophilic/hydrophobic balance and local water floatation. In this context, a model surfactant such as the polyoxyethylene sorbitan monolaurate is used in combination with alcohols at different chain length extents and a traditional polymer such as the polyethersufone. Changes in the interfacial tension and kinematic viscosity taking place in the bulk of composite solutions are explored and examined in relation to competitive droplet nucleation and growth rate. As a result, extensive structurally ordered honeycomb textures are obtained with the rising content of the surfactant while a broad range of well-sized pores is targeted as a function of the hydrophilic-hydrophobic balance and viscosity of the composite polymeric mixture. The experimental findings confirm the consistency of the approach and are expected to give propulsion to the commercially production of breath figures films shortly.

  19. VANGL2 regulates membrane trafficking of MMP14 to control cell polarity and migration.

    Science.gov (United States)

    Williams, B Blairanne; Cantrell, V Ashley; Mundell, Nathan A; Bennett, Andrea C; Quick, Rachel E; Jessen, Jason R

    2012-05-01

    Planar cell polarity (PCP) describes the polarized orientation of cells within the plane of a tissue. Unlike epithelial PCP, the mechanisms underlying PCP signaling in migrating cells remain undefined. Here, the establishment of PCP must be coordinated with dynamic changes in cell adhesion and extracellular matrix (ECM) organization. During gastrulation, the membrane type-1 matrix metalloproteinase (MT1-MMP or MMP14) is required for PCP and convergence and extension cell movements. We report that the PCP protein Vang-like 2 (VANGL2) regulates the endocytosis and cell-surface availability of MMP14 in manner that is dependent on focal adhesion kinase. We demonstrate that zebrafish trilobite/vangl2 mutant embryos exhibit increased Mmp14 activity and decreased ECM. Furthermore, in vivo knockdown of Mmp14 partially rescues the Vangl2 loss-of-function convergence and extension phenotype. This study identifies a mechanism linking VANGL2 with MMP14 trafficking and suggests that establishment of PCP in migrating gastrula cells requires regulated proteolytic degradation or remodeling of the ECM. Our findings implicate matrix metalloproteinases as downstream effectors of PCP and suggest a broadly applicable mechanism whereby VANGL2 affects diverse morphogenetic processes.

  20. Dual curvature acoustically damped concentrating collector. Final technical report

    Energy Technology Data Exchange (ETDEWEB)

    Smith, G.A.; Rausch, R.A.

    1980-05-01

    A development program was conducted to investigate the design and performance parameters of a novel, dual curvature, concentrating solar collector. The reflector of the solar collector is achieved with a stretched-film reflective surface that approximates a hyperbolic paraboloid and is capable of line-focusing at concentration ratios ranging from 10 to 20X. A prototype collector was designed based on analytical and experimental component trade-off activities as well as economic analyses of solar thermal heating and cooling systems incorporating this type of collector. A prototype collector incorporating six 0.66 x 1.22 m (2 x 4 ft) was fabricated and subjected to a limited thermal efficiency test program. A peak efficiency of 36% at 121/sup 0/C (250/sup 0/F) was achieved based upon the gross aperture area. Commercialization activities were conducted, including estimated production costs of $134.44/m/sup 2/ ($12.49/ft/sup 2/) for the collector assembly (including a local suntracker and controls) and $24.33/m/sup 2/ ($2.26/ft/sup 2/) for the reflector subassembly.

  1. The speed-curvature power law in Drosophila larval locomotion.

    Science.gov (United States)

    Zago, Myrka; Lacquaniti, Francesco; Gomez-Marin, Alex

    2016-10-01

    We report the discovery that the locomotor trajectories of Drosophila larvae follow the power-law relationship between speed and curvature previously found in the movements of human and non-human primates. Using high-resolution behavioural tracking in controlled but naturalistic sensory environments, we tested the law in maggots tracing different trajectory types, from reaching-like movements to scribbles. For most but not all flies, we found that the law holds robustly, with an exponent close to three-quarters rather than to the usual two-thirds found in almost all human situations, suggesting dynamic effects adding on purely kinematic constraints. There are different hypotheses for the origin of the law in primates, one invoking cortical computations, another viscoelastic muscle properties coupled with central pattern generators. Our findings are consistent with the latter view and demonstrate that the law is possible in animals with nervous systems orders of magnitude simpler than in primates. Scaling laws might exist because natural selection favours processes that remain behaviourally efficient across a wide range of neural and body architectures in distantly related species. © 2016 The Authors.

  2. Analysis of the control structures for an integrated ethanol processor for proton exchange membrane fuel cell systems

    Energy Technology Data Exchange (ETDEWEB)

    Biset, S; Nieto Deglioumini, L; Basualdo, M [GIAIP-CIFASIS (UTN-FRRo-CONICET-UPCAM-UNR), BV. 27 de Febrero 210 Bis, S2000EZP Rosario (Argentina); Garcia, V M; Serra, M [Institut de Robotica i Informatica Industrial, C. Llorens i Artigas 4-6, 08028 Barcelona (Spain)

    2009-07-01

    The aim of this work is to investigate which would be a good preliminary plantwide control structure for the process of Hydrogen production from bioethanol to be used in a proton exchange membrane (PEM) accounting only steady-state information. The objective is to keep the process under optimal operation point, that is doing energy integration to achieve the maximum efficiency. Ethanol, produced from renewable feedstocks, feeds a fuel processor investigated for steam reforming, followed by high- and low-temperature shift reactors and preferential oxidation, which are coupled to a polymeric fuel cell. Applying steady-state simulation techniques and using thermodynamic models the performance of the complete system with two different control structures have been evaluated for the most typical perturbations. A sensitivity analysis for the key process variables together with the rigorous operability requirements for the fuel cell are taking into account for defining acceptable plantwide control structure. This is the first work showing an alternative control structure applied to this kind of process. (author)

  3. Controlling fuel crossover and hydration in ultrathin proton exchange membrane-based fuel cells using Pt-nanosheet catalysts

    DEFF Research Database (Denmark)

    Wang, Rujie; Zhang, Wenjing (Angela); He, Gaohong

    2014-01-01

    and provided in situ hydration inside Nafion membranes to maintain their proton conductivity level. Furthermore, LDH nanosheets reinforced the Nafion membranes, with 181% improvement in tensile modulus and 166% improvement in yield strength. In a hydrogen fuel cell running with dry fuel, the membrane......An ultra-thin proton exchange membrane with Pt-nanosheet catalysts was designed for a self-humidifying fuel cell running on H2 and O2. In this design, an ultra-thin Nafion membrane was used to reduce ohmic resistance. Pt nanocatalysts were uniformly anchored on exfoliated, layered double hydroxide...

  4. High-definition polymeric membranes: construction of 3D lithographed channel arrays through control of natural building blocks dynamics.

    Science.gov (United States)

    Speranza, Valentina; Trotta, Francesco; Drioli, Enrico; Gugliuzza, Annarosa

    2010-02-01

    The fabrication of well-defined interfaces is in high demand in many fields of biotechnologies. Here, high-definition membrane-like arrays are developed through the self-assembly of water droplets, which work as natural building blocks for the construction of ordered channels. Solution viscosity together with the dynamics of the water droplets can decide the final formation of three-dimensional well-ordered patterns resembling anodic structures, especially because solvents denser than water are used. Particularly, the polymer solution viscosity is demonstrated to be a powerful tool for control of the mobility of submerged droplets during the microfabrication process. The polymeric patterns are structured at very high levels of organization and exhibit well-established transport-surface property relationships, considered basics for any types of advanced biotechnologies.

  5. Sequence periodicity in nucleosomal DNA and intrinsic curvature.

    Science.gov (United States)

    Nair, T Murlidharan

    2010-05-17

    Most eukaryotic DNA contained in the nucleus is packaged by wrapping DNA around histone octamers. Histones are ubiquitous and bind most regions of chromosomal DNA. In order to achieve smooth wrapping of the DNA around the histone octamer, the DNA duplex should be able to deform and should possess intrinsic curvature. The deformability of DNA is a result of the non-parallelness of base pair stacks. The stacking interaction between base pairs is sequence dependent. The higher the stacking energy the more rigid the DNA helix, thus it is natural to expect that sequences that are involved in wrapping around the histone octamer should be unstacked and possess intrinsic curvature. Intrinsic curvature has been shown to be dictated by the periodic recurrence of certain dinucleotides. Several genome-wide studies directed towards mapping of nucleosome positions have revealed periodicity associated with certain stretches of sequences. In the current study, these sequences have been analyzed with a view to understand their sequence-dependent structures. Higher order DNA structures and the distribution of molecular bend loci associated with 146 base nucleosome core DNA sequence from C. elegans and chicken have been analyzed using the theoretical model for DNA curvature. The curvature dispersion calculated by cyclically permuting the sequences revealed that the molecular bend loci were delocalized throughout the nucleosome core region and had varying degrees of intrinsic curvature. The higher order structures associated with nucleosomes of C.elegans and chicken calculated from the sequences revealed heterogeneity with respect to the deviation of the DNA axis. The results points to the possibility of context dependent curvature of varying degrees to be associated with nucleosomal DNA.

  6. Preparation of Nanofibrous Silver/Poly(vinylidene fluoride) Composite Membrane with Enhanced Infrared Extinction and Controllable Wetting Property.

    Science.gov (United States)

    Ren, Da-Ming; Huang, Hua-Kun; Yu, Yun; Li, Zeng-Tian; Jiang, Li-Wang; Chen, Shui-Mei; Lam, Kwok-Ho; Lin, Bo; Shi, Bo; He, Fu-An; Wu, Hui-Jun

    2018-05-01

    Nanofibrous silver (Ag)/poly(vinylidene fluoride) (PVDF) composite membranes were obtained from a two-step preparation method. In the first step, the electrospun silver nitrate (AgNO3)/PVDF membranes were prepared and the influence of the AgNO3 content on the electrospinning process was studied. According to scanning electron microscopy (SEM) results, when the electrospinning solution contained AgNO3 in the range between 3 to 7 wt.%, the nanofiber morphologies can be obtained. In the second step, the electrospun AgNO3/PVDF membranes were reduced by sodium borohydride to form the nanofibrous Ag/PVDF composite membranes. The resultant composite membranes were characterized by SEM, X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), differential scanning calorimetry, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared. The XRD, XPS, and EDS characterizations proved the existence of Ag in the nanofibrous Ag/PVDF composite membranes. The crystallinity degree of PVDF for composite membranes declined with the increase in Ag content. More importantly, the nanofibrous Ag/PVDF composite membranes had obviously higher Rosseland extinction coefficients and lower thermal radiative conductivities in comparison with electrospun PVDF membrane, which demonstrates that such composite membranes with high porosity, low density, and good water vapor permeability are promising thermal insulating materials to block the heat transfer resulting from thermal radiation. In addition, three different methods for surface modification have been used to successfully improve the hydrophobicity of nanofibrous Ag/PVDF composite membranes.

  7. Advanced Supported Liquid Membranes for Ammonia and Formaldehyde Control in Spacesuits, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — With plans to transition to the Rapid Cycle Amine system for CO2 control in the Portable Life Support System used for extra vehicular activities (EVA), NASA has a...

  8. On the geometry of null cones to infinity under curvature flux bounds

    International Nuclear Information System (INIS)

    Alexakis, Spyros; Shao, Arick

    2014-01-01

    The main objective of this paper is to control the geometry of a future outgoing truncated null cone extending smoothly toward infinity in an Einstein-vacuum spacetime. In particular, we wish to do this under minimal regularity assumptions, namely, at the (weighted) L 2 -curvature level. We show that if the curvature flux and the data on an initial sphere of the cone are sufficiently close to the corresponding values in a standard Minkowski or Schwarzschild null cone, then we can obtain quantitative bounds on the geometry of the entire infinite cone. The same bounds also imply the existence of limits at infinity, along the null cone, of naturally scaled geometric quantities. In Alexakis and Shao (2013 Bounds on the Bondi energy by a flux of curvature arXiv:1308.4170), we will apply these results in order to control various physical quantities—e.g., the Bondi energy and (linear and angular) momenta—associated with such infinite null cones in vacuum spacetimes. (paper)

  9. Anionic lipids and the maintenance of membrane electrostatics in eukaryotes.

    Science.gov (United States)

    Platre, Matthieu Pierre; Jaillais, Yvon

    2017-02-01

    A wide range of signaling processes occurs at the cell surface through the reversible association of proteins from the cytosol to the plasma membrane. Some low abundant lipids are enriched at the membrane of specific compartments and thereby contribute to the identity of cell organelles by acting as biochemical landmarks. Lipids also influence membrane biophysical properties, which emerge as an important feature in specifying cellular territories. Such parameters are crucial for signal transduction and include lipid packing, membrane curvature and electrostatics. In particular, membrane electrostatics specifies the identity of the plasma membrane inner leaflet. Membrane surface charges are carried by anionic phospholipids, however the exact nature of the lipid(s) that powers the plasma membrane electrostatic field varies among eukaryotes and has been hotly debated during the last decade. Herein, we discuss the role of anionic lipids in setting up plasma membrane electrostatics and we compare similarities and differences that were found in different eukaryotic cells.

  10. The speed-curvature power law of movements: a reappraisal.

    Science.gov (United States)

    Zago, Myrka; Matic, Adam; Flash, Tamar; Gomez-Marin, Alex; Lacquaniti, Francesco

    2018-01-01

    Several types of curvilinear movements obey approximately the so called 2/3 power law, according to which the angular speed varies proportionally to the 2/3 power of the curvature. The origin of the law is debated but it is generally thought to depend on physiological mechanisms. However, a recent paper (Marken and Shaffer, Exp Brain Res 88:685-690, 2017) claims that this power law is simply a statistical artifact, being a mathematical consequence of the way speed and curvature are calculated. Here we reject this hypothesis by showing that the speed-curvature power law of biological movements is non-trivial. First, we confirm that the power exponent varies with the shape of human drawing movements and with environmental factors. Second, we report experimental data from Drosophila larvae demonstrating that the power law does not depend on how curvature is calculated. Third, we prove that the law can be violated by means of several mathematical and physical examples. Finally, we discuss biological constraints that may underlie speed-curvature power laws discovered in empirical studies.

  11. Biogas-pH automation control strategy for optimizing organic loading rate of anaerobic membrane bioreactor treating high COD wastewater.

    Science.gov (United States)

    Yu, Dawei; Liu, Jibao; Sui, Qianwen; Wei, Yuansong

    2016-03-01

    Control of organic loading rate (OLR) is essential for anaerobic digestion treating high COD wastewater, which would cause operation failure by overload or less efficiency by underload. A novel biogas-pH automation control strategy using the combined gas-liquor phase monitoring was developed for an anaerobic membrane bioreactor (AnMBR) treating high COD (27.53 g·L(-1)) starch wastewater. The biogas-pH strategy was proceeded with threshold between biogas production rate >98 Nml·h(-1) preventing overload and pH>7.4 preventing underload, which were determined by methane production kinetics and pH titration of methanogenesis slurry, respectively. The OLR and the effluent COD were doubled as 11.81 kgCOD·kgVSS(-1)·d(-1) and halved as 253.4 mg·L(-1), respectively, comparing with a constant OLR control strategy. Meanwhile COD removal rate, biogas yield and methane concentration were synchronously improved to 99.1%, 312 Nml·gCODin(-1) and 74%, respectively. Using the biogas-pH strategy, AnMBR formed a "pH self-regulation ternary buffer system" which seizes carbon dioxide and hence provides sufficient buffering capacity. Copyright © 2015 Elsevier Ltd. All rights reserved.

  12. An application of indirect model reference adaptive control to a low-power proton exchange membrane fuel cell

    Science.gov (United States)

    Yang, Yee-Pien; Liu, Zhao-Wei; Wang, Fu-Cheng

    2008-05-01

    Nonlinearity and the time-varying dynamics of fuel cell systems make it complex to design a controller for improving output performance. This paper introduces an application of a model reference adaptive control to a low-power proton exchange membrane (PEM) fuel cell system, which consists of three main components: a fuel cell stack, an air pump to supply air, and a solenoid valve to adjust hydrogen flow. From the system perspective, the dynamic model of the PEM fuel cell stack can be expressed as a multivariable configuration of two inputs, hydrogen and air-flow rates, and two outputs, cell voltage and current. The corresponding transfer functions can be identified off-line to describe the linearized dynamics with a finite order at a certain operating point, and are written in a discrete-time auto-regressive moving-average model for on-line estimation of parameters. This provides a strategy of regulating the voltage and current of the fuel cell by adaptively adjusting the flow rates of air and hydrogen. Experiments show that the proposed adaptive controller is robust to the variation of fuel cell system dynamics and power request. Additionally, it helps decrease fuel consumption and relieves the DC/DC converter in regulating the fluctuating cell voltage.

  13. Interpenetrating network hydrogel membranes of sodium alginate and poly(vinyl alcohol) for controlled release of prazosin hydrochloride through skin.

    Science.gov (United States)

    Kulkarni, Raghavendra V; Sreedhar, V; Mutalik, Srinivas; Setty, C Mallikarjun; Sa, Biswanath

    2010-11-01

    Interpenetrating network (IPN) hydrogel membranes of sodium alginate (SA) and poly(vinyl alcohol) (PVA) were prepared by solvent casting method for transdermal delivery of an anti-hypertensive drug, prazosin hydrochloride. The prepared membranes were thin, flexible and smooth. The X-ray diffraction studies indicated the amorphous dispersion of drug in the membranes. Differential scanning calorimetric analysis confirmed the IPN formation and suggests that the membrane stiffness increases with increased concentration of glutaraldehyde (GA) in the membranes. All the membranes were permeable to water vapors depending upon the extent of cross-linking. The in vitro drug release study was performed through excised rat abdominal skin; drug release depends on the concentrations of GA in membranes. The IPN membranes extended drug release up to 24 h, while SA and PVA membranes discharged the drug quickly. The primary skin irritation and skin histopathology study indicated that the prepared IPN membranes were less irritant and safe for skin application. Copyright © 2010 Elsevier B.V. All rights reserved.

  14. Curvature-induced electron localization in developable Moebius-like nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Korte, A P; Van der Heijden, G H M, E-mail: a.korte@ucl.ac.u, E-mail: g.heijden@ucl.ac.u [Centre for Nonlinear Dynamics, University College London, Chadwick Building, Gower Street, London WC1E 6BT (United Kingdom)

    2009-12-02

    We study curvature effects and localization of non-interacting electrons confined to developable one-sided elastic sheets motivated by recent nanostructured origami techniques for creating and folding extremely thin membrane structures. The most famous one-sided sheet is the Moebius strip but the theory we develop allows for arbitrary linking number. Unlike previous work in the literature we do not assume a shape for the elastic structures. Rather, we find the shape by minimizing the elastic energy, i.e., solving the Euler-Lagrange equations for the bending energy functional. This shape varies with the aspect ratio of the sheet and affects the potential experienced by the particles. Depending on the link there is a number of singular points on the edge of the structure where the bending energy density goes to infinity, leading to deep potential wells. The inverse participation ratio is used to show that electrons are increasingly localized to the higher-curvature regions of the higher-width structures, where sharp creases radiating out from the singular points could form channels for particle transport. Our geometric formulation could be used to study transport properties of Moebius strips and other components in nanoscale devices.

  15. Curvature-induced electron localization in developable Moebius-like nanostructures

    International Nuclear Information System (INIS)

    Korte, A P; Van der Heijden, G H M

    2009-01-01

    We study curvature effects and localization of non-interacting electrons confined to developable one-sided elastic sheets motivated by recent nanostructured origami techniques for creating and folding extremely thin membrane structures. The most famous one-sided sheet is the Moebius strip but the theory we develop allows for arbitrary linking number. Unlike previous work in the literature we do not assume a shape for the elastic structures. Rather, we find the shape by minimizing the elastic energy, i.e., solving the Euler-Lagrange equations for the bending energy functional. This shape varies with the aspect ratio of the sheet and affects the potential experienced by the particles. Depending on the link there is a number of singular points on the edge of the structure where the bending energy density goes to infinity, leading to deep potential wells. The inverse participation ratio is used to show that electrons are increasingly localized to the higher-curvature regions of the higher-width structures, where sharp creases radiating out from the singular points could form channels for particle transport. Our geometric formulation could be used to study transport properties of Moebius strips and other components in nanoscale devices.

  16. An innovative and efficient method to control the shape of push-pull membrane deformable mirror

    NARCIS (Netherlands)

    Polo, A.; Haber, A.; Pereira, S.F.; Verhaegen, M.H.G.; Urbach, H.P.

    2012-01-01

    We carry out performance characterisation of a commercial push and pull deformable mirror with 48 actuators (Adaptica Srl). We present a detailed description of the system as well as a statistical approach on the identification of the mirror influence function. A new efficient control algorithm to

  17. Control of relative radiation pressure in optical traps : application to phagocytic membrane binding studies

    NARCIS (Netherlands)

    Kress, H.; Stelzer, E.H.K.; Griffiths, G.; Rohrbach, A.

    2005-01-01

    We show how to control the relative radiation pressure and thereby the stable trap position of an optically trapped bead by variation of the mean incident axial photon momentum. The thermal position fluctuations of a trapped bead are recorded by a three-dimensional back focal plane interferometry.

  18. Facial Curvature Detects and Explicates Ethnic Differences in Effects of Prenatal Alcohol Exposure.

    Science.gov (United States)

    Suttie, Michael; Wetherill, Leah; Jacobson, Sandra W; Jacobson, Joseph L; Hoyme, H Eugene; Sowell, Elizabeth R; Coles, Claire; Wozniak, Jeffrey R; Riley, Edward P; Jones, Kenneth L; Foroud, Tatiana; Hammond, Peter

    2017-08-01

    Our objective is to help clinicians detect the facial effects of prenatal alcohol exposure by developing computer-based tools for screening facial form. All 415 individuals considered were evaluated by expert dysmorphologists and categorized as (i) healthy control (HC), (ii) fetal alcohol syndrome (FAS), or (iii) heavily prenatally alcohol exposed (HE) but not clinically diagnosable as FAS; 3D facial photographs were used to build models of facial form to support discrimination studies. Surface curvature-based delineations of facial form were introduced. (i) Facial growth in FAS, HE, and control subgroups is similar in both cohorts. (ii) Cohort consistency of agreement between clinical diagnosis and HC-FAS facial form classification is lower for midline facial regions and higher for nonmidline regions. (iii) Specific HC-FAS differences within and between the cohorts include: for HC, a smoother philtrum in Cape Coloured individuals; for FAS, a smoother philtrum in Caucasians; for control-FAS philtrum difference, greater homogeneity in Caucasians; for control-FAS face difference, greater homogeneity in Cape Coloured individuals. (iv) Curvature changes in facial profile induced by prenatal alcohol exposure are more homogeneous and greater in Cape Coloureds than in Caucasians. (v) The Caucasian HE subset divides into clusters with control-like and FAS-like facial dysmorphism. The Cape Coloured HE subset is similarly divided for nonmidline facial regions but not clearly for midline structures. (vi) The Cape Coloured HE subset with control-like facial dysmorphism shows orbital hypertelorism. Facial curvature assists the recognition of the effects of prenatal alcohol exposure and helps explain why different facial regions result in inconsistent control-FAS discrimination rates in disparate ethnic groups. Heavy prenatal alcohol exposure can give rise to orbital hypertelorism, supporting a long-standing suggestion that prenatal alcohol exposure at a particular time causes

  19. Staying Tight: Plasmodesmal Membrane Contact Sites and the Control of Cell-to-Cell Connectivity in Plants.

    Science.gov (United States)

    Tilsner, Jens; Nicolas, William; Rosado, Abel; Bayer, Emmanuelle M

    2016-04-29

    Multicellularity differs in plants and animals in that the cytoplasm, plasma membrane, and endomembrane of plants are connected between cells through plasmodesmal pores. Plasmodesmata (PDs) are essential for plant life and serve as conduits for the transport of proteins, small RNAs, hormones, and metabolites during developmental and defense signaling. They are also the only pathways available for viruses to spread within plant hosts. The membrane organization of PDs is unique, characterized by the close apposition of the endoplasmic reticulum and the plasma membrane and spoke-like filamentous structures linking the two membranes, which define PDs as membrane contact sites (MCSs). This specialized membrane arrangement is likely critical for PD function. Here, we review how PDs govern developmental and defensive signaling in plants, compare them with other types of MCSs, and discuss in detail the potential functional significance of the MCS nature of PDs.

  20. Waterfall field in hybrid inflation and curvature perturbation

    International Nuclear Information System (INIS)

    Gong, Jinn-Ouk; Sasaki, Misao

    2011-01-01

    We study carefully the contribution of the waterfall field to the curvature perturbation at the end of hybrid inflation. In particular we clarify the parameter dependence analytically under reasonable assumptions on the model parameters. After calculating the mode function of the waterfall field, we use the δN formalism and confirm the previously obtained result that the power spectrum is very blue with the index 4 and is absolutely negligible on large scales. However, we also find that the resulting curvature perturbation is highly non-Gaussian and hence we calculate the bispectrum. We find that the bispectrum is at leading order independent of momentum and exhibits its peak at the equilateral limit, though it is unobservably small on large scales. We also present the one-point probability distribution function of the curvature perturbation