WorldWideScience

Sample records for cell surface density

  1. Cell receptor and surface ligand density effects on dynamic states of adhering circulating tumor cells.

    Science.gov (United States)

    Zheng, Xiangjun; Cheung, Luthur Siu-Lun; Schroeder, Joyce A; Jiang, Linan; Zohar, Yitshak

    2011-10-21

    Dynamic states of cancer cells moving under shear flow in an antibody-functionalized microchannel are investigated experimentally and theoretically. The cell motion is analyzed with the aid of a simplified physical model featuring a receptor-coated rigid sphere moving above a solid surface with immobilized ligands. The motion of the sphere is described by the Langevin equation accounting for the hydrodynamic loadings, gravitational force, receptor-ligand bindings, and thermal fluctuations; the receptor-ligand bonds are modeled as linear springs. Depending on the applied shear flow rate, three dynamic states of cell motion have been identified: (i) free motion, (ii) rolling adhesion, and (iii) firm adhesion. Of particular interest is the fraction of captured circulating tumor cells, defined as the capture ratio, via specific receptor-ligand bonds. The cell capture ratio decreases with increasing shear flow rate with a characteristic rate. Based on both experimental and theoretical results, the characteristic flow rate increases monotonically with increasing either cell-receptor or surface-ligand density within certain ranges. Utilizing it as a scaling parameter, flow-rate dependent capture ratios for various cell-surface combinations collapse onto a single curve described by an exponential formula.

  2. Evaluating effect of surface state density at the interfaces in degraded bulk heterojunction organic solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Arora, Swati, E-mail: drswatia@yahoo.com [Department of Physics, Zakir Husain College, University of Delhi, Delhi 110002 (India); Singh, Vinamrita [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Arora, Manoj [Department of Physics, Ramjas College, University of Delhi, Delhi 110007 (India); Pal Tandon, Ram [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India)

    2012-08-01

    Degradation and short shelf life have been observed experimentally in poly(3-hexylthiophene) (P3HT): 6,6-phenyl C61-butyric acid methyl ester (PCBM) based blend solar cells. Both dark and illuminated current-voltage characteristics could be explained quantitatively with a proposed single model for a typical degraded organic solar cell-glass/ITO/PEDOT:PSS/P3HT:PCBM/Al. It has been found that surface state density, interface thickness, tunneling coefficient and occupation probabilities of the interface states becomes important with the passage of time. To look into the problem the activity at ITO/PEDOT:PSS and P3HT:PCBM/Al interfaces are studied using realistic values of the interfaces. The experimental J-V characteristics is well explained with the inclusion of tunneling current through these surface states and becomes the dominant current component for the degraded cell. It is also found that surface state density increases to 10{sup 12}-10{sup 13} cm{sup -2} eV{sup -1}, which has been verified with C-V measurements and also is in agreement with our proposed model for BHJ solar cell after 150 h of fabrication.

  3. Decreased lung carcinoma cell density on select polymer nanometer surface features for lung replacement therapies

    Directory of Open Access Journals (Sweden)

    Lijuan Zhang

    2010-04-01

    Full Text Available Lijuan Zhang1, Young Wook Chun2, Thomas J Webster21Department of Chemistry and 2Division of Engineering, Brown University, Providence, RI USAAbstract: Poly(lactic-co-glycolic acid (PLGA has been widely used as a biomaterial in regenerative medicine because of its biocompatibility and biodegradability properties. Previous studies have shown that cells (such as bladder smooth muscle cells, chondrocytes, and osteoblasts respond differently to nanostructured PLGA surfaces compared with nanosmooth surfaces. The purpose of the present in vitro research was to prepare PLGA films with various nanometer surface features and determine whether lung cancer epithelial cells respond differently to such topographies. To create nanosurface features on PLGA, different sized (190 nm, 300 nm, 400 nm, and 530 nm diameter polystyrene beads were used to cast polydimethylsiloxane (PDMS molds which were used as templates to create nanofeatured PLGA films. Atomic force microscopy (AFM images and root mean square roughness (RMS values indicated that the intended spherical surface nanotopographies on PLGA with RMS values of 2.23, 5.03, 5.42, and 36.90 nm were formed by employing 190, 300, 400, and 530 nm beads. A solution evaporation method was also utilized to modify PLGA surface features by using 8 wt% (to obtain an AFM RMS value of 0.62 nm and 4 wt% (to obtain an AFM RMS value of 2.23 nm PLGA in chloroform solutions. Most importantly, lung cancer epithelial cells adhered less on the PLGA surfaces with RMS values of 0.62, 2.23, and 5.42 nm after four hours of culture compared with any other PLGA surface created here. After three days, PLGA surfaces with an RMS value of 0.62 nm had much lower cell density than any other sample. In this manner, PLGA with specific nanometer surface features may inhibit lung cancer cell density which may provide an important biomaterial for the treatment of lung cancer (from drug delivery to regenerative medicine.Keywords: nanotechnology

  4. The effect of RGD density on osteoblast and endothelial cell behavior on RGD-grafted polyethylene terephthalate surfaces.

    Science.gov (United States)

    Chollet, Celine; Chanseau, Christel; Remy, Murielle; Guignandon, Alain; Bareille, Reine; Labrugère, Christine; Bordenave, Laurence; Durrieu, Marie-C

    2009-02-01

    Hybrid materials combining polyethylene terephthalate and different types of cells (endothelial and osteoblastic cells) have been developed thanks to the covalent grafting of different densities of RGD containing peptides onto the polymer surface. Biomimetic modifications were performed by means of a three-step reaction procedure: creation of COOH functions, coupling agent grafting and the immobilization of the RGDC peptides. High resolution mu-imager was used to evaluate RGD densities (varying between 0.6 and 2.4 pmol/mm(2)) and has exhibited the stability of the surface grafted peptides when treated in harsh conditions. The efficiency of this route for biomimetic modification of a PET surface was demonstrated by measuring the adhesion of MC3T3 and HSVEC cells and by focal adhesion observation. Results obtained prove that a minimal RGDC density of 1 pmol/mm(2) is required to improve MC3T3 and HSVEC cells responses. Indeed, cells seeded onto a RGDC-modified PET with a density higher than 1 pmol/mm(2) were able to establish focal adhesion as visualized by fluorescence microscope compared to cells immobilized onto unmodified PET and RGDC-modified PET with densities lower than 1 pmol/mm(2). Moreover, the number of focal contacts was enhanced by the increase of RGDC peptide densities grafted onto the material surface. With this study we proved that the density of peptides immobilized on the surface is a very important parameter influencing osteoblast or endothelial cell adhesion and focal contact formation.

  5. Forming high efficiency silicon solar cells using density-graded anti-reflection surfaces

    Science.gov (United States)

    Yuan, Hao-Chih; Branz, Howard M.; Page, Matthew R.

    2014-09-09

    A method (50) is provided for processing a graded-density AR silicon surface (14) to provide effective surface passivation. The method (50) includes positioning a substrate or wafer (12) with a silicon surface (14) in a reaction or processing chamber (42). The silicon surface (14) has been processed (52) to be an AR surface with a density gradient or region of black silicon. The method (50) continues with heating (54) the chamber (42) to a high temperature for both doping and surface passivation. The method (50) includes forming (58), with a dopant-containing precursor in contact with the silicon surface (14) of the substrate (12), an emitter junction (16) proximate to the silicon surface (14) by doping the substrate (12). The method (50) further includes, while the chamber is maintained at the high or raised temperature, forming (62) a passivation layer (19) on the graded-density silicon anti-reflection surface (14).

  6. Influence of charge densities of randomly sulfonated polystyrene surfaces on cell attachment and proliferation.

    Science.gov (United States)

    Khatua, Dibyendu; Kwak, Byeongdo; Shin, Kwanwoo; Song, Ju-Myung; Kim, Joon-Seop; Choi, Jai-Hak

    2011-05-01

    Attachment and proliferation of NIH-3T3 fibroblast cells on random polymer surfaces, polystyrene sulfonated acid (PSSAx) with five different degrees of sulfonation (x = 0%, 5%, 10%, 15% and 33%) and on a tissue culture polystyrene (TCPS) surface were studied. The surface properties, wettability and roughness were measured by water-contact angle and atomic force microscopy measurement. The wettability and surface roughness increased with increasing the content of sulfonic acid groups on the surfaces. The number of cells attached on the surface after seeding increased with increasing x and reached to the maximum value on PSSA15. The cell proliferation also increased with increasing x. However, cell proliferation was slow down on PSSA33 in comparison to PSSA10 and PSSA15 surfaces after 48 h culture.

  7. Impurity concentrations and surface charge densities on the heavily doped face of a silicon solar cell

    Science.gov (United States)

    Weinberg, I.; Hsu, L. C.

    1977-01-01

    Increased solar cell efficiencies are attained by reduction of surface recombination and variation of impurity concentration profiles at the n(+) surface of silicon solar cells. Diagnostic techniques are employed to evaluate the effects of specific materials preparation methodologies on surface and near surface concentrations. It is demonstrated that the MOS C-V method, when combined with a bulk measurement technique, yields more complete concentration data than are obtainable by either method alone. Specifically, new solar cell MOS C-V measurements are combined with bulk concentrations obtained by a successive layer removal technique utilizing measurements of sheet resistivity and Hall coefficient.

  8. Regulation of Kv2.1 K+ conductance by cell surface channel density

    OpenAIRE

    Fox, Philip D.; Loftus, Rob J.; Tamkun, Michael M.

    2013-01-01

    The Kv2.1 voltage-gated K+ channel is found both freely diffusing over the plasma membrane and concentrated in micron-sized clusters localized to the soma, proximal dendrites and axon initial segment of hippocampal neurons. In transfected HEK cells, Kv2.1 channels within cluster microdomains are non-conducting. Using TIRF microscopy the number of GFP-tagged Kv2.1 channels on the HEK cell surface was compared to K+ channel conductance measured by whole-cell voltage-clamp of the same cell. This...

  9. Adiabatic density surface, neutral density surface, potential density surface, and mixing path

    Institute of Scientific and Technical Information of China (English)

    HUANG Rui-xin

    2014-01-01

    In this paper, adiabatic density surface, neutral density surface and potential density surface are compared. The adiabatic density surface is defined as the surface on which a water parcellcan move adiabatically, without changing its potential temperature and salinity. For a water parcelltaken at a given station and pressure level, the corresponding adiabatic density surface can be determined through simple calculations. This family of surface is neutrally buoyant in the world ocean, and different from other surfaces that are not truly neutrally buoyant. In order to explore mixing path in the ocean, a mixing ratio m is introduced, which is defined as the portion of potential temperature and salinity of a water parcellthat has exchanged with the environment during a segment of migration in the ocean. Two extreme situations of mixing path in the ocean are m=0 (no mixing), which is represented by the adiabatic density curve, and m=1, where the original information is completely lost through mixing. The latter is represented by the neutral density curve. The reality lies in between, namely, 0

  10. Active Free Surface Density Maps

    Science.gov (United States)

    Çelen, S.

    2016-10-01

    Percolation problems were occupied to many physical problems after their establishment in 1957 by Broadbent and Hammersley. They can be used to solve complex systems such as bone remodeling. Volume fraction method was adopted to set some algorithms in the literature. However, different rate of osteoporosis could be observed for different microstructures which have the same mass density, mechanical stimuli, hormonal stimuli and nutrition. Thus it was emphasized that the bone might have identical porosity with different specific surfaces. Active free surface density of bone refers the used total area for its effective free surface. The purpose of this manuscript is to consolidate a mathematical approach which can be called as “active free surface density maps” for different surface patterns and derive their formulations. Active free surface density ratios were calculated for different Archimedean lattice models according to Helmholtz free energy and they were compared with their site and bond percolation thresholds from the background studies to derive their potential probability for bone remodeling.

  11. The strength of the chemotactic response to a CCR5 binding chemokine is determined by the level of cell surface CCR5 density.

    Science.gov (United States)

    Desmetz, Caroline; Lin, Yea-Lih; Mettling, Clément; Portalès, Pierre; Rabesandratana, Herisoa; Clot, Jacques; Corbeau, Pierre

    2006-12-01

    We have shown that the intensity of expression of the C-C chemokine receptor CCR5 at the single CD4(+) cell level strongly determines the efficiency of its function as a coreceptor for human immunodeficiency virus type 1. By analogy, we examined if the number of CCR5 molecules at the cell surface might determine its chemotactic response to CCR5 ligands. To test this hypothesis, we measured by flow cytometry the migration of primary human T cells towards the CCR5-binding chemokine CCL5 in vitro. First, we observed a dose-dependent blockage of this migration exerted by an anti-CCR5 monoclonal antibody. Second, we sorted peripheral blood mononuclear cells into five subpopulations expressing various cell surface CCR5 densities, and observed a correlation between the intensity of migration towards CCL5 and the level of CCR5 expression on these subpopulations. Third, we transduced CCR5(+) peripheral blood mononuclear cells with the CCR5 gene, and observed that the CCR5 over-expression induced an over-migration towards CCL5. Finally, we observed in healthy donors a correlation between the chemotactic response of peripheral blood CD8(+) T cell to CCL5 and their level of surface CCR5 expression. T-cell surface CCR5 density, which is constant over time for a given individual, but varies drastically among individuals, might therefore be an important personal determinant of T-cell migration in many biological situations where CCR5-binding chemokines play a role, such as graft rejection, T helper 1-mediated auto-immune diseases, and infectious diseases involving CCR5. Moreover, our data highlight the therapeutic potential of CCR5 antagonists in these situations.

  12. Anode biofilm transcriptomics reveals outer surface components essential for high density current production in Geobacter sulfurreducens fuel cells.

    Directory of Open Access Journals (Sweden)

    Kelly P Nevin

    Full Text Available The mechanisms by which Geobacter sulfurreducens transfers electrons through relatively thick (>50 microm biofilms to electrodes acting as a sole electron acceptor were investigated. Biofilms of Geobacter sulfurreducens were grown either in flow-through systems with graphite anodes as the electron acceptor or on the same graphite surface, but with fumarate as the sole electron acceptor. Fumarate-grown biofilms were not immediately capable of significant current production, suggesting substantial physiological differences from current-producing biofilms. Microarray analysis revealed 13 genes in current-harvesting biofilms that had significantly higher transcript levels. The greatest increases were for pilA, the gene immediately downstream of pilA, and the genes for two outer c-type membrane cytochromes, OmcB and OmcZ. Down-regulated genes included the genes for the outer-membrane c-type cytochromes, OmcS and OmcT. Results of quantitative RT-PCR of gene transcript levels during biofilm growth were consistent with microarray results. OmcZ and the outer-surface c-type cytochrome, OmcE, were more abundant and OmcS was less abundant in current-harvesting cells. Strains in which pilA, the gene immediately downstream from pilA, omcB, omcS, omcE, or omcZ was deleted demonstrated that only deletion of pilA or omcZ severely inhibited current production and biofilm formation in current-harvesting mode. In contrast, these gene deletions had no impact on biofilm formation on graphite surfaces when fumarate served as the electron acceptor. These results suggest that biofilms grown harvesting current are specifically poised for electron transfer to electrodes and that, in addition to pili, OmcZ is a key component in electron transfer through differentiated G. sulfurreducens biofilms to electrodes.

  13. Reconstruction of Cell Surface Densities of Ion Pumps, Exchangers, and Channels from mRNA Expression, Conductance Kinetics, Whole-Cell Calcium, and Current-Clamp Voltage Recordings, with an Application to Human Uterine Smooth Muscle Cells.

    Science.gov (United States)

    Atia, Jolene; McCloskey, Conor; Shmygol, Anatoly S; Rand, David A; van den Berg, Hugo A; Blanks, Andrew M

    2016-04-01

    Uterine smooth muscle cells remain quiescent throughout most of gestation, only generating spontaneous action potentials immediately prior to, and during, labor. This study presents a method that combines transcriptomics with biophysical recordings to characterise the conductance repertoire of these cells, the 'conductance repertoire' being the total complement of ion channels and transporters expressed by an electrically active cell. Transcriptomic analysis provides a set of potential electrogenic entities, of which the conductance repertoire is a subset. Each entity within the conductance repertoire was modeled independently and its gating parameter values were fixed using the available biophysical data. The only remaining free parameters were the surface densities for each entity. We characterise the space of combinations of surface densities (density vectors) consistent with experimentally observed membrane potential and calcium waveforms. This yields insights on the functional redundancy of the system as well as its behavioral versatility. Our approach couples high-throughput transcriptomic data with physiological behaviors in health and disease, and provides a formal method to link genotype to phenotype in excitable systems. We accurately predict current densities and chart functional redundancy. For example, we find that to evoke the observed voltage waveform, the BK channel is functionally redundant whereas hERG is essential. Furthermore, our analysis suggests that activation of calcium-activated chloride conductances by intracellular calcium release is the key factor underlying spontaneous depolarisations.

  14. Reconstruction of Cell Surface Densities of Ion Pumps, Exchangers, and Channels from mRNA Expression, Conductance Kinetics, Whole-Cell Calcium, and Current-Clamp Voltage Recordings, with an Application to Human Uterine Smooth Muscle Cells.

    Directory of Open Access Journals (Sweden)

    Jolene Atia

    2016-04-01

    Full Text Available Uterine smooth muscle cells remain quiescent throughout most of gestation, only generating spontaneous action potentials immediately prior to, and during, labor. This study presents a method that combines transcriptomics with biophysical recordings to characterise the conductance repertoire of these cells, the 'conductance repertoire' being the total complement of ion channels and transporters expressed by an electrically active cell. Transcriptomic analysis provides a set of potential electrogenic entities, of which the conductance repertoire is a subset. Each entity within the conductance repertoire was modeled independently and its gating parameter values were fixed using the available biophysical data. The only remaining free parameters were the surface densities for each entity. We characterise the space of combinations of surface densities (density vectors consistent with experimentally observed membrane potential and calcium waveforms. This yields insights on the functional redundancy of the system as well as its behavioral versatility. Our approach couples high-throughput transcriptomic data with physiological behaviors in health and disease, and provides a formal method to link genotype to phenotype in excitable systems. We accurately predict current densities and chart functional redundancy. For example, we find that to evoke the observed voltage waveform, the BK channel is functionally redundant whereas hERG is essential. Furthermore, our analysis suggests that activation of calcium-activated chloride conductances by intracellular calcium release is the key factor underlying spontaneous depolarisations.

  15. Surface current density K: an introduction

    DEFF Research Database (Denmark)

    McAllister, Iain Wilson

    1991-01-01

    The author discusses the vector surface of current density K used in electrical insulation studies. K is related to the vector tangential electric field Kt at the surface of a body by the vector equation K=ΓE t where Γ represents the surface conductivity. The author derives a surface continuity...... equation that represents the boundary condition which the potential distributions in the adjoining media must fulfill. The volume current may be small in comparison to the surface current, and consequently in deriving the potential solutions the first term in this equation can sometimes be neglected....

  16. Comparative study of the surface layer density of liquid surfaces

    Science.gov (United States)

    Chacón, E.; Fernández, E. M.; Duque, D.; Delgado-Buscalioni, R.; Tarazona, P.

    2009-11-01

    Capillary wave fluctuations blur the inherent structure of liquid surfaces in computer simulations. The intrinsic sampling method subtracts capillary wave fluctuations and yields the intrinsic surface structure, leading to a generic picture of the liquid surface. The most relevant magnitude of the method is the surface layer density ns that may be consistently determined from different properties: the layering structure of the intrinsic density profiles, the turnover rate for surface layer particles, and the hydrodynamic damping rate of capillary waves. The good agreement among these procedures provides evidence for the physical consistency of the surface layering hypothesis, as an inherent physical property of the liquid surfaces. The dependence of the surface compactness, roughness, and exchange rate with temperature is analyzed for several molecular interaction models.

  17. Nutrient uptake rate as a function of cell size and surface transporter density: A Michaelis-like approximation to the model of Pasciak and Gavis

    Science.gov (United States)

    Armstrong, Robert A.

    2008-10-01

    Pasciak and Gavis were first to propose a model of nutrient uptake that includes both physical transport by diffusion and active biological transport across the cell membrane. While the Pasciak-Gavis model is not complicated mathematically (it can be expressed in closed form as a quadratic equation), its parameters are not so easily interpretable biologically as are the parameters of the Michaelis-Menten uptake model; this lack of transparency is probably the main reason the Pasciak-Gavis model has not been adopted by ecologically oriented modelers. Here I derive a Michaelis-like approximation to the Pasciak-Gavis model, and show how the parameters of the latter map to those of the Michaelis-like model. The derived approximation differs from a pure Michaelis-Menten model in a subtle but potentially critical way: in a pure Michaelis-Menten model, the half-saturation constant for nutrient uptake is independent of the density of transporter (or "porter") proteins on the cell surface, while in the Pasciak-Gavis model and its Michaelis-like approximation, the half-saturation constant does depend on the density of porter proteins. The Pasciak-Gavis model predicts a unique relationship between cell size, nutrient concentration in the medium, the half-saturation constant of porter-limited nutrient uptake, and the resulting rate of uptake; the Michaelis-like approximation preserves the most important feature of that relationship, the size at which porter limitation gives way to diffusion limitation. Finally I discuss the implications for community structure that are implied by the Pasciak-Gavis model and its Michaelis-like approximation.

  18. Sensor-Free Surface Density Detector

    Science.gov (United States)

    Wu, Huixuan

    2016-11-01

    We have developed an optical-based method to measure the absolute air density on a wall surface in compressible turbulent boundary layers. The temporal resolution can be higher than 1MHz, and the spatial resolution can research 10 micron. For isothermal flows, our system can also be used to obtain the wall pressure distributions or volume-ratio of two-species gas. It is a powerful tool for observing turbulent fluctuations and flow separations in sub-, trans-, and supersonic airflows. The working principle of our method is to detect the air density by measuring the refractive index, which linearly depends on density and determines the transmission coefficient at the interface. For single- or multiple-point measurements, we do not need to install sensors on the wall surface, which is a big advantage compared to conventional methods. In 2D cases, a layer of anti-reflection coating is needed. The optical measurement range is not limited by the surface material or sensor. These advantages make our method a good complement or better alternative to the other approaches, such as focused laser differential interferometry technique, which provides density gradient, and pressure (temperature) sensitive paints, which depends significantly on the material properties.

  19. Scattered surface charge density: A tool for surface characterization

    KAUST Repository

    Naydenov, Borislav

    2011-11-28

    We demonstrate the use of nonlocal scanning tunneling spectroscopic measurements to characterize the local structure of adspecies in their states where they are significantly less perturbed by the probe, which is accomplished by mapping the amplitude and phase of the scattered surface charge density. As an example, we study single-H-atom adsorption on the n-type Si(100)-(4 × 2) surface, and demonstrate the existence of two different configurations that are distinguishable using the nonlocal approach and successfully corroborated by density functional theory. © 2011 American Physical Society.

  20. Mapping surface charge density of lipid bilayers by quantitative surface conductivity microscopy

    Science.gov (United States)

    Klausen, Lasse Hyldgaard; Fuhs, Thomas; Dong, Mingdong

    2016-08-01

    Local surface charge density of lipid membranes influences membrane-protein interactions leading to distinct functions in all living cells, and it is a vital parameter in understanding membrane-binding mechanisms, liposome design and drug delivery. Despite the significance, no method has so far been capable of mapping surface charge densities under physiologically relevant conditions. Here, we use a scanning nanopipette setup (scanning ion-conductance microscope) combined with a novel algorithm to investigate the surface conductivity near supported lipid bilayers, and we present a new approach, quantitative surface conductivity microscopy (QSCM), capable of mapping surface charge density with high-quantitative precision and nanoscale resolution. The method is validated through an extensive theoretical analysis of the ionic current at the nanopipette tip, and we demonstrate the capacity of QSCM by mapping the surface charge density of model cationic, anionic and zwitterionic lipids with results accurately matching theoretical values.

  1. Mapping surface charge density of lipid bilayers by quantitative surface conductivity microscopy

    DEFF Research Database (Denmark)

    Klausen, Lasse Hyldgaard; Fuhs, Thomas; Dong, Mingdong

    2016-01-01

    Local surface charge density of lipid membranes influences membrane-protein interactions leading to distinct functions in all living cells, and it is a vital parameter in understanding membrane-binding mechanisms, liposome design and drug delivery. Despite the significance, no method has so far...... approach, quantitative surface conductivity microscopy (QSCM), capable of mapping surface charge density with high-quantitative precision and nanoscale resolution. The method is validated through an extensive theoretical analysis of the ionic current at the nanopipette tip, and we demonstrate the capacity...

  2. A periodic density functional theory study of tetrazole adsorption on anatase surfaces: potential application of tetrazole rings in dye-sensitized solar cells.

    Science.gov (United States)

    Chermahini, Alireza Najafi; Hosseinzadeh, Behzad; Beni, Alireza Salimi; Teimouri, Abbas; Moradi, Mahmood

    2014-02-01

    A density functional theory (DFT) method (periodic DMol(3)) with full geometry optimization was used to study the adsorption of tautomeric forms of tetrazole on anatase TiO2 (101), (100), and (001) surfaces. It was found that the adsorption of tetrazole on the TiO2 surfaces does not proceed via a dissociative process, and negative shifts in the Fermi level of TiO2 were noted upon N-containing heterocycle adsorption. The configuration of the tetrazole during adsorption and the corresponding adsorption energies on different surfaces and sites were estimated. In addition, it was found that tetrazole may be adsorbed on TiO2 surfaces through an interaction between a cation on the surface and a lone pair on the N1 or N2 atom of the tetrazole molecule. The results indicate that the adsorption of tetrazole through the N2 position (leading to the 1H tautomer) on an anatase TiO2 surface is favored over adsorption through the N1 position. In addition, it was observed that the photocatalytic activity of tetrazole-doped TiO2 is higher than that of a pure anatase TiO2 surface.

  3. Nanofiber density determines endothelial cell behavior on hydrogel matrix

    Energy Technology Data Exchange (ETDEWEB)

    Berti, Fernanda V., E-mail: fernanda@intelab.ufsc.br [Department of Chemical and Food Engineering, Federal University of Santa Catarina, 88040-900 Florianópolis, SC (Brazil); Rambo, Carlos R. [Department of Electrical Engineering, Federal University of Santa Catarina, 88040-900 Florianópolis, SC (Brazil); Dias, Paulo F. [Department of Cell Biology, Embryology and Genetics, Federal University of Santa Catarina, 88040-900 Florianópolis, SC (Brazil); Porto, Luismar M. [Department of Chemical and Food Engineering, Federal University of Santa Catarina, 88040-900 Florianópolis, SC (Brazil)

    2013-12-01

    When cultured under static conditions, bacterial cellulose pellicles, by the nature of the polymer synthesis that involves molecular oxygen, are characterized by two distinct surface sides. The upper surface is denser in fibers (entangled) than the lower surface that shows greater surface porosity. Human umbilical vein endothelial cells (HUVECs) were used to exploit how the microarchitecture (i.e., surface porosity, fiber network structure, surface topology, and fiber density) of bacterial cellulose pellicle surfaces influence cell–biomaterial interaction and therefore cell behavior. Adhesion, cell ingrowth, proliferation, viability and cell death mechanisms were evaluated on the two pellicle surface sides. Cell behavior, including secondary necrosis, is influenced only by the microarchitecture of the surface, since the biomaterial is extremely pure (constituted of cellulose and water only). Cell–cellulose fiber interaction is the determinant signal in the cell–biomaterial responses, isolated from other frequently present interferences such as protein and other chemical traces usually present in cell culture matrices. Our results suggest that microarchitecture of hydrogel materials might determine the performance of biomedical products, such as bacterial cellulose tissue engineering constructs (BCTECs). - Highlights: • Topography of BC pellicle is relevant to determine endothelial cells' fate. • Cell–biomaterial response is affected by the topography of BC-pellicle surface. • Endothelial cells exhibit different behavior depending on the BC topography. • Apoptosis and necrosis of endothelial cells were affected by the BC topography.

  4. A novel maskless approach towards aligned, density modulated and multi-junction ZnO nanowires for enhanced surface area and light trapping solar cells.

    Science.gov (United States)

    Kevin, M; Fou, Y H; Wong, A S W; Ho, G W

    2010-08-06

    A maskless method of employing polymer growth inhibitor layers is used to modulate the conflicting parameters of density and alignment of multi-junction nanowires via large-scale low temperature chemical route. This low temperature chemical route is shown to synthesize multi-junction nanostructures without compromising the crystal quality at the interfaces. The final morphology of optimized multi-junctions nanowire arrays can be demonstrated on various substrates due to substrate independence and low temperature processing. Here, we also fabricated devices based on density modulated multi-junction nanowires tuned to infiltrate nanoparticles. The fabrication of hierarchically structured nanowire/nanoparticles composites presents an advantageous structure, one that allows nanoparticles to provide large surface areas for dye adsorption, whilst the nanowires can enhance the light harvesting, electron transport rate, and also the mechanical properties of the films. This work can be of great scientific and commercial interest since the technique employed is of low temperature (<90 degrees C) and economical for large-scale solution processing, much valued in today's flexible display and photovoltaic industries.

  5. A novel maskless approach towards aligned, density modulated and multi-junction ZnO nanowires for enhanced surface area and light trapping solar cells

    Science.gov (United States)

    Kevin, M.; Fou, Y. H.; Wong, A. S. W.; Ho, G. W.

    2010-08-01

    A maskless method of employing polymer growth inhibitor layers is used to modulate the conflicting parameters of density and alignment of multi-junction nanowires via large-scale low temperature chemical route. This low temperature chemical route is shown to synthesize multi-junction nanostructures without compromising the crystal quality at the interfaces. The final morphology of optimized multi-junctions nanowire arrays can be demonstrated on various substrates due to substrate independence and low temperature processing. Here, we also fabricated devices based on density modulated multi-junction nanowires tuned to infiltrate nanoparticles. The fabrication of hierarchically structured nanowire/nanoparticles composites presents an advantageous structure, one that allows nanoparticles to provide large surface areas for dye adsorption, whilst the nanowires can enhance the light harvesting, electron transport rate, and also the mechanical properties of the films. This work can be of great scientific and commercial interest since the technique employed is of low temperature (economical for large-scale solution processing, much valued in today's flexible display and photovoltaic industries.

  6. Versatile Density Functionals for Computational Surface Science

    DEFF Research Database (Denmark)

    Wellendorff, Jess

    Density functional theory (DFT) emerged almost 50 years ago. Since then DFT has established itself as the central electronic structure methodology for simulating atomicscale systems from a few atoms to a few hundred atoms. This success of DFT is due to a very favorable accuracy-to-computational......–correlation functionals in a language that naturally allows for error prediction within DFT. The optimization methodology includes as a central ingredient establishment of a compromise between high transferability (measured by the smoothness of the resulting functional) and low prediction error using statistical...

  7. Estimation of the space density of low surface brightness galaxies

    NARCIS (Netherlands)

    Briggs, FH

    1997-01-01

    The space density of low surface brightness and tiny gas-rich dwarf galaxies are estimated for two recent catalogs: the Arecibo Survey of Northern Dwarf and Low Surface Brightness Galaxies and the Catalog of Low Surface Brightness Galaxies, List II. The goals are (1) to evaluate the additions to the

  8. Mapping of an Approximate Neutral Density Surface with Ungridded Data

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A neutral density surface is a logical study frame for water-mass mixing since water parcels spread along such a surface without doing work against buoyancy restoring force. Mesoscale eddies are believed to stir and subsequently mix predominantly along such surfaces. Because of the nonlinear nature of the equation of state of seawater, the process of accurately mapping a neutral density surface necessarily involves lateral computation from one conductivity, temperature and depth (CTD) cast to the next in a logical sequence. By contrast, the depth of a potential density surface on any CTD cast is found solely from the data on this cast. The lateral calculation procedure causes a significant inconvenience. In a previous paper by present author published in this journal (You,2006), the mapping of neutral density surfaces with regularly gridded data such as Levitus data has been introduced. In this note, I present a new method to find the depth of a neutral density surface from a cast without having to specify an integration path in space.An appropriate reference point is required that is on the neutral density surface and thereafter the neutral density surface can be determined by using the CTD casts in any order. This method is only approximate and the likely errors can be estimated by plotting a scatter diagram of all the pressures and potential temperatures on the neutral density surfaces. The method assumes that the variations of potential temperature and pressure (with respect to the values at the reference point) on the neutral density surface are proportional.It is important to select the most appropriate reference point in order to approximately satisfy this assumption, and in practice this is found by inspecting the θ-p plot of data on the surface. This may require that the algorithm be used twice. When the straight lines on the θ-p plot, drawn from the reference point to other points on the neutral density surface, enclose an area that is external to the

  9. Experimental surface charge density of the Si (100)-2x1H surface

    DEFF Research Database (Denmark)

    Ciston, J.; Marks, L.D.; Feidenhans'l, R.;

    2006-01-01

    We report a three-dimensional charge density refinement from x-ray diffraction intensities of the Si (100) 2x1H surface. By paying careful attention to parameterizing the bulk Si bonding, we are able to locate the hydrogen atoms at the surface, which could not be done previously. In addition, we...... are able to partially refine the local charge density at the surface. We find experimentally an increased, slightly localized bond density of approximately 0.31 electrons between each Si atom pair at the surface. Both the atomic positions and the charge density are in remarkably good agreement with density...

  10. Impact of density information on Rayleigh surface wave inversion results

    Science.gov (United States)

    Ivanov, Julian; Tsoflias, Georgios; Miller, Richard D.; Peterie, Shelby; Morton, Sarah; Xia, Jianghai

    2016-12-01

    We assessed the impact of density on the estimation of inverted shear-wave velocity (Vs) using the multi-channel analysis of surface waves (MASW) method. We considered the forward modeling theory, evaluated model sensitivity, and tested the effect of density information on the inversion of seismic data acquired in the Arctic. Theoretical review, numerical modeling and inversion of modeled and real data indicated that the density ratios between layers, not the actual density values, impact the determination of surface-wave phase velocities. Application on real data compared surface-wave inversion results using: a) constant density, the most common approach in practice, b) indirect density estimates derived from refraction compressional-wave velocity observations, and c) from direct density measurements in a borehole. The use of indirect density estimates reduced the final shear-wave velocity (Vs) results typically by 6-7% and the use of densities from a borehole reduced the final Vs estimates by 10-11% compared to those from assumed constant density. In addition to the improved absolute Vs accuracy, the resulting overall Vs changes were unevenly distributed laterally when viewed on a 2-D section leading to an overall Vs model structure that was more representative of the subsurface environment. It was observed that the use of constant density instead of increasing density with depth not only can lead to Vs overestimation but it can also create inaccurate model structures, such as a low-velocity layer. Thus, optimal Vs estimations can be best achieved using field estimates of subsurface density ratios.

  11. Cell density monitoring and control of microencapsulated CHO cell cultures

    OpenAIRE

    Cole, Harriet Emma

    2015-01-01

    Though mammalian cells play a key role in the manufacturing of recombinant glycosylated proteins, cell cultures and productivity are limited by the lack of suitable systems to enable stable perfusion culture. Microencapsulation, or entrapping cells within a semi-permeable membrane, offers the potential to generate high cell density cultures and improve the productivity by mimicking the cells natural environment. However, the cells being secluded by the microcapsules membrane are difficult to ...

  12. The Star Formation Law at Low Surface Density

    CERN Document Server

    Wyder, Ted K; Barlow, Tom A; Forster, Karl; Friedman, Peter G; Morrissey, Patrick; Neff, Susan G; Neill, James D; Schiminovich, David; Seibert, Mark; Bianchi, Luciana; Donas, Jose; Heckman, Timothy M; Lee, Young-Wook; Madore, Barrry F; Milliard, Bruno; Rich, R Michael; Szalay, A S; Yi, Sukyoung K

    2009-01-01

    We investigate the nature of the star formation law at low gas surface densities using a sample of 19 low surface brightness (LSB) galaxies with existing HI maps in the literature, UV imaging from the Galaxy Evolution Explorer satellite, and optical images from the Sloan Digital Sky Survey. All of the LSB galaxies have (NUV-r) colors similar to those for higher surface brightness star-forming galaxies of similar luminosity indicating that their average star formation histories are not very different. Based upon four LSB galaxies with both UV and FIR data, we find FIR/UV ratios significantly less than one, implying low amounts of internal UV extinction in LSB galaxies. We use the UV images and HI maps to measure the star formation rate and hydrogen gas surface densities within the same region for all of the galaxies. The LSB galaxy star formation rate surface densities lie below the extrapolation of the power law fit to the star formation rate surface density as a function of the total gas density for higher s...

  13. High power density carbonate fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Yuh, C.; Johnsen, R.; Doyon, J.; Allen, J. [Energy Research Corp., Danbury, CT (United States)

    1996-12-31

    Carbonate fuel cell is a highly efficient and environmentally clean source of power generation. Many organizations worldwide are actively pursuing the development of the technology. Field demonstration of multi-MW size power plant has been initiated in 1996, a step toward commercialization before the turn of the century, Energy Research Corporation (ERC) is planning to introduce a 2.85MW commercial fuel cell power plant with an efficiency of 58%, which is quite attractive for distributed power generation. However, to further expand competitive edge over alternative systems and to achieve wider market penetration, ERC is exploring advanced carbonate fuel cells having significantly higher power densities. A more compact power plant would also stimulate interest in new markets such as ships and submarines where space limitations exist. The activities focused on reducing cell polarization and internal resistance as well as on advanced thin cell components.

  14. Semilocal density functional theory with correct surface asymptotics

    Science.gov (United States)

    Constantin, Lucian A.; Fabiano, Eduardo; Pitarke, J. M.; Della Sala, Fabio

    2016-03-01

    Semilocal density functional theory is the most used computational method for electronic structure calculations in theoretical solid-state physics and quantum chemistry of large systems, providing good accuracy with a very attractive computational cost. Nevertheless, because of the nonlocality of the exchange-correlation hole outside a metal surface, it was always considered inappropriate to describe the correct surface asymptotics. Here, we derive, within the semilocal density functional theory formalism, an exact condition for the imagelike surface asymptotics of both the exchange-correlation energy per particle and potential. We show that this condition can be easily incorporated into a practical computational tool, at the simple meta-generalized-gradient approximation level of theory. Using this tool, we also show that the Airy-gas model exhibits asymptotic properties that are closely related to those at metal surfaces. This result highlights the relevance of the linear effective potential model to the metal surface asymptotics.

  15. Wireless Sensor Node for Surface Seawater Density Measurements

    Directory of Open Access Journals (Sweden)

    Roberto Saletti

    2012-03-01

    Full Text Available An electronic meter to measure surface seawater density is presented. It is based on the measurement of the difference in displacements of a surface level probe and a weighted float, which according to Archimedes’ law depends on the density of the water. The displacements are simultaneously measured using a high-accuracy magnetostrictive sensor, to which a custom electronic board provides a wireless connection and power supply so that it can become part of a wireless sensor network. The electronics are designed so that different kinds of wireless networks can be used, by simply changing the wireless module and the relevant firmware of the microcontroller. Lastly, laboratory and at-sea tests are presented and discussed in order to highlight the functionality and the performance of a prototype of the wireless density meter node in a Bluetooth radio network. The experimental results show a good agreement of the values of the calculated density compared to reference hydrometer readings.

  16. Mapping the energy and diffusion landscapes of membrane proteins at the cell surface using high-density single-molecule imaging and Bayesian inference: application to the multi-scale dynamics of glycine receptors in the neuronal membrane

    CERN Document Server

    Masson, Jean-Baptiste; Salvatico, Charlotte; Renner, Marianne; Specht, Christian G; Triller, Antoine; Dahan, Maxime

    2015-01-01

    Protein mobility is conventionally analyzed in terms of an effective diffusion. Yet, this description often fails to properly distinguish and evaluate the physical parameters (such as the membrane friction) and the biochemical interactions governing the motion. Here, we present a method combining high-density single-molecule imaging and statistical inference to separately map the diffusion and energy landscapes of membrane proteins across the cell surface at ~100 nm resolution (with acquisition of a few minutes). When applying these analytical tools to glycine neurotransmitter receptors (GlyRs) at inhibitory synapses, we find that gephyrin scaffolds act as shallow energy traps (~3 kBT) for GlyRs, with a depth modulated by the biochemical properties of the receptor-gephyrin interaction loop. In turn, the inferred maps can be used to simulate the dynamics of proteins in the membrane, from the level of individual receptors to that of the population, and thereby, to model the stochastic fluctuations of physiologi...

  17. A density gradient theory based method for surface tension calculations

    DEFF Research Database (Denmark)

    Liang, Xiaodong; Michelsen, Michael Locht; Kontogeorgis, Georgios

    2016-01-01

    The density gradient theory has been becoming a widely used framework for calculating surface tension, within which the same equation of state is used for the interface and bulk phases, because it is a theoretically sound, consistent and computationally affordable approach. Based on the observation...... systems, from non-polar binary mixtures to complex multicomponent associating fluids, combined with the Peng-Robinson and the Cubic Plus Association equations of state. From an overall point of view, the approximation method with the density path profile passing the saddle point and the full density...

  18. Revisiting the Fermi Surface in Density Functional Theory

    Science.gov (United States)

    Das, Mukunda P.; Green, Frederick

    2016-06-01

    The Fermi surface is an abstract object in the reciprocal space of a crystal lattice, enclosing the set of all those electronic band states that are filled according to the Pauli principle. Its topology is dictated by the underlying lattice structure and its volume is the carrier density in the material. The Fermi surface is central to predictions of thermal, electrical, magnetic, optical and superconducting properties in metallic systems. Density functional theory is a first-principles method used to estimate the occupied-band energies and, in particular, the isoenergetic Fermi surface. In this review we survey several key facts about Fermi surfaces in complex systems, where a proper theoretical understanding is still lacking. We address some critical difficulties.

  19. Interfacial Tension and Surface Pressure of High Density Lipoprotein, Low Density Lipoprotein, and Related Lipid Droplets

    DEFF Research Database (Denmark)

    Ollila, O. H. S.; Lamberg, A.; Lehtivaara, M.

    2012-01-01

    Lipid droplets play a central role in energy storage and metabolism on a cellular scale. Their core is comprised of hydrophobic lipids covered by a surface region consisting of amphiphilic lipids and proteins. For example, high and low density lipoproteins (HDL and LDL, respectively) are essentia...... of interfacial tension becomes significant for particles with a radius of similar to 5 nm, when the area per molecule in the surface region is...

  20. Density functional theory in surface science and heterogeneous catalysis

    DEFF Research Database (Denmark)

    Nørskov, Jens Kehlet; Scheffler, M.; Toulhoat, H.

    2006-01-01

    Solid surfaces are used extensively as catalysts throughout the chemical industry, in the energy sector, and in environmental protection. Recently, density functional theory has started providing new insight into the atomic-scale mechanisms of heterogeneous catalysis, helping to interpret the large...

  1. Inverse Calculation of Power Density for Laser Surface Treatment

    NARCIS (Netherlands)

    Römer, G.R.B.E.; Meijer, J.

    2000-01-01

    Laser beam surface treatment requires a well-defined temperature profile. In this paper an analytic method is presented to solve the inverse problem of heat conduction in solids, based on the 2-dimensional Fourier transform. As a result, the required power density profile of the laser beam can be ca

  2. High Energy Density aluminum/oxygen cell

    Science.gov (United States)

    Rudd, E. J.; Gibbons, D. W.

    An alternative to a secondary battery as the power source for vehicle propulsion is a fuel cell, an example of which is the metal/air cell using metals such as aluminum, zinc, or iron. Aluminum is a particularly attractive candidate, with high energy and power densities, environmentally acceptable and having a large, established industrial base for production and distribution. An aluminum/oxygen system is currently under development for a prototype unmanned, undersea vehicle (UUV) for the US navy and recent work has focussed upon low corrosion aluminum alloys, and an electrolyte management system for processing the by-products of the energy-producing reactions. This paper summarizes the progress made in both areas. Anode materials capable of providing high utilization factors over current densities ranging from 5 to 150 mA/cm 2 have been identified, such materials being essential to realize mission life for the UUV. With respect to the electrolyte management system, a filter/precipitator unit has been successfully operated for over 250 h in a large scale, half-cell system.

  3. Improved DFT Potential Energy Surfaces via Improved Densities.

    Science.gov (United States)

    Kim, Min-Cheol; Park, Hansol; Son, Suyeon; Sim, Eunji; Burke, Kieron

    2015-10-01

    Density-corrected DFT is a method that cures several failures of self-consistent semilocal DFT calculations by using a more accurate density instead. A novel procedure employs the Hartree-Fock density to bonds that are more severely stretched than ever before. This substantially increases the range of accurate potential energy surfaces obtainable from semilocal DFT for many heteronuclear molecules. We show that this works for both neutral and charged molecules. We explain why and explore more difficult cases, for example, CH(+), where density-corrected DFT results are even better than sophisticated methods like CCSD. We give a simple criterion for when DC-DFT should be more accurate than self-consistent DFT that can be applied for most cases.

  4. Spin density wave order, topological order, and Fermi surface reconstruction

    CERN Document Server

    Sachdev, Subir; Chatterjee, Shubhayu; Schattner, Yoni

    2016-01-01

    In the conventional theory of density wave ordering in metals, the onset of spin density wave (SDW) order co-incides with the reconstruction of the Fermi surfaces into small 'pockets'. We present models which display this transition, while also displaying an alternative route between these phases via an intermediate phase with topological order, no broken symmetry, and pocket Fermi surfaces. The models involve coupling emergent gauge fields to a fractionalized SDW order, but retain the canonical electron operator in the underlying Hamiltonian. We establish an intimate connection between the suppression of certain defects in the SDW order, and the presence of Fermi surface sizes distinct from the Luttinger value in Fermi liquids. We discuss the relevance of such models to the physics of the hole-doped cuprates near optimal doping.

  5. Oxygen adsorption on pyrite (100) surface by density functional theory

    Institute of Scientific and Technical Information of China (English)

    孙伟; 胡岳华; 邱冠周; 覃文庆

    2004-01-01

    Pyrite (FeS2) bulk and (100) surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2 (100) surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe2+ and S2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference.The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.

  6. F-cell levels are altered with erythrocyte density in sickle cell disease.

    Science.gov (United States)

    Basu, Sumanta; Dash, Bisnu Prasad; Patel, Dilip Kumar; Chakravarty, Sudipa; Chakravarty, Amit; Banerjee, Debashis; Chakrabarti, Abhijit

    2011-08-15

    Lighter cells from density fractionated erythrocytes of sickle cell disease (SCD) patients carry higher amount of externalized phosphatidylserine (PS) and cell surface glycophorins compared to the denser counterparts. Further analysis also revealed that the denser cells contained higher levels of fetal hemoglobin (HbF) compared to the lighter cells, supported by the presence of larger number of F-cells in these populations. In this report, we have found direct evidence on the higher survival of the HbF rich erythrocytes in SCD.

  7. Effect of monocular deprivation on rabbit neural retinal cell densities

    Directory of Open Access Journals (Sweden)

    Philip Maseghe Mwachaka

    2015-01-01

    Conclusion: In this rabbit model, monocular deprivation resulted in activity-dependent changes in cell densities of the neural retina in favour of the non-deprived eye along with reduced cell densities in the deprived eye.

  8. Cell Growth on ("Janus") Density Gradients of Bifunctional Zeolite L Crystals.

    Science.gov (United States)

    Kehr, Nermin Seda; Motealleh, Andisheh; Schäfer, Andreas H

    2016-12-28

    Nanoparticle density gradients on surfaces have attracted interest as two-dimensional material surfaces that can mimic the complex nano-/microstructure of the native extracellular matrix, including its chemical and physical gradients, and can therefore be used to systematically study cell-material interactions. In this respect, we report the preparation of density gradients made of bifunctional zeolite L crystals on glass surfaces and the effects of the density gradient and biopolymer functionalization of zeolite L crystals on cell adhesion. We also describe how we created "Janus" density gradient surfaces by gradually depositing two different types of zeolite L crystals that were functionalized and loaded with different chemical groups and guest molecules onto the two distinct sides of the same glass substrate. Our results show that more cells adhered on the density gradient of biopolymer-coated zeolites than on uncoated ones. The number of adhered cells increased up to a certain surface coverage of the glass by the zeolite L crystals, but then it decreased beyond the zeolite density at which a higher surface coverage decreased fibroblast cell adhesion and spreading. Additionally, cell experiments showed that cells gradually internalized the guest-molecule-loaded zeolite L crystals from the underlying density gradient containing bifunctional zeolite L crystals.

  9. Unique cellular events occurring during the initial interaction of macrophages with matrix-retained or methylated aggregated low density lipoprotein (LDL). Prolonged cell-surface contact during which ldl-cholesteryl ester hydrolysis exceeds ldl protein degradation.

    Science.gov (United States)

    Buton, X; Mamdouh, Z; Ghosh, R; Du, H; Kuriakose, G; Beatini, N; Grabowski, G A; Maxfield, F R; Tabas, I

    1999-11-05

    A critical event in atherogenesis is the interaction of arterial wall macrophages with subendothelial lipoproteins. Although most studies have investigated this interaction by incubating cultured macrophages with monomeric lipoproteins dissolved in media, arterial wall macrophages encounter lipoproteins that are mostly bound to subendothelial extracellular matrix, and these lipoproteins are often aggregated or fused. Herein, we utilize a specialized cell-culture system to study the initial interaction of macrophages with aggregated low density lipoprotein (LDL) bound to extracellular matrix. The aggregated LDL remains extracellular for a relatively prolonged period of time and becomes lodged in invaginations in the surface of the macrophages. As expected, the degradation of the protein moiety of the LDL was very slow. Remarkably, however, hydrolysis of the cholesteryl ester (CE) moiety of the LDL was 3-7-fold higher than that of the protein moiety, in stark contrast to the situation with receptor-mediated endocytosis of acetyl-LDL. Similar results were obtained using another experimental system in which the degradation of aggregated LDL protein was delayed by LDL methylation rather than by retention on matrix. Additional experiments indicated the following properties of this interaction: (a) LDL-CE hydrolysis is catalyzed by lysosomal acid lipase; (b) neither scavenger receptors nor the LDL receptor appear necessary for the excess LDL-CE hydrolysis; and (c) LDL-CE hydrolysis in this system is resistant to cellular potassium depletion, which further distinguishes this process from receptor-mediated endocytosis. In summary, experimental systems specifically designed to mimic the in vivo interaction of arterial wall macrophages with subendothelial lipoproteins have demonstrated an initial period of prolonged cell-surface contact in which CE hydrolysis exceeds protein degradation.

  10. Measuring surface state density and energy distribution in InAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Halpern, Eliezer; Cohen, Gilad; Gross, Shahar; Henning, Alexander; Matok, Max; Rosenwaks, Yossi [Department of Physical Electronics, School of Electrical Engineering, Tel-Aviv University (Israel); Kretinin, Andrey V. [School of Physics and Astronomy, University of Manchester (United Kingdom); Shtrikman, Hadas [Department of Condensed Matter Physics, Braun Center for Submicrometer Research, Weizmann Institute of Science, Rehovot (Israel)

    2014-02-15

    Semiconducting nanowires are expected to have applications in various areas as transistors, sensors, resonators, solar cells, and thermoelectric systems. Understanding the surface properties is crucial for the fabrication of high-performance devices. Due to the large surface-to-volume ratio of nanowires, their surface electronic properties, like surface states, can a have a large effect on the performance of both electronic and optoelectronic devices. At present, determination of the surface state density depends on a combination of experimental measurements of the capacitance and/or drain current, in a nanowire field-effect transistor, and a fitting to simulation. This technique follows certain assumptions, which can severely harm the accuracy of the extracted density of states. In this report, we demonstrate a direct measurement of the surface state density of individual InAs and silicon nanowires. The method is based on measuring the surface potential of a nanowire field-effect transistor, with respect to a changing gate bias. The extracted density of states at the surface helps to explain various electronic phenomena in such devices. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Surface cell immobilization within perfluoroalkoxy microchannels

    Energy Technology Data Exchange (ETDEWEB)

    Stojkovič, Gorazd; Krivec, Matic [Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, SI-1000 Ljubljana (Slovenia); Vesel, Alenka [Jožef Stefan Institute, Jamova cesta 39, 1000 Ljubljana (Slovenia); Marinšek, Marjan [Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, SI-1000 Ljubljana (Slovenia); Žnidaršič-Plazl, Polona, E-mail: polona.znidarsic@fkkt.uni-lj.si [Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, SI-1000 Ljubljana (Slovenia)

    2014-11-30

    Graphical abstract: - Highlights: • A very efficient approach for immobilization of cells into microreactors is presented. • It is applicable to various materials, including PFA and cyclic olefin (co)polymers. • It was used to immobilize different prokaryotic and eukaryotic microbes. • Cells were immobilized on the surface in high density and showed good stability. • Mechanisms of APTES interactions with target materials are proposed. - Abstract: Perfluoroalkoxy (PFA) is one of the most promising materials for the fabrication of cheap, solvent resistant and reusable microfluidic chips, which have been recently recognized as effective tools for biocatalytic process development. The application of biocatalysts significantly depends on efficient immobilization of enzymes or cells within the reactor enabling long-term biocatalyst use. Functionalization of PFA microchannels by 3-aminopropyltriethoxysilane (ATPES) and glutaraldehyde was used for rapid preparation of microbioreactors with surface-immobilized cells. X-ray photoelectron spectroscopy and scanning electron microscopy were used to accurately monitor individual treatment steps and to select conditions for cell immobilization. The optimized protocol for Saccharomyces cerevisiae immobilization on PFA microchannel walls comprised ethanol surface pretreatment, 4 h contacting with 10% APTES aqueous solution, 10 min treatment with 1% glutaraldehyde and 20 min contacting with cells in deionized water. The same protocol enabled also immobilization of Escherichia coli, Pseudomonas putida and Bacillus subtilis cells on PFA surface in high densities. Furthermore, the developed procedure has been proved to be very efficient also for surface immobilization of tested cells on other materials that are used for microreactor fabrication, including glass, polystyrene, poly (methyl methacrylate), polycarbonate, and two olefin-based polymers, namely Zeonor{sup ®} and Topas{sup ®}.

  12. Surface interactions involved in flashover with high density electronegative gases.

    Energy Technology Data Exchange (ETDEWEB)

    Hodge, Keith Conquest; Warne, Larry Kevin; Jorgenson, Roy Eberhardt; Wallace, Zachariah Red; Lehr, Jane Marie

    2010-01-01

    This report examines the interactions involved with flashover along a surface in high density electronegative gases. The focus is on fast ionization processes rather than the later time ionic drift or thermalization of the discharge. A kinetic simulation of the gas and surface is used to examine electron multiplication and includes gas collision, excitation and ionization, and attachment processes, gas photoionization and surface photoemission processes, as well as surface attachment. These rates are then used in a 1.5D fluid ionization wave (streamer) model to study streamer propagation with and without the surface in air and in SF6. The 1.5D model therefore includes rates for all these processes. To get a better estimate for the behavior of the radius we have studied radial expansion of the streamer in air and in SF6. The focus of the modeling is on voltage and field level changes (with and without a surface) rather than secondary effects, such as, velocities or changes in discharge path. An experiment has been set up to carry out measurements of threshold voltages, streamer velocities, and other discharge characteristics. This setup includes both electrical and photographic diagnostics (streak and framing cameras). We have observed little change in critical field levels (where avalanche multiplication sets in) in the gas alone versus with the surface. Comparisons between model calculations and experimental measurements are in agreement with this. We have examined streamer sustaining fields (field which maintains ionization wave propagation) in the gas and on the surface. Agreement of the gas levels with available literature is good and agreement between experiment and calculation is good also. Model calculations do not indicate much difference between the gas alone versus the surface levels. Experiments have identified differences in velocity between streamers on the surface and in the gas alone (the surface values being larger).

  13. The central surface density of "dark halos" predicted by MOND

    CERN Document Server

    Milgrom, Mordehai

    2009-01-01

    Prompted by the recent claim, by Donato et al., of a quasi-universal central surface density of galaxy dark matter halos, I look at what MOND has to say on the subject. MOND, indeed, predicts a quasi-universal value of this quantity for objects of all masses and of any internal structure, provided they are mostly in the Newtonian regime; i.e., that their mean acceleration is at or above a0. The predicted value is qSm, with Sm= a0/2 pi G= 138 solar masses per square parsec for the nominal value of a0, and q a constant of order 1 that depends only on the form of the MOND interpolating function. This gives in the above units log(Sm)=2.14, which is consistent with that found by Doanato et al. of 2.15+-0.2. MOND predicts, on the other hand, that this quasi-universal value is not shared by objects with much lower mean accelerations. It permits halo central surface densities that are arbitrarily small, if the mean acceleration inside the object is small enough. However, for such low-surface-density objects, MOND pre...

  14. SURFACE SYMMETRY ENERGY OF NUCLEAR ENERGY DENSITY FUNCTIONALS

    Energy Technology Data Exchange (ETDEWEB)

    Nikolov, N; Schunck, N; Nazarewicz, W; Bender, M; Pei, J

    2010-12-20

    We study the bulk deformation properties of the Skyrme nuclear energy density functionals. Following simple arguments based on the leptodermous expansion and liquid drop model, we apply the nuclear density functional theory to assess the role of the surface symmetry energy in nuclei. To this end, we validate the commonly used functional parametrizations against the data on excitation energies of superdeformed band-heads in Hg and Pb isotopes, and fission isomers in actinide nuclei. After subtracting shell effects, the results of our self-consistent calculations are consistent with macroscopic arguments and indicate that experimental data on strongly deformed configurations in neutron-rich nuclei are essential for optimizing future nuclear energy density functionals. The resulting survey provides a useful benchmark for further theoretical improvements. Unlike in nuclei close to the stability valley, whose macroscopic deformability hangs on the balance of surface and Coulomb terms, the deformability of neutron-rich nuclei strongly depends on the surface-symmetry energy; hence, its proper determination is crucial for the stability of deformed phases of the neutron-rich matter and description of fission rates for r-process nucleosynthesis.

  15. The Plant Cell Surface

    Institute of Scientific and Technical Information of China (English)

    Anne-Mie C.Emons; Kurt V.Fagerstedt

    2010-01-01

    @@ Multicellular organization and tissue construction has evolved along essentially different lines in plants and animals. Since plants do not run away, but are anchored in the soil, their tissues are more or less firm and stiff. This strength stems from the cell walls, which encase the fragile cytoplasm, and protect it.

  16. Solvation of complex surfaces via molecular density functional theory

    CERN Document Server

    Levesque, Maximilien; Rotenberg, Benjamin; Jeanmairet, Guillaume; Vuilleumier, Rodolphe; Borgis, Daniel

    2012-01-01

    We show that classical molecular density functional theory (MDFT), here in the homogeneous reference fluid approximation in which the functional is inferred from the properties of the bulk solvent, is a powerful new tool to study, at a fully molecular level, the solvation of complex surfaces and interfaces by polar solvents. This implicit solvent method allows for the determination of structural, orientational and energetic solvation properties that are on a par with all-atom molecular simulations performed for the same system, while reducing the computer time by two orders of magnitude. This is illustrated by the study of an atomistically-resolved clay surface composed of over a thousand atoms wetted by a molecular dipolar solvent. The high numerical efficiency of the method is exploited to carry a systematic analysis of the electrostatic and non-electrostatic components of the surface-solvent interaction within the popular CLAYFF force field. Solvent energetics and structure are found to depend weakly upon ...

  17. High-Density Infrared Surface Treatments of Refractories

    Energy Technology Data Exchange (ETDEWEB)

    Tiegs, T.N.

    2005-03-31

    Refractory materials play a crucial role in all energy-intensive industries and are truly a crosscutting technology for the Industries of the Future (IOF). One of the major mechanisms for the degradation of refractories and a general decrease in their performance has been the penetration and corrosion by molten metals or glass. Methods and materials that would reduce the penetration, wetting, and corrosive chemistry would significantly improve refractory performance and also maintain the quality of the processed liquid, be it metal or glass. This report presents the results of an R&D project aimed at investigating the use of high-density infrared (HDI) heating to surface treat refractories to improve their performance. The project was a joint effort between Oak Ridge National Laboratory (ORNL) and the University of Missouri-Rolla (UMR). HDI is capable of heating the near-surface region of materials to very high temperatures where sintering, diffusion, and melting can occur. The intended benefits of HDI processing of refractories were to (1) reduce surface porosity (by essentially sealing the surface to prevent liquid penetration), (2) allow surface chemistry changes to be performed by bonding an adherent coating onto the underlying refractory (in order to inhibit wetting and/or improve corrosion resistance), and (3) produce noncontact refractories with high-emissivity surface coatings.

  18. Mast cell density in cardio-esophageal mucosa.

    Science.gov (United States)

    Mahjoub, Fatemeh E; Asefi, Hoda; Farahmand, Fatemeh; Pourpak, Zahra; Amini, Zahra

    2014-12-01

    Mast cells are related to certain gastrointestinal complaints. Mast cell density has not been studied in cardio-esophageal region to the best of our knowledge. In this study we wanted to obtain an estimate of mast cell density in this region and compare it with mast cell density in antrum. From April 2007 till March 2010, we chose children (mast cell density in the cardiac mucosa was 33.41 ± 32.75 in 0.25 mm2 (range: 0-155), which was two times of that in antral mucosa. We found a significant but weak positive correlation at the 0.05 level between mast cell density of cardiac mucosa and the antrum. Higher mast cell counts were seen in cardiac mucosa in this study. Significant positive correlation between mast cell density of cardiac mucosa and the antrum could hint to a single underlying etiology for the inflammatory process in gastro- esophageal junction and gastric mucosa.

  19. Surface cell immobilization within perfluoroalkoxy microchannels

    Science.gov (United States)

    Stojkovič, Gorazd; Krivec, Matic; Vesel, Alenka; Marinšek, Marjan; Žnidaršič-Plazl, Polona

    2014-11-01

    Perfluoroalkoxy (PFA) is one of the most promising materials for the fabrication of cheap, solvent resistant and reusable microfluidic chips, which have been recently recognized as effective tools for biocatalytic process development. The application of biocatalysts significantly depends on efficient immobilization of enzymes or cells within the reactor enabling long-term biocatalyst use. Functionalization of PFA microchannels by 3-aminopropyltriethoxysilane (ATPES) and glutaraldehyde was used for rapid preparation of microbioreactors with surface-immobilized cells. X-ray photoelectron spectroscopy and scanning electron microscopy were used to accurately monitor individual treatment steps and to select conditions for cell immobilization. The optimized protocol for Saccharomyces cerevisiae immobilization on PFA microchannel walls comprised ethanol surface pretreatment, 4 h contacting with 10% APTES aqueous solution, 10 min treatment with 1% glutaraldehyde and 20 min contacting with cells in deionized water. The same protocol enabled also immobilization of Escherichia coli, Pseudomonas putida and Bacillus subtilis cells on PFA surface in high densities. Furthermore, the developed procedure has been proved to be very efficient also for surface immobilization of tested cells on other materials that are used for microreactor fabrication, including glass, polystyrene, poly (methyl methacrylate), polycarbonate, and two olefin-based polymers, namely Zeonor® and Topas®.

  20. Cortical cell and neuron density estimates in one chimpanzee hemisphere.

    Science.gov (United States)

    Collins, Christine E; Turner, Emily C; Sawyer, Eva Kille; Reed, Jamie L; Young, Nicole A; Flaherty, David K; Kaas, Jon H

    2016-01-19

    The density of cells and neurons in the neocortex of many mammals varies across cortical areas and regions. This variability is, perhaps, most pronounced in primates. Nonuniformity in the composition of cortex suggests regions of the cortex have different specializations. Specifically, regions with densely packed neurons contain smaller neurons that are activated by relatively few inputs, thereby preserving information, whereas regions that are less densely packed have larger neurons that have more integrative functions. Here we present the numbers of cells and neurons for 742 discrete locations across the neocortex in a chimpanzee. Using isotropic fractionation and flow fractionation methods for cell and neuron counts, we estimate that neocortex of one hemisphere contains 9.5 billion cells and 3.7 billion neurons. Primary visual cortex occupies 35 cm(2) of surface, 10% of the total, and contains 737 million densely packed neurons, 20% of the total neurons contained within the hemisphere. Other areas of high neuron packing include secondary visual areas, somatosensory cortex, and prefrontal granular cortex. Areas of low levels of neuron packing density include motor and premotor cortex. These values reflect those obtained from more limited samples of cortex in humans and other primates.

  1. Combinatorial Density Functional Theory-Based Screening of Surface Alloys for the Oxygen Reduction Reaction

    DEFF Research Database (Denmark)

    Greeley, Jeffrey Philip; Nørskov, Jens Kehlet

    2009-01-01

    A density functional theory (DFT)-based, combinatorial search for improved oxygen reduction reaction (ORR) catalysts is presented. A descriptor-based approach to estimate the ORR activity of binary surface alloys, wherein alloying occurs only in the surface layer, is described, and rigorous...... for the ORR but, with few exceptions, they are found to be thermodynamically unstable in the acidic environments typical of low-temperature fuel cells. The results suggest that, absent other thermodynamic or kinetic mechanisms to stabilize the alloys, surface alloys are unlikely to serve as useful ORR...

  2. Estimation of Plasma Density by Surface Plasmons for Surface-Wave Plasmas

    Institute of Scientific and Technical Information of China (English)

    CHEN Zhao-Quan; LIU Ming-Hai; LAN Chao-Hui; CHEN Wei; LUO Zhi-Qing; HU Xi-Wei

    2008-01-01

    @@ An estimation method of plasma density based on surface plasmons theory for surface-wave plasmas is proposed. The number of standing-wave is obtained directly from the discharge image, and the propagation constant is calculated with the trim size of the apparatus in this method, then plasma density can be determined with the value of 9.1 × 1017 m-3. Plasma density is measured using a Langmuir probe, the value is 8.1 × 1017 m-3 which is very close to the predicted value of surface plasmons theory. Numerical simulation is used to check the number of standing-wave by the finite-difference time-domain (FDTD) method also. All results are compatible both of theoretical analysis and experimental measurement.

  3. Surface modification for polystyrene colloidal particles with controlled charge densities.

    Science.gov (United States)

    Lee, Jongman; Kwon, Oh-Sun; Shin, Kwanwoo; Song, Ju-Myung; Kim, Joon-Seop; Seo, Young-Soo; Tael, Giyoong; Jon, Sangyong

    2007-11-01

    A significant amount of polystyrene sulfonated acid (PSSA) and poly(styrene-ran-acrylic acid) (PSAA) random copolymer can be adsorbed by dispersion of PS particles via a swelling-quenching process. A THF-water mixed solvent was used in the swelling process and a large amount of pure water was used, to give a low concentration of THF% in quenching process. Our results showed that functional PSSA groups were randomly and tightly adsorbed to the PS particles. When the mol.% of charged segments was increased, the progressive adsorption of PSSA chains to the PS particles leads to an increase in the electrophoretic mobility and zeta-potential of aqueous dispersions. Thus, we were able to obtain well-distributed surface charge density on the PS particles.

  4. Zinc surface complexes on birnessite: A density functional theory study

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, Kideok D.; Refson, Keith; Sposito, Garrison

    2009-01-05

    Biogeochemical cycling of zinc is strongly influenced by sorption on birnessite minerals (layer-type MnO2), which are found in diverse terrestrial and aquatic environments. Zinc has been observed to form both tetrahedral (Zn{sup IV}) and octahedral (Zn{sup VI}) triple-corner-sharing surface complexes (TCS) at Mn(IV) vacancy sites in hexagonal birnessite. The octahedral complex is expected to be similar to that of Zn in the Mn oxide mineral, chalcophanite (ZnMn{sub 3}O{sub 7} {center_dot} 3H{sub 2}O), but the reason for the occurrence of the four-coordinate Zn surface species remains unclear. We address this issue computationally using spin-polarized Density Functional Theory (DFT) to examine the Zn{sub IV}-TCS and Zn{sup VI}-TCS species. Structural parameters obtained by DFT geometry optimization were in excellent agreement with available experimental data on Zn-birnessites. Total energy, magnetic moments, and electron-overlap populations obtained by DFT for isolated Zn{sup IV}-TCS revealed that this species is stable in birnessite without a need for Mn(III) substitution in the octahedral sheet and that it is more effective in reducing undersaturation of surface O at a Mn vacancy than is Zn{sub VI}-TCS. Comparison between geometry-optimized ZnMn{sub 3}O{sub 7} {center_dot} 3H{sub 2}O (chalcophanite) and the hypothetical monohydrate mineral, ZnMn{sub 3}O{sub 7} {center_dot} H{sub 2}O, which contains only tetrahedral Zn, showed that the hydration state of Zn significantly affects birnessite structural stability. Finally, our study also revealed that, relative to their positions in an ideal vacancy-free MnO{sub 2}, Mn nearest to Zn in a TCS surface complex move toward the vacancy by 0.08-0.11 {angstrom}, while surface O bordering the vacancy move away from it by 0.16-0.21 {angstrom}, in agreement with recent X-ray absorption spectroscopic analyses.

  5. Novel negative mass density resonant metamaterial unit cell

    Energy Technology Data Exchange (ETDEWEB)

    Cselyuszka, Norbert, E-mail: cselyu@yahoo.com; Sečujski, Milan, E-mail: secujski@uns.ac.rs; Crnojević-Bengin, Vesna, E-mail: bengin@uns.ac.rs

    2015-01-02

    In this paper a novel resonant unit cell of one-dimensional acoustic metamaterials is presented, which exhibits negative effective mass density. We theoretically analyze the unit cell and develop a closed analytical formula for its effective mass density. Then we proceed to demonstrate left-handed propagation of acoustic waves using the proposed unit cell. Finally, we present its dual-band version, capable of operating at two independent frequencies. - Highlights: • A novel acoustic metamaterial unit cell provides Lorentz-type resonant effective mass density. • Analytical formula for effective mass density is derived. • Acoustic bandstop medium and left-handed metamaterial based on the novel unit cell are presented. • Modified version of the unit cell, operating at two independent frequencies, is proposed.

  6. Phase-sensitive lock-in imaging of surface densities of states

    Science.gov (United States)

    Svec, Martin; Mutombo, Pingo; Shukrinov, Pavel; Dudr, Viktor; Cháb, Vladimír

    2006-01-01

    A new way of imaging the local density of states has been devised through a combination of the constant-height scanning tunnelling microscopy operational mode and lock-in techniques. We have obtained current images simultaneously with real space dynamical conductance maps (d I/d V) for energies around the Fermi level, on the Si(111)-(7 × 7) surface. We reconstructed the normalized dynamical conductance spectra—(d I/d V)/(I/V). Since the (d I/d V)/(I/V) curves are closely related to the local densities of states, we compared their sum over the unit cell to photoelectron spectra and theoretical calculations. We find that the results are in good agreement. Consequently, the extent of localization of surface electronic states at lattice positions was determined.

  7. Surface density effects in quenching: cause or effect?

    CERN Document Server

    Lilly, Simon J

    2016-01-01

    There are very strong observed correlations between the specific star-formation rates (sSFR) of galaxies and their mean surface mass densities, {\\Sigma}, as well as other aspects of their internal structure. These strong correlations have often been taken to indicate that the internal structure of a galaxy must play a major physical role, directly or indirectly, in the control of star-formation. In this paper we show by means of a very simple toy model that these correlations can arise naturally without any such physical role once the observed evolution of the size-mass relation for star-forming galaxies is taken into account. In particular, the model reproduces the sharp threshold in {\\Sigma} between galaxies that are star-forming and those that are quenched, and the evolution of this threshold with redshift. Similarly, it produces iso-quenched-fraction contours in the ${f_Q(m,R_e)}$ plane that are almost exactly parallel to lines of constant {\\Sigma} for centrals and shallower for satellites. It does so wit...

  8. Measuring protoplanetary disk gas surface density profiles with ALMA

    CERN Document Server

    McPartland, Jonathan P Williams Conor

    2016-01-01

    The gas and dust are spatially segregated in protoplanetary disks due to the vertical settling and radial drift of large grains. A fuller accounting of the mass content and distribution in disks therefore requires spectral line observations. We extend the modeling approach presented in Williams & Best (2014) to show that gas surface density profiles can be measured from high fidelity 13CO integrated intensity images. We demonstrate the methodology by fitting ALMA observations of the HD 163296 disk to determine a gas mass, Mgas = 0.048 solar masse, and accretion disk characteristic size Rc = 213au and gradient gamma = 0.39. The same parameters match the C18O 2--1 image and indicates an abundance ratio [13CO]/[C18O] of 700 independent of radius. To test how well this methodology can be applied to future line surveys of smaller, lower mass T Tauri disks, we create a large 13CO 2--1 image library and fit simulated data. For disks with gas masses 3-10 Jupiter masses at 150pc, ALMA observations with a resolutio...

  9. Membrane Tether Formation on a Cell Surface with Reservoir

    Institute of Scientific and Technical Information of China (English)

    JIANG Yu-Qiang; GUO Hong-Lian; LIU Chun-Xiang; LI Zhao-Lin; CHENG Bing-Ying; ZHANG Dao-Zhong; JIA Suo-Tang

    2004-01-01

    @@ We propose a mathematical model to analyse the membrane tether formation process on a cell surface with reservoir. Based on the experimental results, the membrane reservoir density of breast cancer cell was obtained,p = 8.02. The membrane surface viscosity between membrane and environment η is 0.021(pN.s/μm3), and the static force F0 = 5.71 pN.

  10. Flat Central Density Profile and Constant DM Surface Density in Galaxies from Scalar Field Dark Matter

    CERN Document Server

    Robles, Victor H

    2012-01-01

    The scalar field dark matter (SFDM) model proposes that galaxies form by condensation of a scalar field (SF) very early in the universe forming Bose-Einstein Condensates (BEC) drops, i.e., in this model haloes of galaxies are gigantic drops of SF. Here big structures form like in the LCDM model, by hierarchy, thus all the predictions of the LCDM model at big scales are reproduced by SFDM. This model predicts that all galaxies must be very similar and exist for bigger redshifts than in the LCDM model. In this work we show that BEC dark matter haloes fit high-resolution rotation curves of a sample of thirteen low surface brightness galaxies. We compare our fits to those obtained using a Navarro-Frenk-White and Pseudo-Isothermal (PI) profiles and found a better agreement with the SFDM and PI profiles. The mean value of the logarithmic inner density slopes is -0.27 +/- 0.18. As a second result we find a natural way to define the core radius with the advantage of being model-independent. Using this new definition ...

  11. Analysis of cell surface antigens by Surface Plasmon Resonance imaging

    NARCIS (Netherlands)

    Stojanovic, I.; Schasfoort, R.B.M.; Terstappen, L.W.M.M.

    2013-01-01

    Surface Plasmon Resonance (SPR) is most commonly used to measure bio-molecular interactions. SPR is used significantly less frequent for measuring whole cell interactions. Here we introduce a method to measure whole cells label free using the specific binding of cell surface antigens expressed on th

  12. Microvessel and mast cell densities in malignant laryngeal neoplasm

    Directory of Open Access Journals (Sweden)

    Balica Nicolae Constantin

    2014-01-01

    Full Text Available Laryngeal neoplasm contributes to 30-40% of carcinomas of the head and neck. Mast cells are normal connective tissue residents, well represented in the respiratory tract. Experimental evidence suggests that the growth of a tumor beyond a certain size requires angiogenesis, which may also permit metastasis. The aim of this study was to evaluate the correlation between mast cell density, microvascular density, histopathological type and histological grade. Our study included 38 laryngeal carcinomas as follows: adenoid cystic carcinoma (2 cases, malignant papilloma (2 cases and squamous cell carcinoma (34 cases. The combined technique of CD 34-alcian blue safranin (ABS was used to identify microvessel and mast cell density, which was quantified by the hot spot method. A significant correlation was found between both mast cell and microvascular density, and G1/G2 histological grade (p=0.002 and p=0.004, respectively. Squamous cell carcinoma was significantly correlated with mast cell density (p=0.003, but not with microvascular density (p=0.454.

  13. Stability of high cell density brewery fermentations during serial repitching.

    Science.gov (United States)

    Verbelen, Pieter J; Dekoninck, Tinne M L; Van Mulders, Sebastiaan E; Saerens, Sofie M G; Delvaux, Filip; Delvaux, Freddy R

    2009-11-01

    The volumetric productivity of the beer fermentation process can be increased by using a higher pitching rate (i.e. higher inoculum size). However, the decreased yeast net growth observed in these high cell density brewery fermentations can adversely affect the physiological stability throughout subsequent yeast generations. Therefore, different O(2) conditions (wort aeration and yeast preoxygenation) were applied to high cell density fermentation and eight generations of fermentations were evaluated together with conventional fermentations. Freshly propagated high cell density populations adapted faster to the fermentative conditions than normal cell density populations. Preoxygenating the yeast was essential for the yeast physiological and beer flavor compound stability of high cell density fermentations during serial repitching. In contrast, the use of non-preoxygenated yeast resulted in inadequate growth which caused (1) insufficient yield of biomass to repitch all eight generations, (2) a 10% decrease in viability, (3) a moderate increase of yeast age, (4) and a dramatic increase of the unwanted flavor compounds acetaldehyde and total diacetyl during the sequence of fermentations. Therefore, to achieve sustainable high cell density fermentations throughout the economical valuable process of serial repitching, adequate yeast growth is essential.

  14. Surface electrochemical properties of red mud (bauxite residue): zeta potential and surface charge density.

    Science.gov (United States)

    Liu, Yanju; Naidu, Ravendra; Ming, Hui

    2013-03-15

    The surface electrochemical properties of red mud (bauxite residue) from different alumina refineries in Australia and China were studied by electrophoresis and measuring surface charge density obtained from acid/base potentiometric titrations. The electrophoretic properties were measured from zeta potentials obtained in the presence of 0.01 and 0.001 M KNO(3) over a wide pH range (3.5-10) by titration. The isoelectric point (IEP) values were found to vary from 6.35 to 8.70 for the red mud samples. Further investigation into the surface charge density of one sample (RRM) by acid/base potentiometric titration showed similar results for pH(PZC) with pH(IEP) obtained from electrokinetic measurements. The pH(IEP) determined from zeta potential measurements can be used as a characteristic property of red mud. The minerals contained in red mud contributed to the different values of pH(IEP) of samples obtained from different refineries. Different relationships of pH(IEP) with Al/Fe and Al/Si ratios (molar basis) were also found for different red mud samples.

  15. Molecularly engineered surfaces for cell biology: from static to dynamic surfaces.

    Science.gov (United States)

    Gooding, J Justin; Parker, Stephen G; Lu, Yong; Gaus, Katharina

    2014-04-01

    Surfaces with a well-defined presentation of ligands for receptors on the cell membrane can serve as models of the extracellular matrix for studying cell adhesion or as model cell surfaces for exploring cell-cell contacts. Because such surfaces can provide exquisite control over, for example, the density of these ligands or when the ligands are presented to the cell, they provide a very precise strategy for understanding the mechanisms by which cells respond to external adhesive cues. In the present feature article, we present an overview of the basic biology of cell adhesion before discussing surfaces that have a static presentation of immobile ligands. We outline the biological information that such surfaces have given us, before progressing to recently developed switchable surfaces and surfaces that mimic the lipid bilayer, having adhesive ligands that can move around the membrane and be remodeled by the cell. Finally, the feature article closes with some of the biological information that these new types of surfaces could provide.

  16. Mast cell density in cardio-esophageal mucosa.

    Directory of Open Access Journals (Sweden)

    Fatemeh E Mahjoub

    2014-12-01

    Full Text Available Mast cells are related to certain gastrointestinal complaints. Mast cell density has not been studied in cardio-esophageal region to the best of our knowledge. In this study we wanted to obtain an estimate of mast cell density in this region and compare it with mast cell density in antrum. From April 2007 till March 2010, we chose children (<14 years old who underwent upper endoscopy and from whom the taken biopsy was stated to be from lower third of esophagus, but in microscopic examination either cardio- esophageal mucosa or only cardiac mucosa was seen. Mast cells were counted by Giemsa stain at × 1000 magnification in 10 fields. 71 children (<14 years old were included in this study of which, 63.4% (n=45 were female and 36.6% (n=26 were male. The mean age of patients was 7.20 ± 4.21 years (range: 0.2 -14 years. The most common clinical manifestations were recurrent abdominal pain (64.8% and vomiting (23.9% followed by symptoms of gastro-esophageal reflux disorder, poor weight gain, hematemesis and dysphagia. The mean mast cell density in the cardiac mucosa was 33.41 ± 32.75 in 0.25 mm2 (range: 0-155, which was two times of that in antral mucosa. We found a significant but weak positive correlation at the 0.05 level between mast cell density of cardiac mucosa and the antrum. Higher mast cell counts were seen in cardiac mucosa in this study. Significant positive correlation between mast cell density of cardiac mucosa and the antrum could hint to a single underlying etiology for the inflammatory process in gastro- esophageal junction and gastric mucosa.

  17. Theory of optical excitation and relaxation phenomena at semiconductor surfaces: linking density functional and density matrix theory

    Energy Technology Data Exchange (ETDEWEB)

    Buecking, N. [Technische Universitaet Berlin, Institut fuer Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Berlin (Germany); Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany); Scheffler, M. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin (Germany); Kratzer, P. [Universitaet Duisburg-Essen, Fachbereich Physik - Theoretische Physik, Duisburg (Germany); Knorr, A. [Technische Universitaet Berlin, Institut fuer Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Berlin (Germany)

    2007-08-15

    A theory for the description of optical excitation and the subsequent phonon-induced relaxation dynamics of nonequilibrium electrons at semiconductor surfaces is presented. In the first part, the fundamental dynamical equations for electronic occupations and polarisations are derived using density matrix formalism (DMT) for a surface-bulk system including the interaction of electrons with the optical field and electron-phonon interactions. The matrix elements entering these equations are either determined empirically or by density functional theory (DFT) calculations. In the subsequent parts of the paper, the dynamics at two specific semiconductor surfaces are discussed in detail. The electron relaxation dynamics underlying a time-resolved two photon photoemission experiment at an InP surface is investigated in the limit of a parabolic four band model. Moreover, the electron relaxation dynamics at a Si(100) surface is analysed. Here, the coupling parameters and the band structure are obtained from an DFT calculations. (orig.)

  18. Anorexia Reduces GFAP+ Cell Density in the Rat Hippocampus

    Directory of Open Access Journals (Sweden)

    Daniel Reyes-Haro

    2016-01-01

    Full Text Available Anorexia nervosa is an eating disorder observed primarily in young women. The neurobiology of the disorder is unknown but recently magnetic resonance imaging showed a volume reduction of the hippocampus in anorexic patients. Dehydration-induced anorexia (DIA is a murine model that mimics core features of this disorder, including severe weight loss due to voluntary reduction in food intake. The energy supply to the brain is mediated by astrocytes, but whether their density is compromised by anorexia is unknown. Thus, the aim of this study was to estimate GFAP+ cell density in the main regions of the hippocampus (CA1, CA2, CA3, and dentate gyrus in the DIA model. Our results showed that GFAP+ cell density was significantly reduced (~20% in all regions of the hippocampus, except in CA1. Interestingly, DIA significantly reduced the GFAP+ cells/nuclei ratio in CA2 (−23% and dentate gyrus (−48%. The reduction of GFAP+ cell density was in agreement with a lower expression of GFAP protein. Additionally, anorexia increased the expression of the intermediate filaments vimentin and nestin. Accordingly, anorexia increased the number of reactive astrocytes in CA2 and dentate gyrus more than twofold. We conclude that anorexia reduces the hippocampal GFAP+ cell density and increases vimentin and nestin expression.

  19. Anorexia Reduces GFAP+ Cell Density in the Rat Hippocampus

    Science.gov (United States)

    Labrada-Moncada, Francisco Emmanuel; Varman, Durairaj Ragu; Krüger, Janina; Morales, Teresa; Miledi, Ricardo; Martínez-Torres, Ataúlfo

    2016-01-01

    Anorexia nervosa is an eating disorder observed primarily in young women. The neurobiology of the disorder is unknown but recently magnetic resonance imaging showed a volume reduction of the hippocampus in anorexic patients. Dehydration-induced anorexia (DIA) is a murine model that mimics core features of this disorder, including severe weight loss due to voluntary reduction in food intake. The energy supply to the brain is mediated by astrocytes, but whether their density is compromised by anorexia is unknown. Thus, the aim of this study was to estimate GFAP+ cell density in the main regions of the hippocampus (CA1, CA2, CA3, and dentate gyrus) in the DIA model. Our results showed that GFAP+ cell density was significantly reduced (~20%) in all regions of the hippocampus, except in CA1. Interestingly, DIA significantly reduced the GFAP+ cells/nuclei ratio in CA2 (−23%) and dentate gyrus (−48%). The reduction of GFAP+ cell density was in agreement with a lower expression of GFAP protein. Additionally, anorexia increased the expression of the intermediate filaments vimentin and nestin. Accordingly, anorexia increased the number of reactive astrocytes in CA2 and dentate gyrus more than twofold. We conclude that anorexia reduces the hippocampal GFAP+ cell density and increases vimentin and nestin expression. PMID:27579183

  20. Solid Oxide Electrolysis Cells: Degradation at High Current Densities

    DEFF Research Database (Denmark)

    Knibbe, Ruth; Traulsen, Marie Lund; Hauch, Anne;

    2010-01-01

    The degradation of Ni/yttria-stabilized zirconia (YSZ)-based solid oxide electrolysis cells operated at high current densities was studied. The degradation was examined at 850°C, at current densities of −1.0, −1.5, and −2.0 A/cm2, with a 50:50 (H2O:H2) gas supplied to the Ni/YSZ hydrogen electrode...

  1. High power density yeast catalyzed microbial fuel cells

    Science.gov (United States)

    Ganguli, Rahul

    Microbial fuel cells leverage whole cell biocatalysis to convert the energy stored in energy-rich renewable biomolecules such as sugar, directly to electrical energy at high efficiencies. Advantages of the process include ambient temperature operation, operation in natural streams such as wastewater without the need to clean electrodes, minimal balance-of-plant requirements compared to conventional fuel cells, and environmentally friendly operation. These make the technology very attractive as portable power sources and waste-to-energy converters. The principal problem facing the technology is the low power densities compared to other conventional portable power sources such as batteries and traditional fuel cells. In this work we examined the yeast catalyzed microbial fuel cell and developed methods to increase the power density from such fuel cells. A combination of cyclic voltammetry and optical absorption measurements were used to establish significant adsorption of electron mediators by the microbes. Mediator adsorption was demonstrated to be an important limitation in achieving high power densities in yeast-catalyzed microbial fuel cells. Specifically, the power densities are low for the length of time mediator adsorption continues to occur. Once the mediator adsorption stops, the power densities increase. Rotating disk chronoamperometry was used to extract reaction rate information, and a simple kinetic expression was developed for the current observed in the anodic half-cell. Since the rate expression showed that the current was directly related to microbe concentration close to the electrode, methods to increase cell mass attached to the anode was investigated. Electrically biased electrodes were demonstrated to develop biofilm-like layers of the Baker's yeast with a high concentration of cells directly connected to the electrode. The increased cell mass did increase the power density 2 times compared to a non biofilm fuel cell, but the power density

  2. Effect of Random Clustering on Surface Damage Density Estimates

    Energy Technology Data Exchange (ETDEWEB)

    Matthews, M J; Feit, M D

    2007-10-29

    Identification and spatial registration of laser-induced damage relative to incident fluence profiles is often required to characterize the damage properties of laser optics near damage threshold. Of particular interest in inertial confinement laser systems are large aperture beam damage tests (>1cm{sup 2}) where the number of initiated damage sites for {phi}>14J/cm{sup 2} can approach 10{sup 5}-10{sup 6}, requiring automatic microscopy counting to locate and register individual damage sites. However, as was shown for the case of bacteria counting in biology decades ago, random overlapping or 'clumping' prevents accurate counting of Poisson-distributed objects at high densities, and must be accounted for if the underlying statistics are to be understood. In this work we analyze the effect of random clumping on damage initiation density estimates at fluences above damage threshold. The parameter {psi} = a{rho} = {rho}/{rho}{sub 0}, where a = 1/{rho}{sub 0} is the mean damage site area and {rho} is the mean number density, is used to characterize the onset of clumping, and approximations based on a simple model are used to derive an expression for clumped damage density vs. fluence and damage site size. The influence of the uncorrected {rho} vs. {phi} curve on damage initiation probability predictions is also discussed.

  3. Waves in cell monolayer without proliferation: density determines cell velocity and wave celerity

    CERN Document Server

    Tlili, S; Li, B; Cardoso, O; Ladoux, B; Delanoë-Ayari, H; Graner, F

    2016-01-01

    Collective cell migration contributes to morphogenesis, wound healing or tumor metastasis. Culturing epithelial monolayers on a substrate is an in vitro configuration suitable to quantitatively characterize such tissue migration by measuring cell velocity, density and cell-substrate interaction force. Inhibiting cell division, we limit cell density increase and favor steady cell migration, while by using long narrow strips we stabilise the migrating front shape, so that we observe migration over a day or more. In the monolayer bulk, the cell velocity is a function of the cell density, namely it increases as a linear function of the cell radius. At least ten periods of propagating velocity waves are detected with a high signal-to-noise ratio, enabling for their quantitative spatio-temporal analysis. Cell density displays waves, in phase opposition with the velocity, as predicted by mass conservation; similarly, cell-substrate force appear to display small amplitude waves, in phase quadrature with respect to ve...

  4. High Energy Density Regenerative Fuel Cell Systems for Terrestrial Applications

    Science.gov (United States)

    Burke, Kenneth A.

    1999-01-01

    Regenerative Fuel Cell System (RFCS) technology for energy storage has been a NASA power system concept for many years. Compared to battery-based energy storage systems, RFCS has received relatively little attention or resources for development because the energy density and electrical efficiency were not sufficiently attractive relative to advanced battery systems. Even today, RFCS remains at a very low technology readiness level (TRL of about 2 indicating feasibility has been demonstrated). Commercial development of the Proton Exchange Membrane (PEM) fuel cells for automobiles and other terrestrial applications and improvements in lightweight pressure vessel design to reduce weight and improve performance make possible a high energy density RFCS energy storage system. The results from this study of a lightweight RFCS energy storage system for a remotely piloted, solar-powered, high altitude aircraft indicate an energy density up to 790 w-h/kg with electrical efficiency of 53.4% is attainable. Such an energy storage system would allow a solar-powered aircraft to carry hundreds of kilograms of payload and remain in flight indefinitely for use in atmospheric research, earth observation, resource mapping. and telecommunications. Future developments in the areas of hydrogen and oxygen storage, pressure vessel design, higher temperature and higher- pressure fuel cell operation, unitized regenerative fuel cells, and commercial development of fuel cell technology will improve both the energy density and electrical efficiency of the RFCS.

  5. Phonon spectral densities of Cu surfaces: Application to Cu(211)

    Science.gov (United States)

    Mărinică, M.-C.; Raşeev, G.; Smirnov, K. S.

    2001-05-01

    Power phonon spectra of vicinal stepped surfaces of Cu(211) have been calculated using a molecular dynamics method combined with a semiempirical potential. The potential is based on an analytic form of inverse powers proposed by Finnis and Sinclair with the parametrization of Sutton and Chen. One of the four independent parameters of the potential was rescaled to reproduce the bulk phonon spectrum of Cu while retaining other properties of the bulk Cu close to the experimental values. Using this potential, we calculated the power surface phonon spectra, projection of the spectra at the high-symmetry points of surface Brillouin zone (SBZ), and the mean square displacements (MSD's) of atoms of the Cu(211) surface. The calculated projected phonon spectra at Γ¯ and at two new SBZ points (at X¯ and Y¯) compare favorably with experiment and theory when available. The MSD of the Cu(211) surface is also well reproduced and its temperature dependence shows that anharmonicity of the atomic motion becomes important above 200 K.

  6. Programming Surface Chemistry with Engineered Cells.

    Science.gov (United States)

    Zhang, Ruihua; Heyde, Keith C; Scott, Felicia Y; Paek, Sung-Ho; Ruder, Warren C

    2016-09-16

    We have developed synthetic gene networks that enable engineered cells to selectively program surface chemistry. E. coli were engineered to upregulate biotin synthase, and therefore biotin synthesis, upon biochemical induction. Additionally, two different functionalized surfaces were developed that utilized binding between biotin and streptavidin to regulate enzyme assembly on programmable surfaces. When combined, the interactions between engineered cells and surfaces demonstrated that synthetic biology can be used to engineer cells that selectively control and modify molecular assembly by exploiting surface chemistry. Our system is highly modular and has the potential to influence fields ranging from tissue engineering to drug development and delivery.

  7. Study on Surface Properties for Non-polar Fluids with Density Functional Theory

    Institute of Scientific and Technical Information of China (English)

    吴畏; 陆九芳; 付东; 刘金晨; 李以圭

    2004-01-01

    The density functional theory, simplified by the local density approximation and mean-field approximation, is applied to study the surface properties of pure non-polar fluids. A reasonable long rang correction is adopted to avoid the truncation of the potential. The perturbation theory is applied to establish the equation for the phase equilibrium, in which the hard-core chain fluid is as the reference fluid and the Yukawa potential is used as the perturbation term. Three parameters, elk, d and ms, are regressed from the vapor-liquid equilibria, and the surface properties, including density profile, surface tension and local surface tension profile are predicted with these parameters.

  8. Effect of Density and Surface Roughness on Optical Properties of Silicon Carbide Optical Components

    Institute of Scientific and Technical Information of China (English)

    LIU Gui-Ling; HUANG Zheng-Ren; LIU Xue-Jian; JIANG Dong-Liang

    2008-01-01

    @@ The effect of density and surface roughness on the optical properties of silicon carbide optical components is investigated.The density is the major factor of the total reflectance while the surface roughness is the major factor of the diffuse reflectance.The specular reflectance of silicon carbide optical components can be improved by increasing the density and decreasing the surface roughness,in the form of reducing bulk absorption and surface-related scattering,respectively.The contribution of the surface roughness to the specular reflectance is much greater than that of the density.When the rms surface roughness decreases to 2.228nm,the specular reflectance decreases to less than 0.7% accordingly.

  9. The B-ring's surface mass density from hidden density waves: Less than meets the eye?

    CERN Document Server

    Hedman, M M

    2016-01-01

    Saturn's B ring is the most opaque ring in our solar system, but many of its fundamental parameters, including its total mass, are not well constrained. Spiral density waves generated by mean-motion resonances with Saturn's moons provide some of the best constraints on the rings' mass density, but detecting and quantifying such waves in the B ring has been challenging because of this ring's high opacity and abundant fine-scale structure. Using a wavelet-based analyses of 17 occultations of the star gamma Crucis observed by the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft, we are able to examine five density waves in the B ring. Two of these waves are generated by the Janus 2:1 and Mimas 5:2 Inner Lindblad Resonances at 96,427 km and 101,311 km from Saturn's center, respectively. Both of these waves can be detected in individual occultation profiles, but the multi-profile wavelet analysis reveals unexpected variations in the pattern speed of the Janus 2:1 wave that might arise...

  10. Engineered microtopographies and surface chemistries direct cell attachment and function

    Science.gov (United States)

    Magin, Chelsea Marie

    Harrison, in 1914, first recognized that cells respond to physicochemical cues such as substratum topography when he observed that fibroblasts elongated while cultured on spider silk. Recently, techniques developed in the micro-electronics industry have been used to create molds for producing microscaled topographies with various shapes and spatial arrangements. Although these patterning techniques are well-established, very little is known about the mechanisms underlying cell sensing and response to microtopographies. In this work cellular micro-environments with varying surface topographies and chemistries were evaluated with marine organisms and mammalian cells to investigate cellular sensing and response. Biofouling---the accumulation of micro-organisms, plants, and animals on submerged surfaces---is an environmental and economic concern. Engineered topographies, replicated in polydimethylsiloxane elastomer (PDMSe) and functionalized poly(ethylene glycol)-dimethacrylate (PEGDMA) hydrogels, were evaluated for inhibition of marine fouling organism attachment. Microtopographies replicated in PDMSe inhibited attachment of the marine bacterium, Cobetia marina up to 99% versus smooth. The average normalized attachment densities of cells of C. marina and zoospores of the green algae Ulva on PDMSe topographies scaled inversely with the Engineered Roughness Index (ERIII), a representation of surface energy. Attachment densities of Ulva from four assays and C. marina from two growth phases to PDMSe surfaces scaled inversely with one equation: ERI II multiplied by the Reynolds number of the organism (Re) (R 2 = 0.77). The same microtopographies created in PDMSe reduced the initial attachment density and attachment strength of cells of the diatoms Navicula incerta and Seminavis robusta compared to smooth PDMSe. The average normalized attachment density of Navicula after exposure to shear stress (48 Pa) was correlated with the contact area between the diatom and a

  11. Density functional theory in surface chemistry and catalysis

    DEFF Research Database (Denmark)

    Nørskov, Jens Kehlet; Abild-Pedersen, Frank; Studt, Felix

    2011-01-01

    Recent advances in the understanding of reactivity trends for chemistry at transition-metal surfaces have enabled in silico design of heterogeneous catalysts in a few cases. The current status of the field is discussed with an emphasis on the role of coupling theory and experiment and future...

  12. Density Functional Theory in Surface Chemistry and Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Norskov, Jens

    2011-05-19

    Recent advances in the understanding of reactivity trends for chemistry at transition metal surfaces have enabled in silico design of heterogeneous catalysts in a few cases. Current status of the field is discussed with an emphasis on the role of coupling between theory and experiment and future challenges.

  13. Density functional theory study of nitrogen atoms and molecules interacting with Fe(1 1 1) surfaces

    Science.gov (United States)

    Nosir, M. A.; Martin-Gondre, L.; Bocan, G. A.; Díez Muiño, R.

    2016-09-01

    We present Density functional theory (DFT) calculations for the investigation of the structural relaxation of Fe(1 1 1), as well as for the study of the interaction of nitrogen atoms and molecules with this surface. We perform spin polarized DFT calculations using VASP (Vienna Ab-initio Simulation Package) code. We use the supercell approach and up to 19 slab layers for the relaxation of the Fe(1 1 1) surface. We find a contraction of the first two interlayer distances with a relative value of Δ12 = - 7.8 % and Δ23 = - 21.7 % with respect to the bulk reference. The third interlayer distance is however expanded with a relative change of Δ34 = 9.7 % . Early experimental studies of the surface relaxation using Low Energy Electron Diffraction (LEED) and Medium Energy Ion Scattering (MEIS) showed contradictory results, even on the relaxation general trend. Our current theoretical results support the LEED conclusions and are consistent qualitatively with other recent theoretical calculations. In addition, we study the interaction energy of nitrogen atoms and molecules on the Fe(1 1 1) surface. The nitrogen atoms are adsorbed in the hollow site of the unit cell, with an adsorption energy consistent with the one found in previous studies. In addition, we find the three molecularly adsorbed states that are observed experimentally. Two of them correspond to the adsorbed molecule oriented normal to the surface and a third one corresponds to the molecule adsorbed parallel to the surface. We conclude that our results are accurate enough to be used to build a full six-dimensional potential energy surface for the N2 system.

  14. Interaction of low density lipoproteins with rat liver cells

    NARCIS (Netherlands)

    L. Harkes (Leendert)

    1985-01-01

    textabstractThe most marked conclusion is the establishment of the important role of non-parenchymal cells in the catabolism of the low density lipoproteins by the rat liver. Because the liver is responsible for 70-80% of the removal of LDL from blood this conclusion can be extended to total LDL tur

  15. Cell attachment on ion implanted titanium surface

    Directory of Open Access Journals (Sweden)

    P.S. Sreejith

    2008-12-01

    Full Text Available Purpose: Of outmost importance for the successful use of an implant is a good adhesion of the surrounding tissue to the biomaterial. In addition to the surface composition of the implant, the surface topography also influences the properties of the adherent cells. In the present investigation, ion implanted and untreated surfaces were compared for cell adhesion and spreading.Design/methodology/approach: The surface topography of the surfaces were analyzed using AFM and the cell studies with SEM.Findings: The results of our present investigation is indicative of the fact that ion implanted titanium surface offer better cell binding affinity compared to untreated/polished surface.Practical implications: Success of non-biodegradable implants will first and foremost depend on biocompatibility, followed by the capacity of the surface topography of the implants to evince desired cell matrix, surface cell matrix interactions. In the present study, the cell growth on ion implanted Ti material is analyzed and discussed.Originality/value: In this paper, we have utilized ion implantation technique, which will produce nano-texturing of the surface without producing any detrimental effects to both the dimensions and properties of the implants.

  16. Density functional theory study of the effects of alloying additions on sulfur adsorption on nickel surfaces

    Science.gov (United States)

    Malyi, Oleksandr I.; Chen, Zhong; Kulish, Vadym V.; Bai, Kewu; Wu, Ping

    2013-01-01

    Reactions of hydrogen sulfide (H2S) with Nickel/Ytrria-doped zirconia (Ni/YDZ) anode materials might cause degradation of the performance of solid oxide fuel cells when S containing fuels are used. In this paper, we employ density functional theory to investigate S adsorption on metal (M)-doped and undoped Ni(0 0 1) and Ni(1 1 1) surfaces. Based on the performed calculations, we analyze the effects of 12 alloying additions (Ag, Au, Al, Bi, Cd, Co, Cu, Fe, Sn, Sb, V, and Zn) on the temperature of transition between clean (S atoms do not adsorb on the surfaces) and contaminated (S atoms can adsorb on the surfaces spontaneously) M-doped Ni surfaces for different concentrations of H2S in the fuel. Predicted results are consistent with many experimental studies relevant to S poisoning of both Ni/YDZ and M-doped Ni/YDZ anode materials. This study is important to understand S poisoning phenomena and to develop new S tolerant anode materials.

  17. Functions of proteoglycans at the cell surface

    DEFF Research Database (Denmark)

    Höök, M; Woods, A; Johansson, S;

    1986-01-01

    Proteoglycans (primarily heparan sulphate proteoglycans) are found at the surface of most adherent eukaryotic cells. Earlier studies suggest that these molecules can be associated with the cell surface principally by two different mechanisms. Proteoglycans may occur as membrane......-intercalated glycoproteins, where the core protein of the proteoglycan is anchored in the lipid interior of the plasma membrane, or they may be bound via the polysaccharide components of the molecule to specific anchoring proteins present at the cell surface. A number of functions have been proposed for cell surface......-associated proteoglycans, including: regulation of cell-substrate adhesion; regulation of cell proliferation; participation in the binding and uptake of extracellular components; and participation in the regulation of extracellular matrix formation. Evidence is discussed suggesting that the cell-associated heparan...

  18. Human endothelial progenitor cells internalize high-density lipoprotein.

    Science.gov (United States)

    Srisen, Kaemisa; Röhrl, Clemens; Meisslitzer-Ruppitsch, Claudia; Ranftler, Carmen; Ellinger, Adolf; Pavelka, Margit; Neumüller, Josef

    2013-01-01

    Endothelial progenitor cells (EPCs) originate either directly from hematopoietic stem cells or from a subpopulation of monocytes. Controversial views about intracellular lipid traffic prompted us to analyze the uptake of human high density lipoprotein (HDL), and HDL-cholesterol in human monocytic EPCs. Fluorescence and electron microscopy were used to investigate distribution and intracellular trafficking of HDL and its associated cholesterol using fluorescent surrogates (bodipy-cholesterol and bodipy-cholesteryl oleate), cytochemical labels and fluorochromes including horseradish peroxidase and Alexa Fluor® 568. Uptake and intracellular transport of HDL were demonstrated after internalization periods from 0.5 to 4 hours. In case of HDL-Alexa Fluor® 568, bodipy-cholesterol and bodipy-cholesteryl oleate, a photooxidation method was carried out. HDL-specific reaction products were present in invaginations of the plasma membrane at each time of treatment within endocytic vesicles, in multivesicular bodies and at longer periods of uptake, also in lysosomes. Some HDL-positive endosomes were arranged in form of "strings of pearl"- like structures. HDL-positive multivesicular bodies exhibited intensive staining of limiting and vesicular membranes. Multivesicular bodies of HDL-Alexa Fluor® 568-treated EPCs showed multilamellar intra-vacuolar membranes. At all periods of treatment, labeled endocytic vesicles and organelles were apparent close to the cell surface and in perinuclear areas around the Golgi apparatus. No HDL-related particles could be demonstrated close to its cisterns. Electron tomographic reconstructions showed an accumulation of HDL-containing endosomes close to the trans-Golgi-network. HDL-derived bodipy-cholesterol was localized in endosomal vesicles, multivesicular bodies, lysosomes and in many of the stacked Golgi cisternae and the trans-Golgi-network Internalized HDL-derived bodipy-cholesteryl oleate was channeled into the lysosomal intraellular

  19. Human endothelial progenitor cells internalize high-density lipoprotein.

    Directory of Open Access Journals (Sweden)

    Kaemisa Srisen

    Full Text Available Endothelial progenitor cells (EPCs originate either directly from hematopoietic stem cells or from a subpopulation of monocytes. Controversial views about intracellular lipid traffic prompted us to analyze the uptake of human high density lipoprotein (HDL, and HDL-cholesterol in human monocytic EPCs. Fluorescence and electron microscopy were used to investigate distribution and intracellular trafficking of HDL and its associated cholesterol using fluorescent surrogates (bodipy-cholesterol and bodipy-cholesteryl oleate, cytochemical labels and fluorochromes including horseradish peroxidase and Alexa Fluor® 568. Uptake and intracellular transport of HDL were demonstrated after internalization periods from 0.5 to 4 hours. In case of HDL-Alexa Fluor® 568, bodipy-cholesterol and bodipy-cholesteryl oleate, a photooxidation method was carried out. HDL-specific reaction products were present in invaginations of the plasma membrane at each time of treatment within endocytic vesicles, in multivesicular bodies and at longer periods of uptake, also in lysosomes. Some HDL-positive endosomes were arranged in form of "strings of pearl"- like structures. HDL-positive multivesicular bodies exhibited intensive staining of limiting and vesicular membranes. Multivesicular bodies of HDL-Alexa Fluor® 568-treated EPCs showed multilamellar intra-vacuolar membranes. At all periods of treatment, labeled endocytic vesicles and organelles were apparent close to the cell surface and in perinuclear areas around the Golgi apparatus. No HDL-related particles could be demonstrated close to its cisterns. Electron tomographic reconstructions showed an accumulation of HDL-containing endosomes close to the trans-Golgi-network. HDL-derived bodipy-cholesterol was localized in endosomal vesicles, multivesicular bodies, lysosomes and in many of the stacked Golgi cisternae and the trans-Golgi-network Internalized HDL-derived bodipy-cholesteryl oleate was channeled into the lysosomal

  20. Temporal evolution of the snow density near the surface at Dome C on Antarctica Plateau

    Science.gov (United States)

    Champollion, N.; Picard, G.; Arnaud, L.; Macelloni, G.; Remy, F.

    2014-12-01

    Snow density near the surface, i.e. the first 5 - 10 first centimeters, is essential for surface mass balance retrieval from satellite or stakes, thermal diffusion for surface energy budget, firn densification for ice-core interpretation and air / snow chemistry exchange on ice sheets. It is related to the local meteorological conditions such as precipitation, wind and temperature (metamorphism). A long term temporal and spatial evolution of the snow density near the surface on ice sheets could be use to monitor climate evolution. Passive and active microwave offer the possibility to study recent climate evolution with respectively 30 and 20 years of measurements, a very good temporal repeatability and a large spatial coverage. The aim of this paper is (1) to derive the snow density near the surface, called "surface snow density", from AMSR-E passive microwave observations and ENVISAT radar altimetry measurements, and (2) to study the temporal evolution of this density. Surface snow density is also jointly estimated from passive microwave observations and radar altimetry measurements by two independent methods. For both methods, the estimation of density is based on the surface reflection of electromagnetic wave in the microwave domain, which mainly depends on dielectric contrast between air and snow. For passive microwave observations, the polarization ratio is derived in order to be most sensitive to snow density variations near the surface. Then, the Dense Media Radiative Transfer theory is used for modeling and quantify the relationship between polarization ratio and surface snow density. For radar altimetry measurements, the total microwave backscatter coefficient is used because it depends on surface snow density and roughness. Validation of the surface snow density estimations is performed at Dome C on the Antarctica Plateau from in situ measurements of snow density. Uncertainties about the two retrieval methods (from AMSR-E and ENVISAT observations) are

  1. Controlled surface chemistries and quantitative cell response

    Science.gov (United States)

    Plant, Anne L.

    2002-03-01

    Living cells experience a large number of signaling cues from their extracellular matrix. As a result of these inputs, a variety of intracellular signaling pathways are apparently initiated simultaneously. The vast array of alternative responses that result from the integration of these inputs suggests that it may be reasonable to look for cellular response not as an 'on' or 'off' condition but as a distribution of responses. A difficult challenge is to determine whether variations in responses from individual cells arise from the complexity of intracellular signals or are due to variations in the cell culture environment. By controlling surface chemistry so that every cell 'sees' the same chemical and physical environment, we can begin to assess how the distribution of cell response is affected strictly by changes in the chemistry of the cell culture surface. Using the gene for green fluorescent protein linked to the gene for the promoter of the extracellular matrix protein, tenascin, we can easily probe the end product in a signaling pathway that is purported to be linked to surface protein chemistry and to cell shape. Cell response to well-controlled, well-characterized, and highly reproducible surfaces prepared using soft lithography techniques are compared with more conventional ways of preparing extracellular matrix proteins for cell culture. Using fluorescence microscopy and image analysis of populations of cells on these surfaces, we probe quantitatively the relationship between surface chemistry, cell shape and variations in gene expression endpoint.

  2. Lower Salinomycin Concentration Increases Apoptotic Detachment in High-Density Cancer Cells

    Directory of Open Access Journals (Sweden)

    Sungpil Yoon

    2012-10-01

    Full Text Available The present study identified a novel salinomycin (Sal sensitization mechanism in cancer. We tested whether Sal reduced proliferation in a high-density population by counting attached cell numbers after Sal treatment. Sal reduced proliferation in high-density cell populations. Longer exposure to Sal further reduced proliferation. Sal concentrations of 0.1 and 5 μM had similar sensitization effects, suggesting that Sal toxicity was minimal with longer exposure to a high-density cell population. The results suggest that Sal can be applied at a relatively low concentration for a longer time to overcome drug-resistant solid tumors. The 0.5 μM Sal treatment resulted in fewer attached cells than that of the 5 μM Sal treatment with a longer exposure. The lower Sal concentration mainly increased the number of easily detachable cells on the surface. In particular, 0.5 μM Sal increased cellular detachment of newly produced daughter cells. The easily-detachable cells were undergoing apoptosis. It seems that the 0.5 μM Sal treatment also increased cellular toxicity. These novel findings may contribute to the development of Sal-based therapy for patients with drug-resistant cancer or a high-density solid tumor.

  3. The cell surface of Trypanosoma cruzi

    Directory of Open Access Journals (Sweden)

    Wanderley de Souza

    1984-01-01

    Full Text Available The cell surface of trypanosomatids is formed by the plasma membrane and a layer of sub-pellicular microtubules which are connected to the plasma membrane. The plasma membrane is composed by proteins, lipids and carbohydrates which form the glycocalix. In this paper we will review briefly aspects related to the organization of the cell surface of Trypanosoma cruzi.

  4. HI observations of low surface brightness galaxies : Probing low-density galaxies

    NARCIS (Netherlands)

    deBlok, WJG; McGaugh, SS; vanderHulst, JM

    1996-01-01

    We present Very Large Array (VLA) and Westerbork Synthesis Radio Telescope (WSRT) 21-cm HI observations of 19 late-type low surface brightness (LSB) galaxies. Our main findings are that these galaxies, as well as having low surface brightnesses, have low HI surface densities, about a factor of simil

  5. Attachment of human primary osteoblast cells to modified polyethylene surfaces.

    Science.gov (United States)

    Poulsson, Alexandra H C; Mitchell, Stephen A; Davidson, Marcus R; Johnstone, Alan J; Emmison, Neil; Bradley, Robert H

    2009-04-09

    Ultra-high-molecular-weight polyethylene (UHMWPE) has a long history of use in medical devices, primarily for articulating surfaces due to its inherent low surface energy which limits tissue integration. To widen the applications of UHMWPE, the surface energy can be increased. The increase in surface energy would improve the adsorption of proteins and attachment of cells to allow tissue integration, thereby allowing UHMWPE to potentially be used for a wider range of implants. The attachment and function of human primary osteoblast-like (HOB) cells to surfaces of UHMWPE with various levels of incorporated surface oxygen have been investigated. The surface modification of the UHMWPE was produced by exposure to a UV/ozone treatment. The resulting surface chemistry was studied using X-ray photoelectron spectroscopy (XPS), and the topography and surface structure were probed by atomic force microscopy (AFM) and scanning electron microscopy (SEM), which showed an increase in surface oxygen from 11 to 26 atom % with no significant change to the surface topography. The absolute root mean square roughness of both untreated and UV/ozone-treated surfaces was within 350-450 nm, and the water contact angles decreased with increasing oxygen incorporation, i.e., showing an increase in surface hydrophilicity. Cell attachment and functionality were assessed over a 21 day period for each cell-surface combination studied; these were performed using SEM and the alamarBlue assay to study cell attachment and proliferation and energy-dispersive X-ray (EDX) analysis to confirm extracellular mineral deposits, and total protein assay to examine the intra- and extracellular protein expressed by the cells. HOB cells cultured for 21 days on the modified UHMWPE surfaces with 19 and 26 atom % oxygen incorporated showed significantly higher cell densities compared to cells cultured on tissue culture polystyrene (TCPS) from day 3 onward. This indicated that the cells attached and proliferated more

  6. Hot-electron-assisted femtochemistry at surfaces: A time-dependent density functional theory approach

    DEFF Research Database (Denmark)

    Gavnholt, Jeppe; Rubio, Angel; Olsen, Thomas;

    2009-01-01

    Using time-evolution time-dependent density functional theory (TDDFT) within the adiabatic local-density approximation, we study the interactions between single electrons and molecular resonances at surfaces. Our system is a nitrogen molecule adsorbed on a ruthenium surface. The surface is modeled...... resonance and the lowering of the resonance energy due to an image charge effect. Finally we apply the TDDFT procedure to only consider the decay of molecular excitations and find that it agrees quite well with the width of the projected density of Kohn-Sham states....

  7. Conventional and acoustic surface plasmons on noble metal surfaces: a time-dependent density functional theory study

    DEFF Research Database (Denmark)

    Yan, Jun; Jacobsen, Karsten W.; Thygesen, Kristian S.

    2012-01-01

    First-principles calculations of the conventional and acoustic surface plasmons (CSPs and ASPs) on the (111) surfaces of Cu, Ag, and Au are presented. The effect of s-d interband transitions on both types of plasmons is investigated by comparing results from the local density approximation...

  8. Measuring density and compressibility of white blood cells and prostate cancer cells by microchannel acoustophoresis

    DEFF Research Database (Denmark)

    Barnkob, Rune; Augustsson, Per; Magnusson, Cecilia

    2011-01-01

    to determine the density and compressibility of individual cells enables the prediction and alteration of the separation outcome for a given cell mixture. We apply the method on white blood cells (WBCs) and DU145 prostate cancer cells (DUCs) aiming to improve isolation of circulating tumor cells from blood......We present a novel method for the determination of density and compressibility of individual particles and cells undergoing microchannel acoustophoresis in an arbitrary 2D acoustic field. Our method is a critical advancement within acoustophoretic separation of biological cells, as the ability......, an emerging tool in the monitoring and characterizing of metastatic cancer....

  9. Optical excitation and electron relaxation dynamics at semiconductor surfaces: a combined approach of density functional and density matrix theory applied to the silicon (001) surface

    Energy Technology Data Exchange (ETDEWEB)

    Buecking, N.

    2007-11-05

    In this work a new theoretical formalism is introduced in order to simulate the phononinduced relaxation of a non-equilibrium distribution to equilibrium at a semiconductor surface numerically. The non-equilibrium distribution is effected by an optical excitation. The approach in this thesis is to link two conventional, but approved methods to a new, more global description: while semiconductor surfaces can be investigated accurately by density-functional theory, the dynamical processes in semiconductor heterostructures are successfully described by density matrix theory. In this work, the parameters for density-matrix theory are determined from the results of density-functional calculations. This work is organized in two parts. In Part I, the general fundamentals of the theory are elaborated, covering the fundamentals of canonical quantizations as well as the theory of density-functional and density-matrix theory in 2{sup nd} order Born approximation. While the formalism of density functional theory for structure investigation has been established for a long time and many different codes exist, the requirements for density matrix formalism concerning the geometry and the number of implemented bands exceed the usual possibilities of the existing code in this field. A special attention is therefore attributed to the development of extensions to existing formulations of this theory, where geometrical and fundamental symmetries of the structure and the equations are used. In Part II, the newly developed formalism is applied to a silicon (001)surface in a 2 x 1 reconstruction. As first step, density-functional calculations using the LDA functional are completed, from which the Kohn-Sham-wave functions and eigenvalues are used to calculate interaction matrix elements for the electron-phonon-coupling an the optical excitation. These matrix elements are determined for the optical transitions from valence to conduction bands and for electron-phonon processes inside the

  10. Cell-surface remodelling during mammalian erythropoiesis.

    Science.gov (United States)

    Wraith, D C; Chesterton, C J

    1982-10-15

    Current evidence suggests that the major cell-surface modification occurring during mammalian erythropoiesis could be generated by two separate mechanisms: either selective loss of membrane proteins during enucleation or endocytosis at the subsequent reticulocyte and erythrocyte stages. The former idea was tested by collecting developing rabbit erythroid cells before and after the enucleation step and comparing their cell-surface protein composition via radiolabelling and electrophoresis. Few changes were observed. Our data thus lend support to the endocytosis mechanism.

  11. Nanostructured thin solid oxide fuel cells with high power density.

    Science.gov (United States)

    Ignatiev, Alex; Chen, Xin; Wu, Naijuan; Lu, Zigui; Smith, Laverne

    2008-10-28

    Nanostructured thin film solid oxide fuel cells (SOFC) have been developed for reduced temperature operation, with high power density, and to be self reforming. A thin film electrolyte (1-2 microm thickness), e.g., yttria-stabilized zirconia (YSZ), is deposited on a nickel foil substrate. The electrolyte thin film is polycrystalline when deposited on a polycrystalline nickel foil substrate, and is (100) textured when deposited on an atomically textured nickel foil substrate. The Ni foil substrate is then converted into a porous SOFC anode by photolithographic patterning and etching to develop porosity. A composite La(0.5)Sr(0.5)CoO(3) cathode is then deposited on the thin film electrolyte. The resultant thin film hetero structure fuel cells have operated at a significantly reduced temperature: as low as 470 degrees C, with a maximum power density of 140 mW cm(-2) at 575 degrees C, and an efficiency of >50%. This drastic reduction in operating temperature for an SOFC now also allows for the use of hydrocarbon fuels without the need for a separate reformer as the nickel anode effectively dissociates hydrocarbons within this temperature range. These nanostructured fuel cells show excellent potential for high power density, small volume, high efficiency fuel cells for power generation applications.

  12. Tissue non-specific alkaline phosphatase production by human dental pulp stromal cells is enhanced by high density cell culture.

    Science.gov (United States)

    Tomlinson, Matthew J; Dennis, Caitriona; Yang, Xuebin B; Kirkham, Jennifer

    2015-08-01

    The cell surface hydrolase tissue non-specific alkaline phosphatase (TNAP) (also known as MSCA-1) is used to identify a sub-population of bone marrow stromal cells (BMSCs) with high mineralising potential and is found on subsets of cells within the dental pulp. We aim to determine whether TNAP is co-expressed by human dental pulp stromal cells (hDPSCs) alongside a range of BMSC markers, whether this is an active form of the enzyme and the effects of culture duration and cell density on its expression. Cells from primary dental pulp and culture expanded hDPSCs expressed TNAP. Subsequent analyses revealed persistent TNAP expression and co-expression with BMSC markers such as CD73 and CD90. Flow cytometry and biochemical assays showed that increased culture durations and cell densities enhanced TNAP expression by hDPSCs. Arresting the hDPSC cell cycle also increased TNAP expression. These data confirm that TNAP is co-expressed by hDPSCs together with other BMSC markers and show that cell density affects TNAP expression levels. We conclude that TNAP is a potentially useful marker for hDPSC selection especially for uses in mineralised tissue regenerative therapies.

  13. Monte Carlo Simulations of Density Profiles for Hard-Sphere Chain Fluids Confined Between Surfaces

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Covering a wide range of bulk densities, density profiles for hard-sphere chain fluids (HSCFs) with chain length of 3,4,8,20,32 and 64 confined between two surfaces were obtained by Monte Carlo simulations using extended continuum configurational-bias (ECCB) method. It is shown that the enrichment of beads near surfaces is happened at high densities due to the bulk packing effect, on the contrary, the depletion is revealed at low densities owing to the configurational entropic contribution. Comparisons with those calculated by density functional theory presented by Cai et al. indicate that the agreement between simulations and predictions is good. Compressibility factors of bulk HSCFs calculated using volume fractions at surfaces were also used to test the reliability of various equations of state of HSCFs by different authors.

  14. Study of Fusion Dynamics Using Skyrme Energy Density Formalism with Different Surface Corrections

    Institute of Scientific and Technical Information of China (English)

    Ishwar Dutt; Narinder K. Dhiman

    2010-01-01

    @@ Within the framework of Skyrme energy density formalism, we investigate the role of surface corrections on the fusion of colliding nuclei. The coefficient of surface correction is varied between 1/36 and 4/36, and its impact is studied on about 180 reactions. The detailed investigations indicate a linear relationship between the fusion barrier heights and strength of the surface corrections. Our analysis of the fusion barriers advocate the strength of surface correction of 1/36.

  15. Nanostructuring of Solar Cell Surfaces

    DEFF Research Database (Denmark)

    Davidsen, Rasmus Schmidt; Schmidt, Michael Stenbæk

    Solar energy is by far the most abundant renewable energy source available, but the levelized cost of solar energy is still not competitive with that of fossil fuels. Therefore there is a need to improve the power conversion effciency of solar cells without adding to the production cost. The main...... objective of this PhD thesis is to develop nanostructured silicon (Si) solar cells with higher power conversion efficiency using only scalable and cost-efficient production methods. The nanostructures, known as 'black silicon', are fabricated by single-step, maskless reactive ion etching and used as front...... and characterized for comparison. Power conversion eciency of 16.5% was obtained for this batch of RIE-textured Si solar cells. The eciency of the KOH-textured reference cell was 17.8%. Quantum Efficiency measurements and carrier loss analysis show that the lower eciency of the RIE-textured cells is primarily due...

  16. Density-functional calculation of van der Waals forces for free-electron-like surfaces

    DEFF Research Database (Denmark)

    Hult, E.; Hyldgaard, P.; Rossmeisl, Jan;

    2001-01-01

    A recently proposed general density functional for asymptotic van der Waals forces is used to calculate van der Waals coefficients and reference-plane positions for realistic low-indexed Al surfaces. Results are given for a number of atoms and molecules outside the surfaces, as well as for the in......A recently proposed general density functional for asymptotic van der Waals forces is used to calculate van der Waals coefficients and reference-plane positions for realistic low-indexed Al surfaces. Results are given for a number of atoms and molecules outside the surfaces, as well...... as for the interaction between the surfaces themselves. The densities and static image-plane positions that are needed as input in the van der Waals functional are calculated self-consistently within density-functional theory using the generalized-gradient approximation, pseudopotentials, and plane waves. This study...... shows that the van der Waals density functional is applicable to realistic surfaces. The need for physically correct surface models, especially for open surfaces, is also illustrated. Finally the parameters for the anisotropic interaction of O-2 with Al are calculated....

  17. Sensitivity of the Meridional Overturning Circulation to the Pattern of the Surface Density Flux

    Science.gov (United States)

    2010-09-01

    a better prognosis of anthropogenic climate change . Figure 1. Classical representation of the global thermohaline circulation and oceanic...modeling efforts and long-term strategy related to climate change . 15. NUMBER OF PAGES 105 14. SUBJECT TERMS Meridional Overturning Circulation ... Thermohaline Circulation , Thermocline, Residual-Mean Theory, Air-Sea Fluxes, Surface Density Flux , Mixed-Layer Density, Water-mass Transformation

  18. A Density Functional Study of Atomic Carbon Adsorption on δ-Pu(111)Surface

    Institute of Scientific and Technical Information of China (English)

    WEI Hong-Yuan; XIONG Xiao-Ling; SONG Hong-Tao; LUO Shun-Zhong

    2010-01-01

    @@ Adsorption of atomic carbon on δ-Pu(111)surface is investigated systematically using density functional theory with RPBE functional.The adsorption energies,adsorption structures,Mulliken population,work functions,layer and projected density of states are calculated in wide ranges of coverage,which have never been studied before as far as we know.

  19. Cell behaviour on chemically microstructured surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Magnani, Agnese; Priamo, Alfredo; Pasqui, Daniela; Barbucci, Rolando

    2003-03-03

    Micropatterned surfaces with different chemical topographies were synthesised in order to investigate the influence of surface chemistry and topography on cell behaviour. The microstructured materials were synthesised by photoimmobilising natural Hyaluronan (Hyal) and its sulphated derivative (HyalS), both adequately functionalised with a photorective moiety, on glass substrates. Four different grating patterns (10, 25, 50 and 100 {mu}m) were used to pattern the hyaluronan. The micropatterned samples were analysed by Secondary Ions Mass Spectrometry, Scanning Electron Microscopy (SEM) and Atomic Force Microscopy to investigate the chemistry and the topography of the surfaces. The spectroscopic and microscopic analysis of the microstructured surfaces revealed that the photoimmobilisation process was successful, demonstrating that the photomask patterns were well reproduced on the sample surface. The influence of chemical topographies on the cell behaviour was then analysed. Human and 3T3 fibroblasts, bovine aortic and human (HGTFN line) endothelial cells were used and their behaviour on the micropatterned surfaces was analysed in terms of adhesion, proliferation, locomotion and orientation. Both chemical and topographical controls were found to be important for cell guidance. By decreasing the stripe dimensions, a more fusiform shape of cell was observed. At the same time, the cell locomotion and orientation parallel to the structure increased. However, differences in cell behaviour were detected according to both cell type and micropattern dimensions.

  20. Consistent projection methods for variable density incompressible Navier-Stokes equations with continuous surface forces on a rectangular collocated mesh

    Science.gov (United States)

    Ni, Ming-Jiu

    2009-10-01

    Two consistent projection methods of second-order temporal and spatial accuracy have been developed on a rectangular collocated mesh for variable density Navier-Stokes equations with a continuous surface force. Instead of the original projection methods (denoted as algorithms I and II in this paper), in which the updated cell center velocity from the intermediate velocity and the pressure gradient is not guaranteed solenoidal, the consistent projection methods (denoted as algorithms III and IV) obtain the cell center velocity based on an interpolation from a conservative fluxes with velocity unit on surrounding cell faces. Dependent on treatment of the continuous surface force, the pressure gradient in algorithm III or the sum of the pressure gradient and the surface force in algorithm IV at a cell center is then conducted from the difference between the updated velocity and the intermediate velocity in a consistent projection method. A non-viscous 3D static drop with serials of density ratios is numerically simulated. Using the consistent projection methods, the spurious currents can be greatly reduced and the pressure jump across the interface can be accurately captured without oscillations. The developed consistent projection method are also applied for simulation of interface evolution of an initial ellipse driven by the surface tension and of an initial sphere bubble driven by the buoyancy with good accuracy and good resolution.

  1. High-density lipoprotein endocytosis in endothelial cells

    Institute of Scientific and Technical Information of China (English)

    Stefanie; Fruhwürth; Margit; Pavelka; Robert; Bittman; Werner; J; Kovacs; Katharina; M; Walter; Clemens; Rhrl; Herbert; Stangl

    2013-01-01

    AIM: To describe the way stations of high-density lipoprotein(HDL) uptake and its lipid exchange in endothelial cells in vitro and in vivo. METHODS: A combination of fluorescence microscopy using novel fluorescent cholesterol surrogates and electron microscopy was used to analyze HDL endocytosis in great detail in primary human endothelial cells. Further, HDL uptake was quantified using radio-labeled HDL particles. To validate the in vitro findings mice were injected with fluorescently labeled HDL and particle uptake in the liver was analyzed using fluorescencemicroscopy. RESULTS: HDL uptake occurred via clathrin-coated pits, tubular endosomes and multivesicular bodies in human umbilical vein endothelial cells. During uptake and resecretion, HDL-derived cholesterol was exchanged at a faster rate than cholesteryl oleate, resembling the HDL particle pathway seen in hepatic cells. In addition, lysosomes were not involved in this process and thus HDL degradation was not detectable. In vivo, we found HDL mainly localized in mouse hepatic endothelial cells. HDL was not detected in parenchymal liver cells, indicating that lipid transfer from HDL to hepatocytes occurs primarily via scavenger receptor, class B, type Ⅰ mediated selective uptake without concomitant HDL endocytosis. CONCLUSION: HDL endocytosis occurs via clathrincoated pits, tubular endosomes and multivesicular bodies in human endothelial cells. Mouse endothelial cells showed a similar HDL uptake pattern in vivo indicating that the endothelium is one major site of HDL endocytosis and transcytosis.

  2. Regulating the surface poly(ethylene glycol) density of polymeric nanoparticles and evaluating its role in drug delivery in vivo.

    Science.gov (United States)

    Du, Xiao-Jiao; Wang, Ji-Long; Liu, Wei-Wei; Yang, Jin-Xian; Sun, Chun-Yang; Sun, Rong; Li, Hong-Jun; Shen, Song; Luo, Ying-Li; Ye, Xiao-Dong; Zhu, Yan-Hua; Yang, Xian-Zhu; Wang, Jun

    2015-11-01

    Poly(ethylene glycol) (PEG) is usually used to protect nanoparticles from rapid clearance in blood. The effects are highly dependent on the surface PEG density of nanoparticles. However, there lacks a detailed and informative study in PEG density and in vivo drug delivery due to the critical techniques to precisely control the surface PEG density when maintaining other nano-properties. Here, we regulated the polymeric nanoparticles' size and surface PEG density by incorporating poly(ε-caprolactone) (PCL) homopolymer into poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-PCL) and adjusting the mass ratio of PCL to PEG-PCL during the nanoparticles preparation. We further developed a library of polymeric nanoparticles with different but controllable sizes and surface PEG densities by changing the molecular weight of the PCL block in PEG-PCL and tuning the molar ratio of repeating units of PCL (CL) to that of PEG (EG). We thus obtained a group of nanoparticles with variable surface PEG densities but with other nano-properties identical, and investigated the effects of surface PEG densities on the biological behaviors of nanoparticles in mice. We found that, high surface PEG density made the nanoparticles resistant to absorption of serum protein and uptake by macrophages, leading to a greater accumulation of nanoparticles in tumor tissue, which recuperated the defects of decreased internalization by tumor cells, resulting in superior antitumor efficacy when carrying docetaxel.

  3. Volume and surface contributions to the nuclear symmetry energy within the coherent density fluctuation model

    CERN Document Server

    Antonov, A N; Sarriguren, P; de Guerra, E Moya

    2016-01-01

    The volume and surface components of the nuclear symmetry energy (NSE) and their ratio are calculated within the coherent density fluctuation model (CDFM). The estimations use the results of the model for the NSE in finite nuclei based on the Brueckner energy-density functional for nuclear matter. In addition, we present results for the NSE and its volume and surface contributions obtained by using the Skyrme energy-density functional. The CDFM weight function is obtained using the proton and neutron densities from the self-consistent HF+BCS method with Skyrme interactions. We present and discuss the values of the volume and surface contributions to the NSE and their ratio obtained for the Ni, Sn, and Pb isotopic chains studying their isotopic sensitivity. The results are compared with estimations of other approaches which have used available experimental data on binding energies, neutron-skin thicknesses, excitation energies to isobaric analog states (IAS) and also with results of other theoretical methods.

  4. From density to interface fluctuations: the origin of wavelength dependence in surface tension.

    Science.gov (United States)

    Hiester, Thorsten

    2008-12-01

    The height-height correlation function for a fluctuating interface between two coexisting bulk phases is derived by means of general equilibrium properties of the corresponding density-density correlation function. A wavelength-dependent surface tension gamma(q) can be defined and expressed in terms of the direct correlation function c(r,r;{'}) , the equilibrium density profile rho_{0}(r) , and an operator which relates density to surface configurations. Neither the concept of an effective interface Hamiltonian nor the difference in pressure is needed to determine the general structure of the height-height correlations or gamma(q) , respectively. This result generalizes the Mecke-Dietrich surface tension gamma_{MD}(q) [Phys. Rev. E 59, 6766 (1999)] and modifies recently published criticism concerning gamma_{MD}(q) [Tarazona, Checa, and Chacón, Phys. Rev. Lett. 99, 196101 (2007)].

  5. Trends in the chemical properties in early transition metal carbide surfaces: A density functional study

    DEFF Research Database (Denmark)

    Kitchin, J.R.; Nørskov, Jens Kehlet; Barteau, M.A.;

    2005-01-01

    In this paper we present density functional theory (DFT) investigations of the physical, chemical and electronic structure properties of several close-packed surfaces of early transition metal carbides, including beta-Mo2C(0 0 0 1), and the (1 1 1) surfaces of TiC, VC, NbC, and TaC. The results...

  6. Direct alcohol fuel cells: toward the power densities of hydrogen-fed proton exchange membrane fuel cells.

    Science.gov (United States)

    Chen, Yanxin; Bellini, Marco; Bevilacqua, Manuela; Fornasiero, Paolo; Lavacchi, Alessandro; Miller, Hamish A; Wang, Lianqin; Vizza, Francesco

    2015-02-01

    A 2 μm thick layer of TiO2 nanotube arrays was prepared on the surface of the Ti fibers of a nonwoven web electrode. After it was doped with Pd nanoparticles (1.5 mgPd  cm(-2) ), this anode was employed in a direct alcohol fuel cell. Peak power densities of 210, 170, and 160 mW cm(-2) at 80 °C were produced if the cell was fed with 10 wt % aqueous solutions of ethanol, ethylene glycol, and glycerol, respectively, in 2 M aqueous KOH. The Pd loading of the anode was increased to 6 mg cm(-2) by combining four single electrodes to produce a maximum peak power density with ethanol at 80 °C of 335 mW cm(-2) . Such high power densities result from a combination of the open 3 D structure of the anode electrode and the high electrochemically active surface area of the Pd catalyst, which promote very fast kinetics for alcohol electro-oxidation. The peak power and current densities obtained with ethanol at 80 °C approach the output of H2 -fed proton exchange membrane fuel cells.

  7. Influence of additive laser manufacturing parameters on surface using density of partially melted particles

    Science.gov (United States)

    Rosa, Benoit; Brient, Antoine; Samper, Serge; Hascoët, Jean-Yves

    2016-12-01

    Mastering the additive laser manufacturing surface is a real challenge and would allow functional surfaces to be obtained without finishing. Direct Metal Deposition (DMD) surfaces are composed by directional and chaotic textures that are directly linked to the process principles. The aim of this work is to obtain surface topographies by mastering the operating process parameters. Based on experimental investigation, the influence of operating parameters on the surface finish has been modeled. Topography parameters and multi-scale analysis have been used in order to characterize the DMD obtained surfaces. This study also proposes a methodology to characterize DMD chaotic texture through topography filtering and 3D image treatment. In parallel, a new parameter is proposed: density of particles (D p). Finally, this study proposes a regression modeling between process parameters and density of particles parameter.

  8. Self-consistent density functional calculation of the image potential at a metal surface

    Energy Technology Data Exchange (ETDEWEB)

    Jung, J [Departamento de Fisica Fundamental, Universidad Nacional de Educacion a Distancia, Apartado 60141, 28080 Madrid (Spain); Alvarellos, J E [Departamento de Fisica Fundamental, Universidad Nacional de Educacion a Distancia, Apartado 60141, 28080 Madrid (Spain); Chacon, E [Instituto de Ciencias de Materiales de Madrid, Consejo Superior de Investigaciones CientIficas, E-28049 Madrid (Spain); GarcIa-Gonzalez, P [Departamento de Fisica Fundamental, Universidad Nacional de Educacion a Distancia, Apartado 60141, 28080 Madrid (Spain)

    2007-07-04

    It is well known that the exchange-correlation (XC) potential at a metal surface has an image-like asymptotic behaviour given by -1/4(z-z{sub 0}), where z is the coordinate perpendicular to the surface. Using a suitable fully non-local functional prescription, we evaluate self-consistently the XC potential with the correct image behaviour for simple jellium surfaces in the range of metallic densities. This allows a proper comparison between the corresponding image-plane position, z{sub 0}, and other related quantities such as the centroid of an induced charge by an external perturbation. As a by-product, we assess the routinely used local density approximation when evaluating electron density profiles, work functions, and surface energies by focusing on the XC effects included in the fully non-local description.

  9. Maximizing the power density of aqueous electrochemical flow cells with in operando deposition

    Science.gov (United States)

    Goulet, Marc-Antoni; Ibrahim, Omar A.; Kim, Will H. J.; Kjeang, Erik

    2017-01-01

    To transition toward sustainable energy systems, next generation power sources must provide high power density at minimum cost. Using inexpensive and environmentally friendly fabrication methods, this work describes a room temperature electrochemical flow cell with a maximum power density of 2.01 W cm-2 or 13.4 W cm-3. In part, this is achieved by minimizing ohmic resistance through decreased electrode spacing, implementation of current collectors and improvement of electrolyte conductivity. The majority of the performance gain is provided by a novel in operando dynamic flowing deposition method for which the cell design has been optimized. Carbon nanotubes (CNTs) are deposited dynamically at the entrance of and within the carbon paper electrodes during operation of the cell. A natural equilibrium is reached between deposition and detachment of CNTs at which the electrochemical surface area and pore size distribution of the flow-through porous electrodes are greatly enhanced. In this way, the novel deposition method more than doubles the power density of the cell and sets a new performance benchmark for what is practically attainable with aqueous electrochemical flow cells. Overall, it is expected that the design and operation methods illustrated here will enable a wide range of electrochemical flow cell technologies to achieve optimal performance.

  10. Structure and functions of fungal cell surfaces

    Science.gov (United States)

    Nozawa, Y.

    1984-01-01

    A review with 24 references on the biochemistry, molecular structure, and function of cell surfaces of fungi, especially dermatophytes: the chemistry and structure of the cell wall, the effect of polyene antibiotics on the morphology and function of cytoplasmic membranes, and the chemical structure and function of pigments produced by various fungi are discussed.

  11. Modeled Seasonal Variations of Firn Density Induced by Steady State Surface Air Temperature Cycle

    Science.gov (United States)

    Jun, Li; Zwally, H. Jay; Koblinsky, Chester J. (Technical Monitor)

    2001-01-01

    Seasonal variations of firn density in ice-sheet firn layers have been attributed to variations in deposition processes or other processes within the upper firn. A recent high-resolution (mm scale) density profile, measured along a 181 m core from Antarctica, showed small-scale density variations with a clear seasonal cycle that apparently was not-related to seasonal variations in deposition or known near-surface processes (Gerland and others 1999). A recent model of surface elevation changes (Zwally and Li, submitted) produced a seasonal variation in firn densification, and explained the seasonal surface elevation changes observed by satellite radar altimeters. In this study, we apply our 1-D time-dependent numerical model of firn densification that includes a temperature-dependent formulation of firn densification based on laboratory measurements of grain growth. The model is driven by a steady-state seasonal surface temperature and a constant accumulation rate appropriate for the measured Antarctic ice core. The modeled seasonal variations in firn density show that the layers of snow deposited during spring to mid-summer with the highest temperature history compress to the highest density, and the layers deposited during later summer to autumn with the lowest temperature history compress to the lowest density. The initial amplitude of the seasonal difference of about 0.13 reduces to about 0.09 in five years and asymptotically to 0.92 at depth, which is consistent with the core measurements.

  12. Probes for anionic cell surface detection

    Science.gov (United States)

    Smith, Bradley D.

    2013-03-05

    Embodiments of the present invention are generally directed to compositions comprising a class of molecular probes for detecting the presence of anionic cell surfaces. Embodiments include compositions that are enriched for these compositions and preparations, particularly preparations suitable for use as laboratory/clinical reagents and diagnostic indicators, either alone or as part of a kit. An embodiment of the invention provides for a highly selective agent useful in the discernment and identification of dead or dying cells, such as apoptotic cells, in a relatively calcium-free environment. An embodiment of the invention provides a selective agent for the identification of bacteria in a mixed population of bacterial cells and nonbacterial cells.

  13. Nanotomography of Cell Surfaces with Evanescent Fields

    Directory of Open Access Journals (Sweden)

    Michael Wagner

    2008-01-01

    Full Text Available The technique of variable-angle total internal reflection fluorescence microscopy (TIRFM and its application to nanotomography of cell surfaces are described. Present applications include (1 3D imaging of chromosomes in their metaphase to demonstrate axial resolution in the nanometre range, (2 measurements of cell-substrate topology, which upon cholesterol depletion shows some loosening of cell-substrate contacts, and (3 measurements of cell topology upon photodynamic therapy (PDT, which demonstrate cell swelling and maintenance of focal contacts. The potential of the method for in vitro diagnostics, but also some requirements and limitations are discussed.

  14. A Simple Model for the Relationship Between Star Formation and Surface Density

    CERN Document Server

    Dobbs, C L

    2009-01-01

    We investigate the relationship between the star formation rate per unit area and the surface density of the ISM (the local Kennicutt-Schmitt law) using a simplified model of the ISM and a simple estimate of the star formation rate based on the mass of gas in bound clumps, the local dynamical timescales of the clumps, and an efficiency parameter of around 5 per cent. Despite the simplicity of the approach, we are able to reproduce the observed linear relation between star formation rate and surface density of dense (molecular) gas. We use a simple model for the dependence of H_2 fraction on total surface density to argue why neither total surface density nor the HI surface density are good local indicators of star formation rate. We also investigate the dependence of the star formation rate on the depth of the spiral potential. Our model indicates that the mean star formation rate does not depend significantly on the strength of the spiral potential, but that a stronger spiral potential, for a given mean surf...

  15. Diffuse Surface Scattering in the Plasmonic Resonances of Ultra-Low Electron Density Nanospheres

    CERN Document Server

    Monreal, R Carmina; Apell, S Peter

    2015-01-01

    Localized surface plasmon resonances (LSPRs) have recently been identified in extremely diluted electron systems obtained by doping semiconductor quantum dots. Here we investigate the role that different surface effects, namely electronic spill-out and diffuse surface scattering, play in the optical properties of these ultra-low electron density nanosystems. Diffuse scattering originates from imperfections or roughness at a microscopic scale on the surface. Using an electromagnetic theory that describes this mechanism in conjunction with a dielectric function including the quantum size effect, we find that the LSPRs show an oscillatory behavior both in position and width for large particles and a strong blueshift in energy and an increased width for smaller radii, consistent with recent experimental results for photodoped ZnO nanocrystals. We thus show that the commonly ignored process of diffuse surface scattering is a more important mechanism affecting the plasmonic properties of ultra-low electron density ...

  16. Corneal endothelial cell density and morphology in Phramongkutklao Hospital

    Directory of Open Access Journals (Sweden)

    Narumon Sopapornamorn

    2008-03-01

    Full Text Available Narumon Sopapornamorn1, Manapon Lekskul1, Suthee Panichkul21Department of Ophthalmology, Phramongkutklao Hospital, Bangkok, Thailand; 2Department of Obstetrics and Gynecology, Phramongkutklao College of Medicine, Bangkok, ThailandObjective: To describe the corneal endothelial density and morphology in patients of Phramongkutklao Hospital and the relationship between endothelial cell parameters and other factors.Methods: Four hundred and four eyes of 202 volunteers were included. Noncontact specular microscopy was performed after taking a history and testing the visual acuity, intraocular pressure measurement, Schirmer’s test and routine eye examination by slit lamp microscope. The studied parameters included mean endothelial cell density (MCD, coefficient of variation (CV, and percentage of hexagonality.Results: The mean age of volunteers was 45.73 years; the range being 20 to 80 years old. Their MCD (SD, mean percentage of CV (SD and mean (SD percentage of hexagonality were 2623.49(325 cell/mm2, 39.43(8.23% and 51.50(10.99%, respectively. Statistically, MCD decreased significantly with age (p < 0.01. There was a significant difference in the percentage of CV between genders. There was no statistical significance between parameters and other factors.Conclusion: The normative data of the corneal endothelium of Thai eyes indicated that, statistically, MCD decreased significantly with age. Previous studies have reported no difference in MCD, percentage of CV, and percentage of hexagonality between gender. Nevertheless, significantly different percentages of CV between genders were presented in this study.Keywords: Corneal endothelial cell, parameters, age, gender, smoking, Thailand

  17. A comparative study of atomic oxygen adsorption at Pd surfaces from Density Functional Theory

    Science.gov (United States)

    Bukas, Vanessa J.; Reuter, Karsten

    2017-04-01

    Based on density functional theory, we present a detailed investigation into the on-surface adsorption of atomic oxygen at all three low-index Pd facets in the low-coverage regime. Relying on one consistent computational framework allows for a systematic comparison with respect to surface symmetry, while discerning trends in the adsorption geometries, energies, work functions, and electron densities. We overall find a persisting degree of O-Pd hybridization that is accompanied by minimal charge transfer from the substrate to the adsorbate, thereby resulting in comparable binding energies and diffusion barriers at the three surfaces. Small differences in reactivity are nevertheless reflected in subtle variations of the underlying electronic structure which do not, however, follow the expected order according to atom packing density.

  18. Optical coherence tomography identifies lower labial salivary gland surface density in cystic fibrosis.

    Directory of Open Access Journals (Sweden)

    Jan K Nowak

    Full Text Available The labial minor salivary glands (LSGs are easily accessible mucus-secreting structures of the alimentary tract that may provide new information on the basis of gastrointestinal complications of cystic fibrosis (CF. It was shown that they are destructed in the course of cystic fibrosis. We employed wide-field, micrometer resolution in vivo optical coherence tomography to assess the surface density of LSGs in 18 patients with CF and 18 healthy subjects. The median LSGs' surface densities in CF patients, and in the control group were 4.32 glands/cm2 and 6.58 glands/cm2, respectively (p = 0.006; Mann-Whitney U test. A lower LSG surface density is a previously unrecognized CF-related pathology of the alimentary tract.

  19. Electrostatic force density for a scanned probe above a charged surface

    Energy Technology Data Exchange (ETDEWEB)

    Passian, A.; Wig, A.; Meriaudeau, F.; Buncick, M.; Thundat, T.; Ferrell, T. L.

    2001-07-15

    The Coulomb interaction of a dielectric probe tip with a uniform field existing above a semi-infinite, homogeneous dielectric substrate is studied. The induced polarization surface charge density and the field distribution at the bounding surface of the dielectric medium with the geometry of half of a two sheeted hyperboloid of revolution located above the dielectric half space interfaced with a uniform surface charge density is calculated. The force density on the hyperboloidal probe medium is calculated as a function of the probe tip shape. The calculation is based on solving Laplace's equation and employing a newly derived integral expansion for the vanishing dielectric limit of the potential. The involved numerical simulations comprise the evaluation of infinite double integrals involving conical functions.

  20. Electrostatic force density for a scanned probe above a charged surface

    Science.gov (United States)

    Passian, A.; Wig, A.; Meriaudeau, F.; Buncick, M.; Thundat, T.; Ferrell, T. L.

    2001-07-01

    The Coulomb interaction of a dielectric probe tip with a uniform field existing above a semi-infinite, homogeneous dielectric substrate is studied. The induced polarization surface charge density and the field distribution at the bounding surface of the dielectric medium with the geometry of half of a two sheeted hyperboloid of revolution located above the dielectric half space interfaced with a uniform surface charge density is calculated. The force density on the hyperboloidal probe medium is calculated as a function of the probe tip shape. The calculation is based on solving Laplace's equation and employing a newly derived integral expansion for the vanishing dielectric limit of the potential. The involved numerical simulations comprise the evaluation of infinite double integrals involving conical functions.

  1. Critical CuI buffer layer surface density for organic molecular crystal orientation change

    Science.gov (United States)

    Ahn, Kwangseok; Kim, Jong Beom; Kim, Hyo Jung; Lee, Hyun Hwi; Lee, Dong Ryeol

    2015-01-01

    We have determined the critical surface density of the CuI buffer layer inserted to change the preferred orientation of copper phthalocyanine (CuPc) crystals grown on the buffer layer. X-ray reflectivity measurements were performed to obtain the density profiles of the buffer layers and out-of-plane and 2D grazing-incidence X-ray diffraction measurements were performed to determine the preferred orientations of the molecular crystals. Remarkably, it was found that the preferred orientation of the CuPc film is completely changed from edge-on (1 0 0) to face-on (1 1 -2) by a CuI buffer layer with a very low surface density, so low that a large proportion of the substrate surface is bare.

  2. Assessment of Microbial Fuel Cell Configurations and Power Densities

    KAUST Repository

    Logan, Bruce E.

    2015-07-30

    Different microbial electrochemical technologies are being developed for a many diverse applications, including wastewater treatment, biofuel production, water desalination, remote power sources, and as biosensors. Current and energy densities will always be limited relative to batteries and chemical fuel cells, but these technologies have other advantages based on the self-sustaining nature of the microorganisms that can donate or accept electrons from an electrode, the range of fuels that can be used, and versatility in the chemicals that can be produced. The high cost of membranes will likely limit applications of microbial electrochemical technologies that might require a membrane. For microbial fuel cells, which do not need a membrane, questions remain on whether larger-scale systems can produce power densities similar to those obtained in laboratory-scale systems. It is shown here that configuration and fuel (pure chemicals in laboratory media versus actual wastewaters) remain the key factors in power production, rather than the scale of the application. Systems must be scaled up through careful consideration of electrode spacing and packing per unit volume of reactor.

  3. Structure and chemical reactivity of the polar three-fold surfaces of GaPd: a density-functional study.

    Science.gov (United States)

    Krajčí, M; Hafner, J

    2013-03-28

    the lowest energy has been found for a bilayer with three Ga atoms per surface cell in the upper layer and one Ga and one Pd in the lower part. The calculated surface energies are in agreement with a simulated cleavage experiment. However, cleavage does not result in the formation of the lowest-energy surfaces, because all possible {111} cleavage planes expose a low-energy surface on one, and a high-energy surface on the other side. The prediction of Ga-terminated surfaces has been tested against the available experimental information. The calculated surface electronic density of states is in very good agreement with photo-emission spectroscopy. Calculated STM images of the most stable surfaces agree with all details of the available experimental images. The chemical reactivity of the most stable surfaces has been studied by the adsorption of CO molecules. The adsorption energies and maximum coverages calculated for the Ga-terminated surfaces permit a reasonable interpretation of the observed thermal desorption spectra, whereas for the Pd-terminated surfaces the calculated adsorption energies are far too high.

  4. Surface density of dark matter haloes on galactic and cluster scales

    Science.gov (United States)

    Del Popolo, A.; Cardone, V. F.; Belvedere, G.

    2013-02-01

    In this paper, we analysed the correlation between the central surface density and the halo core radius of galaxies, and cluster of galaxies dark matter (DM) haloes, in the framework of the secondary infall model. We used Del Popolo secondary infall model taking into account ordered and random angular momentum, dynamical friction and DM adiabatic contraction to calculate the density profile of haloes, and then these profiles are used to determine the surface density of DM haloes. The main result is that r* (the halo characteristic radius) is not a universal quantity as claimed by Donato et al. and Gentile et al. On the contrary, we find a correlation with the halo mass M200 in agreement with Cardone & Tortora, Boyarsky et al. and Napolitano, Romanowsky & Tortora, but with a significantly smaller scatter, namely 0.16 ± 0.05. We also consider the baryon column density finding this latter being indeed a constant for low-mass systems, such as dwarfs, but correlating with mass with a slope of α = 0.18 ± 0.05. In the case of the surface density of DM for a system composed only of DM, as in dissipationless simulations, we get α = 0.20 ± 0.05. These results leave little room for the recently claimed universality of (dark and stellar) column density.

  5. Influence of particle flux density and temperature on surface modifications of tungsten and deuterium retention

    Energy Technology Data Exchange (ETDEWEB)

    Buzi, Luxherta, E-mail: l.buzi@fz-juelich.de [Ghent University, Department of Applied Physics, Sint-Pietersnieuwstraat 41, B-9000 Ghent (Belgium); FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Edisonbaan 14, 3439 MN, PO Box 1207, 3430 BE Nieuwegein (Netherlands); Institut für Energie und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, 52425 Jülich (Germany); Université de Lorraine, Institut Jean Lamour, CNRS UMR 7198, Bvd. des Aiguillettes, F-54506 Vandoeuvre (France); Temmerman, Greg De [FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, Edisonbaan 14, 3439 MN, PO Box 1207, 3430 BE Nieuwegein (Netherlands); Unterberg, Bernhard; Reinhart, Michael; Litnovsky, Andrey; Philipps, Volker [Institut für Energie und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, 52425 Jülich (Germany); Oost, Guido Van [Ghent University, Department of Applied Physics, Sint-Pietersnieuwstraat 41, B-9000 Ghent (Belgium); Möller, Sören [Institut für Energie und Klimaforschung – Plasmaphysik, Forschungszentrum Jülich GmbH, Leo-Brandt-Straße, 52425 Jülich (Germany)

    2014-12-15

    Systematic study of deuterium irradiation effects on tungsten was done under ITER – relevant high particle flux density, scanning a broad surface temperature range. Polycrystalline ITER – like grade tungsten samples were exposed in linear plasma devices to two different ranges of deuterium ion flux densities (high: 3.5–7 · 10{sup 23} D{sup +}/m{sup 2} s and low: 9 · 10{sup 21} D{sup +}/m{sup 2} s). Particle fluence and ion energy, respectively 10{sup 26} D{sup +}/m{sup 2} and ∼38 eV were kept constant in all cases. The experiments were performed at three different surface temperatures 530 K, 630 K and 870 K. Experimental results concerning the deuterium retention and surface modifications of low flux exposure confirmed previous investigations. At temperatures 530 K and 630 K, deuterium retention was higher at lower flux density due to the longer exposure time (steady state plasma operation) and a consequently deeper diffusion range. At 870 K, deuterium retention was found to be higher at high flux density according to the thermal desorption spectroscopy (TDS) measurements. While blisters were completely absent at low flux density, small blisters of about 40–50 nm were formed at high flux density exposure. At the given conditions, a relation between deuterium retention and blister formation has been found which has to be considered in addition to deuterium trapping in defects populated by diffusion.

  6. Density functional theory calculations of tetracene on low index surfaces of copper crystal

    Institute of Scientific and Technical Information of China (English)

    Dou Wei-Dong; Zhang Han-Jie; Bao Shi-Ning

    2009-01-01

    This paper carries out the density functional theory calculations to study the adsorbate-substrate interaction between tetracene and Cu substrates (Cu (110) and Cu (100) surface). On each of the surfaces, two kinds of geometry are calculated, namely 'flat-lying' mode and 'upright standing' mode. For 'flat-lying' geometry, the molecule is found to be aligned with its longer molecular axis along close-packed direction of the substrata surfaces. For 'upright standing' geometry, the long axis of tetracene is found to be parallel to the surface normal of the substrate on Cu (110) surface. However, tetracene appears as 'tilted' mode on Cu (100) surface. Structures with 'flat-lying' mode have much larger adsorption energy and charge transfer upon adsorption than that with 'upright standing' mode, indicating the preference of 'flat-lying' geometry on both Cu (110) and Cu (100) surface.

  7. Density, Molar Volume, and Surface Tension of Liquid Al-Ti

    Science.gov (United States)

    Wessing, Johanna Jeanette; Brillo, Jürgen

    2017-02-01

    Al-Ti-based alloys are of enormous technical relevance due to their specific properties. For studies in atomic dynamics, surface physics and industrial processing the precise knowledge of the thermophysical properties of the liquid phase is crucial. In the present work, we systematically measure mass density, ρ (g cm-3), and the surface tension, γ (N m-1), as functions of temperature, T, and compositions of binary Al-Ti melts. Electromagnetic levitation in combination with the optical dilatometry method is used for density measurements and the oscillating drop method for surface tension measurements. It is found that, for all compositions, density and surface tension increase linearly upon decreasing temperature in the liquid phase. Within the Al-Ti system, we find the largest values for pure titanium and the smallest for pure aluminum, which amount to ρ(L,Ti) = 4.12 ± 0.04 g cm-3 and γ(L,Ti) = 1.56 ± 0.02 N m-1; and ρ(L,Al) = 2.09 ± 0.01 g cm-3 and γ(L,Al) = 0.87 ± 0.06 N m-1, respectively. The data are analyzed concerning the temperature coefficients, ρ T and γ T, excess molar volume, V E, excess surface tension, γ E, and surface segregation of the surface active component, Al. The results are compared with thermodynamic models. Generally, it is found that Al-Ti is a highly nonideal system.

  8. Analysis of the surface density and reactivity of perfluorophenylazide and the impact on ligand immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Zorn, Gilad, E-mail: zorn@ge.com; Castner, David G. [National ESCA and Surface Analysis Center for Biomedical Problems, Departments of Bioengineering and Chemical Engineering, University of Washington, Box 351653, Seattle, Washington 98195-1653 (United States); Tyagi, Anuradha; Wang, Xin; Wang, Hui; Yan, Mingdi, E-mail: Mingdi-Yan@uml.edu [Department of Chemistry, Portland State University, Portland, Oregon 97207-0751 (United States)

    2015-03-15

    Perfluorophenylazide (PFPA) chemistry is a novel method for tailoring the surface properties of solid surfaces and nanoparticles. It is general and versatile, and has proven to be an efficient way to immobilize graphene, proteins, carbohydrates, and synthetic polymers. The main thrust of this work is to provide a detailed investigation on the chemical composition and surface density of the PFPA tailored surface. Specifically, gold surfaces were treated with PFPA-derivatized (11-mercaptoundecyl)tetra(ethylene glycol) (PFPA-MUTEG) mixed with 2-[2-(2-mercaptoethoxy)ethoxy]ethanol (MDEG) at varying solution mole ratios. Complementary analytical techniques were employed to characterize the resulting films including Fourier transform infrared spectroscopy to detect fingerprints of the PFPA group, x-ray photoelectron spectroscopy and ellipsometry to study the homogeneity and uniformity of the films, and near edge x-ray absorption fine structures to study the electronic and chemical structure of the PFPA groups. Results from these studies show that the films prepared from 90:10 and 80:20 PFPA-MUTEG/MDEG mixed solutions exhibited the highest surface density of PFPA and the most homogeneous coverage on the surface. A functional assay using surface plasmon resonance with carbohydrates covalently immobilized onto the PFPA-modified surfaces showed the highest binding affinity for lectin on the PFPA-MUTEG/MDEG film prepared from a 90:10 solution.

  9. Cell surface engineering with edible protein nanoshells.

    Science.gov (United States)

    Drachuk, Irina; Shchepelina, Olga; Harbaugh, Svetlana; Kelley-Loughnane, Nancy; Stone, Morley; Tsukruk, Vladimir V

    2013-09-23

    Natural protein (silk fibroin) nanoshells are assembled on the surface of Saccharomyces cerevisiae yeast cells without compromising their viability. The nanoshells facilitate initial protection of the cells and allow them to function in encapsulated state for some time period, afterwards being completely biodegraded and consumed by the cells. In contrast to a traditional methanol treatment, the gentle ionic treatment suggested here stabilizes the shell silk fibroin structure but does not compromise the viability of the cells, as indicated by the fast response of the encapsulated cells, with an immediate activation by the inducer molecules. Extremely high viability rates (up to 97%) and preserved activity of encapsulated cells are facilitated by cytocompatibility of the natural proteins and the formation of highly porous shells in contrast to traditional polyelectrolyte-based materials. Moreover, in a high contrast to traditional synthetic shells, the silk proteins are biodegradable and can be consumed by cells at a later stage of growth, thus releasing the cells from their temporary protective capsules. These on-demand encapsulated cells can be considered a valuable platform for biocompatible and biodegradable cell encapsulation, controlled cell protection in a synthetic environment, transfer to a device environment, and cell implantation followed by biodegradation and consumption of protective protein shells.

  10. Collaborative tool for collecting reference data on the density of constructed surfaces worldwide

    Science.gov (United States)

    Elvidge, Christopher D.; Tuttle, Benjamin T.; Sutton, Paul C.

    2010-11-01

    We have developed a web-based interface for the collection of surface cover type data using gridded point counts on displays of high spatial resolution color satellite imagery available in Google Earth. The system is designed to permit a distributed set of analysts to contribute gridded point counts to a common database. Our application of the system is to develop a calibration for estimating the density of constructed surface areas worldwide at 1 km2 resolution based on the brightness of satellite observed lights and population count. The system has been used to collect a test data set and a preliminary calibration for estimating the density of constructed surfaces. We believe the web-based system could have applications for research projects and analyses that require the collection of surface cover type data from diverse locations.

  11. In vitro behaviour of endothelial cells on a titanium surface

    Directory of Open Access Journals (Sweden)

    Oliveira-Filho Ricardo

    2008-07-01

    Full Text Available Abstract Background Endothelial cells play an important role in the delivery of cells to the inflammation site, chemotaxis, cell adhesion and extravasation. Implantation of a foreign material into the human body determines inflammatory and repair reactions, involving different cell types with a plethora of released chemical mediators. The evaluation of the interaction of endothelial cells and implanted materials must take into account other parameters in addition to the analysis of maintenance of cell viability. Methods In the present investigation, we examined the behavior of human umbilical vein endothelial cells (HUVECs harvested on titanium (Ti, using histological and immunohistochemical methods. The cells, after two passages, were seeded in a standard density on commercially plate-shaped titanium pieces, and maintained for 1, 7 or 14 days. Results After 14 days, we could observe a confluent monolayer of endothelial cells (ECs on the titanium surface. Upon one-day Ti/cell contact the expression of fibronectin was predominantly cytoplasmatic and stronger than on the control surface. It was observed strong and uniform cell expression along the time of α5β1 integrin on the cells in contact with titanium. Conclusion The attachment of ECs on titanium was found to be related to cellular-derived fibronectin and the binding to its specific receptor, the α5β1 integrin. It was observed that titanium effectively serves as a suitable substrate for endothelial cell attachment, growth and proliferation. However, upon a 7-day contact with Ti, the Weibel-Palade bodies appeared to be not fully processed and exhibited an anomalous morphology, with corresponding alterations of PECAM-1 localization.

  12. Design of a vapor-liquid-equilibrium, surface tension, and density apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Holcomb, C.D.; Outcalt, S.L. [National Institute of Standards and Technology, Boulder, CO (United States)

    1997-12-31

    The design and performance of a unique vapor-liquid equilibrium (VLE) apparatus with density and surface tension capabilities is presented. The apparatus operates at temperatures ranging from 218 to 423 K, at pressures to 17 MPa, at densities to 1100 kg/m{sup 3}, and at surface tensions ranging from 0.1 to 75 mN/m. Temperatures are measured with a precision of {+-}0.02 K, pressures with a precision of {+-}0.1% of full scale, densities with a precision of {+-}0.5 kg/m{sup 3}, surface tensions with a precision of {+-}0.2 mN/m, and compositions with a precision of {+-}0.005 mole fraction. The apparatus is designed to be both accurate and versatile. Capabilities include: (1) the ability to operate the apparatus as a bubble point pressure or an isothermal pressure-volume-temperature (PVT) apparatus, (2) the ability to measure densities and surface tensions of the coexisting phases, and (3) the ability for either trapped or capillary sampling. We can validate our VLE and density data by measuring PVT or bubble point pressures in the apparatus. The use of the apparatus for measurements of VLE, densities, and surface tensions over wide ranges of temperature and pressure is important in equation of state and transport property model development. The use of different sampling procedures allows measurement of a wider variety of fluid mixtures. VLE measurements on the alternative refrigerant system R32/134a are presented and compared to literature results to verify the performance of the apparatus.

  13. Density functional theory study of water adsorption at reduced and stoichiometric ceria (111) surfaces.

    Science.gov (United States)

    Kumar, Santosh; Schelling, Patrick K

    2006-11-28

    We study the structure and energetics of water molecules adsorbed at ceria (111) surfaces for 0.5 and 1.0 ML coverages using density functional theory. The results of this study provide a theoretical framework for interpreting recent experimental results on the redox properties of water at ceria (111) surfaces. In particular, we have computed the structure and energetics of various absorption geometries at the stoichiometric ceria (111) surface. We find that single hydrogen bonds between the water and the oxide surface are favored in all cases. At stoichiometric surfaces, the water adsorption energy depends rather weakly on coverage. We predict that the observed coverage dependence of the water adsorption energy at stoichiometric surfaces is likely the result of dipole-dipole interactions between adsorbed water molecules. When oxygen vacancies are introduced in various surface layers, water molecules are attracted more strongly to the surface. We find that it is very slightly energetically favorable for adsorbed water to oxidized the reduced (111) surface with the evolution of H(2). In the event that water does not oxidize the surface, we predict that the effective attractive water-vacancy interaction will result in a significant enhancement of the vacancy concentration at the surface in agreement with experimental observations. Finally, we present our results in the context of recent experimental and theoretical studies of vacancy clustering at the (111) ceria surface.

  14. Estimating the amount and distribution of radon flux density from the soil surface in China.

    Science.gov (United States)

    Zhuo, Weihai; Guo, Qiuju; Chen, Bo; Cheng, Guan

    2008-07-01

    Based on an idealized model, both the annual and the seasonal radon ((222)Rn) flux densities from the soil surface at 1099 sites in China were estimated by linking a database of soil (226)Ra content and a global ecosystems database. Digital maps of the (222)Rn flux density in China were constructed in a spatial resolution of 25 km x 25 km by interpolation among the estimated data. An area-weighted annual average (222)Rn flux density from the soil surface across China was estimated to be 29.7+/-9.4 mBq m(-2)s(-1). Both regional and seasonal variations in the (222)Rn flux densities are significant in China. Annual average flux densities in the southeastern and northwestern China are generally higher than those in other regions of China, because of high soil (226)Ra content in the southeastern area and high soil aridity in the northwestern one. The seasonal average flux density is generally higher in summer/spring than winter, since relatively higher soil temperature and lower soil water saturation in summer/spring than other seasons are common in China.

  15. Diffuse Surface Scattering and Quantum Size Effects in the Surface Plasmon Resonances of Low Carrier Density Nanocrystals

    CERN Document Server

    Monreal, R Carmina; Apell, S Peter

    2016-01-01

    The detailed understanding of the physical parameters that determine Localized Surface Plasmon Resonances (LSPRs) is essential to develop new applications for plasmonics. A relatively new area of research has been opened by the identification of LSPRs in low carrier density systems obtained by doping semiconductor quantum dots. We investigate theoretically how diffuse surface scattering of electrons in combination with the effect of quantization due to size (QSE) impact the evolution of the LSPRs with the size of these nanosystems. Two key parameters are the length $R_0$ giving the strength of the QSE and the velocity $\\beta_T$ of the electronic excitations entering in the length scale for diffuse surface scattering. While the QSE itself only produces a blueshift in energy of the LSPRs, the diffuse surface scattering mechanism gives to both energy and linewidth an oscillatory-damped behavior as a function of size, with characteristic lengths that depend on material parameters. Thus, the evolution of the LSPRs...

  16. Solubility of N2O in and density, viscosity, and surface tension of aqueous piperazine solutions

    NARCIS (Netherlands)

    Derks, P. W.; Hogendoorn, K. J.; Versteeg, G. F.

    2005-01-01

    The physical solubility of N2O in and the density and viscosity of aqueous piperazine solutions have been measured over a temperature range of (293.15 to 323.15) K for piperazine concentrations ranging from about (0.6 to 1.8) kmol·mr-3. Furthermore, the present study contains experimental surface t

  17. Influence of particle flux density and temperature on surface modifications of tungsten and deuterium retention

    NARCIS (Netherlands)

    Buzi, L.; De Temmerman, G.; Unterberg, B.; M. Reinhart,; Litnovsky, A.; Philipps, V.; Van Oost, G.; Möller, S.

    2014-01-01

    Systematic study of deuterium irradiation effects on tungsten was done under ITER - relevant high particle flux density, scanning a broad surface temperature range. Polycrystalline ITER - like grade tungsten samples were exposed in linear plasma devices to two different ranges of deuterium ion flux

  18. Density functional theory calculations of the stress of oxidised (110) silicon surfaces

    CERN Document Server

    Melis, C; Colombo, L; Mana, G

    2016-01-01

    The measurement of the lattice-parameter of silicon by x-ray interferometry assumes the use of strain-free crystals. This might not be the case because surface relaxation, reconstruction, and oxidation cause strains without the application of any external force. In a previous work, this intrinsic strain was estimated by a finite element analysis, where the surface stress was modeled by an elastic membrane having a 1 N/m tensile strength. The present paper quantities the surface stress by a density functional theory calculation. We found a value exceeding the nominal value used, which potentially affects the measurement accuracy.

  19. Number Density of Mast Cells in the Primo Nodes of Rats.

    Science.gov (United States)

    Gil, HyunJi; Bae, Kyoung-Hee; Kim, LiJung; Kim, SungChul; Soh, Kwang-Sup

    2015-12-01

    Mast cells (MCs) play a major role in allergic reactions. Surprisingly, the acupuncture points have a higher density of MCs compared with nonacupoints in the skin, which is consistent with the augmentation of the immune function by acupuncture treatment. We hypothesized that the primo vascular system (PVS), which was proposed as the anatomical structure of the acupuncture points and meridians, should have a high density of MCs. In order to test that hypothesis, we investigated the primo nodes isolated from the surfaces of internal organs, such as the liver, the small and the large intestines, and the bladder. The harvested primo nodes were stained with toluidine blue, and the MCs were easily recognized by their red-purple stains and their characteristic granules. The results showed a high density of MCs in the primo nodes and confirmed the hypothesis. The MCs were uniformly distributed in the nodes. The relative concentration of the MCs with respect to other cells was ∼15%. We divided the sizes of the primo nodes into three classes: large, medium, and small. The number density and the relative concentration of MCs did not show a size-dependence. The current work suggests that the PVS may participate in the immune response to allergic inflammation, which closely involves MCs.

  20. The cell surface proteome of Entamoeba histolytica.

    Science.gov (United States)

    Biller, Laura; Matthiesen, Jenny; Kühne, Vera; Lotter, Hannelore; Handal, Ghassan; Nozaki, Tomoyoshi; Saito-Nakano, Yumiko; Schümann, Michael; Roeder, Thomas; Tannich, Egbert; Krause, Eberhard; Bruchhaus, Iris

    2014-01-01

    Surface molecules are of major importance for host-parasite interactions. During Entamoeba histolytica infections, these interactions are predicted to be of prime importance for tissue invasion, induction of colitis and liver abscess formation. To date, however, little is known about the molecules involved in these processes, with only about 20 proteins or protein families found exposed on the E. histolytica surface. We have therefore analyzed the complete surface proteome of E. histolytica. Using cell surface biotinylation and mass spectrometry, 693 putative surface-associated proteins were identified. In silico analysis predicted that ∼26% of these proteins are membrane-associated, as they contain transmembrane domains and/or signal sequences, as well as sites of palmitoylation, myristoylation, or prenylation. An additional 25% of the identified proteins likely represent nonclassical secreted proteins. Surprisingly, no membrane-association sites could be predicted for the remaining 49% of the identified proteins. To verify surface localization, 23 proteins were randomly selected and analyzed by immunofluorescence microscopy. Of these 23 proteins, 20 (87%) showed definite surface localization. These findings indicate that a far greater number of E. histolytica proteins than previously supposed are surface-associated, a phenomenon that may be based on the high membrane turnover of E. histolytica.

  1. Femtosecond fabricated surfaces for cell biology

    Science.gov (United States)

    Day, Daniel; Gu, Min

    2010-08-01

    Microfabrication using femtosecond pulse lasers is enabling access to a range of structures, surfaces and materials that was not previously available for scientific and engineering applications. The ability to produce micrometre sized features directly in polymer and metal substrates is demonstrated with applications in cell biology. The size, shape and aspect ratio of the etched features can be precisely controlled through the manipulation of the fluence of the laser etching process with respect to the properties of the target material. Femtosecond laser etching of poly(methyl methacrylate) and aluminium substrates has enabled the production of micrometre resolution moulds that can be accurately replicated using soft lithography. The moulded surfaces are used in the imaging of T cells and demonstrate the improved ability to observe biological events over time periods greater than 10 h. These results indicate the great potential femtosecond pulse lasers may have in the future manufacturing of microstructured surfaces and devices.

  2. Step density waves on growing vicinal crystal surfaces - Theory and experiment

    Science.gov (United States)

    Ranguelov, Bogdan; Müller, Pierre; Metois, Jean-Jacques; Stoyanov, Stoyan

    2017-01-01

    The Burton, Cabrera and Frank (BCF) theory plays a key conceptual role in understanding and modeling the crystal growth of vicinal surfaces. In BCF theory the adatom concentration on a vicinal surface obeys to a diffusion equation, generally solved within quasi-static approximation where the adatom concentration at a given distance x from a step has a steady state value n (x) . Recently, we show that going beyond this approximation (Ranguelov and Stoyanov, 2007) [6], for fast surface diffusion and slow attachment/detachment kinetics of adatoms at the steps, a train of fast-moving steps is unstable against the formation of steps density waves. More precisely, the step density waves are generated if the step velocity exceeds a critical value related to the strength of the step-step repulsion. This theoretical treatment corresponds to the case when the time to reach a steady state concentration of adatoms on a given terrace is comparable to the time for a non-negligible change of the step configuration leading to a terrace adatom concentration n (x , t) that depends not only on the terrace width, but also on its "past width". This formation of step density waves originates from the high velocity of step motion and has nothing to do with usual kinetic instabilities of step bunching induced by Ehrlich-Schwoebel effect, surface electromigration and/or the impact of impurities on the step rate. The so-predicted formation of step density waves is illustrated by numerical integration of the equations for step motion. In order to complete our previous theoretical treatment of the non-stationary BCF problem, we perform an in-situ reflection electron microscopy experiment at specific temperature interval and direction of the heating current, in which, for the first time, the step density waves instability is evidenced on Si(111) surface during highest possible Si adatoms deposition rates.

  3. Density functional theory calculations on oxygen adsorption on the Cu{sub 2}O surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Xiaohu [College of Physics and Electrical Engineering, Anyang Normal University, Anyang, Henan 455000 (China); State Key laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001 (China); Zhang, Xuemei [College of Physics and Electrical Engineering, Anyang Normal University, Anyang, Henan 455000 (China); Tian, Xinxin [State Key laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001 (China); Wang, Shengguang, E-mail: shengguang.wang@gmail.com [State Key laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001 (China); Synfuels China Co., Ltd., Huairou, Beijing 101407 (China); Feng, Gang, E-mail: fengg.sshy@sinopec.com [State Key laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan, Shanxi 030001 (China); Shanghai Research Institute of Petrochemical Technology SINOPEC, Shanghai 201208 (China)

    2015-01-01

    Graphical abstract: - Highlights: • Atomic oxygen adsorption on Cu{sub 2}O(110) and Cu{sub 2}O(100) induces surface reconstruction. • Atomic O and molecular O{sub 2} adsorption on the Cu{sub 2}O(100) surface is stronger than on the Cu{sub 2}O(111) surface. • Dissociative adsorption was found to be energetically favorable. • Atomic O and molecular O{sub 2} adsorption on the Cu{sub 2}O(111) surface induces magnetism. - Abstract: In order to understand various surface properties such as corrosion and potential catalytic activity of Cu{sub 2}O surfaces in the presence of environmental gases, we report here spin-polarized density functional theory calculations of the adsorptions of atomic and molecular oxygen on three surface Cu{sub 2}O facets. Atomic oxygen adsorbs at the hollow site formed with copper atoms of Cu{sub 2}O(111), while its adsorption on the Cu{sub 2}O(110) and Cu{sub 2}O(100) induces surface reconstruction. Molecular oxygen adsorbs on one coordinated unsaturated surface copper atom and two coordinated saturated copper atoms of Cu{sub 2}O(111), on the top of two surface copper atoms of Cu{sub 2}O(110), and on four surface copper atoms on Cu{sub 2}O(100). It was found that atomic O and molecular O{sub 2} adsorption on the Cu{sub 2}O(100) surface is stronger than on the Cu{sub 2}O(111) surface. Atomic O and molecular O{sub 2} adsorption on the surface of Cu{sub 2}O(111) induces magnetism. This is different from other systems previously known to exhibit point defect ferromagnetism. On all three surfaces, dissociative adsorption was found to be energetically favorable.

  4. The Relation between Stellar and Dynamical Surface Densities in the Central Regions of Disk Galaxies

    Science.gov (United States)

    Lelli, Federico; McGaugh, Stacy S.; Schombert, James M.; Pawlowski, Marcel S.

    2016-08-01

    We use the Spitzer Photometry and Accurate Rotation Curves database to study the relation between the central surface density of stars {{{Σ }}}\\star (0) and dynamical mass {{{Σ }}}{{dyn}}(0) in 135 disk galaxies (S0 to dIrr). We find that {{{Σ }}}{{dyn}}(0) correlates tightly with {{{Σ }}}\\star (0) over 4 dex. This central density relation can be described by a double power law. High surface brightness galaxies are consistent with a 1:1 relation, suggesting that they are self-gravitating and baryon dominated in the inner parts. Low surface brightness (LSB) galaxies systematically deviate from the 1:1 line, indicating that the dark matter contribution progressively increases but remains tightly coupled to the stellar one. The observed scatter is small (˜0.2 dex) and largely driven by observational uncertainties. The residuals show no correlations with other galaxy properties like stellar mass, size, or gas fraction.

  5. The Relation between Stellar and Dynamical Surface Densities in the Central Regions of Disk Galaxies

    CERN Document Server

    Lelli, Federico; Schombert, James M; Pawlowski, Marcel S

    2016-01-01

    We use the SPARC (Spitzer Photometry & Accurate Rotation Curves) database to study the relation between the central surface density of stars Sstar and dynamical mass Sdyn in 135 disk galaxies (S0 to dIrr). We find that Sdyn correlates tightly with Sstar over 4 dex. This central density relation can be described by a double power law. High surface brightness galaxies are consistent with a 1:1 relation, suggesting that they are self-gravitating and baryon dominated in the inner parts. Low surface brightness galaxies systematically deviate from the 1:1 line, indicating that the dark matter contribution progressively increases but remains tightly coupled to the stellar one. The observed scatter is small (~0.2 dex) and largely driven by observational uncertainties. The residuals show no correlations with other galaxy properties like stellar mass, size, or gas fraction.

  6. Construction of 3D micropatterned surfaces with wormlike and superhydrophilic PEG brushes to detect dysfunctional cells.

    Science.gov (United States)

    Hou, Jianwen; Shi, Qiang; Ye, Wei; Fan, Qunfu; Shi, Hengchong; Wong, Shing-Chung; Xu, Xiaodong; Yin, Jinghua

    2014-12-10

    Detection of dysfunctional and apoptotic cells plays an important role in clinical diagnosis and therapy. To develop a portable and user-friendly platform for dysfunctional and aging cell detection, we present a facile method to construct 3D patterns on the surface of styrene-b-(ethylene-co-butylene)-b-styrene elastomer (SEBS) with poly(ethylene glycol) brushes. Normal red blood cells (RBCs) and lysed RBCs (dysfunctional cells) are used as model cells. The strategy is based on the fact that poly(ethylene glycol) brushes tend to interact with phosphatidylserine, which is in the inner leaflet of normal cell membranes but becomes exposed in abnormal or apoptotic cell membranes. We demonstrate that varied patterned surfaces can be obtained by selectively patterning atom transfer radical polymerization (ATRP) initiators on the SEBS surface via an aqueous-based method and growing PEG brushes through surface-initiated atom transfer radical polymerization. The relatively high initiator density and polymerization temperature facilitate formation of PEG brushes in high density, which gives brushes worm-like morphology and superhydrophilic property; the tendency of dysfunctional cells adhered on the patterned surfaces is completely different from well-defined arrays of normal cells on the patterned surfaces, providing a facile method to detect dysfunctional cells effectively. The PEG-patterned surfaces are also applicable to detect apoptotic HeLa cells. The simplicity and easy handling of the described technique shows the potential application in microdiagnostic devices.

  7. Electron density and electron temperature measurements in nanosecond pulse discharges over liquid water surface

    Science.gov (United States)

    Simeni Simeni, M.; Roettgen, A.; Petrishchev, V.; Frederickson, K.; Adamovich, I. V.

    2016-12-01

    Time-resolved electron density, electron temperature, and gas temperature in nanosecond pulse discharges in helium and O2-He mixtures near liquid water surface are measured using Thomson/pure rotational Raman scattering, in two different geometries, (a) ‘diffuse filament’ discharge between a spherical high-voltage electrode and a grounded pin electrode placed in a reservoir filled with distilled water, with the tip exposed, and (b) dielectric barrier discharge between the high-voltage electrode and the liquid water surface. A diffuse plasma filament generated between the electrodes in helium during the primary discharge pulse exhibits noticeable constriction during the secondary discharge pulse several hundred ns later. Adding oxygen to the mixture reduces the plasma filament diameter and enhances constriction during the secondary pulse. In the dielectric barrier discharge, diffuse volumetric plasma occupies nearly the entire space between the high voltage electrode and the liquid surface, and extends radially along the surface. In the filament discharge in helium, adding water to the container results in considerable reduction of plasma lifetime compared to the discharge in dry helium, by about an order of magnitude, indicating rapid electron recombination with water cluster ions. Peak electron density during the pulse is also reduced, by about a factor of two, likely due to dissociative attachment to water vapor during the discharge pulse. These trends become more pronounced as oxygen is added to the mixture, which increases net rate of dissociative attachment. Gas temperature during the primary discharge pulse remains near room temperature, after which it increases up to T ~ 500 K over 5 µs and decays back to near room temperature before the next discharge pulse several tens of ms later. As expected, electron density and electron temperature in diffuse DBD plasmas are considerably lower compared to peak values in the filament discharge. Use of Thomson

  8. Density gradient centrifugation in urografin of Moraxella and Kingella cells and appendages.

    Science.gov (United States)

    Frøholm, L O; Bøvre, K

    1978-04-01

    Purification of fimbriae (pili) by density gradient banding in Urografin medium was attempted. Moraxella nonliquefaciens and Kingella kingae fimbriae were of higher density than their cells of origin, but fimbrial fractions obtained by homogenization and differential centrifugation still banded together with presumed outer membrane fragments and some whole cells in Urografin gradients. The cellular density of genetic variants with different fimbriation/competence levels was also studied. For one strain of M. nonliquefaciens and two strains of K. kingae, cells harvested from agar plates tended to show several bands on isopycnic density gradient centrifugation, with slightly higher general density of fimbriated variants than non-fimbriated. A single density band could be observed with cells from log phase broth cultures of selected strains which showed no distinct difference between fimbriation or competence variants of each strain. Cells of M. nonliquefaciens and M. bovis showed comparable buoyant densities, whereas those of K. kingae had a higher density.

  9. Lens Epithelial Cell Proliferation and Cell Density in Human Age-related Cataract

    Institute of Scientific and Technical Information of China (English)

    Xialin Liu; Yizhi Liu; Jianliang Zheng; Qiang Huang; Huling Zheng

    2000-01-01

    Purpose: To discuss the potential effect of the lens epithelial cell proliferation in age-related cataract.Methods: In vitro cell proliferation was assayed by MTT method to evaluate the lens epithelial cell density, index, and proliferation capacity in normal lens and all kinds of age-related cataract. Capsulotomy specimens from all kinds of patients who underwent cataract phacoemulsification extraction surgery were compared with the lens epithelial specimens from non-cataract lenses of Eye Bank eyes.Results: Lens epithelial cell density of central anterior capsule (LECD) in female normal lens was higher than that in male, LECD in nuclear cataract( > NⅢ ) was higher than that in normal lens, but in the mature cortical cataract, LF CD was lower. Mitotic index of three kinds of age-related cataracts in vivo had no statistical difference, neither did cell proliferation capacity of cultivated cells in vitro.Conclusion: The individual difference of lens epithelial cell density and proliferation capacity in vivo may be an important underlying cause for senile cataract in the cellular level, especially for nuclear cataract.

  10. A new experimental method for determining liquid density and surface tension

    Science.gov (United States)

    Chou, Kjo-Chih; Hu, Jian-Hong

    1991-02-01

    A summary concerning the measurement of liquid density relying on the Archimedes principle has been presented, based on which a new effective method with a specially designed bob for determining liquid density has been suggested. The application of this method to ethyl alcohol solution and liquid glycerol, as well as a theoretical error analysis, shows that this new method is significant, because not only can it simplify the procedure of measurement but it can also offer more precise results. Besides, this method can further provide surface tension or contact angle simultaneously. It is expected that this new method will find its application in hightemperature melts.

  11. Density and stability of soil organic carbon beneath impervious surfaces in urban areas.

    Science.gov (United States)

    Wei, Zongqiang; Wu, Shaohua; Yan, Xiao; Zhou, Shenglu

    2014-01-01

    Installation of impervious surfaces in urban areas has attracted increasing attention due to its potential hazard to urban ecosystems. Urban soils are suggested to have robust carbon (C) sequestration capacity; however, the C stocks and dynamics in the soils covered by impervious surfaces that dominate urban areas are still not well characterized. We compared soil organic C (SOC) densities and their stabilities under impervious surface, determined by a 28-d incubation experiment, with those in open areas in Yixing City, China. The SOC density (0-20 cm) under impervious surfaces was, on average, 68% lower than that in open areas. Furthermore, there was a significantly (Psoils, whereas the correlation was not apparent for the impervious-covered soils, suggesting that the artificial soil sealing in urban areas decoupled the cycle of C and N. Cumulative CO2-C evolved during the 28-d incubation was lower from the impervious-covered soils than from the open soils, and agreed well with a first-order decay model (Ct = C1+C0(1-e-kt)). The model results indicated that the SOC underlying capped surfaces had weaker decomposability and lower turnover rate. Our results confirm the unique character of urban SOC, especially that beneath impervious surface, and suggest that scientific and management views on regional SOC assessment may need to consider the role of urban carbon stocks.

  12. Regulation of cell proliferation and cell density by the inorganic phosphate transporter PiT1

    Directory of Open Access Journals (Sweden)

    Byskov Kristina

    2012-03-01

    Full Text Available Abstact Background The inorganic phosphate (Pi transporter, PiT1 (SLC20A1, is ubiquitously expressed in mammalian cells. It has previously been shown that down-regulation of PiT1 severely impaired the proliferation of two transformed human cells lines, HepG2 and HeLa, and the tumorigenicity of HeLa cells in nude mice. Moreover, PiT1 knock-out mice do not survive past E12.5 and from E10.5, the embryos were found to be growth-retarded and showed reduced proliferation of liver cells. Isolated mouse embryonic fibroblasts with knocked out as well as reduced PiT1 expression levels also exhibited impaired proliferation. Together these results suggest that a certain level of PiT1 is important for proliferation. We have here investigated the role of PiT1 in regulation of cell proliferation using two strictly density-inhibited cells lines, the murine MC3T3-E1 and NIH3T3 cells. Results We found that knock-down of PiT1 in MC3T3-E1 cells led to impaired proliferation supporting that at least a certain level of PiT1 is important for wildtype level of proliferation. We, however, also observed that MC3T3-E1 and NIH3T3 cells themselves regulate their endogenous PiT1 mRNA levels with lower levels in general correlating with decreased proliferation/increased cell density. Moreover, over-expression of human PiT1 led to increased proliferation of both MC3T3-E1 and NIH3T3 cultures and resulted in higher cell densities in cultures of these two strictly density-inhibited cell lines. In addition, when we transformed NIH3T3 cells by cultivation in fetal bovine serum, cells over-expressing human PiT1 formed more colonies in soft agar than control cells. Conclusions We conclude that not only is a certain level of PiT1 necessary for normal cell division as suggested by previously published studies, rather the cellular PiT1 level is involved in regulating cell proliferation and cell density and an increased PiT1 expression can indeed make NIH3T3 cells more sensitive to

  13. Dietary Restriction reduces hippocampal neurogenesis and granule cell neuron density without affecting the density of mossy fibers.

    Science.gov (United States)

    Staples, Miranda C; Fannon-Pavlich, McKenzie J; Mysore, Karthik K; Dutta, Rahul R; Ongjoco, Alexandria T; Quach, Leon W; Kharidia, Khush M; Somkuwar, Sucharita S; Mandyam, Chitra D

    2017-03-08

    The hippocampal formation undergoes significant morphological and functional changes after prolonged caloric and dietary restriction (DR). In this study we tested whether prolonged DR results in deleterious alterations in hippocampal neurogenesis, density of granule cell neurons and mossy fibers, all of which support plasticity in the dentate gyrus. Young adult animals either experienced free access to food (control condition), or every-other-day feeding regimen (DR condition) for 3 months. The number of Ki-67 cells and 28-day old 5-bromo-2'-deoxyuridine (BrdU) cells were quantified in the dorsal and ventral dentate gyrus to determine the effect of DR on cellular proliferation and survival of neural progenitor cells in the anatomically defined regions of the dentate gyrus. The density of granule cell neurons and synaptoporin were also quantified to determine the effect of DR on granule cell neurons and mossy fiber projections in the dentate gyrus. Our results show that DR increases cellular proliferation and concurrently reduces survival of newly born neurons in the ventral dentate gyrus without effecting the number of cells in the dorsal dentate gyrus. DR reduced density of granule cell neurons in the dorsal dentate gyrus. These alterations in the number of granule cell neurons did not affect mossy fiber density in DR animals, which was visualized as no differences in synaptoporin expression. Our findings demonstrate that granule cell neurons in the dentate gyrus are vulnerable to chronic DR and that the reorganization of granule cells in the dentate gyrus subregions is not producing concomitant alterations in dentate gyrus neuronal circuitry with this type of dietary restriction.

  14. Engineering novel cell surface chemistry for selective tumor cell targeting

    Energy Technology Data Exchange (ETDEWEB)

    Bertozzi, C.R. [Univ. of California, Berkeley, CA (United States)]|[Lawrence Berkeley National Lab., CA (United States)

    1997-12-31

    A common feature of many different cancers is the high expression level of the two monosaccharides sialic acid and fucose within the context of cell-surface associated glycoconjugates. A correlation has been made between hypersialylation and/or hyperfucosylation and the highly metastatic phenotype. Thus, a targeting strategy based on sialic acid or fucose expression would be a powerful tool for the development of new cancer cell-selective therapies and diagnostic agents. We have discovered that ketone groups can be incorporated metabolically into cell-surface associated sialic acids. The ketone is can be covalently ligated with hydrazide functionalized proteins or small molecules under physiological conditions. Thus, we have discovered a mechanism to selectively target hydrazide conjugates to highly sialylated cells such as cancer cells. Applications of this technology to the generation of novel cancer cell-selective toxins and MRI contrast reagents will be discussed, in addition to progress towards the use of cell surface fucose residues as vehicles for ketone expression.

  15. The Surface Density Profile of the Galactic Disk from the Terminal Velocity Curve

    CERN Document Server

    McGaugh, Stacy S

    2015-01-01

    The mass distribution of the Galactic disk is constructed from the terminal velocity curve and the mass discrepancy-acceleration relation. Mass models numerically quantifying the detailed surface density profiles are tabulated. For $R_0 = 8$ kpc, the models have stellar mass $5 < M_* < 6 \\times 10^{10}$ M$_{\\odot}$, scale length $2.0 \\le R_d \\le 2.9$ kpc, LSR circular velocity $222 \\le \\Theta_0 \\le 233$ km s$^{-1}$, and solar circle stellar surface density $34 \\le \\Sigma_d(R_0) \\le 61$ M$_{\\odot}$ pc$^{-2}$. The present inter-arm location of the solar neighborhood may have a somewhat lower stellar surface density than average for the solar circle. The Milky Way appears to be a normal spiral galaxy that obeys scaling relations like the Tully-Fisher relation, the size-mass relation, and the disk maximality-surface brightness relation. The stellar disk is maximal, and the spiral arms are massive. The bumps and wiggles in the terminal velocity curve correspond to known spiral features (e.g., the Centaurus A...

  16. Surface roughness and dislocation density in InP/InGaAs layers

    Science.gov (United States)

    Masson, Denis P.; Laframboise, Sylvain

    2004-12-01

    A subtle roughening of the surface of a buried 60 nm InGaAs epitaxial layer was detected using a combination of sample cleaving, selective chemical etching and Field Emission Scanning Electron Microscopy (FESEM). In our technology, InGaAs is the photo-absorbing layer of Metal Organic Chemical Vapor Deposition (MOCVD) grown layers used in the monolithic integration of active photo detectors and a passive mux/demux. Conventional Photo-Luminescence (PL) and X-Ray Diffraction (XRD) techniques used to monitor and optimize the growth of epitaxial layers did not show this microscopic surface roughness. The appearance of roughness in the InGaAs layer was linked to very large changes in the dislocation density of the layers grown over the rough surface. Increases of up to three orders of magnitude in the Etch Pit Density (EPD from 104 to 107 cm-2) were revealed using a standard Huber Etch. The Huber Etch also showed the preferred formation of "pairs" of dislocations threading out from a common point on the rough InGaAs surface. Changes in growth conditions resulted in the complete elimination of roughness and of excessive dislocation densities

  17. High densities of serotonin and peptide YY cells in the colon of patients with lymphocytic colitis

    Institute of Scientific and Technical Information of China (English)

    Magdy El-Salhy; Doris Gundersen; Jan Gunnar Hatlebakk; Trygve Hausken

    2012-01-01

    AIM:To investigate colonic endocrine cells in lymphocytic colitis (LC) patients.METHODS:Fifty-seven patients with LC were included.These patients were 41 females and 16 males,with an average age of 49 years (range 19-84 years).Twenty-seven subjects that underwent colonoscopy with biopsies were used as controls.These subjects underwent colonoscopy because of gastrointestinal bleeding or health worries,where the source of bleeding was identified as haemorrhoids or angiodysplasia.They were 19 females and 8 males with an average age of 49 years (range 18-67 years).Biopsies from the right and left colon were obtained from both patients and controls during colonoscopy.Biopsies were fixed in 4% buffered paraformaldehyde,embedded in paraffin and cut into 5 μm-thick sections.The sections immunostained by the avidin-biotin-complex method for serotonin,peptide YY (PYY),pancreatic polypeptide (pP)enteroglucagon and somatostatin cells.The cell densities were quantified by computerised image analysis using Olympus software.RESULTS:The colon of both the patient and the control subjects were macroscopically normal.Histopathological examination of colon biopsies from controis revealed normal histology.All patients fulfilled the diagnosis criteria required for of LC:an increase in intraepithelial lymphocytes (> 20 lymphocytes/100 epithelial cells) and surface epithelial damage with increased lamina propria plasma cells and absent or minimal crypt architectural distribution.In the colon of both patients and control subjects,serotonin-,PYY-,PP-,enteroglucagon-and somatostatin-immunoreactive cells were primarily located in the upper part of the crypts of Lieberkühn.These cells were basket-or flask-shaped.There was no statistically significant difference between the right and left colon in controls with regards to the densities of serotonin-and PYY-immunoreactive cells (P =0.9 and 0.1,respectively).Serotonin cell density in the right colon in controls was 28.9 ± 1.8 and in LC

  18. Gas surface density, star formation rate surface density, and the maximum mass of young star clusters in a disk galaxy. I. The flocculent galaxy M33

    CERN Document Server

    Gonzalez-Lopezlira, Rosa A; Kroupa, Pavel

    2012-01-01

    We analyze the relationship between maximum cluster mass, M_max, and surface densities of total gas (Sigma_gas), molecular gas (Sigma_H2) and star formation rate (Sigma_SFR) in the flocculent galaxy M33, using published gas data and a catalog of more than 600 young star clusters in its disk. By comparing the radial distributions of gas and most massive cluster masses, we find that M_max is proportional to Sigma_gas^4.7, M_max is proportional Sigma_H2^1.3, and M_max is proportional to Sigma_SFR^1.0. We rule out that these correlations result from the size of sample; hence, the change of the maximum cluster mass must be due to physical causes.

  19. Cell culture density affects the proliferation activity of human adipose tissue stem cells.

    Science.gov (United States)

    Kim, Dae Seong; Lee, Myoung Woo; Ko, Young Jong; Chun, Yong Hoon; Kim, Hyung Joon; Sung, Ki Woong; Koo, Hong Hoe; Yoo, Keon Hee

    2016-01-01

    In this study, we investigated the effect of cell density on the proliferation activity of human mesenchymal stem cells (MSCs) derived from adipose tissue (AT-MSCs) over time in culture. Passage #4 (P4) and #12 (P12) AT-MSCs from two donors were plated at a density of 200 (culture condition 1, CC1) or 5000 (culture condition 2, CC2) cells cm(-2) . After 7 days of incubation, P4 and P12 AT-MSCs cultured in CC1 were thin and spindle-shaped, whereas those cultured in CC2 had extensive cell-to-cell contacts and an expanded cell volume. In addition, P4 and P12 AT-MSCs in CC1 divided more than three times, while those in CC2 divided less than once on average. Flow cytometric analysis using 5(6)-carboxyfluorescein diacetate N-succinimidyl ester dye showed that the fluorescence intensity of AT-MSCs was lower in CC1 than in CC2. Furthermore, expression of proliferation-associated genes, such as CDC45L, CDC20A and KIF20A, in P4 AT-MSCs was higher in CC1 than in CC2, and this difference was also observed in P12 AT-MSCs. These data demonstrated that cell culture density affects the proliferation activity of MSCs, suggesting that it is feasible to design a strategy to prepare suitable MSCs using specific culture conditions.

  20. Bacterial cell surface structures in Yersinia enterocolitica.

    Science.gov (United States)

    Białas, Nataniel; Kasperkiewicz, Katarzyna; Radziejewska-Lebrecht, Joanna; Skurnik, Mikael

    2012-06-01

    Yersinia enterocolitica is a widespread member of the family of Enterobacteriaceae that contains both non-virulent and virulent isolates. Pathogenic Y. enterocolitica strains, especially belonging to serotypes O:3, O:5,27, O:8 and O:9 are etiologic agents of yersiniosis in animals and humans. Y. enterocolitica cell surface structures that play a significant role in virulence have been subject to many investigations. These include outer membrane (OM) glycolipids such as lipopolysaccharide (LPS) and enterobacterial common antigen (ECA) and several cell surface adhesion proteins present only in virulent Y. enterocolitica, i.e., Inv, YadA and Ail. While the yadA gene is located on the Yersinia virulence plasmid the Ail, Inv, LPS and ECA are chromosomally encoded. These structures ensure the correct architecture of the OM, provide adhesive properties as well as resistance to antimicrobial peptides and to host innate immune response mechanisms.

  1. Examination of Poststroke Alteration in Motor Unit Firing Behavior Using High-Density Surface EMG Decomposition.

    Science.gov (United States)

    Li, Xiaoyan; Holobar, Ales; Gazzoni, Marco; Merletti, Roberto; Rymer, William Zev; Zhou, Ping

    2015-05-01

    Recent advances in high-density surface electromyogram (EMG) decomposition have made it a feasible task to discriminate single motor unit activity from surface EMG interference patterns, thus providing a noninvasive approach for examination of motor unit control properties. In the current study, we applied high-density surface EMG recording and decomposition techniques to assess motor unit firing behavior alterations poststroke. Surface EMG signals were collected using a 64-channel 2-D electrode array from the paretic and contralateral first dorsal interosseous (FDI) muscles of nine hemiparetic stroke subjects at different isometric discrete contraction levels between 2 to 10 N with a 2 N increment step. Motor unit firing rates were extracted through decomposition of the high-density surface EMG signals and compared between paretic and contralateral muscles. Across the nine tested subjects, paretic FDI muscles showed decreased motor unit firing rates compared with contralateral muscles at different contraction levels. Regression analysis indicated a linear relation between the mean motor unit firing rate and the muscle contraction level for both paretic and contralateral muscles (p < 0.001), with the former demonstrating a lower increment rate (0.32 pulses per second (pps)/N) compared with the latter (0.67 pps/N). The coefficient of variation (averaged over the contraction levels) of the motor unit firing rates for the paretic muscles (0.21 ± 0.012) was significantly higher than for the contralateral muscles (0.17 ± 0.014) (p < 0.05). This study provides direct evidence of motor unit firing behavior alterations poststroke using surface EMG, which can be an important factor contributing to hemiparetic muscle weakness.

  2. Density functional theory of equilibrium random copolymers: application to surface adsorption of aggregating peptides

    Science.gov (United States)

    Wang, Haiqiang; Forsman, Jan; Woodward, Clifford E.

    2016-06-01

    We generalize a recently developed polymer density functional theory (PDFT) for polydisperse polymer fluids to the case of equilibrium random copolymers. We show that the generalization of the PDFT to these systems allows us to obtain a remarkable simplification compared to the monodispersed polymers. The theory is used to treat a model for protein aggregation into linear filaments in the presence of surfaces. Here we show that, for attractive surfaces, there is evidence of significant enhancement of protein aggregation. This behaviour is a consequence of a surface phase transition, which has been shown to occur with ideal equilibrium polymers in the presence of sufficiently attractive surfaces. For excluding monomers, this transition is suppressed, though an echo of the underlying ideal transition is present in the sudden change in the excess adsorption.

  3. Construction of Larger Area Density-Uniform Plasma with Collisional Inductively Coupled Plasma Cells

    Institute of Scientific and Technical Information of China (English)

    OUYANG Liang; LIU Wandong; BAI Xiaoyan; CHEN Zhipeng; WANG Huihui; LI LUO Chen; JI Liangliang; HU Bei

    2007-01-01

    The plasma density and electron temperature of a multi-source plasma system composed of several collisional inductively coupled plasma (ICP) cells were measured by a double-probe. The discharges of the ICP cells were shown to be independent of each other. Furthermore, the total plasma density at simultaneous multi-cell discharge was observed to be approximately equal to the summation of the plasma density when the cells discharge separately. Based on the linear summation phenomenon, it was shown that a larger area plasma with a uniform density and temperature profile could be constructed with multi-collisional ICP cells.

  4. Smooth muscle myosin regulation by serum and cell density in cultured rat lung connective tissue cells.

    Science.gov (United States)

    Babij, P; Zhao, J; White, S; Woodcock-Mitchell, J; Mitchell, J; Absher, M; Baldor, L; Periasamy, M; Low, R B

    1993-08-01

    RNA and protein analyses were used to detect expression of SM1 and SM2 smooth muscle myosin heavy chain (MHC) in cultured adult rat lung connective tissue cells (RL-90). Smooth muscle MHC mRNA expression in confluent cells grown in 10% serum was approximately 50% of the level in adult stomach. Similar results were obtained in cells cultured at low density (25% confluency) in 1% serum. However, in low-density cultures transferred to 10% serum for 24 h, the level of MHC mRNA decreased to approximately 20% of that in adult stomach. Smooth muscle alpha-actin showed a pattern of expression similar to that for smooth muscle MHC. Expression of nonmuscle MHC-A mRNA was higher in all culture conditions compared to stomach. MHC-A mRNA expression was less in low-density cultures in low serum and increased when low-density cultures were transferred to 10% serum for 24 h. MHC-B mRNA expression was less in low- vs. high-density cultures. In contrast to MHC-A, however, MHC-B mRNA expression in low-density cultures was higher in low serum. Immunofluorescence and immunoblotting with SM1-specific antibody demonstrated the presence of the SM1 protein isoform as well as reactivity to a protein band migrating slightly faster than SM2. These results demonstrate that cultured rat lung connective tissue cells express smooth muscle MHC and that expression is modulated by culture conditions.

  5. Implicit solvation model for density-functional study of nanocrystal surfaces and reaction pathways

    Science.gov (United States)

    Mathew, Kiran; Sundararaman, Ravishankar; Letchworth-Weaver, Kendra; Arias, T. A.; Hennig, Richard G.

    2014-02-01

    Solid-liquid interfaces are at the heart of many modern-day technologies and provide a challenge to many materials simulation methods. A realistic first-principles computational study of such systems entails the inclusion of solvent effects. In this work, we implement an implicit solvation model that has a firm theoretical foundation into the widely used density-functional code Vienna ab initio Software Package. The implicit solvation model follows the framework of joint density functional theory. We describe the framework, our algorithm and implementation, and benchmarks for small molecular systems. We apply the solvation model to study the surface energies of different facets of semiconducting and metallic nanocrystals and the SN2 reaction pathway. We find that solvation reduces the surface energies of the nanocrystals, especially for the semiconducting ones and increases the energy barrier of the SN2 reaction.

  6. Near-exponential surface densities as hydrostatic, nonequilibrium profiles in galaxy discs

    CERN Document Server

    Struck, Curtis

    2016-01-01

    Apparent exponential surface density profiles are nearly universal in galaxy discs across Hubble types, over a wide mass range, and a diversity of gravitational potential forms. Several processes have been found to produce exponential profiles, including the actions of bars and spirals, and clump scattering, with star scattering a common theme in these. Based on reasonable physical constraints, such as minimal entropy gradients, we propose steady state distribution functions for disc stars, applicable over a range of gravitational potentials. The resulting surface density profiles are generally a power-law term times a Sersic-type exponential. Over a modest range of Sersic index values, these profiles are often indistinguishable from Type I exponentials, except at the innermost radii. However, in certain parameter ranges these steady states can appear as broken, Type II or III profiles. The corresponding velocity dispersion profiles are low order power-laws. A chemical potential associated with scattering can...

  7. Correlating the Local Defect-Level Density with the Macroscopic Composition and Energetics of Chalcopyrite Thin-Film Surfaces.

    Science.gov (United States)

    Bröker, Sebastian; Kück, Dennis; Timmer, Alexander; Lauermann, Iver; Ümsür, Bünyamin; Greiner, Dieter; Kaufmann, Christian A; Mönig, Harry

    2015-06-17

    The unusual defect chemistry of polycrystalline Cu(In,Ga)Se2 (CIGSe) thin films is a main issue for a profound understanding of recombination losses in chalcopyrite thin-film solar cells. Especially, impurity-driven passivation of electronic levels due to point defects segregating at the surface and at grain boundaries is extensively debated. By combining current imaging tunneling spectroscopy with photoelectron spectroscopy, the local defect-level density and unusual optoelectronic grain-boundary properties of this material are correlated with the macroscopic energy levels and surface composition. Vacuum annealing of different CIGSe materials provides evidence that Na diffusion from the glass substrate does not affect the surface defect passivation or grain-boundary properties of standard Cu-poor materials. Furthermore, we find no major impact on the observed thermally activated dipole compensation or the accompanying change in surface band bending (up to 0.6 eV) due to Na. In contrast, Cu-rich CIGSe shows an opposing surface defect chemistry with only minor heat-induced band bending. Our results lead to a comprehensive picture, where the highly desirable type inversion at the p/n interface in standard chalcopyrite thin-film solar cells is dominated by band bending within the CIGSe absorber rather than the result of Na impurities or an n-type defect phase segregating at the interface. This is in accordance with recent studies suggesting a surface reconstruction as the origin for Cu depletion and band-gap widening at the surface of chalcopyrite thin films.

  8. Molecular simulation insights on the in vacuo adsorption of amino acids on graphene oxide surfaces with varying surface oxygen densities

    Science.gov (United States)

    Rahmani, Farzin; Nouranian, Sasan; Mahdavi, Mina; Al-Ostaz, Ahmed

    2016-11-01

    In this fundamental study, a series of molecular dynamics simulations were performed in vacuo to investigate the energetics and select geometries of 20 standard amino acids (AAs) on pristine graphene (PG) and graphene oxide (GO) surfaces as a function of graphene surface oxygen density. These interactions are of key interest to graphene/biomolecular systems. Our results indicate that aromatic AAs exhibit the strongest total interactions with the PG surfaces due to π-π stacking. Tryptophan (Trp) has the highest aromaticity due to its indole side chain and, hence, has the strongest interaction among all AAs (-16.66 kcal/mol). Aliphatic, polar, and charged AAs show various levels of affinity to the PG sheets depending on the strength of their side chain hydrophobic interactions. For example, arginine (Arg) with its guanidinium side chain exhibits the strongest interaction with the PG sheets (-13.81 kcal/mol) following aromatic AAs. Also, glycine (Gly; a polar AA) has the weakest interaction with the PG sheets (-7.29 kcal/mol). When oxygen-containing functional groups are added to the graphene sheets, the π-π stacking in aromatic AAs becomes disrupted and perfect parallelism of the aromatic rings is lost. Moreover, hydrogen bonding and/or electrostatic interactions become more pronounced. Charged AAs exhibit the strongest interactions with the GO surfaces. In general, the AA-GO interactions increase with increasing surface oxygen density, and the effect is more pronounced at higher O/C ratios. This study provides a quantitative measure of AA-graphene interactions for the design and tuning of biomolecular systems suitable for biosensing, drug delivery, and gene delivery applications.

  9. Investigation of surface charge density on solid-liquid interfaces by modulating the electrical double layer.

    Science.gov (United States)

    Moon, Jong Kyun; Song, Myung Won; Pak, Hyuk Kyu

    2015-05-20

    A solid surface in contact with water or aqueous solution usually carries specific electric charges. These surface charges attract counter ions from the liquid side. Since the geometry of opposite charge distribution parallel to the solid-liquid interface is similar to that of a capacitor, it is called an electrical double layer capacitor (EDLC). Therefore, there is an electrical potential difference across an EDLC in equilibrium. When a liquid bridge is formed between two conducting plates, the system behaves as two serially connected EDLCs. In this work, we propose a new method for investigating the surface charge density on solid-liquid interfaces. By mechanically modulating the electrical double layers and simultaneously applying a dc bias voltage across the plates, an ac electric current can be generated. By measuring the voltage drop across a load resistor as a function of bias voltage, we can study the surface charge density on solid-liquid interfaces. Our experimental results agree very well with the simple equivalent electrical circuit model proposed here. Furthermore, using this method, one can determine the polarity of the adsorbed state on the solid surface depending on the material used. We expect this method to aid in the study of electrical phenomena on solid-liquid interfaces.

  10. Constructing multiscale gravitational energy spectra from molecular cloud surface density PDF - interplay between turbulence and gravity

    Science.gov (United States)

    Li, Guang-Xing; Burkert, Andreas

    2016-09-01

    Gravity is believed to be important on multiple physical scales in molecular clouds. However, quantitative constraints on gravity are still lacking. We derive an analytical formula which provides estimates on multiscale gravitational energy distribution using the observed surface density probability distribution function (PDF). Our analytical formalism also enables one to convert the observed column density PDF into an estimated volume density PDF, and to obtain average radial density profile ρ(r). For a region with N_col ˜ N^{-γ _N}, the gravitational energy spectra is E_p(k)˜ k^{-4(1 - 1/γ _N)}. We apply the formula to observations of molecular clouds, and find that a scaling index of -2 of the surface density PDF implies that ρ ˜ r-2 and Ep(k) ˜ k-2. The results are valid from the cloud scale (a few parsec) to around ˜ 0.1 pc. Because of the resemblance the scaling index of the gravitational energy spectrum and the that of the kinetic energy power spectrum of the Burgers turbulence (where E ˜ k-2), our result indicates that gravity can act effectively against turbulence over a multitude of physical scales. This is the critical scaling index which divides molecular clouds into two categories: clouds like Orion and Ophiuchus have shallower power laws, and the amount of gravitational energy is too large for turbulence to be effective inside the cloud. Because gravity dominates, we call this type of cloud g-type clouds. On the other hand, clouds like the California molecular cloud and the Pipe nebula have steeper power laws, and turbulence can overcome gravity if it can cascade effectively from the large scale. We call this type of cloud t-type clouds. The analytical formula can be used to determine if gravity is dominating cloud evolution when the column density PDF can be reliably determined.

  11. On the surface recombination current of metal-insulator semiconductor inversion layer solar cells

    DEFF Research Database (Denmark)

    Nielsen, Otto M.

    1981-01-01

    voltages Voc were found to be lower than for ~ cells. The measured differences in Voc were higher than expected from the dark characteristics which is explained as a difference in the surface recombination current due to a higher interface state density Nss of ~ cells. Journal of Applied Physics...

  12. Surface Density of dark matter haloes on galactic and cluster scales

    CERN Document Server

    Del Popolo, A; Belvedere, G

    2013-01-01

    In this paper, in the framework of the secondary infall model, the correlation between the central surface density and the halo core radius of galaxy, and cluster of galaxies, dark matter haloes was analyzed, this having recently been studied on a wide range of scales. We used Del Popolo (2009) secondary infall model taking into account ordered and random angular momentum, dynamical friction, and dark matter (DM) adiabatic contraction to calculate the density profile of haloes, and then these profiles are used to determine the surface density of DM haloes. The main result is that $r_\\ast$ (the halo characteristic radius) is not an universal quantity as claimed by Donato et al. (2009) and Gentile et al. (2009). On the contrary, we find a correlation with the halo mass $M_{200}$ in agreement with Cardone & Tortora (2010), Boyarsky at al. (2009) and Napolitano et al. (2010), but with a significantly smaller scatter, namely $0.16 \\pm 0.05$. We also consider the baryon column density finding this latter being ...

  13. Non-destructive image analysis of soil surface porosity and bulk density dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Pires, L.F., E-mail: lfpires@uepg.b [Laboratory of Soil Physics and Environmental Sciences, State University of Ponta Grossa, UEPG, C.E.P. 84.030-900, Ponta Grossa, PR (Brazil); Cassaro, F.A.M. [Laboratory of Soil Physics and Environmental Sciences, State University of Ponta Grossa, UEPG, C.E.P. 84.030-900, Ponta Grossa, PR (Brazil); Bacchi, O.O.S.; Reichardt, K. [Laboratory of Soil Physics, Center for Nuclear Energy in Agriculture, USP/CENA, C.P. 96, C.E.P. 13.400-970, Piracicaba, SP (Brazil)

    2011-04-15

    A gamma-ray computed tomography (CT) scanner was used to evaluate changes in the structure of clayey soil samples with surface compaction submitted to wetting and drying (W-D) cycles. The obtained results indicate that W-D cycles promoted an increasing of about 10% in soil porosity with a decreasing of about 6% in soil bulk density of this compacted region. With the use of the CT it was also possible to define the thickness of the compacted region that in our case was of about 8.19 mm. This last information is very important, for instance, to estimate hydraulic parameters in infiltration models. Finally, CT analysis showed that the compacted region remained at the surface samples, even after the application of the W-D cycles. -- Research highlights: {yields} Gamma-ray tomography allowed non-destructive analysis of soil bulk density and porosity changes. {yields} Soil porosity increased about 10% with the wetting and drying cycles. {yields} Soil bulk density in the compacted region decreased about 6% with the wetting and drying cycles. {yields} Detailed bulk density and porosity analysis changes were obtained for layers of 1.17 mm.

  14. Application of response surface methodology to optimize uranium biological leaching at high pulp density

    Energy Technology Data Exchange (ETDEWEB)

    Fatemi, Faezeh; Arabieh, Masoud; Jahani, Samaneh [NSTRI, Tehran (Iran, Islamic Republic of). Nuclear Fuel Cycle Research School

    2016-08-01

    The aim of the present study was to carry out uranium bioleaching via optimization of the leaching process using response surface methodology. For this purpose, the native Acidithiobacillus sp. was adapted to different pulp densities following optimization process carried out at a high pulp density. Response surface methodology based on Box-Behnken design was used to optimize the uranium bioleaching. The effects of six key parameters on the bioleaching efficiency were investigated. The process was modeled with mathematical equation, including not only first and second order terms, but also with probable interaction effects between each pair of factors.The results showed that the extraction efficiency of uranium dropped from 100% at pulp densities of 2.5, 5, 7.5 and 10% to 68% at 12.5% of pulp density. Using RSM, the optimum conditions for uranium bioleaching (12.5% (w/v)) were identified as pH = 1.96, temperature = 30.90 C, stirring speed = 158 rpm, 15.7% inoculum, FeSO{sub 4} . 7H{sub 2}O concentration at 13.83 g/L and (NH{sub 4}){sub 2}SO{sub 4} concentration at 3.22 g/L which achieved 83% of uranium extraction efficiency. The results of uranium bioleaching experiment using optimized parameter showed 81% uranium extraction during 15 d. The obtained results reveal that using RSM is reliable and appropriate for optimization of parameters involved in the uranium bioleaching process.

  15. Modeling the Images of Relativistic Jets Lensed by Galaxies with Different Mass Surface Density Distributions

    OpenAIRE

    Larchenkova, T. I.; Lutovinov, A. A.; Lyskova, N. S.

    2011-01-01

    The images of relativistic jets from extragalactic sources produced by gravitational lensing by galaxies with different mass surface density distributions are modeled. In particular, the following models of the gravitational lens mass distribution are considered: a singular isothermal ellipsoid, an isothermal ellipsoid with a core, two- and three-component models with a galactic disk, halo, and bulge. The modeled images are compared both between themselves and with available observations. Dif...

  16. Ice Lines, Planetesimal Composition and Solid Surface Density in the Solar Nebula

    CERN Document Server

    Robinson, Sarah E; Bodenheimer, Peter; Laughlin, Gregory; Turner, Neal J; Beichman, C A

    2008-01-01

    To date, there is no core accretion simulation that can successfully account for the formation of Uranus or Neptune within the observed 2-3 Myr lifetimes of protoplanetary disks. Since solid accretion rate is directly proportional to the available planetesimal surface density, one way to speed up planet formation is to take a full accounting of all the planetesimal-forming solids present in the solar nebula. By combining a viscously evolving protostellar disk with a kinetic model of ice formation, we calculate the solid surface density in the solar nebula as a function of heliocentric distance and time. We find three effects that strongly favor giant planet formation: (1) a decretion flow that brings mass from the inner solar nebula to the giant planet-forming region, (2) recent lab results (Collings et al. 2004) showing that the ammonia and water ice lines should coincide, and (3) the presence of a substantial amount of methane ice in the trans-Saturnian region. Our results show higher solid surface densitie...

  17. Universal MOND relation between the baryonic and `dynamical' central surface densities of disc galaxies

    CERN Document Server

    Milgrom, Mordehai

    2016-01-01

    I derive a new MOND relation for pure-disc galaxies: The `dynamical' central surface density, $\\Sigma^0_D$, deduced from the measured velocities, is a universal function of only the true, `baryonic' central surface density, $\\Sigma^0_B$: $\\Sigma^0_D=\\Sigma_M \\mathcal{S}(\\Sigma^0_B/\\Sigma_M)$, where $\\Sigma_M\\equiv a_0/2\\pi G$ is the MOND surface density constant. This surprising result is shown to hold in both existing, nonrelativistic MOND theories (the nonlinear Poisson formulation, and QUMOND). $\\mathcal{S}(y)$ is derived, giving in the two limits: $\\Sigma^0_D=\\Sigma^0_B$ for very high arguments, and $\\Sigma^0_D=(4\\Sigma_M\\Sigma^0_B)^{1/2}$ for $\\Sigma^0_B/\\Sigma_M\\ll 1$. This study was prompted by the recent finding of a correlation between related attributes in a large sample of disc galaxies by Lelli et al. (2016). The MOND relation is shown to agree very well with these results.

  18. Capillary waves and the decay of density correlations at liquid surfaces

    Science.gov (United States)

    Hernández-Muñoz, Jose; Chacón, Enrique; Tarazona, Pedro

    2016-12-01

    Wertheim predicted strong density-density correlations at free liquid surfaces, produced by capillary wave fluctuations of the interface [M. S. Wertheim, J. Chem. Phys. 65, 2377 (1976), 10.1063/1.433352]. That prediction has been used to search for a link between capillary wave (CW) theory and density functional (DF) formalism for classical fluids. In particular, Parry et al. have recently analyzed the decaying tails of these CW effects moving away from the interface as a clue for the extended CW theory [A. O. Parry et al., J. Phys.: Condens. Matter 28, 244013 (2016), 10.1088/0953-8984/28/24/244013], beyond the strict long-wavelength limit studied by Wertheim. Some apparently fundamental inconsistencies between the CW and the DF theoretical views of the fluid interfaces arose from the asymptotic analysis of the CW signal. In this paper we revisit the problem of the CW asymptotic decay with a separation of local non-CW surface correlation effects from those that are a truly nonlocal propagation of the CW fluctuations from the surface towards the liquid bulk.

  19. X-Ray surface brightness and gas density fluctuations in the Coma cluster

    CERN Document Server

    Churazov, E; Zhuravleva, I; Schekochihin, A; Parrish, I; Sunyaev, R; Forman, W; Boehringer, H; Randall, S

    2011-01-01

    X-ray surface brightness fluctuations in the core ($650 \\times 650$ kpc) region of the Coma cluster observed with XMM-Newton and Chandra are analyzed using a 2D power spectrum approach. The resulting 2D spectra are converted to 3D power spectra of gas density fluctuations. The characteristic amplitude of the volume filling density fluctuations relative to the smooth underlying density distribution varies from 7-10% on scales of $\\sim$500 kpc down to $\\sim$5% at scales $\\sim$ 30 kpc. On smaller spatial scales, projection effects smear the density fluctuations by a large factor, precluding strong limits on the fluctuations in 3D. On the largest scales probed (hundreds of kpc), the dominant contributions to the observed fluctuations most likely arise from perturbations of the gravitational potential by the two most massive galaxies in Coma, NGC4874 and NGC4889, and the low entropy gas brought to the cluster by an infalling group. Other plausible sources of density fluctuations are discussed, including turbulence...

  20. Comparative assessment of surface fluxes from different sources using probability density distributions

    Science.gov (United States)

    Gulev, Sergey; Tilinina, Natalia; Belyaev, Konstantin

    2015-04-01

    Surface turbulent heat fluxes from modern era and first generation reanalyses (NCEP-DOE, ERA-Interim, MERRA NCEP-CFSR, JRA) as well as from satellite products (SEAFLUX, IFREMER, HOAPS) were intercompared using framework of probability distributions for sensible and latent heat fluxes. For approximation of probability distributions and estimation of extreme flux values Modified Fisher-Tippett (MFT) distribution has been used. Besides mean flux values, consideration is given to the comparative analysis of (i) parameters of the MFT probability density functions (scale and location), (ii) extreme flux values corresponding high order percentiles of fluxes (e.g. 99th and higher) and (iii) fractional contribution of extreme surface flux events in the total surface turbulent fluxes integrated over months and seasons. The latter was estimated using both fractional distribution derived from MFT and empirical estimates based upon occurrence histograms. The strongest differences in the parameters of probability distributions of surface fluxes and extreme surface flux values between different reanalyses are found in the western boundary current extension regions and high latitudes, while the highest differences in the fractional contributions of surface fluxes may occur in mid ocean regions being closely associated with atmospheric synoptic dynamics. Generally, satellite surface flux products demonstrate relatively stronger extreme fluxes compared to reanalyses, even in the Northern Hemisphere midlatitudes where data assimilation input in reanalyses is quite dense compared to the Southern Ocean regions.

  1. Periodic Density Functional Theory Study of Water Adsorption on the a-Quartz (101) Surface.

    Energy Technology Data Exchange (ETDEWEB)

    Bandura, Andrei V. [St. Petersburg State University, St. Petersburg, Russia; Kubicki, James D. [Pennsylvania State University; Sofo, Jorge O. [Pennsylvania State University

    2011-01-01

    Plane wave density functional theory (DFT) calculations have been performed to study the atomic structure, preferred H2O adsorption sites, adsorption energies, and vibrational frequencies for water adsorption on the R-quartz (101) surface. Surface energies and atomic displacements on the vacuum-reconstructed, hydrolyzed, and solvated surfaces have been calculated and compared with available experimental and theoretical data. By considering different initial positions of H2O molecules, the most stable structures of water adsorption at different coverages have been determined. Calculated H2O adsorption energies are in the range -55 to -65 kJ/mol, consistent with experimental data. The lowest and the highest O-H stretching vibrational bands may be attributed to different states of silanol groups on the watercovered surface. The dissociation energy of the silanol group on the surface covered by the adsorption monolayer is estimated to be 80 kJ/mol. The metastable states for the protonated surface bridging O atoms (Obr), which may lead to hydrolysis of siloxane bonds, have been investigated. The calculated formation energy of a Q2 center from a Q3 center on the (101) surface with 2/3 dense monolayer coverage is equal to 70 kJ/mol which is in the range of experimental activation energies for quartz dissolution.

  2. Phospholipid polymer-based antibody immobilization for cell rolling surfaces in stem cell purification system.

    Science.gov (United States)

    Mahara, Atsushi; Chen, Hao; Ishihara, Kazuhiko; Yamaoka, Tetsuji

    2014-01-01

    We previously developed an antibody-conjugated cell rolling column that successfully separates stem cell subpopulations depending on the cell surface marker density, but a large amount of the injected cells were retained in the column because of non-specific interactions. In this study, an amphiphilic copolymer, poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-co-n-butyl methacrylate (nBMA)-co-N-vinyl formamide (NVf)], with phospholipid polar side groups was designed as a novel antibody-immobilizing modifier. The formamide groups in NVf units were converted to active maleimide groups. A plastic flow microfluidic chamber was coated with the copolymers, and a reduced anti-CD90 antibody was immobilized. The adipose tissue-derived stem cells isolated from the rat were injected into the flow chamber, and their rolling behavior was observed under a microscope with a high-speed camera. Non-specific cell adhesion was reduced strongly by means of this immobilization method because of the MPC unit, resulting in a high percentage of rolling cells. These results demonstrate that a surface coated with phospholipid polar groups can be used in an effective stem cell separation system based on the cell rolling process.

  3. Estimation of immune cell densities in immune cell conglomerates: an approach for high-throughput quantification.

    Directory of Open Access Journals (Sweden)

    Niels Halama

    Full Text Available BACKGROUND: Determining the correct number of positive immune cells in immunohistological sections of colorectal cancer and other tumor entities is emerging as an important clinical predictor and therapy selector for an individual patient. This task is usually obstructed by cell conglomerates of various sizes. We here show that at least in colorectal cancer the inclusion of immune cell conglomerates is indispensable for estimating reliable patient cell counts. Integrating virtual microscopy and image processing principally allows the high-throughput evaluation of complete tissue slides. METHODOLOGY/PRINCIPAL FINDINGS: For such large-scale systems we demonstrate a robust quantitative image processing algorithm for the reproducible quantification of cell conglomerates on CD3 positive T cells in colorectal cancer. While isolated cells (28 to 80 microm(2 are counted directly, the number of cells contained in a conglomerate is estimated by dividing the area of the conglomerate in thin tissues sections (< or =6 microm by the median area covered by an isolated T cell which we determined as 58 microm(2. We applied our algorithm to large numbers of CD3 positive T cell conglomerates and compared the results to cell counts obtained manually by two independent observers. While especially for high cell counts, the manual counting showed a deviation of up to 400 cells/mm(2 (41% variation, algorithm-determined T cell numbers generally lay in between the manually observed cell numbers but with perfect reproducibility. CONCLUSION: In summary, we recommend our approach as an objective and robust strategy for quantifying immune cell densities in immunohistological sections which can be directly implemented into automated full slide image processing systems.

  4. Density-dependent nerve growth factor regulation of Gs-alpha RNA in pheochromocytoma 12 cells.

    Science.gov (United States)

    Tjaden, G; Aguanno, A; Kumar, R; Benincasa, D; Gubits, R M; Yu, H; Dolan, K P

    1990-01-01

    Nerve growth factor (NGF) affects levels of the alpha subunit of the stimulatory G protein (Gs-alpha) in pheochromocytoma 12 cells in a bidirectional, density-dependent manner. Cells grown at high density responded to NGF treatment with increased levels of Gs-alpha mRNA and protein. Conversely, in cells grown in low-density cultures, levels of this mRNA were lowered by NGF treatment. Images PMID:2160599

  5. Kinetic Control of Histidine-Tagged Protein Surface Density on Supported Lipid Bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Nye, Jeffrey A. [Univ. of California, Berkeley, CA (United States); Groves, Jay T. [Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2008-02-28

    Nickel-chelating lipids are general tools for anchoring polyhistidine-tagged proteins to supported lipid bilayers (SLBs), but controversy exists over the stability of the protein-lipid attachment. In this study, we show that chelator lipids are suitable anchors for building stable, biologically active surfaces but that a simple Langmuirian model is insufficient to describe their behavior. Desorption kinetics from chelator lipids are governed by the valency of surface binding: monovalently bound proteins desorb within minutes (t1/2 ≈ 6 min), whereas polyvalently bound species remain bound for hours (t1/2 ≈ 12 h). Evolution between surface states is slow, so equilibrium is unlikely to be reached on experimental timescales. However, by tuning incubation conditions, the populations of each species can be kinetically controlled, providing a wide range of protein densities on SLBs with a single concentration of chelator lipid. In conclusion, we propose guidelines for the assembly of SLB surfaces functionalized with specific protein densities and demonstrate their utility in the formation of hybrid immunological synapses.

  6. Error estimates for density-functional theory predictions of surface energy and work function

    Science.gov (United States)

    De Waele, Sam; Lejaeghere, Kurt; Sluydts, Michael; Cottenier, Stefaan

    2016-12-01

    Density-functional theory (DFT) predictions of materials properties are becoming ever more widespread. With increased use comes the demand for estimates of the accuracy of DFT results. In view of the importance of reliable surface properties, this work calculates surface energies and work functions for a large and diverse test set of crystalline solids. They are compared to experimental values by performing a linear regression, which results in a measure of the predictable and material-specific error of the theoretical result. Two of the most prevalent functionals, the local density approximation (LDA) and the Perdew-Burke-Ernzerhof parametrization of the generalized gradient approximation (PBE-GGA), are evaluated and compared. Both LDA and GGA-PBE are found to yield accurate work functions with error bars below 0.3 eV, rivaling the experimental precision. LDA also provides satisfactory estimates for the surface energy with error bars smaller than 10%, but GGA-PBE significantly underestimates the surface energy for materials with a large correlation energy.

  7. Functional balance between T cell chimeric receptor density and tumor associated antigen density: CTL mediated cytolysis and lymphokine production.

    Science.gov (United States)

    Weijtens, M E; Hart, E H; Bolhuis, R L

    2000-01-01

    Genetically engineered expression of tumor-specific single chain antibody chimeric receptors (ch-Rec) on human T lymphocytes endow these cells with the parental monoclonal antibody (mAb) dictated tumor specificity and may be useful for clinical immuno-genetherapy. Therefore it was of importance to assess how the densities of tumor-specific receptors and tumor associated antigens (TAA), respectively, affect primary human T lymphocyte functions in relation to target cell susceptibilities to lysis. We therefore studied the functional balance between ch-Rec densities on human T lymphocytes and TAA on tumor cells. The gene construct encoding a ch-Rec derived from (1) a renal carcinoma cell (RCC) specific mouse mAb (G250), and (2) the human signal transducing Fc(epsilon)RI gamma-chain was used. To obtain ch-RecHIGH-POS and ch-RecLOW-POS T lymphocytes, two distinct retroviral vectors were used to introduce the gene constructs into primary human T lymphocytes. Levels of ch-Rec-redirected T lymphocyte mediated tumor cell lysis, as well as lymphokine production were determined using RCC lines as target/stimulator cells, which express either no or increasing densities of the TAA. A functional and dynamic balance between ch-Rec densities on cytotoxic T lymphocytes (CTLs) on the one hand and TAA densities on RCCs on the other, was found. In short, ch-RecHIGH-POS CTLs are triggered by TAAHIGH-POS as well as TAALOW-POS RCCs to lyse tumor cells and produce (IFN-gamma and TNF-alpha) lymphokine. In contrast, ch-RecLOW-POS T lymphocytes are only triggered for cytolysis and lymphokine production by relatively TAAHIGH-POS RCCs. In conclusion, (1) the activation of T lymphocyte responses is co-determined by the expression levels of the ch-Rec on T lymphocytes and the TAA on tumor cells and (2) at relatively high T lymphocyte ch-Rec expression levels the CTLs lyse tumor cells with a wide range of TAA densities. Gene Therapy (2000) 7, 35-42.

  8. α-Tocopherol modulates the low density lipoprotein receptor of human HepG2 cells

    Directory of Open Access Journals (Sweden)

    Bottema Cynthia DK

    2003-05-01

    Full Text Available Abstract The aim of this study was to determine the effects of vitamin E (α-tocopherol on the low density lipoprotein (LDL receptor, a cell surface protein which plays an important role in controlling blood cholesterol. Human HepG2 hepatoma cells were incubated for 24 hours with increasing amounts of α, δ, or γ-tocopherol. The LDL receptor binding activity, protein and mRNA, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA reductase mRNA, cell cholesterol and cell lathosterol were measured. The effect of α-tocopherol was biphasic. Up to a concentration of 50 μM, α-tocopherol progressively increased LDL receptor binding activity, protein and mRNA to maximum levels 2, 4 and 6-fold higher than control, respectively. The HMG-CoA reductase mRNA and the cell lathosterol concentration, indices of cholesterol synthesis, were also increased by 40% over control by treatment with 50 μM α-tocopherol. The cell cholesterol concentration was decreased by 20% compared to control at 50 μM α-tocopherol. However, at α-tocopherol concentrations higher than 50 μM, the LDL receptor binding activity, protein and mRNA, the HMG-CoA reductase mRNA and the cell lathosterol and cholesterol concentrations all returned to control levels. The biphasic effect on the LDL receptor was specific for α-tocopherol in that δ and γ-tocopherol suppressed LDL receptor binding activity, protein and mRNA at all concentrations tested despite the cells incorporating similar amounts of the three homologues. In conclusion, α-tocopherol, exhibits a specific, concentration-dependent and biphasic "up then down" effect on the LDL receptor of HepG2 cells which appears to be at the level of gene transcription. Cholesterol synthesis appears to be similarly affected and the cell cholesterol concentration may mediate these effects.

  9. Density matrix treatment of non-adiabatic photoinduced electron transfer at a semiconductor surface.

    Science.gov (United States)

    Micha, David A

    2012-12-14

    Photoinduced electron transfer at a nanostructured surface leads to localized transitions and involves three different types of non-adiabatic couplings: vertical electronic transitions induced by light absorption emission, coupling of electronic states by the momentum of atomic motions, and their coupling due to interactions with electronic density fluctuations and vibrational motions in the substrate. These phenomena are described in a unified way by a reduced density matrix (RDM) satisfying an equation of motion that contains dissipative rates. The RDM treatment is used here to distinguish non-adiabatic phenomena that are localized from those due to interaction with a medium. The fast decay of localized state populations due to electronic density fluctuations in the medium has been treated within the Lindblad formulation of rates. The formulation is developed introducing vibronic states constructed from electron orbitals available from density functional calculations, and from vibrational states describing local atomic displacements. Related ab initio molecular dynamics calculations have provided diabatic momentum couplings between excited electronic states. This has been done in detail for an indirect photoexcitation mechanism of the surface Ag(3)Si(111):H, which leads to long lasting electronic charge separation. The resulting coupled density matrix equations are solved numerically to obtain the population of the final charge-separated state as it changes over time, for several values of the diabatic momentum coupling. New insight and unexpected results are presented here which can be understood in terms of photoinduced non-adiabatic transitions involving many vibronic states. It is found that the population of long lasting charge separation states is larger for smaller momentum coupling, and that their population grows faster for smaller coupling.

  10. Adsorption of Ar on planar surfaces studied with a density functional theory

    Science.gov (United States)

    Sartarelli, Salvador A.; Szybisz, Leszek

    2009-11-01

    The adsorption of Ar on planar structureless substrates of alkali metals, alkaline-earth metal Mg, CO2 , and Au was analyzed by applying a density functional formalism which includes a recently proposed effective attractive pair potential conditioned to Ar. It is shown that this approach reproduces the experimental surface tension of the liquid-vapor interface over the entire bulk coexistence curve for temperatures T spanning from the triple point Tt up to the critical point Tc . The wetting properties were studied over the entire range temperatures Tt↔Tc . It was found that Ar wets all the investigated surfaces. The adsorption isotherms for alkali metals exhibit first-order phase transitions. Prewetting lines were resolved even for the less attractive surfaces. In the cases of Mg, CO2 , and Au a continuous growth for T≥Tt was obtained. A comparison with experimental data and other microscopic calculations is reported.

  11. CZTSSe thin film solar cells: Surface treatments

    Science.gov (United States)

    Joglekar, Chinmay Sunil

    Chalcopyrite semiconducting materials, specifically CZTS, are a promising alternative to traditional silicon solar cell technology. Because of the high absorption coefficient; films of the order of 1 micrometer thickness are sufficient for the fabrication of solar cells. Liquid based synthesis methods are advantageous because they are easily scalable using the roll to roll manufacturing techniques. Various treatments are explored in this study to enhance the performance of the selenized CZTS film based solar cells. Thiourea can be used as a sulfur source and can be used to tune band gap of CZTSSe. Bromine etching can be used to manipulate the thickness of sintered CZTSSe film. The etching treatment creates recombination centers which lead to poor device performance. Various after treatments were used to improve the performance of the devices. It was observed that the performance of the solar cell devices could not be improved by any of the after treatment steps. Other surface treatment processes are explored including KCN etching and gaseous H2S treatments. Hybrid solar cells which included use of CIGS nanoparticles at the interface between CZTSSe and CdS are also explored.

  12. On the Control of the Fixed Charge Densities in Al2O3-Based Silicon Surface Passivation Schemes.

    Science.gov (United States)

    Simon, Daniel K; Jordan, Paul M; Mikolajick, Thomas; Dirnstorfer, Ingo

    2015-12-30

    A controlled field-effect passivation by a well-defined density of fixed charges is crucial for modern solar cell surface passivation schemes. Al2O3 nanolayers grown by atomic layer deposition contain negative fixed charges. Electrical measurements on slant-etched layers reveal that these charges are located within a 1 nm distance to the interface with the Si substrate. When inserting additional interface layers, the fixed charge density can be continuously adjusted from 3.5 × 10(12) cm(-2) (negative polarity) to 0.0 and up to 4.0 × 10(12) cm(-2) (positive polarity). A HfO2 interface layer of one or more monolayers reduces the negative fixed charges in Al2O3 to zero. The role of HfO2 is described as an inert spacer controlling the distance between Al2O3 and the Si substrate. It is suggested that this spacer alters the nonstoichiometric initial Al2O3 growth regime, which is responsible for the charge formation. On the basis of this charge-free HfO2/Al2O3 stack, negative or positive fixed charges can be formed by introducing additional thin Al2O3 or SiO2 layers between the Si substrate and this HfO2/Al2O3 capping layer. All stacks provide very good passivation of the silicon surface. The measured effective carrier lifetimes are between 1 and 30 ms. This charge control in Al2O3 nanolayers allows the construction of zero-fixed-charge passivation layers as well as layers with tailored fixed charge densities for future solar cell concepts and other field-effect based devices.

  13. Multiple charge density wave states at the surface of TbT e3

    Science.gov (United States)

    Fu, Ling; Kraft, Aaron M.; Sharma, Bishnu; Singh, Manoj; Walmsley, Philip; Fisher, Ian R.; Boyer, Michael C.

    2016-11-01

    We studied TbT e3 using scanning tunneling microscopy (STM) in the temperature range of 298-355 K. Our measurements detect a unidirectional charge density wave (CDW) state in the surface Te layer with a wave vector consistent with that of the bulk qCDW=0.30 ±0.01 c* . However, unlike previous STM measurements, and differing from measurements probing the bulk, we detect two perpendicular orientations for the unidirectional CDW with no directional preference for the in-plane crystal axes (a or c axis) and no noticeable difference in wave vector magnitude. In addition, we find regions in which the bidirectional CDW states coexist. We propose that observation of two unidirectional CDW states indicates a decoupling of the surface Te layer from the rare-earth block layer below, and that strain variations in the Te surface layer drive the local CDW direction to the specific unidirectional or, in rare occurrences, bidirectional CDW orders observed. This indicates that similar driving mechanisms for CDW formation in the bulk, where anisotropic lattice strain energy is important, are at play at the surface. Furthermore, the wave vectors for the bidirectional order we observe differ from those theoretically predicted for checkerboard order competing with stripe order in a Fermi-surface nesting scenario, suggesting that factors beyond Fermi-surface nesting drive CDW order in TbT e3 . Finally, our temperature-dependent measurements provide evidence for localized CDW formation above the bulk transition temperature TCDW.

  14. Physical origins of ruled surfaces on the reduced density matrices geometry

    Science.gov (United States)

    Chen, Ji-Yao; Ji, Zhengfeng; Liu, Zheng-Xin; Qi, Xiaofei; Yu, Nengkun; Zeng, Bei; Zhou, Duanlu

    2017-02-01

    The reduced density matrices (RDMs) of many-body quantum states form a convex set. The boundary of low dimensional projections of this convex set may exhibit nontrivial geometry such as ruled surfaces. In this paper, we study the physical origins of these ruled surfaces for bosonic systems. The emergence of ruled surfaces was recently proposed as signatures of symmetry-breaking phase. We show that, apart from being signatures of symmetry-breaking, ruled surfaces can also be the consequence of gapless quantum systems by demonstrating an explicit example in terms of a two-mode Ising model. Our analysis was largely simplified by the quantum de Finetti's theorem—in the limit of large system size, these RDMs are the convex set of all the symmetric separable states. To distinguish ruled surfaces originated from gapless systems from those caused by symmetry-breaking, we propose to use the finite size scaling method for the corresponding geometry. This method is then applied to the two-mode XY model, successfully identifying a ruled surface as the consequence of gapless systems.

  15. Adsorption/Desorption of Low-density Lipoprotein on a Heparinized Surface of Gold Sensors

    Institute of Scientific and Technical Information of China (English)

    LAN Ping; JI Jing; HUANG Xiao-Jun; GUDURU Deepak; GROTH Thomas; VIENKEN J(o)rg; DING Hui

    2012-01-01

    Heparin has been considered to be a potentially useful ligand for low-density lipoprotein(LDL)detection and analysis in a clinical context.In order to construct an affinity surface for preferential adsorption of LDL,heparin-modified gold surface(GS-Hep)was fabricated by a self-assembling method and hydrophobic-modified gold surfaces(GS-Hydro)was used as a control.The morphologies of the modified gold surfaces were investigated by atomic force microscopy(AFM)and the quantity of heparin bound to gold surface was assayed by the toluidine blue(TB)colorimetric method.Water contact angles were determined to investigate wettability on GS-Hep and GS-Hydro.Surface plasmon resonance(SPR)technique was used subsequently to detect the selective binding of LDL with heparin.And the investigation on the effect of pH on LDL adsorption suggests that lower pH lead to higher quantities of LDL adsorption on GS-Hep.Compared with GS-Hydro,GS-Hep is selective for LDL from both single and binary protein solutions.Moreover,adsorbed LDL on GS-Hep could be washed off by injecting elution solution,such as NaCl solution,for the purpose of the regeneration of GS-Hep for further LDL adsorption.

  16. ADSORPTION OF ASSOCIATING FLUIDS AT ACTIVE SURFACES: A DENSITY FUNCTIONAL THEORY

    Directory of Open Access Journals (Sweden)

    S.Tripathi

    2003-01-01

    Full Text Available We present a density functional theory (DFT to describe adsorption in systems where molecules of associating fluids can bond (or associate with discrete, localized functional groups attached to the surfaces, in addition to other fluid molecules. For such systems as water adsorbing on activated carbon, silica, clay minerals etc. this is a realistic model to account for surface heterogeneity rather than using a continuous smeared surface-fluid potential employed in most of the theoretical works on adsorption on heterogeneous surfaces. Association is modelled within the framework of first order thermodynamic perturbation theory (TPT1. The new theory accurately predicts the distribution of bonded and non-bonded species and adsorption behavior under various conditions of bulk pressure, surface-fluid and fluid-fluid association strengths. Competition between the surface-fluid and fluid-fluid association is analyzed for fluids with multiple association sites and its impact on adsorption is discussed. The theory, supported by simulations demonstrates that the extent and the nature of adsorption (e.g. monolayer vary with the number of association sites on the fluid molecules.

  17. Information in a Network of Neuronal Cells: Effect of Cell Density and Short-Term Depression

    KAUST Repository

    Onesto, Valentina

    2016-05-10

    Neurons are specialized, electrically excitable cells which use electrical to chemical signals to transmit and elaborate information. Understanding how the cooperation of a great many of neurons in a grid may modify and perhaps improve the information quality, in contrast to few neurons in isolation, is critical for the rational design of cell-materials interfaces for applications in regenerative medicine, tissue engineering, and personalized lab-on-a-chips. In the present paper, we couple an integrate-and-fire model with information theory variables to analyse the extent of information in a network of nerve cells. We provide an estimate of the information in the network in bits as a function of cell density and short-term depression time. In the model, neurons are connected through a Delaunay triangulation of not-intersecting edges; in doing so, the number of connecting synapses per neuron is approximately constant to reproduce the early time of network development in planar neural cell cultures. In simulations where the number of nodes is varied, we observe an optimal value of cell density for which information in the grid is maximized. In simulations in which the posttransmission latency time is varied, we observe that information increases as the latency time decreases and, for specific configurations of the grid, it is largely enhanced in a resonance effect.

  18. Simulation and Optimization of Silicon Solar Cell Back Surface Field

    Directory of Open Access Journals (Sweden)

    Souad TOBBECHE

    2015-11-01

    Full Text Available In this paper, TCAD Silvaco (Technology Computer Aided Design software has been used to study the Back Surface Field (BSF effect of a p+ silicon layer for a n+pp+ silicon solar cell. To study this effect, the J-V characteristics and the external quantum efficiency (EQE are simulated under AM 1.5 illumination for two types of cells. The first solar cell is without BSF (n+p structure while the second one is with BSF (n+pp+ structure. The creation of the BSF on the rear face of the cell results in efficiency h of up to 16.06% with a short-circuit current density Jsc = 30.54 mA/cm2, an open-circuit voltage Voc = 0.631 V, a fill factor FF = 0.832 and a clear improvement of the spectral response obtained in the long wavelengths range. An electric field and a barrier of potential are created by the BSF and located at the junction p+/p with a maximum of 5800 V/cm and 0.15 V, respectively. The optimization of the BSF layer shows that the cell performance improves with the p+ thickness between 0.35 – 0.39 µm, the p+ doping dose is about 2 × 1014 cm-2, the maximum efficiency up to 16.19 %. The cell efficiency is more sensitive to the value of the back surface recombination velocity above a value of 103 cm/s in n+p than n+pp+ solar cell.DOI: http://dx.doi.org/10.5755/j01.ms.21.4.9565

  19. Frequency Selective Surfaces with Nanoparticles Unit Cell

    Directory of Open Access Journals (Sweden)

    Nga Hung Poon

    2015-09-01

    Full Text Available The frequency selective surface (FSS is a periodic structure with filtering performance for optical and microwave signals. The general periodic arrays made with patterned metallic elements can act as an aperture or patch on a substrate. In this work, two kinds of materials were used to produce unit cells with various patterns. Gold nanoparticles of 25 nm diameter were used to form periodic monolayer arrays by a confined photocatalytic oxidation-based surface modification method. As the other material, silver gel was used to create multiple layers of silver. Due to the ultra-thin nature of the self-assembled gold nanoparticle monolayer, it is very easy to penetrate the FSS with terahertz radiation. However, the isolated silver islands made from silver gel form thicker multiple layers and contribute to much higher reflectance. This work demonstrated that multiple silver layers are more suitable than gold nanoparticles for use in the fabrication of FSS structures.

  20. High Gas Surface Densities yet Low UV Attenuation in z $\\sim$ 1 Disc Galaxies

    CERN Document Server

    Nordon, Raanan

    2016-01-01

    The gas in galaxies is both the fuel for star formation and a medium that attenuates the light of the young stars. We study the relations between UV attenuation, spectral slope, star formation rates, and molecular gas surface densities in a sample of 28 z$\\sim$1 and a reference sample of 32 z$\\sim$0 galaxies that are detected in CO, far-infrared, and rest frame UV. The samples are dominated by disc-like galaxies close to the main SFR--mass relation. We find that the location of the z$\\sim$1 galaxies on the IRX-$\\beta$ plane is correlated with their gas-depletion time-scale $\\tau_{dep}$ and can predict $\\tau_{dep}$ with a standard deviation of 0.16 dex. We use IRX-$\\beta$ to estimate the mean total gas column densities at the locations of star formation in the galaxies, and compare them to the mean molecular gas surface densities as measured from CO. We confirm previous results regarding high $N_H/A_V$ in z$\\sim$1 galaxies. We estimate an increase in the gas filling factor by a factor of 4--6 from z$\\sim$0 to ...

  1. Gas surface density, star formation rate surface density, and the maximum mass of young star clusters in a disk galaxy. II. The grand-design galaxy M51

    CERN Document Server

    Gonzalez-Lopezlira, Rosa A; Kroupa, Pavel

    2013-01-01

    We analyze the relationship between maximum cluster mass, and surface densities of total gas (Sigma_gas), molecular gas (Sigma_H_2), neutral gas (Sigma_HI) and star formation rate (Sigma_SFR) in the grand design galaxy M51, using published gas data and a catalog of masses, ages, and reddenings of more than 1800 star clusters in its disk, of which 223 are above the cluster mass distribution function completeness limit. We find for clusters older than 25 Myr that M_3rd, the median of the 5 most massive clusters, is proportional to Sigma_HI^0.4. There is no correlation with Sigma_gas, Sigma_H2, or Sigma_SFR. For clusters younger than 10 Myr, M_3rd is proportional to Sigma_HI^0.6, M_3rd is proportional to Sigma_gas^0.5; there is no correlation with either Sigma_H_2 or Sigma_SFR. The results could hardly be more different than those found for clusters younger than 25 Myr in M33. For the flocculent galaxy M33, there is no correlation between maximum cluster mass and neutral gas, but M_3rd is proportional to Sigma_g...

  2. Study of CO adsorption on perfect and defective pyrite(100)surfaces by density functional theory

    Institute of Scientific and Technical Information of China (English)

    Yudong Du; Wenkai Chen; Yongfan Zhang; Xin Guo

    2011-01-01

    First-principles calculations based on density functional theory(DFT)and the generalized gradient approximation(GGA)have been used to study the adsorption of CO molecule on the perfect and defective FeS2(100)surfaces.The defective Fe2S(100)surfaces are caused by sulfur deficiencies.Slab geometry and periodic boundary conditions are employed with partial relaxations of atom positions in calculations.Two molecular orientations,C-and O-down,at various distinct sites have been considered.Total energy calculations indicated that no matter on perfect or deficient surfaces,the Fe position is relatively more favored than the S site with the predicted binding energies of 120.8 kJ/mol and 140.8 kJ/mol,respectively.Moreover,CO was found to be bound to Fe atom in vertical configuration.The analysis of density of states and vibrational frequencies before and after adsorption showed clear changes of the C-O bond.

  3. Self-induced metabolic state switching by a tunable cell density sensor for microbial isopropanol production.

    Science.gov (United States)

    Soma, Yuki; Hanai, Taizo

    2015-07-01

    Chemicals production by engineered microorganisms often requires induction of target gene expression at an appropriate cell density to reduce conflict with cell growth. The lux system in Vibrio fischeri is a well-characterized model for cell density-dependent regulation of gene expression termed quorum sensing (QS). However, there are currently no reports for application of the lux system to microbial chemical production. Here, we constructed a synthetic lux system as a tunable cell density sensor-regulator using a synthetic lux promoter and a positive feedback loop in Escherichia coli. In this system, self-induction of a target gene expression is driven by QS-signal, and its threshold cell density can be changed depending on the concentration of a chemical inducer. We demonstrate auto-redirection of metabolic flux from central metabolic pathways toward a synthetic isopropanol pathway at a desired cell density resulting in a significant increase in isopropanol production.

  4. Optimizing the surface density of polyethylene glycol chains by grafting from binary solvent mixtures

    Science.gov (United States)

    Arcot, Lokanathan; Ogaki, Ryosuke; Zhang, Shuai; Meyer, Rikke L.; Kingshott, Peter

    2015-06-01

    Polyethylene glycol (PEG) brushes are very effective at controlling non-specific deposition of biological material onto surfaces, which is of paramount importance to obtaining successful outcomes in biomaterials, tissue engineered scaffolds, biosensors, filtration membranes and drug delivery devices. We report on a simple 'grafting to' approach involving binary solvent mixtures that are chosen based on Hansen's solubility parameters to optimize the solubility of PEG thereby enabling control over the graft density. The PEG thiol-gold model system enabled a thorough characterization of PEG films formed, while studies on a PEG silane-silicon system examined the versatility to be applied to any substrate-head group system by choosing an appropriate solvent pair. The ability of PEG films to resist non-specific adsorption of proteins was quantitatively assessed by full serum exposure studies and the binary solvent strategy was found to produce PEG films with optimal graft density to efficiently resist protein adsorption.

  5. Density Functional Study on Adsorption of NO on AuSe (010) Surface

    Institute of Scientific and Technical Information of China (English)

    XU,Xiang-Lan; CHEN,Wen-Kai; WANG,Xia; SUN,Bao-Zhen; LI,Yi; LU,Chun-Hai

    2008-01-01

    NO molecule adsorption on (010) surface of gold selenide (AuSe) has been studied with a periodic slab model by means of the GGA-PW91 exchange-correlation functional within the framework of density functional theory (DFT). Four different on-top adsorption sites Au(1), Au(2), Se(1) and Se(2) were considered for α-AuSe and three on-top adsorption sites Au(1), Au(2) and Se(1) for β-AuSe. N-end and O-end adsorptions of NO were investigated for the above sites. The results show that N-end adsorptions are preferred for α- and β-AuSe and O-end adsorptions are not feasible and thought as physisorption with the weak adsorption energies from 6.0 to 10.8 kJ/mol. For the N-end adsorptions on α-and β-AuSe (010) surfaces, Au(2) sites are most favorable with the adsorption energies 89.0 and 78.0 kJ/mol for α-and β-AuSe, respectively. However, the adsorptions at Au1 sites are very weak with the adsorption energies of 27.8 and 7.5 kJ/mol, respectively. In case of the adsorption of N-down orientations of NO at Se sites for α-and β-AuSe (010) surfaces, the adsorption activities of Se(1) and Se(2) sites on the α-AuSe (010) surface and Se(1) site on the β-AuSe (010) surface are almost the same with the adsorption energies 51.2, 52.7 and 49.2 kJ/mol. The geometric optimizations for adsorption configurations were calculated along with accounting for stretching frequency and density of states in our work.

  6. Wettability influences cell behavior on superhydrophobic surfaces with different topographies

    NARCIS (Netherlands)

    Lourenco, B.N.; Marchioli, G.; Song, W; Reis, R.L.; Blitterswijk, van C.A.; Karperien, H.B.J.; Apeldoorn, van A.A.; Mano, J.F.

    2012-01-01

    Surface wettability and topography are recognized as critical factors influencing cell behavior on biomaterials. So far only few works have reported cell responses on surfaces exhibiting extreme wettability in combination with surface topography. The goal of this work is to study whether cell behavi

  7. Multicellular automaticity of cardiac cell monolayers: effects of density and spatial distribution of pacemaker cells

    Science.gov (United States)

    Elber Duverger, James; Boudreau-Béland, Jonathan; Le, Minh Duc; Comtois, Philippe

    2014-11-01

    Self-organization of pacemaker (PM) activity of interconnected elements is important to the general theory of reaction-diffusion systems as well as for applications such as PM activity in cardiac tissue to initiate beating of the heart. Monolayer cultures of neonatal rat ventricular myocytes (NRVMs) are often used as experimental models in studies on cardiac electrophysiology. These monolayers exhibit automaticity (spontaneous activation) of their electrical activity. At low plated density, cells usually show a heterogeneous population consisting of PM and quiescent excitable cells (QECs). It is therefore highly probable that monolayers of NRVMs consist of a heterogeneous network of the two cell types. However, the effects of density and spatial distribution of the PM cells on spontaneous activity of monolayers remain unknown. Thus, a simple stochastic pattern formation algorithm was implemented to distribute PM and QECs in a binary-like 2D network. A FitzHugh-Nagumo excitable medium was used to simulate electrical spontaneous and propagating activity. Simulations showed a clear nonlinear dependency of spontaneous activity (occurrence and amplitude of spontaneous period) on the spatial patterns of PM cells. In most simulations, the first initiation sites were found to be located near the substrate boundaries. Comparison with experimental data obtained from cardiomyocyte monolayers shows important similarities in the position of initiation site activity. However, limitations in the model that do not reflect the complex beat-to-beat variation found in experiments indicate the need for a more realistic cardiomyocyte representation.

  8. Adsorption properties of trifluoroacetic acid on anatase (101) and (001) surfaces: a density functional theory study.

    Science.gov (United States)

    Lamiel-Garcia, Oriol; Fernandez-Hevia, Daniel; Caballero, Amador C; Illas, Francesc

    2015-09-28

    The interaction of trifluoroacetic acid with anatase TiO2(101) and TiO2(001) surfaces has been studied by means of periodic density functional theory based calculations. On the former, the interaction is weak with the adsorbed molecules in a configuration almost indistinguishable from the gas phase structure. On the latter, the interaction is very strong; the molecule adsorbs as trifluoroacetate and releases a proton that binds an oxygen surface atom with a significant distortion of the substrate. The difference in adsorption the mode and strength can be understood from the different structural features of both surfaces and provides arguments to the role of trifluoroacetic as a morphological control agent in the solvothermal synthesis of TiO2 nanoparticles with predominant (001) facets. This, in turn, has a very significant impact on industrial production strategies of value-added TiO2 for photocatalytic applications. Analysis of calculated core level binding energies for F(1s) confirms the experimental assignment to F at the surface as F(-) at Ti surface sites and to F in -CF3 groups of the adsorbed molecule.

  9. Systematic control of surface Dirac fermion density on topological insulator Bi2Te3

    Science.gov (United States)

    Xu, Suyang; Xia, Yuqi; Grauer, David; Hor, Yewsan; Cava, Robert; Hasan, Zahid

    2010-03-01

    Three dimensional (3D) topological insulators are quantum materials with a spin-orbit induced bulk insulating gap that exhibit quantum-Hall-like phenomena in the absence of applied magnetic fields. They feature surface states that are topologically protected against scattering by time reversal symmetry. The proposed applications of topological insulators in device geometries rely on the ability to tune the chemical potential on their surfaces in the vicinity of the Dirac node. Here, we demonstrate a suite of surface control methods based on a combination of photo-doping and molecular-doping to tune the Dirac fermion density on the topological (111) surface of Bi2Te3. Their efficacy is demonstrated via direct electronic structure measurements using high resolution angle-resolved photoemission spectroscopy. These results open up new opportunities for probing topological behavior of Dirac electrons in Bi2Te3. At least one of the methods demonstrated here can be successfully applied to other topological insulators (Bi1-xSbx, Sb2Te3 and Bi2Se3). More importantly, our methods of topological surface state manipulation demonstrated here are highly suitable for future spectroscopic studies of topological phenomena which will complement the transport results gained from the traditional electrical gating techniques.

  10. Strain and Cohesive Energy of TiN Deposit on Al(001) Surface: Density Functional Calculation

    Science.gov (United States)

    Ren, Yuan; Liu, Xuejie

    2016-07-01

    To apply the high hardness of TiN film to soft and hard multilayer composite sheets, we constructed a new type of composite structural material with ultra-high strength. The strain of crystal and cohesive energy between the atoms in the eight structures of N atom, Ti atom, 2N2Ti island and TiN rock salt deposited on the Al(001) surface were calculated with the first-principle ultra-soft pseudopotential approach of the plane wave based on the density functional theory. The calculations of the cohesive energy showed that N atoms could be deposited in the face-centered-cubic vacancy position of the Al(001) surface and results in a cubic structure AlN surface. The TiN film could be deposited on the interface of β-AlN. The calculations of the strains showed that the strain in the TiN film deposited on the Al(001) surface was less than that in the 2N2Ti island deposited on the Al(001) surface. The diffusion behavior of interface atom N was investigated by a nudged elastic band method. Diffusion energy calculation showed that the N atom hardly diffused to the substrate Al layer.

  11. Analytical performance of molecular beacons on surface immobilized gold nanoparticles of varying size and density.

    Science.gov (United States)

    Uddayasankar, Uvaraj; Krull, Ulrich J

    2013-11-25

    The high quenching efficiency of metal nanoparticles has facilitated its use as quenchers in molecular beacons. To optimize this system, a good understanding of the many factors that influence molecular beacon performance is required. In this study, molecular beacon performance was evaluated as a function of gold nanoparticle size and its immobilization characteristics. Gold nanoparticles of 4 nm, 15 nm and 87 nm diameter, were immobilized onto glass slides. Each size regime offered distinctive optical properties for fluorescence quenching of molecular dyes that were conjugated to oligonucleotides that were immobilized to the gold nanoparticles. Rigid double stranded DNA was used as a model to place fluorophores at different distances from the gold nanoparticles. The effect of particle size and also the immobilization density of nanoparticles was evaluated. The 4 nm and 87 nm gold nanoparticles offered the highest sensitivity in terms of the change in fluorescence intensity as a function of distance (3-fold improvement for Cy5). The optical properties of the molecular fluorophore was of significance, with Cy5 offering higher contrast ratios than Cy3 due to the red-shifted emission spectrum relative to the plasmon peak. A high density of gold nanoparticles reduced contrast ratios, indicating preference for a monolayer of immobilized nanoparticles when considering analytical performance. Molecular beacon probes were then used in place of the double stranded oligonucleotides. There was a strong dependence of molecular beacon performance on the length of a linker used for attachment to the nanoparticle surface. The optimal optical performance was obtained with 4 nm gold nanoparticles that were immobilized as monolayers of low density (5.7×10(11)particles cm(-2)) on glass surfaces. These nanoparticle surfaces offered a 2-fold improvement in analytical performance of the molecular beacons when compared to other nanoparticle sizes investigated. The principles developed

  12. Knowledge discovery of cell-cell and cell-surface interactions

    Science.gov (United States)

    Su, Jing

    High-throughput cell culture is an emerging technology that shows promise as a tool for research in tissue engineering, drug discovery, and medical diagnostics. An important, but overlooked, challenge is the integration of experimental methods with information processing suitable for handling large databases of cell-cell and cell-substrate interactions. In this work the traditional global descriptions of cell behaviors and surface characteristics was shown insufficient for investigating short-distance cell-to-cell and cell-to-surface interactions. Traditional summary metrics cannot distinguish information of cell near neighborhood from the average, global features, thus often is not suitable for studying distance-sensitive cell behaviors. The problem of traditional summary metrics was addressed by introducing individual-cell based local metrics that emphasize cell local environment. An individual-cell based local data analysis method was established. Contact inhibition of cell proliferation was used as a benchmark for the effectiveness of the local metrics and the method. Where global, summary metrics were unsuccessful, the local metrics successfully and quantitatively distinguished the contact inhibition effects of MC3T3-E1 cells on PLGA, PCL, and TCPS surfaces. In order to test the new metrics and analysis method in detail, a model of cell contact inhibition was proposed. Monte Carlo simulation was performed for validating the individual-cell based local data analysis method as well as the cell model itself. The simulation results well matched with the experimental observations. The parameters used in the cell model provided new descriptions of both cell behaviors and surface characteristics. Based on the viewpoint of individual cells, the local metrics and local data analysis method were extended to the investigation of cell-surface interactions, and a new high-throughput screening and knowledge discovery method on combinatorial libraries, local cell

  13. A high power density miniaturized microbial fuel cell having carbon nanotube anodes

    Science.gov (United States)

    Ren, Hao; Pyo, Soonjae; Lee, Jae-Ik; Park, Tae-Jin; Gittleson, Forrest S.; Leung, Frederick C. C.; Kim, Jongbaeg; Taylor, André D.; Lee, Hyung-Sool; Chae, Junseok

    2015-01-01

    Microbial fuel cells (MFCs) are a promising technology capable of directly converting the abundant biomass on the planet into electricity. Prior studies have adopted a variety of nanostructured materials with high surface area to volume ratio (SAV), yet the current and power density of these nanostructured materials do not deliver a significant leap over conventional MFCs. This study presents a novel approach to implement a miniaturized MFC with a high SAV of 4000 m-1 using three different CNT-based electrode materials: Vertically Aligned CNT (VACNT), Randomly Aligned CNT (RACNT), and Spin-Spray Layer-by-Layer (SSLbL) CNT. These CNT-based electrodes show unique biofilm morphology and thickness. The study of performance parameters of miniaturized MFCs with these CNT-electrodes are conducted with respect to a control bare gold electrode. The results show that CNT-based materials attract more exoelectrogens, Geobacter sp., than bare gold, yielding thicker biofilm formation. Among CNT-based electrodes, low sheet resistance electrodes result in thick biofilm generation and high current/power density. The miniaturized MFC having an SSLbL CNT anode exhibits a high volumetric power density of 3320 W m-3. This research may help lay the foundation for future research involving the optimization of MFCS with 2D and 3D nanostructured electrodes.

  14. Conformable actively multiplexed high-density surface electrode array for brain interfacing

    Science.gov (United States)

    Rogers, John; Kim, Dae-Hyeong; Litt, Brian; Viventi, Jonathan

    2015-01-13

    Provided are methods and devices for interfacing with brain tissue, specifically for monitoring and/or actuation of spatio-temporal electrical waveforms. The device is conformable having a high electrode density and high spatial and temporal resolution. A conformable substrate supports a conformable electronic circuit and a barrier layer. Electrodes are positioned to provide electrical contact with a brain tissue. A controller monitors or actuates the electrodes, thereby interfacing with the brain tissue. In an aspect, methods are provided to monitor or actuate spatio-temporal electrical waveform over large brain surface areas by any of the devices disclosed herein.

  15. Goethite surface reactivity: III. Unifying arsenate adsorption behavior through a variable crystal face - Site density model

    Science.gov (United States)

    Salazar-Camacho, Carlos; Villalobos, Mario

    2010-04-01

    We developed a model that describes quantitatively the arsenate adsorption behavior for any goethite preparation as a function of pH and ionic strength, by using one basic surface arsenate stoichiometry, with two affinity constants. The model combines a face distribution-crystallographic site density model for goethite with tenets of the Triple Layer and CD-MUSIC surface complexation models, and is self-consistent with its adsorption behavior towards protons, electrolytes, and other ions investigated previously. Five different systems of published arsenate adsorption data were used to calibrate the model spanning a wide range of chemical conditions, which included adsorption isotherms at different pH values, and adsorption pH-edges at different As(V) loadings, both at different ionic strengths and background electrolytes. Four additional goethite-arsenate systems reported with limited characterization and adsorption data were accurately described by the model developed. The adsorption reaction proposed is: lbond2 FeOH +lbond2 SOH +AsO43-+H→lbond2 FeOAsO3[2-]…SOH+HO where lbond2 SOH is an adjacent surface site to lbond2 FeOH; with log K = 21.6 ± 0.7 when lbond2 SOH is another lbond2 FeOH, and log K = 18.75 ± 0.9, when lbond2 SOH is lbond2 Fe 2OH. An additional small contribution of a protonated complex was required to describe data at low pH and very high arsenate loadings. The model considered goethites above 80 m 2/g as ideally composed of 70% face (1 0 1) and 30% face (0 0 1), resulting in a site density for lbond2 FeOH and for lbond2 Fe 3OH of 3.125/nm 2 each. Below 80 m 2/g surface capacity increases progressively with decreasing area, which was modeled by considering a progressively increasing proportion of faces (0 1 0)/(1 0 1), because face (0 1 0) shows a much higher site density of lbond2 FeOH groups. Computation of the specific proportion of faces, and thus of the site densities for the three types of crystallographic surface groups present in

  16. The electrical conductivity, density and surface tension of molten salts containing zirconium fluoride

    Energy Technology Data Exchange (ETDEWEB)

    Katyshev, S F; Teslyuk, L M; Eltsova, N V [Urals State Technical University-UPI, 19 Mira Str., Ekaterinburg 620002 (Russian Federation)], E-mail: tnv@htf.ustu.ru, E-mail: ksf@mail.ustu.ru

    2008-02-15

    The temperature dependencies of specific electric conductivity, density and surface tension of molten LiF-KF-ZrF{sub 4} mixtures in a wide concentration range were investigated using relative capillary method and method of maximum pressure in a gas bubble. The obtained values of molar electric conductivity, molar volumes and excess thermodynamic functions of melt surface layer have noticeable deviations from those calculated for ideal mixtures. This phenomenon can be explained by some specific interaction between the components of studied ternary mixtures. Mixing the components in such melts is accompanied by a noticeable interaction with predominant formation of stable zirconium fluoride complex ions. The values of deviations depend on the ionic composition of the salt mixtures.

  17. Interaction effects of cell diffusion, cell density and public goods properties on the evolution of cooperation in digital microbes.

    Science.gov (United States)

    Dobay, A; Bagheri, H C; Messina, A; Kümmerli, R; Rankin, D J

    2014-09-01

    Microbial cooperation typically consists in the sharing of secreted metabolites (referred to as public goods) within the community. Although public goods generally promote population growth, they are also vulnerable to exploitation by cheating mutants, which no longer contribute, but still benefit from the public goods produced by others. Although previous studies have identified a number of key factors that prevent the spreading of cheaters, little is known about how these factors interact and jointly shape the evolution of microbial cooperation. Here, we address this issue by investigating the interaction effects of cell diffusion, cell density, public good diffusion and durability (factors known to individually influence costs and benefits of public goods production) on selection for cooperation. To be able to quantify these effects across a wide parameter space, we developed an individual-based simulation platform, consisting of digital cooperator and cheater bacteria inhabiting a finite two-dimensional continuous toroidal surface. Our simulations, which closely mimic microbial microcolony growth, revealed that: (i) either reduced cell diffusion (which keeps cooperators together) or reduced public good diffusion (which keeps the public goods closer to the producer) is not only essential but also sufficient for cooperation to be promoted; (ii) the sign of selection for or against cooperation can change as a function of cell density and in interaction with diffusion parameters; and (iii) increased public goods durability has opposing effects on the evolution of cooperation depending on the level of cell and public good diffusion. Our work highlights that interactions between key parameters of public goods cooperation give rise to complex fitness landscapes, a finding that calls for multifactorial approaches when studying microbial cooperation in natural systems.

  18. Chemistry and material science at the cell surface

    Directory of Open Access Journals (Sweden)

    Weian Zhao

    2010-04-01

    Full Text Available Cell surfaces are fertile ground for chemists and material scientists to manipulate or augment cell functions and phenotypes. This not only helps to answer basic biology questions but also has diagnostic and therapeutic applications. In this review, we summarize the most recent advances in the engineering of the cell surface. In particular, we focus on the potential applications of surface engineered cells for 1 targeting cells to desirable sites in cell therapy, 2 programming assembly of cells for tissue engineering, 3 bioimaging and sensing, and ultimately 4 manipulating cell biology.

  19. Effect of particle surface area on ice active site densities retrieved from droplet freezing spectra

    Science.gov (United States)

    Beydoun, Hassan; Polen, Michael; Sullivan, Ryan C.

    2016-10-01

    Heterogeneous ice nucleation remains one of the outstanding problems in cloud physics and atmospheric science. Experimental challenges in properly simulating particle-induced freezing processes under atmospherically relevant conditions have largely contributed to the absence of a well-established parameterization of immersion freezing properties. Here, we formulate an ice active, surface-site-based stochastic model of heterogeneous freezing with the unique feature of invoking a continuum assumption on the ice nucleating activity (contact angle) of an aerosol particle's surface that requires no assumptions about the size or number of active sites. The result is a particle-specific property g that defines a distribution of local ice nucleation rates. Upon integration, this yields a full freezing probability function for an ice nucleating particle. Current cold plate droplet freezing measurements provide a valuable and inexpensive resource for studying the freezing properties of many atmospheric aerosol systems. We apply our g framework to explain the observed dependence of the freezing temperature of droplets in a cold plate on the concentration of the particle species investigated. Normalizing to the total particle mass or surface area present to derive the commonly used ice nuclei active surface (INAS) density (ns) often cannot account for the effects of particle concentration, yet concentration is typically varied to span a wider measurable freezing temperature range. A method based on determining what is denoted an ice nucleating species' specific critical surface area is presented and explains the concentration dependence as a result of increasing the variability in ice nucleating active sites between droplets. By applying this method to experimental droplet freezing data from four different systems, we demonstrate its ability to interpret immersion freezing temperature spectra of droplets containing variable particle concentrations. It is shown that general

  20. Controlled-surface-wettability-based fabrication of hydrogel substrates with matrix tethering density variations

    Science.gov (United States)

    Rahman, Md. Mahmudur; Lee, Donghee; Bhagirath, Divya; Zhao, Xiangshan; Band, Vimla; Ryu, Sangjin

    2014-03-01

    It is widely accepted that cells behave differently responding to the stiffness of extracellular matrix (ECM). Such observations were made by culturing cells on hydrogel substrates of tunable stiffness. However, it was recently proposed that cells actually sense how strongly they are tethered to ECM, not the local stiffness of ECM. To investigate the hypothesis, we develop constant-stiffness hydrogel substrates with varying matrix tethering density (the number of anchoring sites between the gel and the ECM protein molecules). We fabricate polyacrylamide gel of static stiffness and conjugate ECM proteins to the gel using a cross-linker. When treating the gel with the cross-linker, we control positioning of cross-linker solutions with different concentrations using superhydrophobic barriers on glass, functionalize the gel by pressing it to the aligned cross-linker solutions, and conjugate an ECM protein of constant concentration to the gel. We expect that the gel will be functionalized to different degrees depending on the concentration distribution of the cross-linker and thus the gel will have variations of matrix tethering density even with constant ECM protein concentration. We acknowledge support from Bioengineering for Human Health grant of UNL-UNMC.

  1. Chemical surface modification of parylene C for enhanced protein immobilization and cell proliferation.

    Science.gov (United States)

    Zhang, Changhong; Thompson, Mark E; Markland, Frank S; Swenson, Steve

    2011-10-01

    To introduce the adhesion site of proteins and/or cells on parylene C (PC)-coated medical devices that can be used as implantable biosensors or drug delivery capsules, the PC surfaces were initially modified by the Friedel-Crafts acylation reaction to generate active chlorines. These chlorines were then employed to initiate the atom transfer radical polymerization of tert-butyl acrylate (TBA) and form a polymer brush layer of polyTBA on PC; the acrylate groups in the polymer brushes were hydrolyzed to carboxylic acid groups and further activated into succinimidyl ester groups via the 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-hydroxysuccinimide coupling reaction. The PC surface grafted with polymer brushes and activated by succinimide showed efficient attachment of proteins, including gelatin, contortrostatin (CN) and bovine serum albumin (BSA), all at high density on the PC surface. The CN density on the surface was evaluated for both monolayer and polymer brush-based coatings. Based on fluorescence measurements, the polymer brush gives a 60-fold higher surface protein density than the monolayer-based system. Gelatin was used as a model protein and covalently coated onto the modified PC surface for cell culture study. Substrates with gelatin coating showed a significantly higher cell attachment and proliferation in 7 days cultures as compared to the uncoated substrates. In addition, a conventional photolithography technique was coupled with the surface chemistry to successfully pattern the BSA labeled with fluorescein isothiocyanate on the modified PC surfaces.

  2. Microarray of neuroblastoma cells on the selectively functionalized nanocrystalline diamond thin film surface

    Science.gov (United States)

    Park, Young-Sang; Son, Hyeong-Guk; Kim, Dae-Hoon; Oh, Hong-Gi; Lee, Da-Som; Kim, Min-Hye; Lim, Ki-Moo; Song, Kwang-Soup

    2016-01-01

    Nanocrystalline diamond (NCD) film surfaces were modified with fluorine or oxygen by plasma treatment in an O2 or C3F8 gas environment in order to induce wettability. The oxygenated-NCD (O-NCD) film surface was hydrophilic and the fluorinated-NCD (F-NCD) surface was hydrophobic. The efficiency of early cell adhesion, which is dependent on the wettability of the cell culture plate and necessary for the growth and proliferation of cells, was 89.62 ± 3.92% on the O-NCD film and 7.78 ± 0.77% on the F-NCD film surface after 3 h of cell culture. The wettability of the NCD film surface was artificially modified using a metal mask and plasma treatment to fabricate a micro-pattern. Four types of micro-patterns were fabricated (line, circle, mesh, and word) on the NCD film surface. We precisely arrayed the neuroblastoma cells on the micro-patterned NCD film surfaces by controlling the surface wettability and cell seeding density. The neuroblastoma cells adhered and proliferated along the O-NCD film surface.

  3. Adsorption of atomic nitrogen and oxygen on [Formula: see text] surface: a density functional theory study.

    Science.gov (United States)

    Breedon, M; Spencer, M J S; Yarovsky, I

    2009-04-08

    The adsorption of atomic nitrogen and oxygen on the ([Formula: see text]) crystal face of zinc oxide (ZnO) was studied. Binding energies, workfunction changes, vibrational frequencies, charge density differences and electron localization functions were calculated. It was elucidated that atomic oxygen binds more strongly than nitrogen, with the most stable [Formula: see text] structure exhibiting a binding energy of -2.47 eV, indicating chemisorption onto the surface. Surface reconstructions were observed for the most stable minima of both atomic species. Positive workfunction changes were calculated for both adsorbed oxygen and nitrogen if the adsorbate interacted with zinc atoms. Negative workfunction changes were calculated when the adsorbate interacted with both surface oxygen and zinc atoms. Interactions between the adsorbate and the surface zinc atoms resulted in ionic-type bonding, whereas interactions with oxygen atoms were more likely to result in the formation of covalent-type bonding. The positive workfunction changes correlate with an experimentally observed increase in resistance of ZnO conductometric sensor devices.

  4. Micro-strain, dislocation density and surface chemical state analysis of multication thin films

    Science.gov (United States)

    Jayaram, P.; Pradyumnan, P. P.; Karazhanov, S. Zh.

    2016-11-01

    Multication complex metal oxide thin films are rapidly expanding the class of materials with many technologically important applications. Herein this work, the surface of the pulsed laser deposited thin films of Zn2SnO4 and multinary compounds obtained by substitution/co-substitution of Sn4+ with In3+ and Ga3+ are studied by X-ray photoelectron emission spectroscopy (X-PES) method. Peaks corresponding to the elements of Zn, Sn, Ga, In and O on the film surface has been identified and contribution of the elements has been studied by the computer aided surface analysis (CASA) software. Binding energies, full-width at half maximum (FWHM), spin-orbit splitting energies, asymmetric peak-shape fitting parameters and quantification of elements in the films are discussed. Studies of structural properties of the films by x-ray diffraction (XRD) technique showed inverse spinel type lattice with preferential orientation. Micro-strain, dislocation density and crystallite sizes in the film surface have been estimated.

  5. Hydrogen atom addition to the surface of graphene nanoflakes: A density functional theory study

    Science.gov (United States)

    Tachikawa, Hiroto

    2017-02-01

    Polycyclic aromatic hydrocarbons (PAHs) provide a 2-dimensional (2D) reaction surface in 3-dimensional (3D) interstellar space and have been utilized as a model of graphene surfaces. In the present study, the reaction of PAHs with atomic hydrogen was investigated by means of density functional theory (DFT) to systematically elucidate the binding nature of atomic hydrogen to graphene nanoflakes. PAHs with n = 4-37 were chosen, where n indicates the number of benzene rings. Activation energies of hydrogen addition to the graphene surface were calculated to be 5.2-7.0 kcal/mol at the CAM-B3LYP/6-311G(d,p) level, which is almost constant for all PAHs. The binding energies of hydrogen atom were slightly dependent on the size (n): 14.8-28.5 kcal/mol. The absorption spectra showed that a long tail is generated at the low-energy region after hydrogen addition to the graphene surface. The electronic states of hydrogenated graphenes were discussed on the basis of theoretical results.

  6. Bilayer honeycomb lattice with ultracold atoms: Multiple Fermi surfaces and incommensurate spin density wave instability

    Science.gov (United States)

    Dey, Santanu; Sensarma, Rajdeep

    2016-12-01

    We propose an experimental setup using ultracold atoms to implement a bilayer honeycomb lattice with Bernal stacking. In the presence of a potential bias between the layers and at low densities, fermions placed in this lattice form an annular Fermi sea. The presence of two Fermi surfaces leads to interesting patterns in Friedel oscillations and RKKY interactions in the presence of impurities. Furthermore, a repulsive fermion-fermion interaction leads to a Stoner instability towards an incommensurate spin density wave order with a wave vector equal to the thickness of the Fermi sea. The instability occurs at a critical interaction strength which goes down with the density of the fermions. We find that the instability survives interaction renormalization due to vertex corrections and discuss how this can be seen in experiments. We also track the renormalization group flows of the different couplings between the fermionic degrees of freedom, and find that there are no perturbative instabilities, and that Stoner instability is the strongest instability which occurs at a critical threshold value of the interaction. The critical interaction goes to zero as the chemical potential is tuned towards the band bottom.

  7. Collagen Matrix Density Drives the Metabolic Shift in Breast Cancer Cells

    Directory of Open Access Journals (Sweden)

    Brett A. Morris

    2016-11-01

    Full Text Available Increased breast density attributed to collagen I deposition is associated with a 4–6 fold increased risk of developing breast cancer. Here, we assessed cellular metabolic reprogramming of mammary carcinoma cells in response to increased collagen matrix density using an in vitro 3D model. Our initial observations demonstrated changes in functional metabolism in both normal mammary epithelial cells and mammary carcinoma cells in response to changes in matrix density. Further, mammary carcinoma cells grown in high density collagen matrices displayed decreased oxygen consumption and glucose metabolism via the tricarboxylic acid (TCA cycle compared to cells cultured in low density matrices. Despite decreased glucose entry into the TCA cycle, levels of glucose uptake, cell viability, and ROS were not different between high and low density matrices. Interestingly, under high density conditions the contribution of glutamine as a fuel source to drive the TCA cycle was significantly enhanced. These alterations in functional metabolism mirrored significant changes in the expression of metabolic genes involved in glycolysis, oxidative phosphorylation, and the serine synthesis pathway. This study highlights the broad importance of the collagen microenvironment to cellular expression profiles, and shows that changes in density of the collagen microenvironment can modulate metabolic shifts of cancer cells.

  8. Collagen Matrix Density Drives the Metabolic Shift in Breast Cancer Cells.

    Science.gov (United States)

    Morris, Brett A; Burkel, Brian; Ponik, Suzanne M; Fan, Jing; Condeelis, John S; Aguire-Ghiso, Julio A; Castracane, James; Denu, John M; Keely, Patricia J

    2016-11-01

    Increased breast density attributed to collagen I deposition is associated with a 4-6 fold increased risk of developing breast cancer. Here, we assessed cellular metabolic reprogramming of mammary carcinoma cells in response to increased collagen matrix density using an in vitro 3D model. Our initial observations demonstrated changes in functional metabolism in both normal mammary epithelial cells and mammary carcinoma cells in response to changes in matrix density. Further, mammary carcinoma cells grown in high density collagen matrices displayed decreased oxygen consumption and glucose metabolism via the tricarboxylic acid (TCA) cycle compared to cells cultured in low density matrices. Despite decreased glucose entry into the TCA cycle, levels of glucose uptake, cell viability, and ROS were not different between high and low density matrices. Interestingly, under high density conditions the contribution of glutamine as a fuel source to drive the TCA cycle was significantly enhanced. These alterations in functional metabolism mirrored significant changes in the expression of metabolic genes involved in glycolysis, oxidative phosphorylation, and the serine synthesis pathway. This study highlights the broad importance of the collagen microenvironment to cellular expression profiles, and shows that changes in density of the collagen microenvironment can modulate metabolic shifts of cancer cells.

  9. Methodologies to analyze surface bonding properties using parametric and density functional methods

    Science.gov (United States)

    Ruette, Fernando; Sánchez, Morella; Castellano, Olga; Soscún, Humberto

    This work presents two general methodologies to calculate bond adsorption energy (BAE) between surface and adsorbate using parametric quantum (PQM) and density functional (DFM) methods. The first one corresponds to the bond partition energy technique that is directly applied to PQMs by using energy partition approach and considering diatomic and monoatomic energy changes. The second methodology to evaluate BAE, as well as for PQMs and DFMs, is by means of the following equation: {BAE} = E_{ads} - Delta E_{s} - Delta E_{a'} where Eads is the adsorption energy and ΔEs and ΔEa correspond to energy changes in the surface and substrate due to adsorption, respectively. Applications to radical adsorption: H°, CH2°, and CH3° is performed on a grafitic grain model, using a polyaromatic hydrocarbon (PAH), such as coronene. The methods employed are a PQM (CATIVIC program) and DFMs (GAUSSIAN and DMol software packages). Results show that Eads is completely different of BAE, because of distortion of surface and adsorbate. There is a strong destabilization in the region adjacent to the adsorption site and stabilization in the rest of the surface. Two terms for BAE are reported: one that corresponds to direct bonding interaction (BAEb) and other to long range ones, due to electrostatic interaction (BAEe). Owing to the important effects of bond strength adsorbate-surface interaction, results suggest that BAE is fundamental for understanding bond activation in adsorbate and surface, cooperative effects, diffusion, reaction, and desorption process. In general, similar results were found for both CATIVIC and DFMs, by using the second methodology.

  10. The Initial Mass Function and the Surface Density Profile of NGC 6231

    CERN Document Server

    Sung, Hwankyung; Bessell, M S

    2012-01-01

    We have performed new wide-field photometry of the young open cluster NGC 6231 to study the shape of the initial mass function (IMF) and mass segregation. We also investigated the reddening law toward NGC 6231 from optical to mid-infrared color excess ratios, and found that the total-to-selective extinction ratio is Rv = 3.2, which is very close to the normal value. But many early-type stars in the cluster center show large color excess ratios. We derived the surface density profiles of four member groups, and found that they reach the surface density of field stars at about 10', regardless of stellar mass. The IMF of NGC 6231 is derived for the mass range 0.8 -- 45 Msun. The slope of the IMF of NGC 6231 (Gamma = -1.1 +/- 0.1) is slightly shallower than the canonical value, but the difference is marginal. In addition, the mass function varies systematically, and is a strong function of radius - it is is very shallow at the center, and very steep at the outer ring suggesting the cluster is mass segregated. We ...

  11. Near-exponential surface densities as hydrostatic, non-equilibrium profiles in galaxy discs

    Science.gov (United States)

    Struck, Curtis; Elmegreen, Bruce G.

    2017-01-01

    Apparent exponential surface density profiles are nearly universal in galaxy discs across Hubble types, over a wide mass range, and a diversity of gravitational potential forms. Several processes have been found to produce exponential profiles, including the actions of bars and spirals, and clump scattering, with star scattering a common theme in these. Based on reasonable physical constraints, such as minimal entropy gradients, we propose steady-state distribution functions for disc stars, applicable over a range of gravitational potentials. The resulting surface density profiles are generally a power-law term times a Sérsic-type exponential. Over a modest range of Sérsic index values, these profiles are often indistinguishable from Type I exponentials, except at the innermost radii. However, in certain parameter ranges, these steady states can appear as broken, Type II or III profiles. The corresponding velocity dispersion profiles are low-order power laws. A chemical potential associated with scattering can help understand the effects of long-range scattering. The steady profiles are found to persist through constant velocity expansions or contractions in evolving discs. The proposed distributions and profiles are simple and solve the stellar hydrodynamic equations. They may be especially relevant to thick discs that have settled to a steady form via scattering.

  12. Estimation of current density distribution of PAFC by analysis of cell exhaust gas

    Energy Technology Data Exchange (ETDEWEB)

    Kato, S.; Seya, A. [Fuji Electric Co., Ltd., Ichihara-shi (Japan); Asano, A. [Fuji Electric Corporate, Ltd., Yokosuka-shi (Japan)

    1996-12-31

    To estimate distributions of Current densities, voltages, gas concentrations, etc., in phosphoric acid fuel cell (PAFC) stacks, is very important for getting fuel cells with higher quality. In this work, we leave developed a numerical simulation tool to map out the distribution in a PAFC stack. And especially to Study Current density distribution in the reaction area of the cell, we analyzed gas composition in several positions inside a gas outlet manifold of the PAFC stack. Comparing these measured data with calculated data, the current density distribution in a cell plane calculated by the simulation, was certified.

  13. Controlling cell-cell interactions using surface acoustic waves.

    Science.gov (United States)

    Guo, Feng; Li, Peng; French, Jarrod B; Mao, Zhangming; Zhao, Hong; Li, Sixing; Nama, Nitesh; Fick, James R; Benkovic, Stephen J; Huang, Tony Jun

    2015-01-06

    The interactions between pairs of cells and within multicellular assemblies are critical to many biological processes such as intercellular communication, tissue and organ formation, immunological reactions, and cancer metastasis. The ability to precisely control the position of cells relative to one another and within larger cellular assemblies will enable the investigation and characterization of phenomena not currently accessible by conventional in vitro methods. We present a versatile surface acoustic wave technique that is capable of controlling the intercellular distance and spatial arrangement of cells with micrometer level resolution. This technique is, to our knowledge, among the first of its kind to marry high precision and high throughput into a single extremely versatile and wholly biocompatible technology. We demonstrated the capabilities of the system to precisely control intercellular distance, assemble cells with defined geometries, maintain cellular assemblies in suspension, and translate these suspended assemblies to adherent states, all in a contactless, biocompatible manner. As an example of the power of this system, this technology was used to quantitatively investigate the gap junctional intercellular communication in several homotypic and heterotypic populations by visualizing the transfer of fluorescent dye between cells.

  14. Trapped charge densities in Al2O3-based silicon surface passivation layers

    Science.gov (United States)

    Jordan, Paul M.; Simon, Daniel K.; Mikolajick, Thomas; Dirnstorfer, Ingo

    2016-06-01

    In Al2O3-based passivation layers, the formation of fixed charges and trap sites can be strongly influenced by small modifications in the stack layout. Fixed and trapped charge densities are characterized with capacitance voltage profiling and trap spectroscopy by charge injection and sensing, respectively. Al2O3 layers are grown by atomic layer deposition with very thin (˜1 nm) SiO2 or HfO2 interlayers or interface layers. In SiO2/Al2O3 and HfO2/Al2O3 stacks, both fixed charges and trap sites are reduced by at least a factor of 5 compared with the value measured in pure Al2O3. In Al2O3/SiO2/Al2O3 or Al2O3/HfO2/Al2O3 stacks, very high total charge densities of up to 9 × 1012 cm-2 are achieved. These charge densities are described as functions of electrical stress voltage, time, and the Al2O3 layer thickness between silicon and the HfO2 or the SiO2 interlayer. Despite the strong variation of trap sites, all stacks reach very good effective carrier lifetimes of up to 8 and 20 ms on p- and n-type silicon substrates, respectively. Controlling the trap sites in Al2O3 layers opens the possibility to engineer the field-effect passivation in the solar cells.

  15. STIR Proposal For Research Area 2.1.2 Surface Energy Balance: Transient Soil Density Impacts Land Surface Characteristics and Characterization

    Science.gov (United States)

    2015-12-22

    SECURITY CLASSIFICATION OF: Soil density is commonly treated as static in studies on land surface property dynamics. Magnitudes of errors associated...properties, and ii) evaluate impact of changing soil density on surface energy balance and heat and water transfer. Six soil properties were...ABSTRACT 2. REPORT TYPE 17. LIMITATION OF ABSTRACT 15. NUMBER OF PAGES 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 5c. PROGRAM ELEMENT

  16. Response- Surface Analysis for Evaluation of Competition in Different Densities of Sesame (Sesamum indicum) and Bean (Phaseolus vulgaris) Intercropping

    OpenAIRE

    Koocheki, A.; M. Nassiri Mahalati; Y Alizadeh; R. Moradi

    2014-01-01

    Response surface models predict crop yield based on crop density and this is an important tool for evaluation competition at different density and hence selection of optimum density based on yield. In order to study intra and inter specific competition in intercropping bean (Phaseolus vulgaris) and sesame (Sesamum indicum), an experiment was conducted at the Agricultural Research Station, Ferdowsi University of Mashhad during the growing season of 2010. For this purpose a complete randomized ...

  17. Engineered antifouling microtopographies: surface pattern effects on cell distribution.

    Science.gov (United States)

    Decker, Joseph T; Sheats, Julian T; Brennan, Anthony B

    2014-12-23

    Microtopography has been observed to lead to altered attachment behavior for marine fouling organisms; however, quantification of this phenomenon is lacking in the scientific literature. Here, we present quantitative measurement of the disruption of normal attachment behavior of the fouling algae Ulva linza by antifouling microtopographies. The distribution of the diatom Navicula incerta was shown to be unaffected by the presence of topography. The radial distribution function was calculated for both individual zoospores and cells as well as aggregates of zoospores from attachment data for a variety topographic configurations and at a number of different attachment densities. Additionally, the screening distance and maximum values were mapped according to the location of zoospore aggregates within a single unit cell. We found that engineered topographies decreased the distance between spore aggregates compared to that for a smooth control surface; however, the distributions for individual spores were unchanged. We also found that the local attachment site geometry affected the screening distance for aggregates of zoospores, with certain geometries decreasing screening distance and others having no measurable effect. The distribution mapping techniques developed and explored in this article have yielded important insight into the design parameters for antifouling microtopographies that can be implemented in the next generation of antifouling surfaces.

  18. Sea surface density gradients in the Nordic Seas during the Holocene as revealed by paired microfossil and isotope proxies

    DEFF Research Database (Denmark)

    Van Nieuwenhove, Nicolas; Hillaire-Marcel, Claude; Bauch, Henning A.

    2016-01-01

    We attempt to assess the Holocene surface-subsurface seawater density gradient on millennial time-scale based on the reconstruction of potential density (σθ) by combining data from dinoflagellate cyst assemblages and planktic foraminiferal (Neogloboquadrina pachyderma (s)) stable oxygen isotopes (δ...

  19. Cells determine cell density using a small protein bound to a unique tissue-specific phospholipid

    Directory of Open Access Journals (Sweden)

    Christopher J. Petzold

    2013-10-01

    Full Text Available Cell density is the critical parameter controlling tendon morphogenesis. Knowing its neighbors allows a cell to regulate correctly its proliferation and collagen production. A missing link to understanding this process is a molecular description of the sensing mechanism. Previously, this mechanism was shown in cell culture to rely on a diffusible factor (SNZR [sensor] with an affinity for the cell layer. This led to purifying conditioned medium over 4 columns and analyzing the final column fractions for band intensity on SDS gels versus biological activity – a 16 kD band strongly correlated between assays. N-terminal sequencing – EPLAVVDL – identified a large gene (424 AA, extremely conserved between chicken and human. In this paper we probe whether this is the correct gene. Can the predicted large protein be cleaved to a smaller protein? EPLAVVDL occurs towards the C-terminus and cleavage would create a small 94 AA protein. This protein would run at ∼10 kD, so what modifications or cofactor binding accounts for its running at 16 kD on SDS gels? This protein has no prominent hydrophobic regions, so can it be secreted? To validate its role, the chicken cDNA for this gene was tagged with myc and his and transfected into a human osteosarcoma cell line (U2OS. U2OS cells expressed the gene but not passively: differentiating into structures resembling spongy bone and expressing alkaline phosphatase, an early bone marker. Intracellularly, two bands were observed by Western blotting: the full length protein and a smaller form (26 kD. Outside the cell, a small band (28 kD was detected, although it was 40% larger than expected, as well as multiple larger bands. These larger forms could be converted to the predicted smaller protein (94 AA + tags by changing salt concentrations and ultrafiltering – releasing a cofactor to the filtrate while leaving a protein factor in the retentate. Using specific degradative enzymes and mass spectrometry, the

  20. Flame retardancy effect of surface-modified metal hydroxides on linear low density polyethylene

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Metal hydroxides (MAH) consisting of magnesium hydroxide and aluminum hydroxide with a mass ratio of 1:2 were surface-modified by γ-diethoxyphosphorous ester propyldiethoxymethylsilane,boric acid and diphenylsilanediol in xylene under dibutyl tin dilaurate catalyst at 140 ℃.Phosphorus,silicon and boron elements covalently bonded to metal hydroxide particles were detected by X-ray photoelectron spectroscopy.The degradation behavior of the surface-modified MAH was characterized by thermogravimetric analysis.The results show that linear low density polyethylene (LLDPE) composite,filled with 50% (mass fraction) of MAH modified by 5.0% (mass fraction) of modifiers,passes the V-O rating of UL-94 test and shows the limited oxygen index of 34%,and its heat release rate and average effective heat combustion in a cone calorimeter measurement decrease obviously;The mechanical properties of MAH can be improved by surface-modification.The uniform dispersion of particles and strong interfacial bonding between particles and matrix are obtained.

  1. Density, proportion, and dendritic coverage of retinal ganglion cells of the common marmoset (Callithrix jacchus jacchus

    Directory of Open Access Journals (Sweden)

    F.L. Gomes

    2005-06-01

    Full Text Available We performed a quantitative analysis of M and P cell mosaics of the common-marmoset retina. Ganglion cells were labeled retrogradely from optic nerve deposits of Biocytin. The labeling was visualized using horseradish peroxidase (HRP histochemistry and 3-3'diaminobenzidine as chromogen. M and P cells were morphologically similar to those found in Old- and New-World primates. Measurements were performed on well-stained cells from 4 retinas of different animals. We analyzed separate mosaics for inner and outer M and P cells at increasing distances from the fovea (2.5-9 mm of eccentricity to estimate cell density, proportion, and dendritic coverage. M cell density decreased towards the retinal periphery in all quadrants. M cell density was higher in the nasal quadrant than in other retinal regions at similar eccentricities, reaching about 740 cells/mm² at 2.5 mm of temporal eccentricity, and representing 8-14% of all ganglion cells. P cell density increased from peripheral to more central regions, reaching about 5540 cells/mm² at 2.5 mm of temporal eccentricity. P cells represented a smaller proportion of all ganglion cells in the nasal quadrant than in other quadrants, and their numbers increased towards central retinal regions. The M cell coverage factor ranged from 5 to 12 and the P cell coverage factor ranged from 1 to 3 in the nasal quadrant and from 5 to 12 in the other quadrants. These results show that central and peripheral retinal regions differ in terms of cell class proportions and dendritic coverage, and their properties do not result from simply scaling down cell density. Therefore, differences in functional properties between central and peripheral vision should take these distinct regional retinal characteristics into account.

  2. Application of dielectric spectroscopy for monitoring high cell density in monoclonal antibody producing CHO cell cultivations.

    Science.gov (United States)

    Párta, László; Zalai, Dénes; Borbély, Sándor; Putics, Akos

    2014-02-01

    The application of dielectric spectroscopy was frequently investigated as an on-line cell culture monitoring tool; however, it still requires supportive data and experience in order to become a robust technique. In this study, dielectric spectroscopy was used to predict viable cell density (VCD) at industrially relevant high levels in concentrated fed-batch culture of Chinese hamster ovary cells producing a monoclonal antibody for pharmaceutical purposes. For on-line dielectric spectroscopy measurements, capacitance was scanned within a wide range of frequency values (100-19,490 kHz) in six parallel cell cultivation batches. Prior to detailed mathematical analysis of the collected data, principal component analysis (PCA) was applied to compare dielectric behavior of the cultivations. PCA analysis resulted in detecting measurement disturbances. By using the measured spectroscopic data, partial least squares regression (PLS), Cole-Cole, and linear modeling were applied and compared in order to predict VCD. The Cole-Cole and the PLS model provided reliable prediction over the entire cultivation including both the early and decline phases of cell growth, while the linear model failed to estimate VCD in the later, declining cultivation phase. In regards to the measurement error sensitivity, remarkable differences were shown among PLS, Cole-Cole, and linear modeling. VCD prediction accuracy could be improved in the runs with measurement disturbances by first derivative pre-treatment in PLS and by parameter optimization of the Cole-Cole modeling.

  3. Fermi Surface Topology of Na0.5CoO2 from the Hybrid Density Functional

    Institute of Scientific and Technical Information of China (English)

    CHEN Zhao-Ying; XIANG Hong-Jun; YANG Jin-Long

    2005-01-01

    @@ The Fermi surface topology of Na0.5CoO2 is studied using the hybrid density functional theory. We first study a single (CoO2)0.5- layer model with the percentage of the nonlocal Hartree-Fock exchange changing from 0% to 20%. The results show that only when the mixed nonlocal Hartree-Fock exchange is between 1% and 5%, the Fermi surface topology is similar to the experimental one. With 3% HF exchange in the hybrid density functional,considering the effects of Na ions in the Na0.sCoO2 system, we find that the Fermi surface is split to double holes and small gaps open near the intersections between the Brillouin zone and the Fermi surface. Our results show that both the amounts of the nonlocal Hartree-Fock exchange in the hybrid density functional and the Na ions have much influence on the Fermi surface topology.

  4. Implementation of submicrometric periodic surface structures toward improvement of organic-solar-cell performances

    Science.gov (United States)

    Cocoyer, C.; Rocha, L.; Sicot, L.; Geffroy, B.; de Bettignies, R.; Sentein, C.; Fiorini-Debuisschert, C.; Raimond, P.

    2006-03-01

    Submicrometric periodic patterning of an organic solar cell surface is investigated in order to optimize the photovoltaic conversion efficiency of the device. Patterning is achieved using a single-step all-optical technique based on photoinduced mass transport in azopolymer films. The polymer film with a structured surface is used as a substrate for an organic solar cell based on a copper phthalocyanine/C60 heterojunction. The effect of periodic patterning is investigated through the solar-cell optical-absorption properties and external quantum efficiency measurements. The possibility to increase the short circuit current density and the corresponding photovoltaic conversion efficiency is evidenced with one-dimensional periodic structures.

  5. The density of the cell sap and endoplasm of Nitellopsis and Chara

    Science.gov (United States)

    Wayne, R.; Staves, M. P.

    1991-01-01

    We measured the densities of the cell sap, endoplasm and cell wall of Nitellopsis obtusa and Chara corallina using interference microscopy, refractometry, immersion refractometry, equilibrium sedimentation and chemical microanalysis techniques. These values are important for the determination of many rheological properties of the cytoplasm as well as for understanding buoyancy regulation, dispersal mechanisms and how cells respond to gravity. The average densities of the cell sap, endoplasm and cell wall are 1,006.9, 1,016.7 and 1,371 kg m-3 for Nitellopsis and 1,005.0, 1,013.9, and 1,355.3 kg m-3 for Chara.

  6. Silver-capped silicon nanopillar platforms for adsorption studies of folic acid using surface enhanced Raman spectroscopy and density functional theory

    DEFF Research Database (Denmark)

    Castillo, Jaime; Rindzevicius, Tomas; Wu, Kaiyu

    2015-01-01

    The study of the interactions of folic acid (FA) with surface enhanced Raman scattering substrates is relevant for understanding its adsorption mechanismand for fabricating analytical devices for detection ofmalignant cells over-expressing folate receptors. This paper presents a study of the adso......The study of the interactions of folic acid (FA) with surface enhanced Raman scattering substrates is relevant for understanding its adsorption mechanismand for fabricating analytical devices for detection ofmalignant cells over-expressing folate receptors. This paper presents a study...... of the adsorption of FA on silver-capped silicon nanopillar substrates employing surface enhanced Raman scattering spectroscopy and density functional theory calculations. The experimentally observed vibrations from free FA and FA bound to the Ag surface display different vibrational spectra indicating chemical...... interaction of the molecule with the metal surface. Density functional theory calculations show that the Ag–FA interaction is primarily through the nitrogen from the pteridine ring anchoring to the Ag metal surface. To investigate the Ag–FA binding behavior further, the adsorption isotherm of FA on the silver...

  7. Directional Local Density of States of Classical and Quantum Propagating Surface Plasmons

    Science.gov (United States)

    Berthel, Martin; Jiang, Quanbo; Pham, Aline; Bellessa, Joel; Genet, Cyriaque; Huant, Serge; Drezet, Aurélien

    2017-01-01

    We theoretically and experimentally introduce the concept of the local density of states (LDOS) associated with propagative surface plasmons (PSPs) launched along a structured thin gold film (a concept we call PSP LDOS). The alternative method couples a near-field optical microscope, in either the classical or the quantum regime of excitation, to a far-field leakage-radiation microscope. This method allows for selecting and collecting a very narrow portion of the directional SP wave vectors, thereby offering sufficient resolution to probe the collimation efficiency of a SP beam for a source near the focal point of a Bragg parabolic reflector. We are able to build and image the PSP LDOS in a fully integrated quantum SP launcher by depositing a diamond nanocrystal hosting nitrogen-vacancy centers at the focal point of the mirror. Our demonstration of the PSP LDOS with quantized SPs offers alternative prospects in the field of quantum plasmonics.

  8. Modeling the Images of Relativistic Jets Lensed by Galaxies with Different Mass Surface Density Distributions

    CERN Document Server

    Larchenkova, T I; Lyskova, N S

    2011-01-01

    The images of relativistic jets from extragalactic sources produced by gravitational lensing by galaxies with different mass surface density distributions are modeled. In particular, the following models of the gravitational lens mass distribution are considered: a singular isothermal ellipsoid, an isothermal ellipsoid with a core, two- and three-component models with a galactic disk, halo, and bulge. The modeled images are compared both between themselves and with available observations. Different sets of parameters are shown to exist for the gravitationally lensed system B0218+357 in multicomponent models. These sets allow the observed geometry of the system and the intensity ratio of the compact core images to be obtained, but they lead to a significant variety in the Hubble constant determined from the modeling results.

  9. Multidimensionally constrained covariant density functional theories—nuclear shapes and potential energy surfaces

    Science.gov (United States)

    Zhou, Shan-Gui

    2016-06-01

    The intrinsic nuclear shapes deviating from a sphere not only manifest themselves in nuclear collective states but also play important roles in determining nuclear potential energy surfaces (PES’s) and fission barriers. In order to describe microscopically and self-consistently nuclear shapes and PES’s with as many shape degrees of freedom as possible included, we developed multidimensionally constrained covariant density functional theories (MDC-CDFTs). In MDC-CDFTs, the axial symmetry and the reflection symmetry are both broken and all deformations characterized by {β }λ μ with even μ are considered. We have used the MDC-CDFTs to study PES’s and fission barriers of actinides, the non-axial octupole Y 32 correlations in N = 150 isotones and shapes of hypernuclei. In this Review we will give briefly the formalism of MDC-CDFTs and present the applications to normal nuclei.

  10. Multidimensionally-constrained covariant density functional theories --- nuclear shapes and potential energy surfaces

    CERN Document Server

    Zhou, Shan-Gui

    2016-01-01

    The intrinsic nuclear shapes deviating from a sphere not only manifest themselves in nuclear collective states but also play important roles in determining nuclear potential energy surfaces (PES's) and fission barriers. In order to describe microscopically and self-consistently nuclear shapes and PES's with as many shape degrees of freedom as possible included, we developed multidimensionally-constrained covariant density functional theories (MDC-CDFTs). In MDC-CDFTs, the axial symmetry and the reflection symmetry are both broken and all deformations characterized by $\\beta_{\\lambda\\mu}$ with even $\\mu$ are considered. We have used the MDC-CDFTs to study PES's and fission barriers of actinides, the non-axial octupole $Y_{32}$ correlations in $N = 150$ isotones and shapes of hypernuclei. In this Review we will give briefly the formalism of MDC-CDFTs and present the applications to normal nuclei.

  11. Polystyrene sphere monolayer assisted electrochemical deposition of ZnO nanorods with controlable surface density

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez, D., E-mail: daniel.ramirez@ucv.c [Laboratorio de Electroquimica, Pontificia Universidad Catolica de Valparaiso, Valparaiso (Chile); Gomez, H. [Laboratorio de Electroquimica, Pontificia Universidad Catolica de Valparaiso, Valparaiso (Chile); Lincot, D. [Institute de Recherche et Developpement sur l' Energie Photovoltaique-IRDEP, 6 Quai Watier 78401, Chatou Cedex (France)

    2010-02-15

    In this paper we report the zinc oxide nanorods (ZnO NRs) growth by electrochemical deposition onto polycrystalline gold electrodes modified with assemblies of polystyrene sphere monolayers (PSSMs). Growth occurs through the interstitial spaces between the hexagonally close packed spheres. ZnO NRs nucleate in the region where three adjacent spheres leave a space, being able to grow and projected over the PSSMs. The nanorod surface density (N{sub NR}) shows a linear dependence with respect to a PS sphere diameter selected. XRD analysis shows these ZnO NRs are highly oriented along the (0 0 2) plane (c-axis). This open the possibility to have electronic devices with mechanically supported nanometric materials.

  12. Fermi Surface Evolution Across Multiple Charge Density Wave Transitions in ErTe3

    Energy Technology Data Exchange (ETDEWEB)

    Moore, R.G.; /SLAC, SSRL /Stanford U., Geballe Lab.; Brouet, V.; /Orsay, LPS; He, R.; /SLAC, SSRL /Stanford U., Geballe Lab.; Lu, D.H.; /SLAC, SSRL; Ru, N.; Chu, J.-H.; Fisher, I.R.; /Stanford U., Geballe Lab.; Shen, Z.-X.; /SLAC, SSRL /Stanford U., Geballe Lab.

    2010-02-15

    The Fermi surface (FS) of ErTe{sub 3} is investigated using angle-resolved photoemission spectroscopy (ARPES). Low temperature measurements reveal two incommensurate charge density wave (CDW) gaps created by perpendicular FS nesting vectors. A large {Delta}{sub 1} = 175 meV gap arising from a CDW with c* - q{sub CDW1} {approx} 0.70(0)c* is in good agreement with the expected value. A second, smaller {Delta}{sub 2} = 50 meV gap is due to a second CDW with a* - q{sub CDW2} {approx} 0.68(5)a*. The temperature dependence of the FS, the two gaps and possible interaction between the CDWs are examined.

  13. Effect of Ar ion on the surface properties of low density polyethylene

    Science.gov (United States)

    Zaki, M. F.

    2016-04-01

    In this paper, low-density polyethylene (LDPE) was irradiated by argon ion with different fluences up to 1015ions/cm2. The optical, chemical and hardness properties have been investigated using UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and micro-indentation tester, respectively. The results showed the ion beam bombardment induced decreases in the transmittance of the irradiated polymer samples. This change in transmittance can be attributed to the formation of conjugated bonds i.e. possible formation of defects and/or carbon clusters. The indirect optical band gap decreased from 3.0 eV for the pristine sample to 2.3 eV for that sample irradiated with the highest fluence of the Ar ion beam. Furthermore, the number of carbon atoms and clusters increased with increasing Ar ion fluences. FTIR spectra showed the formation of new bands of the bombarded polymer samples. Furthermore, polar groups were created on the surface of the irradiated samples which refer to the increase of the hydrophilic nature of the surface of the irradiated samples. The Vicker's hardness increased from 4.9 MPa for the pristine sample to 17.9 MPa for those bombarded at the highest fluence. This increase is attributed to the increase in the crosslinking and alterations of the bombarded surface into hydrogenated amorphous carbon, which improves the hardness of the irradiated samples. The bombarded LDPE surfaces may be used in special applications to the field of the micro-electronic devices and shock absorbers.

  14. Nanofabrication of Nonfouling Surfaces for Micropatterning of Cell and Microtissue

    Directory of Open Access Journals (Sweden)

    Hidenori Otsuka

    2010-08-01

    Full Text Available Surface engineering techniques for cellular micropatterning are emerging as important tools to clarify the effects of the microenvironment on cellular behavior, as cells usually integrate and respond the microscale environment, such as chemical and mechanical properties of the surrounding fluid and extracellular matrix, soluble protein factors, small signal molecules, and contacts with neighboring cells. Furthermore, recent progress in cellular micropatterning has contributed to the development of cell-based biosensors for the functional characterization and detection of drugs, pathogens, toxicants, and odorants. In this regards, the ability to control shape and spreading of attached cells and cell-cell contacts through the form and dimension of the cell-adhesive patches with high precision is important. Commitment of stem cells to different specific lineages depends strongly on cell shape, implying that controlled microenvironments through engineered surfaces may not only be a valuable approach towards fundamental cell-biological studies, but also of great importance for the design of cell culture substrates for tissue engineering. To develop this kind of cellular microarray composed of a cell-resistant surface and cell attachment region, micropatterning a protein-repellent surface is important because cellular adhesion and proliferation are regulated by protein adsorption. The focus of this review is on the surface engineering aspects of biologically motivated micropatterning of two-dimensional surfaces with the aim to provide an introductory overview described in the literature. In particular, the importance of non-fouling surface chemistries is discussed.

  15. Dynamics of two-phase interfaces and surface tensions: A density-functional theory perspective

    Science.gov (United States)

    Yatsyshin, Petr; Sibley, David N.; Duran-Olivencia, Miguel A.; Kalliadasis, Serafim

    2016-11-01

    Classical density functional theory (DFT) is a statistical mechanical framework for the description of fluids at the nanoscale, where the inhomogeneity of the fluid structure needs to be carefully accounted for. By expressing the grand free-energy of the fluid as a functional of the one-body density, DFT offers a theoretically consistent and computationally accessible way to obtain two-phase interfaces and respective interfacial tensions in a ternary solid-liquid-gas system. The dynamic version of DFT (DDFT) can be rigorously derived from the Smoluchowsky picture of the dynamics of colloidal particles in a solvent. It is generally agreed that DDFT can capture the diffusion-driven evolution of many soft-matter systems. In this context, we use DDFT to investigate the dynamic behaviour of two-phase interfaces in both equilibrium and dynamic wetting and discuss the possibility of defining a time-dependent surface tension, which still remains in debate. We acknowledge financial support from the European Research Council via Advanced Grant No. 247031 and from the Engineering and Physical Sciences Research Council of the UK via Grants No. EP/L027186 and EP/L020564.

  16. Properties of superconductivity on a density wave background with small ungapped Fermi surface parts

    Science.gov (United States)

    Grigoriev, P. D.

    2008-06-01

    We investigate the properties and the microscopic structure of superconductivity (SC) coexisting and sharing the common conducting band with density wave (DW). Such coexistence may take place when the nesting of the Fermi surface (FS) is not perfect, and in the DW state some quasiparticle states remain on the Fermi level and lead to the Cooper instability. The dispersion of such quasiparticle states strongly differs from that without DW, and so do the properties of SC on the DW background. The upper critical field Hc2 in such a SC state increases as the system approaches the critical pressure, where the ungapped quasiparticles and superconductivity just appear, and it may considerably exceed the usual Hc2 value without DW. The spin-density wave (SDW) background strongly suppresses the singlet SC pairing, while it does not affect so much the triplet SC transition temperature. The results obtained explain the experimental observations in layered organic metals (TMTSF)2PF6 and α-(BEDT-TTF)2KHg(SCN)4 , where SC appears in the DW states under pressure and shows many unusual properties.

  17. Adsorption of Ne on alkali surfaces studied with a density functional theory

    Science.gov (United States)

    Sartarelli, Salvador A.; Szybisz, Leszek; Urrutia, Ignacio

    2009-01-01

    A density functional formalism is applied to investigate the wetting behavior of Ne adsorbed on planar substrates. The study is performed over the complete range of temperatures spanned from the triple point Tt up to the critical one Tc . For this purpose, an effective attractive pair potential was built on the basis of a separation procedure. This approach yields a good description of properties of the liquid-vapor interface at coexistence in the whole range of temperatures Tt⩽T⩽Tc . The adsorption of Ne on alkali metals and the alkaline-earth metal Mg is analyzed. This sequence of substrates exhibit increasing attractive strength leading to a variety of wetting situations throughout the interval Tt↔Tc . A comparison with experimental data and other microscopic calculations is done. The predictions of a simple model are discussed. For Ne/Rb we were able to resolve prewetting lines. Results obtained from a density functional are reported for Ne/K and Ne/Mg . In the case of the latter system the interesting behavior occurs close to Tt . According to our results, Ne wets surfaces of Na and Li, and this statement is in agreement with the whole picture of the analyzed substrates.

  18. FGF7 and cell density are required for final differentiation of pancreatic amylase-positive cells from human ES cells.

    Science.gov (United States)

    Takizawa-Shirasawa, Sakiko; Yoshie, Susumu; Yue, Fengming; Mogi, Akimi; Yokoyama, Tadayuki; Tomotsune, Daihachiro; Sasaki, Katsunori

    2013-12-01

    The major molecular signals of pancreatic exocrine development are largely unknown. We examine the role of fibroblast growth factor 7 (FGF7) in the final induction of pancreatic amylase-containing exocrine cells from induced-pancreatic progenitor cells derived from human embryonic stem (hES) cells. Our protocol consisted in three steps: Step I, differentiation of definitive endoderm (DE) by activin A treatment of hES cell colonies; Step II, differentiation of pancreatic progenitor cells by re-plating of the cells of Step I onto 24-well plates at high density and stimulation with all-trans retinoic acid; Step III, differentiation of pancreatic exocrine cells with a combination of FGF7, glucagon-like peptide 1 and nicotinamide. The expression levels of pancreatic endodermal markers such as Foxa2, Sox17 and gut tube endoderm marker HNF1β were up-regulated in both Step I and II. Moreover, in Step III, the induced cells expressed pancreatic markers such as amylase, carboxypeptidase A and chymotrypsinogen B, which were similar to those in normal human pancreas. From day 8 in Step III, cells immunohistochemically positive for amylase and for carboxypeptidase A, a pancreatic exocrine cell product, were induced by FGF7. Pancreatic progenitor Pdx1-positive cells were localized in proximity to the amylase-positive cells. In the absence of FGF7, few amylase-positive cells were identified. Thus, our three-step culture protocol for human ES cells effectively induces the differentiation of amylase- and carboxypeptidase-A-containing pancreatic exocrine cells.

  19. A surface structural model for ferrihydrite I: Sites related to primary charge, molar mass, and mass density

    Science.gov (United States)

    Hiemstra, Tjisse; Van Riemsdijk, Willem H.

    2009-08-01

    A multisite surface complexation (MUSIC) model for ferrihydrite (Fh) has been developed. The surface structure and composition of Fh nanoparticles are described in relation to ion binding and surface charge development. The site densities of the various reactive surface groups, the molar mass, the mass density, the specific surface area, and the particle size are quantified. As derived theoretically, molecular mass and mass density of nanoparticles will depend on the types of surface groups and the corresponding site densities and will vary with particle size and surface area because of a relatively large contribution of the surface groups in comparison to the mineral core of nanoparticles. The nano-sized (˜2.6 nm) particles of freshly prepared 2-line Fh as a whole have an increased molar mass of M ˜ 101 ± 2 g/mol Fe, a reduced mass density of ˜3.5 ± 0.1 g/cm 3, both relatively to the mineral core. The specific surface area is ˜650 m 2/g. Six-line Fh (5-6 nm) has a molar mass of M ˜ 94 ± 2 g/mol, a mass density of ˜3.9 ± 0.1 g/cm 3, and a surface area of ˜280 ± 30 m 2/g. Data analysis shows that the mineral core of Fh has an average chemical composition very close to FeOOH with M ˜ 89 g/mol. The mineral core has a mass density around ˜4.15 ± 0.1 g/cm 3, which is between that of feroxyhyte, goethite, and lepidocrocite. These results can be used to constrain structural models for Fh. Singly-coordinated surface groups dominate the surface of ferrihydrite (˜6.0 ± 0.5 nm -2). These groups can be present in two structural configurations. In pairs, the groups either form the edge of a single Fe-octahedron (˜2.5 nm -2) or are present at a single corner (˜3.5 nm -2) of two adjacent Fe octahedra. These configurations can form bidentate surface complexes by edge- and double-corner sharing, respectively, and may therefore respond differently to the binding of ions such as uranyl, carbonate, arsenite, phosphate, and others. The relatively low PZC of

  20. Growth of fibroblasts and endothelial cells on wettability gradient surfaces

    NARCIS (Netherlands)

    Ruardy, TG; Moorlag, HE; Schakenraad, JM; VanderMei, HC; Busscher, HJ

    1997-01-01

    The growth, spreading, and shape of human skin fibroblasts (PK 84) and human umbilical cord endothelial cells on dichlorodimethylsilane (DDS) and dimethyloctadecylchlorosilane (DOGS) gradient surfaces were investigated in the presence of serum proteins. Gradient surfaces were prepared on glass using

  1. Influence of current density on surface morphology and properties of pulse plated tin films from citrate electrolyte

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Ashutosh; Bhattacharya, Sumit; Das, Siddhartha; Das, Karabi, E-mail: karabi@metal.iitkgp.ernet.in

    2014-01-30

    Bulk polycrystalline tin films have been processed by pulse electrodeposition technique from a simple solution containing triammonium citrate and stannous chloride. The cathodic investigations have been carried out by galvanostatic methods. As deposited samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). XRD analysis of the deposited films shows microcrystalline grains having β-Sn form. The surface morphology is very rough at lower current density, but becomes smooth at higher current density, and exhibits pyramid type morphology at all the current densities. The effect of current density on microhardness, melting behavior, and electrical resistivity are also reported here.

  2. Atomic and molecular adsorption on transition-metal carbide (111) surfaces from density-functional theory: a trend study of surface electronic factors

    DEFF Research Database (Denmark)

    Vojvodic, Aleksandra; Ruberto, C.; Lundqvist, Bengt

    2010-01-01

    This study explores atomic and molecular adsorption on a number of early transition-metal carbides (TMCs) in NaCl structure by means of density-functional theory calculations. The investigated substrates are the TM-terminated TMC(111) surfaces, of interest because of the presence of different types......, surface relaxations, Bader charges, and surface-localized densities of states (DOSs). Detailed comparisons between surface and bulk DOSs reveal the existence of transition-metal localized SRs (TMSRs) in the pseudogap and of several C-localized SRs (CSRs) in the upper valence band on all considered TMC(111......C, delta-MoC, TaC, and WC (in NaCl structure) and the adsorbates H, B, C, N, O, F, NH, NH2, and NH3. Trends in adsorption strength are explained in terms of surface electronic factors, by correlating the calculated adsorption-energy values with the calculated surface electronic structures. The results...

  3. High power density microbial fuel cell with flexible 3D graphene-nickel foam as anode

    Science.gov (United States)

    Wang, Hanyu; Wang, Gongming; Ling, Yichuan; Qian, Fang; Song, Yang; Lu, Xihong; Chen, Shaowei; Tong, Yexiang; Li, Yat

    2013-10-01

    The structure and electrical conductivity of anode play a significant role in the power generation of microbial fuel cells (MFCs). In this study, we developed a three-dimensional (3D) reduced graphene oxide-nickel (denoted as rGO-Ni) foam as an anode for MFC through controlled deposition of rGO sheets onto the nickel foam substrate. The loading amount of rGO sheets and electrode surface area can be controlled by the number of rGO loading cycles. 3D rGO-Ni foam anode provides not only a large accessible surface area for microbial colonization and electron mediators, but also a uniform macro-porous scaffold for effective mass diffusion of the culture medium. Significantly, at a steady state of the power generation, the MFC device with flexible rGO-Ni electrodes produced an optimal volumetric power density of 661 W m-3 calculated based on the volume of anode material, or 27 W m-3 based on the volume of the anode chamber. These values are substantially higher than that of plain nickel foam, and other conventional carbon based electrodes (e.g., carbon cloth, carbon felt, and carbon paper) measured in the same conditions. To our knowledge, this is the highest volumetric power density reported for mL-scale MFC device with a pure strain of Shewanella oneidensis MR-1. We also demonstrated that the MFC device can be operated effectively in a batch-mode at least for a week. These new 3D rGO-Ni electrodes show great promise for improving the power generation of MFC devices.The structure and electrical conductivity of anode play a significant role in the power generation of microbial fuel cells (MFCs). In this study, we developed a three-dimensional (3D) reduced graphene oxide-nickel (denoted as rGO-Ni) foam as an anode for MFC through controlled deposition of rGO sheets onto the nickel foam substrate. The loading amount of rGO sheets and electrode surface area can be controlled by the number of rGO loading cycles. 3D rGO-Ni foam anode provides not only a large accessible

  4. Surface charge dynamics and OH and H number density distributions in near-surface nanosecond pulse discharges at a liquid / vapor interface

    Science.gov (United States)

    Winters, Caroline; Petrishchev, Vitaly; Yin, Zhiyao; Lempert, Walter R.; Adamovich, Igor V.

    2015-10-01

    The present work provides insight into surface charge dynamics and kinetics of radical species reactions in nanosecond pulse discharges sustained at a liquid-vapor interface, above a distilled water surface. The near-surface plasma is sustained using two different discharge configurations, a surface ionization wave discharge between two exposed metal electrodes and a double dielectric barrier discharge. At low discharge pulse repetition rates (~100 Hz), residual surface charge deposition after the discharge pulse is a minor effect. At high pulse repetition rates (~10 kHz), significant negative surface charge accumulation over multiple discharge pulses is detected, both during alternating polarity and negative polarity pulse trains. Laser induced fluorescence (LIF) and two-photon absorption LIF (TALIF) line imaging are used for in situ measurements of spatial distributions of absolute OH and H atom number densities in near-surface, repetitive nanosecond pulse discharge plasmas. Both in a surface ionization wave discharge and in a double dielectric barrier discharge, peak measured H atom number density, [H] is much higher compared to peak OH number density, due to more rapid OH decay in the afterglow between the discharge pulses. Higher OH number density was measured near the regions with higher plasma emission intensity. Both OH and especially H atoms diffuse out of the surface ionization wave plasma volume, up to several mm from the liquid surface. Kinetic modeling calculations using a quasi-zero-dimensional H2O vapor / Ar plasma model are in qualitative agreement with the experimental data. The results demonstrate the experimental capability of in situ radical species number density distribution measurements in liquid-vapor interface plasmas, in a simple canonical geometry that lends itself to the validation of kinetic models.

  5. Bone cell expression on titanium surfaces is altered by sterilization treatments.

    Science.gov (United States)

    Stanford, C M; Keller, J C; Solursh, M

    1994-05-01

    Phenotypic responses of rat calvarial osteoblast-like cells (RCOB) were evaluated on commercially pure titanium (cpTi) surfaces when cultured at high density (5100 cells/mm2). These surfaces were prepared to three different clinically relevant surface preparations (1-micron, 600-grit, and 50-microns-grit sand-blast), followed by sterilization with either ultraviolet light, ethylene oxide, argon plasma-cleaning, or routine clinical autoclaving. Osteocalcin and alkaline phosphatase, but not collagen expression, were significantly affected by surface roughness when these surfaces were altered by argon plasma-cleaning. In general, plasma-cleaned cpTi surfaces demonstrated an inverse relationship between surface roughness and phenotypic markers for a bone-like response. On a per-cell basis, levels of the bone-specific protein, osteocalcin, and the enzymatic activity of alkaline phosphatase were highest on the smooth 1-micron polished surface and lowest on the roughest surfaces for the plasma-cleaned cpTi. Detectable bone cell expression can be altered by clinically relevant surfaces prepared by standard dental implant preparation techniques.

  6. Configurational study of amino-functionalized silica surfaces: A density functional theory modeling.

    Science.gov (United States)

    Hozhabr Araghi, Samira; Entezari, Mohammad H; Sadeghi Googheri, Mohammad Sadegh

    2015-06-01

    Despite extensive studies of the amino-functionalized silica surfaces, a comprehensive investigation of the effects of configuration and hydrolysis of 3-aminopropyltriethoxysilan (APTES) molecules attached on silica has not been studied yet. Therefore, the methods of quantum mechanics were used for the study of configuration and hydrolysis forms of APTES molecules attached on the surface. For this purpose, five different categories based on the number of hydrolyzed ethoxy groups including 16 configurations were designed and analyzed by the density functional theory (DFT) method. The steric hindrance as an effective factor on the stability order was extracted from structural analysis. Other impressive parameters such as the effects of hydrogen bond and electron delocalization energy were obtained by using the atoms in molecules (AIM) and natural bond orbitals (NBO) theories. Consequently, it was found that the stability of configurations was attributed to steric effects, hydrogen bond numbers and electron delocalization energy. The maximum stability was achieved when at least two of these parameters cooperate with each other.

  7. Calreticulin: Roles in Cell-Surface Protein Expression

    Directory of Open Access Journals (Sweden)

    Yue Jiang

    2014-09-01

    Full Text Available In order to perform their designated functions, proteins require precise subcellular localizations. For cell-surface proteins, such as receptors and channels, they are able to transduce signals only when properly targeted to the cell membrane. Calreticulin is a multi-functional chaperone protein involved in protein folding, maturation, and trafficking. However, evidence has been accumulating that calreticulin can also negatively regulate the surface expression of certain receptors and channels. In these instances, depletion of calreticulin enhances cell-surface expression and function. In this review, we discuss the role of calreticulin with a focus on its negative effects on the expression of cell-surface proteins.

  8. Modeling the Excess Cell Surface Stored in a Complex Morphology of Bleb-Like Protrusions

    Science.gov (United States)

    Wessler, Timothy; Yang, Xiaofeng; Chen, Alex; Roach, Nathan; Elston, Timothy C.; Wang, Qi; Jacobson, Ken; Forest, M. Gregory

    2016-01-01

    Cells transition from spread to rounded morphologies in diverse physiological contexts including mitosis and mesenchymal-to-amoeboid transitions. When these drastic shape changes occur rapidly, cell volume and surface area are approximately conserved. Consequently, the rounded cells are suddenly presented with a several-fold excess of cell surface whose area far exceeds that of a smooth sphere enclosing the cell volume. This excess is stored in a population of bleb-like protrusions (BLiPs), whose size distribution is shown by electron micrographs to be skewed. We introduce three complementary models of rounded cell morphologies with a prescribed excess surface area. A 2D Hamiltonian model provides a mechanistic description of how discrete attachment points between the cell surface and cortex together with surface bending energy can generate a morphology that satisfies a prescribed excess area and BLiP number density. A 3D random seed-and-growth model simulates efficient packing of BLiPs over a primary rounded shape, demonstrating a pathway for skewed BLiP size distributions that recapitulate 3D morphologies. Finally, a phase field model (2D and 3D) posits energy-based constitutive laws for the cell membrane, nematic F-actin cortex, interior cytosol, and external aqueous medium. The cell surface is equipped with a spontaneous curvature function, a proxy for the cell surface-cortex couple, that is a priori unknown, which the model “learns” from the thin section transmission electron micrograph image (2D) or the “seed and growth” model image (3D). Converged phase field simulations predict self-consistent amplitudes and spatial localization of pressure and stress throughout the cell for any posited stationary morphology target and cell compartment constitutive properties. The models form a general framework for future studies of cell morphological dynamics in a variety of biological contexts. PMID:27015526

  9. Modeling the Excess Cell Surface Stored in a Complex Morphology of Bleb-Like Protrusions.

    Directory of Open Access Journals (Sweden)

    Maryna Kapustina

    2016-03-01

    Full Text Available Cells transition from spread to rounded morphologies in diverse physiological contexts including mitosis and mesenchymal-to-amoeboid transitions. When these drastic shape changes occur rapidly, cell volume and surface area are approximately conserved. Consequently, the rounded cells are suddenly presented with a several-fold excess of cell surface whose area far exceeds that of a smooth sphere enclosing the cell volume. This excess is stored in a population of bleb-like protrusions (BLiPs, whose size distribution is shown by electron micrographs to be skewed. We introduce three complementary models of rounded cell morphologies with a prescribed excess surface area. A 2D Hamiltonian model provides a mechanistic description of how discrete attachment points between the cell surface and cortex together with surface bending energy can generate a morphology that satisfies a prescribed excess area and BLiP number density. A 3D random seed-and-growth model simulates efficient packing of BLiPs over a primary rounded shape, demonstrating a pathway for skewed BLiP size distributions that recapitulate 3D morphologies. Finally, a phase field model (2D and 3D posits energy-based constitutive laws for the cell membrane, nematic F-actin cortex, interior cytosol, and external aqueous medium. The cell surface is equipped with a spontaneous curvature function, a proxy for the cell surface-cortex couple, that is a priori unknown, which the model "learns" from the thin section transmission electron micrograph image (2D or the "seed and growth" model image (3D. Converged phase field simulations predict self-consistent amplitudes and spatial localization of pressure and stress throughout the cell for any posited stationary morphology target and cell compartment constitutive properties. The models form a general framework for future studies of cell morphological dynamics in a variety of biological contexts.

  10. Adsorption and Reaction of CO on (100) Surface of SrTiO3 by Density Function Theory Calculation

    Institute of Scientific and Technical Information of China (English)

    YUN Jiang-Ni; ZHANG Zhi-Yong; ZHANG Fu-Chun

    2008-01-01

    Adsorption and reaction of CO on two possible terminations of SrTi03 (100) surface are investigated by the first-principles calculation of plane wave ultrasoft pseudopotential based on the density function theory. The adsorption energy, Mulliken population analysis, density of states (DOS) and electronic density difference of CO on SrTi03 (100) surface, which have never been investigated before as far as we know are performed. The calculated results reveal that the Ti-CO orientation is the most stable configuration and the adsorption energy (0.449eV) is quite small. CO molecules adsorb weakly on the SrTiO3 (100) surface, there is predominantly electrostatic attraction between CO and the surface rather than a chemical bonding mechanism.

  11. A mass spectrometric-derived cell surface protein atlas.

    Directory of Open Access Journals (Sweden)

    Damaris Bausch-Fluck

    Full Text Available Cell surface proteins are major targets of biomedical research due to their utility as cellular markers and their extracellular accessibility for pharmacological intervention. However, information about the cell surface protein repertoire (the surfaceome of individual cells is only sparsely available. Here, we applied the Cell Surface Capture (CSC technology to 41 human and 31 mouse cell types to generate a mass-spectrometry derived Cell Surface Protein Atlas (CSPA providing cellular surfaceome snapshots at high resolution. The CSPA is presented in form of an easy-to-navigate interactive database, a downloadable data matrix and with tools for targeted surfaceome rediscovery (http://wlab.ethz.ch/cspa. The cellular surfaceome snapshots of different cell types, including cancer cells, resulted in a combined dataset of 1492 human and 1296 mouse cell surface glycoproteins, providing experimental evidence for their cell surface expression on different cell types, including 136 G-protein coupled receptors and 75 membrane receptor tyrosine-protein kinases. Integrated analysis of the CSPA reveals that the concerted biological function of individual cell types is mainly guided by quantitative rather than qualitative surfaceome differences. The CSPA will be useful for the evaluation of drug targets, for the improved classification of cell types and for a better understanding of the surfaceome and its concerted biological functions in complex signaling microenvironments.

  12. Theory of back-surface-field solar cells

    Science.gov (United States)

    Vonroos, O.

    1979-01-01

    Report describes simple concise theory of back-surface-field (BSF) solar cells (npp + junctions) based on Shockley's depletion-layer approximation and cites superiority of two-junction devices over conventional unijunction cells.

  13. Combining density functional and density matrix theory: Optical excitation and electron relaxation at the Si(001)2 x 1 surface

    Energy Technology Data Exchange (ETDEWEB)

    Buecking, Norbert [Institut fuer Theoretische Physik, Technische Universitaet Berlin (Germany); Fritz-Haber-Institut der MPG, Berlin (Germany); Kratzer, Peter [Fachbereich Physik, Duisburg (Germany); Scheffler, Matthias [Fritz-Haber-Institut der MPG, Berlin (Germany); Knorr, Andreas [Institut fuer Theoretische Physik, Technische Universitaet Berlin (Germany)

    2008-07-01

    A theoretical two-step approach to investigate the optical excitation and subsequent phonon-assisted relaxation dynamics at semiconductor surfaces is presented and applied to the Si(001)2 x 1-surface: In the first step, the electronic band structure and the Kohn-Sham wave functions are calculated by density-functional-theory (DFT) within the LDA. In the second step, dynamical equations are derived from density-matrix theory (DMT), whereby an optical field is considered via A.p-coupling and phonon induced relaxation by a deformation potential coupling term. Into these equations, the numerical results of the DFT calculation (Kohn-Sham eigenvalues and wave functions) enter as coupling matrix elements. By numerically solving the dynamical equations, the time-resolved population of the excited states can be evaluated. The results for the Si(001) surface correspond to the findings of recent experiments, in particular a short (intra-surface-band scattering) and a long (bulk-surface band scattering) timescale are dominating the relaxation process. The value of the experimental short timescale is reproduced by our calculations, whereas the long timescale cannot be accurately described by our theory.

  14. Cell behavior on gallium nitride surfaces: peptide affinity attachment versus covalent functionalization.

    Science.gov (United States)

    Foster, Corey M; Collazo, Ramon; Sitar, Zlatko; Ivanisevic, Albena

    2013-07-02

    Gallium nitride is a wide band gap semiconductor that demonstrates a unique set of optical and electrical properties as well as aqueous stability and biocompatibility. This combination of properties makes gallium nitride a strong candidate for use in chemical and biological applications such as sensors and neural interfaces. Molecular modification can be used to enhance the functionality and properties of the gallium nitride surface. Here, gallium nitride surfaces were functionalized with a PC12 cell adhesion promoting peptide using covalent and affinity driven attachment methods. The covalent scheme proceeded by Grignard reaction and olefin metathesis while the affinity driven scheme utilized the recognition peptide isolated through phage display. This study shows that the method of attaching the adhesion peptide influences PC12 cell adhesion and differentiation as measured by cell density and morphological analysis. Covalent attachment promoted monolayer and dispersed cell adhesion while affinity driven attachment promoted multilayer cell agglomeration. Higher cell density was observed on surfaces modified using the recognition peptide. The results suggest that the covalent and affinity driven attachment methods are both suitable for promoting PC12 cell adhesion to the gallium nitride surface, though each method may be preferentially suited for distinct applications.

  15. Current progress in high cell density yeast bioprocesses for bioethanol production.

    Science.gov (United States)

    Westman, Johan O; Franzén, Carl Johan

    2015-08-01

    High capital costs and low reaction rates are major challenges for establishment of fermentation-based production systems in the bioeconomy. Using high cell density cultures is an efficient way to increase the volumetric productivity of fermentation processes, thereby enabling faster and more robust processes and use of smaller reactors. In this review, we summarize recent progress in the application of high cell density yeast bioprocesses for first and second generation bioethanol production. High biomass concentrations obtained by retention of yeast cells in the reactor enables easier cell reuse, simplified product recovery and higher dilution rates in continuous processes. High local cell density cultures, in the form of encapsulated or strongly flocculating yeast, furthermore obtain increased tolerance to convertible fermentation inhibitors and utilize glucose and other sugars simultaneously, thereby overcoming two additional hurdles for second generation bioethanol production. These effects are caused by local concentration gradients due to diffusion limitations and conversion of inhibitors and sugars by the cells, which lead to low local concentrations of inhibitors and glucose. Quorum sensing may also contribute to the increased stress tolerance. Recent developments indicate that high cell density methodology, with emphasis on high local cell density, offers significant advantages for sustainable second generation bioethanol production.

  16. Durability of Low Platinum Fuel Cells Operating at High Power Density

    Energy Technology Data Exchange (ETDEWEB)

    Polevaya, Olga [Nuvera Fuel Cells Inc.; Blanchet, Scott [Nuvera Fuel Cells Inc.; Ahluwalia, Rajesh [Argonne National Lab; Borup, Rod [Los-Alamos National Lab; Mukundan, Rangachary [Los-Alamos National Lab

    2014-03-19

    Understanding and improving the durability of cost-competitive fuel cell stacks is imperative to successful deployment of the technology. Stacks will need to operate well beyond today’s state-of-the-art rated power density with very low platinum loading in order to achieve the cost targets set forth by DOE ($15/kW) and ultimately be competitive with incumbent technologies. An accelerated cost-reduction path presented by Nuvera focused on substantially increasing power density to address non-PGM material costs as well as platinum. The study developed a practical understanding of the degradation mechanisms impacting durability of fuel cells with low platinum loading (≤0.2mg/cm2) operating at high power density (≥1.0W/cm2) and worked out approaches for improving the durability of low-loaded, high-power stack designs. Of specific interest is the impact of combining low platinum loading with high power density operation, as this offers the best chance of achieving long-term cost targets. A design-of-experiments approach was utilized to reveal and quantify the sensitivity of durability-critical material properties to high current density at two levels of platinum loading (the more conventional 0.45 mgPt.cm–1 and the much lower 0.2 mgPt.cm–2) across several cell architectures. We studied the relevance of selected component accelerated stress tests (AST) to fuel cell operation in power producing mode. New stress tests (NST) were designed to investigate the sensitivity to the addition of electrical current on the ASTs, along with combined humidity and load cycles and, eventually, relate to the combined city/highway drive cycle. Changes in the cathode electrochemical surface area (ECSA) and average oxygen partial pressure on the catalyst layer with aging under AST and NST protocols were compared based on the number of completed cycles. Studies showed elevated sensitivity of Pt growth to the potential limits and the initial particle size distribution. The ECSA loss

  17. Effects of diabetic keratopathy on corneal optical density, central corneal thickness, and corneal endothelial cell counts.

    Science.gov (United States)

    Gao, Feng; Lin, Tao; Pan, Yingzhe

    2016-09-01

    Diabetic keratopathy is an ocular complication that occurs with diabetes. In the present study, the effect of diabetic keratopathy on corneal optical density, central corneal thickness, and corneal endothelial cell count was investigated. One hundred and eighty diabetic patients (360 eyes) were enrolled in the study during the period from March, 2012 to March, 2013. The patients were divided into three age groups: 10 years, with 60 patients per group (120 eyes). During the same period, 60 healthy cases (120 eyes) were selected and labeled as the normal control group. The Pentacam was used to measure the corneal optical density, and central corneal thickness. Specular microscopy was used to examine the corneal endothelial cell density. The coefficient of partial correlation was used to control age and correlate the analysis between the corneal optical density, corneal endothelial cell density, and central corneal thickness. The stage of the disease, the medial and intimal corneal optical density and central corneal thickness was analyzed in the diabetes group. The corneal optical density in the diabetes group increased compared with that of the normal control group. The medial and intimal corneal optical density and central corneal thickness were positively correlated with the course of the disease. However, the corneal endothelial cell density was not associated with the course of diabetes. There was a positive association between the medial and intimal corneal optical density and central corneal thickness of the diabetic patients. In conclusion, the results of the present study show that medial and intimal corneal optical density and central corneal thickness were sensitive indicators for early diabetic keratopathy.

  18. The surface charge of a cell lipid membrane

    CERN Document Server

    Pekker, M

    2014-01-01

    In this paper the problem of surface charge of the lipid membrane is considered. It is shown that the membrane surface is negatively charged. Negative ions are in potential wells formed by the dipole heads of membrane phospholipids. The binding energy of the ion with the membrane surface is much greater than its thermal energy. A self-consistent model of the potential in solution is developed, and a stationary charge density on the membrane surface is found. The estimates given in the paper show that the potential difference across the membrane of the unexcited axon (resting potential) can be explained by the difference in surface densities of the bound charges on the inner and outer surfaces of the membrane.

  19. Measuring the mass, density, and size of particles and cells using a suspended microchannel resonator

    Science.gov (United States)

    Godin, Michel; Bryan, Andrea K.; Burg, Thomas P.; Babcock, Ken; Manalis, Scott R.

    2007-09-01

    We demonstrate the measurement of mass, density, and size of cells and nanoparticles using suspended microchannel resonators. The masses of individual particles are quantified as transient frequency shifts, while the particles transit a microfluidic channel embedded in the resonating cantilever. Mass histograms resulting from these data reveal the distribution of a population of heterogeneously sized particles. Particle density is inferred from measurements made in different carrier fluids since the frequency shift for a particle is proportional to the mass difference relative to the displaced solution. We have characterized the density of polystyrene particles, Escherichia coli, and human red blood cells with a resolution down to 10-4g/cm3.

  20. Reduced Neurite Density in Neuronal Cell Cultures Exposed to Serum of Patients with Bipolar Disorder

    Science.gov (United States)

    Wollenhaupt-Aguiar, Bianca; Pfaffenseller, Bianca; Chagas, Vinicius de Saraiva; Castro, Mauro A A; Passos, Ives Cavalcante; Kauer-Sant’Anna, Márcia; Kapczinski, Flavio

    2016-01-01

    Background: Increased inflammatory markers and oxidative stress have been reported in serum among patients with bipolar disorder (BD). The aim of this study is to assess whether biochemical changes in the serum of patients induces neurotoxicity in neuronal cell cultures. Methods: We challenged the retinoic acid-differentiated human neuroblastoma SH-SY5Y cells with the serum of BD patients at early and late stages of illness and assessed neurite density and cell viability as neurotoxic endpoints. Results: Decreased neurite density was found in neurons treated with the serum of patients, mostly patients at late stages of illness. Also, neurons challenged with the serum of late-stage patients showed a significant decrease in cell viability. Conclusions: Our findings showed that the serum of patients with bipolar disorder induced a decrease in neurite density and cell viability in neuronal cultures. PMID:27207915

  1. Surface modification of poly(dimethylsiloxane) for controlling biological cells' adhesion using a scanning radical microjet

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Helen M.L. [Department of Materials Engineering, School of Engineering, University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, 113-8656 (Japan); Fukuda, H. [Department of Electrical and Electronics Engineering, Toyo University, 2100 Kujirai, Kawagoe, 350-8585 (Japan); Akagi, T. [Department of Bioengineering, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-8656 (Japan); Center for NanoBio Integration, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-8656 (Japan); Ichiki, T. [Department of Bioengineering, School of Engineering, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-8656 (Japan) and Center for NanoBio Integration, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, 113-8656 (Japan)]. E-mail: ichiki@sogo.t.u-tokyo.ac.jp

    2007-04-23

    A scanning radical microjet (SRMJ) equipment using oxygen microplasma has been developed and successfully applied for controlling biological cells' attachment on biocompatible polymer material, poly(dimethylsiloxane) (PDMS). The radical microjet has advantages in localized and high-rate surface treatment. Moreover, maskless hydrophilic patterning using SRMJ has been demonstrated to be applicable to patterned cell cultivation which is useful in emerging biotechnological field such as tissue engineering and cell-based biosensors. Since control of PDMS surface properties is an indispensable prerequisite for cells' attachment, effects of oxygen flow rates and treatment time on localized hydrophilic patterning of PDMS surfaces were first investigated for controlling HeLa cells' (human epitheloid carcinoma cell line) attachment. Relationships between surface conditions of treated PDMS films and attached cell density are also discussed based on surface properties analyzed using atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS)

  2. Impacts of mangrove density on surface sediment accretion, belowground biomass and biogeochemistry in Puttalam Lagoon, Sri Lanka

    Science.gov (United States)

    Phillips, D.H.; Kumara, M.P.; Jayatissa, L.P.; Krauss, Ken W.; Huxham, M.

    2017-01-01

    Understanding the effects of seedling density on sediment accretion, biogeochemistry and belowground biomass in mangrove systems can help explain ecological functioning and inform appropriate planting densities during restoration or climate change mitigation programs. The objectives of this study were to examine: 1) impacts of mangrove seedling density on surface sediment accretion, texture, belowground biomass and biogeochemistry, and 2) origins of the carbon (C) supplied to the mangroves in Palakuda, Puttalam Lagoon, Sri Lanka. Rhizophora mucronata propagules were planted at densities of 6.96, 3.26, 1.93 and 0.95 seedlings m−2along with an unplanted control (0 seedlings m−2). The highest seedling density generally had higher sediment accretion rates, finer sediments, higher belowground biomass, greatest number of fine roots and highest concentrations of C and nitrogen (N) (and the lowest C/N ratio). Sediment accretion rates, belowground biomass (over 1370 days), and C and N concentrations differed significantly between seedling densities. Fine roots were significantly greater compared to medium and coarse roots across all plantation densities. Sulphur and carbon stable isotopes did not vary significantly between different density treatments. Isotope signatures suggest surface sediment C (to a depth of 1 cm) is not derived predominantly from the trees, but from seagrass adjacent to the site.

  3. Density-dependent expression of keratins in transformed rat liver cell lines.

    Science.gov (United States)

    Troyanovsky, S M; Bannikov, G A; Montesano, R; Vasiliev, J M

    1986-04-01

    Immunomorphological examination of the distribution of three keratins in cultured rat liver-derived epithelial cell lines of the IAR series was performed in order to find out the effects of neoplastic evolution on the expression of these epithelium-specific markers. Specific monoclonal antibodies were used to reveal various intermediate filament proteins: keratins with molecular masses of 55, 49 or 40 kD (K55, K49 or K40), and vimentin. The expression of keratins was negligible in sparse and dense cultures of non-transformed lines, which had typical epithelial morphology. The examined keratins were also absent in the sparse cultures of transformed lines, which have lost partially or completely the morphological features of epithelia. However, cells in dense cultures of most transformed lines contained numerous keratin filaments. It is suggested that the paradoxical increase of keratin expression after transformation is due to increased saturation density of transformed cultures; this high density favours the expression. As shown by the experiments with culture wounding, the effects of density are local and reversible. While K55 was present in all the cells of dense cultures, the expression of the other two keratins was dependent on the cell position within these cultures. It is suggested that the expression of the latter two keratins, besides high cell density, also requires the presence (K40) or the absence (K49) of cell-substratum contacts. Possible mechanisms of the effects of cell density on the expression of keratins are discussed.

  4. Cell surface engineering of yeast for applications in white biotechnology.

    Science.gov (United States)

    Kuroda, Kouichi; Ueda, Mitsuyoshi

    2011-01-01

    Cell surface engineering is a promising strategy for the molecular breeding of whole-cell biocatalysts. By using this strategy, yeasts can be constructed by the cell surface display of functional proteins; these yeasts are referred to as arming yeasts. Because reactions using arming yeasts as whole-cell biocatalysts occur on the cell surface, materials that cannot enter the cell can be used as reaction substrates. Numerous arming yeasts have therefore been constructed for a wide range of uses such as biofuel production, synthesis of valuable chemicals, adsorption or degradation of environmental pollutants, recovery of rare metal ions, and biosensors. Here, we review the science of yeast cell surface modification as well as current applications and future opportunities.

  5. Tracking motor units longitudinally across experimental sessions with high‐density surface electromyography

    Science.gov (United States)

    Martinez‐Valdes, E.; Negro, F.; Laine, C. M.; Falla, D.; Mayer, F.

    2017-01-01

    Key points Classic motor unit (MU) recording and analysis methods do not allow the same MUs to be tracked across different experimental sessions, and therefore, there is limited experimental evidence on the adjustments in MU properties following training or during the progression of neuromuscular disorders.We propose a new processing method to track the same MUs across experimental sessions (separated by weeks) by using high‐density surface electromyography.The application of the proposed method in two experiments showed that individual MUs can be identified reliably in measurements separated by weeks and that changes in properties of the tracked MUs across experimental sessions can be identified with high sensitivity.These results indicate that the behaviour and properties of the same MUs can be monitored across multiple testing sessions.The proposed method opens new possibilities in the understanding of adjustments in motor unit properties due to training interventions or the progression of pathologies. Abstract A new method is proposed for tracking individual motor units (MUs) across multiple experimental sessions on different days. The technique is based on a novel decomposition approach for high‐density surface electromyography and was tested with two experimental studies for reliability and sensitivity. Experiment I (reliability): ten participants performed isometric knee extensions at 10, 30, 50 and 70% of their maximum voluntary contraction (MVC) force in three sessions, each separated by 1 week. Experiment II (sensitivity): seven participants performed 2 weeks of endurance training (cycling) and were tested pre–post intervention during isometric knee extensions at 10 and 30% MVC. The reliability (Experiment I) and sensitivity (Experiment II) of the measured MU properties were compared for the MUs tracked across sessions, with respect to all MUs identified in each session. In Experiment I, on average 38.3% and 40.1% of the identified MUs could be

  6. Density functional study of NO adsorption on undefected and oxygen defective Au–BaO(1 0 0) surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Añez, Rafael, E-mail: ranez@ivic.gob.ve [Laboratorio de Química Física y Catálisis Computacional, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado, 21827 Caracas (Venezuela, Bolivarian Republic of); Sierraalta, Aníbal; Bastardo, Anelisse [Laboratorio de Química Física y Catálisis Computacional, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado, 21827 Caracas (Venezuela, Bolivarian Republic of); Coll, David [Laboratorio de Físico Química Teórica de Materiales, Centro de Química, Instituto Venezolano de Investigaciones Científicas, Apartado, 21827 Caracas (Venezuela, Bolivarian Republic of); Garcia, Belkis [Instituto Universitario de Tecnología de Valencia IUTVAL, Valencia, Edo. Carabobo (Venezuela, Bolivarian Republic of)

    2014-07-01

    A periodic density functional approach has been used in order to explore the interaction of NO with undoped and Au doped BaO(1 0 0) surface. Due to oxygen vacancies increase the interaction between the doping metal and the surface, F{sub S} and F{sub S}{sup +} vacancies were studied and compared with the results obtained on the undefected doped BaO(1 0 0). Our results indicate that the high basicity of the BaO surface, besides the electron density changes produced by the oxygen vacancies, modify considerably how the Au atom interacts with the surface increasing the ionic character of the interaction. F{sub S} vacancy shows to be a promise center to activate de NO bond on the BaO(1 0 0) surface.

  7. Minimally modified low density lipoprotein induces monocyte chemotactic protein 1 in human endothelial cells and smooth muscle cells.

    OpenAIRE

    Cushing, S D; Berliner, J A; Valente, A. J.; Territo, M C; Navab, M; Parhami, F; Gerrity, R; Schwartz, C J; Fogelman, A M

    1990-01-01

    After exposure to low density lipoprotein (LDL) that had been minimally modified by oxidation (MM-LDL), human endothelial cells (EC) and smooth muscle cells (SMC) cultured separately or together produced 2- to 3-fold more monocyte chemotactic activity than did control cells or cells exposed to freshly isolated LDL. This increase in monocyte chemotactic activity was paralleled by increases in mRNA levels for a monocyte chemotactic protein 1 (MCP-1) that is constitutively produced by the human ...

  8. Cell-penetrating compounds preferentially bind glycosaminoglycans over plasma membrane lipids in a charge density- and stereochemistry-dependent manner.

    Science.gov (United States)

    Prevette, Lisa E; Benish, Nicolas C; Schoenecker, Amber R; Braden, Kristin J

    2015-12-01

    Cell-penetrating compounds (CPCs) are often conjugated to drugs and genes to facilitate cellular uptake. We hypothesize that the electrostatic interaction between the positively charged amines of the cell-penetrating compounds and the negatively charged glycosaminoglycans (GAGs) extending from cell surfaces is the initiating step in the internalization process. The interactions of generation 5 PAMAM dendrimer, Tat peptide and 25 kDa linear PEI with four different GAGs have been studied using isothermal titration calorimetry to elucidate structure-function relationships that could lead to improved drug and gene delivery methods to a wide variety of cell types. Detailed thermodynamic analysis has determined that CPC-GAG binding constants range from 8.7×10(3) to 2.4×10(6)M(-1) and that affinity is dependent upon GAG charge density and stereochemistry and CPC molecular weight. The effect of GAG composition on affinity is likely due to hydrogen bonding between CPC amines and amides and GAG hydroxyl and amine groups. These results were compared to the association of CPCs with lipid vesicles of varying composition as model plasma membranes to finally clarify the relative importance of each cell surface component in initial cell recognition. CPC-lipid affinity increases with anionic lipid content, but GAG affinity is higher for all cell-penetrating compounds, confirming the role these heterogeneous polysaccharides play in cellular association and clustering.

  9. Cell Surface-based Sensing with Metallic Nanoparticles

    OpenAIRE

    Jiang, Ziwen; Le, Ngoc D. B.; Gupta, Akash; Rotello, Vincent M.

    2015-01-01

    Metallic nanoparticles provide versatile scaffolds for biosensing applications. In this review, we focus on the use of metallic nanoparticles for cell surface sensings. Examples of the use of both specific recognition and array-based “chemical nose” approaches to cell surface sensing will be discussed.

  10. Extracting Extensor Digitorum Communis Activation Patterns using High-Density Surface Electromyography

    Directory of Open Access Journals (Sweden)

    Xiaogang eHu

    2015-10-01

    Full Text Available The extensor digitorum communis muscle plays an important role in hand dexterity during object manipulations. This multi-tendinous muscle is believed to be controlled through separate motoneuron pools, thereby forming different compartments that control individual digits. However, due to the complex anatomical variations across individuals and the flexibility of neural control strategies, the spatial activation patterns of the extensor digitorum communis compartments during individual finger extension have not been fully tracked under different task conditions.The objective of this study was to quantify the global spatial activation patterns of the extensor digitorum communis using high-density (7×9 surface electromyogram (EMG recordings. The muscle activation map (based on the root mean square of the EMG was constructed when subjects performed individual four finger extensions at the metacarpophalangeal joint, at different effort levels and under different finger constraints (static and dynamic. Our results revealed distinct activation patterns during individual finger extensions, especially between index and middle finger extensions, although the activation between ring and little finger extensions showed strong covariance. The activation map was relatively consistent at different muscle contraction levels and for different finger constraint conditions. We also found that distinct activation patterns were more discernible in the proximal-distal direction than in the radial-ulnar direction. The global spatial activation map utilizing surface grid EMG of the extensor digitorum communis muscle provides information for localizing individual compartments of the extensor muscle during finger extensions. This is of potential value for identifying more selective control input for assistive devices. Such information can also provide a basis for understanding hand impairment in individuals with neural disorders.

  11. Is there any role of mast cell density and microvessel density in cervical squamous cell carcinoma? A histologic study with special reference to CD-34 immunomarker staining

    Directory of Open Access Journals (Sweden)

    Santosh Kumar Mondal

    2014-01-01

    Full Text Available Background: Mast cells are involved in induction of angiogenesis in the early-stages of tumor development and in modulating blood vessel growth in the later stages of tumor progression. Aims and Objectives: This study was carried out to evaluate the association between mast cell density (MCD and microvessel density (MVD in carcinoma in situ (CIS, microinvasive carcinoma (CA and invasive squamous cell CA of cervix. Materials and Methods: Six cases of CIS, four cases of microinvasive CA and 38 cases of invasive CA were studied over a period of 2 years from August, 2011 to June, 2013. Ten control samples were included in the study. Routine histologic examination was done. Toluidine blue stain was used for MCD determination. Immunohistochemical analysis with CD-34 was done for assessing MVD. Student′s t-test was used to calculate the statistical significance of MCD and MVD. Results: Both MCD and MVD increased from normal samples through CIS to invasive cervical CA. In the four cases of microinvasive CA, the MCD and MVD were more than that of the control samples, but less than that of the six cases of CIS. Conclusion: There is a correlation between mast cell accumulation and angiogenesis in CIS, microinvasive CA and invasive cervical squamous cell CA. MCD and MVD in invasive CA exceed those in CIS and microinvasive CA. It gives us an opportunity to postulate that therapeutic strategies against mast cell mediators and angiogenesis may be of benefit in patients of early-stage cervical CA.

  12. The local space density of Sb-Sdm galaxies as function of their scalesize, surface brightness and luminosity

    CERN Document Server

    De Jong, R S; Jong, Roelof S. de; Lacey, Cedric

    2000-01-01

    We investigate the dependence of the local space density of spiral galaxies on luminosity, scalesize and surface brightness. We derive bivariate space density distributions in these quantities from a sample of about 1000 Sb-Sdm spiral galaxies, corrected for selection effects in luminosity and surface brightness. The structural parameters of the galaxies were corrected for internal extinction using a description depending on galaxy surface brightness. We find that the bivariate space density distribution of spiral galaxies in the (luminosity, scalesize)-plane is well described by a Schechter luminosity function in the luminosity dimension and a log-normal scale size distribution at a given luminosity. This parameterization of the scalesize distribution was motivated by a simple model for the formation of disks within dark matter halos, with halos acquiring their angular momenta through tidal torques from neighboring objects, and the disk specific angular momentum being proportional to that of the parent halo....

  13. Effect of argon implantation on solid-state dewetting: control of size and surface density of silicon nanocrystals

    Science.gov (United States)

    Almadori, Y.; Borowik, Ł.; Chevalier, N.; Barbé, J.-C.

    2017-01-01

    Thermally induced solid-state dewetting of ultra-thin films on insulators is a process of prime interest, since it is capable of easily forming nanocrystals. If no particular treatment is performed to the film prior to the solid-state dewetting, it is already known that the size, the shape and the density of nanocrystals is governed by the initial film thickness. In this paper, we report a novel approach to control the size and the surface density of silicon nanocrystals based on an argon-implantation preliminary surface treatment. Using 7.5 nm thin layers of silicon, we show that increasing the implantation dose tends to form smaller silicon nanocrystals with diameter and height lower than 50 nm and 30 nm, respectively. Concomitantly, the surface density is increased by a factor greater than 20, going from 5 μm‑2 to values over 100 μm‑2.

  14. Mass balance of the Greenland ice sheet - a study of ICESat data, surface density and firn compaction modelling

    DEFF Research Database (Denmark)

    Sørensen, L. S.; Simonsen, Sebastian Bjerregaard; Nielsen, K.;

    2010-01-01

    in estimating the mass balance of the Greenland ice sheet. We find firn dynamics and surface densities to be important factors in deriving the mass loss from remote sensing altimetry. The volume change derived from ICESat data is corrected for firn compaction, vertical bedrock movement and an intercampaign...... elevation bias in the ICESat data. Subsequently, the corrected volume change is converted into mass change by surface density modelling. The firn compaction and density models are driven by a dynamically downscaled simulation of the HIRHAM5 regional climate model using ERA-Interim reanalysis lateral......ICESat has provided surface elevation measurements of the ice sheets since the launch in January 2003, resulting in a unique data set for monitoring the changes of the cryosphere. Here we present a novel method for determining the mass balance of the Greenland ice sheet derived from ICESat...

  15. Manipulation of the surface density of states of Ag(111) by means of resonators: Experiment and theory

    Science.gov (United States)

    Fernández, J.; Moro-Lagares, María; Serrate, D.; Aligia, A. A.

    2016-08-01

    We show that the density of surface Shockley states of Ag(111) probed by the differential conductance G (V )=d I /d V by a scanning-tunneling microscope (STM) can be enhanced significantly at certain energies and positions introducing simple arrays of Co or Ag atoms on the surface, in contrast to other noble-metal surfaces. Specifically we have studied resonators consisting of two parallel walls of five atoms deposited on the clean Ag(111) surface. A simple model in which the effect of the adatoms is taken into account by an attractive local potential and a small hybridization between surface and bulk at the position of the adatoms explains the main features of the observed G (V ) and allows us to extract the proportion of surface and bulk states sensed by the STM tip. These results might be relevant to engineer the surface spectral density of states, to study the effects of surface states on the Kondo effect, and to separate bulk and surface contributions in STM studies of topological surface states.

  16. Autonomous Bacterial Localization and Gene Expression Based on Nearby Cell Receptor Density

    Science.gov (United States)

    2013-01-22

    Upon detection of B1–5 mM AI-2, these cells express T7 polymerase that amplifies the native lsr operon response by overexpressing DsRed (see...2 for initiating gene expression (lsr operon ). (B) Indicated densities of PCI-15B or HEK293 cells were seeded to wells followed by mouse anti-EGFR

  17. Degradation of Solid Oxide Electrolysis Cells Operated at High Current Densities

    DEFF Research Database (Denmark)

    Tao, Youkun; Ebbesen, Sune Dalgaard; Mogensen, Mogens Bjerg

    2014-01-01

    In this work the durability of solid oxide cells for co-electrolysis of steam and carbon dioxide (45 % H2O + 45 % CO2 + 10 % H2) at high current densities was investigated. The tested cells are Ni-YSZ electrode supported, with a YSZ electrolyte and either a LSM-YSZ or LSCF-CGO oxygen electrode...

  18. Age-related decrease in rod bipolar cell density of the human retina: an immunohistochemical study

    Indian Academy of Sciences (India)

    P Aggarwal; T C Nag; S Wadhwa

    2007-03-01

    During normal ageing, the rods (and other neurones) undergo a significant decrease in density in the human retina from the fourth decade of life onward. Since the rods synapse with the rod bipolar cells in the outer plexiform layer, a decline in rod density (mainly due to death) may ultimately cause an associated decline of the neurones which, like the rod bipolar cells, are connected to them. The rod bipolar cells are selectively stained with antibodies to protein kinase C-. This study examined if rod bipolar cell density changes with ageing of the retina, utilizing donor human eyes (age: 6–91 years). The retinas were fixed and their temporal parts from the macula to the mid-periphery sectioned and processed for protein kinase C- immunohistochemistry. The density of the immunopositive rod bipolar cells was estimated in the mid-peripheral retina (eccentricity: 3–5 mm) along the horizontal temporal axis. The results show that while there is little change in the density of the rod bipolar cells from 6 to 35 years (2.2%), the decline during the period from 35 to 62 years is about 21% and between seventh and tenth decades, it is approximately 27%.

  19. The Distribution of Mass Surface Densities in a High-Mass Protocluster

    CERN Document Server

    Lim, Wanggi; Kainulainen, Jouni; Ma, Bo; Butler, Micheal J

    2016-01-01

    We study the probability distribution function (PDF) of mass surface densities, $\\Sigma$, of infrared dark cloud (IRDC) G028.37+00.07 and its surrounding giant molecular cloud. This PDF constrains the physical processes, such as turbulence, magnetic fields and self-gravity, that are expected to be controlling cloud structure and star formation activity. The chosen IRDC is of particular interest since it has almost 100,000 solar masses within a radius of 8 parsecs, making it one of the most massive, dense molecular structures known and is thus a potential site for the formation of a "super star cluster." We study $\\Sigma$ in two ways. First, we use a combination of NIR and MIR extinction maps that are able to probe the bulk of the cloud structure up to $\\Sigma\\sim1\\:{\\rm{g\\:cm}^{-2}}\\:$($A_V\\simeq200$~mag). Second, we study the FIR and sub-mm dust continuum emission from the cloud utilizing Herschel PACS and SPIRE images and paying careful attention to the effects of foreground and background contamination. We...

  20. Pyrolysis of low density polyethylene waste in subcritical water optimized by response surface methodology.

    Science.gov (United States)

    Wong, S L; Ngadi, N; Amin, N A S; Abdullah, T A T; Inuwa, I M

    2016-01-01

    Pyrolysis of low density polyethylene (LDPE) waste from local waste separation company in subcritical water was conducted to investigate the effect of reaction time, temperature, as well as the mass ratio of water to polymer on the liquid yield. The data obtained from the study were used to optimize the liquid yield using response surface methodology. The range of reaction temperature used was 162-338°C, while the reaction time ranged from 37 min to 143 min, and the ratio of water to polymer ranged from 1.9 to 7.1. It was found that pyrolysis of LDPE waste in subcritical water produced hydrogen, methane, carbon monoxide and carbon dioxide, while the liquid product contained alkanes and alkenes with 10-50 carbons atoms, as well as heptadecanone, dichloroacetic acid and heptadecyl ester. The optimized conditions were 152.3°C, reaction time of 1.2 min and ratio of water solution to polymer of 32.7, with the optimum liquid yield of 13.6 wt% and gases yield of 2.6 wt%.

  1. SURFACE AREA, VOLUME, MASS, AND DENSITY DISTRIBUTIONS FOR SIZED BOMASS PARTICLES

    Energy Technology Data Exchange (ETDEWEB)

    Ramanathan Sampath

    2004-05-01

    This semi-annual technical progress report describes work performed at Morehouse College under DOE Grant No. DE-FC26-04NT42130 during the period July 01, 2004 to December 31, 2004 which covers the first six months of the project. Presently work is in progress to characterize surface area, volume, mass, and density distributions for sized biomass particles. During this reporting period, supply requests were processed and supplies including biomass test particles (hardwood sawdust AI14546) in the size range of 100-200 microns were obtained from a cofiring pilot plant research facility owned by Southern Company, Birmingham, AL. Morehouse has completed setting up of the gravimetric technique measurement system in the heat transfer laboratory, department of physics and dual degree engineering, Morehouse College. Simultaneously, REM, our subcontractor, has completed setting up of the electrodynamic balance (EDB) measurement system to characterize shape and mass for individual biomass particles. Testing of the gravimetric system, and calibration of the cameras and imaging systems using known sizes of polystyrene particles are in progress.

  2. FABRICATION AND BIOCOMPATIBILITY OF CELL OUTER MEMBRANE MIMETIC SURFACES

    Institute of Scientific and Technical Information of China (English)

    Ming-ming Zong; Yong-kuan Gong

    2011-01-01

    The surface design used for improving biocompatibility is one of the most important issues for the fabrication of medical devices. For mimicking the ideal surface structure of cell outer membrane, a large number of polymers bearing phosphorylcholine (PC) groups have been employed to modify the surfaces of biomaterials and medical devices. It has been demonstrated that the biocompatibility of the modified materials whose surface is required to interact with a living organism has been obviously improved by introducing PC groups. In this review, the fabrication strategies of cell outer membrane mimetic surfaces and their resulted biocompatibilities were summarized.

  3. Mapping cell surface adhesion by rotation tracking and adhesion footprinting

    Science.gov (United States)

    Li, Isaac T. S.; Ha, Taekjip; Chemla, Yann R.

    2017-03-01

    Rolling adhesion, in which cells passively roll along surfaces under shear flow, is a critical process involved in inflammatory responses and cancer metastasis. Surface adhesion properties regulated by adhesion receptors and membrane tethers are critical in understanding cell rolling behavior. Locally, adhesion molecules are distributed at the tips of membrane tethers. However, how functional adhesion properties are globally distributed on the individual cell’s surface is unknown. Here, we developed a label-free technique to determine the spatial distribution of adhesive properties on rolling cell surfaces. Using dark-field imaging and particle tracking, we extract the rotational motion of individual rolling cells. The rotational information allows us to construct an adhesion map along the contact circumference of a single cell. To complement this approach, we also developed a fluorescent adhesion footprint assay to record the molecular adhesion events from cell rolling. Applying the combination of the two methods on human promyelocytic leukemia cells, our results surprisingly reveal that adhesion is non-uniformly distributed in patches on the cell surfaces. Our label-free adhesion mapping methods are applicable to the variety of cell types that undergo rolling adhesion and provide a quantitative picture of cell surface adhesion at the functional and molecular level.

  4. Removal of nitric oxide by the highly reactive anatase TiO2 (001) surface: a density functional theory study.

    Science.gov (United States)

    Zhao, Wenwen; Tian, Feng Hui; Wang, Xiaobin; Zhao, Linghuan; Wang, Yun; Fu, Aiping; Yuan, Shuping; Chu, Tianshu; Xia, Linhua; Yu, Jimmy C; Duan, Yunbo

    2014-09-15

    In this paper, density functional theory (DFT) calculation was employed to study the adsorption of nitric oxide (NO) on the highly reactive anatase TiO2 (001) surface. For comparison, the adsorption of NO on the (101) surface was also considered. Different from the physical adsorption on the (101) surface, NO molecules are found to chemisorb on the TiO2 (001) surface. The twofold coordinate oxygen atoms (O2c) on the anatase (001) surface are the active sites. Where NO is oxidized into a nitrite species (NO2(-)) trapping efficiently on the surface, with one of the surface Ti5c-O2c bonds adjacent to the adsorption site broken. Our results, therefore, supply a theoretical guidance to remove NO pollutants using highly reactive anatase TiO2 (001) facets.

  5. Data of continuous harvest of stem cells via partial detachment from thermoresponsive nanobrush surfaces

    Directory of Open Access Journals (Sweden)

    Chin-Chen Yeh

    2016-03-01

    Full Text Available This data article contains two figures and one table supporting the research article entitled: “Continuous harvest of stem cells via partial detachment from thermoresponsive nanobrush surface” [1]. The table shows coating conditions of three copolymers, poly(styrene-co-acrylic acid grafted with oligovitronectin, poly(styrene-co-N-isopropylacrylamide and poly(styrene-co-polyethylene glycol methacrylate to prepare thermoresponsive surface. XPS spectra show the nitrogen peak of the polystyrene surface coated with poly(styrene-co-acrylic acid grafted with oligovitronectin. The surface coating density analyzed from sorption of poly(styrene-co-acrylic acid grafted with oligovitronectin by UV–vis spectroscopy is also presented.

  6. Biomaterial surface proteomic signature determines interaction with epithelial cells.

    Science.gov (United States)

    Abdallah, Mohamed-Nur; Tran, Simon D; Abughanam, Ghada; Laurenti, Marco; Zuanazzi, David; Mezour, Mohamed A; Xiao, Yizhi; Cerruti, Marta; Siqueira, Walter L; Tamimi, Faleh

    2017-03-01

    Cells interact with biomaterials indirectly through extracellular matrix (ECM) proteins adsorbed onto their surface. Accordingly, it could be hypothesized that the surface proteomic signature of a biomaterial might determine its interaction with cells. Here, we present a surface proteomic approach to test this hypothesis in the specific case of biomaterial-epithelial cell interactions. In particular, we determined the surface proteomic signature of different biomaterials exposed to the ECM of epithelial cells (basal lamina). We revealed that the biomaterial surface chemistry determines the surface proteomic profile, and subsequently the interaction with epithelial cells. In addition, we found that biomaterials with surface chemistries closer to that of percutaneous tissues, such as aminated PMMA and aminated PDLLA, promoted higher selective adsorption of key basal lamina proteins (laminins, nidogen-1) and subsequently improved their interactions with epithelial cells. These findings suggest that mimicking the surface chemistry of natural percutaneous tissues can improve biomaterial-epithelial integration, and thus provide a rationale for the design of improved biomaterial surfaces for skin regeneration and percutaneous medical devices.

  7. GaAsP solar cells on GaP/Si with low threading dislocation density

    Science.gov (United States)

    Yaung, Kevin Nay; Vaisman, Michelle; Lang, Jordan; Lee, Minjoo Larry

    2016-07-01

    GaAsP on Si tandem cells represent a promising path towards achieving high efficiency while leveraging the Si solar knowledge base and low-cost infrastructure. However, dislocation densities exceeding 108 cm-2 in GaAsP cells on Si have historically hampered the efficiency of such approaches. Here, we report the achievement of low threading dislocation density values of 4.0-4.6 × 106 cm-2 in GaAsP solar cells on GaP/Si, comparable with more established metamorphic solar cells on GaAs. Our GaAsP solar cells on GaP/Si exhibit high open-circuit voltage and quantum efficiency, allowing them to significantly surpass the power conversion efficiency of previous devices. The results in this work show a realistic path towards dual-junction GaAsP on Si cells with efficiencies exceeding 30%.

  8. Role of the retinoblastoma protein in cell cycle arrest mediated by a novel cell surface proliferation inhibitor

    Science.gov (United States)

    Enebo, D. J.; Fattaey, H. K.; Moos, P. J.; Johnson, T. C.; Spooner, B. S. (Principal Investigator)

    1994-01-01

    A novel cell regulatory sialoglycopeptide (CeReS-18), purified from the cell surface of bovine cerebral cortex cells has been shown to be a potent and reversible inhibitor of proliferation of a wide array of fibroblasts as well as epithelial-like cells and nontransformed and transformed cells. To investigate the possible mechanisms by which CeReS-18 exerts its inhibitory action, the effect of the inhibitor on the posttranslational regulation of the retinoblastoma susceptibility gene product (RB), a tumor suppressor gene, has been examined. It is shown that CeReS-18 mediated cell cycle arrest of both human diploid fibroblasts (HSBP) and mouse fibroblasts (Swiss 3T3) results in the maintenance of the RB protein in the hypophosphorylated state, consistent with a late G1 arrest site. Although their normal nontransformed counterparts are sensitive to cell cycle arrest mediated by CeReS-18, cell lines lacking a functional RB protein, through either genetic mutation or DNA tumor virus oncoprotein interaction, are less sensitive. The refractory nature of these cells is shown to be independent of specific surface receptors for the inhibitor, and another tumor suppressor gene (p53) does not appear to be involved in the CeReS-18 inhibition of cell proliferation. The requirement for a functional RB protein product, in order for CeReS-18 to mediate cell cycle arrest, is discussed in light of regulatory events associated with density-dependent growth inhibition.

  9. Adsorption of H2O,OH,and O on CuCl(111) Surface: A Density Functional Theory Study

    Institute of Scientific and Technical Information of China (English)

    Xia Wang; Wen-kai Chen; Bao-zhen Sun; Chun-hai Lu

    2008-01-01

    The adsorption of H2O molecule and its dissociation products,O and OH,on CuCl(111) surface was studied with periodic slab model by PW91 approach of GGA within the framework of density functional theory.The results of geometry optimization indicate that the top site is stable energetically for H2O adsorbed over the CuCl(111) surface.The threefold hollow site is found to be the most stable adsorption site for OH and O,and the calculated adsorption energies are 309.5 and 416.5 k J/mol,respectively.Adsorption of H2O on oxygen-precovered CuCl(111) surface to form surface hydroxyl groups is predicted to be exothermic by 180.1 kJ/mol.The stretching vibrational frequencies,MuUiken population analysis and density of states analysis are employed to interpret the possible mechanism for the computed results.

  10. Cell multiplication following partial enzymatic removal of surface coat.

    Science.gov (United States)

    Wyroba, E

    1978-08-01

    Treatment of Paramecium aurelia with trypsin or pronase (1 mg per 10(5) cells, at 0 to 4 degrees C) partially removes the surface coat and modifies significantly multiplication of cells. The division rate after 24 hours of cultivation is diminished approximately twice in the case of pronase-treated cells and 1.5 for tyrpsin-digested ciliates as compared with the control. On the second day the division rate increases rapidly and number of cell divisions exceeds the values observed in the control. After 72 hours of cultivation the division rate in both untreated and enzyme-treated cells is almost the same. It is concluded that the observed inhibition of cell fission results from the enzymatic removal of the surface coat--the integrity of this surface coat seems to be necessary in the process of cell division. The influence of environmental factors on the rate of growth is presented.

  11. Surface-modified gold nanorods for specific cell targeting

    Science.gov (United States)

    Wang, Chan-Ung; Arai, Yoshie; Kim, Insun; Jang, Wonhee; Lee, Seonghyun; Hafner, Jason H.; Jeoung, Eunhee; Jung, Deokho; Kwon, Youngeun

    2012-05-01

    Gold nanoparticles (GNPs) have unique properties that make them highly attractive materials for developing functional reagents for various biomedical applications including photothermal therapy, targeted drug delivery, and molecular imaging. For in vivo applications, GNPs need to be prepared with very little or negligible cytotoxicitiy. Most GNPs are, however, prepared using growth-directing surfactants such as cetyl trimethylammonium bromide (CTAB), which are known to have considerable cytotoxicity. In this paper, we describe an approach to remove CTAB to a non-toxic concentration. We optimized the conditions for surface modification with methoxypolyethylene glycol thiol (mPEG), which replaced CTAB and formed a protective layer on the surface of gold nanorods (GNRs). The cytotoxicities of pristine and surface-modified GNRs were measured in primary human umbilical vein endothelial cells and human cell lines derived from hepatic carcinoma cells, embryonic kidney cells, and thyroid papillary carcinoma cells. Cytotoxicity assays revealed that treating cells with GNRs did not significantly affect cell viability except for thyroid papillary carcinoma cells. Thyroid cancer cells were more susceptible to residual CTAB, so CTAB had to be further removed by dialysis in order to use GNRs for thyroid cell targeting. PEGylated GNRs are further modified to present monoclonal antibodies that recognize a specific surface marker, Na-I symporter, for thyroid cells. Antibody-conjugated GNRs specifically targeted human thyroid cells in vitro.

  12. High energy efficiency and high power density proton exchange membrane fuel cells: Electrode kinetics and mass transport

    Science.gov (United States)

    Srinivasan, Supramaniam; Velev, Omourtag A.; Parthasathy, Arvind; Manko, David J.; Appleby, A. John

    1991-01-01

    The development of proton exchange membrane (PEM) fuel cell power plants with high energy efficiencies and high power densities is gaining momentum because of the vital need of such high levels of performance for extraterrestrial (space, underwater) and terrestrial (power source for electric vehicles) applications. Since 1987, considerable progress has been made in achieving energy efficiencies of about 60 percent at a current density of 200 mA/sq cm and high power densities (greater than 1 W/sq cm) in PEM fuel cells with high (4 mg/sq cm) or low (0.4 mg/sq cm) platinum loadings in electrodes. The following areas are discussed: (1) methods to obtain these high levels of performance with low Pt loading electrodes - by proton conductor impregnation into electrodes, localization of Pt near front surface; (2) a novel microelectrode technique which yields electrode kinetic parameters for oxygen reduction and mass transport parameters; (3) demonstration of lack of water transport from anode to cathode; (4) modeling analysis of PEM fuel cell for comparison with experimental results and predicting further improvements in performance; and (5) recommendations of needed research and development for achieving the above goals.

  13. Effects of reduced terrestrial LiDAR point density on high-resolution grain crop surface models in precision agriculture.

    Science.gov (United States)

    Hämmerle, Martin; Höfle, Bernhard

    2014-12-16

    3D geodata play an increasingly important role in precision agriculture, e.g., for modeling in-field variations of grain crop features such as height or biomass. A common data capturing method is LiDAR, which often requires expensive equipment and produces large datasets. This study contributes to the improvement of 3D geodata capturing efficiency by assessing the effect of reduced scanning resolution on crop surface models (CSMs). The analysis is based on high-end LiDAR point clouds of grain crop fields of different varieties (rye and wheat) and nitrogen fertilization stages (100%, 50%, 10%). Lower scanning resolutions are simulated by keeping every n-th laser beam with increasing step widths n. For each iteration step, high-resolution CSMs (0.01 m2 cells) are derived and assessed regarding their coverage relative to a seamless CSM derived from the original point cloud, standard deviation of elevation and mean elevation. Reducing the resolution to, e.g., 25% still leads to a coverage of >90% and a mean CSM elevation of >96% of measured crop height. CSM types (maximum elevation or 90th-percentile elevation) react differently to reduced scanning resolutions in different crops (variety, density). The results can help to assess the trade-off between CSM quality and minimum requirements regarding equipment and capturing set-up.

  14. Modelling and simulation of double chamber microbial fuel cell. Cell voltage, power density and temperature variation with process parameters

    Energy Technology Data Exchange (ETDEWEB)

    Shankar, Ravi; Mondal, Prasenjit; Chand, Shri [Indian Institute of Technology Roorkee, Uttaranchal (India). Dept. of Chemical Engineering

    2013-11-01

    In the present paper steady state models of a double chamber glucose glutamic acid microbial fuel cell (GGA-MFC) under continuous operation have been developed and solved using Matlab 2007 software. The experimental data reported in a recent literature has been used for the validation of the models. The present models give prediction on the cell voltage and cell power density with 19-44% errors, which is less (up to 20%) than the errors on the prediction of cell voltage made in some recent literature for the same MFC where the effects of the difference in pH and ionic conductivity between anodic and cathodic solutions on cell voltage were not incorporated in model equations. It also describes the changes in anodic and cathodic chamber temperature due to the increase in substrate concentration and cell current density. Temperature profile across the membrane thickness has also been studied. (orig.)

  15. Biomaterial arrays with defined adhesion ligand densities and matrix stiffness identify distinct phenotypes for tumorigenic and nontumorigenic human mesenchymal cell types.

    Science.gov (United States)

    Hansen, Tyler D; Koepsel, Justin T; Le, Ngoc Nhi; Nguyen, Eric H; Zorn, Stefan; Parlato, Matthew; Loveland, Samuel G; Schwartz, Michael P; Murphy, William L

    2014-05-01

    Here, we aimed to investigate migration of a model tumor cell line (HT-1080 fibrosarcoma cells, HT-1080s) using synthetic biomaterials to systematically vary peptide ligand density and substrate stiffness. A range of substrate elastic moduli were investigated by using poly(ethylene glycol) (PEG) hydrogel arrays (0.34 - 17 kPa) and self-assembled monolayer (SAM) arrays (~0.1-1 GPa), while cell adhesion was tuned by varying the presentation of Arg-Gly-Asp (RGD)-containing peptides. HT-1080 motility was insensitive to cell adhesion ligand density on RGD-SAMs, as they migrated with similar speed and directionality for a wide range of RGD densities (0.2-5% mol fraction RGD). Similarly, HT-1080 migration speed was weakly dependent on adhesion on 0.34 kPa PEG surfaces. On 13 kPa surfaces, a sharp initial increase in cell speed was observed at low RGD concentration, with no further changes observed as RGD concentration was increased further. An increase in cell speed ~ two-fold for the 13 kPa relative to the 0.34 kPa PEG surface suggested an important role for substrate stiffness in mediating motility, which was confirmed for HT-1080s migrating on variable modulus PEG hydrogels with constant RGD concentration. Notably, despite ~ two-fold changes in cell speed over a wide range of moduli, HT-1080s adopted rounded morphologies on all surfaces investigated, which contrasted with well spread primary human mesenchymal stem cells (hMSCs). Taken together, our results demonstrate that HT-1080s are morphologically distinct from primary mesenchymal cells (hMSCs) and migrate with minimal dependence on cell adhesion for surfaces within a wide range of moduli, whereas motility is strongly influenced by matrix mechanical properties.

  16. Interaction of Epithelial Cells with Surfaces and Surfaces Decorated by Molecules

    CERN Document Server

    Martini, Daniele; Beil, Michael; Paust, T; Huang, C; Moosmann, M; Jin, J; Heiler, T; Gröger, R; Schimmel, Thomas; Walheim, Stefan

    2013-01-01

    A detailed understanding of the interface between living cells and substrate materials is of rising importance in many fields of medicine, biology and biotechnology. Cells at interfaces often form epithelia. The physical barrier that they form is one of their main functions. It is governed by the properties of the networks forming the cytoskeleton systems and by cell-to-cell contacts. Different substrates with varying surface properties modify the migration velocity of the cells. On the one hand one can change the materials composition. Organic and inorganic materials induce differing migration velocities in the same cell system. Within the same class of materials, a change of the surface stiffness or of the surface energy modifies the migration velocity, too. For our cell adhesion studies a variety of different, homogeneous substrates were used (polymers, bio-polymers, metals, oxides). In addition, an effective lithographic method, Polymer Blend Lithography (PBL), is reported, to produce patterned Self-Assem...

  17. High resolution imaging of surface patterns of single bacterial cells

    Energy Technology Data Exchange (ETDEWEB)

    Greif, Dominik; Wesner, Daniel [Experimental Biophysics and Applied Nanoscience, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld (Germany); Regtmeier, Jan, E-mail: jan.regtmeier@physik.uni-bielefeld.de [Experimental Biophysics and Applied Nanoscience, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld (Germany); Anselmetti, Dario [Experimental Biophysics and Applied Nanoscience, Bielefeld University, Universitaetsstrasse 25, 33615 Bielefeld (Germany)

    2010-09-15

    We systematically studied the origin of surface patterns observed on single Sinorhizobium meliloti bacterial cells by comparing the complementary techniques atomic force microscopy (AFM) and scanning electron microscopy (SEM). Conditions ranged from living bacteria in liquid to fixed bacteria in high vacuum. Stepwise, we applied different sample modifications (fixation, drying, metal coating, etc.) and characterized the observed surface patterns. A detailed analysis revealed that the surface structure with wrinkled protrusions in SEM images were not generated de novo but most likely evolved from similar and naturally present structures on the surface of living bacteria. The influence of osmotic stress to the surface structure of living cells was evaluated and also the contribution of exopolysaccharide and lipopolysaccharide (LPS) by imaging two mutant strains of the bacterium under native conditions. AFM images of living bacteria in culture medium exhibited surface structures of the size of single proteins emphasizing the usefulness of AFM for high resolution cell imaging.

  18. Yeast surface display of dehydrogenases in microbial fuel-cells.

    Science.gov (United States)

    Gal, Idan; Schlesinger, Orr; Amir, Liron; Alfonta, Lital

    2016-12-01

    Two dehydrogenases, cellobiose dehydrogenase from Corynascus thermophilus and pyranose dehydrogenase from Agaricus meleagris, were displayed for the first time on the surface of Saccharomyces cerevisiae using the yeast surface display system. Surface displayed dehydrogenases were used in a microbial fuel cell and generated high power outputs. Surface displayed cellobiose dehydrogenase has demonstrated a midpoint potential of -28mV (vs. Ag/AgCl) at pH=6.5 and was used in a mediator-less anode compartment of a microbial fuel cell producing a power output of 3.3μWcm(-2) using lactose as fuel. Surface-displayed pyranose dehydrogenase was used in a microbial fuel cell and generated high power outputs using different substrates, the highest power output that was achieved was 3.9μWcm(-2) using d-xylose. These results demonstrate that surface displayed cellobiose dehydrogenase and pyranose dehydrogenase may successfully be used in microbial bioelectrochemical systems.

  19. Insertion torques influenced by bone density and surface roughness of HA–TiO{sub 2} coatings

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, T.; Chen, Y.; Nie, X., E-mail: xnie@uwindsor.ca

    2013-12-31

    Bio-ceramic TiO{sub 2} coatings containing calcium (Ca) and phosphorous (P) were deposited onto Ti–6Al–4V alloy screws using plasma electrolytic oxidation (PEO) processes in an alkaline electrolyte with hydroxyapatite (HA) suspension. Coating on each screw had different surface roughness and morphology. Insertion torque (IT) of the coated screws in low (10 pcf, pounds per cubic feet), medium–high (20 pcf), and high (40 pcf) density of artificial bones was measured in comparison with that of the uncoated and sandblasted screws having similar surface roughness. Higher insertion torques and final seating torques were obtained in the coated screws which may result in less micro-movement during the primary implantation stage and thus lower the risk of implant failure. Scanning electron microscopy (SEM) analysis indicated that all coatings still adhesively remained on the screw surfaces after inserted into the bones with different densities. The relationship between coefficient of friction and surface roughness was also addressed to better understand the results of insertion torque. It was found that a lower density bone (similar to aged bone) would need a surface-rougher coated screw to achieve a high torque while a high density bone can have a wide range of selections for surface roughness of the screw. - Highlights: • The insertion torque of PEO-coated screws is higher than machined and sandblasting implants. • Lower density bone needs a rougher coated implant to increase the insertion torque. • The composite HA–TiO{sub 2} coating could benefit dental implants in both primary and secondary stability stages.

  20. High-density polymer microarrays: identifying synthetic polymers that control human embryonic stem cell growth.

    Science.gov (United States)

    Hansen, Anne; Mjoseng, Heidi K; Zhang, Rong; Kalloudis, Michail; Koutsos, Vasileios; de Sousa, Paul A; Bradley, Mark

    2014-06-01

    The fabrication of high-density polymer microarray is described, allowing the simultaneous and efficient evaluation of more than 7000 different polymers in a single-cellular-based screen. These high-density polymer arrays are applied in the search for synthetic substrates for hESCs culture. Up-scaling of the identified hit polymers enables long-term cellular cultivation and promoted successful stem-cell maintenance.

  1. Fluid dynamics and noise in bacterial cell-cell and cell-surface scattering

    CERN Document Server

    Drescher, Knut; Cisneros, Luis H; Ganguly, Sujoy; Goldstein, Raymond E; 10.1073/pnas.1019079108

    2011-01-01

    Bacterial processes ranging from gene expression to motility and biofilm formation are constantly challenged by internal and external noise. While the importance of stochastic fluctuations has been appreciated for chemotaxis, it is currently believed that deterministic long-range fluid dynamical effects govern cell-cell and cell-surface scattering - the elementary events that lead to swarming and collective swimming in active suspensions and to the formation of biofilms. Here, we report the first direct measurements of the bacterial flow field generated by individual swimming Escherichia coli both far from and near to a solid surface. These experiments allowed us to examine the relative importance of fluid dynamics and rotational diffusion for bacteria. For cell-cell interactions it is shown that thermal and intrinsic stochasticity drown the effects of long-range fluid dynamics, implying that physical interactions between bacteria are determined by steric collisions and near-field lubrication forces. This dom...

  2. Spatial variability in cortex-muscle coherence investigated with magnetoencephalography and high-density surface electromyography.

    Science.gov (United States)

    Piitulainen, Harri; Botter, Alberto; Bourguignon, Mathieu; Jousmäki, Veikko; Hari, Riitta

    2015-11-01

    Cortex-muscle coherence (CMC) reflects coupling between magnetoencephalography (MEG) and surface electromyography (sEMG), being strongest during isometric contraction but absent, for unknown reasons, in some individuals. We used a novel nonmagnetic high-density sEMG (HD-sEMG) electrode grid (36 mm × 12 mm; 60 electrodes separated by 3 mm) to study effects of sEMG recording site, electrode derivation, and rectification on the strength of CMC. Monopolar sEMG from right thenar and 306-channel whole-scalp MEG were recorded from 14 subjects during 4-min isometric thumb abduction. CMC was computed for 60 monopolar, 55 bipolar, and 32 Laplacian HD-sEMG derivations, and two derivations were computed to mimic "macroscopic" monopolar and bipolar sEMG (electrode diameter 9 mm; interelectrode distance 21 mm). With unrectified sEMG, 12 subjects showed statistically significant CMC in 91-95% of the HD-sEMG channels, with maximum coherence at ∼25 Hz. CMC was about a fifth stronger for monopolar than bipolar and Laplacian derivations. Monopolar derivations resulted in most uniform CMC distributions across the thenar and in tightest cortical source clusters in the left rolandic hand area. CMC was 19-27% stronger for HD-sEMG than for "macroscopic" monopolar or bipolar derivations. EMG rectification reduced the CMC peak by a quarter, resulted in a more uniformly distributed CMC across the thenar, and provided more tightly clustered cortical sources than unrectifed sEMGs. Moreover, it revealed CMC at ∼12 Hz. We conclude that HD-sEMG, especially with monopolar derivation, can facilitate detection of CMC and that individual muscle anatomy cannot explain the high interindividual CMC variability.

  3. Density functional study of adsorptions of CO2, NO2 and SO2 molecules on Zn(0002) surfaces

    Science.gov (United States)

    Nugraha; Saputro, A. G.; Agusta, M. K.; Yuliarto, B.; Dipojono, H. K.; Maezono, R.

    2016-08-01

    We report on a theoretical study of adsorptions of CO2, NO2 and SO2 molecules on ZnO(0002) surfaces using density functional theory-based (DFT-based) calculations. These adsorptions are done on perfect and defective ZnO(0002) surfaces. We find that all of these molecules are chemically adsorbed on the perfect ZnO(0002) surface. In the presence of Zn vacancy, we find that the surface is only active toward SO2 molecule. On the hydroxylated ZnO(0002) surfaces, CO2 and SO2 molecules can react with the preadsorbed OH molecule to form various adsorbates such as: carboxyl (COOH), bicarbonate (CO3H), sulfonyl hydroxide (SO3H), SO3 and water. However, NO2 molecule cannot react with the pre-adsorbed OH molecule and only physically adsorbed on the surface.

  4. Biomechanics of cell rolling: shear flow, cell-surface adhesion, and cell deformability.

    Science.gov (United States)

    Dong, C; Lei, X X

    2000-01-01

    The mechanics of leukocyte (white blood cell; WBC) deformation and adhesion to endothelial cells (EC) has been investigated using a novel in vitro side-view flow assay. HL-60 cell rolling adhesion to surface-immobilized P-selectin was used to model the WBC-EC adhesion process. Changes in flow shear stress, cell deformability, or substrate ligand strength resulted in significant changes in the characteristic adhesion binding time, cell-surface contact and cell rolling velocity. A 2-D model indicated that cell-substrate contact area under a high wall shear stress (20 dyn/cm2) could be nearly twice of that under a low stress (0.5 dyn/cm2) due to shear flow-induced cell deformation. An increase in contact area resulted in more energy dissipation to both adhesion bonds and viscous cytoplasm, whereas the fluid energy that inputs to a cell decreased due to a flattened cell shape. The model also predicted a plateau of WBC rolling velocity as flow shear stresses further increased. Both experimental and computational studies have described how WBC deformation influences the WBC-EC adhesion process in shear flow.

  5. HIGH DENSITY CULTIVATION OF GENETICALLY-ENGINEERED CHO CELL LINES WITH MICROCARRIER CULTURE SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    肖成祖; 黄子才; 刘凤云; 郭志霞; 高丽华

    1994-01-01

    Genetically-enginecred CHO cell lines,rβ-13and CLF-8B2,were cultivated with the MC-1 microcarrier cul-ture system.The cell density could be enhanced by increasing the concentration of microcarrier.At a microcarrier concentration of 10 mg/ml.the cell density could reach 4 to 5×106 cells/ml.It was shown that these cell itnes would spontaneously release from the microcarrier to attach to and proliferate on fresh microcatriera.We were thus able to scale up cultivation using a simple methcd,i.e.by adding fresh mlcrocarriers and medium directiy in-to the culture system to about 2,4 or 8 times the original volume.Using a 2 L bioreactor for several weeks at medium perfusion rates of 0.5 to 3working volumes.Prourokinase was stably secreted.

  6. Very high cell density perfusion of CHO cells anchored in a non-woven matrix-based bioreactor.

    Science.gov (United States)

    Zhang, Ye; Stobbe, Per; Silvander, Christian Orrego; Chotteau, Véronique

    2015-11-10

    Recombinant Chinese Hamster Ovary (CHO) cells producing IgG monoclonal antibody were cultivated in a novel perfusion culture system CellTank, integrating the bioreactor and the cell retention function. In this system, the cells were harbored in a non-woven polyester matrix perfused by the culture medium and immersed in a reservoir. Although adapted to suspension, the CHO cells stayed entrapped in the matrix. The cell-free medium was efficiently circulated from the reservoir into- and through the matrix by a centrifugal pump placed at the bottom of the bioreactor resulting in highly homogenous concentrations of the nutrients and metabolites in the whole system as confirmed by measurements from different sampling locations. A real-time biomass sensor using the dielectric properties of living cells was used to measure the cell density. The performances of the CellTank were studied in three perfusion runs. A very high cell density measured as 200 pF/cm (where 1 pF/cm is equivalent to 1 × 10(6)viable cells/mL) was achieved at a perfusion rate of 10 reactor volumes per day (RV/day) in the first run. In the second run, the effect of cell growth arrest by hypothermia at temperatures lowered gradually from 37 °C to 29 °C was studied during 13 days at cell densities above 100 pF/cm. Finally a production run was performed at high cell densities, where a temperature shift to 31 °C was applied at cell density 100 pF/cm during a production period of 14 days in minimized feeding conditions. The IgG concentrations were comparable in the matrix and in the harvest line in all the runs, indicating no retention of the product of interest. The cell specific productivity was comparable or higher than in Erlenmeyer flask batch culture. During the production run, the final harvested IgG production was 35 times higher in the CellTank compared to a repeated batch culture in the same vessel volume during the same time period.

  7. Microstructure characterisation of solid oxide electrolysis cells operated at high current density

    DEFF Research Database (Denmark)

    Bowen, Jacob R.; Bentzen, Janet Jonna; Chen, Ming;

    High temperature solid oxide cells can be operated either as fuel cells or electrolysis cells for efficient power generation or production of hydrogen from steam or synthesis gas (H2 + CO) from steam and CO2 respectively. When operated under harsh conditions, they often exhibit microstructural......, microstructure evolution of the Ni-yttria stabilized zirconia (YSZ) is followed as a function of galvanostatic steam electrolysis testing at current densities between -0.5 and -1.0 A cm-2 for periods of up to 750 hours at 800 °C. The volume fraction and size of the percolating Ni particles was statistically...... quantified using the mean linear intercept method as a function of current density and correlated to increases in serial resistance. The above structural changes are then compared in terms of electrode degradation observed during the co-electrolysis of steam and CO2 at current densities up to -1.5 A cm-2...

  8. Catalyst-Free Conjugation and In Situ Quantification of Nanoparticle Ligand Surface Density Using Fluorogenic Cu-Free Click Chemistry

    DEFF Research Database (Denmark)

    Jølck, Rasmus Irming; Sun, Honghao; Berg, Rolf Henrik

    2011-01-01

    A highly efficient method for functionalizing nanoparticles and directly quantifying conjugation efficiency and ligand surface density has been developed. Attachment of 3-azido-modifed RGD-peptides to PEGylated liposomes was achieved by using Cu-free click conditions. Upon coupling a fluorophore ...

  9. Mixed time-dependent density-functional theory/classical trajectory surface hopping study of oxirane photochemistry

    NARCIS (Netherlands)

    Tapavicza, Enrico; Tavernelli, Ivano; Rothlisberger, Ursula; Filippi, Claudia; Casida, Mark E.

    2008-01-01

    We present a mixed time-dependent density-functional theory (TDDFT)/classical trajectory surface hopping (SH) study of the photochemical ring opening in oxirane. Previous preparatory work limited to the symmetric CC ring-opening pathways of oxirane concluded that the Tamm-Dancoff approximation (TDA)

  10. Hydrodeoxygenation of Phenol to Benzene and Cyclohexane on Rh(111) and Rh(211) Surfaces: Insights from Density Functional Theory

    DEFF Research Database (Denmark)

    Garcia-Pintos, Delfina; Voss, Johannes; Jensen, Anker Degn

    2016-01-01

    Herein we describe the C-O cleavage of phenol and cyclohexanol over Rh (111) and Rh (211) surfaces using density functional theory calculations. Our analysis is complemented by a microkinetic model of the reactions, which indicates that the C-O bond cleavage of cyclohexanol is easier than that of...

  11. Cell damage from radiation-induced bystander effects for different cell densities simulated by a mathematical model via cellular automata

    Energy Technology Data Exchange (ETDEWEB)

    Meireles, Sincler P. de; Santos, Adriano M.; Grynberg, Suely Epsztein, E-mail: spm@cdtn.b, E-mail: amsantos@cdtn.b, E-mail: seg@cdtn.b [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Nunes, Maria Eugenia S., E-mail: mariaeugenia@iceb.ufop.b [Universidade Federal de Ouro Preto (UFOP), MG (Brazil)

    2011-07-01

    During recent years, there has been a shift from an approach focused entirely on DNA as the main target of ionizing radiation to a vision that considers complex signaling pathways in cells and among cells within tissues. Several newly recognized responses were classified as the so-called non-target responses in which the biological effects are not directly related to the amount of energy deposited in the DNA of cells that were traversed by radiation. In 1992 the bystander effect was described referring to a series of responses such as death, chromosomal instability or other abnormalities that occur in non-irradiated cells that came into contact with irradiated cells or medium from irradiated cells. In this work, we have developed a mathematical model via cellular automata, to quantify cell death induced by the bystander effect. The model is based on experiments with irradiated cells conditioned medium which suggests that irradiated cells secrete molecules in the medium that are capable of damaging other cells. The computational model consists of two-dimensional cellular automata which is able to simulate the transmission of bystander signals via extrinsic route and via Gap junctions. The model has been validated by experimental results in the literature. The time evolution of the effect and the dose-response curves were obtained in good accordance to them. Simulations were conducted for different values of bystander and irradiated cell densities with constant dose. From this work, we have obtained a relationship between cell density and effect. (author)

  12. Surface Plasmon Resonance for Cell-Based Clinical Diagnosis

    Directory of Open Access Journals (Sweden)

    Yuhki Yanase

    2014-03-01

    Full Text Available Non-invasive real-time observations and the evaluation of living cell conditions and functions are increasingly demanded in life sciences. Surface plasmon resonance (SPR sensors detect the refractive index (RI changes on the surface of sensor chips in label-free and on a real-time basis. Using SPR sensors, we and other groups have developed techniques to evaluate living cells’ reactions in response to stimuli without any labeling in a real-time manner. The SPR imaging (SPRI system for living cells may visualize single cell reactions and has the potential to expand application of SPR cell sensing for clinical diagnosis, such as multi-array cell diagnostic systems and detection of malignant cells among normal cells in combination with rapid cell isolation techniques.

  13. Stress signaling from human mammary epithelial cells contributes to phenotypes of mammographic density.

    Science.gov (United States)

    DeFilippis, Rosa Anna; Fordyce, Colleen; Patten, Kelley; Chang, Hang; Zhao, Jianxin; Fontenay, Gerald V; Kerlikowske, Karla; Parvin, Bahram; Tlsty, Thea D

    2014-09-15

    Telomere malfunction and other types of DNA damage induce an activin A-dependent stress response in mortal nontumorigenic human mammary epithelial cells that subsequently induces desmoplastic-like phenotypes in neighboring fibroblasts. Some characteristics of this fibroblast/stromal response, such as reduced adipocytes and increased extracellular matrix content, are observed not only in tumor tissues but also in disease-free breast tissues at high risk for developing cancer, especially high mammographic density tissues. We found that these phenotypes are induced by repression of the fatty acid translocase CD36, which is seen in desmoplastic and disease-free high mammographic density tissues. In this study, we show that epithelial cells from high mammographic density tissues have more DNA damage signaling, shorter telomeres, increased activin A secretion and an altered DNA damage response compared with epithelial cells from low mammographic density tissues. Strikingly, both telomere malfunction and activin A expression in epithelial cells can repress CD36 expression in adjacent fibroblasts. These results provide new insights into how high mammographic density arises and why it is associated with breast cancer risk, with implications for the definition of novel invention targets (e.g., activin A and CD36) to prevent breast cancer.

  14. Comparative density functional theory and density functional tight binding study of arginine and arginine-rich cell penetrating peptide TAT adsorption on anatase TiO2.

    Science.gov (United States)

    Li, Wenxuan; Kotsis, Konstantinos; Manzhos, Sergei

    2016-07-20

    We present a comparative density functional theory (DFT) and density functional tight binding (DFTB) study of geometries and electronic structures of arginine (Arg), arginine adsorbed on the anatase (101) surface of titania in several adsorption configurations, and of an arginine-rich cell penetrating peptide TAT and its adsorption on the surface of TiO2. Two DFTB parameterizations are considered, tiorg-0-1/mio-1-1 and matsci-0-3. While there is good agreement in the structures and relative energies of Arg and peptide conformers between DFT and DFTB, both adsorption geometries and energies are noticeably different for Arg adsorbed on TiO2. The tiorg-0-1/mio-1-1 parameterization performs better than matsci-0-3. We relate this difference to the difference in electronic structures resulting from the two methods (DFT and DFTB) and specifically to the band alignment between the molecule and the oxide. We show that the band alignment of TAT and TiO2 modeled with DFTB is qualitatively correct but that with DFT using the PBE functional is not. This is specific to the modeling of large molecules where the HOMO is close to the conduction band of the oxide. We therefore report a case where the approximate DFT-based method - DFTB (with which the correct band structure can be effectively obtained) - performs better than the DFT itself with a functional approximation feasible for the modeling of large bio-inorganic interfaces, i.e. GGA (as opposed to hybrid functionals which are impractical at such a scale). Our results highlight the utility of the DFTB method for the modeling of bioinorganic interfaces not only from the CPU cost perspective but also from the accuracy point of view.

  15. Investigation of two-dimensional electron systems at low density on hydrogen-terminated silicon (111) surface

    Science.gov (United States)

    Hu, Binhui; Kott, Tomasz M.; Kane, B. E.

    2013-03-01

    Two-dimensional electron systems (2DESs) on hydrogen-terminated Si(111) surfaces show very high quality. The peak electron mobility of 325,000 cm2/Vs can be reached at T =90 mK and 2D electron density n2 d = 4 . 15 ×1011 cm-2, and the device shows the fractional quantum hall effect[1]. 2DESs on H-Si(111) at lower densities may exhibit new physics, because both valley degeneracy and effective mass lead to a large Wigner-Seitz radius rs at accessible densities. In these devices, phosphorus ion implantation is used to defined the contacts to the 2DESs[2]. The contacts themselves work at low temperature. However, at lower 2D electron density (ion implantation annealing parameters are adjusted to mitigate the issue. Possible measurement technique is also explored to overcome the problem.

  16. Density of states measurements in a p-i-n solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Crandall, R.S.; Wang, Q. [National Renewable Energy Lab., Golden, CO (United States)

    1996-05-01

    The authors describe results of density of states (DOS) profiling in p-i-n solar-cell devices using drive-level capacitance (DLC) techniques. Near the p-i interface the defect density is high, decreasing rapidly into the interior, reaching low values in the central region of the cell, and rising rapidly again at the n-i interface. They show that the states in the central region are neutral dangling-bond defects, whereas those near the interfaces with the doped layers are charged dangling bonds.

  17. LTE Micro-cell Deployment for High-Density Railway Areas

    DEFF Research Database (Denmark)

    Sniady, Aleksander; Kassab, Mohamed; Soler, José

    2014-01-01

    Long Term Evolution (LTE) is a serious candidate for the future releases of the European Rail Traffic Management System (ERTMS). LTE offers more capacity and supports new communication-based applications and services for railways. Nevertheless, even with this technology, the classical macro......-cell radio deployments reach overload, especially in high-density areas, such as major train stations. In this paper, an LTE micro-cell deployment is investigated in high-density railway areas. Copenhagen Main Station is considered as a realistic deployment study case, with a set of relevant railway...

  18. Nanoscale crystallinity modulates cell proliferation on plasma sprayed surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Alan M. [School of Applied Sciences, University of Huddersfield, Huddersfield HD1 3DH (United Kingdom); Paxton, Jennifer Z.; Hung, Yi-Pei; Hadley, Martin J.; Bowen, James; Williams, Richard L. [School of Chemical Engineering, University of Birmingham, Edgbaston, B15 2TT (United Kingdom); Grover, Liam M., E-mail: l.m.grover@bham.ac.uk [School of Chemical Engineering, University of Birmingham, Edgbaston, B15 2TT (United Kingdom)

    2015-03-01

    Calcium phosphate coatings have been applied to the surface of metallic prostheses to mediate hard and soft tissue attachment for more than 40 years. Most coatings are formed of high purity hydroxyapatite, and coating methods are often designed to produce highly crystalline surfaces. It is likely however, that coatings of lower crystallinity can facilitate more rapid tissue attachment since the surface will exhibit a higher specific surface area and will be considerably more reactive than a comparable highly crystalline surface. Here we test this hypothesis by growing a population of MC3T3 osteoblast-like cells on the surface of two types of hip prosthesis with similar composition, but with differing crystallinity. The surfaces with lower crystallinity facilitated more rapid cell attachment and increased proliferation rate, despite having a less heterogeneous surface topography. This work highlights that the influence of the crystallinity of HA at the nano-scale is dominant over macro-scale topography for cell adhesion and growth. Furthermore, crystallinity could be easily adjusted by without compromising coating purity. These findings could facilitate designing novel coated calcium phosphate surfaces that more rapidly bond tissue following implantation. - Highlights: • Crystallinity of HA at the nano-scale was dominant over macro-scale topography. • Lower crystallinity caused rapid cell attachment and proliferation rate. • Crystallinity could be easily adjusted by without compromising coating purity.

  19. Cell-Autonomous Regulation of Dendritic Spine Density by PirB

    Science.gov (United States)

    2016-01-01

    Synapse density on cortical pyramidal neurons is modulated by experience. This process is highest during developmental critical periods, when mechanisms of synaptic plasticity are fully engaged. In mouse visual cortex, the critical period for ocular dominance (OD) plasticity coincides with the developmental pruning of synapses. At this time, mice lacking paired Ig-like receptor B (PirB) have excess numbers of dendritic spines on L5 neurons; these spines persist and are thought to underlie the juvenile-like OD plasticity observed in adulthood. Here we examine whether PirB is required specifically in excitatory neurons to exert its effect on dendritic spine and synapse density during the critical period. In mice with a conditional allele of PirB (PirBfl/fl), PirB was deleted only from L2/3 cortical pyramidal neurons in vivo by timed in utero electroporation of Cre recombinase. Sparse mosaic expression of Cre produced neurons lacking PirB in a sea of wild-type neurons and glia. These neurons had significantly elevated dendritic spine density, as well as increased frequency of miniature EPSCs, suggesting that they receive a greater number of synaptic inputs relative to Cre– neighbors. The effect of cell-specific PirB deletion on dendritic spine density was not accompanied by changes in dendritic branching complexity or axonal bouton density. Together, results imply a neuron-specific, cell-autonomous action of PirB on synaptic density in L2/3 pyramidal cells of visual cortex. Moreover, they are consistent with the idea that PirB functions normally to corepress spine density and synaptic plasticity, thereby maintaining headroom for cells to encode ongoing experience-dependent structural change throughout life.

  20. Experimental characterization of active acoustic metamaterial cell with controllable dynamic density

    Science.gov (United States)

    Akl, Wael; Baz, Amr

    2012-10-01

    Controlling wave propagation pattern within acoustic fluid domains has been the motivation for the acoustic metamaterials developments to target applications ranging from acoustic cloaking to passive noise control techniques. Currently, various numerical and analytical approaches exist to predict the fluid domain material properties necessary for specific propagation pattern. Physical attempts to realize such material properties have revealed engineered material constructions that are focused on predefined wave propagation patterns. In the current paper, coupled fluid-structure one-dimensional metamaterial cell, in which piezoelectric active ingredient has been introduced, is manufactured to achieve controllable dynamic density. The density-controllable cell has been manufactured by coupling a water-filled cavity with piezoelectric elements in a cell of 4.5 cm length and 4.1 cm diameter subject to impulse excitation. A finite element model of the cell has been developed and its predictions are validated against the experimental results. The validated model is utilized to predict the changes in the pressure gradient inside the developed cell which is a direct measure of the changes introduced to the dynamic density of the acoustic metamaterial domain. With such predictions, it is demonstrated that densities as high as 3.2 gm/cm3 and as low as 0.72 gm/cm3 can be achieved experimentally for excitation frequencies ranging between 100 Hz and 500 Hz.

  1. Increased apoptosis and decreased density of medial smooth muscle cells in human abdominal aortic aneurysms

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jian张健; Jan Schmidt; Eduard Ryschich; Hardy Schumacher; Jens R Allenberg

    2003-01-01

    Objective To determine the increase of apoptosis and the decrease of smooth muscle cells (SMCs) density in human abdominal aortic aneurysms (AAA). Methods In situ terminal transferase-mediated dUTP nick end labeling (TUNEL) was employed to detect apoptosis of SMCs in patients with AAA (n=25) and normal abdominal aortae (n=10). Positive cells were identified by specific cell marker in combination with immunohistochemistry. Meanwhile SMC counting was performed by anti-α-actin immunohistostaining to compare the SMC density. Results TUNEL staining revealed that there was significantly increased apoptosis in AAAs (average 8.6%) compared with normal abdominal aortae (average 0.95%, P<0.01). Double staining showed that most of these cells were SMCs. Counting of α-actin positive SMCs revealed that medial SMC density of AAAs (37.5±7.6 SMCs /HPF) was reduced by 79.1% in comparison with that of normal abdominal aortae (179.2±16.1 SMCs /HPF, P<0.01). Conclusions Significantly increased SMCs of AAA bear apoptotic markers initiating cell death. Elevated apoptosis may result in a decreased density of SMCs in AAA, which may profoundly influence the development of AAA.

  2. Surface layer structure and average contact temperature of copper-containing materials under dry sliding with high electric current density

    Science.gov (United States)

    Fadin, V. V.; Aleutdinova, M. I.; Rubtsov, V. Ye.; Aleutdinov, K. A.

    2016-11-01

    Dry sliding of copper and powder composites of Cu-Fe and Cu-Fe-graphite compositions against 1045 steel under electric current of contact density higher than 250 A/cm2 has been studied, which demonstrated the change in surface layer structure and formation of tribolayer consisting of iron, copper and FeO oxide. Signs of quasi-viscous flow of worn surface were observed. It was noted that the thin contact layer containing about 40 at % of oxygen and 40% of Fe was the main factor decreasing the adhesion interaction. It was affirmed that the introduction of graphite into the primary structure of the composite leads to rather low content of FeO oxide and to the increased tendency of surface layer to catastrophic deterioration under sliding with contact current density of about 300 A/cm2. The temperature of contact did not exceed 400°C.

  3. Controlling the cytotoxicity of CdSe magic-sized quantum dots as a function of surface defect density.

    Science.gov (United States)

    Silva, Anielle Christine Almeida; Silva, Marcelo José Barbosa; da Luz, Felipe Andrés Cordero; Silva, Danielle Pereira; de Deus, Samantha Luara Vieira; Dantas, Noelio Oliveira

    2014-09-10

    Quantum dots are potentially very useful as fluorescent probes in biological systems. However, they are inherently cytotoxic because of their constituents. We controlled the cytotoxicity of CdSe magic-sized quantum dots (MSQDs) as a function of surface defect density by altering selenium (Se) concentration during synthesis. Higher Se concentrations reduced the cytotoxicity of the CdSe MSQDs and diminished mRNA expression of methallothionein because of the low cadmium ions (Cd(2+)) concentration adsorbed on the surface of the MSQDs. These results agree with luminescence spectra, which show that higher Se concentrations decrease the density of surface defects. Therefore, our results describe for the first time a simple way of controlling the cytotoxicity of CdSe MSQDs and making them safer to use as fluorescence probes in biological systems.

  4. Cell surface engineering of industrial microorganisms for biorefining applications.

    Science.gov (United States)

    Tanaka, Tsutomu; Kondo, Akihiko

    2015-11-15

    In order to decrease carbon emissions and negative environmental impacts of various pollutants, biofuel/biochemical production should be promoted for replacing fossil-based industrial processes. Utilization of abundant lignocellulosic biomass as a feedstock has recently become an attractive option. In this review, we focus on recent efforts of cell surface display using industrial microorganisms such as Escherichia coli and yeast. Cell surface display is used primarily for endowing cellulolytic activity on the host cells, and enables direct fermentation to generate useful fuels and chemicals from lignocellulosic biomass. Cell surface display systems are systematically summarized, and the drawbacks/perspectives as well as successful application of surface display for industrial biotechnology are discussed.

  5. Density functional theory of liquid crystals and surface anchoring: hard Gaussian overlap-sphere and hard Gaussian overlap-surface potentials.

    Science.gov (United States)

    Avazpour, A; Avazpour, L

    2010-12-28

    This article applies the density functional theory to confined liquid crystals, comprised of ellipsoidal shaped particles interacting through the hard Gaussian overlap (HGO) potential. The extended restricted orientation model proposed by Moradi and co-workers [J. Phys.: Condens. Matter 17, 5625 (2005)] is used to study the surface anchoring. The excess free energy is calculated as a functional expansion of density around a reference homogeneous fluid. The pair direct correlation function (DCF) of a homogeneous HGO fluid is approximated, based on the optimized sum of Percus-Yevick and Roth DCF for hard spheres; the anisotropy introduced by means of the closest approach parameter, the expression proposed by Marko [Physica B 392, 242 (2007)] for DCF of HGO, and hard ellipsoids were used. In this study we extend an our previous work [Phys. Rev. E 72, 061706 (2005)] on the anchoring behavior of hard particle liquid crystal model, by studying the effect of changing the particle-substrate contact function instead of hard needle-wall potentials. We use the two particle-surface potentials: the HGO-sphere and the HGO-surface potentials. The average number density and order parameter profiles of a confined HGO fluid are obtained using the two particle-wall potentials. For bulk isotropic liquid, the results are in agreement with the Monte Carlo simulation of Barmes and Cleaver [Phys. Rev. E 71, 021705 (2005)]. Also, for the bulk nematic phase, the theory gives the correct density profile and order parameter between the walls.

  6. Numerical analysis of monocrystalline silicon solar cells with fine nanoimprinted textured surface

    Science.gov (United States)

    Yoshinaga, Seiya; Ishikawa, Yasuaki; Araki, Shinji; Honda, Tatsuki; Jiang, Yunjiang; Uraoka, Yukiharu

    2017-02-01

    We investigated the surface reflectance of nanoimprinted textures on silicon. Zirconium oxide, which is a wide-bandgap inorganic dielectric material, was used as the texturing material. We performed several calculations to optimize the textures for the production of high-efficiency bulk-type monocrystalline silicon solar cells. Our analysis revealed that nanoimprinted textured solar cells exhibit a lower reverse saturation current density than a solar cell with a conventional etched texture. It was also confirmed that the photocarrier generation rate for a solar cell with a submicron-scale nanoimprinted texture has little dependence on the texture shape. Furthermore, the weighted average reflectance of an optimized nanoimprinted textured solar cell was substantially reduced to 3.72%, suggesting that texture formation by nanoimprint lithography is an extremely effective technology for producing high-efficiency solar cells at a low cost.

  7. A posteriori testing of algebraic flame surface density models for LES

    Science.gov (United States)

    Ma, T.; Stein, O. T.; Chakraborty, N.; Kempf, A. M.

    2013-06-01

    In the application of Large Eddy Simulation (LES) to premixed combustion, the unknown filtered chemical source term can be modelled by the generalised flame surface density (FSD) using algebraic models for the wrinkling factor Ξ. The present study compares the behaviour of the various models by first examining the effect of sub-grid turbulent velocity fluctuation on Ξ through a one-dimensional analysis and by the LES of the ORACLES burner (Nguyen, Bruel, and Reichstadt, Flow, Turbulence and Combustion Vol. 82 [2009], pp. 155-183) and the Volvo Rig (Sjunnesson, Nelsson, and Max, Laser Anemometry, Vol. 3 [1991], pp. 83-90; Sjunnesson, Henrikson, and Löfström, AIAA Journal, Vol. 28 [1992], pp. AIAA-92-3650). Several sensitivity studies on parameters such as the turbulent viscosity and the grid resolution are also carried out. A statistically 1-D analysis of turbulent flame propagation reveals that counter gradient transport of the progress variable needs to be accounted for to obtain a realistic flame thickness from the simulations using algebraic FSD based closure. The two burner setups are found to operate mainly within the wrinkling/corrugated flamelet regime based on the premixed combustion diagram for LES (Pitsch and Duchamp de Lageneste, Proceedings of the Combustion Institute, Vol. 29 [2002], pp. 2001-2008) and this suggests that the models are operating within their ideal range. The performance of the algebraic models are then assessed by comparing velocity statistics, followed by a detailed error analysis for the ORACLES burner. Four of the tested models were found to perform reasonably well against experiments, and one of these four further excels in being the most grid-independent. For the Volvo Rig, more focus is placed upon the comparison of temperature data and identifying changes in flame structure amongst the different models. It is found that the few models which largely over-predict velocities in the ORACLES case and volume averaged ? in a

  8. Multi-scale cell/surface interaction on modified titanium aluminum vanadium surfaces

    Science.gov (United States)

    Chen, Jianbo

    This dissertation presents a series of experimental studies of the effects of multi-scale cell/surface interactions on modified Ti-6Al-4V surfaces. These include laser-grooved surfaces; porous structures and RGD-coated laser-grooved surfaces. A nano-second DPSS UV lasers with a Gaussian pulse energy profile was used to introduce the desired micro-groove geometries onto Ti-6Al-4V surfaces. This was done without inducing micro-cracks or significant changes in surface chemistry within the heat affected zones. The desired 8-12 mum groove depths and widths were achieved by the control of pulse frequency, scan speed, and the lens focal length that controls spot size. The interactions between human osteosarcoma (HOS) cells and laser-grooved Ti-6Al-4V surfaces were investigated after 48 hours of cell culture. The cell behavior, including cell spreading, alignment and adhesion, was elucidated using scanning electronic microscopy (SEM), immuno-fluorescence staining and enzymatic detachment. Contact guidance was shown to increase as grooved spacing decreased. For the range of micro-groove geometries studied, micro-grooves with groove spacings of 20 mum provided the best combination of cell orientation and adhesion. Short-term adhesion experiments (15 mins to 1 day) also revealed that there is a positive correlation between cell orientation and cell adhesion. Contact guidance on the micro-grooved surfaces is shown to be enhanced by nano- and micro-scale asperities that provide sites for the attachment of lamellopodia during cell locomotion and spreading. Contact guidance is also promoted by the geometrical confinement provided by laser grooves. An experimental study of initial cell spreading and ingrowth into Ti-6Al-4V porous structures was also carried out on porous structures with different pore sizes and geometries. A combination of SEM, the tetrazolium salt (MTT) colorimetric assay and enzymatic detachment were used to study cell spreading and adhesion. The extent of cell

  9. Cell orientation on a stripe-micropatterned surface

    Institute of Scientific and Technical Information of China (English)

    SUN JianGuo; TANG Jian; DING JianDong

    2009-01-01

    Stripe-micropatterned surfaces have recently been a unique tool to study cell orientation. In this paper,we prepared,by the photolithography transfer technique,stable gold (Au) micropatterns on PEG hydrogel surfaces with defined cell-resistant (PEG hydrogel) and cell-adhesive (gold microstripes) proparties. 3T3 fibroblasts were cultured on Au-microstripe surfaces to observe cell adhesion and orientation. Five statistical parameters were defined and used to describe cell orientation on micropatterns.With the increase of inter-stripe distance,the orientational order parameter,the ratio of long and short axes of a cell,and the occupation fraction of cells on stripes increased gradually,whereas the spreading area of a single cell decreased. The abrupt changes of these four parameters did not happen at the same inter-distance. The adhesion ratio of a cell on Au stripes over cell spreading area did not change monotonically as a function of inter-stripe distance. The combination of the 5 statistical parameters represented well the cell orientation behaviors semi-quantitatively.

  10. Microfabricated surface designs for cell culture and diagnosis.

    Science.gov (United States)

    Matsuda, T; Chung, D J

    1994-01-01

    Grooved and holed surfaces with a well fabricated design may serve as microsubstrates for cell culture and microreactors for diagnosis. In this study, the authors prepared chemically treated, micrometer scale grooved and holed glass surfaces by combined surface modification and ultraviolet (UV) excimer laser ablation techniques, as follows. 1) Microcell-culture substrate: Amino group attached glass surfaces, prepared by the treatment with an aminopropylsilane, were condensed with a carboxylated radical initiator. Subsequently, polyacrylamide was grafted by surface initiated radical polymerization to create a very hydrophilic surface layer. Ultraviolet excimer laser beams (KrF: 248 nm) were irradiated through a microscope onto surfaces to create grooves or holes that were 10 and 50 microns in width or diameter, respectively. The depth, depending on the irradiation light strength, ranged from a few to several tenths of a micrometer. On endothelial cell (EC) seeding, ECs adhered and grew on the bottoms of the grooved or holed surface where glass was exposed on ablation. Little cell adhesion was observed on non ablated, grafted surfaces. Endothelial cells aligned along the groove, resulting in very narrow tube like tissue formation, whereas ECs tended to form a multilayered spherical aggregate in a hole. A single cell resided in a 10 microns square hole. 2) Microreactor for diagnosis: The glass surface, treated with a fluorinated silane, was ablated to create round holes. On addition of a few microliters of water, water could be quantitatively transferred into a hole because of the water repellent characteristics of non ablated, fluorinated glass. As a model of a microreactor, enzyme reactions to affect different levels of glucose were carried out in tiny holed surfaces.

  11. Adhesion, Growth, and Maturation of Vascular Smooth Muscle Cells on Low-Density Polyethylene Grafted with Bioactive Substances

    Directory of Open Access Journals (Sweden)

    Martin Parizek

    2013-01-01

    Full Text Available The attractiveness of synthetic polymers for cell colonization can be affected by physical, chemical, and biological modification of the polymer surface. In this study, low-density polyethylene (LDPE was treated by an Ar+ plasma discharge and then grafted with biologically active substances, namely, glycine (Gly, polyethylene glycol (PEG, bovine serum albumin (BSA, colloidal carbon particles (C, or BSA+C. All modifications increased the oxygen content, the wettability, and the surface free energy of the materials compared to the pristine LDPE, but these changes were most pronounced in LDPE with Gly or PEG, where all the three values were higher than in the only plasma-treated samples. When seeded with vascular smooth muscle cells (VSMCs, the Gly- or PEG-grafted samples increased mainly the spreading and concentration of focal adhesion proteins talin and vinculin in these cells. LDPE grafted with BSA or BSA+C showed a similar oxygen content and similar wettability, as the samples only treated with plasma, but the nano- and submicron-scale irregularities on their surface were more pronounced and of a different shape. These samples promoted predominantly the growth, the formation of a confluent layer, and phenotypic maturation of VSMC, demonstrated by higher concentrations of contractile proteins alpha-actin and SM1 and SM2 myosins. Thus, the behavior of VSMC on LDPE can be regulated by the type of bioactive substances that are grafted.

  12. Adhesion, growth, and maturation of vascular smooth muscle cells on low-density polyethylene grafted with bioactive substances.

    Science.gov (United States)

    Parizek, Martin; Slepickova Kasalkova, Nikola; Bacakova, Lucie; Svindrych, Zdenek; Slepicka, Petr; Bacakova, Marketa; Lisa, Vera; Svorcik, Vaclav

    2013-01-01

    The attractiveness of synthetic polymers for cell colonization can be affected by physical, chemical, and biological modification of the polymer surface. In this study, low-density polyethylene (LDPE) was treated by an Ar(+) plasma discharge and then grafted with biologically active substances, namely, glycine (Gly), polyethylene glycol (PEG), bovine serum albumin (BSA), colloidal carbon particles (C), or BSA+C. All modifications increased the oxygen content, the wettability, and the surface free energy of the materials compared to the pristine LDPE, but these changes were most pronounced in LDPE with Gly or PEG, where all the three values were higher than in the only plasma-treated samples. When seeded with vascular smooth muscle cells (VSMCs), the Gly- or PEG-grafted samples increased mainly the spreading and concentration of focal adhesion proteins talin and vinculin in these cells. LDPE grafted with BSA or BSA+C showed a similar oxygen content and similar wettability, as the samples only treated with plasma, but the nano- and submicron-scale irregularities on their surface were more pronounced and of a different shape. These samples promoted predominantly the growth, the formation of a confluent layer, and phenotypic maturation of VSMC, demonstrated by higher concentrations of contractile proteins alpha-actin and SM1 and SM2 myosins. Thus, the behavior of VSMC on LDPE can be regulated by the type of bioactive substances that are grafted.

  13. The effect of cell size and channel density on neuronal information encoding and energy efficiency.

    Science.gov (United States)

    Sengupta, Biswa; Faisal, A Aldo; Laughlin, Simon B; Niven, Jeremy E

    2013-09-01

    Identifying the determinants of neuronal energy consumption and their relationship to information coding is critical to understanding neuronal function and evolution. Three of the main determinants are cell size, ion channel density, and stimulus statistics. Here we investigate their impact on neuronal energy consumption and information coding by comparing single-compartment spiking neuron models of different sizes with different densities of stochastic voltage-gated Na(+) and K(+) channels and different statistics of synaptic inputs. The largest compartments have the highest information rates but the lowest energy efficiency for a given voltage-gated ion channel density, and the highest signaling efficiency (bits spike(-1)) for a given firing rate. For a given cell size, our models revealed that the ion channel density that maximizes energy efficiency is lower than that maximizing information rate. Low rates of small synaptic inputs improve energy efficiency but the highest information rates occur with higher rates and larger inputs. These relationships produce a Law of Diminishing Returns that penalizes costly excess information coding capacity, promoting the reduction of cell size, channel density, and input stimuli to the minimum possible, suggesting that the trade-off between energy and information has influenced all aspects of neuronal anatomy and physiology.

  14. Enzyme controlled glucose auto-delivery for high cell density cultivations in microplates and shake flasks

    Directory of Open Access Journals (Sweden)

    Casteleijn Marco G

    2008-11-01

    Full Text Available Abstract Background Here we describe a novel cultivation method, called EnBase™, or enzyme-based-substrate-delivery, for the growth of microorganisms in millilitre and sub-millilitre scale which yields 5 to 20 times higher cell densities compared to standard methods. The novel method can be directly applied in microwell plates and shake flasks without any requirements for additional sensors or liquid supply systems. EnBase is therefore readily applicable for many high throughput applications, such as DNA production for genome sequencing, optimisation of protein expression, production of proteins for structural genomics, bioprocess development, and screening of enzyme and metagenomic libraries. Results High cell densities with EnBase are obtained by applying the concept of glucose-limited fed-batch cultivation which is commonly used in industrial processes. The major difference of the novel method is that no external glucose feed is required, but glucose is released into the growth medium by enzymatic degradation of starch. To cope with the high levels of starch necessary for high cell density cultivation, starch is supplied to the growing culture suspension by continuous diffusion from a storage gel. Our results show that the controlled enzyme-based supply of glucose allows a glucose-limited growth to high cell densities of OD600 = 20 to 30 (corresponding to 6 to 9 g l-1 cell dry weight without the external feed of additional compounds in shake flasks and 96-well plates. The final cell density can be further increased by addition of extra nitrogen during the cultivation. Production of a heterologous triosphosphate isomerase in E. coli BL21(DE3 resulted in 10 times higher volumetric product yield and a higher ratio of soluble to insoluble product when compared to the conventional production method. Conclusion The novel EnBase method is robust and simple-to-apply for high cell density cultivation in shake flasks and microwell plates. The

  15. A density functional theory for association of fluid molecules with a functionalized surface: fluid-wall single and double bonding

    Science.gov (United States)

    Haghmoradi, Amin; Wang, Le; Chapman, Walter G.

    2017-02-01

    In this manuscript we extend Wertheim’s two-density formalism beyond its first order to model a system of fluid molecules with a single association site close to a planar hard wall with association sites on its surface in a density functional theory framework. The association sites of the fluid molecules are small enough that they can form only one bond, while the wall association sites are large enough to bond with more than one fluid molecule. The effects of temperature and of bulk fluid and wall site densities on the fluid density profile, extent of association, and competition between single and double bonding of fluid segments at the wall sites versus distance from the wall are presented. The theory predictions are compared with new Monte Carlo simulation results and they are in good agreement. The theory captures the surface coverage over wide ranges of temperature and bulk density by introducing the effect of steric hindrance in fluid association at a wall site.

  16. A mathematical model of the current density distribution in electrochemical cells - AUTHORS’ REVIEW

    Directory of Open Access Journals (Sweden)

    PREDRAG M. ŽIVKOVIĆ

    2011-06-01

    Full Text Available An approach based on the equations of electrochemical kinetics for the estimation of the current density distribution in electrochemical cells is presented. This approach was employed for a theoretical explanation of the phenomena of the edge and corner effects. The effects of the geometry of the system, the kinetic parameters of the cathode reactions and the resistivity of the solution are also discussed. A procedure for a complete analysis of the current distribution in electrochemical cells is presented.

  17. Inverse Relationship Between Leydig Cell Density and Metastatic Potential of Prostatic Adenocarcinoma

    Directory of Open Access Journals (Sweden)

    W. John Wang

    1999-01-01

    Full Text Available Purpose: Evaluate the relationship between metastatic potential of prostatic adenocarcinoma (PC and testicular Leydig cell density. Materials and methods: Tissue samples from 111 men, age 52–85, with PC and bilateral orchiectomy were evaluated for Leydig cell density. The patients were divided into two groups: Group A were patients with metastasis (n=36 and Group B were patients without metastasis (n=75. Leydig cell density was determined by direct manual microscopic cell count on the tissue sections. The means of cell counts by four pathologists, expressed as cell/0.78 mm2 were used for analysis. The normally distributed data were analyzed by two‐tail Student’s t‐test. Thirty‐eight age‐compatible autopsy cases who died of unrelated causes served as normal controls. Results: The mean of Leydig cell count in group A patients was 14.43 (14.43 ± 1.19 SE. Mean of Group B was 47.05 (47.05 ± 4.05 SE whereas normal controls displayed a mean of 48.66 (48.66 ± 2.94 SE. Group A was significantly different from control (p0.75. Conclusions: Patients with metastatic adenocarcinoma of prostate, as a group, have a significantly lower Leydig cell density than patients without metastasis or patients without PC in compatible age groups. The hormonal relationship between this observation is however unknown. One possible explanation is that PC subpopulation with metastatic potential may require different level of endogenous androgen or are androgen‐independent.

  18. Absolute choline concentration measured by quantitative proton MR spectroscopy correlates with cell density in meningioma

    Energy Technology Data Exchange (ETDEWEB)

    Yue, Qiang [University of Tsukuba, Department of Neurosurgery, Institute of Clinical Medicine, Tsukuba Science City, Ibaraki (Japan)]|[West China Hospital of Sichuan University, Huaxi MR Research Center, Department of Radiology, Chengdu (China); Shibata, Yasushi; Kawamura, Hiraku; Matsumura, Akira [University of Tsukuba, Department of Neurosurgery, Institute of Clinical Medicine, Tsukuba Science City, Ibaraki (Japan); Isobe, Tomonori [Kitasato University, Department of Medical Technology, School of Allied Health Sciences, Minato, Tokyo (Japan); Anno, Izumi [University of Tsukuba, Department of Radiology, Institute of Clinical Medicine, Tsukuba, Ibaraki (Japan); Gong, Qi-Yong [West China Hospital of Sichuan University, Huaxi MR Research Center, Department of Radiology, Chengdu (China)]|[University of Liverpool, Division of Medical Imaging, Faculty of Medicine, Liverpool (United Kingdom)

    2009-01-15

    This study was aimed to investigate the relationship between quantitative proton magnetic resonance spectroscopy (1H-MRS) and pathological changes in meningioma. Twenty-two meningioma cases underwent single voxel 1H-MRS (point-resolved spectroscopy sequence, repetition time/echo time = 2,000 ms/68, 136, 272 ms). Absolute choline (Cho) concentration was calculated using tissue water as the internal reference and corrected according to intra-voxel cystic/necrotic parts. Pathological specimens were stained with MIB-1 antibody to measure cell density and proliferation index. Correlation analysis was performed between absolute Cho concentration and cell density and MIB-1 labeled proliferation index. Average Cho concentration of all meningiomas before correction was 2.95 {+-} 0.86 mmol/kg wet weight. It was increased to 3.23 {+-} 1.15 mmol/kg wet weight after correction. Average cell density of all meningiomas was 333 {+-} 119 cells/HPF, and average proliferation index was 2.93 {+-} 5.72%. A linear, positive correlation between cell density and Cho concentration was observed (r = 0.650, P = 0.001). After correction of Cho concentration, the correlation became more significant (r = 0.737, P < 0.001). However, no significant correlation between Cho concentration and proliferation index was found. There seemed to be a positive correlation trend after correction of Cho concentration but did not reach significant level. Absolute Cho concentration, especially Cho concentration corrected according to intra-voxel cystic/necrotic parts, reflects cell density of meningioma. (orig.)

  19. Sperm cell surface dynamics during activation and fertilization

    NARCIS (Netherlands)

    Boerke, A.

    2013-01-01

    Before the sperm cell can reach the oocyte it needs to be activated and to undergo a series of preparative steps. The sperm surface dynamics was studied in relation to this activation process and the modifications and removal of sperm surface components havebeen investigated. Bicarbonate-induced rad

  20. Fabrication of cell container arrays with overlaid surface topographies.

    NARCIS (Netherlands)

    Truckenmuller, R.; Giselbrecht, S.; Escalante-Marun, M.; Groenendijk, M.; Papenburg, B.; Rivron, N.; Unadkat, H.; Saile, V.; Subramaniam, V.; Berg, A. van den; Blitterswijk, C. Van; Wessling, M.; Boer, J. den; Stamatialis, D.

    2012-01-01

    This paper presents cell culture substrates in the form of microcontainer arrays with overlaid surface topographies, and a technology for their fabrication. The new fabrication technology is based on microscale thermoforming of thin polymer films whose surfaces are topographically prepatterned on a

  1. Fabrication of cell container arrays with overlaid surface topographies

    NARCIS (Netherlands)

    Truckenmüller, R.K.; Giselbrecht, S.; Escalante, M.; Groenendijk, M.N.W.; Papenburg, B.J.; Rivron, N.C.; Unadkat, H.V.; Saile, V.; Subramaniam, V.; Blitterswijk, van C.A.; Wessling, M.; Boer, de J.; Stamatialis, D.

    2012-01-01

    This paper presents cell culture substrates in the form of microcontainer arrays with overlaid surface topographies, and a technology for their fabrication. The new fabrication technology is based on microscale thermoforming of thin polymer films whose surfaces are topographically prepatterned on a

  2. Immunogold labels: cell-surface markers in atomic force microscopy

    NARCIS (Netherlands)

    Putman, Constant A.J.; Grooth, de Bart G.; Hansma, Paul K.; Hulst, van Niek F.; Greve, Jan

    1993-01-01

    The feasibility of using immunogold labels as cell-surface markers in atomic force microscopy is shown in this paper. The atomic force microscope (AFM) was used to image the surface of immunogold-labeled human lymphocytes. The lymphocytes were isolated from whole blood and labeled by an indirect imm

  3. [Spatial variation characteristics of surface soil water content, bulk density and saturated hydraulic conductivity on Karst slopes].

    Science.gov (United States)

    Zhang, Chuan; Chen, Hong-Song; Zhang, Wei; Nie, Yun-Peng; Ye, Ying-Ying; Wang, Ke-Lin

    2014-06-01

    Surface soil water-physical properties play a decisive role in the dynamics of deep soil water. Knowledge of their spatial variation is helpful in understanding the processes of rainfall infiltration and runoff generation, which will contribute to the reasonable utilization of soil water resources in mountainous areas. Based on a grid sampling scheme (10 m x 10 m) and geostatistical methods, this paper aimed to study the spatial variability of surface (0-10 cm) soil water content, soil bulk density and saturated hydraulic conductivity on a typical shrub slope (90 m x 120 m, projected length) in Karst area of northwest Guangxi, southwest China. The results showed that the surface soil water content, bulk density and saturated hydraulic conductivity had different spatial dependence and spatial structure. Sample variogram of the soil water content was fitted well by Gaussian models with the nugget effect, while soil bulk density and saturated hydraulic conductivity were fitted well by exponential models with the nugget effect. Variability of soil water content showed strong spatial dependence, while the soil bulk density and saturated hydraulic conductivity showed moderate spatial dependence. The spatial ranges of the soil water content and saturated hydraulic conductivity were small, while that of the soil bulk density was much bigger. In general, the soil water content increased with the increase of altitude while it was opposite for the soil bulk densi- ty. However, the soil saturated hydraulic conductivity had a random distribution of large amounts of small patches, showing high spatial heterogeneity. Soil water content negatively (P conductivity, while there was no significant correlation between the soil bulk density and saturated hydraulic conductivity.

  4. Study of surface cell Madelung constant and surface free energy of nanosized crystal grain

    Institute of Scientific and Technical Information of China (English)

    Zhang Wei-Jia; Wang Tian-Min; Rong Ai-Lun; Cui Min

    2006-01-01

    Surface cell Madelung constant is firstly defined for calculating the surface free energy of nanosized crystal grains,which explains the physical performance of small crystals and may be greatly beneficial to the analysis of surface states and the study of the dynamics of crystal nucleation and growth.A new approximative expression of the surface energy and relevant thermodynamic data are used in this calculation.New formula and computing method for calculating the Madelung constant α of any complex crystals are proposed,and the surface free energies and surface electrostatic energies of nanosized crystal grains and the Madelung constant of some complex crystals are theoretically calculated in this paper.The surface free energy of nanosized-crystal-grain TiO2 and the surface electrostatic energy (absolute value) of nanosized-crystal-grain α-A12O3 are found to be the biggest among all the crystal grains including those of other species.

  5. Study of Surface Cell Madelung Constant and Surface Free Energy of Nanosized Crystal Grain

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wei-Jia; WANG Tian-Min; CUI Min

    2005-01-01

    Surface cell Madelung constant is firstly defined in calculating surface free energy of nanosized crystal grains, which explains the physical performance of small crystals and may be great benefit to make surface analysis and study dynamics of crystal nucleus growth. A new ap- proximative expression of surface energy and relevant thermodynamic data was used in this cal- culation. A new formula and computing method for calculating the Madelung constant α of any complex crystals is proposed, and surface free energies and surface electrostatic energies of nano- sized crystal grains as well as Madelung constant of some complex crystals are theoretically cal- culated in this paper. The surface free energy of nanosized crystal grain TiO2 and surface elec- trostatic energy(absolute value) of nanosized crystal grain α-Al2O3 are found to be the biggest among other crystal grains.

  6. Effect of soil surface salt on the density and distribution of the snail Bithynia siamensis goniomphalos in northeast Thailand.

    Science.gov (United States)

    Suwannatrai, Apiporn; Suwannatrai, Kulwadee; Haruay, Surat; Piratae, Supawadee; Thammasiri, Chalida; Khampoosa, Panita; Kulsantiwong, Jutharat; Prasopdee, Sattrachai; Tarbsripair, Pairat; Suwanwerakamtorn, Rasamee; Sukchan, Somsak; Boonmars, Thidarut; Malone, John B; Kearney, Michael T; Tesana, Smarn

    2011-05-01

    Opisthorchis viverrini infection is associated with human cholangiocarcinoma and northeast Thailand has the highest incidence of this disease in the world. Bithynia siamensis goniomphalos is the major freshwater snail intermediate host of O. viverrini in this area and an analysis based on geographical information systems was used to determine the effect of variation in soil surface salt on the density and distribution of this snail. A malacological survey was carried out in 56 water bodies in the Khorat basin, northeast Thailand at locations with various soil surface salt levels. Mollusk samples were collected from 10 ecologically representative water body sites with 10-20 sampling stations in each. The shoreline of clear, shallow water bodies was found to be the preferred B. s. goniomphalos habitat. The snails were exclusively found in water with salinity levels ranging between 0.05 and 22.11 parts per thousand (ppt), which supports the notion that B. s. goniomphalos prefers water with some saline content over pure, freshwater. The highest snail population densities were in rice fields, ponds, road-side ditches and canals within a water salinity range of 2.5-5.0 ppt. However, the presence of B. s. goniomphalos was negatively correlated with water salinity (P ≤0.05), both with regard to density and distribution. The areas with the highest density of B. s. goniomphalos were those with less than 1% soil surface salt (potential index = 0.314), while the lowest densities were found in areas exceeding 50% soil surface salt (potential index = 0.015).

  7. Effect of soil surface salt on the density and distribution of the snail Bithynia siamensis goniomphalos in northeast Thailand

    Directory of Open Access Journals (Sweden)

    Apiporn Suwannatrai

    2011-05-01

    Full Text Available Opisthorchis viverrini infection is associated with human cholangiocarcinoma and northeast Thailand has the highest incidence of this disease in the world. Bithynia siamensis goniomphalos is the major freshwater snail intermediate host of O. viverrini in this area and an analysis based on geographical information systems was used to determine the effect of variation in soil surface salt on the density and distribution of this snail. A malacological survey was carried out in 56 water bodies in the Khorat basin, northeast Thailand at locations with various soil surface salt levels. Mollusk samples were collected from 10 ecologically representative water body sites with 10-20 sampling stations in each. The shoreline of clear, shallow water bodies was found to be the preferred B. s. goniomphalos habitat. The snails were exclusively found in water with salinity levels ranging between 0.05 and 22.11 parts per thousand (ppt, which supports the notion that B. s. goniomphalos prefers water with some saline content over pure, freshwater. The highest snail population densities were in rice fields, ponds, road-side ditches and canals within a water salinity range of 2.5-5.0 ppt. However, the presence of B. s. goniomphalos was negatively correlated with water salinity (P ≤0.05, both with regard to density and distribution. The areas with the highest density of B. s. goniomphalos were those with less than 1% soil surface salt (potential index = 0.314, while the lowest densities were found in areas exceeding 50% soil surface salt (potential index = 0.015.

  8. Cell-surface expression of Hsp70 on hematopoietic cancer cells after inhibition of HDAC activity

    DEFF Research Database (Denmark)

    Jensen, Helle

    -derived antigenic peptides, a function which is currently explored in immunotherapeutic approaches against cancer. Additionally, membrane-bound Hsp70 can stimulate antigen presenting cells to release proinflammatory cytokines and can provide a target structure for NK cell-mediated lysis. Human cancer cells...... frequently express Hsp70 on their cell surface, whereas the corresponding normal tissues do not. In addition, several clinically applied reagents, such as alkyl-lysophospholipides, chemotherapeutic agents, and anti-inflammatory reagents, have been found to enhance Hsp70 cell surface expression on cancer...... cells. We have found that inhibition of histone deacetylase (HDAC) activity leads to surface expression of Hsp70 on various hematopoietic cancer cells, an occurance that was not observed on naïve or activated peripheral blood cells. HDAC-inhibitor mediated Hsp70 cell surface expression was confined...

  9. Responses of fibroblasts and glial cells to nanostructured platinum surfaces

    Science.gov (United States)

    Pennisi, C. P.; Sevcencu, C.; Dolatshahi-Pirouz, A.; Foss, M.; Lundsgaard Hansen, J.; Nylandsted Larsen, A.; Zachar, V.; Besenbacher, F.; Yoshida, K.

    2009-09-01

    The chronic performance of implantable neural prostheses is affected by the growth of encapsulation tissue onto the stimulation electrodes. Encapsulation is associated with activation of connective tissue cells at the electrode's metallic contacts, usually made of platinum. Since surface nanotopography can modulate the cellular responses to materials, the aim of the present work was to evaluate the 'in vitro' responses of connective tissue cells to platinum strictly by modulating its surface nanoroughness. Using molecular beam epitaxy combined with sputtering, we produced platinum nanostructured substrates consisting of irregularly distributed nanopyramids and investigated their effect on the proliferation, cytoskeletal organization and cellular morphology of primary fibroblasts and transformed glial cells. Cells were cultured on these substrates and their responses to surface roughness were studied. After one day in culture, the fibroblasts were more elongated and their cytoskeleton less mature when cultured on rough substrates. This effect increased as the roughness of the surface increased and was associated with reduced cell proliferation throughout the observation period (4 days). Morphological changes also occurred in glial cells, but they were triggered by a different roughness scale and did not affect cellular proliferation. In conclusion, surface nanotopography modulates the responses of fibroblasts and glial cells to platinum, which may be an important factor in optimizing the tissue response to implanted neural electrodes.

  10. Expanding the diversity of unnatural cell surface sialic acids

    Energy Technology Data Exchange (ETDEWEB)

    Luchansky, Sarah J.; Goon, Scarlett; Bertozzi, Carolyn R.

    2003-10-30

    Novel chemical reactivity can be introduced onto cell surfaces through metabolic oligosaccharide engineering. This technique exploits the substrate promiscuity of cellular biosynthetic enzymes to deliver unnatural monosaccharides bearing bioorthogonal functional groups into cellular glycans. For example, derivatives of N-acetylmannosamine (ManNAc) are converted by the cellular biosynthetic machinery into the corresponding sialic acids and subsequently delivered to the cell surface in the form of sialoglycoconjugates. Analogs of N-acetylglucosamine (GlcNAc) and N-acetylgalactosamine (GalNAc) are also metabolized and incorporated into cell surface glycans, likely through the sialic acid and GalNAc salvage pathways, respectively. Furthermore, GlcNAc analogs can be incorporated into nucleocytoplasmic proteins in place of {beta}-O-GlcNAc residues. These pathways have been exploited to integrate unique electrophiles such as ketones and azides into the target glycoconjugate class. These functional groups can be further elaborated in a chemoselective fashion by condensation with hydrazides and by Staudinger ligation, respectively, thereby introducing detectable probes onto the cell. In conclusion, sialic acid derivatives are efficient vehicles for delivery of bulky functional groups to cell surfaces and masking of their hydroxyl groups improves their cellular uptake and utilization. Furthermore, the successful introduction of photoactivatable aryl azides into cell surface glycans opens up new avenues for studying sialic acid-binding proteins and elucidating the role of sialic acid in essential processes such as signaling and cell adhesion.

  11. Abnormal changes in the density of thermal neutron flux in biocenoses near the earth surface.

    Science.gov (United States)

    Plotnikova, N V; Smirnov, A N; Kolesnikov, M V; Semenov, D S; Frolov, V A; Lapshin, V B; Syroeshkin, A V

    2007-04-01

    We revealed an increase in the density of thermal neutron flux in forest biocenoses, which was not associated with astrogeophysical events. The maximum spike of this parameter in the biocenosis reached 10,000 n/(sec x m2). Diurnal pattern of the density of thermal neutron flux depended only on the type of biocenosis. The effects of biomodulation of corpuscular radiation for balneology are discussed.

  12. Recharging Red Blood Cell Surface by Hemodialysis

    Directory of Open Access Journals (Sweden)

    Katrin Kliche

    2015-02-01

    Full Text Available Background: Similar as in vascular endothelium the negatively charged glycocalyx of erythrocytes selectively buffers sodium. Loss of glycocalyx (i.e. loss of negative charges leads to increased erythrocyte sodium sensitivity (ESS quantified by a recently developed salt-blood-test (SBT. The hypothesis was tested whether a regular 4-hour hemodialysis (4h-HD alters ESS. Methods: In 38 patients with end stage renal disease (ESRD ESS was measured before and after 4h-HD, together with standard laboratory and clinical parameters (electrolytes, acid-base status, urea, creatinine, hemoglobin, c-reactive protein and blood pressure. Results: Before 4h-HD, 20 patients (out of 38 were classified as “salt sensitive” by SBT. After 4h-HD, this number decreased to 11. Erythrocyte sodium buffering power remained virtually constant in patients with already low ESS before dialysis, whereas in patients with high ESS, 4h-HD improved the initially poor sodium buffering power by about 20%. No significant correlations could be detected between standard blood parameters and the respective ESS values except for plasma sodium concentration which was found increased by 3.1 mM in patients with high salt sensitivity. Conclusions: 4h-HD apparently recharges “run-down” erythrocytes and thus restores erythrocyte sodium buffering capacity. Besides the advantage of efficient sodium buffering in blood, erythrocytes with sufficient amounts of free negative charges at the erythrocyte surface will cause less (mechanical injury to the negatively charged endothelial surface due to efficient repulsive forces between blood and vessel wall. Hemodialysis improves erythrocyte surface properties and thus may prevent early vascular damage in patients suffering from ESRD.

  13. A density functional theory study of propylene epoxidation on RuO2(110) surface

    Science.gov (United States)

    Atmaca, Deniz Onay; Düzenli, Derya; Ozbek, M. Olus; Onal, Isik

    2016-11-01

    Propylene epoxidation is investigated on RuO2(110) and oxygen added RuO2-Oot(110) surfaces by periodic DFT computational method. The desired product propylene oxide (PO) as well as the undesired products acetone (AC) or propionaldehyde (PA) form on both surfaces through either surface intermediate oxometallopropylene (OMMP) or direct oxygen insertion mechanisms. On RuO2(110) surface, nucleophilic lattice oxygen at bridge position (Obr) favors the stable surface intermediate mechanism where high energy requirements for forward reactions are demonstrated in our calculations. On RuO2-Oot(110) surface, however, higher reactivity of the electrophilic oxygen (Oot) species lowers the reaction barriers and enables an exothermic reaction path to the direct oxygen insertion for PO production. Therefore, RuO2-Oot surface is expected to show a higher PO rate.

  14. Accurate assessment of cell density in low cellular liquid-based cervical cytology

    NARCIS (Netherlands)

    Siebers, A.G.; Laak, J.A.W.M. van der; Huberts-Manders, R.; Vedder, J.E.M.; Bulten, J.

    2013-01-01

    A. G. Siebers, J. A. W. M. van der Laak, R. Huberts-Manders, J. E. M. Vedder and J. Bulten Accurate assessment of cell density in low cellular liquid-based cervical cytology Objective: Scant cellularity is the most important source of unsatisfactory liquid-based cytology. Although still being debate

  15. Progressive FastICA Peel-Off and Convolution Kernel Compensation Demonstrate High Agreement for High Density Surface EMG Decomposition

    Science.gov (United States)

    Chen, Maoqi

    2016-01-01

    Decomposition of electromyograms (EMG) is a key approach to investigating motor unit plasticity. Various signal processing techniques have been developed for high density surface EMG decomposition, among which the convolution kernel compensation (CKC) has achieved high decomposition yield with extensive validation. Very recently, a progressive FastICA peel-off (PFP) framework has also been developed for high density surface EMG decomposition. In this study, the CKC and PFP methods were independently applied to decompose the same sets of high density surface EMG signals. Across 91 trials of 64-channel surface EMG signals recorded from the first dorsal interosseous (FDI) muscle of 9 neurologically intact subjects, there were a total of 1477 motor units identified from the two methods, including 969 common motor units. On average, 10.6 ± 4.3 common motor units were identified from each trial, which showed a very high matching rate of 97.85 ± 1.85% in their discharge instants. The high degree of agreement of common motor units from the CKC and the PFP processing provides supportive evidence of the decomposition accuracy for both methods. The different motor units obtained from each method also suggest that combination of the two methods may have the potential to further increase the decomposition yield. PMID:27642525

  16. Progressive FastICA Peel-Off and Convolution Kernel Compensation Demonstrate High Agreement for High Density Surface EMG Decomposition.

    Science.gov (United States)

    Chen, Maoqi; Holobar, Ales; Zhang, Xu; Zhou, Ping

    2016-01-01

    Decomposition of electromyograms (EMG) is a key approach to investigating motor unit plasticity. Various signal processing techniques have been developed for high density surface EMG decomposition, among which the convolution kernel compensation (CKC) has achieved high decomposition yield with extensive validation. Very recently, a progressive FastICA peel-off (PFP) framework has also been developed for high density surface EMG decomposition. In this study, the CKC and PFP methods were independently applied to decompose the same sets of high density surface EMG signals. Across 91 trials of 64-channel surface EMG signals recorded from the first dorsal interosseous (FDI) muscle of 9 neurologically intact subjects, there were a total of 1477 motor units identified from the two methods, including 969 common motor units. On average, 10.6 ± 4.3 common motor units were identified from each trial, which showed a very high matching rate of 97.85 ± 1.85% in their discharge instants. The high degree of agreement of common motor units from the CKC and the PFP processing provides supportive evidence of the decomposition accuracy for both methods. The different motor units obtained from each method also suggest that combination of the two methods may have the potential to further increase the decomposition yield.

  17. Progressive FastICA Peel-Off and Convolution Kernel Compensation Demonstrate High Agreement for High Density Surface EMG Decomposition

    Directory of Open Access Journals (Sweden)

    Maoqi Chen

    2016-01-01

    Full Text Available Decomposition of electromyograms (EMG is a key approach to investigating motor unit plasticity. Various signal processing techniques have been developed for high density surface EMG decomposition, among which the convolution kernel compensation (CKC has achieved high decomposition yield with extensive validation. Very recently, a progressive FastICA peel-off (PFP framework has also been developed for high density surface EMG decomposition. In this study, the CKC and PFP methods were independently applied to decompose the same sets of high density surface EMG signals. Across 91 trials of 64-channel surface EMG signals recorded from the first dorsal interosseous (FDI muscle of 9 neurologically intact subjects, there were a total of 1477 motor units identified from the two methods, including 969 common motor units. On average, 10.6±4.3 common motor units were identified from each trial, which showed a very high matching rate of 97.85±1.85% in their discharge instants. The high degree of agreement of common motor units from the CKC and the PFP processing provides supportive evidence of the decomposition accuracy for both methods. The different motor units obtained from each method also suggest that combination of the two methods may have the potential to further increase the decomposition yield.

  18. Atomic and molecular adsorption on transition-metal carbide (111) surfaces from density-functional theory: a trend study of surface electronic factors.

    Science.gov (United States)

    Vojvodic, A; Ruberto, C; Lundqvist, B I

    2010-09-22

    This study explores atomic and molecular adsorption on a number of early transition-metal carbides (TMCs) in NaCl structure by means of density-functional theory calculations. The investigated substrates are the TM-terminated TMC(111) surfaces, of interest because of the presence of different types of surface resonances (SRs) on them and because of their technological importance in growth processes. Also, TM compounds have shown potential in catalysis applications. Trend studies are conducted with respect to both period and group in the periodic table, choosing the substrates ScC, TiC, VC, ZrC, NbC, δ-MoC, TaC, and WC (in NaCl structure) and the adsorbates H, B, C, N, O, F, NH, NH(2), and NH(3). Trends in adsorption strength are explained in terms of surface electronic factors, by correlating the calculated adsorption-energy values with the calculated surface electronic structures. The results are rationalized by use of a concerted-coupling model (CCM), which has previously been applied successfully to the description of adsorption on TiC(111) and TiN(111) surfaces (Ruberto et al 2007 Solid State Commun. 141 48). First, the clean TMC(111) surfaces are characterized by calculating surface energies, surface relaxations, Bader charges, and surface-localized densities of states (DOSs). Detailed comparisons between surface and bulk DOSs reveal the existence of transition-metal localized SRs (TMSRs) in the pseudogap and of several C-localized SRs (CSRs) in the upper valence band on all considered TMC(111) surfaces. The spatial extent and the dangling bond nature of these SRs are supported by real-space analyses of the calculated Kohn-Sham wavefunctions. Then, atomic and molecular adsorption energies, geometries, and charge transfers are presented. An analysis of the adsorbate-induced changes in surface DOSs reveals a presence of both adsorbate-TMSR and adsorbate-CSRs interactions, of varying strengths depending on the surface and the adsorbate. These variations are

  19. Transforming ocular surface stem cell research into successful clinical practice

    Directory of Open Access Journals (Sweden)

    Virender S Sangwan

    2014-01-01

    Full Text Available It has only been a quarter of a century since the discovery of adult stem cells at the human corneo-scleral limbus. These limbal stem cells are responsible for generating a constant and unending supply of corneal epithelial cells throughout life, thus maintaining a stable and uniformly refractive corneal surface. Establishing this hitherto unknown association between ocular surface disease and limbal dysfunction helped usher in therapeutic approaches that successfully addressed blinding conditions such as ocular burns, which were previously considered incurable. Subsequent advances in ocular surface biology through basic science research have translated into innovations that have made the surgical technique of limbal stem cell transplantation simpler and more predictable. This review recapitulates the basic biology of the limbus and the rationale and principles of limbal stem cell transplantation in ocular surface disease. An evidence-based algorithm is presented, which is tailored to clinical considerations such as laterality of affliction, severity of limbal damage and concurrent need for other procedures. Additionally, novel findings in the form of factors influencing the survival and function of limbal stem cells after transplantation and the possibility of substituting limbal cells with epithelial stem cells of other lineages is also discussed. Finally this review focuses on the future directions in which both basic science and clinical research in this field is headed.

  20. Amplified effect of surface charge on cell adhesion by nanostructures

    Science.gov (United States)

    Xu, Li-Ping; Meng, Jingxin; Zhang, Shuaitao; Ma, Xinlei; Wang, Shutao

    2016-06-01

    Nano-biointerfaces with varied surface charge can be readily fabricated by integrating a template-based process with maleimide-thiol coupling chemistry. Significantly, nanostructures are employed for amplifying the effect of surface charge on cell adhesion, as revealed by the cell-adhesion performance, cell morphology and corresponding cytoskeletal organization. This study may provide a promising strategy for developing new biomedical materials with tailored cell adhesion for tissue implantation and regeneration.Nano-biointerfaces with varied surface charge can be readily fabricated by integrating a template-based process with maleimide-thiol coupling chemistry. Significantly, nanostructures are employed for amplifying the effect of surface charge on cell adhesion, as revealed by the cell-adhesion performance, cell morphology and corresponding cytoskeletal organization. This study may provide a promising strategy for developing new biomedical materials with tailored cell adhesion for tissue implantation and regeneration. Electronic supplementary information (ESI) available: Experimental details, SEM, KFM AFM, chemical modification and characterization. See DOI: 10.1039/c6nr00649c

  1. NO2 interaction with Au atom adsorbed on perfect and defective MgO(100) surfaces: density functional theory calculations.

    Science.gov (United States)

    Ammar, H Y; Eid, Kh M

    2013-10-01

    The interactions of nitrogen dioxide molecule (NO2) on Au atom adsorbed on the surfaces of metal oxide MgO (100) on both anionic (O2-) and defect (F(s) and F(s)(+)-centers) sites have been studied using the Density Functional Theory (DFT) in combination with embedded cluster model. The adsorption energies of NO2 molecule (N-down as well as O-down) on O(-2), F(s) and F(s)(+)-sites were considered. Full optimization for the additive materials and partial optimization for MgO substrate surfaces have been done. The formation energies were evaluated for F(s) and F(s)(+) of MgO substrate surfaces. Some parameters, the Ionization Potential (IP) and electron Affinity (eA), for defect free and defect containing surfaces have been calculated. The interaction properties of NO2 have been analyzed in terms of the adsorption energy, the electron donation (basicity), the elongation of N-O bond length and the charge distribution by using Natural Bond Orbital (NBO) analysis. The adsorption properties were examined by calculation of the Density of State (DOS). The presence of the Au atom increases the surface chemistry of the anionic O(2-)-site of MgO substrate surfaces. On the other hand, the presence of the Au atom decreases the surface chemistry of the F(s) and F(s)(+)-sites of MgO substrate surfaces. Generally, the NO2 molecule is strongly adsorbed (chemisorption) on the MgO substrate surfaces containing F(s) and F(s)(+)-centers.

  2. Zinc uptake by brain cells: `surface' versus `bulk'

    Science.gov (United States)

    DeStasio, Gelsomina; Pochon, S.; Lorusso, G. F.; Tonner, B. P.; Mercanti, Delio; Ciotti, M. Teresa; Oddo, Nino; Galli, Paolo; Perfetti, P.; Margaritondo, G.

    1996-08-01

    The uptake of zinc by cerebellar rat cultures upon exposure to 0022-3727/29/8/023/img12 solutions was comparatively investigated using two well known condensed matter physics techniques: synchrotron photoelectron spectromicroscopy and inductively coupled plasma atomic emission spectroscopy. The objective was to apply a strategy - well known in surface physics - to distinguish between `surface' and `bulk' phenomena. The results clearly demonstrate that exposure significantly enhances the bulk (cell cytoplasm) Zn concentration with respect to the physiological level, whereas the effect on the surface (cell membrane) is negligible.

  3. On-line near infrared bioreactor monitoring of cell density and concentrations of glucose and lactate during insect cell cultivation.

    Science.gov (United States)

    Qiu, Jiang; Arnold, Mark A; Murhammer, David W

    2014-03-10

    Near infrared spectroscopy is demonstrated as a suitable method for monitoring real time cell density and concentrations of glucose and lactate during insect cell cultivation. The utility of this approach is illustrated during the cultivation of Trichoplusia ni BTI-Tn-5B1-4 insect cells in a stirred-tank bioreactor. On-line near infrared measurements are made by passing unaltered culture medium through an autoclavable near infrared flow-through sample cell during the cultivation process. Single-beam near infrared spectra were collected over the combination spectral range (5000-4000cm(-1)) through a 1.5mm path length sample. Cell density calibration model was established by uni-variable linear regressions with measured mean absorbance values of on-line spectra collected during a cultivation run. Calibration models are generated for glucose and lactate by regression analysis of both off line and on line spectra collected during a series of pre-measurement cultivation runs. Analyte-specific calibration models are generated by using a combination of spectra from both natural, unaltered samples and samples spiked with known levels of glucose and lactate. Spiked samples are used to destroy concentration correlations between solutes, thereby enhancing the selectivity of the calibration models. Absorbance spectra are used to build partial least squares calibration models for glucose and lactate. The calibration model for cell density corresponds to a univariate linear regression calibration model based on the mean absorbance between 4750 and 4250cm(-1). The standard errors of prediction are 1.54mM, 0.83mM, and 0.38×10(6)cells/mL for the glucose, lactate, and cell density models, respectively.

  4. Location and Density of Immune Cells in Precursor Lesions and Cervical Cancer.

    Science.gov (United States)

    Bedoya, Astrid M; Jaramillo, Roberto; Baena, Armando; Castaño, Jorge; Olaya, Natalia; Zea, Arnold H; Herrero, Rolando; Sanchez, Gloria I

    2013-04-01

    Only a small proportion of women infected with Human Papillomavirus (HPV) develop cervical cancer. Host immune response seems to play a role eliminating the viral infection and preventing progression to cancer. Characterization of tumor infiltrating lymphocytes (TILs) in cervical pre-neoplastic lesions and cervical cancer may be helpful to understand the mechanisms that mediate this protection. The aim of this study was to determine if there are differences in the localization and density (cells/mm(2)) of CD8+ T-cells, CD4+ T-cells and Tregs (CD25 + Foxp3+) in cervical pre-neoplastic lesions and cervical cancer. Immunohistochemical analysis of sections of 96 (26 CIN1, 21 CIN2, 25 CIN3, and 24 SCC) samples revealed that regardless of CIN grades, CD8+ T-cells are more abundant than CD4+, CD25+ and Foxp3+ cells in both the stroma and epithelium. There was a higher density of CD8+ cells in the stroma of cervical cancer compared to CIN3 (OR = 4.20, 95% CI 1.2-15), CIN2 (OR = 7.86, 95% CI 1.7-36.4) and CIN1 (OR = 4.25, 95% CI 1.1-17). Studies evaluating whether these cells are recruited before or after cancer progression will be helpful to understand the role of these cells in the natural history of HPV-induced lesions.

  5. CD44 is the principal cell surface receptor for hyaluronate.

    Science.gov (United States)

    Aruffo, A; Stamenkovic, I; Melnick, M; Underhill, C B; Seed, B

    1990-06-29

    CD44 is a broadly distributed cell surface protein thought to mediate cell attachment to extracelular matrix components or specific cell surface ligands. We have created soluble CD44-immunoglobulin fusion proteins and characterized their reactivity with tissue sections and lymph node high endothelial cells in primary culture. The CD44 target on high endothelial cells is sensitive to enzymes that degrade hyaluronate, and binding of soluble CD44 is blocked by low concentrations of hyaluronate or high concentrations of chondroitin 4- and 6-sulfates. A mouse anti-hamster hyaluonate receptor antibody reacts with COS cells expressing hamster CD44 cDNA. In sections of all tissues examined, including lymph nodes and Peyer's patches, predigestion with hyaluronidase eliminated CD44 binding.

  6. Soluble and cell surface receptors for tumor necrosis factor

    DEFF Research Database (Denmark)

    Wallach, D; Engelmann, H; Nophar, Y

    1991-01-01

    Tumor necrosis factor (TNF) initiates its multiple effects on cell function by binding at a high affinity to specific cell surface receptors. Two different molecular species of these receptors, which are expressed differentially in different cells, have been identified. The cDNAs of both receptor...... have recently been cloned. Antibodies to one of these receptor species (the p55, type I receptor) can trigger a variety of TNF like effects by cross-linking of the receptor molecules. Thus, it is not TNF itself but its receptors that provide the signal for the response to this cytokine...... in certain pathological situations. Release of the soluble receptors from the cells seems to occur by proteolytic cleavage of the cell surface forms and appears to be a way of down-regulating the cell response to TNF. Because of their ability to bind TNF, the soluble receptors exert an inhibitory effect...

  7. Surface modified stainless steels for PEM fuel cell bipolar plates

    Science.gov (United States)

    Brady, Michael P [Oak Ridge, TN; Wang, Heli [Littleton, CO; Turner, John A [Littleton, CO

    2007-07-24

    A nitridation treated stainless steel article (such as a bipolar plate for a proton exchange membrane fuel cell) having lower interfacial contact electrical resistance and better corrosion resistance than an untreated stainless steel article is disclosed. The treated stainless steel article has a surface layer including nitrogen-modified chromium-base oxide and precipitates of chromium nitride formed during nitridation wherein oxygen is present in the surface layer at a greater concentration than nitrogen. The surface layer may further include precipitates of titanium nitride and/or aluminum oxide. The surface layer in the treated article is chemically heterogeneous surface rather than a uniform or semi-uniform surface layer exclusively rich in chromium, titanium or aluminum. The precipitates of titanium nitride and/or aluminum oxide are formed by the nitriding treatment wherein titanium and/or aluminum in the stainless steel are segregated to the surface layer in forms that exhibit a low contact resistance and good corrosion resistance.

  8. Antifouling property of highly oleophobic substrates for solar cell surfaces

    Science.gov (United States)

    Fukada, Kenta; Nishizawa, Shingo; Shiratori, Seimei

    2014-03-01

    Reduction of solar cell conversion efficiency by bird spoor or oil smoke is a common issue. Maintaining the surface of solar cells clean to retain the incident light is of utmost importance. In this respect, there has been growing interest in the area of superhydrophobicity for developing water repelling and self-cleaning surfaces. This effect is inspired by lotus leaves that have micro papillae covered with hydrophobic wax nanostructures. Superhydrophobic surfaces on transparent substrates have been developed for removing contaminants from solar cell surfaces. However, oil cannot be removed by superhydrophobic effect. In contrast, to prevent bird spoor, a highly oleophobic surface is required. In a previous study, we reported transparent-type fabrics comprising nanoparticles with a nano/micro hierarchical structure that ensured both oleophobicity and transparency. In the current study, we developed new highly oleophobic stripes that were constructed into semi-transparent oleophobic surfaces for solar cells. Solar cell performance was successfully maintained; the total transmittance was a key factor for determining conversion efficiency.

  9. Ammonia synthesis over a Ru(0001) surface studied by density functional calculations

    DEFF Research Database (Denmark)

    Logadottir, Ashildur; Nørskov, Jens Kehlet

    2003-01-01

    In this paper we present DFT studies of all the elementary steps in the synthesis of ammonia from gaseous hydrogen and nitrogen over a ruthenium crystal. The stability and configurations of intermediates in the ammonia synthesis over a Ru(0001) surface have been investigated, both over a flat...... surface and over a stepped surface. The calculations show that the step sites on the surface are much more reactive than the terrace sites. The DFT results are then used to study the mechanism of promotion by alkalies over the Ru(0001) and to determine the rate-determining step in the synthesis of ammonia...

  10. Noninvasive prenatal diagnosis. Use of density gradient centrifugation, magnetically activated cell sorting and in situ hybridization

    DEFF Research Database (Denmark)

    Campagnoli, C; Multhaupt, H A; Ludomirski, A;

    1997-01-01

    cells recovered did not differ. Seven of seven male pregnancies were correctly identified. One case of trisomy 21 was detected. CONCLUSION: The in situ hybridization analysis of fetal nucleated erythrocytes isolated from maternal blood using single density gradient centrifugation, anti-CD71/anti...... of the isolated cells were subjected to in situ hybridization with specific DNA probes for the Y chromosome and chromosome 21 to confirm the fetal origin. RESULTS: After MiniMACS the enrichment factors for the CD71/GPA- and CD36/GPA-positive cells from maternal blood were similar, and the percentages of fetal...

  11. Cell-surface expression of Hsp70 on hematopoietic cancer cells after inhibition of HDAC activity

    DEFF Research Database (Denmark)

    Jensen, Helle; Andresen, Lars; Hansen, Karen Aagaard

    , membrane-bound Hsp70 can stimulate antigen presenting cells (APCs) to release proinflammatory cytokines and can provide a target structure for NK cell-mediated lysis. Human cancer cells frequently express Hsp70 on their cell surface, whereas the corresponding normal tissues do not. In addition, several...... clinically applied reagents, such as alkyl-lysophospholipides, chemotherapeutic agents, and anti-inflammatory reagents, have been found to enhance Hsp70 surface expression on cancer cells. We have found that inhibition of histone deacetylase (HDAC) activity leads to surface expression of Hsp70 on various...... hematopoietic cancer cells, an occurance that was not observed on naïve or activated peripheral blood cells. HDAC-inhibitor mediated Hsp70 surface expression was confined to the apoptotic Annexin V positive cells and blocked by inhibition of apoptosis. Other chemotherapeutic inducers of apoptosis...

  12. A density functional theory study of uranium-doped thoria and uranium adatoms on the major surfaces of thorium dioxide

    Science.gov (United States)

    Shields, Ashley E.; Santos-Carballal, David; de Leeuw, Nora H.

    2016-05-01

    Thorium dioxide is of significant research interest for its use as a nuclear fuel, particularly as part of mixed oxide fuels. We present the results of a density functional theory (DFT) study of uranium-substituted thorium dioxide, where we found that increasing levels of uranium substitution increases the covalent nature of the bonding in the bulk ThO2 crystal. Three low Miller index surfaces have been simulated and we propose the Wulff morphology for a ThO2 particle and STM images for the (100), (110), and (111) surfaces studied in this work. We have also calculated the adsorption of a uranium atom and the U adatom is found to absorb strongly on all three surfaces, with particular preference for the less stable (100) and (110) surfaces, thus providing a route to the incorporation of uranium into a growing thoria particle.

  13. The Influence of Surface Morphology of Buffer Layer on the Critical Current Density in YBCO Coated Conductors

    Directory of Open Access Journals (Sweden)

    Jie Xiong

    2013-01-01

    Full Text Available 1 μm-thick YBa2Cu3O7-δ (YBCO films were grown on the Y2O3/yttria stabilized zirconia (YSZ/CeO2 buffer layers with different surface morphologies using direct-current sputtering. The critical current density (Jc value of YBCO was 1.1 MA/cm2 when the root mean square surface roughness (Rrms of the buffer layer was 2.5 nm. As the Rrms of the buffer layer increased to 15 nm, the Jc decreased to 0.3 MA/cm2. X-ray diffraction and scanning electron microscopy showed the strong relevance of the evolution of the structure and surface morphologies of YBCO films with the buffer layer of different Rrms. A model was proposed to explain the influence of surface morphology on the superconducting properties of YBCO films.

  14. Adhesion defective BHK cell mutant has cell surface heparan sulfate proteoglycan of altered properties

    DEFF Research Database (Denmark)

    Couchman, J R; Austria, R; Woods, A;

    1988-01-01

    In the light of accumulating data that implicate cell surface heparan sulfate proteoglycans (HSPGs) with a role in cell interactions with extracellular matrix molecules such as fibronectin, we have compared the properties of these molecules in wild-type BHK cells and an adhesion-defective ricin......-resistant mutant (RicR14). Our results showed that the mutant, unlike BHK cells, cannot form focal adhesions when adherent to planar substrates in the presence of serum. Furthermore, while both cell lines possess similar amounts of cell surface HSPG with hydrophobic properties, that of RicR14 cells had decreased...

  15. Effect of hydroxyapatite surface morphology on cell adhesion.

    Science.gov (United States)

    Iwamoto, Takashi; Hieda, Yohki; Kogai, Yasumichi

    2016-12-01

    We obtained hydroxyapatite (HAp) materials as a block by mixing HAp nanoparticles and polymer, and then calcining the mixtures. The surface morphology of the HAp materials was tuned by varying heat treatment conditions. After calcining the mixtures at 1200 or 800°C for 4h, the surface morphology of the HAp materials was flat or convexo-concave, respectively. The flat surface morphology, which showed micrometer-ordered grain boundaries, was formed by the aggregation of HAp nanoparticles. On the other hand, the convexo-concave surface morphology resulted from the agglomeration of HAp nanoparticles after heat treatment at 800°C for 4h with nanometer-ordered particle size. We tested cell adhesion to HAp materials with flat or convexo-concave surface morphology and found that cells adhered well to the flat HAp materials but not to the convexo-concave HAp materials. This technique for selectively preparing HAp materials with flat or convexo-concave surface morphology was very easy because we merely mixed commercial HAp nanoparticles with polymer and then calcined the mixtures. As a result, the heat treatment temperature affected the surface morphology of our HAp materials, and their surface morphologies contributed to cell adhesion independently of other material properties.

  16. A High Power-Density Mediator-Free Microfluidic Biophotovoltaic Device for Cyanobacterial Cells

    CERN Document Server

    Bombelli, Paolo; Herling, Therese W; Howe, Christopher J; Knowles, Tuomas P J

    2014-01-01

    Biophotovoltaics has emerged as a promising technology for generating renewable energy since it relies on living organisms as inexpensive, self-repairing and readily available catalysts to produce electricity from an abundant resource - sunlight. The efficiency of biophotovoltaic cells, however, has remained significantly lower than that achievable through synthetic materials. Here, we devise a platform to harness the large power densities afforded by miniaturised geometries. To this effect, we have developed a soft-lithography approach for the fabrication of microfluidic biophotovoltaic devices that do not require membranes or mediators. Synechocystis sp. PCC 6803 cells were injected and allowed to settle on the anode, permitting the physical proximity between cells and electrode required for mediator-free operation. We demonstrate power densities of above 100 mW/m2 for a chlorophyll concentration of 100 {\\mu}M under white light, a high value for biophotovoltaic devices without extrinsic supply of additional...

  17. Multi-stage continuous high cell density culture systems: a review.

    Science.gov (United States)

    Chang, Ho Nam; Jung, Kwonsu; Choi, Jin-Dal-Rae; Lee, Joon Chul; Woo, Hee-Chul

    2014-01-01

    A multi-stage continuous high cell density culture (MSC-HCDC) system makes it possible to achieve high productivity together with high product titer of many bioproducts. For long-term continuous operation of MSC-HCDC systems, the cell retention time and hydraulic retention time must be decoupled and strains (bacteria, yeast, plant, and animal cells) must be stable. MSC-HCDC systems are suitable for low-value high-volume extracellular products such as fuel ethanol, lactic acid or volatile fatty acids, and high-value products such as monoclonal antibodies as well as intracellular products such as polyhydroxybutyric acid (PHB), microbial lipids or a number of therapeutics. Better understanding of the fermentation kinetics of a specific product and reliable high-density culture methods for the product-generating microorganisms will facilitate timely industrialization of MSC-HCDC systems for products that are currently obtained in fed-batch bioreactors.

  18. Effective absorption coefficient for graded band-gap semiconductors and the expected photocurrent density in solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Morales-Acevedo, Arturo [CINVESTAV del IPN, Electrical Engineering Department, Avenida IPN No. 2508, 07360 Mexico, D. F. (Mexico)

    2009-01-15

    A simple model for the generation of carriers by photons incident on a (linearly) decreasing band-gap material, such as has been described in recent CIGS solar cells, is developed. The model can be generalized for different cases such as increasing band-gap grading or for having a more complex band-gap profile. The model developed for direct band semiconductors such as CIGS or AlGaAs allows us to define an effective absorption coefficient, so that the ideal photocurrent density can be calculated in a similar manner as for solar cells with non-graded band-gap materials. We show that this model gives completely different results as those expected from intuitive approaches for calculating this ideal photocurrent density. We also show that grading of the band-gap of the absorbing material in solar cells makes the photocurrent less sensitive to the total band-gap change, in such a way that the design of the band-gap variation can be more flexible in order to have other advantages such as higher built-in voltage or higher back surface field in the device structure. (author)

  19. High-Density Array of Well-Ordered HIV-1 Spikes on Synthetic Liposomal Nanoparticles Efficiently Activate B Cells

    Directory of Open Access Journals (Sweden)

    Jidnyasa Ingale

    2016-05-01

    Full Text Available A major step toward an HIV-1 vaccine is an immunogen capable of inducing neutralizing antibodies. Envelope glycoprotein (Env mimetics, such as the NFL and SOSIP designs, generate native-like, well-ordered trimers and elicit tier 2 homologous neutralization (SOSIPs. We reasoned that the display of well-ordered trimers by high-density, particulate array would increase B cell activation compared to soluble trimers. Here, we present the design of liposomal nanoparticles displaying well-ordered Env spike trimers on their surface. Biophysical analysis, cryo- and negative stain electron microscopy, as well as binding analysis with a panel of broadly neutralizing antibodies confirm a high-density, well-ordered trimer particulate array. The Env-trimer-conjugated liposomes were superior to soluble trimers in activating B cells ex vivo and germinal center B cells in vivo. In addition, the trimer-conjugated liposomes elicited modest tier 2 homologous neutralizing antibodies. The trimer-conjugated liposomes represent a promising initial lead toward the development of more effective HIV vaccine immunogens.

  20. Adsorption of Methanol and Methoxy on Cu(111) Surface: A First-principles Periodic Density Functional Theory Study

    Institute of Scientific and Technical Information of China (English)

    CHEN, Wen-Kai; LIU, Shu-Hong; CAO, Mei-Juan; LU, Chun-Hai; XU, Ying; LI, Jun-Qian

    2006-01-01

    Adsorption of methanol and methoxy at four selected sites (top, bridge, hcp, fcc) on Cu(111) surface has been investigated by density functional theory method at the generalized gradient approximation (GGA) level. The calculation on adsorption energies, geometry and electronic structures, Mulliken charges, and vibrational frequencies of CH3OH and CH3O on clean Cu(111) surface was performed with full-geometry optimization, and compared with the experimental data. The obtained results are in agreement with available experimental data. The most favorite adsorption site for methanol on Cu(111) surface is the top site, where C-O axis is tilted to the surface. Moreover,the preferred adsorption site for methoxy on Cu(111) surface is the fcc site, and it adsorbs in an upright geometry with pseudo-C3v local symmetry. Possible decomposition pathways also have been investigated by transition-state searching methods. Methoxy radical, CH3O, was found to be the decomposition intermediate. Methanol can be adsorbed on the surface with its oxygen atom directly on a Cu atom, and weakly chemisorbed on Cu(111) surface. In contrast to methanol, methoxy is strongly chemisorbed to the surface.

  1. Surface modification of closed plastic bags for adherent cell cultivation

    Science.gov (United States)

    Lachmann, K.; Dohse, A.; Thomas, M.; Pohl, S.; Meyring, W.; Dittmar, K. E. J.; Lindenmeier, W.; Klages, C.-P.

    2011-07-01

    In modern medicine human mesenchymal stem cells are becoming increasingly important. However, a successful cultivation of this type of cells is only possible under very specific conditions. Of great importance, for instance, are the absence of contaminants such as foreign microbiological organisms, i.e., sterility, and the chemical functionalization of the ground on which the cells are grown. As cultivation of these cells makes high demands, a new procedure for cell cultivation has been developed in which closed plastic bags are used. For adherent cell growth chemical functional groups have to be introduced on the inner surface of the plastic bag. This can be achieved by a new, atmospheric-pressure plasma-based method presented in this paper. The method which was developed jointly by the Fraunhofer IST and the Helmholtz HZI can be implemented in automated equipment as is also shown in this contribution. Plasma process gases used include helium or helium-based gas mixtures (He + N2 + H2) and vapors of suitable film-forming agents or precursors such as APTMS, DACH, and TMOS in helium. The effect of plasma treatment is investigated by FTIR-ATR spectroscopy as well as surface tension determination based on contact angle measurements and XPS. Plasma treatment in nominally pure helium increases the surface tension of the polymer foil due to the presence of oxygen traces in the gas and oxygen diffusing through the gas-permeable foil, respectively, reacting with surface radical centers formed during contact with the discharge. Primary amino groups are obtained on the inner surface by treatment in mixtures with nitrogen and hydrogen albeit their amount is comparably small due to diffusion of oxygen through the gas-permeable bag, interfering with the plasma-amination process. Surface modifications introducing amino groups on the inner surface turned out to be most efficient in the promotion of cell growth.

  2. Optimal Density Profile of the Plasma Layer Shielded by a Conducting Surface for the Absorption of Electromagnetic Waves

    Institute of Scientific and Technical Information of China (English)

    王舸; 曹金祥; 宋法伦

    2003-01-01

    Based on the Born approximation, we reduce the approximate analysis solution to the normal and oblique incident electromagnetic wave scattering from the weakly ionized plasma layer shielded by a conducting surface. The solution is closely related to the density profile of the plasma layer. Employing the self-consistent base function, we yield the optimal density profile for the nonuniform plasma layer with the frequencies of incident electromagnetic waves ranging from 4-10 GHz. Numerical studies illustrate the optimal density profile can "survive" wide ranges of the plasma parameters. Different from the validity condition for the Wenzell-Kramers-Brillouin-Jeffreys (WKBJ) approximation, the Born approximation is feasible even if the scale length is smaller than the wavelength.Therefore, the Born approximation is universal against the scattering problem from the weakly ionized plasma.

  3. The major surface-associated saccharides of Klebsiella pneumoniae contribute to host cell association.

    Directory of Open Access Journals (Sweden)

    Abigail Clements

    Full Text Available Analysing the pathogenic mechanisms of a bacterium requires an understanding of the composition of the bacterial cell surface. The bacterial surface provides the first barrier against innate immune mechanisms as well as mediating attachment to cells/surfaces to resist clearance. We utilised a series of Klebsiella pneumoniae mutants in which the two major polysaccharide layers, capsule and lipopolysaccharide (LPS, were absent or truncated, to investigate the ability of these layers to protect against innate immune mechanisms and to associate with eukaryotic cells. The capsule alone was found to be essential for resistance to complement mediated killing while both capsule and LPS were involved in cell-association, albeit through different mechanisms. The capsule impeded cell-association while the LPS saccharides increased cell-association in a non-specific manner. The electrohydrodynamic characteristics of the strains suggested the differing interaction of each bacterial strain with eukaryotic cells could be partly explained by the charge density displayed by the outermost polysaccharide layer. This highlights the importance of considering not only specific adhesin:ligand interactions commonly studied in adherence assays but also the initial non-specific interactions governed largely by the electrostatic interaction forces.

  4. Holographic fluid with bulk viscosity, perturbation of pressure and energy density at finite cutoff surface in the Einstein gravity

    CERN Document Server

    Hu, Ya-Peng; Wu, Xiao-Ning

    2014-01-01

    Using the gravity/fluid correspondence in our paper, we investigate the holographic fluid at finite cutoff surface in the Einstein gravity. After constructing the first order perturbative solution of the Schwarzschild-AdS black brane solution in the Einstein gravity, we focus on the stress-energy tensor of the dual fluid with transport coefficients at the finite cutoff surface. Besides the pressure and energy density of dual fluid are obtained, the shear viscosity is also obtained. The most important results are that we find that if we adopt different conditions to fix the undetermined parameters contained in the stress-energy tensor of the dual fluid, the pressure and energy density of the dual fluid can be perturbed. Particularly, the bulk viscosity of the dual fluid can also be given in this case.

  5. Influence of Zinc on the Surface Tension, Density and Molar Volume of (Ag-Sneut +Zn Liquid Alloys

    Directory of Open Access Journals (Sweden)

    Gąsior W.

    2016-03-01

    Full Text Available The dilatometric and maximum bubble pressure methods were applied for the measurements of the density and surface tension of liquid (Ag-Sneut +Zn lead-free solders. The experiments were carried out in the temperature range from 515 to 1223 K for the alloys of the zinc concentration equaling 0.01, 0.02, 0.04, 0.05, 0.1 and 0.2 of the mole fraction. It was found that the temperature dependence of both the density and the surface tension could be thought as linear, so they were interpreted by straight line equations. The experimental data of the molar volume of the investigated alloys were described by the polynomial dependent on the composition and temperature.

  6. Development of exosome surface display technology in living human cells.

    Science.gov (United States)

    Stickney, Zachary; Losacco, Joseph; McDevitt, Sophie; Zhang, Zhiwen; Lu, Biao

    2016-03-25

    Surface display technology is an emerging key player in presenting functional proteins for targeted drug delivery and therapy. Although a number of technologies exist, a desirable mammalian surface display system is lacking. Exosomes are extracellular vesicles that facilitate cell-cell communication and can be engineered as nano-shuttles for cell-specific delivery. In this study, we report the development of a novel exosome surface display technology by exploiting mammalian cell secreted nano-vesicles and their trans-membrane protein tetraspanins. By constructing a set of fluorescent reporters for both the inner and outer surface display on exosomes at two selected sites of tetraspanins, we demonstrated the successful exosomal display via gene transfection and monitoring fluorescence in vivo. We subsequently validated our system by demonstrating the expected intracellular partitioning of reporter protein into sub-cellular compartments and secretion of exosomes from human HEK293 cells. Lastly, we established the stable engineered cells to harness the ability of this robust system for continuous production, secretion, and uptake of displayed exosomes with minimal impact on human cell biology. In sum, our work paved the way for potential applications of exosome, including exosome tracking and imaging, targeted drug delivery, as well as exosome-mediated vaccine and therapy.

  7. A cell cycle and nutritional checkpoint controlling bacterial surface adhesion.

    Directory of Open Access Journals (Sweden)

    Aretha Fiebig

    2014-01-01

    Full Text Available In natural environments, bacteria often adhere to surfaces where they form complex multicellular communities. Surface adherence is determined by the biochemical composition of the cell envelope. We describe a novel regulatory mechanism by which the bacterium, Caulobacter crescentus, integrates cell cycle and nutritional signals to control development of an adhesive envelope structure known as the holdfast. Specifically, we have discovered a 68-residue protein inhibitor of holdfast development (HfiA that directly targets a conserved glycolipid glycosyltransferase required for holdfast production (HfsJ. Multiple cell cycle regulators associate with the hfiA and hfsJ promoters and control their expression, temporally constraining holdfast development to the late stages of G1. HfiA further functions as part of a 'nutritional override' system that decouples holdfast development from the cell cycle in response to nutritional cues. This control mechanism can limit surface adhesion in nutritionally sub-optimal environments without affecting cell cycle progression. We conclude that post-translational regulation of cell envelope enzymes by small proteins like HfiA may provide a general means to modulate the surface properties of bacterial cells.

  8. The role of oxygen in yeast metabolism during high cell density brewery fermentations.

    Science.gov (United States)

    Verbelen, P J; Saerens, S M G; Van Mulders, S E; Delvaux, F; Delvaux, F R

    2009-04-01

    The volumetric productivity of the beer fermentation process can be increased by using a higher pitching rate (i.e., higher inoculum size). However, the decreased yeast net growth observed in these high cell density fermentations can have a negative impact on the physiological stability throughout subsequent yeast generations. The use of different oxygen conditions (wort aeration, wort oxygenation, yeast preoxygenation) was investigated to improve the growth yield during high cell density fermentations and yeast metabolic and physiological parameters were assessed systematically. Together with a higher extent of growth (dependent on the applied oxygen conditions), the fermentation power and the formation of unsaturated fatty acids were also affected. Wort oxygenation had a significant decreasing effect on the formation of esters, which was caused by a decreased expression of the alcohol acetyl transferase gene ATF1, compared with the other conditions. Lower glycogen and trehalose levels at the end of fermentation were observed in case of the high cell density fermentations with oxygenated wort and the reference fermentation. The expression levels of BAP2 (encoding the branched chain amino acid permease), ERG1 (encoding squalene epoxidase), and the stress responsive gene HSP12 were predominantly influenced by the high cell concentrations, while OLE1 (encoding the fatty acid desaturase) and the oxidative stress responsive genes SOD1 and CTT1 were mainly affected by the oxygen availability per cell. These results demonstrate that optimisation of high cell density fermentations could be achieved by improving the oxygen conditions, without drastically affecting the physiological condition of the yeast and beer quality.

  9. An analysis of the impact of native oxide, surface contamination and material density on total electron yield in the absence of surface charging effects

    Science.gov (United States)

    Iida, Susumu; Ohya, Kaoru; Hirano, Ryoichi; Watanabe, Hidehiro

    2016-10-01

    The effects of the presence of a native oxide film or surface contamination as well as variations in material density on the total electron yield (TEY) of Ru and B4C were assessed in the absence of any surface charging effect. The experimental results were analyzed using semi-empirical Monte Carlo simulations and demonstrated that a native oxide film increased the TEY, and that this effect varied with film thickness. These phenomena were explained based on the effect of the backscattered electrons (BSEs) at the interface between Ru and RuO2, as well as the lower potential barrier of RuO2. Deviations in the material density from the theoretical values were attributed to the film deposition procedure based on fitting simulated TEY curves to experimental results. In the case of B4C, the TEY was enhanced by the presence of a 0.8-nm-thick surface contamination film consisting of oxygenated hydrocarbons. The effect of the low potential barrier of the contamination film was found to be significant, as the density of the B4C was much lower than that of the Ru. Comparing the simulation parameters generated in the present work with Joy's database, it was found that the model and the input parameters used in the simulations were sufficiently accurate.

  10. Comparison of the surface ion density of silica gel evaluated via spectral induced polarization versus acid-base titration

    Science.gov (United States)

    Hao, Na; Moysey, Stephen M. J.; Powell, Brian A.; Ntarlagiannis, Dimitrios

    2016-12-01

    Surface complexation models are widely used with batch adsorption experiments to characterize and predict surface geochemical processes in porous media. In contrast, the spectral induced polarization (SIP) method has recently been used to non-invasively monitor in situ subsurface chemical reactions in porous media, such as ion adsorption processes on mineral surfaces. Here we compare these tools for investigating surface site density changes during pH-dependent sodium adsorption on a silica gel. Continuous SIP measurements were conducted using a lab scale column packed with silica gel. A constant inflow of 0.05 M NaCl solution was introduced to the column while the influent pH was changed from 7.0 to 10.0 over the course of the experiment. The SIP measurements indicate that the pH change caused a 38.49 ± 0.30 μS cm- 1 increase in the imaginary conductivity of the silica gel. This increase is thought to result from deprotonation of silanol groups on the silica gel surface caused by the rise in pH, followed by sorption of Na+ cations. Fitting the SIP data using the mechanistic model of Leroy et al. (Leroyet al., 2008), which is based on the triple layer model of a mineral surface, we estimated an increase in the silica gel surface site density of 26.9 × 1016 sites m- 2. We independently used a potentiometric acid-base titration data for the silica gel to calibrate the triple layer model using the software FITEQL and observed a total increase in the surface site density for sodium sorption of 11.2 × 1016 sites m- 2, which is approximately 2.4 times smaller than the value estimated using the SIP model. By simulating the SIP response based on the calibrated surface complexation model, we found a moderate association between the measured and estimated imaginary conductivity (R2 = 0.65). These results suggest that the surface complexation model used here does not capture all mechanisms contributing to polarization of the silica gel captured by the SIP data.

  11. Quantum dot density studies for quantum dot intermediate band solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Thomassen, Sedsel Fretheim; Zhou, Dayong; Vitelli, Stefano; Mayani, Maryam Gholami; Fimland, Bjoern-Ove; Reenaas, Turid Worren

    2010-07-01

    Quantum dots (QDs) have been an active area of research for many years and have been implemented in several applications, such as lasers and detectors. During the last years, some attempts have been made to increase the absorption and efficiency of solar cells by inserting QDs into the intrinsic region of pin solar cells. So far, these attempts have been successful in increasing the absorption, but not the cell efficiency. There are probably several reasons for this lack of efficiency increase, but we believe that one important reason is the low density of the implemented QDs. In this work, samples of single layer InAs QDs on n-GaAs(001) substrates have been grown by molecular beam epitaxy (MBE) and we have performed a systematic study of how deposition parameters affect the QD density. The aim is to achieve densities > 1011 cm-2. The nominal substrate temperature (360 - 500 deg. C), the InAs growth rate (0.085 - 1 ML/s) and thickness (2.0 - 2.8 ML) have been varied in a systematic way for two different deposition methods of InAs, i.e. continuous deposition or deposition with interruptions. In addition, we have for the continuous growth samples also varied the As-flux (0.5 - 6 centre dot10-6 torr). Scanning electron microscopy (SEM) has been the main characterization method to determine quantum dot sizes and densities, and atomic force microscopy (AFM) has been used for evaluation of the quantum dot heights. We find that the QD density increases with reduced growth temperature and that it is higher for samples grown continuously than for samples grown with growth interruptions. The homogeneity is also strongly affected by temperature, InAs deposition method and the As-flux. We have observed QD densities as high as 2.5 centre dot1011 cm-2 for the samples grown at the lowest growth temperatures. (Author)

  12. The reasons for the high power density of fuel cells fabricated with directly deposited membranes

    Science.gov (United States)

    Vierrath, Severin; Breitwieser, Matthias; Klingele, Matthias; Britton, Benjamin; Holdcroft, Steven; Zengerle, Roland; Thiele, Simon

    2016-09-01

    In a previous study, we reported that polymer electrolyte fuel cells prepared by direct membrane deposition (DMD) produced power densities in excess of 4 W/cm2. In this study, the underlying origins that give rise to these high power densities are investigated and reported. The membranes of high power, DMD-fabricated fuel cells are relatively thin (12 μm) compared to typical benchmark, commercially available membranes. Electrochemical impedance spectroscopy, at high current densities (2.2 A/cm2) reveals that mass transport resistance was half that of reference, catalyst-coated-membranes (CCM). This is attributed to an improved oxygen supply in the cathode catalyst layer by way of a reduced propensity of flooding, and which is facilitated by an enhancement in the back diffusion of water from cathode to anode through the thin directly deposited membrane. DMD-fabricated membrane-electrode-assemblies possess 50% reduction in ionic resistance (15 mΩcm2) compared to conventional CCMs, with contributions of 9 mΩcm2 for the membrane resistance and 6 mΩcm2 for the contact resistance of the membrane and catalyst layer ionomer. The improved mass transport is responsible for 90% of the increase in power density of the DMD fuel cell, while the reduced ionic resistance accounts for a 10% of the improvement.

  13. Constructing multi-scale gravitational energy spectra from molecular cloud surface density PDF -- Interplay between turbulence and gravity

    CERN Document Server

    Li, Guang-Xing

    2016-01-01

    Gravity is believed to be important on multiple physical scales in molecular clouds. However, quantitative constraints on gravity are still lacking. We derive an analytical formula which provides estimates on multi-scale gravitational energy distribution using the observed surface density PDF. Our analytical formalism also enables one to convert the observed column density PDF into an estimated volume density PDF, and to obtain average radial profile $\\rho(r)$. For a region with $N_{\\rm col} \\sim N^{-\\gamma_{\\rm N}}$, the gravitational energy spectra is $E_{\\rm p}(k)\\sim k^{-4(1 - 1/\\gamma_{\\rm N})}$. We apply the formula to observations of molecular clouds, and find that a scaling index of $-2$ of the surface density PDF implies that $\\rho \\sim r^{-2}$ and $E_{\\rm p}(k) \\sim k^{-2}$. This indicates that gravity can act effectively against turbulence over a multitude of physical scales. This is the critical scaling index which divides molecular clouds into two categories: clouds like Orion and Ophiuchus have ...

  14. Cell surface differences of Naegleria fowleri and Naegleria lovaniensis exposed with surface markers.

    Science.gov (United States)

    González-Robles, Arturo; Castañón, Guadalupe; Cristóbal-Ramos, Ana Ruth; Hernández-Ramírez, Verónica Ivonne; Omaña-Molina, Maritza; Martínez-Palomo, Adolfo

    2007-12-01

    Differences in the distribution of diverse cell surface coat markers were found between Naegleria fowleri and Naegleria lovaniensis. The presence of carbohydrate-containing components in the cell coat of the two species was detected by selective staining with ruthenium red and alcian blue. Using both markers, N. fowleri presented a thicker deposit than N. lovaniensis. The existence of exposed mannose or glucose residues was revealed by discriminatory agglutination with the plant lectin Concanavalin A. These sugar residues were also visualized at the cell surface of these parasites either by transmission electron microscopy or by fluorescein-tagged Concanavalin A. Using this lectin cap formation was induced only in N. fowleri. The anionic sites on the cell surface detected by means of cationized ferritin were more apparent in N. fowleri. Biotinylation assays confirmed that even though the two amoebae species have some analogous plasma membrane proteins, there is a clear difference in their composition.

  15. Experimental (electrochemistry) and theoretical (ab initio and density functional theory) studies of hydrogen and sulfide adsorption on palladium (100) surface.

    OpenAIRE

    2001-01-01

    The adsorption of H And S2- species on Pd (100) has been studied with ab initio, density-functional calculations and electrochemical methods. A cluster of five Pd atoms with a frozen geometry described the surface. The computational calculations were performed through the GAUSSIAN94 program, and the basis functions adapted to a pseudo-potential obtained by using the Generator Coordinate Method adapted to the this program. Using the cyclic voltammetry technique through a Model 283 Potentiostat...

  16. Infrared spectroscopy and density functional theory investigation of calcite, chalk, and coccoliths-do we observe the mineral surface?

    DEFF Research Database (Denmark)

    Andersson, Martin Peter; Hem, Caroline Piper; Schultz, Logan Nicholas

    2014-01-01

    broadening from macroscopic dielectric effects. We detect water adsorbed on the high surface area synthetic calcite, which permits observation of the chemistry of thin liquid films on calcite using transmission infrared spectroscopy. The combination of infrared spectroscopy and density functional theory also...... allowed us to quantify the amount of polysaccharides associated with the coccoliths. The amount of polysaccharides left in chalk, demonstrated to be present in other work, is below the IR detection limit, which is 0.5% by mass....

  17. Structures and energies of Cu clusters on Fe and Fe3C surfaces from density functional theory computation.

    Science.gov (United States)

    Tian, Xinxin; Wang, Tao; Yang, Yong; Li, Yong-Wang; Wang, Jianguo; Jiao, Haijun

    2014-12-28

    Spin-polarized density functional theory computations have been carried out to study the stable adsorption configurations of Cun (n = 1-7, 13) on Fe and Fe3C surfaces for understanding the initial stages of copper promotion in catalysis. At low coverage, two-dimensional aggregation is more preferred over dispersion and three-dimensional aggregation on the Fe(110) and Fe(100) surfaces as well as the metallic Fe3C(010) surfaces, while dispersion is more favorable over aggregation on the Fe(111) surface. On the Fe3C(001) and Fe3C(100) surfaces with exposed iron and carbon atoms, the adsorbed Cu atoms prefer dispersion at low coverage, while aggregation along the iron regions at high coverage. On the iron surfaces, the adsorption energies of Cun (n = 2-7) are highest on Fe(111), medium on Fe(100) and lowest on Fe(110). On the Fe3C surfaces, the adsorption energies of Cun (n = 1-3) are highest on Fe3C(100), medium on Fe3C(010) and lowest on Fe3C(001), while, for n = 4-7 and 13, Fe3C(010) has stronger adsorption than Fe3C(100). On the basis of their differences in electronegativity, the adsorbed Cu atoms can oxidize the metallic Fe(110), Fe(100) and Fe3C(010) surfaces and become negatively charged. On the Fe3C(001) and Fe3C(100) surfaces with exposed iron and carbon atoms, the adsorbed Cu atoms interacting with surface carbon atoms are oxidized and positively charged. Unlike the most stable Fe(110) and Fe3C(001) surfaces, where the Fe(110) surface has stronger Cu affinity than the Fe3C(001) surface, which is in agreement with the experimental finding, the less and least stable Fe3C(010) and Fe3C(100) surfaces have stronger Cu affinities than the Fe(110) and Fe(100) surfaces. Since less stable facets are not preferably formed thermodynamically, it is crucial to prepare such surfaces to explore Cu adsorption and promotion, and this provides challenges to surface sciences.

  18. High-Temperature Alkali Vapor Cells with Anti-Relaxation Surface Coatings

    CERN Document Server

    Seltzer, S J

    2009-01-01

    Anti-relaxation surface coatings allow long spin relaxation times in alkali-metal cells without buffer gas, enabling free motion of the alkali atoms and giving larger signals due to narrower optical linewidths. Effective coatings were previously unavailable for operation at temperatures above 80 C. We demonstrate that octadecyltrichlorosilane (OTS) can allow potassium or rubidium atoms to experience hundreds of collisions with the cell surface before depolarizing, and that an OTS coating remains effective up to about 170 C for both potassium and rubidium. We consider the experimental concerns of operating without buffer gas at high vapor density, studying the stricter need for effective quenching of excited atoms and deriving the optical rotation signal shape for atoms with resolved hyperfine structure in the spin-temperature regime. As an example of a high-temperature application of anti-relaxation coated alkali vapor cells, we operate a spin-exchange relaxation-free (SERF) atomic magnetometer with sensitivi...

  19. Analysis of charge photogeneration as a key determinant of photocurrent density in polymer: fullerene solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Clarke, Tracey M.; Shoaee, Safa; Soon, Ying W.; Durrant, James R. [Centre for Plastic Electronics, Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Ballantyne, Amy; Nelson, Jenny [Centre for Plastic Electronics, Department of Physics, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Duffy, Warren; Heeney, Martin; McCulloch, Iain [Centre for Plastic Electronics, Department of Chemistry, Imperial College London, Exhibition Road, London SW7 2AZ (United Kingdom); Merck Chemicals, Chilworth Science Park, Southampton SO16 7QD (United Kingdom)

    2010-12-07

    Charge photogeneration: The correlation between the efficiency of photogeneration of dissociated polarons and photocurrent densities for organic solar cells based on polymer:fullerene blend films is investigated. Optical assays of polaron yield measured in films without electrodes show a remarkably clear correlation with short circuit density and quantum yield measured in complete devices. For the blend films studied herein, the primary determinant of photocurrent generation is the efficiency of dissociation of photogenerated charges away from the polymer/fullerene interface and the primary loss pathway is geminate recombination. (Copyright copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Effective dielectric properties of biological cells: generalization of the spectral density function approach.

    Science.gov (United States)

    Goncharenko, Anatoliy V; Chang, Yia-Chung

    2009-07-23

    We suggest an extension of the spectral density function approach to describe the complex dielectric response of suspensions of arbitrarily shaped particles having a thin shell, in particular, biological cells. The approach is shown to give analytical results in some simple but practically important cases. In the general case, for the 3-phase systems it reduces to determination of the spectral density function for the suspension of a certain kind. Prospects and limitations of the approach, as well as practical examples, are also considered.

  1. Atomic hydrogen adsorption and incipient hydrogenation of the Mg(0001) surface: a density-functional theory study.

    Science.gov (United States)

    Li, Yanfang; Zhang, Ping; Sun, Bo; Yang, Yu; Wei, Yinghui

    2009-07-21

    We investigate the atomic hydrogen adsorption on Mg(0001) by using density-functional theory within the generalized gradient approximation and a supercell approach. The coverage dependence of the adsorption structures and energetics is systematically studied for a wide range of coverage Theta [from 0.11 to 2.0 monolayers (ML)] and adsorption sites. In the coverage range 0 atomic hydrogen as well as the activation barriers for hydrogen penetration from the on-surface to the subsurface sites are also presented at low coverage. At high coverage of 1.0 < Theta < or = 2.0, it is found that the coadsorption configuration with 1.0 monolayer of H residing on the surface fcc sites and the remaining (Theta-1.0) monolayer of H occupying the subsurface tetra-I sites is most energetically favorable. The resultant H-Mg-H sandwich structure for this most stable coadsorption configuration displays similar spectral features to the bulk hydride MgH(2) in the density of states. The other properties of the H/Mg(0001) system including the charge distribution, the lattice relaxation, the work function, and the electronic density of states are also studied and discussed in detail. It is pointed out that the H-Mg chemical bonding during surface hydrogenation displays a mixed ionic/covalent character.

  2. Do galaxy global relationships emerge from local ones? The SDSS IV MaNGA surface mass density-metallicity relation

    CERN Document Server

    Barrera-Ballesteros, Jorge K; Zhu, Guangtun B; Zakamska, Nadia L; Sánchez, Sebastian F; Law, David; Wake, David; Green, Jenny E; Bizyaev, Dmitry; Oravetz, Daniel; Simmons, Audrey; Malanushenko, Elena; Pan, Kaike; Lopes, Alexandre Roman; Lane, Richard R

    2016-01-01

    We present the stellar surface mass density {\\it vs.} gas metallicity ($\\Sigma_*-Z$) relation for more than 500,000 spatially-resolved star-forming resolution elements (spaxels) from a sample of 653 disk galaxies included in the SDSS IV MaNGA survey. We find a tight relation between these local properties, with higher metallicities as the surface density increases. This relation extends over three orders of magnitude in the surface mass density and a factor of four in metallicity. We show that this local relationship can simultaneously reproduce two well-known properties of disk galaxies: their global mass-metallicity relationship {\\it and} their radial metallicity gradients. We also find that the $\\Sigma_* - Z$ relation is largely independent of the galaxy's total stellar mass and specific star-formation rate (sSFR), except at low stellar mass and high sSFR. These results suggest that in the present-day universe local properties play a key role in determining the gas-phase metallicity in typical disk galaxie...

  3. Mass balance of the Greenland ice sheet – a study of ICESat data, surface density and firn compaction modelling

    Directory of Open Access Journals (Sweden)

    L. S. Sørensen

    2010-10-01

    Full Text Available ICESat has provided surface elevation measurements of the ice sheets since the launch in January 2003, resulting in a unique data set for monitoring the changes of the cryosphere. Here we present a novel method for determining the mass balance of the Greenland ice sheet derived from ICESat altimetry data.

    Four different methods for deriving the elevation changes from the ICESat altimetry data set are used. This multi method approach gives an understanding of the complexity associated with deriving elevation changes from the ICESat altimetry data set.

    The altimetry can not stand alone in estimating the mass balance of the Greenland ice sheet. We find firn dynamics and surface densities to be important factors in deriving the mass loss from remote sensing altimetry. The volume change derived from ICESat data is corrected for firn compaction, vertical bedrock movement and an intercampaign elevation bias in the ICESat data. Subsequently, the corrected volume change is converted into mass change by surface density modelling. The firn compaction and density models are driven by a dynamically downscaled simulation of the HIRHAM5 regional climate model using ERA-Interim reanalysis lateral boundary conditions.

    We find an annual mass loss of the Greenland ice sheet of 210 ± 21 Gt yr−1 in the period from October 2003 to March 2008. This result is in good agreement with other studies of the Greenland ice sheet mass balance, based on different remote sensing techniques.

  4. Density functionals for surface science: Exchange-correlation model development with Bayesian error estimation

    DEFF Research Database (Denmark)

    Wellendorff, Jess; Lundgård, Keld Troen; Møgelhøj, Andreas

    2012-01-01

    A methodology for semiempirical density functional optimization, using regularization and cross-validation methods from machine learning, is developed. We demonstrate that such methods enable well-behaved exchange-correlation approximations in very flexible model spaces, thus avoiding the overfit...

  5. Cell patterning on polylactic acid through surface-tethered oligonucleotides.

    Science.gov (United States)

    Matsui, Toshiki; Arima, Yusuke; Takemoto, Naohiro; Iwata, Hiroo

    2015-02-01

    Polylactic acid (PLA) is a candidate material to prepare scaffolds for 3-D tissue regeneration. However, cells do not adhere or proliferate well on the surface of PLA because it is hydrophobic. We report a simple and rapid method for inducing cell adhesion to PLA through DNA hybridization. Single-stranded DNA (ssDNA) conjugated to poly(ethylene glycol) (PEG) and to a terminal phospholipid (ssDNA-PEG-lipid) was used for cell surface modification. Through DNA hybridization, modified cells were able to attach to PLA surfaces modified with complementary sequence (ssDNA'). Different cell types can be attached to PLA fibers and films in a spatially controlled manner by using ssDNAs with different sequences. In addition, they proliferate well in a culture medium supplemented with fetal bovine serum. The coexisting modes of cell adhesion through DNA hybridization and natural cytoskeletal adhesion machinery revealed no serious effects on cell growth. The combination of a 3-D scaffold made of PLA and cell immobilization on the PLA scaffold through DNA hybridization will be useful for the preparation of 3-D tissue and organs.

  6. Low Density Lipoprotein Receptor Related Proteins as Regulators of Neural Stem and Progenitor Cell Function

    Directory of Open Access Journals (Sweden)

    Loic Auderset

    2016-01-01

    Full Text Available The central nervous system (CNS is a highly organised structure. Many signalling systems work in concert to ensure that neural stem cells are appropriately directed to generate progenitor cells, which in turn mature into functional cell types including projection neurons, interneurons, astrocytes, and oligodendrocytes. Herein we explore the role of the low density lipoprotein (LDL receptor family, in particular family members LRP1 and LRP2, in regulating the behaviour of neural stem and progenitor cells during development and adulthood. The ability of LRP1 and LRP2 to bind a diverse and extensive range of ligands, regulate ligand endocytosis, recruit nonreceptor tyrosine kinases for direct signal transduction and signal in conjunction with other receptors, enables them to modulate many crucial neural cell functions.

  7. Fabrication of endothelial progenitor cell capture surface via DNA aptamer modifying dopamine/polyethyleneimine copolymer film

    Science.gov (United States)

    Li, Xin; Deng, Jinchuan; Yuan, Shuheng; Wang, Juan; Luo, Rifang; Chen, Si; Wang, Jin; Huang, Nan

    2016-11-01

    Endothelial progenitor cells (EPCs) are mainly located in bone marrow and circulate, and play a crucial role in repairmen of injury endothelium. One of the most promising strategies of stents designs were considered to make in-situ endothelialization in vivo via EPC-capture biomolecules on a vascular graft to capture EPCs directly from circulatory blood. In this work, an EPC specific aptamer with a 34 bases single strand DNA sequence was conjugated onto the stent surface via dopamine/polyethyleneimine copolymer film as a platform and linker. The assembled density of DNA aptamer could be regulated by controlling dopamine percentage in this copolymer film. X-ray photoelectron spectroscopy (XPS), water contact angle (WCA) and fluorescence test confirmed the successful immobilization of DNA aptamer. To confirm its biofunctionality and cytocompatibility, the capturing cells ability of the aptamer modified surface and the effects on the growth behavior of human umbilical vein endothelial cells (HUVECs), smooth muscle cells (SMCs) were investigated. The aptamer functionalized sample revealed a good EPC-capture ability, and had a cellular friendly feature for both EPC and EC growth, while not stimulated the hyperplasia of SMCs. And, the co-culture experiment of three types of cells confirmed the specificity capturing of EPCs to aptamer modified surface, rather than ECs and SMCs. These data suggested that this aptamer functionalized surface may have a large potentiality for the application of vascular grafts with targeted endothelialization.

  8. Fabrication of endothelial progenitor cell capture surface via DNA aptamer modifying dopamine/polyethyleneimine copolymer film

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xin; Deng, Jinchuan; Yuan, Shuheng; Wang, Juan; Luo, Rifang; Chen, Si [Key Lab. of Advanced Technology for Materials of Education Ministry, Southwest Jiaotong University, Chengdu 610031 (China); School of Material Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China); Wang, Jin, E-mail: jinxxwang@263.net [Key Lab. of Advanced Technology for Materials of Education Ministry, Southwest Jiaotong University, Chengdu 610031 (China); Huang, Nan [Key Lab. of Advanced Technology for Materials of Education Ministry, Southwest Jiaotong University, Chengdu 610031 (China); School of Material Science and Engineering, Southwest Jiaotong University, Chengdu 610031 (China)

    2016-11-15

    Highlights: • The dopamine/PEI film with controlled amine density was successfully prepared. • The DNA aptamer was assembled onto the film via electrostatic incorporation. • The A@DPfilmscanspecificallyandeffectivelycaptureEPCs. • The A@DP film can support the survival of ECs, control the hyperplasia of SMCs. • The dynamic/co-culture models are useful for studying cells competitive adhesion. - Abstract: Endothelial progenitor cells (EPCs) are mainly located in bone marrow and circulate, and play a crucial role in repairmen of injury endothelium. One of the most promising strategies of stents designs were considered to make in-situ endothelialization in vivo via EPC-capture biomolecules on a vascular graft to capture EPCs directly from circulatory blood. In this work, an EPC specific aptamer with a 34 bases single strand DNA sequence was conjugated onto the stent surface via dopamine/polyethyleneimine copolymer film as a platform and linker. The assembled density of DNA aptamer could be regulated by controlling dopamine percentage in this copolymer film. X-ray photoelectron spectroscopy (XPS), water contact angle (WCA) and fluorescence test confirmed the successful immobilization of DNA aptamer. To confirm its biofunctionality and cytocompatibility, the capturing cells ability of the aptamer modified surface and the effects on the growth behavior of human umbilical vein endothelial cells (HUVECs), smooth muscle cells (SMCs) were investigated. The aptamer functionalized sample revealed a good EPC-capture ability, and had a cellular friendly feature for both EPC and EC growth, while not stimulated the hyperplasia of SMCs. And, the co-culture experiment of three types of cells confirmed the specificity capturing of EPCs to aptamer modified surface, rather than ECs and SMCs. These data suggested that this aptamer functionalized surface may have a large potentiality for the application of vascular grafts with targeted endothelialization.

  9. Hepatic Bel-7402 Cell Proliferation on Different Phospholipid Surfaces

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Phospholipids are believed to be important biomaterials.However, limited information is available on their cytocompatibilities.The objective of this study is to evaluate the effects of different phospholipids on the proliferation of hepatic Bel-7402 cells by comparing the adhesion, viability and proliferation of Bel-7402 cells cultured on different phospholipid surfaces.The cell adhesion, determined by counting the number of adhered cells to the surface, indicated that the cell adhesion was enhanced on charged phospolipid membranes.The cell viability evaluated by MTT[3 (4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium-bromide] showed that cells cultured on charged phospholipids have greater viability than those cultured on the control, while cells cultured on neutral phospholipids showed lower viability.The cell cycle analysis using flow cytometry demonstrated that S phase entry increased on charged phospholipids, while S phase entry decreased on neutral phospholipids.The results suggested that charged phospholipids, especially positively charged phospholipids, show better cytocompatibilities than neutral phospholipids to hepatic Bel-7402 cell.

  10. Nanoscale mechanical and tribological properties of fluorocarbon films grafted onto plasma-treated low-density polyethylene surfaces

    Science.gov (United States)

    Cheng, Q.; Komvopoulos, K.

    2012-03-01

    Fluorocarbon (FC) films were grafted onto Ar plasma-treated low-density polyethylene (LDPE) surfaces by plasma polymerization and deposition. The evolution of the surface morphology of the grafted FC films was investigated at different scales with an atomic force microscope. Nanoscale sliding experiments performed with a surface force microscope provided insight into the nanotribological properties of Ar plasma-treated LDPE, with and without grafted FC films, in terms of applied normal load and number of sliding cycles. The observed trends are explained in the context of microstructure models accounting for morphological and structure changes at the LDPE surface due to the effects of plasma treatment (e.g., selective etching of amorphous phase, chain crosslinking and FC film grafting) and surface sliding (e.g., crystalline lamellae alignment along the sliding direction). Nanoindentation experiments elucidated the effect of plasma treatment on surface viscoelasticity and global contact stiffness. The results of this study demonstrate that plasma-assisted grafting of FC films is an effective surface modification method for tuning the nanomechanical/tribological properties of polymers.

  11. Adsorption of SF6 decomposed gas on anatase (101) and (001) surfaces with oxygen defect: a density functional theory study.

    Science.gov (United States)

    Zhang, Xiaoxing; Chen, Qinchuan; Tang, Ju; Hu, Weihua; Zhang, Jinbin

    2014-04-23

    The detection of partial discharge by analyzing the components of SF6 gas in gas-insulated switchgears is important to the diagnosis and assessment of the operational state of power equipment. A gas sensor based on anatase TiO2 is used to detect decomposed gases in SF6. In this paper, first-principle density functional theory calculations are adopted to analyze the adsorption of SO2, SOF2, and SO2F2, the primary decomposition by-products of SF6 under partial discharge, on anatase (101) and (001) surfaces. Simulation results show that the perfect anatase (001) surface has a stronger interaction with the three gases than that of anatase (101), and both surfaces are more sensitive and selective to SO2 than to SOF2 and SO2F2. The selection of a defect surface to SO2, SOF2, and SO2F2 differs from that of a perfect surface. This theoretical result is corroborated by the sensing experiment using a TiO2 nanotube array (TNTA) gas sensor. The calculated values are analyzed to explain the results of the Pt-doped TNTA gas sensor sensing experiment. The results imply that the deposited Pt nanoparticles on the surface increase the active sites of the surface and the gas molecules may decompose upon adsorption on the active sites.

  12. Hippo signaling regulates microprocessor and links cell-density-dependent miRNA biogenesis to cancer.

    Science.gov (United States)

    Mori, Masaki; Triboulet, Robinson; Mohseni, Morvarid; Schlegelmilch, Karin; Shrestha, Kriti; Camargo, Fernando D; Gregory, Richard I

    2014-02-27

    Global downregulation of microRNAs (miRNAs) is commonly observed in human cancers and can have a causative role in tumorigenesis. The mechanisms responsible for this phenomenon remain poorly understood. Here, we show that YAP, the downstream target of the tumor-suppressive Hippo-signaling pathway regulates miRNA biogenesis in a cell-density-dependent manner. At low cell density, nuclear YAP binds and sequesters p72 (DDX17), a regulatory component of the miRNA-processing machinery. At high cell density, Hippo-mediated cytoplasmic retention of YAP facilitates p72 association with Microprocessor and binding to a specific sequence motif in pri-miRNAs. Inactivation of the Hippo pathway or expression of constitutively active YAP causes widespread miRNA suppression in cells and tumors and a corresponding posttranscriptional induction of MYC expression. Thus, the Hippo pathway links contact-inhibition regulation to miRNA biogenesis and may be responsible for the widespread miRNA repression observed in cancer.

  13. The active translation of MHCII mRNA during dendritic cells maturation supplies new molecules to the cell surface pool.

    Science.gov (United States)

    Malanga, Donatella; Barba, Pasquale; Harris, Paul E; Maffei, Antonella; Del Pozzo, Giovanna

    2007-04-01

    The transition of human dendritic cells (DCs) from the immature to the mature phenotype is characterized by an increased density of MHC class II (MHCII) molecules on the plasma membrane, a key requirement of their competence as professional antigen presenting cells (APCs). MHCII molecules on the cell surface derive from newly synthesized as well as from preexisting proteins. So far, all the studies done on DCs during maturation, to establish the relative contribution of newly synthesized MHCII molecules to the cell surface pool did not produced a clear, unified scenario. We report that, in human DCs stimulated ex vivo with LPS, the changes in the RNA accumulation specific for at least two MHCII genes (HLA-DRA and HLA-DQA1) due to transcriptional upregulation, is associated with the active translation at high rate of these transcripts. Our finding reveals that, across the 24h of the maturation process in human DCs, newly synthesized MHCII proteins are supplied to the APCs cell surface pool.

  14. Cell density and solvent are critical parameters affecting formazan evaluation in MTT assay

    Directory of Open Access Journals (Sweden)

    Kellen Cristina da Silva Gasque

    2014-06-01

    Full Text Available The aim of this study was to establish the more accurate protocol for fibroblast cell viability using MTT assay. NIH/3T3 fibroblasts were seeded at the following cell densities: 3.125x10³; 1.156x10(4; 3.125x10(4; 1.156x10(5 and 3.125x10(5 cells/cm². Following 24h of seeding, MTT was added to the wells. After 4h of the MTT addition, different solvents were added to solubilize the formazan crystals: 1 HCl/SDS group- 20% SDS and 0.01 M HCl; 2 EtOH/ HAc group-50% ethanol and 1% acetic acid; 3 DMSO group- 99.5% dimethyl sulfoxide; and 4 PropOH group- 99.5% isopropanol. The absorbance values were measured using a spectrophotometer at 570 nm. The data were analyzed by 2-way ANOVA (p<0.05 and showed that the absorbance average varied according to the number of cells and solvents: HCl/SDS (0 to 0.13, EtOH/HAc (0 to 0.22, DMSO (0.76 to 1.31 and PropOH (0.66 to 1.04. The DMSO and PropOH groups presented the most appropriate protocols for NIH/3T3 fibroblasts cell viability, especially at the density of 1.156x10(4 cells/cm².

  15. Longitudinal microarray analysis of cell surface antigens on peripheral blood mononuclear cells from HIV+ individuals on highly active antiretroviral therapy

    Directory of Open Access Journals (Sweden)

    Wang Bin

    2008-03-01

    Full Text Available Abstract Background The efficacy of highly active antiretroviral therapy (HAART determined by simultaneous monitoring over 100 cell-surface antigens overtime has not been attempted. We used an antibody microarray to analyze changes in the expression of 135 different cell-surface antigens overtime on PBMC from HIV+ patients on HAART. Two groups were chosen, one (n = 6 achieved sustainable response by maintaining below detectable plasma viremia and the other (n = 6 responded intermittently. Blood samples were collected over an average of 3 years and 5–8 time points were selected for microarray assay and statistical analysis. Results Significant trends over time were observed for the expression of 7 cell surface antigens (CD2, CD3epsilon, CD5, CD95, CD36, CD27 and CD28 for combined patient groups. Between groups, expression levels of 10 cell surface antigens (CD11a, CD29, CD38, CD45RO, CD52, CD56, CD57, CD62E, CD64 and CD33 were found to be differential. Expression levels of CD9, CD11a, CD27, CD28 and CD52, CD44, CD49d, CD49e, CD11c strongly correlated with CD4+ and CD8+ T cell counts, respectively. Conclusion Our findings not only detected markers that may have potential prognostic/diagnostic values in evaluating HAART efficacy, but also showed how density of cell surface antigens could be efficiently exploited in an array-like manner in relation to HAART and HIV-infection. The antigens identified in this study should be further investigated by other methods such as flow cytometry for confirmation as biological analysis of these antigens may help further clarify their role during HAART and HIV infection.

  16. Measurement of Single Cell Refractive Index, Dry Mass, Volume, and Density Using a Transillumination Microscope

    Science.gov (United States)

    Phillips, Kevin G.; Jacques, Steven L.; McCarty, Owen J. T.

    2012-09-01

    Phase contrast microscopy has become ubiquitous in the field of biology, particularly in qualitative investigations of cellular morphology. However, the use of quantitative phase retrieval methods and their connection to cellular refractive index and dry mass density remain under utilized. This is due in part to the restriction of phase and cellular mass determination to custom built instruments, involved mathematical analysis, and prohibitive sample perturbations. We introduce tomographic bright field imaging, an accessible optical imaging technique enabling the three dimensional measurement of cellular refractive index and dry mass density using a standard transillumination optical microscope. The validity of the technique is demonstrated on polystyrene spheres. The technique is then applied to the measurement of the refractive index, dry mass, volume, and density of red blood cells. This optical technique enables a simple and robust means to perform quantitative investigations of engineered and biological specimens in three dimensions using standard optical microscopes.

  17. A molecular smart surface for spatio-temporal studies of cell mobility.

    Directory of Open Access Journals (Sweden)

    Eun-ju Lee

    Full Text Available Active migration in both healthy and malignant cells requires the integration of information derived from soluble signaling molecules with positional information gained from interactions with the extracellular matrix and with other cells. How a cell responds and moves involves complex signaling cascades that guide the directional functions of the cytoskeleton as well as the synthesis and release of proteases that facilitate movement through tissues. The biochemical events of the signaling cascades occur in a spatially and temporally coordinated manner then dynamically shape the cytoskeleton in specific subcellular regions. Therefore, cell migration and invasion involve a precise but constantly changing subcellular nano-architecture. A multidisciplinary effort that combines new surface chemistry and cell biological tools is required to understand the reorganization of cytoskeleton triggered by complex signaling during migration. Here we generate a class of model substrates that modulate the dynamic environment for a variety of cell adhesion and migration experiments. In particular, we use these dynamic substrates to probe in real-time how the interplay between the population of cells, the initial pattern geometry, ligand density, ligand affinity and integrin composition affects cell migration and growth. Whole genome microarray analysis indicates that several classes of genes ranging from signal transduction to cytoskeletal reorganization are differentially regulated depending on the nature of the surface conditions.

  18. The electrostatic interaction of an external charged system with a metal surface: a simplified density functional theory approach

    Science.gov (United States)

    Scivetti, Iván; Persson, Mats

    2013-09-01

    As a first step to meet the challenge to calculate the electronic structure and total energy of charged states of atoms and molecules adsorbed on ultrathin insulating films supported by a metallic substrate using density functional theory (DFT), we have developed a simplified new DFT scheme that only describes the electrostatic interaction of an external charged system with a metal surface. This purely electrostatic interaction is obtained from the assumption that the electron densities of the two fragments (charged system and metal surface) are non-overlapping and by neglecting non-local exchange-correlation effects such as the van der Waals interactions between the two fragments. In addition, the response of the metal surface to the electrostatic potential from the charged system is treated to linear order, whereas the charged system is treated fully within DFT. In particular, we consider the classical perfect conductor model for the metal response, although our formalism is not limited to this approximation. To test the computational implementation of this new scheme, we have considered the case of a Na+ cation interacting with a perfect conductor. The application of this new methodology to realistic problems involving charged systems adsorbed on insulating films supported by a metal surface are deferred to a separate following publication.

  19. Density Functional Theory Study of Chemical Sensing on Surfaces of Single-Layer MOS2 and Graphene (Postprint)

    Science.gov (United States)

    2014-04-22

    model surface systems of graphene and MoS2. Effects of inclusion of a SiO2 sub- strate to model a realistic material were also examined for selected...calculations. A k-point mesh of 5 5 1 was used for structural optimization and total energy calculations for the MoS2 and graphene surfaces on SiO2 ... graphene surfaces on SiO2 was used because a larger cell was required. In calculation of the total energy of the system for a relaxed configuration, all

  20. Activation of Yes-Associated Protein in Low-Grade Meningiomas Is Regulated by Merlin, Cell Density, and Extracellular Matrix Stiffness.

    Science.gov (United States)

    Tanahashi, Kuniaki; Natsume, Atsushi; Ohka, Fumiharu; Motomura, Kazuya; Alim, Adiljan; Tanaka, Ichidai; Senga, Takeshi; Harada, Ichiro; Fukuyama, Ryuichi; Sumiyoshi, Naoyuki; Sekido, Yoshitaka; Wakabayashi, Toshihiko

    2015-07-01

    The NF2 gene product Merlin is a protein containing ezrin, radixin, and moesin domains; it is a member of the 4.1 protein superfamily associated with the membrane cytoskeleton and also interacts with cell surface molecules. The mammalian Hippo cascade, a downstream signaling cascade of merlin, inactivates the Yes-associated protein (YAP). Yes-associated protein is activated by loss of the NF2 gene and functions as an oncogene in meningioma cells; however, the factors controlling YAP expression, phosphorylation, and subcellular localization in meningiomas have not been fully elucidated. Here, we demonstrate that merlin expression is heterogeneous in 1 NF2 gene-negative and 3 NF2 gene-positive World Health Organization grade I meningiomas. In the NF2 gene-positive meningiomas, regions with low levels of merlin (tumor rims) had greater numbers of cells with nuclear YAP versus regions with high merlin levels (tumor cores). Merlin expression and YAP phosphorylation were also affected by cell density in the IOMM-Lee and HKBMM human meningioma cell lines; nuclear localization of YAP was regulated by cell density and extracellular matrix (ECM) stiffness in IOMM-Lee cells. These results suggest that cell density and ECM stiffness may contribute to the heterogeneous loss of merlin and increased nuclear YAP expression in human meningiomas.

  1. Entropic solvation force between surfaces modified by grafted chains: a density functional approach

    Directory of Open Access Journals (Sweden)

    O. Pizio

    2010-01-01

    Full Text Available The behavior of a hard sphere fluid in slit-like pores with walls modified by grafted chain molecules composed of hard sphere segments is studied using density functional theory. The chains are grafted to opposite walls via terminating segments forming pillars. The effects of confinement and of "chemical" modification of pore walls on the entropic solvation force are investigated in detail. We observe that in the absence of adsorbed fluid the solvation force is strongly repulsive for narrow pores and attractive for wide pores. In the presence of adsorbed fluid both parts of the curve of the solvation force may develop oscillatory behavior dependent on the density of pillars, the number of segments and adsorption conditions. Also, the size ratio between adsorbed fluid species and chain segments is of importance for the development of oscillations. The choice of these parameters is crucial for efficient manipulation of the solvation force as desired for pores of different width.

  2. Investigation of the Cell Surface Proteome of Human Periodontal Ligament Stem Cells

    Directory of Open Access Journals (Sweden)

    Jimin Xiong

    2016-01-01

    Full Text Available The present study examined the cell surface proteome of human periodontal ligament stem cells (PDLSC compared to human fibroblasts. Cell surface proteins were prelabelled with CyDye before processing to extract the membrane lysates, which were separated using 2D electrophoresis. Selected differentially expressed protein “spots” were identified using Mass spectrometry. Four proteins were selected for validation: CD73, CD90, Annexin A2, and sphingosine kinase 1 previously associated with mesenchymal stem cells. Flow cytometric analysis found that CD73 and CD90 were highly expressed by human PDLSC and gingival fibroblasts but not by keratinocytes, indicating that these antigens could be used as potential markers for distinguishing between mesenchymal cells and epithelial cell populations. Annexin A2 was also found to be expressed at low copy number on the cell surface of human PDLSC and gingival fibroblasts, while human keratinocytes lacked any cell surface expression of Annexin A2. In contrast, sphingosine kinase 1 expression was detected in all the cell types examined using immunocytochemical analysis. These proteomic studies form the foundation to further define the cell surface protein expression profile of PDLSC in order to better characterise this cell population and help develop novel strategies for the purification of this stem cell population.

  3. Effects of two copper compounds on Microcystis aeruginosa cell density, membrane integrity, and microcystin release.

    Science.gov (United States)

    Tsai, Kuo-Pei

    2015-10-01

    Microcystin release following Microcystis aeruginosa cell lysis after copper-based algaecide treatment is often cited as a concern leading to restricted use of algaecide in restoration of natural water resources. To examine this concern, bench-scale experiments were conducted to study responses of M. aeruginosa to 8-day copper exposures as copper sulfate and copper-ethanolamine (Cu-EA). M. aeruginosa UTEX 2385 was cultured in BG11 medium to cell density of 10(6)cells/mL with total and extracellular microcystin of 93 and 53μg/L, respectively. Exposures of copper concentration ranged from 40 to 1000μgCu/L. Cell membrane integrity was indicated by erythrosine B. In the end of experiment, total microcystin and cell density in untreated control (313μg/L and 10(7)cells/mL) was 3.3 and 10 times greater than pretreatment value, respectively. Minimum amount of copper required to reduce M. aeruginosa population within 8 days was 160μgCu/L as copper sulfate and 80μgCu/L as Cu-EA, where total and extracellular microcystin concentrations (47 and 44μg/L for copper sulfate; 56 and 44μg/L for Cu-EA) were degraded with degradation rate coefficient 0.1 day(-1) and were less than pretreatment values. Given a copper concentration at 80µgCu/L as Cu-EA, M. aeruginosa cells were intact and less microcystin were released compared to treatments at 160-1000µgCu/L, where lysed cells and relatively greater microcystin release were observed. Based on the laboratory results, a minimum amount of copper required for reducing M. aeruginosa population could decrease total microcystin concentration and not compromise cells and minimize microcystin release.

  4. Regeneration and control of human fibroblast cell density by intermittently delivered pulsed electric fields.

    Science.gov (United States)

    Golberg, Alexander; Bei, Marianna; Sheridan, Robert L; Yarmush, Martin L

    2013-06-01

    Proliferative scarring is a human disease with neither available effective treatment nor relevant animal model. One of the hypotheses for scar formation involves deregulation of fibroblast signaling and delayed apoptosis. Here, we introduce a new chemical-free method for fibroblast density control in culture by intermittently delivered pulsed electric fields (IDPEF), which cause irreversible damage to cell membranes. Using 5-100 pulses with electric field strength of 150 V/mm, pulse duration 70 µs, and frequency of 1 Hz, we investigated the effects of PEF application on growth, death, and regeneration of normal human dermal fibroblasts in culture. We found that the fraction of fibroblasts that survive depends on the number of pulses applied and follows a Weibull distribution. We have successfully developed an IDPEF protocol that controls fibroblasts density in culture. Specifically, through application of IDPEF every 72 h for 12 days, we maintain a normal human dermal fibroblast density in the 3.1 ± 0.2 × 10(5) -1.4 ± 0.2 × 10(5)  cell/mL range. Our results suggest that IDPEFs may prove useful as a non-chemical method for fibroblast density control in human wound healing.

  5. Direct determination of defect density of states in organic bulk heterojunction solar cells

    Science.gov (United States)

    Verma, Upkar K.; Tripathi, Durgesh C.; Mohapatra, Y. N.

    2016-09-01

    The measurement of the occupied trap density of states (DOS) is important for optimization of organic bulk heterojunction solar cells. We demonstrate a direct method for obtaining it from the trap related peak in capacitance-voltage characteristics under different levels of illumination, and its correlation with the dark current density-voltage characteristics. We use the method to measure the parameters of DOS, occupied trap distribution, and its temperature dependence for poly(3-hexathiophene) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM) based solar cells. The total occupied trap concentration is approximately 7 × 1015 cm-3 with a standard deviation for a truncated Gaussian distribution varying between 32 and 44 meV in the temperature range of 310-270 K within a total Gaussian DOS with a standard deviation of 92 meV.

  6. Both electrical stimulation thresholds and SMI-32-immunoreactive retinal ganglion cell density correlate with age in S334ter line 3 rat retina.

    Science.gov (United States)

    Chan, Leanne L H; Lee, Eun-Jin; Humayun, Mark S; Weiland, James D

    2011-06-01

    Electrical stimulation threshold and retinal ganglion cell density were measured in a rat model of retinal degeneration. We performed in vivo electrophysiology and morphometric analysis on normal and S334ter line 3 (RD) rats (ages 84-782 days). We stimulated the retina in anesthetized animals and recorded evoked responses in the superior colliculus. Current pulses were delivered with a platinum-iridium (Pt-Ir) electrode of 75-μm diameter positioned on the epiretinal surface. In the same animals used for electrophysiology, SMI-32 immunolabeling of the retina enabled ganglion cell counting. An increase in threshold currents positively correlated with age of RD rats. SMI-32-labeled retinal ganglion cell density negatively correlated with age of RD rats. ANOVA shows that RD postnatal day (P)100 and P300 rats have threshold and density similar to normal rats, but RD P500 and P700 rats have threshold and density statistically different from normal rats (P < 0.05). Threshold charge densities were within the safety limits of Pt for all groups and pulse configurations, except at RD P600 and RD P700, where pulses were only safe up to 1- and 0.2-ms duration, respectively. Preservation of ganglion cells may enhance the efficiency and safety of electronic retinal implants.

  7. Systems biology. Conditional density-based analysis of T cell signaling in single-cell data.

    Science.gov (United States)

    Krishnaswamy, Smita; Spitzer, Matthew H; Mingueneau, Michael; Bendall, Sean C; Litvin, Oren; Stone, Erica; Pe'er, Dana; Nolan, Garry P

    2014-11-28

    Cellular circuits sense the environment, process signals, and compute decisions using networks of interacting proteins. To model such a system, the abundance of each activated protein species can be described as a stochastic function of the abundance of other proteins. High-dimensional single-cell technologies, such as mass cytometry, offer an opportunity to characterize signaling circuit-wide. However, the challenge of developing and applying computational approaches to interpret such complex data remains. Here, we developed computational methods, based on established statistical concepts, to characterize signaling network relationships by quantifying the strengths of network edges and deriving signaling response functions. In comparing signaling between naïve and antigen-exposed CD4(+) T lymphocytes, we find that although these two cell subtypes had similarly wired networks, naïve cells transmitted more information along a key signaling cascade than did antigen-exposed cells. We validated our characterization on mice lacking the extracellular-regulated mitogen-activated protein kinase (MAPK) ERK2, which showed stronger influence of pERK on pS6 (phosphorylated-ribosomal protein S6), in naïve cells as compared with antigen-exposed cells, as predicted. We demonstrate that by using cell-to-cell variation inherent in single-cell data, we can derive response functions underlying molecular circuits and drive the understanding of how cells process signals.

  8. Poly(glycidyl ether)-Based Monolayers on Gold Surfaces: Control of Grafting Density and Chain Conformation by Grafting Procedure, Surface Anchor, and Molecular Weight.

    Science.gov (United States)

    Heinen, Silke; Weinhart, Marie

    2017-03-07

    For a meaningful correlation of surface coatings with their respective biological response reproducible coating procedures, well-defined surface coatings, and thorough surface characterization with respect to layer thickness and grafting density are indispensable. The same applies to polymeric monolayer coatings which are intended to be used for, e.g., fundamental studies on the volume phase transition of surface end-tethered thermoresponsive polymer chains. Planar gold surfaces are frequently used as model substrates, since they allow a variety of straightforward surface characterization methods. Herein we present reproducible grafting-to procedures performed with thermoresponsive poly(glycidyl ether) copolymers composed of glycidyl methyl ether (GME) and ethyl glycidyl ether (EGE). The copolymers feature different molecular weights (2 kDa, 9 kDa, 24 kDa) and are equipped with varying sulfur-containing anchor groups in order to achieve adjustable grafting densities on gold surfaces and hence control the tethered polymers' chain conformation. We determined "wet" and "dry" thicknesses of these coatings by QCM-D and ellipsometry measurements and deduced anchor distances and degrees of chain overlap of the polymer chains assembled on gold. Grafting under cloud point conditions allowed for higher degrees of chain overlap compared to grafting from a good solvent like ethanol, independent of the used sulfur-containing anchor group for polymers with low (2 kDa) and medium (9 kDa) molecular weights. By contrast, the achieved grafting densities and thus chain overlaps of surface-tethered polymers with high (24 kDa) molecular weights were identical for both grafting methods. Monolayers prepared from an ethanolic solution of poly(glycidyl ether)s equipped with sterically demanding disulfide-containing anchors revealed the lowest degrees of chain overlap. The ratio of the radius of gyration to the anchor distance (2 Rg/l) of the latter coating was found to be lower than 1

  9. Global surface density of water mass variations by using a two-step inversion by cumulating daily satellite gravity information

    Science.gov (United States)

    Ramillien, Guillaume; Frappart, Frédéric; Seoane, Lucia

    2016-04-01

    We propose a new method to produce time series of global maps of surface mass variations by progressive integration of daily geopotential variations measured by orbiting satellites. In the case of the GRACE mission, these geopotential variations can be determined from very accurate inter-satellite K-Band Range Rate (KBRR) measurements of 5-second daily orbits. In particular, the along-track gravity contribution of hydrological mass changes is extracted by removing de-aliasing models for static field, atmosphere, oceans mass variations (including periodical tides), as well as polar movements. Our determination of surface mass sources is composed of two successive dependent Kalman filter stages. The first one consists of reducing the satellite-based potential anomalies by adjusting the longest spatial wavelengths (i.e., low-degree spherical harmonics lower than 2). In the second stage, the residual potential anomalies from the previous stage are used to recover surface mass density changes - in terms of Equivalent-Water Height (EWH) - over a global network of juxtaposed triangular elements. These surface tiles of ~100,000 km x km (or equivalently 330 km by 330 km) are defined to be of equal areas over the terrestrial sphere. However they can be adapted to the local geometry of the surface mass. Our global approach was tested by inverting geopotential data, and successfully applied to estimate time-varying surface mass densities from real GRACE-based residuals. This strategy of combined Kalman filter-type inversions can also be useful for exploring the possibility of improving time and space resolutions for ocean and land studies that would be hopefully brought by future low altitude geodetic missions.

  10. Cell surface topology creates high Ca2+ signalling microdomains

    DEFF Research Database (Denmark)

    Brasen, Jens Christian; Olsen, Lars Folke; Hallett, Maurice B

    2010-01-01

    of a smooth cell surface predicts only moderate localized effects, the more realistic "wrinkled" surface topology predicts that Ca2+ concentrations up to 80 microM can persist within the folds of membranes for significant times. This intra-wrinkle location may account for 5% of the total cell volume. Using...... different geometries of wrinkles, our simulations show that high Ca2+ microdomains will be generated most effectively by long narrow membrane wrinkles of similar dimensions to those found experimentally. This is a new concept which has not previously been considered, but which has ramifications as the intra-wrinkle...

  11. A Density Functional Theory Study of the Adsorption of Benzene on Hematite (α-Fe2O3 Surfaces

    Directory of Open Access Journals (Sweden)

    Nelson Y. Dzade

    2014-02-01

    Full Text Available The reactivity of mineral surfaces in the fundamental processes of adsorption, dissolution or growth, and electron transfer is directly tied to their atomic structure. However, unraveling the relationship between the atomic surface structure and other physical and chemical properties of complex metal oxides is challenging due to the mixed ionic and covalent bonding that can occur in these minerals. Nonetheless, with the rapid increase in computer processing speed and memory, computer simulations using different theoretical techniques can now probe the nature of matter at both the atomic and sub-atomic levels and are rapidly becoming an effective and quantitatively accurate method for successfully predicting structures, properties and processes occurring at mineral surfaces. In this study, we have used Density Functional Theory calculations to study the adsorption of benzene on hematite (α-Fe2O3 surfaces. The strong electron correlation effects of the Fe 3d-electrons in α-Fe2O3 were described by a Hubbard-type on-site Coulomb repulsion (the DFT+U approach, which was found to provide an accurate description of the electronic and magnetic properties of hematite. For the adsorption of benzene on the hematite surfaces, we show that the adsorption geometries parallel to the surface are energetically more stable than the vertical ones. The benzene molecule interacts with the hematite surfaces through π-bonding in the parallel adsorption geometries and through weak hydrogen bonds in the vertical geometries. Van der Waals interactions are found to play a significant role in stabilizing the absorbed benzene molecule. Analyses of the electronic structures reveal that upon benzene adsorption, the conduction band edge of the surface atoms is shifted towards the valence bands, thereby considerably reducing the band gap and the magnetic moments of the surface Fe atoms.

  12. Influence of non-thermal plasma forming gases on improvement of surface properties of low density polyethylene (LDPE)

    Energy Technology Data Exchange (ETDEWEB)

    Pandiyaraj, K. Navaneetha, E-mail: dr.knpr@gmail.com [Surface Engineering Laboratory, Department of Physics, Sri Shakthi Institute of Engineering and Technology, L and T by pass, Chinniyam Palayam (post), Coimbatore 641062 (India); Deshmukh, R.R. [Department of Physics, Institute of Chemical Technology, Matunga, Mumbai 400 019 (India); Ruzybayev, Inci; Shah, S. Ismat [Department of Physics and Astronomy, Department of Materials Science and Engineering, University of Delaware, 208 Dupont Hall, Newark, NJ (United States); Su, Pi-Guey [Department of Chemistry, Chinese Culture University, Taipei 111, Taiwan (China); Halleluyah, Jr. mercy; Halim, Ahmad Sukari [School of Medical Sciences, Health Campus Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan (Malaysia)

    2014-07-01

    Owing to the superior physico-chemical properties, the low density polyethylene (LDPE) has been widely used in the various industrial applications; especially in biomedical field for artificial organs, medical devices and disposable clinical apparatus. However, the poor anticoagulation property is one of the main drawbacks of the LDPE due to its poor surface properties. Therefore, in this paper we present the effect of plasma forming gases such as argon (Ar), oxygen (O{sub 2}), air and argon-oxygen (Ar + O{sub 2}) mixture on improvement of the surfaces properties of LDPE film using direct current (dc) excited glow discharge plasma. Contact angle with evaluation of surface energy, X-ray photo electron spectroscopy (XPS), atomic force microscopy (AFM) techniques were used to examine the change in surface properties such as hydrophilicity, chemical composition and surface topography, respectively. Furthermore, the hydrophobic recovery of the plasma treated LDPE was analyzed using ageing effect under different storage condition i.e. in air and water. The adhesive strength of the LDPE films was determined using T-peel test. In vitro tests were used to examine the blood compatibility of the surface modified LDPE films. It has been found that the hydrophilicity of the various plasma treated LDPE films was improved significantly due to the formation of oxygen containing polar groups such as OH, COO, C-O, C=O as confirmed by contact angle and XPS analysis. AFM revealed the changes in surface topography of plasma processed films. The gas mixture Ar + O{sub 2} plasma influenced the remarkable improvement on the surface properties of a LDPE film compared with other gaseous plasmas. These physiochemical changes induced by the plasma on the surface facilitate to improve the adhesive strength and blood compatibility.

  13. High Population Density of Juvenile Chum Salmon Decreased the Number and Sizes of Growth Hormone Cells in the Pituitary

    OpenAIRE

    Salam, Md. Abdus; Ota, Yuki; Ando, Hironori; Fukuwaka, Masa-aki; Kaeriyama, Masahide; Urano, Akihisa

    1999-01-01

    Juveniles of chum salmon (Oncorhynchus keta) held at high population density were apparently smaller than those held at medium and low population densities. The effects of high population density on pituitary growth hormone (GH) cells in juvenile chum salmon were examined using immunocytochemical and in situ hybridization techniques. The ratio of GH-immunoreactive (ir) area to the whole pituitary was almost constant in all of the high, medium and low population density groups, although the nu...

  14. Adsorption of CO on the LaCoO3 (0 0 1) surface by density functional theory calculation

    Science.gov (United States)

    Sun, Lihui; Li, Guoping; Chen, Wen; Luo, Fenghua; Hu, Jifan; Qin, Hongwei

    2014-08-01

    The adsorption of CO molecule on the LaCoO3 (0 0 1) surface has been investigated using density functional theory calculation. Calculation results show that the most suitable configuration is Cosbnd CO structure for the CoO-terminated LaCoO3 (0 0 1) surface. In the adsorption process electrons transfer from CO molecule to the surface. The Cosbnd C bond is mainly from the hybrid between the CO and Co-d orbital. When CO molecule adsorption on the LaO-terminated LaCoO3 (0 0 1) surface, the most suitable configuration is the Osbnd CO structure and the electrons transfer from the surface to the CO molecule in the adsorption process. The bond between the C atom and the surface O atom is mainly from the hybrid between the C-2p and O-2p orbital. The LaCoO3 could be used as the gas sensing material to detect CO gas.

  15. Dissociation and diffusion of hydrogen on defect-free and vacancy defective Mg (0001) surfaces: A density functional theory study

    Science.gov (United States)

    Han, Zongying; Chen, Haipeng; Zhou, Shixue

    2017-02-01

    First-principles calculations with the density functional theory (DFT) have been carried out to study dissociation and diffusion of hydrogen on defect-free and vacancy defective Mg (0001) surfaces. Results show that energy barriers of 1.42 eV and 1.28 eV require to be overcome for H2 dissociation on defect-free and vacancy defective Mg (0001) surfaces respectively, indicating that reactivity of Mg (0001) surface is moderately increased due to vacancy defect. Besides, the existence of vacancy defect changes the preferential H atom diffusion entrance to the subsurface and reduces the diffusion energy barrier. An interesting remark is that the minimum energy diffusion path of H atom from magnesium surface into bulk is a spiral channel formed by staggered octahedral and tetrahedral interstitials. The diffusion barriers computed for H atom penetration from the surface into inner-layers are all less than 0.70 eV, which is much smaller than the activation energy for H2 dissociation on the Mg (0001) surface. This suggests that H2 dissociation is more likely than H diffusion to be rate-limiting step for magnesium hydrogenation.

  16. Density functional theory study of the interaction of H2 with pure and Ti-doped WO3 (002) surfaces

    Institute of Scientific and Technical Information of China (English)

    Hu Ming; Wang Wei-Dan; Zeng Peng; Zeng Jing; Qin Yu-Xiang

    2012-01-01

    Density functional theory (DFT) calculations are conducted to explore the interaction of H2 with pure and Tidoped WO3 (002) surfaces.Four top adsorption models of H2 on pure and Ti-doped WO3 (002) surfaces are investigated respectively,they are adsorption on bridging oxygen O1c,absorption on plane oxygen O2c,absorption on 5-fold Wsc (Ti),and absorption on 6-fold W6c.The most stable and H2 possible adsorption structure in the pure surface is H-end oriented to the surface plane oxygen O2c site,while the favourable adsorption sites for H2 in a Ti-doped surface is not only an O2c site but also a W6c site.The adsorption energy,the Fermi energy level EF,and the electronic population are investigated and the H2-sensing mechanism of a pure-doped WO3 (002) surface is revealed theoretically:the theoretical results are in good accordance with our existing experimental results.By comparing the above three terms,it is found that Ti doping can obviously enhance the adsorption of H2.It can be predicted that the method of Ti-doped into a WO3 thin film is an effective way to improve WO3 sensor sensitivity to H2 gas.

  17. Surface glycosylation of poly(3-hydroxybutyrate-co-4-hydroxybutyrate) membrane for selective adsorption of low-density lipoprotein.

    Science.gov (United States)

    Wang, Wei; Lan, Ping

    2014-01-01

    A novel method of constructing a glycosylated surface on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)] membrane surface for the selective adsorption of low-density lipoprotein (LDL) was developed, which involved the photoinduced graft polymerization of acrylic acid followed by the chemical binding of carboxyl groups with glucosamine in the presence of 1-ethyl-3-(dimethyl-aminopropyl) carbodiimide hydrochloride and N-hydroxy-succinimide. The chemical structures of the fabricated membranes were characterized by attenuated total reflectance Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Zeta potential and water contact angle measurements were performed to investigate the surface charge and wettability of the membranes, respectively. An enzyme linked immunosorbent assay was used to measure the LDL adsorption on the plain and modified membrane surfaces. It was found that the surface glycosylation of P(3HB-co-4HB) membrane greatly enhanced the affinity interactions with LDL and the absorbed LDL could be easily desorbed with eluents, indicating a specific and reversible binding of LDL to the surface. Furthermore, the hemocompatibility of glycosylated membrane was improved as examined by platelet adhesion. The results suggest that the glycosylated P(3HB-co-4HB) membrane is promising for application in LDL apheresis therapy.

  18. High cell density strategy for poly(3-hydroxybutyrate production by Cupriavidus necator

    Directory of Open Access Journals (Sweden)

    J. L. Ienczak

    2011-12-01

    Full Text Available Poly(3-hydroxybutyrate (P(3HB is a carbon and intracellular storage source for different microorganisms and its production can achieve high productivities by means of high cell density cultures. The aim of this study was to propose a high cell density strategy for P(3HB production by Cupriavidus necator. The exponential growth phase demands an accurate control of the oxygen transfer system in the bioreactor, due to maximum specific growth rate (µXr, and, consequently, a maximum specific oxygen uptake rate (QO2, in addition to significant residual biomass (Xr growth in high cell density cultures. In this context, this work investigated the strategy for obtaining high cell density, with the inclusion of a linear growth phase for P(3HB production by C. necator in a fed-batch culture. The linear growth phase was included between the exponential growth phase and the P(3HB production phase as a strategy to reduce the specific growth rate (µXr and specific oxygen uptake rate (QO2, with constant residual biomass growth rate (d(V.Xr/dt = k = constant and linear increase of biomass. Three strategies of culture were performed. The results showed that a high residual biomass concentration (30 gXr.L-1 can be reached by the inclusion of the linear growth strategy and specific growth rates (µXr between 0.08 and 0.05 h-1, at the beginning of the production phase, are necessary to attain a high P(3HB productivity.

  19. Retinal ganglion cell density of the black rhinoceros (Diceros bicornis): calculating visual resolution.

    Science.gov (United States)

    Pettigrew, John D; Manger, Paul R

    2008-01-01

    A single right retina from a black rhinoceros was whole mounted, stained and analyzed to determine the visual resolution of the rhinoceros, an animal with reputedly poor eyesight. A range of small (15-microm diameter) to large (100-microm diameter) ganglion cell types was seen across the retina. We observed two regions of high density of retinal ganglion cells at either end of a long, but thin, horizontal streak. The temporal specialization, which receives light from the anterior visual field, exhibited a ganglion cell density of approximately 2000/mm2, while the nasal specialization exhibited a density of approximately 1500/mm2. The retina exhibited a ganglion cell density bias toward the upper half, especially so, the upper temporal quadrant, indicating that the rhinoceros would be processing visual information from the visual field below the anterior horizon for the most part. Our calculations indicate that the rhinoceros has a visual resolution of 6 cycles/degree. While this resolution is one-tenth that of humans (60 cycles/deg) and less than that of the domestic cat (9 cycles/deg), it is comparable to that of the rabbit (6 cycles/deg), and exceeds that seen in a variety of other mammals including seals, dolphins, microbats, and rats. Thus, the reputation of the rhinoceros as a myopic, weakly visual animal is not supported by our observations of the retina. We calculate that the black rhinoceros could readily distinguish a 30 cm wide human at a distance of around 200 m given the appropriate visual background.

  20. Fabrication of cell container arrays with overlaid surface topographies.

    Science.gov (United States)

    Truckenmüller, Roman; Giselbrecht, Stefan; Escalante-Marun, Maryana; Groenendijk, Max; Papenburg, Bernke; Rivron, Nicolas; Unadkat, Hemant; Saile, Volker; Subramaniam, Vinod; van den Berg, Albert; van Blitterswijk, Clemens; Wessling, Matthias; de Boer, Jan; Stamatialis, Dimitrios

    2012-02-01

    This paper presents cell culture substrates in the form of microcontainer arrays with overlaid surface topographies, and a technology for their fabrication. The new fabrication technology is based on microscale thermoforming of thin polymer films whose surfaces are topographically prepatterned on a micro- or nanoscale. For microthermoforming, we apply a new process on the basis of temporary back moulding of polymer films and use the novel concept of a perforated-sheet-like mould. Thermal micro- or nanoimprinting is applied for prepatterning. The novel cell container arrays are fabricated from polylactic acid (PLA) films. The thin-walled microcontainer structures have the shape of a spherical calotte merging into a hexagonal shape at their upper circumferential edges. In the arrays, the cell containers are arranged densely packed in honeycomb fashion. The inner surfaces of the highly curved container walls are provided with various topographical micro- and nanopatterns. For a first validation of the microcontainer arrays as in vitro cell culture substrates, C2C12 mouse premyoblasts are cultured in containers with microgrooved surfaces and shown to align along the grooves in the three-dimensional film substrates. In future stem-cell-biological and tissue engineering applications, microcontainers fabricated using the proposed technology may act as geometrically defined artificial microenvironments or niches.

  1. 3D surface topology guides stem cell adhesion and differentiation.

    Science.gov (United States)

    Viswanathan, Priyalakshmi; Ondeck, Matthew G; Chirasatitsin, Somyot; Ngamkham, Kamolchanok; Reilly, Gwendolen C; Engler, Adam J; Battaglia, Giuseppe

    2015-06-01

    Polymerized high internal phase emulsion (polyHIPE) foams are extremely versatile materials for investigating cell-substrate interactions in vitro. Foam morphologies can be controlled by polymerization conditions to result in either open or closed pore structures with different levels of connectivity, consequently enabling the comparison between 2D and 3D matrices using the same substrate with identical surface chemistry conditions. Additionally, here we achieve the control of pore surface topology (i.e. how different ligands are clustered together) using amphiphilic block copolymers as emulsion stabilizers. We demonstrate that adhesion of human mesenchymal progenitor (hES-MP) cells cultured on polyHIPE foams is dependent on foam surface topology and chemistry but is independent of porosity and interconnectivity. We also demonstrate that the interconnectivity, architecture and surface topology of the foams has an effect on the osteogenic differentiation potential of hES-MP cells. Together these data demonstrate that the adhesive heterogeneity of a 3D scaffold could regulate not only mesenchymal stem cell attachment but also cell behavior in the absence of soluble growth factors.

  2. Cell-surface expression of Hsp70 on hematopoietic cancer cells after inhibition of HDAC activity

    DEFF Research Database (Denmark)

    Jensen, Helle; Andresen, Lars; Hansen, Karen Aagaard

    2009-01-01

    We show that inhibition of HDAC activity leads to surface expression of Hsp70 on various hematopoietic cancer cells, an occurance that was not observed on naïve or activated peripheral blood cells. HDAC inhibitor-mediated Hsp70 surface expression was confined to the apoptotic Annexin V...... activity selectively induces surface expression of Hsp70 on hematopoietic cancer cells and that this may increase immunorecognition of these cells.......-positive cells and blocked by inhibition of apoptosis. Other chemotherapeutic inducers of apoptosis such as etoposide and camptothecin also led to a robust induction of Hsp70 surface expression. Hsp70 expression was, however, not caused by induction of apoptosis per se, as activated CD4 T cells remained Hsp70...

  3. Analysis of surface degradation of high density polyethylene (HDPE) insulation material due to tracking

    Indian Academy of Sciences (India)

    R Sarathi; S Chandrasekar; V Sabari G