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Sample records for 2d monolayer cultures

  1. Differences in growth properties of endometrial cancer in three dimensional (3D) culture and 2D cell monolayer

    SciTech Connect

    Chitcholtan, Kenny; Asselin, Eric; Parent, Sophie; Sykes, Peter H.; Evans, John J.

    2013-01-01

    Three-dimensional (3D) in vitro models have an invaluable role in understanding the behaviour of tumour cells in a well defined microenvironment. This is because some aspects of tumour characteristics cannot be fully recapitulated in a cell monolayer (2D). In the present study, we compared growth patterns, expression of signalling molecules, and metabolism-associated proteins of endometrial cancer cell lines in 3D and 2D cell cultures. Cancer cells formed spherical structures in 3D reconstituted basement membrane (3D rBM), and the morphological appearance was cell line dependent. Cell differentiation was observed after 8 days in the 3D rBM. There was reduced proliferation, detected by less expression of PCNA in 3D rBM than in 2D cell monolayers. The addition of exogenous epidermal growth factor (EGF) to cancer cells induced phosphorylation of EGFR and Akt in both cell culture conditions. The uptake of glucose was selectively altered in the 3D rBM, but there was a lack of association with Glut-1 expression. The secretion of vascular endothelial growth factor (VEGF) and prostaglandin E{sub 2} (PGE{sub 2}) was selectively altered in 3D rBM, and it was cell line dependent. Our data demonstrated that 3D rBM as an in vitro model can influence proliferation and metabolism of endometrial cancer cell behaviour compared to 2D cell monolayer. Changes are specific to individual cell types. The use of 3D rBM is, therefore, important in the in vitro study of targeted anticancer therapies.

  2. Glitter in a 2D monolayer.

    PubMed

    Yang, Li-Ming; Dornfeld, Matthew; Frauenheim, Thomas; Ganz, Eric

    2015-10-21

    We predict a highly stable and robust atomically thin gold monolayer with a hexagonal close packed lattice stabilized by metallic bonding with contributions from strong relativistic effects and aurophilic interactions. We have shown that the framework of the Au monolayer can survive 10 ps MD annealing simulations up to 1400 K. The framework is also able to survive large motions out of the plane. Due to the smaller number of bonds per atom in the 2D layer compared to the 3D bulk we observe significantly enhanced energy per bond (0.94 vs. 0.52 eV per bond). This is similar to the increase in bond strength going from 3D diamond to 2D graphene. It is a non-magnetic metal, and was found to be the global minima in the 2D space. Phonon dispersion calculations demonstrate high kinetic stability with no negative modes. This 2D gold monolayer corresponds to the top monolayer of the bulk Au(111) face-centered cubic lattice. The close-packed lattice maximizes the aurophilic interactions. We find that the electrons are completely delocalized in the plane and behave as 2D nearly free electron gas. We hope that the present work can inspire the experimental fabrication of novel free standing 2D metal systems.

  3. Spreading dynamics of 2D dipolar Langmuir monolayer phases.

    PubMed

    Heinig, P; Wurlitzer, S; Fischer, Th M

    2004-07-01

    We study the spreading of a liquid 2D dipolar droplet in a Langmuir monolayer. Interfacial tensions (line tensions) and microscopic contact angles depend on the scale on which they are probed and obey a scaling law. Assuming rapid equilibration of the microscopic contact angle and ideal slippage of the 2D solid/liquid and solid/gas boundary, the driving force of spreading is merely expressed by the shape-dependent long-range interaction integrals. We obtain good agreement between experiment and numerical simulations using this theory. PMID:15278693

  4. Novel exciton systems in 2D TMD monolayers and heterobilayers

    NASA Astrophysics Data System (ADS)

    Yu, Hongyi

    In this talk, two exciton systems in transition metal dichalcogenides (TMDs) monolayer and heterobilayer will be discussed. In TMD monolayers, the strong e-h Coulomb exchange interaction splits the exciton and trion dispersions into two branches with zero and finite gap, respectively. Each branch is a center-of-mass wave vector dependent coherent superposition of the two valleys, which leads to a valley-orbit coupling and possibly a trion valley Hall effect. The exchange interaction also eliminates the linear polarization of the negative trion PL emission. In TMD heterobilayers with a type-II band alignment, the low energy exciton has an interlayer configuration with the e and h localized in opposite layers. Because of the inevitable twist or/and lattice mismatch between the two layers, the bright interlayer excitons are located at finite center-of-mass velocities with a six-fold degeneracy. The corresponding photon emission is elliptically polarized, with the major axis locked to the direction of exciton velocity, and helicity determined by the valley indices of the e and h. Some experimental results on the interlayer excitons in the WSe2-MoSe2 heterobilayers will also be presented. The interlayer exciton exhibits a long lifetime as well as a long depolarization time, which facilitate the observation of a PL polarization ring pattern due to the valley dependent exciton-exciton interaction induced expansion. The works were supported by the Research Grant Council of Hong Kong (HKU17305914P, HKU705513P), the Croucher Foundation, and the HKU OYRA and ROP.

  5. 2-D Pigment Langmuir Monolayer Assemblies for Light Harvesting Applications.

    NASA Astrophysics Data System (ADS)

    Gregory, Brian W.; Vaknin, David; Cotton, Therese M.; Struve, Walter S.

    1996-03-01

    The use of Coulombic forces to isolate charged, water-soluble macrocycles at the air/water interface (through their interactions with the oppositely charged headgroups of a phospholipid Langmuir monolayer) is currently being exploited in this laboratory as a means to create two-dimensional arrays of pigments for light-harvesting purposes. Significant differences have been observed in the surface pressure-molecular area (π-A) isotherms of dihexadecyl phosphate on subphases containing either tetra-(N-methylaza)- phthalocyanine (i.e., tetra-(N-methyl)-2,3-pyridinoporphyrazine) or tetra- (N-methylpyridyl)-porphyrin, both of which are cationic. In situ x-ray specular reflectivity has been employed to determine interfacial organization in these systems and to elucidate the origin of their different phase behavior at the air/water interface. In addition, electronic absorption spectra and electronic linear dichroism have been utilized to determine average pigment orientation in transferred films. * Ames Laboratory is operated by Iowa State University for the U.S. Department of Energy under Cotract No. W-4705-Eng-82.

  6. Exciton dynamics in suspended monolayer and few-layer MoS₂ 2D crystals.

    PubMed

    Shi, Hongyan; Yan, Rusen; Bertolazzi, Simone; Brivio, Jacopo; Gao, Bo; Kis, Andras; Jena, Debdeep; Xing, Huili Grace; Huang, Libai

    2013-02-26

    Femtosecond transient absorption spectroscopy and microscopy were employed to study exciton dynamics in suspended and Si₃N₄ substrate-supported monolayer and few-layer MoS₂ 2D crystals. Exciton dynamics for the monolayer and few-layer structures were found to be remarkably different from those of thick crystals when probed at energies near that of the lowest energy direct exciton (A exciton). The intraband relaxation rate was enhanced by more than 40 fold in the monolayer in comparison to that observed in the thick crystals, which we attributed to defect assisted scattering. Faster electron-hole recombination was found in monolayer and few-layer structures due to quantum confinement effects that lead to an indirect-direct band gap crossover. Nonradiative rather than radiative relaxation pathways dominate the dynamics in the monolayer and few-layer MoS₂. Fast trapping of excitons by surface trap states was observed in monolayer and few-layer structures, pointing to the importance of controlling surface properties in atomically thin crystals such as MoS₂ along with controlling their dimensions.

  7. Prediction of a strain-tunable 2D Topological Dirac semimetal in monolayers of black phosphorus

    NASA Astrophysics Data System (ADS)

    Zhang, Xiuwen; Liu, Qihang; Zunger, Alex; Theory Team

    2015-03-01

    N-dimensional Topological Nonmetals (TNM) such as N = 2D HgTe/CdTe quantum wells or N = 3D Bi2Se3 have a finite (often tiny) band gap between occupied and unoccupied bands, and show conductive Dirac cones in their N-1 dimensional geometric boundaries. On the other hand, examples of topological semimetals (TSM) are known for 3D solids (Cd3As2) where they have Dirac cones in the 3D system itself. Using density functional calculation of bands and the topological invariant Z2 we predict the existence of 2D topological Dirac semimetal in few monolayers of strain tuned black phosphorus (BP), with Dirac cones induced by band inversion. The band structures of few monolayers and bulk crystal of BP under a few percent biaxial and uniaxial strains were calculated using state-of-art electronic structure methods. The critical strain of the transition to TSM was found to decrease as the layer thickness increases. We will discuss the protection of the Dirac cones by the crystalline symmetry in the 2D TSM and the manipulation of crystalline symmetry, which induces further topological phase transitions. Supported by the NSF-DMREF-13-34170.

  8. Electrostatic 2D assembly of bionanoparticles on a cationic lipid monolayer.

    NASA Astrophysics Data System (ADS)

    Kewalramani, Sumit; Wang, Suntao; Fukuto, Masafumi; Yang, Lin; Niu, Zhongwei; Nguyen, Giang; Wang, Qian

    2010-03-01

    We present a grazing-incidence small-angle X-ray scattering (GISAXS) study on 2D assembly of cowpea mosaic virus (CPMV) under a mixed cationic-zwitterionic (DMTAP^+-DMPC) lipid monolayer at the air-water interface. The inter-particle and particle-lipid electrostatic interactions were varied by controlling the subphase pH and the membrane charge density. GISAXS data show that 2D crystals of CPMV are formed above a threshold membrane charge density and only in a narrow pH range just above CPMV's isoelectric point, where the charge on CPMV is expected to be weakly negative. The particle density for the 2D crystals is similar to that for the densest lattice plane in the 3D crystals of CPMV. The results show that the 2D crystallization is achieved in the part of the phase space where the electrostatic interactions are expected to maximize the adsorption of CPMV onto the lipid membrane. This electrostatics-based strategy for controlling interfacial nanoscale assembly should be generally applicable to other nanoparticles.

  9. A new 2D monolayer BiXene, M2C (M = Mo, Tc, Os).

    PubMed

    Sun, Weiwei; Li, Yunguo; Wang, Baotian; Jiang, Xue; Katsnelson, Mikhail I; Korzhavyi, Pavel; Eriksson, Olle; Di Marco, Igor

    2016-08-25

    The existence of BiXenes, a new family of 2D monolayers, is hereby predicted. Theoretically, BiXenes have 1H symmetry (P6[combining macron]m2) and can be formed from the 4d/5d binary carbides. As the name suggests, they are close relatives of MXenes, which instead have 1T symmetry (P3[combining macron]m1). The newly found BiXenes, as well as some new MXenes, are shown to have formation energies close to that of germanene, which suggests that these materials should be possible to be synthesised. Among them, we illustrate that 1H-Tc2C and 1T-Mo2C are dynamically stable at 0 K, while 1H-Mo2C, 1T-Tc2C, 1H-Os2C, and 1T-Rh2C are likely to be stabilised via strain or temperature. In addition, the nature of the chemical bonding is analysed, emphasizing that the covalency between the transition metal ions and carbon is much stronger in BiXenes than in MXenes. The emergence of BiXenes can not only open up a new era of conducting 2D monolayers, but also provide good candidates for carrier materials aimed at energy storage and spintronic devices that have already been unveiled in MXenes. PMID:27528499

  10. 2D attenuated total reflectance infrared spectroscopy reveals ultrafast vibrational dynamics of organic monolayers at metal-liquid interfaces

    NASA Astrophysics Data System (ADS)

    Kraack, Jan Philip; Lotti, Davide; Hamm, Peter

    2015-06-01

    We present two-dimensional infrared (2D IR) spectra of organic monolayers immobilized on thin metallic films at the solid liquid interface. The experiments are acquired under Attenuated Total Reflectance (ATR) conditions which allow a surface-sensitive measurement of spectral diffusion, sample inhomogeneity, and vibrational relaxation of the monolayers. Terminal azide functional groups are used as local probes of the environment and structural dynamics of the samples. Specifically, we investigate the influence of different alkyl chain-lengths on the ultrafast dynamics of the monolayer, revealing a smaller initial inhomogeneity and faster spectral diffusion with increasing chain-length. Furthermore, by varying the environment (i.e., in different solvents or as bare sample), we conclude that the most significant contribution to spectral diffusion stems from intra- and intermolecular dynamics within the monolayer. The obtained results demonstrate that 2D ATR IR spectroscopy is a versatile tool for measuring interfacial dynamics of adsorbed molecules.

  11. 2D attenuated total reflectance infrared spectroscopy reveals ultrafast vibrational dynamics of organic monolayers at metal-liquid interfaces.

    PubMed

    Kraack, Jan Philip; Lotti, Davide; Hamm, Peter

    2015-06-01

    We present two-dimensional infrared (2D IR) spectra of organic monolayers immobilized on thin metallic films at the solid liquid interface. The experiments are acquired under Attenuated Total Reflectance (ATR) conditions which allow a surface-sensitive measurement of spectral diffusion, sample inhomogeneity, and vibrational relaxation of the monolayers. Terminal azide functional groups are used as local probes of the environment and structural dynamics of the samples. Specifically, we investigate the influence of different alkyl chain-lengths on the ultrafast dynamics of the monolayer, revealing a smaller initial inhomogeneity and faster spectral diffusion with increasing chain-length. Furthermore, by varying the environment (i.e., in different solvents or as bare sample), we conclude that the most significant contribution to spectral diffusion stems from intra- and intermolecular dynamics within the monolayer. The obtained results demonstrate that 2D ATR IR spectroscopy is a versatile tool for measuring interfacial dynamics of adsorbed molecules.

  12. Rotational Tunneling of CH2D2 Monolayers on MgO(100)

    NASA Astrophysics Data System (ADS)

    Hicks, Andrew; Larese, John

    2013-03-01

    Understanding the detailed nature of the interactions governing physisorption is a central topic in surface science, with wide ranging energy applications in heterogeneous catalysis, gas separation, and hydrogen storage. For systems with a strong interaction potential relative to the rotational constant of the adsorbate, adsorbed molecules are constrained to minima in the rotational potential. Adsorbed molecules may then tunnel through the rotational barrier between potential minima. Rotational tunneling spectra (RTS) are extremely sensitive to changes in the symmetry and strength of the rotational potential and are unmatched in their ability to probe the electrostatic potentials associated with adsorption sites. Furthermore, RTS can be clearly observed using inelastic neutron scattering. Building upon previous work of CH4 on MgO (see J.Z. Larese, Physica B, 1998), RTS of CH3D and CH2D2 are interpreted using the pocket state (PS) formalism developed by Hüller et al. The ground librational state of the adsorbate is split into twelve ``pockets'', each localized around one of twelve minima in the rotational potential. We report recent RTS of single monolayers of CH3D and CH2D2 adsorbed on the MgO(100) surface using BASIS at the SNS at ORNL. These pioneering measurements represent the highest resolution investigation available for this (or any other) RTS. The discussion will include challenges in reconciling the transitions predicted by PS theory and the features observed in the experimental data.

  13. Generalized Mechanistic Model for the Chemical Vapor Deposition of 2D Transition Metal Dichalcogenide Monolayers.

    PubMed

    Govind Rajan, Ananth; Warner, Jamie H; Blankschtein, Daniel; Strano, Michael S

    2016-04-26

    Transition metal dichalcogenides (TMDs) like molybdenum disulfide (MoS2) and tungsten disulfide (WS2) are layered materials capable of growth to one monolayer thickness via chemical vapor deposition (CVD). Such CVD methods, while powerful, are notoriously difficult to extend across different reactor types and conditions, with subtle variations often confounding reproducibility, particularly for 2D TMD growth. In this work, we formulate the first generalized TMD synthetic theory by constructing a thermodynamic and kinetic growth mechanism linked to CVD reactor parameters that is predictive of specific geometric shape, size, and aspect ratio from triangular to hexagonal growth, depending on specific CVD reactor conditions. We validate our model using experimental data from Wang et al. (Chem. Mater. 2014, 26, 6371-6379) that demonstrate the systemic evolution of MoS2 morphology down the length of a flow CVD reactor where variations in gas phase concentrations can be accurately estimated using a transport model (CSulfur = 9-965 μmol/m(3); CMoO3 = 15-16 mmol/m(3)) under otherwise isothermal conditions (700 °C). A stochastic model which utilizes a site-dependent activation energy barrier based on the intrinsic TMD bond energies and a series of Evans-Polanyi relations leads to remarkable, quantitative agreement with both shape and size evolution along the reactor. The model is shown to extend to the growth of WS2 at 800 °C and MoS2 under varied process conditions. Finally, a simplified theory is developed to translate the model into a "kinetic phase diagram" of the growth process. The predictive capability of this model and its extension to other TMD systems promise to significantly increase the controlled synthesis of such materials. PMID:26937889

  14. Dual functions of 2D WS2 and MoS2-WS2 monolayers coupled with a Ag3PO4 photocatalyst

    NASA Astrophysics Data System (ADS)

    Wei, Zeng-Xi; Huang, Wei-Qing; Xu, Liang; Hu, Wangyu; Peng, P.; Huang, Gui-Fang

    2016-09-01

    The photocatalytic performance of semiconductors can be improved by coupling two-dimensional (2D) layered materials. Understanding the underlying mechanism of this phenomenon at the electronic level is important for the development of photocatalysts with a high efficiency. Here, we first present a theoretical elucidation of the dual functions of 2D layered material as a sensitizer and a co-catalyst by performing density functional theory calculations, taking WS2 and a lateral heterogeneous WS2-MoS2 monolayer as examples to couple with a promising photocatalyst Ag3PO4. The band alignment of a staggered type-II is formed between Ag3PO4 and the 2D monolayer with the latter possessing the higher electron affinity, resulting in the robust separation of photoexcited charge carriers between them, and indicating that the 2D monolayer is an effective sensitizer. Interestingly, the W (Mo) atoms, which are catalytically inert in the isolated 2D monolayer, turn into catalytic active sites, making the 2D monolayer a highly active co-catalyst in hybrids. A better photocatalytic performance in the coupled lateral heterogeneous WS2-MoS2 monolayer and Ag3PO4 can be expected. The calculated results can be rationalized by available experiments. These findings provide theoretical evidence supporting the experimental reports and may be used as a foundation for developing highly efficient 2D layered materials-based photocatalysts.

  15. Dual functions of 2D WS2 and MoS2–WS2 monolayers coupled with a Ag3PO4 photocatalyst

    NASA Astrophysics Data System (ADS)

    Wei, Zeng-Xi; Huang, Wei-Qing; Xu, Liang; Hu, Wangyu; Peng, P.; Huang, Gui-Fang

    2016-09-01

    The photocatalytic performance of semiconductors can be improved by coupling two-dimensional (2D) layered materials. Understanding the underlying mechanism of this phenomenon at the electronic level is important for the development of photocatalysts with a high efficiency. Here, we first present a theoretical elucidation of the dual functions of 2D layered material as a sensitizer and a co-catalyst by performing density functional theory calculations, taking WS2 and a lateral heterogeneous WS2–MoS2 monolayer as examples to couple with a promising photocatalyst Ag3PO4. The band alignment of a staggered type-II is formed between Ag3PO4 and the 2D monolayer with the latter possessing the higher electron affinity, resulting in the robust separation of photoexcited charge carriers between them, and indicating that the 2D monolayer is an effective sensitizer. Interestingly, the W (Mo) atoms, which are catalytically inert in the isolated 2D monolayer, turn into catalytic active sites, making the 2D monolayer a highly active co-catalyst in hybrids. A better photocatalytic performance in the coupled lateral heterogeneous WS2–MoS2 monolayer and Ag3PO4 can be expected. The calculated results can be rationalized by available experiments. These findings provide theoretical evidence supporting the experimental reports and may be used as a foundation for developing highly efficient 2D layered materials-based photocatalysts.

  16. Estradiol Exposure Differentially Alters Monolayer versus Microtissue MCF-7 Human Breast Carcinoma Cultures.

    PubMed

    Vantangoli, Marguerite M; Madnick, Samantha J; Wilson, Shelby; Boekelheide, Kim

    2016-01-01

    The development of three-dimensional (3D) cultures is increasing, as they are able to provide the utility of in vitro models and the strength of testing in physiologically relevant systems. When cultured in a scaffold-free agarose hydrogel system, MCF-7 human breast carcinoma cells organize and develop into microtissues that contain a luminal space, in stark contrast to the flat morphology of MCF-7 two-dimensional (2D) monolayer cultures. Following exposure to 1nM E2, expression of typical estrogen-responsive genes, including progesterone receptor (PGR), PDZ containing domain 1 (PDZK1) and amphiregulin (AREG) is increased in both 2D and 3D cultures. When examining expression of other genes, particularly those involved in cell adhesion, there were large changes in 3D MCF-7 microtissues, with little to no change observed in the MCF-7 monolayer cultures. Together, these results indicate that while the initial estrogen-regulated transcriptional targets respond similarly in 2D and 3D cultures, there are large differences in activation of other pathways related to cell-cell interactions. PMID:27379522

  17. Estradiol Exposure Differentially Alters Monolayer versus Microtissue MCF-7 Human Breast Carcinoma Cultures

    PubMed Central

    Madnick, Samantha J.; Wilson, Shelby; Boekelheide, Kim

    2016-01-01

    The development of three-dimensional (3D) cultures is increasing, as they are able to provide the utility of in vitro models and the strength of testing in physiologically relevant systems. When cultured in a scaffold-free agarose hydrogel system, MCF-7 human breast carcinoma cells organize and develop into microtissues that contain a luminal space, in stark contrast to the flat morphology of MCF-7 two-dimensional (2D) monolayer cultures. Following exposure to 1nM E2, expression of typical estrogen-responsive genes, including progesterone receptor (PGR), PDZ containing domain 1 (PDZK1) and amphiregulin (AREG) is increased in both 2D and 3D cultures. When examining expression of other genes, particularly those involved in cell adhesion, there were large changes in 3D MCF-7 microtissues, with little to no change observed in the MCF-7 monolayer cultures. Together, these results indicate that while the initial estrogen-regulated transcriptional targets respond similarly in 2D and 3D cultures, there are large differences in activation of other pathways related to cell-cell interactions. PMID:27379522

  18. Monitoring Morphological Changes in 2D Monolayer Semiconductors Using Atom-Thick Plasmonic Nanocavities

    PubMed Central

    2015-01-01

    Nanometer-sized gaps between plasmonically coupled adjacent metal nanoparticles enclose extremely localized optical fields, which are strongly enhanced. This enables the dynamic investigation of nanoscopic amounts of material in the gap using optical interrogation. Here we use impinging light to directly tune the optical resonances inside the plasmonic nanocavity formed between single gold nanoparticles and a gold surface, filled with only yoctograms of semiconductor. The gold faces are separated by either monolayers of molybdenum disulfide (MoS2) or two-unit-cell thick cadmium selenide (CdSe) nanoplatelets. This extreme confinement produces modes with 100-fold compressed wavelength, which are exquisitely sensitive to morphology. Infrared scattering spectroscopy reveals how such nanoparticle-on-mirror modes directly trace atomic-scale changes in real time. Instabilities observed in the facets are crucial for applications such as heat-assisted magnetic recording that demand long-lifetime nanoscale plasmonic structures, but the spectral sensitivity also allows directly tracking photochemical reactions in these 2-dimensional solids. PMID:25495220

  19. Mn2C monolayer: a 2D antiferromagnetic metal with high Néel temperature and large spin-orbit coupling.

    PubMed

    Hu, Lin; Wu, Xiaojun; Yang, Jinlong

    2016-07-14

    To realize antiferromagnetic spintronics in the nanoscale, it is highly desirable to identify new nanometer-scale antiferromagnetic metals with both high Néel temperature and large spin-orbit coupling. In this work, on the basis of first-principles calculation and particle swarm optimization (PSO) global structure search, we demonstrate that a two-dimensional Mn2C monolayer is an antiferromagnetic metal with a Mn magnetic moment of ∼3μB. Mn2C monolayer has an anti-site structure of MoS2 sheet with carbon atoms hexagonally coordinated by neighboring Mn atoms. Remarkably, the in-plane carrier mobility of 2D Mn2C is highly anisotropic, amounting to about 47 000 cm(2) V(-1) s(-1) in the a' direction, which is much higher than that of MoS2 monolayer. The Néel temperature of Mn2C monolayer is high up to 720 K. Due to strong spin-orbit coupling in plane, the magnetic anisotropy energy of Mn2C monolayer is larger than those of pure metals, such as Fe, Co, and Ni. These advantages render 2D Mn2C sheet with great potential applications in nanometer-scale antiferromagnetic spintronics. PMID:27304676

  20. A simple method for freeze-fracture of monolayer cultures

    PubMed Central

    1975-01-01

    A simple method is described for the freeze-fracture in situ of monolayer cultures grown on gold carriers coated with a thin layer of silicon monoxide. Preliminary observations on 3T3 mouse embryo fibroblasts indicate that this technique exposes large areas of cell membrane, making it possible to determine how areas of membrane specialization are related to the cell as a whole and to regions of cellular interaction. 3T3 cells cultured on silicon monoxide show no modification of growth properties compared to cells growing on Falcon plastic, and other cell lines also appear to grow well on this substrate. PMID:172516

  1. 3D Cultures of prostate cancer cells cultured in a novel high-throughput culture platform are more resistant to chemotherapeutics compared to cells cultured in monolayer.

    PubMed

    Chambers, Karen F; Mosaad, Eman M O; Russell, Pamela J; Clements, Judith A; Doran, Michael R

    2014-01-01

    Despite monolayer cultures being widely used for cancer drug development and testing, 2D cultures tend to be hypersensitive to chemotherapy and are relatively poor predictors of whether a drug will provide clinical benefit. Whilst generally more complicated, three dimensional (3D) culture systems often better recapitulate true cancer architecture and provide a more accurate drug response. As a step towards making 3D cancer cultures more accessible, we have developed a microwell platform and surface modification protocol to enable high throughput manufacture of 3D cancer aggregates. Herein we use this novel system to characterize prostate cancer cell microaggregates, including growth kinetics and drug sensitivity. Our results indicate that prostate cancer cells are viable in this system, however some non-cancerous prostate cell lines are not. This system allows us to consistently control for the presence or absence of an apoptotic core in the 3D cancer microaggregates. Similar to tumor tissues, the 3D microaggregates display poor polarity. Critically the response of 3D microaggregates to the chemotherapeutic drug, docetaxel, is more consistent with in vivo results than the equivalent 2D controls. Cumulatively, our results demonstrate that these prostate cancer microaggregates better recapitulate the morphology of prostate tumors compared to 2D and can be used for high-throughput drug testing. PMID:25380249

  2. Mn2C monolayer: a 2D antiferromagnetic metal with high Néel temperature and large spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Hu, Lin; Wu, Xiaojun; Yang, Jinlong

    2016-06-01

    To realize antiferromagnetic spintronics in the nanoscale, it is highly desirable to identify new nanometer-scale antiferromagnetic metals with both high Néel temperature and large spin-orbit coupling. In this work, on the basis of first-principles calculation and particle swarm optimization (PSO) global structure search, we demonstrate that a two-dimensional Mn2C monolayer is an antiferromagnetic metal with a Mn magnetic moment of ~3μB. Mn2C monolayer has an anti-site structure of MoS2 sheet with carbon atoms hexagonally coordinated by neighboring Mn atoms. Remarkably, the in-plane carrier mobility of 2D Mn2C is highly anisotropic, amounting to about 47 000 cm2 V-1 s-1 in the a' direction, which is much higher than that of MoS2 monolayer. The Néel temperature of Mn2C monolayer is high up to 720 K. Due to strong spin-orbit coupling in plane, the magnetic anisotropy energy of Mn2C monolayer is larger than those of pure metals, such as Fe, Co, and Ni. These advantages render 2D Mn2C sheet with great potential applications in nanometer-scale antiferromagnetic spintronics.To realize antiferromagnetic spintronics in the nanoscale, it is highly desirable to identify new nanometer-scale antiferromagnetic metals with both high Néel temperature and large spin-orbit coupling. In this work, on the basis of first-principles calculation and particle swarm optimization (PSO) global structure search, we demonstrate that a two-dimensional Mn2C monolayer is an antiferromagnetic metal with a Mn magnetic moment of ~3μB. Mn2C monolayer has an anti-site structure of MoS2 sheet with carbon atoms hexagonally coordinated by neighboring Mn atoms. Remarkably, the in-plane carrier mobility of 2D Mn2C is highly anisotropic, amounting to about 47 000 cm2 V-1 s-1 in the a' direction, which is much higher than that of MoS2 monolayer. The Néel temperature of Mn2C monolayer is high up to 720 K. Due to strong spin-orbit coupling in plane, the magnetic anisotropy energy of Mn2C monolayer is

  3. 3-Dimensional culture systems for anti-cancer compound profiling and high-throughput screening reveal increases in EGFR inhibitor-mediated cytotoxicity compared to monolayer culture systems.

    PubMed

    Howes, Amy L; Richardson, Robyn D; Finlay, Darren; Vuori, Kristiina

    2014-01-01

    3-dimensional (3D) culture models have the potential to bridge the gap between monolayer cell culture and in vivo studies. To benefit anti-cancer drug discovery from 3D models, new techniques are needed that enable their use in high-throughput (HT) screening amenable formats. We have established miniaturized 3D culture methods robust enough for automated HT screens. We have applied these methods to evaluate the sensitivity of normal and tumorigenic breast epithelial cell lines against a panel of oncology drugs when cultured as monolayers (2D) and spheroids (3D). We have identified two classes of compounds that exhibit preferential cytotoxicity against cancer cells over normal cells when cultured as 3D spheroids: microtubule-targeting agents and epidermal growth factor receptor (EGFR) inhibitors. Further improving upon our 3D model, superior differentiation of EC50 values in the proof-of-concept screens was obtained by co-culturing the breast cancer cells with normal human fibroblasts and endothelial cells. Further, the selective sensitivity of the cancer cells towards chemotherapeutics was observed in 3D co-culture conditions, rather than as 2D co-culture monolayers, highlighting the importance of 3D cultures. Finally, we examined the putative mechanisms that drive the differing potency displayed by EGFR inhibitors. In summary, our studies establish robust 3D culture models of human cells for HT assessment of tumor cell-selective agents. This methodology is anticipated to provide a useful tool for the study of biological differences within 2D and 3D culture conditions in HT format, and an important platform for novel anti-cancer drug discovery. PMID:25247711

  4. A Self-Limiting Electro-Ablation Technique for the Top-Down Synthesis of Large-Area Monolayer Flakes of 2D Materials.

    PubMed

    Das, Saptarshi; Bera, Mrinal K; Tong, Sheng; Narayanan, Badri; Kamath, Ganesh; Mane, Anil; Paulikas, Arvydas P; Antonio, Mark R; Sankaranarayanan, Subramanian K R S; Roelofs, Andreas K

    2016-01-01

    We report the discovery of an electrochemical process that converts two dimensional layered materials of arbitrary thicknesses into monolayers. The lateral dimensions of the monolayers obtained by the process within a few seconds time at room temperature were as large as 0.5 mm. The temporal and spatial dynamics of this physical phenomenon, studied on MoS2 flakes using ex-situ AFM imaging, Raman mapping, and photoluminescence measurements trace the origin of monolayer formation to a substrate-assisted self-limiting electrochemical ablation process. Electronic structure and atomistic calculations point to the interplay between three essential factors in the process: (1) strong covalent interaction of monolayer MoS2 with the substrate; (2) electric-field induced differences in Gibbs free energy of exfoliation; (3) dispersion of MoS2 in aqueous solution of hydrogen peroxide. This process was successful in obtaining monolayers of other 2D transition metal dichalcogenides, like WS2 and MoTe2 as well. PMID:27323877

  5. A Self-Limiting Electro-Ablation Technique for the Top-Down Synthesis of Large-Area Monolayer Flakes of 2D Materials

    PubMed Central

    Das, Saptarshi; Bera, Mrinal K.; Tong, Sheng; Narayanan, Badri; Kamath, Ganesh; Mane, Anil; Paulikas, Arvydas P.; Antonio, Mark R.; Sankaranarayanan, Subramanian K. R. S.; Roelofs, Andreas K.

    2016-01-01

    We report the discovery of an electrochemical process that converts two dimensional layered materials of arbitrary thicknesses into monolayers. The lateral dimensions of the monolayers obtained by the process within a few seconds time at room temperature were as large as 0.5 mm. The temporal and spatial dynamics of this physical phenomenon, studied on MoS2 flakes using ex-situ AFM imaging, Raman mapping, and photoluminescence measurements trace the origin of monolayer formation to a substrate-assisted self-limiting electrochemical ablation process. Electronic structure and atomistic calculations point to the interplay between three essential factors in the process: (1) strong covalent interaction of monolayer MoS2 with the substrate; (2) electric-field induced differences in Gibbs free energy of exfoliation; (3) dispersion of MoS2 in aqueous solution of hydrogen peroxide. This process was successful in obtaining monolayers of other 2D transition metal dichalcogenides, like WS2 and MoTe2 as well. PMID:27323877

  6. Enhanced Collective Magnetic Properties in 2D Monolayers of Iron Oxide Nanoparticles Favored by Local Order and Local 1D Shape Anisotropy.

    PubMed

    Toulemon, Delphine; Liu, Yu; Cattoën, Xavier; Leuvrey, Cédric; Bégin-Colin, Sylvie; Pichon, Benoit P

    2016-02-16

    Magnetic nanoparticle arrays represent a very attractive research field because their collective properties can be efficiently modulated as a function of the structure of the assembly. Nevertheless, understanding the way dipolar interactions influence the intrinsic magnetic properties of nanoparticles still remains a great challenge. In this study, we report on the preparation of 2D assemblies of iron oxide nanoparticles as monolayers deposited onto substrates. Assemblies have been prepared by using the Langmuir-Blodgett technique and the SAM assisted assembling technique combined to CuAAC "click" reaction. These techniques afford to control the formation of well-defined monolayers of nanoparticles on large areas. The LB technique controls local ordering of nanoparticles, while adjusting the kinetics of CuAAC "click" reaction strongly affects the spatial arrangement of nanoparticles in monolayers. Fast kinetics favor disordered assemblies while slow kinetics favor the formation of chain-like structures. Such anisotropic assemblies are induced by dipolar interactions between nanoparticles as no magnetic field is applied and no solvent evaporation is performed. The collective magnetic properties of monolayers are studied as a function of average interparticle distance, local order and local shape anisotropy. We demonstrate that local control on spatial arrangement of nanoparticles in monolayers significantly strengthens dipolar interactions which enhances collective properties and results in possible super ferromagnetic order. PMID:26807596

  7. A Self-Limiting Electro-Ablation Technique for the Top-Down Synthesis of Large-Area Monolayer Flakes of 2D Materials

    NASA Astrophysics Data System (ADS)

    Das, Saptarshi; Bera, Mrinal K.; Tong, Sheng; Narayanan, Badri; Kamath, Ganesh; Mane, Anil; Paulikas, Arvydas P.; Antonio, Mark R.; Sankaranarayanan, Subramanian K. R. S.; Roelofs, Andreas K.

    2016-06-01

    We report the discovery of an electrochemical process that converts two dimensional layered materials of arbitrary thicknesses into monolayers. The lateral dimensions of the monolayers obtained by the process within a few seconds time at room temperature were as large as 0.5 mm. The temporal and spatial dynamics of this physical phenomenon, studied on MoS2 flakes using ex-situ AFM imaging, Raman mapping, and photoluminescence measurements trace the origin of monolayer formation to a substrate-assisted self-limiting electrochemical ablation process. Electronic structure and atomistic calculations point to the interplay between three essential factors in the process: (1) strong covalent interaction of monolayer MoS2 with the substrate; (2) electric-field induced differences in Gibbs free energy of exfoliation; (3) dispersion of MoS2 in aqueous solution of hydrogen peroxide. This process was successful in obtaining monolayers of other 2D transition metal dichalcogenides, like WS2 and MoTe2 as well.

  8. A Self-Limiting Electro-Ablation Technique for the Top-Down Synthesis of Large-Area Monolayer Flakes of 2D Materials.

    PubMed

    Das, Saptarshi; Bera, Mrinal K; Tong, Sheng; Narayanan, Badri; Kamath, Ganesh; Mane, Anil; Paulikas, Arvydas P; Antonio, Mark R; Sankaranarayanan, Subramanian K R S; Roelofs, Andreas K

    2016-06-21

    We report the discovery of an electrochemical process that converts two dimensional layered materials of arbitrary thicknesses into monolayers. The lateral dimensions of the monolayers obtained by the process within a few seconds time at room temperature were as large as 0.5 mm. The temporal and spatial dynamics of this physical phenomenon, studied on MoS2 flakes using ex-situ AFM imaging, Raman mapping, and photoluminescence measurements trace the origin of monolayer formation to a substrate-assisted self-limiting electrochemical ablation process. Electronic structure and atomistic calculations point to the interplay between three essential factors in the process: (1) strong covalent interaction of monolayer MoS2 with the substrate; (2) electric-field induced differences in Gibbs free energy of exfoliation; (3) dispersion of MoS2 in aqueous solution of hydrogen peroxide. This process was successful in obtaining monolayers of other 2D transition metal dichalcogenides, like WS2 and MoTe2 as well.

  9. Keratinocyte-releasable factors increased the expression of MMP1 and MMP3 in co-cultured fibroblasts under both 2D and 3D culture conditions.

    PubMed

    Li, Min; Moeen Rezakhanlou, Alireza; Chavez-Munoz, Claudia; Lai, Amy; Ghahary, Aziz

    2009-12-01

    Matrix metalloproteinases (MMPs) are key elements in extracellular matrix (ECM) degradation and scar remodeling during the wound-healing process. Our previous data revealed that keratinocyte-releasable factors significantly increased the expression of fibroblast MMPs in monolayer-cultured fibroblasts. In this study, we analyzed the differences in the MMP expressions of fibroblasts in a three-dimensional fibroblast-populated collagen gel (3D FPCG) from that in a two-dimensional monolayer-cultured fibroblasts when both co-cultured with keratinocytes. Differential mRNA and protein expression of fibroblasts were examined by microarray, RT-PCR, and western blot. Our results showed that fibroblasts co-cultured with keratinocytes in a 3D FPCG expressed significantly higher MMP1 and MMP3 at the gene and protein levels. Due to the physiological advantages of a 3D FPCG model to a 2D system, we concluded that the 3D FPCG model may provide a better means of understanding the fibroblast-keratinocyte cross-talk during the wound-healing process. PMID:19521668

  10. Genotoxic Effects of Low- and High-LET Radiation on Human Epithelial Cells Grown in 2-D Versus 3-D Culture

    NASA Technical Reports Server (NTRS)

    Patel, Z. S.; Cucinotta, F. A.; Huff, J. L.

    2011-01-01

    Risk estimation for radiation-induced cancer relies heavily on human epidemiology data obtained from terrestrial irradiation incidents from sources such as medical and occupational exposures as well as from the atomic bomb survivors. No such data exists for exposures to the types and doses of high-LET radiation that will be encountered during space travel; therefore, risk assessment for space radiation requires the use of data derived from cell culture and animal models. The use of experimental models that most accurately replicate the response of human tissues is critical for precision in risk projections. This work compares the genotoxic effects of radiation on normal human epithelial cells grown in standard 2-D monolayer culture compared to 3-D organotypic co-culture conditions. These 3-D organotypic models mimic the morphological features, differentiation markers, and growth characteristics of fully-differentiated normal human tissue and are reproducible using defined components. Cultures were irradiated with 2 Gy low-LET gamma rays or varying doses of high-LET particle radiation and genotoxic damage was measured using a modified cytokinesis block micronucleus assay. Our results revealed a 2-fold increase in residual damage in 2 Gy gamma irradiated cells grown under organotypic culture conditions compared to monolayer culture. Irradiation with high-LET particle radiation gave similar results, while background levels of damage were comparable under both scenarios. These observations may be related to the phenomenon of "multicellular resistance" where cancer cells grown as 3-D spheroids or in vivo exhibit an increased resistance to killing by chemotherapeutic agents compared to the same cells grown in 2-D culture. A variety of factors are likely involved in mediating this process, including increased cell-cell communication, microenvironment influences, and changes in cell cycle kinetics that may promote survival of damaged cells in 3-D culture that would

  11. Oxygen consumption of human heart cells in monolayer culture.

    PubMed

    Sekine, Kaori; Kagawa, Yuki; Maeyama, Erina; Ota, Hiroki; Haraguchi, Yuji; Matsuura, Katsuhisa; Shimizu, Tatsuya

    2014-09-26

    Tissue engineering in cardiovascular regenerative therapy requires the development of an efficient oxygen supply system for cell cultures. However, there are few studies which have examined human cardiomyocytes in terms of oxygen consumption and metabolism in culture. We developed an oxygen measurement system equipped with an oxygen microelectrode sensor and estimated the oxygen consumption rates (OCRs) by using the oxygen concentration profiles in culture medium. The heart is largely made up of cardiomyocytes, cardiac fibroblasts, and cardiac endothelial cells. Therefore, we measured the oxygen consumption of human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CMs), cardiac fibroblasts, human cardiac microvascular endothelial cell and aortic smooth muscle cells. Then we made correlations with their metabolisms. In hiPSC-CMs, the value of the OCR was 0.71±0.38pmol/h/cell, whereas the glucose consumption rate and lactate production rate were 0.77±0.32pmol/h/cell and 1.61±0.70pmol/h/cell, respectively. These values differed significantly from those of the other cells in human heart. The metabolism of the cells that constitute human heart showed the molar ratio of lactate production to glucose consumption (L/G ratio) that ranged between 1.97 and 2.2. Although the energy metabolism in adult heart in vivo is reported to be aerobic, our data demonstrated a dominance of anaerobic glycolysis in an in vitro environment. With our measuring system, we clearly showed the differences in the metabolism of cells between in vivo and in vitro monolayer culture. Our results regarding cell OCRs and metabolism may be useful for future tissue engineering of human heart.

  12. Synthesis, characterization, monolayer assembly and 2D lanthanide coordination of a linear terphenyl-di(propiolonitrile) linker on Ag(111)

    PubMed Central

    Chen, Zhi; Urgel, José I; Écija, David; Fuhr, Olaf; Auwärter, Willi

    2015-01-01

    Summary As a continuation of our work employing polyphenylene-dicarbonitrile molecules and in particular the terphenyl derivative 1 (TDCN), we have synthesized a novel ditopic terphenyl-4,4"-di(propiolonitrile) (2) linker for the self-assembly of organic monolayers and metal coordination at interfaces. The structure of the organic linker 2 was confirmed by single crystal X-ray diffraction analysis (XRD). On the densely packed Ag(111) surface, the terphenyl-4,4"-di(propiolonitrile) linkers self-assemble in a regular, molecular chevron arrangement exhibiting a Moiré pattern. After the exposure of the molecular monolayer to a beam of Gd atoms, the propiolonitrile groups get readily involved in metal–ligand coordination interactions. Distinct coordination motifs evolve with coordination numbers varying between three and six for the laterally-bound Gd centers. The linker molecules retain an overall flat adsorption geometry. However, only networks with restricted local order were obtained, in marked contrast to previously employed, simpler polyphenylene-dicarbonitrile 1 linkers. PMID:25821671

  13. Regulation of bile acid synthesis in rat hepatocyte monolayer cultures

    SciTech Connect

    Kubaska, W.M.

    1986-01-01

    Primary hepatocyte monolayer cultures (PHC) were prepared and incubated in serum free media. Cells from a cholestyramine fed rat converted exogenous (/sup 14/C)-cholesterol into (/sup 14/C)-bile acids at a 3-fold greater rate than rats fed a normal diet. PHC synthesize bile acids (BA) at a rate of approximately 0.06 ..mu..g/mg protein/h. The major bile acid composition, as determined by GLC, was ..beta..-muricholic acid (BMC) and cholic acid (CA) in a 3:1 ratio, respectively. PHC rapidly converted free BA and BA intermediates into taurine conjugated trihydroxy-BA up to 87h after plating. 3-Hydroxy-3-methylglutaryl-coenzyme A-reductase activity assayed in microsomes prepared from PHC, decreased during the initial 48h, then remained constant. Cholesterol 7..cap alpha..-hydroxylase activity decreased during the initial 48h, then increased during the next 48h. This occurred while whole cells produced BA at a linear rate. The effect of individual BA on bile acid synthesis (BAS) was also studied. Relative rates of BAS were measured as the conversion of (/sup 14/C)-cholesterol into (/sup 14/C)-BA. BA combinations were tested in order to simulate the composition of the enterohepatic circulation. The addition of TCA (525 ..mu..M) plus TCDCA (80..mu..M), in concentrations which greatly exceed the concentration of BA (60..mu..M) in rate portal blood, failed to inhibit BAS. BA plus phospholipid and/or cholesterol also did not inhibit BAS. Surprisingly, crude rat bile with a final concentration comparable to those in the synthetic mix inhibited (/sup 14/C)-cholesterol conversion into (/sup 14/C)-BA.

  14. Transcriptional profiles of valvular interstitial cells cultured on tissue culture polystyrene, on 2D hydrogels, or within 3D hydrogels

    PubMed Central

    Mabry, Kelly M.; Payne, Samuel Z.; Anseth, Kristi S.

    2015-01-01

    Valvular interstitial cells (VICs) actively maintain and repair heart valve tissue; however, persistent activation of VICs to a myofibroblast phenotype can lead to aortic stenosis (Chen and Simmons, 2011) [1]. To better understand and quantify how microenvironmental cues influence VIC phenotype, we compared expression profiles of VICs cultured on/in poly(ethylene glycol) (PEG) gels to those cultured on tissue culture polystyrene (TCPS), as well as fresh isolates. Here, we present both the raw and processed microarray data from these culture conditions. Interpretation of this data can be found in a research article entitled “Microarray analyses to quantify advantages of 2D and 3D hydrogel culture systems in maintaining the native valvular interstitial cell phenotype” (Mabry et al., 2015) [2]. PMID:26702427

  15. Effect of Matrix on Cardiomyocyte Viscoelastic Properties in 2D Culture

    PubMed Central

    Deitch, Sandra; Gao, Bruce Z.; Dean, Delphine

    2012-01-01

    Cardiomyocyte phenotype changes significantly in 2D culture systems depending on the substrate composition and organization. Given the variety of substrates that are used both for basic cardiac cell culture studies and for regenerative medicine applications, there is a critical need to understand how the different matrices influence cardiac cell mechanics. In the current study, the mechanical properties of neonatal rat cardiomyocytes cultured in a subconfluent layer upon aligned and unaligned collagen and fibronectin matrices were assessed over a two week period using atomic force microscopy. The elastic modulus was estimated by fitting the Hertz model to force curve data and the percent relaxation was determined from stress relaxation curves. The Quasilinear Viscoelastic (QLV) and Standard Linear Solid (SLS) models were fit to the stress relaxation data. Cardiomyocyte cellular mechanical properties were found to be highly dependent on matrix composition and organization as well as time in culture. It was observed that the cells stiffened and relaxed less over the first 3 to 5 days in culture before reaching a plateau in their mechanical properties. After day 5, cells on aligned matrices were stiffer than cells on unaligned matrices and cells on fibronectin matrices were stiffer than cells on collagen matrices. No such significant trends in percent relaxation measurements were observed but the QLV model fit the data very well. These results were correlated with observed changes in cellular structure associated with culture on the different substrates and analyzed for cell-to-cell variability. PMID:23285736

  16. Development of drug loaded nanoparticles for tumor targeting. Part 1: synthesis, characterization, and biological evaluation in 2D cell cultures

    NASA Astrophysics Data System (ADS)

    El-Dakdouki, Mohammad H.; Puré, Ellen; Huang, Xuefei

    2013-04-01

    Nanoparticles (NPs) are being extensively studied as carriers for drug delivery, but they often have limited penetration inside tumors. We envision that by targeting an endocytic receptor on the cell surface, the uptake of NPs can be significantly enhanced through receptor mediated endocytosis. In addition, if the receptor is recycled to the cell surface, the NP cargo can be transported out of the cells, which is then taken up by neighboring cells thus enhancing solid tumor penetration. To validate our hypothesis, in the first of two articles, we report the synthesis of doxorubicin (DOX)-loaded, hyaluronan (HA) coated silica nanoparticles (SNPs) containing a highly fluorescent core to target CD44, a receptor expressed on the cancer cell surface. HA was conjugated onto amine-functionalized SNPs prepared through an oil-water microemulsion method. The immobilization of the cytotoxic drug DOX was achieved through an acid sensitive hydrazone linkage. The NPs were fully characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential measurements, thermogravimetric analysis (TGA), UV-vis absorbance, and nuclear magnetic resonance (NMR). Initial biological evaluation experiments demonstrated that compared to ligand-free SNPs, the uptake of HA-SNPs by the CD44-expressing SKOV-3 ovarian cancer cells was significantly enhanced when evaluated in the 2D monolayer cell culture. Mechanistic studies suggested that cellular uptake of HA-SNPs was mainly through CD44 mediated endocytosis. HA-SNPs with immobilized DOX were endocytosed efficiently by the SKOV-3 cells as well. The enhanced tumor penetration and drug delivery properties of HA-SNPs will be evaluated in 3D tumor models in the subsequent paper.Nanoparticles (NPs) are being extensively studied as carriers for drug delivery, but they often have limited penetration inside tumors. We envision that by targeting an endocytic receptor on the cell surface, the uptake of NPs can be

  17. Video lensfree microscopy of 2D and 3D culture of cells

    NASA Astrophysics Data System (ADS)

    Allier, C. P.; Vinjimore Kesavan, S.; Coutard, J.-G.; Cioni, O.; Momey, F.; Navarro, F.; Menneteau, M.; Chalmond, B.; Obeid, P.; Haguet, V.; David-Watine, B.; Dubrulle, N.; Shorte, S.; van der Sanden, B.; Di Natale, C.; Hamard, L.; Wion, D.; Dolega, M. E.; Picollet-D'hahan, N.; Gidrol, X.; Dinten, J.-M.

    2014-03-01

    Innovative imaging methods are continuously developed to investigate the function of biological systems at the microscopic scale. As an alternative to advanced cell microscopy techniques, we are developing lensfree video microscopy that opens new ranges of capabilities, in particular at the mesoscopic level. Lensfree video microscopy allows the observation of a cell culture in an incubator over a very large field of view (24 mm2) for extended periods of time. As a result, a large set of comprehensive data can be gathered with strong statistics, both in space and time. Video lensfree microscopy can capture images of cells cultured in various physical environments. We emphasize on two different case studies: the quantitative analysis of the spontaneous network formation of HUVEC endothelial cells, and by coupling lensfree microscopy with 3D cell culture in the study of epithelial tissue morphogenesis. In summary, we demonstrate that lensfree video microscopy is a powerful tool to conduct cell assays in 2D and 3D culture experiments. The applications are in the realms of fundamental biology, tissue regeneration, drug development and toxicology studies.

  18. Development of drug loaded nanoparticles for tumor targeting. Part 1: synthesis, characterization, and biological evaluation in 2D cell cultures

    PubMed Central

    El-Dakdouki, Mohammad H.; Puré, Ellen; Huang, Xuefei

    2013-01-01

    Nanoparticles (NPs) are being extensively studied as carriers for drug delivery, but they often have limited penetration inside tumor. We envision that by targeting an endocytic receptor on cell surface, the uptake of NPs can be significantly enhanced through receptor mediated endocytosis. In addition, if the receptor is recycled to cell surface, the NP cargo can be transported out of the cells, which are then taken up by neighboring cells thus enhancing solid tumor penetration. To validate our hypothesis, in the first of two articles, we report the synthesis of doxorubicin (DOX)-loaded, hyaluronan (HA) coated silica nanoparticles (SNP) containing a highly fluorescent core to target CD44, a receptor expressed on cancer cell surface. HA was conjugated onto amine-functionalized SNPs prepared through an oil/water microemulsion method. The immobilization of the cytotoxic drug DOX was achieved through an acid sensitive hydrazone linkage. The NPs were fully characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential measurements, thermal gravimetric analysis (TGA), UV-vis absorbance, and nuclear magnetic resonance (NMR). Initial biological evaluation experiments demonstrated that compared to ligand-free SNPs, the uptake of HA-SNP by the CD44-expressing SKOV-3 ovarian cancer cells was significantly enhanced when evaluated in the 2D monolayer cell culture. Mechanistic studies suggested that cellular uptake of HA-SNP was mainly through CD44 mediated endocytosis. HA-SNPs with DOX immobilized were endocytosed efficiently by the SKOV-3 cells as well. The enhanced tumor penetration and drug delivery properties of HA-SNP will be evaluated in 3D tumor models in the subsequent paper. PMID:23529646

  19. Defining an optimal surface chemistry for pluripotent stem cell culture in 2D and 3D

    NASA Astrophysics Data System (ADS)

    Zonca, Michael R., Jr.

    Surface chemistry is critical for growing pluripotent stem cells in an undifferentiated state. There is great potential to engineer the surface chemistry at the nanoscale level to regulate stem cell adhesion. However, the challenge is to identify the optimal surface chemistry of the substrata for ES cell attachment and maintenance. Using a high-throughput polymerization and screening platform, a chemically defined, synthetic polymer grafted coating that supports strong attachment and high expansion capacity of pluripotent stem cells has been discovered using mouse embryonic stem (ES) cells as a model system. This optimal substrate, N-[3-(Dimethylamino)propyl] methacrylamide (DMAPMA) that is grafted on 2D synthetic poly(ether sulfone) (PES) membrane, sustains the self-renewal of ES cells (up to 7 passages). DMAPMA supports cell attachment of ES cells through integrin beta1 in a RGD-independent manner and is similar to another recently reported polymer surface. Next, DMAPMA has been able to be transferred to 3D by grafting to synthetic, polymeric, PES fibrous matrices through both photo-induced and plasma-induced polymerization. These 3D modified fibers exhibited higher cell proliferation and greater expression of pluripotency markers of mouse ES cells than 2D PES membranes. Our results indicated that desirable surfaces in 2D can be scaled to 3D and that both surface chemistry and structural dimension strongly influence the growth and differentiation of pluripotent stem cells. Lastly, the feasibility of incorporating DMAPMA into a widely used natural polymer, alginate, has been tested. Novel adhesive alginate hydrogels have been successfully synthesized by either direct polymerization of DMAPMA and methacrylic acid blended with alginate, or photo-induced DMAPMA polymerization on alginate nanofibrous hydrogels. In particular, DMAPMA-coated alginate hydrogels support strong ES cell attachment, exhibiting a concentration dependency of DMAPMA. This research provides a

  20. Hydroxylation, conjugation and sulfation of bile acids in primary monolayer cultures of rat hepatocytes

    SciTech Connect

    Princen, H.M.; Meijer, P.

    1988-08-15

    Hydroxylation of lithocholic, chenodeoxycholic, deoxycholic and cholic acids was studied in monolayers of rat hepatocytes cultured for 76 h. The majority of added lithocholic and chenodeoxycholic acids was metabolized to beta-muricholic acid (56-76%). A small part of these bile acids (9%), however, and a considerable amount of deoxycholic and cholic acids (21%) were converted into metabolites more polar than cholic acid in the first culture period. Formation of these compounds decreased during the last day of culture. Bile acids synthesized after addition of (4-/sup 14/C)-cholesterol were almost entirely (97%) sulfated and/or conjugated, predominantly with taurine (54-66%), during culture. Sulfated bile acids were mainly composed of free bile acids. The ability of hepatocytes to sulfurylate bile acids declined with culture age. Thus, rat hepatocytes in primary monolayer culture are capable to sulfurylate bile acids and to hydroxylate trihydroxylated bile acids, suggesting formation of polyhydroxylated metabolites.

  1. Polarized location of SLC and ABC drug transporters in monolayer-cultured human hepatocytes.

    PubMed

    Le Vee, Marc; Jouan, Elodie; Noel, Gregory; Stieger, Bruno; Fardel, Olivier

    2015-08-01

    Human hepatocytes cultured in a monolayer configuration represent a well-established in vitro model in liver toxicology, notably used in drug transporter studies. Polarized status of drug transporters, i.e., their coordinated location at sinusoidal or canalicular membranes, remains however incompletely documented in these cultured hepatocytes. The present study was therefore designed to analyze transporter expression and location in such cells. Most of drug transporters were first shown to be present at notable mRNA levels in monolayer-cultured human hepatocytes. Cultured human hepatocytes, which morphologically exhibited bile canaliculi-like structures, were next demonstrated, through immunofluorescence staining, to express the influx transporters organic anion transporting polypeptide (OATP) 1B1, OATP2B1 and organic cation transporter (OCT) 1 and the efflux transporter multidrug resistance-associated protein (MRP) 3 at their sinusoidal pole. In addition, the efflux transporters P-glycoprotein and MRP2 were detected at the canalicular pole of monolayer-cultured human hepatocytes. Moreover, canalicular secretion of reference substrates for the efflux transporters bile salt export pump, MRP2 and P-glycoprotein as well as sinusoidal drug transporter activities were observed. This polarized and functional expression of drug transporters in monolayer-cultured human hepatocytes highlights the interest of using this human in vitro cell model in xenobiotic transport studies.

  2. Intracellular ROS mediates gas plasma-facilitated cellular transfection in 2D and 3D cultures.

    PubMed

    Xu, Dehui; Wang, Biqing; Xu, Yujing; Chen, Zeyu; Cui, Qinjie; Yang, Yanjie; Chen, Hailan; Kong, Michael G

    2016-06-14

    This study reports the potential of cold atmospheric plasma (CAP) as a versatile tool for delivering oligonucleotides into mammalian cells. Compared to lipofection and electroporation methods, plasma transfection showed a better uptake efficiency and less cell death in the transfection of oligonucleotides. We demonstrated that the level of extracellular aqueous reactive oxygen species (ROS) produced by gas plasma is correlated with the uptake efficiency and that this is achieved through an increase of intracellular ROS levels and the resulting increase in cell membrane permeability. This finding was supported by the use of ROS scavengers, which reduced CAP-based uptake efficiency. In addition, we found that cold atmospheric plasma could transfer oligonucleotides such as siRNA and miRNA into cells even in 3D cultures, thus suggesting the potential for unique applications of CAP beyond those provided by standard transfection techniques. Together, our results suggest that cold plasma might provide an efficient technique for the delivery of siRNA and miRNA in 2D and 3D culture models.

  3. Intracellular ROS mediates gas plasma-facilitated cellular transfection in 2D and 3D cultures

    PubMed Central

    Xu, Dehui; Wang, Biqing; Xu, Yujing; Chen, Zeyu; Cui, Qinjie; Yang, Yanjie; Chen, Hailan; Kong, Michael G.

    2016-01-01

    This study reports the potential of cold atmospheric plasma (CAP) as a versatile tool for delivering oligonucleotides into mammalian cells. Compared to lipofection and electroporation methods, plasma transfection showed a better uptake efficiency and less cell death in the transfection of oligonucleotides. We demonstrated that the level of extracellular aqueous reactive oxygen species (ROS) produced by gas plasma is correlated with the uptake efficiency and that this is achieved through an increase of intracellular ROS levels and the resulting increase in cell membrane permeability. This finding was supported by the use of ROS scavengers, which reduced CAP-based uptake efficiency. In addition, we found that cold atmospheric plasma could transfer oligonucleotides such as siRNA and miRNA into cells even in 3D cultures, thus suggesting the potential for unique applications of CAP beyond those provided by standard transfection techniques. Together, our results suggest that cold plasma might provide an efficient technique for the delivery of siRNA and miRNA in 2D and 3D culture models. PMID:27296089

  4. The Cultural Divide: Exponential Growth in Classical 2D and Metabolic Equilibrium in 3D Environments

    PubMed Central

    Kanlaya, Rattiyaporn; Borkowski, Kamil; Schwämmle, Veit; Dai, Jie; Joensen, Kira Eyd; Wojdyla, Katarzyna; Carvalho, Vasco Botelho; Fey, Stephen J.

    2014-01-01

    Introduction Cellular metabolism can be considered to have two extremes: one is characterized by exponential growth (in 2D cultures) and the other by a dynamic equilibrium (in 3D cultures). We have analyzed the proteome and cellular architecture at these two extremes and found that they are dramatically different. Results Structurally, actin organization is changed, microtubules are increased and keratins 8 and 18 decreased. Metabolically, glycolysis, fatty acid metabolism and the pentose phosphate shunt are increased while TCA cycle and oxidative phosphorylation is unchanged. Enzymes involved in cholesterol and urea synthesis are increased consistent with the attainment of cholesterol and urea production rates seen in vivo. DNA repair enzymes are increased even though cells are predominantly in Go. Transport around the cell – along the microtubules, through the nuclear pore and in various types of vesicles has been prioritized. There are numerous coherent changes in transcription, splicing, translation, protein folding and degradation. The amount of individual proteins within complexes is shown to be highly coordinated. Typically subunits which initiate a particular function are present in increased amounts compared to other subunits of the same complex. Summary We have previously demonstrated that cells at dynamic equilibrium can match the physiological performance of cells in tissues in vivo. Here we describe the multitude of protein changes necessary to achieve this performance. PMID:25222612

  5. Intracellular ROS mediates gas plasma-facilitated cellular transfection in 2D and 3D cultures.

    PubMed

    Xu, Dehui; Wang, Biqing; Xu, Yujing; Chen, Zeyu; Cui, Qinjie; Yang, Yanjie; Chen, Hailan; Kong, Michael G

    2016-01-01

    This study reports the potential of cold atmospheric plasma (CAP) as a versatile tool for delivering oligonucleotides into mammalian cells. Compared to lipofection and electroporation methods, plasma transfection showed a better uptake efficiency and less cell death in the transfection of oligonucleotides. We demonstrated that the level of extracellular aqueous reactive oxygen species (ROS) produced by gas plasma is correlated with the uptake efficiency and that this is achieved through an increase of intracellular ROS levels and the resulting increase in cell membrane permeability. This finding was supported by the use of ROS scavengers, which reduced CAP-based uptake efficiency. In addition, we found that cold atmospheric plasma could transfer oligonucleotides such as siRNA and miRNA into cells even in 3D cultures, thus suggesting the potential for unique applications of CAP beyond those provided by standard transfection techniques. Together, our results suggest that cold plasma might provide an efficient technique for the delivery of siRNA and miRNA in 2D and 3D culture models. PMID:27296089

  6. Primary monolayer culture of adult mouse hepatocytes -- a model for the study of hepatotropic viruses.

    PubMed

    Arnheiter, H

    1980-01-01

    Primary monolayer cultures of adult mouse hepatocytes isolated by collagenase perfusion of the liver in situ were exposed to 2 hepatotropic viruses, an avian influenza A virus adapted to grow in mouse liver in vivo and a herpes simplex type I virus. Influenza virus infection led to lysis ofindividual hepatocytes and total monolayer destruction within 18 to 120 hours after infection according to the virus dose used. Virus replication was evidenced by assaying hepatocyte supernates for hemagglutinin and infectivity, by immunofluorescent staining and by electron microscopy. Herpes virus infection resulted in polykaryocyte formation followed by nuclear pycnosis and cell lysis. Virus replication was assayed by titration of supernate infectivity.

  7. Purification of monolayer cell cultures of the endocrine pancreas.

    PubMed

    Braaten, J T; Järlfors, U; Smith, D S; Mintz, D H

    1975-01-01

    Experimental use of primary cultures of endocrine pancreas is constrained by early, vigorous proliferation of fibroblastoid cells. The addition of heavy metals, sodium ethylmercurithiosalicylate, phenyl mercuric acetate, phenyl mercuric nitrate and sodium aurothiomalate to the culture media selectively destroys these fibroblastoid cells yielding highly enriched, morphologically intact, functionally competent endocrine cells that are capable of cell replication. This action of heavy metals appears to be due to reversible inhibition of sulfhydryl enzymes since glutathione and thioglycolate were demonstrated to completely inhibit the cytotoxic effects of the mercury and gold containing agents, respectively. Certain variables in the application of the mercurial agents to pancreatic endocrine cell cultures were defined, most notably the enhanced sensitivity of fetal vs. neonatal tissue, and in inverse relationship of cell density to effective toxicity. After removal of the heavy metal agent from the culture media, many pancreatic islets send out cytoplasmic projections, containing large numbers of oriented microtubules which serve as bridging units to adjacent endocrine cells. The sustained availability of virtually pure pancreatic endocrine cell cultures, which results from the application of mercury to the culture media will undoubtedly permit many aspects of the cell biology of the endocrine pancreas to be directly and sequentially assailed. PMID:1239830

  8. Some but not All Tetrahymena Species Destroy Monolayer Cultures of Cells from a Wide Range of Tissues and Species.

    PubMed

    Pinheiro, Marcel D O; Bols, Niels C

    2015-01-01

    The activities of Tetrahymena corlissi, Tetrahymena thermophila, and Tetrahymena canadensis were studied in coculture with cell lines of insects, fish, amphibians, and mammals. These ciliates remained viable regardless of the animal cell line partner. All three species could engulf animal cells in suspension. However, if the animal cells were monolayer cultures, the monolayers were obliterated by T. corlissi and T. thermophila. Both fibroblast and epithelial monolayers were destroyed but the destruction of human cell monolayers was done more effectively by T. thermophila. By contrast, T. canadensis was unable to destroy any monolayer. At 4 °C T. thermophila and T. corlissi did not carryout phagocytosis and did not destroy monolayers, whereas T. canadensis was able to carryout phagocytosis but still could not destroy monolayers. Therefore, monolayer destruction appeared to require phagocytosis, but by itself this was insufficient. In addition, the ciliates expressed a unique swimming behavior. Tetrahymena corlissi and T. thermophila swam vigorously and repeatedly into the monolayer, which seemed to loosen or dislodge cells, whereas T. canadensis swam above the monolayer. Therefore, differences in swimming behavior might explain why T. corlissi has been reported to be a pathogen but T. canadensis has not.

  9. Epithelial monolayer culture system for real‐time single‐cell analyses

    PubMed Central

    Seo, Jong Bae; Moody, Mark; Koh, Duk‐Su

    2014-01-01

    Abstract Many epithelial cells form polarized monolayers under in vivo and in vitro conditions. Typically, epithelial cells are cultured for differentiation on insert systems where cells are plated on a porous filter membrane. Although the cultured monolayers have been a standard system to study epithelial physiology, there are some limits: The epithelial cells growing inside the commercial inserts are not optimal to visualize directly through lenses on inverted microscopes. The cell images are optically distorted and background fluorescence is bright due to the filter membrane positioned between the cells and the lens. In addition, the cells are not easily accessible by electrodes due to the presence of tall side walls. Here, we present the design, fabrication, and practical applications of an improved system for analysis of polarized epithelial monolayers. This new system allows (1) direct imaging of cells without an interfering filter membrane, (2) electrophysiological measurements, and (3) detection of apical secretion with minimal dilution. Therefore, our culture method is optimized to study differentiated epithelial cells at the single‐cell and subcellular levels, and can be extended to other cell types with minor modifications. PMID:24771696

  10. Planar arrangement of eukaryotic cells in merged hydrogels combines the advantages of 3-D and 2-D cultures.

    PubMed

    Gordeev, Alexander A; Chetverina, Helena V; Chetverin, Alexander B

    2012-05-01

    We report an unordered 2-D array of eukaryotic cells completely embedded in a 3-D matrix. Every cell is located at the same distance from the gel surface, which ensures uniformity of growth conditions and ease of observation characteristic of a 2-D culture. Each cell is firmly immobilized, and each has a unique address in the array. The cells can be rapidly screened, individually monitored during extended time periods, and cultured with the formation of spheroid microcolonies characteristic of a 3-D culture. Individual microcolonies can be extracted from the gel and further propagated, thus enabling isolation of pure cell clones from rather dense cell populations and rapid drug-free generation of stable cell lines.

  11. Chemotherapeutic efficiency of drugs in vitro: Comparison of doxorubicin exposure in 3D and 2D culture matrices.

    PubMed

    Casey, A; Gargotti, M; Bonnier, F; Byrne, H J

    2016-06-01

    The interest in the use of 3D matrices for in vitro analysis, with a view to increasing the relevance of in vitro studies and reducing the dependence on in vivo studies, has been growing in recent years. Cells grown in a 3D in vitro matrix environment have been reported to exhibit significantly different properties to those in a conventional 2D culture environment. However, comparison of 2D and 3D cell culture models have recently been noted to result in differing responses of cytotoxic assays, without any associated change in viability. The effect was attributed to differing conversion rates and effective concentrations of the resazurin assay in 2D and 3D environments, rather than differences in cellular metabolism. In this study, the efficacy of a chemotherapeutic agent, doxorubicin, is monitored and compared in conventional 2D and 3D collagen gel exposures of immortalized human cervical cells. Viability was monitored with the aid of the Alamar Blue assay and drug internalisation was verified using confocal microscopy. Drug uptake and retention within the collagen matrix was monitored by absorption spectroscopy. The viability studies showed apparent differences between the 2D and 3D culture systems, the differences attributed in part to the physical transition from 2D to a 3D environment causing alterations to dye resazurin uptake and conversion rates. The use of 3D culture matrices has widely been interpreted to result in "reduced" toxicity or cellular "resistance" to the chemotherapeutic agent. The results of this study show that the reduced efficiency of the drug to cells grown in the 3D environment can be accounted for by a sequential reduction of the effective concentration of the test compound and assay. This is due to absorption within the collagen gel inducing a higher uptake of both drug and assay thereby influencing the toxic impact of the drug and conversion rate of resazurin, and. The increased effective surface area of the cell exposed to the drug

  12. Ultrasonic differentiation of normal versus malignant breast epithelial cells in monolayer cultures

    PubMed Central

    Doyle, Timothy E.; Goodrich, Jeffrey B.; Ambrose, Brady J.; Patel, Hemang; Kwon, Soonjo; Pearson, Lee H.

    2010-01-01

    Normal and malignant mammary epithelial cells were studied using laboratory measurements, wavelet analysis, and numerical simulations of monolayer cell cultures to determine whether microscopic breast cancer can be detected in vitro with high-frequency ultrasound. Pulse-echo waveforms were acquired by immersing a broadband, unfocused 50-MHz transducer in the growth media of cell culture well plates and collecting the first reflection from the well bottoms. The simulations included a multilayer pulse-reflection model and a model of two-dimensional arrays of spherical cells and nuclei. The results show that normal and malignant cells produce time-domain signals and spectral features that are significantly different. PMID:21110531

  13. PCaAnalyser: a 2D-image analysis based module for effective determination of prostate cancer progression in 3D culture.

    PubMed

    Hoque, Md Tamjidul; Windus, Louisa C E; Lovitt, Carrie J; Avery, Vicky M

    2013-01-01

    Three-dimensional (3D) in vitro cell based assays for Prostate Cancer (PCa) research are rapidly becoming the preferred alternative to that of conventional 2D monolayer cultures. 3D assays more precisely mimic the microenvironment found in vivo, and thus are ideally suited to evaluate compounds and their suitability for progression in the drug discovery pipeline. To achieve the desired high throughput needed for most screening programs, automated quantification of 3D cultures is required. Towards this end, this paper reports on the development of a prototype analysis module for an automated high-content-analysis (HCA) system, which allows for accurate and fast investigation of in vitro 3D cell culture models for PCa. The Java based program, which we have named PCaAnalyser, uses novel algorithms that allow accurate and rapid quantitation of protein expression in 3D cell culture. As currently configured, the PCaAnalyser can quantify a range of biological parameters including: nuclei-count, nuclei-spheroid membership prediction, various function based classification of peripheral and non-peripheral areas to measure expression of biomarkers and protein constituents known to be associated with PCa progression, as well as defining segregate cellular-objects effectively for a range of signal-to-noise ratios. In addition, PCaAnalyser architecture is highly flexible, operating as a single independent analysis, as well as in batch mode; essential for High-Throughput-Screening (HTS). Utilising the PCaAnalyser, accurate and rapid analysis in an automated high throughput manner is provided, and reproducible analysis of the distribution and intensity of well-established markers associated with PCa progression in a range of metastatic PCa cell-lines (DU145 and PC3) in a 3D model demonstrated.

  14. Metal sandwich method to quick-freeze monolayer cultured cells for freeze-fracture.

    PubMed

    Fujimoto, T; Fujimoto, K

    1997-04-01

    We describe a simple quick-freezing method to obtain a large fractured plane of the plasma membrane from monolayer cultured cells. Cells were grown on thin gold foil, inverted on a thin layer of gelatin on thin copper foil, and frozen by a quick press between two gold-plated copper blocks precooled in liquid nitrogen. The frozen cell sandwich was mounted on the cold stage of a freeze-fracture device with the gold side up and was fractured by separating the sandwich with a cold fracture knife. When this technique was applied to confluent monolayer cells, large replicas of the E-face of the upper plasma membrane and the P-face of the lower plasma membrane were obtained. The present metal sandwich method is simple, does not require any expensive equipment, and provides a large fracture plane of the plasma membrane for subsequent histochemical manipulation. PMID:9111237

  15. The activation of cultured keratinocytes by cholesterol depletion during reconstruction of a human epidermis is reminiscent of monolayer cultures.

    PubMed

    De Vuyst, Évelyne; Giltaire, Séverine; Lambert de Rouvroit, Catherine; Chrétien, Aline; Salmon, Michel; Poumay, Yves

    2015-05-01

    Transient cholesterol depletion from plasma membranes of human keratinocytes has been shown to reversibly activate signalling pathways in monolayer cultures. Consecutive changes in gene expression have been characterized in such conditions and were interestingly found to be similar to transcriptional changes observed in keratinocytes of atopic dermatitis (AD) patients. As an inflammatory skin disease, AD notably results in altered histology of the epidermis associated with a defective epidermal barrier. To further investigate whether the activation of keratinocytes obtained by cholesterol depletion could be responsible for some epidermal alterations reported in AD, this study was undertaken to analyse cholesterol depletion in stratified cultures of keratinocytes, i.e. a reconstructed human epidermis (RHE). RHE contains heterogeneous populations of keratinocytes, either proliferating or progressively differentiating and stratifying towards the creation of a cornified barrier. Cholesterol depletion induced in this model was found reversible and resulted in activation of signalling pathways similar to those previously identified in monolayers. In addition, selected changes in the expression of several genes suggested that keratinocytes in RHE respond to cholesterol depletion as monolayers. However, preserved histology and barrier function indicate that some additional activation, likely from the immune system, is required to obtain epidermal alterations such as the ones found in AD.

  16. Two step formation of metal aggregates by surface X-ray radiolysis under Langmuir monolayers: 2D followed by 3D growth

    PubMed Central

    Mukherjee, Smita; Fauré, Marie-Claude; Goldmann, Michel

    2015-01-01

    Summary In order to form a nanostructured metallic layer below a Langmuir monolayer, radiolysis synthesis was carried out in an adapted geometry that we call surface X-ray radiolysis. In this procedure, an X-ray beam produced by a synchrotron beamline intercepts the surface of an aqueous metal-ion solution covered by a Langmuir monolayer at an angle of incidence below the critical angle for total internal reflection. Underneath the organic layer, the X-ray beam induces the radiolytic synthesis of a nanostructured metal–organic layer whose ultrathin thickness is defined by the vertical X-ray penetration depth. We have shown that increasing the X-ray flux on the surface, which considerably enhances the kinetics of the silver layer formation, results in a second growth regime of silver nanocrystals. Here the formation of the oriented thin layer is followed by the appearance of a 3D powder of silver clusters. PMID:26734531

  17. Co-nucleus 1D/2D Heterostructures with Bi2S3 Nanowire and MoS2 Monolayer: One-Step Growth and Defect-Induced Formation Mechanism.

    PubMed

    Li, Yongtao; Huang, Le; Li, Bo; Wang, Xiaoting; Zhou, Ziqi; Li, Jingbo; Wei, Zhongming

    2016-09-27

    Heterostructures constructed by low-dimensional (such as 0D, 1D, and 2D) materials have opened up opportunities for exploring interesting physical properties and versatile (opto)electronics. Recently, 2D/2D heterostructures, in particular, atomically thin graphene and transition-metal dichalcogenides, including graphene/MoS2, WSe2/MoS2, and WS2/WSe2, were efficiently prepared (by transfer techniques, chemical vapor deposition (CVD) growth, etc.) and systematically studied. In contrast, investigation of 1D/2D heterostructures was still very challenging and rarely reported, and the understanding of such heterostructures was also not well established. Herein, we demonstrate the one-step growth of a heterostructure on the basis of a 1D-Bi2S3 nanowire and a 2D-MoS2 monolayer through the CVD method. Multimeans were employed, and the results proved the separated growth of a Bi2S3 nanowire and a MoS2 sheet in the heterostructure rather than forming a BixMo1-xSy alloy due to their large lattice mismatch. Defect-induced co-nucleus growth, which was an important growth mode in 1D/2D heterostructures, was also experimentally confirmed and systematically investigated in our research. Such 1D/2D heterostructures were further fabricated and utilized in (opto)electronic devices, such as field-effect transistors and photodetectors, and revealed their potential for multifunctional design in electrical properties. The direct growth of such nanostructures will help us to gain a better comprehension of these specific configurations and allow device functionalities in potential applications.

  18. Functional expression and regulation of drug transporters in monolayer- and sandwich-cultured mouse hepatocytes.

    PubMed

    Noel, Gregory; Le Vee, Marc; Moreau, Amélie; Stieger, Bruno; Parmentier, Yannick; Fardel, Olivier

    2013-04-11

    Primary hepatocyte cultures are now considered as convenient models for in vitro analyzing liver drug transport. However, if primary human and rat hepatocytes have been well-characterized with respect to drug transporter expression and regulation, much less is known for primary mouse hepatocytes. The present study was therefore designed to gain insights about this point. The profile of sinusoidal and canalicular drug transporter mRNA expression in short time (4h)-cultured mouse hepatocytes was found to be highly correlated with that of freshly isolated hepatocytes; by contrast, those of counterparts cultured for a longer time (until 4 days) either in monolayer configurations on plastic or collagen or in sandwich configuration with matrigel were profoundly altered: uptake drug transporters such as Oct1, Oatps and Oat2 were thus down-regulated, whereas most of efflux transporters such as Mdr1a/b, Mrp3, Mrp4 and Bcrp were induced. Moreover, short time-cultured hepatocytes exhibited the highest levels of sinusoidal influx transporter activities. Transporter-mediated drug secretion into canalicular networks was however only observed in sandwich-cultured hepatocytes. Mouse hepatocytes cultured either in monolayer or sandwich configurations were finally shown to exhibit up-regulation of referent transporters in response to exposure to prototypical activators of the drug sensing receptors pregnane X receptor, aryl hydrocarbon receptor or constitutive androstane receptor. Taken together, these data demonstrate the feasibility of using primary mouse hepatocytes for investigating potential interactions of xenobiotics with hepatic transporter activity or regulation, provided that adequate culture conditions are retained. PMID:23396053

  19. Collagen esterification enhances the function and survival of pancreatic β cells in 2D and 3D culture systems

    SciTech Connect

    Ko, Jae Hyung; Kim, Yang Hee; Jeong, Seong Hee; Lee, Song; Park, Si-Nae; Shim, In Kyong; Kim, Song Cheol

    2015-08-07

    Collagen, one of the most important components of the extracellular matrix (ECM), may play a role in the survival of pancreatic islet cells. In addition, chemical modifications that change the collagen charge profile to a net positive charge by esterification have been shown to increase the adhesion and proliferation of various cell types. The purpose of this study was to characterize and compare the effects of native collagen (NC) and esterified collagen (EC) on β cell function and survival. After isolation by the collagenase digestion technique, rat islets were cultured with NC and EC in 2 dimensional (2D) and 3 dimensional (3D) environments for a long-term duration in vitro. The cells were assessed for islet adhesion, morphology, viability, glucose-induced insulin secretion, and mRNA expression of glucose metabolism-related genes, and visualized by scanning electron microscopy (SEM). Islet cells attached tightly in the NC group, but islet cell viability was similar in both the NC and EC groups. Glucose-stimulated insulin secretion was higher in the EC group than in the NC group in both 2D and 3D culture. Furthermore, the mRNA expression levels of glucokinase in the EC group were higher than those in the NC group and were associated with glucose metabolism and insulin secretion. Finally, SEM observation confirmed that islets had more intact component cells on EC sponges than on NC sponges. These results indicate that modification of collagen may offer opportunities to improve function and viability of islet cells. - Highlights: • We changed the collagen charge profile to a net positive charge by esterification. • Islets cultured on esterified collagen improved survival in both 2D and 3D culture. • Islets cultured on esterified collagen enhanced glucose-stimulated insulin release. • High levels of glucokinase mRNA may be associated with increased insulin release.

  20. Comparison of Genotoxic Damage in Monolayer Cell Cultures and Three-Dimensional Tissue-Like Cell Assemblies

    NASA Technical Reports Server (NTRS)

    Behravesh, E.; Emami, K.; Wu, H.; Gonda, S.

    2004-01-01

    Assessing the biological risks associated with exposure to the high-energy charged particles encountered in space is essential for the success of long-term space exploration. Although prokaryotic and eukaryotic cell models developed in our laboratory and others have advanced our understanding of many aspects of genotoxicity, in vitro models are needed to assess the risk to humans from space radiation insults. Such models must be representative of the cellular interactions present in tissues and capable of quantifying I genotoxic damage. Toward this overall goal, the objectives of this study were to examine the effect of the localized microenvironment of cells, cultured as either 2-dimensional (2D) monolayers or 3-dimensional (3D) aggregates, on the rate and type of genotoxic damage resulting from exposure to iron charged particles, a significant portion of space radiation. We used rodent transgenic cell lines containing 50-70 copies of a LacI transgene to provide the enhanced sensitivity required to quantify mutational frequency and type in the 1,100-bp LacI target as well as assessment of DNA,damage to the entire 45-kbp construct. Cultured cells were exposed to high-enerir on charged particles at Brookhaven National Laboratory s Alternating Gradient Synchrotron facility for a total dose of 0, 0.1, 0.25,0.5, 1.0, or 2.0 Gy and allowed to recover for 0, 1, or 7 days, after which mutational type and frequency were evaluated. The mutational frequency was found to be higher in 3D samples than in 2D samples at all radiation doses. Mutational frequency also was higher at 7 days after irradiation than immediately after exposure. DNA sequencing of the mutant targets revealed that deletional mutations contributed an increasingly high percentage (up to 27%) of all mutations in cells as the dose was increased from 0.5 to 2 Gy. Several mutants also showed large and complex deletions in multiple locations within the Lac1 target. However, no differences in mutational type were

  1. Functional assessment of gap junctions in monolayer and three-dimensional cultures of human tendon cells using fluorescence recovery after photobleaching

    PubMed Central

    Kuzma-Kuzniarska, Maria; Yapp, Clarence; Pearson-Jones, Thomas W.; Jones, Andrew K.; Hulley, Philippa A.

    2014-01-01

    Abstract. Gap junction-mediated intercellular communication influences a variety of cellular activities. In tendons, gap junctions modulate collagen production, are involved in strain-induced cell death, and are involved in the response to mechanical stimulation. The aim of the present study was to investigate gap junction-mediated intercellular communication in healthy human tendon-derived cells using fluorescence recovery after photobleaching (FRAP). The FRAP is a noninvasive technique that allows quantitative measurement of gap junction function in living cells. It is based on diffusion-dependent redistribution of a gap junction-permeable fluorescent dye. Using FRAP, we showed that human tenocytes form functional gap junctions in monolayer and three-dimensional (3-D) collagen I culture. Fluorescently labeled tenocytes following photobleaching rapidly reacquired the fluorescent dye from neighboring cells, while HeLa cells, which do not communicate by gap junctions, remained bleached. Furthermore, both 18 β-glycyrrhetinic acid and carbenoxolone, standard inhibitors of gap junction activity, impaired fluorescence recovery in tendon cells. In both monolayer and 3-D cultures, intercellular communication in isolated cells was significantly decreased when compared with cells forming many cell-to-cell contacts. In this study, we used FRAP as a tool to quantify and experimentally manipulate the function of gap junctions in human tenocytes in both two-dimensional (2-D) and 3-D cultures. PMID:24390370

  2. Functional assessment of gap junctions in monolayer and three-dimensional cultures of human tendon cells using fluorescence recovery after photobleaching

    NASA Astrophysics Data System (ADS)

    Kuzma-Kuzniarska, Maria; Yapp, Clarence; Pearson-Jones, Thomas W.; Jones, Andrew K.; Hulley, Philippa A.

    2014-01-01

    Gap junction-mediated intercellular communication influences a variety of cellular activities. In tendons, gap junctions modulate collagen production, are involved in strain-induced cell death, and are involved in the response to mechanical stimulation. The aim of the present study was to investigate gap junction-mediated intercellular communication in healthy human tendon-derived cells using fluorescence recovery after photobleaching (FRAP). The FRAP is a noninvasive technique that allows quantitative measurement of gap junction function in living cells. It is based on diffusion-dependent redistribution of a gap junction-permeable fluorescent dye. Using FRAP, we showed that human tenocytes form functional gap junctions in monolayer and three-dimensional (3-D) collagen I culture. Fluorescently labeled tenocytes following photobleaching rapidly reacquired the fluorescent dye from neighboring cells, while HeLa cells, which do not communicate by gap junctions, remained bleached. Furthermore, both 18 β-glycyrrhetinic acid and carbenoxolone, standard inhibitors of gap junction activity, impaired fluorescence recovery in tendon cells. In both monolayer and 3-D cultures, intercellular communication in isolated cells was significantly decreased when compared with cells forming many cell-to-cell contacts. In this study, we used FRAP as a tool to quantify and experimentally manipulate the function of gap junctions in human tenocytes in both two-dimensional (2-D) and 3-D cultures.

  3. A Theoretical Study of Single-Atom Catalysis of CO Oxidation Using Au Embedded 2D h-BN Monolayer: A CO-Promoted O2 Activation

    PubMed Central

    Mao, Keke; Li, Lei; Zhang, Wenhua; Pei, Yong; Zeng, Xiao Cheng; Wu, Xiaojun; Yang, Jinlong

    2014-01-01

    The CO oxidation behaviors on single Au atom embedded in two-dimensional h-BN monolayer are investigated on the basis of first-principles calculations, quantum Born-Oppenheim molecular dynamic simulations (BOMD) and micro-kinetic analysis. We show that CO oxidation on h-BN monolayer support single gold atom prefers an unreported tri-molecular Eley-Rideal (E-R) reaction, where O2 molecule is activated by two pre-adsorbed CO molecules. The formed OCOAuOCO intermediate dissociates into two CO2 molecules synchronously, which is the rate-limiting step with an energy barrier of 0.47 eV. By using the micro-kinetic analysis, the CO oxidation following the tri-molecular E-R reaction pathway entails much higher reaction rate (1.43 × 105 s−1) than that of bimolecular Langmuir-Hinshelwood (L-H) pathway (4.29 s−1). Further, the quantum BOMD simulation at the temperature of 300 K demonstrates the complete reaction process in real time. PMID:24962006

  4. A theoretical study of single-atom catalysis of CO oxidation using Au embedded 2D h-BN monolayer: a CO-promoted O₂ activation.

    PubMed

    Mao, Keke; Li, Lei; Zhang, Wenhua; Pei, Yong; Zeng, Xiao Cheng; Wu, Xiaojun; Yang, Jinlong

    2014-01-01

    The CO oxidation behaviors on single Au atom embedded in two-dimensional h-BN monolayer are investigated on the basis of first-principles calculations, quantum Born-Oppenheim molecular dynamic simulations (BOMD) and micro-kinetic analysis. We show that CO oxidation on h-BN monolayer support single gold atom prefers an unreported tri-molecular Eley-Rideal (E-R) reaction, where O2 molecule is activated by two pre-adsorbed CO molecules. The formed OCOAuOCO intermediate dissociates into two CO2 molecules synchronously, which is the rate-limiting step with an energy barrier of 0.47 eV. By using the micro-kinetic analysis, the CO oxidation following the tri-molecular E-R reaction pathway entails much higher reaction rate (1.43 × 10(5) s(-1)) than that of bimolecular Langmuir-Hinshelwood (L-H) pathway (4.29 s(-1)). Further, the quantum BOMD simulation at the temperature of 300 K demonstrates the complete reaction process in real time. PMID:24962006

  5. Characterization and classification of adherent cells in monolayer culture using automated tracking and evolutionary algorithms.

    PubMed

    Zhang, Zhen; Bedder, Matthew; Smith, Stephen L; Walker, Dawn; Shabir, Saqib; Southgate, Jennifer

    2016-08-01

    This paper presents a novel method for tracking and characterizing adherent cells in monolayer culture. A system of cell tracking employing computer vision techniques was applied to time-lapse videos of replicate normal human uro-epithelial cell cultures exposed to different concentrations of adenosine triphosphate (ATP) and a selective purinergic P2X antagonist (PPADS), acquired over a 24h period. Subsequent analysis following feature extraction demonstrated the ability of the technique to successfully separate the modulated classes of cell using evolutionary algorithms. Specifically, a Cartesian Genetic Program (CGP) network was evolved that identified average migration speed, in-contact angular velocity, cohesivity and average cell clump size as the principal features contributing to the separation. Our approach not only provides non-biased and parsimonious insight into modulated class behaviours, but can be extracted as mathematical formulae for the parameterization of computational models. PMID:27267455

  6. Characterization of release of basic fibroblast growth factor from bovine retinal endothelial cells in monolayer cultures.

    PubMed Central

    Brooks, R A; Burrin, J M; Kohner, E M

    1991-01-01

    Release of basic fibroblast growth factor (bFGF) was investigated in bovine retinal endothelial cells (BREC) maintained in monolayer culture. Confluent cells released bFGF into serum-free culture medium or medium containing 5% serum at rates of up to 105.2 and 61.3 pM/day respectively. bFGF release coincided with a decrease in monolayer cell number and increases in lactate dehydrogenase (LDH) concentration and cells and cell-debris particles in the medium, which suggested that cell damage and lysis were responsible for growth-factor release. Maximum bFGF release at 24 h (230 +/- 10 pM) occurred when the cells were treated with lipopolysaccharide (10 micrograms/ml), which also produced the greatest changes in parameters of cell damage. Sub-confluent cells showed little overt damage at 24 h, but released bFGF (78 +/- 20 pM) along with LDH, indicating that some cell lysis had occurred. Insulin-like growth factor 1 (IGF-1) was also released into serum-free culture medium at a rate of 0.34 nM/day, but not into medium containing serum or when the cells were treated with lipopolysaccharide. This implies that the mechanism of IGF-1 release is different from that of bFGF and is not related to cell damage. Culture medium conditioned by BREC stimulated the proliferation of these cells, as measured by an increase in their incorporation of [methyl-3H]thymidine from 7550 +/- 479 to 10467 +/- 924 d.p.m. These results demonstrate that bFGF is released from damaged BREC and that medium conditioned by these cells can stimulate retinal-endothelial-cell proliferation. This strengthens the case for an involvement of this growth factor in retinal neovascularization. Images Fig. 1. PMID:2039465

  7. 2D-DIGE proteomic analysis of mesenchymal stem cell cultured on the elasticity-tunable hydrogels.

    PubMed

    Kuboki, Thasaneeya; Kantawong, Fahsai; Burchmore, Richard; Dalby, Matthew J; Kidoaki, Satoru

    2012-01-01

    The present study focuses on mechanotransduction in mesenchymal stem cells (MSCs) in response to matrix elasticity. By using photocurable gelatinous gels with tunable stiffness, proteomic profiles of MSCs cultured on tissue culture plastic, soft (3 kPa) and stiff (52 kPa) matrices were deciphered using 2-dimensional differential in-gel analysis (2D-DIGE). The DIGE data, tied to immunofluorescence, indicated abundance and organization changes in the cytoskeletonal proteins as well as differential regulation of important signaling-related proteins, stress-responsing proteins and also proteins involved in collagen synthesis. The major CSK proteins including actin, tubulin and vimentin of the cells cultured on the gels were remarkably changed their expressions. Significant down-regulation of α-tubulin and β-actin can be observed on gel samples in comparison to the rigid tissue culture plates. The expression abundance of vimentin appeared to be highest in the MSCs cultured on hard gels. These results suggested that the substrate stiffness significantly affects expression balances in cytoskeletal proteins of MSCs with some implications to cellular tensegrity. PMID:22971925

  8. [Novel methods for studies of testicular development and spermatogenesis: From 2D to 3D culture].

    PubMed

    Zhang, Lian-dong; Li, He-cheng; Zhang, Tong-dian; Wang, Zi-ming

    2016-03-01

    The two-dimensional model of cell culture is an important method in the study of testicular development and spermatogenesis but can not effectively mimic and regulate the testicular microenvironment and the whole process of spermatogenesis due to the lack of relevant cell factors and the disruption of a three-dimensional spatial structure. In the past 20 years, the development and optimization of the in vitro model such as testis organotypic culture and in vivo model such as testis transplantation achieved a transformation from two- to three-dimension. The maintenance and optimization of the testicular niche structure could mimic the testicular microenvironment and cell types including Leydig, Sertoli and germ cells, which showed similar biological behaviors to those in vivo. Besides, the cell suspension or tissue fragment floats in the gas-liquid interface so that the development of somatic and germ cells is well maintained in vitro whilst the feedback linkage between grafted testis tissue and hypothalamus-pituitary of the host rebuilt in the in vitro model provides an endocrinological basis for spermatogenesis, which serves as an effective methodology to better understand the organogenesis and development of the testis as well as testicular function regulation, advancing the concept of treatment of male infertility. Al- though each of the methods may have its limitations, the progress in the processing, freezing, thawing, and transplantation of cells and tissues will surely promote their clinical application and present their value in translational medicine. PMID:27172668

  9. Surface Acoustic Waves (SAW)-Based Biosensing for Quantification of Cell Growth in 2D and 3D Cultures

    PubMed Central

    Wang, Tao; Green, Ryan; Nair, Rajesh Ramakrishnan; Howell, Mark; Mohapatra, Subhra; Guldiken, Rasim; Mohapatra, Shyam Sundar

    2015-01-01

    Detection and quantification of cell viability and growth in two-dimensional (2D) and three-dimensional (3D) cell cultures commonly involve harvesting of cells and therefore requires a parallel set-up of several replicates for time-lapse or dose–response studies. Thus, developing a non-invasive and touch-free detection of cell growth in longitudinal studies of 3D tumor spheroid cultures or of stem cell regeneration remains a major unmet need. Since surface acoustic waves (SAWs) permit mass loading-based biosensing and have been touted due to their many advantages including low cost, small size and ease of assembly, we examined the potential of SAW-biosensing to detect and quantify cell growth. Herein, we demonstrate that a shear horizontal-surface acoustic waves (SH-SAW) device comprising two pairs of resonators consisting of interdigital transducers and reflecting fingers can be used to quantify mass loading by the cells in suspension as well as within a 3D cell culture platform. A 3D COMSOL model was built to simulate the mass loading response of increasing concentrations of cells in suspension in the polydimethylsiloxane (PDMS) well in order to predict the characteristics and optimize the design of the SH-SAW biosensor. The simulated relative frequency shift from the two oscillatory circuit systems (one of which functions as control) were found to be concordant to experimental data generated with RAW264.7 macrophage and A549 cancer cells. In addition, results showed that SAW measurements per se did not affect viability of cells. Further, SH-SAW biosensing was applied to A549 cells cultured on a 3D electrospun nanofiber scaffold that generate tumor spheroids (tumoroids) and the results showed the device's ability to detect changes in tumor spheroid growth over the course of eight days. Taken together, these results demonstrate the use of SH-SAW device for detection and quantification of cell growth changes over time in 2D suspension cultures and in 3D cell

  10. Surface Acoustic Waves (SAW)-Based Biosensing for Quantification of Cell Growth in 2D and 3D Cultures.

    PubMed

    Wang, Tao; Green, Ryan; Nair, Rajesh Ramakrishnan; Howell, Mark; Mohapatra, Subhra; Guldiken, Rasim; Mohapatra, Shyam Sundar

    2015-01-01

    Detection and quantification of cell viability and growth in two-dimensional (2D) and three-dimensional (3D) cell cultures commonly involve harvesting of cells and therefore requires a parallel set-up of several replicates for time-lapse or dose-response studies. Thus, developing a non-invasive and touch-free detection of cell growth in longitudinal studies of 3D tumor spheroid cultures or of stem cell regeneration remains a major unmet need. Since surface acoustic waves (SAWs) permit mass loading-based biosensing and have been touted due to their many advantages including low cost, small size and ease of assembly, we examined the potential of SAW-biosensing to detect and quantify cell growth. Herein, we demonstrate that a shear horizontal-surface acoustic waves (SH-SAW) device comprising two pairs of resonators consisting of interdigital transducers and reflecting fingers can be used to quantify mass loading by the cells in suspension as well as within a 3D cell culture platform. A 3D COMSOL model was built to simulate the mass loading response of increasing concentrations of cells in suspension in the polydimethylsiloxane (PDMS) well in order to predict the characteristics and optimize the design of the SH-SAW biosensor. The simulated relative frequency shift from the two oscillatory circuit systems (one of which functions as control) were found to be concordant to experimental data generated with RAW264.7 macrophage and A549 cancer cells. In addition, results showed that SAW measurements per se did not affect viability of cells. Further, SH-SAW biosensing was applied to A549 cells cultured on a 3D electrospun nanofiber scaffold that generate tumor spheroids (tumoroids) and the results showed the device's ability to detect changes in tumor spheroid growth over the course of eight days. Taken together, these results demonstrate the use of SH-SAW device for detection and quantification of cell growth changes over time in 2D suspension cultures and in 3D cell

  11. Surface Acoustic Waves (SAW)-Based Biosensing for Quantification of Cell Growth in 2D and 3D Cultures.

    PubMed

    Wang, Tao; Green, Ryan; Nair, Rajesh Ramakrishnan; Howell, Mark; Mohapatra, Subhra; Guldiken, Rasim; Mohapatra, Shyam Sundar

    2015-12-19

    Detection and quantification of cell viability and growth in two-dimensional (2D) and three-dimensional (3D) cell cultures commonly involve harvesting of cells and therefore requires a parallel set-up of several replicates for time-lapse or dose-response studies. Thus, developing a non-invasive and touch-free detection of cell growth in longitudinal studies of 3D tumor spheroid cultures or of stem cell regeneration remains a major unmet need. Since surface acoustic waves (SAWs) permit mass loading-based biosensing and have been touted due to their many advantages including low cost, small size and ease of assembly, we examined the potential of SAW-biosensing to detect and quantify cell growth. Herein, we demonstrate that a shear horizontal-surface acoustic waves (SH-SAW) device comprising two pairs of resonators consisting of interdigital transducers and reflecting fingers can be used to quantify mass loading by the cells in suspension as well as within a 3D cell culture platform. A 3D COMSOL model was built to simulate the mass loading response of increasing concentrations of cells in suspension in the polydimethylsiloxane (PDMS) well in order to predict the characteristics and optimize the design of the SH-SAW biosensor. The simulated relative frequency shift from the two oscillatory circuit systems (one of which functions as control) were found to be concordant to experimental data generated with RAW264.7 macrophage and A549 cancer cells. In addition, results showed that SAW measurements per se did not affect viability of cells. Further, SH-SAW biosensing was applied to A549 cells cultured on a 3D electrospun nanofiber scaffold that generate tumor spheroids (tumoroids) and the results showed the device's ability to detect changes in tumor spheroid growth over the course of eight days. Taken together, these results demonstrate the use of SH-SAW device for detection and quantification of cell growth changes over time in 2D suspension cultures and in 3D cell

  12. Lensfree video microscopy: high throughput monitoring and cell tracking of 2D cell cultures

    NASA Astrophysics Data System (ADS)

    Allier, C. P.; Vinjimore Kesavan, S.; Cioni, O.; Momey, F.; Bordy, T.; Hervé, L.; Morel, S.; Navarro, F.; Menneteau, M.; Chalmond, B.; Freida, D.; Sulpice, E.; Gidrol, X.; Dinten, J.-M.

    2015-07-01

    In order to extend the analysis of the datasets produced by lensfree video microscopy we have implemented a cell tracking algorithm to combine and correlate cell motility to the previously devised metrics to quantify e.g. cell adhesion and spreading, cell division, and cell death. In this paper we present the assessment of these new methodology on experiments involving three different cell lines, namely 3T3 fibroblast cells, primary HUVEC cells and macrophage THP1 cells. We demonstrate that the good spatial resolution and the fast frame rate obtained with of our lensfree video microscope allows standard cell tracking algorithm to be computed. The results is the possibility to analyze thousands of cells successfully tracked over tens of hours. The results is the possibility to compare different cell cultures in terms of e.g. cell motility and cell confinement ration. Ultimately we managed to measure the doubling time at single cell level over a large number of N=235 cells tracked over two days.

  13. Human Lung Cancer Cells Grown in an Ex Vivo 3D Lung Model Produce Matrix Metalloproteinases Not Produced in 2D Culture

    PubMed Central

    Mishra, Dhruva K.; Sakamoto, Jason H.; Thrall, Michael J.; Baird, Brandi N.; Blackmon, Shanda H.; Ferrari, Mauro; Kurie, Jonathan M.; Kim, Min P.

    2012-01-01

    We compared the growth of human lung cancer cells in an ex vivo three-dimensional (3D) lung model and 2D culture to determine which better mimics lung cancer growth in patients. A549 cells were grown in an ex vivo 3D lung model and in 2D culture for 15 days. We measured the size and formation of tumor nodules and counted the cells after 15 days. We also stained the tissue/cells for Ki-67, and Caspase-3. We measured matrix metalloproteinase (MMP) levels in the conditioned media and in blood plasma from patients with adenocarcinoma of the lung. Organized tumor nodules with intact vascular space formed in the ex vivo 3D lung model but not in 2D culture. Proliferation and apoptosis were greater in the ex vivo 3D lung model compared to the 2D culture. After 15 days, there were significantly more cells in the 2D culture than the 3D model. MMP-1, MMP-9, and MMP-10 production were significantly greater in the ex vivo 3D lung model. There was no production of MMP-9 in the 2D culture. The patient samples contained MMP-1, MMP-2, MMP-9, and MMP-10. The human lung cancer cells grown on ex vivo 3D model form perfusable nodules that grow over time. It also produced MMPs that were not produced in 2D culture but seen in human lung cancer patients. The ex vivo 3D lung model may more closely mimic the biology of human lung cancer development than the 2D culture. PMID:23028922

  14. Collagen esterification enhances the function and survival of pancreatic β cells in 2D and 3D culture systems.

    PubMed

    Ko, Jae Hyung; Kim, Yang Hee; Jeong, Seong Hee; Lee, Song; Park, Si-Nae; Shim, In Kyong; Kim, Song Cheol

    2015-08-01

    Collagen, one of the most important components of the extracellular matrix (ECM), may play a role in the survival of pancreatic islet cells. In addition, chemical modifications that change the collagen charge profile to a net positive charge by esterification have been shown to increase the adhesion and proliferation of various cell types. The purpose of this study was to characterize and compare the effects of native collagen (NC) and esterified collagen (EC) on β cell function and survival. After isolation by the collagenase digestion technique, rat islets were cultured with NC and EC in 2 dimensional (2D) and 3 dimensional (3D) environments for a long-term duration in vitro. The cells were assessed for islet adhesion, morphology, viability, glucose-induced insulin secretion, and mRNA expression of glucose metabolism-related genes, and visualized by scanning electron microscopy (SEM). Islet cells attached tightly in the NC group, but islet cell viability was similar in both the NC and EC groups. Glucose-stimulated insulin secretion was higher in the EC group than in the NC group in both 2D and 3D culture. Furthermore, the mRNA expression levels of glucokinase in the EC group were higher than those in the NC group and were associated with glucose metabolism and insulin secretion. Finally, SEM observation confirmed that islets had more intact component cells on EC sponges than on NC sponges. These results indicate that modification of collagen may offer opportunities to improve function and viability of islet cells.

  15. 3D rotating wall vessel and 2D cell culture of four veterinary virus pathogens: A comparison of virus yields, portions of infectious particles and virus growth curves.

    PubMed

    Malenovská, Hana

    2016-02-01

    Only very few comparative studies have been performed that evaluate general trends of virus growth under 3D in comparison with 2D cell culture conditions. The aim of this study was to investigate differences when four animal viruses are cultured in 2D and 3D. Suid herpesvirus 1 (SuHV-1), Vesicular stomatitis virus (VSIV), Bovine adenovirus (BAdV) and Bovine parainfluenza 3 virus (BPIV-3) were cultivated in 3D rotating wall vessels (RWVs) and conventional 2D cultures. The production of virus particles, the portion of infectious particles, and the infectious growth curves were compared. For all viruses, the production of virus particles (related to cell density), including the non-infectious ones, was lower in 3D than in 2D culture. The production of only infectious particles was significantly lower in BAdV and BPIV-3 in 3D cultures in relation to cell density. The two cultivation approaches resulted in significantly different virus particle-to-TCID50 ratios in three of the four viruses: lower in SuHV-1 and BPIV-3 and higher in BAdV in 3D culture. The infectious virus growth rates were not significantly different in all viruses. Although 3D RWV culture resulted in lower production of virus particles compared to 2D systems, the portion of infectious particles was higher for some viruses.

  16. Development of a primary mouse intestinal epithelial cell monolayer culture system to evaluate factors that modulate IgA transcytosis

    PubMed Central

    Moon, Clara; VanDussen, Kelli L.; Miyoshi, Hiroyuki; Stappenbeck, Thaddeus S.

    2013-01-01

    There is significant interest in the use of primary intestinal epithelial cells in monolayer culture to model intestinal biology. However, it has proven to be challenging to create functional, differentiated monolayers using current culture methods, likely due to the difficulty in expanding these cells. Here, we adapted our recently developed method for the culture of intestinal epithelial spheroids to establish primary epithelial cell monolayers from the colon of multiple genetic mouse strains. These monolayers contained differentiated epithelial cells that displayed robust transepithelial electrical resistance. We then functionally tested them by examining IgA transcytosis across Transwells. IgA transcytosis required induction of polymeric immunoglobulin receptor (pIgR) expression, which could be stimulated by a combination of LPS and inhibition of γ-secretase. In agreement with previous studies using immortalized cell lines, we found that TNFα, IL-1β, IL-17 and heat-killed microbes also stimulated pIgR expression and IgA transcytosis. We used wild-type and knockout cells to establish that amongst these cytokines, IL-17 was the most potent inducer of pIgR expression/IgA transcytosis. IFNγ however did not induce pIgR expression, and instead led to cell death. This new method will allow the use of primary cells for studies of intestinal physiology. PMID:24220295

  17. Imaging of oxygen gradients in monolayer cultured cells using green fluorescent protein.

    PubMed

    Takahashi, Eiji; Sato, Michihiko

    2010-12-01

    Gradients of Po(2) between capillary blood and mitochondria are the driving force for diffusional O(2) delivery in tissues. Hypoxic microenvironments in tissues that result from diffusional O(2) gradients are especially relevant in solid tumors because they have been related to a poor prognosis. To address the impact of tissue O(2) gradients, we developed a novel technique that permits imaging of intracellular O(2) levels in cultured cells at a subcellular spatial resolution. This was done, with the sensitivity to O(2) ≤3%, by the O(2)-dependent red shift of green fluorescent protein (AcGFP1) fluorescence. Measurements were carried out in a confluent monolayer of Hep3B cells expressing AcGFP1 in the cytoplasm. To establish a two-dimensional O(2) diffusion model, a thin quartz glass slip was placed onto the monolayer cells to prevent O(2) diffusion from the top surface of the cell layer. The magnitude of the red shift progressively increased as the distance from the gas coverslip interface increased. It reached an anoxic level in cells located at ∼220 μm and ∼690 μm from the gas coverslip boundary at 1% and 3% gas phase O(2), respectively. Thus the average O(2) gradient was 0.03 mmHg/μm in the present tissue model. Abolition of mitochondrial respiration significantly dampened the gradients. Furthermore, intracellular gradients of the red shift in mitochondria-targeted AcGFP1 in single Hep3B cells suggest that the origin of tissue O(2) gradients is intracellular. Findings in the present two-dimensional O(2) diffusion model support the crucial role of tissue O(2) diffusion in defining the O(2) microenvironment in individual cells. PMID:20844249

  18. A standardized and reproducible protocol for serum-free monolayer culturing of primary paediatric brain tumours to be utilized for therapeutic assays.

    PubMed

    Sandén, Emma; Eberstål, Sofia; Visse, Edward; Siesjö, Peter; Darabi, Anna

    2015-01-01

    In vitro cultured brain tumour cells are indispensable tools for drug screening and therapeutic development. Serum-free culture conditions tentatively preserve the features of the original tumour, but commonly comprise neurosphere propagation, which is a technically challenging procedure. Here, we define a simple, non-expensive and reproducible serum-free cell culture protocol for establishment and propagation of primary paediatric brain tumour cultures as adherent monolayers. The success rates for establishment of primary cultures (including medulloblastomas, atypical rhabdoid tumour, ependymomas and astrocytomas) were 65% (11/17) and 78% (14/18) for sphere cultures and monolayers respectively. Monolayer culturing was particularly feasible for less aggressive tumour subsets, where neurosphere cultures could not be generated. We show by immunofluorescent labelling that monolayers display phenotypic similarities with corresponding sphere cultures and primary tumours, and secrete clinically relevant inflammatory factors, including PGE2, VEGF, IL-6, IL-8 and IL-15. Moreover, secretion of PGE2 was considerably reduced by treatment with the COX-2 inhibitor Valdecoxib, demonstrating the functional utility of our newly established monolayer for preclinical therapeutic assays. Our findings suggest that this culture method could increase the availability and comparability of clinically representative in vitro models of paediatric brain tumours, and encourages further molecular evaluation of serum-free monolayer cultures.

  19. A standardized and reproducible protocol for serum-free monolayer culturing of primary paediatric brain tumours to be utilized for therapeutic assays

    PubMed Central

    Sandén, Emma; Eberstål, Sofia; Visse, Edward; Siesjö, Peter; Darabi, Anna

    2015-01-01

    In vitro cultured brain tumour cells are indispensable tools for drug screening and therapeutic development. Serum-free culture conditions tentatively preserve the features of the original tumour, but commonly comprise neurosphere propagation, which is a technically challenging procedure. Here, we define a simple, non-expensive and reproducible serum-free cell culture protocol for establishment and propagation of primary paediatric brain tumour cultures as adherent monolayers. The success rates for establishment of primary cultures (including medulloblastomas, atypical rhabdoid tumour, ependymomas and astrocytomas) were 65% (11/17) and 78% (14/18) for sphere cultures and monolayers respectively. Monolayer culturing was particularly feasible for less aggressive tumour subsets, where neurosphere cultures could not be generated. We show by immunofluorescent labelling that monolayers display phenotypic similarities with corresponding sphere cultures and primary tumours, and secrete clinically relevant inflammatory factors, including PGE2, VEGF, IL-6, IL-8 and IL-15. Moreover, secretion of PGE2 was considerably reduced by treatment with the COX-2 inhibitor Valdecoxib, demonstrating the functional utility of our newly established monolayer for preclinical therapeutic assays. Our findings suggest that this culture method could increase the availability and comparability of clinically representative in vitro models of paediatric brain tumours, and encourages further molecular evaluation of serum-free monolayer cultures. PMID:26183281

  20. An omics approach to rational feed: Enhancing growth in CHO cultures with NMR metabolomics and 2D-DIGE proteomics.

    PubMed

    Blondeel, Eric J M; Ho, Raymond; Schulze, Steffen; Sokolenko, Stanislav; Guillemette, Simon R; Slivac, Igor; Durocher, Yves; Guillemette, J Guy; McConkey, Brendan J; Chang, David; Aucoin, Marc G

    2016-09-20

    Expression of recombinant proteins exerts stress on cell culture systems, affecting the expression of endogenous proteins, and contributing to the depletion of nutrients and accumulation of waste metabolites. In this work, 2D-DIGE proteomics was employed to analyze differential expression of proteins following stable transfection of a Chinese Hamster Ovary (CHO) cell line to constitutively express a heavy-chain monoclonal antibody. Thirty-four proteins of significant differential expression were identified and cross-referenced with cellular functions and metabolic pathways to identify points of cell stress. Subsequently, 1D-(1)H NMR metabolomics experiments analyzed cultures to observe nutrient depletion and waste metabolite accumulations to further examine these cell stresses and pathways. From among fifty metabolites tracked in time-course, eight were observed to be completely depleted from the production media, including: glucose, glutamine, proline, serine, cystine, asparagine, choline, and hypoxanthine, while twenty-three excreted metabolites were also observed to accumulate. The differentially expressed proteins, as well as the nutrient depletion and accumulation of these metabolites corresponded with upregulated pathways and cell systems related to anaplerotic TCA-replenishment, NADH/NADPH replenishment, tetrahydrofolate cycle C1 cofactor conversions, limitations to lipid synthesis, and redox modulation. A nutrient cocktail was assembled to improve the growth medium and alleviate these cell stresses to achieve a ∼75% improvement to peak cell densities. PMID:27496566

  1. Traditional Chinese medicine herbal mixture LQ arrests FUCCI-expressing HeLa cells in G₀/G₁ phase in 2D plastic, 2.5D Matrigel, and 3D Gelfoam culture visualized with FUCCI imaging.

    PubMed

    Zhang, Lei; Wu, Chengyu; Bouvet, Michael; Yano, Shuya; Hoffman, Robert M

    2015-03-10

    We used the fluorescence ubiquitination-based cell cycle indicator (FUCCI) to monitor cell cycle arrest after treatment of FUCCI-expressing HeLa cells (FUCCI-HeLa) with a traditional Chinese medicine (TCM) herbal mixture LQ, previously shown to have anti-tumor and anti-metastatic activity in mouse models. Paclitaxel was used as the positive control. In 2D monolayer culture, the untreated control had approximately 45% of the cells in S/G₂/M phase. In contrast, the LQ-treated cells (9 mg/ml) were mostly in the G₀/G₁ (>90%) after 72 hours. After treatment with paclitaxel (0.01 μm), for 72 hours, 95% of the cells were in S/G₂/M. In 2.5D Matrigel culture, the colonies in the untreated control group had 40% of the cells in S/G₂/M. LQ arrested the cells in G₀/G₁ after 72 hours. Paclitaxel arrested almost all the cells in S/G₂/M after 72 hours. In 3D Gelfoam culture, the untreated control culture had approximately 45% of cells in G₂/M. In contrast, the LQ-treated cells were mostly in G₀/G₁ phase (>80%) after 72 hours treatment. Paclitaxel resulted in 90% of the cells arrested in S/G₂/M after 72 hours. The present report suggests the non-toxic LQ has potential to maintain cancers in a quiescent state for long periods of time.

  2. Interaction of insulin-like growth factor I with porcine thyroid cells cultured in monolayer

    SciTech Connect

    Saji, M.; Tsushima, T.; Isozaki, O.; Murakami, H.; Ohba, Y.; Sato, K.; Arai, M.; Mariko, A.; Shizume, K.

    1987-08-01

    The interaction of insulin-like growth factor I (IGF-I) with porcine thyroid cells cultured in monolayer was studied. Specific binding of (/sup 125/I)iodo-IGF-I to thyroid cells was a reversible process dependent on the time and temperature of incubation. A steady state was achieved in 18 h at 4 C and averaged 14.2 +/- 2% (mean +/- SD)/10(6) cells. Binding of (/sup 125/I)iodo-IGF-I was inhibited by unlabeled IGF-I; half-maximal inhibition occurred at concentrations of 2-5 ng/ml. Multiplication-stimulating activity (rat IGF-II) and pork insulin had relative potencies of 1:20 and 1:300 compared with IGF-I. Scatchard analysis of binding data revealed a single class of IGF-I receptors with a Ka of 4.3 X 10(10) M-1, 49,000 binding sites were estimated per cell. Affinity cross-linking and autoradiography demonstrated the presence of type I IGF receptors. Thyroid cells also had specific receptors for insulin, but specific binding of (/sup 125/I)iodoinsulin was much lower than that of (/sup 125/I)iodo-IGF-I. Preincubation of thyroid cells with IGF-I or insulin caused a concentration-dependent decrease in (/sup 125/I)iodo-IGF-I binding due to an apparent loss of receptors. Preincubation with epidermal growth factor, fibroblast growth factor, platelet-derived growth factor, or TSH did not alter subsequent binding of (/sup 125/I)iodo-IGF-I. Low concentrations of IGF-I stimulated DNA synthesis and proliferation of thyroid cells and acted synergistically with epidermal growth factor. Multiplication-stimulating activity and insulin had relative potencies in stimulating DNA synthesis comparable to their abilities to inhibit the binding of (/sup 125/I)iodo-IGF-I to thyroid cells.

  3. Superparamagnetic iron oxide nanoparticles exert different cytotoxic effects on cells grown in monolayer cell culture versus as multicellular spheroids

    NASA Astrophysics Data System (ADS)

    Theumer, Anja; Gräfe, Christine; Bähring, Franziska; Bergemann, Christian; Hochhaus, Andreas; Clement, Joachim H.

    2015-04-01

    The aim of this study was to investigate the interaction of superparamagnetic iron oxide nanoparticles (SPION) with human blood-brain barrier-forming endothelial cells (HBMEC) in two-dimensional cell monolayers as well as in three-dimensional multicellular spheroids. The precise nanoparticle localisation and the influence of the NP on the cellular viability and the intracellular Akt signalling were studied in detail. Long-term effects of different polymer-coated nanoparticles (neutral fluidMAG-D, anionic fluidMAG-CMX and cationic fluidMAG-PEI) and the corresponding free polymers on cellular viability of HBMEC were investigated by real time cell analysis studies. Nanoparticles exert distinct effects on HBMEC depending on the nanoparticles' surface charge and concentration, duration of incubation and cellular context. The most severe effects were caused by PEI-coated nanoparticles. Concentrations above 25 μg/ml led to increased amounts of dead cells in monolayer culture as well as in multicellular spheroids. On the level of intracellular signalling, context-dependent differences were observed. Monolayer cultures responded on nanoparticle incubation with an increase in Akt phosphorylation whereas spheroids on the whole show a decreased Akt activity. This might be due to the differential penetration and distribution of PEI-coated nanoparticles.

  4. Differential effects of MAPK pathway inhibitors on migration and invasiveness of BRAF(V600E) mutant thyroid cancer cells in 2D and 3D culture.

    PubMed

    Ingeson-Carlsson, Camilla; Martinez-Monleon, Angela; Nilsson, Mikael

    2015-11-01

    Tumor microenvironment influences targeted drug therapy. In this study we compared drug responses to RAF and MEK inhibitors on tumor cell migration in 2D and 3D culture of BRAF(V600E) mutant cell lines derived from human papillary (BCPAP) and anaplastic (SW1736) thyroid carcinomas. Scratch wounding was compared to a double-layered collagen gel model developed for analysis of directed tumor cell invasion during prolonged culture. In BCPAP both PLX4720 and U0126 inhibited growth and migration in 2D and decreased tumor cell survival in 3D. In SW1736 drugs had no effect on migration in 2D but decreased invasion in 3D, however this related to reduced growth. Dual inhibition of BRAF(V600E) and MEK reduced but did not prevent SW1736 invasion although rebound phosphorylation of ERK in response to PLX4720 was blocked by U0126. These findings indicate that anti-tumor drug effects in vitro differ depending on culture conditions (2D vs. 3D) and that the invasive features of anaplastic thyroid cancer depend on non-MEK mechanism(s).

  5. Human skin in organ culture and human skin cells (keratinocytes and fibroblasts) in monolayer culture for assessment of chemically induced skin damage.

    PubMed

    Varani, James; Perone, Patricia; Spahlinger, Diana M; Singer, Lisa M; Diegel, Kelly L; Bobrowski, Walter F; Dunstan, Robert

    2007-08-01

    Human skin cells (epidermal keratinocytes and dermal fibroblasts) in monolayer culture and human skin in organ culture were exposed to agents that are known to produce irritation (redness, dryness, edema and scaly crusts) when applied topically to skin. Among the agents used were three well accepted contact irritants (i.e., all-trans retinoic acid [RA], sodium lauryl sulfate [SLS] and benzalkonium chloride) as well as the corrosive organic mercury compound, aminophenyl mercuric acetate (APMA), and 5 contact sensitizers (oxazolone, nickel sulfate, eugenol, isoeugenol and ethylene glycol dimethacrylate [EGDM]). As a group, the contact irritants (including the corrosive mercuric compound) were cytotoxic for keratinocytes and fibroblasts and suppressed growth at lower concentrations than the contact sensitizers. The contact irritants also produced histological changes (hyperplasia, incomplete keratinization, loss of the granular layer, acantholysis and necrosis) in organ-cultured skin at dose levels at which the contact sensitizers appeared to be inert. Finally, the profile of secreted molecules from organ-cultured skin was different in the presence of contact irritants versus contact sensitizers. Taken together, these data suggest that the use of organ-cultured skin in conjunction with cells derived from the skin in monolayer culture may provide an initial approach to screening agents for deleterious changes in skin.

  6. Effect of Aflatoxin B1 on Growth of Bovine Mammary Epithelial Cells in 3D and Monolayer Culture System

    PubMed Central

    Forouharmehr, Ali; Harkinezhad, Taher; Qasemi-Panahi, Babak

    2013-01-01

    Purpose: Many studies have been showed transfer of aflatoxins, toxins produced by Aspergillus flvaus and Aspergillus parasiticus fungi, into milk. These toxins are transferred into the milk through digestive system by eating contaminated food. Due to the toxicity of these materials, it seems that it has side effects on the growth of mammary cells. Therefore, the present work aimed to investigate possible toxic effects of aflatoxin B1 (AFB1) on bovine mammary epithelial cells in monolayer and three-dimensional cultures. Methods: Specimens of the mammary tissue of bovine were sized out in size 2×2 cm in slaughterhouse. After disinfection and washing in sterile PBS, primary cell culture was performed by enzymatic digestion of tissue with collagenase. When proper numbers of cells were achieved in monolayer culture, cells were seeded in a 24-well culture plate for three-dimensional (3D) culture in Matrigel matrix. After 21 days of 3D culture and reaching the required number of cells, the concentrations of 15, 25 and 35 µL of AFB1 were added to the culture in quadruplicate and incubated for 8 hours. Cellular cytotoxicity was examined using standard colorimetric assay and finally, any change in the morphology of the cells was studied by microscopic technique. Results: Microscopic investigations showed necrosis of the AFB1-exposed cells compared to the control cells. Also, bovine mammary epithelial cells were significantly affected by AFB1 in dose and time dependent manner in cell viability assays. Conclusion: According to the results, it seems that AFB1 can induce cytotoxicity and necrosis in bovine mammary epithelial cells. PMID:24312827

  7. Effects of method of detachment on electrophoretic mobility of mammalian cells grown in monolayer culture

    NASA Technical Reports Server (NTRS)

    Plank, L. D.; Kunze, M. E.; Todd, P. W.

    1985-01-01

    A variety of proteolytic and micolytic enzumes, mechanical procedures, and changes in the ionic environment, especially Ca chelation, are used for dispersal of monolayer grown cells. If either chelating agents or mechanical dispersion are used alone, the cell yield is often low and suspensions of single cells are difficult to obtain. Confluent monolayers treated with EDTA tend to be released from their surfaces in sheets, and clumps of cells remain even after further incubation in EDTA. Crude trypsin is the most popular dispersal agent and is known to contain a variety of contaminating enzymes which contribute to the dispersal of cells. A variety of cell injuries resulting from the activity of proteolytic enzymes are reported. It is shown that crystalline trypsin is least harmful to cell integrity as judged by trypan blue uptake.

  8. Lectin binding as a probe of proliferative and differentiative phases in primary monolayer cultures of cutaneous keratinocytes

    SciTech Connect

    Ku, W.W.; Bernstein, I.A. )

    1988-04-01

    The surface of cells in the cutaneous epidermis of the newborn rat exhibits a discrete change in lectin-binding specificity from Griffonia simplicifolia I-B4 (GS I-B4), specific for {alpha}-D-galactosyl residues, to Ulex europeus agglutinin I (UEA), specific for {alpha}-L-fucose, as the cell leaves the basal layer and differentiates. Primary monolayer cultures of rat keratinocytes maintained in low Ca{sup 2+} medium exhibited a characteristic unimodal pattern in the ratio of bound UEA to bound GS I-B4 (UEA/B4 ratio) over a 7-day culture period as determined by a quantitative fluorometric assay. Estimation of DNA synthesis showed (a) a higher ({sup 3}H)thymidine incorporation when the UEA/B4 ratio was low and (b) a steady but lower incorporation between Days 3 and 4, coincident with the higher UEA/B4 ratio. Autoradiographic results further showed that cells stained intensely with UEA failed to incorporate ({sup 3}H)thymidine into their nuclei. Overall, the results suggest that (a) the increase in the UEA/B4 ratio between Days 2 and 4 reflects the progression of a proportion of the cells in the monolayer to an early spinous cell stage, the ultimate fate of which is desquamation into the medium and (b) the decrease in the UEA/B4 ratio between Days 5 and 7 reflects a consequent proliferative response to this loss of cells.

  9. Immobilisation of a thrombopoietin peptidic mimic by self-assembled monolayers for culture of CD34+ cells.

    PubMed

    Lee, Eun-Ju; Be, Cheang Ly; Vinson, Andrew R; Riches, Andrew G; Fehr, Friederike; Gardiner, James; Gengenbach, Thomas R; Winkler, David A; Haylock, David

    2015-01-01

    Compared to soluble cytokines, surface-tethered ligands can deliver biological signalling with precise control of spatial positioning and concentration. A strategy that immobilises ligand molecules on a surface in a uniform orientation using non-cleavable linkages under physiological conditions would enhance the specific and systemic delivery of signalling in the local environment. We used mixed self-assembled monolayers (SAMs) of oxyamine- and oligo(ethylene glycol)-terminated thiols on gold to covalently install aldehyde- or ketone-functionalised ligands via oxime conjugation. Characterisation by electrochemistry and X-ray photoelectron spectroscopy showed quantitative immobilisation of the ligands on SAM surfaces. The thrombopoietin mimetic peptide, RILL, was immobilised on SAMs and the bioactivity of the substrate was demonstrated by culturing factor-dependent cells. We also optimised the immobilisation and wash conditions so that the peptide was not released into the culture medium and the immobilised RILL could be re-used for consecutive cell cultures. The surface also supported the growth of haematopoietic CD34+ cells comparable to the standard thrombopoietin-supplemented culture. Furthermore, the RILL-immobilised SAM surface was as effective in expanding uncommitted CD34+ cells as standard culture. The stimulatory effect of surface-tethered ligands in haematopoietic stem cell expansion supports the use of ligand immobilisation strategies to replicate the haematopoietic stem cell niche.

  10. Rapid authentication of different ages of tissue-cultured and wild Dendrobium huoshanense as well as wild Dendrobium henanense using FTIR and 2D-COS IR

    NASA Astrophysics Data System (ADS)

    Chen, Nai-Dong; Chen, Nai-Fu; Li, Jun; Cao, Cai-Yun; Wang, Jin-Mei

    2015-12-01

    The accumulating of pharmaceutical chemicals in medicinal plants would greatly be affected by their ages and establishing a fast quality-identification method to evaluate the similarity of medicinal herbs at different cultivated ages is a critical step for assurance of quality and safety in the TCM industry. In this work, tri-step IR macro-fingerprinting and 2D-COS IR spectrum techniques combined with statistical pattern recognition were applied for discrimination and similarity evaluation of different ages of tissue-cultured and wild Dendrobium huoshanense C. Z. Tang et S. J. Cheng as well as Dendrobium henanense J.L.Lu et L.X Gao. Both tissue-cultured and wild D. huoshanense were easily differentiated from D. henanense by FTIR and SD-IR spectra, while it's quite difficult to discriminate different cultivated years of the three investigated Dendrobiums. In 2D-COS IR spectra, 1-5 auto-peaks with different indensity and positions were located in the region 1160-1030 cm-1 of the twelve Dendrobium samples and thus could be used to identify Dendrobium samples at different ages. Principle component analysis (PCA) of synchronous 2D-COS data showed that the twelve samples were effectively identified and evaluated. The results indicated that the tri-step infrared macro-fingerprinting combined with PCA method was suitable to differentiate the cultivated ages of Dendrobiums with species and orgins rapidly and nondestructively.

  11. In vitro testing of tensides employing monolayer cultures: a comparison with results of patch tests on human volunteers.

    PubMed

    Benassi, L; Bertazzoni, G; Seidenari, S

    1999-01-01

    Evaluation of the irritant potential of new products or ingredients prior to human testing is generally performed in vivo on animals. However, according to the 6th amendment and following updates of the European Community directive on cosmetic products (93/35/EEC), animal testing will be banned when suitable substitutes will be available. To know whether in vitro tests for assessment of skin irritancy provide results approaching human conditions, comparisons have to be made between data deriving from in vitro tests and skin response in humans. The aim of our study was to assess the validity of the monolayer culture system of normal human keratinocytes as a model for the evaluation of the irritant effects of detergents, by comparing in vitro cell culture data to in vivo acute skin irritancy effects of cocamidopropyl betaine (CAPB), an amphoteric compound, Tween 20 (TW20) (polysorbate 20) and Tween 80 (TW80) (polysorbate 80), representing nonionic compounds, applied to the skin of 24 healthy volunteers at a concentration similar to that employed in commercial products. As parameters for cytotoxicity, cell proliferation, cell membrane integrity and cell metabolism were assessed by cell counts, thymidine incorporation, MTT conversion, and Neutral Red uptake. In order to increase the sensitivity of the in vivo evaluation, bioengineering methods for assessment of the effects of test products on the skin were employed. Whereas all 4 in vitro methods ranked the tensides according to their toxicity in the following order: CAPB>SLS>TW20>TW80, both in vivo methods agreed in identifying SLS as the most irritating substance. Moreover, as compared with the irritation potential on human skin, all 4 in vitro tests overestimated the toxicity of CAPB. This suggests that the keratinocyte monolayer cell culture technique cannot directly replace in vivo methods, and that data obtained by this method should be interpreted cautiously.

  12. Thermoprotection of a functional epithelium: heat stress effects on transepithelial transport by flounder renal tubule in primary monolayer culture.

    PubMed Central

    Brown, M A; Upender, R P; Hightower, L E; Renfro, J L

    1992-01-01

    Primary monolayer cultures of winter flounder renal proximal-tubule cells were used to determine whether transepithelial transport could be protected from the damaging effects of extreme temperature by previous mild heat shock. Renal tubule epithelial cells were enzymatically dispersed and reorganized as confluent monolayer sheets on native rat tail collagen. Transepithelial electrical properties (potential difference, resistance, short-circuit current, and Na(+)-dependent glucose current) and unidirectional [35S]sulfate fluxes were measured in Ussing chambers at 22 degrees C. Examination of transepithelial electrical properties following acute 1-hr elevation of temperature over a range of 22-37 degrees C provided the basis for the "mild" versus "severe" thermal stress protocols. Severe elevation from 22 degrees C to 32 degrees C for 1.5 hr followed by 1.5 hr at 22 degrees C significantly decreased glucose current (7 +/- 0.7 to 3 +/- 0.8 microA/cm2) as well as net sulfate secretion [131 +/- 11 to 33 +/- 11 nmol/(cm2.hr)]. Mild heat shock of 27 degrees C for 6 hr prior to this severe heat shock completely protected both glucose transport (6 +/- 0.7 microA/cm2) and sulfate flux (149 +/- 13 nmol/(cm2.hr)]. Scanning electron microscopy showed that the number of microvilli on the apical (luminal) surface of the epithelium was decreased after a 32 degrees C heat shock. Monolayers exposed to 27 degrees C for 6 hr prior to incubation at 32 degrees C showed no loss of microvilli. SDS/PAGE analysis of protein patterns from the cultures showed that three classes of heat shock proteins were maximally induced at 27 degrees C. Inhibition of protein synthesis by cycloheximide prevented the thermoprotective effect of mild heat shock. This suggests that certain renal transport functions can be protected from sublethal but debilitating thermal stress by prior mild heat shock and that heat shock proteins may play a role in this protection. Images PMID:1565616

  13. Differentiation of Cardiomyocytes from Human Pluripotent Stem Cells Using Monolayer Culture

    PubMed Central

    Batalov, Ivan; Feinberg, Adam W

    2015-01-01

    Human pluripotent stem cells (PSCs) are a promising cell source for cardiac tissue engineering and cell-based therapies for heart repair because they can be expanded in vitro and differentiated into most cardiovascular cell types, including cardiomyocytes. During embryonic heart development, this differentiation occurs under the influence of internal and external stimuli that guide cells to go down the cardiac lineage. In order to differentiate PSCs in vitro, these or similar stimuli need to be provided in a controlled manner. However, because it is not possible to completely recapitulate the embryonic environment, the factors essential for cardiac differentiation of PSCs in vitro need to be experimentally determined and validated. Since PSCs were first developed, significant progress has been made in optimizing techniques for their differentiation toward cardiomyocytes. In this review, we will summarize recent advances in these techniques, with particular focus on monolayer-based methods that have improved the efficiency and scalability of cardiomyocyte differentiation. PMID:26052225

  14. Effects of thrombin on the integrity of monolayers of cultured human endothelial cells

    SciTech Connect

    Galdal, K.S.; Evensen, S.A.; Brosstad, F.

    1982-09-01

    /sup 51/Cr-prelabelled endothelial cells (EC) in confluent monolayers were incubated in RPMI 1640 + foetal calf serum 20% (v/v) to which purified thrombin was added. Thrombin (greater than or equal to 0.1 NIH U/ml) significantly accelerated /sup 51/Cr-release and caused extensive but reversible cell contraction. Thrombin-exposed EC reacted to a new dose of thrombin with no appreciable shape change, but /sup 51/Cr-efflux was again accelerated. EC exposed to thrombin pretreated with N-bromosuccinimide (modifying the macromolecular site) or phenylmethylsulfonyl fluoride (blocking the serine site) retained normal morphology and did not leak excess amounts of /sup 51/Cr. Antithrombin III also inhibited the effect of thrombin. Pretreatment of EC with either indomethacin, aspirin, sulfinpyrazone, pronase or neuraminidase did not influence the effect of subsequent thrombin exposure.

  15. Activities of acyclic nucleoside phosphonates against Orf virus in human and ovine cell monolayers and organotypic ovine raft cultures.

    PubMed

    Dal Pozzo, F; Andrei, G; Holy, A; Van Den Oord, J; Scagliarini, A; De Clercq, E; Snoeck, R

    2005-12-01

    Orf virus, a member of the Parapoxvirus genus, causes a contagious pustular dermatitis in sheep, goats, and humans. Previous studies have demonstrated the activity of (S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine (HPMPC; cidofovir; Vistide) against orf virus in cell culture and humans. We have evaluated a broad range of acyclic nucleoside phosphonates (ANPs) against several orf virus strains in primary lamb keratinocytes (PLKs) and human embryonic lung (HEL) monolayers. HPMPC, (S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]-2,6- diaminopurine (HPMPDAP), and (R)-9-[3-hydroxy-2-(phosphonomethoxy)propoxy]-2,4-diaminopyrimidine (HPMPO-DAPy) were three of the most active compounds that were subsequently tested in a virus yield assay with PLK and HEL cells by virus titration and DNA quantification. HPMPC, HPMPDAP, and HPMPO-DAPy were evaluated for their activities against orf virus replication in organotypic epithelial raft cultures from differentiated PLK cells. At the highest concentrations (50 and 20 microg/ml), full protection was provided by the three drugs, while at 5 microg/ml, only HPMPDAP and HPMPC offered partial protection. The activities of the three compounds in the raft culture system were confirmed by quantification of infectious virus and viral DNA. These findings provide a rationale for the use of HPMPC and other ANPs in the treatment of orf (contagious ecthyma) in humans and animals.

  16. The potential of pulsed low intensity ultrasound to stimulate chondrocytes matrix synthesis in agarose and monolayer cultures.

    PubMed

    Vaughan, Natalie M; Grainger, James; Bader, Dan L; Knight, Martin M

    2010-12-01

    Pulsed low intensity ultrasound (PLIUS) has been used successfully for bone fracture repair and has therefore been suggested for cartilage regeneration. However, previous in vitro studies with chondrocytes show conflicting results as to the effect of PLIUS on the elaboration of extracellular matrix. This study tests the hypothesis that PLIUS, applied for 20 min/day, stimulates the synthesis of sulphated glycosaminoglycan (sGAG) by adult bovine articular chondrocytes cultured in either monolayer or agarose constructs. For both culture models, PLIUS at either 30 or 100 mW/cm(2) intensity had no net effect on the total sGAG content. Although PLIUS at 100 mW/cm(2) did induce a 20% increase in sGAG content at day 2 of culture in agarose, this response was lost by day 5. Intensities of 200 and 300 mW/cm(2) resulted in cell death probably due to heating from the ultrasound transducers. The lack of a sustained up-regulation of sGAG synthesis may reflect the suggestion that PLIUS only induces a stimulatory effect in the presence of a tissue injury response. These results suggest that PLIUS has a limited potential to provide an effective method of stimulating matrix production as part of a tissue engineering strategy for cartilage repair. PMID:20938751

  17. Involvement of nucleotides in glial growth following scratch injury in avian retinal cell monolayer cultures.

    PubMed

    Silva, Thayane Martins; França, Guilherme Rapozeiro; Ornelas, Isis Moraes; Loiola, Erick Correia; Ulrich, Henning; Ventura, Ana Lucia Marques

    2015-06-01

    When retinal cell cultures were mechanically scratched, cell growth over the empty area was observed. Only dividing and migrating, 2 M6-positive glial cells were detected. Incubation of cultures with apyrase (APY), suramin, or Reactive Blue 2 (RB-2), but not MRS 2179, significantly attenuated the growth of glial cells, suggesting that nucleotide receptors other than P2Y1 are involved in the growth of glial cells. UTPγS but not ADPβS antagonized apyrase-induced growth inhibition in scratched cultures, suggesting the participation of UTP-sensitive receptors. No decrease in proliferating cell nuclear antigen (PCNA(+)) cells was observed at the border of the scratch in apyrase-treated cultures, suggesting that glial proliferation was not affected. In apyrase-treated cultures, glial cytoplasm protrusions were smaller and unstable. Actin filaments were less organized and alfa-tubulin-labeled microtubules were mainly parallel to scratch. In contrast to control cultures, very few vinculin-labeled adhesion sites could be noticed in these cultures. Increased Akt and ERK phosphorylation was observed in UTP-treated cultures, effect that was inhibited by SRC inhibitor 1 and PI3K blocker LY294002. These inhibitors and the FAK inhibitor PF573228 also decreased glial growth over the scratch, suggesting participation of SRC, PI3K, and FAK in UTP-induced growth of glial cells in scratched cultures. RB-2 decreased dissociated glial cell attachment to fibronectin-coated dishes and migration through transwell membranes, suggesting that nucleotides regulated adhesion and migration of glial cells. In conclusion, mechanical scratch of retinal cell cultures induces growth of glial cells over the empty area through a mechanism that is dependent on activation of UTP-sensitive receptors, SRC, PI3K, and FAK.

  18. Human thyroid epithelial cells cultured in monolayers. II. Influence of serum on thyroglobulin and cAMP production.

    PubMed

    Rasmussen, A K; Kayser, L; Perrild, H; Brandt, M; Bech, K; Feldt-Rasmussen, U

    1996-02-01

    An in vitro system of secondary cultures of human thyroid follicular epithelial cells in monolayer is described. The 72-h influence of serum and six supplements (thyrotropin, insulin, somatostatin, transferrin, hydrocortisone, glycyl-histidyl-lysine acetate) on growth and function in presence of 3-isobutyl-L-methyl-xanthine (IBMX) was investigated. The function of the cells was evaluated by production of the second messenger adenylate cyclase (cAMP) and the end product thyroglobulin (Tg). Growth was measured as the 3H-thymidine uptake of the cells. Three days of TSH-depletion preceeded the experiments. In presence of IBMX TSH stimulated cAMP production, while stimulation of Tg was only present in some cultures. In absence of IBMX TSH always stimulated the Tg production. The stimulation was independent of the presence of the other five investigated nutritional factors in physiological concentrations. TSH in concentrations from 0.1-10 U/1 stimulated the 72ih 3H-thymidine uptake of the cells. The TSH-stimulated production of Tg and cAMP decreased significantly with increasing concentrations of fetal calf serum (0-10%), (tau = 0.49, P < 0.001, n = 6-29 and tau = 0.75, P < 0.001, n = 6-29, respectively). Thus, serum as a complex, variable and not fully characterized mixture of hormones and growth factors was crucial to the attachment of the cells to the substrate, but inhibited differentiated functions of the human thyroid cells. PMID:8647317

  19. Effects of hydroxybenzyl alcohols on melanogenesis in melanocyte-keratinocyte co-culture and monolayer culture of melanocytes.

    PubMed

    Liu, Szu-Hsiu; Chu, I-Ming; Pan, I-Horng

    2008-08-01

    In mammalian skin, melanocyte proliferation and melanogenesis can be stimulated by keratinocytes, fibroblasts and other regulatory factors. To determine whether hydroxybenzyl alcohols (HBAs) show more inhibitory in melanocytes cultured alone or in melanocytes co-cultured with keratinocytes, we developed a murine melanocyte-keratinocyte co-culture model to investigate the pigmentation regulators in company with other melanogenic inhibitors and stimulators. It was found that the effects of HBAs and melanogenic factors were more evident in melanocytes co-cultured with keratinocytes. Keratinocytes may play a synergistic role in melanocyte melanogenesis and influence the pigment production. The tests in the co-culture model also imply that the inhibitory effects of HBAs on melanogenesis are due to the direct inhibition of melanosomal tyrosinase activity. HBAs showed a low cytotoxicity. The eventual results proved that HBAs are promising and safe agents for skin whitening in melanocyte alone and in co-culture systems. The co-culture model provides a more physiologically realistic condition to study the interaction between melanocytes and keratinocytes, which enables a reliable screening system for depigmenting compounds.

  20. Direct patterning of coplanar polyethylene glycol alkylsilane monolayers by deep-ultraviolet photolithography as a general method for high fidelity, long-term cell patterning and culture.

    PubMed

    Wilson, Kerry; Stancescu, Maria; Das, Mainak; Rumsey, John; Hickman, James

    2011-03-01

    This manuscript details a general method for patterning coplanar alkylsilane monolayers using deep-ultraviolet photolithography that has broad application for high fidelity patterning of cells of varying phenotype in long-term cultures. A polyethylene glycol monolayer was formed on a silica substrate and then patterned using 193 nm light from an ArF excimer laser. The regions of photoablation were then rederivatized with (3-trimethoxysilyl propyl) diethyltriamine (DETA), yielding high contrast cytophilic islands that promoted cell adhesion and growth. Rat hippocampal neurons, motoneurons, and myoblasts were then cultured in a defined, serum-free medium on the patterned surfaces for periods in excess of 40 days. This approach has been shown to be useful as a general method for the long-term culture of multiple cell types in highly defined spatial patterns and can be used for supporting complex cocultures for creating in vitro models for biological systems.

  1. Monolayer co-culture of rat heart cells and bovine adrenal chromaffin paraneurons.

    PubMed

    Trifaró, J M; Tang, R; Novas, M L

    1990-04-01

    This paper describes a method for the preparation of co-cultures of rat heart cells and bovine adrenal chromaffin paraneurons. The most suitable condition for heart cell isolation was when a combination of trypsin-DNAse I in Locke's solution was used for digestion. The best co-culture conditions were obtained when 10(6) heart cells were plated on 7- to 8-d-old adrenal chromaffin paraneuron cultures containing 0.5 x 10(6) cells per 35-mm diameter culture dishes. Measurements of DNA (heart cells and chromaffin paraneurons), monitoring of beating frequency (heart cells), and catecholamine (chromaffin paraneurons) levels and release indicated that both cell types remain viable and functional for several weeks. Heart cells started their characteristic contractile activity 24 h earlier when plated either on viable or lysed chromaffin paraneurons, an effect apparently due to faster surface adhesion of heart cells. The beating frequency of heart cells increased after treatment of co-cultures with either noradrenaline or nicotine, with the latter agent acting indirectly through the release of chromaffin paraneuron catecholamines. Propranolol produced a dose-related inhibition of the responses to either noradrenaline or nicotine, thus suggesting that the increase in myocyte's beating activity was mediated through beta-receptors. Anti-myosin and anti-dopamine-beta-hydroxylase immunostaining was used for cell type identification and for the demonstration of body-to-body and process-to-process contacts between adrenal chromaffin paraneurons and heart cells. This co-culture system will serve as a starting point of further studies directed to understand a) the influence of a cell type on the development and on the phenotypic characteristics of a second cell type and b) the interaction of cells derived from different organs and species.

  2. Establishment of long-term monolayer cultures of somatic cells from human fetal testes and expansion of peritubular myoid cells in the presence of androgen.

    PubMed

    Cowan, Gillian; Childs, Andrew J; Anderson, Richard A; Saunders, Philippa T K

    2010-04-01

    The somatic (Sertoli cell (SC), Leydig cell (LC), and peritubular myoid (PTM) cell) cells play key roles in development of the fetal testis. We established monolayer cultures from second trimester human testes and investigated the pattern of expression of cell-lineage characteristic mRNAs. Expression of some SC-associated genes (SRY, SOX9, WT1, GATA4, and SF1) was detectable up to and including passage 3 (P3), while others (anti-Müllerian hormone; desert hedgehog) present prior to dissociation were not expressed in the cultured cells. Transcripts encoding the androgen receptor were expressed but addition of dihydrotestosterone (DHT) had no impact on expression of mRNAs expressed in SC or LC. Total concentrations of mRNAs encoding smooth muscle actin (ACTA2) and desmin increased from P1 to P3; an increasing proportion of the cells in the cultures were immunopositive for ACTA2 consistent with proliferation/differentiation of PTM cells. In conclusion, somatic cell monolayer cultures were established from human fetal testes; these cultures could form the basis for future studies based on isolation of purified populations of somatic cells and manipulation of gene expression that is difficult to achieve with organ culture systems. Our results suggest that fetal SC do not maintain a fully differentiated phenotype in vitro, yet PTM (ACTA2 positive) cells readily adapt to monolayer culture conditions in the presence of DHT. This culture system provides an opportunity to study the impact of regulatory factors on gene expression in PTM cells, a population thought to play a key role in mediating androgen action within the developing testis. PMID:20089665

  3. Self-assembled monolayer facilitates epithelial-mesenchymal interactions mimicking odontogenesis.

    PubMed

    Muni, Tanvi; Mrksich, Milan; George, Anne

    2014-01-01

    Cell-cell interactions are vital for embryonic organ development and normal function of differentiated cells and tissues. In this study we have developed a self-assembled monolayer-based co-culture system to study tooth morphogenesis. Specifically, we designed a 2-D microenvironment present in the dental tissue by creating a well-structured, laterally organized epithelial and mesenchymal cell co-culture system by patterning the cell-attachment substrate. Chemical modifications were used to develop tunable surface patterns to facilitate epithelial-mesenchymal interactions mimicking the developing tooth. Such a design promoted interactions between monolayer's of the 2 cell types and provided signaling cues that resulted in cellular differentiation and mineralized matrix formation. Gene expression analysis showed that these co-cultures mimicked in-vivo conditions than monolayer cultures of a single cell type.

  4. cGMP-Compliant Expansion of Human iPSC Cultures as Adherent Monolayers.

    PubMed

    Parr, Ann M; Walsh, Patrick J; Truong, Vincent; Dutton, James R

    2016-01-01

    Therapeutic uses of cells differentiated from human pluripotent stem cells (hPSCs), either embryonic stem (ES) cells or induced pluripotent stem cells (iPSCs), are now being tested in clinical trials, and it is likely that this will lead to increased commercial interest in the clinical translation of promising hPSC research. Recent technical advances in the use of defined media and culture substrates have significantly improved both the simplicity and predictability of growing hPSCs, allowing a much more straightforward application of current good manufacturing practices (cGMP) to the culture of these cells. In addition, the adoption of cGMP-compliant techniques in research environments will both improve the replication of results and make the transition of promising investigations to the commercial sector significantly less cumbersome. However, passaging methods for hPSCs are inherently unpredictable and rely on operator experience and expertise. This is problematic for the cell manufacturing process where operator time and process predictability are often determining cost drivers. We have adopted a human iPSC system using defined media and a recombinant substrate that employs cell dissociation with a hypertonic citrate solution which eliminates variability during hPSC cell expansion and provides a simple cGMP-compliant technique for hiPSC cultivation that is appropriate in both research and commercial applications. PMID:25863788

  5. [Variability of the duration of the cell cycle in pig embryo kidney cells in monolayer culture and correlation of the cycle duration in sister cells].

    PubMed

    Blokhin, A V; Voronkova, L N; Sakharov, V N

    1985-07-01

    The distribution of generation time of sister cells for the exponentially proliferating monolayer SPEV culture was obtained with time lapse cinemicrographic technique. The distribution is characterized by the average generation time equal to 24.3 hour, with the variation coefficient, asymmetry coefficient and correlation coefficient for sister pair cell being, respectively, 17%, 0.2 and 0.78. The results obtained are compared with the prediction of "a random transition" in the cell cycle. PMID:3901449

  6. Ontology analysis of global gene expression differences of human bone marrow stromal cells cultured on 3D scaffolds or 2D films.

    PubMed

    Baker, Bryan A; Pine, P Scott; Chatterjee, Kaushik; Kumar, Girish; Lin, Nancy J; McDaniel, Jennifer H; Salit, Marc L; Simon, Carl G

    2014-08-01

    Differences in gene expression of human bone marrow stromal cells (hBMSCs) during culture in three-dimensional (3D) nanofiber scaffolds or on two-dimensional (2D) films were investigated via pathway analysis of microarray mRNA expression profiles. Previous work has shown that hBMSC culture in nanofiber scaffolds can induce osteogenic differentiation in the absence of osteogenic supplements (OS). Analysis using ontology databases revealed that nanofibers and OS regulated similar pathways and that both were enriched for TGF-β and cell-adhesion/ECM-receptor pathways. The most notable difference between the two was that nanofibers had stronger enrichment for cell-adhesion/ECM-receptor pathways. Comparison of nanofibers scaffolds with flat films yielded stronger differences in gene expression than comparison of nanofibers made from different polymers, suggesting that substrate structure had stronger effects on cell function than substrate polymer composition. These results demonstrate that physical (nanofibers) and biochemical (OS) signals regulate similar ontological pathways, suggesting that these cues use similar molecular mechanisms to control hBMSC differentiation. PMID:24840613

  7. Changes in gene expression, protein content and morphology of chondrocytes cultured on a 3D Random Positioning Machine and 2D rotating clinostat

    NASA Astrophysics Data System (ADS)

    Aleshcheva, Ganna; Hauslage, Jens; Hemmersbach, Ruth; Infanger, Manfred; Bauer, Johann; Grimm, Daniela; Sahana, Jayashree

    Chondrocytes are the only cell type found in human cartilage consisting of proteoglycans and type II collagen. Several studies on chondrocytes cultured either in Space or on a ground-based facility for simulation of microgravity revealed that these cells are very resistant to adverse effects and stress induced by altered gravity. Tissue engineering of chondrocytes is a new strategy for cartilage regeneration. Using a three-dimensional Random Positioning Machine and a 2D rotating clinostat, devices designed to simulate microgravity on Earth, we investigated the early effects of microgravity exposure on human chondrocytes of six different donors after 30 min, 2 h, 4 h, 16 h, and 24 h and compared the results with the corresponding static controls cultured under normal gravity conditions. As little as 30 min of exposure resulted in increased expression of several genes responsible for cell motility, structure and integrity (beta-actin); control of cell growth, cell proliferation, cell differentiation and apoptosis; and cytoskeletal components such as microtubules (beta-tubulin) and intermediate filaments (vimentin). After 4 hours disruptions in the vimentin network were detected. These changes were less dramatic after 16 hours, when human chondrocytes appeared to reorganize their cytoskeleton. However, the gene expression and protein content of TGF-β1 was enhanced for 24 h. Based on the results achieved, we suggest that chondrocytes exposed to simulated microgravity seem to change their extracellular matrix production behavior while they rearrange their cytoskeletal proteins prior to forming three-dimensional aggregates.

  8. Spatio-temporal morphology changes in and quenching effects on the 2D spreading dynamics of cell colonies in both plain and methylcellulose-containing culture media.

    PubMed

    Muzzio, N E; Pasquale, M A; Huergo, M A C; Bolzán, A E; González, P H; Arvia, A J

    2016-06-01

    To deal with complex systems, microscopic and global approaches become of particular interest. Our previous results from the dynamics of large cell colonies indicated that their 2D front roughness dynamics is compatible with the standard Kardar-Parisi-Zhang (KPZ) or the quenched KPZ equations either in plain or methylcellulose (MC)-containing gel culture media, respectively. In both cases, the influence of a non-uniform distribution of the colony constituents was significant. These results encouraged us to investigate the overall dynamics of those systems considering the morphology and size, the duplication rate, and the motility of single cells. For this purpose, colonies with different cell populations (N) exhibiting quasi-circular and quasi-linear growth fronts in plain and MC-containing culture media are investigated. For small N, the average radial front velocity and its change with time depend on MC concentration. MC in the medium interferes with cell mitosis, contributes to the local enlargement of cells, and increases the distribution of spatio-temporal cell density heterogeneities. Colony spreading in MC-containing media proceeds under two main quenching effects, I and II; the former mainly depending on the culture medium composition and structure and the latter caused by the distribution of enlarged local cell domains. For large N, colony spreading occurs at constant velocity. The characteristics of cell motility, assessed by measuring their trajectories and the corresponding velocity field, reflect the effect of enlarged, slow-moving cells and the structure of the medium. Local average cell size distribution and individual cell motility data from plain and MC-containing media are qualitatively consistent with the predictions of both the extended cellular Potts models and the observed transition of the front roughness dynamics from a standard KPZ to a quenched KPZ. In this case, quenching effects I and II cooperate and give rise to the quenched

  9. Monolayer culturing and cloning of human pluripotent stem cells on laminin-521-based matrices under xeno-free and chemically defined conditions.

    PubMed

    Rodin, Sergey; Antonsson, Liselotte; Hovatta, Outi; Tryggvason, Karl

    2014-10-01

    A robust method for culturing human pluripotent stem (hPS) cells under chemically defined and xeno-free conditions is an important tool for stem cell research and for the development of regenerative medicine. Here, we describe a protocol for monolayer culturing of Oct-4-positive hPS cells on a specific laminin-521 (LN-521) isoform, under xeno-free and chemically defined conditions. The cells are dispersed into single-cell suspension and then plated on LN-521 isoform at densities higher than 5,000 cells per cm², where they attach, migrate and survive by forming small monolayer cell groups. The cells avidly divide and expand horizontally until the entire dish is covered by a confluent monolayer. LN-521, in combination with E-cadherin, allows cloning of individual hPS cells in separate wells of 96-well plates without the presence of rho-associated protein kinase (ROCK) inhibitors or any other inhibitors of anoikis. Characterization of cells maintained for several months in culture reveals pluripotency with a minimal degree of genetic abnormalities.

  10. Monolayer culturing and cloning of human pluripotent stem cells on laminin-521-based matrices under xeno-free and chemically defined conditions.

    PubMed

    Rodin, Sergey; Antonsson, Liselotte; Hovatta, Outi; Tryggvason, Karl

    2014-10-01

    A robust method for culturing human pluripotent stem (hPS) cells under chemically defined and xeno-free conditions is an important tool for stem cell research and for the development of regenerative medicine. Here, we describe a protocol for monolayer culturing of Oct-4-positive hPS cells on a specific laminin-521 (LN-521) isoform, under xeno-free and chemically defined conditions. The cells are dispersed into single-cell suspension and then plated on LN-521 isoform at densities higher than 5,000 cells per cm², where they attach, migrate and survive by forming small monolayer cell groups. The cells avidly divide and expand horizontally until the entire dish is covered by a confluent monolayer. LN-521, in combination with E-cadherin, allows cloning of individual hPS cells in separate wells of 96-well plates without the presence of rho-associated protein kinase (ROCK) inhibitors or any other inhibitors of anoikis. Characterization of cells maintained for several months in culture reveals pluripotency with a minimal degree of genetic abnormalities. PMID:25211513

  11. Absorption and metabolism of chlorogenic acids in cultured gastric epithelial monolayers.

    PubMed

    Farrell, Tracy L; Dew, Tristan P; Poquet, Laure; Hanson, Peter; Williamson, Gary

    2011-12-01

    Gastric absorption of feruloylquinic acid and di-O-caffeoylquinic acid analogs has never been investigated despite their potential contribution to the proposed beneficial health effects leading to reduced risk of type 2 diabetes. Using a cultured gastric epithelial model, with an acidic apical pH, the relative permeability coefficients (P(app)) and metabolic fate of a series of chlorogenic acids (CGAs) were investigated. Mechanistic studies were performed in the apical to basal direction and demonstrated differential rates of absorption for different CGA subgroups. For the first time, we show intact absorption of feruloylquinic acids and caffeoylquinic acid lactones across the gastric epithelium (P(app) ∼ 0.2 cm/s). Transport seemed to be mainly by passive diffusion, because good linearity was observed over the incubation period and test concentrations, and we speculate that a potential carrier-mediated component may be involved in uptake of certain 4-acyl CGA isomers. In contrast, absorption of intact di-O-caffeoylquinic acids was rapid (P(app) ∼ 2-10 cm/s) but nonlinear with respect to time and concentration dependence, which was potentially limited by interaction with an efflux transporter and/or pH gradient dependence. For the first time, methylation is shown in gastric mucosa. Furthermore, isoferulic acid, dimethoxycinnamic acid, and ferulic acid were identified as novel gastric metabolites of CGA biotransformation. We propose that the stomach is the first location for the release of hydroxycinnamic acids, which could explain their early detection after coffee consumption.

  12. A New In Vitro Model to Study Cellular Responses after Thermomechanical Damage in Monolayer Cultures

    PubMed Central

    Hettler, Alice; Werner, Simon; Eick, Stefan; Laufer, Stefan; Weise, Frank

    2013-01-01

    Although electrosurgical instruments are widely used in surgery to cut tissue layers or to achieve hemostasis by coagulation (electrocautery), only little information is available concerning the inflammatory or immune response towards the debris generated. Given the elevated local temperatures required for successful electrocautery, the remaining debris is likely to contain a plethora of compounds entirely novel to the intracorporal setting. A very common in vitro method to study cell migration after mechanical damage is the scratch assay, however, there is no established model for thermomechanical damage to characterise cellular reactions. In this study, we established a new in vitro model to investigate exposure to high temperature in a carefully controlled cell culture system. Heatable thermostat-controlled aluminium stamps were developed to induce local damage in primary human umbilical vein endothelial cells (HUVEC). The thermomechanical damage invoked is reproducibly locally confined, therefore allowing studies, under the same experimental conditions, of cells affected to various degrees as well as of unaffected cells. We show that the unaffected cells surrounding the thermomechanical damage zone are able to migrate into the damaged area, resulting in a complete closure of the ‘wound’ within 48 h. Initial studies have shown that there are significant morphological and biological differences in endothelial cells after thermomechanical damage compared to the mechanical damage inflicted by using the unheated stamp as a control. Accordingly, after thermomechanical damage, cell death as well as cell protection programs were activated. Mononuclear cells adhered in the area adjacent to thermomechanical damage, but not to the zone of mechanical damage. Therefore, our model can help to understand the differences in wound healing during the early phase of regeneration after thermomechanical vs. mechanical damage. Furthermore, this model lends itself to study the

  13. Controlling self assembled monolayers

    NASA Astrophysics Data System (ADS)

    Wei, Yanhu

    2007-12-01

    In this thesis, we demonstrate novel methods of controlling the morphology of self-assembled monolayers at the solution-graphite interface. Scanning tunneling microscopy is used to evaluate the capacity of chain length and weak dipolar interactions to direct packing and neighboring chain selection within monolayers. We designed and synthesized a series of 1,5-substituted anthracene derivatives and investigated the relationship between side chain structure and monolayer morphology. We report that the morphology of monolayers formed on HOPG from symmetrically substituted anthracene derivatives switches from a 2D racemate to a 2D conglomerate by the addition of a single methylene unit to each side chain, i.e., by changing the side chain lengths from even to odd. We introduced ether groups into the side chains of anthracene derivatives in an attempt to use dipolar interactions to alter monolayer morphology. We report that the insertion of electronegative oxygen atoms into the side chains of anthracene derivatives can disturb the odd - even effect of chain length and influence monolayer morphology. By introducing a proper number of ether groups at specific side chain locations, we designed two self-repelling and complementary chains: COC12OC and C2OC10OC 2. COC12OC (or C2OC10OC2) chains repel themselves but select the other C2OC10OC 2 (or COC12OC) chains as their neighbors in self-assembled monolayers. Taking into account chain length matching and dipolar complementary as mechanisms for adjacent side chain selection, we designed and synthesized two symmetrical anthracenes 12 (COC12OC-An-COC 12OC), 13 (C2OC10OC2-An-C 2OC10OC2) and two unsymmetrical anthracenes 15 (C11OC-An-COC12OC) and 16 (C 18OC2-An-C2OC10OC2). Using a mixture solution of these molecules, we prepared a highly ordered AABB monolayer pattern in which paired rows of 15 alternate with paired rows of 16, and a highly ordered AAB monolayer pattern in which rows consisting of 12 are sandwiched between paired

  14. In Vitro Differentiation of Pluripotent Stem Cells into Functional β Islets Under 2D and 3D Culture Conditions and In Vivo Preclinical Validation of 3D Islets.

    PubMed

    Bose, Bipasha; Sudheer, P Shenoy

    2016-01-01

    Since the advent of pluripotent stem cells, (embryonic and induced pluripotent stem cells), applications of such pluripotent stem cells are of prime importance. Indeed, scientists are involved in studying the basic biology of pluripotent stem cells, but equal impetus is there to direct the pluripotent stem cells into multiple lineages for cell therapy applications. Scientists across the globe have been successful, to a certain extent, in obtaining cells of definitive endoderm and also pancreatic β islets by differentiating human pluripotent stem cells. Pluripotent stem cell differentiation protocols aim at mimicking in vivo embryonic development. As in vivo embryonic development is a complex process and involves interplay of multiple cytokines, the differentiation protocols also involve a stepwise use of multiple cytokines. Indeed the novel markers for pancreas organogenesis serve as the roadmaps to develop new protocols for pancreatic differentiation from pluripotent stem cells. Earliest developed protocols for pancreas differentiation involved "Nestin selection pathway," a pathway common for both neuronal and pancreatic differentiation lead to the generation of cells that were a combination of cells from neuronal lineage. Eventually with the discovery of hierarchy of β cell transcription factors like Pdx1, Pax4, and Nkx2.2, forced expression of such transcription factors proved successful in converting a pluripotent stem cell into a β cell. Protocols developed almost half a decade ago to the recent ones rather involve stepwise differentiations involving various cytokines and could generate as high as 25 % functional insulin-positive cells in vitro. Most advanced protocols for β islet differentiations from human pluripotent stem cells focused on 3D culture conditions, which reportedly produced 60-65 % functional β islet cells. Here, we describe the protocol for differentiation of human pluripotent stem cells into functional β cells under both 2D and 3D

  15. Expression of transcription factors after short-term exposure of Arabidopsis thaliana cell cultures to hypergravity and simulated microgravity (2-D/3-D clinorotation, magnetic levitation)

    NASA Astrophysics Data System (ADS)

    Babbick, M.; Dijkstra, C.; Larkin, O. J.; Anthony, P.; Davey, M. R.; Power, J. B.; Lowe, K. C.; Cogoli-Greuter, M.; Hampp, R.

    Gravity is an important environmental factor that controls plant growth and development. Studies have shown that the perception of gravity is not only a property of specialized cells, but can also be performed by undifferentiated cultured cells. In this investigation, callus of Arabidopsis thaliana cv. Columbia was used to investigate the initial steps of gravity-related signalling cascades, through altered expression of transcription factors (TFs). TFs are families of small proteins that regulate gene expression by binding to specific promoter sequences. Based on microarray studies, members of the gene families WRKY, MADS-box, MYB, and AP2/EREBP were selected for investigation, as well as members of signalling chains, namely IAA 19 and phosphoinositol-4-kinase. Using qRT-PCR, transcripts were quantified within a period of 30 min in response to hypergravity (8 g), clinorotation [2-D clinostat and 3-D random positioning machine (RPM)] and magnetic levitation (ML). The data indicated that (1) changes in gravity induced stress-related signalling, and (2) exposure in the RPM induced changes in gene expression which resemble those of magnetic levitation. Two dimensional clinorotation resulted in responses similar to those caused by hypergravity. It is suggested that RPM and ML are preferable to simulate microgravity than clinorotation.

  16. Effect of Chemotherapeutic Drugs on Caspase-3 Activity, as a Key Biomarker for Apoptosis in Ovarian Tumor Cell Cultured as Monolayer. A Pilot Study

    PubMed Central

    Gregoraszczuk, Ewa L; Rak-Mardyła, Agnieszka; Ryś, Janusz; Jakubowicz, Jerzy; Urbański, Krzysztof

    2015-01-01

    We aimed to develop a cost-effective and robust method to predict drug resistance in individual patients. Representative tissue fragments were obtained from tumors removed from female patients, aged 24-74 years old. The tumor tissue was taken by a histopathology’s or a surgeon under sterile conditions. Cells obtained by enzymatic dissociation from tumor after surgery, were cultured as a monolayer for 6 days. Paclitaxel, doxorubicin, carboplatin and endoxan alone or in combination were added at the beginning of culture and after 6 days, Alamar blue test was used for showing action on cell proliferation why caspase- 3 activity assays for verifying action on apoptosis. Inhibitory action on cell proliferation was noted in 2 of 12 patients tumor treated with both single and combined drugs. Using caspase-3 assay we showed that 50% of tumor cells was resistant to single chemotherapeutic drugs and 40% for combined. In 2 of 12 tumors, which did not reacted on single drugs, positive synergistic action on cell proliferation was observed in combination of D + E and C + E. This pilot study suggests: 1) monolayer culture of tumor cells, derived from individual patients, before chemotherapy could provide a suitable model for studying resistance for drugs; 2) caspase-3 activity is cheap and useful methods; 3) Alamar blue test should be taken into consideration for measuring cell proliferation. PMID:26664382

  17. Dual effect of nitrogen dioxide on barrier properties of guinea pig tracheobronchial epithelial monolayers cultured in an air interface

    SciTech Connect

    Robison, T.W.; Kim, K.J.

    1995-08-01

    Nitrogen dioxide (NO{sub 2}) is an oxidant gas that may injure the airway epithelial lining, leading to decrements in barrier and active ion transport properties. The present studies examined alterations of bioelectric properties and solute flux by guinea pig tracheobronchial epithelial (GPTE) monolayers exposed in vitro to NO{sub 2}. Confluent GPTE monolayers were exposed to NO{sub 2} levels between 0.5 and 5 ppm, while controls were exposed to air. Following exposure, monolayers were mounted in Ussing chambers for measurement of transepithelial resistance (R{sub te}) and short-circuit current (SCC). A 1-h exposure to 1 ppm NO{sub 2} significantly increased SCC to 131.3 {+-} 8.7% of air controls, while R{sub te} with a value of 109.3 {+-} 13.8% was unchanged. In contrast, a 1-h exposure to 2 or 5 ppm NO{sub 2} significantly decreased R{sub te} to 39.0 {+-} 1.6 or 33.5 {+-} 7.3% of air controls, respectively, while SCC values of 140.3 {+-} 10.4 or 153.3 {+-} 8.6%, respectively, were also significantly elevated. A 1-h exposure to 2 or 5 ppm NO{sub 2} significantly increased sucrose permeability across GPTE monolayers to 446.8 {+-} 117 or 313.3 {+-} 39.5% of air controls, respectively, while glycerol permeability was unchanged. In contrast, a 1-h exposure to 1 ppm NO{sub 2} produced no alterations of sucrose or glycerol flux. The SCC of control GPTE monolayers (1-h air exposure) consisted of 50% bumetanide-sensitive and 40% amiloride-sensitive current; exposure for 1 h to 2 ppm NO{sub 2} led to no changes in the corresponding SCC components. Active ion transport (i.e., SCC) across the airway epithelium was significantly increased after exposure to NO{sub 2} levels {le}1 ppm with no change of paracellular pathways for diffusion, suggesting that this reactive gas alters cell membrane function. The increased SCC may lead to impairment of fluid balance and mucociliary clearance. 34 refs., 4 figs.

  18. Traditional Chinese medicine herbal mixture LQ arrests FUCCI-expressing HeLa cells in G0/G1 phase in 2D plastic, 2.5D Matrigel®, and 3D Gelfoam® culture visualized with FUCCI imaging

    PubMed Central

    Bouvet, Michael; Yano, Shuya; Hoffman, Robert M.

    2015-01-01

    We used the fluorescence ubiquitination-based cell cycle indicator (FUCCI) to monitor cell cycle arrest after treatment of FUCCI-expressing HeLa cells (FUCCI-HeLa) with a traditional Chinese medicine (TCM) herbal mixture LQ, previously shown to have anti-tumor and anti-metastatic activity in mouse models. Paclitaxel was used as the positive control. In 2D monolayer culture, the untreated control had approximately 45% of the cells in S/G2/M phase. In contrast, the LQ-treated cells (9 mg/ml) were mostly in the G0/G1 (>90%) after 72 hours. After treatment with paclitaxel (0.01 μm), for 72 hours, 95% of the cells were in S/G2/M. In 2.5D Matrigel® culture, the colonies in the untreated control group had 40% of the cells in S/G2/M. LQ arrested the cells in G0/G1 after 72 hours. Paclitaxel arrested almost all the cells in S/G2/M after 72 hours. In 3D Gelfoam® culture, the untreated control culture had approximately 45% of cells in G2/M. In contrast, the LQ-treated cells were mostly in G0/G1 phase (>80%) after 72 hours treatment. Paclitaxel resulted in 90% of the cells arrested in S/G2/M after 72 hours. The present report suggests the non-toxic LQ has potential to maintain cancers in a quiescent state for long periods of time. PMID:25779660

  19. Multiparametric temporal analysis of the Caco-2/TC7 demonstrated functional and differentiated monolayers as early as 14 days of culture.

    PubMed

    Zeller, Perrine; Bricks, Thibault; Vidal, Guillaume; Jacques, Sébastien; Anton, Pauline M; Leclerc, Eric

    2015-05-25

    Reducing the differentiation period for obtaining an in vitro intestinal barrier model is required to reduce the duration and cost for drug screening assays. In this frame, the Caco-2/TC7 subclone differentiation state was investigated from day 0 (D0) to day 32 (D32). As such, the expression of 45 genes (including cell junction, cell polarization, cell functionality, drug transport and metabolism genes) was followed throughout the 32 days. In parallel, the monolayer polarization and the formation of the cellular junctions were characterized by the immuno-staining of occludin, claudin-1 and actin proteins. The cell monolayer permeability was analyzed via transepithelial electric resistance measurements and paracellular transport of Lucifer Yellow. The P-gp efflux efficiency was assessed by rhodamine 123 transport. Alkaline phosphate activity was quantified to assess the cell differentiation. Three stages of differentiation were observed using the clustering of principal component analysis of the RTqPCR data and the overall assays. From D0 to D10, cells were in a proliferation stage and under-differentiated; from D14 to D21 a stable differentiation stage was reached; from D25 to D32 the epithelium seemed to enter into a post-differentiated stage. This study demonstrates that Caco-2/TC7 cells are functional and ready for use in drug screening permeability assays from 14 days in culture when compared with conventional 21 days for Caco-2 cells. In addition, this study provides a refined set of data allowing temporal and multi scale investigations, due to the intracellular kinetics and mRNA levels that can be correlated with membrane protein kinetics and functional extracellular activities. Therefore, shorter time in culture combined with a better knowledge of the cells during the time in culture will in turn help to improve the quality and cost of Caco-2/TC7 assays for drug development.

  20. Perforated monolayers

    SciTech Connect

    Regen, S.L.

    1989-12-01

    The goals of this DOE-sponsored program are to create novel organic thin films that possess well-defined and adjustable molecular pores; i.e. perforated monolayers,'' and to use such film for fabricating composite membranes that have unique permeation characteristics. The specific strategy that has been adopted involves (1) the synthesis of surfactant molecules bearing internal pores, i.e., porous surfactants,'' (2) the assembly of such molecules at an air--water interface, and (3) the stabilization of the resulting assembly via polymerization, before or after transfer to a macroporous support. Research that has been carried out to date has demonstrated the feasibility of using suitably designed calix(n)arene molecules as a basis for constructing perforated monolayers. Specifically, a broad range of calix(n)arenes have been mercurated with mercury trifluoracetate, and used to form polymerized and porous monolayers at the air--water interface. In related studies, p-tert- butylcalix(6)arene has been shown to produce stable monolayers at the air--water interface; removal of the p-tert-butyl groups afford a unique vesicle-forming surfactant, calix(6)arene.

  1. Determination of infectivity of transforming avian sarcoma virus and parotitis virus in fibrin-embedded monolayer cultures.

    PubMed

    Jandejsek, J; Spohr, P

    1982-09-01

    A sensitive and reproducible technique for titration of transforming avian sarcoma virus, Rous sarcoma virus (RSV), in chick embryo cell monolayers embedded between two layers of a solid fibrin coagulum was developed. The foci of RSV-transformed fibrinolysis-exhibiting cells locally attacked the surrounding fibrin and were identifiable as plaque-like cell-free areas of retraction easily scored against the background of cells stained with neutral red. In comparison to the conventional assay in agar, the assay in fibrin proved more sensitive and less time-consuming. The titration technique in fibrin was also used for plaquing a cytopathogenic virus, parotitis virus, but the titration by conventional plaque assay in agar and the technique in fibrin yielded similar results in this case.

  2. Perforated monolayers

    SciTech Connect

    Regen, S.L.

    1992-01-01

    Our research over this past grant period has focused on (1) developing methods for making in situ permeation measurements at the air-water interface, (2) defining the structural and conformational behavior of selected calix(4)arenes, (3) defining the metal complexation properties of certain upper-rim functionalized calix(4)arenes, and (4) synthesizing a broad series of polymerizable calixarenes, to be used for constructing perforated monolayers and multilayers.

  3. Aniso2D

    2005-07-01

    Aniso2d is a two-dimensional seismic forward modeling code. The earth is parameterized by an X-Z plane in which the seismic properties Can have monoclinic with x-z plane symmetry. The program uses a user define time-domain wavelet to produce synthetic seismograms anrwhere within the two-dimensional media.

  4. Towards 2D nanocomposites

    NASA Astrophysics Data System (ADS)

    Jang, Hyun-Sook; Yu, Changqian; Hayes, Robert; Granick, Steve

    2015-03-01

    Polymer vesicles (``polymersomes'') are an intriguing class of soft materials, commonly used to encapsulate small molecules or particles. Here we reveal they can also effectively incorporate nanoparticles inside their polymer membrane, leading to novel ``2D nanocomposites.'' The embedded nanoparticles alter the capacity of the polymersomes to bend and to stretch upon external stimuli.

  5. Human adipose-derived mesenchymal stem cells improve motor functions and are neuroprotective in the 6-hydroxydopamine-rat model for Parkinson's disease when cultured in monolayer cultures but suppress hippocampal neurogenesis and hippocampal memory function when cultured in spheroids.

    PubMed

    Berg, Jürgen; Roch, Manfred; Altschüler, Jennifer; Winter, Christine; Schwerk, Anne; Kurtz, Andreas; Steiner, Barbara

    2015-02-01

    Adult human adipose-derived mesenchymal stem cells (MSC) have been reported to induce neuroprotective effects in models for Parkinson's disease (PD). However, these effects strongly depend on the most optimal application of the transplant. In the present study we compared monolayer-cultured (aMSC) and spheroid (sMSC) MSC following transplantation into the substantia nigra (SN) of 6-OHDA lesioned rats regarding effects on the local microenvironment, degeneration of dopaminergic neurons, neurogenesis in the hippocampal DG as well as motor and memory function in the 6-OHDA-rat model for PD. aMSC transplantation significantly increased tyrosine hydroxylase (TH) and brain-derived neurotrophic factor (BDNF) levels in the SN, increased the levels of the glial fibrillary acidic protein (GFAP) and improved motor functions compared to untreated and sMSC treated animals. In contrast, sMSC grafting induced an increased local microgliosis, decreased TH levels in the SN and reduced numbers of newly generated cells in the dentate gyrus (DG) without yet affecting hippocampal learning and memory function. We conclude that the neuroprotective potential of adipose-derived MSC in the rat model of PD crucially depends on the applied cellular phenotype.

  6. Mesh2d

    2011-12-31

    Mesh2d is a Fortran90 program designed to generate two-dimensional structured grids of the form [x(i),y(i,j)] where [x,y] are grid coordinates identified by indices (i,j). The x(i) coordinates alone can be used to specify a one-dimensional grid. Because the x-coordinates vary only with the i index, a two-dimensional grid is composed in part of straight vertical lines. However, the nominally horizontal y(i,j0) coordinates along index i are permitted to undulate or otherwise vary. Mesh2d also assignsmore » an integer material type to each grid cell, mtyp(i,j), in a user-specified manner. The complete grid is specified through three separate input files defining the x(i), y(i,j), and mtyp(i,j) variations.« less

  7. In vitro growth, cytopathic effects and clearance of monolayers by clinical isolates of Balamuthia mandrillaris in human skin cell cultures.

    PubMed

    Yera, Hélène; Dupouy-Camet, Jean; Jackson, Jonathan W; Sriram, Rama; Sweat, Stacey; Goldstein, Jason M; Visvesvara, Govinda S

    2015-09-01

    Balamuthia mandrillaris is a free-living ameba (FLA) that has been isolated or its DNA identified in soil, dust and water. It causes a fatal central nervous system infection in humans and animals. Although it is environmental as Acanthamoeba and Naegleria fowleri, the two other free-living amebae that also cause CNS infections in humans and other animals, Balamuthia does not feed on bacteria as the other FLA. In the laboratory, it can be grown on a variety of mammalian cell cultures. In this study we examined the ability of three different Balamuthia isolates to grow on several different human skin cell cultures including the WT/A keratinocyte cell cultures. A corneal isolate of Acanthamoeba castellanii was used for comparison. PMID:25980370

  8. Perforated monolayers

    SciTech Connect

    Regen, S.L.

    1992-12-01

    Goal of this research program is to create ultrathin organic membranes that possess uniform and adjustable pores ( < 7[angstrom] diameter). Such membranes are expected to possess high permeation selectivity (permselectivity) and high permeability, and to provide the basis for energy-efficient methods of molecular separation. Work carried out has demonstrated feasibility of using perforated monolayer''-based composites as molecular sieve membranes. Specifically, composite membranes derived from Langmuir-Blodgett multilayers of the calix[6]arene-based surfactant shown below plus poly[l-(trimethylsilyl)-l-propyne] (PTMSP) were found to exhibit sieving behavior towards He, N[sub 2] and SF[sub 6]. Results of derivative studies that have also been completed are also described in this report.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Differential osteogenicity of multiple donor-derived human mesenchymal stem cells and osteoblasts in monolayer, scaffold-based 3D culture and in vivo.

    PubMed

    Quent, Verena M C; Theodoropoulos, Christina; Hutmacher, Dietmar W; Reichert, Johannes C

    2016-06-01

    We set out to compare the osteogenicity of human mesenchymal stem (hMSCs) and osteoblasts (hOBs). Upon osteogenic induction in monolayer, hMSCs showed superior matrix mineralization expressing characteristic bone-related genes. For scaffold cultures, both cell types presented spindle-shaped, osteoblast-like morphologies forming a dense, interconnected network of high viability. On the scaffolds, hOBs proliferated faster. A general upregulation of parathyroid hormone-related protein (PTHrP), osteoprotegrin (OPG), receptor activator of NF-κB ligand (RANKL), sclerostin (SOST), and dentin matrix protein 1 (DMP1) was observed for both cell types. Simultaneously, PTHrP, RANKL and DMP-1 expression decreased under osteogenic stimulation, while OPG and SOST increased significantly. Following transplantation into NOD/SCID mice, μCT and histology showed increased bone deposition with hOBs. The bone was vascularized, and amounts further increased for both cell types after recombinant human bone morphogenic protein 7 (rhBMP-7) addition also stimulating osteoclastogenesis. Complete bone organogenesis was evidenced by the presence of osteocytes and hematopoietic precursors. Our study results support the asking to develop 3D cellular models closely mimicking the functions of living tissues suitable for in vivo translation.

  11. Van der Waals stacked 2D layered materials for optoelectronics

    NASA Astrophysics Data System (ADS)

    Zhang, Wenjing; Wang, Qixing; Chen, Yu; Wang, Zhuo; Wee, Andrew T. S.

    2016-06-01

    The band gaps of many atomically thin 2D layered materials such as graphene, black phosphorus, monolayer semiconducting transition metal dichalcogenides and hBN range from 0 to 6 eV. These isolated atomic planes can be reassembled into hybrid heterostructures made layer by layer in a precisely chosen sequence. Thus, the electronic properties of 2D materials can be engineered by van der Waals stacking, and the interlayer coupling can be tuned, which opens up avenues for creating new material systems with rich functionalities and novel physical properties. Early studies suggest that van der Waals stacked 2D materials work exceptionally well, dramatically enriching the optoelectronics applications of 2D materials. Here we review recent progress in van der Waals stacked 2D materials, and discuss their potential applications in optoelectronics.

  12. Cytotoxicity of NO2 gas to cultured human and murine cells in an inverted monolayer exposure system.

    PubMed

    Tu, B; Wallin, A; Moldéus, P; Cotgreave, I A

    1995-01-19

    We report the development of an optimised exposure system for the exposure of inverted cell cultures to NO2, which presents several advantages over conventional, right-side-up exposure systems. Firstly, the cells may be directly exposed to NO2 in the gas phase for up to 1 h, without the interposition of an aqueous layer. Secondly, the chamber system allows simple and precise control of the gas concentration during the exposure. Finally, the system allows the simultaneous exposure of large numbers of cells under sterile conditions, facilitating further culture of the cells after the exposure period. We report the application of this system to a comparative study of the toxicity of NO2 in three different cell types involved in the circuit of the inflammatory response, the IC-21 murine macrophage line, the A-549 human pulmonary type II-like epithelial cell line and human umbilical vein endothelial cells. As little as 2 ppm NO2 for 20 min reduced colony-forming efficiency of HUVE cells and A-549 cells and A-549 cells to 35% and 78% of their air controls, respectively. Exposure to 5 ppm NO2 for 1 h increased lactate dehydrogenase release of HUVE cells, IC-21 macrophages and A-549 cells from 7.9% to 21.6%, 5.7% to 10.9% and 2.0% to 3.4%, respectively, whilst 10 ppm NO2 for 1 h lowered cellular glutathione in HUVE cells, IC-21 cells and A-549 cells from 35.2 nmol/mg to 23.3 nmol/mg, from 45.0 nmol/mg to 31.0 nmol/mg and from 86.4 nmol/mg to 69.2 nmol/mg, respectively. Of the cell types tested it was shown that HUVE cells and IC-21 cells were equally sensitive to the toxicity of NO2, whilst A-549 cells displayed considerable resistance, perhaps due to the considerably higher levels of glutathione in this cell line. Further, a comparison of the sensitivity of HUVE cells to NO2, using several modes of exposure (inverted and right-side-up (either rocked or static)) and the assay of lactate dehydrogenase and [3H]deoxyglucose release, revealed that the present inverted exposure

  13. Monolayer graphene from a green solid precursor

    NASA Astrophysics Data System (ADS)

    Kalita, Golap; Wakita, Koichi; Umeno, Masayoshi

    2011-06-01

    Monolayer and bilayer graphene sheets are synthesized by simple control pyrolysis of solid botanical derivative camphor (C 10H 16O), a green and renewable carbon source. Raman studies show much intense 2D peak than that of G peak, signifying presence of monolayer graphene. Transmission electron microscopic study shows predominately monolayer or bilayer graphene sheets, while trilayer graphene sheet were also observed. Synthesized graphene film on copper foil is transferred to poly(ethylene terephthalate) substrate to fabricate transparent electrode. Electrical and optical measurement shows a sheet resistance of 860 Ω/sq with a transmittance of 91% at 550 nm wavelength of the graphene film. The technique to fabricate monolayer or bilayer graphene based film from camphor is both viable and scalable for potential large area electronic applications.

  14. Characteristics and mechanisms of the bystander response in monolayer cell cultures exposed to very low fluences of alpha particles

    NASA Astrophysics Data System (ADS)

    Little, John B.; Azzam, Edouard I.; de Toledo, Sonia M.; Nagasawa, Hatsumi

    2005-02-01

    When confluent cultures of mammalian cells are irradiated with very low fluences of alpha particles whereby only occasional cells receive any radiation exposure, genetic changes are observed in the non-irradiated ("bystander") cells. Upregulation of the p53 damage-response pathway as well as activation of proteins in the MAPK family occurred in bystander cells; p53 was phosphorylated on the serine 15 residue suggesting that the upregulation of p53 was a consequence of DNA damage. Damage signals were transmitted to bystander cells through gap junctions, as confirmed by the use of genetically manipulated cells including connexin43 knockouts. Expression of connexin43 was markedly enhanced by irradiation. A moderate bystander effect was observed for specific gene mutations and chromosomal aberrations. This effect was markedly enhanced in cells defective in the non-homologous end joining DNA repair pathway. Finally, an upregulation of oxidative metabolism occurred in bystander cells; the increased levels of reactive oxygen species appeared to be derived from flavine-containing oxidase enzymes. We hypothesize that genetic effects observed in non-irradiated bystander cells are a consequence of oxidative base damage; >90% of mutations in bystander cells were point mutations. When bystander cells cannot repair DNA double strand breaks, they become much more sensitive to the induction of chromosomal aberrations and mutations, the latter consisting primarily of deletion mutants. While we propose that the genetic effects occurring in bystander cells are a consequence of oxidative stress, the nature of the signal that initiates this process remains to be determined.

  15. Nanocavity absorption enhancement for two-dimensional material monolayer systems.

    PubMed

    Song, Haomin; Jiang, Suhua; Ji, Dengxin; Zeng, Xie; Zhang, Nan; Liu, Kai; Wang, Chu; Xu, Yun; Gan, Qiaoqiang

    2015-03-23

    Here we propose a strategy to enhance the light-matter interaction of two-dimensional (2D) material monolayers based on strong interference effect in planar nanocavities, and overcome the limitation between optical absorption and the atomically-thin thickness of 2D materials. By exploring the role of spacer layers with different thicknesses and refractive indices, we demonstrate that a nanocavity with an air spacer layer placed between a graphene monolayer and an aluminum reflector layer will enhance the exclusive absorption in the graphene monolayer effectively, which is particularly useful for the development of atomically-thin energy harvesting/conversion devices.

  16. Naturally Derived Iron Oxide Nanowires from Bacteria for Magnetically Triggered Drug Release and Cancer Hyperthermia in 2D and 3D Culture Environments: Bacteria Biofilm to Potent Cancer Therapeutic.

    PubMed

    Kumeria, Tushar; Maher, Shaheer; Wang, Ye; Kaur, Gagandeep; Wang, Luoshan; Erkelens, Mason; Forward, Peter; Lambert, Martin F; Evdokiou, Andreas; Losic, Dusan

    2016-08-01

    Iron oxide nanowires produced by bacteria (Mariprofundus ferrooxydans) are demonstrated as new multifunctional drug carriers for triggered therapeutics release and cancer hyperthmia applications. Iron oxide nanowires are obtained from biofilm waste in the bore system used to pump saline groundwater into the River Murray, South Australia (Australia) and processed into individual nanowires with extensive magnetic properties. The drug carrier capabilities of these iron oxide nanowires (Bac-FeOxNWs) are assessed by loading anticancer drug (doxorubicin, Dox) followed by measuring its elution under sustained and triggered release conditions using alternating magnetic field (AMF). The cytotoxicity of Bac-FeOxNWs assessed in 2D (96 well plate) and 3D (Matrigel) cell cultures using MDA-MB231-TXSA human breast cancer cells and mouse RAW 264.7 macrophage cells shows that these Bac-FeOxNWs are biocompatible even at concentrations as high as 250 μg/mL after 24 h of incubation. Finally, we demonstrate the capabilities of Bac-FeOxNWs as potential hyperthermia agent in 3D culture setup. Application of AMF increased the local temperature by 14 °C resulting in approximately 34% decrease in cell viability. Our results demonstrate that these naturally produced nanowires in the form of biofilm can efficiently act as drug carriers with triggered payload release and magnetothermal heating features for potential anticancer therapeutics applications. PMID:27428076

  17. High divergent 2D grating

    NASA Astrophysics Data System (ADS)

    Wang, Jin; Ma, Jianyong; Zhou, Changhe

    2014-11-01

    A 3×3 high divergent 2D-grating with period of 3.842μm at wavelength of 850nm under normal incidence is designed and fabricated in this paper. This high divergent 2D-grating is designed by the vector theory. The Rigorous Coupled Wave Analysis (RCWA) in association with the simulated annealing (SA) is adopted to calculate and optimize this 2D-grating.The properties of this grating are also investigated by the RCWA. The diffraction angles are more than 10 degrees in the whole wavelength band, which are bigger than the traditional 2D-grating. In addition, the small period of grating increases the difficulties of fabrication. So we fabricate the 2D-gratings by direct laser writing (DLW) instead of traditional manufacturing method. Then the method of ICP etching is used to obtain the high divergent 2D-grating.

  18. Application of three-dimensional culture conditions to human embryonic stem cell-derived definitive endoderm cells enhances hepatocyte differentiation and functionality.

    PubMed

    Ramasamy, Thamil Selvee; Yu, Jason S L; Selden, Clare; Hodgson, Humphery; Cui, Wei

    2013-02-01

    Human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) provide an unlimited source for the generation of human hepatocytes, owing to their indefinite self-renewal and pluripotent properties. Both hESC-/iPSC-derived hepatocytes hold great promise in treating liver diseases as potential candidates for cell replacement therapies or as an in vitro platform to conduct new drug trials. It has been previously demonstrated that the initiation of hESC differentiation in monolayer cultures increases the generation of definitive endoderm (DE) and subsequently of hepatocyte differentiation. However, monolayer culture may hinder the maturation of hESC-derived hepatocytes, since such two-dimensional (2D) conditions do not accurately reflect the complex nature of three-dimensional (3D) hepatocyte specification in vivo. Here, we report the sequential application of 2D and 3D culture systems to differentiate hESCs to hepatocytes. Human ESCs were initially differentiated in a monolayer culture to DE cells, which were then inoculated into Algimatrix scaffolds. Treatments of hESC-DE cells with a ROCK inhibitor before and after inoculation dramatically enhanced their survival and the formation of spheroids, which are distinct from HepG2 carcinoma cells. In comparison with monolayer culture alone, sequential 2D and 3D cultures significantly improved hepatocyte differentiation and function. Our results demonstrate that hESC-DE cells can be incorporated into Algimatrix 3D culture systems to enhance hepatocyte differentiation and function.

  19. Ultrafast 2D IR microscopy

    PubMed Central

    Baiz, Carlos R.; Schach, Denise; Tokmakoff, Andrei

    2014-01-01

    We describe a microscope for measuring two-dimensional infrared (2D IR) spectra of heterogeneous samples with μm-scale spatial resolution, sub-picosecond time resolution, and the molecular structure information of 2D IR, enabling the measurement of vibrational dynamics through correlations in frequency, time, and space. The setup is based on a fully collinear “one beam” geometry in which all pulses propagate along the same optics. Polarization, chopping, and phase cycling are used to isolate the 2D IR signals of interest. In addition, we demonstrate the use of vibrational lifetime as a contrast agent for imaging microscopic variations in molecular environments. PMID:25089490

  20. Predicting Two-Dimensional Silicon Carbide Monolayers.

    PubMed

    Shi, Zhiming; Zhang, Zhuhua; Kutana, Alex; Yakobson, Boris I

    2015-10-27

    Intrinsic semimetallicity of graphene and silicene largely limits their applications in functional devices. Mixing carbon and silicon atoms to form two-dimensional (2D) silicon carbide (SixC1-x) sheets is promising to overcome this issue. Using first-principles calculations combined with the cluster expansion method, we perform a comprehensive study on the thermodynamic stability and electronic properties of 2D SixC1-x monolayers with 0 ≤ x ≤ 1. Upon varying the silicon concentration, the 2D SixC1-x presents two distinct structural phases, a homogeneous phase with well dispersed Si (or C) atoms and an in-plane hybrid phase rich in SiC domains. While the in-plane hybrid structure shows uniform semiconducting properties with widely tunable band gap from 0 to 2.87 eV due to quantum confinement effect imposed by the SiC domains, the homogeneous structures can be semiconducting or remain semimetallic depending on a superlattice vector which dictates whether the sublattice symmetry is topologically broken. Moreover, we reveal a universal rule for describing the electronic properties of the homogeneous SixC1-x structures. These findings suggest that the 2D SixC1-x monolayers may present a new "family" of 2D materials, with a rich variety of properties for applications in electronics and optoelectronics. PMID:26394207

  1. Predicting Two-Dimensional Silicon Carbide Monolayers.

    PubMed

    Shi, Zhiming; Zhang, Zhuhua; Kutana, Alex; Yakobson, Boris I

    2015-10-27

    Intrinsic semimetallicity of graphene and silicene largely limits their applications in functional devices. Mixing carbon and silicon atoms to form two-dimensional (2D) silicon carbide (SixC1-x) sheets is promising to overcome this issue. Using first-principles calculations combined with the cluster expansion method, we perform a comprehensive study on the thermodynamic stability and electronic properties of 2D SixC1-x monolayers with 0 ≤ x ≤ 1. Upon varying the silicon concentration, the 2D SixC1-x presents two distinct structural phases, a homogeneous phase with well dispersed Si (or C) atoms and an in-plane hybrid phase rich in SiC domains. While the in-plane hybrid structure shows uniform semiconducting properties with widely tunable band gap from 0 to 2.87 eV due to quantum confinement effect imposed by the SiC domains, the homogeneous structures can be semiconducting or remain semimetallic depending on a superlattice vector which dictates whether the sublattice symmetry is topologically broken. Moreover, we reveal a universal rule for describing the electronic properties of the homogeneous SixC1-x structures. These findings suggest that the 2D SixC1-x monolayers may present a new "family" of 2D materials, with a rich variety of properties for applications in electronics and optoelectronics.

  2. AnisWave 2D

    2004-08-01

    AnisWave2D is a 2D finite-difference code for a simulating seismic wave propagation in fully anisotropic materials. The code is implemented to run in parallel over multiple processors and is fully portable. A mesh refinement algorithm has been utilized to allow the grid-spacing to be tailored to the velocity model, avoiding the over-sampling of high-velocity materials that usually occurs in fixed-grid schemes.

  3. DYNA2D96. Explicit 2-D Hydrodynamic FEM Program

    SciTech Connect

    Whirley, R.G.

    1992-04-01

    DYNA2D is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. The isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.

  4. Exciton Brightening in Monolayer Phosphorene via Dimensionality Modification.

    PubMed

    Xu, Renjing; Yang, Jiong; Myint, Ye Win; Pei, Jiajie; Yan, Han; Wang, Fan; Lu, Yuerui

    2016-05-01

    Exciton brightening in monolayer phosphorene is achieved via the dimensionality modification of excitons from quasi-1D to 0D. The luminescence quantum yield of 0D-like excitons is >33.6 times larger than that of quasi-1D free excitons. 2D phosphorene with quasi-1D free excitons and 0D-like excitons provides a unique platform to investigate the fundamental phenomena in the ideal 2D-1D-0D hybrid system.

  5. Methods of making monolayers

    DOEpatents

    Alford, Kentin L.; Simmons, Kevin L.; Samuels, William D.; Zemanian, Thomas S.; Liu, Jun; Shin, Yongsoon; Fryxell, Glen E.

    2009-09-15

    The invention pertains to methods of forming monolayers on various surfaces. The surfaces can be selected from a wide array of materials, including, for example, aluminum dioxide, silicon dioxide, carbon and SiC. The substrates can be planar or porous. The monolayer is formed under enhanced pressure conditions. The monolayer contains functionalized molecules, and accordingly functionalizes a surface of the substrate. The properties of the functionalized substrate can enhance the substrate's applicability for numerous purposes including, for example, utilization in extracting contaminants, or incorporation into a polymeric matrix.

  6. Methods of making monolayers

    DOEpatents

    Alford, Kentin L.; Simmons, Kevin L.; Samuels, William D.; Zemanian, Thomas S.; Liu, Jun; Shin, Yongsoon; Fryxell, Glen E.

    2009-12-08

    The invention pertains to methods of forming monolayers on various surfaces. The surfaces can be selected from a wide array of materials, including, for example, aluminum dioxide, silicon dioxide, carbon and SiC. The substrates can be planar or porous. The monolayer is formed under enhanced pressure conditions. The monolayer contains functionalized molecules, and accordingly functionalizes a surface of the substrate. The properties of the functionalized substrate can enhance the substrate's applicability for numerous purposes including, for example, utilization in extracting contaminants, or incorporation into a polymeric matrix.

  7. Controlling avalanche criticality in 2D nano arrays.

    PubMed

    Zohar, Y C; Yochelis, S; Dahmen, K A; Jung, G; Paltiel, Y

    2013-01-01

    Many physical systems respond to slowly changing external force through avalanches spanning broad range of sizes. Some systems crackle even without apparent external force, such as bursts of neuronal activity or charge transfer avalanches in 2D molecular layers. Advanced development of theoretical models describing disorder-induced critical phenomena calls for experiments probing the dynamics upon tuneable disorder. Here we show that isomeric structural transitions in 2D organic self-assembled monolayer (SAM) exhibit critical dynamics with experimentally tuneable disorder. The system consists of field effect transistor coupled through SAM to illuminated semiconducting nanocrystals (NCs). Charges photoinduced in NCs are transferred through SAM to the transistor surface and modulate its conductivity. Avalanches of isomeric structural transitions are revealed by measuring the current noise I(t) of the transistor. Accumulated surface traps charges reduce dipole moments of the molecules, decrease their coupling, and thus decrease the critical disorder of the SAM enabling its tuning during experiments.

  8. 2D ice from first principles: structures and phase transitions

    NASA Astrophysics Data System (ADS)

    Chen, Ji; Schusteritsch, Georg; Pickard, Chris J.; Salzmann, Christoph G.; Michaelides, Angelos

    Despite relevance to disparate areas such as cloud microphysics and tribology, major gaps in the understanding of the structures and phase transitions of low-dimensional water ice remain. Here we report a first principles study of confined 2D ice as a function of pressure. We find that at ambient pressure hexagonal and pentagonal monolayer structures are the two lowest enthalpy phases identified. Upon mild compression the pentagonal structure becomes the most stable and persists up to ca. 2 GPa at which point square and rhombic phases are stable. The square phase agrees with recent experimental observations of square ice confined within graphene sheets. We also find a double layer AA stacked square ice phase, which clarifies the difference between experimental observations and earlier force field simulations. This work provides a fresh perspective on 2D confined ice, highlighting the sensitivity of the structures observed to both the confining pressure and width.

  9. MOSS2D V1

    2001-01-31

    This software reduces the data from two-dimensional kSA MOS program, k-Space Associates, Ann Arbor, MI. Initial MOS data is recorded without headers in 38 columns, with one row of data per acquisition per lase beam tracked. The final MOSS 2d data file is reduced, graphed, and saved in a tab-delimited column format with headers that can be plotted in any graphing software.

  10. Diamondoid monolayers as electron emitters

    DOEpatents

    Yang, Wanli; Fabbri, Jason D.; Melosh, Nicholas A.; Hussain, Zahid; Shen, Zhi-Xun

    2013-10-29

    Provided are electron emitters based upon diamondoid monolayers, preferably self-assembled higher diamondoid monolayers. High intensity electron emission has been demonstrated employing such diamondoid monolayers, particularly when the monolayers are comprised of higher diamondoids. The application of such diamondoid monolayers can alter the band structure of substrates, as well as emit monochromatic electrons, and the high intensity electron emissions can also greatly improve the efficiency of field-effect electron emitters as applied to industrial and commercial applications.

  11. Diamondoid monolayers as electron emitters

    DOEpatents

    Yang, Wanli; Fabbri, Jason D.; Melosh, Nicholas A.; Hussain, Zahid; Shen, Zhi-Xun

    2012-04-10

    Provided are electron emitters based upon diamondoid monolayers, preferably self-assembled higher diamondoid monolayers. High intensity electron emission has been demonstrated employing such diamondoid monolayers, particularly when the monolayers are comprised of higher diamondoids. The application of such diamondoid monolayers can alter the band structure of substrates, as well as emit monochromatic electrons, and the high intensity electron emissions can also greatly improve the efficiency of field-effect electron emitters as applied to industrial and commercial applications.

  12. The Intrinsic Ferromagnetism in a MnO2 Monolayer.

    PubMed

    Kan, M; Zhou, J; Sun, Q; Kawazoe, Y; Jena, P

    2013-10-17

    The Mn atom, because of its special electronic configuration of 3d(5)4s(2), has been widely used as a dopant in various two-dimensional (2D) monolayers such as graphene, BN, silicene and transition metal dichalcogenides (TMDs). The distributions of doped Mn atoms in these systems are highly sensitive to the synthesis process and conditions, thus suffering from problems of low solubility and surface clustering. Here we show for the first time that the MnO2 monolayer, synthetized 10 years ago, where Mn ions are individually held at specific sites, exhibits intrinsic ferromagnetism with a Curie temperature of 140 K, comparable to the highest TC value achieved experimentally for Mn-doped GaAs. The well-defined atomic configuration and the intrinsic ferromagnetism of the MnO2 monolayer suggest that it is superior to other magnetic monolayer materials.

  13. Oxidized Monolayers of Epitaxial Silicene on Ag(111)

    NASA Astrophysics Data System (ADS)

    Johnson, Neil W.; Muir, David I.; Moewes, Alexander

    2016-03-01

    The properties of epitaxial silicene monolayers on Ag(111) at various levels of oxidation are determined through complementary density functional theory calculations and soft X-ray spectroscopy experiments. Our calculations indicate that moderate levels of oxidation do not cause a significant bandgap opening in the epitaxial silicene monolayer, suggesting that oxygen functionalization is not a viable mechanism for bandgap tuning while the silicene monolayer remains on its metallic substrate. In addition, moderate oxidation is calculated to strongly distort the hexagonal Si lattice, causing it to cluster in regions of highest oxygen adatom concentration but retain its 2D sheet structure. However, our experiments reveal that beam-induced oxidation is consistent with the formation of islands of bulk-like SiO2. Complete exposure of the monolayer to ambient conditions results in a fully oxidized sample that closely resembles bulk SiO2, of which a significant portion is completely detached from the substrate.

  14. Oxidized Monolayers of Epitaxial Silicene on Ag(111)

    PubMed Central

    Johnson, Neil W.; Muir, David I.; Moewes, Alexander

    2016-01-01

    The properties of epitaxial silicene monolayers on Ag(111) at various levels of oxidation are determined through complementary density functional theory calculations and soft X-ray spectroscopy experiments. Our calculations indicate that moderate levels of oxidation do not cause a significant bandgap opening in the epitaxial silicene monolayer, suggesting that oxygen functionalization is not a viable mechanism for bandgap tuning while the silicene monolayer remains on its metallic substrate. In addition, moderate oxidation is calculated to strongly distort the hexagonal Si lattice, causing it to cluster in regions of highest oxygen adatom concentration but retain its 2D sheet structure. However, our experiments reveal that beam-induced oxidation is consistent with the formation of islands of bulk-like SiO2. Complete exposure of the monolayer to ambient conditions results in a fully oxidized sample that closely resembles bulk SiO2, of which a significant portion is completely detached from the substrate. PMID:26936144

  15. Oxidized Monolayers of Epitaxial Silicene on Ag(111).

    PubMed

    Johnson, Neil W; Muir, David I; Moewes, Alexander

    2016-03-03

    The properties of epitaxial silicene monolayers on Ag(111) at various levels of oxidation are determined through complementary density functional theory calculations and soft X-ray spectroscopy experiments. Our calculations indicate that moderate levels of oxidation do not cause a significant bandgap opening in the epitaxial silicene monolayer, suggesting that oxygen functionalization is not a viable mechanism for bandgap tuning while the silicene monolayer remains on its metallic substrate. In addition, moderate oxidation is calculated to strongly distort the hexagonal Si lattice, causing it to cluster in regions of highest oxygen adatom concentration but retain its 2D sheet structure. However, our experiments reveal that beam-induced oxidation is consistent with the formation of islands of bulk-like SiO2. Complete exposure of the monolayer to ambient conditions results in a fully oxidized sample that closely resembles bulk SiO2, of which a significant portion is completely detached from the substrate.

  16. Fracture Characteristics of Monolayer CVD-Graphene

    PubMed Central

    Hwangbo, Yun; Lee, Choong-Kwang; Kim, Sang-Min; Kim, Jae-Hyun; Kim, Kwang-Seop; Jang, Bongkyun; Lee, Hak-Joo; Lee, Seoung-Ki; Kim, Seong-Su; Ahn, Jong-Hyun; Lee, Seung-Mo

    2014-01-01

    We have observed and analyzed the fracture characteristics of the monolayer CVD-graphene using pressure bulge testing setup. The monolayer CVD-graphene has appeared to undergo environmentally assisted subcritical crack growth in room condition, i.e. stress corrosion cracking arising from the adsorption of water vapor on the graphene and the subsequent chemical reactions. The crack propagation in graphene has appeared to be able to be reasonably tamed by adjusting applied humidity and stress. The fracture toughness, describing the ability of a material containing inherent flaws to resist catastrophic failure, of the CVD-graphene has turned out to be exceptionally high, as compared to other carbon based 3D materials. These results imply that the CVD-graphene could be an ideal candidate as a structural material notwithstanding environmental susceptibility. In addition, the measurements reported here suggest that specific non-continuum fracture behaviors occurring in 2D monoatomic structures can be macroscopically well visualized and characterized. PMID:24657996

  17. Carbon phosphide monolayers with superior carrier mobility.

    PubMed

    Wang, Gaoxue; Pandey, Ravindra; Karna, Shashi P

    2016-04-28

    Two dimensional (2D) materials with a finite band gap and high carrier mobility are sought after materials from both fundamental and technological perspectives. In this paper, we present the results based on the particle swarm optimization method and density functional theory which predict three geometrically different phases of the carbon phosphide (CP) monolayer consisting of sp2 hybridized C atoms and sp3 hybridized P atoms in hexagonal networks. Two of the phases, referred to as α-CP and β-CP with puckered or buckled surfaces are semiconducting with highly anisotropic electronic and mechanical properties. More remarkably, they have the lightest electrons and holes among the known 2D semiconductors, yielding superior carrier mobility. The γ-CP has a distorted hexagonal network and exhibits a semi-metallic behavior with Dirac cones. These theoretical findings suggest that the binary CP monolayer is a yet unexplored 2D material holding great promise for applications in high-performance electronics and optoelectronics. PMID:27067002

  18. Functional characterization of CYP2D6 enhancer polymorphisms

    PubMed Central

    Wang, Danxin; Papp, Audrey C.; Sun, Xiaochun

    2015-01-01

    CYP2D6 metabolizes nearly 25% of clinically used drugs. Genetic polymorphisms cause large inter-individual variability in CYP2D6 enzyme activity and are currently used as biomarker to predict CYP2D6 metabolizer phenotype. Previously, we had identified a region 115 kb downstream of CYP2D6 as enhancer for CYP2D6, containing two completely linked single nucleotide polymorphisms (SNPs), rs133333 and rs5758550, associated with enhanced transcription. However, the enhancer effect on CYP2D6 expression, and the causative variant, remained to be ascertained. To characterize the CYP2D6 enhancer element, we applied chromatin conformation capture combined with the next-generation sequencing (4C assays) and chromatin immunoprecipitation with P300 antibody, in HepG2 and human primary culture hepatocytes. The results confirmed the role of the previously identified enhancer region in CYP2D6 expression, expanding the number of candidate variants to three highly linked SNPs (rs133333, rs5758550 and rs4822082). Among these, only rs5758550 demonstrated regulating enhancer activity in a reporter gene assay. Use of clustered regularly interspaced short palindromic repeats mediated genome editing in HepG2 cells targeting suspected enhancer regions decreased CYP2D6 mRNA expression by 70%, only upon deletion of the rs5758550 region. These results demonstrate robust effects of both the enhancer element and SNP rs5758550 on CYP2D6 expression, supporting consideration of rs5758550 for CYP2D6 genotyping panels to yield more accurate phenotype prediction. PMID:25381333

  19. Three-dimensional Culture Conditions Lead to Decreased Radiation Induced Crytoxicity in Human Mammary Epithelial Cells

    SciTech Connect

    Sowa, Marianne B.; Chrisler, William B.; Zens, Kyra D.; Ashjian, Emily J.; Opresko, Lee K.

    2010-05-01

    For both targeted and non-targeted exposures, the cellular responses to ionizing radiation have predominantly been measured in two dimensional monolayer cultures. Although convenient for biochemical analysis, the true interactions in vivo depend upon complex interactions between cells themselves and the surrounding extra cellular matrix. This study directly compares the influence of culture conditions on radiation induced cytotoxicity following exposure to low-LET ionizing radiation. Using a three dimensional (3D) human mammary epithelial tissue model, we have found a protective effect of 3D cell culture on cell survival after irradiation. The initial state of the cells (i.e., 2D vs. 3D culture) at the time of irradiation does not alter survival, nor does the presence of extracellular matrix during and after exposure to dose, but long term culture in 3D which offers significant reduction in cytotoxicity at a given dose (e.g. ~4 fold increased survival at 5 Gy). The cell cycle delay induced following exposure to 2 and 5 Gy was almost identical between 2D and 3D culture conditions and cannot account for the observed differences in radiation responses. However the amount of apoptosis following radiation exposure is significantly decreased in 3D culture relative to the 2D monolayer after the same dose. A likely mechanism of the cytoprotective effect afforded by 3D culture conditions is the down regulation of radiation induced apoptosis in 3D structures

  20. Carbon phosphide monolayers with superior carrier mobility

    NASA Astrophysics Data System (ADS)

    Wang, Gaoxue; Pandey, Ravindra; Karna, Shashi P.

    2016-04-01

    Two dimensional (2D) materials with a finite band gap and high carrier mobility are sought after materials from both fundamental and technological perspectives. In this paper, we present the results based on the particle swarm optimization method and density functional theory which predict three geometrically different phases of the carbon phosphide (CP) monolayer consisting of sp2 hybridized C atoms and sp3 hybridized P atoms in hexagonal networks. Two of the phases, referred to as α-CP and β-CP with puckered or buckled surfaces are semiconducting with highly anisotropic electronic and mechanical properties. More remarkably, they have the lightest electrons and holes among the known 2D semiconductors, yielding superior carrier mobility. The γ-CP has a distorted hexagonal network and exhibits a semi-metallic behavior with Dirac cones. These theoretical findings suggest that the binary CP monolayer is a yet unexplored 2D material holding great promise for applications in high-performance electronics and optoelectronics.Two dimensional (2D) materials with a finite band gap and high carrier mobility are sought after materials from both fundamental and technological perspectives. In this paper, we present the results based on the particle swarm optimization method and density functional theory which predict three geometrically different phases of the carbon phosphide (CP) monolayer consisting of sp2 hybridized C atoms and sp3 hybridized P atoms in hexagonal networks. Two of the phases, referred to as α-CP and β-CP with puckered or buckled surfaces are semiconducting with highly anisotropic electronic and mechanical properties. More remarkably, they have the lightest electrons and holes among the known 2D semiconductors, yielding superior carrier mobility. The γ-CP has a distorted hexagonal network and exhibits a semi-metallic behavior with Dirac cones. These theoretical findings suggest that the binary CP monolayer is a yet unexplored 2D material holding great

  1. Photoluminescence and photocurrent measurement in monolayer MoTe2

    NASA Astrophysics Data System (ADS)

    Bie, Ya-Qing; Grosso, Gabriele; Efetov, Dmitri; Navarro-Moratalla, Efren; Englund, Dirk; Jarillo-Herrero, Pablo

    2015-03-01

    2D transition metal dichalcogenides (2D-TMD), such as MoS2, WS2, WSe2, MoSe2, have been verified with many remarkable physical properties including the indirect to direct band transition and valley dependent spin polarization. As one of the 2D-TMD family member, monolayer 2H-MoTe2 is proved to be a direct bandgap semicoductor with strong spin orbital interaction and a significantly low bandgap ~ 1.10eV. However, the effect of the enhanced coulomb interaction arising from reduced dielectric screening in monolayer MoTe2 has yet to be experimentally demonstrated. Here we employ the near infrared (NIR) photoluminescence and photocurrent measurement to study the quasi-particle interactions at different carrier concentration. This study sheds light on manipulating excitons in MoTe2 and designing highly efficient NIR optoelectronic devices.

  2. Graphoepitaxy for Pattern Multiplication of Nanoparticle Monolayers

    NASA Astrophysics Data System (ADS)

    Ferraro, Mark E.; Bonnecaze, Roger T.; Truskett, Thomas M.

    2014-08-01

    We compute the free energy minimizing structures of particle monolayers in the presence of enthalpic barriers of a finite height βVext using classical density functional theory and Monte Carlo simulations. We show that a periodic square template with dimensions up to at least 10 times the particle diameter disrupts the formation of the entropically favored hexagonally close-packed 2D lattice in favor of a square lattice. The results illustrate how graphoepitaxy can successfully order nanoparticulate films into desired patterns many times smaller than those of the prepatterned template.

  3. Novel 2D RuPt core-edge nanocluster catalyst for CO electro-oxidation

    NASA Astrophysics Data System (ADS)

    Grabow, Lars C.; Yuan, Qiuyi; Doan, Hieu A.; Brankovic, Stanko R.

    2015-10-01

    A single layer, bi-metallic RuPt catalyst on Au(111) is synthesized using surface limited red-ox replacement of underpotentially deposited Cu and Pb monolayers though a two-step process. The resulting 2D RuPt monolayer nanoclusters have a unique core-edge structure with a Ru core and Pt at the edge along the perimeter. The activity of this catalyst is evaluated using CO monolayer oxidation as the probe reaction. Cyclic voltammetry demonstrates that the 2D RuPt core-edge catalyst morphology is significantly more active than either Pt or Ru monolayer catalysts. Density functional theory calculations in combination with infra-red spectroscopy data point towards oscillating variations (ripples) in the adsorption energy landscape along the radial direction of the Ru core as the origin of the observed behavior. Both, CO and OH experience a thermodynamic driving force for surface migration towards the Ru-Pt interface, where they adsorb most strongly and react rapidly. We propose that the complex interplay between epitaxial strain, ligand and finite size effects is responsible for the formation of the rippled RuPt monolayer cluster, which provides optimal conditions for a quasi-ideal bi-functional mechanism for CO oxidation, in which CO is adsorbed mainly on Pt, and Ru provides OH to the active Pt-Ru interface.

  4. Cryopreservation in situ of cell monolayers on collagen vitrigel membrane culture substrata: ready-to-use preparation of primary hepatocytes and ES cells.

    PubMed

    Miyamoto, Yoshitaka; Enosawa, Shin; Takeuchi, Tomoyo; Takezawa, Toshiaki

    2009-01-01

    Cryopreservation is generally performed on cells in suspension. In the case of adherent cells such as hepatocytes, a loss of their ability to attach is a more serious problem than a decreased viability after cryopreservation. We herein report a novel technology of direct in situ cryopreservation of cells cultured on collagen vitrigel membranes, which have excellent mechanical strength and can be easily handled by tweezers even when coated with cultured cells. Rat primary hepatocytes, mitomycin C-treated mouse fibroblasts (feeder cells for ES cells), and mouse ES cells on the feeder cells were cultured on collagen vitrigel membranes for 1 day. The membranes with cells attached were then plucked up from the dish, soaked in cryopreservation medium containing 10% dimethyl sulfoxide, frozen using a controlled-rate freezer, and transferred to liquid nitrogen. The cells cultured on plastic cell culture dishes were also frozen as controls. After storage in liquid nitrogen for periods from 1 week to 3 months, the cryopreserved membranes with the cells still attached were thawed by adding warmed culture medium. Cell viability estimated by morphology and functional staining with calcein showed significant improvement in comparison to cells cryopreserved without the collagen vitrigel membrane. The recoveries of living cells after cryopreservation were 26.7%, 76.2%, and 58.6% for rat hepatocytes, mitomycin C-treated mouse fibroblasts, and mouse ES cells on collagen vitrigel membranes, respectively. In contrast, essentially no cells at all remained on the plastic cell culture dishes after thawing. Because adherent cell storage under these conditions is very convenient, the use of this technique employing collagen vitrigel membranes should be generally applicable to the cryopreservation of adherent cells that are otherwise problematic to store as frozen stocks. PMID:19775524

  5. Unparticle example in 2D.

    PubMed

    Georgi, Howard; Kats, Yevgeny

    2008-09-26

    We discuss what can be learned about unparticle physics by studying simple quantum field theories in one space and one time dimension. We argue that the exactly soluble 2D theory of a massless fermion coupled to a massive vector boson, the Sommerfield model, is an interesting analog of a Banks-Zaks model, approaching a free theory at high energies and a scale-invariant theory with nontrivial anomalous dimensions at low energies. We construct a toy standard model coupling to the fermions in the Sommerfield model and study how the transition from unparticle behavior at low energies to free particle behavior at high energies manifests itself in interactions with the toy standard model particles.

  6. Control of Radiative Exciton Recombination by Charge Transfer Induced Surface Dipoles in MoS2 and WS2 Monolayers

    PubMed Central

    Hu, Peng; Ye, Jun; He, Xuexia; Du, Kezhao; Zhang, Keke K.; Wang, Xingzhi; Xiong, Qihua; Liu, Zheng; Jiang, Hui; Kloc, Christian

    2016-01-01

    Due to the two dimensional confinement of electrons in a monolayer of 2D materials, the properties of monolayer can be controlled by electrical field formed on the monolayer surface. F4TCNQ was evaporated on MoS2 and WS2 monolayer forming dipoles between strong acceptor, F4TCNQ, and monolayers of MoS2 or WS2. The strong acceptor attracts electrons (charge transfer) and decreases the number of the ionized excitons. Free excitons undergo radiative recombination in both MoS2 and WS2. Moreover, the photoluminescence enhancement is stronger in WS2 where the exciton-phonon coupling is weaker. The theoretical model indicates that the surface dipole controls the radiative exciton recombination and enhances photoluminescence radiation. Deposition of F4TCNQ on the 2D monolayers enables a convenient control of the radiative exciton recombination and leads to the applications of these materials in lasers or LEDs. PMID:27053440

  7. Monolayered mesenchymal stem cells repair scarred myocardium after myocardial infarction.

    PubMed

    Miyahara, Yoshinori; Nagaya, Noritoshi; Kataoka, Masaharu; Yanagawa, Bobby; Tanaka, Koichi; Hao, Hiroyuki; Ishino, Kozo; Ishida, Hideyuki; Shimizu, Tatsuya; Kangawa, Kenji; Sano, Shunji; Okano, Teruo; Kitamura, Soichiro; Mori, Hidezo

    2006-04-01

    Mesenchymal stem cells are multipotent cells that can differentiate into cardiomyocytes and vascular endothelial cells. Here we show, using cell sheet technology, that monolayered mesenchymal stem cells have multipotent and self-propagating properties after transplantation into infarcted rat hearts. We cultured adipose tissue-derived mesenchymal stem cells characterized by flow cytometry using temperature-responsive culture dishes. Four weeks after coronary ligation, we transplanted the monolayered mesenchymal stem cells onto the scarred myocardium. After transplantation, the engrafted sheet gradually grew to form a thick stratum that included newly formed vessels, undifferentiated cells and few cardiomyocytes. The mesenchymal stem cell sheet also acted through paracrine pathways to trigger angiogenesis. Unlike a fibroblast cell sheet, the monolayered mesenchymal stem cells reversed wall thinning in the scar area and improved cardiac function in rats with myocardial infarction. Thus, transplantation of monolayered mesenchymal stem cells may be a new therapeutic strategy for cardiac tissue regeneration. PMID:16582917

  8. Electro-mechanical sensing in freestanding monolayered gold nanoparticle membranes

    NASA Astrophysics Data System (ADS)

    Gauvin, M.; Grisolia, J.; Alnasser, T.; Viallet, B.; Xie, S.; Brugger, J.; Ressier, L.

    2016-06-01

    The electro-mechanical sensing properties of freestanding monolayered membranes of dodecanethiol coated 7 nm gold nanoparticles (NPs) are investigated using AFM force spectroscopy and conductive AFM simultaneously. The electrical resistance of the NP membranes increases sensitively with the point-load force applied in the center of the membranes using an AFM tip. Numerical simulations of electronic conduction in a hexagonally close-packed two-dimensional (2D) array of NPs under point load-deformation are carried out on the basis of electronic transport measurements at low temperatures and strain modeling of the NP membranes by finite element analysis. These simulations, supporting AFM-based electro-mechanical measurements, attribute the high strain sensitivity of the monolayered NP membranes to the exponential dependence of the tunnel electron transport in 2D NP arrays on the strain-induced length variation of the interparticle junctions. This work thus evidences a new class of highly sensitive nano-electro-mechanical systems based on freestanding monolayered gold NP membranes.The electro-mechanical sensing properties of freestanding monolayered membranes of dodecanethiol coated 7 nm gold nanoparticles (NPs) are investigated using AFM force spectroscopy and conductive AFM simultaneously. The electrical resistance of the NP membranes increases sensitively with the point-load force applied in the center of the membranes using an AFM tip. Numerical simulations of electronic conduction in a hexagonally close-packed two-dimensional (2D) array of NPs under point load-deformation are carried out on the basis of electronic transport measurements at low temperatures and strain modeling of the NP membranes by finite element analysis. These simulations, supporting AFM-based electro-mechanical measurements, attribute the high strain sensitivity of the monolayered NP membranes to the exponential dependence of the tunnel electron transport in 2D NP arrays on the strain

  9. Unusual dimensionality effects and surface charge density in 2D Mg(OH)2

    PubMed Central

    Suslu, Aslihan; Wu, Kedi; Sahin, Hasan; Chen, Bin; Yang, Sijie; Cai, Hui; Aoki, Toshihiro; Horzum, Seyda; Kang, Jun; Peeters, Francois M.; Tongay, Sefaattin

    2016-01-01

    We present two-dimensional Mg(OH)2 sheets and their vertical heterojunctions with CVD-MoS2 for the first time as flexible 2D insulators with anomalous lattice vibration and chemical and physical properties. New hydrothermal crystal growth technique enabled isolation of environmentally stable monolayer Mg(OH)2 sheets. Raman spectroscopy and vibrational calculations reveal that the lattice vibrations of Mg(OH)2 have fundamentally different signature peaks and dimensionality effects compared to other 2D material systems known to date. Sub-wavelength electron energy-loss spectroscopy measurements and theoretical calculations show that Mg(OH)2 is a 6 eV direct-gap insulator in 2D, and its optical band gap displays strong band renormalization effects from monolayer to bulk, marking the first experimental confirmation of confinement effects in 2D insulators. Interestingly, 2D-Mg(OH)2 sheets possess rather strong surface polarization (charge) effects which is in contrast to electrically neutral h-BN materials. Using 2D-Mg(OH)2 sheets together with CVD-MoS2 in the vertical stacking shows that a strong change transfer occurs from n-doped CVD-MoS2 sheets to Mg(OH)2, naturally depleting the semiconductor, pushing towards intrinsic doping limit and enhancing overall optical performance of 2D semiconductors. Results not only establish unusual confinement effects in 2D-Mg(OH)2, but also offer novel 2D-insulating material with unique physical, vibrational, and chemical properties for potential applications in flexible optoelectronics. PMID:26846617

  10. Unusual dimensionality effects and surface charge density in 2D Mg(OH)2

    NASA Astrophysics Data System (ADS)

    Suslu, Aslihan; Wu, Kedi; Sahin, Hasan; Chen, Bin; Yang, Sijie; Cai, Hui; Aoki, Toshihiro; Horzum, Seyda; Kang, Jun; Peeters, Francois M.; Tongay, Sefaattin

    2016-02-01

    We present two-dimensional Mg(OH)2 sheets and their vertical heterojunctions with CVD-MoS2 for the first time as flexible 2D insulators with anomalous lattice vibration and chemical and physical properties. New hydrothermal crystal growth technique enabled isolation of environmentally stable monolayer Mg(OH)2 sheets. Raman spectroscopy and vibrational calculations reveal that the lattice vibrations of Mg(OH)2 have fundamentally different signature peaks and dimensionality effects compared to other 2D material systems known to date. Sub-wavelength electron energy-loss spectroscopy measurements and theoretical calculations show that Mg(OH)2 is a 6 eV direct-gap insulator in 2D, and its optical band gap displays strong band renormalization effects from monolayer to bulk, marking the first experimental confirmation of confinement effects in 2D insulators. Interestingly, 2D-Mg(OH)2 sheets possess rather strong surface polarization (charge) effects which is in contrast to electrically neutral h-BN materials. Using 2D-Mg(OH)2 sheets together with CVD-MoS2 in the vertical stacking shows that a strong change transfer occurs from n-doped CVD-MoS2 sheets to Mg(OH)2, naturally depleting the semiconductor, pushing towards intrinsic doping limit and enhancing overall optical performance of 2D semiconductors. Results not only establish unusual confinement effects in 2D-Mg(OH)2, but also offer novel 2D-insulating material with unique physical, vibrational, and chemical properties for potential applications in flexible optoelectronics.

  11. Induction of digitoxigenin monodigitoxoside UDP-glucuronosyltransferase activity by glucocorticoids and other inducers of cytochrome P-450p in primary monolayer cultures of adult rat hepatocytes and in human liver.

    PubMed

    Schuetz, E G; Hazelton, G A; Hall, J; Watkins, P B; Klaassen, C D; Guzelian, P S

    1986-06-25

    We have recently proposed that glucocorticoids induce cytochrome P-450p, a liver microsomal hemoprotein originally isolated from rats treated with the antiglucocorticoid pregnenolone 16 alpha-carbonitrile (PCN), through a mechanism that involves a stereospecific recognition system clearly distinguishable from the classic glucocorticoid receptor (Schuetz, E. G., Wrighton, S. A., Barwick, J. L., and Guzelian, P. S. (1984) J. Biol. Chem. 259, 1999-2012). We now report that digitoxigenin monodigitoxoside UDP-glucuronosyltransferase (DIG UDP-glucuronosyltransferase), a liver microsomal enzyme activity induced by PCN in rats, is also inducible, as is P-450p, in primary monolayer cultures of adult rat hepatocytes. DIG UDP-glucuronosyltransferase activity closely resembled reported characteristics of induction of P-450p in its time course of induction, concentration-response relationships, exclusivity of induction by steroids with glucocorticoid properties, unusual rank order of potency of glucocorticoid agonists, unusually high ED50 for induction by glucocorticoids, enhanced induction rather than inhibition by anti-glucocorticoids in the presence of glucocorticoids, and finally, induction by nonsteroidal inducers of P-450p. DIG UDP-glucuronosyltransferase activity was also readily detected in human liver microsomes and was elevated in two patients who had received inducers of P-450p. We conclude that the liver enzymes controlled by the postulated PCN recognition system include not only P-450p but also one or more UDP-glucuronosyltransferases.

  12. Three dimensional spheroid cell culture for nanoparticle safety testing.

    PubMed

    Sambale, Franziska; Lavrentieva, Antonina; Stahl, Frank; Blume, Cornelia; Stiesch, Meike; Kasper, Cornelia; Bahnemann, Detlef; Scheper, Thomas

    2015-07-10

    Nanoparticles are widely employed for many applications and the number of consumer products, incorporating nanotechnology, is constantly increasing. A novel area of nanotechnology is the application in medical implants. The widespread use of nanoparticles leads to their higher prevalence in our environment. This, in turn, raises concerns regarding potential risks to humans. Previous studies have shown possible hazardous effects of some nanoparticles on mammalian cells grown in two-dimensional (2D) cultures. However, 2D in vitro cell cultures display several disadvantages such as changes in cell shape, cell function, cell responses and lack of cell-cell contacts. For this reason, the development of better models for mimicking in vivo conditions is essential. In the present work, we cultivated A549 cells and NIH-3T3 cells in three-dimensional (3D) spheroids and investigated the effects of zinc oxide (ZnO-NP) and titanium dioxide nanoparticles (TiO2-NP). The results were compared to cultivation in 2D monolayer culture. A549 cells in 3D cell culture formed loose aggregates which were more sensitive to the toxicity of ZnO-NP in comparison to cells grown in 2D monolayers. In contrast, NIH-3T3 cells showed a compact 3D spheroid structure and no differences in the sensitivity of the NIH-3T3 cells to ZnO-NP were observed between 2D and 3D cultures. TiO2-NP were non-toxic in 2D cultures but affected cell-cell interaction during 3D spheroid formation of A549 and NIH-3T3 cells. When TiO2-NP were directly added during spheroid formation in the cultures of the two cell lines tested, several smaller spheroids were formed instead of a single spheroid. This effect was not observed if the nanoparticles were added after spheroid formation. In this case, a slight decrease in cell viability was determined only for A549 3D spheroids. The obtained results demonstrate the importance of 3D cell culture studies for nanoparticle safety testing, since some effects cannot be revealed in 2D

  13. Packing of ganglioside-phospholipid monolayers: an x-ray diffraction and reflectivity study.

    PubMed

    Majewski, J; Kuhl, T L; Kjaer, K; Smith, G S

    2001-11-01

    Using synchrotron grazing-incidence x-ray diffraction (GIXD) and reflectivity, the in-plane and out-of-plane structure of mixed ganglioside-phospholipid monolayers was investigated at the air-water interface. Mixed monolayers of 0, 5, 10, 20, and 100 mol% ganglioside GM(1) and the phospholipid dipalmitoylphosphatidylethanolamine (DPPE) were studied in the solid phase at 23 degrees C and a surface pressure of 45 mN/m. At these concentrations and conditions the two components do not phase-separate and no evidence for domain formation was observed. X-ray scattering measurements reveal that GM(1) is accommodated within the host DPPE monolayer and does not distort the hexagonal in-plane unit cell or out-of-plane two-dimensional (2-D) packing compared with a pure DPPE monolayer. The oligosaccharide headgroups were found to extend normally from the monolayer surface, and the incorporation of these glycolipids into DPPE monolayers did not affect hydrocarbon tail packing (fluidization or condensation of the hydrocarbon region). This is in contrast to previous investigations of lipopolymer-lipid mixtures, where the packing structure of phospholipid monolayers was greatly altered by the inclusion of lipids bearing hydrophilic polymer groups. Indeed, the lack of packing disruptions by the oligosaccharide groups indicates that protein-GM(1) interactions, including binding, insertion, chain fluidization, and domain formation (lipid rafts), can be studied in 2-D monolayers using scattering techniques.

  14. Spotting 2D atomic layers on aluminum nitride thin films.

    PubMed

    Chandrasekar, Hareesh; Bharadwaj B, Krishna; Vaidyuala, Kranthi Kumar; Suran, Swathi; Bhat, Navakanta; Varma, Manoj; Srinivasan Raghavan

    2015-10-23

    Substrates for 2D materials are important for tailoring their fundamental properties and realizing device applications. Aluminum nitride (AIN) films on silicon are promising large-area substrates for such devices in view of their high surface phonon energies and reasonably large dielectric constants. In this paper epitaxial layers of AlN on 2″ Si wafers have been investigated as a necessary first step to realize devices from exfoliated or transferred atomic layers. Significant thickness dependent contrast enhancements are both predicted and observed for monolayers of graphene and MoS2 on AlN films as compared to the conventional SiO2 films on silicon, with calculated contrast values approaching 100% for graphene on AlN as compared to 8% for SiO2 at normal incidences. Quantitative estimates of experimentally measured contrast using reflectance spectroscopy show very good agreement with calculated values. Transistors of monolayer graphene on AlN films are demonstrated, indicating the feasibility of complete device fabrication on the identified layers.

  15. Glucuronidation of thyroxine in primary monolayer cultures of rat hepatocytes: in vitro induction of UDP-glucuronosyltranferases by methylcholanthrene, clofibrate, and dexamethasone alone and in combination.

    PubMed

    Jemnitz, K; Veres, Z; Monostory, K; Vereczkey, L

    2000-01-01

    Induction of UDP-glucuronosyltransferases (UGTs) toward thyroxine (T4) and p-nitrophenol (pNP) by 3-methylcholanthrene (MC), dexamethasone (DEX), clofibrate (Cl), and MC combined with DEX or Cl was studied in rat hepatocyte culture. We have developed a sensitive method for the measurement of glucuronide conjugates of the two substrates based on HPLC analysis of culture medium. MC, Cl, or DEX increased the activity of T4 UGT. Combination of MC and Cl showed additive effect, enzyme activity was enhanced compared with either MC or Cl treatment alone (617, 441, and 217% of the control, respectively). Combination of MC and DEX did not result in higher T4 UGT activity than MC treatment alone. Both MC and DEX enhanced the pNP UGT activity (182 and 162% of the control, respectively). Combination of MC with DEX resulted in additive effect. Cl treatment did not affect pNP conjugation either alone or in combination with MC. Western blot analysis revealed that only the amount of UGT1A1 was elevated by Cl and DEX. In contrast, concentration of UGT1A6 was increased by MC. Previous studies demonstrated that UGT1A1 inducers like phenobarbital have no effect on T4 conjugation (). Our results suggest that Cl, a known inducer of UGT1A1, enhances the activity of other enzyme(s) involved in T4 glucuronidation as well. It is well documented that DEX potentiates the inductory effect of polycyclic aromatic hydrocarbon on UGT1A6 (). In our study, MC increased the rate of T4 glucuronidation, and DEX had no additional effect on this reaction, suggesting that UGT1A6 is not the only enzyme inducible by MC that can catalyze T4 conjugation. PMID:10611137

  16. Organotypic culture in three dimensions prevents radiation-induced transformation in human lung epithelial cells

    NASA Astrophysics Data System (ADS)

    El-Ashmawy, Mariam; Coquelin, Melissa; Luitel, Krishna; Batten, Kimberly; Shay, Jerry W.

    2016-08-01

    The effects of radiation in two-dimensional (2D) cell culture conditions may not recapitulate tissue responses as modeled in three-dimensional (3D) organotypic culture. In this study, we determined if the frequency of radiation-induced transformation and cancer progression differed in 3D compared to 2D culture. Telomerase immortalized human bronchial epithelial cells (HBECs) with shTP53 and mutant KRas expression were exposed to various types of radiation (gamma, +H, 56Fe) in either 2D or 3D culture. After irradiation, 3D structures were dissociated and passaged as a monolayer followed by measurement of transformation, cell growth and expression analysis. Cells irradiated in 3D produced significantly fewer and smaller colonies in soft agar than their 2D-irradiated counterparts (gamma P = 0.0004 +H P = 0.049 56Fe P < 0.0001). The cell culture conditions did not affect cell killing, the ability of cells to survive in a colony formation assay, and proliferation rates after radiation—implying there was no selection against cells in or dissociated from 3D conditions. However, DNA damage repair and apoptosis markers were increased in 2D cells compared to 3D cells after radiation. Ideally, expanding the utility of 3D culture will allow for a better understanding of the biological consequences of radiation exposure.

  17. Organotypic culture in three dimensions prevents radiation-induced transformation in human lung epithelial cells

    PubMed Central

    El-Ashmawy, Mariam; Coquelin, Melissa; Luitel, Krishna; Batten, Kimberly; Shay, Jerry W.

    2016-01-01

    The effects of radiation in two-dimensional (2D) cell culture conditions may not recapitulate tissue responses as modeled in three-dimensional (3D) organotypic culture. In this study, we determined if the frequency of radiation-induced transformation and cancer progression differed in 3D compared to 2D culture. Telomerase immortalized human bronchial epithelial cells (HBECs) with shTP53 and mutant KRas expression were exposed to various types of radiation (gamma, +H, 56Fe) in either 2D or 3D culture. After irradiation, 3D structures were dissociated and passaged as a monolayer followed by measurement of transformation, cell growth and expression analysis. Cells irradiated in 3D produced significantly fewer and smaller colonies in soft agar than their 2D-irradiated counterparts (gamma P = 0.0004; +H P = 0.049; 56Fe P < 0.0001). The cell culture conditions did not affect cell killing, the ability of cells to survive in a colony formation assay, and proliferation rates after radiation—implying there was no selection against cells in or dissociated from 3D conditions. However, DNA damage repair and apoptosis markers were increased in 2D cells compared to 3D cells after radiation. Ideally, expanding the utility of 3D culture will allow for a better understanding of the biological consequences of radiation exposure. PMID:27539227

  18. Interferometric Motion Detection in Atomic Layer 2D Nanostructures: Visualizing Signal Transduction Efficiency and Optimization Pathways.

    PubMed

    Wang, Zenghui; Feng, Philip X-L

    2016-01-01

    Atomic layer crystals are emerging building blocks for enabling new two-dimensional (2D) nanomechanical systems, whose motions can be coupled to other attractive physical properties in such 2D systems. Optical interferometry has been very effective in reading out the infinitesimal motions of these 2D structures and spatially resolving different modes. To quantitatively understand the detection efficiency and its dependence on the device parameters and interferometric conditions, here we present a systematic study of the intrinsic motion responsivity in 2D nanomechanical systems using a Fresnel-law-based model. We find that in monolayer to 14-layer structures, MoS2 offers the highest responsivity among graphene, h-BN, and MoS2 devices and for the three commonly used visible laser wavelengths (633, 532, and 405 nm). We also find that the vacuum gap resulting from the widely used 300 nm-oxide substrate in making 2D devices, fortunately, leads to close-to-optimal responsivity for a wide range of 2D flakes. Our results elucidate and graphically visualize the dependence of motion transduction responsivity upon 2D material type and number of layers, vacuum gap, oxide thickness, and detecting wavelength, thus providing design guidelines for constructing 2D nanomechanical systems with optimal optical motion readout. PMID:27464908

  19. Interferometric Motion Detection in Atomic Layer 2D Nanostructures: Visualizing Signal Transduction Efficiency and Optimization Pathways.

    PubMed

    Wang, Zenghui; Feng, Philip X-L

    2016-07-28

    Atomic layer crystals are emerging building blocks for enabling new two-dimensional (2D) nanomechanical systems, whose motions can be coupled to other attractive physical properties in such 2D systems. Optical interferometry has been very effective in reading out the infinitesimal motions of these 2D structures and spatially resolving different modes. To quantitatively understand the detection efficiency and its dependence on the device parameters and interferometric conditions, here we present a systematic study of the intrinsic motion responsivity in 2D nanomechanical systems using a Fresnel-law-based model. We find that in monolayer to 14-layer structures, MoS2 offers the highest responsivity among graphene, h-BN, and MoS2 devices and for the three commonly used visible laser wavelengths (633, 532, and 405 nm). We also find that the vacuum gap resulting from the widely used 300 nm-oxide substrate in making 2D devices, fortunately, leads to close-to-optimal responsivity for a wide range of 2D flakes. Our results elucidate and graphically visualize the dependence of motion transduction responsivity upon 2D material type and number of layers, vacuum gap, oxide thickness, and detecting wavelength, thus providing design guidelines for constructing 2D nanomechanical systems with optimal optical motion readout.

  20. Interferometric Motion Detection in Atomic Layer 2D Nanostructures: Visualizing Signal Transduction Efficiency and Optimization Pathways

    NASA Astrophysics Data System (ADS)

    Wang, Zenghui; Feng, Philip X.-L.

    2016-07-01

    Atomic layer crystals are emerging building blocks for enabling new two-dimensional (2D) nanomechanical systems, whose motions can be coupled to other attractive physical properties in such 2D systems. Optical interferometry has been very effective in reading out the infinitesimal motions of these 2D structures and spatially resolving different modes. To quantitatively understand the detection efficiency and its dependence on the device parameters and interferometric conditions, here we present a systematic study of the intrinsic motion responsivity in 2D nanomechanical systems using a Fresnel-law-based model. We find that in monolayer to 14-layer structures, MoS2 offers the highest responsivity among graphene, h-BN, and MoS2 devices and for the three commonly used visible laser wavelengths (633, 532, and 405 nm). We also find that the vacuum gap resulting from the widely used 300 nm-oxide substrate in making 2D devices, fortunately, leads to close-to-optimal responsivity for a wide range of 2D flakes. Our results elucidate and graphically visualize the dependence of motion transduction responsivity upon 2D material type and number of layers, vacuum gap, oxide thickness, and detecting wavelength, thus providing design guidelines for constructing 2D nanomechanical systems with optimal optical motion readout.

  1. Interferometric Motion Detection in Atomic Layer 2D Nanostructures: Visualizing Signal Transduction Efficiency and Optimization Pathways

    PubMed Central

    Wang, Zenghui; Feng, Philip X.-L.

    2016-01-01

    Atomic layer crystals are emerging building blocks for enabling new two-dimensional (2D) nanomechanical systems, whose motions can be coupled to other attractive physical properties in such 2D systems. Optical interferometry has been very effective in reading out the infinitesimal motions of these 2D structures and spatially resolving different modes. To quantitatively understand the detection efficiency and its dependence on the device parameters and interferometric conditions, here we present a systematic study of the intrinsic motion responsivity in 2D nanomechanical systems using a Fresnel-law-based model. We find that in monolayer to 14-layer structures, MoS2 offers the highest responsivity among graphene, h-BN, and MoS2 devices and for the three commonly used visible laser wavelengths (633, 532, and 405 nm). We also find that the vacuum gap resulting from the widely used 300 nm-oxide substrate in making 2D devices, fortunately, leads to close-to-optimal responsivity for a wide range of 2D flakes. Our results elucidate and graphically visualize the dependence of motion transduction responsivity upon 2D material type and number of layers, vacuum gap, oxide thickness, and detecting wavelength, thus providing design guidelines for constructing 2D nanomechanical systems with optimal optical motion readout. PMID:27464908

  2. Band structures in silicene on monolayer gallium phosphide substrate

    NASA Astrophysics Data System (ADS)

    Ren, Miaojuan; Li, Mingming; Zhang, Changwen; Yuan, Min; Li, Ping; Li, Feng; Ji, Weixiao; Chen, Xinlian

    2016-07-01

    Opening a sizable band gap in the zero-gap silicene is a key issue for its application in nanoelectronics. We design new 2D silicene and GaP heterobilayer (Si/GaP HBL) composed of silicene and monolayer (ML) GaP. Based on first-principles calculations, we find that the interaction energies are in the range of -295.5 to -297.5 meV per unit cell, indicating a weak interaction between silicene and gallium phosphide (GaP) monolayer. The band gap changes ranging from 0.06 to 0.44 eV in hybrid HBLs. An unexpected indirect-direct band gap crossover is also observed in HBLs, dependent on the stacking pattern. These provide a possible way to design effective FETs out of silicene on GaP monolayer.

  3. A Single-Material Logical Junction Based on 2D Crystal PdS2.

    PubMed

    Ghorbani-Asl, Mahdi; Kuc, Agnieszka; Miró, Pere; Heine, Thomas

    2016-02-01

    A single-material logical junction with negligible contact resistance is designed by exploiting quantum-confinement effects in 1T PdS2 . The metallic bilayer serves as electrodes for the semiconducting channel monolayer, avoiding contact resistance. Heat dissipation is then governed by tunnel loss, which becomes negligible at channel lengths larger than 2.45 nm. This value marks the integration limit for a conventional 2D transistor.

  4. Seeded growth of robust SERS-active 2D Au@Ag nanoparticulate films

    SciTech Connect

    Baker, Gary A; Dai, Sheng; Hagaman, Edward {Ed} W; Mahurin, Shannon Mark; Zhu, Haoguo; Bao, Lili

    2008-01-01

    We demonstrate herein a novel and versatile solution-based methodology for fabricating self-organized two-dimensional (2D) Au nanoparticle arrays on glass using in situ nucleation at an aminosilane monolayer followed by seeded, electroless growth; subsequent deposition of Ag produced Au{at}Ag core-shell nanoparticulate films which proved highly promising as surface-enhanced Raman scattering (SERS) platforms.

  5. A Single-Material Logical Junction Based on 2D Crystal PdS2.

    PubMed

    Ghorbani-Asl, Mahdi; Kuc, Agnieszka; Miró, Pere; Heine, Thomas

    2016-02-01

    A single-material logical junction with negligible contact resistance is designed by exploiting quantum-confinement effects in 1T PdS2 . The metallic bilayer serves as electrodes for the semiconducting channel monolayer, avoiding contact resistance. Heat dissipation is then governed by tunnel loss, which becomes negligible at channel lengths larger than 2.45 nm. This value marks the integration limit for a conventional 2D transistor. PMID:26632273

  6. A computer model of engineered cardiac monolayers.

    PubMed

    Kim, Jong M; Bursac, Nenad; Henriquez, Craig S

    2010-05-19

    Engineered monolayers created using microabrasion and micropatterning methods have provided a simplified in vitro system to study the effects of anisotropy and fiber direction on electrical propagation. Interpreting the behavior in these culture systems has often been performed using classical computer models with continuous properties. However, such models do not account for the effects of random cell shapes, cell orientations, and cleft spaces inherent in these monolayers on the resulting wavefront conduction. This work presents a novel methodology for modeling a monolayer of cardiac tissue in which the factors governing cell shape, cell-to-cell coupling, and degree of cleft space are not constant but rather are treated as spatially random with assigned distributions. This modeling approach makes it possible to simulate wavefront propagation in a manner analogous to performing experiments on engineered monolayer tissues. Simulated results are compared to previously published measured data from monolayers used to investigate the role of cellular architecture on conduction velocities and anisotropy ratios. We also present an estimate for obtaining the electrical properties from these networks and demonstrate how variations in the discrete cellular architecture affect the macroscopic conductivities. The simulations support the common assumption that under normal ranges of coupling strength, tissues with relatively uniform distributions of cell shapes and connectivity can be represented using continuous models with conductivities derived from random discrete cellular architecture using either global or local estimates. The results also reveal that in the presence of abrupt changes in cell orientation, local estimates of tissue properties predict smoother changes in conductivity that may not adequately predict the discrete nature of propagation at the transition sites. PMID:20441739

  7. Ketoconazole blocks bile acid synthesis in hepatocyte monolayer cultures and in vivo in rat by inhibiting cholesterol 7 alpha-hydroxylase.

    PubMed Central

    Princen, H M; Huijsmans, C M; Kuipers, F; Vonk, R J; Kempen, H J

    1986-01-01

    In cultured hepatocytes conversion of [4-14C]cholesterol into bile acids was dose dependently reduced by the antimycotic drug ketoconazole, giving half-maximal inhibition at 10 microM ketoconazole in rat hepatocytes and at 1 microM in human hepatocytes. No change was observed in the ratio of produced cholic, beta-muricholic, and chenodeoxycholic acid with increasing amounts of the drug. Conversion of [4-14C]7 alpha-hydroxycholesterol, an intermediate of bile acid pathway, to bile acids was not affected by ketoconazole. These results together with kinetic studies with rat liver microsomes, demonstrating noncompetitive inhibition (Ki = 0.4 microM), indicate that cholesterol 7 alpha-hydroxylase is the main site of inhibition. In bile-diverted rats a single dose of ketoconazole (50 mg/kg) dramatically impaired bile flow and biliary bile acid output (92% inhibition). A similar blockade was observed using [4-14C]cholesterol as precursor for bile acid synthesis. Therefore, treatment of patients with this drug may inhibit bile acid synthesis, resulting in a reduction of the bile acid pool size after long-term ketoconazole therapy. PMID:3760182

  8. Ultrathin 2D Photodetectors Utilizing Chemical Vapor Deposition Grown WS2 With Graphene Electrodes.

    PubMed

    Tan, Haijie; Fan, Ye; Zhou, Yingqiu; Chen, Qu; Xu, Wenshuo; Warner, Jamie H

    2016-08-23

    In this report, graphene (Gr) is used as a 2D electrode and monolayer WS2 as the active semiconductor in ultrathin photodetector devices. All of the 2D materials are grown by chemical vapor deposition (CVD) and thus pose as a viable route to scalability. The monolayer thickness of both electrode and semiconductor gives these photodetectors ∼2 nm thickness. We show that graphene is different to conventional metal (Au) electrodes due to the finite density of states from the Dirac cones of the valence and conduction bands, which enables the photoresponsivity to be modulated by electrostatic gating and light input control. We demonstrate lateral Gr-WS2-Gr photodetectors with photoresponsivities reaching 3.5 A/W under illumination power densities of 2.5 × 10(7) mW/cm(2). The performance of monolayer WS2 is compared to bilayer WS2 in photodetectors and we show that increased photoresponsivity is achieved in the thicker bilayer WS2 crystals due to increased optical absorption. This approach of incorporating graphene electrodes in lateral TMD based devices provides insights on the contact engineering in 2D optoelectronics, which is crucial for the development of high performing ultrathin photodetector arrays for versatile applications.

  9. Ultrathin 2D Photodetectors Utilizing Chemical Vapor Deposition Grown WS2 With Graphene Electrodes.

    PubMed

    Tan, Haijie; Fan, Ye; Zhou, Yingqiu; Chen, Qu; Xu, Wenshuo; Warner, Jamie H

    2016-08-23

    In this report, graphene (Gr) is used as a 2D electrode and monolayer WS2 as the active semiconductor in ultrathin photodetector devices. All of the 2D materials are grown by chemical vapor deposition (CVD) and thus pose as a viable route to scalability. The monolayer thickness of both electrode and semiconductor gives these photodetectors ∼2 nm thickness. We show that graphene is different to conventional metal (Au) electrodes due to the finite density of states from the Dirac cones of the valence and conduction bands, which enables the photoresponsivity to be modulated by electrostatic gating and light input control. We demonstrate lateral Gr-WS2-Gr photodetectors with photoresponsivities reaching 3.5 A/W under illumination power densities of 2.5 × 10(7) mW/cm(2). The performance of monolayer WS2 is compared to bilayer WS2 in photodetectors and we show that increased photoresponsivity is achieved in the thicker bilayer WS2 crystals due to increased optical absorption. This approach of incorporating graphene electrodes in lateral TMD based devices provides insights on the contact engineering in 2D optoelectronics, which is crucial for the development of high performing ultrathin photodetector arrays for versatile applications. PMID:27440384

  10. Systematic Approach to Electrostatically Induced 2D Crystallization of Nanoparticles at Liquid Interfaces

    SciTech Connect

    Fukuto, M.; Kewalramani, S.; Wang, S.; Lin, Y.; Nguyen, G.; Wang, Q.; Yang, L.

    2011-02-07

    We report an experimental demonstration of a strategy for inducing two-dimensional (2D) crystallization of charged nanoparticles on oppositely charged fluid interfaces. This strategy aims to maximize the interfacial adsorption of nanoparticles, and hence their lateral packing density, by utilizing a combination of weakly charged particles and a high surface charge density on the planar interface. In order to test this approach, we investigated the assembly of cowpea mosaic virus (CPMV) on positively charged lipid monolayers at the aqueous solution surface, by means of in situ X-ray scattering measurements at the liquid-vapor interface. The assembly was studied as a function of the solution pH, which was used to vary the charge on CPMV, and of the mole fraction of the cationic lipid in the binary lipid monolayer, which set the interface charge density. The 2D crystallization of CPMV occurred in a narrow pH range just above the particle's isoelectric point, where the particle charge was weakly negative, and only when the cationic-lipid fraction in the monolayer exceeded a threshold. The observed 2D crystals exhibited nearly the same packing density as the densest lattice plane within the known 3D crystals of CPMV. The above electrostatic approach of maximizing interfacial adsorption may provide an efficient route to the crystallization of nanoparticles at aqueous interfaces.

  11. Evaporative thinning: a facile synthesis method for high quality ultrathin layers of 2D crystals.

    PubMed

    Huang, Yi-Kai; Cain, Jeffrey D; Peng, Lintao; Hao, Shiqiang; Chasapis, Thomas; Kanatzidis, Mercouri G; Wolverton, Christopher; Grayson, Matthew; Dravid, Vinayak P

    2014-10-28

    The palette of two-dimensional materials has expanded beyond graphene in recent years to include the chalcogenides among other systems. However, there is a considerable paucity of methods for controlled synthesis of mono- and/or few-layer two-dimensional materials with desirable quality, reproducibility, and generality. Here we show a facile top-down synthesis approach for ultrathin layers of 2D materials down to monolayer. Our method is based on controlled evaporative thinning of initially large sheets, as deposited by vapor mass-transport. Rather than optimizing conditions for monolayer deposition, our approach makes use of selective evaporation of thick sheets to control the eventual thickness, down to a monolayer, a process which appears to be self-stopping. As a result, 2D sheets with high yield, high reproducibility, and excellent quality can be generated with large (>10 μm) and thin (∼ 1-2 nm) dimensions. Evaporative thinning promises to greatly reduce the difficulty involved in isolating large, mono- and few-layers of 2D materials for subsequent studies.

  12. Switchable polarization in an unzipped graphene oxide monolayer.

    PubMed

    Noor-A-Alam, Mohammad; Shin, Young-Han

    2016-08-14

    Ferroelectricity in low-dimensional oxide materials is generally suppressed at the scale of a few nanometers, and has attracted considerable attention from both fundamental and technological aspects. Graphene is one of the thinnest materials (one atom thick). Therefore, engineering switchable polarization in non-polar pristine graphene could potentially lead to two-dimensional (2D) ferroelectric materials. In the present study, based on density functional theory, we show that an unzipped graphene oxide (UGO) monolayer can exhibit switchable polarization due to its foldable bonds between the oxygen atom and two carbon atoms underneath the oxygen. We find that a free standing UGO monolayer exhibits antiferroelectric switchable polarization. A UGO monolayer can be obtained as an intermediate product during the chemical exfoliation process of graphene. Interestingly, despite its dimensionality, our estimated polarization in a UGO monolayer is comparable to that in bulk ferroelectric materials (e.g., ferroelectric polymers). Our calculations could help realize antiferroelectric switchable polarization in 2D materials, which could find various potential applications in nanoscale devices such as sensors, actuators, and capacitors with high energy-storage density. PMID:27401944

  13. Transport of monocarboxylic acids at the blood-brain barrier: Studies with monolayers of primary cultured bovine brain capillary endothelial cells

    SciTech Connect

    Terasaki, T.; Takakuwa, S.; Moritani, S.; Tsuji, A. )

    1991-09-01

    The kinetics and mechanism of the transport of monocarboxylic acids (MCAs) were studied by using primary cultured bovine brain capillary endothelial cells. Concentration-dependent uptake of acetic acid was observed, and the kinetic parameters were estimated as follows: the Michaelis constant, Kt, was 3.41 {plus minus} 1.87 mM, the maximum uptake rate, Jmax, was 144.7 {plus minus} 55.7 nmol/mg of protein/min and the nonsaturable first-order rate constant, Kd, was 6.66 {plus minus} 1.98 microliters/mg of protein/min. At medium pH below 7.0, the uptake rate of (3H)acetic acid increased markedly with decreasing medium pH, whereas pH-independent uptake was observed in the presence of 10 mM acetic acid. An energy requirement for (3H)acetic acid uptake was also demonstrated, because metabolic inhibitors (2,4-dinitrophenol and rotenone) reduced significantly the uptake rate (P less than .05). Carbonylcyanide-p-trifluoro-methoxyphenylhydrazone, a protonophore, inhibited significantly the uptake of (3H)acetic acid at medium pH of 5.0 and 6.0, whereas 4,4{prime}-diisothiocyanostilben-2,2{prime}-disulfonic acid did not. Several MCAs inhibited significantly the uptake rate of (3H)acetic acid, whereas di- and tricarboxylic acids did not. The uptake of (3H)acetic acid was competitively inhibited by salicylic acid, with an inhibition constant, Ki, of 3.60 mM, suggesting a common transport system between acetic acid and salicylic acid. Moreover, at the medium pH of 7.4, salicylic acid and valproic acid inhibited significantly the uptake of (3H)acetic acid, demonstrating that the transport of MCA drugs could also be ascribed to the MCA transport system at the physiologic pH.

  14. Monolayer II-VI semiconductors: A first-principles prediction

    NASA Astrophysics Data System (ADS)

    Zheng, Hui; Li, Xian-Bin; Chen, Nian-Ke; Xie, Sheng-Yi; Tian, Wei Quan; Chen, Yuanping; Xia, Hong; Zhang, S. B.; Sun, Hong-Bo

    2015-09-01

    A systematic study of 32 honeycomb monolayer II-VI semiconductors is carried out by first-principles methods. While none of the two-dimensional (2D) structures can be energetically stable, it appears that BeO, MgO, CaO, ZnO, CdO, CaS, SrS, SrSe, BaTe, and HgTe honeycomb monolayers have a good dynamic stability. The stability of the five oxides is consistent with the work published by Zhuang et al. [Appl. Phys. Lett. 103, 212102 (2013), 10.1063/1.4831972]. The rest of the compounds in the form of honeycomb are dynamically unstable, revealed by phonon calculations. In addition, according to the molecular dynamic (MD) simulation evolution from these unstable candidates, we also find two extra monolayers dynamically stable, which are tetragonal BaS [P 4 /n m m (129 ) ] and orthorhombic HgS [P 21/m (11 ) ] . The honeycomb monolayers exist in the form of either a planar perfect honeycomb or a low-buckled 2D layer, all of which possess a band gap and most of them are in the ultraviolet region. Interestingly, the dynamically stable SrSe has a gap near visible light, and displays exotic electronic properties with a flat top of the valence band, and hence has a strong spin polarization upon hole doping. The honeycomb HgTe has recently been reported to achieve a topological nontrivial phase under appropriate in-plane tensile strain and spin-orbital coupling (SOC) [J. Li et al., arXiv:1412.2528]. Some II-VI partners with less than 5 % lattice mismatch may be used to design novel 2D heterojunction devices. If synthesized, potential applications of these 2D II-VI families could include optoelectronics, spintronics, and strong correlated electronics.

  15. Rolling Up a Monolayer MoS2 Sheet.

    PubMed

    Meng, Jianling; Wang, Guole; Li, Xiaomin; Lu, Xiaobo; Zhang, Jing; Yu, Hua; Chen, Wei; Du, Luojun; Liao, Mengzhou; Zhao, Jing; Chen, Peng; Zhu, Jianqi; Bai, Xuedong; Shi, Dongxia; Zhang, Guangyu

    2016-07-01

    MoS2 nanoscrolls are formed by argon plasma treatment on monolayer MoS2 sheet. The nanoscale scroll formation is attributed to the partial removal of top sulfur layer in MoS2 during the argon plasma treatment process. This convenient, solvent-free, and high-yielding nanoscroll formation technique is also feasible for other 2D transition metal dichalcogenides.

  16. On the Quantum Spin Hall Gap of Monolayer 1T'-WTe2.

    PubMed

    Zheng, Feipeng; Cai, Chaoyi; Ge, Shaofeng; Zhang, Xuefeng; Liu, Xin; Lu, Hong; Zhang, Yudao; Qiu, Jun; Taniguchi, Takashi; Watanabe, Kenji; Jia, Shuang; Qi, Jingshan; Chen, Jian-Hao; Sun, Dong; Feng, Ji

    2016-06-01

    Positive quantum spin Hall gap in mono-layer 1T'-WTe2 is consistently supported by density-functional theory calculations, ultrafast pump-probe, and electrical transport measurements. It is argued that monolayer 1T'-WTe2 , which was predicted to be a semimetallic quantum spin Hall material, is likely a truly 2D quantum spin Hall insulator with a positive quantum spin Hall gap.

  17. On the Quantum Spin Hall Gap of Monolayer 1T'-WTe2.

    PubMed

    Zheng, Feipeng; Cai, Chaoyi; Ge, Shaofeng; Zhang, Xuefeng; Liu, Xin; Lu, Hong; Zhang, Yudao; Qiu, Jun; Taniguchi, Takashi; Watanabe, Kenji; Jia, Shuang; Qi, Jingshan; Chen, Jian-Hao; Sun, Dong; Feng, Ji

    2016-06-01

    Positive quantum spin Hall gap in mono-layer 1T'-WTe2 is consistently supported by density-functional theory calculations, ultrafast pump-probe, and electrical transport measurements. It is argued that monolayer 1T'-WTe2 , which was predicted to be a semimetallic quantum spin Hall material, is likely a truly 2D quantum spin Hall insulator with a positive quantum spin Hall gap. PMID:27115098

  18. Perspectives for spintronics in 2D materials

    NASA Astrophysics Data System (ADS)

    Han, Wei

    2016-03-01

    The past decade has been especially creative for spintronics since the (re)discovery of various two dimensional (2D) materials. Due to the unusual physical characteristics, 2D materials have provided new platforms to probe the spin interaction with other degrees of freedom for electrons, as well as to be used for novel spintronics applications. This review briefly presents the most important recent and ongoing research for spintronics in 2D materials.

  19. Fatty-acid monolayers at the nematic/water interface: phases and liquid-crystal alignment.

    PubMed

    Price, Andrew D; Schwartz, Daniel K

    2007-02-01

    The two-dimensional (2D) phases of fatty-acid monolayers (hexadecanoic, octadecanoic, eicosanoic, and docosanoic acids) have been studied at the interface of a nematic liquid crystal (LC) and water. When observed between crossed polarizers, the LC responds to monolayer structure owing to mesoscopic alignment of the LC by the adsorbed molecules. Similar to Langmuir monolayers at the air/water interface, the adsorbed monolayer at the nematic/water interface displays distinct thermodynamic phases. Observed are a 2D gas, isotropic liquid, and two condensed mesophases, each with a characteristic anchoring of the LC zenithal tilt and azimuth. By varying the monolayer temperature and surface concentration we observe reversible first-order phase transitions from vapor to liquid and from liquid to condensed. A temperature-dependent transition between two condensed phases appears to be a reversible swiveling transition in the tilt azimuth of the monolayer. Similar to monolayers at the air/water interface, the temperature of the gas/liquid/condensed triple-point temperature increased by about 10 degrees C for a two methylene group increase in chain length. However, the absolute value of the triple-point temperatures are depressed by about 40 degrees C compared to those of analogous monolayers at the air/water interface. We also observe a direct influence by the LC layer on the mesoscopic and macroscopic structure of the monolayer by analyzing the shapes and internal textures of gas domains in coexistence with a 2D liquid. An effective anisotropic line tension arises from elastic forces owing to deformation of the nematic director across phase boundaries. This results in the deformation of the domain from circular to elongated, with a distinct singularity. The LC elastic energy also gives rise to transition zones displaying mesoscopic realignment of the director tilt or azimuth between adjacent regions with a sudden change in anchoring.

  20. Quantitative 2D liquid-state NMR.

    PubMed

    Giraudeau, Patrick

    2014-06-01

    Two-dimensional (2D) liquid-state NMR has a very high potential to simultaneously determine the absolute concentration of small molecules in complex mixtures, thanks to its capacity to separate overlapping resonances. However, it suffers from two main drawbacks that probably explain its relatively late development. First, the 2D NMR signal is strongly molecule-dependent and site-dependent; second, the long duration of 2D NMR experiments prevents its general use for high-throughput quantitative applications and affects its quantitative performance. Fortunately, the last 10 years has witnessed an increasing number of contributions where quantitative approaches based on 2D NMR were developed and applied to solve real analytical issues. This review aims at presenting these recent efforts to reach a high trueness and precision in quantitative measurements by 2D NMR. After highlighting the interest of 2D NMR for quantitative analysis, the different strategies to determine the absolute concentrations from 2D NMR spectra are described and illustrated by recent applications. The last part of the manuscript concerns the recent development of fast quantitative 2D NMR approaches, aiming at reducing the experiment duration while preserving - or even increasing - the analytical performance. We hope that this comprehensive review will help readers to apprehend the current landscape of quantitative 2D NMR, as well as the perspectives that may arise from it.

  1. Extraordinary Second Harmonic Generation in Tungsten Disulfide Monolayers

    PubMed Central

    Janisch, Corey; Wang, Yuanxi; Ma, Ding; Mehta, Nikhil; Elías, Ana Laura; Perea-López, Néstor; Terrones, Mauricio; Crespi, Vincent; Liu, Zhiwen

    2014-01-01

    We investigate Second Harmonic Generation (SHG) in monolayer WS2 both deposited on a SiO2/Si substrate or suspended using transmission electron microscopy grids. We find unusually large second order nonlinear susceptibility, with an estimated value of deff ~ 4.5 nm/V nearly three orders of magnitude larger than other common nonlinear crystals. In order to quantitatively characterize the nonlinear susceptibility of two-dimensional (2D) materials, we have developed a formalism to model SHG based on the Green's function with a 2D nonlinear sheet source. In addition, polarized SHG is demonstrated as a useful method to probe the structural symmetry and crystal orientation of 2D materials. To understand the large second order nonlinear susceptibility of monolayer WS2, density functional theory based calculation is performed. Our analysis suggests the origin of the large nonlinear susceptibility in resonance enhancement and a large joint density of states, and yields an estimate of the nonlinear susceptibility value deff = 0.77 nm/V for monolayer WS2, which shows good order-of-magnitude agreement with the experimental result. PMID:24984953

  2. Common Effects on Cancer Cells Exerted by a Random Positioning Machine and a 2D Clinostat.

    PubMed

    Svejgaard, Benjamin; Wehland, Markus; Ma, Xiao; Kopp, Sascha; Sahana, Jayashree; Warnke, Elisabeth; Aleshcheva, Ganna; Hemmersbach, Ruth; Hauslage, Jens; Grosse, Jirka; Bauer, Johann; Corydon, Thomas Juhl; Islam, Tawhidul; Infanger, Manfred; Grimm, Daniela

    2015-01-01

    In this study we focused on gravity-sensitive proteins of two human thyroid cancer cell lines (ML-1; RO82-W-1), which were exposed to a 2D clinostat (CLINO), a random positioning machine (RPM) and to normal 1g-conditions. After a three (3d)- or seven-day-culture (7d) on the two devices, we found both cell types growing three-dimensionally within multicellular spheroids (MCS) and also cells remaining adherent (AD) to the culture flask, while 1g-control cultures only formed adherent monolayers, unless the bottom of the culture dish was covered by agarose. In this case, the cytokines IL-6 and IL-8 facilitated the formation of MCS in both cell lines using the liquid-overlay technique at 1g. ML-1 cells grown on the RPM or the CLINO released amounts of IL-6 and MCP-1 into the supernatant, which were significantly elevated as compared to 1g-controls. Release of IL-4, IL-7, IL-8, IL-17, eotaxin-1 and VEGF increased time-dependently, but was not significantly influenced by the gravity conditions. After 3d on the RPM or the CLINO, an accumulation of F-actin around the cellular membrane was detectable in AD cells of both cell lines. IL-6 and IL-8 stimulation of ML-1 cells for 3d and 7d influenced the protein contents of ß1-integrin, talin-1, Ki-67, and beta-actin dose-dependently in adherent cells. The ß1-integrin content was significantly decreased in AD and MCS samples compared with 1g, while talin-1 was higher expressed in MCS than AD populations. The proliferation marker Ki-67 was elevated in AD samples compared with 1g and MCS samples. The ß-actin content of R082-W-1 cells remained unchanged. ML-1 cells exhibited no change in ß-actin in RPM cultures, but a reduction in CLINO samples. Thus, we concluded that simulated microgravity influences the release of cytokines in follicular thyroid cancer cells, and the production of ß1-integrin and talin-1 and predicts an identical effect under real microgravity conditions.

  3. Common Effects on Cancer Cells Exerted by a Random Positioning Machine and a 2D Clinostat

    PubMed Central

    Svejgaard, Benjamin; Wehland, Markus; Ma, Xiao; Kopp, Sascha; Sahana, Jayashree; Warnke, Elisabeth; Aleshcheva, Ganna; Hemmersbach, Ruth; Hauslage, Jens; Grosse, Jirka; Bauer, Johann; Corydon, Thomas Juhl; Islam, Tawhidul; Infanger, Manfred; Grimm, Daniela

    2015-01-01

    In this study we focused on gravity-sensitive proteins of two human thyroid cancer cell lines (ML-1; RO82-W-1), which were exposed to a 2D clinostat (CLINO), a random positioning machine (RPM) and to normal 1g-conditions. After a three (3d)- or seven-day-culture (7d) on the two devices, we found both cell types growing three-dimensionally within multicellular spheroids (MCS) and also cells remaining adherent (AD) to the culture flask, while 1g-control cultures only formed adherent monolayers, unless the bottom of the culture dish was covered by agarose. In this case, the cytokines IL-6 and IL-8 facilitated the formation of MCS in both cell lines using the liquid-overlay technique at 1g. ML-1 cells grown on the RPM or the CLINO released amounts of IL-6 and MCP-1 into the supernatant, which were significantly elevated as compared to 1g-controls. Release of IL-4, IL-7, IL-8, IL-17, eotaxin-1 and VEGF increased time-dependently, but was not significantly influenced by the gravity conditions. After 3d on the RPM or the CLINO, an accumulation of F-actin around the cellular membrane was detectable in AD cells of both cell lines. IL-6 and IL-8 stimulation of ML-1 cells for 3d and 7d influenced the protein contents of ß1-integrin, talin-1, Ki-67, and beta-actin dose-dependently in adherent cells. The ß1-integrin content was significantly decreased in AD and MCS samples compared with 1g, while talin-1 was higher expressed in MCS than AD populations. The proliferation marker Ki-67 was elevated in AD samples compared with 1g and MCS samples. The ß-actin content of R082-W-1 cells remained unchanged. ML-1 cells exhibited no change in ß-actin in RPM cultures, but a reduction in CLINO samples. Thus, we concluded that simulated microgravity influences the release of cytokines in follicular thyroid cancer cells, and the production of ß1-integrin and talin-1 and predicts an identical effect under real microgravity conditions. PMID:26274317

  4. Common Effects on Cancer Cells Exerted by a Random Positioning Machine and a 2D Clinostat.

    PubMed

    Svejgaard, Benjamin; Wehland, Markus; Ma, Xiao; Kopp, Sascha; Sahana, Jayashree; Warnke, Elisabeth; Aleshcheva, Ganna; Hemmersbach, Ruth; Hauslage, Jens; Grosse, Jirka; Bauer, Johann; Corydon, Thomas Juhl; Islam, Tawhidul; Infanger, Manfred; Grimm, Daniela

    2015-01-01

    In this study we focused on gravity-sensitive proteins of two human thyroid cancer cell lines (ML-1; RO82-W-1), which were exposed to a 2D clinostat (CLINO), a random positioning machine (RPM) and to normal 1g-conditions. After a three (3d)- or seven-day-culture (7d) on the two devices, we found both cell types growing three-dimensionally within multicellular spheroids (MCS) and also cells remaining adherent (AD) to the culture flask, while 1g-control cultures only formed adherent monolayers, unless the bottom of the culture dish was covered by agarose. In this case, the cytokines IL-6 and IL-8 facilitated the formation of MCS in both cell lines using the liquid-overlay technique at 1g. ML-1 cells grown on the RPM or the CLINO released amounts of IL-6 and MCP-1 into the supernatant, which were significantly elevated as compared to 1g-controls. Release of IL-4, IL-7, IL-8, IL-17, eotaxin-1 and VEGF increased time-dependently, but was not significantly influenced by the gravity conditions. After 3d on the RPM or the CLINO, an accumulation of F-actin around the cellular membrane was detectable in AD cells of both cell lines. IL-6 and IL-8 stimulation of ML-1 cells for 3d and 7d influenced the protein contents of ß1-integrin, talin-1, Ki-67, and beta-actin dose-dependently in adherent cells. The ß1-integrin content was significantly decreased in AD and MCS samples compared with 1g, while talin-1 was higher expressed in MCS than AD populations. The proliferation marker Ki-67 was elevated in AD samples compared with 1g and MCS samples. The ß-actin content of R082-W-1 cells remained unchanged. ML-1 cells exhibited no change in ß-actin in RPM cultures, but a reduction in CLINO samples. Thus, we concluded that simulated microgravity influences the release of cytokines in follicular thyroid cancer cells, and the production of ß1-integrin and talin-1 and predicts an identical effect under real microgravity conditions. PMID:26274317

  5. Proteomic Profiling of Macrophages by 2D Electrophoresis

    PubMed Central

    Bouvet, Marion; Turkieh, Annie; Acosta-Martin, Adelina E.; Chwastyniak, Maggy; Beseme, Olivia; Amouyel, Philippe; Pinet, Florence

    2014-01-01

    The goal of the two-dimensional (2D) electrophoresis protocol described here is to show how to analyse the phenotype of human cultured macrophages. The key role of macrophages has been shown in various pathological disorders such as inflammatory, immunological, and infectious diseases. In this protocol, we use primary cultures of human monocyte-derived macrophages that can be differentiated into the M1 (pro-inflammatory) or the M2 (anti-inflammatory) phenotype. This in vitro model is reliable for studying the biological activities of M1 and M2 macrophages and also for a proteomic approach. Proteomic techniques are useful for comparing the phenotype and behaviour of M1 and M2 macrophages during host pathogenicity. 2D gel electrophoresis is a powerful proteomic technique for mapping large numbers of proteins or polypeptides simultaneously. We describe the protocol of 2D electrophoresis using fluorescent dyes, named 2D Differential Gel Electrophoresis (DIGE). The M1 and M2 macrophages proteins are labelled with cyanine dyes before separation by isoelectric focusing, according to their isoelectric point in the first dimension, and their molecular mass, in the second dimension. Separated protein or polypeptidic spots are then used to detect differences in protein or polypeptide expression levels. The proteomic approaches described here allows the investigation of the macrophage protein changes associated with various disorders like host pathogenicity or microbial toxins. PMID:25408153

  6. Staring 2-D hadamard transform spectral imager

    DOEpatents

    Gentry, Stephen M.; Wehlburg, Christine M.; Wehlburg, Joseph C.; Smith, Mark W.; Smith, Jody L.

    2006-02-07

    A staring imaging system inputs a 2D spatial image containing multi-frequency spectral information. This image is encoded in one dimension of the image with a cyclic Hadamarid S-matrix. The resulting image is detecting with a spatial 2D detector; and a computer applies a Hadamard transform to recover the encoded image.

  7. Measuring the equation of state for a 2D colloidal membrane: A microfluidic approach to buffer exchange

    NASA Astrophysics Data System (ADS)

    Balchunas, Andrew; Cabanas, Rafael; Fraden, Seth; Dogic, Zvonimir

    Previous work has shown that monodisperse rod-like colloidal particles, such as a filamentous bacteriophage, self assemble into a 2D monolayer smectic in the presence of a non-adsorbing depleting polymer. These structures have the same functional form of bending rigidity and lateral compressibility as conventional lipid bi-layers, so we name the monolayer smectic a colloidal membrane. We have developed a microfluidic device such that the osmotic pressure acting on a colloidal membrane may be controlled via a full in situ buffer exchange. Rod density within individual colloidal membranes was measured as a function of osmotic pressure and a first order phase transition, from 2D fluid to 2D solid, was observed. kon and koff rates of rod to membrane binding were measured by lowering the osmotic pressure until membrane evaporation occurred.

  8. Liver Cell Culture Devices

    PubMed Central

    Andria, B.; Bracco, A.; Cirino, G.; Chamuleau, R. A. F. M.

    2010-01-01

    In the last 15 years many different liver cell culture devices, consisting of functional liver cells and artificial materials, have been developed. They have been devised for numerous different applications, such as temporary organ replacement (a bridge to liver transplantation or native liver regeneration) and as in vitro screening systems in the early stages of the drug development process, like assessing hepatotoxicity, hepatic drug metabolism, and induction/inhibition studies. Relevant literature is summarized about artificial human liver cell culture systems by scrutinizing PubMed from 2003 to 2009. Existing devices are divided in 2D configurations (e.g., static monolayer, sandwich, perfused cells, and flat plate) and 3D configurations (e.g., liver slices, spheroids, and different types of bioreactors). The essential features of an ideal liver cell culture system are discussed: different types of scaffolds, oxygenation systems, extracellular matrixes (natural and artificial), cocultures with nonparenchymal cells, and the role of shear stress problems. Finally, miniaturization and high-throughput systems are discussed. All these factors contribute in their own way to the viability and functionality of liver cells in culture. Depending on the aim for which they are designed, several good systems are available for predicting hepatotoxicity and hepatic metabolism within the general population. To predict hepatotoxicity in individual cases genomic analysis might be essential as well. PMID:26998397

  9. Vertical 2D/3D Semiconductor Heterostructures Based on Epitaxial Molybdenum Disulfide and Gallium Nitride.

    PubMed

    Ruzmetov, Dmitry; Zhang, Kehao; Stan, Gheorghe; Kalanyan, Berc; Bhimanapati, Ganesh R; Eichfeld, Sarah M; Burke, Robert A; Shah, Pankaj B; O'Regan, Terrance P; Crowne, Frank J; Birdwell, A Glen; Robinson, Joshua A; Davydov, Albert V; Ivanov, Tony G

    2016-03-22

    When designing semiconductor heterostructures, it is expected that epitaxial alignment will facilitate low-defect interfaces and efficient vertical transport. Here, we report lattice-matched epitaxial growth of molybdenum disulfide (MoS2) directly on gallium nitride (GaN), resulting in high-quality, unstrained, single-layer MoS2 with strict registry to the GaN lattice. These results present a promising path toward the implementation of high-performance electronic devices based on 2D/3D vertical heterostructures, where each of the 3D and 2D semiconductors is both a template for subsequent epitaxial growth and an active component of the device. The MoS2 monolayer triangles average 1 μm along each side, with monolayer blankets (merged triangles) exhibiting properties similar to that of single-crystal MoS2 sheets. Photoluminescence, Raman, atomic force microscopy, and X-ray photoelectron spectroscopy analyses identified monolayer MoS2 with a prominent 20-fold enhancement of photoluminescence in the center regions of larger triangles. The MoS2/GaN structures are shown to electrically conduct in the out-of-plane direction, confirming the potential of directly synthesized 2D/3D semiconductor heterostructures for vertical current flow. Finally, we estimate a MoS2/GaN contact resistivity to be less than 4 Ω·cm(2) and current spreading in the MoS2 monolayer of approximately 1 μm in diameter. PMID:26866442

  10. Vertical 2D/3D Semiconductor Heterostructures Based on Epitaxial Molybdenum Disulfide and Gallium Nitride.

    PubMed

    Ruzmetov, Dmitry; Zhang, Kehao; Stan, Gheorghe; Kalanyan, Berc; Bhimanapati, Ganesh R; Eichfeld, Sarah M; Burke, Robert A; Shah, Pankaj B; O'Regan, Terrance P; Crowne, Frank J; Birdwell, A Glen; Robinson, Joshua A; Davydov, Albert V; Ivanov, Tony G

    2016-03-22

    When designing semiconductor heterostructures, it is expected that epitaxial alignment will facilitate low-defect interfaces and efficient vertical transport. Here, we report lattice-matched epitaxial growth of molybdenum disulfide (MoS2) directly on gallium nitride (GaN), resulting in high-quality, unstrained, single-layer MoS2 with strict registry to the GaN lattice. These results present a promising path toward the implementation of high-performance electronic devices based on 2D/3D vertical heterostructures, where each of the 3D and 2D semiconductors is both a template for subsequent epitaxial growth and an active component of the device. The MoS2 monolayer triangles average 1 μm along each side, with monolayer blankets (merged triangles) exhibiting properties similar to that of single-crystal MoS2 sheets. Photoluminescence, Raman, atomic force microscopy, and X-ray photoelectron spectroscopy analyses identified monolayer MoS2 with a prominent 20-fold enhancement of photoluminescence in the center regions of larger triangles. The MoS2/GaN structures are shown to electrically conduct in the out-of-plane direction, confirming the potential of directly synthesized 2D/3D semiconductor heterostructures for vertical current flow. Finally, we estimate a MoS2/GaN contact resistivity to be less than 4 Ω·cm(2) and current spreading in the MoS2 monolayer of approximately 1 μm in diameter.

  11. Treponema pallidum Invades Intercellular Junctions of Endothelial Cell Monolayers

    NASA Astrophysics Data System (ADS)

    Thomas, D. Denee; Navab, Mahamad; Haake, David A.; Fogelman, Alan M.; Miller, James N.; Lovett, Michael A.

    1988-05-01

    The pathogenesis of syphilis reflects invasive properties of Treponema pallidum, but the actual mode of tissue invasion is unknown. We have found two in vitro parallels of treponemal invasiveness. We tested whether motile T. pallidum could invade host cells by determining the fate of radiolabeled motile organisms added to a HeLa cell monolayer; 26% of treponemes associated with the monolayer in a trypsin-resistant niche, presumably between the monolayer and the surface to which it adhered, but did not attain intracellularity. Attachment of T. pallidum to cultured human and rabbit aortic and human umbilical vein endothelial cells was 2-fold greater than to HeLa cells. We added T. pallidum to aortic endothelial cells grown on membrane filters under conditions in which tight intercellular junctions had formed. T. pallidum was able to pass through the endothelial cell monolayers without altering tight junctions, as measured by electrical resistance. In contrast, heat-killed T. pallidum and the nonpathogen Treponema phagedenis biotype Reiter failed to penetrate the monolayer. Transmission electron micrographs of sections of the monolayer showed T. pallidum in intercellular junctions. Our in vitro observations suggest that these highly motile spirochetes may leave the circulation by invading the junctions between endothelial cells.

  12. 2D materials for nanophotonic devices

    NASA Astrophysics Data System (ADS)

    Xu, Renjing; Yang, Jiong; Zhang, Shuang; Pei, Jiajie; Lu, Yuerui

    2015-12-01

    Two-dimensional (2D) materials have become very important building blocks for electronic, photonic, and phononic devices. The 2D material family has four key members, including the metallic graphene, transition metal dichalcogenide (TMD) layered semiconductors, semiconducting black phosphorous, and the insulating h-BN. Owing to the strong quantum confinements and defect-free surfaces, these atomically thin layers have offered us perfect platforms to investigate the interactions among photons, electrons and phonons. The unique interactions in these 2D materials are very important for both scientific research and application engineering. In this talk, I would like to briefly summarize and highlight the key findings, opportunities and challenges in this field. Next, I will introduce/highlight our recent achievements. We demonstrated atomically thin micro-lens and gratings using 2D MoS2, which is the thinnest optical component around the world. These devices are based on our discovery that the elastic light-matter interactions in highindex 2D materials is very strong. Also, I would like to introduce a new two-dimensional material phosphorene. Phosphorene has strongly anisotropic optical response, which creates 1D excitons in a 2D system. The strong confinement in phosphorene also enables the ultra-high trion (charged exciton) binding energies, which have been successfully measured in our experiments. Finally, I will briefly talk about the potential applications of 2D materials in energy harvesting.

  13. Internal Photoemission Spectroscopy of 2-D Materials

    NASA Astrophysics Data System (ADS)

    Nguyen, Nhan; Li, Mingda; Vishwanath, Suresh; Yan, Rusen; Xiao, Shudong; Xing, Huili; Cheng, Guangjun; Hight Walker, Angela; Zhang, Qin

    Recent research has shown the great benefits of using 2-D materials in the tunnel field-effect transistor (TFET), which is considered a promising candidate for the beyond-CMOS technology. The on-state current of TFET can be enhanced by engineering the band alignment of different 2D-2D or 2D-3D heterostructures. Here we present the internal photoemission spectroscopy (IPE) approach to determine the band alignments of various 2-D materials, in particular SnSe2 and WSe2, which have been proposed for new TFET designs. The metal-oxide-2-D semiconductor test structures are fabricated and characterized by IPE, where the band offsets from the 2-D semiconductor to the oxide conduction band minimum are determined by the threshold of the cube root of IPE yields as a function of photon energy. In particular, we find that SnSe2 has a larger electron affinity than most semiconductors and can be combined with other semiconductors to form near broken-gap heterojunctions with low barrier heights which can produce a higher on-state current. The details of data analysis of IPE and the results from Raman spectroscopy and spectroscopic ellipsometry measurements will also be presented and discussed.

  14. Interface formation in monolayer graphene-boron nitride heterostructures.

    PubMed

    Sutter, P; Cortes, R; Lahiri, J; Sutter, E

    2012-09-12

    The ability to control the formation of interfaces between different materials has become one of the foundations of modern materials science. With the advent of two-dimensional (2D) crystals, low-dimensional equivalents of conventional interfaces can be envisioned: line boundaries separating different materials integrated in a single 2D sheet. Graphene and hexagonal boron nitride offer an attractive system from which to build such 2D heterostructures. They are isostructural, nearly lattice-matched, and isoelectronic, yet their different band structures promise interesting functional properties arising from their integration. Here, we use a combination of in situ microscopy techniques to study the growth and interface formation of monolayer graphene-boron nitride heterostructures on ruthenium. In a sequential chemical vapor deposition process, boron nitride grows preferentially at the edges of existing monolayer graphene domains, which can be exploited for synthesizing continuous 2D membranes of graphene embedded in boron nitride. High-temperature growth leads to intermixing near the interface, similar to interfacial alloying in conventional heterostructures. Using real-time microscopy, we identify processes that eliminate this intermixing and thus pave the way to graphene-boron nitride heterostructures with atomically sharp interfaces.

  15. 2D materials: to graphene and beyond.

    PubMed

    Mas-Ballesté, Rubén; Gómez-Navarro, Cristina; Gómez-Herrero, Julio; Zamora, Félix

    2011-01-01

    This review is an attempt to illustrate the different alternatives in the field of 2D materials. Graphene seems to be just the tip of the iceberg and we show how the discovery of alternative 2D materials is starting to show the rest of this iceberg. The review comprises the current state-of-the-art of the vast literature in concepts and methods already known for isolation and characterization of graphene, and rationalizes the quite disperse literature in other 2D materials such as metal oxides, hydroxides and chalcogenides, and metal-organic frameworks.

  16. Time-lapse ultrashort pulse microscopy of infection in three-dimensional versus two-dimensional culture environments reveals enhanced extra-chromosomal virus replication compartment formation

    NASA Astrophysics Data System (ADS)

    Gibbs, Holly C.; Sing, Garwin; Armas, Juan Carlos González; Campbell, Colin J.; Ghazal, Peter; Yeh, Alvin T.

    2013-03-01

    The mechanisms that enable viruses to harness cellular machinery for their own survival are primarily studied in cell lines cultured in two-dimensional (2-D) environments. However, there are increasing reports of biological differences between cells cultured in 2-D versus three-dimensional (3-D) environments. Here we report differences in host-virus interactions based on differences in culture environment. Using ultrashort pulse microscopy (UPM), a form of two-photon microscopy that utilizes sub-10-fs pulses to efficiently excite fluorophores, we have shown that de novo development of extra-chromosomal virus replication compartments (VRCs) upon murine cytomegalovirus (mCMV) infection is markedly enhanced when host cells are cultured in 3-D collagen gels versus 2-D monolayers. In addition, time-lapse imaging revealed that mCMV-induced VRCs have the capacity to grow by coalescence. This work supports the future potential of 3-D culture as a useful bridge between traditional monolayer cultures and animal models to study host-virus interactions in a more physiologically relevant environment for the development of effective anti-viral therapeutics. These advances will require broader adoption of modalities, such as UPM, to image deep within scattering tissues.

  17. 2-d Finite Element Code Postprocessor

    1996-07-15

    ORION is an interactive program that serves as a postprocessor for the analysis programs NIKE2D, DYNA2D, TOPAZ2D, and CHEMICAL TOPAZ2D. ORION reads binary plot files generated by the two-dimensional finite element codes currently used by the Methods Development Group at LLNL. Contour and color fringe plots of a large number of quantities may be displayed on meshes consisting of triangular and quadrilateral elements. ORION can compute strain measures, interface pressures along slide lines, reaction forcesmore » along constrained boundaries, and momentum. ORION has been applied to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.« less

  18. Matrix models of 2d gravity

    SciTech Connect

    Ginsparg, P.

    1991-01-01

    These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.

  19. Matrix models of 2d gravity

    SciTech Connect

    Ginsparg, P.

    1991-12-31

    These are introductory lectures for a general audience that give an overview of the subject of matrix models and their application to random surfaces, 2d gravity, and string theory. They are intentionally 1.5 years out of date.

  20. Brittle damage models in DYNA2D

    SciTech Connect

    Faux, D.R.

    1997-09-01

    DYNA2D is an explicit Lagrangian finite element code used to model dynamic events where stress wave interactions influence the overall response of the system. DYNA2D is often used to model penetration problems involving ductile-to-ductile impacts; however, with the advent of the use of ceramics in the armor-anti-armor community and the need to model damage to laser optics components, good brittle damage models are now needed in DYNA2D. This report will detail the implementation of four brittle damage models in DYNA2D, three scalar damage models and one tensor damage model. These new brittle damage models are then used to predict experimental results from three distinctly different glass damage problems.

  1. Correlating Structural and Electronic Degrees of Freedom in 2D Transition Metal Dichalcogenides

    NASA Astrophysics Data System (ADS)

    Tung, I.-Cheng; Zhang, Z.; Seyler, K. L.; Jones, A. M.; Clark, G.; Xiao, D.; Laanait, N.; Xu, X.; Wen, H.

    We have conducted a microscopic study of the interplay between structural and electronic degrees of freedom in two-dimensional (2D) transition metal dichalcogenide (TMD) monolayers, multilayers and heterostructures. Using the recently developed full field x-ray reflection interface microscopy with the photoluminescence microscopic probe capability at the Advanced Photon Source, we demonstrated the x-ray reflection imaging of a monolayer 2D material for the first time. The structural variation across an exfoliated WSe2 monolayer is quantified by interlayer spacing relative to the crystal substrate and the smoothness of the layer. This structural information is correlated with the electronic properties of TMDs characterized by the in-situ photoluminescence measurements. This work is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-SC0012509. The use of Advanced Photon Source is supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-06CH11357.

  2. Chemical Approaches to 2D Materials.

    PubMed

    Samorì, Paolo; Palermo, Vincenzo; Feng, Xinliang

    2016-08-01

    Chemistry plays an ever-increasing role in the production, functionalization, processing and applications of graphene and other 2D materials. This special issue highlights a selection of enlightening chemical approaches to 2D materials, which nicely reflect the breadth of the field and convey the excitement of the individuals involved in it, who are trying to translate graphene and related materials from the laboratory into a real, high-impact technology. PMID:27478083

  3. Chemical Approaches to 2D Materials.

    PubMed

    Samorì, Paolo; Palermo, Vincenzo; Feng, Xinliang

    2016-08-01

    Chemistry plays an ever-increasing role in the production, functionalization, processing and applications of graphene and other 2D materials. This special issue highlights a selection of enlightening chemical approaches to 2D materials, which nicely reflect the breadth of the field and convey the excitement of the individuals involved in it, who are trying to translate graphene and related materials from the laboratory into a real, high-impact technology.

  4. 2d index and surface operators

    NASA Astrophysics Data System (ADS)

    Gadde, Abhijit; Gukov, Sergei

    2014-03-01

    In this paper we compute the superconformal index of 2d (2, 2) supersymmetric gauge theories. The 2d superconformal index, a.k.a. flavored elliptic genus, is computed by a unitary matrix integral much like the matrix integral that computes the 4d superconformal index. We compute the 2d index explicitly for a number of examples. In the case of abelian gauge theories we see that the index is invariant under flop transition and under CY-LG correspondence. The index also provides a powerful check of the Seiberg-type duality for non-abelian gauge theories discovered by Hori and Tong. In the later half of the paper, we study half-BPS surface operators in = 2 super-conformal gauge theories. They are engineered by coupling the 2d (2, 2) supersymmetric gauge theory living on the support of the surface operator to the 4d = 2 theory, so that different realizations of the same surface operator with a given Levi type are related by a 2d analogue of the Seiberg duality. The index of this coupled system is computed by using the tools developed in the first half of the paper. The superconformal index in the presence of surface defect is expected to be invariant under generalized S-duality. We demonstrate that it is indeed the case. In doing so the Seiberg-type duality of the 2d theory plays an important role.

  5. Effective enrichment of cholangiocarcinoma secretomes using the hollow fiber bioreactor culture system.

    PubMed

    Weeraphan, Churat; Diskul-Na-Ayudthaya, Penchatr; Chiablaem, Khajeelak; Khongmanee, Amnart; Chokchaichamnankit, Daranee; Subhasitanont, Pantipa; Svasti, Jisnuson; Srisomsap, Chantragan

    2012-09-15

    The Northeastern region of Thailand is well known to have high incidence of bile duct cancer known as cholangiocarcinoma. So there is a continued need to improve diagnosis and treatment, and discovery of biomarkers for early detection of bile duct cancer should greatly improve treatment outcome for these patients. The secretome, a collection of proteins secreted from cells, is a useful source for identifying circulating biomarkers in blood secreted from cancer cells. Here a Hollow Fiber Bioreactor culture system was used for enrichment of cholangiocarcinoma secretomes, since this culture system mimics the dense three-dimensional microenvironment of the tumor found in vivo. Two-dimensional fluorescence difference gel electrophoresis using a sensitive Fluor saturation dye staining, followed by LC/MS/MS, was used to compare protein expression in the secretomes of cells cultured in the Hollow Fiber system and cells cultured in the monolayer culture system. For the first time, the 2D-patterns of cholangiocarcinoma secretomes from the two culture systems could be compared. The Hollow Fiber system improved the quality and quantity of cholangiocarcinoma secreted proteins compared to conventional monolayer system, showing less interference by cytoplasmic proteins and yielding more secreted proteins. Overall, 75 spots were analyzed by LC/MS/MS and 106 secreted proteins were identified. Two novel secreted proteins (C19orf10 and cystatin B) were found only in the Hollow Fiber system and were absent from the traditional monolayer culture system. Among the highly expressed proteins, 22 secreted soluble proteins were enriched by 5 fold in Hollow Fiber system compared to monolayer culture system. The Hollow Fiber system is therefore useful for preparing a wide range of proteins from low-abundance cell secretomes.

  6. Electro-mechanical sensing in freestanding monolayered gold nanoparticle membranes.

    PubMed

    Gauvin, M; Grisolia, J; Alnasser, T; Viallet, B; Xie, S; Brugger, J; Ressier, L

    2016-06-01

    The electro-mechanical sensing properties of freestanding monolayered membranes of dodecanethiol coated 7 nm gold nanoparticles (NPs) are investigated using AFM force spectroscopy and conductive AFM simultaneously. The electrical resistance of the NP membranes increases sensitively with the point-load force applied in the center of the membranes using an AFM tip. Numerical simulations of electronic conduction in a hexagonally close-packed two-dimensional (2D) array of NPs under point load-deformation are carried out on the basis of electronic transport measurements at low temperatures and strain modeling of the NP membranes by finite element analysis. These simulations, supporting AFM-based electro-mechanical measurements, attribute the high strain sensitivity of the monolayered NP membranes to the exponential dependence of the tunnel electron transport in 2D NP arrays on the strain-induced length variation of the interparticle junctions. This work thus evidences a new class of highly sensitive nano-electro-mechanical systems based on freestanding monolayered gold NP membranes. PMID:27194578

  7. Epitaxial MoS2/GaN structures to enable vertical 2D/3D semiconductor heterostructure devices

    NASA Astrophysics Data System (ADS)

    Ruzmetov, D.; Zhang, K.; Stan, G.; Kalanyan, B.; Eichfeld, S.; Burke, R.; Shah, P.; O'Regan, T.; Crowne, F.; Birdwell, A. G.; Robinson, J.; Davydov, A.; Ivanov, T.

    MoS2/GaN structures are investigated as a building block for vertical 2D/3D semiconductor heterostructure devices that utilize a 3D substrate (GaN) as an active component of the semiconductor device without the need of mechanical transfer of the 2D layer. Our CVD-grown monolayer MoS2 has been shown to be epitaxially aligned to the GaN lattice which is a pre-requisite for high quality 2D/3D interfaces desired for efficient vertical transport and large area growth. The MoS2 coverage is nearly 50 % including isolated triangles and monolayer islands. The GaN template is a double-layer grown by MOCVD on sapphire and allows for measurement of transport perpendicular to the 2D layer. Photoluminescence, Raman, XPS, Kelvin force probe microscopy, and SEM analysis identified high quality monolayer MoS2. The MoS2/GaN structures electrically conduct in the out-of-plane direction and across the van der Waals gap, as measured with conducting AFM (CAFM). The CAFM current maps and I-V characteristics are analyzed to estimate the MoS2/GaN contact resistivity to be less than 4 Ω-cm2 and current spreading in the MoS2 monolayer to be approx. 1 μm in diameter. Epitaxial MoS2/GaN heterostructures present a promising platform for the design of energy-efficient, high-speed vertical devices incorporating 2D layered materials with 3D semiconductors.

  8. Universal Scaling of Correlated Diffusion in Colloidal Monolayers

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Li, Na; Bohinc, Klemen; Tong, Penger; Chen, Wei

    2013-10-01

    Using the techniques of optical microscopy and particle tracking, we measure the correlated diffusion in a monolayer of uniform silica spheres dispersed at a water-air interface. It is found that the correlated motion of the interfacial particles can be well described by two universal response functions, the normalized longitudinal and transverse diffusion coefficients D˜∥(r/r0) and D˜⊥(r/r0), where r is the interparticle distance and r0=a(λS/a)3/2 is a new scaling length, which depends on both the Saffman length λS and particle radius a. The obtained response functions characterize the crossover behavior of the colloidal monolayers from the subphase-dominated three-dimensional hydrodynamics at low surface coverage to the monolayer-dominated 2D hydrodynamics at high concentrations. The surface viscosity ηs(2) of the colloidal monolayer obtained by two-particle rheology compares well with the one-particle measurements.

  9. Phenomenological Modeling for Langmuir Monolayers

    NASA Astrophysics Data System (ADS)

    Baptiste, Dimitri; Kelly, David; Safford, Twymun; Prayaga, Chandra; Varney, Christopher N.; Wade, Aaron

    Experimentally, Langmuir monolayers have applications in molecular optical, electronic, and sensor devices. Traditionally, Langmuir monolayers are described by a rigid rod model where the rods interact via a Leonard-Jones potential. Here, we propose effective phenomenological models and utilize Monte Carlo simulations to analyze the phase behavior and compare with experimental isotherms. Research reported in this abstract was supported by UWF NIH MARC U-STAR 1T34GM110517-01.

  10. Digital transfer growth of patterned 2D metal chalcogenides by confined nanoparticle evaporation.

    PubMed

    Mahjouri-Samani, Masoud; Tian, Mengkun; Wang, Kai; Boulesbaa, Abdelaziz; Rouleau, Christopher M; Puretzky, Alexander A; McGuire, Michael A; Srijanto, Bernadeta R; Xiao, Kai; Eres, Gyula; Duscher, Gerd; Geohegan, David B

    2014-11-25

    Developing methods for the facile synthesis of two-dimensional (2D) metal chalcogenides and other layered materials is crucial for emerging applications in functional devices. Controlling the stoichiometry, number of the layers, crystallite size, growth location, and areal uniformity is challenging in conventional vapor-phase synthesis. Here, we demonstrate a method to control these parameters in the growth of metal chalcogenide (GaSe) and dichalcogenide (MoSe2) 2D crystals by precisely defining the mass and location of the source materials in a confined transfer growth system. A uniform and precise amount of stoichiometric nanoparticles are first synthesized and deposited onto a substrate by pulsed laser deposition (PLD) at room temperature. This source substrate is then covered with a receiver substrate to form a confined vapor transport growth (VTG) system. By simply heating the source substrate in an inert background gas, a natural temperature gradient is formed that evaporates the confined nanoparticles to grow large, crystalline 2D nanosheets on the cooler receiver substrate, the temperature of which is controlled by the background gas pressure. Large monolayer crystalline domains (∼100 μm lateral sizes) of GaSe and MoSe2 are demonstrated, as well as continuous monolayer films through the deposition of additional precursor materials. This PLD-VTG synthesis and processing method offers a unique approach for the controlled growth of large-area metal chalcogenides with a controlled number of layers in patterned growth locations for optoelectronics and energy related applications.

  11. Digital Transfer Growth of Patterned 2D Metal Chalcogenides by Confined Nanoparticle Evaporation

    SciTech Connect

    Mahjouri-Samani, Masoud; Tian, Mengkun; Wang, Kai; Boulesbaa, Abdelaziz; Rouleau, Christopher M.; Puretzky, Alexander A.; McGuire, Michael A.; Srijanto, Bernadeta R.; Xiao, Kai; Eres, Gyula; Duscher, Gerd; Geohegan, David B.

    2014-10-19

    Developing methods for the facile synthesis of two-dimensional (2D) metal chalcogenides and other layered materials is crucial for emerging applications in functional devices. Controlling the stoichiometry, number of the layers, crystallite size, growth location, and areal uniformity is challenging in conventional vapor phase synthesis. Here, we demonstrate a new route to control these parameters in the growth of metal chalcogenide (GaSe) and dichalcogenide (MoSe2) 2D crystals by precisely defining the mass and location of the source materials in a confined transfer growth system. A uniform and precise amount of stoichiometric nanoparticles are first synthesized and deposited onto a substrate by pulsed laser deposition (PLD) at room temperature. This source substrate is then covered with a receiver substrate to form a confined vapor transport growth (VTG) system. By simply heating the source substrate in an inert background gas, a natural temperature gradient is formed that evaporates the confined nanoparticles to grow large, crystalline 2D nanosheets on the cooler receiver substrate, the temperature of which is controlled by the background gas pressure. Large monolayer crystalline domains (~ 100 m lateral sizes) of GaSe and MoSe2 are demonstrated, as well as continuous monolayer films through the deposition of additional precursor materials. This novel PLD-VTG synthesis and processing method offers a unique approach for the controlled growth of large-area, metal chalcogenides with a controlled number of layers in patterned growth locations for optoelectronics and energy related applications.

  12. Electronic, transport, and optical properties of bulk and mono-layer PdSe{sub 2}

    SciTech Connect

    Sun, Jifeng; Shi, Hongliang; Siegrist, Theo; Singh, David J.

    2015-10-12

    The electronic and optical properties of bulk and monolayer PdSe{sub 2} are investigated using first-principles calculations. Using the modified Becke-Johnson potential, we find semiconductor behavior for both bulk and monolayer PdSe{sub 2} with indirect gap values of 0.03 eV for bulk and 1.43 eV for monolayer, respectively. Our sheet optical conductivity results support this observation and show similar anisotropic feature in the 2D plane. We further study the thermoelectric properties of the 2D PdSe{sub 2} using Blotzmann transport model and find interestingly high Seebeck coefficients (>200 μV/K) for both p- and n-type up to high doping level (∼2 × 10{sup 13} cm{sup −2}) with an anisotropic character in an electrical conductivity suggesting better thermoelectric performance along y direction in the plane.

  13. Electronic, transport, and optical properties of bulk and mono-layer PdSe2

    DOE PAGES

    Sun, Jifeng; Shi, Hongliang; Siegrist, Theo; Singh, David J.

    2015-10-13

    In this study, the electronic and optical properties of bulk and monolayer PdSe2 are investigated using firstprinciples calculations. Using the modified Becke-Johnson potential, we find semiconductor behavior for both bulk and monolayer PdSe2 with indirect gap values of 0.03 eV for bulk and 1.43 eV for monolayer, respectively. Our sheet optical conductivity results support this observation and show similar anisotropic feature in the 2D plane. We further study the thermoelectric properties of the 2D PdSe2 using Blotzmann transport model and find interestingly high Seebeck coefficients (>200 μV/K) for both p- and n-type up to high doping level (–2 x 1013more » cm2) with an anisotropic character in an electrical conductivity suggesting better thermoelectric performance along y direction in the plane.V« less

  14. Phase Transitions in Dipalmitoylphosphatidylcholine Monolayers.

    PubMed

    Zuo, Yi Y; Chen, Rimei; Wang, Xianju; Yang, Jinlong; Policova, Zdenka; Neumann, A Wilhelm

    2016-08-23

    A self-assembled phospholipid monolayer at an air-water interface is a well-defined model system for studying surface thermodynamics, membrane biophysics, thin-film materials, and colloidal soft matter. Here we report a study of two-dimensional phase transitions in the dipalmitoylphosphatidylcholine (DPPC) monolayer at the air-water interface using a newly developed methodology called constrained drop surfactometry (CDS). CDS is superior to the classical Langmuir balance in its capacity for rigorous temperature control and leak-proof environments, thus making it an ideal alternative to the Langmuir balance for studying lipid polymorphism. In addition, we have developed a novel Langmuir-Blodgett (LB) transfer technique that allows the direct transfer of lipid monolayers from the droplet surface under well-controlled conditions. This LB transfer technique permits the direct visualization of phase coexistence in the DPPC monolayer. With these technological advances, we found that the two-dimensional phase behavior of the DPPC monolayer is analogous to the three-dimensional phase transition of a pure substance. This study has implications in the fundamental understanding of surface thermodynamics as well as applications such as self-assembled monolayers and pulmonary surfactant biophysics. PMID:27479299

  15. Vertical uniformity of cells and nuclei in epithelial monolayers.

    PubMed

    Neelam, Srujana; Hayes, Peter Robert; Zhang, Qiao; Dickinson, Richard B; Lele, Tanmay P

    2016-01-22

    Morphological variability in cytoskeletal organization, organelle position and cell boundaries is a common feature of cultured cells. Remarkable uniformity and reproducibility in structure can be accomplished by providing cells with defined geometric cues. Cells in tissues can also self-organize in the absence of directing extracellular cues; however the mechanical principles for such self-organization are not understood. We report that unlike horizontal shapes, the vertical shapes of the cell and nucleus in the z-dimension are uniform in cells in cultured monolayers compared to isolated cells. Apical surfaces of cells and their nuclei in monolayers were flat and heights were uniform. In contrast, isolated cells, or cells with disrupted cell-cell adhesions had nuclei with curved apical surfaces and variable heights. Isolated cells cultured within micron-sized square wells displayed flat cell and nuclear shapes similar to cells in monolayers. Local disruption of nuclear-cytoskeletal linkages resulted in spatial variation in vertical uniformity. These results suggest that competition between cell-cell pulling forces that expand and shorten the vertical cell cross-section, thereby widening and flattening the nucleus, and the resistance of the nucleus to further flattening results in uniform cell and nuclear cross-sections. Our results reveal the mechanical principles of self-organized vertical uniformity in cell monolayers.

  16. Vertical uniformity of cells and nuclei in epithelial monolayers.

    PubMed

    Neelam, Srujana; Hayes, Peter Robert; Zhang, Qiao; Dickinson, Richard B; Lele, Tanmay P

    2016-01-01

    Morphological variability in cytoskeletal organization, organelle position and cell boundaries is a common feature of cultured cells. Remarkable uniformity and reproducibility in structure can be accomplished by providing cells with defined geometric cues. Cells in tissues can also self-organize in the absence of directing extracellular cues; however the mechanical principles for such self-organization are not understood. We report that unlike horizontal shapes, the vertical shapes of the cell and nucleus in the z-dimension are uniform in cells in cultured monolayers compared to isolated cells. Apical surfaces of cells and their nuclei in monolayers were flat and heights were uniform. In contrast, isolated cells, or cells with disrupted cell-cell adhesions had nuclei with curved apical surfaces and variable heights. Isolated cells cultured within micron-sized square wells displayed flat cell and nuclear shapes similar to cells in monolayers. Local disruption of nuclear-cytoskeletal linkages resulted in spatial variation in vertical uniformity. These results suggest that competition between cell-cell pulling forces that expand and shorten the vertical cell cross-section, thereby widening and flattening the nucleus, and the resistance of the nucleus to further flattening results in uniform cell and nuclear cross-sections. Our results reveal the mechanical principles of self-organized vertical uniformity in cell monolayers. PMID:26795751

  17. Vertical uniformity of cells and nuclei in epithelial monolayers

    PubMed Central

    Neelam, Srujana; Hayes, Peter Robert; Zhang, Qiao; Dickinson, Richard B.; Lele, Tanmay P.

    2016-01-01

    Morphological variability in cytoskeletal organization, organelle position and cell boundaries is a common feature of cultured cells. Remarkable uniformity and reproducibility in structure can be accomplished by providing cells with defined geometric cues. Cells in tissues can also self-organize in the absence of directing extracellular cues; however the mechanical principles for such self-organization are not understood. We report that unlike horizontal shapes, the vertical shapes of the cell and nucleus in the z-dimension are uniform in cells in cultured monolayers compared to isolated cells. Apical surfaces of cells and their nuclei in monolayers were flat and heights were uniform. In contrast, isolated cells, or cells with disrupted cell-cell adhesions had nuclei with curved apical surfaces and variable heights. Isolated cells cultured within micron-sized square wells displayed flat cell and nuclear shapes similar to cells in monolayers. Local disruption of nuclear-cytoskeletal linkages resulted in spatial variation in vertical uniformity. These results suggest that competition between cell-cell pulling forces that expand and shorten the vertical cell cross-section, thereby widening and flattening the nucleus, and the resistance of the nucleus to further flattening results in uniform cell and nuclear cross-sections. Our results reveal the mechanical principles of self-organized vertical uniformity in cell monolayers. PMID:26795751

  18. Orthotropic Piezoelectricity in 2D Nanocellulose

    NASA Astrophysics Data System (ADS)

    García, Y.; Ruiz-Blanco, Yasser B.; Marrero-Ponce, Yovani; Sotomayor-Torres, C. M.

    2016-10-01

    The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V‑1, ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies.

  19. Orthotropic Piezoelectricity in 2D Nanocellulose

    PubMed Central

    García, Y.; Ruiz-Blanco, Yasser B.; Marrero-Ponce, Yovani; Sotomayor-Torres, C. M.

    2016-01-01

    The control of electromechanical responses within bonding regions is essential to face frontier challenges in nanotechnologies, such as molecular electronics and biotechnology. Here, we present Iβ-nanocellulose as a potentially new orthotropic 2D piezoelectric crystal. The predicted in-layer piezoelectricity is originated on a sui-generis hydrogen bonds pattern. Upon this fact and by using a combination of ab-initio and ad-hoc models, we introduce a description of electrical profiles along chemical bonds. Such developments lead to obtain a rationale for modelling the extended piezoelectric effect originated within bond scales. The order of magnitude estimated for the 2D Iβ-nanocellulose piezoelectric response, ~pm V−1, ranks this material at the level of currently used piezoelectric energy generators and new artificial 2D designs. Such finding would be crucial for developing alternative materials to drive emerging nanotechnologies. PMID:27708364

  20. 2D microwave imaging reflectometer electronics

    SciTech Connect

    Spear, A. G.; Domier, C. W. Hu, X.; Muscatello, C. M.; Ren, X.; Luhmann, N. C.; Tobias, B. J.

    2014-11-15

    A 2D microwave imaging reflectometer system has been developed to visualize electron density fluctuations on the DIII-D tokamak. Simultaneously illuminated at four probe frequencies, large aperture optics image reflections from four density-dependent cutoff surfaces in the plasma over an extended region of the DIII-D plasma. Localized density fluctuations in the vicinity of the plasma cutoff surfaces modulate the plasma reflections, yielding a 2D image of electron density fluctuations. Details are presented of the receiver down conversion electronics that generate the in-phase (I) and quadrature (Q) reflectometer signals from which 2D density fluctuation data are obtained. Also presented are details on the control system and backplane used to manage the electronics as well as an introduction to the computer based control program.

  1. Optical modulators with 2D layered materials

    NASA Astrophysics Data System (ADS)

    Sun, Zhipei; Martinez, Amos; Wang, Feng

    2016-04-01

    Light modulation is an essential operation in photonics and optoelectronics. With existing and emerging technologies increasingly demanding compact, efficient, fast and broadband optical modulators, high-performance light modulation solutions are becoming indispensable. The recent realization that 2D layered materials could modulate light with superior performance has prompted intense research and significant advances, paving the way for realistic applications. In this Review, we cover the state of the art of optical modulators based on 2D materials, including graphene, transition metal dichalcogenides and black phosphorus. We discuss recent advances employing hybrid structures, such as 2D heterostructures, plasmonic structures, and silicon and fibre integrated structures. We also take a look at the future perspectives and discuss the potential of yet relatively unexplored mechanisms, such as magneto-optic and acousto-optic modulation.

  2. Activated neutrophils disrupt endothelial monolayer integrity by an oxygen radical-independent mechanism

    SciTech Connect

    Harlan, J.M.; Schwartz, B.R.; Reidy, M.A.; Schwartz, S.M.; Ochs, H.D.; Harker, L.A.

    1985-02-01

    The effect of activated neutrophils on endothelial monolayer integrity in vitro has been measured by assessing the capacity of endothelial monolayers on polycarbonate filters to exclude /sup 125/I-albumin. Although formylmethionyl-leucyl-phenylalanine (FMLP)-activated neutrophils failed to induce /sup 51/Cr-release or detachment after 4 hours of incubation with endothelial monolayers cultured in polystyrene wells, FMLP-activated neutrophils produced a marked increase in the passage of /sup 125/I-albumin across bovine aortic or pulmonary artery endothelial monolayers on polycarbonate filters. This effect was evident as early as 30 minutes following the addition of FMLP-activated neutrophils to the monolayer and reached 180% over control values at 2 hours (p . 0.001). Light and transmission electron microscopic examination of the polycarbonate filters exposed to FMLP-activated neutrophils revealed focal disruption of the endothelial monolayers. Chronic granulomatous disease neutrophils produced similar disruption of the endothelial monolayer at 2 hours. Moreover, catalase and superoxide dismutase failed to reduce significantly the neutrophil-mediated increase in /sup 125/I-albumin passage at 2 hours. Cell-free postsecretory supernatants of FMLP-activated neutrophils, leukotriene C4, and platelet activating factor did not induce a significant increase in /sup 125/I-albumin passage across the endothelial monolayers. Of note, FMLP-activated neutrophils from a patient with a congenital abnormality of neutrophil adhesion and chemotaxis did not induce disruption of the monolayer or increase /sup 125/I-albumin passage.

  3. Exploring the relative bending of a CVD graphene monolayer with gap-plasmons.

    PubMed

    Min, Young Hwan; Park, Won-Hwa

    2014-08-21

    We report a spectroscopic indicator showing the bending of a chemical vapor deposition (CVD) graphene monolayer on Cu foil or an arbitrary substrate after transfer. Using a Au nanoparticle (NP)-graphene monolayer-Au thin film (TF) junction system, the Radial Breathing-Like Mode (RBLM) Raman signal from the sandwiched graphene monolayer is evidently observed by employing a local z-polarized incident field formed at the Au NP-Au TF junction. We also utilized the RBLM intensity as a quantitative tool with a wide dynamic range (∼300%) compared to the 2D peak width (∼35%) for determining the relative degree of bending on the Au TF substrate. The RBLM signal from the CVD graphene monolayer is anticipated to be used as a valuable marker in exploring out-of-plane directional properties.

  4. Inkjet printing of 2D layered materials.

    PubMed

    Li, Jiantong; Lemme, Max C; Östling, Mikael

    2014-11-10

    Inkjet printing of 2D layered materials, such as graphene and MoS2, has attracted great interests for emerging electronics. However, incompatible rheology, low concentration, severe aggregation and toxicity of solvents constitute critical challenges which hamper the manufacturing efficiency and product quality. Here, we introduce a simple and general technology concept (distillation-assisted solvent exchange) to efficiently overcome these challenges. By implementing the concept, we have demonstrated excellent jetting performance, ideal printing patterns and a variety of promising applications for inkjet printing of 2D layered materials. PMID:25169938

  5. Inkjet printing of 2D layered materials.

    PubMed

    Li, Jiantong; Lemme, Max C; Östling, Mikael

    2014-11-10

    Inkjet printing of 2D layered materials, such as graphene and MoS2, has attracted great interests for emerging electronics. However, incompatible rheology, low concentration, severe aggregation and toxicity of solvents constitute critical challenges which hamper the manufacturing efficiency and product quality. Here, we introduce a simple and general technology concept (distillation-assisted solvent exchange) to efficiently overcome these challenges. By implementing the concept, we have demonstrated excellent jetting performance, ideal printing patterns and a variety of promising applications for inkjet printing of 2D layered materials.

  6. Microstructure analysis of monodisperse ferrofluid monolayers: theory and simulation.

    PubMed

    Kantorovich, Sofia; Cerdà, Juan J; Holm, Christian

    2008-04-14

    We try to elucidate the microstructure formation in a monodisperse ferrofluid monolayer. The system under study consists of soft sphere magnetic dipolar particles confined to a thin fluid layer. The positions of the particles are constrained to a 2D geometry, whereas the particle magnetic dipole moments are not fixed to the body systems, and are free to rotate in 3 dimensions, hence forming in what we call a quasi-2D geometry. Using a combination of analytical density functional theory and molecular dynamics (MD) simulations, we find that for the studied range of parameters the majority of aggregates might be divided into two types: chains and rings. Their sizes and area fractions are strongly influenced by the geometrical constraints. We show that for quasi-2D systems the excluded area effects play one of the most important parts in the microstructure formation. The simulation technique and the theoretical model put forward in the present paper agree qualitatively with the results of recent in situ observations of the microstructures observed in ferrofluid monolayers [M. Klokkenberg, R. P. A. Dullens, W. K. Regel, B. H. Erné, A. P. Philipse, Phys. Rev. Lett., 2006, 96, 037203]. PMID:18368181

  7. Microscale 3D collagen cell culture assays in conventional flat-bottom 384-well plates.

    PubMed

    Leung, Brendan M; Moraes, Christopher; Cavnar, Stephen P; Luker, Kathryn E; Luker, Gary D; Takayama, Shuichi

    2015-04-01

    Three-dimensional (3D) culture systems such as cell-laden hydrogels are superior to standard two-dimensional (2D) monolayer cultures for many drug-screening applications. However, their adoption into high-throughput screening (HTS) has been lagging, in part because of the difficulty of incorporating these culture formats into existing robotic liquid handling and imaging infrastructures. Dispensing cell-laden prepolymer solutions into 2D well plates is a potential solution but typically requires large volumes of reagents to avoid evaporation during polymerization, which (1) increases costs, (2) makes drug penetration variable and (3) complicates imaging. Here we describe a technique to efficiently produce 3D microgels using automated liquid-handling systems and standard, nonpatterned, flat-bottomed, 384-well plates. Sub-millimeter-diameter, cell-laden collagen gels are deposited on the bottom of a ~2.5 mm diameter microwell with no concerns about evaporation or meniscus effects at the edges of wells, using aqueous two-phase system patterning. The microscale cell-laden collagen-gel constructs are readily imaged and readily penetrated by drugs. The cytotoxicity of chemotherapeutics was monitored by bioluminescence and demonstrated that 3D cultures confer chemoresistance as compared with similar 2D cultures. Hence, these data demonstrate the importance of culturing cells in 3D to obtain realistic cellular responses. Overall, this system provides a simple and inexpensive method for integrating 3D culture capability into existing HTS infrastructure. PMID:25510473

  8. Epithelial-to-mesenchymal transition in pancreatic ductal adenocarcinoma: Characterization in a 3D-cell culture model

    PubMed Central

    Gagliano, Nicoletta; Celesti, Giuseppe; Tacchini, Lorenza; Pluchino, Stefano; Sforza, Chiarella; Rasile, Marco; Valerio, Vincenza; Laghi, Luigi; Conte, Vincenzo; Procacci, Patrizia

    2016-01-01

    AIM: To analyze the effect of three-dimensional (3D)-arrangement on the expression of epithelial-to-mesenchymal transition markers in pancreatic adenocarcinoma (PDAC) cells. METHODS: HPAF-II, HPAC, and PL45 PDAC cells were cultured in either 2D-monolayers or 3D-spheroids. Ultrastructure was analyzed by transmission electron microscopy. The expression of E-cadherin, β-catenin, N-cadherin, collagen type I (COL-I), vimentin, α-smooth muscle actin (αSMA), and podoplanin was assayed by confocal microscopy in cells cultured on 12-mm diameter round coverslips and in 3D-spheroids. Gene expression for E-cadherin, Snail, Slug, Twist, Zeb1, and Zeb2 was quantified by real-time PCR. E-cadherin protein level and its electrophoretic pattern were studied by Western blot in cell lysates obtained from cells grown in 2D-monolayers and 3D-spheroids. RESULTS: The E-cadherin/β-catenin complex was expressed in a similar way in plasma membrane cell boundaries in both 2D-monolayers and 3D-spheroids. E-cadherin increased in lysates obtained from 3D-spheroids, while cleavage fragments were more evident in 2D-monolayers. N-cadherin expression was observed in very few PDAC cells grown in 2D-monolayers, but was more evident in 3D-spheroids. Some cells expressing COL-I were observed in 3D-spheroids. Podoplanin, expressed in collectively migrating cells, and αSMA were similarly expressed in both experimental conditions. The concomitant maintenance of the E-cadherin/β-catenin complex at cell boundaries supports the hypothesis of a collective migration for these cells, which is consistent with podoplanin expression. CONCLUSION: We show that a 3D-cell culture model could provide deeper insight into understanding the biology of PDAC and allow for the detection of marked differences in the phenotype of PDAC cells grown in 3D-spheroids. PMID:27182158

  9. Experimental Investigation of Microbially Induced Corrosion of Test Samples and Effect of Self-Assembled Hydrophobic Monolayers. Exposure of Test Samples to Continuous Microbial Cultures, Chemical Analysis, and Biochemical Studies

    SciTech Connect

    Laurinavichius, K.S.

    1998-09-30

    The study of biocorrosion of aluminum and beryllium samples were performed under conditions of continuous fermentation of thermophilic anaerobic microorganisms of different groups. This allowed us to examine the effect of various types of metabolic reactions of reduction-oxidation proceeding at different pH and temperatures under highly reduced conditions on aluminum and beryllium corrosion and effect of self-assembled hydrophobic monolayers.

  10. Exploring the relative bending of a CVD graphene monolayer with gap-plasmons

    NASA Astrophysics Data System (ADS)

    Min, Young Hwan; Park, Won-Hwa

    2014-07-01

    We report a spectroscopic indicator showing the bending of a chemical vapor deposition (CVD) graphene monolayer on Cu foil or an arbitrary substrate after transfer. Using a Au nanoparticle (NP)-graphene monolayer-Au thin film (TF) junction system, the Radial Breathing-Like Mode (RBLM) Raman signal from the sandwiched graphene monolayer is evidently observed by employing a local z-polarized incident field formed at the Au NP-Au TF junction. We also utilized the RBLM intensity as a quantitative tool with a wide dynamic range (~300%) compared to the 2D peak width (~35%) for determining the relative degree of bending on the Au TF substrate. The RBLM signal from the CVD graphene monolayer is anticipated to be used as a valuable marker in exploring out-of-plane directional properties.We report a spectroscopic indicator showing the bending of a chemical vapor deposition (CVD) graphene monolayer on Cu foil or an arbitrary substrate after transfer. Using a Au nanoparticle (NP)-graphene monolayer-Au thin film (TF) junction system, the Radial Breathing-Like Mode (RBLM) Raman signal from the sandwiched graphene monolayer is evidently observed by employing a local z-polarized incident field formed at the Au NP-Au TF junction. We also utilized the RBLM intensity as a quantitative tool with a wide dynamic range (~300%) compared to the 2D peak width (~35%) for determining the relative degree of bending on the Au TF substrate. The RBLM signal from the CVD graphene monolayer is anticipated to be used as a valuable marker in exploring out-of-plane directional properties. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr01586j

  11. Parallel stitching of 2D materials

    DOE PAGES

    Ling, Xi; Wu, Lijun; Lin, Yuxuan; Ma, Qiong; Wang, Ziqiang; Song, Yi; Yu, Lili; Huang, Shengxi; Fang, Wenjing; Zhang, Xu; et al

    2016-01-27

    Diverse parallel stitched 2D heterostructures, including metal–semiconductor, semiconductor–semiconductor, and insulator–semiconductor, are synthesized directly through selective “sowing” of aromatic molecules as the seeds in the chemical vapor deposition (CVD) method. Lastly, the methodology enables the large-scale fabrication of lateral heterostructures, which offers tremendous potential for its application in integrated circuits.

  12. Parallel Stitching of 2D Materials.

    PubMed

    Ling, Xi; Lin, Yuxuan; Ma, Qiong; Wang, Ziqiang; Song, Yi; Yu, Lili; Huang, Shengxi; Fang, Wenjing; Zhang, Xu; Hsu, Allen L; Bie, Yaqing; Lee, Yi-Hsien; Zhu, Yimei; Wu, Lijun; Li, Ju; Jarillo-Herrero, Pablo; Dresselhaus, Mildred; Palacios, Tomás; Kong, Jing

    2016-03-23

    Diverse parallel stitched 2D heterostructures, including metal-semiconductor, semiconductor-semiconductor, and insulator-semiconductor, are synthesized directly through selective "sowing" of aromatic molecules as the seeds in the chemical vapor deposition (CVD) method. The methodology enables the large-scale fabrication of lateral heterostructures, which offers tremendous potential for its application in integrated circuits.

  13. Optical Stark effect in 2D semiconductors

    NASA Astrophysics Data System (ADS)

    Sie, Edbert J.; McIver, James W.; Lee, Yi-Hsien; Fu, Liang; Kong, Jing; Gedik, Nuh

    2016-05-01

    Semiconductors that are atomically thin can exhibit novel optical properties beyond those encountered in the bulk compounds. Monolayer transition-metal dichalcogenides (TMDs) are leading examples of such semiconductors that possess remarkable optical properties. They obey unique selection rules where light with different circular polarization can be used for selective photoexcitation at two different valleys in the momentum space. These valleys constitute bandgaps that are normally locked in the same energy. Selectively varying their energies is of great interest for applications because it unlocks the potential to control valley degree of freedom, and offers a new promising way to carry information in next-generation valleytronics. In this proceeding paper, we show that the energy gaps at the two valleys can be shifted relative to each other by means of the optical Stark effect in a controllable valley-selective manner. We discuss the physics of the optical Stark effect, and we describe the mechanism that leads to its valleyselectivity in monolayer TMD tungsten disulfide (WS2).

  14. Superlubric-pinned Aubry transition of two dimensional monolayers in optical lattices

    NASA Astrophysics Data System (ADS)

    Mandelli, Davide; Vanossi, Andrea; Manini, Nicola; Tosatti, Erio

    Two-dimensional (2D) crystalline colloidal monolayers sliding over a laser-induced optical lattice ``corrugation'' potential emulate friction between ideal crystal surfaces. Static friction is always present when the monolayer and the optical lattices are commensurate, but when they are incommensurate the presence or absence of static friction depends upon the system parameters. In 1D, at the Aubry dynamical phase transition the static friction goes continuously from zero (superlubricity) to finite as the periodic corrugation strength is increased. We look for the Aubry-like transition in the more realistic 2D case of a monolayer in an incommensurate periodic potential using molecular dynamics simulations. Results confirm a clear and sharp 2D superlubric-pinned transition upon increasing corrugation strength. Unlike the 1D Aubry transition which is continuous, the 2D transition is first-order, with a jump of static friction. At the 2D Aubry transition there is no change of symmetry, a sudden rise of the colloid-colloid interaction energy, and a compensating drop of the colloid-corrugation energy. The observability of the superlubric-pinned colloid transition is proposed and discussed. This work has been supported by ERC Advanced Grant N. 320796 MODPHYSFRICT.

  15. Lithium-Boron (Li-B) Monolayers: First-Principles Cluster Expansion and Possible Two-Dimensional Superconductivity.

    PubMed

    Wu, Chao; Wang, Hua; Zhang, Jiajia; Gou, Gaoyang; Pan, Bicai; Li, Ju

    2016-02-01

    Recent works demonstrated that the superconductivity at two-dimensional (2-D) can be achieved in Li-decorated graphene (Nature Phys. 2012, 8, 131 and Proc. Natl. Acad. Sci. 2015, 112, 11795). Inspired by the progress made in graphene, we predict by using the first-principles calculations that Li-incorporated B monolayers (Li-B monolayers) can be alternative 2-D superconductors. First-principles cluster expansion approach was used to evaluate the structural diversity and energetic stability of the 2-D Li-B monolayers by treating them as ternary Lix⬡yB1-x-y pseudoalloys (⬡ refers to B hexagonal hole). After thoroughly exploring the Li-B configuration space, several well-ordered and stable Li-B monolayers were identified. Detailed analyses regarding the electronic structures and lattice dynamics properties of the predicted Li-B monolayers were performed. Compared with the non-superconducting pure B-sheet, some predicted Li-B monolayers can exhibit the phonon-mediated superconducting properties above the liquid helium temperature.

  16. Lithium-Boron (Li-B) Monolayers: First-Principles Cluster Expansion and Possible Two-Dimensional Superconductivity.

    PubMed

    Wu, Chao; Wang, Hua; Zhang, Jiajia; Gou, Gaoyang; Pan, Bicai; Li, Ju

    2016-02-01

    Recent works demonstrated that the superconductivity at two-dimensional (2-D) can be achieved in Li-decorated graphene (Nature Phys. 2012, 8, 131 and Proc. Natl. Acad. Sci. 2015, 112, 11795). Inspired by the progress made in graphene, we predict by using the first-principles calculations that Li-incorporated B monolayers (Li-B monolayers) can be alternative 2-D superconductors. First-principles cluster expansion approach was used to evaluate the structural diversity and energetic stability of the 2-D Li-B monolayers by treating them as ternary Lix⬡yB1-x-y pseudoalloys (⬡ refers to B hexagonal hole). After thoroughly exploring the Li-B configuration space, several well-ordered and stable Li-B monolayers were identified. Detailed analyses regarding the electronic structures and lattice dynamics properties of the predicted Li-B monolayers were performed. Compared with the non-superconducting pure B-sheet, some predicted Li-B monolayers can exhibit the phonon-mediated superconducting properties above the liquid helium temperature. PMID:26732306

  17. Monolayer coated aerogels and method of making

    DOEpatents

    Zemanian, Thomas Samuel; Fryxell, Glen; Ustyugov, Oleksiy A.

    2006-03-28

    Aerogels having a monolayer coating are described. The aerogel and a monolayer forming precursor are provided in a supercritical fluid, whereupon the aerogel and the monolayer forming precursor are reacted in said supercritical fluid to form a covalent bond between the aerogel and the monolayer forming precursor. Suitable aerogels are ceramic oxides such as silica, alumina, aluminosilicate, and combinations thereof. Suitable monolayer forming precursors include alkyl silanes, chlorosilanes, boranes, chloroboranes, germanes, and combinations thereof. The method may also include providing a surface preparation agent such as water, or hydroetching an aerogel to enhance the coating of the monolayer.

  18. Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology

    PubMed Central

    Shavanova, Kateryna; Bakakina, Yulia; Burkova, Inna; Shtepliuk, Ivan; Viter, Roman; Ubelis, Arnolds; Beni, Valerio; Starodub, Nickolaj; Yakimova, Rositsa; Khranovskyy, Volodymyr

    2016-01-01

    The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct “beyond graphene” domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials. PMID:26861346

  19. Application of 2D Non-Graphene Materials and 2D Oxide Nanostructures for Biosensing Technology.

    PubMed

    Shavanova, Kateryna; Bakakina, Yulia; Burkova, Inna; Shtepliuk, Ivan; Viter, Roman; Ubelis, Arnolds; Beni, Valerio; Starodub, Nickolaj; Yakimova, Rositsa; Khranovskyy, Volodymyr

    2016-01-01

    The discovery of graphene and its unique properties has inspired researchers to try to invent other two-dimensional (2D) materials. After considerable research effort, a distinct "beyond graphene" domain has been established, comprising the library of non-graphene 2D materials. It is significant that some 2D non-graphene materials possess solid advantages over their predecessor, such as having a direct band gap, and therefore are highly promising for a number of applications. These applications are not limited to nano- and opto-electronics, but have a strong potential in biosensing technologies, as one example. However, since most of the 2D non-graphene materials have been newly discovered, most of the research efforts are concentrated on material synthesis and the investigation of the properties of the material. Applications of 2D non-graphene materials are still at the embryonic stage, and the integration of 2D non-graphene materials into devices is scarcely reported. However, in recent years, numerous reports have blossomed about 2D material-based biosensors, evidencing the growing potential of 2D non-graphene materials for biosensing applications. This review highlights the recent progress in research on the potential of using 2D non-graphene materials and similar oxide nanostructures for different types of biosensors (optical and electrochemical). A wide range of biological targets, such as glucose, dopamine, cortisol, DNA, IgG, bisphenol, ascorbic acid, cytochrome and estradiol, has been reported to be successfully detected by biosensors with transducers made of 2D non-graphene materials.

  20. 2D crystals of transition metal dichalcogenide and their iontronic functionalities

    NASA Astrophysics Data System (ADS)

    Zhang, Y. J.; Yoshida, M.; Suzuki, R.; Iwasa, Y.

    2015-12-01

    2D crystals based on transition metal dichalcogenides (TMDs) provide a unique platform of novel physical properties and functionalities, including photoluminescence, laser, valleytronics, spintronics, piezoelectric devices, field effect transistors (FETs), and superconductivity. Among them, FET devices are extremely useful because of voltage-tunable carrier density and Fermi energy. In particular, high density charge accumulation in electric double layer transistor (EDLT), which is a FET device driven by ionic motions, is playing key roles for expanding the functionalities of TMD based 2D crystals. Here, we report several device concepts which were realized by introducing EDLTs in TMDs, taking the advantage of their extremely unique band structures and phase transition phenomena realized simply by thinning to the monolayer level. We address two kinds of TMDs based on group VI and group V transition metals, which basically yield semiconductors and metals, respectively. For each system, we first introduce peculiar characteristics of TMDs achieved by thinning the crystals, followed by the related FET functionalities.

  1. Convective microsphere monolayer deposition

    NASA Astrophysics Data System (ADS)

    Gilchrist, James

    2011-03-01

    There is perhaps no simpler way of modifying surface chemistry and morphology than surface deposition of particles. Micron-sized microspheres were deposited into thin films via rapid convective deposition, similar to the `coffee ring effect' using a similar method to that studied by Prevo and Velev, Langmuir, 2003. By varying deposition rate and blade angle, the optimal operating ranges in which 2D close-packed arrays of microspheres existed were obtained. Self-assembly of colloidal particles through a balance of electrostatic and capillary forces during solvent evaporation was revealed. These interactions were explored through a model comparing the residence time of a particle in the thin film and the characteristic time of capillary-driven crystallization to describe the morphology and microstructure of deposited particles. Co-deposition of binary suspensions of micron and nanoscale particles was tailored to generate higher-quality surface coatings and a simple theory describes the immergence of instabilities that result in formation of stripes. Optical and biomedical applications that utilize the described nanoscale control over surface morphology will also be discussed.

  2. Stochastic Inversion of 2D Magnetotelluric Data

    SciTech Connect

    Chen, Jinsong

    2010-07-01

    The algorithm is developed to invert 2D magnetotelluric (MT) data based on sharp boundary parametrization using a Bayesian framework. Within the algorithm, we consider the locations and the resistivity of regions formed by the interfaces are as unknowns. We use a parallel, adaptive finite-element algorithm to forward simulate frequency-domain MT responses of 2D conductivity structure. Those unknown parameters are spatially correlated and are described by a geostatistical model. The joint posterior probability distribution function is explored by Markov Chain Monte Carlo (MCMC) sampling methods. The developed stochastic model is effective for estimating the interface locations and resistivity. Most importantly, it provides details uncertainty information on each unknown parameter. Hardware requirements: PC, Supercomputer, Multi-platform, Workstation; Software requirements C and Fortan; Operation Systems/version is Linux/Unix or Windows

  3. Explicit 2-D Hydrodynamic FEM Program

    1996-08-07

    DYNA2D* is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D* contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. Themore » isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.« less

  4. Stochastic Inversion of 2D Magnetotelluric Data

    2010-07-01

    The algorithm is developed to invert 2D magnetotelluric (MT) data based on sharp boundary parametrization using a Bayesian framework. Within the algorithm, we consider the locations and the resistivity of regions formed by the interfaces are as unknowns. We use a parallel, adaptive finite-element algorithm to forward simulate frequency-domain MT responses of 2D conductivity structure. Those unknown parameters are spatially correlated and are described by a geostatistical model. The joint posterior probability distribution function ismore » explored by Markov Chain Monte Carlo (MCMC) sampling methods. The developed stochastic model is effective for estimating the interface locations and resistivity. Most importantly, it provides details uncertainty information on each unknown parameter. Hardware requirements: PC, Supercomputer, Multi-platform, Workstation; Software requirements C and Fortan; Operation Systems/version is Linux/Unix or Windows« less

  5. Static & Dynamic Response of 2D Solids

    1996-07-15

    NIKE2D is an implicit finite-element code for analyzing the finite deformation, static and dynamic response of two-dimensional, axisymmetric, plane strain, and plane stress solids. The code is fully vectorized and available on several computing platforms. A number of material models are incorporated to simulate a wide range of material behavior including elasto-placicity, anisotropy, creep, thermal effects, and rate dependence. Slideline algorithms model gaps and sliding along material interfaces, including interface friction, penetration and single surfacemore » contact. Interactive-graphics and rezoning is included for analyses with large mesh distortions. In addition to quasi-Newton and arc-length procedures, adaptive algorithms can be defined to solve the implicit equations using the solution language ISLAND. Each of these capabilities and more make NIKE2D a robust analysis tool.« less

  6. Static & Dynamic Response of 2D Solids

    SciTech Connect

    Lin, Jerry

    1996-07-15

    NIKE2D is an implicit finite-element code for analyzing the finite deformation, static and dynamic response of two-dimensional, axisymmetric, plane strain, and plane stress solids. The code is fully vectorized and available on several computing platforms. A number of material models are incorporated to simulate a wide range of material behavior including elasto-placicity, anisotropy, creep, thermal effects, and rate dependence. Slideline algorithms model gaps and sliding along material interfaces, including interface friction, penetration and single surface contact. Interactive-graphics and rezoning is included for analyses with large mesh distortions. In addition to quasi-Newton and arc-length procedures, adaptive algorithms can be defined to solve the implicit equations using the solution language ISLAND. Each of these capabilities and more make NIKE2D a robust analysis tool.

  7. Explicit 2-D Hydrodynamic FEM Program

    SciTech Connect

    Lin, Jerry

    1996-08-07

    DYNA2D* is a vectorized, explicit, two-dimensional, axisymmetric and plane strain finite element program for analyzing the large deformation dynamic and hydrodynamic response of inelastic solids. DYNA2D* contains 13 material models and 9 equations of state (EOS) to cover a wide range of material behavior. The material models implemented in all machine versions are: elastic, orthotropic elastic, kinematic/isotropic elastic plasticity, thermoelastoplastic, soil and crushable foam, linear viscoelastic, rubber, high explosive burn, isotropic elastic-plastic, temperature-dependent elastic-plastic. The isotropic and temperature-dependent elastic-plastic models determine only the deviatoric stresses. Pressure is determined by one of 9 equations of state including linear polynomial, JWL high explosive, Sack Tuesday high explosive, Gruneisen, ratio of polynomials, linear polynomial with energy deposition, ignition and growth of reaction in HE, tabulated compaction, and tabulated.

  8. 2D photonic-crystal optomechanical nanoresonator.

    PubMed

    Makles, K; Antoni, T; Kuhn, A G; Deléglise, S; Briant, T; Cohadon, P-F; Braive, R; Beaudoin, G; Pinard, L; Michel, C; Dolique, V; Flaminio, R; Cagnoli, G; Robert-Philip, I; Heidmann, A

    2015-01-15

    We present the optical optimization of an optomechanical device based on a suspended InP membrane patterned with a 2D near-wavelength grating (NWG) based on a 2D photonic-crystal geometry. We first identify by numerical simulation a set of geometrical parameters providing a reflectivity higher than 99.8% over a 50-nm span. We then study the limitations induced by the finite value of the optical waist and lateral size of the NWG pattern using different numerical approaches. The NWG grating, pierced in a suspended InP 265-nm thick membrane, is used to form a compact microcavity involving the suspended nanomembrane as an end mirror. The resulting cavity has a waist size smaller than 10 μm and a finesse in the 200 range. It is used to probe the Brownian motion of the mechanical modes of the nanomembrane. PMID:25679837

  9. Electromelting of Confined Monolayer Ice

    NASA Astrophysics Data System (ADS)

    Qiu, Hu; Guo, Wanlin

    2013-05-01

    In sharp contrast to the prevailing view that electric fields promote water freezing, here we show by molecular dynamics simulations that monolayer ice confined between two parallel plates can melt into liquid water under a perpendicularly applied electric field. The melting temperature of the monolayer ice decreases with the increasing strength of the external field due to the field-induced disruption of the water-wall interaction induced well-ordered network of the hydrogen bond. This electromelting process should add an important new ingredient to the physics of water.

  10. Electromelting of confined monolayer ice.

    PubMed

    Qiu, Hu; Guo, Wanlin

    2013-05-10

    In sharp contrast to the prevailing view that electric fields promote water freezing, here we show by molecular dynamics simulations that monolayer ice confined between two parallel plates can melt into liquid water under a perpendicularly applied electric field. The melting temperature of the monolayer ice decreases with the increasing strength of the external field due to the field-induced disruption of the water-wall interaction induced well-ordered network of the hydrogen bond. This electromelting process should add an important new ingredient to the physics of water. PMID:23705718

  11. Compact 2-D graphical representation of DNA

    NASA Astrophysics Data System (ADS)

    Randić, Milan; Vračko, Marjan; Zupan, Jure; Novič, Marjana

    2003-05-01

    We present a novel 2-D graphical representation for DNA sequences which has an important advantage over the existing graphical representations of DNA in being very compact. It is based on: (1) use of binary labels for the four nucleic acid bases, and (2) use of the 'worm' curve as template on which binary codes are placed. The approach is illustrated on DNA sequences of the first exon of human β-globin and gorilla β-globin.

  12. 2D materials: Graphene and others

    NASA Astrophysics Data System (ADS)

    Bansal, Suneev Anil; Singh, Amrinder Pal; Kumar, Suresh

    2016-05-01

    Present report reviews the recent advancements in new atomically thick 2D materials. Materials covered in this review are Graphene, Silicene, Germanene, Boron Nitride (BN) and Transition metal chalcogenides (TMC). These materials show extraordinary mechanical, electronic and optical properties which make them suitable candidates for future applications. Apart from unique properties, tune-ability of highly desirable properties of these materials is also an important area to be emphasized on.

  13. Layer Engineering of 2D Semiconductor Junctions.

    PubMed

    He, Yongmin; Sobhani, Ali; Lei, Sidong; Zhang, Zhuhua; Gong, Yongji; Jin, Zehua; Zhou, Wu; Yang, Yingchao; Zhang, Yuan; Wang, Xifan; Yakobson, Boris; Vajtai, Robert; Halas, Naomi J; Li, Bo; Xie, Erqing; Ajayan, Pulickel

    2016-07-01

    A new concept for junction fabrication by connecting multiple regions with varying layer thicknesses, based on the thickness dependence, is demonstrated. This type of junction is only possible in super-thin-layered 2D materials, and exhibits similar characteristics as p-n junctions. Rectification and photovoltaic effects are observed in chemically homogeneous MoSe2 junctions between domains of different thicknesses. PMID:27136275

  14. Realistic and efficient 2D crack simulation

    NASA Astrophysics Data System (ADS)

    Yadegar, Jacob; Liu, Xiaoqing; Singh, Abhishek

    2010-04-01

    Although numerical algorithms for 2D crack simulation have been studied in Modeling and Simulation (M&S) and computer graphics for decades, realism and computational efficiency are still major challenges. In this paper, we introduce a high-fidelity, scalable, adaptive and efficient/runtime 2D crack/fracture simulation system by applying the mathematically elegant Peano-Cesaro triangular meshing/remeshing technique to model the generation of shards/fragments. The recursive fractal sweep associated with the Peano-Cesaro triangulation provides efficient local multi-resolution refinement to any level-of-detail. The generated binary decomposition tree also provides efficient neighbor retrieval mechanism used for mesh element splitting and merging with minimal memory requirements essential for realistic 2D fragment formation. Upon load impact/contact/penetration, a number of factors including impact angle, impact energy, and material properties are all taken into account to produce the criteria of crack initialization, propagation, and termination leading to realistic fractal-like rubble/fragments formation. The aforementioned parameters are used as variables of probabilistic models of cracks/shards formation, making the proposed solution highly adaptive by allowing machine learning mechanisms learn the optimal values for the variables/parameters based on prior benchmark data generated by off-line physics based simulation solutions that produce accurate fractures/shards though at highly non-real time paste. Crack/fracture simulation has been conducted on various load impacts with different initial locations at various impulse scales. The simulation results demonstrate that the proposed system has the capability to realistically and efficiently simulate 2D crack phenomena (such as window shattering and shards generation) with diverse potentials in military and civil M&S applications such as training and mission planning.

  15. 2D Spinodal Decomposition in Forced Turbulence

    NASA Astrophysics Data System (ADS)

    Fan, Xiang; Diamond, Patrick; Chacon, Luis; Li, Hui

    2015-11-01

    Spinodal decomposition is a second order phase transition for binary fluid mixture, from one thermodynamic phase to form two coexisting phases. The governing equation for this coarsening process below critical temperature, Cahn-Hilliard Equation, is very similar to 2D MHD Equation, especially the conserved quantities have a close correspondence between each other, so theories for MHD turbulence are used to study spinodal decomposition in forced turbulence. Domain size is increased with time along with the inverse cascade, and the length scale can be arrested by a forced turbulence with direct cascade. The two competing mechanisms lead to a stabilized domain size length scale, which can be characterized by Hinze Scale. The 2D spinodal decomposition in forced turbulence is studied by both theory and simulation with ``pixie2d.'' This work focuses on the relation between Hinze scale and spectra and cascades. Similarities and differences between spinodal decomposition and MHD are investigated. Also some transport properties are studied following MHD theories. This work is supported by the Department of Energy under Award Number DE-FG02-04ER54738.

  16. MAGNUM-2D computer code: user's guide

    SciTech Connect

    England, R.L.; Kline, N.W.; Ekblad, K.J.; Baca, R.G.

    1985-01-01

    Information relevant to the general use of the MAGNUM-2D computer code is presented. This computer code was developed for the purpose of modeling (i.e., simulating) the thermal and hydraulic conditions in the vicinity of a waste package emplaced in a deep geologic repository. The MAGNUM-2D computer computes (1) the temperature field surrounding the waste package as a function of the heat generation rate of the nuclear waste and thermal properties of the basalt and (2) the hydraulic head distribution and associated groundwater flow fields as a function of the temperature gradients and hydraulic properties of the basalt. MAGNUM-2D is a two-dimensional numerical model for transient or steady-state analysis of coupled heat transfer and groundwater flow in a fractured porous medium. The governing equations consist of a set of coupled, quasi-linear partial differential equations that are solved using a Galerkin finite-element technique. A Newton-Raphson algorithm is embedded in the Galerkin functional to formulate the problem in terms of the incremental changes in the dependent variables. Both triangular and quadrilateral finite elements are used to represent the continuum portions of the spatial domain. Line elements may be used to represent discrete conduits. 18 refs., 4 figs., 1 tab.

  17. Engineering light outcoupling in 2D materials.

    PubMed

    Lien, Der-Hsien; Kang, Jeong Seuk; Amani, Matin; Chen, Kevin; Tosun, Mahmut; Wang, Hsin-Ping; Roy, Tania; Eggleston, Michael S; Wu, Ming C; Dubey, Madan; Lee, Si-Chen; He, Jr-Hau; Javey, Ali

    2015-02-11

    When light is incident on 2D transition metal dichalcogenides (TMDCs), it engages in multiple reflections within underlying substrates, producing interferences that lead to enhancement or attenuation of the incoming and outgoing strength of light. Here, we report a simple method to engineer the light outcoupling in semiconducting TMDCs by modulating their dielectric surroundings. We show that by modulating the thicknesses of underlying substrates and capping layers, the interference caused by substrate can significantly enhance the light absorption and emission of WSe2, resulting in a ∼11 times increase in Raman signal and a ∼30 times increase in the photoluminescence (PL) intensity of WSe2. On the basis of the interference model, we also propose a strategy to control the photonic and optoelectronic properties of thin-layer WSe2. This work demonstrates the utilization of outcoupling engineering in 2D materials and offers a new route toward the realization of novel optoelectronic devices, such as 2D LEDs and solar cells.

  18. Haemoglobin synthesis in K562 erythroleukaemia cells is affected by intimate contact with monolayers of various human cell types.

    PubMed

    Zuhrie, S R; Pearson, J D; Wickramasinghe, S N

    1988-01-01

    The haemoglobin content of K562 erythroleukaemia cells was affected by co-culture over monolayers of various human cell types. Haemoglobin synthesis was increased after co-culture with umbilical-cord-derived endothelial cells and most monolayers of bone-marrow-derived macrophages, and inhibited after co-culture with two fibroblast lines, blood-monocyte-derived macrophages, a neuroglial cell line (U-251 MG) and most monolayers of bone-marrow-derived stromal cells. These effects were modified when a thin layer of agar was placed over the monolayers. Cell-free culture media conditioned by all but two of the seven types of monolayer studied inhibited haemoglobin synthesis by K562 cells; those conditioned by blood-monocyte-derived macrophages and two of 11 monolayers of bone-marrow-derived macrophages stimulated haemoglobin synthesis. Thus, the haemoglobin content of K562 cells appeared to be influenced both by intimate contact between K562 cells and the cells of the monolayers and by humoral factors released by the monolayers. The data support the concept that erythroid differentiation is partly dependent on intimate contact between erythroid progenitor cells and microenvironmental cells.

  19. Two-dimensional freezing criteria for crystallizing colloidal monolayers.

    PubMed

    Wang, Ziren; Alsayed, Ahmed M; Yodh, Arjun G; Han, Yilong

    2010-04-21

    Video microscopy was employed to explore crystallization of colloidal monolayers composed of diameter-tunable microgel spheres. Two-dimensional (2D) colloidal liquids were frozen homogenously into polycrystalline solids, and four 2D criteria for freezing were experimentally tested in thermal systems for the first time: the Hansen-Verlet freezing rule, the Lowen-Palberg-Simon dynamical freezing criterion, and two other rules based, respectively, on the split shoulder of the radial distribution function and on the distribution of the shape factor of Voronoi polygons. Importantly, these freezing criteria, usually applied in the context of single crystals, were demonstrated to apply to the formation of polycrystalline solids. At the freezing point, we also observed a peak in the fluctuations of the orientational order parameter and a percolation transition associated with caged particles. Speculation about these percolated clusters of caged particles casts light on solidification mechanisms and dynamic heterogeneity in freezing. PMID:20423183

  20. Two-dimensional freezing criteria for crystallizing colloidal monolayers

    SciTech Connect

    Wang Ziren; Han Yilong; Alsayed, Ahmed M.

    2010-04-21

    Video microscopy was employed to explore crystallization of colloidal monolayers composed of diameter-tunable microgel spheres. Two-dimensional (2D) colloidal liquids were frozen homogenously into polycrystalline solids, and four 2D criteria for freezing were experimentally tested in thermal systems for the first time: the Hansen-Verlet freezing rule, the Loewen-Palberg-Simon dynamical freezing criterion, and two other rules based, respectively, on the split shoulder of the radial distribution function and on the distribution of the shape factor of Voronoi polygons. Importantly, these freezing criteria, usually applied in the context of single crystals, were demonstrated to apply to the formation of polycrystalline solids. At the freezing point, we also observed a peak in the fluctuations of the orientational order parameter and a percolation transition associated with caged particles. Speculation about these percolated clusters of caged particles casts light on solidification mechanisms and dynamic heterogeneity in freezing.

  1. Raman modes of exfoliated black phosphorus down to the monolayer

    NASA Astrophysics Data System (ADS)

    Phaneuf-L'Heureux, Anne-Laurence; Favron, Alexandre; Gaufres, Etienne; Martel, Richard; Francoeur, Sebastien

    2015-03-01

    Exfoliated black phosphorus layers, or 2D-phosphane, are a lamellar direct-gap semiconductor providing high mobilities and enabling a thickness-controlled band gap tunability ranging from 0.3 up to about 2 eV. Using Raman spectroscopy, we have studied vibrational modes of pristine and non-oxidized 2D-phosphane as a function of the number of layers involved (n), and also as a function of temperature, polarization, and excitation wavelength. The evolution of the width and of the frequency of Ag2 as a function of n presents a clear non-monotonic dependence. This can be explained by the presence of new nearly-degenerate Raman-allowed modes that are symmetry-forbidden in both bulk and monolayer samples. We also present Raman spectra of few-layer samples for excitation wavelengths in the viscinity of the expected band gap.

  2. Interplay between intercalated oxygen superstructures and monolayer h -BN on Cu(100)

    DOE PAGES

    Ma, Chuanxu; Park, Jewook; Liu, Lei; Kim, Yong-Sung; Yoon, Mina; Baddorf, Arthur P.; Gu, Gong; Li, An-Ping

    2016-08-18

    The confinement effect of intercalated atoms in van der Waals heterostructures can lead to interesting interactions between the confined atoms or molecules and the overlaying two-dimensional (2D) materials. In this paper, we report the formation of ordered Cu(100) p(2×2) oxygen superstructures by oxygen intercalation under the monolayer hexagonal boron nitride (h-BN) on Cu after annealing. By using scanning tunneling microscopy and x-ray photoelectron spectroscopy, we identify the superstructure and reveal its roles in passivating the exposed Cu surfaces, decoupling h-BN and Cu, and disintegrating h-BN monolayers. The oxygen superstructure appears as a 2D pattern on the exposed Cu surface ormore » quasi-1D stripes of paired oxygen intercalated in the interface of h-BN and Cu predominantly oriented along the moiré modulations. The oxygen superstructure is shown to etch the overlaying h-BN monolayer in a thermal annealing process. After extended annealing, the h-BN monolayer disintegrates into nanoislands with zigzag edges. Finally, we discuss the implications of these findings on the stability and oxidation resistance of h-BN and relate them to challenges in process integration and 2D heterostructures.« less

  3. Interplay between intercalated oxygen superstructures and monolayer h -BN on Cu(100)

    NASA Astrophysics Data System (ADS)

    Ma, Chuanxu; Park, Jewook; Liu, Lei; Kim, Yong-Sung; Yoon, Mina; Baddorf, Arthur P.; Gu, Gong; Li, An-Ping

    2016-08-01

    The confinement effect of intercalated atoms in van der Waals heterostructures can lead to interesting interactions between the confined atoms or molecules and the overlaying two-dimensional (2D) materials. Here we report the formation of ordered Cu(100) p (2 ×2 ) oxygen superstructures by oxygen intercalation under the monolayer hexagonal boron nitride (h -BN) on Cu after annealing. By using scanning tunneling microscopy and x-ray photoelectron spectroscopy, we identify the superstructure and reveal its roles in passivating the exposed Cu surfaces, decoupling h -BN and Cu, and disintegrating h -BN monolayers. The oxygen superstructure appears as a 2D pattern on the exposed Cu surface or quasi-1D stripes of paired oxygen intercalated in the interface of h -BN and Cu predominantly oriented along the moiré modulations. The oxygen superstructure is shown to etch the overlaying h -BN monolayer in a thermal annealing process. After extended annealing, the h -BN monolayer disintegrates into nanoislands with zigzag edges. We discuss the implications of these findings on the stability and oxidation resistance of h -BN and relate them to challenges in process integration and 2D heterostructures.

  4. Culture.

    ERIC Educational Resources Information Center

    1997

    Twelve conference papers on cultural aspects of second language instruction include: "Towards True Multiculturalism: Ideas for Teachers" (Brian McVeigh); Comparing Cultures Through Critical Thinking: Development and Interpretations of Meaningful Observations" (Laurel D. Kamada); "Authority and Individualism in Japan and the USA" (Alisa Woodring);…

  5. Overexpression of IL-10 in C2D macrophages promotes a macrophage phenotypic switch in adipose tissue environments.

    PubMed

    Xie, Linglin; Fu, Qiang; Ortega, Teresa M; Zhou, Lun; Rasmussen, Dane; O'Keefe, Jacy; Zhang, Ke K; Chapes, Stephen K

    2014-01-01

    Adipose tissue macrophages are a heterogeneous collection of classically activated (M1) and alternatively activated (M2) macrophages. Interleukin 10 (IL-10) is an anti-inflammatory cytokine, secreted by a variety of cell types including M2 macrophages. We generated a macrophage cell line stably overexpressing IL-10 (C2D-IL10) and analyzed the C2D-IL10 cells for several macrophage markers after exposure to adipocytes compared to C2D cells transfected with an empty vector (C2D-vector). C2D-IL10 macrophage cells expressed more CD206 when co-cultured with adipocytes than C2D-vector cells; while the co-cultured cell mixture also expressed higher levels of Il4, Il10, Il1β and Tnf. Since regular C2D cells traffic to adipose tissue after adoptive transfer, we explored the impact of constitutive IL-10 expression on C2D-IL10 macrophages in adipose tissue in vivo. Adipose tissue-isolated C2D-IL10 cells increased the percentage of CD206(+), CD301(+), CD11c(-)CD206(+) (M2) and CD11c(+)CD206(+) (M1b) on their cell surface, compared to isolated C2D-vector cells. These data suggest that the expression of IL-10 remains stable, alters the C2D-IL10 macrophage cell surface phenotype and may play a role in regulating macrophage interactions with the adipose tissue.

  6. Superfluid Onset and 2D phase transitions of Helium-4 on Lithium and Sodium

    NASA Astrophysics Data System (ADS)

    Velasco, Angel; Huisman, Fawn; van Cleve, Eli; Taborek, Peter

    2012-02-01

    We have fabricated lithium and sodium films on quartz crystal microbalances (QCM) using in situ low temperature pulsed laser deposition. The frequency shift and dissipation of the QCM was measured as a function of helium pressure and chemical potential and used to construct the phase diagram of helium films on these substrates. Pressure measurement techniques based on an RGA mass spectrometer, which provides accurate measurement below 10-8 Torr will be described. Lithium and sodium are predicted to be intermediate strength substrates which are strong enough to be wetted by He-4 but weak enough that solid-like layers do not form, so they are candidates for observing sub-monolayer superfluidity in direct contact with a metallic surface. Helium adsorption isotherms and quenches between 0.5K and 1.6K on both lithium and sodium indicated continuous, sub-monolayer helium film growth and superfluid onsets in sub-monolayer films. Features below 1K indicate a collision between a classical 2D liquid/vapor phase transition and the Kosterlitz-Thouless superfluid phase transition. We see no evidence for the pre-wetting step instability predicted for helium on sodium.

  7. Magnetic Properties of Restacked 2D Spin 1/2 honeycomb RuCl3Nanosheets

    NASA Astrophysics Data System (ADS)

    Weber, Daniel; Schoop, Leslie M.; Duppel, Viola; Lippmann, Judith M.; Nuss, Jürgen; Lotsch, Bettina V.

    2016-06-01

    Spin $\\frac{1}{2}$ honeycomb materials have gained substantial interest due to their exotic magnetism and possible application in quantum computing. However, in all current materials out-of-plane interactions are interfering with the in-plane order, hence a true 2D magnetic honeycomb system is still of demand. Here, we report the exfoliation of the magnetic semiconductor $\\alpha$-RuCl$_3$ into the first halide monolayers and the magnetic characterization of the spin $\\frac{1}{2}$ honeycomb arrangement of turbostratically stacked RuCl$_3$ monolayers. The exfoliation is based on a reductive lithiation/hydration approach, which gives rise to a loss of cooperative magnetism due to the disruption of the spin $\\frac{1}{2}$ state by electron injection into the layers. After an oxidative treatment, cooperative magnetism similar to the bulk is restored. The oxidized pellets of restacked single layers feature a magnetic transition at T$_N$ = 7 K in the in-plane direction, while the magnetic properties in the out-of-plane direction vastly differ from bulk $\\alpha$-RuCl$_3$. The macroscopic pellets of RuCl$_3$ therefore behave like a stack of monolayers without any symmetry relation in the stacking direction. The deliberate introduction of turbostratic disorder to manipulate the spin structure of RuCl$_3$ is of interest for research in frustrated magnetism and complex magnetic order as predicted by the Kitaev-Heisenberg model.

  8. Differential Permeability of Proton Isotopes through Graphene and Graphene Analogue Monolayer.

    PubMed

    Zhang, Qiuju; Ju, Minggang; Chen, Liang; Zeng, Xiao Cheng

    2016-09-01

    Two-dimensional (2D) monolayer nanomaterials can be exploited as the thinnest membrane with distinct differential sieving properties for proton isotopes. Motivated from the experimental evidence of differential sieving proton isotopes through graphene and hexagonal boron nitrate (h-BN) monolayer, we compute the kinetic barrier of isotope H(+) and D(+) permeation through model graphene and h-BN fragments at the MP2/6-31++G(d,p) level of theory. On the basis of the ratio of tunneling reaction rate constant, the isotope separation ratio of H(+)/D(+) and H(+)/T(+) is predicted to be ∼12 and 37, respectively. The tunneling reaction rate constant can be estimated from the zero-point-energy computed at the transition state for the proton isotope permeation though the 2D model systems. We show that the presence of Stone-Wales (55-77) defect in the model graphene fragment can significantly lower the proton permeation barrier by 0.55 eV. With the defect, the ratio of tunneling reaction rate constant of H(+)/D(+) is increased to ∼25. In addition to model graphene and h-BN, we have examined proton permeation capability of α-boron monolayer. We compute the tunneling reaction pathway for H(+) through α-boron monolayer using both the climbing nudged elastic band (c-NEB) method and the scanning-path method. Both methods suggest that α-boron monolayer entails a relatively low barrier of ∼0.20 eV for H(+) permeation, much lower than that of the model graphene and h-BN fragments. Our studies provide molecular-level insights into the differential permeation of proton isotopes through 2D materials. The methods can be extended to examine isotope separation capability of other 2D materials as well. PMID:27522866

  9. Differential Permeability of Proton Isotopes through Graphene and Graphene Analogue Monolayer.

    PubMed

    Zhang, Qiuju; Ju, Minggang; Chen, Liang; Zeng, Xiao Cheng

    2016-09-01

    Two-dimensional (2D) monolayer nanomaterials can be exploited as the thinnest membrane with distinct differential sieving properties for proton isotopes. Motivated from the experimental evidence of differential sieving proton isotopes through graphene and hexagonal boron nitrate (h-BN) monolayer, we compute the kinetic barrier of isotope H(+) and D(+) permeation through model graphene and h-BN fragments at the MP2/6-31++G(d,p) level of theory. On the basis of the ratio of tunneling reaction rate constant, the isotope separation ratio of H(+)/D(+) and H(+)/T(+) is predicted to be ∼12 and 37, respectively. The tunneling reaction rate constant can be estimated from the zero-point-energy computed at the transition state for the proton isotope permeation though the 2D model systems. We show that the presence of Stone-Wales (55-77) defect in the model graphene fragment can significantly lower the proton permeation barrier by 0.55 eV. With the defect, the ratio of tunneling reaction rate constant of H(+)/D(+) is increased to ∼25. In addition to model graphene and h-BN, we have examined proton permeation capability of α-boron monolayer. We compute the tunneling reaction pathway for H(+) through α-boron monolayer using both the climbing nudged elastic band (c-NEB) method and the scanning-path method. Both methods suggest that α-boron monolayer entails a relatively low barrier of ∼0.20 eV for H(+) permeation, much lower than that of the model graphene and h-BN fragments. Our studies provide molecular-level insights into the differential permeation of proton isotopes through 2D materials. The methods can be extended to examine isotope separation capability of other 2D materials as well.

  10. Band Gap Engineering in a 2D Material for Solar-to-Chemical Energy Conversion.

    PubMed

    Hu, Jun; Guo, Zhenkun; Mcwilliams, Peter E; Darges, John E; Druffel, Daniel L; Moran, Andrew M; Warren, Scott C

    2016-01-13

    The electronic structure of 2D semiconductors depends on their thickness, providing new opportunities to engineer semiconductors for energy conversion, electronics, and catalysis. Here we show how a 3D semiconductor, black phosphorus, becomes active for solar-to-chemical energy conversion when it is thinned to a 2D material. The increase in its band gap, from 0.3 eV (3D) to 2.1 eV (2D monolayer), is accompanied by a 40-fold enhancement in the formation of chemical products. Despite this enhancement, smaller flakes also have shorter excited state lifetimes. We deduce a mechanism in which recombination occurs at flake edges, while the "van der Waals" surface of black phosphorus bonds to chemical intermediates and facilitates electron transfer. The unique properties of black phosphorus highlight its potential as a customizable material for solar energy conversion and catalysis, while also allowing us to identify design rules for 2D photocatalysts that will enable further improvements in these materials. PMID:26651872

  11. Band Gap Engineering in a 2D Material for Solar-to-Chemical Energy Conversion.

    PubMed

    Hu, Jun; Guo, Zhenkun; Mcwilliams, Peter E; Darges, John E; Druffel, Daniel L; Moran, Andrew M; Warren, Scott C

    2016-01-13

    The electronic structure of 2D semiconductors depends on their thickness, providing new opportunities to engineer semiconductors for energy conversion, electronics, and catalysis. Here we show how a 3D semiconductor, black phosphorus, becomes active for solar-to-chemical energy conversion when it is thinned to a 2D material. The increase in its band gap, from 0.3 eV (3D) to 2.1 eV (2D monolayer), is accompanied by a 40-fold enhancement in the formation of chemical products. Despite this enhancement, smaller flakes also have shorter excited state lifetimes. We deduce a mechanism in which recombination occurs at flake edges, while the "van der Waals" surface of black phosphorus bonds to chemical intermediates and facilitates electron transfer. The unique properties of black phosphorus highlight its potential as a customizable material for solar energy conversion and catalysis, while also allowing us to identify design rules for 2D photocatalysts that will enable further improvements in these materials.

  12. Enhanced Absorption in 2D Materials Via Fano- Resonant Photonic Crystals

    DOE PAGES

    Wang, Wenyi; Klotz, Andrey; Yang, Yuanmu; Li, Wei; Kravchenko, Ivan I.; Briggs, Dayrl P.; Bolotin, Kirill; Valentine, Jason

    2015-05-01

    The use of two-dimensional (2D) materials in optoelectronics has attracted much attention due to their fascinating optical and electrical properties. For instance, graphenebased devices have been employed for applications such as ultrafast and broadband photodetectors and modulators while transition metal dichalcogenide (TMDC) based photodetectors can be used for ultrasensitive photodetection. However, the low optical absorption of 2D materials arising from their atomic thickness limits the maximum attainable external quantum efficiency. For example, in the visible and NIR regimes monolayer MoS2 and graphene absorb only ~10% and 2.3% of incoming light, respectively. Here, we experimentally demonstrate the use of Fano-resonant photonicmore » crystals to significantly boost absorption in atomically thin materials. Using graphene as a test bed, we demonstrate that absorption in the monolayer thick material can be enhanced to 77% within the telecommunications band, the highest value reported to date. We also show that the absorption in the Fano-resonant structure is non-local, with light propagating up to 16 μm within the structure. This property is particularly beneficial in harvesting light from large areas in field-effect-transistor based graphene photodetectors in which separation of photo-generated carriers only occurs ~0.2 μm adjacent to the graphene/electrode interface.« less

  13. Enhanced Absorption in 2D Materials Via Fano- Resonant Photonic Crystals

    SciTech Connect

    Wang, Wenyi; Klotz, Andrey; Yang, Yuanmu; Li, Wei; Kravchenko, Ivan I.; Briggs, Dayrl P.; Bolotin, Kirill; Valentine, Jason

    2015-05-01

    The use of two-dimensional (2D) materials in optoelectronics has attracted much attention due to their fascinating optical and electrical properties. For instance, graphenebased devices have been employed for applications such as ultrafast and broadband photodetectors and modulators while transition metal dichalcogenide (TMDC) based photodetectors can be used for ultrasensitive photodetection. However, the low optical absorption of 2D materials arising from their atomic thickness limits the maximum attainable external quantum efficiency. For example, in the visible and NIR regimes monolayer MoS2 and graphene absorb only ~10% and 2.3% of incoming light, respectively. Here, we experimentally demonstrate the use of Fano-resonant photonic crystals to significantly boost absorption in atomically thin materials. Using graphene as a test bed, we demonstrate that absorption in the monolayer thick material can be enhanced to 77% within the telecommunications band, the highest value reported to date. We also show that the absorption in the Fano-resonant structure is non-local, with light propagating up to 16 μm within the structure. This property is particularly beneficial in harvesting light from large areas in field-effect-transistor based graphene photodetectors in which separation of photo-generated carriers only occurs ~0.2 μm adjacent to the graphene/electrode interface.

  14. Ultraclean and large-area monolayer hexagonal boron nitride on Cu foil using chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wen, Yao; Shang, Xunzhong; Dong, Ji; Xu, Kai; He, Jun; Jiang, Chao

    2015-07-01

    Atomically thin hexagonal boron nitride (h-BN) has been demonstrated to be an excellent dielectric layer as well as an ideal van der Waals epitaxial substrate for fabrication of two-dimensional (2D) atomic layers and their vertical heterostructures. Although many groups have obtained large-scale monolayer h-BN through low pressure chemical vapor deposition (LPCVD), it is still a challenge to grow clean monolayers without the reduction of domain size. Here we report the synthesis of large-area (4 × 2 cm2) high quality monolayer h-BN with an ultraclean and unbroken surface on copper foil by using LPCVD. A detailed investigation of the key factors affecting growth and transfer of the monolayer was carried out in order to eliminate the adverse effects of impurity particles. Furthermore, an optimized transfer approach allowed the nondestructive and clean transfer of the monolayer from copper foil onto an arbitrary substrate, including a flexible substrate, under mild conditions. Atomic force microscopy indicated that the root-mean-square (RMS) roughness of the monolayer h-BN on SiO2 was less than 0.269 nm for areas with fewer wrinkles. Selective area electron diffraction analysis of the h-BN revealed a pattern of hexagonal diffraction spots, which unambiguously demonstrated its highly crystalline character. Our work paves the way toward the use of ultraclean and large-area monolayer h-BN as the dielectric layer in the fabrication of high performance electronic and optoelectronic devices for novel 2D atomic layer materials.

  15. GBL-2D Version 1.0: a 2D geometry boolean library.

    SciTech Connect

    McBride, Cory L. (Elemental Technologies, American Fort, UT); Schmidt, Rodney Cannon; Yarberry, Victor R.; Meyers, Ray J.

    2006-11-01

    This report describes version 1.0 of GBL-2D, a geometric Boolean library for 2D objects. The library is written in C++ and consists of a set of classes and routines. The classes primarily represent geometric data and relationships. Classes are provided for 2D points, lines, arcs, edge uses, loops, surfaces and mask sets. The routines contain algorithms for geometric Boolean operations and utility functions. Routines are provided that incorporate the Boolean operations: Union(OR), XOR, Intersection and Difference. A variety of additional analytical geometry routines and routines for importing and exporting the data in various file formats are also provided. The GBL-2D library was originally developed as a geometric modeling engine for use with a separate software tool, called SummitView [1], that manipulates the 2D mask sets created by designers of Micro-Electro-Mechanical Systems (MEMS). However, many other practical applications for this type of software can be envisioned because the need to perform 2D Boolean operations can arise in many contexts.

  16. Molecular Packing of Functionalized Fluorinated Lipids in Langmuir Monolayers

    SciTech Connect

    Landsberg, Michael J.; Ruggles, Jeremy L.; Hussein, Waleed M.; McGeary, Ross P.; Gentle, Ian R.; Hankamer, Ben

    2012-01-20

    Fluorinated amphipaths are a fascinating class of compounds, which, despite significant challenges associated with their syntheses, have found use across a number of areas of biotechnology. Applications range from the in vitro stabilization of membrane proteins to the development of enhanced stability intravenous drug and gene delivery systems. More recently, monolayer-forming fluorinated lipids have found use in the 2D crystallization of detergent-solubilized hydrophobic or partially hydrophobic proteins at the air-water interface. In this study, we investigate the surface properties of a novel suite of monolayer forming, partially fluorinated lipids. These modular lipid structures contain a densely fluorinated insertion in the hydrocarbon tail and a synthetically modifiable headgroup. Analyses of surface-pressure area isotherms and X-ray reflectometry profiles reveal that the lipids spread into fluid monolayers and are more compressible than their non-fluorinated counterparts. Furthermore, the data support a model whereby the partially fluorinated chains of the lipid tails form a film which is fundamentally incompatible with detergents and other destabilizing amphipaths.

  17. Periodically sheared 2D Yukawa systems

    SciTech Connect

    Kovács, Anikó Zsuzsa; Hartmann, Peter; Donkó, Zoltán

    2015-10-15

    We present non-equilibrium molecular dynamics simulation studies on the dynamic (complex) shear viscosity of a 2D Yukawa system. We have identified a non-monotonic frequency dependence of the viscosity at high frequencies and shear rates, an energy absorption maximum (local resonance) at the Einstein frequency of the system at medium shear rates, an enhanced collective wave activity, when the excitation is near the plateau frequency of the longitudinal wave dispersion, and the emergence of significant configurational anisotropy at small frequencies and high shear rates.

  18. ENERGY LANDSCAPE OF 2D FLUID FORMS

    SciTech Connect

    Y. JIANG; ET AL

    2000-04-01

    The equilibrium states of 2D non-coarsening fluid foams, which consist of bubbles with fixed areas, correspond to local minima of the total perimeter. (1) The authors find an approximate value of the global minimum, and determine directly from an image how far a foam is from its ground state. (2) For (small) area disorder, small bubbles tend to sort inwards and large bubbles outwards. (3) Topological charges of the same sign repel while charges of opposite sign attract. (4) They discuss boundary conditions and the uniqueness of the pattern for fixed topology.

  19. Evaluation of in vitro cytotoxicity and paracellular permeability of intact monolayers with mouse embryonic stem cells.

    PubMed

    Calabro, Anthony R; Konsoula, Roula; Barile, Frank A

    2008-08-01

    Mouse embryonic stem (mES) cells were induced to form intact monolayers in cell culture inserts, using combinations of extracellular matrix (ECM) components and growth factors (GFs). Progressive formation of intact monolayers was monitored using transepithelial electrical resistance (TEER) and passage of paracellular permeability (PP) markers. The mES cells were initially inoculated on inactivated mouse embryonic fibroblasts (MEFs) plus leukemia inhibitory factor (LIF). At 75% confluence, cells were passaged in the absence of MEF and LIF to stimulate formation of rounded multicellular aggregates (MA). After 4 days, cultures containing MA were transferred to culture inserts coated with ECM components only, and grown in the presence of selected individual GFs. An additional 10-14 days revealed confluent monolayers with TEER values of 500-700 ohms cm2 (Omega cm2). Monolayers grown on inserts coated with ECM components, such as fibronectin or collagen-IV, in the presence of epidermal growth factor or keratinocyte growth factor in the medium, yielded the highest TEER measurements when compared to cultures grown without GFs or ECM. Acute cytotoxicity (AC) studies with confluent monolayers of mES cells in 96-well plates indicated that there is a high correlation (R2=0.91) between cell viability and TEER for 24-h exposure time. Also, decrease in TEER is inversely proportional with increase in PP of markers. In comparison to standardized Registry of Cytotoxicity (RC) data and TEER measurements, MTT IC50 values for mES cells are lower. Thus, at equivalent concentrations for the same chemicals, cell viability decreases before the integrity of the monolayer is compromised. This system represents a novel approach for the manipulation of mES cells toward specific intact monolayers, as an in vitro model for biological monolayer formation, and most importantly, for applications to cytotoxicity testing.

  20. Band inversion and topological aspects in a TiNI monolayer.

    PubMed

    Wang, Aizhu; Wang, Zhenhai; Du, Aijun; Zhao, Mingwen

    2016-08-10

    To achieve a device application of the quantum spin Hall (QSH) effect, increasing the critical temperature is crucial. A two-dimensional topological insulator (2D-TI) with a sizeable bulk band gap is one of the most promising strategies to reach this goal. Using first-principles calculations, we propose a new 2D-TI, titanium nitride iodide (TiNI) monolayer, which can be exfoliated from a bulk TiNI crystal, thanks to the weak interlayer interaction. We demonstrate that the TiNI monolayer has an inverted band structure accompanied by topologically nontrivial states characterized by a topological invariant of Z2 = 1. The band gap (∼50 meV) opened due to spin-orbit coupling (SOC) is available for achieving the QSH effect at room temperature. The band inversion and topologically nontrivial states are robust under external strain, suggesting that the 2D TiNI monolayer lattice could be a versatile platform for hosting nontrivial topological states with potential applications in 2D spintronics and computer technology. PMID:27443232

  1. Band inversion and topological aspects in a TiNI monolayer.

    PubMed

    Wang, Aizhu; Wang, Zhenhai; Du, Aijun; Zhao, Mingwen

    2016-08-10

    To achieve a device application of the quantum spin Hall (QSH) effect, increasing the critical temperature is crucial. A two-dimensional topological insulator (2D-TI) with a sizeable bulk band gap is one of the most promising strategies to reach this goal. Using first-principles calculations, we propose a new 2D-TI, titanium nitride iodide (TiNI) monolayer, which can be exfoliated from a bulk TiNI crystal, thanks to the weak interlayer interaction. We demonstrate that the TiNI monolayer has an inverted band structure accompanied by topologically nontrivial states characterized by a topological invariant of Z2 = 1. The band gap (∼50 meV) opened due to spin-orbit coupling (SOC) is available for achieving the QSH effect at room temperature. The band inversion and topologically nontrivial states are robust under external strain, suggesting that the 2D TiNI monolayer lattice could be a versatile platform for hosting nontrivial topological states with potential applications in 2D spintronics and computer technology.

  2. Interface exciton at lateral heterojunction of monolayer semiconductors

    NASA Astrophysics Data System (ADS)

    Lau, Ka Wai; Gong, Zhirui; Yu, Hongyi; Yao, Wang

    Heterostructures based on 2D transition metal dichalcogenides (TMDs) have attracted extensive research interest recently due to the appealing physical properties of TMDs and new geometries for forming heterostructures. One such heterostructure is the lateral heterojunctions seamlessly formed in a monolayer crystal between two different types of TMDs, e.g. WSe2 and MoSe2. Such heterojunction exhibits a type II band alignment, with electrons (holes) having lower energy on the MoSe2 (WSe2) region. Here we present the study of an interface exciton at the 1D lateral junction of monolayer TMDs. With the distance dependent screening, we find that the interface exciton can have strong binding even though the electron-hole separation is much larger compare to the 2D excitons in TMDs. Neutral excitons are studied using two different approaches: the solution based on a real-space tight binding model, and the perturbation expansion in a hydrogen-like basis in an effective mass model. We have also used the latter method to study charged excitons at a MoSe2-WSe2-MoSe2 nanoscale junction. The work is supported by the Research Grant Council of Hong Kong (HKU705513P, HKU9/CRF/13G), the Croucher Foundation, and the HKU OYRA.

  3. Repression of multiple CYP2D genes in mouse primary hepatocytes with a single siRNA construct.

    PubMed

    Elraghy, Omaima; Baldwin, William S

    2015-01-01

    The Cyp2d subfamily is the second most abun-dant subfamily of hepatic drug-metabolizing CYPs. In mice, there are nine Cyp2d members that are believed to have redundant catalytic activity. We are testing and optimizing the ability of one short interfering RNA (siRNA) construct to knockdown the expression of multiple mouse Cyp2ds in primary hepatocytes. Expression of Cyp2d10, Cyp2d11, Cyp2d22, and Cyp2d26 was observed in the primary male mouse hepatocytes. Cyp2d9, which is male-specific and growth hormone-dependent, was not expressed in male primary hepatocytes, potentially because of its dependence on pulsatile growth hormone release from the anterior pituitary. Several different siRNAs at different concentrations and with different reagents were used to knockdown Cyp2d expression. siRNA constructs designed to repress only one construct often mildly repressed several Cyp2d isoforms. A construct designed to knockdown every Cyp2d isoform provided the best results, especially when incubated with transfection reagents designed specifically for primary cell culture. Interestingly, a construct designed to knockdown all Cyp2d isoforms, except Cyp2d10, caused a 2.5× increase in Cyp2d10 expression, presumably because of a compensatory response. However, while RNA expression is repressed 24 h after siRNA treatment, associated changes in Cyp2d-mediated metabolism are tenuous. Overall, this study provides data on the expression of murine Cyp2ds in primary cell lines, valuable information on designing siRNAs for silencing multiple murine CYPs, and potential pros and cons of using siRNA as a tool for repressing Cyp2d and estimating Cyp2d's role in murine xenobiotic metabolism. PMID:25124873

  4. WFR-2D: an analytical model for PWAS-generated 2D ultrasonic guided wave propagation

    NASA Astrophysics Data System (ADS)

    Shen, Yanfeng; Giurgiutiu, Victor

    2014-03-01

    This paper presents WaveFormRevealer 2-D (WFR-2D), an analytical predictive tool for the simulation of 2-D ultrasonic guided wave propagation and interaction with damage. The design of structural health monitoring (SHM) systems and self-aware smart structures requires the exploration of a wide range of parameters to achieve best detection and quantification of certain types of damage. Such need for parameter exploration on sensor dimension, location, guided wave characteristics (mode type, frequency, wavelength, etc.) can be best satisfied with analytical models which are fast and efficient. The analytical model was constructed based on the exact 2-D Lamb wave solution using Bessel and Hankel functions. Damage effects were inserted in the model by considering the damage as a secondary wave source with complex-valued directivity scattering coefficients containing both amplitude and phase information from wave-damage interaction. The analytical procedure was coded with MATLAB, and a predictive simulation tool called WaveFormRevealer 2-D was developed. The wave-damage interaction coefficients (WDICs) were extracted from harmonic analysis of local finite element model (FEM) with artificial non-reflective boundaries (NRB). The WFR-2D analytical simulation results were compared and verified with full scale multiphysics finite element models and experiments with scanning laser vibrometer. First, Lamb wave propagation in a pristine aluminum plate was simulated with WFR-2D, compared with finite element results, and verified by experiments. Then, an inhomogeneity was machined into the plate to represent damage. Analytical modeling was carried out, and verified by finite element simulation and experiments. This paper finishes with conclusions and suggestions for future work.

  5. Microwave Assisted 2D Materials Exfoliation

    NASA Astrophysics Data System (ADS)

    Wang, Yanbin

    Two-dimensional materials have emerged as extremely important materials with applications ranging from energy and environmental science to electronics and biology. Here we report our discovery of a universal, ultrafast, green, solvo-thermal technology for producing excellent-quality, few-layered nanosheets in liquid phase from well-known 2D materials such as such hexagonal boron nitride (h-BN), graphite, and MoS2. We start by mixing the uniform bulk-layered material with a common organic solvent that matches its surface energy to reduce the van der Waals attractive interactions between the layers; next, the solutions are heated in a commercial microwave oven to overcome the energy barrier between bulk and few-layers states. We discovered the minutes-long rapid exfoliation process is highly temperature dependent, which requires precise thermal management to obtain high-quality inks. We hypothesize a possible mechanism of this proposed solvo-thermal process; our theory confirms the basis of this novel technique for exfoliation of high-quality, layered 2D materials by using an as yet unknown role of the solvent.

  6. Multienzyme Inkjet Printed 2D Arrays.

    PubMed

    Gdor, Efrat; Shemesh, Shay; Magdassi, Shlomo; Mandler, Daniel

    2015-08-19

    The use of printing to produce 2D arrays is well established, and should be relatively facile to adapt for the purpose of printing biomaterials; however, very few studies have been published using enzyme solutions as inks. Among the printing technologies, inkjet printing is highly suitable for printing biomaterials and specifically enzymes, as it offers many advantages. Formulation of the inkjet inks is relatively simple and can be adjusted to a variety of biomaterials, while providing nonharmful environment to the enzymes. Here we demonstrate the applicability of inkjet printing for patterning multiple enzymes in a predefined array in a very straightforward, noncontact method. Specifically, various arrays of the enzymes glucose oxidase (GOx), invertase (INV) and horseradish peroxidase (HP) were printed on aminated glass surfaces, followed by immobilization using glutardialdehyde after printing. Scanning electrochemical microscopy (SECM) was used for imaging the printed patterns and to ascertain the enzyme activity. The successful formation of 2D arrays consisting of enzymes was explored as a means of developing the first surface confined enzyme based logic gates. Principally, XOR and AND gates, each consisting of two enzymes as the Boolean operators, were assembled, and their operation was studied by SECM. PMID:26214072

  7. Superfluid density through 2D superconductor junctions

    NASA Astrophysics Data System (ADS)

    Nam, Hyoungdo; Shih, Chih-Kang

    As S. Qin et al. reported, two monolayer (2 ML) lead film on a silicon (111) substrate has one of two different atomic structures on the silicon substrate: the unstrained 1x1 and the psedumorphically strained √3x √3 (i.e. the same lattice constant as the Si √3x √3 lattice). Most interestingly, although these two different regions show the same quantum well state features, they have different Tc's (5 K and 4 K). These two different regions of 2 ML film naturally form superconductor-superconductor (SS or SS') junctions along silicon step edges. Physical connection of the junction is only 1 ML thickness because of the step height difference of substrate. We will present this study of SS (or SS') junction system using scanning tunneling microscopy/spectroscopy and in-situ double-coil mutual inductance measurement. The transition of superconducting gaps across either SS or SS' junctions should show how to locally affect each other. Double coil measurement show a global Tc close to the lower Tc region with sizable superfluid density. We will discuss the phase rigidity and its relationship to the superfluid density in this ultra-thin Pb film that is only 2 ML thick.

  8. 2-D or not 2-D, that is the question: A Northern California test

    SciTech Connect

    Mayeda, K; Malagnini, L; Phillips, W S; Walter, W R; Dreger, D

    2005-06-06

    Reliable estimates of the seismic source spectrum are necessary for accurate magnitude, yield, and energy estimation. In particular, how seismic radiated energy scales with increasing earthquake size has been the focus of recent debate within the community and has direct implications on earthquake source physics studies as well as hazard mitigation. The 1-D coda methodology of Mayeda et al. has provided the lowest variance estimate of the source spectrum when compared against traditional approaches that use direct S-waves, thus making it ideal for networks that have sparse station distribution. The 1-D coda methodology has been mostly confined to regions of approximately uniform complexity. For larger, more geophysically complicated regions, 2-D path corrections may be required. The complicated tectonics of the northern California region coupled with high quality broadband seismic data provides for an ideal ''apples-to-apples'' test of 1-D and 2-D path assumptions on direct waves and their coda. Using the same station and event distribution, we compared 1-D and 2-D path corrections and observed the following results: (1) 1-D coda results reduced the amplitude variance relative to direct S-waves by roughly a factor of 8 (800%); (2) Applying a 2-D correction to the coda resulted in up to 40% variance reduction from the 1-D coda results; (3) 2-D direct S-wave results, though better than 1-D direct waves, were significantly worse than the 1-D coda. We found that coda-based moment-rate source spectra derived from the 2-D approach were essentially identical to those from the 1-D approach for frequencies less than {approx}0.7-Hz, however for the high frequencies (0.7{le} f {le} 8.0-Hz), the 2-D approach resulted in inter-station scatter that was generally 10-30% smaller. For complex regions where data are plentiful, a 2-D approach can significantly improve upon the simple 1-D assumption. In regions where only 1-D coda correction is available it is still preferable over 2

  9. A new kind of 2D topological insulators BiCN with a giant gap and its substrate effects.

    PubMed

    Fu, Botao; Ge, Yanfeng; Su, Wenyong; Guo, Wei; Liu, Cheng-Cheng

    2016-01-01

    Based on DFT calculation, we predict that BiCN, i.e., bilayer Bi films passivated with -CN group, is a novel 2D Bi-based material with highly thermodynamic stability, and demonstrate that it is also a new kind of 2D TI with a giant SOC gap (~1 eV) by direct calculation of the topological invariant Z2 and obvious exhibition of the helical edge states. Monolayer h-BN and MoS2 are identified as good candidate substrates for supporting the nontrivial topological insulating phase of the 2D TI films, since the two substrates can stabilize and weakly interact with BiCN via van der Waals interaction and thus hardly affect the electronic properties, especially the band topology. The topological properties are robust against the strain and electric field. This may provide a promising platform for realization of novel topological phases. PMID:27444954

  10. A new kind of 2D topological insulators BiCN with a giant gap and its substrate effects

    PubMed Central

    Fu, Botao; Ge, Yanfeng; Su, Wenyong; Guo, Wei; Liu, Cheng-Cheng

    2016-01-01

    Based on DFT calculation, we predict that BiCN, i.e., bilayer Bi films passivated with -CN group, is a novel 2D Bi-based material with highly thermodynamic stability, and demonstrate that it is also a new kind of 2D TI with a giant SOC gap (~1 eV) by direct calculation of the topological invariant Z2 and obvious exhibition of the helical edge states. Monolayer h-BN and MoS2 are identified as good candidate substrates for supporting the nontrivial topological insulating phase of the 2D TI films, since the two substrates can stabilize and weakly interact with BiCN via van der Waals interaction and thus hardly affect the electronic properties, especially the band topology. The topological properties are robust against the strain and electric field. This may provide a promising platform for realization of novel topological phases. PMID:27444954

  11. A new kind of 2D topological insulators BiCN with a giant gap and its substrate effects

    NASA Astrophysics Data System (ADS)

    Fu, Botao; Ge, Yanfeng; Su, Wenyong; Guo, Wei; Liu, Cheng-Cheng

    2016-07-01

    Based on DFT calculation, we predict that BiCN, i.e., bilayer Bi films passivated with -CN group, is a novel 2D Bi-based material with highly thermodynamic stability, and demonstrate that it is also a new kind of 2D TI with a giant SOC gap (~1 eV) by direct calculation of the topological invariant Z2 and obvious exhibition of the helical edge states. Monolayer h-BN and MoS2 are identified as good candidate substrates for supporting the nontrivial topological insulating phase of the 2D TI films, since the two substrates can stabilize and weakly interact with BiCN via van der Waals interaction and thus hardly affect the electronic properties, especially the band topology. The topological properties are robust against the strain and electric field. This may provide a promising platform for realization of novel topological phases.

  12. Controlling cell growth with tailorable 2D nanoholes arrays.

    PubMed

    Fragal, Vanessa H; Cellet, Thelma Sley P; Fragal, Elizângela H; Pereira, Guilherme M; Garcia, Francielle P; Nakamura, Celso V; Asefa, Tewodros; Rubira, Adley F; Silva, Rafael

    2016-03-15

    A facile and reproducible route that can lead to two-dimensional arrays of nanopores in thin polymer films is demonstrated. The formation of the pores in the polymer films involves breath figure phenomenon and occurs during the film deposition by spin coating. The formation of nanoporous thin films takes only few seconds, and the method does not require complex equipment or expensive chemicals. This method also constitutes a straightforward approach to control the size of the pores formed in thin films. Besides allowing control over the average pore size of the porous films, the use of dynamic deposition with the breath figure phenomenon causes the reduction in the pore size to nanometer scale. The nanoporous arrays obtained by the breath figure are applied as substrates for cell growth, and the effect of their nanopore size on cell growth was evaluated. Notably, it is found that cell viability is related to pore size, where 2D nanoporous structure is more beneficial for cell culture than 2D microporous structures. The change in the average pore size of the polymer films from 1.22 μm to 346 nm results in a threefold increase in cell viability. PMID:26722796

  13. Digital Transfer Growth of Patterned 2D Metal Chalcogenides by Confined Nanoparticle Evaporation

    DOE PAGES

    Mahjouri-Samani, Masoud; Tian, Mengkun; Wang, Kai; Boulesbaa, Abdelaziz; Rouleau, Christopher M.; Puretzky, Alexander A.; McGuire, Michael A.; Srijanto, Bernadeta R.; Xiao, Kai; Eres, Gyula; et al

    2014-10-19

    Developing methods for the facile synthesis of two-dimensional (2D) metal chalcogenides and other layered materials is crucial for emerging applications in functional devices. Controlling the stoichiometry, number of the layers, crystallite size, growth location, and areal uniformity is challenging in conventional vapor phase synthesis. Here, we demonstrate a new route to control these parameters in the growth of metal chalcogenide (GaSe) and dichalcogenide (MoSe2) 2D crystals by precisely defining the mass and location of the source materials in a confined transfer growth system. A uniform and precise amount of stoichiometric nanoparticles are first synthesized and deposited onto a substrate bymore » pulsed laser deposition (PLD) at room temperature. This source substrate is then covered with a receiver substrate to form a confined vapor transport growth (VTG) system. By simply heating the source substrate in an inert background gas, a natural temperature gradient is formed that evaporates the confined nanoparticles to grow large, crystalline 2D nanosheets on the cooler receiver substrate, the temperature of which is controlled by the background gas pressure. Large monolayer crystalline domains (~ 100 m lateral sizes) of GaSe and MoSe2 are demonstrated, as well as continuous monolayer films through the deposition of additional precursor materials. This novel PLD-VTG synthesis and processing method offers a unique approach for the controlled growth of large-area, metal chalcogenides with a controlled number of layers in patterned growth locations for optoelectronics and energy related applications.« less

  14. Colloids in Flatland: a perspective on 2D phase-separated systems, characterisation methods, and lineactant design.

    PubMed

    Bernardini, C; Stoyanov, S D; Arnaudov, L N; Cohen Stuart, M A

    2013-03-01

    In 1861 Thomas Graham gave birth to a new field of science, today known as colloid science. Nowadays, the notion "colloid" is often used referring to systems consisting of two immiscible phases, one of which is finely dispersed into the other. Research on colloids deals mostly with sols (solids dispersed in a liquid), emulsions (liquids dispersed in liquid), and foams (gas dispersed in a liquid). Because the dispersed particles are small, there is a lot of interface per unit mass. Not surprisingly, therefore, the properties of the interface have often a decisive effect on the behaviour of colloids. Water-air interfaces have a special relevance in this field: many water-insoluble molecules can be spread on water and, given the right spreading conditions and enough available surface area, their spreading proceeds until a monolayer (a one-molecule thick layer) eventually remains. Several 2D phases have been identified for such monolayers, like "gas", "liquid expanded", "liquid condensed", and "solid". The central question of this review is whether these 2D phases can also exist as colloidal systems, and what stabilizes the dispersed state in such systems. We shall present several systems capable of yielding 2D phase separation, from those based on either natural or fluorinated amphiphiles, to polymer-based ones. We shall seek for analogies in 3D and we shall try to clarify if the lines between these 2D objects play a similar role as the interfaces between 3D colloidal systems. In particular, we shall consider the special role of molecules that tend to accumulate at the phase boundaries, that is, at the contact lines, which will therefore be denoted "line-actants" (molecules that adsorb at a 1D interface, separating two 2D colloidal entities), by analogy to the term "surfactant" (which indicates a molecule that adsorbs at a 2D interface separating two 3D colloidal entities).

  15. Canard configured aircraft with 2-D nozzle

    NASA Technical Reports Server (NTRS)

    Child, R. D.; Henderson, W. P.

    1978-01-01

    A closely-coupled canard fighter with vectorable two-dimensional nozzle was designed for enhanced transonic maneuvering. The HiMAT maneuver goal of a sustained 8g turn at a free-stream Mach number of 0.9 and 30,000 feet was the primary design consideration. The aerodynamic design process was initiated with a linear theory optimization minimizing the zero percent suction drag including jet effects and refined with three-dimensional nonlinear potential flow techniques. Allowances were made for mutual interference and viscous effects. The design process to arrive at the resultant configuration is described, and the design of a powered 2-D nozzle model to be tested in the LRC 16-foot Propulsion Wind Tunnel is shown.

  16. 2D Electrostatic Actuation of Microshutter Arrays

    NASA Technical Reports Server (NTRS)

    Burns, Devin E.; Oh, Lance H.; Li, Mary J.; Kelly, Daniel P.; Kutyrev, Alexander S.; Moseley, Samuel H.

    2015-01-01

    Electrostatically actuated microshutter arrays consisting of rotational microshutters (shutters that rotate about a torsion bar) were designed and fabricated through the use of models and experiments. Design iterations focused on minimizing the torsional stiffness of the microshutters, while maintaining their structural integrity. Mechanical and electromechanical test systems were constructed to measure the static and dynamic behavior of the microshutters. The torsional stiffness was reduced by a factor of four over initial designs without sacrificing durability. Analysis of the resonant behavior of the microshutters demonstrates that the first resonant mode is a torsional mode occurring around 3000 Hz. At low vacuum pressures, this resonant mode can be used to significantly reduce the drive voltage necessary for actuation requiring as little as 25V. 2D electrostatic latching and addressing was demonstrated using both a resonant and pulsed addressing scheme.

  17. 2D Electrostatic Actuation of Microshutter Arrays

    NASA Technical Reports Server (NTRS)

    Burns, Devin E.; Oh, Lance H.; Li, Mary J.; Jones, Justin S.; Kelly, Daniel P.; Zheng, Yun; Kutyrev, Alexander S.; Moseley, Samuel H.

    2015-01-01

    An electrostatically actuated microshutter array consisting of rotational microshutters (shutters that rotate about a torsion bar) were designed and fabricated through the use of models and experiments. Design iterations focused on minimizing the torsional stiffness of the microshutters, while maintaining their structural integrity. Mechanical and electromechanical test systems were constructed to measure the static and dynamic behavior of the microshutters. The torsional stiffness was reduced by a factor of four over initial designs without sacrificing durability. Analysis of the resonant behavior of the microshutter arrays demonstrates that the first resonant mode is a torsional mode occurring around 3000 Hz. At low vacuum pressures, this resonant mode can be used to significantly reduce the drive voltage necessary for actuation requiring as little as 25V. 2D electrostatic latching and addressing was demonstrated using both a resonant and pulsed addressing scheme.

  18. 2D quantum gravity from quantum entanglement.

    PubMed

    Gliozzi, F

    2011-01-21

    In quantum systems with many degrees of freedom the replica method is a useful tool to study the entanglement of arbitrary spatial regions. We apply it in a way that allows them to backreact. As a consequence, they become dynamical subsystems whose position, form, and extension are determined by their interaction with the whole system. We analyze, in particular, quantum spin chains described at criticality by a conformal field theory. Its coupling to the Gibbs' ensemble of all possible subsystems is relevant and drives the system into a new fixed point which is argued to be that of the 2D quantum gravity coupled to this system. Numerical experiments on the critical Ising model show that the new critical exponents agree with those predicted by the formula of Knizhnik, Polyakov, and Zamolodchikov.

  19. Graphene suspensions for 2D printing

    NASA Astrophysics Data System (ADS)

    Soots, R. A.; Yakimchuk, E. A.; Nebogatikova, N. A.; Kotin, I. A.; Antonova, I. V.

    2016-04-01

    It is shown that, by processing a graphite suspension in ethanol or water by ultrasound and centrifuging, it is possible to obtain particles with thicknesses within 1-6 nm and, in the most interesting cases, 1-1.5 nm. Analogous treatment of a graphite suspension in organic solvent yields eventually thicker particles (up to 6-10 nm thick) even upon long-term treatment. Using the proposed ink based on graphene and aqueous ethanol with ethylcellulose and terpineol additives for 2D printing, thin (~5 nm thick) films with sheet resistance upon annealing ~30 MΩ/□ were obtained. With the ink based on aqueous graphene suspension, the sheet resistance was ~5-12 kΩ/□ for 6- to 15-nm-thick layers with a carrier mobility of ~30-50 cm2/(V s).

  20. Metrology for graphene and 2D materials

    NASA Astrophysics Data System (ADS)

    Pollard, Andrew J.

    2016-09-01

    The application of graphene, a one atom-thick honeycomb lattice of carbon atoms with superlative properties, such as electrical conductivity, thermal conductivity and strength, has already shown that it can be used to benefit metrology itself as a new quantum standard for resistance. However, there are many application areas where graphene and other 2D materials, such as molybdenum disulphide (MoS2) and hexagonal boron nitride (h-BN), may be disruptive, areas such as flexible electronics, nanocomposites, sensing and energy storage. Applying metrology to the area of graphene is now critical to enable the new, emerging global graphene commercial world and bridge the gap between academia and industry. Measurement capabilities and expertise in a wide range of scientific areas are required to address this challenge. The combined and complementary approach of varied characterisation methods for structural, chemical, electrical and other properties, will allow the real-world issues of commercialising graphene and other 2D materials to be addressed. Here, examples of metrology challenges that have been overcome through a multi-technique or new approach are discussed. Firstly, the structural characterisation of defects in both graphene and MoS2 via Raman spectroscopy is described, and how nanoscale mapping of vacancy defects in graphene is also possible using tip-enhanced Raman spectroscopy (TERS). Furthermore, the chemical characterisation and removal of polymer residue on chemical vapour deposition (CVD) grown graphene via secondary ion mass spectrometry (SIMS) is detailed, as well as the chemical characterisation of iron films used to grow large domain single-layer h-BN through CVD growth, revealing how contamination of the substrate itself plays a role in the resulting h-BN layer. In addition, the role of international standardisation in this area is described, outlining the current work ongoing in both the International Organization of Standardization (ISO) and the

  1. Understanding the interaction between energetic ions and freestanding graphene towards practical 2D perforation

    NASA Astrophysics Data System (ADS)

    Buchheim, Jakob; Wyss, Roman M.; Shorubalko, Ivan; Park, Hyung Gyu

    2016-04-01

    We report experimentally and theoretically the behavior of freestanding graphene subjected to bombardment of energetic ions, investigating the capability of large-scale patterning of freestanding graphene with nanometer sized features by focused ion beam technology. A precise control over the He+ and Ga+ irradiation offered by focused ion beam techniques enables investigating the interaction of the energetic particles and graphene suspended with no support and allows determining sputter yields of the 2D lattice. We found a strong dependency of the 2D sputter yield on the species and kinetic energy of the incident ion beams. Freestanding graphene shows material semi-transparency to He+ at high energies (10-30 keV) allowing the passage of >97% He+ particles without creating destructive lattice vacancy. Large Ga+ ions (5-30 keV), in contrast, collide far more often with the graphene lattice to impart a significantly higher sputter yield of ~50%. Binary collision theory applied to monolayer and few-layer graphene can successfully elucidate this collision mechanism, in great agreement with experiments. Raman spectroscopy analysis corroborates the passage of a large fraction of He+ ions across graphene without much damaging the lattice whereas several colliding ions create single vacancy defects. Physical understanding of the interaction between energetic particles and suspended graphene can practically lead to reproducible and efficient pattern generation of unprecedentedly small features on 2D materials by design, manifested by our perforation of sub-5 nm pore arrays. This capability of nanometer-scale precision patterning of freestanding 2D lattices shows the practical applicability of focused ion beam technology to 2D material processing for device fabrication and integration.We report experimentally and theoretically the behavior of freestanding graphene subjected to bombardment of energetic ions, investigating the capability of large-scale patterning of

  2. Electronic, transport, and optical properties of bulk and mono-layer PdSe2

    SciTech Connect

    Sun, Jifeng; Shi, Hongliang; Siegrist, Theo; Singh, David J.

    2015-10-13

    In this study, the electronic and optical properties of bulk and monolayer PdSe2 are investigated using firstprinciples calculations. Using the modified Becke-Johnson potential, we find semiconductor behavior for both bulk and monolayer PdSe2 with indirect gap values of 0.03 eV for bulk and 1.43 eV for monolayer, respectively. Our sheet optical conductivity results support this observation and show similar anisotropic feature in the 2D plane. We further study the thermoelectric properties of the 2D PdSe2 using Blotzmann transport model and find interestingly high Seebeck coefficients (>200 μV/K) for both p- and n-type up to high doping level (–2 x 1013 cm2) with an anisotropic character in an electrical conductivity suggesting better thermoelectric performance along y direction in the plane.V

  3. Two-dimensional binary and ternary nanocrystal superlattices: the case of monolayers and bilayers.

    PubMed

    Dong, Angang; Ye, Xingchen; Chen, Jun; Murray, Christopher B

    2011-04-13

    The modular assembly of multicomponent nanocrystal (NC) superlattices enables new metamaterials with programmable properties. While self-assembly of three-dimensional (3D) binary NC superlattices (BNSLs) has advanced significantly in the past decade, limited progress has been made to grow 2D BNSLs such as monolayers and bilayers over extended areas. Here, we report the growth of large-area (∼ 1 cm(2)), transferable BNSL monolayers using the liquid-air interfacial assembly approach. The BNSL monolayers are formed by an entropy-driven assembly process with structures tunable by varying the NC size ratio. We further demonstrate the liquid-air interfacial assembly of BNSL bilayers which exhibit unique superlattice structures that have not been observed in the 3D BNSLs. As a further extension, bilayered ternary NC superlattices (TNSLs) are obtained by the cocrystallization of three types of NCs at the liquid-air interface. PMID:21413781

  4. CYP2D6*36 gene arrangements within the cyp2d6 locus: association of CYP2D6*36 with poor metabolizer status.

    PubMed

    Gaedigk, Andrea; Bradford, L Dianne; Alander, Sarah W; Leeder, J Steven

    2006-04-01

    Unexplained cases of CYP2D6 genotype/phenotype discordance continue to be discovered. In previous studies, several African Americans with a poor metabolizer phenotype carried the reduced function CYP2D6*10 allele in combination with a nonfunctional allele. We pursued the possibility that these alleles harbor either a known sequence variation (i.e., CYP2D6*36 carrying a gene conversion in exon 9 along the CYP2D6*10-defining 100C>T single-nucleotide polymorphism) or novel sequences variation(s). Discordant cases were evaluated by long-range polymerase chain reaction (PCR) to test for gene rearrangement events, and a 6.6-kilobase pair PCR product encompassing the CYP2D6 gene was cloned and entirely sequenced. Thereafter, allele frequencies were determined in different study populations comprising whites, African Americans, and Asians. Analyses covering the CYP2D7 to 2D6 gene region established that CYP2D6*36 did not only exist as a gene duplication (CYP2D6*36x2) or in tandem with *10 (CYP2D6*36+*10), as previously reported, but also by itself. This "single" CYP2D6*36 allele was found in nine African Americans and one Asian, but was absent in the whites tested. Ultimately, the presence of CYP2D6*36 resolved genotype/phenotype discordance in three cases. We also discovered an exon 9 conversion-positive CYP2D6*4 gene in a duplication arrangement (CYP2D6*4Nx2) and a CYP2D6*4 allele lacking 100C>T (CYP2D6*4M) in two white subjects. The discovery of an allele that carries only one CYP2D6*36 gene copy provides unequivocal evidence that both CYP2D6*36 and *36x2 are associated with a poor metabolizer phenotype. Given a combined frequency of between 0.5 and 3% in African Americans and Asians, genotyping for CYP2D6*36 should improve the accuracy of genotype-based phenotype prediction in these populations.

  5. Understanding the interaction between energetic ions and freestanding graphene towards practical 2D perforation.

    PubMed

    Buchheim, Jakob; Wyss, Roman M; Shorubalko, Ivan; Park, Hyung Gyu

    2016-04-21

    We report experimentally and theoretically the behavior of freestanding graphene subjected to bombardment of energetic ions, investigating the capability of large-scale patterning of freestanding graphene with nanometer sized features by focused ion beam technology. A precise control over the He(+) and Ga(+) irradiation offered by focused ion beam techniques enables investigating the interaction of the energetic particles and graphene suspended with no support and allows determining sputter yields of the 2D lattice. We found a strong dependency of the 2D sputter yield on the species and kinetic energy of the incident ion beams. Freestanding graphene shows material semi-transparency to He(+) at high energies (10-30 keV) allowing the passage of >97% He(+) particles without creating destructive lattice vacancy. Large Ga(+) ions (5-30 keV), in contrast, collide far more often with the graphene lattice to impart a significantly higher sputter yield of ∼50%. Binary collision theory applied to monolayer and few-layer graphene can successfully elucidate this collision mechanism, in great agreement with experiments. Raman spectroscopy analysis corroborates the passage of a large fraction of He(+) ions across graphene without much damaging the lattice whereas several colliding ions create single vacancy defects. Physical understanding of the interaction between energetic particles and suspended graphene can practically lead to reproducible and efficient pattern generation of unprecedentedly small features on 2D materials by design, manifested by our perforation of sub-5 nm pore arrays. This capability of nanometer-scale precision patterning of freestanding 2D lattices shows the practical applicability of focused ion beam technology to 2D material processing for device fabrication and integration.

  6. Effect of surface charge of immortalized mouse cerebral endothelial cell monolayer on transport of charged solutes.

    PubMed

    Yuan, Wei; Li, Guanglei; Gil, Eun Seok; Lowe, Tao Lu; Fu, Bingmei M

    2010-04-01

    Charge carried by the surface glycocalyx layer (SGL) of the cerebral endothelium has been shown to significantly modulate the permeability of the blood-brain barrier (BBB) to charged solutes in vivo. The cultured monolayer of bEnd3, an immortalized mouse cerebral endothelial cell line, is becoming a popular in vitro BBB model due to its easy growth and maintenance of many BBB characteristics over repeated passages. To test whether the SGL of bEnd3 monolayer carries similar charge as that in the intact BBB and quantify this charge, which can be characterized by the SGL thickness (L(f)) and charge density (C(mf)), we measured the solute permeability of bEnd3 monolayer to neutral solutes and to solutes with similar size but opposite charges: negatively charged alpha-lactalbumin (-11) and positively charged ribonuclease (+3). Combining the measured permeability data with a transport model across the cell monolayer, we predicted the L(f) and the C(mf) of bEnd3 monolayer, which is approximately 160 nm and approximately 25 mEq/L, respectively. We also investigated whether orosomucoid, a plasma glycoprotein modulating the charge of the intact BBB, alters the charge of bEnd3 monolayer. We found that 1 mg/mL orosomucoid would increase SGL charge density of bEnd3 monolayer to approximately 2-fold of its control value.

  7. Effect of surface charge of immortalized mouse cerebral endothelial cell monolayer on transport of charged solutes.

    PubMed

    Yuan, Wei; Li, Guanglei; Gil, Eun Seok; Lowe, Tao Lu; Fu, Bingmei M

    2010-04-01

    Charge carried by the surface glycocalyx layer (SGL) of the cerebral endothelium has been shown to significantly modulate the permeability of the blood-brain barrier (BBB) to charged solutes in vivo. The cultured monolayer of bEnd3, an immortalized mouse cerebral endothelial cell line, is becoming a popular in vitro BBB model due to its easy growth and maintenance of many BBB characteristics over repeated passages. To test whether the SGL of bEnd3 monolayer carries similar charge as that in the intact BBB and quantify this charge, which can be characterized by the SGL thickness (L(f)) and charge density (C(mf)), we measured the solute permeability of bEnd3 monolayer to neutral solutes and to solutes with similar size but opposite charges: negatively charged alpha-lactalbumin (-11) and positively charged ribonuclease (+3). Combining the measured permeability data with a transport model across the cell monolayer, we predicted the L(f) and the C(mf) of bEnd3 monolayer, which is approximately 160 nm and approximately 25 mEq/L, respectively. We also investigated whether orosomucoid, a plasma glycoprotein modulating the charge of the intact BBB, alters the charge of bEnd3 monolayer. We found that 1 mg/mL orosomucoid would increase SGL charge density of bEnd3 monolayer to approximately 2-fold of its control value. PMID:20087768

  8. On the 2D-transition, hysteresis and thermodynamic equilibrium of Kr adsorption on a graphite surface.

    PubMed

    Diao, Rui; Fan, Chunyan; Do, D D; Nicholson, D

    2015-12-15

    The adsorption and desorption of Kr on graphite at temperatures in the range 60-88K, was systematically investigated using a combination of several simulation techniques including: Grand Canonical Monte Carlo (GCMC), Canonical kinetic-Monte Carlo (C-kMC) and the Mid-Density Scheme (MDS). Particular emphasis was placed on the gas-solid, gas-liquid and liquid-solid 2D phase transitions. For temperatures below the bulk triple point, the transition from a 2D-liquid-like monolayer to a 2D-solid-like state is manifested as a sub-step in the isotherm. A further increase in the chemical potential leads to another rearrangement of the 2D-solid-like state from a disordered structure to an ordered structure that is signalled by (1) another sub-step in the monolayer region and (2) a spike in the plot of the isosteric heat versus density at loadings close to the dense monolayer coverage concentration. Whenever a 2D transition occurs in a grand canonical isotherm it is always associated with a hysteresis, a feature that is not widely recognised in the literature. We studied in details this hysteresis with the analysis of the canonical isotherm, obtained with C-kMC, which exhibits a van der Waals (vdW) type loop with a vertical segment in the middle. We complemented the hysteresis loop and the vdW curve with the analysis of the equilibrium transition obtained with the MDS, and found that the equilibrium transition coincides exactly with the vertical segment of the C-kMC isotherm, indicating the co-existence of two phases at equilibrium. We also analysed adsorption at higher layers and found that the 2D-coexistence is also observed, provided that the temperature is well below the triple point. Finally the 2D-critical temperatures were obtained for the first three layers and they are in good agreement with the experimental data in the literature.

  9. On the 2D-transition, hysteresis and thermodynamic equilibrium of Kr adsorption on a graphite surface.

    PubMed

    Diao, Rui; Fan, Chunyan; Do, D D; Nicholson, D

    2015-12-15

    The adsorption and desorption of Kr on graphite at temperatures in the range 60-88K, was systematically investigated using a combination of several simulation techniques including: Grand Canonical Monte Carlo (GCMC), Canonical kinetic-Monte Carlo (C-kMC) and the Mid-Density Scheme (MDS). Particular emphasis was placed on the gas-solid, gas-liquid and liquid-solid 2D phase transitions. For temperatures below the bulk triple point, the transition from a 2D-liquid-like monolayer to a 2D-solid-like state is manifested as a sub-step in the isotherm. A further increase in the chemical potential leads to another rearrangement of the 2D-solid-like state from a disordered structure to an ordered structure that is signalled by (1) another sub-step in the monolayer region and (2) a spike in the plot of the isosteric heat versus density at loadings close to the dense monolayer coverage concentration. Whenever a 2D transition occurs in a grand canonical isotherm it is always associated with a hysteresis, a feature that is not widely recognised in the literature. We studied in details this hysteresis with the analysis of the canonical isotherm, obtained with C-kMC, which exhibits a van der Waals (vdW) type loop with a vertical segment in the middle. We complemented the hysteresis loop and the vdW curve with the analysis of the equilibrium transition obtained with the MDS, and found that the equilibrium transition coincides exactly with the vertical segment of the C-kMC isotherm, indicating the co-existence of two phases at equilibrium. We also analysed adsorption at higher layers and found that the 2D-coexistence is also observed, provided that the temperature is well below the triple point. Finally the 2D-critical temperatures were obtained for the first three layers and they are in good agreement with the experimental data in the literature. PMID:26364074

  10. Quantum Spin-Quantum Anomalous Hall Insulators and Topological Transitions in Functionalized Sb(111) Monolayers.

    PubMed

    Zhou, Tong; Zhang, Jiayong; Zhao, Bao; Zhang, Huisheng; Yang, Zhongqin

    2015-08-12

    Electronic and topological behaviors of Sb(111) monolayers decorated with H and certain magnetic atoms are investigated by using ab initio methods. The drastic exchange field induced by the magnetic atoms, together with strong spin-orbit coupling (SOC) of Sb atoms, generates one new category of valley polarized topological insulators, called quantum spin-quantum anomalous Hall (QSQAH) insulators in the monolayer, with a band gap up to 53 meV. The strong SOC is closely related to Sb px and py orbitals, instead of pz orbitals in usual two-dimensional (2D) materials. Topological transitions from quantum anomalous Hall states to QSQAH states and then to time-reversal-symmetry-broken quantum spin Hall states are achieved by tuning the SOC strength. The behind mechanism is revealed. Our work is helpful for future valleytronic and spintronic applications in 2D materials.

  11. Solid-Vapor Reaction Growth of Transition-Metal Dichalcogenide Monolayers.

    PubMed

    Li, Bo; Gong, Yongji; Hu, Zhili; Brunetto, Gustavo; Yang, Yingchao; Ye, Gonglan; Zhang, Zhuhua; Lei, Sidong; Jin, Zehua; Bianco, Elisabeth; Zhang, Xiang; Wang, Weipeng; Lou, Jun; Galvão, Douglas S; Tang, Ming; Yakobson, Boris I; Vajtai, Robert; Ajayan, Pulickel M

    2016-08-26

    Two-dimensional (2D) layered semiconducting transition-metal dichalcogenides (TMDCs) are promising candidates for next-generation ultrathin, flexible, and transparent electronics. Chemical vapor deposition (CVD) is a promising method for their controllable, scalable synthesis but the growth mechanism is poorly understood. Herein, we present systematic studies to understand the CVD growth mechanism of monolayer MoSe2 , showing reaction pathways for growth from solid and vapor precursors. Examination of metastable nanoparticles deposited on the substrate during growth shows intermediate growth stages and conversion of non-stoichiometric nanoparticles into stoichiometric 2D MoSe2 monolayers. The growth steps involve the evaporation and reduction of MoO3 solid precursors to sub-oxides and stepwise reactions with Se vapor to finally form MoSe2 . The experimental results and proposed model were corroborated by ab initio Car-Parrinello molecular dynamics studies. PMID:27490942

  12. Comparative study of normal and branched alkane monolayer films adsorbed on a solid surface. I. Structure

    NASA Astrophysics Data System (ADS)

    Enevoldsen, A. D.; Hansen, F. Y.; Diama, A.; Criswell, L.; Taub, H.

    2007-03-01

    The structure of a monolayer film of the branched alkane squalane (C30H62) adsorbed on graphite has been studied by neutron diffraction and molecular dynamics (MD) simulations and compared with a similar study of the n-alkane tetracosane (n-C24H52). Both molecules have 24 carbon atoms along their backbone and squalane has, in addition, six methyl side groups. Upon adsorption, there are significant differences as well as similarities in the behavior of these molecular films. Both molecules form ordered structures at low temperatures; however, while the melting point of the two-dimensional (2D) tetracosane film is roughly the same as the bulk melting point, the surface strongly stabilizes the 2D squalane film such that its melting point is 91K above its value in bulk. Therefore, squalane, like tetracosane, will be a poor lubricant in those nanoscale devices that require a fluid lubricant at room temperature. The neutron diffraction data show that the translational order in the squalane monolayer is significantly less than in the tetracosane monolayer. The authors' MD simulations suggest that this is caused by a distortion of the squalane molecules upon adsorption on the graphite surface. When the molecules are allowed to relax on the surface, they distort such that all six methyl groups point away from the surface. This results in a reduction in the monolayer's translational order characterized by a decrease in its coherence length and hence a broadening of the diffraction peaks. The MD simulations also show that the melting mechanism in the squalane monolayer is the same footprint reduction mechanism found in the tetracosane monolayer, where a chain melting drives the lattice melting.

  13. Comparative study of normal and branched alkane monolayer films adsorbed on a solid surface. I. Structure.

    PubMed

    Enevoldsen, A D; Hansen, F Y; Diama, A; Criswell, L; Taub, H

    2007-03-14

    The structure of a monolayer film of the branched alkane squalane (C30H62) adsorbed on graphite has been studied by neutron diffraction and molecular dynamics (MD) simulations and compared with a similar study of the n-alkane tetracosane (n-C24H52). Both molecules have 24 carbon atoms along their backbone and squalane has, in addition, six methyl side groups. Upon adsorption, there are significant differences as well as similarities in the behavior of these molecular films. Both molecules form ordered structures at low temperatures; however, while the melting point of the two-dimensional (2D) tetracosane film is roughly the same as the bulk melting point, the surface strongly stabilizes the 2D squalane film such that its melting point is 91 K above its value in bulk. Therefore, squalane, like tetracosane, will be a poor lubricant in those nanoscale devices that require a fluid lubricant at room temperature. The neutron diffraction data show that the translational order in the squalane monolayer is significantly less than in the tetracosane monolayer. The authors' MD simulations suggest that this is caused by a distortion of the squalane molecules upon adsorption on the graphite surface. When the molecules are allowed to relax on the surface, they distort such that all six methyl groups point away from the surface. This results in a reduction in the monolayer's translational order characterized by a decrease in its coherence length and hence a broadening of the diffraction peaks. The MD simulations also show that the melting mechanism in the squalane monolayer is the same footprint reduction mechanism found in the tetracosane monolayer, where a chain melting drives the lattice melting.

  14. A new inversion method for (T2, D) 2D NMR logging and fluid typing

    NASA Astrophysics Data System (ADS)

    Tan, Maojin; Zou, Youlong; Zhou, Cancan

    2013-02-01

    One-dimensional nuclear magnetic resonance (1D NMR) logging technology has some significant limitations in fluid typing. However, not only can two-dimensional nuclear magnetic resonance (2D NMR) provide some accurate porosity parameters, but it can also identify fluids more accurately than 1D NMR. In this paper, based on the relaxation mechanism of (T2, D) 2D NMR in a gradient magnetic field, a hybrid inversion method that combines least-squares-based QR decomposition (LSQR) and truncated singular value decomposition (TSVD) is examined in the 2D NMR inversion of various fluid models. The forward modeling and inversion tests are performed in detail with different acquisition parameters, such as magnetic field gradients (G) and echo spacing (TE) groups. The simulated results are discussed and described in detail, the influence of the above-mentioned observation parameters on the inversion accuracy is investigated and analyzed, and the observation parameters in multi-TE activation are optimized. Furthermore, the hybrid inversion can be applied to quantitatively determine the fluid saturation. To study the effects of noise level on the hybrid method and inversion results, the numerical simulation experiments are performed using different signal-to-noise-ratios (SNRs), and the effect of different SNRs on fluid typing using three fluid models are discussed and analyzed in detail.

  15. The interface between ferroelectric and 2D material for a Ferroelectric Field-Effect Transistor

    NASA Astrophysics Data System (ADS)

    Park, Nahee; Kang, Haeyong; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    We have studied electrical property of ferroelectric field-effect transistor which consists of graphene on hexagonal Boron-Nitride (h-BN) gated by a ferroelectric, PMN-PT (i.e. (1-x)Pb(Mg1/3Nb2/3) O3-xPbTiO3) single-crystal substrate. The PMN-PT was expected to have an effect on polarization field into the graphene channel and to induce a giant amount of surface charge. The hexagonal Boron-Nitride (h-BN) flake was directly exfoliated on the PMN-PT substrate for preventing graphene from directly contacting on the PMN-PT substrate. It can make us to observe the effect of the interface between ferroelectric and 2D material on the device operation. Monolayer graphene as 2D channel material, which was confirmed by Raman spectroscopy, was transferred on top of the hexagonal Boron-Nitride (h-BN) by using the conventional dry-transfer method. Here, we can demonstrate that the structure of graphene/hexagonal-BN/ferroelectric field-effect transistor makes us to clearly understand the device operation as well as the interface between ferroelectric and 2D materials by inserting h-BN between them. The phenomena such as anti-hysteresis, current saturation behavior, and hump-like increase of channel current, will be discussed by in terms of ferroelectric switching, polarization-assisted charge trapping.

  16. Electric-Field-Assisted Directed Assembly of Transition Metal Dichalcogenide Monolayer Sheets.

    PubMed

    Deng, Donna D; Lin, Zhong; Elías, Ana Laura; Perea-Lopez, Nestor; Li, Jie; Zhou, Chanjing; Zhang, Kehao; Feng, Simin; Terrones, Humberto; Mayer, Jeffrey S; Robinson, Joshua A; Terrones, Mauricio; Mayer, Theresa S

    2016-05-24

    Directed assembly of two-dimensional (2D) layered materials, such as transition metal dichalcogenides, holds great promise for large-scale electronic and optoelectronic applications. Here, we demonstrate controlled placement of solution-suspended monolayer tungsten disulfide (WS2) sheets on a substrate using electric-field-assisted assembly. Micrometer-sized triangular WS2 monolayers are selectively positioned on a lithographically defined interdigitated guiding electrode structure using the dielectrophoretic force induced on the sheets in a nonuniform field. Triangular sheets with sizes comparable to the interelectrode gap assemble with an observed preferential orientation where one side of the triangle spans across the electrode gap. This orientation of the sheets relative to the guiding electrode is confirmed to be the lowest energy configuration using semianalytical calculations. Nearly all sheets assemble without observable physical deformation, and postassembly photoluminescence and Raman spectroscopy characterization of the monolayers reveal that they retain their as-grown crystalline quality. These results show that the field-assisted assembly process may be used for large-area bottom-up integration of 2D monolayer materials for nanodevice applications. PMID:27082162

  17. Combined Diffraction and Density Functional Theory Calculations of Halogen-Bonded Cocrystal Monolayers

    PubMed Central

    2013-01-01

    This work describes the combined use of synchrotron X-ray diffraction and density functional theory (DFT) calculations to understand the cocrystal formation or phase separation in 2D monolayers capable of halogen bonding. The solid monolayer structure of 1,4-diiodobenzene (DIB) has been determined by X-ray synchrotron diffraction. The mixing behavior of DIB with 4,4′-bipyridyl (BPY) has also been studied and interestingly is found to phase-separate rather than form a cocrystal, as observed in the bulk. DFT calculations are used to establish the underlying origin of this interesting behavior. The DFT calculations are demonstrated to agree well with the recently proposed monolayer structure for the cocrystal of BPY and 1,4-diiodotetrafluorobenzene (DITFB) (the perfluorinated analogue of DIB), where halogen bonding has also been identified by diffraction. Here we have calculated an estimate of the halogen bond strength by DFT calculations for the DITFB/BPY cocrystal monolayer, which is found to be ∼20 kJ/mol. Computationally, we find that the nonfluorinated DIB and BPY are not expected to form a halogen-bonded cocrystal in a 2D layer; for this pair of species, phase separation of the components is calculated to be lower energy, in good agreement with the diffraction results. PMID:24215390

  18. Radiofrequency Spectroscopy and Thermodynamics of Fermi Gases in the 2D to Quasi-2D Dimensional Crossover

    NASA Astrophysics Data System (ADS)

    Cheng, Chingyun; Kangara, Jayampathi; Arakelyan, Ilya; Thomas, John

    2016-05-01

    We tune the dimensionality of a strongly interacting degenerate 6 Li Fermi gas from 2D to quasi-2D, by adjusting the radial confinement of pancake-shaped clouds to control the radial chemical potential. In the 2D regime with weak radial confinement, the measured pair binding energies are in agreement with 2D-BCS mean field theory, which predicts dimer pairing energies in the many-body regime. In the qausi-2D regime obtained with increased radial confinement, the measured pairing energy deviates significantly from 2D-BCS theory. In contrast to the pairing energy, the measured radii of the cloud profiles are not fit by 2D-BCS theory in either the 2D or quasi-2D regimes, but are fit in both regimes by a beyond mean field polaron-model of the free energy. Supported by DOE, ARO, NSF, and AFOSR.

  19. Monolayer expansion induces an oxidative metabolism and ROS in chondrocytes

    SciTech Connect

    Heywood, H.K. Lee, D.A.

    2008-08-22

    This study tests the hypothesis that articular chondrocytes shift from a characteristically glycolytic to an oxidative energy metabolism during population expansion in monolayer. Bovine articular chondrocytes were cultured in monolayer under standard incubator conditions for up to 14 days. Cellular proliferation, oxygen consumption, lactate production, protein content, ROS generation and mitochondrial morphology were examined. Lactate release increased {approx}5-fold within 1 week, but this was limited to {approx}2-fold increase when normalized to cellular protein content. By contrast, per cell oxidative phosphorylation increased 98-fold in 1 week. The increase in oxidative phosphorylation was evident within 24 h, preceding cell proliferation and was associated with augmented reactive oxygen species generation. The autologous chondrocyte implantation procedure requires 14-21 days for population expansion. The alterations in metabolic phenotype we report within 7 days in vitro are thus pertinent to autologous chondrocyte implantation with significant implications for the chondrocyte functionality.

  20. Competing coexisting phases in 2D water

    PubMed Central

    Zanotti, Jean-Marc; Judeinstein, Patrick; Dalla-Bernardina, Simona; Creff, Gaëlle; Brubach, Jean-Blaise; Roy, Pascale; Bonetti, Marco; Ollivier, Jacques; Sakellariou, Dimitrios; Bellissent-Funel, Marie-Claire

    2016-01-01

    The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules. PMID:27185018

  1. Phase Engineering of 2D Tin Sulfides.

    PubMed

    Mutlu, Zafer; Wu, Ryan J; Wickramaratne, Darshana; Shahrezaei, Sina; Liu, Chueh; Temiz, Selcuk; Patalano, Andrew; Ozkan, Mihrimah; Lake, Roger K; Mkhoyan, K A; Ozkan, Cengiz S

    2016-06-01

    Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations. PMID:27099950

  2. Phase Engineering of 2D Tin Sulfides.

    PubMed

    Mutlu, Zafer; Wu, Ryan J; Wickramaratne, Darshana; Shahrezaei, Sina; Liu, Chueh; Temiz, Selcuk; Patalano, Andrew; Ozkan, Mihrimah; Lake, Roger K; Mkhoyan, K A; Ozkan, Cengiz S

    2016-06-01

    Tin sulfides can exist in a variety of phases and polytypes due to the different oxidation states of Sn. A subset of these phases and polytypes take the form of layered 2D structures that give rise to a wide host of electronic and optical properties. Hence, achieving control over the phase, polytype, and thickness of tin sulfides is necessary to utilize this wide range of properties exhibited by the compound. This study reports on phase-selective growth of both hexagonal tin (IV) sulfide SnS2 and orthorhombic tin (II) sulfide SnS crystals with diameters of over tens of microns on SiO2 substrates through atmospheric pressure vapor-phase method in a conventional horizontal quartz tube furnace with SnO2 and S powders as the source materials. Detailed characterization of each phase of tin sulfide crystals is performed using various microscopy and spectroscopy methods, and the results are corroborated by ab initio density functional theory calculations.

  3. Competing coexisting phases in 2D water

    NASA Astrophysics Data System (ADS)

    Zanotti, Jean-Marc; Judeinstein, Patrick; Dalla-Bernardina, Simona; Creff, Gaëlle; Brubach, Jean-Blaise; Roy, Pascale; Bonetti, Marco; Ollivier, Jacques; Sakellariou, Dimitrios; Bellissent-Funel, Marie-Claire

    2016-05-01

    The properties of bulk water come from a delicate balance of interactions on length scales encompassing several orders of magnitudes: i) the Hydrogen Bond (HBond) at the molecular scale and ii) the extension of this HBond network up to the macroscopic level. Here, we address the physics of water when the three dimensional extension of the HBond network is frustrated, so that the water molecules are forced to organize in only two dimensions. We account for the large scale fluctuating HBond network by an analytical mean-field percolation model. This approach provides a coherent interpretation of the different events experimentally (calorimetry, neutron, NMR, near and far infra-red spectroscopies) detected in interfacial water at 160, 220 and 250 K. Starting from an amorphous state of water at low temperature, these transitions are respectively interpreted as the onset of creation of transient low density patches of 4-HBonded molecules at 160 K, the percolation of these domains at 220 K and finally the total invasion of the surface by them at 250 K. The source of this surprising behaviour in 2D is the frustration of the natural bulk tetrahedral local geometry and the underlying very significant increase in entropy of the interfacial water molecules.

  4. Visualization of two-dimensional single chain conformations solubilized in a miscible polymer blend monolayer by atomic force microscopy.

    PubMed

    Sugihara, Kouki; Kumaki, Jiro

    2012-06-01

    Polymer Langmuir monolayers spread on a water surface are one of the best models for two-dimensional (2D) polymer and have been extensively studied. However, the most fundamental issue in understanding a 2D film, the polymer chain packing in the film, is still not well-understood, especially from the experimental point of view. Direct observation of the chain packing by microscopy at a molecular level, such as by atomic force microscopy (AFM), might be one of the most promising ways to study this issue; however, because of the limited resolution of the method, the chain packing of polymer cannot be resolved by AFM, except for especially large polymers. Here, we show that a mixed monolayer of vinyl polymers, poly(methyl methacrylate) (PMMA) and poly(n-nonyl acrylate) (PNA), was miscible at a low surface pressure, and if a small amount of PMMA chains was solubilized in a PNA monolayer, the isolated PMMA chains in the PNA monolayer were, for the first time, successfully visualized by AFM with a clear contrast, which originated from a difference of rigidities of the polymers due to their different glass transition temperatures (105 °C(PMMA) and -89 °C(PNA)). The PMMA chains were found to strongly interpenetrate into the PNA monolayer, with a radius of gyration (R(g(PMMA))) that was several times larger than that of the 2D ideal chain (segregated-chain). Furthermore, the radius scaled with the molecular weight of the PMMA (M(PMMA)) as R(g(PMMA)) ∝ M(PMMA)(0.63), which was between the scaling of the 2D ideal chain (segregated chain), R(g) ∝ M(0.5), and the 2D chain in good solvent, R(g) ∝ M(0.75). On the other hand, R(g(PMMA)) was independent of the molecular weight of the PNA matrix over a wide range. These results indicate that the PNA/PMMA monolayer is a strongly miscible system, although the R(g(PMMA)) scaling with M(PMMA) (0.63) is somewhat smaller than that expected for a 2D chain in good solvent systems (0.75). The generation of molecular level information

  5. Self-Assembly and Dynamics of Organic 2D Molecular Sieves: Ab Initio and Molecular Dynamics Studies

    NASA Astrophysics Data System (ADS)

    St. John, Alexander; Wexler, Carlos

    2015-03-01

    Spontaneous molecular self-assembly is a promising route for bottom-up manufacturing of two-dimensional (2D) nanostructures with specific topologies on atomically flat surfaces. Of particular interest is the possibility of selective lock-and-key interaction of guest molecules inside cavities formed by complex self-assembled host structures. Our host structure is a monolayer consisting of interdigitated 1,3,5-tristyrylbenzene substituted by alkoxy peripheral chains containing n = 6, 8, 10, 12, or 14 carbon atoms (TSB3,5-C n) deposited on a highly ordered pyrolytic graphite (HOPG) surface. Using ab initio methods from quantum chemistry and molecular dynamics simulations, we construct and analyze the structure and functionality of the TSB3,5-C n monolayer as a molecular sieve. Supported by ACS-PRF 52696-ND5.

  6. Crystal field effect induced topological crystalline insulators in monolayer IV-VI semiconductors.

    PubMed

    Liu, Junwei; Qian, Xiaofeng; Fu, Liang

    2015-04-01

    Two-dimensional (2D) topological crystalline insulators (TCIs) were recently predicted in thin films of the SnTe class of IV-VI semiconductors, which can host metallic edge states protected by mirror symmetry. As thickness decreases, quantum confinement effect will increase and surpass the inverted gap below a critical thickness, turning TCIs into normal insulators. Surprisingly, based on first-principles calculations, here we demonstrate that (001) monolayers of rocksalt IV-VI semiconductors XY (X = Ge, Sn, Pb and Y = S, Se, Te) are 2D TCIs with the fundamental band gap as large as 260 meV in monolayer PbTe. This unexpected nontrivial topological phase stems from the strong crystal field effect in the monolayer, which lifts the degeneracy between p(x,y) and p(z) orbitals and leads to band inversion between cation pz and anion px,y orbitals. This crystal field effect induced topological phase offers a new strategy to find and design other atomically thin 2D topological materials.

  7. Structure and shear response of lipid monolayers

    SciTech Connect

    Dutta, P.; Ketterson, J.B.

    1990-02-01

    Organic monolayers and multilayers are both scientifically fascinating and technologically promising; they are, however, both complex systems and relatively inaccessible to experimental probes. In this Progress Report, we describe our X-ray diffraction studies, which have given us substantial new information about the structures and phase transitions in monolayers on the surface of water; our use of these monolayers as a unique probe of the dynamics of wetting and spreading; and our studies of monolayer mechanical properties using a simple but effective technique available to anyone using the Wilhelmy method to measure surface tension.

  8. 2-D Animation's Not Just for Mickey Mouse.

    ERIC Educational Resources Information Center

    Weinman, Lynda

    1995-01-01

    Discusses characteristics of two-dimensional (2-D) animation; highlights include character animation, painting issues, and motion graphics. Sidebars present Silicon Graphics animations tools and 2-D animation programs for the desktop computer. (DGM)

  9. Generates 2D Input for DYNA NIKE & TOPAZ

    SciTech Connect

    Hallquist, J. O.; Sanford, Larry

    1996-07-15

    MAZE is an interactive program that serves as an input and two-dimensional mesh generator for DYNA2D, NIKE2D, TOPAZ2D, and CHEMICAL TOPAZ2D. MAZE also generates a basic template for ISLAND input. MAZE has been applied to the generation of input data to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.

  10. MAZE96. Generates 2D Input for DYNA NIKE & TOPAZ

    SciTech Connect

    Sanford, L.; Hallquist, J.O.

    1992-02-24

    MAZE is an interactive program that serves as an input and two-dimensional mesh generator for DYNA2D, NIKE2D, TOPAZ2D, and CHEMICAL TOPAZ2D. MAZE also generates a basic template for ISLAND input. MAZE has been applied to the generation of input data to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.

  11. 2d PDE Linear Symmetric Matrix Solver

    1983-10-01

    ICCG2 (Incomplete Cholesky factorized Conjugate Gradient algorithm for 2d symmetric problems) was developed to solve a linear symmetric matrix system arising from a 9-point discretization of two-dimensional elliptic and parabolic partial differential equations found in plasma physics applications, such as resistive MHD, spatial diffusive transport, and phase space transport (Fokker-Planck equation) problems. These problems share the common feature of being stiff and requiring implicit solution techniques. When these parabolic or elliptic PDE''s are discretized withmore » finite-difference or finite-element methods,the resulting matrix system is frequently of block-tridiagonal form. To use ICCG2, the discretization of the two-dimensional partial differential equation and its boundary conditions must result in a block-tridiagonal supermatrix composed of elementary tridiagonal matrices. The incomplete Cholesky conjugate gradient algorithm is used to solve the linear symmetric matrix equation. Loops are arranged to vectorize on the Cray1 with the CFT compiler, wherever possible. Recursive loops, which cannot be vectorized, are written for optimum scalar speed. For matrices lacking symmetry, ILUCG2 should be used. Similar methods in three dimensions are available in ICCG3 and ILUCG3. A general source containing extensions and macros, which must be processed by a pre-compiler to obtain the standard FORTRAN source, is provided along with the standard FORTRAN source because it is believed to be more readable. The pre-compiler is not included, but pre-compilation may be performed by a text editor as described in the UCRL-88746 Preprint.« less

  12. 2d PDE Linear Asymmetric Matrix Solver

    1983-10-01

    ILUCG2 (Incomplete LU factorized Conjugate Gradient algorithm for 2d problems) was developed to solve a linear asymmetric matrix system arising from a 9-point discretization of two-dimensional elliptic and parabolic partial differential equations found in plasma physics applications, such as plasma diffusion, equilibria, and phase space transport (Fokker-Planck equation) problems. These equations share the common feature of being stiff and requiring implicit solution techniques. When these parabolic or elliptic PDE''s are discretized with finite-difference or finite-elementmore » methods, the resulting matrix system is frequently of block-tridiagonal form. To use ILUCG2, the discretization of the two-dimensional partial differential equation and its boundary conditions must result in a block-tridiagonal supermatrix composed of elementary tridiagonal matrices. A generalization of the incomplete Cholesky conjugate gradient algorithm is used to solve the matrix equation. Loops are arranged to vectorize on the Cray1 with the CFT compiler, wherever possible. Recursive loops, which cannot be vectorized, are written for optimum scalar speed. For problems having a symmetric matrix ICCG2 should be used since it runs up to four times faster and uses approximately 30% less storage. Similar methods in three dimensions are available in ICCG3 and ILUCG3. A general source, containing extensions and macros, which must be processed by a pre-compiler to obtain the standard FORTRAN source, is provided along with the standard FORTRAN source because it is believed to be more readable. The pre-compiler is not included, but pre-compilation may be performed by a text editor as described in the UCRL-88746 Preprint.« less

  13. Position control using 2D-to-2D feature correspondences in vision guided cell micromanipulation.

    PubMed

    Zhang, Yanliang; Han, Mingli; Shee, Cheng Yap; Ang, Wei Tech

    2007-01-01

    Conventional camera calibration that utilizes the extrinsic and intrinsic parameters of the camera and the objects has certain limitations for micro-level cell operations due to the presence of hardware deviations and external disturbances during the experimental process, thereby invalidating the extrinsic parameters. This invalidation is often neglected in macro-world visual servoing and affects the visual image processing quality, causing deviation from the desired position in micro-level cell operations. To increase the success rate of vision guided biological micromanipulations, a novel algorithm monitoring the changing image pattern of the manipulators including the injection micropipette and cell holder is designed and implemented based on 2 dimensional (2D)-to 2D feature correspondences and can adjust the manipulator and perform position control simultaneously. When any deviation is found, the manipulator is retracted to the initial focusing plane before continuing the operation.

  14. A Planar Quantum Transistor Based on 2D-2D Tunneling in Double Quantum Well Heterostructures

    SciTech Connect

    Baca, W.E.; Blount, M.A.; Hafich, M.J.; Lyo, S.K.; Moon, J.S.; Reno, J.L.; Simmons, J.A.; Wendt, J.R.

    1998-12-14

    We report on our work on the double electron layer tunneling transistor (DELTT), based on the gate-control of two-dimensional -- two-dimensional (2D-2D) tunneling in a double quantum well heterostructure. While previous quantum transistors have typically required tiny laterally-defined features, by contrast the DELTT is entirely planar and can be reliably fabricated in large numbers. We use a novel epoxy-bond-and-stop-etch (EBASE) flip-chip process, whereby submicron gating on opposite sides of semiconductor epitaxial layers as thin as 0.24 microns can be achieved. Because both electron layers in the DELTT are 2D, the resonant tunneling features are unusually sharp, and can be easily modulated with one or more surface gates. We demonstrate DELTTs with peak-to-valley ratios in the source-drain I-V curve of order 20:1 below 1 K. Both the height and position of the resonant current peak can be controlled by gate voltage over a wide range. DELTTs with larger subband energy offsets ({approximately} 21 meV) exhibit characteristics that are nearly as good at 77 K, in good agreement with our theoretical calculations. Using these devices, we also demonstrate bistable memories operating at 77 K. Finally, we briefly discuss the prospects for room temperature operation, increases in gain, and high-speed.

  15. 'Brukin2D': a 2D visualization and comparison tool for LC-MS data

    PubMed Central

    Tsagkrasoulis, Dimosthenis; Zerefos, Panagiotis; Loudos, George; Vlahou, Antonia; Baumann, Marc; Kossida, Sophia

    2009-01-01

    Background Liquid Chromatography-Mass Spectrometry (LC-MS) is a commonly used technique to resolve complex protein mixtures. Visualization of large data sets produced from LC-MS, namely the chromatogram and the mass spectra that correspond to its compounds is the focus of this work. Results The in-house developed 'Brukin2D' software, built in Matlab 7.4, which is presented here, uses the compound data that are exported from the Bruker 'DataAnalysis' program, and depicts the mean mass spectra of all the chromatogram compounds from one LC-MS run, in one 2D contour/density plot. Two contour plots from different chromatograph runs can then be viewed in the same window and automatically compared, in order to find their similarities and differences. The results of the comparison can be examined through detailed mass quantification tables, while chromatogram compound statistics are also calculated during the procedure. Conclusion 'Brukin2D' provides a user-friendly platform for quick, easy and integrated view of complex LC-MS data. The software is available at . PMID:19534737

  16. Inhibition of human cytochrome P450 2D6 (CYP2D6) by methadone.

    PubMed Central

    Wu, D; Otton, S V; Sproule, B A; Busto, U; Inaba, T; Kalow, W; Sellers, E M

    1993-01-01

    1. In microsomes prepared from three human livers, methadone competitively inhibited the O-demethylation of dextromethorphan, a marker substrate for CYP2D6. The apparent Ki value of methadone ranged from 2.5 to 5 microM. 2. Two hundred and fifty-two (252) white Caucasians, including 210 unrelated healthy volunteers and 42 opiate abusers undergoing treatment with methadone were phenotyped using dextromethorphan as the marker drug. Although the frequency of poor metabolizers was similar in both groups, the extensive metabolizers among the opiate abusers tended to have higher O-demethylation metabolic ratios and to excrete less of the dose as dextromethorphan metabolites than control extensive metabolizer subjects. These data suggest inhibition of CYP2D6 by methadone in vivo as well. 3. Because methadone is widely used in the treatment of opiate abuse, inhibition of CYP2D6 activity in these patients might contribute to exaggerated response or unexpected toxicity from drugs that are substrates of this enzyme. PMID:8448065

  17. AlxC Monolayer Sheets: Two-Dimensional Networks with Planar Tetracoordinate Carbon and Potential Applications as Donor Materials in Solar Cell.

    PubMed

    Dai, Jun; Wu, Xiaojun; Yang, Jinlong; Zeng, Xiao Cheng

    2014-06-19

    We perform a global search of the most stable structures of 2D stoichiometric AlxC (x = 1/3, 1, 2, and 3) monolayer sheets. In the most stable 2D planar AlC network, every carbon atom is tetracoordinated. In addition to the structure of AlC, structures of the most stable Al2C and Al3C monolayer sheets are also predicted for the first time. AlC and Al2C monolayers are semiconducting, while Al3C monolayer is metallic. In particular, Al2C monolayer possesses a bandgap of 1.05 eV (based on HSE06 calculation), a value suitable for photovoltaic applications. Moreover, three Al2C/WSe2, Al2C/MoTe2, and AlC/ZnO van der Waals heterobilayers are investigated, and their power conversion efficiencies are estimated to be in the range of 12-18%. The near-perfect match in lattice constants between the Al2C monolayer and PdO (100) surface suggests strong likelihood of experimental realization of the Al2C monolayer on the PdO (100) substrate. PMID:26270493

  18. AlxC Monolayer Sheets: Two-Dimensional Networks with Planar Tetracoordinate Carbon and Potential Applications as Donor Materials in Solar Cell.

    PubMed

    Dai, Jun; Wu, Xiaojun; Yang, Jinlong; Zeng, Xiao Cheng

    2014-06-19

    We perform a global search of the most stable structures of 2D stoichiometric AlxC (x = 1/3, 1, 2, and 3) monolayer sheets. In the most stable 2D planar AlC network, every carbon atom is tetracoordinated. In addition to the structure of AlC, structures of the most stable Al2C and Al3C monolayer sheets are also predicted for the first time. AlC and Al2C monolayers are semiconducting, while Al3C monolayer is metallic. In particular, Al2C monolayer possesses a bandgap of 1.05 eV (based on HSE06 calculation), a value suitable for photovoltaic applications. Moreover, three Al2C/WSe2, Al2C/MoTe2, and AlC/ZnO van der Waals heterobilayers are investigated, and their power conversion efficiencies are estimated to be in the range of 12-18%. The near-perfect match in lattice constants between the Al2C monolayer and PdO (100) surface suggests strong likelihood of experimental realization of the Al2C monolayer on the PdO (100) substrate.

  19. Using Microfluidics to Measure the Equation of State for a 2D Colloidal Membrane

    NASA Astrophysics Data System (ADS)

    Balchunas, Andrew; Cabanas, Rafael; Fraden, Seth; Dogic, Zvonimir

    2015-03-01

    In the presence of non-adsorbing polymer, monodisperse filamentous viruses assembles into colloidal membranes which are 2D liquid-like one-rod-length-thick monolayers of aligned rods. Colloidal membranes are of particular interest because their properties are accounted for by the same theoretical models that are used to describe biophysics of conventional lipid bilayers. However, bulk membrane formation only occurs over a very limited range of depletant concentrations and ionic strengths. In order to explore the properties of the colloidal membranes under a much wider range of molecular parameters, we have develop a microfluidics technique that allows for in-site exchange of the enveloping polymer suspension thus allowing us to access the region of phase space where membranes are metastable. Using our technique we determine how the colloidal membrane area depends on applied osmotic pressure allowing us to determine its equation of state. We also characterize the dynamics of the constituent rods by using single molecules tracking techniques.

  20. Building gold nanonetworks from 2-D to quasi-3-D: thickness depended properties

    NASA Astrophysics Data System (ADS)

    Yu, Xiaojing; Wan, Xiaowen; Wang, Liqun; Yang, Zhimao; Ding, Bingjun; Yang, Shengchun

    2014-03-01

    In this work, an effective approach to control the thickness and porosity of porous gold nanonetworks (PGNs) was demonstrated. The 3-dimensional (3-D) PGNs were accomplished by repeated overlaying of two-dimensional (2-D) monolayer gold nanonetworks which assembled at the pentanol/water interface. The porosity of the PGNs can be improved by increasing the number of layers, which greatly enhances the intralayer and interlayer plasmon coupling and the mass diffusion of the analyte molecules, resulting in an improved sensitivity for SERS and glucose detection. In addition, the current approach also offered an effect method to produce 3-D porous nanostructures through the self-assembly of the isolated nanoparticles (NPs).

  1. Symmetry origins of the `caldera' valence band distortion in 2D semiconductors

    NASA Astrophysics Data System (ADS)

    Li, Pengke; Appelbaum, Ian; Physics Department Team

    The electronic structures of many two-dimensional van der Waals semiconductors exhibit various fascinating properties distinct from their three-dimensional bulk counterparts. Through an examination of their lattice symmetries, we identify several universal rules dictating their band dispersion in the monolayer limit, where in-plane mirror symmetry and quantum confinement play critical roles. Taking group-III metal monochalcogenides (such as GaSe) as an example, we reveal the origin of the unusual `caldera' shape of the valence band edge (otherwise inelegantly dubbed an `upside down Mexican hat'), which we show is surprisingly common among other 2D semiconductors (such as in phosphorene for k along its zigzag direction). Reference: arXiv:1508.06963

  2. In vivo biomarker expression patterns are preserved in 3D cultures of Prostate Cancer

    SciTech Connect

    Windus, Louisa C.E.; Kiss, Debra L.; Glover, Tristan; Avery, Vicky M.

    2012-11-15

    Here we report that Prostate Cancer (PCa) cell-lines DU145, PC3, LNCaP and RWPE-1 grown in 3D matrices in contrast to conventional 2D monolayers, display distinct differences in cell morphology, proliferation and expression of important biomarker proteins associated with cancer progression. Consistent with in vivo growth rates, in 3D cultures, all PCa cell-lines were found to proliferate at significantly lower rates in comparison to their 2D counterparts. Moreover, when grown in a 3D matrix, metastatic PC3 cell-lines were found to mimic more precisely protein expression patterns of metastatic tumour formation as found in vivo. In comparison to the prostate epithelial cell-line RWPE-1, metastatic PC3 cell-lines exhibited a down-regulation of E-cadherin and {alpha}6 integrin expression and an up-regulation of N-cadherin, Vimentin and {beta}1 integrin expression and re-expressed non-transcriptionally active AR. In comparison to the non-invasive LNCaP cell-lines, PC3 cells were found to have an up-regulation of chemokine receptor CXCR4, consistent with a metastatic phenotype. In 2D cultures, there was little distinction in protein expression between metastatic, non-invasive and epithelial cells. These results suggest that 3D cultures are more representative of in vivo morphology and may serve as a more biologically relevant model in the drug discovery pipeline. -- Highlights: Black-Right-Pointing-Pointer We developed and optimised 3D culturing techniques for Prostate Cancer cell-lines. Black-Right-Pointing-Pointer We investigated biomarker expression in 2D versus 3D culture techniques. Black-Right-Pointing-Pointer Metastatic PC3 cells re-expressed non-transcriptionally active androgen receptor. Black-Right-Pointing-Pointer Metastatic PCa cell lines retain in vivo-like antigenic profiles in 3D cultures.

  3. The 2-D growth of gold on single-layer graphene/Ru(0001): Enhancement of CO adsorption

    SciTech Connect

    Liu, Li; Zhou, Zihao; Guo, Qinlin; Yan, Zhen; Yao, Yunxi; Goodman, D. Wayne

    2011-09-01

    The growth and morphology of two-dimensional (2-D) gold islands on a single-layer graphene supported on Ru(0001) have been studied by scanning tunneling microscopy (STM). Our findings show that gold exhibits 2-D structures up to a gold dosage of 0.75 equivalent monolayers, and that these 2-D gold islands are thermally stable at room temperature. Parallel polarization modulation infrared reflection absorption spectroscopic (PM-IRAS) and high resolution electron energy loss spectroscopic (HREELS) studies indicate that carbon monoxide (CO) adsorbs on these 2-D gold islands at 85 K, showing a characteristic CO stretching feature at 2095 cm-1 for a saturation coverage of CO. The red shift of the CO stretching frequency compared to that on charge neutral gold is consistent with electron transfer from graphene to gold, i.e., an electron-rich gold overlayer. Preliminary data obtained by dosing molecular oxygen onto this CO pre-covered surface suggest that the 2-D gold islands catalyze the oxidation of CO.

  4. Magnetic Properties of Restacked 2D Spin 1/2 honeycomb RuCl3 Nanosheets.

    PubMed

    Weber, Daniel; Schoop, Leslie M; Duppel, Viola; Lippmann, Judith M; Nuss, Jürgen; Lotsch, Bettina V

    2016-06-01

    Spin 1/2 honeycomb materials have gained substantial interest due to their exotic magnetism and possible application in quantum computing. However, in all current materials out-of-plane interactions are interfering with the in-plane order, hence a true 2D magnetic honeycomb system is still in demand. Here, we report the exfoliation of the magnetic semiconductor α-RuCl3 into the first halide monolayers and the magnetic characterization of the spin 1/2 honeycomb arrangement of turbostratically stacked RuCl3 monolayers. The exfoliation is based on a reductive lithiation/hydration approach, which gives rise to a loss of cooperative magnetism due to the disruption of the spin 1/2 state by electron injection into the layers. The restacked, macroscopic pellets of RuCl3 layers lack symmetry along the stacking direction. After an oxidative treatment, cooperative magnetism similar to the bulk is restored. The oxidized pellets of restacked single layers feature a magnetic transition at TN = 7 K if the field is aligned parallel to the ab-plane, while the magnetic properties differ from bulk α-RuCl3 if the field is aligned perpendicular to the ab-plane. The deliberate introduction of turbostratic disorder to manipulate the magnetic properties of RuCl3 is of interest for research in frustrated magnetism and complex magnetic order as predicted by the Kitaev-Heisenberg model. PMID:27176463

  5. Magnetic Properties of Restacked 2D Spin 1/2 honeycomb RuCl3 Nanosheets.

    PubMed

    Weber, Daniel; Schoop, Leslie M; Duppel, Viola; Lippmann, Judith M; Nuss, Jürgen; Lotsch, Bettina V

    2016-06-01

    Spin 1/2 honeycomb materials have gained substantial interest due to their exotic magnetism and possible application in quantum computing. However, in all current materials out-of-plane interactions are interfering with the in-plane order, hence a true 2D magnetic honeycomb system is still in demand. Here, we report the exfoliation of the magnetic semiconductor α-RuCl3 into the first halide monolayers and the magnetic characterization of the spin 1/2 honeycomb arrangement of turbostratically stacked RuCl3 monolayers. The exfoliation is based on a reductive lithiation/hydration approach, which gives rise to a loss of cooperative magnetism due to the disruption of the spin 1/2 state by electron injection into the layers. The restacked, macroscopic pellets of RuCl3 layers lack symmetry along the stacking direction. After an oxidative treatment, cooperative magnetism similar to the bulk is restored. The oxidized pellets of restacked single layers feature a magnetic transition at TN = 7 K if the field is aligned parallel to the ab-plane, while the magnetic properties differ from bulk α-RuCl3 if the field is aligned perpendicular to the ab-plane. The deliberate introduction of turbostratic disorder to manipulate the magnetic properties of RuCl3 is of interest for research in frustrated magnetism and complex magnetic order as predicted by the Kitaev-Heisenberg model.

  6. Multifunctional self-assembled monolayers

    SciTech Connect

    Zawodzinski, T.; Bar, G.; Rubin, S.; Uribe, F.; Ferrais, J.

    1996-06-01

    This is the final report of at three year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The specific goals of this research project were threefold: to develop multifunctional self-assembled monolayers, to understand the role of monolayer structure on the functioning of such systems, and to apply this knowledge to the development of electrochemical enzyme sensors. An array of molecules that can be used to attach electrochemically active biomolecules to gold surfaces has been synthesized. Several members of a class of electroactive compounds have been characterized and the factors controlling surface modification are beginning to be characterized. Enzymes have been attached to self-assembled molecules arranged on the gold surface, a critical step toward the ultimate goal of this project. Several alternative enzyme attachment strategies to achieve robust enzyme- modified surfaces have been explored. Several means of juxtaposing enzymes and mediators, electroactive compounds through which the enzyme can exchange electrons with the electrode surface, have also been investigated. Finally, the development of sensitive biosensors based on films loaded with nanoscale-supported gold particles that have surface modified with the self-assembled enzyme and mediator have been explored.

  7. Correlated Electron Phenomena in 2D Materials

    NASA Astrophysics Data System (ADS)

    Lambert, Joseph G.

    In this thesis, I present experimental results on coherent electron phenomena in layered two-dimensional materials: single layer graphene and van der Waals coupled 2D TiSe2. Graphene is a two-dimensional single-atom thick sheet of carbon atoms first derived from bulk graphite by the mechanical exfoliation technique in 2004. Low-energy charge carriers in graphene behave like massless Dirac fermions, and their density can be easily tuned between electron-rich and hole-rich quasiparticles with electrostatic gating techniques. The sharp interfaces between regions of different carrier densities form barriers with selective transmission, making them behave as partially reflecting mirrors. When two of these interfaces are set at a separation distance within the phase coherence length of the carriers, they form an electronic version of a Fabry-Perot cavity. I present measurements and analysis of multiple Fabry-Perot modes in graphene with parallel electrodes spaced a few hundred nanometers apart. Transition metal dichalcogenide (TMD) TiSe2 is part of the family of materials that coined the term "materials beyond graphene". It contains van der Waals coupled trilayer stacks of Se-Ti-Se. Many TMD materials exhibit a host of interesting correlated electronic phases. In particular, TiSe2 exhibits chiral charge density waves (CDW) below TCDW ˜ 200 K. Upon doping with copper, the CDW state gets suppressed with Cu concentration, and CuxTiSe2 becomes superconducting with critical temperature of T c = 4.15 K. There is still much debate over the mechanisms governing the coexistence of the two correlated electronic phases---CDW and superconductivity. I will present some of the first conductance spectroscopy measurements of proximity coupled superconductor-CDW systems. Measurements reveal a proximity-induced critical current at the Nb-TiSe2 interfaces, suggesting pair correlations in the pure TiSe2. The results indicate that superconducting order is present concurrently with CDW in

  8. Structure and interaction in 2D assemblies of tobacco mosaic viruses

    SciTech Connect

    Yang, L.; Wang. S.; Masafumi, F.; Checco, A.; Zhongwei, N.; Wang, Q.

    2009-08-27

    We created two-dimensional (2D) assemblies of tobacco mosaic viruses (TMVs) and characterized their structures using Atomic Force Microscopy (AFM) and X-ray scattering. The TMVs were adsorbed on an oppositely charged, fluid lipid monolayer supported by a solid substrate and submerged in a buffer solution. The lipid monolayer confined the viral particles within a plane, while providing them with lateral mobility so that overall the TMV assembly behaved like a 2D liquid. We controlled the inter-particle interaction by adjusting the chemical condition in the buffer to induce ordered TMV assemblies. We found that the presence of the lipid layer was essential for forming ordered TMV assemblies. Packed TMV assemblies formed on the lipid layer, with an average inter-particle spacing of 42 nm. By introducing Ca2+ ions into the buffer solution, we were able to improve the in-plane order within the TMV assemblies and reduce the average inter-particle spacing to 20 nm, compared to the TMV diameter of 18 nm. Quantitative analysis of the X-ray scattering data shows that the structural order within the TMV assemblies prepared under a Ca{sup 2+}-free buffer solution is consistent with purely repulsive, electrostatic inter-particle interaction. In contrast, the structural order within Ca{sup 2+}-induced TMV assemblies is consistent with the behavior of a fluid of sticky rods, implying the presence of a strong attraction between TMVs. In addition to the screening of Coulomb repulsion, this behavior is likely the result of counterion-induced as well as membrane-mediated attractions.

  9. Structure and Interaction in 2D Assemblies of Tobacco Mosaic Viruses

    SciTech Connect

    Fukuto, M.; Yang, L.; Wang, S.; Fukuto, M.; Checco, A.; Niu, Z.; Wang, Q.

    2009-12-07

    We created two-dimensional (2D) assemblies of tobacco mosaic viruses (TMVs) and characterized their structures using Atomic Force Microscopy (AFM) and X-ray scattering. The TMVs were adsorbed on an oppositely charged, fluid lipid monolayer supported by a solid substrate and submerged in a buffer solution. The lipid monolayer confined the viral particles within a plane, while providing them with lateral mobility so that overall the TMV assembly behaved like a 2D liquid. We controlled the inter-particle interaction by adjusting the chemical condition in the buffer to induce ordered TMV assemblies. We found that the presence of the lipid layer was essential for forming ordered TMV assemblies. Packed TMV assemblies formed on the lipid layer, with an average inter-particle spacing of 42 nm. By introducing Ca{sup 2+} ions into the buffer solution, we were able to improve the in-plane order within the TMV assemblies and reduce the average inter-particle spacing to 20 nm, compared to the TMV diameter of 18 nm. Quantitative analysis of the X-ray scattering data shows that the structural order within the TMV assemblies prepared under a Ca{sup 2+}-free buffer solution is consistent with purely repulsive, electrostatic inter-particle interaction. In contrast, the structural order within Ca{sup 2+}-induced TMV assemblies is consistent with the behavior of a fluid of sticky rods, implying the presence of a strong attraction between TMVs. In addition to the screening of Coulomb repulsion, this behavior is likely the result of counterion-induced as well as membrane-mediated attractions.

  10. The impact of pore structure and surface roughness on capillary trapping for 2-D and 3-D porous media: Comparison with percolation theory

    NASA Astrophysics Data System (ADS)

    Geistlinger, Helmut; Ataei-Dadavi, Iman; Mohammadian, Sadjad; Vogel, Hans-Jörg

    2015-11-01

    We study the impact of pore structure and surface roughness on capillary trapping of nonwetting gas phase during imbibition with water for capillary numbers between 10-7 and 5 × 10-5, within glass beads, natural sands, glass beads monolayers, and 2-D micromodels. The materials exhibit different roughness of the pore-solid interface. We found that glass beads and natural sands, which exhibit nearly the same grain size distribution, pore size distribution, and connectivity, showed a significant difference of the trapped gas phase of about 15%. This difference can be explained by the microstructure of the pore-solid interface. Based on the visualization of the trapping dynamics within glass beads monolayers and 2-D micromodels, we could show that bypass trapping controls the trapping process in glass beads monolayers, while snap-off trapping controls the trapping process in 2-D micromodels. We conclude that these different trapping processes are the reason for the different trapping efficiency, when comparing glass beads packs with natural sand packs. Moreover, for small capillary numbers of 10-6, we found that the cluster size distribution of trapped gas clusters of all 2-D and 3-D porous media can be described by a universal power law behavior predicted from percolation theory. This cannot be expected a priori for 2-D porous media, because bicontinuity of the two bulk phases is violated. Obviously, bicontinuity holds for the thin-film water phase and the bulk gas phase. The snap-off trapping process leads to ordinary bond percolation in front of the advancing bulk water phase and is the reason for the observed universal power law behavior in 2-D micromodels with rough surfaces.

  11. CYP2D7 Sequence Variation Interferes with TaqMan CYP2D6*15 and *35 Genotyping

    PubMed Central

    Riffel, Amanda K.; Dehghani, Mehdi; Hartshorne, Toinette; Floyd, Kristen C.; Leeder, J. Steven; Rosenblatt, Kevin P.; Gaedigk, Andrea

    2016-01-01

    TaqMan™ genotyping assays are widely used to genotype CYP2D6, which encodes a major drug metabolizing enzyme. Assay design for CYP2D6 can be challenging owing to the presence of two pseudogenes, CYP2D7 and CYP2D8, structural and copy number variation and numerous single nucleotide polymorphisms (SNPs) some of which reflect the wild-type sequence of the CYP2D7 pseudogene. The aim of this study was to identify the mechanism causing false-positive CYP2D6*15 calls and remediate those by redesigning and validating alternative TaqMan genotype assays. Among 13,866 DNA samples genotyped by the CompanionDx® lab on the OpenArray platform, 70 samples were identified as heterozygotes for 137Tins, the key SNP of CYP2D6*15. However, only 15 samples were confirmed when tested with the Luminex xTAG CYP2D6 Kit and sequencing of CYP2D6-specific long range (XL)-PCR products. Genotype and gene resequencing of CYP2D6 and CYP2D7-specific XL-PCR products revealed a CC>GT dinucleotide SNP in exon 1 of CYP2D7 that reverts the sequence to CYP2D6 and allows a TaqMan assay PCR primer to bind. Because CYP2D7 also carries a Tins, a false-positive mutation signal is generated. This CYP2D7 SNP was also responsible for generating false-positive signals for rs769258 (CYP2D6*35) which is also located in exon 1. Although alternative CYP2D6*15 and *35 assays resolved the issue, we discovered a novel CYP2D6*15 subvariant in one sample that carries additional SNPs preventing detection with the alternate assay. The frequency of CYP2D6*15 was 0.1% in this ethnically diverse U.S. population sample. In addition, we also discovered linkage between the CYP2D7 CC>GT dinucleotide SNP and the 77G>A (rs28371696) SNP of CYP2D6*43. The frequency of this tentatively functional allele was 0.2%. Taken together, these findings emphasize that regardless of how careful genotyping assays are designed and evaluated before being commercially marketed, rare or unknown SNPs underneath primer and/or probe regions can impact

  12. CYP2D7 Sequence Variation Interferes with TaqMan CYP2D6 (*) 15 and (*) 35 Genotyping.

    PubMed

    Riffel, Amanda K; Dehghani, Mehdi; Hartshorne, Toinette; Floyd, Kristen C; Leeder, J Steven; Rosenblatt, Kevin P; Gaedigk, Andrea

    2015-01-01

    TaqMan™ genotyping assays are widely used to genotype CYP2D6, which encodes a major drug metabolizing enzyme. Assay design for CYP2D6 can be challenging owing to the presence of two pseudogenes, CYP2D7 and CYP2D8, structural and copy number variation and numerous single nucleotide polymorphisms (SNPs) some of which reflect the wild-type sequence of the CYP2D7 pseudogene. The aim of this study was to identify the mechanism causing false-positive CYP2D6 (*) 15 calls and remediate those by redesigning and validating alternative TaqMan genotype assays. Among 13,866 DNA samples genotyped by the CompanionDx® lab on the OpenArray platform, 70 samples were identified as heterozygotes for 137Tins, the key SNP of CYP2D6 (*) 15. However, only 15 samples were confirmed when tested with the Luminex xTAG CYP2D6 Kit and sequencing of CYP2D6-specific long range (XL)-PCR products. Genotype and gene resequencing of CYP2D6 and CYP2D7-specific XL-PCR products revealed a CC>GT dinucleotide SNP in exon 1 of CYP2D7 that reverts the sequence to CYP2D6 and allows a TaqMan assay PCR primer to bind. Because CYP2D7 also carries a Tins, a false-positive mutation signal is generated. This CYP2D7 SNP was also responsible for generating false-positive signals for rs769258 (CYP2D6 (*) 35) which is also located in exon 1. Although alternative CYP2D6 (*) 15 and (*) 35 assays resolved the issue, we discovered a novel CYP2D6 (*) 15 subvariant in one sample that carries additional SNPs preventing detection with the alternate assay. The frequency of CYP2D6 (*) 15 was 0.1% in this ethnically diverse U.S. population sample. In addition, we also discovered linkage between the CYP2D7 CC>GT dinucleotide SNP and the 77G>A (rs28371696) SNP of CYP2D6 (*) 43. The frequency of this tentatively functional allele was 0.2%. Taken together, these findings emphasize that regardless of how careful genotyping assays are designed and evaluated before being commercially marketed, rare or unknown SNPs underneath primer

  13. Stilling Waves with Ordered Molecular Monolayers

    ERIC Educational Resources Information Center

    Vitz, Ed

    2008-01-01

    A demonstration of the damping effect of an oil monolayer on water waves is described. The history of this remarkable demonstration--with a 2000 (or more) year span--and a brief explanation in terms of the properties of water and the monolayer are presented. If a layer of olive oil, one molecule thick (about one-ten millionth of a centimeter), is…

  14. Interfacial properties in Langmuir monolayers and LB films of DPPC with partially fluorinated alcohol (F8H7OH).

    PubMed

    Nakahara, Hiromichi; Hirano, Chikayo; Fujita, Ichiro; Shibata, Osamu

    2013-01-01

    Two-component interactions between (perfluorooctyl) heptanol (F8H7OH) and dipalmitoylphosphatidylcholine (DPPC), which is a major component of pulmonary surfactants in mammals, were systematically elucidated using Langmuir monolayers and Langmuir-Blodgett (LB) films of the compounds. The interactions such as the miscibility of the compounds and their phase behavior were examined from thermodynamic and morphological perspectives. The surface pressure (π)-molecular area (A) and surface potential (ΔV)-A isotherms of the binary monolayers containing F8H7OH in different mole fractions (XF8H7OH) were measured simultaneously. The excess Gibbs free energy of mixing of the two components was calculated from the π-A isotherms. The resulting isotherm data were employed to construct a two-dimensional (2D) phase diagram of the system. The phase diagram revealed that the transition pressure as well as the monolayer collapse pressure change with changes in XF8H7OH. These thermodynamic analyses suggested that the miscibility of the two components and the solidification of DPPC monolayers can be induced by the addition of F8H7OH. The phase behavior upon monolayer compression was observed morphologically in situ using Brewster angle microscopy (BAM) and fluorescence microscopy (FM), as well as ex situ using atomic force microscopy (AFM). Interestingly, the AFM-based analysis revealed the formation of monodispersed 2D micelles consisting of F8H7OH at low surface pressures.

  15. Dynamics driven by lipophilic force in Langmuir monolayers: In-plane and out-of-plane growth

    NASA Astrophysics Data System (ADS)

    Basak, Uttam Kumar; Datta, Alokmay

    2015-04-01

    While monolayer area fraction versus time (An-t ) curves obtained from surface pressure-area (π -A ) isotherms for desorption-dominated (DD) processes in Langmuir monolayers of fatty acids represent continuous loss, those from Brewster angle microscopy (BAM) also show a two-dimensional (2D) coalescence. For nucleation-dominated (ND) processes both techniques suggest competing processes, with BAM showing 2D coalescence alongside multilayer formation. π enhances both DD and ND processes with a lower cutoff for ND processes, while temperature has a lower cutoff for DD but negligible effect on ND processes. Hydrocarbon chain length has the strongest effect, causing a crossover from DD to ND dynamics. Imaging ellipsometry of horizontally transferred films onto Si(100) shows Stranski-Krastanov-like growth for ND process in an arachidic acid monolayer resulting in successive stages of monolayer, trilayer, and multilayer islands, ridges from lateral island coalescence, and shallow wavelike structures from ridge coalescence on the film surface. These studies show that lipophilic attraction between hydrocarbon chains is the driving force at all stages of long-term monolayer dynamics.

  16. Two-Dimensional Topological Crystalline Insulator and Topological Phase Transition in TlSe and TlS Monolayers.

    PubMed

    Niu, Chengwang; Buhl, Patrick M; Bihlmayer, Gustav; Wortmann, Daniel; Blügel, Stefan; Mokrousov, Yuriy

    2015-09-01

    The properties that distinguish topological crystalline insulator (TCI) and topological insulator (TI) rely on crystalline symmetry and time-reversal symmetry, respectively, which encodes different bulk and surface/edge properties. Here, we predict theoretically that electron-doped TlM (M = S and Se) (110) monolayers realize a family of two-dimensional (2D) TCIs characterized by mirror Chern number CM = -2. Remarkably, under uniaxial strain (≈ 1%), a topological phase transition between 2D TCI and 2D TI is revealed with the calculated spin Chern number CS = -1 for the 2D TI. Using spin-resolved edge states analysis, we show different edge-state behaviors, especially at the time reversal invariant points. Finally, a TlBiSe2/NaCl quantum well is proposed to realize an undoped 2D TCI with inverted gap as large as 0.37 eV, indicating the high possibility for room-temperature observation.

  17. Anisotropic charged impurity-limited carrier mobility in monolayer phosphorene

    SciTech Connect

    Ong, Zhun-Yong; Zhang, Gang; Zhang, Yong Wei

    2014-12-07

    The room temperature carrier mobility in atomically thin 2D materials is usually far below the intrinsic limit imposed by phonon scattering as a result of scattering by remote charged impurities in its environment. We simulate the charged impurity-limited carrier mobility μ in bare and encapsulated monolayer phosphorene. We find a significant temperature dependence in the carrier mobilities (μ ∝ T{sup −γ}) that results from the temperature variability of the charge screening and varies with the crystal orientation. The anisotropy in the effective mass leads to an anisotropic carrier mobility, with the mobility in the armchair direction about one order of magnitude larger than in the zigzag direction. In particular, this mobility anisotropy is enhanced at low temperatures and high carrier densities. Under encapsulation with a high-κ overlayer, the mobility increases by up to an order of magnitude although its temperature dependence and its anisotropy are reduced.

  18. Failure Processes in Embedded Monolayer Graphene under Axial Compression

    PubMed Central

    Androulidakis, Charalampos; Koukaras, Emmanuel N.; Frank, Otakar; Tsoukleri, Georgia; Sfyris, Dimitris; Parthenios, John; Pugno, Nicola; Papagelis, Konstantinos; Novoselov, Kostya S.; Galiotis, Costas

    2014-01-01

    Exfoliated monolayer graphene flakes were embedded in a polymer matrix and loaded under axial compression. By monitoring the shifts of the 2D Raman phonons of rectangular flakes of various sizes under load, the critical strain to failure was determined. Prior to loading care was taken for the examined area of the flake to be free of residual stresses. The critical strain values for first failure were found to be independent of flake size at a mean value of –0.60% corresponding to a yield stress up to -6 GPa. By combining Euler mechanics with a Winkler approach, we show that unlike buckling in air, the presence of the polymer constraint results in graphene buckling at a fixed value of strain with an estimated wrinkle wavelength of the order of 1–2 nm. These results were compared with DFT computations performed on analogue coronene/PMMA oligomers and a reasonable agreement was obtained. PMID:24920340

  19. Chemical Vapor Deposition of Monolayer Mo1−xWxS2 Crystals with Tunable Band Gaps

    PubMed Central

    Wang, Ziqian; Liu, Pan; Ito, Yoshikazu; Ning, Shoucong; Tan, Yongwen; Fujita, Takeshi; Hirata, Akihiko; Chen, Mingwei

    2016-01-01

    Band gap engineering of monolayer transition metal dichalcogenides, such as MoS2 and WS2, is essential for the applications of the two-dimensional (2D) crystals in electronic and optoelectronic devices. Although it is known that chemical mixture can evidently change the band gaps of alloyed Mo1−xWxS2 crystals, the successful growth of Mo1−xWxS2 monolayers with tunable Mo/W ratios has not been realized by conventional chemical vapor deposition. Herein, we developed a low-pressure chemical vapor deposition (LP-CVD) method to grow monolayer Mo1−xWxS2 (x = 0–1) 2D crystals with a wide range of Mo/W ratios. Raman spectroscopy and high-resolution transmission electron microscopy demonstrate the homogeneous mixture of Mo and W in the 2D alloys. Photoluminescence measurements show that the optical band gaps of the monolayer Mo1−xWxS2 crystals strongly depend on the Mo/W ratios and continuously tunable band gap can be achieved by controlling the W or Mo portion by the LP-CVD. PMID:26899364

  20. Coherent Electronic Coupling in Monolayer MoSe2

    NASA Astrophysics Data System (ADS)

    Moody, Galan; Singh, Akshay; Wu, Sanfeng; Wu, Yanwen; Ghimire, Nirmal; Yan, Jiaqiang; Mandrus, David; Xu, Xiaodong; Li, Xiaoqin

    2014-03-01

    Monolayer transition metal dichalcogenides (TMDs) have emerged as an interesting class of two-dimensional materials due to their unique optical properties, such as a crossover from an indirect-to-direct bandgap as well as valley-specific optical selection rules. A striking feature in the linear optical spectra of TMDs is pronounced neutral and charged excitons (trions), with significantly larger binding energies than conventional semiconductors due to reduced screening. Using ultrafast two-color pump-probe spectroscopy, we demonstrate that Coulomb interactions responsible for the large binding energies in monolayer MoSe2 also lead to strong coherent coupling between excitons and trions. Signatures for coherent coupling appear as isolated cross-peaks in a 2D spectrum obtained by tuning the pump and probe wavelengths through the resonances. While incoherent population transfer may partially contribute to one of the peaks, density matrix calculations reveal that the unique peak lineshapes arise from coherent exciton-trion many-body interactions, whose strength is significantly larger compared to conventional semiconductor quantum wells. Strong exciton-trion coherent coupling demonstrated here makes TMDs an excellent platform for future coherent opto-electronic devices. Currently at: National Institute of Standards & Technology, Boulder.

  1. Observation of two distinct negative trions in tungsten disulfide monolayers

    NASA Astrophysics Data System (ADS)

    Boulesbaa, Abdelaziz; Huang, Bing; Wang, Kai; Lin, Ming-Wei; Mahjouri-Samani, Masoud; Rouleau, Christopher; Xiao, Kai; Yoon, Mina; Sumpter, Bobby; Puretzky, Alexander; Geohegan, David

    2015-09-01

    Ultrafast pump-probe spectroscopy of two-dimensional tungsten disulfide monolayers (2 D W S2) grown on sapphire substrates revealed two transient absorption spectral peaks that are attributed to distinct negative trions at ˜2.02 eV (T1) and ˜1.98 eV (T2) . The dynamics measurements indicate that trion formation by the probe is enabled by photodoped 2D WS2 crystals with electrons remaining after trapping of holes from excitons or free electron-hole pairs at defect sites in the crystal or on the substrate. Dynamics of the characteristic absorption bands of excitons XA and XB at ˜2.03 and ˜2.40 eV , respectively, were separately monitored and compared to the photoinduced absorption features. Selective excitation of the lowest exciton level XA using λpump<2.4 eV forms only trion T1, implying that the electron remaining from dissociation of exciton XA is involved in the creation of this trion with a binding energy ˜10 meV with respect to XA. The absorption peak corresponding to trion T2 appears when λpump<2.4 eV , which is just sufficient to excite exciton XB. The dynamics of trion T2 formation are found to correlate with the disappearance of the bleach of the XB exciton, indicating the involvement of holes participating in the bleach dynamics of exciton XB. Static electrical-doping photoabsorption measurements confirm the presence of an induced absorption peak similar to that of T2. Since the proposed trion formation process here involves exciton dissociation through hole trapping by defects in the 2D crystal or substrate, this discovery highlights the strong role of defects in defining optical and electrical properties of 2D metal chalcogenides, which is relevant to a broad spectrum of basic science and technological applications.

  2. Permeability characteristics of human endothelial monolayers seeded on different extracellular matrix proteins.

    PubMed Central

    Nooteboom, A; Hendriks, T; Ottehöller, I; van der Linden, C J

    2000-01-01

    OBJECTIVE: To investigate whether endothelial monolayer permeability changes induced by inflammatory mediators are affected by the extracellular matrix protein used for cell seeding. METHODS: Human umbilical venular endothelial cells (HUVEC) were grown to confluent monolayers on membranes coated with either collagen, fibronectin or gelatin. The permeability to albumin and dextran was then assessed, both under normal conditions and after treatment with tumor necrosis factor-alpha (TNF-alpha) and bacterial lipopolysaccharide (LPS). RESULTS: With any of the three protein coatings, tight junctions were formed all over the monolayers. The permeability of the coated membranes to albumin and dextran was reduced strongly by confluent monolayers; the relative reduction was similar for the three matrix proteins used. Pre-incubation of the monolayers with either TNF-alpha or LPS increased permeability dose dependently. However, the relative increase due to either treatment was independent of the protein used for membrane coating. CONCLUSION: The extracellular matrix protein used for initial seeding of endothelial cultures plays a minor role in determining the permeability changes induced in HUVEC monolayers by inflammatory mediators. PMID:11200364

  3. Comparison of electronic structure between monolayer silicenes on Ag (111)

    NASA Astrophysics Data System (ADS)

    Chun-Liang, Lin; Ryuichi, Arafune; Maki, Kawai; Noriaki, Takagi

    2015-08-01

    The electronic structures of monolayer silicenes (4 × 4 and ) grown on Ag (111) surface are studied by scanning tunneling spectroscopy (STS) and density functional theory (DFT) calculations. While both phases have similar electronic structures around the Fermi level, significant differences are observed in the higher energy unoccupied states. The DFT calculations show that the contributions of Si 3pz orbitals to the unoccupied states are different because of their different buckled configurations. Project supported by the Ministry of Education, Culture, Sports, Science and Technology (MEXT) through Grants-in-Aid for Scientific Research (Grant Nos. 24241040 and 25110008) and the World Premier International Research Center Initiative (WPI), MEXT, Japan.

  4. Mechanical characterization of 2D, 2D stitched, and 3D braided/RTM materials

    NASA Technical Reports Server (NTRS)

    Deaton, Jerry W.; Kullerd, Susan M.; Portanova, Marc A.

    1993-01-01

    Braided composite materials have potential for application in aircraft structures. Fuselage frames, floor beams, wing spars, and stiffeners are examples where braided composites could find application if cost effective processing and damage tolerance requirements are met. Another important consideration for braided composites relates to their mechanical properties and how they compare to the properties of composites produced by other textile composite processes being proposed for these applications. Unfortunately, mechanical property data for braided composites do not appear extensively in the literature. Data are presented in this paper on the mechanical characterization of 2D triaxial braid, 2D triaxial braid plus stitching, and 3D (through-the-thickness) braid composite materials. The braided preforms all had the same graphite tow size and the same nominal braid architectures, (+/- 30 deg/0 deg), and were resin transfer molded (RTM) using the same mold for each of two different resin systems. Static data are presented for notched and unnotched tension, notched and unnotched compression, and compression after impact strengths at room temperature. In addition, some static results, after environmental conditioning, are included. Baseline tension and compression fatigue results are also presented, but only for the 3D braided composite material with one of the resin systems.

  5. A droplet-to-digital (D2D) microfluidic device for single cell assays.

    PubMed

    Shih, Steve C C; Gach, Philip C; Sustarich, Jess; Simmons, Blake A; Adams, Paul D; Singh, Seema; Singh, Anup K

    2015-01-01

    We have developed a new hybrid droplet-to-digital microfluidic platform (D2D) that integrates droplet-in-channel microfluidics with digital microfluidics (DMF) for performing multi-step assays. This D2D platform combines the strengths of the two formats-droplets-in-channel for facile generation of droplets containing single cells, and DMF for on-demand manipulation of droplets including control of different droplet volumes (pL-μL), creation of a dilution series of ionic liquid (IL), and parallel single cell culturing and analysis for IL toxicity screening. This D2D device also allows for automated analysis that includes a feedback-controlled system for merging and splitting of droplets to add reagents, an integrated Peltier element for parallel cell culture at optimum temperature, and an impedance sensing mechanism to control the flow rate for droplet generation and preventing droplet evaporation. Droplet-in-channel is well-suited for encapsulation of single cells as it allows the careful manipulation of flow rates of aqueous phase containing cells and oil to optimize encapsulation. Once single cell containing droplets are generated, they are transferred to a DMF chip via a capillary where they are merged with droplets containing IL and cultured at 30 °C. The DMF chip, in addition to permitting cell culture and reagent (ionic liquid/salt) addition, also allows recovery of individual droplets for off-chip analysis such as further culturing and measurement of ethanol production. The D2D chip was used to evaluate the effect of IL/salt type (four types: NaOAc, NaCl, [C2mim] [OAc], [C2mim] [Cl]) and concentration (four concentrations: 0, 37.5, 75, 150 mM) on the growth kinetics and ethanol production of yeast and as expected, increasing IL concentration led to lower biomass and ethanol production. Specifically, [C2mim] [OAc] had inhibitory effects on yeast growth at concentrations 75 and 150 mM and significantly reduced their ethanol production compared to cells grown

  6. Computational Screening of 2D Materials for Photocatalysis.

    PubMed

    Singh, Arunima K; Mathew, Kiran; Zhuang, Houlong L; Hennig, Richard G

    2015-03-19

    Two-dimensional (2D) materials exhibit a range of extraordinary electronic, optical, and mechanical properties different from their bulk counterparts with potential applications for 2D materials emerging in energy storage and conversion technologies. In this Perspective, we summarize the recent developments in the field of solar water splitting using 2D materials and review a computational screening approach to rapidly and efficiently discover more 2D materials that possess properties suitable for solar water splitting. Computational tools based on density-functional theory can predict the intrinsic properties of potential photocatalyst such as their electronic properties, optical absorbance, and solubility in aqueous solutions. Computational tools enable the exploration of possible routes to enhance the photocatalytic activity of 2D materials by use of mechanical strain, bias potential, doping, and pH. We discuss future research directions and needed method developments for the computational design and optimization of 2D materials for photocatalysis.

  7. Tailoring low-dimensional structures of bismuth on monolayer epitaxial graphene

    PubMed Central

    Chen, H.-H.; Su, S. H.; Chang, S.-L.; Cheng, B.-Y.; Chen, S. W.; Chen, H.-Y.; Lin, M.-F.; Huang, J. C. A.

    2015-01-01

    To improve graphene-based multifunctional devices at nanoscale, a stepwise and controllable fabrication procedure must be elucidated. Here, a series of structural transition of bismuth (Bi) adatoms, adsorbed on monolayer epitaxial graphene (MEG), is explored at room temperature. Bi adatoms undergo a structural transition from one-dimensional (1D) linear structures to two-dimensional (2D) triangular islands and such 2D growth mode is affected by the corrugated substrate. Upon Bi deposition, a little charge transfer occurs and a characteristic peak can be observed in the tunneling spectrum, reflecting the distinctive electronic structure of the Bi adatoms. When annealed to ~500 K, 2D triangular Bi islands aggregate into Bi nanoclusters (NCs) of uniform size. A well-controlled fabrication method is thus demonstrated. The approaches adopted herein provide perspectives for fabricating and characterizing periodic networks on MEG and related systems, which are useful in realizing graphene-based electronic, energy, sensor and spintronic devices. PMID:26100604

  8. Tailoring low-dimensional structures of bismuth on monolayer epitaxial graphene

    NASA Astrophysics Data System (ADS)

    Chen, H.-H.; Su, S. H.; Chang, S.-L.; Cheng, B.-Y.; Chen, S. W.; Chen, H.-Y.; Lin, M.-F.; Huang, J. C. A.

    2015-06-01

    To improve graphene-based multifunctional devices at nanoscale, a stepwise and controllable fabrication procedure must be elucidated. Here, a series of structural transition of bismuth (Bi) adatoms, adsorbed on monolayer epitaxial graphene (MEG), is explored at room temperature. Bi adatoms undergo a structural transition from one-dimensional (1D) linear structures to two-dimensional (2D) triangular islands and such 2D growth mode is affected by the corrugated substrate. Upon Bi deposition, a little charge transfer occurs and a characteristic peak can be observed in the tunneling spectrum, reflecting the distinctive electronic structure of the Bi adatoms. When annealed to ~500 K, 2D triangular Bi islands aggregate into Bi nanoclusters (NCs) of uniform size. A well-controlled fabrication method is thus demonstrated. The approaches adopted herein provide perspectives for fabricating and characterizing periodic networks on MEG and related systems, which are useful in realizing graphene-based electronic, energy, sensor and spintronic devices.

  9. Two-dimensional Cu2Si monolayer with planar hexacoordinate copper and silicon bonding.

    PubMed

    Yang, Li-Ming; Bačić, Vladimir; Popov, Ivan A; Boldyrev, Alexander I; Heine, Thomas; Frauenheim, Thomas; Ganz, Eric

    2015-02-25

    Two-dimensional (2D) materials with planar hypercoordinate motifs are extremely rare due to the difficulty in stabilizing the planar hypercoordinate configurations in extended systems. Furthermore, such exotic motifs are often unstable. We predict a novel Cu2Si 2D monolayer featuring planar hexacoordinate copper and planar hexacoordinate silicon. This is a global minimum in 2D space which displays reduced dimensionality and rule-breaking chemical bonding. This system has been studied with density functional theory, including molecular dynamics simulations and electronic structure calculations. Bond order analysis and partitioning reveals 4c-2e σ bonds that stabilize the two-dimensional structure. We find that the system is quite stable during short annealing simulations up to 900 K, and predict that it is a nonmagnetic metal. This work opens up a new branch of hypercoordinate two-dimensional materials for study.

  10. Interactions among Lung Cancer Cells, Fibroblasts, and Macrophages in 3D Co-Cultures and the Impact on MMP-1 and VEGF Expression.

    PubMed

    Liu, Xiao-Qing; Kiefl, Rosemarie; Roskopf, Claudia; Tian, Fei; Huber, Rudolf M

    2016-01-01

    In vitro cell-based models of lung cancer are frequently employed to study invasion and the mechanisms behind metastasis. However, these models often study only one cell type with two-dimensional (2D) monolayer cell cultures, which do not accurately reflect the complexity of inflammation in vivo. Here, a three-dimensional (3D) cell co-culture collagen gel model was employed, containing human lung adenocarcinoma cells (HCC), human lung fibroblast cells (MRC-5), and macrophages. Cell culture media and cell images were collected, and matrix metalloproteinase-1 (MMP-1) and vascular endothelial growth factor (VEGF) production was monitored under different cell culture conditions. We found that simulating hypoxia and/or serum starvation conditions induced elevated secretion of VEGF in the 3D co-culture model in vitro, but not MMP-1; the morphology of HCC in the 2D versus the 3D co-culture system was extremely different. MMP-1 and VEGF were secreted at higher levels in mixed cell groups rather than mono-culture groups. Therefore, incorporating lung cancer cells, fibroblasts, and macrophages may better reflect physiological metastasis mechanisms compared to mono-culture systems. Tumour stromal cells, macrophages, and fibroblast cells may promote invasion and metastasis, which also provides a new direction for the design of therapies targeted at destroying the stroma of tumor tissues.

  11. Large 2D-arrays of size-controllable silver nanoparticles prepared by hybrid deposition

    NASA Astrophysics Data System (ADS)

    Dieu Thuy Ung, Thi; Hoa Nguyen, Thi; Liem Nguyen, Quang

    2016-09-01

    Two main results are presented in this paper. (i) Silver nanoparticles (AgNPs) with uniform size-distribution and controllability in the range of 20-50 nm were synthesized by seeding and growing at ambient conditions. The single-crystal Ag nano-seeds were created by reduction of AgNO3 in presence of citrate surfactant at 70 °C. Then, importantly, the fresh AgCl precursor was used in the presence of polyvinylpyrrolidone to adjust the reaction rate with ascorbic acid to generate Ag for growing on the surface of single-crystal Ag nano-seeds. The AgNPs size could be well-controlled by varying the amount of Ag nano-seeds while keeping the AgCl precursor concentration to be constant. (ii) The large 2D-arrays with homogeneous and dense monolayers of AgNPs were prepared on ITO substrates by hybrid method, in which the key technological point is the surface functionalization of AgNPs using mixed alkanethiols (dodecanethiol:octadecanethiol = 6:1). We have used the fabricated 2D-arrays from the 50 nm AgNPs as a surface enhanced Raman scattering substrate to take the Raman scattering spectra of rhodamine B (RhB), glucose and viral pathogen (H5N1) at very low concentrations of 10-10 M, 10-12 M and 4 ng μl-1, respectively.

  12. Topologic connection between 2-D layered structures and 3-D diamond structures for conventional semiconductors

    PubMed Central

    Wang, Jianwei; Zhang, Yong

    2016-01-01

    When coming to identify new 2D materials, our intuition would suggest us to look from layered instead of 3D materials. However, since graphite can be hypothetically derived from diamond by stretching it along its [111] axis, many 3D materials can also potentially be explored as new candidates for 2D materials. Using a density functional theory, we perform a systematic study over the common Group IV, III–V, and II–VI semiconductors along different deformation paths to reveal new structures that are topologically connected to but distinctly different from the 3D parent structure. Specifically, we explore two major phase transition paths, originating respectively from wurtzite and NiAs structure, by applying compressive and tensile strain along the symmetry axis, and calculating the total energy changes to search for potential metastable states, as well as phonon spectra to examine the structural stability. Each path is found to further split into two branches under tensile strain–low buckled and high buckled structures, which respectively lead to a low and high buckled monolayer structure. Most promising new layered or planar structures identified include BeO, GaN, and ZnO on the tensile strain side, Ge, Si, and GaP on the compressive strain side. PMID:27090430

  13. Topologic connection between 2-D layered structures and 3-D diamond structures for conventional semiconductors.

    PubMed

    Wang, Jianwei; Zhang, Yong

    2016-01-01

    When coming to identify new 2D materials, our intuition would suggest us to look from layered instead of 3D materials. However, since graphite can be hypothetically derived from diamond by stretching it along its [111] axis, many 3D materials can also potentially be explored as new candidates for 2D materials. Using a density functional theory, we perform a systematic study over the common Group IV, III-V, and II-VI semiconductors along different deformation paths to reveal new structures that are topologically connected to but distinctly different from the 3D parent structure. Specifically, we explore two major phase transition paths, originating respectively from wurtzite and NiAs structure, by applying compressive and tensile strain along the symmetry axis, and calculating the total energy changes to search for potential metastable states, as well as phonon spectra to examine the structural stability. Each path is found to further split into two branches under tensile strain-low buckled and high buckled structures, which respectively lead to a low and high buckled monolayer structure. Most promising new layered or planar structures identified include BeO, GaN, and ZnO on the tensile strain side, Ge, Si, and GaP on the compressive strain side. PMID:27090430

  14. Bonding-restricted structure search for novel 2D materials with dispersed C2 dimers.

    PubMed

    Zhang, Cunzhi; Zhang, Shunhong; Wang, Qian

    2016-01-01

    Currently, the available algorithms for unbiased structure searches are primarily atom-based, where atoms are manipulated as the elementary units, and energy is used as the target function without any restrictions on the bonding of atoms. In fact, in many cases such as nanostructure-assembled materials, the structural units are nanoclusters. We report a study of a bonding-restricted structure search method based on the particle swarm optimization (PSO) for finding the stable structures of two-dimensional (2D) materials containing dispersed C2 dimers rather than individual C atoms. The C2 dimer can be considered as a prototype of nanoclusters. Taking Si-C, B-C and Ti-C systems as test cases, our method combined with density functional theory and phonon calculations uncover new ground state geometrical structures for SiC2, Si2C2, BC2, B2C2, TiC2, and Ti2C2 sheets and their low-lying energy allotropes, as well as their electronic structures. Equally important, this method can be applied to other complex systems even containing f elements and other molecular dimers such as S2, N2, B2 and Si2, where the complex orbital orientations require extensive search for finding the optimal orientations to maximize the bonding with the dimers, predicting new 2D materials beyond MXenes (a family of transition metal carbides or nitrides) and dichalcogenide monolayers. PMID:27403589

  15. Topologic connection between 2-D layered structures and 3-D diamond structures for conventional semiconductors

    NASA Astrophysics Data System (ADS)

    Wang, Jianwei; Zhang, Yong

    2016-04-01

    When coming to identify new 2D materials, our intuition would suggest us to look from layered instead of 3D materials. However, since graphite can be hypothetically derived from diamond by stretching it along its [111] axis, many 3D materials can also potentially be explored as new candidates for 2D materials. Using a density functional theory, we perform a systematic study over the common Group IV, III–V, and II–VI semiconductors along different deformation paths to reveal new structures that are topologically connected to but distinctly different from the 3D parent structure. Specifically, we explore two major phase transition paths, originating respectively from wurtzite and NiAs structure, by applying compressive and tensile strain along the symmetry axis, and calculating the total energy changes to search for potential metastable states, as well as phonon spectra to examine the structural stability. Each path is found to further split into two branches under tensile strain–low buckled and high buckled structures, which respectively lead to a low and high buckled monolayer structure. Most promising new layered or planar structures identified include BeO, GaN, and ZnO on the tensile strain side, Ge, Si, and GaP on the compressive strain side.

  16. Self-Assembled Si(111) Surface States: 2D Dirac Material for THz Plasmonics.

    PubMed

    Wang, Z F; Liu, Feng

    2015-07-10

    Graphene, the first discovered 2D Dirac material, has had a profound impact on science and technology. In the last decade, we have witnessed huge advances in graphene related fundamental and applied research. Here, based on first-principles calculations, we propose a new 2D Dirac band on the Si(111) surface with 1/3 monolayer halogen coverage. The sp(3) dangling bonds form a honeycomb superstructure on the Si(111) surface that results in an anisotropic Dirac band with a group velocity (∼10(6)  m/s) comparable to that in graphene. Most remarkably, the Si-based surface Dirac band can be used to excite a tunable THz plasmon through electron-hole doping. Our results demonstrate a new way to design Dirac states on a traditional semiconductor surface, so as to make them directly compatible with Si technology. We envision this new type of Dirac material to be generalized to other semiconductor surfaces with broad applications.

  17. Bonding-restricted structure search for novel 2D materials with dispersed C2 dimers

    PubMed Central

    Zhang, Cunzhi; Zhang, Shunhong; Wang, Qian

    2016-01-01

    Currently, the available algorithms for unbiased structure searches are primarily atom-based, where atoms are manipulated as the elementary units, and energy is used as the target function without any restrictions on the bonding of atoms. In fact, in many cases such as nanostructure-assembled materials, the structural units are nanoclusters. We report a study of a bonding-restricted structure search method based on the particle swarm optimization (PSO) for finding the stable structures of two-dimensional (2D) materials containing dispersed C2 dimers rather than individual C atoms. The C2 dimer can be considered as a prototype of nanoclusters. Taking Si-C, B-C and Ti-C systems as test cases, our method combined with density functional theory and phonon calculations uncover new ground state geometrical structures for SiC2, Si2C2, BC2, B2C2, TiC2, and Ti2C2 sheets and their low-lying energy allotropes, as well as their electronic structures. Equally important, this method can be applied to other complex systems even containing f elements and other molecular dimers such as S2, N2, B2 and Si2, where the complex orbital orientations require extensive search for finding the optimal orientations to maximize the bonding with the dimers, predicting new 2D materials beyond MXenes (a family of transition metal carbides or nitrides) and dichalcogenide monolayers. PMID:27403589

  18. Bonding-restricted structure search for novel 2D materials with dispersed C2 dimers.

    PubMed

    Zhang, Cunzhi; Zhang, Shunhong; Wang, Qian

    2016-07-12

    Currently, the available algorithms for unbiased structure searches are primarily atom-based, where atoms are manipulated as the elementary units, and energy is used as the target function without any restrictions on the bonding of atoms. In fact, in many cases such as nanostructure-assembled materials, the structural units are nanoclusters. We report a study of a bonding-restricted structure search method based on the particle swarm optimization (PSO) for finding the stable structures of two-dimensional (2D) materials containing dispersed C2 dimers rather than individual C atoms. The C2 dimer can be considered as a prototype of nanoclusters. Taking Si-C, B-C and Ti-C systems as test cases, our method combined with density functional theory and phonon calculations uncover new ground state geometrical structures for SiC2, Si2C2, BC2, B2C2, TiC2, and Ti2C2 sheets and their low-lying energy allotropes, as well as their electronic structures. Equally important, this method can be applied to other complex systems even containing f elements and other molecular dimers such as S2, N2, B2 and Si2, where the complex orbital orientations require extensive search for finding the optimal orientations to maximize the bonding with the dimers, predicting new 2D materials beyond MXenes (a family of transition metal carbides or nitrides) and dichalcogenide monolayers.

  19. Bonding-restricted structure search for novel 2D materials with dispersed C2 dimers

    NASA Astrophysics Data System (ADS)

    Zhang, Cunzhi; Zhang, Shunhong; Wang, Qian

    2016-07-01

    Currently, the available algorithms for unbiased structure searches are primarily atom-based, where atoms are manipulated as the elementary units, and energy is used as the target function without any restrictions on the bonding of atoms. In fact, in many cases such as nanostructure-assembled materials, the structural units are nanoclusters. We report a study of a bonding-restricted structure search method based on the particle swarm optimization (PSO) for finding the stable structures of two-dimensional (2D) materials containing dispersed C2 dimers rather than individual C atoms. The C2 dimer can be considered as a prototype of nanoclusters. Taking Si-C, B-C and Ti-C systems as test cases, our method combined with density functional theory and phonon calculations uncover new ground state geometrical structures for SiC2, Si2C2, BC2, B2C2, TiC2, and Ti2C2 sheets and their low-lying energy allotropes, as well as their electronic structures. Equally important, this method can be applied to other complex systems even containing f elements and other molecular dimers such as S2, N2, B2 and Si2, where the complex orbital orientations require extensive search for finding the optimal orientations to maximize the bonding with the dimers, predicting new 2D materials beyond MXenes (a family of transition metal carbides or nitrides) and dichalcogenide monolayers.

  20. Large 2D-arrays of size-controllable silver nanoparticles prepared by hybrid deposition

    NASA Astrophysics Data System (ADS)

    Dieu Thuy Ung, Thi; Hoa Nguyen, Thi; Liem Nguyen, Quang

    2016-09-01

    Two main results are presented in this paper. (i) Silver nanoparticles (AgNPs) with uniform size-distribution and controllability in the range of 20–50 nm were synthesized by seeding and growing at ambient conditions. The single-crystal Ag nano-seeds were created by reduction of AgNO3 in presence of citrate surfactant at 70 °C. Then, importantly, the fresh AgCl precursor was used in the presence of polyvinylpyrrolidone to adjust the reaction rate with ascorbic acid to generate Ag for growing on the surface of single-crystal Ag nano-seeds. The AgNPs size could be well-controlled by varying the amount of Ag nano-seeds while keeping the AgCl precursor concentration to be constant. (ii) The large 2D-arrays with homogeneous and dense monolayers of AgNPs were prepared on ITO substrates by hybrid method, in which the key technological point is the surface functionalization of AgNPs using mixed alkanethiols (dodecanethiol:octadecanethiol = 6:1). We have used the fabricated 2D-arrays from the 50 nm AgNPs as a surface enhanced Raman scattering substrate to take the Raman scattering spectra of rhodamine B (RhB), glucose and viral pathogen (H5N1) at very low concentrations of 10‑10 M, 10‑12 M and 4 ng μl‑1, respectively.

  1. Synthetic Covalent and Non-Covalent 2D Materials.

    PubMed

    Boott, Charlotte E; Nazemi, Ali; Manners, Ian

    2015-11-16

    The creation of synthetic 2D materials represents an attractive challenge that is ultimately driven by their prospective uses in, for example, electronics, biomedicine, catalysis, sensing, and as membranes for separation and filtration. This Review illustrates some recent advances in this diverse field with a focus on covalent and non-covalent 2D polymers and frameworks, and self-assembled 2D materials derived from nanoparticles, homopolymers, and block copolymers.

  2. Morphological transitions in polymer monolayers under compression.

    PubMed

    Srivastava, S; Basu, J K; Sprung, M; Wang, J

    2009-05-01

    We present a systematic investigation of morphological transitions in poly vinylacetate Langmuir monolayers. On compression, the polymer monolayer is converted to a continuous membrane with a thickness of approximately 2-3 nm. Above a certain surface concentration the monolayer, on water, undergoes a morphological transition-buckling, leading to formation of striped patterns of period of lambda(b) approximately 160 nm, as determined from in situ grazing incidence small angle x-ray scattering measurements. The obtained value is much smaller than what has been typically observed for Langmuir monolayers on water or thin films on soft substrates. Using existing theories for buckling of fluidlike films on fluid substrates, we obtain very low values of bending rigidity and Young's modulus of the polymer monolayer compared to that observed earlier for lipid or polymeric monolayers. Since buckling in these monolayers occurs only above a certain surface concentration, we have looked at the possibility that the buckling in these films occurs due to changes in their mechanical properties under compression. Using the model of Huang and Suo of buckling of solidlike films on viscoelastic substrates, we find values of the mechanical properties, which are much closer to the bulk values but still significantly lower. Although the reduction could be along the lines of what has been observed earlier for ultrathin polymer film or surface layers of polymers, the possibility of micromechanical effects also determining the buckling in such polymer monolayers cannot be ruled out. We have provided possible explanation of the buckling of the poly vinylacetate monolayers in terms of the change in isothermal compression modulus with surface concentration. PMID:19425809

  3. A Geometric Boolean Library for 2D Objects

    2006-01-05

    The 2D Boolean Library is a collection of C++ classes -- which primarily represent 2D geometric data and relationships, and routines -- which contain algorithms for 2D geometric Boolean operations and utility functions. Classes are provided for 2D points, lines, arcs, edgeuses, loops, surfaces and mask sets. Routines are provided that incorporate the Boolean operations Union(OR), XOR, Intersection and Difference. Various analytical geometry routines and routines for importing and exporting the data in various filemore » formats, are also provided in the library.« less

  4. Ultra-high vacuum scanning tunneling microscopy and theoretical studies of 1-halohexane monolayers on graphite

    PubMed Central

    Müller, Thomas; Werblowsky, Tova L.; Florio, Gina M.; Berne, Bruce J.; Flynn, George W.

    2005-01-01

    A simple model system for the 2D self-assembly of functionalized organic molecules on surfaces was examined in a concerted experimental and theoretical effort. Monolayers of 1-halohexanes were formed through vapor deposition onto graphite surfaces in ultrahigh vacuum. Low-temperature scanning tunneling microscopy allowed the molecular conformation, orientation, and monolayer crystallographic parameters to be determined. Essentially identical noncommensurate monolayer structures were found for all 1-halohexanes, with differences in image contrast ascribed mainly to electronic factors. Energy minimizations and molecular dynamics simulations reproduced structural parameters of 1-bromohexane monolayers quantitatively. An analysis of interactions driving the self-assembly process revealed the crucial role played by small but anisotropic electrostatic forces associated with the halogen substituent. While alkyl chain dispersion interactions drive the formation of a close-packed adsorbate monolayer, electrostatic headgroup forces are found to compete successfully in the control of both the angle between lamella and backbone axes and the angle between surface and backbone planes. This competition is consistent with energetic tradeoffs apparent in adsorption energies measured in earlier temperature-programmed desorption studies. In accordance with the higher degree of disorder observed in scanning tunneling microscopy images of 1-fluorohexane, theoretical simulations show that electrostatic forces associated with the fluorine substituent are sufficiently strong to upset the delicate balance of interactions required for the formation of an ordered monolayer. The detailed dissection of the driving forces for self-assembly of these simple model systems is expected to aid in the understanding of the more complex self-assembly processes taking place in the presence of solvent. PMID:15758073

  5. VizieR Online Data Catalog: The 2dF Galaxy Redshift Survey (2dFGRS) (2dFGRS Team, 1998-2003)

    NASA Astrophysics Data System (ADS)

    Colless, M.; Dalton, G.; Maddox, S.; Sutherland, W.; Norberg, P.; Cole, S.; Bland-Hawthorn, J.; Bridges, T.; Cannon, R.; Collins, C.; Couch, W.; Cross, N.; Deeley, K.; de Propris, R.; Driver, S. P.; Efstathiou, G.; Ellis, R. S.; Frenk, C. S.; Glazebrook, K.; Jackson, C.; Lahav, O.; Lewis, I.; Lumsden, S.; Madgwick, D.; Peacock, J. A.; Peterson, B. A.; Price, I.; Seaborne, M.; Taylor, K.

    2007-11-01

    The 2dF Galaxy Redshift Survey (2dFGRS) is a major spectroscopic survey taking full advantage of the unique capabilities of the 2dF facility built by the Anglo-Australian Observatory. The 2dFGRS is integrated with the 2dF QSO survey (2QZ, Cat. VII/241). The 2dFGRS obtained spectra for 245591 objects, mainly galaxies, brighter than a nominal extinction-corrected magnitude limit of bJ=19.45. Reliable (quality>=3) redshifts were obtained for 221414 galaxies. The galaxies cover an area of approximately 1500 square degrees selected from the extended APM Galaxy Survey in three regions: a North Galactic Pole (NGP) strip, a South Galactic Pole (SGP) strip, and random fields scattered around the SGP strip. Redshifts are measured from spectra covering 3600-8000 Angstroms at a two-pixel resolution of 9.0 Angstrom and a median S/N of 13 per pixel. All redshift identifications are visually checked and assigned a quality parameter Q in the range 1-5; Q>=3 redshifts are 98.4% reliable and have an rms uncertainty of 85 km/s. The overall redshift completeness for Q>=3 redshifts is 91.8% but this varies with magnitude from 99% for the brightest galaxies to 90% for objects at the survey limit. The 2dFGRS data base is available on the World Wide Web at http://www.mso.anu.edu.au/2dFGRS/. (6 data files).

  6. Electrochemical Deposition Of Thiolate Monolayers On Metals

    NASA Technical Reports Server (NTRS)

    Porter, Marc D.; Weissharr, Duane E.

    1995-01-01

    Electrochemical method devised for coating metal (usually, gold) surfaces with adherent thiolate monolayers. Affords greater control over location and amount of material deposited and makes it easier to control chemical composition of deposits. One important potential use for this method lies in fabrication of chemically selective thin-film resonators for microwave oscillators used to detect pollutants: monolayer formulated to bind selectively pollutant chemical species of interest, causing increase in mass of monolayer and corresponding decrease in frequency of resonance. Another important potential use lies in selective chemical derivatization for purposes of improving adhesion, lubrication, protection against corrosion, electrocatalysis, and electroanalysis.

  7. Structural prediction for scandium carbide monolayer sheet

    NASA Astrophysics Data System (ADS)

    Ma, Hong-Man; Wang, Jing; Zhao, Hui-Yan; Zhang, Dong-Bo; Liu, Ying

    2016-09-01

    A two-dimensional tetragonal scandium carbide monolayer sheet has been constructed and studied using density functional theory. The results show that the scandium carbide sheet is stable and exhibits a novel tetracoordinated quasiplanar structure, as favored by the hybridization between Sc-3d orbitals and C-2p orbitals. Calculations of the phonon dispersion as well as molecular dynamics simulations also demonstrate the structural stability of this scandium carbide monolayer sheet. Electronic properties show that the scandium carbide monolayer sheet is metallic and non-magnetic.

  8. Drug induced `softening' in phospholipid monolayers

    NASA Astrophysics Data System (ADS)

    Basak, Uttam Kumar; Datta, Alokmay; Bhattacharya, Dhananjay

    2015-06-01

    Compressibility measurements on Langmuir monolayers of the phospholipid Dimystoryl Phospatidylcholine (DMPC) in pristine form and in the presence of the Non-steroidal Anti-inflammatory Drug (NSAID) Piroxicam at 0.025 drug/lipid (D/L) molecular ratio at different temperatures, show that the monolayer exhibits large increase (and subsequent decrease) in compressibility due to the drug in the vicinity of the Liquid Expanded - Liquid Condensed (LE-LC) phase transition. Molecular dynamics simulations of the lipid monolayer in presence of drug molecules show a disordering of the tail tilt, which is consistent with the above result.

  9. Water formation through O2 + D pathway on cold silicate and amorphous water ice surfaces of interstellar interest.

    PubMed

    Chaabouni, H; Minissale, M; Manicò, G; Congiu, E; Noble, J A; Baouche, S; Accolla, M; Lemaire, J L; Pirronello, V; Dulieu, F

    2012-12-21

    The formation of the first monolayer of water molecules on bare dust grains is of primary importance to understand the growth of the icy mantles that cover dust in the interstellar medium. In this work, we explore experimentally the formation of water molecules from O(2) + D reaction on bare silicate surfaces that simulates the grains present in the diffuse interstellar clouds at visual extinctions (A(V) < 3 mag). For comparison, we also study the formation of water molecules on surfaces covered with amorphous water ice representing the dense clouds (A(V) ≥ 3 mag). Our studies focus on the formation of water molecules in the sub-monolayer and monolayer regimes using reflection absorption infrared spectroscopy and temperature-programmed desorption techniques. We provide the fractions of the products, such as D(2)O and D(2)O(2) molecules formed on three astrophysically relevant surfaces held at 10 K (amorphous olivine-type silicate, porous amorphous water ice, and nonporous amorphous water ice). Our results showed that the formation of D(2)O molecules occurs with an efficiency of about 55%-60% on nonporous amorphous water ice and about 18% on bare silicate grains surfaces. We explain the low efficiency of D(2)O water formation on the silicate surfaces by the desorption upon formation of certain products once the reaction occurs between O(2) and D atoms on the surface. A kinetic model taking into account the chemical desorption of newly formed water supports our conclusions.

  10. Klassifikation von Standardebenen in der 2D-Echokardiographie mittels 2D-3D-Bildregistrierung

    NASA Astrophysics Data System (ADS)

    Bergmeir, Christoph; Subramanian, Navneeth

    Zum Zweck der Entwicklung eines Systems, das einen unerfahrenen Anwender von Ultraschall (US) zur Aufnahme relevanter anatomischer Strukturen leitet, untersuchen wir die Machbarkeit von 2D-US zu 3D-CT Registrierung. Wir verwenden US-Aufnahmen von Standardebenen des Herzens, welche zu einem 3D-CT-Modell registriert werden. Unser Algorithmus unterzieht sowohl die US-Bilder als auch den CT-Datensatz Vorverarbeitungsschritten, welche die Daten durch Segmentierung auf wesentliche Informationen in Form von Labein für Muskel und Blut reduzieren. Anschließend werden diese Label zur Registrierung mittels der Match-Cardinality-Metrik genutzt. Durch mehrmaliges Registrieren mit verschiedenen Initialisierungen ermitteln wir die im US-Bild sichtbare Standardebene. Wir evaluierten die Methode auf sieben US-Bildern von Standardebenen. Fünf davon wurden korrekt zugeordnet.

  11. Epitaxial 2D SnSe2/ 2D WSe2 van der Waals Heterostructures.

    PubMed

    Aretouli, Kleopatra Emmanouil; Tsoutsou, Dimitra; Tsipas, Polychronis; Marquez-Velasco, Jose; Aminalragia Giamini, Sigiava; Kelaidis, Nicolaos; Psycharis, Vassilis; Dimoulas, Athanasios

    2016-09-01

    van der Waals heterostructures of 2D semiconductor materials can be used to realize a number of (opto)electronic devices including tunneling field effect devices (TFETs). It is shown in this work that high quality SnSe2/WSe2 vdW heterostructure can be grown by molecular beam epitaxy on AlN(0001)/Si(111) substrates using a Bi2Se3 buffer layer. A valence band offset of 0.8 eV matches the energy gap of SnSe2 in such a way that the VB edge of WSe2 and the CB edge of SnSe2 are lined up, making this materials combination suitable for (nearly) broken gap TFETs. PMID:27537619

  12. CVMAC 2D Program: A method of converting 3D to 2D

    SciTech Connect

    Lown, J.

    1990-06-20

    This paper presents the user with a method of converting a three- dimensional wire frame model into a technical illustration, detail, or assembly drawing. By using the 2D Program, entities can be mapped from three-dimensional model space into two-dimensional model space, as if they are being traced. Selected entities to be mapped can include circles, arcs, lines, and points. This program prompts the user to digitize the view to be mapped, specify the layers in which the new two-dimensional entities will reside, and select the entities, either by digitizing or windowing. The new two-dimensional entities are displayed in a small view which the program creates in the lower left corner of the drawing. 9 figs.

  13. 2D Four-Channel Perfect Reconstruction Filter Bank Realized with the 2D Lattice Filter Structure

    NASA Astrophysics Data System (ADS)

    Sezen, S.; Ertüzün, A.

    2006-12-01

    A novel orthogonal 2D lattice structure is incorporated into the design of a nonseparable 2D four-channel perfect reconstruction filter bank. The proposed filter bank is obtained by using the polyphase decomposition technique which requires the design of an orthogonal 2D lattice filter. Due to constraint of perfect reconstruction, each stage of this lattice filter bank is simply parameterized by two coefficients. The perfect reconstruction property is satisfied regardless of the actual values of these parameters and of the number of the lattice stages. It is also shown that a separable 2D four-channel perfect reconstruction lattice filter bank can be constructed from the 1D lattice filter and that this is a special case of the proposed 2D lattice filter bank under certain conditions. The perfect reconstruction property of the proposed 2D lattice filter approach is verified by computer simulations.

  14. Differentiation capacity and maintenance of differentiated phenotypes of human mesenchymal stromal cells cultured on two distinct types of 3D polymeric scaffolds.

    PubMed

    Leferink, A M; Santos, D; Karperien, M; Truckenmüller, R K; van Blitterswijk, C A; Moroni, L

    2015-12-01

    Many studies have shown the influence of soluble factors and material properties on the differentiation capacity of mesenchymal stromal cells (MSCs) cultured as monolayers. These types of two-dimensional (2D) studies can be used as simplified models to understand cell processes related to stem cell sensing and mechano-transduction in a three-dimensional (3D) context. For several other mechanisms such as cell-cell signaling, cell proliferation and cell morphology, it is well-known that cells behave differently on a planar surface compared to cells in 3D environments. In classical tissue engineering approaches, a combination of cells, 3D scaffolds and soluble factors are considered as the key ingredients for the generation of mechanically stable 3D tissue constructs. However, when MSCs are used for tissue engineering strategies, little is known about the maintenance of their differentiation potential in 3D scaffolds after the removal of differentiation soluble factors. In this study, the differentiation potential of human MSCs (hMSCs) into the chondrogenic and osteogenic lineages on two distinct 3D scaffolds, additive manufactured electrospun scaffolds, was assessed and compared to conventional 2D culture. Human MSCs cultured in the presence of soluble factors in 3D showed to differentiate to the same extent as hMSCs cultured as 2D monolayers or as scaffold-free pellets, indicating that the two scaffolds do not play a consistent role in the differentiation process. In the case of phenotypic changes, the achieved differentiated phenotype was not maintained after the removal of soluble factors, suggesting that the plasticity of hMSCs is retained in 3D cell culture systems. This finding can have implications for future tissue engineering approaches in which the validation of hMSC differentiation on 3D scaffolds will not be sufficient to ensure the maintenance of the functionality of the cells in the absence of appropriate differentiation signals. PMID:26566169

  15. Strain-tunable half-metallicity in hybrid graphene-hBN monolayer superlattices

    NASA Astrophysics Data System (ADS)

    Meng, Fanchao; Zhang, Shiqi; Lee, In-Ho; Jun, Sukky; Ciobanu, Cristian V.

    2016-07-01

    As research in 2-D materials evolves toward combinations of different materials, interesting electronic and spintronic properties are revealed and may be exploited in future devices. A way to combine materials is the formation of spatially periodic domain boundaries in an atom-thick monolayer: as shown in recent reports, when these domains are made of graphene and hexagonal boron nitride, the resulting superlattice has half-metallic properties in which one spin component is (semi)metallic and the other is semiconductor. We explore here the range of spin-dependent electronic properties that such superlattices can develop for different type of domain boundaries, domain widths, and values of tensile strain applied to the monolayer. We show evidence of an interplay between strain and domain width in determining the electronic properties: while for armchair boundaries the bandgap is the same for both spin components, superlattices with zigzag boundaries exhibit rich spin-dependent behavior, including different bandgaps for each spin component, half-metallicity, and reversal of half-metallicity. These findings can lead to new ways of controlling the spintronic properties in hybrid-domain monolayers, which may be exploited in devices based on 2-D materials.

  16. MoS2 monolayers on nanocavities: enhancement in light-matter interaction

    NASA Astrophysics Data System (ADS)

    Janisch, Corey; Song, Haomin; Zhou, Chanjing; Lin, Zhong; Elías, Ana Laura; Ji, Dengxin; Terrones, Mauricio; Gan, Qiaoqiang; Liu, Zhiwen

    2016-06-01

    Two-dimensional (2D) atomic crystals and van der Waals heterostructures constitute an emerging platform for developing new functional ultra-thin electronic and optoelectronic materials for novel energy-efficient devices. However, in most thin-film optical applications, there is a long-existing trade-off between the effectiveness of light-matter interactions and the thickness of semiconductor materials, especially when the materials are scaled down to atom thick dimensions. Consequently, enhancement strategies can introduce significant advances to these atomically thick materials and devices. Here we demonstrate enhanced absorption and photoluminescence generation from MoS2 monolayers coupled with a planar nanocavity. This nanocavity consists of an alumina nanolayer spacer sandwiched between monolayer MoS2 and an aluminum reflector, and can strongly enhance the light-matter interaction within the MoS2, increasing the exclusive absorption of monolayer MoS2 to nearly 70% at a wavelength of 450 nm. The nanocavity also modifies the spontaneous emission rate, providing an additional design freedom to control the interaction between light and 2D materials.

  17. Two-dimensional B-C-O alloys: a promising class of 2D materials for electronic devices.

    PubMed

    Zhou, Si; Zhao, Jijun

    2016-04-28

    Graphene, a superior 2D material with high carrier mobility, has limited application in electronic devices due to zero band gap. In this regard, boron and nitrogen atoms have been integrated into the graphene lattice to fabricate 2D semiconducting heterostructures. It is an intriguing question whether oxygen can, as a replacement of nitrogen, enter the sp2 honeycomb lattice and form stable B-C-O monolayer structures. Here we explore the atomic structures, energetic and thermodynamic stability, and electronic properties of various 2D B-C-O alloys using first-principles calculations. Our results show that oxygen can be stably incorporated into the graphene lattice by bonding with boron. The B and O species favor forming alternate patterns into the chain- or ring-like structures embedded in the pristine graphene regions. These B-C-O hybrid sheets can be either metals or semiconductors depending on the B : O ratio. The semiconducting (B2O)nCm and (B6O3)nCm phases exist under the B- and O-rich conditions, and possess a tunable band gap of 1.0-3.8 eV and high carrier mobility, retaining ∼1000 cm2 V(-1) s(-1) even for half coverage of B and O atoms. These B-C-O alloys form a new class of 2D materials that are promising candidates for high-speed electronic devices.

  18. 2D dynamical arrest transition in a mixed nanoparticle-phospholipid layer studied in real and momentum spaces.

    PubMed

    Orsi, Davide; Guzmán, Eduardo; Liggieri, Libero; Ravera, Francesca; Ruta, Beatrice; Chushkin, Yuriy; Rimoldi, Tiziano; Cristofolini, Luigi

    2015-01-01

    We investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-inspired technological solutions, exploiting the self-organization of DPPC to produce a non-trivial 2D structuration of nanoparticles. The characterization of interfacial dynamics yields information on the effects of NPs on the mechanical properties, important to improve performances of systems such as colloidosomes, foams, creams. For this, we combine micro-tracking in real-space with measurement in momentum-space via x-ray photon-correlation spectroscopy and Digital Fourier Microscopy. Using these complementary techniques, we extend the spatial range of investigation beyond the limits of each one. We find a dynamical transition from Brownian diffusion to an arrested state driven by compression, characterized by intermittent rearrangements, compatible with a repulsive glass phase. The rearrangement and relaxation of the monolayer structure results dramatically hindered by the presence of NPs, which is relevant to explain some the mechanical features observed for the dynamic surface pressure response of these systems and which can be relevant for the respiratory physiology and for future drug-delivery composite systems. PMID:26658474

  19. 2D dynamical arrest transition in a mixed nanoparticle-phospholipid layer studied in real and momentum spaces

    PubMed Central

    Orsi, Davide; Guzmán, Eduardo; Liggieri, Libero; Ravera, Francesca; Ruta, Beatrice; Chushkin, Yuriy; Rimoldi, Tiziano; Cristofolini, Luigi

    2015-01-01

    We investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-inspired technological solutions, exploiting the self-organization of DPPC to produce a non-trivial 2D structuration of nanoparticles. The characterization of interfacial dynamics yields information on the effects of NPs on the mechanical properties, important to improve performances of systems such as colloidosomes, foams, creams. For this, we combine micro-tracking in real-space with measurement in momentum-space via x-ray photon-correlation spectroscopy and Digital Fourier Microscopy. Using these complementary techniques, we extend the spatial range of investigation beyond the limits of each one. We find a dynamical transition from Brownian diffusion to an arrested state driven by compression, characterized by intermittent rearrangements, compatible with a repulsive glass phase. The rearrangement and relaxation of the monolayer structure results dramatically hindered by the presence of NPs, which is relevant to explain some the mechanical features observed for the dynamic surface pressure response of these systems and which can be relevant for the respiratory physiology and for future drug-delivery composite systems. PMID:26658474

  20. 2D dynamical arrest transition in a mixed nanoparticle-phospholipid layer studied in real and momentum spaces

    NASA Astrophysics Data System (ADS)

    Orsi, Davide; Guzmán, Eduardo; Liggieri, Libero; Ravera, Francesca; Ruta, Beatrice; Chushkin, Yuriy; Rimoldi, Tiziano; Cristofolini, Luigi

    2015-12-01

    We investigate the interfacial dynamics of a 2D self-organized mixed layer made of silica nanoparticles interacting with phospholipid (DPPC) monolayers at the air/water interface. This system has biological relevance, allowing investigation of toxicological effects of nanoparticles on model membranes and lung surfactants. It might also provide bio-inspired technological solutions, exploiting the self-organization of DPPC to produce a non-trivial 2D structuration of nanoparticles. The characterization of interfacial dynamics yields information on the effects of NPs on the mechanical properties, important to improve performances of systems such as colloidosomes, foams, creams. For this, we combine micro-tracking in real-space with measurement in momentum-space via x-ray photon-correlation spectroscopy and Digital Fourier Microscopy. Using these complementary techniques, we extend the spatial range of investigation beyond the limits of each one. We find a dynamical transition from Brownian diffusion to an arrested state driven by compression, characterized by intermittent rearrangements, compatible with a repulsive glass phase. The rearrangement and relaxation of the monolayer structure results dramatically hindered by the presence of NPs, which is relevant to explain some the mechanical features observed for the dynamic surface pressure response of these systems and which can be relevant for the respiratory physiology and for future drug-delivery composite systems.

  1. An Incompressible 2D Didactic Model with Singularity and Explicit Solutions of the 2D Boussinesq Equations

    NASA Astrophysics Data System (ADS)

    Chae, Dongho; Constantin, Peter; Wu, Jiahong

    2014-09-01

    We give an example of a well posed, finite energy, 2D incompressible active scalar equation with the same scaling as the surface quasi-geostrophic equation and prove that it can produce finite time singularities. In spite of its simplicity, this seems to be the first such example. Further, we construct explicit solutions of the 2D Boussinesq equations whose gradients grow exponentially in time for all time. In addition, we introduce a variant of the 2D Boussinesq equations which is perhaps a more faithful companion of the 3D axisymmetric Euler equations than the usual 2D Boussinesq equations.

  2. Simulation Evidence of Hexagonal‐to‐Tetragonal ZnSe Structure Transition: A Monolayer Material with a Wide‐Range Tunable Direct Bandgap

    PubMed Central

    Li, Lei; Li, Pengfei; Lu, Ning; Dai, Jun

    2015-01-01

    2D material with tunable direct bandgap in the intermediate region (i.e., ≈2–3 eV) is key to the achievement of high efficiency in visible‐light optical devices. Herein, a simulation evidence of structure transition of monolayer ZnSe from the experimental pseudohexagonal structure to the tetragonal structure (t‐ZnSe) under lateral pressure is shown, suggesting a possible fabrication route to achieve the t‐ZnSe monolayer. The as‐produced t‐ZnSe monolayer exhibits highly tunable bandgap under the biaxial strains, allowing strain engineering of t‐ZnSe's bandgap over a wide range of 2–3 eV. Importantly, even under the biaxial strain up to 7%, the t‐ZnSe monolayer still keeps its direct‐gap property in the desirable range of 2.40–3.17 eV (corresponding to wavelength of green light to ultraviolet). The wide‐range tunability of direct bandgap appears to be a unique property of the t‐ZnSe monolayer, suggesting its potential application as a light‐emitting 2D material in red–green–blue light emission diodes or as complementary light‐absorption material in the blue–yellow region for multijunction solar cells. The straddling of the band edge of the t‐ZnSe monolayer over the redox potential of water splitting reaction also points to its plausible application for visible‐light‐driven water splitting. PMID:27774379

  3. Three-Dimensional Spheroid Cell Culture Model for Target Identification Utilizing High-Throughput RNAi Screens.

    PubMed

    Iles, LaKesla R; Bartholomeusz, Geoffrey A

    2016-01-01

    The intrinsic limitations of 2D monolayer cell culture models have prompted the development of 3D cell culture model systems for in vitro studies. Multicellular tumor spheroid (MCTS) models closely simulate the pathophysiological milieu of solid tumors and are providing new insights into tumor biology as well as differentiation, tissue organization, and homeostasis. They are straightforward to apply in high-throughput screens and there is a great need for the development of reliable and robust 3D spheroid-based assays for high-throughput RNAi screening for target identification and cell signaling studies highlighting their potential in cancer research and treatment. In this chapter we describe a stringent standard operating procedure for the use of MCTS for high-throughput RNAi screens. PMID:27581289

  4. Laser-Induced Spallation of Microsphere Monolayers.

    PubMed

    Hiraiwa, Morgan; Stossel, Melicent; Khanolkar, Amey; Wang, Junlan; Boechler, Nicholas

    2016-08-01

    The detachment of a semiordered monolayer of polystyrene microspheres adhered to an aluminum-coated glass substrate is studied using a laser-induced spallation technique. The microsphere-substrate adhesion force is estimated from substrate surface displacement measurements obtained using optical interferometry, and a rigid-body model that accounts for the inertia of the microspheres. The estimated adhesion force is compared with estimates obtained using an adhesive contact model together with interferometric measurements of the out-of-plane microsphere contact resonance, and with estimated work of adhesion values for the polystyrene-aluminum interface. Scanning electron microscope images of detached monolayer regions reveal a unique morphology, namely, partially detached monolayer flakes composed of single hexagonal close packed crystalline domains. This work contributes to the fields of microsphere adhesion and contact dynamics, and demonstrates a unique monolayer delamination morphology. PMID:27409715

  5. Accurate Molecular Dimensions from Stearic Acid Monolayers.

    ERIC Educational Resources Information Center

    Lane, Charles A.; And Others

    1984-01-01

    Discusses modifications in the fatty acid monolayer experiment to reduce the inaccurate moleculary data students usually obtain. Copies of the experimental procedure used and a Pascal computer program to work up the data are available from the authors. (JN)

  6. Large Friction Anisotropy of a Polydiacetylene Monolayer

    SciTech Connect

    Burns, A.R.; Carpick, R.W.; Sasaki, D.Y.

    1999-05-11

    Friction force microscopy measurements of a polydiacetylene monolayer film reveal a 300% friction anisotropy that is correlated with the film structure. The film consists of a monolayer of the red form of N-(2-ethanol)- 10,12 pentacosadiynamide, prepared on a Langmuir trough and deposited on a mica substrate. As confirmed by atomic force microscopy and fluorescence microscopy, the monolayer consists of domains of linearly oriented conjugated backbones with pendant hydrocarbon side chains above and below the backbones. Maximum friction occurs when the sliding direction is perpendicular to the backbone. We propose that the backbones impose anisotropic packing of the hydrocarbon side chains which leads to the observed friction anisotropy. Friction anisotropy is therefore a sensitive, optically-independent indicator of polymer backbone direction and monolayer structural properties.

  7. Multicellular density fluctuations in epithelial monolayers

    NASA Astrophysics Data System (ADS)

    Zehnder, Steven M.; Wiatt, Marina K.; Uruena, Juan M.; Dunn, Alison C.; Sawyer, W. Gregory; Angelini, Thomas E.

    2015-09-01

    Changes in cell size often accompany multicellular motion in tissue, and cell number density is known to strongly influence collective migration in monolayers. Density fluctuations in other forms of active matter have been explored extensively, but not the potential role of density fluctuations in collective cell migration. Here we investigate collective motion in cell monolayers, focusing on the divergent component of the migration velocity field to probe density fluctuations. We find spatial patterns of diverging and converging cell groups throughout the monolayers, which oscillate in time with a period of approximately 3-4 h. Simultaneous fluorescence measurements of a cytosol dye within the cells show that fluid passes between groups of cells, facilitating these oscillations in cell density. Our findings reveal that cell-cell interactions in monolayers may be mediated by intercellular fluid flow.

  8. Nonequilibrium bubbles in a flowing langmuir monolayer.

    PubMed

    Muruganathan, Rm; Khattari, Z; Fischer, Th M

    2005-11-24

    We investigate the nonequilibrium behavior of two-dimensional gas bubbles in Langmuir monolayers. A cavitation bubble is induced in liquid expanded phase by locally heating a Langmuir monolayer with an IR-laser. At low IR-laser power the cavitation bubble is immersed in quiescent liquid expanded monolayer. At higher IR-laser power thermo capillary flow around the laser-induced cavitation bubble sets in. The thermo capillary flow is caused by a temperature dependence of the gas/liquid line tension. The slope of the line tension with temperature is determined by measuring the thermo capillary flow velocity. Thermodynamically stable satellite bubbles are generated by increasing the surface area of the monolayer. Those satellite bubbles collide with the cavitation bubble. Upon collision the satellite bubbles either coalesce with the cavitation bubble or slide past the cavitation bubble. Moreover we show that the satellite bubbles can also be produced by the emission from the laser-induced cavitation bubbles.

  9. Heterochirality in Langmuir monolayers and antiferromagnetic Blume-Emery-Griffiths model

    NASA Astrophysics Data System (ADS)

    Pelizzola, A.; Pretti, M.; Scalas, E.

    2000-05-01

    Chirality is quite a common property in organic molecules. Chiral molecules exist in two forms (called enantiomers) which cannot be superimposed by rotations and translations and may have very different biochemical properties. Experiments on Langmuir monolayers made up of chiral amphiphiles have shown that, in most cases, heterochiral interactions dominate, implying the formation of a racemic compound. It has been shown that a monolayer mixture of two enantiomers can be simply described by a two-dimensional (2-D) spin-1 lattice gas [Blume-Emery-Griffiths (BEG) model], where the heterochiral preference is represented by an effective antiferromagnetic coupling. By now just mean field calculations have been performed on this model. Here we present a revisitation of the tripod amphiphile model, proposed by Andelman and de Gennes [D. Andelman and P.-G. de Gennes, Compt. Rend. Acad. Sci. (Paris) 307, 233 (1988)], together with a rigorous proof of the heterochiral preference shown by the model in the hypothesis of van der Waals interactions. Moreover, a cluster variation analysis of the antiferromagnetic BEG model on a triangular lattice is performed and possible interpretations in terms of surface pressure-concentration phase diagrams for monolayer mixtures of enantiomers are discussed. The choice of a triangular lattice has been suggested by the triangularlike structure of condensed phases of Langmuir monolayers, shown by x-ray diffraction experiments.

  10. First-Principles Determination of Ultralow Thermal Conductivity of monolayer WSe2

    PubMed Central

    Zhou, Wu-Xing; Chen, Ke-Qiu

    2015-01-01

    By using first-principles calculations combined with the phonon Boltzmann transport equation, we systematically investigate the phonon transport of monolayer WSe2. Compared with other 2D materials, the monolayer WSe2 is found to have an ultralow thermal conductivity due to the ultralow Debye frequency and heavy atom mass. The room temperature thermal conductivity for a typical sample size of 1 μm is 3.935  W/m K, which is one order of magnitude lower than that of MoS2. And the room temperature thermal conductivity can be further decreased by about 95% in 10 nm sized samples. Moreover, we also find the ZA phonons have the dominant contribution to the thermal conductivity, and the relative contribution is almost 80% at room temperature, which is remarkably higher than that for monolayer MoS2. This is because the ZA phonons have longer lifetime than that of LA and TA phonons in monolayer WSe2. PMID:26464052

  11. Enhanced mobility electrons at the monolayer / multilayer MoS2 homo-interface

    NASA Astrophysics Data System (ADS)

    Jia, Y.; Lenferink, E. J.; Stanev, T.; Stern, N. P.

    2015-03-01

    Energy band alignment at interface of heterostructures can give rise to non-trivial local electronic structure and charge states with low dimensionality. In transition metal dichalcogenides (TMDCs), the optical band gap depends on the number of 2D crystal layers, transitioning from 1.29 eV in bulk to 1.88 eV for a monolayer of MoS2, for example, and providing the possibility to create unusual charge state at the monolayer/multilayer homo-interface. Here, we examine the boundaries between MoS2 monolayers and multilayers using scanning photocurrent microscopy and gate-dependent transport. Enhanced photocurrent and conductance were observed at the 1D homo-interface, which can be explained as accumulated carriers in the bent-band region of the junction. Our heterojunction modeling suggests a high local carrier density and enhanced mobility at the homo-interface. Our work presents an opportunity to achieve a 1D electron state in a homojunction and a pathway to break the mobility limit of TMDC monolayer transistors. This work was supported by the Institute for Sustainability and Energy at Northwestern and the U.S. Department of Energy (DE-SC0012130). N.P.S. acknowledges support as an Alfred P. Sloan Research Fellow.

  12. Adaptation algorithms for 2-D feedforward neural networks.

    PubMed

    Kaczorek, T

    1995-01-01

    The generalized weight adaptation algorithms presented by J.G. Kuschewski et al. (1993) and by S.H. Zak and H.J. Sira-Ramirez (1990) are extended for 2-D madaline and 2-D two-layer feedforward neural nets (FNNs).

  13. Integrating Mobile Multimedia into Textbooks: 2D Barcodes

    ERIC Educational Resources Information Center

    Uluyol, Celebi; Agca, R. Kagan

    2012-01-01

    The major goal of this study was to empirically compare text-plus-mobile phone learning using an integrated 2D barcode tag in a printed text with three other conditions described in multimedia learning theory. The method examined in the study involved modifications of the instructional material such that: a 2D barcode was used near the text, the…

  14. Efficient Visible Quasi-2D Perovskite Light-Emitting Diodes.

    PubMed

    Byun, Jinwoo; Cho, Himchan; Wolf, Christoph; Jang, Mi; Sadhanala, Aditya; Friend, Richard H; Yang, Hoichang; Lee, Tae-Woo

    2016-09-01

    Efficient quasi-2D-structure perovskite light-emitting diodes (4.90 cd A(-1) ) are demonstrated by mixing a 3D-structured perovskite material (methyl ammonium lead bromide) and a 2D-structured perovskite material (phenylethyl ammonium lead bromide), which can be ascribed to better film uniformity, enhanced exciton confinement, and reduced trap density. PMID:27334788

  15. CYP2D6: novel genomic structures and alleles

    PubMed Central

    Kramer, Whitney E.; Walker, Denise L.; O’Kane, Dennis J.; Mrazek, David A.; Fisher, Pamela K.; Dukek, Brian A.; Bruflat, Jamie K.; Black, John L.

    2010-01-01

    Objective CYP2D6 is a polymorphic gene. It has been observed to be deleted, to be duplicated and to undergo recombination events involving the CYP2D7 pseudogene and surrounding sequences. The objective of this study was to discover the genomic structure of CYP2D6 recombinants that interfere with clinical genotyping platforms that are available today. Methods Clinical samples containing rare homozygous CYP2D6 alleles, ambiguous readouts, and those with duplication signals and two different alleles were analyzed by long-range PCR amplification of individual genes, PCR fragment analysis, allele-specific primer extension assay, and DNA sequencing to characterize alleles and genomic structure. Results Novel alleles, genomic structures, and the DNA sequence of these structures are described. Interestingly, in 49 of 50 DNA samples that had CYP2D6 gene duplications or multiplications where two alleles were detected, the chromosome containing the duplication or multiplication had identical tandem alleles. Conclusion Several new CYP2D6 alleles and genomic structures are described which will be useful for CYP2D6 genotyping. The findings suggest that the recombination events responsible for CYP2D6 duplications and multiplications are because of mechanisms other than interchromosomal crossover during meiosis. PMID:19741566

  16. Efficient Visible Quasi-2D Perovskite Light-Emitting Diodes.

    PubMed

    Byun, Jinwoo; Cho, Himchan; Wolf, Christoph; Jang, Mi; Sadhanala, Aditya; Friend, Richard H; Yang, Hoichang; Lee, Tae-Woo

    2016-09-01

    Efficient quasi-2D-structure perovskite light-emitting diodes (4.90 cd A(-1) ) are demonstrated by mixing a 3D-structured perovskite material (methyl ammonium lead bromide) and a 2D-structured perovskite material (phenylethyl ammonium lead bromide), which can be ascribed to better film uniformity, enhanced exciton confinement, and reduced trap density.

  17. 2D materials and van der Waals heterostructures.

    PubMed

    Novoselov, K S; Mishchenko, A; Carvalho, A; Castro Neto, A H

    2016-07-29

    The physics of two-dimensional (2D) materials and heterostructures based on such crystals has been developing extremely fast. With these new materials, truly 2D physics has begun to appear (for instance, the absence of long-range order, 2D excitons, commensurate-incommensurate transition, etc.). Novel heterostructure devices--such as tunneling transistors, resonant tunneling diodes, and light-emitting diodes--are also starting to emerge. Composed from individual 2D crystals, such devices use the properties of those materials to create functionalities that are not accessible in other heterostructures. Here we review the properties of novel 2D crystals and examine how their properties are used in new heterostructure devices.

  18. Estrogen-Induced Cholestasis Leads to Repressed CYP2D6 Expression in CYP2D6-Humanized Mice

    PubMed Central

    Pan, Xian

    2015-01-01

    Cholestasis activates bile acid receptor farnesoid X receptor (FXR) and subsequently enhances hepatic expression of small heterodimer partner (SHP). We previously demonstrated that SHP represses the transactivation of cytochrome P450 2D6 (CYP2D6) promoter by hepatocyte nuclear factor (HNF) 4α. In this study, we investigated the effects of estrogen-induced cholestasis on CYP2D6 expression. Estrogen-induced cholestasis occurs in subjects receiving estrogen for contraception or hormone replacement, or in susceptible women during pregnancy. In CYP2D6-humanized transgenic (Tg-CYP2D6) mice, cholestasis triggered by administration of 17α-ethinylestradiol (EE2) at a high dose led to 2- to 3-fold decreases in CYP2D6 expression. This was accompanied by increased hepatic SHP expression and subsequent decreases in the recruitment of HNF4α to CYP2D6 promoter. Interestingly, estrogen-induced cholestasis also led to increased recruitment of estrogen receptor (ER) α, but not that of FXR, to Shp promoter, suggesting a predominant role of ERα in transcriptional regulation of SHP in estrogen-induced cholestasis. EE2 at a low dose (that does not cause cholestasis) also increased SHP (by ∼50%) and decreased CYP2D6 expression (by 1.5-fold) in Tg-CYP2D6 mice, the magnitude of differences being much smaller than that shown in EE2-induced cholestasis. Taken together, our data indicate that EE2-induced cholestasis increases SHP and represses CYP2D6 expression in Tg-CYP2D6 mice in part through ERα transactivation of Shp promoter. PMID:25943116

  19. Substrate control for large area continuous films of monolayer MoS2 by atmospheric pressure chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Wang, Shanshan; Pacios, Merce; Bhaskaran, Harish; Warner, Jamie H.

    2016-02-01

    Growing monolayer MoS2 films that are continuous with large domain sizes by chemical vapor deposition is one of the major challenges in 2D materials research at the moment. Here, we explore how atmospheric pressure CVD can be used to grow centimeter scale continuous films of monolayer MoS2 films directly on Si substrates with an oxide layer whilst also obtaining large domain sizes exceeding 20 μm within the films. This is achieved by orientating the growth substrate in a vertical position to improve the uniformity of precursor feed-stock compared to horizontally orientated growth substrates. This leads to continuous films of monolayer MoS2 over a significantly larger area without the need for low-pressure vacuum systems or volatile precursors. This provides important insights into novel approaches for maximizing domain sizes within MoS2 films, with concomitant large area uniform coverage.

  20. Nucleation control for large, single crystalline domains of monolayer hexagonal boron nitride via Si-doped Fe catalysts.

    PubMed

    Caneva, Sabina; Weatherup, Robert S; Bayer, Bernhard C; Brennan, Barry; Spencer, Steve J; Mingard, Ken; Cabrero-Vilatela, Andrea; Baehtz, Carsten; Pollard, Andrew J; Hofmann, Stephan

    2015-03-11

    The scalable chemical vapor deposition of monolayer hexagonal boron nitride (h-BN) single crystals, with lateral dimensions of ∼0.3 mm, and of continuous h-BN monolayer films with large domain sizes (>25 μm) is demonstrated via an admixture of Si to Fe catalyst films. A simple thin-film Fe/SiO2/Si catalyst system is used to show that controlled Si diffusion into the Fe catalyst allows exclusive nucleation of monolayer h-BN with very low nucleation densities upon exposure to undiluted borazine. Our systematic in situ and ex situ characterization of this catalyst system establishes a basis for further rational catalyst design for compound 2D materials.

  1. Substrate control for large area continuous films of monolayer MoS2 by atmospheric pressure chemical vapor deposition.

    PubMed

    Wang, Shanshan; Pacios, Merce; Bhaskaran, Harish; Warner, Jamie H

    2016-02-26

    Growing monolayer MoS2 films that are continuous with large domain sizes by chemical vapor deposition is one of the major challenges in 2D materials research at the moment. Here, we explore how atmospheric pressure CVD can be used to grow centimeter scale continuous films of monolayer MoS2 films directly on Si substrates with an oxide layer whilst also obtaining large domain sizes exceeding 20 μm within the films. This is achieved by orientating the growth substrate in a vertical position to improve the uniformity of precursor feed-stock compared to horizontally orientated growth substrates. This leads to continuous films of monolayer MoS2 over a significantly larger area without the need for low-pressure vacuum systems or volatile precursors. This provides important insights into novel approaches for maximizing domain sizes within MoS2 films, with concomitant large area uniform coverage.

  2. Nucleation Control for Large, Single Crystalline Domains of Monolayer Hexagonal Boron Nitride via Si-Doped Fe Catalysts

    PubMed Central

    2015-01-01

    The scalable chemical vapor deposition of monolayer hexagonal boron nitride (h-BN) single crystals, with lateral dimensions of ∼0.3 mm, and of continuous h-BN monolayer films with large domain sizes (>25 μm) is demonstrated via an admixture of Si to Fe catalyst films. A simple thin-film Fe/SiO2/Si catalyst system is used to show that controlled Si diffusion into the Fe catalyst allows exclusive nucleation of monolayer h-BN with very low nucleation densities upon exposure to undiluted borazine. Our systematic in situ and ex situ characterization of this catalyst system establishes a basis for further rational catalyst design for compound 2D materials. PMID:25664483

  3. Discrete quantum dot like emitters in monolayer MoSe2: Spatial mapping, magneto-optics, and charge tuning

    NASA Astrophysics Data System (ADS)

    Branny, Artur; Wang, Gang; Kumar, Santosh; Robert, Cedric; Lassagne, Benjamin; Marie, Xavier; Gerardot, Brian D.; Urbaszek, Bernhard

    2016-04-01

    Transition metal dichalcogenide monolayers such as MoSe2, MoS2, and WSe2 are direct bandgap semiconductors with original optoelectronic and spin-valley properties. Here we report on spectrally sharp, spatially localized emission in monolayer MoSe2. We find this quantum dot-like emission in samples exfoliated onto gold substrates and also suspended flakes. Spatial mapping shows a correlation between the location of emitters and the existence of wrinkles (strained regions) in the flake. We tune the emission properties in magnetic and electric fields applied perpendicular to the monolayer plane. We extract an exciton g-factor of the discrete emitters close to -4, as for 2D excitons in this material. In a charge tunable sample, we record discrete jumps on the meV scale as charges are added to the emitter when changing the applied voltage.

  4. Synthesis of a Two-Dimensional Covalent Organic Monolayer through Dynamic Imine Chemistry at the Air/Water Interface.

    PubMed

    Dai, Wenyang; Shao, Feng; Szczerbiński, Jacek; McCaffrey, Ryan; Zenobi, Renato; Jin, Yinghua; Schlüter, A Dieter; Zhang, Wei

    2016-01-01

    A two-dimensional covalent organic monolayer was synthesized from simple aromatic triamine and dialdehyde building blocks by dynamic imine chemistry at the air/water interface (Langmuir-Blodgett method). The obtained monolayer was characterized by optical microscopy, scanning electron microscopy, and atomic force microscopy, which unambiguously confirmed the formation of a large (millimeter range), unimolecularly thin aromatic polyimine sheet. The imine-linked chemical structure of the obtained monolayer was characterized by tip-enhanced Raman spectroscopy, and the peak assignment was supported by spectra simulated by density functional theory. Given the modular nature and broad substrate scope of imine formation, the work reported herein opens up many new possibilities for the synthesis of customizable 2D polymers and systematic studies of their structure-property relationships.

  5. Mass spectrometric analysis of monolayer protected nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhu, Zhengjiang

    Monolayer protected nanoparticles (NPs) include an inorganic core and a monolayer of organic ligands. The wide variety of core materials and the tunable surface monolayers make NPs promising materials for numerous applications. Concerns related to unforeseen human health and environmental impacts of NPs have also been raised. In this thesis, new analytical methods based on mass spectrometry are developed to understand the fate, transport, and biodistributions of NPs in the complex biological systems. A laser desorption/ionization mass spectrometry (LDI-MS) method has been developed to characterize the monolayers on NP surface. LDI-MS allows multiple NPs taken up by cells to be measured and quantified in a multiplexed fashion. The correlations between surface properties of NPs and cellular uptake have also been explored. LDI-MS is further coupled with inductively coupled plasma mass spectrometry (ICP-MS) to quantitatively measure monolayer stability of gold NPs (AuNPs) and quantum dots (QDs), respectively, in live cells. This label-free approach allows correlating monolayer structure and particle size with NP stability in various cellular environments. Finally, uptake, distribution, accumulation, and excretion of NPs in higher order organisms, such as fish and plants, have been investigated to understand the environmental impact of nanomaterials. The results indicate that surface chemistry is a primary determinant. NPs with hydrophilic surfaces are substantially less toxic and present a lower degree of bioaccumulation, making these nanomaterials attractive for sustainable nanotechnology.

  6. Effects of irradiated biodegradable polymer in endothelial cell monolayer formation

    NASA Astrophysics Data System (ADS)

    Arbeitman, Claudia R.; del Grosso, Mariela F.; Behar, Moni; García Bermúdez, Gerardo

    2013-11-01

    In this work we study cell adhesion, proliferation and cell morphology of endothelial cell cultured on poly-L-lactide acid (PLLA) modified by heavy ion irradiation. Thin films of PLLA samples were irradiated with sulfur (S) at energies of 75 MeV and gold (Au) at 18 MeV ion-beams. Ion beams were provided by the Tandar (Buenos Aires, Argentina) and Tandetron (Porto Alegre, Brazil) accelerators, respectively. The growth of a monolayer of bovine aortic endothelial cells (BAEC) onto unirradiated and irradiated surfaces has been studied by in vitro techniques in static culture. Cell viability and proliferation increased on modified substrates. But the results on unirradiated samples, indicate cell death (necrosis/apoptosis) with the consequent decrease in proliferation. We analyzed the correlation between irradiation parameters and cell metabolism and morphology.

  7. Targeted fluorescence imaging enhanced by 2D materials: a comparison between 2D MoS2 and graphene oxide.

    PubMed

    Xie, Donghao; Ji, Ding-Kun; Zhang, Yue; Cao, Jun; Zheng, Hu; Liu, Lin; Zang, Yi; Li, Jia; Chen, Guo-Rong; James, Tony D; He, Xiao-Peng

    2016-08-01

    Here we demonstrate that 2D MoS2 can enhance the receptor-targeting and imaging ability of a fluorophore-labelled ligand. The 2D MoS2 has an enhanced working concentration range when compared with graphene oxide, resulting in the improved imaging of both cell and tissue samples.

  8. Comparison of Electronic and Optical Properties of GaN Monolayer and Bulk Structure: a First Principle Study

    NASA Astrophysics Data System (ADS)

    Imran, Muhammad; Hussain, Fayyaz; Rashid, Muhammad; Ullah, Hafeez; Sattar, Atif; Iqbal, Faisal; Ahmad, Ejaz

    2016-03-01

    The semiconducting two-dimensional (2D) architectures materials have potential applications in electronics and optics. The design and search of new 2D materials have attracted extensive attention recently. In this study, first principle calculation has been done on 2D gallium nitride (GaN) monolayer with respect to its formation and binding energies. The electronic and optical properties are also investigated. It is found that the single isolated GaN sheet is forming mainly ionic GaN bonds despite a slightly weaker GaN interaction as compared with its bulk counterpart. The dielectric constant value of 2D GaN is smaller as compared to 3D GaN due to less effective electronic screening effect in the layer, which is accompanied by lesser optical adsorption range and suggested to be a promising candidate in electronic and optoelectronic devices.

  9. Capturing tumor complexity in vitro: Comparative analysis of 2D and 3D tumor models for drug discovery

    PubMed Central

    Stock, Kristin; Estrada, Marta F.; Vidic, Suzana; Gjerde, Kjersti; Rudisch, Albin; Santo, Vítor E.; Barbier, Michaël; Blom, Sami; Arundkar, Sharath C.; Selvam, Irwin; Osswald, Annika; Stein, Yan; Gruenewald, Sylvia; Brito, Catarina; van Weerden, Wytske; Rotter, Varda; Boghaert, Erwin; Oren, Moshe; Sommergruber, Wolfgang; Chong, Yolanda; de Hoogt, Ronald; Graeser, Ralph

    2016-01-01

    Two-dimensional (2D) cell cultures growing on plastic do not recapitulate the three dimensional (3D) architecture and complexity of human tumors. More representative models are required for drug discovery and validation. Here, 2D culture and 3D mono- and stromal co-culture models of increasing complexity have been established and cross-comparisons made using three standard cell carcinoma lines: MCF7, LNCaP, NCI-H1437. Fluorescence-based growth curves, 3D image analysis, immunohistochemistry and treatment responses showed that end points differed according to cell type, stromal co-culture and culture format. The adaptable methodologies described here should guide the choice of appropriate simple and complex in vitro models. PMID:27364600

  10. Capturing tumor complexity in vitro: Comparative analysis of 2D and 3D tumor models for drug discovery.

    PubMed

    Stock, Kristin; Estrada, Marta F; Vidic, Suzana; Gjerde, Kjersti; Rudisch, Albin; Santo, Vítor E; Barbier, Michaël; Blom, Sami; Arundkar, Sharath C; Selvam, Irwin; Osswald, Annika; Stein, Yan; Gruenewald, Sylvia; Brito, Catarina; van Weerden, Wytske; Rotter, Varda; Boghaert, Erwin; Oren, Moshe; Sommergruber, Wolfgang; Chong, Yolanda; de Hoogt, Ronald; Graeser, Ralph

    2016-01-01

    Two-dimensional (2D) cell cultures growing on plastic do not recapitulate the three dimensional (3D) architecture and complexity of human tumors. More representative models are required for drug discovery and validation. Here, 2D culture and 3D mono- and stromal co-culture models of increasing complexity have been established and cross-comparisons made using three standard cell carcinoma lines: MCF7, LNCaP, NCI-H1437. Fluorescence-based growth curves, 3D image analysis, immunohistochemistry and treatment responses showed that end points differed according to cell type, stromal co-culture and culture format. The adaptable methodologies described here should guide the choice of appropriate simple and complex in vitro models. PMID:27364600

  11. Wedge energy bands of monolayer black phosphorus: a first-principles study

    NASA Astrophysics Data System (ADS)

    Park, Minwoo; Bae, Hyeonhu; Lee, Seunghan; Yang, Li; Lee, Hoonkyung

    2016-08-01

    On the basis of first-principles calculations, we present intriguing electronic properties of halogen-striped functionalized monolayer black phosphorus. The halogen-striped monolayer black phosphorus is found to have a wedge energy band with the energy-momentum relation of E\\propto {{p}y} when the stripe–stripe distance is smaller than ~40 Å. Our tight-binding study shows that the wedge energy band occurs when 2-atom basis 1D lattices are periodically repeated aligned with each other in a 2D lattice. We also discuss the possible applications of this wedge energy band in electron supercollimation with high mobility or severely anisotropic electronic transport, which can be used for the development of optics-like nano-electronics.

  12. Superhigh moduli and tension-induced phase transition of monolayer gamma-boron at finite temperatures

    PubMed Central

    Zhao, Junhua; Yang, Zhaoyao; Wei, Ning; Kou, Liangzhi

    2016-01-01

    Two dimensional (2D) gamma-boron (γ-B28) thin films have been firstly reported by the experiments of the chemical vapor deposition in the latest study. However, their mechanical properties are still not clear. Here we predict the superhigh moduli (785 ± 42 GPa at 300 K) and the tension-induced phase transition of monolayer γ-B28 along a zigzag direction for large deformations at finite temperatures using molecular dynamics (MD) simulations. The new phase can be kept stable after unloading process at these temperatures. The predicted mechanical properties are reasonable when compared with our results from density functional theory. This study provides physical insights into the origins of the new phase transition of monolayer γ-B28 at finite temperatures. PMID:26979283

  13. Crystalline Gibbs monolayers of DNA-capped nanoparticles at the air-liquid interface.

    PubMed

    Campolongo, Michael J; Tan, Shawn J; Smilgies, Detlef-M; Zhao, Mervin; Chen, Yi; Xhangolli, Iva; Cheng, Wenlong; Luo, Dan

    2011-10-25

    Using grazing-incidence small-angle X-ray scattering in a special configuration (parallel SAXS, or parSAXS), we mapped the crystallization of DNA-capped nanoparticles across a sessile droplet, revealing the formation of crystalline Gibbs monolayers of DNA-capped nanoparticles at the air-liquid interface. We showed that the spatial crystallization can be regulated by adjusting both ionic strength and DNA sequence length and that a modified form of the Daoud-Cotton model could describe and predict the resulting changes in interparticle spacing. Gibbs monolayers at the air-liquid interface provide an ideal platform for the formation and study of equilibrium nanostructures and may afford exciting routes toward the design of programmable 2D plasmonic materials and metamaterials.

  14. Large gap Quantum Spin Hall Insulators of Hexagonal III-Bi monolayer

    NASA Astrophysics Data System (ADS)

    Liu, Qunqun; Dai, Ying; Ma, Yandong; Li, Xinru; Li, Tiejun; Niu, Chengwang; Huang, Baibiao

    2016-10-01

    In the present work, we demonstrate that both GaBi3 and InBi3 monolayers are Quantum Spin Hall insulators. Here, the electronic band structures and edge states of the two novel monolayers are systematically investigated by first principle calculation. Our analysis of the band inversion and Z2 number demonstrate that both GaBi3 and InBi3 are promising 2D TIs with large gaps of 283meV and 247meV, respectively. Taking GaBi3 as example, it is illustrated that the edge states are impacted by SOC and finite size effect. In addition, it is found that the compression and tension totally affect differently on the edge states. Finally, the electron velocity is studied in detail, which is highly important in the manufacturing of spintronics device.

  15. Wedge energy bands of monolayer black phosphorus: a first-principles study

    NASA Astrophysics Data System (ADS)

    Park, Minwoo; Bae, Hyeonhu; Lee, Seunghan; Yang, Li; Lee, Hoonkyung

    2016-08-01

    On the basis of first-principles calculations, we present intriguing electronic properties of halogen-striped functionalized monolayer black phosphorus. The halogen-striped monolayer black phosphorus is found to have a wedge energy band with the energy-momentum relation of E\\propto {{p}y} when the stripe-stripe distance is smaller than ~40 Å. Our tight-binding study shows that the wedge energy band occurs when 2-atom basis 1D lattices are periodically repeated aligned with each other in a 2D lattice. We also discuss the possible applications of this wedge energy band in electron supercollimation with high mobility or severely anisotropic electronic transport, which can be used for the development of optics-like nano-electronics.

  16. Multichannel surface imaging and analysis of self-assembled monolayers and proteins

    NASA Astrophysics Data System (ADS)

    Pyo, Hyeon-Bong; Shin, Yong-Beom; Kim, Min-Gon; Yoon, Hyun C.

    2004-03-01

    Multichannel images of 11-Mercaptoundecanoic acid and 11-Mercapto-1-undecanol self-assembled monolayers (SAMs) together with a biospecific interferon-gamma (IFN-gamma)/anti-IFN-gamma antibody immunoreaction were observed by two-dimensional surface plasmon resonance (2D-SPR) imaging system. Patterning process for SAM was simplified by exploiting direct photooxidation of thiol bonding (photolysis) instead of conventional photolithography. Sharper images were resolved by using a white light source in combination with a narrow bandpass filter, minimizing the diffraction patterns on the images. The line profile calibration of the image contrast caused by different resonance conditions at each points on the sensor surface enabled us to discriminate the monolayer thickness in a sub-nanometer scale. For protein patterning, a precipitation scheme induced by biocatalytic reaction was implied for the signal amplification. Specific binding of IFN-gamma antigen with surface-immobilized antibody was found detectable down to the concentration of 1 ng/mL.

  17. Wedge energy bands of monolayer black phosphorus: a first-principles study.

    PubMed

    Park, Minwoo; Bae, Hyeonhu; Lee, Seunghan; Yang, Li; Lee, Hoonkyung

    2016-08-01

    On the basis of first-principles calculations, we present intriguing electronic properties of halogen-striped functionalized monolayer black phosphorus. The halogen-striped monolayer black phosphorus is found to have a wedge energy band with the energy-momentum relation of [Formula: see text] when the stripe-stripe distance is smaller than ~40 Å. Our tight-binding study shows that the wedge energy band occurs when 2-atom basis 1D lattices are periodically repeated aligned with each other in a 2D lattice. We also discuss the possible applications of this wedge energy band in electron supercollimation with high mobility or severely anisotropic electronic transport, which can be used for the development of optics-like nano-electronics. PMID:27299467

  18. Large gap Quantum Spin Hall Insulators of Hexagonal III-Bi monolayer

    PubMed Central

    Liu, Qunqun; Dai, Ying; Ma, Yandong; Li, Xinru; Li, Tiejun; Niu, Chengwang; Huang, Baibiao

    2016-01-01

    In the present work, we demonstrate that both GaBi3 and InBi3 monolayers are Quantum Spin Hall insulators. Here, the electronic band structures and edge states of the two novel monolayers are systematically investigated by first principle calculation. Our analysis of the band inversion and Z2 number demonstrate that both GaBi3 and InBi3 are promising 2D TIs with large gaps of 283meV and 247meV, respectively. Taking GaBi3 as example, it is illustrated that the edge states are impacted by SOC and finite size effect. In addition, it is found that the compression and tension totally affect differently on the edge states. Finally, the electron velocity is studied in detail, which is highly important in the manufacturing of spintronics device. PMID:27713518

  19. Understanding the collapse mechanism in Langmuir monolayers through polarization modulation-infrared reflection absorption spectroscopy.

    PubMed

    Goto, Thiago Eichi; Caseli, Luciano

    2013-07-23

    The collapse of films at the air-water interface is related to a type of 2D-to-3D transition that occurs when a Langmuir monolayer is compressed beyond its stability limit. Studies on this issue are extremely important because defects in ultrathin solid films can be better understood if the molecular mechanisms related to collapse processes are elucidated. This paper explores how the changes of vibration of specific groups of lipid molecules, as revealed by polarization modulation-infrared reflection absorption spectroscopy (PM-IRRAS), are affected by the monolayer collapse. Different mechanisms of collapse were studied, for those lipids that undergo constant-area collapse (such as stearic acid) and for those that undergo constant-pressure collapse (such as DPPC, DPPG, and DODAB). Lipid charges also affect the mechanism of collapse, as demonstrated for two oppositely charged lipids.

  20. Giant bandgap renormalization and excitonic effects in a monolayer transition metal dichalcogenide semiconductor

    NASA Astrophysics Data System (ADS)

    Ugeda, Miguel M.; Bradley, Aaron J.; Shi, Su-Fei; da Jornada, Felipe H.; Zhang, Yi; Qiu, Diana Y.; Ruan, Wei; Mo, Sung-Kwan; Hussain, Zahid; Shen, Zhi-Xun; Wang, Feng; Louie, Steven G.; Crommie, Michael F.

    2014-12-01

    Two-dimensional (2D) transition metal dichalcogenides (TMDs) are emerging as a new platform for exploring 2D semiconductor physics. Reduced screening in two dimensions results in markedly enhanced electron-electron interactions, which have been predicted to generate giant bandgap renormalization and excitonic effects. Here we present a rigorous experimental observation of extraordinarily large exciton binding energy in a 2D semiconducting TMD. We determine the single-particle electronic bandgap of single-layer MoSe2 by means of scanning tunnelling spectroscopy (STS), as well as the two-particle exciton transition energy using photoluminescence (PL) spectroscopy. These yield an exciton binding energy of 0.55 eV for monolayer MoSe2 on graphene—orders of magnitude larger than what is seen in conventional 3D semiconductors and significantly higher than what we see for MoSe2 monolayers in more highly screening environments. This finding is corroborated by our ab initio GW and Bethe-Salpeter equation calculations which include electron correlation effects. The renormalized bandgap and large exciton binding observed here will have a profound impact on electronic and optoelectronic device technologies based on single-layer semiconducting TMDs.

  1. Screening and many-body effects in two-dimensional crystals: Monolayer MoS2

    NASA Astrophysics Data System (ADS)

    Qiu, Diana Y.; da Jornada, Felipe H.; Louie, Steven G.

    2016-06-01

    We present a systematic study of the variables affecting the electronic and optical properties of two-dimensional (2D) crystals within ab initio G W and G W plus Bethe-Salpeter equation (G W -BSE) calculations. As a prototypical 2D transition metal dichalcogenide material, we focus our study on monolayer MoS2. We find that the reported variations in G W -BSE results in the literature for monolayer MoS2 and related systems arise from different treatments of the long-range Coulomb interaction in supercell calculations and convergence of k -grid sampling and cutoffs for various quantities such as the dielectric screening. In particular, the quasi-2D nature of the system gives rise to fast spatial variations in the screening environment, which are computationally challenging to resolve. We also show that common numerical treatments to remove the divergence in the Coulomb interaction can shift the exciton continuum leading to false convergence with respect to k -point sampling. Our findings apply to G W -BSE calculations on any low-dimensional semiconductors.

  2. Efficient 2D MRI relaxometry using compressed sensing

    NASA Astrophysics Data System (ADS)

    Bai, Ruiliang; Cloninger, Alexander; Czaja, Wojciech; Basser, Peter J.

    2015-06-01

    Potential applications of 2D relaxation spectrum NMR and MRI to characterize complex water dynamics (e.g., compartmental exchange) in biology and other disciplines have increased in recent years. However, the large amount of data and long MR acquisition times required for conventional 2D MR relaxometry limits its applicability for in vivo preclinical and clinical MRI. We present a new MR pipeline for 2D relaxometry that incorporates compressed sensing (CS) as a means to vastly reduce the amount of 2D relaxation data needed for material and tissue characterization without compromising data quality. Unlike the conventional CS reconstruction in the Fourier space (k-space), the proposed CS algorithm is directly applied onto the Laplace space (the joint 2D relaxation data) without compressing k-space to reduce the amount of data required for 2D relaxation spectra. This framework is validated using synthetic data, with NMR data acquired in a well-characterized urea/water phantom, and on fixed porcine spinal cord tissue. The quality of the CS-reconstructed spectra was comparable to that of the conventional 2D relaxation spectra, as assessed using global correlation, local contrast between peaks, peak amplitude and relaxation parameters, etc. This result brings this important type of contrast closer to being realized in preclinical, clinical, and other applications.

  3. The 2D:4D-Ratio and Neuroticism Revisited: Empirical Evidence from Germany and China

    PubMed Central

    Sindermann, Cornelia; Li, Mei; Sariyska, Rayna; Lachmann, Bernd; Duke, Éilish; Cooper, Andrew; Warneck, Lidia; Montag, Christian

    2016-01-01

    The 2D:4D-Ratio, as an indirect measure of the fetal testosterone to estradiol ratio, is potentially very important for understanding and explaining different personality traits. It was the aim of the present study to replicate the findings from Fink et al. (2004) about the relation between individual differences in 2D:4D-Ratios and the Five Factor Model in different cultural groups. Therefore a sample of n = 78 Chinese and n = 370 German participants was recruited. Every participant provided hand scans of both hands, from which 2D:4D-Ratios were computed. Moreover, all participants filled in the NEO Five Factor Inventory (NEO-FFI). Significant sex differences were found for ratios of both hands in the expected direction, with females showing higher ratios than males. With respect to links between personality and the digit ratio, a positive association was observed between 2D:4D-Ratio and Neuroticism in females, as shown in the earlier study. These findings were observed in both female subsamples from China and Germany, as well as in the full sample of participants. But in contrast to the results for the whole and the German female sample, where 2D:4D-Ratio of both hands were related to Neuroticism, in the Chinese female sample only left hand 2D:4D-Ratio was significantly and positively related to Neuroticism. There were no significant correlations found in any of the male samples. Thus, prenatal exposure to sex steroids appears to influence the personality factor Neuroticism in females specifically. This finding potentially has implications for mental health, as Neuroticism has been shown to be a risk factor for various forms of psychopathology. PMID:27375513

  4. The 2D:4D-Ratio and Neuroticism Revisited: Empirical Evidence from Germany and China.

    PubMed

    Sindermann, Cornelia; Li, Mei; Sariyska, Rayna; Lachmann, Bernd; Duke, Éilish; Cooper, Andrew; Warneck, Lidia; Montag, Christian

    2016-01-01

    The 2D:4D-Ratio, as an indirect measure of the fetal testosterone to estradiol ratio, is potentially very important for understanding and explaining different personality traits. It was the aim of the present study to replicate the findings from Fink et al. (2004) about the relation between individual differences in 2D:4D-Ratios and the Five Factor Model in different cultural groups. Therefore a sample of n = 78 Chinese and n = 370 German participants was recruited. Every participant provided hand scans of both hands, from which 2D:4D-Ratios were computed. Moreover, all participants filled in the NEO Five Factor Inventory (NEO-FFI). Significant sex differences were found for ratios of both hands in the expected direction, with females showing higher ratios than males. With respect to links between personality and the digit ratio, a positive association was observed between 2D:4D-Ratio and Neuroticism in females, as shown in the earlier study. These findings were observed in both female subsamples from China and Germany, as well as in the full sample of participants. But in contrast to the results for the whole and the German female sample, where 2D:4D-Ratio of both hands were related to Neuroticism, in the Chinese female sample only left hand 2D:4D-Ratio was significantly and positively related to Neuroticism. There were no significant correlations found in any of the male samples. Thus, prenatal exposure to sex steroids appears to influence the personality factor Neuroticism in females specifically. This finding potentially has implications for mental health, as Neuroticism has been shown to be a risk factor for various forms of psychopathology. PMID:27375513

  5. The 2D:4D-Ratio and Neuroticism Revisited: Empirical Evidence from Germany and China.

    PubMed

    Sindermann, Cornelia; Li, Mei; Sariyska, Rayna; Lachmann, Bernd; Duke, Éilish; Cooper, Andrew; Warneck, Lidia; Montag, Christian

    2016-01-01

    The 2D:4D-Ratio, as an indirect measure of the fetal testosterone to estradiol ratio, is potentially very important for understanding and explaining different personality traits. It was the aim of the present study to replicate the findings from Fink et al. (2004) about the relation between individual differences in 2D:4D-Ratios and the Five Factor Model in different cultural groups. Therefore a sample of n = 78 Chinese and n = 370 German participants was recruited. Every participant provided hand scans of both hands, from which 2D:4D-Ratios were computed. Moreover, all participants filled in the NEO Five Factor Inventory (NEO-FFI). Significant sex differences were found for ratios of both hands in the expected direction, with females showing higher ratios than males. With respect to links between personality and the digit ratio, a positive association was observed between 2D:4D-Ratio and Neuroticism in females, as shown in the earlier study. These findings were observed in both female subsamples from China and Germany, as well as in the full sample of participants. But in contrast to the results for the whole and the German female sample, where 2D:4D-Ratio of both hands were related to Neuroticism, in the Chinese female sample only left hand 2D:4D-Ratio was significantly and positively related to Neuroticism. There were no significant correlations found in any of the male samples. Thus, prenatal exposure to sex steroids appears to influence the personality factor Neuroticism in females specifically. This finding potentially has implications for mental health, as Neuroticism has been shown to be a risk factor for various forms of psychopathology.

  6. Protecting the properties of monolayer MoS2 on silicon based substrates with an atomically thin buffer

    DOE PAGES

    Man, Michael K. L.; Deckoff-Jones, Skylar; Winchester, Andrew; Shi, Guangsha; Gupta, Gautam; Mohite, Aditya D.; Kar, Swastik; Kioupakis, Emmanouil; Talapatra, Saikat; Dani, Keshav M.

    2016-02-12

    Semiconducting 2D materials, like transition metal dichalcogenides (TMDs), have gained much attention for their potential in opto-electronic devices, valleytronic schemes, and semi-conducting to metallic phase engineering. However, like graphene and other atomically thin materials, they lose key properties when placed on a substrate like silicon, including quenching of photoluminescence, distorted crystalline structure, and rough surface morphology. The ability to protect these properties of monolayer TMDs, such as molybdenum disulfide (MoS2), on standard Si-based substrates, will enable their use in opto-electronic devices and scientific investigations. Here we show that an atomically thin buffer layer of hexagonal-boron nitride (hBN) protects the rangemore » of key opto-electronic, structural, and morphological properties of monolayer MoS2 on Si-based substrates. The hBN buffer restores sharp diffraction patterns, improves monolayer flatness by nearly two-orders of magnitude, and causes over an order of magnitude enhancement in photoluminescence, compared to bare Si and SiO2 substrates. Lastly, our demonstration provides a way of integrating MoS2 and other 2D monolayers onto standard Si-substrates, thus furthering their technological applications and scientific investigations.« less

  7. Protecting the properties of monolayer MoS₂ on silicon based substrates with an atomically thin buffer.

    PubMed

    Man, Michael K L; Deckoff-Jones, Skylar; Winchester, Andrew; Shi, Guangsha; Gupta, Gautam; Mohite, Aditya D; Kar, Swastik; Kioupakis, Emmanouil; Talapatra, Saikat; Dani, Keshav M

    2016-02-12

    Semiconducting 2D materials, like transition metal dichalcogenides (TMDs), have gained much attention for their potential in opto-electronic devices, valleytronic schemes, and semi-conducting to metallic phase engineering. However, like graphene and other atomically thin materials, they lose key properties when placed on a substrate like silicon, including quenching of photoluminescence, distorted crystalline structure, and rough surface morphology. The ability to protect these properties of monolayer TMDs, such as molybdenum disulfide (MoS2), on standard Si-based substrates, will enable their use in opto-electronic devices and scientific investigations. Here we show that an atomically thin buffer layer of hexagonal-boron nitride (hBN) protects the range of key opto-electronic, structural, and morphological properties of monolayer MoS2 on Si-based substrates. The hBN buffer restores sharp diffraction patterns, improves monolayer flatness by nearly two-orders of magnitude, and causes over an order of magnitude enhancement in photoluminescence, compared to bare Si and SiO2 substrates. Our demonstration provides a way of integrating MoS2 and other 2D monolayers onto standard Si-substrates, thus furthering their technological applications and scientific investigations.

  8. Protecting the properties of monolayer MoS2 on silicon based substrates with an atomically thin buffer

    NASA Astrophysics Data System (ADS)

    Man, Michael K. L.; Deckoff-Jones, Skylar; Winchester, Andrew; Shi, Guangsha; Gupta, Gautam; Mohite, Aditya D.; Kar, Swastik; Kioupakis, Emmanouil; Talapatra, Saikat; Dani, Keshav M.

    2016-02-01

    Semiconducting 2D materials, like transition metal dichalcogenides (TMDs), have gained much attention for their potential in opto-electronic devices, valleytronic schemes, and semi-conducting to metallic phase engineering. However, like graphene and other atomically thin materials, they lose key properties when placed on a substrate like silicon, including quenching of photoluminescence, distorted crystalline structure, and rough surface morphology. The ability to protect these properties of monolayer TMDs, such as molybdenum disulfide (MoS2), on standard Si-based substrates, will enable their use in opto-electronic devices and scientific investigations. Here we show that an atomically thin buffer layer of hexagonal-boron nitride (hBN) protects the range of key opto-electronic, structural, and morphological properties of monolayer MoS2 on Si-based substrates. The hBN buffer restores sharp diffraction patterns, improves monolayer flatness by nearly two-orders of magnitude, and causes over an order of magnitude enhancement in photoluminescence, compared to bare Si and SiO2 substrates. Our demonstration provides a way of integrating MoS2 and other 2D monolayers onto standard Si-substrates, thus furthering their technological applications and scientific investigations.

  9. Atomic MoS2 monolayers synthesized from a metal-organic complex by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Liu, Lina; Qiu, Hailong; Wang, Jingyi; Xu, Guanchen; Jiao, Liying

    2016-02-01

    The controllable synthesis of MoS2 monolayers is the key challenge for their practical applications. Here we report the chemical vapor deposition (CVD) growth of single layered MoS2 by utilizing a bifunctional precursor. This precursor is a metal-organic complex which supplies both Mo sources and organic seeding promoters for the efficient CVD growth of MoS2 monolayers. The successful growth of high quality MoS2 flakes indicates that the rational design of bifunctional precursors will open up a new way for the controllable CVD growth of two-dimensional (2D) transition metal dichalcogenides (TMDCs).The controllable synthesis of MoS2 monolayers is the key challenge for their practical applications. Here we report the chemical vapor deposition (CVD) growth of single layered MoS2 by utilizing a bifunctional precursor. This precursor is a metal-organic complex which supplies both Mo sources and organic seeding promoters for the efficient CVD growth of MoS2 monolayers. The successful growth of high quality MoS2 flakes indicates that the rational design of bifunctional precursors will open up a new way for the controllable CVD growth of two-dimensional (2D) transition metal dichalcogenides (TMDCs). Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr09089j

  10. Protecting the properties of monolayer MoS2 on silicon based substrates with an atomically thin buffer

    PubMed Central

    Man, Michael K. L.; Deckoff-Jones, Skylar; Winchester, Andrew; Shi, Guangsha; Gupta, Gautam; Mohite, Aditya D.; Kar, Swastik; Kioupakis, Emmanouil; Talapatra, Saikat; Dani, Keshav M.

    2016-01-01

    Semiconducting 2D materials, like transition metal dichalcogenides (TMDs), have gained much attention for their potential in opto-electronic devices, valleytronic schemes, and semi-conducting to metallic phase engineering. However, like graphene and other atomically thin materials, they lose key properties when placed on a substrate like silicon, including quenching of photoluminescence, distorted crystalline structure, and rough surface morphology. The ability to protect these properties of monolayer TMDs, such as molybdenum disulfide (MoS2), on standard Si-based substrates, will enable their use in opto-electronic devices and scientific investigations. Here we show that an atomically thin buffer layer of hexagonal-boron nitride (hBN) protects the range of key opto-electronic, structural, and morphological properties of monolayer MoS2 on Si-based substrates. The hBN buffer restores sharp diffraction patterns, improves monolayer flatness by nearly two-orders of magnitude, and causes over an order of magnitude enhancement in photoluminescence, compared to bare Si and SiO2 substrates. Our demonstration provides a way of integrating MoS2 and other 2D monolayers onto standard Si-substrates, thus furthering their technological applications and scientific investigations. PMID:26869269

  11. Practical Algorithm For Computing The 2-D Arithmetic Fourier Transform

    NASA Astrophysics Data System (ADS)

    Reed, Irving S.; Choi, Y. Y.; Yu, Xiaoli

    1989-05-01

    Recently, Tufts and Sadasiv [10] exposed a method for computing the coefficients of a Fourier series of a periodic function using the Mobius inversion of series. They called this method of analysis the Arithmetic Fourier Transform(AFT). The advantage of the AFT over the FN 1' is that this method of Fourier analysis needs only addition operations except for multiplications by scale factors at one stage of the computation. The disadvantage of the AFT as they expressed it originally is that it could be used effectively only to compute finite Fourier coefficients of a real even function. To remedy this the AFT developed in [10] is extended in [11] to compute the Fourier coefficients of both the even and odd components of a periodic function. In this paper, the improved AFT [11] is extended to a two-dimensional(2-D) Arithmetic Fourier Transform for calculating the Fourier Transform of two-dimensional discrete signals. This new algorithm is based on both the number-theoretic method of Mobius inversion of double series and the complex conjugate property of Fourier coefficients. The advantage of this algorithm over the conventional 2-D FFT is that the corner-turning problem needed in a conventional 2-D Discrete Fourier Transform(DFT) can be avoided. Therefore, this new 2-D algorithm is readily suitable for VLSI implementation as a parallel architecture. Comparing the operations of 2-D AFT of a MxM 2-D data array with the conventional 2-D FFT, the number of multiplications is significantly reduced from (2log2M)M2 to (9/4)M2. Hence, this new algorithm is faster than the FFT algorithm. Finally, two simulation results of this new 2-D AFT algorithm for 2-D artificial and real images are given in this paper.

  12. 2D electron cyclotron emission imaging at ASDEX Upgrade (invited)

    SciTech Connect

    Classen, I. G. J.; Boom, J. E.; Vries, P. C. de; Suttrop, W.; Schmid, E.; Garcia-Munoz, M.; Schneider, P. A.; Tobias, B.; Domier, C. W.; Luhmann, N. C. Jr.; Donne, A. J. H.; Jaspers, R. J. E.; Park, H. K.; Munsat, T.

    2010-10-15

    The newly installed electron cyclotron emission imaging diagnostic on ASDEX Upgrade provides measurements of the 2D electron temperature dynamics with high spatial and temporal resolution. An overview of the technical and experimental properties of the system is presented. These properties are illustrated by the measurements of the edge localized mode and the reversed shear Alfven eigenmode, showing both the advantage of having a two-dimensional (2D) measurement, as well as some of the limitations of electron cyclotron emission measurements. Furthermore, the application of singular value decomposition as a powerful tool for analyzing and filtering 2D data is presented.

  13. Comparison of 2D and 3D gamma analyses

    SciTech Connect

    Pulliam, Kiley B.; Huang, Jessie Y.; Howell, Rebecca M.; Followill, David; Kry, Stephen F.; Bosca, Ryan; O’Daniel, Jennifer

    2014-02-15

    Purpose: As clinics begin to use 3D metrics for intensity-modulated radiation therapy (IMRT) quality assurance, it must be noted that these metrics will often produce results different from those produced by their 2D counterparts. 3D and 2D gamma analyses would be expected to produce different values, in part because of the different search space available. In the present investigation, the authors compared the results of 2D and 3D gamma analysis (where both datasets were generated in the same manner) for clinical treatment plans. Methods: Fifty IMRT plans were selected from the authors’ clinical database, and recalculated using Monte Carlo. Treatment planning system-calculated (“evaluated dose distributions”) and Monte Carlo-recalculated (“reference dose distributions”) dose distributions were compared using 2D and 3D gamma analysis. This analysis was performed using a variety of dose-difference (5%, 3%, 2%, and 1%) and distance-to-agreement (5, 3, 2, and 1 mm) acceptance criteria, low-dose thresholds (5%, 10%, and 15% of the prescription dose), and data grid sizes (1.0, 1.5, and 3.0 mm). Each comparison was evaluated to determine the average 2D and 3D gamma, lower 95th percentile gamma value, and percentage of pixels passing gamma. Results: The average gamma, lower 95th percentile gamma value, and percentage of passing pixels for each acceptance criterion demonstrated better agreement for 3D than for 2D analysis for every plan comparison. The average difference in the percentage of passing pixels between the 2D and 3D analyses with no low-dose threshold ranged from 0.9% to 2.1%. Similarly, using a low-dose threshold resulted in a difference between the mean 2D and 3D results, ranging from 0.8% to 1.5%. The authors observed no appreciable differences in gamma with changes in the data density (constant difference: 0.8% for 2D vs 3D). Conclusions: The authors found that 3D gamma analysis resulted in up to 2.9% more pixels passing than 2D analysis. It must

  14. Recent advances in 2D materials for photocatalysis.

    PubMed

    Luo, Bin; Liu, Gang; Wang, Lianzhou

    2016-04-01

    Two-dimensional (2D) materials have attracted increasing attention for photocatalytic applications because of their unique thickness dependent physical and chemical properties. This review gives a brief overview of the recent developments concerning the chemical synthesis and structural design of 2D materials at the nanoscale and their applications in photocatalytic areas. In particular, recent progress on the emerging strategies for tailoring 2D material-based photocatalysts to improve their photo-activity including elemental doping, heterostructure design and functional architecture assembly is discussed.

  15. Continuity of Monolayer-Bilayer Junctions for Localization of Lipid Raft Microdomains in Model Membranes

    PubMed Central

    Ryu, Yong-Sang; Wittenberg, Nathan J.; Suh, Jeng-Hun; Lee, Sang-Wook; Sohn, Youngjoo; Oh, Sang-Hyun; Parikh, Atul N.; Lee, Sin-Doo

    2016-01-01

    We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed between the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates. PMID:27230411

  16. Continuity of monolayer-bilayer junctions for localization of lipid raft microdomains in model membranes

    DOE PAGES

    Ryu, Yong -Sang; Wittenberg, Nathan J.; Suh, Jeng -Hun; Lee, Sang -Wook; Sohn, Youngjoo; Oh, Sang -Hyun; Parikh, Atul N.; Lee, Sin -Doo

    2016-05-27

    We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed betweenmore » the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Furthermore, our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates.« less

  17. Continuity of Monolayer-Bilayer Junctions for Localization of Lipid Raft Microdomains in Model Membranes.

    PubMed

    Ryu, Yong-Sang; Wittenberg, Nathan J; Suh, Jeng-Hun; Lee, Sang-Wook; Sohn, Youngjoo; Oh, Sang-Hyun; Parikh, Atul N; Lee, Sin-Doo

    2016-01-01

    We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed between the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates. PMID:27230411

  18. Continuity of Monolayer-Bilayer Junctions for Localization of Lipid Raft Microdomains in Model Membranes.

    PubMed

    Ryu, Yong-Sang; Wittenberg, Nathan J; Suh, Jeng-Hun; Lee, Sang-Wook; Sohn, Youngjoo; Oh, Sang-Hyun; Parikh, Atul N; Lee, Sin-Doo

    2016-05-27

    We show that the selective localization of cholesterol-rich domains and associated ganglioside receptors prefer to occur in the monolayer across continuous monolayer-bilayer junctions (MBJs) in supported lipid membranes. For the MBJs, glass substrates were patterned with poly(dimethylsiloxane) (PDMS) oligomers by thermally-assisted contact printing, leaving behind 3 nm-thick PDMS patterns. The hydrophobicity of the transferred PDMS patterns was precisely tuned by the stamping temperature. Lipid monolayers were formed on the PDMS patterned surface while lipid bilayers were on the bare glass surface. Due to the continuity of the lipid membranes over the MBJs, essentially free diffusion of lipids was allowed between the monolayer on the PDMS surface and the upper leaflet of the bilayer on the glass substrate. The preferential localization of sphingomyelin, ganglioside GM1 and cholesterol in the monolayer region enabled to develop raft microdomains through coarsening of nanorafts. Our methodology provides a simple and effective scheme of non-disruptive manipulation of the chemical landscape associated with lipid phase separations, which leads to more sophisticated applications in biosensors and as cell culture substrates.

  19. Plasmonic Gold Nanorods Coverage Influence on Enhancement of the Photoluminescence of Two-Dimensional MoS2 Monolayer

    PubMed Central

    Lee, Kevin C. J.; Chen, Yi-Huan; Lin, Hsiang-Yu; Cheng, Chia-Chin; Chen, Pei-Ying; Wu, Ting-Yi; Shih, Min-Hsiung; Wei, Kung-Hwa; Li, Lain-Jong; Chang, Chien-Wen

    2015-01-01

    The 2-D transition metal dichalcogenide (TMD) semiconductors, has received great attention due to its excellent optical and electronic properties and potential applications in field-effect transistors, light emitting and sensing devices. Recently surface plasmon enhanced photoluminescence (PL) of the weak 2-D TMD atomic layers was developed to realize the potential optoelectronic devices. However, we noticed that the enhancement would not increase monotonically with increasing of metal plasmonic objects and the emission drop after the certain coverage. This study presents the optimized PL enhancement of a monolayer MoS2 in the presence of gold (Au) nanorods. A localized surface plasmon wave of Au nanorods that generated around the monolayer MoS2 can provide resonance wavelength overlapping with that of the MoS2 gain spectrum. These spatial and spectral overlapping between the localized surface plasmon polariton waves and that from MoS2 emission drastically enhanced the light emission from the MoS2 monolayer. We gave a simple model and physical interpretations to explain the phenomena. The plasmonic Au nanostructures approach provides a valuable avenue to enhancing the emitting efficiency of the 2-D nano-materials and their devices for the future optoelectronic devices and systems. PMID:26576041

  20. An Anomalous Formation Pathway for Dislocation-Sulfur Vacancy Complexes in Polycrystalline Monolayer MoS2.

    PubMed

    Yu, Zhi Gen; Zhang, Yong-Wei; Yakobson, Boris I

    2015-10-14

    Two-dimensional (2D) molybdenum disulfide (MoS2) has attracted significant attention recently due to its direct bandgap semiconducting characteristics. Experimental studies on monolayer MoS2 show that S vacancy concentration varies greatly; while recent theoretical studies show that the formation energy of S vacancy is high and thus its concentration should be low. We perform density functional theory calculations to study the structures and energetics of vacancy and interstitial in both grain boundary (GB) and grain interior (GI) in monolayer MoS2 and uncover an anomalous formation pathway for dislocation-double S vacancy (V2S) complexes in MoS2. In this pathway, a (5|7) defect in an S-polar GB energetically favorably converts to a (4|6) defect, which possesses a duality: dislocation and double S vacancy. Its dislocation character allows it to glide into GI through thermal activation at high temperatures, bringing the double vacancy with it. Our findings here not only explain why VS is predominant in exfoliated 2D MoS2 and V2S is predominant in chemical vapor deposition (CVD)-grown 2D MoS2 but also reproduce GB patterns in CVD-grown MoS2. The new pathway for sulfur vacancy formation revealed here provides important insights and guidelines for controlling the quality of monolayer MoS2.

  1. A Gene Expression-Based Comparison of Cell Adhesion to Extracellular Matrix and RGD-Terminated Monolayers

    PubMed Central

    Sobers, Courtney J.; Wood, Sarah E.; Mrksich, Milan

    2015-01-01

    This work uses global gene expression analysis to compare the extent to which model substrates presenting peptide adhesion motifs mimic the use of conventional extracellular matrix protein coated substrates for cell culture. We compared the transcriptional activities of genes in cells that were cultured on matrix-coated substrates with those cultured on self-assembled monolayers presenting either a linear or cyclic RGD peptide. Cells adherent to cyclic RGD were most similar to those cultured on native ECM, while cells cultured on monolayers presenting the linear RGD peptide had transcriptional activities that were more similar to cells cultured on the uncoated substrates. This study suggests that biomaterials presenting the cyclic RGD peptide are substantially better mimics of extracellular matrix than are uncoated materials or materials presenting the common linear RGD peptide. PMID:25818445

  2. Free-Standing Monolayer Two-Dimensional Supramolecular Organic Framework with Good Internal Order.

    PubMed

    Pfeffermann, Martin; Dong, Renhao; Graf, Robert; Zajaczkowski, Wojciech; Gorelik, Tatiana; Pisula, Wojciech; Narita, Akimitsu; Müllen, Klaus; Feng, Xinliang

    2015-11-18

    Utilizing dynamic self-assembly and self-sorting to obtain large-area, molecularly precise monolayered structures represents a promising approach toward two-dimensional supramolecular organic frameworks (2D SOF) or 2D supramolecular polymers. So far, related approaches suffer from small domain sizes, fragility and weak long-range internal order. Here we report on the self-assembly of a host-guest enhanced donor-acceptor interaction, consisting of a tris(methoxynaphthyl)-substituted truxene spacer, and a naphthalene diimide substituted with N-methyl viologenyl moieties as donor and acceptor monomers, respectively, in combination with cucurbit[8]uril as host monomer toward monolayers of an unprecedented 2D SOF. Featuring orthogonal solubility, the participating molecules self-assemble at a liquid-liquid interface, yielding exceptionally large-area, insoluble films, which were analyzed by transmission electron microscopy, atomic force microscopy and optical microscopy to be monolayers with a thickness of 1.8 nm, homogeneously covering areas up to 0.25 cm(2), and featuring the ability to be free-standing over holes of 10 μm(2). Characterization with ultraviolet-visible absorption spectroscopy, solid-state nuclear magnetic resonance spectroscopy, infrared spectroscopy, and grazing incidence wide-angle X-ray scattering allowed for confirmation of a successful complexation of all three monomers toward an internal long-range order and gave indications to an expected hexagonal superstructure. Our results extend the existing variety of two-dimensional soft nanomaterials by a versatile supramolecular approach, whereas the possibility of varying the functional monomers is supposed to open adaptability to different applications like membranes, sensors, molecular sieves, and optoelectronics. PMID:26529142

  3. Free-Standing Monolayer Two-Dimensional Supramolecular Organic Framework with Good Internal Order

    PubMed Central

    2015-01-01

    Utilizing dynamic self-assembly and self-sorting to obtain large-area, molecularly precise monolayered structures represents a promising approach toward two-dimensional supramolecular organic frameworks (2D SOF) or 2D supramolecular polymers. So far, related approaches suffer from small domain sizes, fragility and weak long-range internal order. Here we report on the self-assembly of a host–guest enhanced donor–acceptor interaction, consisting of a tris(methoxynaphthyl)-substituted truxene spacer, and a naphthalene diimide substituted with N-methyl viologenyl moieties as donor and acceptor monomers, respectively, in combination with cucurbit[8]uril as host monomer toward monolayers of an unprecedented 2D SOF. Featuring orthogonal solubility, the participating molecules self-assemble at a liquid–liquid interface, yielding exceptionally large-area, insoluble films, which were analyzed by transmission electron microscopy, atomic force microscopy and optical microscopy to be monolayers with a thickness of 1.8 nm, homogeneously covering areas up to 0.25 cm2, and featuring the ability to be free-standing over holes of 10 μm2. Characterization with ultraviolet–visible absorption spectroscopy, solid-state nuclear magnetic resonance spectroscopy, infrared spectroscopy, and grazing incidence wide-angle X-ray scattering allowed for confirmation of a successful complexation of all three monomers toward an internal long-range order and gave indications to an expected hexagonal superstructure. Our results extend the existing variety of two-dimensional soft nanomaterials by a versatile supramolecular approach, whereas the possibility of varying the functional monomers is supposed to open adaptability to different applications like membranes, sensors, molecular sieves, and optoelectronics. PMID:26529142

  4. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-01

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices.

  5. Emerging and potential opportunities for 2D flexible nanoelectronics

    NASA Astrophysics Data System (ADS)

    Zhu, Weinan; Park, Saungeun; Akinwande, Deji

    2016-05-01

    The last 10 years have seen the emergence of two-dimensional (2D) nanomaterials such as graphene, transition metal dichalcogenides (TMDs), and black phosphorus (BP) among the growing portfolio of layered van der Waals thin films. Graphene, the prototypical 2D material has advanced rapidly in device, circuit and system studies that has resulted in commercial large-area applications. In this work, we provide a perspective of the emerging and potential translational applications of 2D materials including semiconductors, semimetals, and insulators that comprise the basic material set for diverse nanosystems. Applications include RF transceivers, smart systems, the so-called internet of things, and neurotechnology. We will review the DC and RF electronic performance of graphene and BP thin film transistors. 2D materials at sub-um channel length have so far enabled cut-off frequencies from baseband to 100GHz suitable for low-power RF and sub-THz concepts.

  6. 2D hexagonal quaternion Fourier transform in color image processing

    NASA Astrophysics Data System (ADS)

    Grigoryan, Artyom M.; Agaian, Sos S.

    2016-05-01

    In this paper, we present a novel concept of the quaternion discrete Fourier transform on the two-dimensional hexagonal lattice, which we call the two-dimensional hexagonal quaternion discrete Fourier transform (2-D HQDFT). The concept of the right-side 2D HQDFT is described and the left-side 2-D HQDFT is similarly considered. To calculate the transform, the image on the hexagonal lattice is described in the tensor representation when the image is presented by a set of 1-D signals, or splitting-signals which can be separately processed in the frequency domain. The 2-D HQDFT can be calculated by a set of 1-D quaternion discrete Fourier transforms (QDFT) of the splitting-signals.

  7. Technical Review of the UNET2D Hydraulic Model

    SciTech Connect

    Perkins, William A.; Richmond, Marshall C.

    2009-05-18

    The Kansas City District of the US Army Corps of Engineers is engaged in a broad range of river management projects that require knowledge of spatially-varied hydraulic conditions such as velocities and water surface elevations. This information is needed to design new structures, improve existing operations, and assess aquatic habitat. Two-dimensional (2D) depth-averaged numerical hydraulic models are a common tool that can be used to provide velocity and depth information. Kansas City District is currently using a specific 2D model, UNET2D, that has been developed to meet the needs of their river engineering applications. This report documents a tech- nical review of UNET2D.

  8. Double resonance rotational spectroscopy of CH2D+

    NASA Astrophysics Data System (ADS)

    Töpfer, Matthias; Jusko, Pavol; Schlemmer, Stephan; Asvany, Oskar

    2016-09-01

    Context. Deuterated forms of CH are thought to be responsible for deuterium enrichment in lukewarm astronomical environments. There is no unambiguous detection of CH2D+ in space to date. Aims: Four submillimetre rotational lines of CH2D+ are documented in the literature. Our aim is to present a complete dataset of highly resolved rotational lines, including millimetre (mm) lines needed for a potential detection. Methods: We used a low-temperature ion trap and applied a novel IR-mm-wave double resonance method to measure the rotational lines of CH2D+. Results: We measured 21 low-lying (J ≤ 4) rotational transitions of CH2D+ between 23 GHz and 1.1 THz with accuracies close to 2 ppb.

  9. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-01

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices. PMID:26839956

  10. ORION96. 2-d Finite Element Code Postprocessor

    SciTech Connect

    Sanford, L.A.; Hallquist, J.O.

    1992-02-02

    ORION is an interactive program that serves as a postprocessor for the analysis programs NIKE2D, DYNA2D, TOPAZ2D, and CHEMICAL TOPAZ2D. ORION reads binary plot files generated by the two-dimensional finite element codes currently used by the Methods Development Group at LLNL. Contour and color fringe plots of a large number of quantities may be displayed on meshes consisting of triangular and quadrilateral elements. ORION can compute strain measures, interface pressures along slide lines, reaction forces along constrained boundaries, and momentum. ORION has been applied to study the response of two-dimensional solids and structures undergoing finite deformations under a wide variety of large deformation transient dynamic and static problems and heat transfer analyses.

  11. High and anisotropic carrier mobility in experimentally possible Ti2CO2 (MXene) monolayers and nanoribbons

    NASA Astrophysics Data System (ADS)

    Zhang, Xu; Zhao, Xudong; Wu, Dihua; Jing, Yu; Zhou, Zhen

    2015-09-01

    MXene, a new kind of two-dimensional (2D) material, has a unique combination of excellent physical and chemical properties. Via computations on density functional theory and deformation potential theory, we investigated the electronic structure and predicted the carrier mobility of Ti2CO2 (a typical MXene) monolayers and nanoribbons. The Ti2CO2 monolayer is a semiconductor with a band gap of 0.91 eV, and the hole mobility in the monolayer reaches 104 orders of magnitude along both x and y directions, which is much higher than that of MoS2, while the electron mobility is about two orders of magnitude lower. The dramatic difference between the hole and electron mobilities also exists in nanoribbons. Moreover, our results suggest that width controlling and edge engineering would be effective in adjusting the carrier mobility of Ti2CO2 nanoribbons, and endow experimentally available Ti2CO2 with wide applications to field-effect transistors and photocatalysts.MXene, a new kind of two-dimensional (2D) material, has a unique combination of excellent physical and chemical properties. Via computations on density functional theory and deformation potential theory, we investigated the electronic structure and predicted the carrier mobility of Ti2CO2 (a typical MXene) monolayers and nanoribbons. The Ti2CO2 monolayer is a semiconductor with a band gap of 0.91 eV, and the hole mobility in the monolayer reaches 104 orders of magnitude along both x and y directions, which is much higher than that of MoS2, while the electron mobility is about two orders of magnitude lower. The dramatic difference between the hole and electron mobilities also exists in nanoribbons. Moreover, our results suggest that width controlling and edge engineering would be effective in adjusting the carrier mobility of Ti2CO2 nanoribbons, and endow experimentally available Ti2CO2 with wide applications to field-effect transistors and photocatalysts. Electronic supplementary information (ESI) available

  12. Delivery of TEM beta-lactamase by gene-transformed Lactococcus lactis subsp. lactis through cervical cell monolayer.

    PubMed

    Kaushal, Gagan; Trombetta, Louis; Ochs, Raymond S; Shao, Jun

    2006-04-26

    Lactococcus lactis subsp. lactis transformed with Plasmid ss80 (encoding the production and secretion of TEM beta-lactamase) was used for the delivery of beta-lactamase through the C-33A (cervix cell) monolayer. The viability of the cell monolayers co-cultured with L. lactis was examined by the trypan blue exclusion method. The integrity of the monolayers was monitored by measuring the transport of mannitol and propranolol as well as the transepithelial electrical resistance. The transport rate of beta-lactamase through C-33A monolayer was increased by four- and nine-folds (p < 0.05) at the first hour by the transformed L. lactis compared to the free solution with or without presence of the untransformed L. lactis, respectively. This increase was gradually diminished after the 1st hour: it became 30 and 50% (p < 0.05) at 10 h. The presence of the untransformed L. lactis with free solution delivery also increased the transport rate by 100% at 1 h (p < 0.05) and 15% at 10h (p>0.05). The increase in transport rate by the transformed L. lactis is most probably due to the concentrate of beta-lactamase on C-33A monolayer. When co-cultured with the L. lactis, the C-33A cell viability and the monolayer TEER remained steady for 10 h. The presence of L. lactis did not change the transport of propranolol and mannitol through the monolayers. In conclusion, the transformed L. lactis significantly (p < 0.05) increased the transport of beta-lactamase through the cervical monolayers, indicating probiotic bacteria delivery may be a promising approach for protein delivery through the vagina.

  13. In-plane heterojunctions enable multiphasic two-dimensional (2D) MoS2 nanosheets as efficient photocatalysts for hydrogen evolution from water reduction

    DOE PAGES

    Peng, Rui; Liang, Liangbo; Hood, Zachary D.; Boulesbaa, Abdelaziz; Puretzky, Alexander; Ievlev, Anton V.; Come, Jeremy; Ovchinnikova, Olga S.; Wang, Hui; Ma, Cheng; et al

    2016-08-30

    Two-dimensional (2D) single-layer MoS2 nanosheets are demonstrated as efficient photocatalysts for hydrogen evolution reaction (HER) from water reduction, thanks to specific in-plane heterojunctions constructed in the MoS2 monolayer. These functional heterojunctions are formed among the different phases of chemically exfoliated MoS2 monolayers: semiconducting 2H, metallic 1T, and quasi-metallic 1T' phases. The proportion of the three MoS2 phases can be systematically controlled via thermal annealing of the nanosheets. Interestingly, a volcano relationship is observed between the photocatalytic HER activity and the annealing temperature with an optimum activity obtained after annealing at 60 °C. First-principles calculations were integrated with experimental studies tomore » shed light on the role of the multiphases of MoS2 and reveal that optimum photocatalytic HER activity results from the formation of the in-plane heterojunctions between 1T' MoS2 and 2H MoS2. Importantly, this facilitates not only balanced light absorption and charge generation by the 2H phase, efficient charge separation at the 1T'/2H interface, but also favorable HER over the basal sites of 1T' MoS2. Furthermore, our work manifests how the confluence of the optical, electronic and chemical properties of 2D MoS2 monolayers can be fully captured for efficient photocatalytic water reduction.« less

  14. Optomechanical Enhancement of Doubly Resonant 2D Optical Nonlinearity.

    PubMed

    Yi, Fei; Ren, Mingliang; Reed, Jason C; Zhu, Hai; Hou, Jiechang; Naylor, Carl H; Johnson, A T Charlie; Agarwal, Ritesh; Cubukcu, Ertugrul

    2016-03-01

    Emerging two-dimensional semiconductor materials possess a giant second order nonlinear response due to excitonic effects while the monolayer thickness of such active materials limits their use in practical nonlinear devices. Here, we report 3300 times optomechanical enhancement of second harmonic generation from a MoS2 monolayer in a doubly resonant on-chip optical cavity. We achieve this by engineering the nonlinear light-matter interaction in a microelectro-mechanical system enabled optical frequency doubling device based on an electrostatically tunable Fabry-Perot microresonator. Our versatile optomechanical approach will pave the way for next generation efficient on-chip tunable light sources, sensors, and systems based on molecularly thin materials. PMID:26854706

  15. Optomechanical Enhancement of Doubly Resonant 2D Optical Nonlinearity.

    PubMed

    Yi, Fei; Ren, Mingliang; Reed, Jason C; Zhu, Hai; Hou, Jiechang; Naylor, Carl H; Johnson, A T Charlie; Agarwal, Ritesh; Cubukcu, Ertugrul

    2016-03-01

    Emerging two-dimensional semiconductor materials possess a giant second order nonlinear response due to excitonic effects while the monolayer thickness of such active materials limits their use in practical nonlinear devices. Here, we report 3300 times optomechanical enhancement of second harmonic generation from a MoS2 monolayer in a doubly resonant on-chip optical cavity. We achieve this by engineering the nonlinear light-matter interaction in a microelectro-mechanical system enabled optical frequency doubling device based on an electrostatically tunable Fabry-Perot microresonator. Our versatile optomechanical approach will pave the way for next generation efficient on-chip tunable light sources, sensors, and systems based on molecularly thin materials.

  16. Monolayer cultivation of osteoprogenitors shortens duration of the embryonic stem cell test while reliably predicting developmental osteotoxicity.

    PubMed

    zur Nieden, Nicole I; Davis, Lesley A; Rancourt, Derrick E

    2010-11-01

    Osteotoxic compounds administered during pregnancy can initiate skeletal congenital anomalies in the embryo. In vitro, developmental osteotoxicity of a compound can be predicted with the embryonic stem cell test (EST), the only in vitro embryotoxicity model identified to date that entirely abrogates the use of animals. Although the previously identified endpoint osteocalcin mRNA expression robustly predicts developmental osteotoxicity, it can only be assayed after 5 weeks of in vitro culture with existing embryoid body (EB)-based differentiation protocols. Therefore, the goal of this study was to characterize novel earlier endpoints of developmental osteotoxicity for the EST. The currently used EB-based differentiation protocol was modified so that a monolayer culture of pre-differentiated cells was inoculated. The expression profile of five bone-specific mRNAs, including osteocalcin, over the course of 30 differentiation days suggested an acceleration of pre-osteoblast specification in the monolayer over the EB-based protocol. Similarly, calcification was already visible after 14 days of culture in monolayer cultures. Employing image and absorption-based techniques to measure the degree of mineralization in these cells after compound treatment, the three compounds Penicillin G, 5-fluorouracil (5-FU) and all-trans retinoic acid (RA) were then tested after 14 days in monolayer cultures and compared to embryoid body-based differentiations at day 30. By modifying the culture the three test substances were classified correctly into non- or strong osteotoxic. Moreover, we were successful in shortening the assay duration from 30 to 14 days.

  17. Corticotropin-releasing factor induces immune escape of cervical cancer cells by downregulation of NKG2D.

    PubMed

    Song, Hyunkeun; Park, Hyunjin; Park, Gabin; Kim, Yeong Seok; Lee, Hyun-Kyung; Jin, Dong-Hoon; Kang, Hyung-Sik; Cho, Dae-Ho; Hur, Daeyoung

    2014-07-01