WorldWideScience

Sample records for polarized monolayer culture

  1. A Route to Permanent Valley Polarization in Monolayer MoS2

    KAUST Repository

    Singh, Nirpendra

    2016-10-24

    Realization of permanent valley polarization in Cr-doped monolayer MoS2 is found to be unfeasible because of extended moment formation. Introduction of an additional hole is suggested as a viable solution. V-doped monolayer MoS2 is demonstrated to sustain permanent valley polarization and therefore can serve as a prototype material for valleytronics.

  2. Optically initialized robust valley-polarized holes in monolayer WSe2

    KAUST Repository

    Hsu, Wei-Ting; Chen, Yen-Lun; Chen, Chiang-Hsiao; Liu, Pang-Shiuan; Hou, Tuo-Hung; Li, Lain-Jong; Chang, Wen-Hao

    2015-01-01

    a unique platform to develop such valleytronic devices, the anticipated long-lived valley pseudospin has not been observed yet. Here we demonstrate that robust valley-polarized holes in monolayer WSe2 can be initialized by optical pumping. Using time

  3. Interferon induction in bovine and feline monolayer cultures by four bluetongue virus serotypes.

    OpenAIRE

    Fulton, R W; Pearson, N J

    1982-01-01

    The interferon inducing ability of bluetongue viruses was studied in bovine and feline monolayer cultures inoculated with each of four bluetongue virus serotypes. Interferon was assayed by a plaque reduction method in monolayer cultures with vesicular stomatitis virus as challenge virus. Interferon was produced by bovine turbinate, Georgia bovine kidney, and Crandell feline kidney monolayer cultures in response to bluetongue virus serotypes 10, 11, 13 and 17. The antiviral substances produced...

  4. Superior Valley Polarization and Coherence of 2s Excitons in Monolayer WSe_{2}.

    Science.gov (United States)

    Chen, Shao-Yu; Goldstein, Thomas; Tong, Jiayue; Taniguchi, Takashi; Watanabe, Kenji; Yan, Jun

    2018-01-26

    We report the experimental observation of 2s exciton radiative emission from monolayer tungsten diselenide, enabled by hexagonal boron nitride protected high-quality samples. The 2s luminescence is highly robust and persists up to 150 K, offering a new quantum entity for manipulating the valley degree of freedom. Remarkably, the 2s exciton displays superior valley polarization and coherence than 1s under similar experimental conditions. This observation provides evidence that the Coulomb-exchange-interaction-driven valley-depolarization process, the Maialle-Silva-Sham mechanism, plays an important role in valley excitons of monolayer transition metal dichalcogenides.

  5. Superior Valley Polarization and Coherence of 2 s Excitons in Monolayer WSe2

    Science.gov (United States)

    Chen, Shao-Yu; Goldstein, Thomas; Tong, Jiayue; Taniguchi, Takashi; Watanabe, Kenji; Yan, Jun

    2018-01-01

    We report the experimental observation of 2 s exciton radiative emission from monolayer tungsten diselenide, enabled by hexagonal boron nitride protected high-quality samples. The 2 s luminescence is highly robust and persists up to 150 K, offering a new quantum entity for manipulating the valley degree of freedom. Remarkably, the 2 s exciton displays superior valley polarization and coherence than 1 s under similar experimental conditions. This observation provides evidence that the Coulomb-exchange-interaction-driven valley-depolarization process, the Maialle-Silva-Sham mechanism, plays an important role in valley excitons of monolayer transition metal dichalcogenides.

  6. Biotransformation of hydralazine (HDZ) in monolayer cultures of rabbit hepatocytes

    International Nuclear Information System (INIS)

    McQueen, C.A.; Rosado, R.R.

    1990-01-01

    Adverse reactions to HDZ have been associated with the acetylator polymorphism; slow acetylators are more likely to develop HDZ-induced lupus erythematosus. In studying the role of this polymorphism in susceptibility to HDZ toxicity, the biotransformation of HDZ was investigated in rabbit hepatocytes. New Zealand white rabbits, like humans, are classified as rapid or slow acetylators. Heptocytes were isolated from rapid acetylator rabbits by collagenase perfusion. Monolayer cultures were initiated and exposed to 14 C-HDZ. Since HDZ is unstable at neutral pH, parallel incubations were done in the absence of cells. Metabolites in the media were determined by reverse phase HPLC. Phthalazine (P), phthalazinone (PZ), triazoloph-thalazine (TP), methyl TP (MTP) and 3-hydroxy MTP were identified. In the absence of cells, more TP was formed than MTP, probably resulting from reaction of HDZ with components in the medium. In the presence of cells, there was a three-fold increase in MTP, while the amount of TP was relatively constant. Only trace amounts of P, PZ 3-hydroxy MTP were detected. These data indicate that monolayer cultures of rapid acetylator rabbit hepatocytes were capable of metabolizing HDZ with acetylation playing a major role. These studies are being extended to cells from slow acetylator rabbits

  7. Polarized neutron reflectivity from monolayers of self-assembled magnetic nanoparticles.

    Science.gov (United States)

    Mishra, D; Petracic, O; Devishvili, A; Theis-Bröhl, K; Toperverg, B P; Zabel, H

    2015-04-10

    We prepared monolayers of iron oxide nanoparticles via self-assembly on a bare silicon wafer and on a vanadium film sputter deposited onto a plane sapphire substrate. The magnetic configuration of nanoparticles in such a dense assembly was investigated by polarized neutron reflectivity. A theoretical model fit shows that the magnetic moments of nanoparticles form quasi domain-like configurations at remanence. This is attributed to the dipolar coupling amongst the nanoparticles.

  8. Velocity barrier-controlled of spin-valley polarized transport in monolayer WSe2 junction

    Science.gov (United States)

    Qiu, Xuejun; Lv, Qiang; Cao, Zhenzhou

    2018-05-01

    In this work, we have theoretically investigated the influence of velocity barrier on the spin-valley polarized transport in monolayer (ML) WSe2 junction with a large spin-orbit coupling (SOC). Both the spin-valley resolved transmission probabilities and conductance are strong dependent on the velocity barrier, as the velocity barrier decreases to 0.06, a spin-valley polarization of exceeding 90% is observed, which is distinct from the ML MoS2 owing to incommensurable SOC. In addition, the spin-valley polarization is further increased above 95% in a ML WSe2 superlattice, in particular, it's found many extraordinary velocity barrier-dependent transport gaps for multiple barrier due to evanescent tunneling. Our results may open an avenue for the velocity barrier-controlled high-efficiency spin and valley polarizations in ML WSe2-based electronic devices.

  9. Optically initialized robust valley-polarized holes in monolayer WSe2

    KAUST Repository

    Hsu, Wei-Ting

    2015-11-25

    A robust valley polarization is a key prerequisite for exploiting valley pseudospin to carry information in next-generation electronics and optoelectronics. Although monolayer transition metal dichalcogenides with inherent spin–valley coupling offer a unique platform to develop such valleytronic devices, the anticipated long-lived valley pseudospin has not been observed yet. Here we demonstrate that robust valley-polarized holes in monolayer WSe2 can be initialized by optical pumping. Using time-resolved Kerr rotation spectroscopy, we observe a long-lived valley polarization for positive trion with a lifetime approaching 1 ns at low temperatures, which is much longer than the trion recombination lifetime (~10–20 ps). The long-lived valley polarization arises from the transfer of valley pseudospin from photocarriers to resident holes in a specific valley. The optically initialized valley pseudospin of holes remains robust even at room temperature, which opens up the possibility to realize room-temperature valleytronics based on transition metal dichalcogenides.

  10. Change of cobalt magnetic anisotropy and spin polarization with alkanethiolates self-assembled monolayers

    International Nuclear Information System (INIS)

    Campiglio, Paolo; Breitwieser, Romain; Repain, Vincent; Guitteny, Solène; Chacon, Cyril; Bellec, Amandine; Lagoute, Jérôme; Girard, Yann; Rousset, Sylvie; Sassella, Adele; Imam, Mighfar; Narasimhan, Shobhana

    2015-01-01

    We demonstrate that the deposition of a self-assembled monolayer of alkanethiolates on a 1 nm thick cobalt ultrathin film grown on Au(111) induces a spin reorientation transition from in-plane to out-of-plane magnetization. Using ab initio calculations, we show that a methanethiolate layer changes slightly both the magnetocrystalline and shape anisotropy, both effects almost cancelling each other out for a 1 nm Co film. Finally, the change in hysteresis cycles upon alkanethiolate adsorption could be assigned to a molecular-induced roughening of the Co layer, as shown by STM. In addition, we calculate how a methanethiolate layer modifies the spin density of states of the Co layer and we show that the spin polarization at the Fermi level through the organic layer is reversed as compared to the uncovered Co. These results give new theoretical and experimental insights for the use of thiol-based self-assembled monolayers in spintronic devices. (paper)

  11. Spin-orbit-induced spin splittings in polar transition metal dichalcogenide monolayers

    KAUST Repository

    Cheng, Yingchun

    2013-06-01

    The Rashba effect in quasi two-dimensional materials, such as noble metal surfaces and semiconductor heterostructures, has been investigated extensively, while interest in real two-dimensional systems has just emerged with the discovery of graphene. We present ab initio electronic structure, phonon, and molecular-dynamics calculations to study the structural stability and spin-orbit-induced spin splitting in the transition metal dichalcogenide monolayers MXY (M = Mo, W and X, Y = S, Se, Te). In contrast to the non-polar systems with X = Y, in the polar systems with X ≠ Y the Rashba splitting at the Γ-point for the uppermost valence band is caused by the broken mirror symmetry. An enhancement of the splitting can be achieved by increasing the spin-orbit coupling and/or the potential gradient. © Copyright EPLA, 2013.

  12. Large Spin-Valley Polarization in Monolayer MoTe2 on Top of EuO(111)

    KAUST Repository

    Zhang, Qingyun

    2015-12-08

    The electronic properties of monolayer MoTe2 on top of EuO(111) are studied by first-principles calculations. Strong spin polarization is induced in MoTe2, which results in a large valley polarization. In a longitudinal electric field this will result in a valley and spin-polarized charge Hall effect. The direction of the Hall current as well as the valley and spin polarizations can be tuned by an external magnetic field. Copyright © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Small Worlds and Cultural Polarization

    NARCIS (Netherlands)

    Flache, Andreas; Macy, Michael W.

    2011-01-01

    Building on Granovetter's theory of the "strength of weak ties,'' research on "small-world'' networks suggests that bridges between clusters in a social network (long-range ties) promote cultural diffusion, homogeneity, and integration. We show that this macro-level implication of network structure

  14. Carrier and polarization dynamics in monolayer MoS2: temperature and power dependence

    Science.gov (United States)

    Urbaszek, Bernhard; Lagarde, D.; Bouet, L.; Amand, T.; Marie, X.; Zhu, C. R.; Liu, B. L.; Tan, P. H.

    2014-03-01

    In monolayer (ML) MoS2 optical transitions across the direct bandgap are governed by chiral selection rules, allowing optical k-valley initialization. Here we present the first time resolved photoluminescence (PL) polarization measurements in MoS2 MLs, providing vital information on the electron valley dynamics. Using quasi-resonant excitation of the A-exciton transitions, we can infer that the PL decays within τ ~= 4ps. The PL polarization of Pc ~ 60 % remains nearly constant in time for experiments from 4K - 300K, a necessary condition for the success of future Valley Hall experiments. τ does not vary significantly over this temperature range. This is surprising when considering the decrease of Pc in continuous wave experiments when going from 4K to 300K reported in the literature. By tuning the laser following the shift of the A-exciton resonance with temperature we are able to recover at 300K ~ 80 % of the polarization observed at 4K. For pulsed laser excitation, we observe a decrease of Pc with increasing laser power at all temperatures.

  15. Spin polarization driven by a charge-density wave in monolayer 1T−TaS2

    KAUST Repository

    Zhang, Qingyun

    2014-08-06

    Using first-principles calculations, we investigate the electronic and vibrational properties of monolayer T-phase TaS2. We demonstrate that a charge-density wave is energetically favorable at low temperature, similar to bulk 1T-TaS2. Electron-phonon coupling is found to be essential for the lattice reconstruction. The charge-density wave results in a strong localization of the electronic states near the Fermi level and consequently in spin polarization, transforming the material into a magnetic semiconductor with enhanced electronic correlations. The combination of inherent spin polarization with a semiconducting nature distinguishes the monolayer fundamentally from the bulk compound as well as from other two-dimensional transition metal dichalcogenides. Monolayer T-phase TaS2 therefore has the potential to enable two-dimensional spintronics. © 2014 American Physical Society.

  16. Spin polarization driven by a charge-density wave in monolayer 1T−TaS2

    KAUST Repository

    Zhang, Qingyun; Gan, Liyong; Cheng, Yingchun; Schwingenschlö gl, Udo

    2014-01-01

    Using first-principles calculations, we investigate the electronic and vibrational properties of monolayer T-phase TaS2. We demonstrate that a charge-density wave is energetically favorable at low temperature, similar to bulk 1T-TaS2. Electron-phonon coupling is found to be essential for the lattice reconstruction. The charge-density wave results in a strong localization of the electronic states near the Fermi level and consequently in spin polarization, transforming the material into a magnetic semiconductor with enhanced electronic correlations. The combination of inherent spin polarization with a semiconducting nature distinguishes the monolayer fundamentally from the bulk compound as well as from other two-dimensional transition metal dichalcogenides. Monolayer T-phase TaS2 therefore has the potential to enable two-dimensional spintronics. © 2014 American Physical Society.

  17. Spin polarized first principles study of Mn doped gallium nitride monolayer nanosheet

    Science.gov (United States)

    Sharma, Venus; Kaur, Sumandeep; Srivastava, Sunita; Kumar, Tankeshwar

    2017-05-01

    The structural, electronic and magnetic properties of gallium nitride nanosheet (GaNs) doped with Mn atoms have been studied using spin polarized density functional theory. The binding energy per atom, Energy Band gap, Fermi energy, magnetic moment, electric dipole moment have been found. The doped nanosheet is found to be more stable than pure GaN monolayer nanosheet. Adsorption of Mn atom has been done at four different sites on GaNs which affects the fermi level position. It is found that depending on the doping site, Mn can behave both like p-type semiconductor and also as n-type semiconductor. Also, it is ascertained that Mn doped GaNs (GaNs-Mn) exhibits ferromagnetic behavior.

  18. Monolayer alignment on azobenzene surfaces during UV light irradiation: Analysis of optical polarized absorption measurement results and theoretical treatment

    International Nuclear Information System (INIS)

    Zakharov, A.V.; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa

    2006-01-01

    The influence of the charge separation during the trans-cis conformational change on the surface of azobenzene 6Az10PVA monolayer on the polar liquid-crystal monolayer film, such as 4-n-pentyl-4 ' -cyanobiphenyl(5CB), is investigated. The effective anchoring energy (in the Rapini-Papolar form) is phenomenologically described in the framework of the molecular model, which takes into account the interaction between the surface polarization and surface electric field, for number of conformational states of the boundary surface. It is shown, using the experimental data for the voltage across the 6Az10PVA+5CB film, provided by the surface-potential technique, that the charge separation during the conformational changing, caused by the UV irradiation, may lead to changing of the surface alignment of liquid-crystalline molecules. The influence of the photoisomerization process on the orientational order parameter S 2 (t) using the optical polarized absorption measurement is also investigated

  19. Clonal differences in generation times of GPK epithelial cells in monolayer culture.

    Science.gov (United States)

    Riley, P A; Hola, M

    1980-01-01

    Pedigrees of cells in eight clones of guinea pig keratocyte (GPK) cells in monolayer culture were analyzed from a time-lapse film. The generation times and the position in the field of observation were recorded up to the sixth generation when the cultures were still subconfluent. Statistical analysis of the results indicates that the position in the culture has less significance than the clonal origin of the cell in determining the interval between successive mitoses.

  20. Culture temperature affects human chondrocyte messenger RNA expression in monolayer and pellet culture systems.

    Directory of Open Access Journals (Sweden)

    Akira Ito

    Full Text Available Cell-based therapy has been explored for articular cartilage regeneration. Autologous chondrocyte implantation is a promising cell-based technique for repairing articular cartilage defects. However, there are several issues such as chondrocyte de-differentiation. While numerous studies have been designed to overcome some of these issues, only a few have focused on the thermal environment that can affect chondrocyte metabolism and phenotype. In this study, the effects of different culture temperatures on human chondrocyte metabolism- and phenotype-related gene expression were investigated in 2D and 3D environments. Human chondrocytes were cultured in a monolayer or in a pellet culture system at three different culture temperatures (32°C, 37°C, and 41°C for 3 days. The results showed that the total RNA level, normalized to the threshold cycle value of internal reference genes, was higher at lower temperatures in both culture systems. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH and citrate synthase (CS, which are involved in glycolysis and the citric acid cycle, respectively, were expressed at similar levels at 32°C and 37°C in pellet cultures, but the levels were significantly lower at 41°C. Expression of the chondrogenic markers, collagen type IIA1 (COL2A1 and aggrecan (ACAN, was higher at 37°C than at 32°C and 41°C in both culture systems. However, this phenomenon did not coincide with SRY (sex-determining region Y-box 9 (SOX9, which is a fundamental transcription factor for chondrogenesis, indicating that a SOX9-independent pathway might be involved in this phenomenon. In conclusion, the expression of chondrocyte metabolism-related genes at 32°C was maintained or enhanced compared to that at 37°C. However, chondrogenesis-related genes were further induced at 37°C in both culture systems. Therefore, manipulating the culture temperature may be an advantageous approach for regulating human chondrocyte metabolic activity and

  1. Culture temperature affects human chondrocyte messenger RNA expression in monolayer and pellet culture systems.

    Science.gov (United States)

    Ito, Akira; Nagai, Momoko; Tajino, Junichi; Yamaguchi, Shoki; Iijima, Hirotaka; Zhang, Xiangkai; Aoyama, Tomoki; Kuroki, Hiroshi

    2015-01-01

    Cell-based therapy has been explored for articular cartilage regeneration. Autologous chondrocyte implantation is a promising cell-based technique for repairing articular cartilage defects. However, there are several issues such as chondrocyte de-differentiation. While numerous studies have been designed to overcome some of these issues, only a few have focused on the thermal environment that can affect chondrocyte metabolism and phenotype. In this study, the effects of different culture temperatures on human chondrocyte metabolism- and phenotype-related gene expression were investigated in 2D and 3D environments. Human chondrocytes were cultured in a monolayer or in a pellet culture system at three different culture temperatures (32°C, 37°C, and 41°C) for 3 days. The results showed that the total RNA level, normalized to the threshold cycle value of internal reference genes, was higher at lower temperatures in both culture systems. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and citrate synthase (CS), which are involved in glycolysis and the citric acid cycle, respectively, were expressed at similar levels at 32°C and 37°C in pellet cultures, but the levels were significantly lower at 41°C. Expression of the chondrogenic markers, collagen type IIA1 (COL2A1) and aggrecan (ACAN), was higher at 37°C than at 32°C and 41°C in both culture systems. However, this phenomenon did not coincide with SRY (sex-determining region Y)-box 9 (SOX9), which is a fundamental transcription factor for chondrogenesis, indicating that a SOX9-independent pathway might be involved in this phenomenon. In conclusion, the expression of chondrocyte metabolism-related genes at 32°C was maintained or enhanced compared to that at 37°C. However, chondrogenesis-related genes were further induced at 37°C in both culture systems. Therefore, manipulating the culture temperature may be an advantageous approach for regulating human chondrocyte metabolic activity and chondrogenesis.

  2. Proteomic Characterization of Primary Mouse Hepatocytes in Collagen Monolayer and Sandwich Culture.

    Science.gov (United States)

    Orsini, Malina; Sperber, Saskia; Noor, Fozia; Hoffmann, Esther; Weber, Susanne N; Hall, Rabea A; Lammert, Frank; Heinzle, Elmar

    2018-01-01

    Dedifferentiation of primary hepatocytes in vitro makes their application in long-term studies difficult. Embedding hepatocytes in a sandwich of extracellular matrix is reported to delay the dedifferentiation process to some extent. In this study, we compared the intracellular proteome of primary mouse hepatocytes (PMH) in conventional monolayer cultures (ML) to collagen sandwich culture (SW) after 1 day and 5 days of cultivation. Quantitative proteome analysis of PMH showed no differences between collagen SW and ML cultures after 1 day. Glycolysis and gluconeogenesis were strongly affected by long-term cultivation in both ML and SW cultures. Interestingly, culture conditions had no effect on cellular lipid metabolism. After 5 days, PMH in collagen SW and ML cultures exhibit characteristic indications of oxidative stress. However, in the SW culture the defense system against oxidative stress is significantly up-regulated to deal with this, whereas in the ML culture a down-regulation of these important enzymes takes place. Regarding the multiple effects of ROS and oxidative stress in cells, we conclude that the down-regulation of these enzymes seem to play a role in the loss of hepatic function observed in the ML cultivation. In addition, enzymes of the urea cycle were clearly down-regulated in ML culture. Proteomics confirms lack in oxidative stress defense mechanisms as the major characteristic of hepatocytes in monolayer cultures compared to sandwich cultures. J. Cell. Biochem. 119: 447-454, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  3. Human disc cells in monolayer vs 3D culture: cell shape, division and matrix formation

    Directory of Open Access Journals (Sweden)

    Hanley Edward N

    2000-10-01

    Full Text Available Abstract Background The relationship between cell shape, proliferation, and extracellular matrix (ECM production, important aspects of cell behavior, is examined in a little-studied cell type, the human annulus cell from the intervertebral disc, during monolayer vs three-dimensional (3D culture. Results Three experimental studies showed that cells respond specifically to culture microenvironments by changes in cell shape, mitosis and ECM production: 1 Cell passages showed extensive immunohistochemical evidence of Type I and II collagens only in 3D culture. Chondroitin sulfate and keratan sulfate were abundant in both monolayer and 3D cultures. 2 Cells showed significantly greater proliferation in monolayer in the presence of platelet-derived growth factor compared to cells in 3D. 3 Cells on Matrigel™-coated monolayer substrates became rounded and formed nodular colonies, a finding absent during monolayer growth. Conclusions The cell's in vivo interactions with the ECM can regulate shape, gene expression and other cell functions. The shape of the annulus cell changes markedly during life: the young, healthy disc contains spindle shaped cells and abundant collagen. With aging and degeneration, many cells assume a strikingly different appearance, become rounded and are surrounded by unusual accumulations of ECM products. In vitro manipulation of disc cells provides an experimental window for testing how disc cells from given individuals respond when they are grown in environments which direct cells to have either spindle- or rounded-shapes. In vitro assessment of the response of such cells to platelet-derived growth factor and to Matrigel™ showed a continued influence of cell shape even in the presence of a growth factor stimulus. These findings contribute new information to the important issue of the influence of cell shape on cell behavior.

  4. Comparative proteome analysis of monolayer and spheroid culture of canine osteosarcoma cells.

    Science.gov (United States)

    Gebhard, Christiane; Miller, Ingrid; Hummel, Karin; Neschi Née Ondrovics, Martina; Schlosser, Sarah; Walter, Ingrid

    2018-04-15

    Osteosarcoma is an aggressive bone tumor with high metastasis rate in the lungs and affects both humans and dogs in a similar way. Three-dimensional tumor cell cultures mimic the in vivo situation of micro-tumors and metastases and are therefore better experimental in vitro models than the often applied two-dimensional monolayer cultures. The aim of the present study was to perform comparative proteomics of standard monolayer cultures of canine osteosarcoma cells (D17) and three-dimensional spheroid cultures, to better characterize the 3D model before starting with experiments like migration assays. Using DIGE in combination with MALDI-TOF/TOF we found 27 unique canine proteins differently represented between these two culture systems, most of them being part of a functional network including mainly chaperones, structural proteins, stress-related proteins, proteins of the glycolysis/gluconeogenesis pathway and oxidoreductases. In monolayer cells, a noticeable shift to more acidic pI values was noticed for several proteins of medium to high abundance; two proteins (protein disulfide isomerase A3, stress-induced-phosphoprotein 1) showed an increase of phosphorylated protein species. Protein distribution within the cells, as detected by immunohistochemistry, displayed a switch of stress-induced-phosphoprotein 1 from the cytoplasm (in monolayer cultures) to the nucleus (in spheroid cultures). Additionally, Western blot testing revealed upregulated concentrations of metastasin (S100A4), triosephosphate isomerase 1 and septin 2 in spheroid cultures, in contrast to decreased concentrations of CCT2, a subunit of the T-complex. Results indicate regulation of stress proteins in the process of three-dimensional organization characterized by a hypoxic and nutrient-deficient environment comparable to tumor micro-metastases. Osteosarcoma is an aggressive bone tumor that early spreads to the lungs. Three-dimensional tumor cell cultures represent the avascular stage of micro

  5. Biogenesis of corticosteroids in monolayer cultures of human foetal adrenal cells

    International Nuclear Information System (INIS)

    Goodyer, C.G.; Torday, J.S.; St George Hall, C.; Smith, B.T.; Giroud, C.J.P.

    1976-01-01

    Human foetal adrenal cells were grown in monolayer culture and their steroidogenic capacity observed for up to a month. The cells produced a complex array of steroids and some of their ester sulphates from endogenous as well as from [ 14 C] and[ 3 H] precursors. ACTH stimulated corticoidogenesis, particularly cortisol secretion, and markedly enhanced the incorporation of progesterone and pregnenolone into cortisol. Following incubation with the same precursors, large amounts of radioactivity remained water soluble. From the butanol extractable material of this fraction, dehydroepiandrosterone sulphate was characterized as the main metabolite of pregnenolone and corticosterone and 11-deoxycorticosterone sulphates as the main metabolites of progesterone. With time in culture there was a decrease in steroidogenesis as well as a steady decline in responsiveness to ACTH, mainly manifested by cortisol secretion. The medium from homologous foetal pituitary cultures stimulated cortisol production by the human adrenal cell monolayer. (author)

  6. Intra-hydrogel culture prevents transformation of mesenchymal stem cells induced by monolayer expansion.

    Science.gov (United States)

    Jiang, Tongmeng; Liu, Junting; Ouyang, Yiqiang; Wu, Huayu; Zheng, Li; Zhao, Jinmin; Zhang, Xingdong

    2018-05-01

    In this study, we report that the intra-hydrogel culture system mitigates the transformation of mesenchymal stem cells (MSCs) induced by two-dimensional (2D) expansion. MSCs expanded in monolayer culture prior to encapsulation in collagen hydrogels (group eMSCs-CH) featured impaired stemness in chondrogenesis, comparing with the freshly isolated bone marrow mononuclear cells seeded directly in collagen hydrogels (group fMSCs-CH). The molecular mechanism of the in vitro expansion-triggered damage to MSCs was detected through genome-wide microarray analysis. Results indicated that pathways such as proteoglycans in cancer and pathways in cancer expansion were highly enriched in eMSCs-CH. And multiple up-regulated oncoma-associated genes were verified in eMSCs-CH compared with fMSCs-CH, indicating that expansion in vitro triggered cellular transformation was associated with signaling pathways related to tumorigenicity. Besides, focal adhesion (FA) and mitogen-activated protein kinase (MAPK) signaling pathways were also involved in in vitro expansion, indicating restructuring of the cell architecture. Thus, monolayer expansion in vitro may contribute to vulnerability of MSCs through the regulation of FA and MAPK. This study indicates that intra-hydrogel culture can mitigate the monolayer expansion induced transformation of MSCs and maintain the uniformity of the stem cells, which is a viable in vitro culture system for stem cell therapy.

  7. Differentiation of oligodendrocyte progenitor cells from dissociated monolayer and feeder-free cultured pluripotent stem cells.

    Science.gov (United States)

    Yamashita, Tomoko; Miyamoto, Yuki; Bando, Yoshio; Ono, Takashi; Kobayashi, Sakurako; Doi, Ayano; Araki, Toshihiro; Kato, Yosuke; Shirakawa, Takayuki; Suzuki, Yutaka; Yamauchi, Junji; Yoshida, Shigetaka; Sato, Naoya

    2017-01-01

    Oligodendrocytes myelinate axons and form myelin sheaths in the central nervous system. The development of therapies for demyelinating diseases, including multiple sclerosis and leukodystrophies, is a challenge because the pathogenic mechanisms of disease remain poorly understood. Primate pluripotent stem cell-derived oligodendrocytes are expected to help elucidate the molecular pathogenesis of these diseases. Oligodendrocytes have been successfully differentiated from human pluripotent stem cells. However, it is challenging to prepare large amounts of oligodendrocytes over a short amount of time because of manipulation difficulties under conventional primate pluripotent stem cell culture methods. We developed a proprietary dissociated monolayer and feeder-free culture system to handle pluripotent stem cell cultures. Because the dissociated monolayer and feeder-free culture system improves the quality and growth of primate pluripotent stem cells, these cells could potentially be differentiated into any desired functional cells and consistently cultured in large-scale conditions. In the current study, oligodendrocyte progenitor cells and mature oligodendrocytes were generated within three months from monkey embryonic stem cells. The embryonic stem cell-derived oligodendrocytes exhibited in vitro myelinogenic potency with rat dorsal root ganglion neurons. Additionally, the transplanted oligodendrocyte progenitor cells differentiated into myelin basic protein-positive mature oligodendrocytes in the mouse corpus callosum. This preparative method was used for human induced pluripotent stem cells, which were also successfully differentiated into oligodendrocyte progenitor cells and mature oligodendrocytes that were capable of myelinating rat dorsal root ganglion neurons. Moreover, it was possible to freeze, thaw, and successfully re-culture the differentiating cells. These results showed that embryonic stem cells and human induced pluripotent stem cells maintained in a

  8. Valley- and spin-polarized oscillatory magneto-optical absorption in monolayer MoS2 quantum rings

    Science.gov (United States)

    Oliveira, D.; Villegas-Lelovsky, L.; Soler, M. A. G.; Qu, Fanyao

    2018-03-01

    Besides optical valley selectivity, strong spin-orbit interaction along with Berry curvature effects also leads to unconventional valley- and spin-polarized Landau levels in monolayer transition metal dichalcogenides (TMDCs) under a perpendicular magnetic field. We find that these unique properties are inherited to the magneto-optical absorption spectrum of the TMDC quantum rings (QRs). In addition, it is robust against variation of the magnetic flux and of the QR geometry. In stark contrast to the monolayer bulk material, the MoS2 QRs manifest themselves in both the optical valley selectivity and unprecedented size tunability of the frequency of the light absorbed. We also find that when the magnetic field setup is changed, the phase transition from Aharonov-Bohm (AB) quantum interference to aperiodic oscillation of magneto-optical absorption spectrum takes place. The exciton spectrum in a realistic finite thickness MoS2 QR is also discussed.

  9. Spin-orbit-induced spin splittings in polar transition metal dichalcogenide monolayers

    KAUST Repository

    Cheng, Yingchun; Zhu, Zhiyong; Tahir, Muhammad; Schwingenschlö gl, Udo

    2013-01-01

    . We present ab initio electronic structure, phonon, and molecular-dynamics calculations to study the structural stability and spin-orbit-induced spin splitting in the transition metal dichalcogenide monolayers MXY (M = Mo, W and X, Y = S, Se, Te

  10. Characteristics of monolayer culture of bone marrow cells of rats bearing 239Pu-induced osteosarcoma

    International Nuclear Information System (INIS)

    Bukhtoyarova, Z.M.; Lemberg, V.K.

    1984-01-01

    The report is concerned with a monolayer culture of bone marrow cells of rats in which optimal blastogenic dose (92.5 kBq/kg) induced osteosarcoma. The cell culture showed an enhanced rate of fibroblast-like cell proliferation (increased number of mitoses and symplasts and larger colonies of cells), apparent signs of radiation in ury (pathologic mitoses, chromosome aberrations and gaps) as well as an increase in ploidy. Diffusion chamber measurements demonstrated osteogenic precursor-cells in osteosarcoma-bearing rats to be highly capable of bone formation. This relatively high ability seems to occur outside bone marrow as well

  11. Kadar dan Daya Luteolitik PGF2? Produksi Sel Monolayer Vesikula Seminalis dan Endometrium Sapi Bali (PROSTAGLANDIN F2? CONCENTRATIONS OF BALI CATTLE ENDOMETRIAL AND SEMINAL VESICLE MONOLAYER CELLS CULTURE PRODUCTS AND ITS IN VITRO TEST ON LUTEAL MONOLAYER

    Directory of Open Access Journals (Sweden)

    Tjok Gde Oka Pemayun

    2012-03-01

    Full Text Available The aims of this research were to determine PGF2? concentration the produced by bali cattlesendometrial and seminal vesicle monolayer cell culture and in vitro luteolytic ability on luteal monolayercell culture. The endometrial and seminal vesicle epithelial cell of bali cattle were cultured in tissueculture medium (TCM 199 growth medium supplemented with 10% fetal calf serum and 10% EstrusMare Serum. The cells were cultured at 1.9 x 106 density per ml medium. Then Followed by incubation at38.50 C in 5% CO2 atmosphere for 12 days. The level of PGF2? in the cell culture medium were assayed byRadioimmnuassay (RIA technique. The luteal cells were cultured in 9 days incubation and divided into 2groups. Group I were added with 10% of cell culture product and group II were added with 1,25 mgdinoprost/ml. The level of progesterone produced by luteal cell culture was measured at day 9th and 11thincubation. The result showed concentration of PGF2? cell product of seminal vesicle cell culture wassignificantly higher (P < 0.05 compared to endometrial cell culture. There was no significant difference(P>0.05 in luteolytic ability between PGF2? cell culture product and dinoprost. In conclusion, the PGF2?could be produced by monolayer cell culture of bali cattle is endometrial and seminal vesicle epithelialcells more over they have similar ability with dinoprost in luteolytic ability.

  12. Oxygen consumption rate and mitochondrial density in human melanoma monolayer cultures and multicellular spheroids.

    Science.gov (United States)

    Hystad, M E; Rofstad, E K

    1994-05-15

    Rate of oxygen consumption per cell has been shown in previous studies to decrease with increasing depth in the viable rim of multicellular spheroids initiated from rodent cells, human colon-carcinoma cells, and human glioma cells, due to progressive accumulation of quiescent cells during spheroid growth. The purpose of our work was to determine oxygen-consumption profiles in human melanoma spheroids. Monolayer cultures of 4 lines (BEX-c, COX-c, SAX-c, and WIX-c) and spheroid cultures of 2 lines (BEX-c and WIX-c) were subjected to investigation. Spheroids were initiated from monolayer cell cultures and grown in spinner flasks. Rate of oxygen consumption was measured with a Clarke-type electrode. Mitochondrial density was determined by stereological analysis of transmission electron micrographs. Thickness of viable rim and cell packing density were assessed by light microscopy of central spheroid sections. Cell-cycle distribution was determined by analysis of DNA histograms measured by flow cytometry. Cell volume was measured by an electronic particle counter. Rate of oxygen consumption per cell differed by a factor of approximately 1.8 between the 4 cell lines and was positively correlated to total volume of mitochondria per cell. Rate of oxygen consumption per cell and total volume of mitochondria per cell were equal for monolayer cell cultures, 600-microns spheroids and 1,200-microns spheroids of the same line. Mitochondrial density and location in the cell did not differ between cells at the spheroid surface, in the middle of the viable rim and adjacent to the central necrosis. Cell-cycle distribution, cell volume, and cell-packing density in the outer and inner halves of the viable rim were not significantly different. Consequently, the rate of oxygen consumption per cell in inner regions of the viable rim was probably equal to that at the spheroid surface, suggesting that oxygen diffusion distances may be shorter in some melanomas than in many other tumor

  13. Correlation of Effective Dispersive and Polar Surface Energies in Heterogeneous Self-Assembled Monolayer Coatings

    DEFF Research Database (Denmark)

    Zhuang, Yanxin; Hansen, Ole

    2009-01-01

    grown oil oxidized (100) silicon Surfaces in a vapor phase process using five different precursors. Experimentally, effective surface energy components of the fluorocarbon self-assembled monolayers were determined from measured contact angles using the Owens-Wendt-Rabel-Kaelble method. We show...

  14. Spatiotemporal stability of neonatal rat cardiomyocyte monolayers spontaneous activity is dependent on the culture substrate.

    Directory of Open Access Journals (Sweden)

    Jonathan Boudreau-Béland

    Full Text Available In native conditions, cardiac cells must continuously comply with diverse stimuli necessitating a perpetual adaptation. Polydimethylsiloxane (PDMS is commonly used in cell culture to study cellular response to changes in the mechanical environment. The aim of this study was to evaluate the impact of using PDMS substrates on the properties of spontaneous activity of cardiomyocyte monolayer cultures. We compared PDMS to the gold standard normally used in culture: a glass substrate. Although mean frequency of spontaneous activity remained unaltered, incidence of reentrant activity was significantly higher in samples cultured on glass compared to PDMS substrates. Higher spatial and temporal instability of the spontaneous rate activation was found when cardiomyocytes were cultured on PDMS, and correlated with decreased connexin-43 and increased CaV3.1 and HCN2 mRNA levels. Compared to cultures on glass, cultures on PDMS were associated with the strongest response to isoproterenol and acetylcholine. These results reveal the importance of carefully selecting the culture substrate for studies involving mechanical stimulation, especially for tissue engineering or pharmacological high-throughput screening of cardiac tissue analog.

  15. Reversible alterations in cultured pulmonary artery endothelial cell monolayer morphology and albumin permeability induced by ionizing radiation

    International Nuclear Information System (INIS)

    Friedman, M.; Ryan, U.S.; Davenport, W.C.; Chaney, E.L.; Strickland, D.L.; Kwock, L.

    1986-01-01

    The effects of ionizing irradiation (0, 600, 1500, or 3000 rads) on the permeability of pulmonary endothelial monolayers to albumin were studied. Pulmonary endothelial cells were grown to confluence on gelatin-coated polycarbonate filters, placed in serum-free medium, and exposed to a 60 Co source. The monolayers were placed in modified flux chambers 24 hours after irradiation; 125 I-albumin was added to the upper well, and both the upper and lower wells were serially sampled over 4 hours. The amount of albumin transferred from the upper well/hour over the period of steady-state clearance (90-240 min after addition of 125 I-albumin) was 2.8 +/- 0.2% in control monolayers and was increased in monolayers exposed to 1500 or 3000 rads (increase of 63 +/- 10% and 61 +/- 10%, respectively, P less than 0.01). No increase was found in monolayers exposed to 600 rads. The increases in endothelial albumin transfer rates were associated with morphologic evidence of monolayer disruption and endothelial injury which paralleled the changes in albumin permeability. Dose-dependent alterations in endothelial actin filament organization were also found. Incubation of the monolayers exposed to 3000 rads with medium supplemented with 10% fetal calf serum for 24 hours resulted in normalization of albumin permeability, improvement in morphologic appearance of the monolayers, and reorganization of the actin filament structure. These studies demonstrate that ionizing radiation is an active principle in the reversible disorganization of cultured pulmonary endothelial cell monolayers without the need of other cell types or serum components

  16. Towards a defined ECM and small molecule based monolayer culture system for the expansion of mouse and human intestinal stem cells.

    Science.gov (United States)

    Tong, Zhixiang; Martyn, Keir; Yang, Andy; Yin, Xiaolei; Mead, Benjamin E; Joshi, Nitin; Sherman, Nicholas E; Langer, Robert S; Karp, Jeffrey M

    2018-02-01

    Current ISC culture systems face significant challenges such as animal-derived or undefined matrix compositions, batch-to-batch variability (e.g. Matrigel-based organoid culture), and complexity of assaying cell aggregates such as organoids which renders the research and clinical translation of ISCs challenging. Here, through screening for suitable ECM components, we report a defined, collagen based monolayer culture system that supports the growth of mouse and human intestinal epithelial cells (IECs) enriched for an Lgr5 + population comparable or higher to the levels found in a standard Matrigel-based organoid culture. The system, referred to as the Bolstering Lgr5 Transformational (BLT) Sandwich culture, comprises a collagen IV-coated porous substrate and a collagen I gel overlay which sandwich an IEC monolayer in between. The distinct collagen cues synergistically regulate IEC attachment, proliferation, and Lgr5 expression through maximizing the engagement of distinct cell surface adhesion receptors (i.e. integrin α2β1, integrin β4) and cell polarity. Further, we apply our BLT Sandwich system to identify that the addition of a bone morphogenetic protein (BMP) receptor inhibitor (LDN-193189) improves the expansion of Lgr5-GFP + cells from mouse small intestinal crypts by nearly 2.5-fold. Notably, the BLT Sandwich culture is capable of expanding human-derived IECs with higher LGR5 mRNA levels than conventional Matrigel culture, providing superior expansion of human LGR5 + ISCs. Considering the key roles Lgr5 + ISCs play in intestinal epithelial homeostasis and regeneration, we envision that our BLT Sandwich culture system holds great potential for understanding and manipulating ISC biology in vitro (e.g. for modeling ISC-mediated gut diseases) or for expanding a large number of ISCs for clinical utility (e.g. for stem cell therapy). Copyright © 2017 Elsevier Ltd. All rights reserved.

  17. Tuning Valley Polarization in a WSe_{2} Monolayer with a Tiny Magnetic Field

    Directory of Open Access Journals (Sweden)

    T. Smoleński

    2016-05-01

    Full Text Available In monolayers of semiconducting transition metal dichalcogenides, the light helicity (σ^{+} or σ^{-} is locked to the valley degree of freedom, leading to the possibility of optical initialization of distinct valley populations. However, an extremely rapid valley pseudospin relaxation (at the time scale of picoseconds occurring for optically bright (electric-dipole active excitons imposes some limitations on the development of opto-valleytronics. Here, we show that valley pseudospin relaxation of excitons can be significantly suppressed in a WSe_{2} monolayer, a direct-gap two-dimensional semiconductor with the exciton ground state being optically dark. We demonstrate that the already inefficient relaxation of the exciton pseudospin in such a system can be suppressed even further by the application of a tiny magnetic field of about 100 mT. Time-resolved spectroscopy reveals the pseudospin dynamics to be a two-step relaxation process. An initial decay of the pseudospin occurs at the level of dark excitons on a time scale of 100 ps, which is tunable with a magnetic field. This decay is followed by even longer decay (>1  ns, once the dark excitons form more complex pseudo-particles allowing for their radiative recombination. Our findings of slow valley pseudospin relaxation easily manipulated by the magnetic field open new prospects for engineering the dynamics of the valley pseudospin in transition metal dichalcogenides.

  18. Magnetic and electric control of spin- and valley-polarized transport across tunnel junctions on monolayer WSe2

    Science.gov (United States)

    Tahir, M.; Krstajić, P. M.; Vasilopoulos, P.

    2017-06-01

    The recent experimental realization of high-quality WSe2 leads to the possibility of an efficient manipulation of its spin and valley degrees of freedom. Its electronic properties comprise a huge spin-orbit coupling, a direct band gap, and a strong anisotropic lifting of the degeneracy of the valley degree of freedom in a magnetic field. We evaluate its band structure and study ballistic electron transport through single and double junctions (or barriers) on monolayer WSe2 in the presence of spin Ms and valley Mv Zeeman fields and of an electric potential U . The conductance versus the field Ms or Mv decreases in a fluctuating manner. For a single junction, the spin Ps and valley Pv polarizations rise with M =Mv=2 Ms , reach a value of more than 55 % , and become perfect above U ≈45 meV while for a double junction this change can occur for U ≥50 meV and M ≥5 meV. In certain regions of the (M ,U ) plane Pv becomes perfect. The conductance gc, its spin-up and spin-down components, and both polarizations oscillate with the barrier width d . The ability to isolate various carrier degrees of freedom in WSe2 may render it a promising candidate for new spintronic and valleytronic devices.

  19. Cultured fibroblast monolayers secrete a protein that alters the cellular binding of somatomedin-C/insulinlike growth factor I

    International Nuclear Information System (INIS)

    Clemmons, D.R.; Elgin, R.G.; Han, V.K.; Casella, S.J.; D'Ercole, A.J.; Van Wyk, J.J.

    1986-01-01

    We studied somatomedin-C/insulinlike growth factor (Sm-C/IGF-I) binding to human fibroblasts in both adherent monolayers and in suspension cultures. The addition of Sm-C/IGF-I in concentrations between 0.5 and 10 ng/ml to monolayers cultures resulted in a paradoxical increase in 125 I-Sm-C/IGF-I binding and concentrations between 25 and 300 ng/ml were required to displace the labeled peptide. The addition of unlabeled insulin resulted in no displacement of labeled Sm-C/IGF-I from the adherent cells. When fibroblast suspensions were used Sm-C/IGF-I concentrations between 1 and 10 ng/ml caused displacement, the paradoxical increase in 125 I-Sm-C/IGF-I binding was not detected, and insulin displaced 60% of the labeled peptide. Affinity cross-linking to fibroblast monolayers revealed a 43,000-mol wt 125 I-Sm-C-binding-protein complex that was not detected after cross-linking to suspended cells. The 43,000-mol wt complex was not detected after cross-linking to smooth muscle cell monolayers, and binding studies showed that 125 I-Sm-C/IGF-I was displaced greater than 90% by Sm-C/IGF-I using concentrations between 0.5 and 10 ng/ml. Because fibroblast-conditioned medium contains the 43,000-mol wt complex, smooth muscle cells were incubated with conditioned medium for 24 h prior to initiation of the binding studies. 125 I-Sm-C/IGF-I-binding increased 1.6-fold compared to control cultures and after cross-linking the 43,000-mol wt complex could be detected on the smooth muscle cell surface. Human fibroblast monolayers secrete a protein that binds 125 I-Sm-C/IGF-I which can be transferred to the smooth muscle cell surface and alters 125I-Sm-C/IGF-I binding

  20. Crystallography and Molecular Arrangement of Polymorphic Monolayer J-Aggregates of a Cyanine Dye: Multiangle Polarized Light Fluorescence Optical Microscopy Study.

    Science.gov (United States)

    Prokhorov, Valery V; Pozin, Sergey I; Perelygina, Olga M; Mal'tsev, Eugene I

    2018-04-24

    The molecular orientation in monolayer J-aggregates of 3,3-di(γ-sulfopropyl)-5,5-dichlorotiamonomethinecyanine dye has been precisely estimated using improved linear polarization measurements in the fluorescence microscope in which a multiangle set of polarization data is obtained using sample rotation. The estimated molecular orientation supplemented with the previously established crystallographic constraints based on the analysis of the well-developed two-dimensional J-aggregate shapes unambiguously indicate the staircase type of molecular arrangement for striplike J-aggregates with the staircases oriented along strips. The molecular transition dipoles are inclined at an angle of ∼25° to the strip direction, whereas the characteristic strip vertex angle ∼45° is formed by the [100] and [1-10] directions of the monoclinic unit cell. Measurements of the geometry of partially unwound tubes and their polarization properties support the model of tube formation by close-packed helical winding of flexible monolayer strips. In the tubes, the long molecular axes are oriented at a small angle in the range of 5-15° to the normal to the tube axis providing low bending energy. At a nanoscale, high-resolution atomic force microscopy imaging of J-aggregate monolayers reveals a complex quasi-one-dimensional organization.

  1. Interleukin 6 regulates metallothionein gene expression and zinc metabolism in hepatocyte monolayer cultures

    International Nuclear Information System (INIS)

    Schroeder, J.J.; Cousins, R.J.

    1990-01-01

    Attention has focused on the cytokine interleukin 6 (IL-6) as a major mediator of acute-phase protein synthesis in hepatocytes in response to infection and tissue injury. The authors have evaluated the effects of IL-6 and IL-1α as well as extracellular zinc and glucocorticoid hormone on metal-lothionein gene expression and cellular zinc accumulation in rat hepatocyte monolayer cultures. Further, they have evaluated the teleological basis for cytokine mediation by examining cyto-protection from CCl 4 -induced damage. Incubation of hepatocytes with IL-6 led to concentration-dependent and time-dependent increases in metallothionein-1 and -2 mRNA and metallothionein protein. The level of each was increased within 3 hr after the addition of IL-6 at 10 ng/ml. Maximal increases the metallothionein mRNA and metallothionein protein were achieved after 12 hr and 36 hr, respectively. Concomitant with the up-regulation of metallothionein gene expression, IL-6 also increased cellular zinc. Responses to IL-6 required the synthetic glucocorticoid hormone dexamethasone and were optimized by increased extracellular zinc. Thus, IL-6 is a major cytokine mediator of metallothionein gene expression and zinc metabolism in hepatocytes and provides cytoprotection from CCl 4 -induced hepatotoxicity via a mode consistent with dependence upon increased cellular metallothionein synthesis and zinc accumulation

  2. 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.

    Science.gov (United States)

    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.

  3. Human RPE Stem Cells Grown into Polarized RPE Monolayers on a Polyester Matrix Are Maintained after Grafting into Rabbit Subretinal Space

    Directory of Open Access Journals (Sweden)

    Boris V. Stanzel

    2014-01-01

    Full Text Available Transplantation of the retinal pigment epithelium (RPE is being developed as a cell-replacement therapy for age-related macular degeneration. Human embryonic stem cell (hESC and induced pluripotent stem cell (iPSC-derived RPE are currently translating toward clinic. We introduce the adult human RPE stem cell (hRPESC as an alternative RPE source. Polarized monolayers of adult hRPESC-derived RPE grown on polyester (PET membranes had near-native characteristics. Trephined pieces of RPE monolayers on PET were transplanted subretinally in the rabbit, a large-eyed animal model. After 4 days, retinal edema was observed above the implant, detected by spectral domain optical coherence tomography (SD-OCT and fundoscopy. At 1 week, retinal atrophy overlying the fetal or adult transplant was observed, remaining stable thereafter. Histology obtained 4 weeks after implantation confirmed a continuous polarized human RPE monolayer on PET. Taken together, the xeno-RPE survived with retained characteristics in the subretinal space. These experiments support that adult hRPESC-derived RPE are a potential source for transplantation therapies.

  4. Low-cost fabrication and polar-dependent switching uniformity of memory devices using alumina interfacial layer and Ag nanoparticle monolayer

    Directory of Open Access Journals (Sweden)

    Peng Xia

    2017-11-01

    Full Text Available A facile and low-cost process was developed for fabricating write-once-read-many-times (WORM Cu/Ag NPs/Alumina/Al memory devices, where the alumina passivation layer formed naturally in air at room temperature, whereas the Ag nanoparticle monolayer was in situ prepared through thermal annealing of a 4.5 nm Ag film in air at 150°C. The devices exhibit irreversible transition from initial high resistance (OFF state to low resistance (ON state, with ON/OFF ratio of 107, indicating the introduction of Ag nanoparticle monolayer greatly improves ON/OFF ratio by four orders of magnitude. The uniformity of threshold voltages exhibits a polar-dependent behavior, and a narrow range of threshold voltages of 0.40 V among individual devices was achieved upon the forward voltage. The memory device can be regarded as two switching units connected in series. The uniform alumina interfacial layer and the non-uniform distribution of local electric fields originated from Ag nanoparticles might be responsible for excellent switching uniformity. Since silver ions in active layer can act as fast ion conductor, a plausible mechanism relating to the formation of filaments sequentially among the two switching units connected in series is suggested for the polar-dependent switching behavior. Furthermore, we demonstrate both alumina layer and Ag NPs monolayer play essential roles in improving switching parameters based on comparative experiments.

  5. Low-cost fabrication and polar-dependent switching uniformity of memory devices using alumina interfacial layer and Ag nanoparticle monolayer

    Science.gov (United States)

    Xia, Peng; Li, Luman; Wang, Pengfei; Gan, Ying; Xu, Wei

    2017-11-01

    A facile and low-cost process was developed for fabricating write-once-read-many-times (WORM) Cu/Ag NPs/Alumina/Al memory devices, where the alumina passivation layer formed naturally in air at room temperature, whereas the Ag nanoparticle monolayer was in situ prepared through thermal annealing of a 4.5 nm Ag film in air at 150°C. The devices exhibit irreversible transition from initial high resistance (OFF) state to low resistance (ON) state, with ON/OFF ratio of 107, indicating the introduction of Ag nanoparticle monolayer greatly improves ON/OFF ratio by four orders of magnitude. The uniformity of threshold voltages exhibits a polar-dependent behavior, and a narrow range of threshold voltages of 0.40 V among individual devices was achieved upon the forward voltage. The memory device can be regarded as two switching units connected in series. The uniform alumina interfacial layer and the non-uniform distribution of local electric fields originated from Ag nanoparticles might be responsible for excellent switching uniformity. Since silver ions in active layer can act as fast ion conductor, a plausible mechanism relating to the formation of filaments sequentially among the two switching units connected in series is suggested for the polar-dependent switching behavior. Furthermore, we demonstrate both alumina layer and Ag NPs monolayer play essential roles in improving switching parameters based on comparative experiments.

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

    International Nuclear Information System (INIS)

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

    1987-01-01

    The interaction of insulin-like growth factor I (IGF-I) with porcine thyroid cells cultured in monolayer was studied. Specific binding of [ 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 [ 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 [ 125 I]iodoinsulin was much lower than that of [ 125 I]iodo-IGF-I. Preincubation of thyroid cells with IGF-I or insulin caused a concentration-dependent decrease in [ 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 [ 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 [ 125 I]iodo-IGF-I to thyroid cells

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

    Energy Technology Data Exchange (ETDEWEB)

    Theumer, Anja; Gräfe, Christine; Bähring, Franziska [Department of Hematology and Oncology, Jena University Hospital, Erlanger Allee 101, 07747 Jena (Germany); Bergemann, Christian [Chemicell GmbH, Eresburgstrasse 22–23, 12103 Berlin (Germany); Hochhaus, Andreas [Department of Hematology and Oncology, Jena University Hospital, Erlanger Allee 101, 07747 Jena (Germany); Clement, Joachim H., E-mail: joachim.clement@med.uni-jena.de [Department of Hematology and Oncology, Jena University Hospital, Erlanger Allee 101, 07747 Jena (Germany)

    2015-04-15

    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.

  8. Scalability and process transfer of mesenchymal stromal cell production from monolayer to microcarrier culture using human platelet lysate.

    Science.gov (United States)

    Heathman, Thomas R J; Stolzing, Alexandra; Fabian, Claire; Rafiq, Qasim A; Coopman, Karen; Nienow, Alvin W; Kara, Bo; Hewitt, Christopher J

    2016-04-01

    The selection of medium and associated reagents for human mesenchymal stromal cell (hMSC) culture forms an integral part of manufacturing process development and must be suitable for multiple process scales and expansion technologies. In this work, we have expanded BM-hMSCs in fetal bovine serum (FBS)- and human platelet lysate (HPL)-containing media in both a monolayer and a suspension-based microcarrier process. The introduction of HPL into the monolayer process increased the BM-hMSC growth rate at the first experimental passage by 0.049 day and 0.127/day for the two BM-hMSC donors compared with the FBS-based monolayer process. This increase in growth rate in HPL-containing medium was associated with an increase in the inter-donor consistency, with an inter-donor range of 0.406 cumulative population doublings after 18 days compared with 2.013 in FBS-containing medium. Identity and quality characteristics of the BM-hMSCs are also comparable between conditions in terms of colony-forming potential, osteogenic potential and expression of key genes during monolayer and post-harvest from microcarrier expansion. BM-hMSCs cultured on microcarriers in HPL-containing medium demonstrated a reduction in the initial lag phase for both BM-hMSC donors and an increased BM-hMSC yield after 6 days of culture to 1.20 ± 0.17 × 10(5) and 1.02 ± 0.005 × 10(5) cells/mL compared with 0.79 ± 0.05 × 10(5) and 0.36 ± 0.04 × 10(5) cells/mL in FBS-containing medium. This study has demonstrated that HPL, compared with FBS-containing medium, delivers increased growth and comparability across two BM-hMSC donors between monolayer and microcarrier culture, which will have key implications for process transfer during scale-up. Copyright © 2016 International Society for Cellular Therapy. Published by Elsevier Inc. All rights reserved.

  9. The uptake of tritium-labelled carnitine by monolayer cultures of human fetal muscle and its potential as a label in cytotoxicity studies

    International Nuclear Information System (INIS)

    Cambridge, G.; Stern, C.M.M.

    1981-01-01

    As a novel approach to the investigation of immune responses directed against muscle antigens in inflammatory muscle disease, the use of tritium-labelled carnitine as a selective marker for myotubes in monolayer cultures was investigated. Tritium-labelled carnitine was incubated either with monolayer cultures of human fetal muscle or with syngeneic monolayer cultures of human fetal fibroblasts. The rate of uptake and loss of tritium-labelled carnitine by muscle cultures was compared with that shown by fibroblast cultures; values for the ratio Ksub(m)/Vsub(max) were 3.1 for muscle cultures and 0.46 for fibroblast cultures. Freeze-dried radioautographs of muscle monolayers, previously incubated with tritium-labelled carnitine confirmed the specific intra-tubular localization of the label. Fetal muscle monolayers, previously incubated with tritium-labelled carnitine, were used as targets in long-term cytotoxicity experiments into lymphocyte-mediated myotoxicity. Peripheral blood lymphocytes from patients with inflammatory muscle disease were shown to be myotoxic, but lymphocytes from normal individuals or those with non-inflammatory muscle disease were not. Carnitine-based measures of myotoxicity closely followed the clinical activity of the disease in one patient and the test shows considerable potential as a means of assessing myotube killing by lymphocytes on a per-cell basis. (author)

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

    Science.gov (United States)

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

    2013-01-01

    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. 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. 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. According to the results, it seems that AFB1 can induce cytotoxicity and necrosis in bovine mammary epithelial cells.

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

    Directory of Open Access Journals (Sweden)

    Babak Qasemi-Panahi

    2013-02-01

    Full Text Available 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.

  12. An insight of in vitro transport of PEGylated non-ionic surfactant vesicles (NSVs) across the intestinal polarized enterocyte monolayers.

    Science.gov (United States)

    Primavera, Rosita; Palumbo, Paola; Celia, Christian; Cinque, Benedetta; Carata, Elisabetta; Carafa, Maria; Paolino, Donatella; Cifone, Maria Grazia; Di Marzio, Luisa

    2018-06-01

    PEGylated non-ionic surfactant-based vesicles (NSVs) are promising drug delivery systems for the local, oral and systemic administrations of therapeutics. The aim of this study was to test the cellular biocompatibility and transport of Nile Red-loaded NSVs (NR-NSVs) across the Caco-2-cell monolayers, which represent an in vitro model of human intestinal epithelium. The NR-NSVs assumed a spherical shape with a mean size of 140 nm, and a narrow size distribution. The NR-NSVs did not modify Caco-2 cell viability, which remained unaltered in vitro up to a concentration of 1 mM. The transport studies demonstrated that the NR-NSVs moved across the Caco-2 monolayers without affecting the transepithelial electrical resistance. These results were supported by flow cytometry analysis, which demonstrated that NR-NSVs were internalized inside the Caco-2 cells. Nanoparticle tracking and Transmission Electron Microscopy (TEM) analysis showed the presence of NR-NSVs in the basolateral side of the Caco-2 monolayers. TEM images also showed that NSVs were transported intact across the Caco-2 monolayers, thus demonstrating a predominant transcytosis mechanism of transport through endocytosis. The NSVs did not affect the integrity of the membrane barrier in vitro, and can potentially be used in clinics to increase the oral bioavailability and delivery of therapeutics. Copyright © 2018 Elsevier B.V. All rights reserved.

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

    International Nuclear Information System (INIS)

    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 2 (PGE 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chitcholtan, Kenny, E-mail: kenny.chitcholtan@otago.ac.nz [Department of Obstetrics and Gynaecology, University of Otago, Christchurch, 2 Riccarton Avenue, Christchurch 8011 (New Zealand); Asselin, Eric, E-mail: Eric.Asselin@uqtr.ca [Department of Chemistry and Biology, University of Quebec, at Trois-Rivières, C.P. 500, Trois-Rivières, Quebec, Canada G9A 5H7 (Canada); Parent, Sophie, E-mail: Sophie.Parent@uqtr.ca [Department of Chemistry and Biology, University of Quebec, at Trois-Rivières, C.P. 500, Trois-Rivières, Quebec, Canada G9A 5H7 (Canada); Sykes, Peter H., E-mail: peter.sykes@otago.ac.nz [Department of Obstetrics and Gynaecology, University of Otago, Christchurch, 2 Riccarton Avenue, Christchurch 8011 (New Zealand); Evans, John J., E-mail: john.evans@otago.ac.nz [Department of Obstetrics and Gynaecology, University of Otago, Christchurch, 2 Riccarton Avenue, Christchurch 8011 (New Zealand); Centre of Neuroendocrinology and The MacDiarmid Institute of Advanced Materials and Nanotechnology, University of Otago, Christchurch, 2 Riccarton Avenue, Christchurch 8011 (New Zealand)

    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.

  15. A novel serum-free monolayer culture for orderly hematopoietic differentiation of human pluripotent cells via mesodermal progenitors.

    Directory of Open Access Journals (Sweden)

    Akira Niwa

    Full Text Available Elucidating the in vitro differentiation of human embryonic stem (ES and induced pluripotent stem (iPS cells is important for understanding both normal and pathological hematopoietic development in vivo. For this purpose, a robust and simple hematopoietic differentiation system that can faithfully trace in vivo hematopoiesis is necessary. In this study, we established a novel serum-free monolayer culture that can trace the in vivo hematopoietic pathway from ES/iPS cells to functional definitive blood cells via mesodermal progenitors. Stepwise tuning of exogenous cytokine cocktails induced the hematopoietic mesodermal progenitors via primitive streak cells. These progenitors were then differentiated into various cell lineages depending on the hematopoietic cytokines present. Moreover, single cell deposition assay revealed that common bipotential hemoangiogenic progenitors were induced in our culture. Our system provides a new, robust, and simple method for investigating the mechanisms of mesodermal and hematopoietic differentiation.

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

    Science.gov (United States)

    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. Crown Copyright © 2014. Published by Elsevier Ltd. All rights reserved.

  17. Growth and Functionality of Cells Cultured on Conducting and Semi-Conducting Surfaces Modified with Self-Assembled Monolayers (SAMs

    Directory of Open Access Journals (Sweden)

    Rajendra K. Aithal

    2016-02-01

    Full Text Available Bioengineering of dermal and epidermal cells on surface modified substrates is an active area of research. The cytotoxicity, maintenance of cell phenotype and long-term functionality of human dermal fibroblast (HDF cells on conducting indium tin oxide (ITO and semi-conducting, silicon (Si and gallium arsenide (GaAs, surfaces modified with self-assembled monolayers (SAMs containing amino (–NH2 and methyl (–CH3 end groups have been investigated. Contact angle measurements and infrared spectroscopic studies show that the monolayers are conformal and preserve their functional end groups. Morphological analyses indicate that HDFs grow well on all substrates except GaAs, exhibiting their normal spindle-shaped morphology and exhibit no visible signs of stress or cytoplasmic vacuolation. Cell viability analyses indicate little cell death after one week in culture on all substrates except GaAs, where cells died within 6 h. Cells on all surfaces proliferate except on GaAs and GaAs-ODT. Cell growth is observed to be greater on SAM modified ITO and Si-substrates. Preservation of cellular phenotype assessed through type I collagen immunostaining and positive staining of HDF cells were observed on all modified surfaces except that on GaAs. These results suggest that conducting and semi-conducting SAM-modified surfaces support HDF growth and functionality and represent a promising area of bioengineering research.

  18. Differential feedback regulation of cholesterol 7α-hydroxylase mRNA and transcriptional activity by rat bile acids in primary monolayer cultures of rat hepatocytes

    NARCIS (Netherlands)

    Twisk, J.; Lehmann, E.M.; Princen, H.M.G.

    1993-01-01

    We have used primary monolayer cultures of rat hepatocytes to study the effects of physiological concentrations of various bile acids, commonly found in bile of normal rats, on the mechanism of regulation of cholesterol 7α-hydroxylase and bile acid synthesis. Addition of taurocholic acid, the most

  19. Preparing nuclei from cells in monolayer cultures suitable for counting and for following synchronized cells through the cell cycle.

    Science.gov (United States)

    Butler, W B

    1984-08-15

    A procedure is described for preparing nuclei from cells in monolayer culture so that they may be counted using an electronic particle counter. It takes only 10 to 15 min, and consists of swelling the cells in hypotonic buffer and then lysing them with the quaternary ammonium salt, ethylhexadecyldimethylammonium bromide. The cells are completely lysed, yielding a suspension of clean single nuclei which is stable, free of debris, and easily counted. The method was developed for a cell line of epithelial origin (MCF-7), which is often difficult to trypsinize to single cells. It works equally well at all cell densities up to and beyond confluence, and has been used with a variety of cells in culture, including 3T3 cells, bovine macrophages, rat mammary epithelial cells, mouse mammary tumor cell lines, and human fibroblasts. The size of the nuclei produced by this procedure is related to their DNA content, and the method is thus suitable for following cultures of synchronized cells through the cell cycle, and for performing differential counts of cells with substantial differences in DNA content.

  20. Collective cell motion in endothelial monolayers

    International Nuclear Information System (INIS)

    Szabó, A; Ünnep, R; Méhes, E; Czirók, A; Twal, W O; Argraves, W S; Cao, Y

    2010-01-01

    Collective cell motility is an important aspect of several developmental and pathophysiological processes. Despite its importance, the mechanisms that allow cells to be both motile and adhere to one another are poorly understood. In this study we establish statistical properties of the random streaming behavior of endothelial monolayer cultures. To understand the reported empirical findings, we expand the widely used cellular Potts model to include active cell motility. For spontaneous directed motility we assume a positive feedback between cell displacements and cell polarity. The resulting model is studied with computer simulations and is shown to exhibit behavior compatible with experimental findings. In particular, in monolayer cultures both the speed and persistence of cell motion decreases, transient cell chains move together as groups and velocity correlations extend over several cell diameters. As active cell motility is ubiquitous both in vitro and in vivo, our model is expected to be a generally applicable representation of cellular behavior

  1. Monte Carlo studies of thermalization of electron-hole pairs in spin-polarized degenerate electron gas in monolayer graphene

    Science.gov (United States)

    Borowik, Piotr; Thobel, Jean-Luc; Adamowicz, Leszek

    2018-02-01

    Monte Carlo method is applied to the study of relaxation of excited electron-hole (e-h) pairs in graphene. The presence of background of spin-polarized electrons, with high density imposing degeneracy conditions, is assumed. To such system, a number of e-h pairs with spin polarization parallel or antiparallel to the background is injected. Two stages of relaxation: thermalization and cooling are clearly distinguished when average particles energy and its standard deviation σ _E are examined. At the very beginning of thermalization phase, holes loose energy to electrons, and after this process is substantially completed, particle distributions reorganize to take a Fermi-Dirac shape. To describe the evolution of and σ _E during thermalization, we define characteristic times τ _ {th} and values at the end of thermalization E_ {th} and σ _ {th}. The dependence of these parameters on various conditions, such as temperature and background density, is presented. It is shown that among the considered parameters, only the standard deviation of electrons energy allows to distinguish between different cases of relative spin polarizations of background and excited electrons.

  2. Gold cleaning methods for preparation of cell culture surfaces for self-assembled monolayers of zwitterionic oligopeptides.

    Science.gov (United States)

    Enomoto, Junko; Kageyama, Tatsuto; Myasnikova, Dina; Onishi, Kisaki; Kobayashi, Yuka; Taruno, Yoko; Kanai, Takahiro; Fukuda, Junji

    2018-05-01

    Self-assembled monolayers (SAMs) have been used to elucidate interactions between cells and material surface chemistry. Gold surfaces modified with oligopeptide SAMs exhibit several unique characteristics, such as cell-repulsive surfaces, micropatterns of cell adhesion and non-adhesion regions for control over cell microenvironments, and dynamic release of cells upon external stimuli under culture conditions. However, basic procedures for the preparation of oligopeptide SAMs, including appropriate cleaning methods of the gold surface before modification, have not been fully established. Because gold surfaces are readily contaminated with organic compounds in the air, cleaning methods may be critical for SAM formation. In this study, we examined the effects of four gold cleaning methods: dilute aqua regia, an ozone water, atmospheric plasma, and UV irradiation. Among the methods, UV irradiation most significantly improved the formation of oligopeptide SAMs in terms of repulsion of cells on the surfaces. We fabricated an apparatus with a UV light source, a rotation table, and HEPA filter, to treat a number of gold substrates simultaneously. Furthermore, UV-cleaned gold substrates were capable of detaching cell sheets without serious cell injury. This may potentially provide a stable and robust approach to oligopeptide SAM-based experiments for biomedical studies. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

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

    Science.gov (United States)

    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.

  4. 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

    CERN Document Server

    Laurinavichius, K S

    1998-01-01

    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

  5. Apical polarity in three-dimensional culture systems: where to now?

    Energy Technology Data Exchange (ETDEWEB)

    Inman, J.L.; Bissell, Mina

    2010-01-21

    Delineation of the mechanisms that establish and maintain the polarity of epithelial tissues is essential to understanding morphogenesis, tissue specificity and cancer. Three-dimensional culture assays provide a useful platform for dissecting these processes but, as discussed in a recent study in BMC Biology on the culture of mammary gland epithelial cells, multiple parameters that influence the model must be taken into account.

  6. Development and Characterization of a Human and Mouse Intestinal Epithelial Cell Monolayer Platform

    Directory of Open Access Journals (Sweden)

    Kenji Kozuka

    2017-12-01

    Full Text Available Summary: We describe the development and characterization of a mouse and human epithelial cell monolayer platform of the small and large intestines, with a broad range of potential applications including the discovery and development of minimally systemic drug candidates. Culture conditions for each intestinal segment were optimized by correlating monolayer global gene expression with the corresponding tissue segment. The monolayers polarized, formed tight junctions, and contained a diversity of intestinal epithelial cell lineages. Ion transport phenotypes of monolayers from the proximal and distal colon and small intestine matched the known and unique physiology of these intestinal segments. The cultures secreted serotonin, GLP-1, and FGF19 and upregulated the epithelial sodium channel in response to known biologically active agents, suggesting intact secretory and absorptive functions. A screen of over 2,000 pharmacologically active compounds for inhibition of potassium ion transport in the mouse distal colon cultures led to the identification of a tool compound. : Siegel and colleagues describe their development of a human and mouse intestinal epithelial cell monolayer platform that maintains the cellular, molecular, and functional characteristics of tissue for each intestinal segment. They demonstrate the platform's application to drug discovery by screening a library of over 2,000 compounds to identify an inhibitor of potassium ion transport in the mouse distal colon. Keywords: intestinal epithelium, organoids, monolayer, colon, small intestine, phenotype screening assays, enteroid, colonoid

  7. Changes in sensitivity to radiation and to bleomycin occurring during the life history of monolayer cultures of a mouse tumour cell line

    International Nuclear Information System (INIS)

    Twentyman, P.R.; Bleehen, N.M.

    1975-01-01

    The response to X-radiation and to bleomycin has been measured at a number of times during the life of monolayer cultures of EMT6 mouse tumour cells. Little change in radiation sensitivity was seen at any time and no loss of the shoulder to the survival curve occurred. Cultures in early plateau phase (where a considerable amount of cell proliferation is balanced by cell loss) showed a reduced sensitivity to bleomycin when compared with cells in exponential growth. However, after a longer period in plateau phase, when proliferation had virtually ceased, the sensitivity became greater than that of exponential phase cells. These findings are discussed with reference to the conflicting results of other workers. (author)

  8. The rate of charge tunneling is insensitive to polar terminal groups in self-assembled monolayers in Ag(TS)S(CH2)(n)M(CH2)(m)T//Ga2O3/EGaIn junctions.

    Science.gov (United States)

    Yoon, Hyo Jae; Bowers, Carleen M; Baghbanzadeh, Mostafa; Whitesides, George M

    2014-01-08

    This paper describes a physical-organic study of the effect of uncharged, polar, functional groups on the rate of charge transport by tunneling across self-assembled monolayer (SAM)-based large-area junctions of the form Ag(TS)S(CH2)(n)M(CH2)(m)T//Ga2O3/EGaIn. Here Ag(TS) is a template-stripped silver substrate, -M- and -T are "middle" and "terminal" functional groups, and EGaIn is eutectic gallium-indium alloy. Twelve uncharged polar groups (-T = CN, CO2CH3, CF3, OCH3, N(CH3)2, CON(CH3)2, SCH3, SO2CH3, Br, P(O)(OEt)2, NHCOCH3, OSi(OCH3)3), having permanent dipole moments in the range 0.5 < μ < 4.5, were incorporated into the SAM. A comparison of the electrical characteristics of these junctions with those of junctions formed from n-alkanethiolates led to the conclusion that the rates of charge tunneling are insensitive to the replacement of terminal alkyl groups with the terminal polar groups in this set. The current densities measured in this work suggest that the tunneling decay parameter and injection current for SAMs terminated in nonpolar n-alkyl groups, and polar groups selected from common polar organic groups, are statistically indistinguishable.

  9. Intensification of the inhibitory effect of X-rays on the growth of Ehrlich ascites tumor cells in monolayer culture by quinacrine (atebrine) or chloroquine (resochine)

    International Nuclear Information System (INIS)

    Biller, H.; Pfab, R.; Hess, F.; Schachtschabel, D.O.; Leising, H.B.

    1980-01-01

    Monolayers of Ehrlich ascites tumor cells in their logarithmic phase of growth were exposed to a single X-ray dose of 1 to 16 Gy. Following exposure, the monolayers were cultured for several days or weeks with or without an addition of 4 x to 6 x 10 -6 M of quinacrine (atebrine) or 3.3 x 10 -5 to 1 x 10 -4 M of chloroquine. Proliferation activity was controlled by the daily microscopical count of representative areas out of the total population. A significant delay resulted from exposure to 4 Gy (particularly during the 1st day), while sole irradiation with 1 or 2 Gy did not much influence the proliferation of the cells. An 8-Gy dose and to a larger extent 16 Gy led to a fall of the cell number down to 20% (8 Gy) or around 10% (16 Gy) of the initial value between the 7th and the 10th day. The cells subsequently multiplied with nearly the growth rate of controls. The inhibitory effect on cells proliferation produced by an exposure to X-rays was distinctly intensified by means of incubation with continuously replaced quinacrine or chloroquine containing culture media. Treatment with 1 x 10 -4 mol chloroquine thus brought about a more pronounced inhibition after pre-irradiation with a single dose of 2 or 8 Gy. If 4 x 10 -6 or 6 x 10 -6 M of quinacrine were added to cultures pretreated with 4 Gy, a more intense inhibition of growth resulted therefrom than from sole treatment with either quinacrine or X-rays. Incubation of cultures pretreated with 8 Gy in the presence of 6 x 10 -6 M quinacrine led to the death of all the cells within 8 days. Quinacrine and chloroquine effects on cells previously exposed to X-rays are discussed in view of the well-known effects these agents exert by inhibiting enzymatic repair processes of DNA damage. (orig.) [de

  10. Drug and radiation sensitivity measurements of successful primary monolayer culturing of human tumor cells using cell-adhesive matrix and supplemented medium

    International Nuclear Information System (INIS)

    Baker, F.L.; Spitzer, G.; Ajani, J.A.

    1986-01-01

    The limitations of the agar suspension culture method for primary culturing of human tumor cells prompted development of a monolayer system optimized for cell adhesion and growth. This method grew 83% of fresh human tumor cell biopsy specimens, cultured and not contaminated, from a heterogeneous group of 396 tumors including lung cancer (93 of 114, 82%); melanoma (54 of 72, 75%); sarcoma (46 of 59, 78%); breast cancer (35 of 39, 90%); ovarian cancer (16 of 21, 76%); and a miscellaneous group consisting of gastrointestinal, genitourinary, mesothelioma, and unknown primaries (78 of 91, 86%). Cell growth was characterized morphologically with Papanicolaoustained coverslip cultures and cytogenetically with Giemsastained metaphase spreads. Morphological features such as nuclear pleomorphism, chromatin condensation, basophilic cytoplasm, and melanin pigmentation were routinely seen. Aneuploid metaphases were seen in 90% of evaluable cultures, with 15 of 28 showing 70% or more aneuploid metaphases. Colony-forming efficiency ranged between 0.01 and 1% of viable tumor cells, with a median efficiency of 0.2%. This culture system uses a low inoculum of 25,000 viable cells per well which permitted chemosensitivity testing of nine drugs at four doses in duplicate from 2.2 X 10(6) viable tumor cells and radiation sensitivity testing at five doses in quadruplicate from 0.6 X 10(6) cells. Cultures were analyzed for survival by computerized image analysis of crystal violet-stained cells. Drug sensitivity studies showed variability in sensitivity and in survival curve shape with exponential cell killing for cisplatin, Adriamycin, and etoposide, and shouldered survival curves for 5-fluorouracil frequently seen. Radiation sensitivity studies also showed variability in both sensitivity and survival curve shape. Many cultures showed exponential cell killing, although others had shouldered survival curves

  11. Photophysical behavior in spread monolayers. Dansyl fluorescence as a probe for polarity at the air-water interface. [N-(5-(dimethylamino)naphthalene-1-sulfonyl)dihexadecylamine

    Energy Technology Data Exchange (ETDEWEB)

    Grieser, F.; Thistlethwaite, P.; Urquhart, R.; Patterson, L.K.

    1987-09-24

    The emission spectrum of N-(5-(dimethylamino)naphthalene-1-sulfonyl)dihexadecylamine (dansyldihexadecylamine) in monolayers at the air-water interface has been studied. In some cases sudden shifts in the dansyl emission can be correlated with particular features of the surface pressure-area isotherms. These spectral shifts can be explained in terms of a change in the conformation of the head group on the surface and with aggregation of the dansyldihexadecylamine. In other cases the dansyl emission shows a blue shift with increasing compression that can be associated with reduced head-group hydration.

  12. Survival and Functionality of hESC-Derived Retinal Pigment Epithelium Cells Cultured as a Monolayer on Polymer Substrates Transplanted in RCS Rats.

    Science.gov (United States)

    Thomas, Biju B; Zhu, Danhong; Zhang, Li; Thomas, Padmaja B; Hu, Yuntao; Nazari, Hossein; Stefanini, Francisco; Falabella, Paulo; Clegg, Dennis O; Hinton, David R; Humayun, Mark S

    2016-05-01

    To determine the safety, survival, and functionality of human embryonic stem cell-derived RPE (hESC-RPE) cells seeded on a polymeric substrate (rCPCB-RPE1 implant) and implanted into the subretinal (SR) space of Royal College of Surgeons (RCS) rats. Monolayers of hESC-RPE cells cultured on parylene membrane were transplanted into the SR space of 4-week-old RCS rats. Group 1 (n = 46) received vitronectin-coated parylene membrane without cells (rMSPM+VN), group 2 (n = 59) received rCPCB-RPE1 implants, and group 3 (n = 13) served as the control group. Animals that are selected based on optical coherence tomography screening were subjected to visual function assays using optokinetic (OKN) testing and superior colliculus (SC) electrophysiology. At approximately 25 weeks of age (21 weeks after surgery), the eyes were examined histologically for cell survival, phagocytosis, and local toxicity. Eighty-seven percent of the rCPCB-RPE1-implanted animals showed hESC-RPE survivability. Significant numbers of outer nuclear layer cells were rescued in both group 1 (rMSPM+VN) and group 2 (rCPCB-RPE1) animals. A significantly higher ratio of rod photoreceptor cells to cone photoreceptor cells was found in the rCPCB-RPE1-implanted group. Animals with rCPCB-RPE1 implant showed hESC-RPE cells containing rhodopsin-positive particles in immunohistochemistry, suggesting phagocytic function. Superior colliculus mapping data demonstrated that a significantly higher number of SC sites responded to light stimulus at a lower luminance threshold level in the rCPCB-RPE1-implanted group. Optokinetic data suggested both implantation groups showed improved visual acuity. These results demonstrate the safety, survival, and functionality of the hESC-RPE monolayer transplantation in an RPE dysfunction rat model.

  13. A new and efficient culture method for porcine bone marrow-derived M1- and M2-polarized macrophages.

    Science.gov (United States)

    Gao, Jiye; Scheenstra, Maaike R; van Dijk, Albert; Veldhuizen, Edwin J A; Haagsman, Henk P

    2018-06-01

    Macrophages play an important role in the innate immune system as part of the mononuclear phagocyte system (MPS). They have a pro-inflammatory signature (M1-polarized macrophages) or anti-inflammatory signature (M2-polarized macrophages) based on expression of surface receptors and secretion of cytokines. However, very little is known about the culture of macrophages from pigs and more specific about the M1 and M2 polarization in vitro. Porcine monocytes or mononuclear bone marrow cells were used to culture M1- and M2-polarized macrophages in the presence of GM-CSF and M-CSF, respectively. Surface receptor expression was measured with flow cytometry and ELISA was used to quantify cytokine secretion in response to LPS and PAM 3 CSK 4 stimulation. Human monocyte-derived macrophages were used as control. Porcine M1- and M2-polarized macrophages were cultured best using porcine GM-CSF and murine M-CSF, respectively. Cultures from bone marrow cells resulted in a higher yield M1- and M2-polarized macrophages which were better comparable to human monocyte-derived macrophages than cultures from porcine monocytes. Porcine M1-polarized macrophages displayed the characteristic fried egg shape morphology, lower CD163 expression and low IL-10 production. Porcine M2-polarized macrophages contained the spindle-like morphology, higher CD163 expression and high IL-10 production. Porcine M1- and M2-polarized macrophages can be most efficiently cultured from mononuclear bone marrow cells using porcine GM-CSF and murine M-CSF. The new culture method facilitates more refined studies of porcine macrophages in vitro, important for both porcine and human health since pigs are increasingly used as model for translational research. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

  14. Generation of hematopoietic stem cells from human embryonic stem cells using a defined, stepwise, serum-free, and serum replacement-free monolayer culture method.

    Science.gov (United States)

    Kim, So-Jung; Jung, Ji-Won; Ha, Hye-Yeong; Koo, Soo Kyung; Kim, Eung-Gook; Kim, Jung-Hyun

    2017-03-01

    Embryonic stem cells (ESCs) can be expanded infinitely in vitro and have the potential to differentiate into hematopoietic stem cells (HSCs); thus, they are considered a useful source of cells for HSC production. Although several technical in vitro methods for engineering HSCs from pluripotent stem cells have been developed, clinical application of HSCs engineered from pluripotent stem cells is restricted because of the possibility of xenogeneic contamination resulting from the use of murine materials. Human ESCs (CHA-hES15) were cultured on growth factor-reduced Matrigel-coated dishes in the mTeSR1 serum-free medium. When the cells were 70% confluent, we initiated HSC differentiation by three methods involving (1) knockout serum replacement (KSR), cytokines, TGFb1, EPO, and FLT3L; (2) KSR, cytokines, and bFGF; or (3) cytokines and bFGF. Among the three differentiation methods, the minimal number of cytokines without KSR resulted in the greatest production of HSCs. The optimized method resulted in a higher proportion of CD34 + CD43 + hematopoietic progenitor cells (HPCs) and CD34 + CD45 + HPCs compared to the other methods. In addition, the HSCs showed the potential to differentiate into multiple lineages of hematopoietic cells in vitro . In this study, we optimized a two-step, serum-free, animal protein-free, KSR-free, feeder-free, chemically defined monolayer culture method for generation of HSCs and hematopoietic stem and progenitor cells (HSPCs) from human ESCs.

  15. Comparison of Chlamydia trachomatis serovar L2 growth in polarized genital epithelial cells grown in three-dimensional culture with non-polarized cells.

    Science.gov (United States)

    Dessus-Babus, Sophie; Moore, Cheryl G; Whittimore, Judy D; Wyrick, Priscilla B

    2008-04-01

    A common model for studying Chlamydia trachomatis and growing chlamydial stocks uses Lymphogranuloma venereum serovar L2 and non-polarized HeLa cells. However, recent publications indicate that the growth rate and progeny yields can vary considerably for a particular strain depending on the cell line/type used, and seem to be partially related to cell tropism. In the present study, the growth of invasive serovar L2 was compared in endometrial HEC-1B and endocervical HeLa cells polarized on collagen-coated microcarrier beads, as well as in HeLa cells grown in tissue culture flasks. Microscopy analysis revealed no difference in chlamydial attachment/entry patterns or in inclusion development throughout the developmental cycle between cell lines. Very comparable growth curves in both cell lines were also found using real-time PCR analysis, with increases in chlamydial DNA content of 400-500-fold between 2 and 36 h post-inoculation. Similar progeny yields with comparable infectivity were recovered from HEC-1B and HeLa cell bead cultures, and no difference in chlamydial growth was found in polarized vs. non-polarized HeLa cells. In conclusion, unlike other C. trachomatis strains such as urogenital serovar E, invasive serovar L2 grows equally well in physiologically different endometrial and endocervical environments, regardless of the host cell polarization state.

  16. Influence of neuraminidase and X-ray irradiation (2 Gy and 8 Gy) on microvilli and membrane invaginations of Ehrlich ascites tumor cells in monolayer culture

    International Nuclear Information System (INIS)

    Laudenbach, G.; Baganz, O.; Pfab, R.; Hess, F.; Schachtschabel, D.O.

    1987-01-01

    A monolayer culture (Eagle basal medium plus 10% of fetal calf serum) of Ehrlich ascites tumor cells was exposed to X-radiation with 2 Gy and 8 Gy and treated with Vibrio cholerae neuraminidase alone or combined with sublethal X-ray irradiation (2 Gy). Pictures of the Ehrlich ascites tumor cells taken with the electron microscope were investigated in order to find out any cell surface modifications due to membrane invaginations and microvilli. The results showed that the rate of microvilli as well as that of membrane invaginations became higher with the increasing X-ray dose (2 Gy; 8 Gy). Following to neuraminidase treatment there was a considerable augmentation of membran invaginations as compared to control cells, whereas the number of microvilli was slightly reduced. As it has been already described before, the influence of neuraminidase produced an increased endocytosis activity and a strengthening of the cytoskeleton. Combined treatment with neuraminidase and sublethal X-radiation (2 Gy) caused a higher rate of membrane invaginations than each method alone; the number of microvilli was slightly increased by combined treatment. The conclusion is drawn that these structure modifications are due to reparation processes induced by radiation on the one hand and to an enzymic action of neuraminidase on the cell surface on the other hand. (orig.) [de

  17. Effects of dexamethasone and insulin on the synthesis of triacylglycerols and phosphatidylcholine and the secretion of very-low-density lipoproteins and lysophosphatidylcholine by monolayer cultures of rat hepatocytes.

    OpenAIRE

    Mangiapane, E H; Brindley, D N

    1986-01-01

    Rat hepatocytes in monolayer culture were preincubated for 19 h with 1 microM-dexamethasone, and the incubation was continued for a further 23 h with [14C]oleate, [3H]glycerol and 1 microM-dexamethasone. Dexamethasone increased the secretion of triacylglycerol into the medium in particles that had the properties of very-low-density lipoproteins. The increased secretion was matched by a decrease in the triacylglycerol and phosphatidylcholine that remained in the hepatocytes. Preincubating the ...

  18. Expression and functional activity of P-glycoprotein in passaged primary human nasal epithelial cell monolayers cultured by the air-liquid interface method for nasal drug transport study.

    Science.gov (United States)

    Cho, Hyun-Jong; Choi, Min-Koo; Lin, Hongxia; Kim, Jung Sun; Chung, Suk-Jae; Shim, Chang-Koo; Kim, Dae-Duk

    2011-03-01

    P-glycoprotein (P-gp) is an efflux transporter encoded by the multidrug resistance gene (MDR1), which is also known as the human ABCB1 gene (ATP-binding cassette, subfamily-B). The objectives of this study were to investigate the expression of P-gp in passaged primary human nasal epithelial (HNE) cell monolayer, cultured by the air-liquid interface (ALI) method, and to evaluate its feasibility as an in-vitro model for cellular uptake and transport studies of P-gp substrates. Reverse transcriptase-polymerase chain reaction (RT-PCR) was performed to verify the expression of the MDR1 gene. Transport and cellular uptake studies with P-gp substrate (rhodamine123) and P-gp inhibitors (verapamil and cyclosporin A) were conducted to assess the functional activity of P-gp in HNE cell monolayers cultured by the ALI method. MDR1 gene expression in primary HNE cell monolayers cultured by ALI method was confirmed by RT-PCR. The apparent permeability coefficient (P(app) ) of the P-gp substrate (rhodamine123) in the basolateral to apical (B to A) direction was 6.9 times higher than that in the apical to basolateral (A to B) direction. B to A transport was saturated at high rhodamine123 concentration, and the treatment of P-gp inhibitors increased cellular uptake of rhodamine123 in a time- and concentration-dependent manner. These results support the MDR1 gene expression and the functional activity of P-gp in primary HNE cell monolayers cultured by the ALI method. © 2011 The Authors. JPP © 2011 Royal Pharmaceutical Society.

  19. Influence of serum extraction from the culture medium and of sublethal X-ray irradiation upon microvilli and invaginations of the membrane of Ehrlich ascites tumor cells in monolayer culture

    International Nuclear Information System (INIS)

    Laudenbach, G.; Pfab, R.; Hess, F.; Schachtschabel, D.O.

    1984-01-01

    In order to find out modifications of microvilli and invaginations, the cellular surfaces of Ehrlich ascites tumor cells in monolayer culture (basal medium of Eagle + 10% fetal calf serum) were investigated with the aid of electron-microscopic cross-sections. The tumor cells had been cultured without serum 24 hours prior to investigation or irradiated with 2 Gy. Morphometric evaluation after cell culture in a serum-free medium showed a reduced number of microvilli and a diminution of sections of microvilli. As already described before, a reduction of cell proliferation, of the microtubule-microfilament system, and of the endocytosis activity occurs under these serum-free conditions. The number of invaginations (related to a constant membrane part) was reduced by nearly 50% after serum extraction. Similarly to serum extraction, sublethal X-ray irradiation reduced the sections of microvilli, whereas the number of microvilli increased slightly. Contrary to the effect of serum extraction, the irradiated cells showed twice as many invaginations as the non-irradiated control cells. These differences in the surface structures are interpreted as a result of modified growth stimulations (+- serum) and radiogenic reparation processes. (orig.) [de

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

    International Nuclear Information System (INIS)

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

    2005-01-01

    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

  1. Preparation of porous monolayer film by immersing the stearic acid Langmuir-Blodgett monolayer on mica in salt solution

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S. [Institute of Near-Field Optics and Nano Technology, School of Physics and Optoelectronic Technology, Dalian University of Technology, Street No. 2 Linggong Road, Dalian 116024 (China); Li, Y.L.; Zhao, H.L.; Liang, H. [Institute of Photo-Biophysics, School of Physics and Electronic, Henan University, Jinming, Kaifeng 475004, Henan (China); Liu, B., E-mail: boliu@henu.edu.cn [Institute of Photo-Biophysics, School of Physics and Electronic, Henan University, Jinming, Kaifeng 475004, Henan (China); Pan, S., E-mail: span@dlut.edu.cn [Institute of Near-Field Optics and Nano Technology, School of Physics and Optoelectronic Technology, Dalian University of Technology, Street No. 2 Linggong Road, Dalian 116024 (China)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer Porous film has been prepared by immersing the stearic acid Langmuir-Blodgett monolayer on mica in salt solution. Black-Right-Pointing-Pointer The mechanism relies on the electrostatic screening effect of the cations in salt solution. Black-Right-Pointing-Pointer The factors influencing the size and area of the pores were investigated. - Abstract: Porous materials have drawn attention from scientists in many fields such as life sciences, catalysis and photonics since they can be used to induce some materials growth as expected. Especially, porous Langmuir-Blodgett (LB) film is an ideal material with controlled thickness and flat surface. In this paper, stearic acid (SA), which has been extensively explored in LB film technique, is chosen as the template material with known parameters to prepare the LB film, and then the porous SA monolayer film is obtained by means of etching in salt solution. The main etching mechanism is suggested that the cations in the solution block the electrostatic interaction between the polar carboxyl group of SA and the electronegative mica surface. The influencing factors (such as concentration of salt solution, valence of cation and surface pressure) of the porous SA film are systematically studied in this work. The novel method proposed in this paper makes it convenient to prepare porous monolayer film for designed material growth or cell culture.

  2. Disorder-dependent valley properties in monolayer WSe2

    KAUST Repository

    Tran, Kha

    2017-07-19

    We investigate the effect of disorder on exciton valley polarization and valley coherence in monolayer WSe2. By analyzing the polarization properties of photoluminescence, the valley coherence (VC) and valley polarization (VP) are quantified across the inhomogeneously broadened exciton resonance. We find that disorder plays a critical role in the exciton VC, while affecting VP less. For different monolayer samples with disorder characterized by their Stokes shift (SS), VC decreases in samples with higher SS while VP does not follow a simple trend. These two methods consistently demonstrate that VC as defined by the degree of linearly polarized photoluminescence is more sensitive to disorder, motivating further theoretical studies.

  3. Large-area and bright pulsed electroluminescence in monolayer semiconductors

    KAUST Repository

    Lien, Der-Hsien; Amani, Matin; Desai, Sujay B.; Ahn, Geun Ho; Han, Kevin; He, Jr-Hau; Ager, Joel W.; Wu, Ming C.; Javey, Ali

    2018-01-01

    Transition-metal dichalcogenide monolayers have naturally terminated surfaces and can exhibit a near-unity photoluminescence quantum yield in the presence of suitable defect passivation. To date, steady-state monolayer light-emitting devices suffer from Schottky contacts or require complex heterostructures. We demonstrate a transient-mode electroluminescent device based on transition-metal dichalcogenide monolayers (MoS, WS, MoSe, and WSe) to overcome these problems. Electroluminescence from this dopant-free two-terminal device is obtained by applying an AC voltage between the gate and the semiconductor. Notably, the electroluminescence intensity is weakly dependent on the Schottky barrier height or polarity of the contact. We fabricate a monolayer seven-segment display and achieve the first transparent and bright millimeter-scale light-emitting monolayer semiconductor device.

  4. Large-area and bright pulsed electroluminescence in monolayer semiconductors

    KAUST Repository

    Lien, Der-Hsien

    2018-04-04

    Transition-metal dichalcogenide monolayers have naturally terminated surfaces and can exhibit a near-unity photoluminescence quantum yield in the presence of suitable defect passivation. To date, steady-state monolayer light-emitting devices suffer from Schottky contacts or require complex heterostructures. We demonstrate a transient-mode electroluminescent device based on transition-metal dichalcogenide monolayers (MoS, WS, MoSe, and WSe) to overcome these problems. Electroluminescence from this dopant-free two-terminal device is obtained by applying an AC voltage between the gate and the semiconductor. Notably, the electroluminescence intensity is weakly dependent on the Schottky barrier height or polarity of the contact. We fabricate a monolayer seven-segment display and achieve the first transparent and bright millimeter-scale light-emitting monolayer semiconductor device.

  5. Primary human polarized small intestinal epithelial barriers respond differently to a hazardous and an innocuous protein.

    Science.gov (United States)

    Eaton, A D; Zimmermann, C; Delaney, B; Hurley, B P

    2017-08-01

    An experimental platform employing human derived intestinal epithelial cell (IEC) line monolayers grown on permeable Transwell ® filters was previously investigated to differentiate between hazardous and innocuous proteins. This approach was effective at distinguishing these types of proteins and perturbation of monolayer integrity, particularly transepithelial electrical resistance (TEER), was the most sensitive indicator. In the current report, in vitro indicators of monolayer integrity, cytotoxicity, and inflammation were evaluated using primary (non-transformed) human polarized small intestinal epithelial barriers cultured on Transwell ® filters to compare effects of a hazardous protein (Clostridium difficile Toxin A [ToxA]) and an innocuous protein (bovine serum albumin [BSA]). ToxA exerted a reproducible decrease on barrier integrity at doses comparable to those producing effects observed from cell line-derived IEC monolayers, with TEER being the most sensitive indicator. In contrast, BSA, tested at concentrations substantially higher than ToxA, did not cause changes in any of the tested variables. These results demonstrate a similarity in response to certain proteins between cell line-derived polarized IEC models and a primary human polarized small intestinal epithelial barrier model, thereby reinforcing the potential usefulness of cell line-derived polarized IECs as a valid experimental platform to differentiate between hazardous and non-hazardous proteins. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  6. Antibiotic interaction with phospholipid monolayers

    International Nuclear Information System (INIS)

    Gambinossi, F.; Mecheri, B.; Caminati, G.; Nocentini, M.; Puggelli, M.; Gabrielli, G.

    2002-01-01

    We studied the interactions of tetracycline (TC) antibiotic molecules with phospholipid monolayers with the two-fold aim of elucidating the mechanism of action and providing a first step for the realization of bio-mimetic sensors for such drugs by means of the Langmuir-Blodgett technique. We examined spreading monolayers of three phospholipids in the presence of tetracycline in the subphase by means of surface pressure-area and surface potential-area isotherms as a function of bulk pH. We selected phospholipids with hydrophobic chains of the same length but polar head groups differing either in dimensions and protonation equilibria, i.e. dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylethanolamine (DPPE) and dipalmitoylphosphatidic acid (DPPA). The interaction of tetracycline with the three phospholipids was found to be highly dependent on the electric charge of the antibiotic and on the ionization state of the lipid. Significant interactions are established between the negatively charged form of dipalmitoylphosphatidic acid and the zwitterionic form of tetracycline. The drug was found to migrate at the interface where it is adsorbed underneath or/and among the head groups, depending on the surface pressure of the film, whereas penetration through the hydrophobic layer was excluded for all the three phospholipids

  7. Antibiotic interaction with phospholipid monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Gambinossi, F.; Mecheri, B.; Caminati, G.; Nocentini, M.; Puggelli, M.; Gabrielli, G

    2002-12-01

    We studied the interactions of tetracycline (TC) antibiotic molecules with phospholipid monolayers with the two-fold aim of elucidating the mechanism of action and providing a first step for the realization of bio-mimetic sensors for such drugs by means of the Langmuir-Blodgett technique. We examined spreading monolayers of three phospholipids in the presence of tetracycline in the subphase by means of surface pressure-area and surface potential-area isotherms as a function of bulk pH. We selected phospholipids with hydrophobic chains of the same length but polar head groups differing either in dimensions and protonation equilibria, i.e. dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylethanolamine (DPPE) and dipalmitoylphosphatidic acid (DPPA). The interaction of tetracycline with the three phospholipids was found to be highly dependent on the electric charge of the antibiotic and on the ionization state of the lipid. Significant interactions are established between the negatively charged form of dipalmitoylphosphatidic acid and the zwitterionic form of tetracycline. The drug was found to migrate at the interface where it is adsorbed underneath or/and among the head groups, depending on the surface pressure of the film, whereas penetration through the hydrophobic layer was excluded for all the three phospholipids.

  8. Diamondoid monolayers as electron emitters

    Science.gov (United States)

    Yang, Wanli [El Cerrito, CA; Fabbri, Jason D [San Francisco, CA; Melosh, Nicholas A [Menlo Park, CA; Hussain, Zahid [Orinda, CA; Shen, Zhi-Xun [Stanford, CA

    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.

  9. WSe2 Monolayer

    KAUST Repository

    Zhang, Shuai; Wang, Chen-Guang; Li, Ming-yang; Huang, Di; Li, Lain-Jong; Ji, Wei; Wu, Shiwei

    2017-01-01

    dichalcogenide materials, intrinsic defects in WSe2 arise surprisingly from single tungsten vacancies, leading to the hole (p-type) doping. Furthermore, we found these defects to dominate the excitonic emission of the WSe2 monolayer at low temperature. Our work

  10. Parallel studies of His-DTrp-Ala-Trp-DPhe-Lys-NH2 and human pancreatic growth hormone-releasing factor-44-NH2 in rat primary pituitary cell monolayer culture.

    Science.gov (United States)

    Sartor, O; Bowers, C Y; Chang, D

    1985-03-01

    His-DTrp-Ala-Trp-DPhe-Lys-NH2 (GH-RP-6) is a synthetic hexapeptide that specifically releases GH both in vivo and in vitro in pituitary incubates. In this study, for the first time, GH-RP-6 was studied in primary pituitary cell monolayer culture. Parallel studies were performed with human pancreatic GH-releasing factor-44 (hpGRF-44). Culture conditions optimal for GH-RP-6 were not optimal for hpGRF-44. Both peptides released GH in a dose- and time-dependent manner. In this assay system, the ED50 for GH-RP-6 was 9 nM, and the ED50 for hp-GRF-44 was 1.6 nM. Calcium-blocking agents inhibited the GH responses of both peptides as well as basal GH release. Pretreatment with GH-RP-6 decreased the subsequent response to both GH-RP-6 and hpGRF-44. hpGRF-44 down regulated itself but not GH-RP-6. Rat sera potentiated the GH response of hpGRF-44 but not that of GH-RP-6. GH-RP-6 and hpGRF-44 GH responses were additive. These results suggest that GH-RP-6 and hpGRF-44 stimulate GH release via different somatotroph receptors.

  11. Conformation, orientation and interaction in molecular monolayers

    International Nuclear Information System (INIS)

    Superfine, R.; Huang, J.Y.; Shen, Y.R.

    1989-01-01

    Knowledge of the conformation and ordering of molecular monolayers is essential for a detailed understanding of a wide variety of surface and interfacial phenomena. Over the past several years, surface second harmonic generation (SHG) has proven to be a valuable and versatile probe of monolayer systems. Our group has recently extended the technique to infrared-visible sum frequency generation (SFG) which has unique capabilities for surface vibrational spectroscopy. Like second harmonic generation, SFG is highly surface specific with submonolayer sensitivity at all interfaces accessible by light. The orientation of individual groups within an adsorbate molecule can be deduced by a polarization analysis of the SFG signal from the vibrational modes of the groups. The authors have used SHG and SFG to study orientations and conformations of surfactant and liquid crystal (LC) monolayers and their interaction on a substrate. The interfacial properties of LC are of great interest to many researchers for both basic science understanding and practical application to LC devices. It is well known that the bulk alignment of a liquid crystal in a cell is strongly affected by the surface treatment of the cell walls. The reason behind it is not yet clear. The theoretical background and experimental arrangement of SHG and SFG have been described elsewhere. In the setup, a 30 psec. Nd:YAG mode-locked laser system together with nonlinear accessories generates a visible beam at .532μm and an infrared beam tunable about 3.4μm. Both beams are focused to a common spot of 300μm dia. The typical signal off the surface from a compact ordered alkyl chain monolayer is ∼500 photons per pulse, easily detected with a photomultiplier tube

  12. Comparison of Chlamydia trachomatis serovar L2 growth in polarized genital epithelial cells grown in three-dimensional culture with non-polarized cells

    OpenAIRE

    Dessus-Babus, Sophie; Moore, Cheryl G.; Whittimore, Judy D.; Wyrick, Priscilla B.

    2008-01-01

    A common model for studying Chlamydia trachomatis and growing chlamydial stocks uses Lymphogranuloma venereum serovar L2 and non-polarized HeLa cells. However, recent publications indicate that the growth rate and progeny yields can vary considerably for a particular strain depending on the cell line/type used, and seem to be partially related to cell tropism. In the present study, the growth of invasive serovar L2 was compared in endometrial HEC-1B and endocervical HeLa cells polarized on co...

  13. Subcellular topological effect of particle monolayers on cell shapes and functions.

    Science.gov (United States)

    Miura, Manabu; Fujimoto, Keiji

    2006-12-01

    We studied topological effects of subcellular roughness displayed by a closely packed particle monolayer on adhesion and growth of endothelial cells. Poly(styrene-co-acrylamide) (SA) particles were prepared by soap-free emulsion copolymerization. Particle monolayers were prepared by Langmuir-Blodgett deposition using particles, which were 527 (SA053) and 1270 nm (SA127) in diameter. After 24-h incubation, cells tightly adhered on a tissue culture polystyrene dish and randomly spread. On the other hand, cells attached on particle monolayers were stretched into a narrow stalk-like shape. Lamellipodia spread from the leading edge of cells attached on SA053 monolayer to the top of the particles and gradually gathered to form clusters. This shows that cell-cell adhesion became stronger than cell-substrate interaction. Cells attached to SA127 monolayer extended to the reverse side of a particle monolayer and engulfed particles. They remained immobile without migration 24h after incubation. This shows that the inhibition of extensions on SA127 monolayer could inhibit cell migration and cell proliferation. Cell growth on the particle monolayers was suppressed compared with a flat TCPS dish. The number of cells on SA053 gradually increased, whereas that on SA127 decreased with time. When the cell seeding density was increased to 200,000 cells cm(-2), some adherent cells gradually became into contact with adjacent cells. F-actin condensations were formed at the frame of adherent cells and the thin filaments grew from the edges to connect each other with time. For the cell culture on SA053 monolayer, elongated cells showed a little alignment. Cells showed not arrangement of actin stress fibers but F-actin condensation at the contact regions with neighboring cells. Interestingly, the formed cell monolayer could be readily peeled from the particle monolayer. These results indicate that endothelial cells could recognize the surface roughness displayed by particle monolayers and

  14. Monolayer Superconductivity in WS2

    NARCIS (Netherlands)

    Zheliuk, Oleksandr; Lu, Jianming; Yang, Jie; Ye, Jianting

    Superconductivity in monolayer tungsten disulfide (2H-WS2) is achieved by strong electrostatic electron doping of an electric double-layer transistor (EDLT). Single crystals of WS2 are grown by a scalable method - chemical vapor deposition (CVD) on standard Si/SiO2 substrate. The monolayers are

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

    International Nuclear Information System (INIS)

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

    1991-01-01

    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 ± 1.87 mM, the maximum uptake rate, Jmax, was 144.7 ± 55.7 nmol/mg of protein/min and the nonsaturable first-order rate constant, Kd, was 6.66 ± 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'-diisothiocyanostilben-2,2'-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

  16. Correction of the exciton Bohr radius in monolayer transition metal dichalcogenides

    Science.gov (United States)

    Li, Run-Ze; Dong, Xi-Ying; Li, Zhi-Qing; Wang, Zi-Wu

    2018-07-01

    We theoretically investigate the correction of exciton Bohr radius in monolayer transition metal dichalcogenides (TMDCs) on different polar substrates arising from the exciton-optical phonon coupling, in which both the intrinsic longitudinal optical phonon and surface optical phonon modes couple with the exciton are taken into account. We find that the exciton Bohr radius is enlarged markedly due to these coupling. Moreover, it can be changed on a large scale by modulating the polarizability of polar substrate and the internal distance between the monolayer TMDCs and polar substrate. Theoretical result provides a potential explanation for the variation of the exciton Bohr radius in experimental measurement.

  17. Effects of dexamethasone and insulin on the synthesis of triacylglycerols and phosphatidylcholine and the secretion of very-low-density lipoproteins and lysophosphatidylcholine by monolayer cultures of rat hepatocytes.

    Science.gov (United States)

    Mangiapane, E H; Brindley, D N

    1986-01-01

    Rat hepatocytes in monolayer culture were preincubated for 19 h with 1 microM-dexamethasone, and the incubation was continued for a further 23 h with [14C]oleate, [3H]glycerol and 1 microM-dexamethasone. Dexamethasone increased the secretion of triacylglycerol into the medium in particles that had the properties of very-low-density lipoproteins. The increased secretion was matched by a decrease in the triacylglycerol and phosphatidylcholine that remained in the hepatocytes. Preincubating the hepatocytes for the total 42 h period with 36 nM-insulin decreased the amount of triacylglycerol in the medium and in the cells after the final incubation for 23 h with radioactive substrates. However, insulin had no significant effect on the triacylglycerol content of the cell and medium when it was present only in the final 23 h incubation. Insulin antagonized the effects of dexamethasone in stimulating the secretion of triacylglycerol from the hepatocytes, especially when it was present throughout the total 42 h period. The labelling of lysophosphatidylcholine in the medium when hepatocytes were incubated with [14C]oleate and [3H]glycerol was greater than that of phosphatidylcholine. The appearance of this lipid in the medium, unlike that of triacylglycerol and phosphatidylcholine, was not stimulated by dexamethasone, or inhibited by colchicine. However, the presence of lysophosphatidylcholine in the medium was decreased when the hepatocytes were incubated with both dexamethasone and insulin. These findings are discussed in relation to the control of the synthesis of glycerolipids and the secretion of very-low-density lipoproteins and lysophosphatidylcholine by the liver, particularly in relation to the interactions of glucocorticoids and insulin. PMID:3513755

  18. Two cell circuits of oriented adult hippocampal neurons on self-assembled monolayers for use in the study of neuronal communication in a defined system.

    Science.gov (United States)

    Edwards, Darin; Stancescu, Maria; Molnar, Peter; Hickman, James J

    2013-08-21

    In this study, we demonstrate the directed formation of small circuits of electrically active, synaptically connected neurons derived from the hippocampus of adult rats through the use of engineered chemically modified culture surfaces that orient the polarity of the neuronal processes. Although synaptogenesis, synaptic communication, synaptic plasticity, and brain disease pathophysiology can be studied using brain slice or dissociated embryonic neuronal culture systems, the complex elements found in neuronal synapses makes specific studies difficult in these random cultures. The study of synaptic transmission in mature adult neurons and factors affecting synaptic transmission are generally studied in organotypic cultures, in brain slices, or in vivo. However, engineered neuronal networks would allow these studies to be performed instead on simple functional neuronal circuits derived from adult brain tissue. Photolithographic patterned self-assembled monolayers (SAMs) were used to create the two-cell "bidirectional polarity" circuit patterns. This pattern consisted of a cell permissive SAM, N-1[3-(trimethoxysilyl)propyl] diethylenetriamine (DETA), and was composed of two 25 μm somal adhesion sites connected with 5 μm lines acting as surface cues for guided axonal and dendritic regeneration. Surrounding the DETA pattern was a background of a non-cell-permissive poly(ethylene glycol) (PEG) SAM. Adult hippocampal neurons were first cultured on coverslips coated with DETA monolayers and were later passaged onto the PEG-DETA bidirectional polarity patterns in serum-free medium. These neurons followed surface cues, attaching and regenerating only along the DETA substrate to form small engineered neuronal circuits. These circuits were stable for more than 21 days in vitro (DIV), during which synaptic connectivity was evaluated using basic electrophysiological methods.

  19. Gastrointestinal cell lines form polarized epithelia with an adherent mucus layer when cultured in semi-wet interfaces with mechanical stimulation.

    Science.gov (United States)

    Navabi, Nazanin; McGuckin, Michael A; Lindén, Sara K

    2013-01-01

    Mucin glycoproteins are secreted in large quantities by mucosal epithelia and cell surface mucins are a prominent feature of the glycocalyx of all mucosal epithelia. Currently, studies investigating the gastrointestinal mucosal barrier use either animal experiments or non-in vivo like cell cultures. Many pathogens cause different pathology in mice compared to humans and the in vitro cell cultures used are suboptimal because they are very different from an in vivo mucosal surface, are often not polarized, lack important components of the glycocalyx, and often lack the mucus layer. Although gastrointestinal cell lines exist that produce mucins or polarize, human cell line models that reproducibly create the combination of a polarized epithelial cell layer, functional tight junctions and an adherent mucus layer have been missing until now. We trialed a range of treatments to induce polarization, 3D-organization, tight junctions, mucin production, mucus secretion, and formation of an adherent mucus layer that can be carried out using standard equipment. These treatments were tested on cell lines of intestinal (Caco-2, LS513, HT29, T84, LS174T, HT29 MTX-P8 and HT29 MTX-E12) and gastric (MKN7, MKN45, AGS, NCI-N87 and its hTERT Clone5 and Clone6) origins using Ussing chamber methodology and (immuno)histology. Semi-wet interface culture in combination with mechanical stimulation and DAPT caused HT29 MTX-P8, HT29 MTX-E12 and LS513 cells to polarize, form functional tight junctions, a three-dimensional architecture resembling colonic crypts, and produce an adherent mucus layer. Caco-2 and T84 cells also polarized, formed functional tight junctions and produced a thin adherent mucus layer after this treatment, but with less consistency. In conclusion, culture methods affect cell lines differently, and testing a matrix of methods vs. cell lines may be important to develop better in vitro models. The methods developed herein create in vitro mucosal surfaces suitable for studies

  20. Gastrointestinal cell lines form polarized epithelia with an adherent mucus layer when cultured in semi-wet interfaces with mechanical stimulation.

    Directory of Open Access Journals (Sweden)

    Nazanin Navabi

    Full Text Available Mucin glycoproteins are secreted in large quantities by mucosal epithelia and cell surface mucins are a prominent feature of the glycocalyx of all mucosal epithelia. Currently, studies investigating the gastrointestinal mucosal barrier use either animal experiments or non-in vivo like cell cultures. Many pathogens cause different pathology in mice compared to humans and the in vitro cell cultures used are suboptimal because they are very different from an in vivo mucosal surface, are often not polarized, lack important components of the glycocalyx, and often lack the mucus layer. Although gastrointestinal cell lines exist that produce mucins or polarize, human cell line models that reproducibly create the combination of a polarized epithelial cell layer, functional tight junctions and an adherent mucus layer have been missing until now. We trialed a range of treatments to induce polarization, 3D-organization, tight junctions, mucin production, mucus secretion, and formation of an adherent mucus layer that can be carried out using standard equipment. These treatments were tested on cell lines of intestinal (Caco-2, LS513, HT29, T84, LS174T, HT29 MTX-P8 and HT29 MTX-E12 and gastric (MKN7, MKN45, AGS, NCI-N87 and its hTERT Clone5 and Clone6 origins using Ussing chamber methodology and (immunohistology. Semi-wet interface culture in combination with mechanical stimulation and DAPT caused HT29 MTX-P8, HT29 MTX-E12 and LS513 cells to polarize, form functional tight junctions, a three-dimensional architecture resembling colonic crypts, and produce an adherent mucus layer. Caco-2 and T84 cells also polarized, formed functional tight junctions and produced a thin adherent mucus layer after this treatment, but with less consistency. In conclusion, culture methods affect cell lines differently, and testing a matrix of methods vs. cell lines may be important to develop better in vitro models. The methods developed herein create in vitro mucosal surfaces

  1. Phase transitions in surfactant monolayers

    International Nuclear Information System (INIS)

    Casson, B.D.

    1998-01-01

    Two-dimensional phase transitions have been studied in surfactant monolayers at the air/water interface by sum-frequency spectroscopy and ellipsometry. In equilibrium monolayers of medium-chain alcohols C n H 2n+1 OH (n = 9-14) a transition from a two-dimensional crystalline phase to a liquid was observed at temperatures above the bulk melting point. The small population of gauche defects in the solid phase increased only slightly at the phase transition. A model of the hydrocarbon chains as freely rotating rigid rods allowed the area per molecule and chain tilt in the liquid phase to be determined. The area per molecule, chain tilt and density of the liquid phase all increased with increasing chain length, but for each chain length the density was higher than in a bulk liquid hydrocarbon. In a monolayer of decanol adsorbed at the air/water interface a transition from a two-dimensional liquid to a gas was observed. A clear discontinuity in the coefficient of ellipticity as a function of temperature showed that the transition is first-order. This result suggests that liquid-gas phase transitions in surfactant monolayers may be more widespread than once thought. A solid-liquid phase transition has also been studied in mixed monolayers of dodecanol with an anionic surfactant (sodium dodecyl sulphate) and with a homologous series of cationic surfactants (alkyltrimethylammonium bromides: C n TABs, n = 12, 14, 16). The composition and structure of the mixed monolayers was studied above and below the phase transition. At low temperatures the mixed monolayers were as densely packed as a monolayer of pure dodecanol in its solid phase. At a fixed temperature the monolayers under-went a first-order phase transition to form a phase that was less dense and more conformationally disordered. The proportion of ionic surfactant in the mixed monolayer was greatest in the high temperature phase. As the chain length of the C n TAB increased the number of conformational defects

  2. Repair during multifraction exposures: spheroids versus monolayers

    International Nuclear Information System (INIS)

    Durand, R.E.

    1984-01-01

    Many type of mammalian cells, when grown in culture as multicell spheroids, display an increased ability to accumulate and repair sublethal radiation damage which has been called the ''contact effect''. Since this effect has the potential to markedly modify the multifraction radiation response of cells in V79 spheroids relative to cells in monolayer cultures, an investigation was made of regimens ranging from 1 to 100 fractions. Effective dose rates were chosen near 1 Gy h -1 to inhibit cell progression and thus simplify analysis of the results. As expected, larger doses per fraction produced more net cell killing in both systems than lower doses per fraction. Additionally, less killing of spheroid cells was observed in all regimens, in accord with their greater potential for repair. However, when the data were expressed as isoeffect curves, the spheroid and monolayer curves converged as the number of fractions increased. Thus, quite similar inherent sensitivity and repair capabilities would be predicted for ultra-low doses per fraction. High precision techniques for defining survival after doses of radiation from 0.2 to 1 Gy were, however, still able to demonstrate a survival advantage for cells grown as spheroids. (author)

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

    Science.gov (United States)

    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.

  4. Growth of cells superinoculated onto irradiated and nonirradiated confluent monolayers

    International Nuclear Information System (INIS)

    Matsuoka, H.; Ueo, H.; Sugimachi, K.

    1990-01-01

    We prepared confluent monolayers of normal BALB/c 3T3 cells and compared differences in the growth of four types of cells superinoculated onto these nonirradiated and irradiated monolayers. The test cells were normal BALB/c 3T3 A31 cells, a squamous cell carcinoma from a human esophageal cancer (KSE-1), human fetal fibroblasts, and V-79 cells from Chinese hamster lung fibroblasts. Cell growth was checked by counting the cell number, determining [3H]thymidine incorporation and assessing colony formation. We found that on nonirradiated monolayers, colony formation of human fetal fibroblasts and normal BALB/c 3T3 cells was completely inhibited. On irradiated cells, test cells did exhibit some growth. KSE-1 cells, which had a low clonogenic efficiency on plastic surfaces, formed colonies on both irradiated and nonirradiated cells. On these monolayers, the clonogenic efficiency of V-79 cells was also higher than that on plastic surfaces. We conclude that the nonirradiated monolayer of BALB/c 3T3 cells completely inhibits the growth of superinoculated normal BALB/c 3T3 and human fetal fibroblasts, while on the other hand, they facilitate the growth of neoplastic KSE-1 and V-79 cells by providing a surface for cell adherence and growth, without affecting the presence of normal cells in co-cultures

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

    Science.gov (United States)

    Zheng, Hui; Chen, Nian-Ke; Zhang, S. B.; Li, Xian-Bin

    A systematic study of 32 honeycomb monolayer II-VI semiconductors is carried out by first-principles methods. It appears that BeO, MgO, CaO, ZnO, CdO, CaS, SrS, SrSe, BaTe, and HgTe honeycomb monolayers have a good dynamic stability which is revealed by phonon calculations. In addition, from the molecular dynamic (MD) simulation of other unstable candidates, we also find two extra monolayers dynamically stable, which are tetragonal BaS and orthorhombic HgS. The honeycomb monolayers exist in 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 been reported to achieve a topological nontrivial phase under appropriate in-plane tensile strain and spin-orbital coupling (SOC). 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. Distinguished Student (DS) Program of APS FIP travel funds.

  6. Photocarrier dynamics in monolayer phosphorene and bulk black phosphorus.

    Science.gov (United States)

    Zereshki, Peymon; Wei, Yaqing; Ceballos, Frank; Bellus, Matthew Z; Lane, Samuel D; Pan, Shudi; Long, Run; Zhao, Hui

    2018-06-13

    We report a combined theoretical and experimental study on photocarrier dynamics in monolayer phosphorene and bulk black phosphorus. Samples of monolayer phosphorene and bulk black phosphorus were fabricated by mechanical exfoliation, identified according to their reflective contrasts, and protected by covering them with hexagonal boron nitride layers. Photocarrier dynamics in these samples was studied by an ultrafast pump-probe technique. The photocarrier lifetime of monolayer phosphorene was found to be about 700 ps, which is about 9 times longer than that of bulk black phosphorus. This trend was reproduced in our calculations based on ab initio nonadiabatic molecular dynamics combined with time-domain density functional theory in the Kohn-Sham representation, and can be attributed to the smaller bandgap and stronger nonadiabatic coupling in bulk. The transient absorption response was also found to be dependent on the sample orientation with respect to the pump polarization, which is consistent with the previously reported anisotropic absorption of phosphorene. In addition, an oscillating component of the differential reflection signal at early probe delays was observed in the bulk sample and was attributed to the layer-breathing phonon mode with an energy of about 1 meV and a decay time of about 1.35 ps. These results provide valuable information for application of monolayer phosphorene in optoelectronics.

  7. A novel three-dimensional cell culture method enhances antiviral drug screening in primary human cells.

    Science.gov (United States)

    Koban, Robert; Neumann, Markus; Daugs, Aila; Bloch, Oliver; Nitsche, Andreas; Langhammer, Stefan; Ellerbrok, Heinz

    2018-02-01

    Gefitinib is a specific inhibitor of the epidermal growth factor receptor (EGFR) and FDA approved for treatment of non-small cell lung cancer. In a previous study we could show the in vitro efficacy of gefitinib for treatment of poxvirus infections in monolayer (2D) cultivated cell lines. Permanent cell lines and 2D cultures, however, are known to be rather unphysiological; therefore it is difficult to predict whether determined effective concentrations or the drug efficacy per se are transferable to the in vivo situation. 3D cell cultures, which meanwhile are widely distributed across all fields of research, are a promising tool for more predictive in vitro investigations of antiviral compounds. In this study the spreading of cowpox virus and the antiviral efficacy of gefitinib were analyzed in primary human keratinocytes (NHEK) grown in a novel 3D extracellular matrix-based cell culture model and compared to the respective monolayer culture. 3D-cultivated NHEK grew in a polarized and thus a more physiological manner with altered morphology and close cell-cell contact. Infected cultures showed a strongly elevated sensitivity towards gefitinib. EGFR phosphorylation, cell proliferation, and virus replication were significantly reduced in 3D cultures at gefitinib concentrations which were at least 100-fold lower than those in monolayer cultures and well below the level of cytotoxicity. Our newly established 3D cell culture model with primary human cells is an easy-to-handle alternative to conventional monolayer cell cultures and previously described more complex 3D cell culture systems. It can easily be adapted to other cell types and a broad spectrum of viruses for antiviral drug screening and many other aspects of virus research under more in vivo-like conditions. In consequence, it may contribute to a more targeted realization of necessary in vivo experiments. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Orientational epitaxy in adsorbed monolayers

    International Nuclear Information System (INIS)

    Novaco, A.D.; McTague, J.P.

    1977-01-01

    The ground state for adsorbed monolayers on crystalline substrates is shown to involve a definite relative orientation of the substrate and adsorbate crystal axes, even when the relative lattice parameters are incommensurate. The rotation angle which defines the structure of the monolayer-substrate system is determined by the competition between adsorbate-substrate and adsorbate-adsorbate energy terms, and is generally not a symmetry angle. Numerical predictions are presented for the rare gas-graphite systems, whose interaction potentials are rather well known. Recent LEED data for some of these systems appear to corroborate these predictions

  9. Transport properties in monolayer-bilayer-monolayer graphene planar junctions

    Institute of Scientific and Technical Information of China (English)

    Kai-Long Chu; Zi-Bo Wang; Jiao-Jiao Zhou; Hua Jiang

    2017-01-01

    The transport study of graphene based junctions has become one of the focuses in graphene research.There are two stacking configurations for monolayer-bilayer-monolayer graphene planar junctions.One is the two monolayer graphene contacting the same side of the bilayer graphene,and the other is the two-monolayer graphene contacting the different layers of the bilayer graphene.In this paper,according to the Landauer-Büttiker formula,we study the transport properties of these two configurations.The influences of the local gate potential in each part,the bias potential in bilayer graphene,the disorder and external magnetic field on conductance are obtained.We find the conductances of the two configurations can be manipulated by all of these effects.Especially,one can distinguish the two stacking configurations by introducing the bias potential into the bilayer graphene.The strong disorder and the external magnetic field will make the two stacking configurations indistinguishable in the transport experiment.

  10. Solution-processable septithiophene monolayer transistor

    NARCIS (Netherlands)

    Defaux, M.; Gholamrezaie, F.; Wang, J.; Kreyes, A.; Ziener, U.; Anokhin, D.V.; Ivanov, D.A.; Moser, A.; Neuhold, A.; Salzmann, I.; Resel, R.; Leeuw, de D.M.; Meskers, S.C.J.; Moeller, M.; Mourran, A.

    2012-01-01

    Septithiophene with endgroups designed to form liquid crystalline phases and allows controlled deposition of an electrically connected monolayer. Field effect mobilies mobilities of charge carriers and spectroscopic properties of the monolayer provide evidence of sustainable transport and

  11. Solution-Processable Septithiophene Monolayer Transistor

    NARCIS (Netherlands)

    Defaux, Matthieu; Gholamrezaie, Fatemeh; Wang, Jingbo; Kreyes, Andreas; Ziener, Ulrich; Anokhin, Denis V.; Ivanov, Dimitri A.; Moser, Armin; Neuhold, Alfred; Salzmann, Ingo; Resel, Roland; de Leeuw, Dago M.; Meskers, Stefan C. J.; Moeller, Martin; Mourran, Ahmed

    2012-01-01

    Septithiophene with endgroups designed to form liquid crystalline phases and allows controlled deposition of an electrically connected monolayer. Field effect mobilies mobilities of charge carriers and spectroscopic properties of the monolayer provide evidence of sustainable transport and

  12. Structures and shear response of lipid monolayers

    International Nuclear Information System (INIS)

    Dutta, P.; Ketterson, J.B.

    1993-02-01

    This report discusses our work during the last 3 years using x-ray diffraction and shear measurements to study lipid monolayers (membranes). The report is divided into: (1) structure: phase diagram of saturated fatty acid Langmuir monolayers, effect of head group interactions, studies of transferred monolayers (LB films); (2) mechanical properties: fiber=optic capillary wave probe and centrosymmetric trough, mechanical behavior of heneicosanoic acid monolayer phases

  13. Structures of sub-monolayered silicon carbide films

    International Nuclear Information System (INIS)

    Baba, Y.; Sekiguchi, T.; Shimoyama, I.; Nath, Krishna G.

    2004-01-01

    The electronic and geometrical structures of silicon carbide thin films are presented. The films were deposited on graphite by ion-beam deposition using tetramethylsilane (TMS) as an ion source. In the Si K-edge near-edge X-ray absorption fine structure (NEXAFS) spectra for sub-monolayered film, sharp peaks due to the resonance from Si 1s to π*-like orbitals were observed, suggesting the existence of Si=C double bonds. On the basis of the polarization dependencies of the Si 1s → π* peak intensities, it is elucidated that the direction of the π*-like orbitals is just perpendicular to the surface. We conclude that the sub-monolayered SiC x film has a flat-lying hexagonal structure of which configuration is analogous to the single sheet of graphite

  14. Metformin affects the features of a human hepatocellular cell line (HepG2) by regulating macrophage polarization in a co-culture microenviroment.

    Science.gov (United States)

    Chen, Miaojiao; Zhang, Jingjing; Hu, Fang; Liu, Shiping; Zhou, Zhiguang

    2015-11-01

    Accumulating evidence suggests an association between diabetes and cancer. Inflammation is a key event that underlies the pathological processes of the two diseases. Metformin displays anti-cancer effects, but the mechanism is not completely clear. This study investigated whether metformin regulated the microenvironment of macrophage polarization to affect the characteristics of HepG2 cells and the possible role of the Notch-signalling pathway. RAW264.7 macrophages were cultured alone or co-cultured with HepG2 cells and treated with metformin. We analysed classical (M1) and alternative (M2) gene expression in RAW264.7 cells using quantitative real-time polymerase chain reaction. Changes in mRNA and protein expressions of Notch signalling in both cell types were also detected using quantitative real-time polymerase chain reaction and Western-blotting analyses. The proliferation, apoptosis and migration of HepG2 cells were detected using Cell Titer 96 AQueous One Solution Cell Proliferation Assay (MTS) (Promega Corporation, Fitchburg, WI, USA), Annexin V-FITC/PI (7SeaPharmTech, Shanghai, China) and the cell scratch assay, respectively. Metformin induced single-cultured RAW264.7 macrophages with an M2 phenotype but attenuated the M2 macrophage differentiation and inhibited monocyte chemoattractant protein-1 (MCP-1) secretion in a co-culture system. The co-cultured group of metformin pretreatment activated Notch signalling in macrophages but repressed it inHepG2 cells. Co-culture also promoted the proliferation and migration of HepG2 cells. However, along with the enhanced apoptosis, the proliferation and the migration of HepG2 cells were remarkably inhibited in another co-culture system with metformin pretreatment. Metformin can skew RAW264.7 macrophages toward different phenotypes according to changes in the microenvironment, which may affect the inflammatory conditions mediated by macrophages, induce apoptosis and inhibit the proliferation and migration of HepG2

  15. Controllable optical bistability and multistability in a graphene monolayer system

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Duo, E-mail: zhangduo10@126.com [School of Electrical and Electronic Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Sun, Zhaoyu [School of Electrical and Electronic Engineering, Wuhan Polytechnic University, Wuhan 430023 (China); Ding, Chunling [School of Physics and Electronics, Henan University, Kaifeng 475004 (China); Yu, Rong [School of Science, Hubei Province Key Laboratory of Intelligent Robot, Wuhan Institute of Technology, Wuhan 430073 (China); Yang, Xiaoxue [Wuhan National Laboratory for Optoelectronics and School of Physics, Huazhong University of Science and Technology, Wuhan 430074 (China)

    2016-02-15

    We theoretically investigate the behavior of optical bistability (OB) and optical multistability (OM) in a graphene monolayer system driven by an elliptically polarized control field and a right-hand circularly polarized probe field. Our numerical results show that it is easy to realize the transition from OB to OM or vice versa by adjusting the frequency detunings of the probe field and the control field, as well as the polarization-dependent phase difference between the two components of the control laser field. The influences of the intensity of the control field and the cooperation parameter on the OB behavior are also discussed in detail. These results may provide some new possibilities for technological applications in optoelectronics and solid-state quantum information science.

  16. Monolayer collapse regulating process of adsorption-desorption of palladium nanoparticles at fatty acid monolayers at the air-water interface.

    Science.gov (United States)

    Goto, Thiago E; Lopez, Ricardo F; Iost, Rodrigo M; Crespilho, Frank N; Caseli, Luciano

    2011-03-15

    In this paper, we investigate the affinity of palladium nanoparticles, stabilized with glucose oxidase, for fatty acid monolayers at the air-water interface, exploiting the interaction between a planar system and spheroids coming from the aqueous subphase. A decrease of the monolayer collapse pressure in the second cycle of interface compression proved that the presence of the nanoparticles causes destabilization of the monolayer in a mechanism driven by the interpenetration of the enzyme into the bilayer/multilayer structure formed during collapse, which is not immediately reversible after monolayer expansion. Surface pressure and surface potential-area isotherms, as well as infrared spectroscopy [polarization modulation infrared reflection adsorption spectroscopy (PM-IRRAS)] and deposition onto solid plates as Langmuir-Blodgett (LB) films, were employed to construct a model in which the nanoparticle has a high affinity for the hydrophobic core of the structure formed after collapse, which provides a slow desorption rate from the interface after monolayer decompression. This may have important consequences on the interaction between the metallic particles and fatty acid monolayers, which implies the regulation of the multifunctional properties of the hybrid material.

  17. Phase transitions in polymer monolayers

    NARCIS (Netherlands)

    Deschênes, Louise; Lyklema, J.; Danis, Claude; Saint-Germain, François

    2015-01-01

    In this paper we investigate the application of the two-dimensional Clapeyron law to polymer monolayers. This is a largely unexplored area of research. The main problems are (1) establishing if equilibrium is reached and (2) if so, identifying and defining phases as functions of the temperature.

  18. The Extracts and Major Compounds Derived from Astragali Radix Alter Mitochondrial Bioenergetics in Cultured Cardiomyocytes: Comparison of Various Polar Solvents and Compounds

    Directory of Open Access Journals (Sweden)

    Yun Huang

    2018-05-01

    Full Text Available Astragali Radix (AR is a widely used “Qi-invigorating” herb in China for its tonic effects in strengthening biological tissues. The extract of AR contains abundant antioxidants, including astragalosides and isoflavonoids. However, very few reports have systematically measured the effects of the major components of AR on cell mitochondrial bioenergetics. Here, a systemic approach employing an extracellular flux analyzer was developed to evaluate mitochondrial respiration in cultured cardiomyocyte cells H9C2. The effects of different polar extractives, as well as of the major compounds of AR, were compared. The contents of astragaloside IV, calycosin, formononetin, and genistein in the AR extracts obtained by using water, 50% ethanol, and 90% ethanol were measured by liquid chromatograph-mass spectrometer (LC–MS. The antioxidant activities of the AR extracts, as well as of their major compounds, were determined by measuring the free radical scavenging activity and protective effects in tert-butyl hydroperoxide (tBHP-treated H9C2 cells. By monitoring the real-time oxygen consumption rate (OCR in tBHP-treated cardiomyocytes with a Seahorse extracellular flux analyzer, the tonic effects of the AR extracts and of their main compounds on mitochondrial bioenergetics were evaluated. AR water extracts possessed the strongest antioxidant activity and protective effects in cardiomyocytes exposed to oxidative stress. The protection was proposed to be mediated via increasing the spare respiratory capacity and mitochondrial ATP production in the stressed cells. The major compounds of AR, astragaloside IV and genistein, showed opposite effects in regulating mitochondrial bioenergetics. These results demonstrate that highly polar extracts of AR, especially astragaloside-enriched extracts, possess better tonic effects on mitochondrial bioenergetics of cultured cardiomyocytes than extracts with a lower polarity.

  19. Electronic and magnetic properties of SnS2 monolayer doped with non-magnetic elements

    Science.gov (United States)

    Xiao, Wen-Zhi; Xiao, Gang; Rong, Qing-Yan; Wang, Ling-Ling

    2018-05-01

    We performed a systematic study of the electronic structures and magnetic properties of SnS2 monolayer doped with non-magnetic elements in groups IA, IIA and IIIA based on the first-principles methods. The doped systems exhibit half-metallic and metallic natures depending on the doping elements. The formation of magnetic moment is attributable to the cooperative effect of the Hund's rule coupling and hole concentration. The spin polarization can be stabilized and enhanced through confining the delocalized impurity states by biaxial tensile strain in hole-doped SnS2 monolayer. Both the double-exchange and p-p exchange mechanisms are simultaneously responsible for the ferromagnetic ground state in those hole-doped materials. Our results demonstrate that spin polarization can be induced and controlled in SnS2 monolayers by non-magnetic doping and tensile strain.

  20. Polarized neutrons

    International Nuclear Information System (INIS)

    Williams, W.G.

    1988-01-01

    The book on 'polarized neutrons' is intended to inform researchers in condensed matter physics and chemistry of the diversity of scientific problems that can be investigated using polarized neutron beams. The contents include chapters on:- neutron polarizers and instrumentation, polarized neutron scattering, neutron polarization analysis experiments and precessing neutron polarization. (U.K.)

  1. Our Polar Past

    Science.gov (United States)

    Clary, Renee; Wandersee, James

    2009-01-01

    The study of polar exploration is fascinating and offers students insights into the history, culture, and politics that affect the developing sciences at the farthest ends of Earth. Therefore, the authors think there is value in incorporating polar exploration accounts within modern science classrooms, and so they conducted research to test their…

  2. Intact penetratin metabolite permeates across Caco-2 monolayers

    DEFF Research Database (Denmark)

    Birch, Ditlev; Christensen, Malene Vinther; Stærk, Dan

    . Previous studies have demonstrated that cell-penetrating peptides (CPPs) may be used as carriers in order to improve the bioavailability of a therapeutic cargo like insulin after oral administration. Penetratin, a commonly used CPP, has been shown to increase the uptake of insulin across Caco-2 cell......-2 cells cultured on permeable filter inserts and in cell lysates, respectively. The epithelial permeation of penetratin and the formed metabolites was assessed by using Caco-2 monolayers cultured on permeable filter inserts. Results Preliminary data revealed that at least one specific metabolite...... is formed upon both intracellular and extracellular degradation of penetratin (figure 1A). Following incubation with epithelium for 4 hours, the metabolite permeated the Caco-2 monolayer and the concentration increased approximately 10-fold when compared to a sample collected following 15 minutes...

  3. Microculture system for studying monolayers of functional beta-cells.

    Science.gov (United States)

    Dobersen, M J; Scharff, J E; Notkins, A L

    1980-04-01

    A method is described for growing monolayers of newborn rat beta-cells in microculture trays. After disruption of the pancreas with collagenase, islets were isolated by Ficoll density gradient centrifugation, trypsinized to obtain individual cells, and plated in 96-well tissue culture trays. The cells were incubated for the first 3 days in growth medium containing 0.1 mM 3-isobutyl-1-methylxanthine to promote monolayer formation. The cultures could be maintained in a functional state, as defined by their responsiveness to known modulators of insulin secretion, for at least 2 weeks. As few as 1 X 10(3) islet cells/well gave results that were reproducible within +/- 10%. It is suggested that the microculture system for islet cells might prove to be a rapid and reproducible screening technique for studying drugs, viruses, or other agents that affect beta-cell function.

  4. Monolayer atomic crystal molecular superlattices

    Science.gov (United States)

    Wang, Chen; He, Qiyuan; Halim, Udayabagya; Liu, Yuanyue; Zhu, Enbo; Lin, Zhaoyang; Xiao, Hai; Duan, Xidong; Feng, Ziying; Cheng, Rui; Weiss, Nathan O.; Ye, Guojun; Huang, Yun-Chiao; Wu, Hao; Cheng, Hung-Chieh; Shakir, Imran; Liao, Lei; Chen, Xianhui; Goddard, William A., III; Huang, Yu; Duan, Xiangfeng

    2018-03-01

    Artificial superlattices, based on van der Waals heterostructures of two-dimensional atomic crystals such as graphene or molybdenum disulfide, offer technological opportunities beyond the reach of existing materials. Typical strategies for creating such artificial superlattices rely on arduous layer-by-layer exfoliation and restacking, with limited yield and reproducibility. The bottom-up approach of using chemical-vapour deposition produces high-quality heterostructures but becomes increasingly difficult for high-order superlattices. The intercalation of selected two-dimensional atomic crystals with alkali metal ions offers an alternative way to superlattice structures, but these usually have poor stability and seriously altered electronic properties. Here we report an electrochemical molecular intercalation approach to a new class of stable superlattices in which monolayer atomic crystals alternate with molecular layers. Using black phosphorus as a model system, we show that intercalation with cetyl-trimethylammonium bromide produces monolayer phosphorene molecular superlattices in which the interlayer distance is more than double that in black phosphorus, effectively isolating the phosphorene monolayers. Electrical transport studies of transistors fabricated from the monolayer phosphorene molecular superlattice show an on/off current ratio exceeding 107, along with excellent mobility and superior stability. We further show that several different two-dimensional atomic crystals, such as molybdenum disulfide and tungsten diselenide, can be intercalated with quaternary ammonium molecules of varying sizes and symmetries to produce a broad class of superlattices with tailored molecular structures, interlayer distances, phase compositions, electronic and optical properties. These studies define a versatile material platform for fundamental studies and potential technological applications.

  5. Effect of single vacancy on the structural, electronic structure and magnetic properties of monolayer graphyne by first-principles

    Energy Technology Data Exchange (ETDEWEB)

    Yun, Jiangni, E-mail: niniyun@nwu.edu.cn; Zhang, Yanni; Xu, Manzhang; Wang, Keyun; Zhang, Zhiyong

    2016-10-01

    The effect of single vacancy on the structural, electronic and magnetic properties of monolayer graphyne is investigated by the first-principles calculations. The calculated results reveal that single vacancy can result in the spin polarization in monolayer graphyne and the spin polarization is sensitive to local geometric structure of the vacancy. In the case of monolayer graphyne with one single vacancy at the sp{sup 2} hybridized C site, the vacancy introduces rather weakly spin-polarized, flat bands in the band gap. Due to the localization nature of the defect-induced bands, the magnetic moment is mainly localized at the vacancy site. As for the monolayer graphyne with one single vacancy at the sp hybridized C site, one defect-induced state which is highly split appears in the band gap. The spin-up band of the defect-induced state is highly dispersive and shows considerable delocalization, suggesting that the magnetic moment is dispersed around the vacancy site. The above magnetization in monolayer graphyne with one single vacancy is possibly explained in terms of the valence-bond theory. - Graphical abstract: Calculated band structure of the monolayer graphyne without (a) and with one single vacancy at Vb site (b) and at Vr site(c), respectively. Blue and red lines represent the spin-up and spin-down bands, respectively. For the sake of clarity, the band structure near the Fermi energy is also presented on the right panel. The Fermi level is set to zero on the energy scale. - Highlights: • A Jahn-Teller distortion occurs in monolayer graphyne with single vacancy. • The spin polarization is sensitive to local geometric structure of the vacancy. • Vacancy lying at sp{sup 2} hybridized C site introduces weakly spin-polarized defect bands. • A strong spin splitting occurs when the vacancy lies at sp hybridized C site. • The magnetization is explained in terms of the valence-bond theory.

  6. Functional properties of hepatocytes in vitro are correlated with cell polarity maintenance.

    Science.gov (United States)

    Zeigerer, Anja; Wuttke, Anne; Marsico, Giovanni; Seifert, Sarah; Kalaidzidis, Yannis; Zerial, Marino

    2017-01-01

    Exploring the cell biology of hepatocytes in vitro could be a powerful strategy to dissect the molecular mechanisms underlying the structure and function of the liver in vivo. However, this approach relies on appropriate in vitro cell culture systems that can recapitulate the cell biological and metabolic features of the hepatocytes in the liver whilst being accessible to experimental manipulations. Here, we adapted protocols for high-resolution fluorescence microscopy and quantitative image analysis to compare two primary hepatocyte culture systems, monolayer and collagen sandwich, with respect to the distribution of two distinct populations of early endosomes (APPL1 and EEA1-positive), endocytic capacity, metabolic and signaling activities. In addition to the re-acquisition of hepatocellular polarity, primary hepatocytes grown in collagen sandwich but not in monolayer culture recapitulated the apico-basal distribution of EEA1 endosomes observed in liver tissue. We found that such distribution correlated with the organization of the actin cytoskeleton in vitro and, surprisingly, was dependent on the nutritional state in vivo. Hepatocytes in collagen sandwich also exhibited faster kinetics of low-density lipoprotein (LDL) and epidermal growth factor (EGF) internalization, showed improved insulin sensitivity and preserved their ability for glucose production, compared to hepatocytes in monolayer cultures. Although no in vitro culture system can reproduce the exquisite structural features of liver tissue, our data nevertheless highlight the ability of the collagen sandwich system to recapitulate key structural and functional properties of the hepatocytes in the liver and, therefore, support the usage of this system to study aspects of hepatocellular biology in vitro. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  7. Effect of surface charge of immortalized mouse cerebral endothelial cell monolayer on transport of charged solutes.

    Science.gov (United States)

    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.

  8. Conformations and orientations of a signal peptide interacting with phospholipid monolayers

    International Nuclear Information System (INIS)

    Cornell, D.G.; Dluhy, R.A.; Briggs, M.S.; McKnight, C.J.; Gierasch, L.M.

    1989-01-01

    The interaction of a chemically synthesized 25-residue signal peptide of LamB protein from Escherichia coli with phospholipids has been studied with a film balance technique. The conformation, orientation, and concentration of the peptides in lipid monolayers have been determined from polarized infrared spectroscopy, ultraviolet spectroscopy, and assay of 14 C-labeled peptide in transferred films. When the LamB signal peptide in injected into the subphase under a phosphatidylethanolamine-phosphatidylglycerol monolayer at low initial pressure, insertion of a portion of the peptide into the lipid film is evidenced by a rapid rise in film pressure. Spectroscopic results obtained on films transferred to quartz plates and Ge crystals show that the peptide is a mixture of α-helix and β-conformation where the long axis of the α-helix penetrates the monolayer plane and the β-structure which is coplanar with the film. By contrast, when peptide is injected under lipid at high initial pressure, no pressure rise is observed, and the spectroscopic results show the presence of only β-structure which is coplanar with the monolayer. The spectroscopic and radioassay results are all consistent with the picture of a peptide anchored to the monolayer through electrostatic binding with a helical portion inserted into the lipid region of the monolayer and a β-structure portion resident in the aqueous phase. The negative charges on the lipid molecules are roughly neutralized by the positive charges of the peptide

  9. Culture.

    Science.gov (United States)

    Smith, Timothy B; Rodríguez, Melanie Domenech; Bernal, Guillermo

    2011-02-01

    This article summarizes the definitions, means, and research of adapting psychotherapy to clients' cultural backgrounds. We begin by reviewing the prevailing definitions of cultural adaptation and providing a clinical example. We present an original meta-analysis of 65 experimental and quasi-experimental studies involving 8,620 participants. The omnibus effect size of d = .46 indicates that treatments specifically adapted for clients of color were moderately more effective with that clientele than traditional treatments. The most effective treatments tended to be those with greater numbers of cultural adaptations. Mental health services targeted to a specific cultural group were several times more effective than those provided to clients from a variety of cultural backgrounds. We recommend a series of research-supported therapeutic practices that account for clients' culture, with culture-specific treatments being more effective than generally culture-sensitive treatments. © 2010 Wiley Periodicals, Inc.

  10. Piezoelectric effect in chemical vapour deposition-grown atomic-monolayer triangular molybdenum disulfide piezotronics

    Science.gov (United States)

    Qi, Junjie; Lan, Yann-Wen; Stieg, Adam Z.; Chen, Jyun-Hong; Zhong, Yuan-Liang; Li, Lain-Jong; Chen, Chii-Dong; Zhang, Yue; Wang, Kang L.

    2015-01-01

    High-performance piezoelectricity in monolayer semiconducting transition metal dichalcogenides is highly desirable for the development of nanosensors, piezotronics and photo-piezotransistors. Here we report the experimental study of the theoretically predicted piezoelectric effect in triangle monolayer MoS2 devices under isotropic mechanical deformation. The experimental observation indicates that the conductivity of MoS2 devices can be actively modulated by the piezoelectric charge polarization-induced built-in electric field under strain variation. These polarization charges alter the Schottky barrier height on both contacts, resulting in a barrier height increase with increasing compressive strain and decrease with increasing tensile strain. The underlying mechanism of strain-induced in-plane charge polarization is proposed and discussed using energy band diagrams. In addition, a new type of MoS2 strain/force sensor built using a monolayer MoS2 triangle is also demonstrated. Our results provide evidence for strain-gating monolayer MoS2 piezotronics, a promising avenue for achieving augmented functionalities in next-generation electronic and mechanical–electronic nanodevices. PMID:26109177

  11. Piezoelectric effect in chemical vapour deposition-grown atomic-monolayer triangular molybdenum disulfide piezotronics

    KAUST Repository

    Qi, Junjie

    2015-06-25

    High-performance piezoelectricity in monolayer semiconducting transition metal dichalcogenides is highly desirable for the development of nanosensors, piezotronics and photo-piezotransistors. Here we report the experimental study of the theoretically predicted piezoelectric effect in triangle monolayer MoS2 devices under isotropic mechanical deformation. The experimental observation indicates that the conductivity of MoS2 devices can be actively modulated by the piezoelectric charge polarization-induced built-in electric field under strain variation. These polarization charges alter the Schottky barrier height on both contacts, resulting in a barrier height increase with increasing compressive strain and decrease with increasing tensile strain. The underlying mechanism of strain-induced in-plane charge polarization is proposed and discussed using energy band diagrams. In addition, a new type of MoS2 strain/force sensor built using a monolayer MoS2 triangle is also demonstrated. Our results provide evidence for strain-gating monolayer MoS2 piezotronics, a promising avenue for achieving augmented functionalities in next-generation electronic and mechanical–electronic nanodevices.

  12. NO2 decreases paracellular resistance to ion and solute flow in alveolar epithelial monolayers

    International Nuclear Information System (INIS)

    Cheek, J.M.; Kim, K.J.; Crandall, E.D.

    1990-01-01

    Primary cultured monolayers of rat alveolar epithelial cells grown on tissue culture-treated Nuclepore filters were exposed to 2.5 ppm nitrogen dioxide NO 2 for 2-20 min. Changes in monolayer bioelectric properties and solute permeabilities were subsequently measured. Exposure to NO 2 produced a dose-dependent decrease in monolayer transepithelial electrical resistance (Rt), whereas monolayer short-circuit current was unaffected. Post-exposure monolayer permeability to 14 C-sucrose (which primarily crosses alveolar epithelium via the paracellular pathway) increased markedly. That for 3 H-glycerol (which permeates through both paracellular and transcellular pathways) increased to a lesser extent. Partial recovery of Rt and solute permeabilities was noted by 48-h post-exposure. The time courses of the decrease in Rt and increase in solute permeabilities were similar. These results suggest that NO 2 primarily impairs passive alveolar epithelial barrier functions in vitro, probably by altering intercellular junctions, and does not appear to directly affect cell membrane active ion transport processes. When correlated with results obtained from experimental approaches, studies of in vitro alveolar epithelial monolayers may facilitate investigations of dosimetry, sites, and mechanisms of oxidant injury in the lung

  13. Packing of ganglioside-phospholipid monolayers

    DEFF Research Database (Denmark)

    Majewski, J.; Kuhl, T.L.; Kjær, K.

    2001-01-01

    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, and the phospholipid...... 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...

  14. Structure and shear response of lipid monolayers

    International Nuclear Information System (INIS)

    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

  15. Lateral pressure profiles in lipid monolayers

    NARCIS (Netherlands)

    Baoukina, Svetlana; Marrink, Siewert J.; Tieleman, D. Peter

    2010-01-01

    We have used molecular dynamics simulations with coarse-grained and atomistic models to study the lateral pressure profiles in lipid monolayers. We first consider simple oil/air and oil/water interfaces, and then proceed to lipid monolayers at air/water and oil/water interfaces. The results are

  16. Self-renewing Monolayer of Primary Colonic or Rectal Epithelial CellsSummary

    Directory of Open Access Journals (Sweden)

    Yuli Wang

    2017-07-01

    Full Text Available Background & Aims: Three-dimensional organoid culture has fundamentally changed the in vitro study of intestinal biology enabling novel assays; however, its use is limited because of an inaccessible luminal compartment and challenges to data gathering in a three-dimensional hydrogel matrix. Long-lived, self-renewing 2-dimensional (2-D tissue cultured from primary colon cells has not been accomplished. Methods: The surface matrix and chemical factors that sustain 2-D mouse colonic and human rectal epithelial cell monolayers with cell repertoires comparable to that in vivo were identified. Results: The monolayers formed organoids or colonoids when placed in standard Matrigel culture. As with the colonoids, the monolayers exhibited compartmentalization of proliferative and differentiated cells, with proliferative cells located near the peripheral edges of growing monolayers and differentiated cells predominated in the central regions. Screening of 77 dietary compounds and metabolites revealed altered proliferation or differentiation of the murine colonic epithelium. When exposed to a subset of the compound library, murine organoids exhibited similar responses to that of the monolayer but with differences that were likely attributable to the inaccessible organoid lumen. The response of the human primary epithelium to a compound subset was distinct from that of both the murine primary epithelium and human tumor cells. Conclusions: This study demonstrates that a self-renewing 2-D murine and human monolayer derived from primary cells can serve as a physiologically relevant assay system for study of stem cell renewal and differentiation and for compound screening. The platform holds transformative potential for personalized and precision medicine and can be applied to emerging areas of disease modeling and microbiome studies. Keywords: Colonic Epithelial Cells, Monolayer, Organoids, Compound Screening

  17. Calculated electronic structure of chromium surfaces and chromium monolayers on iron

    International Nuclear Information System (INIS)

    Victora, R.H.; Falicov, L.M.

    1985-01-01

    A self-consistent calculation of the magnetic and electronic properties of the chromium (100) and (110) surfaces and of a chromium monolayer on the (100) and (110) iron surfaces is presented. It is found that (i) the (100) chromium surface is ferromagnetic with a greatly enhanced spin polarization (3.00 electrons); (ii) a substantial enhancement of the spin imbalance exists several (>5) layers into the bulk; (iii) the (110) chromium surface is antiferromagnetic with a large (2.31) spin imbalance; (iv) the (100) chromium monolayer on ferromagnetic iron is ferromagnetic, with a huge spin imbalance (3.63), and aligned antiferromagnetically with respect to the bulk iron; (v) the (110) chromium monolayer on ferromagnetic iron is also ferromagnetic, with a spin imbalance of 2.25 and antiferromagnetically aligned to the iron. The spin imbalance of chromium on iron (100) is possibly the largest of any transition-metal system

  18. Vapor-transport growth of high optical quality WSe2 monolayers

    Directory of Open Access Journals (Sweden)

    Genevieve Clark

    2014-10-01

    Full Text Available Monolayer transition metal dichalcogenides are atomically thin direct-gap semiconductors that show a variety of novel electronic and optical properties with an optically accessible valley degree of freedom. While they are ideal materials for developing optical-driven valleytronics, the restrictions of exfoliated samples have limited exploration of their potential. Here, we present a physical vapor transport growth method for triangular WSe2 sheets of up to 30 μm in edge length on insulating SiO2 substrates. Characterization using atomic force microscopy and optical microscopy reveals that they are uniform, monolayer crystals. Low temperature photoluminescence shows well resolved and electrically tunable excitonic features similar to those in exfoliated samples, with substantial valley polarization and valley coherence. The monolayers grown using this method are therefore of high enough optical quality for routine use in the investigation of optoelectronics and valleytronics.

  19. Preparation and Photoluminescence of Tungsten Disulfide Monolayer

    Directory of Open Access Journals (Sweden)

    Yanfei Lv

    2018-05-01

    Full Text Available Tungsten disulfide (WS2 monolayer is a direct band gap semiconductor. The growth of WS2 monolayer hinders the progress of its investigation. In this paper, we prepared the WS2 monolayer through chemical vapor transport deposition. This method makes it easier for the growth of WS2 monolayer through the heterogeneous nucleation-and-growth process. The crystal defects introduced by the heterogeneous nucleation could promote the photoluminescence (PL emission. We observed the strong photoluminescence emission in the WS2 monolayer, as well as thermal quenching, and the PL energy redshift as the temperature increases. We attribute the thermal quenching to the energy or charge transfer of the excitons. The redshift is related to the dipole moment of WS2.

  20. Vanadium impurity effects on optical properties of Ti3N2 mono-layer: An ab-initio study

    Directory of Open Access Journals (Sweden)

    Manuchehr Babaeipour

    2018-06-01

    Full Text Available The present work is investigated the effect of vanadium impurity on electronic and optical properties of Ti3N2 monolayer by using density function theory (DFT implemented in Wien2k code. In order to study optical properties in two polarization directions of photons, namely E||x and E||z, dielectric function, absorption coefficient, optical conductivity, refraction index, extinction index, reflectivity, and energy loss function of Ti3N2 and Ti3N2-V monolayer have been evaluated within GGA (PBE approximation. Although, Ti3N2 monolayer is a good infrared reflector and can be used as an infrared mirror, introducing V atom in the infrared area will decrease optical conductivity because optical conductivity of a pure form of a material is higher than its doped form. Keywords: Dielectric function, Optical conductivity, DFT, Ti3N2: V mono-layer

  1. First-principle study of single TM atoms X (X=Fe, Ru or Os) doped monolayer WS2 systems

    Science.gov (United States)

    Zhu, Yuan-Yan; Zhang, Jian-Min

    2018-05-01

    We report the structural, magnetic and electronic properties of the pristine and single TM atoms X (X = Fe, Ru or Os) doped monolayer WS2 systems based on first-principle calculations. The results show that the W-S bond shows a stronger covalent bond, but the covalency is obviously weakened after the substitution of W atom with single X atoms, especially for Ru (4d75s1) with the easily lost electronic configuration. The smaller total energies of the doped systems reveal that the spin-polarized states are energetically favorable than the non-spin-polarized states, and the smallest total energy of -373.918 eV shows the spin-polarized state of the Os doped monolayer WS2 system is most stable among three doped systems. In addition, although the pristine monolayer WS2 system is a nonmagnetic-semiconductor with a direct band gap of 1.813 eV, single TM atoms Fe and Ru doped monolayer WS2 systems transfer to magnetic-HM with the total moments Mtot of 1.993 and 1.962 μB , while single TM atom Os doped monolayer WS2 systems changes to magnetic-metal with the total moments Mtot of 1.569 μB . Moreover, the impurity states with a positive spin splitting energies of 0.543, 0.276 and 0.1999 eV near the Fermi level EF are mainly contributed by X-dxy and X-dx2-y2 states hybridized with its nearest-neighbor atom W-dz2 states for Fe, Ru and Os doped monolayer WS2 system, respectively. Finally, we hope that the present study on monolayer WS2 will provide a useful theoretical guideline for exploring low-dimensional spintronic materials in future experiments.

  2. X-Ray Reflectometry of DMPS Monolayers on a Water Substrate

    Science.gov (United States)

    Tikhonov, A. M.; Asadchikov, V. E.; Volkov, Yu. O.; Roshchin, B. S.; Ermakov, Yu. A.

    2017-12-01

    The molecular structure of dimyristoyl phosphatidylserine (DMPS) monolayers on a water substrate in different phase states has been investigated by X-ray reflectometry with a photon energy of 8 keV. According to the experimental data, the transition from a two-dimensional expanded liquid state to a solid gel state (liquid crystal) accompanied by the ordering of the hydrocarbon tails C14H27 of the DMPS molecule occurs in the monolayer as the surface pressure rises. The monolayer thickness is 20 ± 3 and 28 ± 2 Å in the liquid and solid phases, respectively, with the deflection angle of the molecular tail axis from the normal to the surface in the gel phase being 26° ± 8°. At least a twofold decrease in the degree of hydration of the polar lipid groups also occurs under two-dimensional monolayer compression. The reflectometry data have been analyzed using two approaches: under the assumption about the presence of two layers with different electron densities in the monolayer and without any assumptions about the transverse surface structure. Both approaches demonstrate satisfactory agreement between themselves in describing the experimental results.

  3. Comparison of electronic structure between monolayer silicenes on Ag (111)

    Science.gov (United States)

    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. Ultrafast generation of pseudo-magnetic field for valley excitons in WSe2 monolayers

    KAUST Repository

    Kim, J.

    2014-12-04

    The valley pseudospin is a degree of freedom that emerges in atomically thin two-dimensional transition metal dichalcogenides (MX2). The capability to manipulate it, in analogy to the control of spin in spintronics, can open up exciting opportunities. Here, we demonstrate that an ultrafast and ultrahigh valley pseudo-magnetic field can be generated by using circularly polarized femtosecond pulses to selectively control the valley degree of freedom in monolayer MX2. Using ultrafast pump-probe spectroscopy, we observed a pure and valley-selective optical Stark effect in WSe2 monolayers from the nonresonant pump, resulting in an energy splitting of more than 10 milli-electron volts between the K and K′ valley exciton transitions. Our study opens up the possibility to coherently manipulate the valley polarization for quantum information applications.

  5. Ultrafast generation of pseudo-magnetic field for valley excitons in WSe2 monolayers

    KAUST Repository

    Kim, J.; Hong, X.; Jin, C.; Shi, S.-F.; Chang, C.-Y. S.; Chiu, Ming-Hui; Li, Lain-Jong; Wang, F.

    2014-01-01

    The valley pseudospin is a degree of freedom that emerges in atomically thin two-dimensional transition metal dichalcogenides (MX2). The capability to manipulate it, in analogy to the control of spin in spintronics, can open up exciting opportunities. Here, we demonstrate that an ultrafast and ultrahigh valley pseudo-magnetic field can be generated by using circularly polarized femtosecond pulses to selectively control the valley degree of freedom in monolayer MX2. Using ultrafast pump-probe spectroscopy, we observed a pure and valley-selective optical Stark effect in WSe2 monolayers from the nonresonant pump, resulting in an energy splitting of more than 10 milli-electron volts between the K and K′ valley exciton transitions. Our study opens up the possibility to coherently manipulate the valley polarization for quantum information applications.

  6. Extended Moment Formation in Monolayer WS2 Doped with 3d Transition-Metals

    KAUST Repository

    Singh, Nirpendra

    2016-08-30

    First-principles calculations with onsite Coulomb interaction and spin-orbit coupling are used to investigate the electronic structure of monolayer WS2 doped substitutionally with 3d transition-metals. While neither W vacancies nor strain induce spin polarization, we demonstrate an unprecedented tendency to extended moment formation under doping. The extended magnetic moments are characterized by dopant-specific spin density patterns with rich structural features involving the nearest neighbor W and S atoms.

  7. Tunable thermoelectricity in monolayers of MoS2 and other group-VI dichalcogenides

    KAUST Repository

    Tahir, M

    2014-10-31

    We study the thermoelectric properties of monolayers of MoS2 and other group-VI dichalcogenides under circularly polarized off-resonant light. Analytical expressions are derived for the Berry phase mediated magnetic moment, orbital magnetization, as well as thermal and Nernst conductivities. Tuning of the band gap by off-resonant light enhances the spin splitting in both the valence and conduction bands and, thus, leads to a dramatic improvement of the spin and valley thermoelectric properties.

  8. Excitation of the shear horizontal mode in a monolayer by inelastic helium atom scattering

    DEFF Research Database (Denmark)

    Bruch, L. W.; Hansen, Flemming Yssing

    2005-01-01

    Inelastic scattering of a low-energy atomic helium beam (HAS) by a physisorbed monolayer is treated in the one-phonon approximation using a time-dependent wave,packet formulation. The calculations show that modes with shear horizontal polarization can be excited near high symmetry azimuths....... The diffraction and inelastic processes arise from a strong coupling of the incident atom to the target and the calculated results show large departures from expectations based on analogies to inelastic thermal neutron scattering....

  9. Tunable thermoelectricity in monolayers of MoS2 and other group-VI dichalcogenides

    KAUST Repository

    Tahir, M; Schwingenschlö gl, Udo

    2014-01-01

    We study the thermoelectric properties of monolayers of MoS2 and other group-VI dichalcogenides under circularly polarized off-resonant light. Analytical expressions are derived for the Berry phase mediated magnetic moment, orbital magnetization, as well as thermal and Nernst conductivities. Tuning of the band gap by off-resonant light enhances the spin splitting in both the valence and conduction bands and, thus, leads to a dramatic improvement of the spin and valley thermoelectric properties.

  10. Low temperature carrier transport study of monolayer MoS{sub 2} field effect transistors prepared by chemical vapor deposition under an atmospheric pressure

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xinke, E-mail: xkliu@szu.edu.cn, E-mail: wujing026@gmail.com; He, Jiazhu; Tang, Dan; Lu, Youming; Zhu, Deliang; Liu, Wenjun; Cao, Peijiang; Han, Sun [College of Materials Science and Engineering, Shenzhen Engineering Laboratory for Advanced Technology of Ceramics, Nanshan District Key Lab for Biopolymer and Safety Evaluation, Shenzhen University, 3688 Nanhai Ave, Shenzhen 518060 (China); Liu, Qiang; Wen, Jiao; Yu, Wenjie [State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, CAS, 865 Chang Ning Road, Shanghai 200050 (China); Liu, Wenjun [State Key Laboratory of ASIC and System, Department of Microelectronics, Fudan University, 220 Handan Road, Shanghai 200433 (China); Wu, Jing, E-mail: xkliu@szu.edu.cn, E-mail: wujing026@gmail.com [Department of Physics, National University of Singapore, 21 Lower Kent Ridge Road, 117576 Singapore (Singapore); He, Zhubing [Department of Materials Science and Engineering, South University of Science and Technology of China, 1088 Xueyuan Road, Shenzhen 518055 (China); Ang, Kah-Wee [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, 117583 Singapore (Singapore)

    2015-09-28

    Large size monolayer Molybdenum disulphide (MoS{sub 2}) was successfully grown by chemical vapor deposition method under an atmospheric pressure. The electrical transport properties of the fabricated back-gate monolayer MoS{sub 2} field effect transistors (FETs) were investigated under low temperatures; a peak field effect mobility of 59 cm{sup 2}V{sup −1}s{sup −1} was achieved. With the assist of Raman measurement under low temperature, this work identified the mobility limiting factor for the monolayer MoS{sub 2} FETs: homopolar phonon scattering under low temperature and electron-polar optical phonon scattering at room temperature.

  11. Large Friction Anisotropy of a Polydiacetylene Monolayer

    International Nuclear Information System (INIS)

    Burns, A.R.; Carpick, R.W.; Sasaki, D.Y.

    1999-01-01

    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

  12. Molecular diffusion in monolayer and submonolayer nitrogen

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Bruch, Ludwig Walter

    2001-01-01

    The orientational and translational motions in a monolayer fluid of physisorbed molecular nitrogen are treated using molecular dynamics simulations. Dynamical response functions and several approximations to the coefficient of translational diffusion are determined for adsorption on the basal plane...

  13. Dark excitations in monolayer transition metal dichalcogenides

    DEFF Research Database (Denmark)

    Deilmann, Thorsten; Thygesen, Kristian Sommer

    2017-01-01

    Monolayers of transition metal dichalcogenides (TMDCs) possess unique optoelectronic properties, including strongly bound excitons and trions. To date, most studies have focused on optically active excitations, but recent experiments have highlighted the existence of dark states, which are equally...

  14. Method to synthesize metal chalcogenide monolayer nanomaterials

    Science.gov (United States)

    Hernandez-Sanchez, Bernadette A.; Boyle, Timothy J.

    2016-12-13

    Metal chalcogenide monolayer nanomaterials can be synthesized from metal alkoxide precursors by solution precipitation or solvothermal processing. The synthesis routes are more scalable, less complex and easier to implement than other synthesis routes.

  15. Janus Monolayer Transition-Metal Dichalcogenides.

    Science.gov (United States)

    Zhang, Jing; Jia, Shuai; Kholmanov, Iskandar; Dong, Liang; Er, Dequan; Chen, Weibing; Guo, Hua; Jin, Zehua; Shenoy, Vivek B; Shi, Li; Lou, Jun

    2017-08-22

    The crystal configuration of sandwiched S-Mo-Se structure (Janus SMoSe) at the monolayer limit has been synthesized and carefully characterized in this work. By controlled sulfurization of monolayer MoSe 2 , the top layer of selenium atoms is substituted by sulfur atoms, while the bottom selenium layer remains intact. The structure of this material is systematically investigated by Raman, photoluminescence, transmission electron microscopy, and X-ray photoelectron spectroscopy and confirmed by time-of-flight secondary ion mass spectrometry. Density functional theory (DFT) calculations are performed to better understand the Raman vibration modes and electronic structures of the Janus SMoSe monolayer, which are found to correlate well with corresponding experimental results. Finally, high basal plane hydrogen evolution reaction activity is discovered for the Janus monolayer, and DFT calculation implies that the activity originates from the synergistic effect of the intrinsic defects and structural strain inherent in the Janus structure.

  16. Nanotubes based on monolayer blue phosphorus

    KAUST Repository

    Montes Muñ oz, Enrique; Schwingenschlö gl, Udo

    2016-01-01

    We demonstrate structural stability of monolayer zigzag and armchair blue phosphorus nanotubes by means of molecular dynamics simulations. The vibrational spectrum and electronic band structure are determined and analyzed as functions of the tube

  17. Transepithelial transport of flavanone in intestinal Caco-2 cell monolayers

    International Nuclear Information System (INIS)

    Kobayashi, Shoko; Konishi, Yutaka

    2008-01-01

    Our recent study [S. Kobayashi, S. Tanabe, M. Sugiyama, Y. Konishi, Transepithelial transport of hesperetin and hesperidin in intestinal Caco-2 cell monolayers, Biochim. Biophys. Acta, 1778 (2008) 33-41] shows that the mechanism of absorption of hesperetin involves both proton-coupled active transport and transcellular passive diffusion. Here, as well as analyzing the cell permeability of hesperetin, we also study the transport of other flavanones, naringenin and eriodictyol, using Caco-2 cell monolayers. Similar to hesperetin mentioned, naringenin and eriodictyol showed proton-coupled polarized transport in apical-to-basolateral direction in non-saturable manner, constant permeation in the apical-to-basolateral direction (J ap→bl ) irrespective of the transepithelial electrical resistance (TER), and preferable distribution into the basolateral side after apical loading in the presence of a proton gradient. Furthermore, the proton-coupled J ap→bl of hesperetin, naringenin and eriodictyol, were inhibited by substrates of the monocarboxylic acid transporter (MCT), such as benzoic acid, but not by ferulic acid. In contrast, both benzoic and ferulic acids have no stimulatory effect on J ap→bl of each flavanone by trans-stimulation analysis. These results indicates that proton-driven active transport is commonly participated in the absorption of flavanone in general, and that its transport is presumed to be unique other than MCT-mediated transport for absorption of phenolic acids (PAs), sodium-dependent MCT (SMCT) nor anion exchanger-mediated transport

  18. Density functional study of CaN monolayer on Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Saati asr, Maryam; Zahedifar, Maedeh; Hashemifar, S. Javad; Akbarzadeh, Hadi

    2016-01-01

    In this work, the first-principles computations are performed to study the structural and magnetic properties of CaN/Si(001) interface. Bulk CaN in the zinc-blende (ZB) structure is argued to be an ionic magnetic compound with a total spin moment of 1 μ{sub B} per formula unit, originated from the p electrons of N ions. Various interface configurations of a ZB CaN monolayer on Si (001) surface are investigated and the lowest energy and the highest spin polarized interfaces are extracted. Then the minimum energy path between the lowest energy and the highest spin polarized interfaces are calculated by using the nudged elastic band method and it is argued that both these systems are unstable toward a nonmagnetic interface with a rock–salt arrangement of Ca and N atoms. - Highlights: • Ab-initio studies are done on various structures of CaN monolayer on Si (001). • The lowest energy system was found to be the N-top configuration interface, while the highest spin polarization was observed in the Ca-hollow termination. • Both Ca-hollow and N-top are unstable toward a nonmagnetic rock–salt CaN monolayer on silicon surface. • Realization of a magnetic CaN/Si (001) interface likely requires some buffer layer on silicon surface, prior to the thin film deposition.

  19. Density functional study of CaN monolayer on Si(001)

    International Nuclear Information System (INIS)

    Saati asr, Maryam; Zahedifar, Maedeh; Hashemifar, S. Javad; Akbarzadeh, Hadi

    2016-01-01

    In this work, the first-principles computations are performed to study the structural and magnetic properties of CaN/Si(001) interface. Bulk CaN in the zinc-blende (ZB) structure is argued to be an ionic magnetic compound with a total spin moment of 1 μ_B per formula unit, originated from the p electrons of N ions. Various interface configurations of a ZB CaN monolayer on Si (001) surface are investigated and the lowest energy and the highest spin polarized interfaces are extracted. Then the minimum energy path between the lowest energy and the highest spin polarized interfaces are calculated by using the nudged elastic band method and it is argued that both these systems are unstable toward a nonmagnetic interface with a rock–salt arrangement of Ca and N atoms. - Highlights: • Ab-initio studies are done on various structures of CaN monolayer on Si (001). • The lowest energy system was found to be the N-top configuration interface, while the highest spin polarization was observed in the Ca-hollow termination. • Both Ca-hollow and N-top are unstable toward a nonmagnetic rock–salt CaN monolayer on silicon surface. • Realization of a magnetic CaN/Si (001) interface likely requires some buffer layer on silicon surface, prior to the thin film deposition.

  20. Polarity in Mammalian Epithelial Morphogenesis

    OpenAIRE

    Roignot, Julie; Peng, Xiao; Mostov, Keith

    2013-01-01

    Cell polarity is fundamental for the architecture and function of epithelial tissues. Epithelial polarization requires the intervention of several fundamental cell processes, whose integration in space and time is only starting to be elucidated. To understand what governs the building of epithelial tissues during development, it is essential to consider the polarization process in the context of the whole tissue. To this end, the development of three-dimensional organotypic cell culture model...

  1. Exciton Binding Energy of Monolayer WS2

    Science.gov (United States)

    Zhu, Bairen; Chen, Xi; Cui, Xiaodong

    2015-03-01

    The optical properties of monolayer transition metal dichalcogenides (TMDC) feature prominent excitonic natures. Here we report an experimental approach to measuring the exciton binding energy of monolayer WS2 with linear differential transmission spectroscopy and two-photon photoluminescence excitation spectroscopy (TP-PLE). TP-PLE measurements show the exciton binding energy of 0.71 +/- 0.01 eV around K valley in the Brillouin zone.

  2. cultural

    Directory of Open Access Journals (Sweden)

    Irene Kreutz

    2006-01-01

    Full Text Available Es un estudio cualitativo que adoptó como referencial teorico-motodológico la antropología y la etnografía. Presenta las experiencias vivenciadas por mujeres de una comunidad en el proceso salud-enfermedad, con el objetivo de comprender los determinantes sócio-culturales e históricos de las prácticas de prevención y tratamiento adoptados por el grupo cultural por medio de la entrevista semi-estructurada. Los temas que emergieron fueron: la relación entre la alimentación y lo proceso salud-enfermedad, las relaciones con el sistema de salud oficial y el proceso salud-enfermedad y lo sobrenatural. Los dados revelaron que los moradores de la comunidad investigada tienen un modo particular de explicar sus procedimientos terapéuticos. Consideramos que es papel de los profesionales de la salud en sus prácticas, la adopción de abordajes o enfoques que consideren al individuo en su dimensión sócio-cultural e histórica, considerando la enorme diversidad cultural en nuestro país.

  3. Tuning the Electronic, Optical, and Magnetic Properties of Monolayer GaSe with a Vertical Electric Field

    Science.gov (United States)

    Ke, Congming; Wu, Yaping; Guo, Guang-Yu; Lin, Wei; Wu, Zhiming; Zhou, Changjie; Kang, Junyong

    2018-04-01

    Inspired by two-dimensional material with their unique physical properties and innovative device applications, here we report a design framework on monolayer GaSe, an important member of the two-dimensional material family, in an effort to tune the electronic, optical, and magnetic properties through a vertical electric field. A transition from indirect to direct band gap in monolayer GaSe is found with an electric field of 0.09 V /Å . The giant Stark effect results in a reduction of the band gap with a Stark coefficient of 3.54 Å. Optical and dielectric properties of monolayer GaSe are dependent on the vertical electric field. A large regulation range for polarization E ∥c ^ is found for the static dielectric constant. The optical anisotropy with the dipole transition from E ∥c ^ to E ⊥c ^ is achieved. Induced by the spin-orbit coupling, spin-splitting energy at the valence band maximum increases linearly with the electric field. The effective mass of holes is highly susceptible to the vertical electric field. Switchable spin-polarization features in spin texture of monolayer GaSe are predicted. The tunable electronic, optical, and magnetic properties of monolayer GaSe hold great promise for applications in both the optoelectronic and spintronic devices.

  4. Study of the interaction of lactoferricin B with phospholipid monolayers and bilayers.

    Science.gov (United States)

    Arseneault, Marjolaine; Bédard, Sarah; Boulet-Audet, Maxime; Pézolet, Michel

    2010-03-02

    Bovine lactoferricin (LfcinB) is an antimicrobial peptide obtained from the pepsin cleavage of lactoferrin. The activity of LfcinB has been extensively studied on diverse pathogens, but its mechanism of action still has to be elucidated. Because of its nonspecificity, its mode of action is assumed to be related to interactions with membranes. In this study, the interaction of LfcinB with a negatively charged monolayer of dipalmitoylphosphatidylglycerol has been investigated as a function of the surface pressure of the lipid film using in situ Brewster angle and polarization modulation infrared reflection absorption spectroscopy and on transferred monolayers by atomic force microscopy and polarized attenuated total reflection infrared spectroscopy. The data show clearly that LfcinB forms stable films at the air-water interface. They also reveal that the interaction of LfcinB with the lipid monolayer is modulated by the surface pressure. At low surface pressure, LfcinB inserts within the lipid film with its long molecular axis oriented mainly parallel to the acyl chains, while at high surface pressure, LfcinB is adsorbed under the lipid film, the hairpin being preferentially aligned parallel to the plane of the interface. The threshold for which the behavior changes is 20 mN/m. At this critical surface pressure, LfcinB interacts with the monolayer to form discoidal lipid-peptide assemblies. This structure may actually represent the mechanism of action of this peptide. The results obtained on monolayers are correlated by fluorescent probe release measurements of dye-containing vesicles made of lipids in different phases and support the important role of the lipid fluidity and packing on the activity of LfcinB.

  5. Polarization developments

    International Nuclear Information System (INIS)

    Prescott, C.Y.

    1993-07-01

    Recent developments in laser-driven photoemission sources of polarized electrons have made prospects for highly polarized electron beams in a future linear collider very promising. This talk discusses the experiences with the SLC polarized electron source, the recent progress with research into gallium arsenide and strained gallium arsenide as a photocathode material, and the suitability of these cathode materials for a future linear collider based on the parameters of the several linear collider designs that exist

  6. Effects of irradiated biodegradable polymer in endothelial cell monolayer formation

    Energy Technology Data Exchange (ETDEWEB)

    Arbeitman, Claudia R.; Grosso, Mariela F. del [CONICET – Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina); Gerencia de Investigación y Aplicaciones, TANDAR-CNEA (Argentina); Behar, Moni [Instituto de Física, UFRGS, Porto Alegre, RS (Brazil); García Bermúdez, Gerardo, E-mail: ggb@tandar.cnea.gov.ar [CONICET – Consejo Nacional de Investigaciones Científicas y Técnicas (Argentina); Gerencia de Investigación y Aplicaciones, TANDAR-CNEA (Argentina); Escuela de Ciencia y Tecnología, UNSAM (Argentina)

    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. Effects of irradiated biodegradable polymer in endothelial cell monolayer formation

    International Nuclear Information System (INIS)

    Arbeitman, Claudia R.; Grosso, Mariela F. del; Behar, Moni; García Bermúdez, Gerardo

    2013-01-01

    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

  8. Regulation of endothelial cell shape and monolayer permeability by atrial natriuretic peptide

    International Nuclear Information System (INIS)

    Lofton-Day, C.E.

    1989-01-01

    Atrial natriuretic peptide (ANP), considered to be an important regulator of intravascular fluid volume, binds specifically to receptors on endothelial cells. In this study, the role of ANP-specific binding was investigated by examining the effect of ANP on the morphology and macromolecular permeability of monolayer cultures of bovine aortic endothelial cells. ANP alone had no observable effect on the monolayers. However, incubation of monolayers with ANP antagonized thrombin- or glucose oxidase-induced cell shape changes and intercellular gap formation. ANP pretreatment also opposed the effect of thrombin and glucose oxidase on actin filament distribution as observed by rhodamine-phalloidin staining and digital image analysis of F0actin staining. In addition, ANP reversed cell shape changes and cytoskeletal alterations induced by thrombin treatment but did not reverse alternations induced by glucose oxidase treatment. ANP significantly reduced increases in monolayer permeability to albumin resulting from thrombin or glucose oxidases treatment. Thrombin caused a 2-fold increase in monolayer permeability to 125 I-labeled albumin, which was abolished by 10 -8 -10 -6 M ANP pretreatment. Glucose oxidase caused similar increases in permeability and was inhibited by ANP at slightly shorter time periods

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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. (paper)

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

    Science.gov (United States)

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

    2014-11-01

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

  11. Neutron polarization

    International Nuclear Information System (INIS)

    Firk, F.W.K.

    1976-01-01

    Some recent experiments involving polarized neutrons are discussed; they demonstrate how polarization studies provide information on fundamental aspects of nuclear structure that cannot be obtained from more traditional neutron studies. Until recently, neutron polarization studies tended to be limited either to very low energies or to restricted regions at higher energies, determined by the kinematics of favorable (p, vector n) and (d, vector n) reactions. With the advent of high intensity pulsed electron and proton accelerators and of beams of vector polarized deuterons, this is no longer the case. One has entered an era in which neutron polarization experiments are now being carried out, in a routine way, throughout the entire range from thermal energies to tens-of-MeV. The significance of neutron polarization studies is illustrated in discussions of a wide variety of experiments that include the measurement of T-invariance in the β-decay of polarized neutrons, a search for the effects of meson exchange currents in the photo-disintegration of the deuteron, the determination of quantum numbers of states in the fission of aligned 235 U and 237 Np induced by polarized neutrons, and the double- and triple-scattering of fast neutrons by light nuclei

  12. Electric field effect of GaAs monolayer from first principles

    Directory of Open Access Journals (Sweden)

    Jiongyao Wu

    2017-03-01

    Full Text Available Using first-principle calculations, we investigate two-dimensional (2D honeycomb monolayer structures composed of group III-V binary elements. It is found that such compound like GaAs should have a buckled structure which is more stable than graphene-like flat structure. This results a polar system with out-of-plane dipoles arising from the non-planar structure. Here, we optimized GaAs monolayer structure, then calculated the electronic band structure and the change of buckling height under external electric field within density functional theory using generalized gradient approximation method. We found that the band gap would change proportionally with the electric field magnitude. When the spin-orbit coupling (SOC is considered, we revealed fine spin-splitting at different points in the reciprocal space. Furthermore, the valence and conduction bands spin-splitting energies due to SOC at the K point of buckled GaAs monolayers are found to be weakly dependent on the electric field strength. Finally electric field effects on the spin texture and second harmonic generation are discussed. The present work sheds light on the control of physical properties of GaAs monolayer by the applied electric field.

  13. Electrically tunable magnetic configuration on vacancy-doped GaSe monolayer

    Science.gov (United States)

    Tang, Weiqing; Ke, Congming; Fu, Mingming; Wu, Yaping; Zhang, Chunmiao; Lin, Wei; Lu, Shiqiang; Wu, Zhiming; Yang, Weihuang; Kang, Junyong

    2018-03-01

    Group-IIIA metal-monochalcogenides with the enticing properties have attracted tremendous attention across various scientific disciplines. With the aim to satisfy the multiple demands of device applications, here we report a design framework on GaSe monolayer in an effort to tune the electronic and magnetic properties through a dual modulation of vacancy doping and electric field. A half-metallicity with a 100% spin polarization is generated in a Ga vacancy doped GaSe monolayer due to the nonbonding 4p electronic orbital of the surrounding Se atoms. The stability of magnetic moment is found to be determined by the direction of applied electric field. A switchable magnetic configuration in Ga vacancy doped GaSe monolayer is achieved under a critical electric field of 0.6 V/Å. Electric field induces redistribution of the electronic states. Finally, charge transfers are found to be responsible for the controllable magnetic structure in this system. The magnetic modulation on GaSe monolayer in this work offers some references for the design and fabrication of tunable two-dimensional spintronic device.

  14. Polarization holography

    DEFF Research Database (Denmark)

    Nikolova, L.; Ramanujam, P.S.

    Current research into holography is concerned with applications in optically storing, retrieving, and processing information. Polarization holography has many unique properties compared to conventional holography. It gives results in high efficiency, achromaticity, and special polarization...... properties. This books reviews the research carried out in this field over the last 15 years. The authors provide basic concepts in polarization and the propagation of light through anisotropic materials, before presenting a sound theoretical basis for polarization holography. The fabrication...... and characterization of azobenzene based materials, which remain the most efficient for the purpose, is described in detail. This is followed by a description of other materials that are used in polarization holography. An in-depth description of various applications, including display holography and optical storage...

  15. Thermal ripples in model molybdenum disulfide monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Remsing, Richard C.; Klein, Michael L. [Institute for Computational Molecular Science, Center for the Computational, Design of Functional Layered Materials, and Department of Chemistry, Temple University, 1925 N. 12th St., 19122, Philadelphia, PA (United States); Waghmare, Umesh V. [Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, 560 064, Jakkur, Bangalore (India)

    2017-01-15

    Molybdenum disulfide (MoS{sub 2}) monolayers have the potential to revolutionize nanotechnology. To reach this potential, it will be necessary to understand the behavior of this two-dimensional (2D) material on large length scales and under thermal conditions. Herein, we use molecular dynamics (MD) simulations to investigate the nature of the rippling induced by thermal fluctuations in monolayers of the 2H and 1T phases of MoS{sub 2}. The 1T phase is found to be more rigid than the 2H phase. Both monolayer phases are predicted to follow long wavelength scaling behavior typical of systems with anharmonic coupling between vibrational modes as predicted by classic theories of membrane-like systems. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Monolayer-by-monolayer growth of platinum films on complex carbon fiber paper structure

    Energy Technology Data Exchange (ETDEWEB)

    Pang, Liuqing; Zhang, Yunxia [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); Liu, Shengzhong, E-mail: szliu@dicp.ac.cn [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Key Laboratory for Advanced Energy Devices, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710119 (China); Dalian National Laboratory for Clean Energy, iChEM, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023 (China)

    2017-06-15

    Graphical abstract: A controlled monolayer-by-monolayer deposition process has been developed to fabricate Pt coating on carbon fiber paper with complex network structures using a dual buffer strategy. This development may pave a way to fabricate superior Pt catalysts with the minimal Pt usage. In fact, the present Pt group metal loading is 25 times lower than the U.S. DOE 2017 target value. - Highlights: • Developed a controlled monolayer-by-monolayer Pt deposition using a dual buffer strategy. • The present Pt group metal loading is 25 times lower than the U.S. DOE 2017 target value. • This development may pave a way to fabricate superior Pt catalysts with the minimal Pt usage. - Abstract: A controlled monolayer-by-monolayer deposition process has been developed to fabricate Pt coating on carbon fiber paper with complex network structures using a dual buffer (Au/Ni) strategy. The X-ray diffraction, electrochemical quartz crystal microbalance, current density analyses, and X-ray photoelectron spectroscopy results conclude that the monolayer deposition process accomplishes full coverage on the substrate and that the thickness of the deposition layer can be controlled on a single atom scale. This development may pave a way to fabricate superior Pt catalysts with the minimal Pt usage. In fact, the present Pt group metal loading is 25 times lower than the U.S. DOE 2017 target value.

  17. Large valley splitting in monolayer WS2 by proximity coupling to an insulating antiferromagnetic substrate

    Science.gov (United States)

    Xu, Lei; Yang, Ming; Shen, Lei; Zhou, Jun; Zhu, Tao; Feng, Yuan Ping

    2018-01-01

    Lifting the valley degeneracy is an efficient way to achieve valley polarization for further valleytronics operations. In this Rapid Communication, we demonstrate that a large valley splitting can be obtained in monolayer transition metal dichalcogenides by magnetic proximity coupling to an insulating antiferromagnetic substrate. As an example, we perform first-principles calculations to investigate the electronic structures of monolayer WS2 on the MnO(111) surface. Our calculation results suggest that a large valley splitting of 214 meV, which corresponds to a Zeeman magnetic field of 1516 T, is induced in the valence band of monolayer WS2. The magnitude of valley splitting relies on the strength of interfacial orbital hybridization and can be tuned continually by applying an external out-of-plane pressure and in-plane strain. More interestingly, we find that both spin and valley index will flip when the magnetic ordering of MnO is reversed. Besides, owing to the sizable Berry curvature and time-reversal symmetry breaking in the WS2/MnO heterostructure, a spin- and valley-polarized anomalous Hall current can be generated in the presence of an in-plane electric field, which allows one to detect valleys by the electrical approach. Our results shed light on the realization of valleytronic devices using the antiferromagnetic insulator as the substrate.

  18. Electrochemical behavior of monolayer and bilayer graphene.

    Science.gov (United States)

    Valota, Anna T; Kinloch, Ian A; Novoselov, Kostya S; Casiraghi, Cinzia; Eckmann, Axel; Hill, Ernie W; Dryfe, Robert A W

    2011-11-22

    Results of a study on the electrochemical properties of exfoliated single and multilayer graphene flakes are presented. Graphene flakes were deposited on silicon/silicon oxide wafers to enable fast and accurate characterization by optical microscopy and Raman spectroscopy. Conductive silver paint and silver wires were used to fabricate contacts; epoxy resin was employed as a masking coating in order to expose a stable, well-defined area of graphene. Both multilayer and monolayer graphene microelectrodes showed quasi-reversible behavior during voltammetric measurements in potassium ferricyanide. However, the standard heterogeneous charge transfer rate constant, k°, was estimated to be higher for monolayer graphene flakes. © 2011 American Chemical Society

  19. Sub-THz Characterisation of Monolayer Graphene

    Directory of Open Access Journals (Sweden)

    Ehsan Dadrasnia

    2014-01-01

    Full Text Available We explore the optical and electrical characteristics of monolayer graphene by using pulsed optoelectronic terahertz time-domain spectroscopy in the frequency range of 325–500 GHz based on fast direct measurements of phase and amplitude. We also show that these parameters can, however, be measured with higher resolution using a free space continuous wave measurement technique associated with a vector network analyzer that offers a good dynamic range. All the scattering parameters (both magnitude and phase are measured simultaneously. The Nicholson-Ross-Weir method is implemented to extract the monolayer graphene parameters at the aforementioned frequency range.

  20. Low temperature photoresponse of monolayer tungsten disulphide

    Directory of Open Access Journals (Sweden)

    Bingchen Cao

    2014-11-01

    Full Text Available High photoresponse can be achieved in monolayers of transition metal dichalcogenides. However, the response times are inconveniently limited by defects. Here, we report low temperature photoresponse of monolayer tungsten disulphide prepared by exfoliation and chemical vapour deposition (CVD method. The exfoliated device exhibits n-type behaviour; while the CVD device exhibits intrinsic behaviour. In off state, the CVD device has four times larger ratio of photoresponse for laser on/off and photoresponse decay–rise times are 0.1 s (limited by our setup, while the exfoliated device has few seconds. These findings are discussed in terms of charge trapping and localization.

  1. Nonlinear optical studies of organic monolayers

    International Nuclear Information System (INIS)

    Shen, Y.R.

    1988-02-01

    Second-order nonlinear optical effects are forbidden in a medium with inversion symmetry, but are necessarily allowed at a surface where the inversion summary is broken. They are often sufficiently strong so that a submonolayer perturbation of the surface can be readily detected. They can therefore be used as effective tools to study monolayers adsorbed at various interfaces. We discuss here a number of recent experiments in which optical second harmonic generation (SHG) and sum-frequency generation (SFG) are employed to probe and characterize organic monolayers. 15 refs., 5 figs

  2. Vanadium impurity effects on optical properties of Ti3N2 mono-layer: An ab-initio study

    Science.gov (United States)

    Babaeipour, Manuchehr; Eslam, Farzaneh Ghafari; Boochani, Arash; Nezafat, Negin Beryani

    2018-06-01

    The present work is investigated the effect of vanadium impurity on electronic and optical properties of Ti3N2 monolayer by using density function theory (DFT) implemented in Wien2k code. In order to study optical properties in two polarization directions of photons, namely E||x and E||z, dielectric function, absorption coefficient, optical conductivity, refraction index, extinction index, reflectivity, and energy loss function of Ti3N2 and Ti3N2-V monolayer have been evaluated within GGA (PBE) approximation. Although, Ti3N2 monolayer is a good infrared reflector and can be used as an infrared mirror, introducing V atom in the infrared area will decrease optical conductivity because optical conductivity of a pure form of a material is higher than its doped form.

  3. Proliferation of pulmonary endothelial cells: time-lapse cinematography of growth to confluence and restitution of monolayer after wounding.

    Science.gov (United States)

    Ryan, U S; Absher, M; Olazabal, B M; Brown, L M; Ryan, J W

    1982-01-01

    A fundamental characteristic of vascular endothelium is that it exists as a monolayer, a condition that must be met in both vascular growth and repair. Maintenance of the monolayer is important both for the exchange of nutrients and for interactions between blood solutes and endothelial enzymes and transport systems. We have used time-lapse cinematography to compare proliferative behavior of bovine pulmonary endothelial cells in (1) establishment of a monolayer from a low-density seed (7.5 X 10(4) cells in a 60 mm dish) and (2) restitution of a confluent monolayer (approx. 2.9 x 10(6) cells in a 60 mm dish) following a mechanical wound (removal of cells from an area 5 x 15 mm by scraping). Culture 2 was not refed after wounding. In culture 2, approx. 30% of the cells accounted for repopulation (confluence in 40 hr). In culture 1, all cells entered into division. Participating cells of culture 2 began division immediately (69 divisions/filmed area in 10 hr, vs. four divisions in culture 1). Interdivision times (IDT) were longer and relatively constant in culture 1 until near confluence; none were less than 10 h, whereas in 2, 24% of the IDT's were less than or equal to 10 hr. Remarkably, IDTs of culture 2 decreased steadily until confluence was re-established. Cell migration in culture 1 was multidirectional while direction of migration in culture 2 was always into the wound area. Mean migration rate (MIG) in culture 2 was related to the site of origin of the cells, those dividing farthest from the unwounded area had fastest MIGs. Neither culture formed more than a single layer of cells. Although the cell kinetics of cultures 1 and 2 differed, the same goal, confluence, was achieved in either case.

  4. Ionic polarization

    International Nuclear Information System (INIS)

    Mahan, G.D.

    1992-01-01

    Ferroelectricity occurs in many different kinds of materials. Many of the technologically important solids, which are ferroelectric, can be classified as ionic. Any microscopic theory of ferroelectricity must contain a description of local polarization forces. We have collaborated in the development of a theory of ionic polarization which is quite successful. Its basic assumption is that the polarization is derived from the properties of the individual ions. We have applied this theory successfully to diverse subjects as linear and nonlinear optical response, phonon dispersion, and piezoelectricity. We have developed numerical methods using the local Density approximation to calculate the multipole polarizabilities of ions when subject to various fields. We have also developed methods of calculating the nonlinear hyperpolarizability, and showed that it can be used to explain light scattering experiments. This paper elaborates on this polarization theory

  5. Possible doping strategies for MoS 2 monolayers: An ab initio study

    KAUST Repository

    Dolui, Kapildeb; Rungger, Ivan; Das Pemmaraju, Chaitanya; Sanvito, Stefano

    2013-01-01

    Density functional theory is used to systematically study the electronic properties of doped MoS2 monolayers, where the dopants are incorporated both via S/Mo substitution or as adsorbates. Among the possible substitutional dopants at the Mo site, Nb is identified as suitable p-type dopant, while Re is the donor with the lowest activation energy. When dopants are simply adsorbed on a monolayer we find that alkali metals shift the Fermi energy into the MoS2 conduction band, making the system n type. Finally, the adsorption of charged molecules is considered, mimicking an ionic liquid environment. We find that molecules adsorption can lead to both n- and p-type conductivity, depending on the charge polarity of the adsorbed species. © 2013 American Physical Society.

  6. Possible doping strategies for MoS 2 monolayers: An ab initio study

    KAUST Repository

    Dolui, Kapildeb

    2013-08-14

    Density functional theory is used to systematically study the electronic properties of doped MoS2 monolayers, where the dopants are incorporated both via S/Mo substitution or as adsorbates. Among the possible substitutional dopants at the Mo site, Nb is identified as suitable p-type dopant, while Re is the donor with the lowest activation energy. When dopants are simply adsorbed on a monolayer we find that alkali metals shift the Fermi energy into the MoS2 conduction band, making the system n type. Finally, the adsorption of charged molecules is considered, mimicking an ionic liquid environment. We find that molecules adsorption can lead to both n- and p-type conductivity, depending on the charge polarity of the adsorbed species. © 2013 American Physical Society.

  7. The Interface between Gd and Monolayer MoS2: A First-Principles Study

    KAUST Repository

    Zhang, Xuejing

    2014-12-08

    We analyze the electronic structure of interfaces between two-, four- and six-layer Gd(0001) and monolayer MoS2 by first-principles calculations. Strong chemical bonds shift the Fermi energy of MoS2 upwards into the conduction band. At the surface and interface the Gd f states shift to lower energy and new surface/interface Gd d states appear at the Fermi energy, which are strongly hybridized with the Mo 4d states and thus lead to a high spin-polarization (ferromagnetically ordered Mo magnetic moments of 0.15 μB). Gd therefore is an interesting candidate for spin injection into monolayer MoS2.

  8. Orientation of pentacene molecules on SiO2: From a monolayer to the bulk

    International Nuclear Information System (INIS)

    Zheng, Fan; Park, Byoung-Nam; Seo, Soonjoo; Evans, Paul G.; Himpsel, F. J.

    2007-01-01

    Near edge x-ray absorption fine structure (NEXAFS) spectroscopy is used to study the orientation of pentacene molecules within thin films on SiO 2 for thicknesses ranging from monolayers to the bulk (150 nm). The spectra exhibit a strong polarization dependence of the π * orbitals for all films, which indicates that the pentacene molecules are highly oriented. At all film thicknesses the orientation varies with the rate at which pentacene molecules are deposited, with faster rates favoring a thin film phase with different tilt angles and slower rates leading to a more bulklike orientation. Our NEXAFS results extend previous structural observations to the monolayer regime and to lower deposition rates. The NEXAFS results match crystallographic data if a finite distribution of the molecular orientations is included. Damage to the molecules by hot electrons from soft x-ray irradiation eliminates the splitting between nonequivalent π * orbitals, indicating a breakup of the pentacene molecule

  9. Polarization experiments

    International Nuclear Information System (INIS)

    Halzen, F.

    1977-02-01

    In a theoretical review of polarization experiments two important points are emphasized: (a) their versatility and their relevance to a large variety of aspects of hadron physics (tests of basic symmetries; a probe of strong interaction dynamics; a tool for hadron spectroscopy); (b) the wealth of experimental data on polarization parameters in pp and np scattering in the Regge language and in the diffraction language. (author)

  10. A Model for Spheroid versus Monolayer Response of SK-N-SH Neuroblastoma Cells to Treatment with 15-Deoxy-PGJ2

    Directory of Open Access Journals (Sweden)

    Dorothy I. Wallace

    2016-01-01

    Full Text Available Researchers have observed that response of tumor cells to treatment varies depending on whether the cells are grown in monolayer, as in vitro spheroids or in vivo. This study uses data from the literature on monolayer treatment of SK-N-SH neuroblastoma cells with 15-deoxy-PGJ2 and couples it with data on growth rates for untreated SK-N-SH neuroblastoma cells grown as multicellular spheroids. A linear model is constructed for untreated and treated monolayer data sets, which is tuned to growth, death, and cell cycle data for the monolayer case for both control and treatment with 15-deoxy-PGJ2. The monolayer model is extended to a five-dimensional nonlinear model of in vitro tumor spheroid growth and treatment that includes compartments of the cell cycle (G1,S,G2/M as well as quiescent (Q and necrotic (N cells. Monolayer treatment data for 15-deoxy-PGJ2 is used to derive a prediction of spheroid response under similar treatments. For short periods of treatment, spheroid response is less pronounced than monolayer response. The simulations suggest that the difference in response to treatment of monolayer versus spheroid cultures observed in laboratory studies is a natural consequence of tumor spheroid physiology rather than any special resistance to treatment.

  11. Nonlinear dynamics of trions under strong optical excitation in monolayer MoSe2.

    Science.gov (United States)

    Ye, Jialiang; Yan, Tengfei; Niu, Binghui; Li, Ying; Zhang, Xinhui

    2018-02-05

    By employing ultrafast transient reflection measurements based on two-color pump-probe spectroscopy, the population and valley polarization dynamics of trions in monolayer MoSe 2 were investigated at relatively high excitation densities under near-resonant excitation. Both the nonlinear dynamic photobleaching of the trion resonance and the redshift of the exciton resonance were found to be responsible for the excitation-energy- and density-dependent transient reflection change as a result of many-body interactions. Furthermore, from the polarization-resolved measurements, it was revealed that the initial fast population and polarization decay process upon strong photoexcitation observed for trions was determined by trion formation, transient phase-space filling and the short valley lifetime of excitons. The results provide a basic understanding of the nonlinear dynamics of population and valley depolarization of trions, as well as exciton-trion correlation in atomically thin MoSe 2 and other transition metal dichalcogenide materials.

  12. Photoinduced quantum spin and valley Hall effects, and orbital magnetization in monolayer MoS2

    KAUST Repository

    Tahir, M.

    2014-09-22

    We theoretically demonstrate that 100% valley-polarized transport in monolayers of MoS2 and other group-VI dichalcogenides can be obtained using off-resonant circularly polarized light. By tuning the intensity of the off-resonant light the intrinsic band gap in one valley is reduced, while it is enhanced in the other valley, enabling single valley quantum transport. As a consequence, we predict (i) enhancement of the longitudinal electrical conductivity, accompanied by an increase in the spin polarization of the flowing electrons, (ii) enhancement of the intrinsic spin Hall effect, together with a reduction of the intrinsic valley Hall effect, and (iii) enhancement of the orbital magnetic moment and orbital magnetization. These mechanisms provide appealing opportunities to the design of nanoelectronics based on dichalcogenides.

  13. Photoinduced quantum spin and valley Hall effects, and orbital magnetization in monolayer MoS2

    KAUST Repository

    Tahir, M.; Manchon, Aurelien; Schwingenschlö gl, Udo

    2014-01-01

    We theoretically demonstrate that 100% valley-polarized transport in monolayers of MoS2 and other group-VI dichalcogenides can be obtained using off-resonant circularly polarized light. By tuning the intensity of the off-resonant light the intrinsic band gap in one valley is reduced, while it is enhanced in the other valley, enabling single valley quantum transport. As a consequence, we predict (i) enhancement of the longitudinal electrical conductivity, accompanied by an increase in the spin polarization of the flowing electrons, (ii) enhancement of the intrinsic spin Hall effect, together with a reduction of the intrinsic valley Hall effect, and (iii) enhancement of the orbital magnetic moment and orbital magnetization. These mechanisms provide appealing opportunities to the design of nanoelectronics based on dichalcogenides.

  14. Imidazolide monolayers for versatile reactive microcontact printing

    NARCIS (Netherlands)

    Hsu, S.H.; Reinhoudt, David; Huskens, Jurriaan; Velders, Aldrik

    2008-01-01

    Imidazolide monolayers prepared from the reaction of amino SAMs with N,N-carbonyldiimidazole (CDI) are used as a versatile platform for surface patterning with amino-, carboxyl- and alcohol-containing compounds through reactive microcontact printing (µCP). To demonstrate the surface reactivity of

  15. Nanotubes based on monolayer blue phosphorus

    KAUST Repository

    Montes Muñoz, Enrique

    2016-07-08

    We demonstrate structural stability of monolayer zigzag and armchair blue phosphorus nanotubes by means of molecular dynamics simulations. The vibrational spectrum and electronic band structure are determined and analyzed as functions of the tube diameter and axial strain. The nanotubes are found to be semiconductors with a sensitive indirect band gap that allows flexible tuning.

  16. Integrated circuits based on conjugated polymer monolayer.

    Science.gov (United States)

    Li, Mengmeng; Mangalore, Deepthi Kamath; Zhao, Jingbo; Carpenter, Joshua H; Yan, Hongping; Ade, Harald; Yan, He; Müllen, Klaus; Blom, Paul W M; Pisula, Wojciech; de Leeuw, Dago M; Asadi, Kamal

    2018-01-31

    It is still a great challenge to fabricate conjugated polymer monolayer field-effect transistors (PoM-FETs) due to intricate crystallization and film formation of conjugated polymers. Here we demonstrate PoM-FETs based on a single monolayer of a conjugated polymer. The resulting PoM-FETs are highly reproducible and exhibit charge carrier mobilities reaching 3 cm 2  V -1  s -1 . The high performance is attributed to the strong interactions of the polymer chains present already in solution leading to pronounced edge-on packing and well-defined microstructure in the monolayer. The high reproducibility enables the integration of discrete unipolar PoM-FETs into inverters and ring oscillators. Real logic functionality has been demonstrated by constructing a 15-bit code generator in which hundreds of self-assembled PoM-FETs are addressed simultaneously. Our results provide the state-of-the-art example of integrated circuits based on a conjugated polymer monolayer, opening prospective pathways for bottom-up organic electronics.

  17. Shadow mask evaporation through monolayer modified nanostencils

    NARCIS (Netherlands)

    Kolbel, M.; Tjerkstra, R.W.; Brugger, J.P.; van Rijn, C.J.M.; Nijdam, W.; Huskens, Jurriaan; Reinhoudt, David

    2002-01-01

    Gradual clogging of the apertures of nanostencils used as miniature shadow masks in metal evaporations can be reduced by coating the stencil with self-assembled monolayers (SAM). This is quantified by the dimensions (height and volume) of gold features obtained by nanostencil evaporation as measured

  18. Fullerene monolayer formation by spray coating

    NARCIS (Netherlands)

    Cervenka, J.; Flipse, C.F.J.

    2010-01-01

    Many large molecular complexes are limited in thin film applications by their insufficient thermal stability, which excludes deposition via commonly used vapour phase deposition methods. Here we demonstrate an alternative way of monolayer formation of large molecules by a simple spray coating method

  19. Semiconductor monolayer assemblies with oriented crystal faces

    KAUST Repository

    Ma, Guijun; Takata, Tsuyoshi; Katayama, Masao; Zhang, Fuxiang; Moriya, Yosuke; Takanabe, Kazuhiro; Kubota, Jun; Domen, Kazunari

    2012-01-01

    Fabrication of two-dimensional monolayers of crystalline oxide and oxynitride particles was attempted on glass plate substrates. X-Ray diffraction patterns of the assemblies show only specific crystal facets, indicative of the uniform orientation of the particles on the substrate. The selectivity afforded by this immobilization technique enables the organization of randomly distributed polycrystalline powders in a controlled manner.

  20. Fullerene monolayer formation by spray coating

    Czech Academy of Sciences Publication Activity Database

    Červenka, Jiří; Flipse, C.F.J.

    2010-01-01

    Roč. 21, č. 6 (2010), 065302/1-065302/7 ISSN 0957-4484 Institutional research plan: CEZ:AV0Z10100521 Keywords : monolayer * spray coating * fullerene * atomic force microscopy * scanning tunnelling microscopy * electronic structure * graphite * gold Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.644, year: 2010

  1. Complex magnetism of the Fe monolayer on Ir(111)

    International Nuclear Information System (INIS)

    Bergmann, Kirsten von; Heinze, Stefan; Bode, Matthias; Bihlmayer, Gustav; Bluegel, Stefan; Wiesendanger, Roland

    2007-01-01

    The electronic and magnetic properties of Fe on Ir(111) have been investigated experimentally by spin-polarized scanning tunneling microscopy (SP-STM) and theoretically by first-principles calculations based on density functional theory. While the growth of an Fe monolayer is in-plane commensurate, deposition of a double-layer shows a rearrangement of atoms due to strain relief accompanied by local variations of the electronic structure. Both stackings of the monolayer, i.e. face centered cubic (fcc) and hexagonal closed packed (hcp), are observed experimentally. The magnetic structure of both types is imaged with SP-STM. From these experiments, we propose a nanoscale magnetic mosaic structure for the fcc-stacking with 15 atoms in the unit cell. For hcp-stacking, the tunneling spectra are similar to the fcc case, however, the magnetic contrast in the SP-STM images is not as obvious. In our first-principles calculations, a collinear antiferromagnetic (AFM) state with a 15 atom in-plane unit cell (AFM 7 : 8 state) is found to be more favorable than the ferromagnetic state for both fcc- and hcp-stacking. Calculated SP-STM images and spectra are also in good agreement with the experimental data for the fcc case. We performed spin spiral calculations which are mapped to a classical Heisenberg model to obtain the exchange-interaction constants. From these calculations, it is found that the AFM 7 : 8 state is energetically more favorable than all solutions of the classical Heisenberg model. While the obtained magnetic exchange constants are rather similar for the fcc and hcp stacking, a comparison with the experiments indicates that competing interactions could be responsible for the differences observed in the magnetically sensitive measurements

  2. Polarization measurement for internal polarized gaseous targets

    International Nuclear Information System (INIS)

    Ye Zhenyu; Ye Yunxiu; Lv Haijiang; Mao Yajun

    2004-01-01

    The authors present an introduction to internal polarized gaseous targets, polarization method, polarization measurement method and procedure. To get the total nuclear polarization of hydrogen atoms (including the polarization of the recombined hydrogen molecules) in the target cell, authors have measured the parameters relating to atomic polarization and polarized hydrogen atoms and molecules. The total polarization of the target during our measurement is P T =0.853 ± 0.036. (authors)

  3. Collective cell streams in epithelial monolayers depend on cell adhesion

    International Nuclear Information System (INIS)

    Czirók, András; Varga, Katalin; Méhes, Előd; Szabó, András

    2013-01-01

    We report spontaneously emerging, randomly oriented, collective streaming behavior within a monolayer culture of a human keratinocyte cell line, and explore the effect of modulating cell adhesions by perturbing the function of calcium-dependent cell adhesion molecules. We demonstrate that decreasing cell adhesion induces narrower and more anisotropic cell streams, reminiscent of decreasing the Taylor scale of turbulent liquids. To explain our empirical findings, we propose a cell-based model that represents the dual nature of cell–cell adhesions. Spring-like connections provide mechanical stability, while a cellular Potts model formalism represents surface-tension driven attachment. By changing the relevance and persistence of mechanical links between cells, we are able to explain the experimentally observed changes in emergent flow patterns. (paper)

  4. Electrical control of truly two-dimensional neutral and charged excitons in monolayer MoSe2

    Science.gov (United States)

    Ross, Jason; Wu, Sanfeng; Yu, Hongyi; Ghimire, Nirmal; Jones, Aaron; Aivazian, Grant; Yan, Jiaqiang; Mandrus, David; Xiao, Di; Xiao, Di; Xu, Xiaodong

    2013-03-01

    Monolayer transition metal dichalcogenides (TMDs) have emerged as ideal 2D semiconductors with valley and spin polarized excitations expected to enable true valley-tronics. Here we investigate MoSe2, a TMD which has yet to be characterized in the monolayer limit. Specifically, we examine excitons and trions (their singly charged counterparts) in the ultimate 2D limit. Utilizing high quality exfoliated MoSe2 monolayers, we report the observation and electrostatic tunability of positively charged (X +) , neutral (Xo), and negatively charged (X-) excitons via photoluminescence in FETs. The trion charging energy is large (30 meV), enhanced by strong confinement and heavy effective masses, while the linewidth is narrow (5 meV) at temperatures below 55 K. This is greater spectral contrast than in any known quasi-2D system. Further, the charging energies for X + and X- to are nearly identical implying the same effective mass for electrons and holes, which supports their recent description as massive Dirac fermions. This work demonstrates that monolayer MoSe2 is an ultimate 2D semiconductor opening the door for the investigation of truly 2D exciton physics while laying the ground work necessary to begin valley-spin polarization studies. Support: US DoE, BES, Division of MSE. HY and WY supported by Research Grant Council of Hong Kong

  5. Essential Function for PDLIM2 in Cell Polarization in Three-Dimensional Cultures by Feedback Regulation of the β1-Integrin–RhoA Signaling Axis

    Directory of Open Access Journals (Sweden)

    Ravi Kiran Deevi

    2014-05-01

    Full Text Available PDLIM2 is a cytoskeletal and nuclear PDZ-LIM domain protein that regulates the stability of Nuclear Factor kappa-B (NFκB and other transcription factors, and is required for polarized cell migration. PDLIM2 expression is suppressed by methylation in different cancers, but is strongly expressed in invasive breast cancer cells that have undergone an Epithelial Mesenchymal Transition (EMT. PDLIM2 is also expressed in non-transformed breast myoepithelial MCF10A cells and here we asked whether it is important for maintaining the polarized, epithelial phenotype of these cells. Suppression of PDLIM2 in MCF10A cells was sufficient to disrupt cell polarization and acini formation with increased proliferation and reduced apoptosis in the luminal space compared to control acini with hollow lumina. Spheroids with suppressed PDLIM2 exhibited increased expression of cell-cell and cell-matrix adhesion proteins including beta 1 (β1 integrin. Interestingly, levels of the Insulin-like growth factor 1 receptor (IGF-1 R and Receptor of activated protein kinase C 1 (RACK1, which scaffolds IGF-1R to β1 integrin, were also increased, indicating a transformed phenotype. Focal Adhesion Kinase (FAK and cofilin phosphorylation, and RhoA Guanosine Triphosphatase (GTPase activity were all enhanced in these spheroids compared to control acini. Importantly, inhibition of either FAK or Rho Kinase (ROCK was sufficient to rescue the polarity defect. We conclude that PDLIM2 expression is essential for feedback regulation of the β1-integrin-RhoA signalling axis and integration of cellular microenvironment signals with gene expression to control the polarity of breast epithelial acini structures. This is a mechanism by which PDLIM2 could mediate tumour suppression in breast epithelium.

  6. A high extinction ratio THz polarizer fabricated by double-bilayer wire grid structure

    Science.gov (United States)

    Lu, Bin; Wang, Haitao; Shen, Jun; Yang, Jun; Mao, Hongyan; Xia, Liangping; Zhang, Weiguo; Wang, Guodong; Peng, Xiao-Yu; Wang, Deqiang

    2016-02-01

    We designed a new style of broadband terahertz (THz) polarizer with double-bilayer wire grid structure by fabricating them on both sides of silicon substrate. This THz polarizer shows a high average extinction ratio of 60dB in 0.5 to 2.0 THz frequency range and the maximum of 87 dB at 1.06 THz, which is much higher than that of conventional monolayer wire grid polarizers and single-bilayer wire grid ones.

  7. Sources of polarized neutrons

    International Nuclear Information System (INIS)

    Walter, L.

    1983-01-01

    Various sources of polarized neutrons are reviewed. Monoenergetic source produced with unpolarized or polarized beams, white sources of polarized neutrons, production by transmissions through polarized hydrogen targets and polarized thermal neutronsare discussed, with appropriate applications included. (U.K.)

  8. Spatio-temporal dynamics of an active, polar, viscoelastic ring.

    Science.gov (United States)

    Marcq, Philippe

    2014-04-01

    Constitutive equations for a one-dimensional, active, polar, viscoelastic liquid are derived by treating the strain field as a slow hydrodynamic variable. Taking into account the couplings between strain and polarity allowed by symmetry, the hydrodynamics of an active, polar, viscoelastic body include an evolution equation for the polarity field that generalizes the damped Kuramoto-Sivashinsky equation. Beyond thresholds of the active coupling coefficients between the polarity and the stress or the strain rate, bifurcations of the homogeneous state lead first to stationary waves, then to propagating waves of the strain, stress and polarity fields. I argue that these results are relevant to living matter, and may explain rotating actomyosin rings in cells and mechanical waves in epithelial cell monolayers.

  9. Broadband and high absorption in Fibonacci photonic crystal including MoS2 monolayer in the visible range

    Science.gov (United States)

    Ansari, Narges; Mohebbi, Ensiyeh

    2018-03-01

    2D molybdenum disulfide MoS2, has represented potential applications in optoelectronic devices based on their promising optical absorption responses. However, for practical applications, absorption should increase furthermore in a wide wavelength window. In this paper, we design Fibonacci photonic crystals (PCs) based on Si, SiO2 and MoS2 monolayer and we calculate their absorption responses based on the transfer matrix method. The optical refractive index of the MoS2 monolayer was determined based on the Lorentz-Drude-Gauss model. Effects of Fibonacci order, periodicity, incident light angle and polarization are included in our calculations. Finally, an absorption as large as 90% in a wide optical wavelength range is achieved for both polarizations and incident angle down to 60°. Our results are useful for designing photonic devices with high absorption efficiency.

  10. The Shell Structure Effect on the Vapor Selectivity of Monolayer-Protected Gold Nanoparticle Sensors

    Directory of Open Access Journals (Sweden)

    Rui-Xuan Huang

    2014-02-01

    Full Text Available Four types of monolayer-protected gold nanoclusters (MPCs were synthesized and characterized as active layers of vapor sensors. An interdigitated microelectrode (IDE and quartz crystal microbalance (QCM were used to measure the electrical resistance and mass loading changes of MPC films during vapor sorption. The vapor sensing selectivity was influenced by the ligand structure of the monolayer on the surface of gold nanoparticles. The responses of MPC-coated QCM were mainly determined according to the affinity between the vapors and surface ligands of MPCs. The responses to the resistance changes of the MPC films were due to the effectiveness of the swelling when vapor was absorbed. It was observed that resistive sensitivity to polar organics could be greatly enhanced when the MPC contained ligands that contain interior polar functional groups with exterior nonpolar groups. This finding reveals that reducing interparticle attraction by using non-polar exterior groups could increase effective swelling and therefore enhance the sensitivity of MPC-coated chemiresistors.

  11. Water filtration rate and infiltration/accumulation of low density lipoproteins in 3 different modes of endothelial/smooth muscle cell co-cultures.

    Science.gov (United States)

    Ding, ZuFeng; Fan, YuBo; Deng, XiaoYan

    2009-11-01

    Using different endothelial/smooth muscle cell co-culture modes to simulate the intimal structure of blood vessels, the water filtration rate and the infiltration/accumulation of LDL of the cultured cell layers were studied. The three cell culture modes of the study were: (i) The endothelial cell monolayer (EC/Phi); (ii) endothelial cells directly co-cultured on the smooth muscle cell monolayer (EC-SMC); (iii) endothelial cells and smooth muscle cells cultured on different sides of a Millicell-CM membrane (EC/SMC). It was found that under the same condition, the water filtration rate was the lowest for the EC/SMC mode and the highest for the EC/Phi mode, while the infiltration/accumulation of DiI-LDLs was the lowest in the EC/Phi mode and the highest in the EC-SMC mode. It was also found that DiI-LDL infiltration/accumulation in the cultured cell layers increased with the increasing water filtration rate. The results from the in vitro model study therefore suggest that the infiltration/accumulation of the lipids within the arterial wall is positively correlated with concentration polarization of atherogenic lipids, and the integrity of the endothelium plays an important role in the penetration and accumulation of atherogenic lipids in blood vessel walls.

  12. Molecular tilt on monolayer-protected nanoparticles

    KAUST Repository

    Giomi, L.

    2012-02-01

    The structure of the tilted phase of monolayer-protected nanoparticles is investigated by means of a simple Ginzburg-Landau model. The theory contains two dimensionless parameters representing the preferential tilt angle and the ratio ε between the energy cost due to spatial variations in the tilt of the coating molecules and that of the van der Waals interactions which favors the preferential tilt. We analyze the model for both spherical and octahedral particles. On spherical particles, we find a transition from a tilted phase, at small ε, to a phase where the molecules spontaneously align along the surface normal and tilt disappears. Octahedral particles have an additional phase at small ε characterized by the presence of six topological defects. These defective configurations provide preferred sites for the chemical functionalization of monolayer-protected nanoparticles via place-exchange reactions and their consequent linking to form molecules and bulk materials. Copyright © EPLA, 2012.

  13. Epitaxial growth by monolayer restricted galvanic displacement

    Directory of Open Access Journals (Sweden)

    Vasilić Rastko

    2012-01-01

    Full Text Available The development of a new method for epitaxial growth of metals in solution by galvanic displacement of layers pre-deposited by underpotential deposition (UPD was discussed and experimentally illustrated throughout the lecture. Cyclic voltammetry (CV and scanning tunneling microscopy (STM are employed to carry out and monitor a “quasi-perfect”, two-dimensional growth of Ag on Au(111, Cu on Ag(111, and Cu on Au(111 by repetitive galvanic displacement of underpotentially deposited monolayers. A comparative study emphasizes the displacement stoichiometry as an efficient tool for thickness control during the deposition process and as a key parameter that affects the deposit morphology. The excellent quality of layers deposited by monolayer-restricted galvanic displacement is manifested by a steady UPD voltammetry and ascertained by a flat and uniform surface morphology maintained during the entire growth process.

  14. Molecular tilt on monolayer-protected nanoparticles

    KAUST Repository

    Giomi, L.; Bowick, M. J.; Ma, X.; Majumdar, A.

    2012-01-01

    The structure of the tilted phase of monolayer-protected nanoparticles is investigated by means of a simple Ginzburg-Landau model. The theory contains two dimensionless parameters representing the preferential tilt angle and the ratio ε between the energy cost due to spatial variations in the tilt of the coating molecules and that of the van der Waals interactions which favors the preferential tilt. We analyze the model for both spherical and octahedral particles. On spherical particles, we find a transition from a tilted phase, at small ε, to a phase where the molecules spontaneously align along the surface normal and tilt disappears. Octahedral particles have an additional phase at small ε characterized by the presence of six topological defects. These defective configurations provide preferred sites for the chemical functionalization of monolayer-protected nanoparticles via place-exchange reactions and their consequent linking to form molecules and bulk materials. Copyright © EPLA, 2012.

  15. Polarization study

    International Nuclear Information System (INIS)

    Nurushev, S.B.

    1989-01-01

    Brief review is presented of the high energy polarization study including experimental data and the theoretical descriptions. The mostimportant proposals at the biggest accelerators and the crucial technical developments are also listed which may become a main-line of spin physics. 35 refs.; 10 figs.; 4 tabs

  16. Polar Stratigraphy

    Science.gov (United States)

    1999-01-01

    These three images were taken on three different orbits over the north polar cap in April 1999. Each shows a different part of the same ice-free trough. The left and right images are separated by a distance of more than 100 kilometers (62 miles). Note the similar layers in each image.

  17. Electrochemical behaviour of monolayer and bilayer graphene

    OpenAIRE

    Valota, Anna T.; Kinloch, Ian A.; Novoselov, Kostya S.; Casiraghi, Cinzia; Eckmann, Axel; Hill, Ernie W.; Dryfe, Robert A. W.

    2011-01-01

    Results of a study on the electrochemical properties of exfoliated single and multilayer graphene flakes are presented. Graphene flakes were deposited on silicon/silicon oxide wafers to enable fast and accurate characterization by optical microscopy and Raman spectroscopy. Conductive silver paint and silver wires were used to fabricate contacts; epoxy resin was employed as masking coating in order to expose a stable, well defined area of graphene. Both multilayer and monolayer graphene microe...

  18. Structure of cholesterol/ceramide monolayer mixtures

    DEFF Research Database (Denmark)

    Scheffer, L.; Solomonov, I.; Weygand, M.J.

    2005-01-01

    The structure of monolayers of cholesterol/ ceramide mixtures was investigated using grazing incidence x-ray diffraction, immunofluorescence, and atomic force microscopy techniques. Grazing incidence x-ray diffraction measurements showed the existence of a crystalline mixed phase of the two....... As ceramide incorporates the lipid backbone common to all sphingolipids, this arrangement may be relevant to the understanding of the molecular organization of lipid rafts....

  19. Evaluation of monolayers and mixed monolayers formed from mercaptobenzothiazole and decanethiol as sensing platforms

    Energy Technology Data Exchange (ETDEWEB)

    Mary Vergheese, T.; Berchmans, Sheela

    2004-02-15

    In this investigation, the characterisation of monolayer and mixed monolayers formed from mercaptobenzothiazole (MBT) and decanethiol (DT) has been carried out with cyclic voltammetry. The SAMs have been tested for their stability and electron transfer blocking properties. The redox probes used in the present study are [Fe(China){sub 6}]{sup 4-}, [Ru(NH{sub 3}){sub 6}]{sup 2+} and Cu underpotential deposition (upd). The electron transfer kinetics is investigated in acid and neutral pH range. Electron transfer kinetics is altered by the nature of charge on the redox probe and the charge on the monolayer. Electron transfer kinetics of negatively charged redox probes like ferrocyanide ions is blocked when the surface pK{sub a}pH{sub medium} reversible features is observed for negatively charged probes. An exactly reverse effect is observed in the case of positively charged redox species like [Ru(NH{sub 3}){sub 6}]{sup 2+/3+}. Cu under potential deposition studies reflects the structural integrity and compactness of the SAM layer. The utility of these monolayers and mixed monolayer for selective sensing of dopamine is discussed based on their ability to discriminate between positively and negatively charged redox species at different pH.

  20. Evaluation of monolayers and mixed monolayers formed from mercaptobenzothiazole and decanethiol as sensing platforms

    International Nuclear Information System (INIS)

    Mary Vergheese, T.; Berchmans, Sheela

    2004-01-01

    In this investigation, the characterisation of monolayer and mixed monolayers formed from mercaptobenzothiazole (MBT) and decanethiol (DT) has been carried out with cyclic voltammetry. The SAMs have been tested for their stability and electron transfer blocking properties. The redox probes used in the present study are [Fe(China) 6 ] 4- , [Ru(NH 3 ) 6 ] 2+ and Cu underpotential deposition (upd). The electron transfer kinetics is investigated in acid and neutral pH range. Electron transfer kinetics is altered by the nature of charge on the redox probe and the charge on the monolayer. Electron transfer kinetics of negatively charged redox probes like ferrocyanide ions is blocked when the surface pK a medium and at pK a >pH medium reversible features is observed for negatively charged probes. An exactly reverse effect is observed in the case of positively charged redox species like [Ru(NH 3 ) 6 ] 2+/3+ . Cu under potential deposition studies reflects the structural integrity and compactness of the SAM layer. The utility of these monolayers and mixed monolayer for selective sensing of dopamine is discussed based on their ability to discriminate between positively and negatively charged redox species at different pH

  1. Investigation on gallium ions impacting monolayer graphene

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Xin; Zhao, Haiyan, E-mail: hyzhao@tsinghua.edu.cn; Yan, Dong; Pei, Jiayun [State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, P. R. Chinaand Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China)

    2015-06-15

    In this paper, the physical phenomena of gallium (Ga{sup +}) ion impacting monolayer graphene in the nanosculpting process are investigated experimentally, and the mechanisms are explained by using Monte Carlo (MC) and molecular dynamics (MD) simulations. Firstly, the MC method is employed to clarify the phenomena happened to the monolayer graphene target under Ga{sup +} ion irradiation. It is found that substrate has strong influence on the damage mode of graphene. The mean sputtering yield of graphene under 30 keV Ga{sup +} ion irradiation is 1.77 and the least ion dose to completely remove carbon atoms in graphene is 21.6 ion/nm{sup 2}. Afterwards, the focused ion beam over 21.6 ion/nm{sup 2} is used for the irradiation on a monolayer graphene supported by SiO2 experimentally, resulting in the nanostructures, i.e., nanodot and nanowire array on the graphene. The performances of the nanostructures are characterized by atomic force microscopy and Raman spectrum. A plasma plume shielding model is put forward to explain the nanosculpting results of graphene under different irradiation parameters. In addition, two damage mechanisms are found existing in the fabrication process of the nanostructures by using empirical MD simulations. The results can help us open the possibilities for better control of nanocarbon devices.

  2. Janus monolayers of transition metal dichalcogenides

    KAUST Repository

    Lu, Ang-Yu

    2017-05-15

    Structural symmetry-breaking plays a crucial role in determining the electronic band structures of two-dimensional materials. Tremendous efforts have been devoted to breaking the in-plane symmetry of graphene with electric fields on AB-stacked bilayers or stacked van der Waals heterostructures. In contrast, transition metal dichalcogenide monolayers are semiconductors with intrinsic in-plane asymmetry, leading to direct electronic bandgaps, distinctive optical properties and great potential in optoelectronics. Apart from their in-plane inversion asymmetry, an additional degree of freedom allowing spin manipulation can be induced by breaking the out-of-plane mirror symmetry with external electric fields or, as theoretically proposed, with an asymmetric out-of-plane structural configuration. Here, we report a synthetic strategy to grow Janus monolayers of transition metal dichalcogenides breaking the out-of-plane structural symmetry. In particular, based on a MoS2 monolayer, we fully replace the top-layer S with Se atoms. We confirm the Janus structure of MoSSe directly by means of scanning transmission electron microscopy and energy-dependent X-ray photoelectron spectroscopy, and prove the existence of vertical dipoles by second harmonic generation and piezoresponse force microscopy measurements.

  3. Exploring atomic defects in molybdenum disulphide monolayers

    KAUST Repository

    Hong, Jinhua; Hu, Zhixin; Probert, Matt; Li, Kun; Lv, Danhui; Yang, Xinan; Gu, Lin; Mao, Nannan; Feng, Qingliang; Xie, Liming; Zhang, Jin; Wu, Dianzhong; Zhang, Zhiyong; Jin, Chuanhong; Ji, Wei; Zhang, Xixiang; Yuan, Jun; Zhang, Ze

    2015-01-01

    Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10 13 cm '2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

  4. Exploring atomic defects in molybdenum disulphide monolayers

    KAUST Repository

    Hong, Jinhua

    2015-02-19

    Defects usually play an important role in tailoring various properties of two-dimensional materials. Defects in two-dimensional monolayer molybdenum disulphide may be responsible for large variation of electric and optical properties. Here we present a comprehensive joint experiment-theory investigation of point defects in monolayer molybdenum disulphide prepared by mechanical exfoliation, physical and chemical vapour deposition. Defect species are systematically identified and their concentrations determined by aberration-corrected scanning transmission electron microscopy, and also studied by ab-initio calculation. Defect density up to 3.5 × 10 13 cm \\'2 is found and the dominant category of defects changes from sulphur vacancy in mechanical exfoliation and chemical vapour deposition samples to molybdenum antisite in physical vapour deposition samples. Influence of defects on electronic structure and charge-carrier mobility are predicted by calculation and observed by electric transport measurement. In light of these results, the growth of ultra-high-quality monolayer molybdenum disulphide appears a primary task for the community pursuing high-performance electronic devices.

  5. Affinity of serum apolipoproteins for lipid monolayers

    International Nuclear Information System (INIS)

    Ibdah, J.A.

    1987-01-01

    The effects of lipid composition and packing as well as the structure of the protein on the affinities of apolipoproteins for lipid monolayers have been investigated. The adsorption of 14 C-reductively methylated human apolipoproteins A-I and A-II at saturating subphase concentrations to monolayers prepared with synthetic lipids or lipoprotein surface lipids spread at various initial surface pressures has been studied. The adsorption of apolipoproteins is monitored by following the surface radioactivity using a gas flow counter and Wilhelmy plate, respectively. The physical states of the lipid monolayers are evaluated by measurement of the surface pressure-molecular area isotherms using a Langmuir-Adam surface balance. The probable helical regions in various apolipoproteins have been predicted using a secondary structure analysis computer program. The mean residue hydrophobicity and mean residue hydrophobic moment for the predicted helical segments have been calculated. The surface properties of synthetic peptides which are amphipathic helix analogs have been investigated at the air-water and lipid-water interfaces

  6. Biomimetic nanoparticles with polynucleotide and PEG mixed-monolayers enhance calcium phosphate mineralization

    Energy Technology Data Exchange (ETDEWEB)

    Vasconcellos, Kayla B.; McHugh, Sean M.; Dapsis, Katherine J.; Petty, Alexander R.; Gerdon, Aren E., E-mail: gerdoar@emmanuel.edu [Emmanuel College (United States)

    2013-09-15

    Biomineralization of hydroxyapatite (Ca{sub 10}(PO{sub 4}){sub 6}(OH){sub 2}) is of significant importance in biomedical applications such as bone and dental repair, and biomimetic control of mineral formation may lead to more effective restorative procedures. Gold nanoparticles are functional scaffolds on which to assemble multi-component monolayers capable of mimicking protein activity in the templated synthesis of calcium phosphate. The goal of this research was to explore nanoparticle templates with mixed-monolayers of uncharged polar polyethylene glycol (PEG) molecules and highly charged polynucleotide and amino acid molecules in their ability to influence mineralization rates and mineral particle size and morphology. This research demonstrates through time-resolved optical density and dynamic light scattering measurements that the combination of tiopronin, PEG, and DNA presented on a nanoparticle surface decreases nanoparticle aggregation from 59 to 21 nm solvated radius, increases mineralization kinetics from 1.5 Multiplication-Sign 10{sup -3} to 3.1 Multiplication-Sign 10{sup -3} OD/min, and decreases mineral particle size from 685 to 442 nm average radius. FT-IR and TEM data demonstrate that mineralized material, while initially amorphous, transforms to a semi-crystalline material when guided by template interactions. This demonstrates that surface-tailored monolayer protected cluster scaffolds are successful and controllable mineralization templates with further potential for biomedical applications involving calcium phosphate and other biomaterials.

  7. Biomimetic nanoparticles with polynucleotide and PEG mixed-monolayers enhance calcium phosphate mineralization

    Science.gov (United States)

    Vasconcellos, Kayla B.; McHugh, Sean M.; Dapsis, Katherine J.; Petty, Alexander R.; Gerdon, Aren E.

    2013-09-01

    Biomineralization of hydroxyapatite (Ca10(PO4)6(OH)2) is of significant importance in biomedical applications such as bone and dental repair, and biomimetic control of mineral formation may lead to more effective restorative procedures. Gold nanoparticles are functional scaffolds on which to assemble multi-component monolayers capable of mimicking protein activity in the templated synthesis of calcium phosphate. The goal of this research was to explore nanoparticle templates with mixed-monolayers of uncharged polar polyethylene glycol (PEG) molecules and highly charged polynucleotide and amino acid molecules in their ability to influence mineralization rates and mineral particle size and morphology. This research demonstrates through time-resolved optical density and dynamic light scattering measurements that the combination of tiopronin, PEG, and DNA presented on a nanoparticle surface decreases nanoparticle aggregation from 59 to 21 nm solvated radius, increases mineralization kinetics from 1.5 × 10-3 to 3.1 × 10-3 OD/min, and decreases mineral particle size from 685 to 442 nm average radius. FT-IR and TEM data demonstrate that mineralized material, while initially amorphous, transforms to a semi-crystalline material when guided by template interactions. This demonstrates that surface-tailored monolayer protected cluster scaffolds are successful and controllable mineralization templates with further potential for biomedical applications involving calcium phosphate and other biomaterials.

  8. An oscillating dynamic model of collective cells in a monolayer

    Science.gov (United States)

    Lin, Shao-Zhen; Xue, Shi-Lei; Li, Bo; Feng, Xi-Qiao

    2018-03-01

    Periodic oscillations of collective cells occur in the morphogenesis and organogenesis of various tissues and organs. In this paper, an oscillating cytodynamic model is presented by integrating the chemomechanical interplay between the RhoA effector signaling pathway and cell deformation. We show that both an isolated cell and a cell aggregate can undergo spontaneous oscillations as a result of Hopf bifurcation, upon which the system evolves into a limit cycle of chemomechanical oscillations. The dynamic characteristics are tailored by the mechanical properties of cells (e.g., elasticity, contractility, and intercellular tension) and the chemical reactions involved in the RhoA effector signaling pathway. External forces are found to modulate the oscillation intensity of collective cells in the monolayer and to polarize their oscillations along the direction of external tension. The proposed cytodynamic model can recapitulate the prominent features of cell oscillations observed in a variety of experiments, including both isolated cells (e.g., spreading mouse embryonic fibroblasts, migrating amoeboid cells, and suspending 3T3 fibroblasts) and multicellular systems (e.g., Drosophila embryogenesis and oogenesis).

  9. Two-dimensional multiferroics in monolayer group IV monochalcogenides

    Science.gov (United States)

    Wang, Hua; Qian, Xiaofeng

    2017-03-01

    Low-dimensional multiferroic materials hold great promises in miniaturized device applications such as nanoscale transducers, actuators, sensors, photovoltaics, and nonvolatile memories. Here, using first-principles theory we predict that two-dimensional (2D) monolayer group IV monochalcogenides including GeS, GeSe, SnS, and SnSe are a class of 2D semiconducting multiferroics with giant strongly-coupled in-plane spontaneous ferroelectric polarization and spontaneous ferroelastic lattice strain that are thermodynamically stable at room temperature and beyond, and can be effectively modulated by elastic strain engineering. Their optical absorption spectra exhibit strong in-plane anisotropy with visible-spectrum excitonic gaps and sizable exciton binding energies, rendering the unique characteristics of low-dimensional semiconductors. More importantly, the predicted low domain wall energy and small migration barrier together with the coupled multiferroic order and anisotropic electronic structures suggest their great potentials for tunable multiferroic functional devices by manipulating external electrical, mechanical, and optical field to control the internal responses, and enable the development of four device concepts including 2D ferroelectric memory, 2D ferroelastic memory, and 2D ferroelastoelectric nonvolatile photonic memory as well as 2D ferroelectric excitonic photovoltaics.

  10. Interaction of toremifene with dipalmitoyl-phosphatidyl-glycerol in monolayers at the air–water interface followed by fluorescence microscopy in Langmuir–Blodgett films

    International Nuclear Information System (INIS)

    Romão, Rute I.S.; Maçôas, Ermelinda; Martinho, José M.G.; Gonçalves da Silva, Amélia M.P.S.

    2013-01-01

    Langmuir monolayers of dipalmitoyl-phosphatidyl-glycerol (DPPG) containing toremifene (TOR), an antiestrogen drug derivative of tamoxifen, were prepared in order to study the interaction of the drug with the cell membrane. TOR is not surface active but it remains at the interface in DPPG rich monolayers anchored by electrostatic interaction with the anionic DPPG up to the equimolar composition. The fluidity of mixed monolayers increases up to the TOR mole fraction X TOR = 0.3, remaining practically invariant for higher compositions. Brewster angle microscopy shows that the TOR disturbs the DPPG organization and the liquid condensed (LC) domains of DPPG become undetectable for X TOR ≥ 0.4. Laser scanning confocal fluorescence microscopy images of the LB films doped with rhodamine B-piperazine amide dye confirm the progressive reduction in size of LC domains, from which TOR and rhodamine are excluded. The incorporation of TOR in DPPG monolayers up to the equimolar composition supports the formation of a TOR:DPPG complex (1:1) due to electrostatic interactions between the negatively charged polar groups of DPPG and protonated TOR. - Highlights: • Toremifene (TOR) in dipalmitoyl-phosphatidyl-glycerol (DPPG) monolayers • Electrostatic interactions between DPPG and TOR form a 1:1 complex. • TOR increases the fluidity of DPPG monolayers. • Incorporation of TOR in the fluid phase of DPPG followed by fluorescence imaging

  11. Interaction of toremifene with dipalmitoyl-phosphatidyl-glycerol in monolayers at the air–water interface followed by fluorescence microscopy in Langmuir–Blodgett films

    Energy Technology Data Exchange (ETDEWEB)

    Romão, Rute I.S. [Centro de Química Estrutural, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, P-1049-001 Lisboa (Portugal); Maçôas, Ermelinda [Centro de Química-Física Molecular and IN — Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, P-1049-001 Lisboa (Portugal); Martinho, José M.G. [Centro de Química-Física Molecular and IN — Institute of Nanoscience and Nanotechnology, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, P-1049-001 Lisboa (Portugal); Departamento de Engenharia Química, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, P-1049-001 Lisboa (Portugal); Gonçalves da Silva, Amélia M.P.S., E-mail: ameliags@ist.utl.pt [Centro de Química Estrutural, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, P-1049-001 Lisboa (Portugal); Departamento de Engenharia Química, Instituto Superior Técnico, Universidade Técnica de Lisboa, Av. Rovisco Pais, P-1049-001 Lisboa (Portugal)

    2013-05-01

    Langmuir monolayers of dipalmitoyl-phosphatidyl-glycerol (DPPG) containing toremifene (TOR), an antiestrogen drug derivative of tamoxifen, were prepared in order to study the interaction of the drug with the cell membrane. TOR is not surface active but it remains at the interface in DPPG rich monolayers anchored by electrostatic interaction with the anionic DPPG up to the equimolar composition. The fluidity of mixed monolayers increases up to the TOR mole fraction X{sub TOR} = 0.3, remaining practically invariant for higher compositions. Brewster angle microscopy shows that the TOR disturbs the DPPG organization and the liquid condensed (LC) domains of DPPG become undetectable for X{sub TOR} ≥ 0.4. Laser scanning confocal fluorescence microscopy images of the LB films doped with rhodamine B-piperazine amide dye confirm the progressive reduction in size of LC domains, from which TOR and rhodamine are excluded. The incorporation of TOR in DPPG monolayers up to the equimolar composition supports the formation of a TOR:DPPG complex (1:1) due to electrostatic interactions between the negatively charged polar groups of DPPG and protonated TOR. - Highlights: • Toremifene (TOR) in dipalmitoyl-phosphatidyl-glycerol (DPPG) monolayers • Electrostatic interactions between DPPG and TOR form a 1:1 complex. • TOR increases the fluidity of DPPG monolayers. • Incorporation of TOR in the fluid phase of DPPG followed by fluorescence imaging.

  12. Kadar Prostaglandin F2? pada Cairan Vesikula Seminalis dan Produk Sel Monolayer Vesikula Seminalis Sapi Bali (CONCENTRATIONS OF PROSTAGLANDIN F2? IN SEMINAL VESICLE FLUID AND PRODUCT OF SEMINAL VESICLE MONOLAYER CELLS OF BALI CATTLE

    Directory of Open Access Journals (Sweden)

    Tjok Gde Oka Pemayun

    2007-12-01

    Full Text Available In this study, the concentration of prostaglandin F2 ? (PGF2? in seminal vesicle fluid and seminal vesicle monolayer cell cultures of Bali cattle was determined. The seminal vesicle fluid was aspirated and the epithelial cells of the seminal vesicles were cultured in tissue culture medium (TCM 199 growth medium containing 10% fetal calf serum (FCS and 10% oestrus mares serum (EMS with a density of 1.9 x 106 cells / ml medium. Following an incubation at 38.50 C in 5% CO2 atmosphere for 6 days and the level of PGF2 ? in the original seminal vesicle fluid and in the cell culture medium were determined by radioimmunoassay techniques (RIA. The results showed that the level of PGF2 ? in the non-extracted monolayer culture of seminal vesicle (1287,50 ± 3,39 pg/ml was significantly higher than that of detected in non-extracted seminal vesicle fluid (1,23 ± 0,79 pg/ml. In contrast, after extraction the level of PGF2 ? in seminal vesicle monolayer cell cultures (218,33 ± 2,87 pg/ml significantly decreased as compared to seminal vesicle fluid (1750,83 ± 2,71 pg/ml. In conclusion the highest level of PGF2 ? was found in the extract of seminal vesicle fluid.

  13. Interactions between an anticancer drug - edelfosine - and cholesterol in Langmuir monolayers

    International Nuclear Information System (INIS)

    Wiecek, Agata; Dynarowicz-Latka, Patrycja; Minones, J.; Conde, Olga; Casas, Matilde

    2008-01-01

    Edelfosine (1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine, abbr. Et-18-OCH 3 ) is a new generation anticancer drug based on a phospholipids-like structure. Since its mechanism of action is believed to be related to the lipids of cellular membrane, we have investigated the interactions between edelfosine and main mammalian sterol: cholesterol, using the Langmuir monolayer technique. The interactions have been analyzed by comparing the experimental curves with theoretical ones, obtained basing on the additivity rule. The observed contraction together with negative deviations from ideality observed on the mean molecular area (A 12 ) vs film composition plots proves the existence of strong attractive forces between edelfosine and cholesterol, which have been quantified with the excess free energy of mixing (ΔG exc ) values, calculated from the surface pressure-area isotherms datapoints. The most negative values of ΔG exc have been found for the mixture of equimolar composition, proving its highest thermodynamic stability and the existence of the strongest interactions between film components. Thus, it has been postulated that at the surface edelfosine and cholesterol form stable complexes of 1:1 stoichiometry. The analysis of the collapse pressure values for the investigated mixed monolayers proves that films of edelfosine mole fraction ≤ 0.5 are miscible within the whole range of surface pressures, while monolayers richer in edelfosine mix in the pressure region below ca. 37.6 mN/m, which corresponds to the collapse of pure edelfosine monolayer. At this very surface pressure, edelfosine is expelled from the mixed monolayer and the remaining film is composed by surface complexes of high stability. The hypothesis of complex formation explains the results performed in vitro on cell cultures, indicating that the increase of cholesterol content significantly reduces the uptake of edelfosine

  14. Transfer plate radioassay using cell monolayers to detect anti-cell surface antibodies synthesized by lymphocyte hybridomas

    International Nuclear Information System (INIS)

    Schneider, M.D.; Eisenbarth, G.S.

    1979-01-01

    A solid phase [ 125 I] Protein A radioassay for anti-cell surface antibodies is described, which employs target cell monolayers cultured on fenestrated polyvinyl chloride 96-well plates ('transfer plates'). The calibrated aperture in the bottom of each well is small enough to retain fluid contents by surface tension during monolayer growth, but also permits fluid to enter the wells when transfer plate are lowered into receptacles containing washing buffer on test sera. To assay for antibodies directed against target cell surface antigens, transfer plates bearing monolayers are inserted into microculture plates with corresponding 96-well geometry, thereby simultaneously sampling 96 wells. This assay allows rapid screening of hundreds of hybrid cell colonies for production of antibodies with desired tissue specificity. (Auth.)

  15. Promoting Diversity Through Polar Interdisciplinary Coordinated Education (Polar ICE)

    Science.gov (United States)

    McDonnell, J. D.; Hotaling, L. A.; Garza, C.; Van Dyk, P. B.; Hunter-thomson, K. I.; Middendorf, J.; Daniel, A.; Matsumoto, G. I.; Schofield, O.

    2017-12-01

    Polar Interdisciplinary Coordinated Education (ICE) is an education and outreach program designed to provide public access to the Antarctic and Arctic regions through polar data and interactions with the scientists. The program provides multi-faceted science communication training for early career scientists that consist of a face-to face workshop and opportunities to apply these skills. The key components of the scientist training workshop include cultural competency training, deconstructing/decoding science for non-expert audiences, the art of telling science stories, and networking with members of the education and outreach community and reflecting on communication skills. Scientists partner with educators to provide professional development for K-12 educators and support for student research symposia. Polar ICE has initiated a Polar Literacy initiative that provides both a grounding in big ideas in polar science and science communication training designed to underscore the importance of the Polar Regions to the public while promoting interdisciplinary collaborations between scientists and educators. Our ultimate objective is to promote STEM identity through professional development of scientists and educators while developing career awareness of STEM pathways in Polar science.

  16. Induced Rashba splitting of electronic states in monolayers of Au, Cu on a W(110) substrate

    International Nuclear Information System (INIS)

    Shikin, A M; Rybkina, A A; Rybkin, A G; Marchenko, D; Korshunov, A S; Kudasov, Yu B; Frolova, N V; Sánchez-Barriga, J; Varykhalov, A; Rader, O

    2013-01-01

    The paper sums up a theoretical and experimental investigation of the influence of the spin–orbit coupling in W(110) on the spin structure of electronic states in deposited Au and Cu monolayers. Angle-resolved photoemission spectroscopy reveals that in the case of monolayers of Au and Cu spin–orbit split bands are formed in a surface-projected gap of W(110). Spin resolution shows that these states are spin polarized and that, therefore, the spin–orbit splitting is of Rashba type. The states evolve from hybridization of W 5d, 6p-derived states with the s, p states of the deposited metal. Interaction with Au and Cu shifts the original W 5d-derived states from the edges toward the center of the surface-projected gap. The size of the spin–orbit splitting of the formed states does not correlate with the atomic number of the deposited metal and is even higher for Cu than for Au. These states can be described as W-derived surface resonances modified by hybridization with the p, d states of the adsorbed metal. Our electronic structure calculations performed in the framework of the density functional theory correlate well with the experiment and demonstrate the crucial role of the W top layer for the spin–orbit splitting. It is shown that the contributions of the spin–orbit interaction from W and Au act in opposite directions which leads to a decrease of the resulting spin–orbit splitting in the Au monolayer on W(110). For the Cu monolayer with lower spin–orbit interaction the resulting spin splitting is higher and mainly determined by the W. (paper)

  17. A first-principles study on the magnetic properties of nonmetal atom doped phosphorene monolayers.

    Science.gov (United States)

    Zheng, Huiling; Zhang, Jianmin; Yang, Baishun; Du, Xiaobo; Yan, Yu

    2015-07-07

    In order to induce magnetism in two-dimensional semiconductors for their applications in spintronic devices and novel chemical and electronic properties of semiconducting phosphorene, the geometrical structure, electronic and magnetic properties of doped phosphorene monolayers with a series of nonmetal atoms, including H, F, Cl, Br, I, B, C, Si, N, As, O, S and Se, were systematically investigated using first-principles calculations. The results show that although the substitutional doping of H, F, Cl, Br, I, B, N, O, S or Se results in large structural deformation at the doping sites of phosphorene monolayers, all neutral nonmetal atom doped systems are stable. The calculated formation energies reveal that the substitutional doping of numerous nonmetal atoms in phosphorene monolayer are possible under appropriate experimental conditions, and the charged dopants C(-), Si(-), S(+) and Se(+) are stable. Moreover, the substitutional doping of H, F, Cl, Br, I, B, N, As, C(-), Si(-), S(+) or Se(+) cannot induce magnetism in phosphorene monolayer due to the saturation or pairing of valence electrons of dopant and its neighboring P atoms, whereas ground states of neutral C, Si, O, S or Se doped systems are magnetic due to the appearance of an unpaired valence electron of C and Si or the formation of a nonbonding 3p electron of a neighboring P atom around O, S and Se. Furthermore, the magnetic coupling between the moments induced by two Si, O, S or Se are long-range anti-ferromagnetic and the coupling can be attributed to the hybridization interaction involving polarized electrons, whereas the coupling between the moments induced by two C is weak.

  18. NOx Binding and Dissociation: Enhanced Ferroelectric Surface Chemistry by Catalytic Monolayers

    Science.gov (United States)

    Kakekhani, Arvin; Ismail-Beigi, Sohrab

    2013-03-01

    NOx molecules are regulated air pollutants produced during automotive combustion. As part of an effort to design viable catalysts for NOx decomposition operating at higher temperatures that would allow for improved fuel efficiency, we examine NOx chemistry on ferroelectric perovskite surfaces. Changing the direction of ferroelectric polarization can modify surface electronic properties and may lead to switchable surface chemistry. Here, we describe our recent work on potentially enhanced surface chemistry using catalytic RuO2 monolayers on perovskite ferroelectric substrates. In addition to thermodynamic stabilization of the RuO2 layer, we present results on the polarization-dependent binding of NO, O2, N2, and atomic O and N. We present results showing that one key problem with current catalysts, involving the difficulty of releasing dissociation products (especially oxygen), can be ameliorated by this method. Primary support from Toyota Motor Engineering and Manufacturing, North America, Inc.

  19. Zitterbewegung in monolayer silicene in a magnetic field

    International Nuclear Information System (INIS)

    Romera, E.; Roldán, J.B.; Santos, F. de los

    2014-01-01

    We study the Zitterbewegung in monolayer silicene under a perpendicular magnetic field. Using an effective Hamiltonian, we have investigated the autocorrelation function and the density currents in this material. Moreover, we have analyzed other types of periodicities of the system (classical and revival times). Finally, the above results are compared with their counterparts in two other monolayer materials subject to a magnetic field: graphene and MoS 2 . - Highlights: • We study Zitterbewegung in monolayer silicene in a magnetic field. • We have analyzed other types of periodicities in silicene. • The above results are compared with other monolayer materials (graphene and MoS 2 )

  20. Zitterbewegung in monolayer silicene in a magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Romera, E. [Departamento de Física Atómica, Molecular y Nuclear and Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain); Roldán, J.B. [Departamento de Electrónica y Tecnología de Computadores and CITIC, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain); Santos, F. de los [Departamento de Electromagnetismo y Física de la Materia, and Instituto Carlos I de Física Teórica y Computacional, Universidad de Granada, Fuentenueva s/n, 18071 Granada (Spain)

    2014-07-04

    We study the Zitterbewegung in monolayer silicene under a perpendicular magnetic field. Using an effective Hamiltonian, we have investigated the autocorrelation function and the density currents in this material. Moreover, we have analyzed other types of periodicities of the system (classical and revival times). Finally, the above results are compared with their counterparts in two other monolayer materials subject to a magnetic field: graphene and MoS{sub 2}. - Highlights: • We study Zitterbewegung in monolayer silicene in a magnetic field. • We have analyzed other types of periodicities in silicene. • The above results are compared with other monolayer materials (graphene and MoS{sub 2})

  1. Testing the effectiveness of monolayers under wind and wave conditions.

    Science.gov (United States)

    Palada, C; Schouten, P; Lemckert, C

    2012-01-01

    Monolayers are highly desirable for their evaporation reducing capabilities due to their relatively minimal cost and ease of application. Despite these positive attributes, monolayers have consistently failed to perform effectively due to the harsh wind and wave conditions prevalent across real-world water reserves. An exhaustive and consistent study testing the influence of wind and wave combinations on monolayer performance has yet to be presented in the literature. To remedy this, the effect of simultaneous wind and wave conditions on a benchmark high-performance monolayer (octadecanol suspension, CH(3)(CH(2))(16)CH(2)OH) has been analysed. Subjected only to waves, the monolayer remained intact due to its innate ability to compress and expand. However, the constant simultaneous application of wind and waves caused the monolayer to break up and gather down-wind where it volatilised over time. At wind speeds above 1.3 m s(-1) the monolayer was completely ineffective. For wind speeds below this threshold, the monolayer had an influence on the evaporation rate dependent on wind speed. From these results a series of application protocols can now be developed for the optimised deployment of monolayers in real-world water reserves. This will be of interest to private, commercial and government organisations involved in the storage and management of water resources.

  2. Serum-free media formulations are cell line-specific and require optimization for microcarrier culture.

    Science.gov (United States)

    Tan, Kah Yong; Teo, Kim Leng; Lim, Jessica F Y; Chen, Allen K L; Choolani, Mahesh; Reuveny, Shaul; Chan, Jerry; Oh, Steve Kw

    2015-08-01

    Mesenchymal stromal cells (MSCs) are being investigated as potential cell therapies for many different indications. Current methods of production rely on traditional monolayer culture on tissue-culture plastic, usually with the use of serum-supplemented growth media. However, the monolayer culturing system has scale-up limitations and may not meet the projected hundreds of billions to trillions batches of cells needed for therapy. Furthermore, serum-free medium offers several advantages over serum-supplemented medium, which may have supply and contaminant issues, leading to many serum-free medium formulations being developed. We cultured seven MSC lines in six different serum-free media and compared their growth between monolayer and microcarrier culture. We show that (i) expansion levels of MSCs in serum-free monolayer cultures may not correlate with expansion in serum-containing media; (ii) optimal culture conditions (serum-free media for monolayer or microcarrier culture) differ for each cell line; (iii) growth in static microcarrier culture does not correlate with growth in stirred spinner culture; (iv) and that early cell attachment and spreading onto microcarriers does not necessarily predict efficiency of cell expansion in agitated microcarrier culture. Current serum-free media developed for monolayer cultures of MSCs may not support MSC proliferation in microcarrier cultures. Further optimization in medium composition will be required for microcarrier suspension culture for each cell line. Copyright © 2015 International Society for Cellular Therapy. Published by Elsevier Inc. All rights reserved.

  3. Template-Directed Self-Assembly of Alkanethiol Monolayers: Selective Growth on Preexisting Monolayer Edges

    NARCIS (Netherlands)

    Sharpe, R.B.A.; Burdinski, Dirk; Huskens, Jurriaan; Zandvliet, Henricus J.W.; Reinhoudt, David; Poelsema, Bene

    2007-01-01

    Self-assembled monolayers were investigated for their suitability as two-dimensional scaffolds for the selective growth of alkanethiol edge structures. Heterostructures with chemical contrast could be grown, whose dimensions were governed by both the initial pattern sizes and the process time.

  4. Mixed DPPC/POPC Monolayers: All-atom Molecular Dynamics Simulations and Langmuir Monolayer Experiments

    Czech Academy of Sciences Publication Activity Database

    Olžyńska, Agnieszka; Zubek, M.; Roeselová, Martina; Korchowiec, J.; Cwiklik, Lukasz

    2016-01-01

    Roč. 1858, č. 12 (2016), s. 3120-3130 ISSN 0005-2736 R&D Projects: GA ČR GA15-14292S Institutional support: RVO:61388955 ; RVO:61388963 Keywords : phospholipid monolayers * Lung surfactant * molecular dynamics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.498, year: 2016

  5. Do embryonic polar bodies commit suicide?

    Science.gov (United States)

    Fabian, Dušan; Čikoš, Štefan; Rehák, Pavol; Koppel, Juraj

    2014-02-01

    The extrusion and elimination of unnecessary gametic/embryonic material is one of the key events that determines the success of further development in all living organisms. Oocytes produce the first polar body to fulfill the maturation process just before ovulation, and release the second polar body immediately after fertilization. The aim of this study was to compile a physiological overview of elimination of polar bodies during early preimplantation development in mice. Our results show that three-quarters of the first polar bodies were lost even at the zygotic stage; the 4-cell stage embryos contained only one (second) polar body, and the elimination of second polar bodies proceeded continuously during later development. Both first and second polar bodies showed several typical features of apoptosis: phosphatidylserine redistribution (observed for the first time in the first polar body), specific DNA degradation, condensed nuclear morphology, and inability to exclude cationic dye from the nucleus during the terminal stage of the apoptotic process. Caspase-3 activity was recorded only in the second polar body. From the morphological point of view, mouse polar bodies acted very similarly to damaged embryonic cells which have lost contact with their neighboring blastomeres. In conclusion, polar bodies possess all the molecular equipment necessary for triggering and executing an active suicide process. Furthermore, similarly as in dying embryonic cells, stressing external conditions (culture in vitro) might accelerate and increase the incidence of apoptotic elimination of the polar bodies in embryos.

  6. Polar Polygons

    Science.gov (United States)

    2005-01-01

    18 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark-outlined polygons on a frost-covered surface in the south polar region of Mars. In summer, this surface would not be bright and the polygons would not have dark outlines--these are a product of the presence of seasonal frost. Location near: 77.2oS, 204.8oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  7. Impaired hair follicle morphogenesis and polarized keratinocyte movement upon conditional inactivation of integrin-linked kinase in the epidermis.

    Science.gov (United States)

    Nakrieko, Kerry-Ann; Welch, Ian; Dupuis, Holly; Bryce, Dawn; Pajak, Agnieszka; St Arnaud, René; Dedhar, Shoukat; D'Souza, Sudhir J A; Dagnino, Lina

    2008-04-01

    Integrin-linked kinase (ILK) is key for cell survival, migration, and adhesion, but little is known about its role in epidermal development and homeostasis in vivo. We generated mice with conditional inactivation of the Ilk gene in squamous epithelia. These mice die perinatally and exhibit skin blistering and severe defects in hair follicle morphogenesis, including greatly reduced follicle numbers, failure to progress beyond very early developmental stages, and pronounced defects in follicular keratinocyte proliferation. ILK-deficient epidermis shows abnormalities in adhesion to the basement membrane and in differentiation. ILK-deficient cultured keratinocytes fail to attach and spread efficiently and exhibit multiple abnormalities in actin cytoskeletal organization. Ilk gene inactivation in cultured keratinocytes causes impaired ability to form stable lamellipodia, to directionally migrate, and to polarize. These defects are accompanied by abnormal distribution of active Cdc42 to cell protrusions, as well as reduced activation of Rac1 upon induction of cell migration in scraped keratinocyte monolayers. Significantly, alterations in cell spreading and forward movement in single cells can be rescued by expression of constitutively active Rac1 or RhoG. Our studies underscore a central and distinct role for ILK in hair follicle development and in polarized cell movements, two key aspects of epithelial morphogenesis and function.

  8. Strategic Polarization.

    Science.gov (United States)

    Kalai, Adam; Kalai, Ehud

    2001-08-01

    In joint decision making, similarly minded people may take opposite positions. Consider the example of a marriage in which one spouse gives generously to charity while the other donates nothing. Such "polarization" may misrepresent what is, in actuality, a small discrepancy in preferences. It may be that the donating spouse would like to see 10% of their combined income go to charity each year, while the apparently frugal spouse would like to see 8% donated. A simple game-theoretic analysis suggests that the spouses will end up donating 10% and 0%, respectively. By generalizing this argument to a larger class of games, we provide strategic justification for polarization in many situations such as debates, shared living accommodations, and disciplining children. In some of these examples, an arbitrarily small disagreement in preferences leads to an arbitrarily large loss in utility for all participants. Such small disagreements may also destabilize what, from game-theoretic point of view, is a very stable equilibrium. Copyright 2001 Academic Press.

  9. Recombinant albumin monolayers on latex particles.

    Science.gov (United States)

    Sofińska, Kamila; Adamczyk, Zbigniew; Kujda, Marta; Nattich-Rak, Małgorzata

    2014-01-14

    The adsorption of recombinant human serum albumin (rHSA) on negatively charged polystyrene latex micro-particles was studied at pH 3.5 and the NaCl concentration range of 10(-3) to 0.15 M. The electrophoretic mobility of latex monotonically increased with the albumin concentration in the suspension. The coverage of adsorbed albumin was quantitatively determined using the depletion method, where the residual protein concentration was determined by electrokinetic measurements and AFM imaging. It was shown that albumin adsorption was irreversible. Its maximum coverage on latex varied between 0.7 mg m(-2) for 10(-3) M NaCl to 1.3 mg m(-2) for 0.15 M NaCl. The latter value matches the maximum coverage previously determined for human serum albumin on mica using the streaming potential method. The increase in the maximum coverage was interpreted in terms of reduced electrostatic repulsion among adsorbed molecules. These facts confirm that albumin adsorption at pH 3.5 is governed by electrostatic interactions and proceeds analogously to colloid particle deposition. The stability of albumin monolayers was measured in additional experiments where changes in the latex electrophoretic mobility and the concentration of free albumin in solutions were monitored over prolonged time periods. Based on these experimental data, a robust procedure of preparing albumin monolayers on latex particles of well-controlled coverage and molecule distribution was proposed.

  10. Cavity plasmon polaritons in monolayer graphene

    International Nuclear Information System (INIS)

    Kotov, O.V.; Lozovik, Yu.E.

    2011-01-01

    Plasmon polaritons in a new system, a monolayer doped graphene embedded in optical microcavity, are studied here. The dispersion law for lower and upper cavity plasmon polaritons is obtained. Peculiarities of Rabi splitting for the system are analyzed; particularly, role of Dirac-like spinor (envelope) wave functions in graphene and corresponding angle factors are considered. Typical Rabi frequencies for maximal (acceptable for Dirac-like electron spectra) Fermi energy and frequencies of polaritons near polariton gap are estimated. The plasmon polaritons in considered system can be used for high-speed information transfer in the THz region. -- Highlights: → Plasmon polaritons in a monolayer doped graphene embedded in optical microcavity, are studied here. → The dispersion law for lower and upper cavity plasmon polaritons is obtained. → Peculiarities of Rabi splitting for the system are analyzed. → Role of Dirac-like wave functions in graphene and corresponding angle factors are considered. → Typical Rabi frequencies and frequencies of polaritons near polariton gap are estimated.

  11. Recombinant invasive Lactococcus lactis can transfer DNA vaccines either directly to dendritic cells or across an epithelial cell monolayer.

    Science.gov (United States)

    de Azevedo, Marcela; Meijerink, Marjolein; Taverne, Nico; Pereira, Vanessa Bastos; LeBlanc, Jean Guy; Azevedo, Vasco; Miyoshi, Anderson; Langella, Philippe; Wells, Jerry M; Chatel, Jean-Marc

    2015-09-11

    Lactococcus lactis (L. lactis), a generally regarded as safe (GRAS) bacterium has recently been investigated as a mucosal delivery vehicle for DNA vaccines. Because of its GRAS status, L. lactis represents an attractive alternative to attenuated pathogens. Previous studies showed that eukaryotic expression plasmids could be delivered into intestinal epithelial cells (IECs) by L. lactis, or recombinant invasive strains of L. lactis, leading to heterologous protein expression. Although expression of antigens in IECs might lead to vaccine responses, it would be of interest to know whether uptake of L. lactis DNA vaccines by dendritic cells (DCs) could lead to antigen expression as they are unique in their ability to induce antigen-specific T cell responses. To test this, we incubated mouse bone marrow-derived DCs (BMDCs) with invasive L. lactis strains expressing either Staphylococcus aureus Fibronectin Binding Protein A (LL-FnBPA+), or Listeria monocytogenes mutated Internalin A (LL-mInlA+), both strains carrying a plasmid DNA vaccine (pValac) encoding for the cow milk allergen β-lactoglobulin (BLG). We demonstrated that they can transfect BMDCs, inducing the secretion of the pro-inflammatory cytokine IL-12. We also measured the capacity of strains to invade a polarized monolayer of IECs, mimicking the situation encountered in the gastrointestinal tract. Gentamycin survival assay in these cells showed that LL-mInlA+ is 100 times more invasive than L. lactis. The cross-talk between differentiated IECs, BMDCs and bacteria was also evaluated using an in vitro transwell co-culture model. Co-incubation of strains in this model showed that DCs incubated with LL-mInlA+ containing pValac:BLG could express significant levels of BLG. These results suggest that DCs could sample bacteria containing the DNA vaccine across the epithelial barrier and express the antigen. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  12. Metal ion interaction with phosphorylated tyrosine analogue monolayers on gold.

    Science.gov (United States)

    Petoral, Rodrigo M; Björefors, Fredrik; Uvdal, Kajsa

    2006-11-23

    Phosphorylated tyrosine analogue molecules (pTyr-PT) were assembled onto gold substrates, and the resulting monolayers were used for metal ion interaction studies. The monolayers were characterized by X-ray photoelectron spectroscopy (XPS), infrared reflection-absorption spectroscopy (IRAS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), both prior to and after exposure to metal ions. XPS verified the elemental composition of the molecular adsorbate and the presence of metal ions coordinated to the phosphate groups. Both the angle-dependent XPS and IRAS results were consistent with the change in the structural orientation of the pTyr-PT monolayer upon exposure to metal ions. The differential capacitance of the monolayers upon coordination of the metal ions was evaluated using EIS. These metal ions were found to significantly change the capacitance of the pTyr-PT monolayers in contrast to the nonphosphorylated tyrosine analogue (TPT). CV results showed reduced electrochemical blocking capabilities of the phosphorylated analogue monolayer when exposed to metal ions, supporting the change in the structure of the monolayer observed by XPS and IRAS. The largest change in the structure and interfacial capacitance was observed for aluminum ions, compared to calcium, magnesium, and chromium ions. This type of monolayer shows an excellent capability to coordinate metal ions and has a high potential for use as sensing layers in biochip applications to monitor the presence of metal ions.

  13. A MOLECULAR-DYNAMICS STUDY OF LECITHIN MONOLAYERS

    NARCIS (Netherlands)

    AHLSTROM, P; BERENDSEN, HJC

    1993-01-01

    Two monolayers of didecanoyllecithin at the air-water interface have been studied using molecular dynamics simulations. The model system consisted of two monolayers of 42 lecithin molecules each separated by a roughly 4 nm thick slab of SPC water. The area per lecithin molecule was 0.78 nm(2)

  14. Characterization of self-assembled monolayers on a ruthenium surface

    NARCIS (Netherlands)

    Shaheen, Amrozia; Sturm, Jacobus Marinus; Ricciardi, R.; Huskens, Jurriaan; Lee, Christopher James; Bijkerk, Frederik

    2017-01-01

    We have modified and stabilized the ruthenium surface by depositing a self-assembled monolayer (SAM) of 1-hexadecanethiol on a polycrystalline ruthenium thin film. The growth mechanism, dynamics, and stability of these monolayers were studied. SAMs, deposited under ambient conditions, on

  15. Langmuir monolayer formation of metal complexes from polymerizable amphiphilic ligands

    NARCIS (Netherlands)

    Werkman, P.J; Schouten, A.J.

    1996-01-01

    The monolayer behaviour of 4-(10,12-pentacosadiynoicamidomethyl)-pyridine at the air-water interface was studied by measuring the surface pressure-area isotherms. The amphiphile formed stable monolayers with a clear liquid-expanded (LE) to liquid-condensed phase transition at various temperatures.

  16. Mechanical and electronic properties of Janus monolayer transition metal dichalcogenides

    Science.gov (United States)

    Shi, Wenwu; Wang, Zhiguo

    2018-05-01

    The mechanical and electronic properties of Janus monolayer transition metal dichalcogenides MXY (M  =  Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W; X/Y  =  S, Se, Te) were investigated using density functional theory. Results show that breaking the out-of-plane structural symmetry can be used to tune the electronic and mechanical behavior of monolayer transition metal dichalcogenides. The band gaps of monolayer WXY and MoXY are in the ranges of 0.16–1.91 and 0.94–1.69 eV, respectively. A semiconductor to metallic phase transition occurred in Janus monolayer MXY (M  =  Ti, Zr and Hf). The monolayers MXY (M  =  V, Nb, Ta and Cr) show metallic characteristics, which show no dependence on the structural symmetry breaking. The mechanical properties of MXY depended on the composition. Monolayer MXY (M  =  Mo, Ti, Zr, Hf and W) showed brittle characteristic, whereas monolayer CrXY and VXY are with ductile characteristic. The in-plane stiffness of pristine and Janus monolayer MXY are in the range between 22 and 158 N m‑1. The tunable electronic and mechanical properties of these 2D materials would advance the development of ultra-sensitive detectors, nanogenerators, low-power electronics, and energy harvesting and electromechanical systems.

  17. Protonation of octadecylamine Langmuir monolayer by adsorption of halide counterions

    Science.gov (United States)

    Sung, Woongmo; Avazbaeva, Zaure; Lee, Jonggwan; Kim, Doseok

    Langmuir monolayer consisting of octadecylamine (C18H37NH2, ODA) was investigated by heterodyne vibrational sum-frequency generation (HD-VSFG) spectroscopy in conjunction with surface pressure-area (π- A) isotherm, and the result was compared with that from cationic-lipid (DPTAP) Langmuir monolayer. In case of ODA monolayer on pure water, both SF intensity of water OH band and the surface pressure were significantly smaller than those of the DPTAP monolayer implying that only small portion of the amine groups (-NH3+ is protonated in the monolayer. In the presence of sodium halides (NaCl and NaI) in the subphase water, it was found that the sign of Imχ (2) of water OH band remained the same as that of the ODA monolayer on pure water, but there was a substantial increase in the SF amplitude. From this, we propose that surface excess of the halide counterions (Cl- and I-) makes the solution condition near the ODA monolayer/water interface more acidic so that ODA molecules in the monolayer are more positively charged, which works to align the water dipoles at the interface.

  18. 2D Semiconductors for Valley-Polarized LEDs and Photodetectors

    Science.gov (United States)

    Yu, Ting

    The recently discovered two-dimensional (2D) semiconductors, such as transitional-metal-dichalcogenide monolayers, have aroused great interest due to the underlying quantum physics and the appealing optoelectronic applications like atomically thin light-emitting diodes (LEDs) and photodetectors. On the one hand, valley-polarized electroluminescence and photocurrent from such monolayers have not caused enough attention but highly demanded as building blocks for the new generation valleytronic applications. On the other hand, most reports on these devices are based on the mechanically exfoliated small samples. Considering real applications, a strategy which could offer mass-product and high compatibility to the current planar processes is greatly demanded. Large-area samples prepared by chemical vapour deposition (CVD) are perfect candidates towards such a goal. Here, we report electrically tunable valley-polarized electroluminescence and the selective spin-valley-coupled photocurrent in optoelectronic devices based on monolayer WS2 and MoS2 grown by CVD, exhibiting large electroluminescence and photocurrent dichroisms of 81% and 60%, respectively. The controllable valley polarization and emission components of the electroluminescence have been realized by varying electrical injection of carriers. For the observed helicity-dependent photocurrent, the circular photogalvanic effect at resonant excitations has been found to take the dominant responsibility.

  19. Polarized secondary radioactive beams

    International Nuclear Information System (INIS)

    Zaika, N.I.

    1992-01-01

    Three methods of polarized radioactive nuclei beam production: a) a method nuclear interaction of the non-polarized or polarized charged projectiles with target nuclei; b) a method of polarization of stopped reaction radioactive products in a special polarized ion source with than following acceleration; c) a polarization of radioactive nuclei circulating in a storage ring are considered. Possible life times of the radioactive ions for these methods are determined. General schemes of the polarization method realizations and depolarization problems are discussed

  20. A pentacene monolayer trapped between graphene and a substrate.

    Science.gov (United States)

    Zhang, Qicheng; Peng, Boyu; Chan, Paddy Kwok Leung; Luo, Zhengtang

    2015-09-21

    A self-assembled pentacene monolayer can be fabricated between the solid-solid interface of few-layered graphene (FLG) and the mica substrate, through a diffusion-spreading method. By utilizing a transfer method that allows us to sandwich pentacene between graphene and mica, followed by controlled annealing, we enabled the diffused pentacene to be trapped in the interfaces and led to the formation of a stable monolayer. We found that the formation of a monolayer is kinetically favored by using a 2D Ising lattice gas model for pentacene trapped between the graphene-substrate interfaces. This kinetic Monte Carlo simulation results indicate that, due to the graphene substrate enclosure, the spreading of the first layer proceeds faster than the second layer, as the kinetics favors the filling of voids by molecules from the second layer. This graphene assisted monolayer assembly method provides a new avenue for the fabrication of two-dimensional monolayer structures.

  1. Polar crane

    International Nuclear Information System (INIS)

    Makosinski, S.

    1981-01-01

    In many applications polar cranes have to be repeatedly positioned with high accuracy. A guidance system is disclosed which has two pairs of guides. Each guide consists of two rollers carried by a sheave rotatable mounted on the crane bridge, the rollers being locatable one on each side of a guideway, e.g. the circular track on which the bridge runs. The pairs of guides are interconnected by respective rope loops which pass around and are locked to the respective pairs of sheaves in such a manner that movement of one guide results in equal movement of the other guide in a sense to maintain the repeatability of positioning of the centre of the bridge. A hydraulically-linked guide system is also described. (author)

  2. Three-dimensional Huh7 cell culture system for the study of Hepatitis C virus infection

    Directory of Open Access Journals (Sweden)

    Uprichard Susan L

    2009-07-01

    Full Text Available Abstract Background In order to elucidate how Hepatitis C Virus (HCV interacts with polarized hepatocytes in vivo and how HCV-induced alterations in cellular function contribute to HCV-associated liver disease, a more physiologically relevant hepatocyte culture model is needed. As such, NASA-engineered three-dimensional (3-D rotating wall vessel (RWV bioreactors were used in effort to promote differentiation of HCV-permissive Huh7 hepatoma cells. Results When cultured in the RWV, Huh7 cells became morphologically and transcriptionally distinct from more standard Huh7 two-dimensional (2-D monolayers. Specifically, RWV-cultured Huh7 cells formed complex, multilayered 3-D aggregates in which Phase I and Phase II xenobiotic drug metabolism genes, as well as hepatocyte-specific transcripts (HNF4α, Albumin, TTR and α1AT, were upregulated compared to 2-D cultured Huh7 cells. Immunofluorescence analysis revealed that these HCV-permissive 3-D cultured Huh7 cells were more polarized than their 2D counterparts with the expression of HCV receptors, cell adhesion and tight junction markers (CD81, scavenger receptor class B member 1, claudin-1, occludin, ZO-1, β-Catenin and E-Cadherin significantly increased and exhibiting apical, lateral and/or basolateral localization. Conclusion These findings show that when cultured in 3-D, Huh7 cells acquire a more differentiated hepatocyte-like phenotype. Importantly, we show that these 3D cultures are highly permissive for HCV infection, thus providing an opportunity to study HCV entry and the effects of HCV infection on host cell function in a more physiologically relevant cell culture system.

  3. Extracellular Matrix-Mediated Maturation of Human Pluripotent Stem Cell-Derived Cardiac Monolayer Structure and Electrophysiological Function.

    Science.gov (United States)

    Herron, Todd J; Rocha, Andre Monteiro Da; Campbell, Katherine F; Ponce-Balbuena, Daniela; Willis, B Cicero; Guerrero-Serna, Guadalupe; Liu, Qinghua; Klos, Matt; Musa, Hassan; Zarzoso, Manuel; Bizy, Alexandra; Furness, Jamie; Anumonwo, Justus; Mironov, Sergey; Jalife, José

    2016-04-01

    Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) monolayers generated to date display an immature embryonic-like functional and structural phenotype that limits their utility for research and cardiac regeneration. In particular, the electrophysiological function of hPSC-CM monolayers and bioengineered constructs used to date are characterized by slow electric impulse propagation velocity and immature action potential profiles. Here, we have identified an optimal extracellular matrix for significant electrophysiological and structural maturation of hPSC-CM monolayers. hPSC-CM plated in the optimal extracellular matrix combination have impulse propagation velocities ≈2× faster than previously reported (43.6±7.0 cm/s; n=9) and have mature cardiomyocyte action potential profiles, including hyperpolarized diastolic potential and rapid action potential upstroke velocity (146.5±17.7 V/s; n=5 monolayers). In addition, the optimal extracellular matrix promoted hypertrophic growth of cardiomyocytes and the expression of key mature sarcolemmal (SCN5A, Kir2.1, and connexin43) and myofilament markers (cardiac troponin I). The maturation process reported here relies on activation of integrin signaling pathways: neutralization of β1 integrin receptors via blocking antibodies and pharmacological blockade of focal adhesion kinase activation prevented structural maturation. Maturation of human stem cell-derived cardiomyocyte monolayers is achieved in a 1-week period by plating cardiomyocytes on PDMS (polydimethylsiloxane) coverslips rather than on conventional 2-dimensional cell culture formats, such as glass coverslips or plastic dishes. Activation of integrin signaling and focal adhesion kinase is essential for significant maturation of human cardiac monolayers. © 2016 American Heart Association, Inc.

  4. Translocation of SiO2-NPs across in vitro human bronchial epithelial monolayer

    International Nuclear Information System (INIS)

    George, I; Vranic, S; Boland, S; Borot, M C; Marano, F; Baeza-Squiban, A

    2013-01-01

    Safe development and application of nanotechnologies in many fields require better knowledge about their potential adverse effects on human health. Evidence of abilities of nanoparticles (NPs) to cross epithelial barriers and reach secondary organs via the bloodstream led us to investigate the translocation of SiO 2 NPs of 50 nm (50 nm-SiO 2 -NPs) across human bronchial epithelial cells that are primary targets after exposure to inhaled NPs. We quantified the translocation of fluorescently labelled SiO 2 NPs at non-cytotoxic concentrations (5 and 10 μg/cm 2 ) across Calu-3 epithelial monolayer. After 14 days in culture Calu-3 cells seeded onto 3 μm-polycarbonate Transwell membranes formed an efficient bronchial barrier assessed by measurement of the transepithelial electric resistance and quantification of the permeability of the monolayer. After 24 hours of exposure, we observed a significant translocation of NPs that was more important when the initial NP concentration decreased. Confocal microscopy observations revealed NP uptake by cells and an important NP retention inside the porous membrane. In conclusion, 50 nm-SiO 2 -NPs can cross the human bronchial epithelial barrier without affecting the integrity of the epithelial cell monolayer.

  5. Adsorption of GST-PI3Kγ at the Air-Buffer Interface and at Substrate and Nonsubstrate Phospholipid Monolayers

    Science.gov (United States)

    Hermelink, Antje; Kirsch, Cornelia; Klinger, Reinhard; Reiter, Gerald; Brezesinski, Gerald

    2009-01-01

    The recruitment of phosphoinositide 3-kinase γ (PI3Kγ) to the cell membrane is a crucial requirement for the initiation of inflammation cascades by second-messenger production. In addition to identifying other regulation pathways, it has been found that PI3Kγ is able to bind phospholipids directly. In this study, the adsorption behavior of glutathione S-transferase (GST)-PI3Kγ to nonsubstrate model phospholipids, as well as to commercially available substrate inositol phospholipids (phosphoinositides), was investigated by use of infrared reflection-absorption spectroscopy (IRRAS). The nonsubstrate phospholipid monolayers also yielded important information about structural requirements for protein adsorption. The enzyme did not interact with condensed zwitterionic or anionic monolayers; however, it could penetrate into uncompressed fluid monolayers. Compression to values above its equilibrium pressure led to a squeezing out and desorption of the protein. Protein affinity for the monolayer surface increased considerably when the lipid had an anionic headgroup and contained an arachidonoyl fatty acyl chain in sn-2 position. Similar results on a much higher level were observed with substrate phosphoinositides. No structural response of GST-PI3Kγ to lipid interaction was detected by IRRAS. On the other hand, protein adsorption caused a condensing effect in phosphoinositide monolayers. In addition, the protein reduced the charge density at the interface probably by shifting the pK values of the phosphate groups attached to the inositol headgroups. Because of their strongly polar headgroups, an interaction of the inositides with the water molecules of the subphase can be expected. This interaction is disturbed by protein adsorption, causing the ionization state of the phosphates to change. PMID:19186139

  6. Adsorption of GST-PI3Kgamma at the air-buffer interface and at substrate and nonsubstrate phospholipid monolayers.

    Science.gov (United States)

    Hermelink, Antje; Kirsch, Cornelia; Klinger, Reinhard; Reiter, Gerald; Brezesinski, Gerald

    2009-02-01

    The recruitment of phosphoinositide 3-kinase gamma (PI3Kgamma) to the cell membrane is a crucial requirement for the initiation of inflammation cascades by second-messenger production. In addition to identifying other regulation pathways, it has been found that PI3Kgamma is able to bind phospholipids directly. In this study, the adsorption behavior of glutathione S-transferase (GST)-PI3Kgamma to nonsubstrate model phospholipids, as well as to commercially available substrate inositol phospholipids (phosphoinositides), was investigated by use of infrared reflection-absorption spectroscopy (IRRAS). The nonsubstrate phospholipid monolayers also yielded important information about structural requirements for protein adsorption. The enzyme did not interact with condensed zwitterionic or anionic monolayers; however, it could penetrate into uncompressed fluid monolayers. Compression to values above its equilibrium pressure led to a squeezing out and desorption of the protein. Protein affinity for the monolayer surface increased considerably when the lipid had an anionic headgroup and contained an arachidonoyl fatty acyl chain in sn-2 position. Similar results on a much higher level were observed with substrate phosphoinositides. No structural response of GST-PI3Kgamma to lipid interaction was detected by IRRAS. On the other hand, protein adsorption caused a condensing effect in phosphoinositide monolayers. In addition, the protein reduced the charge density at the interface probably by shifting the pK values of the phosphate groups attached to the inositol headgroups. Because of their strongly polar headgroups, an interaction of the inositides with the water molecules of the subphase can be expected. This interaction is disturbed by protein adsorption, causing the ionization state of the phosphates to change.

  7. Vector assembly of colloids on monolayer substrates

    Science.gov (United States)

    Jiang, Lingxiang; Yang, Shenyu; Tsang, Boyce; Tu, Mei; Granick, Steve

    2017-06-01

    The key to spontaneous and directed assembly is to encode the desired assembly information to building blocks in a programmable and efficient way. In computer graphics, raster graphics encodes images on a single-pixel level, conferring fine details at the expense of large file sizes, whereas vector graphics encrypts shape information into vectors that allow small file sizes and operational transformations. Here, we adapt this raster/vector concept to a 2D colloidal system and realize `vector assembly' by manipulating particles on a colloidal monolayer substrate with optical tweezers. In contrast to raster assembly that assigns optical tweezers to each particle, vector assembly requires a minimal number of optical tweezers that allow operations like chain elongation and shortening. This vector approach enables simple uniform particles to form a vast collection of colloidal arenes and colloidenes, the spontaneous dissociation of which is achieved with precision and stage-by-stage complexity by simply removing the optical tweezers.

  8. Defect-Tolerant Monolayer Transition Metal Dichalcogenides

    DEFF Research Database (Denmark)

    Pandey, Mohnish; Rasmussen, Filip Anselm; Kuhar, Korina

    2016-01-01

    Localized electronic states formed inside the band gap of a semiconductor due to crystal defects can be detrimental to the material's optoelectronic properties. Semiconductors with a lower tendency to form defect induced deep gap states are termed defect-tolerant. Here we provide a systematic first...... the gap. These ideas are made quantitative by introducing a descriptor that measures the degree of similarity of the conduction and valence band manifolds. Finally, the study is generalized to nonpolar nanoribbons of the TMDs where we find that only the defect sensitive materials form edge states within......-principles investigation of defect tolerance in 29 monolayer transition metal dichalcogenides (TMDs) of interest for nanoscale optoelectronics. We find that the TMDs based on group VI and X metals form deep gap states upon creation of a chalcogen (S, Se, Te) vacancy, while the TMDs based on group IV metals form only...

  9. Beam damage of self-assembled monolayers

    International Nuclear Information System (INIS)

    Rieke, P.C.; Baer, D.R.; Fryxell, G.E.; Engelhard, M.H.; Porter, M.S.

    1993-01-01

    X-ray and electron beam damage studies were performed on Br-terminated and methyl-terminated alkylsilane self-assembled monolayers. X-ray beam initiated damage was primarily limited to removal of the labile Br group and did not significantly damage the hydrocarbon chain. Some of the x-ray beam damage could be attributed to low-energy electrons emitted by the non-monochromatic source, but further damage was attributed to secondary electrons produced in the sample by x-ray exposure. Electron beams caused significant damage to the hydrocarbon chains. Maximum damage occurred with a beam energy of 600 eV and a dosage of 6x10 -3 C/cm 2

  10. Enhanced photocurrent in engineered bacteriorhodopsin monolayer.

    Science.gov (United States)

    Patil, Amol V; Premaruban, Thenhuan; Berthoumieu, Olivia; Watts, Anthony; Davis, Jason J

    2012-01-12

    The integration of the transmembrane protein bacteriorhodopsin (BR) with man-made electrode surfaces has attracted a great deal of interest for some two decades or more and holds significant promise from the perspective of derived photoresponse or energy capture interfaces. Here we demonstrate that a novel and strategically engineered cysteine site (M163C) can be used to intimately and effectively couple delipidated BR to supporting metallic electrode surfaces. By virtue of the combined effects of the greater surface molecular density afforded by delipidation, and the vicinity of the electrostatic changes associated with proton pumping to the transducing metallic continuum, the resulting films generate a considerably greater photocurrent density on wavelength-selective illumination than previously achievable with monolayers of BR. Given the uniquely photoresponsive, wavelength-selective, and photostable characteristics of this protein, the work has implications for utilization in solar energy capture and photodetector devices.

  11. Acid monolayer functionalized iron oxide nanoparticle catalysts

    Science.gov (United States)

    Ikenberry, Myles

    Superparamagnetic iron oxide nanoparticle functionalization is an area of intensely active research, with applications across disciplines such as biomedical science and heterogeneous catalysis. This work demonstrates the functionalization of iron oxide nanoparticles with a quasi-monolayer of 11-sulfoundecanoic acid, 10-phosphono-1-decanesulfonic acid, and 11-aminoundecanoic acid. The carboxylic and phosphonic moieties form bonds to the iron oxide particle core, while the sulfonic acid groups face outward where they are available for catalysis. The particles were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), potentiometric titration, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectrometry (XPS), and dynamic light scattering (DLS). The sulfonic acid functionalized particles were used to catalyze the hydrolysis of sucrose at 80° and starch at 130°, showing a higher activity per acid site than the traditional solid acid catalyst Amberlyst-15, and comparing well against results reported in the literature for sulfonic acid functionalized mesoporous silicas. In sucrose catalysis reactions, the phosphonic-sulfonic nanoparticles (PSNPs) were seen to be incompletely recovered by an external magnetic field, while the carboxylic-sulfonic nanoparticles (CSNPs) showed a trend of increasing activity over the first four recycle runs. Between the two sulfonic ligands, the phosphonates produced a more tightly packed monolayer, which corresponded to a higher sulfonic acid loading, lower agglomeration, lower recoverability through application of an external magnetic field, and higher activity per acid site for the hydrolysis of starch. Functionalizations with 11-aminoundecanoic acid resulted in some amine groups binding to the surfaces of iron oxide nanoparticles. This amine binding is commonly ignored in iron oxide

  12. Surface-segregated monolayers: a new type of ordered monolayer for surface modification of organic semiconductors.

    Science.gov (United States)

    Wei, Qingshuo; Tajima, Keisuke; Tong, Yujin; Ye, Shen; Hashimoto, Kazuhito

    2009-12-09

    We report a new type of ordered monolayer for the surface modification of organic semiconductors. Fullerene derivatives with fluorocarbon chains ([6,6]-phenyl-C(61)-buryric acid 1H,1H-perfluoro-1-alkyl ester or FC(n)) spontaneously segregated as a monolayer on the surface of a [6,6]-phenyl-C(61)-butyric acid methyl ester (PCBM) film during a spin-coating process from the mixture solutions, as confirmed by X-ray photoelectron spectroscopy (XPS). Ultraviolet photoelectron spectroscopy (UPS) showed the shift of ionization potentials (IPs) depending on the fluorocarbon chain length, indicating the formation of surface dipole moments. Surface-sensitive vibrational spectroscopy, sum frequency generation (SFG) revealed the ordered molecular orientations of the C(60) moiety in the surface FC(n) layers. The intensity of the SFG signals from FC(n) on the surface showed a clear odd-even effect when the length of the fluorocarbon chain was changed. This new concept of the surface-segregated monolayer provides a facile and versatile approach to modifying the surface of organic semiconductors and is applicable to various organic optoelectronic devices.

  13. Modeling mechanical inhomogeneities in small populations of proliferating monolayers and spheroids.

    Science.gov (United States)

    Lejeune, Emma; Linder, Christian

    2018-06-01

    Understanding the mechanical behavior of multicellular monolayers and spheroids is fundamental to tissue culture, organism development, and the early stages of tumor growth. Proliferating cells in monolayers and spheroids experience mechanical forces as they grow and divide and local inhomogeneities in the mechanical microenvironment can cause individual cells within the multicellular system to grow and divide at different rates. This differential growth, combined with cell division and reorganization, leads to residual stress. Multiple different modeling approaches have been taken to understand and predict the residual stresses that arise in growing multicellular systems, particularly tumor spheroids. Here, we show that by using a mechanically robust agent-based model constructed with the peridynamic framework, we gain a better understanding of residual stresses in multicellular systems as they grow from a single cell. In particular, we focus on small populations of cells (1-100 s) where population behavior is highly stochastic and prior investigation has been limited. We compare the average strain energy density of cells in monolayers and spheroids using different growth and division rules and find that, on average, cells in spheroids have a higher strain energy density than cells in monolayers. We also find that cells in the interior of a growing spheroid are, on average, in compression. Finally, we demonstrate the importance of accounting for stochastic fluctuations in the mechanical environment, particularly when the cellular response to mechanical cues is nonlinear. The results presented here serve as a starting point for both further investigation with agent-based models, and for the incorporation of major findings from agent-based models into continuum scale models when explicit representation of individual cells is not computationally feasible.

  14. Nuclear polarization and neutrons

    International Nuclear Information System (INIS)

    Glaettli, H.

    1985-01-01

    Different possibilities for the use of polarized nuclei in thermal neutron scattering on condensed matter are reviewed. Highly polarized nuclei are the starting point for studying dipolar magnetic order. Systematic measurement of spin-dependent scattering lengths is possible on samples with polarized nuclei. Highly polarized hydrogen should help to unravel complicated structures in chemistry and biology. The use of polarized proton targets as an energy-independent neutron polarizer in the thermal and epithermal region should be considered afresh. (author)

  15. Defect Structure of Localized Excitons in a WSe2 Monolayer

    KAUST Repository

    Zhang, Shuai

    2017-07-26

    The atomic and electronic structure of intrinsic defects in a WSe2 monolayer grown on graphite was revealed by low temperature scanning tunneling microscopy and spectroscopy. Instead of chalcogen vacancies that prevail in other transition metal dichalcogenide materials, intrinsic defects in WSe2 arise surprisingly from single tungsten vacancies, leading to the hole (p-type) doping. Furthermore, we found these defects to dominate the excitonic emission of the WSe2 monolayer at low temperature. Our work provided the first atomic-scale understanding of defect excitons and paved the way toward deciphering the defect structure of single quantum emitters previously discovered in the WSe2 monolayer.

  16. Electrically tunable polarizer based on 2D orthorhombic ferrovalley materials

    Science.gov (United States)

    Shen, Xin-Wei; Tong, Wen-Yi; Gong, Shi-Jing; Duan, Chun-Gang

    2018-03-01

    The concept of ferrovalley materials has been proposed very recently. The existence of spontaneous valley polarization, resulting from ferromagnetism, in such hexagonal 2D materials makes nonvolatile valleytronic applications realizable. Here, we introduce a new member of ferrovalley family with orthorhombic lattice, i.e. monolayer group-IV monochalcogenides (GIVMs), in which the intrinsic valley polarization originates from ferroelectricity, instead of ferromagnetism. Combining the group theory analysis and first-principles calculations, we demonstrate that, different from the valley-selective circular dichroism in hexagonal lattice, linearly polarized optical selectivity for valleys exists in the new type of ferrovalley materials. On account of the distinctive property, a prototype of electrically tunable polarizer is realized. In the ferrovalley-based polarizer, a laser beam can be optionally polarized in x- or y-direction, depending on the ferrovalley state controlled by external electric fields. Such a device can be further optimized to emit circularly polarized radiation with specific chirality and to realize the tunability for operating wavelength. Therefore, we show that 2D orthorhombic ferrovalley materials are the promising candidates to provide an advantageous platform to realize the polarizer driven by electric means, which is of great importance in extending the practical applications of valleytronics.

  17. Neutron polarization in polarized 3He targets

    International Nuclear Information System (INIS)

    Friar, J.L.; Gibson, B.F.; Payne, G.L.; Bernstein, A.M.; Chupp, T.E.

    1990-01-01

    Simple formulas for the neutron and proton polarizations in polarized 3 He targets are derived assuming (1) quasielastic final states; (2) no final-state interactions; (3) no meson-exchange currents; (4) large momentum transfers; (5) factorizability of 3 He SU(4) response-function components. Numerical results from a wide variety of bound-state solutions of the Faddeev equations are presented. It is found that this simple model predicts the polarization of neutrons in a fully polarized 3 He target to be 87%, while protons should have a slight residual polarization of -2.7%. Numerical studies show that this model works very well for quasielastic electron scattering

  18. Coexistence of multiple conformations in cysteamine monolayers on Au(111)

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Bilic, A; Reimers, JR

    2005-01-01

    The structural organization, catalytic function, and electronic properties of cysteamine monolayers on Au(111) have been addressed comprehensively by voltammetry, in situ scanning tunneling microscopy (STM) in anaerobic environment, and a priori molecular dynamics (MD) simulation and STM image si...

  19. Evidence of indirect gap in monolayer WSe2

    KAUST Repository

    Hsu, Wei-Ting; Lu, Li-Syuan; Wang, Dean; Huang, Jing-Kai; Li, Ming-Yang; Chang, Tay-Rong; Chou, Yi-Chia; Juang, Zhen-Yu; Jeng, Horng-Tay; Li, Lain-Jong; Chang, Wen-Hao

    2017-01-01

    Monolayer transition metal dichalcogenides, such as MoS2 and WSe2, have been known as direct gap semiconductors and emerged as new optically active materials for novel device applications. Here we reexamine their direct gap properties

  20. Monolayer MoS2 heterojunction solar cells

    KAUST Repository

    Tsai, Menglin

    2014-08-26

    We realized photovoltaic operation in large-scale MoS2 monolayers by the formation of a type-II heterojunction with p-Si. The MoS 2 monolayer introduces a built-in electric field near the interface between MoS2 and p-Si to help photogenerated carrier separation. Such a heterojunction photovoltaic device achieves a power conversion efficiency of 5.23%, which is the highest efficiency among all monolayer transition-metal dichalcogenide-based solar cells. The demonstrated results of monolayer MoS 2/Si-based solar cells hold the promise for integration of 2D materials with commercially available Si-based electronics in highly efficient devices. © 2014 American Chemical Society.

  1. Using 3D Culture of Primary Mammary Epithelial Cells to Define Molecular Entities Required for Acinus Formation: Analyzing MAP Kinase Phosphatases.

    Science.gov (United States)

    Gajewska, Malgorzata; McNally, Sara

    2017-01-01

    Three-dimensional (3D) cell cultures on reconstituted basement membrane (rBM) enable the study of complex interactions between extracellular matrix (ECM) components and epithelial cells, which are crucial for the establishment of cell polarity and functional development of epithelia. 3D cultures of mammary epithelial cells (MECs) on Matrigel (a laminin-rich ECM derived from the Engelbreth-Holm-Swarm (EHS) murine tumor) promote interactions of MECs with the matrix via integrins, leading to formation of spherical monolayers of polarized cells surrounding a hollow lumen (acini). Acini closely resemble mammary alveoli found in the mammary gland. Thus, it is possible to study ECM-cell interactions and signalling pathways that regulate formation and maintenance of tissue-specific shape and functional differentiation of MECs in 3D under in vitro conditions. Here we present experimental protocols used to investigate the role of mitogen-activated protein kinase phosphatases (MKPs) during development of the alveoli-like structures by primary mouse mammary epithelial cells (PMMEC) cultured on Matrigel. We present detailed protocols for PMMEC isolation, and establishment of 3D cultures using an "on top" method, use of specific kinase and phosphatases inhibitors (PD98059 and pervanadate, respectively) administered at different stages of acinus development, and give examples of analyses carried out post-culture (Western blot, immunofluorescence staining, and confocal imaging).

  2. Structural phase transition in monolayer MoTe2 driven by electrostatic doping

    Science.gov (United States)

    Wang, Ying; Xiao, Jun; Zhu, Hanyu; Li, Yao; Alsaid, Yousif; Fong, King Yan; Zhou, Yao; Wang, Siqi; Shi, Wu; Wang, Yuan; Zettl, Alex; Reed, Evan J.; Zhang, Xiang

    2017-10-01

    Monolayers of transition-metal dichalcogenides (TMDs) exhibit numerous crystal phases with distinct structures, symmetries and physical properties. Exploring the physics of transitions between these different structural phases in two dimensions may provide a means of switching material properties, with implications for potential applications. Structural phase transitions in TMDs have so far been induced by thermal or chemical means; purely electrostatic control over crystal phases through electrostatic doping was recently proposed as a theoretical possibility, but has not yet been realized. Here we report the experimental demonstration of an electrostatic-doping-driven phase transition between the hexagonal and monoclinic phases of monolayer molybdenum ditelluride (MoTe2). We find that the phase transition shows a hysteretic loop in Raman spectra, and can be reversed by increasing or decreasing the gate voltage. We also combine second-harmonic generation spectroscopy with polarization-resolved Raman spectroscopy to show that the induced monoclinic phase preserves the crystal orientation of the original hexagonal phase. Moreover, this structural phase transition occurs simultaneously across the whole sample. This electrostatic-doping control of structural phase transition opens up new possibilities for developing phase-change devices based on atomically thin membranes.

  3. First-principle calculations of optical properties of monolayer arsenene and antimonene allotropes

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Yuanfeng; Peng, Bo; Zhang, Hao; Zhang, Rongjun; Zhu, Heyuan [Shanghai Ultra-precision Optical Manufacturing Engineering Research Center and Key Laboratory of Micro and Nano Photonic Structures (Ministry of Education), Department of Optical Science and Engineering, Fudan University, Shanghai 200433 (China); Shao, Hezhu [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2017-04-15

    Recently a stable monolayer of antimony in buckled honeycomb structure called antimonene was successfully grown on 3D topological insulator Bi{sub 2}Te{sub 3} and Sb{sub 2}Te{sub 3}, which displays novel semiconducting properties. By first-principle calculations, we systematically investigate the electronic and optical properties of α- and β-allotropes of monolayer arsenene/antimonene. The obtained electronic structures reveal that the direct band gap of α-arsenene/antimonene is much smaller than the indirect band gap of their β-counterpart, respectively. Significant absorption is observed in α-antimonene, which can be used as a broad saturable absorber. For β-arsenene/antimonene, the reflectivity is low and the absorption is negligible in the visible region when the polarization along the out-plane direction, indicating that β-arsenene/antimonene are polarizationally transparent materials. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Selectively Plasmon-Enhanced Second-Harmonic Generation from Monolayer Tungsten Diselenide on Flexible Substrates

    KAUST Repository

    Wang, Zhuo

    2018-01-04

    Monolayer two-dimensional transition metal dichalcogenides (2D TMDCs) exhibit promising characteristics in miniaturized nonlinear optical frequency converters, due to their inversion asymmetry and large second-order nonlinear susceptibility. However, these materials usually have a very short light interaction lengths with the pump laser because they are atomically thin, such that second-harmonic generation (SHG) is generally inefficient. In this paper, we fabricate a judiciously structured 150-nm-thick planar surface consisting of monolayer tungsten diselenide and sub-20-nm-wide gold trenches on flexible substrates, reporting ~7000-fold SHG enhancement without peak broadening or background in the spectra as compared to WSe2 on as-grown sapphire substrates. Our proof-of-concept experiment yields effective second-order nonlinear susceptibility of 2.1 × 104 pm/V. Three orders of magnitude enhancement is maintained with pump wavelength ranging from 800 nm to 900 nm, breaking the limitation of narrow pump wavelength range for cavity-enhanced SHG. In addition, SHG amplitude can be dynamically controlled via selective excitation of the lateral gap plasmon by rotating the laser polarization. Such fully open, flat and ultrathin profile enables a great variety of functional samples with high SHG from one patterned silicon substrate, favoring scalable production of nonlinear converters. The surface accessibility also enables integration with other optical components for information processing in an ultrathin and flexible form.

  5. Improving Charge Injection in Organic Electronic Devices Using Self-Assembled Monolayers

    Science.gov (United States)

    Campbell, I. H.; Kress, J. D.; Martin, R. L.; Smith, D. L.; Barashkov, N. N.; Ferraris, J. P.

    1997-03-01

    Organic electronic devices consist of one or more insulating organic layers contacted by metallic conductors. The Schottky energy barrier between the metal and the organic material is determined by the work function of the metal contact as described in the ideal Schottky model. The magnitude of the metal/organic Schottky energy barrier controls charge injection from the metal into the organic layer. Previously, polar alkane-thiol based self-assembled monolayers (SAMs) were used to change the Schottky energy barrier between the metal and an organic film by more than 1 eV. In these SAMs, the large energy gap of the alkane molecules blocks charge injection into the organic layer despite the decrease of the Schottky energy barrier. Here, we demonstrate improved charge injection into the organic material by using conjugated self-assembled monolayers. The conjugated SAMs have modest energy gaps which allow improved charge injection into the organic layer. We present measurements of current-voltage characteristics and metal/organic Schottky energy barriers for device structures both with and without conjugated SAMs.

  6. Selectively Plasmon-Enhanced Second-Harmonic Generation from Monolayer Tungsten Diselenide on Flexible Substrates

    KAUST Repository

    Wang, Zhuo; Dong, Zhaogang; Zhu, Hai; Jin, Lei; Chiu, Ming-Hui; Li, Lain-Jong; Xu, Qing-Hua; Eda, Goki; Maier, Stefan A.; Wee, Andrew T. S.; Qiu, Cheng-Wei; Yang, Joel K.W.

    2018-01-01

    Monolayer two-dimensional transition metal dichalcogenides (2D TMDCs) exhibit promising characteristics in miniaturized nonlinear optical frequency converters, due to their inversion asymmetry and large second-order nonlinear susceptibility. However, these materials usually have a very short light interaction lengths with the pump laser because they are atomically thin, such that second-harmonic generation (SHG) is generally inefficient. In this paper, we fabricate a judiciously structured 150-nm-thick planar surface consisting of monolayer tungsten diselenide and sub-20-nm-wide gold trenches on flexible substrates, reporting ~7000-fold SHG enhancement without peak broadening or background in the spectra as compared to WSe2 on as-grown sapphire substrates. Our proof-of-concept experiment yields effective second-order nonlinear susceptibility of 2.1 × 104 pm/V. Three orders of magnitude enhancement is maintained with pump wavelength ranging from 800 nm to 900 nm, breaking the limitation of narrow pump wavelength range for cavity-enhanced SHG. In addition, SHG amplitude can be dynamically controlled via selective excitation of the lateral gap plasmon by rotating the laser polarization. Such fully open, flat and ultrathin profile enables a great variety of functional samples with high SHG from one patterned silicon substrate, favoring scalable production of nonlinear converters. The surface accessibility also enables integration with other optical components for information processing in an ultrathin and flexible form.

  7. Enhanced valley splitting in monolayer WSe2 due to magnetic exchange field.

    Science.gov (United States)

    Zhao, Chuan; Norden, Tenzin; Zhang, Peiyao; Zhao, Puqin; Cheng, Yingchun; Sun, Fan; Parry, James P; Taheri, Payam; Wang, Jieqiong; Yang, Yihang; Scrace, Thomas; Kang, Kaifei; Yang, Sen; Miao, Guo-Xing; Sabirianov, Renat; Kioseoglou, George; Huang, Wei; Petrou, Athos; Zeng, Hao

    2017-08-01

    Exploiting the valley degree of freedom to store and manipulate information provides a novel paradigm for future electronics. A monolayer transition-metal dichalcogenide (TMDC) with a broken inversion symmetry possesses two degenerate yet inequivalent valleys, which offers unique opportunities for valley control through the helicity of light. Lifting the valley degeneracy by Zeeman splitting has been demonstrated recently, which may enable valley control by a magnetic field. However, the realized valley splitting is modest (∼0.2 meV T -1 ). Here we show greatly enhanced valley spitting in monolayer WSe 2 , utilizing the interfacial magnetic exchange field (MEF) from a ferromagnetic EuS substrate. A valley splitting of 2.5 meV is demonstrated at 1 T by magnetoreflectance measurements and corresponds to an effective exchange field of ∼12 T. Moreover, the splitting follows the magnetization of EuS, a hallmark of the MEF. Utilizing the MEF of a magnetic insulator can induce magnetic order and valley and spin polarization in TMDCs, which may enable valleytronic and quantum-computing applications.

  8. Kohn-Luttinger superconductivity in monolayer and bilayer semimetals with the Dirac spectrum

    International Nuclear Information System (INIS)

    Kagan, M. Yu.; Mitskan, V. A.; Korovushkin, M. M.

    2014-01-01

    The effect of Coulomb interaction in an ensemble of Dirac fermions on the formation of superconducting pairing in monolayer and bilayer doped graphene is studied using the Kohn-Luttinger mechanism disregarding the Van der Waals potential of the substrate and impurities. The electronic structure of graphene is described using the Shubin-Vonsovsky model taking into account the intratomic, interatomic, and interlayer (in the case of bilayer graphene) Coulomb interactions between electrons. The Cooper instability is determined by solving the Bethe-Saltpeter integral equation. The renormalized scattering amplitude is obtained with allowance for the Kohn-Luttinger polarization contributions up to the second order of perturbation theory in the Coulomb interaction. It plays the role of effective interaction in the Bethe-Salpeter integral equation. It is shown that the allowance for the Kohn-Luttinger renormalizations as well as intersite Coulomb interaction noticeably affects the competition between the superconducting phases with the f-wave and d + id-wave symmetries of the order parameter. It is demonstrated that the superconducting transition temperature for an idealized graphene bilayer with significant interlayer Coulomb interaction between electrons is noticeably higher than in the monolayer case

  9. Repolarization of hepatocytes in culture.

    Science.gov (United States)

    Talamini, M A; Kappus, B; Hubbard, A

    1997-01-01

    We have evaluated the biochemical, morphological, and functional redevelopment of polarity in freshly isolated hepatocytes cultured using a double layer collagen gel sandwich technique. Western blot analysis showed increased cellular levels of the cell adhesion protein uvomorulin as cultured hepatocytes repolarized. Immunofluorescence studies using antibodies against domain-specific membrane proteins showed polarity as early as 48 hours, although the pattern of the polymeric Immunoglobulin-A receptor (pIgA-R) differed from in vivo liver. Electron microscopy showed developing bile canaliculi at 1 day. However, the functional presence of tight junctions was absent at 1 day, but present at 5 days. We further showed functional polarity to be present at 4 days by documenting the ability of cultured hepatocytes to metabolize and excrete fluorescein diacetate into visible bile canaliculi. We conclude that hepatocytes cultured appropriately develop morphological and functional polarity. Hepatocyte culture is therefore a useful tool for the study of mechanisms responsible for the development of polarized function.

  10. Optical Kerr effect and two-photon absorption in monolayer black phosphorus

    Science.gov (United States)

    Margulis, Vl A.; Muryumin, E. E.; Gaiduk, E. A.

    2018-05-01

    A theoretical treatment of nonlinear refraction and two-photon absorption is presented for a novel two-dimensional material, monolayer black phosphorus (or phosphorene), irradiated by a normally incident and linearly polarized coherent laser beam of frequency ω. It is found that both the nonlinear refractive index n 2(ω) and the two-photon absorption coefficient α 2(ω) of phosphorene depend upon the polarization of the radiation field relative to phosphorene’s crystallographic axes. For the two principal polarization directions considered—viz, the armchair ({ \\mathcal A }{ \\mathcal C }) and zigzag ({ \\mathcal Z }{ \\mathcal Z }), the calculated values of n 2 and α 2 are distinguished by the order of their magnitude, with the n 2 and α 2 values being greater for the { \\mathcal A }{ \\mathcal C } direction. Furthermore, for almost all the incident photon energies below the fundamental absorption edge, except its neighborhood, the signs of n 2 as well as α 2 for the { \\mathcal A }{ \\mathcal C } and { \\mathcal Z }{ \\mathcal Z } polarization directions are opposed to each other. Also, for both the directions, the change of sign of n 2 is predicted to occur in the way between the two-photon absorption edge and the fundamental absorption edge, as well as in the near vicinity of the latter, where the Kerr nonlinearity has a pronounced resonant character and the magnitude of n 2 for the { \\mathcal A }{ \\mathcal C } and { \\mathcal Z }{ \\mathcal Z } polarization directions reaches its largest positive values of the order of 10‑9 and 10‑10 cm2 W‑1, respectively. The implications of the findings for practical all-optical switching applications are discussed.

  11. Ferroelectric transistors with monolayer molybdenum disulfide and ultra-thin aluminum-doped hafnium oxide

    Science.gov (United States)

    Yap, Wui Chung; Jiang, Hao; Liu, Jialun; Xia, Qiangfei; Zhu, Wenjuan

    2017-07-01

    In this letter, we demonstrate ferroelectric memory devices with monolayer molybdenum disulfide (MoS2) as the channel material and aluminum (Al)-doped hafnium oxide (HfO2) as the ferroelectric gate dielectric. Metal-ferroelectric-metal capacitors with 16 nm thick Al-doped HfO2 are fabricated, and a remnant polarization of 3 μC/cm2 under a program/erase voltage of 5 V is observed. The capability of potential 10 years data retention was estimated using extrapolation of the experimental data. Ferroelectric transistors based on embedded ferroelectric HfO2 and MoS2 grown by chemical vapor deposition are fabricated. Clockwise hysteresis is observed at low program/erase voltages due to slow bulk traps located near the 2D/dielectric interface, while counterclockwise hysteresis is observed at high program/erase voltages due to ferroelectric polarization. In addition, the endurances of the devices are tested, and the effects associated with ferroelectric materials, such as the wake-up effect and polarization fatigue, are observed. Reliable writing/reading in MoS2/Al-doped HfO2 ferroelectric transistors over 2 × 104 cycles is achieved. This research can potentially lead to advances of two-dimensional (2D) materials in low-power logic and memory applications.

  12. Wavepacket revivals in monolayer and bilayer graphene rings.

    Science.gov (United States)

    García, Trinidad; Rodríguez-Bolívar, Salvador; Cordero, Nicolás A; Romera, Elvira

    2013-06-12

    We have studied the existence of quantum revivals in graphene quantum rings within a simplified model. The time evolution of a Gaussian-populated wavepacket shows revivals in monolayer and bilayer graphene rings. We have also studied this behavior for quantum rings in a perpendicular magnetic field. We have found that revival time is an observable that shows different values for monolayer and bilayer graphene quantum rings. In addition, the revival time shows valley degeneracy breaking.

  13. Atomic defects and doping of monolayer NbSe2

    OpenAIRE

    Nguyen, Lan; Komsa, Hannu-Pekka; Khestanova, Ekaterina; Kashtiban, Reza J; Peters, Jonathan J.P.; Lawlor, Sean; Sanchez, Ana M.; Sloan, Jeremy; Gorbachev, Roman; Grigorieva, Irina; Krasheninnikov, Arkady V.; Haigh, Sarah

    2017-01-01

    We have investigated the structure of atomic defects within monolayer NbSe2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reve...

  14. Wavepacket revivals in monolayer and bilayer graphene rings

    International Nuclear Information System (INIS)

    García, Trinidad; Rodríguez-Bolívar, Salvador; Cordero, Nicolás A; Romera, Elvira

    2013-01-01

    We have studied the existence of quantum revivals in graphene quantum rings within a simplified model. The time evolution of a Gaussian-populated wavepacket shows revivals in monolayer and bilayer graphene rings. We have also studied this behavior for quantum rings in a perpendicular magnetic field. We have found that revival time is an observable that shows different values for monolayer and bilayer graphene quantum rings. In addition, the revival time shows valley degeneracy breaking. (paper)

  15. Nonequilibrium 2-hydroxyoctadecanoic acid monolayers: effect of electrolytes.

    Science.gov (United States)

    Lendrum, Conrad D; Ingham, Bridget; Lin, Binhua; Meron, Mati; Toney, Michael F; McGrath, Kathryn M

    2011-04-19

    2-Hydroxyacids display complex monolayer phase behavior due to the additional hydrogen bonding afforded by the presence of the second hydroxy group. The placement of this group at the position α to the carboxylic acid functionality also introduces the possibility of chelation, a utility important in crystallization including biomineralization. Biomineralization, like many biological processes, is inherently a nonequilibrium process. The nonequilibrium monolayer phase behavior of 2-hydroxyoctadecanoic acid was investigated on each of pure water, calcium chloride, sodium bicarbonate and calcium carbonate crystallizing subphases as a precursor study to a model calcium carbonate biomineralizing system, each at a pH of ∼6. The role of the bicarbonate co-ion in manipulating the monolayer structure was determined by comparison with monolayer phase behavior on a sodium chloride subphase. Monolayer phase behavior was probed using surface pressure/area isotherms, surface potential, Brewster angle microscopy, and synchrotron-based grazing incidence X-ray diffraction and X-ray reflectivity. Complex phase behavior was observed for all but the sodium chloride subphase with hydrogen bonding, electrostatic and steric effects defining the symmetry of the monolayer. On a pure water subphase hydrogen bonding dominates with three phases coexisting at low pressures. Introduction of calcium ions into the aqueous subphase ensures strong cation binding to the surfactant head groups through chelation. The monolayer becomes very unstable in the presence of bicarbonate ions within the subphase due to short-range hydrogen bonding interactions between the monolayer and bicarbonate ions facilitated by the sodium cation enhancing surfactant solubility. The combined effects of electrostatics and hydrogen bonding are observed on the calcium carbonate crystallizing subphase. © 2011 American Chemical Society

  16. Density determination of langmuir-blodgett monolayer films using x-ray reflectivity technique

    International Nuclear Information System (INIS)

    Damar Yoga Kusuma

    2015-01-01

    Monolayer deposition by Langmuir-Blodgett technique produces monolayer films that are uniform with controllable thickness down to nanometer scale. To evaluate the quality of the monolayer deposition, X-ray reflectivity technique are employed to monitor the monolayers density. Langmuir-Blodgett monolayer with good coverage and uniformity results in film density close to its macroscopic film counterpart whereas films with presence of air gaps shows lower density compared to its macroscopic film counterpart. (author)

  17. Electrical Contacts in Monolayer Arsenene Devices.

    Science.gov (United States)

    Wang, Yangyang; Ye, Meng; Weng, Mouyi; Li, Jingzhen; Zhang, Xiuying; Zhang, Han; Guo, Ying; Pan, Yuanyuan; Xiao, Lin; Liu, Junku; Pan, Feng; Lu, Jing

    2017-08-30

    Arsenene, arsenic analogue of graphene, as an emerging member of two-dimensional semiconductors (2DSCs), is quite promising in next-generation electronic and optoelectronic applications. The metal electrical contacts play a vital role in the charge transport and photoresponse processes of nanoscale 2DSC devices and even can mask the intrinsic properties of 2DSCs. Here, we present a first comprehensive study of the electrical contact properties of monolayer (ML) arsenene with different electrodes by using ab initio electronic calculations and quantum transport simulations. Schottky barrier is always formed with bulk metal contacts owing to the Fermi level pinning (pinning factor S = 0.33), with electron Schottky barrier height (SBH) of 0.12, 0.21, 0.25, 0.35, and 0.50 eV for Sc, Ti, Ag, Cu, and Au contacts and hole SBH of 0.75 and 0.78 eV for Pd and Pt contacts, respectively. However, by contact with 2D graphene, the Fermi level pinning effect can be reduced due to the suppression of metal-induced gap states. Remarkably, a barrier free hole injection is realized in ML arsenene device with graphene-Pt hybrid electrode, suggestive of a high device performance in such a ML arsenene device. Our study provides a theoretical foundation for the selection of favorable electrodes in future ML arsenene devices.

  18. Specific Ion Effects in Cholesterol Monolayers

    Directory of Open Access Journals (Sweden)

    Teresa Del Castillo-Santaella

    2016-05-01

    Full Text Available The interaction of ions with interfaces and, in particular, the high specificity of these interactions to the particular ions considered, are central questions in the field of surface forces. Here we study the effect of different salts (NaI, NaCl, CaCl2 and MgCl2 on monolayers made of cholesterol molecules, both experimentally (surface area vs. lateral pressure isotherms measured by a Langmuir Film Balance and theoretically (molecular dynamics (MD all-atomic simulations. We found that surface isotherms depend, both quantitatively and qualitatively, on the nature of the ions by altering the shape and features of the isotherm. In line with the experiments, MD simulations show clear evidences of specific ionic effects and also provide molecular level details on ion specific interactions with cholesterol. More importantly, MD simulations show that the interaction of a particular ion with the surface depends strongly on its counterion, a feature ignored so far in most theories of specific ionic effects in surface forces.

  19. Optical absorption in disordered monolayer molybdenum disulfide

    Science.gov (United States)

    Ekuma, C. E.; Gunlycke, D.

    2018-05-01

    We explore the combined impact of sulfur vacancies and electronic interactions on the optical properties of monolayer MoS2. First, we present a generalized Anderson-Hubbard Hamiltonian that accounts for both randomly distributed sulfur vacancies and the presence of dielectric screening within the material. Second, we parametrize this energy-dependent Hamiltonian from first-principles calculations based on density functional theory and the Green's function and screened Coulomb (GW) method. Third, we apply a first-principles-based many-body typical medium method to determine the single-particle electronic structure. Fourth, we solve the Bethe-Salpeter equation to obtain the charge susceptibility χ with its imaginary part being related to the absorbance A . Our results show that an increased vacancy concentration leads to decreased absorption both in the band continuum and from exciton states within the band gap. We also observe increased absorption below the band-gap threshold and present an expression, which describes Lifshitz tails, in excellent qualitative agreement with our numerical calculations. This latter increased absorption in the 1.0 -2.5 eV range makes defect engineering of potential interest for solar cell applications.

  20. Edge Delamination of Monolayer Transition Metal Dichalcogenides.

    Science.gov (United States)

    Ly, Thuc Hue; Yun, Seok Joon; Thi, Quoc Huy; Zhao, Jiong

    2017-07-25

    Delamination of thin films from the supportive substrates is a critical issue within the thin film industry. The emergent two-dimensional, atomic layered materials, including transition metal dichalcogenides, are highly flexible; thus buckles and wrinkles can be easily generated and play vital roles in the corresponding physical properties. Here we introduce one kind of patterned buckling behavior caused by the delamination from a substrate initiated at the edges of the chemical vapor deposition synthesized monolayer transition metal dichalcogenides, led by thermal expansion mismatch. The atomic force microscopy and optical characterizations clearly showed the puckered structures associated with the strain, whereas the transmission electron microscopy revealed the special sawtooth-shaped edges, which break the geometrical symmetry for the buckling behavior of hexagonal samples. The condition of the edge delamination is in accordance with the fracture behavior of thin film interfaces. This edge delamination and buckling process is universal for most ultrathin two-dimensional materials, which requires more attention in various future applications.

  1. Technique for etching monolayer and multilayer materials

    Science.gov (United States)

    Bouet, Nathalie C. D.; Conley, Raymond P.; Divan, Ralu; Macrander, Albert

    2015-10-06

    A process is disclosed for sectioning by etching of monolayers and multilayers using an RIE technique with fluorine-based chemistry. In one embodiment, the process uses Reactive Ion Etching (RIE) alone or in combination with Inductively Coupled Plasma (ICP) using fluorine-based chemistry alone and using sufficient power to provide high ion energy to increase the etching rate and to obtain deeper anisotropic etching. In a second embodiment, a process is provided for sectioning of WSi.sub.2/Si multilayers using RIE in combination with ICP using a combination of fluorine-based and chlorine-based chemistries and using RF power and ICP power. According to the second embodiment, a high level of vertical anisotropy is achieved by a ratio of three gases; namely, CHF.sub.3, Cl.sub.2, and O.sub.2 with RF and ICP. Additionally, in conjunction with the second embodiment, a passivation layer can be formed on the surface of the multilayer which aids in anisotropic profile generation.

  2. Defects and oxidation of group-III monochalcogenide monolayers

    Science.gov (United States)

    Guo, Yu; Zhou, Si; Bai, Yizhen; Zhao, Jijun

    2017-09-01

    Among various two-dimensional (2D) materials, monolayer group-III monochalcogenides (GaS, GaSe, InS, and InSe) stand out owing to their potential applications in microelectronics and optoelectronics. Devices made of these novel 2D materials are sensitive to environmental gases, especially O2 molecules. To address this critical issue, here we systematically investigate the oxidization behaviors of perfect and defective group-III monochalcogenide monolayers by first-principles calculations. The perfect monolayers show superior oxidation resistance with large barriers of 3.02-3.20 eV for the dissociation and chemisorption of O2 molecules. In contrast, the defective monolayers with single chalcogen vacancy are vulnerable to O2, showing small barriers of only 0.26-0.36 eV for the chemisorption of an O2 molecule. Interestingly, filling an O2 molecule to the chalcogen vacancy of group-III monochalcogenide monolayers could preserve the electronic band structure of the perfect system—the bandgaps are almost intact and the carrier effective masses are only moderately disturbed. On the other hand, the defective monolayers with single vacancies of group-III atoms carry local magnetic moments of 1-2 μB. These results help experimental design and synthesis of group-III monochalcogenides based 2D devices with high performance and stability.

  3. Nonlinear optical characteristics of monolayer MoSe{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Le, Chinh Tam; Ullah, Farman; Senthilkumar, Velusamy; Kim, Yong Soo [Department of Physics and Energy Harvest Storage Research Center, University of Ulsan (Korea, Republic of); Clark, Daniel J.; Jang, Joon I. [Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton, NY (United States); Sim, Yumin; Seong, Maeng-Je [Department of Physics, Chung-Ang University, Seoul (Korea, Republic of); Chung, Koo-Hyun [School of Mechanical Engineering, University of Ulsan (Korea, Republic of); Park, Hyoyeol [Electronics, Communication and Semiconductor Applications Department, Ulsan College (Korea, Republic of)

    2016-08-15

    In this study, we utilized picosecond pulses from an Nd:YAG laser to investigate the nonlinear optical characteristics of monolayer MoSe{sub 2}. Two-step growth involving the selenization of pulsed-laser-deposited MoO{sub 3} film was employed to yield the MoSe{sub 2} monolayer on a SiO{sub 2}/Si substrate. Raman scattering, photoluminescence (PL) spectroscopy, and atomic force microscopy verified the high optical quality of the monolayer. The second-order susceptibility χ{sup (2)} was calculated to be ∝50 pm V{sup -1} at the second harmonic wavelength λ{sub SHG} ∝810 nm, which is near the optical gap of the monolayer. Interestingly, our wavelength-dependent second harmonic scan can identify the bound excitonic states including negatively charged excitons much more efficiently, compared with the PL method at room temperature. Additionally, the MoSe{sub 2} monolayer exhibits a strong laser-induced damage threshold ∝16 GW cm{sup -2} under picosecond-pulse excitation{sub .} Our findings suggest that monolayer MoSe{sub 2} can be considered as a promising candidate for high-power, thin-film-based nonlinear optical devices and applications. (copyright 2016 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  4. Controlled electrodeposition of Au monolayer film on ionic liquid

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Qiang; Pang, Liuqing; Li, Man; Zhang, Yunxia; Ren, Xianpei [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710062 (China); Liu, Shengzhong Frank, E-mail: szliu@dicp.ac.cn [Key Laboratory of Applied Surface and Colloid Chemistry, National Ministry of Education, Shaanxi Engineering Lab for Advanced Energy Technology, School of Materials Science and Engineering, Shaanxi Normal University, Xi’an 710062 (China); Dalian Institute of Chemical Physics, Dalian National Laboratory for Clean Energy, Chinese Academy of Sciences, Dalian 116023 (China)

    2016-05-15

    Highlights: • We fabricate Au monolayer film on Ionic liquid substrate using an electrochemical deposition technique. • Au monolayer film was deposited on a “soft substrate” for the first time. • Au monolayer film can contribute extra Raman enhancement. - Abstract: Gold (Au) nanoparticles have been attractive for centuries for their vibrant appearance enhanced by their interaction with sunlight. Nowadays, there have been tremendous research efforts to develop them for high-tech applications including therapeutic agents, sensors, organic photovoltaics, medical applications, electronics and catalysis. However, there remains to be a challenge to fabricate a monolayer Au coating with complete coverage in controlled fashion. Here we present a facile method to deposit a uniform Au monolayer (ML) film on the [BMIM][PF{sub 6}] ionic liquid substrate using an electrochemical deposition process. It demonstrates that it is feasible to prepare a solid phase coating on the liquid-based substrate. Moreover, the thickness of the monolayer coating can be controlled to a layer-by-layer accuracy.

  5. Surface Charge Transfer Doping of Monolayer Phosphorene via Molecular Adsorption.

    Science.gov (United States)

    He, Yuanyuan; Xia, Feifei; Shao, Zhibin; Zhao, Jianwei; Jie, Jiansheng

    2015-12-03

    Monolayer phosphorene has attracted much attention owing to its extraordinary electronic, optical, and structural properties. Rationally tuning the electrical transport characteristics of monolayer phosphorene is essential to its applications in electronic and optoelectronic devices. Herein, we study the electronic transport behaviors of monolayer phosphorene with surface charge transfer doping of electrophilic molecules, including 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), NO2, and MoO3, using density functional theory combined with the nonequilibrium Green's function formalism. F4TCNQ shows optimal performance in enhancing the p-type conductance of monolayer phosphorene. Static electronic properties indicate that the enhancement is originated from the charge transfer between adsorbed molecule and phosphorene layer. Dynamic transport behaviors demonstrate that additional channels for hole transport in host monolayer phosphorene were generated upon the adsorption of molecule. Our work unveils the great potential of surface charge transfer doping in tuning the electronic properties of monolayer phosphorene and is of significance to its application in high-performance devices.

  6. Self-assembled monolayers of shape-persistent macrocycles on graphite: interior design and conformational polymorphism.

    Science.gov (United States)

    Vollmeyer, Joscha; Eberhagen, Friederike; Höger, Sigurd; Jester, Stefan-S

    2014-01-01

    Three shape-persistent naphthylene-phenylene-acetylene macrocycles of identical backbone structures and extraannular substitution patterns but different (empty, apolar, polar) nanopore fillings are self-assembled at the solid/liquid interface of highly oriented pyrolytic graphite and 1,2,4-trichlorobenzene. Submolecularly resolved images of the resulting two-dimensional (2D) crystalline monolayer patterns are obtained by in situ scanning tunneling microscopy. A concentration-dependent conformational polymorphism is found, and open and more dense packing motifs are observed. For all three compounds alike lattice parameters are found, therefore the intermolecular macrocycle distances are mainly determined by their size and symmetry. This is an excellent example that the graphite acts as a template for the macrocycle organization independent from their specific interior.

  7. Silicon Mie resonators for highly directional light emission from monolayer MoS2

    Science.gov (United States)

    Cihan, Ahmet Fatih; Curto, Alberto G.; Raza, Søren; Kik, Pieter G.; Brongersma, Mark L.

    2018-05-01

    Controlling light emission from quantum emitters has important applications, ranging from solid-state lighting and displays to nanoscale single-photon sources. Optical antennas have emerged as promising tools to achieve such control right at the location of the emitter, without the need for bulky, external optics. Semiconductor nanoantennas are particularly practical for this purpose because simple geometries such as wires and spheres support multiple, degenerate optical resonances. Here, we start by modifying Mie scattering theory developed for plane wave illumination to describe scattering of dipole emission. We then use this theory and experiments to demonstrate several pathways to achieve control over the directionality, polarization state and spectral emission that rely on a coherent coupling of an emitting dipole to optical resonances of a silicon nanowire. A forward-to-backward ratio of 20 was demonstrated for the electric dipole emission at 680 nm from a monolayer MoS2 by optically coupling it to a silicon nanowire.

  8. Measurement of molecular length of self-assembled monolayer probed by localized surface plasmon resonance

    Science.gov (United States)

    Ito, Juri; Kajikawa, Kotaro

    2016-02-01

    We propose a method to measure the variation of the molecular length of self-assembled monolayers (SAMs) when it is exposed to solutions at different pH conditions. The surface immobilized gold nanospheres (SIGNs) shows strong absorption peak at the wavelengths of 600-800 nm when p-polarized light is illuminated. The peak wavelength depends on the length of the gap distance between the SIGNs and the substrate. The gap is supported by the SAM molecules. According to the analytical calculation based on multiple expansion, the relation between the peak wavelength of the SIGN structures and the gap distance is calculated, to evaluate the molecular length of the SAM through the optical absorption spectroscopy for the SIGN structures. The molecular length of the SIGN structure was measured in air, water, acidic, and basic solutions. It was found that the molecular lengths are longer in acidic solutions.

  9. Self-assembled monolayers of shape-persistent macrocycles on graphite: interior design and conformational polymorphism

    Directory of Open Access Journals (Sweden)

    Joscha Vollmeyer

    2014-11-01

    Full Text Available Three shape-persistent naphthylene–phenylene–acetylene macrocycles of identical backbone structures and extraannular substitution patterns but different (empty, apolar, polar nanopore fillings are self-assembled at the solid/liquid interface of highly oriented pyrolytic graphite and 1,2,4-trichlorobenzene. Submolecularly resolved images of the resulting two-dimensional (2D crystalline monolayer patterns are obtained by in situ scanning tunneling microscopy. A concentration-dependent conformational polymorphism is found, and open and more dense packing motifs are observed. For all three compounds alike lattice parameters are found, therefore the intermolecular macrocycle distances are mainly determined by their size and symmetry. This is an excellent example that the graphite acts as a template for the macrocycle organization independent from their specific interior.

  10. Self assembled monolayer based liquid crystal biosensor for free cholesterol detection

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, Mukta; Agrawal, V. V. [Department of Science and Technology, Centre on Bimolecular Electronics, Biomedical Instrumentation Section, CSIR—National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110 012 (India); Chandran, Achu; Joshi, Tilak [Polymeric and Soft Materials Section, CSIR—National Physical Laboratory (CSIR), Dr. K. S. Krishnan Road, New Delhi 110 012 (India); Prakash, Jai [Centre for Physical and Mathematical Sciences, School of Basic and Applied Sciences, Central University of Punjab, City Campus, Mansa Road, Bathinda 151 001 (India); Biradar, A. M., E-mail: abiradar@mail.nplindia.ernet.in [Department of Science and Technology, Centre on Bimolecular Electronics, Biomedical Instrumentation Section, CSIR—National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110 012 (India); Polymeric and Soft Materials Section, CSIR—National Physical Laboratory (CSIR), Dr. K. S. Krishnan Road, New Delhi 110 012 (India)

    2014-04-14

    A unique cholesterol oxidase (ChOx) liquid crystal (LC) biosensor, based on the disruption of orientation in LCs, is developed for cholesterol detection. A self-assembled monolayer (SAM) of Dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DMOAP) and (3-Aminopropyl)trimethoxy-silane (APTMS) is prepared on a glass plate by adsorption. The enzyme (ChOx) is immobilized on SAM surface for 12 h before utilizing the film for biosensing purpose. LC based biosensing study is conducted on SAM/ChOx/LC (5CB) cells for cholesterol concentrations ranging from 10 mg/dl to 250 mg/dl. The sensing mechanism has been verified through polarizing optical microscopy, scanning electron microscopy, and spectrometric techniques.

  11. Self assembled monolayer based liquid crystal biosensor for free cholesterol detection

    International Nuclear Information System (INIS)

    Tyagi, Mukta; Agrawal, V. V.; Chandran, Achu; Joshi, Tilak; Prakash, Jai; Biradar, A. M.

    2014-01-01

    A unique cholesterol oxidase (ChOx) liquid crystal (LC) biosensor, based on the disruption of orientation in LCs, is developed for cholesterol detection. A self-assembled monolayer (SAM) of Dimethyloctadecyl[3-(trimethoxysilyl)propyl]ammonium chloride (DMOAP) and (3-Aminopropyl)trimethoxy-silane (APTMS) is prepared on a glass plate by adsorption. The enzyme (ChOx) is immobilized on SAM surface for 12 h before utilizing the film for biosensing purpose. LC based biosensing study is conducted on SAM/ChOx/LC (5CB) cells for cholesterol concentrations ranging from 10 mg/dl to 250 mg/dl. The sensing mechanism has been verified through polarizing optical microscopy, scanning electron microscopy, and spectrometric techniques

  12. Polarized electron sources

    International Nuclear Information System (INIS)

    Prepost, R.

    1994-01-01

    The fundamentals of polarized electron sources are described with particular application to the Stanford Linear Accelerator Center. The SLAC polarized electron source is based on the principle of polarized photoemission from Gallium Arsenide. Recent developments using epitaxially grown, strained Gallium Arsenide cathodes have made it possible to obtain electron polarization significantly in excess of the conventional 50% polarization limit. The basic principles for Gallium and Arsenide polarized photoemitters are reviewed, and the extension of the basic technique to strained cathode structures is described. Results from laboratory measurements of strained photocathodes as well as operational results from the SLAC polarized source are presented

  13. Polarized electron sources

    Energy Technology Data Exchange (ETDEWEB)

    Prepost, R. [Univ. of Wisconsin, Madison, WI (United States)

    1994-12-01

    The fundamentals of polarized electron sources are described with particular application to the Stanford Linear Accelerator Center. The SLAC polarized electron source is based on the principle of polarized photoemission from Gallium Arsenide. Recent developments using epitaxially grown, strained Gallium Arsenide cathodes have made it possible to obtain electron polarization significantly in excess of the conventional 50% polarization limit. The basic principles for Gallium and Arsenide polarized photoemitters are reviewed, and the extension of the basic technique to strained cathode structures is described. Results from laboratory measurements of strained photocathodes as well as operational results from the SLAC polarized source are presented.

  14. Mode damping in a commensurate monolayer solid

    DEFF Research Database (Denmark)

    Bruch, Ludwig Walter; Hansen, Flemming Yssing

    1997-01-01

    with an elastic-continuum theory of the response of modes of either parallel or perpendicular polarization for a spherical adsorbate on a hexagonal substrate. The results are applied to the discussion of computer simulations and inelastic atomic-scattering experiments for adsorbates on graphite. The extreme...... of substrate modes with strong anomalous dispersion, and enables a semiquantitative account of observed avoided crossings of the adlayer perpendicular vibration mode and the substrate Rayleigh mode....

  15. Covalent Surface Modification of Silicon Oxides with Alcohols in Polar Aprotic Solvents.

    Science.gov (United States)

    Lee, Austin W H; Gates, Byron D

    2017-09-05

    Alcohol-based monolayers were successfully formed on the surfaces of silicon oxides through reactions performed in polar aprotic solvents. Monolayers prepared from alcohol-based reagents have been previously introduced as an alternative approach to covalently modify the surfaces of silicon oxides. These reagents are readily available, widely distributed, and are minimally susceptible to side reactions with ambient moisture. A limitation of using alcohol-based compounds is that previous reactions required relatively high temperatures in neat solutions, which can degrade some alcohol compounds or could lead to other unwanted side reactions during the formation of the monolayers. To overcome these challenges, we investigate the condensation reaction of alcohols on silicon oxides carried out in polar aprotic solvents. In particular, propylene carbonate has been identified as a polar aprotic solvent that is relatively nontoxic, readily accessible, and can facilitate the formation of alcohol-based monolayers. We have successfully demonstrated this approach for tuning the surface chemistry of silicon oxide surfaces with a variety of alcohol containing compounds. The strategy introduced in this research can be utilized to create silicon oxide surfaces with hydrophobic, oleophobic, or charged functionalities.

  16. Polarized neutron spectrometer

    International Nuclear Information System (INIS)

    Abov, Yu.G.; Novitskij, V.V.; Alfimenkov, V.P.; Galinskij, E.M.; Mareev, Yu.D.; Pikel'ner, L.B.; Chernikov, A.N.; Lason', L.; Tsulaya, V.M.; Tsulaya, M.I.

    2000-01-01

    The polarized neutron spectrometer, intended for studying the interaction of polarized neutrons with nuclei and condensed media in the area of energies from thermal up to several electron-volt, is developed at the IBR-2 reactor (JINR, Dubna). Diffraction on the Co(92%)-Fe(8%) magnetized monocrystals is used for the neutron polarization and polarization analysis. The neutron polarization within the whole energy range equals ∼ 95% [ru

  17. A high extinction ratio THz polarizer fabricated by double-bilayer wire grid structure

    Directory of Open Access Journals (Sweden)

    Bin Lu

    2016-02-01

    Full Text Available We designed a new style of broadband terahertz (THz polarizer with double-bilayer wire grid structure by fabricating them on both sides of silicon substrate. This THz polarizer shows a high average extinction ratio of 60dB in 0.5 to 2.0 THz frequency range and the maximum of 87 dB at 1.06 THz, which is much higher than that of conventional monolayer wire grid polarizers and single-bilayer wire grid ones.

  18. Heterointerface Screening Effects between Organic Monolayers and Monolayer Transition Metal Dichalcogenides

    KAUST Repository

    Zheng, Yu Jie; Huang, Yu Li; Chen, Yifeng; Zhao, Weijie; Eda, Goki; Spataru, Catalin D.; Zhang, Wenjing; Chang, Yung-Huang; Li, Lain-Jong; Chi, Dongzhi; Quek, Su Ying; Wee, Andrew Thye Shen

    2016-01-01

    © 2016 American Chemical Society. The nature and extent of electronic screening at heterointerfaces and their consequences on energy level alignment are of profound importance in numerous applications, such as solar cells, electronics etc. The increasing availability of two-dimensional (2D) transition metal dichalcogenides (TMDs) brings additional opportunities for them to be used as interlayers in "van der Waals (vdW) heterostructures" and organic/inorganic flexible devices. These innovations raise the question of the extent to which the 2D TMDs participate actively in dielectric screening at the interface. Here we study perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) monolayers adsorbed on single-layer tungsten diselenide (WSe2), bare graphite, and Au(111) surfaces, revealing a strong dependence of the PTCDA HOMO-LUMO gap on the electronic screening effects from the substrate. The monolayer WSe2 interlayer provides substantial, but not complete, screening at the organic/inorganic interface. Our results lay a foundation for the exploitation of the complex interfacial properties of hybrid systems based on TMD materials.

  19. Heterointerface Screening Effects between Organic Monolayers and Monolayer Transition Metal Dichalcogenides

    KAUST Repository

    Zheng, Yu Jie

    2016-01-21

    © 2016 American Chemical Society. The nature and extent of electronic screening at heterointerfaces and their consequences on energy level alignment are of profound importance in numerous applications, such as solar cells, electronics etc. The increasing availability of two-dimensional (2D) transition metal dichalcogenides (TMDs) brings additional opportunities for them to be used as interlayers in "van der Waals (vdW) heterostructures" and organic/inorganic flexible devices. These innovations raise the question of the extent to which the 2D TMDs participate actively in dielectric screening at the interface. Here we study perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA) monolayers adsorbed on single-layer tungsten diselenide (WSe2), bare graphite, and Au(111) surfaces, revealing a strong dependence of the PTCDA HOMO-LUMO gap on the electronic screening effects from the substrate. The monolayer WSe2 interlayer provides substantial, but not complete, screening at the organic/inorganic interface. Our results lay a foundation for the exploitation of the complex interfacial properties of hybrid systems based on TMD materials.

  20. Alpha-Melanocyte Stimulating Hormone Protects against Cytokine-Induced Barrier Damage in Caco-2 Intestinal Epithelial Monolayers.

    Directory of Open Access Journals (Sweden)

    Judit Váradi

    Full Text Available Alpha-melanocyte-stimulating hormone (α-MSH is a potent anti-inflammatory peptide with cytoprotective effect in various tissues. The present investigation demonstrates the ability of α-MSH to interact with intestinal epithelial cell monolayers and mitigate inflammatory processes of the epithelial barrier. The protective effect of α-MSH was studied on Caco-2 human intestinal epithelial monolayers, which were disrupted by exposure to tumor necrosis factor-α and interleukin-1β. The barrier integrity was assessed by measuring transepithelial electric resistance (TEER and permeability for marker molecules. Caco-2 monolayers were evaluated by immunohistochemistry for expression of melanocortin-1 receptor and tight junction proteins ZO-1 and claudin-4. The activation of nuclear factor kappa beta (NF-κB was detected by fluorescence microscopy and inflammatory cytokine expression was assessed by flow cytometric bead array cytokine assay. Exposure of Caco-2 monolayers to proinflammatory cytokines lowered TEER and increased permeability for fluorescein and albumin, which was accompanied by changes in ZO-1 and claudin-4 immunostaining. α-MSH was able to prevent inflammation-associated decrease of TEER in a dose-dependent manner and reduce the increased permeability for paracellular marker fluorescein. Further immunohistochemistry analysis revealed proinflammatory cytokine induced translocation of the NF-κB p65 subunit into Caco-2 cell nuclei, which was inhibited by α-MSH. As a result the IL-6 and IL-8 production of Caco-2 monolayers were also decreased with different patterns by the addition of α-MSH to the culture medium. In conclusion, Caco-2 cells showed a positive immunostaining for melanocortin-1 receptor and α-MSH protected Caco-2 cells against inflammatory barrier dysfunction and inflammatory activation induced by tumor necrosis factor-α and interleukin-1β cytokines.

  1. Effect of time and deposition method on quality of phosphonic acid modifier self-assembled monolayers on indium zinc oxide

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Lingzi [Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721 (United States); Knesting, Kristina M. [Department of Chemistry, University of Washington, Seattle, WA 98195-1700 (United States); Bulusu, Anuradha [School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Sigdel, Ajaya K. [National Renewable Energy Laboratory, Golden, CO 80401 (United States); Giordano, Anthony J.; Marder, Seth R. [School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, Atlanta, GA 30332-0400 (United States); Berry, Joseph J. [National Renewable Energy Laboratory, Golden, CO 80401 (United States); Graham, Samuel [School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Ginger, David S. [Department of Chemistry, University of Washington, Seattle, WA 98195-1700 (United States); Pemberton, Jeanne E., E-mail: pembertn@email.arizona.edu [Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721 (United States)

    2016-12-15

    Highlights: • Deposition of phosphonic acid monolayers on oxides from ethanol solutions occurs by rapid adsorption within 10 s with slower equilibration complete in 48 h. • The slower equilibration step involves molecular reorientation and vacancy filling on the oxide surface. • Soak-free deposition by spray coating and microcontact printing do not provide reproducible, fully-covered, uniform monolayers without substrate etching. • Adjustments to exposure time, substrate temperature, and solution/substrate contact efficiency are necessary to optimize soak-free methods. - Abstract: Phosphonic acid (PA) self-assembled monolayers (SAMs) are utilized at critical interfaces between transparent conductive oxides (TCO) and organic active layers in organic photovoltaic devices (OPVs). The effects of PA deposition method and time on the formation of close-packed, high-quality monolayers is investigated here for SAMs fabricated by solution deposition, micro-contact printing, and spray coating. The solution deposition isotherm for pentafluorinated benzylphosphonic acid (F{sub 5}BnPA) on indium-doped zinc oxide (IZO) is studied using polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS) at room temperature as a model PA/IZO system. Fast surface adsorption occurs within the first min; however, well-oriented high-quality SAMs are reached only after ∼48 h, presumably through a continual process of molecular adsorption/desorption and monolayer filling accompanied by molecular reorientation. Two other rapid, soak-free deposition techniques, micro-contact printing and spray coating, are also explored. SAM quality is compared for deposition of phenyl phosphonic acid (PPA), F{sub 13}-octylphosphonic acid (F{sub 13}OPA), and pentafluorinated benzyl phosphonic acid (F{sub 5}BnPA) by solution deposition, micro-contact printing and spray coating using PM-IRRAS. In contrast to micro-contact printing and spray coating techniques, 48–168 h solution

  2. Onset wear in self-assembled monolayers

    International Nuclear Information System (INIS)

    D'Acunto, Mario

    2006-01-01

    Self-assembled monolayers (SAMs) are very useful for the systematic modification of the physical, chemical and structural properties of a surface by varying the chain length, tail group and composition. Many of these properties can be studied making use of atomic force microscopy (AFM), and the interaction between the AFM probe tip and the SAMs can also be considered an excellent reference to study the fundamental properties of dissipation phenomena and onset wear for viscoelastic materials on the nanoscale. We have performed a numerical study showing that the fundamental mechanism for the onset wear is a process of nucleation of domains starting from initial defects. An SAM surface repeatedly sheared by an AFM probe tip with enough applied loads shows the formation of progressive damages nucleating in domains. The AFM induced surface damages involve primarily the formation of radicals from the carbon chain backbones, but the deformations of the chains resulting in changes of period lattice also have to be taken into consideration. The nucleation of the wear domains generally starts at the initial surface defects where the energy cohesion between chains is lower. Moreover, the presence of surface defects is consistent with the changes in lateral force increasing the probability of the activation for the removal of carbon debris from the chain backbone. The quantification of the progressive worn area is performed making use of the Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory for phase transition kinetic processes. The advantage of knowing the general conditions for onset wear on the SAM surfaces can help in studying the fundamental mechanisms for the tribological properties of viscoelastic materials, in solid lubrication applications and biopolymer mechanics

  3. A comparative study of post-irradiation growth kinetics of spheroids and monolayers

    International Nuclear Information System (INIS)

    Dertinger, J.; Luecke-Huhle, C.

    1975-01-01

    Post-irradiation growth kinetics of γ-irradiated spheroid and monolayer cells in exponential growth phase was investigated by means of dose-response curves based on cell counts after specified time intervals following irradiation. A mathematical model of cell-growth after irradiation was fitted to these curves. The model parameters (related to division delay and growth of non-surviving cells) obtained from this analysis consistently indicated increasing resistance to sub-lethal damage of cells cultured as multicellular spheroids under conditions of increasing three-dimensional contact. In contrast, no indication of an increased radiation-resistance was found with cells cultured on a substratum under a variety of conditions. (author)

  4. Polarized targets and beams

    International Nuclear Information System (INIS)

    Meyer, W.

    1985-01-01

    First the experimental situation of the single-pion photoproduction and the photodisintegration of the deuteron is briefly discussed. Then a description of the Bonn polarization facilities is given. The point of main effort is put on the polarized target which plays a vital role in the program. A facility for photon induced double polarization experiments at ELSA will be presented in section 4. Properties of a tensor polarized deuteron target are discussed in section 5. The development in the field of polarized targets, especially on new target materials, enables a new generation of polarized target experiments with (polarized) electrons. Some comments on the use of a polarized target in combination with electron beams will be discussed in section 6. Electron deuteron scattering from a tensor polarized deuteron target is considered and compared with other experimental possibilities. (orig./HSI)

  5. Effect of Time and Deposition Method on Quality of Phosphonic Acid Modifier Self-Assembled Monolayers on Indium Zinc Oxide

    Energy Technology Data Exchange (ETDEWEB)

    Sang, Lingzi; Knesting, Kristina M.; Bulusu, Anuradha; Sigdel, Ajaya K.; Giordano, Anthony J.; Marder, Seth R.; Berry, Joseph J.; Graham, Samuel; Ginger, David S.; Pemberton, Jeanne E.

    2016-12-15

    Phosphonic acid (PA) self-assembled monolayers (SAMs) are utilized at critical interfaces between transparent conductive oxides (TCO) and organic active layers in organic photovoltaic devices (OPVs). The effects of PA deposition method and time on the formation of close-packed, high-quality monolayers is investigated here for SAMs fabricated by solution deposition, micro-contact printing, and spray coating. The solution deposition isotherm for pentafluorinated benzylphosphonic acid (F5BnPA) on indium-doped zinc oxide (IZO) is studied using polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS) at room temperature as a model PA/IZO system. Fast surface adsorption occurs within the first min; however, well-oriented high-quality SAMs are reached only after -48 h, presumably through a continual process of molecular adsorption/desorption and monolayer filling accompanied by molecular reorientation. Two other rapid, soak-free deposition techniques, micro-contact printing and spray coating, are also explored. SAM quality is compared for deposition of phenyl phosphonic acid (PPA), F13-octylphosphonic acid (F13OPA), and pentafluorinated benzyl phosphonic acid (F5BnPA) by solution deposition, micro-contact printing and spray coating using PM-IRRAS. In contrast to micro-contact printing and spray coating techniques, 48-168 h solution deposition at both room temperature and 70 degrees C result in contamination- and surface etch-free close-packed monolayers with good reproducibility. SAMs fabricated by micro-contact printing and spray coating are much less well ordered.

  6. 40 CFR 798.5300 - Detection of gene mutations in somatic cells in culture.

    Science.gov (United States)

    2010-07-01

    ... cells in culture. 798.5300 Section 798.5300 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY....5300 Detection of gene mutations in somatic cells in culture. (a) Purpose. Mammalian cell culture... selected by resistance to ouabain. (2) Description. Cells in suspension or monolayer culture are exposed to...

  7. Evidence of indirect gap in monolayer WSe2

    KAUST Repository

    Hsu, Wei-Ting

    2017-10-09

    Monolayer transition metal dichalcogenides, such as MoS2 and WSe2, have been known as direct gap semiconductors and emerged as new optically active materials for novel device applications. Here we reexamine their direct gap properties by investigating the strain effects on the photoluminescence of monolayer MoS2 and WSe2. Instead of applying stress, we investigate the strain effects by imaging the direct exciton populations in monolayer WSe2–MoS2 and MoSe2–WSe2 lateral heterojunctions with inherent strain inhomogeneity. We find that unstrained monolayer WSe2 is actually an indirect gap material, as manifested in the observed photoluminescence intensity–energy correlation, from which the difference between the direct and indirect optical gaps can be extracted by analyzing the exciton thermal populations. Our findings combined with the estimated exciton binding energy further indicate that monolayer WSe2 exhibits an indirect quasiparticle gap, which has to be reconsidered in further studies for its fundamental properties and device applications.

  8. Enhanced piezoelectricity of monolayer phosphorene oxides: a theoretical study.

    Science.gov (United States)

    Yin, Huabing; Zheng, Guang-Ping; Gao, Jingwei; Wang, Yuanxu; Ma, Yuchen

    2017-10-18

    Two-dimensional (2D) piezoelectric materials have potential applications in miniaturized sensors and energy conversion devices. In this work, using first-principles simulations at different scales, we systematically study the electronic structures and piezoelectricity of a series of 2D monolayer phosphorene oxides (POs). Our calculations show that the monolayer POs have tunable band gaps along with remarkable piezoelectric properties. The calculated piezoelectric coefficient d 11 of 54 pm V -1 in POs is much larger than those of 2D transition metal dichalcogenide monolayers and the widely used bulk α-quartz and AlN, and almost reaches the level of the piezoelectric effect in recently discovered 2D GeS. Furthermore, two other considerable piezoelectric coefficients, i.e., d 31 and d 26 with values of -10 pm V -1 and 21 pm V -1 , respectively, are predicted in some monolayer POs. We also examine the correlation between the piezoelectric coefficients and energy stability. The enhancement of piezoelectricity for monolayer phosphorene by oxidation will broaden the applications of phosphorene and phosphorene derivatives in nano-sized electronic and piezotronic devices.

  9. Piezoelectric effect on the thermal conductivity of monolayer gallium nitride

    Science.gov (United States)

    Zhang, Jin

    2018-01-01

    Using molecular dynamics and density functional theory simulations, in this work, we find that the heat transport property of the monolayer gallium nitride (GaN) can be efficiently tailored by external electric field due to its unique piezoelectric characteristic. As the monolayer GaN possesses different piezoelectric properties in armchair and zigzag directions, different effects of the external electric field on thermal conductivity are observed when it is applied in the armchair and zigzag directions. Our further study reveals that due to the elastoelectric effect in the monolayer GaN, the external electric field changes the Young's modulus and therefore changes the phonon group velocity. Also, due to the inverse piezoelectric effect, the applied electric field induces in-plane stress in the monolayer GaN subject to a length constraint, which results in the change in the lattice anharmonicity and therefore affects the phonon mean free path. Furthermore, for relatively long GaN monolayers, the in-plane stress may trigger the buckling instability, which can significantly reduce the phonon mean free path.

  10. Thermal conductivity of a h-BCN monolayer.

    Science.gov (United States)

    Zhang, Ying-Yan; Pei, Qing-Xiang; Liu, Hong-Yuan; Wei, Ning

    2017-10-18

    A hexagonal graphene-like boron-carbon-nitrogen (h-BCN) monolayer, a new two-dimensional (2D) material, has been synthesized recently. Herein we investigate for the first time the thermal conductivity of this novel 2D material. Using molecular dynamics simulations based on the optimized Tersoff potential, we found that the h-BCN monolayers are isotropic in the basal plane with close thermal conductivity magnitudes. Though h-BCN has the same hexagonal lattice as graphene and hexagonal boron nitride (h-BN), it exhibits a much lower thermal conductivity than the latter two materials. In addition, the thermal conductivity of h-BCN monolayers is found to be size-dependent but less temperature-dependent. Modulation of the thermal conductivity of h-BCN monolayers can also be realized by strain engineering. Compressive strain leads to a monotonic decrease in the thermal conductivity while the tensile strain induces an up-then-down trend in the thermal conductivity. Surprisingly, the small tensile strain can facilitate the heat transport of the h-BCN monolayers.

  11. Subretinal Implantation of Retinal Pigment Epithelial Cells Derived From Human Embryonic Stem Cells: Improved Survival When Implanted as a Monolayer

    Science.gov (United States)

    Diniz, Bruno; Thomas, Padmaja; Thomas, Biju; Ribeiro, Ramiro; Hu, Yuntao; Brant, Rodrigo; Ahuja, Ashish; Zhu, Danhong; Liu, Laura; Koss, Michael; Maia, Mauricio; Chader, Gerald; Hinton, David R.; Humayun, Mark S.

    2013-01-01

    Purpose. To evaluate cell survival and tumorigenicity of human embryonic stem cell–derived retinal pigment epithelium (hESC-RPE) transplantation in immunocompromised nude rats. Cells were transplanted as a cell suspension (CS) or as a polarized monolayer plated on a parylene membrane (PM). Methods. Sixty-nine rats (38 male, 31 female) were surgically implanted with CS (n = 33) or PM (n = 36). Cohort subsets were killed at 1, 6, and 12 months after surgery. Both ocular tissues and systemic organs (brain, liver, kidneys, spleen, heart, and lungs) were fixed in 4% paraformaldehyde, embedded in paraffin, and sectioned. Every fifth section was stained with hematoxylin and eosin and analyzed histologically. Adjacent sections were processed for immunohistochemical analysis (as needed) using the following antibodies: anti-RPE65 (RPE-specific marker), anti-TRA-1-85 (human cell marker), anti-Ki67 (proliferation marker), anti-CD68 (macrophage), and anti-cytokeratin (epithelial marker). Results. The implanted cells were immunopositive for the RPE65 and TRA-1-85. Cell survival (P = 0.006) and the presence of a monolayer (P < 0.001) of hESC-RPE were significantly higher in eyes that received the PM. Gross morphological and histological analysis of the eye and the systemic organs after the surgery revealed no evidence of tumor or ectopic tissue formation in either group. Conclusions. hESC-RPE can survive for at least 12 months in an immunocompromised animal model. Polarized monolayers of hESC-RPE show improved survival compared to cell suspensions. The lack of teratoma or any ectopic tissue formation in the implanted rats bodes well for similar results with respect to safety in human subjects. PMID:23833067

  12. Fullerene nanostructures, monolayers and thin films

    International Nuclear Information System (INIS)

    Cotier, B.N.

    2000-10-01

    The interaction of submonolayer, monolayer and multilayer coverages of C 60 with the Ag/Si(111)-(√3x√3)R30 deg. (√3Ag/Si) and Si(111)-7x7 surfaces has been investigated using atomic force microscopy (AFM), photoelectron spectroscopy (PES) and ultra high vacuum scanning tunneling microscopy (UHV-STM). It is shown that it is possible to preserve the √3Ag/Si surface, normally corrupted by exposure to air, in ambient conditions when immersed beneath a few layers of C 60 molecules. Upon removal of the fullerene layers in the UHV-STM some corruption is observed which is linked to the morphology of the fullerene film (defined by the nature of the interaction of C 60 with √3Ag/Si). This technique opens up the possibility of performing experiments on the clean √3Ag/Si surface outside of UHV conditions. With the discovery of techniques whereby structures may be formed that are composed of only a few atoms/molecules, there is a need to perform electrical measurements in order to probe the fascinating properties of these 'nano-scale' devices. Using AFM, PES and STM evaporated metals and ion implantation have been investigated as materials for use in forming sub-micron scale contacts to nanostructures. It is found that ion implantation is a more promising approach after studying the response to annealing of treated surfaces. Electrical measurements between open/short circuited contacts and through Ag films clearly demonstrate the validity of the method, further confirmed by a PES study which probes the chemical nature of the near surface region of ion-implanted samples. Attempts have been made to form nanostructure templates between sub-micron scale contacts as a possible precursor to forming nanostructures. The bonding state of C 60 molecules on the Si(111)-7x7 surface has been in dispute for many years. To properly understand the system a comprehensive AFM, PES and STM study has been performed. PES results indicate covalent bond formation, with the number of bonds

  13. Lateral Interactions in Monolayer Thick Mercury Films

    Science.gov (United States)

    Kime, Yolanda Jan

    An understanding of lateral adatom-adatom interactions is often an important part of understanding electronic structure and adsorption energetics in monolayer thick films. In this dissertation I use angle-resolved photoemission and thermal desorption spectroscopies to explore the relationship between the adatom-adatom interaction and other characteristics of the adlayer, such as electronic structure, defects, or coexistent structural phases in the adlayer. Since Hg binds weakly to many substrates, the lateral interactions are often a major contribution to the dynamics of the overlayer. Hg adlayer systems are thus ideal for probing lateral interactions. The electronic structures of Hg adlayers on Ag(100), Cu(100), and Cu_3Au(100) are studied with angle-resolved ultraviolet photoemission. The Hg atomic 5d_{5/2} electronic band is observed to split into two levels following adsorption onto some surfaces. The energetic splitting of the Hg 5d_{5/2} level is found to be directly correlated to the adlayer homogeneous strain energy. The existence of the split off level also depends on the order or disorder of the Hg adlayer. The energetics of Hg adsorption on Cu(100) are probed using thermal desorption spectroscopy. Two different ordered adlayer structures are observed for Hg adsorption on Cu(100) at 200 K. Under some adsorption conditions and over a range of exposures, the two phases are seen to coexist on the surface prior to the thermal desorption process. A phase transition from the more dense to the less dense phase is observed to occur during the thermal desorption process. Inherent differences in defect densities are responsible for the observed differences between lateral interactions measured previously with equilibrium (atom beam scattering) and as measured by the non-equilibrium (thermal desorption) technique reported here. Theoretical and experimental evidence for an indirect through-metal interaction between adatoms is also discussed. Although through

  14. Scattering with polarized neutrons

    International Nuclear Information System (INIS)

    Schweizer, J.

    2007-01-01

    In the history of neutron scattering, it was shown very soon that the use of polarized neutron beams brings much more information than usual scattering with unpolarized neutrons. We shall develop here the different scattering methods that imply polarized neutrons: 1) polarized beams without polarization analysis, the flipping ratio method; 2) polarized beams with a uniaxial polarization analysis; 3) polarized beams with a spherical polarization analysis. For all these scattering methods, we shall give examples of the physical problems which can been solved by these methods, particularly in the field of magnetism: investigation of complex magnetic structures, investigation of spin or magnetization densities in metals, insulators and molecular compounds, separation of magnetic and nuclear scattering, investigation of magnetic properties of liquids and amorphous materials and even, for non magnetic material, separation between coherent and incoherent scattering. (author)

  15. Polarized Light Corridor Demonstrations.

    Science.gov (United States)

    Davies, G. R.

    1990-01-01

    Eleven demonstrations of light polarization are presented. Each includes a brief description of the apparatus and the effect demonstrated. Illustrated are strain patterns, reflection, scattering, the Faraday Effect, interference, double refraction, the polarizing microscope, and optical activity. (CW)

  16. Techniques in polarization physics

    International Nuclear Information System (INIS)

    Clausnitzer, G.

    1974-01-01

    A review of the current status of the technical tools necessary to perform different kinds of polarization experiments is presented, and the absolute and relative accuracy with which data can be obtained is discussed. A description of polarized targets and sources of polarized fast neutrons is included. Applications of polarization techniques to other fields is mentioned briefly. (14 figures, 3 tables, 110 references) (U.S.)

  17. Self assembled monolayers of octadecyltrichlorosilane for dielectric materials

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Vijay, E-mail: cirivijaypilani@gmail.com [Centre for Nanoscience and Engineering, Indian Institute of Science-Bangalore (India); Mechanical Engineering Department, Birla Institute of Technology and Science-Pilani (India); Puri, Paridhi; Nain, Shivani [Mechanical Engineering Department, Birla Institute of Technology and Science-Pilani (India); Bhat, K. N. [Centre for Nanoscience and Engineering, Indian Institute of Science-Bangalore (India); Sharma, N. N. [Mechanical Engineering Department, Birla Institute of Technology and Science-Pilani (India); School of Automobile, Mechanical & Mechatronics, Manipal University-Jaipur (India)

    2016-04-13

    Treatment of surfaces to change the interaction of fluids with them is a critical step in constructing useful microfluidics devices, especially those used in biological applications. Selective modification of inorganic materials such as Si, SiO{sub 2} and Si{sub 3}N{sub 4} is of great interest in research and technology. We evaluated the chemical formation of OTS self-assembled monolayers on silicon substrates with different dielectric materials. Our investigations were focused on surface modification of formerly used common dielectric materials SiO{sub 2}, Si{sub 3}N{sub 4} and a-poly. The improvement of wetting behaviour and quality of monolayer films were characterized using Atomic force microscope, Scanning electron microscope, Contact angle goniometer, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) monolayer deposited oxide surface.

  18. Measuring the Edge Recombination Velocity of Monolayer Semiconductors.

    Science.gov (United States)

    Zhao, Peida; Amani, Matin; Lien, Der-Hsien; Ahn, Geun Ho; Kiriya, Daisuke; Mastandrea, James P; Ager, Joel W; Yablonovitch, Eli; Chrzan, Daryl C; Javey, Ali

    2017-09-13

    Understanding edge effects and quantifying their impact on the carrier properties of two-dimensional (2D) semiconductors is an essential step toward utilizing this material for high performance electronic and optoelectronic devices. WS 2 monolayers patterned into disks of varying diameters are used to experimentally explore the influence of edges on the material's optical properties. Carrier lifetime measurements show a decrease in the effective lifetime, τ effective , as a function of decreasing diameter, suggesting that the edges are active sites for carrier recombination. Accordingly, we introduce a metric called edge recombination velocity (ERV) to characterize the impact of 2D material edges on nonradiative carrier recombination. The unpassivated WS 2 monolayer disks yield an ERV ∼ 4 × 10 4 cm/s. This work quantifies the nonradiative recombination edge effects in monolayer semiconductors, while simultaneously establishing a practical characterization approach that can be used to experimentally explore edge passivation methods for 2D materials.

  19. Triptycene-terminated thiolate and selenolate monolayers on Au(111

    Directory of Open Access Journals (Sweden)

    Jinxuan Liu

    2017-04-01

    Full Text Available To study the implications of highly space-demanding organic moieties on the properties of self-assembled monolayers (SAMs, triptycyl thiolates and selenolates with and without methylene spacers on Au(111 surfaces were comprehensively studied using ultra-high vacuum infrared reflection absorption spectroscopy, X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy and thermal desorption spectroscopy. Due to packing effects, the molecules in all monolayers are substantially tilted. In the presence of a methylene spacer the tilt is slightly less pronounced. The selenolate monolayers exhibit smaller defect densities and therefore are more densely packed than their thiolate analogues. The Se–Au binding energy in the investigated SAMs was found to be higher than the S–Au binding energy.

  20. Infrared spectroscopy of self-assembled monolayer films on silicon

    Science.gov (United States)

    Rowell, N. L.; Tay, Lilin; Boukherroub, R.; Lockwood, D. J.

    2007-07-01

    Infrared vibrational spectroscopy in an attenuated total reflection (ATR) geometry has been employed to investigate the presence of organic thin layers on Si-wafer surfaces. The phenomena have been simulated to show there can be a field enhancement with the presented single-reflection ATR (SR-ATR) approach which is substantially larger than for conventional ATR or specular reflection. In SR-ATR, a discontinuity of the field normal to the film contributes a field enhancement in the lower index thin film causing a two order of magnitude increase in sensitivity. SR-ATR was employed to characterize a single monolayer of undecylenic acid self-assembled on Si(1 1 1) and to investigate a two monolayer system obtained by adding a monolayer of bovine serum albumin protein.

  1. Controlled electrodeposition of Au monolayer film on ionic liquid

    Science.gov (United States)

    Ma, Qiang; Pang, Liuqing; Li, Man; Zhang, Yunxia; Ren, Xianpei; Liu, Shengzhong Frank

    2016-05-01

    Gold (Au) nanoparticles have been attractive for centuries for their vibrant appearance enhanced by their interaction with sunlight. Nowadays, there have been tremendous research efforts to develop them for high-tech applications including therapeutic agents, sensors, organic photovoltaics, medical applications, electronics and catalysis. However, there remains to be a challenge to fabricate a monolayer Au coating with complete coverage in controlled fashion. Here we present a facile method to deposit a uniform Au monolayer (ML) film on the [BMIM][PF6] ionic liquid substrate using an electrochemical deposition process. It demonstrates that it is feasible to prepare a solid phase coating on the liquid-based substrate. Moreover, the thickness of the monolayer coating can be controlled to a layer-by-layer accuracy.

  2. Polarized Moessbauer transitions

    International Nuclear Information System (INIS)

    Barb, D.

    1975-01-01

    Theoretical aspects of the emission, absorption and scattering of polarized gamma rays are reviewed for a general case of combined magnetic and electric hyperfine interactions; various possibilities of obtaining polarized gamma sources are described and examples are given of the applications of Moessbauer spectroscopy with polarized gamma rays in solving problems of solid state physics. (A.K.)

  3. Geographical Income Polarization

    DEFF Research Database (Denmark)

    Azhar, Hussain; Jonassen, Anders Bruun

    inter municipal income inequality. Counter factual simulations show that rising property prices to a large part explain the rise in polarization. One side-effect of polarization is tendencies towards a parallel polarization of residence location patterns, where low skilled individuals tend to live...

  4. Calculation of polarization effects

    International Nuclear Information System (INIS)

    Chao, A.W.

    1983-09-01

    Basically there are two areas of accelerator applications that involve beam polarization. One is the acceleration of a polarized beam (most likely a proton beam) in a synchrotron. Another concerns polarized beams in an electron storage ring. In both areas, numerical techniques have been very useful

  5. Electrochemical Properties of Alkanethiol Monolayers Adsorbed on Nanoporous Au Surfaces

    International Nuclear Information System (INIS)

    Chu, Yeon Yi; Seo, Bora; Kim, Jong Won

    2010-01-01

    We investigated the electrochemical properties of alkanethiol monolayers adsorbed on NPG surfaces by cyclic voltammetry and electrochemical impedance spectroscopy, and the results are compared to those on flat Au surfaces. The reductive desorption of alkanethiols on NPG surfaces is observed in more negative potential regions than that on flat Au surfaces due the stronger S-Au interaction on NPG surfaces. While the electron transfer through alkanethiol monolayers on flat Au surfaces occurs via a tunneling process through the monolayer films, the redox species can permeate through the monolayers on NPG surfaces to transfer the electrons to the Au surfaces. The results presented here will help to elucidate the intrinsic electrochemical properties of alkanethiol monolayers adsorbed on curved Au surfaces, particularly on the surface of AuNPs. Self-assembled monolayers (SAMs) of thiolate molecules on Au surfaces have been the subject of intensive research for the last few decades due to their unique physical and chemical properties. The well-organized surface structures of thiolate SAMs with various end-group functionalities can be further utilized for many applications in biology and nanotechnology. In addition to the practical applications, SAMs of thiolate molecules on Au surfaces also provide unique opportunities to address fundamental issues in surface chemistry such as self-organized surface structures, electron transfer behaviors, and moleculesubstrate interactions. Although there have been numerous reports on the fundamental physical and chemical properties of thiolate SAMs on Au surfaces, most of them were investigated on flat Au surfaces, typically on well-defined Au(111) surfaces

  6. Retention of differentiated characteristics by cultures of defined rabbit kidney epithelia.

    Science.gov (United States)

    Wilson, P D; Anderson, R J; Breckon, R D; Nathrath, W; Schrier, R W

    1987-02-01

    Rabbit nephron segments of proximal convoluted tubules (PCT); proximal straight tubules (PST); cortical and medullary thick ascending limbs of Henle's loop (CAL, MAL); and cortical, outer medullary, and inner medullary collecting tubules (CCT, OMCT, IMCT) were individually microdissected and grown in monolayer culture in hormone supplemented, defined media. Factors favoring a rapid onset of proliferation included young donor age, distal tubule origin, and the addition of 3% fetal calf serum to the medium. All primary cultures had polarized morphology with apical microvilli facing the medium and basement membrane-like material adjacent to the dish. Differentiated properties characteristic of the tubular epithelium of origin retained in cultures included ultrastructural characteristics and cytochemically demonstrable marker enzyme proportions. PCT and PST were rich in alkaline phosphatase; CAL stained strongly for NaK-ATPase; CCT contained two cell populations with regard to cytochrome oxidase reaction. A CCT-specific anti-keratin antibody (aLEA) was immunolocalized in CCT cultures, and a PST cytokeratin antibody stained PST cultures. The biochemical response of adenylate cyclase to putative stimulating agents was the same in primary cultures as in freshly isolated tubules. In PCT and PST adenylate cyclase activity was stimulated by parathyroid hormone (PTH) but not by arginine vasopressin (AVP); CAL and MAL adenylate cyclase was stimulated by neither PTH nor AVP; CCT, OMCT, and IMCT adenylate cyclase was stimulated by AVP but not by PTH. NaF stimulated adenylate cyclase activity in every cultured segment. It is concluded that primary cultures of individually microdissected rabbit PCT, PST, CAL, MAL, CCT, OMCT, and IMCT retain differentiated characteristics with regard to ultrastructure, marker enzymes, cytoskeletal proteins, and hormone response of adenylate cyclase and provide a new system for studying normal and abnormal functions of the heterogeneous tubular

  7. Electron dynamics and optical properties modulation of monolayer MoS{sub 2} by femtosecond laser pulse: a simulation using time-dependent density functional theory

    Energy Technology Data Exchange (ETDEWEB)

    Su, Xiaoxing; Jiang, Lan [Beijing Institute of Technology, Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing (China); Wang, Feng [Beijing Institute of Technology, School of Physics, Beijing (China); Su, Gaoshi [Beijing Institute of Technology, School of Mechatronical Engineering, Beijing (China); Qu, Liangti [Beijing Institute of Technology, Key Laboratory of Cluster Science, Ministry of Education, School of Chemistry, Beijing (China); Lu, Yongfeng [University of Nebraska-Lincoln, Department of Electrical Engineering, Lincoln, NE (United States)

    2017-07-15

    In this study, we adopted time-dependent density functional theory to investigate the optical properties of monolayer MoS{sub 2} and the effect of intense few-cycle femtosecond laser pulses on these properties. The electron dynamics of monolayer MoS{sub 2} under few-cycle and multi-cycle laser irradiation were described. The polarization direction of the laser had a marked effect on the energy absorption and electronic excitation of monolayer MoS{sub 2} because of anisotropy. Change in the polarization direction of few-cycle pulse changed the absorbed energy by a factor over 4000. Few-cycle pulse showed a higher sensitivity to the electronic property of material than multi-cycle pulse. The modulation of the dielectric properties of the material was observed on the femtosecond time scale. The negative divergence appeared in the real part of the function at low frequencies and photoinduced blue shift occurred due to Burstein-Moss effect. The irradiation of femtosecond laser caused the dielectric response within the infrared region and introduced anisotropy to the in-plane optical properties. Laser-based engineering of optical properties through controlling transient electron dynamics expands the functionality of MoS{sub 2} and has potential applications in direction-dependent optoelectronic devices. (orig.)

  8. Valley dynamics of intravalley and intervalley multiexcitonic states in monolayer WS2

    Science.gov (United States)

    Fu, Jiyong; Bezerra, Andre; Qu, Fanyao

    2018-03-01

    We present a comprehensive model comprising of a complete set of rate equations, which account for charge transfer among multiexcitonic channels including excitons, trions, and biexcitons, to investigate valley (locked with spin) dynamics in monolayer WS2. The steady-state photoluminescence (PL) spectra, underlying the laser power dependence of excitonic populations, are also determined. Our computed PL for all excitonic states agrees with the experimental data of Paradisanos et al. [Appl. Phys. Lett. 110, 193102 (2017), 10.1063/1.4983285]. We find that the relative weight of PL, stemmed from different excitonic channels, strongly depends on the laser power even under dynamical conditions. Remarkably, the biexciton channel, having the weakest PL intensity at low laser powers, tends to prevail in PL over other excitonic states as the power strengthens. In addition, by accounting for intervalley scatterings, which enable transfer of excitonic states from one valley to the other, we determine the valley polarization, which strongly depends on intervalley scatterings and the exciton generation rates in the two valleys. On the other hand, the valley polarization for all excitonic channels is found almost independent of the laser power, consistent with experimental measurements as well. Finally, the valley dynamics involving both intra- and intervalley trions is discussed. Our model and numerical outcome should be beneficial to experiments especially featuring the interplay of multiexcitonic channels in, e.g., elucidating experimental data, estimating central excitonic quantities including recombination times and transition rates, and in widening possible new experimental scopes.

  9. Monolayer structures of alkyl aldehydes: Odd-membered homologues

    International Nuclear Information System (INIS)

    Phillips, T.K.; Clarke, S.M.; Bhinde, T.; Castro, M.A.; Millan, C.; Medina, S.

    2011-01-01

    Crystalline monolayers of three aldehydes with an odd number of carbon atoms in the alkyl chain (C 7 , C 9 and C 11 ) at low coverages are observed by a combination of X-ray and neutron diffraction. Analysis of the diffraction data is discussed and possible monolayer crystal structures are proposed; although unique structures could not be ascertained for all molecules. We conclude that the structures are flat on the surface, with the molecules lying in the plane of the layer. The C 11 homologue is determined to have a plane group of either p2, pgb or pgg, and for the C 7 homologue the p2 plane group is preferred.

  10. Magnetism of Ta dichalcogenide monolayers tuned by strain and hydrogenation

    Energy Technology Data Exchange (ETDEWEB)

    Manchanda, Priyanka; Sellmyer, D. J.; Skomski, Ralph [Department of Physics and Astronomy and Nebraska Center for Materials and Nanoscience, University of Nebraska, Lincoln, Nebraska 68588 (United States); Sharma, Vinit [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Yu, Hongbin [School of Electrical, Computer, and Energy Engineering, Arizona State University, Tempe, Arizona 85287 (United States)

    2015-07-20

    The effects of strain and hydrogenation on the electronic, magnetic, and optical properties of monolayers of Ta based dichalcogenides (TaX{sub 2}; X = S, Se, and Te) are investigated using density-functional theory. We predict a complex scenario of strain-dependent magnetic phase transitions involving paramagnetic, ferromagnetic, and modulated antiferromagnetic states. Covering one of the two chalcogenide surfaces with hydrogen switches the antiferromagnetic/nonmagnetic TaX{sub 2} monolayers to a semiconductor, and the optical behavior strongly depends on strain and hydrogenation. Our research opens pathways towards the manipulation of magnetic as well as optical properties for future spintronics and optoelectronics applications.

  11. Unconventional fractional quantum Hall effect in monolayer and bilayer graphene

    Science.gov (United States)

    Jacak, Janusz; Jacak, Lucjan

    2016-01-01

    The commensurability condition is applied to determine the hierarchy of fractional fillings of Landau levels in monolayer and in bilayer graphene. The filling rates for fractional quantum Hall effect (FQHE) in graphene are found in the first three Landau levels in one-to-one agreement with the experimental data. The presence of even denominator filling fractions in the hierarchy for FQHE in bilayer graphene is explained. Experimentally observed hierarchy of FQHE in the first and second Landau levels in monolayer graphene and in the zeroth Landau level in bilayer graphene is beyond the conventional composite fermion interpretation but fits to the presented nonlocal topology commensurability condition. PMID:27877866

  12. Hypoxia/reoxygenation increases the permeability of endothelial cell monolayers: Role of oxygen radicals

    International Nuclear Information System (INIS)

    Inauen, W.; Payne, D.K.; Kvietys, P.R.; Granger, D.N.

    1990-01-01

    We assessed the effect of hypoxia/reoxygenation on 14C-albumin flux across endothelial monolayers. Cultured bovine pulmonary artery endothelial cells were grown to confluence on nitrocellulose filters (pore size 12 microns). The endothelialized filters were mounted in Ussing-type chambers which were filled with cell culture medium (M 199). Equimolar amounts (33 nM) of 14C-labeled and unlabeled albumin were added to the hot and cold chambers, respectively. The monolayers were then exposed to successive periods (90 min) of normoxia (pO2 145 mmHg), hypoxia (pO2 20 mmHg), and reoxygenation (pO2 145 mmHg). A gas bubbling system was used to control media pO2 and to ensure adequate mixing. Four aliquots of culture media were taken during each period in order to calculate the 14C-albumin permeability across the endothelialized filter. In some experiments, either the xanthine oxidase inhibitor, oxypurinol (10 microM), or superoxide dismutase (600 U/mL), was added to the media immediately prior to the experiments. As compared to the normoxic control period, albumin permeability was 1.5 times higher during hypoxia (p less than 0.01) and 2.3 times higher during reoxygenation (p less than 0.01). The reoxygenation-induced increase in albumin permeability was prevented by either oxypurinol or superoxide dismutase. These data indicate that xanthine oxidase-derived oxygen radicals contribute to the hypoxia/reoxygenation-induced endothelial cell dysfunction. The altered endothelial barrier function induced by hypoxia/reoxygenation is consistent with the microvascular dysfunction observed following reperfusion of ischemic tissues

  13. Fluorescein transport properties across artificial lipid membranes, Caco-2 cell monolayers and rat jejunum.

    Science.gov (United States)

    Berginc, Katja; Zakelj, Simon; Levstik, Lea; Ursic, Darko; Kristl, Albin

    2007-05-01

    Membrane transport characteristics of a paracellular permeability marker fluorescein were evaluated using artificial membrane, Caco-2 cell monolayers and rat jejunum, all mounted in side-by-side diffusion cells. Modified Ringer buffers with varied pH values were applied as incubation salines on both sides of artificial membrane, cell culture monolayers or rat jejunum. Passive transport according to pH partition theory was determined using all three permeability models. In addition to that, active transport of fluorescein in the M-S (mucosal-to-serosal) direction through rat jejunum was observed. The highest M-S P(app) values regarding the active transport through the rat jejunum were observed in incubation saline with pH 6.5. Fluorescein transport through the rat jejunum was inhibited by DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid) and alpha-CHC (alpha-cyano-4-hydroxycinnamic acid). Thus, we assume that two pH-dependent influx transporters could be involved in the fluorescein membrane transport through the intestinal (jejunal) epithelium. One is very likely an MCT (monocarboxylic acid cotransporter) isoform, inhibited by specific MCT inhibitor alpha-CHC, while the involvement of the second one with overlapping substrate/inhibitor specificities (most probably a member of the organic anion-transporting polypeptide family, inhibited at least partially by DIDS) could not be excluded.

  14. Electroactive oligoaniline-containing self-assembled monolayers for tissue engineering applications.

    Science.gov (United States)

    Guo, Yi; Li, Mengyan; Mylonakis, Andreas; Han, Jingjia; MacDiarmid, Alan G; Chen, Xuesi; Lelkes, Peter I; Wei, Yen

    2007-10-01

    A novel electroactive silsesquioxane precursor, N-(4-aminophenyl)-N'-(4'-(3-triethoxysilyl-propyl-ureido) phenyl-1,4-quinonenediimine) (ATQD), was successfully synthesized from the emeraldine form of amino-capped aniline trimers via a one-step coupling reaction and subsequent purification by column chromatography. The physicochemical properties of ATQD were characterized using mass spectrometry as well as by nuclear magnetic resonance and UV-vis spectroscopy. Analysis by cyclic voltammetry confirmed that the intrinsic electroactivity of ATQD was maintained upon protonic acid doping, exhibiting two distinct reversible oxidative states, similar to polyaniline. The aromatic amine terminals of self-assembled monolayers (SAMs) of ATQD on glass substrates were covalently modified with an adhesive oligopeptide, cyclic Arg-Gly-Asp (RGD) (ATQD-RGD). The mean height of the monolayer coating on the surfaces was approximately 3 nm, as measured by atomic force microscopy. The biocompatibility of the novel electroactive substrates was evaluated using PC12 pheochromocytoma cells, an established cell line of neural origin. The bioactive, derivatized electroactive scaffold material, ATQD-RGD, supported PC12 cell adhesion and proliferation, similar to control tissue-culture-treated polystyrene surfaces. Importantly, electroactive surfaces stimulated spontaneous neuritogenesis in PC12 cells, in the absence of neurotrophic growth factors, such as nerve growth factor (NGF). As expected, NGF significantly enhanced neurite extension on both control and electroactive surfaces. Taken together, our results suggest that the newly electroactive SAMs grafted with bioactive peptides, such as RGD, could be promising biomaterials for tissue engineering.

  15. Chitosan-modified porous silicon microparticles for enhanced permeability of insulin across intestinal cell monolayers.

    Science.gov (United States)

    Shrestha, Neha; Shahbazi, Mohammad-Ali; Araújo, Francisca; Zhang, Hongbo; Mäkilä, Ermei M; Kauppila, Jussi; Sarmento, Bruno; Salonen, Jarno J; Hirvonen, Jouni T; Santos, Hélder A

    2014-08-01

    Porous silicon (PSi) based particulate systems are emerging as an important drug delivery system due to its advantageous properties such as biocompatibility, biodegradability and ability to tailor the particles' physicochemical properties. Here, annealed thermally hydrocarbonized PSi (AnnTHCPSi) and undecylenic acid modified AnnTHCPSi (AnnUnTHCPSi) microparticles were developed as a PSi-based platform for oral delivery of insulin. Chitosan (CS) was used to modify the AnnUnTHCPSi microparticles to enhance the intestinal permeation of insulin. Surface modification with CS led to significant increase in the interaction of PSi microparticles with Caco-2/HT-29 cell co-culture monolayers. Compared to pure insulin, the CS-conjugated microparticles significantly improved the permeation of insulin across the Caco-2/HT-29 cell monolayers, with ca. 20-fold increase in the amount of insulin permeated and ca. 7-fold increase in the apparent permeability (P(app)) value. Moreover, among all the investigated particles, the CS-conjugated microparticles also showed the highest amount of insulin associated with the mucus layer and the intestinal Caco-2 cells and mucus secreting HT-29 cells. Our results demonstrate that CS-conjugated AnnUnTHCPSi microparticles can efficiently enhance the insulin absorption across intestinal cells, and thus, they are promising microsystems for the oral delivery of proteins and peptides across the intestinal cell membrane. Copyright © 2014 Elsevier Ltd. All rights reserved.

  16. Acceleration of polarized particles

    International Nuclear Information System (INIS)

    Buon, J.

    1992-05-01

    The spin kinetics of polarized beams in circular accelerators is reviewed in the case of spin-1/2 particles (electrons and protons) with emphasis on the depolarization phenomena. The acceleration of polarized proton beams in synchrotrons is described together with the cures applied to reduce depolarization, including the use of 'Siberian Snakes'. The in-situ polarization of electrons in storage rings due to synchrotron radiation is studied as well as depolarization in presence of ring imperfections. The applications of electron polarization to accurately calibrate the rings in energy and to use polarized beams in colliding-beam experiments are reviewed. (author) 76 refs., 19 figs., 1 tab

  17. Emergence of Dirac and quantum spin Hall states in fluorinated monolayer As and AsSb

    KAUST Repository

    Zhang, Qingyun; Schwingenschlö gl, Udo

    2016-01-01

    Using first-principles calculations, we investigate the electronic and vibrational properties of monolayer As and AsSb. While the pristine monolayers are semiconductors (direct band gap at the Γ point), fluorination results in Dirac cones at the K

  18. Morphological and Immunohistochemical Characterization of Canine Osteosarcoma Spheroid Cell Cultures.

    Science.gov (United States)

    Gebhard, C; Gabriel, C; Walter, I

    2016-06-01

    Spheroid cell culture emerges as powerful in vitro tool for experimental tumour research. In this study, we established a scaffold-free three-dimensional spheroid system built from canine osteosarcoma (OS) cells (D17). Spheroids (7, 14 and 19 days of cultivation) and monolayer cultures (2 and 7 days of cultivation) were evaluated and compared on light and electron microscopy. Monolayer and spheroid cultures were tested for vimentin, cytokeratin, alkaline phosphatase, osteocalcin and collagen I by means of immunohistochemistry. The spheroid cell culture exhibited a distinct network of collagen I in particular after 19-day cultivation, whereas in monolayer cultures, collagen I was arranged as a lamellar basal structure. Necrotic centres of large spheroids, as observed in 14- and 19-day cultures, were characterized by significant amounts of osteocalcin. Proliferative activity as determined by Ki-67 immunoreactivity showed an even distribution in two-dimensional cultures. In spheroids, proliferation was predominating in the peripheral areas. Metastasis-associated markers ezrin and S100A4 were shown to be continuously expressed in monolayer and spheroid cultures. We conclude that the scaffold-free spheroid system from canine OS cells has the ability to mimic the architecture of the in vivo tumour, in particular cell-cell and cell-matrix interactions. © 2015 The Authors. Anatomia, Histologia, Embryologia Published by Blackwell Verlag GmbH.

  19. Polarization effects. Volume 2

    Energy Technology Data Exchange (ETDEWEB)

    Courant, E.

    1981-01-01

    The use of polarized proton beams in ISABELLE is important for several general reasons: (1) With a single longitudinally polarized proton beam, effects involving parity violation can be identified and hence processes involving weak interactions can be separated from those involving strong and electromagnetic interactions. (2) Spin effects are important in the strong interactions and can be useful for testing QCD. The technique for obtaining polarized proton beams in ISABELLE appears promising, particularly in view of the present development of a polarized proton beam for the AGS. Projections for the luminosity in ISABELLE for collisions of polarized protons - one or both beams polarized with longitudinal or transverse polarization - range from 1/100 to 1 times the luminosity for unpolarized protons.

  20. The Physics of Polarization

    Science.gov (United States)

    Landi Degl'Innocenti, Egidio

    2015-10-01

    The introductory lecture that has been delivered at this Symposium is a condensed version of an extended course held by the author at the XII Canary Island Winter School from November 13 to November 21, 2000. The full series of lectures can be found in Landi Degl'Innocenti (2002). The original reference is organized in 20 Sections that are here itemized: 1. Introduction, 2. Description of polarized radiation, 3. Polarization and optical devices: Jones calculus and Muller matrices, 4. The Fresnel equations, 5. Dichroism and anomalous dispersion, 6. Polarization in everyday life, 7. Polarization due to radiating charges, 8. The linear antenna, 9. Thomson scattering, 10. Rayleigh scattering, 11. A digression on Mie scattering, 12. Bremsstrahlung radiation, 13. Cyclotron radiation, 14. Synchrotron radiation, 15. Polarization in spectral lines, 16. Density matrix and atomic polarization, 17. Radiative transfer and statistical equilibrium equations, 18. The amplification condition in polarized radiative transfer, and 19. Coupling radiative transfer and statistical equilibrium equations.

  1. Advanced chemistry of monolayers at interfaces trends in methodology and technology

    CERN Document Server

    Imae, Toyoko

    2007-01-01

    Advanced Chemistry of Monolayers at Interfaces describes the advanced chemistry of monolayers at interfaces. Focusing on the recent trends of methodology and technology, which are indispensable in monolayer science. They are applied to monolayers of surfactants, amphiphiles, polymers, dendrimers, enzymes, and proteins, which serve many uses.Introduces the methodologies of scanning probe microscopy, surface force instrumentation, surface spectroscopy, surface plasmon optics, reflectometry, and near-field scanning optical microscopy. Modern interface reaction method, lithographic tech

  2. Clientalism and polarized voting: empirical evidence

    NARCIS (Netherlands)

    Gërxhani, K.; Schram, A.

    2009-01-01

    One must take country-specific institutional features into account when analyzing former communist countries’ transformation process to new political institutions. We do so for post-communist Albania, where the regional and cultural polarization that has existed for centuries has evolved to

  3. Pressure-dependent optical and vibrational properties of monolayer molybdenum disulfide

    KAUST Repository

    Nayak, Avinash P.; Pandey, Tribhuwan; Voiry, Damien; Liu, Jin; Moran, Samuel T.; Sharma, Ankit; Tan, Cheng; Chen, Changhsiao; Li, Lain-Jong; Chhowalla, Manish U.; Lin, Jungfu; Singh, Abhishek Kumar; Akinwande, Deji

    2015-01-01

    vibrational dynamics of the distorted monolayer 1T-MoS2 (1T′) and the monolayer 2H-MoS2 via a diamond anvil cell (DAC) and density functional theory (DFT) calculations. The direct optical band gap of the monolayer 2H-MoS2 increases by 11.7% from 1.85 to 2.08 e

  4. Anomalously temperature-dependent thermal conductivity of monolayer GaN with large deviations from the traditional 1 /T law

    Science.gov (United States)

    Qin, Guangzhao; Qin, Zhenzhen; Wang, Huimin; Hu, Ming

    2017-05-01

    Efficient heat dissipation, which is featured by high thermal conductivity, is one of the crucial issues for the reliability and stability of nanodevices. However, due to the generally fast 1 /T decrease of thermal conductivity with temperature increase, the efficiency of heat dissipation quickly drops down at an elevated temperature caused by the increase of work load in electronic devices. To this end, pursuing semiconductor materials that possess large thermal conductivity at high temperature, i.e., slower decrease of thermal conductivity with temperature increase than the traditional κ ˜1 /T relation, is extremely important to the development of disruptive nanoelectronics. Recently, monolayer gallium nitride (GaN) with a planar honeycomb structure emerges as a promising new two-dimensional material with great potential for applications in nano- and optoelectronics. Here, we report that, despite the commonly established 1 /T relation of thermal conductivity in plenty of materials, monolayer GaN exhibits anomalous behavior that the thermal conductivity almost decreases linearly over a wide temperature range above 300 K, deviating largely from the traditional κ ˜1 /T law. The thermal conductivity at high temperature is much larger than the expected thermal conductivity that follows the general κ ˜1 /T trend, which would be beneficial for applications of monolayer GaN in nano- and optoelectronics in terms of efficient heat dissipation. We perform detailed analysis on the mechanisms underlying the anomalously temperature-dependent thermal conductivity of monolayer GaN in the framework of Boltzmann transport theory and further get insight from the view of electronic structure. Beyond that, we also propose two required conditions for materials that would exhibit similar anomalous temperature dependence of thermal conductivity: large difference in atom mass (huge phonon band gap) and electronegativity (LO-TO splitting due to strong polarization of bond). Our

  5. Tuning of metal work functions with self-assembled monolayers

    NARCIS (Netherlands)

    de Boer, B; Hadipour, A; Mandoc, MM; van Woudenbergh, T; Blom, PWM

    2005-01-01

    Work functions of gold and silver are varied by over 1.4 and 1.7 eV, respectively, by using self-assembled monolayers. Using these modified electrodes, the hole current in a poly(2-methoxy-5-(2'-ethylhexyloxy)- 1,4-phenylene vinylene) light-emitting diode is tuned by more than six orders of

  6. Applications of self-assembled monolayers in materials chemistry

    Indian Academy of Sciences (India)

    Unknown

    Physical and Materials Chemistry Division, National Chemical Laboratory,. Pune 411 008, India e-mail: viji@ems.ncl.res.in. Abstract. Self-assembly provides a simple route to organise suitable organic molecules on noble metal and selected nanocluster surfaces by using monolayers of long chain organic molecules with ...

  7. Melting mechanism in monolayers of flexible rod-shaped molecules

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Taub, H.

    1992-01-01

    The melting of butane and hexane monolayers adsorbed on a graphite basal-plane surface has been studied by molecular-dynamics simulations and experimentally by neutron diffraction. The simulation results are qualitatively consistent with the observed diffraction patterns and suggest a general...

  8. Direct measurement of the microscale conductivity of conjugated polymer monolayers

    DEFF Research Database (Denmark)

    Bøggild, Peter; Grey, Francois; Hassenkam, T.

    2000-01-01

    The in-plane conductivity of conjugated polymer monolayers is mapped here for the first time on the microscale using a novel scanning micro four-point probe (see Figure). The probe allows the source, drain, and voltage electrodes to be positioned within the same domain and the mapping results...

  9. Suppressing segregation in highly phosphorus doped silicon monolayers

    NARCIS (Netherlands)

    Keizer, Joris; Kölling, Sebastian; Koenraad, Paul; Simmons, Michelle Y.

    2015-01-01

    Sharply defined dopant profiles and low resistivity are highly desired qualities in the microelectronic industry, and more recently, in the development of an all epitaxial Si:P based quantum computer. In this work, we use thin (monolayers thick) room temperature grown silicon layers, so-called

  10. Formation and optical characterisation of colloidal gold monolayers

    NARCIS (Netherlands)

    Kooij, Ernst S.; Brouwer, E.A.M.; Wormeester, Herbert; Poelsema, Bene

    2003-01-01

    We study the deposition of charge-stabilised gold nanocolloids on silicon substrates, which have been derivatised with (aminopropyl)triethoxysilane. Atomic force microscopy (AFM) and spectroscopic ellipsometry are employed to investigate the nanocrystal monolayers ex situ. Analysis of AFM images

  11. Monolayer-functionalized microfluidics devices for optical sensing of acidity

    NARCIS (Netherlands)

    Mela, P.; Onclin, S.; Goedbloed, M.H.; Levi, S.; Garcia Parajo, M.F.; van Hulst, N.F.; Ravoo, B.J.; Reinhoudt, David; van den Berg, Albert

    This paper describes the integration of opto-chemosensors in microfluidics networks. Our technique exploits the internal surface of the network as a platform to build a sensing system by coating the surface with a self-assembled monolayer and subsequently binding a fluorescent sensing molecule to

  12. Electrical Transport Properties of Polycrystalline Monolayer Molybdenum Disulfide

    Science.gov (United States)

    2014-07-14

    Lou, Sina Najmaei, Matin Amani, Matthew L. Chin, Zheng Se. TASK NUMBER Liu Sf. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAMES AND ADDRESSES 8...Transport Properties of Polycrystalline Monolayer Molybdenum Disulfide Sina Najmaei,t.§ Matin Ama ni,M Matthew L. Chin,* Zhe ng liu/ ·"·v: A. Gle n

  13. Chiral and herringbone symmetry breaking in water-surface monolayers

    DEFF Research Database (Denmark)

    Peterson, I.R.; Kenn, R.M.; Goudot, A.

    1996-01-01

    We report the observation from monolayers of eicosanoic acid in the L(2)' phase of three distinct out-of-plane first-order diffraction peaks, indicating molecular tilt in a nonsymmetry direction and hence the absence of mirror symmetry. At lower pressures the molecules tilt in the direction of th...

  14. Theory of lithium islands and monolayers: Electronic structure and stability

    International Nuclear Information System (INIS)

    Quassowski, S.; Hermann, K.

    1995-01-01

    Systematic calculations on planar clusters and monolayers of lithium are performed to study geometries and stabilities of the clusters as well as their convergence behavior with increasing cluster size. The calculations are based on ab initio methods using density-functional theory within the local-spin-density approximation for exchange and correlation. The optimized nearest-neighbor distances d NN of the Li n clusters, n=1,...,25, of both hexagonal and square geometry increase with cluster size, converging quite rapidly towards the monolayer results. Further, the cluster cohesive energies E c increase with cluster size and converge towards the respective monolayer values that form upper bounds. Clusters of hexagonal geometry are found to be more stable than square clusters of comparable size, consistent with the monolayer results. The size dependence of the cluster cohesive energies can be described approximately by a coordination model based on the concept of pairwise additive nearest-neighbor binding. This indicates that the average binding in the Li n clusters and their relative stabilities can be explained by simple geometric effects which derive from the nearest-neighbor coordination

  15. Permethylated 12-Vertex p-Carborane Self-Assembled Monolayers

    Czech Academy of Sciences Publication Activity Database

    Scholz, F.; Nothofer, H. G.; Wessels, J. M.; Nelles, G.; Wrochem von, F.; Roy, S.; Chen, X.; Michl, Josef

    2011-01-01

    Roč. 115, č. 46 (2011), s. 22998-23007 ISSN 1932-7447 Grant - others:National Science Foundation(US) CHE-0848477 Institutional research plan: CEZ:AV0Z40550506 Keywords : p-carbone * monolayer * scanning tunneling microscopy * ultraviolet photoelectron spectroscopy * X-ray photoelectron Subject RIV: CC - Organic Chemistry Impact factor: 4.805, year: 2011

  16. Overcrowding drives the unjamming transition of gap-free monolayers

    Science.gov (United States)

    Lan, Ganhui; Su, Tao

    Collective cell motility plays central roles in various biological phenomena such as wound healing, cancer metastasis and embryogenesis. These are demonstrations of the unjamming transition in biology. However, contradictory to the typical density-driven jamming in particulate assemblies, cellular systems often get unjammed in highly packed, sometimes overcrowding environments. Here, we investigate monolayers' collective behaviors when cell number changes under the gap-free constraint. We report that overcrowding can unjam gap-free monolayers through increasing isotropic compression. We show that the transition boundary is determined by the isotropic compression and the cell-cell adhesion. Furthermore, we construct the free energy landscape for the T1 topological transition during monolayer rearrangement, and discover that the landscape evolves from single-barrier W shape to double-barrier M shape during the unjamming process. We also discover a distributed-to-disordered morphological transition of cells' geometry, coinciding with the unjamming transition. Our analyses reveal that the overcrowding and adhesion induced unjamming reflects the mechanical yielding of the highly deformable monolayer, suggesting an alternative mechanism that cells may robustly gain collective mobility through proliferation in confined environments, which differs from those caused by loosing up a packed particulate assembly. This work is supported by the GWU College Facilitating Funds.

  17. Illustrative view on the magnetocrystalline anisotropy of adatoms and monolayers

    Czech Academy of Sciences Publication Activity Database

    Šipr, Ondřej; Mankovsky, S.; Polesya, S.; Bornemann, S.; Minár, J.; Ebert, H.

    2016-01-01

    Roč. 93, č. 17 (2016), s. 1-13, č. článku 174409. ISSN 2469-9950 R&D Projects: GA ČR(CZ) GAP108/11/0853 Institutional support: RVO:68378271 Keywords : magnetic anisotropy * adatom * monolayer * spin-orbit coupling Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.836, year: 2016

  18. Topography and instability of monolayers near domain boundaries

    International Nuclear Information System (INIS)

    Diamant, H.; Witten, T. A.; Ege, C.; Gopal, A.; Lee, K. Y. C.

    2001-01-01

    We theoretically study the topography of a biphasic surfactant monolayer in the vicinity of domain boundaries. The differing elastic properties of the two phases generally lead to a nonflat topography of 'mesas,' where domains of one phase are elevated with respect to the other phase. The mesas are steep but low, having heights of up to 10 nm. As the monolayer is laterally compressed, the mesas develop overhangs and eventually become unstable at a surface tension of about K(δc 0 ) 2 (δc 0 being the difference in spontaneous curvature and K a bending modulus). In addition, the boundary is found to undergo a topography-induced rippling instability upon compression, if its line tension is smaller than about Kδc 0 . The effect of diffuse boundaries on these features and the topographic behavior near a critical point are also examined. We discuss the relevance of our findings to several experimental observations related to surfactant monolayers: (i) small topographic features recently found near domain boundaries; (ii) folding behavior observed in mixed phospholipid monolayers and model lung surfactants; (iii) roughening of domain boundaries seen under lateral compression; (iv) the absence of biphasic structures in tensionless surfactant films

  19. Self-assembled monolayers on metal oxides : applications in nanotechnology

    NARCIS (Netherlands)

    Yildirim, O.

    2010-01-01

    The thesis describes the use of phosph(on)ate-based self-assembled monolayers (SAMs) to modify and pattern metal oxides. Metal oxides have interesting electronic and magnetic properties such as insulating, semiconducting, metallic, ferromagnetic etc. and SAMs can tailor the surface properties. FePt

  20. Transepithelial transport of aliphatic carboxylic acids studied in Madin Darby canine kidney (MDCK) cell monolayers

    International Nuclear Information System (INIS)

    Cho, M.J.; Adson, A.; Kezdy, F.J.

    1990-01-01

    Transport of 14C-labeled acetic, propionic (PA), butyric, valeric, heptanoic (HA), and octanoic (OA) acids across the Madin Darby canine kidney (MDCK) epithelial cell monolayer grown on a porous polycarbonate membrane was studied in Hanks' balanced salt solution (HBSS) at 37 degrees C in both apical-to-basolateral and basolateral-to-apical directions. At micromolar concentrations of solutes, metabolic decomposition was significant as evidenced by [14C]CO2 production during the OA transport. The apparent permeability (Pe) indicates that as lipophilicity increases, diffusion across the unstirred boundary layer becomes rate limiting. In support of this notion, transport of OA and HA was enhanced by agitation, showed an activation energy of 3.7 kcal/mol for OA, and resulted in identical Pe values for both transport directions. Analysis of Pe changes with varying alkyl chain length resulted in a delta G of -0.68 +/- 0.09 kcal/mol for -CH2-group transfer from an aqueous phase to the MDCK cells. When the intercellular tight junctions were opened by the divalent chelator EGTA in Ca2+/Mg2(+)-free HBSS, transport of the fluid-phase marker Lucifer yellow greatly increased because of paracellular leakage. PA transport also showed a significant increase, but OA transport was independent of EGTA. Although albumin also undergoes paracellular transport in the presence of EGTA and OA binds strongly to albumin, OA transport in EGTA solution was unchanged by albumin. These observations indicate that transmembrane transport is the major mechanism for lipophilic substances. The present study, together with earlier work on the transport of polar substances, shows that the MDCK cell monolayer is an excellent model of the transepithelial transport barrier

  1. Workshop on polarized neutron filters and polarized pulsed neutron experiments

    International Nuclear Information System (INIS)

    Itoh, Shinichi

    2004-07-01

    The workshop was held in KEK by thirty-three participants on April 26, 2004. The polarized neutron filter method was only discussed. It consists of three parts; the first part was discussed on the polarized neutron methods, the second part on the polarized neutron experiments and the third on the pulse neutron spectrometer and polarized neutron experiments. The six papers were presented such as the polarized 3 He neutron spin filter, neutron polarization by proton polarized filter, soft master and neutron scattering, polarized neutron in solid physics, polarization experiments by chopper spectroscope and neutron polarization system in superHRPD. (S.Y.)

  2. Bacterial invasion of HT29-MTX-E12 monolayers: effects of human breast milk.

    Science.gov (United States)

    Hall, Tim; Dymock, David; Corfield, Anthony P; Weaver, Gillian; Woodward, Mark; Berry, Monica

    2013-02-01

    The supramucosal gel, crucial for gut barrier function, might be compromised in necrotizing enterocolitis (NEC). Breast milk is associated with a reduced incidence of NEC. We compared the effects of human breast milk (BM) versus a neonatal formula, Nutriprem 1 (FF), on adherence, internalisation, and penetration of NEC-associated Escherichia coli through monolayers of mucus producing intestinal cells, HT29-MTX-E12 (E12). E12 cells were grown to confluence on membranes permeable to bacteria. E. coli, reference strain and isolated from a NEC-affected intestine, were cultured in LB broth, labelled with fluorescein and biotinylated. Bacteria were suspended in tissue culture medium (TC) or mixtures of TC with BM or FF and applied to the E12 cultures. Bacterial numbers were assessed by fluorescence. DyLight 650-labelled neutravidin, which cannot cross cell membrane, evaluated extracellular bacteria. Fluorescence of basolateral medium was measured to quantify translocation. Bacterial concentrations were compared using the Mann Whitney U test. After 1h exposure, E12 cultures adhered or internalised more NEC-derived bacteria than standard strain E. coli and more suspended in FF than BM (Pmilk was associated with relatively less adhesion and internalisation of NEC-associated E. coli to mucus covered E12s compared to formula milk. Copyright © 2013 Elsevier Inc. All rights reserved.

  3. Instrumentation with polarized neutrons

    International Nuclear Information System (INIS)

    Boeni, P.; Muenzer, W.; Ostermann, A.

    2009-01-01

    Neutron scattering with polarization analysis is an indispensable tool for the investigation of novel materials exhibiting electronic, magnetic, and orbital degrees of freedom. In addition, polarized neutrons are necessary for neutron spin precession techniques that path the way to obtain extremely high resolution in space and time. Last but not least, polarized neutrons are being used for fundamental studies as well as very recently for neutron imaging. Many years ago, neutron beam lines were simply adapted for polarized beam applications by adding polarizing elements leading usually to unacceptable losses in neutron intensity. Recently, an increasing number of beam lines are designed such that an optimum use of polarized neutrons is facilitated. In addition, marked progress has been obtained in the technology of 3 He polarizers and the reflectivity of large-m supermirrors. Therefore, if properly designed, only factors of approximately 2-3 in neutron intensity are lost. It is shown that S-benders provide neutron beams with an almost wavelength independent polarization. Using twin cavities, polarized beams with a homogeneous phase space and P>0.99 can be produced without significantly sacrificing intensity. It is argued that elliptic guides, which are coated with large m polarizing supermirrors, provide the highest flux.

  4. In vitro culture of functionally active buffalo hepatocytes isolated by using a simplified manual perfusion method.

    Directory of Open Access Journals (Sweden)

    Santanu Panda

    Full Text Available In farm animals, there is no suitable cell line available to understand liver-specific functions. This has limited our understanding of liver function and metabolism in farm animals. Culturing and maintenance of functionally active hepatocytes is difficult, since they survive no more than few days. Establishing primary culture of hepatocytes can help in studying cellular metabolism, drug toxicity, hepatocyte specific gene function and regulation. Here we provide a simple in vitro method for isolation and short-term culture of functionally active buffalo hepatocytes.Buffalo hepatocytes were isolated from caudate lobes by using manual enzymatic perfusion and mechanical disruption of liver tissue. Hepatocyte yield was (5.3 ± 0.66×107 cells per gram of liver tissue with a viability of 82.3 ± 3.5%. Freshly isolated hepatocytes were spherical with well contrasted border. After 24 hours of seeding onto fibroblast feeder layer and different extracellular matrices like dry collagen, matrigel and sandwich collagen coated plates, hepatocytes formed confluent monolayer with frequent clusters. Cultured hepatocytes exhibited typical cuboidal and polygonal shape with restored cellular polarity. Cells expressed hepatocyte-specific marker genes or proteins like albumin, hepatocyte nuclear factor 4α, glucose-6-phosphatase, tyrosine aminotransferase, cytochromes, cytokeratin and α1-antitrypsin. Hepatocytes could be immunostained with anti-cytokeratins, anti-albumin and anti α1-antitrypsin antibodies. Abundant lipid droplets were detected in the cytosol of hepatocytes using oil red stain. In vitro cultured hepatocytes could be grown for five days and maintained for up to nine days on buffalo skin fibroblast feeder layer. Cultured hepatocytes were viable for functional studies.We developed a convenient and cost effective technique for hepatocytes isolation for short-term culture that exhibited morphological and functional characteristics of active hepatocytes

  5. Proton and hydrogen transport through two-dimensional monolayers

    International Nuclear Information System (INIS)

    Seel, Max; Pandey, Ravindra

    2016-01-01

    Diffusion of protons and hydrogen atoms in representative two-dimensional materials is investigated. Specifically, density functional calculations were performed on graphene, hexagonal boron nitride (h-BN), phosphorene, silicene, and molybdenum disulfide (MoS 2 ) monolayers to study the surface interaction and penetration barriers for protons and hydrogen atoms employing finite cluster models. The calculated barrier heights correlate approximately with the size of the opening formed by the three-fold open sites in the monolayers considered. They range from 1.56 eV (proton) and 4.61 eV (H) for graphene to 0.12 eV (proton) and 0.20 eV (H) for silicene. The results indicate that only graphene and h-BN monolayers have the potential for membranes with high selective permeability. The MoS 2 monolayer behaves differently: protons and H atoms become trapped between the outer S layers in the Mo plane in a well with a depth of 1.56 eV (proton) and 1.5 eV (H atom), possibly explaining why no proton transport was detected, suggesting MoS 2 as a hydrogen storage material instead. For graphene and h-BN, off-center proton penetration reduces the barrier to 1.38 eV for graphene and 0.11 eV for h-BN. Furthermore, Pt acting as a substrate was found to have a negligible effect on the barrier height. In defective graphene, the smallest barrier for proton diffusion (1.05 eV) is found for an oxygen-terminated defect. Therefore, it seems more likely that thermal protons can penetrate a monolayer of h-BN but not graphene and defects are necessary to facilitate the proton transport in graphene. (paper)

  6. Proton and hydrogen transport through two-dimensional monolayers

    Science.gov (United States)

    Seel, Max; Pandey, Ravindra

    2016-06-01

    Diffusion of protons and hydrogen atoms in representative two-dimensional materials is investigated. Specifically, density functional calculations were performed on graphene, hexagonal boron nitride (h-BN), phosphorene, silicene, and molybdenum disulfide (MoS2) monolayers to study the surface interaction and penetration barriers for protons and hydrogen atoms employing finite cluster models. The calculated barrier heights correlate approximately with the size of the opening formed by the three-fold open sites in the monolayers considered. They range from 1.56 eV (proton) and 4.61 eV (H) for graphene to 0.12 eV (proton) and 0.20 eV (H) for silicene. The results indicate that only graphene and h-BN monolayers have the potential for membranes with high selective permeability. The MoS2 monolayer behaves differently: protons and H atoms become trapped between the outer S layers in the Mo plane in a well with a depth of 1.56 eV (proton) and 1.5 eV (H atom), possibly explaining why no proton transport was detected, suggesting MoS2 as a hydrogen storage material instead. For graphene and h-BN, off-center proton penetration reduces the barrier to 1.38 eV for graphene and 0.11 eV for h-BN. Furthermore, Pt acting as a substrate was found to have a negligible effect on the barrier height. In defective graphene, the smallest barrier for proton diffusion (1.05 eV) is found for an oxygen-terminated defect. Therefore, it seems more likely that thermal protons can penetrate a monolayer of h-BN but not graphene and defects are necessary to facilitate the proton transport in graphene.

  7. The formation of quiescent glomerular endothelial cell monolayer in vitro is strongly dependent on the choice of extracellular matrix coating

    Energy Technology Data Exchange (ETDEWEB)

    Pajęcka, Kamilla, E-mail: kpaj@novonordisk.com [Global Research, Novo Nordisk A/S, Måløv (Denmark); Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus (Denmark); Nielsen, Malik Nygaard [Global Research, Novo Nordisk A/S, Måløv (Denmark); Hansen, Troels Krarup [Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus (Denmark); Williams, Julie M. [Global Research, Novo Nordisk A/S, Måløv (Denmark)

    2017-04-01

    Background and aims: Nephropathy involves pathophysiological changes to the glomerulus. The primary glomerular endothelial cells (GEnCs) have emerged as an important tool for studying glomerulosclerotic mechanisms and in the screening process for drug-candidates. The success of the studies is dependent on the quality of the cell model. Therefore, we set out to establish an easy, reproducible model of the quiescent endothelial monolayer with the use of commercially available extracellular matrices (ECMs). Methods: Primary hGEnCs were seeded on various ECMs. Cell adhesion was monitored by an impedance sensing system. The localization of junctional proteins was assessed by immunofluorescence and the barrier function by passage of fluorescent dextrans and magnitude of VEGF response. Results: All ECM matrices except recombinant human laminin 111 (rhLN111) supported comparable cell proliferation. Culturing hGEnCs on rhLN521, rhLN511 or fibronectin resulted in a physiologically relevant barrier to 70 kDa dextrans which was 82% tighter than that formed on collagen type IV. Furthermore, only hGEnCs cultured on rhLN521 or rhLN511 showed plasma-membrane localized zonula occludens-1 and vascular endothelial cadherin indicative of proper tight and adherens junctions (AJ). Conclusion: We recommend culturing hGEnCs on the mature glomerular basement membrane laminin - rhLN521 – which, as the only commercially available ECM, promotes all of the characteristics of the quiescent hGEnC monolayer: cobblestone morphology, well-defined AJs and physiological perm-selectivity. - Highlights: • rhLN521, rhLN511 and hFN assure physiologically relevant permeability. • rhLN521 and rhLN511 ensure best cell morphology and adherens junction formation. • Collagen IV and I based coating results in disorganized hGEnC monolayer. • Physiologically relevant ECM may lead to down-regulation of self-produced matrices.

  8. The formation of quiescent glomerular endothelial cell monolayer in vitro is strongly dependent on the choice of extracellular matrix coating

    International Nuclear Information System (INIS)

    Pajęcka, Kamilla; Nielsen, Malik Nygaard; Hansen, Troels Krarup; Williams, Julie M.

    2017-01-01

    Background and aims: Nephropathy involves pathophysiological changes to the glomerulus. The primary glomerular endothelial cells (GEnCs) have emerged as an important tool for studying glomerulosclerotic mechanisms and in the screening process for drug-candidates. The success of the studies is dependent on the quality of the cell model. Therefore, we set out to establish an easy, reproducible model of the quiescent endothelial monolayer with the use of commercially available extracellular matrices (ECMs). Methods: Primary hGEnCs were seeded on various ECMs. Cell adhesion was monitored by an impedance sensing system. The localization of junctional proteins was assessed by immunofluorescence and the barrier function by passage of fluorescent dextrans and magnitude of VEGF response. Results: All ECM matrices except recombinant human laminin 111 (rhLN111) supported comparable cell proliferation. Culturing hGEnCs on rhLN521, rhLN511 or fibronectin resulted in a physiologically relevant barrier to 70 kDa dextrans which was 82% tighter than that formed on collagen type IV. Furthermore, only hGEnCs cultured on rhLN521 or rhLN511 showed plasma-membrane localized zonula occludens-1 and vascular endothelial cadherin indicative of proper tight and adherens junctions (AJ). Conclusion: We recommend culturing hGEnCs on the mature glomerular basement membrane laminin - rhLN521 – which, as the only commercially available ECM, promotes all of the characteristics of the quiescent hGEnC monolayer: cobblestone morphology, well-defined AJs and physiological perm-selectivity. - Highlights: • rhLN521, rhLN511 and hFN assure physiologically relevant permeability. • rhLN521 and rhLN511 ensure best cell morphology and adherens junction formation. • Collagen IV and I based coating results in disorganized hGEnC monolayer. • Physiologically relevant ECM may lead to down-regulation of self-produced matrices.

  9. Spin-polarized spin excitation spectroscopy

    International Nuclear Information System (INIS)

    Loth, Sebastian; Lutz, Christopher P; Heinrich, Andreas J

    2010-01-01

    We report on the spin dependence of elastic and inelastic electron tunneling through transition metal atoms. Mn, Fe and Cu atoms were deposited onto a monolayer of Cu 2 N on Cu(100) and individually addressed with the probe tip of a scanning tunneling microscope. Electrons tunneling between the tip and the substrate exchange energy and spin angular momentum with the surface-bound magnetic atoms. The conservation of energy during the tunneling process results in a distinct onset threshold voltage above which the tunneling electrons create spin excitations in the Mn and Fe atoms. Here we show that the additional conservation of spin angular momentum leads to different cross-sections for spin excitations depending on the relative alignment of the surface spin and the spin of the tunneling electron. For this purpose, we developed a technique for measuring the same local spin with a spin-polarized and a non-spin-polarized tip by exchanging the last apex atom of the probe tip between different transition metal atoms. We derive a quantitative model describing the observed excitation cross-sections on the basis of an exchange scattering process.

  10. Multiphoton polarization Bremsstrahlung effect

    International Nuclear Information System (INIS)

    Golovinskij, P.A.

    2001-01-01

    A general approach to induced polarization effects was formulated on the basis of theory of many particles in a strong periodic field. Correlation with the perturbation theory is shown and the types of effective polarization potentials both for isolated atoms and ions, and for ions in plasma, are provided. State of art in the theory of forced polarization Bremsstrahlung effect is analyzed and some outlooks for further experimental and theoretical studies are outlined [ru

  11. Analysis of Reparative Activity of Platelet Lysate: Effect on Cell Monolayer Recovery In Vitro and Skin Wound Healing In Vivo.

    Science.gov (United States)

    Sergeeva, N S; Shanskii, Ya D; Sviridova, I K; Karalkin, P A; Kirsanova, V A; Akhmedova, S A; Kaprin, A D

    2016-11-01

    Platelet lysate prepared from donor platelet concentrate and pooled according to a developed technique stimulates migration of multipotent mesenchymal stromal cells of the human adipose tissue and promotes healing of the monolayer defect in cultures of human fibroblasts and multipotent mesenchymal stromal cells in vitro in concentrations close those of fetal calf serum (5-10%). Lysate of platelets from platelet-rich rat blood plasma stimulated healing of the skin defect by promoting epithelialization and granulation tissue formation. The regenerative properties of platelet lysate in vivo increased with increasing its concentration.

  12. Airborne Laser Polarization Sensor

    Science.gov (United States)

    Kalshoven, James, Jr.; Dabney, Philip

    1991-01-01

    Instrument measures polarization characteristics of Earth at three wavelengths. Airborne Laser Polarization Sensor (ALPS) measures optical polarization characteristics of land surface. Designed to be flown at altitudes of approximately 300 m to minimize any polarizing or depolarizing effects of intervening atmosphere and to look along nadir to minimize any effects depending on look angle. Data from measurements used in conjunction with data from ground surveys and aircraft-mounted video recorders to refine mathematical models used in interpretation of higher-altitude polarimetric measurements of reflected sunlight.

  13. Polarization of Be stars

    International Nuclear Information System (INIS)

    Johns, M.W.

    1975-01-01

    Linear polarization of starlight may be produced by electron scattering in the extended atmospheres of early type stars. Techniques are investigated for the measurement and interpretation of this polarization. Polarimetric observations were made of twelve visual double star systems in which at least one member was a B type star as a means of separating the intrinsic stellar polarization from the polarization produced in the interstellar medium. Four of the double stars contained a Be star. Evidence for intrinsic polarization was found in five systems including two of the Be systems, one double star with a short period eclipsing binary, and two systems containing only normal early type stars for which emission lines have not been previously reported. The interpretation of these observations in terms of individual stellar polarizations and their wavelength dependence is discussed. The theoretical basis for the intrinsic polarization of early type stars is explored with a model for the disk-like extended atmospheres of Be stars. Details of a polarimeter for the measurement of the linear polarization of astronomical point sources are also presented with narrow band (Δ lambda = 100A) measurements of the polarization of γ Cas from lambda 4000 to lambda 5800

  14. Polarization at SLC

    International Nuclear Information System (INIS)

    Swartz, M.L.

    1988-07-01

    The SLAC Linear Collider has been designed to readily accommodate polarized electron beams. Considerable effort has been made to implement a polarized source, a spin rotation system, and a system to monitor the beam polarization. Nearly all major components have been fabricated. At the current time, several source and polarimeter components have been installed. The installation and commissioning of the entire system will take place during available machine shutdown periods as the commissioning of SLC progresses. It is expected that a beam polarization of 45% will be achieved with no loss in luminosity. 13 refs., 15 figs

  15. Polarization-independent transparency window induced by complementary graphene metasurfaces

    International Nuclear Information System (INIS)

    Lu, Wei Bing; Liu, Ji Long; Zhang, Jin; Wang, Jian; Liu, Zhen Guo

    2017-01-01

    A fourfold symmetric graphene-based complementary metasurface featuring a polarization-independent transparency window is proposed and numerically analysed in this paper. The unit cell of the metamaterial consists of a monolayer graphene perforated with a cross and four identical split-ring resonators deposited on a substrate. Our analysis shows that the transparency window can be interpreted as a plasmonic analogy of Autler–Townes splitting. The polarization independence is achieved due to the fourfold symmetry of graphene’s complementary structure. In addition, the frequency range of the transparency window can be dynamically tuned over a broad band by changing the chemical potential of graphene, and the width of the transparency window can also be controlled by changing the split-gap orientation. This work may lead to potential applications in many area, such as slow-light devices and optical sensing. (paper)

  16. Structural, electronic and magnetic properties of Au-based monolayer derivatives in honeycomb structure

    Energy Technology Data Exchange (ETDEWEB)

    Kapoor, Pooja, E-mail: pupooja16@gmail.com; Sharma, Munish; Ahluwalia, P. K. [Physics Department, Himachal Pradesh University, Shimla, Himachal Pradesh, India 171005 (India); Kumar, Ashok [Centre for Physical Sciences, School of Basic and Applied Sciences, Central University of Punjab, Bathinda, India, 151001 (India)

    2016-05-23

    We present electronic properties of atomic layer of Au, Au{sub 2}-N, Au{sub 2}-O and Au{sub 2}-F in graphene-like structure within the framework of density functional theory (DFT). The lattice constant of derived monolayers are found to be higher than the pristine Au monolayer. Au monolayer is metallic in nature with quantum ballistic conductance calculated as 4G{sub 0}. Similarly, Au{sub 2}-N and Au{sub 2}-F monolayers show 4G{sub 0} and 2G{sub 0} quantum conductance respectively while semiconducting nature with calculated band gap of 0.28 eV has been observed for Au{sub 2}-O monolayer. Most interestingly, half metalicity has been predicted for Au{sub 2}-N and Au{sub 2}-F monolayers. Our findings may have importance for the application of these monolayers in nanoelectronic and spintronics.

  17. Emergence of Dirac and quantum spin Hall states in fluorinated monolayer As and AsSb

    KAUST Repository

    Zhang, Qingyun

    2016-01-21

    Using first-principles calculations, we investigate the electronic and vibrational properties of monolayer As and AsSb. While the pristine monolayers are semiconductors (direct band gap at the Γ point), fluorination results in Dirac cones at the K points. Fluorinated monolayer As shows a band gap of 0.16 eV due to spin-orbit coupling, and fluorinated monolayer AsSb a larger band gap of 0.37 eV due to inversion symmetry breaking. Spin-orbit coupling induces spin splitting similar to monolayer MoS2. Phonon calculations confirm that both materials are dynamically stable. Calculations of the edge states of nanoribbons by the tight-binding method demonstrate that fluorinated monolayer As is topologically nontrivial in contrast to fluorinated monolayer AsSb.

  18. Structural and electronic properties of polar MnO ultrathin film grown on Ag(111)

    Energy Technology Data Exchange (ETDEWEB)

    Kundu, Asish K., E-mail: asish.kundu@saha.ac.in; Menon, Krishnakumar S. R. [Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 70064 (India)

    2016-05-23

    Surface electronic structure of ultrathin polar MnO film was studied by Low-energy Electron Diffraction (LEED) and Photoemission Spectroscopic (PES) techniques. Epitaxial monolayer to facet formation with increasing film thickness has been observed by LEED. Our LEED result shows p(2x2) surface reconstruction along with facet formation, stabilize the polar MnO(111) surface. The core levels and the valence band electronic structure of MnO films have been studied as a function of film thickness using X-ray and ultraviolet photoelectron spectroscopy techniques.

  19. Monolayer to MTS: using SEM, HIM, TEM and SERS to compare morphology, nanosensor uptake and redox potential in MCF7 cells

    Science.gov (United States)

    Jamieson, L. E.; Bell, A. P.; Harrison, D. J.; Campbell, C. J.

    2015-06-01

    Cellular redox potential is important for the control and regulation of a vast number of processes occurring in cells. When the fine redox potential balance within cells is disturbed it can have serious consequences such as the initiation or progression of disease. It is thought that a redox gradient develops in cancer tumours where the peripheral regions are well oxygenated and internal regions, further from vascular blood supply, become starved of oxygen and hypoxic. This makes treatment of these areas more challenging as, for example, radiotherapy relies on the presence of oxygen. Currently techniques for quantitative analysis of redox gradients are limited. Surface enhanced Raman scattering (SERS) nanosensors (NS) have been used to detect redox potential in a quantitative manner in monolayer cultured cells with many advantages over other techniques. This technique has considerable potential for use in multicellular tumour spheroids (MTS) - a three dimensional (3D) cell model which better mimics the tumour environment and gradients that develop. MTS are a more realistic model of the in vivo cellular morphology and environment and are becoming an increasingly popular in vitro model, replacing traditional monolayer culture. Imaging techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM) and helium ion microscopy (HIM) were used to investigate differences in morphology and NS uptake in monolayer culture compared to MTS. After confirming NS uptake, the first SERS measurements revealing quantitative information on redox potential in MTS were performed.

  20. TRANSVERSELY POLARIZED Λ PRODUCTION

    International Nuclear Information System (INIS)

    BORER, D.

    2000-01-01

    Transversely polarized Λ production in hard scattering processes is discussed in terms of a leading twist T-odd fragmentation function which describes the fragmentation of an unpolarized quark into a transversely polarized Λ. We focus on the properties of this function and its relevance for the RHIC and HERMES experiments

  1. Marine polar steroids

    International Nuclear Information System (INIS)

    Stonik, Valentin A

    2001-01-01

    Structures, taxonomic distribution and biological activities of polar steroids isolated from various marine organisms over the last 8-10 years are considered. The peculiarities of steroid biogenesis in the marine biota and their possible biological functions are discussed. Syntheses of some highly active marine polar steroids are described. The bibliography includes 254 references.

  2. Polarized proton beams

    International Nuclear Information System (INIS)

    Roser, T.

    1995-01-01

    The acceleration of polarized proton beams in circular accelerators is complicated by the presence of numerous depolarizing spin resonances. Careful and tedious minimization of polarization loss at each of these resonances allowed acceleration of polarized proton beams up to 22 GeV. It has been the hope that Siberian Snakes, which are local spin rotators inserted into ring accelerators, would eliminate these resonances and allow acceleration of polarized beams with the same ease and efficiency that is now routine for unpolarized beams. First tests at IUCF with a full Siberian Snake showed that the spin dynamics with a Snake can be understood in detail. The author now has results of the first tests of a partial Siberian Snake at the AGS, accelerating polarized protons to an energy of about 25 GeV. These successful tests of storage and acceleration of polarized proton beams open up new possibilities such as stored polarized beams for internal target experiments and high energy polarized proton colliders

  3. Transport and sorting of sphingolipids in polarized cells : the involvement of the sub-apical compartment

    NARCIS (Netherlands)

    IJzendoorn, Sven Christian David van

    1999-01-01

    The work described in this thesis has provided a novel insight into the process of sphingolipid transport and sorting in polarized cells. We have used HepG2 cells as a model system to study polarized traffic in hepatic cells. Under specific culture conditions, HepG2 cells acquire a polarized

  4. Polarization Optics in Telecommunications

    CERN Document Server

    Damask, Jay N

    2005-01-01

    The strong investments into optical telecommunications in the late 1990s resulted in a wealth of new research, techniques, component designs, and understanding of polarization effects in fiber. Polarization Optics in Telecommunications brings together recent advances in the field to create a standard, practical reference for component designers and optical fiber communication engineers. Beginning with a sound foundation in electromagnetism, the author offers a dissertation of the spin-vector formalism of polarization and the interaction of light with media. Applications discussed include optical isolators, optical circulators, fiber collimators, and a variety of applied waveplate and prism combinations. Also included in an extended discussion of polarization-mode dispersion (PMD) and polarization-dependent loss (PDL), their representation, behavior, statistical properties, and measurement. This book draws extensively from the technical and patent literature and is an up-to-date reference for researchers and c...

  5. Parallel Polarization State Generation.

    Science.gov (United States)

    She, Alan; Capasso, Federico

    2016-05-17

    The control of polarization, an essential property of light, is of wide scientific and technological interest. The general problem of generating arbitrary time-varying states of polarization (SOP) has always been mathematically formulated by a series of linear transformations, i.e. a product of matrices, imposing a serial architecture. Here we show a parallel architecture described by a sum of matrices. The theory is experimentally demonstrated by modulating spatially-separated polarization components of a laser using a digital micromirror device that are subsequently beam combined. This method greatly expands the parameter space for engineering devices that control polarization. Consequently, performance characteristics, such as speed, stability, and spectral range, are entirely dictated by the technologies of optical intensity modulation, including absorption, reflection, emission, and scattering. This opens up important prospects for polarization state generation (PSG) with unique performance characteristics with applications in spectroscopic ellipsometry, spectropolarimetry, communications, imaging, and security.

  6. Neutron Reflectivity Measurement for Polymer Dynamics near Graphene Oxide Monolayers

    Science.gov (United States)

    Koo, Jaseung

    We investigated the diffusion dynamics of polymer chains confined between graphene oxide layers using neutron reflectivity (NR). The bilayers of polymethylmetacrylate (PMMA)/ deuterated PMMA (d-PMMA) films and polystyrene (PS)/d-PS films with various film thickness sandwiched between Langmuir-Blodgett (LB) monolayers of graphene oxide (GO) were prepared. From the NR results, we found that PMMA diffusion dynamics was reduced near the GO surface while the PS diffusion was not significantly changed. This is due to the different strength of GO-polymer interaction. In this talk, these diffusion results will be compared with dewetting dynamics of polymer thin films on the GO monolayers. This has given us the basis for development of graphene-based nanoelectronics with high efficiency, such as heterojunction devices for polymer photovoltaic (OPV) applications.

  7. Organosilicon derivatives of BTBT for monolayer organic field effect transistors

    Science.gov (United States)

    Agina, Elena V.; Polinskaya, Marina S.; Trul, Askold A.; Chekusova, Viktoria P.; Sizov, Alexey S.; Borshchev, Oleg V.; Ponomarenko, Sergey A.

    2017-08-01

    Synthesis of novel organosilicon derivatives of [1]benzothieno[3,2-b][1]-benzothiophene (BTBT) linked though flexible aliphatic spacers to a disiloxane anchor group is reported. They were successfully used in monolayer OFETs with the charge carrier mobilities up to 0.02 cm2 /Vs, threshold voltage close to 0 V and On/Off ratio up to 10,000. Influence of the chemical structure of the molecules synthesized on the morphology, molecular 2D ordering in the monolayers and their semiconducting properties is considered. The effect of different methods of the ultrathin semiconducting layer preparation, such as Langmuir-Blodgett, Langmuir-Schaefer, spin coating or doctor blade, on the OFET performance is discussed.

  8. Defective interfering particles in monolayer-propagated Newcastle disease virus

    International Nuclear Information System (INIS)

    Roman, J.M.; Simon, E.H.

    1976-01-01

    Newcastle disease virus (NDV) serially passaged in chick embryo fibroblasts (M-NDV) gives rise to defective interfering (NDV-DI) particles, while NDV passaged in embryonated eggs (E-NDV) does not. Co-infection with these particles and infectious virions results in a 99 percent reduction in yield. Interference is not due to interferon or to prevention of absorption of infectious virions and is specific for NDV. The particles mediating interference sediment at the same velocity as infectious virions. The accumulation of NDV-DI particles in monolayers but not in eggs may be a consequence of the fact that M-NDV virions are larger and probably contain more RNA, or it may reflect differences in NDV replicative processes in eggs and monolayers, or both

  9. Point defect weakened thermal contraction in monolayer graphene.

    Science.gov (United States)

    Zha, Xian-Hu; Zhang, Rui-Qin; Lin, Zijing

    2014-08-14

    We investigate the thermal expansion behaviors of monolayer graphene and three configurations of graphene with point defects, namely the replacement of one carbon atom with a boron or nitrogen atom, or of two neighboring carbon atoms by boron-nitrogen atoms, based on calculations using first-principles density functional theory. It is found that the thermal contraction of monolayer graphene is significantly decreased by point defects. Moreover, the corresponding temperature for negative linear thermal expansion coefficient with the maximum absolute value is reduced. The cause is determined to be point defects that enhance the mechanical strength of graphene and then reduce the amplitude and phonon frequency of the out-of-plane acoustic vibration mode. Such defect weakening of graphene thermal contraction will be useful in nanotechnology to diminish the mismatching or strain between the graphene and its substrate.

  10. Studies of lipid interactions in mixed Langmuir monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Gzyl-Malcher, Barbara [Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland)], E-mail: gzyl@chemia.uj.edu.pl; Paluch, Maria [Department of Physical Chemistry and Electrochemistry, Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow (Poland)

    2008-10-31

    The mixed monolayers of dipalmitoyl phosphatidylcholine (DPPC) with 3-monopalmitoyl glycerol (PG) and palmitic acid 4-methylumbelliferyl ester (4-MU) were compared. Relevant thermodynamic parameters such as excess area ({delta}A{sup E}) and excess free energy of mixing ({delta}G{sub mix}{sup E}) were derived from the surface pressure data obtained from compression measurements performed in a Langmuir trough. Generally, DPPC formed more condensed monolayers with PG and greater negative values of {delta}A{sup E} and {delta}G{sub mix}{sup E} were observed for DPPC/PG system than for DPPC/4-MU one. The positive values of the excess free entropy of mixing ({delta}S{sub mix}{sup E}) were calculated for DPPC/4-MU system at lower temperatures and for DPPC/PG system at higher temperatures.

  11. MgO monolayer epitaxy on Ni (100)

    Science.gov (United States)

    Sarpi, B.; Putero, M.; Hemeryck, A.; Vizzini, S.

    2017-11-01

    The growth of two-dimensional oxide films with accurate control of their structural and electronic properties is considered challenging for engineering nanotechnological applications. We address here the particular case of MgO ultrathin films grown on Ni (100), a system for which neither crystallization nor extended surface ordering has been established previously in the monolayer range. Using Scanning Tunneling Microscopy and Auger Electron Spectroscopy, we report on experiments showing MgO monolayer (ML) epitaxy on a ferromagnetic nickel surface, down to the limit of atomic thickness. Alternate steps of Mg ML deposition, O2 gas exposure, and ultrahigh vacuum thermal treatment enable the production of a textured film of ordered MgO nano-domains. This study could open interesting prospects for controlled epitaxy of ultrathin oxide films with a high magneto-resistance ratio on ferromagnetic substrates, enabling improvement in high-efficiency spintronics and magnetic tunnel junction devices.

  12. Integrated quantitative fractal polarimetric analysis of monolayer lung cancer cells

    Science.gov (United States)

    Shrestha, Suman; Zhang, Lin; Quang, Tri; Farrahi, Tannaz; Narayan, Chaya; Deshpande, Aditi; Na, Ying; Blinzler, Adam; Ma, Junyu; Liu, Bo; Giakos, George C.

    2014-05-01

    Digital diagnostic pathology has become one of the most valuable and convenient advancements in technology over the past years. It allows us to acquire, store and analyze pathological information from the images of histological and immunohistochemical glass slides which are scanned to create digital slides. In this study, efficient fractal, wavelet-based polarimetric techniques for histological analysis of monolayer lung cancer cells will be introduced and different monolayer cancer lines will be studied. The outcome of this study indicates that application of fractal, wavelet polarimetric principles towards the analysis of squamous carcinoma and adenocarcinoma cancer cell lines may be proved extremely useful in discriminating among healthy and lung cancer cells as well as differentiating among different lung cancer cells.

  13. Magnetic tunnel junctions with monolayer hexagonal boron nitride tunnel barriers

    Energy Technology Data Exchange (ETDEWEB)

    Piquemal-Banci, M.; Galceran, R.; Bouzehouane, K.; Anane, A.; Petroff, F.; Fert, A.; Dlubak, B.; Seneor, P. [Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau 91767 (France); Caneva, S.; Martin, M.-B.; Weatherup, R. S.; Kidambi, P. R.; Robertson, J.; Hofmann, S. [Department of Engineering, University of Cambridge, Cambridge CB21PZ (United Kingdom); Xavier, S. [Thales Research and Technology, 1 avenue Augustin Fresnel, Palaiseau 91767 (France)

    2016-03-07

    We report on the integration of atomically thin 2D insulating hexagonal boron nitride (h-BN) tunnel barriers into Co/h-BN/Fe magnetic tunnel junctions (MTJs). The h-BN monolayer is directly grown by chemical vapor deposition on Fe. The Conductive Tip Atomic Force Microscopy (CT-AFM) measurements reveal the homogeneity of the tunnel behavior of our h-BN layers. As expected for tunneling, the resistance depends exponentially on the number of h-BN layers. The h-BN monolayer properties are also characterized through integration into complete MTJ devices. A Tunnel Magnetoresistance of up to 6% is observed for a MTJ based on a single atomically thin h-BN layer.

  14. Monolayers and thin films of dextran hydrophobically modified

    International Nuclear Information System (INIS)

    Leiva, Angel; Munoz, Natalia; Gargallo, Ligia; Radic, Deodato; Urzua, Marcela

    2010-01-01

    A series of biodegradable graft copolymers were synthesized by grafting e-caprolactone over dextran of different molecular weights. The obtained copolymers were characterized by Fourier transform infrared spectroscopy FTIR, proton nuclear magnetic resonance 1H NMR, thermogravimetry and elemental analysis. Stable monolayers at the air-water interface and spin coated thin films were prepared and characterized by the Langmuir technique and by contact angle measurements respectively. The compressibility and static surface elasticity of the monolayers and the surface energy of copolymer thin films show dependence with the e-caprolactone content. >From these results it can be concluded that the surface properties of grafted copolymers can be modulated by their composition. Additionally, according to the obtained results, e-caprolactone grafted-dextrans show potential for being used in different applications where surface properties are important. (author)

  15. Atomic Defects and Doping of Monolayer NbSe2.

    Science.gov (United States)

    Nguyen, Lan; Komsa, Hannu-Pekka; Khestanova, Ekaterina; Kashtiban, Reza J; Peters, Jonathan J P; Lawlor, Sean; Sanchez, Ana M; Sloan, Jeremy; Gorbachev, Roman V; Grigorieva, Irina V; Krasheninnikov, Arkady V; Haigh, Sarah J

    2017-03-28

    We have investigated the structure of atomic defects within monolayer NbSe 2 encapsulated in graphene by combining atomic resolution transmission electron microscope imaging, density functional theory (DFT) calculations, and strain mapping using geometric phase analysis. We demonstrate the presence of stable Nb and Se monovacancies in monolayer material and reveal that Se monovacancies are the most frequently observed defects, consistent with DFT calculations of their formation energy. We reveal that adventitious impurities of C, N, and O can substitute into the NbSe 2 lattice stabilizing Se divacancies. We further observe evidence of Pt substitution into both Se and Nb vacancy sites. This knowledge of the character and relative frequency of different atomic defects provides the potential to better understand and control the unusual electronic and magnetic properties of this exciting two-dimensional material.

  16. Channel formation in single-monolayer pentacene thin film transistors

    International Nuclear Information System (INIS)

    Park, B-N; Seo, Soonjoo; Evans, Paul G

    2007-01-01

    The geometrical arrangement of single-molecule-high islands and the contact between them have large roles in determining the electrical properties of field effect transistors (FETs) based on monolayer-scale pentacene thin films. As the pentacene coverage increases through the submonolayer regime there is a percolation transition where islands come into contact and a simultaneous rapid onset of current. At coverages just above the percolation threshold, the electrical properties vary with geometrical changes in the contacts between the pentacene islands. At higher coverages, the FET mobility is much lower than the mobility measured by the van der Pauw method because of high contact resistances in monolayer-scale pentacene film devices. An increase in the van der Pauw mobility of holes as a function of pentacene coverage shows that second layer islands take part in charge transport

  17. Acoustic analog of monolayer graphene and edge states

    International Nuclear Information System (INIS)

    Zhong, Wei; Zhang, Xiangdong

    2011-01-01

    Acoustic analog of monolayer graphene has been designed by using silicone rubber spheres of honeycomb lattices embedded in water. The dispersion of the structure has been studied theoretically using the rigorous multiple-scattering method. The energy spectra with the Dirac point have been verified and zigzag edge states have been found in ribbons of the structure, which are analogous to the electronic ones in graphene nanoribbons. The guided modes along the zigzag edge excited by a point source have been numerically demonstrated. The open cavity and 'Z' type edge waveguide with 60 o corners have also been realized by using such edge states. -- Highlights: → Acoustic analog of monolayer graphene has been designed. → The energy spectra with the Dirac point have been verified. → The zigzag edge states have been found in ribbons of the structure. → The guided modes excited by a point source have been demonstrated. → The open cavity and 'Z' type edge waveguide have been realized.

  18. Plasmonic light-sensitive skins of nanocrystal monolayers

    Science.gov (United States)

    Akhavan, Shahab; Gungor, Kivanc; Mutlugun, Evren; Demir, Hilmi Volkan

    2013-04-01

    We report plasmonically coupled light-sensitive skins of nanocrystal monolayers that exhibit sensitivity enhancement and spectral range extension with plasmonic nanostructures embedded in their photosensitive nanocrystal platforms. The deposited plasmonic silver nanoparticles of the device increase the optical absorption of a CdTe nanocrystal monolayer incorporated in the device. Controlled separation of these metallic nanoparticles in the vicinity of semiconductor nanocrystals enables optimization of the photovoltage buildup in the proposed nanostructure platform. The enhancement factor was found to depend on the excitation wavelength. We observed broadband sensitivity improvement (across 400-650 nm), with a 2.6-fold enhancement factor around the localized plasmon resonance peak. The simulation results were found to agree well with the experimental data. Such plasmonically enhanced nanocrystal skins hold great promise for large-area UV/visible sensing applications.

  19. Actinide Sequestration Using Self-Assembled Monolayers on Mesoporous Supports

    International Nuclear Information System (INIS)

    Fryxell, Glen E.; Lin, Yuehe; Fiskum, Sandra K.; Birnbaum, Jerome C.; Wu, Hong; Kemner, K. M.; Kelly, Shelley

    2005-01-01

    Surfactant templated synthesis of mesoporous ceramics provides a versatile foundation upon which to create high efficiency environmental sorbents. These nanoporous ceramic oxides condense a huge amount of surface area into a very small volume. The ceramic oxide interface is receptive to surface functionalization through molecular self-assembly. The marriage of mesoporous ceramics with self-assembled monolayer chemistry creates a powerful new class of environmental sorbent materials called self-assembled monolayers on mesoporous supports (SAMMS). These SAMMS materials are highly efficient sorbents, whose interfacial chemistry can be fine-tuned to selectively sequester a specific target species, such as heavy metals, tetrahedral oxometallate anions and radionuclides. Details addressing the design, synthesis and characterization of SAMMS materials specifically designed to sequester actinides, of central importance to the environmental clean-up necessary after 40 years of weapons grade plutonium production, as well as evaluation of their binding affinities and kinetics are presented

  20. Functional Molecular Junctions Derived from Double Self-Assembled Monolayers.

    Science.gov (United States)

    Seo, Sohyeon; Hwang, Eunhee; Cho, Yunhee; Lee, Junghyun; Lee, Hyoyoung

    2017-09-25

    Information processing using molecular junctions is becoming more important as devices are miniaturized to the nanoscale. Herein, we report functional molecular junctions derived from double self-assembled monolayers (SAMs) intercalated between soft graphene electrodes. Newly assembled molecular junctions are fabricated by placing a molecular SAM/(top) electrode on another molecular SAM/(bottom) electrode by using a contact-assembly technique. Double SAMs can provide tunneling conjugation across the van der Waals gap between the terminals of each monolayer and exhibit new electrical functions. Robust contact-assembled molecular junctions can act as platforms for the development of equivalent contact molecular junctions between top and bottom electrodes, which can be applied independently to different kinds of molecules to enhance either the structural complexity or the assembly properties of molecules. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. ELECTROCATALYSIS ON SURFACES MODIFIED BY METAL MONOLAYERS DEPOSITED AT UNDERPOTENTIALS.

    Energy Technology Data Exchange (ETDEWEB)

    ADZIC,R.

    2000-12-01

    The remarkable catalytic properties of electrode surfaces modified by monolayer amounts of metal adatoms obtained by underpotential deposition (UPD) have been the subject of a large number of studies during the last couple of decades. This interest stems from the possibility of implementing strictly surface modifications of electrocatalysts in an elegant, well-controlled way, and these bi-metallic surfaces can serve as models for the design of new catalysts. In addition, some of these systems may have potential for practical applications. The UPD of metals, which in general involves the deposition of up to a monolayer of metal on a foreign substrate at potentials positive to the reversible thermodynamic potential, facilitates this type of surface modification, which can be performed repeatedly by potential control. Recent studies of these surfaces and their catalytic properties by new in situ surface structure sensitive techniques have greatly improved the understanding of these systems.

  2. Polarity control and growth mode of InN on yttria-stabilized zirconia (111) surfaces

    International Nuclear Information System (INIS)

    Kobayashi, Atsushi; Okubo, Kana; Ohta, Jitsuo; Oshima, Masaharu; Fujioka, Hiroshi

    2012-01-01

    We have found that polarity of epitaxial InN layers has been controlled by choice of a capping material during high-temperature annealing of yttria-stabilized zirconia (YSZ) (111) substrates in air. Angle-resolved X-ray photoelectron spectroscopy has revealed that the amount of segregation of Y atoms to the YSZ surface depended on the capping material of the substrates. In-polar and N-polar InN have been reproducibly grown on Y-segregated and Y-segregation-free YSZ surfaces, respectively. We have also found that the growth of the first monolayer (ML) of N-polar InN proceeds in a step-flow mode which then switches to layer-by-layer mode after the coverage by 1-ML-thick InN. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  3. Simultaneously 'pushing' and 'pulling' graphene oxide into low-polar solvents through a designed interface.

    Science.gov (United States)

    Liu, Zhen; Liu, Jingquan; Wang, Yichao; Razal, Joselito M; Francis, Paul S; Biggs, Mark J; Barrow, Colin J; Yang, Wenrong

    2018-08-03

    Dispersing graphene oxide (GO) in low-polar solvents can realize a perfect self-assembly with functional molecules and application in removal of organic impurities that only dissolve in low-polar solvents. The surface chemistry of GO plays an important role in its dispersity in these solvents. The direct transfer of hydrophilic GO into low-polar solvents, however, has remained an experimental challenge. In this study, we design an interface to transfer GO by simultaneously 'pushing and pulling' the nanosheets into low-polar solvents. Our approach is outstanding due to the ability to obtain monolayers of chemically reduced GO (CRGO) with designed surface properties in the organic phase. Using the transferred GO or CRGO dispersions, we have fabricated GO/fullerene nanocomposites and assessed the ability of CRGOs for dye adsorption. We hope our work can provide a universal approach for the phase transfer of other nanomaterials.

  4. Electrochemical detection of Cd2+ ions by a self-assembled monolayer of 1,9-nonanedithiol on gold

    International Nuclear Information System (INIS)

    Malel, Esteban; Sinha, Jatin K.; Zawisza, Izabella; Wittstock, Gunther; Mandler, Daniel

    2008-01-01

    The application of 1,9-nonanedithiol (NDT) self-assembled monolayer (SAM) on gold for the electrochemical determination of Cd 2+ was studied. Interestingly, we found that a NDT SAM strongly affects the stripping wave of Cd, resulting in a sharp peak that was used for electroanalytical determination of Cd 2+ in aqueous solutions. The different parameters, such as potential and time of deposition of Cd, were examined. Furthermore, polarization-modulated infrared reflection absorption spectroscopy (PM IRRAS) and X-ray photoelectron spectroscopy (XPS) were used for exploring the interaction between the deposited Cd and the thiol groups on Au. FTIR measurements clearly indicate that NDT is assembled in a disordered liquid type monolayer interacting with the Au electrode via both thiol moieties. XPS reveals that Cd is stripped at two different potentials and that the signal of sulfur is almost unchanged by deposition and desorption of Cd. All these finding allude to the interesting conclusion that Cd is deposited on Au lifting to some extent the thiol groups

  5. Properties of thiolate monolayers formed on different amalgam electrodes

    Czech Academy of Sciences Publication Activity Database

    Josypčuk, Bohdan; Mareček, Vladimír

    2011-01-01

    Roč. 653, 1-2 (2011), s. 7-13 ISSN 1572-6657 R&D Projects: GA AV ČR IAA400400806; GA ČR GAP206/11/1638; GA MŠk(CZ) LC06063 Institutional research plan: CEZ:AV0Z40400503 Keywords : thiolate monolayer * reductive desorption * charge effect Subject RIV: CG - Electrochemistry Impact factor: 2.905, year: 2011

  6. Immobilization of transition metal ions on zirconium phosphate monolayers

    International Nuclear Information System (INIS)

    Melezhik, A.V.; Brej, V.V.

    1998-01-01

    It is shown that ions of transition metals (copper, iron, vanadyl, titanium) are adsorbed on zirconium phosphate monolayers. The zirconium phosphate threshold capacity corresponds to substitution of all protons of hydroxyphosphate groups by equivalent amounts of copper, iron or vanadyl. Adsorption of polynuclear ions is possible in case of titanium. The layered substance with specific surface up to 300 m 2 /g, wherein ultradispersed titanium dioxide particles are intercalirated between zirconium-phosphate layers, is synthesized

  7. Superior Gas Sensing Properties of Monolayer PtSe2

    KAUST Repository

    Sajjad, Muhammad

    2016-12-15

    First-principles calculations of the structural and electronic properties of monolayer 1T-PtSe2 with adsorbed (a) NO2, (b) NO, (c) NH3, (d) H2O, (e) CO2, and (f) CO molecules are discussed. The results point to great potential of the material in gas sensor applications. Superior sensitivity is demonstrated by transport calculations using the nonequilibrium Green\\'s function method.

  8. Influence of calcium on ceramide-1-phosphate monolayers

    Directory of Open Access Journals (Sweden)

    Joana S. L. Oliveira

    2016-02-01

    Full Text Available Ceramide-1-phosphate (C1P plays an important role in several biological processes, being identified as a key regulator of many protein functions. For instance, it acts as a mediator of inflammatory responses. The mediation of the inflammation process happens due to the interaction of C1P with the C2 domain of cPLA2α, an effector protein that needs the presence of submicromolar concentrations of calcium ions. The aim of this study was to determine the phase behaviour and structural properties of C1P in the presence and absence of millimolar quantities of calcium in a well-defined pH environment. For that purpose, we used monomolecular films of C1P at the soft air/liquid interface with calcium ions in the subphase. The pH was varied to change the protonation degree of the C1P head group. We used surface pressure versus molecular area isotherms coupled with other monolayer techniques as Brewster angle microscopy (BAM, infrared reflection–absorption spectroscopy (IRRAS and grazing incidence X-ray diffraction (GIXD. The isotherms indicate that C1P monolayers are in a condensed state in the presence of calcium ions, regardless of the pH. At higher pH without calcium ions, the monolayer is in a liquid-expanded state due to repulsion between the negatively charged phosphate groups of the C1P molecules. When divalent calcium ions are added, they are able to bridge the highly charged phosphate groups, enhancing the regular arrangement of the head groups. Similar solidification of the monolayer structure can be seen in the presence of a 150 times larger concentration of monovalent sodium ions. Therefore, calcium ions have clearly a strong affinity for the phosphomonoester of C1P.

  9. Thermal stability of thiol and silane monolayers: A comparative study

    International Nuclear Information System (INIS)

    Chandekar, Amol; Sengupta, Sandip K.; Whitten, James E.

    2010-01-01

    The stability of self-assembled monolayers (SAMs) at elevated temperatures is of considerable technological importance. The thermal stability of 1-octadecanethiol (ODT), 16-mercaptohexadecanoic acid (MHDA) and 1H,1H,2H,2H-perfluorodecanethiol (PFDT) SAMs on gold surfaces, and of 4-aminobutyltriethoxysilane (ABTES) and 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (PFDS) assembled on hydroxylated silicon surfaces, was studied by X-ray photoelectron spectroscopy (XPS). The samples were heated in ultrahigh vacuum to temperatures in excess of that required for SAM degradation. ODT monolayers were stable to ca. 110 deg. C, while MHDA and PFDT SAMs were stable to ca. 145 deg. C. ABTES SAMs were found to be indefinitely stable to 250 deg. C, while PFDS SAMs were stable to 350 deg. C. These studies demonstrate the advantages of using silane monolayers for moderate to high temperature applications and illustrate differences that arise due to the nature of the tail group. To demonstrate the feasibility of silanes for template-directed patterning, a hydroxylated silicon oxide surface containing microcontact-printed PFDS patterns was spin-coated with a mainly hydrophilic block copolymer. Annealing the surface at 90 deg. C for 2 h caused the block copolymer to dewet the hydrophobic PFDS-patterned regions and adsorb exclusively on the unpatterned regions of the surface.

  10. Platinum Monolayer Electrocatalysts for Anodic Oxidation of Alcohols.

    Science.gov (United States)

    Li, Meng; Liu, Ping; Adzic, Radoslav R

    2012-12-06

    The slow, incomplete oxidation of methanol and ethanol on platinum-based anodes as well as the high price and limited reserves of Pt has hampered the practical application of direct alcohol fuel cells. We describe the electrocatalysts consisting of one Pt monolayer (one atom thick layer) placed on extended or nanoparticle surfaces having the activity and selectivity for the oxidation of alcohol molecules that can be controlled with platinum-support interaction. The suitably expanded Pt monolayer (i.e., Pt/Au(111)) exhibits a factor of 7 activity increase in catalyzing methanol electrooxidation relative to Pt(111). Sizable enhancement is also observed for ethanol electrooxidation. Furthermore, a correlation between substrate-induced lateral strain in a Pt monolayer and its activity/selectivity is established and rationalized by experimental and theoretical studies. The knowledge we gained with single-crystal model catalysts was successfully applied in designing real nanocatalysts. These findings for alcohols are likely to be applicable for the oxidation of other classes of organic molecules.

  11. Nanoscale Trapping and Squeeze-Out of Confined Alkane Monolayers.

    Science.gov (United States)

    Gosvami, N N; O'Shea, S J

    2015-12-01

    We present combined force curve and conduction atomic force microscopy (AFM) data for the linear alkanes CnH2n+2 (n = 10, 12, 14, 16) confined between a gold-coated AFM tip and a graphite surface. Solvation layering is observed in the force curves for all liquids, and conduction AFM is used to study in detail the removal of the confined (mono)layer closest to the graphite surface. The squeeze-out behavior of the monolayer can be very different depending upon the temperature. Below the monolayer melting transition temperatures the molecules are in an ordered state on the graphite surface, and fast and complete removal of the confined molecules is observed. However, above the melting transition temperature the molecules are in a disordered state, and even at large applied pressure a few liquid molecules are trapped within the tip-sample contact zone. These findings are similar to a previous study for branched alkanes [ Gosvami Phys. Rev. Lett. 2008, 100, 076101 ], but the observation for the linear alkane homologue series demonstrates clearly the dependence of the squeeze-out and trapping on the state of the confined material.

  12. Measurement of Exciton Binding Energy of Monolayer WS2

    Science.gov (United States)

    Chen, Xi; Zhu, Bairen; Cui, Xiaodong

    Excitonic effects are prominent in monolayer crystal of transition metal dichalcogenides (TMDCs) because of spatial confinement and reduced Coulomb screening. Here we use linear differential transmission spectroscopy and two-photon photoluminescence excitation spectroscopy (TP-PLE) to measure the exciton binding energy of monolayer WS2. Peaks for excitonic absorptions of the direct gap located at K valley of the Brillouin zone and transitions from multiple points near Γ point of the Brillouin zone, as well as trion side band are shown in the linear absorption spectra of WS2. But there is no gap between distinct excitons and the continuum of the interband transitions. Strong electron-phonon scattering, overlap of excitons around Γ point and the transfer of the oscillator strength from interband continuum to exciton states make it difficult to resolve the electronic interband transition edge even down to 10K. The gap between excited states of the band-edge exciton and the single-particle band is probed by TP-PLE measurements. And the energy difference between 1s exciton and the single-particle gap gives the exciton binding energy of monolayer WS2 to be about 0.71eV. The work is supported by Area of excellency (AoE/P-04/08), CRF of Hong Kong Research Grant Council (HKU9/CRF/13G) and SRT on New Materials of The University of Hong Kong.

  13. Immobilization of Colloidal Monolayers at Fluid–Fluid Interfaces

    Directory of Open Access Journals (Sweden)

    Peter T. Bähler

    2016-07-01

    Full Text Available Monolayers of colloidal particles trapped at an interface between two immiscible fluids play a pivotal role in many applications and act as essential models in fundamental studies. One of the main advantages of these systems is that non-close packed monolayers with tunable inter-particle spacing can be formed, as required, for instance, in surface patterning and sensing applications. At the same time, the immobilization of particles locked into desired structures to be transferred to solid substrates remains challenging. Here, we describe three different strategies to immobilize monolayers of polystyrene microparticles at water–decane interfaces. The first route is based on the leaking of polystyrene oligomers from the particles themselves, which leads to the formation of a rigid interfacial film. The other two rely on in situ interfacial polymerization routes that embed the particles into a polymer membrane. By tracking the motion of the colloids at the interface, we can follow in real-time the formation of the polymer membranes and we interestingly find that the onset of the polymerization reaction is accompanied by an increase in particle mobility determined by Marangoni flows at the interface. These results pave the way for future developments in the realization of thin tailored composite polymer-particle membranes.

  14. Monolayer MoS{sub 2} self-switching diodes

    Energy Technology Data Exchange (ETDEWEB)

    Al-Dirini, Feras, E-mail: alf@unimelb.edu.au; Hossain, Md Sharafat [Department of Electrical and Electronic Engineering, University of Melbourne, Victoria (Australia); Centre for Neural Engineering, University of Melbourne, Victoria (Australia); Victorian Research Laboratory, National ICT Australia, West Melbourne, Victoria (Australia); Hossain, Faruque M.; Skafidas, Efstratios [Department of Electrical and Electronic Engineering, University of Melbourne, Victoria (Australia); Centre for Neural Engineering, University of Melbourne, Victoria (Australia); Mohammed, Mahmood A. [Princess Sumaya University for Technology, Amman (Jordan); Nirmalathas, Ampalavanapillai [Department of Electrical and Electronic Engineering, University of Melbourne, Victoria (Australia); Melbourne Networked Society Institute (MNSI), University of Melbourne, Victoria (Australia)

    2016-01-28

    This paper presents a new molybdenum disulphide (MoS{sub 2}) nanodevice that acts as a two-terminal field-effect rectifier. The device is an atomically-thin two-dimensional self-switching diode (SSD) that can be realized within a single MoS{sub 2} monolayer with very minimal process steps. Quantum simulation results are presented confirming the device's operation as a diode and showing strong non-linear I-V characteristics. Interestingly, the device shows p-type behavior, in which conduction is dominated by holes as majority charge carriers and the flow of reverse current is enhanced, while the flow of forward current is suppressed, in contrast to monolayer graphene SSDs, which behave as n-type devices. The presence of a large bandgap in monolayer MoS{sub 2} results in strong control over the channel, showing complete channel pinch-off in forward conduction, which was confirmed with transmission pathways plots. The device exhibited large leakage tunnelling current through the insulating trenches, which may have been due to the lack of passivation; nevertheless, reverse current remained to be 6 times higher than forward current, showing strong rectification. The effect of p-type substitutional channel doping of sulphur with phosphorus was investigated and showed that it greatly enhances the performance of the device, increasing the reverse-to-forward current rectification ratio more than an order of magnitude, up to a value of 70.

  15. A trough for improved SFG spectroscopy of lipid monolayers

    Science.gov (United States)

    Franz, Johannes; van Zadel, Marc-Jan; Weidner, Tobias

    2017-05-01

    Lipid monolayers are indispensable model systems for biological membranes. The main advantage over bilayer model systems is that the surface pressure within the layer can be directly and reliably controlled. The sensitive interplay between surface pressure and temperature determines the molecular order within a model membrane and consequently determines the membrane phase behavior. The lipid phase is of crucial importance for a range of membrane functions such as protein interactions and membrane permeability. A very reliable method to probe the structure of lipid monolayers is sum frequency generation (SFG) vibrational spectroscopy. Not only is SFG extremely surface sensitive but it can also directly access critical parameters such as lipid order and orientation, and it can provide valuable information about protein interactions along with interfacial hydration. However, recent studies have shown that temperature gradients caused by high power laser beams perturb the lipid layers and potentially obscure the spectroscopic results. Here we demonstrate how the local heating problem can be effectively reduced by spatially distributing the laser pulses on the sample surface using a translating Langmuir trough for SFG experiments at lipid monolayers. The efficiency of the trough is illustrated by the detection of enhanced molecular order due to reduced heat load.

  16. Photo-induced travelling waves in condensed Langmuir monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Tabe, Y [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan); Yamamoto, T [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan); Yokoyama, H [Yokoyama Nano-Structured Liquid Crystal Project, ERATO, Japan Science and Technology Corporation, 5-9-9 Tokodai, Tsukuba, Ibaraki 300-2635, Japan (Japan)

    2003-06-01

    We report the detailed properties of photo-induced travelling waves in liquid crystalline Langmuir monolayers composed of azobenzene derivatives. When the monolayer, in which the constituent rodlike molecules are coherently tilted from the layer normal, is weakly illuminated to undergo the trans-cis photo-isomerization, spatio-temporal periodic oscillations of the molecular azimuth begin over the entire excited area and propagate as a two-dimensional orientational wave. The wave formation takes place only when the film is formed at an asymmetric interface with broken up-down symmetry and when the chromophores are continuously excited near the long-wavelength edge of absorption to induce repeated photo-isomerizations between the trans and cis forms. Under proper illumination conditions, Langmuir monolayers composed of a wide variety of azobenzene derivatives have been confirmed to exhibit similar travelling waves with velocity proportional to the excitation power irrespective of the degree of amphiphilicity. The dynamics can be qualitatively explained by the modified reaction-diffusion model proposed by Reigada, Sagues and Mikhailov.

  17. Strain engineering on transmission carriers of monolayer phosphorene.

    Science.gov (United States)

    Zhang, Wei; Li, Feng; Hu, Junsong; Zhang, Ping; Yin, Jiuren; Tang, Xianqiong; Jiang, Yong; Wu, Bozhao; Ding, Yanhuai

    2017-11-22

    The effects of uniaxial strain on the structure, band gap and transmission carriers of monolayer phosphorene were investigated by first-principles calculations. The strain induced semiconductor-metal as well as direct-indirect transitions were studied in monolayer phosphorene. The position of CBM which belonged to indirect gap shifts along the direction of the applied strain. We have concluded the change rules of the carrier effective mass when plane strains are applied. In band structure, the sudden decrease of band gap or the new formation of CBM (VBM) causes the unexpected change in carrier effective mass. The effects of zigzag and armchair strain on the effective electron mass in phosphorene are different. The strain along zigzag direction has effects on the electrons effective mass along both zigzag and armchair direction. By contrast, armchair-direction strain seems to affect only on the free electron mass along zigzag direction. For the holes, the effective masses along zigzag direction are largely affected by plane strains while the effective mass along armchair direction exhibits independence in strain processing. The carrier density of monolayer phosphorene at 300 K is calculated about [Formula: see text] cm -2 , which is greatly influenced by the temperature and strain. Strain engineering is an efficient method to improve the carrier density in phosphorene.

  18. Establishing linear solvation energy relationships between VOCs and monolayer-protected gold nanoclusters using quartz crystal microbalance.

    Science.gov (United States)

    Li, Chi-Lin; Lu, Chia-Jung

    2009-08-15

    Linear solvation energy relationships (LSERs) have been recognized as a useful model for investigating the chemical forces behind the partition coefficients between vapor molecules and absorbents. This study is the first to determine the solvation properties of monolayer-protected gold nanoclusters (MPCs) with different surface ligands. The ratio of partition coefficients/MPC density (K/rho) of 18 volatile organic compounds (VOCs) for four different MPCs obtained through quartz crystal microbalance (QCM) experiments were used for the LSER model calculations. LSER modeling results indicate that all MPC surfaces showed a statistically significant (pattraction, 4-methoxythiophenol-capped MPCs can also interact with polar organics (s=1.04). Showing a unique preference for the hydrogen bond basicity of vapors (b=1.11), 2-benzothiazolethiol-capped MPCs provide evidence of an intra-molecular, proton-shift mechanism on surface of nano-gold.

  19. Chiral Spin Texture in the Charge-Density-Wave Phase of the Correlated Metallic Pb /Si (111 ) Monolayer

    Science.gov (United States)

    Tresca, C.; Brun, C.; Bilgeri, T.; Menard, G.; Cherkez, V.; Federicci, R.; Longo, D.; Debontridder, F.; D'angelo, M.; Roditchev, D.; Profeta, G.; Calandra, M.; Cren, T.

    2018-05-01

    We investigate the 1 /3 monolayer α -Pb /Si (111 ) surface by scanning tunneling spectroscopy (STS) and fully relativistic first-principles calculations. We study both the high-temperature √{3 }×√{3 } and low-temperature 3 ×3 reconstructions and show that, in both phases, the spin-orbit interaction leads to an energy splitting as large as 25% of the valence-band bandwidth. Relativistic effects, electronic correlations, and Pb-substrate interaction cooperate to stabilize a correlated low-temperature paramagnetic phase with well-developed lower and upper Hubbard bands coexisting with 3 ×3 periodicity. By comparing the Fourier transform of STS conductance maps at the Fermi level with calculated quasiparticle interference from nonmagnetic impurities, we demonstrate the occurrence of two large hexagonal Fermi sheets with in-plane spin polarizations and opposite helicities.

  20. Ab-initio study of electronic and magnetic properties of Co-doped Mo2C monolayer

    Science.gov (United States)

    Mehta, Veenu; Tankeshwar, K.; Saini, Hardev S.

    2018-05-01

    The spin polarized density functional theory (DFT) based calculations has been performed to investigate the electronic and magnetic properties of pristine and Co-doped Mo2C using VASP code. The calculated results show that the pristine Mo2C is found to be non-magnetic whereas the Co dopant at Mo-site in the Mo2C monolayer generates the ferromagnetism in the resultant compound. The total magnetic moment of the system has been found to be 1.2µB which increases to 2.03µB as the concentration of Co increase from 3% to 8%, respectively. The electronic structure calculations of the pristine and Co-doped Mo2C show its metallic behavior which may found its application in magnetic energy storage devices, magnetic tape etc.

  1. Monolayer Boron Nitride Substrate Interactions with Graphene Under In-Plane and Perpendicular Strains: A First-Principles Study

    Science.gov (United States)

    Behzad, Somayeh

    2018-04-01

    Effects of strain on the electronic and optical properties of graphene on monolayer boron nitride (BN) substrate are investigated using first-principle calculations based on density functional theory. Strain-free graphene/BN has a small band gap of 97 meV at the K point. The magnitude of band gap increases with in-plane biaxial strain while it decreases with the perpendicular uniaxial strain. The ɛ2 (ω ) spectrum of graphene/BN bilayer for parallel polarization shows red and blue shifts by applying the in-plane tensile and compressive strains, respectively. Also the positions of peaks in the ɛ2 (ω ) spectrum are not significantly changed under perpendicular strain. The calculated results indicate that graphene on the BN substrate has great potential in microelectronic and optoelectronic applications.

  2. The interaction of insulin, glucose, and insulin-glucose mixtures with a phospholipid monolayer.

    Science.gov (United States)

    Shigenobu, Hayato; McNamee, Cathy E

    2012-12-15

    We determined how glucose or insulin interacts with a phospholipid monolayer at the air/water interface and explained these mechanisms from a physico-chemical point of view. The 1,2-dipalmitoyl-2-sn-glycero-3-phosphatidylcholine (DPPC) monolayer at an air/water interface acted as a model membrane, which allowed the effect of the molecular packing density in the monolayer on the interactions to be determined. The interaction of glucose, insulin, and a mixture of glucose and insulin to the DPPC monolayer were investigated via surface pressure-area per molecule Langmuir isotherms and fluorescence microscopy. Glucose adsorbed to the underside of the DPPC monolayer, while insulin was able to penetrate through the monolayer when the phospholipid molecules were not densely packed. The presence of a mixture of insulin and glucose affected the molecular packing in the DPPC monolayer differently than the pure insulin or glucose solutions, and the glucose-insulin mixture was seen to be able to penetrate through the monolayer. These results indicated that glucose and insulin interact with one another, giving a material that may then transported through a pore in the monolayer or through the spaces between the molecules of the monolayer. Copyright © 2012 Elsevier Inc. All rights reserved.

  3. Monolayer arrangement of fatty hydroxystearic acids on graphite: Influence of hydroxyl groups

    Energy Technology Data Exchange (ETDEWEB)

    Medina, S. [Laboratorio de Rayos-X, Centro de Investigación Tecnología e Innovación, de la Universidad de Sevilla (CITIUS), Universidad de Sevilla, Avenida Reina Mercedes, 4B. 41012, Sevilla (Spain); Benítez, J.J.; Castro, M.A. [Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Avenida Américo Vespucio, 49. 41092, Sevilla (Spain); Cerrillos, C. [Servicio de Microscopía, Centro de Investigación Tecnología e Innovación, de la Universidad de Sevilla (CITIUS), Universidad de Sevilla, Avenida Reina Mercedes, 4B. 41012, Sevilla (Spain); Millán, C. [Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Avenida Américo Vespucio, 49. 41092, Sevilla (Spain); Alba, M.D., E-mail: alba@icmse.csic.es [Instituto de Ciencia de Materiales de Sevilla, Consejo Superior de Investigaciones Científicas-Universidad de Sevilla, Avenida Américo Vespucio, 49. 41092, Sevilla (Spain)

    2013-07-31

    Previous studies have indicated that long-chain linear carboxylic acids form commensurate packed crystalline monolayers on graphite even at temperatures above their melting point. This study examines the effect on the monolayer formation and structure of adding one or more secondary hydroxyl, functional groups to the stearic acid skeleton (namely, 12-hydroxystearic and 9,10-dihydroxystearic acid). Moreover, a comparative study of the monolayer formation on recompressed and monocrystalline graphite has been performed through X-ray diffraction (XRD) and Scanning Tunneling Microscopy (STM), respectively. The Differential Scanning Calorimetry (DSC) and XRD data were used to confirm the formation of solid monolayers and XRD data have provided a detailed structural analysis of the monolayers in good correspondence with obtained STM images. DSC and XRD have demonstrated that, in stearic acid and 12-hydroxystearic acid adsorbed onto graphite, the monolayer melted at a higher temperature than the bulk form of the carboxylic acid. However, no difference was observed between the melting point of the monolayer and the bulk form for 9,10-dihydroxystearic acid adsorbed onto graphite. STM results indicated that all acids on the surface have a rectangular p2 monolayer structure, whose lattice parameters were uniaxially commensurate on the a-axis. This structure does not correlate with the initial structure of the pure compounds after dissolving, but it is conditioned to favor a) hydrogen bond formation between the carboxylic groups and b) formation of hydrogen bonds between secondary hydroxyl groups, if spatially permissible. Therefore, the presence of hydroxyl functional groups affects the secondary structure and behavior of stearic acid in the monolayer. - Highlights: • Hydroxyl functional groups affect structure and behavior of acids in the monolayer. • Acids on the surface have a rectangular p2 monolayer structure. • Lattice parameters of acids are uniaxially

  4. Polar bears at risk

    Energy Technology Data Exchange (ETDEWEB)

    Norris, S.; Rosentrater, L.; Eid, P.M. [WWF International Arctic Programme, Oslo (Norway)

    2002-05-01

    Polar bears, the world's largest terrestrial carnivore, spend much of their lives on the arctic sea ice. This is where they hunt and move between feeding, denning, and resting areas. The world population, estimated at 22,000 bears, is made up of 20 relatively distinct populations varying in size from a few hundred to a few thousand animals. About 60 per cent of all polar bears are found in Canada. In general, the status of this species is stable, although there are pronounced differences between populations. Reductions in the extent and thickness of sea ice has lead the IUCN Polar Bear Specialist Group to describe climate change as one of the major threats facing polar bears today. Though the long-term effects of climate change will vary in different areas of the Arctic, impacts on the condition and reproductive success of polar bears and their prey are likely to be negative. Longer ice-free periods resulting from earlier break-up of sea ice in the spring and later formation in the fall is already impacting polar bears in the southern portions of their range. In Canada's Hudson Bay, for example, bears hunt on the ice through the winter and into early summer, after which the ice melts completely, forcing bears ashore to fast on stored fat until freeze-up in the fall. The time bears have on the ice to hunt and build up their body condition is cut short when the ice melts early. Studies from Hudson Bay show that for every week earlier that ice break-up occurs, bears will come ashore 10 kg lighter and in poorer condition. It is likely that populations of polar bears dividing their time between land and sea will be severely reduced and local extinctions may occur as greenhouse gas emissions continue to rise and sea ice melts. Expected changes in regional weather patterns will also impact polar bears. Rain in the late winter can cause maternity dens to collapse before females and cubs have departed, thus exposing occupants to the elements and to predators. Such

  5. Polarized atomic beams for targets

    International Nuclear Information System (INIS)

    Grueebler, W.

    1984-01-01

    The basic principle of the production of polarized atomic hydrogen and deuterium beams are reviewed. The status of the present available polarization, density and intensity are presented. The improvement of atomic beam density by cooling the hydrogen atoms to low velocity is discussed. The possible use of polarized atomic beams as targets in storage rings is shown. It is proposed that polarized atomic beams can be used to produce polarized gas targets with high polarization and greatly improved density

  6. Conformational order of n-dodecanethiol and n-dodecaneselenol monolayers on polycrystalline copper investigated by PM-IRRAS and SFG spectroscopy

    Science.gov (United States)

    Fonder, G.; Cecchet, F.; Peremans, A.; Thiry, P. A.; Delhalle, J.; Mekhalif, Z.

    2009-08-01

    Self-assembled monolayers (SAMs) of n-dodecanethiol (C 12H 25SH) and n-dodecaneselenol (C 12H 25SeH) on polycrystalline copper have been elaborated with the purpose of achieving densely packed and crystalline-like assemblies. By combining the surface sensitivity of polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) and sum-frequency generation spectroscopy (SFG), the effect of the self-assembly time (15 min, 30 min, 1 h, 2 h and 24 h) on the formation of n-dodecanethiol and n-dodecaneselenol monolayers on untreated and electrochemically reduced polycrystalline copper has been investigated. On electrochemically reduced copper, PM-IRRAS spectroscopy shows that both molecules are able to form well organized layers. SFG spectroscopy indicates that the C 12H 25SeH SAMs are slightly better ordered than those achieved with C 12H 25SH. On untreated copper, the two molecules lead to different film organizations. Both PM-IRRAS and SFG indicate that C 12H 25SH SAMs are of the same film quality as those obtained on electrochemically reduced copper. On the contrary, C 12H 25SeH monolayers are invariably poorly organized at the molecular level.

  7. GUIDE FOR POLARIZED NEUTRONS

    Science.gov (United States)

    Sailor, V.L.; Aichroth, R.W.

    1962-12-01

    The plane of polarization of a beam of polarized neutrons is changed by this invention, and the plane can be flipped back and forth quicitly in two directions in a trouble-free manner. The invention comprises a guide having a plurality of oppositely directed magnets forming a gap for the neutron beam and the gaps are spaced longitudinally in a spiral along the beam at small stepped angles. When it is desired to flip the plane of polarization the magnets are suitably rotated to change the direction of the spiral of the gaps. (AEC)

  8. Heidelberg polarized alkali source

    International Nuclear Information System (INIS)

    Kraemer, D.; Steffens, E.; Jaensch, H.; Philipps Universitaet, Marburg, Germany)

    1984-01-01

    A new atomic beam type polarized alkali ion source has been installed at Heidelberg. In order to improve the beam polarization considerably optical pumping is applied in combination with an adiabatic medium field transition which results in beams in single hyperfine sublevels. The m state population is determined by laser-induced fluorescence spectroscopy. Highly polarized beams (P/sub s/ > 0.9, s = z, zz) with intensities of 30 to 130 μA can be extracted for Li + and Na + , respectively

  9. Synchronization modulation increases transepithelial potentials in MDCK monolayers through Na/K pumps.

    Directory of Open Access Journals (Sweden)

    Vu Tran

    Full Text Available Transepithelial potential (TEP is the voltage across a polarized epithelium. In epithelia that have active transport functions, the force for transmembrane flux of an ion is dictated by the electrochemical gradient in which TEP plays an essential role. In epithelial injury, disruption of the epithelial barrier collapses the TEP at the wound edge, resulting in the establishment of an endogenous wound electric field (∼100 mV/mm that is directed towards the center of the wound. This endogenous electric field is implicated to enhance wound healing by guiding cell migration. We thus seek techniques to enhance the TEP, which may increase the wound electric fields and enhance wound healing. We report a novel technique, termed synchronization modulation (SM using a train of electric pulses to synchronize the Na/K pump activity, and then modulating the pumping cycles to increase the efficiency of the Na/K pumps. Kidney epithelial monolayers (MDCK cells maintain a stable TEP and transepithelial resistance (TER. SM significantly increased TEP over four fold. Either ouabain or digoxin, which block Na/K pump, abolished SM-induced TEP increases. In addition to the pump activity, basolateral distribution of Na/K pumps is essential for an increase in TEP. Our study for the first time developed an electrical approach to significantly increase the TEP. This technique targeting the Na/K pump may be used to modulate TEP, and may have implication in wound healing and in diseases where TEP needs to be modulated.

  10. Calculation of Quasi-Particle Energies of Aromatic Self-Assembled Monolayers on Au(111).

    Science.gov (United States)

    Li, Yan; Lu, Deyu; Galli, Giulia

    2009-04-14

    We present many-body perturbation theory calculations of the electronic properties of phenylene diisocyanide self-assembled monolayers (SAMs) on a gold surface. Using structural models obtained within density functional theory (DFT), we have investigated how the SAM molecular energies are modified by self-energy corrections and how they are affected by the presence of the surface. We have employed a combination of GW (G = Green's function; W = screened Coulomb interaction) calculations of the SAM quasi-particle energies and a semiclassical image potential model to account for surface polarization effects. We find that it is essential to include both quasi-particle corrections and surface screening in order to provide a reasonable estimate of the energy level alignment at a SAM-metal interface. In particular, our results show that within the GW approximation the energy distance between phenylene diisocyanide SAM energy levels and the gold surface Fermi level is much larger than that found within DFT, e.g., more than double in the case of low packing densities of the SAM.

  11. Well separated trion and neutral excitons on superacid treated MoS{sub 2} monolayers

    Energy Technology Data Exchange (ETDEWEB)

    Cadiz, Fabian, E-mail: cadiz@insa-toulouse.fr; Tricard, Simon; Gay, Maxime; Lagarde, Delphine; Wang, Gang; Robert, Cedric; Renucci, Pierre; Urbaszek, Bernhard; Marie, Xavier [Université de Toulouse, INSA-CNRS-UPS, LPCNO, 135 Av. Rangueil, 31077 Toulouse (France)

    2016-06-20

    Developments in optoelectronics and spin-optronics based on transition metal dichalcogenide monolayers (MLs) need materials with efficient optical emission and well-defined transition energies. In as-exfoliated MoS{sub 2} MLs, the photoluminescence (PL) spectra even at low temperature consist typically of broad, overlapping contributions from neutral, charged excitons (trions) and localized states. Here, we show that in superacid treated MoS{sub 2} MLs, the PL intensity increases by up to 60 times at room temperature. The neutral and charged exciton transitions are spectrally well separated in PL and reflectivity at T = 4 K, with linewidth for the neutral exciton of 15 meV, but both transitions have similar intensities compared to the ones in as-exfoliated MLs at the same temperature. Time resolved experiments uncover picoseconds recombination dynamics analyzed separately for charged and neutral exciton emissions. Using the chiral interband selection rules, we demonstrate optically induced valley polarization for both complexes and valley coherence for only the neutral exciton.

  12. Anisotropic optical absorption induced by Rashba spin-orbit coupling in monolayer phosphorene

    Science.gov (United States)

    Li, Yuan; Li, Xin; Wan, Qi; Bai, R.; Wen, Z. C.

    2018-04-01

    We obtain the effective Hamiltonian of the phosphorene including the effect of Rashba spin-orbit coupling in the frame work of the low-energy theory. The spin-splitting energy bands show an anisotropy feature for the wave vectors along kx and ky directions, where kx orients to ΓX direction in the k space. We numerically study the optical absorption of the electrons for different wave vectors with Rashba spin-orbit coupling. We find that the spin-flip transition from the valence band to the conduction band induced by the circular polarized light closes to zero with increasing the x-component wave vector when ky equals to zero, while it can be significantly increased to a large value when ky gets a small value. When the wave vector varies along the ky direction, the spin-flip transition can also increase to a large value, however, which shows an anisotropy feature for the optical absorption. Especially, the spin-conserved transitions keep unchanged and have similar varying trends for different wave vectors. This phenomenon provides a novel route for the manipulation of the spin-dependent property of the fermions in the monolayer phosphorene.

  13. Ozone Oxidation of Self-Assembled Monolayers on SiOx-Coated Zinc Selenide Surfaces

    Science.gov (United States)

    McIntire, T. M.; Ryder, O. S.; Finlayson-Pitts, B. J.

    2008-12-01

    Airborne particles are important for visibility, human health, climate, and atmospheric reactions. Atmospheric particles contain a significant fraction of organics and such compounds present on airborne particles are susceptible to oxidation by atmospheric oxidants, such as OH, ozone, halogen atoms, and nitrogen trioxide. Oxidized organics associated with airborne particles are thought to be polar, hygroscopic species with enhanced cloud-nucleating properties. Oxide layers on silicon, or SiO2-coated substrates, act as models of environmentally relevant surfaces such as dust particles upon which organics adsorb. We have shown previously that ozone oxidation of unsaturated self-assembled monolayers (SAMs) on silicon attenuated total reflectance (ATR) crystals leads to the formation of carbonyl groups and micron-sized, hydrophobic organic aggregates surrounded by carbon depleted substrate that do not have increased water uptake as previously assumed. Reported here are further ATR-FTIR studies of the oxidation of alkene SAMs on ZnSe and SiO2-coated ZnSe. These substrates have the advantage that they transmit below 1500 cm-1, allowing detection of additional product species. These experiments show that the loss of C=C and formation of carbonyl groups is also accompanied by formation of a peak at 1110 cm-1, attributed to the secondary ozonide. Details concerning the products and mechanism of ozonolysis of alkene SAMs on surfaces based on these new data are presented and the implications for the oxidation of alkenes on airborne dust particles are discussed.

  14. Radiation Effects on the Cytoskeleton of Endothelial Cells and Endothelial Monolayer Permeability

    International Nuclear Information System (INIS)

    Gabrys, Dorota; Greco, Olga; Patel, Gaurang; Prise, Kevin M.; Tozer, Gillian M.; Kanthou, Chryso

    2007-01-01

    Purpose: To investigate the effects of radiation on the endothelial cytoskeleton and endothelial monolayer permeability and to evaluate associated signaling pathways, which could reveal potential mechanisms of known vascular effects of radiation. Methods and Materials: Cultured endothelial cells were X-ray irradiated, and actin filaments, microtubules, intermediate filaments, and vascular endothelial (VE)-cadherin junctions were examined by immunofluorescence. Permeability was determined by the passage of fluorescent dextran through cell monolayers. Signal transduction pathways were analyzed using RhoA, Rho kinase, and stress-activated protein kinase-p38 (SAPK2/p38) inhibitors by guanosine triphosphate-RhoA activation assay and transfection with RhoAT19N. The levels of junction protein expression and phosphorylation of myosin light chain and SAPK2/p38 were assessed by Western blotting. The radiation effects on cell death were verified by clonogenic assays. Results: Radiation induced rapid and persistent actin stress fiber formation and redistribution of VE-cadherin junctions in microvascular, but not umbilical vein endothelial cells, and microtubules and intermediate filaments remained unaffected. Radiation also caused a rapid and persistent increase in microvascular permeability. RhoA-guanosine triphosphatase and Rho kinase were activated by radiation and caused phosphorylation of downstream myosin light chain and the observed cytoskeletal and permeability changes. SAPK2/p38 was activated by radiation but did not influence either the cytoskeleton or permeability. Conclusion: This study is the first to show rapid activation of the RhoA/Rho kinase by radiation in endothelial cells and has demonstrated a link between this pathway and cytoskeletal remodeling and permeability. The results also suggest that the RhoA pathway might be a useful target for modulating the permeability and other effects of radiation for therapeutic gain

  15. The representation of neutron polarization

    International Nuclear Information System (INIS)

    Byrne, J.

    1979-01-01

    Neutron beam polarization representation is discussed under the headings; transfer matrices, coherent parity violation for neutrons, neutron spin rotation in helical magnetic fields, polarization and interference. (UK)

  16. Establishment of a long-term three-dimensional primary culture of mouse glandular stomach epithelial cells within the stem cell niche

    International Nuclear Information System (INIS)

    Katano, Takahito; Ootani, Akifumi; Mizoshita, Tsutomu; Tanida, Satoshi; Tsukamoto, Hironobu; Ozeki, Keiji; Ebi, Masahide; Mori, Yoshinori; Kataoka, Hiromi; Kamiya, Takeshi; Toda, Shuji; Joh, Takashi

    2013-01-01

    Highlights: ► We established a 3D culture system to allow long-term culture of stomach cells. ► In this culture system, gastric epithelial cells grew for about 3 months. ► The cultured cells differentiated into multi-units of the stomach. ► This culture method should be useful for elucidating the cause of gastric diseases. -- Abstract: Compared to the small intestine and colon, little is known about stem cells in the stomach because of a lack of specific stem cell markers and an in vitro system that allows long-term culture. Here we describe a long-term three-dimensional (3D) primary gastric culture system within the stem cell niche. Glandular stomach cells from neonatal mice cultured in collagen gel yielded expanding sphere-like structures for 3 months. The wall of the gastrospheres consisted of a highly polarized epithelial monolayer with an outer lining of myofibroblasts. The epithelial cells showed a tall columnar cell shape, basal round nuclei, and mucus-filled cytoplasm as well as expression of MUC5AC, indicating differentiation into gastric surface mucous cells. These cells demonstrated the features of fully differentiated gastric surface mucous cells such as microvilli, junctional complexes, and glycogen and secretory granules. Fewer than 1% of cultured epithelial cells differentiated into enteroendocrine cells. Active proliferation of the epithelial cells and many apoptotic cells in the inner lumen revealed the rapid cell turnover in gastrospheres in vitro. This method enables us to investigate the role of signaling between cell–cell and epithelial–mesenchymal interactions in an environment that is extremely similar to the in vivo environment

  17. Establishment of a long-term three-dimensional primary culture of mouse glandular stomach epithelial cells within the stem cell niche

    Energy Technology Data Exchange (ETDEWEB)

    Katano, Takahito [Department of Gastroenterology and Metabolism, Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601 (Japan); Ootani, Akifumi [Department of Gastroenterology and GI Endoscopy Center, Shin-Kokura Hospital, Federation of National Public Service Personnel Mutual Aid Associations, 1-3-1 Kanada, Kokurakita-ku, Kitakyushu 803-0816 (Japan); Department of Internal Medicine, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga 849-8501 (Japan); Mizoshita, Tsutomu, E-mail: tmizoshi@med.nagoya-cu.ac.jp [Department of Gastroenterology and Metabolism, Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601 (Japan); Tanida, Satoshi; Tsukamoto, Hironobu; Ozeki, Keiji; Ebi, Masahide; Mori, Yoshinori; Kataoka, Hiromi; Kamiya, Takeshi [Department of Gastroenterology and Metabolism, Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601 (Japan); Toda, Shuji [Department of Pathology and Microbiology, Faculty of Medicine, Saga University, 5-1-1 Nabeshima, Saga 849-8501 (Japan); Joh, Takashi [Department of Gastroenterology and Metabolism, Nagoya City University Graduate School of Medical Sciences, 1 Kawasumi, Mizuho-cho, Mizuho-ku, Nagoya 467-8601 (Japan)

    2013-03-22

    Highlights: ► We established a 3D culture system to allow long-term culture of stomach cells. ► In this culture system, gastric epithelial cells grew for about 3 months. ► The cultured cells differentiated into multi-units of the stomach. ► This culture method should be useful for elucidating the cause of gastric diseases. -- Abstract: Compared to the small intestine and colon, little is known about stem cells in the stomach because of a lack of specific stem cell markers and an in vitro system that allows long-term culture. Here we describe a long-term three-dimensional (3D) primary gastric culture system within the stem cell niche. Glandular stomach cells from neonatal mice cultured in collagen gel yielded expanding sphere-like structures for 3 months. The wall of the gastrospheres consisted of a highly polarized epithelial monolayer with an outer lining of myofibroblasts. The epithelial cells showed a tall columnar cell shape, basal round nuclei, and mucus-filled cytoplasm as well as expression of MUC5AC, indicating differentiation into gastric surface mucous cells. These cells demonstrated the features of fully differentiated gastric surface mucous cells such as microvilli, junctional complexes, and glycogen and secretory granules. Fewer than 1% of cultured epithelial cells differentiated into enteroendocrine cells. Active proliferation of the epithelial cells and many apoptotic cells in the inner lumen revealed the rapid cell turnover in gastrospheres in vitro. This method enables us to investigate the role of signaling between cell–cell and epithelial–mesenchymal interactions in an environment that is extremely similar to the in vivo environment.

  18. Interferometric polarization control

    International Nuclear Information System (INIS)

    Chuss, David T.; Wollack, Edward J.; Moseley, S. Harvey; Novak, Giles

    2006-01-01

    We develop the Jones and Mueller matrices for structures that allow control of the path length difference between two linear orthogonal polarizations and consider the effect of placing multiple devices in series. Specifically, we find that full polarization modulation (measurement of Stokes Q, U, and V) can be achieved by placing two such modulators in series if the relative angles of the beam-splitting grids with respect to the analyzer orientation are appropriately chosen. Such a device has several potential advantages over a spinning wave plate modulator for measuring astronomical polarization in the far infrared through millimeter: (i) The use of small, linear motions eliminates the need for cryogenic rotational bearings; (ii) the phase flexibility allows measurement of circular as well as linear polarization; and (iii) this architecture allows for both multiwavelength and broadband modulation. We also present initial laboratory results

  19. Dynamic nuclear spin polarization

    Energy Technology Data Exchange (ETDEWEB)

    Stuhrmann, H B [GKSS-Forschungszentrum Geesthacht GmbH (Germany)

    1996-11-01

    Polarized neutron scattering from dynamic polarized targets has been applied to various hydrogenous materials at different laboratories. In situ structures of macromolecular components have been determined by nuclear spin contrast variation with an unprecedented precision. The experiments of selective nuclear spin depolarisation not only opened a new dimension to structural studies but also revealed phenomena related to propagation of nuclear spin polarization and the interplay of nuclear polarisation with the electronic spin system. The observation of electron spin label dependent nuclear spin polarisation domains by NMR and polarized neutron scattering opens a way to generalize the method of nuclear spin contrast variation and most importantly it avoids precontrasting by specific deuteration. It also likely might tell us more about the mechanism of dynamic nuclear spin polarisation. (author) 4 figs., refs.

  20. Polarized proton colliders

    International Nuclear Information System (INIS)

    Roser, T.

    1995-01-01

    High energy polarized beam collisions will open up the unique physics opportunities of studying spin effects in hard processes. This will allow the study of the spin structure of the proton and also the verification of the many well documented expectations of spin effects in perturbative QCD and parity violation in W and Z production. Proposals for polarized proton acceleration for several high energy colliders have been developed. A partial Siberian Snake in the AGS has recently been successfully tested and full Siberian Snakes, spin rotators, and polarimeters for RHIC are being developed to make the acceleration of polarized beams to 250 GeV possible. This allows for the unique possibility of colliding two 250 GeV polarized proton beams at luminosities of up to 2 x 10 32 cm -2 s -1

  1. Unanticipated C=C bonds in covalent monolayers on silicon revealed by NEXAFS.

    Science.gov (United States)

    Lee, Michael V; Lee, Jonathan R I; Brehmer, Daniel E; Linford, Matthew R; Willey, Trevor M

    2010-02-02

    Interfaces are crucial to material properties. In the case of covalent organic monolayers on silicon, molecular structure at the interface controls the self-assembly of the monolayers, which in turn influences the optical properties and electrical transport. These properties intrinsically affect their application in biology, tribology, optics, and electronics. We use near-edge X-ray absorption fine structure spectroscopy to show that the most basic covalent monolayers formed from 1-alkenes on silicon retain a double bond in one-fifth to two-fifths of the resultant molecules. Unsaturation in the predominantly saturated monolayers will perturb the regular order and affect the dependent properties. The presence of unsaturation in monolayers produced by two different methods also prompts the re-evaluation of other radical-based mechanisms for forming covalent monolayers on silicon.

  2. Plasma polarization spectroscopy

    International Nuclear Information System (INIS)

    Iwamae, Atsushi; Horimoto, Yasuhiro; Fujimoto, Takashi; Hasegawa, Noboru; Sukegawa, Kouta; Kawachi, Tetsuya

    2005-01-01

    The electron velocity distribution function (EVDF) in plasma can be anisotropic in laser-produced plasmas. We have developed a new technique to evaluate the polarization degree of the emission lines in the extreme vacuum ultra violet wavelength region. The polarization of the emission lines and the continuums from the lithium-like nitrogen and from helium- and hydrogen-like carbon in recombining plasma is evaluated. Particle simulation in the velocity space gives the time scale for relaxation of anisotropic EVDFs. (author)

  3. No More Polarization, Please!

    OpenAIRE

    Reinholt, Mia

    2006-01-01

    The organizational science literature on motivation has for long been polarized into two main positions; the organizational economic position focusing on extrinsic motivation and the organizational behavior position emphasizing intrinsic motivation. With the rise of the knowledge economy and the increasing levels of complexities it entails, such polarization is not fruitful in the attempt to explain motivation of organizational members. This paper claims that a more nuanced perspective on mot...

  4. Inertial polarization of dielectrics

    OpenAIRE

    Zavodovsky, A. G.

    2011-01-01

    It was proved that accelerated motion of a linear dielectric causes its polarization. Accelerated translational motion of a dielectric's plate leads to the positive charge of the surface facing the direction of motion. Metal plates of a capacitor were used to register polarized charges on a dielectric's surface. Potential difference between the capacitor plates is proportional to acceleration, when acceleration is constant potential difference grows with the increase of a dielectric's area, o...

  5. Secondary structure of spiralin in solution, at the air/water interface, and in interaction with lipid monolayers.

    Science.gov (United States)

    Castano, Sabine; Blaudez, Daniel; Desbat, Bernard; Dufourcq, Jean; Wróblewski, Henri

    2002-05-03

    The surface of spiroplasmas, helically shaped pathogenic bacteria related to the mycoplasmas, is crowded with the membrane-anchored lipoprotein spiralin whose structure and function are unknown. In this work, the secondary structure of spiralin under the form of detergent-free micelles (average Stokes radius, 87.5 A) in water and at the air/water interface, alone or in interaction with lipid monolayers was analyzed. FT-IR and circular dichroism (CD) spectroscopic data indicate that spiralin in solution contains about 25+/-3% of helices and 38+/-2% of beta sheets. These measurements are consistent with a consensus predictive analysis of the protein sequence suggesting about 28% of helices, 32% of beta sheets and 40% of irregular structure. Brewster angle microscopy (BAM) revealed that, in water, the micelles slowly disaggregate to form a stable and homogeneous layer at the air/water interface, exhibiting a surface pressure up to 10 mN/m. Polarization modulation infrared reflection absorption spectroscopy (PMIRRAS) spectra of interfacial spiralin display a complex amide I band characteristic of a mixture of beta sheets and alpha helices, and an intense amide II band. Spectral simulations indicate a flat orientation for the beta sheets and a vertical orientation for the alpha helices with respect to the interface. The combination of tensiometric and PMIRRAS measurements show that, when spiroplasma lipids are used to form a monolayer at the air/water interface, spiralin is adsorbed under this monolayer and its antiparallel beta sheets are mainly parallel to the polar-head layer of the lipids without deep perturbation of the fatty acid chains organization. Based upon these results, we propose a 'carpet model' for spiralin organization at the spiroplasma cell surface. In this model, spiralin molecules anchored into the outer leaflet of the lipid bilayer by their N-terminal lipid moiety are composed of two colinear domains (instead of a single globular domain) situated at

  6. The Polarization of Achernar

    Science.gov (United States)

    McDavid, D.

    2005-11-01

    Recent near-infrared measurements of the angular diameter of Achernar (the bright Be star alpha Eridani) with the ESO VLT interferometer have been interpreted as the detection of an extremely oblate photosphere, with a ratio of equatorial to polar radius of at least 1.56 ± 0.05 and a minor axis orientation of 39° ± 1° (from North to East). The optical linear polarization of this star during an emission phase in 1995 September was 0.12 ± 0.02% at position angle 37° ± 8° (in equatorial coordinates), which is the direction of the projection of the rotation axis on the plane of the sky according to the theory of polarization by electron scattering in an equatorially flattened circumstellar disk. These two independent determinations of the orientation of the rotation axis are therefore in agreement. The observational history of correlations between Hα emission and polarization as found in the literature is that of a typical Be star, with the exception of an interesting question raised by the contrast between Schröder's measurement of a small polarization perpendicular to the projected rotation axis in 1969--70 and Tinbergen's measurement of zero polarization in 1974.5, both at times when emission was reportedly absent.

  7. Induction and differentiation of human induced pluripotent stem cells into functional cardiomyocytes on a compartmented monolayer of gelatin nanofibers

    Science.gov (United States)

    Tang, Yadong; Liu, Li; Li, Junjun; Yu, Leqian; Wang, Li; Shi, Jian; Chen, Yong

    2016-07-01

    Extensive efforts have been devoted to develop new substrates for culture and differentiation of human induced pluripotent stem cells (hiPSCs) toward cardiac cell-based assays. A more exciting prospect is the construction of cardiac tissue for robust drug screening and cardiac tissue repairing. Here, we developed a patch method by electrospinning and crosslinking of monolayer gelatin nanofibers on a honeycomb frame made of poly(ethylene glycol) diacrylate (PEGDA). The monolayer of the nanofibrous structure can support cells with minimal exogenous contact and a maximal efficiency of cell-medium exchange whereas a single hiPSC colony can be uniformly formed in each of the honeycomb compartments. By modulating the treatment time of the ROCK inhibitor Y-27632, the shape of the hiPSC colony could be controlled from a flat layer to a hemisphere. Afterwards, the induction and differentiation of hiPSCs were achieved on the same patch, leading to a uniform cardiac layer with homogeneous contraction. This cardiac layer could then be used for extracellular recording with a commercial multi-electrode array, showing representative field potential waveforms of matured cardiac tissues with appropriate drug responses.Extensive efforts have been devoted to develop new substrates for culture and differentiation of human induced pluripotent stem cells (hiPSCs) toward cardiac cell-based assays. A more exciting prospect is the construction of cardiac tissue for robust drug screening and cardiac tissue repairing. Here, we developed a patch method by electrospinning and crosslinking of monolayer gelatin nanofibers on a honeycomb frame made of poly(ethylene glycol) diacrylate (PEGDA). The monolayer of the nanofibrous structure can support cells with minimal exogenous contact and a maximal efficiency of cell-medium exchange whereas a single hiPSC colony can be uniformly formed in each of the honeycomb compartments. By modulating the treatment time of the ROCK inhibitor Y-27632, the shape

  8. Fusion of a polarized projectile with a polarized target

    International Nuclear Information System (INIS)

    Christley, J.A.; Johnson, R.C.; Thompson, I.J.

    1995-01-01

    The fusion cross sections for a polarized target with both unpolarized and polarized projectiles are studied. Expressions for the observables are given for the case when both nuclei are polarized. Calculations for fusion of an aligned 165 Ho target with 16 O and polarized 7 Li beams are presented

  9. Neutrophil-endothelial cell interactions on endothelial monolayers grown on micropore filters.

    Science.gov (United States)

    Taylor, R F; Price, T H; Schwartz, S M; Dale, D C

    1981-01-01

    We have developed a technique for growing endothelial monolayers on micropore filters. These monolayers demonstrate confluence by phase and electron microscopy and provide a functional barrier to passage of radiolabeled albumin. Neutrophils readily penetrate the monolayer in response to chemotaxin, whereas there is little movement in the absence of chemotaxin. This system offers unique advantages over available chemotaxis assays and may have wider applications in the study of endothelial function. Images PMID:7007441

  10. The additional phase transition of DPPC monolayers at high surface pressure confirmed by GIXD study

    DEFF Research Database (Denmark)

    Shen, Chen; Serna, Jorge B. de la; Struth, Bernd

    Pulmonary surfactant forms the alveolar monolayer at the air/aqueous interface within the lung. During the breathing process, the surface pressure periodically varies from ~40mN/m up to ~70mN/m. The film is mechanically stable during this rapid and reversible expansion. The monolayer consists...... of the alveolae monolayer and at the same time allows reduction of the interfacial tension to ~0mN/m....

  11. The langmuir monolayer: an efficient model for studying interfacial properties of biomembranes

    International Nuclear Information System (INIS)

    Cirak, J.; Sokolsky, M.; Dobrocka, E.; Weis, M.

    2012-01-01

    In this communication, we describe aspects of monolayer technology by focusing on effects of calcium ions on physical properties of phospholipid monolayers using results of measurements of surface pressure, x-ray reflectivity and AFM. These experiments are motivated by the search for lipid-DNA complexes with high transfection efficiency but without toxicity which might be a promising tool in gene therapy. In each part methodological importance is stressed and its specificity for studying molecular interactions at a lipid monolayer. (authors)

  12. Primary culture of cat intestinal epithelial cells in vitro and the cDNA library construction.

    Science.gov (United States)

    Zhao, Gui Hua; Liu, Ye; Cheng, Yun Tang; Zhao, Qing Song; Qiu, Xiao; Xu, Chao; Xiao, Ting; Zhu, Song; Liu, Gong Zhen; Yin, Kun

    2018-06-26

    Felids are the only definitive hosts of Toxoplasma gondii. To lay a foundation for screening the T. gondii-felids interaction factors, we have developed a reproducible primary culture method for cat intestinal epithelial cells (IECs). The primary IECs were isolated from a new born cat's small intestine jejunum region without food ingress, and respectively in vitro cultured by tissue cultivation and combined digestion method with collagenase XI and dispase I, then purified by trypsinization. After identification, the ds cDNA of cat IECs was synthesized for constructing pGADT7 homogenization three-frame plasmid, and transformed into the yeast Y187 for generating the cDNA library. Our results indicated that cultivation of primary cat IECs relays on combined digestion to form polarized and confluent monolayers within 3 days with typical features of normal epithelial cells. The purified cells cultured by digestion method were identified to be nature intestinal epithelial cells using immunohistochemical analysis and were able to maintain viability for at least 15 passages. The homogenizable ds cDNA, which is synthesized from the total RNA extracted from our cultured IECs, distributed among 0.5-2.0 kb, and generated satisfying three-frame cDNA library with the capacity of 1.2 × 106 and the titer of 5.2 × 107 pfu/mL. Our results established an optimal method for the culturing and passage of cat IECs model in vitro, and laid a cDNA library foundation for the subsequent interaction factors screening by yeast two-hybrid.

  13. Collapse of Langmuir monolayer at lower surface pressure: Effect of hydrophobic chain length

    Energy Technology Data Exchange (ETDEWEB)

    Das, Kaushik, E-mail: kaushikdas2089@gmail.com; Kundu, Sarathi [Physical Sciences Division, Institute of Advanced Study in Science and Technology, Vigyan Path, Paschim Boragaon, Garchuk, Guwahati, Assam 781035 (India)

    2016-05-23

    Long chain fatty acid molecules (e.g., stearic and behenic acids) form a monolayer on water surface in the presence of Ba{sup 2+} ions at low subphase pH (≈ 5.5) and remain as a monolayer before collapse generally occurs at higher surface pressure (π{sub c} > 50 mN/m). Monolayer formation is verified from the surface pressure vs. area per molecule (π-A) isotherms and also from the atomic force microscopy (AFM) analysis of the films deposited by single upstroke of hydrophilic Si (001) substrate through the monolayer covered water surface. At high subphase pH (≈ 9.5), barium stearate molecules form multilayer structure at lower surface pressure which is verified from the π-A isotherms and AFM analysis of the film deposited at 25 mN/m. Such monolayer to multilayer structure formation or monolayer collapse at lower surface pressure is unusual as at this surface pressure generally fatty acid salt molecules form a monolayer on the water surface. Formation of bidentate chelate coordination in the metal containing headgroups is the reason for such monolayer to multilayer transition. However, for longer chain barium behenate molecules only monolayer structure is maintained at that high subphase pH (≈ 9.5) due to the presence of relatively more tail-tail hydrophobic interaction.

  14. Thermodynamic and real-space structural evidence of a 2D critical point in phospholipid monolayers

    DEFF Research Database (Denmark)

    Nielsen, Lars K.; Bjørnholm, Thomas; Mouritsen, Ole G.

    2007-01-01

    The two-dimensional phase diagram of phospholipid monolayers at air-water interfaces has been constructed from Langmuir compression isotherms. The coexistence region between the solid and fluid phases of the monolayer ends at the critical temperature of the transition. The small-scale lateral...... structure of the monolayers has been imaged by atomic force microscopy in the nm to mu m range at distinct points in the phase diagram. The lateral structure is immobilized by transferring the monolayer from an air-water interface to a solid mica support using Langmuir-Blodgett techniques. A transfer...

  15. Studies of the structure and properties of organic monolayers, multilayers and superlattices

    International Nuclear Information System (INIS)

    Dutta, P.; Ketterson, J.B.

    1990-01-01

    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. 20 refs., 11 figs

  16. Atomic scattering from an adsorbed monolayer solid with a helium beam that penetrates to the substrate

    DEFF Research Database (Denmark)

    Hansen, Flemming Yssing; Bruch, L.W.; Dammann, Bernd

    2013-01-01

    Diffraction and one-phonon inelastic scattering of a thermal energy helium atomic beam are evaluated in the situation that the target monolayer lattice is so dilated that the atomic beam penetrates to the interlayer region between the monolayer and the substrate. The scattering is simulated......(1 × 1) commensurate monolayer solid of H2/KCl(001). For the latter, there are cases where part of the incident beam is trapped in the interlayer region for times exceeding 50 ps, depending on the spacing between the monolayer and the substrate and on the angle of incidence. The feedback effect...

  17. Active cell-matrix coupling regulates cellular force landscapes of cohesive epithelial monolayers

    Science.gov (United States)

    Zhao, Tiankai; Zhang, Yao; Wei, Qiong; Shi, Xuechen; Zhao, Peng; Chen, Long-Qing; Zhang, Sulin

    2018-03-01

    Epithelial cells can assemble into cohesive monolayers with rich morphologies on substrates due to competition between elastic, edge, and interfacial effects. Here we present a molecularly based thermodynamic model, integrating monolayer and substrate elasticity, and force-mediated focal adhesion formation, to elucidate the active biochemical regulation over the cellular force landscapes in cohesive epithelial monolayers, corroborated by microscopy and immunofluorescence studies. The predicted extracellular traction and intercellular tension are both monolayer size and substrate stiffness dependent, suggestive of cross-talks between intercellular and extracellular activities. Our model sets a firm ground toward a versatile computational framework to uncover the molecular origins of morphogenesis and disease in multicellular epithelia.

  18. Polarized Light Microscopy

    Science.gov (United States)

    Frandsen, Athela F.

    2016-01-01

    Polarized light microscopy (PLM) is a technique which employs the use of polarizing filters to obtain substantial optical property information about the material which is being observed. This information can be combined with other microscopy techniques to confirm or elucidate the identity of an unknown material, determine whether a particular contaminant is present (as with asbestos analysis), or to provide important information that can be used to refine a manufacturing or chemical process. PLM was the major microscopy technique in use for identification of materials for nearly a century since its introduction in 1834 by William Fox Talbot, as other techniques such as SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared spectroscopy), XPD (X-ray Powder Diffraction), and TEM (Transmission Electron Microscopy) had not yet been developed. Today, it is still the only technique approved by the Environmental Protection Agency (EPA) for asbestos analysis, and is often the technique first applied for identification of unknown materials. PLM uses different configurations in order to determine different material properties. With each configuration additional clues can be gathered, leading to a conclusion of material identity. With no polarizing filter, the microscope can be used just as a stereo optical microscope, and view qualities such as morphology, size, and number of phases. With a single polarizing filter (single polars), additional properties can be established, such as pleochroism, individual refractive indices, and dispersion staining. With two polarizing filters (crossed polars), even more can be deduced: isotropy vs. anisotropy, extinction angle, birefringence/degree of birefringence, sign of elongation, and anomalous polarization colors, among others. With the use of PLM many of these properties can be determined in a matter of seconds, even for those who are not highly trained. McCrone, a leader in the field of polarized light microscopy, often

  19. When measured spin polarization is not spin polarization

    International Nuclear Information System (INIS)

    Dowben, P A; Wu Ning; Binek, Christian

    2011-01-01

    Spin polarization is an unusually ambiguous scientific idiom and, as such, is rarely well defined. A given experimental methodology may allow one to quantify a spin polarization but only in its particular context. As one might expect, these ambiguities sometimes give rise to inappropriate interpretations when comparing the spin polarizations determined through different methods. The spin polarization of CrO 2 and Cr 2 O 3 illustrate some of the complications which hinders comparisons of spin polarization values. (viewpoint)

  20. Transport of curcumin derivatives in Caco-2 cell monolayers.

    Science.gov (United States)

    Zeng, Zhen; Shen, Zhe L; Zhai, Shuo; Xu, Jia L; Liang, Hui; Shen, Qin; Li, Qing Y

    2017-08-01

    Curcumin (Cur) is a strong natural antioxidant, who can prevent multiple diseases such as anti-cancer, anti-inflammatory, have a resistance to alzheimer's disease and various malignant diseases. But it has poor oral bioavailability due to its poor aqueous solubility, as well as instability. While its novel derivatives (CB and FE), showed better anti-tumor activity, better anti-oxidant activity and better stability than the original drug (Cur). The aim of this study was to study the intestinal transport of Cur, CB and FE using an in vitro Caco-2 cell monolayer model. The results showed that Cur had a lower permeability coefficient (1.13×10 -6 ±0.11×10 -6 cm/s) for apical-to-basolated (AP-BL) transport at 25μM, while the transport rate for AP to BL flux of CB (3.18×10 -6 ±0.31×10 -6 cm/s) and FE (5.28×10 -6 ±0.83×10 -6 cm/s) were significantly greater than that of Cur. The efflux ratio (ER) value at the concentration of 25μM was 1.31 for Cur, 1.26 for CB and 1.33 for FE, suggesting there was no active efflux involved in the translocation across the Caco-2 cell monolayers for the three compounds. Furthermore, the transport flux of CB and FE was in a concentration dependent manner, suggesting the intestinal transport mechanism in them was passive transport. In summary, the results demonstrated that both the intestinal permeability of CB and FE across Caco-2 cell monolayers was significantly improved compare to Cur. Thus they might show a higher oral bioavailability in vivo, and show the potential application in clinic or nutraceutical. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Polycyclic aromatic hydrocarbons in model bacterial membranes - Langmuir monolayer studies.

    Science.gov (United States)

    Broniatowski, Marcin; Binczycka, Martyna; Wójcik, Aneta; Flasiński, Michał; Wydro, Paweł

    2017-12-01

    High molecular weight polycyclic aromatic hydrocarbons (HMW-PAHs) are persistent organic pollutants which due to their limited biodegradability accumulate in soils where their increased presence can lead to the impoverishment of the decomposer organisms. As very hydrophobic PAHs easily penetrate cellular membranes of soil bacteria and can be incorporated therein, changing the membrane fluidity and other functions which in consequence can lead to the death of the organism. The structure and size of PAH molecule can be crucial for its membrane activity; however the correlation between PAH structure and its interaction with phospholipids have not been investigated so far. In our studies we applied phospholipid Langmuir monolayers as model bacterial membranes and investigated how the incorporation of six structurally different PAH molecules change the membrane texture and physical properties. In our studies we registered surface pressure and surface potential isotherms upon the monolayer compression, visualized the monolayer texture with the application of Brewster angle microscopy and searched the ordering of the film-forming molecules with molecular resolution with the application of grazing incidence X-ray diffraction (GIXD) method. It turned out that the phospholipid-PAH interactions are strictly structure dependent. Four and five-ring PAHs of the angular or cluster geometry can be incorporated into the model membranes changing profoundly their textures and fluidity; whereas linear or large cluster PAHs cannot be incorporated and separate from the lipid matrix. The observed phenomena were explained based on structural similarities of the applied PAHs with membrane steroids and hopanoids. Copyright © 2017. Published by Elsevier B.V.

  2. Metal adsorption on monolayer blue phosphorene: A first principles study

    Science.gov (United States)

    Khan, Imran; Son, Jicheol; Hong, Jisang

    2018-01-01

    We investigated the electronic structure, adsorption energies, magnetic properties, dipole moment and work function of metal adatoms (Mg, Cr, Mo, Pd, Pt, and Au) adsorption on a blue phosphorene monolayer. For Mg, Pt and Au metals, the most stable state was found in hollow site while for Cr, Mo and Pd metals we found an adsorption in valley site. We suggest that the Pd and Pt atoms prefer 2D growth mode while the Mg, Cr, Mo and Au atoms prefer 3D island growth mode on monolayer phosphorene. The electronic band structures and magnetic properties were dependent on the doping site and dopant materials. For instance, the semiconducting features were preserved in Mg, Pd, Pt, and Au doped systems. However, the Cr and Mo doped systems displayed half-metallic band structures. The total magnetic moment of 4.05, 2.0 and 0.77 μB /impurity atom were obtained in Cr, Mo and Au doped systems whereas the Mg, Pd and Pt doped systems remained nonmagnetic. We also investigated the magnetic interaction between two transition metal impurities. We observed ferromagnetic coupling between two transition metal impurities in Cr and Mo doped systems while the Au doped system displayed almost degenerated magnetic state. For Mg, Cr, and Mo adsorptions, we found relatively large values of dipole moments compared to those in the Pd, Pt and Au adsorptions. This resulted in a significant suppression of the work function in Mg, Cr and Mo adsorptions. Overall, adsorption can tune the physical and magnetic properties of phosphorene monolayer.

  3. The evolution of tensor polarization

    International Nuclear Information System (INIS)

    Huang, H.; Lee, S.Y.; Ratner, L.

    1993-01-01

    By using the equation of motion for the vector polarization, the spin transfer matrix for spin tensor polarization, the spin transfer matrix for spin tensor polarization is derived. The evolution equation for the tensor polarization is studied in the presence of an isolate spin resonance and in the presence of a spin rotor, or snake

  4. The polarization of fast neutrons

    International Nuclear Information System (INIS)

    Talov, V.V.

    2000-01-01

    The present work is the review of polarization of fast neutrons and methods of polarization analysis. This also includes information about polarization of fast neutrons from first papers, which described polarization in the D(d,n) 3 He, 7 Li(p,n) 7 Be, and T(p,n) 3 He reactions. (authors)

  5. Differential sensitivity of epithelial cells to extracellular matrix in polarity establishment.

    Directory of Open Access Journals (Sweden)

    Shigenobu Yonemura

    Full Text Available Establishment of apical-basal polarity is crucial for epithelial sheets that form a compartment in the body, which function to maintain the environment in the compartment. Effects of impaired polarization are easily observed in three-dimensional (3-D culture systems rather than in two-dimensional (2-D culture systems. Although the mechanisms for establishing the polarity are not completely understood, signals from the extracellular matrix (ECM are considered to be essential for determining the basal side and eventually generating polarity in the epithelial cells. To elucidate the common features and differences in polarity establishment among various epithelial cells, we analyzed the formation of epithelial apical-basal polarity using three cell lines of different origin: MDCK II cells (dog renal tubules, EpH4 cells (mouse mammary gland, and R2/7 cells (human colon expressing wild-type α-catenin (R2/7 α-Cate cells. These cells showed clear apical-basal polarity in 2-D cultures. In 3-D cultures, however, each cell line displayed different responses to the same ECM. In MDCK II cells, spheroids with a single lumen formed in both Matrigel and collagen gel. In R2/7 α-Cate cells, spheroids showed similar apical-basal polarity as that seen in MDCK II cells, but had multiple lumens. In EpH4 cells, the spheroids displayed an apical-basal polarity that was opposite to that seen in the other two cell types in both ECM gels, at least during the culture period. On the other hand, the three cell lines showed the same apical-basal polarity both in 2-D cultures and in 3-D cultures using the hanging drop method. The three lines also had similar cellular responses to ECM secreted by the cells themselves. Therefore, appropriate culture conditions should be carefully determined in advance when using various epithelial cells to analyze cell polarity or 3-D morphogenesis.

  6. Nanocomposite Materials of Alternately Stacked C60 Monolayer and Graphene

    Directory of Open Access Journals (Sweden)

    Makoto Ishikawa

    2010-01-01

    Full Text Available We synthesized the novel nanocomposite consisting alternately of a stacked single graphene sheet and a C60 monolayer by using the graphite intercalation technique in which alkylamine molecules help intercalate large C60 molecules into the graphite. Moreover, it is found that the intercalated C60 molecules can rotate in between single graphene sheets by using C13 NMR measurements. This preparation method provides a general way for intercalating huge fullerene molecules into graphite, which will lead to promising materials with novel mechanical, physical, and electrical properties.

  7. Nanocomposite Materials of Alternately Stacked C60 Monolayer and Graphene

    International Nuclear Information System (INIS)

    Ishikawa, M.; Miura, K.; Kamiya, S.; Yoshimoto, S.; Suzuki, M.; Kuwahara, D.; Sasaki, N.

    2010-01-01

    We synthesized the novel nanocomposite consisting alternately of a stacked single graphene sheet and a C 60 monolayer by using the graphite intercalation technique in which alkylamine molecules help intercalate large C 60 molecules into the graphite. Moreover, it is found that the intercalated C 60 molecules can rotate in between single graphene sheets by using C 13 NMR measurements. This preparation method provides a general way for intercalating huge fullerene molecules into graphite, which will lead to promising materials with novel mechanical, physical, and electrical properties.

  8. Friction anisotropy-driven domain imaging on exfoliated monolayer graphene.

    Science.gov (United States)

    Choi, Jin Sik; Kim, Jin-Soo; Byun, Ik-Su; Lee, Duk Hyun; Lee, Mi Jung; Park, Bae Ho; Lee, Changgu; Yoon, Duhee; Cheong, Hyeonsik; Lee, Ki Ho; Son, Young-Woo; Park, Jeong Young; Salmeron, Miquel

    2011-07-29

    Graphene produced by exfoliation has not been able to provide an ideal graphene with performance comparable to that predicted by theory, and structural and/or electronic defects have been proposed as one cause of reduced performance. We report the observation of domains on exfoliated monolayer graphene that differ by their friction characteristics, as measured by friction force microscopy. Angle-dependent scanning revealed friction anisotropy with a periodicity of 180° on each friction domain. The friction anisotropy decreased as the applied load increased. We propose that the domains arise from ripple distortions that give rise to anisotropic friction in each domain as a result of the anisotropic puckering of the graphene.

  9. Fractal growth in impurity-controlled solidification in lipid monolayers

    DEFF Research Database (Denmark)

    Fogedby, Hans C.; Sørensen, Erik Schwartz; Mouritsen, Ole G.

    1987-01-01

    A simple two-dimensional microscopic model is proposed to describe solidifcation processes in systems with impurities which are miscible only in the fluid phase. Computer simulation of the model shows that the resulting solids are fractal over a wide range of impurity concentrations and impurity...... diffusional constants. A fractal-forming mechanism is suggested for impurity-controlled solidification which is consistent with recent experimental observations of fractal growth of solid phospholipid domains in monolayers. The Journal of Chemical Physics is copyrighted by The American Institute of Physics....

  10. Kinetics of monolayer graphene growth by segregation on Pd(111)

    Energy Technology Data Exchange (ETDEWEB)

    Mok, H. S.; Murata, Y.; Kodambaka, S., E-mail: kodambaka@ucla.edu [Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, California 90095 (United States); Ebnonnasir, A.; Ciobanu, C. V. [Department of Mechanical Engineering and Materials Science Program, Colorado School of Mines, Golden, Colorado 80401 (United States); Nie, S.; McCarty, K. F. [Sandia National Laboratories, Livermore, California 94550 (United States)

    2014-03-10

    Using in situ low-energy electron microscopy and density functional theory calculations, we follow the growth of monolayer graphene on Pd(111) via surface segregation of bulk-dissolved carbon. Upon lowering the substrate temperature, nucleation of graphene begins on graphene-free Pd surface and continues to occur during graphene growth. Measurements of graphene growth rates and Pd surface work functions establish that this continued nucleation is due to increasing C adatom concentration on the Pd surface with time. We attribute this anomalous phenomenon to a large barrier for attachment of C adatoms to graphene coupled with a strong binding of the non-graphitic C to the Pd surface.

  11. Stability of FDTS monolayer coating on aluminum injection molding tools

    DEFF Research Database (Denmark)

    Cech, Jiri; Taboryski, Rafael J.

    2012-01-01

    microns can obliterate small features. The nanoimprint lithography community extensively uses functional monolayer coatings on silicon/SiO2 lithographic stamps [7–11]. This treatment dramatically reduces stiction, and improves yield and quality of replicated nanostructures. Here we report on a fluorinated...... trichloro-silane based coating deposited on aluminum or its alloys by molecular vapor deposition. We have tested the stability of this coating in challenging conditions of injection molding, an environment with high shear stress from the molten polymer, pressures up to 200 MPa, temperatures up to 250 ◦C...

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

    Science.gov (United States)

    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.

  13. Kinetics of monolayer graphene growth by segregation on Pd(111)

    International Nuclear Information System (INIS)

    Mok, H. S.; Murata, Y.; Kodambaka, S.; Ebnonnasir, A.; Ciobanu, C. V.; Nie, S.; McCarty, K. F.

    2014-01-01

    Using in situ low-energy electron microscopy and density functional theory calculations, we follow the growth of monolayer graphene on Pd(111) via surface segregation of bulk-dissolved carbon. Upon lowering the substrate temperature, nucleation of graphene begins on graphene-free Pd surface and continues to occur during graphene growth. Measurements of graphene growth rates and Pd surface work functions establish that this continued nucleation is due to increasing C adatom concentration on the Pd surface with time. We attribute this anomalous phenomenon to a large barrier for attachment of C adatoms to graphene coupled with a strong binding of the non-graphitic C to the Pd surface

  14. Conduction quantization in monolayer MoS2

    Science.gov (United States)

    Li, T. S.

    2016-10-01

    We study the ballistic conduction of a monolayer MoS2 subject to a spatially modulated magnetic field by using the Landauer-Buttiker formalism. The band structure depends sensitively on the field strength, and its change has profound influence on the electron conduction. The conductance is found to demonstrate multi-step behavior due to the discrete number of conduction channels. The sharp peak and rectangular structures of the conductance are stretched out as temperature increases, due to the thermal broadening of the derivative of the Fermi-Dirac distribution function. Finally, quantum behavior in the conductance of MoS2 can be observed at temperatures below 10 K.

  15. The dependence of lipid monolayer lipolysis on surface pressure.

    OpenAIRE

    Hall, D G

    1992-01-01

    Brönsted-Bjerrum theory [Brönsted (1922) Z. Phys. Chem. 102, 169-207; (1925) Z. Phys. Chem. 115, 337-364; Bjerrum (1924) Z. Phys. Chem. 108, 82-100] as applied to reactions at interfaces is used to interpret published data on the lipolysis of dinonanoyl phosphatidylcholine monolayers by pancreatic phospholipase A2. Reasonable quantitative agreement between theoretical and experimental results occurs when the reported effects of surface pressure on the amount of adsorbed enzyme are used togeth...

  16. Structure of adsorbed monolayers. The surface chemical bond

    International Nuclear Information System (INIS)

    Somorjai, G.A.; Bent, B.E.

    1984-06-01

    This paper attempts to provide a summary of what has been learned about the structure of adsorbed monolayers and about the surface chemical bond from molecular surface science. While the surface chemical bond is less well understood than bonding of molecules in the gas phase or in the solid state, our knowledge of its properties is rapidly accumulating. The information obtained also has great impact on many surface science based technologies, including heterogeneous catalysis and electronic devices. It is hoped that much of the information obtained from studies at solid-gas interfaces can be correlated with molecular behavior at solid-liquid interfaces. 31 references, 42 figures, 1 table

  17. Polarized particles in storage rings

    International Nuclear Information System (INIS)

    Derbenev, Ya.S.; Kondratenko, A.M.; Serednyakov, S.I.; Skrinskij, A.N.; Tumajkin, G.M.; Shatunov, Yu.M.

    1977-01-01

    Experiments with polarized beams on the VEPP-2M and SPEAK storage rings are described. Possible methods of producing polarized particle beams in storage rings as well as method of polarization monitoring are counted. Considered are the processes of radiation polarization of electrons and positrons. It is shown, that to preserve radiation polarization the introduction of regions with a strong sign-variable magnetic field is recommended. Methods of polarization measurement are counted. It is suggested for high energies to use dependence of synchrotron radiation power on transverse polarization of electrons and positrons. Examples of using polarizability of colliding beams in storage rings are presented

  18. Temperature-dependent Raman spectroscopy studies of the interface coupling effect of monolayer ReSe2 single crystals on Au foils

    Science.gov (United States)

    Jiang, Shaolong; Zhao, Liyun; Shi, Yuping; Xie, Chunyu; Zhang, Na; Zhang, Zhepeng; Huan, Yahuan; Yang, Pengfei; Hong, Min; Zhou, Xiebo; Shi, Jianping; Zhang, Qing; Zhang, Yanfeng

    2018-05-01

    Rhenium diselenide (ReSe2), which bears in-plane anisotropic optical and electrical properties, is of considerable interest for its excellent applications in novel devices, such as polarization-sensitive photodetectors and integrated polarization-controllers. However, great challenges to date in the controllable synthesis of high-quality ReSe2 have hindered its in-depth investigations and practical applications. Herein, we report a feasible synthesis of monolayer single-crystal ReSe2 flakes on the Au foil substrate by using a chemical vapor deposition route. Particularly, we focus on the temperature-dependent Raman spectroscopy investigations of monolayer ReSe2 grown on Au foils, which present concurrent red shifts of Eg-like and Ag-like modes with increasing measurement temperature from 77–290 K. Linear temperature dependences of both modes are revealed and explained from the anharmonic vibration of the ReSe2 lattice. More importantly, the strong interaction of ReSe2 with Au, with respect to that with SiO2/Si, is further confirmed by temperature-dependent Raman characterization. This work is thus proposed to shed light on the optical and thermal properties of such anisotropic two-dimensional three-atom-thick materials.

  19. Polarized electrons at Jefferson laboratory

    International Nuclear Information System (INIS)

    Sinclair, C.K.

    1998-01-01

    The CEBAF accelerator at Jefferson laboratory can deliver CW electron beams to three experimental halls simultaneously. A large fraction of the approved scientific program at the lab requires polarized electron beams. Many of these experiments, both polarized and unpolarized, require high average beam current as well. Since all electrons delivered to the experimental halls originate from the same cathode, delivery of polarized beam to a single hall requires using the polarized source to deliver beam to all experiments in simultaneous operation. The polarized source effort at Jefferson Lab is directed at obtaining very long polarized source operational lifetimes at high average current and beam polarization; at developing the capability to deliver all electrons leaving the polarized source to the experimental halls; and at delivering polarized beam to multiple experimental halls simultaneously. Initial operational experience with the polarized source will be presented. copyright 1998 American Institute of Physics

  20. Polarized Electrons at Jefferson Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Sinclair, C.K.

    1997-12-31

    The CEBAF accelerator at Jefferson laboratory can deliver CW electron beams to three experimental halls simultaneously. A large fraction of the approved scientific program at the lab requires polarized electron beams. Many of these experiments, both polarized and unpolarized, require high average beam current as well. Since all electrons delivered to the experimental halls originate from the same cathode, delivery of polarized beam to a single hall requires using the polarized source to deliver beam to all experiments in simultaneous operation. The polarized source effort at Jefferson Lab is directed at obtaining very long polarized source operational lifetimes at high average current and beam polarization; at developing the capability to deliver all electrons leaving the polarized source to the experimental halls; and at delivering polarized beam to multiple experimental halls simultaneously.initial operational experience with the polarized source will be presented.