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Sample records for broad growth substrate

  1. Differentially expressed myo-inositol monophosphatase gene (CaIMP) in chickpea (Cicer arietinum L.) encodes a lithium-sensitive phosphatase enzyme with broad substrate specificity and improves seed germination and seedling growth under abiotic stresses.

    PubMed

    Saxena, Saurabh C; Salvi, Prafull; Kaur, Harmeet; Verma, Pooja; Petla, Bhanu Prakash; Rao, Venkateswara; Kamble, Nitin; Majee, Manoj

    2013-12-01

    myo-Inositol monophosphatase (IMP) is an essential enzyme in the myo-inositol metabolic pathway where it primarily dephosphorylates myo-inositol 1-phosphate to maintain the cellular inositol pool which is important for many metabolic and signalling pathways in plants. The stress-induced increased accumulation of inositol has been reported in a few plants including chickpea; however, the role and regulation of IMP is not well defined in response to stress. In this work, it has been shown that IMP activity is distributed in all organs in chickpea and was noticeably enhanced during environmental stresses. Subsequently, using degenerate oligonucleotides and RACE strategy, a full-length IMP cDNA (CaIMP) was cloned and sequenced. Biochemical study revealed that CaIMP encodes a lithium-sensitive phosphatase enzyme with broad substrate specificity, although maximum activity was observed with the myo-inositol 1-phosphate and l-galactose 1-phosphate substrates. Transcript analysis revealed that CaIMP is differentially expressed and regulated in different organs, stresses and phytohormones. Complementation analysis in Arabidopsis further confirmed the role of CaIMP in l-galactose 1-phosphate and myo-inositol 1-phosphate hydrolysis and its participation in myo-inositol and ascorbate biosynthesis. Moreover, Arabidopsis transgenic plants over-expressing CaIMP exhibited improved tolerance to stress during seed germination and seedling growth, while the VTC4/IMP loss-of-function mutants exhibited sensitivity to stress. Collectively, CaIMP links various metabolic pathways and plays an important role in improving seed germination and seedling growth, particularly under stressful environments. PMID:24123252

  2. Film Growth on Nanoporous Substrate

    NASA Astrophysics Data System (ADS)

    Zhang, Xue; Joy, James; Zhao, Chenwei; Xu, J. M.; Valles, James

    Self-ordered nanoporous anodic aluminum oxide (AAO) provides an easy way to fabricate nano structured material, such as nano wires and nano particles. We employ AAO as substrates and focus on the thermally evaporated film growth on the surface of the substrate. With various materials deposited onto the substrate, we find the films show different structures, e,g. ordered array of nano particles for Lead and nanohoneycomb structure for Silver. We relate the differing behaviors to the difference of surface energy and diffusion constant. To verify this, the effect of substrate temperature on the film growth has been explored and the structure of the film has been successfully changed through the process. We are grateful for the support of NSF Grants No. DMR-1307290.

  3. Broad Band Antireflection Coatings for Silicon and Germanium Substrates.

    NASA Astrophysics Data System (ADS)

    Bezuidenhout, Dirk Francois

    Infrared antireflection coatings for silicon and germanium substrates and some of the associated problems are addressed in this thesis. One of the first problems identified and investigated was that of the adhesion of ZnS films to germanium substrates. The cleaning of the Ge discs was evaluated by means of Auger spectroscopy. The main contaminant species found were carbon, oxygen and in the case of germanium substrates sulphur. No sulphur was found on silicon substrates. A wash in a series of organic solutions followed by a bake inside the vacuum chamber lead to much improved though still not acceptable adhesion of ZnS films to germanium substrates. The influence of a contact layer between the substrate and ZnS was investigated. Firstly, metal contact layers (Ni, Cr, Cu) were tried to improve the adhesion of the ZnS films. These samples (germanium-metal-zinc sulphide) were annealed in air in order to transfer the germanium -metal film to a germanide region and thus high optical transmission at long wave-lengths. Slight absorption still results even after the annealing of these samples. A dielectric material, Y_2O_3 , was therefore tested replacing the metal films. The system Ge-Y_2O_3 -ZnS in conjunction with an organic wash and vacuum bake lead to excellent adhesion of the ZnS layers to the germanium substrates. The next problem area addressed was that of a low refractive index material replacement for ThF _4. Four materials were investigated, i.e. ZnS, PbF_2, Y_2O _3 and YF_3. The refractive indices found for these compounds in thin film form at a wavelength of 10 μm is 2,18 for ZnS, 1,7 for PbF_2, 1,42 for Y_2O_3 and 1,3 for YF_3. From these results YF_3 was chosen as low refractive index material in the coating designs. Multi-layer coatings incorporating ZnS, Ge and YF_3 films were designed and evaporated. Measured reflectance values below 0,2% were obtained from 9 μm to 11 mum. These systems were stable and robust. Finally, a silicon ball lens was

  4. Substrate solder barriers for semiconductor epilayer growth

    DOEpatents

    Drummond, T.J.; Ginley, D.S.; Zipperian, T.E.

    1989-05-09

    During the growth of compound semiconductors by epitaxial processes, substrates are typically mounted to a support. In modular beam epitaxy, mounting is done using indium as a solder. This method has two drawbacks: the indium reacts with the substrate, and it is difficult to uniformly wet the back of a large diameter substrate. Both of these problems have been successfully overcome by sputter coating the back of the substrate with a thin layer of tungsten carbide or tungsten carbide and gold. In addition to being compatible with the growth of high quality semiconductor epilayers this coating is also inert in all standard substrate cleaning etchants used for compound semiconductors, and provides uniform distribution of energy in radiant heating.

  5. Substrate solder barriers for semiconductor epilayer growth

    DOEpatents

    Drummond, Timothy J.; Ginley, David S.; Zipperian, Thomas E.

    1989-01-01

    During the growth of compound semiconductors by epitaxial processes, substrates are typically mounted to a support. In modular beam epitaxy, mounting is done using indium as a solder. This method has two drawbacks: the indium reacts with the substrate, and it is difficult to uniformly wet the back of a large diameter substrate. Both of these problems have been successfully overcome by sputter coating the back of the substrate with a thin layer of tungsten carbide or tungsten carbide and gold. In addition to being compatible with the growth of high quality semiconductor epilayers this coating is also inert in all standard substrate cleaning etchants used for compound semiconductors, and provides uniform distribution of energy in radiant heating.

  6. Substrate solder barriers for semiconductor epilayer growth

    DOEpatents

    Drummond, T.J.; Ginley, D.S.; Zipperian, T.E.

    1987-10-23

    During the growth of compound semiconductors by epitaxial processes, substrates are typically mounted to a support. In molecular beam epitaxy, mounting is done using indium as a solder. This method has two drawbacks: the indium reacts with the substrate, and it is difficult to uniformly wet the back of a large diameter substrate. Both of these problems have been successfully overcome by sputter coating the back of the substrate with a thin layer of tungsten carbide or tungsten carbide and gold. In addition to being compatible with the growth of high quality semiconductor epilayers this coating is also inert in all standard substate cleaning etchants used for compound semiconductors, and provides uniform distribution of energy in radiant heating. 1 tab.

  7. Broad Substrate Specificity of the Loading Didomain of the Lipomycin Polyketide Synthase

    SciTech Connect

    Yuzawa, S; Eng, CH; Katz, L; Keasling, JD

    2013-06-04

    LipPks1, a polyketide synthase subunit of the lipomycin synthase, is believed to catalyze the polyketide chain initiation reaction using isobutyryl-CoA as a substrate, followed by an elongation reaction with methylmalonyl-CoA to start the biosynthesis of antibiotic alpha-lipomycin in Streptomyces aureofaciens Tu117. Recombinant LipPks1, containing the thioesterase domain from the 6-deoxyerythronolide B synthase, was produced in Escherichia coli, and its substrate specificity was investigated in vitro. Surprisingly, several different acyl-CoAs, including isobutyryl-CoA, were accepted as the starter substrates, while no product was observed with acetyl-CoA. These results demonstrate the broad substrate specificity of LipPks1 and may be applied to producing new antibiotics.

  8. Understanding the Broad Substrate Repertoire of Nitroreductase Based on Its Kinetic Mechanism*

    PubMed Central

    Pitsawong, Warintra; Hoben, John P.; Miller, Anne-Frances

    2014-01-01

    The oxygen-insensitive nitroreductase from Enterobacter cloacae (NR) catalyzes two-electron reduction of nitroaromatics to the corresponding nitroso compounds and, subsequently, to hydroxylamine products. NR has an unusually broad substrate repertoire, which may be related to protein dynamics (flexibility) and/or a simple non-selective kinetic mechanism. To investigate the possible role of mechanism in the broad substrate repertoire of NR, the kinetics of oxidation of NR by para-nitrobenzoic acid (p-NBA) were investigated using stopped-flow techniques at 4 °C. The results revealed a hyperbolic dependence on the p-NBA concentration with a limiting rate of 1.90 ± 0.09 s−1, indicating one-step binding before the flavin oxidation step. There is no evidence for a distinct binding step in which specificity might be enforced. The reduction of p-NBA is rate-limiting in steady-state turnover (1.7 ± 0.3 s−1). The pre-steady-state reduction kinetics of NR by NADH indicate that NADH reduces the enzyme with a rate constant of 700 ± 20 s−1 and a dissociation constant of 0.51 ± 0.04 mm. Thus, we demonstrate simple transient kinetics in both the reductive and oxidative half-reactions that help to explain the broad substrate repertoire of NR. Finally, we tested the ability of NR to reduce para-hydroxylaminobenzoic acid, demonstrating that the corresponding amine does not accumulate to significant levels even under anaerobic conditions. Thus E. cloacae NR is not a good candidate for enzymatic production of aromatic amines. PMID:24706760

  9. Spatiospectral and picosecond spatiotemporal properties of a broad area operating channeled-substrate-planar laser array

    NASA Technical Reports Server (NTRS)

    Yu, NU; Defreez, Richard K.; Bossert, David J.; Wilson, Geoffrey A.; Elliott, Richard A.

    1991-01-01

    Spatiospectral and spatiotemporal properties of an eight-element channeled-substrate-planar laser array are investigated in both CW and pulsed operating conditions. The closely spaced CSP array with strong optical coupling between array elements is characterized by a broad area laserlike operation determined by its spatial mode spectra. The spatiotemporal evolution of the near and far field exhibits complex dynamic behavior in the picosecond to nanosecond domain. Operating parameters for the laser device have been experimentally determined. These results provide important information for the evaluation of the dynamic behavior of coherent semiconductor laser arrays.

  10. Transmembrane aromatic amino acid distribution in P-glycoprotein. A functional role in broad substrate specificity.

    PubMed

    Pawagi, A B; Wang, J; Silverman, M; Reithmeier, R A; Deber, C M

    1994-01-14

    Multidrug resistance (MDR) in cancer cells is associated with overexpression of P-glycoprotein (Pgp), a membrane protein which interacts with structurally diverse hydrophobic molecules of high membrane affinity. In an analysis of the molecular basis for this broad range of substrate specificity, we found that the transmembrane (TM) regions of Pgp are rich in highly conserved aromatic amino acid residues. Computer-generated three-dimensional model structures showed that a typical substrate, rhodamine 123, can intercalate between three to four phenylalanine side-chains in any of several Pgp TM helices with minimal protrusion of the drug into bulk lipid, and that five to six (of the 12 Pgp putative TM segments) helices can facilitate transport through creation of a sterically compatible pore. In contrast to the case for proteins involved in the transport of membrane-impermeable, relatively polar substrates, the "transport path" for Pgp substrates need not be polar, and may involve either an internal channel occupied largely by aromatic side-chains, or external gaps along TM helix-lipid interfaces. Weakly polar interactions between drug cationic sites and Pgp aromatic residues contribute additionally to overall protein/drug binding. The ability of Pgp to recognize and efflux structurally diverse molecules suggests that rather than a unique structure, the Pgp channel may maintain the intrinsic capacity to undergo wide-ranging drug-dependent dynamic reorganization. PMID:7904655

  11. Step-controlled homoepitaxial growth of 4H-SiC on vicinal substrates

    NASA Astrophysics Data System (ADS)

    Kallinger, Birgit; Berwian, Patrick; Friedrich, Jochen; Thomas, Bernd

    2013-10-01

    A comprehensive study on the step-controlled homoepitaxial growth on the (0001)Si-face of vicinal 4H-SiC substrates was performed in order to establish epitaxial growth on 2° towards <112bar0> off-cut substrates and 4° towards <11bar00> off-cut substrates. A standard epitaxial growth process was developed by optimizing the growth temperature T, Si/H ratio and C/Si ratio for growth on 4° towards <112bar0> off-cut substrates. Thereby, step-controlled epitaxial growth was achieved within a broad operating window. The surface roughness of such epilayers varies typically between rms=0.5 nm and rms=2.5 nm and step-controlled growth is conserved even at a growth rate of 27 μm/h. Then, the standard growth process was applied to substrates with different off-cut angles α of 2°, 4° and 8° as well as with different off-cut directions <112bar0> and <11bar00>. The step-controlled growth was achieved also within a wide range of Si/H ratio and C/Si ratio for growth on 8° and 4° off-cut substrates, but the process window narrows strongly for growth on 2° off-cut substrates. The epilayers' surface roughness increases with decreasing off-cut angle of the substrate. Epilayers grown on 4° towards <11bar00> off-cut substrates were significantly smoother than epilayers grown on 4° towards <112bar0> off-cut substrates. No influence of the substrates' off-cut angle and direction on the growth rate was found. The experimental results of this comprehensive study are discussed globally in consideration of other relevant publications.

  12. Physiological characterization of the ARO10-dependent, broad-substrate-specificity 2-oxo acid decarboxylase activity of Saccharomyces cerevisiae.

    PubMed

    Vuralhan, Zeynep; Luttik, Marijke A H; Tai, Siew Leng; Boer, Viktor M; Morais, Marcos A; Schipper, Dick; Almering, Marinka J H; Kötter, Peter; Dickinson, J Richard; Daran, Jean-Marc; Pronk, Jack T

    2005-06-01

    Aerobic, glucose-limited chemostat cultures of Saccharomyces cerevisiae CEN.PK113-7D were grown with different nitrogen sources. Cultures grown with phenylalanine, leucine, or methionine as a nitrogen source contained high levels of the corresponding fusel alcohols and organic acids, indicating activity of the Ehrlich pathway. Also, fusel alcohols derived from the other two amino acids were detected in the supernatant, suggesting the involvement of a common enzyme activity. Transcript level analysis revealed that among the five thiamine-pyrophospate-dependent decarboxylases (PDC1, PDC5, PDC6, ARO10, and THI3), only ARO10 was transcriptionally up-regulated when phenylalanine, leucine, or methionine was used as a nitrogen source compared to growth on ammonia, proline, and asparagine. Moreover, 2-oxo acid decarboxylase activity measured in cell extract from CEN.PK113-7D grown with phenylalanine, methionine, or leucine displayed similar broad-substrate 2-oxo acid decarboxylase activity. Constitutive expression of ARO10 in ethanol-limited chemostat cultures in a strain lacking the five thiamine-pyrophosphate-dependent decarboxylases, grown with ammonia as a nitrogen source, led to a measurable decarboxylase activity with phenylalanine-, leucine-, and methionine-derived 2-oxo acids. Moreover, even with ammonia as the nitrogen source, these cultures produced significant amounts of the corresponding fusel alcohols. Nonetheless, the constitutive expression of ARO10 in an isogenic wild-type strain grown in a glucose-limited chemostat with ammonia did not lead to any 2-oxo acid decarboxylase activity. Furthermore, even when ARO10 was constitutively expressed, growth with phenylalanine as the nitrogen source led to increased decarboxylase activities in cell extracts. The results reported here indicate the involvement of posttranscriptional regulation and/or a second protein in the ARO10-dependent, broad-substrate-specificity decarboxylase activity. PMID:15933030

  13. Plasmonic substrates for multiplexed protein microarrays with femtomolar sensitivity and broad dynamic range

    PubMed Central

    Tabakman, Scott M.; Lau, Lana; Robinson, Joshua T.; Price, Jordan; Sherlock, Sarah P.; Wang, Hailiang; Zhang, Bo; Chen, Zhuo; Tangsombatvisit, Stephanie; Jarrell, Justin A.; Utz, Paul J.; Dai, Hongjie

    2012-01-01

    Protein chips are widely used for high-throughput proteomic analysis, but to date, the low sensitivity and narrow dynamic range have limited their capabilities in diagnostics and proteomics. Here we present protein microarrays on a novel nanostructured, plasmonic gold film with near-infrared fluorescence enhancement of up to 100-fold, extending the dynamic range of protein detection by three orders of magnitude towards the fM regime. We employ plasmonic protein microarrays for the early detection of a cancer biomarker, carcinoembryonic antigen, in the sera of mice bearing a xenograft tumour model. Further, we demonstrate a multiplexed autoantigen array for human autoantibodies implicated in a range of autoimmune diseases with superior signal-to-noise ratios and broader dynamic range compared with commercial nitrocellulose and glass substrates. The high sensitivity, broad dynamic range and easy adaptability of plasmonic protein chips presents new opportunities in proteomic research and diagnostics applications. PMID:21915108

  14. Epitaxial crystalline growth upon cold substrates

    NASA Technical Reports Server (NTRS)

    Lebduska, R. L.

    1969-01-01

    By sputtering a material with a high-energy ion-beam bombardment, the molecules of the target can be dislodged and ejected for subsequent deposition on a cold substrate of the desired crystallographic type and orientation.

  15. Substrate and nutrient limitation regulating microbial growth in soil

    NASA Astrophysics Data System (ADS)

    Bååth, Erland

    2015-04-01

    Microbial activity and growth in soil is regulated by several abiotic factors, including temperature, moisture and pH as the most important ones. At the same time nutrient conditions and substrate availability will also determine microbial growth. Amount of substrate will not only affect overall microbial growth, but also affect the balance of fungal and bacterial growth. The type of substrate will also affect the latter. Furthermore, according to Liebig law of limiting factors, we would expect one nutrient to be the main limiting one for microbial growth in soil. When this nutrient is added, the initial second liming factor will become the main one, adding complexity to the microbial response after adding different substrates. I will initially describe different ways of determining limiting factors for bacterial growth in soil, especially a rapid method estimating bacterial growth, using the leucine incorporation technique, after adding C (as glucose), N (as ammonium nitrate) and P (as phosphate). Scenarios of different limitations will be covered, with the bacterial growth response compared with fungal growth and total activity (respiration). The "degree of limitation", as well as the main limiting nutrient, can be altered by adding substrate of different stoichiometric composition. However, the organism group responding after alleviating the nutrient limitation can differ depending on the type of substrate added. There will also be situations, where fungi and bacteria appear to be limited by different nutrients. Finally, I will describe interactions between abiotic factors and the response of the soil microbiota to alleviation of limiting factors.

  16. Growth Kinetics of Suspended Microbial Cells: From Single-Substrate-Controlled Growth to Mixed-Substrate Kinetics

    PubMed Central

    Kovárová-Kovar, Karin; Egli, Thomas

    1998-01-01

    Growth kinetics, i.e., the relationship between specific growth rate and the concentration of a substrate, is one of the basic tools in microbiology. However, despite more than half a century of research, many fundamental questions about the validity and application of growth kinetics as observed in the laboratory to environmental growth conditions are still unanswered. For pure cultures growing with single substrates, enormous inconsistencies exist in the growth kinetic data reported. The low quality of experimental data has so far hampered the comparison and validation of the different growth models proposed, and only recently have data collected from nutrient-controlled chemostat cultures allowed us to compare different kinetic models on a statistical basis. The problems are mainly due to (i) the analytical difficulty in measuring substrates at growth-controlling concentrations and (ii) the fact that during a kinetic experiment, particularly in batch systems, microorganisms alter their kinetic properties because of adaptation to the changing environment. For example, for Escherichia coli growing with glucose, a physiological long-term adaptation results in a change in KS for glucose from some 5 mg liter−1 to ca. 30 μg liter−1. The data suggest that a dilemma exists, namely, that either “intrinsic” KS (under substrate-controlled conditions in chemostat culture) or μmax (under substrate-excess conditions in batch culture) can be measured but both cannot be determined at the same time. The above-described conventional growth kinetics derived from single-substrate-controlled laboratory experiments have invariably been used for describing both growth and substrate utilization in ecosystems. However, in nature, microbial cells are exposed to a wide spectrum of potential substrates, many of which they utilize simultaneously (in particular carbon sources). The kinetic data available to date for growth of pure cultures in carbon-controlled continuous culture

  17. A study of substrate factor on carbon nanotube forest growth

    NASA Astrophysics Data System (ADS)

    Read, Carlos; Call, Robert; Shen, T. C.

    2010-10-01

    Carbon Nanotube Forests (CNFs) are vertically grown carbon nanotubes. They can be as tall as millimeters with radii from less than one nm (single-walled) to more than a hundred nm (multi-walled). Their high surface to volume ratio provides a unique material system for EM radiation absorption, dry adhesive and biosensor applications. There have been numerous, but not all consistent reports on successful CNF growth. We find that the optimal growth conditions depend critically on the substrate, at least by the spray pyrolysis method we have adopted. To determine the substrate factor, we have investigated two grades of copper, stainless steel, silicon and quartz as substrates on which the catalytic particles and carbon source are delivered simultaneously by a ferrocine-xylene solution. We find that the interplay of lateral and in-diffusion of the iron atoms and interactions with existing gas molecules such as H2, O2, H2O on the substrates dictate the CNF growth.

  18. Influence of substrate micropatterning on biofilm growth

    NASA Astrophysics Data System (ADS)

    Koehler, Stephan; Li, Yiwei; Liu, Bi-Feng Liu; Weitz, David

    2015-11-01

    We culture triple reporter Bacillus Subtilis biofilm on micropatterned agar substrates. We track the biofilm development in terms of size, thickness, shape, and phenotype expression. For a tiling composed of elevated rectangles, we observe the biofilm develops an oval shape or triangular shape depending on the rectangle's aspect ratio and orientation. The motile cells are primarily located in the valleys between the rectangles and the matrix producing cells are mostly located on the rectangles. Wrinkles form at the edges of the elevated surfaces, and upon merging form channels centered on the elevated surface. After a few days, the spore-forming cells appear at the periphery. Since biofilms in nature grow on irregular surfaces, our work may provide insight into the complex patterns observed.

  19. Direct growth of Si nanowires on flexible organic substrates.

    PubMed

    Tian, Lin; Di Mario, Lorenzo; Minotti, Antonio; Tiburzi, Giorgio; Mendis, Budhika G; Zeze, Dagou A; Martelli, Faustino

    2016-06-01

    A key characteristic of semiconductor nanowires (NWs) is that they grow on any substrate that can withstand the growth conditions, paving the way for their use in flexible electronics. We report on the direct growth of crystalline silicon nanowires on polyimide substrates. The Si NWs are grown by plasma-enhanced chemical vapor deposition, which allows the growth to proceed at temperatures low enough to be compatible with plastic substrates (350 °C), where gold or indium are used as growth seeds. In is particularly interesting as the seed not only because it leads to a better NW crystal quality but also because it overcomes a core problem induced by the use of Au in silicon processing, i.e. Au creates deep carrier traps when incorporated in the nanowires. PMID:27098523

  20. Direct growth of Si nanowires on flexible organic substrates

    NASA Astrophysics Data System (ADS)

    Tian, Lin; Di Mario, Lorenzo; Minotti, Antonio; Tiburzi, Giorgio; Mendis, Budhika G.; Zeze, Dagou A.; Martelli, Faustino

    2016-06-01

    A key characteristic of semiconductor nanowires (NWs) is that they grow on any substrate that can withstand the growth conditions, paving the way for their use in flexible electronics. We report on the direct growth of crystalline silicon nanowires on polyimide substrates. The Si NWs are grown by plasma-enhanced chemical vapor deposition, which allows the growth to proceed at temperatures low enough to be compatible with plastic substrates (350 °C), where gold or indium are used as growth seeds. In is particularly interesting as the seed not only because it leads to a better NW crystal quality but also because it overcomes a core problem induced by the use of Au in silicon processing, i.e. Au creates deep carrier traps when incorporated in the nanowires.

  1. Growth and Characterization of Graphene on Single Crystal Cu Substrates

    NASA Astrophysics Data System (ADS)

    Robinson, Z. R.; Tyagi, P.; Geisler, H.; Ventrice, C. A., Jr.; Bol, A. A.; Hannon, J. B.

    2012-02-01

    One of the key issues for the use of CVD graphene in device applications is the influence of defects on the transport properties of the graphene. Therefore, it is important to understand the influence of the substrate on the orientation of the graphene. Growth of graphene films on Cu(111) has the potential for producing films with a low defect density because of the hexagonal symmetry of the substrate and relatively small lattice mismatch, whereas growth on Cu(100) is expected to result in multi-domain growth because of its square symmetry. In this study, graphene films were grown on Cu single crystal substrates, and characterized with LEEM, LEED, SEM, AFM, and Raman spectroscopy. The clean Cu substrates were prepared by sputtering and annealing in UHV. For the initial growth studies, the samples were transferred to a tube furnace for graphene growth using a technique optimized for Cu foils. The UHV system has recently been modified with a button heater compatible with the conditions needed for graphene growth to enable in-situ growth and characterization.

  2. Bacterial Anabaena variabilis phenylalanine ammonia lyase: a biocatalyst with broad substrate specificity.

    PubMed

    Lovelock, Sarah L; Turner, Nicholas J

    2014-10-15

    Phenylalanine ammonia lyases (PALs) catalyse the regio- and stereoselective hydroamination of cinnamic acid analogues to yield optically enriched α-amino acids. Herein, we demonstrate that a bacterial PAL from Anabaena variabilis (AvPAL) displays significantly higher activity towards a series of non-natural substrates than previously described eukaryotic PALs. Biotransformations performed on a preparative scale led to the synthesis of the 2-chloro- and 4-trifluoromethyl-phenylalanine derivatives in excellent ee, highlighting the enormous potential of bacterial PALs as biocatalysts for the synthesis of high value, non-natural amino acids. PMID:25037641

  3. Synergistic growth in bacteria depends on substrate complexity

    PubMed Central

    Deng, Yi-Jie; Wang, Shiao Y.

    2016-01-01

    Both positive and negative interactions among bacteria take place in the environment. We hypothesize that the complexity of the substrate affects the way bacteria interact with greater cooperation in the presence of recalcitrant substrate. We isolated lignocellulolytic bacteria from salt marsh detritus and compared the growth, metabolic activity and enzyme production of pure cultures to those of three-species mixed cultures in lignocellulose and glucose media. Synergistic growth was common in lignocellulose medium containing carboxyl methyl cellulose, xylan and lignin but absent in glucose medium. Bacterial synergism promoted metabolic activity in synergistic mixed cultures but not the maximal growth rate (μ). Bacterial synergism also promoted the production of β-1,4-glucosidase but not the production of cellobiohydrolase or β-1,4-xylosidase. Our results suggest that the chemical complexity of the substrate affects the way bacteria interact. While a complex substrate such as lignocellulose promotes positive interactions and synergistic growth, a labile substrate such as glucose promotes negative interactions and competition. Synergistic interactions among indigenous bacteria are suggested to be important in promoting lignocellulose degradation in the environment. PMID:26727898

  4. Synergistic growth in bacteria depends on substrate complexity.

    PubMed

    Deng, Yi-Jie; Wang, Shiao Y

    2016-01-01

    Both positive and negative interactions among bacteria take place in the environment. We hypothesize that the complexity of the substrate affects the way bacteria interact with greater cooperation in the presence of recalcitrant substrate. We isolated lignocellulolytic bacteria from salt marsh detritus and compared the growth, metabolic activity and enzyme production of pure cultures to those of three-species mixed cultures in lignocellulose and glucose media. Synergistic growth was common in lignocellulose medium containing carboxyl methyl cellulose, xylan and lignin but absent in glucose medium. Bacterial synergism promoted metabolic activity in synergistic mixed cultures but not the maximal growth rate (μ). Bacterial synergism also promoted the production of β-1,4-glucosidase but not the production of cellobiohydrolase or β-1,4-xylosidase. Our results suggest that the chemical complexity of the substrate affects the way bacteria interact. While a complex substrate such as lignocellulose promotes positive interactions and synergistic growth, a labile substrate such as glucose promotes negative interactions and competition. Synergistic interactions among indigenous bacteria are suggested to be important in promoting lignocellulose degradation in the environment. PMID:26727898

  5. Growth and characterization of graphene on CuNi substrates

    NASA Astrophysics Data System (ADS)

    Tyagi, Parul

    Graphene is a single layer of sp2 bonded carbon atoms that crystallizes in the honeycomb structure. Because of its true two-dimensional structure, it has very unique electrical properties, including a very high carrier mobility that is symmetric for holes and electrons. To realize these unique properties, it is important to develop a method for growing graphene films with uniform thickness and low defect density. One of the most popular methods of growth is by chemical vapor deposition on Cu substrates, because it is self-limited. However many applications require the growth of graphene films that are more than one atomic layer thick. In this research project, the growth of graphene on CuNi substrates has been studied. The presence of Ni in the alloy results in an increase in the catalytic activity of the surface. This results in lower deposition pressures than for pure Cu and also increases the carbon solubility, which allows the growth of films that are more than one atomic layer thick. Two types of substrates were used for the growth of the graphene films: CuNi foils with an alloy composition of 90:10 and 70:30 Cu-Ni by weight and a CuNi(111) single crystal with a composition of 90:10 by weight. For the 70:30 substrates, it was very difficult to control the graphene thickness. On the other hand, the controlled growth of graphene films that were more than one layer thick was achieved on the 90:10 substrates. The growth morphology and the crystal structure of graphene grown on the CuNi(111) surface was determined by performing these studies in an ultra-high vacuum chamber to achieve very high purity conditions. The low energy electron diffraction analysis of the graphene films showed that the graphene films always nucleated in more than one rotational orientation with respect to the substrate. The growth was achieved at temperatures as low as 500 °C, which is much lower in temperature than for Cu substrates. Scanning electron microscopy analysis of the graphene

  6. Mechanistic Basis for High Stereoselectivity and Broad Substrate Scope in the (salen)Co(III)-Catalyzed Hydrolytic Kinetic Resolution

    PubMed Central

    Ford, David D.; Nielsen, Lars P. C.; Zuend, Stephan J.; Jacobsen, Eric N.

    2013-01-01

    In the (salen)Co(III)-catalyzed hydrolytic kinetic resolution (HKR) of terminal epoxides, the rate- and stereoselectivity-determining epoxide ring-opening step occurs by a cooperative bimetallic mechanism with one Co(III) complex acting as a Lewis acid and another serving to deliver the hydroxide nucleophile. In this paper, we analyze the basis for the extraordinarily high stereoselectivity and broad substrate scope observed in the HKR. We demonstrate that the stereochemistry of each of the two (salen)Co(III) complexes in the rate-determining transition structure is important for productive catalysis: a measurable rate of hydrolysis occurs only if the absolute stereochemistry of each of these (salen)Co(III) complexes is the same. Experimental and computational studies provide strong evidence that stereochemical communication in the HKR is mediated by the stepped conformation of the salen ligand, and not the shape of the chiral diamine backbone of the ligand. A detailed computational analysis reveals that the epoxide binds the Lewis acidic Co(III) complex in a well-defined geometry imposed by stereoelectronic, rather than steric effects. This insight serves as the basis of a complete stereochemical and transition structure model that sheds light on the reasons for the broad substrate generality of the HKR. PMID:24041239

  7. Epitaxial growth mechanisms of graphene and effects of substrates

    NASA Astrophysics Data System (ADS)

    Özçelik, V. Ongun; Cahangirov, S.; Ciraci, S.

    2012-06-01

    The growth process of single layer graphene with and without substrate is investigated using ab initio, finite temperature molecular dynamic calculations within density functional theory. An understanding of the epitaxial graphene growth mechanisms in the atomic level is provided by exploring the transient stages which occur at the growing edges of graphene. These stages are formation and collapse of large carbon rings together with the formation and healing of Stone-Wales like pentagon-heptagon defects. The activation barriers for the healing of these growth induced defects on various substrates are calculated using the climbing image nudge elastic band method and compared with that of the Stone-Wales defect. It is found that the healing of pentagon-heptagon defects occurring near the edge in the course of growth is much easier than that of Stone-Wales defect. The role of the substrate in the epitaxial growth and in the healing of defects are also investigated in detail, along with the effects of using carbon dimers as the building blocks of graphene growth.

  8. Growth of Woody Plants in Clean Chip Residual Substrate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Clean chip residual (CCR) is a potential replacement for pine bark (PB) in nursery crop substrates. It is a by-product of in-field forestry harvesting practices and has been shown to produce annual plants and perennials similar in size to plants grown in PB. This study evaluated growth of woody orna...

  9. MBE growth of GaP on a Si substrate

    SciTech Connect

    Sobolev, M. S. Lazarenko, A. A.; Nikitina, E. V.; Pirogov, E. V.; Gudovskikh, A. S.; Egorov, A. Yu.

    2015-04-15

    It is shown that single-crystal GaP buffer layers can be formed on a Si substrate by molecular-beam epitaxy, with the “migration-enhanced epitaxy” procedure applied in the stage in which the nucleating layer is formed. When a GaP layer is produced on a p-type silicon substrate, a p-n junction is created in a natural way between the p-Si substrate and the surface n-Si layer produced by the diffusion of phosphorus into the substrate during the course of the epitaxial growth of GaP. This p-n junction can be used as the first junction of a silicon-based multijunction photovoltaic converter.

  10. Substrate Preparations in Epitaxial ZnO Film Growth

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, C.-H.; Lehoczky, S. L.; Harris, M. T.; Callahan, M. J.; George, M. A.

    2000-01-01

    Epitaxial ZnO films were grown on the two polar surfaces (O-face and Zn-face) of (0001) ZnO single crystal substrates using off-axis magnetron sputtering deposition. Annealing-temperature dependence of ZnO substrates was studied. ZnO films grown on sapphire substrates have also been investigated for comparison purposes and the annealing temperature of A1203 substrates is 1000 C. Substrates and films were characterized using photoluminescence (PL) spectrum, x-ray diffraction, atomic force microscope, energy dispersive spectrum, and electric transport measurements. It has been found that the ZnO film properties were different when films were grown on the two polarity surfaces of ZnO substrates and the A1203 substrates. An interesting result shows that high temperature annealing of ZnO single crystals will improve the surface structure on the O-face surface rather than the opposite surface. The measurements of homoepitaxial ZnO films indicate that the O-terminated surface is better for ZnO epitaxial film growth.

  11. Characterization of a Naphthalene Dioxygenase Endowed with an Exceptionally Broad Substrate Specificity Toward Polycyclic Aromatic Hydrocarbons

    SciTech Connect

    Jouanneau,Y.; Meyer, C.; Jakoncic, J.; Stojanoff, V.; Gaillard, J.

    2006-01-01

    In Sphingomonas CHY-1, a single ring-hydroxylating dioxygenase is responsible for the initial attack of a range of polycyclic aromatic hydrocarbons (PAHs) composed of up to five rings. The components of this enzyme were separately purified and characterized. The oxygenase component (ht-PhnI) was shown to contain one Rieske-type [2Fe-2S] cluster and one mononuclear Fe center per {alpha} subunit, based on EPR measurements and iron assay. Steady-state kinetic measurements revealed that the enzyme had a relatively low apparent Michaelis constant for naphthalene (K{sub m} = 0.92 {+-} 0.15 {mu}M) and an apparent specificity constant of 2.0 {+-} 0.3 M{sup -1} s{sup -1}. Naphthalene was converted to the corresponding 1,2-dihydrodiol with stoichiometric oxidation of NADH. On the other hand, the oxidation of eight other PAHs occurred at slower rates and with coupling efficiencies that decreased with the enzyme reaction rate. Uncoupling was associated with hydrogen peroxide formation, which is potentially deleterious to cells and might inhibit PAH degradation. In single turnover reactions, ht-PhnI alone catalyzed PAH hydroxylation at a faster rate in the presence of organic solvent, suggesting that the transfer of substrate to the active site is a limiting factor. The four-ring PAHs chrysene and benz[a]anthracene were subjected to a double ring-dihydroxylation, giving rise to the formation of a significant proportion of bis-cis-dihydrodiols. In addition, the dihydroxylation of benz[a]anthracene yielded three dihydrodiols, the enzyme showing a preference for carbons in positions 1,2 and 10,11. This is the first characterization of a dioxygenase able to dihydroxylate PAHs made up of four and five rings.

  12. Characterization of a naphthalene dioxygenase endowed with an exceptionally broad substrate specificity toward polycyclic aromatic hydrocarbons.

    PubMed

    Jouanneau, Yves; Meyer, Christine; Jakoncic, Jean; Stojanoff, Vivian; Gaillard, Jacques

    2006-10-10

    In Sphingomonas CHY-1, a single ring-hydroxylating dioxygenase is responsible for the initial attack of a range of polycyclic aromatic hydrocarbons (PAHs) composed of up to five rings. The components of this enzyme were separately purified and characterized. The oxygenase component (ht-PhnI) was shown to contain one Rieske-type [2Fe-2S] cluster and one mononuclear Fe center per alpha subunit, based on EPR measurements and iron assay. Steady-state kinetic measurements revealed that the enzyme had a relatively low apparent Michaelis constant for naphthalene (K(m) = 0.92 +/- 0.15 microM) and an apparent specificity constant of 2.0 +/- 0.3 mM(-)(1) s(-)(1). Naphthalene was converted to the corresponding 1,2-dihydrodiol with stoichiometric oxidation of NADH. On the other hand, the oxidation of eight other PAHs occurred at slower rates and with coupling efficiencies that decreased with the enzyme reaction rate. Uncoupling was associated with hydrogen peroxide formation, which is potentially deleterious to cells and might inhibit PAH degradation. In single turnover reactions, ht-PhnI alone catalyzed PAH hydroxylation at a faster rate in the presence of organic solvent, suggesting that the transfer of substrate to the active site is a limiting factor. The four-ring PAHs chrysene and benz[a]anthracene were subjected to a double ring-dihydroxylation, giving rise to the formation of a significant proportion of bis-cis-dihydrodiols. In addition, the dihydroxylation of benz[a]anthracene yielded three dihydrodiols, the enzyme showing a preference for carbons in positions 1,2 and 10,11. This is the first characterization of a dioxygenase able to dihydroxylate PAHs made up of four and five rings. PMID:17014090

  13. Use of alternative growth substrates to enhance PAH degradation

    SciTech Connect

    Tittle, P.C.; Liu, Y.T.; Strand, S.E.; Stensel, H.D.

    1995-12-31

    Freshwater and saltwater polycyclic aromatic hydrocarbons (PAH)-degrading enrichments were developed from seed from a manufactured gas plant site and contaminated marine sediment, respectively. Both enrichments were able to maintain specific degradation rates of 3- and 4-ring PAHs after growth with salicylate or phthalate, which increased their biomass concentrations by a factor of 9 to 10. Phthalate was a more effective alternative substrate than was salicylate. Specific degradation rates of phenanthrene and anthracene by the freshwater enrichment were increased after growth with phthalate. Growth with phthalate increased the specific degradation rates of phenanthrene and pyrene by the saltwater enrichment.

  14. Differential growth responses of soil bacterial taxa to carbon substrates of varying chemical recalcitrance

    SciTech Connect

    Goldfarb, K.C.; Karaoz, U.; Hanson, C.A.; Santee, C.A.; Bradford, M.A.; Treseder, K.K.; Wallenstein, M.D.; Brodie, E.L.

    2011-04-18

    Soils are immensely diverse microbial habitats with thousands of co-existing bacterial, archaeal, and fungal species. Across broad spatial scales, factors such as pH and soil moisture appear to determine the diversity and structure of soil bacterial communities. Within any one site however, bacterial taxon diversity is high and factors maintaining this diversity are poorly resolved. Candidate factors include organic substrate availability and chemical recalcitrance, and given that they appear to structure bacterial communities at the phylum level, we examine whether these factors might structure bacterial communities at finer levels of taxonomic resolution. Analyzing 16S rRNA gene composition of nucleotide analog-labeled DNA by PhyloChip microarrays, we compare relative growth rates on organic substrates of increasing chemical recalcitrance of >2,200 bacterial taxa across 43 divisions/phyla. Taxa that increase in relative abundance with labile organic substrates (i.e., glycine, sucrose) are numerous (>500), phylogenetically clustered, and occur predominantly in two phyla (Proteobacteria and Actinobacteria) including orders Actinomycetales, Enterobacteriales, Burkholderiales, Rhodocyclales, Alteromonadales, and Pseudomonadales. Taxa increasing in relative abundance with more chemically recalcitrant substrates (i.e., cellulose, lignin, or tannin-protein) are fewer (168) but more phylogenetically dispersed, occurring across eight phyla and including Clostridiales, Sphingomonadalaes, Desulfovibrionales. Just over 6% of detected taxa, including many Burkholderiales increase in relative abundance with both labile and chemically recalcitrant substrates. Estimates of median rRNA copy number per genome of responding taxa demonstrate that these patterns are broadly consistent with bacterial growth strategies. Taken together, these data suggest that changes in availability of intrinsically labile substrates may result in predictable shifts in soil bacterial composition.

  15. Controlled growth of vertically aligned carbon nanotubes on metal substrates

    NASA Astrophysics Data System (ADS)

    Gao, Zhaoli

    Carbon nanotube (CNT) is a fascinating material with extraordinary electrical thermal and mechanical properties. Growing vertically aligned CNT (VACNT) arrays on metal substrates is an important step in bringing CNT into practical applications such as thermal interface materials (TIMs) and microelectrodes. However, the growth process is challenging due to the difficulties in preventing catalyst diffusion and controlling catalyst dewetting on metal substrates with physical surface heterogeneity. In this work, the catalyst diffusion mechanism and catalyst dewetting theory were studied for the controlled growth of VACNTs on metal substrates. The diffusion time of the catalyst, the diffusion coefficients for the catalyst in the substrate materials and the number density of catalyst nanoparticles after dewetting are identified as the key parameters, based on which three strategies are developed. Firstly, a fast-heating catalyst pretreatment strategy was used, aiming at preserving the amount of catalyst prior to CNT growth by reducing the catalyst diffusion time. The catalyst lifetime is extended from half an hour to one hour on a patterned Al thin film and a VACNT height of 106 mum, about twenty fold of that reported in the literature, was attained. Secondly, a diffusion barrier layer strategy is employed for a reduction of catalyst diffusion into the substrate materials. Enhancement of VACNT growth on Cu substrates was achieved by adopting a conformal Al2O 3 diffusion barrier layer fabricated by a specially designed atomic layer deposition (ALD) system. Lastly, a novel catalyst glancing angle deposition (GLAD) strategy is performed to manipulate the morphology of a relatively thick catalyst on metal substrates with physical surface heterogeneity, aiming to obtain uniform and dense catalyst nanoparticles after dewetting in the pretreatment process for enhanced VACNT growth. We are able to control the VACNT growth conditions on metal substrates in terms of their

  16. A Potential Substrate Binding Conformation of β-Lactams and Insight into the Broad Spectrum of NDM-1 Activity

    PubMed Central

    Yuan, Qinghui; He, Lin

    2012-01-01

    New Delhi metallo-β-lactamase 1 (NDM-1) is a key enzyme that the pathogen Klebsiella pneumonia uses to hydrolyze almost all β-lactam antibiotics. It is currently unclear why NDM-1 has a broad spectrum of activity. Docking of the representatives of the β-lactam families into the active site of NDM-1 is reported here. All the β-lactams naturally fit the NDM-1 pocket, implying that NDM-1 can accommodate the substrates without dramatic conformation changes. The docking reveals two major binding modes of the β-lactams, which we tentatively name the S (substrate) and I (inhibitor) conformers. In the S conformers of all the β-lactams, the amide oxygen and the carboxylic group conservatively interact with two zinc ions, while the substitutions on the fused rings show dramatic differences in their conformations and positions. Since the bridging hydroxide ion/water in the S conformer is at the position for the nucleophilic attack, the S conformation may simulate the true binding of a substrate to NDM-1. The I conformer either blocks or displaces the bridging hydroxide ion/water, such as in the case of aztreonam, and is thus inhibitory. The docking also suggests that substitutions on the β-lactam ring are required for β-lactams to bind in the S conformation, and therefore, small β-lactams such as clavulanic acid would be inhibitors of NDM-1. Finally, our docking shows that moxalactam uses its tyrosyl-carboxylic group to compete with the S conformer and would thus be a poor substrate of NDM-1. PMID:22825119

  17. Growth of Carbon Nanotubes on Different Types of Substrates

    NASA Astrophysics Data System (ADS)

    Zhu, Jiangtao

    We report the growth of carbon nanotubes (CNTs) on different types of substrates with or without catalytic materials by using different approaches. The roles of the substrates and the catalysts in the formation of the CNTs are studied. We also characterized and identified the structural properties of the CNTs products. In this work, three types of substrates had been used, namely biomorphic bamboo charcoal, Au-coated silicon wafer, and copper foil. The CNTs were grown on different substrates by chemical vapor deposition (CVD) method at temperature range between 700°C and 1400°C. Ethanol vapor was used as the carbon source, while tetraethyl orthosilicate (TEOS) vapor was also applied to the process for bamboo charcoal. The products formed on different substrates had their own characteristic features. Hollow or silicate filled CNTs with silicate droplet tips were formed on the surface of bamboo charcoal. Their diameter was in hundreds of nanometers and the length was about several microns. CNT-coated silica core-shell structures were obtained on Au-coated silicon wafer. The graphitic carbon shell was formed in thickness about 145 nm for the sample prepared at 1185°C, but amorphous carbon shell was produced in thickness more than 300 nm for the sample prepared at 1236°C. Lastly, CNTs with bamboo-like structure were synthesized on the copper foil substrate. The CNTs were getting thicker from 70 nm to 170 nm when temperature was increased from 700°C to 1000°C. The yield increased with temperature and annealing time if the sample was annealed for less than 30 min. Apart from being a support, the three substrates had their own roles in the growth of CNTs. Bamboo charcoal also acted as a catalyst provider. Au-coated silicon wafer participated in the formation of the silica/CNT composite nanowires. Copper foil itself was a catalyst. The silicate, the Au/Si droplet, and the copper particles were the catalysts for the growth of CNTs in these three substrates

  18. Use of lunar regolith as a substrate for plant growth

    NASA Technical Reports Server (NTRS)

    Ming, D. W.; Henninger, D. L.

    1994-01-01

    Regenerative Life Support Systems (RLSS) will be required to regenerate air, water, and wastes, and to produce food for human consumption during long-duration missions to the Moon and Mars. It may be possible to supplement some of the materials needed for a lunar RLSS from resources on the Moon. Natural materials at the lunar surface may be used for a variety of lunar RLSS needs, including (1) soils or solid-support substrates for plant growth, (2) sources for extraction of essential, plant-growth nutrients, (3) substrates for microbial populations in the degradation of wastes, (4) sources of O2 and H2, which may be used to manufacture water, (5) feed stock materials for the synthesis of useful minerals (e.g., molecular sieves), and (6) shielding materials surrounding the outpost structure to protect humans, plants, and microorganisms from harmful radiation. Use of indigenous lunar regolith as a terrestrial-like soil for plant growth could offer a solid support substrate, buffering capacity, nutrient source/storage/retention capabilities, and should be relatively easy to maintain. The lunar regolith could, with a suitable microbial population, play a role in waste renovation; much like terrestrial waste application directly on soils. Issues associated with potentially toxic elements, pH, nutrient availability, air and fluid movement parameters, and cation exchange capacity of lunar regolith need to be addressed before lunar materials can be used effectively as soils for plant growth.

  19. Use of lunar regolith as a substrate for plant growth.

    PubMed

    Ming, D W; Henninger, D L

    1994-01-01

    Regenerative Life Support Systems (RLSS) will be required to regenerate air, water, and wastes, and to produce food for human consumption during long-duration missions to the Moon and Mars. It may be possible to supplement some of the materials needed for a lunar RLSS from resources on the Moon. Natural materials at the lunar surface may be used for a variety of lunar RLSS needs, including (i) soils or solid-support substrates for plant growth, (ii) sources for extraction of essential, plant-growth nutrients, (iii) substrates for microbial populations in the degradation of wastes, (iv) sources of O2 and H2, which may be used to manufacture water, (v) feed stock materials for the synthesis of useful minerals (e.g., molecular sieves), and (vi) shielding materials surrounding the outpost structure to protect humans, plants, and microorganisms from harmful radiation. Use of indigenous lunar regolith as a terrestrial-like soil for plant growth could offer a solid support substrate, buffering capacity, nutrient source/storage/retention capabilities, and should be relatively easy to maintain. The lunar regolith could, with a suitable microbial population, play a role in waste renovation; much like terrestrial waste application directly on soils. Issues associated with potentially toxic elements, pH, nutrient availability, air and fluid movement parameters, and cation exchange capacity of lunar regolith need to be addressed before lunar materials can be used effectively as soils for plant growth. PMID:11538023

  20. Use of lunar regolith as a substrate for plant growth

    NASA Astrophysics Data System (ADS)

    Ming, D. W.; Henninger, D. L.

    1994-11-01

    Regenerative Life Support Systems (RLSS) will be required to regenerate air, water, and wastes, and to produce food for human consumption during long-duration missions to the Moon and Mars. It may be possible to supplement some of the materials needed for a lunar RLSS from resources on the Moon. Natural materials at the lunar surface may be used for a variety of lunar RLSS needs, including (i) soils or solid-support substrates for plant growth, (ii) sources for extraction of essential, plant-growth nutrients, (iii) substrates for microbial populations in the degradation of wastes, (iv) sources of O2 and H2, which may be used to manufacture water, (v) feed stock materials for the synthesis of useful minerals (e.g., molecular sieves), and (vi) shielding materials surrounding the outpost structure to protect humans, plants, and microorganism from harmful radiation. Use of indigenous lunar regolith as a terrestrial-like soil for plant growth could offer a solid support substrate, buffering capacity, nutrient source/storage/retention capabilities, and should be relatively easy to maintain. The lunar regolith could, with a suitable microbial population, play a role in waste renovation; much like terrestrial waste application directly on soils. Issues associated with potentially toxic elements, pH, nutrient availability, air and fluid movement parameters, and cation exchange capacity of lunar regolith need to be addressed before lunar materials can be used effectively as soils for plant growth.

  1. Cellular response to micropatterned growth promoting and inhibitory substrates

    PubMed Central

    2013-01-01

    Background Normal development and the response to injury both require cell growth, migration and morphological remodeling, guided by a complex local landscape of permissive and inhibitory cues. A standard approach for studying by such cues is to culture cells on uniform substrates containing known concentrations of these molecules, however this method fails to represent the molecular complexity of the natural growth environment. Results To mimic the local complexity of environmental conditions in vitro, we used a contact micropatterning technique to examine cell growth and differentiation on patterned substrates printed with the commonly studied growth permissive and inhibitory substrates, poly-L-lysine (PLL) and myelin, respectively. We show that micropatterning of PLL can be used to direct adherence and axonal outgrowth of hippocampal and cortical neurons as well as other cells with diverse morphologies like Oli-neu oligodendrocyte progenitor cell lines and fibroblast-like COS7 cells in culture. Surprisingly, COS7 cells exhibited a preference for low concentration (1 pg/mL) PLL zones over adjacent zones printed with high concentrations (1 mg/mL). We demonstrate that micropatterning is also useful for studying factors that inhibit growth as it can direct cells to grow along straight lines that are easy to quantify. Furthermore, we provide the first demonstration of microcontact printing of myelin-associated proteins and show that they impair process outgrowth from Oli-neu oligodendrocyte precursor cells. Conclusion We conclude that microcontact printing is an efficient and reproducible method for patterning proteins and brain-derived myelin on glass surfaces in order to study the effects of the microenvironment on cell growth and morphogenesis. PMID:24119185

  2. Growth behavior of cochlear nucleus neuronal cells on semiconductor substrates.

    PubMed

    Rak, Kristen; Wasielewski, Natalia; Radeloff, Andreas; Scherzed, Agmal; Jablonka, Sibylle; Hagen, Rudolf; Mlynski, Robert

    2011-05-01

    Auditory brainstem implants provide sound information by direct stimulation of the cochlear nucleus to patients with dysfunctional or absent cranial nerve VIII. In contrast to patients with cochlear implants, the use of the auditory brainstem implants is less successful. This cannot be fully explained by the difference location of stimulation but a rather unspecific neuronal stimulation. The aim of this study was to further examine neuronal cells of the cochlear nucleus and to test their interactions with semiconductor substrates as a potential electrode material for improved auditory brainstem implants. The cochlear nuclei of postnatal day 7 rats were microsurgically dissected. The tissue was dissociated enzymatically and plated on coverslips as control and on the semiconductor substrates silicon or silicon nitride. After 4 days in culture the morphology and growth of dissociated cells was determined by fluorescence and scanning electron microscopy. Dissociated cells of the cochlear nucleus showed reduced cell growth on semiconductor substrates compared with controls. SEM analysis demonstrated close contact of neurons with supporting cells in culture and good adherence of neuronal growth cones on the used materials. These findings present basic knowledge for the development of neuron-electrode interfaces for future auditory brainstem implants. PMID:21370446

  3. The Cleaning of Indium Phosphide Substrates for Growth by MBE

    NASA Astrophysics Data System (ADS)

    Hofstra, Peter

    1995-11-01

    A novel technique of using an in-situ ECR generated H-plasma to produce high quality surfaces on InP substrates, for growth of n-and p-type InP layers by GSMBE, has been investigated. The initial substrate surface quality determines the quality of the subsequently grown layers and therefore, the cleaning procedure is of critical importance. The standard approach entails a thermal desorption of a passivating oxide; however, this technique leaves carbon on the surface and, because oxides may vary in composition depending on the growth conditions, a consistent temperature for desorption may not be obtained. The desorption process is also dependent on the atmosphere in which it is carried out; i.e. whether an overpressure of P_2 or As _2 is used. Thermal desorption of oxides from InP requires the substrate to reach temperatures higher than normal GSMBE growth temperatures which can lead to substrate decomposition and, for regrowth applications, can alter dopant profiles and layer composition in ternary and quaternary layer growths. As an alternative, H-plasmas in separate vacuum chambers have been used to remove oxides from InP but this typically produces highly defective substrates due to a loss of phosphorus from the substrate. In this work the combination of an in-situ H-plasma with a stabilizing atmosphere of P_2 is used for the removal of oxides at temperatures equal to growth temperature and below. The mechanism involved in the thermal desorption of an oxide is first clarified and this procedure is compared with oxide removal by H-plasma etch in a phosphorus atmosphere. The ECR source can produce various plasma modes which have been thoroughly characterized. The effect of the different plasma conditions on clean InP is determined. These modes have different properties which result in different oxide etch rates. Various modes are compared and the mechanism of oxide removal is documented. As an alternative to oxide growth S-passivation has recently received

  4. Tailored surfaces of perovskite oxide substrates for conducted growth of thin films.

    PubMed

    Sánchez, Florencio; Ocal, Carmen; Fontcuberta, Josep

    2014-04-01

    Oxide electronics relies on the availability of epitaxial oxide thin films. The extreme flexibility of the chemical composition of ABO3 perovskites and the broad spectrum of properties they cover, inspire the creativity of scientists and place perovskites in the lead of functional materials for advanced technologies. Moreover, emerging properties are being discovered at interfaces between distinct perovskites that could not be anticipated on the basis of those of the adjacent epitaxial layers. All dreamed new prospects require the use of suitable substrates for epitaxial growth. Perovskite single crystals are the workhorses of this activity and understanding and controlling their surface properties have become critical. In this tutorial review we will chiefly focus on the impact of the morphology and composition of the surface of ABO3 perovskite substrates on the growth mechanisms and properties of thin films epitaxially grown on them. As SrTiO3 is the most popular substrate, we will mostly concentrate on describing the current understanding and achievements for it. Illustrative examples of other perovskite substrates (LaAlO3, LSAT and DyScO3) will be also included. We will show that distinct chemical terminations can exist on the surfaces used for growth and we will review methods employed either to select the most appropriate one for specific growth to allow, for instance, tailoring the ultimate outmost epilayer, or to induce self-ordering to engineer long-range nanoscale patterns of chemical terminations. We will demonstrate the capacity of this knowledge by the growth of low-dimensional organic and inorganic structures. PMID:24553667

  5. Multiple substrate growth kinetics of Leptothrix discophora SP-6.

    PubMed

    Yurt, Nurdan; Sears, John; Lewandowski, Zbigniew

    2002-01-01

    The growth parameters of Leptothrix discophora SP-6 were quantified on the basis of the steady-state concentrations and utilization rates of pyruvate, dissolved oxygen, and concentration of microorganisms in a chemostat operated at 25 degrees C, pH 7.2, and an agitation rate of 350 rpm. The results showed that the microbial growth was limited by both pyruvate and dissolved oxygen. A combined growth kinetics model using Monod growth kinetics for pyruvate and Tessier growth kinetics for oxygen showed the best correlation with the experimental data when analyzed using an interactive multiple substrate model. The growth kinetics parameters and the respective confidence limits, estimated using the Monte Carlo simulation, were mu(max) = 0.576 +/- 0.021 h(-1), K(sMp) = 38.81 +/- 4.24 mg L(-1), K(sTo) = 0.39 +/- 0.04 mg L(-1), Y(X/p) = 0.150 (mg microorganism mg(-1) pyruvate), Y(X/o) = 1.24 (mg microorganism mg(-1) oxygen), the maintenance factors for pyruvate and oxygen were m(p) = 0.129 (mg pyruvate consumed mg(-1) microorganism h(-1)) and m(o) = 0.076 (mg oxygen consumed mg(-1) microorganism h(-1)), respectively. PMID:12363350

  6. ``Electric growth`` of metal overlayers on semiconductor substrates

    SciTech Connect

    Zhang, Z.; Cho, J.H. |; Niu, Q.; Shih, C.K.; Suo, Z.

    1998-02-01

    In this article, the authors present the main results from their recent studies of metal overlayer growth on semiconductor substrates. They show that a variety of novel phenomena can exist in such systems, resulting from several competing interactions. The confined motion of the conduction electrons within the metal overlayer can mediate a surprisingly long-range repulsive force between the metal-semiconductor interface and the growth front, acting to stabilize the overlayer. Electron transfer from the overlayer to the substrate leads to an attractive force between the two interfaces, acting to destabilize the overlayer. Interface-induced Friedel oscillations in electron density can further impose an oscillatory modulation onto the two previous interactions. These three competing factors, of all electronic nature, can make a flat metal overlayer critically, marginally, or magically stable, or totally unstable against roughening. The authors further show that, for many systems, these electronic effects can easily win over the effect of stress. First-principles studies of a few representative systems support the main features of the present electronic growth concept.

  7. Graphene on Pt(111): Growth and Substrate interaction

    SciTech Connect

    Sutter, P.; Sadowski, J.T.; Sutter, E.

    2009-12-01

    In situ low-energy electron microscopy (LEEM) of graphene growth combined with measurements of the graphene structure and electronic band structure has been used to study graphene on Pt(111). Growth by carbon segregation produces macroscopic monolayer graphene domains extending continuously across Pt(111) substrate steps and bounded by strongly faceted edges. LEEM during cooling from the growth temperature shows the propagation of wrinkles in the graphene sheet, driven by thermal stress. The lattice mismatch between graphene and Pt(111) is accommodated by moire structures with a large number of different rotational variants, without a clear preference for a particular interface geometry. Fast and slow growing graphene domains exhibit moire structures with small [e.g., (3 x 3){sub G}, ({radical}6 x {radical}6)R2{sub G}, and (2 x 2)R4{sub G}] and large unit cells [e.g., ({radical}44 x {radical}44)R15{sub G}, ({radical}52 x {radical}52)R14{sub G}, and (8 x 8){sub G}], respectively. A weak substrate coupling, suggested by the growth and structural properties of monolayer graphene on Pt(111), is confirmed by maps of the band structure, which is close to that of isolated graphene aside from minimal hole doping due to charge transfer from the metal. Finally, the decoupled graphene monolayer on Pt(111) appears impenetrable to carbon diffusion, which self-limits the graphene growth at monolayer thickness. Thicker graphene domains, which can form at boundaries between monolayer domains, have been used to characterize the properties of few-layer graphene on Pt(111).

  8. Laser direct growth of graphene on silicon substrate

    SciTech Connect

    Wei Dapeng; Xu Xianfan

    2012-01-09

    We demonstrate laser direct growth of few layer graphene on a silicon substrate. In our study, a continuous wave laser beam was focused on a poly(methyl methacrylate) (PMMA)-coated silicon wafer to evaporate PMMA and melt the silicon wafer. Carbon atoms, decomposed from PMMA, were absorbed by the molten silicon surface, and then separated from silicon in the cooling process to form few-layer graphene. This Si-catalyzed method will provide a new approach and platform for applications of graphene.

  9. Atomistic mechanisms for bilayer growth of graphene on metal substrates

    SciTech Connect

    Chen, Wei; Cui, Ping; Zhu, Wenguang; Kaxiras, Efthimios; Gao, Yanfei; Zhang, Zhenyu

    2015-01-08

    Epitaxial growth on metal substrates has been shown to be the most powerful approach in producing large-scale high-quality monolayer graphene, yet it remains a major challenge to realize uniform bilayer graphene growth. Here we carry out a comparative study of the atomistic mechanisms for bilayer graphene growth on the (111) surfaces of Cu and Ni, using multiscale approaches combining first-principles calculations and rate-equation analysis. We first show that the relatively weak graphene-Cu interaction enhances the lateral diffusion and effective nucleation of C atoms underneath the graphene island, thereby making it more feasible to grow bilayer graphene on Cu. In contrast, the stronger graphene-Ni interaction suppresses the lateral mobility and dimerization of C atoms underneath the graphene, making it unlikely to achieve controlled growth of bilayer graphene on Ni. We then determine the critical graphene size beyond which nucleation of the second layer will take place. Intriguingly, the critical size exhibits an effective inverse "Ehrlich-Schwoebel barrier" effect, becoming smaller for faster C migration from the Cu surface to the graphene-Cu interface sites across the graphene edge. Lastly, these findings allow us to propose a novel alternating growth scheme to realize mass production of bilayer graphene.

  10. Atomistic mechanisms for bilayer growth of graphene on metal substrates

    DOE PAGESBeta

    Chen, Wei; Cui, Ping; Zhu, Wenguang; Kaxiras, Efthimios; Gao, Yanfei; Zhang, Zhenyu

    2015-01-08

    Epitaxial growth on metal substrates has been shown to be the most powerful approach in producing large-scale high-quality monolayer graphene, yet it remains a major challenge to realize uniform bilayer graphene growth. Here we carry out a comparative study of the atomistic mechanisms for bilayer graphene growth on the (111) surfaces of Cu and Ni, using multiscale approaches combining first-principles calculations and rate-equation analysis. We first show that the relatively weak graphene-Cu interaction enhances the lateral diffusion and effective nucleation of C atoms underneath the graphene island, thereby making it more feasible to grow bilayer graphene on Cu. In contrast,more » the stronger graphene-Ni interaction suppresses the lateral mobility and dimerization of C atoms underneath the graphene, making it unlikely to achieve controlled growth of bilayer graphene on Ni. We then determine the critical graphene size beyond which nucleation of the second layer will take place. Intriguingly, the critical size exhibits an effective inverse "Ehrlich-Schwoebel barrier" effect, becoming smaller for faster C migration from the Cu surface to the graphene-Cu interface sites across the graphene edge. Lastly, these findings allow us to propose a novel alternating growth scheme to realize mass production of bilayer graphene.« less

  11. Atomistic mechanisms for bilayer growth of graphene on metal substrates

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Cui, Ping; Zhu, Wenguang; Kaxiras, Efthimios; Gao, Yanfei; Zhang, Zhenyu

    2015-01-01

    Epitaxial growth on metal substrates has been shown to be the most powerful approach in producing large-scale high-quality monolayer graphene, yet it remains a major challenge to realize uniform bilayer graphene growth. Here we carry out a comparative study of the atomistic mechanisms for bilayer graphene growth on the (111) surfaces of Cu and Ni, using multiscale approaches combining first-principles calculations and rate-equation analysis. We first show that the relatively weak graphene-Cu interaction enhances the lateral diffusion and effective nucleation of C atoms underneath the graphene island, thereby making it more feasible to grow bilayer graphene on Cu. In contrast, the stronger graphene-Ni interaction suppresses the lateral mobility and dimerization of C atoms underneath the graphene, making it unlikely to achieve controlled growth of bilayer graphene on Ni. We then determine the critical graphene size beyond which nucleation of the second layer will take place. Intriguingly, the critical size exhibits an effective inverse "Ehrlich-Schwoebel barrier" effect, becoming smaller for faster C migration from the Cu surface to the graphene-Cu interface sites across the graphene edge. These findings allow us to propose a novel alternating growth scheme to realize mass production of bilayer graphene.

  12. Titanium oxide as substrate for neural cell growth.

    PubMed

    Carballo-Vila, Mónica; Moreno-Burriel, Berta; Chinarro, Eva; Jurado, José R; Casañ-Pastor, Nieves; Collazos-Castro, Jorge E

    2009-07-01

    Titanium oxide has antiinflammatory activity and tunable electrochemical behavior that make it an attractive material for the fabrication of implantable devices. The most stable composition is TiO2 and occurs mainly in three polymorphs, namely, anatase, rutile, and brookite, which differ in its crystallochemical properties. Here, we report the preparation of rutile surfaces that permit good adherence and axonal growth of cultured rat cerebral cortex neurons. Rutile disks were obtained by sinterization of TiO2 powders of commercial origin or precipitated from hydrolysis of Ti(IV)-isopropoxide. Commercial powders sintered at 1300-1600 degrees C produced rutile surfaces with abnormal grain growth, probably because of impurities of the powders. Neurons cultured on those surfaces survived in variable numbers and showed fewer neurites than on control materials. On the other hand, rutile sintered from precipitated powders had less contaminants and more homogenous grain growth. By adjusting the thermal treatment it was possible to obtain surfaces performing well as substrate for neuron survival for at least 10 days. Some surfaces permitted normal axonal elongation, whereas dendrite growth was generally impaired. These findings support the potential use of titanium oxide in neuroprostheses and other devices demanding materials with enhanced properties in terms of biocompatibility and axon growth promotion. PMID:18481786

  13. The growth of cubic silicon carbide on a compliant substrate

    NASA Technical Reports Server (NTRS)

    Mitchell, Sharanda; Soward, Ida

    1995-01-01

    Research has shown that silicon carbide grown on silicon and 6H silicon carbide has problems associated with these substrates. This is because silicon and silicon carbide has a 20% lattice mismatch and cubic silicon carbide has not been successfully achieved on 6H silicon carbide. We are investigating the growth of silicon carbide on a compliant substrate in order to grow defect free silicon carbide. This compliant substrate consists of silicon/silicon dioxide with 1200 A of single crystal silicon on the top layer. We are using this compliant substrate because there is a possibility that the silicon dioxide layer and the carbonized layer will allow the silicon lattice to shrink or expand to match the lattice of the silicon carbide. This would improve the electrical properties of the film for the use of device fabrication. When trying to grow silicon carbide, we observed amorphous film. To investigate, we examined the process step by step using RHEED. RHEED data showed that each step was amorphous. We found that just by heating the substrate in the presence of hydrogen it changed the crystal structure. When heated to 1000 C for 2 minutes, RHEED showed that there was an amorphous layer on the surface. We also heated the substrate to 900 C for 2 minutes and RHEED data showed that there was a deterioration of the single crystalline structure. We assumed that the presence of oxygen was coming from the sides of the silicon dioxide layer. Therefore, we evaporated 2500 A of silicon to all four edges of the wafer to try to enclose the oxygen. When heating the evaporated wafer to 900 C the RHEED data showed single crystalline structure however at 1000 C the RHEED data showed deterioration of the single crystalline structure. We conclude that the substrate itself is temperature dependent and that the oxygen was coming from the sides of the silicon dioxide layer. We propose to evaporate more silicon on the edges of the wafer to eliminate the escape of oxygen. this will allow

  14. Growth of Quantum Wires on Step-Bunched Substrate

    SciTech Connect

    Liu, Feng

    2005-02-01

    This proposal initiates a combined theoretical and experimental multidisciplinary research effort to explore a novel approach for growing metallic and magnetic nanowires on step-bunched semiconductor and dielectric substrates, and to lay the groundwork for understanding the growth mechanisms and the electronic, electrical, and magnetic properties of metallic and magnetic nanowires. The research will focus on four topics: (1) fundamental studies of step bunching and self-organization in a strained thin film for creating step-bunched substrates. (2) Interaction between metal adatoms (Al,Cu, and Ni) and semiconductor (Si and SiGe) and dielectric (CaF2) surface steps. (3) growth and characterization of metallic and magnetic nanowires on step-bunched templates. (4) fabrication of superlattices of nanowires by growing multilayer films. We propose to attack these problems at both a microscopic and macroscopic level, using state-of-the-art theoretical and experimental techniques. Multiscale (electronic-atomic-continuum) theories will be applied to investigate growth mechanisms of nanowires: mesoscopic modeling and simulation of step flow growth of strained thin films, in particular, step bunching and self-organization will be carried out within the framework of continuum linear elastic theory; atomistic calculation of interaction between metal adatoms and semiconductor and dielectric surface steps will be done by large-scale computations using first-principles total-energy methods. In parallel, thin films and nanowires will be grown by molecular beam epitaxy (MBE), and the resultant structure and morphology will be characterized at the atomic level up to micrometer range, using a combination of different surface/interface probes, including scanning tunneling microscopy (STM, atomic resolution), atomic force microscopy (AFM, nanometer resolution), low-energy electron microscopy (LEEM, micrometer resolution), reflectance high-energy electron diffraction (RHEED), and x

  15. Cyclic stretching of soft substrates induces spreading and growth.

    PubMed

    Cui, Yidan; Hameed, Feroz M; Yang, Bo; Lee, Kyunghee; Pan, Catherine Qiurong; Park, Sungsu; Sheetz, Michael

    2015-01-01

    In the body, soft tissues often undergo cycles of stretching and relaxation that may affect cell behaviour without changing matrix rigidity. To determine whether transient forces can substitute for a rigid matrix, we stretched soft pillar arrays. Surprisingly, 1-5% cyclic stretching over a frequency range of 0.01-10 Hz caused spreading and stress fibre formation (optimum 0.1 Hz) that persisted after 4 h of stretching. Similarly, stretching increased cell growth rates on soft pillars comparative to rigid substrates. Of possible factors linked to fibroblast growth, MRTF-A (myocardin-related transcription factor-A) moved to the nucleus in 2 h of cyclic stretching and reversed on cessation; but YAP (Yes-associated protein) moved much later. Knockdown of either MRTF-A or YAP blocked stretch-dependent growth. Thus, we suggest that the repeated pulling from a soft matrix can substitute for a stiff matrix in stimulating spreading, stress fibre formation and growth. PMID:25704457

  16. Cyclic stretching of soft substrates induces spreading and growth

    PubMed Central

    Cui, Yidan; Hameed, Feroz M.; Yang, Bo; Lee, Kyunghee; Pan, Catherine Qiurong; Park, Sungsu; Sheetz, Michael

    2015-01-01

    In the body, soft tissues often undergo cycles of stretching and relaxation that may affect cell behaviour without changing matrix rigidity. To determine whether transient forces can substitute for a rigid matrix, we stretched soft pillar arrays. Surprisingly, 1–5% cyclic stretching over a frequency range of 0.01–10 Hz caused spreading and stress fibre formation (optimum 0.1 Hz) that persisted after 4 h of stretching. Similarly, stretching increased cell growth rates on soft pillars comparative to rigid substrates. Of possible factors linked to fibroblast growth, MRTF-A (myocardin-related transcription factor-A) moved to the nucleus in 2 h of cyclic stretching and reversed on cessation; but YAP (Yes-associated protein) moved much later. Knockdown of either MRTF-A or YAP blocked stretch-dependent growth. Thus, we suggest that the repeated pulling from a soft matrix can substitute for a stiff matrix in stimulating spreading, stress fibre formation and growth. PMID:25704457

  17. Epitaxial growth of germanium thin films on crystal silicon substrates by solid phase crystallization

    NASA Astrophysics Data System (ADS)

    Isomura, Masao; Kanai, Mikuri

    2015-04-01

    We have investigated the solid phase crystallization (SPC) of amorphous germanium (a-Ge) precursors on single crystalline silicon (c-Si) substrates as seed layers and successfully obtained the epitaxial growth of Ge. The n-type (100) Si substrate is most suitable for preferential growth following the substrate orientation, because the velocity of preferential growth is higher than those on the other substrates and preferential growth is completed before random nucleation. The impurity contamination in the a-Ge precursors probably enhances random nucleation. The epitaxial growth is disturbed by the impurity contamination at a relatively high SPC temperature in the intrinsic and p-type Si substrates with the (100) orientation and the n-type and intrinsic Si substrates with the (111) orientation, because the lower velocity of preferential growth allows random crystallization. Almost no epitaxial growth is observed on the p-type (111) Si substrates even when low-impurity a-Ge precursors are used.

  18. Seedless Pattern Growth of Quasi-Aligned ZnO Nanorod Arrays on Cover Glass Substrates in Solution

    NASA Astrophysics Data System (ADS)

    Ahsanulhaq, Q.; Kim, Jin Hwan; Kim, Jeong Hyun; Hahn, Y. B.

    2010-03-01

    A hybrid technique for the selective growth of ZnO nanorod arrays on wanted areas of thin cover glass substrates was developed without the use of seed layer of ZnO. This method utilizes electron-beam lithography for pattern transfer on seedless substrate, followed by solution method for the bottom-up growth of ZnO nanorod arrays on the patterned substrates. The arrays of highly crystalline ZnO nanorods having diameter of 60 ± 10 nm and length of 750 ± 50 nm were selectively grown on different shape patterns and exhibited a remarkable uniformity in terms of diameter, length, and density. The room temperature cathodluminescence measurements showed a strong ultraviolet emission at 381 nm and broad visible emission at 585-610 nm were observed in the spectrum.

  19. Connective tissue progenitor cell growth characteristics on textured substrates.

    PubMed

    Mata, Alvaro; Boehm, Cynthia; Fleischman, Aaron J; Muschler, George F; Roy, Shuvo

    2007-01-01

    Growth characteristics of human connective tissue progenitor (CTP) cells were investigated on smooth and textured substrates, which were produced using MEMS (microelectromechanical systems) fabrication technology. Human bone marrow derived cells were cultured for 9 days under conditions promoting osteoblastic differentiation on polydimethylsiloxane (PDMS) substrates comprising smooth (non-patterned) surfaces (SMOOTH), 4 different cylindrical post micro-textures (POSTS) that were 7-10 microm high and 5, 10, 20, and 40 microm diameter, respectively, and channel micro-textures (CHANNELS) with curved cross-sections that were 11 microm high, 45 microm wide, and separated by 5 microm wide ridges. Standard glass-tissue culture surfaces were used as controls. Micro-textures resulted in the modification of CTP morphology, attachment, migration, and proliferation characteristics. Specifically, cells on POSTS exhibited more contoured morphology with closely packed cytoskeletal actin microfilaments compared to the more random orientation in cells grown on SMOOTH. CTP colonies on 10 gm-diameter POSTS exhibited higher cell number than any other POSTS, and a significant increase in cell number (442%) compared to colonies on SMOOTH (71%). On CHANNELS, colonies tended to be denser (229%) than on POSTS (up to 140% on 10 microm POSTS), and significantly more so compared to those on SMOOTH (104%). PMID:18019838

  20. A propionate CoA-transferase of Ralstonia eutropha H16 with broad substrate specificity catalyzing the CoA thioester formation of various carboxylic acids.

    PubMed

    Lindenkamp, Nicole; Schürmann, Marc; Steinbüchel, Alexander

    2013-09-01

    In this study, we have investigated a propionate CoA-transferase (Pct) homologue encoded in the genome of Ralstonia eutropha H16. The corresponding gene has been cloned into the vector pET-19b to yield a histidine-tagged enzyme which was expressed in Escherichia coli BL21 (DE3). After purification, high-performance liquid chromatography/mass spectrometry (HPLC/MS) analyses revealed that the enzyme exhibits a broad substrate specificity for carboxylic acids. The formation of the corresponding CoA-thioesters of acetate using propionyl-CoA as CoA donor, and of propionate, butyrate, 3-hydroxybutyrate, 3-hydroxypropionate, crotonate, acrylate, lactate, succinate and 4-hydroxybutyrate using acetyl-CoA as CoA donor could be shown. According to the substrate specificity, the enzyme can be allocated in the family I of CoA-transferases. The apparent molecular masses as determined by gel filtration and detected by SDS polyacrylamide gel electrophoresis were 228 and 64 kDa, respectively, and point to a quaternary structure of the native enzyme (α4). The enzyme exhibited similarities in sequence and structure to the well investigated Pct of Clostridium propionicum. It does not contain the typical conserved (S)ENG motif, but the derived motif sequence EXG with glutamate 342 to be, most likely, the catalytic residue. Due to the homo-oligomeric structure and the sequence differences with the subclasses IA-C of family I CoA-transferases, a fourth subclass of family I is proposed, comprising - amongst others - the Pcts of R. eutropha H16 and C. propionicum. A markerless precise-deletion mutant R. eutropha H16∆pct was generated. The growth and accumulation behaviour of this mutant on gluconate, gluconate plus 3,3'-dithiodipropionic acid (DTDP), acetate and propionate was investigated but resulted in no observable phenotype. Both, the wild type and the mutant showed the same growth and storage behaviour with these carbon sources. It is probable that R. eutropha H16 is upregulating

  1. Co-Gradient Variation in Growth Rate and Development Time of a Broadly Distributed Butterfly

    PubMed Central

    Barton, Madeleine; Sunnucks, Paul; Norgate, Melanie; Murray, Neil; Kearney, Michael

    2014-01-01

    Widespread species often show geographic variation in thermally-sensitive traits, providing insight into how species respond to shifts in temperature through time. Such patterns may arise from phenotypic plasticity, genetic adaptation, or their interaction. In some cases, the effects of genotype and temperature may act together to reduce, or to exacerbate, phenotypic variation in fitness-related traits across varying thermal environments. We find evidence for such interactions in life-history traits of Heteronympha merope, a butterfly distributed across a broad latitudinal gradient in south-eastern Australia. We show that body size in this butterfly is negatively related to developmental temperature in the laboratory, in accordance with the temperature-size rule, but not in the field, despite very strong temperature gradients. A common garden experiment on larval thermal responses, spanning the environmental extremes of H. merope's distribution, revealed that butterflies from low latitude (warmer climate) populations have relatively fast intrinsic growth and development rates compared to those from cooler climates. These synergistic effects of genotype and temperature across the landscape (co-gradient variation) are likely to accentuate phenotypic variation in these traits, and this interaction must be accounted for when predicting how H. merope will respond to temperature change through time. These results highlight the importance of understanding how variation in life-history traits may arise in response to environmental change. Without this knowledge, we may fail to detect whether organisms are tracking environmental change, and if they are, whether it is by plasticity, adaptation or both. PMID:24743771

  2. Co-gradient variation in growth rate and development time of a broadly distributed butterfly.

    PubMed

    Barton, Madeleine; Sunnucks, Paul; Norgate, Melanie; Murray, Neil; Kearney, Michael

    2014-01-01

    Widespread species often show geographic variation in thermally-sensitive traits, providing insight into how species respond to shifts in temperature through time. Such patterns may arise from phenotypic plasticity, genetic adaptation, or their interaction. In some cases, the effects of genotype and temperature may act together to reduce, or to exacerbate, phenotypic variation in fitness-related traits across varying thermal environments. We find evidence for such interactions in life-history traits of Heteronympha merope, a butterfly distributed across a broad latitudinal gradient in south-eastern Australia. We show that body size in this butterfly is negatively related to developmental temperature in the laboratory, in accordance with the temperature-size rule, but not in the field, despite very strong temperature gradients. A common garden experiment on larval thermal responses, spanning the environmental extremes of H. merope's distribution, revealed that butterflies from low latitude (warmer climate) populations have relatively fast intrinsic growth and development rates compared to those from cooler climates. These synergistic effects of genotype and temperature across the landscape (co-gradient variation) are likely to accentuate phenotypic variation in these traits, and this interaction must be accounted for when predicting how H. merope will respond to temperature change through time. These results highlight the importance of understanding how variation in life-history traits may arise in response to environmental change. Without this knowledge, we may fail to detect whether organisms are tracking environmental change, and if they are, whether it is by plasticity, adaptation or both. PMID:24743771

  3. Growth and characterization of rutile TiO2 nanorods on various substrates with fabricated fast-response metal-semiconductor-metal UV detector based on Si substrate

    NASA Astrophysics Data System (ADS)

    Selman, Abbas M.; Hassan, Z.

    2015-07-01

    Rutile-phase titanium dioxide nanorods (NRs) were synthesized successfully on p-type silicon (Si) (1 1 1), c-plane sapphire (Al2O3), glass coated with fluorine-doped tin oxide (FTO), glass, and quartz substrates via chemical bath deposition method. All substrates were seeded with a TiO2 seed layer synthesized with a radio frequency reactive magnetron sputtering system prior to NRs growth. The effect of substrate type on structural, morphological, and optical properties of rutile TiO2 NRs was studied. X-ray diffraction, Raman spectroscopy, and field-emission scanning electron microscopy analyses showed the tetragonal rutile structure of the synthesized TiO2 NRs. Optical properties were examined with photoluminescence (PL) spectroscopy of the grown rutile NRs on all substrates, with the spectra exhibiting one strong ultraviolet emission peak intensity compared with broad visible peak. The optimal sample of rutile NRs was grown on Si substrate. Thus, a fast-response metal-semiconductor-metal ultraviolet (UV) detector was fabricated. Upon exposure to 365 nm light (2.3 mW/cm2) at 5 V bias, the device displays 2.62 × 10-5 A photocurrent, and the response and recovery times are calculated as 18.5 and 19.1 ms, respectively. These results demonstrate that the fabricated high-quality photodiode is a promising candidate as a low-cost UV photodetector for commercially integrated photoelectronic applications.

  4. Connective tissue growth factor is a substrate of ADAM28

    SciTech Connect

    Mochizuki, Satsuki; Tanaka, Rena; Shimoda, Masayuki; Onuma, Junko; Fujii, Yutaka; Jinno, Hiromitsu; Okada, Yasunori

    2010-11-26

    Research highlights: {yields} The hyper-variable region in the cysteine-rich domain of ADAM28 binds to C-terminal domain of CTGF. {yields} ADAM28 cleaves CTGF alone and CTGF in the CTGF/VEGF{sub 165} complex. {yields} CTGF digestion by ADAM28 releases biologically active VEGF{sub 165} from the complex. {yields} ADAM28, CTGF and VEGF{sub 165} are commonly co-expressed by carcinoma cells in human breast carcinoma tissues. {yields} These suggest that ADAM28 promotes VEGF{sub 165}-induced angiogenesis in the breast carcinomas by selective CTGF digestion in the CTGF/VEGF{sub 165} complex. -- Abstract: ADAM28, a member of the ADAM (a disintegrin and metalloproteinase) gene family, is over-expressed by carcinoma cells and the expression correlates with carcinoma cell proliferation and progression in human lung and breast carcinomas. However, information about substrates of ADAM28 is limited. We screened interacting molecules of ADAM28 in human lung cDNA library by yeast two-hybrid system and identified connective tissue growth factor (CTGF). Binding of CTGF to proADAM28 was demonstrated by yeast two-hybrid assay and protein binding assay. ADAM28 cleaved CTGF in dose- and time-dependent manners at the Ala{sup 181}-Tyr{sup 182} and Asp{sup 191}-Pro{sup 192} bonds in the hinge region of the molecule. ADAM28 selectively digested CTGF in the complex of CTGF and vascular endothelial growth factor{sub 165} (VEGF{sub 165}), releasing biologically active VEGF{sub 165} from the complex. RT-PCR and immunohistochemical analyses demonstrated that ADAM28, CTGF and VEGF are commonly co-expressed in the breast carcinoma tissues. These data provide the first evidence that CTGF is a novel substrate of ADAM28 and suggest that ADAM28 may promote VEGF{sub 165}-induced angiogenesis in the breast carcinomas by the CTGF digestion in the CTGF/VEGF{sub 165} complex.

  5. Methods of preparing flexible photovoltaic devices using epitaxial liftoff, and preserving the integrity of growth substrates used in epitaxial growth

    DOEpatents

    Forrest, Stephen R; Zimmerman, Jeramy; Lee, Kyusang; Shiu, Kuen-Ting

    2013-02-19

    There is disclosed methods of making photosensitive devices, such as flexible photovoltaic (PV) devices, through the use of epitaxial liftoff. Also described herein are methods of preparing flexible PV devices comprising a structure having a growth substrate, wherein the selective etching of protective layers yields a smooth growth substrate that us suitable for reuse.

  6. Methods of preparing flexible photovoltaic devices using epitaxial liftoff, and preserving the integrity of growth substrates used in epitaxial growth

    DOEpatents

    Forrest, Stephen R; Zimmerman, Jeramy; Lee, Kyusang; Shiu, Kuen-Ting

    2015-01-06

    There is disclosed methods of making photosensitive devices, such as flexible photovoltaic (PV) devices, through the use of epitaxial liftoff. Also described herein are methods of preparing flexible PV devices comprising a structure having a growth substrate, wherein the selective etching of protective layers yields a smooth growth substrate that us suitable for reuse.

  7. Direct Optical Characterization of Graphene Growth and Domains on Growth Substrates

    PubMed Central

    Jia, Chuancheng; Jiang, Jiaolong; Gan, Lin; Guo, Xuefeng

    2012-01-01

    We detailed a facile detection technique to optically characterize graphene growth and domains directly on growth substrates through a simple thermal annealing process. It was found that thermal annealing transformed the naked Cu to Cu oxides while keeping graphene and graphene-covered Cu intact. This increases the interference color contrast between Cu oxides and Cu, thus making graphene easily visible under an optical microscope. By using this simple method, we studied the factors that affect graphene nucleation and growth and achieved graphene domains with the domain size as large as ~100 μm. The concept of chemically making graphene visible is universal, as demonstrated by the fact that a solution process based on selective H2O2 oxidation has been developed to achieve the similar results in a shorter time. These techniques should be valuable for studies towards elucidating the parameters that control the grains, boundaries, structures and properties of graphene. PMID:23050091

  8. Substrate temperature changes during molecular beam epitaxy growth of GaMnAs

    SciTech Connect

    Novak, V.; Olejnik, K.; Cukr, M.; Smrcka, L.; Remes, Z.; Oswald, J.

    2007-10-15

    Our band gap spectroscopy measurements reveal a remarkably big increase of the substrate temperature during the low-temperature molecular beam epitaxy growth of GaMnAs layers. With the help of numerical simulations we explain the effect as a consequence of changing absorption/emission characteristics of the growing epilayer. We discuss possibilities for reducing the substrate temperature variations during the growth.

  9. Investigation of Drainage and Plant Growth from Nursery Container Substrate

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The amount of water and major nutrients lost through drainage from a nursery container substrate treated with different amounts of nitrogen (N), phosphate (P), and potassium (K), and potted with butterfly bush plants were investigated. The substrate was mainly composed of aged pine bark and steamed...

  10. Strawberry Production in Soilless Substrate Troughs – Plant Growth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soilless substrates made of peat moss, coconut coir, perlite, rockwool or bark are pathogen free and they have been used in strawberry production in Europe in troughs or containers. Open field strawberry production in soilless substrate is new to California growers. The objective of this study was t...

  11. In situ growth of monolayer porous gold nanoparticles film as high-performance SERS substrates

    NASA Astrophysics Data System (ADS)

    Song, Chunyuan; Wei, Yuhan; Da, Bingtao; Zhang, Haiting; Cong, Xing; Yang, Boyue; Yang, Yanjun; Wang, Lianhui

    2016-07-01

    Surface-enhanced Raman scattering (SERS) has recently received considerable attention as an ultrasensitive analytic technique. However, its wide application is limited by lack of excellent SERS-active substrates. In this work a SERS substrate with arrayed monolayer films of porous gold nanoparticles is prepared on a solid substrate by a facile, in situ and one-step growth approach. Specifically, the solid substrate was coated with a layer of dense positive charges first by layer-by-layer assembly, followed by patterned a PDMS film with arrayed wells on the substrate. Then the growth solution including chlorauric acid, cetyltrimethylammonium chloride, and ascorbic acid in a certain proportion was transferred into the wells for in situ and one-step growth of porous gold nanoparticles on the substrate. The growth time, feed ratio of the reagents, and repeat times of the in situ growth were studied systematically to obtain optimal parameters for preparing an optimal SERS substrate. The as-prepared optimal SERS substrate not only has good SERS performance with the enhancement factor up to ∼1.10 × 106, but also shows good uniformity and stability. The SERS substrate was further utilized to be ultrasensitive SERS-based chemical sensors for ppb-level detection of highly toxic dyfonate. The preliminary result indicates that the as-prepared SERS substrate has good SERS performance and shows a number of great potential applications in SERS-based sensors.

  12. Substrate specificity screening of oat (Avena sativa) seeds aminopeptidase demonstrate unusually broad tolerance in S1 pocket.

    PubMed

    Gajda, Anna D; Pawełczak, Małgorzata; Drag, Marcin

    2012-05-01

    Aminopeptidases are proteolytic enzymes that remove one amino acid at a time from N-terminus of peptidic substrates. In plants, inhibitors of aminopeptidases can find potential applications in agriculture as herbicides. In this report we have used a library of fluorogenic derivatives of natural and unnatural amino acids for substrate specificity profiling of oat (Avena sativa) aminopeptidase. Interestingly, we have found that this enzyme recognizes effectively among the natural amino acids basic residues like Arg and Lys, hydrophobic Phe, Leu and Met, but also to some extent acidic residues Asp and Glu. In the case of unnatural amino acids hydrophobic residues (hPhe and hCha) and basic hArg were preferentially recognized. PMID:22366636

  13. Substrate-bound growth of Au-Pd diblock nanowire and hybrid nanorod-plate

    NASA Astrophysics Data System (ADS)

    He, Jiating; Wang, Yawen; Fan, Zhanxi; Lam, Zhenhui; Zhang, Hua; Liu, Bin; Chen, Hongyu

    2015-04-01

    We expand the scope of the previously developed Active Surface Growth mode for growing substrate-bound ultrathin Pd (d = 4 nm) and Ag nanowires (d = 30 nm) in aqueous solution under ambient conditions. Using Au nanorods as the seeds, selective growth at the contact line between the rod and the substrate eventually leads to an attached Pd nanoplate. The unique growth mode also allows sequential growth of different materials via a single seed, giving substrate-bound Au-Pd diblock nanowires. The new abilities to use seed shape to pre-define the active sites and to apply sequential growth open windows for new pathways to hybrid nanostructures.We expand the scope of the previously developed Active Surface Growth mode for growing substrate-bound ultrathin Pd (d = 4 nm) and Ag nanowires (d = 30 nm) in aqueous solution under ambient conditions. Using Au nanorods as the seeds, selective growth at the contact line between the rod and the substrate eventually leads to an attached Pd nanoplate. The unique growth mode also allows sequential growth of different materials via a single seed, giving substrate-bound Au-Pd diblock nanowires. The new abilities to use seed shape to pre-define the active sites and to apply sequential growth open windows for new pathways to hybrid nanostructures. Electronic supplementary information (ESI) available: Supporting TEM and SEM images of control experiments with different reaction conditions and another type of diblock nanowires. See DOI: 10.1039/c5nr00361j

  14. Lattice matched semiconductor growth on crystalline metallic substrates

    DOEpatents

    Norman, Andrew G; Ptak, Aaron J; McMahon, William E

    2013-11-05

    Methods of fabricating a semiconductor layer or device and said devices are disclosed. The methods include but are not limited to providing a metal or metal alloy substrate having a crystalline surface with a known lattice parameter (a). The methods further include growing a crystalline semiconductor alloy layer on the crystalline substrate surface by coincident site lattice matched epitaxy. The semiconductor layer may be grown without any buffer layer between the alloy and the crystalline surface of the substrate. The semiconductor alloy may be prepared to have a lattice parameter (a') that is related to the lattice parameter (a). The semiconductor alloy may further be prepared to have a selected band gap.

  15. Direct Growth Properties of Graphene Layers on Sapphire Substrate by Alcohol-Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Nakamura, Atsushi; Miyasaka, Yuta; Temmyo, Jiro

    2012-04-01

    Few nanometers thick graphene layers were directly grown on a-plane (11bar 20) sapphire substrates by alcohol-chemical vapor deposition (alcohol-CVD) using ethanol as a carbon source and without any catalytic metal on the substrate surface. The growth relationship between the graphene layer and substrate was analyzed using a transmission electron microscope (TEM). The growth rate of graphene layers with different growth temperatures revealed that the Al atom act as a catalyst for synthesizing a graphitic material during the decomposition of ethanol. An optical transmittance and a sheet resistance of the graphene sheet directly grown on sapphire substrate were observed. SiO2/Si and n-6H-SiC substrates were also examined for graphene direct growth to discuss the catalytic behavior of Si atoms compared with Al atoms.

  16. Direct Image-Based Enumeration of Clostridium phytofermentans Cells on Insoluble Plant Biomass Growth Substrates.

    PubMed

    Alvelo-Maurosa, Jesús G; Lee, Scott J; Hazen, Samuel P; Leschine, Susan B

    2016-02-01

    A dual-fluorescent-dye protocol to visualize and quantify Clostridium phytofermentans ISDg (ATCC 700394) cells growing on insoluble cellulosic substrates was developed by combining calcofluor white staining of the growth substrate with cell staining using the nucleic acid dye Syto 9. Cell growth, cell substrate attachment, and fermentation product formation were investigated in cultures containing either Whatman no. 1 filter paper, wild-type Sorghum bicolor, or a reduced-lignin S. bicolor double mutant (bmr-6 bmr-12 double mutant) as the growth substrate. After 3 days of growth, cell numbers in cultures grown on filter paper as the substrate were 6.0- and 2.2-fold higher than cell numbers in cultures with wild-type sorghum and double mutant sorghum, respectively. However, cells produced more ethanol per cell when grown with either sorghum substrate than with filter paper as the substrate. Ethanol yields of cultures were significantly higher with double mutant sorghum than with wild-type sorghum or filter paper as the substrate. Moreover, ethanol production correlated with cell attachment in sorghum cultures: 90% of cells were directly attached to the double mutant sorghum substrate, while only 76% of cells were attached to wild-type sorghum substrate. With filter paper as the growth substrate, ethanol production was correlated with cell number; however, with either wild-type or mutant sorghum, ethanol production did not correlate with cell number, suggesting that only a portion of the microbial cell population was active during growth on sorghum. The dual-staining procedure described here may be used to visualize and enumerate cells directly on insoluble cellulosic substrates, enabling in-depth studies of interactions of microbes with plant biomass. PMID:26637592

  17. Direct Image-Based Enumeration of Clostridium phytofermentans Cells on Insoluble Plant Biomass Growth Substrates

    PubMed Central

    Alvelo-Maurosa, Jesús G.; Lee, Scott J.; Hazen, Samuel P.

    2015-01-01

    A dual-fluorescent-dye protocol to visualize and quantify Clostridium phytofermentans ISDg (ATCC 700394) cells growing on insoluble cellulosic substrates was developed by combining calcofluor white staining of the growth substrate with cell staining using the nucleic acid dye Syto 9. Cell growth, cell substrate attachment, and fermentation product formation were investigated in cultures containing either Whatman no. 1 filter paper, wild-type Sorghum bicolor, or a reduced-lignin S. bicolor double mutant (bmr-6 bmr-12 double mutant) as the growth substrate. After 3 days of growth, cell numbers in cultures grown on filter paper as the substrate were 6.0- and 2.2-fold higher than cell numbers in cultures with wild-type sorghum and double mutant sorghum, respectively. However, cells produced more ethanol per cell when grown with either sorghum substrate than with filter paper as the substrate. Ethanol yields of cultures were significantly higher with double mutant sorghum than with wild-type sorghum or filter paper as the substrate. Moreover, ethanol production correlated with cell attachment in sorghum cultures: 90% of cells were directly attached to the double mutant sorghum substrate, while only 76% of cells were attached to wild-type sorghum substrate. With filter paper as the growth substrate, ethanol production was correlated with cell number; however, with either wild-type or mutant sorghum, ethanol production did not correlate with cell number, suggesting that only a portion of the microbial cell population was active during growth on sorghum. The dual-staining procedure described here may be used to visualize and enumerate cells directly on insoluble cellulosic substrates, enabling in-depth studies of interactions of microbes with plant biomass. PMID:26637592

  18. Substrate Facet Effect on the Growth of Monolayer MoS2 on Au Foils.

    PubMed

    Shi, Jianping; Zhang, Xiaona; Ma, Donglin; Zhu, Jianbao; Zhang, Yu; Guo, Zhenxi; Yao, Yu; Ji, Qingqing; Song, Xiuju; Zhang, Yanshuo; Li, Cong; Liu, Zhongfan; Zhu, Wenguang; Zhang, Yanfeng

    2015-04-28

    MoS2 on polycrystalline metal substrates emerges as an intriguing growth system compared to that on insulating substrates due to its direct application as an electrocatalyst in hydrogen evolution. However, the growth is still indistinct with regard to the effects of the inevitably evolved facets. Herein, we demonstrate for the first time that the crystallography of Au foil substrates can mediate a strong effect on the growth of monolayer MoS2, where large-domain single-crystal MoS2 triangles are more preferentially evolved on Au(100) and Au(110) facets than on Au(111) at relative high growth temperatures (>680 °C). Intriguingly, this substrate effect can be weakened at a low growth temperature (∼530 °C), reflected with uniform distributions of domain size and nucleation density among the different facets. The preferential nucleation and growth on some specific Au facets are explained from the facet-dependent binding energy of MoS2 according to density functional theory calculations. In brief, this work should shed light on the effect of substrate crystallography on the synthesis of monolayer MoS2, thus paving the way for achieving batch-produced, large-domain or domain size-tunable growth through an appropriate selection of the growth substrate. PMID:25801730

  19. Growth patterns of the slime mold Physarum on a nonuniform substrate

    NASA Astrophysics Data System (ADS)

    Halvorsrud, Ragnhild; Wagner, Geri

    1998-01-01

    The Myxomycete Physarum polycephalum has been grown on nonuniform substrates, where the nutrients were confined in separated drops of agar medium. Spatial and temporal aspects of the resulting growth structures were studied by time-lapse video techniques and analyzed using image processing software. The growth process on a linear substrate of drops can be described in terms of a searching phase alternating with a feeding phase. On a linear array of drops, the Physarum advanced uniformly after an initial lag phase. On a two-dimensional drop substrate two different growth regimes could be distinguished: branched growth was observed on substrates with small drop diameters and compact growth, similar to growth on uniform substrates, was observed on substrates with larger drop diameters. The drop size is a crucial parameter that mediates characteristic plasmodial morphologies. A crossover from branched to compact growth was observed in some of the experiments. A spatial correlation function was used that could quantitatively distinguish between the different growth regimes.

  20. Substrate flexibility regulates growth and apoptosis of normal but not transformed cells

    NASA Technical Reports Server (NTRS)

    Wang, H. B.; Dembo, M.; Wang, Y. L.

    2000-01-01

    One of the hallmarks of oncogenic transformation is anchorage-independent growth (27). Here we demonstrate that responses to substrate rigidity play a major role in distinguishing the growth behavior of normal cells from that of transformed cells. We cultured normal or H-ras-transformed NIH 3T3 cells on flexible collagen-coated polyacrylamide substrates with similar chemical properties but different rigidity. Compared with cells cultured on stiff substrates, nontransformed cells on flexible substrates showed a decrease in the rate of DNA synthesis and an increase in the rate of apoptosis. These responses on flexible substrates are coupled to decreases in cell spreading area and traction forces. In contrast, transformed cells maintained their growth and apoptotic characteristics regardless of substrate flexibility. The responses in cell spreading area and traction forces to substrate flexibility were similarly diminished. Our results suggest that normal cells are capable of probing substrate rigidity and that proper mechanical feedback is required for regulating cell shape, cell growth, and survival. The loss of this response can explain the unregulated growth of transformed cells.

  1. Relationship between substrate morphology and growth of aligned carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Bartsch, Karl; Leistikow, Annette; Graff, Andreas; Leonhardt, Albrecht

    2002-10-01

    Aligned multi-walled carbon nanotubes (MWNT) were deposited by bias enhanced microwave chemical vapor deposition on oxidized silicon substrates coated with thin Co layers. The obtained tubes were characterized with respect to the structure and catalyst particle size. No significant difference in size between the particles on the substrate after a plasma treatment and the particles included in the tubes after the deposition process was observed. Two structure types (tubular and bamboo-like) were detected and reasons for their formation are discussed.

  2. High-yield growth of vertically aligned carbon nanotubes on a continuously moving substrate.

    PubMed

    Guzmán de Villoria, R; Figueredo, S L; Hart, A J; Steiner, S A; Slocum, A H; Wardle, B L

    2009-10-01

    Vertically aligned carbon nanotube (CNT) arrays are grown on a moving substrate, demonstrating continuous growth of nanoscale materials with long-range order. A cold-wall chamber with an oscillating moving platform is used to locally heat a silicon growth substrate coated with an Fe/Al2O3 catalyst film for CNT growth via chemical vapor deposition. The reactant gases are introduced over the substrate through a directed nozzle to attain high-yield CNT growth. Aligned multi-wall carbon nanotube arrays (or 'forests') with heights of approximately 1 mm are achieved at substrate speeds up to 2.4 mm s(-1). Arrays grown on moving substrates at different velocities are studied in order to identify potential physical limitations of repeatable and fast growth on a continuous basis. No significant differences are noted between static and moving growth as characterized by scanning electron microscopy and Raman spectroscopy, although overall growth height is marginally reduced at the highest substrate velocity. CNT arrays produced on moving substrates are also found to be comparable to those produced through well-characterized batch processes consistent with a base-growth mechanism. Growth parameters required for the moving furnace are found to differ only slightly from those used in a comparable batch process; thermal uniformity appears to be the critical parameter for achieving large-area uniform array growth. If the continuous-growth technology is combined with a reaction zone isolation scheme common in other types of processing (e.g., in the manufacture of carbon fibers), large-scale dense and aligned CNT arrays may be efficiently grown and harvested for numerous applications including providing interlayers for advanced composite reinforcement and improved electrical and thermal transport. PMID:19752503

  3. A thermophilic endo-1,4-β-glucanase from Talaromyces emersonii CBS394.64 with broad substrate specificity and great application potentials.

    PubMed

    Wang, Kun; Luo, Huiying; Bai, Yingguo; Shi, Pengjun; Huang, Huoqing; Xue, Xianli; Yao, Bin

    2014-08-01

    Thermophilic cellulases are of significant interest to the efficient conversion of plant cell wall polysaccharides into simple sugars. In this study, a thermophilic and thermostable endo-1,4-β-glucanase, TeEgl5A, was identified in the thermophilic fungus Talaromyces emersonii CBS394.64 and functionally expressed in Pichia pastoris. Purified recombinant TeEgl5A exhibits optimal activity at pH 4.5 and 90 °C. It is highly stable at 70 °C and over a broad pH range of 1.0-10.0, and shows strong resistance to most metal ions, sodium dodecyl sulfate (SDS), and proteases. TeEgl5A has broad substrate specificity and exhibits high activity on substrates containing β-1,4-glycosidic bonds and β-1,3-glycosidic bonds (barley β-glucan, laminarin, lichenan, CMC-Na, carob bean gum, and birchwood xylan). Under simulated mashing conditions, addition of 60 U TeEgl5A reduced more viscosity (10.0 vs.7.6 %) than 80 U of Ultraflo XL from Novozymes. These properties make TeEgl5A a good candidate for extensive application in the detergent, textile, feed, and food industries. PMID:24668246

  4. Lattice matched crystalline substrates for cubic nitride semiconductor growth

    SciTech Connect

    Norman, Andrew G; Ptak, Aaron J; McMahon, William E

    2015-02-24

    Disclosed embodiments include methods of fabricating a semiconductor layer or device and devices fabricated thereby. The methods include, but are not limited to, providing a substrate having a cubic crystalline surface with a known lattice parameter and growing a cubic crystalline group III-nitride alloy layer on the cubic crystalline substrate by coincident site lattice matched epitaxy. The cubic crystalline group III-nitride alloy may be prepared to have a lattice parameter (a') that is related to the lattice parameter of the substrate (a). The group III-nitride alloy may be a cubic crystalline In.sub.xGa.sub.yAl.sub.1-x-yN alloy. The lattice parameter of the In.sub.xGa.sub.yAl.sub.1-x-yN or other group III-nitride alloy may be related to the substrate lattice parameter by (a')= 2(a) or (a')=(a)/ 2. The semiconductor alloy may be prepared to have a selected band gap.

  5. A novel three-unit tRNA splicing endonuclease found in ultrasmall Archaea possesses broad substrate specificity

    PubMed Central

    Fujishima, Kosuke; Sugahara, Junichi; Miller, Christopher S.; Baker, Brett J.; Di Giulio, Massimo; Takesue, Kanako; Sato, Asako; Tomita, Masaru; Banfield, Jillian F.; Kanai, Akio

    2011-01-01

    tRNA splicing endonucleases, essential enzymes found in Archaea and Eukaryotes, are involved in the processing of pre-tRNA molecules. In Archaea, three types of splicing endonuclease [homotetrameric: α4, homodimeric: α2, and heterotetrameric: (αβ)2] have been identified, each representing different substrate specificity during the tRNA intron cleavage. Here, we discovered a fourth type of archaeal tRNA splicing endonuclease (ε2) in the genome of the acidophilic archaeon Candidatus Micrarchaeum acidiphilum, referred to as ARMAN-2 and its closely related species, ARMAN-1. The enzyme consists of two duplicated catalytic units and one structural unit encoded on a single gene, representing a novel three-unit architecture. Homodimeric formation was confirmed by cross-linking assay, and site-directed mutagenesis determined that the conserved L10-pocket interaction between catalytic and structural unit is necessary for the assembly. A tRNA splicing assay reveal that ε2 endonuclease cleaves both canonical and non-canonical bulge–helix–bulge motifs, similar to that of (αβ)2 endonuclease. Unlike other ARMAN and Euryarchaeota, tRNAs found in ARMAN-2 are highly disrupted by introns at various positions, which again resemble the properties of archaeal species with (αβ)2 endonuclease. Thus, the discovery of ε2 endonuclease in an archaeon deeply branched within Euryarchaeota represents a new example of the coevolution of tRNA and their processing enzymes. PMID:21880595

  6. The Prophage-encoded Hyaluronate Lyase Has Broad Substrate Specificity and Is Regulated by the N-terminal Domain*

    PubMed Central

    Singh, Sudhir Kumar; Bharati, Akhilendra Pratap; Singh, Neha; Pandey, Praveen; Joshi, Pankaj; Singh, Kavita; Mitra, Kalyan; Gayen, Jiaur R.; Sarkar, Jayanta; Akhtar, Md. Sohail

    2014-01-01

    Streptococcus equi is the causative agent of the highly contagious disease “strangles” in equines and zoonotic meningitis in human. Spreading of infection in host tissues is thought to be facilitated by the bacterial gene encoded extracellular hyaluronate lyase (HL), which degrades hyaluronan (HA), chondroitin 6-sulfate, and dermatan sulfate of the extracellular matrix). The clinical strain S. equi 4047 however, lacks a functional extracellular HL. The prophages of S. equi and other streptococci encode intracellular HLs which are reported to partially degrade HA and do not cleave any other glycosaminoglycans. The phage HLs are thus thought to play a role limited to the penetration of streptococcal HA capsules, facilitating bacterial lysogenization and not in the bacterial pathogenesis. Here we systematically looked into the structure-function relationship of S. equi 4047 phage HL. Although HA is the preferred substrate, this HL has weak activity toward chondroitin 6-sulfate and dermatan sulfate and can completely degrade all of them. Even though the catalytic triple-stranded β-helix domain of phage HL is functionally independent, its catalytic efficiency and specificity is influenced by the N-terminal domain. The phage HL also interacts with human transmembrane glycoprotein CD44. The above results suggest that the streptococci can use phage HLs to degrade glycosaminoglycans of the extracellular matrix for spreading virulence factors and toxins while utilizing the disaccharides as a nutrient source for proliferation at the site of infection. PMID:25378402

  7. Substrate Shape Effect on the Sn Whisker Growth in the Electroplating Matte Sn System

    NASA Astrophysics Data System (ADS)

    Yen, Yee-Wen; Li, Chao-Kang; Tsou, Meng-Yu; Shao, Pei-Sheng

    2011-01-01

    In this study, the substrate shape effect on the Cu substrates for Sn whisker growth has been investigated. A Cu foil, as a substrate, was bent to 90° by a universal testing machine. The matte Sn layers were electroplated on the Cu substrate under various current densities. Then, the samples were given heat treatment under various temperatures for 250 h. The results indicate that Sn whisker growth was promoted by the compression stress on the concave side and was restrained by the tension stress on the convex side. The increase of plating thickness in electroplating process offered the extensive residual stress to mitigate the Sn whisker growth. Increasing the aging temperatures also enhanced the thickness of the oxide layer. Thick oxide layers can prevent Sn whisker growth.

  8. Nonlinear estimation of Monod growth kinetic parameters from a single substrate depletion curve.

    PubMed Central

    Robinson, J A; Tiedje, J M

    1983-01-01

    Monod growth kinetic parameters were estimated by fitting sigmoidal substrate depletion data to the integrated Monod equation, using nonlinear least-squares analysis. When the initial substrate concentration was in the mixed-order region, nonlinear estimation of simulated data sets containing known measurement errors provided accurate estimates of the mu max, Ks, and Y values used to create these data. Nonlinear regression analysis of sigmoidal substrate depletion data was also evaluated for H2-limited batch growth of Desulfovibrio sp. strain G11. The integrated Monod equation can be more convenient for the estimation of growth kinetic parameters, particularly for gaseous substrates, but it must be recognized that the estimates of mu max, Ks, and Y obtained may be influenced by the growth rate history of the inoculum. PMID:6870238

  9. A thraustochytrid diacylglycerol acyltransferase 2 with broad substrate specificity strongly increases oleic acid content in engineered Arabidopsis thaliana seeds

    PubMed Central

    Zhang, Chunyu; Iskandarov, Umidjon; Cahoon, Edgar B.

    2013-01-01

    Diacylglycerol acyltransferase (DGAT) catalyses the last step in acyl-CoA-dependent triacylglycerol (TAG) biosynthesis and is an important determinant of cellular oil content and quality. In this study, a gene, designated TaDGAT2, encoding a type 2 DGAT (DGAT2)-related enzyme was identified from the oleaginous marine protist Thraustochytrium aureum. The deduced TaDGAT2 sequence contains a ~460 amino acid domain most closely related to DGAT2s from Dictyostelium sp. (45–50% identity). Recombinant TaDGAT2 restored TAG biosynthesis to the Saccharomyces cerevisiae H1246 TAG-deficient mutant, and microsomes from the complemented mutant displayed DGAT activity with C16 and C18 saturated and unsaturated fatty acyl-CoA and diacylglycerol substrates. To examine its biotechnological potential, TaDGAT2 was expressed under control of a strong seed-specific promoter in wild-type Arabidopsis thaliana and the high linoleic acid fad3fae1 mutant. In both backgrounds, little change was detected in seed oil content, but a striking increase in oleic acid content of seeds was observed. This increase was greatest in fad3fae1 seeds, where relative amounts of oleic acid increased nearly 2-fold to >50% of total fatty acids. In addition, >2-fold increase in oleic acid levels was detected in the triacylglycerol sn-2 position and in the major seed phospholipid phosphatidylcholine. These results suggest that increased seed oleic acid content mediated by TaDGAT2 is influenced in part by the fatty acid composition of host cells and occurs not by enhancing oleic acid content at the TAG sn-3 position directly but by increasing total oleic acid levels in seeds, presumably by limiting flux through phosphatidylcholine-based desaturation reactions. PMID:23814277

  10. One-dimensional crystal growth model on a square lattice substrate

    NASA Astrophysics Data System (ADS)

    Cheng, Yi; Lu, Chenxi; Yang, Bo; Tao, Xiangming; Wang, Jianfeng; Ye, Gaoxiang

    2016-08-01

    A one-dimensional crystal growth model along the preferential growth direction is established. The simulation model is performed on a square lattice substrate. First, particles are deposited homogeneously and, as a result, each of the lattice sites is occupied by one particle. In the subsequent stage, N nuclei are selected randomly on the substrate, then the growth process starts by adsorbing the surrounding particles along the preferential growth directions of the crystals. Finally, various one-dimensional crystals with different length and width form. The simulation results are in good agreement with the experimental findings.

  11. Mathematical modeling of the growth and development of the mussel Mytilus galloprovincialis on artificial substrates

    NASA Astrophysics Data System (ADS)

    Vasechkina, E. F.; Kazankova, I. I.

    2014-11-01

    A mathematical model simulating the growth and development of the mussel Mytilus galloprovincialis Lam. on artificial substrates has been constructed. The model is based on experimental data and contains mathematical descriptions of the filtration, respiration, excretion, spawning, and growth of an individual during its ontogenesis from the moment it attaches to a solid substrate to the attainment of a marketable size. The test computations have been compared to the available observation data for mussel farms.

  12. Influence of substrate material, orientation, and surface termination on GaN nanowire growth

    SciTech Connect

    Schuster, Fabian Weiszer, Saskia; Hetzl, Martin; Winnerl, Andrea; Garrido, Jose A.; Stutzmann, Martin

    2014-08-07

    In this work, we investigate the fundamental role of the substrate material, surface orientation, and termination on GaN nanowire (NW) nucleation and growth. First of all, the use of a patterned a-Si/diamond substrate confirms that NW shape and dimension are mainly determined by the applied growth conditions instead of the nature of the substrate. More important is the surface orientation as it defines growth direction and epitaxial relationship towards the GaN NWs, where both (111) and (100) surfaces yield NW growth for equivalent growth conditions. (110) substrates are found to be not suited for NW growth. Finally, the surface termination of diamond is demonstrated to survive the employed growth conditions and, therefore, to affect the nucleation of nanowires and the electronic properties of the heterointerface by its surface dipoles. This difference in nucleation is exploited as an alternative approach for selective area growth without deposition of a foreign mask material, which might also be transferable to other substrates.

  13. Broad substrate specificity of phosphotransbutyrylase from Listeria monocytogenes: A potential participant in an alternative pathway for provision of acyl CoA precursors for fatty acid biosynthesis.

    PubMed

    Sirobhushanam, Sirisha; Galva, Charitha; Sen, Suranjana; Wilkinson, Brian J; Gatto, Craig

    2016-09-01

    Listeria monocytogenes, the causative organism of the serious food-borne disease listeriosis, has a membrane abundant in branched-chain fatty acids (BCFAs). BCFAs are normally biosynthesized from branched-chain amino acids via the activity of branched chain α-keto acid dehydrogenase (Bkd), and disruption of this pathway results in reduced BCFA content in the membrane. Short branched-chain carboxylic acids (BCCAs) added as media supplements result in incorporation of BCFAs arising from the supplemented BCCAs in the membrane of L. monocytogenes bkd mutant MOR401. High concentrations of the supplements also effect similar changes in the membrane of the wild type organism with intact bkd. Such carboxylic acids clearly act as fatty acid precursors, and there must be an alternative pathway resulting in the formation of their CoA thioester derivatives. Candidates for this are the enzymes phosphotransbutyrylase (Ptb) and butyrate kinase (Buk), the products of the first two genes of the bkd operon. Ptb from L. monocytogenes exhibited broad substrate specificity, a strong preference for branched-chain substrates, a lack of activity with acetyl CoA and hexanoyl CoA, and strict chain length preference (C3-C5). Ptb catalysis involved ternary complex formation. Additionally, Ptb could utilize unnatural branched-chain substrates such as 2-ethylbutyryl CoA, albeit with lower efficiency, consistent with a potential involvement of this enzyme in the conversion of the carboxylic acid additives into CoA primers for BCFA biosynthesis. PMID:27320015

  14. Plant Growth Experiments in Zeoponic Substrates: Applications for Advanced Life Support Systems

    NASA Technical Reports Server (NTRS)

    Ming, Douglas W.; Gruener, J. E.; Henderson, K. E.; Steinberg, S. L.; Barta, D. J.; Galindo, C.; Henninger, D. L.

    2001-01-01

    A zeoponic plant-growth system is defined as the cultivation of plants in artificial soils, which have zeolites as a major component (Allen and Ming, 1995). Zeolites are crystalline, hydrated aluminosilicate minerals that have the ability to exchange constituent cations without major change of the mineral structure. Recently, zeoponic systems developed at the National Aeronautics and Space Administration (NASA) slowly release some (Allen et at., 1995) or all of the essential plant-growth nutrients (Ming et at., 1995). These systems have NH4- and K-exchanged clinoptilolite (a natural zeolite) and either natural or synthetic apatite (a calcium phosphate mineral). For the natural apatite system, Ca and P were made available to the plant by the dissolution of apatite. Potassium and NH4-N were made available by ion-exchange reactions involving Ca(2+) from apatite dissolution and K(+) and NH4(+) on zeolitic exchange sites. In addition to NH4-N, K, Ca, and P, the synthetic apatite system also supplied Mg, S, and other micronutrients during dissolution (Figure 1). The overall objective of this research task is to develop zeoponic substrates wherein all plant growth nutrients are supplied by the plant growth medium for several growth seasons with only the addition of water. The substrate is being developed for plant growth in Advanced Life Support (ALS) testbeds (i.e., BioPLEX) and microgravity plant growth experiments. Zeoponic substrates have been used for plant growth experiments on two Space Shuttle flight experiments (STS-60; STS-63; Morrow et aI., 1995). These substrates may be ideally suited for plant growth experiments on the International Space Station and applications in ALS testbeds. However, there are several issues that need to be resolved before zeoponics will be the choice substrate for plant growth experiments in space. The objective of this paper is to provide an overview on recent research directed toward the refinement of zeoponic plant growth substrates.

  15. Effects of substrate orientation on the growth of InSb nanostructures by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Chou, C. Y.; Torfi, A.; Pei, C.; Wang, W. I.

    2016-05-01

    In this work, the effects of substrate orientation on InSb quantum structure growth by molecular beam epitaxy (MBE) are presented. Motivated by the observation that (411) evolves naturally as a stable facet during MBE crystal growth, comparison studies have been carried out to investigate the effects of the crystal orientation of the underlying GaSb substrate on the growth of InSb by MBE. By depositing InSb on a number of different substrate orientations, namely: (100), (311), (411), and (511), a higher nanostructure density was observed on the (411) surface compared with the other orientations. This result suggests that the (411) orientation presents a superior surface in MBE growth to develop a super-flat GaSb buffer surface, naturally favorable for nanostructure growth.

  16. Ammothermal Growth of Gan Substrates For Leds: High-Pressure Ammonothermal Process for Bulk Gallium Nitride Crystal Growth for Energy Efficient Commercially Competitive Lighting

    SciTech Connect

    2011-01-01

    Broad Funding Opportunity Announcement Project: The new GaN crystal growth method is adapted from that used to grow quartz crystals, which are very inexpensive and represent the second-largest market for single crystals for electronic applications (after silicon). More extreme conditions are required to grow GaN crystals and therefore a new type of chemical growth chamber was invented that is suitable for large-scale manufacturing. A new process was developed that grows GaN crystals at a rate that is more than double that of current processes. The new technology will enable GaN substrates with best-in-world quality at lowest-in-world prices, which in turn will enable new generations of white LEDs, lasers for full-color displays, and high-performance power electronics.

  17. New Crystal-Growth Methods for Producing Lattice-Matched Substrates for High-Temperature Superconductors

    SciTech Connect

    Boatner, L.A.

    2008-06-24

    This effort addressed the technical problem of identifying and growing, on a commercial scale, suitable single-crystal substrates for the subsequent deposition of epitaxial thin films of high temperature semiconductors such as GaN/AlN. The lack of suitable lattice-matched substrate materials was one of the major problem areas in the development of semiconducting devices for use at elevated temperatures as well as practical opto-electronic devices based on Al- and GaN technology. Such lattice-matched substrates are necessary in order to reduce or eliminate high concentrations of defects and dislocations in GaN/AlN and related epitaxial thin films. This effort concentrated, in particular, on the growth of single crystals of ZnO for substrate applications and it built on previous ORNL experience in the chemical vapor transport growth of large single crystals of zinc oxide. This combined expertise in the substrate growth area was further complemented by the ability of G. Eres and his collaborators to deposit thin films of GaN on the subject substrates and the overall ORNL capability for characterizing the quality of such films. The research effort consisted of research on the growth of two candidate substrate materials in conjunction with concurrent research on the growth and characterization of GaN films, i.e. the effort combined bulk crystal growth capabilities in the area of substrate production at both ORNL and the industrial partner, Commercial Crystal Growth Laboratories (CCL), Naples, Florida, with the novel thin-film deposition techniques previously developed in the ORNL SSD.

  18. Acclimation of Foliar Antioxidant Systems to Growth Irradiance in Three Broad-Leaved Evergreen Species.

    PubMed Central

    Grace, S. C.; Logan, B. A.

    1996-01-01

    The protective role of leaf antioxidant systems in the mechanism of plant acclimation to growth irradiance was studied in Vinca major, Schefflera arboricola, and Mahonia repens, which were grown for several months at 20, 100, and 1200 [mu]mol photons m-2 s-1. As growth irradiance increased, several constituents of the "Mehler-peroxidase" pathway also increased: superoxide dismutase, ascorbate peroxidase, glutathione reductase, ascorbate, and glutathione. This occurred concomitantly with increases in the xanthophyll cycle pool size and in the rate of nonphotochemical energy dissipation under steady-state conditions. There was no evidence for photosystem II overreduction in plants grown at high irradiance, although the reduction state of the stromal NADP pool, estimated from measurements of NADP-malate dehydrogenase activity, was greater than 60% in V. major and S. arboricola. Ascorbate, which removes reactive O2 species generated by O2 photoreduction in the chloroplast and serves as a reductant for the conversion of the xanthophyll cycle pigments to the de-epoxidized forms A plus Z, generally exhibited the most dramatic increases in response to growth irradiance. We conclude from these results that O2 photoreduction occurs at higher rates in leaves acclimated to high irradiance, despite increases in xanthophyll cycle-dependent energy dissipation, and that increases in leaf antioxidants protect against this potential oxidative stress. PMID:12226469

  19. Growth and characterization of GaP nanowires on Si substrate

    NASA Astrophysics Data System (ADS)

    Zhang, G.; Tateno, K.; Sogawa, T.; Nakano, H.

    2008-01-01

    The integration of III-V semiconductor materials with Si technology is of great interest for optoelectronic integration circuits. We have studied the growth and structural aspects of GaP nanowires (NWs) grown on Si substrate in a metalorganic vapor phase epitaxy system. Au colloid particles dispersed on Si substrate were used as catalysts to conduct the NW growth. The growth temperature considerably affected the growth rate and shape of GaP NWs. The growth rate showed a maximum value of 14.69nm/s at 480°C. When growth temperature increased the radial growth on NW sides was enhanced and the NWs therefore exhibited a tapering shape. GaP NWs with a uniform diameter could be grown at a growth temperature as low as 420°C using a two-temperature process. The NW diameter could be well controlled by using size-selective Au colloid particles. The growth rate dependence showed that the thin NWs grew more slowly than thick ones and the V/III source ratio had a significant effect on the growth rate dependence. An analysis of the GaP/Si interface by transmission electron microscopy indicated that the NWs were epitaxially grown on the Si(111) substrate. Based on these experimental results, the growth mechanism of the GaP NWs on Si was discussed.

  20. Relationship between planar GaAs nanowire growth direction and substrate orientation

    NASA Astrophysics Data System (ADS)

    Dowdy, Ryan S.; Walko, Donald A.; Li, Xiuling

    2013-01-01

    Planar GaAs nanowires are epitaxially grown on GaAs substrates of various orientations, via the Au-catalyzed vapor-liquid-solid mechanism using metal organic chemical vapor deposition. The nanowire geometry and growth direction are examined using scanning electron microscopy and x-ray microdiffraction. A hypothesis relating the planar nanowire growth direction to the surface projections of <111> B crystal directions is proposed. GaAs planar nanowire growth on vicinal substrates is performed to test this hypothesis. Good agreement between the experimental results and the projection model is found.

  1. Modeling carbon nanotube growth on the catalyst-substrate surface subjected to reactive plasma [

    SciTech Connect

    Tewari, Aarti; Sharma, Suresh C.

    2014-06-15

    The paper presents a theoretical model to study the growth of the carbon nanotube (CNT) on the catalyst substrate surface subjected to reactive plasma. The charging rate of the CNT, kinetics of electron, ions and neutral atoms, the growth rate of the CNT because of diffusion and accretion of ions on the catalyst nanoparticle inclusion of the issue of the plasma sheath is undertaken in the present model. Numerical calculations on the effect of ion density and temperature and the substrate bias on the growth of the CNT have been carried out for typical glow discharge plasma parameters. It is found that the height of CNT increases with the ion density of carbon ions and radius of CNT decreases with hydrogen ion density. The substrate bias also affects the growth rate of the CNT. The field emission characteristics from the CNTs can be analyzed from the results obtained.

  2. Enhanced Graphene Mechanical Properties through Ultrasmooth Copper Growth Substrates.

    PubMed

    Griep, Mark H; Sandoz-Rosado, Emil; Tumlin, Travis M; Wetzel, Eric

    2016-03-01

    The combination of extraordinary strength and stiffness in conjunction with exceptional electronic and thermal properties in lightweight two-dimensional materials has propelled graphene research toward a wide array of applications including flexible electronics and functional structural components. Tailoring graphene's properties toward a selected application requires precise control of the atomic layer growth process, transfer, and postprocessing procedures. To date, the mechanical properties of graphene are largely controlled through postprocess defect engineering techniques. In this work, we demonstrate the role of varied catalytic surface morphologies on the tailorability of subsequent graphene film quality and breaking strength, providing a mechanism to tailor the physical, electrical, and mechanical properties at the growth stage. A new surface planarization methodology that results in over a 99% reduction in Cu surface roughness allows for smoothness parameters beyond that reported to date in literature and clearly demonstrates the role of Cu smoothness toward a decrease in the formation of bilayer graphene defects, altered domain sizes, monolayer graphene sheet resistance values down to 120 Ω/□ and a 78% improvement in breaking strength. The combined electrical and mechanical enhancements achieved through this methodology allows for the direct growth of application quality flexible transparent conductive films with monolayer graphene. PMID:26882091

  3. Characterization of an Alkaline Family I.4 Lipase from Bacillus sp. W130-35 Isolated from a Tidal Mud Flat with Broad Substrate Specificity.

    PubMed

    Kim, Hee Jung; Jung, Won Kyeong; Lee, Hyun Woo; Yoo, Wanki; Kim, T Doohun; Kim, Hoon

    2015-12-28

    A gene encoding lipolytic enzyme, lip7-3, was isolated from Bacillus sp. W130-35 isolated from a tidal mud flat. The gene encoded a protein of 215 amino acids with a signal peptide composed of 34 amino acid residues. Lip7-3 belonged to the family I.4 lipase and showed its maximal activity at pH 9.0 and 60°C. Its activity increased in the presence of 30% methanol and, remarkably, increased as well to 154.6% in the presence of Ca(2+). Lip7-3 preferred pnitrophenyl octanoate (C8) as a substrate and exhibited broad specificity for short- to longchain fatty acid esters. Additionally, Lip7-3 showed a low degree of enantioselectivity for an S-enantiomer (e.g., (S)-methyl-3-hydroxy-2-methylpropionate). It efficiently hydrolyzed glyceryl tributyrate, but did not hydrolyze glyceryl trioleate, fish oil, or olive oil. Its substrate specificity and activation by the solvent might offer a merit to the biotechnological enzyme applications like transesterification in the production of biodiesel. PMID:26370800

  4. Kinetic modeling of Moorella thermoacetica growth on single and dual-substrate systems.

    PubMed

    Schmitt, Elliott; Bura, Renata; Gustafson, Rick; Ehsanipour, Mandana

    2016-10-01

    Acetic acid is an important chemical raw material that can be produced directly from sugars in lignocellulosic biomass. Development of kinetic models that capture the bioconversion dynamics of multiple sugar systems will be critical to optimization and process control in future lignocellulosic biorefinery processes. In this work, a kinetic model was developed for the single- and dual-substrate conversion of xylose and glucose to acetic acid using the acetogen Moorella thermoacetica. Batch fermentations were performed experimentally at 20 g L(-1) total sugar concentration using synthetic glucose, xylose, and a mixture of glucose and xylose at a 1:1 ratio. The product yield, calculated as total product formed divided by total sugars consumed, was 79.2, 69.9, and 69.7 % for conversion of glucose, xylose, and a mixture of glucose and xylose (1:1 ratio), respectively. During dual-substrate fermentation, M. thermoacetica demonstrated diauxic growth where xylose (the preferred substrate) was almost entirely consumed before consumption of glucose began. Kinetic parameters were similar for the single-substrate fermentations, and a strong linear correlation was determined between the maximum specific growth rate μ max and substrate inhibition constant, K s . Parameters estimated for the dual-substrate system demonstrated changes in the specific growth rate of both xylose and glucose consumption. In particular, the maximum growth rate related to glucose tripled compared to the single-substrate system. Kinetic growth is affected when multiple substrates are present in a fermentation system, and models should be developed to reflect these features. PMID:27262717

  5. Growth evolution of AlN films on silicon (111) substrates by pulsed laser deposition

    SciTech Connect

    Wang, Haiyan; Wang, Wenliang; Yang, Weijia; Zhou, Shizhong; Lin, Zhiting; Li, Guoqiang

    2015-05-14

    AlN films with various thicknesses have been grown on Si(111) substrates by pulsed laser deposition (PLD). The surface morphology and structural property of the as-grown AlN films have been investigated carefully to comprehensively explore the epitaxial behavior. The ∼2 nm-thick AlN film initially grown on Si substrate exhibits an atomically flat surface with a root-mean-square surface roughness of 0.23 nm. As the thickness increases, AlN grains gradually grow larger, causing a relatively rough surface. The surface morphology of ∼120 nm-thick AlN film indicates that AlN islands coalesce together and eventually form AlN layers. The decreasing growth rate from 240 to 180 nm/h is a direct evidence that the growth mode of AlN films grown on Si substrates by PLD changes from the islands growth to the layer growth. The evolution of AlN films throughout the growth is studied deeply, and its corresponding growth mechanism is hence proposed. These results are instructional for the growth of high-quality nitride films on Si substrates by PLD, and of great interest for the fabrication of AlN-based devices.

  6. Increased monolayer domain size and patterned growth of tungsten disulfide through controlling surface energy of substrates

    NASA Astrophysics Data System (ADS)

    Godin, Kyle; Kang, Kyungnam; Fu, Shichen; Yang, Eui-Hyeok

    2016-08-01

    We report a surface energy-controlled low-pressure chemical vapor deposition growth of WS2 monolayers on SiO2 using pre-growth oxygen plasma treatment of substrates, facilitating increased monolayer surface coverage and patterned growth without lithography. Oxygen plasma treatment of the substrate caused an increase in the average domain size of WS2 monolayers by 78%  ±  2% while having a slight reduction in nucleation density, which translates to increased monolayer surface coverage. This substrate effect on growth was exploited to grow patterned WS2 monolayers by patterned plasma treatment on patterned substrates and by patterned source material with resolutions less than 10 µm. Contact angle-based surface energy measurements revealed a dramatic increase in polar surface energy. A growth model was proposed with lowered activation energies for growth and increased surface diffusion length consistent with the range of results observed. WS2 samples grown with and without oxygen plasma were similar high quality monolayers verified through transmission electron microscopy, selected area electron diffraction, atomic force microscopy, Raman, and photoluminescence measurements. This technique enables the production of large-grain size, patterned WS2 without a post-growth lithography process, thereby providing clean surfaces for device applications.

  7. Direct Growth of Graphene Film on Germanium Substrate

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Zhang, Miao; Zhu, Yun; Ding, Guqiao; Jiang, Da; Guo, Qinglei; Liu, Su; Xie, Xiaoming; Chu, Paul K.; di, Zengfeng; Wang, Xi

    2013-08-01

    Graphene has been predicted to play a role in post-silicon electronics due to the extraordinary carrier mobility. Chemical vapor deposition of graphene on transition metals has been considered as a major step towards commercial realization of graphene. However, fabrication based on transition metals involves an inevitable transfer step which can be as complicated as the deposition of graphene itself. By ambient-pressure chemical vapor deposition, we demonstrate large-scale and uniform depositon of high-quality graphene directly on a Ge substrate which is wafer scale and has been considered to replace conventional Si for the next generation of high-performance metal-oxide-semiconductor field-effect transistors (MOSFETs). The immiscible Ge-C system under equilibrium conditions dictates graphene depositon on Ge via a self-limiting and surface-mediated process rather than a precipitation process as observed from other metals with high carbon solubility. Our technique is compatible with modern microelectronics technology thus allowing integration with high-volume production of complementary metal-oxide-semiconductors (CMOS).

  8. Direct Growth of Graphene Film on Germanium Substrate

    PubMed Central

    Wang, Gang; Zhang, Miao; Zhu, Yun; Ding, Guqiao; Jiang, Da; Guo, Qinglei; Liu, Su; Xie, Xiaoming; Chu, Paul K.; Di, Zengfeng; Wang, Xi

    2013-01-01

    Graphene has been predicted to play a role in post-silicon electronics due to the extraordinary carrier mobility. Chemical vapor deposition of graphene on transition metals has been considered as a major step towards commercial realization of graphene. However, fabrication based on transition metals involves an inevitable transfer step which can be as complicated as the deposition of graphene itself. By ambient-pressure chemical vapor deposition, we demonstrate large-scale and uniform depositon of high-quality graphene directly on a Ge substrate which is wafer scale and has been considered to replace conventional Si for the next generation of high-performance metal-oxide-semiconductor field-effect transistors (MOSFETs). The immiscible Ge-C system under equilibrium conditions dictates graphene depositon on Ge via a self-limiting and surface-mediated process rather than a precipitation process as observed from other metals with high carbon solubility. Our technique is compatible with modern microelectronics technology thus allowing integration with high-volume production of complementary metal-oxide-semiconductors (CMOS). PMID:23955352

  9. Direct growth of graphene film on germanium substrate.

    PubMed

    Wang, Gang; Zhang, Miao; Zhu, Yun; Ding, Guqiao; Jiang, Da; Guo, Qinglei; Liu, Su; Xie, Xiaoming; Chu, Paul K; Di, Zengfeng; Wang, Xi

    2013-01-01

    Graphene has been predicted to play a role in post-silicon electronics due to the extraordinary carrier mobility. Chemical vapor deposition of graphene on transition metals has been considered as a major step towards commercial realization of graphene. However, fabrication based on transition metals involves an inevitable transfer step which can be as complicated as the deposition of graphene itself. By ambient-pressure chemical vapor deposition, we demonstrate large-scale and uniform depositon of high-quality graphene directly on a Ge substrate which is wafer scale and has been considered to replace conventional Si for the next generation of high-performance metal-oxide-semiconductor field-effect transistors (MOSFETs). The immiscible Ge-C system under equilibrium conditions dictates graphene depositon on Ge via a self-limiting and surface-mediated process rather than a precipitation process as observed from other metals with high carbon solubility. Our technique is compatible with modern microelectronics technology thus allowing integration with high-volume production of complementary metal-oxide-semiconductors (CMOS). PMID:23955352

  10. Initial growth behavior of Cu(In,Ga)Se 2 on molybdenum substrates

    NASA Astrophysics Data System (ADS)

    Schlenker, T.; Schock, H. W.; Werner, J. H.

    2003-11-01

    We study the initial growth stage of Cu(In,Ga)Se 2 on Mo films on glass, as the typical back contact for Cu(In,Ga)Se 2 solar cells. A thermal evaporation process deposits Cu(In,Ga)Se 2 of nominal 3 nm thickness at different rates R and substrate temperatures TSub. An ultrahigh resolution scanning electron microscope serves to visualize the nucleation behavior. The deposited Cu(In,Ga)Se 2 forms three-dimensional isolated nuclei, known as Volmer-Weber growth mode. Deposition rate R and substrate temperature TSub control the areal density n of the Cu(In,Ga)Se 2 nuclei. For the growth on polycrystalline Mo substrates fabricated by sputter process, we observe a power law dependence between the island density n and the deposition rate R, and an exponential dependence of the island density n on substrate temperature TSub. The theory of homogeneous nucleation explains the Cu(In,Ga)Se 2 cluster formation on sputtered Mo substrates and the dependence of the island density on the growth conditions. On electron gun evaporated molybdenum, the cluster growth shows a similar behavior, but the nucleation mechanism deviates from the model of homogeneous nucleation and strong island density fluctuations occur.

  11. Effect of 'Azotobacter' Bioinoculant on the Growth and Substrate Utilization Potential of Pleurotus eous Seed Spawn

    PubMed Central

    Parani, K.; Pothiraj, C.; Rajapandy, V.

    2005-01-01

    We investigated the effect of nitrogen fixing Azotobacter bioinoculant on the mycelial growth and the rate of substrate utilization by Pleurotus eous. The synergistic or antagonistic role of the microorganism during dual culturing with the mushroom or the competitor molds Trichoderma viride, and Trichoderma reesi was studied. Azotobacter was inhibitory to the molds, which are competitive to the mushroom in the seed spawn substrate, but was synergistic towards the mushroom. The growth, substrate utilization potential as total nitrogen content and cellulase enzyme activities of the mushroom in the seed spawn substrate were also enhanced in the presence of the bioinoculant at lower inoculum concentrations, upto 5 ml broth culture per spawn bottle. PMID:24049469

  12. Live substrate positively affects root growth and stolon direction in the woodland strawberry, Fragaria vesca

    PubMed Central

    Waters, Erica M.; Watson, Maxine A.

    2015-01-01

    Studies of clonal plant foraging generally focus on growth responses to patch quality once rooted. Here we explore the possibility of true plant foraging; the ability to detect and respond to patch resource status prior to rooting. Two greenhouse experiments were conducted to investigate the morphological changes that occur when individual daughter ramets of Fragaria vesca (woodland strawberry) were exposed to air above live (non-sterilized) or dead (sterilized) substrates. Contact between daughter ramets and substrate was prohibited. Daughter ramet root biomass was significantly larger over live versus dead substrate. Root:shoot ratio also increased over live substrate, a morphological response we interpret as indicative of active nutrient foraging. Daughter ramet root biomass was positively correlated with mother ramet size over live but not dead substrate. Given the choice between a live versus a dead substrate, primary stolons extended preferentially toward live substrates. We conclude that exposure to live substrate drives positive nutrient foraging responses in F. vesca. We propose that volatiles emitted from the substrates might be effecting the morphological changes that occur during true nutrient foraging. PMID:26483826

  13. Carbon nanotube growth from metallic nanoparticles deposited by pulsed-laser deposition on different substrates

    NASA Astrophysics Data System (ADS)

    Gaillard, Mireille; Boulmer-Leborgne, Chantal; Semmar, Nadjib; Millon, Éric; Petit, Agnès

    2012-09-01

    Carbon nanotubes carpets were grown by RF plasma enhanced chemical vapor deposition on various substrates coated by Fe and Ni transition metals that act as catalyst. C2H2 gas was used for the carbon source. The results show that carbon nanotubes CNT can be grown on Si3N4/Si and SiO2/Si substrates only with an Fe catalyst. They are typically formed by multi-walled graphene layers, and can be obtained for a temperature as low as 550 °C. Nanotubes grown on TiN/SiO2/Si substrate from Fe or Ni catalysts present bamboo-like nanostructures and are obtained for particular experimental conditions. This study demonstrates substrate-to-catalyst effect on the CNT growth and their microstructures indicating that the adhesion force of nanoparticles on substrates is a main parameter. Catalyst particles are spherical and several tens of nm in diameter (weak adhesion strength) when deposited onto SiO2/Si or Si3N4/Si, the tip growth mode of nanotube is favored. On TiN/SiO2/Si substrate, particles are larger (large adhesion strength) and CNT growth is no more in tip mode, bamboo-like structures are obtained. When an Fe-Ni catalyst multilayer has been deposited onto the different substrates, carbon nanotube microstructures show multi-walled graphene parallel layers on Si3N4/Si and SiO2/Si insulating substrates, and bamboo-like microstructures on TiN/SiO2/Si conductor substrate.

  14. Direct observation of graphene growth and associated copper substrate dynamics by in situ scanning electron microscopy.

    PubMed

    Wang, Zhu-Jun; Weinberg, Gisela; Zhang, Qiang; Lunkenbein, Thomas; Klein-Hoffmann, Achim; Kurnatowska, Michalina; Plodinec, Milivoj; Li, Qing; Chi, Lifeng; Schloegl, R; Willinger, Marc-Georg

    2015-02-24

    This work highlights the importance of in situ experiments for an improved understanding of graphene growth on copper via metal-catalyzed chemical vapor deposition (CVD). Graphene growth inside the chamber of a modified environmental scanning electron microscope under relevant low-pressure CVD conditions allows visualizing structural dynamics of the active catalyst simultaneously with graphene nucleation and growth in an unparalleled way. It enables the observation of a complete CVD process from substrate annealing through graphene nucleation and growth and, finally, substrate cooling in real time and nanometer-scale resolution without the need of sample transfer. A strong dependence of surface dynamics such as sublimation and surface premelting on grain orientation is demonstrated, and the influence of substrate dynamics on graphene nucleation and growth is presented. Insights on the growth mechanism are provided by a simultaneous observation of the growth front propagation and nucleation rate. Furthermore, the role of trace amounts of oxygen during growth is discussed and related to graphene-induced surface reconstructions during cooling. Above all, this work demonstrates the potential of the method for in situ studies of surface dynamics on active metal catalysts. PMID:25584770

  15. Amorphous carbon film growth on Si: Correlation between stress and generation of defects into the substrate

    SciTech Connect

    Brusa, R.S.; Macchi, C.; Mariazzi, S.; Karwasz, G.P.; Laidani, N.; Bartali, R.; Anderle, M.

    2005-05-30

    Amorphous carbon films of several thicknesses were prepared by graphite sputtering on crystalline silicon substrate. The samples were depth profiled with positron annihilation spectroscopy for open-volume measurements and characterized for their residual internal stress. It was found that after film growth the substrate presents vacancy-like defects decorated by oxygen in a layer extending in the substrate by several tens of nanometers beyond the film/Si interface. The width of the defected layer and the decoration of vacancy-like defects are directly and inversely proportional to the measured intensity of the residual stress, respectively. These findings indicate the existence of a relaxation mechanism of the stress in the films that involves deeply the substrate. The decorated vacancy-like defects are suggested to be bounded to dislocations induced in the substrate by the stress relaxation.

  16. LmbE proteins from Bacillus cereus are de-N-acetylases with broad substrate specificity and are highly similar to proteins in Bacillus anthracis

    SciTech Connect

    Deli, Alexandra; Koutsioulis, Dimitrios; Fadouloglou, Vasiliki E.; Spiliotopoulou, Panagiota; Balomenou, Stavroula; Arnaouteli, Sofia; Tzanodaskalaki, Maria; Mavromatis, Konstantinos; Kokkinidis, Michalis; Bouriotis, Vassilis

    2010-05-19

    The genomes of Bacillus cereus and its closest relative Bacillus anthracis each contain two LmbE protein family homologs: BC1534 (BA1557) and BC3461 (BA3524). Only a few members of this family have been biochemically characterized including N-acetylglucosaminylphosphatidyl inositol (GlcNAc-PI), 1-D-myo-inosityl-2-acetamido-2-deoxy-α-D-glucopyranoside (GlcNAc-Ins), N,N'-diacetylchitobiose (GlcNAc2) and lipoglycopeptide antibiotic de-N-acetylases. All these enzymes share a common feature in that they de-N-acetylate the N-acetyl-D-glucosamine (GlcNAc) moiety of their substrates. The bc1534 gene has previously been cloned and expressed in Escherichia coli. The recombinant enzyme was purified and its 3D structure determined. In this study, the bc3461 gene from B. cereus ATCC14579 was cloned and expressed in E. coli. The recombinant enzymes BC1534 (EC 3.5.1.-) and BC3461 were biochemically characterized. The enzymes have different molecular masses, pH and temperature optima and broad substrate specificity, de-N-acetylating GlcNAc and N-acetylchito-oligomers (GlcNAc2, GlcNAc3 and GlcNAc4), as well as GlcNAc-1P, N-acetyl-d-glucosamine-1 phosphate; GlcNAc-6P, N-acetyl-d-glucosamine-6 phosphate; GalNAc, N-acetyl-d-galactosamine; ManNAc, N-acetyl-d-mannosamine; UDP-GlcNAc, uridine 5'-diphosphate N-acetyl-d-glucosamine. However, the enzymes were not active on radiolabeled glycol chitin, peptidoglycan from B. cereus, N-acetyl-d-glucosaminyl-(β-1,4)-N-acetylmuramyl-l-alanyl-d-isoglutamine (GMDP) or N-acetyl-d-GlcN-Nα1-6-d-myo-inositol-1-HPO4-octadecyl (GlcNAc-I-P-C18). Kinetic analysis of the activity of BC1534 and BC3461 on GlcNAc and GlcNAc2 revealed that GlcNAc2 is the favored substrate for both native enzymes. Based on the recently determined crystal structure of BC1534, a mutational analysis identified functional key residues, highlighting their

  17. Comparative analysis of some models of gene regulation in mixed-substrate microbial growth.

    PubMed

    Narang, Atul

    2006-09-21

    Mixed-substrate microbial growth is of fundamental interest in microbiology and bioengineering. Several mathematical models have been developed to account for the genetic regulation of such systems, especially those resulting in diauxic growth. In this work, we compare the dynamics of three such models (Narang, 1998a. The dynamical analogy between microbial growth on mixtures of substrates and population growth of competing species. Biotechnol. Bioeng. 59, 116-121; Thattai and Shraiman, 2003. Metabolic switching in the sugar phosphotransferase system of Escherichia coli. Biophys. J. 85(2), 744-754; Brandt et al., 2004. Modelling microbial adaptation to changing availability of substrates. Water Res. 38, 1004-1013). We show that these models are dynamically similar--the initial motion of the inducible enzymes in all the models is described by the Lotka-Volterra equations for competing species. In particular, the prediction of diauxic growth corresponds to "extinction" of one of the enzymes during the first few hours of growth. The dynamic similarity occurs because in all the models, the inducible enzymes possess properties characteristic of competing species: they are required for their own synthesis, and they inhibit each other. Despite this dynamic similarity, the models vary with respect to the range of dynamics captured. The Brandt et al. model always predicts the diauxic growth pattern, whereas the remaining two models exhibit both diauxic and non-diauxic growth patterns. The models also differ with respect to the mechanisms that generate the mutual inhibition between the enzymes. In the Narang model, mutual inhibition occurs because the enzymes for each substrate enhance the dilution of the enzymes for the other substrate. The Brandt et al. model superimposes upon this dilution effect an additional mechanism of mutual inhibition. In the Thattai and Shraiman model, the mutual inhibition is entirely due to competition for the phosphoryl groups. For quantitative

  18. Kinetic characteristics and modelling of growth and substrate removal by Alcaligenes faecalis strain NR.

    PubMed

    Chen, Jie; Zhao, Bin; An, Qiang; Wang, Xia; Zhang, Yi Xin

    2016-04-01

    Alcaligenes faecalis strain NR has the capability of simultaneous ammonium and organic carbon removal under sole aerobic conditions. The growth and substrate removal characteristics of A. faecalis strain NR were studied and appropriate kinetic models were developed. The maximum substrate removal rate of NH4 (+)-N and TOC were determined as 2.27 mg NH4 (+)-N/L/h and 30.00 mg TOC/L/h, respectively with initial NH4 (+)-N = 80 mg/L and TOC = 800 mg/L. Single-substrate models and double-substrate models based on Monod, Contois, Moser and Teissier were employed to describe the bioprocess kinetic coefficients. As a result, two double-substrate models, Teissier-Contois and Contois-Contois, were considered to be appropriate to model growth kinetics with both NH4 (+)-N and TOC as limiting substrates. The kinetic constants of maximum growth rate (μ max) and half-saturation constant (K S and B S) were obtained by solving multiple equations with regression. This work can be used to further understand and predict the performance of heterotrophic nitrifiers, and thus provides specific guidance of these functional strains in practical wastewater treatment process. PMID:26796583

  19. Chemical vapor deposition growth of graphene on copper substrates: current trends

    NASA Astrophysics Data System (ADS)

    Antonova, I. V.

    2013-10-01

    The most interesting recent developments and trends in graphene growth technologies on copper substrates are reviewed. An analysis is given of how the substrate preparation quality and other process parameters affect the properties of films obtained at different pressures and temperatures on a copper foil and lower-thickness copper films. The fabrication methods and properties of large single-crystal graphene domains are discussed together with technologies that do not require graphene film transfer onto a dielectric substrate. Another important possible approach, that of graphene growing laterally from specially formed few-layer graphene and carbon-containing seeds or metal catalysts, is also discussed.

  20. Improved GaSb-based quantum well laser performance through metamorphic growth on GaAs substrates

    SciTech Connect

    Richardson, Christopher J. K. He, Lei; Apiratikul, Paveen; Siwak, Nathan P.; Leavitt, Richard P.

    2015-03-09

    The promise of the metamorphic growth paradigm is to enable design freedom of the substrate selection criteria beyond current choices that are limited by lattice matching requirements. A demonstration of this emerging degree of freedom is reported here by directly comparing identical laser structures grown both pseudomorphically on a GaSb substrate and metamorphically on a GaAs substrate. Improved thermal performance of the metamorphic laser material enables a higher output power before thermal roll-over begins. These performance gains are demonstrated in minimally processed gain-guided broad-area type-I lasers emitting close to 2-μm wavelengths and mounted p-side up. Continuous wave measurements at room temperature yield a T{sub 0} of 145 K and peak output power of 192 mW from metamorphic lasers, compared to a T{sub 0} of 96 K and peak output power of 164 mW from identical lasers grown pseudomorphically on GaSb.

  1. Growth of carbon nanotubes on stainless steel substrates by DC-PECVD

    NASA Astrophysics Data System (ADS)

    Duy, Dao Quang; Kim, Hyun Suk; Yoon, Dang Mo; Lee, Kang Jae; Ha, Jung Woong; Hwang, Yong Gyoo; Lee, Choong Hun; Cong, Bach Thanh

    2009-11-01

    We report on the fabrication of carbon nanotubes (CNTs) on Ni-coated stainless steel (SUS) substrates by using dc plasma enhanced chemical vapor deposition. The synthesized CNTs have the diameter of about 30 nm and the length of about 1.2 μm. To verify the effects of SUS substrates on the growth of CNTs, CNTs had also been grown on Ni-coated Si substrates. CNTs grown on the SUS substrates were more uniform compared with those grown on the Si substrates. Field emission properties of the CNT films were measured in the diode configuration, and the turn-on electric field of 3.87 V/μm and field enhancement factor β of about 1737 were obtained from the synthesized CNTs at the gap of 500 μm between the SUS substrate and the anode. These results have not only clarified the effects of the substrate on the growth of CNTs, but also shown the potential of CNTs in field emission applications, especially CNT-based cold-cathode X-ray tubes.

  2. Mammalian cell growth on gold nanoparticle-decorated substrates is influenced by the nanoparticle coating

    PubMed Central

    Rosman, Christina; Pierrat, Sebastien; Tarantola, Marco; Schneider, David; Sunnick, Eva; Janshoff, Andreas

    2014-01-01

    Summary In this work, we study epithelial cell growth on substrates decorated with gold nanorods that are functionalized either with a positively charged cytotoxic surfactant or with a biocompatible polymer exhibiting one of two different end groups, resulting in a neutral or negative surface charge of the particle. Upon observation of cell growth for three days by live cell imaging using optical dark field microscopy, it was found that all particles supported cell adhesion while no directed cell migration and no significant particle internalization occurred. Concerning cell adhesion and spreading as compared to cell growth on bare substrates after 3 days of incubation, a reduction by 45% and 95%, respectively, for the surfactant particle coating was observed, whereas the amino-terminated polymer induced a reduction by 30% and 40%, respectively, which is absent for the carboxy-terminated polymer. Furthermore, interface-sensitive impedance spectroscopy (electric cell–substrate impedance sensing, ECIS) was employed in order to investigate the micromotility of cells added to substrates decorated with various amounts of surfactant-coated particles. A surface density of 65 particles/µm2 (which corresponds to 0.5% of surface coverage with nanoparticles) diminishes micromotion by 25% as compared to bare substrates after 35 hours of incubation. We conclude that the surface coating of the gold nanorods, which were applied to the basolateral side of the cells, has a recognizable influence on the growth behavior and thus the coating should be carefully selected for biomedical applications of nanoparticles. PMID:25671143

  3. Enhancement of island size by dynamic substrate disorder in simulations of graphene growth.

    PubMed

    Enstone, Gwilym; Brommer, Peter; Quigley, David; R Bell, Gavin

    2016-06-01

    We demonstrate a new mechanism in the early stages of sub-monolayer epitaxial island growth, using Monte Carlo simulations motivated by experimental observations on the growth of graphene on copper foil. In our model, the substrate is "dynamically rough", by which we mean (i) the interaction strength between Cu and C varies randomly from site to site, and (ii) these variable strengths themselves migrate from site to site. The dynamic roughness provides a simple representation of the near-molten state of the Cu substrate in the case of real graphene growth. Counterintuitively, the graphene island size increases when dynamic roughness is included, compared to a static and smooth substrate. We attribute this effect to destabilisation of small graphene islands by fluctuations in the substrate, allowing them to break up and join larger islands which are more stable against roughness. In the case of static roughness, when process (ii) is switched off, island growth is strongly inhibited and the scale-free behaviour of island size distributions, present in the smooth-static and rough-dynamic cases, is destroyed. The effects of the dynamic substrate roughness cannot be mimicked by parameter changes in the static cases. PMID:27199250

  4. Mammalian cell growth on gold nanoparticle-decorated substrates is influenced by the nanoparticle coating.

    PubMed

    Rosman, Christina; Pierrat, Sebastien; Tarantola, Marco; Schneider, David; Sunnick, Eva; Janshoff, Andreas; Sönnichsen, Carsten

    2014-01-01

    In this work, we study epithelial cell growth on substrates decorated with gold nanorods that are functionalized either with a positively charged cytotoxic surfactant or with a biocompatible polymer exhibiting one of two different end groups, resulting in a neutral or negative surface charge of the particle. Upon observation of cell growth for three days by live cell imaging using optical dark field microscopy, it was found that all particles supported cell adhesion while no directed cell migration and no significant particle internalization occurred. Concerning cell adhesion and spreading as compared to cell growth on bare substrates after 3 days of incubation, a reduction by 45% and 95%, respectively, for the surfactant particle coating was observed, whereas the amino-terminated polymer induced a reduction by 30% and 40%, respectively, which is absent for the carboxy-terminated polymer. Furthermore, interface-sensitive impedance spectroscopy (electric cell-substrate impedance sensing, ECIS) was employed in order to investigate the micromotility of cells added to substrates decorated with various amounts of surfactant-coated particles. A surface density of 65 particles/µm(2) (which corresponds to 0.5% of surface coverage with nanoparticles) diminishes micromotion by 25% as compared to bare substrates after 35 hours of incubation. We conclude that the surface coating of the gold nanorods, which were applied to the basolateral side of the cells, has a recognizable influence on the growth behavior and thus the coating should be carefully selected for biomedical applications of nanoparticles. PMID:25671143

  5. Growth map for Ga-assisted growth of GaAs nanowires on Si(111) substrates by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Bastiman, Faebian; Küpers, Hanno; Somaschini, Claudio; Geelhaar, Lutz

    2016-03-01

    For the Ga-assisted growth of GaAs nanowires on Si(111) substrates by molecular beam epitaxy, growth temperature, As flux, and Ga flux have been systematically varied across the entire window of growth conditions that result in the formation of nanowires. A range of GaAs structures was observed, progressing from pure Ga droplets under negligible As flux through horizontal nanowires, tilted nanowires, vertical nanowires, and nanowires without droplets to crystallites as the As flux was increased. Quantitative analysis of the resulting sample morphology was performed in terms of nanowire number and volume density, number yield and volume yield of vertical nanowires, diameter, length, as well as the number and volume density of parasitic growth. The result is a growth map that comprehensively describes all nanowire and parasitic growth morphologies and hence enables growth of nanowire samples in a predictive manner. Further analysis indicates the combination of global Ga flux and growth temperature determines the total density of all objects, whereas the global As/Ga flux ratio independently determines the resultant sample morphology. Several dependencies observed here imply that all objects present on the substrate surface, i.e. both nanowires and parasitic structures, originate from Ga droplets.

  6. Quantum Dots: Growth of InAs Quantum Dots on GaAs (511)A Substrates: The Competition between Thermal Dynamics and Kinetics (Small 31/2016).

    PubMed

    Wen, Lei; Gao, Fangliang; Zhang, Shuguang; Li, Guoqiang

    2016-08-01

    On page 4277, G. Li and co-workers aim to promote III-V compound semiconductors and devices for a broad range of applications with various technologies. The growth process of InAs quantum dots on GaAs (511)A substrates is systematically studied. By carefully controlling the competition between growth thermal-dynamics and kinetics, InAs quantum dots with high size uniformity are prepared, which are highly desirable for the fabrication of high-efficiency solar cells. PMID:27510365

  7. [Effects of substrate-aeration cultivation pattern on tomato growth].

    PubMed

    Zhao, Xu; Li, Tian-Lai; Sun, Zhou-Ping

    2010-01-01

    Aeroponics can increase the fruit yield of tomato plant, but its cost is very high. In this paper, tomato seedlings were planted with three cultures, i. e., whole perlite culture (CK), perlite-aeration culture (T1), and aeroponics (T2), and a comparative study was made on the seedlings growth. Compared with CK, T1 improved the gas environment in root zone significantly, with the CO2 and O2 concentrations in root zone being 0.2 and 1.17 times higher, and increased the plant height and stem diameter after 60 days of transplanting by 5.1% and 8.4%, respectively. The plant net photosynthetic rate of T1 was significantly higher than that of CK, with the maximum value after transplanting 45 days increased by 13%. T1 also increased the root activity and ion absorbing ability significantly, with the root activity after transplanting 45 days being 1.23 times of CK, and the root K, Ca, and Mg contents after transplanting 60 days increased by 31%, 37%, and 27%, respectively. The fruit yield of T1 was 1.16 times of CK. No significant differences in these indices were observed between T1 and T2, and less difference in the fruit soluble sugar and organic acid contents as well as the sugar-acid ratio was found among CK, T1, and T2. It was suggested that perlite-aeration cultivation pattern was an easy and feasible way to markedly improve the fruit yield of tomato plant. PMID:20387426

  8. Growth of Well-Aligned InN Nanorods on Amorphous Glass Substrates

    NASA Astrophysics Data System (ADS)

    Li, Huijie; Zhao, Guijuan; Wei, Hongyuan; Wang, Lianshan; Chen, Zhen; Yang, Shaoyan

    2016-05-01

    The growth of well-aligned nanorods on amorphous substrates can pave the way to fabricate large-scale and low-cost devices. In this work, we successfully prepared vertically well-aligned c-axis InN nanorods on amorphous glass substrate by metal-organic chemical vapor deposition. The products formed directly on bare glass are randomly oriented without preferential growth direction. By inserting a GaN/Ti interlayer, the nanowire alignment can be greatly improved as indicated by scanning electron microscopy and X-ray diffraction.

  9. Growth of Well-Aligned InN Nanorods on Amorphous Glass Substrates.

    PubMed

    Li, Huijie; Zhao, Guijuan; Wei, Hongyuan; Wang, Lianshan; Chen, Zhen; Yang, Shaoyan

    2016-12-01

    The growth of well-aligned nanorods on amorphous substrates can pave the way to fabricate large-scale and low-cost devices. In this work, we successfully prepared vertically well-aligned c-axis InN nanorods on amorphous glass substrate by metal-organic chemical vapor deposition. The products formed directly on bare glass are randomly oriented without preferential growth direction. By inserting a GaN/Ti interlayer, the nanowire alignment can be greatly improved as indicated by scanning electron microscopy and X-ray diffraction. PMID:27229517

  10. Growth and characterization of CdTe on GaAs/Si substrates

    NASA Technical Reports Server (NTRS)

    Radhakrishnan, G.; Nouhi, A.; Liu, J.

    1988-01-01

    Epitaxial CdTe has been grown on both (100) GaAs/Si and (111) GaAs/Si substrates. A combination of molecular beam epitaxy and metal organic chemical vapor deposition have been employed to achieve this growth. The GaAs layers are grown in Si substrates by molecular beam epitaxy, followed by the growth of CdTe on GaAs/Si substra by metalorganic chemical vapor deposition. X-ray diffraction, photoluminescence, and scanning electron microscopy have been used to characterize the CdTe films.

  11. Self-organized MBE growth of II VI epilayers on patterned GaSb substrates

    NASA Astrophysics Data System (ADS)

    Wissmann, H.; Tran Anh, T.; Rogaschewski, S.; von Ortenberg, M.

    1999-05-01

    We report on the self-organized MBE growth of II-VI epilayers on patterned and unpatterned GaSb substrates resulting in quantum wires and quantum wells, respectively. The HgSe : Fe quantum wires were grown on (0 0 1)GaSb substrates with a buffer of lattice-matched ZnTe 1- xSe x. Due to the anisotropic growth of HgSe on the A-oriented stripes roof-like overgrowth with a definite ridge was obtained. Additional Fe doping in the direct vicinity of the ridge results in a highly conductive quantum wire.

  12. MHC-restricted phosphopeptides derived from Insulin receptor substrate-2 and CDC25b offer broad-based immunotherapeutic agents for cancer

    PubMed Central

    Zarling, Angela L.; Obeng, Rebecca C.; Desch, A. Nicole; Pinczewski, Joel; Cummings, Kara L.; Deacon, Donna H.; Conaway, Mark; Slingluff, Craig L.; Engelhard, Victor H.

    2014-01-01

    Cancer cells display novel phosphopeptides in association with MHC class I and II molecules. In this study, we evaluated two HLA-A2-restricted phosphopeptides derived from the insulin receptor substrate (IRS)-2 and the cell cycle regulator CDC25b. These proteins are both broadly expressed in multiple malignancies and linked to cancer cell survival. Two phosphopeptides, termed pIRS-21097-1105 and pCDC25b38-46, served as targets of strong and specific CD8 T-cell memory responses in normal human donors. We cloned T-cell receptor (TCR) cDNAs from murine CD8 T-cell lines specific for either pIRS-21097-1105 or pCDC25b38-46. Expression of these TCR in human CD8 T-cells imparted high-avidity phosphopeptide-specific recognition and cytotoxic and cytokine-secreting effector activities. Using these cells, we found that endogenously processed pIRS-21097-1105 was presented on HLA-A2+ melanomas and breast, ovarian, and colorectal carcinomas. Presentation was correlated with the level of the Ser1100-phosphorylated IRS-2 protein in metastatic melanoma tissues. The highest expression of this protein was evident on dividing malignant cells. Presentation of endogenously processed pCDC25b38-46 was narrower, but still evident on HLA-A2+ melanoma, breast carcinoma and lymphoblastoid cells. Notably, pIRS-21097-1105-specific and pCDC25b38-46-specific TCR-expressing human CD8 T-cells markedly slowed tumor outgrowth in vivo. Our results define two new antigens that may be developed as immunotherapeutic agents for a broad range of HLA-A2+ cancers. PMID:25297629

  13. Critical aspects of substrate nanopatterning for the ordered growth of GaN nanocolumns.

    PubMed

    Barbagini, Francesca; Bengoechea-Encabo, Ana; Albert, Steven; Martinez, Javier; Sanchez García, Miguel Angel; Trampert, Achim; Calleja, Enrique

    2011-01-01

    Precise and reproducible surface nanopatterning is the key for a successful ordered growth of GaN nanocolumns. In this work, we point out the main technological issues related to the patterning process, mainly surface roughness and cleaning, and mask adhesion to the substrate. We found that each of these factors, process-related, has a dramatic impact on the subsequent selective growth of the columns inside the patterned holes. We compare the performance of e-beam lithography, colloidal lithography, and focused ion beam in the fabrication of hole-patterned masks for ordered columnar growth. These results are applicable to the ordered growth of nanocolumns of different materials. PMID:22168918

  14. Critical aspects of substrate nanopatterning for the ordered growth of GaN nanocolumns

    PubMed Central

    2011-01-01

    Precise and reproducible surface nanopatterning is the key for a successful ordered growth of GaN nanocolumns. In this work, we point out the main technological issues related to the patterning process, mainly surface roughness and cleaning, and mask adhesion to the substrate. We found that each of these factors, process-related, has a dramatic impact on the subsequent selective growth of the columns inside the patterned holes. We compare the performance of e-beam lithography, colloidal lithography, and focused ion beam in the fabrication of hole-patterned masks for ordered columnar growth. These results are applicable to the ordered growth of nanocolumns of different materials. PMID:22168918

  15. Direct growth of single-crystalline III-V semiconductors on amorphous substrates

    NASA Astrophysics Data System (ADS)

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager, Joel W., III; Chrzan, Daryl C.; Javey, Ali

    2016-01-01

    The III-V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III-V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III-V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III-V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III-V's on application-specific substrates by direct growth.

  16. Direct growth of single-crystalline III–V semiconductors on amorphous substrates

    DOE PAGESBeta

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; et al

    2016-01-27

    The III–V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III–V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III–V’s on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III–V’s of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. Themore » patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. In conclusion, the work presents an important advance towards universal integration of III–V’s on application-specific substrates by direct growth.« less

  17. Comparative study on graphene growth mechanism using Ni films, Ni/Mo sheets, and Pt substrates

    NASA Astrophysics Data System (ADS)

    Lee, Byeong-Joo; Jeong, Goo-Hwan

    2014-07-01

    We demonstrate a comparative study on graphene growth mechanism using various catalytic metal substrates such as Ni thin films, Ni-deposited Mo (Ni/Mo) sheets, and Pt sheets during chemical vapor deposition (CVD). Depending on the substrates, two kinds of graphene growth mechanisms that involve either precipitation or surface adsorption of carbon have been reported. We synthesized graphene, focusing especially on the initial growth stage during CVD, by varying synthesis parameters such as synthesis time, amount of feedstock, and cooling rate after synthesis. We concluded that precipitation-driven synthesis is dominant in the case of Ni substrates whereas adsorption-driven growth is dominant in the Ni/Mo system. In the case of the Pt substrate, which is generally believed to grow by carbon precipitation, graphene growth by adsorption was found to be dominant. We believe that our results will contribute to a clearer understanding of the graphene synthesis mechanism, and development of manufacturing routes for controllable synthesis of high-quality graphenes.

  18. Direct growth of single-crystalline III–V semiconductors on amorphous substrates

    PubMed Central

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M.; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager III, Joel W.; Chrzan, Daryl C.; Javey, Ali

    2016-01-01

    The III–V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III–V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III–V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III–V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III–V's on application-specific substrates by direct growth. PMID:26813257

  19. Direct growth of single-crystalline III-V semiconductors on amorphous substrates.

    PubMed

    Chen, Kevin; Kapadia, Rehan; Harker, Audrey; Desai, Sujay; Seuk Kang, Jeong; Chuang, Steven; Tosun, Mahmut; Sutter-Fella, Carolin M; Tsang, Michael; Zeng, Yuping; Kiriya, Daisuke; Hazra, Jubin; Madhvapathy, Surabhi Rao; Hettick, Mark; Chen, Yu-Ze; Mastandrea, James; Amani, Matin; Cabrini, Stefano; Chueh, Yu-Lun; Ager Iii, Joel W; Chrzan, Daryl C; Javey, Ali

    2016-01-01

    The III-V compound semiconductors exhibit superb electronic and optoelectronic properties. Traditionally, closely lattice-matched epitaxial substrates have been required for the growth of high-quality single-crystal III-V thin films and patterned microstructures. To remove this materials constraint, here we introduce a growth mode that enables direct writing of single-crystalline III-V's on amorphous substrates, thus further expanding their utility for various applications. The process utilizes templated liquid-phase crystal growth that results in user-tunable, patterned micro and nanostructures of single-crystalline III-V's of up to tens of micrometres in lateral dimensions. InP is chosen as a model material system owing to its technological importance. The patterned InP single crystals are configured as high-performance transistors and photodetectors directly on amorphous SiO2 growth substrates, with performance matching state-of-the-art epitaxially grown devices. The work presents an important advance towards universal integration of III-V's on application-specific substrates by direct growth. PMID:26813257

  20. Growth mechanisms and crystallographic structure of InP nanowires on lattice-mismatched substrates

    NASA Astrophysics Data System (ADS)

    Moewe, Michael; Chuang, Linus C.; Dubrovskii, Vladimir G.; Chang-Hasnain, Connie

    2008-08-01

    We present a growth model that predicts the growth phase and mechanism of InP nanowires (NWs) and the experimental verifications of the model. The NWs were grown on lattice-mismatched GaAs substrates using metal-organic chemical vapor deposition via Au nanodrop-assisted vapor-liquid-solid growth. Nanodrops with larger diameters are shown to grow longer NWs because growth is governed mainly by direct precursor impingement on the nanodrop surface. The theoretical and experimental results also show that growth phase is dependent on NW diameter. We show that InP NWs with a diameter less than a certain value exhibit coherent growth of a single crystalline wurtzite (WZ) phase, whereas larger diameter InP NWs often contain sequences of WZ and zincblende phases and stacking faults. These findings allow one to achieve coherent NW growth and WZ phases free from twinning if the NW diameter is below certain material-dependent critical diameters.

  1. Topotaxial growth of α-Fe2O3 nanowires on iron substrate

    NASA Astrophysics Data System (ADS)

    Srivastava, Himanshu; Srivastava, A. K.; Babu, Mahendra; Rai, S. K.; Ganguli, Tapas

    2016-05-01

    α-Fe2O3 (hematite) nanowires have been grown by simple thermal oxidation of iron foil at 700°C in a moist oxygen flow. It was observed that the growth of nanowires highly depends on the texture of the iron substrate, in particular the presence of [110] oriented iron grains. Cross-sectional Transmission Electron Microscopy (TEM) investigation of as-grown sample revealed that the growth of nanowires has definite orientation relation with the underlying oxide grains Fe3O4 (magnetite) and FeO (wustite), which can be interpreted by the primary orientation relationships of topotaxial growth of iron oxides. The observation can pave the way for patterning of the nanowire growth by controlling the texture of original substrate. Samples were also characterized with Scanning Electron Microscope (SEM) and X-ray diffraction (XRD).

  2. Growth and wetting of water droplet condensed between micron-sized particles and substrate

    NASA Astrophysics Data System (ADS)

    Quang, Tran Si Bui; Leong, Fong Yew; An, Hongjie; Tan, Beng Hau; Ohl, Claus-Dieter

    2016-08-01

    We study heterogeneous condensation growth of water droplets on micron-sized particles resting on a level substrate. Through numerical simulations on equilibrium droplet profiles, we find multiple wetting states towards complete wetting of the particle. Specifically, a partially wetting droplet could undergo a spontaneous transition to complete wetting during condensation growth, for contact angles above a threshold minimum. In addition, we find a competitive wetting behavior between the particle and the substrate, and interestingly, a reversal of the wetting dependence on contact angles during late stages of droplet growth. Using quasi-steady assumption, we simulate a growing droplet under a constant condensation flux, and the results are in good agreement with our experimental observations. As a geometric approximation for particle clusters, we propose and validate a pancake model, and with it, show that a particle cluster has greater wetting tendency compared to a single particle. Together, our results indicate a strong interplay between contact angle, capillarity and geometry during condensation growth.

  3. Molecular Beam Epitaxial Growth of GaAs on (631) Oriented Substrates

    SciTech Connect

    Cruz Hernandez, Esteban; Rojas Ramirez, Juan-Salvador; Contreras Hernandez, Rocio; Lopez Lopez, Maximo; Pulzara Mora, Alvaro; Mendez Garcia, Victor H.

    2007-02-09

    In this work, we report the study of the homoepitaxial growth of GaAs on (631) oriented substrates by molecular beam epitaxy (MBE). We observed the spontaneous formation of a high density of large scale features on the surface. The hilly like features are elongated towards the [-5, 9, 3] direction. We show the dependence of these structures with the growth conditions and we present the possibility of to create quantum wires structures on this surface.

  4. Molecular-mediated crystal growth of PbTiO 3 nanostructure on silicon substrate

    NASA Astrophysics Data System (ADS)

    Chao, Chunying; Ren, Zhaohui; Liu, Zhenya; Xiao, Zhen; Xu, Gang; Li, Xiang; Wei, Xiao; Shen, Ge; Han, Gaorong

    2011-09-01

    A simple approach based on an organically modified sol-gel process has been developed to fabricate PbTiO3 (PT) nanocrystals on Si (1 0 0) substrate, where the amorphous powder modified by acetylacetone (acac) was used as precursor. After dropping the amorphous powder precursor prepared by freeze-drying process, PT nanocrystals on Si (1 0 0) substrate were obtained after heat treatment at 720 °C for 30 min in air. PT nanocrystals have been detected by XRD to be tetragonal perovskite structure. With the increase of acac/Pb molar ratio, the relative (1 0 0)/(0 0 1) diffraction peak intensity gradually increases, which probably suggested an oriented growth of PT nanocrystal along [1 0 0] on Si (1 0 0) substrates. In addition, Atomic force microscopy (AFM) results indicated that the height and the average lateral size of PT nanocrystal increased and then decreased as the acac/Pb molar ratio increased. Piezoelectric force microscopy (PFM) results demonstrated that all the samples show obvious piezoelectric activity. These results implied that the acetylacetone molecular mediated the growth of PT nanocrystals on Si (1 0 0) substrates possibly by the acac/Pb molar ratio. This simple method has been suggested to be attractive for tailoring an oriented growth of the nanostructures of perovskite oxide systems on Si substrates.

  5. Thin crystalline 3C-SiC layer growth through carbonization of differently oriented Si substrates

    NASA Astrophysics Data System (ADS)

    Severino, A.; D'Arrigo, G.; Bongiorno, C.; Scalese, S.; La Via, F.; Foti, G.

    2007-07-01

    The growth of thin cubic silicon carbide (3C-SiC) buffer layers in an horizontal hot-wall chemical vapor deposition reactor, through the carbonization of differently oriented Si surfaces, is presented. A qualitative and quantitative study has been performed on statistical parameters related to voids due to the buffer layer growth on the different substrate orientations emphasizing shape, size, and density as a function of the substrate orientation. Variation in the void parameters can be attributed to the atomic packing density related to the substrate orientations, which were (100) Si, (111) Si, and (110) Si in this study. Scanning electron microscopy and transmission electron microscopy were performed to analyze the surface and the crystalline quality of the 3C-SiC films grown and, eventually, an empirical model for the carbonization of Si surfaces formulated. Large platens characterize the 3C-SiC films with shapes related to the orientations of the substrate. These platens derive from the two-dimensional growth of different SiC islands which enlarge during the process due to the continuous reaction between Si and C atoms. The interior part of platens was characterized by the presence of a pure crystalline material with the presence of small tilts affecting some grains in the 3C-SiC layer in order to relief the stress generated with the substrate.

  6. Low-Dislocation-Density GaN from a Single Growth on a Textured Substrate

    SciTech Connect

    ASHBY,CAROL I.; WILLAN,CHRISTINE C.; HAN,JUNG; MISSERT,NANCY A.; PROVENCIO,PAULA P.; FOLLSTAEDT,DAVID M.; PEAKE,GREGORY M.; GRIEGO,LEONARDO

    2000-07-31

    The density of threading dislocations (TD) in GaN grown directly on flat sapphire substrates is typically greater than 10{sup 9}/cm{sup 2}. Such high dislocation densities degrade both the electronic and photonic properties of the material. The density of dislocations can be decreased by orders of magnitude using cantilever epitaxy (CE), which employs prepatterned sapphire substrates to provide reduced-dimension mesa regions for nucleation and etched trenches between them for suspended lateral growth of GaN or AlGaN. The substrate is prepatterned with narrow lines and etched to a depth that permits coalescence of laterally growing III-N nucleated on the mesa surfaces before vertical growth fills the etched trench. Low dislocation densities typical of epitaxial lateral overgrowth (ELO) are obtained in the cantilever regions and the TD density is also reduced up to 1 micrometer from the edge of the support regions.

  7. Growth of bi- and tri-layered graphene on silicon carbide substrate via molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Min, Tjun Kit; Lim, Thong Leng; Yoon, Tiem Leong

    2015-04-01

    Molecular dynamics (MD) simulation with simulated annealing method is used to study the growth process of bi- and tri-layered graphene on a 6H-SiC (0001) substrate via molecular dynamics simulation. Tersoff-Albe-Erhart (TEA) potential is used to describe the inter-atomic interactions among the atoms in the system. The formation temperature, averaged carbon-carbon bond length, pair correlation function, binding energy and the distance between the graphene formed and the SiC substrate are quantified. The growth mechanism, graphitization of graphene on the SiC substrate and characteristics of the surface morphology of the graphene sheet obtained in our MD simulation compare well to that observed in epitaxially grown graphene experiments and other simulation works.

  8. Growth of bi- and tri-layered graphene on silicon carbide substrate via molecular dynamics simulation

    SciTech Connect

    Min, Tjun Kit; Yoon, Tiem Leong; Lim, Thong Leng

    2015-04-24

    Molecular dynamics (MD) simulation with simulated annealing method is used to study the growth process of bi- and tri-layered graphene on a 6H-SiC (0001) substrate via molecular dynamics simulation. Tersoff-Albe-Erhart (TEA) potential is used to describe the inter-atomic interactions among the atoms in the system. The formation temperature, averaged carbon-carbon bond length, pair correlation function, binding energy and the distance between the graphene formed and the SiC substrate are quantified. The growth mechanism, graphitization of graphene on the SiC substrate and characteristics of the surface morphology of the graphene sheet obtained in our MD simulation compare well to that observed in epitaxially grown graphene experiments and other simulation works.

  9. Availability of Clean Chip Residual as a Growth Substrate in the Southeast United States

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Residual chipping material (also called clean chip residual or CCR) has potential use as a growth substrate in the nursery industry. The objective of this study was to quantify the amount and type of CCR material available in the Southeast United States for possible horticultural use by surveying wo...

  10. Interactive effects of substrate, hydroperiod, and nutrients on seedling growth of Salix nigra and Taxodium distichum

    USGS Publications Warehouse

    Day, R.H.; Doyle, T.W.; Draugelis-Dale, R. O.

    2006-01-01

    The large river swamps of Louisiana have complex topography and hydrology, characterized by black willow (Salix nigra) dominance on accreting alluvial sediments and vast areas of baldcypress (Taxodium distichum) deepwater swamps with highly organic substrates. Seedling survival of these two wetland tree species is influenced by their growth rate in relation to the height and duration of annual flooding in riverine environments. This study examines the interactive effects of substrate, hydroperiod, and nutrients on growth rates of black willow and baldcypress seedlings. In a greenhouse experiment with a split-split-plot design, 1-year seedlings of black willow and baldcypress were subjected to two nutrient treatments (unfertilized versus fertilized), two hydroperiods (continuously flooded versus twice daily flooding/draining), and two substrates (sand versus commercial peat mix). Response variables included height, diameter, lateral branch count, biomass, and root:stem ratio. Black willow growth in height and diameter, as well as all biomass components, were significantly greater in peat substrate than in sand. Black willow showed a significant hydroperiod-nutrient interaction wherein fertilizer increased stem and root biomass under drained conditions, but flooded plants did not respond to fertilization. Baldcypress diameter and root biomass were higher in peat than in sand, and the same two variables increased with fertilization in flooded as well as drained treatments. These results can be used in Louisiana wetland forest models as inputs of seedling growth and survival, regeneration potential, and biomass accumulation rates of black willow and baldcypress.

  11. Growth of ternary and quaternary compounds on non-planar InP substrates

    SciTech Connect

    Mullan, C.A.; Robinson, B.J.; Thompson, D.A.; Weatherly, G.C.

    1996-12-31

    InP based ternary and quaternary materials are in wide use for optoelectronic systems. It has been well documented that phase separation occurs when these are deposited onto planar substrates. The use of non-planar substrates is becoming increasingly popular for the fabrication of novel devices. Obviously, epitaxial growth of these materials onto a non-planar surface will differ from growth on a planar surface. The effect of simultaneously growing on two or more crystal planes which have different atom migration lengths and sticking coefficients must now be considered. Since phase segregation occurs in InP-based materials the question arises, what effect will growth on a patterned substrate have? The authors have previously shown how InP, InGaAs and InGaAsP deposited onto etched DFB gratings under the same conditions act differently and here they will show both how the atomic concentrations change in deposited InGaAs and InGaAsP layers with position above the grating and how the total incorporation rate changes when compared to growth on a planar substrate.

  12. Raman measurements of substrate temperature in a molecular beam epitaxy growth chamber

    NASA Astrophysics Data System (ADS)

    Hutchins, T.; Nazari, M.; Eridisoorya, M.; Myers, T. M.; Holtz, M.

    2015-01-01

    A method is described for directly measuring the temperature of a substrate in a molecular-beam epitaxy (MBE) growth system. The approach relies on the establishment of the temperature dependence of Raman-active phonons of the substrate material using independently known calibration points across the range of interest. An unknown temperature in this range is then determined based on the Raman peak position with the substrate in situ the MBE chamber. The apparatus relies on conventional optics and Raman components. Shifting and broadening of the Raman spectrum are described based on the effects of thermal expansion and anharmonic decay. The choice of reference temperature is discussed. The method is qualified by examining the substrate temperature dependence, relative to that of a standard thermocouple, during a commonly used ramp procedure. Both temperature difference and time lag are obtained.

  13. Epitaxial Growth of GaN-based LEDs on Simple Sacrificial Substrates

    SciTech Connect

    Ian Ferguson; Chris Summers

    2009-12-31

    The objective of this project is to produce alternative substrate technologies for GaN-based LEDs by developing an ALD interlayer of Al{sub 2}O{sub 3} on sacrificial substrates such as ZnO and Si. A sacrificial substrate is used for device growth that can easily be removed using a wet chemical etchant leaving only the thin GaN epi-layer. After substrate removal, the GaN LED chip can then be mounted in several different ways to a metal heat sink/reflector and light extraction techniques can then be applied to the chip and compared for performance. Success in this work will lead to high efficiency LED devices with a simple low cost fabrication method and high product yield as stated by DOE goals for its solid state lighting portfolio.

  14. System for monitoring the growth of crystalline films on stationary substrates

    DOEpatents

    Sheldon, Peter

    1996-01-01

    A system for monitoring the growth of crystalline films on stationary or rotating substrates includes a combination of some or all of the elements including a photodiode sensor for detecting the intensity of incoming light and converting it to a measurable current, a lens for focusing the RHEED pattern emanating from the phosphor screen onto the photodiode, an interference filter for filtering out light other than that which emanates from the phosphor screen, a current amplifier for amplifying and convening the current produced by the photodiode into a voltage, a computer for receiving the amplified photodiode current for RHEED data analysis, and a graphite impregnated triax cable for improving the signal to noise ratio obtained while sampling a stationary or rotating substrate. A rotating stage for supporting the substrate with diametrically positioned electron beam apertures and an optically encoded shaft can also be used to accommodate rotation of the substrate during measurement.

  15. System for monitoring the growth of crystalline films on stationary substrates

    DOEpatents

    Sheldon, P.

    1995-10-10

    A system for monitoring the growth of crystalline films on stationary or rotating substrates includes a combination of some or all of the elements including a photodiode sensor for detecting the intensity of incoming light and converting it to a measurable current, a lens for focusing the RHEED pattern emanating from the phosphor screen onto the photodiode, an interference filter for filtering out light other than that which emanates from the phosphor screen, a current amplifier for amplifying and converting the current produced by the photodiode into a voltage, a computer for receiving the amplified photodiode current for RHEED data analysis, and a graphite impregnated triaxial cable for improving the signal-to-noise ratio obtained while sampling a stationary or rotating substrate. A rotating stage for supporting the substrate with diametrically positioned electron beam apertures and an optically encoded shaft can also be used to accommodate rotation of the substrate during measurement. 16 figs.

  16. System for monitoring the growth of crystalline films on stationary substrates

    DOEpatents

    Sheldon, P.

    1996-12-31

    A system for monitoring the growth of crystalline films on stationary or rotating substrates includes a combination of some or all of the elements including a photodiode sensor for detecting the intensity of incoming light and converting it to a measurable current, a lens for focusing the RHEED pattern emanating from the phosphor screen onto the photodiode, an interference filter for filtering out light other than that which emanates from the phosphor screen, a current amplifier for amplifying and convening the current produced by the photodiode into a voltage, a computer for receiving the amplified photodiode current for RHEED data analysis, and a graphite impregnated triaxial cable for improving the signal to noise ratio obtained while sampling a stationary or rotating substrate. A rotating stage for supporting the substrate with diametrically positioned electron beam apertures and an optically encoded shaft can also be used to accommodate rotation of the substrate during measurement. 16 figs.

  17. System for monitoring the growth of crystalline films on stationary substrates

    DOEpatents

    Sheldon, Peter

    1995-01-01

    A system for monitoring the growth of crystalline films on stationary or rotating substrates includes a combination of some or all of the elements including a photodiode sensor for detecting the intensity of incoming light and converting it to a measurable current, a lens for focusing the RHEED pattern emanating from the phosphor screen onto the photodiode, an interference filter for filtering out light other than that which emanates from the phosphor screen, a current amplifier for amplifying and converting the current produced by the photodiode into a voltage, a computer for receiving the amplified photodiode current for RHEED data analysis, and a graphite impregnated triax cable for improving the signal to noise ratio obtained while sampling a stationary or rotating substrate. A rotating stage for supporting the substrate with diametrically positioned electron beam apertures and an optically encoded shaft can also be used to accommodate rotation of the substrate during measurement.

  18. Raman measurements of substrate temperature in a molecular beam epitaxy growth chamber

    SciTech Connect

    Hutchins, T.; Nazari, M.; Eridisoorya, M.; Myers, T. M.; Holtz, M.

    2015-01-15

    A method is described for directly measuring the temperature of a substrate in a molecular-beam epitaxy (MBE) growth system. The approach relies on the establishment of the temperature dependence of Raman-active phonons of the substrate material using independently known calibration points across the range of interest. An unknown temperature in this range is then determined based on the Raman peak position with the substrate in situ the MBE chamber. The apparatus relies on conventional optics and Raman components. Shifting and broadening of the Raman spectrum are described based on the effects of thermal expansion and anharmonic decay. The choice of reference temperature is discussed. The method is qualified by examining the substrate temperature dependence, relative to that of a standard thermocouple, during a commonly used ramp procedure. Both temperature difference and time lag are obtained.

  19. Effect of Different Substrates and Casing Materials on the Growth and Yield of Calocybe indica

    PubMed Central

    Amin, Ruhul; Khair, Abul; Alam, Nuhu

    2010-01-01

    Calocybe indica, a tropical edible mushroom, is popular because it has good nutritive value and it can be cultivated commercially. The current investigation was undertaken to determine a suitable substrate and the appropriate thickness of casing materials for the cultivation of C. indica. Optimum mycelial growth was observed in coconut coir substrate. Primordia initiation with the different substrates and casing materials was observed between the 13th and 19th day. The maximum length of stalk was recorded from sugarcane leaf, while diameter of stalk and pileus, and thickness of pileus were found in rice straw substrate. The highest biological and economic yield, and biological efficiency were also obtained in the rice straw substrate. Cow dung and loamy soil, farm-yard manure, loamy soil and sand, and spent oyster mushroom substrates were used as casing materials to evaluate the yield and yield-contributing characteristics of C. indica. The results indicate that the number of effective fruiting bodies, the biological and economic yield, and the biological efficiency were statistically similar all of the casing materials used. The maximum biological efficiency was found in the cow dung and loamy soil casing material. The cow dung and loamy soil (3 cm thick) was the best casing material and the rice straw was the best substrate for the commercial cultivation of C. indica. PMID:23956634

  20. Growth and characterization of GaN-based structures on SiCOI-engineered substrates

    NASA Astrophysics Data System (ADS)

    Dikme, Y.; van Gemmern, P.; Lin, Y. C.; Szymakowski, A.; Kalisch, H.; Faure, B.; Richtarch, C.; Larhèche, H.; Bove, P.; Letertre, F.; Woitok, J. F.; Efthimiadis, K.; Jansen, R. H.; Heuken, M.

    2004-12-01

    Silicon carbide (SiC) still shows the best properties as substrate for the growth of GaN and its alloys but suffers from a very high price. An innovative alternative for this substrate are SiC/SiO 2/Si (SiCOI) substrates, combining SiC and Si (silicon) substrate advantages thanks to the Smart Cut™ technology. These substrates consist of thin SiC layers (˜270 nm) bonded on (0 0 1) Si substrates. Using SiCOI substrates, up to 3 μm of GaN could be grown crack-free. The structures were investigated by atomic force microscopy (root mean square=0.86 nm), high-resolution X-ray diffraction and low-temperature (20 K) photoluminescence (PL) (FWHM (full-width at half-maximum)=4.9 meV). Electroluminescence test heterostructures consisting of InGaN/GaN multiple quantum wells (MQWs) were also deposited on SiCOI. Room temperature PL measurements resulted in a QW emission at around 440 nm with a FWHM of 7.8 nm. At electrical excitation, blue light emission was observed.

  1. Effect of substrate offcut angle on BGaN epitaxial growth

    NASA Astrophysics Data System (ADS)

    Ueyama, Kohei; Mimura, Hidenori; Inoue, Yoku; Aoki, Toru; Nakano, Takayuki

    2016-05-01

    Researchers expect the material BGaN to be useful in neutron detectors and ultraviolet (UV) light-emitting devices. In this study, we investigate the effect of the substrate offcut angle and polarity upon BGaN growth. In particular, BGaN is grown on top of GaN upon Al2O3 substrates with various offcut angles. In the case of Ga-polar BGaN growth, the BN mole fraction increases as the offcut angle increases. Furthermore, as the offcut angle increases, the terrace width becomes reduced, which inhibits the formation of nuclei on the terrace and promotes the incorporation of B atoms at the step edges. Such incorporation is important at the step edge (which is the stable site) during BGaN growth because B atoms are easily desorbed from the surface and easily react in the gas phase. In the case of N-polar BGaN growth, the BN mole fraction exhibits different behavior in response to the offcut angle of the substrate. For this reason, the surface of N-polar BGaN is different from that of Ga-polar BGaN as it has facets of N-polar GaN and step bunching. These results indicate that the incorporation of B atoms at step edges significantly affects the BN mole fraction in BGaN growth.

  2. Graphene growth on Ge(100)/Si(100) substrates by CVD method

    PubMed Central

    Pasternak, Iwona; Wesolowski, Marek; Jozwik, Iwona; Lukosius, Mindaugas; Lupina, Grzegorz; Dabrowski, Pawel; Baranowski, Jacek M.; Strupinski, Wlodek

    2016-01-01

    The successful integration of graphene into microelectronic devices is strongly dependent on the availability of direct deposition processes, which can provide uniform, large area and high quality graphene on nonmetallic substrates. As of today the dominant technology is based on Si and obtaining graphene with Si is treated as the most advantageous solution. However, the formation of carbide during the growth process makes manufacturing graphene on Si wafers extremely challenging. To overcome these difficulties and reach the set goals, we proposed growth of high quality graphene layers by the CVD method on Ge(100)/Si(100) wafers. In addition, a stochastic model was applied in order to describe the graphene growth process on the Ge(100)/Si(100) substrate and to determine the direction of further processes. As a result, high quality graphene was grown, which was proved by Raman spectroscopy results, showing uniform monolayer films with FWHM of the 2D band of 32 cm−1. PMID:26899732

  3. Graphene growth on Ge(100)/Si(100) substrates by CVD method

    NASA Astrophysics Data System (ADS)

    Pasternak, Iwona; Wesolowski, Marek; Jozwik, Iwona; Lukosius, Mindaugas; Lupina, Grzegorz; Dabrowski, Pawel; Baranowski, Jacek M.; Strupinski, Wlodek

    2016-02-01

    The successful integration of graphene into microelectronic devices is strongly dependent on the availability of direct deposition processes, which can provide uniform, large area and high quality graphene on nonmetallic substrates. As of today the dominant technology is based on Si and obtaining graphene with Si is treated as the most advantageous solution. However, the formation of carbide during the growth process makes manufacturing graphene on Si wafers extremely challenging. To overcome these difficulties and reach the set goals, we proposed growth of high quality graphene layers by the CVD method on Ge(100)/Si(100) wafers. In addition, a stochastic model was applied in order to describe the graphene growth process on the Ge(100)/Si(100) substrate and to determine the direction of further processes. As a result, high quality graphene was grown, which was proved by Raman spectroscopy results, showing uniform monolayer films with FWHM of the 2D band of 32 cm-1.

  4. Growth of AlN layer on patterned sapphire substrate by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Lee, Gang Seok; Lee, Chanmi; Jeon, Hunsoo; Lee, Chanbin; Bae, Sung Geun; Ahn, Hyung Soo; Yang, Min; Yi, Sam Nyung; Yu, Young Moon; Lee, Jae Hak; Honda, Yoshio; Sawaki, Nobuhiko; Kim, Suck-Whan

    2016-05-01

    Even though a patterned sapphire substrate (PSS) has been used for the growth of a high-quality epilayer because of its many advantages, it has not been successfully used to grow an AlN epilayer for ultraviolet (UV) light-emitting diodes (LEDs) on a PSS up to now. We report the growth of a high-quality AlN epilayer on a PSS, as a substrate for the manufacture of UV LEDs, by hydride vapor phase epitaxy (HVPE). The X-ray diffraction (XRD) peaks for the AlN epilayer grown on the PSS indicate that crystalline AlN with a wurtzite structure was grown successfully on the PSS. Furthermore, HVPE combining both in situ HVPE technology and liquid-phase epitaxy (LPE) using a mixed source is proposed as a novel method for the growth of a flat AlN epilayer on a PSS.

  5. Effects of substrate crystallinity and dopant on the growth kinetics of platinum silicides

    NASA Astrophysics Data System (ADS)

    Takai, H.; Psaras, P. A.; Tu, K. N.

    1985-12-01

    The growth kinetics of platinum silicides have been studied on four substrate categories: single-crystal, amorphous, undoped polycrystalline, and phosphorus-doped (8×1020 at./cm3) polycrystalline silicon. The sequential growth of Pt2Si and PtSi were analyzed by Rutherford backscattering spectroscopy (RBS), Seeman-Bohlin x-ray diffraction, and cross-section transmission electron microscopy. Phosphorus depth profiles were measured by secondary ion mass spectroscopy (SIMS). Our results conclude that the activation energies for the growth of Pt2Si and PtSi are not affected by substrate crystallinity and doping of phosphorus. Analysis of the phosphorus profile by SIMS clearly showed that phosphorus atoms are segregated near the interface between PtSi and polycrystalline silicon, but not at the Pt2Si/polycrystalline silicon interface.

  6. Growth-substrate dependent dechlorination of 1,2-dichloroethane by a homoacetogenic bacterium.

    PubMed

    De Wildeman, Stefaan; Neumann, Anke; Diekert, Gabriele; Verstraete, Willy

    2003-08-01

    A rod shaped, gram positive, non sporulating Acetobacterium strain was isolated that dechlorinated 1,2dichloroethane (1,2-DCA) to ethene at a dechlorination rate of up to 2 nmol Cl- min(-1) mg(-1) of protein in the exponential growth phase with formate (40 mM) as the substrate. Although with other growth substrates such as pyruvate, lactate, H2/CO2, and ethanol higher biomass productions were obtained, the dechlorination rate with these substrates was more than 10-fold lower compared with formate growing cells. Neither cell extracts nor autoclaved cells of the isolated Acetobacterium strain mediated the dechlorination of 1,2-DCA at significant rates. The addition of 1,2-DCA to the media did not result in increased cell production. No significant differences in corrinoid concentrations could be measured in cells growing on several growth-substrates. However, these measurements indicated that differences in corrinoid structure might cause the different dechlorination activity. The Acetobacterium sp. strain gradually lost its dechlorination ability during about 10 transfers in pure culture, probably due to undefined nutritional requirements. 16S rDNA analysis of the isolate revealed a 99.7% similarity with Acetobacterium wieringae. However, the type strains of A. wieringae and A. woodii did not dechlorinate 1,2-DCA. PMID:12948054

  7. Growth mechanism of pulsed laser fabricated few-layer MoS₂ on metal substrates.

    PubMed

    Loh, Tamie A J; Chua, Daniel H C

    2014-09-24

    Pulsed laser deposition (PLD) on metal substrates has recently been discovered to present an alternative method for producing highly crystalline few-layer MoS2. However, not every metal behaves in the same manner during film growth, and hence, it is crucial that the ability of various metals to produce crystalline MoS2 be thoroughly investigated. In this work, MoS2 was deposited on metal substrates, Al, Ag, Ni, and Cu, using a pulsed laser. Highly crystalline few-layer MoS2 was successfully grown on Ag, but is absent in Al, Ni, and Cu under specific growth conditions. This discrepancy was attributed to either excessively strong or insufficient adlayer-substrate interactions. In the case of Al, the effects of the strong interface interactions can be offset by increasing the amount of source atoms supplied, thereby producing semicrystalline few-layer MoS2. The results show that despite PLD being a physical vapor deposition technique, both physical and chemical processes play an important role in MoS2 growth on metal substrates. PMID:25203278

  8. Growth of long and aligned multi-walled carbon nanotubes on carbon and metal substrates.

    PubMed

    Delmas, M; Pinault, M; Patel, S; Porterat, D; Reynaud, C; Mayne-L'Hermite, M

    2012-03-16

    Well aligned, long and dense multi-walled carbon nanotubes (CNT) can be grown on both carbon fibres and any metal substrates compatible with the CNT synthesis temperature. The injection-CVD process developed involves two stages, including fibre pretreatment by depositing a SiO(2)-based sub-layer from an organometallic precursor followed by CNT growth from toluene/ferrocene precursor mixture. Carbon substrates, as well as metals, can easily be treated with this process, which takes place in the same reactor and does not need any handling in between the two stages. The aligned CNT carpets obtained are similar to the ones grown on reference quartz substrates. The CNT growth rate is fairly high (ca. 30 μm min(-1)) and it is possible to control CNT length by varying the CNT synthesis duration. The thickness of the SiO(2)-based sub-layer can be varied and is shown to have an influence on the CNT growth. This layer is assumed to play a diffusion barrier layer role between the substrate and the iron based catalyst nanoparticles producing CNT. The CNT anchorage to the carbon fibres has been checked and good overall adhesion proved, which is in favour of a good transfer of electrical charge and heat between the nanotubes and fibre. PMID:22362164

  9. Growth of indium oxide nanowalls on patterned conducting substrates: towards direct fabrication of gas sensors.

    PubMed

    Chen, Changlong; Wei, Yuling; Sun, Guoxin; Shao, Baiqi

    2012-05-01

    Nanowall materials are ideal two-dimensional structures with high surface-to-volume ratios and open edge geometries. We first report on the growth and characterization of indium oxide nanowalls on transparent and conducting indium tin oxide substrates. The nanosheets that compose the nanowalls are single-crystalline and are approximately 8 nm in thickness. The density and the lateral dimensions of the nanosheets on the substrate can be controlled by the growth time. Adopting a bridgework-like strategy, we directly construct indium oxide nanowall gas sensors on the patterned indium tin oxide substrates. The pattern lines on the substrates are etched using transparent plastic adhesive tape as shadow mask, which is both simple and cheap in comparison with the conventional photolithography technique. The sensors exhibit fast response/recovery behavior and good reproducibility to NO(2) gas under mild testing conditions, such as room temperature, ambient pressure, dry air background, and 1.5 V dc bias, and can achieve a detection limit as low as 50 ppb. We propose an assumption that the gas adsorption is composed of deep adsorption and probe adsorption to explain the interesting gas-sensing behavior of the indium oxide nanowalls. We suggest that the work reported herein, including the facile growth of indium oxide nanowalls, the bridgework-like strategy to directly construct electronic devices, and the high gas-sensing performance of the indium oxide nanowalls sensors, is a significant step towards the real applications of novel semiconductor nanostructures. PMID:22328146

  10. Conformal growth of Mo/Si multilayers on grating substrates using collimated ion beam sputtering

    SciTech Connect

    Gawlitza, Peter; Cambie, Rossana; Dhuey, Scott; Gullikson, Eric; Warwick, Tony; Braun, Stefan; Yashchuk, Valeriy; Padmore, Howard

    2012-01-23

    Deposition of multilayers on saw-tooth substrates is a key step in the fabrication of multilayer blazed gratings (MBG) for extreme ultraviolet and soft x-rays. Growth of the multilayers can be perturbed by shadowing effects caused by the highly corrugated surface of the substrates, which results in distortion of the multilayer stack structure and degradation of performance of MBGs. To minimize the shadowing effects we used an ionbeam sputtering machine with a highly collimated atomic flux to deposit Mo/Si multilayers on saw-tooth substrates. The sputtering conditions were optimized by finding a balance between smoothening and roughening processes in order to minimize degradation of the groove profile in the course of deposition and at the same time to keep the interfaces of a multilayer stack smooth enough for high efficiency. An optimal value of energy of 200 eV for sputtering Kr{sup +} ions was found by deposition of test multilayers on flat substrates at a range of ion energies. Two saw-tooth substrates were deposited at energies of 200 eV and 700 eV for the sputtering ions. It was found that reduction of the ion energy improved the blazing performance of the MBG and resulted in a 40% gain in the diffraction efficiency due to better replication of the groove profile by the multilayer. As a result of the optimization performed, an absolute diffraction efficiency of 28.8% was achieved for the 2nd blaze order of the MBG with a groove density of 7350 lines/mm at a wavelength of 13.5 nm. Details of the growth behavior of the multilayers on flat and saw-tooth substrates are discussed in terms of the Linear Continuous Model of film growth.

  11. Conformal growth of Mo/Si multilayers on grating substrates using collimated ion beam sputtering

    NASA Astrophysics Data System (ADS)

    Voronov, D. L.; Gawlitza, P.; Cambie, R.; Dhuey, S.; Gullikson, E. M.; Warwick, T.; Braun, S.; Yashchuk, V. V.; Padmore, H. A.

    2012-05-01

    Deposition of multilayers on saw-tooth substrates is a key step in the fabrication of multilayer blazed gratings (MBG) for extreme ultraviolet and soft x-rays. Growth of the multilayers can be perturbed by shadowing effects caused by the highly corrugated surface of the substrates, which results in distortion of the multilayer stack structure and degradation of performance of MBGs. To minimize the shadowing effects, we used an ion-beam sputtering machine with a highly collimated atomic flux to deposit Mo/Si multilayers on saw-tooth substrates. The sputtering conditions were optimized by finding a balance between smoothening and roughening processes in order to minimize degradation of the groove profile in the course of deposition and at the same time to keep the interfaces of a multilayer stack smooth enough for high efficiency. An optimal value of energy of 200 eV for sputtering Kr+ ions was found by deposition of test multilayers on flat substrates at a range of ion energies. Two saw-tooth substrates were deposited at energies of 200 eV and 700 eV for the sputtering ions. It was found that reduction of the ion energy improved the blazing performance of the MBG and resulted in a 40% gain in the diffraction efficiency due to better replication of the groove profile by the multilayer. As a result of the optimization performed, an absolute diffraction efficiency of 28.8% was achieved for the 2nd blaze order of the MBG with a groove density of 7350 lines/mm at a wavelength of 13.5 nm. Details of the growth behavior of the multilayers on flat and saw-tooth substrates are discussed in terms of the linear continuous model of film growth.

  12. Conformal growth of Mo/Si multilayers on grating substrates using collimated ion beam sputtering

    SciTech Connect

    Voronov, D. L.; Cambie, R.; Dhuey, S.; Gullikson, E. M.; Warwick, T.; Yashchuk, V. V.; Padmore, H. A.; Gawlitza, P.; Braun, S.

    2012-05-01

    Deposition of multilayers on saw-tooth substrates is a key step in the fabrication of multilayer blazed gratings (MBG) for extreme ultraviolet and soft x-rays. Growth of the multilayers can be perturbed by shadowing effects caused by the highly corrugated surface of the substrates, which results in distortion of the multilayer stack structure and degradation of performance of MBGs. To minimize the shadowing effects, we used an ion-beam sputtering machine with a highly collimated atomic flux to deposit Mo/Si multilayers on saw-tooth substrates. The sputtering conditions were optimized by finding a balance between smoothening and roughening processes in order to minimize degradation of the groove profile in the course of deposition and at the same time to keep the interfaces of a multilayer stack smooth enough for high efficiency. An optimal value of energy of 200 eV for sputtering Kr{sup +} ions was found by deposition of test multilayers on flat substrates at a range of ion energies. Two saw-tooth substrates were deposited at energies of 200 eV and 700 eV for the sputtering ions. It was found that reduction of the ion energy improved the blazing performance of the MBG and resulted in a 40% gain in the diffraction efficiency due to better replication of the groove profile by the multilayer. As a result of the optimization performed, an absolute diffraction efficiency of 28.8% was achieved for the 2nd blaze order of the MBG with a groove density of 7350 lines/mm at a wavelength of 13.5 nm. Details of the growth behavior of the multilayers on flat and saw-tooth substrates are discussed in terms of the linear continuous model of film growth.

  13. Modeling gravity effects on water retention and gas transport characteristics in plant growth substrates

    NASA Astrophysics Data System (ADS)

    Chamindu Deepagoda, T. K. K.; Jones, Scott B.; Tuller, Markus; de Jonge, Lis Wollesen; Kawamoto, Ken; Komatsu, Toshiko; Moldrup, Per

    2014-08-01

    Growing plants to facilitate life in outer space, for example on the International Space Station (ISS) or at planned deep-space human outposts on the Moon or Mars, has received much attention with regard to NASA’s advanced life support system research. With the objective of in situ resource utilization to conserve energy and to limit transport costs, native materials mined on Moon or Mars are of primary interest for plant growth media in a future outpost, while terrestrial porous substrates with optimal growth media characteristics will be useful for onboard plant growth during space missions. Due to limited experimental opportunities and prohibitive costs, liquid and gas behavior in porous substrates under reduced gravity conditions has been less studied and hence remains poorly understood. Based on ground-based measurements, this study examined water retention, oxygen diffusivity and air permeability characteristics of six plant growth substrates for potential applications in space, including two terrestrial analogs for lunar and Martian soils and four particulate substrates widely used in reduced gravity experiments. To simulate reduced gravity water characteristics, the predictions for ground-based measurements (1 - g) were scaled to two reduced gravity conditions, Martian gravity (0.38 - g) and lunar gravity (0.16 - g), following the observations in previous reduced gravity studies. We described the observed gas diffusivity with a recently developed model combined with a new approach that estimates the gas percolation threshold based on the pore size distribution. The model successfully captured measured data for all investigated media and demonstrated the implications of the poorly-understood shift in gas percolation threshold with improved gas percolation in reduced gravity. Finally, using a substrate-structure parameter related to the gaseous phase, we adequately described the air permeability under reduced gravity conditions.

  14. Initial growth on microcrystalline silicon on atomically flat hetero-substrate

    SciTech Connect

    Saitoh, K.; Kondo, M.; Matsuda, A.

    1997-07-01

    Initial growth of microcrystalline silicon ({micro}c-Si:H) deposited on an atomically flat GaAs (001) wafer using a RF glow-discharge decomposition of hydrogen diluted monosilane gas mixture has been studied by means of atomic force microscope (AFM), Auger electron spectroscopy (AES), and cross-sectional transmission electron microscopy (XTEM). It is shown that the initial growth of {micro}c-Si:H deposited at a substrate temperature of 50--250 C consists of four successive stages, i.e., (1) a layer-by-layer growth of a-Si:H up to d {approximately}5 {angstrom}, (2) island formation of a-Si:H, (3) the coalescence of the islands and the nucleation of microcrystalline at d{approximately}10{approximately}40 {angstrom} depending on the growth temperature, and (4) a rapid roughening with microcrystalline growth.

  15. Report on the growth of bulk aluminum nitride and subsequent substrate preparation

    NASA Astrophysics Data System (ADS)

    Carlos Rojo, J.; Slack, Glen A.; Morgan, Kenneth; Raghothamachar, Balaji; Dudley, Michael; Schowalter, Leo J.

    2001-10-01

    High-quality, bulk aluminum nitride crystal grains exceeding 1 cm in dimension have been obtained using a self-seeded sublimation-recondensation growth technique at 0.9 mm/h driving rate. X-ray double crystal diffraction and topography show a full-width-at-half-maximum of around 100 arcsec and extensive areas with a density of dislocations less than 10 4 cm -2, respectively. These substrates have been prepared by chemical mechanical polishing techniques to obtain a surface roughness of 1.4-1.6 nm. The size, structural quality, and surface roughness prove these substrates to be adequate for III-nitride device fabrication.

  16. Effect of Substrate Composition on Sn Whisker Growth in Pure Sn Films

    NASA Astrophysics Data System (ADS)

    Miller, Sarah M.; Sahaym, Uttara; Norton, M. Grant

    2010-12-01

    Pure Sn films deposited on Cu and Cu alloys are prone to spontaneous whisker formation. One way of preventing whisker formation is to alloy Pb into Sn coatings. However, restriction on the use of Pb demands the development of alternative methods for preventing whisker growth. The present work reports the effect of substrate composition on whisker formation and morphology. Despite employing identical plating conditions, long filament-like whiskers grew only on Sn-plated Cu samples and not on brass. The presence or lack of Sn whiskers has been explained via the thermodynamic stability of various intermetallic compounds at the Sn/substrate interface.

  17. Direct growth of nanocrystalline hexagonal boron nitride films on dielectric substrates

    NASA Astrophysics Data System (ADS)

    Tay, Roland Yingjie; Tsang, Siu Hon; Loeblein, Manuela; Chow, Wai Leong; Loh, Guan Chee; Toh, Joo Wah; Ang, Soon Loong; Teo, Edwin Hang Tong

    2015-03-01

    Atomically thin hexagonal-boron nitride (h-BN) films are primarily synthesized through chemical vapor deposition (CVD) on various catalytic transition metal substrates. In this work, a single-step metal-catalyst-free approach to obtain few- to multi-layer nanocrystalline h-BN (NCBN) directly on amorphous SiO2/Si and quartz substrates is demonstrated. The as-grown thin films are continuous and smooth with no observable pinholes or wrinkles across the entire deposited substrate as inspected using optical and atomic force microscopy. The starting layers of NCBN orient itself parallel to the substrate, initiating the growth of the textured thin film. Formation of NCBN is due to the random and uncontrolled nucleation of h-BN on the dielectric substrate surface with no epitaxial relation, unlike on metal surfaces. The crystallite size is ˜25 nm as determined by Raman spectroscopy. Transmission electron microscopy shows that the NCBN formed sheets of multi-stacked layers with controllable thickness from ˜2 to 25 nm. The absence of transfer process in this technique avoids any additional degradation, such as wrinkles, tears or folding and residues on the film which are detrimental to device performance. This work provides a wider perspective of CVD-grown h-BN and presents a viable route towards large-scale manufacturing of h-BN substrates and for coating applications.

  18. Direct growth of nanocrystalline hexagonal boron nitride films on dielectric substrates

    SciTech Connect

    Tay, Roland Yingjie; Tsang, Siu Hon; Loeblein, Manuela; Chow, Wai Leong; Loh, Guan Chee; Toh, Joo Wah; Ang, Soon Loong; Teo, Edwin Hang Tong

    2015-03-09

    Atomically thin hexagonal-boron nitride (h-BN) films are primarily synthesized through chemical vapor deposition (CVD) on various catalytic transition metal substrates. In this work, a single-step metal-catalyst-free approach to obtain few- to multi-layer nanocrystalline h-BN (NCBN) directly on amorphous SiO{sub 2}/Si and quartz substrates is demonstrated. The as-grown thin films are continuous and smooth with no observable pinholes or wrinkles across the entire deposited substrate as inspected using optical and atomic force microscopy. The starting layers of NCBN orient itself parallel to the substrate, initiating the growth of the textured thin film. Formation of NCBN is due to the random and uncontrolled nucleation of h-BN on the dielectric substrate surface with no epitaxial relation, unlike on metal surfaces. The crystallite size is ∼25 nm as determined by Raman spectroscopy. Transmission electron microscopy shows that the NCBN formed sheets of multi-stacked layers with controllable thickness from ∼2 to 25 nm. The absence of transfer process in this technique avoids any additional degradation, such as wrinkles, tears or folding and residues on the film which are detrimental to device performance. This work provides a wider perspective of CVD-grown h-BN and presents a viable route towards large-scale manufacturing of h-BN substrates and for coating applications.

  19. Process for selectively patterning epitaxial film growth on a semiconductor substrate

    DOEpatents

    Sheldon, Peter; Hayes, Russell E.

    1986-01-01

    A process is disclosed for selectively patterning epitaxial film growth on a semiconductor substrate. The process includes forming a masking member on the surface of the substrate, the masking member having at least two layers including a first layer disposed on the substrate and the second layer covering the first layer. A window is then opened in a selected portion of the second layer by removing that portion to expose the first layer thereunder. The first layer is then subjected to an etchant introduced through the window to dissolve a sufficient amount of the first layer to expose the substrate surface directly beneath the window, the first layer being adapted to preferentially dissolve at a substantially greater rate than the second layer so as to create an overhanging ledge portion with the second layer by undercutting the edges thereof adjacent to the window. The epitaxial film is then deposited on the exposed substrate surface directly beneath the window. Finally, an etchant is introduced through the window to dissolve the remainder of the first layer so as to lift-off the second layer and materials deposited thereon to fully expose the balance of the substrate surface.

  20. Process for selectively patterning epitaxial film growth on a semiconductor substrate

    DOEpatents

    Sheldon, P.; Hayes, R.E.

    1984-12-04

    Disclosed is a process for selectively patterning epitaxial film growth on a semiconductor substrate. The process includes forming a masking member on the surface of the substrate, the masking member having at least two layers including a first layer disposed on the substrate and the second layer covering the first layer. A window is then opened in a selected portion of the second layer by removing that portion to expose the first layer thereunder. The first layer is then subjected to an etchant introduced through the window to dissolve the first layer a sufficient amount to expose the substrate surface directly beneath the window, the first layer being adapted to preferentially dissolve at a substantially greater rate than the second layer so as to create an overhanging ledge portion with the second layer by undercutting the edges thereof adjacent the window. The epitaxial film is then deposited on the exposed substrate surface directly beneath the window. Finally, an etchant is introduced through the window to dissolve the remainder of the first layer so as to lift-off the second layer and materials deposited thereon to fully expose the balance of the substrate surface.

  1. Layered transition metal dichalcogenides: promising near-lattice-matched substrates for GaN growth

    PubMed Central

    Gupta, Priti; Rahman, A. A.; Subramanian, Shruti; Gupta, Shalini; Thamizhavel, Arumugam; Orlova, Tatyana; Rouvimov, Sergei; Vishwanath, Suresh; Protasenko, Vladimir; Laskar, Masihhur R.; Xing, Huili Grace; Jena, Debdeep; Bhattacharya, Arnab

    2016-01-01

    Most III-nitride semiconductors are grown on non-lattice-matched substrates like sapphire or silicon due to the extreme difficulty of obtaining a native GaN substrate. We show that several layered transition-metal dichalcogenides are closely lattice-matched to GaN and report the growth of GaN on a range of such layered materials. We report detailed studies of the growth of GaN on mechanically-exfoliated flakes WS2 and MoS2 by metalorganic vapour phase epitaxy. Structural and optical characterization show that strain-free, single-crystal islands of GaN are obtained on the underlying chalcogenide flakes. We obtain strong near-band-edge emission from these layers, and analyse their temperature-dependent photoluminescence properties. We also report a proof-of-concept demonstration of large-area growth of GaN on CVD MoS2. Our results show that the transition-metal dichalcogenides can serve as novel near-lattice-matched substrates for nitride growth. PMID:27025461

  2. Layered transition metal dichalcogenides: promising near-lattice-matched substrates for GaN growth

    NASA Astrophysics Data System (ADS)

    Gupta, Priti; Rahman, A. A.; Subramanian, Shruti; Gupta, Shalini; Thamizhavel, Arumugam; Orlova, Tatyana; Rouvimov, Sergei; Vishwanath, Suresh; Protasenko, Vladimir; Laskar, Masihhur R.; Xing, Huili Grace; Jena, Debdeep; Bhattacharya, Arnab

    2016-03-01

    Most III-nitride semiconductors are grown on non-lattice-matched substrates like sapphire or silicon due to the extreme difficulty of obtaining a native GaN substrate. We show that several layered transition-metal dichalcogenides are closely lattice-matched to GaN and report the growth of GaN on a range of such layered materials. We report detailed studies of the growth of GaN on mechanically-exfoliated flakes WS2 and MoS2 by metalorganic vapour phase epitaxy. Structural and optical characterization show that strain-free, single-crystal islands of GaN are obtained on the underlying chalcogenide flakes. We obtain strong near-band-edge emission from these layers, and analyse their temperature-dependent photoluminescence properties. We also report a proof-of-concept demonstration of large-area growth of GaN on CVD MoS2. Our results show that the transition-metal dichalcogenides can serve as novel near-lattice-matched substrates for nitride growth.

  3. Growth of Aeromonas hydrophila at Low Concentrations of Substrates Added to Tap Water

    PubMed Central

    van der Kooij, D.; Visser, A.; Hijnen, W. A. M.

    1980-01-01

    The ability of an Aeromonas hydrophila isolate obtained from filtered river water to grow at low substrate concentrations was studied in batch experiments with tap water supplied with low concentrations of substrates. Growth was assessed by colony count determinations. The isolate only multiplied in the used tap water (2 to 3 mg of dissolved organic carbon per liter) after the addition of a small amount of an assimilable carbon compound. d-Glucose especially caused growth of the organism even at initial concentrations below 10 μg of C per liter. At initial glucose concentrations below the Ks value (12 μg of C per liter), generation times and yield (colony-forming units per milligram of substrate-C) were nonlinear with 1/initial glucose concentrations and initial glucose concentrations, respectively. From these observations, the maintenance coefficient m was calculated (m = 0.015 mg of glucose per mg [dry wt] per h at 12°C). At initial concentrations below the Ks value of starch (73 μg of C per liter), no growth was observed, but complete use of starch occurred in these situations after the addition of 10 μg of glucose-C per liter. The results of this study show that information of ecological significance may be obtained by very simple batch experiments. Moreover, the isolate studied may be used in growth experiments to assess the maximum concentration of glucose which might be present in water, particularly tap water. PMID:16345582

  4. Direct growth of cerium oxide nanorods on diverse substrates for superhydrophobicity and corrosion resistance

    NASA Astrophysics Data System (ADS)

    Cho, Young Jun; Jang, Hanmin; Lee, Kwan-Soo; Kim, Dong Rip

    2015-06-01

    Superhydrophobic surfaces with anti-corrosion properties have attracted great interest in many industrial fields, particularly to enhance the thermal performance of offshore applications such as heat exchangers, pipelines, power plants, and platform structures. Nanostructures with hydrophobic materials have been widely utilized to realize superhydrophobicity of surfaces, and cerium oxide has been highlighted due to its good corrosion resistive and intrinsically hydrophobic properties. However, few studies of direct growth of cerium oxide nanostructures on diverse substrates have been reported. Herein we report a facile hydrothermal method to directly grow cerium oxide nanorods on diverse substrates, such as aluminum alloy, stainless steel, titanium, and silicon. Diverse substrates with cerium oxide nanorods exhibited superhydrophobicity with no hydrophobic modifiers on their surfaces, and showed good corrosion resistive properties in corrosive medium. We believe our method could pave the way for realization of scalable and sustainable corrosion resistive superhydrophobic surfaces in many industrial fields.

  5. Spent mushroom substrates as component of growing media for germination and growth of horticultural plants.

    PubMed

    Medina, E; Paredes, C; Pérez-Murcia, M D; Bustamante, M A; Moral, R

    2009-09-01

    This research work was conducted in order to investigate the possibility of using spent mushroom substrate (SMS) in the production of horticultural seedlings replacing part of the peat in the growing media. Three vegetable species with different salt sensitivities, the less sensitive being tomato (Lycopersicon esculentum var. Muchamiel), the moderately salt-sensitive being courgette (Cucurbita pepo L. var. Afrodite F1) and the most salt-sensitive being pepper (Capsicum annum L. var. Lamuyo F1) were grown in 12 media containing SMS of two types of mushroom (Agaricus bisporus (SMS-AB) and Pleurotus ostreatus (SMS-PO)) or a mixture of both 50% (v/v) (SMS-50), as well as peat in various ratios. The proportions of each residue in the mixtures elaborated with peat were 25%, 50%, 75% and 100% v/v residue. A substrate of 100% peat was used as control. The experiment was arranged in a completely-randomised design with two replicates per treatment under greenhouse conditions. Prior to sowing, some physical, physico-chemical and chemical properties of the growing media were determined and seed germination and fresh weight of seedling were also measured. In most of the cases, the addition of SMS to the growing media produced an increase in the pH values, salt contents, macro and micronutrient concentrations and a decrease in the water holding capacity contents in comparison to peat, whereas great differences were found in the air capacity values between SMS-based substrates and peat. Up to 75% SMS can be used in mixtures with peat for seed germination of the plant species studied. Regarding the most suitable SMS-based substrates for plant growth, any substrate could be used for tomato seedling production. However, all SMS-AB-based substrates and the media containing low dose of SMS-PO and SMS-50 were adequate for growth of courgette and pepper. PMID:19409775

  6. Development of a Xeno-Free Substrate for Human Embryonic Stem Cell Growth

    PubMed Central

    Zhu, Hailin; Yang, Jinliang; Wei, Yuquan; Chen, Harry Huimin

    2015-01-01

    Traditionally, human embryonic stem cells (hESCs) are cultured on inactivated live feeder cells. For clinical application using hESCs, there is a requirement to minimize the risk of contamination with animal components. Extracellular matrix (ECM) derived from feeder cells is the most natural way to provide xeno-free substrates for hESC growth. In this study, we optimized the step-by-step procedure for ECM processing to develop a xeno-free ECM that supports the growth of undifferentiated hESCs. In addition, this newly developed xeno-free substrate can be stored at 4°C and is ready to use upon request, which serves as an easier way to amplify hESCs for clinical applications. PMID:25861280

  7. Growth of metal-free carbon nanotubes on glass substrate with an amorphous carbon catalyst layer.

    PubMed

    Seo, Jae Keun; Choi, Won Seok; Kim, Hee Dong; Lee, Jae-Hyeoung; Choi, Eun Chang; Kim, Hyung Jin; Hong, Byungyou

    2011-12-01

    We have investigated the direct growth of metal-free carbon nanotubes (CNTs) on glass substrates with microwave-plasma enhanced chemical vapor deposition (MPECVD). Amorphous carbon (a-C) films were used as a catalyst layer to grow metal-free CNTs. The a-C films were deposited on Corning glass substrates using RF magnetron sputtering with the use of a carbon target (99.99%) at room temperature. They were pretreated with hydrogen plasma using a microwave PECVD at 600 degrees C. Then, CNTs were prepared using microwave PECVD with a mixture of methane (CH4) and hydrogen (H2) gases. The CNTs were grown at different substrate temperatures (400 degrees C, 500 degrees C, and 600 degrees C) for 30 minutes. Other conditions were fixed. The growth trends of CNTs against substrate temperature were observed by field emission scanning electron microscopy (FE-SEM). The structure of a-C catalyst layer and grown CNTs were measured by Raman spectroscopy. High-resolution transmission electron microscopy (HR-TEM) images showed that the CNTs had bamboo-like multi-walled structures. Energy dispersive spectroscopy (EDS) measurements confirmed that the CNTs consisted of only carbon. PMID:22409050

  8. Dracaena marginata biofilter: design of growth substrate and treatment of stormwater runoff.

    PubMed

    Vijayaraghavan, K; Praveen, R S

    2016-01-01

    The purpose of this research was to investigate the efficiency of Dracaena marginata planted biofilters to decontaminate urban runoff. A new biofilter growth substrate was prepared using low-cost and locally available materials such as red soil, fine sand, perlite, vermiculite, coco-peat and Sargassum biomass. The performance of biofilter substrate was compared with local garden soil based on physical and water quality parameters. Preliminary analyses indicated that biofilter substrate exhibited desirable characteristics such as low bulk density (1140 kg/m(3)), high water holding capacity (59.6%), air-filled porosity (7.82%) and hydraulic conductivity (965 mm/h). Four different biofilter assemblies, with vegetated and non-vegetated systems, were examined for several artificial rain events (un-spiked and metal-spiked). Results from un-spiked artificial rain events suggested that concentrations of most of the chemical components in effluent were highest at the beginning of rain events and thereafter subsided during the subsequent rain events. Biofilter growth substrate showed superior potential over garden soil to retain metal ions such as Al, Fe, Cu, Cr, Ni, Zn, Cd and Pb during metal-spiked rain events. Significant differences were also observed between non-vegetated and vegetated biofilter assemblies in runoff quality, with the latter producing better results. PMID:26512973

  9. Low Temperature Direct Growth of Graphene Films on Transparent Substrates by Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Antoine, Geoffrey Sandosh Jeffy

    Graphene, two dimensional sheet of carbon atoms has recently gained attention as some of its properties are very useful for electronics, optoelectronics and photovoltaic applications. Its high mobility makes it useful in radio-frequency applications and its transparency makes it useful as transparent electrodes in photovoltaics. It is known that chemical vapor deposition (CVD) is one of the techniques that can be used to synthesize graphene. A lot of work has been done on selecting appropriate substrates and hydrocarbon sources. Nickel, having a high solubility at high temperatures has been in focus lately. Ethylene which has a lower breaking point compared to other hydrocarbons has a good efficiency in the synthesis of graphene. Complexity associated with graphene synthesis and transfers onto transparent substrates constitute the major obstacles to using this material for photovoltaics and optoelectronics applications. Here we show a novel method of obtaining graphene directly on glass via chemical vapor deposition (CVD) using ethylene as the hydrocarbon source and nickel as the catalyst. The low cracking temperature of ethylene which is 542.8 °C permits us to use glass substrates directly in the CVD furnace. To improve the thickness of graphene, a good manipulation of pressure and hydrogen during the growth process will be useful. We introduce a novel catalyst etching technique after the growth results in graphene settling down on the glass substrate in a transfer-free process. Raman spectroscopy indicated good uniformity and high quality before and after the etching process.

  10. Enhancing trichloroethylene degradation using non-aromatic compounds as growth substrates.

    PubMed

    Kim, Seungjin; Hwang, Jeongmin; Chung, Jinwook; Bae, Wookeun

    2014-06-30

    The effect of non-aromatic compounds on the trichloroethylene (TCE) degradation of toluene-oxidizing bacteria were evaluated using Burkholderia cepacia G4 that expresses toluene 2-monooxygenase and Pseudomonas putida that expresses toluene dioxygenase. TCE degradation rates for B. cepacia G4 and P. putida with toluene alone as growth substrate were 0.144 and 0.123 μg-TCE/mg-protein h, respectively. When glucose, acetate and ethanol were fed as additional growth substrates, those values increased up to 0.196, 0.418 and 0.530 μg-TCE/mg-protein h, respectively for B. cepacia G4 and 0.319, 0.219 and 0.373 μg-TCE/mg-protein h, respectively for P. putida. In particular, the addition of ethanol resulted in a high TCE degradation rate regardless of the initial concentration. The use of a non-aromatic compound as an additional substrate probably enhanced the TCE degradation because of the additional supply of NADH that is consumed in co-metabolic degradation of TCE. Also, it is expected that the addition of a non-aromatic substrate can reduce the necessary dose of toluene and, subsequently, minimize the potential competitive inhibition upon TCE co-metabolism by toluene. PMID:24857894

  11. Polarity Effects of Substrate Surface in Epitaxial ZnO Film Growth

    NASA Technical Reports Server (NTRS)

    Zhu, Shen; Su, C.-H.; Lehoczky, S. L.; Harris, M. T.; Callahan, M. J.; George, M. A.; McCarty, P.

    1999-01-01

    Epitaxial ZnO films were grown on the two polar surfaces (0-face and Zn-face) of (0001) ZnO single crystal substrates using off-axis magnetron sputtering deposition. As a comparison, films are also deposited on the (000 I) Al203 substrates. It is found that the two polar surfaces have different photoluminescence (PL) spectrum, surface structure and morphology, which are strongly inference the epitaxial film growth. The morphology and structure of epitaxial films on the ZnO substrates are different from the film on the Al203 substrates. An interesting result shows that high temperature annealing of ZnO single crystals will improve the surface structure on the O-face surface rather than the opposite Surface. The measurements of PL, low-angle incident x-ray diffraction, and atomic force microscopy of ZnO films indicate that the O-terminated surface is better for ZnO epitaxial film growth using reactive sputtering deposition.

  12. Metal Catalyst for Low-Temperature Growth of Controlled Zinc Oxide Nanowires on Arbitrary Substrates

    PubMed Central

    Kim, Baek Hyun; Kwon, Jae W.

    2014-01-01

    Zinc oxide nanowires generated by hydrothermal method present superior physical and chemical characteristics. Quality control of the growth has been very challenging and controlled growth is only achievable under very limited conditions using homogeneous seed layers with high temperature processes. Here we show the controlled ZnO nanowire growth on various organic and inorganic materials without the requirement of a homogeneous seed layer and a high temperature process. We also report the discovery of an important role of the electronegativity in the nanowire growth on arbitrary substrates. Using heterogeneous metal oxide interlayers with low-temperature hydrothermal methods, we demonstrate well-controlled ZnO nanowire arrays and single nanowires on flat or curved surfaces. A metal catalyst and heterogeneous metal oxide interlayers are found to determine lattice-match with ZnO and to largely influence the controlled alignment. These findings will contribute to the development of novel nanodevices using controlled nanowires. PMID:24625584

  13. On a geometric model of crystal growth on a flat substrate

    NASA Astrophysics Data System (ADS)

    Brednikhina, Anna; Debelov, Victor A.

    2009-01-01

    This paper is devoted to computer simulation of crystalline aggregates growth from a homogeneous solution. This process is considered from the geometric point of view, when crystals can be represented as a collection of flat faces, growing layer by layer with stable relative growth rates in the directions of their perpendiculars. Simply speaking, we extend Frank's model [H. Muller-Krumbhaar, Yu. Saito, Crystal Growth and Solidification, in: Surfactant Science Series, vol. 89, CRC Press, Boca Raton, FL, 2000, pp. 853-854] to the case of simultaneous growth of several individuals placed on a flat unbounded static substrate. Attention is given not only to finding the outer boundary of an aggregate but to determining the interfacing surfaces between individuals. In other words, our goal is to construct detailed bounding surfaces of all individuals included in an aggregate.

  14. Growth Process of Vacuum Deposited Copper Phthalocyanine Thin Films on Rubbing-Treated Substrates

    NASA Astrophysics Data System (ADS)

    Ofuji, Masato; Inaba, Katsuhiko; Omote, Kazuhiko; Hoshi, Hajime; Takanishi, Yoichi; Ishikawa, Ken; Takezoe, Hideo

    2003-12-01

    Surface morphology, crystal lattice spacings and crystallite size of copper phthalocyanine (CuPc) thin films grown on rubbed surfaces were probed at different stages of growth, by means of atomic force microscopy (AFM) and X-ray diffraction (XRD). The films consisted of many slender crystallites extending along the rubbing direction, due to the α-type columnar structure along the same direction. AFM revealed that the aspect ratio of crystal domains increases as the films grow, implying a change in the ratio of crystal growth rates in the two different directions parallel to the substrates. XRD demonstrated marked differences in the two intercolumnar directions. The molecular spacing is expanded in the thickness direction at the initial stage of growth, while it remains constant throughout the growth in the lateral (c-axis) direction. The crystallite size in the thickness direction is always comparable to the film thickness, while the size in the c-axis direction shows no change.

  15. CONTROLLED GROWTH OF CARBON NANOTUBES ON CONDUCTIVE METAL SUBSTRATES FOR ENERGY STORAGE APPLICATIONS

    SciTech Connect

    Brown, P.; Engtrakul, C.

    2009-01-01

    The impressive mechanical and electronic properties of carbon nanotubes (CNTs) make them ideally suited for use in a variety of nanostructured devices, especially in the realm of energy production and storage. In particular, vertically-aligned CNT “forests” have been the focus of increasing investigation for use in supercapacitor electrodes and as hydrogen adsorption substrates. Vertically-aligned CNT growth was attempted on metal substrates by waterassisted chemical vapor deposition (CVD). CNT growth was catalyzed by iron-molybdenum (FeMo) nanoparticle catalysts synthesized by a colloidal method, which were then spin-coated onto Inconel® foils. The substrates were loaded into a custom-built CVD apparatus, where CNT growth was initiated by heating the substrates to 750 °C under the fl ow of He, H2, C2H4 and a controlled amount of water vapor. The resultant CNTs were characterized by a variety of methods including Raman spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and the growth parameters were varied in an attempt to optimize the purity and growth yield of the CNTs. The surface area and hydrogen adsorption characteristics of the CNTs were quantifi ed by the Brunauer- Emmett-Teller (BET) and Sieverts methods, and their capacitance was measured via cyclic voltammetry. While vertically-aligned CNT growth could not be verifi ed, TEM and SEM analysis indicated that CNT growth was still obtained, resulting in multiwalled CNTs of a wide range in diameter along with some amorphous carbon impurities. These microscopy fi ndings were reinforced by Raman spectroscopy, which resulted in a G/D ratio ranging from 1.5 to 3 across different samples, suggestive of multiwalled CNTs. Changes in gas fl ow rates and water concentration during CNT growth were not found to have a discernable effect on the purity of the CNTs. The specifi c capacitance of a CNT/FeMo/Inconel® electrode was found to be 3.2 F/g, and the BET surface area of

  16. Equilibrium-restricted solid-on-solid growth model on fractal substrates.

    PubMed

    Lee, Sang Bub; Kim, Jin Min

    2009-08-01

    The equilibrium-restricted solid-on-solid growth model on fractal substrates is studied by introducing a fractional Langevin equation. The growth exponent beta and the roughness exponent alpha defined, respectively, by the surface width via W approximately t(beta) and the saturated width via W(sat) approximately L(alpha), L being the system size, were obtained by a power-counting analysis, and the scaling relation 2alpha+d(f)=z(RW) was found to hold. The numerical simulation data on Sierpinski gasket, checkerboard fractal, and critical percolation cluster were found to agree well with the analytical predictions of the fractional Langevin equation. PMID:19792071

  17. Generalization of Monod kinetics for analysis of growth data with substrate inhibition

    SciTech Connect

    Luong, J.H.T.

    1987-02-05

    The inhibitory effect of butanol on yeast growth has been studied for the strain Candida utilis ATCC 8205 growing aerobically on butanol under batch conditions. A mathematical expression was then proposed to fit the kinetic pattern of butanol inhibition on the specific growth rate. The maximum allowable butanol concentration above which cells do not grow was predicted to be 9.16 g/l. The proposed model appears to accurately represent the experimental data obtained in this study and the literature data developed for a variety of batch culture systems at widely ranging substrate concentrations. 20 references.

  18. Ultraviolet radiation on innate immunity and growth of broad-snouted caiman (Caiman latirostris): implications for facilities design.

    PubMed

    Siroski, Pablo Ariel; Poletta, Gisela Laura; Fernandez, Lucia; Ortega, Hugo Héctor; Merchant, Mark Edwin

    2012-01-01

    Sunlight is a key environmental factor in almost all ecosystems, and it is necessary for many physiological functions. Many vertebrates require ultraviolet (UV) radiation to perform different physiological processes. Artificial light is used to supplement UV in captive animals, through appropriate photoperiods and UV wavelengths. Previous studies reported that repeated exposure to artificial UV radiation may cause damage to the immune system. Taking into account the importance of UV effects and the serum complement system, the relationship between them was investigated. The study lasted 90 days and was carried out in plastic chambers. Ninety six broad-snouted caiman (C. latirostris) were assigned to four treatment groups with two replicates each: total darkness (TD), 8 hr per day (8 hr) and 16 hr per day (16 hr) of artificial UV/visible light exposure, and normal photoperiod of natural light (NP). Snout-vent length was measured to determine animal growth. Hemolytic assays were performed to evaluate the effects of artificial UV/visible light, TD, and NP on the serum complement system. Results showed that animals grew more in the NP group. The capacity of C. latirostris serum to hemolyze sheep red blood cells was higher in the NP group than when they are maintained in constant light-dark cycles (8 and 16 hr) or in TD. These data demonstrate that artificial UV should be considered as a potential hazard for captive crocodilians if it is not properly managed, and this should be taken into account in the general design of facilities for reptilian husbandry. PMID:21850705

  19. Growth and Characterization of III-Nitride LEDs on Vicinal Sapphire Substrates

    NASA Astrophysics Data System (ADS)

    Khan, N.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2006-03-01

    GaN and related III-N alloys have great potential applications in optoelectronic devices such as light emitting diodes (LEDs), laser diodes (LDs) and high power electronic devices such as transistors. For improved performance and greater versatility of these devices, it is essential to improve the quality of materials and devices. It has been reported that growth on vicinal or misaligned substrates compared to flat ones, lead to smoother and higher crystalline quality thin films. Improved brightness and quantum efficiency, and a reduction of the forward current at which maximum quantum efficiency occurs are among the improved optical properties resulting from the use of misaligned substrates and a thick base layer. We report on the characteristics of InGaN based blue/green LEDs grown by metal organic chemical vapor deposition (MOCVD) on specially fabricated dome shaped sapphire substrates. These dome shaped substrates provide varying degrees of off-cut within a single wafer. Surface morphologies, crystalline qualities and emission properties across the entire wafer surface have been mapped by various techniques, including optical and atomic force microscopy (AFM), x-ray diffraction and electroluminescence and photoluminescence spectroscopy. The results are compared with those of blue/green LEDs grown on conventional on-axis substrates.

  20. L: -Stereoselective amino acid amidase with broad substrate specificity from Brevundimonas diminuta: characterization of a new member of the leucine aminopeptidase family.

    PubMed

    Komeda, Hidenobu; Hariyama, Nozomi; Asano, Yasuhisa

    2006-04-01

    Brevundimonas diminuta TPU 5720 produces an amidase acting L-stereoselectively on phenylalaninamide. The enzyme (LaaA(Bd)) was purified to electrophoretic homogeneity by ammonium sulfate fractionation and four steps of column chromatography. The final preparation gave a single band on SDS-PAGE with a molecular weight of approximately 53,000. The native molecular weight of the enzyme was about 288,000 based on gel filtration chromatography, suggesting that the enzyme is active as a homohexamer. It had maximal activity at 50 degrees C and pH 7.5. LaaA(Bd) lost its activity almost completely on dialysis against potassium phosphate buffer (pH 7.0), and the amidase activity was largely restored by the addition of Co(2+) ions. The enzyme was, however, inactivated in the presence of ethylenediaminetetraacetic acid even in the presence of Co(2+), suggesting that LaaA(Bd) is a Co(2+)-dependent enzyme. LaaA(Bd) had hydrolyzing activity toward a broad range of L-amino acid amides including L-phenylalaninamide, L-glutaminamide, L-leucinamide, L-methioninamide, L-argininamide, and L-2-aminobutyric acid amide. Using information on the N-terminal amino acid sequence of the enzyme, the gene encoding LaaA(Bd) was cloned from the chromosomal DNA of the strain and sequenced. Analysis of 4,446 bp of the cloned DNA revealed the presence of seven open-reading frames (ORFs), one of which (laaA ( Bd )) encodes the amidase. LaaA(Bd) is composed of 491 amino acid residues (calculated molecular weight 51,127), and the deduced amino acid sequence exhibits significant similarity to that of ORFs encoding hypothetical cytosol aminopeptidases found in the genomes of Caulobacter crescentus, Bradyrhizobium japonicum, Rhodopseudomonas palustris, Mesorhizobium loti, and Agrobacterium tumefaciens, and leucine aminopeptidases, PepA, from Rickettsia prowazekii, Pseudomonas putida ATCC 12633, and Escherichia coli K-12. The laaA ( Bd ) gene modified in the nucleotide sequence upstream from its start codon

  1. Sub-surface alloying largely influences graphene nucleation and growth over transition metal substrates.

    PubMed

    Zhang, Liying; Zhao, Xingju; Xue, Xinlian; Shi, Jinlei; Li, Chong; Ren, Xiaoyan; Niu, Chunyao; Jia, Yu; Guo, Zhengxiao; Li, Shunfang

    2015-11-11

    Sub-surface alloying (SSA) can be an effective approach to tuning surface functionalities. Focusing on Rh(111) as a typical substrate for graphene nucleation, we show strong modulation by SSA atoms of both the energetics and kinetics of graphene nucleation simulated by first-principles calculations. Counter-intuitively, when the sub-surface atoms are replaced by more active solute metal elements to the left of Rh in the periodic table, such as the early transition metals (TMs), Ru and Tc, the binding between a C atom and the substrate is weakened and two C atoms favor dimerization. Alternatively, when the alloying elements are the late TMs to the right of Rh, such as the relatively inert Pd and Ag, the repulsion between the two C atoms is enhanced. Such distinct results can be well addressed by the delicately modulated activities of the surface host atoms in the framework of the d-band theory. More specifically, we establish a very simple selection rule for optimizing the metal substrate for high quality graphene growth: the introduction of an early (late) solute TM in the SSA lowers (raises) the d-band center and the activity of the top-most host metal atoms, weakening (strengthening) the C-substrate binding, meanwhile both energetically and kinetically facilitating (hindering) the graphene nucleation, and simultaneously promoting (suppressing) the orientation disordering the graphene domains. Importantly, our preliminary theoretical results also show that such a simple rule is also proposed to be operative for graphene growth on the widely invoked Cu(111) catalytic substrate. PMID:26257125

  2. One-step catalytic growth of carbon nanofiber arrays vertically aligned on carbon substrate

    SciTech Connect

    Li, Xun; State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 ; Xu, Zheng

    2012-06-15

    Highlights: ► Acetylene as carbon resource and copper foil as catalyst. ► Three carbon nanostructures are synthesized by modulating feeding gas compositions. ► NH{sub 3} is a key factor in the growth of VA-CNF arrays. -- Abstract: Vertically aligned carbon nanofiber (VA-CNF) arrays on carbon substrate have been synthesized via one-step chemical vapor deposition process on copper foil, by using acetylene as carbon resource. Three types of carbon nanostructures, viz. bare carbon films, CNFs and VA-CNFs grown on carbon substrate, could be selectively synthesized by only modulating the concentration of C{sub 2}H{sub 2} and NH{sub 3} in the feeding gases. It was found that NH{sub 3} was a key factor in the growth of VA-CNF arrays, which could increase the diffusion capability of copper atoms in carbon materials, therefore promote forming larger spherical Cu NPs catalysts for the growth of VA-CNFs. Furthermore, a growth mechanism in different feeding gas compositions was proposed.

  3. Growth and wetting of water droplet condensed between micron-sized particles and substrate.

    PubMed

    Quang, Tran Si Bui; Leong, Fong Yew; An, Hongjie; Tan, Beng Hau; Ohl, Claus-Dieter

    2016-01-01

    We study heterogeneous condensation growth of water droplets on micron-sized particles resting on a level substrate. Through numerical simulations on equilibrium droplet profiles, we find multiple wetting states towards complete wetting of the particle. Specifically, a partially wetting droplet could undergo a spontaneous transition to complete wetting during condensation growth, for contact angles above a threshold minimum. In addition, we find a competitive wetting behavior between the particle and the substrate, and interestingly, a reversal of the wetting dependence on contact angles during late stages of droplet growth. Using quasi-steady assumption, we simulate a growing droplet under a constant condensation flux, and the results are in good agreement with our experimental observations. As a geometric approximation for particle clusters, we propose and validate a pancake model, and with it, show that a particle cluster has greater wetting tendency compared to a single particle. Together, our results indicate a strong interplay between contact angle, capillarity and geometry during condensation growth. PMID:27487977

  4. Growth and wetting of water droplet condensed between micron-sized particles and substrate

    PubMed Central

    Quang, Tran Si Bui; Leong, Fong Yew; An, Hongjie; Tan, Beng Hau; Ohl, Claus-Dieter

    2016-01-01

    We study heterogeneous condensation growth of water droplets on micron-sized particles resting on a level substrate. Through numerical simulations on equilibrium droplet profiles, we find multiple wetting states towards complete wetting of the particle. Specifically, a partially wetting droplet could undergo a spontaneous transition to complete wetting during condensation growth, for contact angles above a threshold minimum. In addition, we find a competitive wetting behavior between the particle and the substrate, and interestingly, a reversal of the wetting dependence on contact angles during late stages of droplet growth. Using quasi-steady assumption, we simulate a growing droplet under a constant condensation flux, and the results are in good agreement with our experimental observations. As a geometric approximation for particle clusters, we propose and validate a pancake model, and with it, show that a particle cluster has greater wetting tendency compared to a single particle. Together, our results indicate a strong interplay between contact angle, capillarity and geometry during condensation growth. PMID:27487977

  5. MBE Growth of AlN Nanowires on Si Substrates by Aluminizing Nucleation.

    PubMed

    E, Yanxiong; Hao, Zhibiao; Yu, Jiadong; Wu, Chao; Liu, Runze; Wang, Lai; Xiong, Bing; Wang, Jian; Han, Yanjun; Sun, Changzheng; Luo, Yi

    2015-12-01

    By introducing an aluminization process to achieve nucleation of nanowires (NWs), spontaneous growth of AlN NWs on Si substrates has been realized by plasma-assisted molecular beam epitaxy. The AlN NWs are grown from the nuclei formed by the aluminization process, and the NW density and diameter can be controlled by the aluminization parameters. The influence of growth conditions on the morphologies of AlN NWs is carefully investigated. Island-like films are found to grow between the NWs due to poor migration ability of Al adatoms. The films are proved to be Al-polar different from the N-polar AlN NWs, which can explain the absence of newly formed NWs. Increasing the V/III ratio can efficiently suppress the growth of Al-polar AlN films. PMID:26437653

  6. MBE Growth of AlN Nanowires on Si Substrates by Aluminizing Nucleation

    NASA Astrophysics Data System (ADS)

    E, Yanxiong; Hao, Zhibiao; Yu, Jiadong; Wu, Chao; Liu, Runze; Wang, Lai; Xiong, Bing; Wang, Jian; Han, Yanjun; Sun, Changzheng; Luo, Yi

    2015-10-01

    By introducing an aluminization process to achieve nucleation of nanowires (NWs), spontaneous growth of AlN NWs on Si substrates has been realized by plasma-assisted molecular beam epitaxy. The AlN NWs are grown from the nuclei formed by the aluminization process, and the NW density and diameter can be controlled by the aluminization parameters. The influence of growth conditions on the morphologies of AlN NWs is carefully investigated. Island-like films are found to grow between the NWs due to poor migration ability of Al adatoms. The films are proved to be Al-polar different from the N-polar AlN NWs, which can explain the absence of newly formed NWs. Increasing the V/III ratio can efficiently suppress the growth of Al-polar AlN films.

  7. Purely sonochemical route for oriented zinc oxide nanowire growth on arbitrary substrate

    NASA Astrophysics Data System (ADS)

    Nayak, Avinash P.; Katzenmeyer, Aaron M.; Kim, Ja-Yeon; Kwon, Min Ki; Gosho, Yasuhiro; Islam, M. Saif

    2010-04-01

    We report a simple sonochemical method for the seeding and synthesis of Zinc Oxide nanowire arrays that can be formed on a number of substrates that are stable in alcohol and aqueous solution. Vertically aligned ZnO NWs were synthesized from a single solution at room-ambient via ultrasonic excitation. Prior to the NW growth, a ZnO seed layer was deposited using the same system with a different solution. The optimal conditions to produce a high density of oriented wires along with their optical characteristics are presented for ZnO NWs with a significantly high growth rate compared with traditional growth techniques such as evaporation, chemical vapor deposition and sputtering. Our method promises a mass-manufacturable process for fast and inexpensive ZnO NW production for practical low cost electronics, photonics and energy conversion applications.

  8. Ni nanoparticle catalyzed growth of MWCNTs on Cu NPs @ a-C:H substrate

    NASA Astrophysics Data System (ADS)

    Ghodselahi, T.; Solaymani, S.; Akbarzadeh Pasha, M.; Vesaghi, M. A.

    2012-11-01

    NiCu NPs @ a-C:H thin films with different Cu content were prepared by co-deposition by RF-sputtering and RF-plasma enhanced chemical vapor deposition (RF-PECVD) from acetylene gas and Cu and Ni targets. The prepared samples were used as catalysts for growing multi-wall carbon nanotubes (MWCNTs) from liquid petroleum gas (LPG) at 825 °C by thermal chemical vapor deposition (TCVD). By addition of Cu NPs @ a-C:H thin layer as substrate for Ni NPs catalyst, the density of the grown CNTs is greatly enhanced in comparison to bare Si substrate. Furthermore the average diameter of the grown CNTs decreases by decreasing of Cu content of Cu NPs @ a-C:H thin layer. However Cu NPs @ a-C:H by itself has no catalytic property in MWCNTs growth. Morphology and electrical and optical properties of Cu NPs @ a-C:H thin layer is affected by Cu content and each of them is effective parameter on growth of MWCNTs based on Ni NPs catalyst. Moreover, adding of a low amount of Ni NPs doesn't vary optical, electrical and morphology properties of Cu NPs @ a-C:H thin layer but it has a profound effect on its catalytic activity. Finally the density and diameter of MWCNTs can be optimized by selection of the Cu NPs @ a-C:H thin layer as substrate of Ni NPs.

  9. Kinetics of substrate utilization and bacterial growth of crude oil degraded by Pseudomonas aeruginosa.

    PubMed

    Talaiekhozani, Amirreza; Jafarzadeh, Nematollah; Fulazzaky, Mohamad Ali; Talaie, Mohammad Reza; Beheshti, Masoud

    2015-01-01

    Pollution associated with crude oil (CO) extraction degrades the quality of waters, threatens drinking water sources and may ham air quality. The systems biology approach aims at learning the kinetics of substrate utilization and bacterial growth for a biological process for which very limited knowledge is available. This study uses the Pseudomonas aeruginosa to degrade CO and determines the kinetic parameters of substrate utilization and bacterial growth modeled from a completely mixed batch reactor. The ability of Pseudomonas aeruginosa can remove 91 % of the total petroleum hydrocarbons and 83 % of the aromatic compounds from oily environment. The value k of 9.31 g of substrate g(-1) of microorganism d(-1) could be far higher than the value k obtained for petrochemical wastewater treatment and that for municipal wastewater treatment. The production of new cells of using CO as the sole carbon and energy source can exceed 2(3) of the existing cells per day. The kinetic parameters are verified to contribute to improving the biological removal of CO from oily environment. PMID:26413306

  10. Halo(natrono)archaea isolated from hypersaline lakes utilize cellulose and chitin as growth substrates

    PubMed Central

    Sorokin, Dimitry Y.; Toshchakov, Stepan V.; Kolganova, Tatyana V.; Kublanov, Ilya V.

    2015-01-01

    Until recently, extremely halophilic euryarchaeota were considered mostly as aerobic heterotrophs utilizing simple organic compounds as growth substrates. Almost nothing is known on the ability of these prokaryotes to utilize complex polysaccharides, such as cellulose, xylan, and chitin. Although few haloarchaeal cellulases and chitinases were recently characterized, the analysis of currently available haloarchaeal genomes deciphered numerous genes-encoding glycosidases of various families including endoglucanases and chitinases. However, all these haloarchaea were isolated and cultivated on simple substrates and their ability to grow on polysaccharides in situ or in vitro is unknown. This study examines several halo(natrono)archaeal strains from geographically distant hypersaline lakes for the ability to grow on insoluble polymers as a sole growth substrate in salt-saturated mineral media. Some of them belonged to known taxa, while other represented novel phylogenetic lineages within the class Halobacteria. All isolates produced extracellular extremely salt-tolerant cellulases or chitinases, either cell-free or cell-bound. Obtained results demonstrate a presence of diverse populations of haloarchaeal cellulo/chitinotrophs in hypersaline habitats indicating that euryarchaea participate in aerobic mineralization of recalcitrant organic polymers in salt-saturated environments. PMID:26441877

  11. Transhydrogenase and Growth Substrate Influence Lipid Hydrogen Isotope Ratios in Desulfovibrio alaskensis G20.

    PubMed

    Leavitt, William D; Flynn, Theodore M; Suess, Melanie K; Bradley, Alexander S

    2016-01-01

    Microbial fatty acids preserve metabolic and environmental information in their hydrogen isotope ratios ((2)H/(1)H). This ratio is influenced by parameters that include the (2)H/(1)H of water in the microbial growth environment, and biosynthetic fractionations between water and lipid. In some microbes, this biosynthetic fractionation has been shown to vary systematically with central energy metabolism, and controls on fatty acid (2)H/(1)H may be linked to the intracellular production of NADPH. We examined the apparent fractionation between media water and the fatty acids produced by Desulfovibrio alaskensis G20. Growth was in batch culture with malate as an electron donor for sulfate respiration, and with pyruvate and fumarate as substrates for fermentation and for sulfate respiration. A larger fractionation was observed as a consequence of respiratory or fermentative growth on pyruvate than growth on fumarate or malate. This difference correlates with opposite apparent flows of electrons through the electron bifurcating/confurcating transhydrogenase NfnAB. When grown on malate or fumarate, mutant strains of D. alaskensis G20 containing transposon disruptions in a copy of nfnAB show different fractionations than the wild type strain. This phenotype is muted during fermentative growth on pyruvate, and it is absent when pyruvate is a substrate for sulfate reduction. All strains and conditions produced similar fatty acid profiles, and the (2)H/(1)H of individual lipids changed in concert with the mass-weighted average. Unsaturated fatty acids were generally depleted in (2)H relative to their saturated homologs, and anteiso-branched fatty acids were generally depleted in (2)H relative to straight-chain fatty acids. Fractionation correlated with growth rate, a pattern that has also been observed in the fractionation of sulfur isotopes during dissimilatory sulfate reduction by sulfate-reducing bacteria. PMID:27445998

  12. Transhydrogenase and Growth Substrate Influence Lipid Hydrogen Isotope Ratios in Desulfovibrio alaskensis G20

    PubMed Central

    Leavitt, William D.; Flynn, Theodore M.; Suess, Melanie K.; Bradley, Alexander S.

    2016-01-01

    Microbial fatty acids preserve metabolic and environmental information in their hydrogen isotope ratios (2H/1H). This ratio is influenced by parameters that include the 2H/1H of water in the microbial growth environment, and biosynthetic fractionations between water and lipid. In some microbes, this biosynthetic fractionation has been shown to vary systematically with central energy metabolism, and controls on fatty acid 2H/1H may be linked to the intracellular production of NADPH. We examined the apparent fractionation between media water and the fatty acids produced by Desulfovibrio alaskensis G20. Growth was in batch culture with malate as an electron donor for sulfate respiration, and with pyruvate and fumarate as substrates for fermentation and for sulfate respiration. A larger fractionation was observed as a consequence of respiratory or fermentative growth on pyruvate than growth on fumarate or malate. This difference correlates with opposite apparent flows of electrons through the electron bifurcating/confurcating transhydrogenase NfnAB. When grown on malate or fumarate, mutant strains of D. alaskensis G20 containing transposon disruptions in a copy of nfnAB show different fractionations than the wild type strain. This phenotype is muted during fermentative growth on pyruvate, and it is absent when pyruvate is a substrate for sulfate reduction. All strains and conditions produced similar fatty acid profiles, and the 2H/1H of individual lipids changed in concert with the mass-weighted average. Unsaturated fatty acids were generally depleted in 2H relative to their saturated homologs, and anteiso-branched fatty acids were generally depleted in 2H relative to straight-chain fatty acids. Fractionation correlated with growth rate, a pattern that has also been observed in the fractionation of sulfur isotopes during dissimilatory sulfate reduction by sulfate-reducing bacteria. PMID:27445998

  13. Features of SOI substrates heating in MBE growth process obtained by low-coherence tandem interferometry

    NASA Astrophysics Data System (ADS)

    Volkov, P. V.; Goryunov, A.. V.; Lobanov, D. N.; Luk'yanov, A. Yu.; Novikov, A. V.; Tertyshnik, A. D.; Shaleev, M. V.; Yurasov, D. V.

    2016-08-01

    Differences in heating of silicon and silicon-on-insulator (SOI) substrates in molecular beam epitaxy were revealed by low-coherence tandem interferometry. Using this technique the interference effects which impede the correct evaluation of SOI substrate temperature by infrared pyrometers can be eliminated and so the reliable temperature readout can be achieved. It was shown that at the same thermocouple and heater power settings the real temperature of SOI substrates is higher than of silicon ones and the difference may be as high as 40-50 °C at temperatures close to 600 °C. It is supposed that such effect is caused by the additional absorption of heater radiation by the buried oxide layer in the mid-infrared range. Independent proof of this effect was obtained by growing on both types of substrates a series of structures with self-assembled Ge nanoislands whose parameters are known to be very temperature sensitive. The proposed low-coherence interferometry technique provides precise real-time control of the growth temperature and so allows formation of SiGe nanostructures with desired parameters.

  14. Novel Growth Regime of MDCK II Model Tissues on Soft Substrates

    PubMed Central

    Kaliman, Sara; Jayachandran, Christina; Rehfeldt, Florian; Smith, Ana-Sunčana

    2014-01-01

    It is well established that MDCK II cells grow in circular colonies that densify until contact inhibition takes place. Here, we show that this behavior is only typical for colonies developing on hard substrates and report a new growth phase of MDCK II cells on soft gels. At the onset, the new phase is characterized by small, three-dimensional droplets of cells attached to the substrate. When the contact area between the agglomerate and the substrate becomes sufficiently large, a very dense monolayer nucleates in the center of the colony. This monolayer, surrounded by a belt of three-dimensionally packed cells, has a well-defined structure, independent of time and cluster size, as well as a density that is twice the steady-state density found on hard substrates. To release stress in such dense packing, extrusions of viable cells take place several days after seeding. The extruded cells create second-generation clusters, as evidenced by an archipelago of aggregates found in a vicinity of mother colonies, which points to a mechanically regulated migratory behavior. PMID:24703316

  15. Novel growth regime of MDCK II model tissues on soft substrates.

    PubMed

    Kaliman, Sara; Jayachandran, Christina; Rehfeldt, Florian; Smith, Ana-Sunčana

    2014-04-01

    It is well established that MDCK II cells grow in circular colonies that densify until contact inhibition takes place. Here, we show that this behavior is only typical for colonies developing on hard substrates and report a new growth phase of MDCK II cells on soft gels. At the onset, the new phase is characterized by small, three-dimensional droplets of cells attached to the substrate. When the contact area between the agglomerate and the substrate becomes sufficiently large, a very dense monolayer nucleates in the center of the colony. This monolayer, surrounded by a belt of three-dimensionally packed cells, has a well-defined structure, independent of time and cluster size, as well as a density that is twice the steady-state density found on hard substrates. To release stress in such dense packing, extrusions of viable cells take place several days after seeding. The extruded cells create second-generation clusters, as evidenced by an archipelago of aggregates found in a vicinity of mother colonies, which points to a mechanically regulated migratory behavior. PMID:24703316

  16. Successive selective growth of semipolar (11-22) GaN on patterned sapphire substrate

    NASA Astrophysics Data System (ADS)

    Tendille, Florian; Hugues, Maxime; Vennéguès, Philippe; Teisseire, Monique; De Mierry, Philippe

    2015-06-01

    Thanks to the use of two successive selective growths by metal organic chemical vapor deposition reactor, high quality semipolar (11-22) GaN with a homogenous defect repartition over the surface was achieved. The procedure starts with a first selective growth on a patterned sapphire substrate, leading to continuous stripes of three dimensional (3D) GaN crystals of low defect density. Then, a second selective growth step is achieved by depositing a SiNx nano-mask and a low temperature GaN nano-layer on the top of the GaN stripes. Hereby, we demonstrate an original way to obtain a homoepitaxial selective growth on 3D GaN crystals by taking advantage of the different crystallographic planes available. Basal stacking faults (BSFs) are generated during this second selective growth but could be eliminated by using a three-step growth method in which elongated voids are created above the defective area. For a fully coalesced sample grown using the 2 step method, dislocation density of 1.2 × 108 cm-2 and BSFs density of 154 cm-1 with a homogenous distribution have been measured by cathodoluminescence at 80 K. Consequently the material quality of this coalesced semipolar layer is comparable to the one of polar GaN on c-plane sapphire.

  17. Dual inoculation with an Aarbuscular Mycorrhizal fungus and Rhizobium to facilitate the growth of alfalfa on coal mine substrates

    SciTech Connect

    Wu, F.Y.; Bi, Y.L.; Wong, M.H.

    2009-07-01

    A pot experiment was conducted to investigate the effects of Glomus mosseae and Rhizobium on Medicago sativa grown on three types of coal mine substrates, namely a mixture of coal wastes and sands (CS), coal wastes and fly ash (CF), and fly ash (FA). Inoculation with Rhizobium alone did not result in any growth response but G. mosseae alone displayed a significant effect on plant growth. G. mosseae markedly increased the survival rate of M. sativa in CS substrate. In CF and FA substrates the respective oven dry weights of M. sativa inoculated with G. mosseae were 1.8 and 5.1 times higher than those without inoculation. Based on nitrogen (N), phosphorus (P) and potassium (K) uptake and legume growth, the results also show that dual inoculation in CS and CF substrates elicited a synergistic effect. This indicates that inoculation with arbuscular mycorrhizal (AM) fungi may be a promising approach for revegetation of coal mine substrates.

  18. Pressate from peat dewatering as a substrate for bacterial growth. [Rhizopus arrhizus; Xanthomonas campestris; Aureobasidium

    SciTech Connect

    Mulligan, C.N.; Cooper, D.G.

    1985-07-01

    This study considered the possibility of using water expressed during the drying of fuel-grade peat as a substrate for microbial growth. Highly humified peat pressed for 2.5 min at 1.96 MPa produced water with a chemical oxygen demand of 690 mg/liter. Several biological compounds could be produced by using the organic matter inexpressed peat water as a substrate. These included polymers such as chitosan, contained in the cell wall of Rhizopus arrhizus, and two extracellular polysaccharides, xanthan gum and pullulan, produced by Bacillus subtilis grown in the expressed water. Small additions of nutrients to the peat pressate were necessary to obtain substantial yields of products. The addition of peptone, yeast extract, and glucose improved production of the various compounds. Biological treatment improved the quality of the expressed water to the extent that in an industrial process it could be returned to the environment.

  19. Fabrication of Nanodot Decorated Sapphire Substrates for Abbreviated Growth Mode Deposition of Gallium Nitride

    NASA Astrophysics Data System (ADS)

    Biser, Jeffrey M.

    The overarching theme of this body of work is the development and demonstration of sapphire substrates with sub-micron scale surface features laid out in arrays with controlled shape, size, and distribution. The key contributions of the work are: (1) the collaborative demonstration that such substrates enable novel GaN fabrication options like the Abbreviated Growth Mode (AGM) approach that can lead to lower cost, higher quality LED devices, (2) the proof-of-concept demonstration that large scale surface patterning with the use of anodic aluminum oxide (AAO) templates is a feasible approach for creating low-cost patterns that should be compatible with AGM, and (3) that the Aluminum-to-sapphire conversion process used to fabricate the surface structures has distinct zones of behavior with regard to feature size and temperature that can be used to suggest an optimized set of process conditions.

  20. Low-Temperature in Situ Growth of Graphene on Metallic Substrates and Its Application in Anticorrosion.

    PubMed

    Zhu, Minmin; Du, Zehui; Yin, Zongyou; Zhou, Wenwen; Liu, Zhengdong; Tsang, Siu Hon; Teo, Edwin Hang Tong

    2016-01-13

    Metal or alloy corrosion brings about huge economic cost annually, which is becoming one area of growing concern in various industries, being in bulk state or nanoscale range. Here, single layer or few layers of graphene are deposited on various metallic substrates directly at a low temperature down to 400 °C. These substrates can be varied from hundreds-micrometer bulk metallic or alloy foils to tens of nanometer nanofibers (NFs). Corrosion analysis reveals that both graphene-grown steel sheets and NFs have reduced the corrosion rate of up to ten times lower than that of their bare corresponding counterparts. Moreover, such low-temperature in situ growth of graphene demonstrates stable and long-lasting anticorrosion after long-term immersion. This new class of graphene coated nanomaterials shows high potentials in anticorrosion applications for submarines, oil tankers/pipelines, and ruggedized electronics. PMID:26683895

  1. Epitaxial growth of ZnO nanowall networks on GaN/sapphire substrates

    NASA Astrophysics Data System (ADS)

    Kim, Sang-Woo; Park, Hyun-Kyu; Yi, Min-Su; Park, Nae-Man; Park, Jong-Hyurk; Kim, Sang-Hyeob; Maeng, Sung-Lyul; Choi, Chel-Jong; Moon, Seung-Eon

    2007-01-01

    Heteroepitaxy of vertically well-aligned ZnO nanowall networks with a honeycomblike pattern on GaN /c-Al2O3 substrates by the help of a Au catalyst was realized. The ZnO nanowall networks with wall thicknesses of 80-140nm and an average height of about 2μm were grown on a self-formed ZnO thin film during the growth on the GaN /c-Al2O3 substrates. It was found that both single-crystalline ZnO nanowalls and catalytic Au have an epitaxial relation to the GaN thin film in synchrotron x-ray scattering experiments. Hydrogen-sensing properties of the ZnO nanowall networks have also been investigated.

  2. Effect of GaAs substrate orientation on the growth kinetic of GaN layer grown by MOVPE

    NASA Astrophysics Data System (ADS)

    Laifi, J.; Chaaben, N.; Bouazizi, H.; Fourati, N.; Zerrouki, C.; El Gmili, Y.; Bchetnia, A.; Salvestrini, J. P.; El Jani, B.

    2016-06-01

    We have investigated the kinetic growth of low temperature GaN nucleation layers (LT-GaN) grown on GaAs substrates with different crystalline orientations. GaN nucleation layers were grown by metal organic vapor phase epitaxy (MOVPE) in a temperature range of 500-600 °C on oriented (001), (113), (112) and (111) GaAs substrates. The growth was in-situ monitored by laser reflectometry (LR). Using an optical model, including time-dependent surface roughness and growth rate profiles, simulations were performed to best approach the experimental reflectivity curves. Results are discussed and correlated with ex-situ analyses, such as atomic force microscopy (AFM) and UV-visible reflectance (SR). We show that the GaN nucleation layers growth results the formation of GaN islands whose density and size vary greatly with both growth temperature and substrate orientation. Arrhenius plots of the growth rate for each substrate give values of activation energy varying from 0.20 eV for the (001) orientation to 0.35 eV for the (113) orientation. Using cathodoluminescence (CL), we also show that high temperature (800-900 °C) GaN layers grown on top of the low temperature (550 °C) GaN nucleation layers, grown themselves on the GaAs substrates with different orientations, exhibit cubic or hexagonal phase depending on both growth temperature and substrate orientation.

  3. A CENSUS OF BROAD-LINE ACTIVE GALACTIC NUCLEI IN NEARBY GALAXIES: COEVAL STAR FORMATION AND RAPID BLACK HOLE GROWTH

    SciTech Connect

    Trump, Jonathan R.; Fang, Jerome J.; Faber, S. M.; Koo, David C.; Kocevski, Dale D.

    2013-02-15

    We present the first quantified, statistical map of broad-line active galactic nucleus (AGN) frequency with host galaxy color and stellar mass in nearby (0.01 < z < 0.11) galaxies. Aperture photometry and z-band concentration measurements from the Sloan Digital Sky Survey are used to disentangle AGN and galaxy emission, resulting in estimates of uncontaminated galaxy rest-frame color, luminosity, and stellar mass. Broad-line AGNs are distributed throughout the blue cloud and green valley at a given stellar mass, and are much rarer in quiescent (red sequence) galaxies. This is in contrast to the published host galaxy properties of weaker narrow-line AGNs, indicating that broad-line AGNs occur during a different phase in galaxy evolution. More luminous broad-line AGNs have bluer host galaxies, even at fixed mass, suggesting that the same processes that fuel nuclear activity also efficiently form stars. The data favor processes that simultaneously fuel both star formation activity and rapid supermassive black hole accretion. If AGNs cause feedback on their host galaxies in the nearby universe, the evidence of galaxy-wide quenching must be delayed until after the broad-line AGN phase.

  4. A Census of Broad-line Active Galactic Nuclei in Nearby Galaxies: Coeval Star Formation and Rapid Black Hole Growth

    NASA Astrophysics Data System (ADS)

    Trump, Jonathan R.; Hsu, Alexander D.; Fang, Jerome J.; Faber, S. M.; Koo, David C.; Kocevski, Dale D.

    2013-02-01

    We present the first quantified, statistical map of broad-line active galactic nucleus (AGN) frequency with host galaxy color and stellar mass in nearby (0.01 < z < 0.11) galaxies. Aperture photometry and z-band concentration measurements from the Sloan Digital Sky Survey are used to disentangle AGN and galaxy emission, resulting in estimates of uncontaminated galaxy rest-frame color, luminosity, and stellar mass. Broad-line AGNs are distributed throughout the blue cloud and green valley at a given stellar mass, and are much rarer in quiescent (red sequence) galaxies. This is in contrast to the published host galaxy properties of weaker narrow-line AGNs, indicating that broad-line AGNs occur during a different phase in galaxy evolution. More luminous broad-line AGNs have bluer host galaxies, even at fixed mass, suggesting that the same processes that fuel nuclear activity also efficiently form stars. The data favor processes that simultaneously fuel both star formation activity and rapid supermassive black hole accretion. If AGNs cause feedback on their host galaxies in the nearby universe, the evidence of galaxy-wide quenching must be delayed until after the broad-line AGN phase.

  5. Real-time characterization of film growth on transparent substrates by rotating-compensator multichannel ellipsometry.

    PubMed

    Lee, J; Collins, R W

    1998-07-01

    A multichannel spectroscopic ellipsometer in the fixed-polarizer-sample-rotating-compensator-fixed-analyzer (PSC(R)A) configuration has been developed and applied for real-time characterization of the nucleation and growth of thin films on transparent substrates. This rotating-compensator design overcomes the major disadvantages of the multichannel ellipsometer in the rotating-polarizer-sample-fixed-analyzer (P(R)SA) configuration while retaining its high speed and precision for the characterization of thin-film processes in real time. The advantages of the PSC(R)A configuration include (i) its high accuracy and precision for the detection of low-ellipticity polarization states that are generated upon reflection of linearly polarized light from transparent film-substrate systems, and (ii) the ability to characterize depolarization of the reflected light, an effect that leads to errors in ellipticity when measured with the P(R)SA configuration. A comparison of the index of refraction spectra for a glass substrate obtained in the real-time PSC(R)A mode in 2.5 s and in the ex situ fixed-polarizer-fixed-compensator-sample-rotating-analyzer (PCSA(R)) mode in ~10 min show excellent agreement, with a standard deviation between the two data sets of 8 x 10(-4), computed over the photon energy range from 1.5 to 3.5 eV. First, we describe the PSC(R)A ellipsometer calibration procedures developed specifically for transparent substrates. In addition, we describe the application of the multichannel PSC(R)A instrument for a study of thin-film diamond nucleation and growth on glass in a low-temperature microwave plasma-enhanced chemical vapor deposition process. PMID:18285868

  6. Growth of epitaxial silicon nanowires on a Si substrate by a metal-catalyst-free process

    NASA Astrophysics Data System (ADS)

    Ishiyama, Takeshi; Nakagawa, Shuhei; Wakamatsu, Toshiki

    2016-07-01

    The growth of epitaxial Si nanowires by a metal-catalyst-free process has been investigated as an alternative to the more common metal-catalyzed vapor–liquid–solid process. The well-aligned Si nanowires are successfully grown on a (111)-oriented Si substrate without any metal catalysts by a thermal treatment using silicon sulfide as a Si source at approximately 1200 °C. The needle-shaped Si nanowires, which have a core–shell structure that consists of a single-crystalline Si core along the <111> direction consistent with the substrate direction and a surface coating of silicon oxide, are grown by a metal-catalyst-free process. In this process, the silicon sulfide in the liquid phase facilitates the nucleation and nanowire growth. In contrast, oxygen-rich nanowires that consist of crystalline Si at the tip and lumpy silicon oxide on the body are observed in a sample grown at 1300 °C, which disturbs the epitaxial growth of Si nanowires.

  7. Electric field stimulation through a biodegradable polypyrrole-co-polycaprolactone substrate enhances neural cell growth

    PubMed Central

    Nguyen, Hieu T; Wei, Claudia; Chow, Jacqueline K; Nguyen, Alvin; Coursen, Jeff; Sapp, Shawn; Luebben, Silvia; Chang, Emily; Ross, Robert; Schmidt, Christine E

    2014-01-01

    Nerve guidance conduits (NGCs) are FDA-approved devices used to bridge gaps across severed nerve cables and help direct axons sprouting from the proximal end toward the distal stump. In this paper we present the development of a novel electrically conductive, biodegradable NGC made from a polypyrrole-block-polycaprolactone (PPy-PCL) copolymer material laminated with poly(lactic-co-glycolic acid) (PLGA). The PPy-PCL has a bulk conductivity ranging 10–20 S/cm and loses 40 wt% after 7 months under physiologic conditions. Dorsal root ganglia (DRG) grown on flat PPy-PCL/PLGA material exposed to direct current electric fields (EF) of 100 mV/cm for 2 h increased axon growth by 13% (± 2%) towards either electrode of a 2-electrode setup, compared to control grown on identical substrates without EF exposure. Alternating current increased axon growth by 21% (± 3%) without an observable directional preference, compared to the same control group. The results from this study demonstrate PLGA-coated PPy-PCL is a unique biodegradable material that can deliver substrate EF stimulation to improve axon growth for peripheral nerve repair. PMID:23964001

  8. Study of the surface cleaning of GOI and SGOI substrates for Ge epitaxial growth

    NASA Astrophysics Data System (ADS)

    Moriyama, Yoshihiko; Hirashita, Norio; Usuda, Koji; Nakaharai, Shu; Sugiyama, Naoharu; Toyoda, Eiji; Takagi, Shin-ichi

    2009-11-01

    An effective wet cleaning process, optimized for low temperature Ge epitaxial growth on thin Ge or SiGe structures with reduced surface roughening, is proposed. It is found that HF + HCl cleaning is the most effective wet cleaning method that is applicable to the low temperature thermal cleaning. It is also found that temperature of the thermal cleaning appropriate to 25-30 nm thick germanium on insulator (GOI) or silicon-germanium on insulator (SGOI) substrates is approximately 450 °C. Moreover, it is also found that the temperatures of Ge epitaxial growth even in lattice-matched systems must be reduced to around 400 °C to prevent surface roughening and those in lattice-mismatched systems also must be reduced sufficiently (300 °C for strained Ge growth on SGOI ( Xeff = 0.6)) to prevent lattice relaxation as well as surface roughening. Finally, the successful formation of the compressively strained GOI structures is demonstrated by applying these wet cleaning and low temperature thermal cleaning processes and low temperature Ge epitaxy to thin SGOI substrates.

  9. Growth of epitaxial silicon nanowires on a Si substrate by a metal-catalyst-free process

    PubMed Central

    Ishiyama, Takeshi; Nakagawa, Shuhei; Wakamatsu, Toshiki

    2016-01-01

    The growth of epitaxial Si nanowires by a metal-catalyst-free process has been investigated as an alternative to the more common metal-catalyzed vapor–liquid–solid process. The well-aligned Si nanowires are successfully grown on a (111)-oriented Si substrate without any metal catalysts by a thermal treatment using silicon sulfide as a Si source at approximately 1200 °C. The needle-shaped Si nanowires, which have a core–shell structure that consists of a single-crystalline Si core along the <111> direction consistent with the substrate direction and a surface coating of silicon oxide, are grown by a metal-catalyst-free process. In this process, the silicon sulfide in the liquid phase facilitates the nucleation and nanowire growth. In contrast, oxygen-rich nanowires that consist of crystalline Si at the tip and lumpy silicon oxide on the body are observed in a sample grown at 1300 °C, which disturbs the epitaxial growth of Si nanowires. PMID:27465800

  10. Growth of oriented vanadium pentaoxide nanostructures on transparent conducting substrates and their applications in photocatalysis

    SciTech Connect

    Liu, Hongjiang; Gao, Yanfeng; Zhou, Jiadong; Liu, Xinling; Chen, Zhang; Cao, Chuanxiang; Luo, Hongjie; Kanehira, Minoru

    2014-06-01

    A novel, hydrothermal and hard-template-free method was developed for the first time to grow oriented, single-crystalline monoclinic VO{sub 2} (B) flower-like nanorod films on transparent conductive fluorine-doped tin oxide (FTO) substrates. The length and morphology of the nanorods can be tuned by changing the growth parameters, such as growth time and initial precursor concentration. The flower-like V{sub 2}O{sub 5} films were obtained after post-calcination treatment of VO{sub 2} (B) films. The photocatalytic activity of V{sub 2}O{sub 5} films was investigated by the degradation of methylene blue (MB) under UV and visible light. The prepared V{sub 2}O{sub 5} film exhibited good photocatalytic performance (74.6% and 63% under UV and visible light for 210 min, respectively) and more practical application in industry. - Graphical abstract: Flower nanostructured vanadium oxide film was prepared by hydrothermal reaction for photocatalysis application. - Highlights: • Monoclinic VO{sub 2} nanorod array and flower-like nanostructure were directly grown on FTO substrate by hydrothermal reaction. • The growth mechanism was analyzed by FESEM at different time. • V{sub 2}O{sub 5} flower-like nanostructure film was obtained after calcining VO{sub 2} film. • V{sub 2}O{sub 5} film exhibited good light activity and potential application in photocatalysis.

  11. Effect of substrate temperature on the growth and properties of boron-doped microcrystalline silicon films

    NASA Astrophysics Data System (ADS)

    Lei, Qing-Song; Wu, Zhi-Meng; Geng, Xin-Hua; Zhao, Ying; Sun, Jian; Xi, Jian-Ping

    2006-01-01

    Highly conductive boron-doped hydrogenated microcrystalline silicon (μc-Si:H) films are prepared by very high frequency plasma enhanced chemical vapour deposition (VHF PECVD) at the substrate temperatures (TS) ranging from 90°C to 270°C. The effects of TS on the growth and properties of the films are investigated. Results indicate that the growth rate, the electrical (dark conductivity, carrier concentration and Hall mobility) and structural (crystallinity and grain size) properties are all strongly dependent on TS. As TS increases, it is observed that 1) the growth rate initially increases and then arrives at a maximum value of 13.3 nm/min at TS=210°C, 2) the crystalline volume fraction (Xc) and the grain size increase initially, then reach their maximum values at TS=140°C and finally decrease, 3) the dark conductivity (σd), carrier concentration and Hall mobility have a similar dependence on TS and arrive at their maximum values at TS=190°C. In addition, it is also observed that at a lower substrate temperature TS, a higher dopant concentration is required in order to obtain a maximum σd.

  12. Growth of epitaxial silicon nanowires on a Si substrate by a metal-catalyst-free process.

    PubMed

    Ishiyama, Takeshi; Nakagawa, Shuhei; Wakamatsu, Toshiki

    2016-01-01

    The growth of epitaxial Si nanowires by a metal-catalyst-free process has been investigated as an alternative to the more common metal-catalyzed vapor-liquid-solid process. The well-aligned Si nanowires are successfully grown on a (111)-oriented Si substrate without any metal catalysts by a thermal treatment using silicon sulfide as a Si source at approximately 1200 °C. The needle-shaped Si nanowires, which have a core-shell structure that consists of a single-crystalline Si core along the <111> direction consistent with the substrate direction and a surface coating of silicon oxide, are grown by a metal-catalyst-free process. In this process, the silicon sulfide in the liquid phase facilitates the nucleation and nanowire growth. In contrast, oxygen-rich nanowires that consist of crystalline Si at the tip and lumpy silicon oxide on the body are observed in a sample grown at 1300 °C, which disturbs the epitaxial growth of Si nanowires. PMID:27465800

  13. Atomistic view in the initial stages of growth of epitaxial graphene on metal substrates

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu

    2011-03-01

    For both fundamental studies and potential development of graphene electronics, it is pressing to search for reliable methods for mass production of quality graphene. Epitaxial growth of graphene on catalytic metal substrates combined with post-growth transfer has become a promising route towards this goal [1,2]. However, to better control the quality and yield of graphene, a comprehensive understanding of the growth kinetics is essential. In particular, how the carbon atoms adsorbed on the metal surface (or dissolved into the metal) meet to nucleate into stable carbon islands will greatly influence both the growth rate and quality of larger carbon entities such as graphene sheets. In this talk, we first show that the delicate competition between carbon-carbon bonding and carbon-metal bonding dictates the initial nucleation sites of graphene on metal surfaces. These results are discussed in connection with the experimental findings that on Ir(111) and Ru(0001) substrates graphene nucleates from the step edges [4,5]. We also predict that on Cu(111) nucleation should take place everywhere on a terrace. Next we study larger carbon clusters on Cu(111) and explicitly compare the stability of linear and compact structures. We find that the linear carbon ``nanoarches'' are more stable than compact islands consisting of up to 13 carbon atoms, and these nanoarched structures may serve as the missing bridge between carbon dimers and larger graphene nanodomes. Based on these improved understanding of the atomistic rate processes involved, we propose a few kinetic pathways that may lead to better growth control of bilayer graphene and graphene nanoribbons as elemental building blocks for developing graphene electronics. Work done in collaboration with Hua Chen, Wenguang Zhu, Robert Van Wesep, Wei Chen, Ping Cui, and Haiping Lan, and supported by USDOE, USNSF, and NNSF of China.

  14. Demonstrating benthic control of anomalous solute transport: biofilm growth interacts with substrate size.

    NASA Astrophysics Data System (ADS)

    Aubeneau, A. F.; Tank, J. L.; Bolster, D.; Hanrahan, B.

    2014-12-01

    In fluvial systems, biofilms are the main driver of biogeochemical transformations. Biofilms grow on most surfaces in the benthic and hyporheic regions, where they process waterborne solutes. These solutes are transported in the regional flow and their fluxes near the biofilms are controlled by local physical properties, such as head gradients and hydraulic conductivity. These properties are in turn influenced by the growth of the biofilm itself, which can clog porous media and/or develop its own network of porous space. Therefore, the residence time of a solute in proximity to biofilm surfaces, where it can be processed, should be influenced by the properties not only of the physical environment, but by that of the biofilm itself. We hypothesized that the presence of biofilms would increase residence times in the benthic and shallow subsurface regions of the stream bed. We performed controlled experiments in 4 experimental streams at Notre Dame's Linked Experimental Ecosystem Facility (ND-LEEF) to quantify the interaction between substrate and biofilm in controlling anomalous solute transport. Each stream at ND-LEEF had a different substrate configuration: 2 with homogeneous substrate but with different sizes (pea gravel vs. coarse gravel) and 2 with heterogeneous substrate (alternating sections vs. well-mixed reaches). We measured the evolution of the residence time distributions in the streams by injecting rhodamine tracer (RWT) multiple times over the course of a 5 month colonization gradient. Analysis of breakthrough curves demonstrated that in addition to the influence of substrate, biofilm colonization and growth significantly influenced the residence time in the system. Specifically, as biofilms grew, the power-law exponent of the RTD decreased, i.e. the tails of the distributions became heavier, suggesting prolonged retention due to the presence of the biofilms. Although the substrate signature persisted over time, with the coarser gravel bed washing out

  15. Au impact on GaAs epitaxial growth on GaAs (111)B substrates in molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Liao, Zhi-Ming; Chen, Zhi-Gang; Lu, Zhen-Yu; Xu, Hong-Yi; Guo, Ya-Nan; Sun, Wen; Zhang, Zhi; Yang, Lei; Chen, Ping-Ping; Lu, Wei; Zou, Jin

    2013-02-01

    GaAs growth behaviour under the presence of Au nanoparticles on GaAs {111}B substrate is investigated using electron microscopy. It has been found that, during annealing, enhanced Ga surface diffusion towards Au nanoparticles leads to the GaAs epitaxial growth into {113}B faceted triangular pyramids under Au nanoparticles, governed by the thermodynamic growth, while during conventional GaAs growth, growth kinetics dominates, resulting in the flatted triangular pyramids at high temperature and the epitaxial nanowires growth at relatively low temperature. This study provides an insight of Au nanoparticle impact on GaAs growth, which is critical for understanding the formation mechanisms of semiconductor nanowires.

  16. Glycothermal Growth of Silver Core/TiO2 Shell Nano-Wires on FTO Substrate.

    PubMed

    Song, Duck-Hyun; Hirato, Tetsuji

    2015-01-01

    Silver core/TiO2 shell nano-wires have been successfully prepared on fluorine doped tin oxide coated glass substrate via a glycothermal process assisted by a photochemical process. The morphology, diameter, length, and density of synthesized core/shell nano-wires could be varied by photochemical reaction time. The fabricated samples were characterized with X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray. We suggested a mechanism to explain the growth of the silver core/TiO2 shell nano-wires. PMID:26328391

  17. Ordered growth of germanium hut islands on Si (001) molecular bonded substrates

    SciTech Connect

    Poydenot, V.; Dujardin, R.; Rouviere, J.L.; Barski, A.; Fournel, F.

    2004-12-06

    Ordered germanium hut islands are grown by molecular-beam epitaxy on high twist angle molecular bonded silicon (001) substrates (twist angle higher than 20 deg.). We show that the growth organization is induced by an array of interfacial tilt dislocations. Plan-view transmission electron microscopy and atomic force microscopy observations show that the orientation and period of the tilt dislocation array determine the orientation, period, and length of elongated germanium hut islands. The strain field generated by an array of tilt dislocations is proposed as the driving force of the reported organization.

  18. Growth of InAs on Si substrates at low temperatures using metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Jha, Smita; Song, Xueyan; Babcock, S. E.; Kuech, T. F.; Wheeler, Dane; Wu, Bin; Fay, P.; Seabaugh, Alan

    2008-11-01

    The growth behavior of InAs on Si using metalorganic vapor phase epitaxy (MOVPE) was studied. The large lattice mismatch of InAs to Si, ˜12%, results in island formation under typical MOVPE growth conditions, which prevents the development of the thin coherent films of InAs needed for high-speed device applications. The growth of InAs at low temperature is expected to lead to rapid nucleation and low surface mobility, resulting in the formation of a coherent film at low thicknesses. This study explored the growth behavior of InAs on Si at low temperatures, i.e. <350 °C and varying V/III ratio. InAs films were grown on {1 0 0}-, {1 1 1}- and {2 1 1}-oriented Si substrates using trimethyl indium, tertiary butyl arsine and AsH 3. Small islands ranging from 15 to 30 nm form on the samples at growth temperatures <325 °C. Subsequent annealing of this thin layer at 600 °C for 5 min leads to island coarsening. High-resolution X-ray diffraction, atomic force microscopy and scanning electron microscopy were used to characterize InAs layer grown on Si.

  19. Peptide-modified Substrate for Modulating Gland Tissue Growth and Morphology In Vitro

    PubMed Central

    Taketa, Hiroaki; Sathi, Gulsan Ara; Farahat, Mahmoud; Rahman, Kazi Anisur; Sakai, Takayoshi; Hirano, Yoshiaki; Kuboki, Takuo; Torii, Yasuhiro; Matsumoto, Takuya

    2015-01-01

    In vitro fabricated biological tissue would be a valuable tool to screen newly synthesized drugs or understand the tissue development process. Several studies have attempted to fabricate biological tissue in vitro. However, controlling the growth and morphology of the fabricated tissue remains a challenge. Therefore, new techniques are required to modulate tissue growth. RGD (arginine-glycine-aspartic acid), which is an integrin-binding domain of fibronectin, has been found to enhance cell adhesion and survival; it has been used to modify substrates for in vitro cell culture studies or used as tissue engineering scaffolds. In addition, this study shows novel functions of the RGD peptide, which enhances tissue growth and modulates tissue morphology in vitro. When an isolated submandibular gland (SMG) was cultured on an RGD-modified alginate hydrogel sheet, SMG growth including bud expansion and cleft formation was dramatically enhanced. Furthermore, we prepared small RGD-modified alginate beads and placed them on the growing SMG tissue. These RGD-modified beads successfully induced cleft formation at the bead position, guiding the desired SMG morphology. Thus, this RGD-modified material might be a promising tool to modulate tissue growth and morphology in vitro for biological tissue fabrication. PMID:26098225

  20. Growth of carbon nanotubes on surfaces: the effects of catalyst and substrate.

    PubMed

    Murcia, Angel Berenguer; Geng, Junfeng

    2013-08-01

    We report a study of synthesising air-stable, nearly monodispersed bimetallic colloids of Co/Pd and Fe/Mo of varying compositions as active catalysts for the growth of carbon nanotubes. Using these catalysts we have investigated the effects of catalyst and substrate on the carbon nanostructures formed in a plasma-enhanced chemical vapour deposition (PECVD) process. We will show how it is possible to assess the influence of both the catalyst and the support on the controlled growth of carbon nanotube and nanofiber arrays. The importance of the composition of the catalytic nuclei will be put into perspective with other results from the literature. Furthermore, the influence of other synthetic parameters such as the nature of the nanoparticle catalysts will also be analysed and discussed in detail. PMID:23882847

  1. Simple method for the growth of 4H silicon carbide on silicon substrate

    NASA Astrophysics Data System (ADS)

    Asghar, M.; Shahid, M. Y.; Iqbal, F.; Fatima, K.; Nawaz, Muhammad Asif; Arbi, H. M.; Tsu, R.

    2016-03-01

    In this study we report thermal evaporation technique as a simple method for the growth of 4H silicon carbide on p-type silicon substrate. A mixture of Si and C60 powder of high purity (99.99%) was evaporated from molybdenum boat. The as grown film was characterized by XRD, FTIR, UV-Vis Spectrophotometer and Hall Measurements. The XRD pattern displayed four peaks at 2Θ angles 28.550, 32.700, 36.100 and 58.900 related to Si (1 1 1), 4H-SiC (1 0 0), 4H-SiC (1 1 1) and 4H-SiC (2 2 2), respectively. FTIR, UV-Vis spectrophotometer and electrical properties further strengthened the 4H-SiC growth.

  2. Undulate Cu(111) Substrates: A Unique Surface for CVD Graphene Growth

    NASA Astrophysics Data System (ADS)

    Zhang, Yaqian; Zhang, Haoran; Zhang, Yanhui; Chen, Zhiying; Tang, Chunmiao; Sui, Yanping; Wang, Bin; Li, Xiaoliang; Xie, Xiaoming; Yu, Guanghui; Jin, Zhi; Liu, Xinyu

    2015-10-01

    Cu(111) is a suitable substrate for sixfold graphene domain synthesis, as confirmed theoretically and experimentally. However, an undulate striped structure, where stretched flower-like or approximate diamond-shaped graphene domains had formed, appeared on Cu(111) after annealing and growth in our study. Graphene domains were stretched along the undulate stripes. The Cu surface coated with graphene domains was flatter than the surrounding undulate striped structure. Oxygen plasma was used to remove the graphene coating, and the exposed Cu was also flat. We propose that slight steps formed on Cu(111) in the annealing process. The faster rate of graphene growth along these steps contributed to the stretching domain shape. Furthermore, the release of internal stress or the shrinking of Cu during cooling promotes the expansion step to form an undulate striped structure. However, the coated Cu step motion is limited by graphene. Consequently, the resulting surface is flat, thereby clearly indicating a graphene-Cu interaction.

  3. Patterned growth of neuronal cells on modified diamond-like carbon substrates.

    PubMed

    Kelly, Stephen; Regan, Edward M; Uney, James B; Dick, Andrew D; McGeehan, Joseph P; Mayer, Eric J; Claeyssens, Frederik

    2008-06-01

    Diamond-like carbon (DLC) has been explored as a biomaterial with potential use for coating implantable devices and surgical instruments. In this study the interaction of DLC with mammalian neuronal cells has been studied along with its modifications to improve its function as a biomaterial. We describe the use of DLC, oxidised DLC and phosphorus-doped DLC to support the growth and survival of primary central nervous system neurones and neuroblastoma cells. None of these substrates were cytotoxic and primary neurones adhered better to phosphorus-doped DLC than unmodified DLC. This property was used to culture cortical neurones in a predetermined micropattern. This raises the potential of DLC as a biomaterial for central nervous system (CNS) implantation. Furthermore, patterned DLC and phosphorus-doped DLC can direct neuronal growth, generating a powerful tool to study neuronal networks in a spatially distinct way. This study reports the generation of nerve cell patterns via patterned deposition of DLC. PMID:18359076

  4. Substrate orientation dependence on the solid phase epitaxial growth rate of Ge

    NASA Astrophysics Data System (ADS)

    Darby, B. L.; Yates, B. R.; Martin-Bragado, I.; Gomez-Selles, J. L.; Elliman, R. G.; Jones, K. S.

    2013-01-01

    The solid phase epitaxial growth process has been studied at 330 °C by transmission electron microscopy for Ge wafers polished at 10°-15° increments from the [001] to [011] orientations. The velocity showed a strong dependence on substrate orientation with the [001] direction displaying a velocity 16 times greater than the [111] direction. A lattice kinetic Monte Carlo model was used to simulate solid phase epitaxial growth (SPEG) rates at different orientations, and simulations compared well with experimental results. Cross sectional transmission electron microscopy and plan view transmission electron microscopy revealed stacking fault and twin defect formation in the [111] orientation where all other orientations showed only hairpin dislocations. The twin defects formed from Ge SPEG were comparatively less dense than what has previously been reported for Si, which gave rise to higher normalized velocities and a constant [111] SPEG velocity for Ge.

  5. Screening of Rhizobacteria for Their Plant Growth Promotion Ability and Antagonism Against Damping off and Root Rot Diseases of Broad Bean (Vicia faba L.).

    PubMed

    Indira Devi, S; Talukdar, N C; Chandradev Sharma, K; Jeyaram, K; Rohinikumar, M

    2011-01-01

    Development of microbial inoculants from rhizobacterial isolates with potential for plant growth promotion and root disease suppression require rigorous screening. Fifty-four (54) fluorescent pseudomonads, out of a large collection of rhizobacteria from broad bean fields of 20 different locations within Imphal valley of Manipur, were initially screened for antifungal activity against Macrophomina phaseolina and Rhizoctonia solani, of diseased roots of broad bean and also three other reference fungal pathogens of plant roots. Fifteen fluorescent pseudomonas isolates produced inhibition zone (8-29 mm) of the fungal growth in dual plate assay and IAA like substances (24.1-66.7 μg/ml) and soluble P (12.7-56.80 μg/ml) in broth culture. Among the isolates, RFP 36 caused a marked increase in seed germination, seedling biomass and control of the root borne pathogens of broad bean. PCR-RAPD analysis of these isolates along with five MTCC reference fluorescent pseudomonas strains indicated that the RFP-36 belonged to a distinct cluster and the PCR of its genomic DNA with antibiotic specific primers Phenazine-1-carboxylic acid and 2, 4-diacetyl phloroglucinol suggested possible occurrence of gene for the potent antibiotics. Overall, the result of the study indicated the potential of the isolate RFP 36 as a microbial inoculant with multiple functions for broad bean. PMID:22282623

  6. Carbon dimers as the dominant feeding species in epitaxial growth and morphological phase transition of graphene on different Cu substrates.

    PubMed

    Wu, Ping; Zhang, Yue; Cui, Ping; Li, Zhenyu; Yang, Jinlong; Zhang, Zhenyu

    2015-05-29

    Cu substrates are highly preferred for the potential mass production of high-quality graphene, yet many of the important aspects of the atomistic growth mechanisms involved remain to be explored. Using multiscale modeling, we identify C-C dimers as the dominant feeding species in the epitaxial growth of graphene on both Cu(111) and Cu(100) substrates. By contrasting the different activation energies involved in C-C dimer diffusion on terraces and its attachment at graphene island edges, we further reveal why graphene growth is diffusion limited on Cu(111), but attachment limited on Cu(100). We also find even higher potential energy barriers against dimer diffusion along the island edges; consequently, a dendritic-to-compact transition is predicted to take place during graphene enlargement on either substrate, but at different growth temperatures. These findings serve as new insights for better control of epitaxial graphene growth. PMID:26066446

  7. Carbon Dimers as the Dominant Feeding Species in Epitaxial Growth and Morphological Phase Transition of Graphene on Different Cu Substrates

    NASA Astrophysics Data System (ADS)

    Wu, Ping; Zhang, Yue; Cui, Ping; Li, Zhenyu; Yang, Jinlong; Zhang, Zhenyu

    2015-05-01

    Cu substrates are highly preferred for the potential mass production of high-quality graphene, yet many of the important aspects of the atomistic growth mechanisms involved remain to be explored. Using multiscale modeling, we identify C-C dimers as the dominant feeding species in the epitaxial growth of graphene on both Cu(111) and Cu(100) substrates. By contrasting the different activation energies involved in C-C dimer diffusion on terraces and its attachment at graphene island edges, we further reveal why graphene growth is diffusion limited on Cu(111), but attachment limited on Cu(100). We also find even higher potential energy barriers against dimer diffusion along the island edges; consequently, a dendritic-to-compact transition is predicted to take place during graphene enlargement on either substrate, but at different growth temperatures. These findings serve as new insights for better control of epitaxial graphene growth.

  8. Graphene growth at the interface between Ni catalyst layer and SiO2/Si substrate.

    PubMed

    Lee, Jeong-Hoon; Song, Kwan-Woo; Park, Min-Ho; Kim, Hyung-Kyu; Yang, Cheol-Woong

    2011-07-01

    Graphene was synthesized deliberately at the interface between Ni film and SiO2/Si substrate as well as on top surface of Ni film using chemical vapor deposition (CVD) which is suitable for large-scale and low-cost synthesis of graphene. The carbon atom injected at the top surface of Ni film can penetrate and reach to the Ni/SiO2 interface for the formation of graphene. Once we have the graphene in between Ni film and SiO2/Si substrate, the substrate spontaneously provides insulating SiO2 layer and we may easily get graphene/SiO2/Si structure simply by discarding Ni film. This growth of graphene at the interface can exclude graphene transfer step for electronic application. Raman spectroscopy and optical microscopy show that graphene was successfully synthesized at the back of Ni film and the coverage of graphene varies with temperature and time of synthesis. The coverage of graphene at the interface depends on the amount of carbon atoms diffused into the back of Ni film. PMID:22121737

  9. Correlation between substrate bias, growth process and structural properties of phosphorus incorporated tetrahedral amorphous carbon films

    NASA Astrophysics Data System (ADS)

    Liu, Aiping; Zhu, Jiaqi; Han, Jiecai; Wu, Huaping; Jia, Zechun

    2007-09-01

    We investigate the growth process and structural properties of phosphorus incorporated tetrahedral amorphous carbon (ta-C:P) films which are deposited at different substrate biases by filtered cathodic vacuum arc technique with PH 3 as the dopant source. The films are characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy, Raman spectroscopy, residual stress measurement, UV/VIS/NIR absorption spectroscopy and temperature-dependent conductivity measurement. The atomic fraction of phosphorus in the films as a function of substrate bias is obtained by XPS analysis. The optimum bias for phosphorus incorporation is about -80 V. Raman spectra show that the amorphous structures of all samples with atomic-scaled smooth surface are not remarkably changed when PH 3 is implanted, but some small graphitic crystallites are formed. Moreover, phosphorus impurities and higher-energetic impinging ions are favorable for the clustering of sp 2 sites dispersed in sp 3 skeleton and increase the level of structural ordering for ta-C:P films, which further releases the compressive stress and enhances the conductivity of the films. Our analysis establishes an interrelationship between microstructure, stress state, electrical properties, and substrate bias, which helps to understand the deposition mechanism of ta-C:P films.

  10. Growth of textured MgO through e-beam evaporation and inclined substrate deposition

    NASA Astrophysics Data System (ADS)

    Xu, Y.; Lei, C. H.; Ma, B.; Evans, H.; Efstathiadis, H.; Manisha, R.; Massey, M.; Balachandran, U.; Bhattacharya, R.

    2006-08-01

    Long length textured MgO template on Hastelloy C276™ (HC) has been successfully deposited in a reel-to-reel (R2R) electron beam (e-beam) evaporation system by inclined substrate deposition (ISD). High deposition rate up to 10 nm s-1 with exposure length of 7 cm has been realized. The MgO template showed good in-plane texture of 9.5°-11.5° measured from the (002) phi scans. Experimental results reveal that MgO in-plane texture is formed by the preferred growth direction of [11n]\\parallel \\mathrm {substrate} normal and one of the MgO {200} planes rotates to the in-flux direction. A new expression, termed the 'two-thirds relationship', between the inclination angle α and the tilted angle of the (00l) plane from the substrate normal, β, has been summarized. YBa2Cu3O7-δ (YBCO) film deposited by pulsed laser deposition (PLD) on strontium ruthenate (SRO) buffered ISD MgO showed Tc of 91 K with transition width of 1 K. Critical current measurement indicated an Ic of 110 A cm-1 at 77 K in self-field for 0.68 µm YBCO film, corresponding to a Jc of 1.6 MA cm-2.