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Sample records for vapor-liquid-solid vls growth

  1. Extended vapor-liquid-solid growth of silicon carbide nanowires.

    Science.gov (United States)

    Rajesh, John Anthuvan; Pandurangan, Arumugam

    2014-04-01

    We developed an alloy catalytic method to explain extended vapor-liquid-solid (VLS) growth of silicon carbide nanowires (SiC NWs) by a simple thermal evaporation of silicon and activated carbon mixture using lanthanum nickel (LaNi5) alloy as catalyst in a chemical vapor deposition process. The LaNi5 alloy binary phase diagram and the phase relationships in the La-Ni-Si ternary system were play a key role to determine the growth parameters in this VLS mechanism. Different reaction temperatures (1300, 1350 and 1400 degrees C) were applied to prove the established growth process by experimentally. Scanning electron microscopy and transmission electron microscopy studies show that the crystalline quality of the SiC NWs increases with the temperature at which they have been synthesized. La-Ni alloyed catalyst particles observed on the top of the SiC NWs confirms that the growth process follows this extended VLS mechanism. The X-ray diffraction and confocal Raman spectroscopy analyses demonstrate that the crystalline structure of the SiC NWs was zinc blende 3C-SiC. Optical property of the SiC NWs was investigated by photoluminescence technique at room temperature. Such a new alloy catalytic method may be extended to synthesis other one-dimensional nanostructures.

  2. Predicting the growth of S i3N4 nanowires by phase-equilibrium-dominated vapor-liquid-solid mechanism

    Science.gov (United States)

    Zhang, Yongliang; Cai, Jing; Yang, Lijun; Wu, Qiang; Wang, Xizhang; Hu, Zheng

    2017-09-01

    Nanomaterial synthesis is experiencing a profound evolution from empirical science ("cook-and-look") to prediction and design, which depends on the deep insight into the growth mechanism. Herein, we report a generalized prediction of the growth of S i3N4 nanowires by nitriding F e28S i72 alloy particles across different phase regions based on our finding of the phase-equilibrium-dominated vapor-liquid-solid (PED-VLS) mechanism. All the predictions about the growth of S i3N4 nanowires, and the associated evolutions of lattice parameters and geometries of the coexisting Fe -Si alloy phases, are experimentally confirmed quantitatively. This progress corroborates the general validity of the PED-VLS mechanism, which could be applied to the design and controllable synthesis of various one-dimensional nanomaterials.

  3. Phase-field model of vapor-liquid-solid nanowire growth

    Science.gov (United States)

    Wang, Nan; Upmanyu, Moneesh; Karma, Alain

    2018-03-01

    We present a multiphase-field model to describe quantitatively nanowire growth by the vapor-liquid-solid (VLS) process. The free-energy functional of this model depends on three nonconserved order parameters that distinguish the vapor, liquid, and solid phases and describe the energetic properties of various interfaces, including arbitrary forms of anisotropic γ plots for the solid-vapor and solid-liquid interfaces. The evolution equations for those order parameters describe basic kinetic processes including the rapid (quasi-instantaneous) equilibration of the liquid catalyst to a droplet shape with constant mean curvature, the slow incorporation of growth atoms at the droplet surface, and crystallization within the droplet. The standard constraint that the sum of the phase fields equals unity and the conservation of the number of catalyst atoms, which relates the catalyst volume to the concentration of growth atoms inside the droplet, are handled via separate Lagrange multipliers. An analysis of the model is presented that rigorously maps the phase-field equations to a desired set of sharp-interface equations for the evolution of the phase boundaries under the constraint of force balance at three-phase junctions (triple points) given by the Young-Herring relation that includes torque term related to the anisotropy of the solid-liquid and solid-vapor interface excess free energies. Numerical examples of growth in two dimensions are presented for the simplest case of vanishing crystalline anisotropy and the more realistic case of a solid-liquid γ plot with cusped minima corresponding to two sets of (10 ) and (11 ) facets. The simulations reproduce many of the salient features of nanowire growth observed experimentally, including growth normal to the substrate with tapering of the side walls, transitions between different growth orientations, and crawling growth along the substrate. They also reproduce different observed relationships between the nanowire growth

  4. Microspheres for the Growth of Silicon Nanowires via Vapor-Liquid-Solid Mechanism

    Directory of Open Access Journals (Sweden)

    Arancha Gómez-Martínez

    2014-01-01

    Full Text Available Silicon nanowires have been synthesized by a simple process using a suitable support containing silica and carbon microspheres. Nanowires were grown by thermal chemical vapor deposition via a vapor-liquid-solid mechanism with only the substrate as silicon source. The curved surface of the microsized spheres allows arranging the gold catalyst as nanoparticles with appropriate dimensions to catalyze the growth of nanowires. The resulting material is composed of the microspheres with the silicon nanowires attached on their surface.

  5. Theoretical analysis of the axial growth of nanowires starting with a binary eutectic droplet via vapor-liquid-solid mechanism

    Science.gov (United States)

    Liu, Qing; Li, Hejun; Zhang, Yulei; Zhao, Zhigang

    2018-06-01

    A series of theoretical analysis is carried out for the axial vapor-liquid-solid (VLS) growth of nanowires starting with a binary eutectic droplet. The growth model considering the entire process of axial VLS growth is a development of the approaches already developed by previous studies. In this model, the steady and unsteady state growth are considered both. The amount of solute species in a variable liquid droplet, the nanowire length, radius, growth rate and all other parameters during the entire axial growth process are treated as functions of growth time. The model provides theoretical predictions for the formation of nanowire shape, the length-radius and growth rate-radius dependences. It is also suggested by the model that the initial growth of single nanowire is significantly affected by Gibbs-Thompson effect due to the shape change. The model was applied on predictions of available experimental data of Si and Ge nanowires grown from Au-Si and Au-Ge systems respectively reported by other works. The calculations with the proposed model are in satisfactory agreement with the experimental results of the previous works.

  6. Understanding the vapor-liquid-solid growth and composition of ternary III-V nanowires and nanowire heterostructures

    Science.gov (United States)

    Dubrovskii, V. G.

    2017-11-01

    Based on the recent achievements in vapor-liquid-solid (VLS) synthesis, characterization and modeling of ternary III-V nanowires and axial heterostructures within such nanowires, we try to understand the major trends in their compositional evolution from a general theoretical perspective. Clearly, the VLS growth of ternary materials is much more complex than in standard vapor-solid epitaxy techniques, and even maintaining the necessary control over the composition of steady-state ternary nanowires is far from straightforward. On the other hand, VLS nanowires offer otherwise unattainable material combinations without introducing structural defects and hence are very promising for next-generation optoelectronic devices, in particular those integrated with a silicon electronic platform. In this review, we consider two main problems. First, we show how and by means of which parameters the steady-state composition of Au-catalyzed or self-catalyzed ternary III-V nanowires can be tuned to a desired value and why it is generally different from the vapor composition. Second, we present some experimental data and modeling results for the interfacial abruptness across axial nanowire heterostructures, both in Au-catalyzed and self-catalyzed VLS growth methods. Refined modeling allows us to formulate some general growth recipes for suppressing the unwanted reservoir effect in the droplet and sharpening the nanowire heterojunctions. We consider and refine two approaches developed to date, namely the regular crystallization model for a liquid alloy with a critical size of only one III-V pair at high supersaturations or classical binary nucleation theory with a macroscopic critical nucleus at modest supersaturations.

  7. Epitaxy-enabled vapor-liquid-solid growth of tin-doped indium oxide nanowires with controlled orientations

    KAUST Repository

    Shen, Youde

    2014-08-13

    Controlling the morphology of nanowires in bottom-up synthesis and assembling them on planar substrates is of tremendous importance for device applications in electronics, photonics, sensing and energy conversion. To date, however, there remain challenges in reliably achieving these goals of orientation-controlled nanowire synthesis and assembly. Here we report that growth of planar, vertical and randomly oriented tin-doped indium oxide (ITO) nanowires can be realized on yttria-stabilized zirconia (YSZ) substrates via the epitaxy-assisted vapor-liquid-solid (VLS) mechanism, by simply regulating the growth conditions, in particular the growth temperature. This robust control on nanowire orientation is facilitated by the small lattice mismatch of 1.6% between ITO and YSZ. Further control of the orientation, symmetry and shape of the nanowires can be achieved by using YSZ substrates with (110) and (111), in addition to (100) surfaces. Based on these insights, we succeed in growing regular arrays of planar ITO nanowires from patterned catalyst nanoparticles. Overall, our discovery of unprecedented orientation control in ITO nanowires advances the general VLS synthesis, providing a robust epitaxy-based approach toward rational synthesis of nanowires. © 2014 American Chemical Society.

  8. Phase diagram of nanoscale alloy particles used for vapor-liquid-solid growth of semiconductor nanowires.

    Science.gov (United States)

    Sutter, Eli; Sutter, Peter

    2008-02-01

    We use transmission electron microscopy observations to establish the parts of the phase diagram of nanometer sized Au-Ge alloy drops at the tips of Ge nanowires (NWs) that determine their temperature-dependent equilibrium composition and, hence, their exchange of semiconductor material with the NWs. We find that the phase diagram of the nanoscale drop deviates significantly from that of the bulk alloy, which explains discrepancies between actual growth results and predictions on the basis of the bulk-phase equilibria. Our findings provide the basis for tailoring vapor-liquid-solid growth to achieve complex one-dimensional materials geometries.

  9. Pattern formation of nanoflowers during the vapor-liquid-solid growth of silicon nanowires

    International Nuclear Information System (INIS)

    Bae, Joonho; Thompson-Flagg, Rebecca; Ekerdt, John G.; Shih, C.-K.

    2008-01-01

    Pattern formation of nanoflowers during the vapor-liquid-solid growth of Si nanowires is reported. Using transmission electron microscopy, scanning electron microscopy, and energy dispersive spectrometer analysis, we show that the flower consists of an Au/SiO x core-shell structure. Moreover, the growth of flower starts at the interface between the gold catalyst and the silicon nanowire, presumably by enhanced oxidation at this interface. The pattern formation can be classified as dense branching morphology (DBM). It is the first observation of DBM in a spherical geometry and at the nanoscale. The analysis of the average branching distance of this pattern shows that the pattern is most likely formed during the growth process, not the cooling process, and that the curvature of the gold droplet plays a crucial role in the frequency of branching

  10. Engineering scale development of the vapor-liquid-solid (VLS) process for the production of silicon carbide fibrils. Phase 2

    Energy Technology Data Exchange (ETDEWEB)

    Ohnsorg, R.W.; Hollar, W.E. Jr.; Lau, S.K. [Carborundum Co., Niagara Falls, NY (United States). Technology Div.; Ko, F.K.; Schatz, K. [Advanced Product Development, Bristol, PA (United States)

    1995-04-01

    As reinforcements for composites, VLS SiC fibrils have attractive mechanical properties including high-strength, high modulus, and excellent creep resistance. To make use of their excellent mechanical properties in a composite, a significant volume fraction (>10%) of aligned, long fibrils (>2 mm) needs to be consolidated in the ceramic matrix. The fibrils must be processed into an assembly that will allow for composite fabrication while maintaining fibril alignment and length. With Advanced Product Development (APD) as the yam fabrication subcontractor, Carborundum investigated several approaches to achieve this goaL including traditional yam-forming processes such as carding and air-vortex spinning and nontraditional processes such as tape forming and wet casting. Carborundum additionally performed an economic analysis for producing 500 and 10,000 pounds of SiC fibrils annually using both conservative and more aggressive processing parameters. With the aggressive approach, the projected costs for SiC fibril production for 500 and 10,000 pounds per year are $1,340/pound and $340/pound, respectively.

  11. High quality junctions by interpenetration of vapor liquid solid grown nanostructures for microchip integration

    Energy Technology Data Exchange (ETDEWEB)

    Jebril, Seid; Kuhlmann, Hanna; Adelung, Rainer [Funktionale Nanomaterialien, CAU Kiel (Germany); Mueller, Sven [Nanowires and Thin Films, II. Physikalisches Institut, Goettingen (Germany); Ronning, Carsten [Institute for Solid State Physics, Universitaet Jena (Germany); Kienle, Lorenz [Synthese und Realstruktur, CAU Kiel (Germany); Duppel, Viola [MPI fuer Festkoerperforschung, Stuttgart (Germany)

    2009-07-01

    The usability of nanostructures in electrical devices like gas sensors depends critically on the ability to form high quality contacts and junctions. For the fabrication of various nanostructures, vapor-liquid-solid (VLS) growth is a wide spread and very efficient technique. However, forming contacts with the VLS grown structures to utilize them in a device is still tedious, because either the substrate has to be epitaxial to the VLS material or a manual alignment is necessary. Here we demonstrate the contact formation by simply using the ability of individual crystals to interpenetrate each other during the straight forward VLS growth. This allows growing VLS structures directly on two neighboring gold circuit paths of a microchip; bridges over predefined gaps will be formed. Moreover, TEM investigations confirm the high quality of the crystalline junctions that allow demonstrations as UV and hydrogen-sensor. The VLS devices are compared with conventional produced.

  12. Vapor-Liquid-Solid Etch of Semiconductor Surface Channels by Running Gold Nanodroplets.

    Science.gov (United States)

    Nikoobakht, Babak; Herzing, Andrew; Muramoto, Shin; Tersoff, Jerry

    2015-12-09

    We show that Au nanoparticles spontaneously move across the (001) surface of InP, InAs, and GaP when heated in the presence of water vapor. As they move, the particles etch crystallographically aligned grooves into the surface. We show that this process is a negative analogue of the vapor-liquid-solid (VLS) growth of semiconductor nanowires: the semiconductor dissolves into the catalyst and reacts with water vapor at the catalyst surface to create volatile oxides, depleting the dissolved cations and anions and thus sustaining the dissolution process. This VLS etching process provides a new tool for directed assembly of structures with sublithographic dimensions, as small as a few nanometers in diameter. Au particles above 100 nm in size do not exhibit this process but remain stationary, with oxide accumulating around the particles.

  13. One step growth of GaN/SiO2 core/shell nanowire in vapor-liquid-solid route by chemical vapor deposition technique

    Science.gov (United States)

    Barick, B. K.; Yadav, Shivesh; Dhar, S.

    2017-11-01

    GaN/SiO2 core/shell nanowires are grown by cobalt phthalocyanine catalyst assisted vapor-liquid-solid route, in which Si wafer coated with a mixture of gallium and indium is used as the source for Ga and Si and ammonia is used as the precursor for nitrogen and hydrogen. Gallium in the presence of indium and hydrogen, which results from the dissociation of ammonia, forms Si-Ga-In alloy at the growth temperature ∼910 °C. This alloy acts as the source of Si, Ga and In. A detailed study using a variety of characterization tools reveals that these wires, which are several tens of micron long, has a diameter distribution of the core ranging from 20 to 50 nm, while the thickness of the amorphous SiO2 shell layer is about 10 nm. These wires grow along [ 1 0 1 bar 0 ] direction. It has also been observed that the average diameter of these wires decreases, while their density increases as the gallium proportion in the Ga-In mixture is increased.

  14. Epitaxy-enabled vapor-liquid-solid growth of tin-doped indium oxide nanowires with controlled orientations

    KAUST Repository

    Shen, Youde; Turner, Stuart G.; Yang, Ping; Van Tendeloo, Gustaaf; Lebedev, Oleg I.; Wu, Tao

    2014-01-01

    challenges in reliably achieving these goals of orientation-controlled nanowire synthesis and assembly. Here we report that growth of planar, vertical and randomly oriented tin-doped indium oxide (ITO) nanowires can be realized on yttria-stabilized zirconia

  15. Structural and electronic properties of InN nanowire network grown by vapor-liquid-solid method

    Directory of Open Access Journals (Sweden)

    B. K. Barick

    2015-05-01

    Full Text Available Growth of InN nanowires have been carried out on quartz substrates at different temperatures by vapor-liquid-solid (VLS technique using different thicknesses of Au catalyst layer. It has been found that a narrow window of Au layer thickness and growth temperature leads to multi-nucleation, in which each site acts as the origin of several nanowires. In this multi-nucleation regime, several tens of micrometer long wires with diameter as small as 20 nm are found to grow along [ 11 2 ̄ 0 ] direction (a-plane to form a dense network. Structural and electronic properties of these wires are studied. As grown nanowires show degenerate n-type behavior. Furthermore, x-ray photoemission study reveals an accumulation of electrons on the surface of these nanowires. Interestingly, the wire network shows persistence of photoconductivity for several hours after switching off the photoexcitation.

  16. Structural and electronic properties of InN nanowire network grown by vapor-liquid-solid method

    Science.gov (United States)

    Barick, B. K.; Rodríguez-Fernández, Carlos; Cantarero, Andres; Dhar, S.

    2015-05-01

    Growth of InN nanowires have been carried out on quartz substrates at different temperatures by vapor-liquid-solid (VLS) technique using different thicknesses of Au catalyst layer. It has been found that a narrow window of Au layer thickness and growth temperature leads to multi-nucleation, in which each site acts as the origin of several nanowires. In this multi-nucleation regime, several tens of micrometer long wires with diameter as small as 20 nm are found to grow along [ 11 2 ¯ 0 ] direction (a-plane) to form a dense network. Structural and electronic properties of these wires are studied. As grown nanowires show degenerate n-type behavior. Furthermore, x-ray photoemission study reveals an accumulation of electrons on the surface of these nanowires. Interestingly, the wire network shows persistence of photoconductivity for several hours after switching off the photoexcitation.

  17. Structural and electronic properties of InN nanowire network grown by vapor-liquid-solid method

    Energy Technology Data Exchange (ETDEWEB)

    Barick, B. K., E-mail: bkbarick@gmail.com, E-mail: subho-dh@yahoo.co.in; Dhar, S., E-mail: bkbarick@gmail.com, E-mail: subho-dh@yahoo.co.in [Department of Physics, Indian Institute of Technology, Bombay, Mumbai-400076 (India); Rodríguez-Fernández, Carlos; Cantarero, Andres [Materials Science Institute, University of Valencia, PO Box 22085, 46071 Valencia (Spain)

    2015-05-15

    Growth of InN nanowires have been carried out on quartz substrates at different temperatures by vapor-liquid-solid (VLS) technique using different thicknesses of Au catalyst layer. It has been found that a narrow window of Au layer thickness and growth temperature leads to multi-nucleation, in which each site acts as the origin of several nanowires. In this multi-nucleation regime, several tens of micrometer long wires with diameter as small as 20 nm are found to grow along [112{sup -}0] direction (a-plane) to form a dense network. Structural and electronic properties of these wires are studied. As grown nanowires show degenerate n-type behavior. Furthermore, x-ray photoemission study reveals an accumulation of electrons on the surface of these nanowires. Interestingly, the wire network shows persistence of photoconductivity for several hours after switching off the photoexcitation.

  18. Synthesis and growth mechanisms of ZrC whiskers fabricated by a VLS process

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dongju [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of). Nuclear Materials Development Division; Song, Sung Ho [Kongju National Univ., Chungnam (Korea, Republic of). Division of Advanced Materials Engineering

    2017-08-15

    The mechanisms of nano-sized ZrC whisker formation by a vapor-liquid-solid process (VLS) are investigated, which produces a very high purity, single crystal whisker. Rectangular ZrC whiskers with a cross-sectional diameter of 100-200 nm and lengths up to tens of microns are formed under the catalytic effect of nickel. The ZrC whiskers are characterized using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. ZrC whiskers can be used as a potential reinforcing and strengthening phase for ceramic composites.

  19. Vapor-liquid-solid mechanisms: Challenges for nanosized quantum cluster/dot/wire materials

    Science.gov (United States)

    Cheyssac, P.; Sacilotti, M.; Patriarche, G.

    2006-08-01

    The growth mechanism model of a nanoscaled material is a critical step that has to be refined for a better understanding of a nanostructure's dot/wire fabrication. To do so, the growth mechanism will be discussed in this paper and the influence of the size of the metallic nanocluster starting point, referred to later as "size effect," will be studied. Among many of the so-called size effects, a tremendous decrease of the melting point of the metallic nanocluster changes the physical properties as well as the physical/mechanical interactions inside the growing structure composed of a metallic dot on top of a column. The thermodynamic size effect is related to the bending or curvature of chains of atoms, giving rise to the weakening of bonds between them; this size or curvature effect is described and approached to crystal nanodot/wire growth. We will describe this effect as that of a "cooking machine" when the number of atoms decreases from ˜1023at./cm3 for a bulk material to a few tens of them in a 1-2nm diameter sphere. The decrease of the number of atoms in a metallic cluster from such an enormous quantity is accompanied by a lowering of the melting temperature that extends from 200 up to 1000K, depending on the metallic material and its size under study. In this respect, the vapor-liquid-solid (VLS) model, which is the most utilized growth mechanism for quantum nanowires and nanodots, is critically exposed to size or curvature effects (CEs). More precisely, interactions in the vicinity of the growth regions should be reexamined. Some results illustrating the growth of micrometer-/nanometer-sized materials are presented in order to corroborate the CE/VLS models utilized by many research groups in today's nanosciences world. Examples of metallic clusters and semiconducting wires will be presented. The results and comments presented in this paper can be seen as a challenge to be overcome. From them, we expect that in a near future an improved model can be exposed

  20. Atomic characterization of Au clusters in vapor-liquid-solid grown silicon nanowires

    International Nuclear Information System (INIS)

    Chen, Wanghua; Roca i Cabarrocas, Pere; Pareige, Philippe; Castro, Celia; Xu, Tao; Grandidier, Bruno; Stiévenard, Didier

    2015-01-01

    By correlating atom probe tomography with other conventional microscope techniques (scanning electron microscope, scanning transmission electron microscope, and scanning tunneling microscopy), the distribution and composition of Au clusters in individual vapor-liquid-solid grown Si nanowires is investigated. Taking advantage of the characteristics of atom probe tomography, we have developed a sample preparation method by inclining the sample at certain angle to characterize the nanowire sidewall without using focused ion beam. With three-dimensional atomic scale reconstruction, we provide direct evidence of Au clusters tending to remain on the nanowire sidewall rather than being incorporated into the Si nanowires. Based on the composition measurement of Au clusters (28% ± 1%), we have demonstrated the supersaturation of Si atoms in Au clusters, which supports the hypothesis that Au clusters are formed simultaneously during nanowire growth rather than during the cooling process

  1. Atomic characterization of Au clusters in vapor-liquid-solid grown silicon nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wanghua; Roca i Cabarrocas, Pere [Laboratoire de Physique des Interfaces et Couches Minces (LPICM), UMR 7647, CNRS, Ecole Polytechnique, 91128 Palaiseau (France); Pareige, Philippe; Castro, Celia [Groupe de Physique des Matériaux (GPM), Université et INSA de Rouen, UMR 6634, CNRS, Av. de l' Université, BP 12, 76801 Saint Etienne du Rouvray (France); Xu, Tao; Grandidier, Bruno; Stiévenard, Didier [Institut d' Electronique et de Microélectronique et de Nanotechnologies (IEMN), UMR 8520, CNRS, Département ISEN, 41 bd Vauban, 59046 Lille Cedex (France)

    2015-09-14

    By correlating atom probe tomography with other conventional microscope techniques (scanning electron microscope, scanning transmission electron microscope, and scanning tunneling microscopy), the distribution and composition of Au clusters in individual vapor-liquid-solid grown Si nanowires is investigated. Taking advantage of the characteristics of atom probe tomography, we have developed a sample preparation method by inclining the sample at certain angle to characterize the nanowire sidewall without using focused ion beam. With three-dimensional atomic scale reconstruction, we provide direct evidence of Au clusters tending to remain on the nanowire sidewall rather than being incorporated into the Si nanowires. Based on the composition measurement of Au clusters (28% ± 1%), we have demonstrated the supersaturation of Si atoms in Au clusters, which supports the hypothesis that Au clusters are formed simultaneously during nanowire growth rather than during the cooling process.

  2. Modeling of vapor-liquid-solid equilibrium in gas - aqueous electrolyte systems

    DEFF Research Database (Denmark)

    Thomsen, Kaj; Rasmussen, Peter

    1999-01-01

    A thermodynamic model for the description of vapor-liquid-solid equilibria is introduced. This model is a combination of the extended UNIQUAC model for electrolytes and the Soave-Redlich-Kwong cubic equation of state. The model has been applied to aqueous systems containing ammonia and/or carbon ...

  3. Broad compositional tunability of indium tin oxide nanowires grown by the vapor-liquid-solid mechanism

    Directory of Open Access Journals (Sweden)

    M. Zervos

    2014-05-01

    Full Text Available Indium tin oxide nanowires were grown by the reaction of In and Sn with O2 at 800 °C via the vapor-liquid-solid mechanism on 1 nm Au/Si(001. We obtain Sn doped In2O3 nanowires having a cubic bixbyite crystal structure by using In:Sn source weight ratios > 1:9 while below this we observe the emergence of tetragonal rutile SnO2 and suppression of In2O3 permitting compositional and structural tuning from SnO2 to In2O3 which is accompanied by a blue shift of the photoluminescence spectrum and increase in carrier lifetime attributed to a higher crystal quality and Fermi level position.

  4. Parallel-aligned GaAs nanowires with (110) orientation laterally grown on [311]B substrates via the gold-catalyzed vapor-liquid-solid mode

    International Nuclear Information System (INIS)

    Zhang Guoqiang; Tateno, Kouta; Gotoh, Hideki; Nakano, Hidetoshi

    2010-01-01

    We report parallel aligned GaAs nanowires (NWs) with (110) orientation laterally grown on [311]B substrates via the vapor-liquid-solid mode and demonstrate their controllability and growth mechanism. We control the size, density, and site of the lateral NWs by using size- and density-selective Au colloidal particles and Au dot arrays defined by electron-beam lithography. The lateral NWs grow only along the [110] and [1-bar 1-bar 0] directions and formation of the stable facets of (111)B and (001) on the sides of the lateral NWs is crucial for lateral NW growth. We clarify the growth mechanism by comparing the growth results on [311]B, (311)A, and (001) substrates and the surface energy change of lateral and freestanding NWs.

  5. Selective growth of gallium nitride nanowires by femtosecond laser patterning

    Energy Technology Data Exchange (ETDEWEB)

    Ng, D.K.T. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Data Storage Institute, Agency for Science, Technology and Research, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore); Hong, M.H. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Data Storage Institute, Agency for Science, Technology and Research, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore)], E-mail: HONG_Minghui@dsi.a-star.edu.sg; Tan, L.S. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore); Zhou, Y. [Data Storage Institute, Agency for Science, Technology and Research, DSI Building, 5 Engineering Drive 1, Singapore 117608 (Singapore); Department of Mechanical Engineering, National University of Singapore, 2 Engineering Drive 3, Singapore 117576 (Singapore); Chen, G.X. [Department of Electrical and Computer Engineering, National University of Singapore, 4 Engineering Drive 3, Singapore 117576 (Singapore)

    2008-01-31

    We report on gallium nitride (GaN) nanowires grown using pulsed laser ablation, adopting the vapor-liquid-solid (VLS) growth mechanism. The GaN nanowires are obtained based on the principle that a catalyst is required to initiate the nanowires growth. Locations of the GaN nanowires are patterned using femtosecond laser and focused ion beam. Scanning electron microscopy (SEM) is used to characterize the nanowires. This patterning of GaN nanowires will enable selective growth of nanowires and bottom-up assembly of integrated electronic and photonic devices.

  6. Selective growth of gallium nitride nanowires by femtosecond laser patterning

    International Nuclear Information System (INIS)

    Ng, D.K.T.; Hong, M.H.; Tan, L.S.; Zhou, Y.; Chen, G.X.

    2008-01-01

    We report on gallium nitride (GaN) nanowires grown using pulsed laser ablation, adopting the vapor-liquid-solid (VLS) growth mechanism. The GaN nanowires are obtained based on the principle that a catalyst is required to initiate the nanowires growth. Locations of the GaN nanowires are patterned using femtosecond laser and focused ion beam. Scanning electron microscopy (SEM) is used to characterize the nanowires. This patterning of GaN nanowires will enable selective growth of nanowires and bottom-up assembly of integrated electronic and photonic devices

  7. Demonstration of GaAsSb/InAs nanowire backward diodes grown using position-controlled vapor-liquid-solid method

    Science.gov (United States)

    Kawaguchi, Kenichi; Takahashi, Tsuyoshi; Okamoto, Naoya; Sato, Masaru

    2018-02-01

    p-GaAsSb/n-InAs type-II nanowire (NW) diodes were fabricated using the position-controlled vapor-liquid-solid growth method. InAs and GaAsSb NW segments were grown vertically on GaAs(111)B substrates with the assistance of Au catalysts. Transmission electron microscopy-energy-dispersive X-ray spectroscopy analysis revealed that the GaAsSb segments have an Sb content of 40%, which is sufficient to form a tunnel heterostructure. Scanning capacitance microscope images clearly indicated the formation of a p-n junction in the NWs. Backward diode characteristics, that is, current flow toward negative bias originating from a tunnel current and current suppression toward positive bias by a heterobarrier, were demonstrated.

  8. Direct Evidence of Mg Incorporation Pathway in Vapor-Liquid-Solid Grown p-type Nonpolar GaN Nanowires

    OpenAIRE

    Patsha, Avinash; Amirthapandian, S.; Pandian, Ramanathaswamy; Bera, S.; Bhattacharya, Anirban; Dhara, Sandip

    2015-01-01

    Doping of III-nitride based compound semiconductor nanowires is still a challenging issue to have a control over the dopant distribution in precise locations of the nanowire optoelectronic devices. Knowledge of the dopant incorporation and its pathways in nanowires for such devices is limited by the growth methods. We report the direct evidence of incorporation pathway for Mg dopants in p-type nonpolar GaN nanowires grown via vapour-liquid-solid (VLS) method in a chemical vapour deposition te...

  9. Growth of Gold-assisted Gallium Arsenide Nanowires on Silicon Substrates via Molecular Beam Epitaxy

    Directory of Open Access Journals (Sweden)

    Ramon M. delos Santos

    2008-06-01

    Full Text Available Gallium arsenide nanowires were grown on silicon (100 substrates by what is called the vapor-liquid-solid (VLS growth mechanism using a molecular beam epitaxy (MBE system. Good quality nanowires with surface density of approximately 108 nanowires per square centimeter were produced by utilizing gold nanoparticles, with density of 1011 nanoparticles per square centimeter, as catalysts for nanowire growth. X-ray diffraction measurements, scanning electron microscopy, transmission electron microscopy and Raman spectroscopy revealed that the nanowires are epitaxially grown on the silicon substrates, are oriented along the [111] direction and have cubic zincblende structure.

  10. Diameter optimization of VLS-synthesized ZnO nanowires, using statistical design of experiment

    International Nuclear Information System (INIS)

    Shafiei, Sepideh; Nourbakhsh, Amirhasan; Ganjipour, Bahram; Zahedifar, Mostafa; Vakili-Nezhaad, Gholamreza

    2007-01-01

    The possibility of diameter optimization of ZnO nanowires by using statistical design of experiment (DoE) is investigated. In this study, nanowires were synthesized using a vapor-liquid-solid (VLS) growth method in a horizontal reactor. The effects of six synthesis parameters (synthesis time, synthesis temperature, thickness of gold layer, distance between ZnO holder and substrate, mass of ZnO and Ar flow rate) on the average diameter of a ZnO nanowire were examined using the fractional factorial design (FFD) coupled with response surface methodology (RSM). Using a 2 III 6-3 FFD, the main effects of the thickness of the gold layer, synthesis temperature and synthesis time were concluded to be the key factors influencing the diameter. Then Box-Behnken design (BBD) was exploited to create a response surface from the main factors. The total number of required runs for the DoE process is 25, 8 runs for FFD parameter screening and 17 runs for the response surface obtained by BBD. Three extra runs are done to confirm the predicted results

  11. Controlling growth density and patterning of single crystalline silicon nanowires

    International Nuclear Information System (INIS)

    Chang, Tung-Hao; Chang, Yu-Cheng; Liu, Fu-Ken; Chu, Tieh-Chi

    2010-01-01

    This study examines the usage of well-patterned Au nanoparticles (NPs) as a catalyst for one-dimensional growth of single crystalline Si nanowires (NWs) through the vapor-liquid-solid (VLS) mechanism. The study reports the fabrication of monolayer Au NPs through the self-assembly of Au NPs on a 3-aminopropyltrimethoxysilane (APTMS)-modified silicon substrate. Results indicate that the spin coating time of Au NPs plays a crucial role in determining the density of Au NPs on the surface of the silicon substrate and the later catalysis growth of Si NWs. The experiments in this study employed optical lithography to pattern Au NPs, treating them as a catalyst for Si NW growth. The patterned Si NW structures easily produced and controlled Si NW density. This approach may be useful for further studies on single crystalline Si NW-based nanodevices and their properties.

  12. Growth and characterization of iridium dioxide nanorods

    International Nuclear Information System (INIS)

    Chen, R.S.; Huang, Y.S.; Liang, Y.M.; Tsai, D.S.; Tiong, K.K.

    2004-01-01

    Conductive iridium dioxide (IrO 2 ) nanorods have been successfully grown on the Si(1 0 0) substrates via metalorganic chemical vapor deposition (MOCVD). A wedge-shaped morphology and naturally formed sharp tips are observed for IrO 2 nanorods using field-emission scanning electron microscopy (FESEM). High-resolution transmission electron microscopy (TEM) image and electron diffraction pattern show the growth of IrO 2 nanorods preferentially along c-axis. Structure and composition of IrO 2 nanorods have also been characterized using the techniques of Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively. It is noted that the IrO 2 nanorods are self-mediated instead of the conventional vapor-liquid-solid (VLS) approach or catalyst-mediated method

  13. Vapor phase epitaxial growth of FeS sub 2 pyrite and evaluation of the carrier collection in liquid-junction solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Ennaoui, A.; Schlichthoerl, G.; Fiechter, S.; Tributsch, H. (Hahn-Meitner-Inst., Abt. Solare Energetik und Materialforschung, Berlin (Germany))

    1992-01-01

    Photoactive epitaxial layers of FeS{sub 2} were grown using bromine as a transport agent and a simple closed ampoule technique. The substrates used were (100)-oriented slices of natural pyrite 1 mm thick. A vapor-liquid-solid (VLS) growth mechanism was elucidated by means of optical microscopy. Macrosteps, terrace surfaces and protuberances are often accompanied with the presence of liquid FeBr{sub 3} droplets. In the absence of a liquid phase growth hillocks are found. Localized photovoltaic response for the evaluation of carrier collection using a scanning laser spot system has been used to effectively locate and characterize non-uniformities present in the epitaxial thin films. (orig.).

  14. Aluminum-catalyzed silicon nanowires: Growth methods, properties, and applications

    Energy Technology Data Exchange (ETDEWEB)

    Hainey, Mel F.; Redwing, Joan M. [Department of Materials Science and Engineering, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

    2016-12-15

    Metal-mediated vapor-liquid-solid (VLS) growth is a promising approach for the fabrication of silicon nanowires, although residual metal incorporation into the nanowires during growth can adversely impact electronic properties particularly when metals such as gold and copper are utilized. Aluminum, which acts as a shallow acceptor in silicon, is therefore of significant interest for the growth of p-type silicon nanowires but has presented challenges due to its propensity for oxidation. This paper summarizes the key aspects of aluminum-catalyzed nanowire growth along with wire properties and device results. In the first section, aluminum-catalyzed nanowire growth is discussed with a specific emphasis on methods to mitigate aluminum oxide formation. Next, the influence of growth parameters such as growth temperature, precursor partial pressure, and hydrogen partial pressure on nanowire morphology is discussed, followed by a brief review of the growth of templated and patterned arrays of nanowires. Aluminum incorporation into the nanowires is then discussed in detail, including measurements of the aluminum concentration within wires using atom probe tomography and assessment of electrical properties by four point resistance measurements. Finally, the use of aluminum-catalyzed VLS growth for device fabrication is reviewed including results on single-wire radial p-n junction solar cells and planar solar cells fabricated with nanowire/nanopyramid texturing.

  15. VLS growth of alternating InAsP/InP heterostructure nanowires for multiple-quantum-dot structures.

    Science.gov (United States)

    Tateno, Kouta; Zhang, Guoqiang; Gotoh, Hideki; Sogawa, Tetsuomi

    2012-06-13

    We investigated the Au-assisted growth of alternating InAsP/InP heterostructures in wurtzite InP nanowires on InP(111)B substrates for constructing multiple-quantum-dot structures. Vertical InP nanowires without stacking faults were obtained at a high PH(3)/TMIn mole flow ratio of 300-1000. We found that the growth rate changed largely when approximately 40 min passed. Ten InAsP layers were inserted in the InP nanowire, and it was found that both the InP growth rate and the background As level increased after the As supply. We also grew the same structure using TBAs/TBP and could reduce the As level in the InP segments. A simulation using a finite-difference time-domain method suggests that the nanowire growth was dominated by the diffusion of the reaction species with long residence time on the surface. For TBAs/TBP, when the source gases were changed, the formed surface species showed a short diffusion length so as to reduce the As background after the InAsP growth.

  16. Low temperature and self catalytic growth of ultrafine ITO nanowires by electron beam evaporation method and their optical and electrical properties

    International Nuclear Information System (INIS)

    Kumar, R. Rakesh; Rao, K. Narasimha; Rajanna, K.; Phani, A.R.

    2014-01-01

    Highlights: • ITO nanowires were grown by e-beam evaporation method. • ITO nanowires growth done at low substrate temperature of 350 °C. • Nanowires growth was carried out without use of catalyst and reactive oxygen gas. • Nanowires growth proceeds via self catalytic VLS growth. • Grown nanowires have diameter 10–20 nm and length 1–4 μm long. • ITO nanowire films have shown good antireflection property. - Abstract: We report the self catalytic growth of Sn-doped indium oxide (ITO) nanowires (NWs) over a large area glass and silicon substrates by electron beam evaporation method at low substrate temperatures of 250–400 °C. The ITO NWs growth was carried out without using an additional reactive oxygen gas and a metal catalyst particle. Ultrafine diameter (∼10–15 nm) and micron long ITO NWs growth was observed in a temperature window of 300–400 °C. Transmission electron microscope studies confirmed single crystalline nature of the NWs and energy dispersive spectroscopy studies on the NWs confirmed that the NWs growth proceeds via self catalytic vapor-liquid-solid (VLS) growth mechanism. ITO nanowire films grown on glass substrates at a substrate temperature of 300–400 °C have shown ∼2–6% reflection and ∼70–85% transmission in the visible region. Effect of deposition parameters was systematically investigated. The large area growth of ITO nanowire films would find potential applications in the optoelectronic devices

  17. Defect-induced polytype transformations in LPE grown SiC epilayers on (1 1 1) 3C-SiC seeds grown by VLS on 6H-SiC

    International Nuclear Information System (INIS)

    Marinova, Maya; Zoulis, Georgios; Robert, Teddy; Mercier, Frederic; Mantzari, Alkioni; Galben, Irina; Kim-Hak, Olivier; Lorenzzi, Jean; Juillaguet, Sandrine; Chaussende, Didier; Ferro, Gabriel; Camassel, Jean; Polychroniadis, Efstathios K.

    2009-01-01

    The results of transmission electron microscopy (TEM) with low-temperature photoluminescence (LTPL) and Raman studies of liquid phase grown epilayers on top of a vapor liquid solid (VLS) grown 3C-SiC buffer layer are compared. While the 6H-SiC substrate was completely covered by the 3C-SiC seed after the first VLS process, degradation occurred during the early stage of the liquid phase epitaxy process. This resulted in polytype instabilities, such that several rhombohedral forms stabilized one after the other. These (21R-SiC, 57R-SiC) eventually led after few microns to a final transition back to 6H-SiC. This interplay of polytypes resulted in a complex optical signature, with specific LTPL and Raman features.

  18. Gold catalyzed nickel disilicide formation: a new solid-liquid-solid phase growth mechanism.

    Science.gov (United States)

    Tang, Wei; Picraux, S Tom; Huang, Jian Yu; Liu, Xiaohua; Tu, K N; Dayeh, Shadi A

    2013-01-01

    The vapor-liquid-solid (VLS) mechanism is the predominate growth mechanism for semiconductor nanowires (NWs). We report here a new solid-liquid-solid (SLS) growth mechanism of a silicide phase in Si NWs using in situ transmission electron microcopy (TEM). The new SLS mechanism is analogous to the VLS one in relying on a liquid-mediating growth seed, but it is fundamentally different in terms of nucleation and mass transport. In SLS growth of Ni disilicide, the Ni atoms are supplied from remote Ni particles by interstitial diffusion through a Si NW to the pre-existing Au-Si liquid alloy drop at the tip of the NW. Upon supersaturation of both Ni and Si in Au, an octahedral nucleus of Ni disilicide (NiSi2) forms at the center of the Au liquid alloy, which thereafter sweeps through the Si NW and transforms Si into NiSi2. The dissolution of Si by the Au alloy liquid mediating layer proceeds with contact angle oscillation at the triple point where Si, oxide of Si, and the Au alloy meet, whereas NiSi2 is grown from the liquid mediating layer in an atomic stepwise manner. By using in situ quenching experiments, we are able to measure the solubility of Ni and Si in the Au-Ni-Si ternary alloy. The Au-catalyzed mechanism can lower the formation temperature of NiSi2 by 100 °C compared with an all solid state reaction.

  19. Controlling Growth High Uniformity Indium Selenide (In2Se3) Nanowires via the Rapid Thermal Annealing Process at Low Temperature.

    Science.gov (United States)

    Hsu, Ya-Chu; Hung, Yu-Chen; Wang, Chiu-Yen

    2017-09-15

    High uniformity Au-catalyzed indium selenide (In 2 Se 3) nanowires are grown with the rapid thermal annealing (RTA) treatment via the vapor-liquid-solid (VLS) mechanism. The diameters of Au-catalyzed In 2 Se 3 nanowires could be controlled with varied thicknesses of Au films, and the uniformity of nanowires is improved via a fast pre-annealing rate, 100 °C/s. Comparing with the slower heating rate, 0.1 °C/s, the average diameters and distributions (standard deviation, SD) of In 2 Se 3 nanowires with and without the RTA process are 97.14 ± 22.95 nm (23.63%) and 119.06 ± 48.75 nm (40.95%), respectively. The in situ annealing TEM is used to study the effect of heating rate on the formation of Au nanoparticles from the as-deposited Au film. The results demonstrate that the average diameters and distributions of Au nanoparticles with and without the RTA process are 19.84 ± 5.96 nm (30.00%) and about 22.06 ± 9.00 nm (40.80%), respectively. It proves that the diameter size, distribution, and uniformity of Au-catalyzed In 2 Se 3 nanowires are reduced and improved via the RTA pre-treated. The systemic study could help to control the size distribution of other nanomaterials through tuning the annealing rate, temperatures of precursor, and growth substrate to control the size distribution of other nanomaterials. Graphical Abstract Rapid thermal annealing (RTA) process proved that it can uniform the size distribution of Au nanoparticles, and then it can be used to grow the high uniformity Au-catalyzed In 2 Se 3 nanowires via the vapor-liquid-solid (VLS) mechanism. Comparing with the general growth condition, the heating rate is slow, 0.1 °C/s, and the growth temperature is a relatively high growth temperature, > 650 °C. RTA pre-treated growth substrate can form smaller and uniform Au nanoparticles to react with the In 2 Se 3 vapor and produce the high uniformity In 2 Se 3 nanowires. The in situ annealing TEM is used to realize the effect of heating

  20. Growth Mechanism of Nanowires: Binary and Ternary Chalcogenides

    Science.gov (United States)

    Singh, N. B.; Coriell, S. R.; Su, Ching-Hua; Hopkins, R. H.; Arnold, B.; Choa, Fow-Sen; Cullum, Brian

    2016-01-01

    Semiconductor nanowires exhibit very exciting optical and electrical properties including high transparency and a several order of magnitude better photocurrent than thin film and bulk materials. We present here the mechanism of nanowire growth from the melt-liquid-vapor medium. We describe preliminary results of binary and ternary selenide materials in light of recent theories. Experiments were performed with lead selenide and thallium arsenic selenide systems which are multifunctional material and have been used for detectors, acousto-optical, nonlinear and radiation detection applications. We observed that small units of nanocubes and elongated nanoparticles arrange and rearrange at moderate melt undercooling to form the building block of a nanowire. Since we avoided the catalyst, we observed self-nucleation and uncontrolled growth of wires from different places. Growth of lead selenide nanowires was performed by physical vapor transport method and thallium arsenic selenide nanowire by vapor-liquid-solid (VLS) method. In some cases very long wires (>mm) are formed. To achieve this goal experiments were performed to create situation where nanowires grew on the surface of solid thallium arsenic selenide itself.

  1. Vapor-solid-solid growth mechanism driven by an epitaxial match between solid Au Zn alloy catalyst particle and Zn O nano wire at low temperature

    International Nuclear Information System (INIS)

    Campos, Leonardo C.; Tonezzer, Matteo; Ferlauto, Andre S.; Magalhaes-Paniago, Rogerio; Oliveira, Sergio; Ladeira, Luiz O.; Lacerda, Rodrigo G.

    2008-01-01

    Nowadays, the growth of nano materials, like nano wires and nano tubes, is one of the key research areas of nano technology. However, a full picture of the growth mechanism of these quasi-one dimensional systems still needs to be achieved if these materials are to be applied electronics, biology and medicinal fields. Nevertheless, in spite of considerable advances on the growth of numerous nano wires, a clear understanding of the growth mechanism is still controversial and highly discussed. The present work provides a comprehensive picture of the precise mechanism of Zn O vapor-solid-solid (VSS) nano wire growth at low temperatures and gives the fundamental reasons responsible. We demonstrate by using a combination of synchrotron XRD and high resolution TEM that the growth dynamics at low temperatures is not governed by the well-known vapor-liquid solid (VLS) mechanisms. A critical new insight on the driving factor of VSS growth is proposed in which the VSS process occurs by a solid diffusion mechanism that is driven by a preferential oxidation process of the Zn inside the alloy catalyst induced by an epitaxial match between the Zn O(10-10) plane and the γ-Au Zn(222) plane. We believe that these results are not only important for the understanding of Zn O nano wire growth but could also have significant impact on the understanding of growth mechanisms of other nano wire systems. (author)

  2. Flow-Solution-Liquid-Solid Growth of Semiconductor Nanowires: A Novel Approach for Controlled Synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Hollingsworth, Jennifer A. [Los Alamos National Laboratory; Palaniappan, Kumaranand [Los Alamos National Laboratory; Laocharoensuk, Rawiwan [National Science and Technology Center, Thailand; Smith, Nickolaus A. [Los Alamos National Laboratory; Dickerson, Robert M. [Los Alamos National Laboratory; Casson, Joanna L. [Los Alamos National Laboratory; Baldwin, Jon K. [Los Alamos National Laboratory

    2012-06-07

    Semiconductor nanowires (SC-NWs) have potential applications in diverse technologies from nanoelectronics and photonics to energy harvesting and storage due to their quantum-confined opto-electronic properties coupled with their highly anisotropic shape. Here, we explore new approaches to an important solution-based growth method known as solution-liquid-solid (SLS) growth. In SLS, molecular precursors are reacted in the presence of low-melting metal nanoparticles that serve as molten fluxes to catalyze the growth of the SC-NWs. The mechanism of growth is assumed to be similar to that of vapor-liquid-solid (VLS) growth, with the clear distinctions of being conducted in solution in the presence of coordinating ligands and at relatively lower temperatures (<300 C). The resultant SC-NWs are soluble in common organic solvents and solution processable, offering advantages such as simplified processing, scale-up, ultra-small diameters for quantum-confinement effects, and flexible choice of materials from group III-V to groups II-VI, IV-VI, as well as truly ternary I-III-VI semiconductors as we recently demonstrates. Despite these advantages of SLS growth, VLS offers several clear opportunities not allowed by conventional SLS. Namely, VLS allows sequential addition of precursors for facile synthesis of complex axial heterostructures. In addition, growth proceeds relatively slowly compared to SLS, allowing clear assessments of growth kinetics. In order to retain the materials and processing flexibility afforded by SLS, but add the elements of controlled growth afforded by VLS, we transformed SLS into a flow based method by adapting it to synthesis in a microfluidic system. By this new method - so-called 'flow-SLS' (FSLS) - we have now demonstrated unprecedented fabrication of multi-segmented SC-NWs, e.g., 8-segmented CdSe/ZnSe defined by either compositionally abrupt or alloyed interfaces as a function of growth conditions. In addition, we have studied growth

  3. Homo- and heteroepitaxial growth behavior of upright InAs nanowires on InAs and GaAs substrates

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Jens; Gottschalch, Volker; Paetzelt, Hendrik [Institut fuer Anorganische Chemie, Universitaet Leipzig, Johannesallee 29, D-04103 Leipzig (Germany); Wagner, Gerald [Institut fuer Kristallographie und Mineralogie, Universitaet Leipzig, Linnestr. 5, D-04103 Leipzig (Germany); Pietsch, Ulrich [Festkoerperphysik, Universitaet Siegen, D-57068 Siegen (Germany)

    2008-07-01

    Semiconductor nanowires (NW) acquire recently attraction because of promising new application fields in electronics and optoelectronic. We applied the vapor-liquid-solid mechanism with gold seeds in combination with low-pressure metal-organic vapor phase epitaxy (LP-MOVPE) to achieve replicable InAs NW growth with high growth rates. Since the initial alloying of the gold seeds with the substrate material plays a deciding role for the inceptive NW growth, InAs free standing nanowires were grown on GaAs(111)B substrate as well as on InAs/GaAs(111)B quasi-substrate. The influence of the MOVPE parameters will be discussed with respect to NW morphology and real-structure. A special focus will be set on the heteroepitaxial InAs NW growth on GaAs substrates. Gracing-incidence X-ray studies and transmission electron microscopy investigations revealed the existence of a thin Ga{sub x}In{sub 1-x}As graduated alloy layer with embedded crystalline gold alloy particles at the NW substrate interface. The effect of droplet composition on the VLS growth will be presented in a thermodynamic model.

  4. The continuous and persistent periodical growth induced by substrate accommodation in In{sub 2}O{sub 3} nanostructure chains and their photoluminescence properties

    Energy Technology Data Exchange (ETDEWEB)

    Shariati, Mohsen [Islamic Azad University, Department of Physics, Faculty of Science, Roudehen (Iran, Islamic Republic of)

    2014-12-10

    The growth of pyramidal and triangular beaded In{sub 2}O{sub 3} nanocrystal chains by using oxygen-assisted thermal evaporation, substrate accommodation and condensation method has been articulated. Self-assembled In{sub 2}O{sub 3} nanocrystal chains have been synthesized by the vapor-solid (VS) and vapor-liquid-solid (VLS) growth mechanism and also through controlling the kinetics factors (saturation ratio). A periodical one-dimensional (1-D) and persistent (0-D) growth was proposed to explain the formation of lateral nanostructures, and this formation aspect was ascribed to the alternate 1-D and 0-D growth. Preparing the needed growth factor, the In{sub 2}O{sub 3} nanocrystal chains extended to several micrometers. The growth mechanism analysis was useful to realize the relation between the kinetics factors and the complex nanostructure. The morphology and size of nanocrystals intensively were changed by oxygen concentration and led to interesting photoluminescence property. (orig.)

  5. Selective growth of silica nanowires using an Au catalyst for optical recognition of interleukin-10

    Energy Technology Data Exchange (ETDEWEB)

    Sekhar, Praveen K; Ramgir, Niranjan S; Joshi, Rakesh K; Bhansali, Shekhar [Bio-MEMS and Microfabrication Laboratory, Department of Electrical Engineering, University of South Florida, 4202 E Fowler Avenue, ENB 118, Tampa, FL 33620 (United States)], E-mail: bhansali@eng.usf.edu

    2008-06-18

    The vapor-liquid-solid (VLS) growth procedure has been extended for the selective growth of silica nanowires on SiO{sub 2} layer by using Au as a catalyst. The nanowires were grown in an open tube furnace at 1100 deg. C for 60 min using Ar as a carrier gas. The average diameter of these bottom-up nucleated wires was found to be 200 nm. Transmission electron microscopy analysis indicates the amorphous nature of these nanoscale wires and suggests an Si-silica heterostructure. The localized silica nanowires have been used as an immunoassay template in the detection of interleukin-10 which is a lung cancer biomarker. Such a nanostructured platform offered a tenfold enhancement in the optical response, aiding the recognition of IL-10 in comparison to a bare silica substrate. The role of nanowires in the immunoassay was verified through the quenching behavior in the photoluminescence (PL) spectra. Two orders of reduction in PL intensity have been observed after completion of the immunoassay with significant quenching after executing every step of the protocol. The potential of this site-specific growth of silica nanowires on SiO{sub 2} as a multi-modal biosensing platform has been discussed.

  6. Early Stages of Pulsed-Laser Growth of Silicon Microcolumns and Microcones in Air and SF6

    International Nuclear Information System (INIS)

    Fowlkes, J.D.; Lowndes, D.H.; Pedraza, A.J.

    1999-01-01

    Dense arrays of high-aspect-ratio silicon microcolumns and microcones are formed by cumulative nanosecond pulsed excimer laser irradiation of single-crystal silicon in oxidizing atmospheres such as air and SF 6 . Growth of such surface microstructures requires a redeposition model and also involves elements of self-organization. The shape of the microstructures, i.e. straight columns vs steeply sloping cones and connecting walls, is governed by the type and concentration of the oxidizing species, e.g. oxygen vs fluorine. Growth is believed to occur by a catalyst-free VLS (vapor-liquid-solid) mechanism that involves repetitive melting of the tips of the columns/cones and deposition there of the ablated flux of Si-containing vapor. Results are presented of a new investigation of how such different final microstructures as microcolumns or microcones joined by walls nucleate and develop. The changes in silicon surface morphology were systematically determined and compared as the number of pulsed KrF (248 nm) laser shots was increased from 25 to several thousand in both air and SF 6 . The experiments in air and SF 6 reveal significant differences in initial surface cracking and pattern formation. Consequently, local protrusions are first produced and column or cone/wall growth is initiated by different processes and at different rates. Differences in the spatial organization of column or cone/wall growth also are apparent

  7. Epitaxial III-V nanowires on silicon for vertical devices

    NARCIS (Netherlands)

    Bakkers, E.P.A.M.; Borgström, M.T.; Einden, Van Den W.; Weert, van M.H.M.; Helman, A.; Verheijen, M.A.

    2006-01-01

    We show the epitaxial integration of III-V semiconductor nanowires with silicon technology. The wires are grown by the Vapor-Liquid-Solid (VLS) mechanism with laser ablation as well as metal organic vapor phase epitaxy. The VLS growth enables the fabrication of complex axial and radial

  8. Investigation of the growth and in situ heating transmission electron microscopy analysis of Ag2S-catalyzed ZnS nanowires

    Science.gov (United States)

    Kim, Jung Han; Kim, Jong Gu; Song, Junghyun; Bae, Tae-Sung; Kim, Kyou-Hyun; Lee, Young-Seak; Pang, Yoonsoo; Oh, Kyu Hwan; Chung, Hee-Suk

    2018-04-01

    We investigated the semiconductor-catalyzed formation of semiconductor nanowires (NWs) - silver sulfide (Ag2S)-catalyzed zinc sulfide (ZnS) NWs - based on a vapor-liquid-solid (VLS) growth mechanism through metal-organic chemical vapor deposition (MOCVD) with a Ag thin film. The Ag2S-catalyzed ZnS NWs were confirmed to have a wurtzite structure with a width and length in the range of ∼30 nm to ∼80 nm and ∼1 μm, respectively. Using extensive transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDS) analyses from plane and cross-sectional viewpoints, the ZnS NWs were determined to have a c-axis, [0001] growth direction. In addition, the catalyst at the top of the ZnS NWs was determined to consist of a Ag2S phase. To support the Ag2S-catalyzed growth of the ZnS NWs by a VLS reaction, an in situ heating TEM experiment was conducted from room temperature to 840 °C. During the experiment, the melting of the Ag2S catalyst in the direction of the ZnS NWs was first observed at approximately 480 °C along with the formation of a carbon (C) shell. Subsequently, the Ag2S catalyst melted completely into the ZnS NWs at approximately 825 °C. As the temperature further increased, the Ag2S and ZnS NWs continuously melted and vaporized up to 840 °C, leaving only the C shell behind. Finally, a possible growth mechanism was proposed based on the structural and chemical investigations.

  9. Creating New VLS Silicon Nanowire Contact Geometries by Controlling Catalyst Migration

    DEFF Research Database (Denmark)

    Alam, Sardar Bilal; Panciera, Federico; Hansen, Ole

    2015-01-01

    The formation of self-assembled contacts between vapor-liquid-solid grown silicon nanowires and flat silicon surfaces was imaged in situ using electron microscopy. By measuring the structural evolution of the contact formation process, we demonstrate how different contact geometries are created b...

  10. Growth of High-Density Zinc Oxide Nanorods on Porous Silicon by Thermal Evaporation

    Directory of Open Access Journals (Sweden)

    Nurul Izni Rusli

    2012-12-01

    Full Text Available The formation of high-density zinc oxide (ZnO nanorods on porous silicon (PS substrates at growth temperatures of 600–1000 °C by a simple thermal evaporation of zinc (Zn powder in the presence of oxygen (O2 gas was systematically investigated. The high-density growth of ZnO nanorods with (0002 orientation over a large area was attributed to the rough surface of PS, which provides appropriate planes to promote deposition of Zn or ZnOx seeds as nucleation sites for the subsequent growth of ZnO nanorods. The geometrical morphologies of ZnO nanorods are determined by the ZnOx seed structures, i.e., cluster or layer structures. The flower-like hexagonal-faceted ZnO nanorods grown at 600 °C seem to be generated from the sparsely distributed ZnOx nanoclusters. Vertically aligned hexagonal-faceted ZnO nanorods grown at 800 °C may be inferred from the formation of dense arrays of ZnOx clusters. The formation of disordered ZnO nanorods formed at 1000 °C may due to the formation of a ZnOx seed layer. The growth mechanism involved has been described by a combination of self-catalyzed vapor-liquid-solid (VLS and vapor-solid (VS mechanism. The results suggest that for a more precise study on the growth of ZnO nanostructures involving the introduction of seeds, the initial seed structures must be taken into account given their significant effects.

  11. Genetic variation of the Borrelia burgdorferi gene vlsE involves cassette-specific, segmental gene conversion.

    Science.gov (United States)

    Zhang, J R; Norris, S J

    1998-08-01

    The Lyme disease spirochete Borrelia burgdorferi possesses 15 silent vls cassettes and a vls expression site (vlsE) encoding a surface-exposed lipoprotein. Segments of the silent vls cassettes have been shown to recombine with the vlsE cassette region in the mammalian host, resulting in combinatorial antigenic variation. Despite promiscuous recombination within the vlsE cassette region, the 5' and 3' coding sequences of vlsE that flank the cassette region are not subject to sequence variation during these recombination events. The segments of the silent vls cassettes recombine in the vlsE cassette region through a unidirectional process such that the sequence and organization of the silent vls loci are not affected. As a result of recombination, the previously expressed segments are replaced by incoming segments and apparently degraded. These results provide evidence for a gene conversion mechanism in VlsE antigenic variation.

  12. Examination Of Si-Ge Heterostructure Nanowire Growth Using Monte Carlo Simulation

    International Nuclear Information System (INIS)

    Nastovjak, A. G.; Neizvestny, I. G.; Shwartz, N. L.

    2011-01-01

    The process of Si-Ge heterostructures formation in nanowires (NWs) grown by vapor-liquid-solid mechanism was investigated using Monte Carlo simulation. Dependences of catalyst drop composition on temperature, flux intensity and nanowire diameter were obtained. Periodical oscillations of drop composition near mean value were observed. Oscillation results from layer-by-layer growth at the drop-whisker interface and necessity of supersaturation onset to start new layer formation. It was demonstrated that it is impossible to grow atomically abrupt axial heterojunctions via classical vapor-liquid-solid mechanism due to gradual change of catalyst drop composition when switching the fluxes. This phenomenon is the main reason of heterojunction blurriness. Junction abruptness was found to be dependent on nanowhisker diameter: in adsorption-induced growth mode abruptness of heterojunction decreases with diameter and in diffusion-induced mode it increases.

  13. X-ray investigation of the interface structure of free standing InAs nanowires grown on GaAs[ anti 1 anti 1 anti 1]{sub B}

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Jens; Gottschalch, Volker; Wagner, Gerald [Universitaet Leipzig, Halbleiterchemie, Leipzig (Germany); Pietsch, Ullrich; Davydok, Anton; Biermanns, Andreas [Universitaet Siegen, Festkoerperphysik, Siegen (Germany); Grenzer, Joerg [Forschungszentrum Rossendorf, Institut fuer Ionenstrahlphysik und Materialforschung, Dresden (Germany)

    2009-09-15

    The heteroepitaxial growth process of InAs nanowires (NW) on GaAs[ anti 1 anti 1 anti 1]{sub B} substrate was investigated by X-ray grazing-incidence diffraction using synchrotron radiation. For crystal growth we applied the vapor-liquid-solid (VLS) growth mechanism via gold seeds. The general sample structure was extracted from various electron microscopic and X-ray diffraction experiments. We found a closed Ga{sub x}In{sub 1-x} As graduated alloy layer at the substrate to NW interface which was formed in the initial stage of VLS growth with a Au-Ga-In liquid alloy. With ongoing growth time a transition from this VLS layer growth to the conventional VLS NW growth was observed. The structural properties of both VLS grown crystal types were examined. Furthermore, we discuss the VLS layer growth process. (orig.)

  14. Transcriptional regulation of the Borrelia burgdorferi antigenically variable VlsE surface protein.

    Science.gov (United States)

    Bykowski, Tomasz; Babb, Kelly; von Lackum, Kate; Riley, Sean P; Norris, Steven J; Stevenson, Brian

    2006-07-01

    The Lyme disease agent Borrelia burgdorferi can persistently infect humans and other animals despite host active immune responses. This is facilitated, in part, by the vls locus, a complex system consisting of the vlsE expression site and an adjacent set of 11 to 15 silent vls cassettes. Segments of nonexpressed cassettes recombine with the vlsE region during infection of mammalian hosts, resulting in combinatorial antigenic variation of the VlsE outer surface protein. We now demonstrate that synthesis of VlsE is regulated during the natural mammal-tick infectious cycle, being activated in mammals but repressed during tick colonization. Examination of cultured B. burgdorferi cells indicated that the spirochete controls vlsE transcription levels in response to environmental cues. Analysis of PvlsE::gfp fusions in B. burgdorferi indicated that VlsE production is controlled at the level of transcriptional initiation, and regions of 5' DNA involved in the regulation were identified. Electrophoretic mobility shift assays detected qualitative and quantitative changes in patterns of protein-DNA complexes formed between the vlsE promoter and cytoplasmic proteins, suggesting the involvement of DNA-binding proteins in the regulation of vlsE, with at least one protein acting as a transcriptional activator.

  15. MOCVD growth and structural characterization of In-Sb-Te nanowires

    International Nuclear Information System (INIS)

    Selmo, S.; Fanciulli, M.; Cecchi, S.; Cecchini, R.; Wiemer, C.; Longo, M.; Rotunno, E.; Lazzarini, L.

    2016-01-01

    In this work, the self-assembly of In 3 Sb 1 Te 2 and In-doped Sb 4 Te 1 nanowires (NWs) for phase change memories application was achieved by metal organic chemical vapor deposition, coupled with vapor-liquid-solid (VLS) mechanism, catalyzed by Au nanoparticles. Single crystal In 3 Sb 1 Te 2 and In-doped Sb 4 Te 1 NWs were obtained for different reactor pressures at 325 C. The parameters influencing the NW self-assembly were studied and the compositional, morphological, and structural analysis of the grown structures was performed, also comparing the effect of the used substrate (crystalline Si and SiO 2 ). In both cases, NWs of several micrometer in length and with diameters as small as 15 nm were obtained. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Vertical epitaxial wire-on-wire growth of Ge/Si on Si(100) substrate.

    Science.gov (United States)

    Shimizu, Tomohiro; Zhang, Zhang; Shingubara, Shoso; Senz, Stephan; Gösele, Ulrich

    2009-04-01

    Vertically aligned epitaxial Ge/Si heterostructure nanowire arrays on Si(100) substrates were prepared by a two-step chemical vapor deposition method in anodic aluminum oxide templates. n-Butylgermane vapor was employed as new safer precursor for Ge nanowire growth instead of germane. First a Si nanowire was grown by the vapor liquid solid growth mechanism using Au as catalyst and silane. The second step was the growth of Ge nanowires on top of the Si nanowires. The method presented will allow preparing epitaxially grown vertical heterostructure nanowires consisting of multiple materials on an arbitrary substrate avoiding undesired lateral growth.

  17. Optical properties of Mg doped p-type GaN nanowires

    Science.gov (United States)

    Patsha, Avinash; Pandian, Ramanathaswamy; Dhara, S.; Tyagi, A. K.

    2015-06-01

    Mg doped p-type GaN nanowires are grown using chemical vapor deposition technique in vapor-liquid-solid (VLS) process. Morphological and structural studies confirm the VLS growth process of nanowires and wurtzite phase of GaN. We report the optical properties of Mg doped p-type GaN nanowires. Low temperature photoluminescence studies on as-grown and post-growth annealed samples reveal the successful incorporation of Mg dopants. The as-grwon and annealed samples show passivation and activation of Mg dopants, respectively, in GaN nanowires.

  18. VLS-grown diffusion doped ZnO nanowires and their luminescence properties

    International Nuclear Information System (INIS)

    Roy, Pushan Guha; Dutta, Amartya; Das, Arpita; Bhattacharyya, Anirban; Sen, Sayantani; Pramanik, Pallabi

    2015-01-01

    Zinc Oxide (ZnO) nanowires were deposited by vapor–liquid–solid (VLS) method on to aluminum doped ZnO (AZO) thin films grown by sol-gel technique. For various device applications, current injection into such nanowires is critical. This is expected to be more efficient for ZnO nanowires deposited on to AZO compared to those deposited on to a foreign substrate such as silicon. In this work we compare the morphological and optical properties of nanowires grown on AZO with those grown under similar conditions on silicon (Si) wafers. For nanowires grown on silicon, diameters around 44 nm with heights around 2.2 μm were obtained. For the growth on to AZO, the diameters were around 90 nm while the heights were around 520 nm. Room temperature photoluminescence (RT-PL) measurements show improved near band-edge emission for nanowires grown on to AZO, indicating higher material quality. This is further established by low temperature photoluminescence (LT-PL) measurements where excitonic transitions with width as small as 14 meV have been obtained at 4 K for such structures. Electron energy loss spectroscopy (EELS) studies indicate the presence of Al in the nanowires, indicating a new technique for introduction of dopants into these structures. These results indicate that ZnO nanowires on sol-gel grown AZO thin films show promise in the development of various optoelectronic devices. (paper)

  19. Detailed analysis of sequence changes occurring during vlsE antigenic variation in the mouse model of Borrelia burgdorferi infection.

    Directory of Open Access Journals (Sweden)

    Loïc Coutte

    2009-02-01

    Full Text Available Lyme disease Borrelia can infect humans and animals for months to years, despite the presence of an active host immune response. The vls antigenic variation system, which expresses the surface-exposed lipoprotein VlsE, plays a major role in B. burgdorferi immune evasion. Gene conversion between vls silent cassettes and the vlsE expression site occurs at high frequency during mammalian infection, resulting in sequence variation in the VlsE product. In this study, we examined vlsE sequence variation in B. burgdorferi B31 during mouse infection by analyzing 1,399 clones isolated from bladder, heart, joint, ear, and skin tissues of mice infected for 4 to 365 days. The median number of codon changes increased progressively in C3H/HeN mice from 4 to 28 days post infection, and no clones retained the parental vlsE sequence at 28 days. In contrast, the decrease in the number of clones with the parental vlsE sequence and the increase in the number of sequence changes occurred more gradually in severe combined immunodeficiency (SCID mice. Clones containing a stop codon were isolated, indicating that continuous expression of full-length VlsE is not required for survival in vivo; also, these clones continued to undergo vlsE recombination. Analysis of clones with apparent single recombination events indicated that recombinations into vlsE are nonselective with regard to the silent cassette utilized, as well as the length and location of the recombination event. Sequence changes as small as one base pair were common. Fifteen percent of recovered vlsE variants contained "template-independent" sequence changes, which clustered in the variable regions of vlsE. We hypothesize that the increased frequency and complexity of vlsE sequence changes observed in clones recovered from immunocompetent mice (as compared with SCID mice is due to rapid clearance of relatively invariant clones by variable region-specific anti-VlsE antibody responses.

  20. Central role of the Holliday junction helicase RuvAB in vlsE recombination and infectivity of Borrelia burgdorferi.

    Directory of Open Access Journals (Sweden)

    Tao Lin

    2009-12-01

    Full Text Available Antigenic variation plays a vital role in the pathogenesis of many infectious bacteria and protozoa including Borrelia burgdorferi, the causative agent of Lyme disease. VlsE, a 35 kDa surface-exposed lipoprotein, undergoes antigenic variation during B. burgdorferi infection of mammalian hosts, and is believed to be a critical mechanism by which the spirochetes evade immune clearance. Random, segmental recombination between the expressed vlsE gene and adjacent vls silent cassettes generates a large number of different VlsE variants within the infected host. Although the occurrence and importance of vlsE sequence variation is well established, little is known about the biological mechanism of vlsE recombination. To identify factors important in antigenic variation and vlsE recombination, we screened transposon mutants of genes known to be involved in DNA recombination and repair for their effects on infectivity and vlsE recombination. Several mutants, including those in BB0023 (ruvA, BB0022 (ruvB, BB0797 (mutS, and BB0098 (mutS-II, showed reduced infectivity in immunocompetent C3H/HeN mice. Mutants in ruvA and ruvB exhibited greatly reduced rates of vlsE recombination in C3H/HeN mice, as determined by restriction fragment polymorphism (RFLP screening and DNA sequence analysis. In severe combined immunodeficiency (C3H/scid mice, the ruvA mutant retained full infectivity; however, all recovered clones retained the 'parental' vlsE sequence, consistent with low rates of vlsE recombination. These results suggest that the reduced infectivity of ruvA and ruvB mutants is the result of ineffective vlsE recombination and underscores the important role that vlsE recombination plays in immune evasion. Based on functional studies in other organisms, the RuvAB complex of B. burgdorferi may promote branch migration of Holliday junctions during vlsE recombination. Our findings are consistent with those in the accompanying article by Dresser et al., and together

  1. Growth of InAs Wurtzite Nanocrosses from Hexagonal and Cubic Basis

    DEFF Research Database (Denmark)

    Krizek, Filip; Kanne, Thomas; Razmadze, Davydas

    2017-01-01

    . Two methods use conventional wurtzite nanowire arrays as a 6-fold hexagonal basis for growing single crystal wurtzite nanocrosses. A third method uses the 2-fold cubic symmetry of (100) substrates to form well-defined coherent inclusions of zinc blende in the center of the nanocrosses. We show......Epitaxially connected nanowires allow for the design of electron transport experiments and applications beyond the standard two terminal device geometries. In this Letter, we present growth methods of three distinct types of wurtzite structured InAs nanocrosses via the vapor-liquid-solid mechanism...

  2. Vapor-solid-solid grown Ge nanowires at integrated circuit compatible temperature by molecular beam epitaxy

    Science.gov (United States)

    Zhu, Zhongyunshen; Song, Yuxin; Zhang, Zhenpu; Sun, Hao; Han, Yi; Li, Yaoyao; Zhang, Liyao; Xue, Zhongying; Di, Zengfeng; Wang, Shumin

    2017-09-01

    We demonstrate Au-assisted vapor-solid-solid (VSS) growth of Ge nanowires (NWs) by molecular beam epitaxy at the substrate temperature of ˜180 °C, which is compatible with the temperature window for Si-based integrated circuit. Low temperature grown Ge NWs hold a smaller size, similar uniformity, and better fit with Au tips in diameter, in contrast to Ge NWs grown at around or above the eutectic temperature of Au-Ge alloy in the vapor-liquid-solid (VLS) growth. Six ⟨110⟩ growth orientations were observed on Ge (110) by the VSS growth at ˜180 °C, differing from only one vertical growth direction of Ge NWs by the VLS growth at a high temperature. The evolution of NWs dimension and morphology from the VLS growth to the VSS growth is qualitatively explained by analyzing the mechanism of the two growth modes.

  3. Selective growth of Ge nanowires by low-temperature thermal evaporation.

    Science.gov (United States)

    Sutter, Eli; Ozturk, Birol; Sutter, Peter

    2008-10-29

    High-quality single-crystalline Ge nanowires with electrical properties comparable to those of bulk Ge have been synthesized by vapor-liquid-solid growth using Au growth seeds on SiO(2)/Si(100) substrates and evaporation from solid Ge powder in a low-temperature process at crucible temperatures down to 700 °C. High nanowire growth rates at these low source temperatures have been identified as being due to sublimation of GeO from substantial amounts of GeO(2) on the powder. The Ge nanowire synthesis from GeO is highly selective at our substrate temperatures (420-500 °C), i.e., occurs only on Au vapor-liquid-solid growth seeds. For growth of nanowires of 10-20 µm length on Au particles, an upper bound of 0.5 nm Ge deposition was determined in areas of bare SiO(2)/Si substrate without Au nanoparticles.

  4. Growth and applicability of radiation-responsive silica nanowires

    Science.gov (United States)

    Bettge, Martin

    Surface energetics play an important role in processes on the nanoscale. Nanowire growth via vapor-liquid-solid (VLS) mechanism is no exception in this regard. Interfacial and line energies are found to impose some fundamental limits during three-phase nanowire growth and lead to formation of stranded nanowires with fascinating characteristics such as high responsiveness towards ion irradiation. By using two materials with a relatively low surface energy (indium and silicon oxide) this is experimentally and theoretically demonstrated in this doctoral thesis. The augmentation of VLS nanowire growth with ion bombardment enables fabrication of vertically aligned silica nanowires over large areas. Synthesis of their arrays begins with a thin indium film deposited on a Si or SiO 2 surface. At temperatures below 200ºC, the indium film becomes a self-organized seed layer of molten droplets, receiving a flux of atomic silicon by DC magnetron sputtering. Simultaneous vigorous ion bombardment through substrate biasing aligns the growing nanowires vertically and expedites mixing of oxygen and silicon into the indium. The vertical growth rate can reach up to 1000 nm-min-1 in an environment containing only argon and traces of water vapor. Silicon oxide precipitates from each indium seed in the form of multiple thin strands having diameters less than 9 nm and practically independent of droplet size. The strands form a single loose bundle, eventually consolidating to form one vertically aligned nanowire. These observations are in stark contrast to conventional VLS growth in which one liquid droplet precipitates a single solid nanowire and in which the precipitated wire diameter is directly proportional to the droplet diameter. The origin of these differences is revealed through a detailed force balance analysis, analogous to Young's relation, at the three-phase line. The liquid-solid interfacial energy of indium/silica is found to be the largest energy contribution at the three

  5. Growth strategies to control tapering in Ge nanowires

    Directory of Open Access Journals (Sweden)

    P. Periwal

    2014-04-01

    Full Text Available We report the effect of PH3 on the morphology of Au catalyzed Ge nanowires (NWs. Ge NWs were grown on Si (111 substrate at 400 °C in the presence of PH3, using vapor-liquid-solid method by chemical vapor deposition. We show that high PH3/GeH4 ratio causes passivation at NW surface. At high PH3 concentration phosphorous atoms attach itself on NW surface and form a self-protection coating that prevents conformal growth and leads to taper free nanostructures. However, in case of low PH3 flux the combination of axial and radial growth mechanism occurs resulting in conical structure. We have also investigated axial PH3-intrinsic junctions in Ge NWs. The unusual NW shape is attributed to a combination of catalyzed, uncatalyzed and diffusion induced growth.

  6. In-Situ Growth and Characterization of Indium Tin Oxide Nanocrystal Rods

    Directory of Open Access Journals (Sweden)

    Yan Shen

    2017-11-01

    Full Text Available Indium tin oxide (ITO nanocrystal rods were synthesized in-situ by a vapor-liquid-solid (VLS method and electron beam evaporation technique. When the electron-beam gun bombarded indium oxide (In2O3 and tin oxide (SnO2 mixed sources, indium and tin droplets appeared and acted as catalysts. The nanocrystal rods were in-situ grown on the basis of the metal catalyst point. The nanorods have a single crystal structure. Its structure was confirmed by X-ray diffraction (XRD and transmission electron microscopy (TEM. The surface morphology was analyzed by scanning electron microscopy (SEM. During the evaporation, a chemical process was happened and an In2O3 and SnO2 solid solution was formed. The percentage of doped tin oxide was calculated by Vegard’s law to be 3.18%, which was in agreement with the mixture ratio of the experimental data. The single crystal rod had good semiconductor switch property and its threshold voltage of single rod was approximately 2.5 V which can be used as a micro switch device. The transmission rate of crystalline nanorods ITO film was over 90% in visible band and it was up to 95% in the blue green band as a result of the oxygen vacancy recombination luminescence.

  7. MOCVD growth and structural characterization of In-Sb-Te nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Selmo, S.; Fanciulli, M. [Laboratorio MDM, IMM-CNR, Unita di Agrate Brianza (Italy); Dipartimento di Scienza dei Materiali, University of Milano Bicocca, Milano (Italy); Cecchi, S.; Cecchini, R.; Wiemer, C.; Longo, M. [Laboratorio MDM, IMM-CNR, Unita di Agrate Brianza (Italy); Rotunno, E.; Lazzarini, L. [IMEM-CNR, Parma (Italy)

    2016-02-15

    In this work, the self-assembly of In{sub 3}Sb{sub 1}Te{sub 2} and In-doped Sb{sub 4}Te{sub 1} nanowires (NWs) for phase change memories application was achieved by metal organic chemical vapor deposition, coupled with vapor-liquid-solid (VLS) mechanism, catalyzed by Au nanoparticles. Single crystal In{sub 3}Sb{sub 1}Te{sub 2} and In-doped Sb{sub 4}Te{sub 1} NWs were obtained for different reactor pressures at 325 C. The parameters influencing the NW self-assembly were studied and the compositional, morphological, and structural analysis of the grown structures was performed, also comparing the effect of the used substrate (crystalline Si and SiO{sub 2}). In both cases, NWs of several micrometer in length and with diameters as small as 15 nm were obtained. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Magnetic movement of biological fluid droplets

    International Nuclear Information System (INIS)

    Garcia, Antonio A.; Egatz-Gomez, Ana; Lindsay, Solitaire A.; Dominguez-Garcia, P.; Melle, Sonia; Marquez, Manuel; Rubio, Miguel A.; Picraux, S.T.; Yang, Dongqing; Aella, P.; Hayes, Mark A.; Gust, Devens; Loyprasert, Suchera; Vazquez-Alvarez, Terannie; Wang, Joseph

    2007-01-01

    Magnetic fields can be used to control the movement of aqueous drops on non-patterned, silicon nanowire superhydrophobic surfaces. Drops of aqueous and biological fluids are controlled by introducing magnetizable carbonyl iron microparticles into the liquid. Key elements of operations such as movement, coalescence, and splitting of water and biological fluid drops, as well as electrochemical measurement of an analyte are demonstrated. Superhydrophobic surfaces were prepared using vapor-liquid-solid (VLS) growth systems followed by coating with a perfluorinated hydrocarbon molecule. Drops were made from aqueous and biological fluid suspensions with magnetizable microparticle concentrations ranging from 0.1 to 10 wt%

  9. Comparative genome analysis: selection pressure on the Borrelia vls cassettes is essential for infectivity

    Directory of Open Access Journals (Sweden)

    Wilske Bettina

    2006-08-01

    Full Text Available Abstract Background At least three species of Borrelia burgdorferi sensu lato (Bbsl cause tick-borne Lyme disease. Previous work including the genome analysis of B. burgdorferi B31 and B. garinii PBi suggested a highly variable plasmid part. The frequent occurrence of duplicated sequence stretches, the observed plasmid redundancy, as well as the mainly unknown function and variability of plasmid encoded genes rendered the relationships between plasmids within and between species largely unresolvable. Results To gain further insight into Borreliae genome properties we completed the plasmid sequences of B. garinii PBi, added the genome of a further species, B. afzelii PKo, to our analysis, and compared for both species the genomes of pathogenic and apathogenic strains. The core of all Bbsl genomes consists of the chromosome and two plasmids collinear between all species. We also found additional groups of plasmids, which share large parts of their sequences. This makes it very likely that these plasmids are relatively stable and share common ancestors before the diversification of Borrelia species. The analysis of the differences between B. garinii PBi and B. afzelii PKo genomes of low and high passages revealed that the loss of infectivity is accompanied in both species by a loss of similar genetic material. Whereas B. garinii PBi suffered only from the break-off of a plasmid end, B. afzelii PKo lost more material, probably an entire plasmid. In both cases the vls gene locus encoding for variable surface proteins is affected. Conclusion The complete genome sequences of a B. garinii and a B. afzelii strain facilitate further comparative studies within the genus Borrellia. Our study shows that loss of infectivity can be traced back to only one single event in B. garinii PBi: the loss of the vls cassettes possibly due to error prone gene conversion. Similar albeit extended losses in B. afzelii PKo support the hypothesis that infectivity of Borrelia

  10. Coalescence and the initial stage of formation of nanofibers by the 'vapor-liquid-solid' scheme

    International Nuclear Information System (INIS)

    Zhdanok, S.A.; Martynenko, V.V.; Fisenko, S.P.; Shabunya, S.I.

    2010-01-01

    It has been shown that the diffusion interaction of growing impurity clusters within catalytic nanodroplets determines the important geometric parameters of a nanofiber. The characteristic time of coalescence of the clusters has been found. (authors)

  11. Self-assembly of tetrapod-shaped CdS nanostructures into 3D networks by a transverse growth process

    International Nuclear Information System (INIS)

    Fu Xiuli; Li Dan; Zhang Lei; Xiao Jinghua; Li Jiangyan; Peng Zhijian; Fang Zheyu

    2011-01-01

    Spontaneous formation of 3D tetrapod-shaped CdS nanostructure networks has been achieved for the first time by vapor diffusion-deposition growth from CdS powders. The growth mechanism of the hexagonal and preferentially oriented CdS tetrapod-shaped nanostructures is a combination of the classic vapor-liquid-solid and vapor-solid processes, and the formation of a 3D network results from the spontaneous growths along the longitudinal and across the axial directions of the primarily formed CdS nanorods. Micro-photoluminescence measurements and near-field scanning optical microscopy investigations show that the synthesized CdS tetrapod networks have an excellent luminescence property and can be used as an optical waveguide cavities in which the guided light can be extremely confined.

  12. Transfer-free synthesis of highly ordered Ge nanowire arrays on glass substrates

    Energy Technology Data Exchange (ETDEWEB)

    Nakata, M.; Toko, K., E-mail: toko@bk.tsukuba.ac.jp; Suemasu, T. [Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Jevasuwan, W.; Fukata, N. [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan); Saitoh, N.; Yoshizawa, N. [Electron Microscope Facility, TIA, AIST, 16-1 Onogawa, Tsukuba 305-8569 (Japan)

    2015-09-28

    Vertically aligned Ge nanowires (NWs) are directly synthesized on glass via vapor-liquid-solid (VLS) growth using chemical-vapor deposition. The use of the (111)-oriented Ge seed layer, formed by metal-induced crystallization at 325 °C, dramatically improved the density, uniformity, and crystal quality of Ge NWs. In particular, the VLS growth at 400 °C allowed us to simultaneously achieve the ordered morphology and high crystal quality of the Ge NW array. Transmission electron microscopy demonstrated that the resulting Ge NWs had no dislocations or stacking faults. Production of high-quality NW arrays on amorphous insulators will promote the widespread application of nanoscale devices.

  13. Effect of Temperature on Nucleation of Nanocrystalline Indium Tin Oxide Synthesized by Electron-Beam Evaporation

    Science.gov (United States)

    Shen, Yan; Zhao, Yujun; Shen, Jianxing; Xu, Xiangang

    2017-07-01

    Indium tin oxide (ITO) has been widely applied as a transparent conductive layer and optical window in light-emitting diodes, solar cells, and touch screens. In this paper, crystalline nano-sized ITO dendrites are obtained using an electron-beam evaporation technique. The surface morphology of the obtained ITO was studied for substrate temperatures of 25°C, 130°C, 180°C, and 300°C. Nano-sized crystalline dendrites were synthesized only at a substrate temperature of 300°C. The dendrites had a cubic structure, confirmed by the results of x-ray diffraction and transmission electron microscopy. The growth mechanism of the nano-crystalline dendrites could be explained by a vapor-liquid-solid (VLS) growth model. The catalysts of the VLS process were indium and tin droplets, confirmed by varying the substrate temperature, which further influenced the nucleation of the ITO dendrites.

  14. RECONSTRUCTION OF 3D VECTOR MODELS OF BUILDINGS BY COMBINATION OF ALS, TLS AND VLS DATA

    Directory of Open Access Journals (Sweden)

    H. Boulaassal

    2012-09-01

    Full Text Available Airborne Laser Scanning (ALS, Terrestrial Laser Scanning (TLS and Vehicle based Laser Scanning (VLS are widely used as data acquisition methods for 3D building modelling. ALS data is often used to generate, among others, roof models. TLS data has proven its effectiveness in the geometric reconstruction of building façades. Although the operating algorithms used in the processing chain of these two kinds of data are quite similar, their combination should be more investigated. This study explores the possibility of combining ALS and TLS data for simultaneously producing 3D building models from bird point of view and pedestrian point of view. The geometric accuracy of roofs and façades models is different due to the acquisition techniques. In order to take these differences into account, the surfaces composing roofs and façades are extracted with the same algorithm of segmentation. Nevertheless the segmentation algorithm must be adapted to the properties of the different point clouds. It is based on the RANSAC algorithm, but has been applied in a sequential way in order to extract all potential planar clusters from airborne and terrestrial datasets. Surfaces are fitted to planar clusters, allowing edge detection and reconstruction of vector polygons. Models resulting from TLS data are obviously more accurate than those generated from ALS data. Therefore, the geometry of the roofs is corrected and adapted according to the geometry of the corresponding façades. Finally, the effects of the differences between raw ALS and TLS data on the results of the modeling process are analyzed. It is shown that such combination could be used to produce reliable 3D building models.

  15. Growth and optical properties of CdTe quantum dots in ZnTe nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Wojnar, Piotr; Janik, Elzbieta; Baczewski, Lech T.; Kret, Slawomir; Karczewski, G.; Wojtowicz, Tomasz [Institute of Physics, Polish Academy of Sciences, Al Lotnikow 32/46, 02-668 Warsaw (Poland); Goryca, Mateusz; Kazimierczuk, Tomasz; Kossacki, Piotr [Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul Hoza 69, 00-681 Warsaw (Poland)

    2011-09-12

    We report on the formation of optically active CdTe quantum dots in ZnTe nanowires. The CdTe/ZnTe nanostructures have been grown by a gold nanocatalyst assisted molecular beam epitaxy in a vapor-liquid solid growth process. The presence of CdTe insertions in ZnTe nanowire results in the appearance of a strong photoluminescence band in the 2.0 eV-2.25 eV energy range. Spatially resolved photoluminescence measurements reveal that this broad emission consists of several sharp lines with the spectral width of about 2 meV. The large degree of linear polarization of these individual emission lines confirms their nanowire origin, whereas the zero-dimensional confinement is proved by photon correlation spectroscopy.

  16. Increased Optoelectronic Quality and Uniformity of Hydrogenated p-InP Thin Films

    KAUST Repository

    Wang, Hsin-Ping; Sutter-Fella, Carolin M.; Lobaccaro, Peter; Hettick, Mark; Zheng, Maxwell; Lien, Der-Hsien; Miller, D. Westley; Warren, Charles W.; Roe, Ellis T; Lonergan, Mark C; Guthrey, Harvey L.; Haegel, Nancy M.; Ager, Joel W.; Carraro, Carlo; Maboudian, Roya; He, Jr-Hau; Javey, Ali

    2016-01-01

    The thin-film vapor-liquid-solid (TF-VLS) growth technique presents a promising route for high quality, scalable and cost-effective InP thin films for optoelectronic devices. Towards this goal, careful optimization of material properties and device performance is of utmost interest. Here, we show that exposure of polycrystalline Zn-doped TF-VLS InP to a hydrogen plasma (in the following referred to as hydrogenation) results in improved optoelectronic quality as well as lateral optoelectronic uniformity. A combination of low temperature photoluminescence and transient photocurrent spectroscopy were used to analyze the energy position and relative density of defect states before and after hydrogenation. Notably, hydrogenation reduces the intra-gap defect density by one order of magnitude. As a metric to monitor lateral optoelectronic uniformity of polycrystalline TF-VLS InP, photoluminescence and electron beam induced current mapping reveal homogenization of the grain versus grain boundary upon hydrogenation. At the device level, we measured more than 260 TF-VLS InP solar cells before and after hydrogenation to verify the improved optoelectronic properties. Hydrogenation increased the average open-circuit voltage (VOC) of individual TF-VLS InP solar cells by up to 130 mV, and reduced the variance in VOC for the analyzed devices.

  17. Increased Optoelectronic Quality and Uniformity of Hydrogenated p-InP Thin Films

    KAUST Repository

    Wang, Hsin-Ping

    2016-06-08

    The thin-film vapor-liquid-solid (TF-VLS) growth technique presents a promising route for high quality, scalable and cost-effective InP thin films for optoelectronic devices. Towards this goal, careful optimization of material properties and device performance is of utmost interest. Here, we show that exposure of polycrystalline Zn-doped TF-VLS InP to a hydrogen plasma (in the following referred to as hydrogenation) results in improved optoelectronic quality as well as lateral optoelectronic uniformity. A combination of low temperature photoluminescence and transient photocurrent spectroscopy were used to analyze the energy position and relative density of defect states before and after hydrogenation. Notably, hydrogenation reduces the intra-gap defect density by one order of magnitude. As a metric to monitor lateral optoelectronic uniformity of polycrystalline TF-VLS InP, photoluminescence and electron beam induced current mapping reveal homogenization of the grain versus grain boundary upon hydrogenation. At the device level, we measured more than 260 TF-VLS InP solar cells before and after hydrogenation to verify the improved optoelectronic properties. Hydrogenation increased the average open-circuit voltage (VOC) of individual TF-VLS InP solar cells by up to 130 mV, and reduced the variance in VOC for the analyzed devices.

  18. Different growth regimes in InP nanowire growth mediated by Ag nanoparticles.

    Science.gov (United States)

    Oliveira, D S; Zavarize, M; Tizei, L H G; Walls, M; Ospina, C A; Iikawa, F; Ugarte, D; Cotta, M A

    2017-12-15

    We report on the existence of two different regimes in one-step Ag-seeded InP nanowire growth. The vapor-liquid-solid-mechanism is present at larger In precursor flows and temperatures, ∼500 °C, yielding high aspect ratio and pure wurtzite InP nanowires with a semi-spherical metal particle at the thin apex. Periodic diameter oscillations can be achieved under extreme In supersaturations at this temperature range, showing the presence of a liquid catalyst. However, under lower temperatures and In precursor flows, large diameter InP nanowires with mixed wurtzite/zincblende segments are obtained, similarly to In-assisted growth. Chemical composition analysis suggest that In-rich droplet formation is catalyzed at the substrate surface via Ag nanoparticles; this process might be facilitated by the sulfur contamination detected in these nanoparticles. Furthermore, part of the original Ag nanoparticle remains solid and is embedded inside the actual catalyst, providing an in situ method to switch growth mechanisms upon changing In precursor flow. Nevertheless, our Ag-seeded InP nanowires exhibit overall optical emission spectra consistent with the observed structural properties and similar to Au-catalyzed InP nanowires. We thus show that Ag nanoparticles may be a suitable replacement for Au in InP nanowire growth.

  19. Research on SiC Whisker Prepared by H-PSO

    Directory of Open Access Journals (Sweden)

    WANG Yao

    2017-10-01

    Full Text Available SiC whiskers were prepared on the matrix of graphite by using high hydrogenous silicone oil(PSO as raw material. The effect of surface conditions of graphite and heating temperature on the growth of SiC whisker was mainly studied in this paper. The main factor which affects the nucleation and growth of SiC whisker is the heating temperature, with the heating temperature rising, the production of SiC whisker increases. The surface condition of graphite matrix also influences the growth of SiC whisker. With the nucleation points provided by graphite matrix defects increasing, the production of SiC whisker incleases and SiC whisker starts to overlap with each other. The formation process of SiC whisker includes two steps:nucleation and growth. SiC whisker nucleates at low temperature and grows at high temperature, which follows the VLS (vapor-liquid-solid growth mechanism.

  20. Axial Ge/Si nanowire heterostructure tunnel FETs

    Energy Technology Data Exchange (ETDEWEB)

    Picraux, Sanuel T [Los Alamos National Laboratory; Daych, Shadi A [Los Alamos National Laboratory

    2010-01-01

    The vapor-liquid-solid (VLS) growth of semiconductor nanowires allows doping and composition modulation along their axis and the realization of axial 1 D heterostructures. This provides additional flexibility in energy band-edge engineering along the transport direction which is difficult to attain by planar materials growth and processing techniques. We report here on the design, growth, fabrication, and characterization of asymmetric heterostructure tunnel field-effect transistors (HTFETs) based on 100% compositionally modulated Si/Ge axial NWs for high on-current operation and low ambipolar transport behavior. We discuss the optimization of band-offsets and Schottky barrier heights for high performance HTFETs and issues surrounding their experimental realization. Our HTFET devices with 10 nm PECVD SiN{sub x} gate dielectric resulted in a measured current drive exceeding 100 {mu}A/{mu}m (I/{pi}D) and 10{sup 5} I{sub on}/I{sub off} ratios.

  1. Quantum transport in semiconductor nanowires

    NARCIS (Netherlands)

    Van Dam, J.

    2006-01-01

    This thesis describes a series of experiments aimed at understanding the low-temperature electrical transport properties of semiconductor nanowires. The semiconductor nanowires (1-100 nm in diameter) are grown from nanoscale gold particles via a chemical process called vapor-liquid-solid (VLS)

  2. Fabrication of SiC Composites with Synergistic Toughening of Carbon Whisker and In Situ 3C-SiC Nanowire

    Directory of Open Access Journals (Sweden)

    Zhang Yunlong

    2016-01-01

    Full Text Available The SiC composites with synergistic toughening of carbon whisker and in situ 3C-SiC nanowire have been fabricated by hot press sinter technology and annealed treatment technology. Effect of annealed time on the morphology of SiC nanowires and mechanical properties of the Cw/SiC composites was surveyed in detail. The appropriate annealed time improved mechanical properties of the Cw/SiC composites. The synergistic effect of carbon whisker and SiC nanowire can improve the fracture toughness for Cw/SiC composites. The vapor-liquid-solid growth (VLS mechanism was proposed. TEM photo showed that 3C-SiC nanowire can be obtained with preferential growth plane ({111}, which corresponded to interplanar spacing about 0.25 nm.

  3. Electrodeposition of Metal on GaAs Nanowires

    Science.gov (United States)

    Liu, Chao; Einabad, Omid; Watkins, Simon; Kavanagh, Karen

    2010-10-01

    Copper (Cu) electrical contacts to freestanding gallium arsenide (GaAs) nanowires have been fabricated via electrodeposition. The nanowires are zincblende (111) oriented grown epitaxially on n-type Si-doped GaAs (111)B substrates by gold-catalyzed Vapor Liquid Solid (VLS) growth in a metal organic vapour phase epitaxy (MOVPE) reactor. The epitaxial electrodeposition process, based on previous work with bulk GaAs substrates, consists of a substrate oxide pre-etch in dilute ammonium-hydroxide carried out prior to galvanostatic electrodeposition in a pure Cu sulphate aqueous electrolyte at 20-60^oC. For GaAs nanowires, we find that Cu or Fe has a preference for growth on the gold catalyst avoiding the sidewalls. After removing gold, both metals still prefer to grow only on top of the nanowire, which has the largest potential field.

  4. Gibbs–Thomson Effect in Planar Nanowires: Orientation and Doping Modulated Growth

    KAUST Repository

    Shen, Youde; Chen, Renjie; Yu, Xuechao; Wang, Qijie; Jungjohann, Katherine L.; Dayeh, Shadi A.; Wu, Tao

    2016-01-01

    Epitaxy-enabled bottom-up synthesis of self-assembled planar nanowires via the vapor-liquid-solid mechanism is an emerging and promising approach toward large-scale direct integration of nanowire-based devices without postgrowth alignment. Here, by examining large assemblies of indium tin oxide nanowires on yttria-stabilized zirconia substrate, we demonstrate for the first time that the growth dynamics of planar nanowires follows a modified version of the Gibbs-Thomson mechanism, which has been known for the past decades to govern the correlations between thermodynamic supersaturation, growth speed, and nanowire morphology. Furthermore, the substrate orientation strongly influences the growth characteristics of epitaxial planar nanowires as opposed to impact at only the initial nucleation stage in the growth of vertical nanowires. The rich nanowire morphology can be described by a surface-energy-dependent growth model within the Gibbs-Thomson framework, which is further modulated by the tin doping concentration. Our experiments also reveal that the cutoff nanowire diameter depends on the substrate orientation and decreases with increasing tin doping concentration. These results enable a deeper understanding and control over the growth of planar nanowires, and the insights will help advance the fabrication of self-assembled nanowire devices. © 2016 American Chemical Society.

  5. Gibbs–Thomson Effect in Planar Nanowires: Orientation and Doping Modulated Growth

    KAUST Repository

    Shen, Youde

    2016-06-02

    Epitaxy-enabled bottom-up synthesis of self-assembled planar nanowires via the vapor-liquid-solid mechanism is an emerging and promising approach toward large-scale direct integration of nanowire-based devices without postgrowth alignment. Here, by examining large assemblies of indium tin oxide nanowires on yttria-stabilized zirconia substrate, we demonstrate for the first time that the growth dynamics of planar nanowires follows a modified version of the Gibbs-Thomson mechanism, which has been known for the past decades to govern the correlations between thermodynamic supersaturation, growth speed, and nanowire morphology. Furthermore, the substrate orientation strongly influences the growth characteristics of epitaxial planar nanowires as opposed to impact at only the initial nucleation stage in the growth of vertical nanowires. The rich nanowire morphology can be described by a surface-energy-dependent growth model within the Gibbs-Thomson framework, which is further modulated by the tin doping concentration. Our experiments also reveal that the cutoff nanowire diameter depends on the substrate orientation and decreases with increasing tin doping concentration. These results enable a deeper understanding and control over the growth of planar nanowires, and the insights will help advance the fabrication of self-assembled nanowire devices. © 2016 American Chemical Society.

  6. Tailoring uniform gold nanoparticle arrays and nanoporous films for next-generation optoelectronic devices

    Science.gov (United States)

    Farid, Sidra; Kuljic, Rade; Poduri, Shripriya; Dutta, Mitra; Darling, Seth B.

    2018-06-01

    High-density arrays of gold nanodots and nanoholes on indium tin oxide (ITO)-coated glass surfaces are fabricated using a nanoporous template fabricated by the self-assembly of diblock copolymers of poly (styrene-block-methyl methacrylate) (PS-b-PMMA) structures. By balancing the interfacial interactions between the polymer blocks and the substrate using random copolymer, cylindrical block copolymer microdomains oriented perpendicular to the plane of the substrate have been obtained. Nanoporous PS films are created by selectively etching PMMA cylinders, a straightforward route to form highly ordered nanoscale porous films. Deposition of gold on the template followed by lift off and sonication leaves a highly dense array of gold nanodots. These materials can serve as templates for the vapor-liquid-solid (VLS) growth of semiconductor nanorod arrays for next generation hybrid optoelectronic applications.

  7. Thin-Film Solar Cells with InP Absorber Layers Directly Grown on Nonepitaxial Metal Substrates

    KAUST Repository

    Zheng, Maxwell

    2015-08-25

    The design and performance of solar cells based on InP grown by the nonepitaxial thin-film vapor-liquid-solid (TF-VLS) growth technique is investigated. The cell structure consists of a Mo back contact, p-InP absorber layer, n-TiO2 electron selective contact, and indium tin oxide transparent top electrode. An ex situ p-doping process for TF-VLS grown InP is introduced. Properties of the cells such as optoelectronic uniformity and electrical behavior of grain boundaries are examined. The power conversion efficiency of first generation cells reaches 12.1% under simulated 1 sun illumination with open-circuit voltage (VOC) of 692 mV, short-circuit current (JSC) of 26.9 mA cm-2, and fill factor (FF) of 65%. The FF of the cell is limited by the series resistances in the device, including the top contact, which can be mitigated in the future through device optimization. The highest measured VOC under 1 sun is 692 mV, which approaches the optically implied VOC of ≈795 mV extracted from the luminescence yield of p-InP. The design and performance of solar cells based on indium phosphide (InP) grown by the nonepitaxial thin-film vapor-liquid-solid growth technique is investigated. The cell structure consists of a Mo back contact, p-InP absorber layer, n-TiO2 electron selective contact, and an indium tin oxide transparent top electrode. The highest measured open circuit voltage (VOC) under 1 sun is 692 mV, which approaches the optically implied VOC of ≈795 mV extracted from the luminescence yield of p-InP.

  8. Epitaxial thin film growth of LiH using a liquid-Li atomic template

    Energy Technology Data Exchange (ETDEWEB)

    Oguchi, Hiroyuki, E-mail: oguchi@nanosys.mech.tohoku.ac.jp [Department of Nanomechanics, Tohoku University, Sendai 980-8579 (Japan); Micro System Integration Center (muSIC), Tohoku University, Sendai 980-0845 (Japan); Ikeshoji, Tamio; Orimo, Shin-ichi [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577 (Japan); Ohsawa, Takeo; Shiraki, Susumu; Hitosugi, Taro [Advanced Institute for Materials Research (AIMR), Tohoku University, Sendai 980-8577 (Japan); Kuwano, Hiroki [Department of Nanomechanics, Tohoku University, Sendai 980-8579 (Japan)

    2014-11-24

    We report on the synthesis of lithium hydride (LiH) epitaxial thin films through the hydrogenation of a Li melt, forming abrupt LiH/MgO interface. Experimental and first-principles molecular dynamics studies reveal a comprehensive microscopic picture of the crystallization processes, which sheds light on the fundamental atomistic growth processes that have remained unknown in the vapor-liquid-solid method. We found that the periodic structure that formed, because of the liquid-Li atoms at the film/MgO-substrate interface, serves as an atomic template for the epitaxial growth of LiH crystals. In contrast, films grown on the Al{sub 2}O{sub 3} substrates indicated polycrystalline films with a LiAlO{sub 2} secondary phase. These results and the proposed growth process provide insights into the preparation of other alkaline metal hydride thin films on oxides. Further, our investigations open the way to explore fundamental physics and chemistry of metal hydrides including possible phenomena that emerge at the heterointerfaces of metal hydrides.

  9. Epitaxial thin film growth of LiH using a liquid-Li atomic template

    International Nuclear Information System (INIS)

    Oguchi, Hiroyuki; Ikeshoji, Tamio; Orimo, Shin-ichi; Ohsawa, Takeo; Shiraki, Susumu; Hitosugi, Taro; Kuwano, Hiroki

    2014-01-01

    We report on the synthesis of lithium hydride (LiH) epitaxial thin films through the hydrogenation of a Li melt, forming abrupt LiH/MgO interface. Experimental and first-principles molecular dynamics studies reveal a comprehensive microscopic picture of the crystallization processes, which sheds light on the fundamental atomistic growth processes that have remained unknown in the vapor-liquid-solid method. We found that the periodic structure that formed, because of the liquid-Li atoms at the film/MgO-substrate interface, serves as an atomic template for the epitaxial growth of LiH crystals. In contrast, films grown on the Al 2 O 3 substrates indicated polycrystalline films with a LiAlO 2 secondary phase. These results and the proposed growth process provide insights into the preparation of other alkaline metal hydride thin films on oxides. Further, our investigations open the way to explore fundamental physics and chemistry of metal hydrides including possible phenomena that emerge at the heterointerfaces of metal hydrides

  10. Why droplet dimension can be larger than, equal to, or smaller than the nanowire dimension

    Science.gov (United States)

    Mohammad, S. Noor

    2009-11-01

    Droplets play central roles in the nanowire (NW) growth by vapor phase mechanisms. These mechanisms include vapor-liquid-solid (VLS), vapor-solid-solid or vapor-solid (VSS), vapor-quasisolid-solid or vapor-quasiliquid-solid (VQS), oxide-assisted growth (OAG), and self-catalytic growth (SCG) mechanisms. Fundamentals of the shape, size, characteristics, and dynamics of droplets and the impacts of them on the NW growth, have been studied. The influence of growth techniques, growth parameters (e.g., growth temperature, partial pressure, gas flow rates, etc.), thermodynamic conditions, surface and interface energy, molar volume, chemical potentials, etc. have been considered on the shapes and sizes of droplets. A model has been presented to explain why droplets can be larger than, equal to, or smaller than the associated NWs. Various growth techniques have been analyzed to understand defects created in NWs. Photoluminescence characteristics have been presented to quantify the roles of droplets in the creation of NW defects. The study highlights the importance of the purity of the droplet material. It attests to the superiority of the SCG mechanism, and clarifies the differences between the VSS, VQS, VLS, and SCG mechanisms. It explains why droplets produced by some mechanisms are visible but droplets produced by some other mechanisms are not visible. It elucidates the formation mechanisms of very large and very small droplets, and discusses the ground rules for droplets creating necked NWs. It puts forth reasons to demonstrate that very large droplets may not behave as droplets.

  11. Solution growth of microcrystalline silicon on amorphous substrates

    Energy Technology Data Exchange (ETDEWEB)

    Heimburger, Robert

    2010-07-05

    This work deals with low-temperature solution growth of micro-crystalline silicon on glass. The task is motivated by the application in low-cost solar cells. As glass is an amorphous material, conventional epitaxy is not applicable. Therefore, growth is conducted in a two-step process. The first step aims at the spatial arrangement of silicon seed crystals on conductive coated glass substrates, which is realized by means of vapor-liquid-solid processing using indium as the solvent. Seed crystals are afterwards enlarged by applying a specially developed steady-state solution growth apparatus. This laboratory prototype mainly consists of a vertical stack of a silicon feeding source and the solvent (indium). The growth substrate can be dipped into the solution from the top. The system can be heated to a temperature below the softening point of the utilized glass substrate. A temperature gradient between feeding source and growth substrate promotes both, supersaturation and material transport by solvent convection. This setup offers advantages over conventional liquid phase epitaxy at low temperatures in terms of achievable layer thickness and required growth times. The need for convective solute transport to gain the desired thickness of at least 50 {mu}m is emphasized by equilibrium calculations in the binary system indium-silicon. Material transport and supersaturation conditions inside the utilized solution growth crucible are analyzed. It results that the solute can be transported from the lower feeding source to the growth substrate by applying an appropriate heating regime. These findings are interpreted by means of a hydrodynamic analysis of fluid flow and supporting FEM simulation. To ensure thermodynamic stability of all materials involved during steady-state solution growth, the ternary phase equilibrium between molybdenum, indium and silicon at 600 C was considered. Based on the obtained results, the use of molybdenum disilicide as conductive coating

  12. Shell morphology and Raman spectra of epitaxial Ge-SixGe1-x and Si-SixGe1-x core-shell nanowires

    Science.gov (United States)

    Wen, Feng; Dillen, David C.; Kim, Kyounghwan; Tutuc, Emanuel

    2017-06-01

    We investigate the shell morphology and Raman spectra of epitaxial Ge-SixGe1-x and Si-SixGe1-x core-shell nanowire heterostructures grown using a combination of a vapor-liquid-solid (VLS) growth mechanism for the core, followed by in-situ epitaxial shell growth using ultra-high vacuum chemical vapor deposition. Cross-sectional transmission electron microscopy reveals that the VLS growth yields cylindrical Ge, and Si nanowire cores grown along the ⟨111⟩, and ⟨110⟩ or ⟨112⟩ directions, respectively. A hexagonal cross-sectional morphology is observed for Ge-SixGe1-x core-shell nanowires terminated by six {112} facets. Two distinct morphologies are observed for Si-SixGe1-x core-shell nanowires that are either terminated by four {111} and two {100} planes associated with the ⟨110⟩ growth direction or four {113} and two {111} planes associated with the ⟨112⟩ growth direction. We show that the Raman spectra of Si- SixGe1-x are correlated with the shell morphology thanks to epitaxial growth-induced strain, with the core Si-Si mode showing a larger red shift in ⟨112⟩ core-shell nanowires compared to their ⟨110⟩ counterparts. We compare the Si-Si Raman mode value with calculations based on a continuum elasticity model coupled with the lattice dynamic theory.

  13. Water-vapor-enhanced growth of Ge-GeOx core-shell nanowires and Si1-xGexOy nanowires

    International Nuclear Information System (INIS)

    Hsu, T-J; Ko, C-Y; Lin, W-T

    2007-01-01

    The effects of moist Ar on the growth of Ge-GeO x core-shell nanowires (Ge-GeO x NWs) and Si 1-x Ge x O y nanowires (SiGeONWs) on Si substrates without adding a metal catalyst via the carbothermal reduction of GeO 2 powders at 1100 deg. C were studied. No significant nanowires were grown in dry Ar at a flow rate of 100-300 sccm until a bit of water in the range of 0.5-2 ml was loaded into the furnace. More water suppressed the growth of nanowires because of the exhaustion of more graphite powder. The growth of Ge-GeO x NWs and SiGeONWs follows the vapor-solid and vapor-liquid-solid processes, respectively. The present study showed that the water vapor serves as an oxidizer as well as a reducer at 1100 deg. C in enhancing the growth of SiGeONWs and Ge-GeO x NWs, respectively. The growth mechanisms of Ge-GeO x NWs and SiGeONWs are also discussed

  14. Growth of defect-free GaAsSbN axial nanowires via self-catalyzed molecular beam epitaxy

    Science.gov (United States)

    Sharma, Manish; Deshmukh, Prithviraj; Kasanaboina, Pavan; Reynolds, C. Lewis, Jr.; Liu, Yang; Iyer, Shanthi

    2017-12-01

    Bandgap reduction of 10% by incorporation of a dilute amount of N is reported for the first time, in axial GaAsSb nanowires (NWs) grown on Si (111) via Ga-assisted molecular beam epitaxy. Impact of N incorporation on the surface morphology, NW growth kinetics, and their structural and optical properties were examined. Dilute nitride NWs with Sb composition of 7 at% did not exhibit any noticeable planar defects, as revealed by the absence of satellite twin peaks in the selected-area diffraction pattern and high-resolution transmission electron microscopy imaging. Point defects were also minimal in as-grown dilute nitride NWs, as ascertained from the comparison of low-temperature photoluminescence spectra as well as the shape and shift of Raman modes, with in situ annealed NWs in different ambients. Evidence of enhanced incorporation of N was found in the NWs in situ annealed in N ambient, but with deteriorated optical quality due to simultaneous creation of N-induced defects. The lack of any noticeable defects in the as-grown GaAsSbN NWs demonstrates the advantage of the vapor-liquid-solid mechanism responsible for growth of axial configuration over the vapor-solid growth mechanism for core-shell NWs as well as their thin film counterpart, which commonly exhibit N-induced point defects.

  15. Dislocation-induced nanoparticle decoration on a GaN nanowire.

    Science.gov (United States)

    Yang, Bing; Yuan, Fang; Liu, Qingyun; Huang, Nan; Qiu, Jianhang; Staedler, Thorsten; Liu, Baodan; Jiang, Xin

    2015-02-04

    GaN nanowires with homoepitaxial decorated GaN nanoparticles on their surface along the radial direction have been synthesized by means of a chemical vapor deposition method. The growth of GaN nanowires is catalyzed by Au particles via the vapor-liquid-solid (VLS) mechanism. Screw dislocations are generated along the radial direction of the nanowires under slight Zn doping. In contrast to the metal-catalyst-assisted VLS growth, GaN nanoparticles are found to prefer to nucleate and grow at these dislocation sites. High-resolution transmission electron microscopy (HRTEM) analysis demonstrates that the GaN nanoparticles possess two types of epitaxial orientation with respect to the corresponding GaN nanowire: (I) [1̅21̅0]np//[1̅21̅0]nw, (0001)np//(0001)nw; (II) [1̅21̅3]np//[12̅10]nw, (101̅0)np//(101̅0)nw. An increased Ga signal in the energy-dispersive spectroscopy (EDS) profile lines of the nanowires suggests GaN nanoparticle growth at the edge surface of the wires. All the crystallographic results confirm the importance of the dislocations with respect to the homoepitaxial growth of the GaN nanoparticles. Here, screw dislocations situated on the (0001) plane provide the self-step source to enable nucleation of the GaN nanoparticles.

  16. Understanding the true shape of Au-catalyzed GaAs nanowires.

    Science.gov (United States)

    Jiang, Nian; Wong-Leung, Jennifer; Joyce, Hannah J; Gao, Qiang; Tan, Hark Hoe; Jagadish, Chennupati

    2014-10-08

    With increasing interest in nanowire-based devices, a thorough understanding of the nanowire shape is required to gain tight control of the quality of nanowire heterostructures and improve the performance of related devices. We present a systematic study of the sidewalls of Au-catalyzed GaAs nanowires by investigating the faceting process from the beginning with vapor-liquid-solid (VLS) nucleation, followed by the simultaneous radial growth on the sidewalls, and to the end with sidewall transformation during annealing. The VLS nucleation interface of our GaAs nanowires is revealed by examining cross sections of the nanowire, where the nanowire exhibits a Reuleaux triangular shape with three curved surfaces along {112}A. These curved surfaces are not thermodynamically stable and adopt {112}A facets during radial growth. We observe clear differences in radial growth rate between the ⟨112⟩A and ⟨112⟩B directions with {112}B facets forming due to the slower radial growth rate along ⟨112⟩B directions. These sidewalls transform to {110} facets after high temperature (>500 °C) annealing. A nucleation model is proposed to explain the origin of the Reuleaux triangular shape of the nanowires, and the sidewall evolution is explained by surface kinetic and thermodynamic limitations.

  17. Flat-Top and Stacking-Fault-Free GaAs-Related Nanopillars Grown on Si Substrates

    Directory of Open Access Journals (Sweden)

    Kouta Tateno

    2012-01-01

    Full Text Available The VLS (vapor-liquid-solid method is one of the promising techniques for growing vertical III-V compound semiconductor nanowires on Si for application to optoelectronic circuits. Heterostructures grown in the axial direction by the VLS method and in the radial direction by the general layer-by-layer growth method make it possible to fabricate complicated and functional three-dimensional structures in a bottom-up manner. We can grow some vertical heterostructure nanopillars with flat tops on Si(111 substrates, and we have obtained core-multishell Ga(InP/GaAs/GaP nanowires with flat tops and their air-gap structures by using selective wet etching. Simulations indicate that a high- factor of over 2000 can be achieved for this air-gap structure. From the GaAs growth experiments, we found that zincblende GaAs without any stacking faults can be grown after the GaP nanowire growth. Pillars containing a quantum dot and without stacking faults can be grown by using this method. We can also obtain flat-top pillars without removing the Au catalysts when using small Au particles.

  18. Synthesis and characterization of beta-Ga2O3 nanorod array clumps by chemical vapor deposition.

    Science.gov (United States)

    Shi, Feng; Wei, Xiaofeng

    2012-11-01

    beta-Ga2O3 nanorod array clumps were successfully synthesized on Si (111) substrates by chemical vapor deposition. The composition, microstructure, morphology, and light-emitting property of these clumps were characterized by X-ray diffraction, Fourier transform infrared spectrophotometry, X-ray photoelectron spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, Raman spectroscopy, and photoluminescence. The results demonstrate that the sample synthesized at 1050 degrees C for 15 min was composed of monoclinic beta-Ga2O3 nanorod array clumps, where each single nanorod was about 300 nm in diameter with some nano-droplets on its tip. These results reveal that the growth mechanism agrees with the vapor-liquid-solid (VLS) process. The photoluminescence spectrum shows that the Ga2O3 nanorods have a blue emission at 438 nm, which may be attributed to defects, such as oxygen vacancies and gallium-oxygen vacancy pairs. Defect-energy aggregation confinement growth theory was proposed to explain the growth mechanism of Ga2O3 nanorod array clumps collaborated with the VLS mechanism.

  19. Self-Catalyzed Growth and Characterization of In(As)P Nanowires on InP(111)B Using Metal-Organic Chemical Vapor Deposition.

    Science.gov (United States)

    Park, Jeung Hun; Pozuelo, Marta; Setiawan, Bunga P D; Chung, Choong-Heui

    2016-12-01

    We report the growth of vertical -oriented InAs x P1-x (0.11 ≤ x ≤ 0.27) nanowires via metal-organic chemical vapor deposition in the presence of indium droplets as catalysts on InP(111)B substrates at 375 °C. Trimethylindium, tertiarybutylphosphine, and tertiarybutylarsine are used as the precursors, corresponding to P/In and As/In molar ratios of 29 and 0.01, respectively. The as-grown nanowire growth morphologies, crystallinity, composition, and optical characteristics are determined using a combination of scanning and transmission electron microscopies, electron diffraction, and X-ray photoelectron, energy dispersive X-ray, and Raman spectroscopies. We find that the InAs x P1-x nanowires are tapered with narrow tops, wider bases, and In-rich In-As alloy tips, characteristic of vapor-liquid-solid process. The wires exhibit a mixture of zinc blende and wurtzite crystal structures and a high density of structural defects such as stacking faults and twins. Our results suggest that the incorporation of As into InP wires decreases with increasing substrate temperature. The Raman spectra obtained from the In(As)P nanowires reveal a red-shift and lower intensity of longitudinal optical mode relative to both InP nanowires and InP(111)B bulk, due to the incorporation of As into the InP matrix.

  20. Parameters study on the growth of GaAs nanowires on indium tin oxide by metal-organic chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Dan; Tang, Xiaohong, E-mail: exhtang@ntu.edu.sg, E-mail: wangk@sustc.edu.cn; Li, Xianqiang [OPTIMUS, Photonics Centre of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore (Singapore); Wang, Kai, E-mail: exhtang@ntu.edu.sg, E-mail: wangk@sustc.edu.cn [Department of Electrical & Electronic Engineering, South University of Science and Technology of China, 1088 Xueyuan Avenue, Shenzhen 518055 (China); Olivier, Aurelien [CINTRA UMI 3288, School of Electrical and Electronic Engineering, Nanyang Technological University, Research Techno Plaza, 50 Nanyang Drive, Border X Block, Level 6, 637553 Singapore (Singapore)

    2016-03-07

    After successful demonstration of GaAs nanowire (NW) epitaxial growth on indium tin oxide (ITO) by metal organic chemical vapor deposition, we systematically investigate the effect of growth parameters' effect on the GaAs NW, including temperature, precursor molar flow rates, growth time, and Au catalyst size. 40 nm induced GaAs NWs are observed with zinc-blende structure. Based on vapor-liquid-solid mechanism, a kinetic model is used to deepen our understanding of the incorporation of growth species and the role of various growth parameters in tuning the GaAs NW growth rate. Thermally activated behavior has been investigated by variation of growth temperature. Activation energies of 40 nm Au catalyst induced NWs are calculated at different trimethylgallium (TMGa) molar flow rates about 65 kJ/mol. The GaAs NWs growth rates increase with TMGa molar flow rates whereas the growth rates are almost independent of growth time. Due to Gibbs-Thomson effect, the GaAs NW growth rates increase with Au nanoparticle size at different temperatures. Critical radius is calculated as 2.14 nm at the growth condition of 430 °C and 1.36 μmol/s TMGa flow rate. It is also proved experimentally that Au nanoparticle below the critical radius such as 2 nm cannot initiate the growth of NWs on ITO. This theoretical and experimental growth parameters investigation enables great controllability over GaAs NWs grown on transparent conductive substrate where the methodology can be expanded to other III–V material NWs and is critical for potential hybrid solar cell application.

  1. 2-tiered antibody testing for early and late Lyme disease using only an immunoglobulin G blot with the addition of a VlsE band as the second-tier test.

    Science.gov (United States)

    Branda, John A; Aguero-Rosenfeld, Maria E; Ferraro, Mary Jane; Johnson, Barbara J B; Wormser, Gary P; Steere, Allen C

    2010-01-01

    Standard 2-tiered immunoglobulin G (IgG) testing has performed well in late Lyme disease (LD), but IgM testing early in the illness has been problematic. IgG VlsE antibody testing, by itself, improves early sensitivity, but may lower specificity. We studied whether elements of the 2 approaches could be combined to produce a second-tier IgG blot that performs well throughout the infection. Separate serum sets from LD patients and control subjects were tested independently at 2 medical centers using whole-cell enzyme immunoassays and IgM and IgG immunoblots, with recombinant VlsE added to the IgG blots. The results from both centers were combined, and a new second-tier IgG algorithm was developed. With standard 2-tiered IgM and IgG testing, 31% of patients with active erythema migrans (stage 1), 63% of those with acute neuroborreliosis or carditis (stage 2), and 100% of those with arthritis or late neurologic involvement (stage 3) had positive results. Using new IgG criteria, in which only the VlsE band was scored as a second-tier test among patients with early LD (stage 1 or 2) and 5 of 11 IgG bands were required in those with stage 3 LD, 34% of patients with stage 1, 96% of those with stage 2, and 100% of those with stage 3 infection had positive responses. Both new and standard testing achieved 100% specificity. Compared with standard IgM and IgG testing, the new IgG algorithm (with VlsE band) eliminates the need for IgM testing; it provides comparable or better sensitivity, and it maintains high specificity.

  2. Trends in maar crater size and shape using the global Maar Volcano Location and Shape (MaarVLS) database

    Science.gov (United States)

    Graettinger, A. H.

    2018-05-01

    A maar crater is the top of a much larger subsurface diatreme structure produced by phreatomagmatic explosions and the size and shape of the crater reflects the growth history of that structure during an eruption. Recent experimental and geophysical research has shown that crater complexity can reflect subsurface complexity. Morphometry provides a means of characterizing a global population of maar craters in order to establish the typical size and shape of features. A global database of Quaternary maar crater planform morphometry indicates that maar craters are typically not circular and frequently have compound shapes resembling overlapping circles. Maar craters occur in volcanic fields that contain both small volume and complex volcanoes. The global perspective provided by the database shows that maars are common in many volcanic and tectonic settings producing a similar diversity of size and shape within and between volcanic fields. A few exceptional populations of maars were revealed by the database, highlighting directions of future research to improve our understanding on the geometry and spacing of subsurface explosions that produce maars. These outlying populations, such as anomalously large craters (>3000 m), chains of maars, and volcanic fields composed of mostly maar craters each represent a small portion of the database, but provide opportunities to reinvestigate fundamental questions on maar formation. Maar crater morphometry can be integrated with structural, hydrological studies to investigate lateral migration of phreatomagmatic explosion location in the subsurface. A comprehensive database of intact maar morphometry is also beneficial for the hunt for maar-diatremes on other planets.

  3. Fermi energy dependence of the optical emission in core/shell InAs nanowire homostructures

    Science.gov (United States)

    Möller, M.; Oliveira, D. S.; Sahoo, P. K.; Cotta, M. A.; Iikawa, F.; Motisuke, P.; Molina-Sánchez, A.; de Lima, M. M., Jr.; García-Cristóbal, A.; Cantarero, A.

    2017-07-01

    InAs nanowires grown by vapor-liquid-solid (VLS) method are investigated by photoluminescence. We observe that the Fermi energy of all samples is reduced by ˜20 meV when the size of the Au nanoparticle used for catalysis is increased from 5 to 20 nm. Additional capping with a thin InP shell enhances the optical emission and does not affect the Fermi energy. The unexpected behavior of the Fermi energy is attributed to the differences in the residual donor (likely carbon) incorporation in the axial (low) and lateral (high incorporation) growth in the VLS and vapor-solid (VS) methods, respectively. The different impurity incorporation rate in these two regions leads to a core/shell InAs homostructure. In this case, the minority carriers (holes) diffuse to the core due to the built-in electric field created by the radial impurity distribution. As a result, the optical emission is dominated by the core region rather than by the more heavily doped InAs shell. Thus, the photoluminescence spectra and the Fermi energy become sensitive to the core diameter. These results are corroborated by a theoretical model using a self-consistent method to calculate the radial carrier distribution and Fermi energy for distinct diameters of Au nanoparticles.

  4. Nonepitaxial Thin-Film InP for Scalable and Efficient Photocathodes.

    Science.gov (United States)

    Hettick, Mark; Zheng, Maxwell; Lin, Yongjing; Sutter-Fella, Carolin M; Ager, Joel W; Javey, Ali

    2015-06-18

    To date, some of the highest performance photocathodes of a photoelectrochemical (PEC) cell have been shown with single-crystalline p-type InP wafers, exhibiting half-cell solar-to-hydrogen conversion efficiencies of over 14%. However, the high cost of single-crystalline InP wafers may present a challenge for future large-scale industrial deployment. Analogous to solar cells, a thin-film approach could address the cost challenges by utilizing the benefits of the InP material while decreasing the use of expensive materials and processes. Here, we demonstrate this approach, using the newly developed thin-film vapor-liquid-solid (TF-VLS) nonepitaxial growth method combined with an atomic-layer deposition protection process to create thin-film InP photocathodes with large grain size and high performance, in the first reported solar device configuration generated by materials grown with this technique. Current-voltage measurements show a photocurrent (29.4 mA/cm(2)) and onset potential (630 mV) approaching single-crystalline wafers and an overall power conversion efficiency of 11.6%, making TF-VLS InP a promising photocathode for scalable and efficient solar hydrogen generation.

  5. Towards engineered branch placement: Unreal™ match between vapour-liquid-solid glancing angle deposition nanowire growth and simulation

    International Nuclear Information System (INIS)

    Taschuk, M. T.; Tucker, R. T.; LaForge, J. M.; Beaudry, A. L.; Kupsta, M. R.; Brett, M. J.

    2013-01-01

    The vapour-liquid-solid glancing angle deposition (VLS-GLAD) process is capable of producing complex nanotree structures with control over azimuthal branch orientation and height. We have developed a thin film growth simulation including ballistic deposition, simplified surface diffusion, and droplet-mediated cubic crystal growth for the VLS-GLAD process using the Unreal TM Development Kit. The use of a commercial game engine has provided an interactive environment while allowing a custom physics implementation. Our simulation's output is verified against experimental data, including a volumetric film reconstruction produced using focused ion beam and scanning-electron microscopy (SEM), crystallographic texture, and morphological characteristics such as branch orientation. We achieve excellent morphological and texture agreement with experimental data, as well as qualitative agreement with SEM imagery. The simplified physics in our model reproduces the experimental films, indicating that the dominant role flux geometry plays in the VLS-GLAD competitive growth process responsible for azimuthally oriented branches and biaxial crystal texture evolution. The simulation's successful reproduction of experimental data indicates that it should have predictive power in designing novel VLS-GLAD structures

  6. Towards engineered branch placement: Unreal™ match between vapour-liquid-solid glancing angle deposition nanowire growth and simulation

    Science.gov (United States)

    Taschuk, M. T.; Tucker, R. T.; LaForge, J. M.; Beaudry, A. L.; Kupsta, M. R.; Brett, M. J.

    2013-12-01

    The vapour-liquid-solid glancing angle deposition (VLS-GLAD) process is capable of producing complex nanotree structures with control over azimuthal branch orientation and height. We have developed a thin film growth simulation including ballistic deposition, simplified surface diffusion, and droplet-mediated cubic crystal growth for the VLS-GLAD process using the UnrealTM Development Kit. The use of a commercial game engine has provided an interactive environment while allowing a custom physics implementation. Our simulation's output is verified against experimental data, including a volumetric film reconstruction produced using focused ion beam and scanning-electron microscopy (SEM), crystallographic texture, and morphological characteristics such as branch orientation. We achieve excellent morphological and texture agreement with experimental data, as well as qualitative agreement with SEM imagery. The simplified physics in our model reproduces the experimental films, indicating that the dominant role flux geometry plays in the VLS-GLAD competitive growth process responsible for azimuthally oriented branches and biaxial crystal texture evolution. The simulation's successful reproduction of experimental data indicates that it should have predictive power in designing novel VLS-GLAD structures.

  7. Solution synthesis of lead seeded germanium nanowires and branched nanowire networks and their application as Li-ion battery anodes

    Science.gov (United States)

    Flynn, Grace; Palaniappan, Kumaranand; Sheehan, Martin; Kennedy, Tadhg; Ryan, Kevin M.

    2017-06-01

    Herein, we report the high density growth of lead seeded germanium nanowires (NWs) and their development into branched nanowire networks suitable for application as lithium ion battery anodes. The synthesis of the NWs from lead seeds occurs simultaneously in both the liquid zone (solution-liquid-solid (SLS) growth) and solvent rich vapor zone (vapor-liquid-solid (VLS) growth) of a high boiling point solvent growth system. The reaction is sufficiently versatile to allow for the growth of NWs directly from either an evaporated catalyst layer or from pre-defined nanoparticle seeds and can be extended to allowing extensive branched nanowire formation in a secondary reaction where these seeds are coated onto existing wires. The NWs are characterized using TEM, SEM, XRD and DF-STEM. Electrochemical analysis was carried out on both the single crystal Pb-Ge NWs and the branched Pb-Ge NWs to assess their suitability for use as anodes in a Li-ion battery. Differential capacity plots show both the germanium wires and the lead seeds cycle lithium and contribute to the specific capacity that is approximately 900 mAh g-1 for the single crystal wires, rising to approximately 1100 mAh g-1 for the branched nanowire networks.

  8. Synthesis, characterization and photoluminescence of tin oxide nanoribbons and nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Duraia, El-Shazly M.A., E-mail: duraia_physics@yahoo.co [Suez Canal University, Faculty of Science, Physics Department, Ismailia (Egypt); Al-Farabi Kazakh National University, Almaty (Kazakhstan); Institute of Physics and Technology, 11 Ibragimov Street, 050032 Almaty (Kazakhstan); Mansorov, Z.A. [Al-Farabi Kazakh National University, Almaty (Kazakhstan); Tokmolden, S. [Institute of Physics and Technology, 11 Ibragimov Street, 050032 Almaty (Kazakhstan)

    2009-11-15

    In this work we report the successful formation of tin oxide nanowires and tin oxide nanoribbons with high yield and by using simple cheap method. We also report the formation of curved nanoribbon, wedge-like tin oxide nanowires and star-like nanowires. The growth mechanism of these structures has been studied. Scanning electron microscope was used in the analysis and the EDX analysis showed that our samples is purely Sn and O with ratio 1:2. X-ray analysis was also used in the characterization of the tin oxide nanowire and showed the high crystallinity of our nanowires. The mechanism of the growth of our1D nanostructures is closely related to the vapor-liquid-solid (VLS) process. The photoluminescence PL measurements for the tin oxide nanowires indicated that there are three stable emission peaks centered at wavelengths 630, 565 and 395 nm. The nature of the transition may be attributed to nanocrystals inside the nanobelts or to Sn or O vacancies occurring during the growth which can induce trapped states in the band gap.

  9. Growth

    Science.gov (United States)

    John R. Jones; George A. Schier

    1985-01-01

    This chapter considers aspen growth as a process, and discusses some characteristics of the growth and development of trees and stands. For the most part, factors affecting growth are discussed elsewhere, particularly in the GENETICS AND VARIATION chapter and in chapters in PART 11. ECOLOGY. Aspen growth as it relates to wood production is examined in the WOOD RESOURCE...

  10. The SERS and TERS effects obtained by gold droplets on top of Si nanowires.

    Science.gov (United States)

    Becker, M; Sivakov, V; Andrä, G; Geiger, R; Schreiber, J; Hoffmann, S; Michler, J; Milenin, A P; Werner, P; Christiansen, S H

    2007-01-01

    We show that hemispherical gold droplets on top of silicon nanowires when grown by the vapor-liquid-solid (VLS) mechanism, can produce a significant enhancement of Raman scattered signals. Signal enhancement for a few or even just single gold droplets is demonstrated by analyzing the enhanced Raman signature of malachite green molecules. For this experiment, trenches (approximately 800 nm wide) were etched in a silicon-on-insulator (SOI) wafer along crystallographic directions that constitute sidewalls ({110} surfaces) suitable for the growth of silicon nanowires in directions with the intention that the gold droplets on the silicon nanowires can meet somewhere in the trench when growth time is carefully selected. Another way to realize gold nanostructures in close vicinity is to attach a silicon nanowire with a gold droplet onto an atomic force microscopy (AFM) tip and to bring this tip toward another gold-coated AFM tip where malachite green molecules were deposited prior to the measurements. In both experiments, signal enhancement of characteristic Raman bands of malachite green molecules was observed. This indicates that silicon nanowires with gold droplets atop can act as efficient probes for tip-enhanced Raman spectroscopy (TERS). In our article, we show that a nanowire TERS probe can be fabricated by welding nanowires with gold droplets to AFM tips in a scanning electron microscope (SEM). TERS tips made from nanowires could improve the spatial resolution of Raman spectroscopy so that measurements on the nanometer scale are possible.

  11. Bismuth-catalyzed and doped silicon nanowires for one-pump-down fabrication of radial junction solar cells.

    Science.gov (United States)

    Yu, Linwei; Fortuna, Franck; O'Donnell, Benedict; Jeon, Taewoo; Foldyna, Martin; Picardi, Gennaro; Roca i Cabarrocas, Pere

    2012-08-08

    Silicon nanowires (SiNWs) are becoming a popular choice to develop a new generation of radial junction solar cells. We here explore a bismuth- (Bi-) catalyzed growth and doping of SiNWs, via vapor-liquid-solid (VLS) mode, to fabricate amorphous Si radial n-i-p junction solar cells in a one-pump-down and low-temperature process in a single chamber plasma deposition system. We provide the first evidence that catalyst doping in the SiNW cores, caused by incorporating Bi catalyst atoms as n-type dopant, can be utilized to fabricate radial junction solar cells, with a record open circuit voltage of V(oc) = 0.76 V and an enhanced light trapping effect that boosts the short circuit current to J(sc) = 11.23 mA/cm(2). More importantly, this bi-catalyzed SiNW growth and doping strategy exempts the use of extremely toxic phosphine gas, leading to significant procedure simplification and cost reduction for building radial junction thin film solar cells.

  12. Nanostructures of Boron, Carbon and Magnesium Diboride for High Temperature Superconductivity

    Energy Technology Data Exchange (ETDEWEB)

    Pfefferle, Lisa [Yale Univ., New Haven, CT (United States); Fang, Fang [Yale Univ., New Haven, CT (United States); Iyyamperumal, Eswarmoorthi [Yale Univ., New Haven, CT (United States); Keskar, Gayatri [Yale Univ., New Haven, CT (United States)

    2013-12-23

    Direct fabrication of MgxBy nanostructures is achieved by employing metal (Ni,Mg) incorporated MCM-41 in the Hybrid Physical-Chemical Vapor Deposition (HPCVD) reaction. Different reaction conditions are tested to optimize the fabrication process. TEM analysis shows the fabrication of MgxBy nanostructures starting at the reaction temperature of 600oC, with the yield of the nanostructures increasing with increasing reaction temperature. The as-synthesized MgxBy nanostructures have the diameters in the range of 3-5nm, which do not increase with the reaction temperature consistent with templated synthesis. EELS analysis of the template removed nanostructures confirms the existence of B and Mg with possible contamination of Si and O. NEXAFS and Raman spectroscopy analysis suggested a concentric layer-by-layer MgxBy nanowire/nanotube growth model for our as-synthesized nanostructures. Ni k-edge XAS indicates that the formation of MgNi alloy particles is important for the Vapor-Liquid-Solid (VLS) growth of MgxBy nanostructures with fine diameters, and the presence of Mg vapor not just Mg in the catalyst is crucial for the formation of Ni-Mg clusters. Physical templating by the MCM-41 pores was shown to confine the diameter of the nanostructures. DC magnetization measurements indicate possible superconductive behaviors in the as-synthesized samples.

  13. Synthesis, characterization and magnetic properties of Fe-Al nanopins

    International Nuclear Information System (INIS)

    Zhang, W.S.; Brueck, E.; Li, W.F.; Si, P.Z.; Geng, D.Y.; Zhang, Z.D.

    2005-01-01

    We report the synthesis of Fe-Al nanopins using arc discharge. The morphology and chemical composition of the Fe-Al nanopins were studied by means of X-ray diffraction, X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), and high-resolution transmission electron microscopy (HRTEM). The nanopins are composed of a spherical base of about 20-100 nm and a needle-like tip of about several hundred nanometers. EDX and HRTEM studies indicate that the spherical base is mainly composed of α-Fe and FeAl core coated with a thin Al 2 O 3 layer, while the needle-like part contains only Al and O and corresponds to Al 2 O 3 . The formation mechanism of the nanopins is suggestive of a vapor-liquid-solid (VLS) growth process. The as-prepared Fe-Al nanopins show ferromagnetic properties. The temperature dependence of the magnetization at high temperatures indicates the existence of some phase transformations

  14. Twins and strain relaxation in zinc-blende GaAs nanowires grown on silicon

    Energy Technology Data Exchange (ETDEWEB)

    Piñero, J.C., E-mail: josecarlos.pinero@uca.es [Dpto. Ciencias de los Materiales, Universidad de Cádiz, 11510, Puerto Real, Cádiz (Spain); Araújo, D.; Pastore, C.E.; Gutierrez, M. [Dpto. Ciencias de los Materiales, Universidad de Cádiz, 11510, Puerto Real, Cádiz (Spain); Frigeri, C. [Istituto CNR-IMEM Parco Area delle Scienze 37/A, Fontanini, 43010, Parma (Italy); Benali, A.; Lelièvre, J.F.; Gendry, M. [INL-Institut des Nanotechnologies de Lyon, UMR 5270 Ecole Centrale de Lyon 36, Avenue Guy de Collongue, 69134, Ecully Cedex (France)

    2017-02-15

    Highlights: • A TEM-HREM study of GaAs nanowires, growth over Si, is presented. • Misfit dislocations are detected in the Si/GaAs magma interface. • The study demonstrates strain relaxation through twin formation in some nanowires. - Abstract: To integrate materials with large lattice mismatch as GaAs on silicon (Si) substrate, one possible approach, to improve the GaAs crystalline quality, is to use nanowires (NWs) technology. In the present contribution, NWs are grown on <111> oriented Si substrates by molecular beam epitaxy (MBE) using vapor-liquid-solid (VLS) method. Transmission electron microscopy (TEM) analyses show that NWs are mainly grown alternating wurtzite and zinc blend (ZB) phases, and only few are purely ZB. On the latter, High Resolution Electron Microscopy (HREM) evidences the presence of twins near the surface of the NW showing limited concordance with the calculations of Yuan (2013) [1], where {111} twin planes in a <111>-oriented GaAs NW attain attractive interactions mediated by surface strain. In addition, such twins allow slight strain relaxation and are probably induced by the local huge elastic strain observed by HREM in the lattice between the twin and the surface. The latter is attributed to some slight bending of the NW as shown by the inversion of the strain from one side to the other side of the NW.

  15. SiC nanofibers grown by high power microwave plasma chemical vapor deposition

    International Nuclear Information System (INIS)

    Honda, Shin-ichi; Baek, Yang-Gyu; Ikuno, Takashi; Kohara, Hidekazu; Katayama, Mitsuhiro; Oura, Kenjiro; Hirao, Takashi

    2003-01-01

    Silicon carbide (SiC) nanofibers have been synthesized on Si substrates covered by Ni thin films using high power microwave chemical vapor deposition (CVD). Characterization using transmission electron microscopy (TEM) combined with electron energy-dispersive X-ray spectroscopy (EDX) revealed that the resultant fibrous nanostructures were assigned to β-SiC with high crystallinity. The formation of SiC nanofibers can be explained by the vapor liquid solid (VLS) mechanism in which precipitation of SiC occurs from the supersaturated Ni nanoparticle containing Si and C

  16. InP nanowire array solar cell with cleaned sidewalls

    NARCIS (Netherlands)

    Cui, Y.; Plissard, S.; Wang, J.; Vu, T.T.T.; Smalbrugge, E.; Geluk, E.J.; de Vries, T.; Bolk, J.; Trainor, M.J.; Verheijen, M.A.; Haverkort, J.E.M.; Bakkers, E.P.A.M.

    2013-01-01

    We have fabricated InP nanowire array solar cells with an axial p-n junction. Catalyst gold nanoparticles were first patterned into an array by nanoimprint lithography. The nanowire array was grown in 19 minutes by vapor-liquid-solid growth. The sidewalls were in-situ etched by HCl and ex-situ

  17. Localized synthesis, assembly and integration of silicon nanowires

    Science.gov (United States)

    Englander, Ongi

    Localized synthesis, assembly and integration of one-dimensional silicon nanowires with MEMS structures is demonstrated and characterized in terms of local synthesis processes, electric-field assisted self-assembly, and a proof-of-concept nanoelectromechanical system (HEMS) demonstration. Emphasis is placed on the ease of integration, process control strategies, characterization techniques and the pursuit of integrated devices. A top-down followed by a bottom-up integration approach is utilized. Simple MEMS heater structures are utilized as the microscale platforms for the localized, bottom-up synthesis of one-dimensional nanostructures. Localized heating confines the high temperature region permitting only localized nanostructure synthesis and allowing the surroundings to remain at room temperature thus enabling CMOS compatible post-processing. The vapor-liquid-solid (VLS) process in the presence of a catalytic nanoparticle, a vapor phase reactant, and a specific temperature environment is successfully employed locally. Experimentally, a 5nm thick gold-palladium layer is used as the catalyst while silane is the vapor phase reactant. The current-voltage behavior of the MEMS structures can be correlated to the approximate temperature range required for the VLS reaction to take place. Silicon nanowires averaging 45nm in diameter and up to 29mum in length synthesized at growth rates of up to 1.5mum/min result. By placing two MEMS structures in close proximity, 4--10mum apart, localized silicon nanowire growth can be used to link together MEMS structures to yield a two-terminal, self-assembled micro-to-nano system. Here, one MEMS structure is designated as the hot growth structure while a nearby structure is designated as the cold secondary structure, whose role is to provide a natural stopping point for the VLS reaction. The application of a localized electric-field, 5 to 13V/mum in strength, during the synthesis process, has been shown to improve nanowire

  18. Origin of the near-band-edge photoluminescence in ZnO nanorods realised by vapour phase epitaxy and aqueous chemical growth

    Energy Technology Data Exchange (ETDEWEB)

    Bekeny, C.; Hilker, B.; Wischmeier, L.; Voss, T. [IFP, University of Bremen, P.O Box 330440, 28334 Bremen (Germany); Postels, B.; Mofor, A.; Bakin, Andrey; Waag, A. [IHT, TU Braunschweig, P.O Box 3329, 38023 Braunschweig (Germany)

    2007-07-01

    Well established high temperature growth techniques like the vapourliquid-solid (VLS: 1100 C) and vapour-phase-epitaxy (VPE: 800 C) have been successfully optimized while the low-temperature aqueous chemical growth (ACG: 90 C) is being extended to yield large-scale high quality ZnO nanorods. Here, a detailed and systematic photoluminescence (PL) study is presented to understand the microscopic processes responsible for the near-band-edge (NBE) emission in nanorods obtained from these processes. For the ACG samples, the as-grown nanorods show relatively broad NBE emission (15 meV) attributed to the presence of large donor densities. After annealing in various atmospheres at {proportional_to}800 C, a significant reduction of the linewidth ({proportional_to}4 meV) and even the appearance of relatively sharp excitonic transitions is explained by the drastic reduction of the donor density. In contrast, the as-grown VPE and VLS samples exhibit well-resolved and sharp peaks resulting from exciton-related transitions. There is a shift in the room-temperature PL peak for VLS and VPE samples and is shown to result from contributions of the free exciton peak, its first and second order phonon replicas and not due to quantum confinement and or laser heating as assumed in literature.

  19. Non-Epitaxial Thin-Film Indium Phosphide Photovoltaics: Growth, Devices, and Cost Analysis

    Science.gov (United States)

    Zheng, Maxwell S.

    In recent years, the photovoltaic market has grown significantly as module prices have continued to come down. Continued growth of the field requires higher efficiency modules at lower manufacturing costs. In particular, higher efficiencies reduce the area needed for a given power output, thus reducing the downstream balance of systems costs that scale with area such as mounting frames, installation, and soft costs. Cells and modules made from III-V materials have the highest demonstrated efficiencies to date but are not yet at the cost level of other thin film technologies, which has limited their large-scale deployment. There is a need for new materials growth, processing and fabrication techniques to address this major shortcoming of III-V semiconductors. Chapters 2 and 3 explore growth of InP on non-epitaxial Mo substrates by MOCVD and CSS, respectively. The results from these studies demonstrate that InP optoelectronic quality is maintained even by growth on non-epitaxial metal substrates. Structural characterization by SEM and XRD show stoichiometric InP can be grown in complete thin films on Mo. Photoluminescence measurements show peak energies and widths to be similar to those of reference wafers of similar doping concentrations. In chapter 4 the TF-VLS growth technique is introduced and cells fabricated from InP produced by this technique are characterized. The TF-VLS method results in lateral grain sizes of >500 mum and exhibits superior optoelectronic quality. First generation devices using a n-TiO2 window layer along with p-type TF-VLS grown InP have reached ˜12.1% power conversion efficiency under 1 sun illumination with VOC of 692 mV, JSC of 26.9 mA/cm2, and FF of 65%. The cells are fabricated using all non-epitaxial processing. Optical measurements show the InP in these cells have the potential to support a higher VOC of ˜795 mV, which can be achieved by improved device design. Chapter 5 describes a cost analysis of a manufacturing process using an

  20. Growth dynamics of SiGe nanowires by the Vapour Liquid Solid method and its impact on SiGe/Si axial heterojunction abruptness.

    Science.gov (United States)

    Pura, Jose Luis; Periwal, Priyanka; Baron, Thierry; Jimenez, Juan

    2018-06-05

    The Vapour Liquid Solid (VLS) method is by far the most extended procedure for bottom-up nanowire growth. This method also allows for the manufacture of nanowire axial heterojunctions in a straightforward way. To do this, during the growth process the precursor gases are switched on/off to obtain the desired change in the nanowire composition. Using this technique axially heterostructured nanowires can be grown, which are crucial for the fabrication of electronic and optoelectronic devices. SiGe/Si nanowires are compatible with Complementary Metal Oxide Semiconductor (CMOS) technology, this improves their versatility and the possibility of integration with the current electronic technologies. Abrupt heterointerfaces are fundamental for the development and correct operation of electronic and optoelectronic devices. Unfortunately, VLS growth of SiGe/Si heterojunctions does not provide abrupt transitions because of the high solubility of group IV semiconductors in Au, with the corresponding reservoir effect that precludes the growth of sharp interfaces. In this work, we studied the growth dynamics of SiGe/Si heterojunctions based on already developed models for VLS growth. A composition map of the Si-Ge-Au liquid alloy is proposed to better understand the impact of the growing conditions on the nanowire growth process and the heterojunction formation. The solution of our model provides heterojunction profiles in good agreement with experimental measurements. Finally, the in-depth study of the composition map provides a practical approach to reduce drastically the heterojunction abruptness by reducing the Si and Ge concentrations in the catalyst droplet. This converges with previous approaches that use catalysts aiming to reduce the solubility of the atomic species. This analysis opens new paths to reduce the heterojunction abruptness using Au catalysts, but the model can be naturally extended to other catalysts and semiconductors. © 2018 IOP Publishing Ltd.

  1. Glass fabrics self-cracking catalytic growth of boron nitride nanotubes

    Science.gov (United States)

    Wang, Jilin; Peng, Daijang; Long, Fei; Wang, Weimin; Gu, Yunle; Mo, Shuyi; Zou, Zhengguang; Fu, Zhengyi

    2017-02-01

    Glass fabrics were used to fabricate boron nitride nanotubes (BNNTs) with a broad diameter range through a combined chemical vapor deposition and self-propagation high-temperature synthesis (CVD-SHS) method at different holding times (0min, 30min, 90min, 180min and 360min). SEM characterization has been employed to investigate the macro and micro structure/morphology changes of the glass fabrics and BNNTs in detail. SEM image analysis has provided direct experimental evidences for the rationality of the optimized self-cracking catalyst VLS growth mechanism, including the transformation situations of the glass fabrics and the BNNTs growth processes respectively. This paper was the further research and compensation for the theory and experiment deficiencies in the new preparation method of BNNTs reported in our previous work. In addition, it is likely that the distinctive self-cracking catalyst VLS growth mechanism could provide a new idea to preparation of other inorganic functional nano-materials using similar one-dimensional raw materials as growth templates and catalysts.

  2. Catalyst-free combined synthesis of Zn/ZnO core/shell hollow microspheres and metallic Zn microparticles by thermal evaporation and condensation route

    Energy Technology Data Exchange (ETDEWEB)

    Khan, Waheed S. [Research Centre of Materials Science, Beijing Institute of Technology, Beijing 100081 (China); Cao Chuanbao, E-mail: cbcao@bit.edu.c [Research Centre of Materials Science, Beijing Institute of Technology, Beijing 100081 (China); Nabi, Ghulam; Yao Ruimin; Bhatti, Sajjad H. [Research Centre of Materials Science, Beijing Institute of Technology, Beijing 100081 (China)

    2010-09-17

    Research highlights: {yields} Catalyst-free combined synthesis of metal/semiconductor Zn/ZnO core/shell microspheres with hollow interiors on Si substrate and metallic Zn polygonal microparticles on glass substrate in a single experiment via thermal evaporation and condensation technique was reported. The Zn/ZnO hollow microspheres were observed to have dimensions in the range of 70-80 {mu}m whereas metallic Zn microparticles with polygonal cross section and oblate spherical shape were found to be of 8-10 {mu}m. Some of the Zn/ZnO core/shell hollow spheres were also observed to have single crystalline ZnO pointed rods in extremely low density grown on the outer shell. A vapor-liquid-solid (VLS) process based growth mechanism was proposed for the formation of Zn/ZnO core/shell microspheres with hollow interior. The optical properties of Zn/ZnO core/shell microspheres were investigated by measuring the photoluminescence (PL) spectra at room temperature (RT). Two very strong emission bands were observed at 373 and 469 nm in the ultraviolet and visible regions respectively under excitation wavelength of 325 nm. Also the effect of the various excitation wavelengths on the PL behaviour was studied at room temperature. PL studies of Zn/ZnO core/shell microspheres show the promise of the material for applications in UV and blue light optical devices. - Abstract: Here we report catalyst-free combined synthesis of metal/semiconductor Zn/ZnO core/shell microspheres with hollow interiors on Si substrate and metallic Zn polygonal microparticles on glass substrate in a single experiment via thermal evaporation and condensation technique using nitrogen (N{sub 2}) as carrier agent at 800 {sup o}C for 120 min. The Zn/ZnO hollow microspheres were observed to have dimensions in the range of 70-80 {mu}m whereas metallic Zn microparticles with polygonal cross section and oblate spherical shape were found to be of 8-10 {mu}m. Some of the Zn/ZnO core/shell hollow spheres were also

  3. Effect of Growth Parameters on SnO2 Nanowires Growth by Electron Beam Evaporation Method

    Science.gov (United States)

    Rakesh Kumar, R.; Manjula, Y.; Narasimha Rao, K.

    2018-02-01

    Tin oxide (SnO2) nanowires were synthesized via catalyst assisted VLS growth mechanism by the electron beam evaporation method at a growth temperature of 450 °C. The effects of growth parameters such as evaporation rate of Tin, catalyst film thickness, and different types of substrates on the growth of SnO2 nanowires were studied. Nanowires (NWs) growth was completely seized at higher tin evaporation rates due to the inability of the catalyst particle to initiate the NWs growth. Nanowires diameters were able to tune with catalyst film thickness. Nanowires growth was completely absent at higher catalyst film thickness due to agglomeration of the catalyst film. Optimum growth parameters for SnO2 NWs were presented. Nanocomposites such as Zinc oxide - SnO2, Graphene oxide sheets- SnO2 and Graphene nanosheets-SnO2 were able to synthesize at a lower substrate temperature of 450 °C. These nanocompsoites will be useful in enhancing the capacity of Li-ion batteries, the gas sensing response and also useful in increasing the photo catalytic activity.

  4. Synthesis of In2O3 nanostructures with different morphologies as potential supercapacitor electrode materials

    Science.gov (United States)

    Tuzluca, Fatma Nur; Yesilbag, Yasar Ozkan; Ertugrul, Mehmet

    2018-01-01

    In this study performed using a chemical vapor deposition (CVD) system, one-dimensional (1-D) single crystal indium oxide (In2O3) nanotowers, nanobouqets, nanocones, and nanowires were investigated as a candidate for a supercapacitor electrode material. These nanostructures were grown via Vapor-Liquid-Solid (VLS) and Vapor-Solid (VS) mechanisms according to temperature differences (1000-600 °C). The morphologies, growth mechanisms and crystal structures of these 1-D single crystal In2O3 nanostructures were defined by Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Microscopy (HR-TEM), X-Ray Diffraction (XRD) and Raman Spectroscopy analyses. The elemental analyses of the nanostructures were carried out by energy dispersive X-Ray Spectroscopy (EDS); they gave photoluminescence (PL) spectra with 3.39, 2.65, and 1.95 eV band gap values, corresponding to 365 nm, 467 nm, and 633 wavelengths, respectively. The electrochemical performances of these 1-D single crystal In2O3 nanostructures in an aqueous electrolyte solution (1 M Na2SO4) were determined by Cyclic Voltammetry (CV), Galvanostatic Charge Discharge (GCD) and Electrochemical Impedance Spectroscopy (EIS) analyses. According to GCD measurements at 0.04 mA cm-2 current density, areal capacitance values were 10.1 mF cm-2 and 6.7 mF cm-2 for nanotowers, 12.5 mF cm-2 for nanobouquets, 4.9 mF cm-2 for nanocones, and 16.6 mF cm-2 for nanowires. The highest areal capacitance value was observed in In2O3 nanowires, which retained 66.8% of their initial areal capacitance after a 10000 charge-discharge cycle, indicating excellent cycle stability.

  5. Sputtered gold-coated ITO nanowires by alternating depositions from Indium and ITO targets for application in surface-enhanced Raman scattering

    Science.gov (United States)

    Setti, Grazielle O.; Mamián-López, Mónica B.; Pessoa, Priscila R.; Poppi, Ronei J.; Joanni, Ednan; Jesus, Dosil P.

    2015-08-01

    Indium Tin oxide (ITO) nanowires were deposited by RF sputtering over oxidized silicon using ITO and Indium targets. The nanowires grew on the substrate with a catalyst layer of Indium by the vapor-liquid-solid (VLS) mechanism. Modifications in the deposition conditions affected the morphology and dimensions of the nanowires. The samples, after being covered with gold, were evaluated as surface-enhanced Raman scattering (SERS) substrates for detection of dye solutions and very good intensifications of the Raman signal were obtained. The SERS performance of the samples was also compared to that of a commercial SERS substrate and the results achieved were similar. To the best of our knowledge, this is the first time ITO nanowires were grown by the sputtering technique using oxide and metal targets.

  6. Understanding the Room Temperature Ferromagnetism in GaN Nanowires with Pd Doping

    International Nuclear Information System (INIS)

    Manna, S; De, S K

    2011-01-01

    We report the first synthesis and characterization of 4d transition metal palladium-doped GaN nanowires (NWs). Room temperature ferromagnetism has been observed in high quality Vapor Liquid Solid (VLS) epitaxy grown undoped n-type GaN nanowires. It was proposed that this type of magnetism is due to defects which are not observed in Bulk GaN because of large formation energy of defects in bulk GaN. Here we have successfully doped 4d transition metal Pd in GaN NWs. We find fairly strong and long-range ferromagnetic coupling between Pd substituted for Ga in GaN . The results suggest that 4d metals such as Pd may also be considered as candidates for ferromagnetic dopants in semiconductors.

  7. One-step synthesis of CdTe branched nanowires and nanorod arrays

    International Nuclear Information System (INIS)

    Hou Junwei; Yang Xiuchun; Lv Xiaoyi; Peng Dengfeng; Huang Min; Wang Qingyao

    2011-01-01

    Single crystalline CdTe branched nanowires and well-aligned nanorod arrays were simultaneously synthesized by a simple chemical vapor deposition (CVD) technique. X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and selected area electronic diffraction (SAED) were used to study the crystalline structure, composition and morphology of different samples. Vapor-liquid-solid (VLS) and vapor-solid (VS) processes were proposed for the formation of the CdTe branched nanowires and nanorod arrays, respectively. As-grown CdTe nanorod arrays show a strong red emission band centered at about 620 nm, which can be well fitted by two Gaussian curves centered at 610 nm and 635 nm, respectively.

  8. Plasmonic Properties of Vertically Aligned Nanowire Arrays

    Directory of Open Access Journals (Sweden)

    Hua Qi

    2012-01-01

    Full Text Available Nanowires (NWs/Ag sheath composites were produced to investigate plasmonic coupling between vertically aligned NWs for surface-enhanced Raman scattering (SERS applications. In this investigation, two types of vertical NW arrays were studied; those of ZnO NWs grown on nanosphere lithography patterned sapphire substrate via vapor-liquid-solid (VLS mechanism and Si NW arrays produced by wet chemical etching. Both types of vertical NW arrays were coated with a thin layer of silver by electroless silver plating for SERS enhancement studies. The experimental results show extremely strong SERS signals due to plasmonic coupling between the NWs, which was verified by COMSOL electric field simulations. We also compared the SERS enhancement intensity of aligned and random ZnO NWs, indicating that the aligned NWs show much stronger and repeatable SERS signal than those grown in nonaligned geometries.

  9. Real-time impedance analysis of silica nanowire toxicity on epithelial breast cancer cells.

    Science.gov (United States)

    Alexander, Frank A; Huey, Eric G; Price, Dorielle T; Bhansali, Shekhar

    2012-12-21

    Silica nanowires have great potential for usage in the development of highly sensitive in vivo biosensors used for biomarker monitoring. However, careful analysis of nanowire toxicity is required prior to placing these sensors within the human body. This paper describes a real-time and quantitative analysis of nanowire cytotoxicity using impedance spectroscopy; improving upon studies that have utilized traditional endpoint assays. Silica nanowires were grown using the vapor liquid solid (VLS) method, mixed with Dulbecco's Modified Eagle Medium (DMEM) and exposed to Hs578T epithelial breast cancer cells at concentrations of 0 μg ml(-1), 1 μg ml(-1), 50 μg ml(-1) and 100 μg ml(-1). Real-time cellular responses to silica nanowires confirm that while not cytotoxic, silica nanowires at high concentrations (≥50 μg ml(-1)) are toxic to cells, and also suggest that cell death is due to mechanical disturbances of high numbers of nanowires.

  10. Comparative study of initial growth stage in PVT growth of AlN on SiC and on native AlN substrates

    Energy Technology Data Exchange (ETDEWEB)

    Epelbaum, B.M.; Heimann, P.; Bickermann, M.; Winnacker, A. [Department of Materials Science 6, University of Erlangen-Nuernberg, Martensstr. 7, 91058 Erlangen (Germany)

    2005-05-01

    The main issue in homoepitaxial growth of aluminum nitride (AlN) on native seed substrates appears to be aluminum oxynitride poisoning of seed surface leading to polycrystalline growth at 1750-1850 C. This is well below the lowest growth temperature appropriate for physical vapor transport (PVT) of bulk AlN, which is about 2150 C. Contrary, heteroepitaxial growth of AlN on SiC is relatively easy to achieve because of natural formation of a thin molten layer on the seed surface and VLS growth of AlN via the molten buffer layer. The most critical issue of AlN growth on SiC is cracking of the grown layer upon cooling as a result of different thermal expansion. Optimization of seeded growth process can be achieved by proper choice of SiC seed orientation and by use of ultra-pure starting material. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  11. Nanostructured Semiconductor Electrodes for Solar Energy Conversion and Innovations in Undergraduate Chemical Lab Curriculum

    Science.gov (United States)

    Lee, Sudarat

    This dissertation presents the methodology and discussion of preparing nanostructured, high aspect ratio p-type phosphide-based binary and ternary semiconductors via "top-down" anodic etching, a process which creates nanostructures from a large parent entity, and "bottom-up" vapor-liquid-solid growth, a mechanism which builds up small clusters of molecules block-by-block. Such architecture is particularly useful for semiconducting materials with incompatible optical absorption depth and charge carrier diffusion length, as it not only relaxes the requirement for high-grade crystalline materials, but also increases the carrier collection efficiencies for photons with energy greater than or equal to the band gap. The main focus of this dissertation is to obtain nanostructured p-type phosphide semiconductors for photoelectrochemical (PEC) cell applications. Chapter II in the thesis describes a methodology for creating high-aspect ratio p-GaP that function as a photocathode under white light illumination. Gallium phosphide (GaP, band gap: 2.26 eV) is a suitable candidate for solar conversion and energy storage due to its ability to generate large photocurrent and photovoltage to drive fuel-forming reactions. Furthermore, the band edge positions of GaP can provide sufficient kinetics for the reduction of protons and carbon dioxide. The structure is prepared by anodic etching, and the resulting macroporous structures are subsequently doped with Zn by thermally driving in Zn from conformal ZnO films prepared by atomic layer deposition (ALD). The key finding of this work is a viable doping strategy involving ALD ZnO films for making functioning p-type GaP nanostructures. Chapter III compares the GaP nanowires grown from gold (Au) and tin (Sn) VLS catalysts in a benign solid sublimation growth scheme in terms of crystal structure and photoactivity. Sn is less noble than Au, allowing complete removal of Sn metal catalysts from the nanowires through wet chemical etching which

  12. Growth of GaAs-nanowires on GaAs (111)B substrates induced by focused ion beam

    Energy Technology Data Exchange (ETDEWEB)

    Schott, Ruediger; Reuter, Dirk; Wieck, Andreas D. [Lehrstuhl fuer Angewandte Festkoerperphysik, Ruhr-Universitaet Bochum (Germany)

    2011-07-01

    Semiconductor nanowires are a promising system for applications in the areas of electronics and photonics and also for exploring phenomena at the nanoscale. There are several approaches to grow nanowires at arbitrary sites on the wafer. We report about growing GaAs-nanowires on GaAs(111)B substrates via the vapour-liquid-solid (VLS) mechanism in an ultra-high-vacuum (UHV)-cluster of a molecular beam epitaxy (MBE) and a focused ion beam (FIB) system. Our idea is to implant metal seeds (especially Au) for the nanowire growth by in situ patterning using FIB. Due to the UHV transfer between the FIB and the MBE chamber, no further cleaning step of the substrate surface is necessary. Formations of organized GaAs-nanowires and high aspect ratios are observed.

  13. Plasma-plasmonics synergy in the Ga-catalyzed growth of Si-nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Bianco, Giuseppe Valerio, E-mail: giuseppevalerio.bianco@cnr.it [Institute of Inorganic Methodologies and Plasmas, IMIP-CNR, Department of Chemistry, University of Bari, via Orabona 4, 70126 Bari (Italy); Giangregorio, Maria M.; Capezzuto, Pio [Institute of Inorganic Methodologies and Plasmas, IMIP-CNR, Department of Chemistry, University of Bari, via Orabona 4, 70126 Bari (Italy); Losurdo, Maria [Institute of Inorganic Methodologies and Plasmas, IMIP-CNR, Department of Chemistry, University of Bari, via Orabona 4, 70126 Bari (Italy); Department of Electrical and Computer Engineering, Duke University, Durham, NC 27708 (United States); Kim, Tong-Ho; Brown, April S. [Department of Electrical and Computer Engineering, Duke University, Durham, NC 27708 (United States); Bruno, Giovanni, E-mail: giovanni.bruno@ba.imip.cnr.it [Institute of Inorganic Methodologies and Plasmas, IMIP-CNR, Department of Chemistry, University of Bari, via Orabona 4, 70126 Bari (Italy)

    2012-06-05

    This paper reports on the growth of Si nanowires (NWs) by SiH{sub 4}/H{sub 2} plasmas using the non-noble Ga-nanoparticles (NPs) catalysts. A comparative investigation of conventional Si-NWs vapour-liquid-solid (VLS) growth catalyzed by Au NPs is also reported. We investigate the use of a hydrogen plasma and of a SiH{sub 4}/H{sub 2} plasma for removing Ga oxide shell and for enhancing the Si dissolution into the catalyst, respectively. By exploiting the Ga NPs surface plasmon resonance (SPR) sensitivity to their surface chemistry, the SPR characteristic of Ga NPs has been monitored by real time spectroscopic ellipsometry in order to control the hydrogen plasma/Ga NPs interaction and the involved processes (oxide removal and NPs dissolution by volatile gallium hydride). Using in situ laser reflectance interferometry the metal catalyzed Si NWs growth process has been investigated to find the effect of the plasma activation on the growth kinetics. The role of atomic hydrogen in the NWs growth mechanism and, in particular, in the SiH{sub 4} dissolution into the catalysts, is discussed. We show that while Au catalysts because of the re-aggregation of NPs yields NWs that do not correspond to the original size of the Au NPs catalyst, the NWs grown by the Ga catalyst retains the diameter dictated by the size of the Ga NPs. Therefore, the advantage of Ga NPs as catalysts for controlling NWs diameter is demonstrated.

  14. Controllable synthesis of p-type Cu{sub 2}S nanowires for self-driven NIR photodetector application

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Chun-Yan, E-mail: cywu@hfut.edu.cn; Pan, Zhi-Qiang; Liu, Zhu; Wang, You-Yi [Hefei University of Technology, School of Electronic Science and Applied Physics (China); Liang, Feng-Xia [Hefei University of Technology, School of Materials Science and Engineering and Anhui Provincial Key Laboratory of Advanced Functional Materials and Devices (China); Yu, Yong-Qiang; Wang, Li; Luo, Lin-Bao, E-mail: luolb@hfut.edu.cn [Hefei University of Technology, School of Electronic Science and Applied Physics (China)

    2017-02-15

    Face-centered cubic Cu{sub 2}S nanowires with length of up to 50 μm and diameters in the range of 100–500 nm are synthesized on Si substrates through the chemical vapor deposition method using a mixed gas of Ar and H{sub 2} as the carrier gas under a chamber pressure of about 700 Torr. It was found that the growth of quasi 1D nanostructure followed a typical vapor-liquid-solid (VLS) mechanism in which the element Cu was reduced by H{sub 2} as the catalyst. The as-synthesized Cu{sub 2}S nanowires exhibited typical p-type semiconducting characteristics with a conductivity of about 600 S cm{sup −1} and a hole mobility (μ{sub h}) of about 72 cm{sup 2} V{sup −1} s{sup −1}. Further study reveals that p-Cu{sub 2}S nanowires/n-Si heterojunction exhibits distinct rectifying characteristics with a turn-on voltage of ~0.6 V and a rectification ratio of ~300 at ±1 V in the dark and a pronounced photovoltaic behavior with an open circuit voltage (V{sub oc}) of 0.09 V and a short circuit current (I{sub sc}) of 65 nA when illuminated by the NIR light (790 nm, 0.35 mW cm{sup −1}), giving rise to a responsivity (R) about 0.8 mA W{sup −1} and specific detectivity (D*) 6.7 × 10{sup 10} cm Hz{sup 1/2} W{sup −1} at zero bias, which suggests the potential of as-synthesized Cu{sub 2}S nanowires applied in the field of self-driven NIR photodetector.

  15. Semiconductor Nano wires and Nano tubes: From Fundamentals to Diverse Applications

    International Nuclear Information System (INIS)

    Xiong, Q.; Grimes, C.A.; Zacharias, M.; Morral, A.F.; Hiruma, K.; Shen, G.

    2012-01-01

    written by K. Tateno et al. also reviews the vapor-liquid-solid (VLS-) grown core-multi shell Ga(In)P/GaAs/GaP nano wires on Si substrates and introduces an interesting phenomenon of formation of flat-top nano wires achieved by using small-sized Au particles in one growth procedure. The remaining papers illustrate the research on metal oxides semiconducting materials which are well known for wide band gap and transparent conducting properties

  16. Molecular beam epitaxy of GaAs nanowires and their sustainability for optoelectronic applications. Comparing Au- and self-assisted growth methods

    Energy Technology Data Exchange (ETDEWEB)

    Breuer, Steffen

    2011-09-28

    In this work the synthesis of GaAs nanowires by molecular beam epitaxy (MBE) using the vapour-liquid-solid (VLS) mechanism is investigated. A comparison between Au- and self-assisted VLS growth is at the centre of this thesis. While the Au-assisted method is established as a versatile tool for nanowire growth, the recently developed self-assisted variation results from the exchange of Au by Ga droplets and thus eliminates any possibility of Au incorporation. By both methods, we achieve nanowires with epitaxial alignment to the Si(111) substrates. Caused by differences during nanowire nucleation, a parasitic planar layer grows between the nanowires by the Au-assisted method, but can be avoided by the self-assisted method. Au-assisted nanowires grow predominantly in the metastable wurtzite crystal structure, while their self-assisted counterparts have the zincblende structure. All GaAs nanowires are fully relaxed and the strain arising from the lattice mismatch between GaAs and Si of 4.1 % is accommodated by misfit dislocations at the interface. Self-assisted GaAs nanowires are generally found to have vertical and non-polar side facets, while tilted and polar nanofacets were described for Au-assisted GaAs nanowires. We employ VLS nucleation theory to understand the effect of the droplet material on the lateral facets. Optoelectronic applications require long minority carrier lifetimes at room temperature. We fabricate GaAs/(Al,Ga)As core-shell nanowires and analyse them by transient photoluminescence (PL) spectroscopy. The results are 2.5 ns for the self-assisted nanowires as well as 9 ps for the Au-assisted nanowires. By temperature-dependent PL measurements we find a characteristic activation energy of 77 meV that is present only in the Au-assisted nanowires. We conclude that most likely Au is incorporated from the droplets into the GaAs nanowires and acts as a deep, non-radiative recombination centre.

  17. Quantitative measurements of C-reactive protein using silicon nanowire arrays

    Directory of Open Access Journals (Sweden)

    Min-Ho Lee

    2008-03-01

    Full Text Available Min-Ho Lee, Kuk-Nyung Lee, Suk-Won Jung, Won-Hyo Kim, Kyu-Sik Shin, Woo-Kyeong SeongKorea Electronics Technology Institute, Gyeonggi, KoreaAbstract: A silicon nanowire-based sensor for biological application showed highly desirable electrical responses to either pH changes or receptor-ligand interactions such as protein disease markers, viruses, and DNA hybridization. Furthermore, because the silicon nanowire can display results in real-time, it may possess superior characteristics for biosensing than those demonstrated in previously studied methods. However, despite its promising potential and advantages, certain process-related limitations of the device, due to its size and material characteristics, need to be addressed. In this article, we suggest possible solutions. We fabricated silicon nanowire using a top-down and low cost micromachining method, and evaluate the sensing of molecules after transfer and surface modifications. Our newly designed method can be used to attach highly ordered nanowires to various substrates, to form a nanowire array device, which needs to follow a series of repetitive steps in conventional fabrication technology based on a vapor-liquid-solid (VLS method. For evaluation, we demonstrated that our newly fabricated silicon nanowire arrays could detect pH changes as well as streptavidin-biotin binding events. As well as the initial proof-of-principle studies, C-reactive protein binding was measured: electrical signals were changed in a linear fashion with the concentration (1 fM to 1 nM in PBS containing 1.37 mM of salts. Finally, to address the effects of Debye length, silicon nanowires coupled with antigen proteins underwent electrical signal changes as the salt concentration changed.Keywords: silicon nanowire array, C-reactive protein, vapor-liquid-solid method

  18. Delayed growth

    Science.gov (United States)

    ... Slow rate of growth; Retarded growth and development; Growth delay Images Toddler development References Cooke DW, Divall SA, Radovick S. Normal and aberrant growth in children. In: Melmed S, Polonsky KS, Larsen PR, ...

  19. Efficient photogeneration of charge carriers in silicon nanowires with a radial doping gradient

    International Nuclear Information System (INIS)

    Murthy, D H K; Houtepen, A J; Savenije, T J; Siebbeles, L D A; Xu, T; Nys, J P; Krzeminski, C; Grandidier, B; Stievenard, D; Chen, W H; Pareige, P; Jomard, F; Patriarche, G; Lebedev, O I

    2011-01-01

    by performing electrodeless time-resolved microwave conductivity measurements, the efficiency of charge carrier generation, their mobility, and the decay kinetics on photoexcitation were studied in arrays of Si nanowires grown by the vapor-liquid-solid mechanism. Large enhancements in the magnitude of the photoconductance and charge carrier lifetime are found depending on the incorporation of impurities during the growth. They are explained by the internal electric field that builds up, due to higher doped sidewalls, as revealed by detailed analysis of the nanowire morphology and chemical composition.

  20. Growth Disorders

    Science.gov (United States)

    ... too little of it may be very short. Treatment with growth hormone can stimulate growth. People can also have too much growth hormone. Usually the cause is a pituitary gland tumor, which is not cancer. Too much growth hormone can cause gigantism in children, where their bones and their body ...

  1. growth stimulant

    African Journals Online (AJOL)

    Effects of timing and duration of supplementation of LIVFIT VET ® (growth stimulant) as substitute for fish meal on the growth performance, haematology and clinical enzymes concentration of growing pigs.

  2. Growth references

    NARCIS (Netherlands)

    Buuren, S. van

    2007-01-01

    A growth reference describes the variation of an anthropometric measurement within a group of individuals. A reference is a tool for grouping and analyzing data and provides a common basis for comparing populations.1 A well known type of reference is the age-conditional growth diagram. The

  3. Alumina nanowire growth by water decomposition and the peritectic reaction of decagonal Al{sub 65}Cu{sub 15}Co{sub 20} quasicrystals

    Energy Technology Data Exchange (ETDEWEB)

    Téllez-Vázquez, J.O., E-mail: oswald.tellez@gmail.com [Instituto de Investigaciones en Metalurgia y Materiales, UMSNH, Edificio U, Ciudad Universitaria, CP 58060 Morelia Michoacán, México (Mexico); Patiño-Carachure, C., E-mail: cpatino@pampano.unacar.mx [Facultad de Ingeniería, Universidad Autónoma del Carmen, Campus III, Avenida Central S/N, Esq. Con Fracc. Mundo Maya, C.P. 24115 Ciudad del Carmen, Campeche, México (Mexico); Rosas, G., E-mail: grtrejo@yahoo07.com.mx [Instituto de Investigaciones en Metalurgia y Materiales, UMSNH, Edificio U, Ciudad Universitaria, CP 58060 Morelia Michoacán, México (Mexico)

    2016-02-15

    In this paper, the results of the Al{sub 2}O{sub 3} nanowires' growth through a chemical reaction between Al and water vapor at 1050 °C are presented. Our approach is based on two primary considerations. First, at room temperature, the Al{sub 65}Cu{sub 15}Co{sub 20} alloy is affected by the following mechanism: 2Al (s) + 3H{sub 2}O (g) → Al{sub 2}O{sub 3} (s) + H{sub 2} (g). In this reaction, the released hydrogen induces cleavage fracture of the material to form small particles. Second, the Al{sub 65}Cu{sub 15}Co{sub 20} quasicrystalline phase is transformed on heating to liquid + Al (Cu, Co) cubic phase through a peritectic reaction at 1050 °C. The Al-rich liquid then reacts with water vapor, forming Al{sub 2}O{sub 3} nanowires. X-ray diffraction (XRD) analysis shows that the formed nanowires have a hexagonal structure, and infrared analysis further confirms the presence of α-Al{sub 2}O{sub 3} phase in the final products. Transmission electron microscopy observations show that nanoparticles are present at the end of nanowires, suggesting the VLS growth mechanism. Elemental analysis by energy dispersive spectroscopy (EDS) indicates that the particles at the tip of the nanowires are mainly formed by Co and Cu alloying elements and small amounts of Al. Electron microscopy observations showed nanowires with diameters ranging from 20 to 70 nm; the average diameter was 37 nm and the nanowire lengths were up to several micrometers. - Highlights: • Hexagonal alumina nanowires are grown at 1050 °C through the VLS process. • Alumina nanowires are obtained by the decomposition of decagonal quasicrystalline phase. • The decagonal phase decomposition follows a peritectic reaction at 1030 °C. • Nanoparticles are obtained by hydrogen embrittlement mechanism. • The nanoparticles catalyze the water decomposition to form wires.

  4. Growth Problems

    Science.gov (United States)

    ... Development Infections Diseases & Conditions Pregnancy & Baby Nutrition & Fitness Emotions & Behavior School & Family Life First Aid & Safety Doctors & ... hypothyroidism is feeling tired or sluggish. A blood test measuring thyroid ... not affect intelligence or brain function. The cause of growth hormone ...

  5. Growth Disorders

    Science.gov (United States)

    ... the changes your body goes through during puberty. Puberty is the stage of your life when sexual development happens, like breast development and menstrual periods in girls and growth of the penis and testicles in boys. One of the body ...

  6. Population growth and economic growth.

    Science.gov (United States)

    Narayana, D L

    1984-01-01

    This discussion of the issues relating to the problem posed by population explosion in the developing countries and economic growth in the contemporary world covers the following: predictions of economic and social trends; the Malthusian theory of population; the classical or stationary theory of population; the medical triage model; ecological disaster; the Global 2000 study; the limits to growth; critiques of the Limits to Growth model; nonrenewable resources; food and agriculture; population explosion and stabilization; space and ocean colonization; and the limits perspective. The Limits to Growth model, a general equilibrium anti-growth model, is the gloomiest economic model ever constructed. None of the doomsday models, the Malthusian theory, the classical stationary state, the neo-Malthusian medical triage model, the Global 2000 study, are so far reaching in their consequences. The course of events that followed the publication of the "Limits to Growth" in 1972 in the form of 2 oil shocks, food shock, pollution shock, and price shock seemed to bear out formally the gloomy predictions of the thesis with a remarkable speed. The 12 years of economic experience and the knowledge of resource trends postulate that even if the economic pressures visualized by the model are at work they are neither far reaching nor so drastic. Appropriate action can solve them. There are several limitations to the Limits to Growth model. The central theme of the model, which is overshoot and collapse, is unlikely to be the course of events. The model is too aggregative to be realistic. It exaggerates the ecological disaster arising out of the exponential growth of population and industry. The gross underestimation of renewable resources is a basic flaw of the model. The most critical weakness of the model is its gross underestimation of the historical trend of technological progress and the technological possiblities within industry and agriculture. The model does correctly emphasize

  7. Synthesis of p-type GaN nanowires.

    Science.gov (United States)

    Kim, Sung Wook; Park, Youn Ho; Kim, Ilsoo; Park, Tae-Eon; Kwon, Byoung Wook; Choi, Won Kook; Choi, Heon-Jin

    2013-09-21

    GaN has been utilized in optoelectronics for two decades. However, p-type doping still remains crucial for realization of high performance GaN optoelectronics. Though Mg has been used as a p-dopant, its efficiency is low due to the formation of Mg-H complexes and/or structural defects in the course of doping. As a potential alternative p-type dopant, Cu has been recognized as an acceptor impurity for GaN. Herein, we report the fabrication of Cu-doped GaN nanowires (Cu:GaN NWs) and their p-type characteristics. The NWs were grown vertically via a vapor-liquid-solid (VLS) mechanism using a Au/Ni catalyst. Electrical characterization using a nanowire-field effect transistor (NW-FET) showed that the NWs exhibited n-type characteristics. However, with further annealing, the NWs showed p-type characteristics. A homo-junction structure (consisting of annealed Cu:GaN NW/n-type GaN thin film) exhibited p-n junction characteristics. A hybrid organic light emitting diode (OLED) employing the annealed Cu:GaN NWs as a hole injection layer (HIL) also demonstrated current injected luminescence. These results suggest that Cu can be used as a p-type dopant for GaN NWs.

  8. Topological Insulator Nanowires and Nanoribbons

    KAUST Repository

    Kong, Desheng

    2010-01-13

    Recent theoretical calculations and photoemission spectroscopy measurements on the bulk Bi2Se3 material show that it is a three-dimensional topological insulator possessing conductive surface states with nondegenerate spins, attractive for dissipationless electronics and spintronics applications. Nanoscale topological insulator materials have a large surface-to-volume ratio that can manifest the conductive surface states and are promising candidates for devices. Here we report the synthesis and characterization of high quality single crystalline Bi2Se5 nanomaterials with a variety of morphologies. The synthesis of Bi 2Se5 nanowires and nanoribbons employs Au-catalyzed vapor-liquid-solid (VLS) mechanism. Nanowires, which exhibit rough surfaces, are formed by stacking nanoplatelets along the axial direction of the wires. Nanoribbons are grown along [1120] direction with a rectangular cross-section and have diverse morphologies, including quasi-one-dimensional, sheetlike, zigzag and sawtooth shapes. Scanning tunneling microscopy (STM) studies on nanoribbons show atomically smooth surfaces with ∼ 1 nm step edges, indicating single Se-Bi-Se-Bi-Se quintuple layers. STM measurements reveal a honeycomb atomic lattice, suggesting that the STM tip couples not only to the top Se atomic layer, but also to the Bi atomic layer underneath, which opens up the possibility to investigate the contribution of different atomic orbitais to the topological surface states. Transport measurements of a single nanoribbon device (four terminal resistance and Hall resistance) show great promise for nanoribbons as candidates to study topological surface states. © 2010 American Chemical Society.

  9. Excessive growth.

    Science.gov (United States)

    Narayanaswamy, Vasudha; Rettig, Kenneth R; Bhowmick, Samar K

    2008-09-01

    Tall stature and excessive growth syndrome are a relatively rare concern in pediatric practice. Nevertheless, it is important to identify abnormal accelerated growth patterns in children, which may be the clue in the diagnosis of an underlying disorder. We present a case of pituitary gigantism in a 2 1/2-year-old child and discuss the signs, symptoms, laboratory findings, and the treatment. Brief discussions on the differential diagnosis of excessive growth/tall stature have been outlined. Pituitary gigantism is very rare in the pediatrics age group; however, it is extremely rare in a child that is less than 3 years of age. The nature of pituitary adenoma and treatment options in children with this condition have also been discussed.

  10. Zinc oxide nanorod based photonic devices: recent progress in growth, light emitting diodes and lasers

    Energy Technology Data Exchange (ETDEWEB)

    Willander, M; Nur, O; Zhao, Q X; Yang, L L [Department of Science and Technology, Linkoeping University, SE-601 74 Norrkoeping (Sweden); Lorenz, M; Cao, B Q; Zuniga Perez, J; Czekalla, C; Zimmermann, G; Grundmann, M [Institut fuer Experimentelle Physik II, Universitaet Leipzig, Linnestrasse 5, D-04103 Leipzig (Germany); Bakin, A; Behrends, A; Al-Suleiman, M; El-Shaer, A; Che Mofor, A; Postels, B; Waag, A [Institute of Semiconductor Technology, Technical University of Braunschweig, Hans-Sommer-Strasse 66, D-38106 Braunschweig (Germany); Boukos, N; Travlos, A [National Center for Scientific Research ' Demokritos' , Institute of Materials Science, GR 15310 Agia Paraskevi Attikis, Athens (Greece); Kwack, H S, E-mail: magwi@itn.liu.s [CEA-CNRS Group ' Nanophysique et Semiconducteurs' , Institut Neel, CNRS and Universit' e Joseph Fourier, F-38042 Grenoble (France)

    2009-08-19

    Zinc oxide (ZnO), with its excellent luminescent properties and the ease of growth of its nanostructures, holds promise for the development of photonic devices. The recent advances in growth of ZnO nanorods are discussed. Results from both low temperature and high temperature growth approaches are presented. The techniques which are presented include metal-organic chemical vapour deposition (MOCVD), vapour phase epitaxy (VPE), pulse laser deposition (PLD), vapour-liquid-solid (VLS), aqueous chemical growth (ACG) and finally the electrodeposition technique as an example of a selective growth approach. Results from structural as well as optical properties of a variety of ZnO nanorods are shown and analysed using different techniques, including high resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), photoluminescence (PL) and cathodoluminescence (CL), for both room temperature and for low temperature performance. These results indicate that the grown ZnO nanorods possess reproducible and interesting optical properties. Results on obtaining p-type doping in ZnO micro- and nanorods are also demonstrated using PLD. Three independent indications were found for p-type conducting, phosphorus-doped ZnO nanorods: first, acceptor-related CL peaks, second, opposite transfer characteristics of back-gate field effect transistors using undoped and phosphorus doped wire channels, and finally, rectifying I-V characteristics of ZnO:P nanowire/ZnO:Ga p-n junctions. Then light emitting diodes (LEDs) based on n-ZnO nanorods combined with different technologies (hybrid technologies) are suggested and the recent electrical, as well as electro-optical, characteristics of these LEDs are shown and discussed. The hybrid LEDs reviewed and discussed here are mainly presented for two groups: those based on n-ZnO nanorods and p-type crystalline substrates, and those based on n-ZnO nanorods and p-type amorphous substrates. Promising electroluminescence

  11. In situ observation of morphological change in CdTe nano- and submicron wires

    Energy Technology Data Exchange (ETDEWEB)

    Davami, Keivan; Lee, Jeong-Soo; Meyyappan, M [Division of IT Convergence Engineering, Pohang University of Science and Technology, Pohang (Korea, Republic of); Ghassemi, Hessam M; Yassar, Reza S [Department of Mechanical Engineering, Michigan Technological University, Houghton, MI 49931 (United States); Sun, Xuhui, E-mail: ljs6951@postech.ac.kr, E-mail: m.meyyappan@nasa.gov [Institute of Functional Nano and Soft Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123 (China)

    2011-10-28

    We report growth and characterization of CdTe wires 30-400 nm in diameter by the vapor-liquid-solid technique. Individual nanowires were placed on a movable piezotube, which allowed three-dimensional motion toward a scanning tunneling microscope (STM). A bias was applied to the STM tip in contact with the nanowire, and the morphological changes due to Joule heating were observed in situ using a transmission electron microscope (TEM) in real time. For thick CdTe wires (d > {approx} 150 nm), the process results in the growth of superfine nanowires (SFNWs) of 2-4 nm diameter on the surface of the wire. Smaller diameter nanowires, in contrast, disintegrate under the applied bias before the complete evolution of SFNWs on the surface.

  12. Synthesis of GeSe2 Nanobelts Using Thermal Evaporation and Their Photoelectrical Properties

    Directory of Open Access Journals (Sweden)

    Lijie Zhang

    2014-01-01

    Full Text Available GeSe2 nanobelts were synthesized via a simple thermal-evaporation process by using gold particles as catalyst and GeSe2 flakes as starting materials. The morphology, crystal structure, and composition were characterized with scanning electron microscopy (SEM, high-resolution transmission electron microscopy (TEM, X-ray diffraction spectroscopy (XRD, X-ray photoelectron spectroscopy (XPS, and energy-dispersive X-ray spectroscopy (EDS. SEM micrographs show that most of GeSe2 nanobelts have distinct segmented structures (wide belt, zigzag belt, and narrow belt. A possible mechanism was proposed for the growth of segmented nanobelts. It is possible that the growth of the segmented nanobelts is dominated by both vapor-liquid-solid and vapor-solid mechanisms. Devices made of single GeSe2 nanobelt have been fabricated and their photoelectrical property has been investigated. Results indicate that these nanobelt devices are potential building blocks for optoelectronic applications.

  13. Sn-doped β-Ga2O3 nanowires deposited by radio frequency powder sputtering

    Science.gov (United States)

    Lee, Su Yong; Kang, Hyon Chol

    2018-01-01

    We report the synthesis and characterization of Sn-doped β-Ga2O3 nanowires (NWs) deposited using radio frequency powder sputtering. The growth sequence of Sn-doped β-Ga2O3 NWs is similar to that of the undoped β-Ga2O3 NWs. Self-assembled Ga clusters act as seeds for initiating the growth of Sn-doped β-Ga2O3 NWs through a vapor-liquid-solid process, while Sn atoms are incorporated into the trunk of NWs uniformly. Different from the straight shape of undoped NWs, the conical shape of NWs is observed, which is attributed to the change in supersaturation conditions and the diffusion of the catalyst tip and reaction species.

  14. Silicide/Silicon Heterointerfaces, Reaction Kinetics and Ultra-short Channel Devices

    Science.gov (United States)

    Tang, Wei

    Nickel silicide is one of the electrical contact materials widely used on very large scale integration (VLSI) of Si devices in microelectronic industry. This is because the silicide/silicon interface can be formed in a highly controlled manner to ensure reproducibility of optimal structural and electrical properties of the metal-Si contacts. These advantages can be inherited to Si nanowire (NW) field-effect transistors (FET) device. Due to the technological importance of nickel silicides, fundamental materials science of nickel silicides formation (Ni-Si reaction), especially in nanoscale, has raised wide interest and stimulate new insights and understandings. In this dissertation, in-situ transmission electron microscopy (TEM) in combination with FET device characterization will be demonstrated as useful tools in nano-device fabrication as well as in gaining insights into the process of nickel silicide formation. The shortest transistor channel length (17 nm) fabricated on a vapor-liquid-solid (VLS) grown silicon nanowire (NW) has been demonstrated by controlled reaction with Ni leads on an in-situ transmission electron microscope (TEM) heating stage at a moderate temperature of 400 ºC. NiSi2 is the leading phase, and the silicide-silicon interface is an atomically sharp type-A interface. At such channel lengths, high maximum on-currents of 890 (microA/microm) and a maximum transconductance of 430 (microS/microm) were obtained, which pushes forward the performance of bottom-up Si NW Schottky barrier field-effect transistors (SB-FETs). Through accurate control over the silicidation reaction, we provide a systematic study of channel length dependent carrier transport in a large number of SB-FETs with channel lengths in the range of (17 nm -- 3.6 microm). Our device results corroborate with our transport simulations and reveal a characteristic type of short channel effects in SB-FETs, both in on- and off-state, which is different from that in conventional MOSFETs

  15. Observation of hole accumulation in Ge/Si core/shell nanowires using off-axis electron holography.

    Science.gov (United States)

    Li, Luying; Smith, David J; Dailey, Eric; Madras, Prashanth; Drucker, Jeff; McCartney, Martha R

    2011-02-09

    Hole accumulation in Ge/Si core/shell nanowires (NWs) has been observed and quantified using off-axis electron holography and other electron microscopy techniques. The epitaxial [110]-oriented Ge/Si core/shell NWs were grown on Si (111) substrates by chemical vapor deposition through the vapor-liquid-solid growth mechanism. High-angle annular-dark-field scanning transmission electron microscopy images and off-axis electron holograms were obtained from specific NWs. The excess phase shifts measured by electron holography across the NWs indicated the presence of holes inside the Ge cores. Calculations based on a simplified coaxial cylindrical model gave hole densities of (0.4 ± 0.2) /nm(3) in the core regions.

  16. Simulating Population Growth.

    Science.gov (United States)

    Byington, Scott

    1997-01-01

    Presents a strategy to help students grasp the important implications of population growth. Involves an interactive demonstration that allows students to experience exponential and logistic population growth followed by a discussion of the implications of population-growth principles. (JRH)

  17. AMSAA Reliability Growth Guide

    National Research Council Canada - National Science Library

    Broemm, William

    2000-01-01

    ... has developed reliability growth methodology for all phases of the process, from planning to tracking to projection. The report presents this methodology and associated reliability growth concepts.

  18. Green growth in fisheries

    DEFF Research Database (Denmark)

    Nielsen, Max; Ravensbeck, Lars; Nielsen, Rasmus

    2014-01-01

    harming the environment. Fishery is an environment-dependent sector and it has been argued that there is no potential for green growth in the sector owing to global overexploitation, leaving no scope for production growth. The purpose of this paper is to explain what green growth is and to develop......Climate change and economic growth have gained a substantial amount of attention over the last decade. Hence, in order to unite the two fields of interest, the concept of green growth has evolved. The concept of green growth focuses on how to achieve growth in environment-dependent sectors, without...... a conceptual framework. Furthermore, the aim is to show that a large green growth potential actually exists in fisheries and to show how this potential can be achieved. The potential green growth appears as value-added instead of production growth. The potential can be achieved by reducing overcapacity...

  19. Globalization, Growth and Poverty

    International Development Research Centre (IDRC) Digital Library (Canada)

    One-pagers are a publication of IDRC's “Globalization, Growth and Poverty” Program Initiative, and are based on ... countries, mainly the fast-growing economies of East Asia. ... had no significant overall impact on investment and growth. Other.

  20. Measuring multifactor productivity growth

    Czech Academy of Sciences Publication Activity Database

    Wölfl, A.; Hájková, Dana

    -, 2007/5 (2007), s. 1-45 Institutional research plan: CEZ:AV0Z70850503 Keywords : multifactor productivity growth * GDP growth * measuring Subject RIV: AH - Economics http://www.oecd.org/dataoecd/61/17/39522985.pdf

  1. Growth hormone test

    Science.gov (United States)

    ... is called acromegaly . In children it is called gigantism . Too little growth hormone can cause a slow ... growth due to excess GH during childhood, called gigantism. (A special test is done to confirm this ...

  2. CDC Child Growth Charts

    Data.gov (United States)

    U.S. Department of Health & Human Services — CDC child growth charts consist of a series of percentile curves that illustrate the distribution of selected body measurements in U.S. children. Pediatric growth...

  3. Growth hormone stimulation test

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/003377.htm Growth hormone stimulation test To use the sharing features on this page, please enable JavaScript. The growth hormone (GH) stimulation test measures the ability of ...

  4. Normal growth and development

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/002456.htm Normal growth and development To use the sharing features on this page, please enable JavaScript. A child's growth and development can be divided into four periods: ...

  5. Systemic Crises and Growth

    OpenAIRE

    Romain Ranciere; Aaron Tornell; Frank Westermann

    2005-01-01

    In this paper, we document the fact that countries that have experienced occasional financial crises have, on average, grown faster than countries with stable financial conditions. We measure the incidence of crisis with the skewness of credit growth, and find that it has a robust negative effect on GDP growth. This link coexists with the negative link between variance and growth typically found in the literature. To explain the link between crises and growth we present a model where contract...

  6. Urban tree growth modeling

    Science.gov (United States)

    E. Gregory McPherson; Paula J. Peper

    2012-01-01

    This paper describes three long-term tree growth studies conducted to evaluate tree performance because repeated measurements of the same trees produce critical data for growth model calibration and validation. Several empirical and process-based approaches to modeling tree growth are reviewed. Modeling is more advanced in the fields of forestry and...

  7. Unemployment and endogenous growth

    NARCIS (Netherlands)

    van Schaik, A.B.T.M.; de Groot, H.L.F.

    1995-01-01

    In this paper we develop a two-sector endogenous growth model with a dual labour market, based on efficiency wages. Growth is driven by intentional R&D performed in the high-tech and high-wage sector. It is examined how a change in rivalry among firms affects simultaneously growth and unemployment.

  8. Toddler Growth and Development

    Science.gov (United States)

    ... the AAP Schedule of Well-Child Care Visits . ​​ Toddler Growth & Development Physical Skills Walks alone Pulls toys behind when ... 18 to 23 Month Old Language Delays in Toddlers: Information for Parents ... Physical Appearance and Growth: Your 1 Year Old Physical Appearance and Growth: ...

  9. Growth Charts (For Parents)

    Science.gov (United States)

    ... Staying Safe Videos for Educators Search English Español Growth Charts KidsHealth / For Parents / Growth Charts What's in ... Problem? Print en español Tablas de crecimiento About Growth Charts Look at any class picture, and you' ...

  10. Growth hormone, growth factors, and acromegaly

    Energy Technology Data Exchange (ETDEWEB)

    Ludecke, D.K.; Tolis, G.T.

    1987-01-01

    This book contains five sections, each consisting of several papers. The section headings are: Biochemistry and Physiology of GH and Growth Factors, Pathology of Acromegaly, Clinical Endocrinology of Acromegaly, Nonsurgical Therapy of Acromegaly, and Surgical Therapy of Acromegaly.

  11. Lung growth and development.

    Science.gov (United States)

    Joshi, Suchita; Kotecha, Sailesh

    2007-12-01

    Human lung growth starts as a primitive lung bud in early embryonic life and undergoes several morphological stages which continue into postnatal life. Each stage of lung growth is a result of complex and tightly regulated events governed by physical, environmental, hormonal and genetic factors. Fetal lung liquid and fetal breathing movements are by far the most important determinants of lung growth. Although timing of the stages of lung growth in animals do not mimic that of human, numerous animal studies, mainly on sheep and rat, have given us a better understanding of the regulators of lung growth. Insight into the genetic basis of lung growth has helped us understand and improve management of complex life threatening congenital abnormalities such as congenital diaphragmatic hernia and pulmonary hypoplasia. Although advances in perinatal medicine have improved survival of preterm infants, premature birth is perhaps still the most important factor for adverse lung growth.

  12. Research Article Special Issue

    African Journals Online (AJOL)

    pc

    2018-03-07

    Mar 7, 2018 ... 1Department of Engineering, Universiti Selangor, Malaysia ... vapor-liquid-solid deposition [4], chemical bath deposition [5] and metal organic chemical ... Applying immersion or chemical bath deposition method can fulfill the ...

  13. Si Nano wires Produced by Very High Frequency Plasma Enhanced Chemical Vapor Deposition (PECVD) via VLS Mechanism

    International Nuclear Information System (INIS)

    Yussof Wahab; Yussof Wahab; Habib Hamidinezhad; Habib Hamidinezhad

    2013-01-01

    Silicon nano wires (SiNWs) with diameter of about a few nanometers and length of 3 μm on silicon wafers were synthesized by very high frequency plasma enhanced chemical vapor deposition. Scanning electron microscopy (SEM) observations showed that the silicon nano wires were grown randomly and energy-dispersive X-ray spectroscopy analysis indicates that the nano wires have the composition of Si, Au and O elements. The SiNWs were characterized by high resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. SEM micrographs displayed SiNWs that are needle-like with a diameter ranged from 30 nm at the top to 100 nm at the bottom of the wire and have length a few of micrometers. In addition, HRTEM showed that SiNWs consist of crystalline silicon core and amorphous silica layer. (author)

  14. Adult growth hormone deficiency

    Directory of Open Access Journals (Sweden)

    Vishal Gupta

    2011-01-01

    Full Text Available Adult growth hormone deficiency (AGHD is being recognized increasingly and has been thought to be associated with premature mortality. Pituitary tumors are the commonest cause for AGHD. Growth hormone deficiency (GHD has been associated with neuropsychiatric-cognitive, cardiovascular, neuromuscular, metabolic, and skeletal abnormalities. Most of these can be reversed with growth hormone therapy. The insulin tolerance test still remains the gold standard dynamic test to diagnose AGHD. Growth hormone is administered subcutaneously once a day, titrated to clinical symptoms, signs and IGF-1 (insulin like growth factor-1. It is generally well tolerated at the low-doses used in adults. Pegylated human growth hormone therapy is on the horizon, with a convenient once a week dosing.

  15. Aid and growth regressions

    DEFF Research Database (Denmark)

    Hansen, Henrik; Tarp, Finn

    2001-01-01

    This paper examines the relationship between foreign aid and growth in real GDP per capita as it emerges from simple augmentations of popular cross country growth specifications. It is shown that aid in all likelihood increases the growth rate, and this result is not conditional on ‘good’ policy....... investment. We conclude by stressing the need for more theoretical work before this kind of cross-country regressions are used for policy purposes.......This paper examines the relationship between foreign aid and growth in real GDP per capita as it emerges from simple augmentations of popular cross country growth specifications. It is shown that aid in all likelihood increases the growth rate, and this result is not conditional on ‘good’ policy...

  16. City Population Growth and Economic Growth

    DEFF Research Database (Denmark)

    Freire-Gibb, L. Carlos

    2008-01-01

    This article looks at the relationship between city population growth (intimately related to population proximity), and economic development. The hypothesis is that wherever dynamic and inclusive networks exist, there are more opportunities for economic development in this place. When these types...... of networks choose a tool (project, policy) to implement in the city, success will be more likely. Furthermore, virtuous circles will arise. The author gives an overview of two historical cases in urban growth, in Europe (1200-1800) and the U.S.A. (1800 to today)....

  17. Earthquakes and economic growth

    OpenAIRE

    Fisker, Peter Simonsen

    2012-01-01

    This study explores the economic consequences of earthquakes. In particular, it is investigated how exposure to earthquakes affects economic growth both across and within countries. The key result of the empirical analysis is that while there are no observable effects at the country level, earthquake exposure significantly decreases 5-year economic growth at the local level. Areas at lower stages of economic development suffer harder in terms of economic growth than richer areas. In addition,...

  18. Luxury-based Growth

    OpenAIRE

    Shiro Kuwahara

    2006-01-01

    Assuming that there exists a preference for luxury goods and a knowledge spillover from luxury goods production to goods production, this paper constructs an endogenous economic growth model. The model predicts two steady states: one is a steady positive growth state with regard to luxury goods production, and the other is a zero growth state in the absence of luxury goods production. Thus, this study examines the polarization of economies based on luxury goods consumption

  19. Robust Growth Determinants

    OpenAIRE

    Doppelhofer, Gernot; Weeks, Melvyn

    2011-01-01

    This paper investigates the robustness of determinants of economic growth in the presence of model uncertainty, parameter heterogeneity and outliers. The robust model averaging approach introduced in the paper uses a flexible and parsi- monious mixture modeling that allows for fat-tailed errors compared to the normal benchmark case. Applying robust model averaging to growth determinants, the paper finds that eight out of eighteen variables found to be significantly related to economic growth ...

  20. Thailand's growth rebalancing

    OpenAIRE

    Jitsuchon, Somchai; Sussangkarn, Chalongphob

    2009-01-01

    This paper reviews Thailand's structural changes, the 1997 crisis experience, and recovery and lessons from the crisis. The paper then discusses the impacts of the subprime crisis on the Thai economy and the policy responses to date. The paper ends by discussing strategies to rebalance growth by reducing the dependence on exports as the main growth engine. The recovery from the 1997 crisis left Thailand more dependent than ever on exports as the main engine of growth, with the ratio of export...

  1. Smart Growth and Transportation

    Science.gov (United States)

    Describes the relationship between smart growth and transportation, focusing smart and sustainable street design, transit-oriented development, parking management, sustainable transportation planning, and related resources.

  2. FDI- Economic Growth Nexus

    DEFF Research Database (Denmark)

    Bujac, Andreea Ioana; Corado Cretu, Emanuel

    2017-01-01

    Conducting a systematic literature review on the topic of FDI and Economic Growth and investigating this relationship, along with the determinants of an economy that attract FDI and the externalities resulting from Foreign activities, it is found that FDI does have a positive effect on a host...... country’s economic growth but only with the preexistence of certain determinants which facilitate the absorption capacity of the host country on reaping the spillover effects (externalities) of FDI. Lastly, a framework was built to illustrate the interaction between FDI, Determinants and condition...... of the host economy, barriers to growth, economic growth and externalities....

  3. Aid, growth, and development

    DEFF Research Database (Denmark)

    Arndt, Channing; Jones, Edward Samuel; Tarp, Finn

    2010-01-01

    The micro-macro paradox has been revived. Despite broadly positive evaluations at the micro- and meso-levels, recent literature doubts the ability of foreign aid to foster economic growth and development. This paper assesses the aid-growth literature and, taking inspiration from the program...... evaluation literature, we re-examine key hypotheses. In our findings, aid has a positive and statistically significant causal effect on growth over the long run, with confidence intervals conforming to levels suggested by growth theory. Aid remains a key tool for enhancing the development prospects of poor...

  4. Optimising growth in phenylketonuria

    DEFF Research Database (Denmark)

    Dokoupil, Katharina; Gokmen-Ozel, Hulya; Lammardo, Anna Maria

    2012-01-01

    populations. We reviewed the literature searching for evidence regarding PKU and growth as well as possible links between dietary management of PKU and growth. The search retrieved only limited evidence on the effect of PKU and its dietary management on growth. Physical development in PKU remains an under....... Protein requirements in dietary management of PKU are met mostly from Phe-free protein substitutes with the intake of natural protein restricted to patient tolerance. Several reports have suggested that growth in early childhood in PKU is sub-optimal, relative to non-PKU control groups or reference...

  5. Triplet ultrasound growth parameters.

    Science.gov (United States)

    Vora, Neeta L; Ruthazer, Robin; House, Michael; Chelmow, David

    2006-03-01

    To create ultrasound growth curves for normal growth of fetal triplets using statistical methodology that properly accounts for similarities of growth of fetuses within a mother as well as repeated measurements over time for each fetus. In this longitudinal study, all triplet pregnancies managed at a single tertiary center from 1992-2004 were reviewed. Fetuses with major anomalies, prior selective reduction, or fetal demise were excluded. Data from early and late gestation in which there were fewer than 30 fetal measurements available for analysis were excluded. We used multilevel models to account for variation in growth within a single fetus over time, variations in growth between multiple fetuses within a single mother, and variations in fetal growth between mothers. Medians (50th), 10th, and 90th percentiles were estimated by the creation of multiple quadratic growth models from bootstrap samples adapting a previously published method to compute prediction intervals. Estimated fetal weight was derived from Hadlock's formula. One hundred fifty triplet pregnancies were identified. Twenty-seven pregnancies were excluded for the following reasons: missing records (23), fetal demise (3), and fetal anomaly (1). The study group consisted of 123 pregnancies. The gestational age range was restricted to 14-34 weeks. Figures and tables were developed showing medians, 10th and 90th percentiles for estimated fetal weight, femur length, biparietal diameter, abdominal circumference, and head circumference. Growth curves for triplet pregnancies were derived. These may be useful for identification of abnormal growth in triplet fetuses. III.

  6. Incentives and Earnings Growth

    DEFF Research Database (Denmark)

    Frederiksen, Anders

    2013-01-01

    The career prospects of newly recruited employees differ substantially within an organization. The stars experience considerable growth in earnings; others can hardly maintain their entry salaries. This article sheds light on the mechanisms generating the observed heterogeneity in earnings growth...... by investigating the effects that explicit short-run incentives and implicit incentives have on earnings growth. The model’s predictions are tested using personnel records from a large bank and are found to be consistent with the observed earnings growth during the first half of the employees’ careers....

  7. Sustainable growth in Europe

    International Nuclear Information System (INIS)

    Andreini, P.

    1993-01-01

    The measures till now adopted did not stop environmental deterioration in Europe and the growth of economic activities in the future will make the situation more and more heavy. The European Communities (EEC) Cabinet launched a long term program for a sustainable growth in Europe, which could conciliate economic needs with environmental protection. This paper presents the first part of the program

  8. Nutrition and growth

    Energy Technology Data Exchange (ETDEWEB)

    Forbes, G.B.

    1977-07-01

    Longitudinal growth data on children who developed obesity during childhood reveal a distinct tendency for height gain to accelerate coincident with or after the onset of excessive weight gain. The magnitude of the relative height increment is related to the degree of overweight. Overnutrition accelerates growth, just as undernutrition retards it.

  9. Growth Modulation in Achondroplasia.

    Science.gov (United States)

    McClure, Philip K; Kilinc, Eray; Birch, John G

    2017-09-01

    Achondroplasia is the most common skeletal dysplasia with a rate of nearly 1/10,000. The development of lower extremity deformity is well documented, and various modes of correction have been reported. There are no reports on the use of growth modulation to correct angular deformity in achondroplasia. Medical Records from 1985 to 2015 were reviewed for the diagnosis of achondroplasia and growth modulation procedures. Patients who had been treated for angular deformity of the legs by growth modulation were identified. A detailed analysis of their medical record and preoperative and final lower extremity radiographs was completed. Four patients underwent growth modulation procedures, all to correct existing varus deformity of the legs. Three of the 4 patients underwent bilateral distal femoral and proximal tibial growth modulation. The remaining patient underwent tibial correction only. Two of the 4 patients had a combined proximal fibular epiphysiodesis. All limbs had some improvement of alignment; however, 1 patient went on to bilateral osteotomies. Only 1 limb corrected to a neutral axis with growth modulation alone at last follow-up, initial implantation was done before 5 years of age. Growth modulation is an effective means for deformity correction in the setting of achondroplasia. However implantation may need to be done earlier than would be typical for patients without achondroplasia. Osteotomy may still be required after growth modulation for incomplete correction.

  10. Empowering growth in Pakistan?

    NARCIS (Netherlands)

    K.A. Siegmann (Karin Astrid); H. Majid (Hadia)

    2014-01-01

    textabstractPakistan's Vision 2025 connects a policy commitment to greater gender equality with inclusive growth. It prioritises a "good quality of life and high living standard for all citizens across regions, gender" and to "achieve an annual average growth rate of 7 to 8 per cent that is

  11. Strategic growth options

    NARCIS (Netherlands)

    Kulatilaka, N.; Perotti, E.C.

    1998-01-01

    We provide a strategic rationale for growth options under uncertainty and imperfect corn-petition. In a market with strategic competition, investment confers a greater capability to take advantage of future growth opportunities. This strategic advantage leads to the capture of a greater share of the

  12. Modeling Exponential Population Growth

    Science.gov (United States)

    McCormick, Bonnie

    2009-01-01

    The concept of population growth patterns is a key component of understanding evolution by natural selection and population dynamics in ecosystems. The National Science Education Standards (NSES) include standards related to population growth in sections on biological evolution, interdependence of organisms, and science in personal and social…

  13. Cluster growth kinetics

    International Nuclear Information System (INIS)

    Dubovik, V.M.; Gal'perin, A.G.; Rikhvitskij, V.S.; Lushnikov, A.A.

    2000-01-01

    Processes of some traffic blocking coming into existence are considered as probabilistic ones. We study analytic solutions for models for the dynamics of both cluster growth and cluster growth with fragmentation in the systems of finite number of objects. Assuming rates constancy of both coalescence and fragmentation, the models under consideration are linear on the probability functions

  14. SLOWER BUT HEALTHIER GROWTH

    Institute of Scientific and Technical Information of China (English)

    LAN XINZHEN

    2010-01-01

    @@ China's economic growth has slowed,economic statistics released on July 15 show,confirming market expectations.But officials said the country's economy is still on track. The recovery has gained traction in China,which registered a double-digit growth of 11.1 percent in the first half of this year.

  15. Trade, Growth, and Poverty

    OpenAIRE

    Dollar, David; Kraay, Aart

    2001-01-01

    The evidence from individual cases and from cross-country analysis supports the view that globalization leads to faster growth and poverty reduction in poor countries. To determine the effect of globalization on growth, poverty, and inequality, the authors first identify a group of developing countries that are participating more in globalization. China, India, and several other large coun...

  16. Measures of Student Growth

    Science.gov (United States)

    Texas Education Agency, 2016

    2016-01-01

    Beginning in the 2017-2018 school year, appraisal systems in Texas, whether the state-recommended system or a locally developed system, will need to include a measure of student growth at the individual teacher level. Student growth measures how much a student progresses academically during his or her time with a particular teacher. It takes into…

  17. Aid and Growth

    DEFF Research Database (Denmark)

    Arndt, Channing; Jones, Edward Samuel; Tarp, Finn

    , are being drawn on the basis of fragile evidence. This paper first assesses the aid-growth literature with a focus on recent contributions. The aid-growth literature is then framed, for the first time, in terms of the Rubin Causal Model, applied at the macroeconomic level. Our results show that aid has......The micro-macro paradox has been revived. Despite broadly positive evaluations at the micro and meso-levels, recent literature has turned decidedly pessimistic with respect to the ability of foreign aid to foster economic growth. Policy implications, such as the complete cessation of aid to Africa...... a positive and statistically significant causal effect on growth over the long run with point estimates at levels suggested by growth theory. We conclude that aid remains an important tool for enhancing the development prospects of poor nations....

  18. Rejuveniles and Growth

    DEFF Research Database (Denmark)

    Barnett, Richard C.; Bhattacharya, Joydeep

    Rejuveniles are "people who cultivate tastes and mind-sets tradi- tionally associated with those younger than themselves." (Noxon, 2006) In this paper, we study a standard AK growth model of overlapping generations populated by rejuve- niles. For our purposes, rejuveniles are old agents who derive...... utility from "keeping up" their consumption with that of the current young. We find that such cross-generational keeping up is capable of generating interesting equilibrium growth dynamics, including growth cycles. No such growth dynamics is possible either in the baseline model, one where...... no such generational consumption externality exists, or for almost any other form of keeping up. Steady-state growth in a world with rejuveniles may be higher than that obtained in the baseline model....

  19. Aid Effectiveness on Growth

    DEFF Research Database (Denmark)

    Doucouliagos, Hristos; Paldam, Martin

    The AEL (aid effectiveness literature) is econo¬metric studies of the macroeconomic effects of development aid. It contains about 100 papers of which 68 are reduced form estimates of theeffect of aid on growth in the recipient country. The raw data show that growth is unconnected to aid......, but the AEL has put so much structure on the data that all results possible have emerged. The present meta study considers both the best-set of the 68 papers and the all-set of 543 regressions published. Both sets have a positive average aid-growth elasticity, but it is small and insignificant: The AEL has...... betweenstudies is real. In particular, the aid-growth association is stronger for Asian countries, and the aid-growth association is shown to have been weaker in the 1970s....

  20. Aid and Growth

    DEFF Research Database (Denmark)

    Tarp, Finn; Mekasha, Tseday Jemaneh

    2013-01-01

    Recent litterature in the meta-analysis category where results from a range of studies are brought together throws doubt on the ability of foreign aid to foster economic growth and development. This article assesses what meta-analysis has to contribute to the litterature on the effectiveness...... of foreign aid in terms of growth impact. We re-examine key hypotheses, and find that the effect of aid on growth is positive and statistically significant. This significant effect is genuine, and not an artefact of publication selection. We also show why our results differ from those published elsewhere....

  1. Aid and Growth

    DEFF Research Database (Denmark)

    Mekasha, Tseday Jemaneh; Tarp, Finn

    Some recent literature in the meta-analysis category where results from a range of studies are brought together throws doubt on the ability of foreign aid to foster economic growth and development. This paper assesses what meta-analysis has to say about the effectiveness of foreign aid in terms...... of the growth impact. We re-examine key hypotheses, and find that the effect of aid on growth is positive and statistically significant. This significant effect is genuine, and not an artefact of publication selection. We also show why our results differ from those published elsewhere....

  2. Environment and Growth

    DEFF Research Database (Denmark)

    Horii, Ryo; Ikefuji, Masako

    . In a less developed country, this link, which we call “limits to growth,” emerges as the “poverty-environment trap,” which explains the persistent international inequality both in terms of income and environment. This link also threatens the sustainability of the world’s economic growth, particularly when...... the emission of greenhouse gases raises the risk of natural disasters. Stronger environmental policies are required to overcome this link. While there is a trade-off between the environment and growth in the short run, we show that an appropriate policy can improve both in the long run....

  3. Normal and abnormal growth plate

    International Nuclear Information System (INIS)

    Kumar, R.; Madewell, J.E.; Swischuk, L.E.

    1987-01-01

    Skeletal growth is a dynamic process. A knowledge of the structure and function of the normal growth plate is essential in order to understand the pathophysiology of abnormal skeletal growth in various diseases. In this well-illustrated article, the authors provide a radiographic classification of abnormal growth plates and discuss mechanisms that lead to growth plate abnormalities

  4. Growth assessment in diagnosis of Fetal Growth Restriction. Review.

    Science.gov (United States)

    Albu, A R; Horhoianu, I A; Dumitrascu, M C; Horhoianu, V

    2014-06-15

    The assessment of fetal growth represents a fundamental step towards the identification of the true growth restricted fetus that is associated to important perinatal morbidity and mortality. The possible ways of detecting abnormal fetal growth are taken into consideration in this review and their strong and weak points are discussed. An important debate still remains about how to discriminate between the physiologically small fetus that does not require special surveillance and the truly growth restricted fetus who is predisposed to perinatal complications, even if its parameters are above the cut-off limits established. In this article, we present the clinical tools of fetal growth assessment: Symphyseal-Fundal Height (SFH) measurement, the fetal ultrasound parameters widely taken into consideration when discussing fetal growth: Abdominal Circumference (AC) and Estimated Fetal Weight (EFW); several types of growth charts and their characteristics: populational growth charts, standard growth charts, individualized growth charts, customized growth charts and growth trajectories.

  5. Plant Growth Promoting Rhizobacteria

    Indian Academy of Sciences (India)

    IAS Admin

    known to improve plant growth in many ways when compared to ... roles in agricultural productivity. ... Sustainable agriculture: Sustainable agriculture involves the successful management of agricultural re- ... For the first time Kloepper et al.

  6. Planar elliptic growth

    Energy Technology Data Exchange (ETDEWEB)

    Mineev, Mark [Los Alamos National Laboratory

    2008-01-01

    The planar elliptic extension of the Laplacian growth is, after a proper parametrization, given in a form of a solution to the equation for areapreserving diffeomorphisms. The infinite set of conservation laws associated with such elliptic growth is interpreted in terms of potential theory, and the relations between two major forms of the elliptic growth are analyzed. The constants of integration for closed form solutions are identified as the singularities of the Schwarz function, which are located both inside and outside the moving contour. Well-posedness of the recovery of the elliptic operator governing the process from the continuum of interfaces parametrized by time is addressed and two examples of exact solutions of elliptic growth are presented.

  7. Floods and Mold Growth

    Science.gov (United States)

    Mold growth may be a problem after flooding. Excess moisture in the home is cause for concern about indoor air quality primarily because it provides breeding conditions for pests, molds and other microorganisms.

  8. Environmentally Sustainable Economic Growth

    Directory of Open Access Journals (Sweden)

    Stelian Brad

    2016-05-01

    Full Text Available Economic growth and sustainable development are important issues for social prosperity. Sustainable development strives for moderate and responsible use within the economic activity of the limited resources of our planet, whereas economic growth does not limit the resource exploitation and energy, being mainly focused on productivity increase. From this perspective, both conceptual and operational contradictions occur between the two pillars of prosperity. This paper looks to these contradictions and proposes some streams of intervention such as economic growth and environmental sustainability to operate in harmony. A structured framework for innovative problem solving is considered in this respect. Results of this research show that it is possible to induce smart measures in the economic system for directing businesses towards new paradigms where economic growth is possible without negative effects on environmental sustainability.

  9. Growth and Your Newborn

    Science.gov (United States)

    ... drink alcohol, or use illegal drugs during pregnancy. Nutrition during pregnancy . Good nutrition is essential for a baby's growth in the uterus and beyond. A poor diet during pregnancy can affect how much a newborn weighs and ...

  10. Globalization, Growth and Poverty

    International Development Research Centre (IDRC) Digital Library (Canada)

    One-pagers are a publication of IDRC's “Globalization, Growth and Poverty” Program Initiative, and are based on findings from the ... Does exporting matter for the poor in South Africa? ... strategies to promote employment and higher wages in.

  11. Globalization, Growth and Poverty

    International Development Research Centre (IDRC) Digital Library (Canada)

    One-pagers are a publication of IDRC's “Globalization, Growth and Poverty” Program Initiative, and are ... great disparities, with earnings among urban workers with higher education being four or five times larger than those of illiterate rural.

  12. Growth of dopamine crystals

    Energy Technology Data Exchange (ETDEWEB)

    Patil, Vidya, E-mail: vidya.patil@ruparel.edu; Patki, Mugdha, E-mail: mugdha.patki@ruparel.edu [D. G. Ruparel College, Senapati Bapat Marg, Mahim, Mumbai – 400 016 (India)

    2016-05-06

    Many nonlinear optical (NLO) crystals have been identified as potential candidates in optical and electro-optical devices. Use of NLO organic crystals is expected in photonic applications. Hence organic nonlinear optical materials have been intensely investigated due to their potentially high nonlinearities, and rapid response in electro-optic effect compared to inorganic NLO materials. There are many methods to grow organic crystals such as vapor growth method, melt growth method and solution growth method. Out of these methods, solution growth method is useful in providing constraint free crystal. Single crystals of Dopamine have been grown by evaporating the solvents from aqueous solution. Crystals obtained were of the size of orders of mm. The crystal structure of dopamine was determined using XRD technique. Images of crystals were obtained using FEG SEM Quanta Series under high vacuum and low KV.

  13. Intrauterine Growth Restriction

    Science.gov (United States)

    ... org editorial staff Categories: Family Health, Infants and Toddlers, Pregnancy and Childbirth, WomenTags: Amniocentesis, Delivery - Cesarean, female, Growth and Development, Obstetrical, Obstetrical ultrasound, Pregnant Women, prenatal care September ...

  14. Growth in liquid media.

    Science.gov (United States)

    Elbing, Karen; Brent, Roger

    2002-08-01

    The procedure for inoculating overnight (starter) cultures of E. coli from a single colony is described along with considerations for growing larger cultures. Also included are two methods for monitoring cell growth using a spectrophotometer or a hemacytometer.

  15. Armenia's Economic Growth Sustainability

    OpenAIRE

    Hayakawa, Tatsuji

    2015-01-01

    Armenia enjoyed 15 years of uninterrupted high economic growth prior to the global financial crisis in 2009. Investment, particularly in the mining and metallurgy sectors, played a key role as a driver of economic growth. Remittances,mostly from Russia, had an effect in sustaining consumption and boosting construction. Armenia has shown some weaknesses in the external sector, due to demands for natural gas, mineral products, machinery, and equipment. Armenia's exports and FDI suffer from the ...

  16. Macroeconomics and Growth Policies

    OpenAIRE

    Jayati Ghosh

    2007-01-01

    This United Nations Background Note on Macroeconomics and Growth provides practical guidance on how to operationalize alternative equitable and employment-generating macroeconomic and growth policies in National Development Strategies. This Policy Note has been developed in cooperation with UN agencies, and has been officially reviewed by distinguished academics/ development specialists such as Jose Antonio Ocampo, Jomo K.S. and Nobel Laureate Joseph Stiglitz.

  17. SMEs, Growth, and Poverty

    OpenAIRE

    Beck, Thorsten; Demirgüç-Kunt, Asli

    2004-01-01

    This Note explores the relationship between the size of the small and medium-size enterprise (SME) sector and economic growth and poverty reduction. A new study finds no support for the widely held belief that SMEs promote higher growth and lower pover ty. But it does provide some support for the view that the quality of the business environment facing all firms, large and small, influen...

  18. FGF growth factor analogs

    Science.gov (United States)

    Zamora, Paul O [Gaithersburg, MD; Pena, Louis A [Poquott, NY; Lin, Xinhua [Plainview, NY; Takahashi, Kazuyuki [Germantown, MD

    2012-07-24

    The present invention provides a fibroblast growth factor heparin-binding analog of the formula: ##STR00001## where R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, X, Y and Z are as defined, pharmaceutical compositions, coating compositions and medical devices including the fibroblast growth factor heparin-binding analog of the foregoing formula, and methods and uses thereof.

  19. Entrepreneurship, Information, and Growth

    Science.gov (United States)

    Bunten, Devin; Weiler, Stephan; Weiler, Stephan; Zahran, Sammy

    2016-01-01

    We examine the contribution to economic growth of entrepreneurial “marketplace information” within a regional endogenous growth framework. Entrepreneurs are posited to provide an input to economic growth through the information revealed by their successes and failures. We empirically identify this information source with the regional variation in establishment births and deaths, which create geographic information asymmetries that influence subsequent entrepreneurial activity and economic growth. We find that local establishment birth and death rates are significantly and positively correlated with subsequent entrepreneurship for US counties. To account for the potential endogeneity caused by forward-looking entrepreneurs, we utilize instruments based on historic mining activity. We find that the information spillover component of local establishment birth and death rates have significant positive effects on subsequent entrepreneurship and employment growth for US counties and metropolitan areas. With the help of these intruments, we show that establishment births have a positive and significant effect on future employment growth within all counties, and that in line with the information hypothesis, local establishment death rates have a similar positive effect within metropolitan counties. PMID:27516625

  20. Bacterial growth kinetics

    International Nuclear Information System (INIS)

    Boonkitticharoen, V.; Ehrhardt, J.C.; Kirchner, P.T.

    1989-01-01

    Quantitative measurement of bacterial growth may be made using a radioassay technique. This method measures, by scintillation counting, the 14 CO 2 derived from the bacterial metabolism of a 14 C-labeled substrate. Mathematical growth models may serve as reliable tools for estimation of the generation rate constant (or slope of the growth curve) and provide a basis for evaluating assay performance. Two models, i.e., exponential and logistic, are proposed. Both models yielded an accurate fit to the data from radioactive measurement of bacterial growth. The exponential model yielded high precision values of the generation rate constant, with an average relative standard deviation of 1.2%. Under most conditions the assay demonstrated no changes in the slopes of growth curves when the number of bacteria per inoculation was changed. However, the radiometric assay by scintillation method had a growth-inhibiting effect on a few strains of bacteria. The source of this problem was thought to be hypersensitivity to trace amounts of toluene remaining on the detector

  1. Endogenous growth and the environment

    NARCIS (Netherlands)

    Withagen, C.A.A.M.; Vellinga, N.

    2001-01-01

    This paper examines the relationship between environmental policy and growth, from the perspective of endogenous growth theory. In particular three standard endogenous growth models are supplemented with environmental issues, such as pollution and exhaustibility of natural resources. It is found

  2. Endogenous growth and environmental policy

    NARCIS (Netherlands)

    Withagen, C.A.A.M.; Vellinga, N.

    2001-01-01

    This paper examines the relationship between environmental policy and growth, from the perspective of endogenous growth theory. In particular three standard endogenous growth models are supplemented with environmental issues, such as pollution and exhaustibility of natural resources. It is found

  3. Rapid population growth.

    Science.gov (United States)

    1972-01-01

    At the current rate of population growth, world population by 2000 is expected to reach 7 billion or more, with developing countries accounting for some 5.4 billion, and economically advanced nations accounting for 1.6 billion. 'Population explosion' is the result of falling mortality rates and continuing high birth rates. Many European countries, and Japan, have already completed what is termed as demographic transition, that is, birth rates have fallen to below 20 births per 1000 population, death rates to 10/1000 population, and annual growth rates are 1% or less; annual growth rates for less developed countries ranged from 2 to 3.5%. Less developed countries can be divided into 3 groups: 1) countries with both high birth and death rates; 2) countries with high birth rates and low death rates; and 3) countries with intermediate and declining birth rates and low death rates. Rapid population growth has serious economic consequences. It encourages inequities in income distribution; it limits rate of growth of gross national product by holding down level of savings and capital investments; it exerts pressure on agricultural production and land; and it creates unemployment problems. In addition, the quality of education for increasing number of chidren is adversely affected, as high proportions of children reduce the amount that can be spent for the education of each child out of the educational budget; the cost and adequacy of health and welfare services are affected in a similar way. Other serious consequences of rapid population growth are maternal death and illness, and physical and mental retardation of children of very poor families. It is very urgent that over a billion births be prevented in the next 30 years to reduce annual population growth rate from the current 2% to 1% per year.

  4. Population growth and consumption.

    Science.gov (United States)

    Chalkley, K

    1997-04-01

    The relationship between population growth, resource consumption, and environmental degradation is complex. The rise in "greenhouse gases" that will cause climatic change is clearly due to human activity, and pollutants are often concentrated in densely populated areas. However, even an area with a negative population growth, such as Russia, can experience severe environmental degradation due to poor management. Consumption patterns have the most effect on ozone depletion, while population growth threatens biodiversity of and within species through the destruction of ecosystems. Migration joins population growth and social factors, such as land inequality, as major causes of deforestation, and global demand for water is expected to increase faster than the rate of population growth. Coastal development and over-fishing threaten to deplete the oceans, while soil quality is threatened by inappropriate land use. Estimates of the earth's carrying capacity range from less than 3 billion to more than 44 billion people, indicating how difficult it is to assess this figure. Development efforts throughout the world may lead to human gains that will ultimately be negated by environmental losses. These factors have led to growing support for environmentally sustainable development.

  5. The Growth Delusion

    Directory of Open Access Journals (Sweden)

    Bob Lloyd

    2009-08-01

    Full Text Available Concern for the environment and a move towards “sustainable development” has assisted progress in a wide range of renewable energy technologies in recent years. The science suggests that a transition from fossil fuels to sustainable sources of energy in a time frame commensurate with the demise of the fossil fuels and prevention of runaway climate change is needed. However, while the movement towards sustainable energy technologies is underway, the World does not want to give up the idea of continuing economic growth. In recent times the financial collapse of October 2008 has given rise to yet another set of pleas from corporations and politicians alike to restart the growth machine. The transition to renewable energy technologies will be difficult to achieve as nowhere within existing economic and political frameworks are the limits to when growth will be curtailed being set. It is possible that the irrational insistence on endless growth as a non negotiable axiom, by a large proportion of the world’s population, may in fact be akin to the similarly irrational belief, by a similarly large proportion of the world’s population, that a supernatural being controls our existence and destiny. The irrationality of religion has recently been examined by Richard Dawkins in “The God Delusion”. Dawkins’ book is used as a starting point to investigate similarities between a belief in God and a belief in continuous growth.

  6. From Limits to Growth to Limitless Growth

    Directory of Open Access Journals (Sweden)

    Garry Jacobs

    2012-04-01

    Full Text Available The publication of the Club of Rome’s landmark report ‘The Limits to Growth’ in 1972 shook the intellectual foundations of social theory and challenged the very premises on which modern economy and prosperity are based. Once set in motion, it led to a revolutionary re-evaluation of human aspirations and economic activities. Among its many consequences, it has stimulated creative minds to look freshly at the underlying processes governing the wealth and welfare of nations. The article then traces their creative impact on the mind of one of the most original economic theorists of our age – Orio Giarini.[*] As ‘The Limits to Growth’ alarmed the world by the unsustainability and dire consequences of unbridled economic growth, Giarini offers a correspondingly affirmative vision of economics with unlimited potential for wealth and welfare.

  7. Experimental intrauterine growth retardation.

    Science.gov (United States)

    van Marthens, E; Harel, S; Zamenshof, S

    1975-01-01

    The effects of experimental intrauterine growth retardation on subsequent fetal development, especially with respect to brain development, were studied in a new animal model. The rabbit was chosen since it has a perinatal pattern of brain development similar to that of the human. Experimental ischemia was induced during the last trimester by ligation of spiral arterioles and the differential effects on fetal development at term (30th gestational day) are reported. Specific brain regions were examined for wet weight, total cell number (DNA) and total protein content. Highly significant decreases in all these parameters were found in both the cortex and cerebellum following experimental intrauterine growth retardation; these two organs were differentially affected. The prospects and advantages of using this animal model for the study of the postnatal "catch-up growth" are discussed.

  8. Urban growth management

    DEFF Research Database (Denmark)

    Jørgensen, Gertrud; Alexander Sick Nielsen, Thomas; Grünfelder, Julien

    2011-01-01

    , and finally urban attractivity policies. Effective regional bodies are needed to deal with urban expansion and peri-urbanisation at a relevant scale; European rural and agricultural policies makes up the main ‘policy complex’ targeting the non-urban area including its land uses; while lastly leverage of urban...... urban growth and curb urban sprawl in a wider sense. Methodology The main methodology of the paper is a desk-research based review of policy options supplemented with field study and interviews in selected cased study regions. This paper consists of two parts. The first part is based on literature...... there are contradictions in the evidence presented in the literature, we believe that it may be safely said that urban growth management policies have an influence on urban growth under certain preconditions including: sufficient time for implementation and continuity of efforts; choice of appropriate policy measures...

  9. New microbial growth factor

    Science.gov (United States)

    Bok, S. H.; Casida, L. E., Jr.

    1977-01-01

    A screening procedure was used to isolate from soil a Penicillium sp., two bacterial isolates, and a Streptomyces sp. that produced a previously unknown microbial growth factor. This factor was an absolute growth requirement for three soil bacteria. The Penicillium sp. and one of the bacteria requiring the factor, an Arthrobacter sp., were selected for more extensive study concerning the production and characteristics of the growth factor. It did not seem to be related to the siderochromes. It was not present in soil extract, rumen fluid, or any other medium component tested. It appears to be a glycoprotein of high molecular weight and has high specific activity. When added to the diets for a meadow-vole mammalian test system, it caused an increased consumption of diet without a concurrent increase in rate of weight gain.

  10. Moral Personality Growth

    Directory of Open Access Journals (Sweden)

    Jana Kalin

    1998-12-01

    Full Text Available Learning in terms of personality growth is a life-long process, just as personality growth itself is a life-long process. Kalin presents a number of psychological theories and their impact on moral development - which is an integral part of personality growth. The paper further treats the formation and changing of beliefs, and the role of education in the two processes. Great emphasis is put on cognitive theories; Kalin explains those formulated by L. Kohlberg and J. Rest. In discussing the process of shaping and changing one's views, special emphasis is put on the environment, or rather the social group an individual belongs to, and on the influence of personality traits and experience. The paper juxtaposes the influence - strengths and weaknesses - of the psychology of persuasion and education on forming and changing one's views, taken into consideration that views consist of cognitive, emotive and conative dimensions.

  11. The double Laplacian growth

    International Nuclear Information System (INIS)

    Loutsenko, I.; Yermolayeva, O.

    2008-06-01

    The dynamics of the idealized Laplacian growth (or the Hele-Shaw problem) can be approximated by the Poiselle flow which in appropriate units takes the form of the Darcy law. In this paper we account for the liquid inertia in the Hele-Shaw problem at zero surface tension limit. The Laplace dynamics for the pressure is extended here with one more for the velocity potential for which we call this growth process the Double Laplacian. The application of the conformal mappings technique leads to doubled dynamics for both the conformal map and the complex potential, which is presented in the paper for the radial and the planar growth. We apply the stability analysis and discuss the integrability for the stated problem. (author)

  12. Stochastic ontogenetic growth model

    Science.gov (United States)

    West, B. J.; West, D.

    2012-02-01

    An ontogenetic growth model (OGM) for a thermodynamically closed system is generalized to satisfy both the first and second law of thermodynamics. The hypothesized stochastic ontogenetic growth model (SOGM) is shown to entail the interspecies allometry relation by explicitly averaging the basal metabolic rate and the total body mass over the steady-state probability density for the total body mass (TBM). This is the first derivation of the interspecies metabolic allometric relation from a dynamical model and the asymptotic steady-state distribution of the TBM is fit to data and shown to be inverse power law.

  13. Time for Growth

    DEFF Research Database (Denmark)

    Boerner, Lars; Severgnini, Battista

    This paper studies the impact of the early adoption of one of the most important high-technology machines in history, the public mechanical clock, on long-run growth in Europe. We avoid endogeneity by considering the relationship between the adoption of clocks with two sets of instruments: distance...... from the first adopters and the appearance of repeated solar eclipses. The latter instrument is motivated by the predecessor technologies of mechanical clocks, astronomic instruments that measured the course of heavenly bodies. We find significant growth rates between 1500 and 1700 in the range of 30...

  14. Inequality, Tolerance, and Growth

    DEFF Research Database (Denmark)

    Bjørnskov, Christian

    This paper argues for the importance of individuals' tolerance of inequality for economic growth. By using the political ideology of governments as a measure of revealed tolerance of inequality, the paper shows that controlling for ideology improves the accuracy with which the effects of inequality...... are measured. Results show that inequality reduces growth but more so in societies where people perceive it as being relatively unfair. Further results indicate that legal quality and social trust are likely transmission channels for the effects of inequality....

  15. Inequality, Tolerance, and Growth

    DEFF Research Database (Denmark)

    Bjørnskov, Christian

    2004-01-01

    This paper argues for the importance of individuals' tolerance of inequality for economic growth. By using the political ideology of governments as a measure of revealed tolerance of inequality, the paper shows that controlling for ideology improves the accuracy with which the effects of inequality...... are measured. Results show that inequality reduces growth but more so in societies where people perceive it as being relatively unfair. Further results indicate that legal quality and social trust are likely transmission channels for the effects of inequality....

  16. Gaussian radial growth

    DEFF Research Database (Denmark)

    Jónsdóttir, Kristjana Ýr; Jensen, Eva B. Vedel

    The growth of planar and spatial objects is often modelled using one-dimensional size parameters, e.g. volume, area or average radius. We take a more detailed approach and model how the boundary of a growing object expands in time. We mainly consider star-shaped planar objects. The model can...... be regarded as a dynamic deformable template model. The limiting shape of the object may be circular but this is only one possibility among a range of limiting shapes. An application to tumour growth is presented. Two extensions of the model, involving time series and Lévy bases, respectively, are briefly...

  17. Intrauterine growth restriction

    Directory of Open Access Journals (Sweden)

    Bernardita Donoso Bernales

    2012-07-01

    Full Text Available It is estimated that the true prevalence of intrauterine growth restriction is 3-10% of all pregnancies, making this fetal condition one of the most frequent obstetric problems, together with premature labor and premature rupture of membranes. The article stresses the importance of early diagnosis because of the associated risks.

  18. Crystal growth and doping

    International Nuclear Information System (INIS)

    Paorici, C.

    1980-01-01

    Section 1 contains a self-consistent review of the basic growth features. After a short introduction concerning the driving force acting in a crystallization process, three main topics are broadly discussed: (i) interface kinetics; (ii) transport kinetics, and (iii) growth stability conditions. On point (i), after definition of the nature of interface, using Temkin's model, the growth mechanisms predicted by Burton, Cabrera and Frank (BCF) and bidimensional nucleation theories are fully developed. On points (ii) and (iii), the differential equations of the constitutional (concentration) and thermal fields are presented and discussed in terms of relevant approximations, suitable boundary conditions and limit values expected in order to have growth stability. Section 2 reports various experimental procedures for growing bulk crystals from the melt, from solutions and from the vapour phase. The basic concepts of Section 1 are amply employed for a critical discussion of possibilities, advantages and drawbacks of the methods described. Along the same lines, in Section 3 the principal epitaxial deposition procedures are highlighted. Section 4 contains a brief account of doping and of stoichiometry-defect control procedures. There is a long, carefully chosen list of bibliographical references. (author)

  19. [Growth of the neurocranium].

    Science.gov (United States)

    Hodacová, Z; Skalská, H

    1998-01-01

    The present study demonstrates the results of evaluation of growth changes of the neurocranium in a set of 98 human skulls of immature individuals aged 6-18/20/ years from the XIII.-XVIII. century. Craniometric values were matched with the corresponding values measured on the skulls of the same age groups from the IX. century and IX.-XII. centuries.

  20. Carboxydotrophic growth of

    NARCIS (Netherlands)

    Geelhoed, J.; Henstra, A.M.; Stams, A.J.M.

    2016-01-01

    This study shows that Geobacter sulfurreducensgrows on carbon monoxide (CO) as electron donor with fumarateas electron acceptor. Geobacter sulfurreducens wastolerant to high CO levels, with up to 150 kPa in the headspacetested. During growth, hydrogen was detected in very slightamounts (~5 Pa). In

  1. Economic Growth Models Transition

    Directory of Open Access Journals (Sweden)

    Coralia Angelescu

    2006-03-01

    Full Text Available The transitional recession in countries of Eastern Europe has been much longer than expected. The legacy and recent policy mistakes have both contributed to the slow progress. As structural reforms and gradual institution building have taken hold, the post-socialist economics have started to recover, with some leading countries building momentum toward faster growth. There is a possibility that in wider context of globalization several of these emerging market economies will be able to catch up with the more advanced industrial economies in a matter of one or two generations. Over the past few years, most candidate countries have made progress in the transition to a competitive market economy, macroeconomic stabilization and structural reform. However their income levels have remained far below those in the Member States. Measured by per capita income in purchasing power standards, there has been a very limited amount of catching up over the past fourteen years. Prior, the distinctions between Solow-Swan model and endogenous growth model. The interdependence between transition and integration are stated in this study. Finally, some measures of macroeconomic policy for sustainable growth are proposed in correlation with real macroeconomic situation of the Romanian economy. Our study would be considered the real convergence for the Romanian economy and the recommendations for the adequate policies to achieve a fast real convergence and sustainable growth.

  2. Economic Growth Models Transition

    Directory of Open Access Journals (Sweden)

    Coralia Angelescu

    2006-01-01

    Full Text Available The transitional recession in countries of Eastern Europe has been much longer than expected. The legacy and recent policy mistakes have both contributed to the slow progress. As structural reforms and gradual institution building have taken hold, the post-socialist economics have started to recover, with some leading countries building momentum toward faster growth. There is a possibility that in wider context of globalization several of these emerging market economies will be able to catch up with the more advanced industrial economies in a matter of one or two generations. Over the past few years, most candidate countries have made progress in the transition to a competitive market economy, macroeconomic stabilization and structural reform. However their income levels have remained far below those in the Member States. Measured by per capita income in purchasing power standards, there has been a very limited amount of catching up over the past fourteen years. Prior, the distinctions between Solow-Swan model and endogenous growth model. The interdependence between transition and integration are stated in this study. Finally, some measures of macroeconomic policy for sustainable growth are proposed in correlation with real macroeconomic situation of the Romanian economy. Our study would be considered the real convergence for the Romanian economy and the recommendations for the adequate policies to achieve a fast real convergence and sustainable growth.

  3. Aid, Growth, and Development

    DEFF Research Database (Denmark)

    Arndt, Channing; Jones, Edward Samuel; Tarp, Finn

    ) ability to pay, and (iv) level of interaction with public officials. Moreover, when informal firms become formal the probability of paying bribes increases. Becoming formal is also associated with a revenue growth premium that is not driven by self-selection of well-performing firms. On average...

  4. Fibroblast growth factor 23

    African Journals Online (AJOL)

    Dr Olaleye

    Systemic phosphate homeostasis is maintained through several hormonal mechanisms which involve fibroblast growth factor 23 (FGF-23), α-klotho, vitamin D and parathyroid hormone. FGF-23 is known to be the major regulator of phosphate balance (Mirams et al., 2004). FGF-23 is a phosphaturic hormone, which is.

  5. Perspectives on population growth.

    Science.gov (United States)

    1996-09-01

    Assume that everyone has the same information on population growth. There are many different opinions on what that information means and what should be done about it. Some people worry about current rates of growth, especially in the context of growing per capita consumption, and believe that all reasonable steps should be taken to reduce rates and stabilize population size. Others believe that growing populations can be accommodated by reducing consumption in rich countries, that technological progress will supply the new resources needed, that the development needed to support a larger population can be sustained, that large population size fosters prosperity, or that birth rates are falling and current growth is just temporary. These are all valid positions worthy of at least debate. Interest groups commonly acknowledgement population growth as a significant issue, but offer no response to it. Sometimes the issue goes unrecognized because it conflicts with a more highly valued personal agenda item. Finally, some responses come from confusion and anger rather than reasoning or self-interest. The proponents of these latter arguments bring nothing constructive to the debate.

  6. Consumption growth accounting

    NARCIS (Netherlands)

    Dietzenbacher, Erik; de Groot, Olaf J.; Los, Bart

    The methodology in this paper combines an input-output structural decomposition approach with the supply-side perspective of mainstream growth accounting. In explaining the intertemporal change in consumption per worker, three sets of effects are distinguished. First, contributions due to several

  7. Global Green Growth Institute

    DEFF Research Database (Denmark)

    Müller, Anders Riel

    2017-01-01

    Har man fulgt historien om Venstres gruppeformand Lars Løkkes rejser på 1. klasse i forbindelse med formandsposten for Global Green Growth Institute (GGGI) er der sikkert nogle der undrer sig over, hvad GGGI er for en størrelse. Medierne præsenterer GGGI som en international klimaorganisation, der...

  8. Geometrical approach to tumor growth

    OpenAIRE

    Escudero, Carlos

    2006-01-01

    Tumor growth has a number of features in common with a physical process known as molecular beam epitaxy. Both growth processes are characterized by the constraint of growth development to the body border, and surface diffusion of cells/particles at the growing edge. However, tumor growth implies an approximate spherical symmetry that makes necessary a geometrical treatment of the growth equations. The basic model was introduced in a former article [C. Escudero, Phys. Rev. E 73, 020902(R) (200...

  9. Epidermal growth factor and growth in vivo

    International Nuclear Information System (INIS)

    Rhodes, J.A.

    1986-01-01

    Epidermal growth factor (EGF) causes a dose-dependent thickening of the epidermis in suckling mice. The cellular mechanisms underlying this thickening were analyzed by measuring the effect of EGF on the cell-cycle. Neonatal mice were given daily injections of either 2ug EGF/g body weight/day or an equivalent volume of saline, and on the seventh day received a single injection of 3 H-thymidine. At various times the mice were perfused with fixative; 1um sections of skin were stained with a modification of Harris' hematoxylin and were autoradiographed. The sections were analyzed using three methods based on the dependence on time after injection of 3 H-thymidine of: frequency of labelled mitoses, labelling index, and reciprocal grains/nucleus. It was found that EGF caused a two-fold increase in the cell production rate. The effect of exogenous EGF on the morphology of gastric mucosa and incisors of suckling mice was also studied. The gastric mucosa appeared thicker in EGF-treated animals, but the effect was not statistically significant. In contrast to its effect on epidermis and gastric mucosa, EGF caused a significant, dose-dependent decrease in the size of the incisors. Because the mouse submandibular salivary gland is the major source of EGF the effect of sialoadenectomy on female reproductive functions was examined. Ablation of the submandibular gland had no effect on: length of estrus cycle, ability of the female to produce litters, length of the gestation period, litter size, and weight of the litter at birth. There was also no effect on survival of the offspring or on age at which the eyelids separated

  10. Unsustainable growth, unsustainable capitalism

    DEFF Research Database (Denmark)

    Næss, Petter

    2006-01-01

    problems, but serve to further highlight the difficulties of changing capitalism towards sustainability. In a profit-oriented economy, capital accumulation is a prime driving force, and non-growth for the economy at large tends to result in serious economic and social crises. On the other hand, a de...... according to which the powers and mechanisms of the natural world are considered totally controllable by humans as if they were mere epiphenomena of the human world. On the other hand, the assumptions of certain ecological economists about the possibility of steady-state capitalism disregard the relation...... between capital and surplus value, which constitutes a strong mechanism driving the capitalist economy toward limitless growth....

  11. Growth and Poverty

    DEFF Research Database (Denmark)

    Arndt, Channing; Leyaro, Vincent; Mahrt, Kristi

    2017-01-01

    This chapter considers the evolution of welfare of the Tanzanian population using a multi-dimensional approach. It also employs a detailed economy-wide model of the Tanzanian economy to explore growth and monetary poverty reduction scenarios from 2007 to 2015. This approach permits assessment...... of the coherence of observed trends in macroeconomic variables and projects consumption poverty outcomes to 2015. In the multi-dimensional approach, we find that real gains have been achieved. On monetary poverty, our model broadly reproduces key macroeconomic features of the past eight years. We find...... that published consumption poverty reductions for 2007 to 2011/12 from the most recent assessment fall within a reasonable to optimistic range. And, the simulations generate broader based growth across the income distribution compared with the recent assessment. Looking forward, the simulations from 2012 to 2105...

  12. Old-growth Policy

    Directory of Open Access Journals (Sweden)

    Diane Vosick

    2007-12-01

    Full Text Available Most federal legislation and policies (e.g., the Wilderness Act, Endangered Species Act, National Forest Management Act fail to speak directly to the need for old-growth protection, recruitment, and restoration on federal lands. Various policy and attitudinal barriers must be changed to move beyond the current situation. For example, in order to achieve the goal of healthy old growth in frequent-fire forests, the public must be educated regarding the evolutionary nature of these ecosystems and persuaded that collaborative action rather than preservation and litigation is the best course for the future of these forests. Land managers and policy makers must be encouraged to look beyond the single-species management paradigm toward managing natural processes, such as fire, so that ecosystems fall within the natural range of variability. They must also see that, given their recent evidence of catastrophic fires, management must take place outside the wildland-urban interface in order to protect old-growth forest attributes and human infrastructure. This means that, in some wilderness areas, management may be required. Land managers, researchers, and policy makers will also have to agree on a definition of old growth in frequent-fire landscapes; simply adopting a definition from the mesic Pacific Northwest will not work. Moreover, the culture within the federal agencies needs revamping to allow for more innovation, especially in terms of tree thinning and wildland fire use. Funding for comprehensive restoration treatments needs to be increased, and monitoring of the Healthy Forest Initiative and Healthy Forest Restoration Act must be undertaken.

  13. Analyzing growth trajectories

    Czech Academy of Sciences Publication Activity Database

    McKeague, I. W.; López-Pintado, S.; Hallin, M.; Šiman, Miroslav

    2011-01-01

    Roč. 2, č. 6 (2011), s. 322-329 ISSN 2040-1744 R&D Projects: GA MŠk(CZ) 1M06047 Institutional research plan: CEZ:AV0Z10750506 Keywords : data depth contours * growth curves * nonparametric Bayes Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 1.556, year: 2011 http://library.utia.cas.cz/separaty/2011/SI/siman-0376411.pdf

  14. Globalization, Growth and Poverty

    International Development Research Centre (IDRC) Digital Library (Canada)

    One-pagers are a publication of IDRC's “Globalization, Growth and Poverty” Program Initiative, ... was among the largest in the world, at 90 percent of the entire value of ... the workforce—including young adults, women, and the elderly who are ... UN ECLAC, 2010. 0. 1. 2. 3. 4. 5. 0. 10. 20. 30. 40. 50. 60. 70. 80. 90+. C o n.

  15. Valuation relationships under growth

    OpenAIRE

    Benavides Franco, Julián

    2003-01-01

    One of the most important topics on valuation is the appropriate relationships between cash flows and rate of returns. I review those relationships under the premise, by Myers (1974), of the cost of debt as the right discount for the tax shield. Different hypotheses have been advanced for the tax shield risk, each one producing different valuation results, especially when growth is present. The consequences of some common mistakes on valuation are explored. One difference between the results ...

  16. DETERMINANTS OF ECONOMIC GROWTH

    OpenAIRE

    Bartosz Totleben

    2013-01-01

    The article is examines the impact of macroeconomic indicators, in particular: human capital, government spending, innovation, political and social stability, on economic growth. In total 12 different indicators describing the economical, political and social conditions are taken into account. The study considers 102 countries between years 1960 and 2012 and two methods of estimation are performed: generalized method of moments (GMM) and fixed effects (FE). The results show the positive impac...

  17. Geography, Depreciation, and Growth

    OpenAIRE

    Solomon M. Hsiang; Amir S. Jina

    2015-01-01

    It has been proposed that geography influences economic growth for many reasons. Previous analyses of comparative development seem to have sidestepped the question of location-dependent depreciation. However the construction of new measures of tropical cyclone exposure enables us to consider the potential impact of this single source of capital depreciation. Using an estimate of asset destruction due to tropical cyclones, we identify the "sandcastle depreciation" rate, and find support for lo...

  18. Can Growth Be Green?

    Science.gov (United States)

    Gough, Ian

    2015-01-01

    This short article, based on a presentation at the London School of Economics, criticizes the common opinion that "green growth" offers a relatively painless - some even say pain-free - transition path for capitalist economies. After a brief summary of the daunting arithmetic entailed in combining fast decarbonization with continuing growth, the article advances 3 propositions. First, market-based carbon mitigation programs, such as carbon trading, cannot be sufficient and must be coupled with other policy pillars that foster transformative investment and widespread regulation. Second, a political economy of climate policy needs to draw on the lessons of comparative social policy research, which emphasizes the role of international pressures, interests, institutions, and ideas. Taking these into account gives a more realistic perspective on climate policy making in today's neoliberal world. Third, more radical policies on both consumption and production are called for, to ensure that carbon mitigation is not pursued at the expense of equity and social welfare. These include policies to restrain high-carbon luxury consumption and a transition toward shorter paid working time. The conclusion is that a realistic program of green growth will be immensely difficult and entail radical political change. © SAGE Publications 2015.

  19. Facilitating post traumatic growth

    Directory of Open Access Journals (Sweden)

    Cox Helen

    2004-07-01

    Full Text Available Abstract Background Whilst negative responses to traumatic injury have been well documented in the literature, there is a small but growing body of work that identifies posttraumatic growth as a salient feature of this experience. We contribute to this discourse by reporting on the experiences of 13 individuals who were traumatically injured, had undergone extensive rehabilitation and were discharged from formal care. All participants were injured through involvement in a motor vehicle accident, with the exception of one, who was injured through falling off the roof of a house. Methods In this qualitative study, we used an audio-taped in-depth interview with each participant as the means of data collection. Interviews were transcribed verbatim and analysed thematically to determine the participants' unique perspectives on the experience of recovery from traumatic injury. In reporting the findings, all participants' were given a pseudonym to assure their anonymity. Results Most participants indicated that their involvement in a traumatic occurrence was a springboard for growth that enabled them to develop new perspectives on life and living. Conclusion There are a number of contributions that health providers may make to the recovery of individuals who have been traumatically injured to assist them to develop new views of vulnerability and strength, make changes in relationships, and facilitate philosophical, physical and spiritual growth.

  20. Crystal Growth Technology

    Science.gov (United States)

    Scheel, Hans J.; Fukuda, Tsuguo

    2004-06-01

    This volume deals with the technologies of crystal fabrication, of crystal machining, and of epilayer production and is the first book on industrial and scientific aspects of crystal and layer production. The major industrial crystals are treated: Si, GaAs, GaP, InP, CdTe, sapphire, oxide and halide scintillator crystals, crystals for optical, piezoelectric and microwave applications and more. Contains 29 contributions from leading crystal technologists covering the following topics: General aspects of crystal growth technology Silicon Compound semiconductors Oxides and halides Crystal machining Epitaxy and layer deposition Scientific and technological problems of production and machining of industrial crystals are discussed by top experts, most of them from the major growth industries and crystal growth centers. In addition, it will be useful for the users of crystals, for teachers and graduate students in materials sciences, in electronic and other functional materials, chemical and metallurgical engineering, micro-and optoelectronics including nanotechnology, mechanical engineering and precision-machining, microtechnology, and in solid-state sciences.

  1. [Hormones and hair growth].

    Science.gov (United States)

    Trüeb, R M

    2010-06-01

    With respect to the relationship between hormones and hair growth, the role of androgens for androgenetic alopecia (AGA) and hirsutism is best acknowledged. Accordingly, therapeutic strategies that intervene in androgen metabolism have been successfully developed for treatment of these conditions. Clinical observations of hair conditions involving hormones beyond the androgen horizon have determined their role in regulation of hair growth: estrogens, prolactin, thyroid hormone, cortisone, growth hormone (GH), and melatonin. Primary GH resistance is characterized by thin hair, while acromegaly may cause hypertrichosis. Hyperprolactinemia may cause hair loss and hirsutism. Partial synchronization of the hair cycle in anagen during late pregnancy points to an estrogen effect, while aromatase inhibitors cause hair loss. Hair loss in a causal relationship to thyroid disorders is well documented. In contrast to AGA, senescent alopecia affects the hair in a diffuse manner. The question arises, whether the hypothesis that a causal relationship exists between the age-related reduction of circulating hormones and organ function also applies to hair and the aging of hair.

  2. Multiple growth regimes: Insights from unified growth theory

    OpenAIRE

    Galor, Oded

    2007-01-01

    Unified Growth Theory uncovers the forces that contributed to the existence of multiple growth regimes and the emergence of convergence clubs. It suggests that differential timing of take-offs from stagnation to growth segmented economies into three fundamental regimes: slow growing economies in a Malthusian regime, fast growing countries in a sustained growth regime, and economies in the transition between these regimes. In contrast to existing research that links regime switching thresholds...

  3. Gambling on growth.

    Science.gov (United States)

    Feeney, A

    1990-01-01

    When the assumption is made that economic growth must be increased by 10% to accommodate population increases and to reduce poverty, the question is raised as to whether or not sustainable development is possible. The human population increased 3 times since 1900, and global economic activity has increased 7 times faster than population. Use of fossil fuels has increased by 30 times, and industrial production has increased by 50 times. The by-products of population growth and economic activity are loss of tropical rainforests; species extinction; desertification in Africa, India, and the US; toxic and radioactive pollution; and greenhouse warming and ozone depletion. The atmosphere's stability and human habitation is threatened. Sustainable development, as defined by the World Commission on Environment and Development (WCED) in "Our Common Future," is meeting present needs but not at the expense of future needs. Economic growth must proceed at different rates in different countries to close the gap between the rich and poor. Economic expansion has been criticized by the president of Negative Population Growth and the Environmental Defense Fund's coordinator of reform for the World Bank's environmental policies and Third World countries. US government response during the Reagan administration has been indifference, while support has come from the World Resources Institute, the Worldwatch Institute, the US National Wildlife Federation, and the Population Reference Bureau. Recent support has come from signers of the "G-7 Summit" and from IBM and the Dow Chemical Company. A few shared tenets are 1) that economic development is not sustainable, 2) environmental reforms are necessary to make development sustainable, 3) a trade-off is needed to increase Third World energy use, and 4) population must be stabilized. Many proposals have been offered including reducing population to 2 billion, or 40% of the current level. Reducing poverty globally is an environmentally sound

  4. Growth arrest despite growth hormone replacement, post-craniopharyngioma surgery.

    Science.gov (United States)

    DeVile, C J; Hayward, R D; Neville, B G; Grant, D B; Stanhope, R

    1995-01-01

    Children with growth failure, whether secondary to an endocrinopathy such as growth hormone deficiency or secondary to neurological handicap with poor nutrient intake, grow at a subnormal rate but it is most unusual for a child to have complete growth arrest. PMID:7745571

  5. Growth throughout childhood of children born growth restricted

    NARCIS (Netherlands)

    Beukers, Fenny; Rotteveel, Joost; van Weissenbruch, Mirjam M.; Ganzevoort, Wessel; van Goudoever, Johannes B.; van Wassenaer-Leemhuis, Aleid G.

    2017-01-01

    Many studies that examine growth in growth-restricted children at birth do not discriminate between fetal growth restriction (FGR) and small for gestational age (SGA). These terms however are not synonymous. In SGA, stunting and increased weight gain have been reported. We do not know if this holds

  6. Entrepreneurial Diversity and Economic Growth

    NARCIS (Netherlands)

    I. Verheul (Ingrid); A.J. van Stel (André)

    2007-01-01

    textabstractMost studies investigating the relationship between entrepreneurship and economic growth treat entrepreneurs as a homogeneous group. This study investigates the impact of entrepreneurial diversity on national economic growth. Using data for 36 countries participating in the Global

  7. Market Acceptance of Smart Growth

    Science.gov (United States)

    This report finds that smart growth developments enjoy market acceptance because of stability in prices over time. Housing resales in smart growth developments often have greater appreciation than their conventional suburban counterparts.

  8. Your Baby's Growth: 12 Months

    Science.gov (United States)

    ... Safe Videos for Educators Search English Español Your Baby's Growth: 12 Months KidsHealth / For Parents / Your Baby's ... doubled his or her birth weight. Is My Baby Growing Normally? Babies' growth begins to slow as ...

  9. Tax Havens, Growth, and Welfare

    OpenAIRE

    Chu, Hsun; Lai, Ching-Chong; Cheng, Chu-Chuan

    2013-01-01

    This paper develops an endogenous growth model featuring tax havens, and uses it to examine how the existence of tax havens affects the economic growth rate and social welfare in high-tax countries. We show that the presence of tax havens generates two conflicting channels in determining the growth effect. First, the public investment effect states that tax havens may erode tax revenues and in turn decrease the government’s infrastructure expenditure, thereby reducing growth. Second, the t...

  10. Corporate Stability and Economic Growth

    OpenAIRE

    He, Kathy S.; Morck, Randall; Yeung, Bernard

    2003-01-01

    Greater instability in a country's list of top corporations is associated with faster economic growth. This faster growth is primarily due to faster growth in total factor productivity in industrialized countries, and faster capital accumulation in developing countries. These findings are consistent with the view that economic growth is more closely tied to the rise of new large firms than to the prosperity of established large firms. Although a stable list of leading corporations is highly c...

  11. The poverty elasticity of growth

    OpenAIRE

    Heltberg, Rasmus

    2002-01-01

    How much does economic growth contribute to poverty reduction? I discuss analytical and empirical approches to assess the poverty elasticity of growth, and emphasize that the relationship between growth and poverty change is non-constant. For a given poverty measure, it depends on initial inequality and on the location of the poverty line relative to mean income. In most cases, growth is more important for poverty reduction than changes in inequality, but this does not tender inequality unimp...

  12. Economic growth and business cycles

    NARCIS (Netherlands)

    Canton, E.J.F.

    1997-01-01

    This thesis contains five essays on economic growth and business cycles. The main focus is on the interaction between economic growth and the cycle: is cyclical variability good or bad for the long-run rate of economic growth? The introduction aims to provide some empirical evidence for an

  13. PUBLIC GOODS, CORRUPTION AND GROWTH???

    OpenAIRE

    Ratbek Dzhumashev

    2006-01-01

    In this paper, we analyse implications of corruption on growth. We extend existing growth models by incorporating ubiquitous corruption as a by-product of the public sector. Corruption affects both taxation and public good provision, and therefore causes income redistribution and inefficiencies in the public sector. These effects of corruption lead to lower growth through distortions of investment incentives and resources allocation.

  14. Advanced dendritic web growth development

    Science.gov (United States)

    Hopkins, R. H.

    1985-01-01

    A program to develop the technology of the silicon dendritic web ribbon growth process is examined. The effort is being concentrated on the area rate and quality requirements necessary to meet the JPL/DOE goals for terrestrial PV applications. Closed loop web growth system development and stress reduction for high area rate growth is considered.

  15. Regulators of growth plate maturation

    NARCIS (Netherlands)

    Emons, Joyce Adriana Mathilde

    2010-01-01

    Estrogen is known to play an important role in longitudinal bone growth and growth plate maturation, but the mechanism by which estrogens exert their effect is not fully understood. In this thesis this role is further explored. Chapter 1 contains a general introduction to longitudinal bone growth

  16. Great growth debate: an argument for rational growth policies

    Energy Technology Data Exchange (ETDEWEB)

    Bond, E; Koven, A

    1978-05-01

    The argument for rational growth policies in Canada advocates an expanding economy as the only one able to compensate both winners and losers. A constant growth rate--whether it is positive, negative, or zero--cannot work. A desirable growth rate must be flexible in the long term, which means that policies for zero growth must select only parts of the economy. On one hand, the creation of aritifical needs by advertising, urban expansion, and demographic growth in over-populated countries should be halted. On the other hand, we must expand necessary human welfare services. Zero growth does not mean that we must go back to poverty, asceticism, and constraint. An optimum growth policy will aim for moderation in all things. (Abstract, edited)

  17. Growth hormone in intra-uterine growth retarded newborns.

    Science.gov (United States)

    Setia, Sajita; Sridhar, M G; Bhat, Vishnu; Chaturvedula, Latha

    2007-11-01

    To study growth hormone levels in IUGR and healthy controls and its association with birth weight and ponderal index. We studied 50 Intra uterine growth retarded (IUGR) and 50 healthy newborns born at term by vaginal delivery in JIPMER, Pondicherry, India. Cord blood was collected at the time of delivery for measurement of growth hormone. When compared with healthy newborns, IUGR newborns had higher growth hormone levels (mean +/- SD, 23.5 +/- 15.6 vs 16.2 +/- 7.61 ngm/ml, P = 0.019). A negative correlation was identified between growth hormone levels and birth weight (r2 = - 0.22, P = 0.03) and ponderal index (r2 = - 0.36, P = 0.008). Correlation of growth hormone levels was much more confident with ponderal index than with birth weight. At birth IUGR infants display increased growth hormone levels which correlate with ponderal index much more confidently than with birth weight.

  18. Biofuels, poverty, and growth

    DEFF Research Database (Denmark)

    Arndt, Channing; Benfica, Rui; Tarp, Finn

    2010-01-01

    and accrual of land rents to smallholders, compared with the more capital-intensive plantation approach. Moreover, the benefits of outgrower schemes are enhanced if they result in technology spillovers to other crops. These results should not be taken as a green light for unrestrained biofuels development...... Mozambique's annual economic growth by 0.6 percentage points and reduces the incidence of poverty by about 6 percentage points over a 12-year phase-in period. Benefits depend on production technology. An outgrower approach to producing biofuels is more pro-poor, due to the greater use of unskilled labor...

  19. Aid and sectoral growth

    DEFF Research Database (Denmark)

    Selaya, Pablo; Thiele, Rainer

    2010-01-01

    This article examines empirically the proposition that aid to poor countries is detrimental for external competitiveness, giving rise to Dutch disease type effects. At the aggregate level, aid is found to have a positive effect on growth. A sectoral decomposition shows that the effect is (i......) significant and positive in the tradable and the nontradable sectors, and (ii) equally strong in both sectors. The article thus provides no empirical support for the hypothesis that aid reduces external competitiveness in developing countries. A possible reason for this finding is the existence of large idle...

  20. Modeling urban fire growth

    International Nuclear Information System (INIS)

    Waterman, T.E.; Takata, A.N.

    1983-01-01

    The IITRI Urban Fire Spread Model as well as others of similar vintage were constrained by computer size and running costs such that many approximations/generalizations were introduced to reduce program complexity and data storage requirements. Simplifications were introduced both in input data and in fire growth and spread calculations. Modern computational capabilities offer the means to introduce greater detail and to examine its practical significance on urban fire predictions. Selected portions of the model are described as presently configured, and potential modifications are discussed. A single tract model is hypothesized which permits the importance of various model details to be assessed, and, other model applications are identified

  1. Growth, Development and Sustainability

    Directory of Open Access Journals (Sweden)

    Irina-Virginia Dragulanescu

    2013-11-01

    Full Text Available Describing the relationship of interdependence through the materials balance, will be argued how the economy is a subset of the environment and the environment the natural limit to any economic initiative, or the limits imposed by the laws of thermodynamics. The theoretical debate moves, then, from the concept of growth to that of development, understood this in its three dimensions: economic, social, environmental. Bring the different environmental positions in four versions of sustainability, with the gained awareness that it’s “a spectrum of overlapping sustainability positions from very weak to very strong”.

  2. Urban Growth and Transportation

    OpenAIRE

    Gilles Duranton; Matthew A. Turner

    2012-01-01

    We estimate the effects of major roads and public transit on the growth of major cities in the US between 1980 and 2000. We find that a 10% increase in a city’s stock of roads causes about a 2% increase in its population and employment and a small decrease in its share of poor households over this 20 year period. We also find that a 10% increase in a city’s stock of large buses causes about a 0.8% population increase and a small increase in the share of poor households over this period. To es...

  3. Developing principles of growth

    DEFF Research Database (Denmark)

    Neergaard, Helle; Fleck, Emma

    of the principles of growth among women-owned firms. Using an in-depth case study methodology, data was collected from women-owned firms in Denmark and Ireland, as these countries are similar in contextual terms, e.g. population and business composition, dominated by micro, small and medium-sized enterprises....... Extending on principles put forward in effectuation theory, we propose that women grow their firms according to five principles which enable women’s enterprises to survive in the face of crises such as the current financial world crisis....

  4. Controlled 1.1-1.6 μm luminescence in gold-free multi-stacked InAs/InP heterostructure nanowires.

    Science.gov (United States)

    Zhang, Guoqiang; Tateno, Kouta; Birowosuto, Muhammad Danang; Notomi, Masaya; Sogawa, Tetsuomi; Gotoh, Hideki

    2015-03-20

    We report controlled 1.1-1.6 μm luminescence in gold-free multi-stacked InAs/InP heterostructure nanowires (NWs). We realized the NWs by using an indium-particle-assisted vapor-liquid-solid synthesis approach. The growth temperature, as low as 320 °C, enables the formation of an atomically abrupt InP/InAs interface by supressing the diffusion and weakening the reservoir effect in the indium droplet. The low growth temperature also enables us to grow multi-stacked InAs/InP NWs in the axial direction without any growth on the NW side face. The high controllability of the growth technology ensures that the luminescence can be tailored by the thickness of InAs segment in InP NWs and cover the 1.3-1.5 μm telecommunication window range. By using the nanoscale-spatial-resolution technology combing cathodoluminescence with scanning electron microscopy, we directly correlated the site of different-thickness InAs segments with its luminescence property in a single NW and demonstrate the InAs-thickness-controlled energy of optical emission in 1.1-1.6 μm.

  5. Ion beam assisted film growth

    CERN Document Server

    Itoh, T

    2012-01-01

    This volume provides up to date information on the experimental, theoretical and technological aspects of film growth assisted by ion beams.Ion beam assisted film growth is one of the most effective techniques in aiding the growth of high-quality thin solid films in a controlled way. Moreover, ion beams play a dominant role in the reduction of the growth temperature of thin films of high melting point materials. In this way, ion beams make a considerable and complex contribution to film growth. The volume will be essential reading for scientists, engineers and students working in thi

  6. Leverage, Investment, and Firm Growth

    OpenAIRE

    Larry Lang; Eli Ofek; Rene M. Stulz

    1995-01-01

    We show that there is a negative relation between leverage and future growth at the firm level and, for diversified firms, at the segment level. Further, this negative relation between leverage and growth holds for firms with low Tobin's q, but not for high-q firms or firms in high-q industries. Therefore, leverage does not reduce growth for firms known to have good investment opportunities, but is negatively related to growth for firms whose growth opportunities are either not recognized by ...

  7. Probabilistic Mass Growth Uncertainties

    Science.gov (United States)

    Plumer, Eric; Elliott, Darren

    2013-01-01

    Mass has been widely used as a variable input parameter for Cost Estimating Relationships (CER) for space systems. As these space systems progress from early concept studies and drawing boards to the launch pad, their masses tend to grow substantially, hence adversely affecting a primary input to most modeling CERs. Modeling and predicting mass uncertainty, based on historical and analogous data, is therefore critical and is an integral part of modeling cost risk. This paper presents the results of a NASA on-going effort to publish mass growth datasheet for adjusting single-point Technical Baseline Estimates (TBE) of masses of space instruments as well as spacecraft, for both earth orbiting and deep space missions at various stages of a project's lifecycle. This paper will also discusses the long term strategy of NASA Headquarters in publishing similar results, using a variety of cost driving metrics, on an annual basis. This paper provides quantitative results that show decreasing mass growth uncertainties as mass estimate maturity increases. This paper's analysis is based on historical data obtained from the NASA Cost Analysis Data Requirements (CADRe) database.

  8. FACET Emittance Growth

    Energy Technology Data Exchange (ETDEWEB)

    Frederico, J; Hogan, M.J.; Nosochkov, Y.; Litos, M.D.; Raubenheimer, T.; /SLAC

    2011-04-05

    FACET, the Facility for Advanced Accelerator and Experimental Tests, is a new facility being constructed in sector 20 of the SLAC linac primarily to study beam driven plasma wakefield acceleration. The FACET beamline consists of a chicane and final focus system to compress the 23 GeV, 3.2 nC electron bunches to {approx}20 {micro}m long and {approx}10 {micro}m wide. Simulations of the FACET beamline indicate the short-duration and large, 1.5% rms energy spread beams may suffer a factor of four emittance growth from a combination of chromaticity, incoherent synchrotron radiation (ISR), and coherent synchrotron radiation (CSR). Emittance growth is directly correlated to head erosion in plasma wakefield acceleration and is a limiting factor in single stage performance. Studies of the geometric, CSR, and ISR components are presented. Numerical calculation of the rms emittance can be overwhelmed by long tails in the simulated phase space distributions; more useful definitions of emittance are given. A complete simulation of the beamline is presented as well, which agrees with design specifications.

  9. China urges rapid growth

    International Nuclear Information System (INIS)

    Hendry, S.

    1993-01-01

    This time last year China's paramount leader, Deng Xiaoping, launched the country on another bout of fast-paced economic growth and restructuring. After three years of riding out political and economic clampdown, foreign chemical companies were jerked awake by major changes in China's chemical industry. As the state becomes less involved with managing the economy, unleashing 12% gross national product growth, closer involvement with domestic factories has become attractive and essential. MCI officials say government funds will now be channeled toward clearing energy and transport bottlenecks, and chemical enterprises will be given more chance to turn a profit. They will be allowed to issue shares, seek foreign investment partners themselves, and bypass trading companies like China National Import-Export Corp. (Sinochem), the former state monopoly. Foreign analysts question whether China's finances and oil resources can support expansion. Even if they can, Cai estimates that ethylene imports will remain around the present level of 1 million tons. To further guarantee chemical supplies, China has invested in urea and polypropylene plants in the US and polystyrene plant in Hong Kong

  10. FACET Emittance Growth

    International Nuclear Information System (INIS)

    Frederico, Joel

    2011-01-01

    FACET, the Facility for Advanced Accelerator and Experimental Tests, is a new facility being constructed in sector 20 of the SLAC linac primarily to study beam driven plasma wakefield acceleration. The FACET beamline consists of a chicane and final focus system to compress the 23 GeV, 3.2 nC electron bunches to ∼20 (micro)m long and ∼10 (micro)m wide. Simulations of the FACET beamline indicate the short-duration and large, 1.5% rms energy spread beams may suffer a factor of four emittance growth from a combination of chromaticity, incoherent synchrotron radiation (ISR), and coherent synchrotron radiation (CSR). Emittance growth is directly correlated to head erosion in plasma wakefield acceleration and is a limiting factor in single stage performance. Studies of the geometric, CSR, and ISR components are presented. Numerical calculation of the rms emittance can be overwhelmed by long tails in the simulated phase space distributions; more useful definitions of emittance are given. A complete simulation of the beamline is presented as well, which agrees with design specifications.

  11. Molecular mechanisms of crystal growth

    International Nuclear Information System (INIS)

    Pina, C. M.

    2000-01-01

    In this paper I present an example of the research that the Mineral Surface Group of the Munster University is conducting in the field of Crystal Growth. Atomic Force Microscopy (Am) in situ observations of different barite (BaSO4) faces growing from aqueous solutions, in combination with computer simulations of the surface attachment of growth units allows us to test crystal growth models. Our results demonstrate the strong structural control that a crystal can exert on its own growth, revealing also the limitation of the classical crystal growth theories (two dimensional nucleation and spiral growth models) in providing a complete explanation for the growth behaviour at a molecular scale. (Author) 6 refs

  12. Springer Handbook of Crystal Growth

    CERN Document Server

    Dhanaraj, Govindhan; Prasad, Vishwanath; Dudley, Michael

    2010-01-01

    Over the years, many successful attempts have been made to describe the art and science of crystal growth. Most modern advances in semiconductor and optical devices would not have been possible without the development of many elemental, binary, ternary, and other compound crystals of varying properties and large sizes. The objective of the Springer Handbook of Crystal Growth is to present state-of-the-art knowledge of both bulk and thin-film crystal growth. The goal is to make readers understand the basics of the commonly employed growth processes, materials produced, and defects generated. Almost 100 leading scientists, researchers, and engineers from 22 different countries from academia and industry have been selected to write chapters on the topics of their expertise. They have written 52 chapters on the fundamentals of bulk crystal growth from the melt, solution, and vapor, epitaxial growth, modeling of growth processes and defects, techniques of defect characterization as well as some contemporary specia...

  13. Geometrical approach to tumor growth.

    Science.gov (United States)

    Escudero, Carlos

    2006-08-01

    Tumor growth has a number of features in common with a physical process known as molecular beam epitaxy. Both growth processes are characterized by the constraint of growth development to the body border, and surface diffusion of cells and particles at the growing edge. However, tumor growth implies an approximate spherical symmetry that makes necessary a geometrical treatment of the growth equations. The basic model was introduced in a former paper [C. Escudero, Phys. Rev. E 73, 020902(R) (2006)], and in the present work we extend our analysis and try to shed light on the possible geometrical principles that drive tumor growth. We present two-dimensional models that reproduce the experimental observations, and analyze the unexplored three-dimensional case, for which interesting conclusions on tumor growth are derived.

  14. Rapid growth within India

    International Nuclear Information System (INIS)

    Hayes, D.

    2000-01-01

    The Indian government has published (in Hydrocarbon Vision 2025) its ideas for a long term strategy for its oil industry which is currently growing at an unprecedented rate. Increasing domestic production and investment in oil exploration and production overseas figure strongly in the plan. At present, India has a refining surplus but with an annual growth of 8-10%, this will disappear in the next 2-3 years. The report recommends that India should maintain 90% self-sufficiency in refining. The report sees development of the domestic oil industry as globally competitive and helping safeguard India's assets. The capability of India's refineries, current upgrading, the newer refineries and plans for new projects are all mentioned

  15. 2010 responsible growth report

    International Nuclear Information System (INIS)

    2010-01-01

    The report addresses several development and growth perspectives for AREVA: its integrated business model, the synergy and complementarities between nuclear and renewable energies, the sustainable development dimension of its industrial development, its sales revenue result, the reduction of its environmental footprint, its development on all continents, its balanced governance, the simplification of its capital structure, and the actions performed by its Foundation. Then, it discusses ten challenges for the company: ensuring safety and performance throughout the reactor life cycle, making the EPR reactor a standard of safety, maintaining relations based on trust with our stake holders, staying in the lead, accelerating the development of renewable energies, being a trusted partner to growing economies, being a model in mine management, promoting sustainable, effective and safe recycling of used fuel, improving performance continuously, offering development prospects to all employees. It briefly presents ten successes achieved in 2010 and indicates ten sustainable development commitments. Document in French and in English

  16. Employment without Growth

    DEFF Research Database (Denmark)

    Nørgaard, Jørgen

    work over more income and consumption. Lower work input to production can take many differnet forms, such as job sharing, lowering production efficiency, reduction in labor force, etc. In this light it seems ridiculous to argue for certain economic development course on the ground that it will create...... more work. There are no indication that growth at Western economies increases satisfaction or happiness. A new look at the full economy divides it into professional economy and amateur economy, and it is suggested that a reversal of the trend hitherto to draw still more of the whole economy...... into the professional sphere, GDP, could contribute at the same time to a better satisfaction and a more sustainable development....

  17. Growth outside the core.

    Science.gov (United States)

    Zook, Chris; Allen, James

    2003-12-01

    Growth in an adjacent market is tougher than it looks; three-quarters of the time, the effort fails. But companies can change those odds dramatically. Results from a five-year study of corporate growth conducted by Bain & Company reveal that adjacency expansion succeeds only when built around strong core businesses that have the potential to become market leaders. And the best place to look for adjacency opportunities is inside a company's strongest customers. The study also found that the most successful companies were able to consistently, profitably outgrow their rivals by developing a formula for pushing out the boundaries of their core businesses in predictable, repeatable ways. Companies use their repeatability formulas to expand into any number of adjacencies. Some companies make repeated geographic moves, as Vodafone has done in expanding from one geographic market to another over the past 13 years, building revenues from $1 billion in 1990 to $48 billion in 2003. Others apply a superior business model to new segments. Dell, for example, has repeatedly adapted its direct-to-customer model to new customer segments and new product categories. In other cases, companies develop hybrid approaches. Nike executed a series of different types of adjacency moves: it expanded into adjacent customer segments, introduced new products, developed new distribution channels, and then moved into adjacent geographic markets. The successful repeaters in the study had two common characteristics. First, they were extraordinarily disciplined, applying rigorous screens before they made an adjacency move. This discipline paid off in the form of learning curve benefits, increased speed, and lower complexity. And second, in almost all cases, they developed their repeatable formulas by studying their customers and their customers' economics very, very carefully.

  18. International growth of neuropsychology.

    Science.gov (United States)

    Ponsford, Jennie

    2017-11-01

    Twenty-five years ago, the field of neuropsychology was well established in North America, Europe, and Australia, with less presence elsewhere. This article discusses the development of neuropsychology over the last 25 years in other regions. The growth of neuropsychology in Asia, Africa, the Middle East, Central and South America, and New Zealand is reviewed. Sources drawn on include a 2016 edition of The Clinical Neuropsychologist describing the practice of neuropsychology in 18 countries; papers on the profession of neuropsychology in Latin America (Arango-Lasprilla, Stevens, Paredes, Ardila, & Rivera, 2016), the history of neuropsychology in Asia (Lee, Wang, & Collinson, 2016), and neuropsychology in Central America (Judd, 2017); INSNET; and personal communications. There has been tremendous variability in the development of neuropsychology across these regions over the last 25 years. Obstacles to the growth of neuropsychology have included economic constraints on health care provision, limited availability of appropriate assessment and treatment methods, linguistic diversity and illiteracy, stigma toward and/or lack of awareness of neuropsychological disorders, lack of graduate training and clinical supervision, absence of accreditation of neuropsychologists as a clinical profession, poor pay, and diminished visibility of the field within the regional culture. Despite these obstacles, neuropsychological research and practice is establishing itself in these regions and has grown significantly over the last quarter century. Major challenges remain in establishing awareness of the significance of and developing culturally appropriate methods of assessing and rehabilitating cognitive aspects of brain disorders, training programs, recognition as a profession, and dedicated funding for neuropsychology positions. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

  19. Thermodynamics of firms' growth

    Science.gov (United States)

    Zambrano, Eduardo; Hernando, Alberto; Hernando, Ricardo; Plastino, Angelo

    2015-01-01

    The distribution of firms' growth and firms' sizes is a topic under intense scrutiny. In this paper, we show that a thermodynamic model based on the maximum entropy principle, with dynamical prior information, can be constructed that adequately describes the dynamics and distribution of firms' growth. Our theoretical framework is tested against a comprehensive database of Spanish firms, which covers, to a very large extent, Spain's economic activity, with a total of 1 155 142 firms evolving along a full decade. We show that the empirical exponent of Pareto's law, a rule often observed in the rank distribution of large-size firms, is explained by the capacity of economic system for creating/destroying firms, and that can be used to measure the health of a capitalist-based economy. Indeed, our model predicts that when the exponent is larger than 1, creation of firms is favoured; when it is smaller than 1, destruction of firms is favoured instead; and when it equals 1 (matching Zipf's law), the system is in a full macroeconomic equilibrium, entailing ‘free’ creation and/or destruction of firms. For medium and smaller firm sizes, the dynamical regime changes, the whole distribution can no longer be fitted to a single simple analytical form and numerical prediction is required. Our model constitutes the basis for a full predictive framework regarding the economic evolution of an ensemble of firms. Such a structure can be potentially used to develop simulations and test hypothetical scenarios, such as economic crisis or the response to specific policy measures. PMID:26510828

  20. [Economic growth with zero population growth and with declining population].

    Science.gov (United States)

    Kurz, R

    1982-05-01

    The effects of both zero population growth and a declining population on economic growth are considered. Although the neoclassical theory of economic growth leads to optimistic results in such cases, the author suggests that this theory cannot be used as a basis for political action. The need for further research into the economic effects of a stationary or declining population is stressed. (summary in ENG)

  1. Growth assessment in diagnosis of Fetal Growth Restriction. Review

    OpenAIRE

    Albu, AR; Horhoianu, IA; Dumitrascu, MC; Horhoianu, V

    2014-01-01

    Abstract The assessment of fetal growth represents a fundamental step towards the identification of the true growth restricted fetus that is associated to important perinatal morbidity and mortality. The possible ways of detecting abnormal fetal growth are taken into consideration in this review and their strong and weak points are discussed. An important debate still remains about how to discriminate between the physiologically small fetus that does not require special surveillance and the t...

  2. Structure and optical properties of cored wurtzite (Zn,Mg)O heteroepitaxial nanowires

    International Nuclear Information System (INIS)

    Heo, Y.W.; Abernathy, C.; Pruessner, K.; Sigmund, W.; Norton, D.P.; Overberg, M.; Ren, F.; Chisholm, M.F.

    2004-01-01

    The synthesis, structure, and optical properties of one-dimensional heteroepitaxial cored (Zn,Mg)O semiconductor nanowires grown by a catalyst-driven molecular beam epitaxy technique are discussed. The structures form spontaneously in a Zn, Mg and O 2 /O 3 flux, consisting of a single crystal, Zn-rich Zn 1-x Mg x O(x 1-y Mg y O(y>>0.02) sheath. High resolution Z-contrast scanning transmission electron microscopy shows core diameters as small as 4 nm. The cored structure forms spontaneously under constant flux due to a bimodal growth mechanism in which the core forms via bulk like vapor-liquid-solid growth, while the outer sheath grows as a heteroepitaxial layer. Temperature-dependent photoluminescence shows a slight blueshift in the near band edge peak, which is attributed to a few percent Mg doping in the nanoscale ZnO core. The catalyst-driven molecular beam epitaxy technique provides for site-specific nanorod growth on arbitrary substrates

  3. Structural and luminescence properties of GaN nanowires grown using cobalt phthalocyanine as catalyst

    Science.gov (United States)

    Yadav, Shivesh; Rodríguez-Fernández, Carlos; de Lima, Mauricio M.; Cantarero, Andres; Dhar, Subhabrata

    2015-12-01

    Catalyst free methods have usually been employed to avoid any catalyst induced contamination for the synthesis of GaN nanowires with better transport and optical properties. Here, we have used a catalytic route to grow GaN nanowires, which show good optical quality. Structural and luminescence properties of GaN nanowires grown by vapor-liquid-solid technique using cobalt phthalocyanine as catalyst are systematically investigated as a function of various growth parameters such as the growth temperature and III/V ratio. The study reveals that most of the nanowires, which are several tens of microns long, grow along [ 10 1 ¯ 0 ] direction. Interestingly, the average wire diameter has been found to decrease with the increase in III/V ratio. It has also been observed that in these samples, defect related broad luminescence features, which are often present in GaN, are completely suppressed. At all temperatures, photoluminescence spectrum is found to be dominated only by a band edge feature, which comprises of free and bound excitonic transitions. Our study furthermore reveals that the bound excitonic feature is associated with excitons trapped in certain deep level defects, which result from the deficiency of nitrogen during growth. This transition has a strong coupling with the localized vibrational modes of the defects.

  4. Bi-Sn alloy catalyst for simultaneous morphology and doping control of silicon nanowires in radial junction solar cells

    International Nuclear Information System (INIS)

    Yu, Zhongwei; Lu, Jiawen; Qian, Shengyi; Xu, Jun; Xu, Ling; Wang, Junzhuan; Shi, Yi; Chen, Kunji; Misra, Soumyadeep; Roca i Cabarrocas, Pere; Yu, Linwei

    2015-01-01

    Low-melting point metals such as bismuth (Bi) and tin (Sn) are ideal choices for mediating a low temperature growth of silicon nanowires (SiNWs) for radial junction thin film solar cells. The incorporation of Bi catalyst atoms leads to sufficient n-type doping in the SiNWs core that exempts the use of hazardous dopant gases, while an easy morphology control with pure Bi catalyst has never been demonstrated so far. We here propose a Bi-Sn alloy catalyst strategy to achieve both a beneficial catalyst-doping and an ideal SiNW morphology control. In addition to a potential of further growth temperature reduction, we show that the alloy catalyst can remain quite stable during a vapor-liquid-solid growth, while providing still sufficient n-type catalyst-doping to the SiNWs. Radial junction solar cells constructed over the alloy-catalyzed SiNWs have demonstrated a strongly enhanced photocurrent generation, thanks to optimized nanowire morphology, and largely improved performance compared to the reference samples based on the pure Bi or Sn-catalyzed SiNWs

  5. Si Wire-Array Solar Cells

    Science.gov (United States)

    Boettcher, Shannon

    2010-03-01

    Micron-scale Si wire arrays are three-dimensional photovoltaic absorbers that enable orthogonalization of light absorption and carrier collection and hence allow for the utilization of relatively impure Si in efficient solar cell designs. The wire arrays are grown by a vapor-liquid-solid-catalyzed process on a crystalline (111) Si wafer lithographically patterned with an array of metal catalyst particles. Following growth, such arrays can be embedded in polymethyldisiloxane (PDMS) and then peeled from the template growth substrate. The result is an unusual photovoltaic material: a flexible, bendable, wafer-thickness crystalline Si absorber. In this paper I will describe: 1. the growth of high-quality Si wires with controllable doping and the evaluation of their photovoltaic energy-conversion performance using a test electrolyte that forms a rectifying conformal semiconductor-liquid contact 2. the observation of enhanced absorption in wire arrays exceeding the conventional light trapping limits for planar Si cells of equivalent material thickness and 3. single-wire and large-area solid-state Si wire-array solar cell results obtained to date with directions for future cell designs based on optical and device physics. In collaboration with Michael Kelzenberg, Morgan Putnam, Joshua Spurgeon, Daniel Turner-Evans, Emily Warren, Nathan Lewis, and Harry Atwater, California Institute of Technology.

  6. Growth Mechanism of Microbial Colonies

    Science.gov (United States)

    Zhu, Minhui; Martini, K. Michael; Kim, Neil H.; Sherer, Nicholas; Lee, Jia Gloria; Kuhlman, Thomas; Goldenfeld, Nigel

    Experiments on nutrient-limited E. coli colonies, growing on agar gel from single cells reveal a power-law distribution of sizes, both during the growth process and in the final stage when growth has ceased. We developed a Python simulation to study the growth mechanism of the bacterial population and thus understand the broad details of the experimental findings. The simulation takes into account nutrient uptake, metabolic function, growth and cell division. Bacteria are modeled in two dimensions as hard circle-capped cylinders with steric interactions and elastic stress dependent growth characteristics. Nutrient is able to diffuse within and between the colonies. The mechanism of microbial colony growth involves reproduction of cells within the colonies and the merging of different colonies. We report results on the dynamic scaling laws and final state size distribution, that capture in semi-quantitative detail the trends observed in experiment. Supported by NSF Grant 0822613.

  7. SECTORAL SHARES AND ECONOMIC GROWTH

    DEFF Research Database (Denmark)

    Ahmad, Nisar; Naveed, Amjad; Naz, Amber

    2013-01-01

    believe that structural change is an unimportant side effect of the economic development. On the contrary, economists associated with the World Bank and some others posit that growth is brought about by the changes in sectoral composition. The objective of this study is to empirically test...... the relationship between sectoral shares and economic growth by using the panel data for 20 developed countries. The results of the granger causality suggest that both services and agriculture sectors do granger cause economic growth, whereas industrial sector does not granger cause growth. Reverse causality does...... not hold for any of the three sectors. The results of Barro and Non-Barro regressions along with the set of control variables have suggested that services sector is negatively affecting growth, whereas both industrial and agriculture shares are positively affect economic growth....

  8. Hopper Growth of Salt Crystals.

    Science.gov (United States)

    Desarnaud, Julie; Derluyn, Hannelore; Carmeliet, Jan; Bonn, Daniel; Shahidzadeh, Noushine

    2018-06-07

    The growth of hopper crystals is observed for many substances, but the mechanism of their formation remains ill understood. Here we investigate their growth by performing evaporation experiments on small volumes of salt solutions. We show that sodium chloride crystals that grow very fast from a highly supersaturated solution form a peculiar form of hopper crystal consisting of a series of connected miniature versions of the original cubic crystal. The transition between cubic and such hopper growth happens at a well-defined supersaturation where the growth rate of the cubic crystal reaches a maximum (∼6.5 ± 1.8 μm/s). Above this threshold, the growth rate varies as the third power of supersaturation, showing that a new mechanism, controlled by the maximum speed of surface integration of new molecules, induces the hopper growth of cubic crystals in cascade.

  9. Growth patterns and annual growth cycle of Acacia karroo Hayne in ...

    African Journals Online (AJOL)

    ... karroo; alice; botany; compensatory growth; condition; development; eastern cape; emergence; environmental conditions; field study; growth cycle; growth initiation; growth patterns; growth strategy; leaf growth; plant growth; savanna; shoot growth; soil depth; soil moisture; south africa; university of fort hare; water stress ...

  10. Growth factor involvement in tension-induced skeletal muscle growth

    Science.gov (United States)

    Vandenburgh, Herman H.

    1993-01-01

    Long-term manned space travel will require a better understanding of skeletal muscle atrophy which results from microgravity. Astronaut strength and dexterity must be maintained for normal mission operations and for emergency situations. Although exercise in space slows the rate of muscle loss, it does not prevent it. A biochemical understanding of how gravity/tension/exercise help to maintain muscle size by altering protein synthesis and/or degradation rate should ultimately allow pharmacological intervention to prevent muscle atrophy in microgravity. The overall objective is to examine some of the basic biochemical processes involved in tension-induced muscle growth. With an experimental in vitro system, the role of exogenous and endogenous muscle growth factors in mechanically stimulated muscle growth are examined. Differentiated avian skeletal myofibers can be 'exercised' in tissue culture using a newly developed dynamic mechanical cell stimulator device which simulates different muscle activity patterns. Patterns of mechanical activity which significantly affect muscle growth and metabolic characteristics were found. Both exogenous and endogenous growth factors are essential for tension-induced muscle growth. Exogenous growth factors found in serum, such as insulin, insulin-like growth factors, and steroids, are important regulators of muscle protein turnover rates and mechanically-induced muscle growth. Endogenous growth factors are synthesized and released into the culture medium when muscle cells are mechanically stimulated. At least one family of mechanically induced endogenous factors, the prostaglandins, help to regulate the rates of protein turnover in muscle cells. Endogenously synthesized IGF-1 is another. The interaction of muscle mechanical activity and these growth factors in the regulation of muscle protein turnover rates with our in vitro model system is studied.

  11. Population growth and infant mortality

    OpenAIRE

    Fabella, Christina

    2008-01-01

    The relationship between population growth and economic outcomes is an issue of great policy significance. In the era of the Millennium Development Goals, poverty and its correlates have become the compelling issues. Economic growth may not automatically translate into reductions in poverty and its correlates (may not trickle down) if income distribution is at the same time worsening. We therefore investigate the direct effect of population growth on infant mortality for various income catego...

  12. Financing Asia’s Growth

    OpenAIRE

    Estrada, Gemma; Noland, Marcus; Park, Donghyun; Ramayandi, Arief

    2015-01-01

    Recent key challenges highlight the need to revisit Asia's financial development. These include the region's growth slowdown since the global crisis, compounded by a less benign external environment; internal structural challenges, such as population aging; and the maturing of much of the region into middle-income status. The evolving shift in the region's growth paradigm from one based primarily on investment to one based on both investment and productivity growth also underscores the urgenc...

  13. Linking Ethics and Economic Growth

    DEFF Research Database (Denmark)

    Foss, Nicolai Juul

    2012-01-01

    Hunt (2012) builds on his work concerning ethics and resource-advantage theory to link personal ethical standards, societal norms, and economic growth but offers few details concerning the precise mechanisms that link ethics and growth. This comment suggests a number of such mechanisms – for exam...... – for example, the influence of prevailing ethical norms on the aggregate elasticity of substitution and, therefore, total factor productivity and growth....

  14. Stochastic models for tumoral growth

    OpenAIRE

    Escudero, Carlos

    2006-01-01

    Strong experimental evidence has indicated that tumor growth belongs to the molecular beam epitaxy universality class. This type of growth is characterized by the constraint of cell proliferation to the tumor border, and surface diffusion of cells at the growing edge. Tumor growth is thus conceived as a competition for space between the tumor and the host, and cell diffusion at the tumor border is an optimal strategy adopted for minimizing the pressure and helping tumor development. Two stoch...

  15. Growth curves for Laron syndrome.

    OpenAIRE

    Laron, Z; Lilos, P; Klinger, B

    1993-01-01

    Growth curves for children with Laron syndrome were constructed on the basis of repeated measurements made throughout infancy, childhood, and puberty in 24 (10 boys, 14 girls) of the 41 patients with this syndrome investigated in our clinic. Growth retardation was already noted at birth, the birth length ranging from 42 to 46 cm in the 12/20 available measurements. The postnatal growth curves deviated sharply from the normal from infancy on. Both sexes showed no clear pubertal spurt. Girls co...

  16. Electricity regulation and economic growth

    OpenAIRE

    Costa, M. Teresa (Maria Teresa), 1951-; Garcia-Quevedo, Jose; Trujillo-Baute, Elisa

    2018-01-01

    The main objective of this paper is to analyse the effect of electricity regulation on economic growth. Although the relationship between electricity consumption and economic growth has been extensively analysed in the empirical literature, this framework has not been used to estimate the effect of electricity regulation on economic growth. Understanding this effect is essential for the assessment of regulatory policy. Specifically, we assess the effects of two major areas of regulation, rene...

  17. Political Instability and Economic Growth

    OpenAIRE

    Alberto Alesina; Sule Ozler; Nouriel Roubini; Phillip Swagel

    1992-01-01

    This paper investigates the relationship between political instability and per capita GDP growth in a sample of 113 countries for the period 1950-1982. We define ?political instability? as the propensity of a government collapse, and we estimate a model in which political instability and economic growth are jointly determined. The main result of this paper is that in countries and time periods with a high propensity of government collapse, growth is significantly lower than otherwise. This ef...

  18. Insulin-Like Growth Factor-Independent Effects of Growth Hormone on Growth Plate Chondrogenesis and Longitudinal Bone Growth.

    Science.gov (United States)

    Wu, Shufang; Yang, Wei; De Luca, Francesco

    2015-07-01

    GH stimulates growth plate chondrogenesis and longitudinal bone growth directly at the growth plate. However, it is not clear yet whether these effects are entirely mediated by the local expression and action of IGF-1 and IGF-2. To determine whether GH has any IGF-independent growth-promoting effects, we generated (TamCart)Igf1r(flox/flox) mice. The systemic injection of tamoxifen in these mice postnatally resulted in the excision of the IGF-1 receptor (Igf1r) gene exclusively in the growth plate. (TamCart)Igf1r(flox/flox) tamoxifen-treated mice [knockout (KO) mice] and their Igf1r(flox/flox) control littermates (C mice) were injected for 4 weeks with GH. At the end of the 4-week period, the tibial growth and growth plate height of GH-treated KO mice were greater than those of untreated C or untreated KO mice. The systemic injection of GH increased the phosphorylation of Janus kinase 2 and signal transducer and activator of transcription 5B in the tibial growth plate of the C and KO mice. In addition, GH increased the mRNA expression of bone morphogenetic protein-2 and the mRNA expression and protein phosphorylation of nuclear factor-κB p65 in both C and KO mice. In cultured chondrocytes transfected with Igf1r small interfering RNA, the addition of GH in the culture medium significantly induced thymidine incorporation and collagen X mRNA expression. In conclusion, our findings demonstrate that GH can promote growth plate chondrogenesis and longitudinal bone growth directly at the growth plate, even when the local effects of IGF-1 and IGF-2 are prevented. Further studies are warranted to elucidate the intracellular molecular mechanisms mediating the IGF-independent, growth-promoting GH effects.

  19. Gene regulation by growth factors

    International Nuclear Information System (INIS)

    Metz, R.; Gorham, J.; Siegfried, Z.; Leonard, D.; Gizang-Ginsberg, E.; Thompson, M.A.; Lawe, D.; Kouzarides, T.; Vosatka, R.; MacGregor, D.; Jamal, S.; Greenberg, M.E.; Ziff, E.B.

    1988-01-01

    To coordinate the proliferation and differentiation of diverse cell types, cells of higher eukaryotes communicate through the release of growth factors. These peptides interact with specific transmembrane receptors of other cells and thereby generate intracellular messengers. The many changes in cellular physiology and activity that can be induced by growth factors imply that growth factor-induced signals can reach the nucleus and control gene activity. Moreover, current evidence also suggests that unregulated signaling along such pathways can induce aberrant proliferation and the formation of tumors. This paper reviews investigations of growth factor regulation of gene expression conducted by the authors' laboratory

  20. Growth, Employment and Structural Change

    DEFF Research Database (Denmark)

    Aggarwal, Aradhna

    2016-01-01

    This paper studies the decomposition of GSDP growth per capita in Punjab via-a-vis 15 other states in India during 1993–94 and 2011–12 in terms of employment and productivity growth. Specifically, it focuses on the role of employment growth and structural change in employment on economic growth...... but structural shifts have paid off well in terms of diversification of the economy and their contribution to labour productivity especially for manufacturing. Overall employment effect had been negative but this was essentially due to contraction in the labour force; the employment rate effect turned out...

  1. Quality, Export and Economic Growth

    DEFF Research Database (Denmark)

    Madsen, Erik Strøjer; Pedersen, Kurt

    1998-01-01

    in an international context. The paper, therefore, addresses the complicated interactions between economic growth, export performance and quality. The contribution of the paper, compared to other growth accounting research, is the inclusion of quality data, quality being a significant mirror of technological...... development. The countries covered by the research represent a wide variation in terms of economic development, from poor LDC's to the most developed industrial nations. The empirical results reveal a probable strong relationship between quality/price and export growth as well as economic growth. This new...

  2. Variations in growth pattern and predictablity of liveweight growth of ...

    African Journals Online (AJOL)

    The prediction equations results for rate of liveweight growth showed that of the four models used, the quadratic function was the best predictor of liveweight growth, as indicated by the highest and significant R2 value of 90.7 %. This was closely followed by the linear function which had a significant R2 value of 88.1 %.

  3. Can extrauterine growth approximate intrauterine growth? Should it?

    NARCIS (Netherlands)

    Sauer, Pieter J. J.

    Most studies evaluating the growth of preterm infants use the so-called intrauterine growth curve and reference fetus as standards. These curves might not be the optimal standards, however, for several reasons. The curves were constructed from small numbers of infants with uncertainty about

  4. Growth of the Pamir

    Science.gov (United States)

    Gloaguen, R.; Ratschbacher, L.

    2009-04-01

    We aim to establish the Late Cenozoic deformation field of the Pamir by localizing and characterizing active and neotectonic deformation structures, and setting up the drainage-basin, river-capture, river- reversal, and regional erosion history. The project thus aims to record the short-term, upper crustal response to active intra-continental subduction, orocline formation, and erosion. Our hypothesis is that the neotectonics is governed by subduction beneath the frontal part of the orocline, E-W extension in the intra-plateau Karakul-lake rift, and transtension (east) and transpression (west) along the lateral margins of the orocline, a result of oroclinal formation, rotation of the Indian indenter, and focused precipitation caused by the Westerlies. The model for the evolution of the drainage system involves: growth of the Pamir by N-ward propagating deformation, establishing E-trending belts of shortening and rivers/drainages; diversion and blocking of these rivers by the development of the lateral boundaries of the orocline that resulted in river capture and reversal. Even the present-day Panj (Amu Darya) is affected by ongoing uplift: tilted river terraces, wind gaps, and abnormal intersection of streams of different order indicate that large parts of the river have changed flow direction. The determination of a number of geomorphic indices with remote sensing techniques help us to identify areas experiencing tectonic deformation.

  5. Posttraumatic growth in psychosis

    Directory of Open Access Journals (Sweden)

    Yael Mazor

    2016-12-01

    Full Text Available Objective: Recent research has shown high rates of exposure to trauma among people with serious mental illness (SMI. In addition studies suggest that psychosis and mental illness-related experiences can be extremely traumatic. While some individuals develop full blown PTSD related to these experiences, it has been noted that some may also experience posttraumatic growth (PTG. However, few studies have examined PTG as a possible outcome in people who have experienced psychosis. Method: To further understand the relationships between psychosis and PTG, 121 participants were recruited from community mental health rehabilitation centers and administered trauma and psychiatric questionnaires. Results: High levels of traumatic exposure were found in the sample. Regarding our main focus of study we observed that people who endured psychosis can experience PTG, and that PTG is mediated by meaning making and coping self-efficacy appraisal. Psychotic symptoms were found to be a major obstacle to meaning making, coping self-efficacy, and PTG, whereas negative symptoms were found to be significantly related to PTG when mediated by meaning making and coping self-efficacy. Conclusion: The current research provides preliminary evidence for potential role of meaning making and coping self-efficacy as mediators of PTG in the clinical, highly traumatized population of people with SMI who have experienced psychosis. This may have both research as well as clinical practice relevance for the field of psychiatric rehabilitation.

  6. ECOLOGICAL GROWTH BOUNDARIES

    Directory of Open Access Journals (Sweden)

    Anna BLUSZCZ

    2017-01-01

    Full Text Available The trends of the society for the continuous growth, combined with the demographic changes, today have led to the important ecological problems on a global scale, which include, among others: the increased use of non-renewable natu-ral resources, an increase of the greenhouse gas emissions, contamination of soil, water, air and the progressive degra-dation of ecosystems. In the face of such serious threats the global initiatives of all countries are important to limit the results of the excessive consumption. The aim of the article is to present the methods of measurement of the consump-tion level of natural resources by the societies and the examination of relationships between the level of development of the societies and the use of resources. The popular measure – the ecological footprint – was used as a measurement method for the consumption of the today’s generations in relation to the regenerative possibilities of the natural envi-ronment. On the other hand, as the assessment method for the level of development of societies – the Human Develop-ment Index (HDI, including three basic areas: the life expectancy, GDP level per capita and education was used. The results of the research indicate that the current trend of the unlimited consumption of the highly developed countries takes place at the expense of the future generations.

  7. The initial growth stage in PVT growth of aluminum nitride

    Energy Technology Data Exchange (ETDEWEB)

    Heimann, P.; Epelbaum, B.M.; Bickermann, M.; Winnacker, A. [Department of Materials Science 6, University of Erlangen-Nuernberg, Martensstr. 7, 91058 Erlangen (Germany); Nagata, S. [Functional Materials Development Center, Research Laboratories, JFE Mineral Company, Ltd., 1, Niihama-cho, Chuou-ku, Chiba-shi, Chiba 260-0826 (Japan)

    2006-06-15

    The main issue in homoepitaxial growth of aluminum nitride (AlN) on native seed substrates is the formation of an aluminum oxynitride (AlON) layer at temperatures between 1850-1950 C leading to polycrystalline growth. On the contrary, heteroepitaxial growth of AlN on silicon carbide (SiC) is relatively easy to achieve due to natural formation of a thin molten layer of (Al{sub 2}OC{sub x}) on the seed surface and consequent growth of AlN via the molten buffer layer. Optimization of the seeding process can be achieved by use of ultra-pure starting material. Another critical issue of AlN growth on SiC is cracking of the grown layer upon cooling as a result of different thermal expansion coefficients. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. Corruption and economic growth with non constant labor force growth

    Science.gov (United States)

    Brianzoni, Serena; Campisi, Giovanni; Russo, Alberto

    2018-05-01

    Based on Brianzoni et al. [1] in the present work we propose an economic model regarding the relationship between corruption in public procurement and economic growth. We extend the benchmark model by introducing endogenous labor force growth, described by the logistic equation. The results of previous studies, as Del Monte and Papagni [2] and Mauro [3], show that countries are stuck in one of the two equilibria (high corruption and low economic growth or low corruption and high economic growth). Brianzoni et al. [1] prove the existence of a further steady state characterized by intermediate levels of capital per capita and corruption. Our aim is to investigate the effects of the endogenous growth around such equilibrium. Moreover, due to the high number of parameters of the model, specific attention is given to the numerical simulations which highlight new policy measures that can be adopted by the government to fight corruption.

  9. Extracellular matrix organization modulates fibroblast growth and growth factor responsiveness.

    Science.gov (United States)

    Nakagawa, S; Pawelek, P; Grinnell, F

    1989-06-01

    To learn more about the relationship between extracellular matrix organization, cell shape, and cell growth control, we studied DNA synthesis by fibroblasts in collagen gels that were either attached to culture dishes or floating in culture medium during gel contraction. After 4 days of contraction, the collagen density (initially 1.5 mg/ml) reached 22 mg/ml in attached gels and 55 mg/ml in floating gels. After contraction, attached collagen gels were well organized; collagen fibrils were aligned in the plane of cell spreading; and fibroblasts had an elongated, bipolar morphology. Floating collagen gels, however, were unorganized; collagen fibrils were arranged randomly; and fibroblasts had a stellate morphology. DNA synthesis by fibroblasts in contracted collagen gels was suppressed if the gels were floating in medium but not if the gels were attached, and inhibition was independent of the extent of gel contraction. Therefore, growth of fibroblasts in contracted collagen gels could be regulated by differences in extracellular matrix organization and cell shape independently of extracellular matrix density. We also compared the responses of fibroblasts in contracted collagen gels and monolayer culture to peptide growth factors including fibroblast growth factor, platelet-derived growth factor, transforming growth factor-beta, and interleukin 1. Cells in floating collagen gels were generally unresponsive to any of the growth factors. Cells in attached collagen gels and monolayer culture were affected similarly by fibroblast growth factor but not by the others. Our results indicate that extracellular matrix organization influenced not only cell growth, but also fibroblast responsiveness to peptide growth factors.

  10. Growth at adolescence. Clinical correlates.

    Science.gov (United States)

    Daniel, W A

    1985-03-01

    Several highly significant changes occur within a relatively short period of time during adolescence. Great alteration in physique, developmental progress in thinking, and psychologic gains toward attaining ego identity take place but not always synchronously. Attention is paid to physical changes because they are visible and are of intense concern to adolescents, but physicians and other professionals should remember cognitive and psychosocial growth are affected by physical growth, and vice versa. Often there is a temporary disequilibrium in the relationship of these three areas of growth, and this can affect one or another part of the developmental pattern. It is therefore necessary to remind ourselves of the diversity of adolescent growth, and of adolescents, when caring for a young patient and be cognizant of growth in areas other than physical. More and more children with congenital or acquired handicaps are living to become adolescents and perhaps adults. Handicaps can be limited to one of the three major areas of growth or involve them all in varying degrees. For example, sickle cell disease, Crohn's disease, or ulcerative colitis may postpone physical growth for a significant period; this lack of pubertal change can affect psychosocial development but usually does not impair cognitive growth. Mental retardation may have no apparent effect on physical growth but can handicap the adolescent's psychosocial development. Growth still occurs in a sequential pattern but often it seems that handicapped youngsters reach a developmental milestone by a series of "detours." Physicians must recognize these lags or differences and try to facilitate progress, promote self-esteem, and provide understanding. Much can be done with anticipatory guidance. Adolescence often provides the opportunity to overcome past damage or, in some instances, to start anew on a more optimal program for physical and psychosocial growth. Young adolescent boys and girls usually look to the

  11. Nutritional catch-up growth.

    Science.gov (United States)

    Gat-Yablonski, Galia; Pando, Rakefet; Phillip, Moshe

    2013-01-01

    Malnutrition, marked by variant nutrient deficiencies, is considered a leading cause of stunted growth worldwide. In developing countries, malnutrition is caused mainly by food shortage and infectious diseases. Malnutrition may also be found in the developed world, where it is due mostly to prematurity, chronic diseases, and anorexia nervosa. In most cases, when food consumption is corrected, spontaneous catch-up (CU) growth occurs. However, CU growth is not always complete, leading to growth deficits. Therefore, it is important to understand the mechanisms that govern this process. Using a rat model of food restriction followed by refeeding, we established a nutrition-induced CU growth model. Levels of leptin and insulin-like growth factor-1 were found to significantly decrease when food was restricted and to increase already 1 day after refeeding. Gene expression analysis of the growth plate revealed that food restriction specifically affects transcription factors such as the hypoxia inducible factor-1 and its downstream targets on the one hand, and global gene expression, indicating epigenetic regulation, on the other. Food restriction also reduced the level of several microRNAs, including the chondrocyte-specific miR-140, which led to an increase in its target, SIRT1, a class III histone deacetylase. These findings may explain the global changes in gene expression observed under nutritional manipulation. We suggest that multiple levels of regulation, including transcription factors, epigenetic mechanisms, and microRNAs respond to nutritional cues and offer a possible explanation for some of the effects of food restriction on epiphyseal growth plate growth. The means whereby these components sense changes in nutritional status are still unknown. Deciphering the role of epigenetic regulation in growth may pave the way for the development of new treatments for children with growth disorders. Copyright © 2013 S. Karger AG, Basel.

  12. Entrepreneurship Education and Economic Growth

    DEFF Research Database (Denmark)

    Pedersen, Jonna; Lindquist, Carl Rickard

    . This paper addresses the presumptions behind the project. The presumptions in relation to entrepreneurship demonstrate that the effort should target both growth entrepreneurs and SMEs in a wide sense; there is a need for growth entrepreneurs with ambitions to generate breakthrough innovation as well...

  13. Ecological economics and economic growth.

    Science.gov (United States)

    Victor, Peter A

    2010-01-01

    Boulding's 1966 paper on the economics of spaceship Earth established the framework for ecological economics and an understanding of economic growth. In ecological economics, economies are conceptualized as open subsystems of the closed biosphere and are subject to biophysical laws and constraints. Economic growth measured as an increase in real gross domestic product (GDP) has generally been associated with increases in the use of energy and materials and the generation of wastes. Scale, composition, and technology are the proximate determinants of environmental impacts. They are often reduced to two: scale (GDP) and intensity (impact per unit GDP). New work described in this paper defines "green" growth as intensity that declines faster than scale increases. Similarly, "brown" growth occurs when intensity declines more slowly than increases in scale, and "black" growth happens when both scale and intensity increase. These concepts are then related to the environmental Kuznets curve, which can be understood as a transition from brown to green growth. Ecological economics provides a macroperspective on economic growth. It offers broad policy principles, and it challenges the primacy of economic growth as a policy objective, but many important questions remain.

  14. Technical Education and Economic Growth

    Indian Academy of Sciences (India)

    First page Back Continue Last page Graphics. Technical Education and Economic Growth. Technical Education and Economic Growth. Review of the Present Status. Expanding no.s and impairment of quality; Faculty shortage; Grim situation at Masters and PhD levels; Regional imbalance; Absence of International flavour ...

  15. Chemical Control of Plant Growth.

    Science.gov (United States)

    Agricultural Research Center (USDA), Beltsville, MD.

    Seven experiments are presented in this Science Study Aid to help students investigate the control of plant growth with chemicals. Plant growth regulators, weed control, and chemical pruning are the topics studied in the experiments which are based on investigations that have been and are being conducted at the U. S. Agricultural Research Center,…

  16. Growth curves for Laron syndrome.

    Science.gov (United States)

    Laron, Z; Lilos, P; Klinger, B

    1993-01-01

    Growth curves for children with Laron syndrome were constructed on the basis of repeated measurements made throughout infancy, childhood, and puberty in 24 (10 boys, 14 girls) of the 41 patients with this syndrome investigated in our clinic. Growth retardation was already noted at birth, the birth length ranging from 42 to 46 cm in the 12/20 available measurements. The postnatal growth curves deviated sharply from the normal from infancy on. Both sexes showed no clear pubertal spurt. Girls completed their growth between the age of 16-19 years to a final mean (SD) height of 119 (8.5) cm whereas the boys continued growing beyond the age of 20 years, achieving a final height of 124 (8.5) cm. At all ages the upper to lower body segment ratio was more than 2 SD above the normal mean. These growth curves constitute a model not only for primary, hereditary insulin-like growth factor-I (IGF-I) deficiency (Laron syndrome) but also for untreated secondary IGF-I deficiencies such as growth hormone gene deletion and idiopathic congenital isolated growth hormone deficiency. They should also be useful in the follow up of children with Laron syndrome treated with biosynthetic recombinant IGF-I. PMID:8333769

  17. ICT, Innovation and Productivity Growth

    DEFF Research Database (Denmark)

    Fosse, Henrik; Jacobsen, Joannes; Sørensen, Anders

    This CEBR report presents new evidence which suggests that investments in Information and Communication Technology (ICT) further productivity growth in Danish firms by stimulating innovation activities.......This CEBR report presents new evidence which suggests that investments in Information and Communication Technology (ICT) further productivity growth in Danish firms by stimulating innovation activities....

  18. The Growth-Inequality Association:

    DEFF Research Database (Denmark)

    Bjørnskov, Christian

    2008-01-01

    This note suggests that the association between income inequality and economic growth rates might arguably depend on the political ideology of incumbent governments. Estimates indicate that under leftwing governments, inequality is negatively associated with growth while the association is positive...... under rightwing governments. This may provide a qualification to recent studies of inequality....

  19. Forces Influencing Rural Community Growth.

    Science.gov (United States)

    Rainey, Kenneth D.

    The paper briefly focuses on two questions: Can the recent growth trend be expected to continue into the future? and What does this imply as far as public policy and programs are concerned? Statistics on growth in the seventies suggest three possibilities: a change in the functions of metropolitan and nonmetropolitan areas; the decline of the city…

  20. Mould growth on building materials

    DEFF Research Database (Denmark)

    Fog Nielsen, K.

    Mould growth in buildings is associated with adverse health effects among the occupants of the building. However actual growth only occurs in damp and water-damaged materials, and is an increasing problem in Denmark, due to less robust constructions, inadequate maintenance, and too little...

  1. Enhanced Electron Mobility in Nonplanar Tensile Strained Si Epitaxially Grown on SixGe1-x Nanowires.

    Science.gov (United States)

    Wen, Feng; Tutuc, Emanuel

    2018-01-10

    We report the growth and characterization of epitaxial, coherently strained Si x Ge 1-x -Si core-shell nanowire heterostructure through vapor-liquid-solid growth mechanism for the Si x Ge 1-x core, followed by an in situ ultrahigh-vacuum chemical vapor deposition for the Si shell. Raman spectra acquired from individual nanowire reveal the Si-Si, Si-Ge, and Ge-Ge modes of the Si x Ge 1-x core and the Si-Si mode of the shell. Because of the compressive (tensile) strain induced by lattice mismatch, the core (shell) Raman modes are blue (red) shifted compared to those of unstrained bare Si x Ge 1-x (Si) nanowires, in good agreement with values calculated using continuum elasticity model coupled with lattice dynamic theory. A large tensile strain of up to 2.3% is achieved in the Si shell, which is expected to provide quantum confinement for electrons due to a positive core-to-shell conduction band offset. We demonstrate n-type metal-oxide-semiconductor field-effect transistors using Si x Ge 1-x -Si core-shell nanowires as channel and observe a 40% enhancement of the average electron mobility compared to control devices using Si nanowires due to an increased electron mobility in the tensile-strained Si shell.

  2. Coherently Strained Si-SixGe1-x Core-Shell Nanowire Heterostructures.

    Science.gov (United States)

    Dillen, David C; Wen, Feng; Kim, Kyounghwan; Tutuc, Emanuel

    2016-01-13

    Coherently strained Si-SixGe1-x core-shell nanowire heterostructures are expected to possess a positive shell-to-core conduction band offset, allowing for quantum confinement of electrons in the Si core. We report the growth of epitaxial, coherently strained Si-SixGe1-x core-shell heterostructures through the vapor-liquid-solid mechanism for the Si core, followed in situ by the epitaxial SixGe1-x shell growth using ultrahigh vacuum chemical vapor deposition. The Raman spectra of individual nanowires reveal peaks associated with the Si-Si optical phonon mode in the Si core and the Si-Si, Si-Ge, and Ge-Ge vibrational modes of the SixGe1-x shell. The core Si-Si mode displays a clear red-shift compared to unstrained, bare Si nanowires thanks to the lattice mismatch-induced tensile strain, in agreement with calculated values using a finite-element continuum elasticity model combined with lattice dynamic theory. N-type field-effect transistors using Si-SixGe1-x core-shell nanowires as channel are demonstrated.

  3. Strong sp-d exchange coupling in ZnMnTe/ZnMgTe core/shell nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Wojnar, Piotr; Janik, Elzbieta; Szymura, Malgorzata; Zaleszczyk, Wojciech; Kret, Slawomir; Klopotowski, Lukasz; Wojciechowski, Tomasz; Baczewski, Lech T.; Wiater, Maciej; Karczewski, Grzegorz; Wojtowicz, Tomasz; Kossut, Jacek [Institute of Physics, Polish Academy of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland); Suffczynski, Jan; Papierska, Joanna [Institute of Experimental Physics, Warsaw University, ul. Hoza 69, 00-681 Warsaw (Poland)

    2014-07-15

    In this work, our recent progress in the growth and optical studies of telluride nanowire heterostructures containing a small molar fraction of magnetic Mn-ions of only a few percent is overviewed. ZnMnTe/ZnMgTe core/shell nanowires (NWs) are grown by molecular beam epitaxy by employing the vapor-liquid-solid growth mechanism assisted with gold catalyst. The structures are studied by means of photoluminescence and microphotoluminescence in an external magnetic field. In the first step, however, an activation of the near band edge emission from ZnTe and ZnMnTe nanowires is described, which is achieved by coating the nanowires with shells made of ZnMgTe. The role of these shells is to passivate Zn(Mn)Te surface states. The incorporation of Mn ions into the crystalline lattice of ZnMnTe nanowires is manifested as a considerable blue shift of near band edge emission with increasing Mn concentration inside the nanowire cores, which reflects directly the increase of their energy gap. In an external magnetic field the near band edge emission exhibits a giant spectral redshift accompanied by an increase of the circular polarization of the emitted light. Both effect are fingerprints of giant Zeeman splitting of the band edges due to sp-d exchange interaction between the band carriers and magnetic Mn-ions. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Bottom-Up Tri-gate Transistors and Submicrosecond Photodetectors from Guided CdS Nanowalls.

    Science.gov (United States)

    Xu, Jinyou; Oksenberg, Eitan; Popovitz-Biro, Ronit; Rechav, Katya; Joselevich, Ernesto

    2017-11-08

    Tri-gate transistors offer better performance than planar transistors by exerting additional gate control over a channel from two lateral sides of semiconductor nanowalls (or "fins"). Here we report the bottom-up assembly of aligned CdS nanowalls by a simultaneous combination of horizontal catalytic vapor-liquid-solid growth and vertical facet-selective noncatalytic vapor-solid growth and their parallel integration into tri-gate transistors and photodetectors at wafer scale (cm 2 ) without postgrowth transfer or alignment steps. These tri-gate transistors act as enhancement-mode transistors with an on/off current ratio on the order of 10 8 , 4 orders of magnitude higher than the best results ever reported for planar enhancement-mode CdS transistors. The response time of the photodetector is reduced to the submicrosecond level, 1 order of magnitude shorter than the best results ever reported for photodetectors made of bottom-up semiconductor nanostructures. Guided semiconductor nanowalls open new opportunities for high-performance 3D nanodevices assembled from the bottom up.

  5. Synthesis and Characterization of CdS/CdSxSe1-x Nanowires

    Science.gov (United States)

    Agueda Lopez, Kleyser; Wu, Marvin

    Semiconductor nanowire heterostructures are of interest for potential applications in solar cells and other advanced optoelectronic devices. We report here on synthesis of CdS/CdSxSe1-x nanowires (NWs) using a dual source vapor = liquid - solid technique, and characterization of these NWs with scanning electron microscopy and optical microscopy. We determine the effect of growth parameters, including source / substrate temperatures and time of exposure, on NW size, shape, and composition. The crystal structure and optical properties individual NWs from selected substrates has been mapped using transmission Kikuchi diffraction and photoluminescence (PL) microscopy. NWs consistently exhibit a hexagonal structure, with growth along the c-axis. Strong PL peaks are observed between the expected bandgap emission from CdS and CdSe, confirming formation of CdSxSe1-x. PL peaks vary significantly with intensity along the long axis of the nanowire, suggesting that the NW surface is not uniformly passivated. These nanowires show promise for future investigation and manipulation of energy band gaps contain in CdS/CdSe. CREST.

  6. Growth Hormone and Endocrinopathies

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K W; Choe, K O; Park, C Y; Lee, H; Son, H Y; Huh, K B; Ryu, K J [Yonsei University College of Medicine, Seoul (Korea, Republic of)

    1979-03-15

    This is an analysis of 39 patients studied at the Yonsei Medical Center from January, 1976 to March 1979. Of these 35 patient were suspected of having hypothalamic insufficiency and subjected to the L-Dopa stimulation test to observe growth hormone secretary function while four acromegaly patient received the glucose loading test and L-Dopa stimulation test. The results are as follows: 1) The basal level of GH in the various disease was as follows: a) The basal level was lower than the control level but was not statistically significant b) In diabetes the mean value tended to higher than the control level but was not significant statistically c) In all four acromegaly patients the GH level was significantly higher than the control level 2) Of 13 patients with diabetes, nine had diabetic retinopathy, and of those nine, six showed increased L-Dopa response. However, of the four non retinopathic DM patients, only one showed increased response to L-Dopa. 3) Two patients out of ten with Sheehan's syndrome responded to L-Dopa stimulation. 4) One Patient of eight with pituitary chromophobe adenoma responded to L-Dopa stimulation. 5) Four acromegaly patients revealed 3 acidophilic adenoma and one chromophobe adenoma histologically. Of patients receiving the L-Dopa stimulation test. Two showed a paradoxical response. Two patients who received the glucose loading test showed suppressed response. 6) Of two craniopharyngioma patients, one showed increased GH response after L-Dopa stimulation. Increased response of GH after L-Dopa stimulation was seen in one two craniopharyngioma patients and also in one of two patients with short structure.

  7. Growth Hormone and Endocrinopathies

    Energy Technology Data Exchange (ETDEWEB)

    Kim, K. W.; Choe, K. O.; Park, C. Y.; Lee, H.; Son, H. Y.; Huh, K. B.; Ryu, K. J. [Yonsei University College of Medicine, Seoul (Korea, Republic of)

    1979-03-15

    This is an analysis of 39 patients studied at the Yonsei Medical Center from January, 1976 to March 1979. Of these 35 patient were suspected of having hypothalamic insufficiency and subjected to the L-Dopa stimulation test to observe growth hormone secretary function while four acromegaly patient received the glucose loading test and L-Dopa stimulation test. The results are as follows: 1) The basal level of GH in the various disease was as follows: a) The basal level was lower than the control level but was not statistically significant b) In diabetes the mean value tended to higher than the control level but was not significant statistically c) In all four acromegaly patients the GH level was significantly higher than the control level 2) Of 13 patients with diabetes, nine had diabetic retinopathy, and of those nine, six showed increased L-Dopa response. However, of the four non retinopathic DM patients, only one showed increased response to L-Dopa. 3) Two patients out of ten with Sheehan's syndrome responded to L-Dopa stimulation. 4) One Patient of eight with pituitary chromophobe adenoma responded to L-Dopa stimulation. 5) Four acromegaly patients revealed 3 acidophilic adenoma and one chromophobe adenoma histologically. Of patients receiving the L-Dopa stimulation test. Two showed a paradoxical response. Two patients who received the glucose loading test showed suppressed response. 6) Of two craniopharyngioma patients, one showed increased GH response after L-Dopa stimulation. Increased response of GH after L-Dopa stimulation was seen in one two craniopharyngioma patients and also in one of two patients with short structure.

  8. Growth Hormone and Endocrinopathies

    International Nuclear Information System (INIS)

    Kim, K. W.; Choe, K. O.; Park, C. Y.; Lee, H.; Son, H. Y.; Huh, K. B.; Ryu, K. J.

    1979-01-01

    This is an analysis of 39 patients studied at the Yonsei Medical Center from January, 1976 to March 1979. Of these 35 patient were suspected of having hypothalamic insufficiency and subjected to the L-Dopa stimulation test to observe growth hormone secretary function while four acromegaly patient received the glucose loading test and L-Dopa stimulation test. The results are as follows: 1) The basal level of GH in the various disease was as follows: a) The basal level was lower than the control level but was not statistically significant b) In diabetes the mean value tended to higher than the control level but was not significant statistically c) In all four acromegaly patients the GH level was significantly higher than the control level 2) Of 13 patients with diabetes, nine had diabetic retinopathy, and of those nine, six showed increased L-Dopa response. However, of the four non retinopathic DM patients, only one showed increased response to L-Dopa. 3) Two patients out of ten with Sheehan's syndrome responded to L-Dopa stimulation. 4) One Patient of eight with pituitary chromophobe adenoma responded to L-Dopa stimulation. 5) Four acromegaly patients revealed 3 acidophilic adenoma and one chromophobe adenoma histologically. Of patients receiving the L-Dopa stimulation test. Two showed a paradoxical response. Two patients who received the glucose loading test showed suppressed response. 6) Of two craniopharyngioma patients, one showed increased GH response after L-Dopa stimulation. Increased response of GH after L-Dopa stimulation was seen in one two craniopharyngioma patients and also in one of two patients with short structure.

  9. Stochastic models for tumoral growth

    Science.gov (United States)

    Escudero, Carlos

    2006-02-01

    Strong experimental evidence has indicated that tumor growth belongs to the molecular beam epitaxy universality class. This type of growth is characterized by the constraint of cell proliferation to the tumor border and the surface diffusion of cells at the growing edge. Tumor growth is thus conceived as a competition for space between the tumor and the host, and cell diffusion at the tumor border is an optimal strategy adopted for minimizing the pressure and helping tumor development. Two stochastic partial differential equations are reported in this paper in order to correctly model the physical properties of tumoral growth in (1+1) and (2+1) dimensions. The advantage of these models is that they reproduce the correct geometry of the tumor and are defined in terms of polar variables. An analysis of these models allows us to quantitatively estimate the response of the tumor to an unfavorable perturbation during growth.

  10. Dietary arginine and linear growth

    DEFF Research Database (Denmark)

    van Vught, Anneke J A H; Dagnelie, Pieter C; Arts, Ilja C W

    2013-01-01

    Child Intervention Study during 2001-2 (baseline), and at 3-year and 7-year follow-up, were used. Arginine intake was estimated via a 7 d precoded food diary at baseline and 3-year follow-up. Data were analysed in a multilevel structure in which children were embedded within schools. Random intercept......The amino acid arginine is a well-known growth hormone (GH) stimulator and GH is an important modulator of linear growth. The aim of the present study was to investigate the effect of dietary arginine on growth velocity in children between 7 and 13 years of age. Data from the Copenhagen School...... and slopes were defined to estimate the association between arginine intake and growth velocity, including the following covariates: sex; age; baseline height; energy intake; puberty stage at 7-year follow-up and intervention/control group. The association between arginine intake and growth velocity...

  11. A nonpeptidyl growth hormone secretagogue.

    Science.gov (United States)

    Smith, R G; Cheng, K; Schoen, W R; Pong, S S; Hickey, G; Jacks, T; Butler, B; Chan, W W; Chaung, L Y; Judith, F

    1993-06-11

    A nonpeptidyl secretagogue for growth hormone of the structure 3-amino-3-methyl-N-(2,3,4,5-tetrahydro-2-oxo-1-([2'-(1H-tetrazol-5 -yl) (1,1'-biphenyl)-4-yl]methyl)-1H-1-benzazepin-3(R)-yl)-butanamid e (L-692,429) has been identified. L-692,429 synergizes with the natural growth hormone secretagogue growth hormone-releasing hormone and acts through an alternative signal transduction pathway. The mechanism of action of L-692,429 and studies with peptidyl and nonpeptidyl antagonists suggest that this molecule is a mimic of the growth hormone-releasing hexapeptide His-D-Trp-Ala-Trp-D-Phe-Lys-NH2 (GHRP-6). L-692,429 is an example of a nonpeptidyl specific secretagogue for growth hormone.

  12. Population growth, poverty and health.

    Science.gov (United States)

    Kibirige, J S

    1997-07-01

    One of the most popular explanations for the many problems that face Africa is population growth. Africa's population has doubled since 1960. Africa has the highest fertility rate in the world and the rate of population growth is higher than in any other region. At the same time, Africa faces a social and economic situation that is viewed by many as alarming. Among the problems that devastate Africa is that of persistent poor health. Africa has lower life expectancy, higher mortality rates and is affected by more disease and illness conditions than any other region. Focusing on sub-Saharan Africa, this paper examines the relationship between population growth, poverty and poor health. While most analyses have focused on population growth as an original cause of poverty and underdevelopment, this paper argues that while both population growth and poor health play a significant role in exacerbating the problem of poverty, they are themselves primary consequences of poverty rather than its cause.

  13. Growth morphologies of crystal surfaces

    Science.gov (United States)

    Xiao, Rong-Fu; Alexander, J. Iwan D.; Rosenberger, Franz

    1991-03-01

    We have expanded our earlier Monte Carlo model [Phys. Rev. A 38, 2447 (1988); J. Crystal Growth 100, 313 (1990)] to three dimensions and included reevaporation after accommodation and growth on dislocation-induced steps. We found again that, for a given set of growth parameters, the critical size, beyond which a crystal cannot retain its macroscopically faceted shape, scales linearly with the mean free path in the vapor. However, the three-dimensional (3D) the systems show increased shape stability compared to corresponding 2D cases. Extrapolation of the model results to mean-free-path conditions used in morphological stability experiments leads to order-of-magnitude agreement of the predicted critical size with experimental findings. The stability region for macroscopically smooth (faceted) surfaces in the parameter space of temperature and supersaturation depends on both the surface and bulk diffusion. While surface diffusion is seen to smooth the growth morphology on the scale of the surface diffusion length, bulk diffusion is always destabilizing. The atomic surface roughness increases with increase in growth temperature and supersaturation. That is, the tendency of surface kinetics anisotropies to stabilize the growth shape is reduced through thermal and kinetic roughening. It is also found that the solid-on-solid assumption, which can be advantageously used at low temperatures and supersaturations, is insufficient to describe the growth dynamics of atomically rough interfaces where bulk diffusion governs the process. For surfaces with an emerging screw dislocation, we find that the spiral growth mechanism dominates at low temperatures and supersaturations. The polygonization of a growth spiral decreases with increasing temperature or supersaturation. When the mean free path in the nutrient is comparable to the lattice constant, the combined effect of bulk and surface diffusion reduces the terrace width of a growth spiral in its center region. At elevated

  14. Growth of maize coleoptiles in the presence of natural and synthetic growth regulators. Growth correlations

    Directory of Open Access Journals (Sweden)

    Ewa Raczek

    2014-01-01

    Full Text Available The effect of natural (IAA, FC, ABA and synthetic (2,4-D growth substances on the increase of the fresh weight of maize coleoptile segments and change of the pH of the incubation medium, accepted here as criteria of maize coleoptile growth, was studied. The growth of maize coleoptiles depended on the concentration of the growth substances, as well as, on the composition of the incubation medium. The highest stimulation of coleoptile growth was seen with FC at a concentration of 10-4M, whereas ABA at 10-3 M gave the highest inhibition of maize coleoptile fresh weight increase and caused alkalization of the medium. The presence of K+ ions in the incubation medium enhanced the stimulatory effect of IAA and FC on the increase of the coleoptile fresh weight, whereas the presence of these ions and phosphate buffer abolished the growth-promoting effect of IAA and FC. The best correlation of the "fresh weight" and "pH" effects was found in the case of the growth of maize coleoptiles in the presence of FC (rxy = 0.67. The inhibition of maize coleoptile growth in the presence of high concentrations of IAA can be explained by the destructive effect of natural auxin at these concentrations on the integrity of mitochondrial membranes, and therefore on the normal functioning of mitochondria.

  15. The relative value of growth.

    Science.gov (United States)

    Mass, Nathaniel J

    2005-04-01

    Most executives would say that adding a point of growth and gaining a point of operating-profit margin contribute about equally to shareholder value. Margin improvements hit the bottom line immediately, while growth compounds value over time. But the reality is that the two are rarely equivalent. Growth often is far more valuable than managers think. For some companies, convincing the market that they can grow by just one additional percentage point can be worth six, seven, or even ten points of margin improvement. This article presents a new strategic metric, called the relative value of growth (RVG), which gives managers a clear picture of how growth projects and margin improvement initiatives affect shareholder value. Using basic balance sheet and income sheet data, managers can determine their companies' RVGs, as well as those of their competitors. Calculating RVGs gives managers insights into which corporate strategies are working to deliver value and whether their companies are pulling the most powerful value-creation levers. The author examines a number of well-known companies and explains what their RVG numbers say about their strategies. He reviews the unspoken assumption that growth and profits are incompatible over the long term and shows that a fair number of companies are effective at delivering both. Finally, he explains how managers can use the RVG framework to help them define strategies that balance growth and profitability at both the corporate and business unit levels.

  16. Sociological explanations of economic growth.

    Science.gov (United States)

    Marsh, R M

    1988-01-01

    Even if questions of how resources are distributed within and between societies are the main concern, it is necessary to continue to grapple with the issue of the causes of economic growth since economic growth and level of development continue to be among the most important causes of inequality, poverty, unemployment, and the quality of life. This paper's dependent variable is the economic growth rate of 55 less developed countries (LDCs) over 2 time periods. 1970-78 and 1965-84. The causal model consists of control variables--level of development and domestic investment in 1965--and a variety of independent variables drawn from major sociological theories of economic growth published during the last 3 decades. Multiple regression analysis shows that, net of the effects of the 2 control variables, the variables which have the strongest effect on economic growth are: 1) direct foreign investment, which has a negative effect, 2) the proportion of the population in military service, and 3) the primary school enrollment ratio, both of which have positive effects on economic growth. On the other hand, variables drawn from some theories receive no empirical support. The mass media of communications, ethnolinguistic heterogeneity, democracy and human rights, income inequality, and state-centric theory's key variable, state strength, all fail to show any significant impact on economic growth rates when the control variables and the significant independent variables are held constant. The theoretical implications of these findings are discussed.

  17. Growth factors and new periodontology

    Directory of Open Access Journals (Sweden)

    Paknejad M

    1999-06-01

    Full Text Available Growth factors are biological mediators that have a key roll in proliferation, chemotaxy and"ndifferentiation by acting on specific receptors on the surface of cells and regulating events in wound"nhealing.They can be considered hormones that are not released in to the blood stream but have one a"nlocal action. Some of these factors can regulate premature change in GO to Gl phase in cell devesion"ncycle and even may stimulate synthesis of DNA in suitable cells, Growth substances, primarily secreted"nby fibroblasts, endothelia! cells, macrophages and platelet, include platelet derived growth factor"n(PDGF, insulin like growth factor (IGF transforming growth factor (TGFa and (3 and bone"nmorphogenetic proteins BMPs that approximately are the most important of them. (BMPs could be"nused to control events during periodontal, craniofacial and implant wound healing through favoring bone"nformation"nAccording toLynch, combination of PGDF and IGF1 would be effective in promoting growth of all the"ncomponents of the periodontium."nThe aim of this study was to characterize growth factor and review the literature to determine the"nmechanism of their function, classification and application in implant and periodontal treatment.

  18. Pro Poor Growth in Cameroon

    Directory of Open Access Journals (Sweden)

    Samuel Fambon

    2017-06-01

    Full Text Available The purpose of this paper is to analyze the relationship between economic growth, poverty and income distribution in Cameroon, using both the data derived from three Cameroonian household surveys and the Poverty Equivalent Growth Rate (PEGR methodology developed by Kakwani et al. (2004, The study found that economic growth in Cameroon was pro poor over the period 1996–2007, which suggests that instead of increasing the economic growth rate alone, the poverty equivalent growth rate should also be maximized to achieve the poverty reduction objective, meaning that on the one hand, the growth rate should be boosted, and on the other, the distribution of income should also be concurrently improved. A decomposition of changes in poverty using the Kakwani (1997 approach reveal that the growth component dominates the redistribution component in the reduction of poverty. This suggests that the fall in absolute poverty over the survey period may be attributed to an increase in average household income, and not to the redistributive policies of the government.

  19. Towards Sustainable Growth Business Models

    Energy Technology Data Exchange (ETDEWEB)

    Kamp-Roelands, N.; Balkenende, J.P.; Van Ommen, P.

    2012-03-15

    The Dutch Sustainable Growth Coalition (DSGC) has the following objectives: The DSGC aims to pro-actively drive sustainable growth business models along three lines: (1) Shape. DSGC member companies aim to connect economic profitability with environmental and social progress on the basis of integrated sustainable growth business models; (2) Share. DSGC member companies aim for joint advocacy of sustainable growth business models both internationally and nationally; and (3) Stimulate. DSGC member companies aim to stimulate and influence the policy debate on enabling sustainable growth - with a view to finding solutions to the environmental and social challenges we are facing. This is their first report. The vision, actions and mission of DSGC are documented in the Manifesto in Chapter 2 of this publication. Chapter 3 contains an overview of key features of an integrated sustainable growth business model and the roadmap towards such a model. In Chapter 4, project examples of DSGC members are presented, providing insight into the hands-on reality of implementing the good practices. Chapter 5 offers an overview of how the Netherlands provides an enabling environment for sustainable growth business models. Chapter 6 offers the key conclusions.

  20. Growth Data - Characterization of Sexual Growth Dimorphism in Sablefish

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Sexual growth dimorphism (SGD) is a common phenomenon in nature. Numerous marine fishes exhibit SGD, with females often growing faster and attaining larger sizes...

  1. Juvenile eye growth, when completed?

    DEFF Research Database (Denmark)

    Fledelius, Hans C; Christensen, Anders S; Fledelius, Christian

    2014-01-01

    PURPOSE: To test Sorsby's classical statement of axial eye growth as completed at the age of 13 years, with a view also to differentiating between basic eye growth and juvenile elongation associated with eventual refractive change towards myopia. METHODS: (i) A total of 160 healthy eyes close...... about age 13 as general limit found support from the cross-sectional data, which suggested stable emmetropic eye size from about 11-12 years, with an average apparently outgrown male emmetropic value of 23.5 mm versus females' 22.9 mm. The longitudinal data, however, showed emmetropic growth also beyond...

  2. The biophysics of neuronal growth

    International Nuclear Information System (INIS)

    Franze, Kristian; Guck, Jochen

    2010-01-01

    For a long time, neuroscience has focused on biochemical, molecular biological and electrophysiological aspects of neuronal physiology and pathology. However, there is a growing body of evidence indicating the importance of physical stimuli for neuronal growth and development. In this review we briefly summarize the historical background of neurobiophysics and give an overview over the current understanding of neuronal growth from a physics perspective. We show how biophysics has so far contributed to a better understanding of neuronal growth and discuss current inconsistencies. Finally, we speculate how biophysics may contribute to the successful treatment of lesions to the central nervous system, which have been considered incurable until very recently.

  3. A Model of Controlled Growth

    Science.gov (United States)

    Bressan, Alberto; Lewicka, Marta

    2018-03-01

    We consider a free boundary problem for a system of PDEs, modeling the growth of a biological tissue. A morphogen, controlling volume growth, is produced by specific cells and then diffused and absorbed throughout the domain. The geometric shape of the growing tissue is determined by the instantaneous minimization of an elastic deformation energy, subject to a constraint on the volumetric growth. For an initial domain with C}^{2,α boundary, our main result establishes the local existence and uniqueness of a classical solution, up to a rigid motion.

  4. Gold catalytic Growth of Germanium Nanowires by chemical vapour deposition method

    Directory of Open Access Journals (Sweden)

    M. Zahedifar

    2013-03-01

    Full Text Available Germanium nanowires (GeNWs were synthesized using chemical vapor deposition (CVD based on vapor–liquid–solid (VLS mechanism with Au nanoparticles as catalyst and germanium tetrachloride (GeCl4 as a precursor of germanium. Au catalysts were deposited on silicon wafer as a thin film, firstly by sputtering technique and secondly by submerging the silicon substrates in Au colloidal solution, which resulted in Au nanoparticles with different sizes. GeNWs were synthesized at 400 °C, which is a low temperature for electrical device fabrication. Effect of different parameters such as Au nanoparticles size, carrier gas (Ar flow and mixture of H2 with the carrier gas on GeNWs diameter and shape was studied by SEM images. The chemical composition of the nanostructure was also examined by energy dispersive X-ray spectroscopy (EDS.

  5. Epitaxial growth of hybrid nanostructures

    Science.gov (United States)

    Tan, Chaoliang; Chen, Junze; Wu, Xue-Jun; Zhang, Hua

    2018-02-01

    Hybrid nanostructures are a class of materials that are typically composed of two or more different components, in which each component has at least one dimension on the nanoscale. The rational design and controlled synthesis of hybrid nanostructures are of great importance in enabling the fine tuning of their properties and functions. Epitaxial growth is a promising approach to the controlled synthesis of hybrid nanostructures with desired structures, crystal phases, exposed facets and/or interfaces. This Review provides a critical summary of the state of the art in the field of epitaxial growth of hybrid nanostructures. We discuss the historical development, architectures and compositions, epitaxy methods, characterization techniques and advantages of epitaxial hybrid nanostructures. Finally, we provide insight into future research directions in this area, which include the epitaxial growth of hybrid nanostructures from a wider range of materials, the study of the underlying mechanism and determining the role of epitaxial growth in influencing the properties and application performance of hybrid nanostructures.

  6. VT Designated Growth Center Boundary

    Data.gov (United States)

    Vermont Center for Geographic Information — Growth centers aim to align public infrastructure and private building investments with a local framework of policies and regulations to ensure that 20 years of...

  7. Corruption, Growth, and Public Finances

    OpenAIRE

    Vito Tanzi; Hamid R Davoodi

    2000-01-01

    The paper discusses some channels through which corruption affects growth such as the impact of corruption on enterprises, on the allocation of talent, and on investment. It also discusses the impact of corruption on some aspects of public finance.

  8. The Market for Smart Growth

    Science.gov (United States)

    Based on several studies of market demand, the authors determined that consumer demand for smart growth would translate into more than 600,000 houses out of the approximately 2 million new housing units built in 2007.

  9. Your Baby's Growth: 5 Months

    Science.gov (United States)

    ... Safe Videos for Educators Search English Español Your Baby's Growth: 5 Months KidsHealth / For Parents / Your Baby's ... a cause for concern. How Much Will My Baby Grow? By 5 months, your baby's birth weight ...

  10. Investor Protections and Economic Growth

    OpenAIRE

    Haidar, Jamal Ibrahim

    2009-01-01

    Using objective measures of investor protections in 170 countries, I establish that the level of investor protection matters for cross-country differences in GDP growth: countries with stronger protections tend to grow faster than those with poor investor protections.

  11. Traffic fatalities and economic growth

    Science.gov (United States)

    2003-04-01

    As countries develop death rates usually fall, especially for diseases that affect the young and result in substantial life-years lost. Deaths due to traffic accidents are a notable exception: the growth in motor vehicles that accompanies economic gr...

  12. National Survey of Family Growth

    Data.gov (United States)

    U.S. Department of Health & Human Services — The National Survey of Family Growth (NSFG) gathers information on family life, marriage and divorce, pregnancy, infertility, use of contraception, and men's and...

  13. Limits to the growth debate

    Energy Technology Data Exchange (ETDEWEB)

    Gordon, L.

    The first two major studies sponsored by the club of Rome were the report of the Meadows team at MIT, The Limits to Growth, published in 1972, and the Mesarovic and Pestel report, Mankind at the Turning Point, published in 1974. When the Club of Rome met in Philadelphia in April of 1976, its pronouncements reflected a frame of mind quite different from that of 1972. Recently, Herman Kahn and his colleagues at the Hudson Institute have published The Next 200 Years, a book evidently inspired as much by antagonism to the limits-to-growth school of thought as by affirmative faith in its own vision of technological optimism. The author discusses the content of the studies and summarizes his own position in four areas. (1) While no trend of growth of anything can continue indefinitely in the real world, there are not global physical limits to economic growth within a time frame susceptible to plausible foresight or relevant to policy making. (2) In some world regions, notably South Asia and tropical Africa, population growth rates do indeed threaten to create a kind of Malthusian trap, and the rapid reduction of fertility is critically important to their development prospects and urgent in time. (3) For other parts of the world, both rates and directions of growth will be more influenced by changes in preferences for consumption and in attitudes toward production than by physical constraints, although higher energy costs and environmental pressures will also be important influences in generating such changes in growth patterns. (4) Probable changes in directions of growth will generate new and important issues in international economic and political relations, with both dangers and opportunities for the evolving world order. (MCW)

  14. Military Expenditure, Threats, and Growth

    OpenAIRE

    Aizenman, Joshua; Glick, Reuven

    2003-01-01

    This paper clarifies one of the puzzling results of the economic growth literature: the impact of military expenditure is frequently found to be non-significant or negative, yet most countries spend a large fraction of their GDP on defense and the military. We start by empirical evaluation of the non- linear interactions between military expenditure, external threats, corruption, and other relevant controls. While growth falls with higher levels of military spending, given the values of the o...

  15. Retail payments and economic growth

    OpenAIRE

    Hasan, Iftekhar; De Renzis, Tania; Schmiedel , Heiko

    2012-01-01

    This paper examines the fundamental relationship between retail payments and overall economic growth. Using data from across 27 European markets over the period 1995–2009, the results confirm that migration to efficient electronic retail payments stimulates overall economic growth, consumption and trade. Among different payment instruments, this relationship is strongest for card payments, followed by credit transfers and direct debits. Cheque payments are found to have a relatively low macro...

  16. Growth, unemployment and wage inertia

    OpenAIRE

    Raurich, Xavier; Sorolla, Valeri

    2014-01-01

    We introduce wage setting via efficiency wages in the neoclassical one-sector growth model to study the growth effects of wage inertia. We compare the dynamic equilibrium of an economy with wage inertia with the equilibrium of an economy without wage inertia. We show that wage inertia affects the long run employment rate and that the transitional dynamics of the main economic variables will be different because wages are a state variable when wage inertia is introduced. In particular, we show...

  17. International Outsourcing and Productivity Growth

    OpenAIRE

    Martin Falk; Yvonne Wolfmayr

    2008-01-01

    This study investigates the impact of international outsourcing to low? and high income countries on total factor productivity growth based on manufacturing industry data for 14 OECD countries from 1995 ? 2000. We find that the broad measure of international outsourcing of material inputs to low income countries is significantly negatively related to productivity growth. Furthermore, while the narrow measure of international outsourcing of materials is not significant, purchased services from...

  18. Human Development and Economic Growth

    OpenAIRE

    Ranis, Gustav

    2004-01-01

    Recent literature has contrasted Human Development, described as the ultimate goal of the development process, with economic growth, described as an imperfect proxy for more general welfare, or as a means toward enhanced human development. This debate has broadened the definitions and goals of development but still needs to define the important interrelations between human development (HD) and economic growth (EG). To the extent that greater freedom and capabilities improve economic performan...

  19. [Saarland Growth Study: sampling design].

    Science.gov (United States)

    Danker-Hopfe, H; Zabransky, S

    2000-01-01

    The use of reference data to evaluate the physical development of children and adolescents is part of the daily routine in the paediatric ambulance. The construction of such reference data is based on the collection of extensive reference data. There are different kinds of reference data: cross sectional references, which are based on data collected from a big representative cross-sectional sample of the population, longitudinal references, which are based on follow-up surveys of usually smaller samples of individuals from birth to maturity, and mixed longitudinal references, which are a combination of longitudinal and cross-sectional reference data. The advantages and disadvantages of the different methods of data collection and the resulting reference data are discussed. The Saarland Growth Study was conducted for several reasons: growth processes are subject to secular changes, there are no specific reference data for children and adolescents from this part of the country and the growth charts in use in the paediatric praxis are possibly not appropriate any more. Therefore, the Saarland Growth Study served two purposes a) to create actual regional reference data and b) to create a database for future studies on secular trends in growth processes of children and adolescents from Saarland. The present contribution focusses on general remarks on the sampling design of (cross-sectional) growth surveys and its inferences for the design of the present study.

  20. Phenomenology of stochastic exponential growth

    Science.gov (United States)

    Pirjol, Dan; Jafarpour, Farshid; Iyer-Biswas, Srividya

    2017-06-01

    Stochastic exponential growth is observed in a variety of contexts, including molecular autocatalysis, nuclear fission, population growth, inflation of the universe, viral social media posts, and financial markets. Yet literature on modeling the phenomenology of these stochastic dynamics has predominantly focused on one model, geometric Brownian motion (GBM), which can be described as the solution of a Langevin equation with linear drift and linear multiplicative noise. Using recent experimental results on stochastic exponential growth of individual bacterial cell sizes, we motivate the need for a more general class of phenomenological models of stochastic exponential growth, which are consistent with the observation that the mean-rescaled distributions are approximately stationary at long times. We show that this behavior is not consistent with GBM, instead it is consistent with power-law multiplicative noise with positive fractional powers. Therefore, we consider this general class of phenomenological models for stochastic exponential growth, provide analytical solutions, and identify the important dimensionless combination of model parameters, which determines the shape of the mean-rescaled distribution. We also provide a prescription for robustly inferring model parameters from experimentally observed stochastic growth trajectories.

  1. Placental Adaptations in Growth Restriction

    Science.gov (United States)

    Zhang, Song; Regnault, Timothy R.H.; Barker, Paige L.; Botting, Kimberley J.; McMillen, Isabella C.; McMillan, Christine M.; Roberts, Claire T.; Morrison, Janna L.

    2015-01-01

    The placenta is the primary interface between the fetus and mother and plays an important role in maintaining fetal development and growth by facilitating the transfer of substrates and participating in modulating the maternal immune response to prevent immunological rejection of the conceptus. The major substrates required for fetal growth include oxygen, glucose, amino acids and fatty acids, and their transport processes depend on morphological characteristics of the placenta, such as placental size, morphology, blood flow and vascularity. Other factors including insulin-like growth factors, apoptosis, autophagy and glucocorticoid exposure also affect placental growth and substrate transport capacity. Intrauterine growth restriction (IUGR) is often a consequence of insufficiency, and is associated with a high incidence of perinatal morbidity and mortality, as well as increased risk of cardiovascular and metabolic diseases in later life. Several different experimental methods have been used to induce placental insufficiency and IUGR in animal models and a range of factors that regulate placental growth and substrate transport capacity have been demonstrated. While no model system completely recapitulates human IUGR, these animal models allow us to carefully dissect cellular and molecular mechanisms to improve our understanding and facilitate development of therapeutic interventions. PMID:25580812

  2. Preferential nucleation, guiding, and blocking of self-propelled droplets by dislocations

    Science.gov (United States)

    Kanjanachuchai, Songphol; Wongpinij, Thipusa; Kijamnajsuk, Suphakan; Himwas, Chalermchai; Panyakeow, Somsak; Photongkam, Pat

    2018-04-01

    Lattice-mismatched layers of GaAs/InGaAs are grown on GaAs(001) using molecular beam epitaxy and subsequently heated in vacuum while the surface is imaged in situ using low-energy electron microscopy, in order to study (i) the nucleation of group-III droplets formed as a result of noncongruent sublimation and (ii) the dynamics of these self-propelled droplets as they navigate the surface. It is found that the interfacial misfit dislocation network not only influences the nucleation sites of droplets, but also exerts unusual steering power over their subsequent motion. Atypical droplet flow patterns including 90° and 180° turns are found. The directions of these dislocations-guided droplets are qualitatively explained in terms of in-plane and out-of-plane stress fields associated with the buried dislocations and the driving forces due to chemical potential and stress gradients typical of Marangoni flow. The findings would benefit processes and devices that employ droplets as catalysts or active structures such as droplet epitaxy of quantum nanostructures, vapor-liquid-solid growth of nanowires, or the fabrication of self-integrated circuits.

  3. The ITO-capped WO3 nanowires biosensor based on field-effect transistor in label-free protein sensing

    International Nuclear Information System (INIS)

    Shariati, Mohsen

    2017-01-01

    The fabrication of ITO-capped WO 3 nanowires associated with their bio-sensing properties in field-effect transistor diagnostics basis as a biosensor has been reported. The bio-sensing property for manipulated nanowires elucidated that the grown nanostructures were very sensitive to protein. The ITO-capped WO 3 nanowires biosensor showed an intensive bio-sensing activity against reliable protein. Polylysine strongly charged bio-molecule was applied as model system to demonstrate the implementation of materialized biosensor. The employed sensing mechanism was 'label-free' and depended on bio-molecule's intrinsic charge. For nanowires synthesis, the vapor-liquid-solid mechanism was used. Nanowires were beyond a few hundred nanometers in lengths and around 15-20 nm in diameter, while the globe cap's size on the nanowires was around 15-25 nm. The indium tin oxide (ITO) played as catalyst in nanofabrication for WO 3 nanowires growth and had outstanding role in bio-sensing especially for bio-molecule adherence. In applied electric field presence, the fabricated device showed the great potential to enhance medical diagnostics. (orig.)

  4. The ITO-capped WO{sub 3} nanowires biosensor based on field-effect transistor in label-free protein sensing

    Energy Technology Data Exchange (ETDEWEB)

    Shariati, Mohsen [Sharif University of Technology, Institute for Nanoscience and Nanotechnology, Tehran (Iran, Islamic Republic of)

    2017-05-15

    The fabrication of ITO-capped WO{sub 3} nanowires associated with their bio-sensing properties in field-effect transistor diagnostics basis as a biosensor has been reported. The bio-sensing property for manipulated nanowires elucidated that the grown nanostructures were very sensitive to protein. The ITO-capped WO{sub 3} nanowires biosensor showed an intensive bio-sensing activity against reliable protein. Polylysine strongly charged bio-molecule was applied as model system to demonstrate the implementation of materialized biosensor. The employed sensing mechanism was 'label-free' and depended on bio-molecule's intrinsic charge. For nanowires synthesis, the vapor-liquid-solid mechanism was used. Nanowires were beyond a few hundred nanometers in lengths and around 15-20 nm in diameter, while the globe cap's size on the nanowires was around 15-25 nm. The indium tin oxide (ITO) played as catalyst in nanofabrication for WO{sub 3} nanowires growth and had outstanding role in bio-sensing especially for bio-molecule adherence. In applied electric field presence, the fabricated device showed the great potential to enhance medical diagnostics. (orig.)

  5. Magnetic Doping and Kondo Effect in Bi 2 Se 3 Nanoribbons

    KAUST Repository

    Cha, Judy J.; Williams, James R.; Kong, Desheng; Meister, Stefan; Peng, Hailin; Bestwick, Andrew J.; Gallagher, Patrick; Goldhaber-Gordon, David; Cui, Yi

    2010-01-01

    A simple surface band structure and a large bulk band gap have allowed Bi2Se3 to become a reference material for the newly discovered three-dimensional topological insulators, which exhibit topologically protected conducting surface states that reside inside the bulk band gap. Studying topological insulators such as Bi2Se3 in nanostructures is advantageous because of the high surfaceto-volume ratio, which enhances effects from the surface states; recently reported Aharonov-Bohm oscillation in topological insulator nanoribbons by some of us is a good example. Theoretically, introducing magnetic impurities in topological insulators is predicted to open a small gap in the surface states by breaking time-reversal symmetry. Here, we present synthesis of magnetically doped Bi 2Se3 nanoribbons by vapor-liquid-solid growth using magnetic metal thin films as catalysts. Although the doping concentration is less than ∼2 %. low-temperature transport measurements of the Fe-doped Bi2Se3 nanoribbon devices show a clear Kondo effect at temperatures below 30 K, confirming the presence of magnetic impurities in the Bi2Se3 nanoribbons. The capability to dope topological insulator nanostructures magnetically opens up exciting opportunities for spintronics. © 2010 American Chemical Society.

  6. Influence of helium-ion bombardment on the optical properties of ZnO nanorods/p-GaN light-emitting diodes

    Science.gov (United States)

    Alvi, Naveed Ul Hassan; Hussain, Sajjad; Jensen, Jen; Nur, Omer; Willander, Magnus

    2011-12-01

    Light-emitting diodes (LEDs) based on zinc oxide (ZnO) nanorods grown by vapor-liquid-solid catalytic growth method were irradiated with 2-MeV helium (He+) ions. The fabricated LEDs were irradiated with fluencies of approximately 2 × 1013 ions/cm2 and approximately 4 × 1013 ions/cm2. Scanning electron microscopy images showed that the morphology of the irradiated samples is not changed. The as-grown and He+-irradiated LEDs showed rectifying behavior with the same I-V characteristics. Photoluminescence (PL) measurements showed that there is a blue shift of approximately 0.0347 and 0.082 eV in the near-band emission (free exciton) and green emission of the irradiated ZnO nanorods, respectively. It was also observed that the PL intensity of the near-band emission was decreased after irradiation of the samples. The electroluminescence (EL) measurements of the fabricated LEDs showed that there is a blue shift of 0.125 eV in the broad green emission after irradiation and the EL intensity of violet emission approximately centered at 398 nm nearly disappeared after irradiations. The color-rendering properties show a small decrease in the color-rendering indices of 3% after 2 MeV He+ ions irradiation.

  7. Templated Control of Au nanospheres in Silica Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Tringe, J W; Vanamu, G; Zaidi, S H

    2007-03-15

    The formation of regularly-spaced metal nanostructures in selectively-placed insulating nanowires is an important step toward realization of a wide range of nano-scale electronic and opto-electronic devices. Here we report templated synthesis of Au nanospheres embedded in silica nanowires, with nanospheres consistently spaced with a period equal to three times their diameter. Under appropriate conditions, nanowires form exclusively on Si nanostructures because of enhanced local oxidation and reduced melting temperatures relative to templates with larger dimensions. We explain the spacing of the nanospheres with a general model based on a vapor-liquid-solid mechanism, in which an Au/Si alloy dendrite remains liquid in the nanotube until a critical Si concentration is achieved locally by silicon oxide-generated nanowire growth. Additional Si oxidation then locally reduces the surface energy of the Au-rich alloy by creating a new surface with minimum area inside of the nanotube. The isolated liquid domain subsequently evolves to become an Au nanosphere, and the process is repeated.

  8. Magnetic Doping and Kondo Effect in Bi 2 Se 3 Nanoribbons

    KAUST Repository

    Cha, Judy J.

    2010-03-10

    A simple surface band structure and a large bulk band gap have allowed Bi2Se3 to become a reference material for the newly discovered three-dimensional topological insulators, which exhibit topologically protected conducting surface states that reside inside the bulk band gap. Studying topological insulators such as Bi2Se3 in nanostructures is advantageous because of the high surfaceto-volume ratio, which enhances effects from the surface states; recently reported Aharonov-Bohm oscillation in topological insulator nanoribbons by some of us is a good example. Theoretically, introducing magnetic impurities in topological insulators is predicted to open a small gap in the surface states by breaking time-reversal symmetry. Here, we present synthesis of magnetically doped Bi 2Se3 nanoribbons by vapor-liquid-solid growth using magnetic metal thin films as catalysts. Although the doping concentration is less than ∼2 %. low-temperature transport measurements of the Fe-doped Bi2Se3 nanoribbon devices show a clear Kondo effect at temperatures below 30 K, confirming the presence of magnetic impurities in the Bi2Se3 nanoribbons. The capability to dope topological insulator nanostructures magnetically opens up exciting opportunities for spintronics. © 2010 American Chemical Society.

  9. Direct observation of doping incorporation pathways in self-catalytic GaMnAs nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Kasama, T., E-mail: tk@cen.dtu.dk; Yazdi, S. [Center for Electron Nanoscopy, Technical University of Denmark, DK-2800 Kongens Lyngby (Denmark); Thuvander, M. [Department of Applied Physics, Chalmers University of Technology, SE-41296 Gothenburg (Sweden); Siusys, A. [Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, PL-02-668 Warszawa (Poland); Gontard, L. C. [Instituto de Ciencia de Materiales de Sevilla (CSIC-US), C/Américo Vespucio 49, 41092 Seville (Spain); Kovács, A.; Duchamp, M.; Dunin-Borkowski, R. E. [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons and Peter Grünberg Institute, Forschungszentrum Jülich, D-52425 Jülich (Germany); Gustafsson, A. [Solid State Physics and the Nanometer Structure Consortium, Lund University, P.O. Box 118, SE-221 00 Lund (Sweden); Sadowski, J. [Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, PL-02-668 Warszawa (Poland); MAX-IV Laboratory, Lund University, P.O. Box 118, SE-221 00 Lund (Sweden)

    2015-08-07

    Doping mechanisms of Mn in GaAs nanowires (NWs) that have been grown self-catalytically at 600 °C by molecular beam epitaxy (MBE) are investigated using advanced electron microscopy techniques and atom probe tomography. Mn is found to be incorporated primarily in the form of non-magnetic tetragonal Ga{sub 0.82}Mn{sub 0.18} nanocrystals in Ga catalyst droplets at the ends of the NWs, while trace amounts of Mn (22 ± 4 at. ppm) are also distributed randomly in the NW bodies without forming clusters or precipitates. The nanocrystals are likely to form after switching off the reaction in the MBE chamber, since they are partially embedded in neck regions of the NWs. The Ga{sub 0.82}Mn{sub 0.18} nanocrystals and the low Mn concentration in the NW bodies are insufficient to induce a ferromagnetic phase transition, suggesting that it is difficult to have high Mn contents in GaAs even in 1-D NW growth via the vapor-liquid-solid process.

  10. Anticavitation and Differential Growth in Elastic Shells

    KAUST Repository

    Moulton, Derek E.; Goriely, Alain

    2010-01-01

    infinite growth or resorption is imposed at the inner surface of the shell. However, void collapse can occur in a limiting sense when radial and circumferential growth are properly balanced. Growth functions which diverge or vanish at a point arise

  11. Economic growth and gender equality | IDRC - International ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    And conversely, does gender equality impact economic growth? ... change and growth in the economy on women's employment opportunities and the type ... sectors and their overall effect on development outcomes, such as economic growth ...

  12. Student Augmentation for Crystal Growth Research

    National Research Council Canada - National Science Library

    Prasad, V

    1999-01-01

    ... intelligent modeling, design and control of crystal growth processes. One doctoral student worked on integrating the radiation heat transfer model into MASTRAPP, the crystal growth model developed by the Consortium for Crystal Growth Research...

  13. Best practices for rural smart growth.

    Science.gov (United States)

    2010-07-01

    Smart growth is a development strategy that encompasses economic, environmental and social objectives to manage : the growth of a community. The basic principles of smart growth are to: : Mix land uses. : Take advantage of compact building de...

  14. Growth and Economic Opportunities for Women: Strengthening ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    Asian outlook: New growth dependent on new productivity. There is no doubt that Canada is tying its future growth prospects to Asia. View moreAsian outlook: New growth dependent on new productivity ...

  15. Understanding "Inclusive Growth": Advancing the global agenda ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    2013-03-27

    Mar 27, 2013 ... Increasingly, the concept of "inclusive growth," where the benefits of economic growth are ... Growth is less likely to be sustainable with high and/or growing inequalities, and ... A global vision for small business in Egypt.

  16. Nutritionally-Induced Catch-Up Growth

    Directory of Open Access Journals (Sweden)

    Galia Gat-Yablonski

    2015-01-01

    Full Text Available Malnutrition is considered a leading cause of growth attenuation in children. When food is replenished, spontaneous catch-up (CU growth usually occurs, bringing the child back to its original growth trajectory. However, in some cases, the CU growth is not complete, leading to a permanent growth deficit. This review summarizes our current knowledge regarding the mechanism regulating nutrition and growth, including systemic factors, such as insulin, growth hormone, insulin- like growth factor-1, vitamin D, fibroblast growth factor-21, etc., and local mechanisms, including autophagy, as well as regulators of transcription, protein synthesis, miRNAs and epigenetics. Studying the molecular mechanisms regulating CU growth may lead to the establishment of better nutritional and therapeutic regimens for more effective CU growth in children with malnutrition and growth abnormalities. It will be fascinating to follow this research in the coming years and to translate the knowledge gained to clinical benefit.

  17. Alves VLS, Feldman LB, organizers. Managers of Health in the Scope of Quality: Acting and Competences, multi-disciplined approach. São Paulo (SP: Martinari; 2011

    Directory of Open Access Journals (Sweden)

    Cláudio José de Souza

    2013-07-01

    Full Text Available The changes of the contemporaneity demanded that the professionals in the area of health, besides contemplating the scope of care, also absorbed the managing area. The authors of the reviewed work reaffirmed that, in these two decades of XXI century, there is a close relation between care and management.

  18. Determinants of economic growth in BRIC countries

    OpenAIRE

    Rajjev K. Goel

    2011-01-01

    We study economic growth in four emerging economies - Brazil, Russia, India, and China (BRIC). Questions addressed are: (a) How do medium term growth determinants differ from short term determinants? (b) What are differences between growth effects of aggregate versus disaggregated exports? And (c) Does lower institutional quality hinder growth? Results show that while BRIC nations have higher growth, there are significant within-group differences. China and Russia mostly showed higher growth,...

  19. Stem secondary growth of tundra shrubs

    DEFF Research Database (Denmark)

    Campioli, Matteo; Leblans, Niki; Michelsen, Anders

    2012-01-01

    Our knowledge of stem secondary growth of arctic shrubs (a key component of tundra net primary production, NPP) is very limited. Here, we investigated the impact of the physical elements of the environment on shrub secondary growth by comparing annual growth rates of model species from similar...... growth (stem apical growth, stem length, and apical growth of stem plus leaves), in some cases even with opposite responses. Thus caution should be taken when estimating the impact of the environment on shrub growth from apical growth only. Integration of our data set with the (very limited) previously...

  20. Growth and Predictors of Growth Restraint in Moderately Preterm Children Aged 0 to 4 Years

    NARCIS (Netherlands)

    Bocca-Tjeertes, I.F.; Kerstjens, J.M.; Reijneveld, S.A.; de Winter, A.F.; Bos, A.F.

    2011-01-01

    OBJECTIVE: To describe growth in moderately preterm-born children, determine the prevalence of growth restraint at the age of 4, and identify predictors of growth restraint. We hypothesized that growth in moderately preterm-born children differs from growth in term-born children and that growth

  1. Green growth in the Netherlands

    International Nuclear Information System (INIS)

    Balde, K.; Boelens, A.; Brinksma, E.; Edens, B.; Hiethaar, S.; Klein, P.; Schenau, S.

    2011-04-01

    In 2009 the Ministerial Council Meeting of the Organisation for Economic Co-operation and Development (OECD) committed itself to a green growth strategy. Such a strategy fosters economic growth and development while ensuring that natural resources can continue to provide the ecosystem services on which our well-being relies. It also endorses investment, competition and innovation which will underpin sustained growth and give rise to new economic opportunities. Green growth provides both a policy strategy for implementing this economic transformation and a monitoring framework with a proposed set of indicators. This report presents an overview of the state of green growth in the Netherlands. It should be regarded as a benchmark for a more thorough and comprehensive assessment of green growth in the future. It is based on the set of indicators proposed by the OECD in their intermediate report of February 2011. Data relevant to the Dutch situation are presented for twenty of these indicators, illustrating the observed trends. The indicators are grouped in four themes. For the first theme, environmental efficiency of production, on the whole the indicators show increased efficiency. However, indicators such as greenhouse gas intensity, energy efficiency and material intensity show only relative decoupling, which on its own is not enough to ensure green growth. In addition, the increase in environmental efficiency is partly explained by substitution of imports for domestic production, which is not conducive to green growth on a global scale: the efficiency gains in domestic production, for example, are offset by increases in foreign greenhouse gas emissions. Water use and agricultural nutrient surpluses are the only indicators where absolute decoupling has occurred. The second theme contains indicators regarding the natural assets base. This group of indicators provides a mixed picture. Natural gas reserves are decreasing and the overall level of threat to animal

  2. Phytochrome, plant growth and flowering

    Science.gov (United States)

    King, R. W.; Bagnall, D. J.

    1994-01-01

    Attempts to use artificially lit cabinets to grow plants identical to those growing in sunlight have provided compelling evidence of the importance of light quality for plant growth. Changing the balance of red (R) to far-red (FR) radiation, but with a fixed photosynthetic input can shift the phytochrome photoequilibrium in a plant and generate large differences in plant growth. With FR enrichment the plants elongate, and may produce more leaf area and dry matter. Similar morphogenic responses are also obtained when light quality is altered only briefly (15-30 min) at the end-of-the-day. Conversely, for plants grown in natural conditions the response of plant form to selective spectral filtering has again shown that red and far-red wavebands are important as found by Kasperbauer and coworkers. Also, where photosynthetic photon flux densities (PPFD) of sunlight have been held constant, the removal of far-red alone alters plant growth. With FR depletion plants grown in sunlight are small, more branched and darker green. Here we examine the implications for plant growth and flowering when the far-red composition of incident radiation in plant growth chambers is manipulated.

  3. Universality in stochastic exponential growth.

    Science.gov (United States)

    Iyer-Biswas, Srividya; Crooks, Gavin E; Scherer, Norbert F; Dinner, Aaron R

    2014-07-11

    Recent imaging data for single bacterial cells reveal that their mean sizes grow exponentially in time and that their size distributions collapse to a single curve when rescaled by their means. An analogous result holds for the division-time distributions. A model is needed to delineate the minimal requirements for these scaling behaviors. We formulate a microscopic theory of stochastic exponential growth as a Master Equation that accounts for these observations, in contrast to existing quantitative models of stochastic exponential growth (e.g., the Black-Scholes equation or geometric Brownian motion). Our model, the stochastic Hinshelwood cycle (SHC), is an autocatalytic reaction cycle in which each molecular species catalyzes the production of the next. By finding exact analytical solutions to the SHC and the corresponding first passage time problem, we uncover universal signatures of fluctuations in exponential growth and division. The model makes minimal assumptions, and we describe how more complex reaction networks can reduce to such a cycle. We thus expect similar scalings to be discovered in stochastic processes resulting in exponential growth that appear in diverse contexts such as cosmology, finance, technology, and population growth.

  4. Phytochrome, plant growth and flowering

    Energy Technology Data Exchange (ETDEWEB)

    King, R.W.; Bagnall, D.J. [CSIRO, Canberra (Australia)

    1994-12-31

    Attempts to use artificially lit cabinets to grow plants identical to those growing in sunlight have provided compelling evidence of the importance of light quality for plant growth. Changing the balance of red (R) to far-red (FR) radiation, but with a fixed photosynthetic input can shift the phytochrome photoequilibrium in a plant and generate large differences in plant growth. With FR enrichment the plants elongate, and may produce more leaf area and dry matter. Similar morphogenic responses are also obtained when light quality is altered only briefly (15-30 min) at the end-of-the-day. Conversely, for plants grown in natural conditions the response of plant form to selective spectral filtering has again shown that red and far-red wavebands are important as found by Kasperbauer and coworkers. Also, where photosynthetic photon flux densities (PPFD) of sunlight have been held constant, the removal of far-red alone alters plant growth. As shown for chrysanthemum, with FR depletion plants grown in sunlight are small, more branched and darker green. We examine the implications for plant growth and flowering when the far-red composition of incident radiation in plant growth chambers is manipulated.

  5. American growth and Napoleonic Wars

    Directory of Open Access Journals (Sweden)

    Vergil Hasan

    2013-01-01

    Full Text Available Four years after the French Revolution, in 1793 a series of wars among France and other major powers of Europe began and they lasted until 1815. There is disagreement among economic historians about the effects of these wars on the trend of US economic growth. This paper aims to answer the following question. Did America as a neutral nation take advantage of economic possibilities caused by Europe at war through trade? To put it differently, this paper questions whether there was an export-led growth due to the war. To answer this question, we re-examined the export-led growth hypothesis for the period 1790-1860 using the ARDL methodology. Based on this methodology, a cointegrated relationship is found among the variables of real GDP, labor, exports and exchange rates. The results suggest that the economic growth of the US was not export-driven. In addition, parallel to the results of unit root tests with structural breaks, the coefficient of the dummy variable was statistically significant in the long run, implying that the war did have a significant effect on the economic growth trend of the US.

  6. SME Cooperation on Innovation & Growth

    DEFF Research Database (Denmark)

    Brink, Tove; Neville, Mette

    2016-01-01

    The research in this paper reveals how cooperation of SMEs can enable innovation and growth. The research is conducted in a four-year period with 24 SMEs participating from different industry branches. The research is now in the late part of the 3rd. year starting in 2013 and finished January 2017....... Preliminary findings are revealed here and discussed with the SMEs. Shorter-term cooperation and especially longer-term collaboration is important for SMEs to enable innovation and growth. The content of collaboration is based on the cross-disciplinary trinity of organisational- and managerial development......, business model development and financial development. The trinity requires time to get the specific insight on application for each SME. An enhanced contribution is made to the field of SMEs, to academia and to public bodies to understand the needed initiatives to support SMEs for innovation and growth...

  7. Filamentous Growth in Eremothecium Fungi

    DEFF Research Database (Denmark)

    Oskarsson, Therese

    , this thesis deals with some of the aspects of hyphal growth, which is an important virulence factor for pathogenic fungi infecting both humans and plants. Hyphal establishment through continuous polar growth is a complex process, requiring the careful coordination of a large subset of proteins involved......-regulatory activity of AgGts1, the protein could have additional actin organizing properties. In the second and third part, this thesis addresses the use of A. gossypii and its relative E. cymbalariae as model organisms for filamentous growth. A series of assays analyzed the capability of Eremothecium genus fungi...... of molecular tools for E. cymbalariae to enable a faster and more efficient approach for genetic comparisons between Eremothecium genus fungi....

  8. Energy consumption and economic growth

    Energy Technology Data Exchange (ETDEWEB)

    Brookes, L G

    1972-10-01

    A mathematical model relating Gross National Product (GNP) per capita to useful energy consumed per capita is demonstrated to predict the shift in this relationship actually experienced in the U.K. and the U.S. over a period of years. World GNP growths in the recent past are used to forecast GNP growth to the year 2030 and also (via the model) the necessary fuel consumption for such growth; likewise, potential production of fossil fuels (exclusive of tar sands and oil shale) is shown to 2030, based on two different assumptions about total world reserves. Fossil fuel ceases to meet world requirements for energy at some time between 1985 and 1995. The most likely candidate for filling the gap is nuclear power.

  9. Employment growth and regional development

    DEFF Research Database (Denmark)

    Eriksson, Rikard; Hansen, Høgni Kalsø; Winther, Lars

    2017-01-01

    This paper explores the potential drivers behind uneven regional development in the context of employment growth in Denmark and Sweden. In particular, we are interested in the roles of urbanization, industrial change and the rise of the new economy as manifested in the growth of the two economies...... in 2002–2007. The aim of this paper is, therefore, to analyse the impact of a number of key industrial sectors on regional employment growth in the two countries. The empirical analysis is based on longitudinal matched employer–employee data retrieved from official registers in each economy from 2002...... economies, we find that, although in general these economies react relatively similarly to changes, embarking on a narrower analysis of the individual sectors reveals marked national differences. This indicates that context matters in the analysis of regional economic dynamics in terms of structure, system...

  10. Nerve growth factor promotes human hemopoietic colony growth and differentiation

    International Nuclear Information System (INIS)

    Matsuda, H.; Coughlin, M.D.; Bienenstock, J.; Denburg, J.A.

    1988-01-01

    Nerve growth factor (NGF) is a neurotropic polypeptide necessary for the survival and growth of some central neurons, as well as sensory afferent and sympathetic neurons. Much is now known of the structural and functional characteristics of NGF, whose gene has recently been clones. Since it is synthesized in largest amounts by the male mouse submandibular gland, its role exclusively in nerve growth is questionable. These experiments indicate that NGF causes a significant stimulation of granulocyte colonies grown from human peripheral blood in standard hemopoietic methylcellulose assays. Further, NGF appears to act in a relatively selective fashion to induce the differentiation of eosinophils and basophils/mast cells. Depletion experiments show that the NGF effect may be T-cell dependent and that NGF augments the colony-stimulating effect of supernatants from the leukemic T-cell (Mo) line. The hemopoietic activity of NGF is blocked by 125 I-polyclonal and monoclonal antibodies to NGF. The authors conclude that NGF may indirectly act as a local growth factor in tissues other than those of the nervous system by causing T cells to synthesize or secrete molecules with colony-stimulating activity. In view of the synthesis of NGF in tissue injury, the involvement of basophils/mast cells and eosinophils in allergic and other inflammatory processes, and the association of mast cells with fibrosis and tissue repair, they postulate that NGF plays an important biological role in a variety of repair processes

  11. Surfactant-Mediated Growth Revisited

    International Nuclear Information System (INIS)

    Meyerheim, H. L.; Sander, D.; Popescu, R.; Pan, W.; Kirschner, J.; Popa, I.

    2007-01-01

    The x-ray structure analysis of the oxygen-surfactant-mediated growth of Ni on Cu(001) identifies up to 0.15 monolayers of oxygen in subsurface octahedral sites. This questions the validity of the general view that surfactant oxygen floats on top of the growing Ni film. Rather, the surfactant action is ascribed to an oxygen-enriched zone extending over the two topmost layers. Surface stress measurements support this finding. Our results have important implications for the microscopic understanding of surfactant-mediated growth and the change of the magnetic anisotropy of the Ni films

  12. Monitoring crack growth using thermography

    International Nuclear Information System (INIS)

    Djedjiga, Ait Aouita; Abdeldjalil, Ouahabi

    2008-01-01

    The purpose of this work is to present a novel strategy for real-time monitoring crack growth of materials. The process is based on the use of thermal data extracted along the horizontal axis of symmetry of single edge notch tension (SENT) specimens, during fatigue tests. These data are exploited using an implemented program to detect in situ the growth of fatigue crack, with the critical size and propagation speed of the crack. This technique has the advantage to be applicable to a wide range of materials regardless of their electrical conductivity and their surface texture. (authors)

  13. Innovation, resources and economic growth

    International Nuclear Information System (INIS)

    Curzio, A.Q.; Fortis, M.; Zoboli, R.

    1994-01-01

    The book is concerned with the following items: 1. Technological Creativity and Institutions, 2. Innovation at Work in an Historical-Economic Perspective: Energy and Industrial Materials, 3. Scientific Revolutions and Strategies of Economic Supremacy: Advanced Materials and Biotechnologies, 4. Economic Growth and Agro-Food Policies in Key Problem Regions: Former USSR and LDCs, 5. Economic Growth and Natural Resources at Risk: Climate Change, Forests and Water and in Conclusion: Innovation and Resources in a Global Policy Perspective. Only one chapter have regard to energy problems: Energie efficient technologies: past and future perspectives. (UA)

  14. The gendered politics of growth

    DEFF Research Database (Denmark)

    Neergaard, Helle; Bøllingtoft, Anne

    Based on a review of existing research on growth and gender, this paper challenges the traditional financial and economic assumptions about new venture growth. It proposes that there are numerous ways in which a new venture may 'grow' other than growing the business organically and that women...... simply choose other strategic avenues for growing their business that do not produce performance data measurable in traditional ways. Nevertheless, they contribute considerably to turning the wheels of the economy, wherefore it is necessary to produce an understanding of their choices which goes beyond...

  15. The Simplest Unified Growth Theory

    DEFF Research Database (Denmark)

    Strulik, Holger; Weisdorf, Jacob Louis

    This paper provides a unified growth theory, i.e. a model that explains the very long-run economic and demographic development path of industrialized economies, stretching from the pre-industrial era to present-day and beyond. Making strict use of Malthus' (1798) so-called preventive check...... hypothesis - that fertility rates vary inversely with the price of food - the current study offers a new and straightforward explanation for the demographic transition and the break with the Malthusian era. The current framework lends support to existing unified growth theories and is well in tune...

  16. Growth Factors and Tension-Induced Skeletal Muscle Growth

    Science.gov (United States)

    Vandenburgh, Herman H.

    1994-01-01

    The project investigated biochemical mechanisms to enhance skeletal muscle growth, and developed a computer based mechanical cell stimulator system. The biochemicals investigated in this study were insulin/(Insulin like Growth Factor) IGF-1 and Steroids. In order to analyze which growth factors are essential for stretch-induced muscle growth in vitro, we developed a defined, serum-free medium in which the differentiated, cultured avian muscle fibers could be maintained for extended periods of time. The defined medium (muscle maintenance medium, MM medium) maintains the nitrogen balance of the myofibers for 3 to 7 days, based on myofiber diameter measurements and myosin heavy chain content. Insulin and IGF-1, but not IGF-2, induced pronounced myofiber hypertrophy when added to this medium. In 5 to 7 days, muscle fiber diameters increase by 71 % to 98% compared to untreated controls. Mechanical stimulation of the avian muscle fibers in MM medium increased the sensitivity of the cells to insulin and IGF-1, based on a leftward shift of the insulin dose/response curve for protein synthesis rates. (54). We developed a ligand binding assay for IGF-1 binding proteins and found that the avian skeletal muscle cultures produced three major species of 31, 36 and 43 kD molecular weight (54) Stretch of the myofibers was found to have no significant effect on the efflux of IGF-1 binding proteins, but addition of exogenous collagen stimulated IGF-1 binding protein production 1.5 to 5 fold. Steroid hormones have a profound effect on muscle protein turnover rates in vivo, with the stress-related glucocorticoids inducing rapid skeletal muscle atrophy while androgenic steroids induce skeletal muscle growth. Exercise in humans and animals reduces the catabolic effects of glucocorticoids and may enhance the anabolic effects of androgenic steroids on skeletal muscle. In our continuing work on the involvement of exogenrus growth factors in stretch-induced avian skeletal muscle growth, we

  17. When economic growth is less than exponential

    DEFF Research Database (Denmark)

    Groth, Christian; Koch, Karl-Josef; Steger, Thomas

    2010-01-01

    This paper argues that growth theory needs a more general notion of "regularity" than that of exponential growth. We suggest that paths along which the rate of decline of the growth rate is proportional to the growth rate itself deserve attention. This opens up for considering a richer set...

  18. When Economic Growth is Less than Exponential

    DEFF Research Database (Denmark)

    Groth, Christian; Koch, Karl-Josef; Steger, Thomas M.

    This paper argues that growth theory needs a more general notion of "regularity" than that of exponential growth. We suggest that paths along which the rate of decline of the growth rate is proportional to the growth rate itself deserve attention. This opens up for considering a richer set...

  19. The Growth Opportunity Channel of Debt Structure

    NARCIS (Netherlands)

    Giambona, E.; Golec, J.

    2013-01-01

    This paper studies the importance of growth opportunities for debt structure decisions. High growth firms use more unsecured debt to preserve financial flexibility (in the form of untapped secured debt capacity) in connection with future growth opportunities: the growth opportunity channel of debt

  20. Nonlinear Growth Curves in Developmental Research

    Science.gov (United States)

    Grimm, Kevin J.; Ram, Nilam; Hamagami, Fumiaki

    2011-01-01

    Developmentalists are often interested in understanding change processes, and growth models are the most common analytic tool for examining such processes. Nonlinear growth curves are especially valuable to developmentalists because the defining characteristics of the growth process such as initial levels, rates of change during growth spurts, and…

  1. The relative volume growth of minimal submanifolds

    DEFF Research Database (Denmark)

    Markvorsen, Steen; Palmer, V.

    2002-01-01

    The volume growth of certain well-defined subsets of minimal submanifolds in riemannian spaces are compared with the volume growth of balls and spheres ill space forms of constant curvature.......The volume growth of certain well-defined subsets of minimal submanifolds in riemannian spaces are compared with the volume growth of balls and spheres ill space forms of constant curvature....

  2. Energy, economic growth, and human welfare

    International Nuclear Information System (INIS)

    Schurr, S.H.

    1984-01-01

    The subject is covered in sections, entitled: economic growth and human welfare; world-wide economic growth; economic growth and energy consumption; assessing the future; caution advised; energy supply and economic growth; supply as constraint; sound policies needed. (U.K.)

  3. Obesity, growth hormone and weight loss

    DEFF Research Database (Denmark)

    Rasmussen, Michael Højby

    2009-01-01

    Growth hormone (GH) is the most important hormonal regulator of postnatal longitudinal growth in man. In adults GH is no longer needed for longitudinal growth. Adults with growth hormone deficiency (GHD) are characterised by perturbations in body composition, lipid metabolism, cardiovascular risk...

  4. Understanding "Inclusive Growth": Advancing the global agenda ...

    International Development Research Centre (IDRC) Digital Library (Canada)

    27 mars 2013 ... Increasingly, the concept of "inclusive growth," where the benefits of economic growth are enjoyed across societies, is being recognized and advanced by many countries. Growth is less likely to be sustainable with high and/or growing inequalities, and inequality can hamper growth.

  5. Evaluating growth performance of young stands

    Science.gov (United States)

    A. L. Roe; R. E. Benson

    1966-01-01

    A simple procedure for evaluating the diameter growth of young stands in relation to potential growth is described. A comparison technique is developed which contrasts relative diameter of crop trees to the relative diameter growth of the last decade to show the condition and trend of growth in the stand. The method is objective, easy to use, and has several...

  6. Homeorhetic hormones, metabolites and accelerated growth ...

    African Journals Online (AJOL)

    Blood samples were drawn from surgically implanted catheters in the caudal aorta and vena cava during normal growth, maintenance (zero) growth and accelerated growth.These samples were assayed for glucose, free fatty acids, glycerol, alanine, lysine, growth hormone, insulin and thyroxine. It was found that during the ...

  7. Resveratrol prevents endothelial cells injury in high-dose interleukin-2 therapy against melanoma.

    Directory of Open Access Journals (Sweden)

    Hongbing Guan

    Full Text Available Immunotherapy with high-dose interleukin-2 (HDIL-2 is an effective treatment for patients with metastatic melanoma and renal cell carcinoma. However, it is accompanied by severe toxicity involving endothelial cell injury and induction of vascular leak syndrome (VLS. In this study, we found that resveratrol, a plant polyphenol with anti-inflammatory and anti-cancer properties, was able to prevent the endothelial cell injury and inhibit the development of VLS while improving the efficacy of HDIL-2 therapy in the killing of metastasized melanoma. Specifically, C57BL/6 mice were injected with B16F10 cells followed by resveratrol by gavage the next day and continued treatment with resveratrol once a day. On day 9, mice received HDIL-2. On day 12, mice were evaluated for VLS and tumor metastasis. We found that resveratrol significantly inhibited the development of VLS in lung and liver by protecting endothelial cell integrity and preventing endothelial cells from undergoing apoptosis. The metastasis and growth of the tumor in lung were significantly inhibited by HDIL-2 and HDIL-2 + resveratrol treatment. Notably, HDIL-2 + resveratrol co-treatment was more effective in inhibiting tumor metastasis and growth than HDIL-2 treatment alone. We also analyzed the immune status of Gr-1(+CD11b(+ myeloid-derived suppressor cells (MDSC and FoxP3(+CD4(+ regulatory T cells (Treg. We found that resveratrol induced expansion and suppressive function of MDSC which inhibited the development of VLS after adoptive transfer. However, resveratrol suppressed the HDIL-2-induced expansion of Treg cells. We also found that resveratrol enhanced the susceptibility of melanoma to the cytotoxicity of IL-2-activated killer cells, and induced the expression of the tumor suppressor gene FoxO1. Our results suggested the potential use of resveratrol in HDIL-2 treatment against melanoma. We also demonstrated, for the first time, that MDSC is the dominant suppressor cell than regulatory

  8. Fibroblast growth factor receptors in breast cancer.

    Science.gov (United States)

    Wang, Shuwei; Ding, Zhongyang

    2017-05-01

    Fibroblast growth factor receptors are growth factor receptor tyrosine kinases, exerting their roles in embryogenesis, tissue homeostasis, and development of breast cancer. Recent genetic studies have identified some subtypes of fibroblast growth factor receptors as strong genetic loci associated with breast cancer. In this article, we review the recent epidemiological findings and experiment results of fibroblast growth factor receptors in breast cancer. First, we summarized the structure and physiological function of fibroblast growth factor receptors in humans. Then, we discussed the common genetic variations in fibroblast growth factor receptors that affect breast cancer risk. In addition, we also introduced the potential roles of each fibroblast growth factor receptors isoform in breast cancer. Finally, we explored the potential therapeutics targeting fibroblast growth factor receptors for breast cancer. Based on the biological mechanisms of fibroblast growth factor receptors leading to the pathogenesis in breast cancer, targeting fibroblast growth factor receptors may provide new opportunities for breast cancer therapeutic strategies.

  9. Emittance growth in rf linacs

    International Nuclear Information System (INIS)

    Jameson, R.A.

    1979-01-01

    As the space-charge limit is approached, the current that can be accelerated in an rf linac and the output emittance that can be expected are discussed. The role of the envelope equations to estimate limits is outlined. The results of numerical experiments to explore general properties of emittance growth are given

  10. Exhaustible resources and economic growth

    International Nuclear Information System (INIS)

    Campbell, H.F.

    1984-09-01

    This study examines the effect of a booming natural resource sector on regional economic growth, with particular attention to the impact of regional government policy on mineral rent taxation and the allocation of resource revenues. The author's approach is first to document the relevant theory and then apply it to the case of the uranium industry in Saskatchewan

  11. Knowledge Spillovers and Economic Growth

    NARCIS (Netherlands)

    A.J. van Stel (André); H.R. Nieuwenhuijsen

    2002-01-01

    textabstractThe importance of knowledge spillovers for achieving innovation and economic growth is widely recognized. It is not straightforward which type of spillovers is most effective: intra-sectoral spillovers or inter-sectoral spillovers. We investigate this controversy using a model of

  12. Intrauterine growth restriction - part 2.

    Science.gov (United States)

    Sharma, Deepak; Farahbakhsh, Nazanin; Shastri, Sweta; Sharma, Pradeep

    2016-12-01

    Small for gestational age (SGA) infants have been classically defined as having birth weight less than two standard deviations below the mean or less than the 10th percentile of a population-specific birth weight for specific gestational age, whereas intrauterine growth restriction (IUGR) has been defined as a rate of foetal growth that is less than normal for the population and for the growth potential of a specific infant. SGA infants have more frequent problems such as perinatal asphyxia, hypothermia, hypoglycaemia, polycythaemia and many more when compared with their appropriate for gestational age counterpart. They too have growth retardation and various major and subtle neurodevelopmental handicaps, with higher rates of perinatal and neonatal mortality. With the advent of newer technologies, even though the perinatal diagnosis of these SGA/IUGR foetuses has increased, but still perinatal morbidity and mortality rates are higher than normal foetuses and infants. In this part, we have covered neonatal IUGR classification, postnatal diagnosis, short-term and long-term complications faced by these IUGR infants.

  13. Effective growth paths for SMEs

    NARCIS (Netherlands)

    Wakkee, I.A.M.; van der Veen, M.; Eurlings, W.

    2015-01-01

    How firms grow forms a key question in the research on small and medium-sized enterprises (SMEs). Based on a survey amongst 1,535 SMEs, we show that the presence of growth capability factors, such as, innovation capacity, financing capacity and human capital, offers inadequate explanation for

  14. Globalization and limit to growth

    International Nuclear Information System (INIS)

    Gros, D.

    2009-01-01

    A global financial crisis is not the only concern the world should have. From oil and other commodities new challenges arise, that could be difficult to face properly and could provide another limit to growth. This Malthusian feature of the 21. century emerges clearly if one focuses on climate change. [it

  15. Growth and photosynthesis of lettuce

    NARCIS (Netherlands)

    Holsteijn, van H.M.C.

    1981-01-01

    Butterhead lettuce is an important glass-house crop in the poor light period in The Netherlands. Fundamental data about the influence of temperature, light and CO 2 on growth and photosynthesis are important e.g. to facilitate selection criteria for new cultivars. In

  16. Financial Liberalization and Economic Growth

    NARCIS (Netherlands)

    Bumann, S.; Hermes, N.; Lensink, B.W.

    2013-01-01

    This study provides a systematic analysis of the empirical literature on the relationship between financial liberalization and economic growth by conducting a meta-analysis, based on 441 t-statistics reported in 60 empirical studies. We focus on explaining the heterogeneity of results in our sample

  17. Dynamic dewetting through micropancake growth

    NARCIS (Netherlands)

    Seddon, James Richard Thorley; Bliznyuk, O.; Bliznyuk, Olesya; Kooij, Ernst S.; Poelsema, Bene; Zandvliet, Henricus J.W.; Lohse, Detlef

    2010-01-01

    We experimentally investigate the dynamics of nanometer-high, micrometer-wide gassy layers at the interface between a hydrophobic solid and bulk water. These micropancakes grow laterally in time, on the timescale of an hour, leading to partial dewetting of the solid. The growth is directional,

  18. Numerical prediction of rose growth

    NARCIS (Netherlands)

    Bernsen, E.; Bokhove, Onno; van der Sar, D.M.

    2006-01-01

    A new mathematical model is presented for the prediction of rose growth in a greenhouse. Given the measured ambient environmental conditions, the model consists of a local photosynthesis model, predicting the photosynthesis per unit leaf area, coupled to a global greenhouse model, which predicts the

  19. Intangible capital and economic growth

    NARCIS (Netherlands)

    Chen, Wen

    2016-01-01

    Modern economic growth stems in good part from investments in knowledge-based intangible assets, such as research and development (R&D), organisational know-how, product design, branding and marketing. By capitalising expenditures on these intangibles as business investments, this thesis

  20. Cultural diversity and economic growth

    DEFF Research Database (Denmark)

    Ager, Philipp; Brückner, Markus

    2013-01-01

    We exploit the large inflow of immigrants to the US during the 1870–1920 period to examine the effects that within-county changes in the cultural composition of the US population had on output growth. We construct measures of fractionalization and polarization to distinguish between the different...

  1. Growth of the zebrafish heart

    NARCIS (Netherlands)

    de Pater, E.M.

    2010-01-01

    Outline of this thesis In order to find new genetic factors, which are involved in cardiac growth we performed a forward genetic screen and we report the outcome of this screen in chapter 2. We screened at 5 days post fertilization (dpf) for mutants with either an enlarged heart or reduced heart

  2. Mudcake growth: Model and implications

    KAUST Repository

    Liu, Q.; Santamarina, Carlos

    2017-01-01

    cementing, and to prevent partial differential sticking. We developed a robust mud cake growth model for water-based mud based on wide stress-range constitutive equations within a Lagrangian reference system to avoid non-natural moving boundary solutions

  3. Growth charts of human development

    NARCIS (Netherlands)

    Van Buuren, Stef

    2014-01-01

    This article reviews and compares two types of growth charts for tracking human development over age. Both charts assume the existence of a continuous latent variable, but relate to the observed data in different ways. The D-score diagram summarizes developmental indicators into a single aggregate

  4. Employment Growth and International Trade

    DEFF Research Database (Denmark)

    Ibsen, Rikke; Warzynski, Frederic; Westergård-Nielsen, Niels Chr.

    In this paper, we use a detailed dataset containing information about all international trade transactions of the population of Danish ?rms over more than a decade to analyze the relationship between export and import decisions and employment growth. We further distinguish between imports of ?nal...

  5. Stochastic theory of grain growth

    International Nuclear Information System (INIS)

    Hu Haiyun; Xing Xiusan.

    1990-11-01

    The purpose of this note is to set up a stochastic theory of grain growth and to derive the statistical distribution function and the average value of the grain radius so as to match them with the experiment further. 8 refs, 1 fig

  6. Multimodel ensembles of wheat growth

    DEFF Research Database (Denmark)

    Martre, Pierre; Wallach, Daniel; Asseng, Senthold

    2015-01-01

    , but such studies are difficult to organize and have only recently begun. We report on the largest ensemble study to date, of 27 wheat models tested in four contrasting locations for their accuracy in simulating multiple crop growth and yield variables. The relative error averaged over models was 24...

  7. Growth with Time Zone Differences

    OpenAIRE

    Toru Kikuchi; Sugata Marjit

    2010-01-01

    We propose a two-country growth model of intermediate business-services trade that captures the role of time zone differences. It is shown that a time-saving improvement in intermediate business-services trade involving production in different time zones can have a permanent impact on productivity.

  8. Growth Pattern of Atherosclerotic Calcifications

    DEFF Research Database (Denmark)

    Larsen, Lene Lillemark; Ganz, Melanie; Dam, Erik

    2008-01-01

    of the calcifications are matched longitudinally using thin plate spline registration and area overlap calculations. The growth of the calcifications is measured by the distribution of the geometry statistics of the calcifications. The method was evaluated on 135 subjects with a total number of 611 calcifications. Our...

  9. Carboxydotrophic growth of Geobacter sulfurreducens

    NARCIS (Netherlands)

    Geelhoed, J.S.; Henstra, A.M.; Stams, A.J.M.

    2016-01-01

    This study shows that Geobacter sulfurreducens grows on carbon monoxide (CO) as electron donor with fumarate as electron acceptor. Geobacter sulfurreducens was tolerant to high CO levels, with up to 150 kPa in the headspace tested. During growth, hydrogen was detected in very slight amounts (∼5

  10. Modeling Population Growth and Extinction

    Science.gov (United States)

    Gordon, Sheldon P.

    2009-01-01

    The exponential growth model and the logistic model typically introduced in the mathematics curriculum presume that a population grows exclusively. In reality, species can also die out and more sophisticated models that take the possibility of extinction into account are needed. In this article, two extensions of the logistic model are considered,…

  11. Growth Enterprise Board on Track

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ In Premier Wen Jiabao's Government Work Report to the NPC,he said,"China will establish a stock market for high growth enterprises this year,accelerate development of the bond market and steadily develop the futures market."But he didn't layout a fixed timetable.

  12. Simulating the growth of tafoni

    NARCIS (Netherlands)

    Huinink, H.P.; Pel, L.; Kopinga, K.

    2004-01-01

    Throughout the world, large caves in rocks (tafoni) are found, which originate from salt weathering. The mechanisms that control their development are poorly understood. The growth of tafoni has been studied with a model that describes how a rock surface, containing a small pit, disintegrates by

  13. Two-sector disequilibrium growth

    NARCIS (Netherlands)

    J.G.M. van Marrewijk (Charles); J.B.L.M. Verbeek (Jos)

    1994-01-01

    textabstractWe investigate the effects of (i) profit distribution to either laborers or capital-owners, (ii) sector-specific or efficient rationing schemes, and (iii) government consumption in a two-sector disequilibrium growth model with sluggish real wage rate adjustment (which affects capital

  14. The Growth Opportunities For SMC?

    DEFF Research Database (Denmark)

    Madsen, Erik Strøjer; Smith, Valdemar; Bentzen, Jan Børsen

    2006-01-01

    The extensive empirical literature on the validity of Gibrat's law does not in general verify the law as it finds that firms' growth rates are negatively correlated with both firm size and age. However, some studies find that Gibrat's law holds for sub-samples of firms such as large firms or firms...

  15. Ketogenic Diet: Effects on Growth

    Directory of Open Access Journals (Sweden)

    J Gordon Millichap

    2002-12-01

    Full Text Available The effects of the ketogenic diet on growth of 237 children (130 males, 107 females treated for intractable epilepsy has been evaluated in a prospective cohort study (average follow-up 308 days at the Johns Hopkins Hospital, Baltimore, MD.

  16. Height Growth of Mahogany Seedlings

    Science.gov (United States)

    C. B. Briscoe; R. W. Nobles

    1962-01-01

    Since the recognition of natural hybridization of small-leaf (West Indies) mahogany (Swietenia mahagoni Jacq.) with bigleaf (Honduras) mahogany (S. macrophylla King) there has been conjecture about their relative growth rates. One would expect small-leaf to be the fastest growing on dry sites, the hybrids to be fastest on intermediate sites, and bigleaf to excel on wet...

  17. Model uncertainty in growth empirics

    NARCIS (Netherlands)

    Prüfer, P.

    2008-01-01

    This thesis applies so-called Bayesian model averaging (BMA) to three different economic questions substantially exposed to model uncertainty. Chapter 2 addresses a major issue of modern development economics: the analysis of the determinants of pro-poor growth (PPG), which seeks to combine high

  18. ECONOMIC gROWTH, GLOBALIZATION AND TRADE

    OpenAIRE

    Nuno Carlos LEITÃO

    2012-01-01

    The purpose of this article is to investigate the relationship between economic growth, globalization and trade. The manuscript uses the assumptions of the economic growth exogenous and endogenous models. It introduces new proxies for explain the economic growth as in intra-industry trade, foreign direct investment and globalization index. The results indicate that economic growth is a dynamic process. The intra-industry has a positive impact on economic growth. This paper confirms relevan...

  19. Money and Growth: An Alternative Approach.

    OpenAIRE

    Ireland, Peter N

    1994-01-01

    This paper takes an alternative approach to the topic of money and growth by developing a model in which the effects of sustained capital accumulation on an evolving system of payments, in addition to the conventional effects of sustained inflation on growth, are examined. While the effects of inflation on growth are small, the effects of growth on the monetary system are substantial. The results are consistent with ideas about money and growth contained in work that predates that of James To...

  20. Cointegration growth, poverty and inequality in Sudan

    OpenAIRE

    Mohamed Hassan, Hisham

    2008-01-01

    This analytical review explores the links between growth, poverty and inequality in Sudan for the period 1956-2003. This paper build upon different models to investigate empirically the relationship between economic growth - as measured by GDP per capita growth- and inequality as measured by Gini coefficient (the growth, inequality and poverty triangle hypotheses), using data from the national and international sources. The paper tries to answer the following questions: i) whether growth, ine...

  1. Is Urban Economic Growth Inclusive in India?

    OpenAIRE

    Tripathi, Sabyasachi

    2013-01-01

    This paper measures the overall inclusive growth of a city by considering changing trends in the key economic variables based on ‘Borda ranking’ and establishes a relationship between city economic growth and overall city inclusive growth. By using data of 52 large cities in India, this paper finds that higher urban economic growth is associated with an increase in urban inequality, a reduction in urban poverty, and a lower level of overall inclusive growth of a city.

  2. Education Vouchers, Growth and Income Inequality

    OpenAIRE

    Buly A Cardak

    2004-01-01

    This paper uses a growth model with public and private education alternatives to investigate the implications of education voucher for economic growth and the evolution of income inequality. The results indicate that introducing education vouchers can increase economic growth. families that switch from public to private education due to vouchers experience higher incomes, leading to growth in the tax base which in turn raises public education expenditures and increases the growth of the whole...

  3. Ellipsometry of anodic film growth

    Energy Technology Data Exchange (ETDEWEB)

    Smith, C.G.

    1978-08-01

    An automated computer interpretation of ellisometer measurements of anodic film growth was developed. Continuous mass and charge balances were used to utilize more fully the time dependence of the ellipsometer data and the current and potential measurements. A multiple-film model was used to characterize the growth of films which proceeds via a dissolution--precipitation mechanism; the model also applies to film growth by adsorption and nucleation mechanisms. The characteristic parameters for film growth describe homogeneous and heterogeneous crystallization rates, film porosities and degree of hydration, and the supersaturation of ionic species in the electrolyte. Additional descriptions which may be chosen are patchwise film formation, nonstoichiometry of the anodic film, and statistical variations in the size and orientation of secondary crystals. Theories were developed to describe the optical effects of these processes. An automatic, self-compensating ellipsometer was used to study the growth in alkaline solution of anodic films on silver, cadmium, and zinc. Mass-transport conditions included stagnant electrolyte and forced convection in a flow channel. Multiple films were needed to characterize the optical properties of these films. Anodic films grew from an electrolyte supersatuated in the solution-phase dissolution product. The degree of supersaturation depended on transport conditions and had a major effect on the structure of the film. Anodic reaction rates were limited by the transport of charge carriers through a primary surface layer. The primary layers on silver, zinc, and cadmium all appeared to be nonstoichiometric, containing excess metal. Diffusion coefficients, transference numbers, and the free energy of adsorption of zinc oxide were derived from ellipsometer measurements. 97 figures, 13 tables, 198 references.

  4. Growth hormone and the heart.

    Science.gov (United States)

    Cittadini, A; Longobardi, S; Fazio, S; Saccà, L

    1999-01-01

    Until a few years ago, growth hormone (GH) and insulin-like growth factor-1 (IGF-1) were considered essential only to the control of linear growth, glucose homeostasis, and for the maintenance of skeletal muscle mass. A large body of evidence recently coming from animal and human studies has unequivocally proven that the heart is a target organ for the GH/IGF-1 axis. Specifically GH exerts both direct and indirect cardiovascular actions. Among the direct effects, the ability of GH to trigger cardiac tissue growth plays a pivotal role. Another direct effect is to augment cardiac contractility, independent of myocardial growth. Direct effects of GH also include the improvement of myocardial energetics and mechanical efficiency. Indirect effects of GH on the heart include decreased peripheral vascular resistance (PVR), expansion of blood volume, increased glomerular filtration rate, enhanced respiratory activity, increased skeletal muscle performance, and psychological well-being. Among them, the most consistently found is the decrease of PVR. GH may also raise preload through its sodium-retaining action and its interference with the hormonal system that regulates water and electrolyte metabolism. Particularly important is the effect of GH on skeletal muscle mass and performance. Taking into account that heart failure is characterized by left ventricular dilation, reduced cardiac contractility, and increase of wall stress and peripheral vascular resistance, GH may be beneficial for treatment of heart failure. Animal studies and preliminary human trials have confirmed the validity of the GH approach to the treatment of heart failure. Larger placebo-controlled human studies represent the main focus of future investigations.

  5. Canada's population: growth and dualism.

    Science.gov (United States)

    Beaujot, R P

    1978-04-01

    In Canada the current 1.3% population growth rate is causing some concern. Those concerned argue that such a rate of growth in combination with high levels of consumption could jeopardize the country's resource base and its comfortable style of living. Many Canadians are questioning high levels of immigration, for now that the fertility level is below replacement level, net immigration contributes substantially to population growth (over 1/3 in 1976). The growing proportion of non-Europeans among recent immigrants is causing resentment, and, in a tight job market, immigrants are regarded as threats to the World War 2 baby boom cohort who are now at working ages. The baby boom generation also puts stress on housing and health services, and it will increase the need for pension checks as it ages. Although French fertility is no longer high and immigration is no longer dominated by the British, the French group's 200-year struggle to preserve its identity continues on in the current effort of the Quebec government to enforce the use of French language by law within that province. Geography and climate dictate another demographic fact that divides the country and pervades its history. In addition to intense regionalism, uneven population distribution is responsible for 2 other concerns: the rapid growth of several already large cities and depopulation of many small communities. Focus in this discussion is on Canada's population growth in the past and as projected for the future, historical and current fertility, mortality and immigration trends, the search for a new immigration policy, the impact of the baby boom generation on the population's age structure and the problems this creates, and recent shifts in population distribution and in the country's ethnic and linguistic makeup. The population policy proposals evolved thus far involve to a great extent the use of immigration as a lever for achieving given population objectives.

  6. Physiological factors influencing capillary growth.

    Science.gov (United States)

    Egginton, S

    2011-07-01

    (1) Angiogenesis (growth of new capillaries from an existing capillary bed) may result from a mismatch in microvascular supply and metabolic demand (metabolic error signal). Krogh examined the distribution and number of capillaries to explore the correlation between O(2) delivery and O(2) consumption. Subsequently, the heterogeneity in angiogenic response within a muscle has been shown to reflect either differences in fibre type composition or mechanical load. However, local control leads to targetted angiogenesis in the vicinity of glycolytic fibre types following muscle stimulation, or oxidative fibres following endurance training, while heterogeneity of capillary spacing is maintained during ontogenetic growth. (2) Despite limited microscopy resolution and lack of specific markers, Krogh's interest in the structure of the capillary wall paved the way for understanding the mechanisms of capillary growth. Angiogenesis may be influenced by the response of perivascular or stromal cells (fibroblasts, macrophages and pericytes) to altered activity, likely acting as a source for chemical signals modulating capillary growth such as vascular endothelial growth factor. In addition, haemodynamic factors such as shear stress and muscle stretch play a significant role in adaptive remodelling of the microcirculation. (3) Most indices of capillarity are highly dependent on fibre size, resulting in possible bias because of scaling. To examine the consequences of capillary distribution, it is therefore helpful to quantify the area of tissue supplied by individual capillaries. This allows the spatial limitations inherent in most models of tissue oxygenation to be overcome generating an alternative approach to Krogh's tissue cylinder, the capillary domain, to improve descriptions of intracellular oxygen diffusion. © 2010 The Author. Acta Physiologica © 2010 Scandinavian Physiological Society.

  7. Method of Promoting Single Crystal Growth During Melt Growth of Semiconductors

    Science.gov (United States)

    Su, Ching-Hua (Inventor)

    2013-01-01

    The method of the invention promotes single crystal growth during fabrication of melt growth semiconductors. A growth ampoule and its tip have a semiconductor source material placed therein. The growth ampoule is placed in a first thermal environment that raises the temperature of the semiconductor source material to its liquidus temperature. The growth ampoule is then transitioned to a second thermal environment that causes the semiconductor source material in the growth ampoule's tip to attain a temperature that is below the semiconductor source material's solidus temperature. The growth ampoule so-transitioned is then mechanically perturbed to induce single crystal growth at the growth ampoule's tip.

  8. Crossover from Nonequilibrium Fractal Growth to Equilibrium Compact Growth

    DEFF Research Database (Denmark)

    Sørensen, Erik Schwartz; Fogedby, Hans C.; Mouritsen, Ole G.

    1988-01-01

    Solidification controlled by vacancy diffusion is studied by Monte Carlo simulations of a two-dimensional Ising model defined by a Hamiltonian which models a thermally driven fluid-solid phase transition. The nonequilibrium morphology of the growing solid is studied as a function of time as the s...... as the system relaxes into equilibrium described by a temperature. At low temperatures the model exhibits fractal growth at early times and crossover to compact solidification as equilibrium is approached....

  9. Tax Evasion and Economic Growth in an Endogenous Growth Model

    OpenAIRE

    加藤, 秀弥; KATO, Hideya

    2004-01-01

    This paper presents an endogenous growth model with tax evasion where government expenditures affect production. An individual evades a tax so as to maximize his or her utility, the tax authority controls the detection probability to maximize net tax revenue, and the government chooses the income tax rate to maximize individuals’ utility. The main conclusions are as follows. First, the optical income tax rate with tax evasion is higher than that without tax evasion. Second, the rise in a ...

  10. Position-controlled epitaxial III-V nanowires on silicon

    NARCIS (Netherlands)

    Roest, A.L.; Verheijen, M.A.; Wunnicke, O.; Serafin, S.N.; Wondergem, H.J.; Bakkers, E.P.A.M.

    2006-01-01

    We show the epitaxial integration of III-V semiconductor nanowires with silicon technology. The wires are grown by the VLS mechanism with laser ablation as well as metal-organic vapour phase epitaxy. The hetero-epitaxial growth of the III-V nanowires on silicon was confirmed with x-ray diffraction

  11. ELEMENTS OF THE NEOCLASSICAL GROWTH THEORY

    Directory of Open Access Journals (Sweden)

    Florina Popa

    2014-12-01

    Full Text Available One of the relevant components of the contemporary economic science is the economic growth theory, the economic background of the time leading to new guidelines of the research. The neoclassical growth theory - the core of modern analysis - explains how the capital accumulation and technological changes affect the economy, significant for the analysis of the economic growth process being the Solow’s neoclassical growth model. The paper brief describes the elements of the economic growth model developed by Solow, both for the situation when it allows the explanation of extensive growth and that wherein the growth is of intensive nature, as a result of the intervention of exogenous technical progress – a determinant of factors productivity growth. It is highlighted the importance of the exogenous neoclassical model, proposed by Solow, who showed the determinant role of the technical progress in the economic growth phenomenon.

  12. Trajectories and models of individual growth

    Directory of Open Access Journals (Sweden)

    Arseniy Karkach

    2006-11-01

    Full Text Available It has long been recognized that the patterns of growth play an important role in the evolution of age trajectories of fertility and mortality (Williams, 1957. Life history studies would benefit from a better understanding of strategies and mechanisms of growth, but still no comparative research on individual growth strategies has been conducted. Growth patterns and methods have been shaped by evolution and a great variety of them are observed. Two distinct patterns - determinate and indeterminate growth - are of a special interest for these studies since they present qualitatively different outcomes of evolution. We attempt to draw together studies covering growth in plant and animal species across a wide range of phyla focusing primarily on the noted qualitative features. We also review mathematical descriptions of growth, namely empirical growth curves and growth models, and discuss the directions of future research.

  13. Dynamics of anisotropic tissue growth

    Energy Technology Data Exchange (ETDEWEB)

    Bittig, Thomas; Juelicher, Frank [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, 01187 Dresden (Germany); Wartlick, Ortrud; Kicheva, Anna; Gonzalez-Gaitan, Marcos [Department of Biochemistry and Department of Molecular Biology, Geneva University, Sciences II, Quai Ernest-Ansermet 30, 1211 Geneva 4 (Switzerland)], E-mail: Marcos.Gonzalez@biochem.unige.ch, E-mail: julicher@pks.mpg.de

    2008-06-15

    We study the mechanics of tissue growth via cell division and cell death (apoptosis). The rearrangements of cells can on large scales and times be captured by a continuum theory which describes the tissue as an effective viscous material with active stresses generated by cell division. We study the effects of anisotropies of cell division on cell rearrangements and show that average cellular trajectories exhibit anisotropic scaling behaviors. If cell division and apoptosis balance, there is no net growth, but for anisotropic cell division the tissue undergoes spontaneous shear deformations. Our description is relevant for the study of developing tissues such as the imaginal disks of the fruit fly Drosophila melanogaster, which grow anisotropically.

  14. Environmental impact of population growth

    Science.gov (United States)

    Naylor, Rosamond; Matson, Pamela

    Earth's population currently numbers 5.4 billion; even given optimistic assumptions for reduction in growth rates, the number will double by the middle of the next century with most of the increase in the developing countries. Rapid population growth in the developing world raises the fundamental dilemma of how to alleviate chronic hunger and poverty in the short run while preserving the atmosphere and ecosystem services required for long-term human and biospheric sustenance. This dilemma, and the compromises required to solve it, were discussed by twenty-five researchers from five countries at the Aspen Global Change Institute 1992 Summer Science Session III, Food, Conservation, and Global Environmental Change: Is Compromise Possible?, held from August 16 to 28, in Aspen, Colo.

  15. Inhomogeneous microstructural growth by irradiation

    DEFF Research Database (Denmark)

    Krishan, K.; Singh, Bachu Narain; Leffers, Torben

    1985-01-01

    In the present paper we discuss the development of heterogeneous microstructure for uniform irradiation conditions. It is shown that microstructural inhomogeneities on a scale of 0.1 μm can develop purely from kinematic considerations because of the basic structure of the rate equations used...... to describe such evolution. Two aspects of the growth of such inhomogeneities are discussed. Firstly, it is shown that a local variation in the sink densities of the various microstructural defects will tend to enhance the inhomogeneity rather than remove it. Secondly, such inhomogeneities will lead to point...... defect fluxes that result in a spatial growth of the inhomogeneous region, which will be stopped only when the microstructural density around this region becomes large. The results have important implications in the formation of denuded zones and void formation in metals....

  16. Maintaining flexibility pushes NYSEG's growth

    International Nuclear Information System (INIS)

    German, M.I.

    1997-01-01

    New York State Electric and Gas Corporation (NYSEG) recorded 1996 as one of its most successful years of natural gas expansion activity. In this landmark year, they opened their first storage facility, built more than 100 miles of new gas transmission and distribution pipelines, added nine new municipal franchises, and another 2+ Bcf of new gas load. The economy in NYSEG's service territory is not as robust as other LDCs enjoy elsewhere in the nation, yet they have created a significant momentum of growth that will continue through the end of the decade. It's due to the corporate strategy, which is straightforward in name and nature: Growth By Building On Our Unique Strengths. Their unique strengths dictate this strategy, which, in turn, demands that they focus intently on the performance of the core business. The paper discusses examples of how this strategy is being implemented

  17. Growth kinetics in multicomponent fluids

    International Nuclear Information System (INIS)

    Chen, S.; Lookman, T.

    1995-01-01

    The hydrodynamic effects on the late-stage kinetics in spinodal decomposition of multicomponent fluids are examined using a lattice Boltzmann scheme with stochastic fluctuations in the fluid and at the interface. In two dimensions, the three- and four-component immiscible fluid mixture (with a 1024 2 lattice) behaves like an off-critical binary fluid with an estimated domain growth of t 0.4 +/= 0.03 rather than t 1/3 as previously estimated, showing the significant influence of hydrodynamics. In three dimensions (with a 256 3 lattice), we estimate the growth as t 0.96 +/= 0.05 for both critical and off-critical quenches, in agreement with phenomenological theory

  18. Vascular Morphodynamics During Secondary Growth.

    Science.gov (United States)

    de Reuille, Pierre Barbier; Ragni, Laura

    2017-01-01

    Quantification of vascular morphodynamics during secondary growth has been hampered by the scale of the process. Even in the tiny model plant Arabidopsis thaliana, the xylem can include more than 2000 cells in a single cross section, rendering manual counting impractical. Moreover, due to its deep location, xylem is an inaccessible tissue, limiting live imaging. A novel method to visualize and measure secondary growth progression has been proposed: "the Quantitative Histology" approach. This method is based on a detailed anatomical atlas, and image segmentation coupled with machine learning to automatically extract cell shapes and identify cell type. Here we present a new version of this approach, with a user-friendly interface implemented in the open source software LithoGraphX.

  19. Institutions, Entrepreneurship, and Economic Growth

    DEFF Research Database (Denmark)

    Bjørnskov, Christian; Foss, Nicolai Juul

    2016-01-01

    sample limitations, omitted variable biases, causality issues, and response heterogeneity. We argue that theories in management research, such as the resource-based view, transaction cost economics, and strategic entrepreneurship theory, can fill some of the conceptual and theoretical gaps.......We review the literature that links institutions, entrepreneurship, and economic growth outcomes, focusing in particular on empirical research. Most of the literature has an economics orientation, but we also review relevant literature from other social sciences, including management research...

  20. Population growth and economic development.

    Science.gov (United States)

    Corbridge, S

    1989-01-01

    The Malthusian and neo-Malthusian approaches to the role of population growth in economic development and resource depletion are briefly outlined. Three arguments are then presented that emphasize demographic determinism, empirical evidence, and cause and effect. The author concludes that non-coercive family planning programs may have a role to play in countries that are unable to reduce inequalities, particularly for the poor and for women.

  1. Poverty, governance and economic growth

    Directory of Open Access Journals (Sweden)

    Kefi Mohamed Karim

    2013-07-01

    Full Text Available The objective of this paper is to study the effect of governance and povrety on economic growth of a set of eight developing countries during the period 2000-2009, using a dynamic and static panel data model and a simultaneous equations model. The key findings generated from these three empirical tests stipulate a negative effect of governance on povrety and a positive effect of political instability and corruption on poverty

  2. Clean versus Dirty Economic Growth

    OpenAIRE

    Palokangas, Tapio

    2012-01-01

    This document considers an economy with many regions and two engines of growth: horizontal R&D, which increases the number of polluting product lines; and vertical R&D, which improves productivity in these lines. Pollution in any region decreases welfare in all regions. Any group of regions can form a jurisdiction where a common policy maker controls pollution. Large jurisdictions, which can better internalize externality through pollution, perform vertical R&D. Because jurisdictions face dec...

  3. Reduced Deforestation and Economic Growth

    OpenAIRE

    Patrick Doupe

    2014-01-01

    The clearing of forests for agricultural land and other marketable purposes is a well-trodden path of economic development. With these private benefits from deforestation come external costs: emissions from deforestation currently account for 12 per cent of global carbon emissions. A widespread intervention in reducing emissions from deforestation will affect the paths of agricultural expansion and economic growth of lower income nations. To investigate these processes, this paper presents a ...

  4. Green attitude and economic growth

    OpenAIRE

    Ott, Ingrid; Soretz, Susanne

    2015-01-01

    We analyse the interdependence between green attitude and equilibrium development of environmental quality in an endogenous growth model. Individuals take only part of their impact on pollution into account, hence there is a negative externality of capital accumulation on environmental quality. Increasing wealth or increasing pollution enhance green attitude and reduce the externality, because individuals care more about the environment if their income is higher or if pollution is more obviou...

  5. Econmic Growth and Productive Knowledge

    OpenAIRE

    H. Gürak

    2003-01-01

    The relations between the riches of nations and the riches of Productive Knowledge (Technology) gains increasing acknowledgment among economists. Classical economists had assumed that the key to progress was the accumulation of homogenous capital goods. But, as P. Romer, among others, claims we cannot grow rich by accumulating more of the same capital goods. So the Classical growth theory falls short of expectations. Capitalism’s inherent feature is “destructive creation”, said Marx. Decades ...

  6. Growth hormone and bone health.

    Science.gov (United States)

    Bex, Marie; Bouillon, Roger

    2003-01-01

    Growth hormone (GH) and insulin-like growth factor-I have major effects on growth plate chondrocytes and all bone cells. Untreated childhood-onset GH deficiency (GHD) markedly impairs linear growth as well as three-dimensional bone size. Adult peak bone mass is therefore about 50% that of adults with normal height. This is mainly an effect on bone volume, whereas true bone mineral density (BMD; g/cm(3)) is virtually normal, as demonstrated in a large cohort of untreated Russian adults with childhood-onset GHD. The prevalence of fractures in these untreated childhood-onset GHD adults was, however, markedly and significantly increased in comparison with normal Russian adults. This clearly indicates that bone mass and bone size matter more than true bone density. Adequate treatment with GH can largely correct bone size and in several studies also bone mass, but it usually requires more than 5 years of continuous treatment. Adult-onset GHD decreases bone turnover and results in a mild deficit, generally between -0.5 and -1.0 z-score, in bone mineral content and BMD of the lumbar spine, radius and femoral neck. Cross-sectional surveys and the KIMS data suggest an increased incidence of fractures. GH replacement therapy increases bone turnover. The three controlled studies with follow-up periods of 18 and 24 months demonstrated a modest increase in BMD of the lumbar spine and femoral neck in male adults with adult-onset GHD, whereas no significant changes in BMD were observed in women. GHD, whether childhood- or adult-onset, impairs bone mass and strength. Appropriate substitution therapy can largely correct these deficiencies if given over a prolonged period. GH therapy for other bone disorders not associated with primary GHD needs further study but may well be beneficial because of its positive effects on the bone remodelling cycle. Copyright 2003 S. Karger AG, Basel

  7. (Plant growth with limited water)

    Energy Technology Data Exchange (ETDEWEB)

    1991-01-01

    The work supported by DOE in the last year built on our earlier findings that stem growth in soybean subjected to limited water is inhibited first by a physical limitation followed in a few hours by metabolic changes that reduce the extensibility of the cell walls. With time, there is modest recovery in extensibility and a 28kD protein accumulates in the walls of the growth-affected cells. A 31kD protein that was 80% similar in amino acid sequence also was present but did not accumulate in the walls of the stem cells. Explorations of the mRNA for these proteins showed that the mRNA for the 28kD protein increased in the shoot in response to water deprivation but the mRNA for the 31kD protein did not accumulate. In contrast, the roots continued to grow and the mRNA for the 31kD protein accumulated but the mRNA for the 28kD protein was undetectable. We also explored how growth occurs in the absence of an external water supply. We found that, under these conditions, internal water is mobilized from surrounding nongrowing or slowly growing tissues and is used by rapidly growing cells. We showed that a low water potential is normally present in the enlarging tissues and is the likely force that extracts water from the surrounding tissues. We found that it involved a gradient in water potential that extended from the xylem to the outlying cells in the enlarging region and was not observed in the slowly growing basal tissue of the stems of the same plant. The gradient was measured directly with single cell determinations of turgor and osmotic potential in intact plants. The gradient may explain instances of growth inhibition with limited water when there is no change in the turgor of the enlarging cells. 17 refs.

  8. How persistent is civilization growth?

    OpenAIRE

    Garrett, Timothy J.

    2011-01-01

    In a recent study (Garrett, 2011), I described theoretical arguments and empirical evidence showing how civilization evolution might be considered from a purely physical basis. One implication is that civilization exhibits the property of persistence in its growth. Here, this argument is elaborated further, and specific near-term forecasts are provided for key economic variables and anthropogenic CO2 emission rates at global scales. Absent some external shock, civilization wealth, energy cons...

  9. Growth Hacking a Global Community

    OpenAIRE

    Sarkkinen, Laura; Rauhala, Marita

    2015-01-01

    As technology is developing at a fast phase people are engaging in community activities more and more online, either by extending their offline social life or by creating themselves a whole new parallel life as a member of virtual community. Companies behind communities are rivaling for attention and need to come up with increasingly clever tactics to attract and engage new members. In this thesis the relatively new phenomenon of growth hacking, the use of unconventional methods in order ...

  10. Error estimation in plant growth analysis

    Directory of Open Access Journals (Sweden)

    Andrzej Gregorczyk

    2014-01-01

    Full Text Available The scheme is presented for calculation of errors of dry matter values which occur during approximation of data with growth curves, determined by the analytical method (logistic function and by the numerical method (Richards function. Further formulae are shown, which describe absolute errors of growth characteristics: Growth rate (GR, Relative growth rate (RGR, Unit leaf rate (ULR and Leaf area ratio (LAR. Calculation examples concerning the growth course of oats and maize plants are given. The critical analysis of the estimation of obtained results has been done. The purposefulness of joint application of statistical methods and error calculus in plant growth analysis has been ascertained.

  11. Does tax competition really promote growth?

    DEFF Research Database (Denmark)

    Köthenbürger, Marko; Lockwood, Ben

    2010-01-01

    This paper considers the relationship between tax competition and growth in an endogenous growth model where there are stochastic shocks to productivity, and capital taxes fund a public good which may be for final consumption or an infrastructure input. Absent stochastic shocks, decentralized tax...... the centralized level. Growth can be lower with decentralization. Our results also predict a negative relationship between output volatility and growth with decentralization.......This paper considers the relationship between tax competition and growth in an endogenous growth model where there are stochastic shocks to productivity, and capital taxes fund a public good which may be for final consumption or an infrastructure input. Absent stochastic shocks, decentralized tax...

  12. Thiazolidinediones abrogate cervical cancer growth

    Energy Technology Data Exchange (ETDEWEB)

    Wuertz, Beverly R., E-mail: knier003@umn.edu; Darrah, Lindsay, E-mail: ldarrah@obgynmn.com; Wudel, Justin, E-mail: drwudel@drwudel.com; Ondrey, Frank G., E-mail: ondre002@umn.edu

    2017-04-15

    Peroxisome proliferator-activated receptor gamma (PPAR γ) is activated by thiazolidinedione drugs (TZDs) and can promote anti-cancer properties. We used three TZDs (pioglitazone, rosiglitazone, and ciglitazone) to target cervical cancer cell lines and a nude mouse animal model. Each agent increased activation of PPAR γ, as judged by a luciferase reporter gene assay in three HPV-associated cell lines (CaSki, SiHa, and HeLa cells) while decreasing cellular proliferation in a dose-dependent manner. They also promoted Oil Red O accumulation in treated cell lines and upregulated the lipid differentiation marker adipsin. Interestingly, xenograft HeLa tumors in nude mice treated with 100 mg/kg/day pioglitazone exhibited decreased growth compared to control mice or mice treated with standard cervical chemotherapy. In conclusion, TZDs slow tumor cell growth in vitro and in vivo with decreases in cell proliferation and increases in PPAR γ and adipsin. These agents may be interesting treatments or treatment adjuncts for HPV-associated cancers or perhaps even precancerous conditions. - Highlights: • Thiazolidinediones decreases cervical cancer proliferation. • Pioglitazone increases cervical cancer differentiation. • Pioglitazone decreases tumor growth in mice. • Pioglitazone may be a useful treatment adjunct.

  13. Energetic Constraints on Fungal Growth.

    Science.gov (United States)

    Heaton, Luke L M; Jones, Nick S; Fricker, Mark D

    2016-02-01

    Saprotrophic fungi are obliged to spend energy on growth, reproduction, and substrate digestion. To understand the trade-offs involved, we developed a model that, for any given growth rate, identifies the strategy that maximizes the fraction of energy that could possibly be spent on reproduction. Our model's predictions of growth rates and bioconversion efficiencies are consistent with empirical findings, and it predicts the optimal investment in reproduction, resource acquisition, and biomass recycling for a given environment and timescale of reproduction. Thus, if the timescale of reproduction is long compared to the time required for the fungus to double in size, the model suggests that the total energy available for reproduction is maximal when a very small fraction of the energy budget is spent on reproduction. The model also suggests that fungi growing on substrates with a high concentration of low-molecular-weight compounds will not benefit from recycling: they should be able to grow more rapidly and allocate more energy to reproduction without recycling. In contrast, recycling offers considerable benefits to fungi growing on recalcitrant substrates, where the individual hyphae are not crowded and the time taken to consume resource is significantly longer than the fungus doubling time.

  14. Hydrothermal Growth of Polyscale Crystals

    Science.gov (United States)

    Byrappa, Kullaiah

    In this chapter, the importance of the hydrothermal technique for growth of polyscale crystals is discussed with reference to its efficiency in synthesizing high-quality crystals of various sizes for modern technological applications. The historical development of the hydrothermal technique is briefly discussed, to show its evolution over time. Also some of the important types of apparatus used in routine hydrothermal research, including the continuous production of nanosize crystals, are discussed. The latest trends in the hydrothermal growth of crystals, such as thermodynamic modeling and understanding of the solution chemistry, are elucidated with appropriate examples. The growth of some selected bulk, fine, and nanosized crystals of current technological significance, such as quartz, aluminum and gallium berlinites, calcite, gemstones, rare-earth vanadates, electroceramic titanates, and carbon polymorphs, is discussed in detail. Future trends in the hydrothermal technique, required to meet the challenges of fast-growing demand for materials in various technological fields, are described. At the end of this chapter, an Appendix 18.A containing a more or less complete list of the characteristic families of crystals synthesized by the hydrothermal technique is given with the solvent and pressure-temperature (PT) conditions used in their synthesis.

  15. Fetal growth and developmental programming.

    Science.gov (United States)

    Galjaard, Sander; Devlieger, Roland; Van Assche, Frans A

    2013-01-01

    The environment in utero and in early neonatal life may induce a permanent response in the fetus and the newborn, leading to enhanced susceptibility to later diseases. This review concentrates on the role and mechanisms of events during the antenatal and immediate postnatal period resulting in later life diseases, concentrating on abnormal growth patterns of the fetus. Fetal overgrowth is related to exposure to a diabetic intra uterine environment, increasing the vulnerability to transgenerational obesity and hence an increased sensitivity to more diabetic mothers. This effect has been supported by animal data. Fetal growth restriction is complex due to malnutrition in utero, catch up growth due to a high caloric intake and low physical activity in later life. Metabolic changes and a transgenerational effect of intra uterine malnutrition has been supported by animal data. In recent years the discovery of alterations of the genome due to different influences during embryonic life, called epigenetics, has led to the phenomenon of fetal programming resulting in changing transgenerational metabolic effects.

  16. Grain growth in UO2

    International Nuclear Information System (INIS)

    Hastings, I.J.; Scoberg, J.A.; Walden, W.

    1979-06-01

    Grain growth studies have been carried out on UO 2 to provide data for the fuel modelling program and to evaluate fuel fabricated in commissioning the Mixed Oxide Fuel Fabrication Laboratory at Chalk River Nuclear Laboratories. Fuel examined includes natural UO 2 commercially fabricated from ADU powder for CANDU reactors; natural UO 2 commercially fabricated from AU powder; natural UO 2 from ADU and AU powder, fabricated in the MOFFL; and commercially fabricated UO 2 enriched 1.7, 4.5, and 9.6 wt. percent U-235 in U. Samples were step-annealed in vacuo at 1870-2070 K for up to 32.5 h. All data fit a (grain size)sup(2.5) versus annealing time relationship. Apparent activation energy for grain growth, Q, depends on fuel type and varies from 150+-10 kJ/mol for early AU powder to 360+-10 kJ/mol for pellets from ADU fabricated in the MOFFL. Grain sizes calculated using the laboratory equation in a fuel performance code tend to be greater than those measured in irradiated natural fuel, suggesting irradiation-induced inhibition of grain growth. However, any inhibition is equivalent to that expected for a systematic 5 percent underpredicition in reactor power. (author)

  17. Political economy of population growth.

    Science.gov (United States)

    Mehta, S; Mehta, H S

    1987-01-01

    Tracing the origin of political economy as a class-science, this paper focuses on the political economy of population growth. Exposing the limitations of Malthusian ideas and their invalidity even for the capitalist economies, it discusses the subsequent revival of the Malthusian model during the period of de-colonization and the misinterpretation of the relationship between population growth and development in the developing and developed countries. Taking India, China, and Japan as some case studies, the paper examines the relationship between birth rate levels and some correlates. It elaborates on the Indian experience, emphasizing the association of population growth with poverty and unemployment and lays bare some of the hidden causes of these phenomena. The authors examine some interstate variations in India and identify constraints and prospects of the existing population policy. The paper proposes outlines of a democratic population policy as an integral part of India's development strategy which should recognize human beings not simply as consumers but also as producers of material values. It pleads for 1) restructuring of property relations; 2) bringing down the mortality rates and raising of the literacy levels, especially among females; and 3) improving nutritional levels, as prerequisites for bringing down birth rates.

  18. Balanced growth path solutions of a Boltzmann mean field game model for knowledge growth

    KAUST Repository

    Burger, Martin; Lorz, Alexander; Wolfram, Marie Therese

    2016-01-01

    events or by producing goods with the knowledge they already have. The existence of balanced growth path solutions implies exponential growth of the overall production in time. We prove existence of balanced growth path solutions if the initial

  19. Inequality and growth in neo-Kaleckian and Cambridge growth theory

    OpenAIRE

    Palley, Thomas I.

    2016-01-01

    This paper examines the relationship between inequality and growth in the neo-Kaleckian and Cambridge growth models. The paper explores the channels whereby functional and personal income distribution impact growth. The growth - inequality relationship can be negative or positive, depending on the economy's characteristics. Contrary to widespread claims, inequality per se does not impact growth through macroeconomic channels. Instead, both growth and inequality are impacted by changes in the ...

  20. Population growth and its implications

    Directory of Open Access Journals (Sweden)

    Badii, M. H.

    2005-01-01

    Full Text Available Human populations have grown at an unprecedented rate over the past three centuries. By 2001, the world population stood at 6.2 billion people. If the current trend of 1.4 % per year persists, the population will double in 51years. Most of that growth will occur in the less developed countries of Asia, Africa, and Latin America. There is a serious concern that the number of humans in the world and our impact on the environment will overload the life support systems of the earth. The crude birth rate is the number of births in a year divided by the average population. A more accurate measure of growth is the general fertility rate, which takes into account the age structure and fecundity of the population. The crude birth rate minus the crude death rate gives the rate of natural increase. When this rate reaches a level at which people are just replacing themselves, zero population growth is achieved. In the more highly developed countries of the world, growth has slowed are even reversed in recent years so that without immigration from other areas, population would be declining. The change from high birth and death rates that accompanies in industrialization is called a demographic transition. Many developing nations have already begun this transition. Death rates have fallen, but birth rates remain high. Some demographers believe that as infant mortality drops and economic development progresses so that people in these countries can be sure of secure future, they will complete the transition to a stable population or a high standard living. While larger populations bring many problems, they also may be a valuable resource of energy, intelligence, and enterprise that will make it possible to overcome resource limitation problems. A social just view argues that a more equitable distribution of wealth might reduce both excess population growth and environmental degradation. We have many more options now for controlling fertility than were available