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Sample records for altered nanotube dimension

  1. Collective diffusion in carbon nanotubes: Crossover between one dimension and three dimensions

    Science.gov (United States)

    Chen, Pei-Rong; Xu, Zhi-Cheng; Gu, Yu; Zhong, Wei-Rong

    2016-08-01

    Using non-equilibrium molecular dynamics and Monte Carlo methods, we study the collective diffusion of helium in carbon nanotubes. The results show that the collective diffusion coefficient (CDC) increases with the dimension of the channel. The collective diffusion coefficient has a linear relationship with the temperature and the concentration. There exist a ballistic transport in short carbon nanotubes and a diffusive transport in long carbon nanotubes. Fick’s law has an invalid region in the nanoscale channel. Project supported by the National Natural Science Foundation of China (Grant Nos. 11004082 and 11291240477), the Natural Science Foundation of Guangdong Province, China (Grant No. 2014A030313367), and the Fundamental Research Funds for the Central Universities, Jinan University (Grant No. 11614341).

  2. INFLUENCES OF DENSITY AND DIMENSION OF CARBON NANOTUBES ON THEIR FIELD EMISSION

    Institute of Scientific and Technical Information of China (English)

    Y.B. Zhu; W.L. Wang; C.G. Hu

    2003-01-01

    The influences of density and dimension of carbon nanotubes on their electron emission from arrays are studied. The tip electric field of nanotubes, electric field enhancement factor, and optimum nanotube density are expressed by analytic equations. The theoretical analyses show that the field enhancement factor is sensitive to nanotube density, and can be sharply improved at a specific and optimum density. Some experiments have demonstrated these. Owning to electrostatic screening effect, the length of carbon nanotubes has little effect on their emission. A uniformly-distributed carbon nanotube array model is set up, and applied to analysis of carbon nanotube arrays.The results obtained here are in good agreement with the experimental data.

  3. Dimension and morphology controlled fabrication of TiO2 nanotubes by electrochemical anodization method

    International Nuclear Information System (INIS)

    We report the fabrication of titanium dioxide (TiO2) nanotubes by electrochemical anodization of titanium foils using fluoride-based electrolytes such as ethylene glycol, diethylene glycol and glycerol. The effects of anodization voltage, time and electrolytes on the morphology and dimensions (length and pore diameter) of the tubes were investigated by scanning electron microscope (SEM). On increasing anodization voltage and time, the tube length and pore diameter were varied. In addition to this, various tubes morphologies such as circular and hexagonal structures were obtained under different electrolytic conditions. The Raman spectroscopy studies revealed the anatase phase of TiO2 nanotubes

  4. Dimension effect on the performance of carbon nanotube nanobolometers

    International Nuclear Information System (INIS)

    Carbon nanotube (CNT) film nanobolometers take advantages of high infrared absorption of CNTs, proving a promising alternative for low-cost, uncooled infrared detection. The performance of the CNT nanobolometers is determined by the optoelectronic process on CNTs at a microscopic scale, which links intimately to the diameter of the CNT—a critical parameter that intrinsically affects the band gap and hence infrared absorption, as well as extrinsically affects the surface oxygen adsorption effect and thermal-link of the CNT detector element to the environment. Both the intrinsic and extrinsic factors play important roles in the photoresponse, noise spectrum and the figure-of-merit detectivity D* of the CNT nanobolometers and their interplay determines the device’s ultimate performance. In this work, we present a systematic study of the effect of CNT diameter in the range of 1–50 nm on the physical properties relevant to CNT nanobolometers. The optimal CNT diameter was found to be in the range of 2–12 nm with the D* up to 3.3 × 107 cm(Hz)1/2 W−1, which represents an order of magnitude improvement over the best D* reported previously on CNT film nanobolometers. (paper)

  5. Multi-functional Carbon Nanotube Assemblies with Dimension Controllable Gold Nanocrystals

    OpenAIRE

    Xin, Wenbo

    2016-01-01

    Carbon nanotube (CNT) and graphene as representative carbon allotropes have attracted considerable attention due to their exceptional properties in mechanical, electrical and thermal aspects. The assemblied CNT such as CNT yarns and sheets are particularly interesting regarding their promising applications in macro-scaled form. This work aims to develop multi-functional CNT assemblies coupling with gold nanocrystals with controllable dimensions. A novel strategy of growing two-dimensional gol...

  6. Image formation mechanisms in scanning electron microscopy of carbon nanotubes,and retrieval of their intrinsic dimensions.

    OpenAIRE

    Jackman, Henrik; Krakhmalev, Pavel; Svensson, Krister

    2013-01-01

    We present a detailed analysis of the image formation mechanisms that are involved in the imaging of carbon nanotubes with scanning electron microscopy (SEM). We show how SEM images can be modelled by accounting for surface enhancement effects together with the absorption coefficient for secondary electrons, and the electron-probe shape. Images can then be deconvoluted, enabling retrieval of the intrinsic nanotube dimensions. Accurate estimates of their dimensions can thereby be obtained even...

  7. The investigation of the diameter dimension effect on the Si nano-tube transistors

    OpenAIRE

    M.-H. Liao; C.-H. Yeh; C.-C. Lee; C.-P. Wang

    2016-01-01

    The vertical gate-all-around (V-GAA) Si nano-tube (NT) devices with different diameter dimensions are studied in this work with the promising device performance. The V-GAA structure makes the transistor easy to be scaled down continuously to meet the complementary metal-oxide-semiconductor (CMOS) scaling requirements of the 7/10 nm technology node and beyond. The Si NT device with the hollow structure is demonstrated to have the capability to “deplete” and “screen-out” the out-of gate control...

  8. The investigation of the diameter dimension effect on the Si nano-tube transistors

    Science.gov (United States)

    Liao, M.-H.; Yeh, C.-H.; Lee, C.-C.; Wang, C.-P.

    2016-03-01

    The vertical gate-all-around (V-GAA) Si nano-tube (NT) devices with different diameter dimensions are studied in this work with the promising device performance. The V-GAA structure makes the transistor easy to be scaled down continuously to meet the complementary metal-oxide-semiconductor (CMOS) scaling requirements of the 7/10 nm technology node and beyond. The Si NT device with the hollow structure is demonstrated to have the capability to "deplete" and "screen-out" the out-of gate control carriers in the center of the NT and further result in the better device short channel control. Based on the study in this work, the V-GAA Si NT device with the optimized diameter dimension (=20 nm) can benefit the Ion-state current and reduce the Ioff-state stand-by power simultaneously, due to the less surface roughness scattering and the better short channel control characteristics. The proposed V-GAA Si NT device is regarded as one of the most promising candidates for the future application of the sub-7/10 nm logic era.

  9. Altered sleep in Borderline Personality Disorder in relation to the core dimensions of psychopathology.

    Science.gov (United States)

    Simor, Péter; Horváth, Klára

    2013-08-01

    The aim of the study was to review the literature regarding sleep disturbances in Borderline Personality Disorder (BPD) and to relate the reported sleep alterations to the underlying core dimensions of BPD pathology. We present a qualitative and theoretical review regarding the empirical studies that investigated objective and subjective sleep quality in BPD and in different psychiatric conditions showing high co-morbidity with this disorder. We show that disturbed sleep including sleep fragmentation, alterations in Slow Wave Sleep and REM sleep, and dysphoric dreaming are prevalent symptoms in BPD. We provide a framework relating the specific sleep alterations to the core dimensions of BPD pathology in order to clarify the inconsistencies of the different findings. The specific sleep disturbances in BPD seem to be related to different dimensions of psychopathological functioning and may have detrimental consequences on waking affect and cognition. Investigating disturbed sleep in BPD in relation to waking symptoms and underlying neural functioning would shed more light on the nature of this complex disorder. Moreover, a stronger emphasis on sleep disturbances would enrich the treatment protocols of BPD. PMID:23574575

  10. Study of modification methods of probes for critical-dimension atomic-force microscopy by the deposition of carbon nanotubes

    International Nuclear Information System (INIS)

    The results of an experimental study of the modification of probes for critical-dimension atomicforce microscopy (CD-AFM) by the deposition of carbon nanotubes (CNTs) to improve the accuracy with which the surface roughness of vertical walls is determined in submicrometer structures are presented. Methods of the deposition of an individual CNT onto the tip of an AFM probe via mechanical and electrostatic interaction between the probe and an array of vertically aligned carbon nanotubes (VACNTs) are studied. It is shown that, when the distance between the AFM tip and a VACNT array is 1 nm and the applied voltage is within the range 20–30 V, an individual carbon nanotube is deposited onto the tip. On the basis of the results obtained in the study, a probe with a carbon nanotube on its tip (CNT probe) with a radius of 7 nm and an aspect ratio of 1:15 is formed. Analysis of the CNT probe demonstrates that its use improves the resolution and accuracy of AFM measurements, compared with the commercial probe, and also makes it possible to determine the roughness of the vertical walls of high-aspect structures by CD-AFM. The results obtained can be used to develop technological processes for the fabrication and reconditioning of special AFM probes, including those for CD-AFM, and procedures for the interoperational express monitoring of technological process parameters in the manufacturing of elements for micro- and nanoelectronics and micro- and nanosystem engineering

  11. Study of modification methods of probes for critical-dimension atomic-force microscopy by the deposition of carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Ageev, O. A., E-mail: ageev@sfedu.ru [Southern Federal University, Institute for Nanotechnologies, Electronics, and Electronic Equipment Engineering (Russian Federation); Bykov, Al. V. [NT-MDT (Russian Federation); Kolomiitsev, A. S.; Konoplev, B. G.; Rubashkina, M. V.; Smirnov, V. A.; Tsukanova, O. G. [Southern Federal University, Institute for Nanotechnologies, Electronics, and Electronic Equipment Engineering (Russian Federation)

    2015-12-15

    The results of an experimental study of the modification of probes for critical-dimension atomicforce microscopy (CD-AFM) by the deposition of carbon nanotubes (CNTs) to improve the accuracy with which the surface roughness of vertical walls is determined in submicrometer structures are presented. Methods of the deposition of an individual CNT onto the tip of an AFM probe via mechanical and electrostatic interaction between the probe and an array of vertically aligned carbon nanotubes (VACNTs) are studied. It is shown that, when the distance between the AFM tip and a VACNT array is 1 nm and the applied voltage is within the range 20–30 V, an individual carbon nanotube is deposited onto the tip. On the basis of the results obtained in the study, a probe with a carbon nanotube on its tip (CNT probe) with a radius of 7 nm and an aspect ratio of 1:15 is formed. Analysis of the CNT probe demonstrates that its use improves the resolution and accuracy of AFM measurements, compared with the commercial probe, and also makes it possible to determine the roughness of the vertical walls of high-aspect structures by CD-AFM. The results obtained can be used to develop technological processes for the fabrication and reconditioning of special AFM probes, including those for CD-AFM, and procedures for the interoperational express monitoring of technological process parameters in the manufacturing of elements for micro- and nanoelectronics and micro- and nanosystem engineering.

  12. Altered Cell Mechanics from the Inside: Dispersed Single Wall Carbon Nanotubes Integrate with and Restructure Actin

    Directory of Open Access Journals (Sweden)

    Mohammad F. Islam

    2012-05-01

    Full Text Available With a range of desirable mechanical and optical properties, single wall carbon nanotubes (SWCNTs are a promising material for nanobiotechnologies. SWCNTs also have potential as biomaterials for modulation of cellular structures. Previously, we showed that highly purified, dispersed SWCNTs grossly alter F-actin inside cells. F-actin plays critical roles in the maintenance of cell structure, force transduction, transport and cytokinesis. Thus, quantification of SWCNT-actin interactions ranging from molecular, sub-cellular and cellular levels with both structure and function is critical for developing SWCNT-based biotechnologies. Further, this interaction can be exploited, using SWCNTs as a unique actin-altering material. Here, we utilized molecular dynamics simulations to explore the interactions of SWCNTs with actin filaments. Fluorescence lifetime imaging microscopy confirmed that SWCNTs were located within ~5 nm of F-actin in cells but did not interact with G-actin. SWCNTs did not alter myosin II sub-cellular localization, and SWCNT treatment in cells led to significantly shorter actin filaments. Functionally, cells with internalized SWCNTs had greatly reduced cell traction force. Combined, these results demonstrate direct, specific SWCNT alteration of F-actin structures which can be exploited for SWCNT-based biotechnologies and utilized as a new method to probe fundamental actin-related cellular processes and biophysics.

  13. Titania nanotubes with adjustable dimensions for drug reservoir sites and enhanced cell adhesion

    Energy Technology Data Exchange (ETDEWEB)

    Çalışkan, Nazlı; Bayram, Cem; Erdal, Ebru; Karahaliloğlu, Zeynep; Denkbaş, Emir Baki, E-mail: denkbas@hacettepe.edu.tr

    2014-02-01

    This study aims to generate a bactericidal agent releasing surface via nanotube layer on titanium metal and to investigate how aspect ratio of nanotubes affects drug elution time and cell proliferation. Titania nanotube layers were generated on metal surfaces by anodic oxidation at various voltage and time parameters. Gentamicin loading was carried out via simple pipetting and the samples were tested against S. aureus for the efficacy of the applied modification. Drug releasing time and cell proliferation were also tested in vitro. Titania nanotube layers with varying diameters and lengths were prepared after anodization and anodizing duration was found as the most effective parameter for amount of loaded drug and drug releasing time. Drug elution lasted up to 4 days after anodizing for 80 min of the samples, whereas release completed in 24 h when the samples were anodized for 20 min. All processed samples had bactericidal properties against S. aureus organism except unmodified titanium, which was also subjected to drug incorporation step. The anodization also enhanced water wettability and cell adhesion results. Anodic oxidation is an effective surface modification to enhance tissue–implant interactions and also resultant titania layer can act as a drug reservoir for the release of bactericidal agents. The use of implants as local drug eluting devices is promising but further in vivo testing is required. - Highlights: • Titanium surfaces were anodized and a nanotubular titania layer was obtained. • Drug eluting time was found to be increasing with anodizaton time. • Varying nanotube diameters has no effect in drug elution time but amount of incorporated drug.

  14. Application of finite-difference time domain to dye-sensitized solar cells: The effect of nanotube-array negative electrode dimensions on light absorption

    Energy Technology Data Exchange (ETDEWEB)

    Ong, Keat G. [Department of Biomedical Engineering, Michigan Technological University, Houghton, MI 49931 (United States); Varghese, Oomman K.; Mor, Gopal K.; Shankar, Karthik; Grimes, Craig A. [The Pennsylvania State University, 217 Materials Research Laboratory, University Park, PA 16802 (United States)

    2007-02-15

    We examine the light absorbing behavior of dye-sensitized solar cells (DSCs) having cathodes (negative electrodes) comprised of highly ordered TiO{sub 2} nanotube arrays using the electromagnetic computational technique, finite-difference time domain (FDTD). The highly ordered nanotube arrays, grown using anodic oxidation of titanium foils or thin films, feature an open end with the other end fixed on a dense oxide layer (barrier layer). The numerical simulation model is comprised of nanotube arrays on a transparent conducting glass substrate under front-side illumination. In the FDTD analysis, a transverse electromagnetic (TEM) wave is incident onto a N719 dye-coated nanotube array initially passing through the barrier layer; light that emerges from the nanotubes is reflected by a perfectly conducting layer (perfect electric conductor-PEC) boundary that simulates the effect of the DSC platinum counter electrode. An observation plane placed between the electromagnetic source and DSC detects the intensity of both the incident wave and the wave returning back from the DSC structure. The absorbance and transmittance spectra are determined in the wavelength range 300-700nm as a function of nanotube-array dimensions including length, pore size, barrier layer thickness, and surface roughness while keeping the wall thickness constant at 12nm. The validity of the computational simulations is experimentally verified. A significant increase in the light absorption by the dye-coated nanotubes was observed for increasing nanotube length; smaller pore sizes, and increased surface roughness. Changes in the barrier layer thickness had a negligible effect on the absorbance spectrum. Our efforts demonstrate FDTD to be a broadly applicable technique capable of guiding design of an optimal DSC architecture. (author)

  15. Fermionic condensate and Casimir densities in the presence of compact dimensions with applications to nanotubes

    CERN Document Server

    Elizalde, E; Saharian, A A

    2011-01-01

    We investigate the fermionic condensate and the vacuum expectation value of the energy-momentum tensor for a massive fermionic field in the geometry of two parallel plate on the background of Minkowski spacetime with an arbitrary number of toroidally compactified spatial dimensions, in the presence of a constant gauge field. Bag boundary conditions are imposed on the plates and periodicity conditions with arbitrary phases are considered along the compact dimensions. The boundary induced parts in the fermionic condensate and the vacuum energy density are negative, with independence of the phases in the periodicity conditions and of the value of the gauge potential. Interaction forces between the plates are thus always attractive. However, in physical situations where the quantum field is confined to the region between the plates, the pure topological part contributes as well, and then the resulting force can be either attractive or repulsive, depending on the specific phases encoded in the periodicity conditio...

  16. Carbon nanotube-based mode-locked wavelength-switchable fiber laser via net gain cross section alteration

    Science.gov (United States)

    Latif, A. A.; Mohamad, H.; Abu Bakar, M. H.; Muhammad, F. D.; Mahdi, M. A.

    2016-02-01

    We have proposed and demonstrated a carbon nanotube-based mode-locked erbium-doped fiber laser with switchable wavelength in the C-band wavelength region by varying the net gain cross section of erbium. The carbon nanotube is coated on a tapered fiber to form the saturable absorber for the purpose of mode-locking by exploiting the concept of evanescent field interaction on the tapered fiber with the carbon nanotube in a ring cavity configuration. The propagation loss is adjusted by inducing macrobend losses of the optical fiber in the cavity through a fiber spooling technique. Since the spooling radius can be gradually adjusted to achieve continuous tuning of attenuation, this passive tuning approach can be an alternative to optical tunable attenuator, with freedom of external device integration into the laser cavity. Based on this alteration, the net gain cross section of the laser system can be tailored to three different lasing wavelength ranges; 1533, 1560 nm and both (1533 and 1560 nm) with the minimum pulse duration of 734 fs. The proposed design is simple and stable with high beam quality and good reliability for multiple applications.

  17. Self-organized anodic TiO.sub.2./sub. nanotube layers: influence of the Ti substrate on nanotube growth and dimensions

    Czech Academy of Sciences Publication Activity Database

    Sopha, H.; Jäger, Aleš; Knotek, P.; Tesař, Karel; Jarošová, Markéta; Macák, J. M.

    2016-01-01

    Roč. 190, Feb (2016), 744-752. ISSN 0013-4686 R&D Projects: GA ČR GBP108/12/G043 Institutional support: RVO:68378271 Keywords : titanium * anodization * titanium dioxide * nanotubes * ordering Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 4.504, year: 2014

  18. Confinement by Carbon Nanotubes Drastically Alters the Boiling and Critical Behavior of Water Droplets

    OpenAIRE

    Chaban, Vitaly V.; Prezhdo, Victor V.; Prezhdo, Oleg V.

    2012-01-01

    Vapor pressure grows rapidly above the boiling temperature, and past the critical point liquid droplets disintegrate. Our atomistic simulations show that this sequence of events is reversed inside carbon nanotubes (CNT). Droplets disintegrate first and at low temperature, while pressure remains small. The droplet disintegration temperature is independent of the CNT diameter. In contrast, depending on CNT diameter, a temperature that is much higher than the bulk boiling temperature is required...

  19. Performances of carbon nanotube field effect transistors with altered channel length

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The influence of channel length on the performances of carbon nanotube field effect transistors(CNT-FETs) has been studied.Buffered oxide etching was used to remove approximately a 60 nm layer from the original 100 nm silicon dioxide layer,to thin the dielectric layer of the back gate.Channel length of the CNT-FETs was changed along with the etching process.The dependence of drain-source current on gate voltage was measured to analyze the performance of the CNT-FETs,including the transconductance,carrier mobility,current ON/OFF ratio,etc.The results indicate that the devices still keep good quality.

  20. Shape- and dimension-controlled single-crystalline silicon and SiGe nanotubes: toward nanofluidic FET devices.

    Science.gov (United States)

    Ben Ishai, Moshit; Patolsky, Fernando

    2009-03-18

    We report here on the formation of robust and entirely hollow single-crystalline silicon nanotubes, from various tubular to conical structures, with uniform and well-controlled inner diameter, ranging from as small as 1.5 up to 500 nm, and controllable wall thickness. Second, and most important, these nanotubes can be doped in situ with different concentrations of boron and phosphine to give p/n-type semiconductor nanotubes. Si(x)Ge(1-x)-alloy nanotubes can also be prepared. This synthetic approach enables independent and precise control of diameter, wall thickness, shape, taper angle, crystallinity, and chemical/electrical characteristics of the nanotubular structures obtained. Notably, diameter and wall thickness of nearly any size can be obtained. This unique advantage allows the achievement of novel and perfectly controlled high-quality electronic materials and the tailoring of the tube properties to better fit many biological, chemical, and electrical applications. Electrical devices based on this new family of electrically active nanotubular building-block structures are also described with a view toward the future realization of nanofluidic FET devices. PMID:19226180

  1. Altered excitability of cultured chromaffin cells following exposure to multi-walled carbon nanotubes.

    Science.gov (United States)

    Gavello, Daniela; Vandael, David H F; Cesa, Roberta; Premoselli, Federica; Marcantoni, Andrea; Cesano, Federico; Scarano, Domenica; Fubini, Bice; Carbone, Emilio; Fenoglio, Ivana; Carabelli, Valentina

    2012-02-01

    We studied the effects of multi-walled carbon nanotubes (MWCNTs) on the electrophysiological properties of cultured mouse chromaffin cells, a model of spontaneously firing cells. The exposure of chromaffin cells to MWCNTs at increasing concentrations (30-263 μg/ml) for 24 h reduced, in a dose-dependent way, both the cell membrane input resistance and the number of spontaneously active cells (from 80-52%). Active cells that survived from the toxic effects of MWCNTs exhibited more positive resting potentials, higher firing frequencies and unaltered voltage-gated Ca(2+), Na(+) and K+ current amplitudes. MWCNTs slowed down the inactivation kinetics of Ca(2+)-dependent BK channels. These electrophysiological effects were accompanied by MWCNTs internalization, as confirmed by transmission electron microscopy, indicating that most of the toxic effects derive from a dose-dependent MWCNTs-cell interaction that damages the spontaneous cell activity. PMID:21322767

  2. Applications of Carbon Nanotubes

    Science.gov (United States)

    Ajayan, Pulickel M.; Zhou, Otto Z.

    Carbon nanotubes have attracted the fancy of many scientists worldwide. The small dimensions, strength and the remarkable physical properties of these structures make them a very unique material with a whole range of promising applications. In this review we describe some of the important materials science applications of carbon nanotubes. Specifically we discuss the electronic and electrochemical applications of nanotubes, nanotubes as mechanical reinforcements in high performance composites, nanotube-based field emitters, and their use as nanoprobes in metrology and biological and chemical investigations, and as templates for the creation of other nanostructures. Electronic properties and device applications of nanotubes are treated elsewhere in the book. The challenges that ensue in realizing some of these applications are also discussed from the point of view of manufacturing, processing, and cost considerations.

  3. PEGylated Carbon Nanotubes Impair Retrieval of Contextual Fear Memory and Alter Oxidative Stress Parameters in the Rat Hippocampus

    Directory of Open Access Journals (Sweden)

    Lidiane Dal Bosco

    2015-01-01

    Full Text Available Carbon nanotubes (CNT are promising materials for biomedical applications, especially in the field of neuroscience; therefore, it is essential to evaluate the neurotoxicity of these nanomaterials. The present work assessed the effects of single-walled CNT functionalized with polyethylene glycol (SWCNT-PEG on the consolidation and retrieval of contextual fear memory in rats and on oxidative stress parameters in the hippocampus. SWCNT-PEG were dispersed in water at concentrations of 0.5, 1.0, and 2.1 mg/mL and infused into the rat hippocampus. The infusion was completed immediately after training and 30 min before testing of a contextual fear conditioning task, resulting in exposure times of 24 h and 30 min, respectively. The results showed that a short exposure to SWCNT-PEG impaired fear memory retrieval and caused lipid peroxidation in the hippocampus. This response was transient and overcome by the mobilization of antioxidant defenses at 24 h. These effects occurred at low and intermediate but not high concentration of SWCNT-PEG, suggesting that the observed biological response may be related to the concentration-dependent increase in particle size in SWCNT-PEG dispersions.

  4. Interactions of multiwalled carbon nanotubes with algal cells: quantification of association, visualization of uptake, and measurement of alterations in the composition of cells.

    Science.gov (United States)

    Rhiem, Stefan; Riding, Matthew J; Baumgartner, Werner; Martin, Francis L; Semple, Kirk T; Jones, Kevin C; Schäffer, Andreas; Maes, Hanna M

    2015-01-01

    Carbon nanotubes (CNTs) are considered promising materials in nanotechnology. We quantified CNT accumulation by the alga Desmodesmus subspicatus. Cells were exposed to radiolabeled CNTs ((14)C-CNTs;1 mg/L) to determine uptake and association, as well as elimination and dissociation in clear media.Attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) was used to detect effects of CNTs on algae. CNT-cell interactions were visualized by electron microscopy and related to alterations in their cell composition. A concentration factor of 5000 L/kg dry weight was calculated. Most of the material agglomerated around the cells, but single tubes were detected in the cytoplasm. Computational analyses of the ATR-FTIR data showed that CNT treated algae differed from controls at all sampling times.CNT exposure changed the biochemical composition of cells. The fact that CNTs are bioavailable for algae and that they influence the cell composition is important with regard to environmental risk assessment of this nanomaterial. PMID:25467692

  5. Magnetic nanotubes

    Science.gov (United States)

    Matsui, Hiroshi; Matsunaga, Tadashi

    2010-11-16

    A magnetic nanotube includes bacterial magnetic nanocrystals contacted onto a nanotube which absorbs the nanocrystals. The nanocrystals are contacted on at least one surface of the nanotube. A method of fabricating a magnetic nanotube includes synthesizing the bacterial magnetic nanocrystals, which have an outer layer of proteins. A nanotube provided is capable of absorbing the nanocrystals and contacting the nanotube with the nanocrystals. The nanotube is preferably a peptide bolaamphiphile. A nanotube solution and a nanocrystal solution including a buffer and a concentration of nanocrystals are mixed. The concentration of nanocrystals is optimized, resulting in a nanocrystal to nanotube ratio for which bacterial magnetic nanocrystals are immobilized on at least one surface of the nanotubes. The ratio controls whether the nanocrystals bind only to the interior or to the exterior surfaces of the nanotubes. Uses include cell manipulation and separation, biological assay, enzyme recovery, and biosensors.

  6. Multiscale Modeling with Carbon Nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Maiti, A

    2006-02-21

    Technologically important nanomaterials come in all shapes and sizes. They can range from small molecules to complex composites and mixtures. Depending upon the spatial dimensions of the system and properties under investigation computer modeling of such materials can range from equilibrium and nonequilibrium Quantum Mechanics, to force-field-based Molecular Mechanics and kinetic Monte Carlo, to Mesoscale simulation of evolving morphology, to Finite-Element computation of physical properties. This brief review illustrates some of the above modeling techniques through a number of recent applications with carbon nanotubes: nano electromechanical sensors (NEMS), chemical sensors, metal-nanotube contacts, and polymer-nanotube composites.

  7. Cephalometric Evaluation of the Effect of Complete Dentures on Retropharyngeal Space and Its Effect on Spirometric Values in Altered Vertical Dimension

    OpenAIRE

    Sameer Singhal; Pakhan, A. J.; Ram Thombare; Prachi Gupta

    2011-01-01

    Role of complete dentures in reducing apnea-hypoapnea index in edentulous obstructive sleep apnea patient has shown promising results in previous studies. This study was undertaken to ascertain the role of complete denture and complete denture with slight increase in vertical dimension using custom made occlussal jig, on retropharyngeal space, posterior airway space, pharyngeal depth, and spirometric readings in comparison with those in edentulous group. Significant changes were observed in b...

  8. Synthesis and Characterization Of Fe-modified Imogolite Nanotubes

    OpenAIRE

    Shafia, Ehsan

    2015-01-01

    During the past decades, and after introducing the most famous carbon nanotubes, the main role in these fields has been playing by the single- and multi-wall carbon nanotubes which have received tremendous research interest due to their superior mechanical, chemical, electrical and thermal properties. However, several problems in carbon nanotube technology, such as high-temperature process with low yield product, imprecise control over nanotube dimensions and chirality, limitations of chemica...

  9. Heteroporphyrin nanotubes and composites

    Science.gov (United States)

    Shelnutt, John A.; Medforth, Craig J.; Wang, Zhongchun

    2007-05-29

    Heteroporphyrin nanotubes, metal nanostructures, and metal/porphyrin-nanotube composite nanostructures formed using the nanotubes as photocatalysts and structural templates, and the methods for forming the nanotubes and composites.

  10. Heteroporphyrin nanotubes and composites

    Science.gov (United States)

    Shelnutt, John A.; Medforth, Craig J.; Wang, Zhongchun

    2006-11-07

    Heteroporphyrin nanotubes, metal nanostructures, and metal/porphyrin-nanotube composite nanostructures formed using the nanotubes as photocatalysts and structural templates, and the methods for forming the nanotubes and composites.

  11. Carbon nanotubes affect the toxicity of CuO nanoparticles to denitrification in marine sediments by altering cellular internalization of nanoparticle

    Science.gov (United States)

    Zheng, Xiong; Su, Yinglong; Chen, Yinguang; Wan, Rui; Li, Mu; Huang, Haining; Li, Xu

    2016-06-01

    Denitrification is an important pathway for nitrate transformation in marine sediments, and this process has been observed to be negatively affected by engineered nanomaterials. However, previous studies only focused on the potential effect of a certain type of nanomaterial on microbial denitrification. Here we show that the toxicity of CuO nanoparticles (NPs) to denitrification in marine sediments is highly affected by the presence of carbon nanotubes (CNTs). It was found that the removal efficiency of total NOX‑-N (NO3‑-N and NO2‑-N) in the presence of CuO NPs was only 62.3%, but it increased to 81.1% when CNTs appeared in this circumstance. Our data revealed that CuO NPs were more easily attached to CNTs rather than cell surface because of the lower energy barrier (3.5 versus 36.2 kT). Further studies confirmed that the presence of CNTs caused the formation of large, incompact, non-uniform dispersed, and more negatively charged CuO-CNTs heteroaggregates, and thus reduced the nanoparticle internalization by cells, leading to less toxicity to metabolism of carbon source, generation of reduction equivalent, and activities of nitrate reductase and nitrite reductase. These results indicate that assessing nanomaterial-induced risks in real circumstances needs to consider the “mixed” effects of nanomaterials.

  12. A statistical mechanics model of carbon nanotube macro-films

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Carbon nanotube macro-films are two-dimensional films with micrometer thickness and centimeter by centimeter in-plane dimension.These carbon nanotube macroscopic assemblies have attracted significant attention from the material and mechanics communities recently because they can be easily handled and tailored to meet specific engineering needs.This paper reports the experimental methods on the preparation and characterization of single-walled carbon nanotube macro-films,and a statistical mechanics model on ...

  13. Quantum transport in carbon nanotubes

    Science.gov (United States)

    Laird, Edward A.; Kuemmeth, Ferdinand; Steele, Gary A.; Grove-Rasmussen, Kasper; Nygârd, Jesper; Flensberg, Karsten; Kouwenhoven, Leo P.

    2015-07-01

    Carbon nanotubes are a versatile material in which many aspects of condensed matter physics come together. Recent discoveries have uncovered new phenomena that completely change our understanding of transport in these devices, especially the role of the spin and valley degrees of freedom. This review describes the modern understanding of transport through nanotube devices. Unlike in conventional semiconductors, electrons in nanotubes have two angular momentum quantum numbers, arising from spin and valley freedom. The interplay between the two is the focus of this review. The energy levels associated with each degree of freedom, and the spin-orbit coupling between them, are explained, together with their consequences for transport measurements through nanotube quantum dots. In double quantum dots, the combination of quantum numbers modifies the selection rules of Pauli blockade. This can be exploited to read out spin and valley qubits and to measure the decay of these states through coupling to nuclear spins and phonons. A second unique property of carbon nanotubes is that the combination of valley freedom and electron-electron interactions in one dimension strongly modifies their transport behavior. Interaction between electrons inside and outside a quantum dot is manifested in SU(4) Kondo behavior and level renormalization. Interaction within a dot leads to Wigner molecules and more complex correlated states. This review takes an experimental perspective informed by recent advances in theory. As well as the well-understood overall picture, open questions for the field are also clearly stated. These advances position nanotubes as a leading system for the study of spin and valley physics in one dimension where electronic disorder and hyperfine interaction can both be reduced to a low level.

  14. The inner dimension of sustainability

    NARCIS (Netherlands)

    Horlings, L.G.

    2015-01-01

    Transformation to sustainability has been defined as the fundamental alteration of the nature of a system, once the current conditions become untenable or undesirable. Transformation requires a shift in people's values, referred to as the inner dimension of sustainability, or change from the inside-

  15. Multiplying dimensions

    CERN Multimedia

    2013-01-01

    A few weeks ago, I had a vague notion of what TED was, and how it worked, but now I’m a confirmed fan. It was my privilege to host CERN’s first TEDx event last Friday, and I can honestly say that I can’t remember a time when I was exposed to so much brilliance in such a short time.   TEDxCERN was designed to give a platform to science. That’s why we called it Multiplying Dimensions – a nod towards the work we do here, while pointing to the broader importance of science in society. We had talks ranging from the most subtle pondering on the nature of consciousness to an eighteen year old researcher urging us to be patient, and to learn from our mistakes. We had musical interludes that included encounters between the choirs of local schools and will.i.am, between an Israeli pianist and an Iranian percussionist, and between Grand Opera and high humour. And although I opened the event by announcing it as a day off from physics, we had a quite brill...

  16. Electrically Percolating Clusters in Sheared Carbon Nanotube Composites

    Science.gov (United States)

    Migler, Kalman; Moon, Doyoung; Obrzut, Jan; Douglas, Jack; Lam, Thomas; Sharma, Renu; Liddle, Alex James

    2013-03-01

    The electrical conductivity of polymer nanotube composites can be dramatically modified by processing flows and subsequent annealing. The mechanism is widely believed to be nanotube structural rearrangements that occur during flow and alter the percolating pathways. We seek to directly visualize these flow-induced three-dimensional percolating clusters through three-dimensional confocal microscopy and image analysis.

  17. Chiral Anomaly in Toroidal Carbon Nanotubes

    OpenAIRE

    Sasaki, K.

    2001-01-01

    It is pointed out that the chiral anomaly in 1+1 dimensions should be observed in toroidal carbon nanotubes on a planar geometry with varying magnetic field. We show that the chiral anomaly is closely connected with the persistent current in a one-dimensional metallic ring.

  18. Modification of Carbon Nanotube Powder Microelectrode and Nitrite Reduction

    Institute of Scientific and Technical Information of China (English)

    PeiFangLIU; JunFuHU

    2002-01-01

    The properties of the carbon nanotube powder microelectroes (denoted CNTPME) are remarkably altered by anodic pretreatment and preadsorption of mediators. It seems that anodic pretreatment leads the long and tangled carbon nanotubes to be partially cut shorter, resulting in more openings as shown by TEM. Besides, the anodic pretreatment may adjust the hydrophobicity of nanotubes to match with that of Os(bpy)32+. As a result, the real surface area and the ability of adsorbing mediator Os(bpy)32+ of the nanotubes are markedly increased so as to effectively catalyze NO2- reduction in acidic solution.

  19. Modification of Carbon Nanotube Powder Microelectrode and Nitrite Reduction

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The properties of the carbon nanotube powder microelectrodes (denoted CNTPME) are remarkably altered by anodic pretreatment and preadsorption of mediators. It seems that anodic pretreatment leads the long and tangled carbon nanotubes to be partially cut shorter, resulting in more openings as shown by TEM. Besides, the anodic pretreatment may adjust the hydrophobicity of nanotubes to match with that of Os(bpy)32+. As a result, the real surface area and the ability of adsorbing mediator Os(bpy)32+ of the nanotubes are markedly increased so as to effectively catalyze NO2- reduction in acidic solution.

  20. Atomic Layer Deposition Coating of Carbon Nanotubes with Aluminum Oxide Alters Pro-Fibrogenic Cytokine Expression by Human Mononuclear Phagocytes In Vitro and Reduces Lung Fibrosis in Mice In Vivo

    Science.gov (United States)

    Taylor, Alexia J.; McClure, Christina D.; Shipkowski, Kelly A.; Thompson, Elizabeth A.; Hussain, Salik; Garantziotis, Stavros; Parsons, Gregory N.; Bonner, James C.

    2014-01-01

    Background Multi-walled carbon nanotubes (MWCNTs) pose a possible human health risk for lung disease as a result of inhalation exposure. Mice exposed to MWCNTs develop pulmonary fibrosis. Lung macrophages engulf MWCNTs and produce pro-fibrogenic cytokines including interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and osteopontin (OPN). Atomic layer deposition (ALD) is a novel process used to enhance functional properties of MWCNTs, yet the consequence of ALD-modified MWCNTs on macrophage biology and fibrosis is unknown. Methods The purpose of this study was to determine whether ALD coating with aluminum oxide (Al2O3) would alter the fibrogenic response to MWCNTs and whether cytokine expression in human macrophage/monocytes exposed to MWCNTs in vitro would predict the severity of lung fibrosis in mice. Uncoated (U)-MWCNTs or ALD-coated (A)-MWCNTs were incubated with THP-1 macrophages or human peripheral blood mononuclear cells (PBMC) and cell supernatants assayed for cytokines by ELISA. C57BL6 mice were exposed to a single dose of A- or U-MWCNTs by oropharyngeal aspiration (4 mg/kg) followed by evaluation of histopathology, lung inflammatory cell counts, and cytokine levels at day 1 and 28 post-exposure. Results ALD coating of MWCNTs with Al2O3 enhanced IL-1β secretion by THP-1 and PBMC in vitro, yet reduced protein levels of IL-6, TNF-α, and OPN production by THP-1 cells. Moreover, Al2O3 nanoparticles, but not carbon black NPs, increased IL-1β but decreased OPN and IL-6 in THP-1 and PBMC. Mice exposed to U-MWCNT had increased levels of all four cytokines assayed and developed pulmonary fibrosis by 28 days, whereas ALD-coating significantly reduced fibrosis and cytokine levels at the mRNA or protein level. Conclusion These findings indicate that ALD thin film coating of MWCNTs with Al2O3 reduces fibrosis in mice and that in vitro phagocyte expression of IL-6, TNF-α, and OPN, but not IL-1β, predict MWCNT-induced fibrosis in the lungs of mice in vivo

  1. Finitistic dimension through infinite projective dimension

    OpenAIRE

    Huard, Francois; Lanzilotta, Marcelo; Mendoza, Octavio

    2007-01-01

    We show that an artin algebra having at most three radical layers of infinite projective dimension has finite finitistic dimension, generalizing the known result for algebras with vanishing radical cube.

  2. Designing a nanotube using naturally occurring protein building blocks.

    Directory of Open Access Journals (Sweden)

    Chung-Jung Tsai

    2006-04-01

    Full Text Available Here our goal is to carry out nanotube design using naturally occurring protein building blocks. Inspection of the protein structural database reveals the richness of the conformations of proteins, their parts, and their chemistry. Given target functional protein nanotube geometry, our strategy involves scanning a library of candidate building blocks, combinatorially assembling them into the shape and testing its stability. Since self-assembly takes place on time scales not affordable for computations, here we propose a strategy for the very first step in protein nanotube design: we map the candidate building blocks onto a planar sheet and wrap the sheet around a cylinder with the target dimensions. We provide examples of three nanotubes, two peptide and one protein, in atomistic model detail for which there are experimental data. The nanotube models can be used to verify a nanostructure observed by low-resolution experiments, and to study the mechanism of tube formation.

  3. Synthesis of anisotropic gold shell on carbon nanotube

    International Nuclear Information System (INIS)

    This paper reports a simple procedure to synthesize gold-coated carbon nanotubes. The method involves the reduction of gold precursor on oxidized carbon nanotubes. UV–Visible absorption spectroscopy and electron microscopy were used to study the gold precursor reduction on the carbon nanotubes. Scanning and transmission electron microscopy analysis showed the formation of an irregular gold layer around the CNT surface. The resulting nanoparticles show an anisotropic shape with dimensions between 100 and 200 nm. This hybrid material displays an intense absorption in the near infrared range with an absorption maximum at 840 nm

  4. Conformational changes of fibrinogen in dispersed carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Park SJ

    2012-08-01

    Full Text Available Sung Jean Park,1 Dongwoo Khang21College of Pharmacy, Gachon University, Yeonsu-gu, Incheon, South Korea; 2School of Nano and Advanced Materials Science Engineering and Center for PRC and RIGET, Gyeongsang National University, Jinju, South KoreaAbstract: The conformational changes of plasma protein structures in response to carbon nanotubes are critical for determining the nanotoxicity and blood coagulation effects of carbon nanotubes. In this study, we identified that the functional intensity of carboxyl groups on carbon nanotubes, which correspond to the water dispersity or hydrophilicity of carbon nanotubes, can induce conformational changes in the fibrinogen domains. Also, elevation of carbon nanotube density can alter the secondary structures (ie, helices and beta sheets of fibrinogen. Furthermore, fibrinogen that had been in contact with the nanoparticle material demonstrated a different pattern of heat denaturation compared with free fibrinogen as a result of a variation in hydrophilicity and concentration of carbon nanotubes. Considering the importance of interactions between carbon nanotubes and plasma proteins in the drug delivery system, this study elucidated the correlation between nanoscale physiochemical material properties of carbon nanotubes and associated structural changes in fibrinogen.Keywords: carbon nanotubes, fibrinogen, nanotoxicity, conformational change, denaturation

  5. Plumbing carbon nanotubes

    Science.gov (United States)

    Jin, Chuanhong; Suenaga, Kazu; Iijima, Sumio

    2008-01-01

    Since their discovery, the possibility of connecting carbon nanotubes together like water pipes has been an intriguing prospect for these hollow nanostructures. The serial joining of carbon nanotubes in a controlled manner offers a promising approach for the bottom-up engineering of nanotube structures-from simply increasing their aspect ratio to making integrated carbon nanotube devices. To date, however, there have been few reports of the joining of two different carbon nanotubes. Here we demonstrate that a Joule heating process, and associated electro-migration effects, can be used to connect two carbon nanotubes that have the same (or similar) diameters. More generally, with the assistance of a tungsten metal particle, this technique can be used to seamlessly join any two carbon nanotubes-regardless of their diameters-to form new nanotube structures.

  6. Carbon nanotube nanoelectrode arrays

    Science.gov (United States)

    Ren, Zhifeng; Lin, Yuehe; Yantasee, Wassana; Liu, Guodong; Lu, Fang; Tu, Yi

    2008-11-18

    The present invention relates to microelectode arrays (MEAs), and more particularly to carbon nanotube nanoelectrode arrays (CNT-NEAs) for chemical and biological sensing, and methods of use. A nanoelectrode array includes a carbon nanotube material comprising an array of substantially linear carbon nanotubes each having a proximal end and a distal end, the proximal end of the carbon nanotubes are attached to a catalyst substrate material so as to form the array with a pre-determined site density, wherein the carbon nanotubes are aligned with respect to one another within the array; an electrically insulating layer on the surface of the carbon nanotube material, whereby the distal end of the carbon nanotubes extend beyond the electrically insulating layer; a second adhesive electrically insulating layer on the surface of the electrically insulating layer, whereby the distal end of the carbon nanotubes extend beyond the second adhesive electrically insulating layer; and a metal wire attached to the catalyst substrate material.

  7. Characterization of bionanocomposite scaffolds comprised of amine-functionalized single-walled carbon nanotubes crosslinked to an acellular porcine tendon.

    Science.gov (United States)

    Deeken, Corey R; Cozad, Matthew J; Bachman, Sharon L; Ramshaw, Bruce J; Grant, Sheila A

    2011-03-01

    Carbon nanotubes (CNT) possess many unique electrical and mechanical properties that make them useful for a variety of industrial and biomedical applications. They are especially attractive materials for biomedical applications since their dimensions are similar to components of the extracellular matrix. In this study, amine-functionalized single-walled carbon nanotubes were crosslinked to an acellular porcine diaphragm tendon. The resulting bionanocomposite scaffolds were subjected to a number of materials characterization techniques including a collagenase assay, uniaxial tensile testing, modulated differential scanning calorimetry, and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy to determine whether the properties of the original extracellular matrix were altered by the treatment processes. A variety of SWCNT concentrations were investigated. While none of the conditions investigated resulted in bionanocomposites with significantly improved physicochemical properties, no detrimental effects were observed due to any of the processing steps. Future studies should be performed to determine if carbon nanotubes can influence cellular adhesion and function in order to promote rapid integration and remodeling. PMID:21254390

  8. Novel Bismuth Nanotubes

    Institute of Scientific and Technical Information of China (English)

    苏长荣; 李家明

    2002-01-01

    Theoretical investigations show that bismuth nanotubes are semiconductors for all diameters. For smalldiameter bismuth nanotubes, the band structures and bandgaps vary strongly with the strong hybridization effect. When the diameters are larger than 18 A, the bandgaps ofBi (n, n) and (n, 0) nanotubes approach 0.63 e V, corresponding to the bandgap of bismuth sheet at the Γ point. Thus, bismuth nanotubes are expected to be a potential semiconductor nanomaterial in future nanoelectronics.

  9. Water desalination using carbon-nanotube-enhanced membrane distillation.

    Science.gov (United States)

    Gethard, Ken; Sae-Khow, Ornthida; Mitra, Somenath

    2011-02-01

    Carbon nanotube (CNT) enhanced membrane distillation is presented for water desalination. It is demonstrated that the immobilization of the CNTs in the pores of a hydrophobic membrane favorably alters the water-membrane interactions to promote vapor permeability while preventing liquid penetration into the membrane pores. For a salt concentration of 34 000 mg L(-1) and at 80 °C, the nanotube incorporation led to 1.85 and 15 times increase in flux and salt reduction, respectively. PMID:21188976

  10. Strongly Gorenstein Flat Dimensions

    Institute of Scientific and Technical Information of China (English)

    Chun Xia ZHANG; Li Min WANG

    2011-01-01

    This article is concerned with the strongly Gorenstein flat dimensions of modules and rings.We show this dimension has nice properties when the ring is coherent,and extend the well-known Hilbert's syzygy theorem to the strongly Gorenstein flat dimensions of rings.Also,we investigate the strongly Gorenstein flat dimensions of direct products of rings and (almost)excellent extensions of rings.

  11. DIFFERENT DIMENSIONS OF TEAMS

    OpenAIRE

    Goparaju Purna SUDHAKAR

    2013-01-01

    Popularity of teams is growing in 21st Century. Organizations are getting their work done through different types of teams. Teams have proved that the collective performance is more than the sum of the individual performances. Thus, the teams have got different dimensions such as quantitative dimensions and qualitative dimensions. The Quantitative dimensions of teams such as team performance, team productivity, team innovation, team effectiveness, team efficiency, team decision making and tea...

  12. Computability and Fractal Dimension

    OpenAIRE

    Reimann, Jan

    2004-01-01

    This thesis combines computability theory and various notions of fractal dimension, mainly Hausdorff dimension. An algorithmic approach to Hausdorff measures makes it possible to define the Hausdorff dimension of individual points instead of sets in a metric space. This idea was first realized by Lutz (2000). Working in the Cantor space of all infinite binary sequences, we study the theory of Hausdorff and other dimensions for individual sequences. After giving an overview over the classical...

  13. Dimension of chaotic attractors

    Energy Technology Data Exchange (ETDEWEB)

    Farmer, J.D.; Ott, E.; Yorke, J.A.

    1982-09-01

    Dimension is perhaps the most basic property of an attractor. In this paper we discuss a variety of different definitions of dimension, compute their values for a typical example, and review previous work on the dimension of chaotic attractors. The relevant definitions of dimension are of two general types, those that depend only on metric properties, and those that depend on probabilistic properties (that is, they depend on the frequency with which a typical trajectory visits different regions of the attractor). Both our example and the previous work that we review support the conclusion that all of the probabilistic dimensions take on the same value, which we call the dimension of the natural measure, and all of the metric dimensions take on a common value, which we call the fractal dimension. Furthermore, the dimension of the natural measure is typically equal to the Lyapunov dimension, which is defined in terms of Lyapunov numbers, and thus is usually far easier to calculate than any other definition. Because it is computable and more physically relevant, we feel that the dimension of the natural measure is more important than the fractal dimension.

  14. On asymptotic extension dimension

    OpenAIRE

    Repovš, Dušan; Zarichnyi, Mykhailo

    2011-01-01

    The aim of this paper is to introduce an asymptotic counterpart of the extension dimension defined by Dranishnikov. The main result establishes a relation between the asymptotic extensional dimension of a proper metric space and extension dimension of its Higson corona.

  15. VC dimension of ellipsoids

    OpenAIRE

    Akama, Yohji; Irie, Kei

    2011-01-01

    We will establish that the VC dimension of the class of d-dimensional ellipsoids is (d^2+3d)/2, and that maximum likelihood estimate with N-component d-dimensional Gaussian mixture models induces a geometric class having VC dimension at least N(d^2+3d)/2. Keywords: VC dimension; finite dimensional ellipsoid; Gaussian mixture model

  16. Immobilization of enzymes onto carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Prlainović Nevena Ž.

    2011-01-01

    Full Text Available The discovery of carbon nanotubes (CNTs has opened a new door in nanotechnology. With their high surface area, unique electronic, thermal and mechanical properties, CNTs have been widely used as carriers for protein immobilization. In fact, carbon nanotubes present ideal support system without diffusional limitations, and also have the possibility of surface covalent functionalization. It is usually the oxidation process that introduces carboxylic acid groups. Enzymes and other proteins could be adsorbed or covalently attached onto carbon nanotubes. Adsorption of enzyme is a very simple and inexpensive immobilization method and there are no chemical changes of the protein. It has also been found that this technique does not alter structure and unique properties of nanotubes. However, a major problem in process designing is relatively low stability of immobilized protein and desorption from the carrier. On the other hand, while covalent immobilization provides durable attachment the oxidation process can reduce mechanical and electronic properties of carbon nanotubes. It can also affect the active site of enzyme and cause the loss of enzyme activity. Bioimmobilization studies have showed that there are strong interactions between carbon nanotubes surface and protein. The retention of enzyme structure and activity is critical for their application and it is of fundamental interest to understand the nature of these interactions. Atomic force microscopy (AFM, transmission electron microscopy (TEM, scanning electron microscopy (SEM and circular dichroism (CD spectroscopy provide an insight into the structural changes that occur during the immobilization. The aim of this paper is to summarize progress of protein immobilization onto carbon nanotubes.

  17. Synthesis of cadmium chalcogenide nanotubes at room temperature

    KAUST Repository

    Pan, Jun

    2012-10-01

    Cadmium chalcogenide (CdE, E=S, Se, Te) polycrystalline nanotubes have been synthesized from precursor of CdS/cadmium thiolate complex at room temperature. The precursor was hydrothermally synthesized at 180 °C using thioglycolic acid (TGA) and cadmium acetate as starting materials. The transformation from the rod-like precursor of CdS/cadmium thiolate complex to CdS, CdSe and CdTe nanotubes were performed under constant stirring at room temperature in aqueous solution containing S 2-, Se 2- and Te 2-, respectively. The nanotube diameter can be controlled from 150 to 400 nm related to the dimension of templates. The XRD patterns show the cadmium chalcogenide nanotubes all corresponding to face-centered cubic structure. © 2012 Elsevier B.V. All rights reserved.

  18. Recent Advances in Directed Assembly of Nanowires or Nanotub es

    Institute of Scientific and Technical Information of China (English)

    Mei Liu; Zhizheng Wu; Woon Ming Lau; Jun Yang

    2012-01-01

    Nanowires and nanotubes of diverse material compositions, properties and/or functions have been produced or fabricated through various bottom-up or top-down approaches. These nanowires or nanotubes have also been utilized as potential building blocks for functional nanodevices. The key for the integration of those nanowire or nanotube based devices is to assemble these one dimensional nanomaterials to specific locations using techniques that are highly controllable and scalable. Ideally such techniques should enable assembly of highly uniform nanowire/nanotube arrays with precise control of density, location, dimension or even ma-terial types of nanowires/nanotubes. Numerous assembly techniques are being developed that can quickly align and assemble large quantities of one type or multiple types of nanowires through parallel processes, in-cluding flow-assisted alignment, Langmuir-Blodgett assembly, bubble-blown technique, electric/magnetic- field directed assembly, contact/roll printing, knocking-down, etc.. With these assembling techniques, applications of nanowire/nanotube based devices such as flexible electronics and sensors have been demonstrated. This paper delivers an overall review of directed nanowire/nanotube assembling approaches and analyzes advantages and limitations of each method. The future research directions have also been discussed.

  19. Hollow dimension of modules

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    In this paper, we are interested in the following general question: Given a module Mwhich has finite hollow dimension and which has a finite collection of submodules Ki (1≤i≤n) such that M=K1+... +Kn, can we find an expression for the hollow dimension of Min terms of hollow dimensions of modules built up in some way from K1 Kn? We prove the following theorem:Let Mbe an amply supplemented module having finite hollow dimension and let Ki (1≤i≤n) be a finite collection of submodules of Msuch that M=K1+...+Kn. Then the hollow dimension h(M) of Mis the sum of the hollow dimensions of Ki (1≤i≤n) ifand only if Ki is a supplement of K1+...+Ki-1+Ki+1+...+Kn in Mfor each 1≤i≤n.

  20. User Experience Dimensions

    DEFF Research Database (Denmark)

    Lykke, Marianne; Jantzen, Christian

    2016-01-01

    The present study develops a set of 10 dimensions based on a systematic understanding of the concept of experience as a holistic psychological. Seven of these are derived from a psychological conception of what experiencing and experiences are. Three supplementary dimensions spring from the...... observation that experiences apparently have become especially valuable phenomena in Western societies. The 10 dimensions are tried out in a field study at the Center for Art and Media (ZKM) in Germany with the purpose to study their applicability in the evaluation of interactive sound archives. 29 walk......-alongs were carried out with 58 museums visitors. Our analysis showed that it was possible to identify the 10 experience dimensions in the study material. Some dimensions were expressed more frequently than others. The distribution of expressed dimensions and the content of the user comments provided a clear...

  1. Nanotubes and nanowires

    Indian Academy of Sciences (India)

    C N R Rao; A Govindaraj

    2001-10-01

    Synthesis and characterization of nanotubes and nanowires constitute an important part of nanoscience since these materials are essential bui lding units for several devices. We have prepared aligned carbon nanotube bundles and Y-junction nanotubes by the pyrolysis of appropriate organic precursors. The aligned bundles are useful for field emission display while the Y-junction nanotubes are likely to be useful as nanochips since they exhibit diode properties at the junction. By making use of carbon nanotubes, nanowires of metals, metal oxides and GaN have be en obt a ined. Both the oxide and GaN nanowires are single crystalline. Gold nanowires exhibit plasmon bands varying markedly with the aspect ratio. GaN nanowires show excellent photoluminescence characteristics. It has been possible to synthesise nanotubes and nanowires of metal chalcogenides by employing different strategies.

  2. Dimension of linear models

    DEFF Research Database (Denmark)

    Høskuldsson, Agnar

    1996-01-01

    Determination of the proper dimension of a given linear model is one of the most important tasks in the applied modeling work. We consider here eight criteria that can be used to determine the dimension of the model, or equivalently, the number of components to use in the model. Four of these...... the basic problems in determining the dimension of linear models. Then each of the eight measures are treated. The results are illustrated by examples....

  3. Dimension of Physical Space

    Directory of Open Access Journals (Sweden)

    Quznetsov G.

    2014-10-01

    Full Text Available Each vector of state has its own corresponing element of the CayleyDickson algebra. Properties of a state vector require that this algebra was a normalized division algebra. By the Hurwitz and Frobenius theorems maximal dimension of s uch algebra is 8. Con- sequently, a dimension of corresponding complex state vectors is 4, and a dimension of the Clifford set elements is 4 × 4. Such set contains 5 matrices — among them — 3-diagonal. Hence, a dimension of the dot events space is equal to 3 + 1.

  4. Carbon nanotubes decorating methods

    OpenAIRE

    A.D. Dobrzańska-Danikiewicz; D. Łukowiec; D. Cichock; W. Wolany

    2013-01-01

    Purpose: The work is to present and characterise various methods of depositing carbon nanotubes with nanoparticles of precious metals, and also to present the results of own works concerning carbon nanotubes coated with platinum nanoparticles.Design/methodology/approach: Electron transmission and scanning microscopy has been used for imaging the structure and morphology of the nanocomposites obtained and the distribution of nanoparticles on the surface of carbon nanotubes.Findings: The studie...

  5. Functionalization of Carbon Nanotubes

    OpenAIRE

    Abraham, Jürgen

    2005-01-01

    Carbon nanotubes have an enormous potential due to their outstanding electronic, optical, and mechanical properties. However, any technological application is still hindered due to problems regarding the processibility of the pristine carbon nanotubes. In the past few years, it has been shown that the chemical modification of the carbon nanotubes is an inevitable step prior to their application. The first part of this work (chapter 3.1) was focused on the purification of pristine laser ablati...

  6. Synthesis of Carbon Nanotube (CNT Composite Membranes

    Directory of Open Access Journals (Sweden)

    Dusan Losic

    2010-12-01

    Full Text Available Carbon nanotubes are attractive approach for designing of new membranes for advanced molecular separation because of their unique transport properties and ability to mimic biological protein channels. In this work the synthetic approach for fabrication of carbon nanotubes (CNTs composite membranes is presented. The method is based on growth of multi walled carbon nanotubes (MWCNT using chemical vapour deposition (CVD on the template of nanoporous alumina (PA membranes. The influence of experimental conditions including carbon precursor, temperature, deposition time, and PA template on CNT growth process and quality of fabricated membranes was investigated. The synthesis of CNT/PA composites with controllable nanotube dimensions such as diameters (30–150 nm, and thickness (5–100 µm, was demonstrated. The chemical composition and morphological characteristics of fabricated CNT/PA composite membranes were investigated by various characterisation techniques including scanning electron microscopy (SEM, energy-dispersive x-ray spectroscopy (EDXS, high resolution transmission electron microscopy (HRTEM and x-ray diffraction (XRD. Transport properties of prepared membranes were explored by diffusion of dye (Rose Bengal used as model of hydrophilic transport molecule.

  7. THE DISTRIBUTIONAL DIMENSION OF FRACTALS

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In the book [1] H.Triebel introduces the distributional dimension of fractals in and distributional dimension, respectively. Thus we might say that the distributional dimension is an analytical definition for Hausdorff dimension. Therefore we can study Hausdorff dimension through the distributional dimension analytically.By discussing the distributional dimension, this paper intends to set up a criterion for estimating the upper and lower bounds of Hausdorff dimension analytically. Examples illustrating the criterion are included in the end.

  8. Quantum Physics in One Dimension

    International Nuclear Information System (INIS)

    To a casual ostrich the world of quantum physics in one dimension may sound a little one-dimensional, suitable perhaps for those with an unhealthy obsession for the esoteric. Nothing of course could be further from the truth. The field is remarkably rich and broad, and for more than fifty years has thrown up innumerable challenges. Theorists, realising that the role of interactions in 1D is special and that well known paradigms of higher dimensions (Fermi liquid theory for example) no longer apply, took up the challenge of developing new concepts and techniques to understand the undoubted peculiarities of one-dimensional systems. And experimentalists have succeeded in turning pipe dreams into reality, producing an impressive and ever increasing array of experimental realizations of 1D systems, from the molecular to the mesoscopic - spin and ladder compounds, organic superconductors, carbon nanotubes, quantum wires, Josephson junction arrays and so on. Many books on the theory of one-dimensional systems are however written by experts for experts, and tend as such to leave the non-specialist a touch bewildered. This is understandable on both fronts, for the underlying theoretical techniques are unquestionably sophisticated and not usually part of standard courses in many-body theory. A brave author it is then who aims to produce a well rounded, if necessarily partial, overview of quantum physics in one dimension, accessible to a beginner yet taking them to the edge of current research, and providing en route a thorough grounding in the fundamental ideas, basic methods and essential phenomenology of the field. It is of course the brave who succeed in this world, and Thierry Giamarchi does just that with this excellent book, written by an expert for the uninitiated. Aimed in particular at graduate students in theoretical condensed matter physics, and assuming little theoretical background on the part of the reader (well just a little), Giamarchi writes in a

  9. Adsorptive fractionation of dissolved organic matter (DOM) by carbon nanotubes

    International Nuclear Information System (INIS)

    Dissolved organic matter (DOM) and carbon nanotubes are introduced into aquatic environments. Thus, it is important to elucidate whether their interaction affects DOM amount and composition. In this study, the composition of DOM, before and after interactions with single-walled carbon nanotubes (SWCNTs), was measured and the adsorption affinity of the individual structural fractions of DOM to SWCNTs was investigated. Adsorption of DOM to SWCNTs was dominated by the hydrophobic acid fraction, resulting in relative enhancement of the hydrophilic character of non-adsorbed DOM. The preferential adsorption of the HoA fraction was concentration-dependent, increasing with increasing concentration. Adsorption affinities of bulk DOM calculated as the normalized sum of affinities of the individual structural fractions were similar to the measured affinities, suggesting that the structural fractions of DOM act as independent adsorbates. The altered DOM composition may affect the nature and reactivity of DOM in aquatic environments polluted with carbon nanotubes. - Highlights: • Interaction with carbon nanotubes alters DOM amount and composition. • Hydrophobic acid fraction governs DOM adsorption to carbon nanotubes. • Adsorbed DOM composition is concentration-dependent. • Adsorption affinity and capacity are dependent on hydrophobicity of DOM. - Dissolved organic matter (DOM)–single walled carbon nanotubes interactions result in the relative enrichment of the hydrophilic character of the DOM

  10. Dimensions of Creative Evaluation

    DEFF Research Database (Denmark)

    Christensen, Bo; Ball, Linden J.

    2016-01-01

    We examined evaluative reasoning taking place during expert ‘design critiques’. We focused on key dimensions of creative evaluation (originality, functionality and aesthetics) and ways in which these dimensions impact reasoning strategies and suggestions offered by experts for how the student could...

  11. Entropies and fractal dimensions

    OpenAIRE

    Sparavigna, Amelia Carolina

    2016-01-01

    In this paper, we discuss the relation between entropy and the fractal dimension, a statistical index which is measuring the complexity of a given pattern, embedded in given spatial dimensions. We will consider the Shannon entropy and the generalized entropies of Tsallis and Kaniadakis

  12. Comparative study on different carbon nanotube materials in terms of transparent conductive coatings.

    Science.gov (United States)

    Li, Zhongrui; Kandel, Hom R; Dervishi, Enkeleda; Saini, Viney; Xu, Yang; Biris, Alexandru R; Lupu, Dan; Salamo, Gregory J; Biris, Alexandru S

    2008-03-18

    We compared conductive transparent carbon nanotube coatings on glass substrates made of differently produced single-wall (SWNT), double-wall, and multiwall carbon nanotubes. The airbrushing approach and the vacuum filtration method were utilized for the fabrication of carbon nanotube films. The optoelectronic performance of the carbon nanotube film was found to strongly depend on many effects including the ratio of metallic-to-semiconducting tubes, dispersion, length, diameter, chirality, wall number, structural defects, and the properties of substrates. The electronic transportability and optical properties of the SWNT network can be significantly altered by chemical doping with thionyl chloride. Hall effect measurements revealed that all of these thin carbon nanotube films are of p-type probably due to the acid reflux-based purification and atmospheric impurities. The competition between variable-range hoping and fluctuation-assisted tunneling in the functionized carbon nanotube system could lead to a crossover behavior in the temperature dependence of the network resistance. PMID:18251555

  13. Carbon nanotube macroelectronics

    Science.gov (United States)

    Zhang, Jialu

    In this dissertation, I discuss the application of carbon nanotubes in macroelectronis. Due to the extraordinary electrical properties such as high intrinsic carrier mobility and current-carrying capacity, single wall carbon nanotubes are very desirable for thin-film transistor (TFT) applications such as flat panel display, transparent electronics, as well as flexible and stretchable electronics. Compared with other popular channel material for TFTs, namely amorphous silicon, polycrystalline silicon and organic materials, nanotube thin-films have the advantages of low-temperature processing compatibility, transparency, and flexibility, as well as high device performance. In order to demonstrate scalable, practical carbon nanotube macroelectroncis, I have developed a platform to fabricate high-density, uniform separated nanotube based thin-film transistors. In addition, many other essential analysis as well as technology components, such as nanotube film density control, purity and diameter dependent semiconducting nanotube electrical performance study, air-stable n-type transistor fabrication, and CMOS integration platform have also been demonstrated. On the basis of the above achievement, I have further demonstrated various kinds of applications including AMOLED display electronics, PMOS and CMOS logic circuits, flexible and transparent electronics. The dissertation is structured as follows. First, chapter 1 gives a brief introduction to the electronic properties of carbon nanotubes, which serves as the background knowledge for the following chapters. In chapter 2, I will present our approach of fabricating wafer-scale uniform semiconducting carbon nanotube thin-film transistors and demonstrate their application in display electronics and logic circuits. Following that, more detailed information about carbon nanotube thin-film transistor based active matrix organic light-emitting diode (AMOLED) displays is discussed in chapter 3. And in chapter 4, a technology to

  14. Carbon nanotube materials for hydrogen storage

    Energy Technology Data Exchange (ETDEWEB)

    Dillon, A.C.; Jones, K.M.; Heben, M.J. [National Renewable Energy Lab., Golden, CO (United States)

    1996-10-01

    Hydrogen burns pollution-free and may be produced from renewable energy resources. It is therefore an ideal candidate to replace fossil fuels as an energy carrier. However, the lack of a convenient and cost-effective hydrogen storage system greatly impedes the wide-scale use of hydrogen in both domestic and international markets. Although several hydrogen storage options exist, no approach satisfies all of the efficiency, size, weight, cost and safety requirements for transportation or utility use. A material consisting exclusively of micropores with molecular dimensions could simultaneously meet all of the requirements for transportation use if the interaction energy for hydrogen was sufficiently strong to cause hydrogen adsorption at ambient temperatures. Small diameter ({approx}1 mm) carbon single-wall nanotubes (SWNTs) are elongated micropores of molecular dimensions, and materials composed predominantly of SWNTs may prove to be the ideal adsorbent for ambient temperature storage of hydrogen. Last year the authors reported that hydrogen could be adsorbed on arc-generated soots containing 12{Angstrom} diameter nanotubes at temperatures in excess of 285K. In this past year they have learned that such adsorption does not occur on activated carbon materials, and that the cobalt nanoparticles present in their arc-generated soots are not responsible for the hydrogen which is stable at 285 K. These results indicate that enhanced adsorption forces within the internal cavities of the SWNTs are active in stabilizing hydrogen at elevated temperatures. This enhanced stability could lead to effective hydrogen storage under ambient temperature conditions. In the past year the authors have also demonstrated that single-wall carbon nanotubes in arc-generated soots may be selectively opened by oxidation in H{sub 2}O resulting in improved hydrogen adsorption, and they have estimated experimentally that the amount of hydrogen stored is {approximately}10% of the nanotube weight.

  15. Molybdenum nitride nanotubes

    International Nuclear Information System (INIS)

    Molybdenum nitride nanotubes were prepared by depositing nitride film on anodized aluminum oxide (AAO) template by atomic layer deposition and then etching away the template with sodium hydroxide solution. The effect of deposition parameters on film growth and the properties of the nanotubes was investigated. The maximum depth of intrusion of the molybdenum nitride film into the AAO pores was found to be 20 μm, achieved with 7-second precursor pulses. Precursor diffusion into the AAO pores dominated over the intrusion. Three different architectures of molybdenum nitride nanotubes were isolated. Separated nanotubes were found when the template was etched in an ultrasonic bath, while bundling dominated when template etching was conducted without ultrasound. When the nitride-coated AAO template was mounted onto a steel plate before etching the nanotubes remained on the surface with the tips strongly intertwined

  16. Organic modification of carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The organic modification of carbon nanotubes is a novel research field being developed recently. In this article, the history and newest progress of organic modification of carbon nanotubes are reviewed from two aspects:organic covalent modification and organic noncovalent modification of carbon nanotubes. The preparation and properties of organic modified carbon nanotubes are discussed in detail. In addition, the prospective development of organic modification of carbon nanotubes is suggested.

  17. Carbon nanotubes: synthesis and functionalization

    OpenAIRE

    Andrews, Robert

    2007-01-01

    This thesis focuses on two of the major challenges of carbon nanotube (CNT) research: understanding the growth mechanism of nanotubes by chemical vapour deposition (CVD) and the positioning of nanotubes on surfaces. The mechanism of growth of single–walled nanotubes (SWNTs) has been studied in two ways. Firstly, a novel iron nanoparticle catalyst for the production of single–walled nanotubes was developed. CVD conditions were established that produced high quality tubes. These optimised C...

  18. Vacuum template synthesis of multifunctional nanotubes with tailored nanostructured walls

    Science.gov (United States)

    Filippin, A. Nicolas; Macias-Montero, Manuel; Saghi, Zineb; Idígoras, Jesús; Burdet, Pierre; Barranco, Angel; Midgley, Paul; Anta, Juan A.; Borras, Ana

    2016-02-01

    A three-step vacuum procedure for the fabrication of vertical TiO2 and ZnO nanotubes with three dimensional walls is presented. The method combines physical vapor deposition of small-molecules, plasma enhanced chemical vapor deposition of inorganic functional thin films and layers and a post-annealing process in vacuum in order to remove the organic template. As a result, an ample variety of inorganic nanotubes are made with tunable length, hole dimensions and shapes and tailored wall composition, microstructure, porosity and structure. The fabrication of multishell nanotubes combining different semiconducting oxides and metal nanoparticles is as well explored. This method provides a feasible and reproducible route for the fabrication of high density arrays of vertically alligned nanotubes on processable substrates. The emptying mechanism and microstructure of the nanotubes have been elucidated through SEM, STEM, HAADF-STEM tomography and energy dispersive X-ray spectroscopy. In this article, as a proof of concept, it is presented the straightforward integration of ZnO nanotubes as photoanode in a photovoltaic cell and as a photonic oxygen gas sensor.

  19. Gorenstein homological dimensions

    DEFF Research Database (Denmark)

    Holm, Henrik Granau

    2004-01-01

    In basic homological algebra, the projective, injective and 2at dimensions of modules play an important and fundamental role. In this paper, the closely related Gorenstein projective, Gorenstein injective and Gorenstein 2at dimensions are studied. There is a variety of nice results about Gorenstein...... dimensions over special commutative noetherian rings; very often local Cohen–Macaulay rings with a dualizing module. These results are done by Avramov, Christensen, Enochs, Foxby, Jenda, Martsinkovsky and Xu among others. The aim of this paper is to generalize these results, and to give homological...

  20. DIFFERENT DIMENSIONS OF TEAMS

    Directory of Open Access Journals (Sweden)

    Goparaju Purna SUDHAKAR

    2014-01-01

    Full Text Available Popularity ofteams is growing in 21st Century. Organizations are getting theirwork done through different types of teams. Teams have proved that thecollective performance is more than the sum of the individual performances.Thus, the teams have got different dimensions such as quantitative dimensionsand qualitative dimensions. The Quantitative dimensions of teams such as teamperformance, team productivity, team innovation, team effectiveness, teamefficiency, team decision making and team conflicts and Qualitative dimensionsof teams such as team communication, team coordination, team cooperation, teamcohesion, team climate, team creativity, team leadership and team conflictshave been discussed in this article.

  1. The fourth dimension

    CERN Document Server

    Rucker, Rudy

    2014-01-01

    ""This is an invigorating book, a short but spirited slalom for the mind."" - Timothy Ferris, The New York Times Book Review ""Highly readable. One is reminded of the breadth and depth of Hofstadter's Gödel, Escher, Bach."" - Science""Anyone with even a minimal interest in mathematics and fantasy will find The Fourth Dimension informative and mind-dazzling... [Rucker] plunges into spaces above three with a zest and energy that is breathtaking."" - Martin Gardner ""Those who think the fourth dimension is nothing but time should be encouraged to read The Fourth Dimension, along with anyone else

  2. Carbon nanotube materials for hydrogen storage

    Energy Technology Data Exchange (ETDEWEB)

    Dillon, A.C.; Parilla, P.A.; Jones, K.M.; Riker, G.; Heben, M.J. [National Renewable Energy Lab., Golden, CO (United States)

    1998-08-01

    Carbon single-wall nanotubes (SWNTs) are essentially elongated pores of molecular dimensions and are capable of adsorbing hydrogen at relatively high temperatures and low pressures. This behavior is unique to these materials and indicates that SWNTs are the ideal building block for constructing safe, efficient, and high energy density adsorbents for hydrogen storage applications. In past work the authors developed methods for preparing and opening SWNTs, discovered the unique adsorption properties of these new materials, confirmed that hydrogen is stabilized by physical rather than chemical interactions, measured the strength of interaction to be {approximately} 5 times higher than for adsorption on planar graphite, and performed infrared absorption spectroscopy to determine the chemical nature of the surface terminations before, during, and after oxidation. This year the authors have made significant advances in synthesis and characterization of SWNT materials so that they can now prepare gram quantities of high-purity SWNT samples and measure and control the diameter distribution of the tubes by varying key parameters during synthesis. They have also developed methods which purify nanotubes and cut nanotubes into shorter segments. These capabilities provide a means for opening the tubes which were unreactive to the oxidation methods that successfully opened tubes, and offer a path towards organizing nanotube segments to enable high volumetric hydrogen storage densities. They also performed temperature programmed desorption spectroscopy on high purity carbon nanotube material obtained from collaborator Prof. Patrick Bernier and finished construction of a high precision Seivert`s apparatus which will allow the hydrogen pressure-temperature-composition phase diagrams to be evaluated for SWNT materials.

  3. Vacuum template synthesis of multifunctional nanotubes with tailored nanostructured walls

    OpenAIRE

    A. Nicolas Filippin; Manuel Macias-Montero; Zineb Saghi; Jesús Idígoras; Pierre Burdet; Angel Barranco; Paul Midgley; Juan A. Anta; Ana Borras

    2016-01-01

    A three-step vacuum procedure for the fabrication of vertical TiO2 and ZnO nanotubes with three dimensional walls is presented. The method combines physical vapor deposition of small-molecules, plasma enhanced chemical vapor deposition of inorganic functional thin films and layers and a post-annealing process in vacuum in order to remove the organic template. As a result, an ample variety of inorganic nanotubes are made with tunable length, hole dimensions and shapes and tailored wall composi...

  4. Vanadium pentoxide nanotubes by eelectrospinning

    Science.gov (United States)

    Lala, Neeta L.; Jose, R.; Yusoff, M. M.

    2012-11-01

    Nanofibers of vanadium pentoxide (V2O5) were synthesized by electrospinning a polymeric solution containing vanadium ion and with subsequent sintering. Conventionally, electrospun TNFs were produced by using a co-axial spinneret; however, TNFs in the present study were obtained by manipulating the concentration ratio of the precursor solution, distance, humidity and flow rate during electrospinning using a single spinneret and sintering with time and temperature change. On the basis of this hypothesis, nanofibers could be altered from elongated 1-D nanofibers to nanowires, nanotubes, spheres and flakes respectively. The surface morphology, structure, roughness and the crystal structure were analyzed using Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), and X-ray diffraction (XRD). The current work has demonstrated a case study for energy storage where V2O5 nanotubes when tested shows the capacitance of 190 Fg-1 in 2M KCl electrolyte indicating an example for the energy storage which may be applicable for other electrochemical devices such as Li-ion batteries, fuel cells, hydrogen storage etc.

  5. Cultural dimensions and innovation

    OpenAIRE

    Anna Strychalska-Rudzewicz

    2015-01-01

    This paper examines the effect of culture’s dimensions on national innovation index. The results of Pearson correlation coefficient between culture dimensions and the Global Innovation Index (GII) are very similar to the results obtained in the case of Summary Innovation Index (SII) in European countries. The strong negative correlation was observed in the case of power distance and uncertainty avoidance whereas individualism has a positive effect on innovation index. The results suggest that...

  6. EF & den sociale dimension

    DEFF Research Database (Denmark)

    Due, Jesper Jørgen; Madsen, Jørgen Steen; Jensen, Carsten Strøby

    En analyse af EU's institutioner og udviklingen af den sociale dimension i forbindelse med etbaleringen af det indre marked med særlig henblik på effekterne på det danske aftalesystem.......En analyse af EU's institutioner og udviklingen af den sociale dimension i forbindelse med etbaleringen af det indre marked med særlig henblik på effekterne på det danske aftalesystem....

  7. Echoing the extra dimension

    CERN Document Server

    Barvinsky, A O; Solodukhin, Sergey N.

    2003-01-01

    We study the propagating gravitational waves as a tool to probe the extra dimensions. In the set-up with one compact extra dimension and non-gravitational physics resigning on the 4-dimensional subspace (brane) of 5-dimensional spacetime we find the Green's function describing the propagation of 5-dimensional signal along the brane. The Green's function has a form of the sum of contributions from large number of images due to the compactness of the fifth dimension. Additionally, a peculiar feature of the causal wave propagation in five dimensions (making a five-dimensional spacetime very much different from the familiar four-dimensional case) is that the entire region inside the past light-cone contributes to the signal at the observation point. The 4-dimensional propagation law is nevertheless reproduced at large (compared to the size of extra dimension) intervals from the source as a superposition of signals from large number of images. The fifth dimension however shows up in the form of corrections to the ...

  8. Manipulation of individual double-walled carbon nanotubes packed in a casing shell

    International Nuclear Information System (INIS)

    Controlled placement of carbon nanotubes is important for carbon-based nanodevice assembly. However, it is difficult to manipulate individual nanotubes because of their extremely small dimensions. Ultra-fine tubes are often in the form of bundles and are hard to efficiently move on a surface due to the strong adhesion among themselves and between the tubes and the substrate. This paper presents a novel manipulation approach of individual double-walled carbon nanotubes encased in a thick amorphous carbon shell. With an atomic force microscope, we are able to freely displace the nanotubes within a casing shell, and unpack it from the shell on a silicon surface. The theoretical analysis demonstrates that the unpacking process is determined by the difference of the static friction between the shell and the substrate and the resistance force between the shell and the embedded nanotube.

  9. A variational principle for the Hausdorff dimension of fractal sets

    DEFF Research Database (Denmark)

    Olsen, Lars; Cutler, Colleen D.

    1994-01-01

    Matematik, fraktal (fractal), Hausdorff dimension, Renyi dimension, pakke dimension (packing dimension)......Matematik, fraktal (fractal), Hausdorff dimension, Renyi dimension, pakke dimension (packing dimension)...

  10. Structure et croissance de nanotubes de Ge-imogolite simple et double-paroi

    OpenAIRE

    Maillet, Perrine

    2010-01-01

    Imogolites are natural materials discovered during the sixties in japanese volcanic soils. Their structure is analogue to carbone nanotubes. Imogolite synthesis, described since 1977, gives nanotubes whose dimensions are well defined and monodisperse. Recently, it has been shown that it is possible to synthesize analogues containing germanium in concentration conditions that are much higher than classical silicium imogolites. That's why we have chosen this material to study the preparation of...

  11. EMI shielding effectiveness of silver nanoparticle-decorated multi-walled carbon nanotube sheets

    OpenAIRE

    Zhao, Wenming; Mei LI; Zhang, Zhongyi; Peng, Hua-Xin

    2010-01-01

    With the aim of exploring the excellent properties of multi-walled carbon nanotubes (MWNTs) in modern composite technologies, various macrostructures of nanotubes have been developed from one to three dimensions, e.g. fibers, networks, sheets (buckypapers) and pellets. The MWNT sheets discussed here were fabricated by a vacuum filtration procedure, a process that has potential for large-scale manufacturing. In order to further enhance the transport properties of MWNT sheets by reducing the co...

  12. Carbon nanotube solar cells.

    Directory of Open Access Journals (Sweden)

    Colin Klinger

    Full Text Available We present proof-of-concept all-carbon solar cells. They are made of a photoactive side of predominantly semiconducting nanotubes for photoconversion and a counter electrode made of a natural mixture of carbon nanotubes or graphite, connected by a liquid electrolyte through a redox reaction. The cells do not require rare source materials such as In or Pt, nor high-grade semiconductor processing equipment, do not rely on dye for photoconversion and therefore do not bleach, and are easy to fabricate using a spray-paint technique. We observe that cells with a lower concentration of carbon nanotubes on the active semiconducting electrode perform better than cells with a higher concentration of nanotubes. This effect is contrary to the expectation that a larger number of nanotubes would lead to more photoconversion and therefore more power generation. We attribute this to the presence of metallic nanotubes that provide a short for photo-excited electrons, bypassing the load. We demonstrate optimization strategies that improve cell efficiency by orders of magnitude. Once it is possible to make semiconducting-only carbon nanotube films, that may provide the greatest efficiency improvement.

  13. Novel Silicon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Novel silicon nanotubes with inner-diameter of 60-80 nm was prepared using hydrogen-added dechlorination of SiCl4 followed by chemical vapor deposition (CVD) on a NixMgyO catalyst. The TEM observation showed that the suitable reaction temperature is 973 K for the formation of silicon nanotubes. Most of silicon nanotubes have one open end and some have two closed ends. The shape ofnanoscale silicon, however, is a micro-crystal type at 873 K, a rod or needle type at 993 K and an onion-type at 1023 K, respectively.

  14. Nanotube resonator devices

    Energy Technology Data Exchange (ETDEWEB)

    Jensen, Kenneth J; Zettl, Alexander K; Weldon, Jeffrey A

    2014-05-06

    A fully-functional radio receiver fabricated from a single nanotube is being disclosed. Simultaneously, a single nanotube can perform the functions of all major components of a radio: antenna, tunable band-pass filter, amplifier, and demodulator. A DC voltage source, as supplied by a battery, can power the radio. Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation techniques, successful music and voice reception has been demonstrated. Also disclosed are a radio transmitter and a mass sensor using a nanotube resonator device.

  15. Nanotube composite carbon fibers

    Science.gov (United States)

    Andrews, R.; Jacques, D.; Rao, A. M.; Rantell, T.; Derbyshire, F.; Chen, Y.; Chen, J.; Haddon, R. C.

    1999-08-01

    Single walled carbon nanotubes (SWNTs) were dispersed in isotropic petroleum pitch matrices to form nanotube composite carbon fibers with enhanced mechanical and electrical properties. We find that the tensile strength, modulus, and electrical conductivity of a pitch composite fiber with 5 wt % loading of purified SWNTs are enhanced by ˜90%, ˜150%, and 340% respectively, as compared to the corresponding values in unmodified isotropic pitch fibers. These results serve to highlight the potential that exits for developing a spectrum of material properties through the selection of the matrix, nanotube dispersion, alignment, and interfacial bonding.

  16. Electrochemical synthesis and crystal structure of ordered arrays of Со – nanotubes

    Directory of Open Access Journals (Sweden)

    Artem Kozlovskiy

    2015-09-01

    Full Text Available In this paper, using the method of electrochemical template synthesis, ordered arrays of metallic nanostructures on the basis of cobalt with various dimensions (180-380 nm were obtained. The diameter of Co-nanotubes was controlled by original polymer matrix, which provided to prepare arrays consisting of individually standing cobalt nanotubes. The crystal structure of the synthesized samples was studied by X-ray diffraction to determine cell parameters and crystallite size. Decrease of the conductive properties of Co - nanotubes can be explained by inhomogeneity of the crystallites formed during synthesis, because the growth rate of nanostructures directly affects the size of the crystallites.

  17. Neurocognitve Dimensions of Self-consciousness

    Directory of Open Access Journals (Sweden)

    Dario Grossi

    2016-04-01

    Full Text Available Self-consciousness is considered in a framework comprising four dimensions which are theoretically defined and supported by clinical neuropsychological evidence. Self-monitoring is defined as the ability to reflect on one’s own behaviour, with supporting evidence for deficits in this capacity noted in anosognosia syndrome. Self-feeling is defined as the capacity to feel all sensations related to one’s own body (interoception and exteroception, with supporting evidence from deficiencies occurring in alexithymia, psychosomatic states and Cotard’s delusion. Identity refers to the capacity to recognize an object as identical to oneself, based on autobiographic memory; pathological conditions related to this dimension include delusions of identity and the Zelig syndrome. Ownership is the capacity to perceive the status of ones’ own body, and is clinically altered in somatoparaphrenia. All four dimensions are related to specific brain networks.

  18. Low Genetic Quality Alters Key Dimensions of the Mutational Spectrum.

    Directory of Open Access Journals (Sweden)

    Nathaniel P Sharp

    2016-03-01

    Full Text Available Mutations affect individual health, population persistence, adaptation, diversification, and genome evolution. There is evidence that the mutation rate varies among genotypes, but the causes of this variation are poorly understood. Here, we link differences in genetic quality with variation in spontaneous mutation in a Drosophila mutation accumulation experiment. We find that chromosomes maintained in low-quality genetic backgrounds experience a higher rate of indel mutation and a lower rate of gene conversion in a manner consistent with condition-based differences in the mechanisms used to repair DNA double strand breaks. These aspects of the mutational spectrum were also associated with body mass, suggesting that the effect of genetic quality on DNA repair was mediated by overall condition, and providing a mechanistic explanation for the differences in mutational fitness decline among these genotypes. The rate and spectrum of substitutions was unaffected by genetic quality, but we find variation in the probability of substitutions and indels with respect to several aspects of local sequence context, particularly GC content, with implications for models of molecular evolution and genome scans for signs of selection. Our finding that the chances of mutation depend on genetic context and overall condition has important implications for how sequences evolve, the risk of extinction, and human health.

  19. Low Genetic Quality Alters Key Dimensions of the Mutational Spectrum.

    Science.gov (United States)

    Sharp, Nathaniel P; Agrawal, Aneil F

    2016-03-01

    Mutations affect individual health, population persistence, adaptation, diversification, and genome evolution. There is evidence that the mutation rate varies among genotypes, but the causes of this variation are poorly understood. Here, we link differences in genetic quality with variation in spontaneous mutation in a Drosophila mutation accumulation experiment. We find that chromosomes maintained in low-quality genetic backgrounds experience a higher rate of indel mutation and a lower rate of gene conversion in a manner consistent with condition-based differences in the mechanisms used to repair DNA double strand breaks. These aspects of the mutational spectrum were also associated with body mass, suggesting that the effect of genetic quality on DNA repair was mediated by overall condition, and providing a mechanistic explanation for the differences in mutational fitness decline among these genotypes. The rate and spectrum of substitutions was unaffected by genetic quality, but we find variation in the probability of substitutions and indels with respect to several aspects of local sequence context, particularly GC content, with implications for models of molecular evolution and genome scans for signs of selection. Our finding that the chances of mutation depend on genetic context and overall condition has important implications for how sequences evolve, the risk of extinction, and human health. PMID:27015430

  20. FLUIDIZATION OF CARBON NANOTUBES

    Institute of Scientific and Technical Information of China (English)

    Fei Wei; Cang Huang; Yao Wang

    2005-01-01

    Carbon nanotubes (CNTs) can be fluidized in the form of fluidlike agglomerates made of many three-dimensional sub-agglomerates, having a multi-stage agglomerate (MSA) structure and containing large amounts of twisting CNTs of micrometer magnitude.

  1. Carbon nanotubes: Fibrillar pharmacology

    Science.gov (United States)

    Kostarelos, Kostas

    2010-10-01

    The mechanisms by which chemically functionalized carbon nanotubes flow in blood and are excreted through the kidneys illustrate the unconventional behaviour of these fibrillar nanostructures, and the opportunities they offer as components for the design of advanced delivery vehicles.

  2. Chalcogenide Cobalt telluride nanotubes

    Science.gov (United States)

    Dahal, Bishnu; Dulal, Rajendra; Pegg, Ian L.; Philip, John

    Cobalt telluride nanotubes are grown using wet chemical and hydrothermal syntheses. Wet chemical synthesized nanotubes display nearly 1: 1 Co to Te ratio. On the other hand, CoTe nanotubes synthesized using hydrothermal method show excess Co content leading to the compound Co58Te42. Both CoTe and Co58Te42 display magnetic properties, but with totally different characteristics. The Curie temperature of CoTe is higher than 400 K. However, the Tc of Co58Te42 is below 50 K. Transport properties of cobalt telluride (CoTe) nanotube devices show that they exhibit p-type semiconducting behavior. The magnetoresistance measured at 10 K show a magnetoresistance of 54%. . National Science Foundation under ECCS-0845501 and NSF-MRI, DMR-0922997.

  3. Cultural dimensions and innovation

    Directory of Open Access Journals (Sweden)

    Anna Strychalska-Rudzewicz

    2015-11-01

    Full Text Available This paper examines the effect of culture’s dimensions on national innovation index. The results of Pearson correlation coefficient between culture dimensions and the Global Innovation Index (GII are very similar to the results obtained in the case of Summary Innovation Index (SII in European countries. The strong negative correlation was observed in the case of power distance and uncertainty avoidance whereas individualism has a positive effect on innovation index. The results suggest that low power distance and uncertainty-accepting countries may be more innovative than high power distance and uncertainty-avoiding societies.

  4. Dimension decreasing of featurespace

    Czech Academy of Sciences Publication Activity Database

    Klimešová, Dana; Ocelíková, E.; Zolotová, I.

    Košice: TU Košice, 2008 - (Vokorokos,, L.), s. 49-53 ISBN 978-80-553-0066-5. [International Conference on Applied Electrical Engineering and Informatics 2008. Athens (GR), 08.09.2008-11.09.2008] Institutional research plan: CEZ:AV0Z10750506 Keywords : decision * feature space * dimension reduction * Karhunen - Loeve transformation * principal component method Subject RIV: BC - Control Systems Theory http://library.utia.cas.cz/separaty/2008/ZOI/klimesova-dimension decreasing of featurespace.pdf

  5. Fractal sets and dimensions

    OpenAIRE

    Leifsson, Patrik

    2006-01-01

    Fractal analysis is an important tool when we need to study geometrical objects less regular than ordinary ones, e.g. a set with a non-integer dimension value. It has developed intensively over the last 30 years which gives a hint to its young age as a branch within mathematics. In this thesis we take a look at some basic measure theory needed to introduce certain definitions of fractal dimensions, which can be used to measure a set's fractal degree. Comparisons of these definitions are done ...

  6. Inflation from extra dimensions

    CERN Document Server

    Levin, J

    1994-01-01

    A gravity-driven inflation is shown to arise from a simple higher dimensional universe. In vacuum, the shear of n>1 contracting dimensions is able to inflate the remaining three spatial dimensions. Said another way, the expansion of the 3-volume is accelerated by the contraction of the n-volume. Upon dimensional reduction, the theory is equivalent to a four dimensional cosmology with a dynamical Planck mass. A connection can therefore be made to recent examples of inflation powered by a dilaton kinetic energy. Unfortunately, the graceful exit problem encountered in dilaton cosmologies will haunt this cosmology as well.

  7. Selective Attention to Perceptual Dimensions and Switching between Dimensions

    Science.gov (United States)

    Meiran, Nachshon; Dimov, Eduard; Ganel, Tzvi

    2013-01-01

    In the present experiments, the question being addressed was whether switching attention between perceptual dimensions and selective attention to dimensions are processes that compete over a common resource? Attention to perceptual dimensions is usually studied by requiring participants to ignore a never-relevant dimension. Selection failure…

  8. Nanotubes for Battery Applications

    OpenAIRE

    Nordlinder, Sara

    2005-01-01

    Nanomaterials have attracted great interest in recent years, and are now also being considered for battery applications. Reducing the particle size of some electrode materials can increase battery performance considerably, especially with regard to capacity, power and rate capability. This thesis presents a study focused on the performance of such a material, vanadium oxide nanotubes, as cathode material for rechargeable lithium batteries. These nanotubes were synthesized by a sol-gel process...

  9. Titanium dioxide nanotube films

    Energy Technology Data Exchange (ETDEWEB)

    Roman, Ioan, E-mail: roman@metav-cd.ro [S.C. METAV-Research and Development S.R.L., Bucharest, 31C. A. Rosetti, 020011 (Romania); Trusca, Roxana Doina; Soare, Maria-Laura [S.C. METAV-Research and Development S.R.L., Bucharest, 31C. A. Rosetti, 020011 (Romania); Fratila, Corneliu [Research and Development National Institute for Nonferrous and Rare Metals, Pantelimon, 102 Biruintei, 077145 (Romania); Krasicka-Cydzik, Elzbieta [University of Zielona Gora, Department of Biomedical Engineering Division, 9 Licealna, 65-417 (Poland); Stan, Miruna-Silvia; Dinischiotu, Anca [University of Bucharest, Department of Biochemistry and Molecular Biology, 36-46 Mihail Kogalniceanu, 050107 (Romania)

    2014-04-01

    Titania nanotubes (TNTs) were prepared by anodization on different substrates (titanium, Ti6Al4V and Ti6Al7Nb alloys) in ethylene glycol and glycerol. The influence of the applied potential and processing time on the nanotube diameter and length is analyzed. The as-formed nanotube layers are amorphous but they become crystalline when subjected to subsequent thermal treatment in air at 550 °C; TNT layers grown on titanium and Ti6Al4V alloy substrates consist of anatase and rutile, while those grown on Ti6Al7Nb alloy consist only of anatase. The nanotube layers grown on Ti6Al7Nb alloy are less homogeneous, with supplementary islands of smaller diameter nanotubes, spread across the surface. Better adhesion and proliferation of osteoblasts was found for the nanotubes grown on all three substrates by comparison to an unprocessed titanium plate. The sensitivity towards bovine alkaline phosphatase was investigated mainly by electrochemical impedance spectroscopy in relation to the crystallinity, the diameter and the nature of the anodization electrolyte of the TNT/Ti samples. The measuring capacity of the annealed nanotubes of 50 nm diameter grown in glycerol was demonstrated and the corresponding calibration curve was built for the concentration range of 0.005–0.1 mg/mL. - Highlights: • Titania nanotubes (TNTs) on Ti, Ti6Al4V and Ti6Al7Nb substrates were prepared. • Quantitative dependences of anodization conditions on TNT features were established. • Morphology and electrochemical tests revealed inhomogeneity of TNT/Ti6Al7Nb films. • Particular characteristics of TNT films induce electrochemical sensitivity to ALP. • Annealed TNT/Ti impedimetric sensitivity towards ALP was demonstrated and quantified.

  10. Magic Gold Nanotubes

    OpenAIRE

    SENGER, R. Tuğrul; DAĞ, Sefa; ÇIRACI, Salim

    2005-01-01

    In recent ultra-high-vacuum transmission-electron-microscopy experiments evidence is found for the formation of suspended gold single-wall nanotubes (SWNTs) composed of five helical strands. Similar to carbon nanotubes, the (n,m) notation defines the structure of the gold SWNTs. Experimentally, only the (5,3) tube has been observed to form among several other possible alternatives. Using first-principles calculations we demonstrate that gold atoms can form both freestanding and tip-...

  11. Conducting carbonized polyaniline nanotubes

    Science.gov (United States)

    Mentus, Slavko; Ćirić-Marjanović, Gordana; Trchová, Miroslava; Stejskal, Jaroslav

    2009-06-01

    Conducting nitrogen-containing carbon nanotubes were synthesized by the carbonization of self-assembled polyaniline nanotubes protonated with sulfuric acid. Carbonization was carried out in a nitrogen atmosphere at a heating rate of 10 °C min-1 up to a maximum temperature of 800 °C. The carbonized polyaniline nanotubes which have a typical outer diameter of 100-260 nm, with an inner diameter of 20-170 nm and a length extending from 0.5 to 0.8 µm, accompanied with very thin nanotubes with outer diameters of 8-14 nm, inner diameters 3.0-4.5 nm and length extending from 0.3 to 1.0 µm, were observed by scanning and transmission electron microscopies. Elemental analysis showed 9 wt% of nitrogen in the carbonized product. Conductivity of the nanotubular PANI precursor, amounting to 0.04 S cm-1, increased to 0.7 S cm-1 upon carbonization. Molecular structure of carbonized polyaniline nanotubes has been analyzed by FTIR and Raman spectroscopies, and their paramagnetic characteristics were compared with the starting PANI nanotubes by EPR spectroscopy.

  12. Conducting carbonized polyaniline nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Mentus, Slavko; Ciric-Marjanovic, Gordana [Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, 11158 Belgrade (Serbia); Trchova, Miroslava; Stejskal, Jaroslav [Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky Square 2, 162 06 Prague 6 (Czech Republic)], E-mail: gordana@ffh.bg.ac.rs

    2009-06-17

    Conducting nitrogen-containing carbon nanotubes were synthesized by the carbonization of self-assembled polyaniline nanotubes protonated with sulfuric acid. Carbonization was carried out in a nitrogen atmosphere at a heating rate of 10 deg. C min{sup -1} up to a maximum temperature of 800 deg. C. The carbonized polyaniline nanotubes which have a typical outer diameter of 100-260 nm, with an inner diameter of 20-170 nm and a length extending from 0.5 to 0.8 {mu}m, accompanied with very thin nanotubes with outer diameters of 8-14 nm, inner diameters 3.0-4.5 nm and length extending from 0.3 to 1.0 {mu}m, were observed by scanning and transmission electron microscopies. Elemental analysis showed 9 wt% of nitrogen in the carbonized product. Conductivity of the nanotubular PANI precursor, amounting to 0.04 S cm{sup -1}, increased to 0.7 S cm{sup -1} upon carbonization. Molecular structure of carbonized polyaniline nanotubes has been analyzed by FTIR and Raman spectroscopies, and their paramagnetic characteristics were compared with the starting PANI nanotubes by EPR spectroscopy.

  13. Transparent conducting oxide nanotubes

    Science.gov (United States)

    Alivov, Yahya; Singh, Vivek; Ding, Yuchen; Nagpal, Prashant

    2014-09-01

    Thin film or porous membranes made of hollow, transparent, conducting oxide (TCO) nanotubes, with high chemical stability, functionalized surfaces and large surface areas, can provide an excellent platform for a wide variety of nanostructured photovoltaic, photodetector, photoelectrochemical and photocatalytic devices. While large-bandgap oxide semiconductors offer transparency for incident light (below their nominal bandgap), their low carrier concentration and poor conductivity makes them unsuitable for charge conduction. Moreover, materials with high conductivity have nominally low bandgaps and hence poor light transmittance. Here, we demonstrate thin films and membranes made from TiO2 nanotubes heavily-doped with shallow Niobium (Nb) donors (up to 10%, without phase segregation), using a modified electrochemical anodization process, to fabricate transparent conducting hollow nanotubes. Temperature dependent current-voltage characteristics revealed that TiO2 TCO nanotubes, doped with 10% Nb, show metal-like behavior with resistivity decreasing from 6.5 × 10-4 Ωcm at T = 300 K (compared to 6.5 × 10-1 Ωcm for nominally undoped nanotubes) to 2.2 × 10-4 Ωcm at T = 20 K. Optical properties, studied by reflectance measurements, showed light transmittance up to 90%, within wavelength range 400 nm-1000 nm. Nb doping also improves the field emission properties of TCO nanotubes demonstrating an order of magnitude increase in field-emitter current, compared to undoped samples.

  14. Transparent conducting oxide nanotubes

    International Nuclear Information System (INIS)

    Thin film or porous membranes made of hollow, transparent, conducting oxide (TCO) nanotubes, with high chemical stability, functionalized surfaces and large surface areas, can provide an excellent platform for a wide variety of nanostructured photovoltaic, photodetector, photoelectrochemical and photocatalytic devices. While large-bandgap oxide semiconductors offer transparency for incident light (below their nominal bandgap), their low carrier concentration and poor conductivity makes them unsuitable for charge conduction. Moreover, materials with high conductivity have nominally low bandgaps and hence poor light transmittance. Here, we demonstrate thin films and membranes made from TiO2 nanotubes heavily-doped with shallow Niobium (Nb) donors (up to 10%, without phase segregation), using a modified electrochemical anodization process, to fabricate transparent conducting hollow nanotubes. Temperature dependent current–voltage characteristics revealed that TiO2 TCO nanotubes, doped with 10% Nb, show metal-like behavior with resistivity decreasing from 6.5 × 10−4 Ωcm at T = 300 K (compared to 6.5 × 10−1 Ωcm for nominally undoped nanotubes) to 2.2 × 10−4 Ωcm at T = 20 K. Optical properties, studied by reflectance measurements, showed light transmittance up to 90%, within wavelength range 400 nm–1000 nm. Nb doping also improves the field emission properties of TCO nanotubes demonstrating an order of magnitude increase in field-emitter current, compared to undoped samples. (paper)

  15. Quantum Physics in One Dimension

    Energy Technology Data Exchange (ETDEWEB)

    Logan, David [University of Oxford (United Kingdom)

    2004-05-14

    To a casual ostrich the world of quantum physics in one dimension may sound a little one-dimensional, suitable perhaps for those with an unhealthy obsession for the esoteric. Nothing of course could be further from the truth. The field is remarkably rich and broad, and for more than fifty years has thrown up innumerable challenges. Theorists, realising that the role of interactions in 1D is special and that well known paradigms of higher dimensions (Fermi liquid theory for example) no longer apply, took up the challenge of developing new concepts and techniques to understand the undoubted peculiarities of one-dimensional systems. And experimentalists have succeeded in turning pipe dreams into reality, producing an impressive and ever increasing array of experimental realizations of 1D systems, from the molecular to the mesoscopic - spin and ladder compounds, organic superconductors, carbon nanotubes, quantum wires, Josephson junction arrays and so on. Many books on the theory of one-dimensional systems are however written by experts for experts, and tend as such to leave the non-specialist a touch bewildered. This is understandable on both fronts, for the underlying theoretical techniques are unquestionably sophisticated and not usually part of standard courses in many-body theory. A brave author it is then who aims to produce a well rounded, if necessarily partial, overview of quantum physics in one dimension, accessible to a beginner yet taking them to the edge of current research, and providing en route a thorough grounding in the fundamental ideas, basic methods and essential phenomenology of the field. It is of course the brave who succeed in this world, and Thierry Giamarchi does just that with this excellent book, written by an expert for the uninitiated. Aimed in particular at graduate students in theoretical condensed matter physics, and assuming little theoretical background on the part of the reader (well just a little), Giamarchi writes in a

  16. Physics in One Dimension

    Science.gov (United States)

    Bertel, Erminald

    2013-01-01

    Due to progress in nanotechnology high-quality quantum wires can nowadays be fabricated. The behavior of particles in one dimension differs significantly from that in three-dimensional (3D) systems, yet the physics of such low-dimensional systems is generally not very well represented in standard undergraduate or graduate curricula. For instance,…

  17. Dimension and extensions

    CERN Document Server

    Aarts, JM

    1993-01-01

    Two types of seemingly unrelated extension problems are discussed in this book. Their common focus is a long-standing problem of Johannes de Groot, the main conjecture of which was recently resolved. As is true of many important conjectures, a wide range of mathematical investigations had developed, which have been grouped into the two extension problems. The first concerns the extending of spaces, the second concerns extending the theory of dimension by replacing the empty space with other spaces. The problem of de Groot concerned compactifications of spaces by means of an adjunction of a set of minimal dimension. This minimal dimension was called the compactness deficiency of a space. Early success in 1942 lead de Groot to invent a generalization of the dimension function, called the compactness degree of a space, with the hope that this function would internally characterize the compactness deficiency which is a topological invariant of a space that is externally defined by means of compact extensions of a...

  18. Moving between Dimensions

    Science.gov (United States)

    Stephenson, Paul

    2012-01-01

    The first word of this item is "imagine". This instruction has the potential to signal a journey through a world of geometry that might leave you spellbound. On the other hand, it could be the start of a roller-coaster ride through three dimensions that will tax both your imagination, and your powers of visualisation. It is likely that you will…

  19. The Regional Dimension

    DEFF Research Database (Denmark)

    Eskjær, Mikkel Fugl

    2013-01-01

    largely dependent on regional media systems, yet the role this regional dimension plays has been largely overlooked. This article presents a comparative study of climate-change coverage in three geo-cultural regions, The Middle East, Scandinavia, and North America, and explores the link between global...

  20. Nef dimension of minimal models

    OpenAIRE

    Ambro, Florin

    2003-01-01

    We reduce the Abundance Conjecture in dimension 4 to the following numerical statement: if the canonical divisor K is nef and has maximal nef dimension, then K is big. From this point of view, we ``classify'' in dimension 2 nef divisors which have maximal nef dimension, but which are not big.

  1. Templated Growth of Carbon Nanotubes

    Science.gov (United States)

    Siochik Emilie J. (Inventor)

    2007-01-01

    A method of growing carbon nanotubes uses a synthesized mesoporous si lica template with approximately cylindrical pores being formed there in. The surfaces of the pores are coated with a carbon nanotube precu rsor, and the template with the surfaces of the pores so-coated is th en heated until the carbon nanotube precursor in each pore is convert ed to a carbon nanotube.

  2. Carbon nanotube junctions and devices

    OpenAIRE

    Postma, H. W. Ch.

    2001-01-01

    In this thesis Postma presents transport experiments performed on individual single-wall carbon nanotubes. Carbon nanotubes are molecules entirely made of carbon atoms. The electronic properties are determined by the exact symmetry of the nanotube lattice, resulting in either metallic or semiconducting behaviour. Due to their small diameter, electronic motion is directed in the length direction of the nanotube, making them ideal systems to study e.g. one-dimensional transport phenomena. First...

  3. Transport Through Carbon Nanotube Wires

    Science.gov (United States)

    Anantram, M. P.; Kwak, Dochan (Technical Monitor)

    2001-01-01

    This viewgraph presentation deals with the use of carbon nanotubes as a transport system. Contact, defects, tubular bend, phonons, and mechanical deformations all contribute to reflection within the nanotube wire. Bragg reflection, however, is native to an ideal energy transport system. Transmission resistance depends primarily on the level of energy present. Finally, the details regarding coupling between carbon nanotubes and simple metals are presented.

  4. Carbon nanotubes decorating methods

    Directory of Open Access Journals (Sweden)

    A.D. Dobrzańska-Danikiewicz

    2013-06-01

    Full Text Available Purpose: The work is to present and characterise various methods of depositing carbon nanotubes with nanoparticles of precious metals, and also to present the results of own works concerning carbon nanotubes coated with platinum nanoparticles.Design/methodology/approach: Electron transmission and scanning microscopy has been used for imaging the structure and morphology of the nanocomposites obtained and the distribution of nanoparticles on the surface of carbon nanotubes.Findings: The studies carried out with the HRTEM and SEM techniques have confirmed differences in morphology, homogeneity and density of depositing platinum nanoparticles on the surface of carbon nanotubes and its structure.Research limitations/implications: The studies conducted pertained to the process of decorating carbon nanotubes with platinum nanoparticles. Further works are planned aimed at extending the application scope of the newly developed methodology to include the methods of nanotubes decorating with the nanoparticles of other precious metals (mainly palladium and rhodium.Practical implications: CNTs-NPs (Carbon NanoTube-NanoParticles composites can be used as the active elements of sensors featuring high sensitivity, fast action, high selectivity and accuracy, in particular in medicine as cholesterol and glucoses sensors; in the automotive industry for the precision monitoring of working parameters in individual engine components; in environmental conservation to examine CO2, NOx, and CH4 concentrations and for checking leak-tightness and detecting hazardous substances in household and industrial gas installations.Originality/value: The comprehensive characterisation of the methods employed for fabricating nanocomposites consisting of carbon nanotubes deposited with Pt, Pd, Rh, Au, Ag nanoparticles with special consideration to the colloidal process.

  5. Synthesis of carbon nanotubes and nanotube forests on copper catalyst

    International Nuclear Information System (INIS)

    The growth of carbon nanotubes on bulk copper is studied. We show for the first time, that super growth chemical vapor deposition method can be successfully applied for preparation of nanotubes on copper catalyst, and the presence of hydrogen is necessary. Next, different methods of copper surface activation are studied, to improve catalyst efficiency. Among them, applied for the first time for copper catalyst in nanotubes synthesis, sulfuric acid activation is the most promising. Among tested samples the surface modified for 10 min is the most active, causing the growth of vertically aligned carbon nanotube forests. Obtained results have potential importance in application of nanotubes and copper in electronic chips and nanodevices. (paper)

  6. Enhanced bioactivity of self-organized ZrO2 nanotube layer by annealing and UV irradiation

    International Nuclear Information System (INIS)

    Superhydrophilic ZrO2 nanotube layer was prepared by anodic oxidation of commercial pure Zr in aqueous solutions containing 1 M (NH4)2SO4 and 0.15 M NH4F. The effect of annealing and ultraviolet (UV) irradiation treatment on the microstructure, water contact angle and bioactivity of the ZrO2 nanotube layer was investigated. The as-anodized nanotube layer consists of cubic and amorphous ZrO2, no apatite crystals are deposited on its surface even after immersion in simulated body fluids (SBF) for 30 days, exhibiting weak apatite-inducing ability. After annealing at 450 deg. C for 3 h, the nanotube layer is composed of cubic and monoclinic ZrO2, and its apatite-forming ability is significantly enhanced because of its lattice structure matching that of apatite, apatite can be induced after immersion in SBF for 15 days. UV irradiation of the ZrO2 nanotube layers does not alter their surface morphologies and phase components, however, can improve the bioactivity only when the ZrO2 nanotube layer is well crystallized. The enhanced bioactivity by UV irradiation is thought to result from the abundant basic Zr-OH groups on the crystallized ZrO2 nanotube layer. Annealing and UV irradiation treatment do not alter the superhydrophilic nature of the ZrO2 nanotubes. - Research highlights: → Annealing treatment of the nanotube layer can significantly enhance its bioactivity. → UV irradiation immproves the bioactivity when ZrO2 nanotubes are well crystallized. → Annealing and UV treatment don't alter the superhydrophilicity of ZrO2 nanotubes.

  7. Warped Universal Extra Dimensions

    CERN Document Server

    Medina, Anibal D

    2010-01-01

    We consider a 5D warped scenario with a KK-parity symmetry, where the non-trivial warping arises from the dynamics that stabilizes the size of the extra dimension. Generically, the lightest Kaluza-Klein (KK) particle is the first excitation of the radion field, while the next-to-lightest Kaluza-Klein particle is either the first excitation of the (RH) top quark or the first KK-parity odd Higgs. All these masses are expected to be of order the electroweak scale. We present simple analytical expressions for the masses and wavefunctions of the lowest lying KK modes, and derive the Feynman rules necessary for phenomenological applications. The framework allows to interpolate between a strongly warped scenario a la Randall-Sundrum (RS), and a weakly warped scenario that shares properties of both RS and Universal Extra Dimensions models.

  8. Dimensions of African inequality

    OpenAIRE

    Bigsten, Arne

    2014-01-01

    This paper discusses dimensions of inequality in sub-Saharan Africa and their causes. It starts with a review of the empirical evidence about inequality during the colonial period as well as the post-independence era. Then it discusses the forces that determine inequality change, focusing on factor accumulation and structural change. Next it considers the relationship between inequality and growth, the role of agriculture in the development process, the relationships between ethnicity and soc...

  9. Knowledge Economy Dimensions

    OpenAIRE

    Constantin BRATIANU; Violeta Mihaela DINCA

    2010-01-01

    The purpose of this paper is to present an analysis of the emergent knowledge economy and its dimensions. The knowledge economy is based primarily on the development of intangibles, and knowledge processing. The knowledge revolution is changing the way we think and work, and the knowledge worker reflects the nature of the new economic driving forces. The knowledge economy opens new directions, and offers unprecedented opportunities to produce and sell on a mass scale, reduce costs, and custom...

  10. Introduction to Extra Dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Rizzo, Thomas G.; /SLAC

    2010-04-29

    Extra dimensions provide a very useful tool in addressing a number of the fundamental problems faced by the Standard Model. The following provides a very basic introduction to this very broad subject area as given at the VIII School of the Gravitational and Mathematical Physics Division of the Mexican Physical Society in December 2009. Some prospects for extra dimensional searches at the 7 TeV LHC with {approx}1 fb{sup -1} of integrated luminosity are provided.

  11. Soldering of Nanotubes onto Microelectrodes

    DEFF Research Database (Denmark)

    Madsen, Dorte Nørgaard; Mølhave, Kristian; Mateiu, Ramona Valentina;

    2003-01-01

    Suspended bridges of individual multiwalled carbon nanotubes were fabricated inside a scanning electron microscope by soldering the nanotube onto microelectrodes with highly conducting gold-carbon material. By the decomposition of organometallic vapor with the electron beam, metal-containing solder...... bonds were formed at the intersection of the nanotube and the electrodes. Current-voltage curves indicated metallic conduction of the nanotubes, with resistances in the range of 9-29 kOmega. Bridges made entirely of the soldering material exhibited resistances on the order of 100 Omega, and the solder...... bonds were consistently found to be mechanically stronger than the carbon nanotubes....

  12. PI spaces with analytic dimension 1 and arbitrary topological dimension

    OpenAIRE

    Kleiner, Bruce; Schioppa, Andrea

    2015-01-01

    For every n, we construct a metric measure space that is doubling, satisfies a Poincare inequality in the sense of Heinonen-Koskela, has topological dimension n, and has a measurable tangent bundle of dimension 1.

  13. Carbon Nanotubes for Supercapacitor

    Directory of Open Access Journals (Sweden)

    Li Jianyi

    2010-01-01

    Full Text Available Abstract As an electrical energy storage device, supercapacitor finds attractive applications in consumer electronic products and alternative power source due to its higher energy density, fast discharge/charge time, low level of heating, safety, long-term operation stability, and no disposable parts. This work reviews the recent development of supercapacitor based on carbon nanotubes (CNTs and their composites. The purpose is to give a comprehensive understanding of the advantages and disadvantages of carbon nanotubes-related supercapacitor materials and to find ways for the improvement in the performance of supercapacitor. We first discussed the effects of physical and chemical properties of pure carbon nanotubes, including size, purity, defect, shape, functionalization, and annealing, on the supercapacitance. The composites, including CNTs/oxide and CNTs/polymer, were further discussed to enhance the supercapacitance and keep the stability of the supercapacitor by optimally engineering the composition, particle size, and coverage.

  14. Biophotofuel cell anode containing self-organized titanium dioxide nanotube array

    International Nuclear Information System (INIS)

    Graphical abstract: Highlights: · A photoactive anode containing highly ordered TiO2 nanotube array was made and the formation mechanism of self-organized TiO2 nanotube array on Ti was revealed. · Effect of electrolyte concentration and voltage on the size distribution of the nanotubes was investigated. · Self-organized TiO2 nanotube array anode possesses good photo-catalytic behavior of biomass decomposition under ultraviolet (UV) radiation. · The fuel cell generates electricity and hydrogen via photoelectrochemical decomposition of ethanol, apple vinegar, sugar and tissue paper. - Abstract: We made a biophotofuel cell consisting of a titanium dioxide nanotube array photosensitive anode for biomass decomposition, and a low-hydrogen overpotential metal, Pt, as the cathode for hydrogen production. The titanium dioxide nanotubes (TiO2 NTs) were prepared via electrochemical oxidation of pure Ti in NaF solutions. Scanning electron microscopy was used to analyze the morphology of the nanotubes. The average diameter, wall thickness and length of the as-prepared TiO2 NTs were 88 ± 16 nm, 10 ± 2 nm and 491 ± 56 nm, respectively. Such dimensions are affected by the NaF concentration and the applied voltage during processing. Higher NaF concentrations result in the formation of longer and thicker nanotubes. The higher the voltage is, the thicker the nanotubes. The photosensitive anode made from the highly ordered TiO2 NTs has good photo-catalytic property, as can be seen from the test results of ethanol, apple vinegar, sugar and tissue paper decomposition under ultraviolet (UV) radiation. It is concluded that the biophotofuel cell with the TiO2 nanotube photoanode and a Pt cathode can generate electricity, hydrogen and clean water depending on the pH value and the oxygen presence in the solutions.

  15. Biophotofuel cell anode containing self-organized titanium dioxide nanotube array

    Energy Technology Data Exchange (ETDEWEB)

    Gan, Yong X., E-mail: yong.gan@utoledo.edu [Mechanical, Industrial and Manufacturing Engineering, College of Engineering, University of Toledo, 2801 W Bancroft Street, Toledo, OH 43606 (United States); Gan, Bo J. [Ottawa Hills High School, 2532 Evergreen Road, Toledo, OH 43606 (United States); Su Lusheng [Mechanical, Industrial and Manufacturing Engineering, College of Engineering, University of Toledo, 2801 W Bancroft Street, Toledo, OH 43606 (United States)

    2011-09-15

    Graphical abstract: Highlights: {center_dot} A photoactive anode containing highly ordered TiO{sub 2} nanotube array was made and the formation mechanism of self-organized TiO{sub 2} nanotube array on Ti was revealed. {center_dot} Effect of electrolyte concentration and voltage on the size distribution of the nanotubes was investigated. {center_dot} Self-organized TiO{sub 2} nanotube array anode possesses good photo-catalytic behavior of biomass decomposition under ultraviolet (UV) radiation. {center_dot} The fuel cell generates electricity and hydrogen via photoelectrochemical decomposition of ethanol, apple vinegar, sugar and tissue paper. - Abstract: We made a biophotofuel cell consisting of a titanium dioxide nanotube array photosensitive anode for biomass decomposition, and a low-hydrogen overpotential metal, Pt, as the cathode for hydrogen production. The titanium dioxide nanotubes (TiO{sub 2} NTs) were prepared via electrochemical oxidation of pure Ti in NaF solutions. Scanning electron microscopy was used to analyze the morphology of the nanotubes. The average diameter, wall thickness and length of the as-prepared TiO{sub 2} NTs were 88 {+-} 16 nm, 10 {+-} 2 nm and 491 {+-} 56 nm, respectively. Such dimensions are affected by the NaF concentration and the applied voltage during processing. Higher NaF concentrations result in the formation of longer and thicker nanotubes. The higher the voltage is, the thicker the nanotubes. The photosensitive anode made from the highly ordered TiO{sub 2} NTs has good photo-catalytic property, as can be seen from the test results of ethanol, apple vinegar, sugar and tissue paper decomposition under ultraviolet (UV) radiation. It is concluded that the biophotofuel cell with the TiO{sub 2} nanotube photoanode and a Pt cathode can generate electricity, hydrogen and clean water depending on the pH value and the oxygen presence in the solutions.

  16. Horizontal carbon nanotube alignment.

    Science.gov (United States)

    Cole, Matthew T; Cientanni, Vito; Milne, William I

    2016-09-21

    The production of horizontally aligned carbon nanotubes offers a rapid means of realizing a myriad of self-assembled near-atom-scale technologies - from novel photonic crystals to nanoscale transistors. The ability to reproducibly align anisotropic nanostructures has huge technological value. Here we review the present state-of-the-art in horizontal carbon nanotube alignment. For both in and ex situ approaches, we quantitatively assess the reported linear packing densities alongside the degree of alignment possible for each of these core methodologies. PMID:27546174

  17. Carbon Nanotube Solar Cells

    OpenAIRE

    Klinger, Colin; Patel, Yogeshwari; Postma, Henk W. Ch.

    2012-01-01

    We present proof-of-concept all-carbon solar cells. They are made of a photoactive side of predominantly semiconducting nanotubes for photoconversion and a counter electrode made of a natural mixture of carbon nanotubes or graphite, connected by a liquid electrolyte through a redox reaction. The cells do not require rare source materials such as In or Pt, nor high-grade semiconductor processing equipment, do not rely on dye for photoconversion and therefore do not bleach, and are easy to fabr...

  18. Homochiral metal phosphonate nanotubes.

    Science.gov (United States)

    Liu, Xun-Gao; Bao, Song-Song; Huang, Jian; Otsubo, Kazuya; Feng, Jian-Shen; Ren, Min; Hu, Feng-Chun; Sun, Zhihu; Zheng, Li-Min; Wei, Shiqiang; Kitagawa, Hiroshi

    2015-10-21

    A new type of homochiral metal-organic nanotubular structures based on metal phosphonates are reported, namely, (R)- or (S)-[M(pemp)(H2O)2][M = Co(II) (1), Ni(II) (2)] [pemp(2-) = (R)- or (S)-(1-phenylethylamino)methylphosphonate]. In these compounds, the tube-walls are purely inorganic, composed of metal ions and O-P-O bridges. The cavity of the nanotube is hydrophilic with one coordination water pointing towards the center, while the outer periphery of the nanotube is hydrophobic, decorated by the phenylethyl groups of pemp(2-). The thermal stabilities, adsorption and proton conductivity properties are investigated. PMID:26324662

  19. Non-covalent interactions between carbon nanotubes and conjugated polymers

    Science.gov (United States)

    Tuncel, Dönüs

    2011-09-01

    Carbon nanotubes (CNTs) are interest to many different disciplines including chemistry, physics, biology, material science and engineering because of their unique properties and potential applications in various areas spanning from optoelectronics to biotechnology. However, one of the drawbacks associated with these materials is their insolubility which limits their wide accessibility for many applications. Various approaches have been adopted to circumvent this problem including modification of carbon nanotube surfaces by non-covalent and covalent attachments of solubilizing groups. Covalent approach modification may alter the intrinsic properties of carbon nanotubes and, in turn make them undesirable for many applications. On the other hand, a non-covalent approach helps to improve the solubility of CNTs while preserving their intrinsic properties. Among many non-covalent modifiers of CNTs, conjugated polymers are receiving increasing attention and highly appealing because of a number of reasons. To this end, the aim of this feature article is to review the recent results on the conjugated polymer-based non-covalent functionalization of CNTs with an emphasis on the effect of conjugated polymers in the dispersibility/solubility, optical, thermal and mechanical properties of carbon nanotubes as well as their usage in the purification and isolation of a specific single-walled nanotube from the mixture of the various tubes.

  20. Pressure sensing using vertically aligned carbon nanotubes on a flexible substrate

    OpenAIRE

    Carter, E. L.; Brown, P.; Smith, R L; Griffin, J.

    2016-01-01

    Sensing technologies have been under research and development for their varied applications from microelectronics to space exploration. With the end of Moores law in sight, there is growing demand for shrinking materials and improving sensitivity and range of sensing of sensors. Carbon nanotubes (CNTs) offer an excellent combination of small size (in the order of nanometers in two dimensions and micrometers in the third dimension), varied current conductivity (from insulating to metallic), fl...

  1. Using the E22 transition of carbon nanotubes for fiber laser mode-locking

    International Nuclear Information System (INIS)

    We characterize the saturable absorption of the second (E22) electronic transition of a sample of single-walled carbon nanotubes and use it to mode-lock an ytterbium fiber ring laser. The modulation depth of ∼ 15% was found to be similar to the corresponding E11 transition (∼ 13%), but the saturation intensity (∼ 220 MW cm-2) about an order of magnitude larger (∼ 10 MW cm-2). We achieved a 15 MHz mode-locked pulse train with an output pulse duration of 6.5 ps. For comparison we also demonstrate stable mode-locking on the E11 transition, of the same nanotubes, with an erbium fiber ring laser, producing 1.1 ps pulses. Using the E22 transition should enable the use of carbon nanotube saturable absorbers at shorter wavelengths than currently possible with the E11 transition, which are limited by the smallest achievable nanotube dimensions

  2. Gravitational Law in Extra Dimensions

    OpenAIRE

    Bühlmann, Michael

    2013-01-01

    Some recent theories which try to amend shortcomings of current models in physics suggest the existence of additional dimensions. Such extra dimensions would modify the inverse square law of gravity. A short overview over gravitational theory is presented and some of the extensions to general relativity and models which use extra dimensions, so-called Kaluza–Klein theories are discussed. A derivation of the correction to Newton’s gravitational law due to extra dimensions is performed and yiel...

  3. Smectite alteration

    International Nuclear Information System (INIS)

    This report contains the proceedings of a second workshop in Washington DC December 8-9, 1983 on the alteration of smectites intended for use as buffer materials in the long-term containment of nuclear wastes. It includes extended summaries of all presentations and a transcript of the detailed scientific discussion. The discussions centered on three main questions: What is the prerequisite for and what is the precise mechanism by which smectite clays may be altered to illite. What are likly sources of potassium with respect to the KBS project. Is it likely that the conversion of smectite to illite will be of importance in the 10 5 to the 10 6 year time frame. The workshop was convened to review considerations and conclusions in connection to these questions and also to broaden the discussion to consider the use of smectite clays as buffer materials for similar applications in different geographical and geological settings. SKBF/KBS technical report 83-03 contains the proceedings from the first workshop on these matters that was held at the State University of New York, Buffalo May 26-27, 1982. (Author)

  4. Three-dimensional imaging of single nanotube molecule endocytosis on plasmonic substrates

    CERN Document Server

    Hong, Guosong; Robinson, Joshua T; Wang, Hailiang; Zhang, Bo; Dai, Hongjie

    2012-01-01

    Investigating the cellular internalization pathways of single molecules or single nano-objects is important to understanding cell-matter interactions and to applications in drug delivery and discovery. Imaging and tracking the motion of single molecules on cell plasma membrane require high spatial resolution in three dimensions (3D). Fluorescence imaging along the axial dimension with nanometer resolution has been highly challenging but critical to revealing displacements in trans-membrane events. Here, utilizing a plasmonic ruler based on the sensitive distance dependence of near-infrared fluorescence enhancement (NIR-FE) of carbon nanotubes on a gold plasmonic substrate, we probe ~10 nm scale trans-membrane displacements through changes in nanotube fluorescence intensity, enabling observations of single nanotube endocytosis in 3D. Cellular uptake and trans-membrane displacements show clear dependences to temperature and clathrin assembly on cell membrane, suggesting that the cellular entry mechanism for a n...

  5. Adjoint Functors and Representation Dimensions

    Institute of Scientific and Technical Information of China (English)

    Chang Chang XI

    2006-01-01

    We study the global dimensions of the coherent functors over two categories that are linked by a pair of adjoint functors. This idea is then exploited to compare the representation dimensions of two algebras. In particular, we show that if an Artin algebra is switched from the other, then they have the same representation dimension.

  6. Coarse geometry and asymptotic dimension

    OpenAIRE

    Grave, Bernd

    2006-01-01

    We consider asymptotic dimension of coarse spaces. We analyse coarse structures induced by metrisable compactifications. We calculate asymptotic dimension of coarse cell complexes. We calculate the asymptotic dimension of certain negatively curved spaces, e.g. for complete, simply connected manifolds with bounded, strictly negative sectional curvature.

  7. Complete intersection dimension for complexes

    OpenAIRE

    Sather-Wagstaff, Sean

    2003-01-01

    We extend the notions of complete intersection dimension and lower complete intersection dimension to the category of complexes with finite homology and verify basic properties analogous to those holding for modules. We also discuss the question of the behavior of complete intersection dimension with respect to short exact sequences.

  8. Extra Dimensions and ``Branes''

    Science.gov (United States)

    Sundrum, Raman

    2011-04-01

    We do not yet know the nature of fundamental physics above the weak scale, but we are about to probe it this decade. It may come in the form of a few new weakly-coupled particles, captured by ordinary Feynman diagrams in standard spacetime, or alternatively in the form of large ``towers'' of new elementary or composite states, requiring a different set of concepts and analytic tools. Extra spatial dimensions provide the simplest, but very rich, class of such possibilities. I will explain how extra-dimensions can provide an elegant and intuitive geometrization of subtle physics, in particular flowing from the powerful AdS/CFT correspondence. This geometrization allows one to ``view'' central issues ranging from electroweak, grand unified, strongly-coupled, flavor, supersymmetry, or collider physics, in terms of the overlap of extra-dimensional wavefunctions, the curvature (``warping'') of the higher dimensional spacetime, and ``branes'' (3-dimensional defects). I will illustrate the kind of physics and experimental signals that flow from the most plausible extra-dimensional scenarios.

  9. From Carbon Nanotube Crystals to Carbon Nanotube Flowers

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zhengjun; ZHAO Ye; ZHOU Ya

    2005-01-01

    We have investigated the very initial deposition stages of chemical vapor deposition (CVD) with ferrocene (Fe(C5H5)2) and xylene (C8H10) for growing carbon nanotubes, and made clear that the mechanism for the self-organization behaviors of nanotubes at different growth stages by this approach. For instance, the organization of nanotubes into flower-like structures at prolonged deposition is developed from the crystal-like structures formed at early growth stages, both of which are closely related to and determined by the very initial deposition stages of this CVD approach. Based on this approach, ways have been established to build up different architectures of carbon nanotubes, by controlling the initial deposition stages of the CVD process, with which we have realized the selective growth of self-organized carbon nanotube structures. This study provides a new idea for growing carbon nanotube architectures by CVD.

  10. Spin stripes in nanotubes

    OpenAIRE

    Kleiner, Alex

    2002-01-01

    It is shown here that electrons on the surface of a nanotube in a perpendicular magnetic field undergo spin-chirality separation along the circumference. Stripes of spin-polarization propagate along the tube, with a spatial pattern that can be modulated by the electron filling.

  11. Dual-Responsive Lipid Nanotubes: Two-Way Morphology Control by pH and Redox Effects.

    Science.gov (United States)

    Unsal, Hande; Schmidt, Judith; Talmon, Yeshayahu; Yildirim, Leyla Tatar; Aydogan, Nihal

    2016-05-31

    Lipid nanotubes are the preferred structures for many applications, especially biological ones, and thus have attracted much interest recently. However, there is still a significant need for developing more lipid nanotubes that are reversibly controllable to improve their functionality and usability. Here, we presented a two-way reversible morphology control of the nanotubes formed by the recently designed molecule AQUA (C25H29NO4). Because of its special design, the AQUA has both pH-sensitive and redox-active characters provided by the carboxylic acid and anthraquinone groups. Upon chemical reduction, the nanotubes turned into thinner ribbons, and this structural transformation was significantly reversible. The reduction of the AQUA nanotubes also switched the nanotubes from electrically conductive to insulative. Nanotube morphology can additionally be altered by decreasing the pH below the pKa value of the AQUA, at ∼4.9. Decreasing the pH caused the gradual unfolding of the nanotubes, and the interlayer distance in the nanotube's walls increased. This morphological change was fast and reversible at a wide pH range, including the physiological pH. Thus, the molecular design of the AQUA allowed for an unprecedented two-way and reversible morphology control with both redox and pH effects. These unique features make AQUA a very promising candidate for many applications, ranging from electronics to controlled drug delivery. PMID:27148756

  12. Carbon Nanotubes - Polymer Composites with Enhanced Conductivity using Functionalized Nanotubes

    Science.gov (United States)

    Ramasubramaniam, Rajagopal; Chen, Jian; Gupta, Rishi

    2003-03-01

    Individual carbon nanotubes show superior electrical, mechanical and thermal properties [1]. Composite materials using carbon nanotubes as fillers are predicted to show similar superior properties. However, realization of such composites has been plagued by poor dispersion of carbon nanotubes in solvents and in polymer matrices. We have developed a method to homogenously disperse carbon nanotubes in polymer matrices using functionalized nanotubes [2]. Thin films of functionalized single walled nanotubes (SWNT) - polystyrene composites and functionalized SWNT - polycarbonate composites were prepared using solution evaporation and spin coating. Both of the composites show several orders of magnitude increase in conductivity for less than 1 wt thresholds of the composites are less than 0.2 wt nanotubes. We attribute the enhanced conduction to the superior dispersion of the functionalized nanotubes in the polymer matrix and to the reduced nanotube waviness resulting from the rigid backbone of the conjugated polymer. References: [1]. R. H. Baughman, A. A. Zakhidov and W. A. de Heer, Science v297, p787 (2002); [2]. J. Chen, H. Liu, W. A. Weimer, M. D. Halls, D. H. Waldeck and G. C. Walker, J. Am. Chem. Soc. v124, p9034 (2002).

  13. Nonlinear optical transmission in VOx nanotubes and VOx nanotube composites

    Science.gov (United States)

    Xu, J.-F.; Czerw, R.; Webster, S.; Carroll, D. L.; Ballato, J.; Nesper, R.

    2002-08-01

    Optical-limiting behavior of vanadium oxide nanotubes is characterized for the visible and infrared spectral ranges using 8 ns pulses from a Nd:YAG laser with an f/40 optical system. Vanadium oxide nanotube dispersions were investigated in both water suspensions and embedded in solid polymethyl methacrylate films. In each case, these nanotubes exhibit strong optical-limiting at 532 nm (in comparison to carbon nanotubes); however, no nonlinear behavior is observed for 1064 nm. This suggests that a two photon or excited state absorption mechanism is responsible for the observed nonlinearity.

  14. The fourth Dimension

    CERN Document Server

    Schweitzer, Eugen

    2009-01-01

    In different passages of his dialogues, Plato showed deep mathematically-based physical insights. Regrettably most readers overlooked the respective statements, or they utterly did not understand those hints since they were full of philological fallacious terms. Respectable translators misinterpreted such statements and therefore Plato's respective remarks were not recognized as substantial knowledge. Furthermore, Plato often supplemented such basic remarks by diffusely veiled and varied allusions that were often ironically hidden somewhere in his dialogues by inconspicuous double meanings. However, this mode of intentionally coded discrete communication was generally not understood because such irony is not to everyone's taste. However, the attempts to reconstruct Plato's system on the basis of admittedly individually interpreted double meanings lead to a conclusive mathematical-physical cyclical system of dimensions. Additionally it was possible to assign Plato's system of philosophical ideas analogously to...

  15. Method card design dimensions

    DEFF Research Database (Denmark)

    Wölfel, Christiane; Merritt, T.

    2013-01-01

    There are many examples of cards used to assist or provide structure to the design process, yet there has not been a thorough articulation of the strengths and weaknesses of the various examples. We review eighteen card-based design tools in order to understand how they might benefit designers....... The card-based tools are explained in terms of five design dimensions including the intended purpose and scope of use, duration of use, methodology, customization, and formal/material qualities. Our analysis suggests three design patterns or archetypes for existing card-based design method tools...... and highlights unexplored areas in the design space. The paper concludes with recommendations for the future development of card-based methods for the field of interaction design....

  16. Unification in One Dimension

    CERN Document Server

    Jackson, David J

    2016-01-01

    A physical theory of the world is presented under the unifying principle that all of nature is laid out before us and experienced through the passage of time. The one-dimensional progression in time is opened out into a multi-dimensional mathematically consistent flow, with the simplicity of the former giving rise to symmetries of the latter. The act of perception identifies an extended spacetime arena of intermediate dimension, incorporating the symmetry of geometric spatial rotations, against which physical objects are formed and observed. The spacetime symmetry is contained as a subgroup of, and provides a natural breaking mechanism for, the higher general symmetry of time. It will be described how the world of gravitation and cosmology, as well as quantum theory and particle physics, arises from these considerations.

  17. Hiding an extra dimension

    International Nuclear Information System (INIS)

    We propose a new geometry and/or topology of a single extra dimension whose Kaluza-Klein excitations do appear at much higher scale than the inverse of the length/volume. For a single extra dimenion with volume Nπρ which is made of N intervals with size πρ attached at one point, Kaluza-Klein excitations can appear at 1/ρ rather than 1/Nρ which can hide the signal of the extra dimenion sufficiently for large N. The geometry considered here can be thought of a world volume theory of self intersecting branes or an effective description of complicated higher dimensional geometry such as Calabi-Yau with genus or multi-throat configurations. This opens a wide new domain of possible compactifications which deserves a serious investigation

  18. Dimensions of Openness

    DEFF Research Database (Denmark)

    Dalsgaard, Christian; Thestrup, Klaus

    2015-01-01

    The objective of the paper is to present a pedagogical approach to openness. The paper develops a framework for understanding the pedagogical opportunities of openness in education. Based on the pragmatism of John Dewey and sociocultural learning theory, the paper defines openness in education as a...... matter of engaging educational activities in sociocultural practices of a surrounding society. Openness is not only a matter of opening up the existing, but of developing new educational practices that interact with society. The paper outlines three pedagogical dimensions of openness: transparency......, communication, and engagement. Transparency relates to the opening up of student work, thoughts, activities, and products in order to provide students with insight into each other’s activities. Communication aims at establishing interaction between educational activities of an institution and surrounding...

  19. Growth of nanotubes for electronics

    Directory of Open Access Journals (Sweden)

    John Robertson

    2007-01-01

    Full Text Available The roadmap for semiconductor devices envisages that carbon nanotubes or semiconducting nanowires could become important in about ten years. This article reviews where carbon nanotubes could contribute to microelectronics, in terms of vias, interconnects, and field-effect transistors. It focuses particularly on the requirements microelectronics places on the growth of nanotubes. That is, control over the formation of semiconducting or metallic tubes, controlling the growth location and direction, and achieving high enough nucleation densities.

  20. Connecting carbon nanotubes using Sn.

    Science.gov (United States)

    Mittal, Jagjiwan; Lin, Kwang Lung

    2013-08-01

    Process of Sn coating on mutiwalled carbon nanotubes (MWCNT) and formation of interconnections among nanotubes are studied using high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDX). Surface oxidation of nanotubes during heating with HNO3 prior to the SnCl2 treatment and the bonding between functional groups and Sn are found to be responsible for the coating and its stability. Open nanotubes are filled as well as coated during tin chloride treatment. Coating and filling are converted into the coatings on the inner as well as outer walls of the nanotubes during reduction with H2/N2. EDX studies show the formation of intermetallic compounds e.g., Cu6Sn5 and Cu3Sn at the joints between nanotubes. Formation of intermetallic compounds is supposed to be responsible for providing the required strength for bending and twisting of nanotubes joining of nanotubes. Paper presents a detailed mechanism of coating and filling processes, and interconnections among nanotubes. PMID:23882800

  1. Carbon nanotube IR detectors (SV)

    Energy Technology Data Exchange (ETDEWEB)

    Leonard, F. L.

    2012-03-01

    Sandia National Laboratories (Sandia) and Lockheed Martin Corporation (LMC) collaborated to (1) evaluate the potential of carbon nanotubes as channels in infrared (IR) photodetectors; (2) assemble and characterize carbon nanotube electronic devices and measure the photocurrent generated when exposed to infrared light;(3) compare the performance of the carbon nanotube devices with that of traditional devices; and (4) develop and numerically implement models of electronic transport and opto-electronic behavior of carbon nanotube infrared detectors. This work established a new paradigm for photodetectors.

  2. Fabricating Copper Nanotubes by Electrodeposition

    Science.gov (United States)

    Yang, E. H.; Ramsey, Christopher; Bae, Youngsam; Choi, Daniel

    2009-01-01

    Copper tubes having diameters between about 100 and about 200 nm have been fabricated by electrodeposition of copper into the pores of alumina nanopore membranes. Copper nanotubes are under consideration as alternatives to copper nanorods and nanowires for applications involving thermal and/or electrical contacts, wherein the greater specific areas of nanotubes could afford lower effective thermal and/or electrical resistivities. Heretofore, copper nanorods and nanowires have been fabricated by a combination of electrodeposition and a conventional expensive lithographic process. The present electrodeposition-based process for fabricating copper nanotubes costs less and enables production of copper nanotubes at greater rate.

  3. Luminescence of carbon nanotube bulbs

    Institute of Scientific and Technical Information of China (English)

    LI ChuanGang; WU DeHai; WANG KunLin; WEI JinQuan; WEI BingQing; ZHU HongWei; WANG ZhiCheng; LUO JianBin; LIU WenJin; ZHENG MingXin

    2007-01-01

    Carbon nanotube (CNT) bulbs made of decimeter-scale double-walled carbon nanotube (DWCNT) strands and films were fabricated and their luminescence properties, including the lighting efficiency, voltage-current relation and thermal stability were investigated. The results show that the DWCNT bulb has a comparable spectrum of visible light with tungsten bulb and its average efficiency is 40% higher than that of a tungsten filament at the same temperature (1400-2300 K). The nanotube filaments show both resistance and thermal stability over a large temperature region. No obvious damage was found for a nanotube bulb illuminating at 2300 K for more than 24 hours in vacuum.

  4. Interactive Dimensioning of Parametric Models

    KAUST Repository

    Kelly, T.

    2015-05-01

    We propose a solution for the dimensioning of parametric and procedural models. Dimensioning has long been a staple of technical drawings, and we present the first solution for interactive dimensioning: A dimension line positioning system that adapts to the view direction, given behavioral properties. After proposing a set of design principles for interactive dimensioning, we describe our solution consisting of the following major components. First, we describe how an author can specify the desired interactive behavior of a dimension line. Second, we propose a novel algorithm to place dimension lines at interactive speeds. Third, we introduce multiple extensions, including chained dimension lines, controls for different parameter types (e.g. discrete choices, angles), and the use of dimension lines for interactive editing. Our results show the use of dimension lines in an interactive parametric modeling environment for architectural, botanical, and mechanical models. © 2015 The Author(s) Computer Graphics Forum © 2015 The Eurographics Association and John Wiley & Sons Ltd. Published by John Wiley & Sons Ltd.

  5. Microtribology of aqueous carbon nanotube dispersions

    KAUST Repository

    Kristiansen, Kai De Lange

    2011-09-23

    The tribological behavior of carbon nanotubes (CNTs) in aqueous humic acid (HA) solutions was studied using a surface forces apparatus (SFA) and shows promising lubricant additive properties. Adding CNTs to the solution changes the friction forces between two mica surfaces from "adhesion controlled" to "load controlled" friction. The coefficient of friction with either single-walled (SW) or multi-walled (MW) CNT dispersions is in the range 0.30-0.55 and is independent of the load and sliding velocity. More importantly, lateral sliding promotes a redistribution or accumulation, rather than squeezing out, of nanotubes between the surfaces. This accumulation reduced the adhesion between the surfaces (which generally causes wear/damage of the surfaces), and no wear or damage was observed during continuous shearing experiments that lasted several hours even under high loads (pressures â∼10 MPa). The frictional properties can be understood in terms of the Cobblestone Model where the friction force is related to the fraction of the adhesion energy dissipated during impacts of the nanoparticles. We also develop a simple generic model based on the van der Waals interactions between particles and surfaces to determine the relation between the dimensions of nanoparticles and their tribological properties when used as additives in oil- or water-based lubricants. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Multiwalled carbon nanotube film for strain sensing

    International Nuclear Information System (INIS)

    We have studied the possibility of using multiwalled carbon nanotube (MWCNT) films as strain sensors. The MWCNT films were prepared by a solution/filtration method and were bonded directly onto specimens by a nonconductive adhesive. For comparison, conventional foil strain gages were also bonded to the structure on the opposite side. The specimens then underwent a uniaxial tensile load-unload cycle to evaluate them as strain sensors. To ensure good electrical contact between carbon nanotube film and the wires, a thin layer of copper was thermally deposited on both ends of the film as electrodes, and the wires were connected to the electrodes by silver ink. Wheatstone bridges were used to convert the resistance changes of the MWCNTs to voltage output. Results indicated that the output voltages were proportional to the strain readings from the stain indicator. The effect of temperature on the resistance was measured and the MWCNT film resistance was found to be independent of temperature over the range 273-363 K. The optimal film dimension for strain sensing was evaluated as well. Dynamic tests suggest that the MWCNTs were able to extract the structural signature. Our results indicate that MWCNT film is potentially useful for structural health monitoring and vibration control applications

  7. Carbon nanotubes: artificial nanomaterials to engineer single neurons and neuronal networks.

    Science.gov (United States)

    Fabbro, Alessandra; Bosi, Susanna; Ballerini, Laura; Prato, Maurizio

    2012-08-15

    In the past decade, nanotechnology applications to the nervous system have often involved the study and the use of novel nanomaterials to improve the diagnosis and therapy of neurological diseases. In the field of nanomedicine, carbon nanotubes are evaluated as promising materials for diverse therapeutic and diagnostic applications. Besides, carbon nanotubes are increasingly employed in basic neuroscience approaches, and they have been used in the design of neuronal interfaces or in that of scaffolds promoting neuronal growth in vitro. Ultimately, carbon nanotubes are thought to hold the potential for the development of innovative neurological implants. In this framework, it is particularly relevant to document the impact of interfacing such materials with nerve cells. Carbon nanotubes were shown, when modified with biologically active compounds or functionalized in order to alter their charge, to affect neurite outgrowth and branching. Notably, purified carbon nanotubes used as scaffolds can promote the formation of nanotube-neuron hybrid networks, able per se to affect neuron integrative abilities, network connectivity, and synaptic plasticity. We focus this review on our work over several years directed to investigate the ability of carbon nanotube platforms in providing a new tool for nongenetic manipulations of neuronal performance and network signaling. PMID:22896805

  8. Thermal dimension of quantum spacetime

    CERN Document Server

    Amelino-Camelia, Giovanni; Gubitosi, Giulia; Santos, Grasiele

    2016-01-01

    Recent results suggest that a crucial crossroad for quantum gravity is the characterization of the effective dimension of spacetime at short distances, where quantum properties of spacetime become significant. This is relevant in particular for various scenarios of "dynamical dimensional reduction" which have been discussed in the literature. We are here concerned with the fact that the related research effort has been based exclusively on analyses of the "spectral dimension", which involves an unphysical Euclideanization of spacetime and is highly sensitive to the off-shell properties of a theory. As here shown, different formulations of the same physical theory can have wildly different spectral dimension. We propose that dynamical dimensional reduction should be described in terms of the "thermal dimension" which we here introduce, a notion that only depends on the physical content of the theory. We analyze a few models with dynamical reduction both of the spectral dimension and of our thermal dimension, f...

  9. Synergistic effect in conductive networks constructed with carbon nanofillers in different dimensions

    OpenAIRE

    Fu, Q; S. M. Zhang; Lin, L; Deng, H.; Gao, X; E. Bilotti; Peijs, T.; Zhang, Q

    2012-01-01

    Herein, investigation on synergistic effect during network formation for conductive network constructed with carbon nanofillers in different dimensions is conducted. Multi-walled carbon nanotubes (MWNTs) and carbon black (CB) are employed as conductive fillers in this system. Morphological control of the conductive network is realized by adjusting the ratio between different fillers. Classical percolation threshold theory and adjusted excluded volume theory are used to analyze the electrical ...

  10. Anomalous Dimensions of Conformal Baryons

    CERN Document Server

    Pica, Claudio

    2016-01-01

    We determine the anomalous dimensions of baryon operators for the three color theory as function of the number of massless flavours within the conformal window to the maximum known order in perturbation theory. We show that the anomalous dimension of the baryon is controllably small for a wide range of number of flavours. We also find that this is always smaller than the anomalous dimension of the fermion mass operator. These findings challenge the partial compositeness paradigm.

  11. Dimensions of ecosystem theory

    International Nuclear Information System (INIS)

    Various dimensions of ecosystem structure and behavior that seem to develop from the ubiquitous phenomena of system growth and persistence were studied. While growth and persistence attributes of ecosystems may appear to be simplistic phenomena upon which to base a comprehensive ecosystem theory, these same attributes have been fundamental to the theoretical development of other biological disciplines. These attributes were explored at a hierarchical level in a self-organizing system, and adaptive system strategies that result were analyzed. Previously developed causative relations (Reichle et al., 1975c) were examined, their theoretical implications expounded upon, and the assumptions tested with data from a variety of forest types. The conclusions are not a theory in themselves, but a state of organization of concepts contributing towards a unifying theory, along the lines promulgated by Bray (1958). The inferences drawn rely heavily upon data from forested ecosystems of the world, and have yet to be validated against data from a much more diverse range of ecosystem types. Not all of the interpretations are logically tight - there is room for other explanations, which it is hoped will provide fruitful grounds for further speculation

  12. Flying in Two Dimensions

    CERN Document Server

    Prakash, Manu

    2011-01-01

    Diversity and specialization of behavior in insects is unmatched. Insects hop, walk, run, jump, row, swim, glide and fly to propel themselves in a variety of environments. We have uncovered an unusual mode of propulsion of aerodynamic flight in two dimensions in Waterlilly Beetles \\emph{(Galerucella)}. The adult beetles, often found in water lilly ponds, propel themselves strictly in a two-dimensional plane on the surface of water via flapping wing flight. Here we analyze the aerodynamics of this peculiar flight mode with respect to forces exerted on the organism during flight. The complexity of 2-D flight is captured by accounting for additional forces beyond gravitational, thrust, lift and drag, exerted on the insect body in 3D flight. Understanding this constrained propulsion mode requires accounting for viscous drag, surface tension, buoyancy force, and capillary-wave drag. Moreover, dramatic differences exist in the magnitude of the resultant forces in 2D vs. 3D flight. Here, in this fluid dynamics video...

  13. Physics in one dimension

    Science.gov (United States)

    van Houselt, A.; Schäfer, J.; Zandvliet, H. J. W.; Claessen, R.

    2013-01-01

    With modern microelectronics moving towards smaller and smaller length scales on the (sub-) nm scale, quantum effects (apart from band structure and band gaps) have begun to play an increasingly important role. This especially concerns dimensional confinement to 2D (high electron mobility transistors and integer/fractional quantum Hall effect physics, graphene and topological insulators) and 1D (with electrical connections eventually reaching the quantum limit). Recent developments in the above-mentioned areas have revealed that the properties of electron systems become increasingly exotic as one progresses from the 3D case into lower dimensions. As compared to 2D electron systems, much less experimental progress has been achieved in the field of 1D electron systems. The main reason for the lack of experimental results in this field is related to the difficulty of realizing 1D electron systems. Atom chains created in quantum mechanical break junction set-ups are too short to exhibit the typically 1D signatures. As an alternative, atomic chains can be produced on crystal surfaces, either via assembling them one-by-one using a scanning tunnelling microscope or via self-assembly. The drawback of the latter systems is that the atomic chains are not truly 1D since they are coupled to the underlying crystal and sometimes even to the neighbouring chains. In retrospect, this coupling turns out to be an absolute necessity in the experiment since true 1D systems are disordered at any non-zero temperature [1]. The coupling to the crystal and/or neighbouring chains shifts the phase transition, for example, a Peierls instability, to a non-zero temperature and thus allows experiments to be performed in the ordered state. Here, we want to emphasize that the electronic properties of the 1D electron system are fundamentally different from its 2D and 3D counterparts. The Fermi liquid theory, which is applicable to 2D and 3D electron systems, breaks down spectacularly in the 1D case

  14. Transport of a liquid water and methanol mixture through carbon nanotubes under a chemical potential gradient

    Science.gov (United States)

    Zheng, Jie; Lennon, Erin M.; Tsao, Heng-Kwong; Sheng, Yu-Jane; Jiang, Shaoyi

    2005-06-01

    In this work, we report a dual-control-volume grand canonical molecular dynamics simulation study of the transport of a water and methanol mixture under a fixed concentration gradient through nanotubes of various diameters and surface chemistries. Methanol and water are selected as fluid molecules since water represents a strongly polar molecule while methanol is intermediate between nonpolar and strongly polar molecules. Carboxyl acid (-COOH) groups are anchored onto the inner wall of a carbon nanotube to alter the hydrophobic surface into a hydrophilic one. Results show that the transport of the mixture through hydrophilic tubes is faster than through hydrophobic nanotubes although the diffusion of the mixture is slower inside hydrophilic than hydrophobic pores due to a hydrogen network. Thus, the transport of the liquid mixture through the nanotubes is controlled by the pore entrance effect for which hydrogen bonding plays an important role.

  15. Fractal Dimension for Fractal Structures

    OpenAIRE

    Fernández-Martínez, M.; Sánchez-Granero, M. A.

    2010-01-01

    The main goal of this paper has a double purpose. On the one hand, we propose a new definition in order to compute the fractal dimension of a subset respect to any fractal structure, which completes the theory of classical box-counting dimension. Indeed, if we select the so called natural fractal structure on each euclidean space, then we will get the box-counting dimension as a particular case. Recall that box-counting dimension could be calculated over any euclidean space, although it can b...

  16. Carbon nanotube-polymer composite actuators

    Science.gov (United States)

    Gennett, Thomas; Raffaelle, Ryne P.; Landi, Brian J.; Heben, Michael J.

    2008-04-22

    The present invention discloses a carbon nanotube (SWNT)-polymer composite actuator and method to make such actuator. A series of uniform composites was prepared by dispersing purified single wall nanotubes with varying weight percents into a polymer matrix, followed by solution casting. The resulting nanotube-polymer composite was then successfully used to form a nanotube polymer actuator.

  17. Carbon nanotube network varactor

    International Nuclear Information System (INIS)

    Microelectromechanical system (MEMS) varactors based on a freestanding layer of single-walled carbon nanotube (SWCNT) films were designed, fabricated and tested. The freestanding SWCNT film was employed as a movable upper patch in the parallel plate capacitor of the MEMS. The measurements of the SWCNT varactors show very high tunability, nearly 100%, of the capacitance with a low actuation voltage of 10 V. The functionality of the varactor is improved by implementing a flexible nanocellulose aerogel filling. (paper)

  18. Carbon nanotube network varactor

    Science.gov (United States)

    Generalov, A. A.; Anoshkin, I. V.; Erdmanis, M.; Lioubtchenko, D. V.; Ovchinnikov, V.; Nasibulin, A. G.; Räisänen, A. V.

    2015-01-01

    Microelectromechanical system (MEMS) varactors based on a freestanding layer of single-walled carbon nanotube (SWCNT) films were designed, fabricated and tested. The freestanding SWCNT film was employed as a movable upper patch in the parallel plate capacitor of the MEMS. The measurements of the SWCNT varactors show very high tunability, nearly 100%, of the capacitance with a low actuation voltage of 10 V. The functionality of the varactor is improved by implementing a flexible nanocellulose aerogel filling.

  19. Progress in Research on Carbon Nanotubes Reinforced Cementitious Composites

    Directory of Open Access Journals (Sweden)

    Qinghua Li

    2015-01-01

    Full Text Available As one-dimensional (1D nanofiber, carbon nanotubes (CNTs have been widely used to improve the performance of nanocomposites due to their high strength, small dimensions, and remarkable physical properties. Progress in the field of CNTs presents a potential opportunity to enhance cementitious composites at the nanoscale. In this review, current research activities and key advances on multiwalled carbon nanotubes (MWCNTs reinforced cementitious composites are summarized, including the effect of MWCNTs on modulus of elasticity, porosity, fracture, and mechanical and microstructure properties of cement-based composites. The issues about the improvement mechanisms, MWCNTs dispersion methods, and the major factors affecting the mechanical properties of composites are discussed. In addition, large-scale production methods of MWCNTs and the effects of CNTs on environment and health are also summarized.

  20. Flow-induced properties of nanotube-filled polymer materials.

    Science.gov (United States)

    Kharchenko, Semen B; Douglas, Jack F; Obrzut, Jan; Grulke, Eric A; Migler, Kalman B

    2004-08-01

    Carbon nanotubes (CNTs) are under intense investigation in materials science owing to their potential for modifying the electrical conductivity sigma, shear viscosity eta, and other transport properties of polymeric materials. These particles are hybrids of filler and nanoscale additives because their lengths are macroscopic whereas their cross-sectional dimensions are closer to molecular scales. The combination of extended shape, rigidity and deformability allows CNTs to be mechanically dispersed in polymer matrices in the form of disordered 'jammed' network structures. Our measurements on representative network-forming multiwall nanotube (MWNT) dispersions in polypropylene indicate that these materials exhibit extraordinary flow-induced property changes. Specifically, sigma and eta both decrease strongly with increasing shear rate, and these nanocomposites exhibit impressively large and negative normal stress differences, a rarely reported phenomenon in soft condensed matter. We illustrate the practical implications of these nonlinear transport properties by showing that MWNTs eliminate die swell in our nanocomposites, an effect crucial for their processing. PMID:15273745

  1. Teslaphoresis of Carbon Nanotubes.

    Science.gov (United States)

    Bornhoeft, Lindsey R; Castillo, Aida C; Smalley, Preston R; Kittrell, Carter; James, Dustin K; Brinson, Bruce E; Rybolt, Thomas R; Johnson, Bruce R; Cherukuri, Tonya K; Cherukuri, Paul

    2016-04-26

    This paper introduces Teslaphoresis, the directed motion and self-assembly of matter by a Tesla coil, and studies this electrokinetic phenomenon using single-walled carbon nanotubes (CNTs). Conventional directed self-assembly of matter using electric fields has been restricted to small scale structures, but with Teslaphoresis, we exceed this limitation by using the Tesla coil's antenna to create a gradient high-voltage force field that projects into free space. CNTs placed within the Teslaphoretic (TEP) field polarize and self-assemble into wires that span from the nanoscale to the macroscale, the longest thus far being 15 cm. We show that the TEP field not only directs the self-assembly of long nanotube wires at remote distances (>30 cm) but can also wirelessly power nanotube-based LED circuits. Furthermore, individualized CNTs self-organize to form long parallel arrays with high fidelity alignment to the TEP field. Thus, Teslaphoresis is effective for directed self-assembly from the bottom-up to the macroscale. PMID:27074626

  2. Building Highly Flexible Polyelectrolyte Nanotubes

    Institute of Scientific and Technical Information of China (English)

    2004-01-01

    @@ Flexibility of polyelectrolyte nanotubes is necessary if they are to be exploited in applications such as developing photoelectric devices with strong mechanical properties. In a recent attempt, high flexibility has been observed from such nanotubes prepared by a research team headed by Prof. Li Junbai of the CAS Institute of Chemistry (ICCAS).

  3. Influence of the structural properties on the pseudocritical magnetic behavior of single-wall ferromagnetic nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Salazar-Enriquez, C.D. [PCM Computational Applications, Universidad Nacional de Colombia - Sede Manizales, A.A. 127 Manizales (Colombia); Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.co [PCM Computational Applications, Universidad Nacional de Colombia - Sede Manizales, A.A. 127 Manizales (Colombia); Restrepo, J. [Grupo de Magnetismo y Simulacion Gplus, Instituto de Fisica, Universidad de Antioquia, A.A. 1226 Medellin (Colombia)

    2012-04-15

    In this work we address the influence of the crystalline structure, concretely when the system under study is formed by square or hexagonal unit cells, upon the magnetic properties and pseudocritical behavior of single-wall ferromagnetic nanotubes. We focus not only on the effect of the geometrical shape of the unit cell but also on their dimensions. The model employed is based on the Monte Carlo method, the Metropolis dynamics and a nearest neighbors classical Heisenberg Hamiltonian. Magnetization per magnetic site, magnetic susceptibility, specific heat and magnetic energy were computed. These properties were computed varying the system size, unit cell dimension and temperature. The dependence of the nearest neighbor exchange integral on the nanotubes geometrical characteristics is also discussed. Results revealed a strong influence of the system topology on the magnetic properties caused by the difference in the coordination number between square and hexagonal unit cell. Moreover, the nanotubes diameter influence on magnetic properties is only observed at very low values, when the distance between atoms is less than it, presented by the 2D sheet. On the other hand, it was concluded that the surface-related finite-size effects do not influence the magnetic nanotubes properties, contrary to the case of other nano-systems as thin films and nanoparticles among others. - Highlights: Black-Right-Pointing-Pointer Unit cell geometry has strong influence on the magnetic properties in ferromagnetic nanotubes. Black-Right-Pointing-Pointer The nanotube diameter increase produces a decrease of interaction between nearest neighbor. Black-Right-Pointing-Pointer Surface-related finite-size effects do not influence the magnetic nanotubes properties.

  4. Preparation of isolated carbon nanotubes

    International Nuclear Information System (INIS)

    Full text: Carbon nanotubes are of great interest for a large range of applications from physical chemistry, solid state physics to molecular quantum optics. We propose the preparation of molecular beams of isolated carbon nanotubes for future matter wave experiments, as well as for applications in the material sciences and spectroscopy. Carbon nanotubes may be particularly interesting for quantum experiments because of their low ionization threshold, high mechanical stability and high polarizability. This is expected to facilitate the cooling, coherent manipulation and efficient detection of such molecular beams. For this purpose we are investigating different methods of solvation, isolation and shortening of carbon nanotubes from commercial bundles. Length and diameter distributions are recorded by SPM whereas the unbundling of the tubes is determined by absorption spectroscopy. Established methods from physical chemistry, such as laser desorption are currently being modified and studied as potential tools for generating beams of nanotubes in the mass range of around 50.000-100.000 amu. (author)

  5. Boron carbide nanolumps on carbon nanotubes

    Science.gov (United States)

    Lao, J. Y.; Li, W. Z.; Wen, J. G.; Ren, Z. F.

    2002-01-01

    Boron carbide nanolumps are formed on the surface of multiwall carbon nanotubes by a solid-state reaction between boron and carbon nanotubes. The reaction is localized so that the integrity of the structure of carbon nanotubes is maintained. Inner layers of multiwall carbon nanotubes are also bonded to boron carbide nanolumps. These multiwall carbon nanotubes with boron carbide nanolumps are expected to be the ideal reinforcing fillers for high-performance composites because of the favorable morphology.

  6. Breaking of Nanotube Symmetry by Substrate Polarization

    OpenAIRE

    Petrov, Alexey G.; Rotkin, Slava V.

    2003-01-01

    Substrate and nanotube polarization are shown to change qualitatively a nanotube bandstructure. The effect is studied in a linear approximation in an external potential which causes the changes. A work function difference between the nanotube and gold surface is estimated to be large enough to break the band symmetry and lift a degeneracy of a lowest but one subband of a metallic nanotube. This subband splitting for [10,10] nanotube is about 50 meV in absence of other external potential.

  7. The Hausdorff Dimension of Sections

    Institute of Scientific and Technical Information of China (English)

    Min NIU; Lifeng XI

    2007-01-01

    The notion of finite-type open set condition is defined to calculate the Hausdorff dimensions of the sections of some self-similar sets, such as the dimension of intersection of the Koch curve and the line x = a with a ∈(Q).

  8. Quantum scattering in one dimension

    Energy Technology Data Exchange (ETDEWEB)

    Barlette, Vania E. [Centro Universitario Franciscano, Santa Maria, RS (Brazil); Leite, Marcelo M. [Departamento de Fisica, Instituto Tecnologico de Aeronautica, Centro Tecnico Aeroespacial, Sao Jose dos Campos, SP (Brazil); Adhikari, Sadhan K. [Instituto de Fisica Teorica, Universidade Estadual Paulista, Sao Paulo, SP (Brazil)

    2000-09-01

    A self-contained discussion of non-relativistic quantum scattering is presented in the case of central potentials in one space dimension, which will facilitate the understanding of the more complex scattering theory in two and three dimensions. The present discussion illustrates in a simple way the concepts of partial-wave decomposition, phase shift, optical theorem and effective-range expansion. (author)

  9. The Hidden Dimensions of Art.

    Science.gov (United States)

    Klein, Bruce

    1982-01-01

    Describes an art program for preschool children that includes four social dimensions of art in order to heighten aesthetic perception, improve artistic creativity, and nurture self-esteem. The social dimensions are children having power, children acting on norms legitimate in their own eyes, children functioning "nonestrangedly," and children…

  10. How Many Dimensions are There?

    Science.gov (United States)

    Rowlands, Peter

    Dimensionality has been a much discussed subject since Minkowski formalized special relativity by extending 3D space to 4D space-time. However, there has never been any consensus on the number of dimensions that nature requires and there has been no explanation of why dimensions are needed at all. It is proposed here that dimensions originate in the theory of numbers, that extending the number of dimensions beyond the 3 required by Euclidean space necessarily requires a fundamental change in the meaning of the concept, and that, although various algebraic techniques allow such extension of dimensionality, the structures required always ensure that the number of dimensions and their fundamental characteristics remain ambiguous, leaving the final question unanswerable.

  11. Nanotube mechanical resonators with quality factors of up to 5 million

    OpenAIRE

    Moser, Joel; Eichler, Alexander; Güttinger, Johannes; Dykman, Mark I.; Bachtold, Adrian

    2015-01-01

    Carbon nanotube mechanical resonators have attracted considerable interest because of their small mass, the high quality of their surface, and the pristine electronic states they host. However, their small dimensions result in fragile vibrational states that are difficult to measure. Here we observe quality factors $Q$ as high as $5\\times10^6$ in ultra-clean nanotube resonators at a cryostat temperature of 30 mK, where we define $Q$ as the ratio of the resonant frequency over the linewidth. M...

  12. Nanoengineering of carbon nanotubes for nanotools

    International Nuclear Information System (INIS)

    We have developed a well controlled method for manipulating carbon nanotubes. The first crucial process involved is to prepare a nanotube array, named a nanotube cartridge. We have discovered ac electrophoresis of nanotubes by which nanotubes are aligned at the knife-edge. The nanotubes used were multiwalled and prepared by an arc discharge with a relatively high gas temperature. The second important process is to transfer a nanotube from the nanotube cartridge onto a substrate in a scanning electron microscope (SEM). Using this method, we have developed nanotube tips and nanotube tweezers that operate in a scanning probe microscope (SPM). The nanotube probes have been applied for the observation of biological samples and industrial samples to clarify their advantages. The nanotube tweezers have demonstrated their motion in an SEM and have operated to carry nanomaterials in a SPM. We have also developed the electron ablation of a nanotube to adjust its length and the sharpening of a multiwall nanotube to have its inner layer with or without an end cap at the tip. For the sharpening process, the free end of a nanotube protruding from the cartridge was attached to a metal-coated Si tip and a voltage was applied to the nanotube. When a high voltage was used in the saturation current regime, the current decreased stepwise in the temporal variation, indicating the sequential destruction of individual nanotube layers. The nanotube was finally cut at the middle of the nanotube bridge, and its tip was sharpened to have an inner layer with an opened end. Moving up the cartridge before cutting enables us to extract the inner layer with an end cap. It is evidenced that the maximum current in each layer during the stepwise decrease depends on its circumference, and the force for extracting the inner layer with ∼5-nm diameter is ∼4-nN

  13. Dimension of spatially embedded networks

    Science.gov (United States)

    Daqing, Li; Kosmidis, Kosmas; Bunde, Armin; Havlin, Shlomo

    2011-06-01

    The dimension of a system is one of the most fundamental quantities to characterize its structure and basic physical properties. Diffusion and vibrational excitations, for example, as well as the universal features of a system near a critical point depend crucially on its dimension. However, in the theory of complex networks the concept of dimension has been rarely discussed. Here we study models for spatially embedded networks and show how their dimension can be determined. Our results indicate that networks characterized by a broad distribution of link lengths have a dimension higher than that of the embedding space. We illustrate our findings using the global airline network and the Internet and argue that although these networks are embedded in two-dimensional space they should be regarded as systems with dimension close to 3 and 4.5, respectively. We show that the network dimension is a key concept to understand not only network topology, but also dynamical processes on networks, such as diffusion and critical phenomena including percolation.

  14. Carbon Nanotube Based Molecular Electronics

    Science.gov (United States)

    Srivastava, Deepak; Saini, Subhash; Menon, Madhu

    1998-01-01

    Carbon nanotubes and the nanotube heterojunctions have recently emerged as excellent candidates for nanoscale molecular electronic device components. Experimental measurements on the conductivity, rectifying behavior and conductivity-chirality correlation have also been made. While quasi-one dimensional simple heterojunctions between nanotubes with different electronic behavior can be generated by introduction of a pair of heptagon-pentagon defects in an otherwise all hexagon graphene sheet. Other complex 3- and 4-point junctions may require other mechanisms. Structural stability as well as local electronic density of states of various nanotube junctions are investigated using a generalized tight-binding molecular dynamics (GDBMD) scheme that incorporates non-orthogonality of the orbitals. The junctions investigated include straight and small angle heterojunctions of various chiralities and diameters; as well as more complex 'T' and 'Y' junctions which do not always obey the usual pentagon-heptagon pair rule. The study of local density of states (LDOS) reveal many interesting features, most prominent among them being the defect-induced states in the gap. The proposed three and four pointjunctions are one of the smallest possible tunnel junctions made entirely of carbon atoms. Furthermore the electronic behavior of the nanotube based device components can be taylored by doping with group III-V elements such as B and N, and BN nanotubes as a wide band gap semiconductor has also been realized in experiments. Structural properties of heteroatomic nanotubes comprising C, B and N will be discussed.

  15. Torsional Electromechanics of Carbon Nanotubes

    Science.gov (United States)

    Joselevich, Ernesto; Cohen-Karni, Tzahi; Segev, Lior; Srur-Lavi, Onit; Cohen, Sidney R.

    2007-03-01

    Carbon nanotubes are known to be distinctly metallic or semiconducting depending on their diameter and chirality. Here we show that continuously varying the chirality by mechanical torsion can induce conductance oscillations, which can be attributed to metal-semiconductor periodic transitions. The phenomenon is observed in multi-walled carbon nanotubes, where both the torque and the current are shown to be carried predominantly by the outermost wall. The oscillation period with torsion is consistent with the theoretical shifting of the corners of the first Brillouin zone of graphene across different subbands allowed in the nanotube. Beyond a critical torsion, the conductance irreversibly drops due to torsional failure, allowing us to determine the torsional strength of carbon nanotubes. Our experiments indicate that carbon nanotubes could be used as self-sensing torsional springs for nanoelectromechanical systems (NEMS). [1] E. Joselevich, Twisting nanotubes: From torsion to chirality, ChemPhysChem 2006, 7, 1405. [2] T. Cohen-Karni, L. Segev, O. Srur-Lavi, S. R. Cohen, E. Joselevich, Torsional electromechanical quantum oscillations in carbon nanotubes, Nature Nanotechnology, 2006, 1, 36.

  16. Multifractal characterization of single wall carbon nanotube thin films surface upon exposure to optical parametric oscillator laser irradiation

    International Nuclear Information System (INIS)

    This study presents a multifractal approach, obtained with atomic force microscopy analysis, to characterize the structural evolution of single wall carbon nanotube thin films upon exposure to optical parametric oscillator laser irradiation at wavelength of 430 nm. Microstructure and morphological changes of carbon nanotube films deposited on different substrates (mica and TGX grating) were recorded by atomic force microscope. A detailed methodology for surface multifractal characterization, which may be applied for atomic force microscopy data, was presented. Multifractal analysis of surface roughness revealed that carbon nanotube films surface has a multifractal geometry at various magnifications. The generalized dimension Dq and the singularity spectrum f(α) provided quantitative values that characterize the local scale properties of carbon nanotube films surface morphology at nanometer scale. Multifractal analysis provides different yet complementary information to that offered by traditional surface statistical parameters.

  17. Preimage entropy dimension of topological dynamical systems

    OpenAIRE

    Liu, Lei; Zhou, Xiaomin; Zhou, Xiaoyao

    2014-01-01

    We propose a new definition of preimage entropy dimension for continuous maps on compact metric spaces, investigate fundamental properties of the preimage entropy dimension, and compare the preimage entropy dimension with the topological entropy dimension. The defined preimage entropy dimension holds various basic properties of topological entropy dimension, for example, the preimage entropy dimension of a subsystem is bounded by that of the original system and topologically conjugated system...

  18. Black Holes in Higher Dimensions

    International Nuclear Information System (INIS)

    In four space-time dimensions black holes of Einstein-Maxwell theory satisfy a number of theorems. In more than four space-time dimensions, however, some of the properties of black holes can change. In particular, uniqueness of black holes no longer holds. In five and more dimensions black rings arise. Thus in a certain region of the phase diagram there are three black objects with the same global charges present. Here we discuss properties of higher-dimensional vacuum and charged black holes, which possess a spherical horizon topology, and of vacuum and charged black rings, which have a ringlike horizon topology

  19. Spectal dimension of fractal sets

    International Nuclear Information System (INIS)

    We consider an optimal partial covering of fractal sets in a two-dimensional space using ellipses which become increasingly anisotropic as their size is reduced: if the semi-minor axis is ϵ and the semi-major axis is δ, we set δ = ϵα, where 0 ∼εβ, where β is a generalized dimension. We term β the spectal dimension, because our covering strategy may be used to characterize specular light scattering from fractal sets. We investigate the function β(α) numerically for various sets, showing that it may be different for sets which have the same fractal dimension. (paper)

  20. Cohomological dimension of Markov compacta

    OpenAIRE

    Dranishnikov, Alexander

    2006-01-01

    We rephrase Gromov's definition of Markov compacta, introduce a subclass of Markov compacta defined by one building block and study cohomological dimensions of these compacta. We show that for a Markov compactum $X$, $\\dim_{\\Z_{(p)}}X=\\dim_{\\Q}X$ for all but finitely many primes $p$ where $\\Z_{(p)}$ is the localization of $\\Z$ at $p$. We construct Markov compacta of arbitrarily large dimension having $\\dim_{\\Q}X=1$ as well as Markov compacta of arbitrary large rational dimension with $\\dim_{\\...

  1. Wafer-level assembly of carbon nanotube networks using dielectrophoresis

    International Nuclear Information System (INIS)

    We use dielectrophoresis (DEP) to controllably and simultaneously assemble multiple carbon nanotube (CNT) networks at the wafer level. By an appropriate choice of electrode dimensions and geometry, an electric field is generated that captures CNTs from a sizable volume of suspension, resulting in good CNT network uniformity and alignment. During the DEP process, the electrical characteristics of the CNT network are measured and correlated with the network morphology. These experiments give novel insight into the physics of DEP assembly of CNT networks, and demonstrate the scalability of DEP for future device applications

  2. Nanotube electronics and optoelectronics

    Directory of Open Access Journals (Sweden)

    Phaedon Avouris

    2006-10-01

    Full Text Available Among the many materials that have been proposed to supplement and, in the long run, possibly succeed Si as a basis for nanoelectronics, carbon nanotubes (CNTs have attracted the most attention. CNTs are quasi-one-dimensional materials with unique properties ideally suited for electronics. We briefly discuss the electrical and optical properties of CNTs and how they can be employed in electronics and optoelectronics. We focus on single CNT transistors, their fabrication, assembly, doping, electrical characteristics, and integration. We also address the possible use of CNTs in optoelectronic devices such as electroluminescent light emitters and photodetectors.

  3. Electronic properties of nanotube junctions

    Science.gov (United States)

    Lambin, Ph.; Meunier, V.

    1998-08-01

    The possibility of realizing junctions between two different nanotubes has recently attracted a great interest, even though much remains to be done for putting this idea in concrete form. Pentagon-heptagon pair defects in the otherwise perfect graphitic network make such connections possible, with virtually infinite varieties. In this paper, the literature devoted to nanotube junctions is briefly reviewed. A special emphasize is put on the electronic properties of C nanotube junctions, together with an indication on how their current-voltage characteristics may look like.

  4. NASA Innovation Builds Better Nanotubes

    Science.gov (United States)

    2008-01-01

    Nanotailor Inc., based in Austin, Texas, licensed Goddard Space Flight Center's unique single-walled carbon nanotube (SWCNT) fabrication process with plans to make high-quality, low-cost SWCNTs available commercially. Carbon nanotubes are being used in a wide variety of applications, and NASA's improved production method will increase their applicability in medicine, microelectronics, advanced materials, and molecular containment. Nanotailor built and tested a prototype based on Goddard's process, and is using this technique to lower the cost and improve the integrity of nanotubes, offering a better product for use in biomaterials, advanced materials, space exploration, highway and building construction, and many other applications.

  5. A Periodic Table in Three Dimensions

    Science.gov (United States)

    Rosén, Arne

    Access to techniques to produce and characterize free clusters built up from two to thousands of atoms has during the last decades generated several exciting discoveries and established cluster science as a research field of its own. This field is highly interdisciplinary, and knowledge from different areas of physics and chemistry has been of considerable importance for this rapid development. One of the objectives is to gain an understanding of the material growth i. e. how many atoms are needed in a cluster to make its physical or chemical properties similar to what is known for the corresponding solid. Studies of various properties for some clusters have, however, revealed large fluctuations and periodicities which can be interpreted either as geometric or electronic shell closings, with the appearance of so-called magic numbers. This kind of periodicity is quite different from what is known from the periodic table in atomic physics but has some similarities with the magic numbers in nuclear physics. In addition to clusters characterized by shell structure, also very unique clusters exist such as the fullerenes, in particular Buckminsterfullerene or Ceo discovered in 1985, which was a new form of carbon different from the earlier known forms of graphite and diamond. The field of fullerenes has, especially, after the invention of a method for production of macroscopic amounts in 1990, developed in an extremely exciting way with several serendipitous advances including fabrication of crystals, films and new materials with unique properties such as the nanotubes, carbon onions and met cars. Many of these discoveries have opened up new areas of modern mesoscopic physics and materials science. Particularly interesting is how some data available for clusters and fullerenes show periodicities which might be classified in "A Periodic Table in Three Dimensions".

  6. Dimension reduction for $-\\Delta_1$

    OpenAIRE

    Amendola, Maria Emilia; Gargiulo, Giuliano; Zappale, Elvira

    2012-01-01

    A 3D-2D dimension reduction for $-\\Delta_1$ is obtained. A power law approximation from $-\\Delta_p$ as $p \\to 1$ in terms of $\\Gamma$- convergence, duality and asymptotics for least gradient functions has also been provided.

  7. Internal DLA in Higher Dimensions

    CERN Document Server

    Jerison, David; Sheffield, Scott

    2010-01-01

    Let A(t) denote the cluster produced by internal diffusion limited aggregation (internal DLA) with t particles in dimension d > 2. We show that A(t) is approximately spherical, up to an O(\\sqrt{\\log t}) error.

  8. Fractal dimensions of wildfire spreading

    OpenAIRE

    Wang, S.-L.; Lee, H.-I.; Li, S.-P.

    2014-01-01

    The time series data of 31 wildfires in 2012 in the US were analyzed. The fractal dimensions (FD) of the wildfires during spreading were studied and their geological features were identified. A growth model based on the cellular automata method is proposed here. Numerical study was performed and is shown to give good agreement with the fractal dimensions and scaling behaviors of the corresponding empirical data.

  9. Ethical dimension of scientific investigation

    OpenAIRE

    Antônio Joaquim Severino

    2014-01-01

    After emphasizing the growing concern about ethical issues related to scientific research involving human subjects by bodies responsible for the promotion of science in Brazil, this paper discusses the different perspectives under which relationships between ethics and production knowledge are established, highlighting the close connection of the ethical dimension to the political dimension, given the need for affirmation of otherness, for the presence of the other, so that one can discuss th...

  10. Carbon nanotube core graphitic shell hybrid fibers.

    Science.gov (United States)

    Hahm, Myung Gwan; Lee, Jae-Hwang; Hart, Amelia H C; Song, Sung Moo; Nam, Jaewook; Jung, Hyun Young; Hashim, Daniel Paul; Li, Bo; Narayanan, Tharangattu N; Park, Chi-Dong; Zhao, Yao; Vajtai, Robert; Kim, Yoong Ahm; Hayashi, Takuya; Ku, Bon-Cheol; Endo, Morinobu; Barrera, Enrique; Jung, Yung Joon; Thomas, Edwin L; Ajayan, Pulickel M

    2013-12-23

    A carbon nanotube yarn core graphitic shell hybrid fiber was fabricated via facile heat treatment of epoxy-based negative photoresist (SU-8) on carbon nanotube yarn. The effective encapsulation of carbon nanotube yarn in carbon fiber and a glassy carbon outer shell determines their physical properties. The higher electrical conductivity (than carbon fiber) of the carbon nanotube yarn overcomes the drawbacks of carbon fiber/glassy carbon, and the better properties (than carbon nanotubes) of the carbon fiber/glassy carbon make up for the lower thermal and mechanical properties of the carbon nanotube yarn via synergistic hybridization without any chemical doping and additional processes. PMID:24224730

  11. Effect of calcination temperature on the photocatalytic reduction and oxidation processes of hydrothermally synthesized titania nanotubes.

    Energy Technology Data Exchange (ETDEWEB)

    Viayan, B.; Dimitrijevic, N. M.; Rajh, T.; Gray, K.; Northwestern Univ.

    2010-08-05

    Titania nanotubes having diameters 8 to 12 nm and lengths of 50-300 nm were prepared using a hydrothermal method. Further, the titania nanotubes were calcined over the temperature range 200-800 C in order to enhance their photocatalytic properties by altering their morphology. The calcined titania nanotubes were characterized by using X-ray diffraction and surface area analysis and their morphological features were studied by scanning and transmission electron microscopy. Nanotubes calcined at 400 C showed the maximum extent of photocatalyitc reduction of carbon dioxide to methane, whereas samples calcined at 600 C produced maximum photocatalytic oxidation of acetaldehyde. Electron paramagnetic resonance (EPR) spectroscopy was used to interrogate the effects of nanotube structure on the charge separation and trapping as a function of calcination temperature. EPR results indicated that undercoordinated titania sites are associated with maximum CO{sub 2} reduction occurring in nanotubes calcined at 400 C. Despite the collapse of the nantube structure to form nanorods and the concomitant loss of surface area, the enhanced charge separation associated with increased crystallinity promoted high rates of oxidation of acetaldehyde in titania materials calcined at 600 C. These results illustrate that calcination temperature allows us to tune the morphological and surface features of the titania nanostructures for particular photocatalytic reactions.

  12. Variational Principles For BS Dimension of Subsets

    OpenAIRE

    Wang, Chenwei; Chen, Ercai

    2011-01-01

    We redefine BS-dimension for Caratheodory structure by packing method. We have the same dimension properties with respect to the cover method and check the Bowen's equation for the new dimension as well. Besides, we consider the relation between the new BS-dimension and upper and lower BS-density respectively. We extend the variational principles of entropy to BS dimension.

  13. Collider phenomenology for models of extra dimensions

    International Nuclear Information System (INIS)

    In this talk, we summarize the collider phenomenology and recent experimental results for various models of extra dimensions, including the large extra dimensions (ADD model), warped extra dimensions (Randall-Sundrum model), TeV-1-sized extra dimensions with gauge bosons in the bulk, universal extra dimensions, and an 5D SU(5) SUSY GUT model in AdS space. (author)

  14. Collider Phenomenology for models of extra dimensions

    OpenAIRE

    Cheung, Kingman

    2003-01-01

    In this talk, we summarize the collider phenomenology and recent experimental results for various models of extra dimensions, including the large extra dimensions (ADD model), warped extra dimensions (Randall-Sundrum model), TeV$^{-1}$-sized extra dimensions with gauge bosons in the bulk, universal extra dimensions, and an 5D SU(5) SUSY GUT model in AdS space.

  15. Studies of Carbon Nanotubes

    Science.gov (United States)

    Caneba, Gerard T.

    2005-01-01

    The fellowship experience for this summer for 2004 pertains to carbon nanotube coatings for various space-related applications. They involve the following projects: (a) EMI protection films from HiPco-polymers, and (b) Thermal protection nanosilica materials. EMI protection films are targeted to be eventually applied onto casings of laptop computers. These coatings are composites of electrically-conductive SWNTs and compatible polymers. The substrate polymer will be polycarbonate, since computer housings are typically made of carbon composites of this type of polymer. A new experimental copolymer was used last year to generate electrically-conductive and thermal films with HiPco at 50/50 wt/wt composition. This will be one of the possible formulations. Reference films will be base polycarbonate and neat HiPco onto polycarbonate films. Other coating materials that will be tried will be based on HiPco composites with commercial enamels (polyurethane, acrylic, polyester), which could be compatible with the polycarbonate substrate. Nanosilica fibers are planned for possible use as thermal protection tiles on the shuttle orbiter. Right now, microscale silica is used. Going to the nanoscale will increase the surface-volume-per-unit-area of radiative heat dissipation. Nanoscale carbon fibers/nanotubes can be used as templates for the generation of nanosilica. A sol-gel operation is employed for this purpose.

  16. Dimension-based statistical learning of vowels.

    Science.gov (United States)

    Liu, Ran; Holt, Lori L

    2015-12-01

    Speech perception depends on long-term representations that reflect regularities of the native language. However, listeners rapidly adapt when speech acoustics deviate from these regularities due to talker idiosyncrasies such as foreign accents and dialects. To better understand these dual aspects of speech perception, we probe native English listeners' baseline perceptual weighting of 2 acoustic dimensions (spectral quality and vowel duration) toward vowel categorization and examine how they subsequently adapt to an "artificial accent" that deviates from English norms in the correlation between the 2 dimensions. At baseline, listeners rely relatively more on spectral quality than vowel duration to signal vowel category, but duration nonetheless contributes. Upon encountering an "artificial accent" in which the spectral-duration correlation is perturbed relative to English language norms, listeners rapidly down-weight reliance on duration. Listeners exhibit this type of short-term statistical learning even in the context of nonwords, confirming that lexical information is not necessary to this form of adaptive plasticity in speech perception. Moreover, learning generalizes to both novel lexical contexts and acoustically distinct altered voices. These findings are discussed in the context of a mechanistic proposal for how supervised learning may contribute to this type of adaptive plasticity in speech perception. PMID:26280268

  17. Noble-Metal Chalcogenide Nanotubes

    Directory of Open Access Journals (Sweden)

    Nourdine Zibouche

    2014-10-01

    Full Text Available We explore the stability and the electronic properties of hypothetical noble-metal chalcogenide nanotubes PtS2, PtSe2, PdS2 and PdSe2 by means of density functional theory calculations. Our findings show that the strain energy decreases inverse quadratically with the tube diameter, as is typical for other nanotubes. Moreover, the strain energy is independent of the tube chirality and converges towards the same value for large diameters. The band-structure calculations show that all noble-metal chalcogenide nanotubes are indirect band gap semiconductors. The corresponding band gaps increase with the nanotube diameter rapidly approaching the respective pristine 2D monolayer limit.

  18. Quantum transport in carbon nanotubes

    DEFF Research Database (Denmark)

    Laird, Edward A.; Kuemmeth, Ferdinand; Steele, Gary A.;

    2015-01-01

    Carbon nanotubes are a versatile material in which many aspects of condensed matter physics come together. Recent discoveries, enabled by sophisticated fabrication, have uncovered new phenomena that completely change our understanding of transport in these devices, especially the role of the spin...... of Pauli blockade. This can be exploited to read out spin and valley qubits, and to measure the decay of these states through coupling to nuclear spins and phonons. A second unique property of carbon nanotubes is that the combination of valley freedom and electron-electron interactions in one...... and valley degrees of freedom. This review describes the modern understanding of transport through nanotube devices. Unlike conventional semiconductors, electrons in nanotubes have two angular momentum quantum numbers, arising from spin and from valley freedom. We focus on the interplay between the...

  19. Enhanced Carbon Nanotube Ultracapacitors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed innovation utilizes carbon nanotubes (CNTs) coated with pseudo-capacitive MnO2 material as nano-composite electrode and ionic electrolyte for the...

  20. Molybdenum Disulfide Sheathed Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Xu Chun SONG; Zhu De XU; Yi Fan ZHENG; Gui HAN; Bo LIU; Wei Xiang CHEN

    2004-01-01

    Single and double layered MoS2-coated multiwalled carbon nanotubes (MWCNs) were successfully prepared by pyrolyzing (NH4)2MoS4-coated multiwalled carbon nanotubes in an H2 atmosphere at 900℃. MoS2-coated MWCNs would be expected to have different tribological and mechanical properties compared to MoS2, so it may have potential applications in many fields.

  1. Selective functionalization of carbon nanotubes

    Science.gov (United States)

    Strano, Michael S. (Inventor); Usrey, Monica (Inventor); Barone, Paul (Inventor); Dyke, Christopher A. (Inventor); Tour, James M. (Inventor); Kittrell, W. Carter (Inventor); Hauge, Robert H. (Inventor); Smalley, Richard E. (Inventor)

    2009-01-01

    The present invention is directed toward methods of selectively functionalizing carbon nanotubes of a specific type or range of types, based on their electronic properties, using diazonium chemistry. The present invention is also directed toward methods of separating carbon nanotubes into populations of specific types or range(s) of types via selective functionalization and electrophoresis, and also to the novel compositions generated by such separations.

  2. Carbon nanotubes for coherent spintronics

    DEFF Research Database (Denmark)

    Kuemmeth, Ferdinand; Churchill, H O H; Herring, P K;

    2010-01-01

    Carbon nanotubes bridge the molecular and crystalline quantum worlds, and their extraordinary electronic, mechanical and optical properties have attracted enormous attention from a broad scientific community. We review the basic principles of fabricating spin-electronic devices based on individual......, electrically-gated carbon nanotubes, and present experimental efforts to understand their electronic and nuclear spin degrees of freedom, which in the future may enable quantum applications....

  3. Gold(I)-Alkanethiolate Nanotubes

    KAUST Repository

    Zhang, Yu Xin

    2009-12-28

    (Figure Presented) A solution approach to assembling Au(I) - alkanethiolates into nanotube structures at room temperature is presented, in which Au(I) cations and alkanethiolate ligands are coordinated into thin platelet forms that then evolve into an open tubular configuration (see figure). The organic-inorganic hybrid nature of the nanotubes, their ability to be modified, and their high stability make them of interest for practical applications. © 2009 WILEY-VCH Verlag GmbH & Co. KGaA.

  4. Kondo physics in carbon nanotubes

    OpenAIRE

    Nygard, Jesper; Cobden, David Henry; Lindelof, Poul Erik

    2000-01-01

    The connection of electrical leads to wire-like molecules is a logical step in the development of molecular electronics, but also allows studies of fundamental physics. For example, metallic carbon nanotubes are quantum wires that have been found to act as one-dimensional quantum dots, Luttinger-liquids, proximity-induced superconductors and ballistic and diffusive one-dimensional metals. Here we report that electrically-contacted single-wall nanotubes can serve as powerful probes of Kondo ph...

  5. Carbon nanotubes for coherent spintronics

    Directory of Open Access Journals (Sweden)

    F. Kuemmeth

    2010-03-01

    Full Text Available Carbon nanotubes bridge the molecular and crystalline quantum worlds, and their extraordinary electronic, mechanical and optical properties have attracted enormous attention from a broad scientific community. We review the basic principles of fabricating spin-electronic devices based on individual, electrically-gated carbon nanotubes, and present experimental efforts to understand their electronic and nuclear spin degrees of freedom, which in the future may enable quantum applications.

  6. CARBON NANOTUBES AND PHARMACEUTICAL APPLICATIONS

    OpenAIRE

    Ram Pavani; Kodithyala Vinay

    2011-01-01

    Carbon nanotubes (CNTs) are often described as a graphene sheet rolled up into the shape of a cylinder. These have fascinated scientists with their extraordinary properties. These compounds have become increasingly popular in various fields simply because of their small size and amazing optical, electric and magnetic properties when used alone or with additions of metals. Carbon nanotubes have potential therapeutic applications in the field of drug delivery, diagnostics, and biosensing. Funct...

  7. Atomistic simulations of the mechanical properties of 'super' carbon nanotubes

    International Nuclear Information System (INIS)

    The mechanical properties of the so-called 'super' carbon nanotubes (STs) are investigated using classical molecular dynamics simulations. The STs are built from single-walled carbon nanotubes (SWCNTs) connected by Y-like junctions forming an ordered carbon nanotube network that is then rolled into a seamless cylinder. We observed that the ST behaviour under tensile tests is similar to the one presented by fishing nets. This interesting behaviour provides a way to vary the accessible channels to the inner parts of STs by applying an external mechanical load. The Young's modulus is dependent on the ST chirality and it inversely varies with the ST radius. Smaller reduction of breaking strain values due to temperature increase is predicted for zigzag STs compared to SWCNTs. The results show that, for STs with radius ∼5 nm, the junctions between the constituent SWCNTs play an important role in the fracture process. The Young's modulus and tensile strength were estimated for hierarchical higher-order STs using scaling laws related to the ST fractal dimension. The obtained mechanical properties suggest that STs may be used in the development of new porous, flexible, and high-strength materials

  8. On Gorenstein projective, injective and flat dimensions

    DEFF Research Database (Denmark)

    Christensen, Lars Winther; Frankild, Anders Juel; Holm, Henrik Granau

    2006-01-01

    Gorenstein homological dimensions are refinements of the classical homological dimensions, and finiteness singles out modules with amenable properties reflecting those of modules over Gorenstein rings. As opposed to their classical counterparts, these dimensions do not immediately come with pract...

  9. The lattice dimension of a tree

    OpenAIRE

    Ovchinnikov, Sergei

    2004-01-01

    The lattice dimension of a graph G is the minimal dimension of a cubic lattice in which G can be isometrically embedded. We prove that the lattice dimension of a tree with n leaves is $\\lceil n/2 \\rceil$.

  10. The Fourier dimension is not finitely stable

    OpenAIRE

    Ekström, Fredrik

    2014-01-01

    The Fourier dimension is not in general stable under finite unions of sets. Moreover, the stability of the Fourier dimension on particular pairs of sets is independent from the stability of the compact Fourier dimension.

  11. Negative dimension in general and asymptotic topology

    OpenAIRE

    Maslov, V. P.

    2006-01-01

    We introduce the notion of negative topological dimension and the notion of weight for the asymptotic topological dimension. Quantizing of spaces of negative dimension is applied to linguistic statistics.

  12. On transfinite extension of asymptotic dimension

    OpenAIRE

    Radul, Taras

    2006-01-01

    We prove that a transfinite extension of asymptotic dimension asind is trivial. We introduce a transfinite extension of asymptotic dimension asdim and give an example of metric proper space which has transfinite infinite dimension.

  13. The Kodaira Dimension of Lefschetz Fibrations

    OpenAIRE

    Dorfmeister, Josef G.; Zhang, Weiyi

    2008-01-01

    In this note, we verify that the complex Kodaira dimension $\\kappa^h$ equals the symplectic Kodaira dimension $\\kappa^s$ for smooth 4-manifolds with complex and symplectic structures. We also calculate the Kodaira dimension for many Lefschetz fibrations.

  14. Symplectic 4-manifolds with Kodaira dimension zero

    OpenAIRE

    Li, Tian-Jun

    2006-01-01

    We discuss the notion of the Kodaira dimension for symplectic manifolds in dimension 4. In particular, we propose and partially verify Betti number bounds for symplectic 4-manifolds with Kodaira dimension zero.

  15. Hemocompatibility of titania nanotube arrays.

    Science.gov (United States)

    Smith, Barbara S; Yoriya, Sorachon; Grissom, Laura; Grimes, Craig A; Popat, Ketul C

    2010-11-01

    Hemocompatibility is a key consideration for the long-term success of blood contacting biomaterials; hence, there is a critical need to understand the physiological response elicited from blood/nano-biomaterial interactions. In this study, we have investigated the adsorption of key blood serum proteins, in vitro adhesion and activation of platelets, and clotting kinetics of whole blood on titania nanotube arrays. Previous studies have demonstrated improved mesenchymal stem cell functionality, osteoblast phenotypic behavior, localized drug delivery, and the production of endothelial cell ECM on titania nanotube arrays. Furthermore, these titania nanotube arrays have elicited minimal levels of monocyte activation and cytokine secretion, thus exhibiting a very low degree of immunogenicity. Titania nanotube arrays were fabricated using anodization technique and the surface morphology was examined through scanning electron microscopy (SEM). The crystalline phases were identified using glancing angled X-ray diffraction (GAXRD). Nanoindentation and scratch tests were used to characterize the mechanical properties of titania nanotube arrays. The adsorption of key blood proteins (albumin, fibrinogen, and immunoglobulin-g) was evaluated using a micro-BCA assay and X-ray photoelectron spectroscopy (XPS). The adhesion and activation of platelets was investigated using live-cell staining, MTT assay, and SEM. Whole blood clotting kinetics was evaluated by measuring the free hemoglobin concentration, and SEM was used to visualize the clot formation. Our results indicate increased blood serum protein adsorption, platelet adhesion and activation, and whole blood clotting kinetics on titania nanotube arrays. PMID:20629021

  16. Sensor and Macroelectronic Applications of C Nanotubes

    Science.gov (United States)

    Snow, Eric

    2004-03-01

    The unique structure of the SWNT produces near-ballistic electron transport and a high sensitivity to its local chemical environment. This combination of high electronic quality and chemical sensitivity forms the basis for a promising nanocomponent for electronic and sensor applications. In order to bypass the assembly problems associated with fabricating SWNT-based devices we utilize the interface properties of internanotube contacts. A strong van der Waals interaction between crossed SWNTs produces a high internanotube tunneling probability. We use this feature to form a new electronic material that is composed of an electrically interconnected network of C nanotubes. In such C nanotube networks (CNNs) the individual SWNTs are interwoven into a semiconducting film that is electrically continuous over macroscopic dimensions. Macroscopic CNN devices average the properties of many individual SWNTs and allow us to fabricate devices with high yield using conventional fabrication technology. For macroelectronic applications, CNNs can be fabricated into both n- and p-type thin-film transistors (TFTs) with a field-effect mobility an order of magnitude higher than commercial TFT materials. In addition, CNN TFTs have the advantage that they can be deposited at room temperature onto arbitrary substrates, including polymeric and flexible materials. For sensor applications we show that the adsorption of certain molecular analytes onto the surface of SWNTs perturbs their electronic properties to such a degree that CNN-based sensors can detect the presence of chemical warfare agents and other toxic chemicals with a sensitivity much higher than commercial chemical detectors. In addition, we can achieve a high degree of chemical specificity and additional gain in the sensor response by coating the SWNTs with a chemoselective polymer that concentrates the analyte of choice.

  17. Thermal and structural stability of single- and multi-walled carbon nanotubes up to 1800 °C in Argon studied by Raman spectroscopy and transmission electron microscopy

    International Nuclear Information System (INIS)

    Graphical abstract: Display Omitted Highlights: ► Structural stability of carbon nanotubes up to 1800 °C in Argon (∼0.05 MPa). ► Thorough TEM and Raman spectroscopy of as received and heat treated CNTs. ► Analyses on the extent of structural changes during high temperature exposure. ► Discussion on safe upper temperature limit for practical use of SWCNTs and MWCNTs. -- Abstract: Effect of high temperature exposure (up to 1800 °C) on morphology of single- and multi-walled carbon nanotubes in Argon atmosphere has been studied using Raman spectroscopy and transmission electron microscopy. Although, as received nanotubes contained irregular graphene layers and other structural defects, microscopic observations revealed that heat treatment in Argon reduced the defect density and helped proper alignment of graphene layers. Raman spectra of as received and heat treated nanotubes strongly reinforced the microscopic observations. While, D-band to G-band intensity ratio in Raman spectra of 1800 °C heat treated multiwalled nanotubes reduced by ∼43% over as received one, this ratio for heat treated singlewalled nanotubes was ∼27% lower than that of the untreated specimen. Present study suggested that although, multiwalled nanotubes were structurally stable up to 1800 °C in an inert atmosphere having only a few nano-scale defects, singlewalled nanotubes suffered considerable damage at 1800 °C due to much thinner dimension than the former.

  18. Probing Photosensitization by Functionalized Carbon Nanotubes

    Science.gov (United States)

    Carbon nanotubes (CNTs) photosensitize the production of reactive oxygen species that can damage organisms by biomembrane oxidation or mediate CNTs' environmental transformations. The photosensitized nature of derivatized carbon nanotubes from various synthetic methods, and thus ...

  19. Glucose oxidase immobilization onto carbon nanotube networking

    CERN Document Server

    Karachevtsev, V A; Zarudnev, E S; Karachevtsev, M V; Leontiev, V S; Linnik, A S; Lytvyn, O S; Plokhotnichenko, A M; Stepanian, S G

    2012-01-01

    When elaborating the biosensor based on single-walled carbon nanotubes (SWNTs), it is necessary to solve such an important problem as the immobilization of a target biomolecule on the nanotube surface. In this work, the enzyme (glucose oxidase (GOX)) was immobilized on the surface of a nanotube network, which was created by the deposition of nanotubes from their solution in 1,2-dichlorobenzene by the spray method. 1-Pyrenebutanoic acid succinimide ester (PSE) was used to form the molecular interface, the bifunctional molecule of which provides the covalent binding with the enzyme shell, and its other part (pyrene) is adsorbed onto the nanotube surface. First, the usage of such a molecular interface leaves out the direct adsorption of the enzyme (in this case, its activity decreases) onto the nanotube surface, and, second, it ensures the enzyme localization near the nanotube. The comparison of the resonance Raman (RR) spectrum of pristine nanotubes with their spectrum in the PSE environment evidences the creat...

  20. Oligomer functionalized nanotubes and composites formed therewith

    Science.gov (United States)

    Zettl, Alexander K; Sainsbury, Toby; Frechet, Jean M.J.

    2014-03-18

    Disclosed herein is a sequential functionalization methodology for the covalent modification of nanotubes with between one and four repeat units of a polymer. Covalent attachment of oligomer units to the surface of nanotubes results in oligomer units forming an organic sheath around the nanotubes, polymer-functionalized-nanotubes (P-NTs). P-NTs possess chemical functionality identical to that of the functionalizing polymer, and thus provide nanoscale scaffolds which may be readily dispersed within a monomer solution and participate in the polymerization reaction to form a polymer-nanotube/polymer composite. Formation of polymer in the presence of P-NTs leads to a uniform dispersion of nanotubes within the polymer matrix, in contrast to aggregated masses of nanotubes in the case of pristine-NTs. The covalent attachment of oligomeric units to the surface of nanotubes represents the formation of a functional nanoscale building block which can be readily dispersed and integrated within the polymer to form a novel composite material.

  1. Application of Thomas-Fermi model to fullerene molecule and nanotube

    Directory of Open Access Journals (Sweden)

    Kornyushin Yuri

    2007-01-01

    Full Text Available Semiclassical description, based on electrostatics and Thomas-Fermi model is applied here to calculate dimensions of the electronic shell of a fullerene molecule and a nanotube. The internal radius of the electronic shell of a fullerene molecule, calculated within the framework of the model is 0.2808 nm. The external radius is 0.4182 nm. The experimental values are 0.279 nm and 0.429 nm correspondingly. This shows that semiclassical approach provides rather good description of the dimensions of the electronic shell in a fullerene molecule. Two types of dipole oscillations in a fullerene molecule are considered and their frequencies are calculated. Similar calculations are performed for a nanotube also. For a nanotube with a radius of the cylinder of the ions, Rn = 0.7 nm, the internal radius of the electronic shell, calculated within the framework of the model is 0.577 nm. The external radius is 0.816 nm. Three types of dipole oscillations in nanotube are considered and their frequencies are calculated.

  2. Attachment of Gold Nanoparticles to Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Xi Cheng MA; Ning LUN; Shu Lin WEN

    2005-01-01

    Carbon nanotubes were initially chemically modified with an H2SO4-HNO3 treatment,and subsequently activated with Pd-Sn catalytic nuclei via a one-step activation approach. These activated nanotubes were used as precursors for obtaining gold nanoparticles-attached nanotubes via simple electroless plating. This approach provides an efficient method for attachment of metal nanostructures to carbon nanotubes. Such novel hybrid nanostructures are attractive for many applications.

  3. Formation and Structure of Boron Nitride Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Jiang ZHANG; Zongquan LI; Jin XU

    2005-01-01

    Boron nitride (BN) nanotubes were simply synthesized by heating well-mixed boric acid, urea and iron nitrate powders at 1000℃. A small amount of BN nanowires was also obtained in the resultants. The morphological and structural characters of the BN nanostructures were studied using transmission electron microscopy. Other novel BN nanostructures, such as Y-junction nanotubes and bamboo-like nanotubes, were simultaneously observed. The growth mechanism of the BN nanotubes was discussed briefly.

  4. Vibrational properties of carbon nanotubes and graphite

    OpenAIRE

    Maultzsch, Janina

    2004-01-01

    In dieser Arbeit werden die Phononen von Kohlenstoff-Nanotubes und Graphit untersucht. Kohlenstoff-Nanotubes sind quasi-eindimensionale Kristalle und bestehen aus einer oder mehreren Graphit-Ebenen, die zu einem Zylinder aufgerollt sind. Deshalb können in erster Näherung viele Eigenschaften der Nanotubes von Graphit hergeleitet werden, indem das Nanotube als ein schmales Rechteck aus Graphit mit periodischen Randbedingungen betrachtet wird. Die hier verwendeten experimentellen Methoden sind R...

  5. Study of Carbon Nanotube-Substrate Interaction

    OpenAIRE

    Soares, Jaqueline S.; Ado Jorio

    2012-01-01

    Environmental effects are very important in nanoscience and nanotechnology. This work reviews the importance of the substrate in single-wall carbon nanotube properties. Contact with a substrate can modify the nanotube properties, and such interactions have been broadly studied as either a negative aspect or a solution for developing carbon nanotube-based nanotechnologies. This paper discusses both theoretical and experimental studies where the interaction between the carbon nanotubes and the ...

  6. Epoxide composite materials with carbon nanotubes

    International Nuclear Information System (INIS)

    Methods of formation and physical properties of epoxide composite materials reinforced with carbon nanotubes are considered. An analogy is made between the relaxation properties of carbon nanotubes and macromolecules. The concentration dependences of the electrical conductivity of the epoxy polymers filled with single-walled and multi-walled carbon nanotubes are discussed. Modern views on the mechanism of reinforcement of polymers with nanotubes are outlined. The bibliography includes 143 references.

  7. Functionalization of Carbon Nanotubes

    Science.gov (United States)

    Khare, Bishun N. (Inventor); Meyyappan, Meyya (Inventor)

    2009-01-01

    Method and system for functionalizing a collection of carbon nanotubes (CNTs). A selected precursor gas (e.g., H2 or F2 or CnHm) is irradiated to provide a cold plasma of selected target species particles, such as atomic H or F, in a first chamber. The target species particles are d irected toward an array of CNTs located in a second chamber while suppressing transport of ultraviolet radiation to the second chamber. A CNT array is functionalized with the target species particles, at or below room temperature, to a point of saturation, in an exposure time interval no longer than about 30 sec. *Discrimination against non-target species is provided by (i) use of a target species having a lifetime that is much greater than a lifetime of a non-target species and/or (2) use of an applied magnetic field to discriminate between charged particle trajectories for target species and for non-target species.

  8. Carbon nanotube optical mirrors

    Science.gov (United States)

    Chen, Peter C.; Rabin, Douglas

    2015-01-01

    We report the fabrication of imaging quality optical mirrors with smooth surfaces using carbon nanotubes (CNT) embedded in an epoxy matrix. CNT/epoxy is a multifunctional composite material that has sensing capabilities and can be made to incorporate self-actuation. Moreover, as the precursor is a low density liquid, large and lightweight mirrors can be fabricated by processes such as replication, spincasting, and three-dimensional printing. Therefore, the technology holds promise for the development of a new generation of lightweight, compact "smart" telescope mirrors with figure sensing and active or adaptive figure control. We report on measurements made of optical and mechanical characteristics, active optics experiments, and numerical modeling. We discuss possible paths for future development.

  9. Carbon Nanotube Electron Gun

    Science.gov (United States)

    Nguyen, Cattien V. (Inventor); Ribaya, Bryan P. (Inventor)

    2013-01-01

    An electron gun, an electron source for an electron gun, an extractor for an electron gun, and a respective method for producing the electron gun, the electron source and the extractor are disclosed. Embodiments provide an electron source utilizing a carbon nanotube (CNT) bonded to a substrate for increased stability, reliability, and durability. An extractor with an aperture in a conductive material is used to extract electrons from the electron source, where the aperture may substantially align with the CNT of the electron source when the extractor and electron source are mated to form the electron gun. The electron source and extractor may have alignment features for aligning the electron source and the extractor, thereby bringing the aperture and CNT into substantial alignment when assembled. The alignment features may provide and maintain this alignment during operation to improve the field emission characteristics and overall system stability of the electron gun.

  10. Carbon nanotube biconvex microcavities

    Energy Technology Data Exchange (ETDEWEB)

    Butt, Haider, E-mail: h.butt@bham.ac.uk; Ahmed, Rajib [Nanotechnology Laboratory, School of Mechanical Engineering, University of Birmingham, Birmingham B15 2TT (United Kingdom); Yetisen, Ali K.; Yun, Seok Hyun [Harvard Medical School and Wellman Center for Photomedicine, Massachusetts General Hospital, 50 Blossom Street, Boston, Massachusetts 02114 (United States); Dai, Qing [National Center for Nanoscience and Technology, Beijing 100190 (China)

    2015-03-23

    Developing highly efficient microcavities with predictive narrow-band resonance frequencies using the least amount of material will allow the applications in nonlinear photonic devices. We have developed a microcavity array that comprised multi-walled carbon nanotubes (MWCNT) organized in a biconvex pattern. The finite element model allowed designing microcavity arrays with predictive transmission properties and assessing the effects of the microarray geometry. The microcavity array demonstrated negative index and produced high Q factors. 2–3 μm tall MWCNTs were patterned as biconvex microcavities, which were separated by 10 μm in an array. The microcavity was iridescent and had optical control over the diffracted elliptical patterns with a far-field pattern, whose properties were predicted by the model. It is anticipated that the MWCNT biconvex microcavities will have implications for the development of highly efficient lenses, metamaterial antennas, and photonic circuits.

  11. Reduced-Dimension Multiuser Detection

    CERN Document Server

    Xie, Yao; Goldsmith, Andrea

    2011-01-01

    We explore several reduced-dimension multiuser detection (RD-MUD) structures that significantly decrease the number of required correlation branches at the receiver front-end, while still achieving performance similar to that of the conventional matched-filter (MF) bank. RD-MUD exploits the fact that the number of active users is typically small relative to the total number of users in the system and relies on ideas of analog compressed sensing to reduce the number of correlators. We first develop a general framework for both linear and nonlinear RD-MUD detectors. We then present theoretical performance analysis for two specific detectors: the linear reduced-dimension decorrelating (RDD) detector, which combines subspace projection and thresholding to determine active users and sign detection for data recovery, and the nonlinear reduced-dimension decision-feedback (RDDF) detector, which combines decision-feedback orthogonal matching pursuit for active user detection and sign detection for data recovery. The t...

  12. Twist operators in higher dimensions

    CERN Document Server

    Hung, Ling-Yan; Smolkin, Michael

    2014-01-01

    We study twist operators in higher dimensional CFT's. In particular, we express their conformal dimension in terms of the energy density for the CFT in a particular thermal ensemble. We construct an expansion of the conformal dimension in power series around n=1, with n being replica parameter. We show that the coefficients in this expansion are determined by higher point correlations of the energy-momentum tensor. In particular, the first and second terms, i.e. the first and second derivatives of the scaling dimension, have a simple universal form. We test these results using holography and free field theory computations, finding agreement in both cases. We also consider the `operator product expansion' of spherical twist operators and finally, we examine the behaviour of correlators of twist operators with other operators in the limit n ->1.

  13. Physics with large extra dimensions

    CERN Document Server

    Antoniadis, Ignatios

    2004-01-01

    The recent understanding of string theory opens the possibility that the string scale can be as low as a few TeV. The apparent weakness of gravitational interactions can then be accounted by the existence of large internal dimensions, in the submillimeter region. Furthermore, our world must be confined to live on a brane transverse to these large dimensions, with which it interacts only gravitationally. In my lecture, I describe briefly this scenario which gives a new theoretical framework for solving the gauge hierarchy problem and the unification of all interactions. I also discuss its main properties and implications for observations at both future particle colliders, and in non-accelerator gravity experiments. Such effects are for instance the production of Kaluza-Klein resonances, graviton emission in the bulk of extra dimensions, and a radical change of gravitational forces in the submillimeter range.

  14. Correlated Electrons in Reduced Dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Bonesteel, Nicholas E [Florida State Univ., Tallahassee, FL (United States)

    2015-01-31

    This report summarizes the work accomplished under the support of US DOE grant # DE-FG02-97ER45639, "Correlated Electrons in Reduced Dimensions." The underlying hypothesis of the research supported by this grant has been that studying the unique behavior of correlated electrons in reduced dimensions can lead to new ways of understanding how matter can order and how it can potentially be used. The systems under study have included i) fractional quantum Hall matter, which is realized when electrons are confined to two-dimensions and placed in a strong magnetic field at low temperature, ii) one-dimensional chains of spins and exotic quasiparticle excitations of topologically ordered matter, and iii) electrons confined in effectively ``zero-dimensional" semiconductor quantum dots.

  15. Collider searches for extra dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Landsberg, Greg; /Brown U.

    2004-12-01

    Searches for extra spatial dimensions remain among the most popular new directions in our quest for physics beyond the Standard Model. High-energy collider experiments of the current decade should be able to find an ultimate answer to the question of their existence in a variety of models. Until the start of the LHC in a few years, the Tevatron will remain the key player in this quest. In this paper, we review the most recent results from the Tevatron on searches for large, TeV{sup -1}-size, and Randall-Sundrum extra spatial dimensions, which have reached a new level of sensitivity and currently probe the parameter space beyond the existing constraints. While no evidence for the existence of extra dimensions has been found so far, an exciting discovery might be just steps away.

  16. A six degree of freedom nanomanipulator design based on carbon nanotube bundles

    International Nuclear Information System (INIS)

    Scanning probe imaging and manipulation of matter is of crucial importance for nanoscale science and technology. However, its resolution and ability to manipulate matter at the atomic scale is limited by rather poor control over the fine structure of the probe. In the present paper, a strategy is proposed to construct a molecular nanomanipulator from ultrathin single-walled carbon nanotubes. Covalent modification of a nanotube cap at predetermined atomic sites makes the nanotube act as a support for a functional 'tooltip' molecule. Then, a small bundle of nanotubes (three or four) with aligned ends can act as an extremely high aspect ratio parallel nanomanipulator for a suspended molecule, where protraction or retraction of individual nanotubes results in controlled tilting of the tooltip in two dimensions. Together with the usual scanning probe microscopy three degrees of freedom and augmented with rotation of the system as a whole, the design offers six degrees of freedom for imaging and manipulation of matter with the precision and freedom so much needed for advanced nanotechnology. A similar design might be possible to implement with other high aspect ratio nanostructures, such as oxide nanowires.

  17. Enhanced wettability performance of ultrathin ZnO nanotubes by coupling morphology and size effects

    Science.gov (United States)

    Yang, Peihua; Wang, Kun; Liang, Zhiwen; Mai, Wenjie; Wang, Cheng-Xin; Xie, Weiguang; Liu, Pengyi; Zhang, Long; Cai, Xiang; Tan, Shaozao; Song, Jinhui

    2012-08-01

    In this work, we report on the detailed characterization and mechanism analysis of the improved wettability performance of a new type of ZnO nanostructure, the ultrathin ZnO nanotube, whose growth is induced by screw-dislocation. The newly discovered enhanced wettability properties are suggested to be caused by coupling the morphology and size effects of the nanostructured surface. These ultrathin nanotubes with low density and small dimension form a wet-hair-like hierarchical morphology, which shows a further improved superhydrophobic property with an 8.6 +/- 1.6° larger contact angle than that of ZnO nanorods due to the morphology effect. In addition, owing to the large surface to volume ratio and increased effective UV-irradiated area of the ultrathin tubular structure, the ZnO nanotubes exhibit ~5 times faster superhydrophobicity to superhydrophilicity conversion speed than nanorods under 254 nm UV illumination. Furthermore, UV light with a wavelength of 254 nm exhibits ~40 times faster wettability conversion speed for nanotubes than that of 365 nm, which is suggested to be a result of the band gap shift at the nanoscale. The combined advantages of enhanced superhydrophobicity, improved sensitivity, and faster conversion speed by coupling morphology and size effects of these ZnO nanotubes should give them broad applications in self-cleaning surfaces and wettability switches.

  18. Hybrid Composite of Polyaniline Containing Carbon Nanotube

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Carbon nanotube-polyaniline hybrid material was synthesized by emulsion polymerization in-situ. The morphology of hybrid material was studied by TEM and X-ray diffraction. The conductivity of nanocomposite increases with the increasing of carbon nanotube content because of the new conductivity passageways formed by carbon nanotubes.

  19. Synthesis and Application of Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    Qun Zeng; Zhenhua Li; Yuhong Zhou

    2006-01-01

    Owing to the unique structure, the superior physical and chemical properties, the super strong mechanical performances, and so on, carbon nanotubes have attracted the attention of researchers all over the world. In this article, the basic properties and the main production processes of carbon nanotubes are introduced in brief, and the progress of applied research for carbon nanotubes is reviewed.

  20. Computational Evidence for the Smallest Boron Nanotube

    Institute of Scientific and Technical Information of China (English)

    Xian Jie LIN; Dong Ju ZHANG; Cheng Bu LIU

    2006-01-01

    The structure of boron nanotubes (BNTs) was found not to be limited to hexagonal pyramidal structures. Based on density functional theory calculations we provided evidence for the smallest boron nanotube, a geometrical analog of the corresponding carbon nanotube. As shown by our calculations, the smallest BNT possesses highly structural, dynamical, and thermal stability, which should be interest for attempts at its synthesis.

  1. Nanotubes in Nanoelectronics: Transport, Growth and Modeling

    Science.gov (United States)

    Anantram, M.; Delzeit, Lance; Cassell, Alan; Han, Jie; Meyyappan, M.; Arnold, Jim (Technical Monitor)

    2001-01-01

    Carbon nanotube (CNT) baud nanotechnology appears to be promising for future Theoretical analysis and results for the ballistic current carrying capacity of nanotube wires am presented. Aspects of metal-nanotube coupling are examined. Results am also presented for chemical vapor deposition of CNT from hydrocarbon feedstock.

  2. Dispersions of Carbon nanotubes in Polymer Matrices

    Science.gov (United States)

    Wise, Kristopher Eric (Inventor); Park, Cheol (Inventor); Siochi, Emilie J. (Inventor); Harrison, Joycelyn S. (Inventor); Lillehei, Peter T. (Inventor); Lowther, Sharon E. (Inventor)

    2010-01-01

    Dispersions of carbon nanotubes exhibiting long term stability are based on a polymer matrix having moieties therein which are capable of a donor-acceptor complexation with carbon nanotubes. The carbon nanotubes are introduced into the polymer matrix and separated therein by standard means. Nanocomposites produced from these dispersions are useful in the fabrication of structures, e.g., lightweight aerospace structures.

  3. Quantum control in infinite dimensions

    CERN Document Server

    Karwowski, W; Karwowski, Witold

    2004-01-01

    Accurate control of quantum evolution is an essential requirement for quantum state engineering, laser chemistry, quantum information and quantum computing. Conditions of controllability for systems with a finite number of energy levels have been extensively studied. By contrast, results for controllability in infinite dimensions have been mostly negative, stating that full control cannot be achieved with a finite dimensional control Lie algebra. Here we show that by adding a discrete operation to a Lie algebra it is possible to obtain full control in infinite dimensions with a small number of control operators.

  4. The Territorial Dimensions of Education

    OpenAIRE

    Moore, Niamh; Ancien, Delphine

    2013-01-01

    The ‘Europe 2020 Strategy’ was issued in 2010 by the European Commission. This document constitutes a growth scheme for the decade 2010-2020 that aims to help the European Union to emerge from the current crisis through the so-called smart, sustainable and inclusive dimensions of growth. In this context, the basic aim of the SIESTA (“Spatial Indicators for a ‘Europe 2020 Strategy’ Territorial Analysis”) Project has been to illustrate the territorial dimension of the ‘Europe 2020 Strategy’. In...

  5. Hertz potentials in higher dimensions

    International Nuclear Information System (INIS)

    We generalise the Hertz potentials to all spacetime dimensions D ≥4 and to all antisymmetric tensor fields. We show that the Whittaker-Debye-Bromwich reduction of the Hertz potential can be successfully exploited in all dimensions and for all antisymmetric tensor fields if the underlying spacetime is a warped product manifold. We illustrate the Hertzian approach by constructing the multipole expansions of all antisymmetric tensor fields on a D-dimensional Schwarzschild solution. A no-hair theorem for the D-dimensional black holes follows from these multipole expansions. (author)

  6. Physics with large extra dimensions

    Indian Academy of Sciences (India)

    Ignatios Antoniadis

    2004-02-01

    The recent understanding of string theory opens the possibility that the string scale can be as low as a few TeV. The apparent weakness of gravitational interactions can then be accounted by the existence of large internal dimensions, in the sub-millimeter region. Furthermore, our world must be confined to live on a brane transverse to these large dimensions, with which it interacts only gravitationally. In my lecture, I describe briefly this scenario which gives a new theoretical framework for solving the gauge hierarchy problem and the unification of all interactions. I also discuss a minimal embedding of the standard model, gauge coupling unification and proton stability.

  7. Physics with large extra dimensions

    CERN Document Server

    Antoniadis, Ignatios

    2004-01-01

    A theory with such a mathematical beauty cannot be wrong: this was one of the main arguments in favor of string theory, which unifies all known physical theories of fundamental interactions in a single coherent description of the universe. But no one has ever observed strings, not even indirectly, neither the space of extra dimensions where they live. However, there is a hope that the “hidden”dimensions of string theory are much larger than what we thought in the past and they become within experimental reach in the near future, together with the strings themselves.

  8. Effect of the rheological properties of carbon nanotube dispersions on the processing and properties of transparent conductive electrodes.

    Science.gov (United States)

    Maillaud, Laurent; Poulin, Philippe; Pasquali, Matteo; Zakri, Cécile

    2015-06-01

    Transparent conductive films are made from aqueous surfactant stabilized dispersions of carbon nanotubes using an up-scalable rod coating method. The processability of the films is governed by the amount of surfactant which is shown to alter strongly the wetting and viscosity of the ink. The increase of viscosity results from surfactant mediated attractive interactions between the carbon nanotubes. Links between the formulation, ink rheological properties, and electro-optical properties of the films are determined. The provided guidelines are generalized and used to fabricate optimized electrodes using conductive polymers and carbon nanotubes. In these electrodes, the carbon nanotubes act as highly efficient viscosifiers that allow the optimized ink to be homogeneously spread using the rod coating method. From a general point of view and in contrast to previous studies, the CNTs are optimally used in the present approach as conductive additives for viscosity enhancements of electronic inks. PMID:25961667

  9. Characterization of X-ray charge neutralizer using carbon-nanotube field emitter

    Science.gov (United States)

    Okawaki, Shuhei; Abo, Satoshi; Wakaya, Fujio; Yamashita, Hayato; Abe, Masayuki; Takai, Mikio

    2016-06-01

    An X-ray charge neutralizer using a screen-printed carbon-nanotube field emitter is demonstrated to show the possibility of a large-area flat-panel charge neutralizer, although the device dimensions in the present work are not very large. The X-ray yields and spectra are characterized to estimate the ion generation rate as one of the figures of merit of neutralizers. Charge neutralization characteristics are measured and show good performance.

  10. The necessary length of carbon nanotubes required to optimize solar cells

    OpenAIRE

    Barghi Tirdad; Saeedi Mohammad; Vaezzadeh Majid; Sadeghi Mohammad

    2007-01-01

    Abstract Background In recent years scientists have been trying both to increase the efficiency of solar cells, whilst at the same time reducing dimensions and costs. Increases in efficiency have been brought about by implanting carbon nanotubes onto the surface of solar cells in order to reduce the reflection of sunrays, as well as through the insertion of polymeric arrays into the intrinsic layer for charge separation. Results The experimental results show power rising linearly for intrinsi...

  11. Angle-Dependent Electron Spectroscopy Studies of C60 Compounds and Carbon Nanotubes

    OpenAIRE

    Schiessling, Joachim

    2003-01-01

    Fullerenes have been shown to constitute a prototypical building block for truly nanometer-sized devices and exotic nanounit-based materials, e.g., high-temperature superconductors. This makes the detailed understanding of fullerene electronic states in compounds and at interfaces of primary importance, since the high symmetry of the molecule greatly simplifies the starting point of the analysis. Carbon nanotubes, which combine one macroscopic with two nanoscopic dimensions, are perhaps of e...

  12. Electrical transport measurements of individual bismuth nanowires and carbon nanotubes

    Science.gov (United States)

    Jang, Wan Young

    Nanostructures are defined by reducing dimensions. When the reduced size of materials is comparable to the Fermi wavelength, quantum size effect occurs. Dimensionality plays a critical role in determining the electronic properties of materials, because the density of states of materials is quite different. Nanowires have attracted much attention recently due to their fundamental interest and potential applications. A number of materials have been tried. Among them, bismuth has unique properties. Bismuth has the smallest effective mass as small as 0.001me. This small effective mass of Bi nanowires allows one to observe the quantum confinement effect easily. Also Bi nanowires are good candidates for a low-dimensional transport study due to long mean free path. Because of these remarkable properties of Bi nanowires, many efforts have been made to study Bi nanowires. However, because bismuth is extremely sensitive to the oxide, it is very difficult to make a reliable device. So far, array measurements of Bi nanowires have been reported. The study is focused on the synthesis and electric transport measurements of individual Bi nanowires. Bi nanowires are synthesized by electrodeposition using either anodic aluminum oxide (AAO) templates or commercially available track etched polycarbonate membranes (PCTE). The desired nanowire has a heterostructure of Au - Bi - Au. Au wires on both sides serve as contact electrodes with Bi. To extract nanowires from PCTE or AAO, several attempts have been made. Devices consisting of single Bi nanowires grown by hydrothermal method are fabricated and electrical measurements have been carried out after in-situ deposition of Pt electrodes. The temperature dependence of resistance of majority of nanowires increases with decreasing temperature, showing polycrystalline nature of nanowires. However, some nanowires show resistance peaks at low temperature, suggesting quantum size effect (QSE). Magnetoresistance (MR) has also been measured. We

  13. BOOK REVIEW: Quantum Physics in One Dimension

    Science.gov (United States)

    Logan, David

    2004-05-01

    To a casual ostrich the world of quantum physics in one dimension may sound a little one-dimensional, suitable perhaps for those with an unhealthy obsession for the esoteric. Nothing of course could be further from the truth. The field is remarkably rich and broad, and for more than fifty years has thrown up innumerable challenges. Theorists, realising that the role of interactions in 1D is special and that well known paradigms of higher dimensions (Fermi liquid theory for example) no longer apply, took up the challenge of developing new concepts and techniques to understand the undoubted pecularities of one-dimensional systems. And experimentalists have succeeded in turning pipe dreams into reality, producing an impressive and ever increasing array of experimental realizations of 1D systems, from the molecular to the mesoscopic---spin and ladder compounds, organic superconductors, carbon nanotubes, quantum wires, Josephson junction arrays and so on. Many books on the theory of one-dimensional systems are however written by experts for experts, and tend as such to leave the non-specialist a touch bewildered. This is understandable on both fronts, for the underlying theoretical techniques are unquestionably sophisticated and not usually part of standard courses in many-body theory. A brave author it is then who aims to produce a well rounded, if necessarily partial, overview of quantum physics in one dimension, accessible to a beginner yet taking them to the edge of current research, and providing en route a thorough grounding in the fundamental ideas, basic methods and essential phenomenology of the field. It is of course the brave who succeed in this world, and Thierry Giamarchi does just that with this excellent book, written by an expert for the uninitiated. Aimed in particular at graduate students in theoretical condensed matter physics, and assumimg little theoretical background on the part of the reader (well just a little), Giamarchi writes in a refreshingly

  14. Influence of sterilization methods on cell behavior and functionality of osteoblasts cultured on TiO2 nanotubes

    International Nuclear Information System (INIS)

    We investigated the adhesion, proliferation and osteogenic functionality of osteoblasts cultured on titanium dioxide (TiO2) nanotubes in response to different sterilization methods (dry autoclaving vs. wet autoclaving). We prepared various sizes (30-100 nm diameter) of TiO2 nanotubes on titanium substrates by anodization, sterilized nanotubes by different conditions, and seeded osteoblast cells onto the nanotube surfaces with two different cell seeding densities (10,000 vs. 50,000 cells/well in 12-culture well). The result of this study indicates that the adhesion, proliferation and alkaline phosphatase activity of osteoblasts cultured on only the larger 70 and 100 nm TiO2 nanotube arrays were dramatically changed by the different sterilization conditions at a low cell seeding density. However, with a higher cell seeding density (50,000 cells/well in 12-cell culture well), the results revealed no significant difference among altered nanotube geometry, 30-100 nm diameters, nor sterilization methods. Next, it was revealed that the nanofeatures of proteins adhered on nanotubular TiO2 morphology are altered by the sterilization method. It was determined that this protein adhesion effect, in combination with the cell density of osteoblasts seeded onto such TiO2 nanotube surfaces, has profound effects on cell behavior. This study clearly shows that these are some of the important in vitro culture factors that need to be taken into consideration, as well as TiO2 nanotube diameters which play an important role in the improvement of cell behavior and functionality.

  15. Graphene: carbon in two dimensions

    Directory of Open Access Journals (Sweden)

    Mikhail I. Katsnelson

    2007-01-01

    Full Text Available Carbon is one of the most intriguing elements in the Periodic Table. It forms many allotropes, some known from ancient times (diamond and graphite and some discovered 10-20 years ago (fullerenes and nanotubes. Interestingly, the two-dimensional form (graphene was only obtained very recently, immediately attracting a great deal of attention. Electrons in graphene, obeying a linear dispersion relation, behave like massless relativistic particles. This results in the observation of a number of very peculiar electronic properties – from an anomalous quantum Hall effect to the absence of localization – in this, the first two-dimensional material. It also provides a bridge between condensed matter physics and quantum electrodynamics, and opens new perspectives for carbon-based electronics.

  16. Conductivity of transparent electrodes made from interacting nanotubes

    Science.gov (United States)

    Maillaud, Laurent; Zakri, Cécile; Ly, Isabelle; Pénicaud, Alain; Poulin, Philippe

    2013-12-01

    Interactions in carbon nanotube (CNT) dispersions alter the morphology of films made from such dispersions. Weak attractive interactions induce an enhancement of the electrical conductivity. This phenomenon is observed in thin films that lie in a near percolated regime. Strong interactions instead induce a decrease of conductivity. In spite of strong morphological differences, the conductivity of thick films, away from percolated regimes, do not depend on interactions between the CNTs. These experiments support a recent theoretical scenario of the percolation of interacting rods and provide guidance for the optimal formulations of CNT inks in transparent electrode applications.

  17. Massive Gravity in Three Dimensions

    CERN Document Server

    Bergshoeff, Eric A; Townsend, Paul K

    2009-01-01

    A particular higher-derivative extension of the Einstein-Hilbert action in three spacetime dimensions is shown to be equivalent at the linearized level to the (unitary) Pauli-Fierz action for a massive spin-2 field. We discuss the extension to massive ${\\cal N}$-extended supergravity, and we present a `cosmological' extension admitting a supersymmetric anti-de Sitter vacuum.

  18. Selfdual Substitutions in Dimension One

    CERN Document Server

    Berthé, Valérie; Sirvent, Victor

    2011-01-01

    There are several notions of the 'dual' of a word/tile substitution. We show that the most common ones are equivalent for substitutions in dimension one, where we restrict ourselves to the case of two letters/tiles. Furthermore, we obtain necessary and sufficient arithmetic conditions for substitutions being selfdual in this case.

  19. Quantum Gravity in Two Dimensions

    DEFF Research Database (Denmark)

    Ipsen, Asger Cronberg

    The topic of this thesis is quantum gravity in 1 + 1 dimensions. We will focus on two formalisms, namely Causal Dynamical Triangulations (CDT) and Dy- namical Triangulations (DT). Both theories regularize the gravity path integral as a sum over triangulations. The difference lies in the class...

  20. A small dimension intraoperative probe

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    This article introduces the usage of the intraoperative probe in surgical based on RGS and proposes one method to design the probe. Also, a charge-sensitive preamplifier used in semiconductor detector was constructed which can reduce the dimension of the probe. At last the probe is tested by some animal experiments. Results showed that the property of this system are reliable.

  1. The Ethical Dimension of Innovation

    DEFF Research Database (Denmark)

    Nogueira, Leticia Antunes; Nogueira, Tadeu Fernando

    2014-01-01

    The view of innovation as a positive concept has been deeply rooted in business and academic cultures ever since Schumpeter coined the concept of creative destruction. Even though there is a large body of literature on innovation studies, limited attention has been given to its ethical dimension...

  2. Correlation Dimension Estimation for Classification

    Czech Academy of Sciences Publication Activity Database

    Jiřina, Marcel; Jiřina jr., M.

    2006-01-01

    Roč. 1, č. 3 (2006), s. 547-557. ISSN 1895-8648 R&D Projects: GA MŠk(CZ) 1M0567 Institutional research plan: CEZ:AV0Z10300504 Keywords : correlation dimension * probability density estimation * classification * UCI MLR Subject RIV: BA - General Mathematics

  3. Massive Gravity in Three Dimensions

    NARCIS (Netherlands)

    Bergshoeff, Eric A.; Hohm, Olaf; Townsend, Paul K.

    2009-01-01

    A particular higher-derivative extension of the Einstein-Hilbert action in three spacetime dimensions is shown to be equivalent at the linearized level to the (unitary) Pauli-Fierz action for a massive spin-2 field. A more general model, which also includes "topologically-massive" gravity as a speci

  4. The Dimensions of Residential Segregation.

    Science.gov (United States)

    Massey, Douglas S.; Denton, Nancy A.

    1988-01-01

    Evaluates 20 potential indicators of residential segregation using census data on Hispanics, Blacks, Asians, and non-Hispanic Whites in 60 U.S. metropolitan areas. Factor-analyzes the results to select a single best indicator for each of five dimensions of residential segregation. Contains 69 references and 22 statistical formulas. (SV)

  5. Competitive dimensions of human resources

    Directory of Open Access Journals (Sweden)

    Neykova Rumyana Mykolaivna

    2015-02-01

    Full Text Available This article deals with the essence of human resources competitive dimensions. Their competitive priorities are analyzed in dynamic business environment, with an emphasis on the quality of human resources, their adaptive skills, communication skills and mobility. The attention is paid to the role behavior of personnel and the policies for its management in the context of cutting down management costs.

  6. Competitive dimensions of human resources

    OpenAIRE

    Neykova Rumyana Mykolaivna; Prokopenko Olha Volodymyrіvna; Shcherbachenko Viktoriia Oleksiivna

    2015-01-01

    This article deals with the essence of human resources competitive dimensions. Their competitive priorities are analyzed in dynamic business environment, with an emphasis on the quality of human resources, their adaptive skills, communication skills and mobility. The attention is paid to the role behavior of personnel and the policies for its management in the context of cutting down management costs.

  7. Manual tracking in three dimensions.

    NARCIS (Netherlands)

    Mrotek, L.A.; Gielen, C.C.A.M.; Flanders, M.

    2006-01-01

    Little is known about the manual tracking of targets that move in three dimensions. In the present study, human subjects followed, with the tip of a hand-held pen, a virtual target moving four times (period 5 s) around a novel, unseen path. Two basic types of target paths were used: a peanut-shaped

  8. The European Dimension in Education.

    Science.gov (United States)

    Council of Europe, Strasbourg (France). Directorate of Education, Culture and Sport, Documentation Section.

    This paper addresses concerns about a European dimension in education that has been created by the enlargement of the European Union (EU) (the inclusion of Austria, Finland, and Sweden) and the gradual transformations of institutions into a future federal state. Sections of the paper include: (1) "Introduction"; (2) "Defining the European…

  9. String theory in four dimensions

    CERN Document Server

    1988-01-01

    ``String Theory in Four Dimensions'' contains a representative collection of papers dealing with various aspects of string phenomenology, including compactifications on smooth manifolds and more general conformal field theories. Together with the lucid introduction by M. Dine, this material gives the reader a good working knowledge of our present ideas for connecting string theory to nature.

  10. Representation dimension for Hopf actions

    Institute of Scientific and Technical Information of China (English)

    SUN JuXiang; LIU GongXiang

    2012-01-01

    Let H be a finite-dimensional Hopf algebra and assume that both H and H* are semisimple.The main result of this paper is to show that the representation dimension is an invariant under cleft extensions of H,that is,rep.dim(A) =rep.dim(A#σH).Some of the applications of this equality are also given.

  11. The Hidden Dimensions of Databases.

    Science.gov (United States)

    Jacso, Peter

    1994-01-01

    Discusses methods of evaluating commercial online databases and provides examples that illustrate their hidden dimensions. Topics addressed include size, including the number of records or the number of titles; the number of years covered; and the frequency of updates. Comparisons of Readers' Guide Abstracts and Magazine Article Summaries are…

  12. Correlation Dimension-Based Classifier

    Czech Academy of Sciences Publication Activity Database

    Jiřina, Marcel; Jiřina jr., M.

    2014-01-01

    Roč. 44, č. 12 (2014), s. 2253-2263. ISSN 2168-2267 R&D Projects: GA MŠk(CZ) LG12020 Institutional support: RVO:67985807 Keywords : classifier * multidimensional data * correlation dimension * scaling exponent * polynomial expansion Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 3.469, year: 2014

  13. Extra dimensions round the corner?

    International Nuclear Information System (INIS)

    How many dimensions are we living in? This question is fundamental and yet, astonishingly, it remains unresolved. Of course, on the everyday level it appears that we are living in four dimensions three space plus one time dimension. But in recent months theoretical physicists have discovered that collisions between high-energy particles at accelerators may reveal the presence of extra space-time dimensions. On scales where we can measure the acceleration of falling objects due to gravity or study the orbital motion of planets or satellites, the gravitational force seems to be described by a 1/r2 law. The most sensitive direct tests of the gravitational law are based on torsion-balance experiments that were first performed by Henry Cavendish in 1798. However, the smallest scales on which this type of experiment can be performed are roughly 1 mm (see J C Long, H W Chan and J C Price 1999 Nucl. Phys. B 539 23). At smaller distances, objects could be gravitating in five or more dimensions that are rolled up or ''compactified'' - an idea that is bread-and-butter to string theorists. Most string theorists however believe that the gravitational effects of compact extra dimensions are too small to be observed. Now Nima Arkani-Hamed from the Stanford Linear Accelerator Center (SLAC) in the US, Savas Dimopoulos at Stanford University and Gia Dvali, who is now at New York University, suggest differently (Phys. Lett. B 1998 429 263). They advanced earlier ideas from string theory in which the strong, weak and electromagnetic forces are confined to membranes, like dirt particles trapped in soap bubbles, while the gravitational force operates in the entire higher-dimensional volume. In their theory extra dimensions should have observable effects inside particle colliders such as the Tevatron accelerator at Fermilab in the US or at the future Large Hadron Collider at CERN. The effect will show up as an excess of events in which a single jet of particles is produced with no

  14. Gears Based on Carbon Nanotubes

    Science.gov (United States)

    Jaffe, Richard; Han, Jie; Globus, Al; Deardorff, Glenn

    2005-01-01

    Gears based on carbon nanotubes (see figure) have been proposed as components of an emerging generation of molecular- scale machines and sensors. In comparison with previously proposed nanogears based on diamondoid and fullerene molecules, the nanotube-based gears would have simpler structures and are more likely to be realizable by practical fabrication processes. The impetus for the practical development of carbon-nanotube- based gears arises, in part, from rapid recent progress in the fabrication of carbon nanotubes with prescribed diameters, lengths, chiralities, and numbers of concentric shells. The shafts of the proposed gears would be made from multiwalled carbon nanotubes. The gear teeth would be rigid molecules (typically, benzyne molecules), bonded to the nanotube shafts at atomically precise positions. For fabrication, it may be possible to position the molecular teeth by use of scanning tunneling microscopy (STM) or other related techniques. The capability to position individual organic molecules at room temperature by use of an STM tip has already been demonstrated. Routes to the chemical synthesis of carbon-nanotube-based gears are also under investigation. Chemical and physical aspects of the synthesis of molecular scale gears based on carbon nanotubes and related molecules, and dynamical properties of nanotube- based gears, have been investigated by computational simulations using established methods of quantum chemistry and molecular dynamics. Several particularly interesting and useful conclusions have been drawn from the dynamical simulations performed thus far: The forces acting on the gears would be more sensitive to local molecular motions than to gross mechanical motions of the overall gears. Although no breakage of teeth or of chemical bonds is expected at temperatures up to at least 3,000 K, the gears would not work well at temperatures above a critical range from about 600 to about 1,000 K. Gear temperature could probably be controlled by

  15. ICTP lectures on large extra dimensions

    International Nuclear Information System (INIS)

    I give a brief and elementary introduction to braneworld models with large extra dimensions. Three conceptually distinct scenarios are outlined: (i) Large compact extra dimensions; (ii) Warped extra dimensions; (iii) Infinite volume extra dimensions. As an example I discuss in detail an application of (iii) to the late-time cosmology and acceleration problem of the Universe. (author)

  16. Roping and wrapping carbon nanotubes

    Science.gov (United States)

    Ausman, Kevin D.; O'Connell, Michael J.; Boul, Peter; Ericson, Lars M.; Casavant, Michael J.; Walters, Deron A.; Huffman, Chad; Saini, Rajesh; Wang, Yuhuang; Haroz, Erik; Billups, Edward W.; Smalley, Richard E.

    2001-11-01

    Single-walled carbon nanotubes can be dispersed into solvents by ultrasonication to the point that primarily individual tubes, cut to a few hundred nanometers in length, are present. However, when such dispersions are filtered to a thick mat, or paper, only tangles of uniform, seemingly endless ropes are observed. The factors contributing to this "roping" phenomenon, akin to aggregation or crystallization, will be discussed. We have developed methods for generating "super-ropes" more than twenty times the diameter of those formed by filtration, involving the extraction of nanotube material from an oleum dispersion. Nanotubes have been solubilized in water, largely individually, by non-covalently wrapping them with linear polymers. The general thermodynamic drive for this wrapping involves the polymer disrupting both the hydrophobic interface with water and the smooth tube-tube interaction in aggregates. The nanotubes can be recovered from their polymeric wrapping by changing their solvent system. This solubilization process opens the door to solution chemistry on pristine nanotubes, as well as their introduction into biologically relevant systems.

  17. Novel nanotubes and encapsulated nanowires

    International Nuclear Information System (INIS)

    Carbon nanotubes, with or without encapsulated material, generated by arcdischarge and electrolytic techniques have been studied. Microcrystals of refractory carbides (i.e. NbC, TaC, MoC), contained in nanotubes and polyhedral particles, produced by arcing electrodes of graphite/metal mixtures, were analysed by high resolution transmission electron microscopy (HRTEM) and X-ray powder diffraction. Encapsulation of MoC was found to give rise to an unusual stable form, namely face-centered-cubic MoC. SQUID measurements indicate that the encapsulated carbides exhibit superconducting transitions at about 10-12 K, thus they differ from carbon nanotubes/nanoparticles which do not superconduct. Four-probe and microwave (contactless) conductivity measurements indicate that most of the analysed samples behave as semiconductors. However, metallic transport was observed in specimens containing single conglomerated carbon nanotube bundles and boron-doped carbon nanotubes. Novel metallic βSn nanowires were produced by electrolysis of graphite electrodes immersed in molten LiCl/SnCl2 mixtures. Prolonged electron irradiation of these nanowiresleads to axial growth and to dynamic transformations. These observations suggest ways in which materials may be modified by microencapsulation and irradiation. (orig.)

  18. Novel nanotubes and encapsulated nanowires

    Science.gov (United States)

    Terrones, M.; Hsu, W. K.; Schilder, A.; Terrones, H.; Grobert, N.; Hare, J. P.; Zhu, Y. Q.; Schwoerer, M.; Prassides, K.; Kroto, H. W.; Walton, D. R. M.

    Carbon nanotubes, with or without encapsulated material, generated by arc discharge and electrolytic techniques have been studied. Microcrystals of refractory carbides (i.e. NbC, TaC, MoC), contained in nanotubes and polyhedral particles, produced by arcing electrodes of graphite/metal mixtures, were analysed by high hesolution transmission electron microscopy (HRTEM) and X-ray powder diffraction. Encapsulation of MoC was found to give rise to an unusual stable form, namely face-centered-cubic MoC. SQUID measurements indicate that the encapsulated carbides exhibit superconducting transitions at about 10-12 K, thus they differ from carbon nanotubes/nanoparticles which do not superconduct. Four-probe and microwave (contactless) conductivity measurements indicate that most of the analysed samples behave as semiconductors. However, metallic transport was observed in specimens containing single conglomerated carbon nanotube bundles and boron-doped carbon nanotubes. Novel metallic βSn nanowires were produced by electrolysis of graphite electrodes immersed in molten LiCl/SnCl2 mixtures. Prolonged electron irradiation of these nanowires leads to axial growth and to dynamic transformations. These observations suggest ways in which materials may be modified by microencapsulation and irradiation.

  19. Nanomechanical Energy Storage in Twisted Nanotube Ropes

    Science.gov (United States)

    Teich, David; Fthenakis, Zacharias G.; Seifert, Gotthard; Tománek, David

    2012-12-01

    We determine the deformation energetics and energy density of twisted carbon nanotubes and nanotube ropes that effectively constitute a torsional spring. Using ab initio and parametrized density functional calculations, we identify structural changes in these systems and determine their elastic limits. The deformation energy of twisted nanotube ropes contains contributions associated not only with twisting but also with stretching, bending, and compression of individual nanotubes. We quantify these energy contributions and show that their relative role changes with the number of nanotubes in the rope.

  20. Electrostatics of straight and bent nanotubes

    OpenAIRE

    Mishchenko, E. G.; Raikh, M. E.

    2005-01-01

    Response of a single-walled carbon nanotube to external electric field, F, is calculated analytically within the classical electrostatics. Field-induced charge density distribution is approximately linear along the axis of metallic nanotube and depends rather weakly, as ln(h/r), on the nanotube length, h, (here r is the nanotube radius). In a semiconducting nanotube with a gap, E_g, charge separation occurs as F exceeds the threshold value F_{th}=E_g/eh. For F>F_{th}, positively and negativel...

  1. ZnO-CNT composite nanotubes as nanoresonators

    International Nuclear Information System (INIS)

    This Letter reports the very first vibration analysis of the novel composite nanotubes (NTs) synthesized by coating carbon nanotubes (CNTs) with piezoelectric zinc oxide (ZnO). Timoshenko beam theory was used and modified to account for the interlayer van der Waals (vdW) interaction in the inner CNT and hybrid structures of the NTs. The distinctive vibration behaviours of the NTs were captured and the physics behind these unique features was investigated in terms of the critical role of the vdW interaction and the effect of the ZnO coating layer on the structural rigidity of the NTs. The composite NTs are found to be promising for gigahertz/terahertz electromechanical nanoresonators whose frequency can be even higher than that of the core CNTs. -- Highlights: → A model is developed for the vibration of novel ZnO-CNT composite nanotubes (NTs). → ZnO changes the frequency of NTs by altering its bending rigidity and mass inertia. → The van der Waals force in CNTs raises the frequency of core SWCNT up to terahertz. → The composite NTs are promising for high-frequency piezoelectric nanoresonators.

  2. Fibroblast functionality on novel Ti-30Ta nanotube array

    International Nuclear Information System (INIS)

    In this study, the mechanical substrate and topographical surface properties of anodized Ti-30Ta alloy were investigated using scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS) and contact angle measurement. The anodization process was performed in an electrolyte solution containing HF (48%) and H2SO4 (98%) in the volumetric ratios 1:9 with the addition of 5% dimethyl sulfoxide (DMSO) at 15 V, 25 V and 35 V for 20 and 40 min, producing a nanotube architecture when anodized at 35 V for 40 min. Human dermal fibroblasts (HDF, neonatal) were utilized to evaluate the biocompatibility of Ti-30Ta nanotubes and Ti-30Ta alloy after 1 and 3 days of culture. Cellular adhesion, proliferation, viability, cytoskeletal organization and morphology were investigated using fluorescence microscope imaging, biochemical assay and SEM imaging respectively. The results presented identify altered material properties and improved cellular interaction on Ti-30Ta nanotubes as compared to Ti-30 Ta alloy. - Highlights: ► The surface was modified by anodization, biomimetic treatment and ion bean etching. ► SEM, EDS and contact angle measurements were used to characterize the surface. ► Group 5 the most hydrophobic. ► Group 4 the most hydrophilic. ► Group 3 and 4 are the more indicated for biomedical application.

  3. Growing carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Yoshinori Ando

    2004-10-01

    Full Text Available The discovery of ‘fullerenes’ added a new dimension to the knowledge of carbon science1; and the subsequent discovery of ‘carbon nanotubes’ (CNTs, the elongated fullerene added a new dimension to the knowledge of technology2;. Today, ‘nanotechnology’ is a hot topic attracting scientists, industrialists, journalists, governments, and even the general public. Nanotechnology is the creation of functional materials, devices, and systems through control of matter on the nanometer scale and the exploitation of novel phenomena and properties of matter (physical, chemical, biological, electrical, etc. at that length scale. CNTs are supposed to be a key component of nanotechnology. Almost every week a new potential application of CNTs is identified, stimulating scientists to peep into this tiny tube with ever increasing curiosity.

  4. Adsorption on the carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    DING Yi; YANG Xiao-bao; NI Jun

    2006-01-01

    Adsorption on single walled carbon nanotubes (SWCNTs) is a subject of growing experimental and theoretical interest.The possible adsorbed patterns of atoms and molecules on the single-walled carbon nanotubes vary with the diameters and chirality of the tubes due to the confinement.The curvature of the carbon nanotube surface enlarges the distance of the adsorbate atoms and thus enhances the stability of high coverage structures of adsorbate.There exist two novel high-coverage stable structures of potassium adsorbed on SWCNTs,which are not stable on graphite.The electronic properties of SWCNTs can be modified by adsorbate atoms and metal-semiconductor and semiconductor-semi-conductor transitions can be achieved by the doping of alkali atoms.

  5. Novel Nanotube Manufacturing Streamlines Production

    Science.gov (United States)

    2007-01-01

    Nanotubes have novel qualities that make them uniquely qualified for a plethora of uses, including applications in electronics, optics, and other scientific and industrial fields. The NASA process for creating these nanostructures involves using helium arc welding to vaporize an amorphous carbon rod and then form nanotubes by depositing the vapor onto a water-cooled carbon cathode, which then yields bundles, or ropes, of single-walled nanotubes at a rate of 2 grams per hour using a single setup. This eliminates costs associated with the use of metal catalysts, including the cost of product purification, resulting in a relatively inexpensive, high-quality, very pure end product. While managing to be less expensive, safer, and simpler, the process also increases the quality of the nanotubes. Goddard's Innovative Partnerships Program (IPP) Office promoted the technology, and in 2005, Boise-based Idaho Space Materials Inc. (ISM) was formed and applied for a nonexclusive license for the single-walled carbon nanotube (SWCNT) manufacturing technology. ISM commercialized its products, and the inexpensive, robust nanotubes are now in the hands of the scientists who will create the next generation of composite polymers, metals, and ceramics that will impact the way we live. In fact, researchers are examining ways for these newfound materials to be used in the manufacture of transistors and fuel cells, large screen televisions, ultra-sensitive sensors, high-resolution atomic force microscopy probes, supercapacitors, transparent conducting films, drug carriers, catalysts, and advanced composite materials, to name just a few of the myriad technologies to benefit.

  6. Carbon nanotubes and graphene towards soft electronics

    Science.gov (United States)

    Chae, Sang Hoon; Lee, Young Hee

    2014-04-01

    Although silicon technology has been the main driving force for miniaturizing device dimensions to improve cost and performance, the current application of Si to soft electronics (flexible and stretchable electronics) is limited due to material rigidity. As a result, various prospective materials have been proposed to overcome the rigidity of conventional Si technology. In particular, nano-carbon materials such as carbon nanotubes (CNTs) and graphene are promising due to outstanding elastic properties as well as an excellent combination of electronic, optoelectronic, and thermal properties compared to conventional rigid silicon. The uniqueness of these nano-carbon materials has opened new possibilities for soft electronics, which is another technological trend in the market. This review covers the recent progress of soft electronics research based on CNTs and graphene. We discuss the strategies for soft electronics with nano-carbon materials and their preparation methods (growth and transfer techniques) to devices as well as the electrical characteristics of transparent conducting films (transparency and sheet resistance) and device performances in field effect transistor (FET) (structure, carrier type, on/off ratio, and mobility). In addition to discussing state of the art performance metrics, we also attempt to clarify trade-off issues and methods to control the trade-off on/off versus mobility). We further demonstrate accomplishments of the CNT network in flexible integrated circuits on plastic substrates that have attractive characteristics. A future research direction is also proposed to overcome current technological obstacles necessary to realize commercially feasible soft electronics.

  7. Diameter-dependent hydrophobicity in carbon nanotubes

    Science.gov (United States)

    Kyakuno, Haruka; Fukasawa, Mamoru; Ichimura, Ryota; Matsuda, Kazuyuki; Nakai, Yusuke; Miyata, Yasumitsu; Saito, Takeshi; Maniwa, Yutaka

    2016-08-01

    Single-wall carbon nanotubes (SWCNTs) are a good model system that provides atomically smooth nanocavities. It has been reported that water-SWCNTs exhibit hydrophobicity depending on the temperature T and the SWCNT diameter D. SWCNTs adsorb water molecules spontaneously in their cylindrical pores around room temperature, whereas they exhibit a hydrophilic-hydrophobic transition or wet-dry transition (WDT) at a critical temperature Twd ≈ 220-230 K and above a critical diameter Dc ≈ 1.4-1.6 nm. However, details of the WDT phenomenon and its mechanism remain unknown. Here, we report a systematic experimental study involving X-ray diffraction, optical microscopy, and differential scanning calorimetry. It is found that water molecules inside thick SWCNTs (D > Dc) evaporate and condense into ice Ih outside the SWCNTs at Twd upon cooling, and the ice Ih evaporates and condenses inside the SWCNTs upon heating. On the other hand, residual water trapped inside the SWCNTs below Twd freezes. Molecular dynamics simulations indicate that upon lowering T, the hydrophobicity of thick SWCNTs increases without any structural transition, while the water inside thin SWCNTs (D < Dc) exhibits a structural transition, forming an ordered ice. This ice has a well-developed hydrogen bonding network adapting to the cylindrical pores of the SWCNTs. Thus, the unusual diameter dependence of the WDT is attributed to the adaptability of the structure of water to the pore dimension and shape.

  8. Processing and Characterization of Carbon Nanotube Composites

    Science.gov (United States)

    Can, Roberto J.; Grimsley, Brian W.; Czabaj, Michael W.; Siochi, Emilie J.; Hull, Brandon

    2014-01-01

    Recent advances in the synthesis of large-scale quantities of carbon nanotubes (CNT) have provided the opportunity to study the mechanical properties of polymer matrix composites using these novel materials as reinforcement. Nanocomp Technologies, Inc. currently supplies large sheets with dimensions up to 122 cm x 244 cm containing both single-wall and few-wall CNTs. The tubes are approximately 1 mm in length with diameters ranging from 8 to 12 nm. In the present study being conducted at NASA Langley Research Center (LaRC), single and multiple layers of CNT sheets were infused or coated with various polymer solutions that included commercial toughened-epoxies and bismaleimides, as well as a LaRC developed polyimide. The resulting CNT composites were tested in tension using a modified version of ASTM D882-12 to determine their strength and modulus values. The effects of solvent treatment and mechanical elongation/alignment of the CNT sheets on the tensile performance of the composite were determined. Thin composites (around 50 wt% CNT) fabricated from acetone condensed and elongated CNT sheets with either a BMI or polyimide resin solution exhibited specific tensile moduli approaching that of toughened epoxy/ IM7 carbon fiber unidirectional composites.

  9. Gold nanotube: structure and melting

    OpenAIRE

    Bilalbegovic, G.

    2002-01-01

    In the process of molecular dynamics simulation studies of gold nanowires an interesting structure is discovered. This is a finite double-wall nanowire with a large empty core similar to single-wall and double-wall carbon nanotubes. The structure of the 16-10 gold nanotube is studied at the room temperature. An investigation of the high-temperature stability has also been carried out. An unusual inward evaporation of atoms from cylindrical liquid walls is found at T>= 1200 K.

  10. Atomistic Simulations of Nanotube Fracture

    CERN Document Server

    Belytschko, T; Schatz, G; Ruoff, R S

    2002-01-01

    The fracture of carbon nanotubes is studied by atomistic simulations. The fracture behavior is found to be almost independent of the separation energy and to depend primarily on the inflection point in the interatomic potential. The rangle of fracture strians compares well with experimental results, but predicted range of fracture stresses is marketly higher than observed. Various plausible small-scale defects do not suffice to bring the failure stresses into agreement with available experimental results. As in the experiments, the fracture of carbon nanotubes is predicted to be brittle. The results show moderate dependence of fracture strength on chirality.

  11. CMOS Integrated Carbon Nanotube Sensor

    International Nuclear Information System (INIS)

    Recently carbon nanotubes (CNTs) have been gaining their importance as sensors for gases, temperature and chemicals. Advances in fabrication processes simplify the formation of CNT sensor on silicon substrate. We have integrated single wall carbon nanotubes (SWCNTs) with complementary metal oxide semiconductor process (CMOS) to produce a chip sensor system. The sensor prototype was designed and fabricated using a 0.30 um CMOS process. The main advantage is that the device has a voltage amplifier so the electrical measure can be taken and amplified inside the sensor. When the conductance of the SWCNTs varies in response to media changes, this is observed as a variation in the output tension accordingly.

  12. Neutrinos Confronting Large Extra Dimensions

    CERN Document Server

    Maalampi, J; Vilja, I

    2001-01-01

    We study neutrino physics in a model with one large extra dimension. We assume the existence of two four-dimensional branes in the five-dimensional space-time, one for the ordinary particles and the other one for mirror particles, and we investigate neutrino masses and mixings in this scheme. Comparison of experimental neutrino data with the predictions of the model leads to various restrictions on the parameters of the model. For instance, the size of the extra dimension, R, turns out to be bounded from below. Cosmological considerations seem to favor a large R. The usual mixing schemes proposed as solutions to the solar and atmospheric neutrino anomalies are compatible with our model.

  13. Bulk charges in eleven dimensions

    CERN Document Server

    Hawking, Stephen William

    1998-01-01

    Eleven dimensional supergravity has electric type currents arising from the Chern-Simon and anomaly terms in the action. However the bulk charge integrates to zero for asymptotically flat solutions with topological trivial spatial sections. We show that by relaxing the boundary conditions to generalisations of the ALE and ALF boundary conditions in four dimensions one can obtain static solutions with a bulk charge preserving between 1/16 and 1/4 of the supersymmetries. One can introduce membranes with the same sign of charge into these backgrounds. This raises the possibility that these generalized membranes might decay quantum mechanically to leave just a bulk distribution of charge. Alternatively and more probably, a bulk distribution of charge can decay into a collection of singlely charged membranes. Dimensional reductions of these solutions lead to novel representations of extreme black holes in four dimensions with up to four charges. We discuss how the eleven-dimensional Kaluza-Klein monopole wrapped a...

  14. INTERDEPENDENCE BETWEEN RELATIONSHIP QUALITY DIMENSIONS

    Directory of Open Access Journals (Sweden)

    Mario Pepur

    2011-02-01

    Full Text Available Tourism-dependent economy, unfavourable structure of accommodation and hotel capacity, seasonality of business and liquidity problems indicate importance of the relationships between hotels and banks in Croatia. Since the capital investments in new and modern capacities are necessity, the quality of their relationship would determine the future of Croatian economy as a whole in the long run. Regarding the capital investments, it is crucially important that cooperation between the employees in both business entities is based on the satisfaction, trust and commitment. In this way, every potential uncertainty as a consequence of the entity’s actions could be minimized. In this paper, 356 tourist objects are hierarchically clustered according to the relationship quality dimensions for the purpose of testing the characteristics according to which the clusters significantly differentiate. Consequently, the interdependence between the observed relationship quality dimensions is examined.

  15. The Creative Dimension of Visuality

    DEFF Research Database (Denmark)

    Michelsen, Anders Ib

    2013-01-01

    analysis relying on language/linguistics as a model for explaining culture? More specifically, how can the – creative – novelty of visual culture be addressed by a notion of discourse? This essay will argue that the debate on visual culture is lacking with regard to discerning the creative dimension of its...... own appearance. It will indicate an alternative conceptual framework based on Johann P. Arnason’s draft of tripartite culturalization which focuses on a shift from essences to dimensions of culture. This will be further developed by relating Maurice Merleau-Ponty’s idea of ‘chiasm’ of ‘the visible and......This essay reflects critically on the notion of visuality, a centrepiece of current theory on visual culture and its underlying idea of a structural ‘discursive determination’ of visual phenomena. Is the visual really to be addressed through the post-war heritage of discourse and representation...

  16. Cytotoxicity of carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    ZHU Ying; LI WenXin

    2008-01-01

    With large-scale production and application at large scale, carbon nanotubes (CNTs) may cause ad-verse response to the environment and human health. Thus, study on bio-effects and safety of CNTs has attracted great attention from scientists and governments worldwide. This report briefly summa-rizes the main results from the in vitro toxicity study of CNTs. The emphasis is placed on the descrip-tion of a variety of factors affecting CNTs cytotoxicity, including species of CNTs, impurities contained,lengths of CNTs, aspect ratios, chemical modification, and assaying methods of cytotoxicity. However,experimental information obtained thus far on CNTs' cytotoxicity is lacking in comparability, and some-times there is controversy about it. In order to assess more accurately the potential risks of CNTs to human health, we suggest that care should be taken for issues such as chemical modification and quantitative characterization of CNTa in cytotoxicity assessment. More importantly, studies on physical and chemical mechanisms of CNTs' cytotoxicity should be strengthened; assaying methods and evaluating criteria characterized by nanotoxicology should be gradually established.

  17. Cytotoxicity of carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    With large-scale production and application at large scale, carbon nanotubes (CNTs) may cause ad-verse response to the environment and human health. Thus, study on bio-effects and safety of CNTs has attracted great attention from scientists and governments worldwide. This report briefly summa-rizes the main results from the in vitro toxicity study of CNTs. The emphasis is placed on the descrip-tion of a variety of factors affecting CNTs cytotoxicity, including species of CNTs, impurities contained, lengths of CNTs, aspect ratios, chemical modification, and assaying methods of cytotoxicity. However, experimental information obtained thus far on CNTs’ cytotoxicity is lacking in comparability, and some-times there is controversy about it. In order to assess more accurately the potential risks of CNTs to human health, we suggest that care should be taken for issues such as chemical modification and quantitative characterization of CNTs in cytotoxicity assessment. More importantly, studies on physical and chemical mechanisms of CNTs’ cytotoxicity should be strengthened; assaying methods and evaluating criteria characterized by nanotoxicology should be gradually established.

  18. Cosmic censorship in higher dimensions

    International Nuclear Information System (INIS)

    We show that the naked singularities arising in dust collapse from smooth initial data (which include those discovered by Eardley and Smarr, Christodoulou, and Newman) are removed when we make a transition to higher dimensional spacetimes. Cosmic censorship is then restored for dust collapse, which will always produce a black hole as the collapse end state for dimensions D≥6, under conditions to be motivated physically such as the smoothness of initial data from which the collapse develops

  19. Administrative Dimensions of Tax Reform

    OpenAIRE

    Bird, Richard M.

    2003-01-01

    The best tax policy in the world is worth little if it cannot be implemented effectively. Tax policy design in developing countries must therefore take the administrative dimension of taxation carefully into account. What can be done may to a considerable extent determine what is done in any country. This paper discusses the relationship between tax policy and tax administration. When can policy lead administration? When must policy initiatives wait on administrative reform? How exactly can b...

  20. Optical Tomography in Two Dimensions

    OpenAIRE

    Stefanov, Plamen

    2003-01-01

    We consider in two dimensions, the inverse boundary problem of reconstructing the absorption and scattering coefficient of an inhomogeneous medium by probing it with diffuse light. The problem is modeled as an inverse boundary problem for the stationary linear Boltzmann equation. The information is encoded in the albedo operator. We show that we can recover the absorption and the scattering kernel from this information provided that the latter is small in an appropriate t...

  1. Gravity Waves in Three Dimensions

    CERN Document Server

    Gurses, Metin; Tekin, Bayram

    2015-01-01

    We find the explicit forms of the anti-de Sitter plane, anti-de Sitter spherical, and pp waves that solve both the linearized and exact field equations of the most general higher derivative gravity theory in three dimensions. As a sub-class, we work out the six derivative theory and the critical version of it where the masses of the two spin-2 excitations vanish and the spin-0 excitations decouple.

  2. Massive Gravity in Three Dimensions

    OpenAIRE

    Bergshoeff, Eric A.; Hohm, Olaf; Townsend, Paul K

    2009-01-01

    A particular higher-derivative extension of the Einstein-Hilbert action in three spacetime dimensions is shown to be equivalent at the linearized level to the (unitary) Pauli-Fierz action for a massive spin-2 field. A more general model, which also includes `topologically-massive' gravity as a special case, propagates the two spin 2 helicity states with different masses. We discuss the extension to massive ${\\cal N}$-extended supergravity, and we present a `cosmological' extension that admits...

  3. Spherical Harmonics in p Dimensions

    OpenAIRE

    Frye, Christopher; Efthimiou, Costas J.

    2012-01-01

    The authors prepared this booklet in order to make several useful topics from the theory of special functions, in particular the spherical harmonics and Legendre polynomials for any dimension, available to undergraduates studying physics or mathematics. With this audience in mind, nearly all details of the calculations and proofs are written out, and extensive background material is covered before beginning the main subject matter. The reader is assumed to have knowledge of multivariable calc...

  4. The dimensions of purchasing competence

    OpenAIRE

    Rodrigues, Cristina S.; Fernandes, Edite Manuela da G. P.; Martins, F. Vitorino

    2006-01-01

    As firms recognize the purchasing function as an important resource for obtaining high quality levels, fast deliveries and cost savings, it reveals opportunities for the purchasing management to become a key contributor. The new product development is one example where acquisition capabilities may confirm to be particularly critical. This paper presents a construct of purchasing competence using three dimensions identified from literature: purchasing interaction, purchasing importance, and...

  5. Identification of Sustainable Architecture Dimensions

    OpenAIRE

    Leila Etminan; Siavash Rashidi Sharif Abad; Mansour Nikpor

    2014-01-01

    The main purpose in this research is identification of sustainable architecture dimensions. Nowadays, one of the most necessary complicated and main specifications of architecture with which architects are face is the issue of sustainability in various types of its interpretations. The issue of sustainability is interpretable and general according to many aspects. Therefore, it is necessary to identify this concept (architecture and its related categories). At the beginning of this discussion...

  6. DIMENSIONS OF THE MARKET RISK

    OpenAIRE

    Cornelia Marcela Danu

    2014-01-01

    The present work presents the concept approach and the types of the market risks, considering the representatives of the two correlative dimensions of the market: the supply and the demand. This approach dissociates from the other ways to define and to manage the market risks by the message that it communicates: all the types of risk caused by the market activities are market risks. These are anthropic risks, based on information and decision. From the point of view of source, the market risk...

  7. Global Dimension in Engineering Education

    OpenAIRE

    Global Dimension in Engineering Education

    2014-01-01

    Obra formada per: Block A "The global engineer" (Vol. 1. Making the case for a critical global engineer. Vol. 2. Key elements for addressing the global dimension of engineering. Vol. 3. The global engineer in sustainable human development), Block B "Supervising BS/MS thesis with fieldwork" (Vol. 4. Supervising engineering students. Vol. 5. Knowing the context and partners. Vol. 6. Knowing international cooperation) i Block C "Integrating GDE into teaching and research" (Vol. 7. Integrating...

  8. Signal detection in high dimension

    OpenAIRE

    Hallin, Marc; Moreira, Marcelo J.; Onatski, Alexei

    2012-01-01

    This paper deals with the local asymptotic structure, in the sense of Le Cam’s asymptotic theory of statistical experiments, of the signal detection problem in high dimension. More precisely, we consider the problem of testing the null hypothesis of sphericity of a high-dimensional covariance matrix against an alternative of (unspecified) multiple symmetry-breaking directions (multispiked alternatives). Simple analytical expressions for the asymptotic power envelope and the ...

  9. Quantum control in infinite dimensions

    OpenAIRE

    Karwowski, Witold; Mendes, R. Vilela

    2003-01-01

    Accurate control of quantum evolution is an essential requirement for quantum state engineering, laser chemistry, quantum information and quantum computing. Conditions of controllability for systems with a finite number of energy levels have been extensively studied. By contrast, results for controllability in infinite dimensions have been mostly negative, stating that full control cannot be achieved with a finite dimensional control Lie algebra. Here we show that by adding a discrete operati...

  10. The spatial dimensions of innovation

    OpenAIRE

    Lorentzen, Anne

    2005-01-01

    The paper discusseses the spatial dimensions of innovation in Polish manufacturing companies. The conceptual framework of the paper is an understanding of social networks as a potential resource of the company, whether they are internal or external. Whether the company benefits from the potential resources attached to the network depends on the capabilities characterising the firm in terms of qualifications, organisational characteristics and attitude towards employees and towards other firms...

  11. The social dimensions of entrepreneurship

    DEFF Research Database (Denmark)

    Ulhøi, John Parm

    2005-01-01

    This paper proposes an integrative framework to conceptualize important social dimensions of entrepreneurship. The paper reviews and evaluates the current status of research dealing with entrepreneurship, social capital and trust. The proposed framework rests on the recognition that entrepreneurial...... activities are results of social interactions and mechanisms. In consequence, entrepreneurship cannot merely be understood in terms of "personality characteristics" or in sterile economic terms. In closing, the paper addresses implications for practitioners and for research. Udgivelsesdato: AUG...

  12. The social dimension of entrepreneurship

    DEFF Research Database (Denmark)

    Ulhøi, John Parm

    2005-01-01

    This paper proposes an integrative framework to conceptualize important social dimensions of entrepreneurship. The paper reviews and evaluates the current status of research dealing with entrepreneurship, social capital and trust. The proposed framework rests on the recognition that entrepreneurial...... activities are results of social interactions and mechanisms. In consequence, entrepreneurship cannot merely be understood in terms of 'personality characteristics' or in sterile economic terms. The paper addresses by concluding implications for practitioners and for research....

  13. The Hausdorff and dynamical dimensions of self-affine sponges: a dimension gap result

    OpenAIRE

    Das, Tushar; Simmons, David

    2016-01-01

    We construct a self-affine sponge in $\\mathbb R^3$ whose dynamical dimension, i.e. the supremum of the Hausdorff dimensions of its invariant measures, is strictly less than its Hausdorff dimension. This resolves a long-standing open problem in the dimension theory of dynamical systems, namely whether every expanding repeller has an ergodic invariant measure of full Hausdorff dimension.

  14. Wave equations in higher dimensions

    CERN Document Server

    Dong, Shi-Hai

    2011-01-01

    Higher dimensional theories have attracted much attention because they make it possible to reduce much of physics in a concise, elegant fashion that unifies the two great theories of the 20th century: Quantum Theory and Relativity. This book provides an elementary description of quantum wave equations in higher dimensions at an advanced level so as to put all current mathematical and physical concepts and techniques at the reader’s disposal. A comprehensive description of quantum wave equations in higher dimensions and their broad range of applications in quantum mechanics is provided, which complements the traditional coverage found in the existing quantum mechanics textbooks and gives scientists a fresh outlook on quantum systems in all branches of physics. In Parts I and II the basic properties of the SO(n) group are reviewed and basic theories and techniques related to wave equations in higher dimensions are introduced. Parts III and IV cover important quantum systems in the framework of non-relativisti...

  15. Wormholes leading to extra dimensions

    CERN Document Server

    Bronnikov, K A

    2016-01-01

    In 6D general relativity with a scalar field as a source of gravity, a new type of static wormhole solutions is presented: such wormholes connect our universe with a small 2D extra subspace with a universe where this extra subspace is large, and the whole space-time is effectively 6-dimensional. We consider manifolds with the structure M0 x M1 x M2 , where M0 is 2D Lorentzian space-time while each of M1 an M2 can be a 2-sphere or a 2-torus. After selecting possible asymptotic behaviors of the metric functions compatible with the field equations, we give two explicit examples of wormhole solutions with spherical symmetry in our space-time and toroidal extra dimensions. In one example, with a massless scalar field (it is a special case of a well-known more general solution), the extra dimensions have a large constant size at the "far end"; the other example contains a nonzero potential $V(\\phi)$ which provides a 6D anti-de Sitter asymptotic, where all spatial dimensions are infinite.

  16. Modified carbon nanotubes and methods of forming carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Heintz, Amy M.; Risser, Steven; Elhard, Joel D.; Moore, Bryon P.; Liu, Tao; Vijayendran, Bhima R.

    2016-06-14

    In this invention, processes which can be used to achieve stable doped carbon nanotubes are disclosed. Preferred CNT structures and morphologies for achieving maximum doping effects are also described. Dopant formulations and methods for achieving doping of a broad distribution of tube types are also described.

  17. Functionality of C(4,4) carbon nanotube as molecular detector.

    Science.gov (United States)

    Malcioğlu, Osman Bariş; Erkoç, Sakir

    2008-02-01

    Alterations in the electronic transport properties of C(4,4) single walled carbon nanotube when an agent is introduced to the outer surface are investigated theoretically. Several chemical agents in this context are investigated. The calculations are performed in two steps: First an optimized geometry for the functionalized carbon nanotube is obtained using semi-empirical calculations at the PM3 level, and then the transport relations are obtained using non equilibrium green-function approach. Gaussian and Transiesta-C simulation packages are used in the calculations correspondingly. The "electrodes" are chosen to be ideal geometry of the particular carbon nanotube, eliminating current quantization effects due to contact region. By varying chemical potential in the electrode regions, an I-V curve is traced for each particular functionalisation. Conductance in carbon nanotubes show a strong dependence on the geometry and aromaticity, both are which altered when the suitable agent is introduced. This dependence results in rather dramatic response in the I-V trace, the current is reduced significantly, and quantization effects are observed, even for a single molecule. However due to chemically stable nature, not all agents form a chemical bond to the surface. Overall, the material is a promising candidate for detector equipment. PMID:18464360

  18. Multiwalled carbon nanotube CVD synthesis, modification, and composite applications

    Science.gov (United States)

    Qian, Dali

    Well-aligned carbon multiwall nanotube (MWNT) arrays have been continuously synthesized by a floating catalytic chemical vapor deposition (CVD) method involving the pyrolysis of xylene-ferrocene mixtures. The CVD parameters have been studied to selectively synthesize nanotubes with required dimensions. A mixed tip-root growth model has been proposed for the floating catalytic CVD synthesis. Coarsening of the catalyst particle at the root end promoted MWNT wall coarsening (addition of new concentric graphene shells), while the smaller catalyst particle at the tip contributed to MWNT elongation. A two-step process in which ferrocene was fed for only five minutes to nucleate the DTs was developed to understand if a continuous supply of catalyst was necessary for continued growth. The results show that the ferrocene was only necessary for initial nucleation. To simplify the CVD process further, another two-step synthesis method was developed in which the ferrocene was pre-decomposed so that the nanotube nucleation could be isolated from the growth, enabling quantification of growth mechanisms and kinetics. Mass spectra and hydrocarbon analyses of the CVD reactor tail gas were performed to understand the pyrolysis chemistry. Well-aligned N-doped and Ru-doped MWNT arrays have been produced by pyrolysis of pyridine ferrocene mixtures and xylene-ferrocene-ruthenocene mixtures, respectively. Various material characterization techniques were used to measure the dopant distributions and correlate the catalyst phase with the novel nanotube structures. High-temperature annealing has been shown to be a viable means to remove both the catalyst particles and certain microstructural defects within the CVD-derived DTs. The phase transformation of catalyst during annealing has also been studied. Homogeneous distribution of MWNTs in polystyrene matrices was achieved by an ultrasonic assisted solution-evaporation method. Addition of only 1 wt % DTs to polystyrene increased the polymer

  19. Emerging Carbon Nanotube Electronic Circuits, Modeling, and Performance

    OpenAIRE

    Ashok Srivastava; Yao Xu; Sharma, Ashwani K.

    2010-01-01

    Current transport and dynamic models of carbon nanotube field-effect transistors are presented. A model of single-walled carbon nanotube as interconnect is also presented and extended in modeling of single-walled carbon nanotube bundles. These models are applied in studying the performances of circuits such as the complementary carbon nanotube inverter pair and carbon nanotube as interconnect. Cadence/Spectre simulations show that carbon nanotube field-effect transistor circuits can operate a...

  20. Carbon nanotube atomic force microscopy probes

    Science.gov (United States)

    Yamanaka, Shigenobu; Okawa, Takashi; Akita, Seiji; Nakayama, Yoshikazu

    2005-05-01

    We have developed a carbon nanotube atomic force microscope probe. Because the carbon nanotube are well known to have high aspect ratios, small tip radii and high stiffness, carbon nanotube probes have a long lifetime and can be applied for the observation deep trenches. Carbon nanotubes were synthesized by a well-controlled DC arc discharge method, because this method can make nanotubes to have straight shape and high crystalline. The nanotubes were aligned on the knife-edge using an alternating current electrophoresis technique. A commercially available Si probe was used for the base of the nanotube probe. The nanotube probe was fabricated by the SEM manipulation method. The nanotube was then attached tightly to the Si probe by deposition of amorphous carbon. We demonstrate the measurement of a fine pith grating that has vertical walls. However, a carbon nanotube has a problem that is called "Sticking". The sticking is a chatter image on vertical like region in a sample. We solved this problem by applying 2 methods, 1. a large cantilever vibration amplitude in tapping mode, 2. an attractive mode measurement. We demonstrate the non-sticking images by these methods.

  1. OPPORTUNITIES OF BIOMEDICAL USE OF CARBON NANOTUBES

    Directory of Open Access Journals (Sweden)

    I. V. Mitrofanova

    2015-12-01

    Full Text Available Nanomaterials  –  materials,  whouse  structure  elements  has  proportions  doesn’t  exceed  100  nm.  In superdispersed state matter acquire new properties. In the last decade, carbon nanotubes become the most popular nanomaterials, that cause attention of representatives of various scientific field. The сarbon nanotubes offer new opportunities for biological and medical applications: imaging at the molecular, cellular and tissue levels, biosensors and electrodes based on carbon nanotubes, target delivery of various substances, radiation and photothermal therapy. The most promising of carbon nanotubes in the context of biomedical applications is their ability to penetrate the various tissues of the body and carry large doses of agents, providing diagnostic and therapeutic effects. Functionalized nanotubes are biodegradable. Other current direction of using carbon nanotubes in medicine and biology is to visualize objects on the molecular, cellular and tissue level. Associated with carbon nanotubes contrasting substances improve the visualization of cells and tissues, which can detected new patterns of development of the pathological process. Due to the vagueness of the question of biocompatibility and cytotoxicity of carbon nanotubes possibility of their practical application is hampered. Before the introduction of carbon nanotubes into practical health care is necessary to provide all the possible consequences of using nanotubes. High rates of properties and development of new nanostructures based on carbon nanotubes in the near future will lead to new advances related to the application and development of new parameters that will determine their properties and effects. In these review attention is paid to the structure, physico-chemical properties of nanotubes, their functionalization, pharmacokinetics and pharmacodynamics and all aspects of using of carbon nanotubes.

  2. Design, fabrication and properties of novel architectures made from carbon nanotubes and nano-porous materials

    Science.gov (United States)

    Kaur, Sumanjeet

    Nanomaterials like carbon nanotubes (CNT) have numerous potential applications due to their unique electrical, thermal and mechanical properties. Building macroscopic architectures using these nanocomponents requires new approaches for organization or assembly of these components. This can be achieved by using various techniques like capillary-induced compaction, template-assisted growth and other synthesis techniques. The vertically aligned multiwalled carbon nanotube arrays were grown using chemical vapor deposition (CVD). Evaporation of liquid from such vertically aligned nanotube arrays induces the assembly of nanotubes into cellular patterns. The role of substrate and orientation of the carbon nanotube array was investigated and analyzed to gain more control over the pattern formation that could help in designing new structures. Electrical measurements on the CNT patterns before and after capillary-induced compaction revealed that compaction results in four-fold increase in electrical conductivity, making them a potential candidate for vertical interconnects. A new method to fabricate a syringe with nanopores by using anodization technique was demonstrated. Experimental parameters were investigated to control the dimension and morphology of the nanopores in the syringe. Capillary force was used to infiltrate and replicate the complete 3D architecture into polymers. The usefulness of syringe as a biological sampler (DNA-RNA separation) was demonstrated. Layered structure of exfoliated mica was used as a substrate for growth of CNTs. This resulted in novel layered hybrid architecture of mica and carbon nanotube arrays. Mechanical properties of such architectures were investigated. Such architectures could be very useful as foams. These simple techniques can be used to assemble nanoscale components into well-defined macroscopic architectures and thus broaden the range of applications where their unique properties can be put into use.

  3. Morphology and growth of titania nanotubes. Nanostructuring and applications

    Energy Technology Data Exchange (ETDEWEB)

    Albu, Sergiu P.

    2012-10-26

    this nanostructure. It draws attention to important aspects that should be considered when using organic electrolytes, poses specific questions regarding the electrochemical methods and provides some solutions to them. The second part is focused on the growth of TiO{sub 2} nanotubes under different conditions. This part deals with a wide range of parameters that influence the formation of nanotubes, their chemical composition, geometry, etc. The most important factors in nanotube growth were found to be the applied voltage, water content, temperature and background electrolyte. Oxidation and metal ion dissolution are reactions governing the anodic process and the efficiency of oxide growth which is directly connected with these reactions determines whether self-ordering takes place or not. Many high-end technologies such as scanning electron microscopy, energy dispersive X-ray spectroscopy and transmission electron microscopy were adopted for the detailed characterization of the nanotubes. In the third part, the crystallization of ''as grown'' amorphous TiO{sub 2} nanotubes is addressed. In addition to the influence of well-known annealing parameters (final temperature, heating ramp-rate) on nanotube crystallization, some specific aspects are provided which may drastically affect the efficiency of devices based on TiO{sub 2} nanotubes. Here it is shown that heat treatment can be successfully used to control the size of the anatase crystals inside nanotube walls or to alter completely the nanotubular structure. In the last chapter, advanced nanostructures based on TiO{sub 2} nanotubes are investigated. Many of these nanostructures are formed via manipulation of electrochemical parameters such as the applied voltage or the chemical etching. Novel ''nanolace'' and ''bamboo-type nanotube'' structures are shown and characterized here. In order to demonstrate the advantageous features of these nanotubes, some

  4. Quantum transport in carbon nanotubes

    NARCIS (Netherlands)

    Laird, E.A.; Kuemmeth, F.; Steele, G.A.; Grove-Rasmussen, K.; Nygard, J.; Flensberg, K.; Kouwenhoven, L.P.

    2015-01-01

    Carbon nanotubes are a versatile material in which many aspects of condensed matter physics come together. Recent discoveries have uncovered new phenomena that completely change our understanding of transport in these devices, especially the role of the spin and valley degrees of freedom. This revie

  5. High frequency carbon nanotube devices

    Science.gov (United States)

    Goffman, M. F.; Chimot, N.; Mile, E.; Monteverde, M. C.; Bourgoin, J.-P.; Derycke, V.

    2008-08-01

    We investigate high frequency electrical and mechanical performances of carbon nanotube based devices. Using configurations with multiple single-wall nanotubes in parallel, we show that HF nanotube transistors with intrinsic cut-off frequencies as high as 30 GHz can be obtained on rigid substrates. Adapting our process to plastic substrates, we also obtained highly flexible HF transistors showing constant transconductances up to at least 6 GHz, as-measured cut-off frequencies as high as 1 GHz (5-8 GHz after de-embedding) and stable DC performances upon bending. We probed electromechanical properties of individual suspended carbon multiwall nanotubes by using a modified AFM. DC deflection measurements on different devices are in agreement with a continuum model prediction and consistent with a Young's modulus of 0.4 TPa. Preliminary HF measurements on a doubly clamped device showed a resonant frequency of 200MHz consistent with a Young's modulus of 0.43 TPa. This implies that built-in mechanical stress in the case of MWNTs is negligeable.

  6. Carbon nanotube-chalcogenide composite

    Czech Academy of Sciences Publication Activity Database

    Stehlík, Š.; Orava, J.; Kohoutek, T.; Wágner, T.; Frumar, M.; Zima, Vítězslav; Hara, T.; Matsui, Y.; Ueda, K.; Pumera, M.

    2010-01-01

    Roč. 183, č. 1 (2010), s. 144-149. ISSN 0022-4596 R&D Projects: GA ČR GA203/08/0208 Institutional research plan: CEZ:AV0Z40500505 Keywords : carbon nanotubes * chalcogenide glasses * composites Subject RIV: CA - Inorganic Chemistry Impact factor: 2.261, year: 2010

  7. CARBON NANOTUBES AND PHARMACEUTICAL APPLICATIONS

    Directory of Open Access Journals (Sweden)

    Ram Pavani

    2011-07-01

    Full Text Available Carbon nanotubes (CNTs are often described as a graphene sheet rolled up into the shape of a cylinder. These have fascinated scientists with their extraordinary properties. These compounds have become increasingly popular in various fields simply because of their small size and amazing optical, electric and magnetic properties when used alone or with additions of metals. Carbon nanotubes have potential therapeutic applications in the field of drug delivery, diagnostics, and biosensing. Functionalized carbon nanotubes can also act as vaccine delivery systems.Carbon nanotubes (CNTs are considered to be one of the innovative resources in nanotechnology with possible use in wide range of biomedical applications viz. cancer treatment, bioengineering, cardiac autonomic regulation, platelet activation and tissue regeneration. The effect of CNTs on cells and tissues are extremely important for their use in various complex biological systems. With the increasing interest shown by the nanotechnology research community in this field, it is expected that plenty of applications of CNTs will be explored in future.

  8. Thermoelectrics: Carbon nanotubes get high

    Science.gov (United States)

    Crispin, Xavier

    2016-04-01

    Waste heat can be converted to electricity by thermoelectric generators, but their development is hindered by the lack of cheap materials with good thermoelectric properties. Now, carbon-nanotube-based materials are shown to have improved properties when purified to contain only semiconducting species and then doped.

  9. Improved synthesis of carbon nanotubes with junctions and of single-walled carbon nanotubes

    Indian Academy of Sciences (India)

    F L Deepak; A Govindaraj; C N R Rao

    2006-01-01

    Pyrolysis of thiophene over nickel nanoparticles dispersed on silica is shown to yield Yjunction carbon nanotubes with smaller diameters than those obtained by the pyrolysis of organometallicthiophene mixtures. In the presence of water vapour, the pyrolysis of organometallic-hydrocarbon mixtures yields single-walled nanotubes, as well as relatively narrow-diameter carbon nanotubes with Y-junctions. Pyrolysis of organometallic-hydrocarbon mixtures, in the absence of water vapour, only gives nanotubes with T- and Y-junctions.

  10. Tantalum coating on TiO{sub 2} nanotubes induces superior rate of matrix mineralization and osteofunctionality in human osteoblasts

    Energy Technology Data Exchange (ETDEWEB)

    Frandsen, Christine J.; Brammer, Karla S. [Materials Science and Engineering, University of California at San Diego, La Jolla, CA 92093 (United States); Noh, Kunbae [Corporate Research Institute, Cheil Industries, Inc., Gocheon-Dong, Uiwang-Si, Gyeonggi-Do, 437-711 (Korea, Republic of); Johnston, Gary [Materials Science and Engineering, University of California at San Diego, La Jolla, CA 92093 (United States); Jin, Sungho, E-mail: jin@ucsd.edu [Materials Science and Engineering, University of California at San Diego, La Jolla, CA 92093 (United States); Mechanical and Aerospace Engineering, University of California at San Diego, La Jolla, CA 92093 (United States)

    2014-04-01

    Nanostructured surface geometries have been the focus of a multitude of recent biomaterial research, and exciting findings have been published. However, only a few publications have directly compared nanostructures of various surface chemistries. The work herein directly compares the response of human osteoblast cells to surfaces of identical nanotube geometries with two well-known orthopedic biomaterials: titanium oxide (TiO{sub 2}) and tantalum (Ta). The results reveal that the Ta surface chemistry on the nanotube architecture enhances alkaline phosphatase activity, and promotes a ∼ 30% faster rate of matrix mineralization and bone-nodule formation when compared to results on bare TiO{sub 2} nanotubes. This study implies that unique combinations of surface chemistry and nanostructure may influence cell behavior due to distinctive physico-chemical properties. These findings are of paramount importance to the orthopedics field for understanding cell behavior in response to subtle alterations in nanostructure and surface chemistry, and will enable further insight into the complex manipulation of biomaterial surfaces. With increased focus in the field of orthopedic materials research on nanostructured surfaces, this study emphasizes the need for careful and systematic review of variations in surface chemistry in concurrence with nanotopographical changes. - Highlights: • A TiO{sub 2} nanotube surface structure was coated with tantalum. • Osteoblast cell response was compared between the tantalum coated and as-formed TiO{sub 2} nanotube surface. • We observed superior rates of bone matrix mineralization and osteoblast maturation on the tantalum coated nanotube surface.

  11. Tantalum coating on TiO2 nanotubes induces superior rate of matrix mineralization and osteofunctionality in human osteoblasts

    International Nuclear Information System (INIS)

    Nanostructured surface geometries have been the focus of a multitude of recent biomaterial research, and exciting findings have been published. However, only a few publications have directly compared nanostructures of various surface chemistries. The work herein directly compares the response of human osteoblast cells to surfaces of identical nanotube geometries with two well-known orthopedic biomaterials: titanium oxide (TiO2) and tantalum (Ta). The results reveal that the Ta surface chemistry on the nanotube architecture enhances alkaline phosphatase activity, and promotes a ∼ 30% faster rate of matrix mineralization and bone-nodule formation when compared to results on bare TiO2 nanotubes. This study implies that unique combinations of surface chemistry and nanostructure may influence cell behavior due to distinctive physico-chemical properties. These findings are of paramount importance to the orthopedics field for understanding cell behavior in response to subtle alterations in nanostructure and surface chemistry, and will enable further insight into the complex manipulation of biomaterial surfaces. With increased focus in the field of orthopedic materials research on nanostructured surfaces, this study emphasizes the need for careful and systematic review of variations in surface chemistry in concurrence with nanotopographical changes. - Highlights: • A TiO2 nanotube surface structure was coated with tantalum. • Osteoblast cell response was compared between the tantalum coated and as-formed TiO2 nanotube surface. • We observed superior rates of bone matrix mineralization and osteoblast maturation on the tantalum coated nanotube surface

  12. Nanotube wall thickness dependent magnetization reversal properties of NiFe nanotubes

    Science.gov (United States)

    Sharif, R.; Shamaila, S.; Shaheen, F.; Naseem, S.; Chen, J. Y.; Khaleeq-ur-Rahman, M.; Hussain, K.; Han, X. F.

    2013-01-01

    Nanotube wall thickness dependent magnetization properties of NiFe nanotube arrays electrodeposited in polycarbonate membranes are investigated. A systematic variation of nanotube wall thickness (tw) has been investigated. The magnetization reversal properties are strongly influenced by the variation of tw keeping length and external radius constant.

  13. NONHOMOGENEOUS HOPF EQUATIONS IN HIGHER DIMENSIONS

    Institute of Scientific and Technical Information of China (English)

    JIU QUANSEN

    1999-01-01

    The existence and uniqueness of the localclassical solution of nonhomogenuous Hopf equationsin higher dimensions are proved in this paper. Thissolution is obtained by vanishing the viscosity termof Burger's equations in higher dimensions.

  14. Personality dimensions and disorders in pathological gambling

    DEFF Research Database (Denmark)

    Odlaug, Brian Lawrence; Schreiber, Liana R N; Grant, Jon E

    2013-01-01

    This review presents the most current research in personality dimensions and disorders with respect to pathological gambling.......This review presents the most current research in personality dimensions and disorders with respect to pathological gambling....

  15. BMS Modules in Three Dimensions

    CERN Document Server

    Campoleoni, Andrea; Oblak, Blagoje; Riegler, Max

    2016-01-01

    We build unitary representations of the BMS algebra and its higher-spin extensions in three dimensions, using induced representations as a guide. Our prescription naturally emerges from an ultrarelativistic limit of highest-weight representations of Virasoro and W algebras, which is to be contrasted with non-relativistic limits that typically give non-unitary representations. To support this dichotomy, we also point out that the ultrarelativistic and non-relativistic limits of generic W algebras differ in the structure of their non-linear terms.

  16. Higgs Searches and Extra Dimensions

    CERN Document Server

    Quiros, M

    2012-01-01

    We present a short review of theories based on warped extra dimensions (motivated by the hierarchy problem of the Standard Model) which can accomodate a Higgs boson in the range suggested by the recent LHC results at 7 TeV. Using the AdS/CFT correspondence the Higgs is composite and can be described in the dual theory by a bound state of the 4D CFT. We have classified the theories in those with a scalar Higgs (5D SM) and those where the Higgs is the fifth component (gauge-Higgs unification) of a bulk gauge field.

  17. Low Dimension Semiconducting Composite Nanomaterials

    Institute of Scientific and Technical Information of China (English)

    WANG Mang; CHEN Hong-zheng; SUN Jing-zhi

    2004-01-01

    Recently, low dimension nanostructures have gained considerable attention due to their technological potential as unique types of nanoscale building blocks for future optoelectronic devices and systems. Semiconducting composite nanomaterials, which can combine the advantages of two or more components, have been the focus in the area of nanomaterials synthesis and device application.In this paper, we report our work on the preparation of composite nanomaterials based on CNTs.CNTs were coated by organic or inorganic species via novel and facile methods (Fig. 1 and Fig.2).These functional CNTs based composites show eminent prospects and opportunities for new applications in a wide variation of areas.

  18. Strings, branes and extra dimensions

    International Nuclear Information System (INIS)

    In an attempt to gain a better understanding of our world, various philosophers, mathematicians and physicists have, over the last few centuries, proposed that we might live in a world with more than four space-time dimensions. In the 17th century, for example, Emmanuel Kant tried to figure out what is special about a three spatial-dimensional world. He concluded that there could be other universes hidden from our senses - an idea that Democritus among others had also entertained. (U.K.)

  19. Localized instanton in four dimensions

    International Nuclear Information System (INIS)

    A family of generalized Yang-Mills- (GYM) Higgs (H) systems is proposed as phenomenological models giving rise to localized instantons in four dimensions. An argument in favor of the (qualified) uniqueness of this system, which features a fundamental-representation Higgs field, is given. Two ''radial'' Ansa$auml: tze are made, and the compatibility of one of them with the field equation is analyzed in detail. It is suggested that such GYMH systems can be used in the computation of the confining potential

  20. Correlation dimension of complex networks

    CERN Document Server

    Lacasa, Lucas

    2012-01-01

    We propose a new measure to characterize the dimension of complex networks based on the ergodic theory of dynamical systems. This measure is derived from the correlation sum of a trajectory generated by a random walker navigating the network, and extends the classical Grassberger-Procaccia algorithm to the context of complex networks. The method is validated with reliable results for both synthetic networks and real-world networks such as the world air-transportation network or urban networks, and provides a computationally fast way for estimating the dimensionality of networks which only relies on the local information provided by the walkers.

  1. Quantum cosmology near two dimensions

    Science.gov (United States)

    Bautista, Teresa; Dabholkar, Atish

    2016-08-01

    We consider a Weyl-invariant formulation of gravity with a cosmological constant in d -dimensional spacetime and show that near two dimensions the classical action reduces to the timelike Liouville action. We show that the renormalized cosmological term leads to a nonlocal quantum momentum tensor which satisfies the Ward identities in a nontrivial way. The resulting evolution equations for an isotropic, homogeneous universe lead to slowly decaying vacuum energy and power-law expansion. We outline the implications for the cosmological constant problem, inflation, and dark energy.

  2. The fourth dimension simply explained

    CERN Document Server

    Manning, Henry P

    2005-01-01

    To remove the contents of an egg without puncturing its shell or to drink the liquor in a bottle without removing the cork is clearly unthinkable - or is it? Understanding the world of Einstein and curved space requires a logical conception of the fourth dimension.This readable, informative volume provides an excellent introduction to that world, with 22 essays that employ a minimum of mathematics. Originally written for a contest sponsored by Scientific American, these essays are so well reasoned and lucidly written that they were judged to merit publication in book form. Their easily unders

  3. Cultural Dimensions Of Legal Discourse

    Directory of Open Access Journals (Sweden)

    Sierocka Halina

    2014-09-01

    Full Text Available Despite the intention for precision and accuracy, legal discourse is oftentimes complex, archaic and ambiguous - which gives rise to contentious interpretation. Moreover, little or no attention is paid to the cultural dimension of legal discourse, which plays a critical role in the translation and interpretation of legal texts, as well as in the application of law. This paper endeavours to illustrate the impact the culture, or, more precisely, legal culture has on the way legal texts are construed or translated and to present problems which arise in the interpretation, translation and application of law as a result of cultural diversities

  4. Liquid surface model for carbon nanotube energetics

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Mathew, Maneesh; Solov'yov, Andrey V.;

    2008-01-01

    In the present paper we developed a model for calculating the energy of single-wall carbon nanotubes of arbitrary chirality. This model, which we call as the liquid surface model, predicts the energy of a nanotube with relative error less than 1% once its chirality and the total number of atoms are...... an important insight in the energetics and stability of nanotubes of different chirality and might be important for the understanding of nanotube growth process. For the computations we use empirical Brenner and Tersoff potentials and discuss their applicability to the study of carbon nanotubes. From...... the calculated energies we determine the elastic properties of the single-wall carbon nanotubes (Young modulus, curvature constant) and perform a comparison with available experimental measurements and earlier theoretical predictions....

  5. Deconvoluting hepatic processing of carbon nanotubes

    Science.gov (United States)

    Alidori, Simone; Bowman, Robert L.; Yarilin, Dmitry; Romin, Yevgeniy; Barlas, Afsar; Mulvey, J. Justin; Fujisawa, Sho; Xu, Ke; Ruggiero, Alessandro; Riabov, Vladimir; Thorek, Daniel L. J.; Ulmert, Hans David S.; Brea, Elliott J.; Behling, Katja; Kzhyshkowska, Julia; Manova-Todorova, Katia; Scheinberg, David A.; McDevitt, Michael R.

    2016-07-01

    Single-wall carbon nanotubes present unique opportunities for drug delivery, but have not advanced into the clinic. Differential nanotube accretion and clearance from critical organs have been observed, but the mechanism not fully elucidated. The liver has a complex cellular composition that regulates a range of metabolic functions and coincidently accumulates most particulate drugs. Here we provide the unexpected details of hepatic processing of covalently functionalized nanotubes including receptor-mediated endocytosis, cellular trafficking and biliary elimination. Ammonium-functionalized fibrillar nanocarbon is found to preferentially localize in the fenestrated sinusoidal endothelium of the liver but not resident macrophages. Stabilin receptors mediate the endocytic clearance of nanotubes. Biocompatibility is evidenced by the absence of cell death and no immune cell infiltration. Towards clinical application of this platform, nanotubes were evaluated for the first time in non-human primates. The pharmacologic profile in cynomolgus monkeys is equivalent to what was reported in mice and suggests that nanotubes should behave similarly in humans.

  6. Facile Synthesis of Ternary Boron Carbonitride Nanotubes

    Directory of Open Access Journals (Sweden)

    Luo Lijie

    2009-01-01

    Full Text Available Abstract In this study, a novel and facile approach for the synthesis of ternary boron carbonitride (B–C–N nanotubes was reported. Growth occurred by heating simple starting materials of boron powder, zinc oxide powder, and ethanol absolute at 1150 °C under a mixture gas flow of nitrogen and hydrogen. As substrate, commercial stainless steel foil with a typical thickness of 0.05 mm played an additional role of catalyst during the growth of nanotubes. The nanotubes were characterized by SEM, TEM, EDX, and EELS. The results indicate that the synthesized B–C–N nanotubes exhibit a bamboo-like morphology and B, C, and N elements are homogeneously distributed in the nanotubes. A catalyzed vapor–liquid–solid (VLS mechanism was proposed for the growth of the nanotubes.

  7. 16 CFR 1508.3 - Dimensions.

    Science.gov (United States)

    2010-01-01

    ... 16 Commercial Practices 2 2010-01-01 2010-01-01 false Dimensions. 1508.3 Section 1508.3 Commercial... FULL-SIZE BABY CRIBS § 1508.3 Dimensions. Full-size baby cribs shall have dimensions as follows: (a) Interior. The interior dimensions shall be 71±1.6 centimeters (28±5/8 inches) wide as measured between...

  8. Effective dimension in some general metric spaces

    OpenAIRE

    Mayordomo, Elvira

    2014-01-01

    We introduce the concept of effective dimension for a general metric space. Effective dimension was defined by Lutz in (Lutz 2003) for Cantor space and has also been extended to Euclidean space. Our extension to other metric spaces is based on a supergale characterization of Hausdorff dimension. We present here the concept of constructive dimension and its characterization in terms of Kolmogorov complexity. Further research directions are indicated.

  9. Carbon nanotubes as heat dissipaters in microelectronics

    DEFF Research Database (Denmark)

    Pérez Paz, Alejandro; García-Lastra, Juan María; Markussen, Troels;

    2013-01-01

    We review our recent modelling work of carbon nanotubes as potential candidates for heat dissipation in microelectronics cooling. In the first part, we analyze the impact of nanotube defects on their thermal transport properties. In the second part, we investigate the loss of thermal properties of...... nanotubes in presence of an interface with various substances, including air and water. Comparison with previous works is established whenever is possible....

  10. Characterization methods of carbon nanotubes: a review

    International Nuclear Information System (INIS)

    Carbon nanotubes due to their specific atomic structure have interesting chemical and physical properties according to those of graphite and diamond. This review covers the characterization methods of carbon nanotubes which are most employed today. The structure of carbon nanotubes is first briefly summarized followed by a description of the characterization methods such as STM, TEM, neutron diffraction, X-ray diffraction, X-ray photoelectron spectroscopy, infrared and Raman spectroscopy. The most interesting features are indexed for each technique

  11. Functional Materials based on Carbon Nanotubes

    OpenAIRE

    Jung, Adrian Thomas

    2007-01-01

    Carbon nanotubes, no matter if they are single-walled or multi-walled, are an integral component in the vastly growing field of nanotechnology. Since their discovery by TEM and the invention of numerous large-scale production techniques, nanotubes are close to making their way into industrial products. Although many properties and modification processes are still under intensive research, the first real-market applications for carbon nanotubes have already been presented. However, if function...

  12. Dielectrophoretic assembly of carbon nanotube devices

    OpenAIRE

    Dimaki, Maria; BØGGILD, Peter

    2004-01-01

    The purpose of this project has been to assemble single-walled carbon nanotubes on electrodes at the tip of a biocompatible cantilever and use these for chemical species sensing in air and liquid, for example in order to measure the local activity from ion channels in the cell membrane. The electrical resistance of carbon nanotubes has been shown to be extremely sensitive to gas molecules. Dielectrophoresis is a method capable of quickly attracting nanotubes on microelectrodes by using an ele...

  13. Structure and properties of carbon nanotubes

    OpenAIRE

    MEYER, Jannik

    2006-01-01

    The properties of nanoscopic objects depend critically on the position of each atom, since finite-size and quantization effects play an important role. For carbon nanotubes, the electronic, mechanical, and vibrational properties vary significantly depending on their structure. For example, a carbon nanotube can be metallic or semiconducting with varying band-gaps depending on its lattice structure. Yet, most investigations on individual carbon nanotubes are carried out on objects with unknown...

  14. Statics and dynamics of fluids in nanotubes

    OpenAIRE

    Gouin, Henri

    2012-01-01

    The purpose of this article is to study the statics and dynamics of nanotubes by using the methods of continuum mechanics. The nanotube can be filled with only a liquid or a vapour phase according to the physicochemical characteristics of the wall and to the disjoining pressure associated with the liquid and vapour mother bulks of the fluid, regardless of the nature of the external mother bulk. In dynamics, flows through nanotubes can be much more important than classical Poiseuille flows. Wh...

  15. Modelling water molecules inside cyclic peptide nanotubes

    Science.gov (United States)

    Tiangtrong, Prangsai; Thamwattana, Ngamta; Baowan, Duangkamon

    2016-03-01

    Cyclic peptide nanotubes occur during the self-assembly process of cyclic peptides. Due to the ease of synthesis and ability to control the properties of outer surface and inner diameter by manipulating the functional side chains and the number of amino acids, cyclic peptide nanotubes have attracted much interest from many research areas. A potential application of peptide nanotubes is their use as artificial transmembrane channels for transporting ions, biomolecules and waters into cells. Here, we use the Lennard-Jones potential and a continuum approach to study the interaction of a water molecule in a cyclo[(- D-Ala- L-Ala)_4-] peptide nanotube. Assuming that each unit of a nanotube comprises an inner and an outer tube and that a water molecule is made up of a sphere of two hydrogen atoms uniformly distributed over its surface and a single oxygen atom at the centre, we determine analytically the interaction energy of the water molecule and the peptide nanotube. Using this energy, we find that, independent of the number of peptide units, the water molecule will be accepted inside the nanotube. Once inside the nanotube, we show that a water molecule prefers to be off-axis, closer to the surface of the inner nanotube. Furthermore, our study of two water molecules inside the peptide nanotube supports the finding that water molecules form an array of a 1-2-1-2 file inside peptide nanotubes. The theoretical study presented here can facilitate thorough understanding of the behaviour of water molecules inside peptide nanotubes for applications, such as artificial transmembrane channels.

  16. Amorphous Carbon-Boron Nitride Nanotube Hybrids

    Science.gov (United States)

    Kim, Jae Woo (Inventor); Siochi, Emilie J. (Inventor); Wise, Kristopher E. (Inventor); Lin, Yi (Inventor); Connell, John (Inventor)

    2016-01-01

    A method for joining or repairing boron nitride nanotubes (BNNTs). In joining BNNTs, the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures. In repairing BNNTs, the damaged site of the nanotube structure is modified with amorphous carbon deposited by controlled electron beam irradiation to form well bonded hybrid a-C/BNNT structures at the damage site.

  17. DIMENSIONS FOR RANDOM SELF-CONFORMAL SETS

    Institute of Scientific and Technical Information of China (English)

    Liu Yanyan; Wu Jun

    2003-01-01

    A set is called regular if its Hausdorff dimension and upper box-counting dimension coincide.In this paper,we prove that the random self-conformal set is regular almost surely.Also we determine the dimensions for a class of random self-conformal sets.

  18. 15 CFR 241.5 - Standard dimensions.

    Science.gov (United States)

    2010-01-01

    ... 15 Commerce and Foreign Trade 1 2010-01-01 2010-01-01 false Standard dimensions. 241.5 Section 241..., VEGETABLES AND OTHER DRY COMMODITIES, AND FOR CRANBERRIES § 241.5 Standard dimensions. Whenever in the rules and regulations in this part the error on a dimension is mentioned, this error shall be determined...

  19. Bulk charges in eleven dimensions

    Science.gov (United States)

    Hawking, S. W.; Taylor-Robinson, M. M.

    1998-07-01

    Eleven dimensional supergravity has electric type currents arising from the Chern-Simon and anomaly terms in the action. However the bulk charge integrates to zero for asymptotically flat solutions with topological trivial spatial sections. We show that by relaxing the boundary conditions to generalisations of the ALE and ALF boundary conditions in four dimensions one can obtain static solutions with a bulk charge. Solutions involving anomaly terms preserve between 1/16 and 1/4 of the supersymmetries but Chern-Simons fluxes generally break all of the remaining supersymmetry. One can introduce membranes with the same sign of charge into these backgrounds. This raises the possibility that these generalized membranes might decay quantum mechanically to leave just a bulk distribution of charge. Alternatively and more probably, a bulk distribution of charge can decay into a collection of singly charged membranes. Dimensional reductions of these solutions lead to novel representations of extreme black holes in four dimensions with up to four charges. We discuss how the eleven-dimensional Kaluza-Klein monopole wrapped around a space with non-zero first Pontryagin class picks up an electric charge proportional to the Pontryagin number.

  20. Topological dimension and dynamical systems

    CERN Document Server

    Coornaert, Michel

    2015-01-01

    Translated from the popular French edition, the goal of the book is to provide a self-contained introduction to mean topological dimension, an invariant of dynamical systems introduced in 1999 by Misha Gromov. The book examines how this invariant was successfully used by Elon Lindenstrauss and Benjamin Weiss to answer a long-standing open question about embeddings of minimal dynamical systems into shifts. A large number of revisions and additions have been made to the original text. Chapter 5 contains an entirely new section devoted to the Sorgenfrey line. Two chapters have also been added: Chapter 9 on amenable groups and Chapter 10 on mean topological dimension for continuous actions of countable amenable groups. These new chapters contain material that have never before appeared in textbook form. The chapter on amenable groups is based on Følner’s characterization of amenability and may be read independently from the rest of the book. Although the contents of this book lead directly to several active ar...

  1. Identification of Sustainable Architecture Dimensions

    Directory of Open Access Journals (Sweden)

    Leila Etminan

    2014-02-01

    Full Text Available The main purpose in this research is identification of sustainable architecture dimensions. Nowadays, one of the most necessary complicated and main specifications of architecture with which architects are face is the issue of sustainability in various types of its interpretations. The issue of sustainability is interpretable and general according to many aspects. Therefore, it is necessary to identify this concept (architecture and its related categories. At the beginning of this discussion, we were faced with titles such as Green architecture2, Sustainable development3, etc. However, the purpose of this study is to study of nature and identify the circumstances and essence of sustainability in all fields in which the architecture is involved. The innovation of this study is to identify and feel the fact of sustainability dimensions that is studied in procedure of library research, a case sample and proposal of common but insufficient ideas related to this discussion. This study studies 3 approaches including main environmental, cultural (value and technical views and it tries to take the proposed topics under the subjection of this 3 factors respectively (presenting a modern model; furthermore, the minor factors are studied under the subjection of these 3 main factors.

  2. Fractal Dimensions of Macromolecular Structures

    Science.gov (United States)

    Todoroff, Nickolay; Kunze, Jens; Schreuder, Herman; Hessler, Gerhard; Baringhaus, Karl-Heinz; Schneider, Gisbert

    2014-01-01

    Quantifying the properties of macromolecules is a prerequisite for understanding their roles in biochemical processes. One of the less-explored geometric features of macromolecules is molecular surface irregularity, or ‘roughness’, which can be measured in terms of fractal dimension (D). In this study, we demonstrate that surface roughness correlates with ligand binding potential. We quantified the surface roughnesses of biological macromolecules in a large-scale survey that revealed D values between 2.0 and 2.4. The results of our study imply that surface patches involved in molecular interactions, such as ligand-binding pockets and protein-protein interfaces, exhibit greater local fluctuations in their fractal dimensions than ‘inert’ surface areas. We expect approximately 22 % of a protein’s surface outside of the crystallographically known ligand binding sites to be ligandable. These findings provide a fresh perspective on macromolecular structure and have considerable implications for drug design as well as chemical and systems biology. PMID:26213587

  3. Theoretical Simulation on the Assembly of Carbon Nanotubes Between Electrodes by AC Dielectrophoresis

    OpenAIRE

    Yang Liu; Lu Yang; Chen Changxin; Zhang Yafei

    2008-01-01

    Abstract The assembly of single-walled carbon nanotubes (SWCNTs) using the AC dielectrophoresis technique is studied theoretically. It is found that the comb electrode bears better position control of SWCNTs compared to the parallel electrode. In the assembly, when some SWCNTs bridge the electrode first, they can greatly alter the local electrical field so as to “screen off” later coming SWCNTs, which contributes to the formation of dispersed SWCNT array. The screening distance sc...

  4. Improved luminescent properties of novel nanostructured Eu3+ doped yttrium borate synthesized with carbon nanotube templates

    International Nuclear Information System (INIS)

    Graphical abstract: The activation spectra (a and c) measured by monitoring the 627 nm emission of Eu3+ and emission spectra (c and d) measured under λex = 247 nm. Figures (a) and (b) show the results for the sample annealed at 1000 °C without carbon nano-tube templates during synthesis. Figures (c) and (d) show the results for the sample annealed at 1000 °C with carbon nano-tube templates during synthesis. Compared with the sample without additive carbon nano-tube during synthesis, the sample with carbon nano-tube exhibited an extra excitation band at 281 nm, the intensity ratio between red (5D0−7F2) and orange (5D0−7F1) was increased from 1.1 to 3.66, and the CIE coordination changed from (0.655, 0.346) to (0.67, 0.33) (almost the same as that (0.665, 0.334) for commercial red phosphors Y2O2S:Eu3+, satisfying the requirement for red phosphors). These results indicate that the luminescent properties can be improved by carbon nano-tube template, which to our knowledge has not been reported before. Highlights: • Carbon nano-tube templates can significantly affect the morphology and enlarge the surface of the final samples. • The color purity can be greatly improved by carbon nano-tube templates. • Template-assisted samples exhibit extra Eu3+−O2− excitation band due to the surface effect. -- Abstract: Eu3+-doped yttrium borate samples were prepared via a hydrothermal method using borate or tributyl borate as B3+ sources, with and without carbon nanotubes as templates. The morphology of the samples is easily altered by varying the carbon nanotube template, B3+ source and post-annealing treatment. Photoluminescence measurements indicate that the color purity of samples is clearly improved by template-assisted synthesis. Furthermore, with tributyl borate as the B3+ source, CIE coordinates of (0.67, 0.33), very similar to the (0.665, 0.334) coordinates for the commercial red phosphor Y2O2S:Eu3+, can be obtained. Finally, an extra Eu3+−O2− excitation

  5. The necessary length of carbon nanotubes required to optimize solar cells

    Directory of Open Access Journals (Sweden)

    Barghi Tirdad

    2007-10-01

    Full Text Available Abstract Background In recent years scientists have been trying both to increase the efficiency of solar cells, whilst at the same time reducing dimensions and costs. Increases in efficiency have been brought about by implanting carbon nanotubes onto the surface of solar cells in order to reduce the reflection of sunrays, as well as through the insertion of polymeric arrays into the intrinsic layer for charge separation. Results The experimental results show power rising linearly for intrinsic layer thicknesses between 0–50 nm. Wider thicknesses increase the possibility of recombination of electrons and holes, leading to perturbation of the linear behaviour of output power. This effect is studied and formulated as a function of thickness. Recognition of the critical intrinsic layer thickness can permit one to determine the length of carbon nanotube necessary for optimizing solar cells. Conclusion In this study the behaviour of output power as a function of intrinsic layer thicknesses has been described physically and also simulated. In addition, the implantation of carbon nanotubes into the intrinsic layer and the necessary nanotube length required to optimize solar cells have been suggested.

  6. Particle trapping using dielectrophoretically patterned carbon nanotubes.

    Science.gov (United States)

    Khoshmanesh, Khashayar; Zhang, Chen; Nahavandi, Saeid; Tovar-Lopez, Francisco J; Baratchi, Sara; Hu, Zheng; Mitchell, Arnan; Kalantar-Zadeh, Kourosh

    2010-04-01

    This study presents the dielectrophoretic (DEP) assembly of multi-walled carbon nanotubes (MWCNTs) between curved microelectrodes for the purpose of trapping polystyrene microparticles within a microfluidic system. Under normal conditions, polystyrene particles exhibit negative DEP behaviour and are repelled from microelectrodes. Interestingly, the addition of MWCNTs to the system alters this situation in two ways: first, they coat the surface of particles and change their dielectric properties to exhibit positive DEP behaviour; second, the assembled MWCNTs are highly conductive and after the deposition serve as extensions to the microelectrodes. They establish an array of nanoelectrodes that initiates from the edge of microelectrodes and grow along the electric field lines. These nanoelectrodes can effectively trap the MWCNT-coated particles, since they cover a large portion of the microchannel bottom surface and also create a much stronger electric field than the primary microelectrodes as confirmed by our numerical simulations. We will show that the presence of MWCNT significantly changes performance of the system, which is investigated by trapping sample polystyrene particles with plain, COOH and goat anti-mouse IgG surfaces. PMID:20301125

  7. Coulomb drag in multiwall armchair carbon nanotubes

    DEFF Research Database (Denmark)

    Lunde, A.M.; Jauho, Antti-Pekka

    2004-01-01

    We calculate the transresistivity rho(21) between two concentric armchair nanotubes in a diffusive multiwall carbon nanotube as a function of temperature T and Fermi level epsilon(F). We approximate the tight-binding band structure by two crossing bands with a linear dispersion near the Fermi...... surface. The cylindrical geometry of the nanotubes and the different parities of the Bloch states are accounted for in the evaluation of the effective Coulomb interaction between charges in the concentric nanotubes. We find a broad peak in rho(21) as a function of temperature at roughly T similar to 0.4T...

  8. Study of Carbon Nanotube-Substrate Interaction

    Directory of Open Access Journals (Sweden)

    Jaqueline S. Soares

    2012-01-01

    Full Text Available Environmental effects are very important in nanoscience and nanotechnology. This work reviews the importance of the substrate in single-wall carbon nanotube properties. Contact with a substrate can modify the nanotube properties, and such interactions have been broadly studied as either a negative aspect or a solution for developing carbon nanotube-based nanotechnologies. This paper discusses both theoretical and experimental studies where the interaction between the carbon nanotubes and the substrate affects the structural, electronic, and vibrational properties of the tubes.

  9. Meta- and hybrid-CNTs: A clue for the future development of carbon nanotubes

    International Nuclear Information System (INIS)

    A new generation of carbon nanotubes (CNTs), which may be named 'meta-nanotubes', is more and more the focus of the research worldwide. They result from the transformation of 'regular' CNTs by various ways such as functionalisation, doping, substitution, etc. The new nanomaterials thereby created are likely to exhibit new behaviors, specifically regarding properties that pristine CNTs do not possess (reactivity, solubility, magnetism...). The paper includes the description of the various routes to synthesize hybrid CNTs and their related advantages and limitations, while providing examples of the resulting materials from both literature and author's team work. Hybrid SWNTs (abbreviated as X at SWNTs) are one example of meta-nanotubes, and consist in SWNTs whose the hollow core is fully or partially filled with foreign atoms, molecules, or compounds. The inserted material may then exhibit a peculiar behavior with respect to the macroscopic state, for several non-exclusive reasons: 1D-dimension preventing electron scattering and enhancing the role of surface atoms, protection from surface adsorption of disturbing molecules by the carbon sheath, anisotropic lattice distortion or creation of new structures due to imposed dimensions, interactions/electron coupling with the surrounding carbon lattice. A wide field is thus open, possibly even wider than for pristine SWNTs

  10. Potential of carbon nanotube field effect transistors for analogue circuits

    KAUST Repository

    Hayat, Khizar

    2013-05-11

    This Letter presents a detailed comparison of carbon nanotube field effect transistors (CNFETs) and metal oxide semiconductor field effect transistors (MOSFETs) with special focus on carbon nanotube FET\\'s potential for implementing analogue circuits in the mm-wave and sub-terahertz range. The latest CNFET lithographic dimensions place it at-par with complementary metal oxide semiconductor in terms of current handling capability, whereas the forecasted improvement in the lithography enables the CNFETs to handle more than twice the current of MOSFETs. The comparison of RF parameters shows superior performance of CNFETs with a g m , f T and f max of 2.7, 2.6 and 4.5 times higher, respectively. MOSFET- and CNFET-based inverter, three-stage ring oscillator and LC oscillator have been designed and compared as well. The CNFET-based inverters are found to be ten times faster, the ring oscillator demonstrates three times higher oscillation frequency and CNFET-based LC oscillator also shows improved performance than its MOSFET counterpart.

  11. G-Quadruplex Guanosine Gels and Single Walled Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Yuehua Yu

    2013-12-01

    Full Text Available Solubilization of single walled carbon nanotubes (SWNTs in aqueous gel phases formed by reversible, G-quadruplex self-assembly of guanosine monophosphate (GMP alone or with guanosine (Guo is described. Unlike other media and methods for aqueous solubilization of SWNTs, the guanosine gels (“G-gels” are found to readily disperse high (>mg/mL concentrations of individual rather than bundled SWNTs. SWNT dispersions in GMP alone precipitate in several hours and re-form upon shaking; however, dispersions in the binary GMP/Guo gels are indefinitely stable. Increasing GMP or KCl concentration in the binary gels increased the relative abundance of large diameter and semi-conducting SWNTs. Different gel compositions also displayed different selectivities toward SWNTs of different chiralities. These results indicate a strong connection between the self-assembled G-gels and the dimensions and structures of the SWNTs that they solubilize.

  12. Higher Curvature Gravity in TeV-Scale Extra Dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Rizzo, Thomas G.

    2006-03-31

    We begin a general exploration of the phenomenology of TeV-scale extra-dimensional models with gravitational actions that contain higher curvature terms. In particular, we examine how the classic collider signatures of the models of Arkani-Hamed, Dimopoulos and Dvali (missing energy and new dimension-8 contact interactions) and of Randall and Sundrum (TeV-scale graviton Kaluza-Klein resonances) are altered by these modifications to the usual Einstein-Hilbert action. We find that not only are the detailed signatures for these gravitationally induced processes altered but new contributions are found to arise due to the existence of additional scalar Kaluza-Klein states in the spectrum.

  13. 4-N-pyridin-2-yl-benzamide nanotubes compatible with mouse stem cell and oral delivery in Drosophila

    Energy Technology Data Exchange (ETDEWEB)

    Yadav, Jhillu S; Das, Pragna P; Bag, Indira; Krishnan, Anita; Jagannadh, Bulusu; Mohapatra, Debendra K; Bhadra, Manika Pal [Division of Organic Chemistry-I, Indian Institute of Chemical Technology, Uppal Road, Hyderabad 500007 (India); Lavanya, Madugula P; Bhadra, Utpal [Functional Genomics and Gene Silencing Group, Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500007 (India)

    2010-04-16

    p-aminobenzoic acid (PABA), a structural moiety of many commercial drugs, is self-assembled with linker alkyl side chains to form tubular nanostructures. The tubes exhibited fluorescence either intrinsic or from fluorescent molecules embedded in the wall during self-assembly. Uptake and inter-cellular delivery of the conjugated nanotubes in human cancer cells and in mouse embryonic stem cells were demonstrated by fluorescence imaging and flow cytometry. Biocompatibility, cytotoxicity and clearance were monitored both ex vivo in mouse multipotent embryonic stem cells and in vivo in adult Drosophila. Accumulation of nanotubes had no adverse effects and abnormalities on stem cell morphology and proliferation rate. A distinct distribution of two separate nanotubes in various internal organs of Drosophila interprets that accumulation of nanomaterials might be interdependent on the side chain modifications and physiological settings of cell or tissue types. Unlike carbon nanomaterials, exposure of PABA nanotubes does not produce any hazards including locomotion defects and mortality of adult flies. Despite differential uptake and clearance from multiple live tissues, the use of self-assembled nanotubes can add new dimensions and scope to the development of dual-purpose oral carriers for the fulfilment of many biological promises.

  14. 4-N-pyridin-2-yl-benzamide nanotubes compatible with mouse stem cell and oral delivery in Drosophila

    Science.gov (United States)

    Yadav, Jhillu S.; Lavanya, Madugula P.; Das, Pragna P.; Bag, Indira; Krishnan, Anita; Jagannadh, Bulusu; Mohapatra, Debendra K.; Pal Bhadra, Manika; Bhadra, Utpal

    2010-04-01

    p-aminobenzoic acid (PABA), a structural moiety of many commercial drugs, is self-assembled with linker alkyl side chains to form tubular nanostructures. The tubes exhibited fluorescence either intrinsic or from fluorescent molecules embedded in the wall during self-assembly. Uptake and inter-cellular delivery of the conjugated nanotubes in human cancer cells and in mouse embryonic stem cells were demonstrated by fluorescence imaging and flow cytometry. Biocompatibility, cytotoxicity and clearance were monitored both ex vivo in mouse multipotent embryonic stem cells and in vivo in adult Drosophila. Accumulation of nanotubes had no adverse effects and abnormalities on stem cell morphology and proliferation rate. A distinct distribution of two separate nanotubes in various internal organs of Drosophila interprets that accumulation of nanomaterials might be interdependent on the side chain modifications and physiological settings of cell or tissue types. Unlike carbon nanomaterials, exposure of PABA nanotubes does not produce any hazards including locomotion defects and mortality of adult flies. Despite differential uptake and clearance from multiple live tissues, the use of self-assembled nanotubes can add new dimensions and scope to the development of dual-purpose oral carriers for the fulfilment of many biological promises.

  15. Dimensions of problem based learning

    DEFF Research Database (Denmark)

    Nielsen, Jørgen Lerche; Andreasen, Lars Birch

    2013-01-01

    The article contributes to the literature on problem based learning and problem-oriented project work, building on and reflecting the experiences of the authors through decades of work with problem-oriented project pedagogy. The article explores different dimensions of problem based learning such...... as the exploration of problems, the project method, online collaboration, and the dialogic nature of students’ working together. A special attention is given to the historical development and theoretical roots of problem-oriented project work in Denmark. The case to be explored will be the Masters...... programme in ICT and Learning (MIL). We discuss changes in the roles of the teachers as supervisors within this learning environment, and we explore the involvement of students as active participants and co-designers of how course and project activities unfold....

  16. Dimensions and Units in Electrodynamics

    CERN Document Server

    Hehl, F W; Hehl, Friedrich W; Obukhov, Yuri N

    2004-01-01

    We sketch the foundations of classical electrodynamics, in particular the transition that took place when Einstein, in 1915, succeeded to formulate general relativity. In 1916 Einstein demonstrated that, with a choice of suitable variables for the electromagnetic field, it is possible to put Maxwell's equation into a form that is covariant under general coordinate transformations. This unfolded, by basic contributions of Kottler, Cartan, van Dantzig, Schouten & Dorgelo, Toupin & Truesdell, and Post, to what one may call {\\em premetric classical electrodynamics.} This framework will be described shortly. An analysis is given of the physical dimensions involved in electrodynamics and subsequently the question of units addressed. It will be pointed out that these results are untouched by the generalization of classical to quantum electrodynamics (QED). We compare critically our results with those of {\\sl L.B. Okun} which he had presented at a recent conference.

  17. Keynote speech: Dimensions of Change

    DEFF Research Database (Denmark)

    Jørgensen, Kenneth Mølbjerg

    2004-01-01

    identities. As such the work of these disciplines is often rather misplaced and it tends to be rather unsuccessful. I argue that we need to adjust knowledge and learning strategies to local circumstances in order to be more successful in creating new knowledge. The presentation has three parts. First I...... introduce a basic framework for understanding knowledge. This is done by means of Wittgenstein's concept of language games. Second, I introduce the four dimensions of reality. Third I relate the model to the disciplines organizational learning and knowledge management....... I argue that this framework leads to a new and critical understanding of the disciplines organizational learning and knowledge management. In particular I argue that these disciplines often contain their own image of work and identity, which may be a sharp contrast to extant work forms and...

  18. CDMS, Supersymmetry and Extra Dimensions

    International Nuclear Information System (INIS)

    The CDMS experiment aims to directly detect massive, cold dark matter particles originating from the Milky Way halo. Charge and lattice excitations are detected after a particle scatters in a Ge or Si crystal kept at ∼30 mK, allowing to separate nuclear recoils from the dominating electromagnetic background. The operation of 12 detectors in the Soudan mine for 75 live days in 2004 delivered no evidence for a signal, yielding stringent limits on dark matter candidates from supersymmetry and universal extra dimensions. Thirty Ge and Si detectors are presently installed in the Soudan cryostat, and operating at base temperature. The run scheduled to start in 2006 is expected to yield a one order of magnitude increase in dark matter sensitivity

  19. Psychological dimensions of Energy Conservation

    Directory of Open Access Journals (Sweden)

    Tonello, Graciela

    2012-12-01

    Full Text Available One of the most serious current environmental problems is the depletion of non renewable natural resources. The vast majority of our daily actions involve the consumption of energy and they increase the problem. Environmental psychology studies the psychological motivations that determine pro-ecological behaviour. In this context the aim of this review was to determine which psychological models and variables are better descriptors of residential energy conservation, comparing the predictive power of different models related to behaviour, residential consumption as well as to the acceptability of energy policies. Results suggest that energy saving is mainly linked to altruistic motivations, followed by egoistic reasons and in a minor way to environmental concerns. People would act according to these dimensions when contextual conditions are perceived as appropriate.

  20. Quantum interest in two dimensions

    CERN Document Server

    Teo, E; Teo, Edward

    2002-01-01

    The quantum interest conjecture of Ford and Roman asserts that any negative-energy pulse must necessarily be followed by an over-compensating positive-energy one within a certain maximum time delay. Furthermore, the minimum amount of over-compensation increases with the separation between the pulses. In this paper, we first study the case of a negative-energy square pulse followed by a positive-energy one for a minimally coupled, massless scalar field in two-dimensional Minkowski space. We obtain explicit expressions for the maximum time delay and the amount of over-compensation needed, using a previously developed eigenvalue approach. These results are then used to give a proof of the quantum interest conjecture for massless scalar fields in two dimensions, valid for general energy distributions.

  1. String Universality in Six Dimensions

    CERN Document Server

    Kumar, Vijay

    2009-01-01

    In six dimensions, cancellation of gauge, gravitational, and mixed anomalies strongly constrains the set of quantum field theories which can be coupled consistently to gravity. We show that for some classes of six-dimensional supersymmetric gauge theories coupled to gravity, the anomaly cancellation conditions are equivalent to tadpole cancellation and other constraints on the matter content of heterotic/type I compactifications on K3. In these cases, all consistent 6D supergravity theories have a realization in string theory. We find one example which may arise from a novel string compactification, and we identify a new infinite family of models satisfying anomaly factorization. We find, however, that this infinite family of models, as well as other infinite families of models previously identified by Schwarz are pathological. We suggest that it may be feasible to demonstrate that there is a string theoretic realization of all consistent six-dimensional supergravity theories which have Lagrangian description...

  2. Extended Supersymmetries in One Dimension

    Directory of Open Access Journals (Sweden)

    F. Toppan

    2008-01-01

    Full Text Available This work covers part of the material presented at the Advanced Summer School in Prague. It is mostly devoted to the structural properties of Extended Supersymmetries in One Dimension. Several results are presented on the classification of linear, irreducible representations realized on a finite number of time-dependent fields. The connections between supersymmetry transformations, Clifford algebras and division algebras are discussed. A manifestly supersymmetric framework for constructing invariants without using the notion of superfields is presented. A few examples of one-dimensional, N-extended, off-shell invariant sigma models are computed. The relation between supersymmetry transformations and graph theory is outlined. The notion of the fusion algebra of irreps tensor products is presented. The relevance of one-dimensional Supersymmetric Quantum Mechanics as a way to extract information on higher dimensional supersymmetric field theories is discussed. 

  3. Nanotube reinforced thermoplastic polymer matrix composites

    Science.gov (United States)

    Shofner, Meisha Lei

    The inherent high strength, thermal conductivity, and electrical conductivity make nanotubes attractive reinforcements for polymer matrix composites. However, the structure that makes them desirable also causes highly anisotropic properties and limited reactivity with other materials. This thesis isolates these problems in two separate studies aimed at improving mechanical properties with single wall nanotube (SWNT) reinforced thermoplastic polymer composites. The two studies demonstrate the effect of solid freeform fabrication (SFF) and chemical functionalization on anisotropy and limited reactivity, respectively. Both studies showed mechanical property improvements. The alignment study demonstrates a maximum increase of 93% in tensile modulus with single wall nanotubes (SWNTs). The chemical functionalization study shows a larger increase in storage modulus for functionalized SWNTs as compared to purified SVWNTs with respective increases of 9% and 44% in storage modulus. Improved interfacial properties are also observed as a decrease in mechanical damping. Maximum property increases in composites are obtained when nanotubes are aligned, requiring additional processing consideration to the anisotropic structure. Melt spinning and extrusion processing effectively align nanotubes, but the end product of these techniques, composite fibers, requires further processing to be incorporated into finished parts. Extrusion-based SFF is a novel technique for processing nanotube reinforced composites because it allows for the direct fabrication of finished parts containing aligned nanotubes. SFF processing produces parts containing preferentially oriented nanotubes with improved mechanical properties when compared to isotropic composites. Functionalization of the nanotube surface disrupts the rope structure to obtain smaller ropes and promote further interfacial bonding. The chemically inert nature of nanotubes resulting from a structure containing few defects and the

  4. New direction in nanotube science

    Directory of Open Access Journals (Sweden)

    M. Terrones

    2004-10-01

    Full Text Available We review the latest advances in the production and state-of-the art characterization of B- and N-doped carbon nanotubes (CNTs and nanofibers. We briefly discuss different approaches to producing these novel doped nano-systems. The use of high-resolution transmission electron microscopy (HRTEM, electron energy loss spectroscopy (EELS, scanning tunneling spectroscopy (STS, Raman spectroscopy, and allied techniques to characterize these doped systems is reviewed. The field emission properties as well as some applications to the fabrication of novel polymer composites, Li+ batteries, and gas sensors are also discussed. It is clear that these materials possess outstanding properties when compared with pure CNTs, and it is foreseen that these systems will revolutionize some aspects of nanotube science and technology, thus opening a vast field of experimental and theoretical research.

  5. Mechanics of filled carbon nanotubes

    KAUST Repository

    Monteiro, A.O.

    2014-04-01

    The benefits of filling carbon nanotubes (CNTs) with assorted molecular and crystalline substances have been investigated for the past two decades. Amongst the study of new structural phases, defects, chemical reactions and varied types of host-guest interactions, there is one fundamental characterisation aspect of these systems that continues to be overlooked: the mechanical behaviour of filled CNTs. In contrast to their empty counterparts, the mechanics of filled CNTs is a subject where reports appear far and apart, this despite being key to the application of these materials in technological devices. In the following paragraphs, we review the work that has been carried out up to the present on the mechanics of filled CNTs. The studies discussed range from experimental resonant frequency essays performed within electron microscopes to modelling, via molecular dynamics, of three-point bending of nanotubes filled with gases. (C) 2014 Elsevier B.V. All rights reserved.

  6. On the metric dimension, the upper dimension and the resolving number of graphs

    OpenAIRE

    Garijo Royo, Delia; González Herrera, Antonio; Márquez Pérez, Alberto

    2013-01-01

    This paper deals with three resolving parameters: the metric dimension, the upper dimension and the resolving number. We first answer a question raised by Chartrand and Zhang asking for a characterization of the graphs with equal metric dimension and resolving number. We also solve in the affirmative a conjecture posed by Chartrand, Poisson and Zhang about the realization of the metric dimension and the upper dimension. Finally we prove that no integer $a\\geq 4$ is realizable as the resolving...

  7. Estimate for the fractal dimension of the Apollonian gasket in d dimensions.

    Science.gov (United States)

    Farr, R S; Griffiths, E

    2010-06-01

    We adapt a recent theory for the random close packing of polydisperse spheres in three dimensions [R. S. Farr and R. D. Groot, J. Chem. Phys. 131, 244104 (2009)] in order to predict the Hausdorff dimension dA of the Apollonian gasket in dimensions 2 and above. Our approximate results agree with published values in two and three dimensions to within 0.05% and 0.6%, respectively, and we provide predictions for dimensions 4-8. PMID:20866417

  8. Estimate for the fractal dimension of the Apollonian gasket in d dimensions

    OpenAIRE

    Farr, R. S.; Griffiths, E.

    2010-01-01

    We adapt a recent theory for the random close packing of polydisperse spheres in three dimensions [R. S. Farr and R. D. Groot, J. Chem. Phys. {\\bf 131} 244104 (2009)] in order to predict the Hausdorff dimension $d_{A}$ of the Apollonian gasket in dimensions 2 and above. Our approximate results agree with published values in $2$ and $3$ dimensions to within $0.05%$ and $0.6%$ respectively, and we provide predictions for dimensions $4$ to $8$.

  9. Photonics based on carbon nanotubes

    OpenAIRE

    Gu, Qingyuan; Gicquel-Guézo, Maud; Loualiche, Slimane; Pouliquen, Julie Le; Batte, Thomas; Folliot, Hervé; Dehaese, Olivier; Grillot, Frederic; Battie, Yann; Loiseau, Annick; Liang, Baolai; Huffaker, Diana

    2013-01-01

    Among direct-bandgap semiconducting nanomaterials, single-walled carbon nanotubes (SWCNT) exhibit strong quasi-one-dimensional excitonic optical properties, which confer them a great potential for their integration in future photonics devices as an alternative solution to conventional inorganic semiconductors. In this paper, we will highlight SWCNT optical properties for passive as well as active applications in future optical networking. For passive applications, we directly compare the effi...

  10. Hydrogen storage in nanotubes & nanostructures

    OpenAIRE

    Froudakis, George E.

    2011-01-01

    Over the last several years, a significant share of the scientific community has focused its attention on the hydrogen storage problem. Since 1997, when carbon nanotubes appeared to be a promising storage material, many theoretical and experimental groups have investigated the hydrogen storage capacity of these carbon nanostructures. These efforts were not always successful and consequently, the results obtained were often controversial. In the current review we attempt to summarize some the ...

  11. Photoluminescence Study of Carbon Nanotubes

    OpenAIRE

    Han, H. X.; Li, G. H.; Ge, W. K.; Wang, Z. P.; Xu, Z. Y.; Xie, S. S.; Chang, B H; Sun, L. F.; Wang, B S; G. Xu; Su, Z.B.

    2000-01-01

    ultiwalled carbon nanotubes, prepared by both electric arc discharge and chemical vapor deposition methods, show a strong visible light emission in photoluminescence experiments. All the samples employed in the experiments exhibit nearly same super-linear intensity dependence of the emission bands on the excitation intensity, and negligible temperature dependence of the central position and the line shapes of the emission bands. Based upon theoretical analysis of the electronic band structure...

  12. Large Bandgap Shrinkage from Doping and Dielectric Interface in Semiconducting Carbon Nanotubes

    Science.gov (United States)

    Comfort, Everett; Lee, Ji Ung

    2016-06-01

    The bandgap of a semiconductor is one of its most important electronic properties. It is often considered to be a fixed property of the semiconductor. As the dimensions of semiconductors reduce, however, many-body effects become dominant. Here, we show that doping and dielectric, two critical features of semiconductor device manufacturing, can dramatically shrink (renormalize) the bandgap. We demonstrate this in quasi-one-dimensional semiconducting carbon nanotubes. Specifically, we use a four-gated device, configured as a p-n diode, to investigate the fundamental electronic structure of individual, partially supported nanotubes of varying diameter. The four-gated construction allows us to combine both electrical and optical spectroscopic techniques to measure the bandgap over a wide doping range.

  13. 4D electron microscopy visualization of anisotropic atomic motions in carbon nanotubes.

    Science.gov (United States)

    Park, Sang Tae; Flannigan, David J; Zewail, Ahmed H

    2012-06-01

    We report the anisotropic atomic expansion dynamics of multi-walled carbon nanotubes, using 4D electron microscopy. From time-resolved diffraction on the picosecond to millisecond scale, following ultrafast heating at the rate of 10(13) K/s, it is shown that nanotubes expand only in the radial (intertubule) direction, whereas no significant change is observed in the intratubular axial or equatorial dimensions. The non-equilibrium heating occurs on an ultrafast time scale, indicating that the anisotropy is the result of an efficient electron-lattice coupling and is maintained up to equilibration. The recovery time, which measures the heat dissipation rate for equilibration, was found to be on the order of ∼100 μs. This recovery is reproduced theoretically by considering the composite specimen-substrate heat exchange. PMID:22591381

  14. Large Bandgap Shrinkage from Doping and Dielectric Interface in Semiconducting Carbon Nanotubes.

    Science.gov (United States)

    Comfort, Everett; Lee, Ji Ung

    2016-01-01

    The bandgap of a semiconductor is one of its most important electronic properties. It is often considered to be a fixed property of the semiconductor. As the dimensions of semiconductors reduce, however, many-body effects become dominant. Here, we show that doping and dielectric, two critical features of semiconductor device manufacturing, can dramatically shrink (renormalize) the bandgap. We demonstrate this in quasi-one-dimensional semiconducting carbon nanotubes. Specifically, we use a four-gated device, configured as a p-n diode, to investigate the fundamental electronic structure of individual, partially supported nanotubes of varying diameter. The four-gated construction allows us to combine both electrical and optical spectroscopic techniques to measure the bandgap over a wide doping range. PMID:27339272

  15. Hydrogen storage in nanotubes & nanostructures

    Directory of Open Access Journals (Sweden)

    George E. Froudakis

    2011-07-01

    Full Text Available Over the last several years, a significant share of the scientific community has focused its attention on the hydrogen storage problem. Since 1997, when carbon nanotubes appeared to be a promising storage material, many theoretical and experimental groups have investigated the hydrogen storage capacity of these carbon nanostructures. These efforts were not always successful and consequently, the results obtained were often controversial. In the current review we attempt to summarize some the highlights of the work on hydrogen storage in various types of nanotube and nanostructure, in a critical way. The nature of the interaction between hydrogen and the host nanomaterials, as revealed through theoretical modeling, helps us understand the basic mechanisms of hydrogen storage. Analysis of the results reveals why high hydrogen storage capacity at ambient conditions, which meets the DOE targets, cannot occur in bare carbon nanotubes. Through our analysis we also propose guidelines to enhance the hydrogen storage capacity of already synthesized materials and recommend advanced materials for this application.

  16. Method for nano-pumping using carbon nanotubes

    Science.gov (United States)

    Insepov, Zeke; Hassanein, Ahmed

    2009-12-15

    The present invention relates generally to the field of nanotechnology, carbon nanotubes and, more specifically, to a method and system for nano-pumping media through carbon nanotubes. One preferred embodiment of the invention generally comprises: method for nano-pumping, comprising the following steps: providing one or more media; providing one or more carbon nanotubes, the one or more nanotubes having a first end and a second end, wherein said first end of one or more nanotubes is in contact with the media; and creating surface waves on the carbon nanotubes, wherein at least a portion of the media is pumped through the nanotube.

  17. Molecular Dynamics Modeling of Carbon Nanotubes and Their Composites

    Science.gov (United States)

    Jensen, Lars R.; Pyrz, Ryszard

    2004-06-01

    The tensile modulus of individual nanotubes and nanotube-polypropylene composites has been determined using molecular dynamics simulations. Simulations of individual single-walled carbon nanotubes showed that their tensile modulus was dependent on the tube structure and the diameter if the diameter was below 1,6 nm. The tensile modulus was determined for an infinite single-walled carbon nanotube embedded in an amorphous polypropylene matrix and for a finite and capped single-walled carbon nanotube embedded in a polypropylene matrix. For the infinite nanotube-polypropylene system the modulus was found to correspond to the one given by the Voigt approximation. For the finite nanotube-polypropylene system the reinforcing effect of the nanotube was not very pronounced. A pull out simulation showed that the length of the nanotube in the simulation was much smaller than the critical length and hence no load transfer between the nanotube and the matrix existed.

  18. Qualitative Mapping of Structural Different Polypeptide Nanotubes

    DEFF Research Database (Denmark)

    Clausen, Casper Hyttel; Jensen, Jason; Castillo, Jaime;

    2008-01-01

    paper, electrostatic force microscopy (EFM) was used to distinguish between hollow nanotubes formed by self-assembly by a simple aromatic dipeptide, L-phenylalanine, silver-filled peptide-based nanotubes, and silver wires placed on prefabricated SiO(2) surfaces with a backgate. The investigation shows...

  19. Charge Screening Effect in Metallic Carbon Nanotubes

    OpenAIRE

    Sasaki, K

    2001-01-01

    Charge screening effect in metallic carbon nanotubes is investigated in a model including the one-dimensional long-range Coulomb interaction. It is pointed out that an external charge which is being fixed spatially is screened by internal electrons so that the resulting object becomes electrically neutral. We found that the screening length is given by about the diameter of a nanotube.

  20. Nanotubes based on monolayer blue phosphorus

    KAUST Repository

    Montes, E.

    2016-07-08

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

  1. Batch fabrication of nanotubes suspended between microelectrodes

    DEFF Research Database (Denmark)

    Mateiu, Ramona Valentina; Stöckli, T.; Knapp, H. F.;

    2007-01-01

    done with a simple lift-off process with standard photolithographic resist. An applied electric field is sustained between the microelectrodes during CVD to guide the nanotube growth. Comparison with simulations shows that the location and the orientation of the grown carbon nanotubes (CNT) correspond...

  2. Channeling of protons through BN nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Borka Jovanović, V., E-mail: vborka@vinca.rs; Borka, D.

    2015-07-01

    In this paper we study the angular and spatial distributions of protons channeled through boron–nitride (BN) nanotubes. The BN nanotubes have very similar structures like carbon nanotubes, but they are more thermally and chemically stable, and they also present good candidates for future channeling experiments. We present the angular and spatial distributions of MeV energy protons through the straight short (10, 10) single-wall BN nanotubes (SWBNNs). They were generated by a computer simulation method Borka et al. (2011, 2012a,b). Also, the effect of focusing of channeled protons is observed. A possible application of the obtained results for characterization of BN nanotubes is discussed. Analysis of angular and spatial distributions could be used to provide detailed information on the projectile–target interaction potentials inside BN nanotubes. We also varied the proton incident angle and energy and demonstrate that we can get a significant rearrangement of the propagating protons within the BN nanotube. This investigation may be used for proton beam guiding, to locate atomic impurities in nanotubes as well as for creating nanosized proton beams to be used in materials science, biology and medicine.

  3. Defect-Free Carbon Nanotube Coils.

    Science.gov (United States)

    Shadmi, Nitzan; Kremen, Anna; Frenkel, Yiftach; Lapin, Zachary J; Machado, Leonardo D; Legoas, Sergio B; Bitton, Ora; Rechav, Katya; Popovitz-Biro, Ronit; Galvão, Douglas S; Jorio, Ado; Novotny, Lukas; Kalisky, Beena; Joselevich, Ernesto

    2016-04-13

    Carbon nanotubes are promising building blocks for various nanoelectronic components. A highly desirable geometry for such applications is a coil. However, coiled nanotube structures reported so far were inherently defective or had no free ends accessible for contacting. Here we demonstrate the spontaneous self-coiling of single-wall carbon nanotubes into defect-free coils of up to more than 70 turns with identical diameter and chirality, and free ends. We characterize the structure, formation mechanism, and electrical properties of these coils by different microscopies, molecular dynamics simulations, Raman spectroscopy, and electrical and magnetic measurements. The coils are highly conductive, as expected for defect-free carbon nanotubes, but adjacent nanotube segments in the coil are more highly coupled than in regular bundles of single-wall carbon nanotubes, owing to their perfect crystal momentum matching, which enables tunneling between the turns. Although this behavior does not yet enable the performance of these nanotube coils as inductive devices, it does point a clear path for their realization. Hence, this study represents a major step toward the production of many different nanotube coil devices, including inductors, electromagnets, transformers, and dynamos. PMID:26708150

  4. Mechanical properties of hybrid polymer nanotube systems

    Science.gov (United States)

    Coleman, Jonathan N.; Cadek, Martin; Dalton, Alan B.; Munoz, Edgar; Razal, Joselito; Baughman, Ray H.; Blau, Werner J.

    2003-04-01

    In this work, mechanical properties of hybrid materials fabricated from nanotubes and commercially available polymers were investigated. It was found that, by adding various concentrations of arc discharge multiwall nanotubes, both Young"s modulus and hardness increased by factors of 1.8 and 1.6 at 1wt% in PVA and 2.8 and 2.0 at 8wt% in PVK, in reasonable agreement with the Halpin-Tsai theory. Furthermore, the presence of the nanotubes was found to nucleate crystallization of the PVA. This crystal growth is thought to enhance matrix-nanotube stress transfer. In addition, microscopy studies suggest extremely strong interfacial bonding in the PVA-based composite. This is manifested by the fracture of the polymer rather that the polymer-nanotube interface. The dependence of the polymer nanotube interfacial interaction on host polymer was studied by intercalating various polymers (PVA, PVP and PS) into single wall nanotube buckypaper. Even for short soak times, significant polymer intercalation into existing free volume was observed. Depending on the polymer and the level of intercalation tensile tests on intercalated sheets showed that the Young"s modulus, strength and toughness increased by factors of 3, 9 and 28, respectively. This indicates that the intercalated polymer enhances load transmission between nanotubes due the significant stress transfer. The level of stress transfer was observed to scale with polymer hydrophobicity as expected.

  5. Invisible Hyperbolic Metamaterial Nanotube at Visible Frequency.

    Science.gov (United States)

    Kim, Kyoung-Ho; No, You-Shin; Chang, Sehwan; Choi, Jae-Hyuck; Park, Hong-Gyu

    2015-01-01

    Subwavelength-scale metal and dielectric nanostructures have served as important building blocks for electromagnetic metamaterials, providing unprecedented opportunities for manipulating the optical response of the matter. Recently, hyperbolic metamaterials have been drawing particular interest because of their unusual optical properties and functionalities, such as negative refraction and hyperlensing of light. Here, as a promising application of a hyperbolic metamaterial at visible frequency, we propose an invisible nanotube that consists of metal and dielectric alternating thin layers. The theoretical study of the light scattering of the layered nanotube reveals that almost-zero scattering can be achieved at a specific wavelength when the transverse-electric- or transverse-magnetic-polarized light is incident to the nanotube. In addition, the layered nanotube can be described as a radial-anisotropic hyperbolic metamaterial nanotube. The low scattering occurs when the effective permittivity of the hyperbolic nanotube in the angular direction is near zero, and thus the invisibility of the layered nanotube can be efficiently obtained by analyzing the equivalent hyperbolic nanotube. Our new method to design and tune an invisible nanostructure represents a significant step toward the practical implementation of unique nanophotonic devices such as invisible photodetectors and low-scattering near-field optical microscopes. PMID:26522815

  6. Carbon nanotubes composites for microwave applications

    OpenAIRE

    Herrero Fernández, Diego

    2015-01-01

    Carbon nanotubes have become a focus of study due to the great applications you can have and its excellent properties. In this thesis the compounds formed by a host and a percentage of carbon nanotubes are modelled. The models used are the Debye model, the Maxwell Garnett model and McLachlan model. These models have been implemented in ...

  7. Carbon nanotube flow sensor device and method

    OpenAIRE

    Sood, Ajay Kumar; Ghosh, Shankar

    2004-01-01

    A method and device for measuring the flow of a liquid utilizes at least one carbon nanotube. More particularly, the velocity of a liquid along the direction of the flow is measured as a function of them current/voltage generated in at least one carbon nanotube due to the flow of the liquid along its surface.

  8. CARBON NANOTUBES: PROPERTIES AND APPLICATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, John, E.

    2009-07-24

    Carbon nanotubes were discovered in 1991 as a minority byproduct of fullerene synthesis. Remarkable progress has been made in the ensuing years, including the discovery of two basic types of nanotubes (single-wall and multi-wall), great strides in synthesis and purification, elucidation of many fundamental physical properties, and important steps towards practical applications. Both the underlying science and technological potential of SWNT can profitably be studied at the scale of individual tubes and on macroscopic assemblies such as fibers. Experiments on single tubes directly reveal many of the predicted quantum confinement and mechanical properties. Semiconductor nanowires have many features in common with nanotubes, and many of the same fundamental and practical issues are in play – quantum confinement and its effect on properties; possible device structures and circuit architectures; thermal management; optimal synthesis, defect morphology and control, etc. In 2000 we began a small effort in this direction, conducted entirely by undergraduates with minimal consumables support from this grant. With DOE-BES approval, this grew into a project in parallel with the carbon nanotube work, in which we studied of inorganic semiconductor nanowire growth, characterization and novel strategies for electronic and electromechanical device fabrication. From the beginnings of research on carbon nanotubes, one of the major applications envisioned was hydrogen storage for fuel-cell powered cars and trucks. Subsequent theoretical models gave mixed results, the most pessimistic indicating that the fundamental H2-SWNT interaction was similar to flat graphite (physisorption) with only modest binding energies implying cryogenic operation at best. New material families with encouraging measured properties have emerged, and materials modeling has gained enormously in predictive power, sophistication, and the ability to treat a realistically representative number of atoms. One of

  9. Light Emission in Silicon from Carbon Nanotubes

    CERN Document Server

    Gaufrès, Etienne; Noury, Adrien; Roux, Xavier Le; Rasigade, Gilles; Beck, Alexandre; Vivien, Laurent

    2015-01-01

    The use of optics in microelectronic circuits to overcome the limitation of metallic interconnects is more and more considered as a viable solution. Among future silicon compatible materials, carbon nanotubes are promising candidates thanks to their ability to emit, modulate and detect light in the wavelength range of silicon transparency. We report the first integration of carbon nanotubes with silicon waveguides, successfully coupling their emission and absorption properties. A complete study of this coupling between carbon nanotubes and silicon waveguides was carried out, which led to the demonstration of the temperature-independent emission from carbon nanotubes in silicon at a wavelength of 1.3 {\\mu}m. This represents the first milestone in the development of photonics based on carbon nanotubes on silicon.

  10. Development of supercapacitors based on carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    马仁志; 魏秉庆; 徐才录; 梁吉; 吴德海

    2000-01-01

    Block-type electrodes made of carbon nanotubes were fabricated by different processes. The volumetric specific capacitance based on such electrodes reached 107 F/cm3, which proves carbon nanotubes to be ideal candidate materials for supercapacitors. The composite electrodes consisting of carbon nanotubes and RuO2 ·xH2O were developed by the deposition of RuO2 on the surface of carbon nanotubes. Supercapacitors based on the composite electrodes show much higher specific capacitance than those based on pure carbon nanotube ones. A specific capacitance of 600 F/g can be achieved when the weight percent of RuO2· xH2O in the composite electrodes reaches 75% . In addition , supercapacitors based on the composite electrodes show both high energy density and high power density characteristics.

  11. Development of supercapacitors based on carbon nanotubes

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Block-type electrodes made of carbon nanotubes were fabricated by different processes. The volumetric specific capacitance based on such electrodes reached 107 F/cm3, which proves carbon nanotubes to be ideal candidate materials for supercapacitors. The composite electrodes consisting of carbon nanotubes and RuO2.xH2O were developed by the deposition of RuO2 on the surface of carbon nanotubes. Supercapacitors based on the composite electrodes show much higher specific capacitance than those based on pure carbon nanotube ones. A specific capacitance of 600 F/g can be achieved when the weight percent of RuO2.xH2O in the composite electrodes reaches 75%. In addition, supercapacitors based on the composite electrodes show both high energy density and high power density characteristics.

  12. Pure and doped boron nitride nanotubes

    Directory of Open Access Journals (Sweden)

    M. Terrones

    2007-05-01

    Full Text Available More than ten years ago, it was suggested theoretically that boron nitride (BN nanotubes could be produced. Soon after, various reports on their synthesis appeared and a new area of nanotube science was born. This review aims to cover the latest advances related to the synthesis of BN nanotubes. We show that these tubes can now be produced in larger amounts and, in particular, that the chemistry of BN tubes appears to be very important to the production of reinforced composites with insulating characteristics. From the theoretical standpoint, we also show that (BN-C heteronanotubes could have important implications for nanoelectronics. We believe that BN nanotubes (pure and doped could be used in the fabrication of novel devices in which pure carbon nanotubes do not perform very efficiently.

  13. Characterization of chrysotile, tellurium and iImogolite nanotubes

    OpenAIRE

    Métraux, Cédric; Grobéty, Bernard; Jenny, Titus

    2009-01-01

    The discovery of C60 (R. Smalley et al.) and carbon nanotubes CNTs (S. Iijima) in 1985 and 1991 respectively was a milestone in the field of nanoscience. Since 1991, WS2, MoS2, BN, Se, Te nanotubes were synthesized and analyzed. These nanotubes are promising materials for many applications in the field of catalysis, electronic, polymer synthesis, etc. In this study, we characterized the crystallographic and chemical properties of two natural and one synthetic nanotubes: 1) chrysotile nanotube...

  14. Schottky barriers at metal-finite semiconducting carbon nanotube interfaces

    OpenAIRE

    Xue, Yongqiang; Mark A. Ratner

    2003-01-01

    Electronic properties of metal-finite semiconducting carbon nanotube interfaces are studied as a function of the nanotube length using a self-consistent tight-binding theory. We find that the shape of the potential barrier depends on the long-range tail of the charge transfer, leading to an injection barrier thickness comparable to half of the nanotube length until the nanotube reaches the bulk limit. The conductance of the nanotube junction shows a transition from tunneling to thermally-acti...

  15. Chitosan-mediated synthesis of carbon nanotube-gold nanohybrids

    Institute of Scientific and Technical Information of China (English)

    GRAVEL; Edmond; FOILLARD; Stéphanie; DORIS; Eric

    2010-01-01

    Metal-nanotube nanohybrids were produced by in situ synthesis and stabilization of gold nanoparticles on chitosan-functionalized carbon nanotubes.The formation of gold nanoparticles from tetrachloroauric acid was observed after only a few minutes of contact with the functionalized nanotubes,at room temperature.These results suggest that adsorption of chitosan at the surface of carbon nanotubes permits smooth reduction of the metallic salt and efficient anchoring of gold nanoparticles to the nanotubes.

  16. Space: The Hunt for Hidden Dimensions

    International Nuclear Information System (INIS)

    Extra dimensions of space may be present in our universe. Their discovery would dramatically change our view of the cosmos and would prompt many questions. How do they hide? What is their shape? How many are there? How big are they? Do particles and forces feel their presence? This lecture will explain the concept of dimensions and show that current theoretical models predict the existence of extra spatial dimensions which could be in the discovery reach of present and near-term experiments. The manner by which these additional dimensions reveal their existence will be described. Searches for modifications of the gravitational force, astrophysical effects, and collider signatures already constrain the size of extra dimensions and will be summarized. Once new dimensions are discovered, the technology by which the above questions can be answered will be discussed.

  17. Delimiting Maximal Kissing Configurations in Four Dimensions

    CERN Document Server

    Altschuler, Eric Lewin

    2013-01-01

    How many unit $n-$dimensional spheres can simultaneously touch or kiss a central $n-$dimensional unit sphere? Beyond mathematics this question has implications for fields such as cryptography and the structure of biologic and chemical macromolecules. The kissing number is only known for dimensions 1-4, 8 and 24 (2, 6, 12, 24, 240, 19650, respectively) and only particularly obvious for dimensions one and two. Indeed, in four dimensions it is not even known if Platonic polytope unique to that dimension known as the 24-cell is the unique kissing configuration. We have not been able to prove that the 24-cell is unique, but, using a physical approach utilizing the hopf map from four to three dimensions, we for the first time delimit the possible other configurations which could be kissing in four dimensions.

  18. Electrochemical p-doping modification of carbon nanotubes with Prussian Blue

    Energy Technology Data Exchange (ETDEWEB)

    Forment-Aliaga, Alicia; Weitz, Ralf Thomas; Burghard, Marko [Max-Planck Institute for Solid State Research, Stuttgart (Germany); Kern, Klaus [Max-Planck Institute for Solid State Research, Stuttgart (Germany); Institut de Physique des Nanostructures, EPFL, Lausanne (Switzerland)

    2008-07-01

    Electrochemical modification is an effective method to tune the properties of carbon nanotubes. In this communication, we report on the modification of individual carbon nanotubes (SWCNTs) by electrodeposition of the molecular magnet Prussian Blue (PB) FeIII{sub 4}[FeII(CN){sub 6}]3{sup *}nH{sub 2}O (n=14-16). While previous studies have primarily addressed the electrocatalytic properties of PB-modified bulk nanotube electrodes,1 the motivation behind the present work is to investigate the influence of inorganic coatings on the charge transport characteristics of individual SWCNTs. The formation of PB under the applied electrochemical conditions has been proven by various characterization techniques. In contrast to metallic SWCNTs whose electrical conductivity remained largely unaffected, semiconducting tubes exhibited a strongly altered behavior after PB deposition. Specifically, in the latter case, the conductance vs. gate voltage curves were substantially shifted toward more positive gate voltages, indicative of enhanced p-type doping of the tubes. Temperature-dependent measurements revealed that the threshold voltage decreases significantly upon cooling, which is attributed to freezing out of the hole transfer from PB to the underlying nanotubes.

  19. Potential in vitro effects of carbon nanotubes on human aortic endothelial cells

    International Nuclear Information System (INIS)

    Respiratory exposure of mice to carbon nanotubes induces pulmonary toxicity and adverse cardiovascular effects associated with atherosclerosis. We hypothesize that the direct contact of carbon nanotubes with endothelial cells will result in dose-dependent effects related to altered cell function and cytotoxicity which may play a role in potential adverse pulmonary and cardiovascular outcomes. To test this hypothesis, we examined the effects of purified single- and multi-walled carbon nanotubes (SWCNT and MWCNT) on human aortic endothelial cells by evaluating actin filament integrity and VE-cadherin distribution by fluorescence microscopy, membrane permeability by measuring the lactate dehydrogenase (LDH) release, proliferation/viability by WST-1 assay, and overall functionality by tubule formation assay. Marked actin filament and VE-cadherin disruption, cytotoxicity, and reduced tubule formation occurred consistently at 24 h post-exposure to the highest concentrations [50-150 μg/106 cells (1.5-4.5 μg/ml)] for both SWCNT and MWCNT tested in our studies. These effects were not observed with carbon black exposure and carbon nanotube exposure in lower concentrations [1-10 μg/106 cells (0.04-0.4 μg/ml)] or in any tested concentrations at 3 h post-exposure. Overall, the results indicate that SWCNT and MWCNT exposure induce direct effects on endothelial cells in a dose-dependent manner.

  20. Exploring Extra Dimensions in Spectroscopy Experiments

    Institute of Scientific and Technical Information of China (English)

    LUO Feng; LIU Hong-Ya

    2006-01-01

    @@ We propose an idea in spectroscopy to search for extra spatial dimensions as well as to detect the possible deviation from Newton's inverse-square law at small scale, and we take high-Z hydrogenic systems and muonic atoms as illustrations. The relevant experiments might help to explore a more than two extra dimensions scenario in the brane world model proposed by Arkani-Hamed, Dimopoulos, Dvali (ADD) and to set constraints for fundamental parameters such as the size of extra dimensions.

  1. On Hopf algebras of dimension 4p

    CERN Document Server

    Cheng, Yi-Lin

    2010-01-01

    In this paper, we prove that a non-semisimple Hopf algebra H of dimension 4p with p an odd prime over an algebraically closed field of characteristic zero is pointed provided H contains more than two group-like elements. In particular, we prove that non-semisimple Hopf algebras of dimensions 20, 28 and 44 are pointed or their duals are pointed, and this completes the classification of Hopf algebras in these dimensions.

  2. Green Lifestyle Dimensions : An Empirical Study

    OpenAIRE

    Arfida Handoyo; Popy

    2012-01-01

    Exploring green lifestyles is an interesting subject. Given the increase of awareness among global customers worldwide, investigating green lifestyle dimensions is a challenging task, particularly in a developing country like Indonesia. The purpose of this paper is to identify the green lifestyle among Indonesians by using lifestyle patterns. The dimensions applied for this study use the nine-dimension green lifestyle from Arminda do Pac¸o & Ma´rio Raposo (2008:371). These are environmentally...

  3. Percolation transitions in two dimensions

    Science.gov (United States)

    Feng, Xiaomei; Deng, Youjin; Blöte, Henk W. J.

    2008-09-01

    We investigate bond- and site-percolation models on several two-dimensional lattices numerically, by means of transfer-matrix calculations and Monte Carlo simulations. The lattices include the square, triangular, honeycomb kagome, and diced lattices with nearest-neighbor bonds, and the square lattice with nearest- and next-nearest-neighbor bonds. Results are presented for the bond-percolation thresholds of the kagome and diced lattices, and the site-percolation thresholds of the square, honeycomb, and diced lattices. We also include the bond- and site-percolation thresholds for the square lattice with nearest- and next-nearest-neighbor bonds. We find that corrections to scaling behave according to the second temperature dimension Xt2=4 predicted by the Coulomb gas theory and the theory of conformal invariance. In several cases there is evidence for an additional term with the same exponent, but modified by a logarithmic factor. Only for the site-percolation problem on the triangular lattice does such a logarithmic term appear to be small or absent. The amplitude of the power-law correction associated with Xt2=4 is found to be dependent on the orientation of the lattice with respect to the cylindrical geometry of the finite systems.

  4. Moving into the third dimension

    CERN Multimedia

    Alizée Dauvergne

    2010-01-01

    One detail at a time, digital 3-D models of CERN’s various machines are being created by the Integration Section in the Machines & Experimental Facilities Group (EN/MEF) . The work, which requires painstaking attention to detail on a colossal scale, facilitates improvements to existing accelerators and the design of new machines in the future.   Virtual representation of the LHC A complete digital mockup of the LHC in three dimensions already exists, including of course the tunnel, the machine systems including magnets and vacuum chambers, but also all of the various services such as cable ladders, piping systems and access control and so on. Only the colour and the texture of the surfaces betray that it is a mockup and not the real thing! The mockup of LINAC4 is finished too. The mockups for the SPS, ISOLDE and the entire PS complex, including transfer lines, are still being created. “Creating these 3-D mockups will allow us to work on forthcoming machine improvements, esp...

  5. Extra dimensions at particle colliders

    Energy Technology Data Exchange (ETDEWEB)

    Dvergsnes, Erik Wolden

    2004-08-01

    This thesis consists of an introduction where we consider different aspects of theories involving extra dimensions, together with four research publications (Papers I-IV) attached at the end. The introductional chapters should serve as background material for better understanding the models on which the articles are based. In Chap. 4 we also present some plots not included in the papers. The topic of Papers I-III is graviton induced Bremsstrahlung. In Paper I we consider the contribution to this process from graviton exchange through gluon-gluon fusion at the LHC, compared to the QED background. Only final-state radiation is considered in Paper I, whereas in Paper II we extend this work to include also the quark-antiquark annihilation with graviton exchange, as well as initial-state radiation for both graviton and Standard Model exchange. Paper III is a study of graviton-induced Bremsstrahlung at e{sup +}e{sup -} colliders, including both initial- and final-state radiation. Paper IV is devoted to a study of the center-edge asymmetry at hadron colliders, an asymmetry which previously had been studied for e{sup +}e{sup -} colliders. The center-edge asymmetry can be used as a method of distinguishing between spin-1 and spin-2 exchange, something which will be of major importance if a signal is observed.

  6. Optoacoustic imaging in five dimensions

    Science.gov (United States)

    Deán-Ben, X. L.; Gottschalk, Sven; Fehm, Thomas F.; Razansky, Daniel

    2015-03-01

    We report on an optoacoustic imaging system capable of acquiring volumetric multispectral optoacoustic data in real time. The system is based on simultaneous acquisition of optoacoustic signals from 256 different tomographic projections by means of a spherical matrix array. Thereby, volumetric reconstructions can be done at high frame rate, only limited by the pulse repetition rate of the laser. The developed tomographic approach presents important advantages over previously reported systems that use scanning for attaining volumetric optoacoustic data. First, dynamic processes, such as the biodistribution of optical biomarkers, can be monitored in the entire volume of interest. Second, out-of-plane and motion artifacts that could degrade the image quality when imaging living specimens can be avoided. Finally, real-time 3D performance can obviously save time required for experimental and clinical observations. The feasibility of optoacoustic imaging in five dimensions, i.e. real time acquisition of volumetric datasets at multiple wavelengths, is reported. In this way, volumetric images of spectrally resolved chromophores are rendered in real time, thus offering an unparallel imaging performance among the current bio-imaging modalities. This performance is subsequently showcased by video-rate visualization of in vivo hemodynamic changes in mouse brain and handheld visualization of blood oxygenation in deep human vessels. The newly discovered capacities open new prospects for translating the optoacoustic technology into highly performing imaging modality for biomedical research and clinical practice with multiple applications envisioned, from cardiovascular and cancer diagnostics to neuroimaging and ophthalmology.

  7. A Note on FP-Injective Dimension

    Institute of Scientific and Technical Information of China (English)

    Yang SONG; Xian Neng DU; Zhi Bing ZHAO

    2011-01-01

    Let R and S be a left coherent ring and a right coherent ring respectively, Rωs be a faithfully balanced self-orthogonal bimodule. We give a sufficient condition to show that l. FP-idR(ω) <∞ implies G-dinω(M) <∞, where M ∈ mod R. This result generalizes the result by Huang and Tang about the relationship between the FP-injective dimension and the generalized Gorenstein dimension in 2001. In addition, we get that the left orthogonal dimension is equal to the generalized Gorenstein dimension when G- dimω (M) is finite.

  8. A Divergence Formula for Randomness and Dimension

    OpenAIRE

    Lutz, Jack H.

    2008-01-01

    If $S$ is an infinite sequence over a finite alphabet $\\Sigma$ and $\\beta$ is a probability measure on $\\Sigma$, then the {\\it dimension} of $ S$ with respect to $\\beta$, written $\\dim^\\beta(S)$, is a constructive version of Billingsley dimension that coincides with the (constructive Hausdorff) dimension $\\dim(S)$ when $\\beta$ is the uniform probability measure. This paper shows that $\\dim^\\beta(S)$ and its dual $\\Dim^\\beta(S)$, the {\\it strong dimension} of $S$ with respect to $\\beta$, can b...

  9. Fractal Dimension of Voice-Signal Waveforms

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The fractal dimension is one important parameter that characterizes waveforms. In this paper, we derive a new method to calculate fractal dimension of digital voice-signal waveforms. We show that fractal dimension is an efficient tool for speaker recognition or speech recognition. It can be used to identify different speakers or distinguish speech. We apply our results to Chinese speaker recognition and numerical experiment shows that fractal dimension is an efficient parameter to characterize individual Chinese speakers. We have developed a semiautomatic voiceprint analysis system based on the theory of this paper and former researches.

  10. Relaxation Principle in (n+1) Dimensions

    CERN Document Server

    Um, Choong Min

    2014-01-01

    Why do we live in a (3+1) dimensional universe? In this paper, I review the "relaxation principle" first introduced by Karch and Randall (arXiv:hep-th/0506053v2) and generalize its ideas to an arbitrary (n+1) dimensions. This is done by referring to the Friedman equation and the scaling solution to derive the energy densities of the non-interacting and interacting branes, and then formulating their dimensionalities. I also demonstrate that the largest interacting d-brane in n spatial dimensions is always the (n-2)-brane, and that such dimensionality constraint "relaxed" our universe from nine dimensions to three dimensions.

  11. Relationship between tooth dimensions and malocclusion

    International Nuclear Information System (INIS)

    Objective: To observe the difference in dimension of teeth among adult females with and without malocclusion. Methods: The cross-sectional study was conducted at Dr. Ishrat-ul-Ebad Khan Institute of Oral Health Sciences, Dow University of Health Sciences, Karachi, from April 2011 to April 2013, and used non-probability consecutive sampling. Mesiodistal and buccolingual crown dimensions were measured on study casts by using digital sliding caliper in 2 groups of females. Group1 had 150 subjects with normal occlusion, while Group 2 had 234 with malocclusion. Independent t test was conducted to evaluate the difference between the dimensions of teeth of the two groups. Statistical analysis was done on SPSS version 16, and p value was considered significant at 0.05. Results: Overall, the difference between the groups showed a greater tooth dimension in the malocclusion group of population compared to the normal group, and the most significant difference was observed in the mesiodistal dimension of maxillary 2nd premolar, which was 0.9+-0.6801mm greater in dimension in the malocclusion group compared to the normal group. The least difference was observed in the buccolingual dimension of the mandibular central incisor where the malocclusion group had only 0.08+-0.5247mm larger mandibular central incisors in the buccolingual dimension compared to the normal group. Conclusion: Mesiodistal and buccolingual crown dimensions were characteristically larger in the malocclusion group. (author)

  12. Investigating the effect of carbon nanotube diameter and wall number in carbon nanotube/silicon heterojunction solar cells

    OpenAIRE

    Tom Grace; LePing Yu; Christopher Gibson; Daniel Tune; Huda Alturaif; Zeid Al Othman; Joseph Shapter

    2016-01-01

    Suspensions of single-walled, double-walled and multi-walled carbon nanotubes (CNTs) were generated in the same solvent at similar concentrations. Films were fabricated from these suspensions and used in carbon nanotube/silicon heterojunction solar cells and their properties were compared with reference to the number of walls in the nanotube samples. It was found that single-walled nanotubes generally produced more favorable results; however, the double and multi-walled nanotube films used in...

  13. Origin of Everything and the 21 Dimensions of the Universe

    Science.gov (United States)

    Loev, Mark

    2009-03-01

    The Dimensions of the Universe correspond with the Dimensions of the human body. The emotion that is a positive for every dimension is Love. The negative emotion that effects each dimension are listed. All seven negative emotions effect Peace, Love and Happiness. 21st Dimension: Happiness Groin & Heart 20th Dimension: Love Groin & Heart 19th Dimension: Peace Groin & heart 18th Dimension: Imagination Wave Eyes Anger 17th Dimension: Z Wave / Closed Birth 16th Dimension: Electromagnetic Wave Ears Anger 15th Dimension: Universal Wave Skin Worry 14th Dimension: Lover Wave Blood Hate 13th Dimension: Disposal Wave Buttocks Fear 12th Dimension: Builder Wave Hands Hate 11th Dimension: Energy Wave Arms Fear 10th Dimension: Time Wave Brain Pessimism 9th Dimension: Gravity Wave Legs Fear 8th Dimension: Sweet Wave Pancreas Fear 7th Dimension: File Wave Left Lung Fear 6th Dimension: Breathing Wave Right Lung Fear 5th Dimension: Digestive Wave Stomach Fear 4th Dimension: Swab Wave Liver Guilt 3rd Dimension: Space Wave Face Sadness 2nd Dimension: Line Wave Mouth Revenge 1st Dimension: Dot Wave Nose Sadness The seven deadly sins correspond: Anger Hate Sadness Fear Worry Pessimism Revenge Note: Guilt is fear

  14. Titania nanotube arrays as potential interfaces for neurological prostheses

    Science.gov (United States)

    Sorkin, Jonathan Andrew

    Neural prostheses can make a dramatic improvement for those suffering from visual and auditory, cognitive, and motor control disabilities, allowing them regained functionality by the use of stimulating or recording electrical signaling. However, the longevity of these devices is limited due to the neural tissue response to the implanted device. In response to the implant penetrating the blood brain barrier and causing trauma to the tissue, the body forms a to scar to isolate the implant in order to protect the nearby tissue. The scar tissue is a result of reactive gliosis and produces an insulated sheath, encapsulating the implant. The glial sheath limits the stimulating or recording capabilities of the implant, reducing its effectiveness over the long term. A favorable interaction with this tissue would be the direct adhesion of neurons onto the contacts of the implant, and the prevention of glial encapsulation. With direct neuronal adhesion the effectiveness and longevity of the device would be significantly improved. Titania nanotube arrays, fabricated using electrochemical anodization, provide a conductive architecture capable of altering cellular response. This work focuses on the fabrication of different titania nanotube array architectures to determine how their structures and properties influence the response of neural tissue, modeled using the C17.2 murine neural stem cell subclone, and if glial encapsulation can be reduced while neuronal adhesion is promoted.

  15. Use of Functionalized Carbon Nanotubes for Covalent Attachment of Nanotubes to Silicon

    Science.gov (United States)

    Tour, James M.; Dyke, Christopher A.; Maya, Francisco; Stewart, Michael P.; Chen, Bo; Flatt, Austen K.

    2012-01-01

    The purpose of the invention is to covalently attach functionalized carbon nanotubes to silicon. This step allows for the introduction of carbon nanotubes onto all manner of silicon surfaces, and thereby introduction of carbon nano - tubes covalently into silicon-based devices, onto silicon particles, and onto silicon surfaces. Single-walled carbon nanotubes (SWNTs) dispersed as individuals in surfactant were functionalized. The nano - tube was first treated with 4-t-butylbenzenediazonium tetrafluoroborate to give increased solubility to the carbon nanotube; the second group attached to the sidewall of the nanotube has a silyl-protected terminal alkyne that is de-protected in situ. This gives a soluble carbon nanotube that has functional groups appended to the sidewall that can be attached covalently to silicon. This reaction was monitored by UV/vis/NJR to assure direct covalent functionalization.

  16. Improved synthesis of carbon nanotubes with junctions and of single-walled carbon nanotubes

    OpenAIRE

    Deepak, FL; Govindaraj, A.; Rao, CNR

    2006-01-01

    Pyrolysis of thiophene over nickel nanoparticles dispersed on silica is shown to yield Y-junction carbon nanotubes with smaller diameters than those obtained by the pyrolysis of organometallic-thiophene mixtures. In the presence of water vapour, the pyrolysis of organometallic-hydrocarbon mixtures yields single-walled nanotubes, as well as relatively narrow-diameter carbon nanotubes with Y-junctions. Pyrolysis-of organometallic-hydrocarbon mixtures, in the absence of water vapour, only gives ...

  17. Carbon nanotube transistor optimization by chemical control of the nanotube-metal interface

    Science.gov (United States)

    Auvray, S.; Borghetti, J.; Goffman, M. F.; Filoramo, A.; Derycke, V.; Bourgoin, J. P.; Jost, O.

    2004-06-01

    Most carbon nanotube transistors work as Schottky barrier transistors. We show that chemical treatment of operational p-type nanotube transistors by trifluoro-acetic acid (TFA) leads to the drastic improvement of all the key device parameters. This effect is due to the highly polar nature of the TFA molecule which, once adsorbed at the metal-nanotube interface, lowers the Schottky barrier for the holes and thus favors their injection.

  18. Functionalization of carbon nanotubes with silver clusters

    Science.gov (United States)

    Cveticanin, Jelena; Krkljes, Aleksandra; Kacarevic-Popovic, Zorica; Mitric, Miodrag; Rakocevic, Zlatko; Trpkov, Djordje; Neskovic, Olivera

    2010-09-01

    In this paper, an advanced method of one-step functionalization of single and multi walled carbon nanotubes (SWCNTs and MWCNTs) using γ-irradiation was described. Two synthesis procedures, related with different reduction species, were employed. For the first time, poly(vinyl alcohol) PVA is successfully utilized as a source to reduce silver (Ag) metal ions without having any additional reducing agents to obtain Ag nanoparticles on CNTs. The decoration of carbon nanotubes with Ag nanoparticles takes place through anchoring of (PVA) on nanotube's surface. Optical properties of as-prepared samples and mechanism responsible for the functionalization of carbon nanotubes were investigated using UV-vis and FTIR spectroscopy, respectively. Decorated carbon nanotubes were visualized using microscopic techniques: transmission electron microscopy and scanning tunneling microscopy. Also, the presence of Ag on the nanotubes was confirmed using energy dispersive X-ray spectroscopy. This simple and effective method of making a carbon nanotube type of composites is of interest not only for an application in various areas of technology and biology, but for investigation of the potential of radiation technology for nanoengineering of materials.

  19. Real Time Observation of DNA Nanotube Assembly

    Science.gov (United States)

    Verde, Lisa Val

    2006-03-01

    DNA nanotubes are of interest for applications ranging from nanofabrication to biophysical studies. The DNA Nanotubes used in this research are self-assembling structures composed of DNA double-crossover tiles. These tiles are simply two connected helices composed of five single stranded DNA oligomers. Each tile exposes four sticky ends responsible for the linkage between neighboring tiles. This linkage creates the nanotube lattice, with intrinsic curvature. The curvature orients each tile with a 60^o angle from the previous one so that six tiles make up the circumference of a nanotube. Nanotube stability depends on conditions such as ionic strength and temperature. A PCR machine is used to anneal the strands into nanotubes. A duplicated annealing process was constructed under a light microscope. PVP (polyvinyl prolidone) coated glass both confined the DNA nanotubes to a 2-3 μm focal plane and prevented them from sticking to the sample surface. By the time the tubes were long enough to track (>= 3 μm), they continued to lengthen primarily via end-to-end joining with some reaching lengths greater than 100 μm. These observations helped define more efficient annealing protocols that resulted in tubes with fewer imperfections.

  20. Functionalization of carbon nanotubes with silver clusters

    International Nuclear Information System (INIS)

    In this paper, an advanced method of one-step functionalization of single and multi walled carbon nanotubes (SWCNTs and MWCNTs) using γ-irradiation was described. Two synthesis procedures, related with different reduction species, were employed. For the first time, poly(vinyl alcohol) PVA is successfully utilized as a source to reduce silver (Ag) metal ions without having any additional reducing agents to obtain Ag nanoparticles on CNTs. The decoration of carbon nanotubes with Ag nanoparticles takes place through anchoring of (PVA) on nanotube's surface. Optical properties of as-prepared samples and mechanism responsible for the functionalization of carbon nanotubes were investigated using UV-vis and FTIR spectroscopy, respectively. Decorated carbon nanotubes were visualized using microscopic techniques: transmission electron microscopy and scanning tunneling microscopy. Also, the presence of Ag on the nanotubes was confirmed using energy dispersive X-ray spectroscopy. This simple and effective method of making a carbon nanotube type of composites is of interest not only for an application in various areas of technology and biology, but for investigation of the potential of radiation technology for nanoengineering of materials.

  1. Global dimension in Noetherian rings and rings with Gabriel and Krull dimension

    OpenAIRE

    Simón Pinero, Juan Jacobo

    1992-01-01

    In this paper we compute the global dimension of Noetherian rings and rings with Gabriel and Krull dimension by taking a subclass of cyclic modules determined by the Gabriel filtration in the lattice of hereditary torsion theories.

  2. Representation dimension of m-replicated algebras

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Let A be a finite-dimensional hereditary algebra over an algebraically closed field and A(m) be the m-replicated algebra of A.We prove that the representation dimension of A(m) is at most 3,and that the dominant dimension of A(m) is at least m.

  3. The pointwise dimensions of Moran measures

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    In this paper,we get the formulas of upper(lower) pointwise dimensions of some Moran measures on Moran sets in Rd under the strong separation condition.We also obtain formulas for the dimension of the Moran measures.Our results extend the known results of some self-similar measures and Moran measures studied by Cawley and Mauldin.

  4. Selforthogonal modules with finite injective dimension

    Institute of Scientific and Technical Information of China (English)

    黄兆泳

    2000-01-01

    The category consisting of finitely generated modules which are left orthogonal with a cotilting bimodule is shown to be functorially finite. The notion of left orthogonal dimension is introduced , and then a necessary and sufficient condition of selforthogonal modules having finite injective dimension and a characterization of cotilting modules are given.

  5. Selforthogonal modules with finite injective dimension

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The category consisting of finitely generated modules which are left orthogonal with a cotilting bimodule is shown to be functorially finite. The notion of left orthogonal dimension is introduced, and then a necessary and sufficient condition of selforthogonal modules having finite injective dimension and a characterization of cotilting modules are given.

  6. On the dimension of Archimedean solids

    OpenAIRE

    Tomáš Madaras; Pavol Široczki

    2014-01-01

    We study the dimension of graphs of the Archimedean solids. For most of these graphs we find the exact value of their dimension by finding unit-distance embeddings in the euclidean plane or by proving that such an embedding is not possible.

  7. On the dimension of Archimedean solids

    Directory of Open Access Journals (Sweden)

    Tomáš Madaras

    2014-01-01

    Full Text Available We study the dimension of graphs of the Archimedean solids. For most of these graphs we find the exact value of their dimension by finding unit-distance embeddings in the euclidean plane or by proving that such an embedding is not possible.

  8. Quantum Field Theory in (0 + 1) Dimensions

    Science.gov (United States)

    Boozer, A. D.

    2007-01-01

    We show that many of the key ideas of quantum field theory can be illustrated simply and straightforwardly by using toy models in (0 + 1) dimensions. Because quantum field theory in (0 + 1) dimensions is equivalent to quantum mechanics, these models allow us to use techniques from quantum mechanics to gain insight into quantum field theory. In…

  9. The SYMLOG Dimensions and Small Group Conflict.

    Science.gov (United States)

    Wall, Victor D., Jr.; Galanes, Gloria J.

    1986-01-01

    Explores the potential usefulness of R.F. Bales' systematic method for the multiple level observation of groups (SYMLOG) by testing the predictive capability of the three SYMLOG dimensions and the amount of member dispersion on each dimension with the amounts of conflict, reported satisfaction, styles of conflict management, and quality of…

  10. Four Essential Dimensions of Workplace Learning

    Science.gov (United States)

    Hopwood, Nick

    2014-01-01

    Purpose: This conceptual paper aims to argue that times, spaces, bodies and things constitute four essential dimensions of workplace learning. It examines how practices relate or hang together, taking Gherardi's texture of practices or connectedness in action as the foundation for making visible essential but often overlooked dimensions of…

  11. 49 CFR 178.360-3 - Dimensions.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Dimensions. 178.360-3 Section 178.360-3 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY... Specifications for Packagings for Class 7 (Radioactive) Materials § 178.360-3 Dimensions. (a) The inside...

  12. Mathematics Teachers' Criteria of Dimension

    Science.gov (United States)

    Ural, Alattin

    2014-01-01

    The aim of the study is to determine mathematics teachers' decisions about dimensions of the geometric figures, criteria of dimension and consistency of decision-criteria. The research is a qualitative research and the model applied in the study is descriptive method on the basis of general scanning model. 15 mathematics teachers attended the…

  13. An Inventory of Listening Competency Dimensions

    Science.gov (United States)

    Wolvin, Andrew D.; Cohen, Steven D.

    2012-01-01

    This article proposes the use of a one-page listening inventory sheet that helps students explore five dimensions of listening competency: cognitive, affective, behavioral, contextual, and ethical. After crafting their own responses, students will have the opportunity to engage in a class discussion about the impact of various dimensions of…

  14. World View: The Second Hidden Dimension.

    Science.gov (United States)

    Skow, Lisa; And Others

    Proposing that world view is a dimension of culture which lies below the surface of human behavior at the level of the subconscious, this paper argues that this often ignored dimension of culture profoundly influences human communication. The paper is divided into two sections. First, world view is defined and its importance in explaining how…

  15. Simulation Studies of the Damaging Effect of Molecular Hydrogen gas on Double Walled Carbon Nanotubes.

    Directory of Open Access Journals (Sweden)

    Ali Ershadi

    2015-06-01

    Full Text Available The hydrogen damage in the double walled carbon nanotubes (DWCNTs was studied through molecular simulation.The simulation performed in the measuring domain has the dimensions of about 20×20×13 A. Our calculations revealed that the partial pressure of the hydrogen gas between the two walls is 180 atm and this pressure is equal to hydrogen density of 7.6 mol/L.This simulation procedure showed that the partial amount of the hydrogen molecules gas at first dissociated and then penetrate to the external wall of DWCNT.This approach is similar to hydrogen embrittlement on metals surface.

  16. Attention Alters Perceived Attractiveness.

    Science.gov (United States)

    Störmer, Viola S; Alvarez, George A

    2016-04-01

    Can attention alter the impression of a face? Previous studies showed that attention modulates the appearance of lower-level visual features. For instance, attention can make a simple stimulus appear to have higher contrast than it actually does. We tested whether attention can also alter the perception of a higher-order property-namely, facial attractiveness. We asked participants to judge the relative attractiveness of two faces after summoning their attention to one of the faces using a briefly presented visual cue. Across trials, participants judged the attended face to be more attractive than the same face when it was unattended. This effect was not due to decision or response biases, but rather was due to changes in perceptual processing of the faces. These results show that attention alters perceived facial attractiveness, and broadly demonstrate that attention can influence higher-level perception and may affect people's initial impressions of one another. PMID:26966228

  17. Electro-optic properties of organic nanotubes.

    Science.gov (United States)

    Stoylov, Stoyl P; Stoilova-McPhie, Svetla

    2011-08-10

    In this review article the theoretical and experimental possibilities of applying EO-methods for estimation of the physico-chemical properties of the organic nanotubes (ONTs) are studied. The ONTs are highly organized nanostructures of strongly elongated, anysometric, and hollow cylinders with a size range of 1 nm to 10,000 nm, e.g. in aqueous solutions they could behave as colloid (disperse) particles. They have high interaction ability due to their extremely large curved, rolled-up external surfaces (bilayers of membrane walls) and unique properties because of their specific electric charge distribution and dynamics that make possible the functionalization of their surfaces. Thus they could template guestsubstances such as membrane proteins and protein complexes on the exterior surfaces and in the membrane. We performed our investigations for the case of ONT aqueous colloid suspension. Following our earlier proposition of the general expression for the electro-optic (EO) effect we derived equations for the evaluation of the electric properties of ONT particles such as mechanism of electric polarization and identification of their most important electric Dipole Moments (DM), permanent (pDM) and induced (iDMs). Further we recommend ways for the calculation of their magnitude and direction. Also we evaluated some geometrical properties such as length of the ONT particles and their polydispersity. The knowledge that we provided about the ONT properties may enable us to elucidate and predict their biological activity. Templating biological active ligands (such as membrane proteins and protein complexes) on the inner and outer surfaces as well as in the surface membrane creates their potential usefulness as carrier and deliverer of biopharmaceuticals in bio-nanodevices. The theoretical equations were compared with the experimental data for ONTs such as (lipid) LNT, Tobacco Mosaic Virus (TMV) and microtubules (MT). Comparison of EO methods with other methods used till

  18. Utilizing real time transmission electron microscopy to understand the mechanisms of nanotube nucleation, growth and growth termination

    Science.gov (United States)

    Stach, Eric A.

    2011-03-01

    In order for carbon nanotubes to find widespread application, we must have a deeper understanding of the mechanisms by which they nucleate, growth and cease growth, in an effort to fully control the resulting structures. Here we will describe how we can exploit the unique capabilities of in-situ environmental cell transmission electron microscopy to observe multiple aspects of these processes. With this approach we can directly visualize how the catalysts that mediate nanotube growth respond to various changes in the growth environment, and correlate these changes with the resulting nanotube structures. In the first part of the presentation, we will investigate how dynamic changes in the catalyst morphology are correlated with the termination of growth in vertically aligned SWNT arrays. In particular, we have investigate how the processes of catalyst coarsening, Ostwald ripening and diffusion into the catalyst support can lead to growth termination, and we will describe how changes in the growth feedstock - in particular the incorporation of controlled amounts of water vapor - can alter the catalyst evolution. In the second portion of the presentation, we will describe how altering other aspects of the growth feedstock - in this case the carrier gas, in combination with the water vapor content - can not only affect catalyst morphological evolution, but can also significantly bias the chiral distribution of the resulting nanotubes. We will correlate the changes in growth ambient with a faceting / defacting transition, as well as a resulting change in the rate of Ostwald ripening.

  19. Silicon nanotubes: Synthesis and characterization

    International Nuclear Information System (INIS)

    Transmission electron microscopy (TEM) and electron energy loss near-edge structure (EELNES) revealed the presence of mostly non-oxidised silicon tubular structures among the reaction products synthesized by gas phase condensation technique. Scanning tunneling microscopy (STM) showed a hexagonal atomic arrangement for straight ones. The presence of Y-, T-branched and coiled tubular structure, like in carbon nanotubes, suggests a partially sp2 hybridization. Reflection energy loss measurements confirmed the presence of thin tubular structures and gave hint of sp3 bonds

  20. Vanadium molybdenum complex oxide nanotubes

    International Nuclear Information System (INIS)

    Nanotubes (NTs) of complex vanadium molybdenum oxide V0.78Mo0.22O2.49(C2H3)0.46 are prepared from the (V1.67Mo0.33O16 · nH2O gel/PVA) composite (PVA stands for poly(vinyl alcohol)) by hydrothermal treatment for 30-50 h at 150-180 deg C. The outer tube diameters are 10-20 and 70-80 nm; the tube lengths are no longer than 1 μm. The X-ray photoelectron and IR spectra, electrical conductivity, and thermal properties of the NTs are studied

  1. Carbon nanotube growth density control

    Science.gov (United States)

    Delzeit, Lance D. (Inventor); Schipper, John F. (Inventor)

    2010-01-01

    Method and system for combined coarse scale control and fine scale control of growth density of a carbon nanotube (CNT) array on a substrate, using a selected electrical field adjacent to a substrate surface for coarse scale density control (by one or more orders of magnitude) and a selected CNT growth temperature range for fine scale density control (by multiplicative factors of less than an order of magnitude) of CNT growth density. Two spaced apart regions on a substrate may have different CNT growth densities and/or may use different feed gases for CNT growth.

  2. Charge-tunable insertion process of carbon nanotubes into DNA nanotubes.

    Science.gov (United States)

    Liang, Lijun; Zhang, Zhisen; Kong, Zhe; Liu, Yong; Shen, Jia-Wei; Li, Debing; Wang, Qi

    2016-05-01

    Control over interactions with biomolecules holds the key of the applications of carbon nanotubes (CNTs) in biotechnology. Here we report a molecule dynamics study on the encapsulation process of different charged CNTs into DNA nanotubes. Our results demonstrated that insertion process of CNTs into DNA nanotubes are charge-tunable. The positive charged CNTs could spontaneously encapsulate and confined in the hollow of DNA nanotubes under the combination of electrostatic and vdW interaction in our ns scale simulation. The conformation of DNA nanotubes is very stable even after the insertion of CNTs. For pristine CNTs, it could not entirely encapsulated by DNA nanotubes in simulation scale in this study. The encapsulation time of pristine CNTs into DNA nanotubes was estimated about 21.9s based on the potential of mean force along the reaction coordination of encapsulation process of CNTs into DNA nanotubes. In addition, the encapsulation process was also affected by the diameter of CNTs. These findings highlight the charge-tunable self-assembly process of nanomaterials and biomolecules. Our study suggests that the encapsulated CNTs-DNA nanotubes could be used as building blocks for constructing organic-inorganic hybrid materials and has the potential applications in the field of biosensor, drug delivery system and biomaterials etc. PMID:27017425

  3. Dimension Reduction of Health Data Clustering

    CERN Document Server

    Sembiring, Rahmat Widia; Embong, Abdullah

    2011-01-01

    The current data tends to be more complex than conventional data and need dimension reduction. Dimension reduction is important in cluster analysis and creates a smaller data in volume and has the same analytical results as the original representation. A clustering process needs data reduction to obtain an efficient processing time while clustering and mitigate curse of dimensionality. This paper proposes a model for extracting multidimensional data clustering of health database. We implemented four dimension reduction techniques such as Singular Value Decomposition (SVD), Principal Component Analysis (PCA), Self Organizing Map (SOM) and FastICA. The results show that dimension reductions significantly reduce dimension and shorten processing time and also increased performance of cluster in several health datasets.

  4. Is cosmic censorship restored in higher dimensions?

    Science.gov (United States)

    Mkenyeleye, M. D.; Goswami, Rituparno; Maharaj, Sunil D.

    2015-07-01

    In this paper we extend the analysis of gravitational collapse of spherically symmetric generalized Vaidya spacetimes to higher dimensions, in the context of the cosmic censorship conjecture. We present the sufficient conditions on the generalized Vaidya mass function that will generate a locally naked singular end state. Our analysis here generalizes all the earlier works on collapsing higher dimensional generalized Vaidya spacetimes. With specific examples, we show the existence of classes of mass functions that lead to a naked singularity in four dimensions, which gets covered on transition to higher dimensions. Hence for these classes of mass function cosmic censorship gets restored in higher dimensions and the transition to higher dimensions restricts the set of initial data that results in a naked singularity.

  5. A new information dimension of complex networks

    International Nuclear Information System (INIS)

    Highlights: •The proposed measure is more practical than the classical information dimension. •The difference of information for box in the box-covering algorithm is considered. •Results indicate the measure can capture the fractal property of complex networks. -- Abstract: The fractal and self-similarity properties are revealed in many complex networks. The classical information dimension is an important method to study fractal and self-similarity properties of planar networks. However, it is not practical for real complex networks. In this Letter, a new information dimension of complex networks is proposed. The nodes number in each box is considered by using the box-covering algorithm of complex networks. The proposed method is applied to calculate the fractal dimensions of some real networks. Our results show that the proposed method is efficient when dealing with the fractal dimension problem of complex networks.

  6. Heteronuclear carbon nanotubes: applications to study carbon nanotube growth

    International Nuclear Information System (INIS)

    Full text: Synthesis of heteronuclear carbon nanotubes and their application for a variety of studies is presented. SWCNTs peapods encapsulating highly 13C enriched fullerenes and double wall carbon nanotubes (DWCNTs) based on the peapods were prepared. Raman studies indicate that the inner tubes are highly 13C enriched with no carbon exchange between the two walls during the synthesis. The material enables the straightforward identification of the inner and outer tube vibrational spectra. An inhomogeneous broadening, assigned to the random distribution of 12C and 13C nuclei is observed and is explained by ab initio vibrational analysis. The growth of inner tubes from organic solvents was proven by the use of 13C labeled organic materials such as toluene. The simultaneous encapsulation of fullerenes with the solvents was found crucial as these prevent the solvents from evaporating during the high temperature synthesis of the inner tubes. Nuclear magnetic resonance on the peapods and DWCNTs with highly 13C enriched fullerenes or inner walls proves the significant contrast of the isotope enriched SWCNTs as compared to other carbon phases. The NMR experiment on the DWCNTs yield direct information on the electronic properties of small diameter SWCNTs. The significantly different chemical shift of the inner tubes is related to a curvature effect. Relaxation data on the inner tubes shows a deviation from a Fermi-liquid behavior. (author)

  7. Nuclear transport - The regulatory dimension

    International Nuclear Information System (INIS)

    The benefits that the peaceful applications of nuclear energy have brought to society are due in no small part to industry's capacity to transport radioactive materials safely, efficiently and reliably. The nuclear transport industry has a vital role in realising a fundamental objective of the International Atomic Energy Agency (IAEA) as stated in its statute to accelerate and enlarge the contribution of atomic energy to peace, health and prosperity throughout the world. The context in which transports currently take place is complex, and rapidly changing. In many respects transport is being viewed as an integral market issue and not a subsidiary concern. The availability of carriers drives routing decisions and changes in material flows necessitate new approaches to packaging and transport scenarios. Pressures on the transport sector are not without serious consequences; they can cause delays and in some cases cancellation of planned movements. Complex routings and the necessary use of chartered carriers can push up costs and work against cost efficiency. Since the events of 11 September 2001 the security of nuclear transports has contributed an added dimension to how transports take place. Transports of radioactive material have an outstanding safety record, indeed the transport of such materials could be regarded as a model for the transport of other classes of dangerous goods. This safety record is achieved by two inter-related factors. It is due primarily to well founded regulations developed by such key intergovernmental organisations as the IAEA, with the essential contributions of the member states who participate in the implementation of regulations and the review process. It is due also to the professionalism of those in the industry. There is a necessary synergy between the two - between the regulators whose task it is to make and to enforce the rules for safe, efficient and reliable transport and those whose job it is to transport within the rules. It

  8. Transport theory of carbon nanotube Y junctions

    International Nuclear Information System (INIS)

    We describe a generalization of Landauer-Buettiker theory for networks of interacting metallic carbon nanotubes. We start with symmetric starlike junctions and then extend our approach to asymmetric systems. While the symmetric case is solved in closed form, the asymmetric situation is treated by a mixture of perturbative and non-perturbative methods. For N > 2 repulsively interacting nanotubes, the only stable fixed point of the symmetric system corresponds to an isolated node. Detailed results for both symmetric and asymmetric systems are shown for N = 3, corresponding to carbon nanotube Y junctions

  9. Carbon nanotube fiber spun from wetted ribbon

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Yuntian T; Arendt, Paul; Zhang, Xiefei; Li, Qingwen; Fu, Lei; Zheng, Lianxi

    2014-04-29

    A fiber of carbon nanotubes was prepared by a wet-spinning method involving drawing carbon nanotubes away from a substantially aligned, supported array of carbon nanotubes to form a ribbon, wetting the ribbon with a liquid, and spinning a fiber from the wetted ribbon. The liquid can be a polymer solution and after forming the fiber, the polymer can be cured. The resulting fiber has a higher tensile strength and higher conductivity compared to dry-spun fibers and to wet-spun fibers prepared by other methods.

  10. Statics and dynamics of fluids in nanotubes

    CERN Document Server

    Gouin, Henri

    2013-01-01

    The purpose of this article is to study the statics and dynamics of nanotubes by using the methods of continuum mechanics. The nanotube can be filled with only a liquid or a vapour phase according to the physicochemical characteristics of the wall and to the disjoining pressure associated with the liquid and vapour mother bulks of the fluid, regardless of the nature of the external mother bulk. In dynamics, flows through nanotubes can be much more important than classical Poiseuille flows. When the external mother bulk is of vapour, the flow can be a million times larger than the classical flows when slippage on wall does not exist.

  11. Channeling of high energy beams in nanotubes

    CERN Document Server

    Bellucci, S; Chesnokov, Yu A; Guidi, V; Scandale, Walter; Chesnokov, Yu. A.

    2003-01-01

    We present simulations of particle beam channeling in carbon nanotubes and evaluate the possibilities for experimental observation of channeling effect in straight and bent nanotubes at IHEP and LNF. Different particle species are considered: protons of 1.3 and 70 GeV, and positrons of 0.5 GeV. Predictions are made for the experiments, with analysis of requirements on the quality of nanosamples and resolution of the experimental set-up. Based on Monte Carlo simulations, the capabilities of nanotube channeling technique for particle beam steering are discussed.

  12. Carbon Nanotube Paper-Based Electroanalytical Devices

    OpenAIRE

    Youngmi Koo; Vesselin N. Shanov; Yeoheung Yun

    2016-01-01

    Here, we report on carbon nanotube paper-based electroanalytical devices. A highly aligned-carbon nanotube (HA-CNT) array, grown using chemical vapor deposition (CVD), was processed to form bi-layered paper with an integrated cellulose-based Origami-chip as the electroanalytical device. We used an inverse-ordered fabrication method from a thick carbon nanotube (CNT) sheet to a thin CNT sheet. A 200-layered HA-CNT sheet and a 100-layered HA-CNT sheet are explored as a working electrode. The de...

  13. ON THE CONTINUUM MODELING OF CARBON NANOTUBES

    Institute of Scientific and Technical Information of China (English)

    张鹏; 黄永刚; Philippe H.Geubelle; 黄克智

    2002-01-01

    We have recently proposed a nanoscale continuum theory for carbonnanotubes. The theory links continuum analysis with atomistic modeling by incor-porating interatomic potentials and atomic structures of carbon nanotubes directlyinto the constitutive law. Here we address two main issues involved in setting upthe nanoscale continuum theory for carbon nanotubes, namely the multi-body in-teratomic potentials and the lack of centrosymmetry in the nanotube structure. Weexplain the key ideas behind these issues in establishing a nanoscale continuum theoryin terms of interatomic potentials and atomic structures.

  14. Ordered phases of cesium in carbon nanotubes

    International Nuclear Information System (INIS)

    We investigate the structural phases of Cs in carbon nanotubes by using a structural optimization process applied to an atomistic simulation method. As the radius of the carbon nanotubes is increased, the structures are found in various phases from an atomic strand to multishell packs composed of coaxial cylindrical shells. Both helical structures and layered structures are found. The numbers of helical atom rows composed of coaxial tubes and the orthogonal vectors of the circular rolling of a triangular network can explain the structural phases of Cs in carbon nanotubes.

  15. Ordered phases of cesium in carbon nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Jeong Won; Hwang, Ho Jung; Song, Ki Oh; Choi, Won Young; Byun, Ki Ryang [Chung-Ang University, Seoul (Korea, Republic of); Kwon, Oh Keun [Semyung University, Jecheon (Korea, Republic of); Lee, Jun Ha [Sangmyung University, Chonan (Korea, Republic of); Kim, Won Woo [Juseong College, Cheongwon (Korea, Republic of)

    2003-10-15

    We investigate the structural phases of Cs in carbon nanotubes by using a structural optimization process applied to an atomistic simulation method. As the radius of the carbon nanotubes is increased, the structures are found in various phases from an atomic strand to multishell packs composed of coaxial cylindrical shells. Both helical structures and layered structures are found. The numbers of helical atom rows composed of coaxial tubes and the orthogonal vectors of the circular rolling of a triangular network can explain the structural phases of Cs in carbon nanotubes.

  16. Stability of diphenylalanine peptide nanotubes in solution

    Science.gov (United States)

    Andersen, Karsten Brandt; Castillo-Leon, Jaime; Hedström, Martin; Svendsen, Winnie Edith

    2011-03-01

    Over the last couple of years, self-organizing nanotubes based on the dipeptide diphenylalanine have received much attention, mainly as possible building blocks for the next generation of biosensors and as drug delivery systems. One of the main reasons for this large interest is that these peptide nanotubes are believed to be very stable both thermally and chemically. Previously, the chemical and thermal stability of self-organizing structures has been investigated after the evaporation of the solvent. However, it was recently discovered that the stability of the structures differed significantly when the tubes were in solution. It has been shown that, in solution, the peptide nanotubes can easily be dissolved in several solvents including water. It is therefore of critical importance that the stability of the nanotubes in solution and not after solvent evaporation be investigated prior to applications in which the nanotube will be submerged in liquid. The present article reports results demonstrating the instability and suggests a possible approach to a stabilization procedure, which drastically improves the stability of the formed structures. The results presented herein provide new information regarding the stability of self-organizing diphenylalanine nanotubes in solution.Over the last couple of years, self-organizing nanotubes based on the dipeptide diphenylalanine have received much attention, mainly as possible building blocks for the next generation of biosensors and as drug delivery systems. One of the main reasons for this large interest is that these peptide nanotubes are believed to be very stable both thermally and chemically. Previously, the chemical and thermal stability of self-organizing structures has been investigated after the evaporation of the solvent. However, it was recently discovered that the stability of the structures differed significantly when the tubes were in solution. It has been shown that, in solution, the peptide nanotubes can

  17. Nanotube Arrays in Porous Anodic Alumina Membranes

    Institute of Scientific and Technical Information of China (English)

    Liang LI; Naoto KOSHIZAKI; Guanghai LI

    2008-01-01

    This review summarizes the various techniques developed for fabricating nanotube arrays in porous anodic alumina membranes (AAMs). After a brief introduction to the fabrication process of AAMs, taking carbons, metals, semiconductors, organics, biomoleculars, and heterojunctions as typical examples, attention will be focused on the recently established methods to fabricate nanotubes in AAM, including electrochemical deposition, surface sol-gel, modified chemical vapor deposition, atomic layer deposition, and layer-by-layer growth. Every method is demonstrated by one or two reported results. Finally, this review is concluded with some perspectives on the research directions and focuses on the AAM-based nanotubes fields.

  18. Effects of nitrogen-doped multi-walled carbon nanotubes compared to pristine multi-walled carbon nanotubes on human small airway epithelial cells

    International Nuclear Information System (INIS)

    Nitrogen-doped multi-walled carbon nanotubes (ND-MWCNTs) are modified multi-walled carbon nanotubes (MWCNTs) with enhanced electrical properties that are used in a variety of applications, including fuel cells and sensors; however, the mode of toxic action of ND-MWCNT has yet to be fully elucidated. In the present study, we compared the interaction of ND-MWCNT or pristine MWCNT-7 with human small airway epithelial cells (SAEC) and evaluated their subsequent bioactive effects. Transmission electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction suggested the presence of N-containing defects in the lattice of the nanotube. The ND-MWCNTs were determined to be 93.3% carbon, 3.8% oxygen, and 2.9% nitrogen. A dose–response cell proliferation assay showed that low doses of ND-MWCNT (1.2 μg/ml) or MWCNT-7 (0.12 μg/ml) increased cellular proliferation, while the highest dose of 120 μg/ml of either material decreased proliferation. ND-MWCNT and MWCNT-7 appeared to interact with SAEC at 6 h and were internalized by 24 h. ROS were elevated at 6 and 24 h in ND-MWCNT exposed cells, but only at 6 h in MWCNT-7 exposed cells. Significant alterations to the cell cycle were observed in SAEC exposed to either 1.2 μg/ml of ND-MWCNT or MWCNT-7 in a time and material-dependent manner, possibly suggesting potential damage or alterations to cell cycle machinery. Our results indicate that ND-MWCNT induce effects in SAEC over a time and dose-related manner which differ from MWCNT-7. Therefore, the physicochemical characteristics of the materials appear to alter their biological effects

  19. Mechanical and emission properties of thinnest stable bamboolike nanotubes

    International Nuclear Information System (INIS)

    We investigate the stability of carbon bamboo-like nanotubes (BCNTs) with different diameters. It is shown that BCNTs with a diameter of 2.024 nm are the most stable bamboo-like nanotubes with the smallest diameter. It is shown that bamboo-like nanotubes with a certain distance between the bridges have superior emission properties than that the hollow nanotubes. Emission properties of the infinite bamboo-like nanotubes can be improved by adding the potassium atoms into the nanotube atomic structure. In this case the potassium atoms concentration should exceed 0.59%.

  20. Excitation transfer and luminescence in porphyrin-carbon nanotube complexes

    CERN Document Server

    Magadur, G; Alain-Rizzo, V; Voisin, C; Roussignol, Ph; Deleporte, E; Delaire, J A

    2007-01-01

    Functionalization of carbon nanotubes with hydrosoluble porphyrins (TPPS) is achieved by "$\\pi$-stacking". The porphyrin/nanotube interaction is studied by means of optical absorption, photoluminescence and photoluminescence excitation spectroscopies. The main absorption line of the porphyrins adsorbed on nanotubes exhibits a 120 meV red shift, which we ascribe to a flattening of the molecule in order to optimize $\\pi-\\pi$ interactions. The porphyrin-nanotube complex shows a strong quenching of the TPPS emission while the photoluminescence intensity of the nanotubes is enhanced when the excitation laser is in resonance with the porphyrin absorption band. This reveals an efficient excitation transfer from the TPPS to the carbon nanotube.